JP2007336697A - Linear motor and exposure scanning device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that power consumption becomes high and the moving speed of a moving member cannot easily and precisely be controlled since a thrust force constant is low in the vicinity of a movement start position, when the movement of the moving member is started from a position where the center of a first U phase coil is matched with a magnet end. <P>SOLUTION: In the movement start position of the moving member 73, a regulating member 332a of a moving board 33 fixed to the moving member 73 is made abut on an upper part of a linear motor holder 72. Thus, the movement start position of the moving member 73 is regulated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a linear motor that regulates a movement start position of a mover that moves along an outer peripheral surface of a pipe-shaped member, and an exposure scanning apparatus that uses the linear motor.

  In recent years, in the field of OA equipment and medical equipment, devices using linear motors have been proposed for parts that require linear movement. As an example of a medical device using this linear motor, a radiation image reading apparatus that images radiation transmitted through a subject such as a patient is known.

  In general, a radiation image reading apparatus obtains a radiation image from a photostimulable phosphor plate having a photostimulable phosphor layer formed on a support. That is, the radiation transmitted through the object is accumulated in the photostimulable phosphor layer of the photostimulable phosphor plate to form a latent image, and then the photostimulable phosphor plate is scanned with photostimulated excitation light. Thus, the radiation energy accumulated in the photostimulable phosphor layer is radiated and converted into photostimulated light. Then, the intensity of the stimulated emission light is converted into an electric signal through a photoelectric conversion means such as a photomultiplier to obtain a radiation image as digital image data.

  In such a radiation image reading apparatus, when the photostimulable phosphor plate is scanned with the photostimulable excitation light, the photostimulable phosphor plate or the optical unit that scans the photostimulated excitation light is precisely set at a constant speed. Must move in a straight line.

  For this reason, for example, Patent Document 1 discloses a radiation image reading apparatus that linearly moves a stimulable phosphor plate using the linear motor described above. The linear motor used in this apparatus includes a fixed magnet (stator) formed in a shaft shape by connecting a plurality of magnets, and a movable coil (movable element) that moves in the extending direction of the fixed magnet. The stimulable phosphor is held in the movable coil by causing the movable coil to generate a thrust due to the interaction between the current and the magnetic flux by passing a current through the movable coil so as to cross the magnetic flux generated by the fixed magnet. The plate is moved linearly along the fixed magnet.

  On the other hand, as a specific structure of the linear motor, for example, the structure shown in FIG. 11 is generally used. FIG. 11 is a schematic cross-sectional view of a linear motor. The linear motor 1000 includes a plurality of coils 1021a to 1021f formed by winding a stator 1010 including a plurality of magnets 1012 and a pipe-like member 1011 for housing the plurality of magnets 1012 and a wire disposed so as to wrap the stator 1010. A mover 1020 is included.

  Both ends of the pipe-like member 1011 are opened to accommodate the magnet 1012 therein, and a cap 1030 is provided to close the opening. And inside the pipe-shaped member 1011, a plurality of magnets 1012 are accommodated so that the same poles face each other so as to repel adjacent magnets.

  The mover 1020 has a configuration in which a plurality of coils 1021 are aligned at a predetermined interval and in the same direction, with the axis centers positioned on the same straight line. The coil 1021 includes, in order from the left side in FIG. 11, a first U-phase coil 1021a, a first V-phase coil 1021b, a first W-phase coil 1021c, a second U-phase coil 1021d, and a second V-phase coil 1021e. The second W phase 1021f is connected in series.

  When the first U-phase coil 1021a to the first W-phase coil 1021c and the second U-phase coil 1021d to the second W-phase coil 1021f are each set, the pitch width and magnet of this one set of coils By setting the pitch width of 1012 to the same length L, a phase shift between the coil 1021 and the magnet 1012 is prevented.

  An attachment member 1040 for mounting the object to be conveyed is bonded and fixed to the mover 1020. Accordingly, when the linear motor 1000 is incorporated into a device such as a radiation image reading device, for example, a stimulable phosphor plate or an optical unit that scans stimulated excitation light is installed on the mounting member 1040 to move the linear motor 1000. As the child 1020 moves, the photostimulable phosphor plate and the optical unit can be precisely moved at a constant speed.

  In such a linear motor 1000, as shown in FIG. 11, the center position of the moving direction of the mover 1020 in the first U-phase coil 1021a is a cap 1030 of a magnet 1012a disposed at the end of the pipe-shaped member 1011. The position at the side end D1 ′ is taken as the movement start position, and the mover 1020 starts to move from this movement start position.

FIG. 12 is a thrust characteristic graph showing the relationship between the center position of the first U-phase coil 1021a and the thrust constant obtained by the mover 1020 when the mover 1020 is moved from the movement start position. That is, in FIG. 12, the horizontal axis indicates the position where the center position of the first U-phase coil 1021a is opposed to the end D1 ′ of the magnet 1012a as the reference position (coil position 0), and the other position of the magnet 1012a from the reference position. The center position of the first U-phase coil 1021a when the mover 1020 is moved toward the end side A1 ′ is shown. The vertical axis indicates the thrust constant obtained by the mover 1020 corresponding to the center position of the first U-phase coil 1021a (thrust obtained when a unit current is passed through the coil 1021), and the coil position is L. The thrust constant obtained sometimes is expressed as 100%.
This graph is obtained when the pitch width of one set of coils and the pitch width of the magnet 1012 are L.
JP 2005-73021 A

  However, as shown in FIG. 11, when the movement of the mover is started from the position where the center position of the first U-phase coil coincides with the magnet end (coil position 0 in FIG. 12), it is obtained near the movement start position. The thrust constant is low. Therefore, when accelerating the mover to a constant speed, power is consumed extremely near the movement start position, resulting in an increase in power consumption.

  In addition, when the apparatus itself is installed in an inclined state, the thrust generated in the mover is low near the movement start position, so that it is difficult to move the mover against gravity. Although it is possible to increase the thrust generated in the mover by supplying a large current to the coil in the vicinity of the movement start position, not only does the power consumption increase, but the coil generates heat due to the large current. Since the coil is damaged or the resistance value of the coil increases due to heat, there is a concern that the thrust generated in the mover may be weakened as a result.

  Also, the vicinity of the movement start position is unstable because the thrust constant rises steeply, and it is not easy to accurately control the moving speed of the mover. If the moving speed of the mover cannot be controlled with high accuracy, it becomes difficult to move the optical unit linked to the mover at a constant exposure speed, and as a result, image unevenness may occur. On the other hand, although it is possible to move it with high accuracy, complicated control is required for that purpose.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a linear motor that can move a mover easily and accurately with low power consumption.

1. In order to achieve the above object, a linear motor of the present invention includes a plurality of magnets arranged in series so that the same poles face each other, a pipe-shaped member that houses the plurality of magnets, and the pipe-shaped member A movable element that is arranged so as to surround the outer periphery of the pipe-shaped member and is movable along the longitudinal direction of the pipe-shaped member, and movement of the movable element In a linear motor having a position restricting means for restricting a starting position, the pitch width of the plurality of magnets is L, and among the plurality of coils, in the coil installed at the rear end portion in the movement start direction of the mover, The central position in the moving direction of the mover is at position C, and the same pole formed by the magnet at the end of the movement start position side and the magnet adjacent to the magnet among the plurality of magnets arranged in series faces each other. Position A, front When the position B is a position 3L / 4 away from the position A in the direction opposite to the movement start direction, the position restricting means is such that the position C includes the position B and is closer to the movement start direction than the position B. Thus, the moving start position of the mover is regulated.
2. In order to achieve the above object, a linear motor of the present invention includes a plurality of magnets arranged in series so that the same poles face each other, a pipe-shaped member that houses the plurality of magnets, and the pipe A mover including a plurality of coils arranged in parallel in the longitudinal direction of the pipe-like member, arranged so as to surround an outer periphery of the pipe-like member, and movable along the longitudinal direction of the pipe-like member, and the mover In the linear motor having the position restriction means for restricting the position of the movement start of the plurality of magnets formed by the magnet at the end of the movement start position side and the magnet adjacent to the magnet among the plurality of magnets arranged in series When the same pole position where the same poles are opposed to each other is defined as position A, the position restricting means is configured such that the number of positions A facing the mover at the movement start position of the mover is equal to the thrust of the mover. Against the mover at the time So as to maximize the number as many positions A to, characterized by regulating the position of the movement start of the movable element.
3. In order to achieve the above object, an exposure scanning apparatus of the present invention includes the linear motor described in 1 or 2 above.

  According to the present invention, the mover can be easily and accurately moved with low power consumption.

Embodiments of the present invention will be described below with reference to the drawings. The technical scope of the present invention is not limited by the description in the description of the present embodiment.
[First Embodiment]
1 is a schematic perspective view of a radiographic image reading apparatus using a linear motor of the present invention, FIG. 2 is an XY plan view of FIG. 1, and FIG. 3 is a block diagram showing a speed control unit of the radiographic image reading apparatus. FIG.

  As shown in FIGS. 1 and 2, the radiation image reading apparatus 1 irradiates the stimulable phosphor plate P while scanning with stimulating excitation light from a light source (not shown), and irradiates this stimulating excitation light. The optical unit 2 that collects the photostimulated luminescence emitted from the photostimulable phosphor plate P, photoelectrically converts the photostimulated luminescence and reads the radiation image information, and the optical unit 2 provided on the base 4. Support member 3 that supports the optical unit 2 in a horizontal direction, a linear motor 7 that moves the optical unit 2, and a guide rail 31 that is provided on the support member 3 and guides the optical unit 2 in the horizontal direction.

  Further, the rotary encoder unit 5 is connected to the moving plate 33 to which the optical unit 2 is attached, and detects the movement of the optical unit 2, and the detection result of the rotary encoder unit 5 is compared with a preset set speed. And a speed control unit 100 that controls the linear motor 7.

  The base 4 has a substantially rectangular plate shape, and the fixing plate 8 that supports the stimulable phosphor plate P is fixed on the base 4, so that the base 4 is stimulable with respect to the upper surface of the base 4. The photostimulable phosphor plate P is held on the base 4 so that the surface of the phosphor plate P irradiated with the stimulating excitation light is substantially vertical.

  The guide rail 31 is a rod-shaped member having a substantially rectangular shape in cross section, and a guided member 32 having a substantially U shape in cross section guided by the guide rail 31 is engaged as shown in FIG. The guided member 32 is attached to the lower surface of the moving plate 33.

  The linear motor 7 is provided on a side of the support member 3 on the upper surface of the base 4. The linear motor 7 is provided on a stator 71 that houses a plurality of magnets, a linear motor holding portion 72 that holds both ends of the stator 71, and a moving plate 33. A movable element 73 is provided in series. The details of the linear motor 7 will be described later.

  The rotary encoder unit 5 is connected to a support base 53 fixed to the moving plate 33 and movable together with the moving plate 33, a rotary encoder 51 provided on the support base 53, and a rotary shaft (not shown) of the rotary encoder 51. And a pulley 52 attached to the lower surface of the support base 53. Thus, the rotary shaft of the rotary encoder 51 and the pulley 52 have an integral shape.

  A wire 6 is wound around the pulley 52, and the pulley 52 rotates in conjunction with the movement of the optical unit 2 and the moving plate 33. Then, the rotary encoder 51 detects the rotational speed from the pulley 52 rotated by the movement of the optical unit 2 and the rotary shaft of the rotary encoder 51. The detected rotational speed information is output to a speed control unit 100 that controls the speed of the linear motor 7.

  The speed control unit 100 includes a difference circuit 101 and a motor drive control circuit 102 as shown in FIG. The above-described rotation speed information corresponding to the moving speed along the horizontal direction of the photostimulable phosphor plate P is input to the difference circuit 101. Then, the difference circuit 101 processes this rotation speed information and outputs it as a speed signal, and generates a difference signal by comparing it with a set speed signal obtained from a preset set speed. This is output to the motor drive circuit 102 as a control signal. The motor drive circuit 102 controls the linear motor 7 based on the difference signal.

Next, the operation of the radiation image reading apparatus 1 having the above configuration will be described.
The photostimulable phosphor plate P is taken into the radiation image reading apparatus 1 by a plate conveying means (not shown) and fixed to the fixed plate 8. When performing an image reading process, first, the linear motor 7 is driven, and the moving plate 33 that supports the optical unit 2 is moved in the horizontal direction along the guide rail 31.

  As a result, the optical unit 2 is moved to a position facing the stimulating excitation light irradiation surface of the stimulable phosphor plate P, and the stimulating excitation light is moved along the horizontal direction of the stimulable phosphor plate P. Scanned. At this time, the excitation light is irradiated while scanning in a direction orthogonal to the moving direction of the optical unit 2. The stimulated emission light excited by the excitation light is converted into an electrical signal by the photoelectric conversion means built in the optical unit 2.

  At this time, when the optical unit 2 moves in the horizontal direction, the movement is transmitted to the wire 6 via the support base 53 provided on the moving plate 33, and the rotation shafts of the pulley 52 and the rotary encoder 51 rotate. To do. Along with this, the rotational speed is detected by the rotary encoder 51 connected to the rotating shaft, and the detection result is output to the speed control unit 100.

  The rotation speed detected by the rotary encoder 51 is compared with a set speed signal obtained from a preset speed set in advance by the difference circuit 101, and the motor drive circuit 102 controls the driving of the linear motor 7 according to the result. To do.

  A known driving method is used as the driving method of the linear motor 7. For example, the moving speed of the linear motor 7 can be controlled by changing the frequency and voltage of the AC drive current by inverter control. Moreover, it is good also as what controls by the pulse width of the pulse voltage input into the needle | mover 73 of the linear motor 7 by PWM control.

  Thus, by always detecting the rotational speed of the rotary encoder 51 and controlling the moving speed of the linear motor 7 based on the detection result, the moving speed of the optical unit 2 can be kept constant. Therefore, the radiation energy accumulated in the photostimulable phosphor plate P can be excited uniformly to obtain a good image without image unevenness.

  When the reading process by the optical unit 2 is completed up to one end of the photostimulable phosphor plate P, the linear motor 7 is stopped once.

  Thereafter, the photostimulable phosphor plate P is irradiated with erasing light by an erasing means (not shown) while the optical unit 2 is fed back, thereby erasing the radiation image remaining on the photostimulable phosphor plate P. . Further, the photostimulable phosphor plate P is carried out of the radiation image reading apparatus 1 by the plate conveying means.

  FIG. 4 is a schematic sectional view of the linear motor 7 in the YZ plane of FIG. The configuration of the linear motor 7 of the present embodiment will be described with reference to this figure.

  As described above, the linear motor 7 includes the linear motor holding portion 72 (holding portion in the present invention) continuously provided on the base 4, the stator 71 held by the linear motor holding portion 72, and the stator 71. And a mover 73 that moves linearly along the outer peripheral surface. The stator 71 includes a pipe-shaped member 711, a plurality of magnets 712, and a lid 713.

  The pipe-like member 711 is a structure having a cylindrical shape that is arranged in parallel with the guide rail 31 so as to move the optical unit 2 in the sub-scanning direction (see FIG. 1) and has both ends opened. The pipe-shaped member 711 is preferably formed of a nonmagnetic metal, and is formed of a nonmagnetic material such as an aluminum alloy, a copper alloy, or nonmagnetic stainless steel. As will be described later, since the movable element 73 moves along the outer peripheral surface of the pipe-shaped member 711, the pipe-shaped member 711 is preferably as thin as possible so as not to reduce the magnetic field acting on the movable element 73.

  The magnet 712 has a cylindrical shape formed so as to have substantially the same diameter as the inner diameter of the pipe-shaped member 711 and a width in the longitudinal direction of L. And this magnet 712 is inserted from the opening of the both ends of the pipe-shaped member 711, and is accommodated in the inside of the pipe-shaped member 711 in the state arrange | positioned in series. The magnets 712 are arranged so that adjacent magnets and N poles or S poles face each other, and the same pole positions A1 to AN are formed between the magnets. In addition, since the longitudinal width of each magnet 712 is L, if the distance between the same-polar positions A1 to AN of the magnet 712 is the pitch width of the magnet 712, the pitch width is also L.

  In the present embodiment, adjacent magnets are arranged so as to be in close contact with each other, but it is not always necessary to make close contact. For example, if the gap is about an error dimension in general machining, ,No problem. When the magnets are not in close contact, the same pole positions A1 to AN are the center positions from the respective magnet ends.

  As a material of the magnet 712, a rare earth magnet having a high magnetic flux density is preferable. In particular, the rare earth magnet is preferably a neodymium-based magnet, such as a neodymium-iron-boron magnet (Nd—Fe—B magnet), and can provide a higher thrust than other magnets. Further, the present invention is not limited to this, and there is no particular limitation as long as there is magnet energy sufficient to provide a necessary coercive force, irreversible demagnetization does not occur in the operating temperature range, and necessary thrust can be obtained.

  The lid body 713 includes a lid body 713 a disposed at one end of the pipe-shaped member 711 and a lid body 713 b disposed at the other end of the pipe-shaped member 711. The lid 713 has a cylindrical shape having substantially the same diameter as the magnet 712, is inserted from both ends of a pipe-like member 711 in which the magnet 712 is accommodated, and is fixed by an adhesive or an adhesive (not shown). The lid 713 seals the opening of the pipe member 711 and prevents the magnet 712 from falling off from both ends of the pipe member 711. One end of the lid 713 is in contact with the magnets 712 a and 712 b disposed at both ends of the pipe-shaped member 711, while the other end is in contact with the linear motor holding unit 72.

  The linear motor holding portion 72 is a structure having a rectangular parallelepiped shape continuously provided on the base 4, and a concave portion having a diameter slightly larger than the outer diameter of the pipe-shaped member 711 is formed at the central portion of one end. Yes. Both ends of the pipe-shaped member 711 are inserted into the recesses, and the lid 713 and the linear motor holding portion 72 disposed at both ends of the pipe-shaped member 711 are fixed by screw members 721. Thereby, the outer peripheral surface of the pipe-shaped member 711 and the inner peripheral surface of the mover 73 are held so as to maintain a certain distance.

  The mover 73 includes a plurality of coils 731a to 731f disposed so as to surround the outer periphery of the pipe-shaped member 711, and a box-shaped cover member 732 that covers the plurality of coils 731a to 731f.

  The coils 731 are arranged so that the respective coils 731 are arranged in parallel in the longitudinal direction of the pipe-like member 711 and the axial centers are located on the same straight line. That is, the coil 731 includes a first U-phase coil 731a, a first V-phase coil 731b, a first W-phase coil 731c, a second U-phase coil 731d, and a second V-phase in order from the left side in FIG. The coil 731e and the second W phase 731f are arranged in series, respectively.

  When the first U-phase 731a to the first W-phase 731c and the second U-phase 731d to the second W-phase 731f are respectively set as one set, the pitch width of the one set of coils and the pitch width of the magnet 712 The coils 731a to 731f are arranged at a predetermined interval so that the lengths L are equal to each other. Thereby, the phase shift between the coil 731 and the magnet 712 can be prevented, and the optimum thrust can be generated in the mover 73. In the present embodiment, the pitch width of one set of coils and the pitch width of the magnets 712 are L, and the widths of the coils 731a to 731f are each L / 3.

  A pipe-like member 711 passes through the axial center of the coil 731. Therefore, when a current is passed through the coil 731 so as to cross the magnetic flux generated by the magnet 712, a thrust is generated in the mover 73 due to the interaction between the current and the magnetic flux, and along the longitudinal direction of the pipe-shaped member 711. The mover 73 moves. Here, the coil 731 is supplied with a three-phase alternating current or a three-phase alternating voltage which is a sine wave whose phase is shifted by 120 degrees with respect to the U phase to the W phase.

  Note that the coil 731 may or may not slide on the outer peripheral surface of the pipe-shaped member 711. In addition, the number of turns of the coil 731 is determined so as to be equal to or greater than the desired thrust and so that the voltage drop of the linear motor 7 and the voltage drop in the drive circuit are less than the power supply voltage, It is preferable to determine the winding diameter.

  The coil 731 is covered with a box-shaped cover member 732. Since the cover member 732 is bonded to the lower surface of the moving plate 33, the moving plate 33 moves as the mover 73 moves.

  FIG. 7 is a perspective view when the moving plate 33 is viewed from the base 4 side. As shown in the drawing, the moving plate 33 is a U-shaped structure having a convex portion at both ends. That is, the moving plate 33 includes a placement table 331 on which the optical unit 2 is placed, and a regulation member 332 disposed at both ends of the placement table 331.

  The placement table 331 is a rectangular parallelepiped having a height H, a lateral width W, and a depth D, and the optical unit 2 is placed on the upper surface 331a of the rectangular parallelepiped. In addition, on the lower surface 331b side facing the upper surface 331a of the table 331, the movable element 73 is bonded and fixed to a recess formed by the lower surface 331b and the regulating member 332 (see FIG. 4). Thus, since the optical unit 2 is placed on the upper surface 331a of the placing table 331 and the movable element 73 is fixed to the lower surface 331b, the movable element 73 moves linearly along the pipe-shaped member 711. The optical unit 2 moves in the same manner.

  The restricting member 332 includes rectangular parallelepipeds 332 a and 332 b that have substantially the same length as the height H and depth D of the table 331 and are shorter than the lateral width W of the table 331. As described above, the regulating members 332a and 332b are bonded and fixed to both ends of the lower surface 331a of the table 331, respectively.

  The lateral width W1 of the restricting member 332a is such that the center position of the first U-phase coil 731a at the movement start position of the mover 73 and the magnet 712a disposed at the end of the pipe-shaped member 711 are as described later. It is formed with a length that is a predetermined distance from the same pole position A1 formed by the magnet adjacent to the magnet 712a toward the other pole of the magnet 712a. Further, the lateral width W2 of the restricting member 332b is such that, at the movement start position on the other end side, the central position of the second W-phase coil 731f is from the same pole position AN formed by the magnet 712b and the magnet adjacent to this magnet. The length of the magnet 712b is a predetermined distance toward the other pole.

  The operation of the linear motor 7 configured as described above will be described with reference to FIGS. 5 is an enlarged cross-sectional view when the mover 73 is located at the left movement start position in FIG. 4, and FIG. 6 is a linear motor when the mover 73 is located at the right movement start position in FIG. 7 is a schematic cross-sectional view of FIG.

  First, the mover 73 and the moving plate 33 are set at a movement start position on one end side (left side in FIG. 4) of the stator 71. At this time, the restricting member 332a of the moving plate 33 is in contact with the upper portion of the linear motor holding portion 72 and restricts the movement start position of the movable element 73 (the position restricting means of the present invention restricts the restricting member 332 of the moving plate 33). And a linear motor holding unit 72).

  That is, as shown in FIG. 5, when the regulating member 332 a comes into contact with the linear motor holding portion 72, the first U-phase coil 731 a located at the rear end portion in the movement start direction X of the mover 73 has the mover The central position C in the movement direction of 73 is the direction opposite to the movement start direction X of the mover 73 from the same pole position A1 formed by the magnet 712a arranged on the movement start position side and the magnet 712c adjacent to the magnet 712a. At position B 3L / 4 away. That is, the position B is a position of L / 4 in the movement start direction X from the position D1 where the magnet 712a contacts the lid 713a.

  Then, in a state where the mover 73 is arranged so that the center position C of the first U-phase coil 731a is the position described above, a current is passed through the coil 731 to generate a thrust in the mover 73. At this time, the central position C of the first U-phase coil 731a is located at a position B that is L / 4 away from the position D1 in the movement start direction X, and this position is set as the movement start position of the mover 73. Even in the initial stage, a sufficient thrust constant can be obtained.

  FIG. 8 shows the relationship between the center position C of the first U-phase coil 731a and the thrust constant obtained by the mover 73 when the mover 73 is moved from the movement start position in the present embodiment. It is a thrust characteristic graph. That is, in FIG. 8, the horizontal axis is the reference position (coil position 0) when the center position C of the first U-phase coil 731a is located at the position B, and the mover 73 is moved in the movement start direction X from the reference position. The position of the center position C of the first U-phase coil 731a when moved is shown. The vertical axis represents the thrust constant obtained by the mover 73 corresponding to the position of the central position C of the first U-phase coil 731a, and the thrust constant obtained when the coil position is 3L / 4 from the reference position. It is expressed as 100%. The graph of FIG. 8 is the same as the graph of FIG. 12 shifted L / 4 to the right, and the coil position corresponding to FIG. 12 is shown in parentheses.

  As apparent from comparison with FIG. 12, when the center position C of the first U-phase coil 731a is located at the position B and the movement of the mover 73 is started from this position, the movement start of the mover 73 is at the initial stage. However, it is possible to obtain a thrust constant of 90% or more, and the change of the thrust constant is gentle, and the speed control of the mover is facilitated. Further, in FIG. 8, the center position C of the first U-phase coil 731a is located at L / 12 (that is, the coil position L / 3, the same pole position A1 to 2L / 3 in FIG. 12). Starting the movement of the mover 73 is more preferable because a thrust constant of 95% or more can be obtained even at the beginning of the movement of the mover 73, and the rise is also gentle.

Hereinafter, a mechanism capable of obtaining such a thrust constant will be described.
As described above, the linear motor 7 according to the present embodiment generates a thrust in the movable element 73 by the interaction between the current flowing through the coil 731 and the magnetic flux generated by the magnet 712, and the movable element 73 becomes the stator 71. It is moved along. Therefore, the thrust generated in the mover 73 is proportional to the magnetic flux intensity and the current.

  On the other hand, since the plurality of magnets 712 are arranged in series so that the same poles face each other, the magnetic fluxes generated from the respective magnets 712 are generated by the magnets 712 at the same pole positions A1 to AN where the magnetic poles repel each other. The magnetic flux has the property of becoming the strongest. Therefore, if the movable element 73 is arranged so that the number of the same-polar positions A1 to AN is opposed to each other at a certain moment, the thrust generated in the movable element 73 is also increased.

  In the linear motor according to the prior art shown in FIG. 11, the movement start position is when the center position of the first U-phase coil 1021a is located at the position D1 ′ of the end of the cap 1030 of the magnet 1012a. The number of the same polarity positions of the magnets 1020 facing the mover 1020 at the start position is one of the same polarity positions A1 ′ where the south pole and the south pole face each other.

  On the other hand, in the present embodiment, as shown in FIG. 4, since the movement start position of the mover 73 is restricted by the restriction member 332a, it is movable as compared with the position of the mover 1020 (see FIG. 11) in the prior art. The child 73 is located at a position advanced by L / 4 toward the center of the pipe-shaped member 711. Therefore, the number of the same pole positions facing the mover 73 at the movement start position is two, the same pole position A1 and the same pole position A2. This is the same number as the maximum number of homopolar positions facing the mover 73 when the thrust obtained by the mover 73 is stable.

  When the thrust is stable, the same pole position may face both ends and the center of the mover 73, but when the three same pole positions face each other in this way, it is instantaneous and almost to the mover 73. In this embodiment, the maximum number of homopolar positions when the thrust is stable is assumed to be two. Here, the time when the thrust is stable refers to a region where a predetermined thrust can be obtained in the mover 73 with respect to a predetermined current supply to the coil 731. In the present embodiment, the thrust is shown in FIGS. It means a region where the constant is 90% or more. In addition, since the expected thrust in the mover 73 differs depending on the magnet strength of the magnet to be used, the thrust constant is not limited to the region where the thrust constant is 90% or more. For example, the thrust constant is 80% or more, or It can be set as appropriate, such as an area of 85% or more.

  Thus, the number of the same polarity positions of the magnets 712 facing the mover 73 at the movement start position is the same as the maximum number of the same pole positions facing the mover 73 when the thrust is stable. A sufficient thrust constant can be obtained even at the beginning of movement. Accordingly, it is possible to move the mover 73 with low power consumption, and it is possible to easily control the moving speed of the mover 73 because the thrust does not rise steeply.

  Then, when the movable element 73 is moved from the movement start position, the optical unit 2 placed on the movable plate 33 is also moved along the stator 71 and the stimulable excitation light of the stimulable phosphor plate P is moved. The stimulated excitation light is scanned on the irradiated surface.

  When scanning of the photostimulable phosphor plate P is completed and the movable element 73 moves to the other end side, the regulating member 332b comes into contact with the upper portion of the linear motor holding portion 72 as shown in FIG. At this time, when the regulating member 332b contacts the linear motor holding portion 72, the center position of the second W-phase coil 731f of the mover 73 is adjacent to the magnet 712b disposed on the movement start position side and the magnet 712b. It is located at a position of 3L / 4 in the direction opposite to the movement start direction X of the mover 73 from the same pole position AN formed by the magnet 712d. This position is L / 4 from the position D2 in contact with the lid 713b of the magnet 712b.

  Then, in the same manner as described above, a current is passed through the coil 731 to generate a thrust in the mover 73, and the mover 73 is fed back. Here, the center position of the second W-phase coil 731f is located at a position 3L / 4 (coil position L / 4 in FIG. 12) in the direction opposite to the movement start direction X from the same pole position AN, and this position is movable. Since it is set as the movement start position of the child 73, a sufficient thrust constant can be obtained even at the beginning of movement.

  In addition, although the center position C of the first U-phase coil 731a has been described as being 3L / 4 from the same pole position A1 in the direction opposite to the moving direction X, the present invention is not limited to this, and is 3L / 4 or less. If it is a position, a sufficient thrust constant can be obtained. In particular, as described above, when the central position C of the first U-phase coil 731a is located at 2L / 3 or less from the same-pole position A1, the same-pole positions A1 and A2 are surely opposed to the mover 73. In addition, it is preferable because a thrust constant can be obtained more.

  If the central position C is located at a position advanced from the same-polarity position A1 by 3L / 4, the obtained thrust constant is low, and the slope of the graph indicating the thrust characteristics becomes steep. In the case where the movable element 73 is installed, it becomes difficult to move the movable element 73, or it is difficult to control the moving speed of the movable element 73. The same applies to the second W-phase coil 731f at the movement start position on the other end side.

Moreover, the lower limit in the position of these 1st U-phase coils 731a and the 2nd W-phase coil 731f is not specifically limited. In other words, at the movement start position of the mover 73, the thrust constant obtained increases as the center positions of the first U-phase coil 731a and the second W-phase coil 731f approach the homopolar positions A1 and AN, respectively. However, since the moving range of the mover 73 is shortened on the contrary, it is preferable to set the lower limit appropriately according to the apparatus configuration.
[Second Embodiment]
Next, a second embodiment of the linear motor 7 will be described. FIG. 9 is a schematic cross-sectional view of the linear motor 7 in the second embodiment. In addition, about the thing which has the same function as the linear motor which concerns on 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. That is, in the linear motor 7 according to the second embodiment, the longitudinal lengths of the magnets 712a and 712b arranged at both ends of the pipe-shaped member 711 are L / 2 that is half of the pitch width L of the magnet 712. Except for a certain point and the lateral widths W1 and W2 of the regulating members 331a and 331b are shorter than the lateral width of the regulating member 331 in the first embodiment, the configuration is the same as that of the first embodiment.

  FIG. 10 is a thrust characteristic graph showing the relationship between the coil position and the thrust constant. That is, in FIG. 10, the horizontal axis indicates the center position of the first U-phase coil 731a, and the vertical axis indicates the thrust constant obtained by the mover 73 corresponding to the center position of the first U-phase coil 731a. Shown in the display.

  Thus, even if the longitudinal lengths of the end magnets 712a and 712b are set to a length L / 2 that is half the pitch width L of the magnet 712, a sufficient thrust constant can be obtained. That is, the center position of the first U-phase coil 731a of the mover 73 is located at a position 3L / 4 from the same pole position A1 formed by the magnet 712a and the magnet 713c adjacent to the magnet 712a. A sufficient thrust constant can be obtained by setting this position as the movement start position of the mover 73.

  Furthermore, since the stator 71 can be shortened by the amount of the magnets 712a and 712b being short, the apparatus can be reduced in the sub-scanning direction. Note that the length of the magnets 712a and 712b in the longitudinal direction is preferably less than L and not less than L / 2 because the permeance coefficient decreases and demagnetization is likely to occur if the length is extremely shortened.

  In the present embodiment, the moving plate 33 includes the restricting member 332, and the restricting member 332 contacts the linear motor holding portion 72 to restrict the movement start position of the mover 73. Alternatively, a restricting member may be provided on the side surface of the mover 33, and the restricting member of the mover 33 may contact the linear motor holding portion 72 to restrict the movement start position of the mover 73. Further, the linear motor holding part 72 itself may have a function of a regulating member. That is, as long as the movement start position of the mover 73 is regulated so as to satisfy the present invention, any configuration may be used.

  In addition, as an example of the exposure scanning apparatus, the radiation image reading apparatus that reads the photostimulable phosphor plate P supported by the fixed plate 8 with the optical unit 2 has been described. However, the exposure scanning apparatus is limited to this. For example, a drum-type exposure scanning device that wraps a sheet coated with a photosensitive material around the surface of the drum and exposes the photosensitive material while moving the optical unit in the longitudinal direction of the drum may be used. .

It is a schematic perspective view of the radiographic image reading apparatus using the linear motor of this invention. FIG. 2 is an XY plan view in FIG. 1. It is a block diagram which shows the speed control part of a radiographic image reading apparatus. It is a schematic sectional drawing of the linear motor in the YZ plane of FIG. It is an expanded sectional view when a needle | mover is located in the movement start position of the left side in FIG. It is a schematic sectional drawing of a linear motor when a needle | mover is located in the movement start position of the right side in FIG. It is a perspective view when a moving plate is seen from the base side. It is a thrust characteristic graph which shows the relationship between the coil position and thrust constant in 1st Embodiment. It is a schematic sectional drawing of the linear motor in 2nd Embodiment. It is a thrust characteristic graph which shows the relationship between a coil position and a thrust constant in 2nd Embodiment. It is a schematic sectional drawing of the linear motor which concerns on a prior art. 12 is a thrust characteristic graph showing a relationship between a coil position and a thrust constant in the linear motor shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiographic image reading apparatus 2 Optical unit 7 Linear motor 33 Moving plate 71 Stator 72 Linear motor holding part 73 Movable element 331 Displacement stand 332 Restriction member 711 Pipe-shaped member 712 Magnet 731 Coil A1-AN Same pole position B Same pole position A1 Position 3L / 4 away from the movement start direction from C C Center position of the first U-phase coil X Movement start direction of the mover

Claims (7)

A plurality of magnets arranged in series so that the same poles face each other;
A pipe-shaped member that houses the plurality of magnets;
A mover that includes a plurality of coils arranged in parallel in the longitudinal direction of the pipe-shaped member, is arranged so as to surround an outer periphery of the pipe-shaped member, and is movable along the longitudinal direction of the pipe-shaped member;
Position restricting means for restricting the movement start position of the mover;
In a linear motor having
The pitch width of the plurality of magnets is L,
The central position in the moving direction of the mover in the coil installed at the rear end of the moving start direction of the mover among the plurality of coils is a position C,
The same polarity position where the same polarity formed by the magnet at the end on the movement start position side and the magnet adjacent to the magnet among the plurality of magnets arranged in series is opposed to the position A,
A position that is 3 L / 4 away from the position A in the direction opposite to the movement start direction is the position B,
When
The linear motor is characterized in that the position restricting means restricts the movement start position of the mover so that the position C includes the position B and is located closer to the movement start direction than the position B. The position restricting means includes a holding portion that holds both ends of the pipe-shaped member, and a moving plate that is connected to the mover and contacts the holding portion at a movement start position of the mover. The linear motor according to claim 1. 3. The linear motor according to claim 1, wherein the magnet at the end of the movement start position side has a length of less than L and not less than L / 2. Assuming that a position 2L / 3 away from the position A in the direction opposite to the movement start direction is B ', the position restricting means includes a position C that includes the position B' and is closer to the movement start direction than the position B '. 4. The linear motor according to claim 1, wherein the movement start position of the mover is regulated so as to be positioned at a distance from the linear motor. 5. A plurality of magnets arranged in series so that the same poles face each other;
A pipe-shaped member that houses the plurality of magnets;
A mover that includes a plurality of coils arranged in parallel in the longitudinal direction of the pipe-shaped member, is arranged so as to surround an outer periphery of the pipe-shaped member, and is movable along the longitudinal direction of the pipe-shaped member;
Position restricting means for restricting the movement start position of the mover;
In a linear motor having
When the same pole position where the same pole formed by the magnet at the end on the movement start position side and the magnet adjacent to the magnet of the plurality of magnets arranged in series is opposed to the position A,
The position restricting means is configured such that the number of positions A facing the mover at the movement start position of the mover is the same as the maximum number of positions A facing the mover when the thrust of the mover is stable. In addition, the linear motor is characterized in that the position at which the mover starts to move is regulated. The linear motor moves the mover by supplying a three-phase alternating current or alternating voltage with a predetermined phase shift to the coil, and is supplied with the three-phase alternating current or alternating voltage, respectively. When the three coils are one set, the mover is configured to include at least one coil of the one set, and the pitch width of the one set of coils and the pitch width of the plurality of magnets are The linear motor according to claim 1, wherein the linear motor is equal. An exposure scanning apparatus using the linear motor according to claim 1.

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