JPH0797898B2 - Voice coil type linear DC motor with linear magnetic encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voice coil type linear DC motor suitable for head feeding of a magnetic disk and having a linear magnetic encoder in which a linear magnetic encoder is reasonably built. .

(Technical field of the invention) The voice coil type linear DC motor has a relatively simple structure, and various magnetic flux types such as a uniform magnetic flux type, a uniform magnetic flux type, and a non-uniform magnetic flux type can be easily formed at a relatively low cost. It is often used in various devices such as an optical pickup mechanism for an optical disc, a tone arm driving device for a record player, etc.

Here, in this voice coil type linear DC motor, information on the movement of the mover, for example, information on the moving length of the mover, information on the moving speed of the mover,
It has become necessary to know information such as the position of the mover.

Furthermore, it has become necessary to move the voice coil type linear DC motor in various ways.

Such various movements can be performed by directly connecting the voice coil type linear DC motor and the encoder.

However, when a conventional encoder, particularly a rotary encoder, is directly connected, the voice coil type linear DC motor becomes very large and costly, and it is often limited depending on the applied device. .

Therefore, one of the inventors of the present invention previously disclosed a voice coil type linear DC motor having a linear magnetic encoder in Japanese Patent Application No. 59-11482 (Japanese Patent Laid-Open No. 60-156256).

However, in order to obtain a larger thrust, the voice coil type linear DC motor disclosed above is rod (cylindrical).
If the magnetic flux is designed to have a uniform magnetic flux shape, a part of the field magnet for driving the cylindrical linear DC motor (if all the magnets is used, a large amount of power cannot be obtained. It is desirable to make it part of a magnetic magnet)
In addition, the magnetic poles of the linear magnetic encoder must be formed by double magnetizing means.

When the linear magnetic encoder magnetic pole is formed in a part of the field magnet for forming the driving magnetic pole portion in this way, the magnetic flux of the field magnet is reduced due to the linear magnetic encoder magnetic pole, It becomes impossible to obtain a voice coil type linear DC motor having a linear magnetic encoder capable of obtaining a large thrust.

Alternatively, if the field magnet has a cylindrical shape, a linear magnetic encoder magnetic pole part should be formed by alternately magnetizing N and S magnetic poles along this longitudinal direction along the longitudinal direction at multiple fine pitches. Is an inconvenient voice coil type linear DC motor having a linear magnetic encoder which is very troublesome and not suitable for mass production.

Even if the linear magnetic encoder magnetic pole portion is not a rod type, the linear magnetic encoder magnetic pole portion is not strongly magnetized except that the magnetic flux of the field magnet is deteriorated as described above when the linear magnetic encoder magnetic pole portion is formed in the field magnet. When the magnetic pole portion is detected by the magnetic sensor, there is a drawback that a strong magnetic encoder signal cannot be obtained and a higher precision linear magnetic encoder cannot be obtained.

(Problems of the invention) The present invention has been made based on the above circumstances. (1) Any type of voice coil linear DC motor, including a cylindrical (rod type) voice coil linear DC motor Even if there is, a linear magnetic encoder can be easily and inexpensively incorporated therein, and a voice coil type linear magnetic encoder incorporating the linear magnetic encoder can be formed in a small size. (2) The linear magnetic encoder To facilitate the formation of a linear magnetic scale having magnetic poles, and (3) to strongly magnetize the magnetic encoder magnetic poles for the above-mentioned linear magnetic encoder so that a linear magnetic encoder with good performance can be formed. (4) Install a linear magnetic encoder that can take A-phase and B-phase signals in the voice coil type linear DC motor. By doing so, it is possible to obtain a voice coil type linear DC motor with a built-in propulsion speed / speed detection mechanism reasonably, and a compact and inexpensive linear magnetic encoder. (5) Moreover, the linear magnetic encoder is suitable for use. In position,
The purpose is to enable various controls such as forward / reverse running control, variable speed control, step drive control, and predetermined position stop control. Other purposes will be apparent from the description below.

(Means for Achieving the Object of the Invention) An object of the present invention is to provide a voice coil type linear DC motor in which a drive coil is movably supported by a center yoke in a magnetic field, and a magnetized body is provided in the center yoke along the longitudinal direction. A linear magnetic encoder magnetic pole having a plurality of N and S magnetic poles alternately arranged at a minute pitch along the moving direction of the drive coil on the magnetized body to form a linear magnetic scale on the center yoke. And forming a linear magnetic encoder in the voice coil type linear DC motor by disposing a magnetic sensor for detecting the N and S magnetic poles of the linear magnetic scale in the mover having the drive coil. Achieved by

(Embodiment of the Invention) (First Embodiment) With reference to FIGS. 1 to 4, a field coil double-sided type non-uniform magnetic flux type voice coil type linear DC motor 1 will be described.

This linear DC motor 1 is of a movable coil type, and a stator yoke 2 having a square cross section formed of a magnetic material such as an iron plate is closed at both ends by side yokes 3 also made of a magnetic material such as an iron plate. It has a magnetic circuit configuration that closes the magnetic path. On both sides 2-1 and 2-2 of the yoke 2,
Long plate-shaped field magnets 4 with N pole faces facing each other 4-
The field magnets 4-1 and 4-2 are used as a stator by fixing the 1,4-2 to each other by a method such as sticking.

The field magnets 4-1 and 4-2 have a third parallel
The center yoke 5 made of a magnetic material as shown in the figure forms guide rails for the drive coil 10 by fixing both ends of the center yoke 5 to the side yokes 3.

The center yoke 5 has a linear magnetic scale insertion groove 7 for accommodating and fixing the sheet-like linear magnetic scale 6 shown in FIG. 4 along the longitudinal direction on the side surface facing the field magnet 4-2. is doing.

As shown in FIGS. 1 and 2, the linear magnetic scale 6 is fixed in the linear magnetic scale insertion groove 7 by means such as insertion and attachment.

The linear magnetic scale 6 and a magnetic sensor 12 described later form a linear magnetic encoder.

In the linear magnetic scale 6, a sheet-shaped plastic magnet 8 is selected as a magnetized body. As shown in FIG. 4, a linear magnetic encoder magnetic pole is formed on the plastic magnet 8 by vertically magnetizing N and S magnetic poles alternately in the thickness direction by multi-pole magnetization in units of microns along the longitudinal direction. 9 is formed.

A drive coil 10 toroidally wound so as to have a rectangular frame cross section is inserted into the center yoke 5, and the drive coil 10 is movably supported along the longitudinal direction of the center yoke 5.

The drive coil 10 is a rectangular frame-shaped fluorine resin (for example, 4
It is wound on a bobbin 11 in the shape of a rectangular frame formed of ethylene fluoride, which has a trade name of Teflon.

The drive coil 10 wound around the bobbin 11 includes a magnetic sensor 12.

In providing the magnetic sensor 12 on the drive coil 10, it is necessary to enable the magnetic sensor 12 to detect the linear magnetic encoder magnetic pole 9 of the linear magnetic scale 6.

Therefore, in this embodiment, the field magnet 4 of the bobbin 11 is used.
-2, a magnetic substrate, such as an iron substrate 13, on which a printed power distribution pattern (not shown) is formed by etching means or the like is disposed on the surface facing -2, and the surface of the center yoke 5 of the iron substrate 13 facing the linear magnetic scale 6 A magnetic sensor 12 is provided in the.

In this case, the thickness of the magnetic sensor 12 is usually the iron substrate 13
Will be disposed away from the bobbin 11, but since this increases by the thickness of the magnetic sensor 12, in order to avoid this, the bobbin 11 has a through hole 14 for accommodating the magnetic sensor 12. The magnetic sensor 12 is formed so as to face the through hole 14, and the magnetic sensor 12 detects the linear magnetic encoder magnetic pole 9 of the linear magnetic scale 6.

The reason for using the iron substrate 13 is that the magnetic sensor 12 is affected by the strong magnetic flux of the field magnet 4-2.
This is to prevent the accurate detection of the magnetic pole 9 of the linear magnetic encoder and to magnetically shield the magnetic sensor 12 by using the iron substrate 13.

Therefore, in magnetically shielding the magnetic sensor 12,
Needless to say, if another method is used, a printed board made of a non-magnetic material may be used instead of the iron board 13.

The iron substrate 13 is formed by forming an insulating layer on the surface of an iron material and further forming the printed power distribution pattern on the surface of the insulating layer. Both terminals of the drive coil 10 are electrically connected to appropriate portions of the printed power distribution pattern by means such as soldering.

The output terminal of the magnetic sensor 12 is also electrically connected to the printed power distribution pattern of the iron substrate 13 by means such as soldering.

In the printed power distribution pattern of the iron substrate 13, lead wires (not shown) for controlling energization of the drive coil 10 and the magnetic sensor 12 are provided.
A lead wire (not shown) for guiding the magnetic encoder signal from is connected by soldering or the like.

As the magnetic sensor 12, a magnetic resistance element (MR element) is used to obtain two-phase encoder signals of A phase and B phase from this linear magnetic encoder.

This magnetoresistive element utilizes the effect of changing the electric resistance of the element when a magnetic field is applied.
Some use semiconductor magnetic resistance element of Sb,
In this embodiment, the magnetic sensor 12 uses a ferromagnetic magnetoresistive element having a high sensitivity in a low magnetic field, which is formed of Ni-Fe system or Ni-Co system as a main raw material.

This magnetoresistive element has a pattern of 1
Not only can the A-phase and B-phase encoder signals be easily obtained with a single element, but the Z-phase signal can also be obtained depending on the pattern forming method, which is extremely convenient.

As the magnetic sensor, a Hall element, a Hall IC, or a magnetic head, which is often used as a position detecting element of a brushless motor as a magnetoelectric conversion element, may be used.

However, in order to construct a linear magnetic encoder, A
In order to obtain the phase B and phase B signals, the two elements must be arranged so as to be shifted by an electrical angle of 90 degrees, which has the drawback of increasing the assembly and adjustment time.

Moreover, if the Z phase is required, a total of three magnetic sensors are required, and the above-mentioned drawbacks are further increased.

Furthermore, in order to obtain the linear DC motor 1 and the linear magnetic encoder with higher accuracy, the above-mentioned linear magnetic encoder magnetic pole 9 is formed by magnetizing the magnetic pole pitch of N and S to a fine width (for example, 50 μ pitch). , It is possible to arrange a plurality of magnetic sensors while aligning them with human intervals.
Very cumbersome, difficult and unsuitable for mass production.

Moreover, since the magnetic head is large and expensive, it is desirable to avoid this use if possible.

Therefore, in this embodiment, as the magnetic sensor 12, A phase, B phase
It is assumed that a magnetoresistive element that can obtain a phase signal even though it is a single element is used.

The voice coil type linear DC motor 1 of the first embodiment of the present invention has the above-mentioned configuration.

Therefore, the drive coil 10 is controlled by an energization control circuit (not shown).
The drive coil 10 reciprocates in the forward and reverse directions by passing a current in the forward and reverse directions.

When the drive coil 10 travels, the magnetic sensor 12 mounted on the iron substrate 13 fixed to the bobbin 11 that moves with it moves while detecting the linear magnetic encoder magnetic pole 9 of the linear magnetic scale 6. It is possible to know the information on the movement of the mover such as the position of the mover of the linear DC motor 1, the propulsion speed or the moving direction.

That is, by taking out a signal from the magnetic sensor 12 and controlling it by feeding back the signal, the linear DC motor 1 can be made to perform various movements and controls such as step driving like a linear step motor.

(Second Embodiment) FIG. 5 shows another center yoke 5'for showing a second embodiment of the present invention. One surface of this center yoke 5 '(for example, a field magnet 4-2 and The linear magnetic scale insertion recess 7'is provided only on the upper part of the facing surface.

(Third Embodiment) FIG. 6 is an explanatory view of a linear magnetic scale 6'for showing a third embodiment of the present invention. This linear magnetic scale 6'is formed on a plastic magnet 8 with an origin signal magnetized track 15 and a linear magnetic scale. An encoder magnetic pole track 16 is provided, and an N pole origin signal magnetizing portion 17 is formed at the end of the origin signal magnetizing track 15.

In this case, the origin signal magnetizing unit 17 may be magnetized and formed on the S pole.

The other portions of the origin signal magnetized track 15 except the origin signal magnetized portion 17 are non-magnetized portions.

The origin signal magnetizing section 17 may be formed on the other end of the origin signal magnetizing track 15.

In the linear magnetic encoder magnetic pole magnetizing track 16, as in the first embodiment, N and S magnetic poles are vertically magnetized along the longitudinal direction (note that horizontal magnetizing is preferable, but vertical magnetizing is It is preferable that the linear magnetic encoder magnetic pole 9'is magnetized.

18, 19 and 20 are Hall elements used as magnetic sensors, the Hall element 18 is for detecting the origin signal magnetizing portion 17, and the Hall element 19 is for obtaining an A-phase linear magnetic encoder signal. The Hall element 20 is for obtaining a B-phase linear magnetic encoder signal.

The Hall elements 19 and 20 are arranged on the iron substrate 13 while being shifted in the longitudinal direction by an electrical angle of 90 degrees.

It is not preferable to use the three Hall elements 18, ..., 20 in this way in order to obtain a high-precision linear magnetic encoder in practice, so if possible, as described in the first embodiment during mass production. It is desirable to use one magnetoresistive element having the same function as the three Hall elements 18 ,.

When this linear magnetic scale 6'is used, the magnetic sensors 19 and 20 forming the linear magnetic encoder detect the magnetic pole 9'for the linear magnetic encoder, so that the A phase and B phase are detected.
Since the two-phase signals of the phases are obtained, the traveling amount and traveling speed of the drive coil 10 can be determined, and the forward and reverse traveling can be performed. Further, since the magnetic sensor 18 and the origin signal magnetizing unit 17 are provided even if there is no position detecting element such as a Hall element or a Hall IC for energizing the drive coil 10 as in the conventional case, the magnetic sensor 18 is attached to the origin signal. A detection pulse obtained by the magnetic sensors 19 and 20 detecting the magnetic encoder magnetic pole portion 9'is detected by a counter with the time point when the magnetic portion 17 is detected as a reference point, and a predetermined pulse is obtained by using, for example, a pulse distributor. By appropriately supplying a signal to the drive coil 10 for each time, the drive coil 10 and the field magnets 4-1 and 4-2 can obtain thrust in a predetermined direction and move the drive coil 10 in the predetermined direction.

When the magnetic sensor 18 does not detect the origin signal magnetizing unit 17, for example, the drive coil 10 is supplied with a pulse current in a predetermined direction to drive the drive coil 10 in a predetermined direction, and the magnetic sensor 18 causes the origin to pass. The signal magnetizing unit 17 is detected.

When the magnetic sensor 18 detects the origin signal magnetizing unit 17, by operating the digital circuit including the counter as described above, a current in a predetermined direction is applied to the drive coil 10 by the digital circuit even without the position detection element. Since the power is supplied, the drive coil 10 can be run in a predetermined direction.

To reverse the traveling direction of the drive coil 10, the polarity of the polarity conversion circuit may be converted.

If the memory function circuit is provided, once the origin (origin signal magnetizing part 17) is stored, it is not necessary to search for the origin signal magnetizing part 17 from the next time, and always use the origin signal position as a reference. Since the counter operates, the drive coil 10 can be moved in the predetermined direction in the predetermined direction without performing the origin search at the same time as turning on the power supply to the drive circuit.

(Fourth Embodiment) FIG. 7 is an explanatory diagram of a linear magnetic scale 6 ″ used in a voice coil type linear DC motor as a fourth embodiment of the present invention.

In this linear magnetic scale 6 ″, unevenness 21 is formed along the longitudinal direction of the plastic magnet 8 at a fine pitch like the magnetic pole pitch of N and S of the linear magnetic encoder magnetic poles 9 and 9 ′.
Is formed, and one of the N pole and the S pole is magnetized on the surface of the irregularities 21.

Now, when the N pole is magnetized along the longitudinal direction on the concave and convex 21 surface, the concave and convex 21b of the plastic magnet 8 is strongly magnetized with the magnetic pole of the N pole, and the concave 21a is weakly magnetized with the N pole. Is magnetized.

In this case, the N ′ pole, in which the N pole is weakly magnetized in the recess 21a, is
In the magnetic circuit, since it is the same as when the S pole is actually magnetized, the surface of the irregularities 21 is substantially the same as the magnetic poles of N and S being alternately magnetized. A linear magnetic encoder 9 ″ similar to the above is formed.

(Fifth Embodiment) FIG. 8 is an explanatory diagram of a linear magnetic scale 6 ″ of a voice coil type linear DC motor as a fifth embodiment of the present invention.

In the linear magnetic scale 6 ″ shown in FIG. 8, in addition to the linear magnetic encoder magnetizing track 16 ″ similar to that shown in FIG. Upper part (still,
Origin signal magnetized track 1)
5 ′ is formed, and the origin signal magnetized portion forming projection 22 is formed at this end.
Is formed.

The remaining portion of the magnetic track 15 'except the convex portion 21 is a concave portion 23.

Incidentally, the linear magnetic encoder magnetic pole 9 ″ is provided on the convex portion 22.
Since the convex portion 21b is magnetized to the N pole, the convex portion 22 is magnetized to the N pole.

(Other Embodiments) In the linear DC motors in the above embodiments, the field magnets are arranged on both sides. However, the field magnets may be arranged on one side, a rod shape, or the like, and the stator yoke is surrounded by the surroundings. The structure may be such that a part of the structure is not closed but a part of the structure is opened.

Also, regarding the mounting structure of the magnetic sensor, it is not necessary to dispose it inside the drive coil as described above, and it is natural to adopt the optimum method according to the design specifications. It goes without saying that the present invention belongs to the present invention as long as it is not changed.

For example, there is a method of providing an iron substrate extending in the longitudinal direction and disposing a magnetic sensor on the iron substrate.

Further, regarding the linear magnetic scale, a sheet-shaped plastic magnet in which a linear magnetic encoder magnetic pole is multi-pole magnetized is fixed to the center yoke by means such as sticking, but the invention is not limited to this. .

For example, a magnetized layer such as a plastic magnet layer may be formed in advance on the center yoke, and a linear magnetic encoder magnetic pole may be formed on this magnetized layer.

It should be noted that as the magnetized body, an optimum one such as a rubber magnet, a ferrite magnet, a metal tape for magnetic recording may be selected.

(Effects) As is apparent from the above, the present invention (1) has the linear magnetic encoder formed in the center yoke, so that the traveling speed detection mechanism can be reasonably built in and the speed control is easy. Type linear DC motor can be inexpensively formed. (2) In the case of the voice coil type linear DC motor described in (1) above, the linear magnetic encoder used therefor can also be inexpensively formed. (3) Forward / reverse running of the linear DC motor Multi-function control such as control, variable speed control and pulse (step drive) control can be performed. (4) Since no position sensing element other than linear magnetic encoder is required, many leads for position sensing element as in the past Since there are no lines, the appearance is neat and it can be manufactured easily and cheaply. (5) By the double magnetizing means to the field magnet as in the past Unlike the case where the linear magnetic encoder magnetic pole part is formed, a linear magnetic scale is provided in the center yoke, and the linear magnetic encoder is formed with the magnetic sensor for detecting the linear magnetic scale. Since the linear magnetic encoder magnetic pole can be accurately detected by the magnetic sensor without being affected by the strong magnetic flux of the magnetic magnet, it is possible to form a linear magnetic encoder that can obtain a highly accurate linear magnetic encoder signal. 6) Since the center yoke is provided with the linear magnetic scale, the magnetic circuit configuration is different even in the case of a long stroke as compared with the case where the linear magnetic encoder magnetic pole is formed by the double magnetizing means in the conventional field magnet. It is extremely easy to form the magnetic pole of the linear magnetic encoder Kill. Therefore, an inexpensive linear magnetic encoder with various different shapes and high accuracy can be easily built in the voice coil type linear DC motor.
And so on.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a first embodiment of a voice coil type linear DC motor of the present invention, and FIG. 2 is a longitudinal sectional view of the same.
3 is a perspective view of the same center yoke, FIG. 4 is a perspective view of the same linear magnetic scale, FIG. 5 is a perspective view of the center yoke of the second embodiment of the present invention, and FIG. 6 is a third embodiment of the present invention. FIG. 7 is a perspective view of a linear magnetic scale of FIG. 7, FIG. 7 is a perspective view of a linear magnetic scale of a fourth embodiment of the present invention, and FIG.
It is a perspective view of the linear magnetic scale of an Example. (Description of symbols) 1 ... Voice coil type linear DC motor, 2 ... stator yoke, 2-1,2-2 ... side surface, 3 ... side yoke, 4-1,4-2 ... field magnet , 5,5 ′ …… Center yoke, 6,6 ′, 6 ″ …… Linear magnetic scale, 7 ……
Linear magnetic scale insertion groove, 7 '... Linear magnetic scale insertion recess, 8 ... Plastic magnet, 9, 9',
9 ″ …… linear magnetic encoder magnetic pole, 10 …… drive coil, 11 …… bobbin, 12 …… magnetic sensor, 13 …… iron substrate,
14 …… Through hole, 15,15 ′ …… Origin signal magnetized track, 16,1
6'Linear magnetic encoder magnetic pole magnetized track, 17 ... origin signal magnetized part, 18, 19, 20 ... Hall element (magnetic sensor), 21 ... unevenness, 21a ... concave part, 21b ... convex part, 22 ......
Origin signal magnetized part forming convex part, 23 ... concave part.

Claims (4)

[Claims] 1. A voice coil type linear DC motor in which a drive coil is movably supported by a center yoke in a magnetic field. A magnetized body is provided in the center yoke along the longitudinal direction, and the drive coil is attached to the magnetized body. A linear magnetic encoder magnetic pole having a plurality of N and S magnetic poles alternately arranged at a minute pitch along the moving direction of the magnetic pole is magnetized to form a linear magnetic scale on the center yoke. A voice coil having a linear magnetic encoder, in which a linear magnetic encoder is formed in the voice coil type linear DC motor by disposing a magnetic sensor for detecting the magnetic poles of S and S in the mover having the drive coil. Type linear DC motor. 2. The linear magnetic encoder, wherein a magnetic pole portion for a linear magnetic encoder having N and S magnetic poles alternately arranged at a fine pitch on the linear magnetic scale and an origin signal magnetization are formed by magnetization. A voice coil type linear DC motor having a linear magnetic encoder as set forth in claim (1), wherein a magnetic sensor for detecting a magnetic pole for magnetic pole and a magnetized portion of an origin signal is arranged on the mover. 3. The linear magnetic scale is characterized in that unevenness is formed at a fine pitch along the longitudinal direction, and the uneven surface is magnetized with an N pole or an S pole to thereby magnetize the uneven surface. A voice coil type having a linear magnetic encoder according to claim (1) or (2), in which a linear magnetic encoder magnetic pole having N and S magnetic poles is formed at a substantially fine pitch by Linear DC motor. 4. The magnetic sensor is magnetically shielded so as not to be affected by the magnetic flux of a field magnet for driving a voice coil type linear DC motor. A voice coil type linear DC motor having the linear magnetic encoder according to any one of 3).