U.S. patent application number 14/719804 was filed with the patent office on 2016-11-24 for hub reduction gear of an axle.
The applicant listed for this patent is Meritor Heavy Vehicle Systems Cameri SpA. Invention is credited to Wagner Yukio Hirao.
Application Number | 20160341292 14/719804 |
Document ID | / |
Family ID | 55968971 |
Filed Date | 2016-11-24 |
United States Patent
Application |
20160341292 |
Kind Code |
A1 |
Hirao; Wagner Yukio |
November 24, 2016 |
Hub Reduction Gear of an Axle
Abstract
A hub reduction gear of a drive axle and a method of providing a
hub reduction gear. The hub reduction gear may include a plurality
of bevel planet gears in mesh with a bevel sun gear, a planet
carrier adapted to drive a vehicle wheel; and an internal bevel
gear annulus in mesh with the bevel planet gears and adapted for
connection to an axle side shaft casing.
Inventors: |
Hirao; Wagner Yukio;
(Rochester Hills, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Meritor Heavy Vehicle Systems Cameri SpA |
Cameri (Novara) |
|
IT |
|
|
Family ID: |
55968971 |
Appl. No.: |
14/719804 |
Filed: |
May 22, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60K 17/046 20130101;
B60K 17/08 20130101; F16H 37/082 20130101; B60K 17/165 20130101;
F16H 1/2854 20130101; F16H 3/50 20130101 |
International
Class: |
F16H 37/08 20060101
F16H037/08; B60K 17/16 20060101 B60K017/16; B60K 17/08 20060101
B60K017/08; F16H 1/28 20060101 F16H001/28; F16H 3/50 20060101
F16H003/50 |
Claims
1. A drive axle comprising: a hub reduction gear that includes: a
bevel sun gear that is rotatable about an axis and is adapted to be
driven by an axle side shaft; a plurality of bevel planet gears in
mesh with the bevel sun gear; a planet carrier adapted to drive a
vehicle wheel; and an internal bevel gear annulus in mesh with the
bevel planet gears and adapted for connection to an axle side shaft
casing, wherein the internal bevel gear annulus is an internal gear
having teeth that face toward the axis in which a radially
outermost portion of each tooth is disposed further from the axis
and from a plane of rotation than a radially innermost portion of
each tooth, wherein the plane of rotation is disposed perpendicular
to the axis and is disposed proximate a side of the internal bevel
gear annulus that is disposed opposite the teeth.
2. The drive axle of claim 1 having a reduction ratio in a range of
3:1 to 6:1.
3. The drive axle of claim 1 wherein the plurality of bevel planet
gears has straight teeth.
4. The drive axle of claim 3 wherein the plurality of bevel planet
gears has a plurality of teeth in a range of 15-30.
5. The drive axle of claim 1 wherein the bevel sun gear has
straight teeth.
6. The drive axle of claim 5 wherein the bevel sun gear has a
plurality of teeth in a range of 14-20.
7. The drive axle of claim 1 wherein the internal bevel gear
annulus has straight teeth.
8. The drive axle of claim 7 wherein the internal bevel gear
annulus has a plurality of teeth in a range of 40-70.
9. The drive axle of claim 1 wherein teeth of the bevel sun gear,
plurality of bevel planet gears, and internal bevel gear annulus
are forged.
10. The drive axle of claim 1 wherein a pitch angle of the bevel
sun gear is in a range of 5-30.degree..
11. The drive axle of claim 1 wherein a pitch angle of the
plurality of bevel planet gears is in a range of 20-45.degree..
12. The drive axle of claim 1 wherein a pitch angle of the internal
bevel gear annulus is in a range of 90.01.degree.-150.degree..
13. The drive axle of claim 1 further comprising a second axle side
shaft disposed opposite the axle side shaft, wherein the axle side
shaft is connected to the bevel sun gear of the hub reduction gear
and the second axle side shaft is connected to a sun gear of a
second hub reduction gear and a first side shaft housing that is
connected to the internal bevel gear annulus, and a second side
shaft housing that is disposed opposite the first side shaft
housing and is connected to a second internal bevel gear annulus of
the second hub reduction gear.
14. The drive axle of claim 13 further comprising a differential
gear between the axle side shaft and the second axle side
shaft.
15. The drive axle of claim 13 further comprising a first brake
drum connected to the planet carrier of the hub reduction gear and
a second brake drum connected to a planet carrier of the second hub
reduction gear.
16. A method of providing a hub reduction gear for a vehicle drive
axle, the hub reduction gear having a ratio selectable in a range
of 1.5:1 to 6:1, the method comprising: providing a bevel sun gear
that is rotatable about an axis; providing a plurality of bevel
gears for each ratio in the range, wherein the plurality of bevel
gears mesh with the bevel sun gear and are rotatable about planet
gear axes that are disposed at an angle that is non-perpendicular
and non-parallel with respect to the axis, the plurality of bevel
gears including an internal bevel gear annulus for ratios in the
range of 3:1 to 6:1, wherein the internal bevel gear annulus is an
internal gear having teeth that face toward the axis in which a
radially outermost portion of each tooth is disposed further from
the axis and from a plane of rotation than a radially innermost
portion of each tooth, wherein the plane of rotation is disposed
perpendicular to the axis.
17. The method of claim 16 wherein the plurality of bevel gears
have straight teeth.
18. The method of claim 17 wherein the straight teeth are
radial.
19. The method of claim 17 and comprising direct forging of the
teeth of the plurality of bevel gears.
20. The method of claim 16 wherein the vehicle drive axle includes
opposing side shafts, each side shaft being connected to a bevel
sun gear of a respective hub reduction gear.
21. A drive axle comprising: a hub reduction gear that includes: a
bevel sun gear that is rotatable about an axis and is driven by an
axle side shaft that extends through a side shaft housing; a planet
pin support that is disposed on the axle side shaft between the
bevel sun gear and the side shaft housing, wherein the planet pin
support is spaced apart from the side shaft housing and the bevel
sun gear; a plurality of bevel planet gears in mesh with the bevel
sun gear wherein the plurality of bevel planet gears are rotatable
about planet gear axes that are disposed in a non-perpendicular
angle with respect to the axis; a planet carrier adapted to drive a
vehicle wheel; and an internal bevel gear annulus in mesh with the
bevel planet gears and adapted for connection to an axle side shaft
casing, wherein the internal bevel gear annulus is an internal gear
having teeth that face toward the axis in which a radially
outermost portion of each tooth is disposed further from the axis
and from a plane of rotation than a radially innermost portion of
each tooth, wherein the plane of rotation is disposed perpendicular
to the axis.
Description
TECHNICAL FIELD
[0001] This invention relates to a hub reduction gear of an axle,
in particular an axle of a heavy vehicle such as a truck.
BACKGROUND
[0002] In order to effectively harness the output of an internal
combustion engine, motor vehicles are typically provided with a
gear transmission having a plurality of speed ratios. In use, these
speed ratios are selected one by one in a progressive manner, and
allow a vehicle to be provided with a desirable balance of
acceleration, cruising speed and fuel economy. Typically a driven
axle of a heavy vehicle also provides a fixed speed ratio whereby
the input (propeller shaft) speed is reduced via a pinion and crown
wheel, so that the output (side shaft) speed is lower; this further
ratio reduction may be in the range 3:1 to 5:1.
[0003] In some cases, the fixed ratio speed reduction provided in
the rear axle is insufficient, particularly in the case of heavy
vehicles that are required to move slowly in a controllable manner
within a useful range of engine speed. Generally speaking it is not
desirable to provide a greater speed reduction at the crown wheel
and pinion, because either the pinion becomes too small to transmit
the required torque, or the crown wheel is so large that ground
clearance is insufficient.
[0004] In order to address this problem it has been proposed to
provide hub reduction gearing at the wheel ends of an axle.
Typically an epicyclic gear set is incorporated in each wheel hub,
whereby the sun gear is driven by the respective side shaft, the
annulus is connected to the axle (side shaft) casing, and the
planet carrier is coupled to the rotatable output components,
namely the wheel hub, brake drum and road wheel.
[0005] A compact hub reduction gear can be incorporated at each end
of an axle, in particular where double wheels are provided, and may
also allow the crown wheel and pinion ratio to be reduced, thus
permitting a more robust pinion and a smaller diameter crown
wheel.
[0006] The epicyclic gears of a hub reduction gear may comprise
cylindrical gears. This arrangement is axially compact but is
radially confined by the aperture in the center of the
corresponding vehicle wheel. For this reason, and also to ensure
that pinion gears have adequate strength, the range of hub
reduction ratios available is approximately in the range 3:1 to
6:1.
[0007] An alternative cylindrical gear arrangement, with the
annulus driven by the respective side shaft, can give a ratio range
of about 1.2:1 to 1.5:1. Thus cylindrical gears do not provide a
continuous spread of hub reduction ratios.
[0008] It is also possible to provide a hub reduction gear with
conventional bevel gears. This arrangement is radially compact as
compared with cylindrical gears, but takes up more axial space. For
practical reasons of pinion size, the available range of hub
reduction ratios using conventional bevel gears is about 1.5:1 to
3:1.
[0009] It will be appreciated from the foregoing that the full
range of desirable speed reduction ratios cannot be provided by
either cylindrical gears or bevel gears. On the other hand it is
not desirable to have two different kinds of hub reduction gear
with substantially different radial and axial space
constraints.
[0010] Accordingly it would be advantageous to expand the ratio
range of one or other of the known hub reduction gears in order to
facilitate drive axles which have more components in common.
SUMMARY
[0011] According to the invention there is provided a hub reduction
gear of an axle, and comprising a bevel sun gear adapted to be
driven by an axle side shaft, a plurality of bevel planet gears in
mesh with the bevel sun gear, a planet carrier adapted to drive a
vehicle wheel, and an internal bevel gear annulus in mesh with the
bevel planet gears and adapted for connection to an axle side shaft
casing.
[0012] By internal bevel gear, we mean an internally dished gear in
which a radially outer tooth portion is relatively higher than a
radially inner tooth portion.
[0013] The use of an internal bevel gear allows an increase in the
range of hub reduction bevel gear ratios to 6:1, which ratio range
could previously only be provided by cylindrical gears. Accordingly
the full range of bevel gear hub reduction ratios, incorporating
the invention, is about 1.5:1 to 6:1.
[0014] Advantageously the bevel gears have straight teeth, and can
thus be formed by precision forging.
[0015] Other features of the invention will be apparent from the
accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Other features of the invention will be apparent from the
following description of several embodiments illustrated by way of
example only in the accompanying drawings, in which:
[0017] FIG. 1 illustrates an exemplar off-highway truck, in side
elevation.
[0018] FIG. 2 illustrates in plan an exemplar drive axle for the
truck of FIG. 1.
[0019] FIG. 3 illustrates in axial section a schematic
representation of a prior art hub reduction gear incorporating
cylindrical gear wheels.
[0020] FIG. 4 illustrates in axial section a hub reduction gear
according to the invention.
[0021] FIG. 5 illustrates another hub reduction gear according to
the invention.
[0022] FIG. 6 is a comparative table of some different reduction
ratios achievable by use of the invention.
DETAILED DESCRIPTION
[0023] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
invention.
[0024] FIG. 1 illustrates an exemplar off-highway quarry truck 10
of a kind for which a hub reduction gear may be provided. The truck
comprises a driver's cab 11, an open body 12 for stone or other
quarry material, a front steering axle 13, two rear drive axles 14,
15, and vehicle wheels 16. Such a truck is typically required to
carry heavy loads over rough terrain at low speeds, and for this
reason engine speed must be reduced by suitable gearing to achieve
the desired wheel speed.
[0025] The truck 10 may typically use a conventional internal
combustion engine and change speed gear transmission with drive
output to rear axles via an open propeller shaft. At the rear axle,
drive is divided to the rear wheels via a conventional differential
gear incorporating speed ratio reduction via a crown wheel and
pinion. To achieve a greater speed ratio reduction, a reduction
gear is provided in each wheel hub.
[0026] Other kinds of truck and wheeled vehicle may also
incorporate hub reduction gears.
[0027] FIG. 2 illustrates a typical drive axle 20 in plan. An axle
casing 21 incorporates a conventional differential gear with crown
wheel and pinion (not shown). Drive input is via a propeller shaft
22 and universal joint 23, which provides for axle suspension
movement relative to the vehicle chassis.
[0028] Opposed side shaft housings 24, which may also be referred
to as side shaft casings, may incorporate and support respective
rotatable side shafts (not shown), which terminate in respective
wheel hubs. Each hub typically comprises a brake drum 25 from which
threaded studs protrude for attachment of vehicle wheels 16.
[0029] Typically the drive axis 27 of the propeller shaft on the
longitudinal axis of the vehicle, and orthogonal to the axis of
rotation 28 or drive axis of the drive axle 20. The side shafts are
usually of the same axial length, but in some circumstances the
axle casing may be offset to one side.
[0030] FIG. 3 illustrates schematically a prior art hub reduction
gear 30 comprising cylindrical gear wheels. A side shaft housing
24, forming one side of a drive axle, contains within a rotatable
side shaft 31 supported by bearings (not shown). The axis of
rotation 28 of the side shaft 31 is illustrated.
[0031] A cylindrical sun gear 32 is rotatable with the side shaft
31, and meshes conventionally with a plurality of equispaced planet
wheels 33, which in turn mesh with a cylindrical ring gear or
annulus 34. The annulus 34 is fixed to the side shaft housing 24
and thus relatively unmovable.
[0032] The usual planet carrier 35, on which the planet wheels 33
are rotatable, is coupled to an output element 36 of the reduction
gear. The output element 36 is typically a vehicle brake drum or
other rotatable hub member which is in turn connected to a driving
wheel of the vehicle.
[0033] In use rotation of the side shaft 31 and sun gear 32 causes
the planet wheels 33 to rotate within the (fixed) annulus 34 and
thereby to turn the planet carrier 35 at a relatively reduced
speed. Cylindrical hub reduction gears allow a ratio reduction in
the range 3:1 to 6:1, but ratios of less than 3:1 are not possible
if gear tooth strength is to be sufficient.
[0034] As noted above, bevel gear hub reduction is also known, but
restricted to a ratio spread in the approximate range 1.5:1 to
3:1.
[0035] FIG. 4 illustrates a hub reduction gear 40 according to the
invention. A side shaft housing 24 of a drive axle contains within
a rotatable side shaft 31 supported by bearings (not shown). The
axis of rotation 28 is illustrated.
[0036] A bevel sun gear 41 is rotatable with the side shaft 31 and
meshes with one of a plurality of equispaced bevel planet wheels
42, which in turn mesh with a bevel ring gear or annulus 43. The
annulus 43 is fixed to the side shaft housing 24, and thus
relatively unmovable.
[0037] The usual planet carrier 44, in which the planet wheels 42
are rotatable via planet pins 45, is coupled to an output element
36, such as a wheel hub which is supported for rotation on the side
shaft housing 24 by taper roller bearings 46, 47. The wheel hub is
in use coupled to a vehicle driving wheel or wheels.
[0038] Also illustrated in FIG. 4 are the planet pin support 48, a
planet pin needle roller bearing 49, a sun gear thrust bearing 50,
a planet pinion thrust bearing 51 and a planet pinion thrust washer
52. Such support and thrust bearings may be required in the prior
art example of FIG. 1, but are omitted to improve clarity.
[0039] The bevel gear reduction gear of FIG. 2 is of relatively
lesser diameter than the cylindrical reduction gear of FIG. 1, but
relatively longer in the direction of the axis of rotation 28.
[0040] In use, rotation of the side shaft 31 and sun gear 41 causes
the planet wheels 42 to rotate within the (fixed) annulus 43, and
thereby to turn the planet carrier 44 at a relatively reduced
speed.
[0041] The annulus 43 is an internal bevel gear, in which the
radially outermost portion 53 of each tooth has a greater height
than the radially innermost portion 54 of each tooth, thus giving
the bevel gear a dished appearance from the gear tooth side, by
reference to the plane of rotation 55.
[0042] In an embodiment of the invention, each bevel gear tooth is
straight, that is to say each tooth extends radially at the dish
angle 56; such a tooth form may be forged and/or milled with
greater ease than a corresponding arcuate tooth, as may for example
be provided on a helical gear wheel. It will be understood that if
a straight tooth form is selected for the annulus 43, the sun gear
41 and each pinion are required to have a corresponding tooth form
for effective gear tooth meshing.
[0043] The internal bevel gear annulus 43 permits a wider range of
hub reduction ratios than previously available from an external
bevel gear annulus.
[0044] In the case of a hub reduction gear in which the sun gear is
driving, the annulus is fixed, and the output is from the planet
carrier, the reduction ratio is determined by the formula:
Ratio=1+N.sub.A/N.sub.S
[0045] where: [0046] N.sub.A is the number of teeth on the annulus
(ring) gear, and [0047] N.sub.S is the number of teeth on the sun
wheel.
[0048] The number of teeth on the planet wheel N.sub.P is selected
according to geometry of the reduction gear, but does not affect
gear ratio as such.
Example 1
[0049] A reduction ratio of 3:1 can be achieved using bevel gears
having the following number of teeth: [0050] N.sub.A=40 [0051]
N.sub.P=20 [0052] N.sub.S=20
[0053] In this case: [0054] the shaft angle between the rotational
axis of the sun gear and that of the planet pinions
SA.sub.SP=60.degree.; [0055] the shaft angle between the rotational
axis of the annulus and the planet pinions SA.sub.AP=120.degree.;
[0056] the pitch angle of the sun gear PA.sub.S=30.degree.; [0057]
the pitch angle of the planet pinions PA.sub.P=30.degree.; and
[0058] the pitch angle of the annulus PA.sub.A=90.degree..
Example 2
[0059] A reduction ratio of 3:1 can also be achieved using bevel
gears having the following number of teeth: [0060] N.sub.A=40
[0061] N.sub.P=15 [0062] N.sub.S=20
[0063] In this case: [0064] SA.sub.SP=48.19.degree. [0065]
SA.sub.AP=131.81.degree. [0066] PA.sub.S=27.75.degree. [0067]
PA.sub.P=20.44.degree. [0068] PA.sub.A=111.37.degree.
Example 3
[0069] A further example of a reduction ratio of 3:1 uses bevel
gears with the following number of teeth: [0070] N.sub.A=40 [0071]
N.sub.P=30 [0072] N.sub.S=20
[0073] In this case: [0074] SA.sub.SP=70.53.degree. [0075]
SA.sub.AP=109.47.degree. [0076] PA.sub.S=27.21.degree. [0077]
PA.sub.P=43.31.degree. [0078] PA.sub.A=66.16.degree.
[0079] Examples 1-3 illustrate that a desired reduction ratio can
be achieved in a number of ways, according to space constraints
imposed by the available design envelope within which the hub
reduction gear is to be contained.
Example 4
[0080] A reduction ratio of 6:1 can be achieved by using bevel
gears having the following number of teeth: [0081] N.sub.A=70
[0082] N.sub.P=30 [0083] N.sub.S=14
[0084] In this case: [0085] SA.sub.SP=21.039.degree. [0086]
SA.sub.PA=158.961.degree. [0087] PA.sub.S=6.657.degree. [0088]
PA.sub.P=14.383.degree. [0089] PA.sub.A=144.578.degree.
[0090] FIG. 5 corresponds to FIG. 4, and illustrates the
arrangement of Example 4, giving a reduction ratio of 6:1; other
axle components are omitted for reasons of clarity, but common
reference numerals are employed to identify equivalent parts.
Example 5
[0091] A reduction ratio of 4.5:1 can be achieved by using bevel
gears having the following number of teeth: [0092] N.sub.A=70
[0093] N.sub.P=30 [0094] N.sub.S=20
[0095] In this case: [0096] SA.sub.SP=33.557.degree. [0097]
SA.sub.PA=146.443.degree. [0098] PA.sub.S=13.328.degree. [0099]
PA.sub.P=20.230.degree. [0100] PA.sub.A=126.213.degree.
[0101] Examples 4 and 5 illustrate that a range of hub reduction
ratios can be achieved, according to the invention.
[0102] The values of Examples 1-5 are summarized in FIG. 6, which
is a comparative table of reduction ratio (R), number of annulus
teeth (N.sub.A); number of planet teeth (N.sub.P); number of sun
teeth (Ns); shaft angle between sun and planet (SA.sub.SP); shaft
angle between planet and annulus (SA.sub.PA); pitch angle of
annulus (PA.sub.A); pitch angle of planet (PA.sub.P) and pitch
angle of sun (PA.sub.S).
[0103] Other ratios can of course be devised, it being understood
that each of the gear wheels must have a whole number of teeth.
[0104] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms of the
invention. Rather, the words used in the specification are words of
description rather than limitation, and it is understood that
various changes may be made without departing from the spirit and
scope of the invention. Additionally, the features of various
implementing embodiments may be combined to form further
embodiments of the invention.
* * * * *