JP2023163096A - rotary encoder - Google Patents

Abstract

To solve the problem in which: conventionally, a magnetic detection type rotary encoder needs to alternately magnetize N poles and S poles in a divided manner on a magnet substrate created in a ring shape; magnets themselves are thus increased in size and strongly affected by a centrifugal force and the like due to rotation, and the entire structure is increased in size to withstand such forces; the magnets are difficult to be arranged at precise positions, and a manufacturing cost tends to be increased.SOLUTION: In place of ring-shaped magnets, general-purpose magnets are arranged in a ring shape so that surfaces facing each other have the same polarity. A Hall IC with a latch function is mounted on a sensor unit to eliminate the presence of the boundary between poles in the gap, if any, between the magnets, and the Hall IC can maintain its output until the boundary of poles in the next magnet. The magnets do not need to be adhered to each other. The combination of small-size magnets can form a magnet disk. Consequently, a rotary encoder can be reduced in size and formed at an inexpensive price.SELECTED DRAWING: Figure 7

Description

The present invention relates to a rotary encoder that is attached to a brushless DC motor or other rotating body and detects its rotational position.

Conventionally, optical encoders or magnetic encoders have been used to detect the rotational position of a motor. Among these, the magnetic detection type is comprised of a magnetic disk that rotates together with a rotating body and a sensor unit that detects the magnetic disk.

In order to clarify the detection position of a magnetic detection type encoder, it was necessary to configure the integrated magnet in a ring shape and arrange it around the rotation axis. Therefore, a holder disk is required to attach the integrated magnet to the motor rotor.

The magnetic disk rotates together with the rotating body, and in order to detect its rotational position, it is necessary to accurately grasp the position of the polar boundary (hereinafter referred to as zero cross point) of the magnet. The magnet is circular and has a structure that makes it difficult to accurately determine the polarity position. Therefore, it was necessary to attach the magnet to the holder disk and then magnetize it. Furthermore, it is difficult to reduce the size of the annular magnet.

It is necessary to have a structure in which the attached annular magnet does not shift or fall off due to centrifugal force due to rotation, inertial force, impact force in the axial direction, etc. Therefore, the holder disk needs to be of sufficient size.

It is difficult to miniaturize the rotary encoder device itself, and it also becomes expensive.

The same effect can be obtained by replacing the annular magnet (31b) with a general-purpose simple rectangular magnet (6) (hereinafter referred to as "general-purpose magnet").

Attach the general-purpose magnet (6) to the designated position on the holder disk (5a). As shown in FIG. 7, the general-purpose magnets are arranged in an annular shape so that the opposing surfaces have the same polarity. By arranging them in this way, the spaces between the general-purpose magnets have the same polarity, and the zero-crossing point to be determined exists only in the middle of the general-purpose magnets.

The Hall IC (4b) mounted on the sensor unit (4) can detect this zero cross point. If a Hall IC with a latch function reads this boundary, the Hall IC will maintain its output state until the next zero-crossing point, even if there is a gap with an adjacent general-purpose magnet.

As shown in Figure 7, general-purpose magnets are basically placed at the same position on the circumference, but as shown in Figure 8, general-purpose magnets must be placed at a level where the Hall IC does not deviate from the zero cross point. The effect can be maintained.

For these reasons, by replacing the magnets constituting the rotary encoder with inexpensive general-purpose magnets, performance equivalent to that of annular magnets can be ensured, and the entire device can be downsized and manufactured at low cost.

An example constructed using a conventional annular magnet. A view in the direction of arrow A in FIG. 1. Magnetic disc (exploded view). Circular magnet polar pattern. (There is no polarity display or polar boundary display on the magnet itself.) Example of the present invention. Magnetic disk of this invention (exploded view). Magnet layout diagram of this invention. (There is no polarity indication or polar boundary indication on the magnet itself.) Magnet arrangement diagram of the present invention (example where they are not arranged on the same circumference) General purpose magnet diagram. Magnetic flux density pattern diagram of annular magnet Magnetic flux density pattern diagram of this invention

The present invention is built into a brushless DC motor, and is used to detect the rotational position of a rotor and control the rotational status of the rotor. Similarly, by incorporating it into equipment that requires rotation control, it can be used as an inexpensive and compact detection device.

1 Brushless DC motor 1a Motor housing 1b Rotor 1c Shaft 2a Motor cover 2b Motor cover mounting bolt 3 Magnet disc 31a Holder disc 31b Annular magnet 4 Sensor unit 4a Sensor board 4b Hall IC
4c Sensor board mounting screw 4d Hall IC center locus 5 Magnet disk 5a Holder disk 6 General-purpose magnet 6a General-purpose magnet polarity boundary (the magnet itself does not have "N" or "S" polarity markings or polarity border markings) )
7a Zero cross point 7b Zero cross point

Claims (1)

In a magnet detection type rotary encoder, multiple general-purpose simple rectangular magnets are used instead of the annular magnet to be detected, and by arranging adjacent magnets so that the same polarity faces each other, it is possible to achieve the same or higher performance. A rotary encoder characterized by having the following functions.

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