JPH023024Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of a hydraulically operated switching valve, and more specifically, it is possible to switch between 3 positions with one pilot line, and even when the pilot pressure is zero, the spool position with all ports closed can be changed. This invention relates to a hydraulically operated switching valve that can hold

Conventionally, a hydraulically operated 3-position switching valve in which 3-position switching is operated by a single pilot line generally has the configuration shown in FIGS. 1 and 2. The former model shown in FIG. Strong spring 21
and a weak spring 22 are provided, and the spool 2
When the pilot pressure (PP) applied to the other side of 0 is zero, the weak spring 22 pushes the spool 20 to the left end position as shown in the figure, and connects the cylinder port A and pressure port P, and the cylinder port B and tank port T. When the pilot pressure is low, all ports are held in the neutral position with the strong spring 21 closed against the low oil pressure _P2 , and when the pilot pressure is high, the high oil pressure _P1
The spool 20 is moved to the right end position, and the cylinder port A and the tank port T are communicated with each other, and the cylinder port B and the pressure port P are communicated with each other. However, when all ports are closed, this switching valve always maintains pilot pressure (PP) in order to keep the switching valve spool in the neutral position even though the main pressure line from the pump is under no load. Must be set to _P2 . For this reason, part of the main pressure line cannot be used for the pilot line, and a pump dedicated to the pilot line must be used.
Not only do they require a motor unit and hydraulic power source, but they also have the disadvantage of consuming power for a long time to maintain the neutral position, and there is also the risk of oil temperature rising. In addition, with this switching valve, in an emergency such as when a pilot line malfunctions, the actuator (cylinder)
When it is necessary to operate the hand pump (HP), the pilot pressure (PP) is zero, so the spool 20 is pushed to the left end position as shown in the figure, and the cylinder port B and tank port Since the pipe T is in communication with the cylinder port B, the pipe C connecting the cylinder port B and the cylinder S
Simply connect a hand pump (HP) in the middle of the
Even if this is activated, the pressure cannot be increased. Therefore, a stop valve (S) is installed between the hand pump (HP) connection port of pipe C and cylinder port B.
It is necessary to insert the valve (V), block it, and then operate the hand pump (HP) to raise the pressure. This increases the number of valves, etc., and increases the number of man-hours.

The latter one shown in FIG. 2 branches one pilot line 23 and connects one branch pilot line 24.
is connected to a hydraulically operated switching valve 28 that switches at a predetermined high pressure via a flow rate regulating valve 26 with a check valve, and the other branch pilot line 25 is connected to a predetermined level via a flow rate regulating valve 27 with a check valve. This is connected to the hydraulic operation switching valve 29 that switches at low pressure.When the pilot pressure is zero, the spring maintains the neutral position of all ports closed as shown in the figure, and when the pilot pressure is low, the hydraulic operation is activated. Only the switching valve 29 switches and the cylinder port A
and pressure port P, cylinder port B, and tank port T are in communication with each other, and when the pilot pressure is high, both hydraulically operated switching valves 28 and 29 are switched, and cylinder port A and tank port T are connected.
Also, the cylinder port B and the pressure port P are communicated with each other. Note that the flow rate adjustment valve 27 with a check valve is not hydraulically operated because if the hydraulically operated switching valves 28 and 29 are switched at the same time when the pilot pressure is high, the hydraulically switched to the cylinder ports A and B will not go smoothly. Switching valve 29
Reduce the pilot flow rate to delay the switching time,
First, the hydraulically operated switching valve 28 is switched first, and then the hydraulically operated switching valve 29 is switched. In addition, when the pilot pressure becomes zero due to an accident or the like, the flow rate adjustment valve 26 with a check valve throttles the return oil flow rate from the hydraulically operated switching valve 28 and delays the return time of the hydraulically operated switching valve 28, thereby reducing the hydraulic pressure. The hydraulically operated switching valve 28 is provided so that the operating switching valve 29 returns to the neutral position first and then the hydraulic operating switching valve 28 returns to the neutral position. This is because if the hydraulically operated switching valve 28 returns to the neutral position before the hydraulically operated switching valve 29, the cylinder ports A and B will have opposite pressures, and this is to be prevented.

However, switching valves with this type of structure require one set each of a hydraulically operated switching valve and a flow control valve with a check valve, so the device itself becomes a mold, which increases manufacturing costs and increases the risk of failure. In addition, there are disadvantages such as the need to adjust the switching speeds of the two switching valves.

The purpose of the present invention is to improve the shortcomings of conventional switching valves of this type, in that only one main spool is required, and there is no need for a flow rate adjustment valve or the like in the pilot line.
To provide a hydraulically operated valve that is simple in structure, inexpensive, and reliable in operation, which maintains a neutral position, that is, all ports are closed, when pilot pressure is zero.

This invention consists of a main spool that switches its spool position by hydraulic pilot pressure applied to pistons with different cross-sectional areas, and a main spool that supplies pilot pressure only to the piston side with a small cross-sectional area when the pilot pressure is low, and when the pressure becomes high, it switches the spool position between the pistons. A hydraulically actuated switching system that combines a pilot spool that supplies pilot pressure to the piston so that it can be operated with a single pilot line and maintains the spool position with all ports closed even when the pilot pressure is zero. It is a valve.

Hereinafter, the structure and operation of the hydraulically operated switching valve of the present invention will be explained in detail based on an embodiment of the present invention shown in FIG.

1 is a valve body, 2 is a main spool slidably inserted into the valve hole in the center of the valve body 1, 3 and 4 are end covers attached to both sides of the valve body 1, and 5
6 is a large diameter piston (with a large cross-sectional area) housed in the hole in the end cover 3, 6 is a small diameter piston (with a small cross-sectional area) housed in the hole in the end cover 4, and 7 and 8 are main spools. 2 a spring inserted between both ends and each piston 5, 6; 9 a pilot valve body stacked on the valve body 1; 10 a pilot valve body stacked on the valve body 1;
1 is a pilot spool slidably inserted into a valve hole provided in the pilot valve body 9; 11 is a spring receiver; 12 is an adjustment screw; 13 is a spring;
4 is a pilot passage communicating between the left end oil chamber 19 of the pilot spool 10 and the back surface of the small diameter piston 6;
15 is a pilot passage that communicates the valve hole groove near the right end of the land portion of the pilot spool 10 with the back surface of the large diameter piston 5; 16 is a pilot passage that communicates the valve hole groove near the right end of the small diameter portion of the pilot spool 10 with the tank port T of the valve body 1; 17 and 18 are oil chambers,
P is pressure port, ((PP) is pilot port,
A and B are cylinder ports, and T is a tank port.

Now, when low pilot pressure is supplied from the pilot port (PP), it flows into the left oil chamber 19 of the pilot spool 10 through an oil passage (not shown).
An attempt is made to move the pilot spool 10 to the right, but it is pushed back by the reaction force of the spring 13 and moves only slightly. On the other hand, the pilot pressure flowing into the oil chamber 19 is supplied to the back of the small diameter piston 6 through the pilot passage 14, moves the main spool 2 to the right against the spring 8, and connects the pressure port P, cylinder port A, and cylinder port B. and tank port T, respectively. Next, when high pilot pressure is supplied, the pressure in the oil chamber 19 overcomes the reaction force of the spring 13 and moves the pilot spool 10 to the right. As a result, pilot pressure flows from the through hole of the pilot spool 10 through the valve hole groove into the pilot passage 15 and is supplied to the back surface of the large diameter piston 5. Of course, pilot pressure is also supplied to the back of the small diameter piston 6, but since the cross-sectional area of the large diameter piston 5 is approximately twice that of the small diameter piston 6, the main spool 2 is switched to the left, and the pressure port P and Cylinder port B
Also, the cylinder port A and the tank port T are communicated with each other.

If the pilot pressure is zero, springs 7 and 8
Main spool 2 is in neutral position (position shown)
Therefore, the pressure port P, tank port T, and cylinder ports A and B all maintain a closed state in which communication between them is cut off.

Based on the structure and operation explained above, the present invention has the following features:
With one pilot line and two pistons of small diameter and large diameter installed at both ends of the main spool, it is possible to switch the main spool to three positions with one hydraulically operated switching valve, instead of the conventional two hydraulics. There is no need for two flow rate adjustment valves with check valves to adjust the switching speed, which were required for each branch pilot line of the two switching valves as in the case of using actuated switching valves.
The valve is compact and inexpensive, and in an emergency when pilot pressure cannot be used, all ports are closed, so the pressure can be increased using a hand pump without the need for a stop valve, etc., and has excellent practical effects. .

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a conventional three-position hydraulically operated switching valve, and FIG. 3 is a sectional view showing an embodiment of the hydraulically operated switching valve of the present invention. Below is an explanation of the symbols in the drawings. 1... Valve body, 2... Main spool, 3, 4
...End cover, 5...Large diameter piston, 6...
Small diameter piston, 7, 8... Spring, 9... Pilot valve body, 10... Pilot spool, 1
1...Spring receiver, 12...Adjustment screw, 13
... Spring, 14, 15 ... Pilot passage, 16 ... Return passage, 17, 18, 19 ... Oil chamber, 20 ... Spool, 21 ... Strong spring, 22 ... Weak spring, 23 ... Pilot line , 24, 25... Branch pilot line, 26, 27... Flow rate adjustment valve with check valve, 28,
29...Hydraulic switching valve, P...Pressure port, PP...
...Pilot port, T...Tank port, A,
B...Cylinder port.

Claims (1)

[Scope of utility model registration request] The main spout 2 accommodated in the central valve hole of the valve body 1, the large diameter portions at both ends of the valve hole, and the end covers 3 and 4 that close both ends of the valve body have a cross-sectional area coaxially with the valve hole. Pistons 5, 6 and springs 7, 8 corresponding to the inner diameters of the oil chambers are accommodated in oil chambers 17, 18, which have different diameters, respectively, and both the pistons 5,
A switching valve that switches the main spool 2 to three positions via springs 7 and 8 in response to pilot pressure applied to the pilot valve 6, and a valve hole in the center of the pilot valve body 9 stacked above the valve body, one end of which is connected to the pressure receiving surface and the other end of which is connected to the valve hole. Pilot spool 10 with an internal through hole communicating with the valve hole
and a pilot valve in which a spring receiver 11 and a spring 13 are inserted in contact with the rear part of the pilot spool, and the back surface of the small diameter piston 6 of the main spool 2 and the pilot spool 10 are combined.
The pilot passage 14 communicates with the oil chamber 19 of the main spool 2 and the sliding valve hole of the pilot spool 10 with another pilot passage 15.
By connecting the tank port T and the rear end of the sliding valve hole of the pilot spool 10 through the return passage 16, when the pilot pressure applied to the oil chamber 19 of the pilot spool 10 is below a predetermined pressure, the spring 13 is released. The movement of the pilot spool 10 is suppressed by pressure, and the pilot pressure in the oil chamber 19 is supplied from the pilot passage 14 only to the small diameter piston 6 side of the main spool 2.
to one side, and the pilot spool oil pressure 19
When the pilot pressure applied to the oil chamber exceeds a predetermined pressure, the pilot spool 10 moves backward in the valve hole against the reaction force of the spring 13, and the oil chamber 1
9 is supplied from the pilot passage 14 to the small diameter piston 6 side of the main spool 2, and the pilot pressure is supplied to the pilot passage 15 through the through hole of the pilot spool 10.
The main spool 2 is also supplied to the large diameter piston 5 side of the main spool 2, and the main spool 2 is switched to the other side due to the pressure difference due to the difference in cross-sectional area of both pistons 5 and 6, and the pilot pressure applied to the oil chamber 19 of the pilot spool 10 is A hydraulically actuated switching valve characterized in that, when the power is zero, the main spool 2 is held in a neutral position with all ports closed by springs 7 and 8 on its left and right sides.