Kabushiki Kaisha Toyoda Jidoshokki Seisakusho

Yasuhiko Naruse

Toshiyuki Takeuchi

Shigeto Nakajima

Takeharu Matsuzaki

Makio Tsukada

Katsumi Nagai

Takaki Ogawa

Masanao Kobayakawa

A device for controlling tilt of a forklift mast. A fork for carrying an object is supported by the mast so that the fork is lifted or lowered. A tilt cylinder operates to tilt the mast hydraulically. A hydraulic valve supplies oil to the tilt cylinder in correspondence with the position of a tilt lever. The tilt cylinder tilts the mast at a speed corresponding to the flow rate of the oil supplied by the valve. A restricting valve is provided for restricting the maximum flow rate of the oil. When the fork is located below a predetermined reference position, the controller fully opens the restricting valve. However, when the fork is located at the reference position or higher, the controller restricts the opening of the restricting valve, thus restricting the maximum tilt speed of the mast. This stabilizes the forklift.

Tilt control device for forklift

An ultrasonic sensor detects whether a piston is at the lowest position. The sensor is not affected by the environment or damaged by contact with other objects. The sensor is located in the bottom of a mast cylinder, transmits ultrasonic waves to the bottom of a piston and receives ultrasonic waves reflected by the piston. The sensor then outputs electric signals based on the received ultrasonic waves. The ultrasonic sensor is electrically connected to a transmitter-receiver, which, in turn, is electrically connected to a controller. The transmitter-receiver includes an ultrasonic wave generator and sends ultrasonic wave transmitting signal having a predetermined frequency to the ultrasonic sensor based on control signals from the controller. The controller measures time from when it outputs the ultrasonic wave transmitting signal to when the sensor receives a reflected wave. The controller then compares the measured time with a threshold value thereby judging whether the piston is at the lowest position.

Lift cylinder and mast assembly of forklift

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.

Hydraulic device for forklift

Control levers for controlling load handling devices are pivotally supported by an eccentric shaft portion of an adjusting shaft. The rotation of the adjusting shaft allows the control levers to move along a circular locus together with the eccentric shaft portion, thereby changing the grip positions of the control levers. Also, the grip positions of a plurality of the control lever can be simultaneously changed.

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Kariya, Japan

Yasuhiko Naruse