The clutch release cylinder moves the piston with hydraulic pressure from the master cylinder and operates the release fork through the push rod.

Self-adjusting release cylinder

The conical spring in the release cylinder constantly presses the push rod against the release fork with its spring force to hold the clutch pedal freeplay constant.

Adjustable release cylinder

When the diaphragm spring tip position has changed due to wear of the clutch disc, it is necessary to adjust the freeplay with the push rod.

Clutch Release Bearing

The clutch release bearing absorbs the rotational difference between the release fork (which is not turning) and the diaphragm spring (which is turning) to transmit the movement of the release fork to the diaphragm spring.

Self-centering release bearing

In transaxles for FF vehicles, the crankshaft and input shaft shift slightly. This results in noise caused by friction between the diaphragm spring and the release bearing. To prevent this noise, this mechanism supplies the center line of the diaphragm and release bearing to be aligned automatically

The tilt steering mechanism allows selection of the steering wheel position (in the vertical direction) to match the driver’s driving posture. The tilt steering mechanisms are classified into the upper fulcrum type and the lower fulcrum type. Here, the lower fulcrum type is explained.

2. Construction

The tilt steering mechanism consists of a pair of tilt steering stoppers, tilt lock bolt, breakaway bracket, tilt lever, etc.

3. Operation

The tilt steering stoppers turn together with the operation of the tilt lever. When the tilt lever is in the lock position, the peaks of the tilt steering stoppers are lifted up and the stoppers push against the breakaway bracket and tilt attachment, locking the break away bracket and tilt attachment. On the other hand, when the tilt lever is moved to the free position, the height difference on the tilt steering stoppers is eliminated, and the steering column can be adjusted in the vertical direction.

SERVICE HINT:

If the wheels are given excessive positive or negative camber, this causes uneven tire wear. If the wheels are given excessive negative camber, the tires wear quicker on the inside; if the wheels are given excessive positive camber, the tires wear quicker on the outside.

Negative Camber

When a vertical load is applied to a cambered tire, force is generated in the horizontal direction. This force is called “camber thrust” and operates to the inside of the vehicle for negative camber and the outside of the vehicle for positive camber. During cornering, because the vehicle leans to the outside, the tire camber becomes more positive, the camber thrust to the inside of the vehicle is reduced, and cornering force is reduced. The negative camber suppresses the positive camber of the tires during cornering and helps maintain proper cornering force.

Camber During Cornering

When a vehicle turns a corner, the camber thrust on the outside tires acts to reduce the cornering force due to the increase in positive camber. Centrifugal force tilts the turning vehicle due to the action of the suspension springs, changing the camber.

HINT:

Cornering is always accompanied by centrifugal force, which tires to force the vehicle to turn in a larger arc than intended by the driver unless the vehicle can generate a sufficient counterforce – that is, centripetal force – to balance this. This centripetal force is generated by the deformation and side-slipping of the tread that occurs due to friction between the tire and the road surface. This called cornering force.

Camber During Cornering

When a vehicle turns a corner, the camber thrust on the outside tires acts to reduce the cornering force due to the increase in positive camber. Centrifugal force tilts the turning vehicle due to the action of the suspension springs, changing the camber.

HINT:

Cornering is always accompanied by centrifugal force, which tires to force the vehicle to turn in a larger arc than intended by the driver unless the vehicle can generate a sufficient counterforce – that is, centripetal force – to balance this. This centripetal force is generated by the deformation and side-slipping of the tread that occurs due to friction between the tire and the road surface. This called cornering force.

The telescopic steering mechanism allows forward or backward adjustment of the steering wheel position to suit the driver’s posture.

2. Construction

The telescopic mechanism consists of the sliding shaft tube, two wedge locks, stopper bolt, telescopic lever, etc.

3. Operation

The wedge locks move together with operation of the telescopic lever. When the telescopic lever is in the lock position, the telescopic lever presses the wedge locks against the sliding shaft tube, locking the sliding shaft tube. On the other hand, when the telescopic lever is moved to the free position, a gap is created between the wedge locks and the sliding shaft tube and the steering column can be adjusted in the forward or backward direction.

SERVICE HINT:

If the wheels are given excessive positive caster, the straight-line stability is improved, but cornering becomes difficult.

Straight-line Stability and Wheel Recovery

Straight-line stability due to caster angle When the steering axis rotates, during cornering, if the wheels have caster angle, the tires are inclined relative to the ground and jack-up torque is generated that attempts to lift the vehicle body as in the figure. This jack-up torque functions as a recovery force that attempts to return the vehicle body to the horizontal and maintains the straight-line stability of the vehicle.

Wheel recovery due to caster trail If the wheels are given caster angle, the contact point of the line extending from the steering axis is forward of the center of tire-road contact. Therefore, since the tires are pulled from the forward direction, the force pulling the tires holds down the force attempting to destabilize the tires and maintains straight-line performance. Also, when the tires face sideways due to steering or disturbance during straight-line travel, side forces (F2 and F’ 2) are generated. These side forces act as rotation forces around the steering axis due to the caster trail and are forces attempting to return the tires to their original positions (recovery force). At this time, if the caster trail is long, for the same magnitude side force, a larger force works to return the steering wheel. Therefore, the longer the caster trail, the greater the straightline performance and recovery force.

Nachlauf and Vorlauf Geometry

In general, the caster angle must be increased in order to increase caster trail. However, even if the caster angle remains the same, the caster trail can be set as desired by offsetting the steering axis to the front or rear from the wheel center. Nachlauf geometry enables caster trail to be increased by offsetting the steering axis to the front from the wheel center. Vorlauf geometry enables caster trail to be decreased by offsetting the steering axis to the rear from the wheel center. In actual vehicles, various settings are made by Nachlauf and Vorlauf geometry in order to match vehicle characteristics.

Roles of Steering Axis Inclination

1. Reduction of steering effort Since the wheel turns to the right or left with the steering axis as its center and the offset as the radius, a large offset will generate a great moment around the steering axis due to the rolling resistance of the tire, thus increasing steering effort. This offset can be reduced in order to reduce the steering effort. Either of the following two methods can be used to make the offset small:

(1) Give the tires positive camber

(2) Incline the steering axis.

2. Reduction of kick-back and pulling to one side If the offset is excessively large, the force due to driving or braking generates a moment around the steering axis whose magnitude is proportional to the amount of offset. Also, any road shock applied to a wheel will cause the steering wheel to jerk or kick-back. These phenomena can be improved by reducing the amount of offset. If there is a difference between the left and right steering axis inclination angles, the vehicle will typically pull to the side of the smaller angle (having the larger offset).

3. Improvement straight-line stability The steering axis inclination causes the wheels to automatically return to the straight-ahead position after the completion of turning.

HINT:

In front engine, front-wheel-drive cars, the offset is generally kept small (zero or negative) to prevent the transmission to the steering wheel of shock from the tires generated during braking or by striking an obstruction, and to minimize the moment created around the steering axis by the driving force at the time of quick starting or acceleration.

SERVICE HINT:

If there is a difference between the steering angle on the left and right, there will also be a difference between the moments around the steering axis on the left and right during braking and the braking force will be greater on the side with the smaller steering angle. Also, any difference between the left and right offsets generates a difference in the drive reaction force (torque steer) on the left and right. In either case, a force acts that attempts to turn the vehicle.

SERVICE HINT:

If toe-in is excessive, the side slip force causes uneven wear of the tires. If toe-out is excessive, it is difficult to secure straight-line stability.

HINT:

Side slip is the total distance that the left and right tires slip to the side while the vehicle is running. Both in the case of toe-in and negative camber, side slip occurs towards the outside.

1. General

Wheel alignment covers several items such as camber, caster, steering axis inclination, etc., and each item is closely related to the other items. When inspecting and correcting, it is necessary to consider all items and how they relate to each other.

2. Where to measure and cautions concerning tester handling

Recently a large number of new alignment tester models have come into use. However, note that the high-precision testers may be quite complex, and errors may occur without your being aware of it. Therefore, maintenance of the testers must be performed periodically to assure that they are always reliable. Always measure wheel the alignment with the vehicle parked on a flat, level area. This is necessary because, no matter how accurate the alignment tester is, correct values cannot be obtained if the place where the measurement are to be carried out is not level.

3. Necessity of inspection before measurement of wheel alignment

Before measuring the wheel alignment, each factor that could affect the wheel alignment must be checked and necessary corrections made. Proper execution of this preparatory operation will give the correct values. Standard wheel alignment values are determined by the manufacturer with the vehicle in its “normal” condition. Therefore, when inspecting wheel alignment, it is necessary to have the vehicle as close to its normal condition as possible in which standard values are determined. (See Repair Manual for standard values.) Items to be checked before measurement of wheel alignment area.

• Tire inflation pressure (under standard conditions)
• Markedly uneven wearing of tires or difference in the sizes.
• Tire runout (radial and face)
• Ball joint play due to wear
• Tie rod play due to wear
• Front wheel bearing play due to wear
• Lengths of left and right strut bars
• Difference between left and right wheelbase
• Deformation or wear of steering linkage parts
• Deformation or wear of parts related to front suspension
• Lateral body inclination (chassis ground clearance)

4. Importance of chassis-to-ground clearance

adjustment before alignment measurement

In a vehicle with independent front suspension, wheel alignment factors will vary depending upon the load because of changes in chassis-to-ground clearance. It is therefore necessary to specify the wheel alignment factors for the specified clearance. Unless otherwise specified, refer to the Repair Manual, etc.

5. Road test

After adjusting the front axle, suspension, steering, and/or front wheel alignment, carry out following road test to check the result of the adjustments:

Straight-ahead driving

(1) The steering wheel must be at the correct position

(2) The vehicle should run straight ahead on a flat road.

(3) Excessive steering shimmy or flutter should not occur.

Turning

The steering wheel should turn easily in either direction, and should return quickly and smoothly to the neutral position when released.

Braking

The steering wheel should not pull to either side when the vehicle is broken on a flat, smooth road.

Checking for abnormal noise

No abnormal noise must be heard during the driving test.

6. Measurement results and how to use them

If the measured values deviate from the standard values, it makes the measured values within the standard values by adjusting adjustment mechanisms or replacing parts.

• Bending bracket type

• Ball type

• Sealed-in pulverized silicon-rubber type

• Mesh type

• Bellows type

The piston in the power cylinder is positioned on the rack, and the rack moves due to fluid pressurized by the vane pump acting on the piston in either direction. Fluid pressure leakage is prevented by a seal ring on the piston. Also, there is an oil seal on both sides of the cylinder to prevent external leakage of the fluid. The control valve shaft is connected to the steering wheel. When the steering wheel is in the neutral (straight-ahead) position, the control valve is also in the neutral position, so the fluid from the vane pump does not act on either chamber but flows back to the reservoir tank. However, when the steering wheel is turned in either direction, the control valve changes the passage so the fluid flows into one of the chambers. The fluid in the opposite chamber is forced out and flows back to the reservoir tank by way of the control valve. Currently, there are three different types of control valves which perform this changeover action of the passage; spool valves, rotary valves and flapper valves. All types have a torsion bar between the control valve shaft and pinion, and the control valve functions in accordance with the amount of twist applied to the torsion bar.

2. Type of control valve

A control valve is located in the gear housing. The gear housing houses a rackand- pinion type power steering mechanism or a recirculating- bail type power steering mechanism. The control valve is one of three types: a rotary valve type, a spool valve type, or a flapper valve type. Currently, rotary valve types are used in many models.

3. Construction

Here, the rotary valve type is explained. The control valve in the gear housing determines to which chamber the fluid from the vane pump goes. The control valve shaft (to which steering wheel torque is applied) and the pinion gear are connected by means of a torsion bar. The rotary valve and pinion gear are secured by a pin and rotate integrally. If no vane pump pressure is applied, the torsion bar is fully twisted and the control valve shaft and pinion gear make contact at the stopper so the control valve shaft torque is applied directly to the pinion gear.

4. Operation

A restriction in the hydraulic circuit is formed by rotary movement of the control valve shaft in relation to the rotary valve. When the steering wheel is turned to the right, pressure is restricted at orifices X and Y. When it is turned to the left, a restriction is formed at X’ and Y’. When the steering wheel is turned, the control valve shaft rotates, turning the pinion gear via the torsion bar. In contrast to the pinion gear, as the torsion bar twists in proportion to road surface force at this time, the control valve shaft rotates only to the extent of the amount of twist, and moves to the right or left in relation to the rotary valve. Thus orifices X and Y (or X’ and Y’) are formed and a difference in hydraulic pressure between the right and left cylinder chambers is created. In this manner, rotation of the control valve shaft directly performs changeover of the passages and regulates the fluid pressure. The fluid from the vane pump enters from the outer circumference of the rotary valve, and the fluid returning to the reservoir tank passes between the torsion bar and the control valve shaft.

(1) Neutral position

As the control valve shaft does not revolve, it is in a neutral position in relation to the rotary valve. Fluid supplied by the pump returns to the reservoir tank through port “D” and chamber “D”. The right and left chambers of the cylinder are slightly pressurized but as there is no pressure difference between the two, no power steering assist occurs.

(2) Turning right

When the vehicle makes a right turn, the torsion bar is twisted and the control valve shaft revolves to the right accordingly. Fluid from the pump is constricted by orifices X and Y of the control edge in order to stop flow to ports “C” and “D”. As a result, fluid flows from port “B” to sleeve “B” and then to the right cylinder chamber, causing the rack to move to the left and resulting in power steering assist. At the same time, the fluid in the left cylinder chamber flows back to the reservoir tank via sleeve “C” -> port “C” -> port “D” -> chamber “D”.

(3) Turning left

In the same manner as for a right turn, when the vehicle makes a left turn, the torsion bar is twisted and the control shaft rotates to the left accordingly. The fluid sent from the pump is constricted by orifices X’ and Y’ of the control edge in order to stop flow to ports “B” and “D”. As a result, fluid flows from port “C” to sleeve “C” and then to the left cylinder chamber, causing the rack to move to the right and resulting in power steering assist. At the same time, the fluid in the right cylinder chamber flows back to the reservoir tank via sleeve “B” -> port “B” -> port “D” -> chamber “D”.