JP6025761B2 - Drive unit - Google Patents

Description

  The present invention relates to a drive unit in which an electric motor is incorporated in a gear reducer such as a wave gear device or a planetary gear device.

  Conventionally, a drive unit in which a speed reducer is connected to an actuator is used in various technical fields. For example, applications such as industrial robots and machine tools require high positioning accuracy and large torque. Therefore, a drive unit in which a gear reducer such as a wave gear device or a planetary gear device is connected to a rotating shaft of an electric motor is provided. It is used.

  In recent years, in particular, multi-joint robots have been required to reduce the size and weight of drive units arranged at joints in order to be able to cope with more diverse work. Therefore, it has been proposed to reduce the size and weight of the drive unit by incorporating an actuator inside the gear reducer.

  Here, as a drive unit in which an actuator is incorporated in a gear reducer, for example, Patent Document 1 discloses a flex spline (flexible gear) that meshes with a circular spline (rigid gear) of a wave gear device and an inner side of the flex spline. A configuration is disclosed in which a plurality of elastic bodies that expand and contract in the radial direction by the pressure of a fluid are arranged radially between the holding member and the holding member. Patent Document 2 discloses a configuration in which a plurality of ring-shaped shape memory alloys that are deformed into elliptical shapes whose directions are different from each other by heating are arranged side by side in the axial direction. Further, in Patent Document 3, an elastic body having a plurality of pressure chambers is arranged inside an annular rotor, and pressure is sequentially supplied to each pressure chamber to move a contact point between the elastic body and the rotor. Thus, a configuration in which the rotor is rotated along the outer peripheral surface of the elastic body without causing the rotor to slide and the rotor is rotated is disclosed.

  On the other hand, in the field of industrial robots and the like, higher positioning accuracy is required than before, and as a result, the displacement or vibration caused when the power transmission system such as the drive unit is twisted around the axis is reduced. It is demanded.

Japanese Unexamined Patent Publication No. 7-77158 JP 7-98048 A JP-A-10-78010

  However, in Patent Documents 1 and 2, a cup-shaped flexspline supports the output unit, and in Patent Document 3, an elastic body that is a low-rigid actuator supports the output unit. Also, it has a low rigidity part from the drive part to the output part. When a large load torque is applied to the output portion, twisting occurs in this low rigidity portion, so that it is difficult to rotationally drive with high rotational accuracy due to the structure.

  In general, actuators using fluid pressure and heat as described in Patent Documents 1 to 3 are somewhat difficult to control the position and speed as compared with electric motors, and have poor controllability. Therefore, in the prior art, it is difficult to perform rotational driving with high rotational accuracy also from the control surface.

  Therefore, the object of the present invention is to realize an excellent controllability while reducing the size and weight by incorporating an electric motor into the gear reducer, and to further improve the rotation accuracy by increasing the torsional rigidity. It is in providing the drive unit which performs.

In order to achieve the above object, the drive unit according to the present invention is:
A first gear member in which first and second inner teeth are formed coaxially apart from each other, and the first and second inner teeth are integrally configured via a central shaft portion;
A second gear member having a third inner tooth disposed coaxially between the first and second inner teeth;
A cylindrical flexible intermediate gear member formed coaxially with first, second and third external teeth which mesh with the first, second and third internal teeth in a part of the circumferential direction, respectively;
A cylindrical rotor that is rotatably provided inside the flexible intermediate gear member and that has a cam portion that presses the flexible intermediate gear member from the inside, and an inner side of the rotor via a gap. And an electric motor having a stator fixed to the central shaft portion,
The ratio of the number of teeth of the first internal teeth and the first external teeth and the ratio of the numbers of teeth of the second internal teeth and the second external teeth are equal to each other, and Unlike the tooth ratio of the inner teeth and the third outer teeth,
By the rotational drive of the electric motor, the first to third external teeth of the flexible intermediate gear member move in the circumferential direction where the first to third internal teeth respectively mesh with the first to third internal teeth in a part of the circumferential direction. As described above, the flexible intermediate gear member is deformed in the radial direction by the rotation of the cam portion, and the first gear member and the second gear member rotate relative to each other.

  According to the present invention, an electric motor is incorporated into the gear reducer to achieve good controllability while achieving a reduction in size and weight, and to improve torsional rigidity by further increasing torsional rigidity. .

They are sectional drawing (a) and a partially enlarged view (b) which cut | disconnected the drive unit which shows Embodiment 1 of this invention by the plane which passes along the axis line. They are sectional drawing (a) which cut | disconnected the drive unit of FIG. 1 in the AA cross section, and sectional drawing (b) cut | disconnected by the BB cross section. It is explanatory drawing explaining operation | movement of the drive unit of FIG. It is a conceptual diagram explaining the torsional rigidity of the drive unit of FIG. It is sectional drawing (a) and the partially expanded view (b) which cut | disconnected the drive unit which shows Embodiment 2 of this invention by the plane which passes along the axis line. It is sectional drawing (a) which cut | disconnected the drive unit of FIG. 5 by the AA cross section, and sectional drawing (b) cut | disconnected by the BB cross section. It is explanatory drawing explaining operation | movement of the drive unit of FIG. It is a conceptual diagram explaining the torsional rigidity of the drive unit of FIG.

Embodiment 1 FIG.
As a first embodiment of the present invention, a configuration of a drive unit 100 in which an electric motor is incorporated in a wave gear device will be described with reference to FIGS.

  As shown in FIG. 1A, the drive unit 100 is a device that is provided between a base member 80 and a rotated body (not shown) and rotates the rotated body relative to the base member 80. The rotation is performed around the rotation axis 1.

  The drive unit 100 includes a first gear member 10 formed of a rigid material as a main component. The first gear member 10 has a central shaft portion 11 extending in the direction of the rotation axis 1 (hereinafter referred to as “axial direction”), and expands in the radial direction at both axial ends of the central shaft portion 11. The 1st and 2nd disk parts 12 and 15 are each provided continuously. As for the 1st disk part 12, the base member 80 is being fixed to the outer side end surface (right side of FIG. 1) of the axial direction with a fastening bolt etc. (not shown). The first and second disk portions 12 and 15 are arranged in parallel to each other, and first and second cylindrical portions 13 and 16 are continuously provided on the surfaces facing each other. The first and second cylindrical portions 13 and 16 are arranged such that their center lines are coaxial with the rotation axis 1, and the axial length is such that their mutually facing surfaces are separated in the axial direction. It is prepared. The first and second cylindrical portions 13 and 16 have substantially the same outer diameter as the first and second disk portions 12 and 15, respectively, and substantially the same inner diameter. First and second internal teeth 14 and 17 are formed.

  The above-described central shaft portion 11, second disk portions 12 and 15, and first and second cylindrical portions 13 and 16 provided on the first gear member 10 are configured integrally with each other, and in the drive unit 100. It functions as one part. In addition, it is arbitrary whether these center axis | shaft part 11, the 2nd disk parts 12 and 15, and the 1st and 2nd cylindrical parts 13 and 16 are manufactured separately as one part, respectively. . When manufactured separately, separate adjacent parts may be connected to each other, for example, by welding, fastening bolts, shrink fitting, and the like.

  The drive unit 100 is a second gear member formed of a rigid material and disposed so as to surround the second disk portion 15 and the second cylindrical portion 16 of the first gear member 10 via a gap. 20 In the drive unit 100, the second gear member 20 is disposed coaxially with the first gear member 10, and is provided to be rotatable relative to the first gear member 10 about the rotation axis 1. . The second gear member 20 includes a disk portion 21 that extends in the radial direction at one end in the axial direction, and a cylindrical portion 22 is provided on the end surface of the disk portion 21 on the first gear member 10 side (right side in FIG. 1). It is provided continuously. The cylindrical portion 22 has substantially the same outer diameter as the disk portion 21 and an inner diameter slightly larger than the outer diameter of the second cylindrical portion 16 of the first gear member 10. Further, the cylindrical portion 22 is provided with an annular portion 23 continuously on the end face thereof. The annular portion 23 has a length in the axial direction slightly shorter than the distance between the opposing end surfaces of the first and second cylindrical portions 13 and 16 of the first gear member 10, and its center line rotates. It is coaxial with the axis 1 and is disposed between the first and second cylindrical portions 13 and 16 with a gap in the axial direction. The annular portion 23 has substantially the same outer diameter as the cylindrical portion 22, and has substantially the same inner diameter as the first and second cylindrical portions 13 and 16 of the first gear member 10, and the inner peripheral surface has a first inner diameter. Three internal teeth 24 are formed.

  The disk portion 21, the cylindrical portion 22, and the annular portion 23 provided in the second gear member 20 are configured integrally with each other and function as one component in the drive unit 100. In addition, it is arbitrary whether these disk parts 21, the cylindrical part 22, and the annular part 23 are manufactured separately or as an integral part. When manufactured separately, adjacent parts may be connected to each other, for example, by welding, fastening bolts, shrink fitting, or the like.

  In the case of the first embodiment, the rotated body is fixed to the disk portion 21 of the second gear member 20 with fastening bolts or the like (not shown). Furthermore, in order to support the second gear member 20 so as to be relatively rotatable with respect to the first gear member 10, the cylindrical portion 22 of the second gear member 20 and the second gear member 10 of the first gear member 10 facing each other are supported. For example, a cross roller bearing (not shown) may be provided between the cylindrical portion 16.

  The drive unit 100 has an annular space surrounded by the first gear member 10 and the second gear member 20 described above. In this space, a flexible thin cylindrical intermediate gear member 30 that can be elastically deformed into an elliptical shape is provided, and a drive unit 70 is further provided inside the intermediate gear member 30. The intermediate gear member 30 has an axial length slightly shorter than the distance between the opposing end surfaces of the first and second disk portions 12 and 15 of the first gear member 10, and its center line rotates. It is coaxial with the axis 1 and is disposed between the first and second disk portions 12 and 15 with a gap in the axial direction. The intermediate gear member 30 has first, second, and third external teeth 32, 34, 36 formed on the outer peripheral surface thereof in this order in the axial direction. When the intermediate gear member 30 is not deformed (cylindrical shape not shown), The gear member 10 and the second gear member 20 have an outer diameter smaller than the inner diameter.

  As shown in FIG. 1 (b), the first and second internal teeth 14, 17 of the first gear member 10 are axially spaced from each other, and the first and second internal teeth 14, 17, the third internal teeth 24 of the second gear member 20 are arranged coaxially. As will be described later, when the intermediate gear member 30 is deformed into an elliptical shape, the first and second external teeth 32 and 34 of the intermediate gear member 30 are connected to the first and second inner teeth of the first gear member 10. The third outer teeth 36 of the intermediate gear member 30 mesh with the third inner teeth 24 of the second gear member 20 at a part in the circumferential direction while meshing with the teeth 14 and 17 at a part in the circumferential direction. It is configured. In other words, the intermediate gear member 30 is configured to mesh with the first gear member 10 at both ends in the axial direction and mesh with the second gear member 20 at the center in the axial direction.

  The internal teeth 14, 17, 24 and the external teeth 32, 34, 36 are the ratio of the number of the first internal teeth 14 and the first external teeth 32, and the second internal teeth 17 and the second external teeth. The tooth number ratio of 34 is equal to each other and is different from the tooth number ratio of the third inner teeth 24 and the third outer teeth 36. Usually, when a difference in the number of teeth is provided between the internal teeth and external teeth that mesh with each other, the number of internal teeth is reduced by 2n (n is a positive integer) with respect to the external teeth. As an example of satisfying the above-described gear ratio, in the first embodiment, the number of teeth of the first and second inner teeth 14 and 17 and the first to third outer teeth 32, 34, and 36 is set to 100. The number of teeth of the three internal teeth 24 is 102.

  As shown in FIG. 2, the drive unit 70 has an elliptical bearing 40 inside the intermediate gear member 30. The oval bearing 40 is an oval bearing, and is mainly composed of an outer ring 41, rolling elements 42 and an inner ring 43. The outer ring 41 is formed of a flexible material that fits inside the intermediate gear member 30 on the outer peripheral surface thereof and can be deformed into an elliptical shape together with the intermediate gear member 30. The inner ring 43 is configured to be fitted to the outside of an elliptical cam portion 50 described later on the inner peripheral surface thereof. A plurality of spherical rolling elements 42 are provided between the outer ring 41 and the inner ring 43 so that the outer ring 41 and the inner ring 43 can rotate relative to each other. Note that the rolling element 42 is not limited to a spherical shape, and may be, for example, a cylindrical shape. In FIG. 1, the rolling elements 42 are provided in three rows in the axial direction, but the present invention is not limited to this.

  Further, the drive unit 70 has an elliptical cam portion 50 inside the elliptical bearing 40. The elliptical cam portion 50 is a cylindrical cam having an elliptical outer shape, and is fitted to the inner ring 43 of the elliptical bearing 40. The elliptic cam portion 50 includes an inner peripheral surface that can be fitted to the outside of the rotor 62 of the electric motor 60 described later.

  Furthermore, the drive unit 70 includes an electric motor 60 inside the elliptical cam unit 50. The electric motor 60 has a cylindrical rotor 62 into which the elliptical cam portion 50 is fitted. In the first embodiment, the rotor 62 has a plurality of permanent magnets 66 fixed to the inner circumferential surface thereof at equal intervals in the circumferential direction. The electric motor 60 has a stator 64 disposed inside the rotor 62 via a gap. The stator 64 is formed by winding an annular iron core made of electromagnetic steel plates laminated in the axial direction, and the iron core is fitted and fixed to the central shaft portion 11 of the first gear member 10. Has been. By energizing the stator 64 to generate a rotating magnetic field, rotational torque is generated in the plurality of permanent magnets 66 arranged to face the outer peripheral surface of the iron core, so that the rotor 62 can be rotated. As shown in FIG. 1, in order to rotatably support the rotor 62 with respect to the stator 64, bearings are arranged at both ends of the rotor 62. The positions where the bearings are arranged are illustrated. Not limited to.

  Further, the electric motor 60 includes a rotation sensor (not shown) such as an absolute type encoder for detecting the motor rotation speed, and is connected to a motor driver (not shown) outside the drive unit 100. The rotation of the motor driver is controlled based on the output signal of the rotation sensor. As the electric motor 60, a general servo motor, stepping motor, or the like can be used. The electric motor 60 may be provided with a brake (not shown) for stopping the rotation of the rotor 62 by friction.

  As shown in FIG. 2, the central shaft portion 11 of the first gear member 10 has a plurality of holes 18 extending in the axial direction so as to wire between the motor driver outside the drive unit 100 and the electric motor 60. Are formed at equal intervals in the circumferential direction. Instead of the plurality of holes 18, one large-diameter through hole may be formed at the center of the central shaft portion 11. According to this, by providing a large-diameter through hole in the center of the disk portion 21 of the second gear member 20 as well, the output unit side (base member) from the base member 80 side of the drive unit 100 through the through hole. Various wirings and pipes can be passed through to the opposite side to 80).

  Further, when the intermediate gear member 30 is deformed into an elliptical shape using the elliptical cam portion 50 as in the first embodiment, the inner teeth 14, 17, 24 and the outer teeth 32, 34, 36 are in the circumferential direction. The number of portions that mesh with each other is two, but the number of portions that mesh with each other is not limited to two. For example, the intermediate gear member 30 may be deformed into a substantially M-square shape using a cam portion having a substantially M-square shape (M = 3, 4,...) So that the number of meshing portions is M. According to this, since the number of meshing teeth of the internal teeth 14, 17, 24 and the external teeth 32, 34, 36 can be increased, the maximum torque that can be transmitted by the drive unit 100 can be increased. In addition, the above-described substantially M-gonal shape includes a slightly deformed shape that can be seen only in a substantially circular shape.

  Next, the operation of the drive unit 100 will be described with reference to FIG. FIG. 3 schematically shows a cross-sectional view of the drive unit 100 taken along the line AA in FIG. In order to explain the relative rotation of the second gear member 20, the intermediate gear member 30, and the elliptical cam portion 50, arrows are attached to the predetermined phases of the members 20, 30, 50 as marks.

  First, FIG. 3A shows the drive unit 100 at a certain time. As shown in FIG. 3A, the flexible intermediate gear member 30 is deformed by the elliptic cam portion 50 so as to be long in the vertical direction and short in the horizontal direction via the elliptical bearing 40. At this time, the inner teeth 14, 17, 24 and the outer teeth 32, 34, 36 are engaged with each other in the vertical position.

  Next, when the elliptical cam portion 50 further rotates from the state of FIG. 3A, the first and second internal teeth 14 and 17 of the first gear member 10 and the intermediate gear member 30 having the same number of teeth are used. Since the three external teeth 36 are engaged with each other, the intermediate gear member 30 itself does not rotate. The intermediate gear member 30 that has been deformed into an elliptical shape by the elliptical cam portion 50 rotates in the direction of the major axis of the elliptical shape as the elliptical cam portion 50 rotates. Therefore, the portions where the outer teeth 32, 34, 36 of the intermediate gear member 30 and the inner teeth 14, 17, 24 of the first and second gear members 10, 20 mesh with each other move in the circumferential direction. At this time, the first and second external teeth 32, 34 of the intermediate gear member 30 have the same number of teeth as the first and second internal teeth 14, 17 of the first gear member 10. The member 30 does not rotate relative to the first gear member 10. On the other hand, the third external teeth 36 of the intermediate gear member 30 have a different number of teeth from the third internal teeth 24 of the second gear member 20, so that the intermediate gear member 30 is different from the second gear member 20. Rotate relatively. Therefore, the second gear member 20 rotates relative to the first gear member 10.

  For example, as shown in FIG. 3B, when the elliptical cam portion 50 is rotated 90 ° clockwise, the intermediate gear member 30 is deformed into an elliptical shape that is long in the left-right direction and short in the vertical direction according to the rotation. The inner teeth 14, 17, 24 and the outer teeth 32, 34, 36 mesh at the left and right positions. At this time, in the case of the first embodiment, the first gear member 10 is fixed to the base member 80, and the second gear member 20 has more teeth than the intermediate gear member 30, so the second gear member 20 Is the phase difference (the difference in the number of teeth between the third internal teeth 24 of the second gear member 20 and the third external teeth 36 of the intermediate gear member 30) × 90/360 ((102-100) × 90/360). Rotate clockwise by = 0.5 teeth).

  Further, as shown in FIG. 3 (c), when the elliptical cam portion 50 is rotated 360 ° clockwise, the intermediate gear member 30 is long in the vertical direction and short in the horizontal direction, as in FIG. 3 (a). The inner teeth 14, 17, 24 and the outer teeth 32, 34, 36 mesh in the vertical position. At this time, in the case of the first embodiment, the second gear member 20 rotates clockwise by the number of teeth difference between the second gear member 20 and the intermediate gear member 30 (102-100 = 2 teeth). Turn around.

  Thereafter, similarly, every time the elliptical cam portion 50 makes one rotation, the second gear member 20 rotates relative to the base member 80 by a difference in the number of teeth between the second gear member 20 and the intermediate gear member 30. . Therefore, when the first gear member 10 is fixed to the base member 80 and the second gear member 20 is used as the output portion as in the first embodiment, the difference in the number of teeth between the gear members 20 and 30 is obtained. Accordingly, the output can be taken out from the second gear member 20 which has been decelerated and rotated according to the above.

  Here, the torsional rigidity of the drive unit 100 with respect to the load torque acting on the output unit will be described with reference to FIG. 4 as an example where the second gear member 20 is used as the output unit. FIG. 4 is a perspective view conceptually showing a state in which the intermediate gear member 30 is twisted by the load torque.

  As shown in FIG. 4A, when the elliptical cam portion 50 accelerates, for example, when the elliptical cam portion 50 shifts from a stopped state to a rotating state, the second gear member 20 (third internal teeth 24). Begins to rotate in the same direction as the rotational direction of the elliptical cam portion 50 (see the dotted arrow). At this time, a load torque acts on the second gear member 20 in the direction opposite to the rotation direction (see the solid line arrow). That is, since the intermediate gear member 30 receives a force in the direction opposite to both ends at the center in the axial direction, the third outside of the intermediate gear member 30 that has been deformed into an elliptical shape along the outer shape of the elliptical cam portion 50. The teeth 36 are deformed, and the intermediate gear member 30 extending in the axial direction is in a state where the third external teeth 36 are most twisted with respect to the first and second external teeth 32 and 34 at both ends. . The maximum twist angle at this time is defined as θ. The elliptic cam portion 50 is also twisted by the load torque, but the torsion angle of the rigid elliptic cam portion 50 is very small compared to the flexible intermediate gear member 30.

  Next, as shown in FIG. 4 (b), the intermediate gear member 30 ′ is composed only of the first gear member 10 ′ and one end in the axial direction (first outer teeth 32 ′ and first inner teeth 14 ′). The drive unit 100 ′ is configured such that the intermediate gear member 30 ′ meshes with the second gear member 20 ′ only at the other end in the axial direction (the third outer teeth 36 ′ and the third inner teeth 24 ′). Considered as a comparative example. In the case of this comparative example, a load torque acts on the second gear member 20 'in the direction opposite to the rotation direction. That is, since the intermediate gear member 30 ′ receives forces in opposite directions at both ends, the third external teeth 36 ′ of the intermediate gear member 30 ′ that has been deformed into an elliptical shape is deformed, and the intermediate gear member that extends in the axial direction 30 'is in a state where the portion of the third external tooth 36' at one end is most twisted with respect to the portion of the first external tooth 32 'at the other end. The maximum twist angle at this time is defined as θ ′. Note that a conventional drive unit having a thin cup-shaped flexspline usually has one end of the flexspline fixed relatively to the circular spline, and has the same configuration as this comparative example.

  Here, the torsional rigidity of these drive units 100 and 100 'will be compared and examined. In general, when twisting a bar, it is more difficult to twist the center part by fixing both ends of the bar than when fixing one end of the bar and twisting the other end. Therefore, the third external gear 30 of the intermediate gear member 30 is more than the drive unit 100 ′ in which only the first external teeth 32 ′ at the other end are fixed to the third external teeth 36 ′ of the intermediate gear member 30 ′. In the drive unit 100 to which the first and second external teeth 32 and 34 at both ends of the tooth 36 are fixed, the intermediate gear member 30 (30 ′) is less likely to twist (θ <θ ′). Therefore, the drive unit 100 according to the first embodiment has higher torsional rigidity, and the load torque has less influence on the rotational accuracy.

  Therefore, in the case of the first embodiment, the intermediate gear member 30 and the first gear member 10 are engaged at both ends in the axial direction, and the intermediate gear member 30 and the second gear member 20 are engaged at the center thereof. By doing so, the intermediate gear member 30 is difficult to twist, and torque can be transmitted with high rotational accuracy.

  As described above, according to the drive unit 100 of the first embodiment, the torsional rigidity can be increased while reducing the size and weight by adopting the configuration in which the electric motor 60 is incorporated in the wave gear device, so that positioning with high rotational accuracy can be achieved. Is possible.

  In the case of the drive unit 100 according to the first embodiment, the bending rigidity is also improved. That is, the second gear member 20 as the output portion includes the third internal teeth 24 of the second gear member 20, the first to third external teeth 32, 34, 36, and the first of the intermediate gear member 30. The gear member 10 is supported by the base member 80 via the first and second internal teeth 14 and 17. In addition, the second gear member 20 includes the third internal teeth 24 of the second gear member 20, the first to third external teeth 32, 34, and 36 of the intermediate gear member 30, the electric motor 60, and the first. The gear member 10 is supported by the base member 80 via the central shaft portion 11. For this reason, bending rigidity can be made high compared with the case where an output part is supported only with an actuator like a prior art. Further, the intermediate gear member 30 is supported by the first gear member 10 having rigidity, and the bending rigidity can be increased as compared with the case where the intermediate gear member 30 is supported using a conventional thin cup-shaped component. Since the bending rigidity is improved in this way, the output portion is unlikely to be bent, tilted, or eccentric as in the conventional case. Therefore, in the case of this Embodiment 1, it also has the effect of reducing the vibration and energy loss resulting from the above-mentioned bending, inclination, and eccentricity.

  Furthermore, according to the drive unit 100 of the first embodiment, since the electric motor 60 that can rotate bidirectionally is used as the actuator, it has back drivability. Further, since the electric motor 60 is incorporated in the first embodiment, the shaft length is particularly shortened and further miniaturization is achieved as compared with the conventional drive unit in which the gear reducer is connected to the rotating shaft of the electric motor. realizable.

Embodiment 2. FIG.
In the first embodiment, the drive unit 100 in which the electric motor is incorporated in the wave gear device has been described. Next, as the second embodiment, the configuration of the drive unit 200 in which the electric motor is incorporated in the planetary gear device will be described with reference to FIG. Will be described with reference to FIG. In addition, description is abbreviate | omitted about the structural member which has the function and effect | action similar to Embodiment 1, and attaches | subjects the same code | symbol to drawing.

  As shown in FIG. 5A, the drive unit 200 is provided between the base member 80 and the rotated body (not shown), like the above-described drive unit 100, and the rotated body is attached to the base member 80. The rotation is performed around the rotation axis 1. The drive unit 200 includes first and second gear members 10 and 20 formed of a rigid material as main components, and the first and second gear members 10 and 20 include the drive unit. The same configuration as 100 is provided.

  The drive unit 200 has an annular space surrounded by the first gear member 10 and the second gear member 20 described above. In this space, a rigid cylindrical intermediate gear member 130 is provided, and a drive unit 170 is further provided inside the intermediate gear member 130. The intermediate gear member 130 has an axial length slightly shorter than the distance between the opposing end faces of the first and second disk portions 12 and 15 of the first gear member 10, and its center line rotates. It is coaxial with the axis 1 and is disposed between the first and second disk portions 12 and 15 with a gap in the axial direction. The intermediate gear member 130 has first, second, and third external teeth 132, 134, 136 formed on the outer peripheral surface thereof in this order in the axial direction, and the first gear member 10 and the second gear member. The outer diameter is smaller than the inner diameter of 20.

  As shown in FIG. 5 (b), the first and second internal teeth 14, 17 of the first gear member 10 are axially spaced from each other, and the first and second internal teeth 14, 17, the third internal teeth 24 of the second gear member 20 are arranged coaxially. As will be described later, when the intermediate gear member 130 is eccentric, the first and second external teeth 32 and 34 of the intermediate gear member 130 are the first and second internal teeth 14 and 17 of the first gear member 10. And the third outer teeth 136 of the intermediate gear member 130 are configured to mesh with the third inner teeth 24 of the second gear member 20 in a part of the circumferential direction. Yes. In other words, the intermediate gear member 130 is configured to mesh with the first gear member 10 at both ends in the axial direction and mesh with the second gear member 20 at the center in the axial direction.

  These internal teeth 14, 17, 24 and external teeth 132, 134, 136 are the number ratio of the first internal teeth 14 and the first external teeth 132, and the second internal teeth 17 and the second external teeth. The tooth number ratio of 134 is equal to each other and is different from the tooth number ratio of the third inner teeth 24 and the third outer teeth 136, respectively. Usually, when a difference in the number of teeth is provided between the internal teeth and external teeth that mesh with each other, the number of internal teeth is reduced by 2n (n is a positive integer) with respect to the external teeth. As an example of satisfying the above-mentioned gear ratio, in the first embodiment, the number of teeth of the first and second internal teeth 14 and 17 and the first to third external teeth 132, 134, and 136 is 100, The number of teeth of the three internal teeth 24 is 102.

  As shown in FIG. 6, the drive unit 170 has a bearing 140 inside the intermediate gear member 130. The bearing 140 is a general bearing having a circular outer shape, and mainly includes an outer ring 141, rolling elements 142, and an inner ring 143. In the case of the second embodiment, the outer ring 141 is formed of a rigid material that fits inside the intermediate gear member 130 on the outer peripheral surface thereof. The inner ring 143 is configured to be fitted to the outside of an eccentric cam portion 150 described later on the inner peripheral surface thereof. A plurality of spherical rolling elements 142 are provided between the outer ring 141 and the inner ring 143 so that the outer ring 141 and the inner ring 143 can rotate relative to each other. In addition, the rolling element 142 is not limited to a spherical shape, and may be, for example, a cylindrical shape. In FIG. 5, the rolling elements 142 are arranged in three rows in the axial direction, but the present invention is not limited to this.

  In addition, the drive unit 170 has an eccentric cam portion 150 inside the bearing 140. The eccentric cam portion 150 is a cylindrical cam having a circular outer shape that is eccentric from the rotation axis 1, and is arranged to be fitted to the inner ring 143 of the bearing 140. Further, the eccentric cam portion 150 has a circular through hole centering on the rotation axis 1, and an inner peripheral surface that can be fitted to the outside of the rotor 62 of the electric motor 60 described later in the through hole.

  Furthermore, the drive unit 170 has the electric motor 60 inside the eccentric cam unit 150. As shown in FIG. 6, the electric motor 60 provided in the drive unit 200 also has the same configuration as that of the drive unit 100 described above, but in the case of the second embodiment, an eccentric cam portion 150 is provided on the outer periphery of the rotor 62. It is fixed.

  Next, the operation of the drive unit 200 will be described with reference to FIG. FIG. 7 schematically shows a cross-sectional view of the drive unit 200 taken along the line AA of FIG. In order to explain the relative rotation of the second gear member 20, the intermediate gear member 130, and the eccentric cam portion 150, arrows are attached to the predetermined phases of the members 20, 130, and 150 as marks.

  First, FIG. 7A shows the drive unit 200 at a certain point in time. As shown in FIG. 7A, the intermediate gear member 130 is eccentrically shifted upward via the bearing 140 by the eccentric cam portion 150. At this time, the inner teeth 14, 17, 24 and the outer teeth 132, 134, 136 are engaged with each other at the upper position.

  Next, when the eccentric cam portion 150 further rotates from the state of FIG. 7A, the first and second internal teeth 14 and 17 of the first gear member 10 and the intermediate gear member 130 having the same number of teeth are used. Since the three external teeth 136 are engaged with each other, the intermediate gear member 130 does not rotate (spin) around its center. The center of the intermediate gear member 130 that is eccentric by the eccentric cam portion 150 rotates and revolves (revolves) as the eccentric cam portion 150 rotates. Therefore, the portions where the external teeth 132, 134, 136 of the intermediate gear member 130 mesh with the internal teeth 14, 17, 24 of the first and second gear members 10, 20 move in the circumferential direction. At this time, since the first and second external teeth 132, 134 of the intermediate gear member 130 have the same number of teeth as the first and second internal teeth 14, 17 of the first gear member 10, the intermediate gear The member 130 does not rotate relative to the first gear member 10. On the other hand, since the third external teeth 136 of the intermediate gear member 130 are different in the number of teeth from the third internal teeth 24 of the second gear member 20, the intermediate gear member 130 is different from the second gear member 20. Rotate relatively. Therefore, the second gear member 20 rotates relative to the first gear member 10.

  For example, as shown in FIG. 7B, when the eccentric cam portion 150 rotates 90 ° clockwise, the intermediate gear member 130 is eccentric rightward according to the rotation, and the internal teeth 14, 17, 24 and The external teeth 132, 134, 136 mesh with each other at the right position. At this time, in the case of the second embodiment, the first gear member 10 is fixed to the base member 80, and the second gear member 20 has more teeth than the intermediate gear member 130. Is the phase difference (the difference in the number of teeth between the third internal teeth 24 of the second gear member 20 and the third external teeth 136 of the intermediate gear member 130) × 90/360 ((102-100) × 90/360). Rotate clockwise by = 0.5 teeth).

  Further, as shown in FIG. 7 (c), when the eccentric cam portion 150 rotates 360 ° clockwise, the intermediate gear member 130 is eccentric upward as in FIG. 7 (a), and the internal teeth 14, 17, 24 and the external teeth 132, 134, 136 mesh with each other at the upper position. At this time, in the case of the second embodiment, the second gear member 20 rotates clockwise by the difference in the number of teeth between the second gear member 20 and the intermediate gear member 130 (102-100 = 2 teeth). Turn around.

  Thereafter, similarly, every time the eccentric cam portion 150 makes one rotation, the second gear member 20 rotates relative to the base member 80 by a difference in the number of teeth between the second gear member 20 and the intermediate gear member 130. . Therefore, when the first gear member 10 is fixed to the base member 80 and the second gear member 20 is used as the output portion as in the second embodiment, the difference in the number of teeth between the gear members 20 and 30 is obtained. Accordingly, the output can be taken out from the second gear member 20 which has been decelerated and rotated according to the above.

  Here, the torsional rigidity of the drive unit 200 with respect to the load torque acting on the output unit will be described with reference to FIG. 8, taking the second gear member 20 as an output unit as an example. FIG. 8 is a perspective view conceptually showing a state in which the intermediate gear member 130 is twisted by the load torque.

  As shown in FIG. 8A, when the eccentric cam portion 150 accelerates, for example, when the elliptical cam portion 50 shifts from the stopped state to the rotating state, the second gear member 20 (third internal teeth 24). Starts to rotate in the same direction as the rotation direction of the eccentric cam portion 150 (see the dotted arrow). At this time, a load torque acts on the second gear member 20 and the eccentric cam portion 150 in the direction opposite to the rotational direction (see the solid line arrow). That is, since the intermediate gear member 130 and the eccentric cam portion 150 receive a force in the direction opposite to both ends at the central portion in the axial direction, the intermediate gear member 130 extending in the axial direction has the third external teeth 136 at both ends. The first and second external teeth 132 and 134 are most twisted. The maximum twist angle of the intermediate gear member 130 at this time is defined as θ.

  Next, as shown in FIG. 8 (b), the intermediate gear member 130 ′ is composed only of the first gear member 10 ′ and one end in the axial direction (first outer teeth 132 ′ and first inner teeth 14 ′). The drive unit 200 ′ is configured so that the intermediate gear member 130 ′ meshes with the second gear member 20 ′ only at the other end in the axial direction (the third outer teeth 136 ′ and the third inner teeth 24 ′). Considered as a comparative example. In the case of this comparative example, a load torque acts on the second gear member 20 'and the eccentric cam portion 150' in the direction opposite to the rotational direction. That is, since the intermediate gear member 130 ′ and the eccentric cam portion 150 ′ receive forces in opposite directions at both ends, the intermediate gear member 130 ′ extending in the axial direction has a third external tooth 136 ′ at one end. It will be in the state twisted most with respect to the part of 1st external tooth 132 'in an end. At this time, the maximum twist angle of the intermediate gear member 130 ′ is θ ′.

  Here, the torsional rigidity of these drive units 200 and 200 'will be compared. In general, when twisting a bar, it is more difficult to twist the center part by fixing both ends of the bar than when fixing one end of the bar and twisting the other end. Therefore, the third external gear of the intermediate gear member 130 is more than the drive unit 200 ′ in which only the first external teeth 132 ′ at the other end are fixed to the third external teeth 136 ′ of the intermediate gear member 130 ′. In the drive unit 200 to which the first and second external teeth 132 and 134 at both ends of the tooth 136 are fixed, the intermediate gear member 130 (130 ′) is less likely to twist (θ <θ ′). Therefore, the drive unit 200 according to the second embodiment has higher torsional rigidity, and the load torque has less influence on the rotation accuracy.

  Therefore, in the case of the second embodiment, the intermediate gear member 130 and the first gear member 10 are engaged with each other at both axial ends, and the intermediate gear member 130 and the second gear member 20 are engaged with each other at the center. By doing so, the intermediate gear member 130 is difficult to twist and torque can be transmitted with high rotational accuracy.

  As described above, according to the drive unit 200 of the second embodiment, the torsional rigidity can be increased while reducing the size and weight by adopting the configuration in which the electric motor 60 is incorporated in the wave gear device, so that positioning with high rotational accuracy can be achieved. Is possible.

  It should be noted that the present invention is not limited to the illustrated embodiment, and it goes without saying that various improvements and design changes can be made without departing from the gist of the present invention.

  For example, in the first and second embodiments, the first gear member 10 is fixed to the base member 80. However, the second gear member 20 is fixed to the base member 80, and the first gear member 10 is output to the output unit. It is good. In this case as well, since the torsional rigidity of the support portion of the output portion can be increased, positioning with high rotational accuracy is possible.

  In the second embodiment, a so-called oscillating inscribed planetary gear device (also referred to as a KHV planetary gear or a hypocycloid reducer) is used as the planetary gear device, but the present invention is not limited to this. A planetary gear device of this type, for example, a cyclo reducer (registered trademark) using an arc tooth profile and a roller may be used. When a cyclo reducer (registered trademark) is used, the sliding contact is converted into a rolling contact by the roller, so that mechanical loss is very small and extremely high gear efficiency is obtained.

  As described above, according to the present invention, in a drive unit in which an electric motor is incorporated in a gear reducer such as a wave gear device or a planetary gear device, the rotational accuracy can be further improved. It may be suitably used in the field.

DESCRIPTION OF SYMBOLS 10 1st gear member, 14 1st internal tooth, 17 2nd internal tooth, 11 center axis | shaft part, 18 hole part, 20 2nd gear member, 24 3rd internal tooth, 30 intermediate | middle gear member (possible Flexible intermediate gear member), 32, 132 first external teeth, 34, 134 second external teeth, 36, 136 third external teeth, 50 elliptical cam portion, 60 electric motor, 62 rotor, 64 stator, 66 Permanent magnet, 130 intermediate gear member (rigid intermediate gear member), 150 eccentric cam

Claims (3)

A first gear member in which the first and second inner teeth are formed coaxially apart from each other in the axial direction, and the first and second inner teeth are integrally configured via a central shaft portion;
A second gear member having a third inner tooth disposed coaxially between the first and second inner teeth;
A cylindrical rigid intermediate gear member having first, second and third outer teeth coaxially formed to mesh with the first, second and third inner teeth respectively in a circumferential direction;
A cylindrical rotor that is rotatably provided inside the rigid intermediate gear member and has an eccentric cam portion that is eccentric from the center of the central shaft portion, and is disposed inside the rotor via a gap; An electric motor having a stator fixed to the central shaft portion,
The ratio of the number of teeth of the first internal teeth and the first external teeth and the ratio of the numbers of teeth of the second internal teeth and the second external teeth are equal to each other, and Unlike the tooth ratio of the inner teeth and the third outer teeth,
By rotating and driving the electric motor, the first to third outer teeth of the rigid intermediate gear member are moved in the circumferential direction at positions where the first to third inner teeth mesh with the first to third inner teeth in a part of the circumferential direction. Further, the rigid intermediate gear member is swung and rotated by the eccentric rotation of the eccentric cam portion, and the first gear member and the second gear member rotate relative to each other. The stator has an annular iron core made of electromagnetic steel plates fitted into the central shaft portion and laminated in the axial direction,
2. The drive unit according to claim 1, wherein the rotor includes a plurality of permanent magnets arranged at equal intervals in the circumferential direction on the inner circumferential surface thereof and provided facing the outer circumferential surface of the iron core. In the first gear member, a hole extending in the axial direction is formed in the central shaft portion,
3. The drive unit according to claim 1, wherein the electric motor is supplied with electric power to the stator via a wire passing through the hole.

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