Hydraulic system for a work vehicle

• US 9,353,770 B2
• Filed: 02/08/2011
• Issued: 05/31/2016
• Est. Priority Date: 03/31/2010
• Status: Active Grant

• Current Assignee: Kubota Corporation
• Original Assignee: Kubota Corporation
• Inventors: Fukumoto, Toshiya
• Primary Examiner(s): Wiehe, Nathaniel
• Assistant Examiner(s): Teka, Abiy
• Application Number:
  US13/389,570
• Publication Number:
  US 20120198832A1
• Time in Patent Office: 1,939 Days
• Field of Search: 604/21, 604/22, 603/24
• US Class Current: 1/1
• CPC Class Codes: F15B 11/162 for giving priority to particular servomotors or users
• CPC Class Codes: F15B 13/024 Pressure relief valves
• CPC Class Codes: F15B 2211/30535 the pressure compensating valve is arranged between pressure source and directional control valve
• CPC Class Codes: F15B 2211/3111 the pump port being closed in the centre position, e.g. so-called closed centre
• CPC Class Codes: F15B 2211/4053 using valves
• CPC Class Codes: F15B 2211/781 one or more output members having priority

Abstract

A hydraulic system for a work vehicle is disclosed. A preferential flow-dividing valve supplies a fixed amount of oil discharged from a variable displacement pump preferentially to a preferential hydraulic oil section and a surplus oil flow from the pump to a non-preferential hydraulic oil section. A plurality of electromagnetic proportional control valves are provided in the non-preferential hydraulic oil section for controlling oil flows relative to a plurality of hydraulically operated devices provided in the non-preferential hydraulic oil section. A necessary flow rate calculating module calculates a necessary oil flow rate in each of the preferential hydraulic oil section and the non-preferential hydraulic oil section based on a preferential oil flow rate of the preferential flow-dividing valve supplied to the preferential hydraulic oil section and an amount of current distributed to each of the plurality of electromagnetic proportional control valves in the non-preferential hydraulic oil section.

Claims

1. A hydraulic system for a work vehicle, comprising:

a variable displacement pump operable with drive power form an engine;

an actuator for regulating a discharge rate of the variable displacement pump;

a preferential flow-dividing valve for supplying a fixed amount of oil discharged from the variable displacement pump preferentially to a preferential hydraulic oil section and supplying a surplus oil flow from the pump to a non-preferential hydraulic oil section;

a plurality of electromagnetic proportional control valves provided in the non-preferential hydraulic oil section for controlling oil flows relative to a plurality of hydraulically operated devices included in the non-preferential hydraulic oil section, the plurality of electromagnetic proportional control valves including a high priority electromagnetic proportional control valve and a low priority electromagnetic proportional control valve;

a second preferential flow-dividing valve provided in the non-preferential hydraulic oil section for supplying a preferential oil flow to the high priority electromagnetic proportional control valve, and supplying a surplus oil flow of the preferential oil to the low priority electromagnetic proportional control valve;

a necessary flow rate calculating module for directly calculating a necessary oil flow rate in each of the preferential hydraulic oil section and the non-preferential hydraulic oil section based on a preferential oil flow rate of the preferential flow-dividing valve supplied oil to the preferential hydraulic oil section and an amount of current distributed to each of the plurality of electromagnetic proportional control valves in the non-preferential hydraulic oil section;

correlation data showing relationship among the discharge rate of the variable displacement pump, a rotational speed of the engine and an operational amount of the actuator;

a target operational amount setting module for providing a control target operational amount of the actuator for obtaining the necessary oil flow rate calculated at the necessary flow rate calculating module based on the necessary oil flow rate calculated at the necessary flow rate calculating module, an output from a rotary sensor for detecting the rotational speed of the engine, and the correlation data; and

an operation control module for controlling the actuator based on the control target operational amount.

2. The hydraulic system according to in claim 1, wherein the target operational amount setting module is

configured to obtain a volume efficiency of the variable displacement pump based on an output from an oil temperature sensor for detecting a temperature of oil and an output from a pressure sensor for detecting discharge pressure of the variable displacement pump, and to correct the control target operational amount of the actuator based on the obtained volume efficiency.

3. The hydraulic system according to in claim 2, further comprising:

an oil pressure detecting module for detecting pressure of oil supplied to a most downstream electromagnetic proportional control valve,

wherein the target operational amount setting module is configured to correct the control target operational amount of the actuator to allow the pressure of oil supplied to the most downstream electromagnetic proportional control valve to reach a predetermined pressure based on an output from the oil pressure detecting module.

4. The hydraulic system according to in claim 2, wherein the second preferential flow-dividing valve provided in the non-preferential hydraulic oil section is a variable preferential flow-dividing valve;

a plurality of the high priority electromagnetic proportional control valves are provided in the non-preferential hydraulic oil section,

each of the high priority electromagnetic proportional control valves comprises a closed-center type valve, and

wherein each of the electromagnetic proportional control valves forms a hydraulic unit which comprises a closed load-sensing type hydraulic unit for regulating the preferential flow rate of the variable preferential flow-dividing valve based on load-sensing pressure.

5. The hydraulic system according to in claim 1, further comprising:

an oil pressure detecting module for detecting pressure of oil supplied to a most downstream electromagnetic proportional control valve,

wherein the target operational amount setting module is configured to correct the control target operational amount of the actuator to allow the pressure of oil supplied to the most downstream electromagnetic proportional control valve to reach a predetermined pressure based on an output from the oil pressure detecting module.

6. The hydraulic system according to in claim 5, wherein

the second preferential flow-dividing valve provided in the non-preferential hydraulic oil section is a variable preferential flow-dividing valve;

a plurality of the high priority electromagnetic proportional control valves are provided in the non-preferential hydraulic oil section,

each of the high priority electromagnetic proportional control valves comprises a closed-center type valve, and

wherein each of the electromagnetic proportional control valves forms a hydraulic unit which comprises a closed load-sensing type hydraulic unit for regulating the preferential flow rate of the variable preferential flow-dividing valve based on load-sensing pressure.

7. The hydraulic system according to in claim 1, wherein

the second preferential flow-dividing valve provided in the non-preferential hydraulic oil section is a variable preferential flow-dividing valve;

a plurality of the high priority electromagnetic proportional control valves are provided in the non-preferential hydraulic oil section,

each of the high priority electromagnetic proportional control valves comprises a closed-center type valve, and

wherein each of the electromagnetic proportional control valves forms a hydraulic unit which comprises a closed load-sensing type hydraulic unit for regulating the preferential flow rate of the variable preferential flow-dividing valve based on load-sensing pressure.