JPH078720U - Rotary encoder - Google Patents

Abstract

(57) [Abstract] [Purpose] The pulse disc is also used as a shield to prevent noise from entering the detection circuit and reduce detection error. The conductive grid pattern 2 of the pulse disk 1 is always electrically connected to the signal ground 20b of the printed circuit board 20 through the relay member 7, so that noise from the drive motor 11 as a noise source is shielded. It is possible to prevent noise from entering the detection circuit of the printed circuit board 20 by flowing from the pulse disc 1 to the signal ground 20b.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rotary encoder, and more particularly to a rotary encoder that prevents a detection signal from being affected by noise from the outside.

[0002]

[Prior art]

 Usually, the encoder is mounted on the rotary shaft of the drive motor of the NC machine tool, and the rotary shaft is mounted on the rotor of the drive motor, and the magnetic fields generated by the multiple stators around the rotor have a phase difference, whereby the rotor is rotated. The rotation axis also rotates by the rotation of. In order to make the magnetic field of the drive motor have a phase difference, it is necessary to control the electric power supplied from the motor power supply, and the control method is performed by a waveform signal such as the switching frequency. This control method is generally called PWM (Pulse Width Modulation) control.

When the encoder is attached to the drive motor using this control method, the switching frequency affects the light receiving unit and the signal processing unit via the housing of the encoder as inductive noise, causing a detection error. It was a factor.

In a conventional encoder, in order to prevent a detection error due to noise, a ground line (hereinafter referred to as a signal ground) of a printed circuit board built in the rotary encoder and a metal portion (hereinafter referred to as a frame ground) of a rotary encoder housing are referred to. A configuration was adopted in which common mode noise was eliminated by directly connecting and, and letting noise from the case flow into the signal ground.

[0005]

[Problems to be solved by the device]

 However, when the signal ground and the frame ground are directly connected and the encoder is attached to the rotary shaft of the drive motor of the NC machine tool, the following problems occur.

That is, the induced noise is very strong noise, and the strong noise enters the detection circuit from the signal ground, and a reverse voltage is applied to the detection circuit. Instead of preventing the detection error, the detection circuit is destroyed. There was a possibility to do.

The present invention has been made in view of such circumstances, and its problem is a rotary encoder capable of removing noise even when strong noise is applied to the signal ground and the frame ground and preventing a detection error. Is to provide.

[0008]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, a rotary encoder according to a first aspect of the present invention rotates by a motor, and a pulse disc having a pattern of a predetermined pitch formed in the circumferential direction, and one of the pulse discs sandwiching the pulse disc. A light emitting section arranged on the other side, and a light receiving section arranged on the other side so as to sandwich the pulse disc and receiving the light emitted by the light emitting section through the slit, and the light received by the light receiving section on the pulse disc. In the rotary encoder having a signal processing unit for converting into a rotation amount, the pulse disc is arranged between the motor and the signal processing unit, and the pattern is formed of a conductive material. A common pattern formed on the pulse disc and connected to the pattern; and a relay unit electrically connecting the common pattern and the signal ground of the signal processing unit. A.

The rotary encoder according to the second aspect of the present invention is rotated by a motor, and a pulse disc having a light transmission pattern of a predetermined pitch formed in the circumferential direction, and one side so as to sandwich the pulse disc. A light emitting section arranged and a light receiving section which is arranged on the other side so as to sandwich the pulse disc and receives light emitted from the light emitting section through the slit; and the light received by the light receiving section of the pulse disc. In a rotary encoder having a signal processing unit for converting into a rotation amount, the pulse disc is arranged between the motor and the signal processing unit, and a portion other than the light transmission pattern is made of a conductive material. Relay means for electrically connecting the conductive material of the pulse disc and the signal ground of the signal processing unit.

Further, in the rotary encoder according to the third aspect of the present invention, the pulse disc is made of a conductive material, and the light transmission pattern is a slit provided in the pulse disc. .

[0011]

[Action]

 Since the grid pattern of the pulse disc or the conductive metal film is always in conduction with the signal ground of the signal processing unit via the relay member, noise from the drive motor, which is the noise source, is transmitted from the pulse disc as a shield means. It is possible to prevent noise from flowing into the signal ground and entering the signal processing section.

[0012]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a rotary encoder according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view showing a connecting portion between a pulse disc and a rotary shaft, and FIG. 3 is an enlarged perspective view of the pulse disc. Is.

The rotating shaft 8 is attached to the rotor 12 (magnet) of the drive motor 11, and the PWM control causes the magnetic fields generated from the plurality of coils 13 around the rotor 12 to have a phase difference. The rotary shaft 8 also rotates. The rotating shaft 8 is rotatably supported by bearings 16 and 17 attached to a motor housing 14.

As shown in FIG. 3, a metal lattice pattern 2 is vapor-deposited at a constant pitch along the circumferential direction on the upper surface of the transparent glass pulse disk 1. In addition, an electrical conducting portion 9 made of an annular metal is vapor-deposited on the central portion of the upper surface of the pulse disk 1, and the electrical conducting portion 9 is connected to the grid pattern 2 via the conducting path 10.

The pulse disc 1 is attached to a metal rotary shaft 8 via an insulator 18, and the rotation of the rotary shaft 8 also rotates the pulse disc 1. As shown in FIG. 2, a recess 8a is provided on the upper end surface of the rotary shaft 8, an insulator 18 is fitted in the recess 8a, and the pulse disk 1 is joined to the insulator 18 by a metal screw 30. There is.

A printed circuit board 20 is arranged above the pulse disk 1, and the printed circuit board 20 is attached to the pulse disk facing surface 14 a of the motor housing 14 via a column 19. A light source 3 such as a light emitting diode is provided on the pulse disk facing surface 14a of the motor housing 14 and is arranged to face a part of the grid pattern 2 of the pulse disk 1. A light receiving element 5 (for example, a silicon photodiode or the like) facing the light source 3 is provided on the pulse disk facing surface 20a of the printed board 20.

The signal ground 20b of the printed circuit board 20 and the electrical conducting portion 9 of the pulse disc 1 are electrically conducted via a relay member 7 such as a brush or a slip ring. The brush 7 is connected to the signal ground, and the tip of the relay member 7 is slidably in contact with the electrical conducting portion 9 of the pulse disc 1.

The light from the light source 3 is applied to the pulse disc 1, and the light transmitted through the pulse disc 1 is received by the light receiving element 5 and photoelectrically converted, and the detection signal is output from the light receiving element 5.

When the pulse disc 1 is rotated by the rotation of the rotary shaft 8, the tip of the relay member 7 is in sliding contact with the electrical conduction portion 9 of the pulse disc 1, and the grid pattern 2 Since the signal ground is always conducted through the relay member 7, the noise from the coil 13 as the noise source is flown from the pulse disc 1 as the shield means to the signal ground 20b, and the detection circuit (signal Prevent noise from entering the processing unit. Therefore, it is possible to prevent a detection error without destroying the detection circuit.

In the above-mentioned embodiment, the case where the pulse disk 1 is formed by vapor-depositing the metal grid pattern 2 on the upper surface of the transparent glass along the circumferential direction at a constant pitch has been described. A metal disk with slits at a constant pitch to form a grid pattern, or a metal film on the entire upper surface of transparent glass is vapor-deposited, and slits or transmissive parts are provided at a constant pitch along the circumferential direction. It is also possible to use a grid pattern to form a grid pattern.

[0022]

[Effect of device]

 As described above, according to the rotary encoder of the present invention, since the grid pattern of the pulse disk or the light-shielding conductive film is always electrically connected to the signal ground of the signal processing unit via the relay member, the noise source drive motor. It is possible to prevent noise from flowing from the pulse disk as a shield means to the signal ground and to prevent noise from entering the signal processing unit, and prevent detection errors without destroying the signal processing unit.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a rotary encoder according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a connecting portion between a pulse disc and a rotary shaft.

FIG. 3 is an enlarged perspective view of a pulse disc.

[Explanation of symbols]

 1 pulse disk 3 light source 2 lattice pattern 5 light receiving element 7 relay member 9 electric conduction part 10 conduction path 11 drive motor 20 printed circuit board

Claims (3)

[Scope of utility model registration request] 1. A pulse disc, which is rotated by a motor and has a pattern of a predetermined pitch formed in the circumferential direction, a light-emitting portion arranged on one side so as to sandwich the pulse disc, and the pulse disc is sandwiched. And a signal processing unit arranged on the other side so as to receive the light emitted by the light emitting unit through the slit, and a signal processing unit for converting the light received by the light receiving unit into the rotation amount of the pulse disk. In the rotary encoder, the pulse disc is disposed between the motor and the signal processing unit, the pattern is formed of a conductive material, is formed into the pulse disc, and is connected to the pattern. A rotary encoder, comprising: a common pattern; and a relay unit electrically connecting the common pattern and a signal ground of the signal processing unit. 2. A pulse disc, which is rotated by a motor and in which a light transmission pattern of a predetermined pitch is formed in the circumferential direction, a light emitting unit arranged on one side so as to sandwich the pulse disc, and the pulse disc. A light receiving unit disposed on the other side so as to sandwich the light receiving unit that receives the light emitted by the light emitting unit through the slit, and a signal processing unit that converts the light received by the light receiving unit into the rotation amount of the pulse disk. In the rotary encoder provided, the pulse disc is disposed between the motor and the signal processing unit, and a portion other than the light transmission pattern is formed of a conductive material, and the pulse disc is formed of a conductive material. A rotary encoder comprising a relay unit electrically connecting the signal ground of the signal processing unit. 3. The rotary encoder according to claim 2, wherein the pulse disc is made of a conductive material, and the light transmission pattern is a slit formed in the pulse disc.