JP2005048903A - Differential gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the durability of a straight bevel gear used in a differential gear. <P>SOLUTION: An extension line of a tooth tip of a differential pinion 20 and a differential side gear 22 is set to pass through an intersection O of axial lines L1, L2 of the differential pinion 20 and the differential side gear 22 to enlarge length i of a simultaneous meshing line at meshing start time and meshing end time of the differential pinion 20 and the differential side gear 22 from a limited region in the vicinity of a large diameter end part of the conventional straight bevel gear to the whole region from the large diameter end part to a small diameter end part, thereby increasing the durability of the differential pinion 20 and the differential side gear 22 by preventing the concentration of meshing load only in the vicinity of the large diameter end part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a differential gear in which a differential pinion made of a straight bevel gear and a differential side gear are engaged with each other.

In general, the conventional straight bevel gear is adjusted so that it contacts the mating straight bevel gear in the vicinity of the large-diameter end where the tooth width is large in order to transmit a large torque. Is the same from the small-diameter end to the large-diameter end, and there is a problem that a large load is concentrated on the tooth base of the large-diameter end and is easily damaged. Therefore, the straight bevel gear described in the following Patent Document 1 increases the radius of curvature of the fillet curve at the tooth root gradually from the small diameter end portion toward the large diameter end portion, that is, the tooth root meat at the large diameter end portion. By actively increasing the thickness compared to the thickness of the tooth root of the small-diameter end portion, the strength of the large-diameter end portion that has been easily damaged in the past is increased.
JP 2002-295642 A

  However, since the contact width (the length of the simultaneous meshing line) at the start of meshing and at the end of meshing is limited to a part on the large-diameter end part side, a large load is still concentrated on the large-diameter end part. There was a problem that it was easily damaged.

  The present invention has been made in view of the above circumstances, and an object thereof is to improve the durability of a straight bevel gear used for a differential gear.

  In order to achieve the above object, according to the first aspect of the present invention, in a differential gear in which a differential pinion and a differential side gear made of a straight bevel gear are meshed, an extension line of a tooth tip of the differential pinion and a tooth of the differential side gear. A differential gear is proposed in which the previous extension line passes through the intersection of the axis of the differential pinion and the axis of the differential side gear.

  According to the configuration of the first aspect, since the extension line of the tooth tip of the differential pinion and the extension line of the tooth tip of the differential side gear pass through the intersection of the axis line of the differential pinion and the axis line of the differential side gear, the differential pinion and the differential side gear The length of the simultaneous meshing line at the start of meshing and at the end of meshing can be expanded from a limited area in the vicinity of the conventional large diameter end to the entire area from the large diameter end to the small diameter end. It is possible to increase the durability of the differential pinion and the differential side gear by preventing the load from being concentrated only in the vicinity of the large diameter end portion.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  FIGS. 1 to 6 show an embodiment of the present invention. FIG. 1 is a sectional view of a differential gear of a vehicle, FIG. 2 is an enlarged view of a meshing portion of a differential pinion and a differential side gear, and FIG. FIG. 4 is an enlarged view of a portion 4 in FIG. 2, FIG. 5 is a diagram showing a tooth profile of a differential pinion, and FIG. 6 is a diagram showing a tooth profile of a differential side gear.

  FIG. 1 shows a differential gear D of a front engine / front drive vehicle, which is fixed to the outer periphery of a differential case 13 rotatably supported by a transmission case 11 via a pair of roller bearings 12 and 12 with bolts 14. The final driven gear 15 is engaged with and driven by a final drive gear 17 formed integrally with the counter shaft 16. A pinion shaft 18 is fixed to the differential case 13 with a pin 19, and a pair of differential pinions 20 and 20 rotatably supported by the pinion shaft 18 has left and right axles 21 that pass through the differential case 13 rotatably. , 21 mesh with a pair of differential side gears 22, 22 splined to the shaft ends.

表１は比較例および実施例のストレートベベルギヤの諸元を比較するもので、比較例の諸元に対して異なっている実施例の諸元に※印が付してある。

Table 1 compares the specifications of the straight bevel gears of the comparative example and the example. The specifications of the example different from the specifications of the comparative example are marked with *.

  First, spherical involute tooth profiles are adopted as the tooth shapes of the differential pinion 20 and the differential side gear 22 of the embodiment, whereas the tooth shapes of the differential pinion 20 and the differential side gear 22 of the comparative example are representative of the Gleason lever cycle tooth profile. An arc tooth profile is adopted.

  Further, the tooth tip angles θa and θf of the embodiment are smaller than those of the comparative example, and as shown in FIG. 3, the extension lines (lines passing through the tooth tips) of the tooth tip angles θa and θf of the embodiment are differential pinions. The 20 axis lines L1 and the axis line L2 of the differential side gear 22 intersect each other at the center point O. On the other hand, in the comparative example in which the tooth tip angles θa and θf are large, the extension lines of the tooth tip angles θa and θf intersect at a point O ′ before the center point O, as shown in FIG.

  In FIG. 3, the radial simultaneous mesh line centered on the center point O indicates a line where the differential pinion 20 and the differential side gear 22 mesh simultaneously, and these simultaneous mesh lines are sequentially when the differential pinion 20 and the differential side gear 22 rotate. Moving. The simultaneous meshing line extends from the intersection of the tooth tip R and the tooth surface toward the center point O where the axis L1 of the differential pinion 20 and the axis L2 of the differential side gear 22 intersect. In the embodiment of FIG. 3, since the extension lines of the tooth tip angles θa and θf are directed to the center point O, the simultaneous meshing line passing through the center point O and the extension lines of the tooth tip angles θa and θf overlap each other. At the start and end of meshing of the differential pinion 20 and the differential side gear 22, a sufficient length i of the simultaneous meshing line from the small-diameter end to the large-diameter end can be secured. Durability can be improved by preventing a local heavy load from acting on the tooth surface at the end.

  On the other hand, in the comparative example shown in FIG. 4, since the extension lines of the tooth tip angles θa and θf are directed to the point O ′ before the center point O, the simultaneous meshing line particularly at the start of meshing and at the end of meshing. Is limited to a part on the large-diameter end portion side, and the length i of the simultaneous meshing line is shorter than that of the embodiment, so that the teeth near the large-diameter end portion at the start of meshing and at the end of meshing A large local load acts on the surface, causing a decrease in durability.

  The requirement that the extension lines of the tooth tip angles θa and θf are directed to the center point O, which is a feature of the tooth profile of the differential pinion 20 and the differential side gear 22 of the embodiment, is the height of the tooth tip (from the pitch circle to the tooth tip). This is realized by setting a value obtained by dividing the distance to the module (the diameter of the pitch circle / the number of teeth) to a constant value from the small diameter end to the large diameter end.

  In addition, the tooth profile of the embodiment has an increased meshing ratio due to an increase in the tooth height on the small diameter end side compared to the tooth profile of the comparative example (see Table 1), thereby reducing the contact area of the meshing section. Durability can be further improved.

  Further, as apparent from FIGS. 5 and 6, the tooth profile (spherical involute tooth profile) of the differential pinion 20 and the differential side gear 22 according to the embodiment is thicker at the tooth tip and the tooth root than the tooth profile (arc tooth profile) of the comparative example. The backlash is constant by meshing the gears at one pitch, and smooth torque transmission can be achieved.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, the tooth profiles of the differential pinion 20 and the differential side gear 22 of the present invention are not limited to those shown in Table 1, but include all those that satisfy the requirements described in claim 1.

Cross section of vehicle differential gear Enlarged view of meshing part of differential pinion and differential side gear Part 3 enlarged view of FIG. 4 enlarged view of FIG. Diagram showing tooth profile of differential pinion Diagram showing tooth profile of differential side gear

Explanation of symbols

20 Differential pinion 22 Differential side gear L1 Differential pinion axis L2 Differential side gear axis O Center point (intersection)

Claims (1)

In a differential gear in which a differential pinion (20) and a differential side gear (22) made of a straight bevel gear are meshed,
The extension line of the tip of the differential pinion (20) and the extension line of the tip of the differential side gear (22) are the intersection of the axis (L1) of the differential pinion (20) and the axis (L2) of the differential side gear (22). A differential gear characterized by passing.

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