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US-12618421-B2 - Hydraulic drive system

US12618421B2US 12618421 B2US12618421 B2US 12618421B2US-12618421-B2

Abstract

This hydraulic drive system includes: a hydraulic pump that supplies a working fluid to a hydraulic actuator; a meter-in control valve that controls a flow rate of the working fluid flowing from the hydraulic pump to the hydraulic actuator; a meter-out control valve that controls a flow rate of the working fluid being drained from the hydraulic actuator into a tank; and a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator. The meter-out control valve is connected to the hydraulic actuator in parallel with the regeneration valve.

Inventors

  • Tomomichi Nose
  • Hayato Kawasaki
  • Hideyasu Muraoka
  • Nobuyuki Kinoshita

Assignees

  • KAWASAKI JUKOGYO KABUSHIKI KAISHA

Dates

Publication Date
20260505
Application Date
20241217
Priority Date
20200619

Claims (6)

  1. 1 . A hydraulic drive system comprising: a hydraulic pump that supplies a working fluid to a hydraulic actuator including two ports; a first control valve that is a spool valve connected to one of the two ports, and controls a meter-in flow rate of the working fluid being supplied from the hydraulic pump to the one of the two ports and a meter-out flow rate of the working fluid being drained from the one of the two ports into a tank; a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator; a second control valve that is a spool valve connected to the hydraulic actuator in parallel with the regeneration valve and connected to the other of the two ports, and controls a meter-in flow rate of the working fluid being supplied from the hydraulic pump to the other of the two ports and a meter-out flow rate of the working fluid being drained from the other of the two ports into the tank; an operation device that outputs an operation signal corresponding to an amount of operation of an operation tool; and a control device that controls an opening of each of the regeneration valve and the second control valve to drain the working fluid from the hydraulic actuator at a flow rate corresponding to the operation signal from the operation device, wherein: the control device estimates a regeneration flow rate on the basis of an opening degree of the regeneration valve and controls the opening of the second control valve to cause the working fluid to flow into the tank at a meter-out flow rate which is a difference between a drainage flow rate of the working fluid being drained from the hydraulic actuator according to the operation signal from the operation device and the estimated regeneration flow rate.
  2. 2 . The hydraulic drive system according to claim 1 , further comprising: a first pressure sensor that measures a drainage pressure which is a pressure of the working fluid being drained from the hydraulic actuator, wherein: the control device estimates a regeneration flow rate on the basis of a downstream pressure of the regeneration valve and the drainage pressure measured by the first pressure sensor; and the downstream pressure of the regeneration valve is estimated on the basis of the drainage pressure measured by the first pressure sensor and the opening degree of the regeneration valve.
  3. 3 . The hydraulic drive system according to claim 2 , further comprising: a second pressure sensor that measures a supply pressure which is a pressure of the working fluid being supplied to the hydraulic actuator, wherein: the control device estimates the downstream pressure of the regeneration valve on the basis of the drainage pressure measured by the first pressure sensor, the supply pressure measured by the second pressure sensor, and the opening degree of the regeneration valve.
  4. 4 . The hydraulic drive system according to claim 1 , wherein: the control device sets, according to a load state of the hydraulic actuator, a regeneration ratio which is a ratio of the regeneration flow rate to the drainage flow rate of the working fluid being drained from the hydraulic actuator, and controls the opening of the regeneration valve according to the regeneration ratio.
  5. 5 . A hydraulic drive system comprising: a hydraulic pump that supplies a working fluid to a hydraulic actuator including two ports; a first control valve that is a spool valve connected to one of the two ports, and controls a meter-in flow rate of the working fluid being supplied from the hydraulic pump to the one of the two ports and a meter-out flow rate of the working fluid being drained from the one of the two ports into a tank; a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator; a second control valve that is a spool valve connected to the hydraulic actuator in parallel with the regeneration valve and connected to the other of the two ports, and controls a meter-in flow rate of the working fluid being supplied from the hydraulic pump to the other of the two ports and a meter-out flow rate of the working fluid being drained from the other of the two ports into the tank; a first pressure sensor that measures a drainage pressure which is a pressure of the working fluid being drained from the hydraulic actuator; an operation device that outputs an operation signal corresponding to an amount of operation of an operation tool; and a control device that controls an opening of each of the regeneration valve and the second control valve to drain the working fluid from the hydraulic actuator at a flow rate corresponding to the operation signal from the operation device, wherein: the control device estimates a regeneration flow rate on the basis of a downstream pressure of the regeneration valve and the drainage pressure measured by the first pressure sensor; and the downstream pressure of the regeneration valve is estimated on the basis of the drainage pressure measured by the first pressure sensor and an opening degree of the regeneration valve.
  6. 6 . A hydraulic drive system comprising: a hydraulic pump that supplies a working fluid to a hydraulic actuator including two ports; a first control valve that is a spool valve connected to one of the two ports, and controls a meter-in flow rate of the working fluid being supplied from the hydraulic pump to the one of the two ports and a meter-out flow rate of the working fluid being drained from the one of the two ports into a tank; a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator; a second control valve that is a spool valve connected to the hydraulic actuator in parallel with the regeneration valve and connected to the other of the two ports, and controls a meter-in flow rate of the working fluid being supplied from the hydraulic pump to the other of the two ports and a meter-out flow rate of the working fluid being drained from the other of the two ports into the tank; an operation device that outputs an operation signal corresponding to an amount of operation of an operation tool; and a control device that controls an opening of each of the regeneration valve and the second control valve to drain the working fluid from the hydraulic actuator at a flow rate corresponding to the operation signal from the operation device, wherein: the control device sets, according to a load state of the hydraulic actuator, a regeneration ratio which is a ratio of a regeneration flow rate to a drainage flow rate of the working fluid being drained from the hydraulic actuator, and controls the opening of the regeneration valve according to the regeneration ratio.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) The present application is a divisional of U.S. patent application Ser. No. 18/001,650, filed Dec. 13, 2022, and entitled HYDRAULIC DRIVE SYSTEM, which is a national stage of the international application PCT/JP2021/016850, filed on Apr. 27, 2021, which in turn claims priority to Japanese Patent Application No. 2020-106204, filed on Jun. 19, 2020, the entire disclosures of each of which are hereby incorporated herein by reference for all purposes. TECHNICAL FIELD The present invention relates to a hydraulic drive system capable of regenerating a working fluid drained from a hydraulic actuator. BACKGROUND ART In a hydraulic drive system, a working fluid drained from a hydraulic actuator is regenerated in order to obtain energy-saving effects. Known examples of this hydraulic drive system include the hydraulic drive device disclosed in Japanese Laid-Open Patent Application Publication (PTL) 1. CITATION LIST Patent Literature PTL 1: Japanese Laid-Open Patent Application Publication No. 2018-028358 SUMMARY OF INVENTION Technical Problem In the hydraulic drive system disclosed in PTL 1, a working fluid drained to a meter-out line is regenerated to a hydraulic cylinder via a regeneration line. Therefore, the working fluid drained to the meter-out line is directly regenerated to the hydraulic cylinder, causing a change in a regeneration flow rate depending on, for example, a load and an attitude of an attachment attached to the hydraulic cylinder. In this case, the load and the attitude of the attachment have impact on the responsiveness of the cylinder to lever operation. Furthermore, at the time of draining the working fluid to a tank during regeneration, the working fluid is routed to the tank through a control valve and a regeneration release valve. Therefore, the pressure loss in the working fluid during the regeneration is great. Thus, an object of the present invention is to provide a hydraulic drive system capable of reducing the impact of variations in a regeneration flow rate on the responsiveness of a hydraulic actuator. Furthermore, according to the present invention, it is possible to provide a hydraulic drive system capable of reducing a pressure loss in a working fluid that occurs during regeneration. Solution to Problem A hydraulic drive system according to the present invention includes: a hydraulic pump that supplies a working fluid to a hydraulic actuator; a meter-in control valve that controls a flow rate of the working fluid flowing from the hydraulic pump to the hydraulic actuator; a meter-out control valve that controls a flow rate of the working fluid being drained from the hydraulic actuator into a tank; and a regeneration valve that supplies, to the hydraulic actuator, the working fluid drained from the hydraulic actuator. The meter-out control valve is connected to the hydraulic actuator in parallel with the regeneration valve. According to the present invention, at each of the meter-in control valve, the meter-out control valve, and the regeneration valve, the flow rate of the working fluid flowing therethrough can be controlled independently. Thus, the meter-out flow rate can be adjusted in line with variations in the regeneration flow rate. Thus, it is possible to reduce the impact of variations in the regeneration flow rate on the responsiveness of the hydraulic actuator. Furthermore, according to the present invention, the working fluid to be drained into the tank is drained from the hydraulic actuator into the tank without passing through the regeneration valve. Therefore, it is possible to reduce the pressure loss in the working fluid that is drained into the tank. Advantageous Effects of Invention According to the present invention, it is possible to reduce the impact of variations in the regeneration flow rate on the responsiveness of the hydraulic actuator. Furthermore, according to the present invention, it is possible to reduce the pressure loss in the working fluid that occurs during the regeneration. The above object, other objects, features, and advantages of the present invention will be made clear by the following detailed explanation of preferred embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive system according to an embodiment of the present invention. FIG. 2 is a block diagram of a control device included in the hydraulic drive system shown in FIG. 1 that is related to opening control for a regeneration valve. FIG. 3 is a block diagram of a control device included in the hydraulic drive system shown in FIG. 1 that is related to opening control for a meter-out control valve. FIG. 4 is a hydraulic circuit diagram showing a hydraulic drive system according to another embodiment of the present invention. DESCRIPTION OF EMBODIMENTS Hereinafter, a hydraulic drive system 1 according to an embodiment of the present invention will be descr