JPH0651820U - Magnetic encoder - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the output fluctuation of the magnetic sensor due to temperature change. [Structure] A magnetic sensor 40 is fixed to an inner wall of a hollow cylindrical sensor base 10 made of a magnetic material. Inside the sensor base 10, a rotatable magnetizing drum 20 is arranged. The magnetizing drum 20 includes a cored bar 21 having a hollow bottomed cylindrical shape, a shaft section 22, and a magnetic recording section 30 provided on an outer peripheral surface of the cored bar 21. Since the material of the cored bar 21 is a magnetic material such as S45C like the sensor base 10, it is possible to suppress the variation of the gap length L due to the temperature change. Therefore, it is possible to prevent the output fluctuation of the magnetic sensor due to the temperature change.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetic encoder, and more specifically, by using a magnetic material for the core bar on the surface of which a magnetic recording portion is arranged, as in the sensor base, the gap length between the core bar and the magnetic sensor can be reduced. The present invention relates to a magnetic encoder that can reduce temperature changes.

[0002]

[Prior art]

 A magnetic encoder is, for example, a cylindrical sensor base, a magnetic sensor mounted on the inner wall of the sensor base, a core bar rotatably mounted inside the sensor base, and a side surface of the core bar. The magnetic sensor detects the magnetic flux emitted from the magnetic recording unit and detects the rotation angle of the core metal. In the conventional magnetic encoder, a non-magnetic material such as aluminum or stainless is mainly used as the material of the core metal. On the other hand, as the material of the sensor base, a ferromagnetic material such as iron was used for the purpose of magnetic shielding.

[0003]

[Problems to be solved by the device]

 However, in the conventional magnetic encoder, the material of the cored bar is a non-magnetic material different from the material of the sensor base, and the difference in thermal expansion coefficient between the two causes the cored bar and the inner wall of the sensor base to change due to temperature changes. Distance will change. That is, the temperature change changes the distance (gap length) between the magnetic sensor and the magnetic recording portion on the surface of the core metal, and the output signal of the magnetic sensor becomes unstable. As a result, it has been difficult to accurately detect the rotation angle of the core metal.

[0004]

[The purpose of the device]

 Therefore, the present invention aims to prevent the output fluctuation of the magnetic sensor by suppressing the change in the distance (gap length) between the core metal and the sensor base due to the temperature change.

[0005]

[Means for Solving the Problems]

 A magnetic encoder according to a first aspect of the present invention includes a rotatable cored bar, a magnetized magnetic recording unit disposed on the surface of the cored bar, and a magnetic recording unit located at a predetermined distance from the magnetic recording unit. In a magnetic encoder provided with a sensor and a sensor base made of a magnetic material and supporting the magnetic sensor, the core metal is made of a magnetic material.

[0006]

[Action]

 In the magnetic encoder according to the first aspect of the present invention, the material of the core metal is the same magnetic material as the material of the sensor base. Therefore, even if the ambient temperature changes, the core metal and the sensor base also expand and contract, and the distance from the magnetic sensor to the core metal becomes substantially constant regardless of the temperature change. Therefore, it is possible to accurately detect the rotation angle of the magnetizing drum by suppressing the fluctuation of the output of the magnetic sensor due to the temperature change.

[0007]

【Example】

 Hereinafter, a magnetic encoder according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a magnetic encoder according to a first embodiment of the present invention. In the figure, reference numeral 10 is a sensor base, which is made of an iron-based magnetic material (ferromagnetic material). The sensor base 10 has a hollow cylindrical shape with a bottom, and a magnetic sensor 40 including a magnetoresistive element or a Hall element is fixed to the inner wall thereof. For example, the magnetoresistive element is made of NiFe or the like and detects a change in magnetic flux as a resistance change. The output signal of the magnetic sensor 40 is output as a voltage signal via a differential amplifier circuit (not shown).

A rotatable magnetizing drum 20 is arranged inside the sensor base 10. The magnetizing drum 20 includes a cored bar 21 having a hollow bottomed cylindrical shape, a shaft section 22, and a magnetic recording section 30 provided on the outer peripheral surface of the cored bar. A shaft portion 22 is arranged at an axial position of the cored bar 21, and the cored bar 21 is rotatable around the shaft 22. The material of the cored bar 21 is an iron-based magnetic material (for example, S45C) as in the sensor base 10. The magnetic recording unit 30 is configured by applying a magnetic material to the outer peripheral surface of the cored bar 21, and is magnetized in positive and negative directions at predetermined intervals in the circumferential direction. The distance (gap length L) between the magnetic recording unit 30 and the magnetic sensor 40 is about several hundred μm.

FIG. 2 is a perspective view of the cored bar 21 and the like. FIG. 2A shows the cored bar 21 and the magnetic recording portion 30 applied to the outer peripheral surface thereof. The magnetic recording unit 30 is configured by attaching magnetic powder to the outer peripheral surface of the cored bar 21 together with an adhesive. The thickness of the magnetic recording section 30 is preferably 100 μm or more. As shown in (B) of the figure, the cored bar 21 may be press-fitted into the opening of the media ring 301 made of an iron-based magnetic material (for example, Fe-Cr-Co alloy). In this case, the inner diameter of the media ring 301 may be larger than the outer diameter of the cored bar 21 by about 1%.

In the magnetic encoder configured as described above, when the magnetizing drum 20 rotates, the magnetic flux density received by the magnetic recording unit 30 from the magnetic sensor 40 changes, and the magnetic sensor 40 outputs a pulse or sinusoidal signal. Is output. The rotation angle of the magnetizing drum 20 can be detected based on this output signal.

According to the magnetic encoder of the present embodiment, since the material of the cored bar 21 is an iron-based magnetic material like the material of the sensor base 10, each of the cored bar 21 and the sensor base 10 is Similarly, it expands and contracts due to temperature changes. That is, the distance (gap length L) from the magnetic sensor 40 fixed to the inner wall of the sensor base 10 to the cored bar 21 is substantially constant regardless of the temperature change. Therefore, the fluctuation of the output voltage of the magnetic sensor 40 due to the temperature change is suppressed, and the rotation angle of the magnetizing drum can be accurately detected. In addition, since S45C and the like are easier to manufacture and process than non-magnetic materials such as stainless steel, there is an advantage that the cost of the cored bar 21 can be suppressed.

FIG. 3 is a graph showing the characteristics of the output voltage (Vpp) of the magnetic sensor 40 with respect to the gap length L for each material (S45C, aluminum) of the cored bar 21. As can be seen from this graph, even if the material of the cored bar 21 is changed from aluminum to a magnetic material such as S45C, the output voltage of the magnetic sensor 40 does not decrease. Note that this graph was created with the output voltage of the magnetic sensor 40 at a gap length L of 150 μm being 100% and the thickness of the magnetic recording portion 30 being 100 μm.

FIG. 4 shows the envelope of the magnetic sensor with respect to the gap length L (deviation of the output voltage of the magnetic sensor 40 in one rotation of the magnetizing drum 20) for each material (S45C, aluminum) of the cored bar 21. It is a graph. As can be seen from this figure, even if the material of the cored bar 21 is changed from aluminum to S45C, the characteristic of the envelope of the magnetic sensor 40 does not deteriorate. Similar to the graph of FIG. 3, this graph is created with the magnetic recording portion 30 having a thickness of 100 μm.

The material of the cored bar 21 is not limited to S45C, and may be of any type as long as it is the same magnetic material as the sensor base 10.

[0016]

[Effect of device]

 As described above, in the magnetic encoder according to the present invention, the material of the core metal is the same magnetic material as the material of the sensor base. Therefore, even if the ambient temperature changes, the core metal and the sensor base also expand and contract, and the distance (gap length) from the magnetic sensor to the core metal becomes substantially constant regardless of temperature change. Therefore, the rotation angle of the magnetizing drum can be accurately detected by suppressing the fluctuation of the output of the magnetic sensor due to the temperature change.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic encoder according to an embodiment of the present invention.

FIG. 2 is a perspective view of a cored bar and the like according to an embodiment of the present invention.

FIG. 3 is a graph showing the characteristics of the output voltage of the magnetic sensor with respect to the gap length according to one embodiment of the present invention, for each material of the cored bar.

FIG. 4 is a graph showing an envelope of a magnetic sensor with respect to a gap length according to an embodiment of the present invention, for each material of a cored bar.

[Explanation of symbols]

10 sensor base, 21 core metal, 30 magnetic recording unit,
40 magnetic sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Miki Akira Miki 10-1 Nakazawa-machi, Hamamatsu-shi, Shizuoka Yamaha Stock Company (72) Masayoshi Yamashita 10-1 Nakazawa-machi, Hamamatsu-shi, Shizuoka Yamaha Stock Company

Claims (1)

[Scope of utility model registration request] 1. A rotatable cored bar, a magnetic recording section disposed on the surface of the cored bar and magnetized, a magnetic sensor located at a predetermined distance from the magnetic recording section, and a magnetic material made of a magnetic material. A magnetic encoder including a sensor base that supports a sensor, wherein the core metal is made of a magnetic material.