JPH022963Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic power unit that is easy to adjust hydraulic pressure and is used for lifting and lowering work equipment mainly mounted on vehicles, such as forklifts, construction machines, and agricultural machines.

Conventionally, in this type of hydraulic power unit, the pressure oil discharged from the pump is switched between two paths, one for sending it to the load and the other for returning it to the tank, using a slide valve or a rotary valve, or the pressure oil is sent to the load. A flow path is provided that branches off from the flow path and returns to the tank via an unload valve, and the operation of the load equipment is controlled by switching the flow of pressure oil by opening and closing the unload valve. However, the conventional valves in the hydraulic circuit simply send out the pressure oil from the pump to the load at the same pump discharge pressure by opening and closing, and do not have a pressure adjustment function.

Therefore, it is difficult to smoothly start and stop the actuator of the load by simply switching the valves, and it is difficult to smoothly operate the work equipment. In addition, in cases such as battery forklifts, where electric power from a storage battery is used to rotate a motor and drive a pump, it is necessary to save as much electricity as possible to drive the pump in order to reduce the number of times the storage battery needs to be charged. be. In a conventional hydraulic circuit that directly sends the pump's discharge pressure to the load, the pump ends up discharging oil at a pressure higher than necessary, resulting in wasted power consumption.

In view of the above, the present invention allows for easy and smooth operation of work equipment by freely adjusting the discharge pressure of pressure oil to the actuator, and also provides a hydraulic power unit that consumes less energy for driving. The purpose is to provide. Another object of the present invention is to provide a hydraulic power unit that can switch the hydraulic circuit from the pump to the actuator and continuously raise and lower the hydraulic pressure supplied to the actuator by operating a single handle. Our goal is to provide the following.

The present invention includes a tank, a pump that delivers oil from the tank, a circuit that discharges the oil from the pump through an inlet and a check valve to a flow path from a discharge port to an actuator, and a safety valve that branches from the inlet. A circuit that returns to the tank via an unload valve that also serves as
A circuit that branches from the discharge port and returns to the tank via a return valve, and a compression spring that compresses the unload valve to the valve seat and slides in the axial direction to change the amount of compression of the compression spring. an unload valve opening/closing push rod that opens and closes the unload valve by changing the pressure applied to the valve seat of the unload valve; and a return valve closing compression spring that urges the return valve to press against the valve seat. and a return valve opening/closing push rod that is disposed parallel to the unload valve opening/closing push rod and slides in the axial direction to push the return valve open/close against the return valve closing compression spring; The push rods are oscillated about a fulcrum located between the push rods, and in accordance with the swing, alternately push the ends of the push rods for opening and closing the unload valve and the push rods for opening and closing the return valve. a link that slides in the axial direction to alternately open and close the unload valve and the return valve; and a link that is biased to rotate in a direction away from the push rod for opening and closing the unload valve to close it. and a link restoration spring that automatically restores the rotation of the link to the neutral stop position where the link contacts the end of the return valve opening/closing push rod that contacts the unload valve. The compression spring expands to its natural length when the link is stopped at the neutral stop position, releases the pressing force against the valve seat of the unload valve, and switches the flow path of the pressure oil by displacing the link. The gist of the present invention is a hydraulic power unit characterized in that: and the discharge pressure and discharge amount of the pressure oil to an actuator are continuously adjusted.

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a partially sectional front view of the power unit of the present invention, FIG. 2 is a partially sectional side view of the same, and FIG. 3 is a hydraulic circuit diagram of the power unit of the present invention. 25 is a valve block, and tank 16
is attached airtight to one end of the Valve block 25
The pump 2 is driven by the rotation of the drive shaft 24.
2 is installed, and a passage 17 is bored leading from the inlet 4 of the oil from the pump 22 to the discharge port 20, and a check valve 5 is provided in the middle of the passage 17. Reference numeral 18 denotes a return passage for returning the return oil from the actuator to the tank 16. A branch passage 15 is provided which branches off from the passage 17 and communicates with the return passage 18 via the unload valve 2. The unload valve has a spherical valve body attached to the tip of a rod 28 that is slidably inserted into the inner hole 27 of the push rod 13 for opening and closing the unload valve, which slides airtight inside the sliding hole 26. A coiled compression spring 6 fitted on the outside of the rod 28 presses the valve body against the valve port 21 to close the unload valve 2. Reference numeral 3 denotes a return valve provided in a passage communicating between the discharge port 20 and the return passage 18, which is pressed against a valve seat by a return valve closing compression spring 19 and slides airtightly into a sliding hole 29 to open and close the return valve. It is designed to be opened and closed by a push rod 12. Reference numeral 1 denotes a valve switching link that is oscillated by the operation of a handle 8 and about a support shaft 9, and is rotated clockwise by a compression spring 7 fitted on the outside of a push rod 13 for restoring the link. The rocking motion pressurizes the push rods 12 and 13 via the ball seats 10 and 11, or releases the pressurizing force, thereby opening the return valve 3 and the unload valve 2 which also serves as a safety valve. It is designed to open and close.

Next, the operation will be explained. The oil in the tank 16 is sucked from the suction tube 23 by a pump 22 driven by a drive motor or the like via a drive shaft 24, pressurized, and discharged into the inlet portion 4. When no force is applied to the handle 8, the link 1 is biased by the compression spring 7, and the ball seat 10 is pressed against the push rod 1.
It is in the neutral position of contacting with 2. At this time, the torque exerted by the compression spring 19 on the link 1 via the push rod 12 is greater than the opposite torque exerted by the compression spring 7, so the return valve 3 is in the closed state and the push rod 12 The position regulates the natural stop position of link 1. In this neutral position, the compression spring 6 is extended to its natural length and does not apply any pressing force to the unload valve, and the unload valve 2 is in a so-called unloaded state, and the flow of fluid from the pump 22 through the inlet portion 4 occurs. Pressure oil is supplied through the unload valve 2, branch passage 15, and return passage 18.
It returns to the inside of the tank 16. When link 1 is gradually rotated from the neutral position against the repulsive force of compression spring 7, push rod 13 is pushed toward 14 through ball seat 11, and compression spring 6 is gradually compressed. , the pressing force of the unload valve 2 against the valve port 21 via the compression spring 6 gradually increases. Correspondingly, the pressure at the inlet portion 4 of the oil, which had previously been returned to the tank 16 via the unload valve while the oil pressure remained almost zero in the unloaded state, gradually increases. However, the unload valve 2 is still pushed open by the hydraulic pressure and is not closed. When the link 1 is rotated and the discharge pressure of the pressure oil reaches the pressure required to drive the actuator, a portion of the oil pushes up the check valve 5 and is discharged through the discharge port 20 to the flow path on the actuator A side. . When link 1 is further rotated and the oil pressure increases, all the pressure oil flows to the actuator,
At the same time, the unload valve 2 is closed. In this case, the unloading valve 2 closes the valve port 21 by receiving a constant pressure depending on the rotational position of the link 1 due to the elasticity of the compression spring 6, but the hydraulic pressure flowing toward the actuator A increases. , when a load greater than the pressure of the compression spring 6 is applied to the unload valve 2, it is naturally pushed open and functions as a safety valve, allowing the valve to escape into the tank 16 via the branch passage 15, and the hydraulic pressure is reduced. It is designed to maintain a constant pressure at all times.

Next, when the link 1 is returned to the neutral position from the operating position, the pressure oil that has been flowing to the actuator A via the passage 17 is changed from the discharge port 20 to the actuator A by the return valve 3 and the check valve. While being kept on the roadside,
Pressure oil from the pump 22 flows directly into the tank 16 from the branch passage 15 via the unload valve 2 whose back pressure has been released.

Finally, when the link 1 is placed in the pressure oil return operation position, the unload valve 2 is in the unload state, so all the pressure oil from the pump passes through the unload valve 2 and the branch passage 15 to the tank. 16
The return valve 3 flows directly through the link 1, the ball seat 10, the push rod 12 and the compression spring 19.
The pressure oil held on the actuator side is returned to the tank 16 through the return passage 18. At this time, the pressure oil
Since it passes through a narrow annular gap around the push rod 12 behind the return valve 3, it is constricted and cannot return suddenly, but is gradually returned. After the operation of the link 1 is completed, the elasticity of the spring 7 or the spring 19 causes the link 1 to
is automatically returned to the neutral position. In the operating position, the return oil from the actuator A flows into the tank 16 through the passage 18 from the direction of arrow a.

According to the present invention, by rotating the link from the neutral position to the operating position, the closing pressure of the unload valve can be freely adjusted, and the equipment driven by the actuator can be adjusted from the state where the entire flow of pressure oil is returned directly to the tank. The flow of pressure oil can be gradually switched to the actuator side by moving the handle while visually observing the movement and gradually increasing the discharge pressure. This allows for extremely smooth starting and stopping of the work equipment, and also reduces the operating speed. Can be adjusted freely. Furthermore, since the discharge pressure of the pump can be suppressed to the necessary minimum, it is possible to save energy in driving the pump. Furthermore, the unload valve functions as a safety valve, and the pressure at which the safety valve operates can be freely adjusted according to the load.

The return valve is integrated into the valve block, and the return valve is opened and closed by swinging the link for opening and closing the unload valve, so operating the work equipment can be done by operating a single handle that swings the link. start, stop,
The return operation can be performed, and the entire hydraulic power unit can be made extremely compact.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of the hydraulic power unit of the present invention, FIG. 2 is a partially sectional side view of the same, and FIG. 3 is a hydraulic circuit diagram of the hydraulic power unit of the present invention. Explanation of symbols, 1...Link, 2...Unload valve, 3...Return valve, 5...Check valve, 6, 7,
19... Compression spring, 12, 13... Push rod,
15...branch passage, 16...tank, 17,18
...Aisle, 22...Pump.

Claims (1)

[Scope of utility model registration request] A tank, a pump for discharging the oil in the tank, a circuit for discharging the oil from the pump through an inlet and a check valve to a flow path from a discharge port to an actuator, and a circuit that branches from the inlet and doubles as a safety valve. A circuit that returns to the tank via the unload valve, a circuit that branches from the discharge port and returns to the tank via the return valve, and a compression spring that presses the unload valve against the valve seat and slides in the axial direction. an unload valve opening/closing push rod that opens and closes the unload valve by changing the amount of compression of the compression spring and changing the pressing force against the valve seat of the unload valve; and a push rod that presses the return valve against the valve seat. a compression spring for closing the return valve, which is biased so as to press the return valve; and a push rod for opening and closing the unload valve, which is arranged parallel to the push rod and slides in the axial direction to push the return valve against the compression spring for closing the return valve. A push rod for opening and closing the return valve that opens and closes, and a push rod for opening and closing the unload valve and a push rod for opening and closing the return valve that oscillates around a fulcrum located between the two push rods and follows the swinging movement. a link for alternately opening and closing the unload valve and the return valve by alternately pushing the ends of the push rods and sliding each push rod in the axial direction; and separating the link from the push rod for opening and closing the unload valve. A link that automatically restores rotation to a neutral stop position where the link contacts the end of the return valve opening/closing push rod that contacts the return valve in the closed position by being biased to rotate in the direction of the return valve. The compression spring of the unload valve expands to its natural length when the link is stopped at the neutral stop position to release the pressing force against the valve seat of the unload valve. A hydraulic power unit characterized in that the flow path of pressure oil is switched and the discharge pressure and discharge amount of the pressure oil to an actuator are continuously adjusted by displacement operation of a link.