Fluid-pressure and analogous brake systems – Multiple systems – Fluid pressure and electric
Reexamination Certificate
1999-11-15
2001-03-13
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Multiple systems
Fluid pressure and electric
C303S122050, C303S155000, C303S191000, C303S116100, C303S020000
Reexamination Certificate
active
06199957
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 with care for a battery forming an electric power source for 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.
In view of such a difficulty, the present inventor has proposed in a co-pending application No. 09/440,587 filed Nov. 15, 1999 a device for controlling an electro-hydraulic brake system of a vehicle incorporating a particular system for correctly checking the operating condition of the battery of the vehicle.
SUMMARY OF THE INVENTION
The inventor now turns his contemplation on a concept how the battery can be cared when the output voltage of the battery has lowered as detected by an appropriate device such as proposed by the above-mentioned separate application, or when it is anticipated that the battery will lose its normal operating condition in the near future, because an alternator for charging the battery is not normally operating, or further when the vehicles are driven by some drivers who have a habit of pumping the brake pedal when the vehicle is at a substantial standstill, thereby uselessly consuming the electric power of the battery.
In the electro-hydraulic brake system in which the brake fluid supplied to the wheel cylinders is pressurized by a pump driven by a motor energized by the battery of the vehicle, and is selectively supplied to a selected one or more of the wheel cylinders as controlled by electrically operated on-off valves such as solenoid valves energized by the battery according to depressions of the brake pedal by the driver, a substantial amount of electric power is consumed each time when an adjustment of the braking force is made, as the electrically energized on-off valve or valves must be changed over in the manner of reciprocation. When the adjustment of the braking force is to increase it, of course a further electric energy is consumed to pressurize the brake fluid to be supplied for increasing the braking force.
Particularly when the driver has a habit of pumping the brake pedal at a standstill of the vehicle, a substantial electric power of the battery is uselessly consumed, or in other words, herein there exists a good chance of caring the battery against losing its normal operating condition, or the life, if such a useless consumption of the battery is avoided.
Therefore, it is a primary object of the present invention to provide a device for controlling an electro-hydraulic brake system of a vehicle such as an automobile in such a construction that a care is provided for its battery when it suffers a trouble such as a lowering of the output voltage thereof, or when it is anticipated that such a trouble will occur in the near future, or further when a saving of a useless consumption of the electric power of the battery is possible.
According to the present invention, the above-mentioned primary object is first accomplished by a device for controlling an electro-hydraulic brake system of a vehicle having wheels, a battery, an alternator for charging the 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 the battery is normally operating;
wherein the electric control means control the operation of the pump and the on-off valves such that the pressure of the brake fluid supplied to the wheel cylinders is restricted not to be higher than a first predetermined value lower than a standard output voltage of the battery when the battery detection means detect that the battery is not normally operating.
By the device of the above-mentioned construction, the electro-hydraulic brake system of a vehicle is controlled such that it operates at such lowered pressure values which do not exceed the first medium pressure value when at least it is detected that the battery is not normally operating, so that the battery is cared for its suffering, so as to be able to operate a longer until it is repaired or replaced by a new one.
The device according to the present invention may further comprise means for detecting if the alternator is normally operating, and the electric control means may control the operation of the pump and the on-off valves such that the pressure of the brake fluid supplied to the wheel cylinders is restricted not to be higher than a second predetermined medium pressure value when the alternator detection means detect that the alternator is not normally operating. By such an arrangement, the battery is cared against failing due to a failure of the alternator.
The device according to the present invention may further comprising means for detecting if the vehicle is substantially at a standstill, and means for detecting if the brake pedal is pumped by a driver, and the electric control means may control the operation of the pump and the on-off valves such that the pressure of the brake fluid supplied to the wheel cylinders is restricted not to be higher than a third predetermined medium pressure value when the brake pedal is pumped at a substantial standstill of the vehicle. By such an arrangement, the battery is further cared against a useless consumption by the habit of pumping the brake pedal at a substantial standstill of the vehicles of some drivers.
Since drivers will not do such a pumping of the brake pedal under a condition that a strong braking is required to hold the vehicle, it will be appreciated that t
Butler Douglas C.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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