Komatsu Corporation

Shunji Oka

Tomohiro Nakagawa

Shigeru Yamamoto

Toshikazu Okada

Osamu Takatori

Keita Naito

A construction machine includes a negative parking brake whose braking state is released by a supply of hydraulic fluid. It also includes a parking brake hydraulic circuit that is branched from a hydraulic fluid supplying circuit, which supplies the hydraulic fluid to a transmission of the construction machine, and supplies the hydraulic fluid to the parking brake. The parking brake hydraulic circuit includes a check valve that prevents backflow of the hydraulic fluid of the parking brake to the hydraulic fluid supplying circuit, and it includes an operation switching valve, which is provided closer to the parking brake than the check valve, for switching between an activation and a release of the parking brake. The parking brake hydraulic circuit also includes a relief valve, which is interposed between the check valve and the operation switching valve and which discharges the hydraulic fluid of the parking brake when the relief valve is opened.

Construction machine

In the oil pressure system, a control unit sets a flow passage changeover valve to be in a merging state, and sets a relief pressure to a low relief pressure via a relief pressure changeover unit in the case that the rotational speed of the engine is lower than a predetermined threshold level. Also, the control unit sets the flow passage changeover valve to be in a branching state, and sets the relief pressure to a high relief pressure via the relief pressure changeover unit in the case that the rotational speed of the engine is the predetermined threshold level or higher.

Oil pressure system and valve assembly used in oil pressure system

A shift control device and a shift control method for a vehicle for reducing shift shock by taking into account the difference in vehicle speeds before and after shifting. In one of the main inventions, the clutch pressure of another clutch (forward clutch) is controlled to match a target vehicle speed to a calculated actual vehicle speed by the time of start of the connecting operation of a selected speed stage clutch. Since such control is performed so that the vehicle speed is caused to match the target vehicle speed, an actual vehicle speed change rate is held within a predetermined range in at least the instant that the connecting operation of the selected speed stage clutch is started. Also, in another one of the main inventions, as shown in FIG., control is performed to adjust the clutch pressure of the other clutch (forward clutch) so that the vehicle speed change rate reaches a predetermined value in the period from when the connecting operation of the selected speed stage clutch is started until when the connecting operation is completed.

Shift control device and shift control method for vehicle

The present invention provides a drive device for a working vehicle whereby gear change shock during the forward/reverse running changeover action can be reduced while achieving shortening of cycle time and protecting various clutch mechanisms in the transmission. If a reverse running command is output from a running control device while the vehicle is running forward, an ECMV controls a braking force of a brake device so as to reduce a vehicle speed through a first prescribed speed to a second prescribed speed, and disengages the forward clutch. When the vehicle speed reaches the first prescribed speed, the ECMV puts the reverse clutch in a slipping action condition and, after the vehicle speed reaches the second prescribed speed, gradually engages the reverse clutch.

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Ishikawa, Japan

Shunji Oka