Swing gear mechanism, reducer, and robot arm

Abstract

In the present invention, a swing gear mechanism 12 includes: a first shaft 31 that is capable of rotating; an inclined shaft 32 that is obliquely connected to the first shaft 31, the rotation of the first shaft 31 being transmitted to the inclined shaft 32; a second shaft 33 capable of rotating and disposed coaxially with the first shaft 31 on the opposite side to the first shaft 31 across the inclined shaft 32; a first gear 1 fixed to a fixed member 11; a second gear 2 that is disposed coaxially with the first gear 1, said second gear 2 rotating integrally with the second gear 33, and being capable of moving in the axial direction with respect to the second shaft 33; a swing gear 3 disposed between the first gear 1 and the second gear 2, said swing gear 3 being rotatably provided on the inclined shaft 32, and being obliquely engaged with the first gear 1 and the second gear 2; and an urging member 63 that urges the second gear 2 in the axial direction toward the swing gear 3. At least a portion of the second gear 2 that is in contact with the swing gear 3 is configured as a unitary member.

Description

Oscillating gear mechanism, reducer and robot arm

[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.

[0002] In general, in industrial robots, the output of a high-speed, low-torque drive motor is converted to low-speed, high-torque output by a reducer and used to drive joints. Many types of reducers are in practical use for industrial robots, including a reducer using an oscillating gear mechanism, which achieves a large reduction ratio through the oscillating motion of an oscillating gear. An oscillating gear mechanism has a fixed gear mounted coaxially with an input shaft, and an oscillating gear with a different number of teeth is inclined and meshed with the input shaft, causing oscillating motion through the rotation of the input shaft. An output gear mounted coaxially with the input shaft is then meshed with the oscillating gear, and speed is reduced by the differential movement of these two sets of gears.

[0003] Such oscillating gear mechanisms have had problems such as backlash at the meshing portions of the gears caused by dimensional or assembly errors of each component, and reduced accuracy in rotation transmission between the input and output shafts caused by wear on the tooth surfaces over long periods of operation.

[0004] Therefore, Patent Document 1 proposes a configuration in which a biasing gear is provided for each of the fixed gear and the output gear, which is movable in a straight axial direction while restricting rotation, and at least one of the two biasing gears meshes with the oscillating gear, thereby suppressing backlash and wear on the tooth surface.

[0005] JP 2015-161382 A

[0006] In Patent Document 1, a biasing gear is disposed 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 two 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. If either one of the gears does not sufficiently mesh with the oscillating gear, the meshing tooth width may become narrow and rigidity may decrease. The same can be said for a configuration in which a biasing gear is disposed on the outer or inner circumferential side of a fixed gear.

[0007] The present invention has been made in view of the above points, and has as its object 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.

[0008] 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 biasing the second gear in the axial direction toward the oscillating gear, wherein at least a portion of the second gear that contacts the oscillating gear is configured as a single member.

[0009] 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 precision of rotation transmission.

[0010] Fig. 1 is a perspective view showing a configuration of a robot device according to an embodiment; Fig. 2 is a cross-sectional view showing a schematic configuration of a reducer according to an embodiment; Fig. 3 is a view showing a first gear, a second gear, and an oscillating gear; Fig. 4 is an exploded perspective view showing a configuration around an output shaft; Fig. 5 is a cross-sectional view showing a configuration around an output shaft;

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] FIG. 1 is a perspective view of a robot device according to an embodiment.

[0013] 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.

[0014] 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 .

[0015] The robot arm 101 includes a base 103 fixed to a workbench, multiple links 121 to 126 that transmit displacement and force, and multiple joints J1 to J6 that connect the multiple links 121 to 126 so that they can pivot or rotate. Each of the multiple joints J1 to J6 includes a drive motor (not shown), an encoder (not shown) that detects the rotation angle of the rotation shaft of the drive motor, and a reducer (transmission) 10 that reduces the output of the drive motor to increase the torque of the drive motor. The drive motor and reducer 10 form an actuator. The reducer 10 will be described in detail later.

[0016] 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 decelerates 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.

[0017] 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.

[0018] The teaching pendant 140 can be connected to the control device 130 and can input instructions for driving and controlling the robot arm 101 and the end effector 102.

[0019] 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 any position and posture. Then, in any position and posture, the end effector 102 is caused to grip a workpiece W, a part, etc., while detecting stress acting on the gripping jaws 104 with a force sensor, and a task such as assembling the workpiece W is performed.

[0020] The reducer 10 according to the embodiment will be described below with reference to Figures 2 to 5. Figure 2 is a cross-sectional view showing a schematic configuration of the reducer 10. Figure 3 is a diagram showing the first gear 1, the second gear 2, and the oscillating gear 3. Figure 4 is an exploded perspective view showing the configuration around the output shaft 33. Figure 5 is a cross-sectional view showing the configuration around the output shaft 33.

[0021] 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.

[0022] The casing 11 includes an output side casing 21 and an input side casing 22 .

[0023] 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.

[0024] The input shaft 31 is a shaft member connected to a rotating shaft of a drive motor (not shown). The input shaft 31 is rotatably supported about an axis C1 via a bearing 51, such as 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.

[0025] 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 when these engage with each other, the rotation of the input shaft 31 is transmitted to the inclined shaft 32.

[0026] 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 from 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 defined in the present invention.

[0027] 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 that is 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.

[0028] 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 from the first gear 1. The second gear 2, which will be described in detail later, is supported by the output shaft 33 via a plug 61, rotates integrally with the output shaft 33, and is movable axially relative to the output shaft 33. As shown in FIGS. 3 and 4 , the second gear 2 has a cylindrical shape with a circular bottom 2a and a cylindrical wall 2b. The second gear 2 is disposed coaxially with the output shaft 33, with the bottom 2a facing away from the oscillating gear 3, i.e., 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 tip portion formed on the tip side of a predetermined height and a recessed portion formed between the tooth tips on the tooth base side of the predetermined height.

[0029] 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, e.g., a rolling bearing, provided on the inclined shaft 32. The oscillating gear 3 has an annular or cylindrical shape and meshes with the first gear 1 and the second gear 2 at an angle. As shown in FIG. 3 , the oscillating gear 3 has first teeth 43 formed on its end on the first gear 1 side that mesh with the teeth 41 of the first gear 1, and second teeth 44 formed on its end on the second gear 2 side that mesh with the teeth 42 of the second gear 2. The number of teeth of the first teeth 43 is Z3, and the number of teeth of the second teeth 44 is Z4. In this embodiment, Z3 = Z1 + 1, and Z4 = Z2 + 1. Note that 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.

[0030] Next, the configuration around the output shaft 33 will be described with reference to FIGS.

[0031] As shown in Figure 4, the second gear 2 has a cylindrical shape with a bottom, including 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 circumferential surface of the hole 71. The bottom 2a serves as a contact portion to prevent the gear from coming off.

[0032] The plug 61 includes a shaft portion 75 and a flange-shaped retaining portion 76 provided at the end of the shaft portion 75. A through hole 77 that is coaxial with the axis C1 is formed in the shaft portion 75. The shaft portion 75 also includes a pair of flat portions 78, 79.

[0033] A hole 80 is formed in the output shaft 33, coaxial with the axis C1, and having 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. In addition, a screw hole 83 is provided in the bottom of the hole 80, as shown in FIG.

[0034] 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.

[0035] More specifically, 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 2 a 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.

[0036] In this state, the flat surfaces 78, 79 of the plug 61 abut against the flat surfaces 81, 82 of the hole 80 of the output shaft 33, preventing rotation, and the plug 61 rotates integrally with the output shaft 33 around the axis C1. The flat surfaces 78, 79 of the plug 61 abut against the flat surfaces 72, 73 of the hole 71 of the second gear 2, preventing rotation, and the second gear 2 and the plug 61 rotate integrally around the axis C1. That is, the second gear 2 and the output shaft 33 rotate integrally around the axis C1. Meanwhile, the second gear 2 is movable relative to the plug 61 in the direction of the axis C1, and is biased by the disc spring 63 in the axial direction toward the right in FIG. 5 , i.e., toward the oscillating gear 3.

[0037] 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.

[0038] 5 is incorporated into the reducer 10 (when the second gear 2 is engaged with the oscillating gear 3), the bottom portion 2a of the second gear 2 and the retaining portion 76 of the plug 61 are spaced apart, 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.

[0039] Here, a case will be described in which the second gear 2 is not biased and is fixed to the output shaft 33 in the direction of the axis C1.

[0040] In this case, two possible scenarios are possible: the second gear 2 is misaligned toward the oscillating gear 3 due to dimensional errors or assembly errors of the components, or the second gear 2 is misaligned in the opposite direction from the oscillating gear 3. If the second gear 2 is misaligned toward the oscillating gear 3, interference between the components is avoided by elastic deformation of each component, resulting in a large force acting on the meshing portion. This can result in an increase in rotational torque of the input shaft 31 and deterioration of rotation transmission accuracy due to tooth wear and deformation. On the other hand, if the second gear 2 is misaligned in the opposite direction from the oscillating gear 3, backlash occurs, causing increased lost motion, deterioration of rotation transmission accuracy due to a decrease in the meshing ratio, and deterioration of tooth durability due to tooth tip contact. Eliminating the misalignment of the second gear 2, which causes these issues, requires ultra-precision machining to minimize dimensional errors of the components and strict assembly adjustments, which require time and cost.

[0041] By adopting a biasing configuration for the second gear 2 as in this embodiment, the biasing force allows the second gear 2 to be positioned appropriately, 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 an increase in torque, minimize lost motion, improve durability, and improve rotation transmission accuracy.

[0042] Although the disc spring 63 is used as the biasing member, the present invention is not limited to this. Any biasing member that has a through-hole or notch through which the shank 75 of the plug 61 can pass and generates a biasing force when compressed in the axial direction 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.

[0043] Next, the deceleration operation of the reducer 10 using the gear mechanism 12 will be described.

[0044] Rotation input to the input shaft 31 from a drive motor (not shown) is transmitted to the inclined shaft 32, causing the oscillating gear 3 to oscillate. The oscillating gear 3 revolves 360 / (Z1+1) per oscillation relative to the fixed first gear 1. Meanwhile, an orbital revolution due to the oscillation also occurs between the second gear 2 and the oscillating gear 3. The difference between these revolutions is output from the output shaft 33, which rotates integrally with the second gear 2. It is known that the reduction ratio of this type can be calculated as 1-(Z1(Z2+1)) / ((Z1+1)Z2). For example, when Z1 = 24 and Z2 = 48, a reduction ratio of 1 / 50 is obtained. Furthermore, when Z1 = 48 and Z2 = 49, a large reduction ratio of 1 / 2401 is also possible. This type of reducer can achieve a wide range of reduction ratios in a single stage, from a low reduction ratio of about 1 / 20 to a large reduction ratio of several thousandths.

[0045] 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 rotation transmission accuracy.

[0046] Furthermore, unlike Patent Document 1, which divides the output gear into two radially and uses one of the two as a biasing gear, in this embodiment, the second gear 2 is formed as a single cylindrical member with a bottom. By forming the portion of the second gear 2 that contacts the oscillating gear 3 as a single member in this way, 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.

[0047] 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.

[0048] In addition, the second gear 2 only needs to be configured as a single member, at least in the portion that contacts the oscillating gear 3, and may be configured as a member that constitutes the portion that contacts the oscillating gear 3 and a member that constitutes the other portion.

[0049] Although the present invention has been described above with reference to the embodiments, the above embodiments are merely illustrative of specific examples of how the present invention can be implemented, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

[0050] 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.

[0051] The disclosure of this embodiment includes the following configuration.

[0052] (Configuration 1) An oscillating gear mechanism comprising: 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, wherein at least a portion of the second gear that contacts the oscillating gear is configured as a single member.

[0053] (Configuration 2) The second gear has a cylindrical shape with a bottom 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, and a plurality of teeth that mesh with the oscillating gear are formed on the end of the wall on the oscillating gear side, in the oscillating gear mechanism described in Configuration 1.

[0054] (Configuration 3) The oscillating gear mechanism according to configuration 2, wherein the biasing member applies a biasing force to the bottom portion.

[0055] (Configuration 4) A reducer using the oscillating gear mechanism according to any one of configurations 1 to 3 to reduce the speed of input rotation and output it.

[0056] (Configuration 5) A robot arm in which an actuator including a drive motor and a reducer that uses the oscillating gear mechanism according to any one of configurations 1 to 3 to reduce the speed of rotation input from the drive motor and output the reduced speed is attached to a joint.

[0057] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0058] This application claims priority based on Japanese Patent Application No. 2023-127158, filed on August 3, 2023, the entire contents of which are incorporated herein by reference.

[0059] REFERENCE SIGNS LIST 1 First gear 2 Second gear 2a Bottom portion 2b Wall portion 3 Oscillating gear 10 Reducer 11 Fixed member 12 Oscillating gear mechanism 31 Input shaft 32 Inclined shaft 33 Output shaft 63 Disc spring 101 Articulated robot arm

Claims

1. An oscillating gear mechanism comprising: 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, wherein at least a portion of the second gear that contacts the oscillating gear is configured as a single member.

2. The oscillating gear mechanism described in claim 1, characterized in that the second gear is cylindrical with a circular bottom and a cylindrical wall, and is arranged coaxially with the second shaft with the bottom facing away from the oscillating gear, and a plurality of teeth that mesh with the oscillating gear are formed on the end of the wall on the oscillating gear side.

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

4. A reducer using the oscillating gear mechanism according to claim 1 or 2 to reduce the speed of input rotation and output it.

5. A robot arm in which an actuator equipped with a drive motor and a reducer that uses the oscillating gear mechanism described in claim 1 or 2 to reduce the speed of the rotation input from the drive motor and output it is attached to a joint.

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