JP2018091449A - Differential structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the loosening of bolts while suppressing an increase of the number of part items, in a differential structure for fastening a differential case and a ring gear with the bolts.SOLUTION: A differential structure fastens a differential case 2 which has annular fastening faces 5a, 6a, and in which a plurality of annular bolt holes 5b, 6b extending in parallel with an axial direction are formed at the fastening faces 5a, 6a, respectively, and a ring gear 3 with bolts 8 which are inserted into the bolt holes 5b, 6b with the fastening faces 5a, 6a as mating faces. The fastening face 5a of the differential case 2 and the fastening face 6a of the ring gear 3 are tapered faces which are inclined to one side in the axial direction with respect to axial orthogonal directions of the bolts 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a differential structure in which a differential case and a ring gear are fastened with bolts.

  A differential that forms part of a power transmission mechanism in a vehicle includes a ring gear that meshes with a gear that outputs torque transmitted from a drive source via a transmission, a final reduction gear, and the like, and torque that is input via the ring gear. And a differential case in which a differential gear mechanism for transmitting the power to the drive wheels is accommodated.

  By the way, the cast iron used for the differential case has lower fatigue strength than carbon steel used for the ring gear. Therefore, when the differential case and the ring gear are integrally cast, if a special material is not used, The required strength properties are not satisfied. For this reason, the differential case and the ring gear are often bolted or welded.

  And, as a fastening structure between the differential case and the ring gear using bolts, a plurality of annular flat fastening surfaces respectively provided on the differential case and the ring gear are used as a mating surface, and a plurality of these are formed orthogonally to these fastening surfaces. A differential structure has been conventionally known in which both are fastened by bolts inserted through the holes.

  However, in such a structure, only the force that presses the differential case and the ring gear in the axial direction is generated by the fastening force of the bolt, so depending on the number of bolts, when the torque from the drive source is transmitted to the drive wheel, The ring gear may be slightly displaced relative to each other, and a large external force may be applied in the direction perpendicular to the bolt axis. If a large external force is repeatedly applied to the bolt and the bolt is displaced, the screw portion may slip and the bolt may be loosened.

  Therefore, for example, as disclosed in Patent Document 1, an inverted conical hole is formed in a member on the side where the bolt head abuts, and the bolt is inserted with an inverted conical bush provided with a slit therein. It is conceivable to employ a loosening-fastening structure for fastening, and bolt the differential case and the ring gear.

JP-A-2005-090530

  However, when the loosening fastening structure of Patent Document 1 is adopted, an additional part (bush) is required for each of the plurality of bolts, which increases the number of parts. Further, if the number of bolts is increased, the differential case and the ring gear are firmly fastened, so that it is possible to suppress loosening of the bolts. However, in this case as well, there is a problem that the number of parts increases.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a technique for suppressing loosening of a bolt while suppressing an increase in the number of parts in a differential structure in which a differential case and a ring gear are fastened by bolts. It is to provide.

  In order to achieve the above object, in the differential structure according to the present invention, by inclining the fastening surface, a force that cannot be generated by the flat fastening surface is applied to the differential case and the ring gear, thereby increasing the fastening force of both. ing.

  Specifically, the present invention includes a differential case and a ring gear, each having an annular fastening surface, each of which has a plurality of bolt holes extending in parallel to the axial direction of the annular ring. A differential structure in which a fastening surface is used as a mating surface and fastened with a bolt inserted into these bolt holes is intended.

  The differential structure is characterized in that the fastening surface of the differential case and the fastening surface of the ring gear are tapered surfaces inclined with respect to the direction perpendicular to the axis of the bolt.

  In the present invention, the “tapered surface” means an annular fastening surface that extends toward one side (or the other side) in the axial direction of the ring as it goes radially outward. It means that it is inclined like a truncated cone-shaped inclined surface.

  According to this configuration, since the fastening surface of the differential case and the fastening surface of the ring gear are both inclined tapered surfaces, the fastening surface of the differential case and the fastening surface of the ring gear are pivoted when the differential case and the ring gear are tightened with bolts. In addition to the pressing force in the direction, the wedge effect generates a force for shifting the fastening surface of the differential case and the fastening surface of the ring gear in the radial direction.

  More specifically, when the bolt is tightened, a force perpendicular to the mating surface and a force horizontal to the mating surface are generated on the mating surface between the differential case and the ring gear due to the wedge effect. Thus, the axial component of these forces acts as a force pressing the fastening surface of the differential case and the fastening surface of the ring gear in the axial direction.

  Further, the radial component of these forces acts on the differential case side as a force that tends to shrink the portion where the fastening surface is formed radially inward (or a force that tends to expand radially outward), while the ring gear On the side, it acts as a force (or a force trying to shrink the inner side in the radial direction) to expand the portion where the fastening surface is formed radially outward. Here, on the differential case side, for example, a force that is elastic and tries to return to the original (a force that spreads outward in the radial direction) is generated with respect to a force that is to be contracted radially inward. In contrast to the force that tries to spread outward in the direction, a force that tries to return to the original state by elasticity (force that tries to shrink radially inward) is generated. Since the force to return to the original acts as a force to press the fastening surface of the ring gear radially outward on the differential case side, it acts as a force to press the fastening surface of the differential case radially inward on the ring gear side. The differential case and the ring gear are firmly fastened.

  In addition, since the fastening surface of the differential case and the fastening surface of the ring gear are tapered surfaces, the differential case and the ring gear are compared to the case where these fastening surfaces are flat (parallel to the direction perpendicular to the axis of the bolt). Can be increased, and the frictional force between the differential case and the ring gear can be increased.

  As described above, in the present invention, the differential case and the ring gear are firmly fastened together with the force that presses each other in the axial direction and the radial direction, and the increase in the frictional force, so that torque is transmitted. The relative displacement between the differential case and the ring gear can be suppressed, and a large external force can be suppressed from being applied to the bolt. Therefore, it is possible to suppress the displacement of the bolt that fastens the differential case and the ring gear, thereby suppressing the loosening of the bolt without increasing the number of parts.

  As described above, according to the differential structure of the present invention, it is possible to suppress loosening of the bolt that fastens the differential case and the ring gear while suppressing an increase in the number of parts.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the principal part of the differential which concerns on Embodiment 1 of this invention, The figure (a) is a disassembled perspective view, The figure (b) is a longitudinal cross-sectional view, The figure (c) Is a partially enlarged view. It is a figure which illustrates typically the force which acts on a differential case and a ring gear. It is a figure which shows typically the principal part of the differential which concerns on Embodiment 2, The figure (a) is a disassembled perspective view, The figure (b) is a longitudinal cross-sectional view, The figure (c) is a partial expansion. FIG. It is a figure which shows typically the principal part of the conventional differential.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram schematically showing a main part of a differential 1 according to the present embodiment, where FIG. 1 (a) is an exploded perspective view, FIG. 1 (b) is a longitudinal sectional view, c) is a partially enlarged view. In FIG. 1A, only half of the ring-shaped ring gear 3 is shown and the teeth of the inclined gear provided on the gear portion 7 of the ring gear 3 are omitted for the sake of clarity.

-Differential-
The differential 1 includes a differential case 2 and an annular ring gear 3 as shown in FIG. The differential case 2 includes a substantially cylindrical case body 4 in which a pair of side gears (not shown) and a pair of pinions (not shown) are rotatably accommodated, and a circle integrally formed with the case body 4. And an annular flange portion 5. The ring gear 3 includes an annular flange portion 6 and an annular gear portion 7 formed integrally with the outer peripheral portion of the flange portion 6. In the differential 1, as shown in FIG. 1B, a plurality of differential cases 2 and ring gears 3 are provided in a state where the annular ring gear 3 is assembled so as to cover the outer periphery of the annular flange portion 5 of the differential case 2. The bolt 8 is fastened.

  For example, the differential 1 is configured such that a torque input from a final gear that outputs torque transmitted from an engine via a transmission, a final reduction gear, and the like, and the ring gear 3 are engaged with each other. A part of a power transmission mechanism in the vehicle is configured by transmitting to a pair of left and right drive wheels connected to a pair of pinions while allowing a difference.

-Differential case-
An annular fastening surface 5 a is formed on the annular flange portion 5 of the differential case 2 on the other axial side of the annular ring (left side in FIG. 1B). The annular fastening surface 5a is formed as a tapered surface that is inclined so as to extend toward one side in the axial direction (the right side in FIG. 1B) as it goes radially outward. In other words, the fastening surface 5a is inclined like a truncated cone-shaped inclined surface whose outer diameter increases toward the one side in the axial direction.

  The fastening surface 5a is formed with a plurality of bolt holes 5b spaced apart at equal intervals in the circumferential direction and extending in parallel with the axial direction of the ring. A female screw (not shown) that meshes with a male screw (not shown) of the bolt 8 is cut on the inner peripheral surface of each bolt hole 5b, whereby the bolt 8 that fastens the differential case 2 and the ring gear 3 is It is inserted while being screwed into a bolt hole 5b parallel to the axial direction. Therefore, the fastening surface 5 a of the differential case 2 is a tapered surface inclined with respect to the direction perpendicular to the axis of the bolt 8.

-Ring gear-
An annular fastening surface 6 a is formed on the annular flange portion 6 of the ring gear 3 on one side in the axial direction. Similar to the fastening surface 5a of the flange portion 5, the annular fastening surface 6a is formed as a tapered surface that is inclined so as to extend toward the one side in the axial direction as it goes radially outward. In other words, the fastening surface 6a is inclined like a truncated cone-shaped inner peripheral surface (inclined surface) whose inner diameter increases toward the one side in the axial direction.

  A plurality of bolt holes 6 b are formed in the fastening surface 6 a so as to correspond to the bolt holes 5 b of the flange portion 5, spaced apart at equal intervals in the circumferential direction and extending parallel to the axial direction of the ring. Unlike the bolt hole 5b of the flange portion 5, the inner peripheral surface of each bolt hole 6b is not cut by an internal thread (not shown), and the bolt 8 is screwed into the bolt hole 6b parallel to the axial direction. It is designed to be inserted without doing it. Therefore, the fastening surface 6 a of the ring gear 3 is also a tapered surface inclined with respect to the direction perpendicular to the axis of the bolt 8.

-Differential structure-
In the differential 1 configured as described above, as shown in FIGS. 1B and 1C, the differential case 2 and the ring gear 3 have the fastening surfaces 5a and 6a as mating surfaces, and these bolts. A differential structure is used in which the holes 5b and 6b are fastened with bolts 8 inserted from the ring gear 3 side. Hereinafter, the operation and effect of such a differential structure will be described. Prior to this, a conventional differential structure will be described in order to facilitate understanding of the present embodiment.

  FIG. 4 is a diagram schematically showing a main part of a conventional differential 101. As shown in FIGS. 4A to 4C, the differential 101 has a fastening surface 105a of the differential case 102 and a fastening surface 106a of the ring gear 103 formed on a flat surface orthogonal to the axial direction. The configuration is almost the same as that of the differential 1 of the present embodiment.

  In such a differential 101, the differential case 102 and the ring gear 103 are flat bolt fastening surfaces 105a and 106a as mating surfaces, and bolts inserted through bolt holes 105b and 106b formed in the fastening surfaces 105a and 106a. When fastened at 108, only a force pressing the differential case 102 and the ring gear 103 in the axial direction is generated.

  Therefore, in the conventional differential structure, depending on the number of bolts 108, when the torque from the engine is transmitted to the drive wheels, the differential case 102 and the ring gear 103 are slightly displaced relative to each other, resulting in a large external force in the direction perpendicular to the axis of the bolt 108. May be applied. Thus, when a large external force is repeatedly applied and the bolt 108 is displaced, the screw portion slips and the bolt 108 may be loosened.

  Here, for example, it is conceivable to employ a loosening fastening structure in which a bolt fastening is performed with an additional part (for example, a bush) inserted in the bolt hole 106b, and the differential case 102 and the ring gear 103 are bolted. Since additional parts are required for each bolt 108, there is a problem that the number of parts increases. Further, if the number of bolts 108 is increased, the differential case 102 and the ring gear 103 are firmly fastened, so that loosening of the bolts 108 can be suppressed, but in this case, the number of parts increases. In addition, there is a problem that the weight of the vehicle body and the manufacturing cost increase.

  Therefore, in the differential structure of the present embodiment, by inclining the fastening surfaces 5a and 6a as described above, a force that cannot be generated on the flat fastening surface is applied to the differential case 2 and the ring gear 3, and both The fastening force is increased.

  FIG. 2 is a diagram schematically illustrating the force acting on the differential case 2 and the ring gear 3. When the differential case 2 and the ring gear 3 are tightened with the bolt 8, as shown in FIG. 2A, a force Q acts on the flange portion 6 of the ring gear 3 on one side in the axial direction by the tightening force of the bolt 8. And

  Due to the force Q acting on one side in the axial direction with respect to the flange portion 6 of the ring gear 3, the mating surfaces 5a and 6a between the differential case 2 and the ring gear 3 are perpendicular to the mating surfaces 5a and 6a due to the wedge effect. A force Pp and a force Ph horizontal to the mating surfaces 5a and 6a are generated. Thereby, the fastening surface 5a of the differential case 2 is pressed to the one side in the axial direction by the resultant force (= force Q) of the axial direction component Ppa of the force Pp and the axial direction component Pha of the force Ph.

  Further, the fastening surface 5a of the differential case 2 is pressed radially inward by the radial component Ppr of the force Pp, while the fastening surface 6a of the ring gear 3 is pressed radially outward by the radial component Phr of the force Ph. It will be. As described above, in the differential structure of the present embodiment, the wedge effect causes a force Ppr to try to shrink the flange portion 5 radially inward on the differential case 2 side, while the flange portion 6 on the ring gear 3 side in the radial direction. A force Phr that tries to spread outward is generated.

  Here, on the differential case 2 side, an elastic force Rpr (force to expand radially outward) Rpr is generated with respect to the force Ppr that is radially contracted inward, while on the ring gear 3 side In contrast to the force Phr that attempts to expand radially outward, a force (force that attempts to shrink radially inward) Rhr is generated that is elastic. As shown in FIG. 2 (b), the forces Rpr and Rhr for returning to the original force act on the differential case 2 side as a force for pressing the fastening surface 6a of the ring gear 3 outward in the radial direction. Then, since it acts as a force for pressing the fastening surface 5a of the differential case 2 radially inward, the differential case 2 and the ring gear 3 are firmly fastened.

  On the other hand, a force −Q (force Q on the other side in the axial direction) also acts on the differential case 2. Although not shown in order to avoid duplication, the force Q acts on the other side in the axial direction on the differential case 2, so that the fastening surface 6 a of the ring gear 3 is pressed to the other side in the axial direction by the force Q as in the ring gear 3 side. In addition, the fastening surface 5a of the differential case 2 presses the fastening surface 6a of the ring gear 3 radially outward, and the fastening surface 6a of the ring gear 3 presses the fastening surface 5a of the differential case 2 radially inward.

  If the above operation is explained more simply, in the differential structure of the present embodiment, the truncated cone-shaped convex portion (the flange portion 5 of the differential case 2) is replaced with the truncated cone-shaped concave portion (the flange portion 6 of the ring gear 3). Therefore, the differential case 2 and the ring gear 3 can be firmly fastened.

  In addition, since the fastening surface 5a of the differential case 2 and the fastening surface 6a of the ring gear 3 are inclined tapered surfaces, these fastening surfaces are flat (parallel to the direction perpendicular to the axis of the bolt 8). Thus, the contact area between the differential case 2 and the ring gear 3 can be increased, and thereby the frictional force between the differential case 2 and the ring gear 3 can be increased.

  Thus, in the differential structure of the present embodiment, the differential case 2 and the ring gear 3 are firmly fastened due to the combined force of pressing each other in the axial direction and the radial direction and the increase in frictional force. Therefore, the relative displacement between the differential case 2 and the ring gear 3 when transmitting torque can be suppressed, and the application of a large external force to the bolt 8 can be suppressed. Therefore, it is possible to suppress the displacement of the bolt 8 that fastens the differential case 2 and the ring gear 3, thereby suppressing the loosening of the bolt 8 without increasing the number of parts.

(Embodiment 2)
FIG. 3 is a diagram schematically showing a main part of the differential 11 according to the present embodiment, where FIG. 3A is an exploded perspective view, FIG. 3B is a longitudinal sectional view, and FIG. c) is a partially enlarged view. In FIG. 3A, only half of the ring-shaped ring gear 13 is shown and the teeth of the inclined gear provided on the gear portion 17 of the ring gear 13 are omitted for easy understanding of the drawing. This embodiment is different from Embodiment 1 in that the fastening surface 15a of the differential case 12 and the fastening surface 16a of the ring gear 13 are inclined toward the other side in the axial direction with respect to the direction perpendicular to the axis of the bolt 18. . Hereinafter, a description will be given focusing on differences from the embodiment.

  As shown in FIG. 3A, the differential 11 includes an annular ring gear having a differential case 12 having a case main body portion 14 and a flange portion 15, an annular flange portion 16, and an annular gear portion 17. 13.

  An annular fastening surface 15 a is formed on the flange portion 15 of the differential case 12 on the other axial side (the left side in FIG. 3B). The annular fastening surface 15a is formed as a tapered surface that is inclined so as to extend to the other side in the axial direction as it goes radially outward. In other words, the fastening surface 15a is inclined so as to have a truncated cone-shaped inner peripheral surface (inclined surface) whose inner diameter increases toward the other side in the axial direction. The fastening surface 15a is formed with a plurality of bolt holes 15b spaced apart at equal intervals in the circumferential direction and extending in parallel with the axial direction of the ring.

  An annular fastening surface 16a is formed on the flange portion 16 of the ring gear 13 on one axial side (the right side in FIG. 3B). The annular fastening surface 16a is formed as a tapered surface that is inclined so as to extend to the other side in the axial direction as it goes radially outward. In other words, the fastening surface 16a is inclined like a truncated cone-shaped inclined surface whose outer diameter increases toward the other side in the axial direction. The fastening surface 16a is formed with a plurality of bolt holes 16b that are spaced apart at equal intervals in the circumferential direction and extend parallel to the axial direction of the ring.

  In the differential 11 configured as described above, as shown in FIGS. 3B and 3C, the differential case 12 and the ring gear 13 have the fastening surfaces 15a and 16a as mating surfaces, and these bolts. A differential structure that is fastened with bolts 18 inserted through the holes 15b and 16b is employed.

  Although not shown because it is the same as the explanation of FIG. 2, in this differential structure, when the differential case 12 and the ring gear 13 are tightened with the bolt 18, the axial direction of the differential case 12 is the same as in the first embodiment. The fastening surface 15a and the fastening surface 16a of the ring gear 13 press each other.

  On the other hand, in the radial direction, contrary to the first embodiment, on the differential case 12 side, a force is generated to expand the flange portion 15 of the differential case 12 radially outward, while on the ring gear 13 side, the ring gear 13 is generated. A force is generated to shrink the flange portion 16 radially inward. However, the force that tries to return to the force that expands radially outward on the differential case 12 side, and the force that tries to shrink radially inward on the ring gear 13 side tries to return to the original. Since the force to act acts as a force for pressing each other in the radial direction, as in the first embodiment, the differential case 12 and the ring gear 13 are firmly fastened.

  In addition, since the fastening surface 15a of the differential case 12 and the fastening surface 16a of the ring gear 13 are inclined tapered surfaces, these fastening surfaces are flat (parallel to the direction perpendicular to the axis of the bolt 18). The contact area between the differential case 12 and the ring gear 13 can be increased, and thereby the frictional force between the differential case 12 and the ring gear 13 can be increased.

  Thus, also in the differential structure of the present embodiment, the differential case 12 and the ring gear 13 are firmly fastened by the combined force of pressing each other in the axial direction and the radial direction and the increase of the frictional force. be able to. As a result, it is possible to suppress loosening of the bolt 18 that fastens the differential case 12 and the ring gear 13 without increasing the number of parts.

  As described above, according to the differential structures of the first and second embodiments, the differential cases 2 and 12 and the ring gears 3 and 13 can be firmly fastened. It is possible to suppress loosening of the bolts 8 and 18 that fasten the ring gears 3 and 13.

  Moreover, in the differential structure of Embodiments 1 and 2, since the fastening force is increased by inclining the fastening surfaces 5a, 6a, 15a, 16a, the number of bolts can be reduced as compared with the conventional structure. The weight of the vehicle body can be reduced and the manufacturing cost can be reduced.

  Further, in the differential structures of the first and second embodiments, the fastening force is increased by inclining the fastening surfaces 5a, 6a, 15a, and 16a, so that the permissible torque per bolt can be increased as compared with the conventional case. it can. As a result, a small differential with a small number of bolts or small bolts can be realized, and the weight of the vehicle body and the manufacturing cost can be reduced.

  Further, in the conventional ring gear 103, in order to change the width L (see FIG. 4C) of the flange portion at the connection portion with the gear portion, the entire flange portion needs to be thick (or thin). In Embodiments 1 and 2, by inclining the fastening surfaces 5a, 6a, 15a, and 16a, the flange portions at the connection portions with the gear portions 7 and 17 are hardly changed without substantially changing the volume of the flange portions 6 and 16 as a whole. The widths 6 and 16 can be adjusted to be wide (see width L1 in FIG. 1C) or narrow (see width L2 in FIG. 3C). As described above, the rigidity of the ring gears 3 and 13 can be changed by freely adjusting the widths of the flange portions 6 and 16, so that the alignment change accompanying the elastic deformation of the ring gears 3 and 13 can be adjusted. This makes it possible to improve noise vibration.

  The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof. The above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  According to the present invention, it is possible to suppress the loosening of the bolt that fastens the differential case and the ring gear while suppressing an increase in the number of parts, which is extremely useful when applied to a differential structure that fastens the differential case and the ring gear with bolts. .

1, 11 Differential 2, 12 Differential case 3, 13 Ring gear 5a, 15a Fastening surface 5b, 15b Bolt hole 6a, 16a Fastening surface 6b, 16b Bolt hole 8, 18 Bolt

Claims (1)

A differential case and a ring gear each having an annular fastening surface, each of which has a plurality of bolt holes extending in parallel with the axial direction of the annular ring, with these fastening surfaces as mating surfaces, and It is a differential structure that is fastened with bolts inserted through these bolt holes,
The differential structure, wherein the fastening surface of the differential case and the fastening surface of the ring gear are tapered surfaces inclined with respect to a direction perpendicular to the axis of the bolt.

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