Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Reexamination Certificate
1999-11-15
2001-05-29
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
Reexamination Certificate
active
06238016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling an electric or electro-hydraulic brake system of a vehicle such as an automobile against an unusual lowering of the output voltage of a battery forming an electric power source of the electric or electro-hydraulic brake system.
2. Description of the Prior Art
Not only in an electric brake system of a vehicle in which a braking force is directly generated from an electric current supplied from a battery of the vehicle but also in an electro-hydraulic brake system of a vehicle recently developed in a high variety as described in, for example, U.S. patent application Ser. No. 09/263,226 by the same assignee as the present application, in which a pump is driven by a battery of the vehicle to provide a pressurized brake fluid source, so that wheel cylinders of wheels are selectively supplied with the pressurized brake fluid from the source under a control of solenoid-actuated on-off valves, it is essential that the battery is operating at its normal condition.
In Japanese Patent Laid-open Publication 7-17375, it is described that in a brake system in which a brake oil pressure is normally controlled by a solenoid control valve according to a duty ratio of a control current supplied from a battery, when a lowering of the output voltage of the battery is detected by a voltage sensor, the duty ratio control is stopped, while the control valve is maintained at a constant position.
It is not correctly checked if a battery is in a normally operating condition or not when no substantial load is imposed on the battery. Therefore, it is considered to check the battery during an operation of the brake system, such that, for example, the output voltage thereof is detected by a sensor when the brake pedal is depressed beyond a predetermined depth. However, those modern electro-hydraulic brake systems under the recent high variety developments are mostly adapted to execute various automatic behavior controls such as anti-spin controls, anti-driftout controls, anti-overroll controls, etc. depending upon separate applications of a controlled braking to each of the generally four wheels, and therefore, the operation of the brake system is an integration of a driver's braking intention and a control calculation of an automatic behavior controller constructed by an electronic computer. Therefore, in those modern electro-hydraulic brake systems it is very difficult to check the battery operating condition under its prescribed loading condition.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems concerned with an appropriate maintenance of the battery of a vehicle such as an automobile equipped with such a modern electro-hydraulic brake system, it is a primary object of the present invention to provide a device for controlling such a modern electrohydraulic brake system with respect to the maintenance of a battery forming the electric power source thereof.
According to the present invention, the above-mentioned primary object is accomplished by a device for controlling an electro-hydraulic brake system of a vehicle having wheels, a battery and the electro-hydraulic brake system adapted to be energized by the battery and including wheel cylinders, a brake pedal, electric control means, a pump adapted to operate under a control of the electric control means for pressurizing a brake fluid, and on-off valves adapted to operate under a control of the electric control means for selectively supplying the brake fluid pressurized by the pump to each of the wheel cylinders, the device comprising:
means for detecting if vehicle speed is substantially zero;
means for detecting if the brake pedal is not substantially depressed; and
means for detecting output voltage of the battery;
wherein the electric control means control the pump and at least one of the on-off valves such that, when the vehicle speed detection means detect a substantially zero vehicle speed, while the brake pedal depression detection means detect substantially no depression of the brake pedal, the pump is operated with the at least one on-off valve being opened to supply the brake fluid pressurized by the pump to a corresponding one of the wheel cylinders for a predetermined time period, with the battery output voltage detection means detecting the output voltage of the battery in the meanwhile,
whereby the device judges the battery to be in a normal operating condition when the battery output voltage detected by the battery output voltage detection means in the meanwhile is not lower than a predetermined value.
By the device of the above-mentioned construction, the electro-hydraulic brake system of a vehicle is controlled such that the operating condition of the battery is checked always at a prescribed loading condition to be always correctly judged of the operating condition. Further, although such a prescribed loading of the battery for the checking of the operating condition thereof results in a substantial braking of at least one of the wheels of the vehicle, since it occurs while the vehicle is at a standstill, no disadvantageous effect is thereby encountered. When it was judged by the device that the output voltage of the battery in such a prescribed loading condition is lower than the predetermined value, it will be a matter of course that the fact is informed to the driver by an appropriate warning device such as a red lamp or the like.
According to an embodiment of the present invention, the electric control means may further control the operation of the pump so as to lower a delivery pressure thereof when the output voltage of the battery is lower than the predetermined value. By lowering the delivery pressure of the pump, the brake system will be able to operate normally for a longer time before the battery is repaired or replaced by a new one. The pump delivery pressure can be optionally lowered by appropriately lowering the voltage of the electric power supplied to a motor for driving the pump.
Further, when the delivery pressure of the pump is lowered as described above, it is desirable that the electric control means also control the operation of the pump so as to slower an acceleration of the pump. By so controlling, the consumption of the battery is lessened. The acceleration of the pump is optionally controlled by appropriately restricting the current of the electric power supplied to the pump drive motor.
When the vehicle is a four-wheeled vehicle having a pair of front wheels and a pair of rear wheels, the prescribed loading of the battery may be so arranged that the electric control means open the on-off valves for supplying the brake fluid to the wheel cylinders of the front left wheel and the rear right wheel, together with the operation of the pump.
Or, alternatively, the arrangement may be such that the electric control means open the on-off valves for supplying the brake fluid to the wheel cylinders of the front right wheel and the rear left wheel, together with the operation of the pump.
Or, further, the arrangement may be such that the electric control means open the on-off valves for supplying the brake fluid to the wheel cylinders of the front left wheel and the rear right wheel, together with the operation of the pump at one time of checking the battery, and open the on-off valves for supplying the brake fluid to the wheel cylinders of the front right wheel and the rear left wheel, together with the operation of the pump at a next time of checking the battery, and alternately so on.
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Butler Douglas C.
Oliff & Berridg,e PLC
Pezzlo Benjamin A.
Toyota Jidosha & Kabushiki Kaisha
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