JPS62147987A - Positioning device - Google Patents

Abstract

PURPOSE:To enable the positions of high precision and high reliability to be determined, by changing the direction of the winding current of a motor with winding selection signal obtainable from the winding selection pattern of a scale moving according to the moving section of the motor. CONSTITUTION:To the permanent magnet 51 of the movable section of a brushless DC motor 2, the glass scale 11 of the movable section of an encoder 1 is mechanically connected. A detector assembly 12 is irradiated through an illuminant 36, and light passing the glass scale 11 is detected by light receiving units 31-35. From the light receiving units 31-35, the output of index signal, two phase position signal, and winding selection signal is generated, and with the signal, the scale and the direction of the current of the windings 52, 53 of the motor 2 are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a positioning device, and particularly to a positioning device for positioning a magnetic head of a magnetic disk drive.

[Conventional technology]

Conventionally, a voice coil motor, a stainless steel motor, or a brushed DC motor has been used as a drive source for the positioning device of a magnetic disk drive.

[Problem that the invention attempts to solve]

Positioning devices that use voice coil motors have the drawback of limited range of movement, and positioning devices that use step-by-step motors have poor positioning accuracy.
Moreover, there is a drawback that there is a limit to high-speed operation, and positioning devices using brushed DC motors have the drawback that reliability may be reduced due to wear of the brushes.

The object of the present invention is to provide a high-speed, highly reliable positionless device with unlimited movable range by using a -β phase winding type flangeless DC motor as a drive source in combination with a scale which is a position detector. shall be.

Means for Solving Problem 1] The positioning device of the present invention has a multi-phase winding type brushed DC motor, and the position of the movable part of this brushless DC motor (
a scale provided with a position signal pattern and a winding selection pattern for indicating the rotation angle of the movable part (including the rotation angle of the movable part), and a scale that moves relative to the scale in response to the movement of the movable part and the position signal pattern a position detector that outputs a position signal based on opposing portions of the scale; a winding selection detector that outputs a wire selection signal; a winding switching circuit that switches the direction of current in the winding of the flangeless DC motor in accordance with the winding selection signal; and a winding switching circuit that processes the position signal and generates an error signal. The winding switching circuit includes a servo circuit that supplies the winding switching circuit.

Embodiment Next, the present invention will be described with reference to the drawings. 6 FIG. 1 is a block diagram of the main parts of a positioning device using, as an example, a two-phase brushless DC motor equipped with an optical encoder. The encoder 1 consists of a disc-shaped glass school 11 and a detector assembly 12, and on the glass school 1,
The following three types of patterns are provided on concentric circles by combining transparent parts that transmit light and black parts that prevent transmission of light. One is an index signal pattern 21 indicating the starting point, the second is an incremental position signal pattern 22, 23 of two layers with a 90 degree phase difference, and the third is a two-phase winding selection of the brushless DC motor 2. This is Abnlute type winding selection signal pattern 24.25 for.

The detector assembly 12 is composed of a light emitter 36 and photoreceptors 31 to 35 that receive the light that has passed through the glass school 11.

The photoreceptors 31 to 35 each generate a signal corresponding to each pattern on the crow scale 11. That is, the photoreceptor 3
1 detects the Intex signal pattern 21 and outputs the index signal 41, and the photoreceptors 32 and 33 detect the two-phase position signal patterns 22 and 23 and output two-phase position signals 42°43. .35 detects the winding selection signal pattern 24.25 and outputs the winding selection signal 44°45.

The brushless DC motor 2 is composed of a four-pole permanent magnet 51 and two windings 52 and 53, and the permanent magnet 5 serves as a movable part.
1 and a glass scale 11, which is a movable part of the encoder 1, are mechanically coupled.

Windings 52, 53 are connected to power amplifiers 3, 4, respectively. Each power amplifier 3, 4 has a two-phase position signal 42.4
The error signal 61 processed through the servo analog circuit 6 which receives 3 as an input is used as an analog input signal, and the winding selection signal 44, 45 is used as a logic input signal to determine the winding selection, drive current polarity, and drive current amount. A drive signal is input from the circuit 5.

Next, the operation of the flangeless DC motor will be explained with reference to the timing diagram of FIG. Two layers 4 shown in Figure 1
When the pole brushless DC motor is rotated, each winding 52
．． The back electromotive force waveform generated at 53 is as shown in FIG. To drive a DC motor with such characteristics, it is necessary to flow a drive current in a region where the back electromotive force waveform is flat.

Winding selection signals 44, 45 shown in FIG. 2 are used to generate this timing. Winding selection signal 44 is “1”
” and the winding selection signal 45 is “O°”, a unidirectional current (-1> is passed through the winding 53, and the winding selection signal 44 is “1°”).
' When the winding selection signal 45 is also '1', a current (10 I) in the other direction is passed through the winding 52, and the winding selection signal 44 is '0' and the winding selection signal is '1'. When , a current (10r) in the other direction is passed through the winding 53, and when the winding selection signal 44 is "'0°" and the winding selection signal 45 is also "o", a current in one direction is passed through the winding 52. (-■) allows the brushless DC motor to generate torque in a fixed direction.

By changing the polarity of the drive current, the brushless DC motor can generate torque in the other direction.

The logic signal processing described above is performed by the winding switching circuit 5. The details of the logic circuit will be omitted for the time being as it is easy for a basic engineer.

The operation of the closed loop servo positioning device using the brushless DC motor 2 described above as a drive source will be described below. Photoreceptor 3 when rotating brushless DC motor 2
The signal 41 which is the output of the photoreceptor 32.33 has a waveform as shown in FIG. This is a sine wave signal as shown in .In a positioning device that positions a magnetic head, points PO, PI, P2, etc. at the center of the signal amplitude of the position signal 42, 43 are usually set as a positioning point chain as shown in the figure. The position signals 42 and 43 are used as positions corresponding to the tracks on the magnetic disk of the magnetic head.These position signals 42 and 43 are processed in the servo analog circuit 6 and input to the winding switching circuit 5 as an error signal 61. The brushless DC motor is driven with the current value and polarity according to the current value and polarity, forming a closed loop servo circuit.

Note that the glass scale 112, the light emitter 36, and the photoreceptor 3
The present invention is possible by using a magnetic encoder or the like instead of the optical encoder 1 consisting of 1-35. It may also be a linear g) scale that gives linear motion converted by a float or the like.

1゛Effects of the Invention) As explained above, the present invention allows the current direction of the windings of a multiphase winding type flangeless DC motor to be changed by changing the windings obtained by the winding selection pattern of the scale that moves in accordance with the movable parts of the motor. Switching using the line jx selection signal has the effect of realizing a highly accurate and optically reliable positioning device with no limit to the movable range.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
3A to 3C are waveform diagrams of the index signal 41 and position signals 42 and 43 shown in FIG. 1. FIGS. 1... Encoder, 2... Brushless DC motor,
3.4... Power amplifier, 5... Winding switching circuit, 6...
・Kale analog circuit, 11...Glass scale, 1
2...Detector assembly, 21...Index signal pattern, 22.23...Position signal pattern, 24.25
... Winding selection signal pattern, 31-35 ... Photoreceptor, 36 ... Light emitter, 41 ... Index signal, 4
2.43... Position signal, 44.45... Winding selection signal, 51... Permanent magnet, 52.53... Winding wire. Agent Patent Attorney Uchihara Former 1゛＼

Claims (1)

[Claims] A multi-phase winding type brushless DC motor, a scale provided with a position signal pattern and a winding selection pattern for indicating the position of a movable part of the brushless DC motor, and a scale that corresponds to the movement of the movable part. a position detector that moves relative to the scale and outputs a position signal based on opposing portions of the position signal pattern; and a position detector that moves relative to the scale in response to the movement of the movable part and selects the winding. a winding selection detector that outputs a winding selection signal based on a corresponding portion of a pattern; a winding switching circuit that switches the direction of current in the winding of the brushless DC motor in response to the winding selection signal; A positioning device comprising: a servo circuit that processes the position signal and provides an error signal to the winding switching circuit.