Yanmar Co., Ltd.

Masami Kondou

Hideki Seino

A hydraulic shovel including a selection means for an engine which is capable of arbitrarily selecting either of an isochronous control and a droop control, and a traveling detection means for detecting the traveling state of a traveling device. The hydraulic shovel further includes a control means for the engine which selects the isochronous control when the traveling detection means detects the traveling state to maintain the rotational speed of the engine during rated operation while an output is increased, and selects the droop control when the traveling detection means does not detect the traveling state to set the rotational speed of the engine lower than that during the rated operation while the output is increased.

Engine controller of hydraulic shovel

An object is to provide a construction machine containing an engine () and a heat exchanger () in a bonnet (), adapted for easy cleaning of a side of the heat exchanger () toward a cooling fan. A space () into which a hand can be put is provided between a cooling fanattached to the engine () and the heat exchanger () arranged so as to face to the cooling fan (). A part covering a region from the cooling fan () to the heat exchanger () in the bonnet () from above and sides includes a separate cover (). An opening part having a guard () is provided through a portion of the cover (), the portion facing to the heat exchanger (). The cover () is configured to be openable and closable. The cooling fan () is adapted to be of a discharge type. A plurality of the heat exchangers are arranged in a same plane.

Construction machine

A hydraulic circuit of a excavating-and-slewing working vehicle, comprising: actuators for a boom, a bucket, slewing and an arm; directional control valves for the respective actuators; a pair of first and second hydraulic pumps for supplying pressure oil to the actuators through the respective directional control valves; a delivery oil passage of the first hydraulic pump tandem-connecting the boom directional control valve for boom to the bucket directional control valve for bucket on the downstream side of the boom directional control valve; a delivery oil passage of the second hydraulic pump tandem-connecting the slewing directional control valve for slewing to the arm directional control valve for arm.

Hydraulic circuit of excavating and slewing working vehicle

In an excavating/slewing work truck, the boom falls freely at the time of lowering operation without requiring any power but the flow rate of a pump increases excessively when the speed is balanced with other acutuators and power loss is inevitable for enhancing the operability. In order to eliminate this inconvenience, a first oil path () connecting a bottom side cylinder port (CB) and a tank port (T), a second oil path () connecting a pump port (P) and a rod side cylinder port (CR), and a third oil path () connecting a pump port (P) and a tank port (T) are provided, respectively, with first, second and third restrictors (), () and () at the boom down position of a change-over valve () for the boom cylinder of an excavating/slewing work truck, wherein the first restrictor () restricts by such an amount as the work machine lowers gravitationally an the second restrictor () restricts by such an amount as the pressure on the boom side is not exceeded.

Change-over valve for boom cylinder of excavating/slewing work truck

A hydraulic circuit of an excavating and slewing working vehicle of two pump system, wherein a directional control valve for slewing and a directional control valve for arm are tandem-connected to the upstream side and downstream side of the delivery oil passage of a second hydraulic pump, respectively, a directional control valve for bucket are connected to the delivery oil passage of a first hydraulic pump, and then a bleed switching valve connected, through a check valve between the directional control valve for slewing and the directional control valve for arm and switched to connect to or disconnect from a tank on the upstream side of the check valve and the directional control valve for slewing are operated interlockingly with each other.

In a working vehicle which includes left and right traveling devices, a pair of hydraulic traveling motors are installed to drive the respective traveling devices, and a pair of hydraulic directional control valves are provided for the respective hydraulic traveling motors in order to control the traveling of the vehicle. A throttle valve is provided in a pilot oil-passage, and connected to a drain oil-passage after passing serially through the pair of hydraulic directional control valves below the throttle valve. A pressure switch for warning the traveling state is operated by a pilot hydraulic pressure which is pressure of oil within an oil-passage between the throttle valve and an upstream one of the left and right hydraulic directional control valves.

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Osaka, Japan

Masami Kondou