Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-06-01
2001-10-09
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S069000, C701S081000, C303S139000, C303S149000, C303S190000, C303S189000
Reexamination Certificate
active
06301541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a braking force control apparatus for vehicles and a braking force control method for vehicles, which performs control of braking force of the vehicles.
2. Related Background Art
An example of the conventionally known braking force control apparatus is one constructed to detect wheel speeds of driving wheels of a vehicle and apply braking force according to deviation of the wheel speeds of the driving wheels to limit the wheel speeds of the respective driving wheels to within a fixed range, as described in Japanese Patent Application Laid-Open No. 8-133054. This apparatus is intended to restrain slipping or hunting from appearing at the driving wheels, by appropriately controlling the braking force on the driving wheels so as to limit the wheel speeds of the respective driving wheels to within the fixed range.
SUMMARY OF THE INVENTION
The conventional braking force control apparatus of this type, however, presents the following problem when applied to four-wheel drive vehicles equipped with a center differential for distributing the driving force to the front wheels and the rear wheels and absorbing a rotational speed difference between the front and rear axles. If a four-wheel drive vehicle is in an unlocked state of the center differential in order to avoid the tight corner braking phenomenon or the like and travels on an unpaved steep downhill road in that state with use of engine braking, one of the wheels can go into a road-contactless state (in which the wheel loses adhesion to the road) and the engine drag-torque expected to act as braking force to the other wheels will be transmitted to only the wheel in the road-contactless state. In this event sufficient braking force will not be expected from the other wheels. At this time the wheel in the road-contactless state will rotate backward because of the transmission of the engine drag-torque, but the sufficient braking force cannot be expected from the braking of only that wheel, either.
It is also conceivable to assure the sufficient braking of the vehicle by forcedly applying the braking force to the wheels when there occurs such an event of the wheel in the road-contactless state. In this case, however, the master cylinder is kept in a non-communicated state (interrupted state) with respect to the wheel cylinders. If this state continues during the forced braking, the stroke of the brake pedal will be always limited during that braking. Should a hydraulic sensor of the master cylinder break down during the forced braking, a rise in the hydraulic pressure of the master cylinder would not be detected even with driver's actuation of the brake pedal and the stop lamp switch would fail to be switched on, because the stroke of the brake pedal is restricted. This would raise the possibility of failing to release the forced braking, whereby appropriate vehicle braking cannot be made according to the driver's will.
The present invention has been accomplished in order to solve the problem described above and an object of the present invention is, therefore, to provide a braking force control apparatus for vehicles and a braking force control method for vehicles that assures the appropriate vehicle braking even with either of the wheels being in the road-contactless state.
Namely, a braking force control apparatus for vehicles according to the present invention is a braking force control apparatus adapted to a four-wheel drive vehicle comprising a center differential for distributing and transmitting driving force to front wheels and rear wheels, and a braking system capable of exerting braking force on a specific wheel, based on voluntary switching between braking according to driver's brake-pedal actuation and forced braking independent of the brake-pedal actuation, the braking force control apparatus comprising: engine brake determining means for determining whether the vehicle is in an engine brake state; road-contactless state determining means for determining whether at least one of the wheels is in a road-contactless state; and braking control means for exerting the braking force based on the forced braking on the wheels other than the at least one wheel while permitting the braking force based on the driver's brake-pedal actuation to be exerted on the at least one of the wheels, when the engine brake determining means determines that the vehicle is in the engine brake state and when the road-contactless state determining means determines that the at least one of the wheels is in the road-contactless state.
The braking force control apparatus for vehicles according to the present invention is also characterized in that when the engine brake determining means determines that the vehicle is in the engine brake state and when the road-contactless state determining means determines that the at least one of the wheels is in the road-contactless state, the braking control means permits the braking force based on the driver's brake-pedal actuation to be exerted on wheels associated with part of a plurality of brake lines while exerting the braking force based on the forced braking on the wheels associated with the other lines, and the braking control means changes the lines under permission to exert the braking force based on the driver's brake-pedal actuation and the lines subjected to the braking force based on the forced braking at predetermined timing.
The braking force control apparatus for vehicles according to the present invention is also characterized in that the engine brake determining means, the road-contactless state determining means and the braking control means are ECU.
A braking force control method for vehicles according to the present invention is a braking force control method adapted to a four-wheel drive vehicle comprising a center differential for distributing and transmitting driving force to front wheels and rear wheels, and a braking system capable of exerting braking force on a specific wheel, based on voluntary switching between braking according to driver's brake-pedal actuation and forced braking independent of the brake-pedal actuation, the braking force control method comprising the steps of: determining whether the vehicle is in an engine brake state; determining whether at least one of the wheels is in a road-contactless state; and exerting the braking force based on the forced braking on the wheels other than the at least one wheel while permitting the braking force based on the driver's brake-pedal actuation to be exerted on the at least one of the wheels, when determining that the vehicle is in the engine brake state and when determining that the at least one of the wheels is in the road-contactless state.
The braking force control method for vehicles according to the present invention is also characterized in that the step of exerting the braking force includes permitting the braking force based on the driver's brake-pedal actuation to be exerted on wheels associated with part of a plurality of brake lines while exerting the braking force based on the forced braking on the wheels associated with the other lines, and changing the lines under permission to exert the braking force based on the driver's brake-pedal actuation and the lines subjected to the braking force based on the forced braking at predetermined timing when determining that the vehicle is in the engine brake state and when determining that the at least one of the wheels is in the road-contactless state,
According to the invention described above, the braking ability of the vehicle can be improved by exerting the braking force forcedly on the wheels when the vehicle is running in the engine brake state and when at least one of the wheels is in the road-contactless state. On that occasion the braking force according to the driver's brake-pedal actuation is permitted to be exerted on at least one of the wheels, whereby the driver is allowed to actuate the brake pedal even in the forced braki
Hosomi Kazushi
Ishida Yasuhito
Ishikawa Toshimi
Beaulieu Yonel
Cuchlinski Jr. William A.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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