JP7707783B2 - Robot joint mechanism, robot, and method for assembling robot joint mechanism - Google Patents

Description

The present invention relates to a robot joint mechanism, a robot, and a method for assembling a robot joint mechanism.

Patent Document 1 describes a robot joint mechanism having a motor fixed to a fixed frame and a strain wave gear device whose input side is connected to the motor and whose output side is fixed to a movable frame. The strain wave gear device mainly has a wave generator, a flexspline, and a circular spline.

Such a robot joint mechanism is typically assembled by the steps of preparing a first unit in which a flexspline and a circular spline are fixed to a fixed frame and a movable frame, and a second unit in which a wave generator is fixed to the output shaft of a motor, and inserting the wave generator into the flexspline through a through hole formed in the fixed frame and fixing the motor to the fixed frame.

International Publication No. 2018/055752

As mentioned above, when assembling the robot joint mechanism, the wave generator needs to be inserted through a through hole formed in the fixed frame, so the diameter of the through hole must be larger than the major axis of the wave generator. Meanwhile, the fixed frame is formed with a screw hole for fixing the motor, but because the minimum diameter of the through hole is limited to be equal to or larger than the major axis of the wave generator, the screw hole cannot be formed any closer to the central axis of the robot joint mechanism.

For this reason, for example, when the motor is small compared to the wave generator, fixing the motor to the fixed frame becomes problematic. For example, one method could be to use an intermediate member between the motor and fixed frame to connect the two, but as the number of parts increases, tolerances will accumulate and assembly precision will decrease, and there is a risk that unintended excessive stress will be applied to the robot joint mechanism, shortening its lifespan. On the other hand, if part precision is increased and tolerances are reduced in order to improve assembly precision, there is a risk that the yield rate will decrease and manufacturing costs will rise.

The robot joint mechanism of the present invention includes a robot component including a through hole and a first hole and a second hole disposed around the through hole;
a motor that is screwed using the first hole and has an output shaft that is inserted through the through hole;
a wave gear device including a wave generator that is screwed using the second hole and connected to the output shaft,
The diameter of the through hole is smaller than the major axis of the wave generator.

The robot of the present invention includes a first member and
A second member; and
a robot joint mechanism that connects the first member and the second member and rotates the second member relative to the first member,
The robot joint mechanism includes:
a robot component including a through hole and a first hole and a second hole disposed around the through hole;
a motor that is screwed using the first hole and has an output shaft that is inserted through the through hole;
a wave gear device including a wave generator that is screwed using the second hole and connected to the output shaft,
The diameter of the through hole is smaller than the major axis of the wave generator.

A method for assembling a robot joint mechanism of the present invention includes the steps of: preparing a robot component having a through hole and a first hole and a second hole disposed around the through hole;
an output shaft insertion step of inserting an output shaft of a motor into the through hole from one side of the robot component;
a connecting step of connecting a wave generator, which is a part of a wave gear device and has a major diameter larger than a diameter of the through hole, to the output shaft from the other side of the robot component;
a placement step of placing a flexspline and a circular spline that are part of the strain wave gear device from the other side of the robot component;
a first fixing step of screwing the strain wave gear device to the robot component using the second hole from the one side of the robot component;
and a second fixing step of screwing the motor to the robot component using the first hole from the one side of the robot component.

FIG. 1 is a side view of a robot according to a first embodiment. 2 is a cross-sectional view of a robot joint mechanism of the robot of FIG. 1. FIG. 3 is a bottom view of a flange of the robot joint mechanism of FIG. 2 . FIG. FIG. 1 is a cross-sectional view of a conventional robot joint mechanism. 10 is a flowchart showing an assembly process of a robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. FIG. 11 is a bottom view for explaining a method of assembling the robot joint mechanism. FIG. 11 is a bottom view for explaining a method of assembling the robot joint mechanism. FIG. 11 is a bottom view for explaining a method of assembling the robot joint mechanism. FIG. 11 is a bottom view for explaining a method of assembling the robot joint mechanism. 10A to 10C are cross-sectional views for explaining a method of assembling the robot joint mechanism. FIG. 11 is a cross-sectional view of a robot joint mechanism according to a second embodiment.

The robot joint mechanism, robot, and method of assembling the robot joint mechanism of the present invention will be described in detail below based on the embodiments shown in the attached drawings. For ease of explanation, the upper side of Fig. 2 will be referred to as "up" and the lower side as "down". The up-down direction defined in Fig. 2 will also be used for other figures.

Figure 1 is a side view of a robot according to the first embodiment. Figure 2 is a cross-sectional view of a robot joint mechanism included in the robot of Figure 1. Figure 3 is a bottom view of a flange included in the robot joint mechanism of Figure 2. Figure 4 is a bottom view of a robot joint mechanism. Figure 5 is a cross-sectional view of a conventional robot joint mechanism. Figure 6 is a flowchart showing an assembly process of a robot joint mechanism. Figures 7 to 13 are cross-sectional views for explaining a method of assembling a robot joint mechanism. Figures 14 to 17 are bottom views for explaining a method of assembling a robot joint mechanism. Figure 18 is a cross-sectional view for explaining a method of assembling a robot joint mechanism. Note that Figure 2 is a cross-sectional view taken along line A-A in Figure 3.

The robot 1 shown in FIG. 1 is a SCARA robot (horizontal articulated robot) and is used for tasks such as holding, transporting, assembling, and inspecting workpieces such as electronic components. However, the configuration and uses of the robot 1 are not particularly limited.

The robot 1 has a base 2 fixed to the floor surface and an arm 3 connected to the base 2. The arm 3 also has a first arm 31 whose base end is connected to the base 2 and rotates around a first rotation axis J1 that is aligned vertically to the base 2, and a second arm 32 whose base end is connected to the tip of the first arm 31 and rotates around a second rotation axis J2 that is aligned vertically to the first arm 31. The first rotation axis J1 and the second rotation axis J2 are parallel to each other.

A working head 33 is provided at the tip of the second arm 32. The working head 33 has a spline nut 331 and a ball screw nut 332 that are coaxially arranged at the tip of the second arm 32, and a spline shaft 333 that is inserted through the spline nut 331 and the ball screw nut 332. The spline shaft 333 is rotatable around a third rotation axis J3 that is its central axis and aligned in the vertical direction relative to the second arm 32, and can be raised and lowered along the third rotation axis J3. The third rotation axis J3 is parallel to the first rotation axis J1 and the second rotation axis J2.

An end effector 34 is attached to the lower end of the spline shaft 333. The end effector 34 is detachable and is appropriately selected to suit the intended work. Examples of the end effector 34 include a hand that clamps and holds the workpiece by suction, and a work tool that performs a specified process on the workpiece.

The robot 1 also has a robot joint mechanism 51 that connects the base 2 and the first arm 31 and rotates the first arm 31 around the first rotation axis J1 relative to the base 2, and a robot joint mechanism 52 that connects the first arm 31 and the second arm 32 and rotates the second arm 32 around the second rotation axis J2 relative to the first arm 31. The robot 1 also has a drive unit 53 that rotates the spline nut 331 to rotate the spline shaft 333 around the third rotation axis J3, and a drive unit 54 that rotates the ball screw nut 332 to raise and lower the spline shaft 333 in a direction along the third rotation axis J3.

The robot 1 also has a robot control device 4 that is disposed within the base 2 and controls the driving of the robot joint mechanisms 51, 52 and the driving devices 53, 54 based on commands from a host computer (not shown). The robot control device 4 controls the robot joint mechanisms 51, 52 and the driving devices 53, 54 independently, allowing the robot 1 to perform a desired task.

The robot control device 4 is, for example, composed of a computer, and has a processor that processes information, a memory communicatively connected to the processor, and an external interface. In addition, the memory stores various programs that can be executed by the processor, and the processor can read and execute the various programs stored in the memory.

The above is a brief explanation of the overall configuration of the robot 1. Next, the robot joint mechanisms 51 and 52 equipped in the robot 1 will be described in detail. Note that the robot joint mechanisms 51 and 52 have the same configuration except for their different positions, so below, the robot joint mechanism 51 will be described in detail, and a description of the robot joint mechanism 52 will be omitted.

As shown in FIG. 2, the robot joint mechanism 51 has a flange 9, a motor 6 arranged on the underside of the flange 9, an encoder 8 arranged on the underside of the motor 6, and a strain wave gear device 7 arranged on the upper side of the flange 9. In the following, the rotation axis of the shaft 61 of the motor 6 is referred to as the central axis A1 of the robot joint mechanism 51. This central axis A1 constitutes the first rotation axis J1 of the robot 1.

<Flange 9>
The flange 9 is a robot component constituting a part of the robot 1, and is a member for supporting the motor 6 and the strain wave gearing 7, as well as for fixing the robot joint mechanism 51 to the base 2. That is, the motor 6 and the strain wave gearing 7 are fixed to the base 2 via the flange 9. However, the robot component is not limited to the flange 9, and may be, for example, the base 2. That is, in this embodiment, the motor 6 and the strain wave gearing 7 are fixed to the base 2 via the flange 9, but this is not limited thereto, and the motor 6 and the strain wave gearing 7 may be fixed directly to the base 2. This makes it possible to reduce the number of parts of the robot 1. Furthermore, since the number of parts is reduced, there is no need to fasten screws, and rigidity can be improved. Furthermore, the number of assembly steps can be reduced.

As shown in FIG. 2, a through hole 90 is formed in the center of the flange 9, and the shaft 61 of the motor 6 is inserted into this through hole 90 from below. The through hole 90 is also substantially circular and centered on the central axis A1. However, the shape of the through hole 90 is not particularly limited.

Moreover, the diameter R ₉₀ of the through hole 90 is smaller than the major axis R ₇₁ of the wave generator 71 of the strain wave gear device 7. That is, R ₉₀ <R _71. In other words, the through hole 90 overlaps with the wave generator 71 in a plan view from the direction along the central axis A1. As a result, even if the motor 6 is smaller in size than the strain wave gear device 7, as shown in the figure, it can be fixed to the flange 9 without using a relay member as in the conventional case. Therefore, the deterioration of the mounting accuracy of the motor 6 to the flange 9 is suppressed, and the deviation of the central axis A1 can be effectively suppressed. In addition, since no relay member is used, the tolerances of the flange 9 and the housing 63 can be set more leniently, and the decrease in the non-defective rate is suppressed, leading to a reduction in manufacturing costs. This effect will be described in detail later.

As shown in FIG. 2, the flange 9 is formed with a first hole 91 for fixing the motor 6 to the underside of the flange 9, a second hole 92 for fixing the strain wave gear device 7 to the upper surface of the flange 9, and a third hole 93 for fixing the flange 9 to the base 2 as the first member. Of these, the first hole 91 is a threaded hole (female thread) into which the first bolt B1 is screwed, and the second hole 92 and the third hole 93 are through holes that penetrate the upper and lower surfaces and through which the second bolt B2 and the third bolt B3 are inserted.

As shown in FIG. 3, four first holes 91 are arranged at approximately equal intervals along a virtual circle C1 of radius r1 centered on the central axis A1 so as to surround the periphery of the through hole 90. Sixteen second holes 92 are arranged at approximately equal intervals along a virtual circle C2 of radius r2 centered on the central axis A1 so as to surround the periphery of the through hole 90. Six third holes 93 are arranged at approximately equal intervals along a virtual circle C3 of radius r3 centered on the central axis A1 so as to surround the periphery of the through hole 90.

In this way, by arranging multiple first holes 91 along the imaginary circle C1, the motor 6 can be fixed firmly to the flange 9 in a balanced manner. Similarly, by arranging multiple second holes 92 along the imaginary circle C2, the strain wave gear device 7 can be fixed firmly to the flange 9 in a balanced manner. This improves the mechanical strength of the robot joint mechanism 51 and suppresses a decrease in the life span of the robot joint mechanism 51. Furthermore, by arranging multiple third holes 93 along the imaginary circle C3, the robot joint mechanism 51 can be fixed firmly to the base 2 in a balanced manner, thereby improving the mechanical strength of the robot 1.

The three concentrically arranged virtual circles C1, C2, and C3 have a relationship of radius r1 < radius r2 < radius r3. In other words, the second hole 92 is located closer to the central axis A1 than the third hole 93, and the first hole 91 is located closer to the central axis A1 than the second hole 92. In this way, by locating the first hole 91 closer to the central axis A1 than the second hole 92, the motor 6, which is smaller in size than the strain wave gear device 7, can be more reliably fixed to the flange 9 without the need for an intermediate member.

<Motor 6>
As shown in Fig. 2, the motor 6 is disposed below the flange 9. The motor 6 is, for example, an AC servo motor. However, the motor 6 is not particularly limited, and for example, a DC servo motor, a stepping motor, or the like may be used. Such a motor 6 has a shaft 61 that is an output shaft, a stator (not shown) that rotates the shaft 61, and a housing 63 that accommodates these.

The upper end of the housing 63 is formed with four insertion holes 64 for screwing the motor 6 to the flange 9. Each insertion hole 64 overlaps with a first hole 91, and a first bolt B1 is inserted from below into each insertion hole 64, and the first bolt B1 is screwed into the first hole 91 of the flange 9. In this way, the motor 6 is fixed to the flange 9. However, the number of first holes 91 and the corresponding insertion holes 64 is not particularly limited. Furthermore, the number of first holes 91 and the number of insertion holes 64 do not have to be the same.

When the motor 6 is fixed to the flange 9, as shown in FIG. 4, at least one, and in the illustrated configuration, eight, second holes 92 overlap with the motor 6. Even with this configuration, the robot joint mechanism 51 can be assembled using the assembly method described below. This eliminates the need to consider overlap between the second holes 92 and the motor 6, increasing the design freedom of the robot joint mechanism 51. As a result, the robot joint mechanism 51 can be adapted to motors 6 of various sizes, increasing its versatility.

As shown in FIG. 2, the shaft 61 is supported by the housing 63 so as to be rotatable about the central axis A1. The shaft 61 is connected at its upper end to the strain wave gear device 7 and at its lower end to the encoder 8. This allows the rotation of the shaft 61 to be transmitted to the strain wave gear device 7 and the encoder 8, respectively.

The housing 63 also has a protrusion on the upper side, which engages with the side wall of the through hole 90 in the flange 9. An oil seal 67 is disposed between the housing 63 and the flange 9, and an oil seal 65 is disposed in the gap between the shaft 61 and the housing 63. These oil seals 65 and 67 prevent oil leakage from the strain wave gear device 7.

<Encoder 8>
2 , the encoder 8 is disposed alongside the motor 6 along the first rotation axis J1, and is located below the motor 6. The encoder 8 has an optical scale 81 fixed to the shaft 61, and an optical sensor 82 that detects the rotation state of the optical scale 81.

The optical scale 81 rotates together with the shaft 61 around the first rotation axis J1. In addition, a detection pattern (not shown) that can detect the rotation angle of the optical scale 81 is formed on the underside of the optical scale 81. Meanwhile, the optical sensor 82 has a light-emitting element that emits light toward the detection pattern on the optical scale 81, and a light-receiving element that receives light reflected by the detection pattern. In an encoder 8 configured in this way, the waveform of the output signal from the light-receiving element changes as the optical scale 81 rotates around the first rotation axis J1. Therefore, the rotation angle of the shaft 61 can be detected based on this output signal.

<Harmonic gear device 7>
2, the strain wave gear device 7 is disposed on the upper surface side of the flange 9. The strain wave gear device 7 is disposed alongside the motor 6 along the first rotation axis J1 and is located above the motor 6. Such a strain wave gear device 7 reduces the rotation of the shaft 61 at a high reduction ratio and outputs the reduced rotation, generating a high torque proportional to the reduction ratio.

The strain wave gear device 7 has a wave generator 71, a flex spline 73, a circular spline 76, and a cover member 79. In the strain wave gear device 7, the wave generator 71 is the input side to which the power of the motor 6 is input, and the circular spline 76 is the output side that reduces the power of the motor 6 and outputs it.

The circular spline 76 is an annular internal gear made of a rigid body that does not substantially flex. The circular spline 76 has an inner main bearing 761 and an outer main bearing 762 located outside the inner main bearing 761. The inner main bearing 761 and the outer main bearing 762 are connected by a bearing 763, and the outer main bearing 762 and the inner main bearing 761 can rotate relative to each other.

The inner periphery of the inner main bearing 761 is formed with internal teeth 761b that mesh with the flexspline 73. The inner main bearing 761 is formed with 16 screw holes 761a on its underside. Each screw hole 761a overlaps with a second hole 92, and a second bolt B2 is inserted into each second hole 92 from below, and the second bolt B2 is screwed into the screw hole 761a. This fixes the strain wave gear device 7 to the flange 9. However, the number of second holes 92 and the corresponding screw holes 761a is not particularly limited. The number of second holes 92 and the screw holes 761a does not have to be the same.

As described above, the motor 6 and the strain wave gear device 7 are fixed to the flange 9 by the first bolt B1 and the second bolt B2, both of which are inserted from below. By inserting the first and second bolts B1 and B2 from the same side in this way, assembly and disassembly of the robot joint mechanism 51 becomes easy. However, this is not limited to this, and the first and second bolts B1 and B2 may be inserted from different sides.

On the other hand, the outer main bearing 762 has an insertion hole 762a that penetrates the upper and lower surfaces. A fourth bolt B4 is inserted from below into each insertion hole 762a, and the fourth bolt B4 is screwed into the cover member 79. This fixes the outer main bearing 762 and the cover member 79. Furthermore, the cover member 79 is fixed to the first arm 31, which serves as the second member, by a fifth bolt B5. However, the method of fixing the outer main bearing 762 to the first arm 31 is not particularly limited. For example, the cover member 79 may be omitted and the outer main bearing 762 may be fixed directly to the first arm 31.

The flexspline 73 is disposed inside the circular spline 76. The flexspline 73 has a flexible cylindrical portion 731 that can bend and deform along the outer periphery of the wave generator 71, and an annular flange portion 732 connected to the upper end of the cylindrical portion 731.

External teeth 731a that mesh with the internal teeth 761b of the circular spline 76 are formed on the outer periphery of the cylindrical portion 731. The number of teeth of the external teeth 731a is set to be less than the number of teeth of the internal teeth 761b. The flange portion 732 is fixed to the cover member 79 together with the outer main bearing 762 by the fourth bolt B4.

The wave generator 71 also includes a wave generating unit 711 that is fixed to the shaft 61 and rotates in conjunction with the rotation of the shaft 61, and a bearing 712 that is fitted between the wave generating unit 711 and the flexspline 73. The wave generating unit 711 has an outer periphery that is elliptical or oblong in plan view from the direction along the central axis A1. In other words, the wave generator 71 has a shape that has a longitudinal direction and a lateral direction that is perpendicular to the longitudinal direction. The wave generator 71 contacts the inner periphery of the cylindrical portion 731 of the flexspline 73, and bends the cylindrical portion 731 into an elliptical or oblong shape to partially mesh the external teeth 731a of the cylindrical portion 731 with the internal teeth 761b of the circular spline 76. As a result, the teeth of the circular spline 76 mesh with those of the circular spline 76 at the major axis portion, and the teeth are completely separated at the minor axis portion. The length of the major axis of the wave generator 71 is the major axis R ₇₁ , and as described above, the major axis R ₇₁ is larger than the diameter R ₉₀ of the through hole 90 .

When the driving force from the motor 6 is input to the wave generator 71, the flexspline 73 and the circular spline 76 rotate relatively around the central axis A1 due to the difference in the number of teeth, while their meshing positions move sequentially in the circumferential direction. In this embodiment, the flexspline 73 and the outer main bearing 762 are fixed to the first arm 31 via the cover member 79, and the inner main bearing 761 is fixed to the base 2 via the flange 9, so that the first arm 31 rotates around the first rotation axis J1 with respect to the base 2.

With this type of wave gear device 7, the rotation input from the motor 6 to the wave generator 71 is decelerated and output from the outer main bearing of the circular spline 76, and a torque proportional to the reduction ratio can be obtained on the output side.

The configuration of the robot joint mechanism 51 has been described above. As described above, the robot joint mechanism 51 has the relationship R ₉₀ <R _71. This relationship creates a space inside the second hole 92 of the flange 9, and the first hole 91 can be formed in this space. In other words, the first hole 91 for fixing the motor 6 can be disposed inside the second hole 92 for fixing the strain wave gear device 7. Therefore, even if the motor 6 has a smaller size (diameter) than the strain wave gear device 7, it can be fixed to the flange 9 without an intermediate member. For reference, FIG. 5 illustrates a robot joint mechanism 51′ in which R ₉₀ >R ₇₁ and the motor 6 is fixed to the flange 9 via an intermediate member 10.

This improves the accuracy of mounting the motor 6 to the flange 9, and effectively prevents misalignment between the rotation axis of the shaft 61 and the rotation axis of the strain wave gear device 7. This stabilizes the drive of the robot joint mechanism 51 and makes it difficult for unintended excessive stress to be applied to the robot joint mechanism 51. As a result, it is possible to effectively prevent a decrease in the lifespan of the robot joint mechanism 51. On the other hand, since no intermediate members are used, the number of parts is reduced and the tolerances of the flange 9 and housing 63 can be set more leniently, which prevents a decrease in the yield rate and leads to lower manufacturing costs.

Next, a method for assembling the robot joint mechanism 51 will be described. As shown in FIG. 6, the method for assembling the robot joint mechanism 51 includes a preparation step S1 for preparing the flange 9, an insertion step S2 for inserting the shaft 61 of the motor 6 into the through hole 90 of the flange 9, a temporary fixing step S3 for temporarily fixing the motor 6 to the flange 9, a connection step S4 for connecting the wave generator 71 to the shaft 61, an arrangement step S5 for arranging the flex spline 73 and the circular spline 76, a release step S6 for releasing the temporary fixing of the motor 6, a first fixing step S7 for fixing the strain wave gear device 7 to the flange 9, and a second fixing step S8 for fixing the motor 6 to the flange 9. Each of these steps S1 to S8 will be described in order below.

<Preparation Step S1>
First, a flange 9 is prepared as shown in Fig. 7. The flange 9 has a through hole 90, a first hole 91, a second hole 92, and a third hole 93 formed therein.

<<Insertion step S2>>
8, the motor 6 is prepared, and the shaft 61 of the motor 6 is inserted from below into the through-hole 90 of the flange 9. This causes the shaft 61 to protrude upward from the through-hole 90.

<Temporary fastening step S3>
9, the motor 6 is temporarily fixed to the flange 9 using a first bolt B1. In this step, the first bolt B1 is fastened with a fastening force that does not cause the motor 6 to wobble against the flange 9. By eliminating any wobble between the motor 6 and the flange 9, the subsequent connecting step S4 and arranging step S5 can be performed smoothly and accurately.

<Connection step S4>
10 , the wave generator 71 is connected to and fixed on the shaft 61 from the upper surface side of the flange 9. In this way, by inserting the shaft 61 into the through hole 90 and then connecting the wave generator 71 to the shaft 61 from the opposite side, the robot joint mechanism 51 can be easily assembled even if the through hole 90 has a smaller diameter than the major axis R ₇₁ of the wave generator 71.

<<Placement Step S5>>
Next, as shown in FIG. 11, the flexspline 73 and the circular spline 76 are arranged from the upper surface side of the flange 9, and the strain wave gear device 7 is assembled.

<<Release step S6>>
12, the first bolts B1 that secure the motor 6 to the flange 9 are removed, and the temporary fastening of the motor 6 is released. Even if the temporary fastening is released, the shaft 61 is supported by the strain wave gear device 7, so that the motor 6 is prevented from coming off. In addition, with the temporary fastening released, the housing 63 is free to rotate about the central axis A1. This allows the first fixing step S7 to be carried out appropriately.

<<First fixing step S7>>
13 , the second bolts B2 are inserted through the second holes 92 and screwed into the threaded holes 761 a of the inner main bearing 761. In this way, the strain wave gear device 7 is fixed to the flange 9.

To explain in more detail, first, the housing 63 is rotated around the central axis A1 relative to the flange 9 to the state shown in FIG. 14. In FIG. 14, eight second holes 92 overlap with the housing 63, and the remaining eight housings 63 do not overlap with the housing 63. Next, as shown in FIG. 15, the second bolt B2 is inserted into each second hole 92 that does not overlap with the housing 63, and screwed into the threaded hole 761a of the inner main bearing 761.

Next, as shown in FIG. 16, the housing 63 is rotated 45° around the central axis A1 relative to the flange 9. In this state, the second holes 92 that overlapped with the housing 63 in the state of FIG. 14 do not overlap with the housing 63, and conversely, the second holes 92 that did not overlap with the housing 63 in the state of FIG. 14 overlap with the housing 63. Next, as shown in FIG. 17, the second bolts B2 are inserted through each second hole 92 that does not overlap with the housing 63, and screwed into the threaded hole 761a of the inner main bearing 761.

As a result, the second bolts B2 are inserted through all the second holes 92, and the strain wave gear device 7 is fixed to the flange 9. In other words, the strain wave gear device 7 is screwed to the flange 9 using the second holes 92 that overlap the motor 6. This allows the strain wave gear device 7 to be firmly fixed to the flange 9 in a balanced manner around the through hole 90. This improves the mechanical strength of the robot joint mechanism 51, and suppresses a decrease in the lifespan of the robot joint mechanism 51. In addition, according to this method, it is sufficient to rotate the housing 63 so that all the second holes 92 do not overlap the housing 63 in sequence, so there is less need to consider the overlap between the second holes 92 and the motor 6, and the design freedom of the robot joint mechanism 51 is increased. As a result, the robot joint mechanism 51 is capable of being used with motors 6 of various sizes, and its versatility is improved.

<<Second fixing step S8>>
Next, as shown in FIG. 18 , first bolts B1 are inserted from below through each insertion hole 64 of the housing 63 and then screwed into the first holes 91 of the flange 9 to secure the motor 6 to the flange 9 .

The assembly of the robot joint mechanism 51 is thus completed. With this assembly method, even if the motor 6 is smaller in size (diameter) than the strain wave gear device 7, it can be fixed to the flange 9 without using an intermediate member. This improves the accuracy of mounting the motor 6 to the flange 9, and effectively suppresses misalignment between the rotation axis of the shaft 61 and the rotation axis of the strain wave gear device 7. This stabilizes the drive of the robot joint mechanism 51 and makes it difficult for unintended excessive stress to be applied to the robot joint mechanism 51. As a result, it is possible to effectively suppress a decrease in the life of the robot joint mechanism 51. On the other hand, since no intermediate member is used, the number of parts is reduced, and the tolerances of the flange 9 and the housing 63 can be set more leniently, which suppresses a decrease in the yield rate and leads to a decrease in manufacturing costs.

The order of steps S1 to S8 in the above assembly method is not limited to this, and other orders may be used. For example, the order of steps S5 and after may be changed, and part of the first fixing step S7 may be performed before the release step S6. That is, the second bolts B2 may be inserted into the eight second holes 92 that do not overlap with the housing 63, and then screwed into the threaded holes 761a of the inner main bearing 761. By doing so, the flange 9 and the strain wave gear device 7 can be stabilized and assembled.

The above has described the robot 1, the robot joint mechanism 51, and the method of assembling the robot joint mechanism 52. As described above, the robot joint mechanism 51 has the flange 9 as a robot component having the through hole 90 and the first hole 91 and the second hole 92 arranged around the through hole 90, the motor 6 that is screwed using the first hole 91 and has a shaft 61 that is an output shaft inserted into the through hole 90, and the strain wave gear device 7 that is screwed using the second hole 92 and has a wave generator 71 connected to the shaft 61, and the diameter R ₉₀ of the through hole 90 is smaller than the major axis R ₇₁ of the wave generator 71.

In this way, by having the relationship R ₉₀ <R ₇₁ , a space is generated inside the second hole 92 of the flange 9, and the first hole 91 can be formed in this space. In other words, the first hole 91 for fixing the motor 6 can be arranged inside the second hole 92 for fixing the strain wave gear device 7. Therefore, even if the motor 6 has a size (diameter) smaller than the strain wave gear device 7, it can be fixed to the flange 9 without the intermediate member 10 as shown in FIG. 5 . This improves the accuracy of mounting the motor 6 to the flange 9, and effectively suppresses the misalignment between the rotation axis of the shaft 61 and the rotation axis of the strain wave gear device 7. This stabilizes the drive of the robot joint mechanism 51, and makes it difficult for unintended excessive stress to be applied to the robot joint mechanism 51. As a result, the shortening of the life of the robot joint mechanism 51 can be effectively suppressed. On the other hand, the number of parts is reduced by not using the intermediate member 10, and the tolerances of the flange 9 and the housing 63 can be set more leniently, which suppresses the decrease in the yield rate and leads to a reduction in manufacturing costs.

As described above, the motor 6 and the strain wave gear device 7 are screwed to the flange 9 from the same side. This makes it easy to assemble and disassemble the robot joint mechanism 51.

As described above, the second holes 92 are arranged in multiple locations around the through hole 90. This allows the wave gear device 7 to be firmly fixed to the flange 9 in a balanced manner around the through hole 90. This improves the mechanical strength of the robot joint mechanism 51 and suppresses a decrease in the life span of the robot joint mechanism 51.

As described above, in plan view from the direction along the central axis A1 of the shaft 61, at least one of the second holes 92 overlaps with the motor 6, and the harmonic gear device 7 is screwed to the flange 9 using the second hole 92 that overlaps with the motor 6. This allows the harmonic gear device 7 to be firmly fixed to the flange 9 in a balanced manner around the through hole 90. This improves the mechanical strength of the robot joint mechanism 51, and suppresses a decrease in the lifespan of the robot joint mechanism 51.

As mentioned above, the first hole 91 is located closer to the through hole than the second hole 92. This allows the motor 6, which is smaller in size than the harmonic gear device 7, to be more reliably fixed to the flange 9 without using the relay member 10.

As described above, the robot 1 includes the base 2 as a first member, the first arm 31 as a second member, and the robot joint mechanism 51 that connects the base 2 and the first arm 31 and rotates the first arm 31 relative to the base 2. The robot joint mechanism 51 includes the flange 9 as a robot component that includes a through hole 90 and a first hole 91 and a second hole 92 that are arranged around the through hole 90, the motor 6 that is screwed using the first hole 91 and has a shaft 61 that is an output shaft inserted into the through hole 90, and the strain wave gear device 7 that is screwed using the second hole 92 and includes a wave generator 71 that is connected to the shaft 61, and the diameter R ₉₀ of the through hole 90 is smaller than the major axis R ₇₁ of the wave generator 71. This allows the robot 1 to enjoy the effects of the robot joint mechanism 51 described above and has excellent reliability.

As mentioned above, the robot component may be the base 2. In other words, the number of parts can be reduced by fixing the motor 6 and strain wave gear device 7 to the base 2 without using the flange 9. Furthermore, because the number of parts is reduced, there is no need for screws, which improves rigidity. It also reduces the number of assembly steps.

As described above, the assembly method for the robot joint mechanism 51 includes a preparation step S1 of preparing the flange 9 as a robot component having the through hole 90 and the first hole and the second hole arranged around the through hole 90; an insertion step S2 of inserting the shaft 61, which is the output shaft of the motor 6, into the through hole 90 from one side, i.e., the lower side, of the flange 9; a connection step S4 of connecting the wave generator 71, which is a part of the strain wave gearing 7 and has a major diameter R ₇₁ larger than the diameter R ₉₀ of the through hole 90, to the shaft 61 from the other side, i.e., the upper side, of the flange 9; an arrangement step S5 of arranging the flex spline 73 and the circular spline 76, which are parts of the strain wave gearing 7, from the upper side of the flange 9; a first fixing step S7 of screwing the strain wave gearing 7 to the flange 9 using the second hole 92 from the lower side of the flange 9; and a second fixing step S8 of screwing the motor 6 to the flange 9 using the first hole 91 from the underside of the flange 9.

In this way, by having the relationship R ₉₀ <R ₇₁ , a space is generated inside the second hole 92 of the flange 9, and the first hole 91 can be formed in this space. In other words, the first hole 91 for fixing the motor 6 can be arranged inside the second hole 92 for fixing the strain wave gear device 7. Therefore, even if the motor 6 has a size (diameter) smaller than the strain wave gear device 7, it can be fixed to the flange 9 without the intermediate member 10 as shown in FIG. 5 . This improves the accuracy of mounting the motor 6 to the flange 9, and effectively suppresses the misalignment between the rotation axis of the shaft 61 and the rotation axis of the strain wave gear device 7. This stabilizes the drive of the robot joint mechanism 51, and makes it difficult for unintended excessive stress to be applied to the robot joint mechanism 51. As a result, the shortening of the life of the robot joint mechanism 51 can be effectively suppressed. On the other hand, the number of parts is reduced by not using the intermediate member 10, and the tolerances of the flange 9 and the housing 63 can be set more leniently, which suppresses the decrease in the yield rate and leads to a reduction in manufacturing costs.

As described above, the assembly method of the robot joint mechanism 51 includes a temporary fixing step S3, which is performed between the insertion step S2 and the connection step S4, in which the motor 6 is temporarily fixed to the flange 9, and a release step S6, which is performed between the placement step S5 and the first fixing step S7, in which the temporary fixing of the motor 6 is released. This allows each step after the temporary fixing step S3 to be performed optimally.

As described above, multiple second holes 92 are formed around the through hole 90, and when the arrangement step S5 is completed, at least one second hole 92 overlaps with the motor 6 in a plan view from the direction along the central axis A1 of the shaft 61. In the first fixing step S7, the motor 6 is rotated around the central axis A1 to eliminate the overlap with the motor 6, and the strain wave gear device 7 is screwed to the flange 9 using all of the second holes 92. This allows the strain wave gear device 7 to be firmly fixed to the flange 9 in a balanced manner around the through hole 90. This improves the mechanical strength of the robot joint mechanism 51, and suppresses a decrease in the lifespan of the robot joint mechanism 51.

Second Embodiment
FIG. 19 is a cross-sectional view of a robot joint mechanism according to the second embodiment.

The robot joint mechanism 51 of this embodiment is similar to the robot joint mechanism 51 of the first embodiment described above, except that the oil seal 65 is disposed differently. Therefore, in the following explanation, the differences between this embodiment and the first embodiment described above will be mainly described, and explanations of similar points will be omitted. Also, in each figure of this embodiment, the same reference numerals are used for configurations similar to those of the previously described embodiment.

19 , in the robot joint mechanism 51 of this embodiment, the diameter R ₉₀ of the through hole 90 is smaller than that in the first embodiment described above, and the inner surface thereof is close to the outer circumferential surface of the shaft 61. In the first embodiment described above, the oil seal 65 for suppressing oil leakage from the wave gear device 7 is disposed in the gap between the housing 63 and the shaft 61, but in this embodiment, it is disposed between the inner circumferential surface of the through hole 90 and the outer circumferential surface of the shaft 61. With this configuration, for example, the oil seal 67 can be omitted, making the configuration of the robot joint mechanism 51 simpler. In addition, the number of parts can be reduced, leading to a reduction in manufacturing costs.

In this way, the robot joint mechanism 51 of this embodiment has an oil seal 65 disposed between the inner circumferential surface of the through hole 90 and the outer circumferential surface of the shaft 61. This makes the configuration of the robot joint mechanism 51 simpler. In addition, the number of parts is reduced, which allows for reduced manufacturing costs.

The second embodiment described above can achieve the same effects as the first embodiment described above.

The robot joint mechanism, robot, and method of assembling the robot joint mechanism of the present invention have been described above based on the illustrated embodiment, but the present invention is not limited to this, and the configuration of each part can be replaced with any configuration having a similar function. In addition, any other configuration may be added to the present invention.

Reference Signs List 1...robot, 10...relay member, 2...base, 3...arm, 31...first arm, 32...second arm, 33...work head, 331...spline nut, 332...ball screw nut, 333...spline shaft, 34...end effector, 4...robot control device, 51...robot joint mechanism, 51'...robot joint mechanism, 52...robot joint mechanism, 53...driving device, 54...driving device, 6...motor, 61...shaft, 63...housing, 64...through hole, 65...oil seal, 67...oil seal, 7...wave gear device, 71...wave generator, 711...wave generating section, 712...bearing, 73...flexible plastic In, 731...cylindrical portion, 731a...external teeth, 732...flange portion, 76...circular spline, 761...inner main bearing, 761a...screw hole, 761b...inner teeth, 762...outer main bearing, 762a...insertion hole, 763...bearing, 79...cover member, 8...encoder, 81...optical scale, 82...optical sensor, 9...flange, 90...through hole, 91...first hole, 92...second hole, 93...third hole, A1...center axis, B1...first bolt, B2...second bolt, B3...third bolt, B4...fourth bolt, B5...fifth bolt, C1...virtual circle, C2...virtual circle, C3...virtual circle, J1...first rotating shaft, J2...second rotating shaft, J3...third rotating shaft, R ₇₁ ... major axis, R ₉₀ ... diameter, r1 ... radius, r2 ... radius, r3 ... radius, S1 ... preparation step, S2 ... insertion step, S3 ... temporary fixing step, S4 ... connection step, S5 ... arrangement step, S6 ... release step, S7 ... first fixing step, S8 ... second fixing step

Claims (10)

a robot component including a through hole and a first hole and a second hole disposed around the through hole;
a motor including a housing and an output shaft rotatably supported by the housing, the output shaft being inserted through the through hole;
a wave generator connected to the output shaft and having an elliptical outer periphery in a plan view along the output shaft; a flexspline that flexibly deforms along the outer periphery of the wave generator and has external teeth; and a circular spline that has internal teeth that mesh with the external teeth and rotates relatively to the flexspline ,
The circular spline is screwed to the robot component using the second hole;
the motor is screwed to the robot component using the first hole;
The diameter of the through hole is smaller than the major axis of the wave generator,
The housing engages with a side wall of the through hole,
A robot joint mechanism, characterized in that the circular spline engages with a stepped portion provided on the robot component . The robot joint mechanism of claim 1, wherein the motor and the strain wave gear device are screwed to the robot component from the same side. The robot joint mechanism according to claim 1 or 2, wherein the second holes are arranged in a plurality along the periphery of the through hole. When viewed from a plane along a central axis of the output shaft,
At least one of the second holes overlaps the motor;
4. The robot joint mechanism according to claim 3, wherein the strain wave gear device is screwed to the robot component using the second hole overlapping with the motor. The robot joint mechanism according to any one of claims 1 to 4, further comprising an oil seal disposed between the inner circumferential surface of the through hole and the outer circumferential surface of the output shaft. The robot joint mechanism according to any one of claims 1 to 5, wherein the first hole is located closer to the through hole than the second hole. A first member;
A second member; and
a robot joint mechanism that connects the first member and the second member and rotates the second member relative to the first member,
The robot joint mechanism includes:
a robot component including a through hole and a first hole and a second hole disposed around the through hole;
a motor including a housing and an output shaft rotatably supported by the housing, the output shaft being inserted through the through hole;
a wave generator connected to the output shaft and having an elliptical outer periphery in a plan view along the output shaft; a flexspline that flexibly deforms along the outer periphery of the wave generator and has external teeth; and a circular spline that has internal teeth that mesh with the external teeth and rotates relatively to the flexspline ,
The circular spline is screwed to the robot component using the second hole;
the motor is screwed to the robot component using the first hole;
The diameter of the through hole is smaller than the major axis of the wave generator,
The housing engages with a side wall of the through hole,
A robot characterized in that the circular spline engages with a step portion provided on the robot component . The robot according to claim 7, wherein the robot component is the first member. A preparation step of preparing a robot component having a through hole and a first hole and a second hole disposed around the through hole;
an insertion step of inserting an output shaft of a motor into the through hole from one side of the robot component;
a temporary fixing step of temporarily fixing the motor to the robot component;
a connecting step of connecting a wave generator, which is a part of a wave gear device and has a major diameter larger than a diameter of the through hole, to the output shaft from the other side of the robot component;
a placement step of placing a flexspline and a circular spline that are part of the strain wave gear device from the other side of the robot component;
a release step of releasing the temporary fastening of the motor;
a first fixing step of screwing the strain wave gear device to the robot component using the second hole from the one side of the robot component;
a second fixing step of screwing the motor to the robot component using the first hole from the one side of the robot component. A preparation step of preparing a robot component having a through hole and a first hole and a second hole disposed around the through hole;
an insertion step of inserting an output shaft of a motor into the through hole from one side of the robot component;
a connecting step of connecting a wave generator, which is a part of a wave gear device and has a major diameter larger than a diameter of the through hole, to the output shaft from the other side of the robot component;
a placement step of placing a flexspline and a circular spline that are part of the strain wave gear device from the other side of the robot component;
a first fixing step of screwing the strain wave gear device to the robot component using the second hole from the one side of the robot component;
a second fixing step of screwing the motor to the robot component using the first hole from the one side of the robot component ;
The second holes are formed in a plurality of portions along a periphery of the through hole,
In a state where the arranging step is completed, at least one of the second holes overlaps with the motor in a plan view from a direction along a central axis of the output shaft,
a first fixing step of rotating the motor around the central axis to eliminate overlap with the motor, and screwing the strain wave gear device to the robot component using all of the second holes .