Kabushiki Kaisha Toyota Jidoshokki

Nishina Industrial Co., Ltd.

Kabushiki Kaisha Toyoda Jidoshokki Seisakusho

Other

Takeharu Matsuzaki

Shigeto Nakajima

Makio Tsukada

Tetsuya Goto

Toshiyuki Takeuchi

Yasuhiko Naruse

Takeshi Kobayashi

Yasuhiro Maeda

Keinosuke Ichikawa

Tadashi Noguchi

A hydraulic control apparatusincludes a switch valve, a valve support chamber, a flow control valvemovable within the valve support chamber, an on-off valvemovable within the communication path chamber, and a valve control device. The flow control valvehas a communication path chamberand a back pressure chamber. The on-off valveis capable of opening and shutting off a communication path X between a cylinder lineand a switch valve line. A restrictor is formed between the flow control valveand a wall defining the valve support chamber. The restrictor connects the cylinder lineand the communication path chamberto each other. The opening degree of the restrictor is changed in correspondence with movement of the flow control valve. When the switch valveis located at the neutral position or the supply position, the valve control deviceapplies a fluid pressure in the cylinder lineto the back pressure chamberfor urging the on-off valvein a direction for shutting off the communication path. When the switch valveis located at the drainage position, the valve control deviceapplies a pilot pressure lower than the fluid pressure in the cylinder lineto the back pressure chamber, thereby moving the on-off valvein a direction for opening the communication path X.

Hydraulic control apparatus

A valve seatis arranged between the supply circuitand a downstream circuit. A valve bodyblocks a fluid flow between the supply circuitand the downstream circuitby contacting the valve seat. The valve bodyconnects the supply circuitto the downstream circuitfor supplying the fluid to the downstream circuitby separating from the valve seat. A through holeextends through the valve bodyand thus defines a part of the supply circuit. The through holeis defined in such a manner that the fluid that has flowed from the through holeproceeds between the valve seatand the valve bodyand is thus supplied to the downstream circuit. The valve bodyis formed in such a manner that a pressure receiving area at an upstream side of the through holeis smaller than a pressure receiving area at a downstream side of the through hole. This reduces a pressure loss caused by the fluid passing through a backflow prevention structure that permits forward fluid flow from the supply circuitto the downstream circuitbut prohibits backflow of the fluid.

Valve

A hydraulic control apparatusincludes a switch valve, an adjustment valve, and a valve control device. The adjustment valvehas a fluid chamber, a valve body, and a back pressure chamber. A restrictor is formed between the valve bodyand a wall defining the fluid chamberand connects the cylinder lineto the switch valve line. The opening degree of the restrictor changes in correspondence with movement of the valve body. When the switch valveis located at a neutral position or a supply position, the valve control deviceapplies the fluid pressure in the cylinder lineto the back pressure chamber. When the switch valveis located at a drainage position, the valve control deviceapplies a pilot pressure lower than the fluid pressure in the cylinder lineto the back pressure chamber

A supply passage, a discharge passage, an actuator passage, and a spool bore are defined in a housing. The spool bore accommodates a spool and communicates with the supply passage, the discharge passage, and the actuator passage. Load pressure detection circuit sections of load pressure detection circuit are provided in correspondence with two switch. Each of the load pressure detection circuit sections detects load pressure when the actuator passage is connected to the supply passage. Each load pressure detection circuit section is defined by a through hole provided in the housing and connected to the spool bore. Check valves are each arranged in a corresponding one of the load pressure detection circuit sections. This simplifies the configuration of each load pressure detection circuitand saves the space for arranging the load pressure detection circuit., resulting in a relatively compact housing.

Hydraulic pressure control apparatus and hydraulic circuit

A flow divider includes a spool for distributing fluid from a supply flow path to priority and surplus flow paths. First and second surplus restrictions vary flow rate in accordance with the movement of the spool and restrict the flow rate to the surplus flow path respectively from first and second supply passages. The second surplus restriction is formed to restrict the flow rate in at least two steps. The spool includes a cross-sectional area changing portion located at a position corresponding to the second surplus restriction. Therefore, the circuit structure is prevented from becoming complicated and the fluid force acting as a spool urging force is suppressed.

Flow divider

A hydraulic control apparatus for a single action cylinder includes a switch valve for supplying fluid to and draining fluid from the cylinder, a cylinder side passage connected to the cylinder, a switch valve side passage connected to the switch valve, and a valve body accommodation chamber. The valve body accommodation chamber linearly extends between the cylinder side passage and the switch valve side passage. An on-off valve is located in a vicinity of a first end of the valve body accommodation chamber. The on-off valve defines a first back pressure chamber. A flow control valve is located in a vicinity of a second end that is opposite to the first end. The flow control valve defines a second back pressure chamber. The on-off valve and the flow control valve are separated from each other by a partitioning member.

A main spool is located in a bypass line connecting a pump line to a return line. The main spool moves in an axial direction according to the pressure in a spring chamber and the pressure in a pilot chamber, thereby adjusting the opening degree of the bypass line. A pilot switching valve is located in a pressure control passage connecting the spring chamber to the return line. The pilot switching valve controls the flow rate of hydraulic oil that flows from the spring chamber to the return line in accordance with the load pressure of a hydraulic actuator, thereby adjusting the pressure of hydraulic oil in the spring chamber. As a result, the range of the flow rate of hydraulic oil supplied to the hydraulic actuator, which range precludes the influence of the load pressure of the hydraulic actuator, is expanded.

Hydraulic control device and industrial vehicle with hydraulic control device

A tilt control device for a fork lift truck comprises a tilt spool for operating the tilt cylinder, a pilot operation type flow rate control valve connected to the hydraulic pump via the tilt spool and adapted to be switched between a fully opened position and a half opened position which are different in opening from each other in response to addition/deletion of a pilot pressure, a pilot operation type logic valve disposed between the rod side oil compartment of the tilt cylinder and the flow rate control valve and adapted to permit hydraulic oil to flow into the rod side oil compartment and to be operated so as to open/close relative to hydraulic oil flowing out of the rod side oil compartment in response to the addition/deletion of the pilot pressure, and an electromagnetic switching valve for controlling the addition/deletion of the pilot pressure to the flow rate control valve and the logic valve.

Tilt control device for fork lift truck

A lift control valve is switched based on the manipulation of a lift lever, so that a lift cylinder extends or retracts to move a fork, supported on a mast, to move up or down. A check valve, which is actuated with a pilot pressure, is placed between the lift control valve and the lift cylinder. A pilot pipe led out from a pipe directly coupled to an oil tank is connected to a port of the check valve. A tilt control valve is switched based on the manipulation of a tilt lever, so that a tilt cylinder extends or retracts to tilt the mast. An electromagnetic valve is disposed between the tilt cylinder and the tilt control valve. When values necessary to drive the fork are detected, a controller control the electromagnetic valve based on those values.

Hydraulic control apparatus for industrial vehicles

A hydraulic device for a forklift is disclosed. The forklift includes a tilting mast and a fork supported by the mast so that the fork is lifted and lowered. A tilt cylinder operates to tilt the mast by means of oil supplied by a tilt valve. A restricting valve is arranged in an oil passage connecting the tilt cylinder with the tilt valve. When the mast is tilted with the fork carrying an object and located higher than a predetermined reference position, the restricting valve closes the oil passage so that the angle of the tilting mast is limited. A check valve is arranged between the tilt cylinder and the restricting valve. The check valve blocks oil flow from the tilt cylinder to the restricting valve so that the position of the mast is maintained. This prevents unintentional movement of the mast.

Growing community of inventors

Kariya, Japan

Takeharu Matsuzaki