Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-08-25
2002-05-07
Rodriguez, Pam (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S020000, C303S113300, C188S358000
Reexamination Certificate
active
06382737
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for detecting an abnormality of a pressurizing device in a hydraulically operated braking system.
2. Discussion of Related Art
JP-A-10-236294 discloses an example of such an apparatus for detecting an abnormality of a pressurizing device. This apparatus is adapted to detect an abnormality of a pressurizing device in the form of a vacuum booster (hereinafter referred to simply as “booster”), and includes (1) a master cylinder pressure detecting device for detecting a hydraulic pressure in a master cylinder which is arranged to generate the hydraulic pressure corresponding to an output force of the booster provided to boost a brake operating force acting on a brake operating member; (2) a booster pressure detecting device for detecting a hydraulic pressure in a variable-pressure chamber of the booster; and (3) a diagnosing device for determining whether the booster is abnormal, on the basis of a relationship between the hydraulic pressure detected by the master cylinder pressure detecting device and the hydraulic pressure detected by the booster pressure detecting device.
The hydraulic pressure in the variable-pressure chamber of the booster changes towards the atmospheric pressure as the brake operating force is increased. Accordingly, the hydraulic pressure in the variable-pressure chamber increases with an increase of the hydraulic pressure in the master cylinder. When the booster is normal, the hydraulic pressures in the variable-pressure chamber of the booster and the master cylinder have a predetermined relationship, that is, are held within respective predetermined ranges. If these two hydraulic pressures detected by the master cylinder pressure detecting device and the booster pressure detecting device are not held within the respective predetermined ranges, it is possible to determine that the booster is abnormal. Thus, the determination as to whether the booster is abnormal or not is effected in the known booster-diagnosing apparatus, while the brake operating member is in operation.
However, the known booster-diagnosing apparatus disclosed in the publication identified above is not capable of detecting an abnormality of the booster while the brake operating member is not in operation. This is because the booster is activated only when the brake operating member is operated.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus which is capable of detecting an abnormality of a pressurizing device in a hydraulically operated system, even while the brake operating member is not in operation.
The above object may be achieved according to 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, 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 diagnosing apparatus for diagnosing a pressurizing device provided in a hydraulically operated braking system operated by a brake operating member, comprising: a hydraulic pressure detecting device operable to detect a hydraulic pressure which is a sum of a first fluid pressure generated by an operation of said brake operating member, and a second fluid pressure generated by an operation of the pressurizing device; and a diagnosing device operable to determine whether the pressurizing device is abnormal or not, on the basis of the sum of the first and second fluid pressures detected while the brake operating member is not in operation and while the pressurizing device is in operation.
In the diagnosing apparatus according to the above mode (1) of this invention, the pressurizing device is diagnosed on the basis of a hydraulic pressure which is a sum of the first and second fluid pressures which are detected by the hydraulic pressure detecting device while the brake operating member is not in operation and while the pressurizing device is in operation. While the brake operating member is not in operation, the first fluid pressure is not generated by the brake operating member, so that the hydraulic pressure detected by the hydraulic pressure detecting device is equal to the second fluid pressure generated by the pressurizing device, more precisely, the second fluid pressure corresponding to the operating condition of the pressurizing device. Accordingly, the diagnosing device can be diagnosed while the brake operating member is not in operation.
As indicated above, the hydraulic pressure detected by the hydraulic pressure detecting device while the brake operating member is not in operation does not include a fluid pressure generated by the brake operating member.
Where a booster is connected to the brake operating member, as described before, the first fluid pressure corresponds to an output of the booster which is adapted to boost the operating force acting on the brake operating member. Namely, the first fluid pressure corresponds to the brake operating force as boosted by the booster.
(2) A diagnosing apparatus according to the above mode (1), further comprising a vehicle speed detecting device for detecting a running speed of an automotive vehicle on which the hydraulically operated braking system, and wherein the diagnosing device includes a determining portion operable to determine whether the pressurizing device is abnormal or not, on the basis of the hydraulic pressure detected while the running speed of the automotive vehicle detected by the vehicle speed detecting device is lower than a predetermined first threshold value.
While the vehicle running speed is lower than the predetermined first threshold value, there is a low possibility that the brake operating member is operated. In other words, the first threshold value is determined so that the possibility of the brake operating member at a vehicle running speed lower than the first threshold value is low. Accordingly, the pressuring device can be diagnosed while the brake operating member is not in operation, when the diagnosis is effected while the vehicle running speed is lower than the first threshold value.
The vehicle speed detecting device may be adapted to obtain the vehicle running speed on the basis of the rotating speed of the output shaft of a drive power source which drives the vehicle, or alternatively, on the basis of the rotating speeds of the vehicle wheels.
(3) A diagnosing apparatus according to the above mode (1) or (2), further comprising: a ready-state detecting device for determining whether an automotive vehicle on which the hydraulically operated braking system is provided is ready for running, or not; and a braking operation detecting device for determining whether the brake operating member is in operation or not, and wherein said diagnosing device includes a determining portion operable to determine whether the pressurizing device is abnormal or not, on the basis of the hydraulic pressure detected when said brake operation detecting device detects for the first time that the brake operating member is in operation, after the ready-state detecting device has detected that the automotive vehicle becomes ready for running.
In the diagnosing apparatus according to the above mode (3), the pressurizing device is diagnosed upon first detection that the brake operating member is not in operation after, the automotive vehicle becomes ready for running. Where the brake operating member is not in operation at the time when the automotive vehicle has become ready for running, the diagnosis of the pressurizi
Isono Hiroshi
Mizutani Yasuji
Oliff & Berridg,e PLC
Rodriguez Pam
Toyota Jidosha & Kabushiki Kaisha
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