JP3149684B2 - Linear motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor used for conveying a door or the like.

[0002]

2. Description of the Related Art Recently, a linear motor has been used as a transfer device such as a door. This type of linear motor generally includes a stator block, a mover block, a sensor for detecting the position of the mover block, and a motor control circuit as main components.

[0003] The stator block has a generally long cylindrical shape, and has a stator case having a support projection for fixing at the upper portion, and a stator block which is magnetized to have different polarities in the thickness direction and is alternately arranged at regular intervals in the longitudinal direction. And a power supply board disposed on the stator case with the positive and negative conductive portions and insulating portions formed at predetermined intervals in the longitudinal direction and magnetized so that different poles exist in the stator case. have. The mover block is generally U-shaped with both side pieces and connecting pieces, and both sides are wound around a core so as to sandwich a permanent magnet, and are supported by the stator case in a movable state. , A brush for supplying the positive and negative voltages of the power supply board to the coil, and a hanger member having a substantially L-shaped cross section for mounting a roller whose rotation axis is substantially parallel to the connecting piece of the iron core and suspending a load such as a door. have.

The sensor is provided on the mover block using, for example, a Hall element, and detects the position of the mover block using, for example, a permanent magnet of the stator block as a sensing unit. The motor control circuit controls the opening / closing of a load such as a door and the appropriate acceleration / deceleration control of the location.The motor control circuit is provided on a stator block or a fixed support member that supports the stator block. An output signal based on the position detection of the sensor is input. As a result, the motor control circuit obtains the position information of the mover block and speed information based on the position information, and supplies power to the power supply board to perform predetermined speed control.

[0005]

In the above-described linear motor, the position of the mover block is detected by a sensor such as a Hall element, and the motor control circuit performs appropriate acceleration / deceleration control according to the output signal. However, since the sensor is provided on the mover block, the wires and the like, which are the signal lines of the sensor and the motor control circuit, need to have a long and sufficient space so that the mover block can move within a predetermined operation range. is there. Such wires and the like bend when the distance between the sensor and the motor control circuit is in a minimum positional relationship,
When in the maximum positional relationship, the state changes to a state where there is almost no deflection.

Therefore, it is necessary to use such an electric wire having high stress resistance due to repeated deformation, and in some cases, there is a risk of being damaged by the edge of a structural member or of being caught by another member.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a linear motor capable of improving the safety and reliability of a signal line between a sensor and a motor control circuit.

[0008]

According to a first aspect of the present invention, there is provided a linear motor, comprising: a stator case having a substantially long cylindrical shape and having a support projection for fixing at an upper portion; Permanent magnets that are magnetized on the poles and are arranged so that different poles are present alternately at regular intervals in the longitudinal direction, and are disposed on the stator case. And a power supply board provided on the stator case with a portion and an insulating portion formed, and a stator block having a substantially U-shape with both side pieces and a connecting piece, facing each other so as to sandwich the permanent magnet. An electromagnet device supported by a stator case in a movable state by winding a coil around an iron core, a brush for supplying positive and negative voltages of a power supply board to the coil, and a rotating shaft substantially similar to a connection piece of the iron core. Attach parallel rollers and doors, etc. A mover block having a hanger member having a substantially L-shaped cross section for suspending a load, a sensor for detecting the position of the mover block, and an output signal based on the position detection of the sensor are input to perform predetermined speed control. A motor control circuit that supplies power to the power supply board, and a linear motor including the sensor provided in the stator block;
The sensing unit corresponding to the sensor is provided on the mover block.

A linear motor according to a second aspect is configured such that the sensor according to the first aspect is provided on a stator case, and the sensing section is provided on a hanger member.

A linear motor according to a third aspect of the present invention is configured such that the sensor according to the second aspect is provided near both ends of the stator case, and the sensing section is provided near both ends of the hanger member.

Further, the linear motor according to a fourth aspect is configured such that the sensor according to the first to third aspects is a photoelectric sensor having a light emitting element and a light receiving element.

According to a fifth aspect of the present invention, in the linear motor according to the fourth aspect, the sensing section is formed of a band-shaped sheet member having a bright and dark striped pattern.

According to a sixth aspect of the present invention, in the linear motor, the sensing unit according to the fourth aspect is constituted by a strip-shaped rack having alternately unevenness.

According to a seventh aspect of the present invention, there is provided a linear motor in which the sensor according to any one of the first to third aspects is a Hall element, and the sensing section is formed by alternately magnetizing N poles and S poles in the driving direction of the hanger member. Of the magnet plate.

In a linear motor according to an eighth aspect of the present invention, the sensor according to the first to third aspects is a brush made of a conductive material having sliding portions at regular intervals, and the sensing portion is formed of a brush. The sliding member is made of a conductive material having a sliding contact portion that comes into contact with and separates from the sliding contact portion of the brush body when moved.

[0016]

According to the first aspect of the present invention, the sensor is provided on the stator block, and the sensing section corresponding to the sensor is provided on the mover block to detect the position of the mover block. The signal line such as the electric wire is not connected to the mover block and remains fixed to the fixed member of the linear motor. As a result, the signal line does not move while being deformed as the mover block moves. .

According to the second aspect of the present invention, the sensor is provided on the stator case of the stator block, and the sensing portion is provided on the hanger member of the mover block. Since it may be fixed to the outer surface of the stator case, the fixing is facilitated.

According to a third aspect of the present invention, in addition to the function of the second aspect, by providing a sensor near both ends of the stator case and providing a sensing portion near both ends of the hanger member, the acceleration / deceleration can be improved. Position information and speed information of the mover block can be obtained in the vicinity of both ends where control is easily required, and the required size of the sensing unit can be reduced.

Further, according to the structure of the fourth aspect, in addition to the functions of the first to third aspects, the sensor is formed by a photoelectric sensor, so that the sensor is less affected by a magnetic field.

According to the fifth aspect of the invention, in addition to the function of the fourth aspect, since the sensing portion is formed by the sheet member, it can be easily manufactured.

According to the configuration of claim 6, in addition to the function of claim 4, the sensing portion is formed from the rack portion, so that there is no need to attach a separate member to the hanger member, and the assembling time is reduced. Be shortened.

According to the configuration of claim 7, in addition to the effects of claims 1 to 3, the sensor is formed by the Hall element and the sensing section is formed by the magnet plate, so that it is less affected by dust. .

According to the construction of the eighth aspect, in addition to the functions of the first to third aspects, the sensing part is formed by the body to be slid and the sensor is formed by the brush body, so that dust and a magnetic field are prevented. Less susceptible to disturbances.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a linear motor.
The same name is used.

Reference numeral 1 denotes a stator block, and a stator case 2
, A permanent magnet 3, and a power supply board 4.

The stator case 2 includes a permanent magnet 3 and a power supply board.
In order to support the mover block, which will be described later, in a movable state, it is formed in an approximately cylindrical shape having a cross section as shown in FIG. 1 by extrusion molding of aluminum or the like. I have. This stator case 2
The upper and lower walls 2a, 2b and the left and right walls 2c, 2d form a substantially elongated cylindrical shape, and the inside is a movable block housing. Therefore, an I-shaped supporting portion for supporting the permanent magnet 3 on the inner surface of the upper wall 2a.
2e, a substantially L-shaped support portion 2 supporting the power supply board 4 on the right wall 2d.
f, 2f, an opening 2g is formed in the center of the lower wall 2b. Reference numerals 2h and 2h denote support protrusions for attaching the stator case 2 to a bracket described later.

The permanent magnet 3 is a flat plate magnetized in such a manner that different poles are magnetized in the thickness direction and magnetized so that different poles are present alternately at regular intervals in the longitudinal direction. It has a supporting recess 3e corresponding to the portion 2e. The permanent magnet 3 is secured to the stator case by fixing the supporting recess 3e and the supporting portion 2e by appropriate means such as press-fitting or bonding.
2 has different polarities alternately over almost the entire length.

The power supply board 4 is formed with positive and negative conductive portions 4a, 4b and an insulating portion 4c at predetermined intervals in the longitudinal direction, and is fixed to the support portions 2f, 2f of the stator case 2. That is, as shown in FIG. 3, the power supply substrate 4 is provided with the positive and negative conductive portions 4a and 4b by forming a conductive pattern having a constant thickness on one surface of the insulating substrate. The insulating portion 4c is formed such that a portion where no conductive pattern is present eventually separates the positive and negative conductive portions 4a and 4b. The positive and negative conductive portions 4a and 4b and the insulating portion 4c are formed at predetermined intervals in the longitudinal direction so that brushes of a mover block described later can slide.
A positive voltage is applied to the coil of the mover block when the brush is in contact with the positive conductive portion 4a, and a negative voltage is applied when the brush is in contact with the negative conductive portion 4b. There is a step between the positive conductive part 4a and the insulating part 4c and between the negative conductive part 4b and the insulating part 4c. A land 4d is provided on the portion 4c, and is formed so as to control mechanical wear of the brush.

Reference numeral 5 denotes a mover block, which includes an electromagnet device 6 and
The brush 11 and the hanger member 13 are main constituent members. Further, as shown in FIG. 2, the linear motor of the embodiment has three electromagnet devices 6, 6, 6 and a brush 1 for three-phase driving.
The mover block 5 is formed by connecting 1, 11, and 11 to each other. This type is suitable for curve running.

Each electromagnet device 6 includes a movable table 7 made of resin,
It comprises a laminated iron core 8 and a coil 9 wound around it. The movable base 7 has a substantially flat plate shape, has a connecting portion 7a for connecting to an end in the longitudinal direction, connects the respective electromagnet devices 6, and slides inside the stator case 2. In addition, a hanger member 13 described below is attached to the lower surface 7a of the movable base 7 with a joint portion 10.

The iron core 8 has a substantially U-shape with a laminated iron core having a substantially U-shape formed by both side pieces 8a, 8a and a connecting piece 8b.
8a, 8a so that the connecting piece 8b faces the permanent magnet 3
Is embedded in the movable base 7 and fixed. It is desirable to cover resin tip caps 8c, 8c with low frictional resistance, which also serve as mechanical protection, on the tips of both side pieces 8a, 8a.

The coil 9 is wound around coil frames 9a, 9a mounted on both side pieces 8a, 8a. In the three sets of coils 9, 9, 9, one of the terminals is commonly connected, and the other is separately connected to three brushes 11, 11, 11 described later.

As described above, three electromagnet devices are used.
6, 6, 6 are arranged side by side in the longitudinal direction of the stator case 2 by connecting and connecting three movable stands 7, 7, 7 together. In that case, the longitudinal length of each electromagnet device 6 is
The length of the pair of N and S poles is set to L, and is set so as not to exceed L / 3. Therefore, the length of the iron core 8 in the longitudinal direction is set sufficiently smaller than L / 3 in consideration of the dimensions of the coil 9.

The brush 11 has a rectangular parallelepiped shape, and the power supply substrate 4
A conductive spring whose base end is fixed to the movable table 7 so that it slides on
It is fixed to the tip of 11a. This brush 11 is
In order to supply the positive and negative voltages of
is electrically connected to the other terminal of each coil 9 via a. In addition, each brush 11 is set so that the interval is L / 3. A capacitor 12 has one end connected to the terminal of each coil 9 and the other end connected in common in order to reduce electric noise generated when the mover block 5 travels.

As shown in FIG. 1, the hanger member 13 is formed by bending a metal plate into a substantially Z-shaped section, and the roller 14 is attached to the side surface 13a so that the rotation axis is parallel to the connecting piece 8b of the iron core 8. And a load 15 such as a door is attached to the lower surface 13b. The upper surface 13c of the hanger member 13 is
10 is connected to the movable base 8.

Reference numeral 16 denotes an engine case, which is a stator block 1
And guide the mover block 5 in a movable state. The engine case 16 is formed by extruding aluminum or the like, and has an approximately U-shape including an opposing piece composed of a first piece 16a and a second piece 16b and a connecting piece 16c connecting them. The first piece 16a has a stator case 2
The brackets 17, 17 for holding the support projections 2h, 2h are integrally formed, and a roller guide 18 for movably guiding the roller 14 is provided on the second piece 16b.

Next, the main parts of the present invention will be described. 20
Is a photoelectric sensor as a sensor, has a light emitting element 20a and a light receiving element 20b, and is provided on a lower wall 2b of a substantially central portion of the stator case 2 in the longitudinal direction. The light emitting element 20a emits light, and the light receiving element 20b receives reflected light of the light. Although not shown, a motor control circuit is provided on the fixed member side of the linear motor, and a sensor 20 is provided.
And a power line (not shown) as a signal line, and feeds power to the power supply board 4 to control the speed of the mover block 5. This electric wire is fixed at a predetermined position on the fixed side such as the stator block 1 of the linear motor.

Reference numeral 21 denotes a sheet member as a sensing unit.
It is a sheet formed of paper, plastic, or the like having a bright and dark striped pattern on its surface, and is attached over the entire length of the upper surface 13c of the hanger member 13 at a position facing the photoelectric sensor 20.

Next, the operation of the present invention will be described. The linear motor is composed of three coils of the mover block 5.
An electric current is applied to at least two of the 9, 9, 9 through the brushes 11, 11, 11 to generate an electromagnetic force between the permanent magnet 3 of the stator block 1 and the electromagnet device 6 of the mover block 5. Due to the suction repulsion, the mover block 5 is driven in a certain direction. When the driving (running) direction of the mover block 5 is reversed, the polarity of the voltage supplied to the positive / negative conductive portions 4a and 4b may be reversed.

The photoelectric sensor 20 emits light from the light emitting element 20a, reflects the light on the sheet member 21 and receives the light on the light receiving element 20b, thereby obtaining an output signal corresponding to the stripe pattern of the sheet member 21. . That is, when the sheet member 21 has a black color, the light reflectance is low, and when the sheet member 21 has a white color, the light reflectance is high. Therefore, when the mover block 5 moves, the current flowing through the light receiving element 20b changes. By detecting the position, that is, by inputting an output signal to the motor control circuit, position information and speed information of the mover block 5 can be obtained. The electric wire connecting the photoelectric sensor 20 and the motor control circuit is fixed and does not move. Also,
The light emitting element 20a and the light receiving element 20b, which are the photoelectric sensor 20, may be used separately, or may be integrated and incorporated like a photo interrupter.

FIGS. 5 and 6 show a modification of the first embodiment. Fig. 5 shows the photoelectric sensors 20, 20 connected to the end 2 of the stator case 2.
i, 2i, and two sheet members 21, 21 are also provided near the ends 13d, 13d of the hanger member 13. With such a configuration, the mover block 5 is actually
Since the position information and speed information of the mover block 5 can be obtained in the vicinity of the ends 2i, 2i of the stator case 2 where acceleration / deceleration is required, the size for sensing can be small and efficient.

FIG. 6 shows photoelectric sensors 20, 20 mounted on end caps 2j, 2j of a stator case 2.
With such a configuration, assembly and maintenance of the photoelectric sensors 20 and 20 are facilitated. Furthermore, end cap 2j, 2
j functions as a stopper of the mover block 5.

Next, a second embodiment of the present invention will be described. This embodiment differs from the first embodiment in the structure of the sensing unit as shown in FIG. 7, and that point will be described.

Reference numeral 22 denotes a rack portion as a sensing portion, which has an irregular shape having a convex portion 22a and a concave portion 22b, and is integrally formed on the upper surface 13c of the hanger member 13 by, for example, milling. With such a configuration, the sensing unit 22 does not need to add a dedicated component.

FIG. 8 shows a modification of the second embodiment.
In this embodiment, a rack 22 as a sensing unit is formed by providing a groove 22c on the upper surface 13c of the hanger member 13.

Next, a third embodiment of the present invention will be described. This embodiment is different from the first embodiment in the structure of the sensor and the sensing unit, as shown in FIG. 9, and that point will be described.

Reference numeral 23 denotes a Hall element as a sensor, which is provided on the lower wall 2b of the stator case 2 at a substantially central portion in the longitudinal direction.

Numeral 24 denotes a magnet plate serving as a sensing portion, which is a flat plate having N and S poles alternately magnetized in the movable direction of the hanger member 13 and mounted on the upper surface 13c of the hanger member 13.

With such a configuration, the Hall element 23 detects a change in the magnetic field, that is, a change in the amount of magnetic flux when the mover block 5 moves, and
5 position information and speed information can be obtained. Since this is less affected by dust, the reliability of position detection and speed detection is improved.

Next, a fourth embodiment of the present invention will be described. This embodiment differs from the first embodiment in the structure of the sensor and the sensing unit, as shown in FIGS. 10 and 11, and the point will be described.

Numeral 25 denotes a body to be slid as a sensing portion, which is conductive and has a U-shape formed by both side pieces 25a, 25b and a connecting piece 25c, and has a non-conductive shape on the upper surface 13c of the hanger member 13. The connection piece 25c is attached via a terminal board 26 made of a material so as to be in contact therewith. The ends of both side pieces 25a and 25b of the body to be slid 25 are slidable portions and come into contact with and separate from first and second slidable portions of the brush body described later.

Reference numeral 27 denotes a brush member serving as a sensor,
25 has a first sliding contact portion 27a which is always in contact with one of the side pieces and a second sliding contact portion 27b which is in contact with the other of the side pieces at regular intervals. Is installed over almost the entire length of the. With such a configuration,
When the side pieces 25a, 25b are in contact with the respective sliding contact portions 27a, 27b, electrical conduction is performed, and while one side piece passes through the non-conductive portion, there is no electrical conduction. By using the signal, it is possible to obtain position information and speed information of the mover block 5.

If the sliding portions 27a and 27b of the brush body 27 are provided with a spring property so as to elastically press the sliding member 25, the contact performance is improved.

Next, a fifth embodiment of the present invention will be described. This embodiment relates to a mounting structure of a sensing unit as shown in FIG.

Reference numeral 28 denotes a plurality of projections, and a plurality of projections are provided on the upper surface 13c of the hanger member 13 at intervals for sandwiching the sensing portion.

By adopting such a configuration, the mounting of the sensing section is easy and the positioning thereof is ensured. By the way, the sensing unit includes a sheet member 21, a rack unit 22,
Either the magnet plate 24 or the sliding contact body 25 may be used.

Although the roller 14 is provided outside the stator case 2 in the embodiment, the engine case 16
The roller 14 may be provided in the stator case 2 without using a roller. In that case, a bracket for fixing the stator case 2 to a ceiling or the like is required. Further, the positions of the sensor and the sensing unit are not particularly limited to the present embodiment,
In short, a sensor connected to the motor control circuit by a signal line may be provided on the stator block, and a sensing unit which does not require power supply may be provided on the mover block. Further, the motor control circuit is provided near the stator block, such as an end of the stator block and a fixed support member for supporting the end.

[0058]

According to the first aspect of the present invention, in the linear motor, a sensor is provided on the stator block, and a sensing section corresponding to the sensor is provided on the mover block to detect the position of the mover block. The signal lines, such as electric wires between them, are not connected to the mover block and remain fixed to the fixed side member of the linear motor. As a result, the signal lines cannot move while deforming as the mover block moves. Since there is no signal line, the safety and reliability of the signal line are improved.

In the linear motor according to the present invention, the sensor is provided on the stator case of the stator block, and the sensing portion is provided on the hanger member of the movable block. Since it suffices to fix it to the outer surface of the child case, the fixation becomes easy, and the assemblability is improved.

In addition, in the linear motor according to the third aspect, in addition to the effect of the second aspect, acceleration / deceleration control can be achieved by providing sensors near both ends of the stator case and sensing parts near both ends of the hanger member. Since the position information and the speed information of the mover block can be obtained in the vicinity of both ends where it is likely to be required, the required dimensions of the sensing unit can be reduced, which can contribute to cost reduction.

In the linear motor according to the fourth aspect, in addition to the effects of any one of the first to third aspects, since the sensor is formed by the photoelectric sensor, the linear motor is hardly affected by the magnetic field. The reliability of speed detection is improved.

Further, the linear motor according to the fifth aspect can be easily manufactured by forming the sensing portion by the sheet member in addition to the effect of the fourth aspect.
It can further contribute to cost reduction.

In the linear motor according to the sixth aspect, in addition to the effect of the fourth aspect, since the sensing portion is formed from the rack portion, there is no need to attach a separate member to the hanger member, and the assembling time is reduced. Therefore, assemblability is further improved.

In the linear motor according to the present invention, in addition to the effects of any one of the first to third aspects, a sensor is formed by a Hall element and a sensing portion is formed by a magnet plate, thereby being affected by dust. Since it becomes difficult, the reliability of position detection and speed detection is improved.

In the linear motor according to the present invention, in addition to the effects of any one of the first to third aspects, the sensing part is formed by the body to be slid and the sensor is formed by the brush body, so that the dust and the magnetic field can be reduced. Since it is less susceptible to external disturbances, the reliability of position detection and speed detection is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a linear motor according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the mover block.

FIG. 3 is a plan view of the power supply board.

FIG. 4 is a perspective view of the sensor and the sensing unit.

FIG. 5 is a side view of a linear motor showing a modified example thereof.

FIG. 6 is a side view of a linear motor showing another modified example.

FIG. 7 is a perspective view of a sensing unit according to a second embodiment of the present invention.

FIG. 8 is a perspective view of a sensing section showing a modified example thereof.

FIG. 9 is a perspective view of a linear motor according to a third embodiment of the present invention.

FIG. 10 is a sectional view of a linear motor showing a fourth embodiment of the present invention.

FIG. 11 is a plan view of the brush body.

FIG. 12 is a perspective view of a sensing unit according to a fifth embodiment of the present invention.

[Explanation of symbols]

 1 Stator block 2 Stator case 3 Permanent magnet 4 Power supply board 5 Mover block 6 Electromagnet device 7 Movable table 8 Iron core 9 Coil 11 Brush 13 Hanger member 14 Roller 15 Load 16 Joint 17 Engine case 20 Photoelectric sensor (sensor) 21 Sheet member (sensing part) 22 Rack part 23 Hall element 24 Magnet plate 25 Body to be contacted 27 Brush body 28 Projection piece

Continuation of the front page (56) References JP-A-5-328699 (JP, A) JP-A-4-248357 (JP, A) JP-A-62-1104470 (JP, A) JP-A-5-211798 (JP) , A) Hikaru Hei 3-111172 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H02K 41/02-41/03 H02K 11/00

Claims (8)

(57) [Claims] 1. A stator case having a generally cylindrical shape and having a support projection for fixing at an upper portion, and a magnet case having different poles magnetized in a thickness direction and alternately at regular intervals in a longitudinal direction. A permanent magnet that is magnetized so as to exist and disposed in the stator case, and a power supply substrate in which the positive and negative conductive portions and the insulating portion are formed at predetermined intervals in the longitudinal direction and disposed in the stator case. The stator block has a generally U-shaped configuration with both side pieces and connecting pieces, and both sides are wound around a core so as to sandwich a permanent magnet and supported by a stator case in a movable state. Electromagnet device, a brush for supplying the positive and negative voltages of the power supply board to the coil, and a hanger having a substantially L-shaped cross section for mounting a roller whose rotating shaft is substantially parallel to the connecting piece of the iron core and suspending a load such as a door. Mover block having member A sensor that detects the position of the mover block, and a motor control circuit that receives an output signal from the position detection of the sensor and supplies power to a power supply substrate to perform predetermined speed control. A linear motor provided on a stator block, and a sensing unit corresponding to the sensor is provided on a mover block. 2. The linear motor according to claim 1, wherein the sensor is provided on a stator case, and the sensing unit is provided on a hanger member. 3. The linear motor according to claim 2, wherein the sensors are provided near both ends of the stator case, and the sensing portions are provided near both ends of the hanger member. 4. The linear motor according to claim 1, wherein the sensor is a photoelectric sensor having a light emitting element and a light receiving element. 5. The linear motor according to claim 4, wherein the sensing unit is formed of a band-shaped sheet member having a bright and dark striped pattern. 6. The sensing unit according to claim 4, wherein the sensing unit comprises a band-like rack having irregularities.
The linear motor described. 7. The sensor according to claim 1, wherein the sensor is a Hall element, and the sensing portion is formed of a flat magnet plate having N and S poles alternately magnetized in the driving direction of the hanger member. 3. The linear motor according to 3. 8. A brush body made of a conductive material having sliding portions at regular intervals, wherein said sensor is a sliding body which comes into contact with and separates from the sliding portion of the brush body when it moves. 4. A linear motor according to claim 1, wherein said linear motor has a contact portion and is made of a conductive material.