JP5248378B2 - Reduction gear and reduction gear manufacturing method - Google Patents

Description

  The present invention relates to a reduction gear and a method of manufacturing the reduction gear.

  For example, in applications such as high-precision deburring devices, not only there is no backlash, but the “rigidity” that allows the tool to overcome the reaction force from the workpiece side and deburr to the correct dimensions is on the reduction gear side. Is needed to.

  Patent Document 1 discloses a speed reducer that includes two speed reducers that employ a so-called intermeshing planetary gear mechanism, and that each speed reducer is used for forward rotation or reverse rotation. In this speed reducer, the first and second crank bodies of the first and second reducers are connected to each other, and the first and second support bodies or the first and second inner bodies that support the first and second crank bodies are connected. Fix the gears together. In addition, the first and second internal gears or the first and second internal gears or the first and second support members are relatively rotated in the opposite directions (with the preload applied). 1. The second support is fixed to each other.

  Patent Document 2 discloses a reduction gear configured to use two reduction gears for forward rotation or reverse rotation using a coupling. In this speed reducer, the input shaft of one speed reducer is extended to the outside of the speed reducer, and the input shaft of the other speed reducer is connected to the extended portion with initial torque (preload) applied. To do. When applying an initial torque between two input shafts, one input shaft is fixed so as not to rotate by the coupling, and the other input shaft is rotated with a constant torque by a torque wrench. Then, the two input shafts are pressed and fixed using the spun ring at the rotated position. The output of the motor is transmitted in synchronization with the input shafts of the two reduction gears through the coupling released thereafter.

PCT WO2008 / 146748A1 (FIG. 1, paragraph 0014) JP-A-8-11079 (FIGS. 1 to 3)

  However, the reduction gear disclosed in Patent Document 1 is preloaded from the outer periphery of the first and second reduction gears to the internal gears that are casings or the first and second supports that are output shafts. It was the composition which gives. Therefore, the torque required for preloading is large, and the range in which the internal gear and the first and second support bodies can move due to the preloading is narrow. For this reason, it is actually difficult to fix the first and second internal gears or the first and second support bodies to each other after giving a preload.

  Actually, in Patent Document 1, it is said that the backlash can be suppressed to about 0.5 to 0.3 degrees by this configuration, and the backlash that can be reduced is not large (Patent Document 1, paragraph 0014). .

  On the other hand, since the technique disclosed in Patent Document 2 extends the input shafts of the two reduction gears to the coupling position, the shaft length of the input shafts must be increased, and the rigidity is maintained high. There was a bug that it was not possible. For this reason, when a load is applied to the arm from the outside during deburring work or the like, the input shaft is easily twisted, resulting in a problem that the machining accuracy of the workpiece is also lowered.

  The present invention has been made to solve such a conventional problem. By facilitating the backlash reduction work, the backlash is surely reduced and the rigidity of the entire apparatus is maintained high. That is the issue.

The present invention has a first input shaft, a first output shaft, and the first to have a fixed shaft, a first reduction gear having a speed reduction mechanism for transmitting to the first output shaft and reducing the rotational speed of the first input shaft machine and the second input shaft, a second output shaft, and the second have a fixed shaft, a second reduction gear having a speed reduction mechanism for transmitting to the second output shaft and reducing the rotational speed of the second input shaft And the first fixed shaft and the second fixed shaft are coupled, the first output shaft and the second output shaft are coupled so as to be integrally rotatable, and the first input shaft In a state where the second input shaft and the second input shaft are preloaded in directions opposite to each other in the rotational direction, the first and second output shafts or the first and second fixed shafts are integrally rotated at positions inside the axial ends. The above-described problems have been solved by adopting a configuration in which the connections are possible.

  In the present invention, the first and second output shafts or the shafts of the first and second fixed shafts in a state where the first and second input shafts of the first and second speed reducers are preloaded in opposite directions. They are connected at a position inside the direction end. Since the preload is applied to the input shaft, the preload may be small and the range in which the two input shafts can move relatively is large. In addition, since the two input shafts are connected at positions inside the axial ends of the first and second output shafts or the first and second fixed shafts, it is easy to ensure a large outer diameter of each input shaft due to the structure. The rigidity of the rotating system can be kept very high.

  When the first and second casings of the first and second reduction gears are fixed to the fixing portion (outside the reduction gear), the first and second casings are referred to as the first and second fixed shafts. Become. When the first and second casings rotate (so-called frame rotation speed reducers), the first and second casings are the first and second output shafts. In any case, the first and second input shafts are connected at positions inside the axial ends of the first and second output shafts or the first and second fixed shafts.

The present invention relates to a method of manufacturing a speed reducer in which the first and second speed reducers that reduce the rotation of the input shaft and transmit it to the output shaft are used in parallel, and the fixed shafts of the first and second speed reducers are connected to each other. and a connecting step of connecting the output shaft to each other, respectively, and fixing step of fixing the fixed axes which are the connecting rotate the first, the input axes of the second reduction gear relatively opposite directions, predetermined An urging step for applying a preload, and in a state in which the preload is applied , the first and second output shafts or the first and second fixed shafts of the first and second reduction gears are positioned at positions inside the axial ends of the first and second fixed shafts. And an integration step of connecting the input shafts of the first and second reduction gears.

  According to the present invention, the backlash can be reliably reduced by facilitating the backlash reduction operation, and the rigidity of the entire reduction gear can be maintained extremely high.

Sectional drawing which shows the reduction gear device which concerns on an example of embodiment of this invention. Side view seen from the direction of arrow II in FIG. Side view of the vicinity of the second output flange as seen from the direction of arrow III in FIG. Sectional drawing which shows the reduction gear device which concerns on another example of embodiment of this invention. The end view which looked at the 2nd input axis of the embodiment concerning Drawing 4 from arrow V direction Sectional drawing which shows the reduction gear device which concerns on another example of embodiment of this invention. Sectional drawing which shows the reduction gear device which concerns on another example of embodiment of this invention.

  Hereinafter, an example of an embodiment of the present invention will be described in detail based on the drawings.

  FIG. 1 is a cross-sectional view showing a reduction gear device according to an example of an embodiment of the present invention. 2 is a side view seen from the direction of arrow II in FIG. 1, and FIG. 3 is a side view seen from the direction of arrow III in FIG.

  The speed reduction device 10 includes first and second speed reducers 12 and 14 each having the same speed reduction mechanism and connected in parallel. First, the schematic configuration of the first and second reduction gears 12 and 14 will be described.

  The first and second input shafts 16 and 18 of the first and second speed reducers 12 and 14 have three first and second eccentric bodies 20 and 22, respectively. First and second external gears 24 and 26 are fitted on the outer circumferences of the first and second eccentric bodies 20 and 22, respectively. The first and second external gears 24 and 26 are in mesh with the first and second internal gears 28 and 30 while swinging and rotating on the outer circumferences of the first and second eccentric bodies 20 and 22.

  The casing (fixed shaft) 44 of the speed reducer 10 includes a first casing (first fixed shaft) 32 (32A, 32B) of the first speed reducer 12 and a second casing (second fixed shaft) of the second speed reducer 14. ) 34 and a common casing 33 which is also used as the first and second speed reducers 12 and 14 and which is also the first casing and the second casing. The first casing 32 and the second casing 34 are integrally connected by bolts 46, 48, and 50 via a central common casing 33. In the present invention, the first fixed shaft of the first speed reducer and the second fixed shaft of the second speed reducer need only be “combined with each other” as a result. There is no particular problem with respect to what part is formed from the divided (or integrated) members.

  In this embodiment, the first and second internal gears 28 and 30 are integrated with the first casing 32B and the second casing 34, respectively. The number of teeth of the first and second internal gears 28 and 30 is set to be one more than the number of teeth of the first and second external gears 24 and 26.

  The first and second inner pins 36 and 38 pass through (freely fit) the first and second external gears 24 and 26, and are integrated with the first and second inner pins 36 and 38. 1. The rotation components of the first and second external gears 24 and 26 can be output to the first and second output flanges (first and second output shafts) 40 and 42 side.

  The first inner pin 36 of the first speed reducer 12, the first output flange (first output shaft) 40, the second opposing output flange 54 of the second speed reducer 14, the second inner pin 38, and the second output flange (first The two output shafts (42) are connected together via bolts 56, 58, or by press-fitting or the like so as to be integrally rotatable, thereby constituting a single output system. Among these, the 2nd opposing output flange 54 and the 2nd output flange 42 of the 2nd reduction gear 14 are supported by a pair of taper roller bearings 60 and 62, respectively. However, the first output flange 40 of the first reduction gear 12 is not supported by an independent bearing. This is because if the output systems of both the first and second speed reducers 12 and 14 are to be supported by independent bearings, assembly interference due to axial misalignment (radial variation) occurs during connection. It is because it ends up.

  The first input shaft 16 of the first speed reducer 12 and the second input shaft 18 of the second speed reducer 14 are both coaxial hollow shafts having first and second hollow portions 64 and 66, and are connected via a connecting shaft 70. Are connected.

  A key groove 16A for connecting a motor shaft of a motor (not shown) is formed on the axial motor side of the hollow portion 64 of the first input shaft 16, and the connecting shaft 70 is provided on the opposite side of the motor in the axial direction. A first inner spline 16B for meshing with is formed. As shown in FIG. 2, parallel cut surfaces 16 </ b> C and 16 </ b> D are formed on the outer periphery of the first input shaft 16. The first reduction gear 12 can be preloaded by clamping and rotating the cut surfaces 16C and 16D. The number of teeth of the first inner spline 16B is set to “40” in this embodiment. The number of teeth (or the size of the teeth) is the rated torque of the first speed reducer 12 when the first input shaft 16 is further twisted by one tooth from the state where there is no backlash in the first speed reducer 12. Is set to a size that preloads about 40% of the above. Reference numeral 16E denotes a relief hole (for tools and machining powder) used when machining the keyway 16A and the first inner spline 16B on the first input shaft 16.

  A second inner spline 18B having the same tooth shape and the same number of teeth (40) as the first inner spline 16B of the first input shaft 16 is formed on the axial motor side of the second hollow portion 66 of the second input shaft 18. Yes. Parallel cut surfaces 18C and 18D are also formed on the outer periphery of the second input shaft 18 as shown in FIG. The second reduction device 14 can be preloaded by clamping and rotating the cut surfaces 18C and 18D.

  The connection shaft 70 is formed with an outer spline 70B that meshes with both the first and second inner splines 16B and 18B. The first and second input shafts 16 and 18 are connected in a preloaded state via the connecting shaft 70 (described later). The connection between the first and second input shafts 16 and 18 is performed at a position inside the axial end portions of the first and second output shafts or the first and second fixed shafts. Specifically, among the first and second output shafts and the first and second fixed shafts, the axial end portion is positioned at an inner position than the axial end portion of the axial end portion that is positioned more outward in the axial direction. In this embodiment, since the axial end portion 42S of the second output shaft flange 42 and the axial end portion 32S of the first casing 32 correspond to the axial end portion, the inner side (in the region X1) is performed. Is called. For this reason, both the first and second input shafts 16 and 18 can be constituted by shafts having large diameters d1 and d2 (high rigidity). The connecting shaft 70 is positioned in the axial direction with respect to the second input shaft 18 by engagement at the stepped portion 70 </ b> C and insertion of the retaining ring 72.

  Since the first and second input shafts 16 and 18 need to be preloaded with each other and connected by the connecting shaft 70, in this embodiment, the first and second input shafts 16 and 18 are connected to each other. The ball bearings 74, 76, 78, and 80 are supported independently. A shift (radial variation) in the axial centers of the first and second input shafts 16 and 18 is absorbed by the play of the ball bearings 74, 76, 78 and 80. Reference numeral 82 in the drawing is an O-ring that is provided between the first and second input shafts 16 and 18 and seals the lubricant in the speed reducer 10.

  Next, the operation of the speed reducer 10 will be described with a description regarding the connection of the first and second input shafts 16 and 18 in particular.

  The first and second input shafts 16 and 18 are connected by twisting the first and second input shafts 16 and 18 almost evenly in the (relatively) opposite directions. By this twisting, the first and second output flanges 40 and 42 are stopped at a position where the load is balanced. For example, when both of the first and second input shafts 16 and 18 cannot be twisted at the same time, the first and second output flanges 40 and 42 (specifically, of the first and second output flanges 40 and 42 with respect to the casing 44 of the speed reducer 10). After fixing the second output flange 42), one of the first and second input shafts 16 and 18 may be rotated one by one in opposite directions. At this time, the connecting shaft 70 has not been assembled yet.

  The torsion (relative rotation) of the first and second input shafts 16 and 18 clamps the cut surfaces 16C and 16D of the first input shaft 16 and also clamps the cut surfaces 18C and 18D of the second input shaft 18. The first input shaft 16 and the second input shaft 18 are twisted in directions opposite to each other in the rotational direction. For example, when the first input shaft 16 is twisted in the forward rotation direction, the first reduction gear 12 is in a state in which backlash is packed in the forward rotation direction. Similarly, when the second input shaft 18 is twisted in the reverse rotation direction, the second reduction gear 14 is in a state where backlash is packed in the reverse rotation direction.

  Specifically, the size of the preload is set to a size corresponding to 15% to 60% of the rated torque of the first and second speed reducers 12 and 14. In this embodiment, as described above, the number of teeth (the size of the teeth) of the first and second inner splines 16B and 18B is the same as that in the first and second reduction gears 12 and 14 with no backlash. 1. When the first and second input shafts 16 and 18 are further twisted by one tooth, a preload of about 40% of the rated torque of the first and second reduction gears 12 and 14 is applied. For this reason, if the initial overlap of the teeth of the first and second inner splines 16B and 18B is slight, the first and second inner splines 16B and 18B are twisted until the teeth of the first and second inner splines 16B and 18B are aligned. On the other hand, if the teeth of the first and second inner splines 16B and 18B have already overlapped considerably from the beginning, the teeth of the first and second inner splines 16B and 18B are twisted for the second time. As a result, a preload having a magnitude corresponding to 15% to 60% of the rated torque of the first and second speed reducers 12 and 14 with rotation (torsion) of “less than 2 teeth” (without using a measuring machine or the like). Can be multiplied.

  In this state, the connecting shaft 70 is inserted, and the outer spline 70B of the connecting shaft 70 is sequentially engaged with the second inner spline 18B and the first inner spline 16B. After insertion of the connecting shaft 70, the retaining ring 72 is fitted to fix the connecting shaft 70 in the axial direction.

  During operation, for example, when rotation in the forward direction is input from the motor via the first input shaft 16, power is transmitted only through the first speed reducer 12 packed with backlash in the forward direction. Specifically, when the first input shaft 16 rotates in the forward rotation direction, the first external gear 24 is driven (swinged) via the first eccentric body 20 to swing while inscribed in the first internal gear 28. Move. There is no backlash in this movement. In this embodiment, since the first internal gear 28 is in a fixed state, the “meshing position” between the first internal gear 28 and the first external gear 24 is sequentially in the same direction as the rotation of the first input shaft 16. As a result, the first external gear 24 slowly rotates in the direction opposite to the rotation direction of the first input shaft 16 with respect to the first internal gear 28. At this time, the second speed reducer 14 moves in the same manner via the second input shaft 18 connected to the first input shaft 16, but the hacklash is packed in the opposite direction, so that the transmission of power is Not done.

  On the other hand, when rotation in the reverse direction is input from the motor to the second input shaft 18 via the first input shaft 16, the second speed reducer 14 is driven in the same manner without backlash, and the first speed reducer 12 is thus driven. Will only go around.

  In this embodiment, since a preload having a magnitude corresponding to 15% to 60% of the rated torque of the first and second speed reducers 12 and 14 is applied, the speed reducer 10 is operated in either the forward direction or the reverse direction. Even when rotating, operation without backlash is always possible regardless of some load fluctuations. Further, in this embodiment, the first and second input shafts 16 and 18 are positioned on the inner side of the axial end portion 42S of the second output shaft flange 42 and the axial end portion 32S of the first casing 32 (first position). In addition, the second output shaft or the first and second fixed shafts are connected to the inner side position in the region X1), that is, substantially inside the speed reduction device 10. Therefore, the outer diameters d1 and d2 of the first and second input shafts 16 and 18 can be maintained thick, and the first and second reduction gears 12 and 14 including the first and second input shafts 16 and 18 can be maintained. The rigidity can be maintained extremely high. As a result, the entire speed reduction device 10 can be driven extremely powerful without losing load.

  When preload is applied, the preload basically remains applied even if the rotation is started or stopped. However, this embodiment employs an intermeshing planetary gear structure (the rotation of the first and second input shafts 16 and 18 is not simply transmitted sequentially). In this structure, when there is no load, the preload remains applied even when the rotation is started. However, when the load is applied, the preload is reduced. Although the exact mechanism is unknown, the external gear under load is elastically deformed in such a way that a gap is formed in front of its own rotation direction. It is presumed that the deformation is canceled and eliminated.

  In any case, this action can be expressed in other words as follows: “When starting up (when starting to rotate in a certain direction), the backlash is reliably packed by preloading, but when starting rotating, the preloading decreases. This means that when the rotation efficiency is increased and the load is stopped and no load is applied, the preload is applied again, and the backlash is automatically reduced. ” According to experiments, it has been confirmed that when the external torque is applied up to the rated torque, the efficiency is close to that of a single unit, and the influence of the load due to the preload is almost eliminated.

  In the above embodiment, the first and second input shafts 16 and 18 are both hollow shafts, and the connecting shaft 70 is inserted into the first and second hollow portions 64 and 66, whereby the first and second input shafts 16 and 18 are inserted. The input shafts 16 and 18 were fixed. However, the method of fixing the first and second input shafts in a preloaded state in the present invention is not limited to this method.

  4 and 5 show an example of another embodiment of the present invention.

  In the speed reducer 81 according to this embodiment, an example in which the first input shaft 82 is a hollow shaft having a first hollow portion 84 and the second input shaft 86 is a solid shaft is shown. The end of the first input shaft 82 on the second input shaft side is closed by a closing wall 90. In the closing wall 90, a plurality of through holes 90A to 90G (only 90A and 90D are shown in FIG. 4) are formed at equal intervals. On the other hand, on the first input shaft side end face 86 of the second input shaft 86, as shown in FIG. 5, bolt holes 86A to 86G having slightly different phases corresponding to the through holes 90A to 90G are formed. ing. With this configuration, in a state where the first and second input shafts 82 and 86 are preloaded, the first input shaft 82 is inserted into any two or more bolt holes among the bolt holes 86A to 86G of the second input shaft 86. For example, bolts 92 and 93 are screwed from the hollow portion 84 side through any of the through holes 90A to 90G. Thus, the first and second input shafts 82 and 86 can be connected in a state where appropriate preload is applied to the first and second input shafts 82 and 86.

  Since other configurations are the same as those of the previous embodiment, the same reference numerals are given to portions having the same or the same functions in the drawings, and redundant description is omitted.

  FIG. 6 shows an example of still another embodiment of the present invention.

  Also in the speed reducer 91 according to this embodiment, the first input shaft 92 is a hollow shaft having a hollow portion 94, and the second input shaft 96 is a solid shaft. The end of the first input shaft 92 on the second input shaft side is closed by the closing wall 100. However, in this example, the closed wall 100 is formed with an inclined surface 100A having a circular cross section. On the other hand, a protrusion 102 is formed on the end surface of the second input shaft 96 on the first input shaft side. The inclined surface 102A of the protrusion 102 corresponds to the inclined surface 100A on the first input shaft 92 side. A threaded portion 104 is integrally fixed to the tip of the protruding portion 102. With this configuration, by tightening the nut 106 screwed into the threaded portion 104 from the hollow portion 94 side of the first input shaft 92, the inclined surface 100A on the first input shaft 96 side and the second input shaft 96 side The inclined surface 102A can be firmly frictionally fastened. In this configuration, the first and second input shafts 92 and 96 can be connected after the preload is set to an arbitrary continuous value (not stepwise or selectively as in the previous embodiment). Other configurations are the same as in the previous embodiment.

  4 to 6, only the first input shaft is a hollow shaft with a bottom, and the second input shaft is solid. However, in the connection structure of the first and second input shafts according to the configuration of the embodiment of FIGS. 4 to 6, the second input shaft is a bottomed hollow shaft (first input) as with the first input shaft. Even in the case of a hollow shaft having a blocking wall at the end on the shaft side, it can be similarly adopted.

  FIG. 7 shows an example of still another embodiment of the present invention.

  In the reduction gear 105 according to this embodiment, the first and second reduction gears 130 and 132 are completely the same as a single unit. Both the first and second input shafts 106 and 108 are hollow shafts having hollow portions 110 and 112 having a simple circular cross section. The power from the motor side (not shown) is transmitted from the first pulley 114 to the second pulley 118 by the belt 116, and further transmitted to the first input shaft 106 that is bolt-connected to the second pulley 118 (only the bolt hole 120 is shown). Is done.

  In this embodiment, the first and second input shafts 106 and 108 are connected via the friction fastener 122. The friction fastener 122 includes an extended body 124, an extended body 126, and a connecting bolt 128 (only two are shown). The expanded body 124 includes a mortar-shaped first inclined surface 124A having a circular cross section, and the expanded body 126 includes a second inclined surface 126A corresponding thereto. When the extended body 124 and the extended body 126 are pulled in the axial direction by the connecting bolt 128, the inclined surfaces 124A and 126A have a wedge effect, and the extended body 124 is spread outward in the radial direction. Accordingly, a strong pressing force (frictional force) can be generated between the inner peripheral surfaces 106A, 108A of the first and second input shafts 106, 108 and the extended body 124, and the extended body 124 The first and second input shafts 106 and 108 can be connected. Also in this embodiment, the preload can be set to an arbitrary value (not a stepwise or selective value).

  In this embodiment, in order to make the forward / reverse rotation characteristics more completely uniform and further increase the rigidity of the entire reduction gear 105, the first reduction gear 130 also has the same as the second reduction gear 132. The one output flange 134 and the first opposed output flange 136 are supported by dedicated taper roller bearings 138 and 140. As described above, when the output systems of the first and second speed reducers 130 and 132 are supported by the independent tapered roller bearings 138 and 140, assembly interference occurs when the shaft center is shifted due to manufacturing variations. However, in this embodiment, the first output flange 134 of the first speed reducer 130 and the second opposed output flange 142 of the second speed reducer 132 are connected in a radially floated manner via the key 144. The variation in the radial direction of the first and second reduction gears 130 and 132 is absorbed. In this embodiment, since the oil seals 146 to 153 are also arranged independently by the first and second reduction gears 130 and 132, the first and second reduction gears 130 and 132 are independent reduction gears. As a single unit.

  The connection between the first and second output flanges 134 and 142 is not necessarily a key connection. For example, a connection such as an Oldham joint or a large-diameter spline joint may be used. In short, as long as it is a “float connection” capable of absorbing the radial displacement of the first and second output flanges 134 and 142, the same The effect is obtained.

  The other configuration is basically the same as that of the previous embodiment except that the number of first and second external gears 156 and 158 is two.

  As described above, in the present invention, in the present invention, the first input shaft and the second input shaft are basically positioned inside the first and second output shafts or the axial ends of the first and second fixed shafts. As long as it is set as the structure connected by (4), the specific structure for connection is not specifically limited. For example, you may fix on the outer peripheral side instead of the inside of a hollow shaft.

  Further, regarding the configuration of the speed reduction mechanism, if an inscribed mesh planetary gear structure as illustrated is employed, the effect of being able to satisfactorily achieve both reduction in backlash and improvement in efficiency is obtained. The configuration of the speed reduction mechanism is not limited to this gear structure alone, and even when a speed reduction mechanism having an appropriate structure is employed, a speed reduction device having high rigidity and no backlash can be obtained. For example, a speed reduction mechanism such as a simple planetary gear mechanism may be employed, and the present invention can be employed even with a speed reduction mechanism (for example, a parallel shaft gear speed reduction mechanism) whose input and output shafts are not necessarily coaxial. . Furthermore, in the above-described embodiment, the speed reduction mechanism in which the first and second casings are fixed (becomes the first and second fixed shafts) is exemplified, but the first and second fixed shafts of the present invention are The first and second casings are not necessarily required. For example, a specific member (for example, the second output flange 42) of the first and second reduction gears is fixed to constitute the first and second fixed shafts, and the first and second casings are rotated to be the first, The present invention can be applied even when a so-called frame rotation type speed reduction mechanism that constitutes the second output shaft is employed, and similar effects can be obtained.

12, 14 ... first and second reduction gears 16, 18 ... first and second input shafts 32 and 34 ... first and second casings 40 and 42 ... first and second output flanges (output shafts)
64, 66 ... 1st, 2nd hollow part 70 ... Connecting shaft

Claims (10)

The first input shaft, a first output shaft, and have a first fixed shaft, a first reduction gear having a speed reduction mechanism for transmitting by reducing the rotational speed of the first input shaft to the first output shaft,
The second input shaft, a second output shaft, and the second have a fixed shaft, a second reduction gear having a speed reduction mechanism for transmitting to the second output shaft and reducing the rotational speed of the second input shaft, a Prepared,
The first fixed shaft and the second fixed shaft are coupled,
The first output shaft and the second output shaft are coupled so as to be integrally rotatable; and
In a state where the first input shaft and the second input shaft are preloaded in directions opposite to each other in the rotation direction, the first and second output shafts or the axial ends of the first and second fixed shafts. A speed reducer characterized by being connected so as to be integrally rotatable at an inner position. In claim 1,
At least one of the first input shaft and the second input shaft is a hollow shaft having a hollow portion, and the first input shaft and the second input shaft are preloaded and connected inside the hollow portion. A speed reducer characterized by that. In claim 2,
The other end of the hollow shaft on the input shaft side is closed with a blocking wall and two or more through holes are formed in the blocking wall,
A plurality of sets of bolt holes with different phases corresponding to the through holes are formed on the end surface of the other input shaft on the hollow shaft side,
When the bolt is screwed into the bolt hole of any one of the plurality of bolt holes of the other input shaft from the hollow portion of the hollow shaft through the through hole, the first and second inputs A speed reducer characterized in that the shafts are connected in a preloaded state. In claim 2,
The other input shaft side end of the hollow shaft is closed with a blocking wall, and a first inclined surface having a circular cross section is formed on the blocking wall,
A speed reducer characterized in that a second inclined surface capable of friction fastening with the first inclined surface is formed on an end surface of the other input shaft on the hollow shaft side. In claim 2,
Both the first and second input shafts are constituted by hollow shafts, and friction fasteners that can be brought into frictional contact with the respective hollow portions are inserted, and the first and second input shafts are inserted through the friction fasteners. Reducer characterized by frictional connection. In claim 2,
Both the first and second input shafts are constituted by hollow shafts, and first and second inner splines are formed in the hollow portions,
The first and second input shafts are connected in a preloaded state via a connecting shaft formed with an outer spline that meshes with both the first and second inner splines. Reducer. In claim 6,
When the inner splines of the first and second input shafts are preloaded on the first input shaft and the second input shaft as a result of being rotated by less than two teeth and preloaded, A reduction gear comprising a number of teeth that generates a load corresponding to 15% to 60% of the rated torque of the second reduction gear. In the manufacturing method of the reduction gear, the first and second reduction gears that reduce the rotation of the input shaft and transmit it to the output shaft are connected in parallel.
A connecting step of connecting the fixed shafts and the output shafts of the first and second reduction gears;
A fixing step of fixing the connected fixed shafts;
An urging step of rotating the input shafts of the first and second reduction gears relatively in opposite directions to give a predetermined preload;
In a state where the preload is applied, the first and second reduction gears are located at positions inside the axial ends of the first and second output shafts or the first and second fixed shafts of the first and second reduction gears. An integration process for connecting the input shafts of the machine,
The manufacturing method of the speed reducer characterized by including. In claim 8,
The input shafts of the first and second reduction gears are hollow shafts each having an inner spline,
In the biasing step, preload is applied to the position where the teeth of each inner spline coincide with the axial direction,
In the integration step, the connecting shafts having outer splines meshing with both of the inner splines of the first and second reduction gears in the preloaded state are connected to the first and second reduction gears having the same teeth. A method of manufacturing a reduction gear, characterized by being engaged with an inner spline. In claim 8 or 9,
In the biasing step, a preload corresponding to 15% to 60% of the rated torque of the first and second reducers is applied,
In the integration step, the input shafts of the first and second speed reducers are connected in a state where the preload is applied. A method of manufacturing a speed reducer.

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