Internal selfadjustment

A clutch self-adjustment version has teeth cut on the inside of the adjusting ring and a small worm and spring self-adjusting device replaces the lock plate. The worm meshes with the adjusting ring. One end of the spring is located in a hole formed in the release lever hub whilst the other end is in contact with the worm. Each time the clutch is engaged and disengaged, the release lever movement will actuate the spring. Consequently, once the driven plates have worn sufficiently, the increased release lever movement will rotate the worm which in turn will partially screw round the adjusting ring to compensate and so reset the position of the release levers.

2.10 Clutch (upshift) brake (Fig. 2.15) The clutch brake is designed primarily for use with unsynchronized (crash or constant mesh) gearboxes to permit shifting into first and reverse gear without severe dog teeth clash. In addition, the brake will facilitate making unshafts by slowing down the input shaft so that the next higher gear may be engaged without crunching of teeth.

The brake disc assembly consists of a pair of Belleville spring washers which are driven by a hub having internal lugs that engage machined slots in the input shaft. These washers react against the clutch brake cover with facing material positioned between each spring washer and outer cover (Fig. 2.15).

When the clutch pedal is fully depressed, the disc will be squeezed between the clutch release bearing housing and the gearbox bearing housing, causing the input spigot shaft to slow down or stop. The hub and spring washer combination will slip with respect to the cover if the applied torque load exceeds 34 Nm, thus preventing the disc brake being overloaded.

In general, the clutch brake comes into engagement only during the last 25 mm of clutch pedal

Fig. 2.15 Clutch upshift brake (torque limiting)

Fig. 2.16 Multiplate hydraulically actuated clutches

travel. Therefore, the pedal must be fully depressed to squeeze the clutch brake. The clutch pedal should never be fully depressed before the gearbox is put into neutral. If the clutch brake is applied with the gearbox still in gear, a reverse load will be put on the gears making it difficult to get the gearbox out of gear. At the same time it will have the effect of trying to stop or decelerate the vehicle with the clutch brake and rapid wear of the friction disc will take place. Never apply the clutch brake when making down shifts, that is do not fully depress the clutch pedal when changing from a higher to a lower gear.

2.11 Multiplate hydraulically operated automatic transmission clutches (Fig. 2.16) Automatic transmissions use multiplate clutches in addition to band brakes extensively with epicyclic compound gear trains to lock different stages of the gearing or gear carriers together, thereby providing a combination of gear ratios.

These clutches are comprised of a pack of annular discs or plates, alternative plates being internally and externally circumferentially grooved to match up with the input and output splined drive members respectively (Fig. 2.16). When these plates are squeezed together, torque will be transmitted from the input to the output members by way of these splines and grooves and the friction torque generated between pairs of rubbing surfaces. These steel plates are faced with either resinated paper linings or with sintered bronze linings, depending whether moderate or large torques are to be transmitted. Because the whole gear cluster assembly will be submerged in fluid, these linings are designed to operate wet (in fluid). These clutches are hydraul-ically operated by servo pistons either directly or indirectly through a lever disc spring to multiplate, the clamping load which also acts as a piston return spring. In this example of multiplate clutch utilization hydraulic fluid is supplied under pressure through radial and axial passages drilled in the output shaft. To transmit pressurized fluid from one member to another where there is relative angular movement between components, the output shaft has machined grooves on either side of all the radial supply passages. Square sectioned nylon sealing rings are then pressed into these grooves so that when the shaft is in position, these rings expand and seal lengthwise portions of the shaft with their corresponding bore formed in the outer members.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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