GB2193274A

GB2193274A - Two speed drive axle assembly

Info

Publication number: GB2193274A
Application number: GB08714421A
Authority: GB
Inventors: John Daryl Russell
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 1986-07-30
Filing date: 1987-06-19
Publication date: 1988-02-03
Anticipated expiration: 2007-06-19
Also published as: MX168973B; GB8714421D0; ES2007672A6; BR8703748A; GB2193274B; AR240960A1; AR240960A2

Abstract

An improved two-speed drive axis assembly (10) of the sliding clutch gear (60) type is provided. The interengageable clutch teeth (62A, 64A), utilized to engage the low speed mode of operation of the drive axle assembly are modified by utilizing a backlash one-and-six tenths (1.6) to two (2.0) times greater than the normally utilized backlash for providing smoother and quicker engagement of the low speed ratio and allowing utilization of a more compact lower force actuator (70) to reduce wear and tear on the interengageable low speed clutch teeth. <IMAGE>

Description

SPECIFICATION Improved two-speed drive axle clutch structure BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the clutch structure of a two-speed drive axle and, in particular, to an improved clutch structure for a two-speed drive axle comprising a sliding clutch gear selectively engagable with either a high speed clutch member or a low speed clutch member.

More particularly, this invention relates to improved clutch tooth structure for the low speed clutch member and the sliding clutch gear interengagable clutch teeth.

Description of the Prior Art Two-speed drive axles of the type comprising a sliding gear selectively axially shiftable from a first position, wherein a first set of clutch teeth carried thereby are engaged with the clutch teeth of a low speed clutch member, to a second position, wherein a second set of clutch teeth carried thereby are interengaged with the clutch teeth of a high speed clutch member, are well known in the prior art and commercially successful. Examples of such two-speed drive axles may be seen by reference to United States Patent Nos.

3,503,280; 3,502,177; 3,358,517 and 3,265,173; the disclosures of which are hereby incorporated by reference.

While the prior art two-speed drive axles of the sliding clutch gear type are commercially successful, under certain circumstances, engagement of the clutch members, especially of the low speed clutch member by the sliding clutch gear, was not as quickly and smoothly accomplished, especially by less skilled vehicle operators, as desired which resulted in the requirement for larger than desired actuators and/or greater than desired wear and/or damage to the interengagable clutch teeth.

The use of a clutch structure in a change gear transmission having five to fifteen times greater than the normal 0.006 inch (0.015 cm) backlash to proyide quicker, less wear inducing shifts in a blocked resiliently biased, preselect shift type clutch is known in the prior art and disclosed in U.S. Patent No.

4,375,172, the disclosure of which is hereby incorporated by reference.

While the ten times greater than normal (0.006 inch) increased backlash structure disclosed in above-mentioned U.S. Patent No.

4,375,172 is very effective for a resiliently biased, preselect type of blocked change gear transmission, such a structure is not especially well suited for use in two-speed drive axles of the sliding clutch gear type.

SUMMARY OF THE INVENTION In accordance with the present invention, the drawbacks of the prior art are minimized or overcome by the provision of a two-speed drive axle of the sliding clutch gear type wherein selection of low speed (i.e. engagement of the low speed clutch member by the sliding clutch gear) is simplified and accomplished in a quicker and smoother manner, and/or using more compact actuators, than heretofore possible.

The above is accomplished by increasing the backlash between the clutch teeth carried by the low speed clutch member and the corresponding interengageable clutch teeth carried by the sliding -3clutch gear one-and-six-tenths (1.6) to two (2.0) times, preferably about oneand-eight-tenths (1.8) times, greater than the normal about 0.030 inch (0.076cm) backlash.

Accordingly, it is an object of the present invention to provide a new and improved twospeed drive axle utilizing an improved low speed clutch structure.

These and other objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment taken in view of the accompany drawings.

DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of a two-speed drive axle assembly.

Figure 2 is a fragmentary sectional view of a sliding clutch gear and a low speed clutch member in the disengaged position.

Figure 3 is a fragmentary view of a sliding clutch gear and low speed clutch member in the engaged position.

Figure 4 is an enlarged fragmentary sectional view of the clutch teeth of the low speed clutch member and the interengaged clutch teeth of the sliding clutch gear.

DESCRIPTION OF THE PREFERRED EMBODI MENT Certain terminology will be used in the following description for convenience and reference only and will not be limiting. The words "upwardly", "downwardly", "rightwardly" and "leftwardly" will designate directions in the drawings to which reference is made. The terms "inwardly", and "outwardly", will refer to directions towards and away from, respectively, the geometric center of the device at designated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof, and words of similar import.

The term "backlash" is the amount by which the width of a tooth space exceeds the thickness of the engaging tooth on the pitch circles.

The structure and the function of two-speed drive axles, and in particular two-speed drive axles of the sliding clutch gear type, are well known in the heavy duty vehicle industry, as well as in the prior art, and may be appreci ated by reference to above-mentioned United States Patent Nos. 3,503,280; 3,502,177; 3,358,517 and 3,265,173. A typical sliding clutch gear type two-speed drive axle 10 may be seen by reference to Figures 1-3.

Two-speed, planetary drive axle 10 comprises a housing 12 on the forward portion of which a bearing cage assembly 14 rotatably mounts a driven shaft 16 having an integral bevel pinion 18. The bearing cage assembly 14 is mounted on the housing 12 as by bolts 20. Splined to the outer or forward end of driven shaft 16 is a flange coupling or yoke 22, which provides a driving connection to an engine driven propeller shaft (not shown).

As disclosed in United States Patent No.

2,882,752, the disclosure of which is hereby incorporated by reference, power comes through the bevel pinion 18 and is transferred to a bevel drive gear 24, a reduction in rotational speed taken place in this transfer. It is understood, that although a pinion gear 18 and ring gear 24 of the spiral gear bevel type is illustrated, the present invention is also equally applicable to drive axles utilizing hypoid or other types of gearing suitable for a pinion-ring gear meshing engagement.

Ring gear 24 has integral internal gear teeth 26 which are in constant mesh with idler pinions or internal gears 28, of which there are a plurality usually four (4). Ring gear 24 is non-rotatably mounted to a gear support case 30 by means of bolts 32. Rotatably mounted within the gear support case 30, is a rotatable differential cage 34, which comprises a pair of cage halves clamped together by bolt means 36. High speed clutch plate, or clutch member, 38, having internal gear/clutch teeth 40 is supported on the differential case 34 by pin means 42 and therefor rotates at the rotational speed of the differential case 34. The idler pinions or planetary gears 28, fit into the left hand portion of the differential case 34 and are carried by idler pins 44 mounted between the differential case 34 and the high speed clutch plate 38.Gear support case 30 is supported for rotation in housing 12 by means of bearings 46.

Nonrotatably mounted within the differential case 34 is a differential spider 48 which mounts, on its spaced arms, a plurality of bevel pinion gears 50 in constant mesh with both bevel side gears 52 and 54. The side gears 52 and 54 are entirely splined to drivingly engage the splined ends of axle shafts 56 and 58, respectively, and, as disclosed in United States Patent No. 2,882,752, the disclosure of which is hereby incorporated by reference, power is delivered to the wheels through the axle shafts after passing through the planetary gears and differential housing in gear support casing 30.

Sliding clutch gear or sun gear member 60, is mounted about axle shaft 58 for axial movement thereon. The sliding clutch gear 60 is provided with external outer teeth 62 for meshing engagement with internal clutch teeth 64 of a brake plate or clutch member 66. As will be described in greater detail below, clutch teeth 64 are engaged with clutch teeth 66 to provide the low speed operation (i.e.

greatest speed reduction between input shaft 16 and axle shaft 58 and 56) and thus, clutch plate 66 is the low.speed clutch plate or clutch member. Low speed clutch plate 66 is non-rotatably mounted to stationary housing 12. The sliding clutch gear 60 is also provided with a second set of external clutch/gear teeth 68 for meshing engagement with the internal clutch teeth 40 provided on the high speed clutch plate 38, which is rotationally fixed to differential casing 34. The external clutch/gear teeth 68 are constantly meshed with the pinion gears 28 and define the sun gear member of the planetary system comprising ring gear teeth 26, planetary pinion gears 28 and sun gear 68.As is shown in Figures 1 and 3, external clutch teeth 62 of the sliding sun/clutch gear 60 are in meshing engagement with teeth 64 of the low speed clutch plate 66 and thus, the sun gear 68 is held rotationally fixed relative to the housing 12. With the sun gear 68 held stationary, the idler pinions or planetary gears 28 revolve on pins 44 because they are meshed with teeth 68 of the sun gear, the planetary gears will walk around the sun gear 68. In doing so, the planetary gears 28 will carry the differential case 34 with them, since pins 44 are fitted into the differential case. A second gear reduction gear takes place, (the first gear reduction being between the bevel pinion and ring gear as described hereinabove, between the ring gear and the differential which in turn drives the axle shaft 56 and 58.Accordingly, with clutch teeth 62 of the sliding clutch gear engaged with clutch teeth 64 of the low speed clutch plate, as shown in Figure 1, a secondary reduction between the input pinion and the differential is accomplished and this is referred to as the low speed condition of twospeed axle 10.

A shifting mechanism, generally indicated at 70, is provided to effect axial shifting of the sliding clutch gear 60. The shifting mechanism 70 comprises a pivotabie shift fork 72 engaged with a groove 74 provided in the sliding clutch gear 60 and can be actuated by conventional air, hydraulic, electric or air/electric shift control systems. Such shifting arrangements are disclosed in United States Patent Nos. 3,146,842; 3,373,831; 3,358,517; 4,428,248 and 4,550,625, the disclosures of which are hereby incorporated by reference.

As shown in Figure 2, the sliding clutch gear 60 may be shifted leftwardly relative to housing 12 whereby the clutch teeth 62 of the sliding clutch gear 60 are disengaged from the internal teeth 64 of low speed clutch plate 66, and the clutch/gear teeth 68 are interen gaged with the internal teeth 40 on the high speed clutch plate 38. In this position, the high speed position of two-speed drive axle 10, the sliding clutch gear is free to rotate relative to housing 12 while the sun gear 68 is rotationally fixed to the differential housing 34 which acts as a lock on the idler pinions or planetary gears 28 and they cannot rotate about pins 44. In fact, in this position, the ring gear 24, the support case 30, the planetary gears 28 and the differential case 34 are locked together for joint rotation as a unit.In this high speed condition, the power is transmitted from the ring gear 24 directly to the differential gears and from there to the axle shaft with only one reduction, between the pinion gear 18 and ring gear 24 taking place.

Preferably, the interengagable low speed clutch teeth 62 and 64, and interengagable high speed clutch teeth 68 and 40, are provided with the leading edge surfaces inclined at a surface of about thirty five degrees (35 ) relative to the axis of rotation thereof for the reasons set forth in above-mentioned United States Patent No. 3,265,173.

The above defined structure of two-speed drive axle 10 is well known in the prior art, and in wide use in the heavy duty truck industry. As discussed above, the object of the present invention is to provide a more quickly smoothly engaged low speed clutch structure for the low speed clutch members allowing the low speed to be engaged more easily, by smaller more compact actuators, and with less wear and tear on the clutching member. The above is accomplished by utilizing the structure iliustrated in Figure 4. In Figure 4, elements having substantially the same function and similar structure as the elements described in connection with two-speed axle 10 will be assigned the same reference numeral with an "A" appended thereto.

Referring now to Figure 4, a portion of modified low speed clutch plate or clutch member 66A and modified sliding clutch gear 60A is iilustrated. The interengagable teeth 64A and 62A are configured such that the-backlash therebetween is substantially greater than the normally utilized 0.030 inch backlash in the prior art two-speed drive axle sliding clutch gear structures.It has been found, that by increasing the backlash to one-and-sixtenths (1.6) to two (2) times greater than normal backlash (.048 inch to .060 inch (0.122 cm to 0.152 cm)), preferably one-and-eighttenths (1.8) times normal backlash (0.054 inch (0.137 cm)), that quicker axle change gear response time when changing from high speed range to low speed range the use of more compact lower force change gear actuators (which reduces wear and damage of the interengagable range gear clutch teeth), and improved quality and easier synchronization by less skilled operators is achieved.

To accomplish an axle downshift, the sliding clutch gear must be slowed from rotating with the ring gear 24 in high speed to being at zero rotation relative to the housing 12 for synchronization of the low speed clutch teeth 62 and 64. The vehicle operator selects a downshift (i.e. low speed) and either quickly releases and depresses the accelerator or retains the accelerator depressed and quickly disengages and reengages the vehicle master clutch. The above procedures break torque, allowing the high speed clutch, 68 and 40, to disengage and then speeds up the idlers 28 which will cause a reversing of rotation reaction upon the sliding clutch gear 60 engaged therewith. As the speed of rotation of the sliding clutch gear slows and/or actually begins to reverse, teeth 62 and 64 will achieve a substantial synchronous condition and may be engaged.

By increasing the backlash between the low speed interengagable clutch teeth, 62A-64A, in the specific manner set forth above, the window of substantial synchronization is increased sufficiently to provide a noticeably quicker and more easily accomplished positive clutch engagement while not causing an unacceptable weakening of the clutch teeth nor permitting the clutch members to engage at nonsynchronous conditions sufficient to cause undesirably harsh engagement of and/or damage to the clutch teeth.

While the specific embodiment of the invention has been set forth illustrative purposes, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes and the details of construction and combination of arrangement of the parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter

Claims

claimed. CLAIMS

1. A two-speed drive axle assembly (10) comprising a support housing (12), an axle input pinion gear (18), a pair of axle shafts (5658), a ring gear assembly (24, 30) in meshing engagement with said input pinion and supported by said housing, separate differential side gears (52, 54) fixedly mounted on each of said axle shafts, a differential carrier assembly (34) differential pinion gears (50) rotatably mounted on said carrier assembly and in meshing engagement with said differential side gears, spaced planet pinions (28) rotatably mounted on said carrier assembly, on annulus gear assembly (26) rotatably fixed to said ring gear assembly and in meshing engagement with said planet pinions, a sliding clutch gear (60) carrying sun gear teeth (68) fixed thereto and constantly meshed with said pinion gears and having a first set of clutch teeth (62) engagable with low speed clutch teeth (64) carried by a slow speed clutch member (66) ro tatably fixed to said housing and a second set of clutch teeth (68) engagable with high speed clutch teeth (40) carried by a high speed clutch member (38) rotationally fixed to said differential carrier, and shift means (70) for axially moving said sliding clutch gear to a low speed position, wherein said first set of clutch teeth are engaged with said low speed clutch teeth and said second set of clutch teeth are disengaged from said high speed clutch teeth or to a high speed position wherein said first set of clutch teeth are disengaged from said low speed clutch teeth and said second set of clutch teeth are engaged to said high speed clutch teeth, said assembly characterized in that; the backlash between the clutch teeth (62A, 64A) of the low speed clutch members (60A, 66A) are in the range of one-and-six-tenths to two times greater than the about 0.030 inch (0.076 cm) backlash normally utilized with the axially interengagable clutch members (60, 66) for engaging the low speed of two-speed drive axles.

2. The drive axle assembly of claim 1, wherein said backlash is about one-and-eighttenths greater than the about 0.030 inch (0.076 cm) backlash normally utilized to engage the low speed of a two-speed drive axle.

3. The improved drive axte assembly of claim 1, wherein said backlash between said interengagable clutch teeth is in the range of 0.048 inches (0.122 cm) and 0.060 inches (0.152 cm).

4. The drive axle assembly of claim 3, wherein said backlash is about 0.054 inches (0.137 cm).

5. The improved drive axle assembly of claim 4, wherein said sun gear teeth and said second set of clutch teeth are integral.

6. The drive axle assembly of claim 4, wherein the leading edges of said interengagable teeth are inclined at a angle of about 35 with respect to the axes of rotation of said sliding clutch gear.

7. A two-speed drive axle assembly substantially as hereinbefore described with reference to Figure 4 in conjunction with the other Figures of the accompanying drawings.