Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2001-04-26
2003-05-20
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C060S552000, C060S413000
Reexamination Certificate
active
06564553
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a technical field of a pressure intensifying master cylinder in which master cylinder pressure is intensified with fluid pressure regulated according to the input force applied through an operating means and, more particularly, to a technical field of a pressure intensifying master cylinder in which the input side and the output side are separately operated so that the input travel can be set freely without the influence of operation of the output side. In the following description, the term “master cylinder” will be sometimes referred to as “MCY”.
For example, in a conventional brake system of an automobile, a braking pressure intensifying device has been employed which hydraulically intensifies the pedal force on a brake pedal into predetermined magnitude to develop large braking pressure. The braking pressure intensifying device functions to provide large braking force from small pedal force on the brake pedal, thereby securing the braking performance and reducing the fatigue of a driver.
In the conventional braking pressure intensifying devices, a control valve is actuated by an input based on the pedal force applied to the brake pedal to develop hydraulic fluid pressure according to the input and the developed hydraulic fluid pressure is introduced into a power chamber, thereby intensifying the input at a predetermined ratio to output intensified pressure. A piston of a master cylinder is moved by the output of the braking pressure intensifying device so that the master cylinder outputs master cylinder pressure. The master cylinder pressure is introduced as braking pressure into wheel cylinders, thereby actuating the wheel brakes.
By the way, conventional brake systems employ various brake controls such as for controlling the braking force in a brake maneuver, for example, Anti-Lock Control (ABS), Brake Assist Control for assisting pedal force in the event of emergency braking, and Regenerative Brake Coordination Control for controlling the braking pressure produced by a service brake system when a regenerative brake system is used to develop braking pressure during the braking by the service brake system, and automatic brake controls, for example, a brake control for controlling the distance from another vehicle, a brake control for avoiding a collision with an obstacle object, and Traction Control (TRC).
Most of such brake controls are normally conducted in a brake circuit between the master cylinder and the wheel cylinders. However, when the brake control is conducted in the brake circuit after the master cylinder, it is required to prevent the input travel of the braking pressure intensifying device from being influenced by such brake controls, for instance, for obtaining better operational feel.
However, in a brake system in which a conventional braking pressure intensifying device and a brake master cylinder are combined, the travel of a piston of the master cylinder is fixed by the relation between the master cylinder and wheel cylinders. The travel of an input shaft of the braking pressure intensifying device i.e. the pedal travel of a brake pedal, depends on the travel of the piston of the master cylinder. Consequently, the travel of input side is influenced by the brake controls conducted in the brake circuit after the master cylinder. In the combination between the conventional braking pressure intensifying device and the brake master cylinder, it is difficult to securely and sufficiently satisfy the aforementioned requirement.
For changing the travel characteristic of the brake pedal as the input side to obtain better operational feel, the brake master cylinder and the brake circuit after the brake master cylinder are also influenced so that some change on the output side, for instance a size change on the master cylinder, should be required. By the change on the output side, the output characteristic of the brake system is influenced. This means that the overall change on the brake system is required, i.e. large-scale change is required.
It is further desired that the input side is influenced as little as possible by brake circuit which may differ according to the type or size of vehicle.
If the input side and the output side are just separated from each other to produce outputs regardless of the travel of the input side, the input side does not travel so that the travel of the input side can not be ensured.
For this, it has been conventionally proposed that a travel simulator is provided on the brake circuit after the master cylinder to prevent the travel of the input side from being influenced by the brake control after the master cylinder and to ensure the travel of the input side.
However, to add specially the travel simulator, many parts such as a travel cylinder and an electromagnetic shut-off valve used for the travel simulator are required, making the structure complex and increasing the cost.
There is still a problem that brakes must be securely operated in case of a fluid pressure source failure even with a travel simulator.
In an anti-lock control system, it is desired that when one or more braked wheels are in locking tendency, the braking force is controlled to cancel the locking tendency of the wheels. Further, in a regenerative coordination brake system, when the regenerative brake system is operated during the operation of the braking pressure intensifying device, the braking force produced by the braking pressure intensifying device should be reduced by an amount corresponding to the braking force produced by the regenerative brake system. In this case, it is desired to reduce the output of the braking pressure intensifying device to a value obtained by subtracting the output of the regenerative brake system from the output of the braking pressure intensifying device. In a brake system composed of a combination of a service brake system and a brake assist system, it is desired to increase the output of the braking pressure intensifying device to intensify the braking force produced by the braking pressure intensifying device in such case that brake assist operation is needed, for example, a case that a driver can not depress a brake pedal enough during the operation of the braking pressure intensifying device so as not to develop predetermined braking force.
When the brake control is performed in a brake maneuver just like the above case, the brake pedal is not influenced even with the travel simulator.
Further, in a brake system for controlling the distance from a front vehicle, it is desired to hold the distance constant by automatically actuating wheel brakes when the distance becomes short during running. In a brake system for avoiding a collision, it is desired to avoid a collision with an obstacle object by automatically actuating wheel brakes when there is a possibility of collision with the obstacle object. Furthermore, in a traction control system, it is desired to cancel a slipping tendency to ensure the secure starting by automatically actuating the brakes of the driving wheels when the driving wheel(s) is in slipping tendency at the starting.
As mentioned above, it is desired that the brake pedal is not influenced when the automatic braking is conducted even with the travel simulator.
Further, it is desired that such a system for controlling the braking force during braking operation or controlling the automatic braking can be manufactured with a simple structure.
Moreover, it is desired that the input-travel characteristic, the input-braking pressure characteristic, or the travel-braking pressure characteristic is allowed to be changed according to the condition of a vehicle or the like, with the structure remaining simple.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a braking pressure intensifying master cylinder of which the travel characteristic at the input side can be freely changed without the influence of the output side.
It is another object of the present invention to provide a braking pressure intensifying master cylinder with
Kobayashi Michio
Maki Kazuya
Niino Hiroaki
Oka Hiroyuki
Sawada Mamoru
Bosch Braking Systems Co. Ltd.
Kanesaka & Takeuchi
Kershteyn Igor
Look Edward K.
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