Industrial robot arm structure

Abstract

The present invention provides an industrial robot arm structure that can easily implement a variable model by utilizing a plurality of characteristics of a single wrist unit. The industrial robot arm structure includes: a first motor and a second motor, each of which drives the plurality of wrist units within a housing; a first gear mounted on a first output shaft of the first motor and having an outer diameter equal to the first output shaft; and a second gear mounted on a second output shaft of the second motor and having an outer diameter equal to the second output shaft. The second motor is positioned forward of the first motor and is positioned such that the axis of the second output shaft is laterally offset relative to the axis of the first output shaft. A space is provided behind the first motor and behind the second motor.

Description

Technical Field

[0001] The present invention relates to an arm structure of an industrial robot. Background Art

[0002] Industrial robots with multiple wrist units at the top of their arms are known (see, for example, Patent Document 1). Such industrial robots are often modularized to create models with varying characteristics, such as a standard model and a heavy-duty model capable of carrying larger loads.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-185574 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] For example, when upgrading an industrial robot from a standard model to one capable of carrying heavy objects, the reduction ratio of the wrist unit's drive unit must be changed to increase the load capacity of the wrist unit. However, changing the reduction ratio requires changing the size and number of gears that make up the drive unit's reduction mechanism. Therefore, a wrist unit with a new drive unit corresponding to the reduction ratio must be prepared.

[0008] Therefore, in an industrial robot including a plurality of wrist units, it is desirable to be able to easily implement a variable model by utilizing the fact that the same wrist unit has a plurality of types of characteristics.

[0009] Solutions for solving problems

[0010] A technical solution disclosed herein is an arm structure of an industrial robot, which has multiple wrist units, wherein the arm structure of the industrial robot includes: a first motor and a second motor, which respectively drive the multiple wrist units in a shell; a first gear, which is mounted on the first output shaft of the first motor; and a second gear, which is mounted on the second output shaft of the second motor, the second motor is arranged at a position closer to the front than the first motor, and is arranged in a manner such that the axis of the second output shaft is offset laterally relative to the axis of the first output shaft, and space portions are respectively provided behind the first motor and behind the second motor.

[0011] Effects of the Invention

[0012] According to one embodiment, it is possible to provide an industrial robot arm structure that can easily realize a variable model by utilizing a plurality of characteristics of the same wrist unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A This is a side view showing one embodiment of an industrial robot.

[0014] Figure 1B Observed from direction B in the figure Figure 1A Figure 1 shows the wrist of an industrial robot.

[0015] Figure 2 This is a plan view showing the arm structure of an industrial robot.

[0016] Figure 3 This is a cross-sectional view showing the top end of the arm structure of the industrial robot.

[0017] Figure 4 It is along Figure 2 Cross-sectional view along line (iv)-(iv) in FIG.

[0018] Figure 5 It is along Figure 2 Cross-sectional view along the (v)-(v) line. DETAILED DESCRIPTION

[0019] Hereinafter, the arm structure of an industrial robot according to one embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1A 、 Figure 1B As shown, the industrial robot 1 shown in this embodiment includes: an upper arm 3, which is supported on a base 2 in a manner that allows it to rotate; a forearm 4, which is supported on the upper end of the upper arm 3 in a manner that allows it to rotate; and a wrist 5, which is supported on the front end of the forearm 4 in a manner that allows it to rotate.

[0020] The industrial robot 1 can three-dimensionally adopt various postures by rotating its various rotating parts. However, in this specification, for the sake of convenience, the directions of the industrial robot 1 are defined as "front" in the X1 direction shown in the figures, "back" in the X2 direction, "upward" in the Y1 direction, "downward" in the Y2 direction, and "lateral" in the Z1-Z2 direction.

[0021] The wrist 5 corresponds to the arm structure of the industrial robot 1 . The wrist 5 includes a first wrist element 51 , a second wrist element 52 , and a third wrist element 53 .

[0022] The first wrist element 51 extends from the front end of the forearm 4 along the Figure 1A 、 Figure 1B The first wrist element 51 is supported at the front end portion of the forearm 4 so as to be rotatable about a first axis J1 extending in the longitudinal direction of the first wrist element 51 .

[0023] The second wrist element 52 is provided from the front end portion of the first wrist element 51 toward Figure 1B The second wrist element 52 is supported at the front end portion of the first wrist element 51 so as to be rotatable around a second axis J2 intersecting the first axis J1.

[0024] The third wrist element 53 is provided from the front end portion of the second wrist element 52 toward Figure 1A and Figure 1B The third wrist element 53 is supported at the front end of the second wrist element 52 so as to be rotatable about a third axis J3 intersecting the second axis J2. In the present embodiment, the third axis J3 is arranged parallel to the first axis J1.

[0025] The structure of the wrist 5 will be described in further detail. The first wrist element 51 of the wrist 5 extends forward from the front end of the forearm 4. The rear end of the first wrist element 51 is rotatably supported by the front end of the forearm 4. A motor and a reduction mechanism (not shown) are provided within the forearm 4 for rotating the first wrist element 51 at a predetermined reduction ratio. The first wrist element 51 is driven by the motor and rotated about the first axis J1 via the reduction mechanism.

[0026] The first wrist unit 51 has a housing 510, which includes a front housing 510A and a rear housing 510B. The front housing 510A and the rear housing 510B are fastened together via a joint surface MS perpendicular to the first axis J1. A cover 511 for accessing the inner side of the rear housing 510B is provided on the upper side of the rear housing 510B in a detachable manner. Figure 2 As shown, an opening 511 a that largely opens the inside of the rear housing 510B is formed in the rear housing 510B with the cover 511 removed.

[0027] The rear housing 510B houses the first motor 6 that drives the second wrist element 52 and the second motor 7 that drives the third wrist element 53. The first motor 6 and the second motor 7 are driven in response to commands from the robot control device (not shown) of the industrial robot 1. The first output shaft 61 of the first motor 6 and the second output shaft 71 of the second motor 7 are arranged parallel to each other and project forward of the first wrist element 51. The first output shaft 61 and the second output shaft 71 are also parallel to the first axis J1 and the third axis J3.

[0028] like Figure 1A 、 Figure 1B as well as Figure 2As shown, the position of the first motor 6 and the position of the second motor 7 are offset in the front-to-back direction on the inner side of the rear housing 510B. The second motor 7 is arranged in a position further forward than the first motor 6. In detail, the first motor 6 is arranged so as to be biased toward the rear end side of the first wrist unit 51 relative to the second motor 7. The second motor 7 is arranged so as to be biased toward the joint surface MS with the front housing 510A relative to the first motor 6. The second motor 7 is arranged in a position further forward than the first output shaft 61 of the first motor 6. The first output shaft 61 of the first motor 6 and the second output shaft 71 of the second motor 7 do not overlap.

[0029] Moreover, if Figure 2 As shown, the positions of the first motor 6 and the second motor 7 are laterally offset inside the rear housing 510B. The first output shaft 61 of the first motor 6 and the second output shaft 71 of the second motor 7 are not arranged on the same axis, and the second motor 7 is arranged laterally offset relative to the first motor 6. Specifically, the first motor 6 is arranged offset in the Z2 direction relative to the first axis J1. The second motor 7 is arranged offset in the Z1 direction relative to the first axis J1.

[0030] The main body 70 of the second motor 7 is offset in the Z1 direction relative to the axis J6 of the first output shaft 61 of the first motor 6. However, when the first motor 6 and the second motor 7 are viewed from a direction along the first axis J1, the main body 60 of the first motor 6 and the main body 70 of the second motor 7 are arranged so as to partially overlap. This minimizes the cross-sectional area of the first wrist element 51 perpendicular to the first axis J1.

[0031] A first pedestal 63 for mounting the first motor 6 and a second pedestal 73 for mounting the second motor 7 are integrally provided on the inner side of the rear housing 510B. The first output shaft 61 side of the first motor 6 and the second output shaft 71 side of the second motor 7 are attached to the rear housing 510B via the first pedestal 63 and the second pedestal 73, respectively. Thus, the first motor 6 and the second motor 7 are fixed to the rear housing 510B. The mounting structure of the first motor 6 and the second motor 7 to the first pedestal 63 and the second pedestal 73 will be described further below.

[0032] Inside the front housing 510A, there are provided a reduction mechanism 8 for reducing the rotational speed of the first motor 6 at a predetermined reduction ratio, and a reduction mechanism 9 for reducing the rotational speed of the second motor 7 at a predetermined reduction ratio. The reduction mechanisms 8 and 9 are formed of hypoid gear sets, each having pinions 81 and 91, which are driven to rotate by the first motor 6 and the second motor 7, and ring gears 82 and 92, which mesh with the pinions 81 and 91, respectively.

[0033] The pinion 81 is provided at the front end of the first drive shaft 810 which extends longitudinally from the first motor 6 to the ring gear 82. The first drive shaft 810 is arranged parallel to the axis J6 of the first output shaft 61 of the first motor 6. Figure 2 As shown, the main body 70 of the second motor 7 is arranged to be arranged laterally (Z1 direction side) relative to the first drive shaft 810. The first drive shaft 810 is configured to be rotatable around the axis J8 extending along the longitudinal direction. The axis J8 is arranged at a position slightly lower than the axis J6 of the first output shaft 61. The rear end portion of the first drive shaft 810 is arranged near the first output shaft 61. Figure 4 As shown in FIG. 8 , a spur gear 811 is provided at the rear end portion of the first drive shaft 810. As will be described later, the spur gear 811 meshes with the first gear 62 attached to the first output shaft 61.

[0034] The pinion 91 is provided at the front end of the second drive shaft 910 extending longitudinally from the second motor 7 to the ring gear 92. The second drive shaft 910 is arranged parallel to the axis J7 of the second output shaft 71 of the second motor 7 and is configured to be rotatable around the axis J9 extending along the longitudinal direction. The axis J9 is arranged slightly above the axis J7 of the second output shaft 71. The rear end of the second drive shaft 910 is arranged near the second output shaft 71. Figure 5 As shown in FIG. 1 , a spur gear 911 is provided at the rear end portion of the second drive shaft 910. As will be described later, the spur gear 911 meshes with the second gear 72 attached to the second output shaft 71.

[0035] like Figure 2 and Figure 3 As shown, a ring gear 82 meshing with the pinion gear 81 and a ring gear 92 meshing with the pinion gear 91 are provided at the front end portion of the front housing 510A so as to be rotatable about the second axis J2. The diameter of the ring gear 82 is larger than that of the ring gear 92, and the ring gear 82 is arranged below the ring gear 92.

[0036] like Figure 3 As shown, the ring gear 82 is rotatably supported in the first wrist element 51 via a bearing 512. The ring gear 82 is integrally connected to the second wrist element 52. Therefore, the second wrist element 52 is driven to rotate about the second axis J2 by the rotation of the ring gear 82.

[0037] like Figure 3As shown, the ring gear 92 is attached to the outer circumference of a cylindrical body 513 disposed at the front end of the front housing 510A. The cylindrical body 513 is coaxially disposed with the second axis J2 and extends downward from the ring gear 92. The cylindrical body 513 penetrates the ring gear 82 and is rotatably supported on the inner circumference of the ring gear 82 via a bearing 515. A bevel gear 514 is integrally provided on the outer circumference of the lower end of the cylindrical body 513.

[0038] The third wrist element 53 is cylindrically shaped and coaxial with the third axis J3. A bevel gear 531 is integrally provided on the outer periphery of the rear end of the third wrist element 53. Bevel gear 531 meshes with bevel gear 514. Therefore, when the bevel gear 514 rotates about the second axis J2 due to the rotation of the ring gear 92, bevel gear 531 also rotates. This rotation drives the third wrist element 53 about the third axis J3.

[0039] A mounting surface 532 is formed at the front end of the third wrist element 53. Accessories (not shown) corresponding to the work content of the industrial robot 1 are detachably mounted on the mounting surface 532. Examples of the accessories include a manipulator arm and a welding torch.

[0040] like Figure 2 As shown, inside the rear housing 510B, space portions SP1 and SP2 are formed behind the first motor 6 and the second motor 7, respectively. The space portion SP1 is located between the rear end surface 60a of the main body 60 of the first motor 6 and the rear end surface 51a inside the rear housing 510B. The space portion SP2 is located behind the rear end surface 70a of the main body 70 of the second motor 7 and to the side of the first pedestal 63 in the Z1 direction.

[0041] The spaces SP1 and SP2 are large enough to accommodate motors extending rearward from the first motor 6 and the second motor 7 inside the rear housing 510B, instead of the first motor 6 and the second motor 7. Therefore, the spaces SP1 and SP2 can be used as workspace and installation space when replacing the motors driving the second wrist element 52 and the third wrist element 53 with higher-torque motors that are longer along the axes J6 and J7 than the first motor 6 and the second motor 7.

[0042] like Figure 4As shown, a first gear 62 is mounted on the first output shaft 61 of the first motor 6, meshing with the spur gear 811 at the rear end of the first drive shaft 810. The first gear 62 integrally includes a base 621 mounted on the first output shaft 61 by fitting with the outer periphery of the first output shaft 61, and a gear portion 622 extending forward of the first motor 6 along the axis J6 relative to the base 621. The gear portion 622 has an outer diameter equal to that of the first output shaft 61 and has teeth formed on its outer periphery that mesh with the spur gear 811 of the first drive shaft 810. The outer diameter of the gear portion 622 is the diameter of a circle whose outer circumference is the tip of the teeth of the gear portion 622.

[0043] The first motor 6 is mounted on the first pedestal 63 using the base 621 of the first gear 62. Specifically, the first pedestal 63 has a mounting hole 631 that opens toward the rear of the first wrist unit 51 and into which the first output shaft 61 is inserted. An external support bearing 64 is mounted on the outer periphery of the base 621 of the first gear 62. The first gear 62 and the external support bearing 64, mounted on the first output shaft 61, are inserted into the mounting hole 631 from the rear side of the first pedestal 63. The outer ring 641 of the external support bearing 64 engages with the inner circumferential surface of the mounting hole 631 to position the first output shaft 61. Thus, the first motor 6 is rotatably supported on the first pedestal 63 so that the first output shaft 61 and the first gear 62 are coaxial. The first gear 62, supported in the mounting hole 631, protrudes forward from the mounting hole 631 and meshes with the spur gear 811 at the rear end of the first drive shaft 810.

[0044] like Figure 5 As shown, the second gear 72 that meshes with the spur gear 911 at the rear end of the second drive shaft 910 is mounted on the second output shaft 71 of the second motor 7. The second gear 72 integrally includes a base 721 that is mounted by fitting with the outer periphery of the second output shaft 71, and a gear portion 722 that extends toward the front of the second motor 7 along the axis J7 relative to the base 721. The spur gear 911 meshes with the gear portion 722. The gear portion 722 has an outer diameter equal to the outer diameter of the second output shaft 71, and has a tooth portion formed on the outer periphery that meshes with the spur gear 911 of the second drive shaft 910. The outer diameter of the gear portion 722 is the diameter of a circle whose outer periphery is the tip of the tooth portion of the gear portion 722.

[0045] The second motor 7 is mounted on the second pedestal 73 via the base 721 of the second gear 72. Specifically, the second pedestal 73 has a mounting hole 731 that opens toward the rear of the first wrist element 51 and into which the second output shaft 71 is inserted. An external support bearing 74 is mounted on the outer periphery of the base 721 of the second gear 72. The second gear 72 and the external support bearing 74, mounted on the second output shaft 71, are inserted into the mounting hole 731 from the rear side of the second pedestal 73. The outer ring 741 of the external support bearing 74 engages with the inner circumferential surface of the mounting hole 731, positioning the second output shaft 71. Thus, the second motor 7 is rotatably supported on the second pedestal 73 so that the second output shaft 71 and the second gear 72 are coaxial. The second gear 72, supported in the mounting hole 731, protrudes forward from the mounting hole 731 and meshes with the spur gear 911 at the rear end of the second drive shaft 910.

[0046] Furthermore, the "equal" outer diameters of the first output shaft 61 and the gear portion 622 of the first gear 62, and the "equal" outer diameters of the second output shaft 71 and the gear portion 722 of the second gear 72, are not limited to being completely identical. Rather, they refer to being substantially the same. As long as the first gear 62 and the second gear 72 can be removed through the mounting holes 631 and 731, respectively, when replacing the first motor 6 and the second motor 7, slight differences in their outer diameters, such as due to manufacturing errors, are permitted.

[0047] Thus, the first gear 62 attached to the first output shaft 61 of the first motor 6 has an outer diameter equal to that of the first output shaft 61, and the second gear 72 attached to the second output shaft 71 of the second motor 7 has an outer diameter equal to that of the second output shaft 71. Furthermore, spaces SP1 and SP2 are provided behind the first motor 6 and the second motor 7, respectively. With these structures, when an operator removes the first motor 6 and the second motor 7 for replacement, they can easily remove the first motor 6 and the second motor 7 from the first pedestal 63 and the second pedestal 73, as described below.

[0048] When removing the first motor 6, the operator pulls out the first motor 6 straightly toward the rear of the space portion SP1 and removes the external support bearing 64 from the mounting hole 631 of the first base portion 63. This releases the engagement between the first gear 62 and the flat gear 811. Thereafter, the operator lifts the rear end side of the first motor 6 upward and pulls it out further toward the rear while tilting it, thereby pulling the first output shaft 61 and the first gear 62 toward the rear from the mounting hole 631. Since the first gear 62 has an outer diameter equal to that of the first output shaft 61, it can be easily removed from the mounting hole 631 by tilting the first motor 6. The inner diameter of the mounting hole 631 can also be the minimum necessary. Therefore, the first base portion 63 can be miniaturized, and the first wrist unit 51 can also be miniaturized.

[0049] When the second motor 7 is removed, it can be easily removed from the second pedestal 73, similar to the first motor 6. Furthermore, when replacing the first and second motors 6 and 7 with a higher-torque motor that is longer than the first and second motors 6 and 7 to change the arm structure to one with a greater payload capacity, the reverse operation is performed. Since spaces SP1 and SP2 are provided behind the first and second motors 6 and 7, respectively, even motors that are longer than the first and second motors 6 and 7 can be easily installed inside the rear housing 510B. Thus, the industrial robot 1 can change the characteristics of the drive units of the second and third wrist units 52 and 53 to those with a greater payload capacity simply by replacing the motors, without having to replace the wrist units. Consequently, the industrial robot 1 can implement different models with different drive unit characteristics using the same wrist unit.

[0050] The first gear 62 and the second gear 72 are small-diameter gears having outer diameters equal to the outer diameters of the first output shaft 61 and the second output shaft 71, respectively. Therefore, when the first motor 6 and the second motor each generate their maximum torque, a large repulsive force is generated on the tooth surfaces. However, the first gear 62 and the second gear 72 are supported by external support bearings 64 and 74 mounted on the outer peripheries of their respective bases 621 and 721, respectively, in the mounting holes 631 and 731 of the first and second pedestal portions 63 and 73, respectively. Therefore, the first gear 62 and the second gear 72 can stably transmit the rotational torque of the first and second output shafts 61 and 71 to the spur gears 811 and 911.

[0051] Furthermore, the first motor 6 and the second motor 7 are supported by the first output shaft 61 and the second output shaft 71 by fitting the outer rings 641 and 741 of the external support bearings 64 and 74, which are mounted on the outer circumferences of the bases 621 and 721 of the first gear 62 and the second gear 72, into the mounting holes 631 and 731, respectively. This facilitates ensuring the accuracy of mounting the first motor 6 and the second motor 7 to the first pedestal 63 and the second pedestal 73. Since the mounting holes 631 and 731 of the first pedestal 63 and the second pedestal 73 only require a relatively small diameter, the first pedestal 63 and the second pedestal 73 can also be miniaturized.

[0052] Furthermore, the gear portion 622 of the first gear 62 protrudes forward from the external support bearing 64 and meshes with the spur gear 811 of the first drive shaft 810. The gear portion 722 of the second gear 72 protrudes forward from the external support bearing 74 and meshes with the spur gear 911 of the second drive shaft 910. Therefore, the meshing points between the first gear 62 and the spur gear 811, and the meshing points between the second gear 72 and the spur gear 911, are located very close to the fitting points between the external support bearings 64 and 74 and the mounting holes 631 and 731, respectively. This allows the driving forces of the first motor 6 and the second motor 7 to be stably transmitted to the first drive shaft 810 and the second drive shaft 910. Furthermore, it is easy to ensure the positional accuracy of the spur gears 811 and 911 relative to the first gear 62 and the second gear 72.

[0053] Furthermore, since the diameters of the first gear 62 and the second gear 72 are relatively small, it is possible to increase the reduction ratios at the meshing locations between the first gear 62 and the flat gear 811, and at the meshing locations between the second gear 72 and the flat gear 911. Therefore, the industrial robot 1 can also easily cope with increases in the loadable weight.

[0054] In the above embodiment, the second motor 7 is arranged forward of the first wrist element 51 relative to the first motor 6 , but the present invention is not limited thereto. The first motor 6 may be arranged forward of the first wrist element 51 relative to the second motor 7 .

[0055] In the above embodiment, the shell 510 of the first wrist unit 51 is divided into a front shell 510A and a rear shell 510B via a joint surface MS perpendicular to the first axis J1, but the structure of the shell 510 is not limited as long as the first motor 6 and the second motor 7 can be arranged to be offset from each other.

[0056] In the above embodiment, the rear ends of the first drive shaft 810 and the second drive shaft 910 are configured so that the driving force from the first gear 62 and the second gear 72 is transmitted only through the spur gears 811 and 911. However, in order to adjust the reduction ratio, additional gears may be provided between the first gear 62 and the second gear 72 and the first drive shaft 810 and the second drive shaft 910 in addition to the spur gears 811 and 911.

[0057] Description of Reference Numerals

[0058] 1. Industrial robot; 51. First wrist unit; 52. Second wrist unit; 53. Third wrist unit; 510. Housing; 6. First motor; 61. First output shaft; 62. First gear; 7. Second motor; 71. Second output shaft; 72. Second gear; 63. First pedestal; 631. Mounting hole; 64. External support bearing; 641. Outer ring; 73. Second pedestal; 731. Mounting hole; 74. External support bearing; 741. Outer ring; 810. First drive shaft; 811. Spur gear; 910. Second drive shaft; 911. Spur gear; J6, J7, Axis; SP1, SP2, Space portion.

Claims

1. An industrial robot arm structure comprising a plurality of wrist units, wherein: The arm structure of this industrial robot includes: a first motor and a second motor, each of which drives the plurality of wrist units within the housing; a first gear mounted on a first output shaft of the first motor; a second gear mounted on a second output shaft of the second motor; a first base portion having a mounting hole for inserting the first output shaft and the first gear; and The second pedestal has a mounting hole for inserting the second output shaft and the second gear. The second motor is arranged in front of the first motor and arranged so that the axis of the second output shaft is offset laterally with respect to the axis of the first output shaft. A space is provided behind the first motor and behind the second motor, respectively. The first gear includes: a base portion engaged with the outer periphery of the first output shaft; and a gear portion extending forward of the first motor from the base portion. The second gear includes: a base portion fitted with the outer periphery of the second output shaft; and a gear portion extending forward of the second motor from the base portion. External support bearings are respectively installed on the outer periphery of the base of the first gear and the outer periphery of the base of the second gear, and the outer ring of each external support bearing is respectively engaged with the inner peripheral surface of the mounting hole of the first seat portion and the inner peripheral surface of the mounting hole of the second seat portion, so that the first output shaft and the first gear of the first motor, and the second output shaft and the second gear of the second motor are coaxially supported by each external support bearing, so that the first motor and the second motor are respectively positioned on the first seat portion and the second seat portion.

2. The industrial robot arm structure according to claim 1, wherein: The gear portion of the first gear has an outer diameter equal to that of the first output shaft, The gear portion of the second gear has an outer diameter equal to that of the second output shaft.

3. The industrial robot arm structure according to claim 1, wherein: The arm structure of this industrial robot also has: a first drive shaft that transmits the driving force of the first motor to one of the plurality of wrist elements and has a gear at a rear end portion; and a second drive shaft that transmits the driving force of the second motor to another wrist unit among the plurality of wrist units and has a gear at its rear end portion; The gear portion of the first gear protrudes forward from the outer support bearing and meshes with the gear of the first drive shaft. The gear portion of the second gear protrudes forward from the outer support bearing and meshes with the gear of the second drive shaft.

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