A hydraulic fan circuit includes a primary pump, a motor fluidly connected to the primary pump, and a fan operably connected to and driven by the motor. The circuit also includes a supply passage extending from the primary pump to the motor, a return passage extending from the motor to the primary p
A hydraulic fan circuit includes a primary pump, a motor fluidly connected to the primary pump, and a fan operably connected to and driven by the motor. The circuit also includes a supply passage extending from the primary pump to the motor, a return passage extending from the motor to the primary pump, and a pressure limiting valve configured to selectively reduce pressure of a flow of pilot fluid directed to the primary pump. The circuit further includes an override valve configured to selectively connect the supply passage to the pressure limiting valve.
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1. A hydraulic fan circuit, comprising: a primary pump;a motor fluidly connected to the primary pump;a fan operably connected to and driven by the motor;a supply passage extending from the primary pump to the motor;a return passage extending from the motor to the primary pump;a pressure limiting val
1. A hydraulic fan circuit, comprising: a primary pump;a motor fluidly connected to the primary pump;a fan operably connected to and driven by the motor;a supply passage extending from the primary pump to the motor;a return passage extending from the motor to the primary pump;a pressure limiting valve configured to selectively reduce pressure of a flow of pilot fluid directed to the primary pump; andan override valve configured to selectively connect the supply passage to the pressure limiting valve. 2. The hydraulic fan circuit of claim 1, wherein the override valve is configured to selectively disconnect the pressure limiting valve from the return passage. 3. The hydraulic fan circuit of claim 1, wherein the override valve is a two-way, solenoid-actuated valve. 4. The hydraulic fan circuit of claim 1, further comprising a pressure resolver configured to fluidly connect the pressure limiting valve to at least one of the supply passage and the return passage via the override valve. 5. The hydraulic fan circuit of claim 4, wherein the pressure resolver is configured to connect the one of the supply and the return passage having the higher pressure with the pressure limiting valve. 6. The hydraulic fan circuit of claim 4, wherein transitioning the pressure limiting valve toward a flow-passing position permits a portion of the flow of pilot fluid to drain to a low-pressure sump. 7. The hydraulic fan circuit of claim 1, further comprising a pressure control valve operable to control a displacement of the primary pump. 8. The hydraulic fan circuit of claim 7, wherein the pressure control valve is operable to control a speed of the fan. 9. The hydraulic fan circuit of claim 7, further comprising: a displacement actuator operably connected to the primary pump; anda charge pump configured to generate the flow of pilot fluid, the pressure control valve directing the pilot fluid to affect movement of the displacement actuator. 10. The hydraulic fan circuit of claim 9, wherein the charge pump is connected to the primary pump, and the charge and primary pumps are driven by a combustion engine. 11. A hydraulic fan circuit, comprising: a primary pump;a motor driven by the primary pump;a fan connected to and driven by the motor;a pressure control valve configured to receive a flow of pilot fluid and to control a speed of the fan;a supply passage and a return passage, the supply and return passages fluidly connecting the motor to the primary pump in a closed circuit configuration;a pressure resolver fluidly connected to the supply and return passages;a pressure limiting valve fluidly connected to the pressure resolver and configured to prevent the fan from exceeding a maximum cooling speed by limiting pressure of the flow of pilot fluid; andan override valve fluidly connected between the pressure resolver and the pressure limiting valve, the override valve configured to assist in increasing the speed of the fan above the maximum cooling speed. 12. The hydraulic fan circuit of claim 11, wherein the maximum cooling speed is less than a fan speed corresponding to a structural limit of the fan. 13. The hydraulic fan circuit of claim 11, further comprising a displacement actuator associated with the primary pump, and a charge pump configured to generate the flow of pilot fluid. 14. The hydraulic fan circuit of claim 11, wherein the pressure limiting valve is fluidly connected to the pressure control valve. 15. The hydraulic fan circuit of claim 11, wherein the override valve and the pressure control valve are biased toward respective open positions permitting passage of fluid. 16. The hydraulic fan circuit of claim 11, wherein the primary pump is driven by a combustion engine, and wherein transitioning the override valve from an open position permitting passage of fluid between the pressure resolver and the pressure limiting valve, and a closed position blocking passage of fluid between the pressure resolver and the pressure limiting valve reduces a speed of the engine. 17. A method of reducing engine speed with a hydraulic fan circuit, comprising: driving a primary pump with a combustion engine;directing a pressurized flow of fluid from the primary pump to a fan motor;generating a flow of air with a fan connected to the fan motor, the flow of air assisting in cooling the engine;receiving a request for engine speed reduction; andresponsively increasing a speed of the fan above a maximum cooling speed and below a fan speed corresponding to a structural limit of the fan, wherein responsively increasing the speed of the fan comprises overriding a fluid pressure limitation associated with at least one of the primary pump and the fan motor. 18. The method of claim 17, wherein overriding the fluid pressure limitation comprises transitioning an override valve from an open position permitting passage of fluid between a pressure resolver and a pressure limiting valve, and a closed position blocking passage of fluid between the pressure resolver and the pressure limiting valve. 19. The method of claim 17, wherein directing the pressurized flow of fluid comprises: selecting a target fan speed;incrementally increasing the speed of the fan until the speed of the fan is substantially equal to the target fan speed;storing an electrical current value corresponding to the speed of the fan substantially equaling the target fan speed; anddirecting an electrical current having a magnitude equal to the stored electrical current value to a valve in fluid communication with the primary pump and the fan motor. 20. The method of claim 19, further comprising incrementally sensing the speed of the fan with a speed sensor associated with the fan motor.
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이 특허에 인용된 특허 (15)
Hawkins Jeffery Scott ; Weisman Steve Miller, Closed loop fan control using fan motor pressure feedback.
Desjardins,Yvon Clarence; C?t?,Sylvain Raymond; Doutre,Phillippe Louis; Yetter,James Edward, Electro-hydraulic fan drive cooling and steering system for vehicle.
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