Construction
The pretensioner mechanism consists of the retractor shaft, pretensioner shaft, drum, wire, drive plate, piston, cylinder, inflator, etc.
The pretensioner shaft is directly installed on the retractor shaft (for seat belt winding) and goes inside the drum. Since there is clearance between pretensioner shaft and drum in the normal condition, these do not contact each other.
There is a spring portion on the drum. As a result, the drum contracts inward by the force produced when the wire that is wound around the drum is drawn out.
The drive plate is installed so that it turns together with the drum.
The wire is wound around the drum.
An end is fixed on the drive plate and the other is fixed on the cylinder via the piston.

Operation
When an impact that exceeds the specified value occurs, the inflator is ignited according to the signal from the center airbag sensor and generates high-pressure gas. This high-pressure gas strongly pushes the piston in the cylinder. As a result, the wire is retracted. Then the drum contracts in the center direction of the clearance and is pressed on the pretensioner shaft to be a unit with it. After that, the share pin that fixes the drive plate is sheared off, causing the drum, drive plate, and pretensioner shaft to rotate in the winding direction as a unit and the seat belt to retract to restrain the passenger.
The stroke about twice the moving distance of the piston is the length that the wire is drawn.
There are various types of pretensioners, such as one that uses a rack instead of a wire and drives by a gear, etc.
Force limiter mechanism
Construction
The retractor, force limiter and the spool are combined and generally they rotate as a unit.
Operation
If a larger load than the specified value is applied to the seat belt because of the movement of the passenger in a collision, the force limiter plate alters the shape (absorbs the energy) by the rotational force of the spool and winds around the shaft. As a result, the seat belt is released.
The force limiter plate can be deformed until the spool makes approximately 1.3 turns.
There are various types of force limiters, such as one that uses a torsion bar instead of a force limiter plate, etc.

The engagement/disengagement mechanism has two functions.

Engages the pinion gear with the ring gear.

Disengages the pinion gear from the ring gear.

Engagement mechanism

When the end faces of the pinion gear and the ring gear come into contact with each other by the pull-in action of the magnetic switch, the drive spring is compressed. Then the main contact is turned on and the armature revolving force increases. A part of the revolving force is converted into a thrust by the helical spline to push out the pinion gear. In other words, pinion gear is engaged with the ring gear by a pull-in force of the magnetic switch, a revolving force of the armature and a thrust of the helical spline.

The pinion gear and the ring gear are chamfered for easy engagement.

Disengagement mechanism
When the pinion gear rotates the ring gear, a high pressure is applied to the tooth surfaces of the two gears.
Since the revolving speed of the engine (ring gear) becomes faster than that of the pinion gear when the engine starts, the ring gear begins to rotate the pinion gear. A part of the revolving force is converted into a thrust by the helical spline to disengage the pinion gear. The overrunning clutch mechanism prevents the revolving force of the starter from being transmitted to the pinion gear by making the ring gear to rotate the pinion gear. As a result, the pressures applied to the both gears decrease, and the pinion gear is more easily disengaged.
Since the pull-in force from the magnetic switch is released, a compressed return spring pushes back the pinion gear and disengages it from the ring gear.

1. Four-valve mechanism

The valve mechanism of the diesel engine is basically the same as the one on the gasoline engine. However, some valve mechanisms are distinctive to the engine. The four-valve mechanism consists of the valve rocker arm and valve bridge. When the rocker arm is pushed up by the camshaft, the valve bridge slides along the guide pin and pushes down the two valves simultaneously to open them. In this way, a single camshaft is able to operate four valves per cylinder. Through the use of four valves, not only is the intake and exhaust effectiveness improved, but also the injection nozzle can be placed in the center of the combustion chamber.

HINT:

Valve clearance is adjusted using two adjusting screws, (1) and (2).

2. Replacement interval of timing belt

The timing belt of the diesel engine must be replaced every 100,00km (60,00miles) or 150,00km (90,00miles), depending on the engine models. In some diesel engine vehicles, a timing belt replacement warning light is provided. This light will come on at the specified timing belt replacement intervals. The timing belt warning light must be reset after replacing the timing belt. The method for resetting varies by the model.

Example 1:

Remove the grommet under the speedometer and push the warning light reset knob with a thin rod.

Example 2:

Remove the cancel switch screw and reinstall it in the other installation hole.

1. Description

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.

The valve mechanism opens or closes the intake valve and exhaust valve at the proper timing in order to draw the air-fuel mixture into the cylinder and discharge the combustion gas into the outside.

1. Valve opening and closing system

The rotation of the crankshaft is transferred to the camshaft via the timing chain (timing belt), rotating the cam. The number of teeth on the camshaft sprocket (pulley) is double that of the crankshaft so that the camshaft rotates once for every two rotations of the crankshaft. As the camshaft rotates, the cam forces the valve to open or close.

Valve and Related Parts

2. Valve

The intake valve opens during the intake stroke to draw the air-fuel mixture. The exhaust valve opens during the exhaust stroke to exhaust the combustion gas. Both valve closes during the compression and combustion strokes to keep the combustion chamber airtight. Since the valve is exposed to high temperatures and high pressure, it is made of a special metal. Generally, in order to increase the amount of the intake air, the valve diameter of the intake valve is larger than exhaust valve. In order to keep the valve and the valve sheet airtight, the angle of the valve face is generally set at 44.5 or 45.5. Valves are pushed to the closing direction by springs and cams operation cause the valve to move down along the valve guide bushing inside the cylinder head.

3. Valve spring

The valve spring is a coil spring that applies tension in the closing direction of the valve. Most engines have one spring per valve, however some engines use two springs per valve. In order to prevent the valve from vibrating when the engine is running at high speeds, uneven pitch springs or double springs are used.

HINT:

Valve springs have the natural frequency. When the number of the valve opening and closing and the natural frequency match to vibrate together, the waviness vibration may occur irrelevant to camshaft operation. This condition is called surging and it can be a cause of abnormal engine noise as well as damage to the valve spring or interference between the valve and piston.

Asymmetrical type of uneven pitch springs is installed with the wider pitch toward the top.

4. Valve seat

The valve seat is press-fitted into the cylinder head. When the valve closes, the valve face and valve seat fit closely together to make the combustion chamber airtight. The valve seat also transfers heat from the valve to the cylinder head, serving to cool the valve as well. Since the valve seat is exposed to high temperature combustion gas, and repeated contact with the valve, it is constructed of a metal that excels in resistance to heat and wear. When the valve seat wears, it can be ground by the carbide cutter or replaced. In recent years, lasers have been used to weld a wear-resistant alloy valve seat layer directly to the cylinder head making the valve seat and the cylinder head one unit on some engines. With this type of laser clad valve seat, replacement is impossible.

REFERENCE:

Valve seats are generally shaped like a 45 cone in order to fit with the valve face. The valve seat contact width is generally from 1.0 mm to 1.4 mm. The wider the contact area of the valve seat, the greater the cooling effect will be, however air-tightness may suffer since carbon intrusion is likely. In contrast, the narrower the contact area of the valve seat, the lesser the cooling effect and the lesser the likelihood of carbon intrusion will be.

5. Valve guide bushing and oil seal

The valve guide bushing is generally made of cast iron and is press-fitted into the cylinder head. It acts to guide the movement of the valve so that it closely fits the valve seat and valve face. The contact surfaces of the valve guide and valve stem are lubricated with engine oil. To prevent excess oil from entering the combustion chamber, a rubber oil seal is fitted on the topside of the valve guide bushing.

SERVICE HINT:

Valve stickingoccurs when the valve stem in the valve bushing guide stops moving smoothly or stops moving completely. This occurs when the amount of clearance between the valve stem and the valve guide bushing is too small or when they are not sufficiently lubricated. If the valve stem oil seal is broken or hardens, engine oil will enter the combustion chamber and be burned. This can cause excessive oil consumption.

There is a scissors gear (sub-gear) on the driven gear of the camshaft for the compact DOHC which serves to reduce gear noise associated with changes in torque. The sub-gear is pushed toward the rotational direction by the spring at all times and the scissors gear reduces the backlash of the gear by meshing with the drive gear, in order to prevent the noise. Backlash Backlash is the gap between the gear contact surfaces and due to this tolerance in the design and assembly, wear and seizure are prevented.

When a vehicle involved in a collision, this mechanism helps prevent the steering main shaft from injuring the driver in two ways: by the breaking at the time of the collision (primary shock); and by reducing the secondary shock imposed upon the driver’s body when it hits the steering wheel due to inertia. Impact-absorbing steering columns are classified into the following types.

• Bending bracket type

• Ball type

• Sealed-in pulverized silicon-rubber type

• Mesh type

• Bellows type

1. General

This mechanism is provided to reduce brake pedal kickback, thereby improving pedal “feel”, by causing only half of the feedback pressure to be applied to the pedal (the other half being absorbed by the booster piston).

2. Operation

The reaction mechanism is shown in the left. The booster push rod, reaction disc and air valve slide inside the valve body. Since the reaction disc is made of soft rubber, it can be regarded as a non-compressible fluid. For this reason, when the booster push rod is pushed to the right, it attempts to compress the reaction disc, but since it cannot, the force is transmitted to the air valve and the valve body. Therefore, the force is transmitted between the air valve and the valve body in proportion to their surface areas. Assume that 100 N (9.8kgf,.21.6 lbf) is applied to the booster push rod, as shown here. Since the ratio of the areas of the air valve and the valve body is 4 to 1, 80 N (7.8kgf; 17.2 lbf) is transmitted to the valve body and 20 N (2.0 kgf,.4.4lbf)to the air valve.

Gap Adjustment of Push Rod

The length of the booster push rod must be adjusted before the brake master cylinder and the brake booster are assembled. This is required so there will be an appropriate gap between the master cylinder piston and the booster push rod after they are reassembled. A SST is used to adjust the gap. In recent models, there are times when a thickness gauge must be used. Be sure to refer to the repair manual.

HINT:

• When the master cylinder has been replaced and there is an accessory tool in the kit, use the accessory tool to make the adjustment.

• When the label shown in the figure at left is affixed to the booster body, refer repair manual when adjusting the length of the booster push rod.

SERVICE HINT:

If the gap is too small, it will cause brake drag. If the gap is too large, it will cause braking delay.

This is a theft deterrent feature that disables the steering wheel by locking the steering main shaft to the column tube when the ignition key is pulled out. There are two types of steering lock mechanism.

• Push type ignition key cylinder

• Push-button type ignition key cylinder

HINT: In some automatic transaxle vehicles with the shift lock mechanism, the steering lock mechanism is not provided.

(1) When the ignition key is in the ACC or ON position When the ignition key is in the ACC or ON position, the lock stopper and lock bar are pushed to the right by the cam of the camshaft. The lock release lever therefore falls into the groove in the lock stopper, preventing the lock stopper and lock bar from moving to the left, and thus preventing the steering wheel from being locked while the vehicle is being driven.

(2) When the ignition key is turned from ON to ACC position When the ignition key is turned from ON to ACC position (shutting off the engine), the lock release lever strikes against the left edge of the groove in the lock stopper, preventing the lock stopper and lock bar from moving to the left (and thus preventing the steering wheel from being locked).

(3) When the ignition key is in the ACC position As long as the ignition key is not pushed in while the lock is in the ACC position, the push plate is pushed out by the cylinder rotor return spring. For the reason, the stopper plate protrudes out and strikes against the edge of the lock body, preventing the rotor and ignition key from being turned to the LOCK position.

(4) When the ignition key is turned from ACC to LOCK position When the key is pushed in while in the ACC position, the rotor and push plate are pushed in also. The upper part of the stopper plate therefore rides up the diagonal wall of the groove in the push plate, and the lower part of the push plate goes into the camshaft. The ignition key, push plate, and camshaft are therefore free to turn as on unit from the ACC position to the LOCK position. However, since the end of the lock release lever is still being hold down by the key, it prevents the lock stopper and lock bar from moving to the left.

(5) When the ignition key is removed When the key is pulled out from the rotor, the lock release lever disengages (moves up) from the lock stopper, and the lock bar goes into the steering main shaft groove, locking the steering main shaft.

Shift lever lock systems are adopted to prevent mis-operation of the shift lever. With this mechanism, when the shift lever is in the “P” range, the shift lever cannot move unless the ignition key is in the ON position and the brake pedal is depressed. Also, when the shift lever is not in the “P” range, the ignition key cannot be turned from ON or ACC to LOCK and the ignition key cannot be removed. There is a release button for manually canceling the shift lock mechanism if the battery is dead.

2. Components

The shift lever section includes the shift lock plate, shift lock link, shift lock solenoid, shift lock computer, and shift lock release button. The key cylinder section comprises such parts as the lock pin and cam. The lock pin is connected to the shift lock plate via the parking lock cable.

HINT:

Some models eliminate the parking lock cable and control with a solenoid valve.

3. Operation

(1) Shift lever lock mechanism When the shift lever is in the “P” range, unless the ignition key is in the ON position and the brake pedal is depressed, no current flows to the shift lock solenoid, so the shift lever cannot be moved. When shift lock plate moves to the release side by the shift lock solenoid, the shift lever can be moved when pushing the shift lever knob button, the shift lock pin is pushed down and shift lock link moves downward.

(2) Key interlock mechanism When pushing the shift lever knob button, the shift lock pin is pushed down and the shift lock link moves downward. When the shift lever is moved to the ranges except ÅgPÅh range, the shift lock link is fixed at the lock position. And the key cylinder side lock pin is fixed on the lock side. The effect is that unless the shift lever is moved to the “P” range, the ignition key cannot be turned from ON or ACC to LOCK and the ignition key cannot be removed.

Control of ECT

The Engine & ECT ECU controls gear shift timing and lock-up by controls to the solenoid valves of the hydraulic control unit to maintain the optimal driving condition using the signals from the sensors and switches mounted on the engine and automatic transaxle. In addition, the ECU is provided with diagnosis and fail-safe functions when a sensor, etc., fails.

HINT:

The current ECU is an integration ofthe Engine ECU and ECT ECU, butpreviously it was separated.