Claims:
1. A multi speed manual transmission (100) with a fixed planetary gear train (104) comprising:
a main speed gear train (102) coupled to the fixed planetary gear train (104) wherein the fixed planetary gear train (104) is configured with a ring carrier (118), a ring gear (114), a sun gear (116), a reaction plate (120), a planet gear (122), a planet shaft (124), a planet roller (126), a planet carrier (128), a rear housing (130) and an output shaft (132), for transferring the motion from main shaft (110) of main speed gear train (102) to the output shaft (132) of fixed planetary gear train (104) through the ring gear carrier (118), ring gear (114), planet gear (122) revolving around sun gear (116), planet shaft (124) rigidly mounted on planet carrier (128).
2. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the ring carrier (118) mounted on main shaft (110) is configured to provide drive to the ring gear (114).

3. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the planet gear (122) is mounted on the planet shaft (124) through the planet rollers (126) and is configured to be in constant mesh with the ring gear (114) and the sun gear (116) rigidly mounted to the rear housing (130) through the reaction plate (120).

4. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the planet shaft (124) is configured to be rigidly mounted on the planet carrier (128) forming an integral assembly mounted on the output shaft (132) to provide drive to drive axles of a vehicle.

5. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the output shaft (132) is configured with splines to be coupled with an output coupling flange (134) connected to driving axles.

6. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein a planetary gear ratio is configured as (1+ (sun gear teeth ÷ ring gear teeth)).

7. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein an overall gear ratio is configured from the main speed gear ratio and the fixed planetary gear ratio.

8. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the sun gear (116) is configured to be mounted on the reaction plate (120) through spline joint and the reaction plate (120) is configured to be rigidly mounted to the rear housing (130).

9. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the ring carrier (118) is configured to be mounted on the main shaft (110) through spline.

10. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the planet gear (122) is configured to be rotated in direction of the ring gear (114) and revolves around the rigidly mounted sun gear (116) to prevent the rotation in opposite direction.

11. The multi speed manual transmission (100) with the fixed planetary gear train (104) as claimed in claim 1, wherein the output shaft (132) is configured to be concentric to the sun gear (116) with radial clearance, to avoid friction between rigidly mounted sun gear (116) and the output shaft (132) during transmission.
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
MULTI SPEED MANUAL TRANSMISSION WITH FIXED PLANETARY GEAR TRAIN

Applicant:
Tata Motors Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400001,
Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
[001] The present subject matter described herein, in general, relates to a multi speed manual transmission and more specifically relates to the multi speed manual transmission with a fixed planetary gear train.
BACKGROUND
[002] Gear ratio in a gearbox is basically multiplication of constant mesh ratio and individual gear pair ratio. Higher gear ratios give better torque at wheels which is required in case of load carrying vehicles. In multi speed gearboxes especially in a six-speed manual transmission, a deeper or higher first gear ratio is suitable for heavy vehicle application. This higher first gear ratio is required to deliver more torque at wheels for navigating slope conditions of road. Basically, heavy vehicles carrying load are required to drive in first gear on slope conditions as the size of first gear is largest which provides higher gear ratio, more torque at wheels with lower top speed which helps driver to cross the slope. In some cases, generated torque at wheels is not enough to cross the slope in first gear. In conventional layout gearbox includes a drive shaft, a lay shaft and a main shaft, the first gear which is largest (highest), is limited by the size of first gear pinion, which becomes small as ratio increases and creates limitation on torque carrying capacity.
[003] From above explanation, it is clear that higher gear ratio leads to increase in torque carrying capacity at the wheels. In one of the prior art, the higher gear ratio is achieved by increasing the constant mesh ratio and for achieving this, a drive shaft gear diameter has to be reduced which will again create limitation in the torque carrying capacity. In another prior art, for increasing the torque carrying capacity of the gearbox, the gear sizes have been increased and to accommodate larger size gears, a center distance between the lay shaft and the drive shaft has to be increased which results in increase in overall gearbox size, inertia of gears, gear shifting forces and weight of the gearbox and subsequently the cost of the gearbox. Further, increased size of the gearbox has limitation on integration on the vehicle like reduction in ground clearance or fitment in a standard chassis width. Also, this will lead to difficulty in vehicle packaging.
[004] Moreover, the above-explained problems can also be addressed with configuration of 9 speed gearbox which is a combination of 5 speed gearbox (main gearbox) and 2 speed planetary gearbox at rear. For achieving 9 speeds in said gearbox, 5 speed main gearbox is used with one set of planetary ratios at rear gearbox and 4 speed of main speed gearbox is repeated with second ratio of planetary gearbox at rear. This rear planetary gearbox adds the complexity of shifting the gears and in some cases driver training is required to engage the 9 speeds in the vehicle. Further, increase in gearbox parts for planetary shifting increases gearbox cost and additional driver training cost.
[005] Hence, there is need to improve a gear train wherein the higher gear ratio can be achieved to increase a torque carrying capacity of gearbox without gear shifting complexity.
OBJECT OF THE INVENTION
[006] It is a main object of the present invention to enhance a torque carrying capacity of gearbox by achieving higher gear ratios.
[007] It is an object of the present invention to provide a planetary gear system without additional gear shifting system.
[008] It is an object of the present invention to reduce main speed gear sizes in order to minimize inertia of gearbox components and to reduce gear shifting effort.
[009] It is an object of the present invention to provide a fixed planetary gear train with an existing main speed gear train.
STATEMENT OF THE INVENTION
[0010] Accordingly, the present invention discloses a multi speed manual transmission with a fixed planetary gear train comprising a main speed gear train coupled to the fixed planetary gear train wherein the fixed planetary gear train is configured with a ring carrier), a ring gear, a sun gear, a reaction plate, a planet gear, a planet shaft, a planet roller , a planet carrier, a rear housing and an output shaft, for transferring the motion from main shaft of main speed gear train to the output shaft of fixed planetary gear train through the ring gear carrier, ring gear, planet gear revolving around sun gear, planet shaft rigidly mounted on planet carrier.
[0011] The ring carrier mounted on main shaft is configured to provide drive to the ring gear. The planet gear is mounted on the planet shaft through the planet rollers and is configured to be in constant mesh with the ring gear and the sun gear rigidly mounted to the rear housing through the reaction plate. The planet shaft is configured to be rigidly mounted on the planet carrier forming an integral assembly mounted on the output shaft to provide drive to drive axles of a vehicle. The output shaft is configured with splines to be coupled with an output coupling flange connected to driving axles. The planetary gear ratio is configured as (1+ (sun gear teeth ÷ ring gear teeth)).
[0012] The overall gear ratio is configured from the main speed gear ratio and the fixed planetary gear ratio. The sun gear is configured to be mounted on the reaction plate through spline joint and the reaction plate is configured to be rigidly mounted to the rear housing. The ring carrier is configured to be mounted on the main shaft through spline. The planet gear is configured to be rotated in direction of the ring gear and revolves around the rigidly mounted sun gear. The output shaft is configured to be concentric to the sun gear with radial clearance, to avoid friction between rigidly mounted sun gear and the output shaft during transmission.
SUMMARY
[0013] Before the present system and method are described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to a planetary gear train in a manual transmission system. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[0014] The present subject matter discloses a multi speed manual transmission system wherein a fixed range planetary gearbox is introduced with a main speed gearbox. In the proposed invention, a six-speed gearbox comprising a main speed section and planetary gear section is explained. The planetary gearbox of the proposed invention does not require any extra gear shifting arrangement and said gearbox is coupled to the main speed gearbox wherein the main speed gear ratio is multiplied to the planetary gear ratio to obtain a required overall gear ratio. Gear sizes of the main speed gearbox can be reduced, and gear sizes of the planetary gearbox can be selected based on required overall gear ratio and required torque carrying capacity of the gearbox.
[0015] Configuration of the planetary gearbox of the manual transmission system is the innovative concept of the proposed invention wherein said gearbox comprises a sun gear, a ring gear, a ring carrier, a planet gear, a planet carrier, a planet shaft, a planet roller, a reaction plate, an output shaft and an output coupling flange. In said planetary gearbox, an input gear is ring gear, and an output gear is Planet carrier mounted on the output shaft wherein the overall gear ratio is obtained as ratio of the output gear to the input gear. The sun gear is fixed, and the planet gear is in mesh with both the ring gear and the sun gear, hence rotation of ring gear rotates the planet gear which in turn revolves around the sun gear. The planet gear further rotates on the stationary planet shaft through planet rollers. The planet shaft is fixedly mounted to the planet carrier and rotates along with the planet carrier based on the rotation on planet shaft and revolution of the planet gear on sun gear. The planet carrier is integral part of output shaft and hence it rotates the output shaft. The output coupling flange is mounted on the output shaft through splines and drives axles of a vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawing.
[0017] The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0018] Figure 1 illustrates a sectional view of a multi speed manual transmission with fixed planetary gear train, in accordance with the present invention.
[0019] Figure 2 illustrates an isometric view for main speed gearbox of a multi speed manual transmission with fixed planetary gear train.
[0020] Figure 3 illustrates a sectional view of fixed planetary gear train, in accordance with the present invention.
[0021] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0022] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0023] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.
[0024] The present subject matter discloses a multi speed manual transmission comprising a main speed gearbox and a fixed range gearbox or fixed planetary gearbox. A gear ratio of main speed gearbox is multiplied with a planetary gear ratio of the fixed range gearbox to obtain required gear ratios which is also referred as an overall gear ratio. In the proposed invention, the fixed range gearbox is configured to be mounted with either an existing main speed gearbox or with of the main speed gearbox with reduced gear sizes wherein the main speed gearbox is mounted at front side of a drive and the fixed range gearbox is mounted at rear side. The overall gear ratio and a torque carrying capacity of the gearbox is increased by mounting the fixed range gearbox with the existing main speed gearbox. However, for achieving the same overall gear ratio and for same torque carrying capacity of the gearbox as of the conventional gearbox, the fixed range gearbox is mounted with the reduced size main speed gearbox. The reduction in size of the gears subsequently reduces inertia of the gears. Said reduced size main speed gearbox also provide ease in shifting of gears with less efforts as compared to conventional six speed gearbox with similar gear ratios.
[0025] Referring to figure 1 and figure 2, a cross sectional view of a proposed multi speed transmission with a fixed planetary gear train are depicted respectively. Said multi speed transmission (100) mainly comprises two sections a main speed section (102) which is a conventional system of gear train and a fixed range section (104) which is a proposed gear train system. The main speed section (102) is basically a main speed gearbox comprising a drive shaft (106), a lay shaft (108) and a main shaft (110) wherein a drive from an engine is given to the drive shaft (106) and power is further transferred to the lay shaft (108) through a constant mesh gear pair (112). The constant mesh gear pair (112) and other gear including 6 CS, 4 CS, 3 CS, 2 CS are rigidly mounted, or press fitted on the lay shaft (108) and hence rotates as a single unit. The gears including 6 MS, 4 MS, 3 MS, 2 MS, 1 MS and R MS are configured for freely rotating on the main shaft (110) over needle bearings 6 NB, 4 NB, 3 NB, 2 NB, 1 NB and R NB respectively and R MS gear is in mesh with R Idler gear mounted on Reverse idler shaft (109) in mesh with reverse pinion on the lay shaft (108). Further, said gears on lay shaft (108) are in mesh with the gears on the main shaft (110) and as the lay shaft (108) rotates, the gears mounted on main shaft (110) rotates to obtain required gear ratio. Furthermore, the gear shifting in a six-speed transmission system is explained. For first gear, a synchronizer pack (SP 1-2) comprising a shifter sleeve (SS 1-2) and a shifter fork (SF 1-2) is moved towards 1 MS wherein the gear (1 MS) is configured to be connected to the main shaft (110) through spline joint and a first speed ratio of main speed is achieved. The first speed ratio is obtained as ratio of constant mesh teeth to drive shaft teeth multiplied by ratio of 1 MS teeth to 1 CS teeth. For second gear, the synchronizer pack (SP 1-2) is moved towards 2 MS wherein the gear (2 MS) is configured to be connected to the main shaft (110) through spline joint to obtain second speed ratio. The second speed ratio is obtained as ratio of constant mesh teeth to drive shaft teeth multiplied by ratio of 2 MS teeth to 2 CS teeth. Similarly, for third and fourth gear, a synchronizer pack (SP 3-4) comprising a shifter sleeve (SS 3-4) and a shifter fork (SF 3-4) is moved towards 3 MS and 4 MS respectively wherein third and fourth speed ratio is obtained as ratio of constant mesh teeth to drive shaft teeth multiplied by ratio of 3 MS or 4 MS teeth to 3 CS or 4 CS teeth respectively. For fifth gear, a synchronizer pack (5-6) comprising a shifter sleeve (SS 5-6) and a shifter fork (SF 5-6) is moved towards drive shaft (106) connecting directly to main shaft (110). For sixth gear, the synchronizer pack (5-6) comprising the shifter sleeve (SS 5-6) and the shifter fork (SF 5-6) is moved towards 6 MS. Furthermore, for obtaining the speed ratios for the sixth gear, teeth combination of respective gears is selected. The fixed planetary gear train (104) is explained in subsequent paragraphs.
[0026] Referring to figure 3, the fixed range section or the fixed planetary gear train (104) of the proposed invention is explained in detail. The fixed planetary gear train comprises a ring gear (114), a sun gear (116), a ring carrier (118), a reaction plate (120), a planet gear (122), a planet shaft (124), a planet roller (126), a planet carrier (128), a rear housing (130) and an output shaft (132). In the present embodiment, the sun gear (116) is configured to be rigidly mounted or fixed to the reaction plate (120) through spline joint wherein the reaction plate (120) is rigidly mounted/bolted to the rear housing (130). Further, drive from the main shaft (110) is configured to be given to the ring gear (114) through the ring carrier (118) wherein the ring carrier (118) is connected to the main shaft (110) through spline. The planet gear (122) is assembled on the planet shaft (124) over the planet rollers (126) wherein the planet gear (122) is in mesh with the ring gear (114) on one side and with the sun gear (116) on another side. Furthermore, the planet shaft (124) is rigidly mounted/fixed on to the planet carrier (128) wherein the planet carrier (128) is further mounted on the output shaft (132) for transfer of motion to output shaft (132). As seen from the figure, the output shaft (132) is concentric to the sun gear (116) with radial clearance. By above-mentioned arrangement, the sun gear (116) is rigidly mounted/fixed to the rear housing (130) through the reaction plate (120) and motion from the main shaft (110) is configured to be given to the ring gear (114) wherein the planet gear (122) tend to revolve around the sun gear (116) as the planet gear (122) is in mesh with the ring gear (114) and the sun gear (116). Further, the planet carrier (128) also tries to move as it is rigidly mounted/bolted to the planet shaft (124). Finally, the planet carrier (128) rotates the output shaft (132). The output shaft (132) is configured with splines to be coupled with an output coupling flange (134) wherein the output coupling flange (134) is connected to driving axles. In the above-explained fixed range planetary gearbox, planetary gear ratio is obtained as ratio of an output gear to an input gear which is (1+ (number of sun gear teeth ÷ number of ring gear teeth)). Furthermore, the overall gear ratio obtained is, the main speed ratio multiplied by planetary ratio.
[0027] For example, if the constant mesh gear ratio is 1.952 and the first gear ratio is 4.273, then the main speed ratio will be 8.341 which is obtained by multiplying the constant mesh gear ratio and the first gear ratio. Further, if the planetary ratio obtained is 1.389, then the overall ratio will be 11.586 which is obtained by multiplying the main speed ratio with the planetary gear ratio.
[0028] Accordingly, the present invention discloses a multi speed manual transmission (100) with a fixed planetary gear train (104) comprising a main speed gear train (102) coupled to the fixed planetary gear train (104) wherein the fixed planetary gear train (104) is configured with a ring carrier (118), a ring gear (114), a sun gear (116), a reaction plate (120), a planet gear (122), a planet shaft (124), a planet roller (126), a planet carrier (128), a rear housing (130) and an output shaft (132), for transferring the motion from main shaft (110) of main speed gear train (102) to the output shaft (132) of fixed planetary gear train (104) through the ring gear carrier (118), ring gear (114), planet gear (122) revolving around sun gear (116), planet shaft (124) rigidly mounted on planet carrier (128).
[0029] The ring carrier (118) mounted on main shaft (110) is configured to provide drive to the ring gear (114). The planet gear (122) is mounted on the planet shaft (124) through the planet rollers (126) and is configured to be in constant mesh with the ring gear (114) and the sun gear (116) rigidly mounted to the rear housing (130) through the reaction plate (120). The planet shaft (124) is configured to be rigidly mounted on the planet carrier (128) forming an integral assembly mounted on the output shaft (132) to provide drive to drive axles of a vehicle. The output shaft (132) is configured with splines to be coupled with an output coupling flange (134) connected to driving axles. The planetary gear ratio is configured as (1+ (sun gear teeth ÷ ring gear teeth)).
[0030] The overall gear ratio is configured from the main speed gear ratio and the fixed planetary gear ratio. The sun gear (116) is configured to be mounted on the reaction plate (120) through spline joint and the reaction plate (120) is configured to be rigidly mounted to the rear housing (130). The ring carrier (118) is configured to be mounted on the main shaft (110) through spline. The planet gear (122) is configured to be rotated in direction of the ring gear (114) and revolves around the rigidly mounted sun gear (116) to prevent the rotation in opposite direction. The output shaft (132) is configured to be concentric to the sun gear (116) with radial clearance, to avoid friction between rigidly mounted sun gear (116) and the output shaft (132) during transmission.
[0031] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0032] Some object of the present invention provides deeper or higher gear ratios for every gear i.e., first, second, third, fourth, fifth and sixth gear.
[0033] Some object of the present invention improves torque carrying capacity of a gearbox.
[0034] Some object of the present invention provides reduced main speed gear sizes for obtaining required gear ratio.
[0035] Some object of the present invention reduces gear shifting efforts.
[0036] Some object of the present invention reduces weight of a gearbox.
[0037] Some object of the present invention provides reduced inertia of components.
[0038] Following is the list of reference numerals used in overall complete specification.

Reference numeral Part Name
100 Multi speed transmission
102 Main speed section
104 Fixed planetary section
106 Drive shaft
108 Lay shaft
109 Reverse Idler shaft
110 Main shaft
112 Constant mesh gear pair
MS Gears on main shaft
NB Needle bearings
CS Gears on lay shaft
SP Synchronizer pack
SF Shifter fork
SS Shifter sleeve
114 Ring gear
116 Sun gear
118 Ring carrier
120 Reaction plate
122 Planet gear
124 Planet shaft
126 Planet roller
128 Planet carrier
130 Rear housing
132 Output shaft
134 Output coupling flange