JPH09303328A - Position detector of valve device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector of a valve device capable of reducing the overall length, and reducing the detection error. SOLUTION: A position detector 1 is provided with a core 12 which is fixed to an end part of a spool 11 in a valve body 10 through a rod 13 and projected outwardly from a fitting hole in the valve body, a fitting bolt 2 which is screwed in the fitting hole and has a shaft hole, an inner pipe which is fitted to the shaft hole of the fitting bolt to insert the core inside, and a detection coil part 3 which is fitted to the outside of the inner pipe and in which secondary coils are arranged on each side of a primary coil 5, realizing the position detector of differential transformer type to output the signal corresponding to the position of the spool 11. The secondary coil 6 at the base side in the detection coil part 3 is arranged adjacent to the fitting bolt 2, and an adjustment ring 9 made of non-magnetic and conductive metal is arranged at the point adjacent to the secondary coil 7 on the tip side in the detection coil part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential transformer type position detector which detects the position of a spool in a valve device such as a servo valve and outputs the detection signal to a feedback control circuit or the like.

[0002]

2. Description of the Related Art There is a servo valve as a hydraulic device for driving and controlling a hydraulic cylinder or the like. In this servo valve, in general, a valve body has a spool inserted in a sleeve so as to be movable in its axial direction, and a four-way In the case of a nozzle flapper type servo valve which is formed as a valve, the nozzle flapper portion is provided on the sleeve of the valve body, and the torque motor portion including an electromagnetic actuator is provided on the nozzle flapper portion.

This type of servo valve adjusts the hydraulic pressure supplied into the sleeve via the nozzle / flapper section by the operation of the torque motor section, and moves the spool in the sleeve from the neutral point in the left-right axial direction to load the load. To control the hydraulic pressure supply to (hydraulic cylinder, etc.), and to make it feedback control, a differential transformer type position detector that detects the spool position and outputs the detection signal is provided.

As shown in FIG. 3, the position detector 20 generally has a detection coil portion 24 and a core 25 with a rod 26 inserted therein, and the end of the detection coil portion 24 is a mounting bolt. It is fixed to the side of the valve body 21 by 27.

The mounting bolt 27 has an axial hole in the center and is fixed to the end of the detection coil portion 24 so as to be fitted to a part of the outer peripheral portion of the inner pipe 29 fitted inside the detection coil portion 24. It Further, the shaft portion of the mounting bolt 27 is provided with a male screw which is screwed into the female screw of the mounting hole provided on the valve body side, and the seal ring 28 is fitted in the circumferential groove provided on the outer peripheral portion thereof. To be

The detection coil portion 24 having such a mounting bolt 27 fixed at its end has a shaft portion of the mounting bolt 27,
It is completely screwed into the mounting hole of the valve body 21, and the core 25 with the rod 26 is inserted into the inner pipe 29.
The end is screwed to the tip of the spool 30 in the valve body 21.

[0007]

The position detector 20 of the differential transformer type outputs a voltage 0 signal and moves to the left and right when the spool 30 (core 25) is at the neutral point (neutral position). In order to output a voltage signal that linearly changes to the + side and the-side in accordance with the above, the primary coil 31 and the secondary coils on both sides thereof are provided in the detection coil section 24. 32 and 33 are arranged and the secondary coils 32 and 3 are arranged.
3 are connected in series in mutually opposite directions, and outputs are taken out differentially.

However, in practice, the valve body is usually made of steel (magnetic material), which is located close to one of the secondary coils, and the mounting bolt (a conductive non-magnetic material such as stainless steel). (Metal) is nearby, so when the primary coil is energized to generate output by electromagnetic induction in the secondary coil, eddy current is generated in the valve body and mounting bolts, and the output voltage of the secondary coil due to the eddy current loss. Will be affected.
Therefore, as indicated by the curve B in the graph of FIG. 4, the characteristic of the detection signal when the core moves to the valve body side (− side) is lower than the characteristic of the detection signal when moving to the + side. There is a problem that the linearity of the output characteristic of the position detector is deteriorated and the detection error increases.

For this reason, conventionally, as shown in FIG. 3, a spacer 22 made of synthetic resin is provided on the valve body 21 side in the detection coil portion 24 to prevent the valve body 21 of the secondary coil 32 and the mounting bolt 27 from affecting. By reducing the number, the detection signal having good linearity is obtained according to the position of the core 25. However, when the spacer 22 is inserted in this way, the total length of the position detector becomes longer, and the fixing nut 34 and the lid 35 are also provided on the tip side of the detection coil portion 24.
There is a problem in that the spacer 23 needs to be arranged in order to reduce the influence on the characteristics of (1) and to keep the distance from the secondary coil 33, which increases the total length of the position detector 20.

The present invention has been made in view of the above points, and an object of the present invention is to provide a position detector for a valve device, which can have a shorter overall length than conventional ones and can reduce a detection error.

[0011]

In order to achieve the above object, a position detector of the present invention is fixed to a spool end portion in a valve body via a rod and projects outward from a mounting hole of the valve body. The core, a mounting bolt that is screwed into the mounting hole and has an axial hole, an inner pipe that is fitted into the axial hole of the mounting bolt and that inserts the core inside, and a secondary bolt that is fitted to the outside of the inner pipe and that is located on both sides of the primary coil. In a position detector of the differential transformer type, which includes a detection coil section in which a secondary coil is arranged, and which outputs a signal according to the position of the spool, the secondary coil on the base side in the detection coil section is a mounting bolt. And a conductive metal adjusting ring made of a non-magnetic material is arranged at a position adjacent to the secondary coil on the tip side in the detection coil portion.

[0012]

[Operation / Effect] In the position detector having such a configuration, the secondary coil on the base side in the detection coil section is arranged adjacent to the mounting bolt, and the conventional spacer is connected to the secondary coil on the base side. Since it is not inserted between the mounting bolt and the mounting bolt, the length of the position detector can be shortened by the length of the spacer.

Since the spacer on the base side of the detection coil is eliminated, the secondary coil on the base side is affected by the mounting bolts and the like, and the output voltage characteristic on the negative side of the position detector is deteriorated.
Since the adjusting ring made of a non-magnetic material and made of a conductive metal is arranged on the tip side in the detection coil section, the secondary coil on the tip side is also affected by this adjustment ring, and the output voltage characteristics on the + side of the position detector are also affected. It is possible to obtain an output voltage characteristic with good linearity in which the voltage decreases similarly to the − side and linearly changes on both the + side and the − side.

If the adjusting ring is made of a highly conductive metal having a higher conductivity than the mounting bolt,
The adjustment ring can be made more compact, and the length of the position detector can be made shorter. That is, when the position detector is activated and the primary coil is energized and excited, an eddy current is generated in the mounting bolt and the adjustment ring near the coil, and the output voltage decreases due to the eddy current loss. Can be made of a highly conductive metal that is more conductive than the mounting bolt, a similar eddy current can be generated with a smaller shape than the mounting bolt, and the + and-side output voltages can be reduced in the same way. Therefore, it is possible to obtain an output voltage characteristic with good linearity.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a sectional view of a differential transformer type position detector 1 in a servo valve. This position detector 1
Is a core 12 protruding and fixed to the end of the spool 11 in the valve body 10 via a rod 13 and a mounting hole in a side wall of the valve body 10 mounted via a mounting bolt 2 and an inner pipe 4. It is composed of a coil portion 3.

The mounting bolt 2 is formed by providing a shaft hole in the center, a threaded portion 2a on the outer circumference, and a hexagonal head on the tip, and a seal is formed in the circumferential groove provided on the outer circumference of the intermediate portion. The ring (O ring) 2c is fitted. The inner pipe 4 is fitted into the shaft hole of the mounting bolt 2 and fixed by brazing or the like, and the lid body 4a is fitted to the tip of the inner pipe 4 and the lid body 4 is attached.
A male screw portion for the fixing nut 8 is provided around a.

The detection coil unit 3 is composed of a primary coil 5 in which a coil of a predetermined number of turns is wound around a cylindrical bobbin, and two secondary coils 6 and 7 in which a coil of a predetermined number of turns is wound around a similar bobbin. The secondary coils 6 and 7 are arranged on both sides of the primary coil 5 to form a tubular shape, the outer pipe 3a is fitted to the outer peripheral portion, and the circular side plates 3b are fixed to both sides.

Further, on the side opposite to the valve main body (on the right side of the secondary coil 7) in the detection coil portion 3, a non-magnetic and highly conductive adjusting ring 9 is provided, and the outer circumference of the inner pipe 4 is inside the outer pipe 3a. Is installed in. The adjustment ring 9 is made of aluminum, copper alloy, or the like, which is a non-magnetic material and has higher conductivity than stainless steel.

The mounting bolt 2, the inner pipe 4, the lid 4
a, rod 13, and side plate 3b are made of stainless steel, which is a non-magnetic material, in order to reduce the magnetic influence of the output characteristics, and the outer pipe 3a and core 12 are formed with a magnetic path. A magnetic metal such as steel is used.

The adjusting ring 9 is arranged adjacent to the distal side (right side) secondary coil 7 in order to balance the influence with the mounting bolt 2 located near the primary side secondary coil 6. However, when the adjusting ring 9 is made of stainless steel of the same material as the mounting bolt 2, it is necessary to dispose a large ring having the same volume as the mounting bolt 2 in the detection coil portion.

However, since the adjusting ring 9 is made of a material having good conductivity (for example, aluminum or copper alloy) having a conductivity higher than that of stainless steel, the volume of the ring is much smaller than that of the mounting bolt 2, and both secondary coils are used. The outputs of 6 and 7 can be balanced. That is, when the primary coil 5 of the detection coil 3 is energized and excited, an eddy current is generated in the mounting bolt 2 and the adjustment ring 9, and the output voltage of the secondary coils 6 and 7 decreases due to the eddy current loss. , Mounting bolt 2
If the adjustment ring is made of a highly conductive metal having a higher conductivity than (stainless steel), the same eddy current can be generated in a small shape, so that the adjustment ring can be downsized.
Further, by arranging the adjustment ring 9 on the tip side, the core 25 is moved to the right side (− side) and the left side (+) inside the detection coil unit 3.
The output characteristic of the detector when it is moved to the side) can be similarly lowered to improve its linearity.

The detection coil unit 3 as described above includes the inner pipe 4
Is inserted into the outer peripheral portion of the inner pipe 4 up to a position where it abuts the end surface of the mounting bolt 2, and the fixing nut 8 is screwed from the tip side of the inner pipe 4 to the threaded portion of the lid body 4a via the spacer 8a and tightened by the fixing nut 8. , Fixed.

On the other hand, in the valve body 10 of the servo valve, there is provided a spool 11 that moves in the axial direction according to the switching state of the valve, and the end of the spool 11 and the wall portion at a position facing each other are
A mounting hole into which the mounting bolt 2 can be screwed is formed. Core 12
Is fixed to the tip of the rod 13, the end of the rod 13 is screwed into a screw hole provided at the end of the spool 11, and is fixed there by a small fixing nut 13a. Rod 1
The core 12 at the three tips projects outward from the mounting hole.

Then, the assembly of the inner pipe 4, the detection coil portion 3 and the mounting bolt 2 having the above-mentioned structure is mounted by inserting the core 12 and the rod 13 into the inner pipe 4. The male screw portion 2a of the bolt 2 is screwed into the mounting hole for mounting.

Although the detailed description of the structure of the servo valve is omitted, it is a nozzle flapper type servo valve.
The nozzle flapper portion is provided on the sleeve of and the torque motor portion including an electromagnetic actuator is provided on the nozzle flapper portion. The secondary coils 6 and 7 of the detection coil unit 3 of the position detector 1 are connected to the input side of a control circuit that drives and controls the torque motor unit. An AC power supply that supplies AC power having a predetermined frequency is connected to the primary coil 5.

When the AC power is supplied to the primary coil 5 from an AC power supply (not shown), the position detector 1 excites the AC power, and the magnetic flux generated there generates two secondary coils depending on the position of the core 12. Electromagnetic induction is generated in 6 and 7, and a voltage corresponding to the displacement position of the core 12 is differentially output from the secondary coils 6 and 7. When the core 12 is located at the center position of the detection coil unit 3 (when the spool 11 is in the neutral position), the output of the secondary coils 6 and 7 is 0.

When the core 12 (spool 11) moves (displaces) to the-side, the output voltages of the secondary coils 6 and 7 linearly increase the output voltage on the-side in accordance with the displacement, and move to the + side. When moved (displaced), the outputs of the secondary coils 6 and 7 are generated so that the output voltage on the + side increases according to the displacement.

At this time, the secondary coil 6 on the base side of the detection coil section 3 is affected by the mounting bolt 2 and the valve body 10, and the outputs of the secondary coils 6 and 7 are shown by the curve B in FIG. As described above, the voltage is lower than the output characteristic (curve A) that is not affected, but the output of the secondary coil 7 on the tip side of the detection coil unit 3 is also affected by the adjustment ring 9 and is similarly reduced.
The output characteristic of the position detector 1 is that the output voltage is 0 at the neutral point of the core 12 (spool 11) as shown by the curve C in FIG.
Therefore, an output voltage with good linearity that changes linearly on both the + and − sides can be obtained.

As described above, since the spacer conventionally provided in the detection coil portion 3 is eliminated, the total length of the position detector 1 can be made shorter than before. Since the spacer on the base side of the detection coil section 3 is eliminated, one secondary coil 6 is affected by the mounting bolts 2 and the like, and the output voltage characteristic on the negative side of the position detector is deteriorated. Since the adjustment ring 9 made of a non-magnetic material and having good conductivity is arranged on the tip side of the inside,
The other secondary coil 7 is also affected by the adjusting ring 9, and the output voltage characteristic on the + side of the position detector is also reduced like the − side. Therefore, it is possible to obtain an output voltage characteristic with a good linearity that changes linearly on both the positive and negative sides.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a servo valve position detector showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the position of the core and the output voltage in the position detector of the present invention.

FIG. 3 is a sectional view of a conventional position detector.

FIG. 4 is a graph showing the relationship between core position and output voltage in a conventional position detector.

[Explanation of symbols]

 1-Position detector 2-Mounting bolt 3-Detection coil part 4-Inner pipe 8-Fixing nut 9-Adjusting ring 10-Valve body 11-Spool 12-Core 13-Rod

Claims (2)

[Claims] 1. A core fixed to a spool end in a valve body via a rod and protruding outward from a mounting hole of the valve body, a mounting bolt screwed into the mounting hole and having an axial hole, and the mounting. An inner pipe fitted into the axial hole of the bolt for inserting the core therein; and a detection coil unit fitted on the outer side of the inner pipe and having secondary coils arranged on both sides of the primary coil, In a differential transformer type position detector that outputs a signal according to a position of a spool, a secondary coil on a base side in the detection coil unit is arranged adjacent to the mounting bolt, and a tip end in the detection coil unit. A position detector of a valve device, wherein a non-magnetic conductive metal adjusting ring is arranged adjacent to the secondary coil on the side. 2. The position detector for a valve device according to claim 1, wherein the adjusting ring is formed of a highly conductive metal having higher conductivity than the mounting bolt.