JPH0623930Y2 - Differential transformer displacement sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a magnetic core that interlocks with a displacement member, a bobbin arranged around the magnetic core, and a magnetic core wound around the outer periphery of the bobbin. The present invention relates to a differential transformer type displacement sensor including a coil that outputs an electric signal according to the position and a cover that houses the coil inside the main body.

[Conventional technology]

Since the differential transformer type displacement sensor can electrically detect the movement amount of the displacement member, there is no physical contact portion between the displacement member and other members and wear is small, so durability and reliability are improved. Is excellent. Therefore, the amount of movement is large,
This is useful for detecting the position of a member that frequently moves (for example, a control rack of an injection pump that supplies fuel to the engine).

FIG. 2 shows the basic structure of a differential transformer displacement sensor, and FIG. 3 shows the basic principle of a differential transformer. The differential transformer type displacement sensor is basically a magnetic core 2 that interlocks with the displacement member 1, a bobbin 3 that is arranged around the magnetic core 2, and a bobbin 3 that is wound around the outer periphery of the bobbin 3 according to the position of the magnetic core 2. The coil 4 (primary coil 4a and secondary coil 4b) which outputs an electric signal is comprised.

Therefore, when the displacement member 1 moves, the coil 4 can extract an electric signal corresponding to the position of the magnetic core 2, and the position of the displacement member 1 can be accurately detected.

FIG. 4 is a sectional view showing the structure of a main part of a conventional differential transformer displacement sensor. This differential transformer type displacement sensor
Basically, the magnetic core 5, the bobbin 6, the coil 7, the yoke member 8 and the cover 9 are provided. The magnetic core 5
Linked so as to interlock with the displacement member 10,
It is configured so that it can move linearly in a fixed direction. Leak cut rings 5a and 5b are attached to front and rear portions of the magnetic core 5 in the moving direction to prevent oil and the like from entering the magnetic core 5. Bobbin 6
The cross section is formed by a substantially E-shaped cylindrical member, and the magnetic core 5
Is slidably stored inside. The coil 7 is composed of a pair of primary coils 7 a and a pair of secondary coils 7 b, which are exciting coils, and is wound around the bobbin 6. These coils 7 are fixed in the radial direction by a yoke member 8 and fixed in the axial direction by a cover 9.
Yoke member 8 (first yoke member 8a, second yoke member 8
The b) is divided into two by the bobbin 6 and is assembled inside the main body A. A lip seal 11 is attached between the cover 9 and the bobbin 6 to maintain the sealing property.

In the assembly of the differential transformer displacement sensor, for example, the first yoke member 8a is first attached to the main body A and the bobbin 6 is housed. Next, the second yoke member 8b
Is attached between the bobbin 6 and the main body A. Finally, the cover 9 is attached to the opening of the main body A, and the sensor is axially fixed inside the main body A.

[Problems to be solved by the device]

However, in the differential transformer type displacement sensor according to the related art, since the leak cut rings 5a and 5b are attached to the magnetic core 5 fixed to the displacement member 10 and the sliding ring and the like are fixed, the structure is complicated and the cost is high. There was a drawback that

Moreover, since a plurality of parts must be assembled, productivity is poor and it is difficult to ensure accuracy.

Therefore, this device reduces the number of parts,
The purpose is to reduce costs and improve productivity.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a magnetic core that interlocks with a displacement member, a bobbin that accommodates the magnetic core slidably therein, and a magnetic core that is wound around the outer periphery of the bobbin according to the position of the magnetic core. A coil that outputs an electric signal, and a yoke member that is attached around the coil and that fixes the coil,
In a differential transformer type displacement sensor having a cover for accommodating the yoke member inside the main body, the displacement member is formed of a non-magnetic shaft that slides in a bobbin, and the magnetic core is formed of a cylindrical member that fits with the shaft. In addition, a convex portion whose tip is made of a sliding material is formed on the outer periphery at the center of the surface.

In this case, the displacing member may have a convex portion on the surface thereof, the convex portion having the tip portion as a sliding member, formed on the outer periphery.

Alternatively, the magnetic core may have convex portions at both ends.

Further, in the state where the magnetic core is fitted to the displacement member, the convex portion formed on the magnetic core and the convex portion formed on the displacement member are
It is possible to improve durability by disposing the magnetic cores at substantially the same distance from the center of gravity when the magnetic cores are fitted to the displacement member in the moving direction of the magnetic cores.

[Action]

Since the present invention is configured as described above, the sensor can be configured with the minimum required number of parts.

〔Example〕

An embodiment of a differential transformer type displacement sensor according to the present invention will be described below with reference to the accompanying drawings. In the description, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a sectional view showing the structure of the essential part of an embodiment of a differential transformer type displacement sensor according to the present invention. This example
Basically, it includes a magnetic core 12, a bobbin 13 with a cover, a coil 14, and a yoke member 15. The displacement member is composed of a nonmagnetic shaft 16 that slides in the bobbin. The shaft 16 has a convex portion 1 on its surface.
6a is formed on the outer circumference and is in a state of middle bulge. A sliding member a is formed on the tip of the convex portion 16a to improve the slidability with the inner surface of the bobbin. As a method of forming the sliding member a, there is Teflon coating, for example. The magnetic core 12 is formed of a cylindrical member into which the shaft 16 is press fitted. Furthermore, a convex portion 12a is formed on the outer periphery of the central portion of the surface, which is in a bulge state. A sliding member a is formed at the tip of the convex portion 12a to improve slidability with the inner surface of the bobbin.
As a method of forming the sliding member a, there is Teflon coating, for example. The bobbin 13 with a cover is configured to include a bobbin portion 13a around which a coil is wound and a cover portion 13b for sealing the opening of the main body B. Bobbin section 13
A coil 14 is wound around the outer peripheral portion of a.

In this case, since the bobbin portion 13a is formed in a substantially cylindrical shape with the coil 14 wound, the yoke member 15 formed in the cylindrical shape can be fitted in the axial direction.

In this embodiment, the convex portions 12a and 16a are formed on the magnetic core 12 and the shaft 16 one by one, but the convex portions may be formed on both ends of the magnetic core 12 or the shaft 16, for example.

Further, when the magnetic core is fitted to the displacement member, the convex portion formed on the magnetic core and the convex portion formed on the displacement member have a center of gravity when the magnetic core is fitted to the displacement member in the axial direction. The durability of the sliding member can be improved by arranging them at substantially the same distance from the position.

The shape, size, etc. of the bobbin 13 with the cover are not limited to those in the above embodiment. The important thing is that
A sliding member that slides on the inner surface of the bobbin is projected on the magnetic core and the displacing member, and accessory parts such as a leak cut ring and a sliding ring are unnecessary.

[Effect of device]

Since the present invention is configured as described above, the structure is simplified and the accuracy and reliability of the sensor can be improved.

Also, since the number of parts to be assembled is reduced, productivity is improved and cost can be reduced.

Furthermore, by disposing the magnetic core and the convex portion formed on the shaft at substantially the same distance from the center, the durability of the sensor can be improved.

[Brief description of drawings]

FIG. 1 is a structural sectional view of an essential part showing an embodiment of a differential transformer type displacement sensor according to the present invention, and FIG. 2 is a structural sectional view of an essential part showing a basic structure of a differential transformer type displacement sensor. Three
FIG. 4 is an explanatory view showing the basic principle of a differential transformer, and FIG. 4 is a sectional view showing the structure of the essential part of a differential transformer displacement sensor according to the prior art. 1, 10 ... Displacement member 2, 5, 12 ... Magnetic core 3, 6 ... Bobbin 4, 7, 14 ... Coil 8, 15 ... Yoke member 9 ... Cover 11 ... Lip seal 13 ... Cover Bobbin with 16 …… Shaft

Claims (4)

[Scope of utility model registration request] 1. A magnetic core that interlocks with a displacement member, a bobbin that accommodates the magnetic core slidably inside, and an electric signal that is wound around the outer periphery of the bobbin and that corresponds to the position of the magnetic core. In a differential transformer type displacement sensor having a coil, a yoke member mounted around the coil and fixing the coil, and a cover accommodating the yoke member inside the main body, the displacement member slides in the bobbin. The magnetic core is formed of a non-magnetic shaft, the magnetic core is formed of a cylindrical member that fits with the shaft, and a convex portion having a tip made of a sliding member is formed on the outer periphery in the center of the surface of the magnetic core. Differential transformer type displacement sensor. 2. The differential transformer type displacement sensor according to claim 1, wherein the displacement member has a convex portion formed on the outer surface thereof, the convex portion having a tip portion as a sliding member. 3. The differential transformer type displacement sensor according to claim 1, wherein the magnetic core has the convex portions at both ends. 4. A convex portion formed on the magnetic core and a convex portion formed on the displacement member in a state where the magnetic core is fitted to the displacement member, the displacement in the moving direction of the magnetic core. The differential transformer type displacement sensor according to claim 2, wherein the magnetic transformers are arranged at substantially equal distances from the center of gravity when the magnetic core is fitted to the member.