JP2013068241A - Gear and method of manufacturing gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of manufacturing a gear to be carburized.SOLUTION: A planetary gear 36 used in a speed increaser for wind power generation is carburized. A plurality of grooves 104 shallower than a carburizing layer 102 are formed on tooth surfaces 100a of teeth 100 at equal intervals. The plurality of grooves 104 are formed along the direction of an axis of rotation R. A total area of the plurality of grooves 104 occupying the tooth surfaces 100a is smaller than those of other portions. No groove 104 is formed on a surface between a tooth and a tooth including tooth bottom surfaces 100c.

Description

  The present invention relates to a gear and a manufacturing method thereof.

  The gas carburizing treatment is a treatment for improving wear resistance, fatigue strength, etc. by increasing the amount of carbon in the surface layer of low carbon steel or low carbon alloy steel in a carburizing gas atmosphere and quenching and hardening. In addition to the gas carburizing process, the carburizing process includes a solid carburizing process, a liquid carburizing process, a vacuum carburizing process, and a plasma carburizing process. The greater the carburization depth, the harder the surface.

  In recent years, wind power generators are no longer unusual, and their miniaturization and weight reduction are one of the developmental directions (see, for example, Patent Document 1). If the mechanical part of a wind power generator is reduced in size, the gear used there will also be reduced in size. In order to reduce the size of the gear, the surface of the gear needs to be harder to withstand the load. Therefore, carburized gears, particularly gears with a greater carburization depth, are preferred.

JP 2009-144533 A

により求められる。ここでＤは浸炭深さであり、Ｋは温度定数であり、ｔは処理時間である。したがって求める浸炭深さが大きくなるほど処理時間はその２乗で増加していく。浸炭処理の処理時間が長くなると製造効率が悪化する可能性がある。 Carburizing depth is Harris's empirical formula

Is required. Here, D is a carburizing depth, K is a temperature constant, and t is a processing time. Therefore, as the carburization depth to be obtained increases, the processing time increases by the square thereof. If the processing time of the carburizing process is increased, the production efficiency may be deteriorated.

  The above-mentioned problems can occur not only for gears used in wind power generators but also for gears that are carburized in general.

  This invention is made | formed in view of such a condition, The objective is to provide the technique which can improve the manufacture efficiency of the gear carburized.

  One embodiment of the present invention relates to a gear. This gear is a carburized gear and is provided with a plurality of concave portions shallower than the carburized layer on the tooth surface.

  According to this aspect, the carburized layer can be formed efficiently.

  Another aspect of the present invention is a gear manufacturing method. This method includes a step of forming a plurality of recesses on the tooth surface of the gear, and a step of carburizing the gear having the plurality of recesses formed thereon.

  It should be noted 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 apparatuses, methods, systems, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to improve the manufacturing efficiency of a gear to be carburized.

It is sectional drawing of the step-up gear for wind power generation in which the gear concerning an embodiment was built. 2A and 2B are explanatory views for explaining the planetary gear of FIG. FIGS. 3A to 3C are schematic views showing gear teeth according to a first modification. FIGS. 4A to 4C are perspective views showing gears according to second to fourth modified examples, respectively.

  Hereinafter, the same or equivalent components and members shown in the respective drawings are denoted by the same reference numerals, and repeated descriptions thereof are omitted as appropriate. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. Also, in the drawings, some of the members that are not important for describing the embodiment are omitted.

  FIG. 1 is a cross-sectional view of a speed increasing device 20 for wind power generation in which a gear according to an embodiment is incorporated. The speed increaser 20 includes a planetary gear mechanism 22 in the first stage and parallel shaft gear mechanisms 24 and 26 in the middle stage and the rear stage. The rotation input from the input shaft 28 is accelerated by a total of three stages of gear mechanisms 22, 24, 26 and output from the output shaft 30. A generator (not shown) is connected to the output shaft 30.

  The planetary gear mechanism 22 includes a carrier 32 integrated with the input shaft 28, a planetary pin 34 fixed to the carrier 32, a planetary gear 36 according to the embodiment, an internal gear 38, and a sun gear 40. The planetary gear 36 is rotatably supported by the planetary pin 34. The internal gear 38 and the sun gear 40 mesh with the planetary gear 36 at the same time. The planetary gear 36, the internal gear 38, and the sun gear 40 are all made of a material that can be carburized, such as low carbon steel or low carbon alloy steel. The planetary gear 36, the internal gear 38, and the sun gear 40 are all carburized, and a plurality of recesses shallower than the carburized layer are provided on any tooth surface. In the planetary gear mechanism 22, the sun gear 40 is integrated with the output shaft 42 of the planetary gear mechanism 22, and the internal gear 38 is integrated with the casing 44. A roller bearing 46 is interposed between the planetary pin 34 and the planetary gear 36 so that it is possible to cope with a case where the input torque is large.

  FIGS. 2A and 2B are explanatory views for explaining the planetary gear 36. FIG. 2A is a perspective view of the planetary gear 36. FIG. 2B is a cross-sectional view of a part of the tooth surface 100 a of the tooth 100 of the planetary gear 36 taken along a plane perpendicular to the rotation axis R of the planetary gear 36. A carburized layer 102 is formed on the surface of the planetary gear 36 by carburizing. The thickness of the carburized layer 102 is a carburized depth D.

The tooth surface 100 a is provided with a plurality of recesses shallower than the carburized layer 102, that is, a plurality of grooves 104 formed along the rotation axis R direction. The grooves 104 are provided uniformly over the tooth surface 100a, that is, at equal intervals. The cross section of the groove 104 has a substantially U shape. The width w of the groove 104 is desirably uniform between the surface and the bottom. The width w of the groove 104 is smaller than the depth d of the groove 104. The depth d of the groove 104 is smaller than the carburization depth D. That is, the groove 104 is shallower than the carburized layer 102. A similar groove 104 is provided in the tooth tip surface 100b of the tooth 100. There is no groove 104 in the surface between the teeth. The surface between the teeth may be a surface along the root circle or the bottom surface 100c.
In FIG. 2A and the following perspective views, representative ones of the plurality of recesses are shown, and not all of the recesses are shown.

The area (area in plan view) of the groove 104 occupying the tooth surface 100a is smaller than the area of the other part (the part where the groove 104 of the tooth surface 100a is not formed). In particular, since the grooves 104 are provided at equal intervals, the width w of the grooves 104 is smaller than half the pitch P of the grooves 104. Thereby, the fall of the surface pressure intensity | strength of the tooth surface 100a can be suppressed.
Other gears incorporated in the internal gear 38, the sun gear 40, and the speed increaser 20 may be configured in the same manner as the planetary gear 36.

A method for manufacturing a gear according to the embodiment will be described.
In this manufacturing method, first, a low carbon steel material is formed into a predetermined initial gear shape by cutting. The initial gear shape may be set to be slightly larger than the target gear shape that the manufactured gear should have. A plurality of grooves are formed by cutting on the tooth surface of the gear thus formed. A gear having a plurality of grooves formed on the tooth surface is gas carburized. Usually, since the shape of the gear changes when carburizing is performed, the gear is cut so that the tooth surface of the carburized gear has a desired shape. Alternatively, when the initial gear shape is set to be larger than the target gear shape, cutting is performed regardless of the degree of change in the shape due to the carburizing process. In this way, a gear having the target gear shape is manufactured.

In the carburizing process, carburization proceeds from the side surfaces and the bottom surfaces of the plurality of grooves, so that the carburized layer of the gear manufactured in this way becomes deeper than the grooves.
The gear may be cut so that a plurality of grooves are not formed on the tooth surface of the carburized gear. In this case, the reduction in the surface pressure strength of the tooth surface due to the grooves is eliminated.

According to the gear manufacturing method according to the embodiment, since a plurality of grooves are provided on the tooth surface of the gear to be carburized, carburization proceeds from the side and bottom surfaces of the grooves in the carburizing process. Therefore, the carburizing process can be made more efficient. That is, a larger carburization depth can be obtained in the same processing time than when no groove is provided. Alternatively, the same carburization depth can be obtained in a shorter processing time than when no groove is provided. As a result, the gear manufacturing efficiency can be improved.
Further, it is considered that the effect of shortening the time is higher when the depth is longer than the width of the groove.

  In order to shorten the processing time of the carburizing process, it is conceivable to increase the processing temperature or increase the cooling efficiency. However, it is often difficult to make a significant change in such a manufacturing method due to limitations in the performance of the furnace and the cost required to modify the equipment. In contrast, in the gear manufacturing method according to the embodiment, only the material is processed, and it is not necessary to modify the carburizing apparatus. Therefore, the processing time can be shortened at a lower cost.

  Moreover, the effective surface area with respect to lubricating oil can be increased by providing a several recessed part in the surface of a gearwheel. Thereby, the surface of the gear can easily hold the lubricating oil, and the possibility of the oil film being cut can be reduced.

  The cost of the carburizing process is mainly determined by the furnace usage time. Therefore, if the carburizing time can be shortened, the cost reduction effect is expected. Although the actual processing time depends to some extent on various conditions such as processing temperature, carburizing gas concentration, and gear size, a simple calculation calculated from the Harris equation will be described below. Comparing the case where the target carburization depth is 1 mm and the case where it is 2 mm, the latter processing time is four times the processing time of the former. Here, if a groove having a depth of about 1 mm is formed on the surface of the gear, and the gear having such a groove is carburized, the processing time required to achieve the target carburizing depth of 1 mm when there is no groove. A carburization depth of 2 mm can be achieved. That is, the processing time can be reduced to about 1/4.

  Since the tooth surface of the gear is a part in contact with another gear, it is necessary to deepen the carburization there to increase the surface pressure strength. On the other hand, since the surface between the teeth (the root) does not normally contact other gears, the surface pressure strength as much as the tooth surface is not required. Therefore, if the groove 104 is not provided on the surface between the teeth as in the planetary gear 36 according to the embodiment, the carburization is relatively shallow at the portion where the improvement of the surface pressure strength is unnecessary, and the deformation due to the carburization is performed. And increase in brittleness can be suppressed.

More generally, the depth of carburization, that is, the surface pressure strength, can be adjusted by adjusting the number of concave portions provided on the surface of the gear per unit area.
FIGS. 3A to 3C are schematic views showing gear teeth 110 according to a first modification. FIG. 3A is a side view of the tooth 110. FIG. 3B is a cross-sectional view of the tooth portion 110b of the tooth 110 cut along a plane perpendicular to the rotation axis, which is an engagement portion 110b to be engaged with another gear. FIG. 3C is a cross-sectional view of a tooth portion 110c of the tooth surface 110a that does not mesh with other gears, cut along a plane perpendicular to the rotation axis.

  The tooth surface 110a is provided with a plurality of grooves 112 along the rotation axis direction. The number of grooves 112 per unit area of the meshing portion 110b is larger than the number of grooves 112 per unit area of the other portion, for example, the root portion 110c. The pitch P1 of the groove 112 of the meshing portion 110b is smaller than the pitch P2 of the groove 112 of the toothed portion 110c. Since the grooves 112 of the meshing portion 110b are provided more densely, the thickness D1 of the carburized layer 114 is almost constant. Since the groove 112 of the tooth base portion 110c is provided more sparsely, the thickness of the carburized layer 116 varies depending on the position. The average thickness D2 of the carburized layer 116 of the tooth portion 110c is smaller than the thickness D1 of the carburized layer 114 of the meshing portion 110b.

According to the first modification, carburization is shallow in the tooth base portion 110c, which may not have a relatively high surface pressure strength, among the tooth surfaces 110a, so that deformation and increase in brittleness due to carburization there can be suppressed. . Further, in the meshing portion 110b that requires high surface pressure strength, carburization can be deepened to obtain sufficient hardness.
The groove 112 may not be provided in the tooth base portion 110c. Further, the tooth tip portion may be configured in the same manner as the tooth root portion 110c.

  Heretofore, the gear according to the embodiment and the manufacturing method thereof have been described. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements, and such modifications are also within the scope of the present invention.

  In the embodiment, the case where the groove 104 is not provided on the surface between the teeth has been described, but the present invention is not limited to this. For example, the number of recesses per unit area of the surface between teeth may be smaller than the number of recesses per unit area of the tooth surface. Even in this case, the carburization can be made relatively shallow at a portion where the improvement of the surface pressure strength is not required, and deformation due to carburization and an increase in brittleness can be suppressed.

  In the embodiment, the gear incorporated in the gearbox 20 for wind power generation has been described as an example. However, the present invention is not limited to this, and the technical idea according to the present embodiment can be applied to any gear.

In the embodiment, the case where the plurality of grooves 104 are formed along the rotation axis R direction on the tooth surface 100a of the tooth 100 of the planetary gear 36 has been described. However, the present invention is not limited to this. 4A to 4C are perspective views showing gears 120, 130, and 140 according to second to fourth modifications, respectively. The tooth surface of the gear 120 according to the second modification is provided with a plurality of grooves 122 along the circumferential direction of the gear 120, that is, so as to surround the rotation shaft. A plurality of grooves 132 are provided on the tooth surface of the gear 130 according to the third modification so as to be inclined with respect to the rotation axis of the gear 130. A plurality of holes 142 are provided in the tooth surface of the gear 140 according to the fourth modification. According to these modified examples, the carburizing process can be made more efficient as in the embodiment.
When the groove 104 is formed along the direction of the rotation axis R as in the planetary gear 36, it is easier to form the groove by cutting as compared with the second to fourth modifications, and the workability is good.

  In the embodiment, the case where a plurality of recesses having substantially the same size and shape are provided on the tooth surface has been described. However, the present invention is not limited to this, and the size and shape of the recesses may be different. For example, the number of recesses per unit area can be the same between the meshing portion of the tooth surface and the root portion, and the recess in the meshing portion can be made larger than the recess in the tooth base portion. In this case, the area of the concave portion at the meshing portion is larger than the area of the concave portion at the tooth base portion. Alternatively, the number of recesses per unit area in the meshing portion is smaller than the number of recesses per unit area in the tooth root portion, while the area of the recess in the meshing portion is smaller than the area of the recess in the tooth root portion. Can also be increased.

  36 planetary gear, 100 teeth, 100a tooth surface, 102 carburized layer, 104 grooves, R rotation axis.

Claims (9)

  A gear carburized, wherein a plurality of recesses shallower than the carburized layer are provided on a tooth surface.   The gear according to claim 1, wherein the plurality of recesses are a plurality of grooves formed along a rotation axis direction of the gear.   3. The gear according to claim 1, wherein an area of the plurality of recesses occupying a tooth surface is smaller than an area of other portions.   The gear according to any one of claims 1 to 3, wherein a concave portion is not provided on a surface between the teeth.   4. The number of recesses per unit area of the surface between teeth or the area of the recesses is smaller than the number of recesses per unit area of the tooth surface or the area of the recesses. The gear according to Crab.   The number of recesses per unit area or the area of the recesses of a portion of the tooth surface to be engaged with another gear is greater than the number of recesses or the area of the recesses per unit area of the other portion. The gear according to any one of 1 to 5. Forming a plurality of recesses in the tooth surface of the gear;
And a step of carburizing the gear in which the plurality of recesses are formed.   The manufacturing method according to claim 7, further comprising a step of cutting a tooth surface of the carburized gear.   The manufacturing method according to claim 8, wherein the cutting step is a step of cutting a tooth surface so that the plurality of concave portions are eliminated.

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