JP2857726B2 - Direct acting servo valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct-acting servo valve of the 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).

[0004]

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.

An object of the present invention, high precision high response by changing the resistance to displacement of the spool to provide a direct-operated servo valve with high reliability.

[0006]

In order to achieve the object In order to achieve the object, the present invention includes a coil bobbin made of the spool one end fixed to the conductive material that slides inside the sleeve in the axial direction, before
A coil wound around the serial coil bobbin, it includes a magnet for forming a transverse <br/> switching Ru path the coils, an electromagnetic force generated by supplying a current to the co <br/> yl the spool by
In direct acting servo valve sliding axially, the carp
Lubobin has a slit formed by extending in the axial direction.
Having at least one end of the slit,
The position including the end of the winding part around which the coil is wound, and the coil
Between the end of the lubobin and the coil bobbin
Where at least slits are not formed at both ends of the
It is characterized by having a position .

[0007] Also, the portion outside the winding portion of the coil bobbin is
It may be formed thick and the slit may be extended from the winding part to the middle part of the thick part .

An axial slit is formed in the winding portion.
At the same time, one adjacent slit is formed between the other end of the winding part and the middle part of the winding part , and the other slit is formed between one end of the winding part and the middle part of the winding part. The end of each slit may be overlapped with each other at the middle part of the winding part.

Further, in a rolling mill, a reduction jack is used.
And a hydraulic pump that supplies hydraulic oil to the screw-down jack,
A tank for returning the hydraulic oil supplied to the lower jack, and a hydraulic oil
And a servo valve to control the supply and discharge of
The provided, in the rolling mill you processing the plate thickness of the rolled material, Sir
The valve is one end of a spool that slides in the sleeve in the axial direction.
A coil bobbin fixedly mounted on a coil and wound with a coil;
An elastic body that biases the coil bobbin to the other end, and the coil
The magnet, yoke and pole that form the cut magnetic path
Equipped with an electromagnetic force generated by applying current to the coil
The spool is slid in the axial direction against the urging force of the elastic body.
Formed by a direct acting servo valve,
A winding part for winding a coil and a winding part adjacent to this winding part
And a projection protruding from the outer peripheral surface of the winding portion.
Is formed.

[0010]

[0011]

According to the present invention, an electromagnetic force generated in the axial direction by the law left Fleming moving the coil bobbin, eddy current is generated in the direction preventing the movement. However, by providing a partial slit in the winding part 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 portion 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.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. 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 FIG.
A coil bobbin 18 fixed to one end of the spool 4 sliding in the sleeve 6 in the axial direction and wound with the coil 20.
And a cylindrical elastic body for urging the coil bobbin 18 to the other end side
(Elastic body) 24 , a magnet 12, a yoke 14 and a pole 16 which traverse the coil 20 to form a magnetic path. The spool 6 is formed into a cylindrical elastic body by an electromagnetic force generated by applying a current to the coil 20. 24. A direct acting servo valve which slides in the axial direction against the urging force of a cylindrical elastic body 24.
A plurality of slit-shaped openings 24a in the circumferential direction are provided in the axial middle portion of the coil bobbin 18. The coil bobbin 18 is provided with a winding portion of the coil 20 and an outer peripheral surface of the winding portion adjacent to the winding portion.
It has a protruding portion such as a protruding rib 25 and a thick portion 27.
Then, a plurality of axial slits 30 are formed in the winding part. That is, it is composed of a force motor 1 as a driving force generating unit, and a valve unit 2 driven by the force motor 1 to control a flowing direction, a flow rate, a pressure and the like of the fluid. The valve portion 2 includes a spool 4, a sleeve 6, and a valve body 8.
Are the main constituent elements, and by controlling the relative position of the spool 4 with respect to the sleeve 6 with high precision, the flow paths 10 a to 10
The direction, flow rate, pressure and the like of the fluid flowing through 10c are controlled.

On the other hand, the force motor 1 has a magnet 1
2, a yoke 14, 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, and when an electric current is supplied to the drive coil 20 placed in the magnetic path, the electromagnetic force for driving the spool 4 and the coil bobbin 18 based on Fleming's left-hand rule. A force F (F = Bli, where B: magnetic flux density, l: effective length of coil, i: magnitude of current) is generated. 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. A cylindrical elastic body 24 that penetrates the yoke 14 and is in contact with the non-valve portion side end face 22 of the coil bobbin 18 maintains the neutral position of the spool 4 and the drive coil 20, and The spool 4 is displaced in proportion to the generated electromagnetic force F.
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 made 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 an electromagnetic induction action, 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 having a minute width are provided between the rib 25 and the thick portion 27 in the axial direction. When the slit 30 is provided in the winding part of the coil 20 of the coil bobbin 18 in this manner, the eddy current I generated in the coil bobbin 18 of the conductive material is generated.
Since the flow path length e changes as compared with the case where the slit 30 is not provided, the flow path resistance can be changed. As a result,
The ratio L / L of the inductance L and the resistance R of the coil bobbin 18
The time constant determined by R 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 a full slit type, a slitless type, and a partial slit type coil bobbin are used. 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 indicates that the spiral flow generated in the coil bobbin is 10
Since it can be used as 0% damping force, it can be suppressed to about +3 dB, and control stability can be improved.

Thus, according to the embodiment of the present invention, FIG.
As shown in (1), by providing the slit 30 in the coil winding portion 26 of the coil bobbin 18, it is possible to solve both the responsiveness and the control stability of the contradictory problems required for the direct acting servo valve.

FIG. 4 shows a second embodiment according to the present invention. In the present embodiment, the partial slit 32 for the coil bobbin 18 is different from that of FIG. That is, a plurality of partial slits 3 provided in the axial direction of the coil bobbin 18
2 is different in that it extends from the winding part 26 to the middle part of the thick part 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 at the boundary between the winding portion 26 having a large magnetic flux density and the thick portion 27, the eddy current I
The drag by e 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, the partial slit 34 for the coil bobbin 18 is different from the case of FIG. In other words, the plurality of partial slits 34 provided 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, the partial slit 34a provided in the winding portion 26 from the thick portion 27 side of the coil bobbin 18 toward the rib 25 and the partial slit 34b provided in the winding portion 26 from the rib 25 side to the thick portion 27 side The end lengths of both partial slits 34a and 34b are overlapped at an intermediate portion within the width of the winding portion 26. Thus, the partial slits 34a,
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 aims at a synergistic effect by using the second and third embodiments in combination. That is, the partial slits 36a and 36b provided in the winding part 26 and the thick part 27 of the coil bobbin 18 are shifted in phase in the circumferential direction from each other, and the lengths of the adjacent slits are overlapped in the axial direction of the coil bobbin 18. That is, a plurality of slits are provided. 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. This embodiment is a modification of the first and second embodiments. Here, the coil bobbin 18
In the middle of the partial slits 38 and 40 provided in the winding part 26, non-connection parts 38a and 40a are provided. Thus, the flow path of the eddy current generated in the winding portion 26 of the coil bobbin 18 is formed into a throttle shape by the partial slits 38 and 40. 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, a plurality of partial slits 42 are provided in the axial direction of the coil bobbin 18 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. is there. Thus, the boundary between the winding portion 26 and the thick portion 27 and the winding portion 26,
In addition, the drag due to the eddy current can be reduced at three places of the thick portion 27.

According to this embodiment, since the damping effect due to the eddy current can be reduced to the maximum, the response of the direct acting servo valve can be reduced.
Improvement of responsiveness can be realized.

FIG. 10 shows an eighth embodiment in which a pilot valve of a two-stage servo valve is constituted by a coil bobbin having a partial slit according to the present invention. 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 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, against 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 partial slit structure according to the present invention is applied to an electric feedback type direct acting servo valve. That is, a cylindrical elastic body 52 having a relatively weak spring constant is disposed on the end face of the coil bobbin opposite to the valve body,
In addition, a displacement detector 50 is provided on the end face of the spool 4 to electrically detect the position of the spool 4, amplify the detected value by a feedback gain Kx, and input an input command value Xc
The movement of the spool 4 of the direct acting servo valve is controlled by the control mechanism 75 using a deviation signal generated by the comparison. 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 shown below. That is, the position of the spool is electrically detected by a displacement detector, and a feedback control is provided to an amplifier of a direct acting servo valve to form a closed loop position servo system.
In addition, in the direct-acting servo valve, the output is converted into a speed signal in the direct-acting servo valve drive amplifier and negatively fed back to the input side of the power amplifier to electrically add damping. On the body side end surface, a metallic cylindrical elastic body having a spiral or a number of circumferential slit-shaped openings formed in the axial middle part is disposed, and the coil bobbin is a slitless type or a partial slit type. And one of the coil bobbins. With such a configuration, high response and high controllability of the direct acting servo valve can be realized, and even when the electric feedback loop is turned off, the spring constant of the cylindrical elastic body and the movable state of the spool and the like can be improved. Responsiveness determined by the partial mass 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 impart 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 the above problem is solved by optimizing only the position and shape of the partial slit provided on the coil bobbin. it can. 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 the direct acting servo valve of the present invention, it is possible to directly control the position of the pressure reduction jack with high response and high accuracy, and to reduce the thickness of the rolled material 80 to μm. The unit can be controlled with high precision.

[0030]

According to the present invention, only setting the axial portion slit winding portion of the coil of the coil bobbin, to change the flow path length of the eddy current generated in the coil bobbin, and the spool
By changing the resistance to the displacement, an appropriate damping force is applied to the valve, and the 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-57705 (JP, A) JP-A-59-196698 (JP, A) JP-A-61-102153 (JP, A) 26194 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F15B 13/044 H02K 33/18

Claims (6)

(57) [Claims] A coil bobbin made of a conductive material fixed to one end of a spool that slides in a sleeve in an axial direction ;
Axis the spool and a coil wound around the serial coil bobbin, before SL becomes and a magnet forming a lateral <br/> switching Ru magnetic path coil, the electromagnetic force generated by applying a current to said coil in direct acting servo valve sliding direction, the
The coil bobbin has a slit formed to extend in the axial direction.
At least one end of the slit,
A position including an end of a winding portion around which the coil is wound;
Between the end of the coil bobbin and the coil
At least slits are not formed at both ends of the bobbin
Direct-acting servo valve, characterized in that it has a large area . 2. The direct acting servo valve according to claim 1, wherein
The coil bobbin has a thick portion having a diameter larger than that of the winding portion.
The end of the slit is formed adjacent to the winding portion.
A direct-acting servo valve, which is located at an intermediate portion of the thick portion . 3. The direct acting servo valve according to claim 1, wherein
The coil bobbin has a thick portion having a diameter larger than that of the winding portion.
The slit is formed adjacent to the winding portion, and the slit is
A plurality of slits are formed in the circumferential direction of the coil bobbin, and one adjacent slit is formed between the other end of the winding part and an intermediate part of the winding part, and the other slit is formed between one end of the winding part and the one end of the winding part. is formed between the intermediate portion of the winding unit, direct acting servo valve end of each slit, characterized in that the overlap to each other at an intermediate portion of the winding portion. 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
An elastic body for urging the coil bobbin to the other end side, and a magnet, a yoke, and a pole traversing the coil to form a magnetic path, and the spool is moved by an electromagnetic force generated by applying a current to the coil. The coil bobbin is formed by a direct acting servo valve that slides in the axial direction against the urging force of the elastic body, and the coil bobbin is formed to extend in the axial direction.
Having at least one of the slits
Is located at a position including the end of the winding portion around which the coil is wound.
And the end of the coil bobbin
At least slits are formed at both ends of the coil bobbin.
A rolling mill characterized by having a portion that is not provided . 5. The rolling mill according to claim 4, wherein
The coil bobbin has a thick portion having a diameter larger than that of the winding portion.
The end of the slit is formed adjacent to the winding part,
A rolling mill, which is located at an intermediate part of a thick part . 6. A sleeve and an axial slide in the sleeve.
A valve portion having a freely mounted spool;
A coil bobbin connected to one end of the
A coil wound around the coil and a magnetic path crossing the coil.
And a force motor unit having a magnet to be formed.
And the electromagnetic force generated by applying a current to the coil
The direct acting servo valve that slides the spool
The coil bobbin is formed to extend in the axial direction.
Having at least the slit
The end on the spool side is the end of the winding part around which the coil is wound.
And the end of the coil bobbin on the spool side.
Between both ends of the coil bobbin.
At least a part where no slit is formed
A direct acting servo valve characterized by the following: