JPH10201216A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency by providing a magnetic sensor to read magnetic information of a magnetized section for position detection and also providing a magnetic shield member to shield the magnetic flux from magnetized portion for drive to such magnetic sensor. SOLUTION: A rotor 2 is provided with a magnetic sensor 3 to detect magnetic information of the magnetized section 12 for position detection of a stator 1 in such a manner as being opposed to the magnetized section for position detection. The magnetic sensor 3 is surrounded and covered, to shield the magnetic flux from the magnetized section 12 for drive, by four sheets of magnetic shield members 41 formed integrally from the four surfaces crossing orthogonal the detecting surface of magnetic sensor. The rotor 2 is controlled for drive based on the magnetic information of the magnetized section 12 for position detection read by the magnetic sensor 3 driven together with the rotor 2. A detected signal of the magnetic sensor 3 can be used for position detection, velocity detection, position control and velocity control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a linear motor, and more particularly to a linear motor having a magnetic encoder used for position detection, speed detection, position control, speed control, and the like.

[0002]

2. Description of the Related Art Linear motors are used to linearly move articles and members in a wide range of fields, such as OA equipment such as copiers, image scanners and printers, XY tables, FA equipment such as article transporters, and optical equipment such as cameras. It is used to move to. Such a linear motor usually includes an encoder for position detection, speed detection, position control, speed control, and the like of the moving article or the like. When the encoder is of a magnetic type, the encoder usually has a magnetized portion in which N-poles and S-poles are alternately arranged at a fine pitch linearly in the moving direction of an article or the like. A magnetic sensor for detecting magnetic information. In a field in which it is necessary to drive an article or the like with high precision position control and speed control, for example, in the field of the OA equipment, the encoder information detected by the magnetic sensor has a small measurement error and has high accuracy. It is required that there be.

Therefore, for example, Japanese Patent Application Laid-Open No. 7-107706 describes
In the publication, as shown in FIG. 13A, the driving magnetized portion 951 and the position detecting magnetized portion 952 are set so that the offset fluctuation of the output waveform of the position detecting sensor 96 is within 38%. A driving magnet 95 provided side by side with a distance, a driving coil 97 provided facing the driving magnetized portion 951, and a position detecting magnetic sensor 96 provided facing the position detecting magnetized portion 952, Teaches linear motors with In this publication, the driving magnetized portion 951 and the position detecting magnetized portion 952 are separated and juxtaposed so that the offset fluctuation of the output waveform of the position detecting sensor 96 is within 38%. It teaches that the detection magnetized portion 952 is prevented from being interfered by the drive magnetized portion 951. The fact that the offset fluctuation is within 38% is shown as a limit value for accurately performing position detection. Further, it teaches that the driving magnetized portion 951 and the position detecting magnetized portion 952 are provided alongside and integrated with the driving magnet 95, so that a simple structure can be achieved.

[0004] Japanese Patent Application Laid-Open No. Hei 7-181601 discloses that
Coil type mover (not shown) as shown in FIG.
And a magnet-type stator 91 slidably penetrating the coil-type mover and extending in the moving direction of the driven body. A part of the magnet-type stator 91 is provided with a magnetic shield 92 interposed therebetween. A magnetic scale 93 for detecting a linear position is provided, and a magnet-type stator 91, a magnetic shield part 92 and a magnetic scale 93 are integrated to form a guide shaft 90 for a carrier of a driven body. It teaches a linear motor provided with a magnetic sensor 94 for a magnetic scale that reads out positional information from 93. According to this publication, according to this linear motor, since the magnet type stator 91 and the magnetic scale 93 are integrated and used via the magnetic shield part 92, both are formed as an integral body by the interposed magnetic shield part 92. In this case, no magnetic interference occurs, and the magnetic scale magnetic sensor 94 teaches that the signal from the magnetic scale 93 can be detected without being affected by the strong magnetic field of the magnet-type stator 91.

[0005]

However, in the linear motor taught in Japanese Patent Application Laid-Open No. 7-107706, the offset fluctuation of the output waveform of the position detecting magnetic sensor 96 must be within 38%, for example, approximately 38%. Figure 13
As illustrated in (B), the driving magnetized portion 951 can be formed only on the half surface of the driving magnet 95 on the side facing the position detecting magnetized portion 952. FIG.
(B) is a diagram showing a magnetic flux distribution in the circumferential direction of the driving magnet 95, and the position detecting magnetized portion 952 is 0 ° in the drawing.
At the center.

Therefore, the driving magnet 95 in which the driving magnetized portion 951 and the position detecting magnetized portion 952 are formed is magnetized with a sufficient magnetic force with respect to the magnetic force that the material of the driving magnet can have. Is not provided, and thereby the driving magnetized portion 951
The thrust generated by the interaction with the driving coil 97 that is energized becomes small, and the linear motor becomes inefficient. In addition, the portion of the driving magnet 95 that contributes to the generation of thrust is biased to approximately half of the driving magnet 95 having the driving magnetized portion 951.
As a result, the accuracy at the time of driving deteriorates.

In a linear motor taught by Japanese Patent Application Laid-Open No. Hei 7-181601, as shown in FIG. 14B, a magnetic shield is provided on an end face of a magnet type stator 91 with which a magnetic shield portion 92 is in contact and in the vicinity thereof. Since the portion 92 forms a magnetic path, it is possible to prevent magnetic interference with the magnetic scale 93 by the magnetic force of the magnet-type stator 91, but considering the magnetic field in a wider range, as shown in the figure, A part of the magnetic force diverging from 91 also reaches the magnetic scale 93, and deteriorates the detection accuracy by the magnetic sensor 94.
In addition, some of the paths reaching the magnetic scale 93 pass through the magnetic sensor 94, so that the detection accuracy is further deteriorated.

In general, the magnetic pitch of a magnetic scale is reduced and the magnetizing force is reduced. Therefore, a magnetic sensor for detecting information on the scale generally has a gap with the magnetic scale of several tens μm. In the linear motor shown in FIG. 14, the magnetic scale 93 is composed of three parts so as to be held by the magnet type stator 91 via the magnetic shield 92. Therefore, in order to accurately detect the scale information with the magnetic sensor 94, these components require high processing accuracy and assembly accuracy over the entire length in the longitudinal direction. In addition, the number of parts is increased, resulting in higher costs.

Accordingly, the present invention provides a stator having a driving magnetized portion and a position detecting magnetized portion and extending in a fixed direction, and an armature coil facing the driving magnetized portion. A linear motor having a movable element that can move along the movable element and a magnetic sensor that moves together with the movable element and reads magnetic information of the magnetized portion for position detection, the magnetic information being detected by the magnetic sensor. Can be highly accurate, and can be a more efficient linear motor that generates higher thrust than conventional linear motors.Moreover, it is easier to process and assemble than conventional linear motors, It is an object to provide an inexpensive linear motor.

[0010]

According to the present invention, there is provided a stator having a driving magnetized portion and a position detecting magnetized portion which are spaced apart from each other and extending in a predetermined direction; A mover having an armature coil facing the drive magnetizing section and movable along the stator, and a magnetic sensor moving with the mover and reading magnetic information of the position detecting magnetizer And a magnetic shield member for shielding the magnetic sensor from the magnetic flux from the driving magnetized portion is provided.

[0011] The driving magnetized portion may include N
The magnetic poles and the S poles are alternately magnetized at a predetermined pitch along the longitudinal direction of the stator (the moving direction of the mover). The position detecting magnetized portion is formed by magnetizing the stator member with N poles and S poles alternately at a predetermined fine pitch along the longitudinal direction of the stator.

It is considered that the stator is typically a shaft having a circular cross section. In order to suppress the interference of the magnetic flux from the driving magnetized portion with the position detecting magnetized portion, the drive magnetized portion and the position detecting magnetized portion are required to have an offset variation of the output signal of the magnetic sensor. Is within 38% (more preferably, within 30%) of the peak-to-peak value of the output signal.
It is desirable to be separated so that

The magnetic sensor is a magnetic sensor using a magnetoresistive element.
An R sensor and a Hall sensor using a Hall element can be exemplified. A typical example of the magnetic shield member is a member formed of a ferromagnetic material such as iron and silicon steel. According to the linear motor of the present invention, when the armature coil of the mover is energized, a thrust is generated by the interaction with the driving magnetized portion of the stator, and the mover moves along the stator longitudinal direction (the fixed direction). Driven. At this time, the magnetic sensor is driven together with the mover, and the position detection, speed detection, position control, speed control, etc. of the mover can be performed based on the magnetic information from the position detecting magnetized section detected by the magnetic sensor. it can. Since the magnetic sensor is shielded from the magnetic flux from the driving magnetized portion by the magnetic shield member, the detection signal of the magnetic sensor has high accuracy in which the interference of the magnetic flux from the driving magnetized portion is suppressed.

Further, according to the linear motor of the present invention, since the magnetic shield member is provided, if the shield member is not provided, the driving magnetized portion and the position where the offset fluctuation becomes larger than 38%. Even if an arrangement close to the detection magnetizing section is adopted, the accuracy of magnetic information detection by the magnetic sensor is maintained at a high level, and the range of the driving magnetizing section can be increased by such close arrangement. A mover thrust can also be obtained.

The magnetic shield member includes, for example,
It is conceivable to arrange and form as follows. The magnetic shield member is disposed before and after the magnetic sensor in the moving direction of the mover. This arrangement
MR with directionality that can easily sense magnetic force as a magnetic sensor
This is particularly effective when a sensor is employed. The magnetic shield member is disposed so as to surround a detection surface of the magnetic sensor facing the magnetized portion for position detection from a peripheral outer side. This arrangement is effective regardless of the type of the magnetic sensor. At least one of the magnetic shield members has an edge extending in a direction transverse to the moving direction of the mover facing the stator, and the edge of the magnetic shield member is formed at the end of the stator. The shape follows the cross-sectional contour of the portion facing the edge. With this configuration, the magnetic flux from the driving magnetized portion is prevented from flowing to the magnetic sensor. The magnetic shield members are arranged at least before and after the magnetic sensor in the moving direction of the mover, and each magnetic shield member before and after the magnetic sensor is formed so as to become thinner as it goes away from the magnetic sensor.
By doing so, cogging is suppressed, and the driving accuracy of the motor is improved accordingly. The magnetic shield member is disposed at least in front of and behind the magnetic sensor in the mover traveling direction, and the end of each magnetic shield member before and after the magnetic sensor, which is farther from the magnetic sensor in the mover traveling direction, It is formed obliquely to the traveling direction. By doing so, cogging is suppressed, and the driving accuracy of the motor is improved accordingly.

It is also conceivable that the shape of the stator is as follows, for example. At least one of the stators along the longitudinal direction of the stator;
The plane is formed as a plane. For example, a shaft-shaped stator in which a part of a shaft-shaped stator having a circular cross section is cut so as to form a plane along the longitudinal direction, a shaft-shaped stator having a polygonal cross-section, or the like can be considered. In this case, when the magnetized portion for position detection is magnetized on the plane, the gap between the magnetic shield member and the magnetized portion for position detection can be reduced, whereby the magnetic flux from the magnetized portion for driving is transmitted to the magnetic sensor. As a result, the accuracy of the detection signal of the magnetic sensor increases. Two grooves are formed in the stator along the longitudinal direction of the stator. In this case, the magnetized portion for position detection is magnetized between the two grooves, and the magnetized portion for driving is magnetized on a portion other than the magnetized portion for position detection, and serves as the magnetic shield member. A device is provided that enters the inside of the groove so that it can move along the groove. In this way, the magnetic force of the driving magnetized portion is prevented from wrapping around the position detecting magnetized portion, and the accuracy of the detection signal of the magnetic sensor is increased accordingly.

The arrangements, shapes, etc. of the magnetic shield members and stators described above may be used in combination.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a linear motor according to one embodiment of the present invention. This linear motor L
DMa is a shaft-type linear motor in which a mover 2 is externally fitted to a shaft-shaped stator 1 having a circular cross section.

The stator 1 has an N-pole and an S-pole along a longitudinal direction of a shaft member 10 having a circular cross-section and having a circular cross section formed of a machineable and magnetizable material having a smooth surface. A drive magnetized portion (so-called field magnet) 11 alternately magnetized at a pitch of 30 mm, and N poles and S poles are alternately magnetized at a pitch of 200 μm in this example along the longitudinal direction. The position detecting magnetized portion (so-called encoder chart) 12 is formed by magnetizing.

Drive magnetizing section 11 and position detecting magnetizing section 12
Is formed on the peripheral surface of the shaft member 10 at a distance as described later and magnetized. The mover 2 has an armature coil 21 composed of a plurality of ring-shaped coils u, v, w that are fitted to the stator 1 with a gap therebetween.
The armature coil 21 is supported inside a mover yoke 22 made of a cylindrical magnetic material. Mover yoke 22
Bearings 23 are provided at both ends of the movable member 2. The movable member 2 is guided by the stator 1 by the bearing 23 and can move smoothly. The coils u, v, and w of the armature coil 21 are arranged at positions shifted by 2π / 3 in electrical angle (they may be in the same phase as the position shifted by 2π / 3). Is a hall element hu which is a kind of magnetoelectric conversion element as a propulsion sensor, a hall element hv is similarly provided for a v-phase coil, and a hall element hw is similarly provided for a w-phase coil. It is provided.

A magnetic sensor 3 for detecting magnetic information of the position detecting magnetized portion 12 of the stator 1 is attached to the mover 2 so as to face the position detecting magnetized portion 12. ing. The magnetic sensor 3 is an MR sensor using a magnetoresistive element in this example. Note that a Hall sensor using a Hall element may be used. If the distance between the magnetic sensor 3 and the position detecting magnetizing section 12 is too wide, the gain of the output signal of the magnetic sensor 3 needs to be increased. Are arranged at a position of 50 μm.

The magnetic sensor 3 includes four magnetic shield members 4 integrally formed from four surfaces orthogonal to the detection surface of the magnetic sensor in order to shield magnetic flux from the driving magnetized portion 12.
It is surrounded and covered by 1. The magnetic shield member is
It is made of a ferromagnetic material such as iron and silicon steel. If the thickness of the shield member 41 is about 1 mm, the above-described shielding effect can be achieved.

The distance between the driving magnetizing section 11 and the position detecting magnetizing section 12 depends on the offset fluctuation of the output waveform of the magnetic sensor 3 when the magnetic shield member 41 is provided. The distance is set so as to be within 38% of the above. In this example, the distance is set to be approximately 38%. In the above-described linear motor LDMa according to the present invention, when the armature coil 21 is energized, the mover 2 is driven in the longitudinal direction of the stator 1 due to the interaction with the magnetic field by the drive magnetizing section 11. At this time, the drive of the mover 2 is controlled based on the magnetic information of the position detecting magnetized portion 12 read by the magnetic sensor 3 driven together with the mover 2. Magnetic sensor 3
Can be used for position detection, speed detection, position control, speed control, and the like.

Here, the operation control of the linear motor LDMa will be briefly described. As described above, the driving magnetized portion 11 of the stator 1 is magnetized so as to have a magnetic flux density distribution having one cycle of the N pole and the S pole. Also, as already mentioned,
The armature coil 21 of the mover 2 is composed of three-phase coils u, v, w arranged at positions shifted by 2π / 3 in electrical angle (the positions may be in phase with the position shifted by 2π / 3). And the mover 2 has Hall elements hu, hv, h
w is provided. In this example, the Hall element detects the magnitude and direction of the magnetic flux of the driving magnetized portion 11 at that position. The motor is operated by supplying a current of a magnitude and direction corresponding to the magnitude and direction of the magnetic flux detected by these Hall elements to the coil. That is, here, a so-called three-phase drive system is adopted, and a signal whose phase is shifted by 120 degrees is input to the coil, so that a constant thrust is obtained regardless of the position of the mover 2. Here, in addition to employing the three-phase driving method, a phase synchronization control method generally called a PLL is employed to drive the mover 2 at a target speed.

FIG. 2 is a schematic block diagram of a motor drive unit 5 for driving a linear motor.
a and the encoder E are shown. Note that the encoder E
Is composed of a magnetic sensor 3, a position detecting magnetizing section 12, a circuit (not shown) for amplifying an output signal of the magnetic sensor 3 and shaping the waveform. In FIG. 2, 510 is a DC power supply, 520 is an energization control circuit section including the above-described Hall element, etc., E is an encoder for detecting the position and speed of the mover 2, and 530 is a speed control section using a phase synchronization control method. It is.

FIG. 3 shows a main part of an operation control circuit including a speed control circuit based on the phase synchronization control method. In FIG. 3, a microcomputer 532 instructs a predetermined operation of the linear motor and outputs a reference clock signal to the phase synchronization control unit 535.
1, an input / output port, 533 is an amplifier, 534 is a switching unit, 535 is a phase synchronization control unit, 536 is a compensation circuit,
521 is an amplifier circuit.

According to the motor drive unit 5 shown in FIGS. 2 and 3, a reference clock signal corresponding to a target speed is input from the computer 531 to the phase synchronization control unit 535, and the moving speed of the movable element 2 is The signal is fed back to the control unit 535. The phase synchronization control unit 535 outputs a signal corresponding to the difference between the frequency of the pulse of the reference clock and the frequency and phase of the pulse of the feedback signal from the encoder E, and compensates for the advance / delay of the transmission system by the compensating circuit 536. Is the reference input voltage of the Hall element. As described above, the Hall element outputs a voltage corresponding to the magnitude and direction of the magnetic flux at a certain position, and the output voltage has a characteristic proportional to the reference input voltage. Therefore, an output voltage corresponding to the difference between the reference clock signal and the feedback signal is output from the Hall element. The output voltage from the Hall element is proportionally amplified by the amplifier circuit 521 and is supplied to the armature coil. As described above, the frequency and phase of the pulse of the reference clock and the pulse of the feedback signal are matched, in other words, the linear motor LDMa is operated so as to match the target speed of the mover 2.

FIG. 4 shows that the drive magnetizing section 11 and the drive magnetizing section 11 have the offset variation of the output waveform of the magnetic sensor 3 within 38% of the peak-to-peak voltage with the magnetic shield member 41 provided as described above. An example of the magnetic flux distribution in the circumferential direction of the stator 1 when the position detecting magnetized portion 12 is separated from the magnet is shown. Note that the position detecting magnetized portion 12 is formed at a position of 0 ° in the figure.

As shown in FIG. 4, in the linear motor of the present invention, since the magnetic sensor 3 is surrounded by the magnetic shield member 41, the offset fluctuation of the magnetic sensor 3 is 38%.
Even if the magnetization is within the range, the magnetic force can be entirely increased as compared with the magnetic flux distribution of the conventional linear motor shown in FIG. 13B, and the generated thrust can be increased accordingly. Can be. With the same motor configuration, it is possible to obtain a thrust about 1.5 times or more as compared with the conventional motor.

Even if the magnetizing magnetic flux of the driving magnetizing section 11 is increased, the offset signal of the detection signal of the magnetic sensor 3 can be suppressed to within 38% as shown in FIG. it can. FIG. 5A is an example of the output waveform of the magnetic sensor 3 of the linear motor according to the present invention in the magnetic flux distribution of FIG. This is because the driving magnetized portion 11 and the position detecting magnetized portion 12 are formed apart from each other, so that the magnetic interference of the driving magnetized portion 11 with the position detecting magnetized portion 12 is reduced. This is because the suppression and the provision of the magnetic shield member 41 suppress the interference of the magnetic force wrapping around the space from the driving magnetized portion 11, whereby the position can be detected with high accuracy ( See FIG. 6).

For reference, FIG. 5B shows an output signal of a magnetic sensor (using an MR sensor) when the magnetic shield member is not provided in the magnetic flux distribution of FIG. FIG.
As shown in (B), if there is no magnetic shield member, the offset fluctuation of the output signal is large (close to 100% in some cases), and the signal is partially not output in some cases. From such an output signal of the magnetic sensor, highly accurate position detection or the like cannot be performed. This indicates that the magnetic shield member 41 of the present invention sufficiently suppresses interference from the driving magnetized portion 11.

Further, as compared with the conventional linear motor shown in FIG. 14, the linear motor of the present invention magnetizes the shaft member 10 for driving and position detection, so that the number of parts can be reduced and the cost is reduced accordingly. And the magnetic sensor 3
In order to maintain the gap width between the stator 1 and the magnetized portion 12 for position detection over the entire length of the stator 1 in the longitudinal direction, only the shaft member 10 needs to have dimensional accuracy over the entire length in the longitudinal direction.
Processing is also easier than conventional ones.

The shape, arrangement, etc. of the shield member are not limited to those surrounding the four surfaces of the magnetic sensor 3 as shown in FIG. Hereinafter, other examples of the shape, arrangement, and the like of the shield member will be sequentially described with reference to FIGS. Each of the linear motors shown in FIGS. 7 to 10 has a stator 1 and a mover 2 similar to those shown in FIG. 1. The stator 1 has a driving magnetized portion 11 and a position. The magnetized portion for detection 12 is magnetized so as to be separated from the magnetized portion for detection. Each of the movers is not shown, and the magnetic sensor 3 is attached to the mover and moves together with the mover.

The magnetic shield members 42 of the linear motor LDMb shown in FIG. 7 are arranged on two front and rear surfaces in the moving direction of the magnetic sensor 3 (the longitudinal direction of the stator 1). This configuration is particularly effective when an MR sensor is used as the magnetic sensor 3. This is because the MR sensor has a direction in which the magnetic force can be easily sensed, and in general, the MR sensor is arranged so that the direction in which the MR force is easily sensed is aligned with the moving direction of the mover. By providing the magnetic shield members 42 on the front and rear surfaces, it is possible to suppress the interference of the magnetic flux wrapping around from the driving magnetized portion 11 in that direction, and the output signal of the magnetic sensor 3 is highly accurate. Become.

The magnetic shield member 43 in the linear motor LDMc shown in FIG. 8 surrounds four surfaces around the magnetic sensor 3 and has an edge portion facing the stator 1 of each shield member 43 before and after the sensor in the moving element moving direction. 431 is
The stator 1 is formed in a shape that follows the cross-sectional contour of a portion facing the shield member 43. By doing so, although the shape of the magnetic shield member 43 is complicated, the gap formed between the magnetic shield member 43 and the stator 1 can be reduced, so that the magnetic flux from the driving magnetized portion 11 It becomes difficult to wrap around the sensor 3, and the output signal of the magnetic sensor 3 becomes highly accurate accordingly.

The magnetic shield member 44 in the linear motor LDMd shown in FIG. 9 surrounds the four surfaces of the magnetic sensor 3 so that the shield members 44 before and after the sensor in the mover moving direction become thinner as the distance from the sensor 3 increases. Is formed. This is because, in a linear motor, cogging occurs due to fluctuations in magnetic attraction acting on the end in the traveling direction, and the driving accuracy of the motor deteriorates. Is formed, magnetic saturation is likely to occur at its tip, cogging can be suppressed, and the driving accuracy of the motor can be improved accordingly.

The magnetic shield member 45 in the linear motor LDMe shown in FIG. 10 surrounds the four surfaces of the magnetic sensor 3 and the end of the shield member 45 before and after the sensor that crosses the mover moving direction in the mover moving direction. It is formed oblique to the direction. This configuration is also for reducing the cogging. By making the end in the traveling direction oblique as described above, the magnetic shield member 4 can be formed.
The fluctuation period of the magnetic attraction force acting on each part of the end portion in the traveling direction of 5 is shifted, and the fluctuation width of the magnetic attraction force can be suppressed small as a whole, thereby suppressing cogging and driving the motor accordingly. Accuracy can be improved. In addition, cogging can be further reduced by combining with the configuration shown in FIG. 9 in which the tip portion in the traveling direction is thinned.

FIGS. 11 and 12 show examples in which the magnetic shield effect is enhanced by a combination of a stator having a stator shape different from the circular shape described above and a magnetic shield member. In the linear motors shown in FIGS. 11 and 12, the mover is not shown, and the magnetic sensor 3 is attached to the mover and moves together with the mover.
In addition, the driving magnetized portion 11 and the position detecting magnetized portion 12 are formed on the stator so as to be separated from each other.

A stator 1F extending in the moving direction of the mover of the linear motor LDMf shown in FIG. 11 is obtained by cutting a part of a cylindrical shaft member into a planar shape along the longitudinal direction of the stator (moving element moving direction). It is. Magnetization part 12 for position detection
Are magnetized on the plane portion thus cut. The magnetic sensor 3 is arranged so as to face the position detecting magnetized portion 12, that is, is arranged so as to face the cut plane portion. The magnetic shield member 46
It surrounds four surfaces of the magnetic sensor 3. With such a configuration, the gap formed between the magnetic shield member 46 and the stator 1F can be reduced, and the magnetic flux from the driving magnetized portion 11 is less likely to wrap around the magnetic sensor 3, so that the magnetic sensor 3 The output signal is highly accurate. In addition,
The same effect can be obtained even if the stator is formed in a polygonal column shape.

A stator 1G extending in the moving direction of the mover of the linear motor LDMg shown in FIG. 12 is formed by forming grooves 13 and 13 parallel to a cylindrical shaft member along the longitudinal direction of the stator. The position detecting magnetized portion 12 is provided with these grooves 1
3 is magnetized. The driving magnetized portion 11 and the position detecting magnetized portion 12 are separated by the width of the groove 13.
The magnetic sensor 3 is disposed so as to face the position detecting magnetized portion 12. The magnetic shield member 47 surrounds the four surfaces of the magnetic sensor 3, and a part of the magnetic shield member 47 is movable into the groove 13. As described above, by extending the magnetic shield member 47 to the inside of the groove 13, the magnetic flux from the driving magnetized portion 11 is further suppressed from going around to the position detecting magnetized portion 12, and the output of the magnetic sensor 3 is accordingly reduced. The signal will be of high precision.

[0041]

According to the present invention, there is provided a stator having a driving magnetized portion and a position detecting magnetized portion and extending in a fixed direction, and an armature coil facing the driving magnetized portion. A linear motor having a mover that can move along a stator, and a magnetic sensor that moves together with the mover and reads magnetic information of the position detecting magnetizing unit, and detects the magnetic sensor. The magnetic information can be highly accurate, and a highly efficient linear motor that generates a higher thrust than a conventional linear motor can be obtained.
It is possible to provide a low-cost linear motor that is easier to process and assemble than conventional linear motors.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a linear motor according to one embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of a motor drive unit.

FIG. 3 is a diagram showing a main part of an operation control circuit including a speed control circuit based on a phase synchronization control method.

FIG. 4 is a diagram illustrating an example of a magnetic flux distribution in a circumferential direction of a driving magnetized portion of a stator in the linear motor illustrated in FIG. 1;

FIG. 5A is a diagram showing an example of an output signal of a magnetic sensor of the linear motor according to the present invention, and FIG. 5B is a magnetic sensor when the magnetic sensor is not shielded by a magnetic shield member; FIG. 4 is a diagram showing an example of the output signal of FIG.

FIG. 6 is a diagram for explaining the shielding effect of the magnetic shield member of the linear motor according to the present invention.

FIG. 7 is a schematic perspective view of a part of a linear motor according to another embodiment of the present invention.

FIG. 8 is a schematic sectional view of a part of a linear motor according to still another embodiment of the present invention.

FIG. 9 is a schematic perspective view of a part of a linear motor according to still another embodiment of the present invention.

FIG. 10 is a schematic plan view of a part of a linear motor according to still another embodiment of the present invention.

FIG. 11 is a schematic sectional view of a part of a linear motor according to still another embodiment of the present invention.

FIG. 12 is a schematic sectional view of a part of a linear motor according to still another embodiment of the present invention.

FIG. 13A is a schematic side view showing a configuration of a conventional linear motor, and FIG. 13B shows an example of a magnetic flux distribution in a stator circumferential direction by a driving magnetized portion of the linear motor. FIG.

FIG. 14A is a schematic front view showing another configuration of a conventional linear motor, and FIG. 14B is a diagram for explaining the wraparound of magnetic flux to a magnetic sensor in the linear motor.

[Explanation of symbols]

LDMa, LDMb, LDMc, LDMd, LDMe, LDMf, LDMg Linear motor 1, 1F, 1G Stator 10 Shaft member 11 Driving magnetized part 12 Position detecting magnetized part 2 Mover 21 Armature coil 22 Mover yoke 23 Bearing 3 Magnetic sensor 41, 42, 43, 44, 45, 46, 47 Magnetic shield member 5 Motor drive unit 510 DC power supply 520 Energization control unit 521 Amplifier circuit 530 Speed control unit 531 Computer 532 Input / output port 533 Amplifier 534 Switching unit 535 Phase synchronization controller 536 Compensation circuit E Encoder

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsutoshi Taka 2-3-13 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Masami Ishiyama 2-chome Azuchicho, Chuo-ku, Osaka-shi 3-13 Osaka International Building Minolta Co., Ltd.

Claims (10)

[Claims] A stator having a driving magnetized portion and a position detecting magnetized portion spaced apart from each other and extending in a fixed direction, and an armature coil facing the driving magnetized portion; A linear motor having a mover that can move along a stator, and a magnetic sensor that moves together with the mover and reads magnetic information that the position detecting magnetizing unit has. A linear motor having a magnetic shield member for shielding magnetic flux from a driving magnetized portion. 2. The driving magnetized portion and the position detecting magnetized portion are separated from each other such that an offset variation of an output signal of the magnetic sensor is within 38% of a peak-to-peak value of the output signal. The linear motor according to claim 1. 3. The linear motor according to claim 1, wherein said magnetic shield member is made of a ferromagnetic material. 4. The linear motor according to claim 1, wherein the magnetic shield member is disposed before and after the magnetic sensor in a moving direction of the mover. 5. The linear motor according to claim 1, wherein the magnetic shield member is arranged so as to surround a detection surface of the magnetic sensor facing the magnetized portion for position detection from a peripheral outer side. . 6. At least one of said magnetic shield members has an edge portion facing said stator and extending in a direction crossing said mover moving direction. The linear motor according to any one of claims 1 to 5, wherein the linear motor is formed in a shape following a cross-sectional contour of a portion of the stator facing the edge of the magnetic shield member. 7. The magnetic shield member is arranged at least in front of and behind the magnetic sensor in the moving direction of the mover, and each magnetic shield member arranged before and after the magnetic sensor moves away from the magnetic sensor. 4. The linear motor according to claim 1, wherein the linear motor is formed so as to be thinner. 8. The magnetic shield member is disposed at least in front of and behind the magnetic sensor in the moving direction of the mover, and each of the magnetic shield members disposed before and after the magnetic sensor in the moving direction of the mover. 4. The linear motor according to claim 1, wherein an end remote from the magnetic sensor is formed obliquely to the traveling direction. 9. The stator according to claim 1, wherein at least one surface of the stator is flat along the longitudinal direction of the stator, and the position detecting magnetized portion is magnetized on the flat surface. The linear motor according to 1. 10. The stator has two grooves formed along the longitudinal direction of the stator, and the position detecting magnetized portion is magnetized between the two grooves. 4. The linear motor according to claim 1, wherein the magnetic shield member is provided so as to be able to move along the groove so as to enter the inside of the groove.