A working machine comprising a ground engaging structure and an undercarriage connected to the ground engaging structure. A superstructure is rotatably mounted to the undercarriage so as to be rotatable relative to the undercarriage about a first generally upright axis, an operator's cab is rotatably mounted on the superstructure so as to be rotatable relative to the superstructure about a second generally upright axis, and a working arm is rotatably mounted to the superstructure so as to be moveable up and down about a generally horizontal axis. A drive arrangement is provided for driving the ground engaging structure to propel the working machine. The drive arrangement includes an engine and transmission that are housed within the undercarriage, and a majority of the engine is positioned below a level coincident with a lower extent of the superstructure.

A working machine comprising a ground engaging structure and an undercarriage connected to the ground engaging structure. A superstructure is rotatably mounted to the undercarriage so as to be rotatable relative to the undercarriage about a first generally upright axis, an operator's cab is rotatably mounted on the superstructure so as to be rotatable relative to the superstructure about a second generally upright axis, and a working arm is rotatably mounted to the superstructure so as to be moveable up and down about a generally horizontal axis. A drive arrangement is provided for driving the ground engaging structure to propel the working machine. The drive arrangement includes an engine and transmission that are housed within the undercarriage, and a majority of the engine is positioned below a level coincident with a lower extent of the superstructure.

In a hydraulic drive system performing the load sensing control by using a pump device having two delivery ports whose delivery flow rates are controlled by a single pump controller, surplus flow is prevented and energy loss at an unload valve and a pressure compensating valve is reduced in combined operations in which two actuators are driven at the same time while producing a relatively large supply flow rate difference therebetween. A boom cylinder 3a is connected so that the hydraulic fluids delivered from delivery ports P1 and P2 of a pump device 1a are merged and supplied to the boom cylinder 3a. An arm cylinder 3h is connected so that the hydraulic fluids delivered from delivery ports P3 and P4 of a pump device 1b are merged and supplied to the arm cylinder 3h. A travel motor 3d is connected so that the hydraulic fluid delivered from one (delivery port P2) of the delivery ports of the pump device 1a and the hydraulic fluid delivered from one (delivery port P4) of the delivery ports of the pump device 1b are merged and supplied to the travel motor 3d. A travel motor 3e is connected so that the hydraulic fluid delivered from the other (delivery port P1) of the delivery ports of the pump device 1a and the hydraulic fluid delivered from the other (delivery port P3) of the delivery ports of the pump device 1b are merged and supplied to the travel motor 3e.

In a hydraulic drive system performing the load sensing control by using a pump device having two delivery ports whose delivery flow rates are controlled by a single pump controller, surplus flow is prevented and energy loss at an unload valve and a pressure compensating valve is reduced in combined operations in which two actuators are driven at the same time while producing a relatively large supply flow rate difference therebetween. A boom cylinder 3a is connected so that the hydraulic fluids delivered from delivery ports P1 and P2 of a pump device 1a are merged and supplied to the boom cylinder 3a. An arm cylinder 3h is connected so that the hydraulic fluids delivered from delivery ports P3 and P4 of a pump device 1b are merged and supplied to the arm cylinder 3h. A travel motor 3d is connected so that the hydraulic fluid delivered from one (delivery port P2) of the delivery ports of the pump device 1a and the hydraulic fluid delivered from one (delivery port P4) of the delivery ports of the pump device 1b are merged and supplied to the travel motor 3d. A travel motor 3e is connected so that the hydraulic fluid delivered from the other (delivery port P1) of the delivery ports of the pump device 1a and the hydraulic fluid delivered from the other (delivery port P3) of the delivery ports of the pump device 1b are merged and supplied to the travel motor 3e.

A lift machine includes a base having a first end and a second end, a first assembly, and a second assembly. The first end has first and second pivot points defining a first lateral axis. The second end has third and fourth pivot points defining a second lateral axis. The first assembly is pivotably coupled to the first and second pivot points. The first assembly extends away from the base in a first direction such that first and second tractive elements are longitudinally offset from the first lateral axis and spaced from the first end of the base. The second assembly is pivotably coupled to the third and fourth pivot points. The second assembly extends away from the base in a second direction such that third and fourth tractive elements are longitudinally offset from the second lateral axis and spaced from the second end of the base.

A lift machine includes a base having a first end and a second end, a first assembly, and a second assembly. The first end has first and second pivot points defining a first lateral axis. The second end has third and fourth pivot points defining a second lateral axis. The first assembly is pivotably coupled to the first and second pivot points. The first assembly extends away from the base in a first direction such that first and second tractive elements are longitudinally offset from the first lateral axis and spaced from the first end of the base. The second assembly is pivotably coupled to the third and fourth pivot points. The second assembly extends away from the base in a second direction such that third and fourth tractive elements are longitudinally offset from the second lateral axis and spaced from the second end of the base.

A control unit embedded in a work vehicle includes a clutch controlling unit and a motor controlling unit. The clutch controlling unit is configured to disengage a first clutch in a condition that the first clutch is engaged and a second clutch is disengaged, when a first moving direction inputted through a forward/rearward movement switch operating device as an instruction of the operator and a second moving direction determined based on a vehicle speed detected by a vehicle speed detecting unit are different from each other, and in addition, when and the vehicle speed falls in a preliminarily set first range. The motor controlling unit is configured to control a motor to reduce a relative rotational speed of the second clutch after the first clutch is disengaged.

A control unit embedded in a work vehicle includes a clutch controlling unit and a motor controlling unit. The clutch controlling unit is configured to disengage a first clutch in a condition that the first clutch is engaged and a second clutch is disengaged, when a first moving direction inputted through a forward/rearward movement switch operating device as an instruction of the operator and a second moving direction determined based on a vehicle speed detected by a vehicle speed detecting unit are different from each other, and in addition, when and the vehicle speed falls in a preliminarily set first range. The motor controlling unit is configured to control a motor to reduce a relative rotational speed of the second clutch after the first clutch is disengaged.

Control valves 100f, 100g, and 100h that reduce flow passage areas of parallel hydraulic fluid lines 41f, 41g, and 41h respectively when operating devices 34a, 34b for traveling are operated, are each disposed in the parallel hydraulic fluid line 41f, 41g, or 41h so that if saturation occurs during combined operations control likely to generate a significant difference in load pressure between any two actuators, the control valve prevents full closing of a pressure compensating valve lower in load pressure and thus prevents a slowdown and stop of the actuator undergoing the lower load pressure, and so that if saturation occurs during combined operations control likely to generate a particularly significant difference in load pressure between any two actuators, the control valve ensures a necessary supply of hydraulic fluid to the actuator higher in load pressure, thereby preventing a slowdown and stop of the actuator higher in load pressure.

Control valves 100f, 100g, and 100h that reduce flow passage areas of parallel hydraulic fluid lines 41f, 41g, and 41h respectively when operating devices 34a, 34b for traveling are operated, are each disposed in the parallel hydraulic fluid line 41f, 41g, or 41h so that if saturation occurs during combined operations control likely to generate a significant difference in load pressure between any two actuators, the control valve prevents full closing of a pressure compensating valve lower in load pressure and thus prevents a slowdown and stop of the actuator undergoing the lower load pressure, and so that if saturation occurs during combined operations control likely to generate a particularly significant difference in load pressure between any two actuators, the control valve ensures a necessary supply of hydraulic fluid to the actuator higher in load pressure, thereby preventing a slowdown and stop of the actuator higher in load pressure.