HYDRAULIC CONTROL UNIT

In the hydraulic control unit of the MGH-25 system,

- Pump

- Valve block

Are grouped together in one housing, forming one compact unit with the electric motor. The pump and valve concepts are largely identical with the proven MGH ABS production system.

The pump itself is a silenced two-circuit pump driven by an electric motor. The solenoid valves which modulate the pressuring during ESP control are also integrated.

Peculiar things to MGH-25 ESP hydraulic are that shuttle valve is changed to solenoid type from hydraulic type and TC valve is repositioned. This is because ESP system controls the brake pressure of 4 wheels respectively while driving unlike the TCS which controls the brake pressure of 2 driving wheels in operation.

For a diagonal brake circuit split (K), four pairs of valves (4 inlet valves, 4 outlet valves) are provided for modulating the pressure at the wheels plus two isolating valves and two electrically operated shuttle valves.

The common housing furthermore accommodates a low-pressure accumulator and a silencing chamber for each brake circuit.

HYDRAULIC CIRCUIT

INLET SOLENOID VALVE (NO VALVE)

This valve connects or disconnects the hydraulic path between master cylinder and the wheel cylinders. It remains open normally but it is closed when the dump and hold mode begins during ABS operation. Check valve is to help the brake fluid returning from the wheel cylinder to the master cylinder when the brake pedal is released.

OUTLET SOLENOID VALVE (NC VALVE)

This valve is normally closed but it is opened to release the wheel cylinder pressure when a dump mode begins.

SHUTTLE VALVE

The valve type is changed to the solenoid valve type for MGH-25 model from the hydraulic valve type that is used in TCS. When the ESP is in operation, the brake fluid should be supplied to the motor pump from the M/C via the shuttle valve to generate the brake pressure. This solenoid valve is closed and blocks the passage when a brake pedal is applied.

TRACTION CONTROL VALVE (TC VALVE)

In case of a normal condition, this valve remains open and the brake pressure from the M/C can be applied to the front wheel via TC valve. While TCS or ESP in operation, TC valve is closed and the generated pressure by motor delivers to wheel cylinders without returning to the master cylinder. TC valve includes a relief valve and a check valve. When excessive pressure is supplied from the motor, relief valve is opened and the pressure is relieved.

Date: 2016-03-03; view: 965