JP5820298B2 - Power transmission device and assembly method thereof - Google Patents

Description

  The present invention relates to a power transmission device that drives wheels of a work vehicle.

  Patent Document 1 discloses a forklift with a transfer with a built-in wet brake in which a reduction gear including a single-stage parallel shaft reduction mechanism and a simple planetary gear reduction mechanism is provided, and a brake mechanism is disposed in the parallel shaft reduction mechanism. Yes.

JP 2010-159794 A

  Generally, forklift wheels need to support the weight of the load in addition to the weight of the forklift, so the drive transmission unit integrated with the wheels uses bearings that are as large as possible in terms of load resistance and durability. There is a request to do. On the other hand, in a forklift, there is a fork for raising and lowering the load in front of the front wheel, so there is a demand to reduce the wheel diameter in order to bring the center of gravity of the fork and the load loaded on the fork as close as possible to the ground contact position of the front wheel. . When the wheel diameter is reduced, it is difficult to increase the size of the bearing.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technology that enables a larger-sized bearing to be employed even in a limited space in a drive transmission device for a work vehicle such as a forklift. There is.

  One embodiment of the present invention is a power transmission device that drives wheels of a work vehicle. This device is screwed onto a power transmission shaft, a bearing that is externally fitted to the power transmission shaft, supports radial load and axial load, a support that is externally fitted to the outer ring of the bearing, and a support or power transmission shaft. And a bearing nut having a pressing portion that presses the outer ring or the inner ring of the bearing, and the pressing portion of the bearing nut has an outer diameter larger than that of the screw portion of the bearing nut.

  According to this aspect, the outer ring diameter of the bearing can be made larger than the outer diameter of the thread portion of the pressurizing member by using the pressurizing member having different outer diameters between the screw portion and the pressing portion. That is, the outer ring diameter of the bearing is not limited by the outer diameter of the thread portion of the pressurizing member. Therefore, it is possible to employ a bearing having a larger outer ring size than the conventional design.

  Another aspect of the present invention is an assembling method of a power transmission device for driving wheels of a work vehicle. This method applies pressure to the outer ring of the bearing that supports the power transmission shaft, and applies a pressurizing member with a male thread on the outer periphery to the support with a female thread on the inner periphery. The outer ring of the bearing is fitted into the support body from the opposite direction, and the pressurizing member is pressurized against the support body from the side opposite to the side on which the bearing is fitted. The pressure applied to the outer ring of the bearing is adjusted.

  Note that any combination of the above-described constituent elements, and those obtained by replacing the constituent elements and expressions of the present invention with each other among methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  According to the present invention, in a drive transmission device for a work vehicle such as a forklift, a bearing having a size larger than that of a conventional one can be employed even in a limited space.

It is a figure which shows the structure of the power transmission device which drives the wheel of work vehicles, such as a forklift, in which the reduction gear which concerns on one Embodiment of this invention was integrated. It is a figure which shows a part of power transmission device which concerns on a prior art. It is an enlarged view of the center part of the reduction gear of FIG. It is a figure which shows a part of power transmission device which concerns on a prior art. It is the figure which expanded the circumference of a bearing nut among drive transmission devices concerning another embodiment of the present invention.

  FIG. 1 shows a configuration of a power transmission device 100 that drives wheels of a work vehicle such as a forklift, in which a reduction gear 10 according to an embodiment of the present invention is incorporated. FIG. 1 is a cross-sectional view of the power transmission device 100 taken along a vertical plane including the wheels, the motor, and the center axis of the speed reducer.

  The speed reducer 10 is a kind of planetary gear speed reducer called an eccentric swing meshing type.

  An output shaft 12A of the motor 12 is connected to an input shaft (power transmission shaft) 16 of the speed reducer 10 through a spline 14. The input shaft 16 is disposed at the center in the radial direction of external gears 24 and 26 described later. The input shaft 16 is integrally formed with two eccentric bodies 18 and 20 that are offset from the input shaft 16. The two eccentric bodies 18 and 20 are eccentric with a phase difference of 180 degrees from each other. The eccentric bodies 18 and 20 may be configured separately from the input shaft 16 and fixed to the input shaft with a key or the like.

  Two external gears 24 and 26 are fitted on the outer circumferences of the eccentric bodies 18 and 20 via roller bearings 21 and 23 so as to be swingable. The external gears 24 and 26 are in mesh with the internal gear 28, respectively.

  The internal gear 28 includes cylindrical internal pins 28A and 28B that form internal teeth, a holding pin 28C that passes through the internal pins 28A and 28B and rotatably holds the pins, and a holding pin 28C that is rotatable. The internal gear main body 28 </ b> D integrated with the casing 30 is mainly configured.

  The number of internal teeth of the internal gear 28, that is, the number of internal pins 28A and 28B, is slightly larger (by 1 in this embodiment) than the number of external teeth of the external gears 24 and 26.

  A first carrier body 34 fixed to a vehicle body frame (not shown) is disposed on the side of the external gears 24 and 26 in the axial direction of the vehicle body. A second carrier body (first member, support) 38 integrated with the first carrier body 34 is disposed. An inner pin 40 is formed integrally with the second carrier body 38.

  In the external gear 24 (not shown, the same applies to the external gear 26), twelve through holes with the same diameter are formed at equal intervals at positions offset from the axis. Among them, the carrier pin 42 is inserted into three holes arranged at equal intervals of 120 degrees, and the inner pin 40 is inserted into the remaining nine holes. Therefore, the former is called the carrier pin hole 24B and the latter is called the inner pin hole 24A, but there is no difference in the shape and radial position. Corrugated teeth are formed on the outer periphery of the external gear 24, and these teeth move while in contact with the internal gear pins 28 </ b> A of the internal gear 28, so that the external teeth are externally moved in a plane whose normal is the central axis. The toothed gear 24 can swing. Although not shown, the external gear 26 is the same except that there is a phase difference of 180 degrees with respect to the external gear 24.

  The inner pin 40 is inserted into the inner pin holes 24 </ b> A and 26 </ b> A penetratingly formed in the external gears 24 and 26 with a gap, and the tip thereof is fitted into the recess 34 </ b> A of the first carrier body 34. The inner pin 40 is in contact with a part of the inner pin holes 24A, 26A formed in the outer gears 24, 26 via the sliding promotion member 44, and restrains the rotation of the outer gears 24, 26 to Only swinging is allowed.

  The inner pin 40 is only press-fitted into the recess 34A, and is not fixed with a bolt or the like. It can be said that the inner pin is a connecting member that contributes to the transmission of power between the first and second carrier bodies 34 and 38 and the external gears 24 and 26.

  The carrier pin 42 is inserted in a state where there is a gap in the carrier pin holes 24B and 26B formed through the external gears 24 and 26, and a contact portion 42C having an enlarged diameter is formed on the side of the first carrier body 34 opposite to the vehicle body. It is in contact. The carrier pin 42 and the first carrier body 34 are fastened by a carrier bolt 36. The first carrier body 34 is formed with a through hole 34C for inserting the carrier bolt 36 and a counterbore portion 34B, and a screw hole 42E for screwing the carrier bolt 36 is formed on the axial end surface of the carrier pin 42. Is formed. The second carrier body 38 has a female screw hole 38 </ b> A, and is fastened to the male screw at the tip of the carrier pin 42 on the side opposite to the vehicle body to connect the carrier pin 42 and the second carrier body 38.

  The carrier pin 42 is not in contact with the carrier pin holes 24B and 26B of the external gears 24 and 26, and does not contribute to restraining the rotation of the external gears 24 and 26. It can be said that the carrier pin 42 is a connecting member that contributes only to the connection between the first carrier body 34 and the second carrier body 38.

  The casing 30 of the speed reducer 10 is rotatably supported by a first carrier body 34 and a second carrier body 38 fixed to the vehicle body frame via a pair of main bearings 46 and 47. A wheel member 48 is connected to the end surface of the casing 30 on the side opposite to the vehicle body in the axial direction by bolts 49, and a tire 50 of a forklift (not shown) is attached to the wheel member 48. The speed reducer 10 is accommodated in the axial range of the tire 50 (within the range of the two-dot chain line in FIG. 1).

  A second bearing nut (second pressurizing member) 56 is screwed into a screw hole formed in the outer peripheral surface of the second carrier body 38, and the second carrier body 38, the casing 30, and the main bearings 46, 47. , The pressure applied to the main bearings 46 and 47 can be adjusted by changing the pushing amount of the second bearing nut 56.

  The input shaft 16 as an input member of the speed reducer 10 is rotatably supported by the first carrier body 34 and the second carrier body 38 via a pair of angular ball bearings 52 and 54 that are arranged face to face. The angular ball bearings 52 and 54 have rolling elements 52A and 54A and outer rings 52B and 54B, respectively, but do not have an inner ring. Instead, rolling surfaces 52C and 54C are formed on the input shaft 16, and these function as inner rings of the angular ball bearings. In addition, it is not restricted to this structure, You may arrange | position a separate inner ring | wheel.

  A bearing nut (pressurizing member) 39 is screwed into a screw hole formed in the inner peripheral surface of the second carrier body 38, and the first carrier body 34, the second carrier body 38 and the angular ball bearing 52, The pressure applied to the angular ball bearings 52 and 54 can be adjusted by changing the push-in amount of the bearing nut 39 when assembling 54.

  The axial ball bearing 52 on the vehicle body side is restrained in the axial direction by the recess 34 </ b> D of the first carrier body 34 and the rolling surface 52 </ b> C of the input shaft 16. The angular ball bearing 54 on the side opposite to the vehicle body is restrained in the axial direction by a bearing nut 39 screwed into the second carrier body 38 and the rolling surface 54 </ b> C of the input shaft 16. Therefore, the input shaft 16 is positioned in the axial direction without play by the first carrier body 34 and the bearing nut 39 so that the axial movement is restricted in any direction.

  Then, the effect | action of the power transmission device 100 is demonstrated.

  The rotation of the output shaft 12 </ b> A of the motor 12 is transmitted to the input shaft 16 of the speed reducer 10 through the spline 14. When the input shaft 16 rotates, the outer circumferences of the eccentric bodies 18 and 20 perform an eccentric motion, and the external gears 24 and 26 swing through the roller bearings 21 and 23. This swinging causes a phenomenon in which the meshing positions of the external teeth of the external gears 24 and 26 and the internal tooth pins 28A and 28B of the internal gear 28 are sequentially shifted.

  The difference in the number of teeth between the external gears 24 and 26 and the internal gear 28 is set to 1, and the rotation of each external gear 24 and 26 is caused by the first carrier body 34 fixed to the body frame. It is restrained by the fixed inner pin 40. For this reason, every time the input shaft 16 rotates once, the internal gear 28 rotates (rotates) by an amount corresponding to the difference in the number of teeth with respect to the external gears 24 and 26 whose rotation is restricted. . As a result, the casing 30 integrated with the internal gear main body 28 </ b> D rotates at a rotational speed reduced to 1 / (the number of teeth of the internal gear) by the rotation of the input shaft 16. As the casing 30 rotates, the forklift tire 50 rotates through a wheel member 48 fixed to the casing 30 by bolts 49.

  The power transmission device described above is mainly used for driving wheels of a forklift. In general, a forklift has a fork for raising and lowering a load in front of a front wheel, and thus has a structure in which a counterbalance (counterweight) is disposed behind the center of gravity of the forklift. In order to reduce the magnitude of the counter balance, the center of gravity of the fork and the load loaded on the fork must be as close as possible to the ground contact position of the front wheel. In this respect, the smaller the diameter of the forklift wheel, the better. On the other hand, in order to support the heavy weight of the load mounted on the fork, the wheel tire (rubber part) itself must have a large volume. As a result, the inner diameter of the wheel member must be reduced, and the space inside the radial direction of the wheel that houses the power transmission device becomes very small.

  FIG. 2 shows a part of a power transmission device according to the prior art which is used in a state where there is a space limitation described above. The shaft 216 corresponds to the input shaft 16 of the speed reducer 10 described in FIG. A bearing 247 is fitted to a shoulder 216 </ b> A formed on the shaft 216. The shaft 216 is rotatably supported by the carrier body 238 by the bearing 247. In FIG. 2, the bearing 247 is depicted as a tapered roller bearing. However, any type of bearing may be used as long as it can support both the radial load and the axial load of the shaft 216.

  A bearing nut 239 having a male screw formed on the outer periphery is screwed onto the female screw formed on the inner periphery of the carrier body 238. The bearing nut 239 applies pressure to the bearing by pressing the outer ring 247C of the bearing 247 in the axial direction. An oil seal 240 seals between the inner periphery of the bearing nut 239 and the outer periphery of the shaft 216.

As shown in the figure, when the bearing nut 239 for applying pressure to the outer ring 247C of the bearing 247 is used, the outer ring diameter D _O of the bearing 247 is necessarily smaller than the outer diameter D _T of the bearing nut 239 (D _T ≧ D _O ). That is, the outer ring diameter D _O of the bearing is limited by the outer diameter D _T of the bearing nut. Further, since the space on the inner side in the radial direction of the wheel is limited and another member needs to be disposed on the outer periphery of the carrier body 238, the thickness of the carrier body 238 needs to be secured. Therefore, it is not easy to increase the outer diameter _DT of the bearing nut 239. On the other hand, in order to improve the durability and load resistance of the bearing, there is a demand to adopt a bearing 247 having a size as large as possible.

  Therefore, in the present embodiment, the above-described contradictory problem is solved by adopting a stepped configuration of the bearing nut. FIG. 3 is an enlarged view of the central portion of the speed reducer 10 of FIG. The bearing nut 39 includes a screw portion 39A having a male screw formed on the outer periphery, and a pressing portion 39B having a diameter larger than that of the screw portion 39A. The screw portion 39A is screwed into a female screw formed on the inner periphery of the second carrier body 38. The pressing portion 39B has the same thickness as the outer ring 54B of the angular ball bearing 54, and the bottom surface (the surface on the side of the axial vehicle body) of the pressing portion 39B is in contact with the outer ring 54B. The pressure applied to the angular ball bearing 54 is adjusted by rotating and moving the bearing nut 39 toward the vehicle body side with respect to the second carrier body 38.

  A main bearing 47 is disposed on the outer periphery of the second carrier body 38, and a second bearing nut 56 is screwed onto a male screw formed on the outer periphery of the second carrier body 38. The second bearing nut 56 abuts against the inner ring 47 </ b> A of the main bearing 47 to apply pressure.

As shown in the figure, the outer diameter D _O of the angular ball bearing 54 can be made larger than the outer diameter D _T of the threaded portion 39A of the bearing nut 39 by making the bearing nut 39 have a stepped configuration (D _T <D _O ). That is, the outer diameter of the bearing is not limited by the outer diameter of the bearing nut. Therefore, it is possible to employ a bearing having a larger outer ring size than the conventional design.

  In addition, since the diameter of the threaded portion 39A can be reduced by adopting a stepped configuration of the bearing nut 39, the second carrier body of the portion where the bearing nuts 39 and 56 are arranged and the screw is formed on both the inner and outer circumferences. The wall thickness of 38 can be made thicker than other portions.

  Since the bearing nut 39 has a stepped structure, the bearing nut 39 cannot be screwed in from the rear (opposite body side) of the second carrier body 38 after the input shaft 16 and the angular ball bearing 54 are assembled. Therefore, the following assembly procedure is adopted. First, from the inside of the second carrier body 38, that is, from the vehicle body side, the threaded portion 39 </ b> A of the bearing nut 39 is screwed into the innermost part of the female thread of the second carrier body 38. Next, with the outer ring 54B of the bearing 54 fitted in the second carrier body 38 and the rolling element 54A placed on the outer ring 54B, the rolling surface 54C formed on the input shaft 16 comes into contact with the rolling element 54A. The input shaft 16 is assembled to Thereafter, by rotating and advancing the bearing nut 39 toward the bearing 54, the pressure applied to the outer ring 54B of the bearing 54 by the pressing portion 39B can be adjusted. The rolling element 54A may be assembled to the outer ring 54B fitted inside the second carrier body 38 with the rolling element 54A placed on the rolling surface 54C on the input shaft 16.

  In order to enable such assembly, a tool hole 39D into which a dedicated tool for rotating the bearing nut 39 from the outside of the second carrier body 38, that is, the side opposite to the vehicle body is formed at the center of the bearing nut 39. ing. For the tool hole 39D, for example, a shape that fits the tip of the dedicated tool, such as a square or a hexagon, is employed. Further, when the bearing nut 39 is screwed into the female thread of the second carrier body 38, the bearing nut 39 can be screwed in until the upper surface (surface on the side opposite to the vehicle body in the axial direction) of the pressing portion 39B of the bearing nut 39 abuts. A portion 39C whose diameter increases from the screw portion 39A to the pressing portion 39B is bored closer to the inner diameter side than the diameter of the thread valley.

  In the above description, the second bearing nut 56 is used as the second member in the claims to apply pressure to the inner ring 47A of the main bearing 47. Instead, the second carrier body is used. A C-ring (retaining ring) fitted in a groove formed on the outer periphery of 38 may be used.

  The embodiment described with reference to FIGS. 2 and 3 corresponds to a case where a set of bearings are arranged face-to-face and pressure is applied to the outer ring. However, the present invention can also be applied to a case where a set of bearings are arranged back to back to apply pressure to the inner ring. Hereinafter, such an embodiment will be described.

  FIG. 4 shows a part of a power transmission device according to the prior art. The shaft 316 corresponds to the input shaft 16 of the speed reducer 10. On the shaft 316, a pair of bearings 347 and 348 that are back-to-back are fitted. The shaft 316 is rotatably supported with respect to the carrier body 338 by these bearings 347 and 348. In FIG. 4, the bearings 347 and 348 are depicted as tapered roller bearings, but any type of bearing may be used as long as it can support both the radial load and the axial load of the shaft 316. A bearing nut 339 having a female screw formed on the inner periphery is screwed onto the male screw formed on the outer periphery of the shaft 316. The bearing nut 339 applies pressure to the bearing by pressing the inner ring 347B of the bearing 347 in the axial direction. An oil seal 340 is sealed between the outer periphery of the bearing nut 339 and the inner periphery of the shaft 316.

As shown, when using a bearing nut 339 to impart preload to the inner ring 347B of the bearing 347, the inner diameter _{D U} bearing nut 339 is necessarily an inner ring diameter _{D I} of the bearing 347 to is necessary to substantially coincide (D _U = D _I ). In other words, the inner diameter _{D U} bearing nut 339 is limited by the inner diameter _{D I} of the bearing 347. On the other hand, as the oil seal 340 disposed on the outer periphery of the bearing nut 339 increases in size, the cost, the possibility of leakage, and the sliding resistance increase. Therefore, there is a demand for adopting an oil seal as small as possible.

  Therefore, in the present embodiment, the above-described contradictory problem is solved by adopting a stepped configuration of the bearing nut. FIG. 5 is an enlarged view of the periphery of the bearing nut in the drive transmission device according to the present embodiment. The bearing nut 439 includes a screw portion 439A in which a female screw is formed on the inner periphery, and a pressing portion 439B having a diameter larger than that of the screw portion 439A. The screw portion 439A is screwed into a male screw formed on the outer periphery of the shaft 416. The bottom surface of the pressing portion 39B is in contact with the inner ring 447B of the bearing 447. By rotating the bearing nut 439 in the direction of the bearing 447 with respect to the carrier body 438, the pressure applied to the bearing 447 is adjusted.

As shown, by the bearing nut 439 and stepped configuration, the inner diameter _{D U} bearing nut 439, can be made smaller than the inner diameter _{D I} of the bearing _{447 (D U <D I)} . That is, the inner ring diameter D _I of the bearing, thereby preventing the inner diameter D _U bearing nut restricted. Accordingly, since the inner diameter D _S of the oil seal 440 can also be reduced, it is possible than conventional designs employing the oil seal of smaller size. Therefore, the cost of the oil seal, the possibility of leakage, and the sliding resistance are reduced.

  This embodiment can be expressed as follows.

A power transmission device for driving wheels of a work vehicle,
A power transmission shaft;
A bearing externally fitted to the power transmission shaft and supporting a radial load and an axial load;
A support body fitted on the outer ring of the bearing;
A pressurizing member having a threaded portion that is screwed onto the outer periphery of the power transmission shaft, and a pressing portion that presses the inner ring of the bearing;
An oil seal disposed so as to seal between the support and the threaded portion outer diameter of the pressurizing member,
The power transmission device according to claim 1, wherein the pressing portion of the pressurizing member has an outer diameter larger than that of the screw portion of the pressurizing member.

  The embodiment of the present invention has been described above. It is to be understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to combinations of the respective components, and such modifications are within the scope of the present invention.

  In the embodiment, an eccentric oscillating mesh type planetary gear reducer in which the input shaft (eccentric body shaft) 16 is arranged at the center of the internal gear 28 has been described as an example of the power transmission device. However, the present invention is not limited to this type of speed reducer, for example, an eccentric oscillating planetary gear speed reducer of a type in which a plurality of eccentric body shafts are arranged at a position offset from the center of the internal gear, a simple planetary type planetary gear The present invention can also be applied to a power transmission device having any type of speed reduction mechanism including a gear reducer. The present invention can also be applied to a power transmission device that does not include a speed reduction mechanism.

  In the embodiment, the configuration in which the first carrier body 34 and the second carrier body 38 are fixed and the rotation is output from the casing 30 has been described. However, the casing 30 may be fixed and rotation may be output from the first carrier body 34 and the second carrier body 38. In this case, the rotation components of the external gears 24 and 26 are transmitted to the first carrier body 34 and the second carrier body 38 via the inner pin 40.

  The power transmission shaft is not limited to the input shaft of the speed reducer as long as it is a shaft that transmits power.

  In the embodiment, the pressurization adjustment for the angular ball bearing fitted on the power transmission shaft has been described. However, the bearing fitted on the power transmission shaft is not limited to an angular ball bearing, and may be any bearing that supports radial load and axial load, that is, a bearing that needs to be pressurized, such as a tapered roller bearing. May be.

  The first member or the support body referred to in the claims is not limited to the second carrier body 38 described in the embodiment, and may be any structure as long as it is fitted to the outer ring of the bearing.

  Further, the second member referred to in the claims is not limited to the main bearing 47 and the second bearing nut 56. As long as the structure is arranged on the outer periphery of the first member, either the main bearing or the second bearing nut may be used, or other members such as a retaining ring or an oil seal may be used.

  In the embodiment, a forklift has been described as an example of a work vehicle driven by a power transmission device. However, any work vehicle may be used, for example, a work machine for construction, civil engineering, or transportation is mounted. Various working vehicles may be used.

  DESCRIPTION OF SYMBOLS 10 Reduction gear, 12 Motor, 16 Input shaft, 38 2nd carrier body, 39 Bearing nut, 39A Screw part, 39B Press part, 46, 47 Main bearing, 52, 54 Angular ball bearing, 56 2nd bearing nut, 100 Power Transmission device, 238, 438 carrier body, 238A, 438A threaded portion, 238B, 438B pressing portion, 239, 439 bearing nut, 240, 440 oil seal.

Claims (4)

A power transmission device for driving wheels of a work vehicle,
A power transmission shaft;
A bearing externally fitted to the power transmission shaft and supporting a radial load and an axial load;
A first member fitted on the outer ring of the bearing;
A second member disposed on an outer periphery of the first member;
A pressurizing member having a threaded portion that is screwed to the inner periphery of the first member, and a pressing portion that presses the outer ring of the bearing,
Pressing part of the pressurization imparting member is much larger outer diameter than the threaded portion of the pressurization imparting member,
The second member includes a second bearing disposed on the outer side in the radial direction of the bearing, and a second pressurizing member that applies a pressurization to the inner ring of the second bearing,
The portion of the first member where the second pressurizing portion is disposed is thicker than the portion where the second bearing is disposed. 2. The power transmission device according to claim 1, wherein a polygonal hole into which a tool for rotating the pressurizing member with respect to the first member is inserted is formed at the center of the pressurizing member. . 3. The power transmission device according to claim 1, wherein a portion of the pressurizing member that expands from the threaded portion to the pressing portion is bored closer to the inner diameter side than the diameter of the thread valley. . A method of assembling the power transmission device according to any one of claims 1 to 3 ,
A pressurizing member with a male thread formed on the outer periphery, which applies pressure to the outer ring of the bearing that supports the power transmission shaft, is screwed into a support body with a female thread formed on the inner periphery from the direction opposite to the pressurizing direction. And
The outer ring of the bearing is fitted into the support from the opposite direction,
Adjusting the pressurization applied to the outer ring of the bearing by advancing the pressurization applying member in the pressurizing direction of the press with respect to the support from the side opposite to the side in which the bearing is fitted. Method.

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