JP7594234B2 - Drive device, encoder unit, and robot device - Google Patents

Description

The present invention relates to, for example, a drive device equipped with an encoder and a control method thereof, an encoder unit and a control method thereof, and a robot device equipped with a drive device.

To control the rotation angle of a motor used in the drive unit of an industrial robot or machine tool with high precision, an encoder (e.g., a rotary encoder) is attached to the rotating shaft of the motor, and the motor is controlled based on the detection results of the encoder. Also, to monitor the state of the motor while it is in operation, it is preferable to detect the moment acting on the shaft that is rotated by the motor (hereinafter referred to as the output shaft). As prior art, a device that detects the moment acting in the axial direction of the output shaft inside a bearing is known (see, for example, Reference 1).

Recently, motors equipped with encoders have been used in a wider variety of applications, and the moment can fluctuate in various ways. For this reason, there is a need to consider how to detect the moment acting on the motor's output shaft with high accuracy using a simple configuration.

JP 2010-8094 A

According to a first aspect, there is provided a drive device comprising: a motor; an input shaft that transmits rotation of the motor and includes a hollow portion; a transmission that changes the speed of the rotation of the motor transmitted from the input shaft; an output section that includes an output shaft that passes through the hollow portion of the input shaft and outputs the rotation of the motor changed in speed via the transmission from a first end of the output shaft; and a displacement detection section that detects displacement information related to a translational displacement of a second end of the output shaft opposite the first end in a plane perpendicular to the extension direction of the output shaft.

According to a second aspect, there is provided an encoder unit comprising: a transmission that transmits rotation of a motor and changes the speed of the rotation of the motor transmitted from an input shaft including a hollow portion; an output section that includes an output shaft passing through the hollow portion of the input shaft and outputs the rotation of the motor changed in speed via the transmission from a first end of the output shaft ; a first rotation detection section that detects first rotation information of the input shaft; a second rotation detection section that detects second rotation information of the output shaft; a displacement detection section that detects displacement information related to a translational displacement of a second end of the output shaft opposite the first end in a plane perpendicular to the extension direction of the output shaft; and a first calculation section that calculates the amount of rotation of each of the input shaft and the output shaft based on the first rotation information detected by the first rotation detection section and the second rotation information detected by the second rotation detection section.

According to a third aspect, there is provided a robot device including the drive device of the first aspect, an arm driven by the drive device, and a robot control unit that controls the drive device.
According to a fourth aspect, there is provided a control method for a drive device including a motor, an input shaft that transmits rotation of the motor and includes a hollow portion, a transmission that changes the speed of the rotation of the motor transmitted from the input shaft, and an output portion that outputs the rotation of the motor changed in speed via the transmission and includes an output shaft that passes through the hollow portion of the input shaft , the control method for the drive device including detecting displacement information of the output shaft within a plane perpendicular to the extension direction of the output shaft .

According to a fifth aspect, there is provided a control method for an encoder unit including a transmission that transmits the rotation of a motor and changes the speed of the rotation of the motor transmitted from an input shaft including a hollow portion , an output portion that outputs the rotation of the motor changed through the transmission and includes an output shaft that passes through the hollow portion of the input shaft , a first rotation detection portion that detects first rotation information of the input shaft , and a second rotation detection portion that detects second rotation information of the output shaft, the control method including detecting displacement information of the output shaft in a plane perpendicular to the extension direction of the output shaft , and calculating the amount of rotation of each of the input shaft and the output shaft based on the first rotation information detected by the first rotation detection portion and the second rotation information detected by the second rotation detection portion.

1 is a cross-sectional view showing a drive device according to a first embodiment of the present invention. 1 , (B) is a cross-sectional view taken along line BB in FIG. 1 , (C) is a cross-sectional view of a modified example corresponding to the cross-section taken along line BB in FIG. 1 , and (D) is a cross-sectional view showing a main part of the drive device in FIG. 1 . 2 is a flowchart showing an example of a control method for the drive device of FIG. 1 . FIG. 4 is a cross-sectional view showing a drive device according to a modified example of the first embodiment. FIG. 6 is a cross-sectional view showing a drive device according to a second embodiment. 6A is a cross-sectional view showing a main part of the drive device of FIG. 5, and FIG. 6B is a cross-sectional view taken along line BB of FIG. 6A. FIG. 11 is a cross-sectional view showing a drive device according to a third embodiment. 8A is a view taken along the line A in FIG. 7, and FIG. 8B is a cross-sectional view showing a state in which a moment load is applied to the drive device of FIG. 7A is a view from the arrow A showing a state in which a moment acts in the Y direction in the drive device of FIG. 7, and FIG. 7B is a view from the arrow A showing a state in which a moment acts in an arbitrary direction in the drive device of FIG. 7. FIG. 13 is a diagram showing a main part of a first modified example of the third embodiment. FIG. 13A is a diagram showing a detection unit and a calculation device according to a second modified example, and FIG. 13B is a diagram showing a detection unit and a calculation device according to a third modified example. FIG. 1 is a perspective view showing an example of a robot device.

Hereinafter, the first embodiment will be described with reference to FIGS.
FIG. 1 shows a driving device 10 according to this embodiment, FIG. 2(A) is a view seen from the direction A in FIG. 1, and FIG. 2(B) is a cross-sectional view taken along the line BB in FIG. 1. In FIG. 1, the driving device 10 includes a wide and deep dish-shaped cover member 40 (holding member) fixed to the floor (not shown) of a factory where a robot device is installed, for example, via a support member (e.g., an arm, etc.) not shown, and a motor unit 14 having a motor case 30 fixed to the opening side of the cover member 40. The motor unit 14 rotates and drives an elongated cylindrical input shaft (first rotating shaft or motor shaft) 18A. In the following description, the Z axis is taken along the central axis of the input shaft 18A, the X axis is taken in a direction perpendicular to the paper surface of FIG. 1 within a plane perpendicular to the Z axis, and the Y axis is taken in a direction parallel to the paper surface of FIG. 1. The input shaft 18A is rotated around the Z axis by the motor unit 14. Furthermore, both ends of the input shaft 18A protrude outward from the end faces on both sides of the motor case 30 in the Z direction.

The drive unit 10 also includes a cylindrical support member 32 fixed to the -Z end face of the motor case 30 of the motor section 14, a reducer 34 provided on the outer surface of the -Z end 18Aa of the input shaft 18A, a cylindrical connecting portion 36A provided on the outer surface of the reducer 34, a flat connecting plate 36B of a ring-shaped band fixed to the -Z direction side of the connecting portion 36A, a disk-shaped end 18Ba connected to three points on the -Z direction side surface of the connecting plate 36B via disc springs 38A, 38B, 38C (elastic portions) (see FIG. 2A) that are elastically deformable in the Z direction, a cylindrical shaft portion 18Bb fixed to the center of the +Z direction surface of the end 18Ba, and a rotary bearing 28C that rotatably supports the connecting portion 36A around the Z axis on the inner surface of the support member 32. The output shaft (output part) 18B is composed of an end part 18Ba and a shaft part 18Bb, and is driven to rotate around the Z axis by being reduced in speed in conjunction with the input shaft 18A by the reducer 34. A driven part (not shown), such as a robot arm or an end effector, is connected to the end part 18Ba. The reduction ratio of the reducer 34 is, for example, about 1/100. In this embodiment, the input shaft 18A is hollow and cylindrical, and the shaft part 18Bb of the output shaft 18B is arranged to pass through the inside of the input shaft 18A. Note that, as an example, the shaft part 18Bb is cylindrical, but the shaft part 18Bb may also be cylindrical. The disc springs 38A, 38B, 38C, the input shaft 18A, the output shaft 18B, the motor case 30, and the support member 32 are made of metal, for example.

The drive unit 10 also includes an encoder unit 12 that detects rotation information such as the rotation angle and rotation speed of the input shaft 18A (and thus the output shaft 18B), as well as the direction (direction of action) and magnitude (length x force) of a moment M about an arbitrary axis in a plane perpendicular to the Z axis that is applied to, for example, the -Z direction surface (hereinafter also referred to as the action surface) 18Bc of the end 18Ba of the output shaft 18B, and a motor control device 24 that drives the motor unit 14 using the rotation information detected by the encoder unit 12. Note that, hereinafter, the moment M acting on the end 18Ba (action surface 18Bc) is also simply referred to as the moment M acting on the output shaft 18B.

The motor case 30 of the motor section 14 has a cylindrical holding member 30A and a ring-shaped pressing member 30B connected to the holding member 30A so as to cover the +Z direction side of the holding member 30A, and the input shaft 18A is rotatably supported via a pair of rotary bearings 28A and 28B at the openings of the two opposing side portions of the motor case 30. The cover member 40 is provided so as to cover the end face of the motor case 30 in the +Z direction. The motor section 14 also has a plurality of magnets 20 attached to the outer surface of the central shaft portion of the input shaft 18A, and a plurality of coils 22 arranged on the inner surface of the motor case 30 so as to surround the magnets 20. The coils 22 are connected to the motor control device 24 via a plurality of signal lines 26. As an example, the motor section 14 is a three-phase AC motor, but a DC motor or the like can also be used as the motor section 14.

The disc spring 38A between the connecting plate 36B and the end 18Ba of the output shaft 18B is supported by the bolt B1 arranged on the connecting plate 36B side and the nut N1 arranged on the end 18Ba side so that it does not move in the X and Y directions and can be contracted and expanded by elastic deformation in the Z direction. Instead of fixing the bolt B1 using the nut N1, the bolt B1 may be fixed by tapping the output part 18Ba. As shown in FIG. 2(A), disc springs 38A, 38B, and 38C are arranged at three positions at approximately equal angular intervals around the Z axis (output shaft 18B) between the connecting plate 36B and the end 18Ba of the output shaft 18B. The method of supporting the disc springs 38B and 38C is the same as the method of supporting the disc spring 38A. Due to the elastic deformation of the disc springs 38A, 38B, and 38C, the end 18Ba can rotate (tilt) around any axis passing through the Z axis in a plane perpendicular to the Z axis with respect to the connecting plate 36B. Note that any elastic part such as a compression coil spring, a leaf spring, an elastic hinge mechanism, or a so-called flexure structure can be used instead of the disc springs 38A to 38C. Note that when disc springs are used, three or more may be arranged at equal angular intervals. Also, the elastic parts of the disc springs 38A, 38B, and 38C, etc., do not have to be provided.

In addition, in FIG. 1, the intersection of the plane (hereinafter referred to as the support plane 38P) passing through the center of the Z direction of the disc springs 38A to 38C and the Z axis is the rotation center C. When a moment around an axis in a plane perpendicular to the Z axis acts on the output shaft 18B, the output shaft 18B (shaft portion 18Bb) rotates (tilts) approximately around the rotation center C within a predetermined narrow angle range due to the elastic deformation of the disc springs 38A to 38C. In other words, it can be considered that a moment around any axis passing through the rotation center C in a plane perpendicular to the Z axis acts on the output shaft 18B. Note that the configuration that elastically deforms as an elastic body is not limited to disc springs, and for example, the rotary bearing 28C and the reducer 34 also function as elastic bodies. When all of these configurations function as elastic bodies, the rotation center of the output shaft 18B is a predetermined position on the Z axis close to the motor portion 14.

FIG. 2(D) shows the input shaft 18A, the reducer 34, and the output shaft 18B of FIG. 1. In this embodiment, it is assumed that the disc springs 38A to 38C function predominantly as elastic bodies, and the rotation center of the output shaft 18B is the rotation center C on the support plane 38P of the disc springs 38A to 38C in FIG. 1 and FIG. 2(D). As shown in FIG. 2(D), the distance between the end face (the part connected to the end 18Ba) of the shaft portion 18Bb of the output shaft 18B in the -Z direction and the rotation center C is La, and the distance between the rotation center C and the end face of the shaft portion 18Bb in the +Z direction is Lb. In this embodiment, the distance Lb is set to be longer than the distance La, for example, 10 times or more the distance La. At this time, the output shaft 18B is rotated to the dotted line position 18P1 by the moment M acting on the output shaft 18B around an axis passing through the rotation center C and parallel to the X-axis. Then, when the -Z end face of shaft portion 18Bb is displaced in the -Y direction (or +Y direction) by δ1, the displacement δ2 in the +Y direction (or -Y direction) of the +Z end face of shaft portion 18Bb is magnified with respect to displacement δ1 at a ratio of Lb/La as follows:
δ2=δ1(Lb/La)...(1)

For example, when the interval Lb is set to be at least 10 times the interval La, the displacement δ2 is magnified to at least 10 times the displacement δ1. In this manner, the shaft portion 18Bb of the output shaft 18B extends from one end side (the side of the reducer 34) of the motor portion 14 to the other end side of the motor portion 14 and acts as a displacement magnifying portion that magnifies the displacement of the output shaft 18B at the other end side of the motor portion 14.
In FIG. 1, in this embodiment, the encoder unit 12 detects the direction and magnitude of the displacement (in the direction along the plane perpendicular to the Z axis of the end of the shaft portion 18Bb in the +Z direction of the output shaft 18B) in a plane perpendicular to the Z axis, and the direction and magnitude of the moment acting on the output shaft 18B can be obtained using the detection result. For this reason, for example, experimentally, the relationship between the magnitude of the displacement in the Y direction of the end of the shaft portion 18Bb in the +Z direction and the magnitude of the moment acting on the output shaft 18B around the X axis (moment load) (hereinafter referred to as the moment conversion coefficient Mk) is obtained, and the conversion coefficient Mk is stored in the storage unit of the encoder unit 12. The moment conversion coefficient Mk may be a nonlinear function with respect to the magnitude of the displacement. Storing the moment conversion coefficient Mk in the storage unit also includes storing the moment conversion coefficient Mk using cloud storage or the like.

The +Z end 18Ab of the input shaft 18A protrudes outward from the +Z side of the motor case 30, and the +Z end of the shaft portion 18Bb of the output shaft 18B protrudes outward from the end 18Ab. A ring-shaped rotating plate 42A on which a transmission pattern (not shown, hereinafter also referred to as a rotational detection pattern) for detecting the position in the rotational direction (rotation angle) is formed is attached to the +Z end face of the end 18Ab of the input shaft 18A. The shaft portion 18Bb of the output shaft 18B passes through an opening in the center of the rotating plate 42A. A first detection unit 44 that detects the pattern of the rotating plate 42A is provided on the inner surface of the cover member 40. The first detection unit (position detection sensor) 44 has a light source that irradiates detection light onto the pattern of the rotating plate 42A and a light receiving element that receives light (e.g., transmitted light) from the pattern. The pattern of the rotating plate 42A includes, for example, an incremental pattern and an absolute pattern. Note that the first detection unit 44 is a transmissive optical sensor, but the pattern of the rotating plate 42A may be a reflective pattern and a reflective optical sensor may be used as the first detection unit 44.

The encoder unit 12 includes a rotating plate 42A, a first detection unit 44, and a first calculation unit 16 that processes the detection signal S1 of the first detection unit 44 to obtain rotation information (displacement information including rotation angle, angular velocity, and/or multiple rotation information indicating how many times the input shaft 18A has rotated) (hereinafter also referred to as encoder information) about the Z axis of the rotating plate 42A (and the input shaft 18A) and the output shaft 18B relative to the motor unit 14. The first calculation unit 16 can obtain rotation information of the output shaft 18B from the rotation information of the input shaft 18A obtained from the detection signal S1 and the known reduction ratio of the reducer 34. Note that instead of providing the rotating plate 42A at the end 18Ab of the input shaft 18A, the rotating plate 42A may be provided at the end 18Bb of the output shaft 18B to directly detect the rotation information of the output shaft 18B. In addition, the drive device 10 may not be provided with an encoder unit 12 that detects rotation information of the input shaft 18A and the output shaft 18B, but may instead be provided with a detector outside the drive device 10 that detects rotation information of the output shaft 18B (end portion 18Ba and/or shaft portion 18Bb).

The first calculation device 16 supplies the encoder information to the motor control device 24, and the motor control device 24 controls the value of the current supplied to the coil 26 in accordance with, for example, the difference between the detected rotation angle, etc. of the output shaft 18B and a target rotation angle, etc. By this operation, the rotation angle, etc. of the output shaft 18B is controlled to the target value.
Also, on the inner surface of the cover member 40, three gap sensors 46A, 46B, and 46C are arranged near the end face of the shaft portion 18Bb of the output shaft 18B in the +Z direction, for detecting the gap between the end of the shaft portion 18Bb without contact. As shown in FIG. 2B, the gap sensors 46A, 46B, and 46C are arranged at equal angular intervals around the shaft portion 18Bb of the output shaft 18B, and output detection signals S2A, S2B, and S2C corresponding to the gaps gA, gB, and gC between the shaft portion 18Bb, respectively. As an example, the gap sensor 46A is arranged in the +Y direction with respect to the shaft portion 18Bb, and the gap sensors 46B and 46C are arranged symmetrically so as to sandwich the shaft portion 18Bb in the X direction. As the gap sensors 46A to 46C, an optical gap sensor, a capacitance gap sensor, an eddy current gap sensor, a magnetic gap sensor, or an air blowing gap sensor can be used.

In FIG. 1, the encoder unit 12 has distance sensors 46A-46C and a second calculation device 48 that processes the detection signals S2A, S2B, and S2C of the distance sensors 46A-46C to determine the direction and magnitude of the moment acting on the output shaft 18B (moment information). The drive device 10 also has a control device 50 that performs the processing described below in accordance with the moment information determined by the second calculation device 48.

The storage unit of the second calculation device 48 stores the values gA1, gB1, and gC1 of the distances gA, gB, and gC between the end 18Ba and the shaft portion 18Bb detected by the distance sensors 46A to 46C when no load is applied to the end 18Ba, i.e., when no moment is substantially acting on the output shaft 18B, and the moment conversion coefficient Mk. Then, during operation of the drive device 10, the processing unit (displacement conversion unit) of the second calculation device 48 calculates the distances gA, gB, and gC between the end 18Ba and the shaft portion 18Bb detected by the distance sensors 46A to 46C. Then, in the case where the shaft portion 18Bb is displaced as shown in FIG. 2(D), the processing unit calculates the magnitudes δx and δy of the displacements of the end 18Ba in the X and Y directions from the following equations.
δy=gA1-gA...(2A)
δx=cos30° {(gB1-gB)-(gC1-gC)}/2...(2B)

Furthermore, the processing unit determines, as an example, the direction Φ (counterclockwise angle around the Z axis when viewed in the -Z direction) and magnitude E of the moment acting on the output shaft 18B from the following equation: For simplicity, it is assumed that the displacement of the end of the shaft portion 18Bb is proportional to the magnitude of the moment (same below).
Φ (rad) = π + arctan (δy/δx) … (3A)
E=Mk・(δy ² + δx ² ) ^1/2 …(3B)

Next, an example of a control method of the drive device 10 of this embodiment will be described with reference to the flowchart of FIG. 3. First, in step 102 of FIG. 3, the driven part (not shown) and the target rotation angle of the output shaft 18B are input in the motor control device 24. In the next step 104, the motor control device 24 starts the rotation drive of the input shaft 18A by the motor unit 14. Then, in step 106, the first detection unit 44 of the encoder unit 12 detects the rotation angle of the input shaft 18A, and the first calculation unit 16 calculates the rotation angle of the output shaft 18B from the rotation angle and the known reduction ratio of the reducer 34. Information on the rotation angle of the output shaft 18B is supplied to the motor control device 24. In step 108, the motor control device 24 subtracts the target rotation angle from the rotation angle of the output shaft 18B to calculate the correction amount of the rotation angle. Then, in step 110, the motor control device 24 drives the motor unit 14 so as to offset the correction amount. Then, the operation proceeds to step 106, and steps 106, 108, and 110 are repeated.

On the other hand, in step 114 following step 104, the distance sensors 46A-46C of the encoder unit 12 output detection signals S2A-S2C corresponding to the distance between the output shaft 18B and the shaft portion 18Bb, and the second calculation unit 48 uses these detection signals S2A-S2C to determine the displacement in the X- and Y-directions within the cross section of the shaft portion 18Bb. Furthermore, in step 116, the second calculation unit 48 calculates the direction and magnitude of the moment acting on the output shaft 18B from the displacement in the X- and Y-directions within the cross section of the shaft portion 18Bb, and supplies the calculation result to the control device 50. In step 118, as an example, the control device 50 determines whether the magnitude of the moment is within the allowable range. If the magnitude of the moment is within the allowable range, the operation proceeds to step 114, and the operations of steps 114, 116, and 118 are repeated. Instead of calculating the moment from the displacement of the shaft 18Bb in step 116, the relationship between the magnitude (and direction) of the displacement of the shaft 18Bb and the magnitude (and direction) of the moment acting on the output shaft 18B may be created in a lookup table or the like and stored in advance in a storage unit or the like, and in step 116, the moment corresponding to the displacement of the shaft 18Bb calculated in step 114 may be read from the lookup table.

In addition, in step 118, if the magnitude of the moment exceeds the allowable range, the control device 50 outputs alarm information AR1 indicating that the magnitude of the moment has exceeded the allowable range, for example, to an operator of the drive device (not shown) or a higher-level control unit (not shown). In response to this, as an example, the operation of the drive device 10 is stopped manually by the operator or automatically by the control unit, and after the load on the driven part (not shown) is reduced, for example, the drive device 10 is started to be driven. Note that instead of stopping the operation of the drive device 10, the rotation speed of the motor unit 14 may be reduced. According to the control method of this embodiment, the moment acting on the output shaft 18B is calculated from the displacement of the shaft portion 18Bb of the output shaft 18B of the drive device 10, and if the magnitude of the moment exceeds the allowable range, alarm information is output, so that it is possible to prevent the drive device 10 from being damaged due to the moment becoming too large. Furthermore, because the shaft portion 18Bb is long, and the displacement of the end portion 18Ba of the output shaft 18B due to the moment is magnified by Lb/La (see FIG. 2D) and detected by the encoder unit 12, the moment can be detected with high accuracy using a simple configuration.

In step 118, the result of detecting the magnitude (and direction) of the displacement of the output shaft 18Bb in step 114 may be used instead of the result of calculating the magnitude (and direction) of the moment of the output shaft in step 116. In this case, in step 118, when the magnitude of the displacement exceeds the allowable range, the control device 50 may output alarm information AR1 indicating that the magnitude of the displacement has exceeded the allowable range. If the magnitude of the displacement and the magnitude of the moment have a predetermined correspondence relationship, the allowable load according to the magnitude of the moment acting on the end portion 18Ba can be grasped based on the magnitude of the displacement without calculating the moment, so that the calculation time of the moment can be reduced and high-speed control can be achieved.

As described above, the driving device 10 of this embodiment is a driving device including a motor unit 14, a reducer 34 arranged at one end of the motor unit 14 in the direction along the input shaft 18A (rotation axis) to reduce the rotation of the motor unit 14, and an output shaft 18B (output unit) that outputs the rotation of the motor unit 14 via the reducer 34. The output shaft 18B extends from one end (the reducer 34 side) of the motor unit 14 to the other end of the motor unit 14 and has a shaft portion 18Bb (displacement magnifying portion) that magnifies the displacement of the output shaft 18B at the other end of the motor unit 14, and is equipped with interval sensors 46A to 46C (displacement detecting portion) arranged at the other end of the motor unit 14 to detect the displacement information of the output shaft 18B in the direction along a plane (cross section) perpendicular to the extension direction of the shaft portion 18Bb with respect to the shaft portion 18Bb. Therefore, it is possible to grasp the magnitude of the load acting on the output shaft 18B with high accuracy using the displacement of the enlarged shaft portion 18Bb.

In addition, the control method of the drive unit 10 includes a step 114 in which the displacement of the output shaft 18B is magnified at the other end side of the motor unit 14 by the shaft portion 18Bb, and information on the displacement of the output shaft 18B magnified at the other end side is detected by the spacing sensors 46A to 46C, and a step 116 in which the direction and magnitude of the moment acting on the output shaft 18B is determined using the displacement information.
According to this embodiment, the displacement of one end of the output shaft 18B due to the moment acting on the output shaft 18B is magnified by the shaft portion 18Bb, and this magnified displacement of the other end of the output shaft 18B is detected by the gap sensors 46A to 46C. At this time, since the shaft portion 18Bb of the output shaft 18B also serves as a displacement magnifying portion, the displacement of the output shaft 18B due to the moment can be magnified and detected with high accuracy using a drive device 10 with a simple configuration. Therefore, the detected displacement of the output shaft 18B can be used to detect the moment acting on the output shaft 18B with high accuracy using a simple configuration.

In addition, in this embodiment, since the disc springs 38A-38C (elastic portions) are interposed between the connecting plate 36B and the end portion 18Ba, when a moment acts on the output shaft 18B, the shaft portion 18Bb connected to the end portion 18Ba is easily displaced in the direction along this cross section, and the displacement of the shaft portion 18Bb due to the moment can be further increased. Therefore, the moment can be detected with higher accuracy.
In the above-described embodiment, the following modifications are possible.

First, in the above-described embodiment, the rotary bearing 28C is provided independently of the reducer 34. In contrast, as shown in the modified driving device 10A in FIG. 4, the reducer 34A may incorporate a rotary bearing 34Ac for the reducer. In FIG. 4, the reducer 34A is provided on the outer surface of the input shaft 18A. The reducer 34A has a cylindrical support portion 34Aa supported on the side surface on the -Z direction side of the motor case 30, a cylindrical first rotating portion 34Ab with an elliptical cross section fixed to the outer surface of the end portion 18Aa of the input shaft 18A, a flexible cylindrical second rotating portion 34Ad with an elliptical cross section arranged on the outer surface of the first rotating portion 34Ab, and a rotary bearing 34Ac arranged between the first rotating portion 34Ab and the second rotating portion 34Ad. The rotary bearing 34Ac has, for example, a plurality of spherical bearings. The -Z direction end of the second rotating part 34Ad is connected to the inner surface of the cylindrical rotating body 36C, the rotating body 36C is connected to the connecting plate 36B, and the rotary bearing 28D is disposed between the support part 34Aa and the rotating body 36C. Gears are formed on the outer surface of the second rotating part 34Ad and the inner surface of the support part 34Aa with a predetermined gear ratio, and the second rotating part 34Ad and the rotating body 36C rotate at a predetermined reduction ratio with respect to the input shaft 18A (first rotating part 34Ab). The reducer 34 is, for example, a wave gear (wave generator). The other configurations are the same as those of the above-mentioned embodiment. In this modified example, the connecting plate 36B and the disc springs 38A to 38C may be omitted, and the end 18Ba may be directly connected to the rotating body 36C.

The rotary bearing 34Ac is incorporated inside the reducer 34A to support the second rotating part 34Ad constituting the reducer 34A, and the rotary bearing 28D is, for example, a rolling bearing or a cross roller bearing. In the driving device 10A of this modified example, the rotary bearing 34Ac of the reducer 34A also functions as an elastic body. And, for example, in a configuration in which the connecting plate 36B and the disc springs 38A-38C are omitted and the end 18Ba is directly connected to the rotating body 36C, when a moment acts on the output shaft 18B, the output shaft 18B rotates around the rotation center C1 near the intersection of the support plane 28P of the rotary bearing 28D and the Z axis, and the displacement of the shaft part 18Bb is enlarged at the end in the +Z direction. Therefore, it is possible to detect the displacement of the shaft part 18Bb with high accuracy. It is also possible to consider that the output shaft 18B rotates around the intersection of the support surface of the rotary bearing 34Ac and the Z axis. In this example, the intersection of the support surface of the rotary bearing 34Ac and the Z axis is located close to the center of rotation C1, so even if the intersection of the support surface of the rotary bearing 34Ac and the Z axis is considered to be the center of rotation, the displacement magnification effect of the shaft portion 18Bb is approximately the same.

In addition, in the above embodiment, the direction and magnitude of the displacement of the shaft portion 18Bb of the output shaft 18B are detected, so the direction and magnitude of the moment acting on the output shaft 18B can be detected. Alternatively, at least one of the direction and magnitude of the displacement of the shaft portion 18Bb of the output shaft 18B may be detected, and at least one of the direction and magnitude of the moment acting on the output shaft 18B may be detected. In this case, at least one of the direction and magnitude of the moment can be detected with high accuracy using a simple configuration.

In the above embodiment, the displacement of the shaft portion 18Bb in the cross-sectional direction is detected using three spacing sensors 46A to 46C. However, as shown in the modified example of FIG. 2C, the displacement of the shaft portion 18Bb of the rotating shaft 18 in the X and Y directions in the cross-sectional direction may be detected using two spacing sensors 46A, 46B arranged at an interval of 90°. Even in this modified example, the direction and magnitude of the moment acting on the output shaft 18B can be obtained from the displacement of the shaft portion 18Bb in the X and Y directions. The interval between the two spacing sensors 46A, 46B arranged around the shaft portion 18Bb may be any angle other than 180°. Even when three spacing sensors 46A to 46C are used, the arrangement angle of the spacing sensors around the shaft portion 18Bb is not limited to equal angles and may be any angle.

In addition, in the above embodiment, the shaft portion 18Bb of the output shaft 18B also serves as the displacement magnification portion, but the displacement magnification portion may be provided separately from the shaft portion 18Bb. For example, the shaft portion 18Bb may be configured to be short, and a mirror surface may be provided on the end surface of the shaft portion 18Bb in the +Z direction, and detection light may be irradiated onto this mirror surface from an external light source, and the position of the light reflected from this mirror surface may be detected. By detecting the direction and amount of the positional shift of this reflected light, the displacement of the shaft portion 18Bb can be magnified and detected.

In the above embodiment, a reflective or transmissive optical detector is used as the first detection unit 44. Alternatively, a magnetic or capacitive detector may be used as the first detection unit 44. Furthermore, the first detection unit 44 detects the pattern of the rotating plate 42A, but the ends 18Aa, 18Ab of the input shaft 18A may be used as the rotating plate. That is, a magnetized pattern or a reflective pattern indicating the position in the rotation direction may be formed on the surface of the ends 18Aa, 18Ab, and the rotation information may be detected by an optical, magnetic, or capacitive detection unit.

Next, a second embodiment will be described with reference to Figures 5 and 6. In Figures 5 and 6, parts corresponding to Figures 4 and 2 (A) to (D) are given the same reference numerals, and detailed description thereof will be omitted. In addition, for convenience of description, the first rotating portion 34Ab, the rotary bearing 34Ac, and the second rotating portion 34Ad of the reducer 34A in Figure 4 are represented as a single member.
FIG. 5 shows a driving device 10B of this embodiment, FIG. 6(A) shows the main part of the driving device 10B of FIG. 5, and FIG. 6(B) shows a cross-sectional view along the line BB of FIG. 6(A). In FIG. 5, the driving device 10B includes an encoder unit 12 and a motor unit 14. A reducer 34A is connected to an end 18Aa in the -Z direction of an input shaft 18A that is rotated by the motor unit 14, a support unit 34Aa of the reducer 34A is supported on a side surface in the -Z direction of the motor case 30, and a cylindrical rotating body 36C is supported on the outer surface of the support unit 34Aa via a rotary bearing 28D. A disk-shaped end 18Ba of the output shaft 18B is directly connected to the end of the rotating body 36C in the -Z direction. Furthermore, a shaft portion 18Bb is provided at the center of the surface in the +Z direction of the end 18Ba, and the shaft portion 18Bb is supported so as to pass through the hollow portion of the input shaft 18A. The end portion 18Ba and the shaft portion 18Bb constitute an output shaft (output portion) 18B.

Other configurations are similar to those of the first embodiment and the modified example shown in Fig. 5. That is, the reducer 34A has a built-in rotary bearing 34Ac (see Fig. 4, not shown in Fig. 5), the rotation angle of the input shaft 18A is detected by a first detection unit 44, and the displacement (spacing) of the end of the shaft portion 18Bb of the output shaft 18B in the +Z direction in a plane perpendicular to the Z axis is detected by spacing sensors 46A to 46C (see Fig. 6(B)).
In this embodiment, the connecting plate 36B in Fig. 1 and the disc springs 38A to 38C (elastic portion) in Fig. 2(B) are omitted. Therefore, in the drive device 10B of this embodiment, the reducer 34A also serves as the elastic portion. Since the reducer 34A has a built-in rotary bearing 34Ac and a number of gears, etc., the reducer 34A is used as a member having a certain degree of elasticity.

In this embodiment, as shown in FIG. 6A, when a moment M acts on the output shaft 18B around an axis parallel to the X-axis, the reducer 34A is elastically deformed to a certain extent, so that the output shaft 18B rotates, for example, to a dotted line position 18P2 around the rotation center C1 near the intersection of the support surface 28P of the rotary bearing 28D and the Z-axis. At this time, if the distance between the end of the shaft portion 18Bb in the -Z direction and the rotation center C1 is Lc, and the distance between the rotation center C1 and the end of the shaft portion 18Bb in the +Z direction is Ld, the displacement δ3 of the end of the shaft portion 18Bb in the +Z direction in the +Y direction is enlarged at a ratio (Ld/Lc) to the displacement δ1 of the end of the shaft portion 18Bb in the -Z direction. As an example, since the distance Ld is at least twice the distance Lc, the displacement δ3 is enlarged at least twice the displacement δ1.
6B, by detecting the displacement δ3 of the shaft portion 18Bb using the three interval sensors 46A to 46C, the moment acting on the output shaft 18B can be detected with high accuracy with a simple configuration, as in the first embodiment. In this case, since the reducer 34A also serves as the elastic portion, the configuration of the drive unit 10B can be further simplified.

Next, a third embodiment will be described with reference to Figs. 7 to 10. In Figs. 7 and 8(B), parts corresponding to Figs. 5 and 6 are given the same reference numerals, and detailed description thereof will be omitted. Fig. 7 shows the drive unit 10C of this embodiment, Fig. 8(A) is a view seen from the direction of the arrow A in Fig. 7, and Fig. 8(B) is a view showing a state in which the output shaft 18C, described below, is tilted from the state in Fig. 7.

In FIG. 7, the driving device 10C includes an encoder unit 12A and a motor unit 14. A reducer 34A is connected to the -Z end 18Aa of the input shaft 18A, which is rotated by the motor unit 14, and a disk-shaped end 18Ca of the output shaft 18C, which has an opening in the center, is connected to the -Z end of the rotating body 36C connected to the reducer 34A. In this embodiment, the reducer 34A, which incorporates a rotary bearing 34Ac (see FIG. 4; not shown in FIG. 7), acts as an elastic body. Furthermore, a cylindrical shaft portion 18Cb is provided in the center of the +Z surface of the end 18Ca. The shaft portion 18Cb is supported so as to pass through the hollow portion of the input shaft 18A and the central opening of the first rotating plate 42A attached to the end surface of the input shaft 18A. The end 18Ca and the shaft portion 18Cb constitute the output shaft 18C. The rotation angle of the first rotating plate 42A (input shaft 18A) is detected by the first detection unit 44, and the detection signal S1 of the first detection unit 44 is supplied to the first calculation device 16A.

In addition to the first rotating plate 42A, the first detection unit 44, and the first calculation device 16A, the encoder unit 12A of this embodiment also includes a second rotating plate 42B that is disk-shaped and fixed to the end face in the +Z direction of the shaft portion 18Cb of the output shaft 18C, and that has a transparent, rotating pattern 8 (see FIG. 8A) formed thereon, three second detection units 52A, 52B, and 52C that detect the pattern of the second rotating plate 42B, and a second calculation device 48A that processes the detection signals S3A, S3B, and S3C of the detection units 52A, 52B, and 52C.

As shown in FIG. 8A, the pattern 8 of the second rotating plate 42B includes, for example, an incremental and/or absolute type pattern for detecting the circumferential angle of the rotating plate 42B. As an example, the detection unit 52A is disposed at the end of the rotating plate 42B in the +X direction, and the detection units 52B and 52C are disposed at the ends of the rotating plate 42B in the +Y direction and the -Y direction, respectively. That is, the detection units 52A, 52B, and 52C are disposed at 90° intervals around the Z axis with respect to the rotating plate 42B. Each of the detection units 52A to 52C has a light source that irradiates detection light onto the pattern 8 of the rotating plate 42B, and a light receiving element that receives light (for example, transmitted light) from the pattern 8. In reality, the detection units 52A to 52C each have, for example, multiple light receiving elements, and the detection signals S3A to S3C of the detection units 52A to 52C each include, for example, multiple detection signals with different phases. Similarly, the detection signal S1 also includes multiple detection signals with different phases. Note that although the detection units 52A to 52C are transmissive optical sensors, the pattern 8 on the rotating plate 42B may be a reflective pattern, and reflective optical sensors may be used as the detection units 52A to 52C.

7, the second calculation device 48A of the encoder unit 12A has amplifiers 54A, 54B, and 54C that amplify the detection signals S3A, S3B, and S3C, respectively, a preprocessing unit 57 that sequentially processes the output signals of the amplifiers 54A, 54B, and 54C, an accuracy correction unit 59, and a moment conversion unit 63. The preprocessing unit 57 has interpolation units 56A, 56B, and 56C that interpolate the amplified detection signals S3A, S3B, and S3C to obtain the rotation angle of the rotating plate 42B with a resolution finer than the minimum period of the pattern 8, for example. The accuracy correction unit 59 has correction units 58A, 58B, and 58C that store correction tables for the angles obtained by the interpolation units 56A, 56B, and 56C. The correction table records, for example, the difference (angle correction value) between the accurate measurement value of the rotation angle of the output shaft 18C (for example, the value measured by a calibrated reference rotary encoder not shown) and the angle calculated by the interpolation units 56A, 56B, and 56C at a specified angle interval.

The correction units 58A, 58B, and 58C calculate an accurate angle by adding the angle correction value (or the interpolated correction value) of the corresponding angle in the corresponding correction table to the angle obtained by the interpolation units 56A, 56B, and 56C, respectively. The rotation angle CT1 corrected by the correction unit 58A (the rotation angle detected by the detection unit 52A) is output to the first calculation unit 16A. The first calculation unit 16A determines the detection value of the rotation angle of the output shaft 18C as the weighted average of the first rotation angle of the output shaft 18C obtained by multiplying the rotation angle of the input shaft 18A obtained from the detection signal S1 by the known reduction ratio of the reducer 34A and the rotation angle CT1 (the second rotation angle of the output shaft 18C), and outputs this detection value to the motor control unit 24.

Moment conversion unit 63 has difference calculation units 60A and 60B, a direction conversion unit 62A, and a moment load conversion unit 62B. The rotation angle CT1 corrected by correction unit 58A is supplied to the first input units of difference calculation units 60A and 60B, and the rotation angles CT2 and CT3 corrected by correction units 58B and 58C (rotation angles detected by detection units 52B and 52C) are supplied to the second input units of difference calculation units 60A and 60B, respectively. Difference calculation unit 60A supplies the difference between the two rotation angles CT1 and CT2 to the first input units of direction conversion unit 62A and moment load conversion unit 62B, respectively, and difference calculation unit 60B supplies the difference between the two rotation angles CT1 and CT3 to the second input units of direction conversion unit 62A and moment load conversion unit 62B, respectively.

The direction conversion unit 62A performs an arctangent calculation from the two differences as described below to determine the direction Φ of the moment acting on the output shaft 18C, and the moment load conversion unit 62B performs a calculation from the two differences as described below and multiplies the result of this calculation by the moment conversion coefficient Mk described above to determine the magnitude E of the moment. The direction Φ and magnitude E of the moment thus determined are supplied to the control device 50. The rest of the configuration is the same as in the second embodiment of FIG. 5. That is, in this embodiment, the reducer 34A also serves as an elastic part, and the output shaft 18C rotates around the center of rotation C1 near the intersection of the support surface of the rotary bearing 28D built into the reducer 34A and the Z axis.

Next, in this embodiment, as shown in FIG. 8(B), when a moment M acts on the output shaft 18C around an axis parallel to the X-axis passing through the rotation center C1, the shaft portion 18Cb of the output shaft 18C rotates (tilts) around the rotation center C1 due to the elastic deformation of the reducer 34A, and the output shaft 18C tilts to a position 18C1. At this time, as shown in FIG. 9(A), the rotating plate 42B provided on the output shaft 18C with respect to the detection units 52A to 52C is displaced, for example, by ε1 in the +Y direction from the position 42B1 when no moment is acting. Since the pattern 8 of the rotating plate 42B is formed periodically in the circumferential direction, when the rotating plate 42B is displaced by ε1 in the +Y direction, only the rotation angle of the rotating plate 42B (output shaft 18C) detected by the detection unit 52A changes by an angle corresponding to ε1, and the rotation angle of the output shaft 18C detected by the other detection units 52B and 52C does not change.

In this way, when the rotation angle detected by Y-direction detection units 52B and 52C does not change and only the rotation angle detected by detection unit 52A changes, the magnitude of displacement of rotating plate 42B in the Y direction can be detected from the detection result of detection unit 52A. Similarly, when the rotation angle detected by X-direction detection unit 52A does not change and only the rotation angle detected by detection units 52B and 52C changes by the same value with the opposite sign, the magnitude of displacement of rotating plate 42B in the X direction can be detected from the difference between the detection results of detection units 52B and 52C.

In general, when a moment M acting in an arbitrary direction on the output shaft 18C displaces the rotating plate 42B to a position 42B2 in an arbitrary direction relative to the detection units 52A-52C as shown in FIG. 9(B), and the output shaft 18C is rotated by an arbitrary angle by the motor unit 14, the rotation angles CT1, CT2, CT3 detected by the detection units 52A, 52B, 52C (angles output from the accuracy correction unit 59) can be processed by the moment conversion unit 63 to determine the direction Φ and magnitude E of the moment M as follows:

As shown in Fig. 9B, the angle of the direction of displacement of the end of the shaft portion 18Cb of the output shaft 18C in the +Z direction due to the moment acting on the output shaft 18C is φ, the magnitude of the displacement is ε, and the rotation angle of the rotating plate 42B is θ. The angle φ and the rotation angle θ are angles in the counterclockwise direction with respect to the X-axis. Note that the displacement ε is exaggerated. Also, it is assumed that the detection units 52A, 52B, and 52C are arranged at 90° intervals.
At this time, the rotation angle CT1 (rad) detected by the detection unit 52A is as follows:
CT1=ε・sinφ+θ...(5)

Furthermore, the rotation angle CT2 detected by the detection unit 52B is advanced in phase with respect to the rotation angle CT1 by π/2, and is therefore expressed as follows:
CT2=ε・sin(φ+π/2)+θ...(6)
The difference δ12 between the two rotation angles CT1 and CT2 (output of the difference calculation unit 60A) is as follows:
δ12=ε{sinφ−sin(φ+π/2)}=ε(sinφ+cosφ)
=2 ^1/2 ε・sin(φ+π/4)…(7)

Comparing equation (7) with equation (5), it can be seen that the magnitude of the angle is magnified by a factor of 2 ^1/2 by calculating the difference.
On the other hand, the rotation angle CT3 detected by the detection unit 52C is delayed in phase by π/2 with respect to the rotation angle CT1, and is therefore as follows:
CT3=ε・sin(φ−π/2)+θ…(8)
The difference δ13 between the rotation angles CT3 and CT1 (output of the difference calculation unit 60B) is as follows:
δ13=ε{sin(φ−π/2)−sinφ}=−ε(sinφ−cosφ)
=-2 ^1/2 ε・sin (φ-π/4)
=2 ^1/2 ε・cos(φ+π/4)…(9)

From equations (7) and (9), the sum δS of the square of the difference δ12 and the square of the difference δ13 is given as follows:
δS=2ε ² {sin ² (φ+π/4)+cos ² (φ+π/4)}=2ε ² …(10)
Therefore, the moment load conversion unit 62B can obtain 2 ^1/2 times the magnitude ε of the displacement of the output shaft 18C by calculating the square root of δS in equation (10), and can calculate ε by dividing this value by 2 ^1/2 .

At this time, a moment conversion coefficient Mk for determining the magnitude E of the moment acting on the output shaft 18C from the magnitude ε of the displacement is stored in the memory of the moment load conversion unit 62B. Therefore, the moment load conversion unit 62B obtains the magnitude E of the moment by multiplying ε by the conversion coefficient Mk as follows:
E=ε・Mk…(11)

Moreover, the direction conversion unit 62A can obtain the angle φ of the displacement by calculating the arctangent of the equations (7) and (9) as follows.
φ=arctan {sin(φ+π/4)/cos(φ+π/4)}-π/4...(12)
The direction Φ of the moment acting on the output shaft 18C from this angle φ can be calculated as follows:
Φ=φ+π ... (13)
In this manner, by using the three detectors 52A to 52C, it is possible to determine with high accuracy the direction and magnitude of the displacement of the shaft portion 18Cb of the output shaft 18C, and further the direction Φ and magnitude E of the moment acting on the output shaft 18C, even if the output shaft 18C is rotated by an arbitrary angle by the motor portion 14. Furthermore, the rotation angle (rotation information) of the output shaft 18C can also be detected with high accuracy.

The encoder unit (encoder section 12A and reducer 34A) of the drive device 10C of this embodiment thus includes a reducer 34A arranged at one end of the motor section 14 in the direction along the input shaft 18A (rotation shaft) to reduce the rotation of the motor section 14, an output shaft 18C (output section) that outputs the rotation of the motor section 14 via the reducer 34A, a first detection section 44 (first rotation detection section) that detects first rotation information of the input shaft 18A (input section) driven by the motor section 14, and a detection section 52A (second rotation detection section) that detects second rotation information of the output shaft 18C. The output shaft 18C extends from one end of the motor section 14 to the other end and has a shaft section 18Cb (displacement magnification section) that magnifies the displacement of the output shaft 18C at the other end of the motor section 14.

Furthermore, the encoder unit is provided with detection units 52A, 52B, 52C (displacement detection units) that are arranged on the other end side of the motor portion 14 and detect displacement information of the rotation shaft 18C in a direction along a plane perpendicular to the extension direction of the shaft portion 18Cb, and a first calculation device 16A (first calculation unit) that calculates the respective rotation angles (rotation amounts) of the input shaft 18A and the output shaft 18C based on the first rotation information detected by the first detection unit 44 and the second rotation information detected by the detection unit 52A.
In addition, the control method of the encoder unit of this embodiment includes magnifying the displacement of the output shaft 18C at the other end of the motor unit 14 using the shaft portion 18Cb (displacement magnifying portion) of the output shaft 18C, detecting displacement information of the output shaft 18C in a direction along a plane perpendicular to the extension direction of the shaft portion 18Cb at the other end of the motor unit 14, and calculating the amount of rotation of each of the input shaft 18A and the rotating shaft 18C based on the first rotation information detected by the first detection unit 44 and the second rotation information detected by the detection unit 52A.

According to this embodiment, the displacement of one end of shaft portion 18Cb of output shaft 18C due to the moment acting on output shaft 18C is magnified by shaft portion 18Cb, and the displacement of the other end of this enlarged shaft portion 18Cb is detected by detection units 52A-52C. In this case, because shaft portion 18Cb of output shaft 18C also serves as the displacement magnifying unit, the displacement of output shaft 18C due to the moment can be magnified and detected with high accuracy using an encoder unit with a simple configuration. Therefore, the detected displacement of output shaft 18C can be used to detect the moment acting on output shaft 18C with high accuracy using a simple configuration. In addition, when detecting the displacement of the shaft portion 18Cb using the difference between the first detection unit 44, which detects the amount of rotation of the input shaft 18A due to the rotation of the motor portion 14, and one of the detectors of the detection units 52A to 52C, which detect the amount of rotation of the output shaft 18C, the presence of a dead zone in which the rotation of the motor portion 14 is not transmitted to the input shaft 18A in real time at the beginning of the rotation of the motor portion 14 may cause a decrease in detection sensitivity in detecting the displacement of the shaft portion 18Cb. However, in this embodiment, the displacement of the shaft portion 18Cb is calculated using the difference between the detection results of the detection units 52A to 52C, making it possible to perform highly sensitive detection without being affected by the dead zone of the input shaft 18A.

In addition, according to this embodiment, since the first rotation information and the second rotation information are detected, the rotation angle (rotation information) of the output shaft 18C can be detected with higher accuracy, and the rotation angle of the output shaft 18C, etc. can be controlled with higher accuracy.
In addition, the following modifications are possible in this embodiment.
First, in this embodiment, three detectors 52A, 52B, 52C are arranged around the rotating plate 42B at 90° intervals, but the arrangement (opening angle, etc.) of the detectors 52A, 52B, 52C is arbitrary. Also, in the encoder unit 12A of this embodiment, the direction and magnitude of the displacement of the shaft portion 18Cb of the output shaft 18C are detected to determine the direction and magnitude of the moment acting on the output shaft 18C, but at least one of the direction and magnitude of the displacement of the shaft portion 18Cb may be detected to determine at least one of the direction and magnitude of the moment acting on the output shaft 18C.
In this embodiment, the second rotation information can also be detected using at least one of the detection units 52A, 52B, and 52C.

In addition, the encoder unit 12A of this embodiment has three detection units 52A, 52B, and 52C to detect the direction and magnitude of the displacement of the shaft portion 18Cb of the output shaft 18C. On the other hand, as shown in the first modified example of FIG. 10, it is also possible to arrange only two detection units 52A and 52B along the rotating plate 42B on which the pattern 8 is formed. The opening angle of the detection units 52A and 52B can be set to any angle other than 180°. In this modified example, the rotation angle of the output shaft 18C due to the rotation of the motor unit 14 is mixed into the rotation angle detected by the detection units 52A and 52B. In order to remove the influence of the rotation angle of the output shaft 18C, for example, the rotation angle of the output shaft 18C calculated by multiplying the rotation angle of the input shaft 18A that can be detected by the first detection unit 44 in FIG. 7 by the known reduction ratio of the reducer 34A may be subtracted from the rotation angle detected by the detection units 52A and 52B. From the two rotation angles thus obtained, the direction and magnitude of the displacement of the shaft portion 18Cb due to the moment acting on the output shaft 18C can be obtained. In addition, when determining the moment acting on the output shaft 18C when the motor portion 14 is not rotating (when stationary), that is, when the output shaft 18C is not rotated by the motor portion 14 and only the displacement of the shaft portion 18Cb occurs, it is possible to detect the moment by arranging only the two detectors 52A and 52B, since the rotation angle of the output shaft 18C is not mixed in.

Next, a second modification of this embodiment will be described with reference to Fig. 11A. In this second modification, two of the three detectors 52A to 52C in Fig. 8A (e.g., detectors 52A and 52B) are used, but the two detectors 52A and 52B are arranged at an opening angle of 180°.
In the encoder unit 12B in FIG. 11A, the detectors 52A and 52B are disposed at the ends in the +X direction and the -X direction with respect to the pattern 8 of the rotating plate 42B of the output shaft 18C. The detection signals S3A and S3B of the detectors 52A and 52B are respectively supplied to pre-processing units 66A and 66B including the amplifier unit 54A, the interpolation unit 56A and the correction unit 58A in FIG. 7B. Then, the rotation angles CT1 and CT2 output from the pre-processing units 66A and 66B are respectively supplied to the averaging unit 68A and the difference calculation unit 68B. The average value of the rotation angles CT1 and CT2 output from the averaging unit 68A is supplied to the first calculation unit 16A, and the difference (=CT1-CT2) of the rotation angles CT1 and CT2 output from the difference calculation unit 68B is supplied to the moment conversion unit 63A.

In this modified example, when the rotating plate 42B at the tip of the rotating shaft 18C is displaced by ε1 in the -Y direction to position 42B1 due to the moment M in the Y direction acting on the rotating shaft 18C, the values of the rotation angles CT1 and CT2 are (θ-k1·ε1) and (θ+k1·ε1), respectively, for the accurate rotation angle θ (k1 is a predetermined coefficient). In other words, the angles detected by the detection units 52A and 52B change with the same magnitude but different signs. Therefore, the angle output from the averaging unit 68A (second rotation information of the output shaft 18C) becomes the accurate value θ as the effect of the displacement ε1 is offset, and the first calculation unit 16A can accurately calculate the rotation angle of the rotating shaft 18C using this value θ. On the other hand, the value output from the difference calculation unit 68B becomes k1·ε1, which does not include the rotation angle θ, and the moment conversion unit 63A can use this value to calculate the moment M in the Y direction with high accuracy.

Next, the encoder unit 12C of the third modified example in FIG. 11(B) is the second modified example in FIG. 11(A) in which the detectors 52C and 52D are arranged at an opening angle of 180° in the -Y and +Y directions with respect to the pattern 8 of the rotating plate 42B. The detection signals S3C and S3D of the detectors 52C and 52D are respectively supplied to pre-processing units 66C and 66D which are similar to the pre-processing unit 66A. The rotation angles output from the pre-processing units 66C and 66D are then supplied to a difference calculation unit 68C, and the difference between the two rotation angles output from the difference calculation unit 68C is supplied to a moment conversion unit 63B. The output of the difference calculation unit 68B is also supplied to the moment conversion unit 63B.

In this modified example, when the rotating plate 42B at the tip of the rotating shaft 18C is displaced by ε in the direction of an arbitrary angle φ to position 42B2 due to a moment M acting on the rotating shaft 18C in an arbitrary direction, the effect of the displacement of the output shaft 18C is removed from the value output from the averaging unit 68A. Therefore, the first calculation unit 16A can determine the rotation angle of the output shaft 18C with high accuracy. Meanwhile, the difference calculation units 68B and 68C respectively supply the displacement components in the Y and X directions of the tip of the rotating shaft 18C to the moment conversion unit 63B. Therefore, the moment conversion unit 63B can determine the moment M in an arbitrary direction with high accuracy.

Furthermore, the drive device and encoder unit of each of the above-described embodiments can be used as a drive mechanism or part thereof for various machine tools or robot devices.
Fig. 12 is a perspective view showing a robot device RBT using driving devices 10C and 10D similar to the driving device 10 of the above embodiment. In Fig. 12, components that are the same as or equivalent to those in the above embodiment are given the same reference numerals and their description will be omitted.
The robot device RBT includes a first driving device 10C, a first arm 82 connected to an end 18Da of an output shaft of the driving device 10C, a second driving device 10D installed at the tip of the first arm 82, a second arm 84 connected to the driving device 10D, a handling unit 86 attached to the tip of the second arm 84 so as to be vertically movable, and a robot control device 80 that controls the operation of the entire device. In this case, an end 18Ea of the output shaft of the driving device 10D is fixed to the tip of the first arm 82, and a workpiece 88 as a driven part is detachably held at the lower end of the handling unit 86.

In this embodiment, the output shaft of the drive unit 10C is driven to rotate around the rotation axis AX1, causing the first arm 82 to rotate around the rotation axis AX1, and the output shaft of the drive unit 10D is driven to rotate around the rotation axis AX2, causing the second arm 84 to rotate around the rotation axis AX2, so that the workpiece 88 can be positioned three-dimensionally. In addition, the control device 50 (see FIG. 1) of the drive unit 10C supplies information on the direction and magnitude of the moment MC acting on the first arm 82 to the robot control device 80, and the control device 50 (see FIG. 1) of the drive unit 10D supplies information on the direction and magnitude of the moment MD acting on the second arm 84 to the robot control device 80.

Therefore, as an example, when the magnitude of moment MC or MD exceeds a preset threshold value, robot control device 80 reduces the rotation speed of first arm 82 by drive device 10C and the rotation speed of second arm 84 by drive device 10D. Alternatively, robot control device 80 may stop the rotation of first arm 82 by drive device 10C and the rotation of second arm 84 by drive device 10D. Alternatively, robot control device 80 may issue an alarm to reduce the load of workpiece 88. This can prevent malfunctions, etc. of robot device RBT. In addition, the amount and direction of the positional deviation of the tip of the handling unit 86 when the moments MC and MD act, and the relationship between the magnitude and direction of the moments MC and MD may be stored in advance in a storage unit or the like, and when the moments MC and MD act, the robot control device 80 may read the amount and direction of the positional deviation of the tip of the handling unit 86 corresponding to the moments MC and MD from the storage unit or the like, and rotate the first arm 82 and the second arm 84 in a direction that corrects the positional deviation of the handling unit 86. This allows the positioning of the workpiece 88 to be performed with high accuracy. At this time, the relationship between the displacement and direction of the shaft 18Bb and the amount and direction of the positional deviation of the tip of the handling unit 86 may be stored in a storage unit or the like in advance, and the amount and direction of the positional deviation of the tip of the handling unit 86 may be read from the storage unit directly (without using moments) from the displacement and direction of the shaft 18Bb, and the position of the tip of the handling unit 86 may be corrected.

The robot device RBT is not limited to the above configuration, and the driving devices 10C and 10D can be applied to various robot devices equipped with joints (e.g., assembly robots, human-collaborative robots, etc.).

10, 10A to 10D... Drive unit, 12, 12A... Encoder unit, 14... Motor unit, 16, 16A... First calculation unit, 24... Motor control unit, 18A... Input shaft, 18B, 18C... Output shaft, 20... Magnet, 22... Coil, 30... Motor case, 34... Reducer, 34A... Reducer with built-in rotary bearing, 38A to 38C... Disc spring, 42A... First rotating plate, 42B... Second rotating plate, 44... First detection unit, 46A to 46C... Distance sensor, 52A to 52C... Second detection unit, 48, 48A... Second calculation unit, RBT... Robot device

Claims (16)

A motor;
an input shaft that transmits rotation of the motor and includes a hollow portion;
a transmission that changes the speed of the rotation of the motor transmitted from the input shaft;
an output section including an output shaft passing through a hollow portion of the input shaft and outputting the rotation of the motor, the rotation being changed in speed via the transmission, from a first end of the output shaft ;
a displacement detection unit that detects displacement information related to a translational displacement of a second end of the output shaft opposite to the first end in a plane perpendicular to an extension direction of the output shaft;
A drive unit comprising: The drive device according to claim 1, which has an elastic portion that makes it easier to displace the output shaft in a direction along a plane perpendicular to the extension direction of the output shaft. The drive device according to claim 2 , wherein the elastic portion is disposed between the transmission and the output portion and includes at least one of a disc spring, a leaf spring, a coil spring, and an elastic hinge. The drive unit according to claim 2 or 3 , wherein the transmission of the drive unit also serves as at least a part of the elastic portion. The drive device according to claim 2 , wherein the displacement detection unit has at least two distance sensors arranged at different positions around the output shaft, each of which detects a distance from the output shaft . 6. The drive device according to claim 5 , wherein the displacement detection section has three distance sensors arranged at equal angular intervals around the output shaft. The displacement detection unit
5. The drive device according to claim 1, further comprising: a scale body provided on the output shaft and having a pattern formed thereon; at least two pattern detectors arranged at positions where the pattern on the scale body can be detected, each of the pattern detectors detecting the pattern; and a displacement conversion unit that determines the displacement information based on detection results of the at least two pattern detectors. A calculation device that calculates a rotation angle of the output unit is further provided,
the displacement conversion unit supplies an average value of the rotation angle of the output unit to the calculation device;
The drive device according to claim 7 , wherein the calculation device calculates a rotation angle of the output portion based on the average value. The displacement detection unit
a scale body provided on the output shaft and having a pattern formed thereon; first, second and third pattern detectors disposed at positions on the scale body where the pattern can be detected, each detecting the pattern; and a displacement conversion unit that determines the displacement information based on detection results of the first, second and third pattern detectors,
5. The drive device according to claim 1, wherein the displacement conversion unit determines at least one of a direction and a magnitude of a displacement of the output shaft by using a difference between detection results of the first and second pattern detectors and a difference between detection results of the first and third pattern detectors. a transmission that transmits rotation of a motor and changes the speed of the rotation of the motor transmitted from an input shaft including a hollow portion;
an output section including an output shaft passing through a hollow portion of the input shaft and outputting the rotation of the motor, the rotation being changed in speed via the transmission, from a first end of the output shaft ;
A first rotation detection unit that detects first rotation information of the input shaft;
a second rotation detection unit that detects second rotation information of the output shaft,
a displacement detection unit that detects displacement information related to a translational displacement of a second end of the output shaft opposite to the first end in a plane perpendicular to an extension direction of the output shaft;
an encoder unit comprising: a first calculation unit that calculates the amount of rotation of each of the input shaft and the output shaft based on the first rotation information detected by the first rotation detection unit and the second rotation information detected by the second rotation detection unit. The encoder unit according to claim 10 , further comprising an elastic portion for facilitating displacement of the output shaft in a direction along a plane perpendicular to the axial direction of the output shaft. The encoder unit according to claim 10 , wherein the displacement detection section also functions as the second rotation detection section, and detects the second rotation information using a detection result of the displacement detection section. the displacement detection unit includes a scale body provided on the output shaft and having a pattern formed thereon, at least two pattern detectors disposed at positions capable of detecting the pattern on the scale body, each of which detects the pattern, and a displacement conversion unit which determines the displacement information based on detection results of the at least two pattern detectors,
The encoder unit according to claim 12 , wherein the second rotation detection section detects the second rotation information using at least one pattern detector of the at least two pattern detectors. A calculation device that calculates a rotation angle of the output unit is further provided,
the displacement conversion unit supplies an average value of the rotation angle of the output unit to the calculation device;
The encoder unit according to claim 13 , wherein the calculation device calculates a rotation angle of the output section based on the average value. the displacement detection unit comprises: a scale body provided on the output shaft and having a pattern formed thereon; first, second, and third pattern detectors disposed at positions on the scale body where the pattern can be detected, each detecting the pattern; and a displacement conversion unit that determines the displacement information based on detection results of the first, second, and third pattern detectors,
the displacement conversion unit determines at least one of the translation direction and the magnitude by using a difference between the detection results of the first and second pattern detectors and a difference between the detection results of the first and third pattern detectors;
The encoder unit according to claim 12 , wherein the second rotation detection section detects the second rotation information using at least one pattern detector among the first, second, and third pattern detectors. A robot device comprising: the drive device according to claim 2 ; an arm driven by the drive device; and a robot control unit that controls the drive device.

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