JPH08284902A - Hydraulic power unit - Google Patents

Abstract

PURPOSE: To drive a pair of cylinders connected in parallel with an operating fluid source at adjustable speed. CONSTITUTION: A first cylinder 2 and a second cylinder 3 are connected in parallel with operating fluid sources 7, 10 through each operating fluid supply and discharge passage 5, 6 which uses in common partially a discharge flow passage 5a and a return flow passage 6a mutually, and supply and discharge direction change-over means 8, 9 are provided in each operating fluid supply and discharge passage 5, 6. In a hydraulic power unit 22 which drives the first and second cylinders reciprocatingly by changing over the supply and discharge direction change-over means 8, 9 into the operating fluid supply direction and the operating fluid discharge direction, a first variable throttle valve 23 which adjusts the flow rate of operating fluid discharged from the first cylinder 2 and changes return speed of the first cylinder is provided in the return flow passage 6a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic unit capable of efficiently driving a pair of first and second cylinders connected in parallel to a working fluid source.

[0002]

2. Description of the Related Art A vehicle tailgate lifter 1 shown in FIG.
Is equipped with a lift cylinder 2 and a pair of turn cylinders 3 for raising and lowering and opening and closing the tailgate. The hydraulic unit 4 supplies and discharges hydraulic oil to and from these cylinders 2 and 3 for reciprocating drive. It is configured. The lift cylinder 2 for raising and lowering the tailgate has a larger diameter than the turn cylinder 3 for opening and closing the tailgate, and a large amount of hydraulic oil is required to make the same stroke displacement. The hydraulic unit 4 electrically drives these cylinders 2 and 3 via working fluid supply and discharge passages 5 and 6 that partially share the discharge passage 5a and the return passage 6a. The hydraulic pump 7 is connected in parallel, and the working fluid supply / discharge paths 5, 6 are provided with supply / discharge direction switching means 8, 9 so that the supply / discharge direction of the hydraulic oil can be arbitrarily switched. Has become. The feeding / discharging direction switching means 8 and 9 shown in the present example respectively include a pair of electromagnetic switching valves 8a, 8b and 9a, 9b which are selectively switched to one of a check state and a communication state in response to an external command. The hydraulic pump 7 is constructed by connecting in series in the reverse direction.
Drive or stop and electromagnetic switching valves 8a, 8b, 9a, 9
The cylinders 2 and 3 can be moved up and down by combining selective switching of b.

First, when the hydraulic pump 7 is driven in a state where only the electromagnetic switching valve 8a is switched, the hydraulic oil in the tank 10 is electromagnetically switched in the check valve 11 in the discharge passage 5a and in the supply / discharge passage 5. It is sent into the lift cylinder 2 via the valves 8a and 8b, and the lift cylinder 2 is driven forward to raise the tailgate. Further, when the hydraulic pump 7 is stopped and the solenoid switching valve 8b and the solenoid switching valve 12 in the return passage 6a are switched, the hydraulic oil in the lift cylinder 2 is discharged by the load weight of the cylinder 2, and the supply / discharge passage is opened. 5
It is returned to the inside of the tank 10 through the electromagnetic switching valves 8b and 8a therein, the automatic flow rate adjusting valve 13 and the electromagnetic switching valve 12 in the return flow path 6a, and the tailgate descends accordingly. The interconnecting flow path 14 connecting the discharge flow path 5a and the return flow path 6a also serves as a hydraulic oil discharge path for the lift cylinder 2 and a hydraulic oil supply path for the turn cylinder 3. There are no valves in this flow path 14.

On the other hand, when the hydraulic pump 7 is driven and the electromagnetic switching valve 9a is switched, the working oil discharged from the hydraulic pump 7 passes through the check valve 11 in the discharge passage 5a and then the interconnected flow. It is sent into the supply / discharge flow path 6 through the path 14, and further sent out from the hydraulic unit 4 through the electromagnetic switching valves 9a and 9b. A restrictor valve 15 is connected to the hydraulic unit 4, and the restrictor valve 15 is connected to the hydraulic unit 4.
The hydraulic oil that has passed through is supplied to the turn cylinder 3 to close the tailgate. The restrictor valve 15 is the check valve 1
5a and the variable throttle valve 15b are connected in parallel, which does not contribute to the returning speed of the turn cylinder 3,
By adjusting the throttle resistance value of the variable throttle valve 15b, the forward speed of the turn cylinder 3 can be changed.

On the other hand, when the electromagnetic switching valves 9b and 12 are switched after the hydraulic pump 7 is stopped, the turn cylinder 3 is returned while discharging hydraulic oil due to the weight of the load. At this time, the hydraulic oil discharged from the turn cylinder 3 passes through the restrictor valve 15 and flows into the electromagnetic switching valves 9b and 9a in the supply / discharge passage 6, and further the automatic flow rate adjustment in the return passage 6a. It is returned to the tank 10 via the valve 13 and the electromagnetic switching valve 12.

A relief valve 16 is branched and connected to the discharge side of the hydraulic pump 7 and opens when the pump discharge pressure rises above a certain pressure, and a part of the hydraulic oil is stored in the tank 1.
It works to return to the 0 side.

[0007]

In the conventional hydraulic unit 4 described above, the automatic flow rate adjusting valve 13 discharges the lift cylinder 2 from the lift cylinder 2 when the lift cylinder 2 is moved back, that is, when the tailgate is lowered. Since the oil amount is limited, the descending speed of the tailgate is kept constant regardless of the load. However, there is a problem that it is impossible to variably adjust the descending speed of the tailgate, so that it is not possible to meet a wide range of needs of the user. Further, when the tailgate is closed, that is, when the turn cylinder 3 is moved forward, the flow rate is controlled by the restrictor valve 15. Therefore, in order to suppress the closing speed of the tailgate, the variable throttle valve in the restrictor valve 15 is controlled. As the pressure of 15b is narrowed down, the discharge pressure of the hydraulic pump 7 increases, the current consumption of the motor 7a that is the power source thereof increases, and there is a problem that the consumption of the motor and the battery is accelerated.

Therefore, it is an object of the present invention to enable two sets of cylinders connected in parallel to a working fluid source to be driven efficiently and speed-adjustably without increasing the pump pressure.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a working fluid source for a first cylinder and a second cylinder is provided through respective working fluid supply / discharge passages that partially share a discharge passage and a return passage. Is connected in parallel to the first and second cylinders by switching the supply / discharge direction switching means to the working fluid supply direction and the working fluid discharge direction. In a hydraulic unit for forward and backward driving, the flow rate of the working fluid provided in the return passage and discharged from the first cylinder is adjusted, whereby the backward movement of the first cylinder is performed. The above object is achieved by providing a hydraulic unit including a first variable throttle valve that varies the speed.

Further, according to the present invention, there is provided a bypass flow passage which is branched and connected to the working fluid supply / discharge passage for the second cylinder and which returns a part of the working fluid supplied to the second cylinder to the working fluid source side. And a second variable throttle valve that is provided in the bypass flow passage and that adjusts the flow rate of the recirculated working fluid, thereby varying the forward speed of the second cylinder. By doing so, the above-mentioned object is achieved.

Further, according to the present invention, there is provided a bypass passage which is branched and connected to the working fluid supply / discharge passage for the second cylinder and which circulates the working fluid discharged from the second cylinder to the working fluid source side, and the bypass passage. By providing a hydraulic unit that is provided in a flow path and that includes a third variable throttle valve that adjusts the flow rate of the recirculated working fluid, thereby varying the returning speed of the second cylinder, The above object is achieved.

[0012]

According to the present invention, the first variable throttle valve is provided in the return passage in which the respective working fluid supply / discharge passages connecting the first and second cylinders to the working fluid source are partially shared. By adjusting the flow rate of the working fluid discharged from one cylinder and varying the returning speed of the first cylinder, the returning speed of the first cylinder can be arbitrarily changed according to the load weight.

[0013]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a main part hydraulic circuit diagram showing an embodiment of a vehicle tailgate lifter to which a hydraulic unit according to the present invention is applied, and FIG. 2 is a loading amount of the tailgate lifter shown in FIG. 1 and a return flow rate of hydraulic oil. It is a figure which shows the relationship of.

The vehicle tailgate lifter 21 shown in FIG.
Is slightly different from the conventional hydraulic unit 4 in the configuration of the hydraulic unit 22. The differences are roughly the following three points.

The first point is that a first variable throttle valve 23 is newly provided in the return passage 6a so that the returning speed of the lift cylinder 2 can be varied.

The second point is that the use of the restrictor valve 15 that causes an increase in the discharge pressure of the hydraulic pump 7 is abolished, and instead a part of the hydraulic oil is returned to the tank 10 side by-pass passage 24.
Is provided, and the second variable throttle valve 25 is provided in the flow path 24, whereby the forward speed of the turn cylinder 3 can be varied.

The third point is that by providing a bypass flow path 26 for returning the return hydraulic oil from the turn cylinder to the tank 10 side and providing a third variable throttle valve 27 in this flow path 26, This is the point that the returning speed of the working cylinder 3 can be varied.

More specifically, the first variable throttle valve 23 is
It is connected between the automatic flow rate adjusting valve 13 and the electromagnetic switching valve 12 in the return flow path 6a, and adjusts the flow rate of the hydraulic oil that returns to the tank 10 when the lift cylinder 2 returns.

The second variable throttle valve 25 is provided in the bypass passage 24 for returning a part of the hydraulic oil from the output side of the electromagnetic switching valve 9a to the tank 10, and the turn cylinder 3 is moved forward. It functions to adjust the bypass flow rate of the hydraulic oil returning to the tank 10 when the operation is performed. The second variable throttle valve 25 has a function of varying the forward speed of the turn cylinder 3 like the variable throttle valve 15b incorporated in the conventional restrictor valve 15, but the hydraulic pump 7 There is a notable difference in the effect on the.

Further, the third variable throttle valve 27 includes a check valve 28, an electromagnetic switching valve 9a, an automatic flow rate adjusting valve 13 between the input side of the electromagnetic switching valve 9b and the input side of the electromagnetic switching valve 12. The bypass flow passage 26 is provided in a bypass passage 26 that is provided so as to bypass the first variable throttle valve 23, and when the turn cylinder 3 returns, the bypass flow rate of the hydraulic oil that returns from the cylinder 3 to the tank 10. Function to adjust.

Each of the first, second, and third variable throttle valves 23, 25, 27 shown in the embodiment is constituted by a needle valve, and a throttle formed between the needle and its valve seat. The structure is such that the flow path resistance of the flow path can be changed according to the amount of advance / retreat of the needle.

With respect to the lift cylinder 2, the forward movement operation performed by driving the hydraulic pump 7 and switching the electromagnetic switching valve 8a is the same as the conventional one. However, the hydraulic pump 7 is stopped and the electromagnetic switching valves 8b, 1
At the time of the backward movement by switching between the two, the hydraulic oil that has flowed into the return flow path 6a via the automatic flow rate adjusting valve 13 passes through the first variable throttle valve 23 and the electromagnetic switching valve 12 to the tank 10
Is returned to. For this reason, by changing the throttle resistance value of the first variable throttle valve 23, the automatic flow rate adjusting valve 13 allows a constant return speed regardless of the change in the load weight. With the addition of functions, the range of automatic flow rate adjustment can be variably set (see Fig. 2).

Regarding the turn cylinder 3, when the forward movement is performed by driving the hydraulic pump 7 and switching the electromagnetic switching valve 9a, that is, when the tailgate is closed, a second variable valve is provided from the output side of the electromagnetic switching valve 9a. A part of the hydraulic oil is returned to the tank 10 side via the throttle valve 25. Therefore, unlike the conventional hydraulic unit 4 in which the pressure is increased to forcibly reduce the flow rate of the hydraulic oil supplied to the turn cylinder 3, only a part of the hydraulic oil discharged by the hydraulic pump 7 is supplied to the turn cylinder. Since it is used for driving 3, the pump discharge pressure is not increased, and the recirculation amount is variably set by the second variable throttle valve 27, so that the forward speed of the turn cylinder 3 can be freely set. Can be set.

Further, the turning cylinder 3 is operated by stopping the hydraulic pump 7 and switching the electromagnetic switching valves 9b, 12 respectively.
At the time of the return movement, that is, when the tailgate is opened, the hydraulic oil is returned from the output side of the electromagnetic switching valve 9b to the tank 10 side via the third variable throttle valve 27. Therefore, unlike the conventional hydraulic unit 4 in which the restrictor valve 15 is in a communication state and is substantially abolished, the returning speed of the turn cylinder 3 can be widened according to the throttle resistance value of the third variable throttle valve 27. Can be set.

A pair of electromagnetic switching valves 8a and 8b, 9a and 9b, which can selectively switch the feeding / discharging direction switching means 8 and 9 between the check state and the communication state in response to an external command, are connected in series with each other. Since it is configured to be connected in the reverse direction, the electromagnetic switching valves 8a, 8b and 9a, 9b can be deactivated to prevent passage of the working fluid.
Further, by switching one of them, the passage of the working fluid toward the other can be permitted, so that the fluid can be blocked and the direction can be surely switched.

[0026]

As described above, the return passages of the working fluid supply / discharge passages in which the respective working fluid supply / discharge passages that connect the first cylinder and the second cylinder to the working fluid source partially share each other. By providing the first variable throttle valve therein, the flow rate of the working fluid discharged from the first cylinder is controlled by the automatic flow rate adjusting valve 1.
Although the load weight is always kept constant regardless of the change of the load weight by 3, the adjustment range can be made variable while keeping this function.

In addition, a part of the working fluid supplied to the second cylinder is recirculated to the side of the working fluid source, and the second part is provided in the bypass passage.
Since the variable throttle valve is provided and the forward speed of the second cylinder is varied by adjusting the flow rate of the working fluid that is recirculated, unlike the conventional hydraulic unit that throttles the discharge fluid with the restrictor valve. The advantages are that the discharge pressure of the working fluid source is not increased and the power consumption is not increased, and the forward speed of the second cylinder can be arbitrarily changed.

Furthermore, a third variable throttle valve is provided in the bypass passage for returning the working fluid discharged from the second cylinder to the working fluid source side, and the flow rate of the working fluid to be returned is adjusted to the second variable throttle valve. Since the returning speed of the cylinder is variable, the returning speed of the second cylinder can also be changed arbitrarily.

[Brief description of drawings]

FIG. 1 is a main part hydraulic circuit diagram showing an embodiment of a vehicle tailgate lifter using a hydraulic unit of the present invention.

FIG. 2 is a diagram showing a relationship between a load amount of the tailgate lifter shown in FIG. 1 and a return flow rate of hydraulic oil.

FIG. 3 is a main part hydraulic circuit diagram showing an example of a vehicle tailgate lifter using a conventional hydraulic unit.

[Explanation of symbols]

 2 lift cylinder 3 turn cylinder 5,6 working fluid supply / discharge path 5a discharge flow path 6a return flow path 7 hydraulic pump 7a motor 8,9 supply / discharge direction switching means 8a, 8b, 9a, 9b, 12 electromagnetic switching valve 11 , 28 Check valve 13 Automatic flow rate control valve 21 Vehicle tailgate 22 Hydraulic unit 22 23 First variable throttle valve 24, 26 Bypass flow path 25 Second variable throttle valve 27 Third variable throttle valve

Claims (5)

[Claims] 1. A first cylinder and a second cylinder are connected in parallel to a working fluid source via respective working fluid supply / discharge passages that partially share a discharge passage and a return passage, and A supply / discharge direction switching means is provided in the working fluid supply / discharge path, and the supply / discharge direction switching means is switched between the working fluid supply direction and the working fluid discharge direction to respectively drive the first and second cylinders in forward and backward directions. In the hydraulic unit, the flow rate of the working fluid provided in the return passage and discharged from the first cylinder is adjusted,
A hydraulic unit comprising a first variable throttle valve for varying the returning speed of the first cylinder. 2. A bypass flow path branched and connected to the working fluid supply / discharge path for the second cylinder, for returning a part of the working fluid supplied to the second cylinder to the working fluid source side, and the bypass flow. 2. A second variable throttle valve which is provided in a passage and which adjusts the flow rate of the recirculated working fluid, thereby varying the forward speed of the second cylinder. Hydraulic unit. 3. A bypass flow path, which is branched and connected to the working fluid supply / discharge path for the second cylinder, and which circulates the working fluid discharged from the second cylinder to the working fluid source side; 3. A third variable throttle valve, which is provided and adjusts the flow rate of the recirculated working fluid, thereby varying the return speed of the second cylinder. hydraulic unit. 4. The hydraulic unit according to claim 1, wherein the variable throttle valve is a needle valve. 5. The supply / discharge direction switching means comprises a pair of electromagnetic switching valves, which are selectively switched between one of a check state and a communication state in response to an external command, connected in series in opposite directions. The hydraulic unit according to any one of claims 1 to 4, which is characterized.