JP2007221960A - Cylindrical linear motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fluctuation in the magnetic pole pitch of a stator without tightening the dimension tolerance of a permanent magnet, in a cylindrical linear motor. <P>SOLUTION: In the cylindrical shaft 12 which constitutes the outer shell of the stator of a cylindrical linear motor, a large number of the permanent magnets 13 are accommodated with S-poles and N-poles of the adjacent permanent magnets 13 mutually opposed with each other, holding a spacer member 18 for adjusting the magnetic pole pitch between. Then, in order to adjust the magnetic pole pitch (interval of the permanent magnets 13) of the stator 10, the spacer member 18 with a required thickness held between the respective permanent magnets 13 is selected from among a plurality of spacer members with different thickness prepared in advance. Thereby, fluctuations if any, in manufacturing found in the thickness of the permanent magnets can be absorbed by the adjustment of the thickness of the spacer member 18. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cylindrical linear motor having a function of adjusting the magnetic pole pitch of a stator.

  In recent years, a cylindrical linear motor has attracted attention as an actuator for linear reciprocating drive. This cylindrical linear motor is also referred to as a “shaft motor”. For example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2000-139069), Patent Document 2 (Japanese Patent No. 3481759), and the like, N A magnetic sensor in which a mover having a plurality of coils is arranged concentrically with the shaft-like stator outside the shaft-like stator that alternately generates magnetic poles and S-poles, and is provided on the mover In many cases, the mover is linearly driven along the stator by detecting the position of the magnetic pole of the stator with the (Hall element) and switching the energization to the coil.

  As described in Patent Document 1, there is a cylindrical linear motor stator formed by alternately magnetizing N poles and S poles with a magnetizing device on a single bar-shaped magnetic material. It is difficult to strongly magnetize N pole and S pole at the same pitch on a single bar-shaped magnetic material, and it is difficult to increase the magnetic force and the boundary position between the magnetic poles. The demand for improvement cannot be fully met.

In order to solve this problem, in many cases, a shaft-shaped stator is configured by storing a large number of pre-magnetized permanent magnets in a straight line in a cylindrical shaft. In this case, a configuration in which a yoke (magnetic material) is sandwiched between adjacent permanent magnets in order to join the same poles of adjacent permanent magnets facing each other or to increase magnetic flux contributing to thrust generation. (See Patent Document 2)
JP 2000-139069 A Japanese Patent No. 3481759

  In general, a permanent magnet is manufactured by molding with a molding die, or is manufactured by sintering the permanent magnet. Therefore, when a stator is manufactured by arranging a large number of permanent magnets in a straight line, there is a problem that the magnetic pole pitch varies due to manufacturing variations in the thickness dimension of each permanent magnet and the thrust is reduced.

This thrust reduction rate Y [p. u. ] Is calculated by the following equation.
Y = 1−cos {(Xn · D) / D × 360 °} (1)
Here, D is the magnetic pole pitch [mm], and X is the moving distance [mm] of the mover from the origin (the position of one N pole is the origin). n is the number of magnetic pole pitches that the mover passes in the process of moving the distance X from the origin.

For example, when the magnetic pole pitch D = 60 [mm], the movement distance X of the mover X = 910 [mm], and the number n of passes of the magnetic pole pitch n = 15, the positional relationship between the mover and the magnetic pole of the stator is 10 [mm]. The deviation is calculated by the following equation.
Deviation of magnetic pole pitch = | 910−60 × 15 | = 10 [mm]
It can be seen that if the coil of the mover is energized at this shifted position, the thrust is halved by the above equation (1).

  Conventionally, as the countermeasure accuracy has been satisfied by tightening the dimensional tolerance of the permanent magnet, the manufacturing cost of the permanent magnet becomes considerably high, and it is impossible to meet the demand for cost reduction. There was a problem.

  In a system equipped with a linear encoder that detects the moving position of the mover, the magnetic sensor that detects the position of the magnetic pole of the stator is omitted by switching the energization to the coil based on the detected position information of the linear encoder. Although it is conceivable to adopt the magnetic sensorless configuration described above, a reduction in thrust is inevitable because the correspondence between the detected position information of the linear encoder and the actual magnetic pole position is deviated due to the aforementioned variation in magnetic pole pitch. Therefore, in order to avoid a decrease in thrust in the magnetic sensorless configuration, (1) tighten the dimensional tolerance of the permanent magnets to reduce the variation of the magnetic pole pitch, or (2) detect the linear encoder detection position information and The correspondence relationship with the actual magnetic pole position is measured, and the data is stored in the memory of the linear motor control device, and the magnetic pole is detected based on the detected position information of the linear encoder and the stored data in the memory while the linear motor is driven. It is conceivable to detect the position of the coil and switch the energization to the coil. However, any of these methods involves a considerable cost increase and cannot satisfy the demand for cost reduction.

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to reduce the variation in the magnetic pole pitch of the stator even if the dimensional tolerance of the permanent magnet is not strict. An object of the present invention is to provide a cylindrical linear motor that can cope with cost reduction and magnetic sensor-less.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a mover including a plurality of coils is concentrically formed on the outside of a shaft-like stator in which a plurality of permanent magnets are linearly assembled. Each of the permanent magnets of the stator, wherein the permanent magnet is linearly driven along the stator by switching energization to the plurality of coils in accordance with the moving position of the mover. The magnetic pole pitch adjusting means for adjusting the magnetic pole pitch is provided between the two. In this configuration, even if there is a manufacturing variation in the thickness dimension of each permanent magnet, the variation can be absorbed by the adjustment of the magnetic pole pitch adjusting means. Therefore, even if the dimensional tolerance of the permanent magnet is not strict, Variations in the magnetic pole pitch can be reduced, and it is possible to cope with cost reduction and magnetic sensor-less.

  Here, as a specific example of the magnetic pole pitch adjusting means, as in claim 2, a required thickness dimension is selected from a plurality of spacer members having different thickness dimensions prepared in advance. The magnetic pole pitch may be adjusted by being sandwiched between them, or the magnetic pole pitch may be adjusted by increasing or decreasing the number of spacer members sandwiched between the permanent magnets as in claim 3. . In either case, the magnetic pole pitch adjusting means can be realized at low cost.

  In this case, as in the fourth aspect, each permanent magnet and each spacer member are prevented from coming off by inserting a through hole formed in each central portion of each permanent magnet and each spacer member into the central axis and preventing both ends of the central axis. The spacer member may be integrated. If it does in this way, it can assemble easily in the state where many permanent magnets and spacer members were arranged in a straight line.

  Further, as described in claim 5, the spacer member may be formed with a notch that can be inserted into the central axis from the outer peripheral side. In this way, it is possible to easily insert or replace the spacer member into the central axis from the gap between the permanent magnets while the permanent magnets are inserted through the central axis, and to easily adjust the magnetic pole pitch. It can be performed with high accuracy.

  According to another aspect of the present invention, a through hole formed in the center of each permanent magnet is inserted into the center bolt, and the magnetic pole pitch adjusting means is sandwiched between the permanent magnets and screwed into the center bolt. The magnetic pole pitch may be adjusted by adjusting the gap dimension between the pair of nuts by screwing back and forth of the nuts. In this configuration, the magnetic pole pitch can be adjusted very easily and accurately by screwing back and forth of the nut screwed into the center bolt.

  Several embodiments embodying the best mode for carrying out the present invention will be described below.

A first embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the cylindrical linear motor 11 includes a shaft-shaped stator 10 in which a large number of permanent magnets 13 are arranged in a straight line in a cylindrical shaft 12, and the shaft 12 A mover 15 having a plurality of coils 14 built in is arranged concentrically with the shaft 12 on the outside, and by switching the energization to the plurality of coils 14 in accordance with the moving position of the mover 15, the mover 15 is placed on the shaft. 12 is configured to drive linearly along the line 12. The permanent magnets 13 in the shaft 12 are arranged so that the S poles and N poles of the adjacent permanent magnets 13 face each other with a magnetic pole pitch adjusting spacer member 18 (magnetic pole pitch adjusting means) described later. Yes.

  The shaft 12 is formed of a pipe made of a nonmagnetic material (for example, stainless steel) that transmits the magnetic flux of each permanent magnet 13. The coil 14 of the mover 15 is disposed concentrically with the shaft 12 so as to surround the outer periphery of the shaft 12 (permanent magnet 13). Both ends of the shaft 12 are fixed horizontally to a support bracket 17 erected on the base frame 16.

  Next, the assembly structure of the stator 10 will be described in detail with reference to FIG. In the cylindrical shaft 12 constituting the outer shell of the stator 10, a large number of permanent magnets 13 are arranged between the S poles of the adjacent permanent magnets 13 and the N poles are spacer members 18 for adjusting the magnetic pole pitch (the magnetic pole pitch). It is stored so as to face each other across the adjusting means). Each spacer member 18 is formed in a disk shape or a short columnar shape with a magnetic material such as iron so as to serve as a yoke, and each permanent magnet 13 is also formed in a short columnar shape. Each permanent magnet 13 and each spacer member 18 are integrated by inserting a central shaft 23 into through-holes 21 and 22 formed at the center of each permanent magnet 13 and preventing both ends of the central shaft 23 from coming off as follows. Has been.

  Male screw portions 24 and 25 are formed at both ends of the central shaft 23, respectively, and the center portions of the stepped cap members 26 and 27 fitted and fitted to the both end openings of the cylindrical shaft 12 are at the center. Screw holes 28 and 29 for tightening into the male screw portions 24 and 25 of the shaft 23 are formed. When assembling the stator 10, first, the cap member 26 is fastened only to one male screw portion 24 of the central shaft 23, and then a predetermined number of spacer members 18 and permanent magnets 13 are alternately placed on the central shaft 23. Plug in. Thereafter, a nut 30 is fastened to the other male screw portion 25 of the central shaft 23, whereby a predetermined number of permanent magnets 13 and spacer members 18 inserted into the central shaft 23 are sandwiched and fixed by the cap member 26 and the nut 30. Put it in a state.

  Thereafter, the assembly of the permanent magnet 13 and the spacer member 18 is inserted into the cylindrical shaft 12 from the nut 30 side, and the cap member 27 is fastened to the other male screw portion 25 of the central shaft 23, and each cap member 26 is inserted. , 27 is tightened until the cap member 27 is tightened until the outer peripheral stepped portions are fixed in contact with the opening edges of both ends of the cylindrical shaft 12, whereby the assembly of the permanent magnet 13 and the spacer member 18 is placed inside the cylindrical shaft 12. Assemble to.

  In this case, in order to adjust the magnetic pole pitch of the stator 10 (interval of the permanent magnets 13), the spacer member 18 sandwiched between the permanent magnets 13 is necessary from a plurality of spacer members prepared in advance with different thickness dimensions. The thickness dimension is selected.

  Further, in the first embodiment, in order to make it possible to replace the spacer member 18 in a state where each permanent magnet 13 is assembled to the central shaft 23, as shown in FIG. A notch 31 that can be inserted from the outer peripheral side is formed, and as a result, the shape of each spacer member 18 is C-shaped.

  In this case, since the permanent magnet 13 and the spacer member 18 inserted into the central shaft 23 are sandwiched and fixed by the cap member 26 and the nut 30, even if the shape of the spacer member 18 is C-shaped, After tightening, the spacer member 18 does not fall off the central shaft 23.

  Further, in order to more reliably prevent the spacer member 18 from falling off the central shaft 23, as shown in FIG. 5, the notch 32 is formed so as to obliquely intersect the through hole 22 of the spacer member 18. The spacer member 18 may be inclined with respect to the central axis 23 and inserted from the notch 32 to the through hole 22. In this configuration, when the spacer member 18 fitted to the central shaft 23 is sandwiched between the permanent magnets 13 and the spacer member 18 is returned to a state perpendicular to the central shaft 23, the notch 32 and the center of the spacer member 18 are centered. Since the shaft 23 intersects, the spacer member 18 is prevented from falling off from the central shaft 23.

  Further, since the spacer member 18 also serves as a yoke, the balance of the magnetic flux interlinking from the spacer member 18 (yoke) to the coil 14 of the mover 15 is slightly disturbed by the notches 31 and 32, and the thrust force acting on the mover 15 is reduced. There is concern that the balance may be a little worse. As a countermeasure against this, as shown in FIG. 6, a magnetic bolt 33 made of a magnetic material such as iron is provided so as to straddle the notch 31 of the spacer member 18, and the magnetic bolt 33 corrects magnetic flux and spacer member. 18 may be prevented from falling off. Alternatively, an elastically deformable magnetic material (such as magnetic rubber) may be fitted into the notches 31 and 32 of the spacer member 18.

  For example, when the total length of the field portion of the stator 10 is 1500 [mm] and the magnetic pole pitch is 60 [mm], as shown in FIG. There are two spacer members 18 each.

In this example, the period of the magnetic pole of the stator 10 is 1500/60 = 25 [period].
When the dimensional tolerances of the permanent magnet 13 and the spacer member 18 are ± 0.1 [mm], the maximum plus direction error of the total length of the field portion of the stator 10 is 25 × 4 × 0.1 = 10 [mm]. It becomes.

  If the coil 14 is energized with the positional relationship between the magnetic poles of the stator 10 and the coil 14 shifted by 10 [mm], the thrust reduction rate Y [p. u. ] Becomes 0.5, and the thrust is halved.

Y = 1−cos {10/60 × 360 °} = 1−cos 60 ° = 0.5
In this case, if the dimensional tolerance between the permanent magnet 13 and the spacer member 18 is reduced to 1/10 or less of the above-described tolerance, the reduction in thrust can be suppressed to 0.5 [%] or less. Is not practical with a significant cost increase.

  Accordingly, in the first embodiment, in order to adjust the magnetic pole pitch of the stator 10, the spacer member 18 sandwiched between the permanent magnets 13 is required from among a plurality of spacer members prepared in advance with different thickness dimensions. The thing of thickness dimension is selected. As a result, even if there is a manufacturing variation in the thickness dimension of each permanent magnet 13, the variation can be absorbed by adjusting the thickness of the spacer member 18. The variation of the magnetic pole pitch of 10 can be reduced, and the demand for cost reduction can be satisfied.

  In addition, in the first embodiment, the accuracy of the magnetic pole pitch of the stator 10 can be sufficiently secured. Therefore, if a linear encoder (not shown) for detecting the moving position of the mover 15 is mounted, the linear encoder By switching the energization to the coil 14 based on the detected position information, it is possible to adopt a magnetic sensorless configuration in which the magnetic sensor for detecting the position of the magnetic pole of the stator 10 is omitted, and further cost reduction can be realized. .

  However, the present invention may be configured such that a magnetic sensor for detecting the position of the magnetic pole of the stator 10 is mounted and the energization to the coil 14 is switched based on the output signal of the magnetic sensor.

  Further, in the first embodiment, the spacer member 18 is formed with the notch 31 (32) that can be inserted into the central shaft 23 from the outer peripheral side, so that each permanent magnet 13 and spacer member assembled to the central shaft 23 is formed. If the nut 30 holding the pin 18 is loosened, the magnetic forces of the same polarity facing each other between the permanent magnets 13 repel each other, and the interval between the permanent magnets 13 is naturally expanded. Accordingly, the spacer member 18 having an appropriate thickness can be easily inserted into the central shaft 23 from the outer peripheral side or replaced from the gap between the permanent magnets 13 while the permanent magnets 13 are inserted into the central shaft 23. There is an advantage that the work of adjusting the magnetic pole pitch can be performed easily and accurately.

  However, the present invention may use an annular spacer member in which the notch 31 (32) is not formed. Even in this case, if the nut 30 is removed from the central shaft 23 and the permanent magnet 13 and the annular spacer member are extracted from the central shaft 23, the spacer member can be replaced with a spacer member having an appropriate thickness.

  In the first embodiment, one spacer member 18 is sandwiched between the permanent magnets 13, but in the second embodiment of the present invention shown in FIG. 8, the thickness of each spacer member 35 that is a magnetic pole pitch adjusting means is set. The magnetic pole pitch of the stator 10 is adjusted by forming the spacer member 18 thinner than the spacer member 18 of the first embodiment and increasing or decreasing the number of spacer members 35 sandwiched between the permanent magnets 13. In this case, the shape of each spacer member 35 other than the thickness may be any of the shapes shown in FIGS. 4 to 6 described in the first embodiment, and of course, may be other shapes. Yes.

In the second embodiment, the thickness of each spacer member 35 may be the same. However, as in the first embodiment, a thickness of a required thickness is selected from a plurality of spacer members prepared in advance. You may make it choose a thing.
Also in the second embodiment described above, the same effect as in the first embodiment can be obtained.

  In the first embodiment, the male screw portions 24 and 25 are formed only at both ends of the central shaft 23 through which the permanent magnet 13 and the spacer member 18 are inserted. However, in the third embodiment of the present invention shown in FIG. A large number of permanent magnets 13 are inserted into the central bolt 36, and a spacer member 18 and a pair of nuts 37 (magnetic pole pitch adjusting means) are alternately inserted between the permanent magnets 13. Has been. In the example of FIG. 9, the pair of nuts 37 is disposed at an interval between two permanent magnets 13 (interval of one magnetic pole pitch), but the pair of nuts 37 may be disposed at an interval other than this.

  In this case, the pair of nuts 37 is screwed into the center bolt 36, but the permanent magnet 13 and the spacer member 18 are merely inserted through the center bolt 36, and the pair of screws screwed into the center bolt 36 is used. By adjusting the gap dimension between the nuts 37 by screwing back and forth of the nuts 37, the positions of the permanent magnet 13 and the spacer member 18 are shifted along the center bolt 36 to adjust the magnetic pole pitch of the stator 10. . Other configurations are the same as those of the first embodiment.

In this configuration, the adjustment work of the magnetic pole pitch of the stator 10 can be performed very easily and accurately by the screwing back and forth of the nut 37 screwed into the center bolt 36.
Note that an elastically deformable magnetic material (for example, magnetic rubber) may be sandwiched between the pair of nuts 37 to increase the magnetic flux efficiency.

  In each of the first to third embodiments described above, all the permanent magnets 13 and the spacer members 18 (nuts 37) constituting the stator 10 are assembled to one central shaft 23 (central bolt 36). The shaft 23 (center bolt 36) may be divided into a plurality of pieces and assembled individually, and the shaft 23 may be housed in the cylindrical shaft 12 to assemble the center shaft 23.

It is a figure which shows roughly the apparatus carrying the cylindrical linear motor of Example 1 of this invention. It is a perspective view of the principal part of the cylindrical linear motor of Example 1. 1 is a cross-sectional view of a main part of a cylindrical linear motor according to Embodiment 1. FIG. It is a figure explaining the 1st example of a spacer member. It is a figure explaining the 2nd example of a spacer member. It is a figure explaining the 3rd example of a spacer member. It is a figure explaining the arrangement | sequence of the permanent magnet and spacer member per magnetic pole pitch. It is sectional drawing of the principal part of the cylindrical linear motor of Example 2. FIG. It is sectional drawing of the principal part of the cylindrical linear motor of Example 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Stator, 11 ... Cylindrical linear motor, 12 ... Cylindrical shaft, 13 ... Permanent magnet, 14 ... Coil, 15 ... Movable element, 16 ... Base frame, 17 ... Support bracket, 18 ... Spacer member (magnetic pole pitch) Adjusting means) 21, 22 ... through hole, 23 ... center shaft, 26,27 ... cap member, 31, 32 ... notch, 33 ... magnetic bolt, 35 ... spacer member (magnetic pole pitch adjusting means), 36 ... center bolt 37 ... nut (magnetic pole pitch adjusting means)

Claims (6)

A mover incorporating a plurality of coils is arranged concentrically with the stator on the outside of a shaft-like stator in which a plurality of permanent magnets are linearly assembled, and the plurality of movers are moved according to the movement position of the mover. In a cylindrical linear motor that linearly drives the mover along the stator by switching energization to a coil,
A cylindrical linear motor comprising magnetic pole pitch adjusting means for adjusting a magnetic pole pitch between the permanent magnets of the stator.   The magnetic pole pitch adjusting means adjusts the magnetic pole pitch by selecting a required thickness dimension from a plurality of spacer members having different thickness dimensions prepared in advance and sandwiching them between the permanent magnets. The cylindrical linear motor according to claim 1, wherein:   2. The cylindrical linear motor according to claim 1, wherein the magnetic pole pitch adjusting means adjusts the magnetic pole pitch by increasing or decreasing the number of spacer members sandwiched between the permanent magnets.   The permanent magnets and the spacer members are integrated by inserting through holes formed in the central portions of the permanent magnets through the central shaft and preventing both ends of the central shaft from coming off. The cylindrical linear motor according to 2 or 3.   5. The cylindrical linear motor according to claim 4, wherein the spacer member is formed with a notch that can be inserted into the central shaft from an outer peripheral side thereof. Each of the permanent magnets has a through hole formed in the center thereof inserted through a center bolt,
The magnetic pole pitch adjusting means adjusts the magnetic pole pitch by adjusting a gap dimension between a pair of nuts sandwiched between the permanent magnets and screwed into the central bolt by screwing back and forth of the nuts. The cylindrical linear motor according to claim 1.

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