A hydraulic work machine is provided in which left and right hydraulic motors are driven independently of each other by two hydraulic pumps and in which an anomaly of any of the left and right track devices can be detected with high accuracy. The hydraulic work machine includes a first pressure sensor 13 configured to detect a first pump pressure that is a delivery pressure of a first hydraulic pump 11 and a second pressure sensor 23 configured to detect a second pump pressure that is a delivery pressure of a second hydraulic pump 21. When a controller 2 decides, from detection results of a travel operation detector 5 and work operation detectors 3 and 4, that a work implement 103 is not operated but travel operation devices 6 and 7 are operated and besides left and right track devices 50 and 60 are straightly traveling, the controller 2 calculates an anomaly decision evaluation value based on a pressure difference value obtained by subtracting one from the other of the first pump pressure and the second pump pressure and decides, based on a result of comparison between the anomaly decision evaluation value and a predetermined decision reference value 84, that one of the left and right track devices has an anomaly.

A working machine includes a machine body, a prime mover, a traveling device mounted on the machine body, a traveling motor to provide a power to the traveling device and to switch between a first speed and a second speed higher than the first speed, a traveling pump to be driven by the prime mover and to supply operation fluid to the traveling motor, and a controller device including an automatic shifter to automatically shift the traveling motor to the first speed or to the second speed, a timer to count an elapsed time from the automatically shifting, and a shift prohibitor to prohibit the automatically shifting by the automatic shifter when the elapsed time counted by the timer is less than a threshold.

A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is lower than the fourth pressure threshold. The pilot check valve is opened while the pilot pressure is higher than or equal to the fourth pressure threshold. The first hydraulic device is a ride control device.

A hydraulic device includes a braking device to brake a traveling device and release braking of the traveling device, a traveling pump to drive the traveling device with pressure of operation fluid, a brake-operation valve to control operation fluid flowing to the brake device, a traveling operation valve to control operation fluid flowing to the traveling pump, a first discharge fluid tube to discharge operation fluid flowing through the brake-operation valve, the first discharge fluid tube being connected to the brake operation valve, and a second discharge fluid tube to discharge operation fluid flowing through the traveling operation valve, the second discharge fluid tube being connected to the traveling operation valve. The traveling operation valve has a set pressure that is set to be higher than a brake set pressure set by the brake operation valve.

A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is lower than the fourth pressure threshold. The pilot check valve is opened while the pilot pressure is higher than or equal to the second pressure threshold. The first hydraulic device is an operation control valve.

A device for supplying and modifying the cylinder cubic capacity of a hydraulic motor, comprising: a first conduit (1) for supplying and discharging an operating fluid to a first side of the hydraulic motor (M); a second conduit (2) for supplying and discharging an operating fluid to a second side of the motor (M); an actuator (3) provided to modify the cubic capacity of the motor (M); an increase conduit (31) for increasing the cubic capacity of the motor (M), connected to the actuator (3) for supplying operating fluid to a side of the actuator (3) which produces an increase of the cubic capacity of the motor (M); a reduction conduit (32) for reducing the cubic capacity of the motor (M), connected to the actuator (3) for supplying operating fluid to a side of the actuator (3), which produces a reduction of the cubic capacity of the motor (M). The device is structured to supply to the increase conduit (31) and to the reduction conduit (32) a proportional pressure to the load acting on the winch.

A device for supplying and modifying the cylinder cubic capacity of a hydraulic motor, comprising: a first conduit (1) for supplying and discharging an operating fluid to a first side of the hydraulic motor (M); a second conduit (2) for supplying and discharging an operating fluid to a second side of the motor (M); an actuator (3) provided to modify the cubic capacity of the motor (M); an increase conduit (31) for increasing the cubic capacity of the motor (M), connected to the actuator (3) for supplying operating fluid to a side of the actuator (3) which produces an increase of the cubic capacity of the motor (M); a reduction conduit (32) for reducing the cubic capacity of the motor (M), connected to the actuator (3) for supplying operating fluid to a side of the actuator (3), which produces a reduction of the cubic capacity of the motor (M). The device is structured to supply to the increase conduit (31) and to the reduction conduit (32) a proportional pressure to the load acting on the winch.

The invention relates to a hydraulic machine, in particular to a hydraulic motor with two working lines, from one of which a high pressure line and from the other one a low pressure line is branched off. An electronic control unit and a servo displacement unit are provided to control the displacement of the displacement volume of a drive mechanism of the hydraulic machine, wherein the displacement volume can be determinated by the displacement of a servo piston within the servo displacement unit. For this, the servo piston can be loaded at least on one side via a servo pressure line with hydraulic fluid under servo pressure, wherein the servo pressure level can be adjusted by a control spool arranged moveable within a control valve. For this, hydraulic fluid from the low pressure line or, perhaps, from the high pressure line is guidable via the control valve to the servo pressure line if a suitable control signal is available at a switching valve.

The invention relates to a hydraulic machine, in particular to a hydraulic motor with two working lines, from one of which a high pressure line and from the other one a low pressure line is branched off. An electronic control unit and a servo displacement unit are provided to control the displacement of the displacement volume of a drive mechanism of the hydraulic machine, wherein the displacement volume can be determinated by the displacement of a servo piston within the servo displacement unit. For this, the servo piston can be loaded at least on one side via a servo pressure line with hydraulic fluid under servo pressure, wherein the servo pressure level can be adjusted by a control spool arranged moveable within a control valve. For this, hydraulic fluid from the low pressure line or, perhaps, from the high pressure line is guidable via the control valve to the servo pressure line if a suitable control signal is available at a switching valve.

A controller determines a target rotation speed of an engine from an operation amount of an accelerator operating member. The controller determines whether a vehicle is in coasting deceleration. The controller decreases a differential pressure between a first circuit and a second circuit of a hydraulic circuit according to a deviation between an actual rotation speed of the engine and the target rotation speed, or the operation amount of the accelerator operating member when the vehicle is in the coasting deceleration.