JP2019078292A - Robot and gear box - Google Patents

Abstract

To provide a robot and a gear box capable of elongating the life of the gear box.SOLUTION: A robot comprises: a first component; a second component provided rotatably with respect to the first component; and a gear box for transferring the drive power from one side of the first component and the second component to the other side. The gear box includes: an internal gear; a flexible external gear partly meshed with the internal gear; and a wave generator that is in contact with the inner peripheral surface of the external gear for moving the engagement position of the internal gear and the external gear in the circumferential direction. One of the internal gear, the external gear and the wave generator is to connected to the first component; and the other one is to connected to the second component. The component material of the external gear contains nickel chrome molybdenum steel; and the component material of the internal gear contains chrome molybdenum steel.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a robot and a gear device.

  In a robot including a robot arm configured to include at least one arm, for example, a joint of the robot arm is driven by a motor, but in general, the rotation of driving force from the motor is reduced by a reduction gear (gear unit) It is done.

  As such a reduction gear, for example, a wave gear device as described in Patent Document 1 is known. The wave gear device described in Patent Document 1 includes a toroidal rigid internal gear, a cup-shaped flexible external gear disposed on the inside, and an internal gear on the external gear. It consists of a wave generator with an elliptical contour. Here, the internal gear is formed of high strength aluminum alloy or copper alloy, and the external gear is formed of structural steel or stainless steel.

Unexamined-Japanese-Patent No. 2002-349681

  However, in the wave gear device described in Patent Document 1, since the constituent material of the internal gear is a high strength aluminum alloy or copper alloy and the constituent material of the external gear is a structural steel or stainless steel, There is a problem that the mechanical characteristics of the tooth gear and the external gear are not sufficient, and the life of these gears is short.

  An object of the present invention is to provide a robot and a gear device capable of prolonging the life of the gear device.

  The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following applications or embodiments.

The robot according to this application example includes a first member;
A second member rotatably provided relative to the first member;
And a gear device for transmitting a driving force from one side to the other side of the first member and the second member,
The gear unit is
Internal gear,
A flexible external gear partially meshing with the internal gear;
And a wave generator which contacts the inner peripheral surface of the external gear and moves the meshing position of the internal gear and the external gear in the circumferential direction.
One of the internal gear, the external gear and the wave generator is connected to the first member and the other is connected to the second member.
The constituent material of the external gear includes nickel chromium molybdenum steel,
The constituent material of the internal gear includes chromium molybdenum steel.

  According to such a robot, since the constituent material of the external gear includes nickel chromium molybdenum steel, the mechanical characteristics (particularly the fatigue strength) of the external gear can be enhanced and the life of the external gear can be extended. . On the other hand, since the material of the internal gear includes chromium molybdenum steel, the mechanical characteristics of the internal gear are enhanced while the mechanical characteristics of the external gear and the internal gear are balanced, and the life of the internal gear is improved. In addition to lengthening, it is possible to reduce damage to the external gear due to the influence of the worn internal gear and to prolong the life of the external gear. Thus, by prolonging the life of both the external gear and the internal gear, it is possible to prolong the life of the gear device.

  In the robot of this application example, the Vickers hardness of the surface of the external gear is preferably equal to or less than the Vickers hardness of the surface of the internal gear.

  This can reduce the wear of the internal teeth of the internal gear, and as a result, can extend the life of the gear device.

  In the robot of this application example, the Vickers hardness of the surface of the external gear is preferably in the range of 400 or more and 520 or less.

  Thereby, the mechanical strength and toughness of the external gear can be balanced, and the life of the external gear can be suitably extended.

  In the robot according to this application example, it is preferable that the residual stress of the external gear be in a range of -950 MPa or more and -450 MPa or less.

  Thereby, the fatigue strength of the external teeth can be improved, and an external gear that can withstand high load stress can be realized. As a result, the durability of the gear device can be improved.

  In the robot of this application example, the surface roughness Ra of the external teeth of the external gear is preferably in the range of 0.2 μm or more and 1.6 μm or less.

  This makes it possible to easily hold the grease (lubricant) on the external teeth of the external gear while reducing the wear of the internal gear, so that the life of the external gear and the internal gear can be suitably extended. .

  In the robot of this application example, it is preferable that the surface roughness Ra of the external teeth of the external gear be greater than the surface roughness Ra of the internal teeth of the internal gear.

  This makes it easy to hold the grease (lubricant) on the external teeth of the external gear, and reduces the contact resistance between the external gear and the internal gear, which makes the life of the external gear and the internal gear suitable. It can be long.

  In the robot of this application example, the surface roughness Ra of the internal teeth of the internal gear is preferably in the range of 0.1 μm to 0.8 μm.

  Thereby, the contact resistance between the external gear and the internal gear can be reduced while reducing the manufacturing cost of the internal gear.

  In the robot of this application example, it is preferable that the average crystal grain size of the constituent material of the external gear be smaller than the average crystal grain size of the constituent material of the internal gear.

  Thus, the crystal grain size of the constituent material of the external gear can be reduced, and the lubricant can be easily held on the external teeth. Therefore, the lubricant can be retained on the external teeth against the centrifugal force caused by the rotation of the external teeth. On the other hand, the crystal grain size of the constituent material of the internal gear can be increased to facilitate the flow of the lubricant along the internal teeth. Therefore, the lubricant can be prevented from being uneven or solidified on the inner teeth. Then, the two effects of the effect of retaining the lubricant on the external teeth and the effect of reducing the deviation and solidification of the lubricant on the internal teeth, as described above, are synergistically combined to form the lubricant. Can effectively improve the lubrication life. As a result, the lives of the external gear and the internal gear can be suitably extended.

  In the robot of this application example, the constituent material of the external gear is in the range of 0.01% by mass or more and 0.5% by mass or less of at least one element among the group 4 element and the group 5 element It is preferable that

  Thereby, even if heat treatment is performed in the manufacturing process of the external gear, the growth of the crystal grains of the constituent material of the external gear can be suppressed and the crystal grain size can be reduced. Therefore, the mechanical strength of the external gear can be improved.

The robot according to the application example includes a lubricant disposed between the internal gear and the external gear.
The lubricant preferably contains a base oil, a thickener and an organic molybdenum compound, and the oil separation degree is preferably in the range of 4% by mass to 13.8% by mass.

  Since the lubricant disposed between the internal gear and the external gear includes the organic molybdenum compound, the friction at the meshing portion between the internal gear and the external gear can be effectively reduced. Furthermore, when the oil separation degree of the lubricant is in the range of 4% by mass to 13.8% by mass, even if the lubricant contains the organic molybdenum compound, the base oil from the thickener is Exudation is less likely to be inhibited, and base oil can be stably supplied to the contact portion between the external gear and the wave generator. As a result, the lives of the external gear and the internal gear can be suitably extended.

The gear device of this application example is an internal gear;
A flexible external gear partially meshing with the internal gear;
And a wave generator which contacts the inner peripheral surface of the external gear and moves the meshing position of the internal gear and the external gear in the circumferential direction.
The constituent material of the external gear includes nickel chromium molybdenum steel,
The constituent material of the internal gear includes chromium molybdenum steel.

  According to such a gear device, since the constituent material of the external gear includes nickel chromium molybdenum steel, mechanical characteristics (particularly fatigue strength) of the external gear can be enhanced to prolong the life of the external gear. it can. On the other hand, since the material of the internal gear includes chromium molybdenum steel, the mechanical characteristics of the internal gear are enhanced while the mechanical characteristics of the external gear and the internal gear are balanced, and the life of the internal gear is improved. In addition to lengthening, it is possible to reduce damage to the external gear due to the influence of the worn internal gear and to prolong the life of the external gear. Thus, by prolonging the life of both the external gear and the internal gear, it is possible to prolong the life of the gear device.

It is a side view showing a schematic structure of a robot concerning an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view which shows the gear apparatus which concerns on 1st Embodiment of this invention. It is a front view (figure seen from the axis a) of the gear apparatus main body shown in FIG. It is sectional drawing which shows the surface state of the external gear of the flexible gear with which the gear apparatus shown in FIG. 2 is provided. It is a longitudinal cross-sectional view which shows the gear apparatus which concerns on 2nd Embodiment of this invention.

  Hereinafter, a robot and a gear device of the present invention will be described in detail based on preferred embodiments shown in the attached drawings.

1. Robot First, an embodiment of a robot of the present invention will be briefly described.

  FIG. 1 is a side view showing a schematic configuration of a robot according to an embodiment of the present invention. In the following, for convenience of explanation, the upper side in FIG. 1 is referred to as “upper” and the lower side as “lower”. Further, the base side in FIG. 1 is referred to as “proximal side”, and the opposite side (end effector side) is referred to as “distal side”. Further, the vertical direction in FIG. 1 is referred to as “vertical direction”, and the horizontal direction is referred to as “horizontal direction”.

  The robot 100 shown in FIG. 1 is, for example, a robot used for operations such as feeding of precision equipment and parts (objects) constituting the same, removal of materials, transportation, and assembly. As shown in FIG. 1, the robot 100 has a base 110, a first arm 120, a second arm 130, a working head 140, an end effector 150, and a wire routing unit 160. . Hereinafter, each part of the robot 100 will be briefly described in order.

  The base 110 is fixed to, for example, a floor surface (not shown) by a bolt or the like. Inside the base 110, a control device 190 for controlling the robot 100 is installed. Further, the first arm 120 is connected to the base 110 so as to be rotatable about a first axis J1 (pivotal axis) along the vertical direction with respect to the base 110.

  Here, in the base 110, a motor 170 which is a first motor such as a servomotor for generating a driving force for rotating the first arm 120, and a first reduction gear for reducing the rotation of the driving force of the motor 170 And a gear device 10, and a drive source is provided. The input shaft of the gear device 10 is connected to the rotation shaft of the motor 170, and the output shaft of the gear device 10 is connected to the first arm 120. Therefore, when the motor 170 is driven and the driving force is transmitted to the first arm 120 through the gear device 10, the first arm 120 rotates in the horizontal plane around the first axis J1 with respect to the base 110. Do.

  The second arm 130 is connected to the tip of the first arm 120 so as to be rotatable about a second axis J2 (pivotal axis) along the vertical direction with respect to the first arm 120. Although not shown, a drive source having a second motor for generating a drive force for rotating the second arm 130 and a second reduction gear for reducing the rotation of the drive force of the second motor in the second arm 130. Is installed. Then, the driving force of the second motor is transmitted to the second arm 130 via the second reduction gear, so that the second arm 130 rotates in the horizontal plane around the second axis J2 with respect to the first arm 120. Do.

  The working head 140 is disposed at the tip of the second arm 130. The working head 140 has a spline shaft 141 which is inserted through a spline nut and a ball screw nut (both not shown) coaxially arranged at the tip of the second arm 130. The spline shaft 141 is rotatable with respect to the second arm 130 about its axis J3 and can be moved (lifted) up and down.

  In the second arm 130, although not shown, a rotary motor and a lift motor are disposed. The driving force of the rotary motor is transmitted to the spline nut by a driving force transmission mechanism (not shown), and when the spline nut rotates forward and reverse, the spline shaft 141 rotates forward and reverse around an axis J3 along the vertical direction.

  On the other hand, the driving force of the elevating motor is transmitted to the ball screw nut by a driving force transmission mechanism (not shown), and when the ball screw nut rotates forward and reverse, the spline shaft 141 moves up and down.

  An end effector 150 is connected to a tip end (lower end) of the spline shaft 141. The end effector 150 is not particularly limited, and examples thereof include those that hold the transferred object, and those that process the object.

  A plurality of wires connected to respective electronic components (for example, a second motor, a rotary motor, an elevating motor, etc.) disposed in the second arm 130 are tubular wires connecting the second arm 130 and the base 110. The inside of the routing portion 160 is routed to the inside of the base 110. Further, the plurality of wires are put together in the base 110, and are routed to the control device 190 installed in the base 110 together with the wires connected to the motor 170 and an encoder (not shown).

  As described above, the robot 100 includes the base 110 which is the first member, the first arm 120 which is the second member rotatably provided with respect to the base 110, the base 110 and the first member. And a gear device for transmitting a driving force from one side of the arm to the other side.

  The first arm 120 and the second arm 130 may be collectively considered as a "second member". In addition to the first arm 120 and the second arm 130, the “second member” may further include the working head 140 and the end effector 150.

  Moreover, in the present embodiment, the first reduction gear is configured by the gear device 10, but the second reduction gear may be configured by the gear device 10, and the first reduction gear and the second reduction gear Both may be configured by the gear device 10. When the second reduction gear is configured by the gear device 10, the first arm 120 may be regarded as a "first member" and the second arm 130 may be regarded as a "second member". Further, in place of the gear device 10, a gear device 10B described later may be used.

  Moreover, in the present embodiment, the motor 170 and the gear device 10 are provided on the base 110, but the motor 170 and the gear device 10 may be provided on the first arm 120. In this case, the output shaft of the gear unit 10 may be connected to the base 110.

2. Gear device Hereinafter, an embodiment of the gear device of the present invention will be described.

First Embodiment
FIG. 2 is a longitudinal sectional view showing the gear device according to the first embodiment of the present invention. FIG. 3 is a front view (a view from the direction of the axis a) of the gear device main body shown in FIG. FIG. 4 is a cross-sectional view showing the surface condition of the external teeth of the flexible gear provided in the gear device shown in FIG. In the drawings, for convenience of explanation, the dimensions of each part are appropriately exaggerated and shown as needed, and the dimensional ratio between the parts does not necessarily coincide with the actual dimensional ratio.

  The gear device 10 shown in FIG. 2 is a wave gear device, and is used, for example, as a reduction gear. The gear device 10 has a gear device body 1 and a case 5 accommodating the gear device body 1, and these are integrated. Here, the lubricant G is disposed in the case 5 of the gear device 10. Hereinafter, each part of the gear device 10 will be described. Case 5 may be provided as necessary, and may be omitted.

(Gear unit body)
The gear device main body 1 is disposed inside a rigid gear 2 which is an internal gear, a flexible gear 3 which is a cup-shaped external gear disposed inside the rigid gear 2, and a flexible gear 3 And the wave generator 4 that is being

  In the present embodiment, the rigid gear 2 is fixed (connected) to the base 110 (first member) of the robot 100 described above via the case 5, and the flexible gear 3 is described above as the first arm 120 of the robot 100 (the The wave generator 4 is connected to the rotation shaft of the motor 170 disposed on the base 110 of the robot 100 described above.

  When the rotating shaft of the motor 170 rotates (ie, a driving force is generated), the wave generator 4 rotates at the same rotational speed as the rotating shaft of the motor 170. Since the rigid gear 2 and the flexible gear 3 have different numbers of teeth, the meshing positions of the rigid gear 2 and the flexible gear 3 relatively rotate around the axis a while moving in the circumferential direction. In the present embodiment, since the number of teeth of the rigid gear 2 is larger than the number of teeth of the flexible gear 3, the flexible gear 3 can be rotated at a rotation speed lower than the rotation speed of the rotation shaft of the motor 170. . That is, it is possible to realize a reduction gear in which the wave generator 4 is on the input shaft side and the flexible gear 3 is on the output shaft side.

  Depending on the form of the case 5, the gear device 10 can be used as a reduction gear even if the flexible gear 3 is fixed (connected) to the base 110 and the rigid gear 2 is connected to the first arm 120. . Also, even if the rotation shaft of the motor 170 is connected to the flexible gear 3, the gear device 10 can be used as a reduction gear, in which case the wave generator 4 is fixed (connected) to the base 110 and rigid The gear 2 may be connected to the first arm 120. When the gear unit 10 is used as a speed increasing gear (when the flexible gear 3 is rotated at a rotational speed higher than the rotational speed of the rotation shaft of the motor 170), the above-described relationship between the input side and the output side is reversed. You should do it.

  As shown in FIGS. 2 and 3, the rigid gear 2 is a gear configured of a rigid body that does not substantially bend in the radial direction, and is a ring-shaped internal gear having internal teeth 23. In the present embodiment, the rigid gear 2 is a spur gear. That is, the internal teeth 23 have teeth streaks parallel to the axis a. The tooth lines of the internal teeth 23 may be inclined with respect to the axis a. That is, the rigid gear 2 may be a helical gear or a helical gear.

  As shown in FIGS. 2 and 3, the flexible gear 3 is inserted inside the rigid gear 2. The flexible gear 3 is a flexible gear that can be bent and deformed in the radial direction, and is an external gear having external teeth 33 (tooth) that mesh with the internal teeth 23 of the rigid gear 2. Further, the number of teeth of the flexible gear 3 is smaller than the number of teeth of the rigid gear 2. Thus, the reduction gear can be realized by making the numbers of teeth of the flexible gear 3 and the rigid gear 2 different from each other.

  In the present embodiment, the flexible gear 3 has a cup shape having an opening 36 opened at one end in the direction of the axis a (the end on the right side in FIG. 2), and from the opening 36 toward the other end The external teeth 33 are formed. Here, the flexible gear 3 is connected to a cylindrical (more specifically cylindrical) body 31 (cylindrical part) around the axis a and the other end of the body 31 in the direction of the axis a. And a bottom 32. As a result, the end of the opening 36 is more easily bent in the radial direction than the bottom 32 of the body 31, so that good flexible meshing of the flexible gear 3 with the rigid gear 2 can be realized. Furthermore, the rigidity of the bottom 32 to which the shaft 62 (for example, the output shaft) is connected can be increased. Because of this, the gear unit 10 has a very small backlash and is suitable for applications that repeat reversing, and the ratio of the number of simultaneous meshing teeth is large, so that the force applied to one tooth is small and the high torque capacity is achieved. You can also get Lubricants are required to have high lubricating performance because they can be used for such severe applications.

  As shown in FIGS. 2 and 3, the wave generator 4 is disposed inside the flexible gear 3 and is rotatable about an axis a. Then, the wave generator 4 deforms the cross section of the opening 36 of the flexible gear 3 into an oval or an oval having the major axis La and the minor axis Lb, and the external teeth 33 are internal teeth of the rigid gear 2. Engage with 23. Here, the flexible gear 3 and the rigid gear 2 are meshed with each other inside and outside rotatably around the same axis a.

  In the present embodiment, the wave generator 4 has a cam 41 and a bearing 42 mounted on the outer periphery of the cam 41. The cam 41 has a shaft 411 rotating around an axis a, and a cam 412 protruding outward from one end of the shaft 411.

  A shaft 61 (for example, an input shaft) is connected to the shaft 411. The outer peripheral surface of the cam portion 412 has an oval or oval shape when viewed from the direction along the axis a. The bearing 42 has a flexible inner ring 421 and an outer ring 423, and a plurality of balls 422 disposed therebetween. Here, the inner ring 421 is fitted to the outer peripheral surface of the cam portion 412 of the cam 41, and is elastically deformed into an oval or an oval along the outer peripheral surface of the cam portion 412. Along with that, the outer ring 423 is also elastically deformed into an oval or an oval. Further, the outer circumferential surface of the inner ring 421 and the inner circumferential surface of the outer ring 423 each have a raceway surface on which a plurality of balls 422 are guided and rolled along the circumferential direction. Further, the plurality of balls 422 are held by a holder (not shown) so as to keep a constant distance in the circumferential direction. In the bearing 42, grease (not shown) is disposed. This grease may be the same as or different from the lubricant G described later.

  In such a wave generator 4, as the cam 41 rotates around the axis a, the direction of the cam portion 412 changes, and accordingly, the outer peripheral surface of the outer ring 423 is also deformed, and the rigid gear 2 and the flexible gear The three meshing positions are moved in the circumferential direction.

  The rigid gear 2, the flexible gear 3 and the wave generator 4 are each made of a metallic material such as an iron-based material.

  In particular, the rigid gear 2 (internal gear) includes chromium molybdenum steel. Chromium-molybdenum steel, for example, has good fatigue strength even with low hardness compared to spheroidal graphite cast iron (ductile cast iron). Therefore, since the rigid gear 2 includes chromium molybdenum steel, the service life of the rigid gear 2 can be prolonged. Moreover, since chromium molybdenum steel has good machinability and becomes a tough steel by appropriate heat treatment, it can be said that it is suitable as a constituent material of the rigid gear 2. In particular, as the chromium-molybdenum steel used as a constituent material of the rigid gear 2, it is preferable to use, for example, SCM 435 from the viewpoint of excellent balance of mechanical characteristics.

  Also, the flexible gear 3 (external gear) includes nickel chromium molybdenum steel. Nickel-chromium-molybdenum steel is a tough steel by appropriate heat treatment, and has excellent mechanical properties (particularly fatigue strength), so it can be said that it is suitable as a constituent material of the flexible gear 3 on which cyclic stress acts. In particular, as the nickel-chromium-molybdenum steel used as the constituent material of the flexible gear 3, it is preferable to use, for example, SNCM 439 from the viewpoint of excellent mechanical characteristics.

  The Vickers hardness of the surface of the flexible gear 3 (external gear) is preferably equal to or less than the Vickers hardness of the surface of the rigid gear 2 (internal gear). Thereby, the wear of the internal teeth 23 of the rigid gear 2 can be reduced, and as a result, the life of the gear device 10 can be extended. In particular, chromium molybdenum steel used as a constituent material of the rigid gear 2 is easy to adjust its hardness by quenching and tempering, and has high mechanical properties (fatigue strength) compared to other materials (for example, spheroidal graphite cast iron) Have. Therefore, also from this point of view, using chromium molybdenum steel as the constituent material of the rigid gear 2 is effective in enhancing the durability of the gear device 10. In addition, Vickers hardness is measured according to the Vickers hardness test-test method prescribed | regulated to JISZ2244: 2009. Here, the test force of the indenter is 9.8 N (1 kgf), and the holding time of the test force is 15 seconds. And let the average value of the measurement result of ten places be said Vickers hardness.

  The Vickers hardness of the surface of the flexible gear 3 (external gear) is preferably in the range of 400 or more and 520 or less, and more preferably in the range of 450 or more and 520 or less. Thereby, the mechanical strength and the toughness of the flexible gear 3 can be balanced, and the life of the flexible gear 3 can be suitably extended. On the other hand, when the Vickers hardness is too low, the strength of the flexible gear 3 is not sufficient, and the flexible gear 3 tends not to withstand the load stress and tends to be broken. On the other hand, when the Vickers hardness is too high, the toughness of the flexible gear 3 is lowered, and it tends to be easily broken by an impact or the like, and the wear of the rigid gear 2 is advanced, and the durability of the gear device 10 is increased. It may reduce sex.

  Preferably, compressive residual stress is applied to at least the surface of the external gear 33 of the flexible gear 3. Thereby, the fatigue strength of the external teeth 33 can be improved, and the flexible gear 3 that can withstand high load stress can be realized. As a result, the durability of the gear device 10 can be improved.

  Here, in order to obtain the effects as described above, the residual stress (compression residual stress) of the flexible gear 3 is preferably in the range of -950 MPa or more and -450 MPa or less, and -950 MPa or more and -550 MPa or less Is more preferably in the range of −950 MPa to −750 MPa. On the other hand, when the absolute value of the residual stress is too small, the above-mentioned effect tends to decrease. On the other hand, when the absolute value of the residual stress is too large, the deformation of the external gear 33 accompanied by the application of the residual stress becomes too large, and the appropriate operation of the gear device 10 tends to be difficult.

  Further, such compressive residual stress can be applied by subjecting the surface of the flexible gear 3 to shot peening. When the surface of the flexible gear 3 is subjected to shot peening in this way, fine irregularities are formed on the surface of the flexible gear 3 as shown in FIG. Thereby, the lubricant G can be easily held on the surface of the flexible gear 3. As a result, the durability of the gear device 10 can be improved.

  Here, the surface roughness Ra of the external teeth 33 of the flexible gear 3 (external gear) is preferably in the range of 0.2 μm to 1.6 μm, and is 0.2 μm to 0.8 μm. More preferably, it is within the range. This makes it easy to hold the grease (lubricant G) on the external teeth 33 of the flexible gear 3 while reducing the wear of the rigid gear 2, so that the life of the flexible gear 3 and the rigid gear 2 is suitable. It can be long. On the other hand, when the surface roughness is too small, the effect of facilitating the retention of the grease (the lubricant G) on the external teeth 33 of the flexible gear 3 tends to be small. On the other hand, when the surface roughness is too large, the contact resistance of the tooth surfaces of the external teeth 33 becomes large, the efficiency of the gear device 10 decreases, and the rigid gear 2 is easily worn away. It shows a tendency to decrease. In addition, surface roughness Ra is arithmetic mean roughness Ra, and is measured according to the method prescribed | regulated to JISB0601: 2013.

  The surface roughness Ra of the external teeth 33 of the flexible gear 3 (external gear) is preferably larger than the surface roughness Ra of the internal teeth 23 of the rigid gear 2 (internal gear). As a result, the contact resistance between the flexible gear 3 and the rigid gear 2 is reduced while the grease (lubricant G) is easily held on the external teeth 33 of the flexible gear 3, and the flexible gear 3 is thus reduced. And the life of the rigid gear 2 can be suitably extended.

  On the other hand, the surface roughness Ra of the internal teeth 23 of the rigid gear 2 (internal gear) is preferably in the range of 0.1 μm to 0.8 μm, and is preferably in the range of 0.1 μm to 0.4 μm. It is more preferable that Thereby, the contact resistance between the flexible gear 3 and the rigid gear 2 can be reduced while reducing the manufacturing cost of the rigid gear 2. On the other hand, when the surface roughness is too small, the effect of improving the efficiency is small although the cost for finishing the tooth profile surface of the internal teeth 23 increases. On the other hand, when the surface roughness is too large, the contact resistance of the tooth surfaces of the internal teeth 23 increases, and the efficiency of the gear device 10 tends to decrease.

  Moreover, it is preferable that the average crystal grain size of the constituent material of the flexible gear 3 (external gear) is smaller than the average crystal grain size of the constituent material of the rigid gear 2 (internal gear). By making the crystal grain size of the external teeth 33 smaller according to the magnitude relationship of the average crystal grain size of the constituent material of the internal teeth 23 and the external teeth 33 as described above, the lubricant G can be easily held on the external teeth 33 it can. Therefore, the lubricant G can be retained on the external teeth 33 against the centrifugal force caused by the rotation of the external teeth 33. Here, the lubricant G is preferentially held at the grain boundaries present on the surface of the external teeth 33. It is considered that this is because the grain boundaries play a role as fine recesses and grooves for containing the lubricant G. Therefore, by reducing the crystal grain size of the external teeth 33, the density of the grain boundaries present on the surfaces of the external teeth 33 becomes high, and accordingly, the lubricant G is easily held on the surfaces of the external teeth 33. .

  In addition, when the crystal grain size of the external teeth 33 is reduced, the mechanical strength of the external teeth 33 can be enhanced, and the toughness of the external teeth 33 can be enhanced. The external teeth 33 are required to have higher mechanical strength and toughness than the internal teeth 23 because the external teeth 33 repeatedly deform as the rigid gear 2 and the flexible gear 3 move relative to one another as described above. . Therefore, it is extremely useful to improve the mechanical strength and toughness of the external teeth 33. Generally, the mechanical strength of the metal increases in inverse proportion to the half power of the crystal grain size.

  On the other hand, the crystal grain size of the internal teeth 23 is increased according to the magnitude relationship between the average crystal grain sizes of the constituent materials of the internal teeth 23 and the external teeth 33 as described above, and the lubricant G is arranged along the internal teeth 23. Can be made to flow easily. Therefore, the lubricant G can be prevented from being biased or solidified on the internal teeth 23. Here, since the internal teeth 23 are non-rotating, no centrifugal force like the above-mentioned external teeth 33 acts on the internal teeth 23, so the lubricant G tends to be easy to be retained from the beginning. Therefore, by making the lubricant G on the internal teeth 23 easy to flow, it is possible to prevent the lubricant G from adhering and running out of oil at the necessary places. Thereby, the performance of the lubricant G can be sufficiently exhibited.

  Thus, in the gear device 10, the effect of retaining the lubricant G on the external teeth 33 as described above, and the effect of reducing the deviation and solidification of the lubricant G on the internal teeth 23 Two effects can be exhibited at the same time. Then, the two effects are synergistic to effectively improve the lubricating life of the lubricant G. In particular, in wave gear devices such as the gear device 10, generally, the demand for lubricating life of the lubricant is extremely high because the internal and external gears mesh with one another with very little backlash. Therefore, when the present invention is applied to such a gear device, the effect becomes remarkable.

  Here, the "average crystal grain size" is measured in accordance with JIS G 0551 "Steel-Method of microscopic examination of steel grain size". The measurement of the average grain size is carried out by etching the surface of the test piece (inner teeth or outer teeth) with a caustic solution to make grain boundaries appear, and microscopically observing the appearing grain boundaries. As the etchant, 5% nital (5% nitric acid-ethyl alcohol) or aqueous picric acid based etchant (2% picric acid-0.2% sodium chloride-0.1% sulfuric acid-distilled water) is used. Further, the magnitude relationship of the average crystal grain size as described above may be satisfied as long as at least the internal teeth 23 and the external teeth 33 are satisfied, and the rigid gear 2 and the flexible gear 3 may not be satisfied with each other. Although it is good, if the other parts are satisfied, the effect becomes remarkable. The crystal grain sizes of the internal teeth 23 and the external teeth 33 can be adjusted according to, for example, the material (metal composition) constituting them and the heat treatment at the time of manufacture.

  Assuming that the average crystal grain size of the constituent material of the external tooth 33 is A and the average crystal grain size of the constituent material of the internal tooth 23 is B, the relationship of A <B may be satisfied, but the two effects as described above In order to suitably achieve the above, preferably 1.2 ≦ B / A ≦ 100, more preferably 2 ≦ B / A ≦ 50. On the other hand, when B / A is too small, the balance between the two effects described above tends to deteriorate, while when B / A is too large, the strength difference between the internal teeth 23 and the external teeth 33 becomes too large. Thus, the wear of one of the internal teeth 23 and the external teeth 33 tends to be quick.

  The average crystal grain size of the constituent material of the internal teeth 23 is preferably in the range of 20 μm to 150 μm, more preferably in the range of 30 μm to 100 μm, and in the range of 30 μm to 50 μm. Is more preferred. Thereby, the lubricant G can be more effectively flowed along the internal teeth 23. Further, when the internal teeth 23 are made of metal, the mechanical strength of the internal teeth 23 can be made excellent. On the other hand, when the average crystal grain size is too small, the fluidity of the lubricant G on the internal teeth 23 tends to decrease. On the other hand, if the average crystal grain size is too large, the strength of the internal teeth 23 may be insufficient depending on the constituent material of the internal teeth 23. In addition, in the whole rigid gearwheel 2, when the range of the average grain size mentioned above is satisfy | filled, the effect mentioned above becomes remarkable.

  On the other hand, the average crystal grain size of the constituent material of the external teeth 33 is preferably in the range of 0.5 μm to 30 μm, more preferably in the range of 5 μm to 20 μm, and in the range of 5 μm to 15 μm. It is further preferred that Thus, the lubricant G can be more effectively held on the external teeth 33. Further, when the external teeth 33 are made of metal, the mechanical strength of the external teeth 33 can be made excellent. On the other hand, when the average grain size is too small, the processability at the time of manufacturing the external teeth 33 is poor, and the depth of the recess due to the crystal grain boundary present on the surface of the external teeth 33 is also small. On the contrary, it becomes difficult to hold the lubricant G on the external teeth 33. On the other hand, when the average grain size is too large, the effect of retaining the lubricant G on the external teeth 33 tends to be reduced, and it is difficult to secure the mechanical strength and toughness required for the external teeth 33 . In addition, in the whole flexible gearwheel 3, when the range of the average grain size mentioned above is satisfy | filled, the effect mentioned above becomes remarkable.

  In addition, materials other than the above-described materials may be added to the constituent materials of the rigid gear 2 and the flexible gear 3 in the range of 0.01% by mass or more and 2% or less. In particular, the constituent material of the flexible gear 3 (external gear) has a range of 0.01% by mass or more and 0.5% by mass or less of at least one element of the group 4 element and the group 5 element It is preferable to include in it. Thereby, even if heat treatment is performed in the process of manufacturing the flexible gear 3, it is possible to suppress the growth of crystal grains of the iron-based material constituting the flexible gear 3 and to reduce the crystal grain size. Therefore, the mechanical strength of the flexible gear 3 can be improved. Moreover, according to the gear device 10 provided with such a flexible gear 3, by improving the mechanical strength of the flexible gear 3, the durability of the gear device 10 can be improved.

  Here, as the additive element, as described above, at least one element of the Group 4 element and the Group 5 element may be used, but titanium (Ti), zirconium (Zr), hafnium (Hf (Hf) ), Vanadium (V), niobium (Nb) and tantalum (Ta) are preferably used alone or in combination of two or more, and at least one of zirconium (Zr) and niobium (Nb) Is more preferable, and it is even more preferable to contain both zirconium (Zr) and niobium (Nb). Thereby, the effect of suppressing the growth of the crystal grains of the iron-based material constituting the flexible gear 3 (hereinafter, also referred to as the “crystal grain growth suppression effect”) can be more effectively exhibited. The constituent material of the flexible gear 3 may contain an element other than the group 4 element and the group 5 element. For example, a crystal of an iron-based material constituting the flexible gear 3 From the viewpoint of effectively suppressing the grain growth, yttrium (Y) may be contained.

  In addition, the content (addition amount) of the additive element in the constituent material of the flexible gear 3 is preferably in the range of 0.05 mass% or more and 0.3 mass% or less, 0.1 mass% or more More preferably, it is in the range of 0.2% by mass or less. Thereby, the crystal grain growth inhibitory effect can be exhibited more effectively. On the other hand, when the content is too small, the crystal growth suppressing effect tends to be significantly reduced. On the other hand, when the content is too large, not only the grain growth suppressing effect can not be further obtained, but also the toughness of the flexible gear 3 is lowered, and the mechanical strength of the flexible gear 3 is lowered. The processability at the time of manufacturing the flexible gear 3 is extremely deteriorated.

(Case)
The case 5 shown in FIG. 2 supports a substantially plate-like lid 11 supporting a shaft 61 (for example, an input shaft) through a bearing 13 and a shaft 62 (for example, an output shaft) through a bearing 14 And a cup-shaped body 12. Here, the lid 11 and the main body 12 are connected (fixed) to form a space, and the gear device main body 1 described above is accommodated in the space. The rigid gear 2 of the gear device main body 1 described above is fixed to at least one of the lid 11 and the main body 12 by, for example, screwing.

  The inner wall surface 111 of the lid 11 is shaped to expand in the direction perpendicular to the axis a so as to cover the opening 36 of the flexible gear 3. Further, the inner wall surface 121 of the main body 12 is shaped along the outer peripheral surface and the bottom surface of the flexible gear 3. Such case 5 is fixed to the base 110 of the robot 100 described above. Here, the lid 11 may be separate from the base 110, and may be fixed to the base 110 by, for example, screwing, or may be integrated with the base 110. Moreover, it does not specifically limit as a constituent material of case 5 (lid 11, main body 12), For example, a metal material, a ceramic material, etc. are mentioned.

(lubricant)
The lubricant G is, for example, a grease (semi-solid lubricant), and between the rigid gear 2 and the flexible gear 3 as the lubrication target (meshing portion), and the flexible gear as the lubrication target It is disposed in at least one of the contact portion 3 and the wave generator 4 (contact portion / sliding portion) (hereinafter, also simply referred to as "the portion to be lubricated"). Thereby, the friction of the said lubrication object part can be reduced.

  Thus, the gear unit 10 includes the lubricant G disposed between the rigid gear 2 (internal gear) and the flexible gear 3 (external gear). The lubricant G preferably contains a base oil, a thickener and an organic molybdenum compound, and the oil separation degree is preferably in the range of 4% by mass to 13.8% by mass. By the lubricant G containing the organic molybdenum compound, the friction at the meshing portion between the rigid gear 2 and the flexible gear 3 can be effectively reduced. Furthermore, when the oil separation degree of the lubricant G is in the range of 4% by mass to 13.8% by mass, even if the lubricant G contains the organic molybdenum compound, it is possible to use the thickener as the lubricant. Exudation of the base oil is less likely to be inhibited, and the base oil can be stably supplied to the contact portion between the flexible gear 3 and the wave generator 4. As a result, the life of the flexible gear 3 and the rigid gear 2 can be suitably extended.

  Examples of base oils include paraffinic and naphthenic mineral oils (refined mineral oils), polyolefins, esters, synthetic oils such as silicones, and one of these may be used alone or in combination of two or more. It can be used. Moreover, as a thickener, for example, calcium soap, calcium complex soap, sodium soap, aluminum soap, lithium soap, soap system such as lithium complex soap, and polyurea, sodium terephthalate, polytetrafluoroethylene (PTFE) Organic bentonite, non-soap systems such as silica gel, and the like, and one of them may be used alone or in combination of two or more. Thus, in the lubricant G (grease) containing the base oil and the thickener as a composition, the three-dimensional structure formed by the thickener is intricately intertwined to hold the base oil, It exerts a lubricating effect by exuding the base oil little by little.

  Here, the content of the base oil in the lubricant G is 75% by mass to 85% by mass, and the content of the thickener in the lubricant G is 10% by mass to 20% by mass Is preferred. Thereby, the lubricating performance of the lubricant G can be enhanced.

  In addition, the organic molybdenum compound functions as a solid lubricant or an extreme pressure agent. As a result, the friction in the part to be lubricated can be effectively reduced, and even if the part to be lubricated is in the extreme pressure lubrication state, the seizing and scuffing can be effectively prevented. In particular, the organic molybdenum compound exhibits the same extreme pressure property and wear resistance as molybdenum disulfide, and is superior in oxidation stability to molybdenum disulfide. Therefore, the life of the lubricant G can be extended.

  Here, the organic molybdenum compound is added to the lubricant G in the form of particles, but when it is used in the gear device 10, it has the effect of forming a film on the portion to be lubricated by lowering the coefficient of friction. For this reason, the organic molybdenum compound is suitable for lubricating the very small clearance between the flexible gear 3 and the wave generator 4 and the meshing portion between the rigid gear 2 and the flexible gear 3 engaged with very small backlash. There is. On the other hand, in the case of molybdenum disulfide, in order to reduce the friction in the part to be lubricated, the particle state must be maintained even if it adheres to the part to be lubricated, and the rigid gear 2 and the flexible gear It can not be said that it is suitable for lubrication at the meshing portion with 3, and at the contact portion between the flexible gear 3 and the wave generator 4.

  The content of the organic molybdenum compound in the lubricant G is preferably, for example, 1% by mass or more and 5% by mass or less. Thereby, the performance of the organic molybdenum compound as the extreme pressure agent is easily exhibited, and the characteristic improvement of the lubricant G becomes remarkable. In addition to the organic molybdenum compound, another extreme pressure agent such as zinc dialkyl dithiophosphate may be used in combination as the extreme pressure agent or the solid lubricant.

  Here, the average particle size of the organic molybdenum compound is generally relatively large at about 10 μm. Therefore, simply adding the organomolybdenum compound to the lubricant G prevents the base oil from leaking out from the thickener of the lubricant G due to the effect of the particles of the organomolybdenum compound and reduces the amount of lubrication of the part to be lubricated. May lead to For example, in the contact portion between the flexible gear 3 and the wave generator 4, it is difficult to supply the whole grease because the gap is small, and it is important to supply the base oil that has leaked from the thickener. Because of that, it is easy to cause a lack of lubrication.

  Therefore, the oil separation degree of the lubricant G is preferably in the range of 4% by mass to 13.8% by mass, more preferably in the range of 6% by mass to 11% by mass, and 6% by mass. More preferably, it is in the range of 10% by mass to 10% by mass. This makes it difficult to inhibit the penetration of the base oil from the thickener of the lubricant G, and the base oil is stably supplied to the portion to be lubricated (in particular, the contact portion between the flexible gear 3 and the wave generator 4). Can be supplied. Thus, the base oil can be stably supplied to the portion to be lubricated by the exudation of the base oil from the thickener while the lubricant G exhibits the excellent friction reducing effect by the organic molybdenum compound, As a result, the life of the gear device 10 can be extended. In addition, "oil separation degree" is a parameter | index which shows the ability to exude the base oil from a thickener, and is measured based on the measuring method prescribed | regulated to JISK2220.

  Here, from the viewpoint of enhancing the effect of the oil separation degree of the lubricant G as described above, the average particle diameter of the organic molybdenum compound (solid lubricant or extreme pressure agent) added to the lubricant G is 1 μm or more and 10 μm or less It is preferable to be in the range.

  Also, the oil separation degree tends to increase as the consistency increases (that is, becomes softer), and has a certain degree of correlation with the consistency. Therefore, for example, the lubricant G having a desired oil separation degree can be obtained by adjusting the consistency according to the blending ratio of the base oil and the thickener.

  The consistency of the lubricant G is preferably in the range of 325 to 365, more preferably in the range of 330 to 360, and still more preferably in the range of 335 to 355. . As a result, the lubricant G can be easily retained at the portion to be lubricated. There is also an advantage that it becomes easy to make the oil separation degree of the lubricant G within the range described above. On the other hand, if the consistency of the lubricant G is too small, it is difficult to select the base oil and thickener to be in the above-mentioned range of oil separation, and the fluidity of the lubricant G becomes insufficient. It becomes difficult to sufficiently supply the lubricant G to the meshing portion between 2 and the flexible gear 3. On the other hand, when the consistency of the lubricant G is too large, the fluidity of the lubricant G becomes too high, and the lubricant is discharged to the outside of the gear device 10 (for example, the unintended position in the case 5 or the outside of the case 5). Since G is likely to leak, the supply of the lubricant G to the meshing portion between the rigid gear 2 and the flexible gear 3 becomes unstable, which in turn tends to cause a lubrication failure in the meshing portion. In addition, "consistency" is a parameter | index showing the hardness of grease, and is measured based on the measuring method prescribed | regulated to JISK2220.

  The dropping point of the lubricant G is preferably in the range of 248 ° C. or more and 270 ° C. or less. Thereby, the heat resistance of the lubricant G can be made excellent while optimizing the consistency of the lubricant G. In addition, a "drop point" means a temperature when a grease structure is destroyed and it changes from a semisolid to a liquid, and is measured based on the measuring method prescribed | regulated to JISK2220.

  Here, as the thickener used for the lubricant G, among the above-mentioned thickeners, it is preferable to use a lithium complex soap. That is, it is preferable that the thickener used for the lubricant G contains a lithium complex soap. Thereby, the dropping point of the lubricant G can be increased, and the heat resistance of the lubricant G can be made excellent. In addition, when using lithium complex soap as a thickener, lithium complex soap may be used independently as a thickener, and it may mix and use other thickeners and lithium complex soap. When mixing and using other thickeners and lithium compound soaps, it is preferable that content of lithium compound soaps in all thickeners is 70 mass% or more.

  In addition to the base oil, the thickener and the extreme pressure agent (organic molybdenum compound), the lubricant G is an additive such as an antioxidant and a rust inhibitor, and also graphite, molybdenum disulfide, and polytetra A solid lubricant such as fluoroethylene (PTFE) may be included.

  As described above, the gear device 10 includes the rigid gear 2 which is an internal gear, the flexible gear 3 which is a flexible external gear that partially engages with the rigid gear 2, and the flexible gear 3. And a wave generator 4 which contacts the inner peripheral surface and moves the meshing position of the rigid gear 2 and the flexible gear 3 in the circumferential direction. One of the rigid gear 2, the flexible gear 3 and the wave generator 4 is connected to the base 100 (first member) and the other is connected to the first arm 120 (second member) It is done. The constituent material of the flexible gear 3 includes nickel-chromium-molybdenum steel, and the constituent material of the rigid gear 2 includes chromium-molybdenum steel.

  According to such a gear device 10, since the constituent material of the flexible gear 3 includes nickel chromium molybdenum steel, the mechanical characteristics (particularly the fatigue strength) of the flexible gear 3 are enhanced, and the flexible gear 3 is improved. Can extend the life of the On the other hand, since the component material of the rigid gear 2 includes chromium molybdenum steel, the mechanical characteristics of the rigid gear 2 are enhanced while the mechanical characteristics of the flexible gear 3 and the rigid gear 2 are balanced, and the rigid gear 2 is improved. As a result, damage to the flexible gear 3 due to the influence of the worn rigid gear 2 can be reduced, and the life of the flexible gear 3 can be extended. Thus, by prolonging the life of both the flexible gear 3 and the rigid gear 2, the life of the gear device 10 can be extended.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 5 is a longitudinal sectional view showing a gear device according to a second embodiment of the present invention.

  The present embodiment is the same as the first embodiment described above except that the configuration of the external gear and the configuration of the case associated therewith are different. In the following description, the present embodiment will be described focusing on differences from the above-described embodiment, and the description of the same matters will be omitted. Further, in FIG. 5, the same components as those in the embodiment described above are denoted by the same reference numerals.

  The gear device 10B shown in FIG. 5 has a gear device main body 1B and a case 5B accommodating the gear device main body 1B. Case 5B may be omitted.

  The gear device 10B includes a flexible gear 3B which is a hat-shaped (hat-shaped) external gear disposed inside the rigid gear 2. The flexible gear 3B has a flange portion 32B (connection portion) connected to one end of the cylindrical body 31 and protruding in the opposite direction to the axis a. An output shaft (not shown) is attached to the flange portion 32B.

  The case 5B includes a substantially plate-like lid 11B supporting a shaft 61 (for example, an input shaft) via a bearing 13, and a cross roller bearing 18 attached to the flange portion 32B of the flexible gear 3B described above. And.

  Here, the lid 11B is fixed to the side surface on one side (right side in FIG. 5) of the rigid gear 2 by, for example, screwing. The cross roller bearing 18 also has an inner ring 15, an outer ring 16, and a plurality of rollers 17 disposed therebetween. The inner ring 15 is provided along the outer periphery of the trunk portion 31 of the flexible gear 3 and is fixed to the other side (left side in FIG. 5) of the rigid gear 2 by, for example, screwing. On the other hand, the outer ring 16 is fixed, for example, by screwing or the like to the surface of the flange portion 32B of the flexible gear 3B described above on the body 31 side.

  Further, the inner wall surface 111B of the lid 11B is shaped to expand in the direction perpendicular to the axis a so as to cover the opening 36 of the flexible gear 3B. Further, the inner wall surface 151 of the inner ring 15 of the cross roller bearing 18 has a shape along the outer peripheral surface of the body portion 31 of the flexible gear 3B.

  The gear device 10B as described above is disposed in at least one of the portion between the rigid gear 2 and the flexible gear 3B and between the flexible gear 3B and the wave generator 4 (the portion to be lubricated). It has a lubricant G. Here, the rigid gear 2, the flexible gear 3B, and one member of the wave generator 4 (in the present embodiment, the rigid gear 2 may be the flexible gear 3B or the wave generator 4) may be used as the basis. The other arm (the flexible gear 3B in the present embodiment but may be the rigid gear 2 or the wave generator 4) connected to the stand 110 (first member) is connected to the first arm 120 (the first member). It is connected to 2). In particular, as described in the first embodiment described above, the lubricant G contains an organic molybdenum compound, and the oil separation degree is in the range of 4% by mass to 13.8% by mass.

  According to the second embodiment as described above, the same effect as that of the first embodiment described above can be exhibited.

  As mentioned above, although the robot and gear apparatus of the present invention were explained based on an embodiment of illustration, the present invention is not limited to this, and composition of each part is an arbitrary composition which has the same function. Can be replaced by In addition, any other component may be added to the present invention.

  In the embodiment described above, although the base provided to the robot is the "first member" and the first arm is the "second member", the gear device for transmitting the driving force from the first member to the second member has been described. The present invention is not limited to this, and the n-th (n is an integer of 1 or more) arm is the “first member”, the (n + 1) arm is the “second member”, and the n-th arm and the (n + 1) The present invention is also applicable to a gear device that transmits driving force from one of the arms to the other. Moreover, it is applicable also to the gear apparatus which transmits a driving force from a 2nd member to a 1st member.

  Also, in the embodiment described above, the horizontal articulated robot has been described, but the robot of the present invention is not limited to this, for example, the number of joints of the robot is arbitrary, and can also be applied to a vertical articulated robot It is.

  In the embodiment described above, the gear unit is incorporated into the robot as an example, but in the gear unit according to the present invention, the driving force is transmitted from one side to the other side of the first and second members which rotate relative to each other. It can be incorporated into various devices having a configuration for transmission.

Hereinafter, specific examples of the present invention will be described.
1. Manufacture of gear device (reduction gear) (Example 1)
The gear device of a structure as shown in FIG. 2 was manufactured.

  Here, the manufactured gear device had an outer diameter φ70 of the internal gear, an inner diameter of the internal gear and an outer diameter of the external gear (mesh reference circle diameter) 53, and a reduction ratio of 80. Further, chromium molybdenum steel (SCM 435) was used as a constituent material of the internal gear, and nickel chromium molybdenum steel (SNCM 439) was used as a constituent material of the external gear.

  Moreover, the Vickers hardness (HV) of the surface of an external gear and an internal gear was 400 each. The residual stress of the external gear was −750 MPa. The surface roughness Ra of the external teeth of the external gear was 0.4 μm. The average crystal grain size of the constituent material of the external gear was 15 μm. The surface roughness Ra of the internal teeth of the internal gear was 0.2 μm. The average crystal grain size of the constituent material of the internal gear was 25 μm.

  Moreover, base oil (mineral oil): 80% by mass as a lubricant, lithium (Li) complex soap as a thickener: 15% by mass, organic molybdenum compound (organic Mo) as an extreme pressure agent: 4% by mass, 2 A grease having a consistency of 325, an oil separation of 4% by mass and a dropping point of 270 ° C. was used, containing 1% by mass of 6, 6-di-tert-butyl-4-cresol.

(Examples 2 to 6, reference examples 1 to 3)
A gear device was manufactured in the same manner as Example 1 described above except that the Vickers hardness of the surfaces of the external gear and the internal gear was changed as shown in Table 1.

(Examples 7 to 9)
A gear device was manufactured in the same manner as in Example 4 except that the residual stress of the external gear was changed as shown in Table 1.

(Examples 10 to 14)
A gear device was manufactured in the same manner as in Example 4 except that the surface roughness of the external gear and the internal gear was changed as shown in Table 1.

(Examples 15 to 17)
A gear device was manufactured in the same manner as Example 4 described above except that the average crystal grain size of the constituent material of the external gear and the internal gear was changed as shown in Table 1.

(Examples 18 to 25)
A gear device was manufactured in the same manner as Example 4 described above except that fourth and fifth additive elements as shown in Table 1 were added to the constituent materials of the external gear and the internal gear.

2. Evaluation 1 mentioned above. For each gear device obtained in the above, the continuous operation was performed at an input shaft rotation speed (input shaft rotation speed): 3000 rpm and an average load torque of 70 Nm, and the total rotation number of the input shaft until the gear device was broken was measured. Moreover, the result is collectively shown in Table 1 as lifetime.

  As is clear from Table 1, it can be seen that the life of each example is much longer than that of each reference example.

DESCRIPTION OF SYMBOLS 1 ... Gear apparatus main body, 1B ... Gear apparatus main body, 2 ... Rigid gear, 3 ... Flexible gear, 3B ... Flexible gear, 4 ... Wave generator, 5 ... Case, 5B ... Case, 10 ... Gear apparatus, DESCRIPTION OF SYMBOLS 10B ... Gear apparatus, 11 ... Lid, 11B ... Lid, 12 ... Main body, 13 ... Bearing, 14 ... Bearing, 15 ... Inner ring, 16 ... Outer ring, 17 ... Roller, 18 ... Cross roller bearing, 23 ... Inner tooth, Reference Signs List 31 body part 32 bottom part 32B flange part 33 external tooth 36 opening 41 41 cam 42 bearing 61 shaft 62 axis 100 robot 110 base 110 ... Inner wall surface, 111B ... Inner wall surface, 120 ... First arm, 121 ... Inner wall surface, 130 ... Second arm, 140 ... Working head, 141 ... Spline shaft, 150 ... End effector, 151 ... Inner wall surface, 160 ... part, 170: Motor 19 ... Control device, 411 ... Shaft portion, 412 ... Cam portion, 421 ... Inner ring, 422 ... Ball, 423 ... Outer ring, G ... Lubricant, J1 ... First axis, J2 ... Second axis, J3 ... Axis, La ... Length Axis, Lb ... short axis, a ... axis

Claims (11)

A first member,
A second member rotatably provided relative to the first member;
And a gear device for transmitting a driving force from one side to the other side of the first member and the second member,
The gear unit is
Internal gear,
A flexible external gear partially meshing with the internal gear;
And a wave generator which contacts the inner peripheral surface of the external gear and moves the meshing position of the internal gear and the external gear in the circumferential direction.
One of the internal gear, the external gear and the wave generator is connected to the first member and the other is connected to the second member.
The constituent material of the external gear includes nickel chromium molybdenum steel,
A robot characterized in that a constituent material of the internal gear includes chromium molybdenum steel.   The robot according to claim 1, wherein the Vickers hardness of the surface of the external gear is equal to or less than the Vickers hardness of the surface of the internal gear.   The robot according to claim 1, wherein a Vickers hardness of a surface of the external gear is in a range of 400 or more and 520 or less.   The robot according to any one of claims 1 to 3, wherein a residual stress of the external gear is in a range of -950 MPa or more and -450 MPa or less.   The robot according to any one of claims 1 to 4, wherein a surface roughness Ra of external teeth of the external gear is in a range of 0.2 μm to 1.6 μm.   The robot according to any one of claims 1 to 5, wherein surface roughness Ra of the external teeth of the external gear is larger than surface roughness Ra of the internal teeth of the internal gear.   The robot according to any one of claims 1 to 6, wherein the surface roughness Ra of the internal teeth of the internal gear is in the range of 0.1 μm to 0.8 μm.   The robot according to any one of claims 1 to 7, wherein an average crystal grain size of a constituent material of the external gear is smaller than an average crystal grain size of a constituent material of the internal gear.   The constituent material of the external gear includes at least one or more elements of the group 4 element and the group 5 element in a range of 0.01% by mass or more and 0.5% by mass or less. The robot according to any one of the above. A lubricant disposed between the internal gear and the external gear;
10. The lubricant according to any one of claims 1 to 9, wherein the lubricant comprises a base oil, a thickener and an organic molybdenum compound, and the oil separation degree is in the range of 4% by mass to 13.8% by mass. The robot described in Item 1 Internal gear,
A flexible external gear partially meshing with the internal gear;
And a wave generator which contacts the inner peripheral surface of the external gear and moves the meshing position of the internal gear and the external gear in the circumferential direction.
The constituent material of the external gear includes nickel chromium molybdenum steel,
A gear device characterized in that a constituent material of the internal gear includes chromium molybdenum steel.

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