Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-01-11
2002-02-19
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C188S356000
Reexamination Certificate
active
06347842
ABSTRACT:
This application is based on Japanese Patent Applications No. 11-4241 filed Jan. 11, 1999, No. 11-123604 filed Apr. 30, 1999 and No. 11-184816 filed Jun. 30, 1999, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a hydraulically operated braking system, and more particularly to a hydraulic pressure source apparatus for a hydraulically operated braking system.
2. Discussion of the Related Art
JP-A-2-169355 discloses a braking hydraulic pressure source apparatus including (1) a cylinder housing, (2) a pressurizing piston fluid-tightly and slidably received in the cylinder housing and cooperating with the cylinder housing to define a front pressurizing chamber and a rear assisting pressure chamber on respective front and rear sides of the pressurizing piston, the pressurizing piston being advanced in response to an operation of a brake operating member by an operator, to pressurize a working fluid in the front pressurizing chamber, and (3) an assisting pressure control device for controlling a pressure of the working fluid in said rear assisting pressure chamber (hereinafter referred to as “assisting hydraulic pressure”).
Where this braking hydraulic pressure source apparatus is used in a hydraulically operated braking system for an automotive vehicle, the working fluid in the rear assisting pressure chamber is pressurized to develop the assisting hydraulic pressure, so that the braking system performs a traction control for a drive wheel of the vehicle. Described in detail, the traction control is initiated without an operation of the brake operating member by the vehicle operator, with the assisting hydraulic pressure being applied to the rear assisting pressure chamber by the assisting pressure control valve, in response to a signal indicating an excessive amount of traction force acting on the drive wheel, so that the pressurizing piston is advanced to pressurize the working fluid in the front pressurizing chamber. As a result, the working fluid in the front pressurizing chamber pressurized by the pressurizing piston is supplied to a wheel brake cylinder connected to the front pressurizing chamber, so that the pressure of the working fluid in the wheel brake cylinder is increased for braking the drive wheel. The fluid pressure in the wheel brake cylinder is controlled by a pressure control valve device, so as to regulate the traction force of the drive wheel such that the amount of slip of the drive wheel on the road surface is held within an optimum range.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide an improved braking hydraulic pressure source apparatus having an assisting pressure chamber as described above.
A second object of this invention is to provide a hydraulically operated braking system equipped with such an improved braking hydraulic pressure source apparatus.
The first or second object indicated above may be achieved by any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, so as to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A braking hydraulic pressure source apparatus comprising: a cylinder housing; a pressurizing piston fluid-tightly and slidably received within the cylinder housing and cooperating with the cylinder housing to define a front pressurizing chamber and a rear assisting pressure chamber on respective front and rear sides of the pressurizing piston, the pressurizing piston being advanced in response to an operation of a brake operating member, to pressurize a working fluid in the front pressurizing chamber; and an electrically controlled assisting pressure control device for controlling an assisting hydraulic pressure which is a pressure of the working fluid in the rear assisting pressure chamber, such that a boosting ratio which is a ratio of an output of the pressurizing piston to an input of the pressurizing piston is controlled to be a predetermined value.
In the braking hydraulic pressure source apparatus, the pressurizing piston receives a primary drive force based on an operating force acting on the brake operating member, and an assisting drive force based on the assisting hydraulic pressure in the rear assisting pressure chamber. As a result, the pressurizing piston is advanced by a sum of these primary and assisting drive forces, and the working fluid in the front pressurizing chamber is pressurized to a value corresponding to the above-indicated sum. Where the brake operating member is directly connected to the pressurizing piston, the primary drive force is substantially equal to the operating force applied to the brake operating force by an operator. Where a booster is provided between the brake operating member and the pressurizing piston, the primary drive force is an output force of the booster which boosts the operating force applied to the brake operating member.
When the primary drive force is held constant, an increase of an assisting force by increasing the assisting hydraulic pressure results in an increase of the boosting ratio, and a reduction of the assisting force by reducing the assisting hydraulic pressure results in a reduction of the boosting ratio. Thus, the boosting ratio of the braking hydraulic pressure source apparatus can be controlled by controlling the assisting hydraulic pressure in the rear assisting pressure chamber. In the braking hydraulic pressure source apparatus according to the above mode (1) of this invention, the assisting hydraulic pressure is electrically controlled by the electrically controlled assisting pressure control device, such that the boosting ratio is controlled to be the predetermined value. This predetermined value may be either a constant value irrespective of the input and output of the pressurizing piston, or a variable which changes in steps or continuously depending upon the input and output of the pressurizing piston. In the present braking hydraulic pressure source apparatus, the boosting ratio is controlled to be the predetermined value. However, the principle of the present invention does not exclude a control of the boosting ratio depending upon the operating state of the brake operating member, the operating condition of a braking system for which the present braking hydraulic pressure source apparatus is used, and the running condition of an automotive vehicle on which the braking system is provided.
In the conventional braking hydraulic pressure source apparatus, the assisting hydraulic pressure is controlled while the braking system is performing a traction control for a drive wheel, without an operation of the brake operating member. However, the conventional braking hydraulic pressure source apparatus is not adapted to control the assisting hydraulic pressure during an operation of the brake operating member for effecting a normal braking operation. In the present braking hydraulic pressure source apparatus, the assisting hydraulic pressure is controlled at least during a normal braking operation of the braking system with an operation of the brake operating member. This is a departure from the conventional concept, based on a finding of a new application of the assisting pressure chamber for improved performance of the braking hydraulic pressure source apparatus.
As discussed above, the input of the pressurizing piston is boosted into its output by electric control of the assisting hydraulic pressure by
Butler Douglas C.
Nguyen Xuan Lan
Toyota Jidosha & Kabushiki Kaisha
LandOfFree
Braking hydraulic pressure source apparatus wherein... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Braking hydraulic pressure source apparatus wherein..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Braking hydraulic pressure source apparatus wherein... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2982007