Control apparatus of variable delivery pump

• US 4,886,422 A
• Filed: 07/07/1988
• Issued: 12/12/1989
• Est. Priority Date: 07/09/1987
• Status: Expired due to Fees

• Current Assignee: Tokyo Keiki Inc.
• Original Assignee: Tokyo Keiso Company
• Inventors: Takeuchi, Kunihiko, Hayakawa, Osamu, Akita, Yoshisuke
• Primary Examiner(s): Smith, Leonard E.
• Assistant Examiner(s): SCHEUERMANN, DAVID W
• Application Number:
  US07/216,417
• Time in Patent Office: 523 Days
• Field of Search: 417/218, 417/300, 417/38, 417/20, 417/43, 417/219, 417/220, 417/221, 417/222, 417/223
• US Class Current: 417/20
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: G05D 16/2066 using controlling means acting on the pressure source
• CPC Class Codes: G05D 7/0688 by combined action on throttling means and flow sources G05D7/0694 takes precedence

Abstract

A control load such as a cylinder or the like is driven at a constant speed by controlling the flow rate of a variable delivery pump. The control mode is switched to the pressure control to keep the stop pressure constant on the basis of an increase in pressure when the control load stops. A remaining delivery amount which will be necessary to raise the delivery pressure to an object stop pressure when the load stops and an excess delivery volume due to the operation time lag when it is assumed that the delivery by the pump is stopped at the present time are predicted. When they coincide, the delivery amount of the pump is set to zero and the control mode is switched to the pressure control. On the other hand, the product of a load volume and a fluid compressibility is calculated from the increase in pressure when the load stops. The feedback gain of the pressure control is controlled on the basis of the calculated value of this product. Further, the pressure difference and the designated flow rate are compared and either smaller one of them is always set to the designated value of the flow control.

Claims

1. A control apparatus of a variable delivery pump comprising:

flow rate detecting means for detecting a delivery flow rate of said variable delivery pump;

pressure detecting means for detecting a delivery pressure of said pump;

flow rate control means for controlling a delivery amount of the pump so as to keep a designated flow rate value which is indicated by a flow rate setting device until a control load stops;

pressure control means for controlling the delivery amount of the pump such that the delivery pressure which increases when the control load stops is held to a designated pressure value which is indicated by a pressure setting device;

first prediction arithmetic operating means for predicting and calculating every predetermined period a remaining delivery volume which will be necessary until the delivery pressure at the present time reaches said designated pressure value on the basis of an increasing speed of the delivery pressure when the control load stops;

second prediction arithmetic operating means for predicting and calculating every predetermined period an excess delivery volume which will be discharged due to an operation time lag of the pump when it is assumed that the delivery of a fluid from the pump is stopped at the present time from the increasing speed of the delivery pressure when the control load stops; and

prediction control means for indicating the delivery stop of the pump or the control to a fixed delivery amount based on a stop leakage flow rate to said flow rate control means when the remaining delivery volume and excess delivery volume which are obtained from said first and second prediction arithmetic operating means coincide.

2. A control apparatus according to claim 1, wherein said prediction control means has switching means for switching a control mode to the pressure control by said pressure control means after an elapse of a predetermined time from the delivery stop of the pump or from the indication of the control to the fixed delivery amount or when the delivery pressure coincides with the set stop pressure.

3. A control apparatus according to claim 1, wherein said first prediction arithmetic operating means calculates a remaining time t_r from the present time t_n until the delivery pressure reaches the designated pressure value P_c by the following equation,

4. A control apparatus according to claim 1, wherein said second prediction arithmetic operating means calculates the excess delivery volume V_e which will be discharged due to the operation time lag of the pump when it is assumed that the delivery stop of the pump is performed at the present time by the following equation,