Joint structures and robots

Abstract

A robot joint structure (1) comprising a housing (130), a motor (30) fixed to the housing (130), an input section (42) that receives the rotational force of the motor (30), a reduction gear (40) having a reduction mechanism for reducing the rotational force and a lubrication chamber for lubricating the reduction mechanism, and a sealing member (36) that seals the space between the input section (42) and the case (41), wherein at least one of the housing (130) and the reduction gear (40) has passages (D1), (D2), (h) that open a space (S) surrounded by the housing (130) and a portion of the reduction gear (40) including the sealing member (36) to the outside.

Description

Technical Field

[0001] The present disclosure relates to a joint structure and a robot.

Background Art

[0002] There is known a structure in which an oil bath is formed between a speed reducer that reduces the power from a motor and an arm to which the speed reducer is attached at a joint portion such as a multi-joint robot (see, for example, Patent Document 1). In such a structure, a part of the drive portion of the speed reducer is disposed within the oil bath. That is, since it is premised that the lubricant within the oil bath enters inside the case of the speed reducer, an oil seal for sealing between the inside and the outside of the case of the speed reducer is not provided.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, a so-called grease-encapsulated speed reducer in which a lubricant is encapsulated inside the speed reducer is provided with an oil seal to prevent leakage of the internal lubricant. And since the oil seal is disposed in a closed space formed between the arm to which the speed reducer is assembled, if moisture enters and accumulates in the closed space, the oil seal is continuously exposed to moisture and the deterioration is accelerated.

[0005] Therefore, even in a joint structure using a grease-encapsulated speed reducer, it is desired to suppress the acceleration of deterioration due to contact with moisture of the oil seal provided in the speed reducer and the entry of moisture into the inside of the speed reducer.

Means for Solving the Problems

[0006] One aspect of the present disclosure is a robot joint structure comprising a housing, a motor fixed to the housing, an input section for receiving the rotational force of the motor, a case housing a reduction mechanism for reducing the rotational force and a lubrication chamber for lubricating the reduction mechanism, and a sealing member for sealing the space between the input section and the case. Grease-filled type The housing and the reduction gear are provided together. Grease-filled type At least one of the reduction gears is the housing and the Grease-filled type The joint structure includes a passage that opens the space surrounded by the part of the reduction gear, including the aforementioned sealing member, to the outside. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic perspective view showing a robot according to one embodiment of the present disclosure. [Figure 2] This is a partial cross-sectional view showing a joint structure according to one embodiment of the present disclosure. [Figure 3] Figure 2 is an exploded view illustrating the structure of the joint structure shown. [Figure 4] Figure 2 is a schematic diagram showing the drainage route of the joint structure. [Figure 5] Figure 2 is a perspective view showing the shape of a first modified example of the joint structure. [Figure 6] Figure 2 is a schematic diagram showing the shape of the second modified example. [Modes for carrying out the invention]

[0008] An articulated structure 1 and a robot 100 according to one embodiment of this disclosure will be described below with reference to the drawings. The joint structure 1 according to this embodiment is applied to, for example, a vertical 6-axis articulated robot 100 (hereinafter referred to as robot 100) as shown in Figure 1.

[0009] First, let me explain the configuration of robot 100. Robot 100 includes, for example, a base 110 installed on a horizontal floor surface, and a slewing body 120 rotatably supported relative to the base 110 around a first axis J1 extending vertically, as shown in Figure 1. Robot 100 also includes a first arm 130 rotatably supported relative to the slewing body 120 around a horizontal second axis J2, and a second arm 140 rotatably supported relative to the first arm 130 around a horizontal third axis J3. Furthermore, robot 100 includes a three-axis wrist unit 150 connected to the tip of the second arm 140.

[0010] Next, the joint structure 1 according to this embodiment is, for example, a joint structure between the rotating body 120 and the first arm 130. Specifically, as shown in Figure 2, the joint structure 1 includes a slewing body 120, a first arm 130, and a motor 30 and a reduction gear 40 that rotate the first arm 130 around the second axis J2 relative to the slewing body 120.

[0011] As shown in Figure 1, the slewing drum 120 includes a substantially flat main body portion 121 fixed to an output shaft that rotates around the first axis J1 of a reduction gear (not shown) fixed to the base 110. The slewing drum 120 also includes a side wall (housing) 122 that rises upward from one end in the width direction of the main body portion 121. A mounting surface 123 is formed on the outer surface of the side wall 122 to which a motor 30, described later, is fixed, and a recess 124 is formed on the side of the side wall 122 opposite to the mounting surface 123, recessed toward the mounting surface 123.

[0012] As shown in Figure 2, the mounting surface 123 has a through hole 125 that extends through to the recess 124 with the second axis J2 as its central axis. In addition, multiple screw holes (not shown) are formed around the through hole 125, arranged at equal intervals in the circumferential direction.

[0013] As shown in Figure 3, an inner circumferential surface 124i is formed inside the recess 124, with the second axis J2 as its central axis. At positions facing each other across the second axis J2 of the inner peripheral surface 124i, a pair of grooves (passages) D1 that are recessed radially outward are formed in parallel with the second axis J2.

[0014] Also, on the peripheral edge of the recess 124 of the side wall 122, an annular receiving surface 124s is formed against which the flange 41f of the speed reducer 40 described later can abut in the direction of the second axis J2. A plurality of screw holes 120h are formed in the receiving surface 124s at intervals in the circumferential direction. Further, in a region corresponding to the pair of grooves D1 of the receiving surface 124s, a substantially circular stepped portion (passage) D2 that is recessed in the direction of the second axis J2 and has a larger diameter than, for example, the screw holes 120h is formed. A part of the stepped portion D2 is connected to the groove D1.

[0015] As shown in FIG. 2, the motor 30 includes a shaft 31 that rotates around the second axis J2 and a drive gear 35 attached to the tip of the shaft 31. Also, a plurality of through holes (not shown) extending in a direction parallel to the axis of the shaft 31 are formed in the main body portion of the motor 30. Then, the motor 30 is attached to the side wall 122 by fastening each bolt (not shown) passing through the plurality of through holes of the main body portion to a plurality of screw holes on the periphery of the through hole 125 of the mounting surface 123. That is, the motor 30 is disposed at a position where it closes the through hole 125 with the shaft 31 penetrating from the outside.

[0016] The speed reducer 40 is, for example, a grease-sealed type speed reducer, and as shown in FIGS. 2 and 3, includes a substantially cylindrical case (barrel portion) 41, an input portion 42 provided on one end side in the central axis direction of the case 41, and an output portion 43 provided on the other end side. Inside the case 41, a lubrication chamber is provided that houses a transmission mechanism (speed reduction mechanism), not shown, constituted by a plurality of meshing gears and a lubricant for lubricating the transmission mechanism.

[0017] On the outer peripheral surface of the case 41, there are provided a fitting outer surface 41о formed with an outer diameter dimension that can be fitted to the inner peripheral surface 124i of the recess 124 of the swivel body 120, and an annular flange 41f that protrudes radially outward over the entire circumference.

[0018] The flange 41f has a flange surface that abuts against the receiving surface 124s of the swivel body 120 in a state where the fitting outer surface 41о of the case 41 is fitted to the inner peripheral surface 124i of the swivel body 120 along the second axis J2. Further, a plurality of through holes (not shown) extending parallel to the central axis of the case 41 are formed at intervals in the circumferential direction on the flange 41f. Furthermore, as shown in FIGS. 2 and 3, on the flange 41f, a pair of screw holes (through holes) h extending parallel to the central axis of the case 41 are formed at positions corresponding to the stepped portion D2 of the swivel body 120.

[0019] Here, the screw hole h in the present embodiment is a tapping screw for removing the speed reducer 40 fitted in the recess 124 of the swivel body 120. That is, in a state where the speed reducer 40 is fitted to the swivel body 120, by tightening a bolt (not shown) having a length greater than or equal to the thickness of the flange 41f into the screw hole h, the tip of the bolt is pressed against the stepped portion D2. As a result, the speed reducer 40 is pulled away from the swivel body 120, and the fitting state can be released.

[0020] Next, the input portion 42 is supported rotatably about its central axis with respect to the case 41 and meshes with one of the gears constituting the transmission mechanism in the case 41. Further, as shown in FIG. 2, in a state where the case 41 is fitted into the recess 124 of the swivel body 120, a bottomed hole (not shown) that meshes with the drive gear 35 of the motor 30 attached to the swivel body 120 is formed in the input portion 42. That is, the input portion 42 receives the rotational force output by the motor 30 and enables input to the transmission mechanism in the case 41.

[0021] Furthermore, in the example shown in Figure 2, an annular oil seal (sealing member) 36 is positioned between the input section 42 and the case 41, thereby maintaining a sealed state inside the case 41. The oil seal 36 comprises, for example, a metal annular member (not shown), a lip portion (not shown) made of an elastic material such as nitrile rubber or fluororubber, and a metal spring (not shown) that presses the lip portion against a mating member.

[0022] The output unit 43 is supported so as to be rotatable about its central axis relative to the end of the case 41 opposite to the input unit 42, and meshes with one of the gears that constitute the transmission mechanism inside the case 41. The first arm 130 is also fixed to the output unit 43 by a plurality of bolts b2.

[0023] Here, we will explain in more detail the assembly of the rotating drum 120 to which the motor 30 is attached and the reduction gear 40. As shown in Figures 2 and 3, the fitting outer surface 41o of the case 41 of the reduction gear 40 is fitted to the inner circumferential surface 124i of the recess 124 in a direction along the second axis J2, such that the central axis of the case 41 is coaxial with the second axis J2. In addition, when the flange 41f is in contact with the receiving surface 124s of the slewing drum 120, bolts b1 passing through each through hole of the flange 41f are fastened to the corresponding screw holes 120h of the receiving surface 124s. As a result, the opening of the recess 124 is closed by the reduction gear 40, defining a closed space (space) S inside which the input section 42 of the reduction gear 40 and the oil seal 36 are located.

[0024] Furthermore, within the enclosed space S, the drive gear 35 at the tip of the shaft 31, which passes through the through hole 125 blocked by the motor 30, is connected to the input section 42 of the reduction gear 40, which blocks the opening of the recess 124. In other words, the rotational force of the motor 30 is received by the input section 42 and transmitted to the output section 43 as a reduced driving force via the transmission mechanism inside the case 41. As a result, the first arm 130 rotates around the second axis J2 relative to the slewing drum 120.

[0025] The operation of the joint structure 1 and robot 100 according to this embodiment, configured in this manner, will be described below.

[0026] In the joint structure 1 according to this embodiment, since the reduction gear 40 is a grease-filled reduction gear, there is no need to form a lubrication chamber such as a grease bath around the reduction gear 40. Furthermore, since the reduction gear 40 is fitted and fixed to the slewing drum 120, the two, i.e., the fitting portion, are in close contact. Therefore, there is an advantage in that there is no need to place a sealing member such as an oil seal between the slewing drum 120 and the reduction gear 40.

[0027] On the other hand, in such a configuration, minute gaps may occur in the fitting portion between the slewing drum 120 and the reduction gear 40 due to aging or the effects of thermal expansion and contraction. Furthermore, if the joint structure 1 and the robot 100 are used in an environment where liquids such as cleaning water or coolant are scattered, there is a possibility that liquid may enter the closed space S through the minute gaps that have formed in the fitting portion.

[0028] However, in the joint structure 1 according to this embodiment, as shown in Figure 4, the closed space S is connected to the outside space via the groove D1, the stepped portion D2, and the screw hole h. That is, the groove D1, the stepped portion D2, and the screw hole h can be used as drainage passages that allow liquid that has entered the closed space S to be discharged to the outside space. Therefore, as the posture of the joint structure 1 changes due to the movement of the robot 100, the groove D1, the stepped portion D2, and the screw hole h are positioned below the closed space S, and any liquid that enters the closed space S is discharged to the outside by gravity.

[0029] This prevents external liquid from entering the enclosed space S defined around the gearbox 40, even if it does, from remaining in the enclosed space S for an extended period. As a result, rubber components such as the oil seal 36 of the gearbox 40, which are located within the enclosed space S, are not exposed to liquid for extended periods, thus suppressing degradation such as hydrolysis. This reduces the risk of liquid entering the inside of the gearbox 40 and improves the reliability of the joint structure 1 and the robot 100. In addition, the improved durability of the oil seals placed within the enclosed space S has the added benefit of extending the maintenance cycle of the joint structure 1 and the robot 100.

[0030] Furthermore, in this embodiment, the screw hole h, which is a pull tap necessary to release the engagement between the slewing drum 120 and the reduction gear 40, is used as a drainage passage for the liquid in the closed space S. Therefore, since there is no need to provide a dedicated drainage hole or groove in the reduction gear 40, the design of the reduction gear 40 can be simplified.

[0031] Furthermore, in this embodiment, the stepped portion D2 used as a drainage passage is positioned where the tip of the bolt tightened into the screw hole h is pressed when separating the reduction gear 40 from the slewing drum 120. In other words, since the seating surface against which the tip of the bolt used for tapping is pressed is one step lower than the surrounding receiving surface 124s, even if the bolt used for tapping causes irregularities on the seating surface, it does not hinder the fitting of the reduction gear 40.

[0032] In this embodiment, an example is given in which the groove D1 and stepped portion D2 formed in the slewing drum 120, and the screw hole h formed as a tap in the reduction gear 40, are used as drainage passages for liquid that has entered the closed space S. Alternatively, either the slewing drum 120 or the reduction gear 40 may have a portion that can be used as a drainage passage for liquid that has entered the closed space S.

[0033] For example, as shown in Figure 5, if the annular receiving surface 124s is provided with a stepped portion D2' that extends radially from the inner edge to the outer edge, the screw hole h of the reducer 40 may be omitted. Alternatively, the screw hole h, which serves as a tap for the reducer 40, may be placed at a different position from the stepped portion D2'. In other words, the configuration may be such that only the groove D1 and the stepped portion D2' of the slewing drum 120 are used as drainage passages for liquid that has entered the closed space S.

[0034] Furthermore, in this embodiment, if the screw hole h is positioned to connect the closed space S and the external space when the reduction gear 40 is fitted to the slewing drum 120, the groove D1 and the stepped portion D2 may be omitted.

[0035] In this embodiment, instead of the groove portion D1 and the stepped portion D2, a through hole D2'' that penetrates radially may be formed in the inner circumferential surface 124i of the recess 124 of the slewing drum 120, as shown in Figure 6. In this case, the same effect as described above can be obtained even if the groove D1 and screw hole h are omitted. Furthermore, this configuration is particularly useful when the posture of the joint structure 1 does not change, and the lower position where the liquid that has entered the closed space S will accumulate is predetermined.

[0036] Furthermore, in this embodiment, the joint structure 1 is exemplified as the joint between the rotating body 120 and the first arm 130, but the joint structure 1 may also be applied to the joint between the first arm 130 and the second arm 140 of the robot 100, etc.

[0037] Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the invention or from the spirit and intent of the invention derived from the claims and their equivalents. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto.

[0038] The following additional information is disclosed regarding the above embodiments and modifications. (Note 1) A joint structure for a robot, comprising a housing, a motor fixed to the housing, an input section for receiving the rotational force of the motor, a case housing a reduction mechanism for reducing the rotational force and a lubrication chamber for lubricating the reduction mechanism, and a reduction gear having a sealing member for sealing the space between the input section and the case, wherein at least one of the housing and the reduction gear has a passage that opens the space surrounded by the housing and a portion of the reduction gear including the sealing member to the outside. (Note 2) The joint structure according to Appendix 1, wherein the input section is supported so as to be rotatable with respect to the case, the case comprises a cylindrical body with the axis as its central axis and a flange extending radially outward from the body, the housing comprises a recess that defines the space by fitting with the body and a receiving surface that the flange abuts against in the axial direction in the fitted state, and in the fitted state, at least a portion of the passage is positioned at the fitting portion between the body and the recess and the contact portion between the flange and the receiving surface. (Note 3) The joint structure according to Appendix 2, wherein a through hole formed in the flange and extending parallel to the axis constitutes at least a portion of the passage. (Note 4) The joint structure according to Appendix 3, wherein the through hole is a tap for the speed reducer, and a portion of the passage formed in the housing is positioned so that the tip of a bolt tightened into the tap is pressed against it. (Note 5) The joint structure according to Appendix 1, wherein the passage is a through-hole that allows the space formed in the housing to be opened vertically downward. (Note 6) A robot having a joint structure as described in any of the appendices 1 to 5. [Explanation of Symbols]

[0039] 1. Joint structure 30 motors 36. Oil seal (sealing component) 40 Reducer 41 Case (body) 41f flange 42 Input section 122 Side wall (housing) 124 recess 124s receiving surface 100 robots h Screw hole (through hole) J3 3rd axis (axis) S Closed space (space)

Claims

1. A robot joint structure, Housing and A motor fixed to the housing, The grease-filled speed reducer comprises an input section for receiving the rotational force of the motor, a case housing a reduction mechanism for reducing the rotational force and a lubrication chamber for lubricating the reduction mechanism, and a sealing member for sealing the space between the input section and the case. An articulated structure wherein at least one of the housing and the grease-filled speed reducer has a passage that opens the space surrounded by the housing and a portion of the grease-filled speed reducer including the sealing member to the outside.

2. The input unit is supported so as to be rotatable around a predetermined axis relative to the case. The case comprises a cylindrical body with the axis as its central axis, and a flange extending radially outward from the body. The housing comprises a recess that defines the space by fitting with the body portion, and a receiving surface that the flange abuts against in the axial direction in the fitted state, The joint structure according to claim 1, wherein in the fitted state, at least a portion of the passage is arranged in the fitting portion between the body portion and the recess and the contact portion between the flange and the receiving surface.

3. The joint structure according to claim 2, wherein a through hole formed in the flange and extending parallel to the axis constitutes at least a portion of the passage.

4. The through hole is the extraction tap for the grease-filled speed reducer. The joint structure according to claim 3, wherein a portion of the passage formed in the housing is positioned so that the tip of the bolt tightened into the extraction tap is pressed against it.

5. The joint structure according to claim 1, wherein the passage is a through-hole that allows the space formed in the housing to be opened vertically downward.

6. A robot comprising the joint structure described in any one of claims 1 to 5.

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