Abstract: Front wheels (6L, 6R) a steering operation of which is possible by a steering mechanism (12) are mounted on a vehicle body (2). Steering cylinders (22L, 22R) of the steering mechanism (12) extend and contract in response to an operation of a steering handle (27) provided in a cab (5) to perform the steering operation of the front wheels (6L, 6R). The steering mechanism (12) is provided with a rotation angle sensor (28) for detecting a steering angle ? of the left front wheel (6L) and a proximity switch (29) for detecting whether or not the front wheel (6L) is in a straight-ahead state. A controller (30) determines that the rotation angle sensor (28) or the proximity switch (29) is abnormal when the steering angle (?) detected by the rotation angle sensor (28) is different from the detection result by the proximity switch (29).

Abstract: A control valve device (19) controls supply and discharge of pressurized oil to and from a hoist cylinder (12) which tilts a vessel (3). A throttle (24C) that limits a flow rate of hydraulic oil which is discharged from a hydraulic pump (13) and flows in a return line (16) through a pump line (15), a first directional control valve (24) and a center bypass oil passage (23) is provided in the floating position (F) of the first directional control valve (24). When the first directional control valve (24) is in the floating position (F), the upstream side of the throttle (24C) is connected to the pump line (15), and the downstream side of the throttle (24C) is connected to the return line (16). In addition, a rod-side actuator line (18) communicated with rod-side oil chambers (12E, 12F) in the hoist cylinder (12) is connected to the pump line (15).

Abstract: A control valve device (19) controls supply and discharge of pressurized oil to and from a hoist cylinder (12) which tilts a vessel (3). A throttle (24C) that limits a flow rate of hydraulic oil which is discharged from a hydraulic pump (13) and flows in a return line (16) through a pump line (15), a first directional control valve (24) and a center bypass oil passage (23) is provided in the floating position (F) of the first directional control valve (24). When the first directional control valve (24) is in the floating position (F), the upstream side of the throttle (24C) is connected to the pump line (15), and the downstream side of the throttle (24C) is connected to the return line (16). In addition, a rod-side actuator line (18) communicated with rod-side oil chambers (12E, 12F) in the hoist cylinder (12) is connected to the pump line (15).

Abstract: Front wheels (6L, 6R) a steering operation of which is possible by a steering mechanism (12) are mounted on a vehicle body (2). Steering cylinders (22L, 22R) of the steering mechanism (12) extend and contract in response to an operation of a steering handle (27) provided in a cab (5) to perform the steering operation of the front wheels (6L, 6R). The steering mechanism (12) is provided with a rotation angle sensor (28) for detecting a steering angle ? of the left front wheel (6L) and a proximity switch (29) for detecting whether or not the front wheel (6L) is in a straight-ahead state. A controller (30) determines that the rotation angle sensor (28) or the proximity switch (29) is abnormal when the steering angle (?) detected by the rotation angle sensor (28) is different from the detection result by the proximity switch (29).

Abstract: In the course of largely tilting a vessel (3) backward of a vehicle body (2) by a hoist cylinder (10), occasionally the rear end portion of the vessel (3) runs into an embankment (4A) of dumped earth and sand. In consequence, a load by a vehicle weight to be applied to a rear suspension (8A) suspending the side of a rear wheel (8) of a vehicle is rapidly reduced. Therefore, an inner pressure (P) in the rear suspension (8A) detected by a pressure sensor (25) is rapidly lowered. In this case, a controller (27) controls the hoist cylinder (10) according to the inner pressure (P) in the rear suspension (8A) to stop an extension operation of the hoist cylinder (10). This can suppress occurrence of a state where the side of the rear wheel (8) of the vehicle body (2) is raised upward, that is, a jack-up state.

Abstract: In the course of largely tilting a vessel (3) backward of a vehicle body (2) by a hoist cylinder (10), occasionally the rear end portion of the vessel (3) runs into an embankment (4A) of dumped earth and sand. In consequence, a load by a vehicle weight to be applied to a rear suspension (8A) suspending the side of a rear wheel (8) of a vehicle is rapidly reduced. Therefore, an inner pressure (P) in the rear suspension (8A) detected by a pressure sensor (25) is rapidly lowered. In this case, a controller (27) controls the hoist cylinder (10) according to the inner pressure (P) in the rear suspension (8A) to stop an extension operation of the hoist cylinder (10). This can suppress occurrence of a state where the side of the rear wheel (8) of the vehicle body (2) is raised upward, that is, a jack-up state.