Oscillation-type gear mechanism, reduction gear and robot arm

Abstract

To prevent the lowering of the accuracy of rotation transmission while avoiding the lowering of the stiffness of a gear.SOLUTION: An oscillation-type gear mechanism 12 comprises: a rotatable first shaft 31; an inclination shaft 32 connected to the first shaft 31 while inclining thereto, and transmitted with the rotation of the first shaft 31; a rotatable second shaft 33 arranged at a side opposite to the first shaft 31 coaxially with the first shaft 31 with the inclination shaft 32 sandwiched therebetween; a first gear 1 fixed to a fixing member 11; a second gear 2 arranged at the first gear 1 coaxially therewith, rotating integrally with the second shaft 33, and movable to the second shaft 33 in an axial direction; an oscillation gear 3 arranged between the first gear 1 and the second gear 2, provided at the inclination shaft 32 so as to be rotatable, and engaged with the first gear 1 and the second gear 2 while inclining thereto; and an energization member 63 for energizing the second gear 2 in the axial direction progressing toward the oscillation gear 3. A portion contacting with at least the oscillation gear 3 out of the second gear 2 is constituted as a single member.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an oscillating gear mechanism, a reducer using the oscillating gear mechanism, and a robot arm equipped with the reducer. [Background technology]

[0002] In general, in industrial robots, the output of a high-speed, low-torque drive motor is converted to low-speed, high-torque by a reducer and used to drive joints. There are many types of reducers in use for industrial robots, including a reducer that uses an oscillating gear mechanism that achieves a large reduction ratio through the oscillating motion of the oscillating gear. In an oscillating gear mechanism, a fixed gear is provided coaxially with an input shaft, and an oscillating gear with a different number of teeth is tilted and meshed with the input shaft, and oscillating motion is achieved by the rotation of the input shaft. An output gear provided coaxially with the input shaft is then meshed with the oscillating gear, and the speed is reduced by the differential between these two sets of gears. Such oscillating gear mechanisms have had problems such as backlash at the meshing portions of the gears caused by dimensional errors or assembly errors of each component, and reduced accuracy in the rotation transmission between the input and output shafts caused by wear on the tooth surfaces over long periods of operation. Therefore, Patent Document 1 proposes a configuration in which a biasing gear is provided for each of the fixed gear and the output gear, the rotation of which is restricted while the biasing gear is movable in a straight axial direction, and at least one of the two biasing gears meshes with the oscillating gear, thereby suppressing backlash and wear on the tooth surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-161382 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the biasing gear is arranged on the outer or inner circumferential side of the output gear. In other words, the output gear is divided into two in the radial direction, and one of the divided parts is used as the biasing gear. In such a configuration, there may be a difference in the degree to which the output gear and the biasing gear protrude toward the oscillating gear, and if either one of them does not sufficiently mesh with the oscillating gear, the meshing tooth width may become narrow and the rigidity may decrease. The same can be said for a configuration in which the biasing gear is arranged on the outer or inner circumferential side of the fixed gear.

[0005] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to prevent a decrease in the rigidity of the gears in an oscillating gear mechanism, thereby preventing a decrease in the precision of rotation transmission. [Means for solving the problem]

[0006] The oscillating gear mechanism of the present invention comprises a rotatable first shaft, an inclined shaft connected to the first shaft at an angle and to which rotation of the first shaft is transmitted, a rotatable second shaft arranged coaxially with the first shaft on the opposite side of the inclined shaft to the first shaft, a first gear fixed to a fixed member, a second gear arranged coaxially with the first gear, rotating integrally with the second shaft and movable in the axial direction relative to the second shaft, an oscillating gear arranged between the first gear and the second gear, rotatably mounted on the inclined shaft and meshing with the first gear and the second gear at an angle, and a biasing member that biases the second gear in the axial direction toward the oscillating gear, and at least a portion of the second gear that contacts the oscillating gear is configured as a single member. Effect of the Invention

[0007] According to the present invention, in an oscillating gear mechanism, it is possible to prevent a decrease in the rigidity of the second gear and thus prevent a decrease in the accuracy of rotation transmission. [Brief description of the drawings]

[0008] [Figure 1]1 is a perspective view showing a configuration of a robot device according to an embodiment. FIG. [Diagram 2] 1 is a cross-sectional view showing a schematic configuration of a reducer according to an embodiment. [Diagram 3] FIG. 2 is a diagram showing a first gear, a second gear, and a swing gear. [Figure 4] FIG. 2 is an exploded perspective view showing a configuration around an output shaft. [Diagram 5] FIG. 4 is a cross-sectional view showing the configuration around the output shaft. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a robot device according to an embodiment. The robot device 150 is an industrial robot, and includes an articulated robot 100 that performs tasks such as assembling a workpiece W, a control device 130 that controls the articulated robot 100, and a teaching pendant 140 that can be connected to the control device 130.

[0010] The articulated robot 100 includes a six-axis articulated robot arm (hereinafter simply referred to as a robot arm) 101 and an end effector 102 connected to the tip of the robot arm 101. The robot arm 101 includes a base 103 fixed to a workbench, a plurality of links 121-126 for transmitting displacement and force, and a plurality of joints J1-J6 for connecting the plurality of links 121-126 so that they can turn or rotate. Each of the plurality of joints J1-J6 includes a drive motor (not shown), an encoder (not shown) for detecting the rotation angle of the rotation shaft of the drive motor, and a reducer (transmission) 10 for reducing the output of the drive motor to increase the torque of the drive motor. The drive motor and the reducer 10 constitute an actuator. The reducer 10 will be described in detail later. The end effector 102 is a robot hand and includes a plurality of gripping jaws 104 for gripping the workpiece W. The end effector 102 also includes a drive motor (not shown) that drives the plurality of gripping jaws 104, an encoder (not shown) that detects the rotation angle of the drive motor, and a reducer (not shown) that reduces the output of the drive motor. The end effector 102 also includes a force sensor (not shown) that can detect stress (reaction force) acting on the gripping jaws 104, etc.

[0011] The control device 130 controls the articulated robot 100. The control device 130 is configured by a computer device including, for example, a CPU, a RAM for temporarily storing data, a ROM for storing programs for controlling each part, and an input / output interface circuit. The control device 130 supplies the power required for the operation of the drive motor from a power supply main body (not shown) to the drive motor, and changes the position and orientation of the robot arm 101 and the end effector 102. The teaching pendant 140 can be connected to the control device 130 and can input instructions for controlling the drive of the robot arm 101 and the end effector 102.

[0012] In the robot device 150 configured as described above, the control device 130 drives the drive motors of the multiple joints J1 to J6 of the robot arm 101 in accordance with input settings, etc., to move or stop the end effector 102 to an arbitrary position and posture. Then, in the arbitrary position and posture, the end effector 102 is caused to grip a workpiece W, a part, etc., while detecting the stress acting on the gripping jaws 104 with a force sensor, and an operation such as assembling the workpiece W is performed.

[0013] Hereinafter, the reducer 10 according to the embodiment will be described with reference to Figs. 2 to 5. Fig. 2 is a cross-sectional view showing a schematic configuration of the reducer 10. Fig. 3 is a view showing the first gear 1, the second gear 2, and the oscillating gear 3. Fig. 4 is an exploded perspective view showing the configuration around the output shaft 33. Fig. 5 is a cross-sectional view showing the configuration around the output shaft 33. As shown in FIG. 2, the reducer 10 includes a casing 11 as a fixed member, and a set of oscillating gear mechanisms (hereinafter simply referred to as gear mechanisms) 12. The casing 11 includes an output side casing 21 and an input side casing 22 .

[0014] The gear mechanism 12 has as its main components an input shaft 31, an inclined shaft 32 to which the rotation of the input shaft 31 is transmitted, an output shaft 33, a first gear 1, a second gear 2, and an oscillating gear 3 arranged between the first gear 1 and the second gear 2.

[0015] The input shaft 31 is a shaft member connected to a rotating shaft of a drive motor (not shown). The input shaft 31 is supported rotatably about an axis C1 via a bearing 51, for example a rolling bearing, provided in the input casing 22, and is fixed in the axial direction to the input casing 22. In this embodiment, the input shaft 31 corresponds to the first shaft of the present invention.

[0016] The inclined shaft 32 is connected to the input shaft 31 at an angle θ, and transmits the rotation of the input shaft 31. That is, an axis C2, which is the center line of the inclined shaft 32, is inclined at the angle θ with respect to an axis C1, which is the center line of the input shaft 31. The input shaft 31 and the inclined shaft 32 are each provided with, for example, a key-shaped portion and a groove portion, and the rotation of the input shaft 31 is transmitted to the inclined shaft 32 by engaging these portions.

[0017] The output shaft 33 is a shaft member connected to each of the links 121 to 126, and is disposed coaxially with the input shaft 31 on the opposite side of the inclined shaft 32 to the input shaft 31. The output shaft 33 is supported rotatably about the axis C1 via a bearing 52, for example a rolling bearing, provided in the output casing 21, and is fixed in the axial direction to the output casing 21. In this embodiment, the output shaft 33 corresponds to the second shaft according to the present invention.

[0018] The first gear 1 is a fixed gear, arranged coaxially with the input shaft 31, and fixed to the casing 11. As shown in Fig. 3, the first gear 1 has an annular or cylindrical shape coaxial with the input shaft 31, and a plurality of teeth 41 that mesh with the oscillating gear 3 is formed on its end on the oscillating gear 3 side. The teeth 41 have a number of teeth Z1, and have tooth tips formed on the tip side of a predetermined height, and recessed portions formed between the tooth tips on the tooth base side of the predetermined height.

[0019] The second gear 2 is an output gear, and is disposed coaxially with the first gear 1 on the opposite side of the oscillating gear 3 to the first gear 1. The second gear 2 is supported by the output shaft 33 via a plug 61, which will be described later in detail, and rotates integrally with the output shaft 33 and is movable in the axial direction relative to the output shaft 33. As shown in Figs. 3 and 4, the second gear 2 has a bottomed cylindrical shape having a circular bottom 2a and a cylindrical wall 2b, and is disposed coaxially with the output shaft 33 with the bottom 2a facing the opposite side to the oscillating gear 3, i.e., with the bottom 2a facing the end of the output shaft 33. A plurality of teeth 42 that mesh with the oscillating gear 3 are formed on the end of the wall 2b on the oscillating gear 3 side. The teeth 42 have a tooth number Z2, a tooth tip portion formed on the tip side of a predetermined height, and a concave portion formed between the tooth tips on the tooth base side of the predetermined height.

[0020] The oscillating gear 3 is disposed between the first gear 1 and the second gear 2. The oscillating gear 3 is rotatably mounted on the inclined shaft 32 via a bearing 53, which is, for example, a rolling bearing, provided on the inclined shaft 32. The oscillating gear 3 has an annular or cylindrical shape and is inclined to mesh with the first gear 1 and the second gear 2. As shown in FIG. 3, the oscillating gear 3 has a first tooth 43 that meshes with the tooth 41 of the first gear 1 at its end on the first gear 1 side, and a second tooth 44 that meshes with the tooth 42 of the second gear 2 at its end on the second gear 2 side. The number of teeth of the first tooth 43 is Z3, and the number of teeth of the second tooth 44 is Z4. In this embodiment, Z3=Z1+1, Z4=Z2+1. The number of teeth Z1 of the first gear 1 and the number of teeth Z2 of the second gear 2 may be different or the same.

[0021] Next, the configuration around the output shaft 33 will be described with reference to FIG. 4 and FIG. As shown in Fig. 4, the second gear 2 has a cylindrical shape with a circular bottom 2a and a cylindrical wall 2b, and a hole 71 is formed in the center of the bottom 2a, which is coaxial with the axis C1 that serves as the center of rotation. A pair of flat surfaces 72, 73 are provided on the inner peripheral surface of the hole 71. The bottom 2a serves as a stopper abutment.

[0022] The plug 61 includes a shaft portion 75 and a flange-shaped retaining portion 76 provided at an end of the shaft portion 75. A through hole 77 that is coaxial with the axis C1 is formed in the shaft portion 75. In addition, the shaft portion 75 is provided with a pair of flat portions 78, 79.

[0023] A hole 80 is formed in the output shaft 33, which is coaxial with the axis C1 and has the same diameter as the hole 71 of the second gear 2. A pair of flat surfaces 81, 82 are provided on the inner circumferential surface of the hole 80. Also, a screw hole 83 is provided in the bottom of the hole 80, as shown in FIG.

[0024] As shown in FIG. 5, the second gear 2, the plug 61, the screw 62, the disc spring 63, and the output shaft 33 are combined together to form a unit. In detail, the shaft portion 75 of the plug 61 passes through the hole 71 of the second gear 2 and the hole of the disc spring 63, and is inserted into the hole 80 of the output shaft 33. The disc spring 63 and the bottom portion 2a of the second gear 2 are sandwiched between the end face of the output shaft 33 and the retaining portion 76 of the plug 61, and the plug 61 is fixed to the output shaft 33 by the screw 62 fixed in the screw hole 83. In this state, the flat surfaces 78, 79 of the plug 61 come into contact with the flat surfaces 81, 82 of the hole 80 of the output shaft 33 to prevent rotation, and the plug 61 rotates together with the output shaft 33 around the axis C1. The flat surfaces 78, 79 of the plug 61 come into contact with the flat surfaces 72, 73 of the hole 71 of the second gear 2 to prevent rotation, and the second gear 2 and the plug 61 rotate together around the axis C1. That is, the second gear 2 and the output shaft 33 rotate together around the axis C1. Meanwhile, the second gear 2 can move in the direction of the axis C1 relative to the plug 61, and is biased by the disc spring 63 in the right direction of FIG. 5, that is, in the axial direction toward the oscillating gear 3.

[0025] In the state before the unit shown in FIG. 5 is assembled into the reducer 10, the bottom portion 2a of the second gear 2 abuts against the retaining portion 76 of the plug 61 due to the biasing force of the disc spring 63 as shown in FIG. On the other hand, in a state where the unit shown in Fig. 5 is incorporated into the reducer 10 (a state where the second gear 2 is engaged with the oscillating gear 3), the bottom 2a of the second gear 2 and the retaining portion 76 of the plug 61 are spaced apart from each other as shown in Fig. 2. In this state, the oscillating gear 3 receives the biasing force of the disc spring 63 via the second gear 2. That is, the disc spring 63 biases the second gear 2 against the oscillating gear 3. This biasing force biases the second gear 2 and the oscillating gear 3, and further the oscillating gear 3 and the first gear 1.

[0026] Here, a case will be described in which the second gear 2 is not biased and is fixed in the direction of the axis C1 relative to the output shaft 33. In this case, due to dimensional errors or assembly errors of parts, two cases are assumed: the second gear 2 is misaligned in the direction of the oscillating gear 3, and the second gear 2 is misaligned in the opposite direction to the oscillating gear 3. When the second gear 2 is misaligned in the direction of the oscillating gear 3, the interference between the parts is avoided by the elastic deformation of each part, and a large force is applied to the meshing part. This may cause an increase in the rotation torque of the input shaft 31, and a deterioration in the rotation transmission accuracy due to wear and deformation of the teeth. On the other hand, when the second gear 2 is misaligned in the opposite direction to the oscillating gear 3, backlash occurs, which causes an increase in lost motion, a deterioration in the rotation transmission accuracy due to a decrease in the meshing rate, and a deterioration in the durability of the teeth due to tooth tip contact. In order to eliminate the misalignment of the second gear 2, which causes these problems, it is necessary to minimize the dimensional errors of the parts by ultra-precision machining and to perform severe assembly adjustments, which require time and cost.

[0027] By adopting a biasing configuration for the second gear 2 as in this embodiment, the biasing force allows the second gear 2 to be placed in an appropriate position, making it possible to minimize elastic deformation and backlash of each part without minimizing dimensional errors of parts or performing severe assembly adjustments. As a result, it is possible to prevent torque increase, minimize lost motion, improve durability, and improve rotation transmission accuracy. Although the disc spring 63 is used as the urging member, the present invention is not limited to this. Any urging member that has a through hole or a notch through which the shaft portion 75 of the plug 61 can pass and generates a urging force by axial compression can be used, and for example, an elastic body such as a rubber washer, a wave washer, a coil spring, or the like can also be used.

[0028] Next, the deceleration operation of the reducer 10 using the gear mechanism 12 will be described. The rotation input to the input shaft 31 from a drive motor (not shown) is transmitted to the inclined shaft 32, and the oscillating gear 3 oscillates. The oscillating gear 3 revolves 360 / (Z1+1) per oscillation with respect to the fixed first gear 1. Meanwhile, an oscillation-induced revolution also occurs between the second gear 2 and the oscillating gear 3. The difference between these revolutions is output from the output shaft 33 that rotates integrally with the second gear 2. It is known that the reduction ratio of this type can be calculated by 1-(Z1(Z2+1)) / ((Z1+1)Z2). For example, when Z1=24 and Z2=48, a reduction ratio of 1 / 50 is obtained. Also, for example, when Z1=48 and Z2=49, a large reduction ratio of 1 / 2401 is possible, and this type of reducer can realize a wide range of reduction ratios in one stage, from a low reduction ratio of about 1 / 20 to a large reduction ratio of several thousandths.

[0029] As described above, by adopting a biasing configuration for the second gear 2, it is possible to prevent an increase in torque, minimize lost motion, improve durability, and improve the accuracy of rotation transmission. Also, unlike Patent Document 1, which divides the output gear into two in the radial direction and uses one of the two as the biasing gear, in this embodiment, the second gear 2 is configured as a single cylindrical member with a bottom. In this way, by configuring the portion of the second gear 2 that contacts the oscillating gear 3 as a single member, the teeth 42 of the second gear 2 do not have a narrow tooth width and have a smooth surface (a flush surface) in the tooth width direction, thereby ensuring rigidity. As described above, in the oscillating gear mechanism 12, it is possible to prevent the rigidity of the second gear 2 from decreasing, thereby preventing a decrease in the precision of rotation transmission. In addition, it is sufficient that at least the portion of the second gear 2 that contacts the oscillating gear 3 is configured as a single member, and the second gear 2 may be configured of a member that constitutes the portion that contacts the oscillating gear 3 and a member that constitutes the other portion.

[0030] Although the present invention has been described above with reference to the embodiments, the above embodiments are merely illustrative of the specific examples of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be embodied in various forms without departing from its technical concept or main features. The functions, materials, shapes, numbers and relative arrangements of the components described in the present embodiment are not intended to be limited to those unless otherwise specified.

[0031] The disclosure of this embodiment includes the following configuration. (Configuration 1) A rotatable first shaft; An inclined shaft connected to the first shaft at an angle and to which rotation of the first shaft is transmitted; a rotatable second shaft arranged coaxially with the first shaft on the opposite side of the tilted shaft from the first shaft; A first gear fixed to a fixed member; a second gear arranged coaxially with the first gear, rotating integrally with the second shaft, and movable in the axial direction relative to the second shaft; a swing gear disposed between the first gear and the second gear, rotatably mounted on the inclined shaft, and inclinedly meshing with the first gear and the second gear; a biasing member that biases the second gear in an axial direction toward the oscillating gear, 13. An oscillating gear mechanism, wherein at least a portion of the second gear that comes into contact with the oscillating gear is configured as a single member. (Configuration 2) the second gear has a bottomed cylindrical shape having a circular bottom and a cylindrical wall, and is arranged coaxially with the second shaft with the bottom facing away from the oscillating gear; 2. The oscillating gear mechanism according to configuration 1, wherein a plurality of teeth that mesh with the oscillating gear are formed on an end of the wall portion on the oscillating gear side. (Configuration 3) 3. The oscillating gear mechanism according to configuration 2, wherein the biasing member applies a biasing force to the bottom portion. (Configuration 4) 4. A reducer using the oscillating gear mechanism according to any one of configurations 1 to 3, which reduces the speed of an input rotation and outputs it. (Configuration 5) A robot arm in which an actuator having a drive motor and a reducer that reduces the speed of rotation input from the drive motor and outputs the reduced speed using the oscillating gear mechanism described in any one of configurations 1 to 3 is attached to a joint. [Explanation of symbols]

[0032] 1: first gear, 2: second gear, 2a: bottom, 2b: wall, 3: oscillating gear, 10: reducer, 11: fixed member, 12: oscillating gear mechanism, 31: input shaft, 32: tilt shaft, 33: output shaft, 63: disc spring, 101: articulated robot arm

Claims

1. A rotatable first shaft; an inclined shaft connected to the first shaft at an inclination and to which rotation of the first shaft is transmitted; a rotatable second shaft arranged coaxially with the first shaft on the opposite side of the tilt axis from the first shaft; a first gear fixed to a fixed member; a second gear arranged coaxially with the first gear, rotating integrally with the second shaft, and movable in an axial direction relative to the second shaft; a swing gear disposed between the first gear and the second gear, rotatably provided on the inclined shaft, and inclinedly meshing with the first gear and the second gear; a biasing member that biases the second gear in an axial direction toward the oscillating gear, 4. An oscillating gear mechanism, wherein at least a portion of said second gear that comes into contact with said oscillating gear is constructed as a single member.

2. the second gear has a bottomed cylindrical shape having a circular bottom and a cylindrical wall, and is arranged coaxially with the second shaft with the bottom facing away from the oscillating gear; 2. The oscillating gear mechanism according to claim 1, wherein a plurality of teeth meshing with the oscillating gear are formed on an end of the wall portion on the oscillating gear side.

3. 3. The oscillating gear mechanism according to claim 2, wherein the biasing member applies a biasing force to the bottom portion.

4. 3. A reducer using the oscillating gear mechanism according to claim 1 or 2, which reduces the speed of an input rotation and outputs it.

5. 3. A robot arm having an actuator attached to a joint, the actuator including a drive motor and a reducer that reduces the speed of rotation input from the drive motor and outputs the reduced speed rotation using the oscillating gear mechanism according to claim 1 or 2.

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