JPH10331997A - Electrohydraulic servo valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To move a single rod cylinder different in lateral pressure receiving areas, almost at the same moving speed in both elongating and contracting directions. SOLUTION: A first port A1 can be connected to a head side cylinder chamber or a single rod cylinder, and a second port A2 can be connected to a rod side cylinder chamber. When a main spool 3 is moved in the direction of an arrow mark B, an oil pressure feed port P is communicated with the second port A2 , and the first port A1 is communicated with a second tank port T2 . An outflow port 41 normally communicated with the first port A1 is further communicated with the second tank port T2 . Oil flowing out of the head side cylinder chamber with large pressure receiving area therefore flows to the second tank port T2 via two outflow passages, so that a cylinder rod of the single rod cylinder moves in a contracting direction without delay.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrohydraulic servo valve which changes a hydraulic circuit by adjusting a flow rate of oil flowing through a hydraulic circuit in proportion to an input electric command or by switching an oil passage.

[0002]

2. Description of the Related Art Conventionally, as this type of electro-hydraulic servo valve, the position of a spool is moved by various driving methods to adjust the flow rate of oil flowing through a hydraulic circuit,
FIG. 6 shows an example of a pilot spool-following type servo valve in which a main spool is moved by using a pilot spool.

In this electrohydraulic servo valve, a main spool 3 is slidably fitted in a sliding hole 2e formed in a cylindrical sleeve 2 housed in a valve body 1. The sleeve 2 includes edges 2a to 2d each of which is formed at right angles with respective corners for adjusting the flow rate of the oil flowing in accordance with the relative positions of the plurality of lands 3a to 3c formed on the main spool 3, and oil passages 4. , 5, 6, 7, and 8 respectively. The oil passage 4 is connected to the second tank port T2.
The oil passage 5 is connected to a first port A1 connected to an external actuator such as a cylinder, the oil passage 7 is connected to a second port A2 similarly connected to an external actuator, and the oil passage 6 is connected to a hydraulic supply port. P, the oil passage 8 is connected to the first tank port T1.
Are in communication with each other.

The edge 2a of the sleeve 2 and the left edge of the land 3b of the main spool 3 in FIG.
Further, each edge is formed by the edge 2c and the left edge of the land 3c, further by the edge 2b and the right edge of the land 3b, and further by the edge 2d and the right edge of the land 3c. The flow rate of the oil flowing therethrough is controlled by the area of the opening.

In the main spool 3, sliding holes 11 and 12 are formed in the center in the radial direction along the longitudinal direction at predetermined left and right ends, respectively, with a predetermined depth. The oil passage 6 communicates with the oil passage 6 communicating with the hydraulic pressure supply port P via the oil passage 44, and the baby piston 13 is slidably fitted in the sliding hole 11. The other slide hole 12 communicates with the hydraulic pressure supply port P via an oil passage 15 through an inclined oil passage 14 in the spool, and is formed in the sleeve 2 by an oil passage 16 in the similarly inclined spool. It communicates with the oil passage 8. And the sliding hole 12
A pilot spool 17 is slidably fitted therein.

The pilot spool 17 is fixed to one end of a link wire 19 via a fixing member 18 as clearly shown in FIG. 7, and the other end of the link wire 19 has a torque as shown in FIG. Swing arm 2 of motor 20
1 is attached to the lower end. Therefore, when the torque motor 20 is driven, the swing arm 21 swings in the direction of arrow A in proportion to the input current at that time, and the link wire 19 moves in the left and right direction in FIG. Then, the pilot spool 17 moves in the same direction.

In this servo valve, the main spool 3 is
To move the torque motor 20 to the left, the torque motor 20 is driven so that the swing arm 21 swings clockwise in FIG. Then, since the swing arm 21 swings clockwise in proportion to the input current at that time, the link wire 19 moves to the left in FIG. 6 by an amount corresponding to the swing amount. Accordingly, the movement of the link wire 19 causes the pilot spool 17 to move from the neutral position, which is enlarged in FIG. 7, to the left in FIG. 8 as shown in FIG.

[0008] Then, between the right edge of the land portion 17a of the pilot spool 17 in FIG. 8 and the edge 3d of the control hole 25 formed to penetrate the sliding hole 12 in the radial direction of the main spool 3. Of the main spool 3 is widened with an opening proportional to the amount of movement of the main spool 3, the hydraulic supply port P passes through the opening through the oil passage 14 in the spool, and the control hole 25. The pressure acting on the annular pressure receiving surface e formed on the main spool 3 increases.

Therefore, the increased pressure causes the main spool 3 to move to the left in FIG. 8, and the main spool 3 moves to a position where the center of the land 17a coincides with the center of the control hole 25 as shown in FIG. When moved, the main spool 3 balances and stops at its neutral position. Thus, the main spool 3 becomes the pilot spool 1
7 and stops by the amount corresponding to the amount of movement. Also,
Conversely, when the main spool 3 is moved rightward in FIG. 6, the torque motor 20 is driven in the opposite direction to that described above, and the pilot spool 1 is moved via the link wire 19.
7 is moved rightward in FIG.

In this case, an opening is formed between the left edge of the land portion 17a of the pilot spool 17 in FIG. 9 and the edge 3e of the control hole 25 of the main spool 3 this time. 3, the oil chamber 28 facing the annular pressure receiving surface e
The oil inside flows out of the control hole 25 through the above-mentioned opening, and at once from the oil passage 16 in the spool to the first tank port T1. Accordingly, this time, when the main spool 3 moves rightward in FIG. 9 and moves to a position where the center of the land 17a coincides with the center of the control hole 25, the main spool 3 stops in a balanced manner.

[0011]

However, in such a conventional electro-hydraulic servo valve, when a single rod cylinder is used for the actuator connected thereto, the single rod cylinder has a head-side pressure receiving area and a single rod cylinder. When there is a large difference in the pressure receiving area on the rod side, when the area difference is large, the moving speed when the cylinder rod is moved in the contracting direction is extremely slower than when the cylinder rod is moved in the extending direction. There was a problem that it would be.

That is, as shown in FIG. 10 in which only the main part of the electro-hydraulic servo valve described in FIG. 6 is simplified, for example, a single rod cylinder 30 is attached to this electro-hydraulic servo valve.
As shown, the cylinder chamber 31 on the head side is connected to the first port A1, and the cylinder chamber 32 on the rod side is connected to the second port A2.
When the cylinder rod 33 of the single rod cylinder 30 is extended, the main spool 3 is moved to the left as shown in FIG.

Then, an opening a formed by the edge 2b of the sleeve 2 and the right edge of the land 3b and an opening b formed by the edge 2d and the right edge of the land 3c are respectively formed. Since it is opened, the pressure of the hydraulic pressure supply port P acts on the head side cylinder chamber 31 of the single rod cylinder 30 from the oil passage 5 through the opening a through the first port A1.

Further, since the second port A2 communicates with the first tank port T1 from the oil passage 7 through the opening b,
The oil in the cylinder chamber 32 on the rod side of the single rod cylinder 30 flows out from the second port A2 through the oil passage 7 through the opening b to the first tank port T1 via the oil passage 8.
Therefore, the cylinder rod 3 of the single rod cylinder 30
3 expands smoothly.

On the other hand, when the main spool 3 is moved rightward as shown in FIG. 11 to contract the cylinder rod 33, the edge 2a of the sleeve 2 and the left side And the opening d formed by the edge 2c and the left edge of the land 3c are opened, so that the pressure of the hydraulic pressure supply port P increases from the oil passage 6 to the opening d. From the oil passage 7 through the second port A2 to the cylinder chamber 32 on the rod side of the single rod cylinder 30.

Further, since the first port A1 communicates with the second tank port T2 through the opening c, the oil in the cylinder chamber 31 on the head side of the single rod cylinder 30 is discharged from the first port A1.
From the port A1 through the oil passage 5 and from the opening c through the oil passage 4 to the second tank port T2. However, at this time, the cylinder chamber 31 on the head side of the single rod cylinder 30 and the cylinder chamber 32 on the rod side have a difference in pressure receiving area as described above. Since the contraction occurs later than the moving speed, the moving speed of the single rod cylinder 30 varies depending on the driving direction.

Thus, in the case of a single rod cylinder,
The reason why there is a difference in the moving speed between when the cylinder rod is extended and when it is contracted will be described in detail below. In the case of the conventional electro-hydraulic servo valve described with reference to FIGS. 6 to 11, when a single-rod cylinder having a large difference between the head-side pressure receiving area and the rod-side pressure receiving area is driven thereby, when the servo valve is driven, Due to the differential pressure / flow rate characteristic, the relationship between the cylinder rod moving speed and the flow rate, and the balance of the force, the maximum moving speed when the cylinder rod contracts is slower than the maximum moving speed when the cylinder rod extends.

Ps: Supply pressure to servo valve Pt: Return pressure to tank Qr: Flow rate when pressure loss in servo valve is Pv (rated flow rate) Ah: Pressure receiving area on cylinder head side, Ar: Cylinder rod Side pressure receiving area V ': Moving speed at cylinder extension Ph': Head side pressure at cylinder extension Pr ': Rod side pressure at cylinder extension V ": Moving speed at cylinder contraction Ph": Head at cylinder contraction Side pressure Pr ″ Rod-side pressure when cylinder is contracted k: Ratio of return-side opening area to supply-side servo valve opening area when cylinder is contracted Assuming that, the following equations 1 to 4 hold.

[0019]

(Equation 1)

[0020]

## EQU2 ## Ph'.Ah-Pr'.Ar = F '

[0021]

(Equation 3)

[0022]

## EQU4 ## Ph ".Ah-Pr" .Ar = F "

Equations (1) to (4) are expressed by F '= F "= 0, Pt = 0,
When solving under the condition of k = 1, the moving speed ratio when the one rod cylinder is extended and contracted is as shown in Expression 5.

[0024]

(Equation 5)

Here, if the pressure receiving area on the head side of the single rod cylinder is 3 cm ² , and the pressure receiving area on the rod side is 1 cm ²
Then, the moving speed at the time of contraction of the cylinder rod with respect to the moving speed at the time of extension of the cylinder rod is considerably slow, about 58%.

Although the moving speed when the cylinder rod is extended satisfies a certain required value, in order to satisfy the moving speed when the cylinder rod is contracted, the diameter of the spool is increased and the main spool is moved. The area of the opening formed between the sleeve and the sleeve must be increased. This results in a very large and heavy servo valve. Even if the diameter of the spool is increased in this way and a large servo valve is used, when the closed loop control is performed, system instability occurs due to a large difference in gain between expansion and contraction of the cylinder rod. There was a problem that would.

The present invention has been made in view of the above point, and even when a single rod cylinder having a large difference between the pressure receiving area on the head side and the pressure receiving area on the rod side is used as the actuator to be driven, the extension of the cylinder rod is achieved. It is an object of the present invention to realize an electrohydraulic servo valve that can be driven at substantially the same moving speed in the direction and the contraction direction without increasing the size.

[0028]

According to the present invention, in order to achieve the above object, a main spool is slidably fitted in a slide hole formed in a sleeve housed in a valve body,
A hydraulic pressure supply port for communicating with the pressure source and a port for communicating with an external actuator. The main spool communicates with the hydraulic pressure supply port when the main spool moves from the neutral position to the first direction with respect to the sleeve. A first port, a second port connected to a hydraulic supply port after the main spool moves in a second direction opposite to the first direction and exceeds the neutral position, and a main spool. A first tank port that is moved in the first direction to exceed the neutral position and then communicates with the second port; and a main spool that moves in the second direction and crosses the neutral position. A second tank port that communicates with the first port, and a second tank port that always communicates with the first port and moves the main spool in the second direction to exceed the neutral position. It is obtained by the electro-hydraulic servo valve provided with outlet port communicating with.

With this arrangement, when a single rod cylinder (actuator) having a large difference between the head-side pressure receiving area and the rod-side pressure receiving area is driven by the electrohydraulic servo valve, the first port is connected to the one-sided cylinder. The second port may be connected to the cylinder chamber on the head side of the rod cylinder such that the second port communicates with the cylinder chamber on the rod side.

Then, when the main spool is moved in the first direction, the hydraulic supply port is connected to the first port and the second port is connected to the first tank port. The first port communicates with the cylinder chamber on the head side of the single rod cylinder as the actuator, and the second port communicates with the cylinder chamber on the rod side of the single rod cylinder. While the pressure oil flows into the cylinder chamber on the head side, the oil in the cylinder chamber on the rod side flows out to the first tank port through the second port, and the rod of the single rod cylinder extends.

Conversely, when the main spool is moved in the second direction, the hydraulic supply port communicates with the second port, and the first port communicates with the second tank port. The outflow port that is always in communication with the first port also communicates with the second tank port. Therefore,
Oil flowing out of the cylinder chamber on the head side having a pressure receiving area larger than the pressure receiving area of the cylinder chamber on the rod side flows through the first port to the second tank port and the second port through the outflow port. Since the liquid quickly flows out through two paths, that is, the path flowing to the tank port, the cylinder rod of the single rod cylinder moves in the contracting direction at a moving speed substantially equal to the moving speed when the cylinder rod is extended.

This electro-hydraulic servo valve is formed between a main spool and a sleeve to open and close.
When open, the amount of polymerization of each of the two openings communicating with the first port and the second tank port is twice or more the amount of polymerization of one of the openings with respect to the amount of polymerization of the other opening. It is good to Then the main spool will be
, The timing at which the first port communicates with the second tank port and the timing at which the outflow port constantly communicating with the first port communicates with the second tank port are simultaneously performed. Since one of them is delayed without being carried out by an amount corresponding to the difference in the amount of polymerization, the influence of the flow force (fluid force) can be reduced.

In addition, since there is a gap in the radial direction between the sleeve and the main spool to allow sliding, a small amount of leakage (leak) which is not expected from the gap can be obtained from the “hydraulic supply port → first port”, “Hydraulic supply port → second port”, “first port → second tank port”, “second port”
Port → the first tank port ”, but by providing the outflow port, in addition to the leakage to the“ first port → the second tank port ”, the“ first port → the outflow port → the first port ” Since the leakage to the “2 tank port” also occurs, if the amount of polymerization of the two openings is equal, the amount of leakage doubles, and the energy loss increases. In order to prevent such a situation, by increasing the amount of polymerization of one of the openings to at least twice the amount of polymerization of the other opening, it is possible to prevent an increase in leakage and reduce energy loss. Further, in any one of the above electrohydraulic servo valves, the main spool is moved by a hydraulic feedback mechanism in which a pilot spool moves in a sliding direction of the main spool via a link wire attached to a swing part of a torque motor. It is preferable to move following the movement direction. In this way, the size of the electrohydraulic servo valve can be made relatively small.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing an electro-hydraulic servo valve according to the present invention, and portions corresponding to FIG. 6 are denoted by the same reference numerals, and redundant description is omitted. This electro-hydraulic servo valve is greatly different from the electro-hydraulic servo valve described in FIG. 6 in that an outflow port 41 is provided.

The outflow port 41 is always in communication with the first port A1 through an oil passage 43, and the main spool 3 is connected to the first port A1 as shown in FIG.
Then, after moving in the second direction indicated by arrow B and exceeding the neutral position shown in the figure, it communicates with the second tank port T2. Also in this electrohydraulic servo valve, each port communicates with an external actuator, and when the main spool 3 moves from the neutral position with respect to the sleeve 2 in the first direction opposite to the arrow B, the hydraulic pressure increases. A first port A1 communicating with the supply port P, and a second port A2 communicating with the hydraulic supply port P after the main spool 3 moves in the second direction indicated by arrow B and exceeds the neutral position.
This is similar to the electrohydraulic servo valve described with reference to FIG.

In this electrohydraulic servo valve, the first tank port T1 communicates with the second port A2 after the main spool 3 moves in the direction opposite to the arrow B and exceeds the neutral position.
6 and the second tank port T2 which is communicated with the first port A1 after the main spool 3 moves in the direction of arrow B and exceeds the neutral position. Is the same as When connecting a single rod cylinder 30 having a large difference between left and right pressure receiving areas as shown in a hydraulic circuit diagram in FIG. 2, this electrohydraulic servo valve connects a head side cylinder chamber 31 to a first port as shown in the figure. A1 connects the cylinder chamber 32 on the rod side to the second port A2.

When the main spool 3 is at the neutral position as shown in FIG. 1, hydraulic pressure is supplied to an oil chamber formed on the right end of the baby piston 13 in the sliding hole 11 of the main spool 3. The pressure at the port P is led through the oil passages 6 and 44. Because the baby piston 13 is pressed against the right end face of the neutral position adjusting screw 26 by the pressure, the pressure from the hydraulic pressure supply port P acts statically as a force for pushing the main spool 3 rightward in FIG. ing.

On the right side of the main spool 3 in FIG. 1, the main spool 3 is formed by the main spool 3, the sleeve 2, and the collar 27 fitted in the sliding hole 2e. The pilot spool 17 and the main spool 3 are located in the oil chamber 28 facing the
The pressure of 油 圧 of the hydraulic pressure supply port P is guided by the three-way valve composed of

Then, the pressure receiving area Ab of the annular pressure receiving surface e (FIG. 3) of the main spool 3 is represented by Ab = Ab = Ab = Ab of the right end surface 11a of the sliding hole 11 of the main spool 3.
2Aa. Therefore, assuming that the pressure of the hydraulic pressure supply port P is Pp, Pp · Aa = (１ ／) Pp · 2Aa
In this state, the balance of the main spool 3 is maintained, and the main spool 3 is held at the illustrated neutral position.

By the way, as shown in FIG. 3, the hole width Dw of the control hole 25 formed in the main spool 3 is set to be an underlap slightly larger than the land width W of the land portion 17a of the pilot spool 17. It is. Thus, when the center of the control hole 25 and the center of the land width W coincide with each other, the opening area of the opening 22 from the hydraulic pressure supply port P to the oil chamber 28 and the oil chamber 28 Since the opening area of the opening 23 reaching the first tank port T1 through the oil passage 16 becomes equal,
If there is no change in the volume of the oil chamber 28 and there is no leakage,
The pressure of 8 becomes 1/2 of the pressure Pp of the hydraulic pressure supply port P.

When the pilot spool 17 is moving to the left with respect to the main spool 3 as shown in FIG. 4, the opening 22 on the side communicating with the oil chamber 28 from the hydraulic pressure supply port P becomes large. On the contrary, since the opening 23 on the side from the oil chamber 28 to the first tank port T1 is closed, the pressure in the oil chamber 28 becomes higher than 1/2 of the pressure Pp of the hydraulic pressure supply port P.

Accordingly, a force for moving the main spool 3 to the left in FIG. 4 acts, whereby the main spool 3 moves to the left. When the center of the control hole 25 coincides with the center of the land width W, the balance is rebalanced. Then, the main spool 3 stops. This electro-hydraulic servo valve moves the pilot spool 17 by driving the torque motor 20 of FIG. 1 as described above, and thereby moves the main spool 3 in proportion to the input current. 6 as described above.

When connecting the single rod cylinder 30 having a large difference between the left and right pressure receiving areas as shown in FIG. 2, the electrohydraulic servo valve connects the head side cylinder chamber 31 to the first port as shown in FIG. A1 connects the cylinder chamber 32 on the rod side to the second port A2. When the cylinder rod 33 of the one-rod cylinder 30 is moved to the side for contracting, the torque motor 20 of FIG. 1 is driven to move the pilot spool 17 rightward in FIG. Move to the right as shown in 5.

Then, an opening formed by the edge 2c of the sleeve 2 and the left edge of the land 3c opens, so that the pressure of the hydraulic pressure supply port P flows from the oil passage 6 through the opening to the oil passage 7 And acts on the rod-side cylinder chamber 32 of the single rod cylinder 30 through the second port A2. An opening formed by the edge 2a of the sleeve 2 and the left edge of the land 3b, an edge 2f and the land 3
The opening formed by the left edge of a is also opened.

Therefore, oil in the cylinder chamber 31 on the head side of the single rod cylinder 30 flows from the first port A1 through the oil passage 5 to the second tank from the opening between the edge 2a and the land 3b. Outflow to port T2. The oil in the cylinder chamber 31 on the head side is discharged to the first port A1.
Through the oil passages 5 and 43 from the edge 2f and the land 3a
Flows out to the second tank port T2.

Therefore, the edge 2a and the land 3b
And the opening area of the opening formed by
If the opening area of the opening formed by the head and the land 3a is the same size, the opening area of the return line from the cylinder chamber 31 on the head side to the second tank port T2 is doubled (FIG. 6). Through FIG. 11).

Therefore, as compared with the case where the return line is only on the side of the opening formed by the edge 2a and the land 3b, the flow rate can be doubled at the same differential pressure. The moving speed when the cylinder rod 33 is moved to the contracting side can be increased. The edge 2a and the land 3
b and an opening formed by the edge 2f and the land 3a, the amount of polymerization of each of the two openings, the amount of polymerization of one of the openings, and the amount of polymerization of the other opening The amount is preferably at least twice the amount of polymerization.

Then, when the main spool 3 is moved in the direction indicated by the arrow B (second direction) in FIG. 5, the timing at which the first port A1 communicates with the second tank port T2, The timing at which the outflow port 41, which is always in communication with the first port A1, and the second tank port T2 is not performed at the same time, and one of them is delayed by an amount corresponding to the difference in the amount of polymerization. Energy loss can be reduced by reducing the effect of the force.

In FIG. 5, the single rod cylinder 30
When the cylinder rod 33 is extended, the main spool 3 is moved in the same direction by moving the pilot spool 17 leftward in FIG. 1 by the torque motor 20 shown in FIG. 9 to FIG. 9, the description is omitted. As described above, this electrohydraulic servo valve has an outlet port 41 connected to the cylinder chamber 31 on the head side of the single rod cylinder 30 inside the servo valve without increasing the rated flow rate (Qr) as the servo valve. By providing another one in addition to the first port A1, the problem of the conventional electrohydraulic servo valve described with reference to FIGS. 6 to 11 is solved.

Further, merely adding one port deteriorates the pressure gain characteristic which is important as a servo valve. Therefore, in order to make the pressure gain characteristic equal to that of a conventional servo valve, the edge of the sleeve 2 is made as described above. There is a difference in the amount of polymerization between the opening formed by the land 2b and the land 3b of the main spool 3 and the amount of polymerization of the two openings formed by the edge 2f and the land 3a.

When the outflow port 41 is added, the moving speed ratio of the single rod cylinder at the time of extension and contraction is expressed by the following equation
From the following equation (6), assuming that the pressure receiving area on the head side is 3 cm ² and the pressure receiving area on the rod side is 1 cm ^{2 as} in the single-rod cylinder shown above, the cylinder rod has an The moving speed at the time of contraction is about 110%, which is substantially equal at the time of extension and contraction.

[0052]

(Equation 6)

[0053]

As described above, according to the present invention, even when a single rod cylinder having a large difference between the pressure receiving area on the head side and the pressure receiving area on the rod side is used as the actuator to be driven, the extension direction of the cylinder rod can be improved. An electrohydraulic servo valve that can be driven at substantially the same moving speed in the contraction direction and the contraction direction can be realized without increasing the size.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an electrohydraulic servo valve according to the present invention.

FIG. 2 is a hydraulic circuit diagram showing a state where a single rod cylinder is connected to the electrohydraulic servo valve.

FIG. 3 is a schematic diagram showing a state in which a control hole formed in a main spool of the electrohydraulic servo valve and a land portion of a pilot spool are underlapped.

FIG. 4 is a schematic diagram similar to FIG. 3, showing a state where the pilot spool is shifted with respect to a control hole of a main spool.

FIG. 5 is a schematic view showing a state in which a pilot spool of the electrohydraulic servo valve of FIG. 1 is moved to a side where a cylinder rod contracts, in which only main parts are simplified.

FIG. 6 is a configuration diagram showing an example of a conventional pilot spool follow-up type electro-hydraulic servo valve.

FIG. 7 is a schematic view partially showing a state where a pilot spool of the electrohydraulic servo valve of FIG. 6 is in a neutral position.

FIG. 8 is a schematic diagram partially showing a state where the pilot spool is moved to one side from the position of FIG. 7;

9 is a schematic diagram partially showing a state in which the main spool follows the pilot spool from the position of FIG. 8 and returns to the neutral position again.

FIG. 10 is a schematic diagram showing a state in which a cylinder rod of a single rod cylinder is extended by the electrohydraulic servo valve of FIG. 6;

FIG. 11 is a schematic view showing a state in which the cylinder rod of the single rod cylinder is contracted by the electrohydraulic servo valve.

[Explanation of symbols]

1: Valve body 2: Sleeve 2e: Sliding hole 3: Main spool 17: Pilot spool 19: Link wire 20: Torque motor 21: Swing arm (Swing unit) 30: Single rod cylinder (Actuator) 41: Outlet port A1: first port A2: second port T1: first tank port T2: second tank port P: hydraulic supply port

Claims (3)

[Claims] A main spool is slidably fitted in a sliding hole formed in a sleeve housed in a valve body, and a hydraulic supply port communicating with a pressure source and an external actuator communicate with the sleeve. A first port communicating with the hydraulic pressure supply port when the main spool moves in a first direction from a neutral position with respect to the sleeve, and a first port connected to the first spool. A second port that moves in a second direction opposite to the first direction and communicates with the hydraulic pressure supply port after exceeding the neutral position; and the main spool moves in the first direction to move the neutral position to the neutral position. A first port that is communicated with the second port
A second port that is communicated with the first port after the main spool moves in the second direction and exceeds the neutral position.
And an outflow port that communicates with the second tank port after the main spool moves in the second direction and exceeds the neutral position, always communicating with the first port. An electro-hydraulic servo valve characterized by the following. 2. An opening and closing operation is performed by being formed between the main spool and the sleeve. When the main spool and the sleeve are opened, the amount of polymerization of each of the two openings communicating with the first port and the second tank port is determined by: 2. The electrohydraulic servo valve according to claim 1, wherein the amount of polymerization of one of the openings is at least twice the amount of polymerization of the other opening. 3. The electro-hydraulic servo valve according to claim 1, wherein the main spool moves a pilot spool in a sliding direction of the main spool via a link wire attached to a swing portion of a torque motor. An electrohydraulic servo valve that moves following the sliding direction by a hydraulic feedback mechanism.