Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
1999-08-19
2001-09-11
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C701S029000, C303S122120
Reexamination Certificate
active
06289271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to techniques for diagnosing a booster of a braking system for an automotive vehicle.
2. Discussion of the Related Art
JP-A-4-56669 discloses an example of a known technology for diagnosing a vacuum booster of a vehicle braking system, for any abnormality. This known diagnosing technique is based on a fact that the vacuum booster becomes inoperative to perform a normal boosting function when a negative pressure of a negative pressure source to which the vacuum booster is connected has been raised above a predetermined upper limit. According to the known diagnosing technology, a pressure switch is used to either mechanically or electrically detect that the negative pressure of the negative pressure source has exceeded the upper limit.
A study by the assignee of the present application has revealed that when the vacuum booster is abnormal, the input and the output of the booster do not have a predetermined or known nominal relationship, and that this fact can be utilized to effect a diagnosis of the booster for any abnormality.
In the light of the above findings, the assignee of the present application have developed an apparatus for diagnosing a vacuum booster, which is adapted to determine that the vacuum booster is abnormal, if the detected input and output do not meet a predetermined nominal relationship therebetween. This apparatus was not publicly known at the time the present invention was made.
As a result of a study of the developed diagnosing apparatus by the present inventors, the inventors obtained various findings regarding the diagnosis of the vacuum booster.
For instance, the present inventors found a possibility that the actually normal vacuum booster is erroneously diagnosed to be abnormal, due to a delayed operational response of the booster while the booster is in a transient state. It is desirable to reduce this possibility in the diagnosing apparatus.
Various design concepts are available in designing the diagnosing apparatus for the vacuum booster. According to one of the design concepts, the diagnosing apparatus is adapted to indicate that the booster is abnormal, irrespective of whether the booster is in a transient or steady state, if any abnormality of the booster is found. In this case, the diagnosing apparatus does not indicate that the booster is normal. This design concept suffers from a relatively high possibility that the booster is erroneously diagnosed to be abnormal when the booster is in fact normal. It is desirable to prevent such an erroneous diagnosis, and to cancel the erroneous diagnosis if it takes place.
According to another design concept, the diagnosing apparatus is adapted to indicate that the booster is normal, irrespective of whether the booster is in the transient or steady state, if no abnormality of the booster is found. This design concept suffers from a relatively high possibility that the booster is erroneously diagnosed to be normal when the booster is in fact abnormal, that is, a relatively high possibility that the booster is not correctly diagnosed to be abnormal when the booster is in fact abnormal. In this case, it is desirable to prevent a failure to correctly diagnose that the booster is abnormal when the booster is in fact abnormal.
According to a further design concept, the diagnosing apparatus is adapted such that when the operating condition of the booster has changed from the normal condition to an abnormal condition, the apparatus immediately indicate the abnormality of the booster. However, this design concept requires the apparatus to make frequent determinations as to whether the booster has become abnormal, and therefore suffers from a relatively high possibility of unnecessary determinations. It is desirable to eliminate the unnecessary determinations.
The diagnosing apparatus for diagnosing the vacuum booster is generally provided with an alarm indicator for warning the vehicle operator of the presence of an abnormality of the booster. On the other hand, it is considered unnecessary to warn the vehicle operator of the presence of an abnormality of the booster if the braking system is capable of producing a sufficiently large braking force. In this respect, it is desirable that the diagnosis of the booster by the diagnosing apparatus is effected depending upon the necessity for the vehicle operator to pay attention to the operating condition of the braking system.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus which permits optimum diagnosis of a brake booster for any abnormality.
The above object may be achieved according to any one of the following modes (1)-(36) of this invention. Each of these modes of the invention is numbered like the appended claims, and depends from the other mode or modes, where appropriate, so as to indicate possible combinations of technical features of some of the following modes, which fall within the principle of the present invention. However, it is to be understood that the invention is not limited to those features or those combinations of features.
(1) An apparatus for diagnosing a booster of a braking system for an automotive vehicle, the braking system including a brake operating member operated with a brake operating force, a master cylinder for producing a hydraulic pressure on the basis of an output force of the booster produced as a result of boosting of the brake operating force by the booster, and a wheel brake cylinder which is activated by the hydraulic pressure produced by the master cylinder, to brake a wheel of the automotive vehicle, the apparatus comprising: a determining device for making a decision as to whether the booster is abnormal or not, on the basis of a relationship between an input quantity relating to an input of the booster and an output quantity relating to an output of the booster; and an optimizing device for optimizing an operation of the determining device to make the decision.
In the diagnosing apparatus of the present invention constructed according to the above mode (1), the determining device makes a provisional decision as to whether the booster is abnormal or not, on the basis of the relationship between the input quantity and output quantity of the booster, and the optimizing device optimizes the operation of the determining device. The optimizing device is adapted to effect at least one of (a) preventing execution of the decision erroneously made by the determining device that the booster is abnormal when the booster is in fact normal, (b) preventing execution of the decision erroneously made by the determining device that the booster is normal when the booster is in fact abnormal, (c) cancelling the decision erroneously made by the determining device, before a next operation of the brake operating member, and (d) preventing execution of the decision made by the determining device, when the execution of the decision is unnecessary.
The present diagnosing apparatus including the optimizing device is therefore capable of diagnosing the booster for any abnormality, with improved accuracy.
The booster to be diagnosed by the present diagnosing apparatus may be a vacuum booster operated by a negative pressure received from an appropriate vacuum source, or a hydraulic booster operated by a hydraulic pressure received from an appropriate hydraulic pressure source.
The input quantity of the booster may be an input force per se received by the booster, or any physical quantity other than the input force per se, which quantity may be used as an equivalent of the input force. Similarly, the output quantity may be an output force per se produced by the booster, or any physical quantity other than the output force per se, which quantity may be used as an equivalent of the output force. For instance, the input quantity may be an operating force acting on the brake operating member, an operating stroke of the brake operating member, a force applied to an input member of the booster, and an operating stroke of the
Isono Hiroshi
Mizutani Yasuji
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
Zanelli Michael J.
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