Hydraulic power unit

• US 5,240,379 A
• Filed: 07/20/1992
• Issued: 08/31/1993
• Est. Priority Date: 07/19/1991
• Status: Expired due to Fees

• Current Assignee: Zexel Corporation (Robert Bosch GmbH)
• Original Assignee: Zexel Corporation (Robert Bosch GmbH)
• Inventors: Takashi, Homma, Toshihiro, Endoh, Michio, Wakiya
• Primary Examiner(s): Bertsch, Richard A.
• Assistant Examiner(s): Scheuermann, David W.
• Application Number:
  US07/915,504
• Time in Patent Office: 407 Days
• Field of Search: 417/38, 417/44, 417/63, 303/11, 303/DIG. 3, 303/DIG. 4
• US Class Current: 417/38
• CPC Class Codes: F15B 1/033 with electrical control means
• CPC Class Codes: F15B 19/00 Testing; Calibrating; Fault detection or monitoring; Simulation or modelling of fluid-pressure systems or apparatus not otherwise provided for
• CPC Class Codes: Y10S 303/04 Pressure signal used in electrical speed controlled braking circuit

Abstract

A hydraulic power unit for a vehicle comprises a motor, a pump to be driven by the motor to pump up an oil stored in an oil tank, a gas filling type accumulator connected to the pump, a pressure sensor disposed at a portion near an outlet port of the accumulator for detecting a pressure of the oil in the accumulator, a control unit operatively connected to the pressure sensor and a relay opertively connected to the control unit for controlling an operation of the motor. In the control unit, a rate of change of the pressure of the oil detected by the pressure sensor is calculated with respect to transition of time, an inflection point at which the rate of change of the oil pressure at a time of control start time or control stop time of the hydraulic power unit is maximumly changed is obtained, an oil pressure at the inflection point is calculated, the oil pressure at the inflection point is compared with a predetermined oil pressure, and a fact as to whether or not the oil pressure at the inflection point reaches the predetermined oil pressure is discriminated.

Claims

1. A hydraulic power unit comprising:

a motor means;

a pump means to be driven by the motor means to pump up an oil stored in an oil tank;

a gas filling type accumulator connected to the pump means through a line so as to supply the oil from the pump means;

a pressure detecting means disposed at a portion near an outlet port of the accumulator for detecting a pressure of the oil in the accumulator;

a control unit operatively connected to the pressure detecting means; and

means operatively connected to the control unit for controlling an operation of the motor means,

said control unit including means for calculating a rate of change of the pressure of the oil detected by the pressure detecting means with respect to transition of time, means for obtaining an inflection point at which the rate of change of the oil pressure at a time of control start time or control stop time of the hydraulic power unit is maximumly changed and calculating an oil pressure at the inflection point and means for comparing the oil pressure at the inflection point with a predetermined oil pressure and discriminating a fact as to whether or not the oil pressure at the inflection point reaches the predetermined oil pressure.

2. A hydraulic power unit according to claim 1, wherein said pressure detecting means comprises an electrostatic capacitance type pressure intershifter in which a change of capacitance caused in response to a change of hydraulic pressure in a hydraulic circuit is intershifted into a voltage and the intershifted voltage is continuously outputted.

3. A hydraulic power unit according to claim 1, wherein the means for controlling the motor operation comprises a relay means including a switching circuit for carrying out an on-off operation of the motor.

4. A hydraulic power unit according to claim 1, further comprises means for alarming an abnormal gas pressure condition in the accumulator.

5. A hydraulic power unit according to claim 4, wherein the alarming means is a display.

6. A hydraulic power unit according to claim 1, wherein the oil pressure control by means of the control unit is performed in connection with a gas pressure in the accumulator.

7. A hydraulic power unit according to claim 6, wherein the gas pressure in the accumulator corresponds to the predetermined oil pressure in an ordinary operation period of the accumulator.

8. A hydraulic power unit according to claim 6, wherein the pressure control is performed by utilizing a pressure versus time characteristic at a control start time.

9. A hydraulic power unit according to claim 3, wherein the pressure control is performed by utilizing a pressure versus time characteristic at a control stop time.