Laboratory work - Clutches. Device for protecting transmissions from overloads Requirements for clutch drives
1. Pusher. 2. Protective case. 3. The working cylinder of the drive. 4. Valve. 5. Hose. 6. Clutch housing. 7. Flywheel. 8. External pressure spring. 9. Internal pressure spring. 10. Heat insulating washer. 11. Hub. 12. Damper spring. 13. Friction washer. 14. Heat insulating washer. 15. Damper spring. 16. Crankshaft. 17. Clutch cover. 18. Friction lining. 19. Pressure plate. 20. Disk. 21. Finger. 22. Support fork. 23. Clutch release lever. 24. Conical spring. 25. Spherical nut. 26. Clutch release bearing. 27. Bearing sleeve. 28. Foam ring. 29. Intake window. 30. The primary shaft of the gearbox. 31. Bearing cap input shaft. 32. Ball joint. 33. Clutch release fork.
The car is equipped with a dry single-disk, permanently closed clutch with a spring hub and a torsional vibration damper. The outer diameter of the driven disk is 225 mm. The clutch of the car provides:
- transmission of torque from the engine to the cardan shaft and drive wheels of the vehicle;
- disconnection for a short time of the engine from the power transmission of the car;
- smooth movement of the car when starting off and when shifting gears;
- protection of transmission and engine parts from breakdowns due to slipping during overloads.
The device and operation of the clutch. The driving parts of the clutch are the flywheel and clutch disc assembly (consists of casing, pressure plate, clutch release levers and pressure springs). On the side surfaces of the casing 17, attached to the flywheel with six bolts, there are three evenly spaced rectangular windows, into which three machined protrusions of the pressure plate 19 are inserted with a minimum clearance. Such a connection ensures the transmission of torque through the casing to the pressure plate; centering the pressure plate relative to the casing and the possibility of axial movement of the pressure plate when the clutch is released. Nine pairs of pressure springs 8 and 9 are located between the casing and the pressure plate. To prevent jamming, the springs have a different winding direction. The pressing force created by the outer spring is 24.5-27.5 kgf, the inner one is 30.5-33.5 kgf. To protect the pressure springs from the harmful effects of heat generated during slipping of the clutch, heat-insulating washers 10 made of pressed asbestos cardboard are installed between the pressure plate and the springs. Three steel levers 23 for disengaging the clutch are located in the slots of the guides of the pressure plate and are connected with the pressure plate and support forks with the help of axles and needle bearings. Spherical nuts 25 are screwed onto the threaded shanks of the support forks, which are pressed against the spherical surfaces on the casing by conical springs 24. Such an articulated connection of the support forks with the casing provides the possibility of some rocking of the support forks, necessary to compensate for changes in the radial distance between the axes of the levers when the pressure plate is retracted. Spherical nuts also serve to install the ends of the release levers in the same plane. Otherwise, the pressure plate is distorted when the clutch is released, incomplete disengagement and uneven engagement of the clutch. To prevent loosening, the spherical nuts are punched into the slots on the shanks of the support forks.
The clutch master plate assembly is statically balanced by drilling metal out of the pressure plate bosses. Permissible imbalance 25 gsm. Drilling depth no more than 25 mm, including the drill cone.
The driven clutch disc transmits rotation from the engine to the input shaft 30 of the gearbox due to friction forces on the surfaces of the friction linings 18, clamped by the force of the pressure springs between the surfaces of the flywheel and the pressure plate. Friction linings 18 are made of asbestos woven tape with copper or brass wire woven into it. Each of them has 24 grooves, which contribute to better heat dissipation and cleaning of rubbing surfaces from wear products. The pads, independently of one another, are riveted to eight wavy spring plates, which, in turn, are riveted to a steel disk 20. As the pressure on the driven disk increases, the wavy plates gradually straighten out, thereby ensuring smoother engagement of the clutch, and when fully engaged, they practically take flat shape. The second disk is riveted to disk 20 with the help of three fingers 21. Both disks have six windows located opposite each other.
Between the disks there is a hub flange 11 of the driven disk, which has six windows and three U-shaped cutouts through which the fingers pass. Cylindrical damper springs 12 are located simultaneously in the windows of the hub and both disks and transmit torque from the friction linings to the hub, compressing depending on the amount of transmitted torque. The rotation of the friction linings relative to the hub is limited by the stop of the fingers 21 against the edges of the U-shaped cutouts of the hub flange. The damper springs contribute to a smooth engagement of the clutch, and also reduce the natural frequency of the power train, eliminating the possibility of resonant oscillations. Torque changes caused by torsional vibrations of the engine crankshaft cause the disks 20 to rotate relative to the hub in one direction or another, compressing and expanding the damper springs. To reduce the transmission of these vibrations to the transmission, a damper is used, consisting of a steel friction washer 13 sitting on the flats of the hub 11 and pressed against the disk 20 with a force of 60 kg with a spring 15 resting against the flanging of the stop fixed in the groove on the hub. Vibrations are damped due to friction between these parts when the disk rotates relative to the hub.
To disassemble the absorber, it is necessary to press on the stop, slightly compressing the spring, turn the stop by 90 ° and remove it from the hub. The driven disk assembly is statically balanced by installing balancing trucks in the openings of the disk 20. Permissible imbalance is not more than 10 gsm. The beating of the surfaces of fractional overlays relative to the slotted hole of the hub is not more than 1 mm.
The clutch is disengaged by pressing the ends of the bearing release levers 26 mounted on the movable clutch 27. To protect the working surface of the shank of the input shaft bearing cap 31 from dirt, two foam rubber rings 28 are put on it. When assembling, a special lubricant that does not require replacement during the entire period of operation.
Clutch housing 6 is cast from aluminum alloy. It attaches to the engine block with four studs and two bolts and is centered on two dowel pins. To ensure the necessary alignment of the gearbox with the crankshaft of the engine, the rear end and the mounting hole of the clutch housing are machined as an assembly with the engine block, ensuring the beating of the rear end and the mounting hole relative to the axis of the crankshaft is not more than 0.08 mm. At the bottom of the clutch housing there is a hatch closed by the stamped lower part of the clutch housing. Through this hatch, the clutch is dismantled.
Cooling of parts that are very hot during operation and removal of wear products are carried out by sucking in air through the intake window 29 and ejecting it through the outlet window on the side of the clutch housing.
During operation, the clutch does not require any adjustments. The adjustment of the position of the release levers in one plane is carried out only at the factory or when the clutch is repaired. In this case, the drive disk, assembled with the casing, is screwed to the flywheel by installing washers 8 mm thick between the pressure disk and the flywheel in three places. By rotating the adjusting spherical nuts of the support forks, it is achieved that the size from the end of the flywheel to the end of each lever is 48.5 ± 0.25 mm. When assembling the clutch, pressure springs of the same group are installed (they differ from each other in terms of a load of 1.5 kgf). During operation, it is necessary to replace worn friction linings of the clutch disc in a timely manner, and therefore after 80-100 thousand km of the car run under normal conditions and after 40-50 thousand km of the car run in difficult conditions (for example, a taxi car) check the distance between the flywheel and the pressure plate with the clutch engaged. If this distance is less than 6 mm, then it is necessary to remove the driven disk for inspection and replacement of the friction linings. To carry out measurements, it is necessary to install the car in a pit and remove the lower stamped part of the clutch housing.
I. Introduction page 2
II. Main part. page 3
2.1 General information page 3
2.2 Construction of the clutch of the tractor BT-150 page 6
III. Main clutch failures page 11
IV. Maintenance and repair of the clutch of the tractor VT-150 page 13
V. Clutch Repair Safety Page 17
VI. Conclusion page 18
VII. Used Literature page 19
I. INTRODUCTION
The clutch allows you to briefly disconnect the engine and transmission when shifting gears and smoothly connect them when starting the tractor. With a sharp increase in resistance to movement, the clutch can disconnect the transmission from the engine.
In contrast to the clutches used in individual assembly units of tractors, the clutches in question are called the main clutches. Places the main clutch between the engine and gearbox
The clutch must meet the following requirements: transmit without slipping the maximum torque for which this engine is designed; ensure clean shutdown - quickly and completely disconnect the driving and driven parts and soft start - gradually load the transmission assembly units; provide ease of maintenance and adjustments, ease of control and trouble-free operation.
Therefore, friction clutches are used in modern tractors. The operation of such a clutch is based on the use of friction forces. Disks made of a material with a high coefficient of friction are used as rubbing surfaces. Depending on the transmitted torque, it is necessary to use a different number of friction elements, so the clutch can be single-disk, double-disk and multi-disk
My thesis contains information on the device, maintenance and repair of the friction dry, double-disk, permanently closed clutch of the VT-150 tractor.
The purpose of my work is to study the device in the most detail and technological process repair of the clutch of the tractor VT-150.
Tasks:
1. Determine the purpose and type of clutch of the tractor VT-150
2. Consider the clutch device of the tractor BT-150
3. Indicate the main malfunctions of the clutch and how to eliminate them.
4. Designate safety requirements when performing clutch repair work
II. Main part
2.1 General information.
The clutch serves to transmit torque, quickly disconnect and smoothly connect the engine to the transmission, necessary for gear shifting and smooth starting of the tractor or vehicle, as well as to protect the engine and transmission parts from overloads.
The ability of the clutch to transmit the maximum torque of the engine is characterized by a safety factor:
Where Mt is the moment of friction of the clutch;
Memax is the maximum torque of the engine.
The safety factor is chosen in the range of 1.5 ... 4, depending on the type and purpose of the tractor or vehicle.
Basic requirements for clutches: complete disengagement and the possibility of their smooth inclusion; a small moment of inertia of the driven parts and the presence of a brake device necessary for bumpless gear shifting in stepped transmissions of tractors; simplicity and reliability in operation, ease of management.
Clutches can be: with Force closing due to friction forces (mechanical friction) or Magnetic attraction (electromagnetic) and with Dynamic Closure under the action of inertia forces (hydraulic) or Inductive interaction of electromagnetic fields (electric).
On tractors and automobiles, as a rule, mechanical friction disc clutches are used with a force lock due to friction forces.
Consider the scheme and principle of operation of a simple friction clutch. (See Fig. 1)
The clutch has three main parts: driving, driven and control mechanism. Figure 1 shows a simplified diagram of a clutch. The leading part is the flywheel 1 of the engine, the casing 5 and the pressure plate 4; driven - disk 2 with friction linings 3 and shaft 8, interconnected by a splined hub.
Rice. 1 - Scheme of the friction clutch:
1 - flywheel; 2 - driven disk; 3 - friction linings; 4 - pressure plate; 5 - clutch cover; 6 - spring; 7 - pedal; 8 - shaft.
The principle of operation of such a clutch is as follows.
Under the action of springs 6, the driven disk is clamped between the surfaces of the flywheel and the pressure disk. Due to friction, they rotate as one and transmit torque from the engine crankshaft to the transmission shaft 8.
To turn off the clutch, press the pedal 7. In this case, the pressure plate, overcoming the forces of the springs, moves to the right and releases the driven disc. The transmission of rotation to the driven shaft 8. stops.
Classification of clutches
Mechanical friction clutches are classified according to the following criteria:
1) according to the type of friction - Dry and Wet.
Dry clutches, as a rule, have driven discs with friction linings and operate without lubricating fluid, while wet couplings with steel driven discs operate in liquid (oil);
2) by the number of slave disks - Single, Double and Multi-disk.
For example, the clutch of the starting motor gearbox, multi-plate, operates in oil, and the clutch shown in Figure 1 is single-plate, dry;
3) according to the type of pressure device - Permanently closed, if the pressure mechanism is spring-loaded, as, for example, in the clutch in Figure 1, and Non-permanently closed, if the pressure mechanism is of a lever type;
4) according to the principle of control - Without an amplifier and with an amplifier: lever-spring (servo mechanisms), hydraulic, pneumatic,
5) transmission torque transmission - single and double flow.
To transmit torque not to one, but to two consumers, for example, a gearbox and a power take-off mechanism, and independently control them, two-flow clutches are used;
6) by appointment - Main and Additional.
The main clutch is called the clutch, which transmits torque through the transmission to the drive wheels or sprockets. It is installed between the engine and gearbox. Clutches placed in the torque booster, gearbox, power take-off gearbox and other devices are called additional (or special).
The friction double-disk permanently closed clutch consists of driven disks 12 and 15 (See Fig. 2) and two drive disks: intermediate 14 and pressure 11. The drive disks are connected to the casing 10 by fingers 13. If the clutch pedal is in a free state, then driving and driven disks under the action of springs 9 will be pressed against the flywheel, i.e. the clutch is engaged. When you press the pedal, the offset 5 moves forward, presses the release levers 4, which through the bolts 3 move the pressure plate 11 back. The discs disengage and the clutch disengages (as shown in Figure 2).
The intermediate drive disk 14 is moved away from the front driven disk 15 with the help of special springs 1, and the movement of this disk is limited by adjusting bolts 2, which eliminates the possibility of jamming of the disks.
Fig. 2 diagram of a double-disc permanently closed clutch:
1 - squeezing spring of the intermediate disk; 2 - adjusting bolt; 3 - squeezing bolt; 4 - release lever; 5 - layering; 6 - clutch shaft; 7 - shutdown plug; 8 - thrust; 9 - pressure spring; 10 - casing; 11 - pressure plate; 12 - rear driven disk; 13 - guide pin; 14 - intermediate disk; 15 - front driven disk; 16 - flywheel
Dual disc friction clutches have significant frictional torque and can therefore transfer high torque from the engine to the transmission. They are used on heavy-duty vehicles (Ural-5557, KamAZ-5320, KrAZ-221, etc.) and on tractors of traction classes 1.4 and higher (MTZ-100, MTZ-102, DT-75MV, T-150, T -150K, T-130M and our tractor VT-150)
2.2 VT-150 tractor clutch device
The VT-150 tractor is equipped with a D442V4 engine with a P-350-1 starting engine. The main clutch is friction dry, double-disk, permanently closed type with a mechanical shutdown drive having a servomechanism, designed
to transfer torque from the diesel engine to the transmission, and also serves to briefly disconnect the diesel engine from the transmission when the diesel engine is running, to ensure
bumpless gear shifting and smooth starting.
The clutch is mounted on the flywheel of the diesel engine and is closed with a cast-iron housing. The driven clutch discs have torsional vibration dampers of a spring-friction type (dampers).
The elastic element of the absorber is eight twisted cylindrical springs, evenly spaced around the circumference of the hub flange.
The clutch of the VT-150 tractor has the following device:
The leading parts of the clutch are flywheel 5 (Fig. 3), intermediate 2 and pressure 1 disks, casing 27. The protrusions of the intermediate and pressure disks enter four grooves of the flywheel, due to which the disks can move along the axis of the clutch, rotating together with the flywheel.
The driven parts of the clutch are two disks 6 with friction linings and a torsional vibration damper (dampers). These discs are clamped between the flywheel 5, the intermediate and pressure springs 29, which are centered in the cups 28 and 30 of the pressure disc and casing.
On both sides of the intermediate disc, four squeezing springs 8 are installed, which ensure uniform separation of the driven discs and the installation of the intermediate disc 2 in the middle position when the clutch is turned off.
The clutch disengagement mechanism consists of a release 16 and four squeezing levers 13, which are connected by short arms to the tides of the pressure plate, and a pressure ring 26 is attached to the long arms of the levers with brackets 14. The squeezing springs 9 are installed on the levers 13, excluding spontaneous swinging of the levers. The offset 16 consists of a housing, a ball bearing 23 with a stop 17 and a seal. The offset moves along the cylindrical ledge of the rear cup 19 of the housing 18 of the clutch. The trunnion pins are included in the throats of the fork 25, which is fixed on the roller 24. The roller rotates in the bearings of the clutch housing. On the right outer end of the roller 24, a rotary lever 8 is fixed (Fig. 4), connected by a rod 3 to the control pedal 1.
The clutch is equipped with a shoe-type brake that brakes the driven parts of the clutch when it is turned off, which ensures shock-free switching on of the modes. The brake consists of a block 22 (see Fig. 3) with a friction lining 21 riveted to it, which, when the clutch is turned off, is pressed against the shank of the driven shaft 20 of a larger diameter and creates a braking torque.
Rice. 3 - Clutch of tractor BT-150:
1 - pressure plate; 2 - intermediate disk; 3 - seal; 4 and 23 - bearings; 5 - flywheel; 6 - driven disk; 7 and 15 - oilers; 8 and 9 - release springs; 10 - fork; 11 - locking plate; 12 - adjusting nut; 13 - release lever; 14 - bracket; 16 - layering; 17 - emphasis; 18 - body; 19 - rear glass; 20 - driven shaft; 21 - friction lining; 22 - brake shoe; 24 - roller off; 25 - shutdown fork; 26 - pressure ring; 27 - casing; 28 and 30 - spring cups; 29 - pressure spring.
The long arm of the lever 2 through the adjustable rod 3 is connected to the rotary lever 8 of the clutch release shaft.
To turn off the clutch, press the pedal 1. In this case, the two-arm lever 2 rotates around the axis and through the rod 3 turns the lever 8 together with the roller. The fork 9 moves the offset 5 forward, the end (stop) 7 of which acts on the thrust (pressure) ring 6, turning the release levers around the fingers. The short arms of the levers take the pressure plate back, while the intermediate disc is set to the middle position under the action of the springs. The driven disks are released, and the transmission of rotation from the flywheel to the clutch shaft is stopped.
To facilitate disengagement of the clutch, its drive is equipped with a mechanical servo mechanism. Pedal 1 (see Fig. 4) is attached to the long arm of lever 2, which rotates on an axle. The axis is installed in the trunnions of the bracket 14 and fixed with a locking bolt. The bracket is attached to the gearbox housing 15. The short arm of the lever 2 is connected to the earring 13. One end of the spring 12 of the servomechanism is connected to the earring 13, and the other end to the rod 11 pivotally connected to the bracket 10.
Rice. 4 - VT-150 tractor clutch disengagement drive:
1 - pedal; 2 - two-arm lever; 3 - thrust; 4 - rear glass; 5 - layering; 6 - pressure ring; 7 - emphasis; 8 - rotary lever; 9 - shutdown plug; 10 - thrust bracket; 11 - thrust of the servomechanism; 12 - servomechanism spring; 13 - earring; 14 - bracket; 15 - gearbox housing.
During the clutch disengagement, together with the disengagement roller, the brake lever also rotates, moving up the block, which further brakes the clutch shaft under the force of the brake spring.
When you press the pedal at the initial moment, the spring 12 of the servomechanism is stretched. After the axis of symmetry of the short arm of the lever 2 passes through the line of the axis of symmetry of the spring 12, the spring begins to compress and helps to turn the two-arm lever, reducing the force required to disengage the clutch.
When the pedal is released under the action of the force of twenty pressure springs of the clutch, the spring 12 of the servo mechanism is stretched until the axis of symmetry of the short arm of the lever 2 crosses the line of the axis of symmetry of the spring. After that, the spring is compressed and moves the two-arm lever all the way to the cab floor.
Shutdown mechanism
The clutch release mechanism of the VT-150 tractor can be hydraulically driven.
Hydraulic drive. The main elements are reservoir 1 (see Fig. 5) with brake fluid, working and master cylinders, rods, hoses and a pedal. Clutch pedal 7, master cylinder 3 with levers and rods make up a separate unit bolted to the vehicle cab. The pedal is held in its original (rearmost) position by a spring 6. The main cylinder 3 is connected by a supply hose 2 to the tank, and by a flexible hose 8 to the working cylinder 17.
Rice. 5 - Hydraulic clutch of the tractor BT-150:
1 - tank; 2 and 8 - supply and connecting hoses; 3 - main cylinder; 4 - protective cap; 5 and 15 - pushers; 6 and 16 - springs; 7 - pedal; 9 - piston of the main cylinder; 10 - cuff; 11 - clutch release lever; 12 - clutch release bearing; 13 - fork; 14 - adjusting nut; 17 - working cylinder; 18 - piston; 19 - bypass valve cap; A and B - compensation and bypass holes
When you press the clutch pedal 7, the force from it is transmitted to the pusher 5 of the master cylinder. Under the action of the pusher, the piston 9 moves forward and displaces the liquid into the working cylinder. The piston 18 of the working cylinder through the pusher 15 acts on the outer end of the clutch release fork 13, turning it around the support. The inner end of the fork, through the bearing 12 and the release levers, retracts the pressure plate, disengaging the clutch.
When the clutch pedal is released, under the action of springs 6 and 16, the pistons of the cylinders return to their original position, and the liquid from the working cylinder is forced out by the piston into the main cylinder. The clutch and brake hydraulic reservoir is common, divided by partitions into three compartments and, for the convenience of monitoring the fluid level, is made of a translucent material.
To remove air from the hydraulic system, a valve closed with a rubber cap 19 is screwed into the working cylinder.
III. The main malfunctions of the clutch
The tractor driver of agricultural production must know the possible malfunctions of the clutch and how to eliminate them.
Faults can be divided into 2 groups:
- related to the violation of the adjustment, eliminated on the spot (such as slipping of the engaged clutch, violations of the smoothness of inclusion, incomplete disengagement of the clutch);
- associated with wear, eliminated by replacing parts (unit) and repair (such as wear of friction linings, wear of the teeth of the drive disks and the gear drum, wear of the side surfaces of the splines of the gear drum, wear of the coupling and cardan shaft.
The main malfunctions of the columns and ways to eliminate them are given in Table. #1
Possible malfunctions of the clutch and how to eliminate them.
Table #1
Malfunction
Possible reason
Remedy
Clutch slippage
1. clutch adjustment is broken
2. increased lining wear
3. the working surfaces of the coupling are oily
4. loose or broken clutch springs
Adjust clutch
Replace pads
Rinse the working surfaces of the coupling
Tighten or replace springs
Violation of the smoothness of inclusion
1. clutch adjustment is broken (unequal gap between the levers or in the cams)
2. skew or warping of the driven or pressure plate
3. scoring on the working surfaces of the discs
4. Loose or broken disc pads.
Adjust the gap between the levers or in the cams)
straighten the driven disk or pressure plate
Tighten the mount or replace the disc pad
Incomplete clutch disengagement
pedal free travel adjustment (lever) is broken
sticking pressure or driven disk
loose cams or clutch levers.
Adjust pedal free play (lever)
clean the splines of the shaft and hub.
Tighten the fastening of the cams or clutch levers.
When inspecting and maintaining clutches, it is necessary to pay attention to most attention on components and parts, due to which the problems listed above are possible.
IV. Maintenance and repair of the clutch of the tractor VT-150
Maintenance of the machine and tractor fleet is carried out without fail after a certain number of engine hours have been worked out or a certain amount of fuel has been consumed. A machine that has not undergone regular maintenance is not allowed to continue working. For tractors during their use, regardless of their technical condition the following types of scheduled maintenance have been established.
Daily maintenance (ETO);
First maintenance (TO-1) - 125 hours.
Second maintenance (TO-2) - 500 hours.
Third maintenance (TO-3) - 1000 hours.
Seasonal maintenance (SRT). - 2 times per year.
The frequency of maintenance and repair of tractors in hours is the same for all tractors, but in kilograms of consumed fuel it is different and depends on the hourly fuel consumption of the engine. Seasonal maintenance is carried out during the transition from summer to winter operation and vice versa.
Deviation of the terms of maintenance due to production needs is allowed ± 10% of the norm.
For long-term and reliable operation of transmission units, tighten their fastenings in a timely manner, check for leaks through seals, the presence of oil levels in tanks, lubricate bearings in a timely manner and change oil in units, check and adjust mechanisms.
When servicing the tractor, it is necessary to check the operability of the clutch: determine the frequency of disengagement and smooth engagement of the clutch, slippage of the discs and their oiling. Check and adjust the gap between the ring of the release levers and the release bearing race, as well as the stroke of the pressure plate.
The gap between the release bearing stop and the ring should be 3.5 ... 4 mm. It corresponds to a free travel of the clutch pedal of 30 ... 40 mm. Adjust this gap by changing the length of the rod. If the stock of adjustment by the thrust is exhausted (the layer rested against the collar of the bracket), then it is necessary to unscrew each adjusting nut by one and a half turns through the hatch of the clutch housing. After that, by changing the length of the rod, adjust the gap. If the gap is too large (more than 5 mm), the clutch is not fully disengaged and this leads to rapid wear of the friction linings of the driven discs and the brake pad lining, which makes it difficult to shift gears, especially when starting the tractor.
Then check the touch of the end surface of the ring to the end face of the pressure bearing stop. The distortion of the ring is eliminated by turning the nuts by the required number of faces.
Adjusting the gap between the release bearing stop and the ring of the release levers with the BT-150 clutch basket is carried out in the following order:
- loosen the locknuts of the thrust and screw it in, increasing the gap, or unscrew it, reducing the gap;
- tighten the locknuts of the thrust;
- Check the gap with a feeler gauge.
If it is impossible to restore the above gap by changing the length of the rod, in the case when the release bearing housing rests against the end of the glass, it is necessary to adjust the initial position of the release levers
To adjust the position of the release levers of the VT-150 clutch basket:
- Remove the hatch cover of the clutch housing;
- turning crankshaft diesel engine, loosen the bolts of the plates one by one, move them away from the nut and unscrew each adjusting nut by one and a half turns (when the adjusting nut is turned one side, the thrust ring of the release levers moves by 1.1 mm);
- increasing the length of the rod, adjust the gap between the release bearing stop with the ring of the release levers of the VT-150 clutch basket within 3.5-4.0 mm;
- check the uniformity of the gap and the simultaneous touch of the squeezing levers of the ring when the clutch is turned off;
- after setting the required clearance, lock the adjusting nuts with locking plates and tighten the bolts;
Check the amount of stroke of the release bearing housing, which should be within 21-22 mm. At the same time as adjusting the clutch, check and, if necessary, adjust the brakes.
Rice. 6 Adjustment of brake VT-150
1 key; 2 - nut; 3 - brake block.
To check and adjust the gap (see Fig. 6) between the clutch shaft pulley and the friction lining of the brake shoe VT-150, completely turn off the clutch, and then adjust the gap within 3.0-3.5 mm between the end of the bonk using nut 2 of the brake link brake shoe 3 and the end face of the nut.
To obtain the necessary clearance, unscrew the nut 2 until its protrusion completely exits the groove of the brake shoe bonnet, and then tighten it by one or two clicks.
With this regulation, timely engagement and disengagement of the clutch brake is achieved.
Checking the general condition and flushing the clutch (TO-3). Start the engine, turn on the working gear and set the average speed of the crankshaft. When driving on a flat horizontal area, the tractor is completely braked without disengaging the clutch. If the engine stops, then the clutch is working properly. If the engine only slows down and continues to work, then this indicates disc slip.
Stop the tractor and the engine, open the hatch and check the condition of the clutch. The presence of smoke, excessive heating of the body and a specific smell in the space near the hatch indicate disc slippage.
If the adjusted clutch slips, then the discs are washed. Before that, the clutch is turned off and, turning the crankshaft manually, water the working surfaces of the disks with kerosene or gasoline, allowing it to drain completely.
Disk slippage after flushing indicates extreme wear and the need to replace the friction linings.
The main body defects are cracks, wear of surfaces and bushings. Cracks are expanded and repaired by welding, bushings are replaced with new ones. Wear surfaces are restored by soldering metal and processing to the desired dimensions. If the VT-150 clutch cover is cracked, it is better to replace it.
The clutch shaft of the VT-150 tractor is subject to wear of seats for ball bearings and splines, the oil seal, clutch brake VT-150 may also fail. Surfaces for bearings and slots for disks are welded, processed to the required dimensions by milling, turned and hardened by HDTV. If the splines of the connection with the input shaft of the gearbox are worn out, the clutch shaft is replaced with a new one.
The intermediate and pressure discs of the clutch of the BT-150 tractor allow wear of working surfaces up to 3-ring grooves up to 0.1 mm deep. If necessary, the discs are machined and carefully cleaned, while reducing the thickness of the intermediate disc is allowed up to 24 mm, and the pressure one - up to 24.5 mm.
If the driven disc springs are in good condition, only the friction linings are replaced. If not, the entire disk is replaced.
The VT-150 release lever is tested on the cam. If the wear is more than 2 mm, it is welded on and machined to the desired size.
The operation of the clutch springs is checked on special equipment, if the permissible force is less than 450 N, the springs are replaced.
The clutch release clutch VT-150 "sins" with pin wear. They are restored to size (nominal or repair) and HDTV hardened.
After repair, the clutch is installed on the engine and adjusted.
V. Safety precautions when performing clutch repair work.
Maintenance and repair of clutches must be carried out by a fitter who has received appropriate training, is well aware of safety regulations, has passed exams and has the right to carry out relevant similar work.
The working tool must ensure the safety of the work: the hammer heads must not have burrs and cracks, their surface must be slightly convex, smooth and unbroken; hammer handles must be wedged, finished with a wedge of mild steel, the surface of the handles must be smooth, without cracks, burrs and knots; on the impact surface of chisels, barbs, there should be no burrs, potholes, cracks; files, scrapers, hacksaws and other tools with a pointed working end must have handles with bandage rings.
Do not use wrenches whose gaps do not match the size of the nuts; increase and lengthen the keys with another key; use gaskets between the key and the nut. Do not use a chisel or hammer to loosen nuts.
When working with a wrench, the movement of the hand must be directed towards you, and not away from you. It is impossible to work on a vice in the absence of sponges, their increased wear or having diarrhea.
You can start working with pullers after checking the serviceability of their paws, screws, rods, stops.
When installing the puller, it is necessary to ensure the alignment of the power screw and the part to be removed, as well as a secure grip of the part with the paws.
The alignment of the holes of the assembled parts must be checked with a beard, and not with a finger.
Do not operate the grinder without a protective screen or without safety goggles and a dust bag.
VI. Conclusion
In this work, an analysis was made of the process of repair technology, the clutch of the BT-150 tractor. In the introduction, it was said about the use of clutches. First, the device and the principle of operation of the clutch are described. It was pointed out about the maintenance that occurs: malfunctions during operation and how to eliminate them.
Based on the above, it was concluded that it is possible to restore worn parts, assembly units or replace them with new ones. In this case, during the current repair, individual parts are restored or partially replaced, depending on wear. When carrying out a major overhaul, only a small part of the parts is restored, but mostly replaced with new ones. A comparative analysis of the designs of single-disk and double-disk friction clutches of tractors was also made during the internship.
Conclusion: Comparative tests of single-disk and double-disk clutches of experimental designs of tractors showed that the wear resistance of the experimental design of the double-disk clutch of the VT-150 tractor, the driven disks of which are equipped with friction linings made of copper-asbestos material, is 2–2.5 times greater than the single-disk clutch with the driven disk having the same friction linings.
VII. Used Books
1. V.S. Meshkov A.S. Neretin V.A. Biserov and others. The book of a rural machine operator. M., Rosselkhozizdat, 1990.- 431 p. from ill.
2. A.I. Shevchenko P.I. Safronov. Tractor mechanic's handbook. - L .: Mechanical engineering. Leningrad. department, 1998.- 512 p.: ill
3. V.A. Rodichev B.I. Peisakhovich V.A. Tokarev. Handbook of a rural machine operator. - 2nd ed., Revised. and additional .- M .: Rosselkhozizdat, 1994.- 336 p., ill.
4. V.L. Rogovtsev. Cars and tractors. - M., ed. "TRANSPORT" 1990.- 311 p.: ill.
5. Occupational safety in the repair and maintenance of agricultural machinery: (Handbook) / Comp. V.A. Nedrigailov.- M.: Kolos, 1991.- 320 p., ill.
Introduction
clutch drive wear friction
Currently, road transport has been widely used in various sectors of the national economy. More than 80% of the goods transported in our country are delivered by cars. The number of cars is also growing every year. The power of cars is increasing. A car operated in an urban cycle experiences heavy loads on the transmission and especially on the clutch. In this regard, a number of requirements are imposed on the clutch. Depending on them and the purpose of the car, clutch design is selected.
In the process of completing a course project, we gain practical skills in design, calculation, using the example of developing a new design of an assembly (system) of a car. Along with this, we learn to use mandatory vehicle design standards (GOST, industry standards, etc.), drawings, reference books and other sources of technical information.
The solutions to specific problems reflected in the course project correspond to the current level in automotive technology.
Purpose and clutch requirements
The clutch of a car is a transmission unit that transmits torque in the on state and has a device for briefly turning it off. The clutch is designed to smoothly start the car and briefly disconnect the engine and transmission when shifting gears and prevent the transmission from being exposed to large dynamic loads that occur in transient conditions. The rotating parts of the clutch are either assigned to the leading part connected to crankshaft engine, or to the driven part, disengaged from the leading when the clutch is turned off.
The clutch is located between the engine and gearbox.
The following requirements apply to the clutch:
Reliable transmission of torque from the engine to the gearbox. It is provided with the necessary margin of clutch torque (friction torque) in all engine operating modes, maintaining the pressure force within the required limits during operation.
Completeness of inclusion, i.e., the absence of slipping of the leading and driven parts of the clutch, which ensures reliable transmission of engine torque. It is achieved in operation by the presence of a gap in the shutdown mechanism and preventing the lubricant from entering the rubbing surfaces.
Completeness (“purity”) of shutdown, providing complete separation of the engine and transmission. Achieved by the setpoint
stroke of the release bearing and, accordingly, the stroke of the clutch pedal.
Soft start, providing a given intensity of starting off the car or after the gear is engaged. It is achieved by the design of the clutch, its drive and the pace of lowering the pedal by the driver.
Protection of transmission and engine from overloads and dynamic loads. It is achieved by the optimal value of the clutch torque reserve, the installation of a torsional vibration damper in it, and special measures in the design of the driven disks.
Low moment of inertia of the clutch driven parts, which reduces shock loads on the wheel teeth when changing gears.
Ensuring normal thermal operation and high wear resistance due to intensive heat removal from friction surfaces.
Good balance in order to eliminate "beats" and, accordingly, dynamic loads during clutch operation.
Ease and convenience of management, the possibility of automating the processes of switching on and off.
Clutches must also have general design requirements, such as: simplicity of the device, low labor intensity and ease of maintenance; minimum dimensions and weight; manufacturability and low cost of production; maintainability; low noise level .
Everything that connects the engine to the drive wheels is car transmission. The transmission in the car performs, as a rule, the following functions:
transmits torque from the engine to the drive wheels;
changes the magnitude and direction of the torque;
redistributes torque between the drive wheels.
manual transmission ( transfers and converts mechanical energy);
electric transmission ( converts mechanical energy into electrical energy and, after transmission to the drive wheels, electrical energy into mechanical energy);
hydrostatic transmission ( converts mechanical energy into the energy of the fluid flow and, after transfer to the drive wheels, the energy of the fluid flow into mechanical energy);
combined transmission ( electromechanical, hydromechanical - the so-called. "hybrids").
In the design of the transmission, front, rear, as well as both front and rear wheels can be used as driving wheels. If rear wheels are used as driving wheels, the vehicle has rear drive, and if the front - front-wheel drive. Front and rear wheel drive four-wheel drive vehicles.
For cars with different types of drive, the transmission design has significant differences, both in the composition of the elements and in their design.
The transmission of a rear-wheel drive vehicle has the following device:
clutch;
Transmission;
cardan transmission;
main gear;
differential;
semiaxes.
The gearbox is used to change the torque, speed and direction of the car, as well as the long-term separation of the engine from the transmission.
cardan gear provides the transmission of torque from the secondary shaft of the gearbox to the final drive shaft located at an angle to each other.
main gear serves to increase the torque and transfer it to the axle shafts of the drive wheels. Used on rear wheel drive vehicles hypoid final drive(the axes of the gears do not intersect).
Differential designed to distribute torque between the drive wheels. It allows the axle shafts to rotate at different angular speeds, which is necessary when turning the car.
The transmission of a front-wheel drive vehicle has the following device:
clutch;
Transmission;
main gear;
differential;
hinges of equal angular speeds;
drive shafts (half shafts).
CV joints(SHRUS) are used to transmit torque from the differential to the drive wheels. In the design of the transmission, as a rule, two hinges are used to connect to the differential (internal hinges) and two hinges to connect to the wheels (external hinges).
Between the hinges are drive shafts.
transmissions all-wheel drive vehicles have different designs. Together they form all-wheel drive systems. There are the following types of all-wheel drive systems:
permanent four-wheel drive;
all-wheel drive connected automatically;
all-wheel drive connected manually.
efficient use of engine power;
better handling and directional stability on slippery surfaces;
increased vehicle traffic.
Permanent all-wheel drive system
Permanent all-wheel drive system(another name is full time all-wheel drive system, in translation "full time") provides a constant transmission of torque to all wheels of the car.The system has the following general structure:
clutch;
Transmission;
transfer case;
cardan gears of the rear and front axles;
main gears of the rear and front axles;
small-wheel differentials of the rear and front axles;
wheel axles.
Scheme of permanent all-wheel drive system
Permanent four-wheel drive is used both on vehicles with a rear-wheel drive layout (longitudinal arrangement of the engine and gearbox) and on vehicles with a front-wheel drive layout (transverse arrangement of the engine and gearbox). Such systems differ mainly in the design of the transfer case and cardan gears.
Known permanent all-wheel drive systems are the system Quattro from Audi, xDrive from bmw.
The clutch provides a short-term disconnection of the engine from the transmission when shifting gears, as well as protection of the transmission elements from overload.
The gearbox is used to change the torque, speed and direction of the car. In an automatic transmission, the clutch function is performed by a torque converter.
Transfer case designed to distribute torque along the axes of the car and increase it if necessary. A modern transfer case includes a chain transmission that provides torque transmission to the front axle, a reduction gear in the form of a planetary gearbox (in some designs) and an center differential.
Availability center differential is a distinctive feature of the transfer case of the permanent all-wheel drive system. For the full implementation of all-wheel drive capabilities, the design of the system provides center differential lock.
The differential lock can be automatic or manual. Modern designs of automatic locking of the center differential are viscous coupling, self-locking Torsen differential, multi-plate friction clutch.
Manual (forced) differential lock is performed by the driver using a mechanical, pneumatic, electric or hydraulic drive.
On some designs of the transfer case, the functions of both automatic and manual locking of the center differential are provided.
cardan gears provide transmission of torque from the secondary shafts of the transfer case to the shafts of the main gears.
main gear serves to increase the torque and its transmission to the axle shafts of the wheels.
Cross-axle differential ensures the distribution of torque between the drive wheels and allows the axle shafts to rotate at different angular speeds. In all-wheel drive systems, an interwheel differential is used on the front and rear axles.
To implement all-wheel drive capabilities, one or both differentials have the ability to lock. The cross-axle differential can be locked manually or automatically (viscous coupling, Torsen differential). Modern cars use an electronic differential lock.
The principle of operation of the permanent all-wheel drive system is as follows. Torque from the engine is transmitted to the gearbox and then to the transfer case. In the transfer case, the moment is distributed along the axes. If necessary, the driver can turn on a downshift. Further, the torque is transmitted through the cardan shafts to the main gear and the center differential of each of the axles. From the differential, torque is transmitted through the axle shafts to the drive wheels. When the wheels of one of the axles slip, the inter-axle and inter-axle differentials are automatically or forcibly locked.
Automatic all-wheel drive system
Automatic all-wheel drive system(another name is all-wheel drive system On demand, translated as "on demand") is a promising direction for the development of all-wheel drive cars. This system ensures the connection of the wheels of one of the axles in case of slippage of the wheels of the other axle. Under normal operating conditions, the car is front- or rear-wheel drive.Almost all leading automakers have cars with automatically connected all-wheel drive in their model range. Known automatic all-wheel drive systems are 4Motion from Volkswagen, 4Matic from Mercedes.
The automatic all-wheel drive system has the following common device:
clutch;
Transmission;
main gear of the front axle;
cross-axle differential of the front axle;
transfer case;
cardan transmission;
rear axle coupling;
main gear of the rear axle;
cross-axle differential of the rear axle;
semiaxes.
Scheme of the all-wheel drive system connected automatically
Transfer case in the system of automatically connected all-wheel drive, it is, as a rule, a bevel gear. Downshift and center differential are absent.
The following devices are used as a coupling for connecting the rear axle:
viscous coupling;
electronically controlled friction clutch.
The principle of operation of the all-wheel drive system connected automatically equipped with a friction clutch is as follows. Torque from the engine, through the clutch, gearbox, final drive and differential is transmitted to the front axle of the car. Torque through the transfer case and cardan shafts is also transmitted to the friction clutch. In the normal position, the friction clutch has a minimum compression, at which up to 10% of the torque is transmitted to the rear axle. When the wheels of the front axle slip, at the command of the electronic control unit, the friction clutch is activated and transmits torque to the rear axle. The amount of torque transmitted to the rear axle can vary within certain limits.
All-wheel drive system connected manually
All-wheel drive system connected manually(other name - Part Time all-wheel drive system, translated as "partial time") is currently practically not used, because. is inefficient. At the same time, it is this system that provides a rigid connection between the front and rear axles, transmission of torque in a ratio of 50:50 and therefore is truly off-road.The device of the all-wheel drive system connected manually generally similar to a permanent all-wheel drive system. Main differences - no center differential and the ability to connect the front axle in the transfer case. It should be noted that in a number of permanent all-wheel drive designs, the front axle disengagement function is used. True, in this case, disconnecting and connecting is not the same thing.
It is designed for short-term disconnection of the engine from the transmission and their smooth connection when shifting gears, as well as protecting the transmission elements from overloads and damping vibrations. The vehicle's clutch is located between the engine and gearbox.
Depending on the design, the following types of clutch are distinguished: friction, hydraulic, electromagnetic.
Friction clutch transmits torque due to friction forces. In a hydraulic clutch, communication is provided by fluid flow. The electromagnetic clutch is controlled by a magnetic field.
The most common type of clutch is the friction clutch. Depending on the number of discs, the following types of friction clutch are distinguished: single-disk, double-disk and multi-disk.
Depending on the state of the friction surface, the clutch can be dry or wet. Dry clutch uses dry friction between discs. Wet clutch involves the operation of the discs in the fluid.
On modern cars, a dry single-plate clutch is installed. The design of a single-disk clutch includes a flywheel, pressure and driven disks, a diaphragm spring, a clutch release bearing with a clutch and a fork. All structural elements of the clutch are located in the crankcase. The clutch housing is bolted to the engine.
When the clutch pedal is depressed, the clutch actuator moves the clutch fork, which acts on the clutch bearing. The bearing presses on the petals of the diaphragm spring of the pressure plate. The petals of the diaphragm spring bend towards the flywheel, and the outer edge of the spring moves away from the pressure plate, releasing it. In this case, tangential springs press the pressure plate. The transmission of torque from the engine to the gearbox is stopped.
When the clutch pedal is released, the diaphragm spring brings the pressure plate into contact with the driven plate and through it into contact with the flywheel. Torque is transmitted from the engine to the gearbox due to frictional forces.