Drive mechanism

Abstract

A drive mechanism (1) that rotates two driven bodies (M1, M2) around an axis (C) includes a single drive unit (3), a first reducer (70), and a second reducer (80). The drive unit (3) outputs rotational power to a rotating shaft (2) disposed on the axis (C). The first reducer (70) is disposed coaxially with the rotating shaft (2). With the second output unit (72) fixed and non-rotatable, the first reducer (70) reduces the rotational power at a first reduction ratio to rotate an outer peripheral surface (73) of the first output unit (71) in a direction opposite to the rotational direction of the rotating shaft (2). The second reducer (80) is disposed coaxially with the rotating shaft (2). With the third output unit (81) fixed to the first output unit (71), the second reducer (80) reduces the rotational power at a second reduction ratio to rotate an outer peripheral surface (83) of the fourth output unit (82). The first driven member (M1) is attached to the outer peripheral surface (73) of the first output portion (71), and the second driven member (M2) is attached to the outer peripheral surface (83) of the fourth output portion (82).

Description

[Technical Field]

[0001] The present invention relates to a drive mechanism for turning two driven bodies. [Background technology]

[0002] Conventionally, there has been known a drive mechanism for rotating two driven bodies. For example, Patent Document 1 discloses a conveyance device (drive mechanism) for rotating a first arm and a second arm (two driven bodies) around a coaxially arranged rotation axis, the conveyance device including two rotary motors for rotating the rotation axis of each of the first arm and the second arm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-199121 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the drive mechanism disclosed in Patent Document 1, multiple motors are provided to rotate the two driven bodies, making it difficult to reduce the size of the drive mechanism itself. Therefore, there is room for improvement in reducing the size of the drive mechanism.

[0005] The present invention was conceived in light of these problems, and one of its objectives is to reduce the size of the drive mechanism. However, in addition to this objective, another objective of the present invention is to achieve effects derived from the configurations shown in the "Mode for Carrying Out the Invention" below, which are not obtainable with conventional technology. [Means for solving the problem]

[0006] The disclosed drive mechanism can be realized as the following disclosed embodiments (application examples), which solve at least part of the above-mentioned problems. Each of the embodiments from embodiment 2 onwards is an embodiment that can be selected as an additional option, and each of the embodiments can be omitted. None of the embodiments from embodiment 2 onwards discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed drive mechanism rotates two driven bodies arranged around an axis line, the drive mechanism comprising: a single drive unit that outputs rotational power to a rotary shaft arranged on the axis line, a first reducer arranged coaxially with the rotary shaft, and a second reducer arranged coaxially with the rotary shaft. The first reducer has a first output unit through which the rotary shaft is inserted and rotatable around the rotary shaft, and a second output unit rotatable on one side of the rotary shaft in the axial direction relative to the first output unit, and with the second output unit fixed so as not to rotate, the rotational power is reduced at a first reduction ratio and output to the first output unit, thereby rotating the outer circumferential surface of the first output unit in a direction opposite to the rotational direction of the rotary shaft. The second reducer has a third output section, the rotation shaft of which is inserted at the other side of the first output section in the axial direction and which is rotatable around the rotation shaft, and a fourth output section, the rotation power of which is reduced at a second reduction ratio and output to the fourth output section with the third output section fixed to the first output section, thereby rotating an outer circumferential surface of the fourth output section. One of the two driven bodies is attached to the outer circumferential surface of the first output section, and the other of the two driven bodies is attached to the outer circumferential surface of the fourth output section.

[0008] Aspect 2. In the above aspect 1, it is preferable that the first reduction ratio is expressed by the following formula 1, and the second reduction ratio is expressed by the following formula 2.

number

[0009] Aspect 3. In the above aspect 2, it is preferable that the first reduction ratio is different from the second reduction ratio. Aspect 4. In the above aspect 2, it is preferable that the first reduction ratio is less than the second reduction ratio. Aspect 5. In the above aspect 2, it is preferable that the first reduction ratio is half of the second reduction ratio. Aspect 6. In the above aspect 2, it is preferable that the first reduction ratio is greater than the second reduction ratio. Aspect 7. In the above aspect 2, it is preferable that the first reduction ratio is the same as the second reduction ratio. [Effects of the Invention]

[0010] According to the disclosed invention, the drive mechanism can be made smaller. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a perspective view schematically illustrating a drive mechanism according to an embodiment. [Figure 2] 2 is a partially exploded perspective view of a compound reducer included in the drive mechanism of FIG. 1. FIG. [Figure 3] 2 is a perspective view schematically showing a single reducer used in the compound reducer provided in the drive mechanism of FIG. 1. FIG. [Figure 4] 1 is a perspective view schematically showing a welding device to which a drive mechanism according to an embodiment is applied; DETAILED DESCRIPTION OF THE INVENTION

[0012] A drive mechanism according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or applications of techniques not explicitly described in the following embodiments. The configurations of the present embodiment can be modified in various ways without departing from the spirit of the invention. Furthermore, they can be selected or combined as needed.

[0013] I. ONE EMBODIMENT [1. Drive mechanism] Fig. 1 is a perspective view schematically showing a drive mechanism 1 according to one embodiment. The drive mechanism 1 of this embodiment is a mechanism that rotates two driven bodies M1 and M2 arranged around an axis C, about the axis C. As shown in Fig. 1, the drive mechanism 1 includes a single drive unit 3 that outputs rotational power to a rotating shaft 2 arranged on the axis C, and a compound reducer 4 that is arranged coaxially with the rotating shaft 2.

[0014] Hereinafter, the direction of axis C will be referred to as the axial direction. Also, a direction perpendicular to the axial direction and away from axis C will be referred to as the radially outward direction, and a direction perpendicular to the axial direction and towards axis C will be referred to as the radially inward direction. When no distinction is made between inside and outside, the term will simply be used. A direction perpendicular to the axial direction and going around axis C will be referred to as the circumferential direction. The rotating shaft 2 extends in the axial direction, is disposed so that its center line and the axis C are aligned on the same line, and rotates around the axis C. Therefore, the circumferential direction can also be described as the rotation direction of the rotating shaft 2. Furthermore, since the driven bodies M1 and M2 revolve around the axis C, the circumferential direction can also be described as the revolving direction of the driven bodies M1 and M2.

[0015] The two driven bodies M1 and M2 are provided radially outward of the rotating shaft 2 and spaced apart from the rotating shaft 2, and are objects that are driven by the drive mechanism 1. More specifically, the two driven bodies M1 and M2 are attached to the outer peripheral surfaces of the substantially cylindrical compound reducer 4 that is arranged around the rotating shaft 2 (the outer peripheral surface 73 of a first case 71 and the outer peripheral surface 83 of a second output flange 82, which will be described later, respectively).

[0016] Hereinafter, of the two driven bodies M1, M2, the driven body M1 (one of the two driven bodies) attached to the outer peripheral surface 73 of the first case 71 of the compound reducer 4 will be referred to as the first driven body M1. Also, of the two driven bodies M1, M2, the driven body M2 (the other of the two driven bodies) attached to the outer peripheral surface 83 of the second output flange 82 of the compound reducer 4 will be referred to as the second driven body M2.

[0017] In this embodiment, both the first driven body M1 and the second driven body M2 revolve around the rotation axis 2 along an imaginary circle (shown by a two-dot chain line in FIG. 1) centered on the axis C. However, it is sufficient that each of the first driven body M1 and the second driven body M2 revolves at least around the axis C, and they do not necessarily have to revolve along a common imaginary circle as shown in FIG. 1.

[0018] Furthermore, although the driven bodies M1 and M2 are illustrated here as being approximately cylindrical and extending in the axial direction, the shapes and types of the driven bodies M1 and M2 are not particularly limited. For example, the driven bodies M1 and M2 may be prismatic or cylindrical rather than cylindrical, or may be rod-like arms extending in the radial direction. Furthermore, although the two driven bodies M1 and M2 are arranged at the same axial position here, the two driven bodies M1 and M2 may be arranged at different axial positions from each other. Furthermore, the two driven bodies M1 and M2 do not have to be the same objects (machines or devices) or have the same shapes.

[0019] The drive unit 3 is a drive source that rotates the rotating shaft 2. The drive unit 3 is provided with a motor main body that generates rotational power to be output to the rotating shaft 2, and an encoder for adjusting the amount of rotation of the rotating shaft 2 (drive degree, rotation angle, rotation speed). 1, the drive unit 3 is not disposed radially outward of the compound reducer 4 through which the rotating shaft 2 is inserted, but is disposed coaxially with the rotating shaft 2 on one side of the compound reducer 4 in the axial direction (at a position where the entire drive unit 3 completely overlaps the compound reducer 4 when viewed from the axial direction), radially inward of the compound reducer 4. By disposing the drive unit 3 coaxially with the rotating shaft 2, the drive unit 3 is less likely to interfere with the driven bodies M1 and M2 disposed around the rotating shaft 2, and the degree of freedom in the layout of the drive mechanism 1 is ensured.

[0020] The compound reducer 4 reduces and outputs the rotation of the rotating shaft 2. A specific example of the compound reducer 4 will be described below with reference to FIGS. Fig. 2 is an exploded perspective view of a portion of the compound reducer 4 of Fig. 1, omitting a connecting member 78 described later. Fig. 3 is a perspective view schematically showing the reducers 70 and 80 provided in the compound reducer 4.

[0021] 1, the drive mechanism 1 is provided with only one drive unit 3 that rotationally drives the rotating shaft 2, whereas the compound reducer 4 is provided with two, a first reducer 70 and a second reducer 80. The rotational power of the rotating shaft 2 is input to each of the reducers 70, 80. The drive mechanism 1 distributes the rotational power output from the drive unit 3 to both the first reducer 70 and the second reducer 80, thereby rotating both of the two driven bodies M1, M2 about the axis C.

[0022] The rotating shaft 2 is provided with a first rotating shaft 7R, which is a portion that is inserted into the first reducer 70, and a second rotating shaft 8R, which is a portion that is inserted into the second reducer 80. The first rotating shaft 7R and the second rotating shaft 8R are connected to each other along an axis C and rotate integrally.

[0023] First, the configuration common to the reducers 70 and 80 will be described with reference to FIG. The reducers 70, 80 are reducers in which the rotating shafts 7R, 8R, cases 71, 81, and output flanges 72, 82 are arranged coaxially. If the rotating shafts 7R, 8R are considered to be first elements, the cases 71, 81 are considered to be second elements, and the output flanges 72, 82 are considered to be third elements, the reducers 70, 80 can be said to be three-element, two-degree-of-freedom reducers. Here, a three-element, two-degree-of-freedom reducer means a reducer in which, when the rotational speeds of two of the three elements are determined, the rotational speed of the remaining element is uniquely determined.

[0024] The illustrated reducers 70 and 80 are high-precision control reducers that employ a planocentric speed reduction mechanism. TMHowever, each of the reducers 70, 80 may be a three-element, two-degree-of-freedom reducer consisting of at least three coaxially arranged elements, and a well-known planetary gear mechanism, harmonic reducer, or the like may be applied.

[0025] Each reducer 70, 80 is provided with a spur gear 7s, 8s that meshes with each input gear 7i, 8i provided on the outer periphery of the rotating shaft 7R, 8R, and each case 71, 81 and each output flange 72, 82 that are freely rotatable in accordance with the rotation of each spur gear 7s, 8s.

[0026] Specifically, the first reducer 70 includes a first spur gear 7s, a first case 71 (first output portion), and a first output flange 72 (second output portion). A first reduction ratio i1 is set in the first reducer 70. The second reducer 80 is provided with a second spur gear 8s, a second case 81 (third output portion), and a second output flange 82 (fourth output portion). A second reduction ratio i2 is set in the second reducer 80.

[0027] The first case 71 and the second case 81 are provided so as to be rotatable about the rotation shafts 7R, 8R, with the rotation shafts 7R, 8R inserted therethrough. The first output flange 72 is provided rotatably relative to the first case 71. Similarly, the second output flange 82 is provided rotatably relative to the second case 81.

[0028] The cases 71, 81 and the output flanges 72, 82 are coaxial with the rotating shafts 7R, 8R and are provided in a cylindrical (annular) shape centered on the axis C. That is, the rotating shafts 7R, 8R are inserted through the cases 71, 81 and the output flanges 72, 82.

[0029] Each of the cases 71, 81 and each of the output flanges 72, 82 can output rotational power without being constrained by other elements, and can also be used by being attached to another fixed (immovable) member to prevent rotation, or by being constrained to rotate integrally with another rotating element. Therefore, the cases 71, 81 and the output flanges 72, 82 can be said to be elements (output parts) that can reduce the rotational power of the rotating shafts 7R, 8R (i.e., the rotating shaft 2) according to the reduction ratios i1, i2 of the reducers 70, 80 and output the reduced power.

[0030] One common use of the reducers 70, 80 is to output rotational power to the output flanges 72, 82 in a state where the cases 71, 81 are fixed so as not to rotate. The first reduction ratio i1 of the first reducer 70 is defined as the value obtained by dividing the rotational speed of the first output flange 72 by the rotational speed of the first rotating shaft 7R when the first case 71 is fixed so as not to rotate. Also, the second reduction ratio i2 of the second reducer 80 is defined as the value obtained by dividing the rotational speed of the second output flange 82 by the rotational speed of the second rotating shaft 8R when the second case 81 is fixed so as not to rotate.

[0031] The cases 71, 81 are case-shaped members that house the spur gears 7s, 8s on the side of the axis C (i.e., on the radially inner side). These cases 71, 81 are configured to rotate in the direction opposite to the rotation direction of the rotating shaft 2, regardless of the reduction ratios i1, i2 of the reducers 70, 80, as long as the output flanges 72, 82 are fixed so as not to rotate. The output flanges 72, 82 are disposed at different axial positions relative to the cases 71, 81. The output flanges 72, 82 can also be considered as members that protrude in the axial direction like a flange. The rotation direction of the output flanges 72, 82, which are not fixed so as to be non-rotatable, is determined by the reduction ratios i1, i2 of the reducers 70, 80.

[0032] Next, the configuration of each of the reducers 70 and 80 will be described with reference to FIGS. In the compound reducer 4, the first output flange 72 and first case 71 of the first reducer 70, and the second case 81 and second output flange 82 of the second reducer 80 are arranged in this order from one axial side to the other. In other words, the first output flange 72 is located on one axial side of the first case 71, the second case 81 is located on the other axial side of the first case 71, and the second output flange 82 is located on the other axial side of the second case 81. As described above, the first driven body M1 is fixed to the outer peripheral surface 73 of the first case 71, and the second driven body M2 is fixed to the outer peripheral surface 83 of the second output flange 82.

[0033] 1 has a connecting member 78 provided between the first case 71 and the second case 81. The connecting member 78 is a member that connects the first case 71 and the second case 81 so that the cases 71 and 81 rotate together, and is provided in a cylindrical shape centered on the axis C, just like the cases 71 and 81. However, it is also possible to omit the connecting member 78 and use a compound reducer 4 in which the cases 71 and 81 are directly connected to each other.

[0034] With the first output flange 72 fixed so as not to rotate, the first reducer 70 reduces the rotational power of the rotating shaft 2 at a first reduction ratio i1 and outputs the reduced power to the first case 71. With the first output flange 72 fixed so as not to rotate, the first reducer 70 to which the rotational power is transmitted in this manner rotates the outer peripheral surface 73 of the first case 71 in the direction opposite to the rotational direction of the rotating shaft 2 regardless of the reduction ratios i1, i2 of the reducers 70, 80. As a result, the first driven body M1 fixed to the outer peripheral surface 73 of the first case 71 is caused to orbit in the direction opposite to the rotational direction of the rotating shaft 2.

[0035] With the second case 81 fixed to the first case 71, the second reducer 80 reduces the rotational power of the rotating shaft 2 at a second reduction ratio i2 and outputs the reduced power to the second output flange 82. In this way, in the second reducer 80 in which the rotational power of the first case 71, reduced at the first reduction ratio i1, is input to the second case 81, the direction in which the outer circumferential surface 83 of the second output flange 82 rotates is determined by the reduction ratios i1 and i2 of the reducers 70, 80. As a result, the second driven body M2 fixed to the outer circumferential surface 83 of the second output flange 82 is caused to revolve in the rotational direction of the outer circumferential surface 83.

[0036] Specifically, the first reduction ratio i1 of the first reducer 70 is expressed by the following formula 1, and the second reduction ratio i2 of the second reducer 80 is expressed by the following formula 2.

[0037]

number

[0038] The rotational speeds a, b, and c are positive when they rotate in the same direction as the rotational direction of the rotating shaft 2, and are negative when they rotate in the opposite direction. The rotation speed a of the rotary shaft 2 can only take positive values, the rotation speed b of the first case 71 can only take negative values, and the rotation speed c of the second output flange 82 can take positive or negative values ​​depending on the reduction ratios i1 and i2.

[0039] In the compound reducer 4, the rotation direction and rotation speed of the two driven bodies M1, M2 are determined depending on the relative magnitude relationship between the first reduction gear ratio i1 and the second reduction gear ratio i2. Various settings can be adopted for the relative magnitude relationship between the first reduction gear ratio i1 and the second reduction gear ratio i2, for example, as listed in Table 1 below.

[0040] [Table 1]

[0041] When the first reduction ratio i1 is less than the second reduction ratio i2, as in the first setting, the second setting, and the third setting, the second output flange 82 rotates in the direction opposite to the rotation direction of the first case 71. As a result, the first driven body M1 fixed to the outer peripheral surface 73 of the first case 71 and the second driven body M2 fixed to the outer peripheral surface 83 of the second output flange 82 revolve in directions different from each other.

[0042] For example, when viewed from one side in the axial direction to the other, the counterclockwise direction among the circumferential directions is defined as the first direction, and the clockwise direction is defined as the second direction. When the driving unit 3 rotates the rotating shaft 2 in the first direction (the direction of arrow U1 in FIG. 2), the first case 71 rotates in a second direction (the direction of arrow V2 in FIG. 2) opposite to the first direction, and the second output flange 82 rotates in the first direction (the direction of arrow W1 in FIG. 2). As a result, the first driven body M1 pivots in the second direction (the direction of arrow S2 in FIG. 1), and the second driven body M2 pivots in the first direction (the direction of arrow T1 in FIG. 1).

[0043] Conversely, when the driving unit 3 rotates the rotary shaft 2 in the second direction (the direction of arrow U2 in FIG. 2), the first case 71 rotates in the first direction (the direction of arrow V1 in FIG. 2) opposite to the second direction, and the second output flange 82 rotates in the second direction (the direction of arrow W2 in FIG. 2). As a result, the first driven body M1 turns in the first direction (the direction of arrow S1 in FIG. 1), and the second driven body M2 turns in the second direction (the direction of arrow T2 in FIG. 1).

[0044] On the other hand, in the fifth setting where the first reduction ratio i1 is greater than the second reduction ratio i2, the second output flange 82 rotates in the same direction as the rotation direction of the first case 71. As a result, the first driven body M1 and the second driven body M2 revolve in the same direction.

[0045] That is, when the rotary shaft 2 is rotated in a first direction (the direction of arrow U1 in FIG. 2) by the drive unit 3, both the first case 71 and the second output flange 82 rotate in a second direction (the directions of arrows V2 and W2 in FIG. 2) opposite to the first direction, causing both the first driven body M1 and the second driven body M2 to pivot in the second direction (the directions of arrows S2 and T2 in FIG. 1).

[0046] Conversely, when the driving unit 3 rotates the rotary shaft 2 in the second direction (the direction of arrow U2 in FIG. 2), both the first case 71 and the second output flange 82 rotate in the first direction (the directions of arrows V1 and W1 in FIG. 2) opposite to the second direction, causing both the first driven body M1 and the second driven body M2 to pivot in the first direction (the directions of arrows S1 and T1 in FIG. 1).

[0047] In other words, when the first reduction ratio i1 and the second reduction ratio i2 are different, such as in the first setting, the second setting, the third setting, and the fifth setting, both the first case 71 and the second output flange 82 rotate. As a result, both of the two driven bodies M1 and M2 can be rotated by the rotational power of a single driving unit 3. In the fifth setting, the rotational speed c of the second output flange 82 is slower than the rotational speed b of the first case 71 (|b|>|c|). As a result, the second driven body M2 rotates at a slower speed than the first driven body M1.

[0048] Furthermore, in the first setting where the first reduction ratio i1 is less than half the second reduction ratio i2, the rotational speed c of the second output flange 82 is faster than the rotational speed b of the first case 71 (|b|<|c|). As a result, the second driven body M2 rotates at a higher speed than the first driven body M1. In the second setting where the first reduction ratio i1 is half the second reduction ratio i2, the rotational speed b of the first case 71 is equal to the rotational speed c of the second output flange 82 (|b|=|c|), causing the first driven body M1 and the second driven body M2 to revolve at a constant speed. In the third setting where the first reduction ratio i1 is greater than half the second reduction ratio i2 and less than the second reduction ratio i2, the rotational speed b of the first case 71 is faster than the rotational speed c of the second output flange 82 (|b|>|c|). As a result, the second driven body M2 rotates at a slower speed than the first driven body M1.

[0049] In the fourth setting where the first reduction ratio i1 and the second reduction ratio i2 are the same, the rotation of the rotating shaft 2 is canceled out by the rotation of the second case 81, which rotates integrally with the first case 71, within the second reducer 80. As a result, the second output flange 82 does not rotate (c=0), and only the first case 71 rotates, causing only the first driven body M1 to orbit.

[0050] [2. Actions and Effects] The drive mechanism 1 of this embodiment is configured as described above, and therefore provides the following actions and effects. (1) In the drive mechanism 1 of this embodiment, the rotational power output from the single drive unit 3 is distributed to both the first output portion of the first reducer 70 (first case 71 in this embodiment) and the fourth output portion of the second reducer 80 (second output flange 82 in this embodiment). As a result, the two driven bodies M1 and M2 arranged around the axis C can be rotated about the axis C. Therefore, the drive mechanism 1 can be made smaller than a conventional drive mechanism in which multiple drive units are provided according to the number of driven bodies M1 and M2.

[0051] Moreover, in the drive mechanism 1 of this embodiment, the first reducer 70 and the second reducer 80 are arranged coaxially with the rotating shaft 2. Furthermore, the two driven bodies M1, M2 are attached to the outer peripheral surface 73 of the first case 71 of the first reducer 70 and the outer peripheral surface 83 of the second output flange 82 of the second reducer 80, respectively. In other words, in the drive mechanism 1 of this embodiment, the reducers 70, 80 for transmitting the rotational power of the rotating shaft 2 to the two driven bodies M1, M2 are arranged coaxially radially inward of the two driven bodies M1, M2, and therefore the drive mechanism 1 itself can be made sufficiently compact.

[0052] (2) By setting the reduction ratios i1 and i2 expressed by the above formulas 1 and 2 in the reducers 70 and 80, the two driven bodies M1 and M2 can be turned in various ways. (3) If the first reduction ratio i1 and the second reduction ratio i2 are different as shown in the first setting, second setting, third setting, and fifth setting in Table 1 above, both of the two driven bodies M1 and M2 can be rotated.

[0053] (4) If the first reduction ratio i1 is less than the second reduction ratio i2 as in the first setting, second setting, and third setting shown in Table 1 above, the two driven bodies M1 and M2 can be rotated in opposite directions (the directions of the hatched arrows or the dotted arrows shown in Figure 1). (5) Furthermore, if the first reduction ratio i1 is half the second reduction ratio i2 as in the second setting shown in Table 1 above, the two driven bodies M1 and M2 can be rotated in opposite directions and at the same speed.

[0054] (6) If the first reduction ratio i1 is greater than the second reduction ratio i2, as in the fifth setting shown in Table 1 above, both of the two driven bodies M1 and M2 can be rotated in the same direction (the direction of arrows S1 and T1 or the direction of arrows S2 and T2 shown in Figure 1), and the two driven bodies M1 and M2 can be rotated at different speeds. (7) If the first reduction ratio i1 and the second reduction ratio i2 are the same as in the fourth setting shown in Table 1 above, only the first driven body M1 can be rotated while the position of the second driven body M2 remains fixed.

[0055] [3. Examples of drive mechanism applications] FIG. 4 is a perspective view schematically illustrating a welding device 10 to which a drive mechanism 1 according to one embodiment is applied. The welding device 10 is a device that resistance-welds metal materials, such as steel and aluminum, using a pair of welding guns 21 and 22. Each welding gun 21 and 22 corresponds to each of the driven bodies M1 and M2 described above. In other words, the two welding guns 21 and 22 are driven by the drive mechanism 1. The welding device 10 is attached, for example, to the tip of a robot arm of a vertical articulated robot (not shown). The welding device 10 includes the drive mechanism 1, the two welding guns 21 and 22, a control unit 11, and a device main body 12.

[0056] Examples of the workpiece W (welding target, indicated by a two-dot chain line in FIG. 4) to be welded by the welding device 10 include metal members used in vehicles such as electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). A plug-in hybrid vehicle is a hybrid vehicle that can externally charge the battery or receive external power from the battery. A plug-in hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable that supplies power from an external charging facility, and a power outlet for external power supply.

[0057] In the welding device 10, the drive mechanism 1 rotates the two welding guns 21, 22, which serve as the two driven bodies M1, M2, about the axis C, thereby changing the relative positions of the two welding guns 21, 22.

[0058] Hereinafter, a Cartesian coordinate system having three mutually orthogonal coordinate axes, an X-axis, a Y-axis, and a Z-axis, will be used as a reference for directions used in the description of the welding device 10. In this Cartesian coordinate system, the direction along the X-axis will be referred to as the "X direction," the direction along the Y-axis will be referred to as the "Y direction," and the direction along the Z-axis will be referred to as the "Z direction." The X direction has two inherent directions: the direction from negative to positive on the X axis and the direction from positive to negative on the X axis, which are opposite to each other. Therefore, one of the X directions is called the "X1 direction" and the other is called the "X2 direction." Similarly, one of the Y directions is called the "Y1 direction" and the other is called the "Y2 direction." One of the Z directions is called the "Z1 direction" and the other is called the "Z2 direction."

[0059] The X direction corresponds to the "axial direction" in the above description of the drive mechanism 1. The X2 direction corresponds to the direction of "one side in the axial direction" in the above description of the drive mechanism 1, and the X1 direction corresponds to the direction of "the other side in the axial direction" in the above description of the drive mechanism 1. Welding device 10 is formed symmetrically in the Y direction. Two welding guns 21, 22 are arranged symmetrically in the Y direction across axis C. Hereinafter, welding gun 21 arranged on the Y1 side of axis C will be referred to as first welding gun 21, and welding gun 22 arranged on the Y2 side of axis C will be referred to as second welding gun 22. However, welding device 10 does not have to be completely symmetrical in the Y direction, and may be asymmetrical in the Y direction.

[0060] Welding guns 21, 22 each have electrodes 21E, 22E provided at the end (tip) in the X1 direction, actuators 21A, 22A provided at the end (base) in the X2 direction, and main bodies 21B, 22B provided between electrodes 21E, 22E and actuators 21A, 22A in the X direction, and have welding centers C21, C22 extending in the X direction. Electrodes 21E, 22E of welding guns 21, 22 are arranged to overlap with welding centers C21, C22 when viewed in the X direction (when viewed in the axial direction of rotation shaft 2). Preferably, the centers of electrodes 21E, 22E of welding guns 21, 22 and welding centers C21, C22 are arranged on the same line.

[0061] Various known welding guns can be used for welding guns 21 and 22. For example, any of an X-type welding gun, a C-type welding gun, and an indirect welding gun can be used for first welding gun 21. Furthermore, any of an X-type welding gun, a C-type welding gun, and an indirect welding gun can be used for second welding gun 22. The electrodes 21E and 22E extend in the X direction and are provided so as to be able to come into contact with a surface Wf of the workpiece W facing the X2 direction (hereinafter referred to as the "front surface").

[0062] The actuators 21A and 22A are drive sources that urge the electrodes 21E and 22E in the X1 direction. That is, the actuators 21A and 22A urge the electrodes 21E and 22E toward the surface Wf of the workpiece W. The actuators 21A and 22A are provided with a motor main body that generates a urging force that presses the electrodes 21E and 22E toward the surface Wf of the workpiece W, and an encoder for adjusting the amount of rotation (drive degree, rotation angle, rotation speed) of the motor main body. The main bodies 21B and 22B incorporate a mechanism (not shown) that transmits the biasing force of the motor main bodies of the actuators 21A and 22A to the electrodes 21E and 22E. The main bodies 21B and 22B illustrated in Fig. 4 are cylindrical with a cylindrical axis along the X direction.

[0063] Hereinafter, the names of elements such as electrode 21E and actuator 21A provided on first welding gun 21 will be prefixed with "first." Additionally, the names of elements provided on second welding gun 22 will be prefixed with "second." For example, electrode 21E provided on first welding gun 21 will be referred to as "first electrode 21E," and actuator 22A provided on second welding gun 22 will be referred to as "second actuator 22A."

[0064] The control unit 11 is a controller (electronic control device, control board, controller, etc.) that controls the drive unit 3 of the drive mechanism 1 and the actuators 21A and 22A of the welding guns 21 and 22. The device main body 12 is a component fixed to the tip of the robot arm. The drive mechanism 1 is attached to this device main body 12, and various devices and members may also be attached, including a transformer that converts and outputs voltage to the drive unit 3 of the drive mechanism 1 and the actuators 21A, 22A of the welding guns 21, 22. The device main body 12 and the devices and members attached to the device main body 12 are fixed (immovable), and are therefore set at fixed locations that restrain the first output flange 72 so that it cannot rotate. For example, the device main body 12 is disposed on the Z2 direction side of the drive mechanism 1, and the first output flange 72 is fixed to a transformer attached to the device main body 12.

[0065] In this application example, the drive mechanism 1 employs the second setting described above, in which the first case 71 and the second output flange 82 rotate in opposite directions and at the same speed. First welding gun 21 is attached to first case 71 of first reducer 70. Specifically, first body portion 21B of first welding gun 21 is fixed to outer peripheral surface 73 of first case 71. As a result, first electrode 21E is fixed to first case 71 via first body portion 21B, and the position of first electrode 21E is adjusted to a position corresponding to the rotational phase of first case 71.

[0066] A second welding gun 22 is attached to a second output flange 82 of the second reducer 80. Specifically, a second main body portion 22B of the second welding gun 22 is fixed to an outer peripheral surface 83 of the second output flange 82. As a result, the second electrode 22E is fixed to the second output flange 82 via the second main body portion 22B, and the position of the second electrode 22E is adjusted to a position according to the rotational phase of the second output flange 82.

[0067] When moving the welding guns 21, 22 away from each other, the drive unit 3 rotationally drives the rotary shaft 2 in the first direction, rotates the outer peripheral surface 73 of the first case 71 in the second direction, and rotates the outer peripheral surface 83 of the second output flange 82 in the first direction. When moving the welding guns 21, 22 closer to each other, the drive unit 3 rotationally drives the rotary shaft 2 in the second direction, rotates the outer peripheral surface 73 of the first case 71 in the first direction, and rotates the outer peripheral surface 83 of the second output flange 82 in the second direction.

[0068] In welding device 10, first body portion 21B fixed to outer peripheral surface 73 of first case 71 and second body portion 22B fixed to outer peripheral surface 83 of second output flange 82 are rotated in different directions at a constant speed by drive mechanism 1, thereby changing the relative positions of welding guns 21, 22. This increases the degree of freedom in responding to the welding location. In the application example described here, the above-mentioned second setting is adopted for the drive mechanism 1, but a drive mechanism 1 adopting a setting other than the second setting (the relative magnitude relationship between the first reduction ratio i1 and the second reduction ratio i2) may also be applied to the welding device 10.

[0069] [II. Modifications] The above-described embodiment is merely an example, and is not intended to exclude various modifications and application of techniques not explicitly stated in this embodiment. Each configuration of this embodiment can be modified and implemented in various ways without departing from the spirit of the invention. Furthermore, it is possible to select and combine as needed.

[0070] The drive mechanism 1 of this embodiment only needs to include at least a single drive unit 3 and reducers 70, 80. The one and other axial sides of the drive mechanism 1 in the above-described embodiment are merely examples, and these directions may be reversed. In other words, the first output flange 72 and first case 71 of the first reducer 70 and the second case 81 and second output flange 82 of the second reducer 80 only need to be coaxially arranged in this order at least in the axial direction. The reducers 70, 80 are not limited to the embodiment in which the reduction ratios i1, i2 expressed by the above-mentioned formulas 1, 2 are set, and other forms can also be adopted. The device to which the drive mechanism 1 of this embodiment is applied is not limited to the above-described welding device 10. The drive mechanism 1 may be applied to various devices that rotate two driven bodies M1 and M2 about an axis C. [Industrial Applicability]

[0071] The present invention is applicable to manufacturing industries that use drive mechanisms. [Explanation of symbols]

[0072] 1. Drive mechanism 2 rotation axes 3 Drive unit 70 First reducer 71 First case (first output section) 72 First output flange (second output part) 73 Outer surface 80 Second reducer 81 Second case (third output section) 82 Second output flange (fourth output part) 83 Outer surface a Rotational speed of the rotating shaft b Rotational speed of the first case c Rotational speed of the second output flange i1 first reduction ratio i2 second reduction ratio C axis M1 First driven body (driven body) M2 Second driven body (driven body)

Claims

1. A drive mechanism that rotates two driven bodies arranged around an axis around the axis, a single drive unit that outputs rotational power to a rotation shaft disposed on the axis line; a first reducer arranged coaxially with the rotating shaft, the first reducer including: a first output portion through which the rotating shaft is inserted and which is rotatable around the rotating shaft; and a second output portion rotatable on one side of the first output portion in the axial direction of the rotating shaft, the first reducer reducing the rotational power at a first reduction ratio and outputting the reduced power to the first output portion in a state in which the second output portion is fixed so as not to rotate, thereby rotating an outer circumferential surface of the first output portion in a direction opposite to the rotational direction of the rotating shaft; a second reducer arranged coaxially with the rotation shaft, the second reducer including: a third output section, through which the rotation shaft is inserted, on the other side of the first output section in the axial direction, and rotatable around the rotation shaft; and a fourth output section, rotatable on the other side of the third output section, the second reducer reducing the rotational power at a second reduction ratio and outputting the reduced power to the fourth output section, with the third output section fixed to the first output section, thereby rotating an outer circumferential surface of the fourth output section; one of the two driven bodies is attached to the outer circumferential surface of the first output portion, The other of the two driven bodies is attached to the outer circumferential surface of the fourth output portion. A drive mechanism characterized by:

2. The first reduction ratio is expressed by the following equation 1: The second reduction ratio is expressed by the following equation 2:

2. The drive mechanism according to claim 1, wherein the drive mechanism comprises: [Equation 1] Note that a, b, and c are positive values ​​when the rotation direction is the same as the rotation direction of the rotation shaft, and are negative values ​​when the rotation direction is opposite to the rotation direction.

3. The first reduction ratio is different from the second reduction ratio.

3. The drive mechanism according to claim 2, wherein the drive mechanism comprises:

4. The first reduction ratio is less than the second reduction ratio.

3. The drive mechanism according to claim 2, wherein the drive mechanism comprises:

5. The first reduction ratio is half of the second reduction ratio.

3. The drive mechanism according to claim 2, wherein the drive mechanism comprises:

6. The first reduction ratio is greater than the second reduction ratio.

3. The drive mechanism according to claim 2, wherein the drive mechanism comprises:

7. The first reduction ratio is the same as the second reduction ratio 3. The drive mechanism according to claim 2, wherein the drive mechanism comprises: