Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-06-05
2002-03-26
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113300, C303S113400
Reexamination Certificate
active
06361126
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a brake pressure control device and a method for activating and deactivating a hydraulic brake booster.
BACKGROUND INFORMATION
From British Patent No. 2,281,364, describes a brake pressure control device for a hydraulic dual-circuit braking system having a pneumatic brake booster. For each braking circuit, an arrangement of valves is provided as well as a return pump. Furthermore, an electronic control unit is present, which, from processing sensor signals containing information on the manner of the activation of the brake pedal, generates signals for driving switch-over valves, pre-charge control valves, intake and exhaust valves, and the return pumps. A pneumatic brake booster described in this British patent includes two chambers, separated from each other by a valve, of which one is operated as a low-pressure chamber and the other as a working or drive chamber. A modulation valve is provided, using which the working chamber of the brake booster is ventilated. The purpose of the brake pressure control device is to assure the highest possible values for the vehicle deceleration in response to an automatically controlled hard stop. An automatically controlled hard stop of this type is known as a “braking assistant.” The braking pressures necessary for the automatic hard stop are generated with the assistance of the valve arrangement and the return pumps, i.e., through the appropriate driving of the hydraulic unit.
British Patent No. 2,281,364 also describe, a target braking, i.e., a braking process in normal traffic circumstances monitored by the driver, occurs without the support of the hydraulic unit. However, in this case, which nevertheless arises predominantly in normal traffic circumstances, the power boost is accomplished by the pneumatic brake booster alone. The latter must therefore be designed to attain the maximum required braking pressures. In a pneumatic brake booster of this type, the greatest disadvantage is its size, which is determined by the braking pressures to be attained. It is also disadvantageous in this arrangement that the solenoid valves of the valve arrangement, in particular the switch-over and the pre-charge control valves, have to be designed for the comparatively high master cylinder pressures that are produced using a pneumatic brake booster of this type. In contemporary brake boosters, these pressures are in the order of magnitude of up to 250 bar.
German Patent No. 195 01 760 describes, a method and a device for controlling an ABS-ASR system, using which it is possible to replace the vacuum brake booster entirely or partially with a hydraulic brake booster. The hydraulic power boost is accomplished by a controlled driving of the valve arrangement and the return pumps. However, a complete replacement of the pneumatic brake booster has the consequence that the return pumps of the braking system must be set in operation in every braking process in which an increase or boosted braking pressure is to be generated in the wheel cylinders. This has the disadvantage that the return operation can lead to pedal pulsations, which, in particular at lower pedal forces, can be perceived as disturbing. As a further point, a braking system based exclusively on a hydraulic power boost offers less redundancy in the event of a failure or defect in the hydraulic unit.
Unpublished German Patent Application No. 197 56 080 describes, a brake pressure control unit which is improved with regard to contradictory requirements, the greatest possible comfort combined with the greatest possible reliability and smallest possible space. For this purpose, the device described there has a pneumatic brake booster, which is designed such that it reaches its modulation point, i.e., the point at which the brake pressure support can no longer be increased using the pneumatic brake booster, at a master cylinder pressure of more than zero and less than 50 bar. In this context, an essential difference in the functioning of the “braking assistant” lies in the fact that a substantially proportional dependency exists between the control pressures and the braking pressures in the wheel braking cylinders over a broad operational range of the braking system, i.e., as far as possible all of the pedal positions of the brake pedal and therefore for virtually all of the control pressures input by a driver of the vehicle.
It is also known from this application to provide means for displaying the arrival at the modulation point of the pneumatic brake booster. These means can be designed so that they determine a differential pressure between the working chamber of a pneumatic brake booster and an external ambient pressure, and they, in the event that a threshold value is not reached, generate an identifier representing the modulation point. A method of this type yields very good results in quasi static braking processes. However, it has proven to be the case that in response to a rapid application of the brakes, an activation of the hydraulic boost can under certain circumstances occur relatively late, so that a significant resistance threshold is noticeable during braking.
SUMMARY
An objective of the present invention is, inter alia, to make possible a braking process which takes optimal account of the requirements of pedal comfort, capacity for quantitative regulation of the braking force, and reliability even in response to different brake application dynamics (pedal actuation speed).
This object is achieved by providing a brake pressure control unit and a method for activating and/or deactivating a hydraulic brake booster in according with the present invention. In addition, further advantages are yielded.
The brake pressure control unit according to the present invention and the method according to the present invention make possible an optimal driving of a hydraulic brake booster, so that in particular in response to a rapid application of the brakes, an activation of the hydraulic brake booster takes place promptly, so that losses of comfort or of reliability can be effectively avoided. By taking into account the time-related derivation of the master cylinder pressure and the differential pressure between the pressure in the working chamber or the vacuum chamber of the brake booster and the ambient pressure, an optimal application of a hydraulic brake booster using a hydraulic unit can be achieved, without making concessions in driving comfort. The control unit according to the present invention, in an optimal manner, satisfies the requirements of pedal comfort, capacity for quantitative regulation of the braking force, and reliability, and also makes it possible that, in contrast to an evaluation of the differential pressure between the working chamber of a brake booster and an external ambient pressure, the differential pressure between the low-pressure chamber of a brake booster and an external ambient pressure is evaluated. In the event that the differential pressure between the low-pressure chamber of the brake booster and an external ambient pressure is measured, but the pressure in the working chamber of the brake booster is not measured by a measuring signal during the brake actuation, the pressure in the working chamber of the brake booster can be calculated, for example, taking into account the differential pressure between the low-pressure chamber and the ambient pressure, the master cylinder pressure, the time-related derivations of the master cylinder pressure, the duration of braking, and the time intervals of the braking duration.
According to the present invention, it may be advantageous to determine the drive trigger point, at which the hydraulic unit is activated and/or deactivated, by taking into account the differential pressure between the pressure in the working chamber or the pressure in the low-pressure chamber and the ambient pressure when the brake pedal is unactivated. In particular, it is relatively easy to take into account a differential pressure of this type when the brake pedal is unactivated and leads
Pueschel Helmut
Schmidt Hanniel
Wiss Helmut
Robert & Bosch GmbH
Schwartz Christopher P.
LandOfFree
Brake pressure control device and a method for activating... 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 pressure control device and a method for activating..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brake pressure control device and a method for activating... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2821266