JPH061200B2 - Linear encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a linear encoder applied to detection of a moving distance, size, position, etc. of an object.

<Outline of the Invention> The present invention allows a cylindrical stator having spiral magnetic pole teeth on the inner peripheral surface and a guide shaft at the center of a cylindrical hole to be slidable with respect to the guide shaft via a slide bearing. It consists of a linear encoder with a moving element that has a plurality of magnetoresistive elements arranged at equal positions on the circumferential surface of a supported ring-shaped permanent magnet, and simplifies the structure and assembly work to realize cost reduction and resolution. It is an improved one.

<Prior Art> Conventionally, as this type of linear encoder, there is a contact type encoder such as a linear potentiometer, or an optical type encoder by combining an optical sensor and a slit. Since the potentiometer is configured to slide the resistor with a brush,
The reliability is poor, and increasing the resolution is limited by the influence of sliding noise. Further, in the case of the optical type, it is possible to increase the resolution by processing the scale with high accuracy, but this is one of the causes of cost increase, and the adhesion of dust to the scale surface reduces the light transmittance. Causes inconvenience.

<Object of the Invention> It is an object of the present invention to provide a novel linear encoder that solves the above problems and simplifies the structure to realize cost reduction and high resolution.

<Structure and Effect of the Invention> In order to achieve the above object, in the present invention, a cylindrical stator having a spiral magnetic pole tooth on the inner peripheral surface and a guide shaft arranged at the center of the cylindrical hole, and the guide. A linear encoder is configured by a moving element having a plurality of magnetoresistive elements arranged at equal positions on the circumferential surface of a ring-shaped permanent magnet slidably provided on a shaft through a slide bearing.

According to the above configuration, in the present invention, by arranging n magnetoresistive elements on the peripheral surface of the moving element, a linear encoder having a resolution of P / n (where P is the pitch of the magnetic pole teeth) can be easily configured. it can. In particular, the present invention is a general cutting process,
Since the stator can be processed by screw processing, the manufacturing cost can be reduced at low cost. In addition, compared with the optical linear encoder, inconveniences caused by dust and the like are eliminated, and practical effects that achieve the object of the invention are achieved.

<Description of Embodiments> FIG. 1 is a sectional view of an embodiment of a linear encoder according to the present invention. The linear encoder includes magnetoresistive elements 23a to 2a made of nickel alloy or the like, which are located at equal intervals on a circumferential surface of a cylindrical stator 1 having spiral magnetic pole teeth 11 formed on the inner surface thereof.
It is configured by disposing a moving element 2 having 3d. The stator 1 has spiral magnetic pole teeth 11 on its inner peripheral surface, and both end opening surfaces are closed by side plates 12 and 13, and both side plates 1
A guide shaft 14 is installed between 2 and 13 at the center of the cylindrical hole, and the mover 2 is supported by the guide shaft 14.

The mover 2 has a ring-shaped permanent magnet 22 magnetized in a radial direction with respect to a slide bearing 21 such as a linear bearing fitted in the guide shaft 14, and a plurality of magnets 2 at equal positions on the outer circumference of the permanent magnet 22. In the drawing, a cylindrical body 24 having thin-film magnetoresistive elements 23a, 23b, 23c, and 23d arranged at four places is fitted, and a predetermined gap 3 (50) is provided between the moving element 2 and the stator 1. About micron) is set.

A guide plate 25 extending in the direction of the guide shaft 14 is provided on the cylindrical body 24, and the guide plate 25 is projected from the opening of the side plate 12 to the outside of the stator 1 to take out an output signal.

FIG. 3 shows X in the gap 3 between the stator 1 and the mover 2.
4 shows the change in magnetic diametrical density in the direction, and 4 shows the lines of magnetic force.

FIG. 4 shows an example of the circuit configuration of the detector, and FIG. 5 shows an explanatory diagram of its output signal.

Next, the operation of the linear encoder of the present invention will be described.

As shown in FIG. 3 (a), the X component of the magnetic flux density between the magnetic pole teeth 11 of the stator 1 and the permanent magnet 22 of the mover 2 varies sinusoidally with the position X. On the other hand, the magnetoresistive element 23a
23 to 23d are those whose resistance value changes depending on the strength of the magnetic field. Since they are ferromagnetic thin film resistance elements made of nickel alloy,
As shown in FIG. 3 (b), it is output as a resistance change in a changing magnetic field. That is, the resistance value is output from each magnetoresistive element as a position signal. On the other hand, since the magnetic pole teeth 11 are spiral with a constant pitch P, they are 9 on the same circumference as shown in the figure.
When set at the 0 degree position, the screw phase is shifted by P / 4. Therefore, in FIG. 3, the magnetic flux density Bg is also the magnetoresistive element 23.
A phase shift of P / 4 occurs at the positions of a and 23b.

Similarly, 23a and 23c and 23b and 23d have a phase shift of P / 2.

If the bridge circuit configuration is used as shown in FIG. 4, the outputs 27a and 27b of the differential amplifiers 26a and 26b are the same as those shown in FIG.
As shown in (b), the signal is out of phase by P / 4,
Therefore, if the output signals 27a and 27b are input to a comparator or the like, the output signals of FIGS. 5 (c) and 5 (d) can be obtained.
A linear encoder having a resolution of P / 4 is constructed immediately.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a linear encoder according to the present invention, FIG. 2 is a vertical sectional view of a moving element, and FIG. 3 (a).
(b) is an explanatory diagram showing a change in magnetic flux density, FIG. 4 is a diagram showing a circuit configuration example of a detection unit, and FIGS. 5 (a), (b), (c), and (d) are explanatory diagrams of signal processing. . DESCRIPTION OF SYMBOLS 1 ... Stator 11 ... Magnetic pole tooth 14 ... Guide shaft 2 ... Mover 21 ... Sliding bearing 22 ... Permanent magnet 23a-23d ... Magnetoresistive solid element

Claims (1)

[Claims] 1. A cylindrical stator having spiral magnetic pole teeth on the inner peripheral surface thereof and a guide shaft disposed at the center of a cylindrical hole, and slidably supported on the guide shaft via a slide bearing. A linear encoder composed of a moving element having a plurality of magnetoresistive elements arranged at equal positions on the circumferential surface of a ring-shaped permanent magnet.