Clutch VAZ-2121

Contents

Brief technical characteristics of VAZ engine

1. Assignments and clutch requirements. Regulatory documents

2. Analysis of essential structures

3. Proposed design

3.1 Type of clutch and drive

3.2 Type and number of pressure springs

3.3 Number of slave disks

3.4 Clutch margin factor

4. Clutch calculation

4.1 Selection of design main parameters

4.2 Verification calculation

4.3 Calculation of the main elements of the clutch

4.3.1. Calculation of the pressure disc

4.3.2. Move the pressure disc when clutch is activated

4.3.3. Calculation of pressure spring

4.3.4. Calculation of clutch drive

4.4 Calculation of clutch parts for strength

5. Maintenance of the designed structure

Bibliographic list

Brief technical characteristics of VAZ-2121 engine

1. Engine type - carburetor;

2. The number of cylinders is 4;

3. Cylinder diameter - 76mm;

4. Piston stroke - 80mm;

5. Engine displacement - 1.5 l;

6. Compression ratio - 8.5;

7. Effective rated power - 52.3kW;

8. Maximum speed of crankshaft -;

9. Maximum torque -;

10. The mass of a car with a full load is 1610 kg;

11. Gear ratios of the lower stages of the main gear and transmission gear-;

12. The wheel radius is 0.3456m.

1. Assignments and clutch requirements. Regulatory documents

The clutch in the transmission of the car is necessary for the short-term disconnection of the transmission and the engine and their smooth connection during gearshift, as well as to protect the transmission from dynamic overloads during uneven engine operation.

The following requirements apply to the clutches:

1) reliable transmission of torque from the engine to the transmission;

2) smoothness and completeness of actuation;

3) cleanliness of shutdown;

4) minimum moment of inertia of driven parts (elements);

5) good removal of heat from friction surfaces;

6) protection of the transmission from dynamic G-loads;

7) maintaining the pressure force within the specified limits during operation;

8) minimum cost of physical effort for management;

9) good balance.

In addition, the following general requirements apply to the clutch, as well as to all mechanisms of the car:

1) ensuring minimum dimensions and mass;

2) simplicity of device and maintenance;

3) processability;

4) repairability;

5) low noise level.

The design scheme and the main parameters of adhesion are selected on the basis of regulatory documents (GOST 1223876 and GOST 178674), analysis of the best samples of domestic and foreign structures and operating conditions of the designed car.

2. Analysis of essential structures

Currently, many types of clutches are used in practice, differing in both design and purpose.

The adhesion is classified as follows:

I by nature of work:

1) permanently open;

2) constantly closed.

II by the nature of the link between the master and slave elements:

1) hydraulic (hydraulic coupling);

2) electromagnetic (powder);

3) friction:

a) in the form of friction elements:

- special (cone, drum, etc.);

- disk;

- with dry disks (one-, two-, multi-disc);

- with discs in oil.

b) according to the method of pressure force generation:

- centrifugal;

- semi-centerpiece;

- electromagnetic;

- spring;

- with peripheral springs;

- with central spring (cylindrical, conical, diaphragm);

III by drive type:

1) with mechanical;

2) with hydraulic;

3) with combined:

- pneumatic mechanical;

- pneumohydraulic;

- electromechanical;

- electric vacuum.

IV by control method:

1) automatic;

2) non-automatic (foot, manual):

- with amplifier;

- without amplifier.

On most cars, permanently closed clutches are installed, that is, constantly switched on and off by the driver when touching, shifting gears and braking. Permanently open clutches, which are turned off at its increase, are used relatively rarely, mainly in automatic control.

Single-disc dry friction clutches are installed on light and medium duty cars and trucks. Two-disc clutches are used for off-road trucks (URAL), heavy-duty trucks (KAMAZ, MAZ, KrAZ). Multi-disc clutches are used extremely rarely and only on heavy vehicles due to their complexity.

Electromagnetic powder clutches and clutches with electromagnetic pressure generation in the 4050s received some use due to their good adaptability to control automation. However, they are not widely used, as well as automatic clutches of other types, which is mainly due to their complexity. In our country, electromagnetic powder clutches were installed on ZAZ cars for the disabled.

The clutch drive of passenger cars is mainly hydraulic, often with a servo spring, which facilitates control. Recently, mechanical cable drive has been used on cars - quite reliable, simple and less expensive. For light and medium duty trucks, mechanical and hydraulic drives are also used, sometimes with a servo spring. On heavy-duty trucks, a combined drive is installed: mechanical with pneumatic booster (MAZ) and hydraulic with pneumatic booster (KAMAZ).

3. Proposed design

The choice of design scheme includes decisions on the following issues: the type of clutch and drive, the number of driven disks, the type and number of pressure springs, the dimensions of friction linings, the value of the clutch margin factor.

3.1 Type of clutch and drive

In modern cars, dry friction single- and two-disc clutches with non-automatic mechanical drive were most widespread. Other types of clutch are mainly used on special cars. Mechanical drive is used when placing the clutch pedal near the clutch. The hydraulic drive has a higher efficiency, providing better tightness of the cab (body), allows you to use an overhead pedal and is simpler in design with a significant removal of the pedal from the clutch and the overturning cockpit.

On the basis of the above, as well as a sufficiently high efficiency of compliance with all clutch requirements, we choose a dry friction single-disc clutch with a mechanical drive for the designed car.

3.2 Type and number of pressure springs

Diaphragm (poppet) springs are widely used in the clutches of cars and trucks made on their chassis. Typically, a spring is used, although two-spring designs (trucks) are known. On trucks and cars with a classic layout, clutches with the peripheral arrangement of coil coiled springs, for example, the grip of a GAZ53 car, are usually used.

On the basis of the above, for the design engagement, 12 coil coiled springs are selected with their peripheral arrangement.

3.3 Number of slave disks

Domestic cars and trucks with a carrying capacity of up to 5 tons have single-disc clutches. Cars with a lifting capacity of more than 7t (MAZ500A, KAMAZ, ZIL133G), as well as off-road vehicles (URAL375, MAZ-509) have a two-disc clutch. Therefore, for a designed car, a single-disc clutch structure is selected.

3.4 Clutch margin factor

The value of the coefficient is chosen depending on the type of car: for cars 1.3-1.75; single cargo 1.6-2.2.; cargo working with trailer 2.0-2.5; off-road vehicles working with a trailer 2.5-3.0. Large values ​ ​ are taken for clutches operating in difficult conditions (urban-type buses, motorized trucks, off-road vehicles, cars with low specific power).

For the designed clutch we select

4. Clutch calculation

4.1 Selection of design main parameters

The outer and inner diameters of the friction straps are selected according to GOST 1223876 and 178666 depending on the maximum torque of the engine. It is recommended that you first take the smallest value for the outer diameter and the largest value for the inner diameter.

For the designed clutch we preselect:

outer diameter D = 225mm;

internal diameter d = 150 mm.

Correctness of preliminary selection of design basic parameters of clutch is determined by check calculation.

5. Maintenance of the designed structure

Maintenance of the designed clutch consists in adjustment of its drive, timely tightening of bolt connections, lubrication of the fork shaft, disengagement of the clutch and pedal shaft, cleaning of parts from dirt.

Tighten the attachment bolts of the clutch case to the cylinder block carefully. Torque of bolts tightening must be. The bolts need to be tightened evenly cross-crosswise. The clutch shall not slip when ON and the pedal shall be completely OFF when pressed. The free travel of the pedal should be 35... 50 mm, full travel - at least 180 mm.

As the friction straps wear, the free travel of the pedal decreases, as a result of which the clutch can slip. This results in rapid wear of the driven disc and wear of the clutch release bearing. In case of excessive free travel (over 50 mm), when the pedal is pressed, the clutch is not completely disconnected. This leads to increased wear on the driven disk and makes it difficult to change gears (wear on synchronizers in the gearbox increases).

Free travel of pedal is controlled by spherical nut of drive. To reduce free travel, the nut must be screwed onto the rod, then tighten the lock nut.

At TO-2 of the car, lubricate the lubricants until the old lubricant appears in the gaps.