JPH08275491A - Linear motor - Google Patents

Abstract

PURPOSE: To lower a change in magnetic attraction force which is caused by a field magnet and works on an end face in the movement direction of a movable yoke and prevent cogging torque from appearing and thereby obtain smooth thrust of the movable member by bending an end in the movement direction of the movable yoke away from the field magnet of a stator. CONSTITUTION: A linear motor LDMa consists of a strip like flat-type stator 6 which has a field magnet 61 wherein N poles and S poles are alternately arranged in a certain direction and a movable member 7 which has an armature coil 72 located face to face with the field magnet 61. In this motor, an end 711 in the movement direction of a yoke 71 of the movable member is bent- formed. With this end 711, the distance between the yoke 71 and the field magnet 61 is made longer and thereby a change in magnetic attraction force which is caused by the field magnet 61 and works on an end face in the movement direction of the yoke 61 of the movable member is decreased. By this method, cogging torque is prevented from appearing and smooth thrust of the movable member can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor having a stator having a propulsion field magnet extending in a fixed direction and an armature coil facing the field magnet.

[0002]

2. Description of the Related Art A linear motor provided with a stator having a field magnet extending in a certain direction and a mover having an armature coil facing the field magnet is disclosed in, for example, Japanese Patent Laid-Open No. 6-68242.
No. 1-9161 and Japanese Patent Laid-Open No. 58-36162. As shown in FIGS. 6A and 6B, the linear motor taught by Japanese Patent Laid-Open No. 61-9161 has a plate-like shape having a field magnet 11 having N and S poles arranged in a fixed direction on the surface thereof. The linear motor is composed of a stator 1 and a mover 2 having an armature coil 21 arranged to face the field magnet 11.

A field magnet 11 of the stator 1 is supported by a stator yoke 12, and the yoke 12 is a base 1.
It is installed in 3. The armature coil 21 of the mover 2 is composed of a plurality of air-core coils 21a. The coils are arranged in parallel with the field magnet 11 with their air-core portions facing the field magnet 11, and are arranged on the mover yoke 22. It is supported. Both sides of the mover yoke 22 are bent downward, and guide rollers 23 are provided there. The guide roller 23 can move on the base 13 while being guided by the side surface of the stator yoke 12.

As shown in FIG. 6B, the armature coil 2
1 is a position detecting element 24 for detecting the magnetic force of the field magnet 11 at that position for controlling the energization of the coil.
And a magnetic sensor 25 of an encoder for controlling the speed of the mover, the position detecting element 24 faces one side surface of the field magnet 11, and the magnetic sensor 25 is formed on the other side surface of the field magnet 11. Fine magnetizing part 14
Moving along with the mover, the magnetism is detected.

On the other hand, the linear motor taught by Japanese Patent Laid-Open No. 58-36162 has a field magnet 31 having N poles and S poles alternately arranged in a certain direction on the surface, as shown in FIG. 6C. The linear motor is composed of a rod-shaped stator 3 and a mover 30 having an armature coil 301 fitted on the stator 3. The armature coil 301 is composed of a ring-shaped coil 301a fitted onto the field magnet 31,
It is mounted inside a cylindrical mover yoke 302. In the example shown in FIG. 6C, the tubular mover yoke 302 is further added.
Bearings 303 are fitted to both ends of the mover 30.
This bearing 303 allows relative movement along the stator 3. In addition to this, the bearing structure is
Various types are adopted. The above publication discloses that a projection made of plastic provided on the inner surface of the armature coil is fitted and slid into a longitudinal groove provided in the field magnet.

The armature coil 30 is attached to the mover 30.
A position detecting element 24 such as a Hall element for detecting the magnetic force of the field magnet at that position for controlling the energization of the device 1.
Is provided. The linear motor described above has been attempted to be used for driving a cage that supports a scanning optical system member for a document image of an image reading apparatus such as an image forming apparatus such as a copying machine or an image scanner, and various other apparatuses. Is being used.

However, the following problems have been pointed out regarding such a linear motor. That is, when the mover moves relative to the stator, the magnetic attraction force acting from the propulsion field magnet to the end portion of the mover yoke, particularly the end face, fluctuates with the magnetic pole pitch, which causes load fluctuation (cogging). ) Occurs, which hinders the smooth movement of the mover.

In this respect, Japanese Patent Laid-Open No. 2-65656 discloses that
As an improved version of the linear motor shown in FIG. 6A, as shown in FIG. 7, the armature coil 21 of the mover 2 is made to face the plate-shaped stator 1 having the field magnet 11, and the mover yoke 22 is provided. In the linear motor having a structure in which the provided roller 23 rolls on the stator support base 13, in order to suppress the fluctuation of the magnetic attractive force acting on the end portion of the mover yoke 22,
It teaches that the front and rear ends 221 and 222 of the moving direction of the yoke are formed as protrusions having a triangular shape or the like.

[0009]

However, if such a protrusion means is adopted, the mover yoke becomes longer by that amount, which hinders the overall size reduction, and such a protrusion means poses a safety problem. Therefore, the present invention is a linear motor including a stator having a field magnet for propulsion extending in a fixed direction and a mover having an armature coil facing the field magnet, which is capable of suppressing cogging as in the prior art. Therefore, compared with the case where the protrusion means is provided at the end portion of the mover yoke, it does not hinder the compactness, and in a safe state, the fluctuation of the magnetic attraction force acting on the end portion in the moving direction of the mover yoke is prevented. An object of the present invention is to provide a linear motor that can reduce the occurrence of cogging and can smoothly achieve highly accurate mover drive.

[0010]

In order to solve the above problems, the present invention provides a stator having a propulsion field magnet extending in a certain direction and a mover having an armature coil facing the field magnet. In a linear motor provided, there is provided a linear motor characterized in that an end of a mover yoke in a moving direction of the mover is bent in a direction away from a field magnet of the stator.

The linear motor of the present invention has a plate-shaped stator having a propulsion field magnet extending in a fixed direction, and an armature coil arranged so as to face the field magnet. A type having a mover provided with a mover yoke aligned with the stator, having a rod-shaped stator having a propulsion field magnet extending in a certain direction, and an armature coil fitted to the stator Various types such as a type in which the armature coil is provided with a mover housed in a cylindrical mover yoke are conceivable.

In the former linear motor, the ends of the mover yokes aligned with the stator in the moving direction are bent away from the field magnet, and when viewed from the side, the end of the mover yoke is away from the field magnets. The shape is curved so that it goes away. Further, in the latter linear motor, the opening at the end in the moving direction of the tubular mover yoke is formed in such a shape that the diameter is expanded so as to move away from the field magnet.

[0013]

According to the linear motor of the present invention, since the end portion in the moving direction of the mover yoke is formed to be bent away from the field magnet of the stator, the end portion has a long distance from the field magnet. Therefore, the influence of the field magnet is reduced accordingly, and the fluctuation of the magnetic attraction force by the field magnet acting on the end face in the moving direction of the mover yoke is suppressed.

To further explain this, first, when the distance between the field magnet and the end of the mover yoke is changed, the tendency of the magnetic flux density transmitted from the field magnet on the surface of the mover yoke is as shown in FIG. Become. As shown in the figure, as the distance between the field magnet and the mover yoke increases, the magnetic flux density on the mover yoke surface decreases. Since the magnetic flux density is the cause of the magnetic attraction, increasing the distance reduces the attraction.

Further, as shown by the solid line in FIG. 4, the fluctuation of the magnetic attractive force generated at the end face in the moving direction of the mover yoke due to the movement of the mover yoke is periodically changed according to the magnetic pole pitch of the field magnet. appear. Here, as in the present invention, when the end of the mover yoke is bent away from the field magnet to increase the distance from the field magnet, it acts on the end surface of the mover yoke as shown by the dotted line in FIG. It is possible to reduce the fluctuation of the magnetic attractive force.

As described above, in the linear motor of the present invention, the fluctuation of the magnetic attraction force by the field magnet acting on the end face in the moving direction of the mover yoke is suppressed, and therefore the cogging is suppressed and the mover is smooth. Thrust is obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B show an example of a linear motor according to the present invention. FIG. 1A is a side view thereof, and FIG. 1B is a front view thereof. FIG. 2 is a side view showing in cross section a mover of another example of the linear motor according to the present invention.

The linear motor LDMa of FIG. 1 has an N pole and an S pole.
A strip plate-shaped flat plate type stator 6 having field magnets 61 in which poles are alternately arranged in a fixed direction, and the field magnets 6
A mover 7 having an armature coil 72 arranged so as to face 1
It consists of The field magnet 61 of the stator 6 is installed on a band-shaped stator yoke 62. Also,
Although not shown, the stator 6 is also provided with a fine magnetizing section that provides magnetism to be read by the encoder for speed control of the mover 7 described later.

The armature coil 72 of the mover 7 is attached to a plate-like mover yoke 71 parallel to the field magnet 61. The armature coil 72 is composed of three-phase air-core coils of u-phase, v-phase, and w-phase so that it can be driven by a three-phase drive method described later, and each phase coil has an electrical angle of 2π / 3. The surfaces including the air-core portion are arranged parallel to the field magnet 61 at the positions shifted by each (the position may be in the same phase as the position shifted by 2π / 3). The coil of each phase has position detecting elements hu, hv, h for controlling energization.
w is provided. Here, these elements are Hall elements, which are a type of magnetoelectric conversion element, and the element hu is arranged in the u-phase coil, the element hv is arranged in the v-phase coil, and the element hw is arranged in the w-phase coil. Although not shown in FIG. 1, the mover 7 is also provided with a magnetic sensor for detecting the magnetism of the fine magnetized portion of the stator 6. This magnetic sensor is a component of an encoder 43 (see FIG. 5B) described later.

Both sides of the mover yoke 71 along the moving direction are bent downward, and wheels 73 are provided there.
The wheels 73 run on the stator yoke 62. Therefore, the stator yoke 62 is provided with a guide guide 621. As in the conventional motor shown in FIG. 6 (A), a stator yoke is further installed on the base so that the wheels can be guided to the side surfaces of the stator yoke so that the vehicle can run on the base. Other mover guide means may be adopted.

Both ends 711 in the moving direction of the mover yoke 71 are bent away from the field magnet 61 and are bent upward. In the linear motor LDMa described above, thrust is generated by energizing the armature coil 72 of the mover 7 as described later, and the mover 7 is driven along the stator 6.

Therefore, image scanning / reading can be performed by connecting the carriage 7 to a carriage that supports a member of a document image scanning optical system of an image reading apparatus such as a copying machine or an image scanner and driving the carriage. According to this linear motor LDMa, the end portion 711 in the moving direction of the mover yoke 71 is connected to the field magnet 61 of the stator 6.
It is bent so as to keep away from it. Therefore, the end portion 711 has a longer distance from the field magnet 61, and the influence of the field magnet 61 is less. Therefore, the fluctuation of the magnetic attraction force by the field magnet 61 acting on the end face of the mover yoke 71 in the moving direction is suppressed. As a result, a smooth mover thrust can be obtained with cogging suppressed.

The linear motor LDMb shown in FIG. 2 has a rod-shaped stator 60 having a circular cross section having a field magnet 601 in which N poles and S poles are alternately arranged, and this field magnet 60.
1 and a mover 70 having an armature coil 702 fitted on the outer surface of the armature coil 1 with a predetermined gap. Armature coil 70
2 is housed in a cylindrical mover yoke 701. Therefore, the mover 70 has a generally cylindrical shape.

The shapes of the stator 60 and the mover 70 are not limited to the cylindrical shape, but may be other shapes such as a square tube shape. Although not shown, the stator 60 is also provided with a fine magnetizing section that provides magnetism to be read by the encoder for speed control of the mover 70 and the like. Mover 7
The zero armature coil 702 is composed of three-phase coils of u-phase, v-phase, and w-phase so that the armature coil 702 can be driven by the three-phase driving method. The coils of each of these phases are wound on a cylindrical bobbin 703 fitted in the stator 60. The bobbin and the outer peripheral surface of the coil have a cylindrical mover yoke 7
Surrounded by 01.

The coils of each phase are arranged at positions shifted by 2π / 3 in terms of electrical angle (note that the positions may be in phase with the position shifted by 2π / 3). Hall elements hu, hv, hw for controlling energization are provided in the coils of each phase. In addition, although not shown in FIG.
A magnetic sensor of the encoder 43 (see FIG. 5B) for detecting the magnetism of a fine magnetized portion (not shown) of the stator 60 is also provided.

Both ends 701a in the moving direction of the mover yoke 701 are bent so as to move away from the field magnet 601. Therefore, the openings at both ends of the cylindrical mover yoke 701 expand as they move away from the center of the mover yoke. ing. In the linear motor LDMb described above, thrust is generated by energizing the armature coil 702 of the mover 70 as described below, and the mover 70 is driven along the stator 60. At this time, the stator 60 also serves as a guide for the mover 70.

Therefore, image scanning / reading can be performed by connecting to the movable element 70 a carriage that supports a member of the original image scanning optical system of an image reading apparatus such as a copying machine or an image scanner and driving the carriage. In addition,
The guide of the mover 70 may be provided by a separate guide means. Also in this linear motor LDMb, the end portion 701a in the moving direction of the mover yoke 701 has the stator 60.
The end portion 701a has a long distance from the field magnet 601 because it is formed so as to be away from the field magnet 601.
1 has little effect. Therefore, the fluctuation of the magnetic attraction force by the field magnet 601 acting on the end face in the moving direction of the mover yoke 701 is suppressed, and thus a smooth mover thrust can be obtained in a state where cogging is suppressed.

Next, the operation control of the linear motor LDMa will be described. Since the motor LDMb is also controlled and operated in the same manner as the motor LDMa, the motor LDMa will be representatively described below. As described above, the field magnet 61 of the stator 6 is magnetized so as to have a distribution of a sinusoidal magnetic flux density with the N pole and the S pole as one cycle. Further, as described above, the armature coil 72 of the mover 7 has three phases arranged at positions shifted by π · 2/3 in electrical angle (or in the same phase as the position shifted by π · 2/3). Hall coils hu, hv, hw for detecting the magnitude and direction of the magnetic flux of the field magnet 61 at that position. Then, a current having a magnitude and a direction corresponding to the magnitude and the direction of the magnetic flux detected by these Hall elements is applied to the coil to drive the motor LD.
Ma is driven. That is, here, a so-called three-phase driving method is adopted, and signals having a phase shift of 120 degrees are input to the coil, and as a result, a constant thrust is obtained regardless of the position of the mover 7. Also here
In addition to adopting the three-phase drive method, a phase synchronization control method generally called PLL is adopted in order to drive the mover at a target speed.

FIG. 5 (A) shows a schematic block diagram of an electric circuit for controlling the operation of the motor LDMa, and FIG. 5 (B) shows the main part of the operation control circuit including the speed control circuit of the phase synchronization control system. In FIG. 5 (A) and FIG. 5 (B), 41
Is a DC power supply, 42 is an energization control circuit unit including the hall element, 43 is an encoder for detecting the moving speed of the mover 7, and 44 is a speed control unit based on the phase synchronization control method.
The encoder 43 is not limited to this, but here is a magnetic sensor that moves together with the mover 7 along a fine magnetizing portion (not shown) provided on the stator 6, which uses a magnetoresistive element called an MR element here. Sensor) is a magnetic encoder.

In FIG. 5B, 45 is a motor LDM.
In addition to instructing the predetermined operation of a, the phase synchronization control unit 4
Reference numeral 9 is a microcomputer for outputting a reference clock signal, 46 is an input / output port of the computer 45, 47 is an amplifier, 48 is a switching unit, 49 is the phase synchronization control unit, 50 is a compensation circuit, and 51 is an amplification circuit. According to the control circuit shown in FIG. 5, the reference clock signal corresponding to the target speed is sent from the computer 45 to the phase synchronization control unit 49.
In addition, the moving speed signal of the mover 7 is fed back to the controller 49 from the encoder 43. The phase synchronization control unit 49 outputs a signal according to the difference between the frequency and phase of the pulse of the reference clock and the pulse of the feedback signal from the encoder 43, and the compensation circuit 50 performs lead / lag compensation of the transmission system and outputs the output voltage. Is the reference input voltage of the Hall element. The Hall element outputs a voltage corresponding to the magnitude and direction of the magnetic flux at a certain position,
The output voltage has a characteristic proportional to the reference input voltage. Therefore, the 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 51, and the armature coil 72 is energized. From the 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 mover 7
The motor LDMa is operated so as to match the target speed of.

[0031]

According to the present invention, a linear motor provided with a stator having a propulsion field magnet extending in a certain direction and a mover having an armature coil facing the field magnet is provided as in the conventional case. Compared with the case where a protrusion means is provided at the end of the mover yoke to suppress cogging, it does not hinder compactness, and in a safe state, it uses a field magnet that acts on the end of the mover yoke in the moving direction. The fluctuation of the magnetic attractive force can be reduced, the occurrence of cogging can be suppressed, and the mover drive with high accuracy can be achieved smoothly.

[Brief description of drawings]

1 shows an example of a linear motor according to the present invention, FIG. 1 (A) is a side view thereof, and FIG. 1 (B) is a front view thereof.

FIG. 2 is a side view showing in cross section a mover of another example of the linear motor according to the present invention.

FIG. 3 is a diagram showing a state in which the magnetic flux density transmitted from the field magnet to the mover yoke changes according to the distance between the field magnet and the mover yoke.

FIG. 4 is a diagram showing a state in which a magnetic attraction force acting on an end surface of a mover yoke changes as the mover moves.

5A is a block diagram showing an outline of an operation control circuit of a linear motor, and FIG. 5B is a view showing a main part of an operation control circuit including a speed control circuit of a phase synchronization control system.

FIG. 6A is a plan view of a conventional example, FIG. 6B is a front view thereof, and FIG. 6C is a side view of another conventional example.

FIG. 7 is a plan view of still another conventional example.

[Explanation of symbols]

 LDMa linear motor 6 strip-shaped stator 61 field magnet for propulsion 62 stator yoke 7 mover 71 mover yoke 711 mover yoke end 72 armature coil u, v, w forming armature coils Air core coil 73 Wheels hu, hv, hw Hall element LDMb Linear motor 60 Rod-shaped stator 601 Propulsion field magnet 70 Mover 701 Cylindrical mover yoke 701a Mover yoke end 702 Armature coil 703 Bobbin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Matsumoto 2-3-13 Azuchi-cho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd. (72) Inventor Katsuhiro Namba 2-3-3 Azuchi-cho, Chuo-ku, Osaka No. 13 Osaka International Building Minolta Co., Ltd.

Claims (1)

[Claims] 1. A linear motor provided with a stator having a field magnet for propulsion extending in a fixed direction and a mover having an armature coil facing the field magnet,
A linear motor characterized in that an end portion of a mover yoke in a moving direction of the mover is bent in a direction away from a field magnet of the stator.