Positioning device, drive device

Abstract

To provide a positioning device and the like capable of suppressing an increase in a position detection part at a curved part of a trajectory.SOLUTION: A positioning device includes a plurality of magnetic sensors S4 to S6 which are arranged on a rail for positioning magnetic scales C2, C4 fitted to movers movable along the rail and whose intervals are shorter than length in a trajectory direction of the magnetic scales C2, C4. At least one of the magnetic sensors S4 to S6 is arranged at a position deviated outward from a central trajectory RT of the magnetic scales C2, C4 in a curved part of the rail. Distance "a / 2" between end parts (C2", C4') of the magnetic scales C2, C4 and the magnetic sensor S5 when a center of the magnetic scales C2, C4 is at an equal distance from adjacent magnetic sensors S4 to S6 is virtually equal to distance "a / 2" between a center (C3') of the magnetic scales C2, C4 when the center of the magnetic scales C2, C4 approaches the magnetic sensor S5 most and the magnetic sensor S5.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a positioning device for a mover that is movable along a track. [Background technology]

[0002] Patent Document 1 discloses a linear transport system as a drive device that moves a mover along a track. A plurality of magnetic sensors arranged along the track measure the position of a magnetic scale (i.e., the mover) attached to the mover. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-164396 Summary of the Invention [Problem to be solved by the invention]

[0004] The track in a linear conveyance system such as that described in Patent Document 1 may include not only straight sections but also curved sections. In curved sections, radial or lateral misalignment typically occurs between the end of the linear magnetic scale and the track. This raises the risk that the end of the magnetic scale may deviate from the magnetic sensors arranged on the curved track. One possible solution would be to narrow the spacing between the magnetic sensors in curved sections compared to straight sections, but this would increase the number of magnetic sensors required, resulting in higher costs.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a positioning device and the like that can suppress an increase in the number of position detection units in curved sections of a track. [Means for solving the problem]

[0006] In order to solve the above problems, a positioning device according to one aspect of the present invention includes a plurality of position detection units arranged on a track to measure the position of a positioning scale attached to a movable element movable along the track, the position detection units being spaced apart from each other by a distance smaller than the length of the positioning scale in the track direction, and at least one position detection unit being arranged at a position shifted outward from the central locus of the positioning scale on a curved portion of the track.

[0007] In this aspect, by arranging the position detection units at positions shifted outward from the central locus of the positioning scale in the curved portion of the track, radial deviation between the position detection units and the ends of the positioning scale is reduced. This makes it less likely that the ends of the positioning scale will come off the position detection units, eliminating the need to reduce the spacing between the position detection units as in the past. Therefore, according to the present invention, it is possible to suppress an increase in the number of position detection units in the curved portion of the track.

[0008] Another aspect of the present invention is a drive device comprising: a mover that is driven along a track; and a plurality of position detection units that are arranged on the track to measure the position of a positioning scale attached to the mover, the position detection units being spaced apart from each other by an interval shorter than the length of the positioning scale in the track direction, wherein at least one position detection unit is arranged at a position shifted outward from the central locus of the positioning scale on a curved portion of the track.

[0009] Any combination of the above components and any conversion of these expressions into methods, devices, systems, recording media, computer programs, etc. are also encompassed by the present invention. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress an increase in the number of position detection points in curved sections of a track. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing the overall structure of a linear transport system. [Figure 2] 1 is a schematic diagram showing a positioning device configured by a position detection unit and the like in a linear transport system. [Figure 3] 10A and 10B show a schematic diagram of a state in which the position measurement subject of a moving magnetic scale is switched from a magnetic sensor at the source of the movement to a magnetic sensor at the destination of the movement. [Figure 4] 1 is a top view schematically showing a typical arrangement of a plurality of magnetic sensors in a curved section of a rail and the movement of a magnetic scale C. FIG. [Figure 5] 10A and 10B show a schematic representation of a magnetic scale at an intermediate scale position of a magnetic sensor; [Figure 6] 2 is a top view schematically showing the arrangement of a plurality of magnetic sensors and the movement of a magnetic scale in the positioning device according to the present embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as an embodiment) will be described in detail with reference to the drawings. In the description and / or drawings, identical or equivalent components, members, processes, etc. will be assigned the same reference numerals, and redundant explanations will be omitted. The scale and shape of each part shown in the drawings are set for convenience to simplify the explanation, and should not be interpreted as limiting unless otherwise specified. The embodiment is an example and does not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiment are not necessarily essential to the present invention.

[0013] FIG. 1 is a perspective view showing the overall structure of a linear conveyance system 1, which is one embodiment of a driving device according to the present invention. The linear conveyance system 1 includes a stator 2 that forms a circular rail or track, and multiple movers 3A, 3B, 3C, and 3D (hereinafter collectively referred to as movers 3) that are driven relative to the stator 2 and move along the rail. An electromagnet or coil provided on the stator 2 and a permanent magnet provided on the mover 3 face each other, forming a linear motor along the circular rail. The rail formed by the stator 2 is not limited to a circular shape and may have any shape. For example, the rail may be straight or curved, or one rail may branch into multiple rails, or multiple rails may merge into one rail. The installation direction of the rail formed by the stator 2 is also arbitrary. In the example of FIG. 1, the rail is arranged in a horizontal plane, but the rail may also be arranged in a vertical plane, or in a plane or curved surface at any inclination angle.

[0014] The stator 2 has a rail surface 21 whose normal direction is the horizontal direction. The rail surface 21 extends in a strip-like shape along the rail formation direction. When a circular rail is formed as in the example of Figure 1, the rail surface 21 becomes an endless strip with both ends (virtual) connected. On the rail surface 21, which can form a rail of any shape, multiple drive modules (not shown) equipped with electromagnets are embedded or arranged continuously or periodically along the rail. The electromagnets in the drive modules generate a magnetic field that exerts a driving force along the rail on the permanent magnets of the mover 3 and / or the electromagnets themselves. Specifically, when a drive current such as three-phase AC is applied to these multiple electromagnets, a moving magnetic field is generated that linearly drives the mover 3 equipped with the permanent magnets in a desired tangential direction along the rail. Note that in the example of Figure 1, the normal direction of the rail surface 21, which forms the circular rail in a horizontal plane, is horizontal, but the normal direction of the rail surface 21 may be vertical or any other direction.

[0015] In the stator 2, the positioning unit 22, which is provided on the upper or lower surface perpendicular to the rail surface 21, has multiple magnetic sensors (not shown in FIG. 1) embedded continuously or periodically as position detection units capable of measuring the position of a magnetic scale (not shown in FIG. 1) attached to the mover 3 as a positioning target or positioning scale. A magnetic sensor that measures the position of a magnetic scale formed by a striped magnetic pattern or magnetic graduations with a constant pitch generally has multiple magnetic detection heads. By shifting the spacing between the multiple magnetic detection heads with respect to the pitch or period of the magnetic pattern of the magnetic scale, the magnetic sensor can measure the position of the magnetic scale with high precision. In a typical magnetic sensor with two magnetic detection heads, for example, the spacing between the two magnetic detection heads is shifted by 1 / 4 pitch with respect to the magnetic pattern of the magnetic scale (90 degrees out of phase). Note that the magnetic sensor may be provided on the mover 3 and the magnetic scale on the stator 2, inversely. Furthermore, the speed of the mover 3 can be detected by differentiating the position of the mover 3 measured by the positioning unit 22 with respect to time, and the acceleration of the mover 3 can be detected by differentiating the speed with respect to time.

[0016] The position detection unit provided on the stator 2 and the positioning target or positioning scale attached to the mover 3 are not limited to the magnetic type described above, but may also be optical or other types. In the optical type, an optical scale formed by stripes or graduations with a fixed pitch is attached to the mover 3, and an optical sensor capable of optically reading the stripes on the optical scale is provided on the stator 2. In the magnetic and optical types, the position detection unit measures the positioning target (magnetic scale or optical scale) without contact, which reduces the risk of the position detection unit malfunctioning if an object being transported by the mover 3 scatters and enters the positioning location (the upper surface of the stator 2). However, with optical types, positioning accuracy deteriorates if the optical scale is covered by the transported object, such as liquid or powder, that enters the positioning location. Therefore, for transported objects with negligible magnetism, a magnetic type is preferable, as it does not deteriorate positioning accuracy even if the object enters the positioning location.

[0017] The mover 3 comprises a mover body 31 facing the rail surface 21 of the stator 2, a positioned unit 32 that extends horizontally from the top of the mover body 31 and faces the positioning unit 22 of the stator 2, and a transport unit 33 that extends horizontally from the mover body 31 on the opposite side (the side farther from the stator 2) from the positioned unit 32 and on which a transported object is placed or fixed. The mover body 31 comprises one or more permanent magnets (not shown) that face a plurality of electromagnets embedded in the rail surface 21 of the stator 2 along the rail. The moving magnetic field generated by the electromagnets of the stator 2 applies a linear power or propulsion force in the tangential direction of the rail to the permanent magnets of the mover 3 and / or the electromagnets themselves, so that the mover 3 is linearly driven along the rail surface 21 relative to the stator 2.

[0018] A magnetic scale or optical scale serving as the positioning target or positioning scale is provided on the positioned unit 32 of the mover 3 so as to face the position detection unit (magnetic sensor or optical sensor) provided on the positioning unit 22 of the stator 2. In the example of FIG. 1 where the position detection unit is provided on the upper surface of the stator 2, the positioning target such as the magnetic scale is attached to the lower surface of the positioned unit 32 of the mover 3. When the positioning unit 22 and the positioned unit 32 are magnetic, it is preferable that the rail surface 21 and the positioning unit 22 are formed on different surfaces or at separate locations on the stator 2, and that the mover body 31 and the positioned unit 32 are formed on different surfaces or at separate locations on the mover 3, so that the magnetic field between the electromagnets on the rail surface 21 and the permanent magnets on the mover body 31 does not affect the magnetic positioning of the positioning unit 22 and the positioned unit 32.

[0019] Although four movers 3A, 3B, 3C, and 3D are shown as an example in FIG. 1, it is conceivable that, for example, in a linear conveying system 1 that conveys a large number of small loads, more than 1,000 movers 3 may be required.

[0020] 2 is a schematic diagram of a positioning device 4 configured with a position detection unit and the like in the linear conveyance system 1. The positioning device 4 includes a plurality of (four in the illustrated example) magnetic sensors S0 to S3 as position detection units embedded or arranged in the positioning unit 22 (on the top surface of the stator 2 in FIG. 1) along the track direction of the stator 2 or the movement direction of the mover C (the left-right direction in FIG. 2) in order to measure the position of a magnetic scale (hereinafter also referred to as magnetic scale C for convenience) as a positioning scale attached to one or more (one in the illustrated example) movers C.

[0021] The intervals between the magnetic sensors S0 to S3 in the moving direction may be different from each other, but in this embodiment, an example in which all the intervals are equal will be described. Note that the intervals between the magnetic sensors S0 to S3 in a curved section of the rail, which will be described later, may be different from the intervals between the magnetic sensors S0 to S3 in a straight section of the rail, which is schematically shown in Fig. 2. For example, the intervals X between the magnetic sensors S0 to S3 in the straight section of the rail may be different from the intervals X between the magnetic sensors S0 to S3 in the straight section of the rail. 0 / 1 , X 1 / 2 , X 2 / 3 are all 30mm.

[0022] The distance X between each of the magnetic sensors S0 to S3 is 30 mm or more. 0 / 1 , X 1 / 2 , X 2 / 3 In contrast, the length of the magnetic scale C in the movement direction is, for example, 48 mm. Thus, in this embodiment, the interval (30 mm) between the magnetic sensors S0 to S3 in the movement direction or track direction is shorter than the length (48 mm) of the magnetic scale C in the movement direction or track direction.

[0023] The magnetic scale C has opposite ends EL and ER in the direction of movement and a long scale body AB sandwiched between the opposite ends EL and ER in the direction of movement. A large number of magnetic graduations or magnetic patterns are formed on the scale body AB at equal intervals along the direction of movement. Each of the magnetic sensors S0 to S3 detects the magnetic graduations on the scale body AB and outputs A-phase and B-phase pulses, which are common in known linear encoders. Typically, the A-phase pulse and the B-phase pulse are 90 degrees out of phase with each other. Note that the opposite ends EL and ER of the magnetic scale C may also have magnetic graduations similar to those on the scale body AB.

[0024] The length of each end EL, ER of the magnetic scale C in the movement direction is, for example, 8 mm. In this case, the length of the scale body AB in the movement direction is 32 mm, which is obtained by subtracting the total length of both end portions EL, ER, 16 mm, from the length of the magnetic scale C, 48 mm. Thus, in this embodiment, the spacing (30 mm) between each of the magnetic sensors S0 to S3 in the movement direction is shorter than the length (32 mm) of the scale body AB of the magnetic scale C in the movement direction.

[0025] A reference mark Z is provided on the mover C and / or the magnetic scale C as a reference mark. Each of the magnetic sensors S0 to S3 that first magnetically detects the reference mark Z outputs a Z-phase pulse, which is common in known linear encoders. The Z-phase pulse output in response to the reference mark Z is used to identify the reference position of the mover C. Specifically, the magnetic sensor that first detects the reference mark Z and first outputs a Z-phase pulse becomes the reference sensor that starts counting the A- and B-phase magnetic graduations of the magnetic scale C by the counter unit described below. The following describes a case where the 0th magnetic sensor S0 is the reference sensor for the magnetic scale C. In the illustrated state, the reference mark Z is located above the 0th magnetic sensor S0 that serves as the reference sensor, and the counter unit 50 of the 0th magnetic sensor S0 that detected the reference mark Z starts counting the A- and B-phase magnetic graduations of the magnetic scale C from the count value "0."

[0026] The above description of magnetic scale C also applies to other magnetic scales attached to other movers (not shown). However, the dimensions of each of the above components and the positions of the reference marks are determined arbitrarily for each magnetic scale. Unless otherwise specified below, the description of magnetic scale C also applies to other magnetic scales.

[0027] Each of the magnetic sensors S0 to S3 includes a counting unit 50 to 53 that counts the A- and B-phase magnetic graduations formed on the scale body AB and / or both end portions EL and ER of the magnetic scale C. The direction of increase or decrease in the counting value of each of the counting units 50 to 53 corresponds to the direction of movement of the magnetic scale C (i.e., the mover C) detected by each of the magnetic sensors S0 to S3. For example, when the mover C moves from left to right in FIG. 2, the counting value of each of the counting units 50 to 53 increases in accordance with the number of A- and B-phase pulses output by each of the magnetic sensors S0 to S3, and when the mover C moves from right to left in FIG. 2, the counting value of each of the counting units 50 to 53 decreases in accordance with the number of A- and B-phase pulses output by each of the magnetic sensors S0 to S3.

[0028] As the mover C moves on the rail, the magnetic sensors S0 to S3 that measure the position of the magnetic scale C are switched in sequence. FIG. 3 schematically shows how the positioning entity of the magnetic scale C that moves from left to right switches from the magnetic sensor S0 at the source of movement to the magnetic sensor S1 at the destination of movement in Patent Document 1. As shown in the figure, the switching between the magnetic sensors S0 and S1 is performed when the scale body AB of the magnetic scale C straddles the detection ranges of the two adjacent magnetic sensors S0 and S1. In the example shown in the figure, the positioning entity of the magnetic scale C switches from the magnetic sensor S0 to the magnetic sensor S1 at the timing when the magnetic sensors S0 and S1 are at positions SW1 and SW2 that are symmetrical with respect to the center of the movement direction of the magnetic scale C (the position of the reference mark Z).

[0029] The first switching position SW1 is a position within the scale body AB at a predetermined distance from the boundary between the left end EL and the scale body AB, and the second switching position SW2 is a position within the scale body AB at a predetermined distance from the boundary between the right end ER and the scale body AB. In the illustrated example, the distance from the left end of the scale body AB to the first switching position SW1 and the distance from the right end of the scale body AB is, for example, 1 mm. In this case, the distance from the center of the scale body AB to the first switching position SW1 and the distance from the center of the scale body AB to the second switching position SW2 is 15 mm, and the sum of these distances (30 mm) is the spacing X between the magnetic sensors S0 and S1. 0 / 1 matches.

[0030] When the positioning subject of the magnetic scale C switches from magnetic sensor S0 to magnetic sensor S1, the count value of the counting unit 50 of the magnetic sensor S0 at the source is taken over as the count value of the counting unit 51 of the magnetic sensor S1 at the destination. In the following, the count value of each of the counting units 50 to 53 when each of the magnetic sensors S0 to S3 detects the center of the magnetic scale C (the position of the reference mark Z) is set to zero, the count value of each of the counting units 50 to 53 when each of the magnetic sensors S0 to S3 detects the magnetic scale on the opposite side of the center of the magnetic scale C to the movement direction of the mover C (the left side in FIG. 3) is set to positive, and the count value of each of the counting units 50 to 53 when each of the magnetic sensors S0 to S3 detects the magnetic scale on the side of the center of the magnetic scale C toward the movement direction of the mover C (the right side in FIG. 3) is set to negative.

[0031] In the illustrated example, the position of the reference mark Z corresponds to a count value of "0," the first switch position SW1 corresponds to a positive count value of "+15,000" corresponding to the distance from the reference mark Z (15 mm), and the second switch position SW2 corresponds to a negative count value of "-15,000" corresponding to the distance from the reference mark Z (15 mm). The ratio of the absolute value (15,000) of the change in count value to the physical distance (15 mm) is also referred to as the sensor resolution R, and in this embodiment, it is set to a constant value of R = 1,000 (= 15,000 / 15). The count value at the first switch position SW1 is also referred to as the switch count value, and the count value at the second switch position SW2 is also referred to as the start count value. In the illustrated example, the switch count value and the start count value differ only in their positive and negative signs. When the first switching position SW1 of the magnetic scale C comes over the magnetic sensor S0 as shown in the figure, the switching count value "+15,000" of the counting unit 50 is converted into the starting count value "-15,000" of the counting unit 51 of the magnetic sensor S1, which is at the second switching position SW2. Thereafter, the magnetic sensor S1 becomes the main positioning device for the magnetic scale C, and the counting unit 51 counts from the starting count value "-15,000" to the switching count value "+15,000" for the next magnetic sensor.

[0032] As shown in FIG. 1, the rail or track in the linear conveyance system 1 may include not only straight sections but also curved sections. FIG. 4 is a top view schematically illustrating a typical arrangement of multiple magnetic sensors S4 to S6 on a curved section of the rail and the movement of the magnetic scale C. In the example shown in this figure, the magnetic scale C moves along the curved section of the rail with a radius r, in the order of scale positions C1 to C5. Scale center lines L1 to L5 extending in the longitudinal direction of the magnetic scale C (hereinafter also referred to as magnetic scales C1 to C5 for convenience) at each scale position C1 to C5 pass through the center of the magnetic scale C or the mover C (the position of the reference mark Z). Furthermore, the path RT with a radius r is a trajectory through which the center of the magnetic scale C or the mover C (the position of the reference mark Z) passes. Multiple (three in the illustrated example) magnetic sensors S4 to S6 are arranged at substantially equal intervals on the trajectory RT of the center of the magnetic scale C. Specifically, the distance between the magnetic sensors S4 and S5 and the distance between the magnetic sensors S5 and S6 are both expressed by the central angle 2θ and / or the arc length l (=2πr×2θ / 360) in a sector of radius r.

[0033] When the magnetic scale C is at scale position C1, its center and / or the scale center line L1 is directly above the magnetic sensor S4. At this time, the distance between the center of the magnetic scale C1 and the magnetic sensor S4 is substantially "0." Also, as described above, the count value of the counter (not shown) of the magnetic sensor S4 in this state is "0." When the magnetic scale C is at scale position C3, its center and / or the scale center line L3 is directly above the magnetic sensor S5. At this time, the distance between the center of the magnetic scale C3 and the magnetic sensor S5 is substantially "0." Also, as described above, the count value of the counter (not shown) of the magnetic sensor S5 in this state is "0." When the magnetic scale C is at scale position C5, its center and / or the scale center line L5 is directly above the magnetic sensor S6. At this time, the distance between the center of the magnetic scale C5 and the magnetic sensor S6 is substantially "0." Also, as described above, the count value of the counter (not shown) of the magnetic sensor S6 in this state is "0."

[0034] FIG. 5 schematically shows magnetic scale C at scale positions C2 and C4. Scale position C2 is the midpoint between the aforementioned scale positions C1 and C3, and the central angle of the sector of radius r formed by the scale positions C2 and C3 is θ, and the arc length of each is l / 2. Magnetic sensors S4 and S5 for magnetic scale C2 correspond to magnetic sensors S0 and S1 for magnetic scale C in FIG. 3, respectively. That is, as described above, at scale position C2, where magnetic sensors S4 and S5 are at positions SW1 and SW2 symmetrical with respect to the center of the movement direction of magnetic scale C2, the positioning main unit for magnetic scale C2 switches from magnetic sensor S4 to magnetic sensor S5. Scale position C4 is the midpoint between the aforementioned scale positions C3 and C5, and the central angle of the sector of radius r formed by the scale positions C2 and C3 is θ, and the arc length of each is l / 2. Magnetic sensors S5 and S6 for magnetic scale C4 correspond to magnetic sensors S0 and S1 for magnetic scale C in FIG. 3, respectively. That is, as described above, at scale position C4 where magnetic sensors S5 and S6 are at positions SW1 and SW2 symmetrical with respect to the center of the movement direction of magnetic scale C4, the position measurement subject of magnetic scale C4 is switched from magnetic sensor S5 to magnetic sensor S6.

[0035] At these scale positions C2 and C4, the magnetic sensors S4 to S6 detect both ends of the magnetic scale C. At this time, each end of the magnetic scale C and each of the magnetic sensors S4 to S6 are shifted by a distance "a" in the radial or lateral direction (for convenience, only the magnetic sensor S5 is shown in FIG. 5). Note that based on the geometric relationship, this is expressed as "a = r / cosθ-r."

[0036] As described above, when the magnetic scale C moves along a curved section of a rail with a radius r, in the order of scale positions C1 to C5, the distance between the magnetic scale C and the magnetic sensors S4 to S6 varies significantly between "0" at scale positions C1, C3, and C5 and "a" at scale positions C2 and C4. In particular, the offset "a" at scale positions C2 and C4 could cause the end of the magnetic scale C to deviate from the magnetic sensors S4 to S6 arranged on the curved track RT. To address this issue, it might be possible to narrow the spacing (arc length l) between the magnetic sensors S4 to S6 on the curved section compared to the straight section, but this would increase the number of magnetic sensors S4 to S6, resulting in higher costs. The present embodiment, described below, aims to provide a positioning device 4 that can suppress the increase in the number of position detection units, such as the magnetic sensors S4 to S6, on the curved section of the rail.

[0037] FIG. 6 is a top view schematically illustrating the arrangement of multiple magnetic sensors S4 to S6 and the movement of the magnetic scale C in the positioning device 4 according to this embodiment. In this embodiment, the magnetic scale C moves through scale positions C1 to C5 in the same order as in FIG. 4, but for convenience, FIG. 6 shows only scale positions C2 and C4, as in FIG. 5. Scale positions C1, C3, and C5 are not shown, but the central positions C1', C3', and C5' of each magnetic scale C are representatively shown. In this embodiment, at least one magnetic sensor S4 to S6 is disposed in a position that is shifted outward (radially) from the central locus RT of the magnetic scale C on the curved portion of the rail. In the example of FIG. 6, all magnetic sensors S4 to S6 are disposed in positions that are shifted outward by a substantially equal distance, "a / 2," from the central locus RT of the magnetic scale C. This distance "a / 2" is half the radial displacement "a" between each end of the magnetic scale C and each of the magnetic sensors S4 to S6 at scale positions C2 and C4 in FIG.

[0038] When the magnetic scale C is at scale position C1, the distance between its center (C1') and magnetic sensor S4 is "a / 2". When the magnetic scale C is at scale position C3, the distance between its center (C3') and magnetic sensor S5 is "a / 2". When the magnetic scale C is at scale position C5, the distance between its center (C5') and magnetic sensor S6 is "a / 2".

[0039] At scale position C2, magnetic sensor S4 detects one end of the magnetic scale C2 (the upper end or left end in FIG. 6), and magnetic sensor S5 detects the other end of the magnetic scale C2 (the lower end or right end in FIG. 6). At this time, as shown only for magnetic sensor S5 for convenience, the other end (C2") of the magnetic scale C2 and the magnetic sensor S5 are offset by a distance of "a / 2" in the radial or horizontal direction. Here, the other end C2" is the intersection of the scale center line L2 of the magnetic scale C2 and a radial line passing through the center of the magnetic sensor S5. Similarly, one end (C2') of the magnetic scale C2 and the magnetic sensor S4 are offset by a distance of "a / 2" in the radial or horizontal direction. Here, the one end C2' is the intersection of the scale center line L2 of the magnetic scale C2 and a radial line passing through the center of the magnetic sensor S4. In this way, when the center of the magnetic scale C2 is at an equal distance (scale position C2) from the adjacent magnetic sensors S4 and S5, the distance "a / 2" between the end (C2' and / or C2") of the magnetic scale C2 and each of the magnetic sensors S4 and S5 is substantially equal to the distance "a / 2" between the center (C1', C3') of the magnetic scale C1 and C3 and each of the magnetic sensors S4 and S5 when the center of the magnetic scale C is closest to each of the magnetic sensors S4 and S5.

[0040] At scale position C4, magnetic sensor S5 detects one end of the magnetic scale C4 (the upper end or right end in FIG. 6), and magnetic sensor S6 detects the other end of the magnetic scale C4 (the lower end or left end in FIG. 6). At this time, as shown only for magnetic sensor S5 for convenience, one end (C4') of the magnetic scale C4 and magnetic sensor S5 are offset by a distance of "a / 2" in the radial or horizontal direction. Here, one end C4' is the intersection of the scale center line L4 of the magnetic scale C4 and a radial line passing through the center of magnetic sensor S5. Similarly, the other end (C4") of the magnetic scale C4 and magnetic sensor S6 are offset by a distance of "a / 2" in the radial or horizontal direction. Here, the other end C4" is the intersection of the scale center line L4 of the magnetic scale C4 and a radial line passing through the center of the magnetic sensor S6. Thus, when the center of the magnetic scale C4 is at an equal distance (scale position C4) from the adjacent magnetic sensors S5 and S6, the distance "a / 2" between the end (C4' and / or C4") of the magnetic scale C4 and each of the magnetic sensors S5 and S6 is substantially equal to the distance "a / 2" between the center (C3', C5') of the magnetic scale C3 and each of the magnetic sensors S5 and S6 when the center of the magnetic scale C is closest to each of the magnetic sensors S5 and S6.

[0041] As described above, when the magnetic scale C moves from scale position C1 to scale position C5 in order along a curved portion of a rail with a radius r, the distance between the magnetic scale C and the magnetic sensors S4 to S6 is substantially constant at "a / 2" at each scale position C1 to C5. In the example of FIG. 5, the maximum deviation between the magnetic scale C and the magnetic sensors S4 to S6 is "a" at scale positions C2 and C4. In this embodiment, however, the maximum deviation between the magnetic scale C and the magnetic sensors S4 to S6 is reduced to half, "a / 2," at all scale positions C1 to C5 shown. This makes it difficult for the magnetic scales C1 to C5 to deviate from the magnetic sensors S4 to S6, eliminating the need to reduce the spacing between the magnetic sensors S4 to S6 (central angle 2θ and / or arc length l) as shown in FIG. 5. Therefore, this embodiment can prevent the magnetic sensors S4 to S6 from increasing in distance along the curved portion of the rail.

[0042] 6, magnetic sensors S4 to S6 are positioned at positions offset a distance "a / 2" outward from the central locus RT of magnetic scale C, but the distance is not limited to "a / 2" and the same effect as above can be obtained as long as it is greater than "0" and less than "a". For example, the distance is preferably greater than "a / 3" and less than "2a / 3", more preferably greater than "2a / 5" and less than "3a / 5", and optimally "a / 2".

[0043] In FIG. 6, the magnetic sensors S4 to S6 are arranged at substantially equal intervals (central angle 2θ) on a circle with a radius of r+a / 2. The arc length l' between the magnetic sensors S4 to S6 is expressed as 2π(r+a / 2)×2θ / 360. This arc length l' is smaller than the length of the magnetic scale C in the direction of movement or track (48 mm), and preferably smaller than the length of the scale body AB of the magnetic scale C in the direction of movement or track (32 mm). In addition, in the curved portion of the rail in FIG. 6, the magnetic sensors S4 to S6 are arranged at positions shifted outward from the central locus RT of the magnetic scale C. However, in the straight portion of the rail schematically shown in FIG. 2, it is preferable that the magnetic sensors S0 to S3 are arranged on the central locus RT of the magnetic scale C.

[0044] The present invention has been described above based on the embodiments. Various modifications are possible to the combinations of the components and processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included within the scope of the present invention.

[0045] In the embodiment, a linear conveying system is illustrated in which a mover is driven based on the magnetic force between a permanent magnet provided on the mover and an electromagnet provided on the stator, but the present invention can be applied to any driving device based on any principle other than magnetism (for example, electricity or fluid).

[0046] The configuration, operation, and function of each device and method described in the embodiments can be realized by hardware resources, software resources, or a combination of hardware and software resources. Examples of hardware resources include processors, ROMs, RAMs, and various integrated circuits. Examples of software resources include operating systems, applications, and other programs. [Explanation of symbols]

[0047] 1 Linear transport system, 2 Stator, 3 Movable element, 4 Positioning device, 22 Positioning unit, 32 Positioned unit.

Claims

1. a plurality of position detection units disposed on a track to measure the position of a positioning scale attached to a movable element movable along the track, the position detection units being spaced apart from one another at intervals smaller than the length of the positioning scale in the track direction; At least one of the position detection units is disposed at a position shifted on the opposite side of the center of the radius of the curved portion with respect to a locus of the center of the positioning scale in the curved portion of the track, the plurality of position detection units in the curved portion are disposed at positions shifted by substantially equal distances from a central locus of the positioning scale, a distance between an end of the positioning scale and each position detection unit when the center of the positioning scale is at an equal distance from the adjacent position detection units, and a distance between the center of the positioning scale and each position detection unit when the center of the positioning scale is closest to each position detection unit are substantially equal; Positioning device.

2. The positioning device according to claim 1 , wherein the intervals between the plurality of position detection units in the curved section are substantially constant.

3. The positioning device according to claim 1 or 2, wherein the position detection unit is disposed on a central locus of the positioning scale in a straight portion of the track.

4. a mover driven along a track; a plurality of position detection units arranged on the track to measure the position of the positioning scale attached to the mover, the intervals between which are smaller than the length of the positioning scale in the track direction; Equipped with At least one of the position detection units is disposed at a position shifted on the opposite side of the center of the radius of the curved portion with respect to a locus of the center of the positioning scale in the curved portion of the track, the plurality of position detection units in the curved portion are disposed at positions shifted by substantially equal distances from a central locus of the positioning scale, a distance between an end of the positioning scale and each position detection unit when the center of the positioning scale is at an equal distance from the adjacent position detection units, and a distance between the center of the positioning scale and each position detection unit when the center of the positioning scale is closest to each position detection unit are substantially equal; Drive unit.

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