Multifunctional transmission valve with integrated load brake function
A self-propelled work vehicle includes a vehicle frame and a plurality of wheels or tracks supporting the vehicle frame from a ground surface. A battery provides electrical power to an electric motor. A hydraulic pump provides hydraulic fluid to a hydraulic system. A steering valve directs hydraulic fluid from the hydraulic system to a steering actuator. A steering priority valve prioritizes supply of hydraulic fluid from the hydraulic system to the steering valve. A proportional relief valve provides a load sense signal to the load sense port of the steering priority valve which shifts the steering priority spool to build hydraulic system pressure. A controller is configured to detect whether the battery is able to be further charged and to control operation of the proportional relief valve to control a hydraulic braking function provided by the steering priority valve.
1 . A self-propelled work vehicle comprising:
a vehicle frame;
a plurality of wheels or tracks supporting the vehicle frame from a ground surface;
one or more work implements supported from the vehicle frame;
a battery;
an electric motor configured in a drive mode to use electric power from the battery to drive one or more of the wheels or tracks and configured in a regenerative mode to generate electric power to be stored in the battery when the electric motor is driven by kinetic energy of the vehicle;
a hydraulic pump driven directly or indirectly by the electric motor to provide hydraulic fluid to a hydraulic system of the vehicle;
a steering valve configured to direct hydraulic fluid from the hydraulic system to a steering actuator to steer the vehicle;
a steering priority valve configured to prioritize supply of hydraulic fluid from the hydraulic system to the steering valve, the steering priority valve including a load sense input port;
a proportional relief valve communicated with the steering priority valve to provide a load sense signal to the load sense input port of the steering priority valve; and
a controller configured to detect whether the battery is able to be further charged and in response to a determination that the battery should not be further charged to send an adjustment command signal to the proportional relief valve commanding the proportional relief valve to increase the load sense signal from the proportional relief valve to the load sense input port of the steering priority valve so that a standby pressure in the hydraulic system between the pump and the steering priority valve is increased thereby increasing a load on the pump to provide a hydraulic load brake function.
2 . The self-propelled work vehicle of claim 1 , wherein:
the controller is further configured to detect a rate of charging of the battery and the adjustment command signal is based at least in part on the detected rate of charging of the battery.
3 . The self-propelled work vehicle of claim 1 , further comprising:
a transmission connecting the electric motor to one or more of the wheels or tracks; and
a transmission control valve, configured to control supply of hydraulic fluid from the hydraulic system to the transmission, the transmission control valve including the proportional relief valve.
4 . The self-propelled work vehicle of claim 1 , wherein:
the proportional relief valve is configured such that in the absence of the adjustment command signal from the controller the proportional relief valve dumps hydraulic pressure to a reservoir of the hydraulic system so that no load sense signal is provided from the proportional relief valve to the steering priority valve.
5 . The self-propelled work vehicle of claim 1 , wherein:
the steering valve includes a load sense output port communicated with the load sense input port of the steering priority valve so that the steering priority valve detects a hydraulic pressure needed by the steering valve and prioritizes provision of the needed hydraulic pressure to the steering valve.
6 . The self-propelled work vehicle of claim 5 , further comprising:
a check valve included in the hydraulic system between the proportional relief valve and the load sense output port of the steering valve, the check valve being configured to permit flow from the proportional relief valve toward the steering priority valve.
7 . The self-propelled work vehicle of claim 1 , wherein:
the controller is configured to provide a normal steering operation mode wherein no adjustment command signal is provided to the proportional relief valve, no load sense signal is provided from the proportional relief valve to the steering priority valve, and a load sense signal is provided from the steering valve to the steering priority valve.
8 . The self-propelled work vehicle of claim 1 , wherein:
the controller is configured to provide a no steering with transmission standby operation mode wherein the steering valve is not activated and wherein the adjustment command signal is sent to the proportional relief valve commanding the proportional relief valve to provide the load sense signal to the steering priority valve to control a pump standby pressure provided by the hydraulic pump.
9 . The self-propelled work vehicle of claim 1 , wherein:
the controller is configured to provide a no steering with load brake operation mode wherein the steering valve is not activated and wherein the adjustment command signal is sent to the proportional relief valve commanding the proportional relief valve to provide the load sense signal to the steering priority valve to provide the hydraulic load brake function in response to the load sense signal from the proportional relief valve.
10 . The self-propelled work vehicle of claim 9 , wherein:
the controller is configured to detect a level of kinetic energy of the vehicle to be dissipated and to adjust the adjustment command signal to adjust the hydraulic load brake function at least in part in response to the detected level of kinetic energy of the vehicle to be dissipated.
11 . A method of operating a self-propelled work vehicle, the vehicle including a vehicle frame, a plurality of wheels or tracks supporting the vehicle frame from a ground surface, a battery, an electric motor, a hydraulic pump configured to provide hydraulic fluid to a hydraulic system of the vehicle, a steering valve configured to direct hydraulic fluid from the hydraulic system to steer the vehicle, and a steering priority valve configured to prioritize supply of hydraulic fluid from the hydraulic system to the steering valve, the steering priority valve including a load sense input port, the method comprising:
in a drive mode, using electric power from the battery to power the electric motor to drive one or more of the wheels or tracks;
in a regenerative mode, using kinetic energy of the vehicle to drive the electric motor to regenerate electric power;
detecting with a controller whether the battery is able to be further charged when in the regenerative mode;
in response to a determination that the battery should not be further charged, sending an adjustment command signal from the controller to a proportional relief valve communicated with the hydraulic system;
adjusting the proportional relief valve in response to the adjustment command signal to provide a load sense signal to the load sense input port of the steering priority valve; and
increasing a standby pressure in the hydraulic system between the pump and the steering priority valve in response to the load sense signal and thereby increasing a load on the pump to provide a hydraulic load brake function in response to the load sense signal.
12 . The method of claim 11 , further comprising:
in the absence of the adjustment command signal from the controller to the proportional relief valve, dumping hydraulic pressure through the proportional relief valve to a reservoir of the hydraulic system so that no load sense signal is provided from the proportional relief valve to the steering priority valve.
13 . The method of claim 11 , further comprising:
communicating a load sense output port of the steering valve with the load sense input port of the steering priority valve so that the steering priority valve detects a hydraulic pressure needed by the steering valve and prioritizes provision of the needed hydraulic pressure to the steering valve.
14 . The method of claim 11 , further comprising:
providing a load sense signal from the steering valve to the steering priority valve in a normal steering operation mode wherein no adjustment command signal is provided to the proportional relief valve and no load sense signal is provided from the proportional relief valve to the steering priority valve.
15 . The method of claim 11 , wherein:
in a no steering with transmission standby operation mode of the controller, sending the adjustment command signal to the proportional relief valve commanding the proportional relief valve to provide the load sense signal to the steering priority valve to control a pump standby pressure provided by the hydraulic pump.
16 . The method of claim 11 , further comprising:
detecting with the controller a level of kinetic energy of the vehicle to be dissipated and automatically adjusting the adjustment command signal to adjust the hydraulic load brake function at least in part in response to the detected level of kinetic energy of the vehicle to be dissipated.