JP6710796B2 - Transmission - Google Patents

Description

The present invention transmits a power transmission device, in particular, a rotatable transmission member having a flange portion integrally with an outer peripheral portion and a ring gear welded to the flange portion of the transmission member and having a helical gear portion formed on the outer peripheral portion thereof. The present invention relates to a differential device and other transmission devices included in a path.

Conventionally, as such a transmission device, for example, a differential case as a rotatable transmission member having a flange portion integrally on an outer peripheral portion, and a flange portion of the differential case is partially press-fitted and welded at the other portion. A differential device is known that distributes the power transmitted from the drive source to the ring gear and further transmitted to the differential case to the pair of left and right output shafts via the differential mechanism inside the differential case. (For example, refer to the following patent document). In this structure, a space is formed between the differential case and the ring gear, which serves both to relax stress concentration during press fitting and to release gas during welding.

Japanese Patent No. 5614054 JP, 2012-189116, A

By the way, in the above-mentioned conventional device, the axially opposed surfaces of the flange portion of the differential case and the ring gear are butt-welded together. Therefore, especially when the outer peripheral gear part of the ring gear is composed of a helical gear, the large thrust load generated at the meshing part of the helical gear increases the stress acting on the welded part between the differential case and the ring gear, and It may affect the durability.

Therefore, as a countermeasure for the stress concentration, for example, it is conceivable to form a flange portion or the like around the welded portion into a particularly thick wall or to increase the welding depth of the welded portion. There are other disadvantages such as increased weight and increased costs.

Incidentally, in the conventional device, there is also one in which the flange portion of the differential case and the radial facing surfaces of the ring gear are butt-welded together, but this reduces the large stress acting on the welded portion due to the large thrust load. There was no special consideration for.

The present invention has been made in view of such circumstances, and an object thereof is to provide the above-described transmission device that can solve the above problems.

In order to achieve the above object, the present invention provides a rotatable transmission member that integrally has a flange portion on the outer peripheral portion, and a helical gear portion that is welded to the flange portion of the transmission member and on the outer peripheral portion. A transmission device including a ring gear in a transmission path, wherein a first outer peripheral portion for fitting and welding an inner peripheral portion of the ring gear to an outer peripheral surface of the flange portion and a first connection to the first outer peripheral portion. A second outer peripheral portion having a diameter smaller than that of the first outer peripheral portion and adjacent to each other across the surface; and a third outer peripheral portion that abuts on the inner peripheral portion of the ring gear and performs radial positioning with respect to the flange portion of the ring gear. And a space forming portion that defines a space facing the inner end of the welded portion between the first outer peripheral portion and the ring gear is formed in the ring gear, and the space forming portion is formed in the helical gear portion. When the thrust load is generated, the stress acting on the boundary corner between the first connecting surface and the second outer peripheral portion and its vicinity is larger than the stress acting on the inner end of the weld and its vicinity. A first connection surface of the flange portion facing the space, the first connection surface of the flange portion and a surface perpendicular to the axis of the ring gear extending from the inner end of the welded portion toward the boundary corner portion. One flat portion is formed, and in the space forming portion of the ring gear, a surface that is perpendicular to the axis of the flange portion and the ring gear is formed, and is opposite to the boundary corner portion from the inner end of the weld portion. The first feature is that a second flat surface portion extending in the direction is formed.

In addition to the first characteristic, the present invention has a second characteristic that the first plane portion and the second plane portion are continuous on the same plane.

Further, in the present invention, in addition to the first or second feature, the welding of the flange portion and the ring gear is performed by laser welding, and the space has a direction larger than a dimension of a direction in which a welding laser is emitted. The third feature is that the dimension in the direction orthogonal to is larger.

According to the first feature of the present invention, the outer peripheral surface of the flange portion of the transmission member includes a first outer peripheral portion for fitting and welding an inner peripheral portion of a ring gear having a helical gear portion on the outer periphery, and a first outer peripheral portion thereof. A second outer peripheral portion having a small diameter and being adjacent to each other with the first connecting surface sandwiched therebetween, and a third outer peripheral portion that abuts on the inner peripheral portion of the ring gear to position the ring gear in the radial direction are formed. A space forming portion is formed between the flange portion and a space facing the inner end of the welded portion between the ring portion and the ring gear, and when a thrust load is generated in the helical gear portion, the space between the first connecting surface and the second outer peripheral portion is formed. The first connecting surface of the flange portion facing the space is provided with a flange portion and a stress so that the stress acting on the boundary corner portion between them and the vicinity thereof becomes larger than the stress acting on the inner end of the welded portion and the vicinity thereof. A first flat surface portion that is formed by a surface perpendicular to the axis of the ring gear and extends from the inner end of the welded portion toward the boundary corner portion is formed, and a flange portion and a ring gear portion are formed in the space formation portion of the ring gear. Since the second flat surface portion is formed by the surface perpendicular to the axis line of and extends in the direction opposite to the boundary corner portion from the inner end of the welded portion, a large thrust load is generated at the meshing portion of the helical gear. Even if it occurs and acts on the ring gear, due to the special provision of the space defined by the inner end of the welded portion, the flange portion and the flat portion that extends inward and outward in the radial direction perpendicular to the axis of the ring gear, The stress can be effectively dispersed in the peripheral portion of the welded portion, and the stress concentration in the welded portion can be relaxed. As a result, it is not necessary to thicken the peripheral portion of the welded portion or to deepen the welding depth as a measure for stress concentration, which can greatly contribute to weight reduction and cost reduction of the apparatus.

Sectional drawing of the principal part of the differential device which concerns on one Embodiment of this invention. Enlarged sectional view showing the welding/press-fitting portion between the ring gear and the differential case (enlarged sectional view taken along the arrow 2 in FIG. 1) A sectional view corresponding to FIG. 2 showing another embodiment of the welding/press-fitting portion of the ring gear and the differential case, and a reference embodiment. A sectional view corresponding to FIG. 2 showing still another embodiment group of the welding/press-fitting portion between the ring gear and the differential case.

Embodiments and reference modes of the present invention will be described below based on preferred examples and reference examples of the present invention shown in the accompanying drawings.

First, in FIG. 1, a differential device D as a transmission device distributes a rotational driving force output from an engine (not shown) mounted on an automobile to a pair of left and right output shafts J, J′ connected to a pair of left and right axles. Is transmitted and received to drive the left and right axles while permitting their differential rotation, and is housed and supported in, for example, a mission case 4 arranged beside the engine at the front of the vehicle body. It

This differential device D includes a ring gear R as a final driven gear, a differential case DC as a transmission member integrally having an outer peripheral portion with a flange portion 1 coupled to an inner peripheral portion Ri of the ring gear R, and the differential case DC. A differential mechanism DM for distributing and transmitting the rotational force transmitted from the ring gear R to the differential case DC to the pair of left and right output shafts J, J'is provided in the transmission path. As a means for connecting the inner peripheral portion Ri of the ring gear R and the flange portion 1 of the differential case DC, press fitting and welding are used together as described later.

The ring gear R integrally has a helical gear portion Rg on its outer peripheral portion. The helical gear portion Rg meshes with a drive gear (not shown), which is also a helical gear that is rotationally driven by the power of the engine, receives a rotational driving force, and transmits it to the differential case DC side as it is.

The differential mechanism DM in the differential case DC is similar to a conventionally known differential mechanism, and includes a plurality of pinions P, a pinion shaft PS as a pinion support portion that rotatably supports the pinions P, and a pinion P for the pinion P. It is provided with a pair of left and right side gears G, G'which mesh with each other from the left and right sides and are spline-fitted to the pair of left and right output shafts J, J', respectively. The outer end portion of the pinion shaft PS is fitted and supported by the differential case DC, and the pinion shaft PS and the differential case DC are integrally coupled with each other by a coupling means (in the illustrated example, the pinion shaft PS penetrates through the differential case DC. A retaining pin 2) that is press-fitted into DC is provided.

The differential case DC is rotatably supported by the transmission case 4 via left and right bearings 3. Further, between the inner circumference of the through hole formed in the mission case 4 and into which the output shafts J, J′ are inserted and the outer circumference of the output shafts J, J′, a gap is provided to seal the inside of the mission case 4. An annular seal member 5 is interposed to prevent the lubricating oil from leaking to the outside.

Next, with reference to FIG. 2 together, the coupling structure between the inner peripheral portion Ri of the ring gear R and the flange portion 1 of the differential case DC will be described.

On the outer peripheral surface A of the flange portion 1, a first outer peripheral portion A1 for fitting and welding a welded portion Riw formed on the inner peripheral portion Ri of the ring gear R, and a first outer peripheral portion A1 adjacent to the first outer peripheral portion A1. A second outer peripheral portion A2 having a smaller diameter than the outer peripheral portion A1 and a third outer peripheral portion A3 having a smaller diameter than the second outer peripheral portion A2, which is adjacent to the second outer peripheral portion A2 on the opposite side of the first outer peripheral portion A1. It is formed. Then, on the outer peripheral surface A of the flange portion 1, a step surface between the first and second outer peripheral portions A1 and A2, that is, a first connecting surface f1 that connects the step surfaces, and between the second and third outer peripheral portions A2 and A3. Step surface, that is, the second connection surface f2 connecting the step surfaces is formed.

An annular space in which the inner peripheral portion Ri of the ring gear R faces the inner end We of the welded portion W between the first outer peripheral portion A1 and the ring gear R and expands radially inward and outward of the welded portion W. An annular groove-shaped space forming portion Ris that defines S between the flange portion 1 (the second outer peripheral portion A2 and the first connecting surface f1 in the illustrated example) is at least the first outer peripheral portion in the axial direction of the ring gear R. It is formed between A1 and the third outer peripheral portion A3. Moreover, when a thrust load is generated in the helical gear portion Rg, the stress acting on the boundary corner portion 8 between the first connecting surface f1 and the second outer peripheral portion A2 and its vicinity acts on the inner end We of the welded portion W and its vicinity. The first connecting surface f1 of the flange portion 1 facing the annular space S is formed with a surface perpendicular to the axis of the flange portion 1 and the ring gear R so that the inner end of the welding portion W is larger than the stress. A first plane portion p1 extending from We toward the boundary corner portion 8 is formed, and the space forming portion Ris of the ring gear R is formed of a surface perpendicular to the axis of the flange portion 1 and the ring gear R, and is welded. A second plane portion p2 extending from the inner end We of the portion W in the direction opposite to the boundary corner portion 8 is formed. In the present embodiment, the first plane portion p1 and the second plane portion p2 are continuous on the same plane. Thus, the first connecting surface f1 connecting the first and second outer peripheral portions A1 and A2 and the second outer peripheral portion A2 face the space S and are not in contact with the ring gear R.

On the second connection surface f2 that connects the second and third outer peripheral portions A2 and A3, the side surface STs of the annular stopper portion ST that projects from the inner peripheral portion Ri of the ring gear R and is continuous with the space forming portion Ris is provided. Abutting in surface contact. Then, the inner peripheral surface STi of the stopper portion ST is press-fitted into the third outer peripheral portion A3. By the press-fitting, the ring gear R is axially and radially positioned and fixed to the flange portion 1 of the differential case DC.

Further, the surface of the ring gear R facing the space S, that is, the surface of the space forming portion Ris (in particular, the inner side surface Risf far from the welded portion W in the axial direction) and the second connection surface f2 of the stopper portion ST. The contacting side surface STs is smoothly continuous and forms a single plane in the illustrated example. By making the two surfaces Risf, STs having different functions (that is, having the space forming function and the thrust load receiving function, respectively) smooth and continuous, the structure of the ring gear inner peripheral portion Ri can be simplified accordingly. Also becomes easier and the workability is good.

Further, a corner portion 7 having a rounded arc-shaped cross section is formed at a boundary portion between the second connection surface f2 and the third outer peripheral portion A3, and the radius distribution causes stress distribution in the periphery of the corner portion 7. It is designed. On the other hand, a portion STc of the stopper portion ST facing the corner portion 7 is formed into a substantially flat chamfered surface. Therefore, an annular space S'is formed between the chamfered surface STc and the corner portion 7 having an arcuate cross section and facing the chamfered surface STc.

In addition, instead of forming the portion of the stopper portion ST facing the corner portion 7 into the substantially flat chamfered surface STc as described above, in the direction away from the corner portion 7 as shown by the chain line in FIG. It may be formed on the rounded surface STc' having a concave arcuate cross section. In this case, the corner 7 may be formed into a substantially flat chamfered surface.

Next, the operation of the above embodiment will be described. When the ring gear R receives a rotational force from the engine, the differential device D of the present embodiment has the left and right when the pinion P revolves around the axis L together with the differential case DC without rotating around the pinion shaft PS. The side gears G and G'are rotationally driven at the same speed, and the driving force is evenly transmitted to the left and right output shafts J and J'. When a difference in rotational speed occurs between the left and right output shafts J, J'due to turning of the automobile, etc., the pinion P revolves while revolving, so that the pinion P moves to the left and right side gears G, G'. The rotational driving force is transmitted while allowing the differential rotation. The above is the same as the operation of the conventionally known differential device.

By the way, in the present embodiment, the inner peripheral portion Ri of the ring gear R is attached and fixed to the annular flange portion 1 which is integral with the outer periphery of the differential case DC by using both press fitting and welding.

In the mounting and fixing work, first, the welded portion Riw of the ring gear inner peripheral portion Ri is lightly press-fitted to the first outer peripheral portion A1 of the flange portion 1 with a relatively small press-fitting load, and the flange portion 1 The inner peripheral surface STi of the stopper portion ST is fully press-fitted with a relatively large press-fitting load with respect to the outer peripheral portion A3. In order to achieve such a press-fitting mode, the dimensional difference between the outer diameter of the first outer peripheral portion A1 and the inner diameter of the welded portion Riw before the press-fitting process, the outer diameter of the third outer peripheral portion A3, and the stopper portion ST are determined. The dimensional difference from the inner diameter is set differently and appropriately.

After the completion of the press-fitting work, the fitting portion by light press-fitting between the first outer peripheral portion A1 of the flange portion 1 and the welded portion Riw of the ring gear inner peripheral portion Ri is butted and welded from the outside thereof.

In this welding operation, for example, as shown by the chain line in FIG. 2, a laser is emitted from a laser torch T for welding provided outside the flange portion 1 and the ring gear R toward the outer end of the abutting contact portion, and the differential case is used. This is performed by gently rotating the press-fitted joint of the DC and the ring gear R around its rotation axis L. At this time, the annular space S is larger than the dimension in the irradiation laser irradiation direction as shown in FIG. It is desirable that the dimension in the direction orthogonal to the direction be larger. At that time, the first outer peripheral portion A1 of the flange portion 1 and the welded portion Riw of the ring gear inner peripheral portion Ri can be butt welded to each other over the entire circumference by the energy of the laser. The welded portion W may be provided only in a part in the circumferential direction.

Thus, in the present embodiment, the outer peripheral surface A of the flange portion 1 of the differential case DC as the transmission member is fitted with and welded to the welded portion Riw of the inner peripheral portion Ri of the ring gear R, and the first outer peripheral portion A1. A second outer peripheral portion A2 having a small diameter adjacent to the first outer peripheral portion A1 and a third outer peripheral portion A3 having a smaller diameter adjacent to the second outer peripheral portion A2 on the opposite side of the first outer peripheral portion A1 are provided. In the inner peripheral portion Ri of the ring gear R, a space forming portion that defines an annular space S facing the inner end We of the welded portion W between the first outer peripheral portion A1 and the welded portion Riw with the flange portion 1. Ris is formed, and the stress acting on the boundary corner portion 8 between the first connecting surface f1 and the second outer peripheral portion A2 and the vicinity thereof when the thrust load is generated in the helical gear portion Rg is the inner end We of the welded portion W and The first connecting surface f1 of the flange portion 1 facing the annular space S is constituted by a surface perpendicular to the axis of the flange portion 1 and the ring gear R so that the stress acting on the welded portion W becomes larger than the stress acting on the vicinity thereof. A first flat surface portion p1 extending from the inner end We toward the boundary corner portion 8 is formed, and the space forming portion Ris of the ring gear R is formed of a surface perpendicular to the axis of the flange portion 1 and the ring gear R and welded. A second plane portion p2 extending from the inner end We of the portion W in the direction opposite to the boundary corner portion 8 is formed. Therefore, during transmission of power from the engine to the differential case DC side, even if a large thrust load is generated at the meshing portion of the helical gear Rg and acts on the ring gear R (hence, the welding portion W), the inner end We of the welding portion W is From the above, due to the special provision of the space S defined by the flat surface portions p1 and p2 that respectively extend inward and outward in the radial direction perpendicular to the axis of the flange portion 1 and the ring gear R, stress is effectively applied to the peripheral portion of the welded portion W. Stress concentration in the welded portion W is relieved.

Moreover, the side surface STs of the stopper portion ST, in which the ring gear R is formed and the inner peripheral surface STi is press-fitted into the third outer peripheral portion A3, comes into contact with the second connecting surface f2 between the second and third outer peripheral portions A2 and A3. Since a part of the thrust load is received by the flange portion 1 side even through the contact portion, the stress generated due to the thrust load is further dispersed, and the stress concentration at the welded portion W is more effective. Can be relaxed. As a result, it is not necessary to particularly thicken the peripheral portion of the welded portion W or to deepen the welding depth as a measure for stress concentration, which is advantageous in reducing the weight and cost of the apparatus.

Next, the stress dispersion effect will be supplementarily described with reference to the partially enlarged view of FIG. For example, when the ring gear R receives a large thrust load to the left of FIG. 2 with respect to the flange portion 1 of the differential case DC during transmission, as shown in a partially enlarged view of the second outer peripheral portion A2 and The first stress concentration region C1 is located at the boundary corner 8 between the first connecting surfaces f1 and its vicinity, and at the corner 7 between the third outer peripheral portion A3 and the second connecting surface f2 and its vicinity, the first stress The second stress concentration portions C2, in which a larger stress than the stress concentration portion C1 is generated, are generated at positions separated from the welded portion W, respectively. Then, the stress concentration portions C1 and C2 generated due to the thrust load are not concentrated only in the welded portion W and its vicinity, but are dispersed in the portions separated from the welded portion W, so that the inner end We of the welded portion W and It is possible to effectively suppress the occurrence of large stress concentration in the vicinity thereof.

In addition, the above-mentioned stopper portion ST has both a stopper function that regulates the press-fitting depth when press-fitting into the third outer peripheral portion A3 and a stress dispersing function when a thrust load is generated as described above. The structural simplification of the device is achieved accordingly.

The first connecting surface f1 that connects the first and second outer peripheral portions A1 and A2 is not in contact with the ring gear R. Therefore, the thrust load input from the ring gear R to the flange portion 1 side can be efficiently received by the contact portion of the second connecting surface f2 between the second and third outer peripheral portions A2 and A3 with the stopper portion ST. Therefore, the stress concentration at the welded portion W is alleviated more effectively.

Further, in the present embodiment, a corner portion 7 formed at the boundary between the second connection surface f2 and the third outer peripheral portion A3, and a portion STc (or STc') of the stopper portion ST facing the corner portion 7 are formed. A second space S'is formed between the two. Therefore, it is possible to effectively suppress the occurrence of strain due to stress concentration in the corner 7 and the vicinity thereof due to the press-fitting of the stopper portion ST into the third outer peripheral portion A3.

By the way, in the above-described embodiment, the annular space S defined by the space forming portion Ris on the inner circumference of the ring gear R and the outer circumference of the flange portion 1 (in particular, the first connecting surface f1 and the second outer circumference portion A2) is cross-sectioned. Although a space having a substantially rectangular shape that is vertically long in the radial direction is shown, the annular space S can have various transverse cross-sectional shapes and definition modes as illustrated below.

In the reference embodiment illustrated in FIG. 3A, the annular space S is offset from the welded portion W radially inward.

Further, in the embodiments illustrated in FIGS. 3B and 4C, respectively, the annular space S is formed in a triangular cross section.

Further, in the embodiment illustrated in FIG. 4D, the groove width of the space forming portion Ris for defining the annular space S is set to be shorter than the axial width of the second outer peripheral portion A2, and the space formation is performed. A step is formed between the inner side surface Risf of the portion Ris and the side surface STs of the stopper portion ST.

Furthermore, in the embodiment illustrated in FIG. 4(E), the groove width of the space forming portion Ris for defining the annular space S is set longer than the axial width of the second outer peripheral portion A2. Therefore, between the inner side surface Risf of the space forming portion Ris and the side surface STs of the stopper portion ST, there is a step opposite to the step in the embodiment of FIG.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention.

For example, in the above-described embodiment, the differential device D mounted in the automobile is illustrated as the transmission device, but the present invention can be implemented in the differential device used in the transmission system of various machines other than the automobile. Further, various transmission devices other than the differential device (a transmission member which has at least a flange portion integrally with an outer peripheral portion and is rotatable, and a flange portion of the transmission member are welded and a helical gear portion is formed on the outer peripheral portion thereof. The present invention can also be implemented in a transmission device including at least a ring gear included in the transmission path.

Further, in the above-described embodiment, the differential device D as the transmission device allows the rotation difference between the left and right axles, but the present invention can be applied to a center differential that absorbs the rotation difference between the front wheels and the rear wheels.

A... Outer peripheral surfaces A1, A2 , A3 of flange portion... First, second , third outer peripheral portion D... Differential device (transmission device)
DC: Differential case (transmission member)
f1... First connection surface p1... First plane portion p2... Second plane portion R... Ring gear Rg... Helical gear portion Ri... Inner circumference of ring gear Part Ris... Space forming part S... Annular space (space)
W... Welded portion We... Inner end of welded portion 1... Flange portion 8... Boundary corner portion

Claims (3)

A rotatable transmission member (DC) having a flange portion (1) integrally on the outer peripheral portion, and a helical gear portion (Rg) welded to the flange portion (1) of the transmission member (DC) and on the outer peripheral portion. A transmission device including a ring gear (R) to be formed in a transmission path,
A first outer peripheral portion (A1) for fitting and welding an inner peripheral portion (Ri) of the ring gear (R) to the outer peripheral surface (A) of the flange portion (1), and the first outer peripheral portion (A1). The second outer peripheral portion (A2), which has a smaller diameter than the first outer peripheral portion (A1) and is adjacent to the first peripheral surface (f1), and the inner peripheral portion (Ri) of the ring gear (R). And a third outer peripheral portion (A3) for positioning the ring gear (R) in the radial direction with respect to the flange portion (1) ,
The ring gear (R) has a space (S) facing the inner end (We) of the welded portion (W) between the first outer peripheral portion (A1) and the ring gear (R) and the flange portion (1). A space forming part (Ris) that is defined between
When a thrust load is generated in the helical gear portion (Rg), stress acting on the boundary corner portion (8) between the first connection surface (f1) and the second outer peripheral portion (A2) and the vicinity thereof is applied to the welded portion. The first connection surface (f1) of the flange portion (1) facing the space (S) is provided with the flange so as to be larger than the stress acting on the inner end (We) of (W) and its vicinity. A first plane portion (which is formed of a surface perpendicular to the axis of the portion (1) and the ring gear (R) and extends from the inner end (We) of the welded portion (W) toward the boundary corner (8) ( p1) is formed, and in the space forming portion (Ris) of the ring gear (R), the flange portion (1) and a surface perpendicular to the axis of the ring gear (R) are formed, and the welding portion is formed. A transmission device, characterized in that a second flat surface portion (p2) extending from an inner end (We) of (W) in a direction opposite to the boundary corner portion (8) is formed. The transmission device according to claim 1, wherein the first plane portion (p1) and the second plane portion (p2) are continuous on the same plane. Welding of the flange portion (1) and the ring gear (R) is performed by laser welding, and the space (S) has a dimension in a direction orthogonal to the direction in which the welding laser is irradiated, rather than a dimension in the direction in which the welding laser is irradiated. The transmission according to claim 1 or 2, characterized in that

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