# US 12,180,682 B2 · Hydraulic control system

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- Number: US 12,180,682 B2
- Document ID: US12180682B2
- Status: Granted
- Kind: B2
- Application number: 18/276,305
- Filed: 2022-02-03
- Published: 2024-04-11
- Granted: 2024-12-31
- Earliest claimed: 2021-02-08
- Assignees: Caterpillar SARL
- Applicants: Caterpillar SARL
- Inventors: Hideki Nakajima; Koichi Kiyasu
- Web page: https://patentgrep.com/patent/US12180682B2

## CPC

- E02F 9/2242: {including an electronic controller}
- E02F 9/2296: {Systems with a variable displacement pump}
- E02F 9/2235: {including an electronic controller}
- F15B 11/042: by means in the feed line (F15B11/046, F15B11/05 take precedence)
- F15B 11/044: by means in the return line (F15B11/046, F15B11/05 take precedence)
- F15B 11/17: using two or more pumps
- F15B 2211/20546: variable capacity
- F15B 2211/20576: with multiple pumps
- F15B 2211/253: Pressure margin control, e.g. pump pressure in relation to load pressure
- F15B 2211/30595: with additional valves between the groups of valves for multiple output members
- F15B 2211/3111: the pump port being closed in the centre position, e.g. so-called closed centre
- F15B 2211/3127: Floating position connecting the working ports and the return line
- F15B 2211/3144: the positions being continuously variable, e.g. as realised by proportional valves
- F15B 2211/31582: having multiple pressure sources and a single output member
- F15B 2211/327: electrically or electronically
- F15B 2211/329: actuated by fluid pressure
- F15B 2211/351: Flow control by regulating means in feed line, i.e. meter-in control
- F15B 2211/353: Flow control by regulating means in return line, i.e. meter-out control
- F15B 2211/413: the positions being continuously variable, e.g. as realised by proportional valves
- F15B 2211/41509: being connected to a pressure source and a directional control valve
- F15B 2211/426: electrically or electronically
- F15B 2211/428: actuated by fluid pressure
- F15B 2211/455: Control of flow in the feed line, i.e. meter-in control
- F15B 2211/6309: the pressure being a pressure source supply pressure
- F15B 2211/6313: the pressure being a load pressure
- F15B 2211/6346: representing a state of input means, e.g. joystick position
- F15B 2211/6652: Control of the pressure source, e.g. control of the swash plate angle
- F15B 2211/6654: Flow rate control
- F15B 2211/7135: Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
- F15B 2211/7142: the output members being arranged in multiple groups
- 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

To avoid a large size of a direction change-over valve and enable accurate supply flow control when providing a flow control valve at an upstream side of the direction change-over valve to change the relationship between supply flow rate and discharge flow rate for a hydraulic actuator. The configuration is to control a supply flow rate to a stick cylinder based on an opening area of the stick's direction change-over valve and stick's flow control valve, calculate a target opening area of the stick's flow control valve based on a target supply flow rate from hydraulic pumps A, B to the stick cylinder, the opening area of the stick's direction change-over valve, and a target differential pressure between hydraulic pump A and a load pressure of stick cylinder, and control the stick's flow control valve so as to keep the target opening area calculated.

## Claims

### Claim 1

A hydraulic control system comprising a hydraulic pump and a hydraulic actuator using the hydraulic pump as a hydraulic supply source,
wherein the system is provided with a direction change-over valve having supply/discharge valve passages for the hydraulic actuator and changing over supply/discharge directions, a flow control valve arranged at an upstream side of the direction change-over valve for controlling a supply flow rate from the hydraulic pump to the direction change-over valve, and a control means for controlling an operation of the direction change-over valve and the flow control valve;
a discharge flow rate for the hydraulic actuator is configured to be controlled based on an opening area of the discharge valve passage from of the direction change-over valve, and a supply flow rate from the hydraulic pump to the hydraulic actuator is configured to be controlled based on an opening area of the supply valve passage to of the direction change-over valve and an opening area of the flow control valve;
wherein the control means comprises: a target supply flow rate setting means to set up a target supply flow rate from the hydraulic pump to the hydraulic actuator depending on an operating amount of a hydraulic actuator's manipulator; a direction change-over valve's opening area setting means to set up the opening area of the supply/discharge valve passages for the direction change-over valve depending on the operating amount of the hydraulic actuator's manipulator; a target differential pressure setting means to set up a target differential pressure between a hydraulic pump pressure and a load pressure of the hydraulic actuator; and a calculation means to calculate a target opening area of the flow control valve for supplying the target supply flow rate to the hydraulic actuator based on the target supply flow rate preset above, the opening area of the supply valve passage to of the direction change-over valve, and the target differential pressure; and wherein the control means controls an operation of the flow control valve so as to keep the target opening area calculated by the calculation means.

### Claim 2 (depends on 1)

The hydraulic control system of claim 1, wherein when calculating the target opening area of the flow control valve, the calculation means calculates a differential pressure before and after the supply valve passage of the direction change-over valve based on the target supply flow rate and the opening area of the supply valve passage of the direction change-over valve, further calculates a differential pressure before and after the flow control valve based on the differential pressure before and after the supply valve passage of the direction change-over valve and the target differential pressure, and additionally calculates the target opening area of the flow control valve based on the differential pressure before and after the flow control valve.

### Claim 3 (depends on 1)

The hydraulic control system of claim 1, wherein the hydraulic pump comprises: first and second hydraulic pumps; wherein the hydraulic actuator is a large flow hydraulic actuator using both first and second hydraulic pumps as the hydraulic supply source; the direction change-over valve having the supply/discharge valve passages for the large flow hydraulic actuator and changing over the supply/discharge directions; main side/subside supply oil passages respectively connecting the first and second hydraulic pumps to a pump port of the direction change-over valve; wherein the system arranges the flow control valve for controlling a supply flow rate from the second hydraulic pump to the direction change-over valve, the supply flow rate from the hydraulic pump to the direction change-over valve comprising the supply flow rate from the second hydraulic pump to the direction change over valve at the subside supply oil passage;
wherein the operating amount of the hydraulic actuator manipulator comprises an operating amount of the large flow hydraulic actuator manipulator, when the operating amount of the large flow hydraulic actuator manipulator is less than a setting value, only a supply flow passing through the main side supply oil passage is configured to be supplied from first hydraulic pump to the direction change-over valve by closing the flow control valve; when the operating amount of the large flow hydraulic actuator's manipulator is not less than the setting value, the supply flow passing through the subside supply oil passage from the second hydraulic pump and the supply flow passing through the main side oil passage from the first hydraulic pump are configured to be joined together to be supplied to the direction change-over valve by opening the flow control valve;
wherein the discharge flow rate for the hydraulic actuator is a discharge flow rate for the large flow hydraulic actuator and is configured to be controlled based on the opening area of the discharge valve passage of the direction change-over valve; if the flow control valve is closed, the supply flow rate is configured to be controlled based on the opening area of the supply valve passage of the direction change-over valve; and if the flow control valve is opened, the supply flow rate is configured to be controlled based on the opening area of the flow control valve and the opening area of the supply valve passage to of the direction change-over valve;
wherein the target supply flow rate setting means provided to the control means sets up the target supply flow rate supplied from the first and second hydraulic pumps respectively to the large flow hydraulic actuator for each of the hydraulic pumps depending on the operating amount of the large flow hydraulic actuator's manipulator; the direction change-over valve's opening area setting means sets up the opening area of the supply/discharge valve passages for the direction change-over valve depending on the operating amount of the large flow hydraulic actuator's manipulator; the target differential pressure setting means sets up the target differential pressure between the second hydraulic pump pressure and the load pressure of the large flow hydraulic actuator; and the calculation means calculates the target opening area of the flow control valve for supplying the target supply flow rate from the second hydraulic pump to the large flow hydraulic actuator based on the target supply flow rate preset above, the opening area of the supply valve passage of the direction change-over valve, and the target differential pressure.

### Claim 4 (depends on 3)

The hydraulic control system of claim 3, wherein when calculating the target opening area of the flow control valve, the calculation means calculates a differential pressure before and after the supply valve passage of the direction change-over valve based on the target supply flow rate from the first and second hydraulic pumps to the hydraulic actuator and the opening area of the supply valve passage of the direction change-over valve, further calculates the differential pressure before and after the flow control valve based on the differential pressure before and after the supply valve passage of the direction change-over valve and the target differential pressure, and additionally calculates the target opening area of the flow control valve based on a differential pressure before and after the flow control valve from the second hydraulic pump to the hydraulic actuator.