Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-04-21
2001-09-04
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06283559
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a negative pressure control apparatus for a brake booster, and particularly to a negative pressure control apparatus for controlling negative pressure of a brake booster which assists a brake operation by using intake manifold negative pressure of a direct-injection engine as a power source.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Laid-Open Patent Application No. 5-208663, a braking apparatus having a brake booster is known. The brake booster is a mechanism which assists a brake operation by using an intake manifold negative pressure as a power source so that a larger braking force can be generated.
Generally, in a case of a regular engine which controls an opening of a throttle valve in accordance with an acceleration operation, when a driver intends to decelerate a vehicle, that is, when an accelerator pedal is not depressed, the throttle valve is closed so that a relatively large intake manifold negative pressure is generated. Thus, when the driver performs a brake operation, the brake booster can be positively operated.
The above-mentioned conventional braking apparatus has a function of performing an automatic brake control for generating a braking force irrespective of whether or not a brake operation is performed when an obstacle is detected ahead of the vehicle. In the above-mentioned conventional braking apparatus, the brake booster is constructed so that it can generate a required braking force when no brake operation is performed. However, if the automatic brake control is performed when the driver intends to accelerate the vehicle, that is, when the throttle valve is opened, the intake manifold negative pressure is decreased. In this case, the negative pressure in the brake booster may become insufficient and the brake booster in the automatic brake control may not generate the required braking force. In order to avoid such a problem, the above conventional braking apparatus generates an intake manifold negative pressure which is sufficient for performing the automatic brake control by forcibly closing the throttle valve when an establishment of a condition for starting the automatic brake control is predicted.
Conventionally, a direct-injection engine is known which has a fuel injector disposed inside a combustion chamber and directly injects fuel in the combustion chamber. According to the direct-injection engine, fuel economy can be improved by fully opening a throttle valve so that a pumping loss of the engine is reduced when, for example, the engine is operating under a low load. Thus, in the direct-injection engine, the intake manifold negative pressure may be decreased by the throttle valve being fully opened when an acceleration operation is not being performed. Consequently, in a vehicle having the direct-injection engine, the negative pressure in the brake booster may become insufficient when the driver intends to decelerate the vehicle.
However, the above-mentioned conventional braking apparatus is adapted to be applied to the regular engine in which a sufficient intake manifold negative pressure is generated by the throttle valve being closed when a vehicle is decelerated. Therefore, if the above-mentioned conventional braking apparatus is applied to the direct-injection engine, it is possible that a sufficient braking force cannot be generated due to insufficient negative pressure in the brake booster when the driver performs a brake operation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a negative pressure control apparatus for a brake booster which can always maintain a required negative pressure in the brake booster in a system which includes a direct-injection engine.
The above object of the present invention can be achieved by a negative pressure control apparatus for a brake booster for controlling negative pressure in a negative pressure chamber of the brake booster which can be connected to an intake pipe of an engine at a position downstream of a throttle valve, the apparatus comprising:
a brake operation predicting part for predicting execution of a brake operation by a driver; and
a booster negative pressure controller for controlling the negative pressure in the negative pressure chamber to be a required value when execution of a brake operation is predicted.
In this invention, negative pressure in the negative pressure chamber of the brake booster is controlled to be a required value when execution of a brake operation is predicted. Thus, it is possible to maintain a sufficient negative pressure in the negative pressure chamber of the brake booster for assisting a brake operation in a system which includes a direct-injection engine. Therefore, according to the invention, a sufficient braking force can always be generated when a brake operation is performed.
In this case, when a vehicle is running on a downhill road, it can be judged that a driver is likely to perform a brake operation so as to suppress an increase in a vehicle speed. Thus, the brake operation predicting part may predict execution of a brake operation when a vehicle is running on a downhill road.
Additionally, when a vehicle behavior control such as a vehicle stability control (VSC) or a traction control (TRC) for controlling a behavior of a vehicle is being performed, it can be judged that a driver is likely to perform a brake operation so as to decelerate the vehicle. Thus, the brake operation predicting part may predict execution of a brake operation when the vehicle behavior control is being performed.
Additionally, when a between-car time to a car running ahead (that is, a value obtained by dividing a distance to a vehicle running ahead by an approaching speed relative to that car) is small, it can be judged that the driver is likely to perform a brake operation so as to avoid a contact with the car running ahead. Thus, the brake operation predicting part may predict execution of a brake operation when the between-car time to a car running ahead is smaller than a predetermined value.
Additionally, when a vehicle is running towards a crossing or a freeway exit, it can be judged that a driver is likely to decelerate the car. Thus, the brake operation predicting part may predict execution of a brake operation when a vehicle is running towards a crossing or a freeway exit
Additionally, a driver performs a shift-down operation when he intends to decelerate a car. In this case, it can be judged that the driver is likely to perform a brake operation. Thus, the brake operation predicting part may predict execution of a brake operation when a driver performs a shift-down operation.
Similarly, a driver releases a depression of an accelerator pedal at a high speed when he intends to decelerate a vehicle. Thus, the brake operation predicting part may predict execution of a brake operation when a depression of an accelerator pedal is being released at a speed greater than a predetermined value.
Further, when a driver shifts a shift lever to a neutral position or shifts a select lever to an N range, it can be judged that the driver is likely to intend to stop a vehicle. Thus, the brake operation predicting part may predict execution of a brake operation when the shift lever is in a neutral position or the select lever is in an N range.
Additionally, the negative pressure in an intake passage downstream of a throttle valve changes in accordance with an opening of the throttle valve. Thus, the negative pressure controller may control the negative pressure in the negative pressure chamber of the brake booster by changing the opening of the throttle valve.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 3754841 (1973-08-01), Grabb et al.
patent: 3799303 (1974-03-01), Stoltman
patent: 3947073 (1976-03-01), Cattaneo et al.
patent: 5408411 (1995-04-01), Nakamura et al.
patent: 5564796 (1996-
Endo Hiroaki
Watanabe Ryochi
Yamada Yoshihisa
Nguyen Xuan Lan
Oberleitner Robert J.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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