JPH0339566B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to linear magnetic scales.

(Prior art and its problems) Recently, a magnetic linear scale using a magnetoresistive element (hereinafter referred to as MR element) as a detection element has been proposed (for example, Japanese Patent Application No. 1982-
095166).

The conventional linear magnetic scale described above is mounted by arranging the easy magnetization axis A of the MR element perpendicular to the magnetic writing direction and the hard magnetization axis C in the normal direction of the magnetic writing surface, as shown in Figure 1. It was designed to travel above magnetic material. The conventional magnetic scale described above has a drawback in that the distance between the magnetized body and the MR element fluctuates due to vibrations, etc., resulting in output fluctuations, which can cause measurement errors. For example, in the arrangement of the magnetized body and the MR element as shown in FIG. 1, the resistance change of the MR element is as shown by the solid line 5 in FIG. 2. However, while driving, the magnetized object and MR
If the distance between them changes, it will change as shown by the dotted line 6 in FIG. 2, making it impossible to make accurate measurements.

(Object of the Invention) An object of the present invention is to eliminate such conventional drawbacks and provide a linear magnetic scale that is resistant to vibration.

(Structure of the Invention) The present invention provides a bar-shaped magnetized body on which magnetic writing is performed with a predetermined width, or a bar-shaped non-magnetic body in which three or more of the bar-shaped magnetized bodies are arranged in the longitudinal direction of the outer peripheral surface thereof, and one magnetoresistive element having an axis of easy magnetization in a direction perpendicular to the longitudinal direction of the bar-shaped magnetized body and surrounding the outer periphery of the bar-shaped magnetized body or the bar-shaped non-magnetic body, with close spacing of This linear magnetic scale is characterized by a structure including a movable part that is arranged in-plane and movable along the longitudinal direction of the rod-shaped magnetized body.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-described configuration. That is, if the MR element 1 in Fig. 3 moves, for example, one side of the MR element moves away from the magnetized body 2, and the other side of the MR element approaches it. Therefore, the resistance of the MR element 1 becomes as shown in Fig. 4. It always changes. Furthermore, if magnetic writing is applied to all sides of the rod-shaped magnetized body, no problem will occur even if the MR element rotates or vibrates in the circumferential direction of the rod-shaped magnetized body. The C direction in FIGS. 1 and 3 is the next easiest axis to magnetize after the A direction, and the resistance value of the MR element changes depending on the degree of magnetization in the C direction. In Fig. 3, 3 is the magnetic flux, 7 is the lead wire, 4,
4' is a terminal.

Next, embodiments of the present invention will be described in detail.

Example Fig. 5 shows an MR on a Si substrate 9 on the end face of a cylinder 8 with a length of 30 mm finished with an inner diameter of 4.004 mm to 4.016 mm.
The element 1 arranged thereon was glued and fixed so that the distance from the center of the cylinder 8 to the MR element was 4.05±5 μm.

Next, a round bar 2 with a length of 300 mm finished with an accuracy of 3.988 mm to 4.000 mm in diameter is inserted into the cylinder,
The round bar was fixed. The round rod-shaped magnetized body has a coercive force of ~650 (De) and a residual magnetic flux density of ~3000 (G).
permanent magnetic material, S-N pole distance ~40μm
Magnetic writing is applied to the entire circumferential surface and in the length direction of the round bar-shaped magnetized body. Configure as above,
When the cylinder was slid and changes in the resistance of the MR element were continuously observed, the results were as shown by the solid line 10 in Figure 6.
A pulse-like resistance change was observed every 40 μm. Furthermore, Figure 7 shows the relationship between the travel distance of the MR element and the resistance change when a permanent magnet material with magnetic writing applied to the entire circumferential surface and in the length direction of the magnetized body with the S-N pole distance of ~20 μm is used. showed that.

Note that the rectangular waves indicated by solid lines 11 in FIGS. 6 and 7 are reference waves with intervals of 40 μm and 20 μm, respectively.

The magnetized body used in the present invention is as shown in FIG.
A thin magnetized body may be fixed or embedded in a non-magnetic substrate, but in this case, MR
Since the amount of resistance change of the element is small, the S/N ratio becomes poor.

Furthermore, in the magnetic scale of the present invention, if two MR elements are arranged with their phases shifted by λ/4 (λ is the distance between the S and N poles), the left and right movement directions can be discriminated.

As described above, it is clear that the magnetic scale of the present invention is suitable for applications involving large vibrations.

[Brief explanation of the drawing]

Figures 1a and 1b are diagrams showing conventional magnetic scales.
In the figure, 1 is the MR element, 2 is the magnetized body, 3 is the magnetic flux, and 4 and 4' are the terminals of the MR element. FIG. 2 is a diagram showing the rate of change in resistance when the MR element is run in the length direction of the magnetized body in the conventional magnetic scale. FIGS. 3a and 3b are diagrams showing a magnetic scale according to an embodiment of the present invention. In the figure, 7 indicates a lead wire that connects the MR. Figure 4 shows MR on the magnetic scale of the present invention.
FIG. 3 is a diagram showing a change in the rate of change in resistance when an element is run in the length direction of a magnetized body. FIG. 5 is a diagram showing a magnetic scale according to an embodiment of the present invention. 8 is a cylinder, and 9 is a Si substrate. FIG. 6 and FIG. 7 are diagrams showing the resistance change rate waveform and reference wave of MR. FIG. 8 is a diagram showing another embodiment of the present invention. 12 indicates a nonmagnetic substrate.

Claims (1)

[Claims] 1. A bar-shaped magnetized body on which magnetic writing is performed with a predetermined width, or a bar-shaped non-magnetic body in which three or more of the bar-shaped magnetized bodies are arranged in the longitudinal direction of the outer peripheral surface thereof, and a predetermined close interval is maintained between the bar-shaped magnetized body and the bar-shaped magnetized body, One magnetoresistive element having an axis of easy magnetization in a direction perpendicular to the longitudinal direction of the rod-shaped magnetized body is arranged in the same plane so as to surround the outer periphery of the rod-shaped magnetized body or the rod-shaped non-magnetic body. , and a movable part that is movable along the longitudinal direction of the rod-shaped magnetized body.