JPH0542561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electro-hydraulic cylinder in which the piston moves linearly over a distance proportional to the angle of rotation of the electric motor, and in particular to an electro-hydraulic cylinder whose piston moves linearly over a distance proportional to the rotation angle of the electric motor. This invention relates to improvements to control valves that control the flow of water.

Conventional technology A type of electric-hydraulic cylinder was developed in the 1980s.
There is one described in Publication No. 79001. this is,
A spool hole parallel to the center line of the piston of the hydraulic cylinder and a plurality of valve ports opening on the inner peripheral surface of the spool hole are formed in the piston of the hydraulic cylinder, and the spool is slidably fitted into the spool hole, and the spool is slidably fitted into the spool hole. A feed screw threaded onto a spool is rotatably but immovably supported in the axial direction by a housing of a hydraulic cylinder, and the feed screw is rotated by an electric motor such as a stepping motor.

When the electric motor rotates the feed screw, the spool is fed, changing the state of communication between the valve ports formed on the piston, causing hydraulic fluid to flow in and out of the hydraulic pressure chambers on both sides of the piston, and moving the piston. . Then, when the communication state of each valve port returns to its original state due to the movement of the piston, the piston stops. In other words, the piston follows the movement of the spool, and the piston moves linearly by a distance proportional to the rotation angle of the electric motor. By controlling the rotation angle of the electric motor, the piston rod can be moved to the desired position. It is possible to precisely expand or contract the length.

Furthermore, since the control valve consisting of the spool and valve port is provided inside the piston, the entire electro-hydraulic cylinder can be constructed compactly.

However, in the electro-hydraulic cylinder described in this publication, the piston rod is provided only on one side of the piston, so when the piston moves, the second hydraulic pressure chamber, that is, the side where the piston rod is not provided, is There is a problem in that the flow of hydraulic fluid into and out of the pressure chamber is large, and the operating speed of the electro-hydraulic cylinder is limited by the size of the control valve that can be configured in the piston. Moreover, the effective pressure-receiving area of the piston when the piston rod is retracted is the cross-sectional area of the piston minus the cross-sectional area of the piston rod, and the effective pressure-receiving area when the piston rod is extended is the cross-sectional area of the piston rod.
In either case, the cross-sectional area of the piston itself does not become the effective pressure-receiving area, so just because the amount of hydraulic fluid in and out of the second hydraulic chamber is large does not mean that the operating force of the hydraulic cylinder becomes large. do not have.

Therefore, the inventors of the present invention considered extending the piston rod to both sides of the piston in the electro-hydraulic cylinder described in the above-mentioned publication. extending the piston rod to both sides of the piston, and
If the hydraulic pressure chambers on both sides of the piston are supplied with hydraulic fluid directly from the hydraulic pressure source, the conditions of the hydraulic pressure chambers on both sides will be the same, and the amount of hydraulic fluid flowing in and out as the piston moves will be reduced. , the restriction on the operating speed of the electro-hydraulic cylinder by the control valve can be relaxed.

However, it has become clear that a new problem arises in this case, in that the consumption of hydraulic fluid is higher than in electro-hydraulic cylinders in which the piston rod extends only on one side of the piston. That is, what we actually considered was the electro-hydraulic cylinder shown in Figure 4, as shown by the two-dot chain line.
From the pump P to the inlet port 2 via each throttle S
6 and 28, the spool 122 is moved to the left in FIG. 4 by the rotation of the stepping motor 70, and the first hydraulic chamber 22 is filled with oil. Passage 64,1
36. When the pump P is communicated with the tank 58 through the tank port 56, it goes without saying that the hydraulic oil in the first hydraulic chamber 22 flows out to the tank 58, but the pump P is connected to the tank 58 through the oil passage. As a result, a portion of the hydraulic oil supplied from the pump P passes through the first hydraulic chamber 22 and flows out into the tank 58. Similarly, when the spool 122 is moved to the right, a portion of the hydraulic oil supplied from the pump P will pass through the second hydraulic chamber 24, and that amount of hydraulic oil will be wasted. It will be done.

Also, by moving the spool 122, the hydraulic chamber 2
2 or 24 is communicated with the tank 58, it is necessary to provide a throttle S in the pump passage in order to lower the oil pressure in the hydraulic chamber on the side communicated with the tank and move the piston 18. However, it has also become clear that there is a problem in that the maximum operating speed of the electro-hydraulic cylinder is kept relatively low because the flow rate of the hydraulic oil is restricted by the throttle S.

Problems to be Solved by the Invention With the above-mentioned circumstances as a background, the present invention provides a piston rod with a piston that extends on both sides, so that the restriction on the operating speed by the control valve and the restriction on the operating speed due to the presence of the throttle is relaxed. This was done in order to provide an electro-hydraulic cylinder that does not waste hydraulic fluid.

Means for Solving the Problems To this end, an electro-hydraulic cylinder according to the present invention comprises (a) a piston having two piston rods extending in opposite directions from both end faces; (c) a cylinder housing that accommodates both piston rods in a state in which they protrude to the outside and forms a first hydraulic pressure chamber and a second hydraulic pressure chamber on both sides of the piston; and (c) a cylinder housing that axially passes through one of the two piston rods. The spiral member includes a spiral member that is supported by the cylinder housing and rotated by an electric motor so as to reach the inside of the piston, and when the spiral member is stopped, the first hydraulic pressure chamber and the second hydraulic pressure chamber are closed. (d) an electric three-way valve that selectively communicates the first hydraulic chamber and the second hydraulic chamber with the low pressure port according to the rotation of the spiral member in both forward and reverse directions; A first port and a second port each communicating with a second hydraulic pressure chamber and a high pressure port connected to a hydraulic pressure source are provided, and the hydraulic pressure in the first hydraulic pressure chamber and the second hydraulic pressure chamber is controlled by a pilot pressure. When the hydraulic pressures in both hydraulic pressure chambers are equal, the first hydraulic pressure chamber and the second hydraulic pressure chamber are communicated with the high pressure port through the respective throttles, and the first hydraulic pressure chamber and the second hydraulic pressure chamber are in a neutral state. When the hydraulic pressure in the hydraulic pressure chamber is high, the first operating state is established, and the first hydraulic pressure chamber is communicated with the high pressure port, while the second hydraulic pressure chamber is shut off, and the hydraulic pressure in the second hydraulic pressure chamber is high. In the second operating state, the valve is configured to include a pilot type three-way valve that connects the second hydraulic pressure chamber to the high pressure port while blocking the first hydraulic pressure chamber.

In one aspect of the present invention, the electric three-way valve includes a spool hole formed inside the piston, a plurality of valve ports opening to the spool hole, and a spool slidably fitted into the spool hole. The spiral member is screwed onto the spool and serves as a feed screw for feeding the spool. In another aspect, the electric three-way valve includes a spool hole formed inside the piston and a plurality of valve ports opening to the spool hole, and the helical member includes a helical land. The spiral spool is fitted into the spool hole and opens and closes the valve port by rotation.

Function and Effect In the electro-hydraulic cylinder configured as described above, while the electric motor is stopped, the electric three-way valve closes both the first hydraulic chamber and the second hydraulic chamber, A pilot operated three-way valve connects both hydraulic chambers to the high pressure port. Therefore,
Hydraulic pressure from a hydraulic pressure source acts on both hydraulic pressure chambers, and the piston remains stationary because the forces are balanced.

If the electric motor is rotated from this state,
An electric three-way valve is installed in one of the hydraulic chambers on both sides of the piston.
For example, the first hydraulic pressure chamber is communicated with the low pressure port. As a result, the hydraulic fluid flows out from the first hydraulic pressure chamber, and the hydraulic fluid is replenished from the hydraulic pressure source into the first hydraulic pressure chamber by that amount. Due to the restriction in the valve, the hydraulic pressure in the first hydraulic pressure chamber decreases. As a result, the balance of forces on the piston is broken, and the piston is moved toward the first hydraulic pressure chamber. Additionally, if the hydraulic pressure in the first hydraulic pressure chamber decreases, the pilot pressure in the pilot type three-way valve will also become imbalanced, so this three-way valve connects the high-pressure second hydraulic chamber to the high-pressure port, reducing the pressure. Switching to a second operating state in which the first low pressure chamber is shut off. Therefore, from now on, the hydraulic fluid from the hydraulic pressure source will flow only into the second hydraulic pressure chamber, and will not flow into the first hydraulic pressure chamber.

Conversely, if the second hydraulic pressure chamber is communicated with the low pressure port, the working fluid from the hydraulic pressure source will flow only into the first hydraulic pressure chamber, and will eventually be communicated with the low pressure port. The hydraulic fluid will no longer pass through the hydraulic pressure chamber on the side that is closed and flow out from the low pressure port.
This avoids unnecessary consumption of hydraulic fluid.

Moreover, since the pilot type three-way valve does not restrict the flow of hydraulic fluid in the first or second operating state, a sufficient flow rate of hydraulic fluid can be supplied to the hydraulic pressure chamber on the high pressure side. Also, since the piston rods are provided on both sides of the piston,
The flow rate of hydraulic fluid passing through the electric three-way valve as the piston moves is small, and the restriction on operating speed due to the size of the electric three-way valve is relaxed, so this electric-hydraulic cylinder can achieve a sufficiently high speed. This means that it can be operated.

In particular, when the spool of an electric three-way valve is a helical spool, the structure of the three-way valve becomes simple, and it becomes easier to increase the maximum allowable flow rate. A unique effect can be obtained in which a decrease in operating accuracy due to wear of the threaded portion can also be avoided.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 1, 10 is a cylinder housing, which consists of a cylinder tube 12, a cover 14, and a cover 16. A piston 18 is slidably fitted into the cylinder housing 10, and piston rods 20 and 21 extending from both end surfaces of the piston 18 are connected to the cover 1, respectively.
4 and 16 in a fluid-tight manner to seal the cylinder housing 1.
It protrudes outside of 0. As a result, a first hydraulic chamber 22 and a second hydraulic chamber 24 are formed in the cylinder housing 10 with the piston 18 in between. The first hydraulic chamber 22 and the second hydraulic chamber 24 are inlet ports 2 formed in the covers 14 and 16, respectively.
6 and 28 are connected to a pilot type three-way valve 30, and a pump 32 as a hydraulic pressure source is connected to this pilot type three-way valve 30.

the piston 18 and piston rod 20,
A bottomed spool hole 40 is formed across the piston rod 21, and the piston rod 21 is inserted into this spool hole 40.
A helical spool 42 is inserted through the side opening. The helical spool 42 has a helical land 44 formed on the outer periphery of a shaft with a circular cross section, and is rotatable by the cylinder housing 10 via a bearing housing 46 and a bearing 48 fixed to the cover 16 and is rotated in the axial direction. is immovably supported. The spool hole 40 communicates with an oil chamber 54 formed within the bearing housing 46, and this oil chamber 54 is connected to a tank 58 at a tank port 56 serving as a low pressure port.

The center portion of the spool hole 40 is formed by a sleeve 59 that is press-fitted into the piston 18 and forms a part thereof, and has a slightly smaller diameter than the other portions, so that the helical spool 42 and the oil are substantially separated from each other in this portion. Closely fitted. As shown in FIG. 2, this sleeve 59 has a first port 60 and a second port 62 as valve ports formed as elongated holes inclined at an angle equal to the lead angle of the land 44 of the helical spool 42. These first port 60 and second port 62 are always closed together, so that when the helical spool 42 is rotated to the left in FIG. 1, the second port 62 remains closed and the first port 60 opens, and vice versa. The position is determined so that the second port 62 opens when it is rotated to the right. Further, the ports 60 and 62 are located at positions separated in the diametrical direction of the helical spool 42 in order to balance the hydraulic pressure acting on the helical spool 42 in these ports 60 and 62 and to ensure the flow rate of the hydraulic oil. The two ports 60 are each communicated with the first hydraulic chamber 22 through an oil passage 64, and the ports 62 are each communicated with the second hydraulic chamber 24 through an oil passage 66. It is being In other words, two ports 60 and 6
2 each fulfill the same function,
In the end, the first port 60, the second port 62, and the opening of the spool hole 40 to the oil chamber 54 are made into three ports, and the mutual communication state of these three ports is switched by the rotation of the helical spool 42. A three-way valve 68 is configured.

A stepping motor 70 is fixed to the bearing housing 46 via a bracket 69, and its output shaft 72 is connected to the helical spool 42 by a shaft coupling 74. That is,
The three-way valve 68 is an electric three-way valve operated by a stepping motor 70.

Next, the pilot type three-way valve 30 will be explained. As shown in FIG. 3, the three-way valve 30 includes a valve housing 78 and a spool 80 slidably fitted into a spool hole of the valve housing 78. Valve housing 78 includes first and second ports 82 and 84 communicating with inlet ports 26 and 28, respectively, and a high pressure port 86 connected to pump 32, with spool 80 shown in FIG. In the neutral position, the high pressure port 86 communicates with the first port 82 and the second port 84 through respective throttles.
The spool 80 is held in a neutral position by a spring 90 and a washer 92 disposed on both sides of the spool 80, with two lands 94 on the spool 80 being connected to the first port 82 and the second port 84.
The land 94 and the high pressure port 86 are substantially cut off, and a notch 96 formed in the land 94 allows slight communication between the land 94 and the high pressure port 86.

The first port 82 and the second port 84 are communicated with pilot pressure chambers 102 and 104 by pilot passages 98 and 100, respectively, and the pilot passages 98 and 100 are provided with throttles 106 and 108, respectively. .

In the electro-hydraulic cylinder configured as described above, while the stepping motor 70 is stopped, the first port 60 and the second port 62
is closed by the land 44, and there is no flow of hydraulic fluid into or out of the first hydraulic chamber 22 or the second hydraulic chamber 24, and when the pilot type three-way valve 30 is in the neutral state, the first hydraulic chamber 22 and the second hydraulic chamber The piston 18 is stopped while the hydraulic pressure from the pump 32 is applied to both the chamber 24 and the chamber 24.

In this state, if an external force is applied to the piston rod 20 in a direction that causes it to contract, the piston 18 will move back slightly, but the first port 60 will open accordingly, and the hydraulic oil will flow from the first hydraulic chamber 22 to the tank 58. The first hydraulic chamber 22 is replenished with the corresponding amount of hydraulic oil from the pump 32, but this hydraulic oil supply path is formed by a notch 96 in the pilot type three-way valve 30. Because of the restriction, the hydraulic pressure in the first hydraulic chamber 22 decreases. As a result, the piston 18 is pushed back and returns to its original position. The same applies when a force in the opposite direction is applied to the piston rod 20.
will be held in place against external forces.

When the stepping motor 70 is rotated to the left, the first port 60 is opened while the second port 62 remains closed. As a result, the first hydraulic chamber 2
2 leaks out and the hydraulic pressure in the first hydraulic chamber 22 decreases due to the throttling action of the notch 96 in the pilot type three-way valve 30. This breaks the balance of force on the piston 18, causing the piston 18 to move toward the first hydraulic chamber. It will be moved to 22. In addition, the first hydraulic chamber 22
When the oil pressure decreases, the parrot pressure in the pilot pressure chamber 102 of the pilot type three-way valve 30 also decreases, the spool 80 is moved, and the high pressure port 86 and the second port 84 are brought into communication with a sufficient flow area. On the other hand, the first port 82 is blocked. Therefore, from now on, the hydraulic oil from the pump 32 flows only into the second hydraulic chamber 24 at a sufficient flow rate, and the hydraulic oil flows into the first hydraulic chamber 2.
2, wasteful consumption of hydraulic oil is avoided and the piston 18 is moved forward at high speed. The piston 18 continues to move forward until the first port 60 is closed, and eventually, when the stepping motor 70 is rotated by a predetermined angle, the piston rod 20 will extend by a length proportional to the rotation angle.

However, since the pilot passage 98 is provided with a throttle 106 and the spool 80 is kept in a neutral position by a spring 90 and a washer 92, if the stepping motor 70 rotates by only a small angle, the pilot The three-way valve 30 remains in the neutral state, and the piston 18 moves a small distance and then stops. In addition,
The diaphragm 106 (the same applies to the diaphragm 108) also functions to prevent the spool 80 from operating too rapidly, thereby preventing chattering.

Conversely, if the stepping motor 70 is rotated to the right, the first port 60 remains closed, the second port 62 is opened, and the second hydraulic chamber 24 is connected to the tank 5.
8. Therefore, the second hydraulic chamber 24
Hydraulic oil flows out from the second hydraulic chamber 24, and the hydraulic pressure in the second hydraulic chamber 24 decreases, and the balance of force on the piston 18 is broken, causing the piston 18 to retreat. This retraction is also carried out in the same manner as the forward movement described above until the second port 62 is closed, and the piston rod 20 is contracted by a length proportional to the rotation angle of the stepping motor 70.

As is clear from the above description, in this embodiment, the piston 18 is moved forward and backward by simply rotating the helical spool 42 within the spool hole 40, and the piston rod 20 is expanded and contracted. spiral spool 42
Since the piston 18 and the piston 18 are not screwed together, the operating accuracy of the piston 18 does not deteriorate due to wear of the feed screw and the nut, unlike in an electro-hydraulic cylinder using a feed screw.

Moreover, in this embodiment, the first port 60
Further, since an oil passage for communicating the second port 62 with the tank port 56 is formed within the piston 18 and the piston rod 21, there is an advantage that the entire piston can be made smaller. That is, the piston 18
An annular groove is formed on the outer peripheral surface of the piston 1, while a tank port is formed on the cylinder tube 12.
The purpose can also be achieved by keeping the tank port in communication with the annular groove regardless of the position of the annular groove. Naturally, the piston needs to be longer than this, and the electro-hydraulic cylinder becomes longer by that length.
In contrast, in this embodiment, the piston 18
Since it is possible to make the length smaller than the working stroke, it is possible to downsize the electro-hydraulic cylinder.

FIG. 4 shows another embodiment of the invention.

This example differs from the previous example in the electric three-way valve, but other parts are the same, so parts that perform the same functions are given the same reference numerals to indicate correspondence, and detailed explanations are omitted. do.

The electric three-way valve 120 of this embodiment has a piston 18
The spool 122 is substantially liquid-tightly and slidably fitted into the spool hole 40 therein. This spool 122 is provided with a nut 124 in which a feed screw 126 is screwed. The nut 124 holds a large number of balls, and is screwed together with the feed screw 126 via the balls, so that the nut 124 and the feed screw 12
6 constitutes a ball screw mechanism. Spool 1
22 rotates through a groove 128 formed on its outer circumferential surface.
This is prevented by engagement with a pin 130 fixed to the piston. The first port 60 and the second port 62 are communicated with an annular groove 132 formed on the outer peripheral surface of the spool 122 by relative movement of the spool 122 with respect to the piston 18.
This annular groove 132 is communicated with the internal space of the spool 122 through a communication hole 134, and this internal space is communicated with the oil chamber 54 through an oil passage 136 formed through the piston rod 21. .

The operation of the electro-hydraulic cylinder of this embodiment is such that the spool 122 is moved relative to the piston 18 by rotating the feed screw 126 by the stepping motor 70, and the spool 122 is moved relative to the piston 18.
The second embodiment is the same as the previous embodiment except that the second port 62 and the second port 62 are alternatively communicated with the tank port 56, so a description thereof will be omitted.

Two embodiments of the present invention have been described above based on the drawings, but these are literally illustrative, and the present invention can be modified and improved in various ways based on the knowledge of those skilled in the art. It can be implemented.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing an electro-hydraulic cylinder according to an embodiment of the present invention, and FIG. 2 is a plan view showing the sleeve thereof taken out. 3 is a front sectional view schematically showing the structure of the pilot type three-way valve in FIG. 1. FIG. FIG. 4 is a front sectional view of an electro-hydraulic cylinder according to another embodiment of the present invention. 10: cylinder housing, 18: piston,
20, 21: Piston rod, 22: First hydraulic chamber, 24: Second hydraulic chamber, 26, 28: Inlet port, 30: Pilot type three-way valve, 42: Spiral spool, 56: Tank port, 59: Sleeve, 6
0: First port, 62: Second port, 68: Three-way valve, 70: Stepping motor, 78: Valve housing, 80: Spool, 82: First port,
84: Second port, 86: High pressure port, 96: Notch, 98, 100: Pilot passage, 120: Three-way valve, 122: Spool, 124: Nut, 12
6: Feed screw.

Claims (1)

[Scope of Claims] 1. A piston having two piston rods extending in opposite directions from both end faces, the piston being housed in a state in which both piston rods protrude to the outside, and a first hydraulic chamber on both sides of the piston. and a cylinder housing forming a second hydraulic pressure chamber, and a helical member supported by the cylinder housing so as to extend through one of the two piston rods in the axial direction and reach the inside of the piston, and rotated by an electric motor. The first hydraulic pressure chamber and the second hydraulic pressure chamber are closed when the spiral member is stopped, but the first hydraulic pressure chamber and the second hydraulic pressure chamber are closed as the spiral member rotates in both forward and reverse directions. an electric three-way valve that selectively communicates with a low-pressure port; and a high-pressure port that is connected to a hydraulic pressure source and a first port and a second port that communicate with the first hydraulic pressure chamber and the second hydraulic pressure chamber, respectively. and receives the hydraulic pressures of the first hydraulic pressure chamber and the second hydraulic pressure chamber in opposite directions as pilot pressure, and when the hydraulic pressures of both hydraulic pressure chambers are equal, the first hydraulic pressure chamber is in a neutral state. The hydraulic pressure chamber and the second hydraulic pressure chamber are connected to the high pressure port through respective throttles, and when the hydraulic pressure in the first hydraulic pressure chamber is high, the first hydraulic pressure chamber is in the first operating state, and the first hydraulic pressure chamber is connected to the high pressure port. On the other hand, the second hydraulic pressure chamber is shut off, and when the hydraulic pressure in the second hydraulic pressure chamber is high, the second hydraulic pressure chamber is in the second operating state, and the second hydraulic pressure chamber is communicated with the high pressure port, while the first hydraulic pressure chamber is in communication with the high pressure port. An electro-hydraulic cylinder characterized in that it includes a pilot type three-way valve that shuts off a pressure chamber. 2. The electric three-way valve includes a spool hole formed inside the piston, a plurality of valve ports opening to the spool hole, and a spool slidably fitted into the spool hole, and the helical member The electro-hydraulic cylinder according to claim 1, which is a feed screw threaded onto the spool. 3. The electric three-way valve includes a spool hole formed inside the piston and a plurality of valve ports opening to the spool hole, and the helical member has a helical land and fits into the spool hole. 2. The electro-hydraulic cylinder of claim 1, wherein the cylinder is a helical spool that opens and closes the valve port by rotation.