JP5655580B2 - Transmission case - Google Patents

Description

  The present invention relates to a transmission case provided with an internal gear.

  2. Description of the Related Art Conventionally, transmissions using a planetary gear mechanism as transmission means such as a reduction gear are widely known. The planetary gear mechanism is generally composed of a sun gear, a plurality of planetary gears, a carrier, an internal gear, and the like.

  For example, in the case of a reduction gear, each planetary gear is rotatably supported by a carrier connected to the output shaft, and is arranged around the sun gear so as to mesh with the sun gear. The internal gear is non-rotatably disposed around the planetary gear so as to mesh with the planetary gear. When the sun gear is driven to rotate, each planetary gear revolves around the sun gear. The carrier is decelerated and rotated with the revolution of the planetary gear, and the rotational power is output through the output shaft.

  Usually, the internal gear is fitted inside the transmission case, and is fixed to the transmission case, for example, by inserting pins into pin holes formed on both sides.

  In relation to the present invention, a gear manufacturing method (Patent Document 1) and an insert gear (Patent Document 2) are disclosed.

  Patent Document 1 discloses a method of manufacturing a gear whose main body is a resin molded product or a die cast product. Specifically, a belt-shaped steel plate is subjected to roller forming to form a spur-shaped tooth portion, and the tooth portion is rounded to form a tooth portion ring. A gear is integrally formed by injecting a molten synthetic resin or alloy into the inside of the tooth ring using a mold and solidifying it.

  Patent Document 2 discloses a gear that can prevent molten synthetic resin or the like from flowing into a tooth gap when the gear is die-cast. Specifically, the gear has a substantially cylindrical shape, and tooth grooves are formed on the outer peripheral surface. And the collar part which prevents the inflow of a molding material is integrally formed in the periphery of the one side surface of the gearwheel.

Japanese Patent Laid-Open No. 7-125088 Japanese Utility Model Publication No. 51-158961

  Since a large torque is applied to the internal gear in the planetary gear mechanism, in the case of a conventional transmission case in which the internal gear is pinned, there is a possibility that misalignment or rattling may be caused if the connection is insufficient. For this reason, both require high molding accuracy and assembly accuracy, which is an obstacle to improving productivity and production cost.

  Accordingly, an object of the present invention is to provide a transmission case in which an internal gear can be stably and firmly joined to the transmission case, and productivity and production cost can be improved.

  In order to achieve the above object, in the present invention, the shape of the internal gear is devised and the internal gear is insert-molded into the case member.

  Specifically, the transmission case of the present invention is a cylindrical member that is fixed to the inside of the case member in a state where the sun gear and the planetary gear are surrounded, and the sun gear and the rotation shaft are aligned. A transmission case including an internal gear.

  At one end of the internal gear, an annular inflow restricting portion that protrudes inward from the tip of the tooth is provided. The outer peripheral surface of the internal gear is provided with a non-slip portion in which one or more convex portions or concave portions are formed. The case member is die-cast, and the internal gear is insert-molded in the case member.

  According to the transmission case having such a configuration, the internal gear provided with an annular inflow restricting portion that projects inward from the tip of the tooth is insert-molded in the case member to be die-cast. If the inflow restricting portion is in contact with the core when the internal gear is attached to the mold core, the tooth portion (annular tooth) of the internal gear located in the cavity is connected to the core and the inflow restricting portion. It can be sealed with.

  Accordingly, it is possible to prevent a molding material such as a molten aluminum alloy from entering the annular tooth, and the quality of the annular tooth can be prevented from being impaired, and extra work such as removal of molten debris can be omitted.

  Since the internal gear is insert-molded into the case member, the internal gear can be joined more stably and firmly without securing high molding accuracy and assembly accuracy like conventional pinning. it can. Work such as pinning is also unnecessary, which is advantageous for productivity and production cost. In addition, since the outer peripheral surface of the internal gear is provided with a non-slip portion in which one or more convex portions or concave portions are formed, the joint area between the internal gear and the case member is increased, thereby further strengthening the joint. can do.

  It is preferable that the inflow restricting portion is formed of an annular member formed separately from the internal gear and is retrofitted to the internal gear.

  If it does so, since the part of an annular tooth can be formed by broaching, an internal gear can be mass-produced easily and it is excellent in productivity and production cost.

  Moreover, it is preferable that the said antiskid part is comprised with the linear uneven | corrugated structure substantially parallel to a rotating shaft.

  If it does so, since the big torque added to an internal gear at the time of use can be effectively received in a non-slip | skid part, the position shift and rattling of an internal gear can be prevented more stably.

  Further, when the case member has a square-shaped portion extending in the direction of the rotation axis and protruding in cross section outside the portion where the internal gear is fixed, a predetermined volume is obtained together with the casting hole. It is preferable to provide an anti-strain portion that occupies the same area.

  When the case member has such a square-shaped portion, the amount of the molding material is biased depending on the part, so that the cooling rate when the molding material solidifies varies and the case member is distorted. As a result, since a biased distortion force is applied to the internal gear, the roundness of the internal gear is reduced.

  On the other hand, by providing the cast hole, a certain degree of bias can be eliminated, but the length and shape of the cast hole are greatly limited by the sliding direction of the mold because of die cutting. Therefore, if there are only cast holes, the distribution of the molding material may be biased depending on the shape of the case member to be molded. Therefore, by providing a distortion preventing portion separately from the cast hole, a portion that cannot be compensated only by the cast hole can be supplemented. As a result, since the distribution of the aluminum alloy around the internal gear can be made uniform, it is possible to prevent the biased distortion force from being applied to the internal gear and to increase the roundness of the internal gear.

  For example, when the cast hole extends in the direction of the rotation axis, the distortion preventing portion may be provided behind the tip of the cast hole. By doing so, even if a thick portion exists on the tip side of the cast hole, the amount of the molding material of the thick portion can be adjusted by the distortion preventing portion, so that the uneven distribution of the molding material is suppressed. be able to.

  The distortion preventing portion can be provided integrally with the internal gear.

  If it does so, since the effect similar to a non-slip | skid part will be acquired also by a distortion prevention part, an internal gear can be more firmly joined to a case member more stably. Further, the internal gear can be structurally strengthened by the distortion preventing portion, and the roundness of the internal gear can be further increased.

  Compared to the conventional transmission case in which the internal gear is fixed by pinning or the like, the internal gear can be stably and firmly fixed to the transmission case. Since high molding accuracy and assembly accuracy are not required, productivity and production cost can be improved.

It is a schematic perspective view which shows the transmission of this embodiment. A portion of the transmission is cut away to show the interior. It is a schematic sectional drawing of the case member in the XX line in FIG. Only a part of the annular tooth portion is illustrated. It is the schematic of the case member seen from the arrow Y direction in FIG. It is a schematic perspective view which shows an internal gear member. Only a part of the annular tooth and the non-slip portion is shown. It is a schematic plan view of an internal gear member. It is the schematic which shows the formation process of a 1st case member. It is the schematic which shows the formation process of a 1st case member. It is the schematic which shows the measurement result of the roundness of the internal gear in a comparative example. It is the schematic which shows the measurement result of the roundness of the internal gear in an Example. It is a schematic perspective view which shows the modification of an internal gear member. Only a part of the annular tooth and the non-slip portion is shown. (A), (b) is a schematic front view which shows the modification of a transmission case. It is a schematic sectional drawing which shows the modification of a transmission case. It is a schematic sectional drawing which shows the modification of a transmission case.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following description is merely illustrative in nature and does not limit the present invention, its application, or its use.

  FIG. 1 shows a reduction gear (transmission) to which the present invention is applied. The reduction gear includes a case 1 (transmission case), an input unit 2, a planetary gear mechanism 3, an output shaft 4, and the like. In this speed reducer, the driving shaft of the motor and the like are connected to the input unit 2 so that a rotational driving force is input from the input unit 2 to the speed reducer. The rotational speed of the planetary gear mechanism 3 is reduced, and a rotational driving force with increased torque is output through the output shaft 4.

  The planetary gear mechanism 3 includes a sun gear 31, a plurality of planetary gears 32, an internal gear 33, a carrier 34, and the like. The sun gear 31 is rotatably supported by the case 1 and rotates around the rotation axis A by the rotational driving force input from the input unit 2. Each planetary gear 32 is arranged around the sun gear 31 so as to mesh therewith. Each planetary gear 32 is rotatably supported by a carrier 34. The carrier 34 is rotatably supported by the case 1 via a pair of bearings 35a and 35b. In the present embodiment, the output shaft 4 is provided integrally with the carrier 34.

  The internal gear 33 is a gear having teeth formed inside. The internal gear 33 is arranged around the sun gear 31 and the rotation axis A so as to mesh with each planetary gear 32 exposed from the window 34a formed on the side surface of the carrier 34. . The internal gear 33 is disposed inside the case 1 so as not to rotate. Accordingly, each planetary gear 32 rotates and revolves around the sun gear 31 as the sun gear 31 rotates, and the carrier 34 (output shaft 4) rotates around the rotation axis A at a predetermined reduction ratio. To do. Details of the internal gear 33 will be described later.

  The case 1 according to the present embodiment includes a first case member 10 (case member) and a second case member 20 that are integrated with each other. The input unit 2 is accommodated on the second case member 20 side, and the planetary gear mechanism 3 and the output shaft 4 including the internal gear 33 are accommodated on the first case member 10 side. The first case member 10 and the like are die-cast using a molding material such as an aluminum alloy.

  2 and 3 show details of the first case member 10. The first case member 10 includes a peripheral wall portion 11 whose outer side is formed in a quadrangular cross section, and an end wall portion 12 that closes one end of the peripheral wall portion 11. The periphery of the planetary gear mechanism 3 including the sun gear 31 and the planetary gear 32 is surrounded by the peripheral wall portion 11.

  A bearing holding portion 13 protruding in a cylindrical shape is formed at the center portion of the end wall portion 12. The bearing 35a described above is fitted and fixed inside the bearing holding portion 13. Then, the tip end portion of the output shaft 4 projects out of the case 1 through a shaft hole 14 opened in the center of the bearing holding portion 13.

  Bolt holes 15 for fastening to the second case member 20 penetrate through the corner portions (corner-shaped portions 11a) of the peripheral wall portion 11 in the direction of the rotation axis A (four locations). Further, a cast hole 16 is formed in each square-shaped portion 11a.

  The cast hole 16 of the present embodiment extends in the direction of the rotation axis A from the opening side (opposite side of the end wall portion 12), and the inner peripheral surface thereof is an arc-shaped surface 16a having a cross-sectional arc shape and an outer side from the arc-shaped surface 16a. And a W-shaped surface 16b which is formed in a W-shaped cross section while avoiding the bolt holes 15. The cast hole 16 of the present embodiment is formed in a tapered shape with a gradually decreasing cross section toward the tip (draft gradient). It should be noted that the draft angle is not essential for the casting hole 16, and the tip end side is not required to be larger than the base end side.

  Inside the peripheral wall portion 11, a large-diameter hole portion 17 that communicates with the bearing holding portion 13 and has a larger inner diameter than the bearing holding portion 13 is formed from the opening side toward the end wall portion 12. The depth of the large-diameter hole portion 17 is formed to be smaller than the length of the peripheral wall portion 11 (indicated by reference sign t in FIG. 2), and the peripheral wall portion 11 is connected to the end wall portion 12 in the peripheral wall portion 11. There is a thick portion 18 that is thicker than the other portions. An internal gear member 50 is integrally fixed to the back (bottom portion) of the large-diameter hole portion 17 by insert molding.

  FIG. 4 shows details of the internal gear member 50. The internal gear member 50 is a steel member, and includes a cylindrical gear portion 51, a distortion prevention portion 52 formed integrally with the gear portion 51, and a ring plate 53 (inflow restricting portion). Yes. The gear part 51 is a part constituting the internal gear 33. On the inner peripheral surface of the gear portion 51, a group of teeth meshing with each planetary gear 32 is formed in an annular shape by an broaching process (annular teeth 51a).

  The ring plate 53 is an annular member formed by cutting out from a metal plate, separately from the gear portion 51 and the distortion preventing portion 52, and is attached to the gear portion 51 and the like. The ring plate 53 is fixed to one end of the gear portion 51 on the distortion preventing portion 52 side by welding or the like, and is in close contact with one end of the annular tooth 51a. The ring plate 53 is set so that its inner peripheral edge protrudes inward from the tip of each tooth.

  A non-slip part 54 is formed on the outer peripheral surface of the gear part 51 over the entire circumference. The anti-slip portion 54 of the present embodiment is configured by a plurality of linear concavo-convex shapes extending substantially parallel to the rotation axis A. The cross section of the non-slip portion 54 is formed in a sharp polygonal line shape.

  By providing such a non-slip portion 54 on the outer peripheral surface of the gear portion 51, when the internal gear member 50 is insert-molded into the first case member 10, the joint area between the two increases, so that the two are joined more firmly. be able to. In addition, since the non-slip portion 54 is configured by a plurality of linear concavo-convex shapes extending substantially parallel to the rotation axis A, a large torque applied to the annular tooth 51a can be effectively received, so that the position of the gear portion 51 Misalignment and rattling can be prevented.

  The distortion prevention part 52 has a cylindrical extension part 52a that extends continuously to one end of the gear part 51, and a flange part 52b that protrudes radially outward from the tip of the extension part 52a over the entire circumference. . As shown in FIG. 5, the flange portion 52 b is formed substantially parallel to the peripheral wall portion 11 at a portion facing the side portion (side portion) of the peripheral wall portion 11, and is opposed to each angular shape portion 11 a of the peripheral wall portion 11. The part is formed in an arc shape. The square-shaped part 11a side protrudes more greatly than the side part side.

  The internal gear member 50 is insert-molded in the first case member 10 with the ring plate 53 side facing the end wall portion 12, and the distortion preventing portion 52 is embedded in the thick portion 18. As shown in FIGS. 2 and 5, particularly in the rectangular portion 11 a, the flange portion 52 b enters the back (lower side) of the tip of the cast hole 16 and occupies a predetermined volume. Specifically, adjustment is performed between the flange portion 52b and the cast hole 16 so that the volume occupied by the aluminum alloy portion is as equal as possible between the side portion and the rectangular portion 11a in the peripheral portion of the internal gear member 50. ing.

  Because of the die-cutting relationship, it is not easy to secure a sufficient volume with the thick-walled portion 18 with only the die-casting hole 16, although it depends on the die because the tip end side of the die-casting hole 16 cannot be enlarged. . In particular, it is difficult to use a simple mold composed of a pair of molds that slide relative to each other only in one direction. In view of this, the distortion prevention portion 52 is provided separately from the cast hole 16, so that the lack of volume is supplemented by the distortion prevention portion 52. Thus, by making the distribution of the aluminum alloy around the internal gear member 50 uniform, distortion of the gear portion 51 can be effectively suppressed.

  Next, a general molding process of the first case member 10 will be described with reference to FIGS. As illustrated in FIG. 6, the first case member 10 is formed by die casting using a pair of molds including a fixed mold 61 (female mold) and a movable mold 62 (male mold), for example. At that time, the internal gear member 50 is inserted into a cavity of the mold and formed integrally (insert molding).

  The fixed die 61 is provided with a first hole 61a that forms the outer surface side of the peripheral wall portion 11, a second hole portion 61b that forms the outer surface side of the bearing holding portion 13, and the like. The fixed mold 61 is fixed, and the movable mold 62 slides and displaces in the direction of the center line S of the mold with respect to the fixed mold 61. The center line S of the mold coincides with the rotation axis A.

  The movable die 62 is provided with a center core 62a, a columnar core 62b that forms the inner surface side of the bolt hole 15, a cast core 62c that forms the inner surface side of the cast hole 16, and the like. The base portion of the center core 62 a is formed so that the outer shape is slightly smaller than the inner diameter of the gear portion 51 so that the gear portion 51 can be mounted. At the upper end of the base portion of the center core 62 a, a contact portion 63 formed with an outer diameter substantially the same as the inner diameter of the ring plate 53 is provided so as to contact the ring plate 53. Furthermore, a portion for forming the shaft hole 14 and the inner surface side of the bearing holding portion 13 is also provided on the distal end side of the center core 62a.

  The internal gear member 50 is attached to the base of the center core 62 a of the movable die 62 with the ring plate 53 side facing the bottom of the fixed die 61. By doing so, the portion of the annular tooth 51 a of the gear portion 51 is closed by the ring plate 53 and the movable mold 62. As shown by the arrows, the movable mold 62 is inserted into the fixed mold 61, and both are integrally joined as shown in FIG. As a result, a cavity having a predetermined shape is formed inside the mold.

  Then, a hot aluminum alloy melted from an injection port (not shown) provided in the fixed mold 61 is press-fitted and injected into the cavity. At this time, since the portion of the annular tooth 51a is blocked by the ring plate 53 or the like, the aluminum alloy can be prevented from entering the portion of the annular tooth 51a.

  After sufficient aluminum alloy is injected into the cavity, a cooling process by natural cooling is performed in order to solidify the aluminum alloy. At this time, since the volume of the cavity in the peripheral portion of the internal gear member 50 is adjusted by the cast core 62c and the distortion preventing portion 52 so as to be substantially uniform, the side portion and the square-shaped portion 11a, The cooling rate of the aluminum alloy around the internal gear member 50 in a portion having a different total volume such as the thick portion 18 is substantially the same. As a result, since the distortion of the aluminum alloy is reduced and the bias of the distortion force applied to the internal gear member 50 is reduced, the roundness of the gear portion 51 (annular teeth 51a) can be improved.

(Example)
In order to confirm the effect of the distortion preventing portion, a case member using an internal gear member without a distortion preventing portion (comparative example), and a case member using an internal gear member having a distortion preventing portion (example) The roundness of both annular teeth was compared.

  The case member and the internal gear member used for comparison have the same shape and the same molding method as the first case member 10 and the internal gear member 50 of the above-described embodiment except for the presence or absence of the distortion prevention portion. The roundness measurement is performed under the same conditions for the Example product and the Comparative Example product at predetermined three locations in the upper part (opening side), the central part, and the lower part (end wall part side) in the rotation axis direction The pitch circle diameter (PCD) of the annular teeth was measured over the entire circumference.

  In FIG. 8, the measurement result of PCD of a comparative example is shown. In the figure, the curve indicated by the symbol S represents the PCD distribution before insert molding (unprocessed). Moreover, the virtual line of the code | symbol 10 represents the outline of the case member corresponding to the measurement site | part of PCD. As shown in the figure, after molding, the PCD was smaller than that before the treatment, and the distribution of the PCD was larger toward the bottom side. In particular, it was recognized that the PCD tends to be smaller on the side side than on the corner side.

  In FIG. 9, the measurement result of PCD of an Example is shown. In the figure, the curve with the symbol S is an unprocessed PCD distribution, which is almost the same value as in the comparative example. In the case of the example, the difference in PCD before and after molding was smaller than that in the comparative example. Moreover, the dispersion | variation in PCD for every site | part after shaping | molding was also small, and the big improvement of roundness was recognized compared with the comparative example.

(Other)
The transmission case according to the present invention is not limited to the above-described embodiment, and includes various other configurations.

  For example, when the case member has a circular cross section and there is no significant difference in the volume occupied by the aluminum alloy around the gear portion 51 (internal gear 33), as shown in FIG. The distortion prevention unit 52 may not be provided.

  The cross-sectional shape of the case member is not limited to a quadrangle. For example, as shown to (a) of FIG. 11, the cross-sectional shape of the 1st case member 10 (peripheral wall part 11) may be a pentagon etc., and as shown to (b) of the figure, it is partially. The cross section may be circular, and a square portion may be provided in part. Although not shown, the rotation axis A may be arranged so as to be biased with respect to the case member.

  Moreover, although the case where the 1st case member 10 was integrally shape | molded by the surrounding wall part 11 and the end wall part 12 which block | closes the end was shown in embodiment mentioned above, the member and end wall part equivalent to the surrounding wall part 11 were shown. 12 may be formed separately, and the first case member 10 may be configured by combining them (see FIG. 12). In this case, the case member is cylindrical.

  In the above-described embodiment, the case where the movable mold is configured by one part has been described, but the movable mold may be configured by a plurality of parts. In that case, since the cast core is provided corresponding to the sliding direction of each part, the extending direction of the cast hole 16 is not limited to the direction of the center line S. For example, the cast hole 16 may extend in a direction orthogonal to the center line S or in a direction inclined with respect to the center line S.

  If it does so, the casting hole 16 can also be formed so that it may become depressed from the side of the surrounding wall part 11, as shown in FIG.12 and FIG.13.

  The non-slip surface can also be composed of a plurality of point-like protrusions or one or more linear protrusions. The shape of the cast hole and the distortion preventing portion can be appropriately formed according to the shape of the case member. Similarly to the ring plate, the distortion preventing portion may be retrofitted to the internal gear.

1 Case (Transmission case)
2 Input unit 3 Planetary gear mechanism 4 Output shaft 10 First case member (case member)
DESCRIPTION OF SYMBOLS 11 Peripheral wall part 11a Square shape part 12 End wall part 16 Cast hole 18 Thick part 31 Sun gear 32 Planetary gear 33 Internal gear 34 Carrier 50 Internal gear member 51 Gear part 51a Annular tooth 52 Distortion prevention part 53 Ring plate ( Inflow control department)
54 Non-slip part A Rotating shaft

Claims (5)

A case member surrounding the sun gear and the planetary gear;
A cylindrical internal gear fixed to the inside of the case member in a state in which the sun gear and the rotation axis coincide with each other;
A transmission case including
At one end of the internal gear, an annular inflow restricting portion that is configured separately from the internal gear and projects inward from the tip of the tooth is provided as a retrofit ,
The outer peripheral surface of the internal gear is provided with a non-slip portion in which one or more convex portions or concave portions are formed,
A transmission case in which the case member is die-cast and the internal gear and the inflow restricting portion are insert-molded in the case member. The transmission case according to claim 1 ,
The said non-slip | skid part is a transmission case comprised by the linear uneven | corrugated structure substantially parallel to a rotating shaft. In the transmission case according to claim 1 or 2 ,
The case member has an angular shape part extending in the direction of the rotation axis and protruding in cross section on the outside of the portion where the internal gear is fixed
A transmission case in which the square-shaped portion is provided with a cast hole and a distortion preventing portion that occupies a predetermined volume. The transmission case according to claim 3 ,
The casting hole extends in the rotation axis direction,
A transmission case in which the distortion preventing portion is provided behind the tip of the cast hole. In the transmission case according to claim 3 or 4 ,
A transmission case in which the distortion preventing portion is provided integrally with the internal gear.

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