JPH1019603A - Magnetic encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the outer diameter vibration and stabilize the output by fixing a magnetic drum to a rotating shaft by a means such as press fitting, and remachining the outer diameter of the magnetic drum. SOLUTION: A rotating shaft 2 has a plurality of stepped parts on the outside of a hollow shaft hollowly formed. It has a bearing installing part 8 and an installing part for the magnetic drum 1. The magnetic drum 1 having a magnetic medium 4 fixed to the circumference is press fitted to the installing part of the magnetic drum 1 of the hollow shaft 2, and the circumferences of the bearing installing part 8 of the hollow shaft 2 and the magnetic medium 4 of the magnetic drum 1 are integrally machined on the same center to minimize the outer diameter vibration of the magnetic drum 1 to the bearing installing part 8. The cavity between the magnetic drum 1 and a MR (magneto-resistance effect) sensor is held constant, whereby the output is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder, and more particularly to a magnetic encoder having a high accuracy in the outer diameter of a magnetic drum.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view showing the configuration of a conventional magnetic encoder, in which 1 is a magnetic drum, 2 is a rotating shaft, 3 is a magnetic sensor having an MR element, 4 is a magnetic medium, Is a bearing, 6 is a circuit board, and 7 is a set screw.
In FIG. 3, a magnetic drum 1 having a magnetic medium 4 fixed to the outer periphery of a rotating shaft 2 supported by a bearing 5 is fixed with a set screw 7.
The magnetic sensor 3 is arranged to face the outer periphery of the magnetic drum 1 with a gap therebetween. The gap between the outer periphery of the magnetic drum 1 and the magnetic sensor 3 needs to be narrowed as the magnetization pitch of the magnetic drum 1 decreases, and the gap becomes narrower as the pulse becomes higher, and generally the limit is about 50 microns. is there.

FIG. 4 is an explanatory view for explaining a method of fixing the magnetic drum 1 to the rotating shaft 2. The magnetic drum 1 machined with an appropriate hole tolerance for the dimensional tolerance of the rotating shaft 2 is attached to the rotating shaft 2. A method of inserting and fixing with a set screw 7 is adopted.

[0004]

In the structure of the magnetic encoder according to the prior art shown in FIGS. 3 and 4, when the magnetic drum 1 is fixed to the rotating shaft 2 with the set screw 7, the rotation of the rotating shaft is slightly reduced. 2, the magnetic drum 1 tilts, and the outer diameter of the magnetic drum 1 fluctuates. It has been empirically obtained that this value is about 10 to 15 microns. For this reason, particularly in a high-pulse encoder, the ratio of the deflection to the gap between the magnetic drum and the magnetic sensor is large, which has a disadvantage that the output characteristics of the MR element are adversely affected and it is difficult to obtain a high-pulse encoder. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a high-pulse, high-precision magnetic encoder which suppresses the outer diameter fluctuation of a magnetic drum to a small value.

[0005]

According to the conventional method of inserting a magnetic drum into a rotating shaft and fixing it with a set screw, the bias of the magnetic drum is unavoidable due to the fitting dimensions as shown in FIG. As a result, the output characteristics are affected. In the magnetic encoder according to the present invention, the means for fixing the magnetic drum to the rotating shaft with a set screw is abolished, and instead of being inserted into the rotating shaft, the magnetic drum is press-fitted to the rotating shaft or fixed by means such as shrink fitting. In addition, the outer diameter of the magnetic drum is reworked to reduce the deflection of the outer diameter, and the gap between the magnetic drum and the MR sensor is kept constant so that a stable output can be obtained.

[0006]

FIG. 1 is a sectional view showing the structure of a magnetic drum of a magnetic encoder according to a first embodiment of the present invention.
After press-fitting a magnetic drum 1 having a magnetic medium 4 fixed on its outer periphery to a rotating shaft 2, the magnetic drum 1 is
The outer circumference of the magnetic drum is processed to reduce the outer diameter fluctuation of the magnetic drum. The precision in this case is finished to about 5 microns.

FIG. 2 is a sectional view showing the structure of a second embodiment of the magnetic drum of the magnetic encoder according to the present invention.
Is formed in a hollow shape, a plurality of steps are formed on the outer diameter of the hollow shaft, a mounting portion 8 for the bearing and a mounting portion for the magnetic drum are provided, and the magnetic medium 4 is fixed to the outer periphery thereof. After the drum 1 is press-fitted into the magnetic drum mounting portion of the hollow shaft 2, the bearing mounting portion 8 of the hollow shaft 2 and the magnetic drum 1
The outer periphery of the magnetic medium 4 is concentrically integrated into one piece and finished.
The outer diameter fluctuation of the magnetic drum 1 with respect to the bearing mounting portion is reduced. The precision in this case can be finished to 5 microns or less.

[0008]

Since the magnetic encoder according to the present invention has the above-described configuration, it is possible to reduce the fluctuation of the outer diameter of the magnetic drum with respect to the support shaft, thereby providing a high-pulse magnetic encoder.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a second embodiment of the magnetic drum of the magnetic encoder according to the present invention.

FIG. 3 is a cross-sectional view showing a configuration of a magnetic encoder conventionally implemented.

FIG. 4 is a cross-sectional view showing a coupling state between a magnetic drum and a shaft of a conventionally implemented magnetic encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic drum 2 Rotating shaft 3 Magnetic sensor provided with MR element 4 Magnetic medium 5 Bearing 6 Circuit board 7 Set screw 8 Bearing mounting part

Claims (2)

[Claims] A magnetic medium is fixed to an outer peripheral surface of a rotating body supported by a rotating shaft, and is opposed to a magnetic drum magnetized at a predetermined pitch on the magnetic medium via a gap. A magnetic sensor provided with a magnetoresistive effect element (hereinafter referred to as an MR element) on the surface thereof;
The change in resistance of the R element is converted into an electric signal,
In the magnetic encoder for detecting a position or the like, the outer peripheral surface of the magnetic drum is configured to obtain a high-precision predetermined dimension by finishing with reference to a bearing holding portion of the rotating shaft. Encoder. 2. A rotary shaft is formed in a hollow shape, and the magnetic drum is fixed to the hollow shaft, and an outer peripheral surface of the magnetic drum has a predetermined size with high precision by finishing with reference to a bearing holding portion of the hollow shaft. 2. The magnetic encoder according to claim 1, wherein the magnetic encoder is configured to obtain the following.