FIELD OF INVENTION
I This invention relates to a compact manual transmission for passenger cars.
This invention particularly relates to the compact manual transmission with
synchronizer system for reverse gear for Mini segment passenger vehicles. The
present invention results in optimized weight of transmission, improvements in
mechanical efficiency & NVH (Noise, Vibration, and Harshness) characteristics.
Further, it causes improvements in gear shifting and eliminates the gear
sticking in reverse shifting.
PRIOR ART
In the known art, the manual transmission drive train is designed for 130Nm,
whereas it is actually used for 70Nm, which results in higher difference in
desired factor of safety (FOS) and actual FOS. This affects the cost as it is
associated with the design and usage. Further, the reverse gear shifting is
carried out with sliding mesh. Hence, driver feels discomfort during reverse
shifting. Again the synchronized reverse is applicable in higher torque range
(>200nm) due to space availability, which is not available in the Mini segment
vehicles because of higher cost. In the existing drive train, the shifting
mechanism is overweight as it uses more number of components. The known
drive train is also having a higher mechanical loss which leads to lower fuel
economy (FE). Again it is not having good shifting quality. Therefore, it is
I required to be improved.
Hence, the present invention has been proposed that can address the aforesaid
drawbacks.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a compact manual transmission
I
for passenger cars, which overcomes disadvantages associated with the prior
I arts.
Another object of the present invention is to provide a compact manual
transmission for passenger cars which eliminates the problem of reverse gear
blockage.
Yet another object of the present invention is to provide a compact manual
transmission for passenger cars which improves the overall shift feeling over
1 existing transmission.
Still another object of the present invention is to provide a compact manual
transmission for passenger cars which reduces the weight of transmission
thereby making it one of the lightest transmissions for Mini segment vehicles.
I
Further object of the present invention is to provide a compact manual
transmission for passenger cars which improves the NVH of drive train.
Yet further object of the present invention is to provide a compact manual
transmission for passenger cars which improves the mechanical efficiency and
hence providing the improvements in FE.
Still further object of the present invention is to provide a compact manual
transmission for passenger cars which is cost effective.
STATEMENT OF INVENTION
According to this invention, there is provided a compact manual transmission
for passenger cars comprising of input shaft first gear in mesh with counter
shaft in contact with reverse gear, wherein pinion is in mesh with final gear on
differential and a novel shifting system.
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 accompanying
drawings and wherein:
Figure 1 shows: Power flow for reverse gear in prior art.
Figure 2 shows: Power flow for reverse gear according to the present
invention.
Figure 2A shows: Conventional shifting system
Figure 3 shows: Novel shifting system of the present invention.
Figui-e 4 and
5 shows: Shift tower of the present invention.
I Figure 6 shows: Drive train of the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention discloses compact manual transmission for passenger
cars, wherein power from engine is transmitted to input shaft via clutch. For
forward gears power flow is kept same as of base transmission. i.e. Input Shaft
Gear 1 Counter Shaft Gear > Final Gear pinion on counter shaft > Final gear on
differential > wheels. However, for reverse gear shifting this power flow is
different from the base transmission. In base transmission it is Input Shaft
reverse gear (1) > Idler gear (2) > Integrated gear on 1st low sleeve (3) > Final
Gear pinion on counter shaft (4) > Final gear on differential (5) > wheels as
shown in fig. 1.
In the instant invention as shown in fig. 2, the power flow is Input Shaft 1st
gear (1) > Counter shaft (2) (which acts as Idler gear) > Reverse gear on
separate shaft (3) > Final Gear pinion on counter shaft reverse (4)> Final gear
on differential (5) > wheels. In this transmission there are two counter shafts
instead of one in existing transmission, but overall count of shafts in drive
train is same. Again, in the invention two pinions are provided in mesh with
the final gear. In the prior art, the reverse gears are spur gear type which have
inferior NVH characteristics, giving rise to high rattle noise in idle rpm.
However in the present invention the reverse gears are helical gears constant in
mesh provides better NVH characteristics and almost negligible rattle noise
during idle RPM.
Thus, in the present invention the reverse gear shifting is synchronized,
wherein the transmission is compact. The overall shaft arrangement for main
shafts and for the reverse shaft is not known in any of the currently available
transmission in this range. The centre to centre distance (pitch) between the
shafts input and counter is optimized for a particular application. The
arrangement of shafts is improved w.r.t. existing transmission to improve the
overall NVH performance and stability of drive train. This compact drive train
also maintains small centre to centre distance between shafts. There is no knee
that in the new layout all the shafts are provided in straight line. New
positioning of reverse shaft adds stability to the system which leads to the
improvement in overall performance characteristics.
Another provision in this transmission lies in its unique shifting system, which
has added advantages over existing transmission shifting system in terms of
weight, cost and less number of components.
Another provision in the shifting system lies in unique way of integrating 5th
and Reverse gear shifting on single shift shaft, although both the sleeves i.e. for
5th gear shifting and reverse gear shifting lies on different shafts.
The major achievement in this invention is maintaining the significant "H"
pattern on gear shift knob as per standard practice.
Further, reference may be made to Fig. 2A indicating conventional shifting
system comprising of the following components:
1. Low Fork
2: Shaft Low
3. Shaft High Fork
4. Support Shaft 5th & R
5. Reverse Gear Shift Assembly
6. Fork High
7. Fork 5th
8. Yoke 5th & R
Y
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Now, reference may be made to fig.3 indicating the following components:
1. Reverse Fork
2. Low Fork
3. 5th Fork
4. Support Shaft 5th & R
5. Shaft High Fork
6. Shaft Low Fork
7. Fork Low
8. Yoke 5th & R
5th and reverse shift system are integrated on single shaft. Due to provision of
sufficient clearances reverse system can move backward when 5th fork (3) is
under shifting, because of common linked Yoke and vice versa in case of
reverse gear shifting.
Advantageous Features
To save weight and space the provision is made through ball sliding
arrangement which restricts the motion of 5th and reverse forks (3 and 1) only
in their particular gear shift i.e. only one fork is shifted and other remains
stationary. This new shift system has advantage of using less number of
components resulting in less weight.
Shifting device, which is smaller, lighter and efficient than the device currently
available. The advantage lies in its arrangement of components (assembly)
coupled with improvement in tolerance controls, which help in overall
improvement in shifting system.
Arrangement of drive train components, which gives rise to unique layout of
the drive train. The centre distances of the drive train are optimally designed,
in order to balance the whole transmission in terms of stability and NVH
performances. The centre distance between Input-Counter, Counter-
Differential and Counter-Reverse is quite smaller than the known prior art and
suitably designed for low cost transmissions. The arrangement of transmission
is as shown in fig. 6 comprising of:
Input Shaft Assembly (1)
Counter Shaft Assembly (2)
Reverse Shaft Assembly (3)
Differential Assembly (4)
Some of the components which are assembled on transmission case are
assembled directly on the shift towerldevice to control the tolerances at system
level as shown in fig. 4 and 5.
The shift tower involves the following:
- Integrated detent pin and 3D ramp
- Better dimensional control
- Preciseness in shifting.
The power flow for the drive train in forward direction is as follows:
Engine --> Input Shaft (Gear 1) --> Counter Shaft (Gear 2) --> Counter Shaft
(Final Pinion) --> Final Gear on differential --> Drive Shaft --> Tires.
The power flows for other gears remain same depending upon the selected gear.
Further Advantageous Features
1. Elimination of blockage of reverse gears
2. Smooth driving experience
3. Less weight and reduced size
4. Cost effective
5. Lower shift impulse
6. Elimination of noise
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 compact manual transmission for passenger cars
comprising of input shaft first gear in mesh with counter
shaft in contact with reverse gear, wherein pinion is in mesh
with final gear on differential, and a novel shifting system.
2. A compact manual transmission for passenger cars as
claimed in claim 1, wherein the counter shaft acts as idler
gear, the reverse gear is provided on separate shaft and the
final gear pinion is mounted on counter shaft reverse.
3. A compact manual transmission for passenger cars as
claimed in claim 1 or 2, wherein two pinions are provided in
mesh with the final gear.
4. A compact manual transmission for passenger cars as
claimed in any of the preceding claims, wherein the reverse
gears are helical gears constant in mesh, which provides
better NVH characteristics and causes negligible rattle noise
during idle RPM.
5. A compact manual transmission for passenger cars as
claimed in any of the preceding claims, wherein the centre
to centre distance (pitch) between input shaft, counter shaft
and differential shaft is small, in which the shafts are
provided linearly.
6. A compact manual transmission for passenger cars as
claimed in any of the preceding claims, wherein 5th gear and
reverse gear shifting are integrated on single shift shaft with
sleeves of both provided on separate shaft, thereby
maintaining H pattern on gear shift knob.
7. A compact manual transmission for passenger cars as
claimed in claim 6 wherein sufficient clearance is provided
for backward movement of the reverse system when 5th fork
is under shifting because of common linked yoke and vice
versa in case of reverse gear shifting.
8. A compact manual transmission for passenger cars as
claimed in any of the preceding claims is associated with the
advantageous features such as herein described.
9. A compact manual transmission for passenger. cars
substantially as herein described with reference to the
accompanying drawings.