JPH10176701A - Direct acting servo valve - Google Patents

Abstract

(57) [Problem] To make it possible to realize contradictory problems required for a direct-acting servo valve of a force motor drive system, that is, to provide damping and improve response by simple and inexpensive means. A coil bobbin (18) fixed to one end of a spool (4) sliding in a sleeve (6) in the axial direction and wound with a coil (20), a magnet (12), a yoke (14) and a pole (10) traversing the coil (20) to form a magnetic path. The coil bobbin 18 has a winding portion of the coil 20 and a protrusion adjacent to the winding portion and protruding from the outer peripheral surface of the winding portion, and has an axial slit opened in the winding portion. No. 30 was formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a servo valve,
In particular, the present invention relates to a direct-acting servo valve of a type in which a spool is directly driven by a force motor.

[0002]

2. Description of the Related Art In a conventional direct acting servo valve, a coil bobbin fixedly mounted at one end of a spool which slides in a sleeve in an axial direction and wound with a coil, and biasing the coil bobbin toward the other end. A cylindrical elastic body, and a magnet that forms a magnetic path across the coil, a yoke and a pole,
The spool is slid in the axial direction against the urging force of the cylindrical elastic body by the electromagnetic force generated by applying a current to the coil. 2. Description of the Related Art Conventionally, in various hydraulic control systems, a direct-acting servo valve has been used as a control valve in order to control an actuator to be controlled at high speed and with high accuracy. Direct-acting servo valves use a force motor formed of a magnetic circuit and a coil bobbin wound with a coil to directly drive the spool valve, so that the direction of the working fluid output from the spool valve is proportional to the input current. , Pressure and flow rate.

[0003] Means for applying a biasing force to the coil bobbin are roughly classified into two types: mechanical and electrical. For example, as a mechanical system, there is a system using a viscoelastic member (elastic rubber) on one end face of a spool (Japanese Patent Laid-Open No. 555-1).
0198). Further, there is a method of positioning the spool by disposing coil springs having a circular cross section at both ends of the spool (see JP-A-49-133780).

Further, there is a configuration in which a groove is formed in a bobbin, for example, in which a split groove is formed and a non-conductive material is buried in the split groove (see Japanese Patent Application Laid-Open No. 62-23356).

[0005]

A conventional direct acting servo valve using an elastic rubber as a means for applying a biasing force to a coil bobbin utilizes a damping effect by internal hysteresis of the rubber itself. However, the elastic rubber is extremely deteriorated and has a short life. In addition, the elastic rubber swells due to the intrusion of the hydraulic oil. For this reason, there has been a problem that it is difficult to always maintain uniform properties and the product yield is extremely poor. On the other hand, in the case of using a coil spring, when the coil spring is compressed, the line of action of the combined load generally comes to a place slightly deviated from the center axis of the coil spring. Due to the eccentricity of the load, uneven axial forces are generated at both ends of the spool. Since the resultant force of the non-uniform force acts obliquely to the axis of the spool, the spool is pressed radially by the coil spring and pressed against the inner surface of the sleeve.
As a result, the frictional force between the spool and the sleeve is increased,
There has been a problem that the responsiveness of the spool to operation signals deteriorates.

Further, even if a slit is formed in the coil bobbin of the conductive material to change the drag against the displacement of the spool, there is a problem that the drag based on the eddy current cannot be used depending on the shape of the slit.

An object of the present invention is to provide a direct-acting servo valve having high response, high accuracy, and high reliability by changing the resistance to displacement of a spool.

[0008]

In order to achieve the above object, a direct acting servo valve according to the present invention is fixedly mounted on one end of a spool which slides in a sleeve in an axial direction and is wound with a coil. A direct acting servo valve comprising a coil bobbin, a magnet that forms a magnetic path across the coil, a yoke, and a pole, and slides a spool in an axial direction by an electromagnetic force generated by flowing a current through the coil. The coil bobbin has a winding portion for winding a coil, and a protruding portion adjacent to the winding portion and protruding from the outer peripheral surface of the winding portion, and forming an axial slit opened in the winding portion. And

An axial slit opened in the winding portion may be formed, and the slit may be extended to an intermediate portion of the protruding portion.

An axial slit opened in the winding portion is formed, one adjacent slit is formed between the other end of the winding portion and an intermediate portion of the winding portion, and the other slit is formed. A configuration may be formed between one end of the winding part and the middle part of the winding part, and the ends of the slits overlap each other at the middle part of the winding part.

Further, in the rolling mill, a reduction jack, a hydraulic pump for supplying hydraulic oil to the reduction jack, a tank for returning hydraulic oil supplied to the reduction jack, and supply and discharge of hydraulic oil to and from the reduction jack are provided. A controllable servo valve body, and a coil bobbin in which the servo valve body is fixed to one end of a spool that slides in a sleeve in an axial direction and is wound with a coil. And a magnet that forms a magnetic path across the coil, a yoke, and a pole, and is formed by a direct-acting servo valve that slides the spool in the axial direction by an electromagnetic force generated by applying a current to the coil, The coil bobbin has a winding portion for winding a coil, and a protruding portion adjacent to the winding portion and protruding from the outer peripheral surface of the winding portion, and has an axial slit opened in the winding portion. And it formed.

An axial slit opened in the winding portion may be formed, and the slit may be extended to an intermediate portion of the protruding portion.

According to the present invention, when an electromagnetic force generated in the axial direction by the Fleming's left-hand rule moves the coil bobbin, an eddy current is generated in a direction that impedes the movement. However, by providing a partial slit opened in the winding portion of the coil bobbin, the flow path length of the eddy current flowing through the coil bobbin changes. As a result, the inductance (L) and resistance (R) of the coil bobbin change, and the drag (damping force) due to the eddy current also changes. As a result, the time constant determined from L and R of the coil bobbin changes. That is,
By providing a partial slit in the winding part of the coil bobbin, the drag based on the eddy current is changed, and the frequency characteristic of the valve (spool) is changed. In other words, the responsiveness of the valve can be improved by appropriately setting the shape and size of the partial slit.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing the structure of a three-way valve type direct acting servo valve, and FIG. 2 is an enlarged partial sectional view showing the vicinity of a coil bobbin of the direct acting servo valve. As shown in FIGS. 1 and 2, the coil 2 is fixed to one end of a spool 4 that slides in the sleeve 6 in the axial direction.
The coil 6 includes a coil bobbin 18 wound around the coil 20, a magnet 12, a yoke 14, and a pole 16 that traverse the coil 20 to form a magnetic path. The electromagnetic force generated by applying a current to the coil 20 causes the spool 6 to rotate. A direct-acting servo valve that slides in the direction of
0 and a protruding portion such as a rib 25 and a thick portion 27 that are adjacent to the winding portion 26 and protrude from the outer peripheral surface of the winding portion 26. In this configuration, a plurality of axial slits 30 are formed to pass through and open in the vertical direction. A plurality of slit-shaped openings 24a in the circumferential direction are provided at the axially intermediate portion of the cylindrical elastic body 24 that urges the coil bobbin 18 toward the other end.

That is, it is composed of a force motor 1 as a driving force generating section, and a valve section 2 driven by the force motor 1 to control a flowing direction, a flow rate, a pressure and the like of a fluid. The valve portion 2 includes a spool 4, a sleeve 6 and a valve body 8 as main components.
The flow path 10a is controlled by controlling the relative position of
To control the direction, flow rate or pressure of the fluid flowing through to 10c.

On the other hand, the force motor 1 comprises a magnet 1
2, a yoke 14 and a pole 16, a coil bobbin 18 fixed to an end of the spool 4, and a drive coil (coil) 20 attached around the coil bobbin 18 as main components. By controlling the direction and the magnitude, the direction and magnitude of the force generated in the axial direction of the spool 4 are controlled. That is, a magnetic path is formed by the magnet 12, the yoke 14, and the pole 16,
When a current is applied to the drive coil 20 placed in this magnetic path, an electromagnetic force F (F = Bli where B: magnetic flux density, l: coil) drives the spool 4 and the coil bobbin 18 based on Fleming's left-hand rule. Effective length, i: magnitude of current). In this way, the electromagnetic force F generated in the drive coil 20 is transmitted to the spool 4 of the valve section 2 via the coil bobbin 18, and directly drives the spool 4. The cylindrical elastic body 24, which penetrates the yoke 14 and is in contact with the non-valve side end face 22 of the coil bobbin 18,
And the spool 4 is displaced in proportion to the electromagnetic force F generated in the drive coil 20. Here, the tubular elastic body 24 is formed of a metal body having no coil portion of the end winding to be bonded and having a spiral or a large number of circumferential slit-shaped openings formed in an axial middle portion. Therefore, good linear spring characteristics can be obtained. As a result, even when the cylindrical elastic body 24 is used in the compressed and stretched state, it does not apply a radial force to the spool, and does not increase the frictional force between the spool and the sleeve. On the other hand, when the electromagnetic force F is not generated in the drive coil 20 by the action of the cylindrical elastic body 24, the spool 4 is held at the neutral position. Further, the displacement or displacement of the spool 4 in proportion to the electromagnetic force F generated in the drive coil 20 controls the flow rate or pressure of the fluid.

Further, when the coil bobbin 18 is formed of a conductive material, for example, an aluminum alloy or the like, when the coil bobbin 18 crosses the magnetic flux in the magnetic path, a voltage is induced in the coil bobbin 18 by electromagnetic induction, and an eddy current Ie is applied to the coil. It flows in the opposite direction to the flowing current i (Fleming's right-hand rule). Further, a drag f is generated between the eddy current Ie and the magnetic flux in a direction opposite to the electromagnetic force (driving force) F generated in the coil. As a result, the driving force of the force motor becomes Ff. It should be noted that the drag f generated by the eddy current is proportional to the speed at which the coil bobbin 18 crosses the magnetic flux. Therefore, when the frequency of the input current i increases, the drag f due to the eddy current Ie also increases, which gives a large damping force to the movement of the spool 4 of the servo valve.

In the present invention, attention is paid to this point, and as shown in FIG.
A plurality of slits 30 each having a minute width and having an opening in the axial direction are provided between the rib 25 and the thick portion 27. When the slit 30 opened in the winding portion of the coil 20 of the coil bobbin 18 is provided, the coil bobbin 18
Since the length of the flow path of the eddy current Ie generated in this case is changed as compared with the case where the slit 30 is not provided, the flow path resistance can be changed. As a result, the time constant determined by the ratio L / R of the inductance L and the resistance R of the coil bobbin 18 is changed. Thereby, the drag, that is, the damping force based on the eddy current is changed, and appropriate damping can be applied to the spool.

Here, the damping performance according to the present embodiment was confirmed by experiments, and the results are shown in FIG. FIG. 3 shows gain characteristics of frequency response when using the full slit type, the slitless type, and the partial slit type coil bobbin of the present embodiment in comparison. As can be seen from FIG. 3, by forming a partial slit in the coil bobbin, the increase in the peak value of the gain characteristic can be suppressed to about 1 to 2 dB as compared with the case of the slitless coil bobbin.
In the case of a slitless coil bobbin, the damping action by the eddy current can be maximized. As a result, as can be seen from FIG. 3, the value of the response frequency is slightly lower than in the case of the partial slit type coil bobbin. On the other hand, the peak value of the gain characteristic can be suppressed to about +3 dB because the spiral flow generated in the coil bobbin can be used as a 100% damping force, and control stability can be improved.

Thus, according to the embodiment of the present invention,
As shown in FIG. 2, the coil winding portion 2 of the coil bobbin 18
By providing the slit 30 opened in 6, both the responsiveness and the control stability of the contradictory problems required for the direct acting servo valve can be solved.

FIG. 4 shows a second embodiment according to the present invention. In the present embodiment, the partial slit 32 opened for the coil bobbin 18 is different from that of FIG. That is, the difference is that the plurality of partial slits 32 provided in the axial direction of the coil bobbin 18 extend from the winding portion 26 to the middle portion of the thick portion 27 of the coil bobbin 18. Thereby, the flow path resistance of the eddy current Ie can be changed. Further, by providing a partial slit 32 opened at the boundary between the winding portion 26 having a large magnetic flux density and the thick portion 27, the drag due to the eddy current Ie can be reduced. As a result, the damping effect due to the eddy current can be reduced, and the frequency characteristics of the direct acting servo valve can be improved as compared with the case of FIG.

FIG. 5 shows a third embodiment according to the present invention. In the present embodiment, a partial slit 34 opened for the coil bobbin 18 is different from that in FIG. That is, the plurality of partial slits 34 opened in the axial direction of the winding portion 26 of the coil bobbin 18 are not provided for the entire width of the winding portion 26 but extend to the middle (intermediate portion). Moreover, an open portion slit 34a provided in the winding portion 26 from the thick portion 27 side of the coil bobbin 18 toward the rib 25, and an open portion provided in the winding portion 26 from the rib 25 side to the thick portion 27 side. Slit 34
b is such that the end lengths of both partial slits 34a and 34b overlap at an intermediate portion within the width of the winding portion 26. The partial slits 34a thus opened,
By overlapping 34b, the flow path resistance of the eddy current generated in the coil bobbin 18 can be increased. As a result, the drag due to the eddy current is reduced as compared with the case of FIG. 2, and the response of the direct acting servo valve can be improved.

FIG. 6 further aims at a synergistic effect by using the second and third embodiments in combination. That is, the opened partial slits 36a and 36b provided in the winding portion 26 and the thick portion 27 of the coil bobbin 18
That is, a plurality of slits that are opened in the axial direction of the coil bobbin 18 are provided so that the phases thereof are shifted from each other in the circumferential direction, and the lengths of the adjacent slits overlap each other. As a result, the damping force due to the eddy current can be reduced as compared with the above-described embodiment, and the responsiveness of the valve can be further improved.

FIGS. 7 and 8 show the fifth and sixth embodiments according to the present invention.
Is shown. In the present embodiment, the first
And a modification of the second embodiment. Here, the middle of the opened partial slits 38 and 40 provided in the winding portion 26 of the coil bobbin 18 is cut to provide non-connection portions 38a and 40a. Thereby, the winding portion 26 of the coil bobbin 18
Partial slit 38 that opens the flow path of the eddy current generated in
40 indicates that the aperture shape was set. As a result, an eddy current passing through the throttle portion is generated, so that the drag on the direct acting servo valve is increased as compared with the first and second embodiments. As a result, an improvement in control stability of the direct acting servo valve can be expected.

FIG. 9 shows a seventh embodiment according to the present invention. In this embodiment, the partial slit 42 is passed through the winding portion 26 and the thick portion 27 between adjacent holes 44a and 44b provided for reducing the weight of the coil bobbin 18.
Are opened in the axial direction of the coil bobbin 18. Thus, the winding portion 26, the thick portion 27, and the winding portion 2
6 and the thick portion 27 can reduce the drag due to the eddy current.

According to the present embodiment, the coil bobbin is reduced in weight and the damping effect due to the eddy current can be reduced to the maximum, so that the response of the direct acting servo valve can be improved.

FIG. 10 shows an eighth embodiment in which a coil bobbin having an open partial slit according to the present invention constitutes a pilot valve of a two-stage servo valve. In this embodiment, the same or similar members as those of the direct acting servo valve shown in FIG. 1 are denoted by the same reference numerals, and the detailed description thereof will be omitted.

The method of providing a partial slit in a coil bobbin according to the present invention is an effective means as in the case of a direct-acting servo valve for the contradictory problem of improving the response of a two-stage servo valve and providing damping. .

FIG. 11 shows a ninth embodiment in which the open partial slit structure according to the present invention is applied to an electric feedback type direct acting servo valve. That is, the cylindrical elastic body 5 having a relatively weak spring constant is provided on the end face of the coil bobbin opposite to the valve body.
2 and a displacement detector 50 is provided on the end face of the spool 4.
The position of the spool 4 is electrically detected, the detected value is amplified by a feedback gain Kx, and the movement of the spool 4 of the direct acting servo valve is determined by a deviation signal generated by matching the detected value with the input command value Xc. That is, the control is performed by the control mechanism 75. In this case, it is obvious that a high response can be expected because the response of the servo valve is electrically compensated by feedback. Further, the embodiment according to the present invention shown in FIG. 11 can be modified as described below. That is, the position of the spool is electrically detected by a displacement detector, and is fed back to the amplifier of the direct acting servo valve to form a closed loop position servo system. In a direct-acting servo valve of the type that converts to a speed signal and negatively feeds back to the input side of the power amplifier to electrically add damping, the coil bobbin has a spiral or multiple spiral at the axially intermediate portion on the end face opposite the valve body. In addition to disposing a metallic cylindrical elastic body having a slit-shaped opening in the circumferential direction of the coil bobbin, the coil bobbin is configured by one of a coil bobbin of a slitless type or an open partial slit type. Features. With such a configuration, high response and high controllability of the direct acting servo valve can be realized, and the electric feedback loop is turned off.
In this case, the responsiveness determined by the spring constant of the cylindrical elastic body and the mass of the movable portion such as the spool can be ensured. As a result, it is possible to prevent a fatal trouble such as a runaway of the control target by the direct acting servo valve.

On the other hand, in order to provide control stability, a method of generating a speed signal by differentiating the spool displacement once and feeding it back to stabilize, or providing a speed detector separately from the displacement detector has been provided. A method of directly using the signal to stabilize the signal, a method of stabilizing the signal by using an observer, and a method of disposing an oil damper in a valve to stabilize the signal have been considered. However, when these conventional damping methods are applied, the cost is increased, or it is difficult to set an appropriate control gain, and the temperature is directly affected by oil temperature, air mixed in the working fluid, and the like. It has problems such as that.

On the other hand, in the present embodiment, it is not necessary to newly provide a special damping method and a control device as described above, and only the position and shape of the opened partial slit provided on the coil bobbin are optimized. Can handle challenges. As a result, it is possible to provide an inexpensive, highly responsive, and stable direct acting servo valve. In the present embodiment, the embodiment in the case of the three-way valve has been described. However, the present invention is not limited to this, and can be similarly applied to the case of the four-way valve. Similar effects can be expected.

FIG. 12 shows an example in which the direct acting servo valve of the present invention is used in a hydraulic pressure reducing device for a rolling mill. As shown in FIG. 12, the hydraulic oil discharged from the hydraulic pump 64 is supplied to the screw-down jack 61 by the direct-acting servo valve 69 of the present invention, or is returned from the screw-down jack 61 to the tank 63. Direction, flow and pressure are controlled. At this time, a sensor 62 for detecting the height of the pressing down ram is built in the pressing down jack 61, and the output signal of this sensor 62 is taken into the control device 70 so that the direct acting servo valve 69 is provided.
And the stroke of the pressure reduction jack 61 is controlled. By providing the compressor with a hydraulic pressure reduction device using any one of the direct acting servo valves of the present invention, the position of the direct pressure reduction jack can be controlled with high response and high accuracy, and the rolled material 80 Can be controlled with high precision in the order of μm.

[0033]

According to the present invention, an axial partial slit is formed in the winding portion of the coil of the coil bobbin so as to change the length of the flow path of the eddy current generated in the coil bobbin and to reduce the drag against the displacement of the spool. By changing the value, an appropriate damping force is applied to the valve, and at the same time, the coil bobbin is reduced in weight and responsiveness can be improved. Also, control stability and responsiveness of the valve can be improved at low cost by simple means.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view showing the coil bobbin of FIG.

FIG. 3 is a diagram comparing frequency characteristics due to differences in slit shapes of coil bobbins.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

FIG. 8 is a diagram showing another embodiment of the present invention.

FIG. 9 is a diagram showing another embodiment of the present invention.

FIG. 10 is a diagram showing a two-stage servo valve as another embodiment of the present invention.

FIG. 11 is a view showing an electric feedback type direct acting servo valve as another embodiment of the present invention.

FIG. 12 is a view showing a rolling mill hydraulic pressure reduction device as another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 4 spool 6 sleeve 8 body 12 magnet 18 coil bobbin 20 drive coil 26 winding part of coil bobbin 27 thick part of coil bobbin 24, 52 cylindrical elastic body 30, 32, 34a, 34b, 36a, 36b, 38,
40, 42 Slit 50 Displacement detector 69 Direct acting servo valve

Claims (5)

[Claims] A coil bobbin fixed to one end of a spool that slides in a sleeve in an axial direction and wound with a coil, a magnet, a yoke, and a pole traversing the coil to form a magnetic path. In a direct-acting servo valve that slides the spool in the axial direction by an electromagnetic force generated by applying a current to the coil, the coil bobbin includes:
A winding portion for winding the coil, and a protruding portion adjacent to the winding portion and protruding from an outer peripheral surface of the winding portion, and forming an axial slit opened in the winding portion. A direct acting servo valve. A coil bobbin fixedly mounted at one end of a spool that slides in a sleeve in an axial direction and having a coil wound thereon; a magnet, a yoke, and a pole traversing the coil to form a magnetic path. In a direct-acting servo valve that slides the spool in the axial direction by an electromagnetic force generated by applying a current to the coil, the coil bobbin includes:
A winding part for winding the coil, and a protrusion adjacent to the winding part and protruding from the outer peripheral surface of the winding part, and forming an axial slit opened in the winding part. A direct acting servo valve, wherein the slit is extended to an intermediate portion of the projecting portion. 3. The direct acting servo valve according to claim 1, wherein an axial slit opened in the winding portion is formed, and one adjacent slit is connected to the other end of the winding portion and the winding portion. And the other slit is formed between one end of the winding part and the middle part of the winding part, and the end of each slit is the middle part of the winding part. A direct acting servo valve characterized by overlapping each other. 4. A screw-down jack, a hydraulic pump that supplies hydraulic oil to the screw-down jack, a tank that returns the hydraulic oil supplied to the screw-down jack, and a supply and discharge of the hydraulic oil to and from the screw-down jack. And a servo valve body for controlling the thickness of the rolled material, wherein the servo valve body is fixed to one end of a spool that slides in the sleeve in the axial direction and is wound with a coil. Coil bobbin and
It is provided with a magnet, a yoke, and a pole that forms a magnetic path across the coil, and is formed by a direct-acting servo valve that slides the spool in the axial direction by an electromagnetic force generated by applying a current to the coil. The coil bobbin has a winding part that winds the coil, and a protruding part that is adjacent to the winding part and protrudes from the outer peripheral surface of the winding part. A rolling mill characterized by forming a slit. 5. A screw-down jack, a hydraulic pump for supplying hydraulic oil to the screw-down jack, a tank for returning the hydraulic oil supplied to the screw-down jack, and a supply and discharge of the hydraulic oil to and from the screw-down jack. And a servo valve body for controlling the thickness of the rolled material, wherein the servo valve body is fixed to one end of a spool that slides in the sleeve in the axial direction and is wound with a coil. Coil bobbin and
It is provided with a magnet, a yoke, and a pole that forms a magnetic path across the coil, and is formed by a direct-acting servo valve that slides the spool in the axial direction by an electromagnetic force generated by applying a current to the coil. The coil bobbin has a winding part that winds the coil, and a protruding part that is adjacent to the winding part and protrudes from the outer peripheral surface of the winding part. A rolling mill, wherein a slit is formed and the slit is extended to an intermediate portion of the protrusion.