TWI853532B - Positioning device and driving device - Google Patents

Abstract

[Topic] Provide a positioning device capable of suppressing the increase of position detection parts on the curved part of a rail. [Solution] The positioning device has a plurality of magnetic sensors (S4-S6), which are arranged on the rail in order to measure the position of a magnetic scale (C2, C4) mounted on a movable part capable of moving along the rail, and the plurality of magnetic sensors (S4-S6) are arranged at intervals smaller than the length of the magnetic scale (C2, C4) in the rail direction, and at least one magnetic sensor (S4-S6) is arranged on the curved part of the rail at a position deviated outward from the track RT of the center of the magnetic scale (C2, C4). The distance "a/2" between the end (C2", C4') of the magnetic scale (C2, C4) and the magnetic sensor S5 when the center of the magnetic scale (C2, C4) is located at an equal distance to the adjacent magnetic sensor (S4~S6) and the distance "a/2" between the center (C3') of the magnetic scale (C2, C4) and the magnetic sensor (S5) when the center of the magnetic scale (C2, C4) is closest to the magnetic sensor (S5) are substantially equal.

Description

Positioning device and driving device

The present invention relates to a positioning device for a movable part capable of moving along a track.

Patent document 1 discloses a linear transport system as a driving device for moving a movable part along a track. A plurality of magnetic sensors arranged along the track measure the position of a magnetic scale (i.e., movable part) mounted on the movable part. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Application No. 2021-164396

[The problem the invention is trying to solve]

As shown in Patent Document 1, the track in the linear transport system may include not only a straight portion but also a curved portion. In the curved portion, radial or lateral deviation typically occurs between the end of the straight magnetic scale and the track. Therefore, the end of the magnetic scale may deviate from the magnetic sensor arranged on the curved track. Therefore, although it is conceivable to make the interval of the magnetic sensors on the curved portion smaller than that on the straight portion, the cost will increase due to the increase in the number of magnetic sensors arranged.

The present invention was completed in view of these conditions, and its purpose is to provide a positioning device that can suppress the increase of position detection parts on the curved part of the track. [Technical means to solve the problem]

In order to solve the above problem, a positioning device of one aspect of the present invention has a plurality of position detection parts, which are arranged on the track in order to measure the position of a positioning scale mounted on a movable member capable of moving along the track, and the plurality of position detection parts are arranged at intervals smaller than the length of the positioning scale in the track direction. At least one position detection part is arranged at a position on the curved part of the track that is offset to the outside of the track of the center of the positioning scale.

In this aspect, the position detection part is arranged at a position deviated outward from the track of the center of the positioning scale on the curved part of the track, thereby reducing the radial deviation between the position detection part and the end of the positioning scale. Therefore, the end of the positioning scale is unlikely to deviate from the position detection part, and there is no need to reduce the interval between the position detection parts as in the past. Therefore, according to the present invention, the increase of the position detection part on the curved part of the track can be suppressed.

Another aspect of the present invention is a driving device. The device comprises: a movable member that is driven along a track; and a plurality of position detection units that are arranged on the track in order to measure the position of a positioning scale mounted on the movable member, and the spacing between the position detection units is smaller than the length of the positioning scale in the track direction. At least one position detection unit is arranged at a position on the curved portion of the track that is offset to the outside of the track of the center of the positioning scale.

In addition, any combination of the above constituent elements or the method of converting these expressions into methods, devices, systems, recording media, computer programs, etc. is also included in the present invention. [Effects of the invention]

According to the present invention, it is possible to suppress the increase of the position detection portion on the curved portion of the track.

Hereinafter, the form used to implement the present invention (hereinafter also referred to as an implementation method) is described in detail with reference to the drawings. In the following description and/or drawings, the same or equivalent components, components, and processes are marked with the same symbols and repeated descriptions are omitted. In each figure, in order to simplify the description, the scale and shape of each part are appropriately set, and unless otherwise specifically stated, they are not interpreted in a restrictive manner. The implementation method is only an example and is not intended to limit the scope of the present invention. All features or combinations thereof recorded in the implementation method are not necessarily the essence of the present invention.

FIG1 is a perspective view showing the overall structure of a linear transport system 1 which is one embodiment of the drive device of the present invention. The linear transport system 1 has a fixed part 2 constituting an annular guide rail or track and a plurality of movable parts 3A, 3B, 3C, 3D (hereinafter collectively referred to as movable parts 3) which are driven by the fixed part 2 and can move along the guide rail. By making the electromagnet or coil provided on the fixed part 2 and the permanent magnet provided on the movable part 3 face each other, a linear motor is formed along the annular guide rail. In addition, the guide rail formed by the fixed part 2 is not limited to an annular shape, but can be any shape. For example, the guide rail can be straight or curved, one guide rail can branch into a plurality of guide rails, or a plurality of guide rails can be combined into one guide rail. In addition, the direction of the guide rail formed by the fixing member 2 is also arbitrary. In the example of FIG. 1 , the guide rail is arranged in a horizontal plane, but the guide rail can also be arranged in a vertical plane, or in a plane or a curved surface with an arbitrary inclination angle.

The fixing part 2 has a rail surface 21 with the horizontal direction as the normal direction. The rail surface 21 extends in a band shape along the formation direction of the rail. As shown in the example of FIG1 , when the rail is formed into a ring shape, the rail surface 21 becomes a (virtual) ring-shaped band with two ends connected together. On the rail surface 21 that can form a rail of any shape in this way, a plurality of drive modules (not shown) having electromagnets are buried or arranged continuously or periodically along the rail. The electromagnets in the drive modules generate a magnetic field that applies a propulsion force along the rail to the permanent magnets of the movable part 3 and/or the electromagnets themselves. Specifically, if a three-phase AC driving current is passed through the plurality of electromagnetic irons, a moving magnetic field is generated to drive the movable member 3 having a permanent magnet linearly along the rail toward a desired tangential direction. In addition, in the example of FIG. 1 , the normal direction of the rail surface 21 forming the annular rail in the horizontal plane is the horizontal direction, but the normal direction of the rail surface 21 may also be the vertical direction or any other direction.

In the positioning part 22 of the fixed part 2 disposed on the upper surface or the lower surface perpendicular to the guide rail surface 21, a plurality of magnetic sensors (not shown in FIG. 1 ) as position detection parts are continuously or periodically buried, and the magnetic sensors can measure the position of the magnetic scale (not shown in FIG. 1 ) mounted on the movable part 3 as the positioning object or positioning scale. The magnetic sensor that uses the magnetic scale formed by the striped magnetic pattern or magnetic scale with a constant pitch as the positioning object generally has a plurality of magnetic detection heads. By staggering the intervals of the plurality of magnetic detection heads relative to the intervals or periods 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 having two magnetic detection heads, for example, the interval between the two magnetic detection heads is staggered by 1/4 of the magnetic pattern of the magnetic scale (phase is staggered by 90 degrees). In addition, the magnetic sensor may be provided on the movable member 3 and the magnetic scale may be provided on the fixed member 2 in the opposite manner to the above. Furthermore, if the position of the movable member 3 measured by the positioning unit 22 is differentiated by time, the speed of the movable member 3 can be detected, and if the speed is differentiated by time, the acceleration of the movable member 3 can be detected.

The position detection unit provided on the fixed part 2 and the positioning object or positioning scale mounted on the movable part 3 are not limited to the above-mentioned magnetic type, and optical type or other methods may be adopted. In the case of adopting the optical type, an optical scale formed by a pattern or scale with a constant pitch is mounted on the movable part 3, and an optical sensor capable of optically reading the pattern of the optical scale is provided on the fixed part 2. In the magnetic type or optical type, since the position detection unit measures the positioning object (magnetic scale or optical scale) in a non-contact manner, it is possible to reduce the risk of failure of the position detection unit when the transported object transported by the movable part 3 is scattered and enters the positioning part (the upper surface of the fixed part 2). However, in the optical method, if the transported object such as liquid or powder enters the measurement area and covers the optical scale, the measurement accuracy will deteriorate. Therefore, it is better to use the magnetic method because the measurement accuracy will not deteriorate even if the transported object has negligible magnetism and enters the measurement area.

The movable part 3 comprises: a movable part body 31, which is opposite to the guide rail surface 21 of the fixed part 2; a position-detected part 32, which extends horizontally from the upper part of the movable part body 31 and is opposite to the position-detected part 22 of the fixed part 2; and a conveying part 33, which extends horizontally from the movable part body 31 toward a side opposite to the position-detected part 32 (a side away from the fixed part 2) and is used to carry or fix the transported object. The movable part body 31 comprises one or more permanent magnets (not shown) opposite to the plurality of electromagnets buried in the guide rail surface 21 of the fixed part 2 along the guide rail. Since the moving magnetic field generated by the electromagnet of the fixed part 2 applies a linear force or thrust in the tangential direction of the guide rail to the permanent magnet of the movable part 3 and/or the electromagnet itself, the movable part 3 is driven linearly along the guide rail surface 21 relative to the fixed part 2.

On the position-measured portion 32 of the movable member 3, a magnetic scale or an optical scale as a position-measured object or a position-measured scale is disposed opposite to a position-detecting portion (magnetic sensor or optical sensor) disposed on the position-measured portion 22 of the fixed member 2. In the example of FIG. 1 in which the position-detecting portion is disposed on the upper surface of the fixed member 2, the position-measured object such as a magnetic scale is mounted on the lower surface of the position-measured portion 32 of the movable member 3. When the positioning part 22 and the part to be positioned 32 are magnetic, in order to prevent the magnetic field between the electromagnetic iron of the guide surface 21 and the permanent magnet of the movable body 31 from affecting the magnetic positioning of the positioning part 22 and the part to be positioned 32, it is preferred that the guide surface 21 and the positioning part 22 are formed on different surfaces or at locations far away from each other in the fixed part 2, and the movable body 31 and the part to be positioned 32 are formed on different surfaces or at locations far away from each other in the movable part 3.

FIG. 1 shows four movable members 3A, 3B, 3C, and 3D, but it is conceivable that more than 1,000 movable members 3 are required in a linear transport system 1 that transports a large number of objects.

FIG. 2 schematically shows a positioning device 4 composed of a position detection unit and the like in the linear transport system 1. The positioning device 4 has a plurality of (four in the illustrated example) magnetic sensors S0 to S3 as position detection units, and the magnetic sensors S0 to S3 are embedded or arranged on the positioning unit 22 (the upper surface of the fixed member 2 in FIG. 1 ) along the track direction of the fixed member 2 or the moving direction of the movable member 3 (the left-right direction in FIG. 2 ) in order to measure the position of a magnetic scale (hereinafter also referred to as a magnetic scale C for convenience of explanation) mounted on one or more (one in the illustrated example) movable members 3 as a positioning scale.

The intervals of 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 is described. In addition, the intervals of the magnetic sensors S0 to S3 on the curved portion of the guide rail described later may also be different from the intervals of the magnetic sensors S0 to S3 on the straight portion of the guide rail schematically shown in FIG. 2 . For example, the intervals X0 _/1 , X1 _/2 , and X2 _/3 of the magnetic sensors S0 to S3 on the straight portion of the guide rail are all 30 mm.

For the above 30mm intervals X0 _/1 , X1 _/2 , X2 _/3 of the magnetic sensors S0-S3, the length of the magnetic scale C in the moving direction is, for example, 48mm. Thus, in this embodiment, the intervals (30mm) of the magnetic sensors S0-S3 in the moving direction or the track direction are smaller than the length (48mm) of the magnetic scale C in the moving direction or the track direction.

The magnetic scale C has two ends EL and ER in the moving direction and a long scale body AB sandwiched by the two ends EL and ER on both sides of the moving direction. A plurality of magnetic scales or magnetic patterns are formed on the scale body AB and are arranged at equal intervals along the moving direction. In the known linear encoder, each magnetic sensor S0~S3 that detects the magnetic scale of the scale body AB outputs a general A-phase and B-phase pulse. Typically, the phases of the A-phase pulse and the B-phase pulse differ by 90 degrees from each other. In addition, the same magnetic scales as those of the scale body AB can also be formed at the two ends EL and ER of the magnetic scale C.

The length of each end EL, ER of the magnetic scale C in the moving direction is, for example, 8 mm. At this time, the length of the scale body AB in the moving direction is 32 mm, which is obtained by subtracting the total length of the two end portions EL, ER (16 mm) from the length of the magnetic scale C (48 mm). Thus, in this embodiment, the interval (30 mm) of each magnetic sensor S0-S3 in the moving direction is smaller than the length (32 mm) of the scale body AB of the magnetic scale C in the moving direction.

A reference mark Z serving as a reference mark is provided on the movable part 3 and/or the magnetic scale C. In a known linear encoder, each magnetic sensor S0~S3 that initially magnetically detects the reference mark Z outputs a general Z-phase pulse. The Z-phase pulse output corresponding to the reference mark Z is used to determine the reference position of the movable part 3. Specifically, the magnetic sensor that initially detects the reference mark Z and initially outputs the Z-phase pulse becomes a reference sensor that causes the counting unit described later to start counting the A/B phase magnetic scale of the magnetic scale C. The following describes a case where the 0th magnetic sensor S0 becomes the reference sensor of the magnetic scale C. The state shown in the figure is that there is a reference mark Z on the 0th magnetic sensor S0 serving as a reference sensor, and the counting unit 50 of the 0th magnetic sensor S0 that detects the reference mark Z starts counting the magnetic scale of the A/B phase of the magnetic scale C from the count value "0".

The above description of the magnetic scale C is also applicable to other magnetic scales mounted on other movable parts not shown. However, the size of the above parts and the position of the reference marks on each magnetic scale are arbitrarily determined. In the following, unless otherwise specified, the description of the magnetic scale C is also applicable to other magnetic scales.

Each magnetic sensor S0-S3 has a counting unit 50-53, which counts the magnetic scales of the A/B phase formed on the scale body AB and/or the two end portions EL and ER of the magnetic scale C. The increase and decrease direction of the count value in each counting unit 50-53 corresponds to the moving direction of the magnetic scale C (that is, the movable member 3) detected by each magnetic sensor S0-S3. For example, when the movable part 3 moves from the left side to the right side in Figure 2, the count value in each counting unit 50~53 increases according to the number of A/B phase pulses output by each magnetic sensor S0~S3, and when the movable part 3 moves from the right side to the left side in Figure 2, the count value in each counting unit 50~53 decreases according to the number of A/B phase pulses output by each magnetic sensor S0~S3.

When the movable part 3 moves on the guide rail, the magnetic sensors S0~S3 for measuring the position of the magnetic scale C are switched in sequence. FIG3 schematically shows the situation in which the positioning subject of the magnetic scale C moving from the left side to the right side in Patent Document 1 is switched from the magnetic sensor S0 of the moving source to the magnetic sensor S1 of the moving destination. As shown in the figure, the switching of the magnetic sensors S0 and S1 is performed in a state where the scale body AB of the magnetic scale C spans the detection range of the two adjacent magnetic sensors S0 and S1. In the illustrated example, when the magnetic sensors S0 and S1 are located at positions SW1 and SW2 that are symmetrical relative to the center (reference mark Z position) in the moving direction of the magnetic scale C, the positioning subject of the magnetic scale C is switched from the magnetic sensor S0 to the magnetic sensor S1.

The first switching position SW1 is a position in 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 in the scale body AB at a predetermined distance from the boundary between the right end ER and the scale body AB. In the example shown in the figure, the distance between the first switching position SW1 and the left end of the scale body AB and the distance between the second switching position SW2 and the right end of the scale body AB are, for example, 1 mm. At this time, the distance between the first switching position SW1 and the center of the scale body AB and the distance between the second switching position SW2 and the center of the scale body AB are 15 mm, and the sum (30 mm) is consistent with the interval X0 _/1 between the magnetic sensors S0 and S1.

When the positioning body of the magnetic scale C is switched from the magnetic sensor S0 to the magnetic sensor S1, the count value of the counting unit 50 of the magnetic sensor S0 at the moving source is replaced by the count value of the counting unit 51 of the magnetic sensor S1 at the moving destination. Hereinafter, the count value of each counting unit 50~53 when each magnetic sensor S0~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 counting unit 50~53 when each magnetic sensor S0~S3 detects a magnetic scale on the side opposite to the moving direction of the movable part 3 (the left side in FIG. 3) that is closer to the center of the magnetic scale C, is set to positive, and the count value of each counting unit 50~53 when each magnetic sensor S0~S3 detects a magnetic scale on the side closer to the moving direction of the movable part 3 (the right side in FIG. 3) that is closer to the center of the magnetic scale C, is set to negative.

In the example shown in the figure, the position of the reference mark Z corresponds to the count value "0", the first switching position SW1 corresponds to the positive count value "+15,000" which is equivalent to the distance (15 mm) from the reference mark Z, and the second switching position SW2 corresponds to the negative count value "-15,000" which is equivalent to the distance (15 mm) from the reference mark Z. In addition, the ratio of the absolute value (15,000) of the count value change to the physical distance (15 mm) is also called the sensor resolution R. In this embodiment, R=1,000 (=15,000/15) and is constant. In addition, the count value of the first switching position SW1 is also called the switching count value, and the count value of the second switching position SW2 is also called the starting count value. In the example shown in the figure, the switching count value and the starting count value differ only in positive and negative signs. As shown in the figure, if the first switching position SW1 of the magnetic scale C comes above the magnetic sensor S0, the switching count value "+15,000" of its counting unit 50 is converted to the starting count value "-15,000" of the counting unit 51 of the magnetic sensor S1 located at the second switching position SW2. After that, the magnetic sensor S1 becomes the main body of the magnetic scale C, and its counting unit 51 counts from the starting count value "-15,000" to the switching count value "+15,000" when it switches to the next magnetic sensor.

As shown in FIG1 , the guide rail or track in the linear transport system 1 may include not only a straight line portion but also a curved line portion. FIG4 is a top view schematically showing a typical arrangement of a plurality of magnetic sensors S4 to S6 on the curved line portion of the guide rail and the movement of the magnetic scale C. In the example of this figure, the magnetic scale C moves along the curved line portion of the guide rail of radius r in the order of scale positions C1 to C5. The scale center lines L1 to L5 extending in the long side direction of the magnetic scale C (hereinafter also referred to as the magnetic scale C1 to C5 for the sake of convenience) in each scale position C1 to C5 pass through the center of the magnetic scale C or the movable part 3 (reference mark Z position). In addition, the path RT of radius r is the track through which the center of the magnetic scale C or the movable part 3 (reference mark Z position) passes. A plurality of (three in the illustrated example) magnetic sensors S4 to S6 are substantially evenly spaced on the track RT in the center of the magnetic scale C. Specifically, the interval between the magnetic sensor S4 and the magnetic sensor S5, and the interval between the magnetic sensor S5 and the magnetic sensor S6 are represented by the central angle 2θ and/or arc length l (=2πr×2θ/360) in the sector of radius r.

When the magnetic scale C is located at the scale position C1, its center and/or the scale center line L1 are located 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". As described above, the count value of the unillustrated counting unit of the magnetic sensor S4 in this state becomes "0". When the magnetic scale C is located at the scale position C3, its center and/or the scale center line L3 are located 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". As described above, the count value of the unillustrated counting unit of the magnetic sensor S5 in this state becomes "0". When the magnetic scale C is located at the scale position C5, its center and/or the scale center line L5 are located 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". As described above, the count value of the unillustrated counting unit of the magnetic sensor S6 in this state becomes "0".

FIG5 schematically shows the magnetic scale C at scale positions C2 and C4. Scale position C2 is the midpoint between scale position C1 and scale position C3, and the central angles of the sectors of radius r formed by scale position C1 and scale position C3 are both θ, and the arc lengths are both 1/2. Furthermore, magnetic sensors S4 and S5 relative to magnetic scale C2 correspond to magnetic sensors S0 and S1 relative to magnetic scale C in FIG3 , respectively. That is, as described above, at scale position C2 where magnetic sensors S4 and S5 are located at centrally symmetrical positions SW1 and SW2 in the moving direction of magnetic scale C2, the positioning subject of magnetic scale C2 is switched from magnetic sensor S4 to magnetic sensor S5. The scale position C4 is the midpoint between the scale position C3 and the scale position C5, and the central angle of the sector of radius r formed by the scale position C3 and the scale position C5 is θ, and the arc length is l/2. In addition, the magnetic sensors S5 and S6 relative to the magnetic scale C4 correspond to the magnetic sensors S0 and S1 relative to the magnetic scale C in FIG3 . That is, as described above, at the scale position C4 where the magnetic sensors S5 and S6 are located at the central symmetrical positions SW1 and SW2 relative to the moving direction of the magnetic scale C4, the positioning subject of the magnetic scale C4 is switched from the magnetic sensor S5 to the magnetic sensor S6.

At these scale positions C2 and C4, magnetic sensors S4 to S6 detect both ends of the magnetic scale C. At this time, each end of the magnetic scale C is only offset from each magnetic sensor S4 to S6 by a distance "a" in the radial or lateral direction (for ease of explanation in FIG. 5 , only the magnetic sensor S5 is shown). In addition, according to the geometric relationship, it is expressed as "a=r/cosθ-r".

As described above, when the magnetic scale C moves along the curved portion of the guide rail of 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 greatly between "0" at scale positions C1, C3, and C5 and "a" at scale positions C2 and C4. In particular, due to the deviation "a" at scale positions C2 and C4, the end of the magnetic scale C may deviate from the magnetic sensors S4 to S6 arranged on the curved track RT. Therefore, although it is conceivable to make the interval (arc length l) of the magnetic sensors S4 to S6 on the curved portion smaller than that on the straight portion, the cost will increase due to the increase in the number of magnetic sensors S4 to S6 to be arranged. The purpose of the present embodiment described below is to provide a positioning device 4 that can suppress the increase of position detection parts such as magnetic sensors S4~S6 on the curved part of the guide rail.

FIG6 is a top view schematically showing the arrangement of a plurality of magnetic sensors S4 to S6 in the positioning device 4 of the present embodiment and the movement of the magnetic scale C. In the present embodiment, the magnetic scale C moves in the order of scale positions C1 to C5 as in FIG4 , but in FIG6 , for ease of explanation, only scale positions C2 and C4 are shown as in FIG5 . Although the illustration of scale positions C1, C3, and C5 is omitted, the center positions C1', C3', and C5' of each magnetic scale C are representatively shown. In the present embodiment, at least one magnetic sensor S4 to S6 is arranged at a position on the curved portion of the guide rail that is offset outward (radially) from the track RT at the center of the magnetic scale C. In the example of FIG6 , all magnetic sensors S4 to S6 are arranged at positions that are only offset by a substantially equal distance “a/2” outward from the track RT at the center of the magnetic scale C. The distance “a/2” is half of the radial deviation “a” between each end of the magnetic scale C at scale positions C2 and C4 in FIG5 and each magnetic sensor S4 to S6.

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".

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

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

As described above, when the magnetic scale C moves along the curved portion of the guide rail of 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 is "a/2" at each scale position C1 to C5 and is substantially constant. In the example of FIG. 5 , the maximum value of the deviation between the magnetic scale C and the magnetic sensors S4 to S6 is "a" at scale positions C2 and C4. In the present embodiment, the maximum value of the 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 in the figure. Therefore, it is difficult for the magnetic scales C1 to C5 to deviate from the magnetic sensors S4 to S6, and there is no need to reduce the interval (center angle 2θ and/or arc length l) between the magnetic sensors S4 to S6 as shown in FIG. Therefore, according to this embodiment, the increase of magnetic sensors S4~S6 on the curved portion of the guide rail can be suppressed.

In the example of FIG. 6 , the magnetic sensors S4 to S6 are arranged at a distance "a/2" away from the track RT in the center of the magnetic scale C. However, the distance is not limited to "a/2". As long as it is greater than "0" and less than "a", the same effect as above can be obtained. For example, it is better to have a distance greater than "a/3" and less than "2a/3", and it is better to have a distance greater than "2a/5" and less than "3a/5", and "a/2" is the best.

In addition, the magnetic sensors S4 to S6 in FIG6 are substantially arranged at equal intervals (center angle 2θ) on a circle with a radius of "r+a/2". The arc length l' between each magnetic sensor S4 to S6 is expressed as "2π(r+a/2)×2θ/360". The arc length l' is smaller than the length of the magnetic scale C in the moving direction or the track direction (48mm), and preferably smaller than the length of the scale body AB of the magnetic scale C in the moving direction or the track direction (32mm). 6, the magnetic sensors S4~S6 are arranged at a position offset to the outside from the track RT in the center of the magnetic scale C, but in the straight line portion of the guide rail schematically shown in FIG. 2, it is better to arrange the magnetic sensors S0~S3 on the track RT in the center of the magnetic scale C.

The present invention has been described above based on the embodiments. It is understood by those skilled in the art that various modifications may exist for the combinations of the constituent elements or processes in the embodiments shown as examples, and these modifications are also included in the scope of the present invention.

In the embodiment, a linear transport system is illustrated in which a movable part is driven by a magnetic force between a permanent magnet provided on the movable part and an electromagnet provided on the fixed part. However, the present invention can also be applied to any driving device based on any principle other than magnetic force (such as electricity or fluid).

In addition, the structure, role and function of each device or method described in the implementation method can be realized by hardware resources or software resources, or the cooperation of hardware resources and software resources. As hardware resources, for example, processors, ROM, RAM and various integrated circuits can be used. As software resources, for example, operating systems, applications and other programs can be used. This application claims priority based on Japanese patent application No. 2022-093032 filed on June 8, 2022. The entire contents of the Japanese application are cited in this specification by reference.

1: Linear transport system 2: Fixed part 3: Movable part 4: Positioning device 22: Positioning part 32: Part to be measured

[Figure 1] is a perspective view showing the overall structure of the linear transport system. [Figure 2] is a schematic diagram showing a positioning device composed of a position detection unit and the like in the linear transport system. [Figure 3] is a schematic diagram showing the situation in which the positioning body of the moving magnetic scale is switched from the magnetic sensor at the moving source to the magnetic sensor at the moving destination. [Figure 4] is a schematic top view showing a typical arrangement of a plurality of magnetic sensors on the curved portion of the guide rail and the movement of the magnetic scale C. [Figure 5] is a schematic diagram showing a magnetic scale at a scale position located in the middle of the magnetic sensor. [Figure 6] is a schematic top view showing the arrangement of a plurality of magnetic sensors in the positioning device of the present embodiment and the movement of the magnetic scale.

a/2: half of the radial deviation "a"

C1’: The center position of magnetic scale C

C2: ruler position

C2’: One end of the magnetic scale C2

C2”/C4’: the other end of magnetic scale C2/one end of magnetic scale C4

C3’: The center position of magnetic scale C

C4: ruler position

C4”: The other end of the magnetic scale C4

C5’: The center position of magnetic scale C

l: arc length

L2: Center line of magnetic scale C2

L4: Center line of magnetic scale C4

r: Radius

RT: The center track of magnetic scale C

S4: Magnetic sensor

S5: Magnetic sensor

S6: Magnetic sensor

θ: center angle

Claims (5)

A positioning device, characterized in that it has a plurality of position detection parts, the plurality of position detection parts are arranged on the track in order to measure the position of a positioning scale mounted on a movable part capable of moving along the track, and the intervals between the plurality of position detection parts are smaller than the length of the positioning scale in the track direction, at least one of the position detection parts is arranged on the curved part of the track at a position deviated outward from the track at the center of the positioning scale; the plurality of position detection parts on the curved part are arranged at positions that are only offset outward from the track at the center of the positioning scale by substantially equal distances. A positioning device as claimed in claim 1, wherein the distance between the end of the positioning scale and each adjacent position detection unit when the center of the positioning scale is located at an equal distance to the aforementioned position detection unit and the distance between the center of the positioning scale and each position detection unit when the center of the positioning scale is closest to the aforementioned position detection unit are substantially equal. A positioning device as claimed in claim 1 or 2, wherein the intervals between the plurality of position detection portions on the curved portion are substantially constant. A positioning device as claimed in claim 1 or 2, wherein the position detection unit is arranged on the track at the center of the positioning scale on the straight line portion of the track. A driving device, characterized in that it has: a movable part that is driven along a track; and a plurality of position detection parts that are arranged on the track in order to measure the position of a positioning scale mounted on the movable part, and the spacing between them is smaller than the length of the positioning scale in the track direction, at least one of the position detection parts is arranged on the curved part of the track at a position that is offset outward from the track at the center of the positioning scale; and the plurality of position detection parts on the curved part are arranged at positions that are offset outward from the track at the center of the positioning scale by substantially equal distances.

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