FIELD OF INVENTION
This invention relates· to a transmission synchronizer to absorb high relative
speeds in vehicle transmission.
BACKGROUND OF THE INVENTION
Transmission synchronizer is known to have been provided for shifting gears in
vehicle transmissions. There is wide range of synchronizer's types based on
actuation mechanism, number of cones, their shape, their blocking mechanism
etc. The typical or most commonly used single cone and double cone
synchronizers (also known as strut type synchronizers) are shown in Figure A
and Figure B respectively. The similar type of synchronizers are also disclosed
in patents US 5,738,194; US 5,638,930; US 4,566,568 etc.
A conventional single cone synchronizer as shown in Figure A consists of : a
hub (1); a shifting sleeve (2); two synchronizing ring or blocker ring (3); two
engagement rings (4) having counter taper surface and an actuating
mechanism (not shown in Figure) resting in hub's three pockets. The hub,
shifting sleeve, synchronizing rings are rotationally coupled with shaft and
engagement rings are rotationally ~oupled with idler gearwheels. In some
synchronizers tapered cone parts of engagement rings are separately
manufactured and then coupled with the help of lugs and pockets to get
benefits of modular design approach. A different material friction layer can also
be attached with the synchronizer rings to achieve various friction properties.
There are tapered spline teeth or dog teeth on synchronizing ring, engagement
ring and shifting sleeve for smooth meshing while gear shifting. The shifting
sleeve has internal spline teeth coupled with hub external spline teeth. The
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shifting sleeve can go through the synchroniz:ing ring's teeth and finally
engages with engagement ring's teeth to make a positive coupling of shaft and
idler gearwheel when driver shifts the gear. In these single cone synchronizers
there is one pair of friction cones on both sides of synchronizers. These cones
come into contact when driver shifts. the vehicle from one gear to another to
achieve the desired speeds. In starting events of shifting process, friction cones
in synchronizer come into contact and generate the friction torque which
further synchronizes the angular speeds of idler gearwheel and shaft.
Meanwhile synchronizing ring stops the shifting sleeve to pass through its
teeth because of indexing position of synchronizing ring. Friction torque
between these cones helps to match the angular speeds of idler gearwheel and
shaft for a smooth gear shifting in a typical synchromesh transmission. The
synchronizing ring rotates with hub and hence shaft and the engagement ring
rotate with idler gearwheel. Therefore, the relative angular speed between these
friction surfaces is equal to the angular speed difference between shaft and
idler gearwheel.
Depending upon the various requirements, multi-cones synchronizers are also
being used. A typical. double cone synchronizer is shown here in Figure B
indicating the following:- Hub (1), Shifting sleeve (2), Synchorizing ring (3),
Engagement Ring (4), Intermediate Ring (5) and Inner Ring (6). In multi-cones
synchronizers, the number of friction pair incre~ses and hence increases the
frictional torque and this high frictional torque can synchronize high moment
of inertia with less synchronization times or effort. In these synchronizers, each
friction pair consist of two cones, one is linked to shaft and another is linked to
idler gearwheel. For example as shown in Figure B, the synchronizing ring is
linked to shaft through hub, its mating cone ring is connected to idler
gearwheel through lugs connection with engagement ring. Further this cone is
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mating with another innermost cone which is linked to shaft through hub.
Thus, every alternate member of friction cone is connected to shaft and
intermediate member ·is connected to idler gearwheel and relative angular
speed remains the same in friction pairs. As the number of friction pmr
increases, more frictional torque IS generated, thereby improving the
synchronizing capacity of synchronizer.
These conventional synchronizers work well and give good life where relative
speeds between mating cones are low and lies within limits for selected friction
material. However, in some application depending upon the transmission
layout or various other parameters, where relative speeds are high, this is the
primary cause for synchronizer failures, then these synchronizers don't give
satisfactory results. For example in forward/ reverse shifting synchronizers,
relative speeds become very high as compared to other parameters where
forward -reverse section is put before the speed section of transmission. In
these types of forward/ reverse synchronizers, the major challenging design
parameter for frictional material is high relative speeds and all other limiting
values like specific energy, specific power, and specific pressure lies within
desired limits. These high relative speeds between friction cones leads to the
premature synchronizer failures. In these cases higher diameter and multicones
synchronizers cannot solve the problem.
Some special friction material like carbon composite which has high relative
speed absorbing capac!ty are also being used to absorb high relative speed; But
these materials have their own limitation in other areas. For example carbon is
not known for high impact pressure and it fails when there is high shifting
force required to shift the synchronizer. Hence in .this kind of applications,
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these conventional types of synchronizers do not give desired life as compared
to other applications.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a transmission
synchronizer to absorb high relative speeds in. vehicle transmission which
oyercomes disadvantages associates with the prior art(s).
Another object of the present invention is to provide a transmission
synchronizer to absorb high relative speeds in vehicle transmission which is
efficient & reliable.
SUMMARY OF THE INVENTION
According to this invention, there is provided a transmission synchronizer to
absorb high relative speeds in vehicle transmission comprising of a hub having
internal spline for connection with transmission shaft and external splines
meshed with shifting sleeve internal spline, wherein the hub is provided with
the shifting sleeve and an actuation mechanism in which atleast one
synchronizing ring rotationally linked to said hub and atleast one engagement
ring is provided together with atleast one intermediate ring, which is free to
rotate with respect to said engagement and synchronizing rings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from
the ensuing description when read in conjunction with the accompanymg
drawings and wherein:
Fig. A shows: conventional single cone synchronizer.
Fig. B shows: conventional double cone synchronizer.
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Fig. C shows: an examplaty embodiment of transmission synchronizer
according to present invention.
Fig. D shows: another embodiment of transmission synchronizer according to
present invention.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS:-
The present invention is directed to a transmission synchronizer to absorb high
relative speeds in vehicle transmission, wherein a freely rotatable special
intermediate ring is placed between two friction cone rings to reduce the
relative angular speeds between friction cones. The intermediate ring is such
that it can rotate independent of idler gearwheel or shaft speed and surface
properties are such that it can achieve equilibrium between friction torques
generated above and below the cone tapers due to relative speeds between
gearwheel and shaft. In present invention, one of the provisions to achieve
friction torque equilibrium is to have different taper angle on outer cone
surface and inner cone surface of intermediate ring and counter taper on
mating friction cones or provision of different friction coefficient material layer.
With the above provision, the intermediate cone develops the tendency to divide
tpe relative speeds between friction cones into two equal parts by setting
equilibrium between friction torques.
The present invention is shown in Figure C, which shows the basic structure of
typical single cone strut type synchronizer with special intermediate ring.
As shown in Figure C, ~his typical synchronizer comprises the following:-
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a hub 4 which has internal spline 11 to connect it with the transmission
shaft (not shown) and external splines (not shown) meshed with shifting
sleeve internal spline 7. This hub also has three pockets equally spaced
angularly. These pockets posses detents and actuation mechanism;
a shifting sleeve 1 mounted on hub, which can slide over the hub
external spline with the help of fork (not shown) placed in its annular
groove 12.
an actuation mechanism (not shown), for example- detent ball-spring
mechanism, generally placed in three pockets provided in hub.
two synchronizing rings 2 and 2' each having an external dog teeth 8 and
8' respectively arranged to mesh with internal dog teeth 7 of shifting
sleeve 1. These rings are rotationally linked to hub 4, for example with
the help of lugs (not shown). These rings also have an inner conical
surface.
two engagement rings 3 and 3' each having an external dog teeth 9 and
9' respectively arranged to mesh with internal teeth 7 of shifting sleeve 1.
Each engagement ring is rotationally connected to their respective idler
gearwheel (not shown) for example with the help of spline 10 and 1 0'
respectively. These engagement rings can also be integral part of idler
gearwheel.
this present invented synchronizer contains further two intermediate
rings 5 and 5' which are free to rotate with respect to engagement rings
3, 3' and synchrpnizing rings 2, 2' respectively. These intermediate rings
have external taper cone with an angle 'a' which can be brought into
contact with counter taper of synchronizing rings and internal taper cone
with an angle 'b' which can be brought into contact with counter taper
on engagement rings during the shifting process. The taper angle 'a' is
higher than 'b' such that friction torque generated on these cone pair can
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I.' U U\.V so-·be
equalized. A friction material layer 6 and 6' is attached to-r:h'ese taper
cone surfaces of intermediate rings to get desired friction properties.
One synchronizing ring, one intermediate ring and one engagement ring
may also be used in cases where synchronizer for one gear shift is used.
The other alternative to set equilibrium between friction torques is by
means of friction layer of external cone and internal cone with a slightly
different friction co-efficient to set equilibrium between them. As friction
torque is directly proportional to friction co-efficient, therefore the
torques can be equalized by varying friction co-efficient. Both alternatives
are shown in Figure D.
The mam advantage of the present invention is that, it divides the relative
angular speeds into two halves and hence reducirig the relative speeds between
friction pairs. To achieve the equilibrium between external sliding and internal
sliding speeds, two alternatives are described in invention. Because there is
higher friction torque developed at larger diameter with same amount of axial
force applied on synchronizer. So to ensure the equal distribution of relative
speed it is required to equalize the friction torque on both cones - external and
internal. This equal distribution of friction torque also ensures the equal wear
of internal and external cones of intermediate ring. Hence, this invention
increases the capacity of synchronizer to absorb high relative speeds without
excessive wear or failure.
In forward/ reverse applications where relative speeds 1s the mam cause for
synchronizer failures and where prior art do not allow the forward/reverse gear
shifting when vehicle is moving, the instant invention has a great advantage
over conventional synchronizers.
Hence, the present invention provides a synchronizer with high durability and
life even where high relative speeds are to be synchronized.
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Higher is the taper cone diameter of synchronizer, higher will be relative speeds
between friction surfaces, so this concept is more beneficial where bigger size
synchronizers are used.
This invention also has modular design approach and allows to go with multicones
synchronizers. In multicones synchroniz_ers, more number of freely
rotatable intermediate rings can be provided depending upon the number of
friction cone pairs.
It is also applicable to the synchronizers having synchronization on their one
side only or the single cone synchronization on one side and multi-cones
synchronization on other side.
Advantageous Features
Increases capability of synchronizer to absorb high relative speeds
without expensive wear or failure.
A synchronizer with high durability and life even where high relative
speeds are to be synchronized.
Higher is the taper cone diameter of synchronizer, higher will be relative
speeds between friction surfaces, so this concept is more beneficial where
bigger size synchronizers are used.
In multicones synchronizers, more number of freely rotatable
intermediate rings can be provided depending upon the number of
friction cone pai~s.
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It is to be noted that the present invention is susceptible to modifications,
adaptations and changes by those skilled in the art. Such variant embodiments
employing the concepts and features of this invention are intended to be within
the scope of the present invention, which is further set forth under the
following claims:-

WE CLAIM:
1. A transmission synchronizer to absorb high relative speeds in vehicle
transmission comprising of a hub having internal spline for connection
with transmission shaft and external splines meshed with shifting sleeve
internal spline, wherein the hub is provided with the shifting sleeve and
an actuation mechanism in which atleast one synchronizing ring
rotationally linked to said hub and atleast one engagement ring IS
provided together with atleast one intermediate ring, which is free to
rotate with respect to said engagement and synchronizing rings.
2. A transmission synchronizer as claimed in claim 1, wherein said
intermediate nng IS placed between two friction cone nngs
(synchronizing and engagement rings) to reduce the relative angular
speeds between said friction cones.
3. A transmission synchronizer as claimed In claim 1 or 2, wherein the
intermediate rings have external taper cone with an angle 'a' which can
be provided in contact with counter taper of synchronizing rings and
internal taper cone with an angle 'b' which can be provided in contact
with counter taper on engagement rings during the shifting process.
4. A transmission synchronizer as claimed in any of the preceding claims,
wherein the taper angle 'a' is higher than. 'b' such that friction torque
generated on the cone pair can be equalized.
5. A transmission synchronizer as claimed in any of the preceding claims,
wherein a friction material layer is provided on the taper cone surfaces of
intermediate rings to get desired friction properties.
6. A transmission synchronizer as claimed in any of the preceding claims,
comprising of friction layer of external cone and internal cone with a
slightly different friction co-efficient to set equilibrium therebetween.
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7. A transmission synchronizer as claimed in any of the preceding claims, is
associated with the advantageous features such as herein described.
8. A transmission synchronizer to absorb high relative speeds in vehicle
transmission substantially as herein described with reference to the
accompanying drawings.