What mechanisms are used in modern cars. Machine mechanisms

EXCAVATORS

The main purpose of excavators is to dig and move soil by means of a bucket or a continuous action mechanism (chain or rotary). Based on this, excavators are divided into single-bucket, intermittent, and continuous excavators.

Single-bucket, in turn, are construction universal for earthworks and quarry for quarrying.

The main parts of construction excavators are the undercarriage (wheeled or caterpillar), a turntable with a power plant and interchangeable working equipment. Single-bucket excavators are classified according to the following criteria:

- by type of working equipment - to articulated (Fig. 1) and telescopic (Fig. 2);

- by type of chassis - for caterpillar (Fig. 3) and pneumatic wheels (Fig. 4);

- according to the suspension design of the working equipment - on hydraulic cylinders (rigid suspension - Fig. 5) and rope pulleys (flexible suspension - Fig. 3, 4);

- according to the design of the slewing device - into full-turn (Fig. 3, 4) and part-turn (Fig. 6);

- by type of drive - single-engine and multi-engine, and it can be both mechanical and electric drives.

Figure 1.: 1 - turntable; 2 - running gear; 3 - outrigger, 4 - turntable; 5 - engine; 6, 8, 9 - hydraulic drives; 10 - handle; 11 - bucket (backhoe); 12 - dozer blade; 13 - driver's cab

Figure 2.: 1 - turntable; 2 - running gear; 3 - outrigger; 4 - turntable; 5 - telescopic boom; 6 - hydraulic cylinders; 7 - bucket (backhoe); 8 - driver's cab

Figure 3.: 1 - turntable; 2 - bipedal stand; 3 - boom-lifting cable; 4 - front pillar; 5 - handle; 6 - cabin; 7 - lifting cables; 8 - arrow; 9 - caterpillar undercarriage; 10 - bucket (backhoe); 11 - traction cable; 12 - turntable

Figure 4.: 1 - turntable; 2 - bucket (backhoe); 3 - rack; 4 - boom lifting cable; 5 - front desk; 6 - driver's cab; 7 - lifting cables; 8 - arrow; 9 - handle; 10 - running gear; 11 - traction cable; 12 - turntable

Figure 5.: 1 - caterpillar undercarriage; 2 - axis of the turntable; 3 - driver's cab; 4 - turntable; 5 - bucket (straight shovel); 6, 8, 9 - hydraulic drives; 7 - arrow; 11 - handle

Figure 6.: 1 - blade; 2 - blade hydraulic drive; 3 - engine; 4 - rotary column; 5, 6, 7 - hydraulic cylinders; 8 - thrust; 9 - unified bucket; 10 - handle; 11 - arrow; 12 - hydraulic cylinders of outriggers; 13 - outriggers; 14 - stars; 15 - sleeve-roller chain; 16 - hydraulic cylinders of the rotary mechanism; 17 - frame

Excavators with flexible suspension of working equipment (rope chain hoists) are divided into those with working equipment with a front shovel (Fig. 7) and those with equipment with a backhoe (Fig. 8). The choice of a specific modification of the excavator is dictated by the nature of the work performed, their features, and the correct definition (classification) of the machine needed in this case means a lot.

Figure 7.: 1 - arrow; 2 - handle; 3 - bucket; 4, 5, 6 - hydraulic drives; h to - digging depth; R to - digging radius; H in - unloading height; R in - bucket lifting radius

Figure 8.: 1 - arrow; 2, 3, 8 - hydraulic drives; 4 - bucket (backhoe); 5 - handle; 6 - composite knee of the arrow; 7 - thrust; 9 - intermediate insert; H to - digging depth; R to - digging radius; H in - unloading height; R in - bucket lifting radius

In addition to the classification of excavators, one must also know their indexing well so that there is no error in the operational capabilities of the machine. Fig. will help us with this. 9. The first letters will always indicate the classification - in this case: EO (single-bucket excavator). The four main numbers of the index follow: the size group of the excavator, the chassis (type), the design of the working suspension and the serial number of the particular machine. The figure gives a detailed transcript of the four main digits of the index, but at some points everything needs to be stopped.

Figure 9

For each size group, several capacities of buckets are usually indicated - the main and replaceable high-capacity buckets, moreover, for the latter, smaller linear parameters and weaker soils are provided than when working with the main bucket. The main bucket is considered to be the one with which the excavator can develop soil of category IV at maximum linear operating parameters (digging depth and radius, unloading radius and height, etc.).

The capacity of the main buckets of excavators is: for the 2nd size group - 0.25-0.28 m 3; 3rd - 0.40-0.65 m 3; 4th - 0.65-1.00 m 3; 5th - 1.00-1.60 m 3; 6th - 1.60-2.50 m 3; 7th - 2.50-4.00 m 3.

The type of undercarriage is indicated by numbers from 1 to 9: 1 - caterpillar (G); 2 - caterpillar broadened (GU); 3 - pneumatic wheel (P); 4 - special chassis of an automobile type (SSh); 5 - truck chassis (A); 6 - chassis of a serial tractor (Tr); 7 - trailer undercarriage (PR); 8, 9 - reserve. The design of the working equipment is indicated by the numbers: 1 (with a flexible suspension), 2 (with a rigid suspension), 3 (telescopic). The last digit of the index means the serial number of the excavator model. The first of the additional letters after the digital index (A, B, C, etc.) means the serial modernization of this machine, the subsequent ones - the type of special climatic modification (C or HL - northern, T - tropical, TV - for operation in the humid tropics) . For example, index EO-5123KhL is deciphered as follows: single-bucket universal excavator, 5th size group, on a caterpillar undercarriage, with a rigid suspension of working equipment, the third model in the northern version. The excavator is equipped with a main bucket with a capacity of 1.0 m 3 corresponding to the 5th size group, and replaceable buckets with a capacity of 1.25 and 1.6 m 3 .

In addition to the listed attachments, excavators with rope pulleys can be equipped with a dragline suspension (Fig. 10, fragment "A"), crane equipment (fragment "B"), grader equipment (fragment "C").

Figure 10.: A - equipment with a dragline suspension; B - equipping with crane equipment; B - equipping with grader equipment

Excavators with a rigid suspension of working equipment (on hydraulic cylinders) can be equipped with hydraulic hammers (Fig. 11). The hydraulic hammer is hung instead of the backhoe bucket and is connected to the handle through a quick-release fastener. The breaker itself is powered by the excavator's hydraulic pumps, ensuring optimum use of power and lower costs. Recently, small-sized mini- and micro-excavators have been increasingly used (Fig. 12). They can dig pits, trenches, perform work in hard-to-reach places. They are indispensable in cottage construction in summer cottages. To them there is a wide choice of quick-detachable replaceable working equipment.

Figure 11.: 1 - arrow; 2, 3, 6 - hydraulic cylinders; 4 - handle; 5 - hydraulic hammer

Figure 12.: 1 - bucket; 2 - arrow; 3 - sectional hydraulic distributors; 4 - driver's seat; 5 - engine; 6 - hydraulic tank; 7 - back stop; 8 - handle; 9 - middle supports; 10 - driving wheels; 11 - hydraulic motors; 12 - frame; 13 - gear pump; 14 - rear driven wheels

Trench excavators are a separate group. Their main purpose is the preparation of underground communications in an open way. The productivity of trench excavators is higher than that of single-bucket excavators. This is understandable: they are constantly moving in working mode.

Trench excavators consist of three basic parts: a tractor, working equipment and equipment for adjusting the position of all working bodies. On fig. 13 and 14 show a single-chain scraper excavator based on a wheeled tractor and a double-chain trench excavator based on a caterpillar tractor. The indexing of trench excavators is similar to single-bucket excavators, but has its own characteristics. Let's consider this using the example of indexing the most common models: crawler trench excavators with a combined drive (Fig. 15). The first two letters, like those of single-bucket excavators, indicate the type of machine - a trench excavator (ET), but the third letter already indicates the type of working body (C - chain, R - rotary). The first two digits of the index indicate the greatest depth of the trench to be torn off (in dm), the third - the serial number of the model. The first of the additional letters after the digital index (A, B, C, etc.) means the serial modernization of the machine, the subsequent ones - the type of special climatic modification (HL - northern, T - tropical, TV - for work in the humid tropics). For example, the index ETTs-252A means: chain trench excavator, digging depth 25 dm, the second model - 2, which has passed the first modernization - A.

Figure 13.: 1 - hydraulic lifting mechanism; 2 - drive shaft; 3 - additional frame; 4 - inclined frame; 5 - replaceable console cleaning shoe; 6 - sleeve-roller chain; 7 - auger screw conveyor; 8 - three-stage gearbox; 9 - hydromechanical retarder; 10 - power take-off shaft; 11 - blade

Figure 14.: 1 - hydraulic cylinder; 2 - lever; 3 - transverse belt conveyor; 4 - chain drive sprockets; 5 - plate chains; 6 - cutting knives; 7 - inclined frame; 8 - tension sprockets of chains; 9 - intermediate rollers

Figure 15.

LOADING AND UNLOADING MACHINES

The main purpose of these machines and mechanisms is to work on the movement of various goods. Usually these are self-propelled universal vehicles based, as a rule, on wheeled vehicles. They also use quick-detachable working devices - grabs, buckets, crane attachments, etc.

Loaders are divided into bucket, fork and multi-bucket (continuous). In urban, suburban and cottage construction, the most common are front-end loaders (Fig. 16), bulldozer loaders (Fig. 17), and, of course, small-sized loaders (Fig. 18). Front loaders ensure that the bucket is unloaded forward within a given height. The main bucket (1 m 3) has a straight cutting edge with removable teeth.

Figure 16.: 1 - cabin; 2 - engine; 3 - power take-off gearbox; 4 - leading bridges; 5 - chassis with articulated frame; 6 - boom hydraulic cylinder; 7 - arrow; 8 - bucket; 9 - rocker; 10 - hydraulic cylinder for turning the bucket; 11 - thrust

Figure 17.: 1 - bucket; 2 - device for changing working bodies; 3 - arrow; 4, 5 - hydraulic cylinders; 6 - basic tractor; 7 - blade-planner; 8 - thrust; 9 - carrier frame

Figure 18.: 1 - caliper; 2 - arrow; 3 - hydraulic cylinders for turning the caliper; 4 - levers; 5 - thrust; 6 - lifting hydraulic cylinders; 7 - semi-portal

The bulldozer-loader, along with loading and unloading operations, can carry out site planning, backfilling of pits, demolition of small hills. As the main replacement equipment, a hydraulically controlled blade and a bucket with a volume of 0.38 m 3 or 0.5 m 3 are used.

Small-sized loaders are designed to perform work in particularly cramped conditions. They have a large selection of interchangeable equipment and successfully use a cleaning bucket, a backhoe, a cargo boom, a pitchfork, a hydraulic hammer, a drill, a bulldozer blade, a trencher. The loader can make a 180° turn on the spot with a zone width of up to 4 meters, no more.

MACHINES FOR WORKING WITH CONCRETE AND MORTAR

According to their functional purpose, these machines and mechanisms are of three types: the first ones prepare concrete and mortar mixtures, the second ones deliver solutions to the construction site, the third ones stack and compact mixtures and mortars.

The first type includes mixers of various modifications: these are continuous mixers, mixers of a cyclic nature of work, mixers of oar, turbulent types, working on gravitational or forced mixing principles, stationary and mobile mixers. The most modern and mobile representative of this type of machine is shown on rice. 19 truck mixer. It prepares the concrete mixture on the way to the object, directly on the object and, being already loaded with high-quality mixture, activates (mixes) it on the way. The optimum temperature for the operation of these machines is from -30° to +40°.

Figure 19. Concrete mixer truck (ready mix - 4 m 3): 1 - KAMAZ chassis; 2 - dosing and flushing tank; 3 - drum rotation mechanism; 4 - mixing drum; 5 - loading funnel; 6 - unloading funnel; 7 - folding tray; 8 - rotary device; 9 - mixer frame; 10, 12 - equipment control levers; 11 - instrumentation

The second type includes all machines for transporting prepared mixtures. These are mainly specialized vehicles: mortar trucks, concrete trucks, concrete mixer trucks already mentioned by us (since they also combine the function of delivering solutions).
This also includes truck-mounted concrete pumps (Figure 20).

Figure 20.: 1 - KAMAZ chassis; 2 - turntable; 3 - rotary column; 4 - distribution boom; 5, 7, 11 - double-acting hydraulic cylinders; 6 - hydraulic tank; 8 - concrete pump; 9 - concrete pipeline; 10 - water tank; 12 - compressor; 13 - flexible hose; 14 - receiving funnel; 15 - boom frame; 16 - outrigger hydraulic supports

The truck-mounted concrete pump is designed to supply a mixture with a cone draft within 6-12 cm in both horizontal and vertical directions. These are mobile vehicles with a hydraulic drive of a concrete pump and an articulated boom with a concrete pipeline. The device of the concrete pump is piston. The range of the mixture supply horizontally - up to 300 m and vertically - up to 70 m.

The third type includes vibrators of various designs and modifications. Their main purpose is to displace the air contained in the mortar and eliminate all voids between the formwork and reinforcement. The most widely used in construction are pneumatic and electric vibrators with circular vibrations. According to the method of influence on the mixture, surface, external and deep vibrators are distinguished.

Surface vibrators act on the solution through a trough-shaped rectangular platform (Fig. 21, fragment "A"). External vibrators act through the formwork or any other form to which they are attached from the outside (Fig. 21, fragment "B"). Deep vibrators are immersed directly into the solution (Fig. 21, fragment "B").

Figure 21.: A - surface vibrator; B - external vibrator; B - deep vibrator; 1 - vibrator body; 2 - trough-shaped platform; 3 - formwork; 4 - cylindrical vibration tip; 5 - solution

MACHINERY AND EQUIPMENT FOR PILING

Talking about excavators in construction processes, we touched on the possibility of using attachments for using excavators in piling. But there are special settings for this.

When installing foundations, two types of piles are used - ready-made (driven) and bored, the device of which is carried out in wells directly on the construction site. In both cases, pile driving and pile driving installations are used, shown in fig. 22 and 23. Replaceable equipment is hung on them: pile hammers, vibratory hammers, vibratory pile drivers. Piling and pile driving installations are mounted on the basis of self-propelled machines (the same excavators).

Figure 22.: 1 - lower support; 2 - piles; 3 - auger drill; 4 - drive for drilling; 5 - winch; 6 - hydraulic hammer; 7 - lattice boom; 8 - pile mast; 9 - cargo winch; 10 - hook suspension; 11 - head; 12 - hydraulic cylinders; 13 - hydraulic excavator; 14 - mast installation hydraulic cylinder

Figure 23. 1 - base machine; 2 - arrow; 3 - mast; 4 - working tool; 5 - driven pile

Table 1. Machinery for excavation

There are theoretical, technical and operational productivity of earth-moving equipment.

Theoretical productivity "P about" is the productivity provided by the design capabilities of the machine during continuous operation (Table 2).

Table 2. Theoretical number of cycles per minute

Note: The number of cycles per minute is based on normal conditions (normal face height, average rated hoisting line speed, 90° platform turn and dumping).

The technical productivity P t is the highest productivity in the given conditions of soil and slaughter per hour of continuous operation:

where K c - coefficient of cycle duration; K t - coefficient of soil influence, taking into account the degree of filling of the bucket and the effect of soil loosening.

Operational productivity depends on the use of the excavator in time, taking into account the inevitable downtime during operation (maintenance, downtime for organizational reasons, moving machines, preparing a face, etc.)

where K in - the coefficient of use of the excavator in time during the shift.

Usually, K in is taken equal to 0.75 when working in transport and 0.9 when working in a dump.

The performance of a bucket-wheel excavator can be determined by the formula

where q - bucket capacity; V is the speed of the bucket chain in m/s; t - bucket pitch; K n - coefficient of filling of buckets, equal to an average of 0.8; K p - coefficient taking into account the loosening of the soil, is taken equal to 0.7-0.9; K in - the coefficient of use of the excavator in time, equal to 0.8-0.9 with good organization of work (Table 3).

Table 3 Piling mechanisms

The productivity of a concrete mixer can be determined by the formula

where N is the number of batches in 1 hour; G - drum capacity for loading in l; F - concrete output coefficient 0.67 (Table 4).

Table 4 Mechanisms for concrete work

To obtain the performance of lifting equipment in weight units, it is necessary to multiply the number of lifts per hour by the weight of the load being lifted.

As for other auxiliary machines and mechanisms, their data are given for plastering in Table. 6, for roofing - in table. 7, for painting work - in table. 8, for the device of floors - in tab. 9.

Table 5 Lifting mechanisms

Table 6 Mechanisms for plastering works

Table 7 Roofing machines

Table 8 Mechanisms for painting works

Table 9 Flooring machines

1.1. The structure of machines and mechanisms

Most modern cars are built according to the scheme:

Car- a device that performs mechanical movements necessary to perform a work process in order to replace or facilitate the physical and mental labor of a person.

Mechanism is an integral part of the machine and is a set of interconnected parts and assemblies that ensure the performance of specified functions.

Drive unit consists of a motor and a transmission mechanism. It is designed to provide kinematic and power characteristics of the actuator.

transmission mechanism is designed to transfer energy from the engine to the actuator with the transformation of the type and direction of movement, as well as changes in kinematic and power characteristics.

Actuating mechanism is designed to perform directly the workflow (processing, transportation, mixing, etc.).

1.2. Simple transfers. Main characteristics
and calculated dependencies

The need to introduce a transmission mechanism is due to the ability to perform various functions:

Energy (power) transmission;

Transformation (reduction or increase) of forces or moments of forces;

Transformation (decrease or increase) of the speed of movement of links;

Transformation of the type of movement (rotational to translational or vice versa) and change of direction of movement;

Separation of traffic flows from the engine to several executive bodies of the working machine.

Among the transmission mechanisms are widely used rotary motion transmission which can be divided into two main groups:

Gears based on the use of friction forces (friction, belt);

Gears based on the use of gearing (gear, worm, screw, chain).

Consider simple gearing gears, each of which contains two moving links (shafts with gears attached to them) that perform rotational motion, and one fixed link (shaft supports). On fig. 1.1 shows the appearance of gears and image options on block diagrams.

Cylindrical gears characterized parallel the arrangement of the axes of the gears a and b and differ in the location of the engagement: with external engagement and with internal engagement. AT conical gear axle transmission a and b intersect . AT worm worm axle transmission a and worm wheel b cross .

The main kinematic characteristic of transmission mechanisms is gear ratio U, which is the ratio of angular velocities w or rotational frequencies n input (master) a and output (slave) b links. In this case, the designation of the gear ratio has two indices indicating the direction of transmission of movement from the link a to the link b:

.

Rotation frequency n is related to the angular velocity w by the relation:

, rpm

Gears that reduce rotational speed are called gearboxes . In them, the gear ratio is realized due to the ratio of diameters d or number of teeth Z slave b and host a gears in mesh:

.

Thus, gearboxes reduce the rotation speed by a gear ratio due to the ratio of the number of teeth of the engaged wheels:

.

In this case, the drive gear in cylindrical and bevel gears, which has a smaller number of teeth, is called gear , and the driven wheel .

The torque in the gearboxes increases by a gear ratio of times, taking into account friction losses, estimated by the efficiency η :

.

Efficiency (h) is the ratio of useful power P n on the output link, spent on the implementation of useful work in the production or technological process, to the power on the input link, spent by the engine:

.

The efficiency takes into account the power loss to overcome the friction forces in kinematic pairs and is an important criterion for assessing the efficiency of energy use and the technical perfection of the mechanism.

When solving problems, you can use the following efficiency values ​​for various gears: cylindrical - η = 0.97; conical - η = 0.96; worm - η = 0.95 (1 - U / 200), where U- gear ratio in the worm gear.

1.3. Multi-stage gears

If it is necessary to implement a gear ratio, the value of which exceeds the recommended limits for individual gears, use a sequential arrangement of gears (stages) in the gear mechanism.

In this case, the total gear ratio ( U total) and the overall efficiency (h total) of a multi-stage transmission mechanism is determined as the product of gear ratios and the efficiency of all its stages (gears):

,

where m- the number of steps in the mechanism.

Gear ratio of one or group of steps m- step mechanism characterizes the ability to change the rotational speed n and torque T when transferring motion between the master i and slave k links of the considered part of the mechanism:

.

Useful power on the output shaft of the mechanism ( P out, W) is calculated from the dependence:

,

where T out, Nm and n out, rpm - respectively, the torque and the frequency of rotation of the output shaft of the mechanism.

The required (calculated) engine power () is determined taking into account losses in the friction units of the mechanism:

According to the rated power and rotational speed, a standard electric motor is selected from the catalog, which has the nearest higher power value.

1.4. Examples of problem solving

Task 1. Carry out a structural, kinematic and force analysis shown in fig. 1.2 drive, containing an electric motor and a gearbox.

Parameters set:

– number of teeth , , , , , ;

- frequency of rotation of the motor shaft rpm;

– torque on the output shaft of the gearbox Nm.

Solution

Structural analysis. A three-stage transmission mechanism is formed by connecting three separate gears in series.

The first stage is a cylindrical gear with external gearing; pinion axles 1 and wheels 2 are parallel.

The second stage is a bevel gear; pinion axles 3 and wheels 4 intersect.

The third stage is a worm gear; worm axle 5 and worm wheel 6 cross.

The axes of the input I and output IV shafts are crossed.

Kinematic analysis.

- first stage: ;

- second stage: ;

- third stage: ;

– mechanism: .

We determine the frequency of rotation of each shaft of the mechanism, given that the gears are fixed on the shafts and have the same speeds with them:

RPM (according to the condition of the problem);

rpm;

rpm;

rpm

Force analysis. Determine the torque on each shaft:

Nm (according to the condition of the problem);

Nm.

The efficiency of the worm gear is determined by the dependence:

Nm;

Nm.

Thus, the frequency of rotation of the shafts decreases in steps in the gear ratio of times (rpm; rpm; rpm; rpm), and the torques increase (taking into account the efficiency) in the gear ratio of times (Nm; Nm; Nm; Nm).

We calculate the net power on the output shaft of the gearbox:

W = 2.5 kW.

Required (calculated) engine power:

kW,

According to the catalog, we select a standard electric motor 4A100S4 with a speed of rotation / min and a power of kW.

Task 2. Conduct a kinematic analysis of the drive (see Fig. 1.2 in task 1) using other input data.

Parameters set:

– number of teeth: , , , ;

- frequency of rotation of the motor shaft: rpm;

– frequency of rotation of the shaft III of the reducer: rpm.

Solution

Determine the gear ratios:

- first stage: ;

- third stage: ;

- the total gear ratio of the first and second stages:

;

- the gear ratio of the second stage is determined, given that :

;

- the whole mechanism: .

We determine the frequency of rotation of each shaft of the mechanism:

RPM (according to the condition of the problem);

rpm;

rpm (according to the condition of the problem);

rpm

Thus, the gearbox reduces the speed of the motor shaft by 120 times (from 3000 rpm to 25 rpm), changing it in steps: in the first stage 3 times (from 3000 rpm to 1000 rpm), in the second steps 2 times (from 1000 rpm to 500 rpm) and in the third stage 20 times (from 500 rpm to 25 rpm).

test questions

1. What is a drive, transmission mechanism, actuator? What are they for?

2. What functions can the transmission mechanism perform?

3. Name simple gears by gearing and draw their block diagrams. What is the mutual arrangement of the axes of the driving and driven links is typical for each of the gears?

4. What is the gear ratio? How does it characterize the transmission mechanism?

5. What is a reducer? What functions of the transmission mechanism can it perform? How is the required gear ratio implemented in gearboxes? Draw on the diagram: a cylindrical gearbox with a gear ratio; bevel gear with .

6. Make up all possible dependencies by which the gear ratio can be calculated.

7. What is the coefficient of performance (COP)? How does he characterize the transmission mechanism? What operating parameters are calculated taking into account efficiency?

8. What are multi-stage gears intended for? How to determine the overall gear ratio and overall efficiency?

9. Solve the problem. Carry out a structural, kinematic and force analysis shown in fig. 1.3 gearbox.

Parameters set:

– number of teeth , , , ;

– shaft rotation frequency

- torque

Define:

a) the number of steps in the mechanism;

b) the type of transmission in each stage;

c) gear ratio of each stage;

d) rotational speed of shafts I and II;

e) torque on shafts I, III, IV;

f) total gear ratio;

g) overall efficiency;

h) useful and consumed power;

i) the location of the axes of the input I and output IV shafts.

Answers: a) 3; b) 1-Ch, 2-K, 3-C; c) 15, 2, 4; d) 200 and 100; e) 10, 253, 983; e) 120; g) 0.82; h) 2.57 and 3.14; i) cross.

2. BASIC CONCEPTS OF STATICS

2.1. Force and moment of force.
Couple of forces and moment of a couple of forces

Statics is a branch of mechanics in which the conditions for the equilibrium of the links of a mechanism under the action of forces are studied.

Strength (F, H) is a measure of the mechanical interaction of solids. The force is represented as a vector, the action of which is characterized by the point of application (for example, point A), the direction along the line of action and the magnitude F(Fig. 2.1).

Rice. 2.1 Fig. 2.2

Power couple(Fig. 2.2) - a system of parallel forces (), equal in modulus ( F 1 = F 2) and directed in opposite directions ().

Moment of power( , Nm) relative to a point (for example, t. O) is the product of the numerical value of the force F on the shoulder h- the shortest distance from the point to the line of action of the force (see Fig. 2.1):

Moment of a pair of forces (concentrated moment) (m, Hm) is defined as the product of the value of one of the forces and the arm of the pair h- distance between the lines of action of forces (see Fig. 2.2):

.

Torque (T, Nm)- the moment of force, the action of which is accompanied by the rotation of the link (Fig. 2.4, a).

Bending moment (M,Nm)- the moment of force, the action of which is accompanied by a bending of the link (Fig. 2.4, b).

2.2. Connections and their reactions

Any structural element or link of a mechanism is a non-free body whose movements in space are limited by other bodies, called connections . The connection that prevents the movement of a non-free body acts on it by a force called bond reaction .

The direction of bond reactions is determined based on the following rules:

1. The bonding reaction is applied at the point of contact of the contacting surfaces and is directed in the direction opposite to the direction in which the movement is limited.

2. If the connection limits the movement in several directions simultaneously, then the direction of the reaction is unknown and it is represented as components directed along the axes of the selected coordinate system.

Consider the direction of reactions for the main types of bonds (Fig. 2.5).

Smooth surface contact(Fig. 2.5, a). The reaction is directed along the common normal to the contacting surfaces.

Contact of smooth surfaces with corner points and cusps(Fig. 2.5, b). The reaction is directed along the normal to a smooth surface.

Inextensible thread(Fig. 2.5, in). The reactions and are directed along the threads to the suspension points.

Articulated support(Fig. 2.5, G). The reaction is perpendicular to the supporting surface.

Hinged-fixed support(Fig. 2.5, d). The direction of the reaction is unknown. Represented as unknown components and .

Rigid termination(Fig. 2.5, e). In such a support, there can be three components of the reaction: , and the support moment .

2.3. Equilibrium conditions for a plane system of forces

A rigid body is in a state of equilibrium if it is stationary with respect to the reference frame under consideration.

For the equilibrium of a rigid body under the action of an arbitrary system of forces, it is necessary and sufficient that the main vector and the main moment of this system with respect to any point O bodies were zero:

Main vector system of forces is equal to the geometric sum of all the forces of the system:

Main point system of forces is equal to the sum of the moments of all forces relative to the selected reference center 0:

.

As a result, the equilibrium conditions have the form:

.

When solving practical problems, an analytical method for solving vector equations is used, according to which the projection of the sum of vectors on any axis is equal to the sum of the projections of the terms of the vectors on the same axis .

In this regard, the above equilibrium conditions for a plane system of forces can be written in the form of three independent equilibrium equations for a rigid body with respect to a rectangular coordinate system XY:

.

A rigid body is in equilibrium if the algebraic (taking into account the sign) sum of the projections of all forces on each of the coordinate axes is equal to zero and the algebraic sum of the moments of all forces about any point O of the XY plane is equal to zero.

To determine the magnitude and direction of the bond reaction, it is necessary to perform the following actions:

1) replace external connections with their reactions, depicting their possible direction on the force diagram;

2) from the equations of equilibrium of the system of forces, determine the magnitude of unknown reactions;

3) if, as a result of calculations, any reaction turns out to be negative, it is necessary to change its direction on the diagram to the opposite;

4) to carry out a control check of the correctness of determining the reactions both in magnitude and in direction, using additionally one of the equilibrium equations, for example, the equation of moments with respect to a previously not considered point in the plane.

When compiling equilibrium equations, it is convenient to use the following provisions:

- the projection of the force vector on the axis is equal to the product of the module (value) of the force and the cosine of the angle between the line of action of the force and the axis, taken with a plus sign if the directions of the vector and the axis coincide, or minus if they are opposite:

- the moment of force is taken with a plus sign if it acts in the clockwise direction, and with a minus sign if vice versa.

2.4. Example of problem solving

A task. On fig. 2.6 shows a beam on two hinged supports A and C, loaded with a flat system of external forces and moments:

H; H; Nm;

Dimensions of beam sections:

It is required to determine the magnitude and direction of the support reaction vectors and .

Solution

Let's depict on the power diagram the presumable direction of the reactions of the supports and - both vectors are directed upwards.

Let us determine the magnitude and direction of the reactions and , using the equilibrium equations for a flat system of forces.

Let's compose the equation of the moments of forces relative to the support FROM, considering the action of the moment in the clockwise direction as positive (with a plus sign):

Reaction = 400 N,pointing down.

Let's make the equation of projections of all forces on a vertical axis Y, considering the upward direction of the vector as positive (with a plus sign):

The minus sign indicates the wrong direction. We change the direction of the vector in the diagram to the opposite.

Reaction = 200 N,pointing down.

We check the correctness of the solution using the additional equation of the moments of forces with respect to any non-reference point, for example, the point AT:

The “zero” obtained as a result of the calculations indicates the correctness of the determination of the reactions both in magnitude and in direction.

test questions

1. Define strength. What is the effect of force?

2. How to determine the moment of force relative to a point?

3. Define a pair of forces. How to find the moment of a pair of forces? How is it indicated on the diagrams?

4. Define torque and bending moments.

5. What is called a bond, a bond reaction?

6. Formulate the rules for determining the direction of bond reactions.

7. What is called the main vector and the main moment of the system of forces? How are they defined?

8. Formulate the equilibrium conditions for a flat system of forces; write the equilibrium equations.

9. Solve the problem. On fig. 2.7 shows a beam on two hinged supports B and D, loaded with forces H, H and a concentrated moment Nm. Size m. Determine the magnitude and direction of the reactions of the supports and and check.

Answer: H, directed upwards; H, pointing down.

3. BASIC CONCEPTS
RESISTANCE OF MATERIALS

3.1. Strength, rigidity, stability

The performance of a structure depends on the strength, rigidity and stability of its constituent elements.

Strength- the ability of the structure and its elements to perceive the load without destruction.

Rigidity- the ability of a structure and its elements to resist deformation, that is, a change in the original shape and dimensions under the action of loads.

Sustainability- the ability of the structure and its elements to maintain the initial form of elastic equilibrium.

Most parts of mechanisms rely on strength, solving three main tasks:

Determination of rational sizes;

Definition of safe loads;

Selection of the most suitable materials.

In this case, the real design is replaced by a calculation scheme, and the calculation results are verified experimentally.

3.2. Section method. Internal Force Factors

Outside forces acting on structural elements are divided into active (loads) and reactive (bond reactions). They cause the appearance internal forces resistance. If the internal forces exceed the adhesion forces of individual particles of the material, this structural element will be destroyed. Therefore, to assess the strength of the object under study, it is necessary to know the internal forces and the law of their distribution over the object. To solve these problems, we use section method . Consider in equilibrium a structural element of arbitrary shape (Fig. 3.1), loaded by a system of external forces . In any section of this element, internal forces will act, which must be determined. To do this, we mentally cut the object under consideration with an arbitrarily chosen section into two parts: A and B.

External forces and internal forces in the section will act on each of these parts, balancing the action of the cut-off part:

; .

Consequently, the internal forces arising in the section under consideration are equal to the sum of the external forces acting on one of the cut-off parts.

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One of the tasks of the modern theory of mechanisms is the study and systematization of the vast heritage accumulated by practical engineering in the form of various mechanisms used in a wide variety of machines, devices and devices. An analysis of this material by types of mechanisms showed that all work on their systematization should be divided into several stages. The first stage - collections, including mechanisms used in various branches of engineering. The next stage is collections devoted to individual branches of mechanical engineering, for example, mechanisms of precision mechanics, mechanisms of metal-cutting machine tools, mechanisms of aircraft engines, etc.

When selecting mechanisms, the author mainly gave diagrams and descriptions of general-purpose mechanisms, or mechanisms used in various branches of engineering. But individual mechanisms of a targeted, sectoral direction were also included in the directory as being of interest not only for this narrow industry, but also for other branches of engineering. These mechanisms are separated into a separate subgroup - target device mechanisms. Kinematic pairs and movable connections are given by the author not in a schematic, but in a constructive representation, in order to facilitate the designer's process of designing a mechanism. The author used extensive material in Russian and foreign languages.

For the purpose of greater clarity and ease of use of this reference guide when depicting mechanisms, the conditional images of links and elements of kinematic pairs, which were not established by the relevant standards, were taken as the basis, and schematic symbols that are of a constructive nature, i.e., links and elements of kinematic pairs were depicted in the form of conditional rods, sliders, wings, etc., having only approximately the size ratios that they could have in their constructive design.

Further, in the process of processing the material, in most cases it was necessary to abandon the accurate representation of individual parts of mechanisms, as is customary in structural drawings, since this would require the introduction of a number of additional details into the drawing, which are of great structural importance, but obscure the main perception of that form of movement, which can be reproduced by this mechanism. This is especially true for parts of frames, bearings, racks, thrust rings, bushings, etc. Moreover, some of the conventions used in modern structural drawings in terms of sections, projections, shading, images of threads, dotted lines, etc., were not always taken into account, since strict adherence to them would damage the clarity of the reader's perception of the kinematics and structure of the mechanisms.

An example of the calculation of a spur gear
An example of the calculation of a spur gear. The choice of material, the calculation of allowable stresses, the calculation of contact and bending strength were carried out.

An example of solving the problem of beam bending
In the example, diagrams of transverse forces and bending moments are plotted, a dangerous section is found, and an I-beam is selected. In the problem, the construction of diagrams using differential dependencies is analyzed, a comparative analysis of various beam cross sections is carried out.

An example of solving the problem of shaft torsion
The task is to test the strength of a steel shaft for a given diameter, material and allowable stresses. During the solution, diagrams of torques, shear stresses and twist angles are built. Self weight of the shaft is not taken into account

An example of solving the problem of tension-compression of a rod
The task is to test the strength of a steel rod at given allowable stresses. During the solution, plots of longitudinal forces, normal stresses and displacements are built. Self weight of the bar is not taken into account

Application of the kinetic energy conservation theorem
An example of solving the problem of applying the theorem on the conservation of kinetic energy of a mechanical system

Determination of the speed and acceleration of a point according to the given equations of motion
An example of solving the problem of determining the speed and acceleration of a point according to the given equations of motion

Determination of velocities and accelerations of points of a rigid body during plane-parallel motion
An example of solving the problem of determining the velocities and accelerations of points of a rigid body during plane-parallel motion

Determination of Forces in Planar Truss Bars
An example of solving the problem of determining the forces in the bars of a flat truss by the Ritter method and the knot cutting method

Application of the torque change theorem
An example of solving the problem of applying the theorem on the change in angular momentum to determine the angular velocity of a body rotating around a fixed axis.

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Option 7

1.1.5 Functional classification of mechanisms. Give examples of each type (class) of mechanisms

A system of bodies designed to convert the movement of one or more bodies into the required movements of other bodies is called a mechanism. From the point of view of their functional purpose, machine mechanisms are divided into the following types:

1. Mechanisms of engines and converters.

2. Transmission mechanisms.

3. Executive mechanisms.

4. Mechanisms of management, control and regulation.

5. Mechanisms for supply, transportation, feeding and sorting of processed media and objects.

6. Mechanisms for automatic counting, weighing and packaging of finished products.

Engine mechanisms convert various types of energy into mechanical work. The mechanisms of converters (generators) convert mechanical work into other types of energy. The mechanisms of engines include the mechanisms of internal combustion engines, steam engines, electric motors, turbines, etc. The mechanisms of converters include the mechanisms of pumps, compressors, hydraulic drives, etc.

Transmission mechanisms (drive) have as their task the transfer of movements from the engine to the technological machine or actuators. The task of the transmission mechanisms is to reduce the rotational speed of the motor shaft to the level of the rotational speed of the main shaft of the technological machine. For example, reducer.

Executive mechanisms are those mechanisms that directly affect the processed environment or object. Their task is to change the form, state, position and properties of the processed environment or object. Actuating mechanisms, for example, include the mechanisms of presses that deform the object being processed, the mechanisms of screens in energy grain cleaning machines that separate the medium consisting of grain and straw, the mechanisms of metalworking machine tools, etc.

Control, monitoring and regulation mechanisms are various mechanisms and devices for controlling the dimensions of processed objects, for example, mechanical probes following the cutter that processes a curved surface and signaling the deviation of the cutter from the specified processing program; regulators that respond to the deviation of the angular velocity of the main shaft of the machine and set the normal specified angular velocity of this shaft, etc. The same mechanisms include measuring mechanisms for controlling dimensions, pressure, liquid levels, etc.

Mechanisms for feeding, transporting, feeding and sorting processed media and objects include mechanisms for screw augers, scraper and bucket elevators for transporting and supplying bulk materials, mechanisms for loading hoppers for piece blanks, mechanisms for feeding bar material in heading machines, mechanisms for sorting finished products by size , weight and configuration, etc.

Mechanisms for automatic counting, weighing and packaging of finished products are used in machines that produce mass piece products. These mechanisms can also be actuators if they are included in special machines intended for these operations. For example, in tea bagging machines, the weighing and packaging mechanisms are the actuators.

Despite the difference in the functional purpose of the mechanisms of individual types, there is much in common in their structure, kinematics and dynamics.

For example, the piston engine mechanism, the crank press mechanism, and the mower knife drive mechanism are based on the same crank-slider mechanism. The planer cutter drive mechanism and the rotary pump mechanism are based on the same rocker mechanism. The mechanism of the gearbox that transmits the movement from the aircraft engine to its propeller, and the mechanism of the differential of the car are based on a gear mechanism.

1.2.3 Relations between angular velocities, powers and torques on gear shafts

Gear ratio from wheel 1 to wheel n

where ω1 is the angular velocity of shaft 1,

ωn is the angular velocity of the shaft n.

gear efficiency:

where P1 is the power on shaft 1 (input),

Pn - power on shaft n (output).

Torques:

Т1= Р1/ω1 – shaft 1,

Тn= Рn/ωn – shaft n.

Тn= Т1∙ U1n∙ η

1.3.5 Friction in kinematic pairs. Types and characteristics of friction: rolling friction, sliding friction. The concepts of the coefficients of sliding friction and rolling friction. Friction angle

When one body comes into contact with another, regardless of their physical state, a phenomenon called friction occurs, which is a complex set of mechanical, physical and chemical phenomena. Depending on the nature of the relative motion of bodies, sliding friction is distinguished - external friction with relative sliding of contacting bodies and rolling friction - external friction with relative rolling of contacting bodies. The force that prevents the relative motion of the contacting bodies is called the friction force.

The sliding friction force decreases if the contacting bodies are lubricated with special lubricants, and if the material is a liquid that completely separates the contact surfaces, then the friction is called liquid. In the absence of lubrication, dry friction takes place. If the lubricating fluid does not completely separate the rubbing surfaces, then the friction is called semi-liquid or semi-dry, depending on which of the two types of friction prevails.

Basic provisions:

1. The force of sliding friction is proportional to normal pressure.

2. Friction depends on the materials and the condition of the rubbing surfaces.

3. Friction is almost independent of the magnitude of the relative velocity of rubbing bodies.

4. Friction does not depend on the size of the contact surfaces of rubbing bodies.

5. Friction of rest is greater than friction of motion.

6. Friction increases with increasing pre-contact time of the contacting surfaces.

In sliding friction of unlubricated bodies, the coefficient of friction depends on normal pressure. In most technical calculations, the formula is used

where f is the average value of the friction coefficient, determined from experience and taken constant.

FT is the friction force.

Fn is normal pressure.

In sliding friction of lubricated bodies, the concept of the coefficient of fluid friction is introduced, which depends on the speed υ of the movement of lubricant layers relative to each other, on the load p and on the viscosity coefficient μ.

When rolling, it is necessary to overcome a certain moment MT, called the moment of rolling friction, the value of which is equal to:

where: k – rolling friction arm or rolling friction coefficient, has the dimension of length. It is determined empirically for various materials.

In sliding friction, the coefficient of friction and the angle of friction are related by the following relationship:

where φ is the angle of friction.

belt transmission speed shaft gear

2.1.1 Detachable connections. Types of connectors. Areas of application for various types of plug-in connections

Detachable connections are called, the disassembly of which occurs without violating the integrity of the component parts of the products. The most common types of detachable connections in mechanical engineering are: threaded, keyed, slotted, wedge, pin and profile.

Threaded is the connection of the component parts of the product using a part that has a thread. For example, bolted, hairpin, screw. Threaded connections are widely used in mechanical engineering and instrument making for fixed fastening of parts relative to each other. For example, fixing the electric motor and gearbox on the frame.

Keyed connections are detachable connections of component parts of products using keys. Keyed connections consist of a shaft, a key and a wheel hub. The key is a steel bar that is inserted into the grooves of the shaft and hub. It serves to transmit torque between the shaft and the hub of the wheel, pulley, sprocket. Keyed connections are widely used in all branches of engineering for light loads and the need for easy assembly and disassembly. For example, fastening a gear wheel on a gearbox shaft.

Spline connections are formed by protrusions - teeth on the shaft and corresponding depressions - splines in the hub. The working surfaces are the side faces of the teeth. The spline connection can be conditionally considered as a multi-key connection. Spline connections are widely used in mechanical engineering. They are used in the same place as keyed connections, but at higher loads.

Wedge connections are distinguished according to their purpose: power, in which wedges, called fastening, serve to firmly connect machine parts, and installation, in which wedges, respectively called installation, are designed to regulate and install machine parts in the desired position. Power wedge connections are used, for example, when fastening a rod with a bushing with a wedge. Adjusting wedges are used to adjust and install roll bearings of rolling mills, etc. They are widely used in mechanical engineering.

Pin connections are used for fastening parts (connecting a shaft with a sleeve) or for relative orientation of parts that are fastened to each other with screws or bolts (connecting a cover and a gearbox housing, connecting a rack and base, etc.).

Profile connection - connection of machine parts along the surface of their mutual contact, which has a smooth non-circular contour. The generatrix of the profile connection can be located both parallel to the axial line of the shaft, and obliquely to it. In the latter case, the connection can also transmit an axial load in addition to the torque.

Profile connections are used to transfer high torques in gearboxes of cars, tractors and machine tools instead of splined and keyed connections. Such connections are also used to transmit torque to the cutting tool (shell cutters, drills, countersinks, reamers).

Profile connections are reliable, but not technologically advanced, so their use is limited.

2.2.1 Belt drives. General information, principle of operation and classification. Technical characteristics and scope of belt drives

The belt drive consists of two pulleys mounted on shafts and a belt covering the pulleys. The load is transferred by frictional forces that arise between the pulleys and the belt due to the tension of the latter.

Belt drives are classified according to the following criteria.

1. According to the shape of the belt section:

flat belt;

V-belt;

Round belt;

With toothed belts;

With poly V-belts.

2. According to the mutual arrangement of the axes of the shafts:

With parallel axes;

With intersecting axes - angular;

With crossed axles.

3. In the direction of rotation of the pulley:

With the same direction (open and semi-open);

With opposite directions (cross).

4. According to the method of creating belt tension:

simple;

With tension roller;

With tension device.

5. According to the design of the pulleys:

With single row pulleys;

With stepped pulleys.

Belt drives are used in cases where, according to the design conditions, the shafts are located at considerable distances. The power of modern transmissions does not exceed 50 kW. In combination with a gear drive, a belt drive is usually installed on a high-speed stage, as a less loaded one. In modern mechanical engineering, V-belts are most widely used. New design flat belts are gaining ground in high speed transmissions. Round belts are used only for low power: in appliances, household appliances.

Belt drives are used to drive units from electric motors of small and medium power; for the drive from low-power internal combustion engines. V-belt drives are the most widely used in mechanical engineering (in machine tools, motor vehicles, etc.). These transmissions are widely used for small center distances and vertical axes of the pulleys, as well as for the transmission of rotation by several pulleys. If it is necessary to provide a belt transmission with a constant gear ratio and good traction, it is recommended to install toothed belts.

The main criteria for the performance of belt drives are: tractive capacity, determined by the friction force between the belt and the pulley, belt durability, which, under normal operating conditions, is limited to the destruction of the belt from fatigue.

The main characteristics of belt drives: efficiency, belt slip, rotation speeds, torques, power on the driving and driven pulleys.

2.3.9 Describe the designs of the most common types of blind and compensating couplings. Specify the areas of their application, advantages and disadvantages

Deaf couplings form a rigid and fixed connection of the shafts. They do not compensate for manufacturing and installation errors, they require precise alignment of the shafts.

Sleeve coupling - the simplest representative of deaf couplings. The fastening of the bushing with the shafts is carried out using pins, keys or splines. Sleeve couplings are used in light machines with shaft diameters up to 60 ... 70 mm. They are simple in design and small in size. The strength of the coupling is determined by the strength of the pin, key or spline connection, as well as the strength of the bushing.

The flange coupling consists of two coupling halves connected by bolts, which are installed with or without clearance. In the first case, the torque is transmitted by friction forces arising in the junction of the coupling halves from tightening the bolts, in the second case, directly by the bolts working on shear and crushing. Bolts supplied without clearance perform the function of shaft alignment. In another case, a special centering protrusion serves for this. Flange couplings are widely used in mechanical engineering. They are used to connect shafts with a diameter of up to 200 mm or more. The advantage of such couplings is the simplicity of design and relatively small dimensions.

To reduce the requirements for the accuracy of the location of the shafts and reduce harmful loads on the shafts and supports, compensating couplings are used. Compensation is achieved: due to the mobility of almost rigid parts - compensating rigid couplings; due to the deformation of elastic parts - elastic couplings. The most widespread of the groups of compensating rigid couplings are cam-disk and gear. Cross-hinged couplings are also widely used. They are used to connect shafts with large angular misalignment.

The cam-disc clutch consists of two coupling halves and an intermediate disc. At the inner end of each coupling half, one diametrically located groove is formed. On both ends of the disk, one protrusion is made, which are located along mutually perpendicular diameters. In the assembled clutch, the protrusions of the disc are located in the grooves of the coupling halves. Thus, the disc connects the coupling halves. The perpendicular position of the slots allows the coupling to compensate for eccentricity and misalignment of the shafts. In this case, the protrusions slide in the grooves, and the center of the disk describes a circle. These couplings are recommended mainly for eccentricity compensation.

The gear coupling consists of two half-couplings with external teeth and a detachable cage with two rows of internal teeth. The coupling compensates for all types of shaft misalignment. To this end, end gaps and increased side gaps in engagement are performed, and the toothed rims of the coupling halves are processed along spheres with radii, the centers of which are located on the axes of the shafts. Gear couplings are compact and have good compensating properties. They are used to transmit high torques.

Elastic couplings consist of two coupling halves connected by an elastic element. The elastic connection of the coupling halves allows: to compensate for misalignment of the shafts; change the stiffness of the system in order to eliminate resonant oscillations under periodically changing loads, reduce shock overloads. According to the material of the elastic elements, these couplings are divided into two groups: with metallic and non-metallic elastic elements.

The coupling with coil springs consists of a rim with a rib and a hub with discs. The edge of the rim is placed between the disks so that relative rotation of these parts is possible. The rib and discs have the same shaped cutouts, in which springs with limiters are placed. From the ends, the coupling is closed with disks, which are attached to the hub or rim to protect the spring and limiters from falling out and becoming dirty. It is advisable to use such couplings as elastic links in the system of connecting shafts with gear wheels or chain sprockets, as well as for connecting shafts.

Cog-spring clutch or clutch with serpentine springs. It consists of two coupling halves with teeth of a special profile, between which a serpentine spring is placed. The cover holds the spring in position, protects the clutch from dust and serves as a reservoir for lubricant. The main area of ​​application of these couplings is heavy engineering (rolling mills, turbines, reciprocating engines).

Couplings with rubber elastic elements are simpler and cheaper than with steel ones. Advantages of rubber elements: high elasticity, high damping capacity. Disadvantages: less durability, less strength resulting in large dimensions. Couplings with rubber elastic elements are widely used in all areas of mechanical engineering for the transmission of small and medium torques.

Coupling with a rubber star consists of two coupling halves with end projections and a rubber star, the teeth of which are located between the projections. Widely used for connecting high-speed shafts. The coupling is compact and reliable in operation. Disadvantages - when disassembling and assembling, axial displacement of the shafts is necessary.

The coupling is elastic sleeve-finger. Due to the ease of manufacture and replacement of rubber elements, this coupling has become widespread, especially in drives from electric motors with low and medium torques. The elastic elements here are corrugated rubber bushings or trapezoidal rings. Couplings have low flexibility and are mainly used to compensate for misalignment of shafts within a small range.

Coupling with an elastic shell. The elastic element of the coupling, resembling a car tire, works in torsion. This gives the coupling a high energy intensity, high elastic and compensating properties.

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Mechanism - a system of rigid bodies designed to transfer and convert the given movement of one or more bodies into the required movements of other rigid bodies.

A machine is a technical device that converts energy, materials and information in order to facilitate the physical and mental labor of a person, improve its quality and productivity.

A machine unit is a technical system consisting of one or more machines connected in series or in parallel and designed to perform any required functions. The main types of mechanisms:

Lever, gear, cam, Maltese, planetary, manipulators

There are the following types of machines:

1. Energy machines - converting energy of one type into energy of another type. These machines come in two varieties:

Engines which convert any form of energy into mechanical Generators which convert mechanical energy into another form of energy.

2. Working machines - machines that use mechanical energy to perform work on the movement and transformation of materials. These machines also have two varieties:

Transport vehicles, which use mechanical energy to change the position of an object (its coordinates).

Technological machines, which use mechanical energy to transform the shape, properties, dimensions and state of an object.

3. Information machines designed to process and transform information. They are divided into: Math machines, which transform the input information into a mathematical model of the object under study.

control machines, which convert the input information (program) into control signals for a working or power machine.

4. Cybernetic machines machines with elements of artificial intelligence).

1. The structure of mechanisms - types of the simplest typical mechanisms and their elements, kinematic pairs and their classification.

Movement structure- the totality of its elements and the relationships between them.

The main types of mechanisms.

lever

jagged

cam

Maltese

planetary

manipulators

Link- a rigid body or a system of rigidly connected bodies that are part of the mechanism.

Kinematic chain- a system of links that form kinematic pairs with each other.

Kinematic couple- a movable connection of two links, allowing their certain relative movement.

Kinematic pairs (KP) are classified according to the following criteria:

according to the type of contact point (connection point) of the link surfaces:

the lower ones, in which the contact of the links is carried out along a plane or surface (sliding pairs);

higher, in which the contact of the links is carried out along lines or points (pairs that allow sliding with rolling).

according to the relative motion of the links forming a pair:

• rotational;

  progressive;

  screw;

• spherical.

according to the method of closing (ensuring the contact of the links of the pair):

• power (due to the action of weight forces or the force of elasticity of the spring);

  geometric (due to the design of the working surfaces of the pair).

according to the number of connection conditions imposed on the relative movement of the links (the number of connection conditions determines the class of the kinematic pair);

according to the number of mobility (N) in the relative motion of the links.