Abstract: A body hoisting state display device to be mounted on a dump truck includes: an angle detection unit that detects a rotation angle of the body with respect to the frame; a seating detection unit that detects whether or not the body is seated on the frame; a calculation unit that causes an inclination angle of the body at which the body is rotated with respect to the frame from a seated state of the body to be calculated, based on the rotation angle detected by the angle detection unit, as a ratio to an angle of a rotatable range that is defined between the seated state and a state in which the hydraulic cylinder is stopped at the position short of the position at which the hydraulic cylinder is extended to the maximal extent; and a display control unit that causes the ratio of the inclination angle of the body that is calculated by the calculation unit to be displayed on a display screen.

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 body hoisting state display device to be mounted on a dump truck includes: an angle detection unit that detects a rotation angle of the body with respect to the frame; a seating detection unit that detects whether or not the body is seated on the frame; a calculation unit that causes an inclination angle of the body at which the body is rotated with respect to the frame from a seated state of the body to be calculated, based on the rotation angle detected by the angle detection unit, as a ratio to an angle of a rotatable range that is defined between the seated state and a state in which the hydraulic cylinder is stopped at the position short of the position at which the hydraulic cylinder is extended to the maximal extent; and a display control unit that causes the ratio of the inclination angle of the body that is calculated by the calculation unit to be displayed on a display screen.

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 brake system in an electric drive dump truck. The electric drive dump truck has a generator 11 driven by an engine 10 and traveling motors 13L, 13R driven with electric power generated by the generator 11. Hydraulic brakes 20L, 20R, 21L, 20R are operated by brake pedal 18. An oil pressure sensor 22 detects hydraulic fluid pressure produced in accordance with the amount of depression of the brake pedal 18 and a control unit 14 controls the traveling motors 13L, 13R so as to operate them as generator-type retarders when the hydraulic fluid pressure P detected by the oil pressure sensor 22 is not smaller than a predetermined value P1.

Abstract: A drive system of an electrically driven dump truck is capable of achieving an operational feeling in which the operation amount of the accelerator pedal is well balanced with the output horsepower of the electric motors, particularly at the time of slow traveling. To achieve this, the target motor output horsepower Pm0 corresponding to the operation amount of an accelerator pedal 1 is calculated. The target motor torque Tr1R, Tr1L is calculated on the basis of the target motor output horsepower Pm0 and the rotational speed ?R, ?L of electric motors 12R, 12L respectively. The acceleration torque limit values of the electric motors 12R, 12L corresponding to the operation amount of the accelerator pedal 1 are calculated, respectively. Then, smaller values are selected, as motor torque instruction values TrR, TrL, between the acceleration torque limit value and the target motor torque Tr1R, Tr1L to control inverters 73R, 73L, respectively.

Abstract: Engine driving characteristics are achieved for driving a hydraulic system during non-traveling and traveling in an electrically driven dump truck. When a shift lever 16 is located at a neutral position, the target revolution speed Nr1 corresponding to the operation amount (p) of an accelerator pedal 1 is calculated on the basis of first target revolution speed characteristics (Nr1(p)) which are suitable for driving of a hydraulic pump for working so that an electronic governor 4a is controlled on the basis of this target revolution speed. When the shift lever 16 is located at a forward position, the target revolution speed Nr2 corresponding to the operation amount of the accelerator pedal 1 is calculated on the basis of second target revolution speed characteristics (Nr2(p)) which are suitable for driving of electric motors 12R, 12L so that the electronic governor 4a is controlled on the basis of this target revolution speed.

Abstract: An upper cross beam 10 for supporting a rear side of a cab 19 from below is formed as a separate member from a base frame 7. This upper cross beam 10 is separably mounted on left and right column portions 7E of the base frame 7 by using bolts 12. Namely, when an engine 27 is mounted to the base frame 7, the upper cross beam 10 is separated in advance from the base frame 7. Consequently, at the time of the operation of carrying in the engine 27, it merely suffices to vertically hoist or lower the engine 27 by use of a crane. It is thereby possible to carry in the engine 27 between the column portions 7E of the base frame 7 without being hampered by the upper cross beam 10.

Abstract: Detection signals from lever sensor (29), sit-down sensor (30) and vehicle speed sensor (31) are read into a controller (32). A control signal is produced by the controller (32) to switch a directional control valve (20) of a control valve unit (16) instantly from a floating position (c) to a neutral position (a) and to switch another directional control valve (21) from a neutral position (a) to a lowering position (d) when a dump truck (1) is in travel with the directional control valve (20) of the control valve unit (16) is switched in the floating position (c). Whereupon, a hoist cylinder (10) is contracted by a hydraulic pressure force to hold a vessel (3) in a sit-down position on a vehicle body (2), thereby preventing the vessel (3) from shaking movements like floating up while the dump truck (1) is in travel.

Abstract: A drive system for an electrically driven dump truck is capable of enabling electric motors for traveling to make full use of the output horsepower of the prime mover up to an output limit of the prime mover. A target motor horsepower corresponding to an operation amount of an accelerator pedal is calculated and an available maximum horsepower for the electric motors out of the maximum output horsepower of the prime mover is calculated in response to the actual revolution speed of the prime mover. The horsepower coefficient corresponding to the instantaneous revolution speed deviation is calculated. The available maximum horsepower for the electric motors is modified by the horsepower coefficient to determine a second target motor horsepower. The target motor horsepower is limited to not exceed the second target motor horsepower so as to control the torque of the electric motors.

Abstract: In an electric drive system for a vehicle, an alternator is driven by an engine to generate electric power which is used to drive a motor to generate a driving force. During a retardation of the vehicle, the motor is operated as an alternator to convert kinetic energy to electric energy which is used to retard the vehicle. A retard resistor is provided for absorbing electric energy generated during the retardation state. The retard resistor is cooled down by an AC blower.

Abstract: A hydraulic drive system is provided with a generator 8 for outputting electricity corresponding to a rotation speed of an engine 7, an electric motor 11 drivable responsive to the electricity from the generator 8, hydraulic pumps 12a, 12b drivable by the electric motor 11, truck-body elevating cylinders 6 for pivoting a truck body 5 in an up-and-down direction, and a stroke detector 14 for detecting a stroke of the control apparatus of the truck-body elevating cylinders 6, and is also provided with a controller 19 for performing control of engine rotation speed. The controller 19 includes a motor electric-power computing means 19a for determining electric power for the electric motor 11, which corresponds to the stroke detected by the stroke detector 14, and a discrimination means 19b for discriminating whether or not the electricity from the generator 8 has become greater than the thus-determined electric power for the electric motor 1.

Abstract: Engine driving characteristics are achieved for driving a hydraulic system during non-traveling and traveling in an electrically driven dump truck. When a shift lever 16 is located at a neutral position, the target revolution speed Nr1 corresponding to the operation amount (p) of an accelerator pedal 1 is calculated on the basis of first target revolution speed characteristics (Nr1(p)) which are suitable for driving of a hydraulic pump for working so that an electronic governor 4a is controlled on the basis of this target revolution speed. When the shift lever 16 is located at a forward position, the target revolution speed Nr2 corresponding to the operation amount of the accelerator pedal 1 is calculated on the basis of second target revolution speed characteristics (Nr2(p)) which are suitable for driving of electric motors 12R, 12L so that the electronic governor 4a is controlled on the basis of this target revolution speed.

Abstract: In a hydraulic drive device for vertical pivoting movement of a load carrying platform, a first directional control valve has only three switchover positions, including a neutral position relating to operation of stopping and holding a load carrying platform, a switching position relating to operation of lifting the load carrying platform, and a switch over position relating to operation of forced lowering of the load carrying platform. A second directional control valve has only three switchover positions, including a neutral position, a switching position, and a switchover position relating to operation of allowing the load carrying platform to fall by its own weight. The device includes a first on-off valve, a second on-off valve, and a third on-off valve that are proportional control solenoid valves for switching an appropriate one of the first and second directional control valves.

Abstract: Detection signals from lever sensor (29), sit-down sensor (30) and vehicle speed sensor (31) are read into a controller (32). A control signal is produced by the controller (32) to switch a directional control valve (20) of a control valve unit (16) instantly from a floating position (c) to a neutral position (a) and to switch another directional control valve (21) from a neutral position (a) to a lowering position (d) when a dump truck (1) is in travel with the directional control valve (20) of the control valve unit (16) is switched in the floating position (c). Whereupon, a hoist cylinder (10) is contracted by a hydraulic pressure force to hold a vessel (3) in a sit-down position on a vehicle body (2), thereby preventing the vessel (3) from shaking movements like floating up while the dump truck (1) is in travel.

Abstract: An upper cross beam 10 for supporting a rear side of a cab 19 from below is formed as a separate member from a base frame 7. This upper cross beam 10 is separably mounted on left and right column portions 7E of the base frame 7 by using bolts 12. Namely, when an engine 27 is mounted to the base frame 7, the upper cross beam 10 is separated in advance from the base frame 7. Consequently, at the time of the operation of carrying in the engine 27, it merely suffices to vertically hoist or lower the engine 27 by use of a crane. It is thereby possible to carry in the engine 27 between the column portions 7E of the base frame 7 without being hampered by the upper cross beam 10.

Abstract: A drive system for an electrically driven dump truck is capable of preventing a prime mover from stalling and is also capable of enabling electric motors for traveling to make full use of the output horsepower of the prime mover up to an output limit of the prime mover. The target motor horsepower Mr1 corresponding to the operation amount p of an accelerator pedal 1 is calculated and the available maximum horsepower Mr2 for motors 12R, 12L out of the maximum output horsepower of the prime mover 4, is calculated in response to the actual revolution speed Ne of the prime mover 4. The horsepower coefficient Kp corresponding to the instantaneous revolution speed deviation ?N is calculated. The available maximum horsepower for the electric motors is modified by the horsepower coefficient to determine the second target motor horsepower Mr3.

Abstract: In an electric drive system for a vehicle, an alternator is driven by an engine to generate electric power which is used to drive a motor to generate a driving force. During a retardation of the vehicle, the motor is operated as an alternator to convert kinetic energy to electric energy which is used to retard the vehicle. A retard resistor is provided for absorbing electric energy generated during the retardation state. The retard resistor is cooled down by an AC blower.

Abstract: A brake system in an electric drive dump truck. The electric drive dump truck has a generator 11 driven by an engine 10 and traveling motors 13L, 13R driven with electric power generated by the generator 11. Hydraulic brakes 20L, 20R, 21L, 20R are operated by brake pedal 18. An oil pressure sensor 22 detects hydraulic fluid pressure produced in accordance with the amount of depression of the brake pedal 18 and a control unit 14 controls the traveling motors 13L, 13R so as to operate them as generator-type retarders when the hydraulic fluid pressure P detected by the oil pressure sensor 22 is not smaller than a predetermined value P1.

Abstract: [OBJECT] To provide a hydraulic drive system for a dump truck, which can prevent an excessive increase in engine rotation speed upon operation of a truck body. [MEANS FOR ACHIEVING THE OBJECT] A hydraulic drive system is provided with a generator 8 for outputting electricity corresponding to a rotation speed of an engine 7, an electric motor 11 drivable responsive to the electricity from the generator 8, hydraulic pumps 12a, 12b drivable by the electric motor 11, truck-body elevating cylinders 6 for pivoting a truck body 5 in an up-and-down direction, and a stroke detector 14 for detecting a stroke of the control apparatus of the truck-body elevating cylinders 6, and is also provided with a controller 19 for performing control of engine rotation speed.