# US 2023/0407597 A1 · Hydraulic circuit for a construction machine

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- Number: US 2023/0407597 A1
- Document ID: US20230407597A1
- Status: Published application
- Kind: A1
- Application number: 18/210,149
- Filed: 2023-06-15
- Published: 2023-12-21
- Earliest claimed: 2022-06-15
- Assignees: Caterpillar SARL
- Applicants: Caterpillar SARL
- Inventors: Isao KONISHI; Hiroshi MAEDA; Hirotaka MINAMIURA; Kazuya MIYAMORI; Yoshitaka KATO
- Web page: https://patentgrep.com/patent/US20230407597A1

## CPC

- E02F 9/2228: {including an electronic controller}
- E02F 9/2235: {including an electronic controller}
- E02F 9/226: {Safety arrangements, e.g. hydraulic driven fans, preventing cavitation, leakage, overheating}
- E02F 9/2267: {Valves or distributors (position of valves arrangements on upper-structures E02F9/0875)}
- E02F 9/2275: {Hoses and supports therefor and protection therefor}
- E02F 9/2296: {Systems with a variable displacement pump}
- F15B 13/027: {Check valves}
- F15B 19/00: Testing; {Calibrating; Fault detection or monitoring; Simulation or modelling of} fluid-pressure systems or apparatus not otherwise provided for
- F15B 21/0423: Cooling
- F15B 21/0427: Heating
- E02F 3/963: {Arrangements on backhoes for alternate use of different tools (backhoes per se E02F3/30; quick-acting devices to connect tools to arms E02F3/3609, for arms to tractors or the like E02F3/627)}
- E02F 3/966: {of hammer-type tools (arrangements for breaking-up hard ground E02F5/305; percussion -type rippers E02F5/323)}
- F15B 2211/20546: variable capacity
- F15B 2211/30505: Non-return valves, i.e. check valves
- F15B 2211/3144: the positions being continuously variable, e.g. as realised by proportional valves
- F15B 2211/327: electrically or electronically
- F15B 2211/413: the positions being continuously variable, e.g. as realised by proportional valves
- F15B 2211/41581: being connected to an output member and a return line
- F15B 2211/426: electrically or electronically
- F15B 2211/46: Control of flow in the return line, i.e. meter-out control
- F15B 2211/50518: using pressure relief valves
- F15B 2211/611: Diverting circuits, e.g. for cooling or filtering
- F15B 2211/62: Cooling or heating means
- F15B 2211/6343: representing a temperature
- F15B 2211/6346: representing a state of input means, e.g. joystick position
- F15B 2211/7058: Rotary output members
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR

## Abstract

Provide a hydraulic circuit that can prevent damage to the oil cooler while suppressing excessive rise in the temperature of the operating oil. The hydraulic circuit includes a control valve that controls supply of operating oil from the hydraulic pump to the work tool; a first return pipeline that connects the control valve with the operating oil tank; an oil cooler disposed in the first return pipeline on a downstream side of a first check valve; a second return conduit that branches from the first return pipeline and extends to the operating oil tank without passing through the oil cooler; a third return pipeline that branches from the pipeline and extends to the first return pipeline between the first check valve and the oil cooler; a solenoid valve disposed in the third return pipeline; an operating device that outputs an operating signal of the work tool; a controller that opens the control valve and the solenoid valve based on the signal output from the operating device; and an operating oil temperature sensor. The controller reduces the amount of operating oil passing through the oil cooler when a temperature detected by the temperature sensor is less than a predetermined value.

## Claims

### Claim 1

A hydraulic circuit of a construction machine, comprising:
a hydraulic pump having variable capacity,
a work tool operated by operating oil discharged by the hydraulic pump,
a control valve controlling supply of operating oil from the hydraulic pump to the work tool;
a pair of pipelines connecting the control valve and the work tool;
a first return pipeline connecting the control valve and the hydraulic oil tank;
a first check valve disposed in the first return pipeline;
an oil cooler disposed in the first return pipeline on a downstream side of the first check valve;
a second return pipeline that branches from the first return line and extends into the operating oil tank without passing through the oil cooler;
a second check valve disposed in the second return pipeline;
a third return pipeline that branches from one of the pair of pipelines and extends to the first return pipeline between the first check valve and the oil cooler;
a solenoid valve disposed in the third return pipeline;
an operating device to output a signal for operating the work tool,
a controller that opens the control valve and the solenoid valve based on a signal output from the operating device; and
a temperature sensor electrically connected to the controller to detect a temperature of the operating oil,
wherein the controller reduces the amount of operating oil passing through the oil cooler in the case where the temperature detected by the temperature sensor is less than a predetermined value.

### Claim 2 (depends on 1)

The hydraulic circuit of a construction machine according to claim 1, wherein the controller makes an opening area of the control valve in the case where the temperature detected by the temperature sensor is less than the predetermined value be larger than the opening area of the control valve in the case where the temperature detected by the temperature sensor is larger than or equal to the predetermined value.

### Claim 3 (depends on 2)

The hydraulic circuit of a construction machine according to claim 2, wherein the controller gradually increases the opening area of the control valve as the temperature detected by the temperature sensor decreases.

### Claim 4 (depends on 1)

The hydraulic circuit of a construction machine according to claim 1, wherein the controller makes a discharge amount of the hydraulic pump in the case where the temperature detected by the temperature sensor is less than the predetermined value be less than the discharge amount of the hydraulic pump in the case where the temperature detected by the temperature sensor is larger than or equal to the predetermined value.

### Claim 5 (depends on 4)

The hydraulic circuit of a construction machine according to claim 4, wherein the controller gradually reduces the discharge amount of the hydraulic pump as the temperature detected by the temperature sensor decreases.