Actuators and encoders

Abstract

The overall length of the actuator, which is a unit combining a motor and a magnetic encoder, is shortened. [Solution] An actuator comprising a motor, a spindle that rotates by the drive of the motor, a support plate that detects the rotation of the spindle and through which the spindle is rotatably inserted, a spindle gear on one side of the support plate through which the spindle is inserted and fixed to its center, an annular spindle magnet on which the spindle is inserted and fixed to its center, a spindle sensor provided on the side of the spindle magnet, a follower shaft that is rotatably inserted into a follower shaft bearing fixed in a follower shaft insertion hole which is one of the plurality of through holes, a follower shaft gear on which the follower shaft is inserted and fixed to its center and meshes with the spindle gear, a follower shaft magnet mounted on the end of the follower shaft on the other side of the support plate, and a follower shaft sensor provided at a position opposite to the follower shaft magnet.

Description

Technical Field

[0001] The present disclosure relates to an actuator that drives a movable part using a motor as a drive source and detects the movement of the movable part with an encoder, and an encoder used for this actuator.

Background Art

[0002] Patent Document 1 discloses a magnetic encoder including a driving gear connected to the output shaft of a motor, a plurality of driven gears meshing with the driving gear, permanent magnets fixed to the driving gear and the driven gears, and magnetic sensors facing the permanent magnets, and capable of detecting the absolute rotation angle and the rotation speed of the output shaft of the motor. In this encoder, the end of the output shaft of the motor is connected to the driving gear. Further, in Patent Document 1, the driven gears are supported at both ends on the tip side and the rear end side.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the structure of a conventional encoder, since the encoder is connected to the end of a rotating shaft that rotates by driving the motor, at least the total length of the actuator as a unit combining the encoder and the motor becomes longer by the length in the axial direction of the encoder added to the length in the axial direction of the motor.

[0005] Therefore, an object is to provide an actuator capable of shortening the total length of a combination of a motor and a magnetic encoder, and an encoder used for this actuator.

Means for Solving the Problems

[0006] An actuator according to an aspect of the present disclosure comprises a main shaft that rotates by the drive of the motor, and an encoder that detects the rotation of the main shaft. The encoder includes a support plate having a plurality of through holes formed therein, through which the main shaft is rotatably inserted; a main shaft gear on one side of the support plate through which the main shaft is inserted and fixed at its center; an annular main shaft magnet on one side of the support plate through which the main shaft is inserted and fixed at its center; a main shaft sensor provided on the side of the main shaft magnet; a trailing shaft bearing fixed in another trailing shaft insertion hole on the other of the plurality of through holes; a trailing shaft rotatably inserted into the trailing shaft bearing; a trailing shaft gear on which the trailing shaft is inserted and fixed at its center and meshes with the main shaft gear; a trailing shaft magnet mounted on the end of the trailing shaft on the other side of the support plate; and a trailing shaft sensor provided at a position opposite to the trailing shaft magnet.

[0007] Here, while conventional magnetic encoders are connected to the end of the motor's rotating shaft, the encoder used in the actuator of this disclosure has a hollow portion into which the main shaft is inserted, as shown in the configuration above. Therefore, the axial length of the entire actuator, including the motor and encoder, can be shortened compared to conventional actuators. In addition, since the magnetic sensor on the main shaft side and the magnetic sensor on the trailing shaft side can be placed on opposite sides of the support plate, mutual magnetic interference can be suppressed.

[0008] In the actuator described above, it is desirable that the main shaft sensor, the trailing shaft bearing, the trailing shaft, the trailing shaft gear, and the trailing shaft magnet are mounted on the support plate to form a first unit. Furthermore, it is desirable that the support plate be made of metal, the trailing shaft bearing be a ball bearing, and the trailing shaft be cantilevered by the support plate via the trailing shaft bearing. Moreover, it is desirable that a second unit, comprising a substrate having an insertion hole through which the main shaft is rotatably inserted, and the trailing shaft sensor mounted on the substrate, be mounted on the other side of the support plate.

[0009] The above configuration eliminates the need for one of the members that supports the driven shaft at both ends, as in conventional technology. In particular, because the support plate is made of metal, it has sufficient rigidity to cantilever support the driven shaft. Furthermore, since the support plate, on which the main shaft sensor, driven shaft bearing, driven shaft, driven shaft gear, and driven shaft magnet are mounted, can be inserted onto the main shaft and then assembled by meshing the main shaft gear and the driven shaft gear, assembly becomes easier.

[0010] Furthermore, in the actuator described above, it is desirable that the motor is a hollow shaft motor, the main shaft is hollow and cylindrical, and a feed screw shaft that moves axially back and forth by the drive of the motor is inserted through the main shaft. It is also desirable that a feed screw nut is provided inside the main shaft, which rotates together with the main shaft to move the feed screw shaft axially back and forth.

[0011] With the above configuration, the forward and backward movement of the lead screw shaft due to the rotation of the main spindle can be controlled via an encoder. Furthermore, since the main spindle is a hollow, cylindrical rotor, and the lead screw shaft moves axially within this rotor, the axial length of the encoder can also be included in the stroke of the movable part.

[0012] An encoder according to an aspect of the present disclosure is mounted on the main shaft of an actuator motor and comprises: a support plate having a plurality of through holes formed therein, through which the main shaft is inserted; a main shaft gear on one side of the support plate through which the main shaft is inserted and fixed at its center; an annular main shaft magnet on one side of the support plate through which the main shaft is inserted and fixed at its center; a main shaft sensor provided on the side of the main shaft magnet; a trailing shaft bearing fixed in another of the plurality of through holes, which is a trailing shaft insertion hole; a trailing shaft rotatably inserted into the trailing shaft bearing; a trailing shaft gear on which the trailing shaft is inserted and fixed at its center and meshes with the main shaft gear; a trailing shaft magnet mounted on the end of the trailing shaft on the other side of the support plate; and a trailing shaft sensor provided at a position opposite to the trailing shaft magnet.

[0013] Here, while conventional magnetic encoders are connected to the end of the motor's rotating shaft, the encoder used in the actuator of this disclosure has a hollow portion into which the main shaft is inserted, as shown in the above configuration. Therefore, the axial length of the entire actuator, including the motor and encoder, can be shortened compared to conventional encoders. In addition, since the magnetic sensor on the main shaft side and the magnetic sensor on the trailing shaft side can be placed on opposite sides of the support plate, mutual magnetic interference can be suppressed.

[0014] In the encoder described above, the main shaft sensor, the trailing shaft bearing, the trailing shaft, the trailing shaft gear, and the trailing shaft magnet are mounted on the support plate to form a first unit, and a second unit comprising a substrate having an insertion hole through which the main shaft is rotatably inserted, and the trailing shaft sensor mounted on the substrate, is mounted on the other side of the support plate.

[0015] With the above configuration, it is possible to eliminate one of the members that supports the driven shaft at both ends, as in conventional technology. Furthermore, since the support plate on which the main shaft sensor, trailing shaft bearing, trailing shaft, trailing shaft gear, and trailing shaft magnet are mounted can be inserted onto the main shaft and then assembled by meshing the main shaft gear and trailing shaft gear, assembly becomes easier. [Effects of the Invention]

[0016] As the embodiments of this disclosure are configured as described above, it is possible to provide an actuator that can shorten the overall length of a unit combining a motor and a magnetic encoder, and an encoder used in this actuator. [Brief explanation of the drawing]

[0017] [Figure 1] This is a front perspective view of the actuator of the embodiment. [Figure 2] Figure 1 is a side view of the actuator. [Figure 3] Figure 1 is a front view of the actuator. [Figure 4] It is a cross-sectional view taken along line IV-IV of FIG. 3. [Figure 5] It is a rear perspective view of the actuator with the rear cover removed. [Figure 6] It is an exploded perspective view of the actuator in the state of FIG. 5. [Figure 7] It is an exploded perspective view of the first unit shown in FIG. 6. [Figure 8] It is a rear perspective view of the state where the main shaft is inserted into the encoder. [Figure 9] It is a rear view of the state where the main shaft is inserted into the encoder. [Figure 10] It is a side view of the state where the main shaft is inserted into the encoder. [Figure 11] It is a cross-sectional view taken along line XI-XI of FIG. FIG. 9.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings referred to below are schematically shown for explaining the invention, and do not necessarily accurately represent the dimensions and ratios of actual products. In addition, the reference numerals commonly attached to each drawing indicate common members, parts or configurations even if not mentioned in the description of each drawing.

[0019] In the present disclosure, the direction in which the feed screw shaft 13 extends by driving the motor 11 shown in the cross-sectional view of FIG. 4 (specifically, the left direction) is referred to as “front”, and the opposite direction is referred to as “rear”. Further, with respect to each member, the end located on the front side is referred to as “tip”, and the end located on the rear side is referred to as “rear end”. Specifically, the left side in FIGS. 1, 2 and 4, the right side in FIGS. 5 to 7, the lower side in FIGS. 8, 10 and 11, and the back side in FIG. 9 are “front”, and the opposite sides thereof are “rear”.

[0020] (1) Appearance Figure 1 is a front perspective view of the actuator 10 of this embodiment. Figure 2 is a side view of the actuator 10 of this embodiment. Figure 3 is a front view of the actuator 10 of this embodiment.

[0021] The actuator 10 of this embodiment has a housing 14 with a substantially rectangular parallelepiped shape. A circular front cover 14A is fitted onto the front surface of the housing 14. A stopper 13B, which is screwed onto the tip of the lead screw shaft 13 (described later), protrudes from its center. The stopper 13B is a component that restricts the retraction of the lead screw shaft 13, thereby defining the origin position of the lead screw shaft 13. On the tip side of the stopper 13B is a tip fitting 13A, which is fixed with adhesive while being screwed onto the tip of the lead screw shaft 13, and a hexagonal nut 13C is screwed near the tip of the tip fitting 13A. The stopper 13B is fixed between the step at the tip of the lead screw shaft 13 (see Figure 4) and the tip fitting 13A. On the other hand, a rear cover 14B is fitted onto the rear end surface of the housing 14, and a cord 16 connected to a connector 74 (see Figure 8), described later, protrudes rearward from the rear cover 14B. Furthermore, a side cover 18 is attached to one side of the casing 14.

[0022] (2) Internal structure Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. The interior of the actuator 10 housing 14 is a circular space with a cross-section perpendicular to the axial direction. A motor 11, which is made up of a hollow shaft type motor, is housed in the middle part of the interior of the housing 14, and a roughly cylindrical main shaft 12 is inserted through its axis. The front end of the motor 11 is supported by the front partition wall 14C, and the rear end is supported by the rear partition wall 14D, both inside the housing 14. The motor 11 is powered by a control device (not shown) located outside the actuator 10, and its operation is controlled by this power supply. This controls the operation of the actuator 10.

[0023] The outer diameter of the main shaft 12 is slightly smaller in the rear portion 12D compared to the intermediate portion 12C that is directly inserted into the motor 11, while the front portion 12E is larger, including the inner diameter. Inside the front portion 12E of the main shaft 12, specifically in front of the front bulkhead 14C, a feed screw nut 15 with a female thread formed on the inner surface of a central through hole is housed. The outer circumference of the rear end portion of the intermediate portion 12C of the main shaft 12 is supported by a rear bearing 12A, which is made of bearings. This rear bearing 12A is held by an encoder holder 14E mounted on the inner circumference of the housing 14. On the other hand, the space between the outer circumference of the front portion 12E of the main shaft 12 and the inner circumference of the housing 14 is supported by a front bearing 12B, which is also made of bearings.

[0024] Furthermore, a feed screw shaft 13, configured as a rod-shaped ball screw shaft with a length exceeding the axial length of the housing 14, is inserted inside the main spindle 12 with rotatable play. In other words, the inner diameter of the main spindle 12 is larger than the outer diameter of the feed screw shaft 13. On the outer circumferential surface of the feed screw shaft 13, a male thread is formed that screws into the female thread of the feed screw nut 15 via a plurality of rolling elements (for example, steel balls) circulating within the feed screw nut 15. That is, the feed screw nut 15 is configured as a ball screw nut that screws into the feed screw shaft 13, which is a ball screw shaft.

[0025] When the motor 11 is driven, the main shaft 12 rotates freely relative to the housing 14 by the rear bearing 12A and the front bearing 12B. As the main shaft 12 rotates, the feed screw nut 15 housed inside also rotates together with it. The feed screw shaft 13 moves forward with the forward rotation of the feed screw nut 15 and backward with its reverse rotation. As the feed screw shaft 13 moves forward and backward, the end fitting 13A, stopper 13B, and hexagonal nut 13C attached to its tip also move forward and backward.

[0026] An encoder 30, consisting of a spindle gear 40, a spindle magnet 50, a first unit 60, and a second unit 70, is mounted on the outer circumference of the rear portion 12D of the spindle 12. Of the components of the encoder 30, the spindle gear 40 and the spindle magnet 50 are fixed to the outer circumference of the spindle 12 and rotate in accordance with the rotation of the spindle 12. On the other hand, the first unit 60 and the second unit 70 are attached to the housing 14 via an encoder holder 14E using mounting screws 80. Here, because the rear bearing 12A that supports the spindle 12 on the rear side is located near the encoder 30, the rotation of the spindle 12 is less likely to wobble, and consequently the wobble of the spindle magnet 50 is also reduced, so that the rotation detection by the spindle sensor 62 (see Figures 7, 8, and 10), which will be described later, can be performed more accurately.

[0027] (3) Encoder (3-1) Assembly state Figure 5 is a rear perspective view of the actuator 10 with the rear cover 14B (see Figure 4) removed. When the rear cover 14B is removed from the housing 14, the circuit board 71 of the second unit 70 of the encoder 30 is visible in the mounting space 17 at the rear of the housing 14. The rear end portion of the main shaft 12 protrudes from the insertion hole 71A formed in the center of the circuit board 71. A circuit chip 73 and a connector 74 are mounted on the rear surface of the circuit board 71. Of the encoder 30, the second unit 70 and the first unit 60 (see Figure 6), described later, are attached to the housing 14 with three mounting screws 80.

[0028] Figure 6 is an exploded perspective view of the actuator 10 in the state shown in Figure 5. A tip fitting 13A, which is attached to the tip of the feed screw shaft 13 (see Figure 4) inserted through the main shaft 12, protrudes from the front end of the housing 14. On the other hand, the rear end portion of the main shaft 12 protrudes from the center of the mounting space 17 at the rear of the housing 14. The encoder 30, which consists of a main shaft magnet 50, a main shaft gear 40, a first unit 60, and a second unit 70, is mounted while the main shaft 12 is inserted through the center. Specifically, the main shaft magnet 50 and the main shaft gear 40 are mounted on the outer circumference of the main shaft 12 in this order. Next, the first unit 60 and the second unit 70 are fixed to the encoder holder 14E (see Figure 4) of the housing 14 with three mounting screws 80 while the main shaft 12 is inserted through the center in this order. In this way, the encoder 30 is mounted to the housing 14. In this state, the main shaft gear 40 meshes with the two follower gears 64 (see Figure 10) located on the first unit 60, as described later. As a result, the main shaft gear 40 rotates along with the rotation of the main shaft 12, and consequently, the follower gears 64 that mesh with it on both sides rotate in the opposite direction to the main shaft gear 40.

[0029] (3-2) First Unit 60 Figure 7 is an exploded perspective view of the first unit 60 shown in Figure 6. In this embodiment, the first unit 60 is configured as a gear unit. A main spindle insertion hole 61A is formed in the center of a roughly rhomboid support plate 61 made of non-magnetic metal (for example, non-magnetic stainless steel). A pair of secondary spindle insertion holes 61B are formed near the corners on both sides of the main spindle insertion hole 61A. In addition, a rectangular sensor cutout 61D is formed in another corner of the support plate 61. Furthermore, three screw holes 61C are formed around the main spindle insertion hole 61A.

[0030] A pair of follower shaft insertion holes 61B are press-fitted from the rear into each of the follower shaft bearings 63A, which are annular bearings. A substantially cylindrical follower shaft 63 is inserted from the front into each of the two follower shaft bearings 63A. More specifically, the follower shaft 63 is press-fitted into the center of the inner ring of the follower shaft bearing 63A. A follower shaft gear 64 is press-fitted into the tip of each of the two follower shafts 63. Meanwhile, cylindrical follower shaft magnets 65 are fitted into recesses provided on the end faces of the rear ends of the two follower shafts and fixed with adhesive or the like. The follower shaft 63 is supported only at its rear end by the support plate 61 via the press-fitted follower shaft bearing 63A, while its tip is cantilevered and not particularly supported. The follower shaft gear 64 is freely rotatable relative to the support plate 61 by the follower shaft bearing 63A interposed between the follower shaft 63 and the support plate 61.

[0031] The spindle sensor 62 is mounted on a plate-shaped sensor substrate 62A. The sensor substrate 62A, on which the spindle sensor 62 is mounted, is connected to a sensor connector 62B, which also serves as a spacer between it and the substrate 71 (see Figure 10). The sensor connector 62B is mounted on the sensor substrate 62A and connects to a substrate-side connector 71B mounted on the substrate 71, passing through a sensor notch 61D in the support plate 61. This electrically connects the spindle sensor 62 to the connector 74 and the circuit chip 73 (see Figure 5). A sensor spacer 62C with a roughly U-shaped cross-section is interposed between the support plate 61 and the sensor substrate 62A so that the spindle sensor 62 is positioned near the spindle magnet 50. This fixes the spindle sensor 62 to the support plate 61.

[0032] Relatively long cylindrical front spacers 66 are fitted into the front of each of the three screw holes 61C of the support plate 61. Relatively short cylindrical rear spacers 67 are fitted into the rear of each of these screw holes 61C. Mounting screws 80 are inserted from the rear into the internal space of the rear spacers 67 and front spacers 66 and screwed to the encoder holder 14E (see Figure 4). The length of the front spacers 66 is such that there is enough space to accommodate the main shaft gear 40, main shaft magnet 50, trailing shaft gear 64, and main shaft sensor 62 (see Figure 10) between the support plate 61 and the encoder holder 14E (see Figure 4). The length of the rear spacers 67 is such that there is enough space to accommodate the trailing shaft sensor 72 between the support plate 61 and the substrate 71 (see Figure 4).

[0033] (3-3) Second Unit 70 Figures 8, 9, and 10 are rear perspective, rear view, and side view, respectively, of the encoder 30 with the main shaft inserted. Figure 11 is a cross-sectional view taken along line XI-XI in Figure 9. In this embodiment, the second unit 70 is configured as a sensor unit. The second unit 70 is a component located behind the first unit 60 via a rear spacer 67, and comprises a substrate 71, a drive shaft sensor 72, a circuit chip 73, and a connector 74.

[0034] The substrate 71 has an almost identical external shape to the support plate 61 (see Figure 9). An insertion hole 71A is provided in the center of the substrate 71 at a position corresponding to the spindle insertion hole 61A of the support plate 61, and the rear end of the spindle 12 is inserted through this hole. In addition, the substrate 71 is provided with screw holes similar to the three screw holes 61C of the support plate 61, and the rear end of the rear spacer 67 is fitted into these holes.

[0035] On the front surface of the substrate 71, a pair of drive shaft sensors 72 are mounted at positions facing the drive shaft magnets 65 at the rear ends of a pair of drive shafts 63 (see Figure 11). On the other hand, on the rear surface of the substrate 71, a connector 74 is mounted which is involved in supplying power from an external control device (not shown) to the encoder 30 and in communication between the encoder 30 and the control device, as well as a circuit chip 73 which processes signals from the main shaft sensor 62 and the drive shaft sensor 72 and controls communication with the control device.

[0036] The second unit 70, having the above configuration, is screwed to the housing 14 together with the first unit 60 using mounting screws 80 through which the rear spacer 67 and the front spacer 66 are inserted. In this state, the second unit 70 and the first unit 60, together with the spindle magnet 50 and spindle gear 40 that are already mounted on the spindle 12, function as an encoder 30.

[0037] (4) Operation of actuator 10 and function of main axis sensor 62 and trailing axis sensor 72 With the encoder 30 mounted on the actuator 10, the spindle sensor 62 is located to the side of the spindle magnet 50 (see Figure 10). The trailing spindle sensor 72 is positioned opposite the trailing spindle magnet 65, near its rear (see Figure 11).

[0038] When the motor 11 is driven, the rotation of the main spindle 12 causes the feed screw nut 15 to rotate, and the feed screw shaft 13, which is screwed to the feed screw nut 15, moves back and forth. At the same time, the change in magnetic flux density due to the rotation of the main spindle magnet 50 accompanying the rotation of the main spindle 12 is detected by the main spindle sensor 62, thereby determining the rotational position of the main spindle 12. In addition, the rotation of the main spindle gear 40 accompanying the rotation of the main spindle 12 causes the two trailing gears 64 that mesh with the main spindle gear 40 to rotate as well. At this time, the change in magnetic flux density due to the rotation of the trailing magnet 65 accompanying the rotation of the two trailing shafts 63 is detected by the two corresponding trailing shaft sensors 72, thereby determining the rotational positions of the two trailing shafts 63. The main spindle sensor 62 and the two trailing shaft sensors 72 are configured, for example, to include Hall elements and output a voltage signal corresponding to the detected change in magnetic flux density. However, this is not limited to the above, and the main axis sensor 62 and the two secondary axis sensors 72 may be, for example, MR (Magneto-Resistive) sensors that include magnetoresistive elements.

[0039] While I will omit the details here, the number of teeth on the main shaft gear 40 and the two trailing shaft gears 64 are set to be relatively prime. As a result, the combination of rotational positions of the main shaft gear 40 and the two trailing shaft gears 64 corresponds to the product of the number of teeth on each of them. This combination then determines the forward and backward position of the lead screw shaft 13, and the forward and reverse rotation and stopping of the motor 11 are controlled by this forward and backward position.

[0040] (5) Summary As described above, the actuator 10 described in this embodiment comprises a motor 11, a spindle 12 that rotates by the drive of the motor 11, and an encoder 30 that detects the rotation of the spindle 12. The encoder 30 comprises a support plate 61 in which a plurality of through holes are formed and the spindle 12 is rotatably inserted through one of the plurality of through holes, a spindle gear 40 on one side of the support plate 61 in which the spindle 12 is inserted through the center and fixed, and on one side of the support plate 61 the spindle 12 The system includes an annular main shaft magnet 50 inserted through and fixed to the center, a main shaft sensor 62 provided on the side of the main shaft magnet 50, a trailing shaft bearing 63A fixed to a trailing shaft insertion hole 61B, which is one of the plurality of through holes, a trailing shaft 63 rotatably inserted through the trailing shaft bearing 63A, a trailing shaft gear 64 that is inserted through and fixed to the center of the trailing shaft 63 and meshes with the main shaft gear 40, a trailing shaft magnet 65 mounted on the end of the trailing shaft 63 on the other side of the support plate 61, and a trailing shaft sensor 72 provided at a position opposite to the trailing shaft magnet 65.

[0041] In the actuator 10 described above, it is desirable that the main shaft sensor 62, the trailing shaft bearing 63A, the trailing shaft 63, the trailing shaft gear 64, and the trailing shaft magnet 65 are mounted on the support plate 61 to form the first unit 60.

[0042] Furthermore, in the actuator 10 described above, it is preferable that the support plate 61 is made of metal, the following shaft bearing 63A is a ball bearing, and the following shaft 63 is cantilevered by the support plate 61 via the following shaft bearing 63A.

[0043] Furthermore, in the actuator 10 described above, it is desirable that a second unit 70, which includes a substrate 71 having an insertion hole 71A through which the main shaft 12 is rotatably inserted, and a follower shaft sensor 72 mounted on the substrate 71, be mounted on the other side of the support plate 61.

[0044] Furthermore, in the actuator 10 described above, it is desirable that the motor 11 is a hollow shaft motor, the main shaft 12 is a hollow cylindrical rotor, and a feed screw shaft 13 that moves axially back and forth when driven by the motor 11 is inserted through the main shaft 12.

[0045] Furthermore, it is desirable that the actuator 10 described above is provided with a feed screw nut 15 that rotates together with the main shaft 12 to advance the feed screw shaft 13 in the axial direction.

[0046] As described above, the encoder 30 described in this embodiment is mounted on the main shaft 12 of the motor 11 of the actuator 10, and comprises a support plate 61 having a plurality of through holes formed therein, through which the main shaft 12 is inserted, one of the plurality of through holes being a main shaft insertion hole 61A; a main shaft gear 40 on one side of the support plate 61 through which the main shaft 12 is inserted and fixed to the center; and an annular main shaft magnet 50 on one side of the support plate 61 through which the main shaft 12 is inserted and fixed to the center. The system includes a spindle sensor 62 provided on the side of the spindle magnet 50, a follower bearing 63A fixed in a follower insertion hole 61B which is one of the plurality of through holes, a follower shaft 63 rotatably inserted into the follower bearing 63A, a follower gear 64 through which the follower shaft 63 is inserted and fixed and meshes with the spindle gear 40, a follower magnet 65 mounted on the end of the follower shaft 63 on the other side of the support plate 61, and a follower sensor 72 provided at a position opposite to the follower magnet 65.

[0047] In the encoder 30 described above, the main shaft sensor 62, the trailing shaft bearing 63A, the trailing shaft 63, the trailing shaft gear 64, and the trailing shaft magnet 65 are mounted on the support plate 61 to form a first unit 60, and it is desirable that a second unit 70 is mounted on the other side of the support plate 61, comprising a substrate 71 having an insertion hole 71A through which the main shaft 12 is rotatably inserted, and the trailing shaft sensor 72 mounted on the substrate 71.

[0048] In conventional actuators, the encoder is located near the rear end of the shaft rotated by the motor, so the total length of the actuator is the sum of the length of the motor-driven portion and the length of the encoder. On the other hand, in the actuator 10 according to the embodiment of this disclosure, the main shaft 12 rotated by the motor 11 is inserted through the center of the encoder 30. Therefore, in the embodiment of this disclosure, the total length of the actuator 10, including the motor 11 and the magnetic encoder 30, can be shortened compared to the conventional technology.

[0049] In the above embodiment, a ball screw shaft is described as the feed screw shaft 13, but this disclosure is not limited to this, and a sliding screw may also be used as the feed screw shaft 13. [Explanation of symbols]

[0050] 10 Actuators 11 Motors 12 Main shaft 12A Rear bearing 12B Front bearing 12C Middle part 12D Back part 12E Front part 13 Lead screw shaft 13A End fitting 13B Stopper 13C Hex Nut 14. Enclosure 14A. Front cover 14B. Rear cover 14C Front bulkhead 14D Rear bulkhead 14E Encoder holder 15 Lead screw nut 16 Cord 17 Mounting space 18 Side lid 30 encoders 40 Main shaft gear 50 Main shaft magnets 60 First Unit 61 Support plate 61A Main spindle insertion hole 61B Dependent spindle insertion hole 61C Screw hole 61D Sensor notch 62. Main axis sensor 62A. Sensor board 62B. Sensor connector 62C Sensor Spacer 63 Following shaft 63A Following shaft bearing 64 Following shaft gear 65 Sub-axis magnet 66 Front spacer 67 Rear spacer 70 Second Unit 71 Circuit board 71A Through hole 71B Circuit board side connector 72 Sub-axis sensor 73 Circuit chip 74 Connector 80 Mounting screws

Claims

1. An actuator comprising a motor, a spindle that rotates by the drive of the motor, and an encoder that detects the rotation of the spindle, The encoder described above is A support plate having multiple through holes formed therein, through which the spindle is rotatably inserted, On one side of the support plate, a spindle gear is provided through which the spindle is inserted and fixed in the center, On one side of the support plate, an annular main shaft magnet is provided through which the main shaft is inserted and fixed, A spindle sensor is provided on the side of the spindle magnet, A follower bearing is fixed to another of the aforementioned multiple through holes, which is the follower insertion hole, A following shaft that is rotatably inserted into the aforementioned following shaft bearing, The aforementioned follower shaft is inserted through the center and fixed, and a follower gear meshes with the aforementioned main shaft gear, On the other side of the support plate, a follower magnet is attached to the end of the follower shaft, A follower sensor is provided at a position opposite to the follower magnet, An actuator having

2. The actuator according to claim 1, wherein the main shaft sensor, the trailing shaft bearing, the trailing shaft, the trailing shaft gear, and the trailing shaft magnet are mounted on the support plate to form a first unit.

3. The support plate is made of metal. The aforementioned following shaft bearing is a ball bearing, The following shaft is cantilevered by the support plate via the following shaft bearing. The actuator according to claim 2.

4. A substrate having an insertion hole through which the main shaft is rotatably inserted, The substrate is mounted on the aforementioned drive sensor, The actuator according to claim 3, wherein a second unit comprising the above is mounted on the other side of the support plate.

5. The aforementioned motor is a hollow shaft type motor, The aforementioned main shaft is a hollow, cylindrical rotor. The actuator according to any one of claims 1 to 4, wherein a feed screw shaft that moves axially back and forth by the drive of the motor is inserted through the main shaft.

6. The actuator according to claim 5, wherein a feed screw nut is provided inside the main shaft, which rotates together with the main shaft to advance the feed screw shaft axially.

7. An encoder mounted on the main shaft of an actuator motor, A support plate having multiple through holes formed therein, through which the spindle is inserted into one of the multiple through holes, On one side of the support plate, a spindle gear is provided through which the spindle is inserted and fixed in the center, On one side of the support plate, an annular main shaft magnet is provided through which the main shaft is inserted and fixed, A spindle sensor is provided on the side of the spindle magnet, A follower bearing is fixed to another of the aforementioned multiple through holes, which is the follower insertion hole, A following shaft that is rotatably inserted into the aforementioned following shaft bearing, The aforementioned follower shaft is inserted through the center and fixed, and a follower gear meshes with the aforementioned main shaft gear, On the other side of the support plate, a follower magnet is attached to the end of the follower shaft, A follower sensor is provided at a position opposite to the follower magnet, An encoder having the following features.

8. The main shaft sensor, trailing shaft bearing, trailing shaft, trailing shaft gear, and trailing shaft magnet are mounted on the support plate to form the first unit. A substrate having an insertion hole through which the main shaft is rotatably inserted, The substrate is mounted on the aforementioned drive sensor, The encoder according to claim 7, wherein a second unit having the above is mounted on the other side of the support plate.

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