Hydraulic system having low speed operation

Patent metadata

Field	Value
Publication number	US-9366272-B2
Application number	US-201313963150-A
Country	US
Kind code	B2
Filing date	Aug 9, 2013
Priority date	Aug 9, 2013
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

A hydraulic fan circuit is provided. The hydraulic fan circuit includes a tank, a motor having a fluid inlet and a fluid outlet and a pump to draw fluid at a low pressure from the tank and discharge the fluid at elevated pressures to the motor via the fluid inlet. The hydraulic fan circuit further includes a directional control valve disposed between the fluid outlet of the motor and the tank. The directional control valve is operable to move between a flow blocking position and a flow passing position. Further, the directional control valve is configured to reduce a positive speed of the motor below a lowest positive speed attainable through control of pump output. Furthermore, the hydraulic fan circuit includes a pressure control circuit configured to provide a pilot fluid flow at varying pressure to move the directional control valve.

First claim

What is claimed is:

1. A hydraulic system comprising:
a tank;
a motor having a fluid inlet and a fluid outlet;
a pump configured to draw fluid at a low pressure from the tank and discharge the fluid at elevated pressures to the motor via the fluid inlet;
a directional control valve disposed between the fluid outlet of the motor and the tank and operable to move between a flow blocking position and a flow passing position, the directional control valve being configured to reduce a positive speed of the motor below a lowest positive speed attainable through control of pump output;
a pressure control circuit configured to provide a pilot fluid flow at varying pressure to move the directional control valve;
a variable orifice disposed in a parallel relationship with the directional control valve; and
a fixed orifice disposed in a parallel relationship with the directional control valve and with the variable orifice.

2. The hydraulic system of claim 1 , wherein the pressure control circuit includes a solenoid operated valve arrangement configured to adjust the pilot fluid flow.

3. The hydraulic system of claim 2 , wherein the pressure control circuit includes a sensor configured to detect an operational parameter associated with a power source, a controller in communication with the sensor and the solenoid operated valve arrangement, the controller being configured move the solenoid operated valve arrangement to a desired position based on the operational parameter.

4. The hydraulic system of claim 3 , wherein the pump includes a pump compensator configured to receive the pilot fluid flow from the pressure control circuit.

5. The hydraulic system of claim 1 , wherein the pump is a variable displacement hydraulic pump configured to be operated by the pilot fluid flow from the pressure control circuit.

6. A machine having the hydraulic system of claim 1 .

7. A hydraulic system comprising:
a tank;
a motor having a fluid inlet and a fluid outlet;
a pump configured to draw fluid at a low pressure from the tank and discharge the fluid at elevated pressures to the motor via the fluid inlet;
a low speed valve arrangement configured to reduce a positive speed of the motor below a lowest positive speed attainable through control of pump output, the low speed valve arrangement including:
a directional control valve disposed between the fluid outlet of the motor and the tank and operable to move between a flow blocking position and a flow passing position;
a variable orifice disposed in a parallel relationship with the directional control valve; and
a fixed orifice disposed in a parallel relationship with the directional control valve and with the variable orifice.

8. The hydraulic system of claim 7 , wherein the directional control valve is operable based on a pressure associated with the pump.

9. The hydraulic system of claim 7 further comprising a pressure control circuit having a solenoid operated valve arrangement configured to adjust a pilot fluid flow.

10. The hydraulic system of claim 9 , wherein the pressure control circuit adjusts the pilot fluid flow based on an operational parameter associated with a power source.

11. The hydraulic system of claim 10 , wherein the operational parameter is a temperature associated with the power source.

12. The hydraulic system of claim 9 , wherein the pump is a variable displacement hydraulic pump configured to be operated by the pilot fluid flow from the pressure control circuit.

13. The hydraulic system of claim 9 , wherein the pump includes a stroke adjusting mechanism and a pump compensator associated with the stroke adjusting mechanism wherein the pump compensator is configured to receive the pilot flow from the pressure control circuit.

14. A machine having the hydraulic system of claim 7 .

15. A method of operating a motor fluidly coupled to a pump in a hydraulic system, the hydraulic system is associated with a power source, the method comprising:
detecting an operational parameter associated with the power source;
generating a pilot fluid flow by a pressure control circuit based on the detected operational parameter; and
simultaneously operating a directional control valve disposed downstream to the motor to selectively increase a back pressure on the motor and adjusting a displacement of the pump to a first displacement position by the pilot flow from the pressure control circuit.

16. The method of claim 15 , wherein generating a pilot fluid flow further includes receiving an input signal by a solenoid operated valve arrangement of the pressure control circuit, the input signal indicative of an over cooling condition associated with the power source.

17. The method of claim 15 , wherein operating the directional control valve further includes selectively allowing a fluid flow through a variable orifice disposed in parallel relationship with the directional control valve.

18. The method of claim 17 , wherein operating the directional control valve further includes selectively allowing a fluid flow through a fixed orifice disposed in a parallel relationship with the directional valve and with the variable orifice.

Assignees

• Caterpillar Inc

Inventors

• Bieker Susan E
• Jakubiak Eric P
• Barber Dennis R
• Kaufman John J
• Mate Edward W
• Vollmer Scott D
• Hudson Michael D
• Akpan Moses I

Classifications

• E02F9/0875

  Arrangement of valve arrangements on superstructures (arrangement of hydraulic hoses E02F9/2275 takes precedence; valves per se E02F9/2267) · CPC title

• F16H61/433 Primary

  Pump capacity control by fluid pressure control means · CPC title

• F15B2211/41581

  being connected to an output member and a return line · CPC title

• F16H61/465

  for achieving a target input speed · CPC title

• E02F9/0866

  Engine compartment, e.g. heat exchangers, exhaust filters, cooling devices, silencers, mufflers, position of hydraulic pumps in the engine compartment · CPC title