JP6438193B2 - Articulated robot wrist structure - Google Patents

Description

  The present invention relates to a wrist structure of an articulated robot in which a hypoid gear is applied to a power transmission mechanism that transmits a driving force of a motor.

  In the wrist structure of an articulated robot, a hypoid gear may be used to transmit the driving force of a motor to an arm tip or an end effector (see, for example, Patent Document 1). The hypoid gear is composed of a pinion and a bevel gear, and is classified as a staggered shaft gear. The pinion shaft is perpendicular to the bevel gear shaft, but when viewed in the bevel gear shaft direction, the pinion shaft is offset from the bevel gear shaft.

JP2013-52460A

  Since the hypoid gear can be greatly decelerated while keeping a small size, it has been conventionally applied to a power transmission mechanism in an articulated robot, particularly a wrist structure. However, when assembling the hypoid gear, it is necessary to position the pinion with respect to the bevel gear in the three directions of the pinion axis direction, the bevel gear axis direction, and the axis offset direction. For this reason, it is difficult to assemble a hypoid gear so as to eliminate backlash, and when only a hypoid gear is applied to the power transmission mechanism of an articulated robot, it is very difficult to secure the position accuracy by keeping the backlash within an allowable range. It is difficult. Particularly in the wrist structure of an articulated robot, the allowable range of backlash is more severe because fine movement is required. In Patent Document 1, no countermeasure is taken for this point.

  Accordingly, an object of the present invention is to provide a wrist structure for an articulated robot using a hypoid gear as a power transmission mechanism that can easily secure positional accuracy while suppressing a decrease in productivity.

  A wrist structure of an articulated robot according to an aspect of the present invention includes a first wrist member coupled to an arm member of the articulated robot, and the first wrist member coupled to the first wrist member so as to be rotatable around a predetermined rotation axis. A first wrist member; a first motor that drives the second wrist member; and a first power transmission mechanism that transmits a rotational driving force of the first motor to the second wrist member. The transmission mechanism includes a first hypoid gear and a parallel-shaft or cross-shaft first gear train, and the first gear train is connected to the first hypoid gear and the second gear in a power transmission path of the first power transmission mechanism. This is a speed reduction mechanism that is positioned between the wrist member and that outputs an input rotation by decelerating.

  According to the above configuration, the backlash in the hypoid gear is reduced to the second wrist member according to the speed ratio of the gear train that is the speed reduction mechanism. Since the gear train is a parallel shaft type or a cross shaft type, two gears that mesh adjacently among the plurality of gears constituting the gear train need only be positioned in one direction or two directions. For this reason, even if the positioning operation in the gear train is simply performed, the backlash in the gear train can be made minute. Therefore, even if a gear train is added to the power transmission mechanism, backlash in the gear train does not affect the position accuracy of the second wrist member. As a result, the backlash of the entire power transmission mechanism is reduced without performing positioning work when the hypoid gear is assembled. Therefore, it is possible to easily ensure the position accuracy while suppressing a decrease in productivity.

  The first gear train may be a parallel shaft type.

  According to the said structure, two gears which mesh | engage adjacently among the some gears which comprise a gear train should just be positioned only in one direction. For this reason, the gear train can be easily assembled, and the backlash in the gear train can be further reduced.

  The first motor may be attached to the first wrist member, and the first gear train may be an external gear train and may be continuous in the longitudinal direction of the first wrist member.

  According to the said structure, a motor is arrange | positioned only by the dimension required in order to arrange | position an external gear train at the hand side of a 1st wrist member. Thereby, since the weight of the hand is reduced, the hand can be operated lightly, and the dynamic characteristics of the articulated robot are improved. In addition, the hand can be thinned, and the workability of the articulated robot is improved. If the motor is arranged on the proximal side of the first wrist member without a gear train, the hypoid gear is separated from the motor, so that a rod for connecting the motor to the hypoid gear is necessary (see, for example, Patent Document 1). However, such parts cannot reduce backlash. On the other hand, since the gear train which is the external gear train is continuous in the longitudinal direction of the first wrist member and the gear train is interposed between the second wrist member and the hypoid gear, the hypoid gear is accordingly located on the proximal side of the first member. Can be arranged. As a result, the motor can be directly connected to the hypoid gear without using a rod. In other words, in addition to the improvement of the positional accuracy described above, it is possible to omit the position filling parts such as the rod while improving the dynamic characteristics and workability of the robot by arranging the motor on the hand side. .

  A third wrist member rotatably connected to the second wrist member around a predetermined rotation axis; a second motor for driving the third wrist member; and a rotational driving force of the second motor for the third wrist member. A second power transmission mechanism for transmitting to a wrist member, wherein the second power transmission mechanism includes a second hypoid gear and a parallel or cross-axis second gear train, wherein the second gear train is A speed reduction mechanism that is positioned between the second hypoid gear and the third wrist member in the power transmission path of the second power transmission mechanism and that decelerates and outputs the input rotation.

  According to the said structure, when a wrist structure is provided with two independent power transmission mechanisms, the position accuracy of the two wrist members (2nd wrist member and 3rd wrist member) driven by these can be improved. .

  The first motor and the second motor may be attached to the first wrist member and may be distributed on the opposite sides as viewed from the center of the first wrist member.

  According to the said structure, the weight balance of a 1st wrist member is stabilized.

  The first motor and the second motor may be attached to the first wrist member and arranged on the same side as viewed from the center of the first wrist member.

  According to the said structure, the space on the opposite side to the side by which the 1st and 2nd motor is arrange | positioned among the 1st wrist members can be utilized for arrangement | positioning of other components, such as a cable connected to an end effector.

  ADVANTAGE OF THE INVENTION According to this invention, in the wrist structure of the articulated robot using a hypoid gear for a power transmission mechanism, position accuracy can be easily ensured while suppressing a decrease in productivity.

It is a mimetic diagram showing the articulated robot concerning a 1st embodiment. It is sectional drawing of the wrist structure of the articulated robot which concerns on 1st Embodiment. It is sectional drawing of the wrist structure which abbreviate | omits illustration of a 2nd power transmission mechanism from FIG. 2 (a) and (b). It is sectional drawing of the wrist structure which abbreviate | omits illustration of a 1st power transmission mechanism from FIG. 2 (a) and (b). It is sectional drawing of the wrist structure of the articulated robot which concerns on 2nd Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. The same or corresponding elements are denoted by the same reference numerals throughout all the drawings, and redundant description is omitted.

(First embodiment)
FIG. 1 is a schematic diagram showing an articulated robot 1 according to the first embodiment. As shown in FIG. 1, the articulated robot 1 includes a base 2 and a robot arm 3 attached to the base 2. An end effector 91 is detachably attached to the tip of the robot arm 3. The end effector 91 is, for example, a hand, a painting gun, or a welding torch, and is appropriately selected according to work required for the articulated robot 1. The end effector 91 is electrically driven, and a cable 92 for supplying power and control signals to the end effector 91 is attached to the robot arm 3. The cable 92 also supplies material to the end effector 91 as needed. For example, when the end effector 91 is a paint gun or a melting electrode type welding torch, a paint or a filler material is supplied.

  The articulated robot 1 is, for example, a vertical articulated 6-axis robot, and has a base axis 3 axes and a wrist axis 3 axes. The robot arm 3 includes a movable arm member 4 attached to the base 2. The arm member 4 includes a swivel base 5 that is pivotably connected to the base 2, a lower arm 6 that is swingably connected to the turntable 5, and an upper arm 7 that is swingably connected to the lower arm 6. Including. When the arm member 4 is operated, the end effector 91 can be largely moved in the work space.

  The robot arm 3 includes a wrist structure 10 attached to the arm member 4. The wrist structure 10 includes first, second and third wrist members 11-13. The first wrist member 11 is coupled to the distal end portion (for example, the upper arm 7) of the arm member 4 so as to be rotatable around the first rotation axis WA1. The second wrist member 12 is coupled to the first wrist member 11 so as to be rotatable around the second rotation axis WA2. The third wrist member 13 is coupled to the second wrist member 12 so as to be rotatable around the third rotation axis WA3. In this example, the third wrist member 13 constitutes the distal end portion of the wrist structure 10 and thus the distal end portion of the robot arm 3, and the end effector 91 is attached to the distal end portion of the third wrist member 13.

  The first wrist member 11 has, for example, a cylindrical shape that is long in the axial direction. The first rotation axis WA <b> 1 extends in the longitudinal direction of the first wrist member 11 at the center of the first wrist member 11. The second rotation axis WA <b> 2 intersects the first rotation axis WA <b> 1 perpendicularly and is set at the distal end portion of the first wrist member 11. The third rotation axis WA3 intersects the second rotation axis WA2 perpendicularly. If the rotational position around the second rotational axis WA2 is at the reference position shown in FIG. 2, the third rotational axis WA3 is coaxial with the first rotational axis WA1.

  The first wrist member 11 is rotationally driven by a motor 14 attached to the arm member 4 (for example, the upper arm 7). The second wrist member 12 is rotationally driven by the first motor 15. The third wrist member 13 is rotationally driven by the second motor 16. The first and second motors 15 and 16 are attached to the first wrist member 11. The rotational driving force of the first motor 15 is transmitted to the second wrist member 12 via the first power transmission mechanism 20 (see FIGS. 2 and 3). Accordingly, the second wrist member 12 rotates around the second rotation axis WA2 together with the third wrist member 13 and the end effector 91. The rotational driving force of the second motor 16 is transmitted to the third wrist member 13 via the second power transmission mechanism 30 (see FIGS. 2 and 4). Accordingly, the third wrist member 13 rotates around the third rotation axis WA3 together with the end effector 91. When the wrist members 11 to 13 are rotated, the end effector 91 is rotated around the respective rotation axes WA1 to WA3.

  2A to 2C are cross-sectional views of the wrist structure 10 according to the first embodiment. FIGS. 3A and 3B are cross-sectional views in which the second motor 16 and the second power transmission mechanism 30 are partially omitted from FIGS. 2A and 2B, respectively. As shown in FIGS. 2 and 3, the first power transmission mechanism 20 forms a power transmission path for transmitting the rotation of the first motor 15 to the second wrist member 12. The first power transmission mechanism 20 includes a first hypoid gear 21 and a first gear train 22, and the first gear train 22 is connected to the first hypoid gear 21 and the second wrist member 12 in the power transmission path of the first power transmission mechanism 20. Located between. The first hypoid gear 21 is connected to the first gear train 22 via a hypoid output shaft 23. The first gear train 22 is connected to the second wrist member 12 via the speed reduction shaft 24.

  The first hypoid gear 21 is a staggered shaft type bevel gear having a pinion 21a and a bevel gear 21b. The pinion 21a is meshed with the bevel gear 21b in a state of being twisted with the bevel gear 21b. That is, the pinion shaft is oriented 90 degrees different from the bevel gear shaft, and is offset from the bevel gear shaft in a direction perpendicular to the pinion shaft and the bevel gear shaft. The tooth muscle of the pinion 21a is spiral. The bevel gear 21b has a conical surface on which bent teeth that can mesh with the pinion 21a are formed. The bent tooth traces extend in a radial direction and are twisted in either the right-handed or left-handed twisted direction. It has been. When the pinion 21a is used as the input side, the first hypoid gear 21 decelerates and outputs the input rotation. At this time, the rotation axis moves in the offset direction and changes by 90 degrees. In other hypoid gears described below, the pinion and bevel gears have the same teeth as described above and mesh with each other in the same manner as described above, and the hypoid gear moves and changes the direction of the speed reduction function and the rotation axis in the same manner as described above. It has the function to make it.

  The output shaft of the first motor 15 is connected to the pinion 21a. The pinion 21a is meshed with the bevel gear 21b as described above. The bevel gear 21 b is fixed to the hypoid output shaft 23.

  The first gear train 22 is a parallel shaft type gear train having a drive gear 22a and a driven gear 22b. More specifically, the first gear train 22 is an external gear train, and the gears constituting the first gear train 22 are sequentially circumscribed. The first gear train 22 is continuous in the longitudinal direction of the first wrist member 11. The drive gear 22a may be separated from the driven gear 22b, and the first gear train 22 may include an idle gear 22c that is interposed between the gears 22a and 22b and meshes with either of the gears 22a and 22b. The gear teeth constituting the first gear train 22 may be anything.

  The drive gear 22a is fixed to the hypoid output shaft 23 and is arranged in the axial direction with the bevel gear 21b. The driven gear 22 b is fixed to the reduction shaft 24. The speed reduction shaft 24 is parallel to the hypoid output shaft 23, is rotatably supported at the distal end portion of the first wrist member 11, and is fixed to the second wrist member 12.

  The rotation axis of the speed reduction shaft 24 forms a second rotation axis WA2. The rotation axis of the hypoid output shaft 23 is parallel to the second rotation axis WA2 and forms a bevel gear shaft. The pinion shaft is in a twisted position with the bevel gear shaft, and is parallel to the first rotation axis WA1 (the longitudinal direction of the first wrist member 11) of the two directions perpendicular to the second rotation axis WA2. The offset direction of the first hypoid gear 21 is perpendicular to the remaining direction, that is, both the first rotation axis WA1 and the second rotation axis WA2. The first motor 15 is arranged coaxially with the pinion 21a.

  When the first motor 15 operates, the rotational driving force of the first motor 15 is input to the pinion 21a. The first hypoid gear 21 decelerates the rotation input to the pinion 21a and outputs it to the hypoid output shaft 23. At that time, the rotation axis is changed by 90 degrees. The first gear train 22 decelerates the rotation input to the hypoid output shaft 23 and outputs it to the deceleration shaft 24, and the rotation axis maintains the direction at that time. When the speed reduction shaft 24 rotates, the second wrist member 12 rotates around the second rotation axis WA2 with respect to the first wrist member 11 together with the third wrist member 13 and the end effector 91.

  According to the first power transmission mechanism 20 described above, since the first hypoid gear 21 is applied, it is possible to first obtain the advantages. For example, since the first hypoid gear 21 can slip in the tooth trace direction, it is possible to suppress operation noise and vibration. The first hypoid gear 21 is kept small and easily obtains a large deceleration. For this reason, the wrist structure 10 can be reduced in size and weight, and the dynamic characteristics of the articulated robot 1 are improved.

  On the other hand, since the pinion shaft is in a twisted position with the bevel gear shaft, it is difficult to accurately position the pinion 21a with respect to the bevel gear 21b so as to eliminate backlash. Therefore, the occurrence of backlash in the first hypoid gear 21 is already incorporated, and precise positioning is not performed when the first hypoid gear 21 is assembled (for example, the positioning accuracy is set to be the same as before). To maintain.

  Even if the backlash at the first hypoid gear 21 is not allowed by the wrist structure 10 from the viewpoint of positional accuracy, this can be reduced by the first gear train 22. In other words, the first gear train 22 is a speed reduction mechanism located at the rear stage of the first hypoid gear 21, and its speed ratio (here, the number of teeth of the drive gear 22a is divided by the number of teeth of the driven gear 22b). Is less than 1. For example, if the speed ratio of the first gear train 22 is ½, backlash in the first hypoid gear 21 is reduced to ½ times in the reduction shaft 24 via the first gear train 22. Thus, the backlash in the first hypoid gear 21 is reduced to reach the second wrist member 12 according to the speed ratio of the first gear train 22.

  When the first gear train 22 is assembled, it is necessary to position two gears that mesh with each other adjacent to each other among the plurality of gears 22a to 22c constituting the first gear train 22, and the first gear train may depend on the positioning accuracy. A backlash may occur in the row 22. Since the first gear train 22 according to the present embodiment is a parallel shaft type, the adjacent two gears need only be positioned in one direction. Therefore, backlash in the first gear train 22 can be easily suppressed to a minute amount. Even if the first gear train 22 is applied to the first power transmission mechanism 20, backlash in the first gear train 22 does not significantly affect the positional accuracy of the second wrist member 12 and thus the end effector 91.

  As a result, even if precise positioning is not performed when the first hypoid gear 21 is assembled, the backlash of the first power transmission mechanism 20 as a whole is reduced. Therefore, the position accuracy can be easily ensured while suppressing the decrease in productivity of the articulated robot 1 while obtaining the advantage of applying the first hypoid gear 21 to the first power transmission mechanism 20.

  The first gear train 22 is an external gear train and is continuous in the longitudinal direction of the first wrist member 11. The speed reduction shaft 24 is supported at the tip of the first wrist member 11, and the second rotation axis WA <b> 2 is provided at the tip of the first wrist member 11. When viewed from the distal end portion of the first wrist member 11, the first gear train 22 extends from the distal end portion toward the proximal end portion of the first wrist member 11 in the longitudinal direction of the first wrist member 11.

  Accordingly, the first hypoid gear 21 has a first gear train 22 as compared with a wrist structure (hereinafter, “Comparative Example 1”) in which the first gear train does not exist and the hypoid output shaft forms the second rotation axis. The first wrist member 11 is a space necessary for arranging the first wrist member 11 (that is, a distance between the hypoid output shaft 23 to which the drive gear 22a is fixed and the speed reduction shaft 24 to which the driven gear 22b is fixed). It is arrange | positioned from the front-end | tip part of this to the base end side. The first motor 15 is disposed on the base end side with respect to the first hypoid gear 21. For this reason, the first motor 15 can be disposed at the proximal end portion of the first wrist member 11. Then, since the weight of the tip of the wrist structure 10 is reduced, the hand of the robot arm 3 can be operated lightly, and the dynamic characteristics of the articulated robot 1 are improved. Moreover, since the tip part of the wrist structure 10 becomes thin, the workability of the articulated robot 1 is improved.

  Even in the wrist structure according to Comparative Example 1, it is possible to dispose the first motor at the base end portion of the first wrist member itself. In that case, a rod for connecting the output shaft of the first motor to the hypoid gear located at the tip of the first wrist member is required. However, this rod cannot reduce backlash in the first hypoid gear. On the other hand, in the present embodiment, the first gear train 22 is located at the rear stage of the first hypoid gear 21 and fills the space between the first motor 15 and the second rotation axis WA2. As a result, the pinion 21a is brought closer to the output shaft of the first motor 15 while the first motor 15 is disposed at the proximal end portion and the second rotation axis WA2 is disposed at the distal end portion. The first gear train 22 can reduce backlash in the first hypoid gear 21 and contributes to securing positional accuracy by suppressing a decrease in productivity of the articulated robot 1.

  As a result, by applying the first gear train 22 to the first power transmission mechanism 20, not only the positional accuracy can be ensured, but also the dynamic characteristics and workability of the articulated robot 1 can be improved. Further, parts that do not contribute to the reduction of backlash in the hypoid gear, such as rods, and parts that accompany this can be omitted as appropriate.

  In this embodiment, the 1st motor 15 has the cylindrical motor housing | casing 15a long in an axial direction, and the output shaft of the 1st motor 15 is 1st rotation axis WA1 (longitudinal of the 1st wrist member 11). Direction). Therefore, the longitudinal direction of the motor housing is parallel to the longitudinal direction of the first wrist member 11. Therefore, compared with a structure in which the longitudinal direction of the motor housing extends in a direction perpendicular to the longitudinal direction of the first wrist member, the first wrist member 11 is prevented from becoming thicker around the portion where the first motor 15 is disposed. be able to.

  FIGS. 4A and 4B are diagrams in which a part of the first motor 15 and the first power transmission mechanism 20 are omitted from FIGS. 2A and 2B, respectively. As shown in FIGS. 2 and 4, the second power transmission mechanism 30 forms a power transmission path for transmitting the rotation of the second motor 16 to the third wrist member 13. The second power transmission mechanism 30 includes a second hypoid gear 31 and a second gear train 32, and the second gear train 32 is connected to the second hypoid gear 31 and the third wrist member 13 in the power transmission path of the second power transmission mechanism 30. Located between. The second hypoid gear 31 is connected to the second gear train 32 via a hypoid output shaft 33, and the first gear train 32 is connected to the third wrist member 13 via a reduction shaft 34.

  The second hypoid gear 31 is the same as the first hypoid gear 21. The output shaft of the second motor 16 is connected to the pinion 31a. The bevel gear 32 b is fixed to the hypoid output shaft 33.

  The second gear train 32 is a cross shaft type gear train having a drive bevel gear 32a and a driven bevel gear 32b. The drive bevel gear 32 a is provided at the end of the hypoid output shaft 33. The driven bevel gear 32 b is provided at the end of the reduction shaft 34. With the drive bevel gear shaft perpendicularly intersecting the driven bevel gear shaft, the drive bevel gear 32a meshes with the driven bevel gear 32b. Any tooth traces of the gears constituting the second gear train 32 may be used. The speed reduction shaft 34 is fixed to the third wrist member 13.

  The speed reduction shaft 34 forms a third rotation axis WA3. The hypoid output shaft 33 perpendicularly intersects with the third rotation axis WA3, is coaxial with the second rotation axis WA2, and forms a bevel gear shaft. The pinion shaft is in a twisted position with the bevel gear shaft. Also in the second power transmission mechanism 30, the pinion shaft is parallel to the first rotation axis WA1, and the offset direction of the second hypoid gear 31 is perpendicular to both the first rotation axis WA1 and the second rotation axis WA2. The motor 16 is arranged coaxially with the pinion 31a.

  When the second motor 16 operates, the rotational driving force of the second motor 16 is input to the pinion 31a. The second hypoid gear 31 decelerates the rotation input to the pinion 31a and outputs it to the hypoid output shaft 33. At this time, the rotation axis is changed by 90 degrees. The second gear train 32 decelerates the rotation input to the hypoid output shaft 33 and outputs it to the speed reduction shaft 34. At this time, the rotation axis is changed by 90 degrees. When the speed reduction shaft 34 rotates, the third wrist member 13 rotates together with the end effector 91 around the third rotation axis WA3 with respect to the second wrist member 12.

  The second power transmission mechanism 30 can obtain the same operation as that of the first power transmission mechanism 20. That is, since the second hypoid gear 31 is applied to the second power transmission mechanism 30 and the second gear train 32, which is a cross-axis reduction mechanism, is applied to the subsequent stage, the hypoid gear is applied to the second power transmission mechanism 30. While obtaining advantages, it is possible to easily ensure the positional accuracy while suppressing a decrease in productivity of the articulated robot 1. Since the bevel gears 32a and 32b may be positioned in two directions when the cross-shaft type second gear train 32 is assembled, backlash in the second gear train 32 is easily made minute after the parallel shaft type. It is possible to suppress.

  Since the output shaft of the second motor 16 is parallel to the first rotation axis WA <b> 1, it is possible to prevent the first wrist member 11 from becoming thick at the portion where the second motor 16 is disposed. Since the second motor 16 is attached to the proximal end portion of the first wrist member 11, the weight and thickness of the distal end portion of the first wrist member 11 are reduced, and the dynamic characteristics and workability of the articulated robot 1 are improved. To do.

  Hereinafter, the structure of the wrist structure 10 will be described in more detail.

  As shown in FIG. 2, the 1st wrist member 11 is a hollow cylinder shape. In FIG.2 (c), although the 1st wrist member 11 has a square axial orthogonal cross section, a cross section may be circular or another polygon. The first motor 15, a part of the first power transmission mechanism 20, the second motor 16 and a part of the second power transmission mechanism 30 are accommodated in the first wrist member 11. In the present embodiment, the first hypoid gear 21, the hypoid output shaft 23, the first gear train 22, and the second hypoid gear 31 are accommodated in the first wrist member 11.

  The first motor 15 and the second motor 16 are located on the same side when viewed from the center of the first wrist member 11. The first rotation axis WA1 extends in the longitudinal direction of the first wrist member 11 at the center of the first wrist member 11, and the first motor 15 and the second motor 16 have the second rotation axis WA2 as viewed from the first rotation axis WA1. It is biased to the same side in the direction. The first motor 15 and the second motor 16 are arranged at the same position in the direction of the first rotation axis WA1, and overlap in a direction perpendicular to both the first rotation axis WA1 and the second rotation axis WA2.

  Hereinafter, for the convenience of explanation, the direction perpendicular to the first rotation axis WA1 and the second rotation axis WA2 is referred to as the “vertical direction” in accordance with the direction on the paper surface of FIGS. 2A and 2C. There is. The first motor 15 is disposed above (one of the vertical directions) when viewed from the first rotation axis WA1, and the second motor 16 is disposed below (of the vertical directions) as viewed from the first rotation axis WA1. The other). With respect to the direction of the second rotation axis WA2, the side on which the first and second motors 15 and 16 are arranged as viewed from the first rotation axis WA1 is referred to as the “motor side”. Regarding the direction orthogonal to the first rotation axis WA1 including the direction of the second rotation axis WA2, the side approaching the first rotation axis WA1 is referred to as “center side”, and the side away from the first rotation axis WA1 is referred to as “outer side”. .

  The pinion 21 a is attached to the output shaft of the first motor 15. The pinion 21a and its shaft are offset to the motor side and offset upward in the direction of the second rotation axis WA2 when viewed from the first rotation axis WA1. The bevel gear shaft extends in parallel with the second rotation axis WA2 while being slightly offset upward from the first rotation axis WA1. The bevel gear 21b is offset to the motor side in the second rotation axis WA2 direction when viewed from the first rotation axis WA1. In a state where the pinion shaft is offset upward from the bevel gear shaft, the pinion 21a is engaged with the bevel gear 21b.

  The hypoid output shaft 23 is rotatably supported by a shaft holder 40 built in the first wrist member 11. The bevel gear 21b is disposed on the outer peripheral side with respect to the shaft holder 40 in the second rotation axis WA2 direction. The conical surface of the bevel gear 21b is directed toward the center in the second rotation axis WA2 direction, and the pinion 21a engages with the bevel gear 21b from the center in the second rotation axis WA2 direction. The pinion 21a is offset upward and overlaps the shaft holder 40 when viewed in the vertical direction. As described above, the pinion 21a and the shaft holder 40 are arranged compactly in the direction of the second rotation axis WA2 closer to the center than the bevel gear 21b. On the other hand, the drive gear 22a is arranged on the outer peripheral side with respect to the bevel gear 21b in the second rotation axis WA2 direction. For this reason, the drive gear 22a can be brought close to the bevel gear 21b without causing the drive gear 22a to interfere with the pinion 21a and the shaft holder 40. As described above, the hypoid output shaft 23 can be shortened, and the first wrist member 11 can be prevented from being thickened at the portion where the first hypoid gear 21 is disposed.

  The 1st wrist member 11 has a pair of protrusion parts 41 and 42 in the tip part. The protrusions 41 and 42 are separated in the direction of the second rotation axis WA2 and extend in the direction of the first rotation axis WA1. The second wrist member 12 is disposed between the protrusions 41 and 42 and is rotatably supported by the protrusions 41 and 42. The third wrist member 13 is attached to the second wrist member 12. Hereinafter, of the two protrusions 41 and 42, the one on the motor side in the second rotation axis WA2 direction is referred to as a “first protrusion 41”, and the opposite side is referred to as a “second protrusion 42”. The protrusion 41 forms a gear chamber together with the second wrist member 42 disposed on the inner peripheral side. The driven gear 22b is accommodated in the gear chamber, and the reduction shaft 24 penetrates the second wrist member 12 from the gear chamber and is fixed to the second wrist member 12.

  The second hypoid gear 31 is also accommodated in the first gear chamber. The second power transmission mechanism 30 has a rod 36 that connects the output shaft of the second motor 16 to the pinion 31a. The rod 36 is accommodated in the first wrist member 11. The pinion 31a, the rod 36 and their axes are offset to the motor side and offset downward in the direction of the second rotation axis WA2 when viewed from the first rotation axis WA1. The bevel gear shaft is coaxial with the second rotation axis WA2. The bevel gear 31b is offset to the motor side in the second rotation axis WA2 direction when viewed from the first rotation axis WA1, but is not offset in the vertical direction. With the pinion shaft offset downward from the bevel gear shaft, the pinion 31a meshes with the bevel gear 31b.

  The reduction shaft 24 is hollow. The hypoid output shaft 33 is inserted into the reduction shaft 24 and is rotatably supported by the reduction shaft 24. As a result, the hypoid output shaft 33 can rotate relative to the first and second wrist members 11 and 12.

  The bevel gear 31b is disposed on the outer peripheral side with respect to the driven gear 22b in the second rotation axis WA2 direction. The conical surface of the bevel gear 31b is directed to the outer peripheral side in the second rotational axis WA2 direction, and the pinion 31a engages with the bevel gear 31b from the outer peripheral side in the second rotational axis WA2 direction. Therefore, the bevel gear 31b can be brought close to the driven gear 22b, and the first protrusion 41 can be prevented from becoming thick in the direction of the second rotation axis WA2. In order to realize this, the offset amount in the second rotation axis WA2 direction from the first rotation axis WA1 of the second motor 16 and the pinion 31a is larger than the same offset amount of the first motor 15 and the pinion 21a.

  The pinion 31a is arranged on the opposite side to the first gear train 22 in the second rotation axis WA2 direction with respect to the bevel gear 31b. For this reason, it is possible to avoid the rod 36 from interfering with the first hypoid gear 21 and the first gear train 22. Even if the driven gear 22b is enlarged to reduce backlash in the first hypoid gear 21, it is possible to avoid the driven gear 22b from interfering with the second power transmission mechanism 30.

  The shafts of the two pinions 21a and 31a are offset from the shafts of the corresponding bevel gears 21b and 31b to the opposite sides in the vertical direction. The conical surfaces of the two bevel gears 21a and 31a are directed to opposite sides in the direction of the second rotation axis WA2. By carrying out like this, the tooth trace twist direction of two bevel gears 21b and 31b can be made mutually the same. When the first and second hypoid gears 21 and 31 have the same reduction ratio, parts can be shared by the first and second hypoid gears 21 and 31, so that manufacturing costs and maintenance costs can be reduced.

  The hypoid output shaft 33 protrudes from the reduction shaft 24 toward the center in the direction of the second rotation axis WA2, and the drive bevel gear 32a is disposed closer to the center than the reduction shaft 24 in the direction of the second rotation axis WA2. The driven bevel gear 32b meshes with the drive bevel gear 32a, and the reduction shaft 34 extends away from the first wrist member 11 from the driven bevel gear 32b.

  Hereinafter, the handling of the cable 92 in the wrist structure 10 according to the present embodiment will be described in order from the end effector 91 side. The speed reduction shaft 34 is a hollow shaft that is open at both ends. The tip opening is close to the end effector 91 attached to the third wrist member 13. The proximal end opening is formed so as to be surrounded by the driven bevel gear 32 b and is located in the recess 43. The cable 92 enters the speed reduction shaft 34 from the end effector 91 through the distal end opening, and reaches the recess 43 through the proximal end opening. The cable 92 is directed in the concave portion 43 to the side opposite to the side where the drive bevel gear 32a is disposed in the second rotation axis WA2 direction. The cable 92 passes through the inner wall 42 b of the second protrusion 42 and reaches the second protrusion 42. Thereafter, the cable 92 may extend toward the arm member 4 along the outer surface of the first wrist member 11 through the outer wall 42 a of the second protrusion 42. Alternatively, the cable 92 may extend toward the arm member 4 in the first wrist member 11.

  Since the first motor 15 and the second motor 16 are arranged so as to be biased to the same side in the direction of the second rotation axis WA2 when viewed from the center of the first wrist member 11, a wide space is secured on the opposite side. . When the cable 92 is routed in the first wrist member 11, this space can be used effectively.

(Second Embodiment)
FIGS. 5A to 5C are cross-sectional views of the wrist structure 210 according to the second embodiment. Hereinafter, the second embodiment will be described focusing on differences from the above embodiment. For example, in the second embodiment, the first power transmission mechanism 220 and the second power transmission mechanism 230 are arranged apart from each other, the second power transmission mechanism 230 does not include a rod, and the second power transmission mechanism 230 The second gear train 232 is different from the above embodiment in that the second gear train 232 includes both a parallel shaft gear train 232A and a cross shaft gear train 232B.

  As shown in FIG. 5, in the wrist structure 210 according to the present embodiment, the first motor 215 and the second motor 216 are arranged on the opposite sides when viewed from the center of the first wrist member 211. The first rotation axis WA1 extends in the longitudinal direction of the first wrist member 211 at the center of the first wrist member 211, and the first motor 215 and the second motor 216 have the second rotation axis WA2 as viewed from the first rotation axis WA1. Arranged in opposite directions in the direction.

  Hereinafter, in the direction of the second rotation axis WA2, the side on which the first motor 215 is disposed when viewed from the first rotation axis WA1 is referred to as “first motor side”, and the second motor 216 is disposed when viewed from the first rotation axis WA1. This side is called the “second motor side”. The first wrist member 211 has a pair of protrusions 241 and 242 as in the first embodiment, and the first protrusion 241 is located on the first motor side in the second rotation axis WA1 direction, and the second protrusion 242 is located on the second motor side in the second rotation axis WA1 direction. The second wrist member 212 is disposed between the projecting portions 241 and 242, the first projecting portion 241 forms a first gear chamber together with the second wrist member 212, and the second projecting portion 242 is second together with the second wrist member 212. A gear chamber is formed.

  The first motor 215 and the second motor 216 are disposed at the same position in the first rotation axis A1 direction. The first motor 215 is offset in one of the vertical directions (the first rotation axis WA1 and the direction perpendicular to the second rotation axis WA2) as viewed from the first rotation axis WA1. In the present embodiment, the second motor 216 is also offset in the same direction in the vertical direction, and the first motor 215 and the second motor 216 are disposed at the same position in the vertical direction.

  The pinion 221 a of the first hypoid gear 221 is disposed coaxially with the output shaft of the first motor 215. The hypoid output shaft 223 forms a bevel gear shaft of the first hypoid gear 221 and is parallel to the second rotation axis WA2 and perpendicular to the first rotation axis WA1. With the pinion shaft offset upward from the bevel gear shaft, the pinion 221a meshes with the bevel gear 221b. The conical surface of the bevel gear 221b is directed toward the center in the direction of the second rotation axis WA2, and the pinion 221a engages with the bevel gear 221b from the center in the direction of the second rotation axis WA2. The shaft holder 240a that supports the hypoid output shaft 223 is disposed on the outer peripheral side of the bevel gear 221b in the second rotation axis WA2 direction.

  The drive gear 222a of the first gear train 222 is disposed closer to the center than the bevel gear 221b in the second rotation axis WA2 direction. The first gear train 222 is a reduction mechanism located at the rear stage of the first hypoid gear 221, and the drive gear 222a has a relatively small diameter. For this reason, even if the pinion 221a and the drive gear 222a are arranged on the same side in the second rotational axis WA2 direction when viewed from the bevel gear 221b, the pinion 221a is separated upward from the drive gear 222a. Therefore, the pinion 221a and the drive gear 222a can be compactly arranged in the direction of the second rotation axis WA2, and the first wrist member 211 can be prevented from being thickened at the portion where the first hypoid gear 221 is arranged.

  The first gear train 222 is an external gear train and continues in the longitudinal direction of the first wrist member 211. The driven gear 222b of the first gear train 222 is engaged with the drive gear 222a and is accommodated in the first gear chamber. The driven gear 222b is fixed to the reduction shaft 224. The reduction shaft 224 passes through the second wrist member 212 from the first gear chamber and is fixed to the second wrist member 212. The speed reduction shaft 224 is parallel to the hypoid output shaft 223 and forms the second rotation axis WA2.

  Second power transmission mechanism 230 includes a second hypoid gear 231 and a second gear train 232 located between second hypoid gear 231 and third wrist member 213 in the power transmission path of second power transmission path 230. The second gear train 232 includes a parallel shaft gear train 232A and a cross shaft gear train 233B. The parallel shaft gear train 232A crosses the second hypoid gear 231 in the power transmission path of the second power transmission path 230. It is located between the gear train 233B. The second gear train 232 may be a speed reduction mechanism as a whole. The overall reduction ratio of the second gear train 232 (that is, a value obtained by multiplying the reduction ratio of the parallel shaft type gear train 232A and the reduction gear ratio of the cross shaft type gear train 232B) may be less than one. The reduction ratio of the gear train may be 1 or more. In the present embodiment, both gear trains 232A and 232B are speed reduction mechanisms.

  The second hypoid gear 231 is connected to the parallel shaft gear train 232A via a hypoid output shaft 233. The parallel shaft type gear train 232A is connected to the cross shaft type gear train 233B via the primary reduction shaft 234A. The cross shaft type gear train 233B is connected to the third wrist member 213 via the secondary reduction shaft 234B.

  The second hypoid gear 231, the hypoid output shaft 233, and the parallel shaft gear train 232 </ b> A are accommodated in the first wrist member 211. Since the parallel shaft type gear train 232A exists, the second power transmission mechanism is similar to the first power transmission mechanism 20 (see FIG. 3) according to the first embodiment and the first power transmission mechanism 220 according to the present embodiment. From 230, parts such as rods can be omitted.

  In the second hypoid gear 232, the pinion 231 a of the second hypoid gear 232 is attached to the output shaft of the second motor 216 and is arranged coaxially with the output shaft of the second motor 216. The pinion 231a and its axis are offset to the second motor side and offset upward in the direction of the second rotation axis WA2 when viewed from the first rotation axis WA1. The hypoid output shaft 233 forms a bevel gear shaft of the second hypoid gear 231 and is parallel to the second rotation axis WA2 and perpendicular to the first rotation axis WA1. In a state where the pinion shaft is offset upward from the bevel gear shaft, the pinion 231a is engaged with the bevel gear 231b. The shaft holder 240b that supports the hypoid output shaft 233 is disposed on the outer peripheral side of the bevel gear 231b in the second rotation axis WA2 direction.

  The parallel shaft type gear train 232A is a speed reduction mechanism located at the rear stage of the second hypoid gear 231 and has a drive gear 232Aa and a driven gear 232Ab in the same manner as the first gear train 222 of the first power transmission mechanism 220. The drive gear 232Aa is fixed to the hypoid output shaft 233. Also in the second power transmission mechanism 230, the conical surface of the bevel gear 231b is directed to the center side in the second rotation axis WA2 direction, and the pinion 231a is engaged with the bevel gear 231b from the center side in the second rotation axis WA2 direction. The drive gear 232Aa is also arranged on the center side of the bevel gear 231b in the second rotation axis WA2 direction, the pinion 231a is arranged above the drive gear 232Aa, and overlaps with the drive gear 232Aa when viewed in the vertical direction. Accordingly, it is possible to suppress the first wrist member 211 from becoming thick at the portion where the second hypoid gear 231 is disposed.

  The parallel shaft type gear train 232 </ b> A is an external gear train and is continuous in the longitudinal direction of the first wrist member 211. The driven gear 232Ab of the parallel shaft gear train 232A is meshed with the drive gear 232Aa and is accommodated in the second gear chamber. The driven gear 232Ab is fixed to the primary reduction shaft 234A, and the primary reduction shaft 234A passes through the second wrist member 212 from the second gear chamber and is rotatably supported by the second wrist member 212.

  The hypoid output shaft 233 is disposed coaxially with the hypoid output shaft 223 of the first power transmission mechanism 220. The primary reduction shaft 234A is arranged coaxially with the reduction shaft 224 of the first power transmission mechanism 220, that is, coaxially with the second rotation axis WA2.

  The cross shaft type gear train 232B has substantially the same structure as the second gear train 32 (see FIGS. 2 and 4) according to the first embodiment. The cross shaft gear train 232B is a cross shaft gear train having a drive bevel gear 232Ba and a driven bevel gear 232Bb. The drive bevel gear 232Ba is provided at the center side end of the primary reduction shaft 224. The driven bevel gear 232Bb is meshed with the drive bevel gear 232Bb in a state where the drive bevel gear 2 axis intersects the driven bevel gear axis perpendicularly. The driven bevel gear 232Bb is provided at the proximal end of the secondary reduction shaft 234B.

  The secondary reduction shaft 234B extends from the driven bevel gear 232Bb toward the distal end where the end effector 91 is mounted. The secondary reduction shaft 234B is fixed to the third wrist member, and intersects the second rotation axis WA2 perpendicularly to form the third rotation axis WA3.

  The hypoid output shaft 233 extends parallel to the second rotation axis WA2, and the bevel gear 231b and the drive gear 232Ba are fixed to the hypoid output shaft 233. The driven gear 232Bb is accommodated in the second projecting portion 243 and is externally meshed with the drive gear 232Ba.

  The driven gear 232Ab is fixed to the primary reduction shaft 234A, and the primary reduction shaft 234A is rotatably supported on the inner wall 243b of the second protrusion 243. The drive bevel gear 232Ba is provided at the end of the primary reduction shaft 234A. The driven bevel gear 232Bb is provided at the end of the secondary reduction shaft 234B and meshes with the drive bevel gear 232Ba. The secondary reduction shaft 234B is fixed to the third wrist member 213, and the rotation axis thereof forms the third rotation axis WA3.

  When the second motor 216 operates, the rotational driving force of the second motor 216 is input to the pinion 231a of the second hypoid gear 231. The second hypoid gear 231 decelerates the input rotation and outputs it to the hypoid output shaft 233, at which time the rotation axis is changed by 90 degrees. The parallel shaft type gear train 232A decelerates the rotation input to the hypoid output shaft 233 and outputs it to the primary reduction shaft 234A, and maintains the direction of the rotation axis at that time. The cross shaft type gear train 233B decelerates the rotation input to the primary reduction shaft 234A and outputs it to the secondary reduction shaft 234B, and the rotation axis is changed by 90 degrees. When the secondary reduction shaft 234B rotates, the third wrist member 213 rotates around the third rotation axis WA3 with respect to the second wrist member 212 together with the end effector 91.

  Since the second power transmission mechanism 230 according to the present embodiment includes the parallel shaft type gear train 232A that is an external gear train that is continuous in the longitudinal direction of the first wrist member 211, the rod can be omitted. Therefore, the dynamic characteristics and workability of the articulated robot can be improved, and parts that contribute only to fill the space and parts that accompany this can be omitted as appropriate.

  In the present embodiment, since the cross shaft type gear train 232B is a speed reduction mechanism, even if a backlash occurs in the parallel shaft type gear train 232A, the cross shaft type gear train 232B is reduced even though it is originally minute. be able to. Further, since both the parallel shaft type gear train 232A and the cross shaft type gear train 232B are reduction mechanisms, the reduction ratio of the second gear train 232 as a whole can be increased, so that backlash in the second hypoid gear is third. It can be greatly reduced to reach the wrist member. Therefore, the position accuracy of the end effector 91 attached to the third wrist member 213 can be increased.

  In addition, since the first motor 215 and the second motor 216 are arranged on opposite sides when viewed from the center of the first wrist member 211, the combined weight of the first wrist member 211 and the components attached thereto is the first weight. It balances in the circumferential direction of one rotation axis WA1. Therefore, the dynamic characteristics of the articulated robot are improved.

  The cable 92 passes from the end effector 91 through the inside of the secondary reduction shaft 234B, extends to the side opposite to the drive bevel gear, and reaches the first gear chamber. In the present embodiment, since the first motor 215 and the second motor 216 are dispersedly arranged as described above, a large space is secured at the center of the first wrist member 211. When the cable 92 is routed inside the first wrist member 211, the space can be used.

(Modification)
The above-described embodiment is an example, and can be changed, added, and omitted without departing from the spirit of the present invention.

  When the second power transmission mechanism includes only a cross-axis gear train as the second gear train as in the first embodiment, the first motor and the second motor are dispersedly arranged as in the second embodiment. May be. When the first motor and the second motor are arranged on the same side as in the first embodiment, the second power transmission mechanism is a parallel shaft type gear train as the second gear train and A cross shaft type gear train may be provided.

  Only one of the first and second power transmission mechanisms may be composed of a hypoid gear and a parallel-axis or cross-axis gear train. The wrist structure may be provided with only two of the first and second wrist members, in which case the second motor and the second power transmission mechanism can be omitted.

  Even if the speed reduction shaft 24 is omitted, the second wrist member 12 is rotatably supported directly on the distal end portion of the first wrist member 11, and the first power transmission mechanism is configured to directly drive the second wrist member 12 to rotate. Good.

  The present invention can be used for an articulated robot having a wrist structure.

DESCRIPTION OF SYMBOLS 1 Articulated robot 3 Arm member 10,210 Wrist structure 11,211 1st wrist member 12,212 2nd wrist member 13,213 3rd wrist member 15,215 1st motor 16,216 2nd motor 20,220 1st Power transmission mechanisms 21, 211 First hypoid gears 22, 222 First gear trains 30, 230 Second power transmission mechanisms 31, 231 Second hypoid gears 32, 232 Second gear train 232A Parallel shaft gear train 232B Cross shaft gear train 91 End effector 92 cable

Claims (5)

A first wrist member coupled to an arm member of the articulated robot;
A second wrist member rotatably connected to the first wrist member about a predetermined rotation axis;
A first motor for driving the second wrist member;
A first power transmission mechanism for transmitting the rotational driving force of the first motor to the second wrist member;
The first power transmission mechanism includes a first hypoid gear and a parallel or cross-axis first gear train, and the first gear train is connected to the first hypoid gear in a power transmission path of the first power transmission mechanism. And a speed reduction mechanism that decelerates and outputs the input rotation.
The first power transmission mechanism includes a bevel gear of the first hypoid gear and a hypoid output shaft to which a drive gear of the first gear train is fixed. The bevel gear has a conical surface that meshes with a pinion, and the drive gear Is a wrist structure of an articulated robot, which faces the surface of the bevel gear opposite to the conical surface on the hypoid output shaft.   The wrist structure of the articulated robot according to claim 1, wherein the first gear train is a parallel shaft type.   The wrist structure of the articulated robot according to claim 2, wherein the first motor is attached to the first wrist member, and the first gear train is an external gear train and is continuous in a longitudinal direction of the first wrist member. A third wrist member rotatably connected to the second wrist member about a predetermined rotation axis;
A second motor for driving the third wrist member;
A second power transmission mechanism for transmitting the rotational driving force of the second motor to the third wrist member,
The second power transmission mechanism includes a second hypoid gear and a parallel or cross-axis second gear train, and the second gear train is connected to the second hypoid gear in a power transmission path of the second power transmission mechanism. And a speed reduction mechanism that decelerates and outputs the input rotation.
The first hypoid gear and the second hypoid gear are arranged such that the bevel gear shafts are parallel to each other, the conical surfaces are opposite to each other, and the pinion shaft is offset to the opposite side with respect to the bevel gear shaft. The wrist structure of the articulated robot according to any one of claims 1 to 3.   The first motor and the second motor are attached to the first wrist member, and are disposed on the same side in the direction of the rotation axis of the second wrist member as viewed from the center of the first wrist member. Item 5. The wrist structure of the articulated robot according to Item 4.

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