Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1998-12-21
2001-10-23
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C188S356000, C060S397000
Reexamination Certificate
active
06305757
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brake booster negative pressure controller and, more particularly, to a brake booster negative pressure controller for use in an engine operated in a state where a suction negative pressure is low.
In recent years, a vehicle is often provided with a brake booster in order to reduce the stepping force when a brake pedal of the vehicle is stepped on. The brake booster is partitioned into two chambers A and B by a diaphragm therein. An assist force upon braking is obtained by the difference between pressures in the chambers. The chamber A as one of the two chambers is connected to an intake manifold of a suction system of an engine via a one-way valve by piping. When the negative pressure in the intake manifold is higher than that in the brake booster, the one-way valve is opened and the negative pressure in the intake manifold is introduced into the chamber A. In a state where the brake is not applied, the pressures in the two chambers are equal. When the brake is applied, atmosphere is introduced into one of the chambers, causing the pressure difference between the two chambers, and the assist force upon braking is consequently obtained.
In lean-burn engine, cylinder injection engine, or the like, however, operation is performed while taking a large volume of new air, so that only a negative pressure lower than a conventional one is obtained in the intake manifold. Consequently, the negative pressure in the brake booster cannot be sufficiently increased and a sufficient assist force cannot be obtained upon braking.
In order to solve such a problem, the technique (refer to Japanese Patent Application Laid-Open No. 7-247866) of always monitoring the pressure in the brake booster, closing a throttle valve by a predetermined amount while the pressure value is on the atmosphere side more than a predetermined threshold, and increasing the negative pressure in the intake manifold has been proposed.
On the other hand, there is provided the technique (refer to Japanese Patent Application Laid-Open No. 8-164840) of a brake booster negative pressure controller comprising: pressure sensing means for sensing a pressure acting on a brake booster; throttle valve closing means for closing the throttle valve by a predetermined amount when a pressure sensed by the pressure sensing means is lowered below a predetermined threshold pressure; brake operation sensing means for sensing the operation of the brake; and throttle valve closing means for closing the throttle valve by a predetermined amount in the case where the pressure sensed by the pressure sensing means is lowered below the predetermined threshold pressure when the brake is operated by brake operating means.
The braking performance required of the brake is largely influenced by the driving state of the vehicle. When the speed is high, the higher braking performance is necessary. The above-mentioned two techniques of the negative pressure controller intend to always obtain the brake booster negative pressure of a predetermined amount or more at an arbitrary speed. As a result, sufficient braking performance can be always obtained at an arbitrary speed of the vehicle. For this purpose, however, the negative pressure threshold has to be determined on the basis of a case where the highest braking performance is required (at the time of high speed of the vehicle or the like) as a reference.
Consequently, even when the sufficient braking performance is assured at the time of low speed (sufficient negative pressure is assured in the brake booster), the throttle valve is closed by a predetermined amount at the time point when the negative pressure in the brake booster becomes lower than the threshold. Because of the useless operation, there are problems that pumping loss of the engine is increased and the fuel consumption deteriorates.
When the brake is applied while the accel is stepped on, the braking performance higher than that in an ordinary state is required since the braking is already applied. In the conventional brake booster negative pressure controller, however, no measure is taken against the case.
Further, when the negative pressure in the brake booster cannot be normally sensed due to a failure in a sensor or the like, even if the negative pressure in the brake booster is insufficient, there is a case that such a state cannot be detected. There is consequently the possibility that the sufficient braking performance cannot be obtained.
SUMMARY OF THE INVENTION
The present invention is made in consideration of the problem and it is an object of the invention to provide a brake booster negative pressure controller which reduces deterioration in the fuel consumption caused by throttle closing operation for assuring the brake booster negative pressure while assuring a braking capability required according to driving conditions and which can safely assure the braking capability even when a failure occurs in the negative pressure sensing system.
In order to achieve the object, according to the invention, there is provided a brake booster negative pressure controller comprising a brake booster for assuring a master vac negative pressure by using a negative pressure of an engine, a throttle valve whose opening angle can be operated independently from a stroke of an accel, and a brake operation sensing means, characterized in that the negative pressure controller has a vehicle speed sensing means and a means for closing the throttle valve by a predetermined amount when the vehicle speed sensed by the vehicle speed sensing means is equal to or higher than a predetermined value and application of a brake is sensed by the brake operation sensing means.
According to another fundamental embodiment of the invention, there is provided a brake booster negative pressure controller comprising a brake booster for assuring a master vac negative pressure by using a negative pressure of an engine, a throttle valve whose opening angle can be operated independently from a stroke of an accel, a negative pressure sensing means for sensing a negative pressure in the brake booster, a means for closing the throttle valve by a predetermined amount when the detection value obtained by the negative pressure sensing means becomes a value on an atmosphere side more than a predetermined value, and a brake operation sensing means, characterized in that the negative pressure controller has a vehicle speed sensing means and a means for closing the throttle valve by a predetermined amount when the vehicle speed sensed by the vehicle speed sensing means is equal to or larger than a predetermined value and application of a brake is sensed by the brake operation sensing means.
According to an embodiment of the invention, a brake booster negative pressure controller is characterized by comprising a means for changing the throttle valve closing amount on the basis of the vehicle speed sensed by the vehicle speed sensing means or a brake booster negative pressure sensed by the negative pressure sensing means.
Further, according to another preferable embodiment, the brake booster negative pressure controller of the invention is characterized by comprising an accelator hereinafter, accel stroke estimating means for estimating an accel stroke, and that the throttle valve is closed by a predetermined amount when the estimation value of the accel stroke is equal to or larger than a predetermined value and application of the brake is sensed by the brake operation sensing means.
According to one of embodiments, the accel stroke estimating means comprises an engine negative pressure sensing means and an engine negative pressure determining means for determining that the driver performs an operation for continuing the driving when the engine negative pressure is equal to or lower than a predetermined value. According to another embodiment, the accel stroke estimating means comprises an intake air flow rate sensing means and an intake air flow rate determining means for determining that the driver performs an operation for
Ohsaki Satoru
Takano Yoshiya
Yano Hirofumi
Crowell & Moring LLP
Hitachi , Ltd.
Oberleitner Robert J.
Williams Thomas J.
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