JP2006046596A - Planetary reduction gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cost while improving basic quality and performance as a planetary reduction gear. <P>SOLUTION: This planetary reduction gear 110 comprises an inner pin hole 130 formed on an external tooth gear 116, first and second supporting flanges 150, 160 formed on axial both sides of the external tooth gear 116, a plurality of inner pins 140 formed integrally with the first supporting flange 150, freely fitted to the inner pin hole 130, and extended to a second supporting flange 160 side, a knock pin 170 knocked to at least one end part of the inner pin 140 from the second supporting flange 160 side, and a connection bolt 180 knocked from the second supporting flange 160 side to at least one end part of the inner pin 140. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a planetary gear reduction device.

  A planetary gear reduction device that includes an internal gear and an external gear that meshes internally with the internal gear and that extracts a relative rotational component between the internal gear and the external gear as an output is widely used.

  For example, Patent Document 1 discloses a planetary gear reduction device as shown in FIGS. 7 and 8.

  This planetary gear reduction device 10 has an input shaft 12, an eccentric body 14, two external gears 16 (16A, 16B), an internal gear 18, a relative rotation take-out mechanism K, and an output shaft 22 as main components. Prepare.

  Each external gear 16 includes an internal pin hole 30 that passes through the external gear 16. The relative rotation take-out mechanism K includes the inner pin hole 30 and an inner pin 40 that is press-fitted and fixed in the inner pin holding hole 22B of the flange portion 22A of the output shaft 22 and is loosely fitted in the inner pin hole 30. Has been.

  When the input shaft 12 is rotated by a motor (not shown), the eccentric body 14 rotates integrally with the input shaft 12. Since the outer periphery of the eccentric body 14 is eccentric with respect to the axis of the input shaft 12, when the input shaft 12 rotates once, the external gear 16 mounted on the outer periphery of the eccentric body 14 swings once. As a result, the external gear 16 rotates relative to the internal gear 18 by an amount corresponding to the difference in the number of teeth of the two gears 18 and 16. This relative rotation is extracted to the flange portion 22A side of the output shaft 22 through the inner pin hole 30 and the inner pin 40 of the relative rotation extraction mechanism K.

  The swing component of the external gear 16 is absorbed by loose fitting of the inner pin hole 30 and the inner pin 40 in the relative rotation take-out mechanism K. As a result, a reduction ratio corresponding to (the number of teeth difference between the internal gear 18 and the external gear 16) / (the number of teeth of the external gear) can be realized.

  This planetary gear reduction device 10 has an advantage of being compact and capable of obtaining a high reduction ratio, and is applied in various fields.

  By the way, in order to smoothly extract the rotation component of the external gear 16, the corresponding inner pins 40 must slide in a completely matched manner in the inner pin holes 30 formed in plural. Therefore, all of the inner pin holes 30 and the inner pins 40 need to be processed and manufactured with very high accuracy. For this reason, a manufacturing method has been adopted in which the inner pin 40 is press-fitted into the inner pin holding hole 22 </ b> B formed with high accuracy in the flange portion 22 </ b> A in a separate process with high accuracy.

  Although not shown in the drawings, in order to realize further highly accurate support of the inner pin, the inner pin is supported in a both-end supported state by a pair of flange portions arranged on both sides of the external gear. A reduction gear has also been proposed.

JP-A-63-214542

  In the field of this kind of planetary gear speed reducer, particularly in the field of planetary gear speed reducers for driving industrial machines, there has been a strong demand for higher quality and lower cost in recent years.

  The structure in which the inner pin protruding from the flange connected to the output shaft side is loosely fitted into the inner pin hole formed in the external gear has a large number of parts, and the number of processing steps and assembly steps must be increased. Therefore, it was a factor of cost increase.

  For this, a method in which the inner pin and the flange portion are integrally formed from the beginning (as one component) can be considered. However, for example, in the field where high torque such as driving of industrial machinery is required, the inner pins are almost evenly distributed in order to ensure smooth operation, regardless of the product in the torque range that only requires resin molding. In order to be able to bear the load, it is essential to ensure a high degree of positional accuracy or machining accuracy of each of the integrally protruded inner pins.

  On the other hand, the structure in which the inner pin is supported at both ends by the flange portions arranged on both sides of the external gear has a great merit in terms of reducing assembly errors and reliability of long-term operation. Although it is obtained, it is difficult to accurately process the inner pin holding hole into which the inner pin is inserted into the flange portions on both sides of the external gear, which has been a factor in increasing the processing cost.

  The present invention comprehensively captures such incompatible circumstances, and provides a planetary gear reduction device that can realize cost reduction while improving the basic quality or performance as a reduction device rather. That is the issue.

  The present invention relates to a planetary gear reduction device that includes an internal gear and an external gear that is internally meshed with the internal gear, and that extracts a relative rotational component between the internal gear and the external gear as an output. An inner pin hole formed through the toothed gear, a first support flange disposed on one axial side of the external gear, and a second support flange disposed on the other axial side of the external gear A plurality of inner pins formed integrally with the first support flange and extending through the inner pin hole to the second support flange side, and the second support flange and the inner pin The above-described problems are solved by providing a knock pin driven between at least one of the first and second connecting flanges and a connecting bolt that fastens the second support flange and at least one of the inner pins.

  In the present invention, since the inner pin is integrally formed with the first support flange (as a single part), the number of parts can be greatly reduced, and the inner pin holding hole formed on the first support flange side, etc. This processing is also unnecessary, and the cost can be reduced.

  Further, since each inner pin is supported at both ends by the first and second support flanges arranged on both sides in the axial direction of the external gear, even if the post-processing of each inner pin is omitted or simplified, It is possible to maintain accuracy characteristics that do not cause defects and to expect excellent effects in terms of durability and the like.

  On the other hand, if it is going to implement | achieve this both-end support of an inner pin with the method similar to the past, the inner pin holding hole for inserting an inner pin to the 2nd support flange side must be processed with high precision. This processing is not always easy, and in some cases, the cost reduction due to integration may be offset. In the present invention, the knock pin is driven from the second support flange side to the end of the inner pin, and the connection bolt is also driven from the second flange side to the end of the inner pin. Settled. In other words, the knock pin can ensure high-precision positioning between the second support flange and the inner pin, and the connection stress between the inner pin and the second support flange is basically generated between the second support flange and the inner pin. Can be handled by frictional force. The knock pin then provides its own shear stress to assist this frictional force. Therefore, as a result, it is not necessary to form a highly accurate inner pin holding hole on the second support flange side, and a large cost reduction is possible (while adopting a both-end support structure).

  The inner pin into which the knock pin is driven and the inner pin into which the connecting bolt is screwed may be set separately, and the knock pin is driven into the same inner pin and the connecting bolt is also screwed in. Is also possible (described later).

  There may also be an inner pin in which neither the knock pin nor the connecting bolt is driven or screwed. In the present invention, since “all inner pins” are integrated with the first support flange, if accurate positioning is performed on a part of the inner pins, accurate positioning is automatically performed on other inner pins. Made.

  The cost can be reduced while improving the basic quality or performance as a reduction gear.

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

  FIG. 1 is a longitudinal sectional view corresponding to FIG. 7 showing a planetary gear reduction device according to an example of an embodiment of the present invention.

  The planetary gear reduction device 110 includes an input shaft 112, an eccentric body 114, three external gears 116, an internal gear 118, a relative rotation extraction mechanism K1, and an output shaft (150) as main components. In addition, in order to support the inner pin 140 that is one of the components of the relative rotation take-out mechanism K1 in a cantilevered manner, the first support flange 150 and the second support flange 160 are provided on both axial sides of the external gear 116. Prepare. In this embodiment, the first support flange 150 functions as an output shaft.

  The input shaft 112 is rotatably supported by bearings 152 and 162 incorporated in the first and second support flanges 150 and 160. The input shaft 112 includes a hollow portion 112A having a large diameter at the center (hollow structure), and is connected to a motor shaft (not shown) via a spline 112B.

  The eccentric body 114 is formed integrally with the input shaft 112. The eccentric body 114 includes three eccentric portions 114A to 114C. The centers OeA to OeC of the outer circumferences of the eccentric portions 114A to 114C are eccentric (eccentric) by ΔE with respect to the axis Oi of the input shaft 12, respectively. Further, the eccentric phases of the eccentric portions 114A to 114C are shifted from each other by 120 degrees.

  The three external gears 116 (116A to 116C) are rotatably mounted on the eccentric portions 114A to 114C of the eccentric body 114 via bearings 117A to 117C, respectively. The bearings 117A to 117C have only inner rings 117A1 to 117C1 and rollers 117A2 to 117C2, respectively, and the external gears 116A to 116C also function as outer rings. The bearings 117 </ b> A to 117 </ b> C are axially positioned by bearings 152 and 162 that support the input shaft 112. The reason why three external gears 116 are arranged in parallel in the axial direction is to increase the transmission capacity. Each external gear 116 includes an internal pin hole 130 that penetrates the external gear 116 as a component of the relative rotation take-out mechanism K1.

  The internal gear 118 is integrated with the casing 111 of the planetary gear reduction device 110. The casing 111 is fixed to an external member in this embodiment. Specifically, the internal teeth 118A of the internal gear 118 are configured by roller-shaped pins.

  The first support flange 150 and the second support flange 160 are rotatably supported on the casing 111 by bearings 154 and 164, respectively. An external device (not shown) that is a drive target can be connected to the first support flange 150 using a bolt or the like (not shown). Further, the first support flange 150 is integrally provided with an inner pin 140 (as a part of itself).

  The relative rotation take-out mechanism K <b> 1 includes the inner pin 140 and the inner pin hole 130 formed in the external gear 116. An inner roller 142 is rotatably mounted on the outer periphery of each inner pin 140. In other words, the inner pin hole 130 and the inner pin 140 are configured to transmit power through the inner roller 142.

  Here, a connection structure between the inner pin 140 and the second support flange 160 will be described with reference to FIG. 2A is an enlarged view around arrow IIA in FIG. 1, and FIG. 2B is an enlarged view around arrow IIB in FIG.

  As shown in FIG. 2B, the knock pin 170 is driven from the second support flange 160 side into the end portion of the inner pin 140N of some (in this case, several) of the plurality of inner pins 140. The hole 146 is formed in advance. On the other hand, a hole 166 for engaging the knock pin 170 is also formed at a corresponding portion of the second support flange 160.

  The knock pin 170 is a pipe-shaped component having a hollow portion 172. As shown in FIG. 2A, including the inner pin 140 </ b> N into which the knock pin 170 is driven, a screw hole 144 for screwing the connecting bolt 180 from the second support flange 160 side is formed at the end of all the inner pins 140. Has been. In addition, a hole 168 and a connection hole 169 for accommodating the head portion 180 </ b> A of the connection bolt 180 are formed at corresponding portions of the second support flange 160. The connecting bolt 180 is for generating a predetermined frictional force between the end surface 140A of the inner pin 140 and the corresponding surface 160A of the second support flange 160. In the inner pin 140N in which the knock pin 170 is driven, the connecting bolt 180 passes through the hollow portion 172 of the knock pin 170 and is screwed into the inner pin 140N.

  In this embodiment, the hole 166 for engaging the knock pin 170 formed on the second support flange 160 side and the hole 168 for receiving the head 180A of the connecting bolt 180 are not formed continuously. That is, the connecting hole 169 having a small diameter remains and is interposed between the two portions 166 and 168. This is because the knock pin 170 can be prevented from coming off in the axial direction by the bottoms of the hole 146 formed on the inner pin 140N side and the hole 166 formed on the second support flange 160 side.

  In addition, the code | symbol 185 of FIG. 1 is an enclosure port for enclosing grease, and the code | symbol 187 is a sealing member.

  Next, the operation of the planetary gear reduction device 110 will be described.

  When the input shaft 112 is rotated by rotation of a motor shaft (not shown), the eccentric body 114 integrated with the input shaft 112 is rotated. Since the outer periphery of the eccentric body 114 is eccentric by ΔE with respect to the axis Oi of the input shaft 112, the three external gears 116 </ b> A to 116 </ b> C are 120 respectively via the bearings 117 </ b> A to 117 </ b> C by the rotation of the eccentric body 114. It swings and rotates while inscribed in the internal gear 118 with a phase difference of degree. In this example, since the internal gear 118 is integrated with the casing 111 and is fixed to the external member, when the external gear 116 rotates once by rotating the input shaft 112 once, the external gear 116 is rotated. The tooth gear 116 rotates (rotates) relative to the internal gear 118 by an amount corresponding to the difference in the number of teeth of the two gears 116 and 118.

  This relative rotation is taken out to the first and second support flanges 150 and 160 through the inner pin hole 130 and the inner pin 140 constituting the relative rotation take-out mechanism K1. The swing component of the external gear 116 is absorbed by loose fitting of the inner pin hole 130 and the inner pin 140 in the relative rotation take-out mechanism K1. As a result, a reduction ratio corresponding to (the number of teeth difference between the internal gear 118 and the external gear 116) / (the number of teeth of the external gear) can be realized in only one stage.

  In the planetary gear reduction device 110 according to this embodiment, the first support flange 150 and an external device (not shown) to be driven are connected using a bolt (not shown). An external device can be driven through the first support flange 150 side. It is also possible to fix the first support flange 150 and use the casing 111 itself as an output member (so-called frame rotation structure).

  Here, since the inner pin 140 is integrally formed with the first support flange 150 from the beginning, the number of parts can be greatly reduced, and a highly accurate inner pin holding hole is formed on the first support flange 150 side. There is no need to do. Moreover, the process which press-fits the inner pin 140 which exists separately in these inner pin holding holes is also unnecessary.

  Further, since the inner pin 140 is supported at both ends between the first support flange 150 and the second support flange 160, the support rigidity is high, and the support rigidity is hardly lowered over time.

  Further, when the inner pin 140 and the second support flange 160 are connected, positioning with high precision can be performed by driving the knock pin 170. Referring to FIG. 2, the knock pin 170 can be prevented from coming off in the axial direction by the bottoms of the hole 146 formed on the inner pin 140N side and the hole 166 formed on the second support flange 160 side. There is no need to prepare a separate member to prevent the knock pin 170 itself from coming off.

  Further, the connection stress between the inner pin 140 and the second support flange 160 is not based on the shearing stress of the inner pin itself inserted into the second support flange (for example, depending on the connection force of the connection bolt 180). It is ensured by the frictional force (and the shear stress of the knock pin 170) generated between the end surface 140A of the inner pin 140 and the corresponding surface 160A of the second support flange 160. Therefore, it is not necessary to form highly accurate inner pin holding holes corresponding to the number of inner pins 140 in the second support flange 160, and it is possible to prevent a local shearing load from being applied to the inner pins 140 themselves.

  Further, since the knock pin 170 is hollow, the connecting bolt 180 can be screwed into the inner pin 140N into which the knock pin 170 is driven, and the second support flange 160 and the inner pin 140 are more firmly connected. Contribute to the consolidation.

  Furthermore, since the inner roller 142 is covered around the inner pin 140, power transmission by sliding between the inner pin hole 130 and the inner pin 140 can be performed very smoothly. For this reason, in combination with the double-support structure, depending on the application, the integrally formed product is used almost as it is without processing the inner pin 140 integrally formed with the first support flange 150 or only by extremely simple processing. It is also possible.

  FIG. 3 shows a modification (another embodiment) of the planetary gear speed reduction device 110 shown in FIG. The planetary gear speed reduction device 210 has a hole 268 with an inner diameter D2 for receiving the head 280A of the connecting bolt 280 and a hole 266 with an inner diameter D1 for engaging the knock pin 270 in the second support flange 260. It is formed continuously. Therefore, the two holes 268 and 266 can be continuously formed (processed) while maintaining the same chucking from a single direction (direction indicated by X in the figure), and the processing process is further simplified. Is possible.

  3 is a washer for making the contact between the head 280A of the connecting bolt 280 and the hole 268 tighter and preventing the knock pin 270 from coming off.

  Since the other configuration is basically the same as the configuration of the planetary gear reduction device 110 described above, only the same reference numerals are given to the same or similar parts in the figure, and the duplicate description is omitted. To do.

  FIG. 4 shows another modification of the planetary gear reduction device 110 shown in FIG.

  In the planetary gear reduction device 310, the inner rings of the bearings 317A to 317C arranged between the eccentric body 314 and the external gear 316 are omitted. That is, only the rollers 317A2 to 317C2 are interposed between the eccentric body 314 and the external gear 316, and the eccentric body 314 also functions as an inner ring, and the external gear 316 also functions as an outer ring. Yes.

  Since each of the rollers 317A2 to 317C2 does not have its own inner ring, the positioning of each of the rollers 317A2 to 317C2 in the axial direction is performed between the eccentric body 314 and the bearings 352 and 362 of the input shaft 312. The plate 392 (392A, 392B) is used. The plate 392 is a disc-shaped spring body whose outer peripheral side is biased toward the rollers 317A2 to 317C2. Each plate 392 sandwiches the rollers 317A2 to 317C2 from both sides in the axial direction, and applies an appropriate axial direction regulating force to the rollers 317A2 to 317C2. Since the other configuration is basically the same as the configuration of the planetary gear reduction device 110 described above, only the same reference numerals are given to the same or similar parts in the figure, and the duplicate description is omitted. To do.

  FIG. 5 shows still another modification of the planetary gear reduction device 110 shown in FIG. This planetary gear reduction device 410 includes a pre-reduction portion Pr of a simple planetary gear mechanism.

  The input shaft 412 has a recess 412A into which a motor shaft (not shown) is inserted and connected. A spline (491) is formed at the tip of the input shaft 412, and this constitutes the sun gear 491 of the pre-decelerator Pr as it is.

  The pre-reduction portion Pr is mainly composed of the sun gear 491, a planetary gear 492 that is externally meshed with the sun gear 491, a ring gear 493 that is internally meshed with the planetary gear 492, and a carrier 495 that supports the carrier pin 494 of the planetary gear 492. .

  The ring gear 493 of the pre-decelerating portion Pr is integrated with the first support flange 450 on the inner peripheral side of the first support flange 450. The carrier pin 494 has a head portion 494A, and the head portion 494A and the retaining ring 494B sandwich the carrier 495 and the planetary gear 492. The carrier 495 is supported by a bearing 453.

  The eccentric body 414 is supported at both ends by the step 495A of the carrier 495 and the bearing 463, and can rotate integrally with the carrier 495. The eccentric body 414 is a member independent of the input shaft 412 because it rotates at a rotational speed after the rotation of the input shaft 412 is decelerated by the pre-deceleration Pr.

  The power of a motor (not shown) input from the input shaft 412 is transmitted to the planetary gear 492 via a sun gear 491 (of the pre-reduction portion Pr) formed integrally with the tip of the input shaft 412. Since the ring gear 493 of the pre-decelerating portion Pr is integrated with the first support flange 450, the ring gear 493 maintains a relatively stopped state. Therefore, the pre-decelerating portion Pr effectively exhibits a movement similar to a simple planetary gear mechanism in which the sun gear 491 is an input member, the ring gear 493 is a fixed member, and the carrier 495 is an output member. As a result, the input shaft 412 (= sun gear 491) is taken out from the carrier 495 while being decelerated. When the carrier 495 rotates, the eccentric body 414 integrated with the carrier 495 rotates. The subsequent operation is the same as the operation of the planetary gear reduction device 110 already described.

  According to the planetary gear reduction device 410, a higher reduction ratio can be obtained as much as the pre-reduction portion Pr is present. In addition, since the first support flange 450 is used as a support member of the ring gear 493, the size of the entire speed reducer can be hardly increased.

  Since the other configuration is basically the same as the configuration of the planetary gear reduction device 110 described above, only the same reference numerals are given to the same or similar parts in the figure, and the duplicate description is omitted. To do.

  In the example of the above embodiment, an example in which all three external gears are provided in the axial direction is shown. Since the present invention supports the inner pins on both ends, a particularly remarkable effect is obtained when a plurality of external gears are arranged side by side in the axial direction. However, the application of the present invention is not necessarily limited to the case where three or more external gears are arranged side by side as described above. For example, the planetary gear reduction device 510 shown in FIG. As described above, the present invention can be applied to a reduction gear provided with only two external gears 516. Further, although not illustrated, the reduction gear can be similarly applied to a reduction gear having only one external gear. . The planetary gear reduction device 510 has basically the same configuration as the planetary gear reduction device 310 shown in FIG. 4 except for the difference in the number of external gears 516. Therefore, the planetary gear reduction device in FIG. The same reference numerals in the last two digits are given to the same or similar parts as 310, and the duplicated explanation is omitted.

  Moreover, in the example of the said embodiment, the structure by which the inner roller was covered around the inner pin was shown. In the present invention, the presence of the inner roller is not always essential.

  Furthermore, in the example of the above embodiment, the knock pin is driven into only one part of the plurality of inner pins, and the connecting bolts are screwed into all the inner pins including the inner pin into which the knock pin is driven. The driving of the knock pin and the screwing of the connecting bolt in the invention are not necessarily limited to this mode. For example, there may be an inner pin into which only the knock pin is driven, or knock pins may be driven into all the inner pins. Furthermore, the knock pins may be driven only into some of the inner pins in the state where the knock pin insertion holes that allow the knock pins to be driven are formed in all the inner pins.

  As described above, the knock pin is provided with a function of positioning the inner pin and the second support flange and by providing a shearing stress, thereby assisting the connection between the inner pin into which the knock pin is driven and the second support flange. There is a function. Therefore, what is necessary is just to increase / decrease the number of knock pins driven in suitably according to a use. When the torque to be handled is not so large, the number of knock pins may be about 3 to 4 in some cases.

  Of course, there may be an inner pin in which neither the knock pin nor the connecting bolt is driven or screwed. In the present invention, since “all inner pins” are integrated with the first support flange, if accurate positioning is performed on a part of the inner pins, accurate positioning is automatically performed on other inner pins. Made.

  Of course, this type of planetary gear speed reduction device can be applied to fields where it has been applied in the past. Even in fields that were difficult to introduce in terms of application, the scope of application could be expanded.

The longitudinal cross-sectional view of the planetary gear speed reducer which concerns on an example of embodiment of this invention. Enlarged view of the vicinity of IIA and IIB in Fig. 1 The longitudinal cross-sectional view of the planetary gear speed reducer which concerns on an example of other embodiment of this invention. The longitudinal cross-sectional view of the planetary gear speed reducer which concerns on an example of other embodiment of this invention. The longitudinal cross-sectional view of the planetary gear speed reducer which concerns on an example of other embodiment of this invention. The longitudinal cross-sectional view of the planetary gear speed reducer which concerns on an example of other embodiment of this invention. A longitudinal sectional view showing an example of a conventional planetary gear reduction device Sectional view along the line VIII-VIII in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 ... Planetary gear reduction device 112 ... Input shaft 114 ... Eccentric body 116 ... External gear 118 ... Internal gear K1 ... Relative rotation taking out mechanism 130 ... Inner pin hole 140 ... Inner pin 140N ... Inner pin 142 into which a knock pin is driven 142 ... Inner roller 144 ... Screw hole,
146, 166, 168 right ... hole 150 ... first support flange (output shaft)
160 ... second support flange 168 ... hole 170 ... knock pin 172 ... hollow part 180 ... connection bolt Pr ... pre-reduction part 491 ... sun gear 492 ... planetary gear 493 ... ring gear 494 ... carrier pin 495 ... carrier

Claims (5)

In a planetary gear reduction device comprising an internal gear and an external gear internally meshing with the internal gear, and taking out a relative rotational component between the internal gear and the external gear as an output,
An inner pin hole formed through the external gear;
A first support flange disposed on one side in the axial direction of the external gear;
A second support flange disposed on the other axial side of the external gear;
A plurality of inner pins formed integrally with the first support flange and extending to the second support flange side through the inner pin hole;
A knock pin driven between the second support flange and at least one of the inner pins;
A connecting bolt for fastening the second support flange and at least one of the inner pins;
A planetary gear reduction device comprising: In claim 1,
A planetary gear reduction device in which only one of the knock pin or the connecting bolt is driven or fastened to a specific inner pin. In claim 1,
A planetary gear reduction device in which the knock pin is driven into a specific inner pin, and the connecting bolt is also fastened to the same inner pin. In claim 3,
The planetary gear speed reducer in which the knock pin has a hollow portion, and the connecting bolt penetrates the hollow portion of the knock pin and is fastened to the specific inner pin. In claim 4,
A planetary gear reduction device in which a knock pin hole through which the knock pin having an inner diameter D2 passes is formed continuously with respect to a hole having an inner diameter D1 in which the head of the connecting bolt is accommodated in the second support flange.

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