Hydraulic power management system
View Patent ↗A machine having a hydraulic power management system. The machine includes an internal combustion engine driving first and second fixed displacement pumps to produce a combined flow of pressurized fluid. Main and auxiliary implements are operable in response to a flow of pressurized fluid, and a control valve selectively directs the combined flow to the main and auxiliary implements. A power management system is operable to stop the flow of pressurized fluid to the main implement from the second pump when the pressure of the combined flow exceeds a pressure indicative of the impending engine stall. A means for providing the combined flow to the auxiliary implement without regard to the pressure of the combined flow is also provided, and may take the form of a power management override or bypass mechanism.
1. A compact construction vehicle comprising:
a frame;
a lift arm supported by and pivotable with respect to the frame;
a bucket supported by and pivotable with respect to the lift arm;
an internal combustion engine on the frame, the engine having an output threshold below which the internal combustion engine operates and at which the internal combustion engine stalls;
first and second fixed displacement pumps driven by the internal combustion engine to create a combined flow of pressurized fluid;
a lift cylinder adapted to pivot the lift arm in raising and lowering directions in response to receiving pressurized fluid;
a tilt cylinder adapted to pivot the bucket in curling and dumping directions in response to receiving pressurized fluid;
an auxiliary implement adapted to perform work in response to receiving pressurized fluid;
a main control valve receiving the combined flow of pressurized fluid, the main control valve including lift, tilt, and auxiliary spools, each spool having a center position, and each movable from the center position to direct the combined flow of pressurized fluid to the respective lift cylinder, tilt cylinder, and auxiliary implement;
a power management system for preventing pressurized fluid from the second pump to flow to the main control valve when the pressure of pressurized fluid flowing to the main control valve exceeds a stall pressure indicative of the engine reaching the output threshold; and
an auxiliary high flow mechanism for permitting the combined flow of pressurized fluid to flow to the auxiliary implement when the auxiliary spool is moved from its center position, without regard to whether the pressure of pressurized fluid flowing into the main control valve exceeds the stall pressure, wherein the auxiliary high flow mechanism includes a reference signal line providing a reference signal indicative of the auxiliary spool shifting off its center position the reference signal disabling the power management system from preventing pressurized fluid from the second pump to flow to the main control valve and to the lift, tilt, and auxiliary spools.
2. The vehicle of claim 1 , wherein the auxiliary high flow mechanism includes a bypass valve routing pressurized fluid from the second pump to the auxiliary implement without flowing through the main control valve.
3. The vehicle of claim 1 , wherein the power management system includes a power management valve shiftable between a first position in which the second pump provides pressurized fluid to the main control valve, and a second position in which the second pump is prevented from providing pressurized fluid to the main control valve.
4. The vehicle of claim 3 , wherein the power management system includes a reference signal indicative of the pressure of pressurized fluid flowing into the main control valve, wherein the power management valve is shifted to the second position in response to the reference signal indicating the pressure exceeding the stall pressure.
5. The vehicle of claim 1 , wherein the first and second fixed displacement pumps are driven at constant speed under the influence of the engine.
6. A method for operating a machine that includes an internal combustion engine, first and second fixed displacement pumps, a main implement, and an auxiliary implement, the method comprising:
(a) driving operation of the first and second fixed displacement pumps with the internal combustion engine;
(b) producing a combined flow of pressurized fluid with the first and second pumps;
(c) selectively operating the main and auxiliary implements with the combined flow of pressurized fluid;
(d) sensing the pressure of the combined flow;
(e) preventing the flow of pressurized fluid to the main implement from the second pump when the pressure of the combined flow exceeds a pressure indicative of potential engine stall; and
(f) permitting the combined flow of pressurized fluid to the auxiliary implements without regard to the pressure of the combined flow, further comprising sensing whether pressurized fluid is being provided to the auxiliary implement and permitting flow of pressurized fluid to the auxiliary implement and main implement without regard to the pressure of the combined flow while pressurized fluid is being provided to the auxiliary implement.
7. The method of claim 6 , wherein step (e) includes using a redirecting mechanism to route pressurized fluid from the second pump into a reservoir; and wherein step (f) includes disabling the redirecting mechanism.
8. The method of claim 6 , wherein step (c) includes using a control valve to direct the combined flow to the main and auxiliary implements, and wherein step (f) includes routing the flow of pressurized fluid from the second pump to the auxiliary implement without flowing through the control valve.
9. The method of claim 6 , wherein step (a) includes driving the first and second fixed displacement pumps at constant speed under the influence of the engine.
10. A compact construction vehicle comprising:
a frame;
a lift arm supported by and pivotable with respect to the frame;
a bucket supported by and pivotable with respect to the lift arm;
an internal combustion engine on the frame, the engine having an output threshold below which the internal combustion engine operates and at which the internal combustion engine stalls;
first and second fixed displacement pumps driven by the internal combustion engine to create a combined flow of pressurized fluid;
a lift cylinder adapted to pivot the lift arm in raising and lowering directions in response to receiving pressurized fluid;
a tilt cylinder adapted to pivot the bucket in curling and dumping directions in response to receiving pressurized fluid;
an auxiliary implement adapted to perform work in response to receiving pressurized fluid;
a main control valve receiving the combined flow of pressurized fluid, the main control valve including lift, tilt, and auxiliary spools, each spool having a center position, and each movable from the center position to direct the combined flow of pressurized fluid to the respective lift cylinder, tilt cylinder, and auxiliary implement;
a power management system for preventing pressurized fluid from the second pump to flow to the main control valve when the pressure of pressurized fluid flowing to the main control valve exceeds a stall pressure indicative of the engine reaching the output threshold; and
an auxiliary high flow mechanism for permitting the combined flow of pressurized fluid to flow to the auxiliary implement when the auxiliary spool is moved from its center position, without regard to whether the pressure of pressurized fluid flowing into the main control valve exceeds the stall pressure, wherein the auxiliary high flow mechanism disables the power management system; and
a disabling mechanism which selectively disables the auxiliary high flow mechanism to permit the power management system to operate under circumstances in which operation of the auxiliary device is optimized by the supply of fluid from only the first pump.
11. The vehicle of claim 10 , further comprising a control system configured to control the disabling mechanism in response to engine speed dropping below a speed threshold at which the combined flow rate provided by the first and second pumps is lower than a flow rate that would be provided by only the first pump with the engine operating at a speed higher than the speed threshold.
12. The vehicle of claim 11 , wherein the control system enables the power management system through the disabling mechanism when the engine speed drops below the threshold speed.
13. The vehicle of claim 10 , wherein the auxiliary high flow mechanism includes a reference signal indicative of the auxiliary spool shifting off its center position, the reference signal disabling the power management system from preventing pressurized fluid from the second pump to flow to the main control valve.
14. The vehicle of claim 10 , wherein the auxiliary high flow mechanism includes a bypass valve routing pressurized fluid from the second pump to the auxiliary implement without flowing through the main control valve.
15. The vehicle of claim 10 , wherein the power management system includes a power management valve shiftable between a first position in which the second pump provides pressurized fluid to the main control valve, and a second position in which the second pump is prevented from providing pressurized fluid to the main control valve.
16. The vehicle of claim 15 , wherein the power management system includes a reference signal indicative of the pressure of pressurized fluid flowing into the main control valve, wherein the power management valve is shifted to the second position in response to the reference signal indicating the pressure exceeding the stall pressure.
17. The vehicle of claim 10 , wherein the first and second fixed displacement pumps are driven at constant speed under the influence of the engine.