Hitachi Construction Machinery Co., Ltd.

Morio Oshina

Takashi Kanai

Mitsuo Sonoda

Masami Ochiai

Seiji Tamura

Tsuyoshi Takayama

Koji Nozaki

Hirohisa Tanaka

Eiji Egawa

Junichi Narisawa

Kiyoshi Hirasawa

Atsushi Tanaka

Yoshinori Sendai

Junji Tsumura

A crawler carrier capable of smoothly operating a driving force source even at a slant. The driving force source is arranged between a dump body and a cab and laid in a lateral direction and at the same time the driving force source and a heat exchanger are arranged in series in a lateral direction. With such an arrangement as above, the driving force source can be arranged at an upper structure frame under a state in which it becomes substantially horizontal without interfering with the dump body. Even when the crawler carrier performs work at a slant the engine can always be lubricated with lubricant oil and the driving force source can be operated smoothly.

Crawler carrier having an engine, a hydraulic pump and a heat exchanger positioned in a lateral direction

A tired roller is provided with a prime mover and a speed change unit of the HST type. The speed change unit includes an HST hydraulic pump of the variable displacement type driven by the prime mover and an HST hydraulic motor driven by pressure oil from the hydraulic pump, and can change a rotational speed of the hydraulic motor by varying a delivery rate of pressure oil from the hydraulic pump. Rotation of the hydraulic motor is therefore transmitted at a lower speed to a drive-axle tire train. A propeller shaft is connected to the hydraulic motor without interposition of any speed reduction mechanism, so that the propeller shaft is rotated at a high speed with a low torque. This has made it possible to form the propeller shaft smaller in diameter and hence to arrange it in a narrow space between tires in the drive-axle tire train. Further, the rotation of the hydraulic motor is reduced in speed at an output side of the propeller shaft, thereby making it possible to transmit the rotation in a state increased in rotating torque to the drive-axle tire train.

Tired Roller

Operation control device for three-joint type excavator

Hydraulic drive system

A first hydraulic circuit comprises a variable displacement hydraulic pump driven by a prime mover, a variable displacement hydraulic motor connected in a closed circuit to the variable displacement hydraulic pump, and a displacement control means for controlling a displacement of the variable displacement hydraulic motor. A second hydraulic circuit comprises a hydraulic pump driven by the prime mover, and drives a loader attachment. A displacement limitation means limits the maximum value of the displacement of the variable displacement hydraulic motor in accordance with a load pressure of the second hydraulic circuit. For example, the displacement limitation means reduces the maximum value of the displacement of the variable displacement hydraulic motor in proportion to the pressure in the second hydraulic circuit. The motor torque is controlled by directly adjusting the displacement of the motor, and a load of the hydraulic motor can thus be stably controlled.

Hydraulic driving circuit with motor displacement limitation control

Control apparatus for electromagnetic device having proportional solenoid

A variable displacement hydraulic pump and a hydraulic motor are connected in a closed circuit. A pressure oil supply means includes the variable displacement hydraulic pump and a tilting controlling means for controlling a tilt angle of the hydraulic pump and supplies an amount of pressure oil corresponding to the tilt angle of the hydraulic pump to the hydraulic motor. When rotation of a prime mover is detected by a rotation detecting means, an opening and closing valve is changed over to a first position in which the pressure oil supply means is permitted to supply pressure oil. When stopping of the prime mover is detected by the rotation detecting means, the opening and closing valve is changed to a second position in which the pressure oil supply means is inhibited from supplying pressure oil. Upon starting of the prime mover, at least the opening and closing valve remains at the second position, and the tilting controlling means increases its tilt angle from its neutral position so that the pressure oil supply means supplies pressure oil. Consequently, upon re-starting of the prime mover, pressure oil is prevented from being supplied inadvertently to the hydraulic motor, and the safety upon starting is assured.

Safety device for hydraulic closed circuit

A hydraulic drive system is equipped with an engine, a plurality of hydraulic pumps adapted to be driven by the engine and including a variable displacement hydraulic pump provided with a displacement varying mechanism, a hydraulic motor connected to the variable displacement pump, a hydraulic actuator for actuating the displacement varying mechanism of the variable displacement hydraulic pump, a working fluid feeding means for feeding the hydraulic actuator with a hydraulic fluid of a pressure according to the degree of control of an accelerator lever which is adapted to instruct a target revolution number of the engine, and a low-pressure circuit for allowing the hydraulic fluid to be discharged therethrough from the hydraulic actuator. The system is provided with a maximum pressure limiting means for guiding the hydraulic fluid of the hydraulic fluid feeding means to the low-pressure circuit depending on the degree of control of the accelerator lever, thereby limiting the maximum pressure of the hydraulic fluid and a means for selectively actuating the maximum pressure limiting means.

A hydraulic drive circuit system is equipped with an accelerator pedal and an accelerator lever for respectively instructing target revolution numbers for an engine, a link plate for selecting greater one of the instruction values, and a linkage and a switch for controlling valves respectively so as to close the flow passage of a line interposed between a charge pump and a low pressure line irrespective of the instruction value of the accelerator pedal when the accelerator lever has not been controlled but for controlling the valves so as to restrict the flow passage of the line in accordance with the instruction value of the accelerator pedal when the accelerator lever has been controlled.

Growing community of inventors

Ibaraki-ken, Japan

Morio Oshina