Eagle Industry Co., Ltd.

Shin Caterpillar Mitsubishi Ltd.

Caterpillar Sarl

Caterpillar Japan Ltd.

Shin Caterpiller Mitsubishi Co., Ltd.

Yoshiyuki Shimada

Tetsuya Yoshino

Koji Sato

Yutaka Yokoyama

Tatsuhiro Arikawa

Yuta Okamoto

Tomoki Seki

Kazunori Yoshino

Nobuhiro Miki

Hiroyasu Nishikawa

Masaru Mishima

Yuya Kanenawa

Makoto Iga

Takayasu Kitai

There is provided a fluid circuit capable of continuously driving pressure-increasing devices with a simple configuration. A plurality of pressure-increasing devices are connected in parallel to a fluid supply device that delivers a working fluid. A stroke direction of the piston of each of the pressure-increasing device is switched by the working fluid. A phase of the piston of one pressure-increasing device is different from a phase of the piston of the other pressure-increasing device.

Fluid circuit

A fluid circuit includes first switching valve that switches between flow passages and first flow passages according to a change in a fluid pressure to be applied, a second switching valve that is switched to a flow passage which applies the fluid pressure to the first switching valve, when a piston has reached an initial position or an end position, and second flow passages. A biasing force of a biasing member when the piston reaches the end position is smaller than a pressing force acting on the piston due to the fluid pressure caused by a fluid supply device, and a biasing force of the biasing member when the piston reaches the initial position is larger than a sum of a flow passage resistance force acting on the first flow passages and a flow passage resistance force acting on the second flow passages.

There is provided a fluid pressure circuit capable of preventing unintentional operation of a cylinder device. A return flow passage through which a return fluid flows from a cylinder device to a regenerative drive source is provided with a control valve that opens the flow passage in response to an operation of an operating device.

Fluid pressure circuit

A first switching valve that switches between flow passages which allow communication between a first pressure-receiving chamber and a fluid supply device side and flow passages which allow communication between a second pressure-receiving chamber and the fluid supply device side, according to a change in a fluid pressure to be applied, and a second switching valve that is switched to flow passages which apply the fluid pressure to the first switching valve, are provided. The second switching valve includes return device, and is provided to be reciprocatable between an operation position to which the second switching valve is moved by a stroke of a piston and a return position to which the second switching valve is moved by the return device. The piston and the second switching valve are movable independently of each other.

A fluid control device includes a housing partitioned into an input chamber and an output chamber by a housing land portion extending on the radially inner side, a spool arranged inside the housing and provided with a spool land portion that is configured to reciprocatively slide with respect to the housing land portion and that extends on a radially outer side of the spool, and a biasing member configured to bias the spool toward a valve closing position, wherein upon receiving drive force from an exterior, the spool is moved against bias force of the biasing member, and the input chamber and the output chamber communicate with each other, the spool includes a large diameter portion arranged in the input chamber and having a larger diameter than the spool land portion, and the large diameter portion and the housing land portion form a poppet valve structure.

Fluid control device

A fluid pressure circuit includes a directional switching valve arranged between a fixed displacement pump and a fluid pressure actuator and configured to switch a flow passage for a pressurized fluid, an accumulator arranged in a branch flow passage branched from a connection flow passage that connects the fluid pressure actuator and the directional switching valve, an accumulator flow control valve arranged between the connection flow passage and the accumulator, and a pump flow control valve arranged between the fluid pressure actuator and the fixed displacement pump and configured to variably divert a flow rate of the pressurized fluid discharged from the fixed displacement pump into a first system including the tank and a second system including the fluid pressure actuator.

A fluid circuit includes a pressure fluid source configured to supply pressure fluid, multiple actuators connected to the pressure fluid source, a direction switching valve configured to switch a supply destination of the pressure fluid supplied from the pressure fluid source, and a discharge amount control mechanism configured to control the output pressure of the pressure fluid source such that a pressure difference &#x394;P between the output pressure of the pressure fluid source and the maximum load pressure of the load pressures of the multiple actuators reaches a target value &#x394;Pt. The fluid circuit further includes an accumulator configured to accumulate part of return fluid from the actuators.

A fluid pressure circuit for controlling a rod of a cylinder controlled in accordance with an operation command includes a tank, a fluid pressure actuator configured to pressurize fluid supplied from the tank for extending and retracting the cylinder, a flow control valve arranged between the fluid pressure actuator and the cylinder device configured to switch a flow passage of pressurized fluid and discharge via a first throttle return fluid from the cylinder, a variable regeneration switching valve configured to discharge return fluid from the cylinder to the flow control valve upon non-regeneration and upon regeneration, branch part of the return fluid and discharge via a second throttle the fluid branched, a regenerative motor configured for regeneration by fluid branched by the variable regeneration switching valve, and a third throttle connected in series with the first throttle upon the regeneration to limit flow of return fluid.

A fluid pressure circuit includes an HST circuit having a variable capacity fluid pressure pump configured to be driven by a mechanism to perform forward-reverse rotation, a fluid pressure motor configured to be driven by fluid discharged from the fluid pressure pump to perform forward-reverse rotation, a first line configured to connect a first port of the fluid pressure pump and a first port of the fluid pressure motor, and a second line configured to connect a second port of the fluid pressure pump and a second port of the fluid pressure motor; an accumulator connected in parallel with the fluid pressure pump; an accumulator pump configured to accumulate pressure fluid in the accumulator; and an accumulator switching valve configured to switch connection between the fluid pressure motor and the accumulator.

A fluid circuit includes a pressure fluid source, a switching valve, and a cylinder device having first and second chambers and partitioned by a piston. A first accumulator is configured to communicate with the second chamber when pressure fluid is supplied to the first chamber and to accumulate part of the pressure fluid from the second chamber. A pressure booster is connected in hydraulically parallel to the first accumulator, the pressure booster communicative with the second chamber when the pressure fluid is supplied to the first chamber to boost pressure of the pressure fluid by using part of the pressure fluid from the second chamber. A second accumulator accumulates the pressure fluid whose pressure is boosted by the pressure booster.

A hydraulic control circuit includes a hydraulic cylinder, a control valve, a recovery oil passage, a hydraulic pump, an engine rotation speed setting unit, a recovery control valve, and a controller that reduces an engine rotation speed to not more than a preset reduction control engine rotation speed when the load is lowered; and adjusts an increase or decrease in an opening amount of the recovery control valve in accordance with a level of the target rotation speed set by the engine rotation speed setting unit.

Hydraulic control circuit for construction machine

The present invention is intended to provide a technology that can utilize the advantages of both a load sensing control and a regeneration circuit without causing any problem. A regeneration circuit is added to a hydraulic circuit provided with a hydraulic pressure signal line for detecting a hydraulic pressure value of a circuit and controlling a volume of hydraulic fluid to a cylinderwith reference to the detected value. A pressure reducing valvethat outputs a reduced pressure as an operating signal to a pump, and subsequently the controlling meanscauses the pressure reducing valveto output a pressure reduction command to a pumpand thus to reduce a discharge rate from the pump, when the regeneration circuit is in a regeneration state.

Method for controlling pump of working machine

To perform boom-down operation by operating a boom cylinder () by an external load (W) while simultaneously operating an arm cylinder () or a bucket cylinder () in the state the bucket is off the ground, a first boom directional control valve () and a regeneration boom valve () are controlled to the neutral position and the open position respectively so that the hydraulic oil is regenerated from a line () located at the oil-returning side of the boom cylinder () through the regeneration boom valve () to a line () located at the oil-feeding side. Therefore, the volume of the hydraulic oil that can be supplied from the pressurized oil source () to the arm cylinder () or the bucket cylinder () via the second arm directional control valve () or the bucket directional control valve () is increased by the amount equivalent to the amount of the oil that is not supplied from the pressurized oil source () to the boom cylinder (). As the circuit according to the invention enables the arm cylinder () or the bucket cylinder () to work faster, it increases the operating efficiency of the hydraulic excavator when its hydraulic actuators are operated simultaneously.

A hydraulic control circuit for a boom cylinder in a work machine, which, when controlling supply and discharge of pressurized oil with respect to a boom cylinder, improves fuel efficiency, work efficiency in combined operations, and improves work efficiency and operationality in the work of difficult boom operations, such as debris raking-up work and bumping work, wherein the hydraulic control circuit of a boom cylinder is provided with a change valve to hold a first boom control valve at a neutral position, a communication line for causing a head side oil chamber and a rod side oil chamber to communicate with each other, an opening valve for opening and closing the corresponding communication line, and pilot operating check valve that is changed to an unidirectional state where, although an oil flow from the head side oil chamber to the rod side oil chamber is permitted, a reverse flow is hindered, and to a bi-directional state where oil flows in both directions, and further a second boom control valve is provided with discharge means for causing oil discharged from the head side oil chamber to flow into an oil reservoir.

Hydraulic control circuit for boom cylinder in work machine

A hydraulic control circuit of a boom cylinder for a work machine, which, when controlling the supply and discharge of pressurized oil with respect to a boom cylinder, improves fuel efficiency, work efficiency in combined operations, and work efficiency and operationality in work of difficult boom operations, such as debris raking-up work and bumping work, etc. The hydraulic control circuit of a boom cylinder is provided with a first change valve for holding the boom control valve in the neutral position, a communication line for causing the head side oil chamber and the rod side oil chamber to communicate with each other, an opening and closing valve for opening and closing the communication line, and a pilot operation check valve that is changed to an unidirectional state where, although an oil flow from the head side oil chamber to the rod side oil chamber is permitted, a reverse flow is hindered, and a bi-directional state is permitted where the oil flows in both directions.

Growing community of inventors

Tokyo, Japan

Yoshiyuki Shimada