The clutch model YaMZ-238 is a two-disc, dry, friction type, with a peripheral arrangement of cylindrical springs
The casing 16 (Fig. 1) of the clutch, stamped from sheet steel, with the pressure plate 19 as an assembly is mounted on the flywheel 20 of the engine, and the driven discs 21 are mounted on the splined part of the input shaft of the gearbox.
The front and rear driven discs are installed in a specific position, as shown in the figure.
Clutch driven plates are clamped by a constant force of cylindrical pressure springs 17 between the engine flywheel, middle and pressure plates.
Thermal insulating pads 18 are placed under the springs on the pressure plate side. The pressure and middle driving discs are connected to the flywheel by four tires located on the outer surface of the discs.
When clamped, the driven discs transmit the engine torque to the gearbox input shaft.
Clutch disengagement is performed by clutch 11.
The clutch with the bearing, moving towards the engine, takes the pressure plate away from the driven plate, transferring the force through four rigid pull levers 5.
The travel of the clutch release clutch, including free play, must be at least 18.2 mm (dimension "D").
The amount of free play is controlled by the clutch release mechanism. The thrust ring of the release levers moves towards the gearbox by 27 mm due to the allowable wear of the friction linings.
Guaranteed gaps between the driven disks and the friction surfaces of the flywheel, the middle drive and pressure disks when the clutch is turned off as the linings wear out are provided by the mechanism for automatically adjusting the withdrawal of the middle disk
The mechanism consists of rods 1 fixed in each of the four spikes of the middle drive disk, split rings 2, which require a certain force to move along the rod, thrust bars 4, which are bolted to the flywheel with the clutch cover, and Belleville springs 3, installed on the stem between ring 2 and bar 4.
When the clutch is disengaged, the pressure plate 19 moves back by at least 2 mm, and releases the rear driven disc 21.
The middle drive disk 22 under the action of the spring 23 also moves back, until the ring 2 stops against the bar 4 through the Belleville spring, by 1.2 + 0.1 mm, releasing the front driven disk.
As the friction linings of the clutch wear out, the middle driving disk moves to the flywheel under the action of the pressure springs of the pressure disk, while the rings 2 rest against the clutch cover, moving along the rods 1 and maintaining the size between the rings and the Belleville springs.
When the pads of the driven disks are worn, the end of the clutch release clutch will rest against the end of the bearing cover of the input shaft of the gearbox; in this case, replace the worn pads of the driven disks with new ones.
Mounting the clutch on the engine
The clutch is installed on the engine in the following order:
- 1. install front driven disc;
- 2. install the middle driving disk with rods;
- 3. install rear driven disc;
Clutch discs can be installed: front 238-1601130-B, rear 238-160113 1 (not interchangeable); or two discs 238-1601 130-G2 (interchangeable).
Two discs 238-1601130-G2 can be installed instead of front discs 238-1601130-B and rear discs 238-160113 1. And vice versa.
The end of the extended part of the disc hub 238-1601130-G2 is marked 238-1601130-G2.
When installing them, the following conditions must be met:
- - disc to the flywheel - marked side of the hub to the engine;
- - disc to pressure plate - marked side of the hub to the gearbox.
- 4. install the pressure plate with casing assembly, securing it to the flywheel with eight short bolts;
- 5. put the split rings 2 on the rods 1 until it stops in the clutch cover;
- 6. wear four. Belleville springs with convex side towards split rings:
- 7. install four thrust bars and fasten them with the casing to the flywheel with eight long bolts.
After installing the clutch on the flywheel, make sure that the rings on the rods are against the casing, providing a gap of 1.2 + 0.1 mm between the rings and the Belleville springs when the clutch is engaged.
Adjust the clutch release clutch free play.
Attention! Lack of free play in the clutch release will lead to failure of the pressure bearing and slipping of the discs.
After adjustments, check the clutch for lack of “leading”. Carry out this check with the engine running, with the first gear engaged and the clutch disengaged.
Regulus Adjustment of the stop ring position of the release levers
When assembling the pressure plate with casing assembly, adjust the position of the thrust ring.
This adjustment should be made in a fixture with an installation dimension of 27 ± 0.1 mm (Fig. 2) using adjusting nuts 6 release levers with the casing and pressure plate in a fixed position.
By adjusting, ensure the dimension “B” equal to 64 ± 0.1 mm, while the thrust surfaces of all four pull levers 5 must simultaneously touch the thrust ring 4.
Distortion of the thrust ring will cause the pressure plate to move unevenly when the clutch is disengaged or does not operate normally.
After adjusting the position of the thrust ring with the adjusting nuts 6, install the locking 7 and support 8 plates of the adjusting nuts.
Tighten all eight bolts securing the locking and support plates, placing spring washers under the bolt heads.
In the case of using a pressure plate with a casing complete with driven discs after repair, on which friction linings with a thickness of 4.15 mm are installed, when adjusting the position of the thrust ring, set the dimension "B" to 67 + 0.1 mm.</p >
Clutch maintenance
Maintenance of the clutch is carried out in the same way as maintenance of the YaMZ-182 clutch (see above) with the addition:
Check each TO-1 and, if necessary, adjust the free play of the clutch release clutch.
The free play of the clutch release clutch, determined by the gap between the thrust ring and the clutch bearing (dimension "A" Fig. 1. 3.2-4.0 mm) is achieved by adjusting the clutch release mechanism in accordance with the instructions in the vehicle operating instructions.
After adjustments, check the clutch for lack of “leading”. Carry out this check with the engine running, with the first gear engaged and the clutch disengaged.
It is strictly forbidden to adjust the free play of the clutch release lever with the adjusting nuts of the release levers.
Torsional vibration damping and power take-off
Power units can be equipped with a torsional vibration damping and power take-off mechanism (Fig. 3), designed to dampen resonant torsional vibrations and protect transmission systems from destruction.
The mechanism is mounted on the engine flywheel and consists of a clamping flange 1, a driven disk 2 with friction linings and a torsional vibration damping mechanism, cup spring packs 5 and stepped bolts 6.
The driven disk 2 is constantly pressed against the flywheel 3 through the flange 1 by packs of Belleville springs 5 assembled on stepped bolts 6.
The shoulder bolts are fully screwed into the flywheel. When installing stepped bolts, sealant UG-6 TU 6-01-1285-84 is applied to their threaded part, tightening is done with a force of 49-59 Nm (5-6 kgcm).
The number of disc spring packs and bolts is chosen so that the friction torque created by them allows transmitting torque from the flywheel to the power take-off shaft up to 1700 Nm (170 kgcm).
When the driven disk is loaded with a torque of more than 1700 Nm (170 kgcm), the force of the springs is not enough to hold the driven disk and it rotates relative to the flywheel and thereby prevents further kinematic connection from destruction.
During operation, the mechanism does not require maintenance.
Possible malfunctions of the driven disk during operation are similar to malfunctions of the clutch driven disk.
Premature slippage of the driven disk is eliminated by installing additional cup spring packs together with the bolt and further checking the friction torque in the following order:
- 1. Lock the engine flywheel.
- 2. Load the driven disk of the mechanism with a torque of less than 1700 Nm (170 kgcm). the disc must not rotate relative to the flywheel.
- 3. Load the driven disk of the mechanism with a torque of 1700 ... 1900 Nm (170 ... 190 kgcm). The disc must rotate relative to the flywheel.
Clutch repair
Repair of the clutch consists in disassembling the set of pressure plate 22 (see Fig. 1) with the release levers and the clutch cover 19 as an assembly.
Complete disassembly of the clutch pressure plate assembly is carried out only for the replacement or repair of its parts, the need for which is determined by failures in operation or during external inspection.
Before disassembling the clutch, marks should be made on the pressure plate 22 and on the casing 19 in order to ensure the correct relative position of these parts during assembly and thereby maintain the original factory balance of the clutch.
Disassembly of the pressure kit is carried out in a fixture (Fig. 4) or on a wooden stand under a hand press in the following order:
- put the pressure plate 1 assembled with the casing on the fixture 1 with the disc down and fix with four spikes in the grooves.
Pressing on the end of the casing 19 (see Fig. 1), compress the springs 20 so that the release levers 5 with the thrust ring 14 are in a free state, bend the locking bars and unscrew all eight bolts securing the support plates of the adjusting nuts.
Remove the support plates 8 from the adjusting nuts 7, the locking plates 9, unscrew the four adjusting nuts 7 (see Fig. 1) of the release levers and slowly lower the clutch cover;
- remove the clutch cover, remove the pressure springs 20 from the bosses of the pressure plate 22, the heat-insulating gaskets 21 with washers, release the loops 10 of the springs of the release levers and remove the thrust ring 4, the lock washers of the axles on which the release levers are mounted in special lugs of the pressure plate , and carefully remove the axles and needle rollers.
After that, disassemble the release levers 5, for which it is necessary to remove the lock washers, remove the axles of the lever forks and the rollers of the needle bearings.
When checking the technical condition of the clutch pressure plate, special attention should be paid to the condition of the friction working surface.
If on this surface there are burn spots and a cracking network with a crack width of more than 0.2 mm covering more than 40% of the entire surface, or if the warping of the disk, measured with a probe on the plate, is more than 0.5 mm, the disk should be restored or replaced.
The working surface of the pressure plate is corrected (to a roughness of 2.5 microns) by grinding or turning with a thorough cleaning with a fine emery cloth.
After processing, the surface must be flat and, when checked on the slab, a probe with a thickness of 0.07 mm should not pass.
If grinding the disc to an acceptable thickness does not eliminate the defects, the disc should be replaced with a new one.
When inspecting the clutch disc, pay attention to the condition of the surface of the friction linings and the strength of their fastening with rivets.
It is not allowed to break the overlays and oil the working surfaces of the overlays.
It is allowed to have radial cracks in the lining near the rivets without going to the edge or into another hole for the rivet.
Clutch friction linings can wear up to 1.2 mm rivets on each side.
To remove worn out damaged friction linings, it is necessary to drill out the riveted holes of the lining fastening rivets from the drilling side and knock them out with a beard.
After riveting new pads, the driven disk must be checked for runout of the friction planes relative to the axis of the splined hole of the hub. To do this, the driven disk is mounted on a slotted mandrel and fixed in the centers of the fixture or lathe.
The drive shaft of the gearbox can be used as a mandrel.
The runout of the working surfaces relative to the axis of the splined hole of the hub at a radius of 175 mm should not exceed 0.7 mm. to eliminate the beating of the disk, it is allowed to edit it.
The thickness of the driven disc with riveted pads should be (10 ± 0.1) mm. The difference in lining thickness for one driven disk should not exceed 0.3 mm.
Assembly of the pressure kit should be done in the fixture shown in fig. 4 and under hand pressure.
The device consists of a stand with an installation dimension from the mating plane of the clutch cover to the plane of the pressure plate (27 ± 0.1) mm.
In the center of the stand, a mandrel 8 is fastened with a bolt 7 to adjust the control size of the pressure set B (see Fig. 3), equal to (64 ± 0.5) mm. There are four floating thrust crackers 6 in the mandrel (see Fig. 4).
When the pressure kit is installed in the device, the crackers rest against the tabs of the release levers 4 and, depending on their position, protrude or sink relative to the surface of the mandrel.
The length of the mandrel is chosen so that when it is installed on the release levers of the pressure set with a correctly adjusted reference size, the shims are flush with the surface of the mandrel.
The control dimension (64 + 0.5) mm of the clutch pressure kit also includes the thickness of the thrust ring of the release levers,which is (6±0.1) mm; and since the pressure set is adjusted in a fixture without a thrust ring, it must be adjusted to a size reduced by this amount, i.e. by (580.5) mm.
Assembly and adjustment are carried out in the following sequence: a pressure disk is placed on the stand 11 with the working surface down, fixed with four spikes in the grooves of the stand, a needle bearing is inserted into the release levers 4 (20 needles in each hole).
The needles are placed on the cyatim-201 lubricant or other grease corresponding to it.
Forks 6 are installed on the pull levers (see Fig. 1), the axles of the forks are inserted, the assembled levers are installed in the grooves of the lugs of the pressure plate, the axles of the levers are inserted, the springs of the thrust ring are put on the axles of the forks, the axles of the levers and forks are fixed with special lock washers , bending the middle of the jumper of the apron.
Then, four loops 10 are put on the ends of the springs of the thrust ring 14, pressure springs 20 are placed on the bosses of the pressure disk, having previously placed washers with heat-insulating gaskets 21 under them.
When using a pressure plate machined 1 mm along the working surface, a steel washer 1 mm thick is placed under each pressure spring 20 (from the side of the casing guide cups) to maintain the clutch pressure force.
Next, you need to put the clutch cover 19 on the guide pins of the fixture. All guide cups of the casing must enter the pressure springs, and the threaded shanks of the forks of the pull levers should enter the openings of the casing.
Using a press, it is necessary to press the casing with the mating surface to the fixture and fasten it with bolts, then release it from under the press.
Screw the adjusting nuts 3 onto the threaded shanks of the forks, install the mandrel to adjust the position of the release levers 4 and fix it with the bolt 7 (see Fig. 4).
After that, adjust the position of the pull levers 4 with the adjusting nuts 3 so that they all simultaneously touch the stop crackers 16 of the mandrel 8, which should be flush with its upper surface.
This, when installing the thrust ring, provides a control dimension between the working surfaces of the pressure plate and the thrust ring.
Plates 2 are placed on the adjusting nuts 3, then the locking bars and support plates of the forks of the levers, after which all eight locking bolts are wrapped.
After tightening the bolts, the yokes of the pull levers must have no axial play. The bolts are locked by bending the mustache of the locking bars.
Having installed the thrust ring on the pull levers, fix it with loops so that it simultaneously touches the supporting surfaces of all four levers.
The runout of the end of the thrust ring relative to the working surface of the pressure plate should not exceed 0.4 mm at a radius of 45 mm.
Increased runout of these surfaces can lead to failure of the friction linings of the clutch disc and burns of the working surfaces of the flywheel and pressure plate.