Abstract: A directional control valve includes: a housing having a cylindrical spool hole communicating with an inlet port letting a fluid from an external supply source at a predetermined pressure and an outlet port flowing the fluid to a working cylinder; a spool movable in the spool hole axially and changing an amount of flow of the fluid; a first solenoid driving section having a first needle coupled to or integral with a first end portion of the spool and driving the spool; and a second solenoid driving section having a second needle coupled to or integral with a second end portion of the spool and driving the spool, the directional control valve including a pressure equalization circuit equally applying a pressure to the end portions.

Abstract: There is provided a relief valve capable of realizing miniaturization, weight reduction, and simplification of structure, and preventing vibration during operation. A relief valve for releasing a pressure by causing a valve body to separate from a valve seat when a pressure exceeding a set value is applied to the valve body, including an urging member that applies an urging force to the valve body to press-contact the valve body with the valve seat, the urging member being locked to a force receiving section fixedly formed in a middle portion in the axial direction of the valve body either integrally with or separately from the valve body and directly applies the urging force to the force receiving section.

Abstract: A directional control valve includes: a housing having a cylindrical spool hole communicating with an inlet port letting a fluid from an external supply source at a predetermined pressure and an outlet port flowing the fluid to a working cylinder; a spool movable in the spool hole axially and changing an amount of flow of the fluid; a first solenoid driving section having a first needle coupled to or integral with a first end portion of the spool and driving the spool; and a second solenoid driving section having a second needle coupled to or integral with a second end portion of the spool and driving the spool, the directional control valve including a pressure equalization circuit equally applying a pressure to the end portions.

Abstract: When an engine stall is likely to occur, the pressure of the back pressure chamber of a relief pressure valve is released to adjust the relief pressure of the relief pressure valve. This actuates a pressure compensating circuit to release the pressure in a control circuit to an oil tank. Thus, a rapid increase of the pressure due to a cargo handling operation is restricted, and an engine stall due to insufficient torque of the engine is avoided.

Abstract: A hydraulic driving device of an industrial vehicle includes: a tank which stores hydraulic oil; a hydraulic pump which includes a suction port sucking the hydraulic oil and a discharge port discharging the hydraulic oil; a hydraulic cylinder which is driven by the hydraulic oil discharged from the discharge port of the hydraulic pump; a direction switching valve which is disposed among the hydraulic pump, the tank, and the hydraulic cylinder and switches a hydraulic oil flow direction in response to an operation state of operation means for driving the hydraulic cylinder; in which the direction switching valve includes a main spool which moves in response to the operation state of the operation means and a flow regulator which is disposed inside the main spool to control a flow rate of the hydraulic oil flowing from the hydraulic cylinder to the tank.

Abstract: A hydraulic mechanism is mounted on a forklift. The hydraulic mechanism has a control valve and a pressure compensation circuit for compensating pressure within the hydraulic mechanism. The pressure compensation circuit has a relief pressure valve and an unloading valve for releasing pressure within the pressure compensation circuit to a discharge oil passage. Upon instructed to perform cargo handling operation, the unloading valve is switched to an open state, and the relief pressure valve is thereby actuated, so that rapid increase of pressure within the circuit is avoided. Further, the unloading valve is switched to an open state, and the pressure within the hydraulic mechanism is thereby released to the discharge oil passage, so that the cargo handling operation by the tilt cylinder and the lift cylinder is restricted.

Abstract: A hydraulic control device for a forklift includes a hydraulic pump, a single electric motor for driving the hydraulic pump, an outflow control mechanism provided between a lift cylinder and the hydraulic pump, a flow control valve provided between the outflow control mechanism and a draining portion, and a controller. When a lowering operation of a fork and either forward or rearward mast tilting operations of a mast are performed at the same time, the controller controls the electric motor based on a target speed of the hydraulic pump. The flow control valve controls the flow rate of hydraulic fluid from the lift cylinder to the hydraulic pump and the flow rate from the lift cylinder to the draining portion in accordance with the difference between the actual rotation speed of the hydraulic pump and the target rotation speed of the hydraulic pump.

Abstract: An industrial vehicle includes a hydraulic brake device, a hydraulic load handling device, a first hydraulic circuit, a second hydraulic circuit, a pressure compensating circuit, and a controller. The controller sets an electromagnetic valve to a first position during operation of the load handling device. The controller sets the electromagnetic valve to a second position and controls an electric motor to drive a hydraulic pump when determining that pressure needs to be accumulated in a hydraulic accumulator based on a detection result of a detector. When the electromagnetic valve is at the second position, hydraulic pressure generated by driving the hydraulic pump is applied to a pressure compensating valve and produces a force acting in a direction to disconnect the hydraulic pump and an oil tank from each other, so that hydraulic pressure is generated in a first oil passage to be accumulated in the hydraulic accumulator.

Abstract: When an engine stall is likely to occur, the pressure of the back pressure chamber of a relief pressure valve is released to adjust the relief pressure of the relief pressure valve. This actuates a pressure compensating circuit to release the pressure in a control circuit to an oil tank. Thus, a rapid increase of the pressure due to a cargo handling operation is restricted, and an engine stall due to insufficient torque of the engine is avoided.

Abstract: An industrial vehicle includes a hydraulic brake device, a hydraulic load handling device, a first hydraulic circuit, a second hydraulic circuit, a pressure compensating circuit, and a controller. The controller sets an electromagnetic valve to a first position during operation of the load handling device. The controller sets the electromagnetic valve to a second position and controls an electric motor to drive a hydraulic pump when determining that pressure needs to be accumulated in a hydraulic accumulator based on a detection result of a detector. When the electromagnetic valve is at the second position, hydraulic pressure generated by driving the hydraulic pump is applied to a pressure compensating valve and produces a force acting in a direction to disconnect the hydraulic pump and an oil tank from each other, so that hydraulic pressure is generated in a first oil passage to be accumulated in the hydraulic accumulator.

Abstract: A hydraulic mechanism is mounted on a forklift. The hydraulic mechanism has a control valve and a pressure compensation circuit for compensating pressure within the hydraulic mechanism. The pressure compensation circuit has a relief pressure valve and an unloading valve for releasing pressure within the pressure compensation circuit to a discharge oil passage. Upon instructed to perform cargo handling operation, the unloading valve is switched to an open state, and the relief pressure valve is thereby actuated, so that rapid increase of pressure within the circuit is avoided. Further, the unloading valve is switched to an open state, and the pressure within the hydraulic mechanism is thereby released to the discharge oil passage, so that the cargo handling operation by the tilt cylinder and the lift cylinder is restricted.

Abstract: A hydraulic control device for a forklift includes a hydraulic pump, a single electric motor for driving the hydraulic pump, an outflow control mechanism provided between a lift cylinder and the hydraulic pump, a flow control valve provided between the outflow control mechanism and a draining portion, and a controller. When a lowering operation of a fork and either forward or rearward mast tilting operations of a mast are performed at the same time, the controller controls the electric motor based on a target speed of the hydraulic pump. The flow control valve controls the flow rate of hydraulic fluid from the lift cylinder to the hydraulic pump and the flow rate from the lift cylinder to the draining portion in accordance with the difference between the actual rotation speed of the hydraulic pump and the target rotation speed of the hydraulic pump.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, a valve support chamber 35, a flow control valve 12 movable within the valve support chamber 35, an on-off valve 13 movable within the communication path chamber 12a, and a valve control device 14. The flow control valve 12 has a communication path chamber 12a and a back pressure chamber 12d. The on-off valve 13 is capable of opening and shutting off a communication path X between a cylinder line 32 and a switch valve line 33. A restrictor is formed between the flow control valve 12 and a wall defining the valve support chamber 35. The restrictor connects the cylinder line 32 and the communication path chamber 12a to each other. The opening degree of the restrictor is changed in correspondence with movement of the flow control valve 12.

Abstract: A valve seat 20 is arranged between the supply circuit 8 and a downstream circuit 18. A valve body 21 blocks a fluid flow between the supply circuit 8 and the downstream circuit 18 by contacting the valve seat 20. The valve body 21 connects the supply circuit 8 to the downstream circuit 18 for supplying the fluid to the downstream circuit 18 by separating from the valve seat 20. A through hole 24 extends through the valve body 21 and thus defines a part of the supply circuit 8. The through hole 24 is defined in such a manner that the fluid that has flowed from the through hole 24 proceeds between the valve seat 20 and the valve body 21 and is thus supplied to the downstream circuit 18. The valve body 21 is formed in such a manner that a pressure receiving area at an upstream side of the through hole 24 is smaller than a pressure receiving area at a downstream side of the through hole 24.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, an adjustment valve 12, and a valve control device 13. The adjustment valve 12 has a fluid chamber 15, a valve body 14, and a back pressure chamber 17. A restrictor is formed between the valve body 14 and a wall defining the fluid chamber 15 and connects the cylinder line 32 to the switch valve line 33. The opening degree of the restrictor changes in correspondence with movement of the valve body 14. When the switch valve 11 is located at a neutral position or a supply position, the valve control device 13 applies the fluid pressure in the cylinder line 32 to the back pressure chamber 17. When the switch valve 11 is located at a drainage position, the valve control device 13 applies a pilot pressure lower than the fluid pressure in the cylinder line 32 to the back pressure chamber 17.

Abstract: 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 circuit 21 and saves the space for arranging the load pressure detection circuit 21., resulting in a relatively compact housing.

Abstract: 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.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, a valve support chamber 35, a flow control valve 12 movable within the valve support chamber 35, an on-off valve 13 movable within the communication path chamber 12a, and a valve control device 14. The flow control valve 12 has a communication path chamber 12a and a back pressure chamber 12d. The on-off valve 13 is capable of opening and shutting off a communication path X between a cylinder line 32 and a switch valve line 33. A restrictor is formed between the flow control valve 12 and a wall defining the valve support chamber 35. The restrictor connects the cylinder line 32 and the communication path chamber 12a to each other. The opening degree of the restrictor is changed in correspondence with movement of the flow control valve 12.

Abstract: 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.

Abstract: A hydraulic parking brake device is selectively switched between a braking state and a non-braking state. A braking force decreases as a pressure in the control oil chamber increases and increases as the pressure in the control oil chamber decreases. The device includes a discharged oil restrictor located in a discharge passage and an accumulator connected to the control oil chamber. The accumulator is capable of releasing hydraulic oil to the control oil chamber when the braking force is greater than that at the time when the parking brake device is switched from the non-braking state to the braking state and the braking force can further be increased during the braking state of the parking brake device. Thus, the parking brake device can gradually brake the vehicle from the running state.