JPS59189500A - Magnetic type rotary encoder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magnetic rotary encoder, and in particular to an absolute type magnetic rotary encoder that reads a magnetoresistive element and is used as a sensor to obtain an output signal with a high I/)SZN ratio. The present invention relates to a rotary encoder (13-type rotary sensor).

[Background of the invention]

Generally, magnetic rotary encoders are used for various types of NC.
The rotation speed of motors used in machine tools, etc.

It has been widely adopted as a means of accurately measuring rotation angles, rotation angles, etc. This magnetic rotary encoder includes an incremental type encoder that measures only the rotation speed and rotation angle of the motor, and an absolute type encoder that can simultaneously measure the initial position where the motor starts. The present invention relates to the latter absolute type encoder. In addition, some absolute type encoders have only a means for generating pulse signals in response to rotation, and in addition to this, a separate pulse signal is generated once per revolution to clarify the reference point. There are two types: one equipped with means, and the present invention relates to the latter type, and the present invention implements this method magnetically.

FIG. 1 is a configuration diagram showing an example of an absolute type magnetic rotary encoder proposed by the inventors in recent years (unpublished). In the figure, a magnetic drum 4 having a magnetic recording medium 3 having a magnetic pattern magnetized at a constant pitch over the entire circumference is connected to a shaft 2 driven by a motor 1. He's talented.
A substrate 6 is placed on a support base 5 fixed to the housing of the rotating body.
is fixed. A thin film magnetoresistive element 7 is formed on the surface of the substrate 6, and faces the magnetic recording medium 3 on the circumferential surface of the magnetic drum 4 at a constant distance 8.

Figures 2(a) and (b) show the magnetic drum 4 shown in Figure 1.
FIG. 2 is an enlarged configuration diagram and a sectional view taken along line AA'. As shown in the figure, a magnetic recording medium is coated on the circumferential surface of a magnetic drum 4 in order to accurately measure the rotation speed, rotation angle, rotational drive reference point, etc. of the motor 1 (see Figure 1). 3, on the main surface, S-N or N- in the same direction as the drum axis direction.
8 magnetic poles are continuous in the circumferential direction, and multiple types of magnetic patterns with different lengths, widths, and widths are magnetized ψ to form 4 types of magnetic tracks 3a.
+3b+3c, 3d absolute track section 3A and one S-N in the direction orthogonal to the drum axis
Alternatively, a reference point track section 3B is provided in which a reference point magnet &3e is formed by magnetizing a magnetic pattern of N-8 magnetic poles.

The absolute track section 3A and the reference point track section 3B formed on the magnetic recording medium 3 in this way have, for example, an N-8 magnetic pole in the absolute 1-rack section 3^ as shown in the plan view in FIG. Magnetically sensitive parts R1, R2 and Rs, R4 are placed on the magnetized magnetic track 3a+3a'.
Magnetoresistive elements 7 utilizing the magnetoresistive effect, which are formed by connecting a stable power supply E to the magnetic drum 4, are disposed facing each other, and by rotating the magnetic drum 4, the magnetic tracks 3a, 3a' are magnetized and non-magnetized. Pulse signals are obtained from output terminals 7a and 7b by differential output of voltages corresponding to the magnetic regions.

However, according to the magnetoresistive detection method described above, in the magnetized structure of the absolute track section 3A and the reference point track section 3B formed on the magnetic recording medium 3, the magnetic pole is not magnetized. The area will also be used as a signal for differential output detection. In this case, if the non-magnetized region, which should not be magnetized, is magnetized by the external magnetic field for some reason, and an unnecessary magnetic pole P is formed as shown by the dotted arrow in Fig. 3, this region will become υ magnetized. The magnetic poles (unnecessary magnetic poles P) become magnetic noise, and therefore, the above-mentioned magnetic resistance detection method using differential output has the problem of not being able to obtain an output signal with a high S/N ratio. Since the non-magnetized region was also long in part 3B, the rate of occurrence of magnetic noise was particularly high.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above-mentioned problems, and its purpose is to eliminate magnetization problems that have existed in the magnetic recording medium in the absolute track section and the reference point track section of the magnetic recording medium. It is an object of the present invention to provide a magnetic rotary encoder which can remove unspecified magnetic noise and obtain an output signal with a high S/N ratio.

[Summary of the invention]

In order to achieve such an object, the present invention provides a magnetic recording medium in which the absolute track portion is magnetized with a magnetic pole in a direction perpendicular to the signal magnetic field, and the reference point track portion is magnetized with a magnetic pole in the direction perpendicular to the magnetic field for the signal. The effect of the previous history is removed by magnetizing the magnetic poles in opposite directions.

[Embodiments of the invention]

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

FIG. 4 is a side view showing an example of a magnetic drum related to the magnetic rotary encoder according to the present invention, and since the same symbols as in the previous figure represent the same elements, a description thereof will be omitted. In the figure, there are four magnetic tracks 3a on the magnetic recording medium 3.
13b13C93d are formed on the entire circumferential surface of the three absolute track parts in the direction perpendicular to the drum axis, that is, magnetic tracks 3 a + 3 b , 3 c ,
The N-8 magnetic pole 11 is magnetized in a direction perpendicular to the magnetization direction of 3d. In this case, the magnetic strength of the N-8 magnetic pole 11 is smaller than that of the signal magnetic pole, and the length of each magnetic pole in the circumferential direction is the magnetic sensing portion R1, R of the magnetic resistance element 7 described above.
2. Ra, R4 is formed with a size of about 1/2 or less of the long grass in the circumferential direction. Further, a reference point track portion 3B in which a magnetic pole 3e serving as a reference point is formed on a part of this magnetic recording medium 3.
A magnetic pole 12 is formed which is magnetized in a direction completely opposite to that of the magnetic pole 3e at the reference point. In this case, as in the case described above, the magnetic strength of this magnetic pole 12 is smaller than the magnetic pole 3e at the reference point as a signal magnetic pole, and the circumferential length of each magnetic pole is equal to the magnetic sensing part R1, R・z, R+s. , R4 has a dimension that is approximately 1/2 or less of the circumferential length of R4. Moreover, in this case, the magnetic poles 11.12 are the magnetic tracks 3a.
~3d, magnetized before forming the reference point magnetic pole 3e.

According to this configuration, by magnetizing the magnetic pole in a direction that is not detected by the magnetic resistance element before magnetizing the signal magnetic pole, it is possible to check the previous history of the unspecified magnetic pole before the signal magnetic pole is magnetized. Therefore, an output signal with extremely low magnetic noise and a high S/N ratio can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to secure an output signal with a high S/N ratio, so it is possible to put into practical use a magnetic rotary encoder with a high quality and reliable reference point and absolute signal. An extremely excellent effect can be obtained.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams for explaining an example of an absolute type magnetic rotary encoder that has been proposed in recent years (unpublished), and Figure 4 shows an example of a magnetic rotary encoder according to the present invention. FIG. 3 is a side view of a main part of the magnetic drum. 1φ fist...motor, 2@...shaft, 3.-. φ battle・Magnetic recording medium, 3 people @φ...Absolute track section 313-e...Reference point track section, 3a13a
', 3b13C, 3d @ @ * @ Magnetic trunk, 3e...Magnetic pole of reference point, 4...Magnetic drum, 5...Support, 6...Substrate, 7... Φ・Magnetic resistance element, 7 a + 7 b・・φ・Output terminal, 8・
- Coma/interval, 11, 12...magnetic pole. -Fig. 2 (a) (b) -5 (3)- Fig. 3 Fig. 4 1t jOjCjD jG

Claims (1)

[Scope of Claims] 1. An absolute track portion having a signal magnetic track formed by magnetizing a magnetic pole in the same direction as the drum axis on a magnetic recording medium formed on the circumferential surface of a magnetic drum; , a magnetic rotary encoder comprising a reference point track portion formed by magnetizing a magnetic pole serving as a reference point in the same direction or perpendicular direction to the drum axis, wherein the magnetic track of the absolute track portion is The non-magnetized area other than the drum shaft is magnetized with a magnetic pole in a direction perpendicular to the drum axis, and the reference point track portion is magnetized with a magnetic pole in a direction opposite to the reference point magnetic pole. type rotary encoder. 2. The magnetic pole formed in the absolute track section in a direction perpendicular to the drum axis and the magnetic pole formed in the reference point track section in the opposite direction have a magnetic strength smaller than that of the signal magnetic pole and a length of the magnetic pole. 2. The magnetic rotary encoder according to claim 1, wherein the length of the magnetically sensitive part of the magnetoresistive element is 1/2 or less.