Brakes – Operators – Automatic
Reexamination Certificate
2001-09-12
2003-03-18
Lavinder, Jack (Department: 3683)
Brakes
Operators
Automatic
Reexamination Certificate
active
06533081
ABSTRACT:
RELATED APPLICATIONS
This application claims priority to Japanese Patent Application No. P2000-275783 filed on Sep. 11, 2000 in Japan. The contents of the aforementioned application are hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a brake fluid pressure retaining apparatus for continuously retaining brake fluid pressure within a wheel cylinder after releasing the brake pedal. The brake fluid pressure retaining apparatus is mounted on a vehicle, which is equipped with an automatic transmission and a driving force control unit for making a creep driving force smaller at a depression of the brake pedal than at a release of the brake pedal.
BACKGROUND OF THE INVENTION
Various brake fluid pressure retaining apparatus are known. The brake fluid pressure retaining apparatus continuously retains brake fluid pressure within a wheel cylinder after releasing the brake pedal so that the braking force continuously acts on the vehicle. For example, the applicants disclose a brake fluid pressure retaining apparatus in Japanese Patent Application No. Hei-11-164621 (unpublished), in which brake fluid pressure passages are provided with a solenoid valve and a bypass passage bypassing the solenoid valve is provided with a restriction. The brake fluid pressure retaining apparatus gradually decreases and releases the retained brake fluid pressure through the restrictions when a certain time (about 1 second) passes after the driving force is changed into a greater condition. For this reason, the brake fluid pressure retaining apparatus ensures a starting operation of the vehicle on an up slope as well as a smooth starting operation of the vehicle on a down slope, at which a displacement force due to the vehicle's own weight affects on, without a sudden feel of the driver.
However, there is a possibility that the vehicle undesirably moves or displaces backwards when starting from an up slope, because of the relations between the inclination of the slope, the retained brake fluid pressure and the like. If the driver releases the retained brake fluid pressure while the vehicle rolling down the slope, the backward displacement amount of the vehicle is increased and the driver experiences an awkward feel. Therefore, a smooth starting operation of the vehicle is required on an up slope. Meanwhile, a smooth start without sudden impacts is also required on a down slope.
Accordingly, the object of the present invention is to provide a brake fluid pressure retaining apparatus, which ensures a smooth starting operation of the vehicle on an up slope with decreased backward displacement amount of the vehicle and also ensures a smooth starting operation on a down slope.
The term “backward displacement” is also referred to as a “backward movement” throughout the specification and the claims.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a brake fluid pressure retaining apparatus in combination with a vehicle equipped with a driving force control unit, the driving force control unit which transmits a driving force from a driving motor to driving wheels when a transmission is set in a driving range even after a depression of an accelerator pedal is released at a certain or lower vehicle speed, and which switches the magnitude of the driving force transmitted to the driving wheels between a greater condition and a smaller condition in accordance with a depression of a brake pedal, so that the driving force is made smaller at a depression of the brake pedal than at a release of the brake pedal, the brake fluid pressure retaining apparatus comprising:
a brake fluid pressure passage connecting a master cylinder and a wheel cylinder;
a solenoid valve provided in the brake fluid pressure passage and switchable between a communicating position, where the brake fluid pressure passage communicates, and a shut-off position, where the brake fluid pressure passage is shut off;
a bypass passage equipped with a restriction for communicating the master cylinder and the wheel cylinder respective of the shut-off position of the solenoid valve; and
a control unit for switching the solenoid valve between the communicating position and the shut-off position, wherein said control unit is constituted such that the solenoid valve is switched to the shut-off position for retaining brake fluid pressure within the wheel cylinder when the vehicle is stopped with the brake pedal depressed, and that the solenoid valve is switched to the communicating position for releasing the retained brake fluid pressure when a first setting time passes after the driving force is increased to the greater condition due to the release of the brake pedal,
and wherein said brake fluid pressure retaining apparatus further comprises a backward movement state determination device for determining a backward movement state of the vehicle, and wherein said control unit is constituted such that when the vehicle is determined as being in a backward movement state, said solenoid valve is switched to the communicating position after a second setting time passes, so as to retain brake fluid pressure for a period longer than the first setting time.
With such a constitution of the brake fluid pressure retaining apparatus, because brake fluid pressure is continuously retained within the wheel cylinder after releasing the brake pedal, the vehicle is prevented from undesirably rolling down a slope upon starting from the slope. The control means releases the retained brake fluid pressure when the setting time passes after the driving force is increased to the greater condition due to release of the brake pedal. When doing so, the brake fluid pressure is not retained constantly. The retained brake fluid pressure is gradually decreased by the flow rate control of the bypass passage equipped with a restriction. For this reason, the braking force is released gradually and slowly, which leads to a smooth starting operation of the vehicle on both up and down slopes without any sudden impacts.
Meanwhile, when the backward movement state determination device determines that the vehicle is undesirably rolling down a slope (backward movement detected) after the depression of the brake pedal is released and during the first setting time, the control means releases the retained brake fluid pressure when the second setting time passes, so as to retain the brake fluid pressure longer than the first setting time and continuously restrict the backward movement of the vehicle. The second setting time is for extending or delaying the first setting time. Because the second setting time is set only when the vehicle undesirably rolls down a slope, unnecessary brake dragging does not arise at a start of the vehicle unless the vehicle moves backwards.
Herein, the term “a certain vehicle speed” indicates that the vehicle is stopped (or the vehicle speed=0 km/h) or the vehicle runs at a vehicle speed just before stopping. Therefore, if the certain vehicle speed is set to be 0 km/h, the term “at a certain or lower vehicle speed” only indicates the vehicle speed of 0 km/h. Alternatively, as an example of the preferred embodiment to be described later, if the certain vehicle speed is set to be 5 km/h, the term “at a certain or lower vehicle speed” indicates a vehicle speed range from 0 km/h to 5 km/h.
Further, the term “smaller condition” or “made smaller” includes an instance when the driving force is decreased to zero (in the preferred embodiment to be described later, the instance when the engine is stopped). Therefore, the term “the driving force is increased to the greater condition” includes (1) an instance that the driving force arises from zero and thereafter increases (in the preferred embodiment, the instance that the driving force is increased from the engine stop condition to the strong creep condition) and (2) an instance that the existing driving force further increases (in the preferred embodiment, the instance that the driving force is increased from the weak creep condition to the s
Katsuta Keisuke
Totsuka Hirohiko
Yamaguchi Masaaki
Bartz C. T
Honda Giken Kogyo Kabushiki Kaisha
Lavinder Jack
LandOfFree
Brake fluid pressure retaining apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brake fluid pressure retaining apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brake fluid pressure retaining apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3007356