Mitsubishi Jidosha Kogyo Kabushiki Kaisha

Hiromichi Yasunaga

Tadao Tanaka

Takao Morita

Tsutomu Matsukawa

Yasutaka Taniguchi

Masanori Tani

Akihiko Togashi

A control method and an apparatus therefor, in which the braking force distribution to rear wheels is increased in a normal state, while the braking force distribution to the rear wheels is reduced to prevent the rear wheels from being locked in an early stage when the road surface is slippery. There are provided a pressure sensor (74) for detecting a master cylinder pressure, proportioning valves (57.sub.1, 57.sub.2) arranged in passages which connect a master cylinder and rear wheel cylinders and adapted to operate so that the ratios of the wheel cylinder pressures to the master cylinder pressure are low in a region where the master cylinder pressure is not lower than a predetermined pressure, normally-open switching valves (62, 63) by-passing the two valves, and a controller (71). The controller closes the switching valves to actuates the proportioning valves when the master cylinder pressure detected by the pressure sensor is not lower than a set pressure which lowers depending on the slipperiness of the road surface.

Rear wheel braking force control method and an apparatus therefor

A rear wheel braking force control apparatus of a vehicle includes a pressure sensor 74 for detecting master cylinder pressure, right and left proportioning valves 57.sub.1 and 57.sub.2 individually disposed in passages for transmitting master cylinder pressure to right and left wheel cylinders of the rear wheels for controlling to decrease changes in wheel cylinder pressure relative to changes in master cylinder pressure, right and left PCV bypass valves 62 and 63 for individually bypassing the proportioning valves, and a controller 71 which, when the vehicle is determined by a steering angle sensor 77 or the like to be turning, closes the PCV bypass valve at the outer wheel side when the master cylinder pressure is higher than the pressure of the PCV bypass valve at the inner wheel side.

Apparatus and method for controlling rear wheel braking force of vehicle

When a master cylinder pressure detected by way of a pressure sensor (74) attains a level not lower than a target pressure (P.sub.OK), normally-open on-off valves (62, 63) for by-passing proportioning control valves (57.sub.1, 57.sub.2) are opened. If the slip factor of rear wheels, calculated by way of a slip factor calculation section (121), is not lower than a predetermined value, the on-off valves (64, 66) are opened to allow the rear wheel cylinder pressure to escape to accumulators (65, 67). Thus, if there is enough room for the increase of the braking force on the rear wheels, the rear wheel braking force can be increased to reduce the share of the front wheel braking force, depending on braking conditions, such as the road surface conditions, vehicle running conditions, etc. Further the rear wheels can be prevented from being locked.

A first target value is set as an initial value of split point pressure, a master cylinder pressure is set as a second target value of split point pressure in a memory when ABS valves (17, 20, and 23) are operated, thereafter when a sign of locking of the rear wheels is detected, the target value is reduced even further and set in the memory, the target value is maintained for a predetermined time by timer control at every setting of a new target value, and when a braking deceleration generated while the target value is maintained in the memory, a controller (37) controls so that the target value is increased after the completion of braking. When the master cylinder pressure is higher than the target value stored in the memory, proportioning valves (26 and 27) are closed to decrease a ratio of the rear wheel braking force to the front wheel braking force, thereby always achieving appropriate control over the rear wheel braking force allocation.

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Okazaki, Japan

Hiromichi Yasunaga