JPH11201707A - Differential transformer for hydraulic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential transformer for hydraulic equipment capable of sufficiently responding to the requirement of a high-response specification with a simple structure. SOLUTION: This differential transformer 100 is provided with a moving core 1 displaceable in the axial direction, an inner pipe 4 storing the moving core 1 in the oil-immersed state, a primary coil 21 arranged on the outer periphery of the inner pipe 4 and applied with an AC voltage, and secondary coils 22a, 22b arranged on the outer periphery of the inner pipe 4 and inducing the voltage corresponding to the axial position of the moving core 1 via the excitation of the primary coil 21. The inner pipe 4 is made of a nonmagnetic and insulating material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a differential transformer for hydraulic equipment for detecting an axial position of a spool of a hydraulic equipment.

[0002]

2. Description of the Related Art Conventionally, in order to detect the axial position of a spool of a hydraulic device, a movable core is connected to the spool so that the axial position of the spool can be determined based on the axial position of the movable core. Around the core, a primary coil and a secondary coil are provided at fixed positions in the axial direction, and an AC voltage is applied to the primary coil to induce a voltage in the secondary coil according to the axial position of the movable core, There is known a differential transformer for hydraulic equipment configured to detect the axial position of the movable core, that is, the axial position of the spool, based on the induced voltage.

FIG. 5 shows a specific example of a differential transformer for hydraulic equipment as described above.

In FIG. 5, reference numeral 100 denotes a differential transformer, 2
00 represents a valve, and 300 represents a spool.

The differential transformer 100 has a columnar movable core 1 made of a magnetic material. The movable core 1 is fixed to one end of a pin 2 made of a non-magnetic material, and the other end of the pin 2 is fixed to a spool 300 by a fixing nut 3. The spool 300 can be displaced in the axial direction (vertical direction in FIG. 5) by driving means (not shown), and the axial position of the movable core 1 is determined according to the axial position of the spool 300.

The movable core 1 is housed inside a hollow cylindrical inner pipe 4 made of non-magnetic stainless steel. The outer peripheral surface of the valve-side end of the inner pipe 4 is fixed to a base member 5 made of a non-magnetic material by silver brazing or the like. A cap 6 made of a non-magnetic material is fixed to the non-valve end of the inner pipe 4 by welding or the like.

[0007] The base member 5 is screwed into the valve 200. An O-ring 7 is provided between the base member 5 and the valve 200 to ensure the sealing between the two 5 and 200.

A valve-side lid member 8 provided on the inner pipe 4 is pressed against the non-valve-side end surface of the base member 5. The valve-side lid member 8 is fixed to one open end of a hollow cylindrical case 9 made of a non-magnetic material by caulking. At the other open end of the case 9, a non-valve-side lid member 10 that is covered by the inner pipe 4 is fixed by caulking. Inner peripheral surface of case 9, outer peripheral surface of inner pipe 4, inner surface of valve-side lid member 8, and non-valve-side lid member 1
The space defined by the inner surface of the
And a drive circuit unit 30.

The coil section 20 includes a primary coil 21 and secondary coils 22a and 22b arranged on both sides of the primary coil 21.
And Primary coil 21 and secondary coils 22a, 2
2b is configured by winding a primary winding 24 and secondary windings 25a, 25b around a common bobbin 23 provided on the inner pipe 4. The primary coil 21 includes a driving circuit 30
To apply an AC voltage. Secondary coils 22a, 22
The b secondary windings 25a and 25b are connected in series so that their induced voltages have opposite polarities. An outer pipe 26 made of a magnetic material for magnetic shielding is provided on the outer periphery of the primary winding 24 and the secondary windings 25a and 25b.

The drive circuit section 30 is constituted by a printed board 32 on which a circuit element 31 is mounted. Printed board 3
Reference numeral 2 is provided on the outer peripheral surface of the handle 23 a of the bobbin 23. The drive circuit section 30 includes a portion for applying an AC voltage to the primary winding 24, and a portion for rectifying and smoothing the induced voltage generated in the secondary windings 25a and 25b.

A spacer 11 made of a non-magnetic material is disposed between the valve-side end of the bobbin 23 and the valve-side lid member 8. The bobbin 23 and the spacer 11 are sandwiched between the valve-side lid member 8 and the non-valve-side lid member 10, whereby the axial position of the bobbin 23, in other words, the axis of the primary coil 21 and the secondary coil 22. The direction position is fixed.

An inner peripheral edge of a retaining ring 12 is fixed to the outer peripheral surface of the non-valve end of the inner pipe 4, and the retaining ring 12 faces the outer surface of the non-valve side lid member 10 toward the valve 200. As a result, the valve-side lid member 8 is pressed against the non-valve-side end surface of the base member 5.

In the differential transformer 100 having the above configuration, an AC voltage is applied to the primary winding 24 of the primary coil 21. A magnetic flux passing through the movable core 1 is generated by this voltage application, and the secondary winding 25a is set in accordance with the axial position of the movable core 1.
And the other magnetic flux interlinking with the other secondary winding 25b are respectively generated, and the secondary windings 25a and 25b
An induced voltage corresponding to the axial position of the movable core 1 is generated, rectified and smoothed by a part of the drive circuit unit 30, and a voltage signal representing the difference between these induced voltages is output to the outside. The axial position of the movable core 1, in other words, the axial position of the spool 300 is detected.

[0014]

However, in the above-described conventional differential transformer 100, if the frequency of the AC voltage applied to the primary coil 21 is increased in accordance with the requirement of the high response specification, the inner pipe 4 itself becomes The generated eddy current increases, and therefore, the attenuation of each of the magnetic flux linked to the secondary winding 25a and the other magnetic flux linked to the other secondary winding 25b increases, and the secondary winding 25a, It has been found that the induced voltage of 25b is attenuated and cannot sufficiently meet the requirements of the high response specification.

In view of the above, it is an object of the present invention to provide a differential transformer for hydraulic equipment capable of sufficiently responding to a demand for a high response specification with a simple configuration.

[0016]

According to the present invention, there is provided a differential transformer for hydraulic equipment, comprising: a movable core capable of being displaced in an axial direction; an inner pipe accommodating the movable core in an oil-immersed state; A hydraulic device comprising: a primary coil disposed to receive an AC voltage; and a secondary coil disposed on an outer periphery of the inner pipe and inducing a voltage corresponding to an axial position of the movable core by exciting the primary coil. In the differential transformer for
The inner pipe is made of a non-magnetic and insulating material.

[0017]

FIG. 1 shows an embodiment of a differential transformer for hydraulic equipment according to the present invention.

In FIG. 1, 100 is a differential transformer, 2
00 represents a valve, and 300 represents a spool.

The differential transformer 100 has a cylindrical movable core 1 made of a magnetic material. The movable core 1 is fixed to one end 2 a of a pin 2 made of a non-magnetic material, and the other end 2 b of the pin 2 is fixed to a spool 300 by a fixing nut 3. The spool 300 can be displaced in the axial direction (vertical direction in FIG. 1) by driving means (not shown).
It is determined corresponding to the axial position of 00.

The movable core 1 is housed inside a hollow cylindrical inner pipe 4 made of a non-magnetic and insulating material. Specifically, the inner pipe 4 is made of PET, PBT,
The material is a synthetic resin such as nylon or ceramic.

The valve-side end 4a of the inner pipe 4 is fitted into a receiving portion 5a of a base member 5 made of a non-magnetic material.
Valve-side end 4a of inner pipe 4 and receiving portion 5 of base member 5
a O-ring 13 is disposed between the two O-rings.
a, the sealing property between 5a is ensured. Base member 5
Is screwed into the receiving portion 200a of the valve 200.
An O-ring 7 is provided between the base member 5 and the valve 200 to ensure the sealing between the two 5 and 200.

The annular convex portion 5b of the base member 5 has a valve-side opening end 9 of a hollow cylindrical case 9 made of a non-magnetic material.
a is fixed by caulking. The non-valve side open end 9b of the case 9 is provided with a cap 14 made of a non-magnetic material.
Is fixed to the annular convex portion 14a by caulking. An O-ring 15 is provided between the non-valve end 4 b of the inner pipe 4 and the cap 14.
The sealing property between 14 is ensured.

In the space defined by the inner peripheral surface 9c of the case 9, the outer peripheral surface 4c of the inner pipe 4, the non-valve end surface 5c of the base member 5, and the valve end surface 14b of the cap 14, the coil portion 20 and the drive A circuit section 30 is provided.

The coil section 20 includes a primary coil 21 and secondary coils 22a and 22b arranged on both sides of the primary coil 21.
And Primary coil 21 and secondary coils 22a, 2
2b is configured by winding a primary winding 24 and secondary windings 25a, 25b around a common bobbin 23 provided on the inner pipe 4. The primary coil 21 includes a driving circuit 30
To apply an AC voltage. Secondary coils 22a, 22
The b secondary windings 25a and 25b are connected in series so that their induced voltages have opposite polarities. An outer pipe 26 made of a magnetic material for magnetic shielding is provided on the outer periphery of the primary winding 24 and the secondary windings 25a and 25b.

The drive circuit section 30 is constituted by a printed board 32 on which a circuit element 31 is mounted. Printed board 3
2 is disposed on the outer peripheral surface 23c of the handle 23a of the bobbin 23. The drive circuit section 30 includes a portion for applying an AC voltage to the primary winding 24, and a portion for rectifying and smoothing the induced voltage generated in the secondary windings 25a and 25b.

A spacer 11 made of a non-magnetic material is provided between the valve-side end 23b of the bobbin 23 and the annular projection 5b of the base member 5. The bobbin 23 and the spacer 11 are arranged between the base member 5 and the cap 14 so that their axial positions are not displaced.
The axial positions of the primary coil 21 and the secondary coil 22 are not displaced, and the axial position of the movable core 1 can be accurately detected.

In the differential transformer 100 having the above configuration, an AC voltage is applied to the primary winding 24 of the primary coil 21. A magnetic flux passing through the movable core 1 is generated by this voltage application, and the secondary winding 25a is set in accordance with the axial position of the movable core 1.
And the other magnetic flux interlinking with the other secondary winding 25b are respectively generated, and the secondary windings 25a and 25b
An induced voltage corresponding to the axial position of the movable core 1 is generated, rectified and smoothed by a part of the drive circuit unit 30, and a voltage signal representing the difference between these induced voltages is output to the outside. The axial position of the movable core 1, in other words, the axial position of the spool 300 is detected.
Here, the magnetic flux flows across the inner pipe 4. Therefore, when the inner pipe 4 is made of a non-magnetic stainless steel as in the above-described conventional example, an eddy current is generated in the inner pipe 4 itself due to a change in magnetic flux traversing the inner pipe 4, and this eddy current is To attenuate the induced voltage of the secondary windings 25a and 25b. However, the inner pipe 4 in the present embodiment is formed of a material having non-magnetic and insulating properties as described above. Therefore, an eddy current is not generated in the inner pipe 4 due to a change in the magnetic flux traversing the inner pipe 4, and the induced voltage of the secondary windings 25a and 25b can be prevented from attenuating. Therefore, even if the frequency of the AC voltage applied to the primary coil 21 is increased, a sufficient induced voltage can be obtained in the secondary windings 25a and 25b, and the demand for high response specifications can be sufficiently satisfied. .

FIG. 2 shows the differential transformer 100 shown in FIG.
1 shows a differential transformer 100 of a type in which the drive circuit section 30 is built in, whereas a type in which the drive circuit section 30 is provided outside without being built in.

The differential transformer 100 shown in FIG. 2 does not include the drive circuit unit 30, so that the bobbin 23
1 except that the handle portion 23a for mounting is mounted and the spacer 16 is disposed between the non-valve end 23d of the bobbin 23 and the cap 14. It is configured similarly to. This differential transformer 1
Also in 00, since the inner pipe 4 is made of an insulating material, it is possible to prevent generation of eddy current, obtain a sufficient induced voltage in the secondary windings 25a and 25b, and sufficiently meet the requirements of high response specifications. Can be.

The differential transformer 100 shown in FIG. 3 is constructed by integrally molding the inner pipe 4 and the bobbin 23 of the differential transformer 100 shown in FIG. 1 with a non-magnetic and insulating material. , FIG. 1 and FIG.
As in the case of 0, it is possible to sufficiently respond to a request of a high response specification, and it is possible to reduce the number of parts. Further, the non-valve end 4b of the inner pipe 4 is closed, and the O-ring 15 shown in FIG. 1 can be omitted.
Further, as shown in FIGS. 4A and 4B, the inner pipe 4 has projections 4d, 4e, 4f, 4g for positioning and fixing the printed board 32 (FIG. 1) in cooperation with the handle 23a. Is provided, and it is possible to prevent a short circuit accident or the like that may occur when the printed board 32 moves undesirably and comes into contact with the case 9 or the like. Other configurations are the same as those of the differential transformer 100 shown in FIG.

[0031]

According to the differential transformer for hydraulic equipment of the present invention, since the inner pipe is formed of a non-magnetic and insulating material, the generation of eddy current is prevented and a sufficient induced voltage is obtained in the secondary coil. And can sufficiently meet the demands of the high response specification.

The number of parts can be reduced by integrally forming the inner pipe so as to serve also as a bobbin for the primary coil and the secondary coil.

Further, by closing the end of the inner pipe and forming it into a cylindrical shape with a bottom, O
Rings can be omitted.

Further, since a projection for positioning and fixing the printed board is provided on the inner pipe, it is possible to prevent a short circuit accident or the like due to the movement of the printed board.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a differential transformer for hydraulic equipment of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment.

FIG. 3 is a sectional view showing still another embodiment.

FIG. 4A is a perspective view of a main part of the inner pipe in the embodiment, and FIG. 4B is a rear view of a non-valve side end of the inner pipe shown in FIG.

FIG. 5 is a sectional view of a conventional differential transformer.

[Explanation of symbols]

 Reference Signs List 100 differential transformer 1 movable core 4 inner pipe 4d, 4e, 4f, 4g projection 21 primary coil 22a, 22b secondary coil 23 bobbin 30 drive circuit unit 32 printed board

Claims (4)

[Claims] 1. A movable core that can be displaced in an axial direction, an inner pipe that accommodates the movable core in an oil-immersed state, a primary coil that is disposed on an outer periphery of the inner pipe, and to which an AC voltage is applied,
A secondary coil arranged on the outer periphery of the inner pipe and inducing a voltage corresponding to an axial position of the movable core by exciting the primary coil, wherein the inner pipe is non-magnetic and A differential transformer for hydraulic equipment characterized by being formed of an insulating material. 2. The differential transformer for hydraulic equipment according to claim 1, wherein the inner pipe is integrally formed so as to also serve as a bobbin of the primary coil and the secondary coil. 3. The differential transformer according to claim 2, wherein the inner pipe is formed in a cylindrical shape with a bottom. 4. The differential transformer for a hydraulic device according to claim 2, wherein the inner pipe has a projection for positioning and fixing a printed circuit board of the drive circuit unit.