DESC:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“SPEED SENSOR TRIGGER WHEEL ASSEMBLY AND A METHOD OF PROVIDING SPEED SENSOR TRIGGER WHEEL”

APPLICANTS:

Name : Mahindra &Mahindra Ltd

Nationality : India

Address : Mahindra Research Valley, Mahindra World
City Plot No. 41/1, Anjur P.O. Chengalpattu
Kancheepuram Dist, Tamilnadu - 603204

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-
TECHNICAL FIELD
[001] The embodiments herein generally relate to trigger wheels, and more particularly to a speed sensing trigger wheel and method of providing speed sensor triggering wheel in diesel engines.

BACKGROUND
[002] A trigger wheel, generally known asa missing tooth wheel is used in detecting a speed of crankshaft based on hall effect principle. Generally, trigger wheel is mounted directly on the crankshaft or flywheel. For example, in Korean patent application KR2001005366A, an attachment structure for trigger wheel is disclosed. The trigger wheel is formed integrally with a surface of the flywheel, or attached to a surface of an additional plate so as to allow the plate to be mounted, as a coupling member, attachable/detachable to/from a surface of the flywheel. Aforementioned arrangement of trigger wheel is made for axial sensing and therefore, additional space is required for packaging of sensor thereby increasing an overall length of an engine Further, with the aforementioned arrangement, separate pigtail will be required for sensor resulting in increased cost.
[003] In the aforementioned arrangement, machining of tooth on flywheel proves to be non productive. Further, axial sensing is known for strong air gap variations, which will effect adversely the functioning of sensor.
[004] Another patent, US 7541803 B2 relates to a device for measuring the angle of rotation between a camshaft and a crankshaft. The device as disclosed in US 7,541,803 B2 includes a camshaft regulator provided with an electronic regulator and a device for determining the position of the angle of rotation of the camshaft and the crankshaft. US 7,541,803 B2 is directed to camshaft and crankshaft angle of rotation and does not disclose trigger wheel position and detailing.
[005] It may be noted that for implementing the kind of design as disclosed in US 7,541,803 B2, first bearing of crankshaft is moved out to accommodate trigger wheel and sensor. The aforementioned arrangement results in an increase of the engine length and further causes edge loading of first bearing.
[006] In the aforementioned conventional arrangements, as trigger wheel is mounted on crankshaft, material to be added on the web, and for balancing the complete crankshaft, additional material to be added on the other webs result in increase of the overall weight of crankshaft.
[007]
[008] Therefore, there is a need for a trigger wheel mounting method to obviate the aforementioned drawbacks.

OBJECT
[009] The principal object of the embodiments described herein is to provide a trigger wheel assembly, which can be mounted on a mass balancer gear.
[0010] Another object of the embodiments of the present invention is to provide a trigger wheel assembly with radial sensor type.
[0011] Another object of the embodiments is to disclose a method of providing a trigger wheel assembly on a mass balancer driver gear.
[0012] A further object of the embodiments is to provide a trigger wheel assembly that is compact.

BRIEF DESCRIPTION OF FIGURES
[0013] The embodiments of this invention is illustrated in the accompanying drawings, through out which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0014] FIG. 1 depicts a trigger wheel assembly configured to be mounted, according to embodiments as disclosed herein;
[0015] FIG. 2a depicts a side view of the cylinder block with trigger wheel assembly mounted onto a crankshaft, according to embodiments as disclosed herein;
[0016] FIG. 2b depicts a close up view of a portion of the cylinder block A including the trigger wheel assembly of FIG. 2a, according to embodiments as disclosed herein;
[0017] FIG. 3a is an exploded view of the trigger wheel assembly, according to embodiments as disclosed herein;
[0018] FIG. 3b depicts a perspective view of the trigger wheel secured to the mass balancer diver gear, according to embodiments as disclosed herein;
[0019] FIG. 4 depicts a side view of the trigger wheel assembly according to embodiments as disclosed herein; and
FIGs. 5a and 5b depict assembly step to assemble the trigger wheel assembly onto the crankshaft, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
[0020] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0021] The embodiments herein achieve a method of providing speed sensor triggering wheel. Referring now to the drawings, and more particularly to FIGS. 1 through 5b, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0022] FIG. 1 depicts a trigger wheel assembly 200 configured to be provided on a crankshaft 102 provided at the cylinder block 100, according to embodiments as disclosed herein. As is apparent from FIG. 1, the trigger wheel assembly 200 is adapted to be mounted onto a mass balancer driver gear 204, which in turn is configured to be mounted onto the crankshaft 102. Further, the trigger wheel assembly 200 is positioned outside the cylinder block 100 or the engine block.
[0023] The trigger wheel assembly includes a trigger wheel 202T, a sensor 202S, a sensor a trigger wheel positioning mechanism 202D, a trigger wheel locking mechanism 202R. The trigger wheel positioning mechanism is configured to position the trigger wheel 202T in relation to the mass balancer driver gear 204. The trigger wheel locking mechanism 202R is configured to lock the trigger wheel 202T to the mass balancer driver gear 204. The sensor 202S is configured to be mounted onto the cylinder block 100 by a bolt 202B. The sensor 202S is a radial sensor configured to detect radial position of the trigger wheel 202T. The sensor 202S works based on Hall effect principle.
[0024] FIG. 2a depicts a side view of the cylinder block 100 with trigger wheel assembly 200 mounted onto a crankshaft 102. Further, FIG. 2b depicts a close up view of a portion A of the cylinder block 100 including the trigger wheel assembly 200 of FIG. 2a. As is apparent from FIGs 2a and 2b, in a mounted position, the trigger wheel 202T is adapted to be provided closer to the cylinder block 100. In an embodiment, a thickness of the trigger wheel 202T is lesser than a thickness of the mass balancer driver gear 204.
[0025] FIG. 3a is an exploded view of the trigger wheel assembly 200, according to embodiments as disclosed herein. The trigger wheel locking mechanism 202R is configured to engage a corresponding locking mechanism provided in the mass balancer driver gear 204. In an embodiment, the trigger wheel locking mechanism 202R includes a plurality of screws and corresponding through holes O. Each of the through holes O is threaded and is adapted to receive the corresponding screw therein. The locking mechanism provided in the mass balancer driver gear 204 includes a plurality of threaded through holes L corresponding to the through holes O of the trigger wheel locking mechanism 202R.
[0026] As is apparent from FIG. 3b, an outer diameter of the trigger wheel 202T is greater than an outer diameter of the mass balancer driver gear 204 thereby avoiding any failure during sensing of missing tooth. Further, a width or thickness of the mass balancer driver gear 204 is greater than a width or thickness of the trigger wheel 202T. To compensate the reduction in crankshaft counter weight radius, width of the crankshaft is increased.
[0027] Further, the trigger wheel positioning mechanism 202D is configured to position the trigger wheel 202T in relation to the mass balancer driver gear 204. In an embodiment, the trigger wheel positioning mechanism includes a dowel 202D. One end of the dowel 202D is provided inside a slot defined by the mass balancer gear drive 204 and the other end is received inside a slot 202a (as shown in FIG. 4) provided on the trigger wheel 202T. The trigger wheel positioning mechanism 202D ensures guidance and alignment of the mass balancer driver gear 204 and the trigger wheel 202T.
[0028] FIG. 4 depicts a side view of the trigger wheel assembly according to embodiments as disclosed herein.
[0029] Further, for the purpose of this description and for the ease of understanding, it is mentioned herein that the trigger wheel locking mechanism 202R includes a plurality of screws and corresponding holes and, the trigger wheel positioning mechanism 202D includes dowel. However, it is also within the scope of this invention to provide any other means for locking and positioning of the trigger wheel 202T without otherwise deterring the intended function of the trigger wheel 202T and locking and positioning of the trigger wheel 202T with respect to the mass balancer driver gear 204 as can be inferred from the disclosure in this specification and drawings. For example, the trigger wheel 202T can be provided with at least one projection and the mass balancer driver gear 204 can be provided with a slot corresponding to the projection and the trigger wheel 202T can be locked onto the mass balancer driver gear 204 by engaging the slot and the projection without otherwise deteering the intended function of the trigger wheel assembly 200 as can be deduced from this description.
[0030] FIGs. 5a and 5b depict assembly step to assemble the trigger wheel assembly onto the crankshaft, according to embodiments as disclosed herein. For the purpose of this description and for the ease of understanding, the engine is considered as 1.2 liters, 3 cylinder in line internal combustion diesel engine with turbo charged intercooler. As is apparent from FIG. 5a, the trigger wheel 202T is guided to be positioned on the mass balancer driver gear 204 via the trigger wheel positioning mechanism 202D. Thereafter, the trigger wheel 202T is secured to the mass balancer driver gear 204 via the trigger wheel locking mechanism 202R. The sensor 202S is mounted onto the cylinder block 100 and is held in place via the bolt 202B.
[0031] Further, as is apparent from FIG. 5b, the trigger wheel 202T and the mass balancer driver gear 204 securing the trigger wheel 202T thereto is mounted onto the crankshaft 102 so that the trigger wheel 202T is closer to the cylinder block 100 and the mass balancer driver gear 204 is located adjacent to the trigger wheel 202T and away from the cylinder block 100. The mass balancer driver gear 204 along with the trigger wheel 202T is guided and secured to the crankshaft 102 via a crankshaft key 102K. The aforementioned arrangement of the trigger wheel 202T provides for easy removal, replacement or repair of the trigger wheel 202T without having to remove the crankshaft 102.
[0032] In an embodiment, the trigger wheel 202T is made by blanking of sheet metal.
[0033] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

CLAIMS
We claim:

1. A speed sensing trigger wheel assembly, said assembly comprising:
a trigger wheel;
a radial sensor;
a trigger wheel positioning mechanism, said trigger wheel positioning mechanism configured to position the trigger wheel on a mass balancer driver gear; and
a trigger wheel locking mechanism, said trigger wheel locking mechanism configured to secure the trigger wheel to the mass balancer driver gear,
wherein, said trigger wheel is adapted to be positioned external to a cylinder block of an engine.

2. The speed sensing trigger wheel assembly as claimed in claim 1, wherein said trigger wheel positioning mechanism includes a dowel adapted to be inserted, on one end, into a slot provided on the mass balancer driver gear and another end of the dowel adapted to be inserted into a slot provided in the trigger wheel.

3. The speed sensing trigger wheel assembly as claimed in claim 2, wherein said trigger wheel locking mechanism includes a plurality of screws, each of said screws adapted to be secured inside a corresponding hole provided in the trigger wheel and the mass balancer driver gear.

4. The speed sensing trigger wheel assembly as claimed in claim 1, wherein said radial sensor is secured to the cylinder block by a bolt.

5. The speed sensing trigger wheel assembly as claimed in claim 1, wherein an outer diameter of said trigger wheel is greater than an outer diameter of the mass balancer driver gear.

6. The speed sensing trigger wheel assembly as claimed in claim 5, wherein a thickness of said trigger wheel is lesser than a thickness of the mass balancer driver gear.

7. The seed sensing trigger wheel assembly as claimed in claim 1, wherein the mass balancer driver gear along with the trigger wheel is guided and secured to the crankshaft by a crankshaft key.

8. A method of providing a speed sensing trigger wheel assembly to an engine, said method comprising:
positioning the trigger wheel adjacent to a mass balancer driver gear by a trigger wheel positioning mechanism;
locking the trigger wheel to the mass balancer driver gear by a trigger wheel locking mechanism;
guiding and securing the mass balancer driver gear along with the trigger wheel onto a crankshaft by a crankshaft key; and
providing a radial sensor on a cylinder block, wherein
the speed sensing trigger wheel assembly is located external to the engine block; and
the speed sensing trigger wheel is closer to the engine block.

9. The method as claimed in claim 8, wherein wherein an outer diameter of said trigger wheel is greater than an outer diameter of the mass balancer driver gear.

10. The method as claimed in claim 9, wherein a thickness of said trigger wheel is lesser than a thickness of the mass balancer driver gear.

Dated this 28th September 2015

Signature:
Name: Kalyan Chakravarthy

ABSTRACT
The trigger wheel assembly 200 is adapted to be mounted onto a mass balancer driver gear 204, which in turn is configured to be mounted onto the crankshaft 102. Further, the trigger wheel assembly 200 is positioned outside the cylinder block 100 or the engine block. The trigger wheel assembly includes a trigger wheel 202T, a sensor 202S, a sensor a trigger wheel positioning mechanism 202D, a trigger wheel locking mechanism 202R. The trigger wheel positioning mechanism is configured to position the trigger wheel 202T in relation to the mass balancer driver gear 204. The trigger wheel locking mechanism 202R is configured to lock the trigger wheel 202T to the mass balancer driver gear 204. The sensor 202S is configured to be mounted onto the cylinder block 100 by a bolt 202B.
FIG. 1
,CLAIMS:CLAIMS
We claim:

1. A speed sensing trigger wheel assembly, said assembly comprising:
a trigger wheel;
a radial sensor;
a trigger wheel positioning mechanism, said trigger wheel positioning mechanism configured to position the trigger wheel on a mass balancer driver gear; and
a trigger wheel locking mechanism, said trigger wheel locking mechanism configured to secure the trigger wheel to the mass balancer driver gear,
wherein, said trigger wheel is adapted to be positioned external to a cylinder block of an engine.

2. The speed sensing trigger wheel assembly as claimed in claim 1, wherein said trigger wheel positioning mechanism includes a dowel adapted to be inserted, on one end, into a slot provided on the mass balancer driver gear and another end of the dowel adapted to be inserted into a slot provided in the trigger wheel.

3. The speed sensing trigger wheel assembly as claimed in claim 2, wherein said trigger wheel locking mechanism includes a plurality of screws, each of said screws adapted to be secured inside a corresponding hole provided in the trigger wheel and the mass balancer driver gear.

4. The speed sensing trigger wheel assembly as claimed in claim 1, wherein said radial sensor is secured to the cylinder block by a bolt.

5. The speed sensing trigger wheel assembly as claimed in claim 1, wherein an outer diameter of said trigger wheel is greater than an outer diameter of the mass balancer driver gear.

6. The speed sensing trigger wheel assembly as claimed in claim 5, wherein a thickness of said trigger wheel is lesser than a thickness of the mass balancer driver gear.

7. The seed sensing trigger wheel assembly as claimed in claim 1, wherein the mass balancer driver gear along with the trigger wheel is guided and secured to the crankshaft by a crankshaft key.

8. A method of providing a speed sensing trigger wheel assembly to an engine, said method comprising:
positioning the trigger wheel adjacent to a mass balancer driver gear by a trigger wheel positioning mechanism;
locking the trigger wheel to the mass balancer driver gear by a trigger wheel locking mechanism;
guiding and securing the mass balancer driver gear along with the trigger wheel onto a crankshaft by a crankshaft key; and
providing a radial sensor on a cylinder block, wherein
the speed sensing trigger wheel assembly is located external to the engine block; and
the speed sensing trigger wheel is closer to the engine block.

9. The method as claimed in claim 8, wherein wherein an outer diameter of said trigger wheel is greater than an outer diameter of the mass balancer driver gear.

10. The method as claimed in claim 9, wherein a thickness of said trigger wheel is lesser than a thickness of the mass balancer driver gear.

Dated this 28th September 2015

Signature:
Name: Kalyan Chakravarthy