FIELD OF THE INVENTION:
[0001] The present disclosure generally relates to drive trains in a manual
transmission of an automobile, and particularly, to a gear set backlash arrester
mechanism for automobile transmission unit.
5
BACKGROUND OF THE INVENTION:
[0002] In a single gear mesh consisting of two meshed gears, there typically
is a necessary operating clearance between teeth of the two meshed gears due
to manufacturing tolerances, radial play in the gear support bearings, incorrect
10 center-to-center spacing of the gears, temperature variations, and the like. This
clearance results in a backlash between the gears, such that if the two meshed
gears are rotated in one direction, stopped, and then rotated in the opposite
direction, the clearance must be taken up before the teeth of the two meshed
gears come into contact with each other.
15 [0003] However, in manual transmissions, it is desirable for backlash to be
reduced or eliminated in the gear train to reduce noise genreted due to gear
rattling. This type of noise is generated due to continuous heating of the two
meshed gears’ teeth which are in contact during no load condition. This
phenomenon happens due engine power fluctuation and backlash in the teeth of
20 the two meshed gears. There is no countermeasure available to confirm no rattle
condition in a manual transmission drive train. Some interim measures were
done to reduce or eliminate this noise from transmission.
[0004] For instance, a prior art describes a gearwheel pair consisting of two
gearwheels which are mounted on a common rotational axis to rotate in relation
25 to each other and which are commonly in engagement with the mating
gearwheel. Each of the two gearwheels have in the adjacent side faces one or
more cut-outs and in which is installed a common spring element through which
the gearwheels are pretensioned in relation to one another while maintaining the
designed external geometric dimensions. With the help of the common spring
3
element, the play between engaging teeth of the two gearwheels is kept at zero,
thereby preventing the resulting noises.
[0005] In another art, a noise suppressing mechanism for balance gear
system of an engine crankshaft is disclosed. The balance gear system includes
5 a primary gear, a secondary gear, and a torsional spring and is fit on a balance
shaft. The noise suppressing mechanism includes a circular flange formed on
the primary gear and the secondary gear forms a central bore rotatably fit over
the circular flange for free rotation about the circular flange with respect to the
primary gear. The torsional spring is arranged between the primary and
10 secondary gears. The primary gear forming a securing hole in which a stem
section of a limiting pin is received and fixed. The secondary gear forms a
through hole in which a head section of the limiting pin is accommodated with a
gap formed between the head section and an inside diameter of the through hole.
The gap allows for a limited angular shift of the secondary gear with respect to
15 the primary gear. Such an arrangement provides a noise suppressing
mechanism having less number of parts and being ready to assemble.
[0006] A further prior art proposes a split gear assembly including first and
second gears, a spring mechanism that acts to rotate the first gear relative to the
second gear in a first direction, and a one-way clutch mechanism that prevents
20 rotation of the first gear relative to the second gear in a second direction opposite
the first direction. That is, the on-way clutch mechanism is provided to control the
backlash.
[0007] From the state of the art, it can be gathered that backlash is inherent
property of a gear set (gear pair) in automobile transmission unit. The backlash
25 is necessary for free rotation of meshing gears of the gear set during transfer of
power. However, NV performance of the gear set is deteriorated because of
backlash. Also, as mentioned above, backlash becomes root case of the gear
rattle noise in an idle condition.
[0008] Hence, there is need in the state of the art to modify the components
30 of the gear set to arrest the backlash.
4
OBJECTS OF THE INVENTION:
[0009] Some of the objects of the present disclosure, which at least one
embodiment herein satisfy, are listed hereinbelow.
[0010] It is a primary object of the present disclosure to propose a gear set
5 backlash arrester mechanism that is suitable for automobile transmission unit.
[0011] It is a further object of the present disclosure to propose a gear set
backlash arrester mechanism that is suitable to solve the rattle noise problem in
a simple and efficient manner.
[0012] It is yet another object of the present disclosure is to propose a gear
10 set backlash arrester mechanism that eliminates the rattle condition in manual
transmission drive train.
[0013] It is yet another object of the present disclosure to propose a gear set
backlash arrester mechanism that is active during the ideal conditions of the gear
set.
15 [0014] It is yet another object of the present disclsoure to propose a gear set
backlash arrester mechanism that is versatile in applicability.
[0015] It is yet another object of the present disclsoure to propose a gear set
backlash arrester mechanism with less wear and tear that may arise due to
friction.
20 [0016] These and other objects and advantages of the invention will be
apparent from the ensuing description when read in conjunction with the
accompanying drawings.
SUMMARY OF THE INVENTION:
25 [0017] This summary is provided to introduce a selection of concepts in a
simplified format that are further described in the detailed description of the
present disclosure. This summary is not intended to identify key or essential
inventive concepts of the present disclosure, nor is it intended for determining
the scope of the present disclosure.
5
[0018] The present disclosure provides a gear set backlash arrester
mechanism for automobile transmission units. The gear set includes a dog gear,
a main gear, and a friction gear mounted freely between the dog gear and the
main gear. A gear geometry of the friction gear is same as gear geometry of the
5 main gear. The friction gear includes an additional tooth with respect to teeth of
the main gear and the friction gear is mounted between the gear dog and the
main gear with a spring washer.
[0019] In an aspect, the spring washer may be a conical spring washer.
[0020] In an aspect, the thickness of the friction gear is less than or equal to
10 2 mm.
[0021] In an aspect, the additional tooth is adjusted with modification of gear
geometry.
[0022] In an aspect, an inner diameter of the friction gear is more than a
mounting shaft diameter of the main gear.
15 [0023] In an aspect, difference between the inner diameter of friction gear
and the mounting shaft diameter of the main gear is 50 micron.
[0024] The present disclosure further relates to an automobile transmission
unit. The automobile transmission unit includes an input shaft assembly
comprising a gear set including a dog gear, a main gear, and a friction gear
20 mounted freely between the gear dog and the main gear, where gear geometry
of the friction gear and the main gear is same, while the friction gear comprises
an additional tooth with respect to teeth of the main gear. The automobile
transmission unit further includes an output shaft assembly having a driven gear
meshed with the gear set, and a differential system coupled to the output shaft
25 assembly.
[0025] Various objects, features, aspects, and advantages of the inventive
subject matter will become more apparent from the following detailed description
of preferred embodiments, along with the accompanying drawing figures in which
like numerals represent like components.
30
6
BRIEF DESCRIPTION OF DRAWINGS:
[0026] To further clarify the advantages and features of the present
disclosure, a more particular description of the disclosure will be rendered by
reference to specific embodiments thereof, which is illustrated in the appended
5 drawings. It is appreciated that these drawings depict only typical embodiments
of the disclosure and are therefore not to be considered limiting of its scope. The
disclosure will be described and explained with additional specificity and detail
with the accompanying drawings.
[0027] The subject matter that is regarded as the invention is particularly
10 pointed out and distinctly claimed in the claims at the conclusion of the
specification. The foregoing and other aspects, features, and advantages of the
invention are apparent from the following detailed description taken in
conjunction with the accompanying drawings in which:
[0028] Figure 1 illustrates an exploded view of a gear set backlash arrester
15 mechanism, according to an embodiment of the present disclosure;
[0029] Figure 2 illustrates an assembled view of the a gear set backlash
arrester mechanism, according to an embodiment of the present disclosure;
[0030] Figure 3 illustrates the working of a friction gear mounted in the gear
set backlash arrester mechanism, according to an embodiment of the present
20 disclosure;
[0031] Figure 4 illustrates a schematic arrangement of a driving gear and a
driven gear in an automobile transmission unit, according to an embodiment of
the present disclosure; and
[0032] Figure 5 illustrates an overall automobile transmission unit, according
25 to an embodiment of the present invention.
[0033] Further, skilled artisans will appreciate that elements in the drawings
are illustrated for simplicity and may not have necessarily been drawn to scale.
Furthermore, in terms of the construction of the device, one or more components
of the device may have been represented in the drawings by conventional
30 symbols, and the drawings may show only those specific details that are pertinent
7
to understanding the embodiments of the present invention so as not to obscure
the drawings with details that will be readily apparent to those of ordinary skill in
the art having benefit of the description herein.
5 DETAILED DESCRIPTION OF THE INVENTION
[0034] For the purpose of promoting an understanding of the principles of the
invention, reference will now be made to the embodiment illustrated in the
drawings, and specific language will be used to describe the same. It will
nevertheless be understood that no limitation of the scope of the invention is
10 thereby intended. Such alterations and further modifications in the illustrated
system, and such further applications of the principles of the invention as
illustrated therein would be contemplated as would normally occur to one skilled
in the art to which the invention relates. Unless otherwise defined, all technical
and scientific terms used herein have the same meaning as commonly
15 understood by one of ordinary skilled in the art. The system, methods, and
examples provided herein are illustrative only and are not intended to be limiting.
[0035] The term “some” as used herein is to be understood as “none or one
or more than one or all.” Accordingly, the terms “none,” “one,” “more than one,”
“more than one, but not all” or “all” would all fall under the definition of “some.”
20 The term “some embodiments” may refer to no embodiments or to one
embodiment or to several embodiments or to all embodiments, without departing
from the scope of the present disclosure.
[0036] The terminology and structure employed herein is for describing,
teaching, and illuminating some embodiments and their specific features. It does
25 not in any way limit, restrict or reduce the spirit and scope of the claims or their
equivalents.
[0037] More specifically, any terms used herein such as but not limited to
“includes,” “comprises,” “has,” “consists,” and grammatical variants thereof do
not specify an exact limitation or restriction and certainly do not exclude the
30 possible addition of one or more features or elements, unless otherwise stated,
8
and furthermore must not be taken to exclude the possible removal of one or
more of the listed features and elements, unless otherwise stated with the limiting
language “must comprise” or “needs to include.”
[0038] Whether or not a certain feature or element was limited to being used
5 only once, either way, it may still be referred to as “one or more features” or “one
or more elements” or “at least one feature” or “at least one element.”
Furthermore, the use of the terms “one or more” or “at least one” feature or
element do not preclude there being none of that feature or element, unless
otherwise specified by limiting language such as “there needs to be one or more
10 . . . ” or “one or more element is required.”
[0039] Unless otherwise defined, all terms, and especially any technical
and/or scientific terms, used herein may be taken to have the same meaning as
commonly understood by one having ordinary skills in the art.
[0040] Reference is made herein to some “embodiments.” It should be
15 understood that an embodiment is an example of a possible implementation of
any features and/or elements presented in the attached claims. Some
embodiments have been described for the purpose of illuminating one or more
of the potential ways in which the specific features and/or elements of the
attached claims fulfill the requirements of uniqueness, utility and non20 obviousness.
[0041] Use of the phrases and/or terms including, but not limited to, “a first
embodiment,” “a further embodiment,” “an alternate embodiment,” “one
embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,”
“other embodiments,” “further embodiment”, “furthermore embodiment”,
25 “additional embodiment” or variants thereof do not necessarily refer to the same
embodiments. Unless otherwise specified, one or more particular features and/or
elements described in connection with one or more embodiments may be found
in one embodiment, or may be found in more than one embodiment, or may be
found in all embodiments, or may be found in no embodiments. Although one or
30 more features and/or elements may be described herein in the context of only a
single embodiment, or alternatively in the context of more than one embodiment,
9
or further alternatively in the context of all embodiments, the features and/or
elements may instead be provided separately or in any appropriate combination
or not at all. Conversely, any features and/or elements described in the context
of separate embodiments may alternatively be realized as existing together in
5 the context of a single embodiment.
[0042] Any particular and all details set forth herein are used in the context
of some embodiments and therefore should not be necessarily taken as limiting
factors to the attached claims. The attached claims and their legal equivalents
can be realized in the context of embodiments other than the ones used as
10 illustrative examples in the description below. Embodiments of the present
invention will be described below in detail with reference to the accompanying
drawings.
[0043] The present disclosure relates to a gear set backlash arrester
mechanism for an automobile transmission unit. As mentioned above, backlash
15 occurs between two gears when the width of a space between two teeth on one
gear exceeds the thickness of an engaging tooth on another gear on pitch circles.
Backlash is the distance which is a width of the space between two teeth on one
gear exceeds the thickness of an engaging tooth on another gear. Most gear
drives have at least some backlash. When two gears of Gear set transmit torque,
20 driving gear tooth face push the driven gear tooth face. So there is no free space
or back lash in between two gear tooths. However, when the gear set in not
transferring power. Gear mounted on needle bearing is free. It can vibrate at its
position with external vibrations from Engine.
[0044] Machines driven by the gear trains may operate at reduced loads at
25 least part of the time. The torsional vibrations in the drive train can cause gear
oscillations during low torque output operation. Multi-ratio gear transmissions
and reversible transmissions can have driven gears that transmit little or no
torque most of the time. Constant mesh multi-ratio transmissions, for example,
have gears that transmit torque only when one gear is locked to a shaft by a
30 slider. Constant mesh gear trains in these transmissions which do not include a
gear that is locked to a shaft by a slider are driven but do not transmit torque.
10
Torsional vibrations in these transmissions can cause gear oscillations in the
gear trains that are not transmitting torque.
[0045] The gear oscillations are the result of backlash and torsional vibrations
resulting from the gear oscillations cause noise. This noise is referred to as gear
5 rattle. In vehicle transmissions, the gear rattle is very objectionable. It is generally
objectionable in other gear transmissions as well. The gear rattle may also result
in gear damage and eventually gear failure.
[0046] To resolve the issues related to generation of the gear rattle, the
present disclosure herein propose a gear set backlash arrester mechanism 100,
10 shown in Figure 1 in accordance with an embodiment, for automobile
transmission unit. The gear set backlash arrester mechanism 100,
interchangeably referred to as “gear assy” hereinafter, may be used for gears
which are mounted on a shaft with needle roller bearings. The gear assy 100
may include, but not limited to, a clutch or dog gear 102, a spring washer 104, a
15 friction gear 106, and a main gear 108. The dog gear 102 and the main gear 108
may be generic parts that are commonly used in the state of the art.
[0047] In between the dog gear 102 and the main gear 108, the friction gear
106 may be added in accordance with an embodiment of the present disclosure.
In an aspect, the friction gear 106 is formed with a thickness of less than or equal
20 to 3 mm. In said aspect, the thickness of the friction disc gear 106 may be less
than or equal to 2 mm.
[0048] Further, the geometry of the friction gear 106 may be same as that of
the main gear 108; however, the friction gear 106 may include an additional tooth
110 with respect to the number of teeth of the main gear 108. In an aspect, the
25 additional tooth 110 may be adjusted with modification of gear geometry like pitch
circle diameter (PCD), tip diameter, etc. In other words, the friction gear 106 may
be a gear with geometry like that of the main gear 108 with an additional tooth
110 arranged within by way of mechanical process of modification.
[0049] The friction gear 106 may be mounted freely between the dog gear
30 dog 102 and the main gear 108 with the spring washer 104.
11
[0050] In an aspect, the spring washer 104 may be a common spring washer
that may have axial flexibility.
[0051] In another aspect, the spring washer 104 may be a conical spring
washer. The conical spring washer may enable the friction gear 103 to support
5 high loads with relatively small deflections and solid heights compared to helical
springs. The conical-shaped spring washer may have an open center. It may be
smaller than a coiled spring in an example. The conical spring washer may
provide cushioning to heavy loads with short motion. The conical spring washer
may deflect in response to a load and exhibit low deflections relative to high
10 loads. The relationship between the load and deflection may be non-linear,
particularly as load increases. The conical spring washer may prevent fastening
or loosening due to vibrations and have varied applicability. It may conveniently
applied to areas with constant thrust that must stand up to heavy wear.
[0052] In addition, the conical spring washer may offer additional advantages
15 to the friction gear 106 by reserving less space, owing to the structure of the
washer, offering a long service life due to less wear and tear by reduced
vibrations. The conical spring washer may also be used in conjunction with coiled
springs further widening the applicability and versatility. Additional versatility may
also be offered when the conical spring washer may be stacked in series or in
20 parallel. The reliability of the speed gears may be increased, bolt failures may be
prevented, and positioning accuracy of call bearings may also be maintained in
the assembly. Further, the conical spring washer in the gear set 100 may
minimize thermal expansion. The conical spring washer may be self-damping
and distribute loads evenly and absorb shocks efficiently.
25 [0053] In an embodiment, an inner diameter of the friction gear 106 may be
50 micron more than a mounting shaft diameter of the main gear 108. In other
words, the inner diameter of the friction gear 106 may be such that it gets fixed
onto the main gear 108.
[0054] Figure 2 illustrates an assembled view of the gear set 100, according
30 to an embodiment of the present disclosure. The friction gear 106 may be
mounted over the external diameter of the dog gear 102 with the spring washer
12
104 being arrange between the dog gear 102 and the friction gear 106. The
friction gear 106 may be mounted in the gear set 100 so as to be free to rotate
in a gear assembly, say, input gear assembly.
[0055] Figure 3 schematically illustrates working of the friction gear 106 in
5 the gear assy with backlash arrester mechanism 100, according to an
embodiment of the present disclosure. In said embodiment, the gear assy 100
forming an input gear may be a driving gear working against the teeth of a driven
gear 302.
[0056] Referring to Figure 4, the gear assy 100 forming the input gear may
10 be on driving side. In the input gear, the main gear 108 and the friction gear 106
may be rotating in anti-clockwise direction in an embodiment, while the driven
gear 302 may be rotating in clockwise direction, according to an embodiment. In
other words, the driven gear 302 may be in mesh with the input gear 100 having
the main gear 108 and the friction gear 106 mounted on a drive shaft.
15 [0057] Referring to back to Figure 3, teeth 1, 2, and 3 of the input gear 100
have been illustrated as meshed against teeth 1, 2, 3, and 4 of the driven gear
302. The thickness of the tooth of the friction gear 106 may be less than the tooth
thickness of the main gear 108, and also the tooth span may be less than that of
the main gear 108 in order to accommodate the additional tooth 110 in the friction
20 gear geometry. This may make a right hand flank of tooth No. 1 and left hand
flank of tooth No. 3 of the friction gear 106 to always remain in contact with left
hand flank of tooth No. 2 and right left hand flank of tooth No. 3 of the driven gear
302. In other words, the geometry of the friction gear 106 may make a portion of
the friction gear (teeth) to remain in contact with a portion (teeth) of the driven
25 gear 302. This condition may make backlash to “zero” between the driving (input)
gear and the driven gear 302 all the time. With rotation of the gears in opposite
direction, the teeth may change their position but the point of contact may be
maintained all the time due to the free rotation of the friction gear 106.
[0058] In an embodiment, when the gear assy 100 may not be transferring
30 power, i.e., gear assy 100 not set to work, the friction gear 106 may hold the main
gear 108 with friction at a location and may not allow it to move. This condition
13
may automatically avoid the relative vibration between main gear 108 and driven
gear 302. On the other hand, in the state of the gear assy 100 transferring the
power, i.e., the driving gear driving the driven gear 302 and transferring power,
the friction gear 106 may move opposite to the driven gear 302 to adjust the
5 relative position of power transferring tooth of the main gear 108. Since the
friction gear 106 is free to rotate in the input gear assembly, it may rotate so as
to get adjusted by a degree, making a meshing condition with the driven gear
302. In other words, during the power transmission, the friction gear 106 may get
adjusted with respect to the driven gear 302 to create a meshing condition.
10 [0059] Further, the friction gear 106 may have tooth thickness and tooth
span less than that of the main gear 108, it may lead to zero backlash as
explained above. Referring to Figure 4, since the thickness of the friction gear
106 may be less, the friction generated by the friction gear 106 due to its rotation
and contact with the driven gear 302, the driven gear flank may not generate
15 tangible power loss in transmission. The power transmission may not be affected
by the working for friction gear 106.
[0060] Figure 4 illustrates schematically arrangement of driving gear assy
100 and driven gear 302 in an individual automobile transmission unit, according
to an embodiment of the present disclosure. The input gear assy 100 or the
20 driving gear assy 100 or main gear 108 with the friction gear 106 may be meshed
to the driven gear 302 and transmit torque and rotation motion from the driven
gear 108, to the driven gear 302. The driven gear 302 may be connected to the
wheels of the vehicle and thus, may accordingly drive the wheels.
[0061] Figure 5 illustrates an overall assembly 500 layout for manual
25 transmission unit comprising an input shaft assembly 502, an output shaft
assembly 504, and differential system 506, according to an embodiment of the
present disclosure. The input gear assy 100 may be mounted on the input shaft
assembly 502 and the input shaft assembly 502 may be connected directly to a
motor or Engine, thus turning at a motor speed. The input shaft assembly 502
30 may bring drive into a gearbox system and withstand the torque generated by
engaged gears. The output shaft assembly 504 mounting the driven gear 302
14
may carry the power from the input shaft assembly 502 and run at different
speeds, depending on the gears and gear ratio. The differential system 506, in
contact with the output shaft assembly 504, may permit power from the engine
to be transmitted to a pair of driving wheels, dividing the force equally between
5 them but permitting them to follow paths of different lengths, as when turning a
corner or traversing an uneven road.
[0062] The present disclosure thus provides a gear set backlash arrester
mechanism that is suitable for automobile transmission units, as against the
known mechanism that are majorly suitable for industrial and big size vehicle
10 transmission units. The gear set backlash arrester mechanism proposed herein
is suitable for automobile transmission units. With the implementation of the
proposed gear set backlash arrester mechanism, the rattle condition in a manual
transmission drive train is eliminated and the gear set backlash arrester
mechanism is active during the ideal conditions of the gear set. Additionally, the
15 proposed gear set backlash arrester mechanism is versatile in applicability and
has a long life due to less wear and tear that may arise due to friction.
[0063] The figures and the forgoing description give examples of
embodiments. Those skilled in the art will appreciate that one or more of the
described elements may well be combined into a single functional element.
20 Alternatively, certain elements may be split into multiple functional elements.
Elements from one embodiment may be added to another embodiment. For
example, orders of processes described herein may be changed and are not
limited to the manner described herein. Moreover, the actions of any flow
diagram need not be implemented in the order shown; nor do all of the acts
25 necessarily need to be performed. Also, those acts that are not dependent on
other acts may be performed in parallel with the other acts. The scope of the
embodiments is by no means limited by these specific examples. Numerous
variations, whether explicitly given in the specification or not, such as differences
in structure, dimension, and use of material, are possible.
30
15

WE CLAIM
1. An gear set backlash arrester mechanism (100) for automobile
transmission units, comprising:
5 a dog gear (102);
a main gear (108); and
a friction gear (106) mounted freely between the dog gear (102)
and the main gear (108),
wherein gear geometry of the friction gear (106) is same as gear
10 geometry of the main gear (108),
wherein the friction gear (106) comprises an additional tooth (110)
with respect to teeth of the main gear (108), and
wherein the friction gear (106) is mounted between the dog gear
(102) and the main gear (108) with a spring washer (104).
15 2. The gear set backlash arrester mechanism (100) as claimed in claim 1,
wherein the spring washer (104) is a conical spring washer or Belleville
washer.
3. The gear set backlash arrester mechanism (100) as claimed in claim 1,
wherein the thickness of the friction gear (106) is less than or equal to 2
20 mm.
4. The gear set backlash arrester mechanism (100) as claimed in claim 1,
wherein the additional tooth (110) is adjusted with modification of gear
geometry.
5. The gear set backlash arrester mechanism (100) as claimed in claim 1,
25 wherein an inner diameter of the friction gear (106) is more than a
mounting shaft diameter of the main gear (108).
16
6. The gear set backlash arrester mechanism (100) as claimed in claim 5,
wherein the difference between the inner diameter of friction gear (106)
and the mounting shaft diameter of the main gear (108) is 50 micron.
7. An automobile transmission unit (500) comprising:
5 an input shaft assembly (502) comprising a gear set (100) including
a dog gear (102), a main gear (108), and a friction gear (106) mounted
freely between the gear dog (102) and the main gear (108), wherein gear
geometry of the friction gear (106) and the main gear (108) is same, while
the friction gear (106) comprises an additional tooth (110) with respect to
10 teeth of the main gear (108);
an output shaft assembly (504) having a driven gear (302)
meshed with the gear set (100); and
a differential system (506) coupled to the output shaft assembly
(302).