Pumps – With condition responsive pumped fluid control – Plural pump units with individual or relative control
Reexamination Certificate
2000-03-02
2002-01-29
Walberg, Teresa (Department: 3742)
Pumps
With condition responsive pumped fluid control
Plural pump units with individual or relative control
C303S011000
Reexamination Certificate
active
06341947
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a pump device having a plurality of pumps having different operating characteristics, and a hydraulic pressure control system including such a pump device, and more particularly to techniques for dealing with an operating failure of the pumps.
2. Discussion of the Related Art
A pump device of the type described above is disclosed in JP-A-9-256960. This pump device includes not only a plurality of pumps as indicated above, but also a pump control device for controlling those pumps, and a high-pressure pump and a low-pressure pump. The high-pressure pump has a highest delivery pressure which is higher than that of the low-pressure pump, and a highest delivery flow rate which is lower than that of the low-pressure pump. The pump device is provided in a braking system for an automotive vehicle, for delivering the pressurized fluid to wheel brake cylinders. The high-pressure and low-pressure pumps are selectively activated depending upon the desired fluid pressure to be applied to the wheel brake cylinders. When the desired pressure of a given one of the wheel brake cylinders is lower than a predetermined first threshold value, the low-pressure and high-pressure pumps are both activated. When the desired wheel brake cylinder pressure is between the predetermined first threshold value and a predetermined second threshold value larger than the first threshold value, only the low-pressure pump is activated. When the desired wheel brake cylinder pressure is higher than the second threshold value, only the high-pressure pump is activated. This selection of the pumps is based on a fact that a relatively large amount of the pressurized fluid should be the wheel brake cylinder for an initial period of a braking action of a hydraulic brake including the wheel brake cylinder, that is, until the hydraulic brake begins to provide a braking effect with respect to the corresponding vehicle wheel, while a relatively small amount of supply of the pressurized fluid to the wheel brake cylinder is required after the hydraulic brake has begun to provide the braking effect, that is, after the fluid pressure in the wheel brake cylinder has been raised to a relatively high level. Thus, the high-pressure pump and the low-pressure pumps are selectively used depending upon the required amount of supply of the fluid to be supplied to the wheel brake cylinder.
In the event of an operating failure of either one of those two pumps, the wheel brake cylinder pressure cannot be controlled to the desired value, or the amount of supply of the pressurized fluid to the wheel brake cylinder is insufficient, leading to deteriorated response in the control of the wheel brake cylinder pressure.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a pump device which includes a plurality of pumps having different operating characteristics and which is less likely to suffer from problems caused by an operating failure of some of the pumps.
A second object of this invention is to provide a hydraulic pressure control system including such a pump device.
The first or second object of this invention may be achieved according to any one of the following modes of the 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.
(1) A pump device (
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) including a plurality of pumps having respective different operating characteristics, and a pump control device for controlling the plurality of pumps, characterized in that the pump control device comprises a control changing portion operable in response to detection of a failure of at least one of the plurality of pumps, for changing a manner of controlling at least one of the other of the plurality of pumps such that at least a portion of the operating characteristic of each of the above-indicated at least one of the plurality of pumps is compensated for by the changed manner of controlling the above-indicated at least one of the other of the plurality of pumps.
The operating characteristic of each pump includes a delivery pressure, a delivery flow rate, a rate of change of the delivery pressure and a rate of change of the delivery flow rate. In the pump device according to the above mode, the operating characteristic of each of the two or more pumps which is defective or fails to normally function will not be entirely lost, since the manner of controlling at least one of the other of the pumps is changed from the nominal manner, so as to compensate for at least a portion of the operating characteristic of the defective pump. Accordingly, a problem caused by the failure of one of the pumps can be minimized.
(2) A pump device according to the above mode (1), wherein the pump control device further comprises a pump failure detecting device for detecting the failure of the above-indicated at least one of the plurality of pumps, and the control changing portion operates in response to detection of the failure by the pump failure detecting device.
For instance, the pump failure detecting device includes a pump pressure sensor for detecting a delivery pressure of the pump device, and is adapted to detect a failure of at least one of the pumps on the basis of an output of the pump pressure sensor. The pump failure detecting device may be adapted to check whether the delivery pressure of each pump is zero or lower than a predetermined value during an operation of the pump or whether the delivery pressure has not been increased to a predetermined value a predetermined time after the initiation of an operation of the pump. In this case, the pump failure detecting device determines that the pump fails to normally function, if the delivery pressure is zero or lower than the predetermined value during an operation of the pump, or if the delivery pressure has not been increased to the predetermined value after the pump has been operated for the predetermined time. Although a user of the pump device may manually activate the control changing portion when the user has detected a failure of a certain pump, the failure is automatically detected by the pump failure detecting device, and the control changing portion is automatically activated in response to the detection of the failure, in the pump device according to the above mode. This arrangement assures relatively high accuracy of detection of the pump failure.
(3) A pump device according to the above mode (1) or (2), wherein the pump control device further comprises a pump selecting portion operable when the plurality of pumps are normal, for selecting at least one of the plurality of pumps which should be operated, on the basis of at least one of a desired delivery pressure and a desired delivery flow rate of the pump device, and on the basis of information defining an operating range in which each of the plurality of pumps should be operated, which operating range is determined by a capacity of each pump, and wherein the control changing portion changes the operating range of each of the above-indicated at least one of the other of the plurality of pumps.
Although the plurality of pumps have mutually different characteristics, the operating ranges of the pumps usually partially overlap each other, so that the pump selecting portion is desirably adapted to select the pump or pumps to be operated, such that each selected pump is operable under a load more or less smaller than its nominal or maximum load value. Therefore, upon failure of at least one of the pumps, the operating range of at least one of the other of the pumps is changed by the control changing portion so that the at least one other normal pump is selected and operated, in place of the at least one defective pump, such that at
Campbell Thor
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
Walberg Teresa
LandOfFree
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