# Patent

## Title
Helical gear differential

## Abstract

An axle assembly that includes a differential casing, which is rotatable about an axis, a pair of side gears that are disposed within the differential casing, a spacer and a cross pin. The spacer is disposed between the side gears. The cross pin is fixed to the differential casing and extends through the spacer. The cross pin is employed to limit end play of the axle shafts in a direction toward one another. The aperture in the spacer that receives the cross pin is relatively larger than the cross pin so that the spacer can control end play of the side gears independently of the cross pin.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation of U.S. patent application Ser. No. 10/794,780 filed Mar. 5, 2004, now U.S. Pat. No. 7,022,041, entitled “Helical Gear Differential” the disclosure of which is hereby incorporated by reference in its entirety.


FIELD OF THE DISCLOSURE
The present disclosure relates to differentials for use in automotive drivelines and, more particularly, to a pinion pair arrangement for a four pinion pair, C-clip differential having independent control of side gear endplay and axle shaft endplay.
BACKGROUND OF THE DISCLOSURE
Differentials of the type used in automotive drivelines generally include a planetary gearset supported within a differential casing to facilitate relative rotation (i.e., speed differentiation) between a pair of output shafts. The planetary gearset typically includes helical side gears fixed to the end of the output shafts, which are meshed with paired sets of helical pinion gears. This type of differentiation is known as a parallel axis helical gear differential. In response to input torque applied to the differential case, the torque transmitted through meshed engagement of the side gears and pinion gears generates thrust forces. To accommodate these and other operating forces, the wall surface of the gear pockets and other thrust surfaces of the differential casing must provide adequate support.
In some differentials it is necessary to install C-shaped retainers, or C-clips for restraining and positioning the output shafts in the differentials. To install the C-clips it is necessary to gain access to the interior cavity of the differential casing through an access window arranged on the differential casing.
In general, it is desirable to allow the side gear loading to be spread out evenly around the periphery of the differential. One way to achieve even loading is to position the pinion pairs evenly around the periphery of the differential casing. However, because the access window is arranged on the outer periphery of the differential casing, there tends to be incompatibility issues with placement of the pinion pairs.
SUMMARY OF THE DISCLOSURE
In one form, the present disclosure provides an axle assembly for a vehicle that includes a differential casing, a pair of side gears, a pair of axle shafts, a spacer and a cross pin. The differential casing is rotatable about an axis and includes a first pin aperture. The side gears are disposed within the differential casing. Each axle shaft is coupled for rotation with one of the side gears. The spacer is disposed between the side gears and has a second pin aperture. The cross pin is received into the first and second pin apertures such that receipt of the cross pin into the first pin aperture fixedly but removably couples the cross pin to the differential casing. The size of the second pin aperture is greater than a corresponding size of the cross pin such that the spacer is moveable along the rotational axis of the differential casing relative to the cross pin. As such, the cross pin limits movement of the axle shafts in a direction toward one another and the spacer limits movement of the side gears toward one another independently of the cross pin.
In another form, the present disclosure provides a method that includes: providing a differential casing having a rotational axis; installing a pair of side gears within the differential casing; installing a pair of axle shafts to the side gears such that each axle shaft is coupled for rotation with one of the side gears; locating a spacer between the side gears; fixedly coupling a cross pin to the differential casing such that the cross pin is inserted through a pin aperture in the spacer; and moving the side gears and the spacer in a first direction along the rotational axis without moving the cross pin.
In yet another form, the present disclosure provides an axle assembly for a vehicle that includes a differential casing, a pair of side gears, a pair of axle shafts, a spacer and a cross pin. The differential casing is rotatable about an axis and includes a first pin aperture. The side gears are disposed within the differential casing. Each axle shaft is coupled for rotation with one of the side gears. The spacer is disposed between the side gears and includes a second pin aperture. The cross pin is received into the first and second pin apertures. Receipt of the cross pin into the first pin aperture fixedly but removably couples the cross pin to the differential casing. The size of the second pin aperture is greater than a corresponding size of the cross pin such that a void space is disposed between the spacer and the cross pin regardless of a position of the side gears axially along the rotational axis.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.



BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a schematic view of an exemplary motor vehicle into which a differential assembly constructed in accordance with the teachings of the present disclosure is incorporated;
FIG. 2a is a perspective view of the differential assembly of FIG. 1;
FIG. 2b is a perspective view of the differential casing of FIG. 1;
FIG. 3 is an exploded view of the differential assembly of FIG. 1;
FIG. 4 is a sectional view of the differential assembly taken along line 4—4 of FIG. 2a; 
FIG. 5 is a cross-sectional view of the differential assembly taken along line 5—5 of FIG. 4;
FIG. 6 is a perspective view of the differential assembly of FIG. 1 illustrating the cross pin assembly in an exploded condition;
FIG. 7 is a perspective view of the differential assembly of FIG. 1 illustrating the cross pin assembly engaged to the cylindrical boss of the differential casing;
FIG. 8 is a perspective view of the differential assembly of FIG. 1 illustrating the cross pin assembly in an installed condition;
FIG. 9 is an exploded view of a differential assembly according to other features;
FIG. 10 is an exploded view of a differential assembly according to other features; and
FIG. 11 is an exploded view of the differential assembly according to other features.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. The differential assembly according to the present teachings may be utilized with a wide variety of applications and is not intended to be specifically limited to the particular application recited herein.
With initial reference to FIG. 1, a drivetrain 10 for an exemplary motor vehicle may include an engine 12, a transmission 14 having an output shaft 16, and a propeller shaft 18 connecting the output shaft 16 to a pinion shaft 20 of a rear axle assembly 22. The rear axle assembly 22 includes an axle housing 24, a differential assembly 26 supported in the axle housing 24, and a pair of axle shafts 28 and 30, respectively, interconnected to a left and right rear wheel 32 and 34, respectively. The pinion shaft 20 has a pinion shaft gear 36 fixed thereto which drives a ring gear 38 that may be fixed to a differential casing 40 of the differential assembly 26. A gearset 42 supported within the differential casing 40 transfers rotary power from the casing 40 to a pair of output shafts 44 and 45 connected to the axle shafts 28 and 30, respectively, and facilitates relative rotation (i.e., differentiation) therebetween. While the differential assembly 26 is shown in a rear-wheel drive application, the present invention is contemplated for use in differential assemblies installed in transaxles for use in front-wheel drive vehicles, and/or in transfer cases for use in four-wheel drive vehicles.
Turning now to FIGS. 2a–4, the differential assembly 26 will be described in further detail. The differential assembly 26 may be a parallel-axis helical-gear type differential and includes the differential casing 40, which defines an internal chamber 48. The differential casing 40 includes a main drum or body 46 and an end cap 50, each of which having respective mating radial flanges 52 and 54, respectively. The radial flanges 52 and 54 are secured together by a plurality of bolts (not shown) extending through aligned mounting bores 58. As is known, a ring or bevel gear can be fixed to the radial flange 52 on the differential casing 40 to transfer rotary power (i.e., drive torque) thereto. The differential casing 40 defines a pair of axially aligned openings 60a and 60b in communication with the internal chamber 48. The axially aligned openings 60a and 60b are adapted to receive the end segments of the pair of driving output shafts 44 and 45 (FIG. 1), hereinafter referred to as axle shafts.
With specific reference to FIGS. 3 and 4, the differential assembly 26 includes the gearset 42 that is operable for transferring drive torque from the differential casing 40 to the output shafts 44 and 45 (FIG. 1) in a manner that facilitates speed differential therebetween. Gearset 42 may be a helical-type and may be disposed within the internal chamber 48. The gearset 42 includes a pair of side gears 68a and 68b. The side gears have internal splines 70a and 70b meshed with external splines, not specifically shown, on the corresponding output shafts 44 and 45 (FIG. 1). In addition, the side gears 68a and 68b include axial hubs 78a and 78b, respectively, which are retained in corresponding annular sockets, formed in the main body 46 and the end cap 50 of the differential casing 40, and annular chambers 82a and 82b. As will be described in greater detail below, a spacer 86 may be located between the side gears 68a and 68b for limiting the amount of axial endplay of the side gears 68a and 68b within the differential case 40. A cross pin assembly 90 extends through a clearance passage 92 in the spacer 86 and controls endplay of the axle shafts 44 and 45 (FIG. 1).
C-shaped retainers, or C-clips 94, may be retained in the annular chambers 82a and 82b for preventing the axle shafts 44 and 45, respectively, from becoming disengaged with the side gears 68a and 68b. The side gears 68a and 68b may be bounded at their outer ends by washers 96.
The gearset 42 includes four sets of pinion pairs, 100a and 100b, 102a and 102b, 104a and 104b and 106a and 106b, respectively (FIG. 3). For clarity the pinion pairs 100a and 100b, 102a and 102b, 104a and 104b and 106a and 106b are hereinafter referred to as a first, second, third and fourth pair of pinion gears 100, 102, 104 and 106, respectively. Brake shoes 100a′–106b′ cooperate with respective pinion gears 100–106.
In FIGS. 2b and 3, the four sets of pinion pairs 100–106 are rotatably supported in complementary sets of pinion bores 110a and 110b, 112a and 112b, 114a and 114b, and 116a and 116b. The complementary sets of pinion bores 111a and 110b, 112a and 112b, 114a and 114b, and 116a and 116b are hereinafter referred to as a first, second, third and fourth pair of pinion bores 110, 112, 114, and 116, respectively. The pinion bores 110–116 are formed in raised hub segments 120 of the main body 46. The pinion bores 110–116 are arranged in paired sets such that they communicate with each other and with the internal chamber 48. In addition, the pinion bores 110–116 are aligned substantially parallel to the rotational axis A of the axle shafts 44 and 46 (FIG. 1). A window opening 124 may be arranged on the differential casing 40 between the first and the fourth pair of pinion gears 100 and 106.
With reference now to FIG. 5, the spacial relationship of the pinion pairs will be described. The four pinion bores 110–116, and as a result, the four pinion pairs 100–106 (FIG. 3), are radially spaced evenly around the differential casing 40 opposite the window opening 124. More specifically, the first pair of pinion bores 110 are offset a radial distance α1 from the second pair of pinion bores 112. The second pair of pinion bores 112 are offset a radial distance α2 from the third pair of pinion bores 114. The third pair of pinion bores 114 are offset a radial distance α3 from the fourth pair of pinion bores 116. As illustrated, the respective α distances are taken from the centerline of respective first bores 110a–110d. The radial offsets between the pinion bores 110 and 112, 112 and 114, and 114 and 116 may be approximately equivalent (e.g., α1=α2=α3). In the example provided, α1, α2 and α3 are approximately 75 degrees.
With specific reference now to FIGS. 2b, 4 and 6, the configuration of the window opening 124 and the cooperation of the cross pin assembly 90 will be described. The window opening 124 includes an access passage 126 surrounded by a cylindrical boss 128 that may be formed on an outer surface 130 of the differential casing 40. The cylindrical boss 128 defines a counterbore 132 having an inner radial engaging surface 136. The cylindrical boss 128 includes a pair of mounting passages 140 formed on raised flanges 142 for receiving a fastener 146 (FIG. 8) therethrough. A ledge portion 150 extends at least partially about the window opening 124 inwardly of the cylindrical boss 128 on the differential casing 40.
The cross pin assembly 90 generally includes a proximal head portion 154, an intermediate shank portion 158 and a distal end portion 162. The head portion 154 defines a body that may extend generally transverse to the longitudinal axis of the cross pin 90. The head portion 154 may include a throughbore 164 for receiving the fastener 146. The head portion 154 may include arcuate ends 168 that may be slidably disposed against the inner radial engaging surface 136 of the counterbore 132 during assembly. A bottom surface 170 of the head portion 154 locates against the ledge 150. The distal end portion 162 of the cross pin assembly 90 locates into a bore 172 formed into incorporated on the differential casing 40.
The cross pin assembly 90 may be unitarily formed or may comprise two or more components. In the example provided, the cross pin 90 is a two-piece assembly comprising the proximal head portion 154, which may be pressed onto a discrete shank that defines both the intermediate shank portion 158 and the distal end portion 162. It is appreciated that while the distal end portion 162 of the cross pin 90 is shown stepped down from the intermediate shank portion 158, the cross pin may comprise a uniform outer diameter. For example, an alternate pinion gear arrangement may be employed with a differential assembly providing enough space to accommodate a cross pin defining a consistent outer diameter.
With reference to FIGS. 4 and 7, assembly of the cross pin assembly 90 into the differential casing 40 will now be described in greater detail. Once the C-clips 94 are properly located and the spacer 86 is located between the side gears 66a and 66b, the spacer passage 92 may be aligned opposite the window opening 124 on the differential casing 40. The distal end 162 and the intermediate portion 158 of the cross pin assembly 90 are inserted through the window opening 124 and the spacer passage 92. The distal end 162 of the cross pin assembly 90 may be located into the bore 172 on the differential case 40 opposite the window opening 124. The bore 172 and the counterbore 132 pilot the cross pin assembly 90 during installation. The proximal head portion 154 may be inserted in an orientation substantially transverse to the axis of the differential casing 40. In this way, the head portion 154 of the cross pin assembly 90 will not interfere with the adjacent ring gear 38 (FIG. 1) during installation.
As the distal end 162 of the cross pin assembly 90 locates into the bore 172, the bottom surface 170 of the head portion 154 engages the ledge 150 between the counterbore 132 and the window opening 124. Similarly, the arcuate ends 168 of the proximal head 154 engage the inner radial engaging surface 136 of the counterbore 132. The proximal head portion 154 may then be rotated from the position shown in FIG. 7 into a substantially parallel orientation with the axis A of the differential 26 as illustrated in FIG. 8 until the throughbore 164 aligns with the mounting passages 140 of the raised flanges 142 on the cylindrical boss 128. During rotation of the proximal head portion 154, the inner radial engaging surface 136 pilots the arcuate ends 168 of the proximal head portion 154. Concurrently, the ledge 150 maintains the cross pin assembly 90 at the proper depth and assures that the throughbore 164 will be properly aligned with the mounting passages 140 of the raised flanges 142 on the cylindrical boss 128.
With the throughbore 164 and the mounting passages 140 aligned to one another, the fastener 146 may be inserted and secured. With the cross pin assembly 90 thus installed, relative movement between the cross pin assembly 90 and the differential casing 40 is essentially inhibited. As a result, the endplay of the axle shafts 44 and 46 (FIG. 1) may be controlled within desirable tolerances as a function of the diameter of the intermediate portion 158 of the cross pin 90. The spacer 86 is disposed between the sidegears 68a and 68b and controls axial endplay of the sidegears 68a and 68b to keep the differential 26 from binding. The cross pin 90 does not touch the spacer 86 in an assembled condition. The passage 92 in the spacer 86 defines a greater diameter than the diameter of the cross pin 90. In this way, two distinct components are used to control the side gear endplay (namely, the spacer 86), and the axle shaft endplay (namely, the cross pin 90). Such an arrangement allows for a desired amount of side gear endplay without affecting the axle shaft endplay.
The mass of the differential assembly 26 may be distributed to provide rotational balance. Specifically, the mass of the cylindrical boss 128 and the cross pin head 154 cooperate with the mass of the differential casing 40 around the pinion bores 110–116 and the mass of the pinion gears 100–106 to provide a rotationally balanced differential assembly 26. Stated another way, the mass of the several components of the differential assembly 26 are distributed about the rotational axis A so as to minimize or eliminate imbalance when the differential assembly 26 is rotated about the rotational axis A. It is appreciated that a counter weight may additionally, or alternatively be incorporated onto the differential casing 40 or the end cap 50 of the differential assembly 26.
The fastener 146 may be configured the same as an open differential such that the same axle assembly lines may be ran with both open differentials and helical gear differentials without changing tooling or torque wrench settings.
Turning now to FIG. 9, a differential assembly 226 according to other features is shown. The differential assembly 226 incorporates like components as the differential assembly 26 and are identified with a 200 prefix. The differential assembly 226 includes a cross pin 290 having an intermediate shank portion 258 and a distal end portion 262. The cross pin 290 may be adapted to be retained in the differential case 240 by a retaining disk 234. Specifically, the proximal end of the cross pin 290 may be adapted to recess into a counterbore 238 formed on an inboard surface of the retaining disk 234. A retaining ring 244 may be adapted to seat into a radial lip 248 arranged on the counterbore 232 in an assembled position.
With reference now to FIG. 10, a differential assembly 326 according to additional features is shown. The differential assembly 326 incorporates like components as the differential assembly 26 and are identified with a 300 prefix. The differential assembly 326 includes a cross pin 390 having an intermediate shank portion 358 and a distal end portion 362. The cross pin 390 may be adapted to be retained in the differential case 340 by an L-plate 334 and a fastener 341. Specifically, a proximal end of the cross pin 390 may be adapted to pass through an opening 338 arranged on the L-plate 334. In this way, the L-plate cooperates with the cross pin 390 to maintain the cross pin 390 in a substantially perpendicular orientation with axis A. The fastener 341 may be adapted to be secured through passages 348 incorporated in flange portions 332 and a passage 335 arranged in the L-plate 334. As a result, in an installed position, the fastener 341 bounds the proximal end of the cross pin 290 and maintains the cross pin 290 in an installed position.
With reference now to FIG. 11, a differential assembly 426 according to additional features is shown. The differential assembly 426 incorporates like components as the differential assembly 26 and are identified with a 400 prefix. The differential assembly 426 includes a cross pin 490 having an intermediate shank portion 458 and a distal end portion 462. The cross pin 490 may be adapted to be retained in the differential casing 440 by a fastener 441. Specifically, the fastener 441 may be adapted to be secured through passages 448 incorporated in flange portions 432 and a passage 435 arranged in the cross pin 490.
An access passage 426 may be incorporated in the differential casing 440 and defines an access for installing C-clips 92 (FIG. 3). A spacer 486 according to additional features includes a passage 492 for accepting the cross pin 490 therethrough in an assembled position. The spacer 486 may be adapted to be installed into the differential casing 440 axially and be positioned between side gears as described herein.
While the disclosure has been described in the specification and illustrated in the drawings with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this disclosure, but that the disclosure will include any embodiments falling within the foregoing description and the appended claims.

## Claims

1. An axle assembly for a vehicle comprising:
a differential casing rotatable about an axis, the differential casing including a first pin aperture;
a pair of side gears disposed within the differential casing;
a pair of axle shafts, each axle shaft being coupled for rotation with one of the side gears;
a spacer disposed between the side gears, the spacer having a second pin aperture; and
a cross pin received into the first and second pin apertures, wherein receipt of the cross pin into the first pin aperture fixedly but removably couples the cross pin to the differential casing, and wherein a size of the second pin aperture is greater than a corresponding size of the cross pin such that the spacer is moveable along the rotational axis of the differential casing relative to the cross pin;
wherein the cross pin limits movement of the axle shafts in a direction toward one another and the spacer limits movement of the side gears toward one another independently of the cross pin.

2. The axle assembly of claim 1, wherein the spacer is a generally U-shaped structure.

3. The axle assembly of claim 1, wherein the cross pin includes an intermediate shank portion and an end portion, the intermediate shank portion having a tapered portion that is received into the second pin aperture.

4. The axle assembly of claim 3, wherein the cross pin further includes a head portion that is releasably coupled to the differential case.

5. The axle assembly of claim 3, wherein the end portion has a diameter that is less than or equal to a diameter of the intermediate shank portion.

6. An axle assembly for a vehicle comprising:
a differential casing rotatable about an axis, the differential casing including a first pin aperture;
a pair of side gears disposed within the differential casing;
a pair of axle shafts, each axle shaft being coupled for rotation with one of the side gears;
a spacer disposed between the side gears, the spacer having a second pin aperture; and
a cross pin received into the first and second pin apertures;
wherein receipt of the cross pin into the first pin aperture fixedly but removably couples the cross pin to the differential casing, and wherein a size of the second pin aperture is greater than a corresponding size of the cross pin such that a void space is disposed between the spacer and the cross pin regardless of a position of the side gears axially along the rotational axis.

7. The axle assembly of claim 6, wherein the spacer is a generally U-shaped structure.

8. The axle assembly of claim 6, wherein the differential casing defines an assembly window and first, second, third and fourth pairs of pinion bores, the assembly window being formed between the first and fourth pair of pinion bores, the second pair of pinion bores being radially offset an equivalent distance from the first and third pair of pinion bores, and the third pair of pinion bores being radially offset an equivalent distance from the second and fourth pair of pinion bores.

9. The axle assembly of claim 6, wherein the cross pin includes an intermediate shank portion and an end portion, the intermediate shank portion having a tapered portion that is received into the second pin aperture.

10. The axle assembly of claim 9, wherein the end portion has a diameter that is less than or equal to a diameter of the intermediate shank portion.

11. The axle assembly of claim 9, wherein the cross pin further includes a head portion that is releasably coupled to the differential case.

12. The axle assembly of claim 6, the differential casing defines, a first set of pinion bores, a second set of pinion bores, a third set of pinion bores, a fourth set of pinion bores and an assembly window, each of the first, second, third and fourth sets of pinion bores including a first bore and a second bore, each of the first and second bores having a center, wherein a first angle between the centers of the first bores in the first and second sets of pinion bores is approximately equal to a second angle between the centers of the first bores in the third and fourth sets of pinion bores and wherein a third angle between the first bores in the second and third sets of pinion bores is smaller than a fourth angle between the first bores in the first and fourth sets of pinion bores.

13. The axle assembly of claim 12, wherein the third angle is approximately equal to the first angle.

14. The axle assembly of claim 13, wherein the first angle is about 70° to about 80°.