A hydraulic control valve maintains the pressure at a control port at a desired percentage of the pressure at two other ports as the pressure at the two other ports varies. Upon the pressure at the control port reaching a predetermined pressure setting, a fourth port will open to maintain the control port at a second desired percentage of the two other ports.

In one aspect, a system for controlling the torsional output of a hydrostatic transmission of a work vehicle may include pilot-operated first and second valves. The first valve configured to be actuated to a closed position to occlude fluid flow through a first fluid conduit when a pressure within such conduit at a location downstream of the first valve drops below a first threshold. Moreover, the second valve configured to be actuated to a closed position to occlude fluid flow when a pressure within the second fluid conduit at a location downstream of the second valve drops below a second threshold. As such, when one of the first or second valves is actuated to the closed position, an increased flow of fluid is delivered through the other of the first valve or the second valve to increase a torsional output of an associated hydraulic motor.

In one aspect, a system for controlling the torsional output of a hydrostatic transmission of a work vehicle may include pilot-operated first and second valves. The first valve configured to be actuated to a closed position to occlude fluid flow through a first fluid conduit when a pressure within such conduit at a location downstream of the first valve drops below a first threshold. Moreover, the second valve configured to be actuated to a closed position to occlude fluid flow when a pressure within the second fluid conduit at a location downstream of the second valve drops below a second threshold. As such, when one of the first or second valves is actuated to the closed position, an increased flow of fluid is delivered through the other of the first valve or the second valve to increase a torsional output of an associated hydraulic motor.

In one aspect, a system for controlling the torsional output of a hydrostatic transmission of a work vehicle may include pilot-operated first and second valves. The first valve configured to be actuated to a closed position to occlude fluid flow through a first fluid conduit when a pressure within such conduit at a location downstream of the first valve drops below a first threshold. Moreover, the second valve configured to be actuated to a closed position to occlude fluid flow when a pressure within the second fluid conduit at a location downstream of the second valve drops below a second threshold. As such, when one of the first or second valves is actuated to the closed position, an increased flow of fluid is delivered through the other of the first valve or the second valve to increase a torsional output of an associated hydraulic motor.

In one aspect, a system for controlling the torsional output of a hydrostatic transmission of a work vehicle may include pilot-operated first and second valves. The first valve configured to be actuated to a closed position to occlude fluid flow through a first fluid conduit when a pressure within such conduit at a location downstream of the first valve drops below a first threshold. Moreover, the second valve configured to be actuated to a closed position to occlude fluid flow when a pressure within the second fluid conduit at a location downstream of the second valve drops below a second threshold. As such, when one of the first or second valves is actuated to the closed position, an increased flow of fluid is delivered through the other of the first valve or the second valve to increase a torsional output of an associated hydraulic motor.

A vehicle and a hydraulic propulsion system for the vehicle are provided with first and second motors diagonally arranged relative to one another on the vehicle, and third and fourth motors diagonally arranged relative to one another on the vehicle. First, second and third flow divider combiner assemblies are provided and are arranged in a closed fluid loop with the motors. A first port of each of the assemblies are fluidly connected to one another. The first assembly has a second port fluidly coupled to the first and second motors, and a third port fluidly coupled to the third and fourth motors. The second assembly has second and third ports fluidly coupled to the first and third motors, respectively. The third assembly has second and third ports fluidly coupled to the second and fourth motors, respectively. A method of controlling the hydraulic system is also provided.

A vehicle and a hydraulic propulsion system for the vehicle are provided with first and second motors diagonally arranged relative to one another on the vehicle, and third and fourth motors diagonally arranged relative to one another on the vehicle. First, second and third flow divider combiner assemblies are provided and are arranged in a closed fluid loop with the motors. A first port of each of the assemblies are fluidly connected to one another. The first assembly has a second port fluidly coupled to the first and second motors, and a third port fluidly coupled to the third and fourth motors. The second assembly has second and third ports fluidly coupled to the first and third motors, respectively. The third assembly has second and third ports fluidly coupled to the second and fourth motors, respectively. A method of controlling the hydraulic system is also provided.

A working machine includes a prime mover, a traveling pump configured to deliver hydraulic fluid at a flow rate corresponding to an angle of the swashplate, a traveling motor configured to be rotated by the hydraulic fluid delivered from the traveling pump so as to have a rotation speed shiftable between a first speed and a second speed higher than the first speed, a traveling change-over valve shiftable between a first state to set the rotation speed of the traveling motor to the first speed and a second state to set the rotation speed of the traveling motor to the second speed, an operation device, an operation valve configured to change the angle of the swashplate of the traveling pump according to operation of the operation device, an actuation valve provided upstream or downstream of the operation valve and fluidly connected to the operation valve, and a controller configured or programmed to output a control signal to control the actuation valve in such a way that, when the traveling change-over valve is shifted from the second state to the first state, a value of the control signal is reduced from a set value to a mitigation value less than the set value and then restores to the set value. The controller is configured or programmed to reduce the value of the control signal from the set value to the mitigation value for a mitigation period in such a way that a first reduction rate that is a rate of reducing the value of the control signal for a first part of the mitigation period between a start point thereof and an intermediate point thereof larger than a second reduction rate that is a rate of reducing the value of the control signal for a second part of the mitigation period between the intermediate point thereof and an end point thereof.

A working machine includes: a first fluid passage fluidly connecting a traveling operation device to an actuation valve; a first traveling fluid passage; a second traveling fluid passage; a third traveling fluid passage; a fourth traveling fluid passage; a second fluid passage fluidly connecting the first fluid passage to the first traveling fluid passage; and a third fluid passage fluidly connecting the first fluid passage to the third traveling fluid passage. Each of the first, second, third, and fourth traveling fluid passages is configured so that operation fluid to be applied to a first, second, third, and fourth pressure-receiving portions flows through the first, second, third, and fourth traveling fluid passages, respectively, when a traveling operation member is operated.

A vehicle and a hydraulic propulsion system for the vehicle are provided with first and second motors diagonally arranged relative to one another on the vehicle, and third and fourth motors diagonally arranged relative to one another on the vehicle. First, second and third flow divider combiner assemblies are provided and are arranged in a closed fluid loop with the motors. A first port of each of the assemblies are fluidly connected to one another. The first assembly has a second port fluidly coupled to the first and second motors, and a third port fluidly coupled to the third and fourth motors. The second assembly has second and third ports fluidly coupled to the first and third motors, respectively. The third assembly has second and third ports fluidly coupled to the second and fourth motors, respectively. A method of controlling the hydraulic system is also provided.