JP2012139756A - Method for manufacturing internal gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an internal gear having a highly accurate tooth surface shape by controlling a strain caused by a difference between a residual stress generated in lathe-turning an outer peripheral surface and a residual stress generated in machining an inner peripheral surface to form a tooth surface.SOLUTION: A method for manufacturing an internal gear includes: a rough blanking step S1 of applying a rough blanking; a finish lathe-turning step S2 of applying a finish lathe-turning to an outer periphery of a material to form the outer peripheral surface; a gear cutting step S3 of applying a gear cutting to an inner periphery of the material to which the finish lathe-turning is applied, to form the tooth surface; a heating step S4 of applying a heating to the material having the tooth surface formed in the inner periphery; and a grinding finish step S5 of applying a grinding finishing to the material after the heating. The method for manufacturing an internal gear further includes: a residual stress evaluation step S6 of evaluating the residual stress generated on the outer periphery side of the material to which the grinding finishing is applied; and a lathe-turning condition control step S7 of controlling lathe-turning conditions according to the level of an evaluation value of the residual stress obtained in the residual stress evaluation step S6 so that a subsequent residual stress to be generated by applying the grinding finishing on the outer periphery side of the material is reduced lower than the evaluation value.

Description

  The present invention relates to a method for manufacturing an internal gear, and more particularly, to a control technique for turning an outer peripheral surface on the non-tooth surface side.

  The internal gear has a tooth surface on the inner periphery of the cylindrical portion or the annular portion, and is manufactured through the following steps, for example. First, gear shaper processing, broaching and other gear cutting processing (for example, refer to Patent Document 1 below), or rolling processing (for example, refer to Patent Document 2 below) or the like is performed on the inner periphery of the cylindrical portion or the annular portion. Tooth surface is formed. And after performing heat processing, such as carburizing and gas nitriding, the above-mentioned internal gear is completed by giving finish grinding to an outer peripheral surface. Moreover, as the material of the internal gear for performing the above-mentioned gear cutting, etc., in addition to the case where a press-molded one is used as described in Patent Document 2 below, the case where an outer peripheral surface is formed by turning is used. There is also.

JP 2007-216236 A JP-A-5-96337

  As described above, in the internal gear product, in order to improve the wear resistance, the heat treatment is performed after the tooth surface is formed. However, the heat treatment is generally performed at a high temperature of 500 ° C to 900 ° C. The internal stress of the gear is released, and the gear may be distorted by the stress generated during the transformation. This is because, when the outer peripheral surface of the gear is formed by turning, for example, a predetermined residual stress is generated on the outer peripheral side of the material in order to scrape the material while pressing a turning blade (chip) on the outer periphery of the material. This is because a predetermined residual stress is also generated on the tooth surface side (inner peripheral side) by tooth surface molding such as gear cutting, and the difference between these residual stresses appears as strain after the heat treatment. This type of distortion causes abnormal noise during use (gear meshing), so it is necessary to remove it as much as possible. On the other hand, in recent years, it has become more compact for devices incorporating this type of internal gear. There is an increasing demand for reduction in weight and weight, and there is a current situation that thinning of internal gears is being promoted. Therefore, there is a problem that the distortion after the heat treatment is more easily reflected in the finished product than ever.

  In view of the above circumstances, the inner surface has a highly accurate tooth surface shape by suppressing the occurrence of distortion due to the difference between the residual stress generated during turning of the outer peripheral surface and the residual stress generated during tooth surface forming processing of the inner peripheral surface. Manufacturing a gear is a technical problem to be solved by the present invention.

  The solution to the above problem is achieved by the method for manufacturing an internal gear according to the present invention. That is, this manufacturing method is a method for manufacturing an internal gear in which an outer peripheral surface is formed by turning the outer periphery of the material and a tooth surface is formed on the inner periphery of the material. Residual stress generated on the outer peripheral side of the material to be turned next is evaluated according to the residual stress evaluation process for evaluating the residual stress generated on the outer peripheral side, and the magnitude of the residual stress evaluation value obtained in the residual stress evaluation process It is characterized by having a turning condition adjusting step for adjusting the turning condition so as to be smaller than the value.

  Thus, the present invention pays attention to the turning of the outer peripheral surface of the material which is easy to process and has a high degree of freedom of processing compared to the tooth surface, and the residual stress generated on the outer peripheral side of the material to be turned next is already It is characterized by adjusting the turning conditions so as to be smaller than the evaluation value of the residual stress in the material subjected to the turning process. In other words, because the tooth surface is formed on the inner circumference of the material by various gear cutting and rolling, the residual stress generated on the inner circumference side of the material due to the tooth surface formation is relatively stable, while the outer circumference of the material is turned In this case, a turning blade such as a tip used for turning process is easily worn compared to a processing tool used for tooth surface forming process. As a result, it was found that the residual stress generated on the outer peripheral side of the material changes as the turning process continues, and the difference in residual stress between the inner and outer periphery of the material increases. The present invention has been made in view of such circumstances. First, the residual stress generated on the outer peripheral side of the turned material is evaluated, and the evaluated residual stress exceeds, for example, a predetermined value (threshold). In this case, the conditions at the time of turning are adjusted so that the residual stress generated on the outer peripheral side of the material to be turned next is smaller than the evaluation value of the residual stress. As a result, the difference between the residual stress generated on the outer peripheral side of the material by turning and the residual stress generated on the inner peripheral side during tooth surface formation can be reduced, and the amount of strain after heat treatment can be reduced. it can. Therefore, an internal gear excellent in dimensional accuracy and shape accuracy including the tooth surface can be manufactured, and a defect rate due to the distortion can be reduced. Moreover, since the internal gear can be manufactured with high accuracy, it is possible to further reduce the thickness.

  Further, in the method for manufacturing an internal gear according to the present invention, the residual stress evaluation step includes a correlation acquisition step of acquiring in advance a correlation between the wear amount of the turning blade used for the turning and the residual stress, and turning. Wear obtained in the wear amount estimation process, including an outer diameter measurement step for measuring the outer diameter of the material and a wear amount estimation step for estimating the wear amount of the turning blade from the outer diameter measurement value obtained in the outer diameter measurement step. The residual stress on the outer peripheral side may be evaluated based on the amount and the correlation between the wear amount and the residual stress.

  As a means for evaluating the residual stress generated on the outer peripheral side of the material, there is also a means for directly measuring the residual stress by X-ray diffraction or the like, but considering that the series of steps are arranged on the production line, the direct stress It is difficult to adopt measurement means (it is difficult to incorporate the corresponding measurement device into the production line). Here, pay attention to the fact that the wear state of the turning blade used for turning can be indirectly evaluated by measuring the outer diameter of the material subjected to turning with this turning blade, and the outer diameter of the material is measured. By doing so, the residual stress on the outer peripheral side was evaluated. That is, first, the outer diameter of the material subjected to turning is measured, and the amount of wear of the turning blade is estimated from the measured value. In this case, the difference (increase) between the measured outer diameter and the measured outer diameter at the beginning of cutting corresponds to the amount of wear of the turning blade. If the turning amount of the turning blade has already been evaluated and the turning amount of the turning blade has been adjusted, the amount of adjustment is also taken into account (accumulated) to estimate the current amount of wear. Then, the residual stress on the outer peripheral side corresponding to the wear amount can be evaluated by comparing the estimated wear amount with the correlation between the previously obtained wear amount and the residual stress. According to this means, it is only necessary to measure the outer diameter of the material, so that the measurement work is easy and the equipment required for the measurement is small.

  Further, in the method for manufacturing an internal gear according to the present invention, the turning condition adjusting step includes a step of acquiring in advance a relationship between a feed amount or a rotation speed adjustment amount during turning and a residual stress reduction amount at that time. Based on the residual stress evaluation value obtained in the residual stress evaluation process, and the relationship between the feed amount or rotation speed adjustment amount and the residual stress reduction amount at that time, the feed amount or rotation speed during turning is determined. You may adjust.

  As described above, the feed amount or the rotational speed is adopted as the adjustment parameter of the turning processing conditions, and the relationship between the adjustment amount of these parameters and the reduction amount of the residual stress at that time is acquired in advance. Then, a residual stress reduction amount is set according to the magnitude of the residual stress evaluation value obtained in the residual stress evaluation step, and a feed amount or a rotational speed adjustment amount corresponding to this reduction amount (usually a reduction amount). Set. This makes it possible to reliably and automatically control the residual stress that occurs on the outer periphery of the material to be turned next, and to suppress distortion that occurs in the finished product due to heat treatment to a level that does not cause any problems. It becomes. In particular, as described above, when adopting a means to evaluate the residual stress from the measured outer diameter of the material, the outer diameter of the material is substantially measured to adjust the feed amount or rotational speed during turning. Since the residual stress on the outer peripheral side of the material can be controlled simply by doing, it is excellent in terms of work efficiency.

  As described above, according to the present invention, it is possible to suppress the occurrence of distortion caused by the difference between the residual stress generated during the turning process of the outer peripheral surface and the residual stress generated during the tooth surface forming process of the inner peripheral surface, thereby achieving a highly accurate tooth. An internal gear having a surface shape can be manufactured.

It is a flowchart which shows the whole flow of the manufacturing method of the internal gear which concerns on one Embodiment of this invention. It is a flowchart for demonstrating in detail the principal part of the flowchart shown in FIG. It is a perspective view which shows an example of the internal gear manufactured with the manufacturing method which concerns on this invention. It is a side view for demonstrating a turning process process notionally. It is a graph which shows the relationship between the amount of wear of a turning blade, and the residual stress of the raw material outer periphery side in that case. It is a graph which shows the relationship between the amount of wear and the amount of cutting. It is a graph which shows the relationship between abrasion amount and feed amount.

  Hereinafter, an embodiment of a method for manufacturing an internal gear according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the method for manufacturing an internal gear according to an embodiment of the present invention includes a rough blank processing step S <b> 1 for performing a rough blank processing for forming a shape substantially conforming to the outer shape of a finished product, A finishing turning process S2 in which the outer periphery is finished to form an outer peripheral surface, a gear cutting process S3 in which the inner periphery of the material subjected to the finishing turning is subjected to gear cutting to form a tooth surface, The heat treatment process S4 which heat-processes the raw material which formed the tooth surface in the periphery, and the grinding finishing process S5 which grind-finishes the raw material after heat processing are comprised. The internal gear is completed through these steps S1 to S5.

  Here, for example, as shown in FIG. 3, the internal gear 1 as a finished product extends in the rotational axis direction from the cylindrical portion 2 provided with a bottom portion on one end side and the bottom portion of the cylindrical portion 2 in this embodiment. It has the boss | hub part 3 integrally. Further, the outer peripheral surface 4 of the cylindrical portion 2 on the non-tooth surface side is formed by turning (finishing turning), and a tooth surface 5 is formed on the inner periphery of the cylindrical portion 2.

  Further, as shown in FIG. 1, this manufacturing method was obtained in a residual stress evaluation step S6 for evaluating residual stress generated on the outer peripheral side of a material subjected to turning (finish turning), and a residual stress evaluation step S6. Turning condition adjustment process for adjusting the turning conditions so that the residual stress generated on the outer periphery of the material to be subjected to the next turning (finish turning) is smaller than the above evaluation value according to the magnitude of the evaluation value of the residual stress S7. In this embodiment, the residual stress is evaluated for a material subjected to turning every predetermined number of times, and turning conditions are adjusted according to the value of the evaluated residual stress. Hereinafter, the finishing turning process S2, the residual stress evaluation process S6, and the turning condition adjusting process S7 will be described in detail.

As shown in FIG. 4, the turning process (finish turning process) in the finishing turning process S <b> 2 includes a cylindrical portion corresponding region 12 in the raw material 11 processed into an outer shape substantially equal to the finished product in the rough blanking process S <b> 1. In this process, the outer peripheral surface 14 is formed by performing a turning process (finish turning process) on the outer periphery. More specifically, the boss portion corresponding region 13 of the material 11 is gripped by a plurality of chucks 21 attached to the rotation drive unit 22, and a turning blade 23 is disposed on the outer peripheral side of the cylindrical portion corresponding region 12. Then, to rotate the rotary drive unit 22 of the state of holding the blank 11 coaxially chuck 21 at a predetermined rotational speed V _t, depth of cut Cd tubular portion corresponding region turning blade 23 so that a predetermined depth is moved by a predetermined amount on the inner diameter side of 12, thereafter, it is moved toward parallel to and from the tubular portion corresponding region 12 to the boss portion corresponding region 13 of the turning blade 23 with respect to the rotation axis by a predetermined feed amount V _s . Thereby, turning (finish turning) is performed on the outer periphery of the material 11, and the outer peripheral surface 14 of the cylindrical part corresponding | compatible area | region 12 which has a predetermined | prescribed outer diameter is formed. The rotation speed V _{t of} the material 11 (rotation drive unit 22) and the moving speed (feed amount V _s ) of the turning blade 23 can be arbitrarily controlled by a control unit (not shown).

  In this embodiment, as shown in FIG. 2, the residual stress evaluation step S6 is performed by the amount of wear of the turning blade 23 (see FIG. 4) used in the finishing turning step S2 and turning (finishing turning). A correlation acquisition step S61 for acquiring in advance a correlation with the residual stress generated on the outer peripheral side of the material 11, and an outer diameter measurement for measuring the outer diameter of the cylindrical portion corresponding region 12 of the material 11 subjected to turning (finish turning). In step S62, the wear amount estimation step 63 for estimating the wear amount of the turning blade 23 from the outer diameter measurement value obtained in the outer diameter measurement step 62, the wear amount obtained in the wear amount estimation step 63, and the correlation acquisition step S61. It comprises a residual stress calculating step S64 for calculating the residual stress on the outer peripheral side based on the acquired correlation between the amount of wear and the residual stress.

  In the correlation acquisition step S61, the actual wear amount from the start of use of the turning blade 23 is measured directly or indirectly using, for example, a caliper or a displacement sensor, and is generated on the outer peripheral side of the material 11 during each measurement. For example, by measuring the residual stress directly or indirectly by X-ray diffraction or calculating the difference from the outer diameter after heat treatment, and creating a database, for example, the amount of wear and the residual stress as shown in FIG. Create a correlation diagram. Here, the vertical axis of the graph shown in the figure indicates the magnitude of the residual stress, and the positive side belongs to the compressive stress and the negative side belongs to the tensile stress. As shown in the figure, by calculating an approximate straight line (or approximate curve) from the data acquired at this time, the corresponding residual stress is quickly and automatically calculated from the estimated wear amount in the residual stress calculation step S64. Can be calculated automatically.

  In the outer diameter measuring step S62, the outer diameter of the cylindrical portion corresponding region 12 of the material 11 that has actually been turned is directly or indirectly measured by the same means as described above. This measurement is performed every predetermined number of times (for example, every 100 times).

In the wear amount estimation step S63, the wear amount of the turning blade 23 at that time is estimated from the outer diameter measurement value obtained in the outer diameter measurement step S62. Here, the amount of wear of the turning blade 23 when a predetermined number of times of turning (finishing turning) is applied is 1 from the measured outer diameter of the material 11 subjected to the predetermined number of times of turning (finishing turning). Since it can be regarded as being equal to a value obtained by subtracting the outer diameter (in other words, the outer diameter setting value after turning in the first turning process) of the material 11 subjected to the second turning process (finish turning process), the predetermined number of times The difference between the measured outer diameter of the material 11 subjected to the turning and the outer diameter setting value of the material 11 at the first turning is estimated as the wear amount of the turning blade 23 at that time. If the cutting amount C _d of the turning blade 23 has already been corrected one or more times since the start of use of the turning blade 23, the value obtained by adding the correction amount (total integrated amount thereof) The amount of wear of the turning blade 23 at the time is estimated.

The turning condition adjusting step S7 is a stress that acquires in advance the relationship between the adjustment amount of the feed amount V _s of the turning blade 23 at the time of turning (finish turning) and the reduction amount of the residual stress on the outer peripheral side of the material 11 at that time. Relationship between the reduction data acquisition step S71, the evaluation value of the residual stress obtained in the residual stress evaluation step S6, and the adjustment amount of the feed amount V _s obtained in the stress reduction data acquisition step S71 and the reduction amount of the residual stress at that time based on, and a adjustment amount setting step S72 of setting the adjustment amount of feed amount V _s.

Among these, in the stress reduction data acquisition step S71, for example, a plurality of pieces of data related to the reduction amount from the predetermined value of the feed amount V _s of the turning blade 23 and the reduction amount of the residual stress at that time are acquired. This data acquisition operation may be acquired for each different wear amount, for example.

Further, in the adjustment amount setting step S72, the residual stress generated on the outer peripheral side of the material to be subjected to the next turning (finish turning) according to the magnitude of the evaluation value of the residual stress obtained in the residual stress evaluation step S6 is described above. The adjustment amount of the feed amount V _s is set based on the relational data between the adjustment amount of the feed amount V _s obtained in the stress reduction data acquisition step S71 and the reduction amount of the residual stress at that time so as to be smaller than the evaluation value. .

  Hereinafter, an example of the method for manufacturing the internal gear according to the present embodiment will be described focusing on the adjustment of the turning process conditions.

  First, as shown in FIGS. 1 and 4, turning (finish turning) is performed on the outer periphery of the material 11 obtained by rough blanking to form the outer peripheral surface 14 into a cylindrical surface (finish turning process). S2). Then, gear cutting is performed on the inner periphery of the material 11 that has been turned to form the tooth surface 5 shown in FIG. 3 (gear cutting step S3), and then heat treatment such as carburization and gas nitriding is performed (heat treatment step). S4). By subjecting the material 11 that has been subjected to the predetermined heat treatment in this way to a grinding finish, the outer surface of the material 11 including the outer peripheral surface 14 is finished to a predetermined surface roughness and dimensions (grind finishing step S5). Thereby, the internal gear 1 shown in FIG. 3 is completed.

  Further, the residual stress generated on the outer peripheral side of the turned material 11 is evaluated every predetermined number of times after the production of the internal gear is started in the above procedure (residual stress evaluation step S6). In other words, the residual stress generated on the outer peripheral side of the turned material 11 is evaluated every predetermined number of times after the turning (finish turning) is started using the unused turning blade 23. Here, the outer diameter of the cylindrical portion corresponding region 12 of the material 11 that has been specifically turned is measured (outer diameter measuring step S62), and the wear amount of the turning blade 23 at that time is estimated from the measured value. To do. Then, the residual stress corresponding to the estimated wear amount is calculated by comparing the estimated wear amount with the correlation data between the wear amount and the residual stress previously stored in the computer or the like in the correlation acquisition step S61. (Residual stress calculation step S64).

When the residual stress on the outer peripheral side of the material 11 can be evaluated from the measured outer diameter in this way, the conditions during turning (finish turning) are adjusted (turning condition adjusting step S7). Here, as shown in FIG. 6, in order to match the outer diameter dimension of the material 11 after turning to the initial set value, the amount of cutting of the turning blade 23 by the amount of wear W ₁ obtained in the wear amount estimation step S63. correction in the direction of increasing the C _d. In addition, according to the magnitude of the residual stress evaluation value obtained in the residual stress evaluation step S6, stress reduction data acquisition is performed so that the residual stress generated on the outer peripheral side of the material to be turned next is smaller than the above evaluation value. Based on the related data of the adjustment amount of the feed amount V _s obtained in step S71 and the reduction amount of the residual stress at that time, the adjustment amount of the feed amount V _s is set (adjustment amount setting step S72). At this time, for example, as shown in FIG. 5, depending on whether or not the residual stress evaluation value obtained in the residual stress evaluation step S 6 exceeds a preset management value (threshold value) σ _t , turning conditions ( Here, it is determined whether or not adjustment of the feed amount V _s ) is necessary. Here, the management value σ _t is a difference between the residual stress generated on the outer peripheral side of the material 11 by turning and the residual stress generated on the tooth surface 5 formation side (inner peripheral side) of the material 11 by gear cutting. Is set as an upper limit value that satisfies the dimensional tolerance (shape tolerance) of the product when it appears as strain after the heat treatment. Therefore, for example, when the evaluation value of the residual stress is smaller than the control value σ _t , turning conditions other than the cutting depth C _d are maintained (not changed). In FIG. 6 and FIG. 7, this is the case with the wear amount W ₁ .

On the other hand, when the evaluation value of the residual stress is larger than the control value σ _t , the adjustment amount of the feed amount V _s obtained in the stress reduction data acquisition step S71 and the reduction amount of the residual stress at that time Based on the related data, the feed amount V _s is reduced so that the residual stress generated on the outer peripheral side of the material 11 to be subsequently turned (finished turning) is equal to or less than a predetermined value. For example, the amount of decrease in the feed amount V _s is set so that the residual stress on the outer peripheral side of the material 11 changes from the compression side to the tension side (see FIG. 5). In FIG. 6 and FIG. 7, this corresponds to the case of wear amounts W ₂ and W ₃ . Thereby, the residual stress which arises on the outer peripheral side of the raw material 11 which performed the turning process next can be made small, and the distortion which arises after heat processing process S4 can be restrained to an acceptable level. Therefore, even when the thinning of the cylindrical portion 2 having the tooth surface 5 is promoted, the outer diameter of the material 11 is periodically measured and the turning conditions are adjusted appropriately. Can adjust the cutting amount C _d and the feed amount V _s to produce the internal gear 1 including the tooth surface 5 and excellent in dimensional accuracy and shape accuracy.

In the above embodiment, the case where the feed amount V _s of the turning blade 23 is used as an adjustment parameter in the turning condition adjusting step S7 has been described. Of course, other parameters such as the rotational speed V _t and the number of cuttings are adjusted. It can also be a parameter. Alternatively, the two or more parameters (for example, the feed amount V _s and the rotation speed V _t ) can be used as adjustment parameters. In this case, in the stress reduction data acquisition step S71, it is necessary to acquire related data between the adjustment amount (increase / decrease amount) of the adjustment parameter and the residual stress reduction amount at that time.

  Moreover, although the said embodiment measured the outer diameter of the raw material 11 which performed the turning process, and demonstrated the case where the amount of wear of the turning blade 23 was estimated from the measured value, the measurement of an outer diameter was abbreviate | omitted and turned. The amount of wear of the blade 23 may be measured. In this case, the residual stress evaluation step S6 includes a correlation acquisition step S61 between the wear amount and the residual stress, a wear amount measurement step, and a residual stress calculation step S64.

  In the above description, gear cutting processing such as gear shaper processing and broaching processing is illustrated as a processing means for forming the tooth surface 5 on the inner periphery of the material 11, but of course plastic processing such as rolling is adopted. Even in this case, it is possible to apply the present invention.

  In the above description, the internal gear 1 has been described by taking as an example a cylindrical portion 2 having a bottom portion and a boss portion 3. However, the present invention is not limited to an annular portion such as a planetary gear. It is possible to apply to internal gears that form

DESCRIPTION OF SYMBOLS 1 Internal gear 2 Cylindrical part 3 Boss part 4 Outer peripheral surface 5 Tooth surface 11 Material 12 Cylindrical part corresponding | compatible area 13 Boss part corresponding | compatible area | region 14 Outer peripheral surface 21 Chuck 22 Rotation drive part 23 Turning blade C _d Cutting amount V _s Feed amount V _t Rotational speed σ _t Management value (threshold)

Claims (3)

A method of manufacturing an internal gear in which an outer peripheral surface is formed by turning the outer periphery of the material, and a tooth surface is formed on the inner periphery of the material,
A residual stress evaluation step for evaluating the residual stress generated on the outer peripheral side of the material subjected to the turning,
Turning conditions are adjusted so that the residual stress generated on the outer periphery of the material to be turned next is smaller than the evaluation value according to the evaluation value of the residual stress obtained in the residual stress evaluation step. And a turning condition adjusting step for manufacturing the internal gear. The residual stress evaluation step includes
A correlation obtaining step for obtaining in advance a correlation between the amount of wear of the turning blade used for the turning and the residual stress;
An outer diameter measuring step of measuring the outer diameter of the material subjected to the turning process;
A wear amount estimation step for estimating the wear amount of the turning blade from the outer diameter measurement value obtained in the outer diameter measurement step,
The method of manufacturing an internal gear according to claim 1, wherein the residual stress on the outer peripheral side is evaluated based on the wear amount obtained in the wear amount estimation step and the correlation between the wear amount and the residual stress. The turning condition adjusting step includes
A step of acquiring in advance a relationship between a feed amount or a rotation speed adjustment amount during the turning and a reduction amount of the residual stress at that time;
Based on the evaluation value of the residual stress obtained in the residual stress evaluation step and the relationship between the feed amount or the adjustment amount of the rotational speed and the reduction amount of the residual stress at that time, the feed amount during the turning process or The manufacturing method of the internal gear of Claim 1 or 2 which adjusts a rotational speed.

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