JP2023122770A - Gear device and robot - Google Patents

Abstract

To provide a gear device which is elongated in a life, and a robot having the gear device.SOLUTION: A gear device has an inner tooth gear which is constituted with spherical graphite cast iron as a main material, an outer tooth gear having flexibility and partially engaged with the inner tooth gear, and a wave motion generator contacting with an internal peripheral face of the outer tooth gear, and moving an engagement position of the inner tooth gear and the outer tooth gear in a peripheral direction. The spherical graphite cast iron includes a matrix composition, graphite particulates dispersed in the matrix composition, and a ferrite phase which surrounds the graphite particulates. A width of the ferrite phase is 20% or more and 100% or less of grain diameters of the graphite particulates, and a quantity ratio of the graphite particulates being cores out of a total number of the graphite particulates is equal to or larger than 50%.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a gear system and a robot.

In a robot equipped with a robot arm that includes at least one arm, for example, the joints of the robot arm are rotated by motor drive. At this time, the rotation of the driving force from the motor is decelerated by a speed reducer (gear device) and transmitted to the robot arm.

As such a speed reducer, for example, a strain wave gearing as described in Patent Document 1 is known. The strain wave gearing disclosed in Patent Document 1 includes a ring-shaped rigid internal gear, a cup-shaped flexible external gear disposed inside the ring-shaped, and a cup-shaped flexible external gear that is fitted inside the external gear. and a wave generator with an elliptical profile.

JP-A-2002-349681

In the strain wave gearing disclosed in Patent Document 1, the durability is insufficient particularly at the meshing position between the internal gear and the external gear. Therefore, it is an issue to extend the life of the strain wave gearing.

A gear device according to an application example of the present invention includes:
an internal gear made mainly of spheroidal graphite cast iron;
an external gear that is flexible and partially meshes with the internal gear;
a wave generator that contacts the inner peripheral surface of the external gear and moves the meshing position between the internal gear and the external gear in the circumferential direction;
has
The spheroidal graphite cast iron is
base organization and
graphite particles dispersed in the base structure;
a ferrite phase surrounding the graphite particles with a nucleus;
including
The width of the ferrite phase is 20% or more and 100% or less of the particle size of the graphite particles,
The number ratio of the graphite particles serving as the nuclei is 50% or more of the total number of the graphite particles.

A robot according to an application example of the present invention includes:
a first member;
a second member that rotates with respect to the first member;
a gear device according to an application example of the present invention, which transmits a driving force for relatively rotating the second member;
a driving source that outputs the driving force toward the gear device;
characterized by comprising

It is a side view which shows schematic structure of the robot which concerns on embodiment. It is a longitudinal cross-sectional view showing a gear device according to a second embodiment. FIG. 3 is a front view of the gear device main body shown in FIG. 2 as seen from the direction of the axis line a. 3 is a diagram schematically showing an enlarged observation image of a cross section of a material forming a rigid gear included in the gear device shown in FIG. 2; FIG. FIG. 3 is a cross-sectional view showing a surface state of external teeth of a flexible gear included in the gear device shown in FIG. 2; 5 is a partially enlarged view of the vicinity of ferrite phase-associated particles shown in FIG. 4; FIG. It is a longitudinal section showing a gear device concerning a 3rd embodiment. It is an example of an observed image obtained by magnifying and observing a cross section of spheroidal graphite cast iron. It is an example of an observed image obtained by magnifying and observing a cross section of spheroidal graphite cast iron. It is an example of an observed image obtained by magnifying and observing a cross section of spheroidal graphite cast iron.

BEST MODE FOR CARRYING OUT THE INVENTION A gear device and a robot according to the present invention will now be described in detail based on preferred embodiments shown in the accompanying drawings.

1. First Embodiment First, a robot according to a first embodiment will be described.

FIG. 1 is a side view showing the schematic configuration of the robot according to the first embodiment. In addition, below, for convenience of explanation, the upper side in FIG. 1 is called "upper", and the lower side is called "lower". In addition, the side of the base in FIG. 1 is referred to as the "base side", and the opposite side, that is, the side of the end effector is referred to as the "distal side". In addition, the up-down direction in FIG. 1 is defined as the "vertical direction", and the left-right direction is defined as the "horizontal direction".

A robot 100 shown in FIG. 1 is a robot used, for example, for operations such as supplying, removing, transporting, and assembling precision equipment and parts constituting the same. This 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 section 160, as shown in FIG. . Each part of the robot 100 will be briefly described below.

The base 110 is, for example, fixed to a floor (not shown) with bolts or the like. Inside the base 110 , a control device 190 is installed for centrally controlling the robot 100 . A first arm 120 is connected to the base 110 so as to be rotatable around a first axis J1 (rotational axis) extending in a vertical direction with respect to the base 110 . That is, the first arm 120 rotates relative to the base 110 .

In the base 110, a motor 170 (driving source), which is a first motor such as a servomotor that generates a driving force for rotating the first arm 120, and a first reduction gear that decelerates the rotation of the output shaft of the motor 170. A gear device 10, which is a machine, is installed. The input shaft of gear device 10 is connected to the output shaft of motor 170 , and the output shaft of gear device 10 is connected to first arm 120 . Therefore, when the motor 170 is driven and its driving force is transmitted to the first arm 120 via the gear device 10, the first arm 120 moves relative to the base 110 in the horizontal plane around the first axis J1. to rotate. That is, the motor 170 is a driving source that outputs driving force toward the gear device 10 .

A second arm 130 is connected to the distal end of the first arm 120 so as to be rotatable about a second axis J2 (rotational axis) extending vertically with respect to the first arm 120 . In the second arm 130, although not shown, a second motor that generates driving force for rotating the second arm 130 and a second speed reducer that reduces the rotation of the driving force of the second motor are installed. ing. The driving force of the second motor is transmitted to the second arm 130 via the second speed reducer, so that the second arm 130 rotates in the horizontal plane about the second axis J2 with respect to the first arm 120. do.

A working head 140 is arranged at the tip of the second arm 130 . The working head 140 has a spline nut (not shown) coaxially arranged at the tip of the second arm 130 and a spline shaft 141 inserted through a ball screw nut. The spline shaft 141 is rotatable about the third axis J3 shown in FIG. 1 and vertically movable with respect to the second arm 130 .

In the second arm 130, although not shown, a rotating motor and an elevating motor are arranged. 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 backward, the spline shaft 141 rotates forward and backward around the third vertical axis J3.

On the other hand, the driving force of the lifting 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 backward, the spline shaft 141 moves up and down.

An end effector 150 is connected to the tip of the spline shaft 141 . The end effector 150 is not particularly limited, and examples thereof include an end effector that grips an object to be transferred, an object that processes an object to be processed, and the like.

A plurality of wirings connected to each electronic component arranged in the second arm 130, such as a second motor, a rotation motor, an elevating motor, etc., is connected to a tubular wiring routing portion that connects the second arm 130 and the base 110. It is routed through the inside of 160 to the inside of the base 110 . Further, the plurality of wirings are grouped within the base 110 and routed to the control device 190 installed within the base 110 together with the wiring connected to the motor 170 and the encoder (not shown).

As described above, the robot 100 includes the base 110 as a first member, the first arm 120 as a second member provided rotatably with respect to the base 110, the base 110 and the first A gear device 10 that transmits driving force from one side of the arm 120 to the other side, and a motor 170 that is a driving source that outputs the driving force toward the gear device 10 are provided.

Note that the first arm 120 and the second arm 130 may be collectively regarded as a "second member". Also, the “second member” may include the working head 140 and the end effector 150 in addition to the first arm 120 and the second arm 130 .

Further, in the present embodiment, the first reduction gear is composed of the gear device 10, but the second reduction gear may be composed of the gear device 10. Both may be configured with the gear device 10 . When the second speed reducer is configured by the gear device 10, the first arm 120 can be regarded as the "first member" and the second arm 130 can be regarded as the "second member." Also, instead of the gear device 10, a gear device 10B, which will be described later, may be used.

Further, although the motor 170 and the gear device 10 are provided on the base 110 in this embodiment, they may be provided on the first arm 120 . In this case, the output shaft of the gear device 10 should be connected to the base 110 .

2. 2nd Embodiment Next, the gear apparatus which concerns on 2nd Embodiment is demonstrated.

FIG. 2 is a vertical cross-sectional view showing a gear device according to a second embodiment. FIG. 3 is a front view of the gear device main body shown in FIG. 2 as seen from the direction of the axis a. 4 is a diagram schematically showing an enlarged observation image of a cross section of a material forming a rigid gear provided in the gear device shown in FIG. 2. FIG. 5 is a cross-sectional view showing the meshing positions of the rigid gear and the flexible gear provided in the gear device shown in FIG. 2. FIG. In each drawing, for convenience of explanation, the dimensions of each part are exaggerated as necessary, and the dimensional ratio between the parts does not necessarily match the actual dimensional ratio.

A gear device 10 shown in FIG. 2 is a strain wave gear device, and is used as a speed reducer, for example. This gear device 10 has a gear device main body 1 and a case 5 housing the gear device main body 1 . A lubricant G is arranged in the case 5 of the gear device 10 . Each part of the gear device 10 will be described below. Note that the case 5 may be provided as required, and may be omitted.

2.1. Gear Device Main Body The gear device main body 1 includes a rigid gear 2 which is an internal gear, a flexible gear 3 which is a cup-shaped external gear arranged inside the rigid gear 2, and a flexible gear 3. and a wave generator 4 arranged inside.

In this embodiment, the rigid gear 2 is connected to the base 110 (first member) of the robot 100 via the case 5, and the flexible gear 3 is connected to the first arm 120 (second member) of the robot 100. , the wave generator 4 is connected to the output shaft of the motor 170 arranged on the base 110 of the robot 100 .

When the output shaft of motor 170 rotates, wave generator 4 rotates at the same rotational speed as the output shaft of motor 170 . Since the rigid gear 2 and the flexible gear 3 have different numbers of teeth, they relatively rotate about the axis a while their meshing positions move in the circumferential direction. In this embodiment, since the number of teeth of the rigid gear 2 is larger than that of the flexible gear 3, the flexible gear 3 can be rotated at a rotational speed lower than that of the output shaft of the motor 170. . That is, it is possible to realize a reduction gear having the wave generator 4 on the input shaft side and the flexible gear 3 on the output shaft side.

Depending on the form of the case 5, even if the flexible gear 3 is connected to the base 110 and the rigid gear 2 is connected to the first arm 120, the gear device 10 can be used as a speed reducer. Further, even if the output shaft of the motor 170 is connected to the flexible gear 3, the gear device 10 can be used as a speed reducer. It may be connected to the first arm 120 . When the gear device 10 is used as a gearbox, that is, when the flexible gear 3 is rotated at a rotational speed higher than the rotational speed of the output shaft of the motor 170, the relationship between the input side and the output side described above is reversed. should be

As shown in FIGS. 2 and 3, the rigid gear 2 is a ring-shaped internal gear having internal teeth 23, which is made of a rigid body that does not substantially flex in the radial direction. In this embodiment the rigid gear 2 is a spur gear. That is, the internal teeth 23 have tooth lines parallel to the axis a. Note that the tooth traces 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 double 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 radially flexibly deformable gear, and is an external gear having external teeth 33 meshing with a portion of the internal teeth 23 of the rigid gear 2 . Also, the number of teeth of the flexible gear 3 is smaller than the number of teeth of the rigid gear 2 . Since the number of teeth of the flexible gear 3 and the number of teeth of the rigid gear 2 are different from each other in this manner, a speed reducer can be realized.

In this embodiment, the flexible gear 3 has a cup shape with an opening 36 opened at one end in the direction of the axis a, that is, the right end in FIG. External teeth 33 are formed. Here, the flexible gear 3 has a cylindrical body portion 31 around the axis a and a bottom portion 32 connected to the other end of the body portion 31 in the direction of the axis a. This makes it easier for the end of the opening 36 to flex in the radial direction than the bottom 32 of the body 31 , so that the flexible gear 3 meshes well with the rigid gear 2 . Furthermore, the rigidity of the bottom portion 32 to which the shaft 62, which is the output shaft of the gear device 10, is connected can be increased. For this reason, the gear device 10 has a very small backlash and is suitable for applications in which reversal is repeated. In addition, since the ratio of the number of teeth that mesh at the same time is large, the force applied to each tooth is small, and the torque capacity of the gear device 10 can be increased.

As shown in FIGS. 2 and 3, the wave generator 4 is arranged inside the flexible gear 3 and is rotatable around the axis a. Then, the wave generator 4 deforms the cross section of the opening 36 of the flexible gear 3 into an elliptical or elliptical shape having a major axis La and a minor axis Lb, so that the external teeth 33 of the flexible gear 3 meshes with the internal teeth 23 of the rigid gear 2 . The flexible gear 3 and the rigid gear 2 are meshed internally and externally so as to be rotatable around the same axis a.

In this embodiment, the wave generator 4 has a cam 41 and a bearing 42 attached to the outer circumference of the cam 41 . The cam 41 has a shaft portion 411 rotating around the axis a and a cam portion 412 projecting from one end of the shaft portion 411 .

A shaft 61 that serves as an input shaft of the gear device 10 , for example, is connected to the shaft portion 411 . The outer peripheral surface of the cam portion 412 has an elliptical 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 arranged therebetween. The inner ring 421 is fitted on the outer peripheral surface of the cam portion 412 of the cam 41 and elastically deforms along the outer peripheral surface of the cam portion 412 into an elliptical or oval shape. Along with this, the outer ring 423 is also elastically deformed into an elliptical or oval shape. The outer peripheral surface of the inner ring 421 and the inner peripheral surface of the outer ring 423 each have a raceway surface that guides and rolls the plurality of balls 422 along the circumferential direction. The plurality of balls 422 are held by a retainer (not shown) so as to maintain constant intervals in the circumferential direction. Note that grease (not shown) is arranged in the bearing 42 . This grease may be the same as or different from the lubricant G described below.

In such a wave generator 4, the orientation of the cam portion 412 changes as the cam 41 rotates about the axis a, and accordingly the outer peripheral surface of the outer ring 423 also deforms. 3 are moved in the circumferential direction.

Next, each constituent material of the rigid gear 2, the flexible gear 3 and the wave generator 4 will be described. Examples of these constituent materials include iron-based materials.

Although the flexible gear 3 may be made of other types of steel as the main material, it is preferably made of nickel-chromium-molybdenum steel as the main material. Nickel-chromium-molybdenum steel becomes a strong steel through appropriate heat treatment, and has excellent mechanical properties such as fatigue strength.

Examples of nickel-chromium-molybdenum steel include steel materials of the type specified in JIS G 4053:2016. Specifically, the symbols defined in the JIS standard include steel materials such as SNCM220, SNCM240, SNCM415, SNCM420, SNCM431, SNCM439, SNCM447, SNCM616, SNCM625, SNCM630, and SNCM815. Of these, as the nickel-chromium-molybdenum steel used as the constituent material of the flexible gear 3, it is particularly preferable to use SNCM439 from the viewpoint of excellent mechanical properties.

In addition, the constituent material of the flexible gear 3 may include materials other than nickel-chromium-molybdenum steel. That is, the flexible gear 3 may be made of a composite material in which nickel-chromium-molybdenum steel and other materials are combined. However, it is sufficient that nickel-chromium-molybdenum steel accounts for a larger mass ratio of the whole than other materials, that is, the main material. Also, the mass ratio of the nickel-chromium-molybdenum steel in the constituent material of the flexible gear 3 is preferably 70% or more, more preferably 90% or more.

On the other hand, the rigid gear 2 is mainly made of spheroidal graphite cast iron. Spheroidal graphite cast iron is also called ductile cast iron, and is cast iron containing spherical graphite particles 21 and a matrix structure 22 existing around them, as shown in FIG. 4, for example. In the present embodiment, in the classification based on the roundness coefficient of the graphite particles 21 specified in Annex B of JIS G 5505: 2013, the roundness coefficient of the graphite particles 21 by image analysis is within the range of 0.56 to 1.00. The graphite cast iron in is referred to as "spheroidal graphite cast iron". That is, graphite cast iron containing graphite particles 21 having a certain degree of roundness or more on the image is spheroidal graphite cast iron. Note that this image analysis refers to analysis by an image analysis apparatus that obtains the roundness coefficient fully automatically or semi-automatically. The area of the target area for image analysis shall be 4 mm ² or more.

In such a spheroidal graphite cast iron, since the graphite particles 21 are spherical, the graphite particles 21 are less likely to be the starting point of cracks. can be demonstrated. As a result, the spheroidal graphite cast iron has excellent strength and toughness. Therefore, the life of the rigid gear 2 can be extended.

In addition, since the graphite particles 21 contained in the spheroidal graphite cast iron act as a lubricant, the internal teeth 23 of the rigid gear 2 are less likely to adhere. Therefore, the wear of the rigid gear 2 can be further reduced, and the life of the rigid gear 2 can be extended.

In addition, the spheroidal graphite cast iron can convert transmitted vibrations into thermal energy at the boundaries between the graphite particles 21 and the matrix structure 22 and dissipate them. That is, spheroidal graphite cast iron has high vibration damping properties. Therefore, vibration and noise generated in the rigid gear 2 can be reduced.

Furthermore, spheroidal graphite cast iron has high thermal conductivity and excellent heat dissipation. For this reason, the heat dissipation of the rigid gear 2 is also improved, and it is possible to prevent the rigid gear 2 from becoming extremely hot.
Due to the effects described above, the life of the gear device 10 can be extended.

Note that the life of the gear device 10 means, for example, the time from the start of use of the gear device 10 to the occurrence of damage to any part of the gear device 10 . Such damage includes, for example, breaking of the rigid gear 2 or the flexible gear 3 .

The spheroidal graphite cast iron, which is the main material of the rigid gear 2, includes, for example, materials of the type specified in JIS G 5502:2001. Specifically, the symbols specified in the JIS standard are FCD350-22, FCD350-22L, FCD400-18, FCD400-18L, FCD400-15, FCD400-10, FCD450-10, FCD500-7, FCD600-3 , FCD700-2, FCD800-2 and the like.

Further, the alloy composition of the spheroidal graphite cast iron is, for example, mainly composed of Fe (iron), C (carbon): 2.0% by mass or more and 6.0% by mass or less, Si (silicon): 0.5% by mass. 3.5% by mass or less, and Mn (manganese): 0.4% by mass or more and 1.0% by mass or less. Furthermore, the spheroidal graphite cast iron may contain Cu (copper), Ni (nickel), Cr (chromium), Sn (tin), Mg (magnesium), and the like.

Here, the spheroidal graphite cast iron, which is the main material of the rigid gear 2, contains a ferrite phase 25 in addition to the graphite particles 21 and the base structure 22 described above. The ferrite phase 25 is adjacent to and surrounds the core of the graphite particles 21 in the structure composed of ferrite, and the width in the radial direction is 20% or more of the particle size of the graphite particles 21. 100% or less. That is, the spheroidal graphite cast iron may contain a ferrite structure, and among these, the ferrite structure adjacent to the graphite particles 21 and having a width within the above range is called "ferrite phase 25". Graphite grains 21 having adjacent ferrite phases 25 are particularly referred to as “ferrite phase-associated grains 26”.

The ferrite phase 25 may be adjacent to all of the graphite particles 21 contained in the spheroidal graphite cast iron, or some may not be adjacent to the ferrite phase 25 . Further, a ferrite structure that does not correspond to the ferrite phase 25 may be adjacent to the graphite particles 21 .

In this specification, the graphite particles 21 to which the ferrite phase 25 is not adjacent and the graphite particles 21 to which the ferrite structure not corresponding to the ferrite phase 25 is adjacent are particularly referred to as "other particles".

In the spheroidal graphite cast iron, which is the main material of the rigid gear 2, the number ratio of the ferrite phase-associated particles 26 to the total number of the graphite particles 21 is 50% or more. Thereby, in the spheroidal graphite cast iron, both mechanical properties represented by fatigue strength and surface lubricity can be achieved.

First, the width of the ferrite phase 25 will be explained. In the spheroidal graphite cast iron, which is the main material of the rigid gear 2, the width of the ferrite phase 25 is 20% or more and 100% or less of the particle size of the graphite particles 21, as described above. That is, the ferrite phase-associated particles 26 are accompanied by the ferrite phase 25 whose width is optimized. Since the spheroidal graphite cast iron contains such ferrite phase-associated particles 26 , the ferrite phase 25 with an appropriate width is exposed around the graphite particles 21 on the surface of the internal tooth 23 , particularly on the tooth surface. The ferrite phase 25 has a lower hardness than the base structure 22 . Therefore, the ferrite phase 25 is worn relatively faster than the base structure 22 and is dented, thereby promoting the formation of the recesses 24 on the surface. Further, since the concave portions 24 are adjacent to the ferrite phase-associated particles 26, the exposed area of the ferrite phase-associated particles 26 (the exposed area of graphite) is increased. This further improves the lubricity of the surfaces of the internal teeth 23 .

The concave portion 24 serves as a space for the lubricant G to enter and accumulate at the meshing position between the internal teeth 23 and the external teeth 33 . In other words, the rigid gear 2 having the recesses 24 is excellent in holding the lubricant G on the surface. As a result, wear of the surfaces of the internal teeth 23 and the external teeth 33 can be suppressed, and durability can be enhanced. As a result, the life of the gear device 10 can be extended.

The ferrite phase 25 is a structure mainly composed of ferrite. Ferrite is a structure that is also called an α solid solution. When the cross section of the spheroidal graphite cast iron is enlarged and observed, the ferrite phase 25 appears in a color different from that of the graphite particles 21 and the matrix structure 22 due to appropriate etching treatment, so the range of the ferrite phase 25 can be specified based on the appearance. . For example, in an image observed with an optical microscope, the ferrite phase 25 appears closer to white than the graphite particles 21 and the base structure 22 . As an etching solution used for the etching process, for example, nitric acid alcohol having a concentration of 5% is used. For magnifying observation, an optical microscope or an electron microscope is used.

FIG. 6 is a partially enlarged view of the vicinity of the ferrite phase-associated particles 26 shown in FIG.
The width W of the ferrite phase 25 shown in FIG. 6 means the length of the ferrite phase 25 in the radial direction of the ferrite phase-associated particles 26 . The radial direction means that when a straight line is drawn to connect the center O of the ferrite phase-associated particle 26 and the points P1 to P4 on the outer periphery of the ferrite phase 25 adjacent to the ferrite phase-associated particle 26, each straight line extension direction. The width W of the ferrite phase 25 is obtained as follows. First, as shown in FIG. 6, four points P1 to P4 are placed on the outer circumference of the ferrite phase 25, and the radial widths w1 to w4 at each point are measured. Next, the average value of the widths w1 to w4 is calculated. This average value becomes the width W of the ferrite phase 25 . The center O of the ferrite phase-associated particles 26 is the center of a circumscribed circle having a diameter equal to the major axis of the ferrite phase-associated particles 26 . Also, the number of points placed on the outer circumference of the ferrite phase 25 may be five or more.

Moreover, the particle size of the graphite particles 21 is the diameter of a circle having the same area as the ferrite phase-associated particles 26 .

The ferrite phase 25 may be adjacent to the ferrite phase-associated particles 26, but preferably has an annular shape surrounding the ferrite phase-associated particles 26 as shown in FIG. Since the ferrite phase 25 is ring-shaped, the exposed range of the ferrite-phase-associated particles 26 becomes wider. As a result, the lubricity of the surfaces of the internal teeth 23 is further enhanced.

Next, the number ratio of the ferrite phase-associated particles 26 will be described. In the spheroidal graphite cast iron, which is the main material of the rigid gear 2, the ferrite phase-associated particles 26 account for 50% or more of the total number of the graphite particles 21, as described above.

The spheroidal graphite cast iron may contain not only the ferrite phase-associated particles 26 but also the other particles described above. In the target region, when the number of ferrite phase-associated particles 26 is N1 and the number of other particles is N2, the number ratio [%] of ferrite phase-associated particles 26 is calculated as N1/(N1+N2)×100. calculated by the formula.

If the number ratio of the ferrite-phase-associated particles 26 is within the above range, the effect of the ferrite-phase 25 adjacent to the ferrite-phase-associated particles 26, that is, the lubricant G The effect of increasing the lubricity due to the accumulation of dust and the effect of increasing the lubricity due to the increase in the exposed area of the ferrite phase-associated particles 26 can be sufficiently obtained.

On the other hand, when the number ratio of the ferrite phase-associated particles 26 is below the above range, the following concerns may arise.

First, when the width W of the ferrite phase 25 is less than 20% of the particle size of the graphite particles 21, the effect of the ferrite phase 25, that is, the effect of increasing the lubricity due to the accumulation of the lubricant G in the recesses 24, is obtained. become limited. Therefore, the life of the gear device 10 cannot be sufficiently extended.

Moreover, when the width W of the ferrite phase 25 is more than 100% of the particle size of the graphite particles 21, the ferrite phase 25 exists excessively. In this case, since the base structure 22 is relatively reduced, mechanical properties such as fatigue strength are lowered. Therefore, the life of the gear device 10 cannot be sufficiently extended.

Furthermore, when the ferrite phase 25 is not adjacent to the ferrite phase-associated particles 26, that is, when the ferrite phase 25 is separated from the ferrite phase-associated particles 26, the exposed area of the ferrite phase-associated particles 26 cannot be increased. Therefore, the effect of increasing lubricity due to an increase in exposed area is limited. Therefore, the life of the gear device 10 cannot be sufficiently extended.

Based on the above, from the viewpoint of increasing both the lubricity of the surface of the internal teeth 23 and the mechanical properties such as fatigue strength, it is required to reduce the existence ratio of other particles. Therefore, by setting the number ratio of the ferrite phase-associated particles 26 to 50% or more of the total number of the graphite particles 21 contained in the target region, the number ratio of the other particles is relatively suppressed to less than 50%. be able to. As a result, the mechanical properties such as the fatigue strength of the rigid gear 2 can be enhanced while the lubricity of the surfaces of the internal teeth 23 is enhanced. As a result, the life of the gear device 10 can be extended.

The number ratio of the ferrite phase-associated particles 26 is preferably 60% or more, more preferably 80% or more.

The ferrite phase 25 and the ferrite phase-associated particles 26 have been described above, but the width W of the ferrite phase 25 and the number ratio of the ferrite phase-associated particles 26 can be controlled by the production conditions when producing the spheroidal graphite cast iron.

For example, by reducing the ratio of pearlite structure in spheroidal graphite cast iron, the ferrite phase 25 relatively increases and the width W increases. In order to reduce the ratio of the pearlite structure, for example, if the amount of elements that promote the formation of silicon ferrite structure contained in the raw material is increased, or the pearlite stabilizing elements such as copper, tin, manganese, and chromium are reduced, good. If the width W can be adjusted in this way, the number ratio of the ferrite phase-associated particles 26 can also be controlled.

In addition, when the spheroidal graphite cast iron is solidified, the cooling rate may be controlled to a condition that facilitates the formation of ferrite structure, or heat treatment may be performed to promote the formation of ferrite structure. Such a method can also increase the width W of the ferrite phase 25 .

Next, the base structure 22 will be explained. The base structure 22 includes, for example, a pearlite structure or a mixed structure of a pearlite structure and a ferrite structure.

Among them, the pearlite structure is a mixed structure in which a ferrite structure and a layered cementite structure are alternately arranged, and the cementite structure contains a large amount of iron carbide. Also, the term "layered" refers to a state in which the aspect ratio defined by the major axis/minor axis of the crystal structure is, for example, 5 or more. By including such a pearlite structure in the matrix structure 22, the fatigue strength of the spheroidal graphite cast iron can be particularly enhanced.

The pearlite structure may exist alone or may exist as a mixed structure with a ferrite structure. In the mixed structure of the pearlite structure and the ferrite structure, the hardness is mainly increased in the pearlite structure, and the toughness is mainly increased in the ferrite structure, so that both high strength and toughness can be achieved.

In the base structure 22, the total area ratio of the pearlite structure and the ferrite structure is preferably 60% or more, more preferably 90% or more. As a result, the above effects are exhibited more reliably.

Note that the base structure 22 may contain a martensite structure, an austenite structure, a sorbite structure, a bainite structure, etc., in addition to the structures described above.

Also, the rigid gear 2 may contain materials other than the spheroidal graphite cast iron described above. However, in that case, the area ratio of the above-described spheroidal graphite cast iron in the entire rigid gear 2 should be larger than the area ratio of other materials, that is, the main material should be spheroidal graphite cast iron. Further, the area ratio of the spheroidal graphite cast iron in the rigid gear 2 is preferably 70% or more, more preferably 90% or more.

As described above, the gear device 10 includes the rigid gear 2 that is an internal gear, the flexible gear 3 that is an external gear that has flexibility and partially meshes with the rigid gear 2, and the flexible and a wave generator 4 that contacts the inner peripheral surface of the gear 3 and moves the meshing position between the rigid gear 2 and the flexible gear 3 in the circumferential direction. The rigid gear 2 is mainly made of spheroidal graphite cast iron. This spheroidal graphite cast iron includes a base structure 22 , graphite particles 21 dispersed in the base structure 22 , and a ferrite phase 25 . The ferrite phase 25 surrounds the graphite particles 21 as nuclei. Moreover, the width of the ferrite phase 25 is 20% or more and 100% or less of the particle size of the graphite particles 21 . Then, the number ratio of the graphite particles 21 serving as the nuclei, that is, the number ratio of the ferrite phase-associated particles 26, out of the total number of the graphite particles 21 is 50% or more.

According to the gear device 10 as described above, it is possible to improve mechanical properties such as fatigue strength of the rigid gear 2 while improving the lubricity of the surfaces of the internal teeth 23 of the rigid gear 2 . As a result, the durability of the meshing position between the rigid gear 2 and the flexible gear 3 can be enhanced. As a result, the life of the gear device 10 can be extended.

Moreover, the base structure 22 preferably includes a pearlite structure or a mixed structure of a pearlite structure and a ferrite structure. Thereby, the fatigue strength of the spheroidal graphite cast iron can be particularly enhanced.

Moreover, it is preferable that the flexible gear 3 is mainly made of nickel-chromium-molybdenum steel. Nickel-chromium-molybdenum steel becomes a strong steel through appropriate heat treatment, and has excellent mechanical properties such as fatigue strength.

Moreover, the Vickers hardness of the surface of the rigid gear 2, which is an internal gear, is preferably equal to or less than the Vickers hardness of the surface of the flexible gear 3, which is an external gear. As a result, the surfaces of the internal teeth 23 are appropriately worn, so that the concave portions 24 are formed more easily, and the lubricant G can be retained more effectively. In addition, the graphite particles 21 are easily exposed, thereby further enhancing the lubricity of the surfaces of the internal teeth 23 . As a result, it is particularly easy to extend the life of the gear device 10 .

The Vickers hardness is measured according to the Vickers hardness test-test method specified in JIS Z 2244:2009. Here, the test force of the indenter is 2.0 N, and the test force holding time is 15 seconds. Then, the average value of the measurement results at 10 locations is taken as the Vickers hardness.

The Vickers hardness of the surface of the flexible gear 3 which is an external gear is preferably in the range of more than 350 to 520 or less, more preferably in the range of 450 to 520. As a result, the mechanical strength and 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, if the Vickers hardness is too low, the strength of the flexible gear 3 is insufficient, and the flexible gear 3 may not withstand the load stress and may be easily broken. On the other hand, if the Vickers hardness is too high, the toughness of the flexible gear 3 will be reduced, and it will tend to break easily due to impact or the like. may reduce the durability of

The Vickers hardness of the surface of the rigid gear 2, which is an internal gear, is preferably in the range of 250 or more and 350 or less, more preferably in the range of 280 or more and 330 or less. As a result, the mechanical strength and toughness of the rigid gear 2 can be balanced, and the life of the rigid gear 2 can be suitably extended. On the other hand, if the Vickers hardness is too low, the wear of the rigid gear 2 may proceed excessively, and the transmission efficiency of the gear device 10 may decrease. Moreover, the rigid gear 2 may not withstand the load stress and may be easily broken. On the other hand, if the Vickers hardness is too high, the impact when the rigid gear 2 and the flexible gear 3 are meshed becomes large, and the flexible gear 3 is broken or the durability of the gear device 10 is reduced. There is a risk.

Moreover, it is preferable that compressive residual stress is applied to at least the surfaces of the external teeth 33 of the flexible gear 3 . As a result, the fatigue strength of the external teeth 33 can be increased, 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.

In order to obtain the effects described above, the residual stress of the flexible gear 3, for example, the compressive residual stress, is preferably in the range of -950 MPa or more and -450 MPa or less, and in the range of -950 MPa or more and -550 MPa or less. is more preferably in the range of −950 MPa or more and −750 MPa or less. On the other hand, if the absolute value of the residual stress is too small, the aforementioned effects may be reduced. On the other hand, if the absolute value of the residual stress is too large, the deformation of the external teeth 33 due to the application of the residual stress increases, which may hinder proper operation of the gear device 10 .

Moreover, such compressive residual stress can be imparted by subjecting the surface of the flexible gear 3 to shot peening. When shot peening is applied to the surface of the flexible gear 3 in this way, minute irregularities are formed on the surface of the flexible gear 3 as shown in FIG. As a result, the lubricant G can be easily retained on the surface of the flexible gear 3 . As a result, the life of the gear device 10 can be further extended.

The surface roughness Ra of the external teeth 33 of the flexible gear 3, which is an external gear, is preferably in the range of 0.2 μm or more and 1.6 μm or less, and is in the range of 0.2 μm or more and 0.8 μm or less. It is more preferable to have As a result, the wear of the rigid gear 2 is reduced, and the lubricant G is easily retained on the external teeth 33 of the flexible gear 3, thereby suitably extending the life of the flexible gear 3 and the rigid gear 2. be able to. On the other hand, if the surface roughness is too small, the effect of retaining the lubricant G on the external teeth 33 of the flexible gear 3 may be reduced. On the other hand, if the surface roughness is too large, the contact resistance of the surface of the external teeth 33 will increase, the efficiency of the gear device 10 will decrease, and the rigid gear 2 will wear easily, reducing the durability of the gear device 10. There is a risk of The surface roughness Ra is the arithmetic average roughness Ra of the external teeth 33 and is measured according to the method specified in JIS B 0601:2013.

On the other hand, the surface roughness Ra of the internal teeth 23 of the rigid gear 2, which is an internal gear, is preferably in the range of 0.1 μm or more and 0.8 μm or less, and more preferably in the range of 0.1 μm or more and 0.4 μm or less. It is more preferable to have 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, if the surface roughness is too small, the cost for finishing the tooth profile surface of the internal teeth 23 increases, but the efficiency improvement effect may decrease. On the other hand, if the surface roughness is too large, the contact resistance of the surfaces of the internal teeth 23 increases, and the efficiency of the gear device 10 may decrease. The surface roughness Ra is the arithmetic mean roughness Ra of the internal teeth 23, and is measured according to the method specified in JIS B 0601:2013.

Moreover, the surface roughness Ra of the external teeth 33 of the flexible gear 3, which is an external gear, is preferably larger than the surface roughness Ra of the internal teeth 23 of the rigid gear 2, which is an internal gear. As a result, while facilitating holding of the lubricant G on the external teeth 33 of the flexible gear 3, the contact resistance between the flexible gear 3 and the rigid gear 2 is reduced, so that the flexible gear 3 and the rigid gear 2 can be suitably extended.

In addition, the average crystal grain size of the constituent material of the flexible gear 3, which is an external gear, is preferably smaller than the average crystal grain diameter of the constituent material of the rigid gear 2, which is an internal gear. By setting such a size relationship for the average crystal grain size of the constituent materials of the internal teeth 23 and the external teeth 33 , the crystal grain size of the external teeth 33 is reduced, and the lubricant G is retained on the external teeth 33 . can be made easier. Therefore, the lubricant G can be retained on the external teeth 33 against the centrifugal force due to the rotation of the external teeth 33 . Here, the lubricant G is preferentially retained at grain boundaries present on the surfaces of the external teeth 33 . It is considered that this is because the grain boundaries play a role like minute recesses or grooves for containing the lubricant G. Therefore, by reducing the crystal grain size of the external teeth 33, the density of the crystal grain boundaries existing on the surfaces of the external teeth 33 is increased, and along with this, the lubricant G is easily retained on the surfaces of the external teeth 33. .

Further, by reducing the crystal grain size of the external teeth 33, the mechanical strength of the external teeth 33 can be increased, and the toughness of the external teeth 33 can be increased. As described above, the external teeth 33 are required to have higher mechanical strength and toughness than the internal teeth 23 because they repeatedly deform as the meshing positions of the rigid gear 2 and the flexible gear 3 move. . Therefore, increasing the mechanical strength and toughness of the external teeth 33 is extremely beneficial.

The average grain size is measured according to JIS G 0551:2013 "Steel-Microscopic test method for grain size". The average grain size is measured by etching the test piece, that is, the surface of the internal or external teeth with a corrosive solution to make grain boundaries appear, and observing the grain boundaries that have appeared with a microscope. As the etchant, 5% Nital, that is, 5% nitric acid-ethyl alcohol, or a picric acid aqueous solution-based etchant, that is, 2% picric acid-0.2% sodium chloride-0.1% sulfuric acid-distilled water use. In addition, it is sufficient that at least the internal teeth 23 and the external teeth 33 satisfy the size relationship of the average crystal grain size as described above, and even if the other portions of the rigid gear 2 and the flexible gear 3 do not satisfy each other. This is good, but if other portions are also satisfied, the effect will be remarkable. In addition, the crystal grain size of the internal teeth 23 and the external teeth 33 can be adjusted, for example, according to the materials constituting these and the heat treatment at the time of manufacture.

Assuming that the average crystal grain size of the constituent material of the external teeth 33 is d33 and the average crystal grain size of the constituent material of the internal teeth 23 is d23, d33 and d23 should satisfy the relationship d33<d23 as described above. , preferably 1.2 ≤ d23/d33 ≤ 100, more preferably 2 ≤ d23/d33 ≤ 50, in order to suitably exhibit the two effects as described above. On the other hand, if d23/d33 is too small, there is a possibility that the balance between the above-mentioned two effects will deteriorate. On the other hand, if d23/d33 is too large, the strength difference between the internal teeth 23 and the external teeth 33 becomes too large, and one of the internal teeth 23 and the external teeth 33 may wear out quickly.

The average crystal grain size of the constituent material of the internal teeth 23 is preferably in the range of 20 μm or more and 150 μm or less, more preferably in the range of 30 μm or more and 100 μm or less, and is in the range of 30 μm or more and 50 μm or less. is more preferred. Thereby, the lubricant G can be effectively retained on the internal teeth 23 . Moreover, when the internal teeth 23 are made of metal, the mechanical strength of the internal teeth 23 can be improved. On the other hand, if the average crystal grain size is too small, the formed graphite particles 21 will also be small, and the lubricity of the internal teeth 23 may deteriorate. 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 . If the entire rigid gear 2 satisfies the above-described average crystal grain size range, the above-described effect becomes remarkable.

The average crystal grain size of the constituent material of the external teeth 33 is preferably in the range of 0.5 μm or more and 30 μm or less, more preferably in the range of 5 μm or more and 20 μm or less, and in the range of 5 μm or more and 15 μm or less. It is even more preferable to have Thereby, the lubricant G can be effectively retained on the external teeth 33 . Moreover, when the external teeth 33 are made of metal, the mechanical strength of the external teeth 33 can be improved. On the other hand, if the average crystal grain size is too small, the workability in manufacturing the external teeth 33 is poor, and the depth of the recesses caused by the crystal grain boundaries existing on the surface of the external teeth 33 becomes small. On the contrary, it may become difficult to hold the lubricant G on the external teeth 33 . On the other hand, if the average crystal grain size is too large, the effect of retaining the lubricant G on the external teeth 33 tends to decrease, and it is difficult to ensure the mechanical strength and toughness required for the external teeth 33. may become In addition, if the entire flexible gear 3 satisfies the range of the average crystal grain size described above, the above-described effect becomes remarkable.

The constituent material of the flexible gear 3, which is an external gear, preferably contains a group 4 element or a group 5 element within the range of 0.01% by mass or more and 0.5% by mass or less. As a result, even if heat treatment is performed in the manufacturing process of the flexible gear 3, the growth of crystal grains of the iron-based material forming the flexible gear 3 can be suppressed to reduce the crystal grain size. Therefore, the mechanical strength of the flexible gear 3 can be improved.

Examples of Group 4 elements and Group 5 elements include titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), and tantalum (Ta). One of them is used alone or in combination of two or more. Moreover, the constituent material of the flexible gear 3 preferably contains at least one of zirconium (Zr) and niobium (Nb), and contains both zirconium (Zr) and niobium (Nb). is more preferred. As a result, the effect of suppressing the growth of crystal grains of the ferrous material forming the flexible gear 3, that is, the effect of suppressing the growth of crystal grains, can be exhibited more effectively. It should be noted that the constituent material of the flexible gear 3 may contain elements other than the Group 4 elements and Group 5 elements. Yttrium (Y) may be included from the viewpoint of effectively suppressing grain growth.

In addition, the content of the Group 4 element or Group 5 element is preferably in the range of 0.05% by mass or more and 0.3% by mass or less, and 0.1% by mass or more and 0.2% by mass or less. It is more preferable to be within the range. As a result, the effect of suppressing grain growth can be exhibited more effectively. On the other hand, if the content is too small, the effect of suppressing grain growth may be significantly reduced. On the other hand, if the content is too large, not only is it not possible to obtain any further effect of suppressing grain growth, but also the toughness of the flexible gear 3 is lowered, and the mechanical strength of the flexible gear 3 is rather lowered. , the workability in manufacturing the flexible gear 3 may be extremely deteriorated. In addition, when multiple types of elements are added, the above content is the total content of the multiple types of elements.

Further, the robot 100 described above includes a base 110 that is a first member, a first arm 120 that is a second member that rotates with respect to the base 110, and a drive mechanism that rotates the first arm 120 relatively. A gear device 10 that transmits force and a motor 170 that is a drive source that outputs a driving force to the gear device 10 are provided.

According to such a robot 100, since the life of the gear device 10 is extended, the frequency of replacement or repair of the gear device 10 can be reduced. As a result, it is possible to secure a longer substantial operating time of the robot 100 , improve the work efficiency of the robot 100 , and improve the reliability of the robot 100 .

2.2. Case The case 5 shown in FIG. 2 includes a substantially plate-like lid 11 supporting a shaft 61 via a bearing 13 and a cup-shaped main body 12 supporting a shaft 62 via a bearing 14 . have. Here, the cover 11 and the main body 12 are connected 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 body 1 is fixed to at least one of the lid 11 and the body 12 by screwing or the like.

An inner wall surface 111 of the lid 11 has a shape extending in a 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 has a shape along the outer peripheral surface and the bottom surface of the flexible gear 3 . Such a case 5 is fixed to the base 110 of the robot 100 . Here, the cover 11 may be separate from the base 110 and may be fixed to the base 110 by screwing or the like, or may be integrated with the base 110 . Also, the material of the case 5 including the lid 11 and the main body 12 is not particularly limited, but examples thereof include metal materials and ceramic materials.

2.3. Lubricant Lubricant G is, for example, grease, ie a semi-solid lubricant, and is arranged at least at the meshing positions of the rigid gear 2 and the flexible gear 3 . Alternatively, it may be arranged between the flexible gear 3 and the wave generator 4 . Hereinafter, the portion where the lubricant G is arranged is referred to as a "lubrication target portion". By supplying the lubricant G to such a lubrication target portion, the friction of the lubrication target portion can be reduced.

Lubricant G preferably contains a base oil, a thickener, and an organomolybdenum compound. Since the lubricant G contains an organic molybdenum compound, it is possible to effectively reduce the friction at the meshing portion between the rigid gear 2 and the flexible gear 3 .

Examples of base oils include mineral oils such as paraffinic and naphthenic oils, and synthetic oils such as polyolefins, esters, and silicones, and these oils may be used alone or in combination of two or more. Examples of thickeners include soaps such as calcium soap, calcium complex soap, sodium soap, aluminum soap, lithium soap, lithium complex soap, polyurea, sodium terephthalate, and polytetrafluoroethylene (PTFE). , organic bentonite, silica gel and the like, and the like, and one of these can be used alone or two or more of them can be used in combination. Thus, in the lubricant G containing a base oil and a thickener as a composition, the three-dimensional structure formed by the thickener is intricately entwined to hold the base oil. It exerts a lubricating action by letting it seep out little by little.

The content of the base oil in the lubricant G is preferably 75% by mass or more and 85% by mass or less, and the content of the thickener in the lubricant G is preferably 10% by mass or more and 20% by mass or less. . Thereby, the lubricating performance of the lubricant G can be improved.

Organomolybdenum compounds function as solid lubricants or extreme pressure agents. As a result, it is possible to effectively reduce the friction in the lubrication target portion, and effectively prevent seizure and scuffing even when the lubrication target portion is in an extreme pressure lubrication state. In particular, organic molybdenum compounds exhibit extreme pressure properties and wear resistance equivalent to those of molybdenum disulfide, and are superior in oxidation stability to molybdenum disulfide. Therefore, the life of the lubricant G can be extended.

The content of the organic molybdenum compound in the lubricant G is preferably 1% by mass or more and 5% by mass or less. As a result, the performance of the organomolybdenum compound as an extreme-pressure agent can be exhibited more easily, and the properties of the lubricant G are significantly improved. In addition to the organic molybdenum compound, other extreme pressure agents such as zinc dialkyldithiophosphate may be used as the extreme pressure agent or solid lubricant.

In addition to the base oil, thickener and organic molybdenum compound described above, the lubricant G includes additives such as antioxidants and rust inhibitors, solid lubricants such as graphite, molybdenum disulfide, and polytetrafluoroethylene. may contain.

3. 3rd Embodiment Next, the gear apparatus which concerns on 3rd Embodiment is demonstrated.
FIG. 7 is a vertical cross-sectional view showing a gear device according to the third embodiment.

This embodiment is the same as the above-described second embodiment, except that the configuration of the external gear and the configuration of the case associated therewith are different. In addition, in the following description, regarding this embodiment, differences from the above-described embodiment will be mainly described, and the description of the same matters will be omitted. Moreover, in FIG. 7, the same code|symbol is attached|subjected about the structure similar to embodiment mentioned above.

A gear device 10B shown in FIG. 7 has a gear device main body 1B, a case 5B housing the gear device main body 1B, and a lubricant G. Case 5B may be omitted.

The gear device 10B has a flexible gear 3B, which is a hat-shaped external gear arranged inside the rigid gear 2, that is, a cap-shaped external gear. This flexible gear 3B has a flange portion 32B that is connected to one end of a cylindrical body portion 31 and protrudes on the side opposite to the axis a. An output shaft of the gear device 10B (not shown) is attached to the flange portion 32B. The materials and the like of the flexible gear 3B are the same as those of the flexible gear 3 according to the second embodiment.

The case 5B includes a substantially plate-like lid body 11B supporting, via bearings 13, a shaft 61, for example, the input shaft of the gear device 10B, and a cross attached to the flange portion 32B of the flexible gear 3B. and a roller bearing 18 .

The cover 11B is fixed to one side of the rigid gear 2, ie, the right side in FIG. 7, by screwing or the like. Also, the cross roller bearing 18 has an inner ring 15, an outer ring 16, and a plurality of rollers 17 arranged therebetween. The inner ring 15 is provided along the outer periphery of the body portion 31 of the flexible gear 3 and fixed to the other side of the rigid gear 2, that is, the left side in FIG. On the other hand, the outer ring 16 is fixed to the surface of the flange portion 32B of the flexible gear 3B on the body portion 31 side by screwing or the like.

An inner wall surface 111B of the lid 11B has a shape extending in a direction perpendicular to the axis a so as to cover the opening 36 of the flexible gear 3B. In addition, 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.

According to the third embodiment as described above, it is possible to exhibit the same effect as the above-described second embodiment.

As described above, the gear device and the robot of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to this, and the configuration of each part may be any configuration having similar functions. can be replaced with Also, other optional components may be added to the present invention.

Further, in the above-described embodiment, the base provided in the robot is the "first member", the first arm is the "second member", and the gear device that transmits the driving force from the first member to the second member has been described. However, the present invention is not limited to this. It can also be applied to a gear device that transmits driving force. Note that n is an integer of 1 or more.

In addition, in the above-described embodiment, a horizontal articulated robot has been described, but the robot of the present invention is not limited to this. is.

Further, in the above-described embodiment, the case of incorporating the gear device into the robot has been described as an example, but in the gear device of the present invention, the driving force is applied from one side of the first member and the second member that rotate to each other to the other side. It can also be used by being incorporated in various devices having a configuration for transmission.

Specific examples of the present invention will be described below.
4. Friction wear test and fatigue strength test 4.1. Experimental example 1 for implementation
Using the materials shown in Table 1, a friction wear test specified in JIS K 7218:1986 was conducted. Specifically, first, test pins were produced from nickel-chromium-molybdenum steel SNCM439 (material for external gears), which is the material for pins shown in Table 1, and spheroidal graphite cast iron (material for internal gears), which is the material for discs ) to prepare a test disk.

Next, these test pin and test disk were set in a pin-on-disk tester, which is a reciprocating frictional wear tester, and the test pin was slid back and forth on the surface of the test disk. Then, the coefficient of dynamic friction was measured at an air temperature of 25° C. after reciprocally sliding a length of 10 mm 600 times. Table 1 shows the measurement results.

Next, a plane bending fatigue test specified in JIS Z 2275:1978 was performed using spheroidal graphite cast iron (FCD). Specifically, first, test pieces were produced from spheroidal graphite cast iron shown in Table 1.

Next, this test piece was set in a plane bending fatigue tester, and a repeated bending test was performed at an air temperature of 25° C. with a repetition number of 1×10 ⁷ times. Then, while increasing the stress amplitude, that is, the difference between the maximum stress and the minimum stress in the repeated bending test, the repeated bending test was conducted each time, and the maximum value of the stress amplitude that did not lead to failure was obtained. Table 1 shows this as the fatigue limit.

4.2. Practical Experimental Examples 2-5
The dynamic friction coefficient and fatigue limit were measured in the same manner as in Experimental Example 1, except that the number ratio of ferrite phase-associated particles and the number ratio of other particles in the spheroidal graphite cast iron were changed as shown in Table 1. Table 1 shows the measurement results.

4.3. Comparative Experimental Examples 1 and 2
The dynamic friction coefficient and fatigue limit were measured in the same manner as in Experimental Example 1, except that the number ratio of ferrite phase-associated particles and the number ratio of other particles in the spheroidal graphite cast iron were changed as shown in Table 1. Table 1 shows the measurement results.

As is clear from Table 1, the spheroidal graphite cast iron used in each experimental example has a number ratio of the aforementioned ferrite phase-associated particles of 50% or more. Such spheroidal graphite cast iron was found to have a small coefficient of dynamic friction and a large fatigue limit.

In contrast, the spheroidal graphite cast iron used in each comparative experimental example was found to have a large coefficient of dynamic friction or a small fatigue limit. It is presumed that such spheroidal graphite cast iron cannot sufficiently improve the durability of the meshing position when used as a constituent material of an internal gear.

5. Manufacture of Gear Device 5.1. Example 1
First, a gear device having a configuration as shown in FIG. 2 was manufactured. The manufactured gear device had an internal gear with an outer diameter of φ70 mm, a mesh reference circle diameter of φ53 mm, and a reduction ratio of 80. In addition, spheroidal graphite cast iron was used as a constituent material of the internal gear, and nickel-chromium-molybdenum steel SNCM439 was used as a constituent material of the external gear.

Then, the cross section of the spheroidal graphite cast iron, which is the constituent material of the internal gear, was observed under magnification, and the number ratio of ferrite phase-associated particles was calculated. As described above, the ferrite phase-associated particles refer to graphite particles in which the width of the ferrite phase in the radial direction is 20% or more and 100% or less of the particle size of the graphite particles. Table 2 shows the calculated number ratio.

In addition, the number ratio of graphite particles in which the width of the ferrite phase is less than 20% of the particle size of the graphite particles, and the number ratio of graphite particles in which the width of the ferrite phase is more than 100% of the particle size of the graphite particles , are shown in Table 2, respectively.

Furthermore, the Vickers hardness of the external gear and the internal gear, the residual stress of the external gear, the surface roughness Ra of the external gear and the internal gear, the average crystal grains of the material constituting the external gear and the material constituting the internal gear Table 2 shows the diameter, and the types and amounts of additive elements contained in the constituent materials of the external gear.

Also, a lubricant was used for the gear device. This lubricant contains mineral oil: 80% by mass, lithium complex soap as a thickener: 15% by mass, organic molybdenum compound as an extreme pressure agent: 4% by mass, 2,6-di-tert-butyl-4- A grease containing 1% by mass of cresol and having a consistency of 325, an oil separation degree of 4.00% by mass, and a dropping point of 270° C. was used.

5.2. Examples 2-25 and Comparative Examples 1-4
A gear device was manufactured in the same manner as in Example 1 described above, except that the configurations of the external gear and the internal gear were changed as shown in Table 2.

The constituent materials shown in Table 2 are as follows.
・SNCM439: Nickel chromium molybdenum steel SNCM439
・Structural steel: S45C carbon steel for machine structural use
・SUS: Stainless steel SUS420J2
・FCD: Spheroidal graphite cast iron ・Al alloy: Aluminum alloy casting AC4D
・Cu alloy: Phosphor bronze casting CAC502

6. Evaluation of Gear Device 6.1. Lifetime The gear devices of each example and each comparative example were continuously operated at an input shaft rotation speed of 3000 rpm and an average load torque of 70 Nm, and the total number of rotations of the input shaft until the gear device was damaged was measured. This total number of revolutions is shown in Table 2 as the service life.

As is clear from Table 2, each example was found to have a significantly longer life than each comparative example.

6.2. Structure Observation FIGS. 8 to 10 are examples of observation images obtained by magnifying and observing the cross section of spheroidal graphite cast iron.

The observation image shown in FIG. 8 is an observation image of a cross section of the spheroidal graphite cast iron used in Experimental Example 1. FIG. The observation image shown in FIG. 8 shows ferrite phase-associated particles 26 (graphite particles 21), ferrite phase 25, and matrix structure 22. FIG. The ferrite phase 25 is annular so as to surround the ferrite phase-associated particles 26 .

The observation images shown in FIGS. 9 and 10 are observation images of a cross section of spheroidal graphite cast iron (comparative example) in which no ferrite phase exists. In FIG. 9, the matrix structure (pearlite structure) is adjacent to the graphite particles. Also in FIG. 10, the matrix structure (bainite structure) is adjacent to the graphite particles. In the observed images shown in FIGS. 9 and 10, no ferrite phase is observed between the graphite particles and the matrix structure. Therefore, it is considered that the spheroidal graphite cast iron shown in FIGS. 9 and 10 cannot achieve the effects of the present invention.

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 body, 11B... Lid body, 12... Main body, 13... Bearing, 14... Bearing, 15... Inner ring, 16... Outer ring, 17... Roller, 18... Cross roller bearing, 21... Graphite particles, 22... Base structure, 23... Internal tooth, 24... Concave part, 25... Ferrite phase, 26... Particles associated with ferrite phase, 31... Body part, 32... Bottom part, 32B... Flange part, 33... External tooth, 36... Opening part, 41 Cam 42 Bearing 61 Shaft 62 Shaft 100 Robot 110 Base 111 Inner wall surface 111B Inner wall surface 120 First arm 121 Inner wall surface 130 Second second Arm 140 Working head 141 Spline shaft 150 End effector 151 Inner wall surface 160 Wiring part 170 Motor 190 Control device 411 Shaft part 412 Cam part 421 Inner ring , 422... Ball, 423... Outer ring, G... Lubricant, J1... First axis, J2... Second axis, J3... Third axis, La... Long axis, Lb... Short axis, O... Center, P1... Point, P2...point, P3...point, P4...point, a...axis line, w1...width, w2...width, w3...width, w4...width

Claims (10)

an internal gear made mainly of spheroidal graphite cast iron;
an external gear that is flexible and partially meshes with the internal gear;
a wave generator that contacts the inner peripheral surface of the external gear and moves the meshing position between the internal gear and the external gear in the circumferential direction;
has
The spheroidal graphite cast iron is
base organization and
graphite particles dispersed in the base structure;
a ferrite phase surrounding the graphite particles with a nucleus;
including
The width of the ferrite phase is 20% or more and 100% or less of the particle size of the graphite particles,
A gear device, wherein the number ratio of the graphite particles forming the core is 50% or more of the total number of the graphite particles. 2. The gear device according to claim 1, wherein the base structure includes a pearlite structure or a mixed structure of a pearlite structure and a ferrite structure. 3. The gear unit according to claim 1, wherein the external gear is mainly made of nickel-chromium-molybdenum steel. The gear device according to any one of claims 1 to 3, wherein the Vickers hardness of the surface of the internal gear is in the range of 250 or more and 350 or less. The gear unit according to any one of claims 1 to 4, wherein the surface roughness Ra of the external teeth of the external gear is in the range of 0.2 µm or more and 1.6 µm or less. The gear unit according to any one of claims 1 to 5, wherein the surface roughness Ra of the internal teeth of the internal gear is in the range of 0.1 µm or more and 0.8 µm or less. The gear unit according to any one of claims 1 to 6, wherein the surface roughness Ra of the external teeth of the external gear is larger than the surface roughness Ra of the internal teeth of the internal gear. The gear unit according to any one of claims 1 to 7, wherein an average crystal grain size of a constituent material of said external gear is smaller than an average crystal grain size of a constituent material of said internal gear. The gear according to any one of claims 1 to 8, wherein the constituent material of the external gear contains a group 4 element or a group 5 element within a range of 0.01% by mass or more and 0.5% by mass or less. Device. a first member;
a second member that rotates with respect to the first member;
The gear device according to any one of claims 1 to 9, which transmits a driving force for relatively rotating the second member;
a driving source that outputs the driving force toward the gear device;
A robot characterized by comprising:

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