FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
VARIABLE DIAMETER CLUTCH MECHANISM FOR
COMPRESSORS
MAHINDRA AND MAHINDRA LIMITED
an Indian company of R&D centre, Automotive Division, 89, M.I.D.C., Satpur, Nashik- 322007
Maharashtra, India.
Inventor:
VERMA NISHITH
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO
BE PERFORMED.

FIELD OF THE DISCLOSURE
The present disclosure relates to compressors.
More particularly, the present disclosure relates to clutch mechanism for compressors.
BACKGROUND
An air-conditioning system includes a compressor, a condenser, an evaporator and an expansion device. The compressor works as a pump to increase pressure and accordingly the temperature of the refrigerant. The compressor needs an external drive or prime mover for its operation and compressing gas to a high temperature and pressure. In automobile operations, compressors are operated with the help of a belt connected to engine crank pulley in a feed system. Compressors are one of the few contributors of reduced fuel efficiency of vehicles. Also compressor engagement/disengagement process in itself gives an impulsive load on the engine. Typically, a conventional compressor comprises a pulley and an electromagnetic clutch attached to a pump. The electromagnetic clutch is engaged or disengaged based on an electric signal from the engine control unit. The clutch engages the pulley and starts rotating it. The normal engine RPM for a compressor ranges from 800 to 3000rpm.
Compressors with conventional clutches provide limited idling cooling performance when engine starts. Generally compressors are customized according to the requirement of a particular vehicle. For increasing fuel efficiency of vehicles, small capacity compressors are used that are costly and their integration with heating, ventilation, and air conditioning (HVAC) systems is difficult.
Thus, there is felt a need to provide a clutch mechanism for compressors that operate with varying pulley diameters and can be integrated with different types of vehicles.

OBJECTS
Some of the objects of the present disclosure aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative are described herein below:
An object of the present disclosure is to provide a clutch mechanism for compressors that provide flexibility in RPM (revolution per minute) of compressors.
Another object of the present disclosure is to provide a clutch mechanism for compressors that can be integrated with all types of compressors.
An additional object of the present disclosure is to provide a clutch mechanism for compressor that is simple in construction.
Yet another object of the present disclosure is to provide a clutch mechanism for compressors that improve low RPM cooling performance.
Yet another object of the present disclosure is to provide a clutch mechanism for compressors that eliminate use of thermistors.
Another object of the present disclosure is to provide a clutch mechanism for compressors that provide relatively better durability performance.
An additional object of the present disclosure is to provide a clutch mechanism for compressors that eliminate use of magnetic clutches in compressors. Yet another object of the present disclosure is to provide a clutch mechanism for compressors that make compressor RPM independent of engine RPM.

Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
A clutch mechanism for a compressor of a vehicle air conditioning system is disclosed in accordance with an embodiment of the present disclosure. The clutch mechanism includes an axis shaft and a variable diameter pulley assembly. The axis shaft derives drive from an engine of the vehicle. The axis shaft is functionally coupled to the compressor and drives the compressor. The variable diameter pulley assembly mounted on the axis shaft and dynamically transmits drive from the engine to the compressor via a flexible drive by utilizing variable pulley ratios. The variable diameter pulley assembly includes an expandable, resilient, continuous sleeve element and a radially expanding sub-system. The expandable, resilient, continuous sleeve element is supported on the axis shaft and supports the flexible drive. The radially expanding sub-system is mounted on the axis shaft and is co-axially disposed within the expandable, resilient, continuous sleeve element. The radially expanding subsystem moves between a retracted normal configuration during engine idling and a radially expanded configuration during high engine speeds, wherein at high engine speeds centrifugal forces acting on the radially expanding sub-system urges the radially expanding sub-system towards the expandable, resilient, continuous sleeve to expand the expandable, resilient, continuous sleeve radially outwards, thereby enabling the variable diameter pulley to rotate at lesser rpm during high engine speeds than during engine idling when improved cooling is required.
In accordance with a preferred embodiment, the radially expanding sub-system includes a first disc, a second disc, a spring element and a centrifugally actuated urging mechanism. The first disc is mounted on the axis shaft and is axially movable thereon. The first disc is having first internal guides configured thereon. The second disc is securely mounted on the axis shaft and is having second internal guides

configured thereon, wherein the second internal guides are complimentary to the first internal guides. The spring element is disposed between the first disc and the second disc and maintains pre-determined gap there-between. The centrifugally actuated urging mechanism includes an expansion ring and a plurality of ball elements. The expansion ring is configured of a plurality of arcuate elements that moves relative to each other to change dimension of the expansion ring. The expansion ring is mounted on the axis shaft and is co-axially disposed within the expandable, resilient, continuous sleeve element. The ball elements are disposed between the first and second discs and move radially outwardly due to centrifugal forces acting thereon. Each ball element is disposed and guided between adjacent first and second internal guides of the first and second discs respectively. Further, each ball element is connected to a corresponding arcuate element of the expansion ring via a linkage to change dimension of the expansion ring and facilitate urging of the expansion ring towards the expandable, resilient, continuous sleeve element to expand the expandable, resilient, continuous sleeve radially outwards.
Typically, the ball elements are of metallic material.
In accordance with an embodiment, the clutch mechanism includes a plurality of keys for mounting the first disc and the second disc on the axis shaft.
Generally, the expandable, resilient, continuous sleeve element is of rubber material.
Typically, the flexible drive maintains three-point contact with the expandable, resilient, continuous sleeve element.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The clutch mechanism for compressors of the present disclosure will now be described with the help of accompanying drawings, in which:

FIGURE 1 illustrates a sectional view of a clutch mechanism in accordance with the present disclosure;
FIGURE 2 illustrates a schematic representation of the first disc of FIGURE 1;
FIGURE 3 illustrates a schematic representation of the second disc of FIGURE 1;
FIGURE 4 illustrates a schematic representation of the expansion mechanism of FIGURE 1;
FIGURE 5 illustrates a schematic representation of the shaft of FIGURE 1;
FIGURE 6 illustrates plurality of first springs mounted on the first disc of FIGURE 1;
FIGURE 7 illustrates a schematic representation of the second spring of FIGURE 1;
FIGURE 8 illustrates a schematic representation of the expansion mechanism of FIGURE 4 mounted on the shaft of FIGURE 5 along with the second spring of
FIGURE 7;
FIGURE 9 illustrates a schematic representation of the rubber sleeve of FIGURE 1;
FIGURE 10 illustrates a schematic representation of the expansion ring of FIGURE 1;
FIGURE 11 illustrates a schematic representation of the belt of FIGURE 1;
FIGURE 12 illustrates a graph representing variation of evaporator air exit temperature with respect to time duration of operation; and
FIGURE 13 illustrates a graph representing variation of cabin temperature with respect to time duration of operation.

DETAILED DISCRITION OF THE ACCOMPANYING DRAWINGS
A preferred embodiment of the clutch mechanism for compressors will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiment herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiment in the following description. Description of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiment herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiment herein may be practiced and to further enable those of skill in the art to practice the embodiment herein. Accordingly, the example should not be construed as limiting the scope of the embodiment herein.
The present disclosure envisages a clutch mechanism 10 in accordance with an embodiment of the present disclosure. The clutch mechanism 10 includes an axis shaft 12 and a variable diameter pulley assembly. The axis shaft 12 derives drive from an engine of the vehicle. The axis shaft 12 is functionally coupled to the compressor and drives the compressor. The variable diameter pulley assembly is mounted on the axis shaft 12 and dynamically transmits drive from the engine to the compressor via a flexible drive, particularly, a belt 28 by utilizing variable pulley ratios. More specifically, the variable diameter pulley can changes its diameter from a smaller diameter during engine idling to larger diameter during high engine speeds to get different pulley ratios during engine idling and high engine speeds, thereby enabling the variable diameter pulley to rotate at higher rpm during engine idling when improved cooling is required and rotate at lower rpm during high engine speeds. The variable diameter pulley assembly includes an expandable, resilient, continuous sleeve 24 also referred to as the rubber sleeve 24 and a radially expanding sub-system. The expandable, resilient, continuous sleeve element 24 is supported on the axis shaft 12

and supports the flexible drive, particularly, the belt 28. The radially expanding sub-system is mounted on the axis shaft 12 and is co-axially disposed within the expandable, resilient, continuous sleeve element 24. The radially expanding sub-system moves between a retracted/contracted normal configuration during engine idling and a radially expanded configuration during high engine speeds, wherein at high engine speeds centrifugal forces acting on the radially expanding sub-system urges the radially expanding sub-system towards the expandable, resilient, continuous sleeve element 24 to expand the expandable, resilient, continuous sleeve element 24 radially outwards, thereby enabling the variable diameter pulley to rotate at lesser rpm during high engine speeds than during engine idling when improved cooling is required.
In accordance with the present disclosure, the radially expanding sub-system of a variable diameter clutch for an Air-conditioner (AC) compressor typically includes following components:
- a first disc 14;
- a second disc 16;
- a plurality of ball elements 18 typically metallic balls;
- a plurality of first spring 20;
- a second spring 22, also referred to as spring element 22; and
- an expansion ring 26.
The first disc 14 is mounted on the axis shaft 12 and is axially movable thereon. The first disc 14 is having first internal guides 15 configured thereon. The second disc 16 is securely mounted on the axis shaft 12 and is having second internal guides 17 configured thereon, wherein the second internal guides 17 are complimentary to the first internal guides 15. The spring element 22 is disposed between the first disc 14 and second disc 16 and maintains pre-determined gap there-between. The radially expanding sub-system further includes centriftigally actuated urging mechanism. The centrifugally actuated urging mechanism includes the expansion ring 26 and the

plurality of ball elements 18. The expansion ring 26 is configured of a plurality of arcuate elements that move relative to each other to change dimension of the expansion ring 26. The expansion ring 26 is mounted on the axis shaft and is co-axially disposed within the expandable, resilient, continuous sleeve element 24. The plurality of ball elements 18 are disposed between the first and second discs (14, 16) and moves radially outwardly due to centrifugal forces acting thereon. The plurality of ball elements 18 are attached to the expansion ring 26 through a plurality of linkages/connecting members 30. More specifically, each ball element is disposed and guided between adjacent first and second internal guides (15, 17) of the first and second discs (14, 16) respectively. Further each ball element is connected to a corresponding arcuate element of the expansion ring 26 via a linkage to change dimension of the expansion ring 26 and facilitate urging the expansion ring 26 towards the expandable, resilient, continuous sleeve element 24 to expand the expandable, resilient, continuous sleeve element 24 radially outwards. The assembly of plurality of ball elements 18 and expansion ring 26 along with the connecting members 30 is herein after termed as expansion mechanism 32. The expansion mechanism 32, the first disc 14 and the second disc 16 are coaxially mounted on the shaft 12 with the help of the plurality of keys 34 such that the first disc 14 is movable along the axis of the shaft 12. The first disc 14 is sandwiched between the expansion ring 26 and the second disc 16. Further, the balls 18 are sandwiched between the first disc 14 and the second disc 16. The expansion ring 26 is covered by the rubber sleeve 24 to hold the expansion mechanism together. The second spring, also referred to as the spring element 22 is provided co-axial to the shaft 12 and is sandwiched between the first disc 14 and the second disc 16. The plurality of balls 18 is attached to the first disc 14 via the plurality of first springs 20. The belt 28 is provided such that it couples the surfaces of the first disc 14, the second disc 16 and the rubber sleeve 24, respectively to an external drive system. The compressor end 36 of the clutch mechanism in accordance with the present disclosure can be easily attached to any compressor.

When the vehicle starts, the engine operates at an idling RPM (revolution per minute) and the plurality of balls 18 is pulled towards the axis of the shaft 12 by the plurality of first springs 20. At the same time the second disc 16 is pulled by the second spring 22, thereby decreasing the diameter of the expansion ring 26 that results in higher compressor RPM at idling and hence a better cooling performance at idling. At this time, the second spring 22 operates in a contracted position.
When the engine operates at a higher RPM, the plurality of balls 18 experiences a centrifugal force and moves outwards thereby actuating the expansion mechanism 32 and increasing the diameter of the expansion ring 26 that results in reduction of the RPM of the compressor. The first disc 14 is movable to provide safety to the plurality of connecting members 30 and prevents the connecting members 30 from bending.
All the intermediate engine RPM's work on corresponding variable diameters of the expansion mechanism 32. The belt 28 helps in maintaining contact with the three surfaces while the diameter of the expansion mechanism 32 increases or decreases as required. The flexible drive, belt 28 is having such a configuration that it maintains three-point contact with the expandable, resilient, continuous sleeve element 24. Thus the compressor RPM is independent of the engine RPM and not driven by it as is seen in the compressors known in the art.
TEST RESULTS
A simulation is performed in Kuli software for testing the advantages and improvement in compressors by using the clutch mechanism in accordance with the present disclosure.

Tablel: simulation data showing values of pulley ratio (engine pulley diameter/ compressor pulley diameter) with respect to time duration of operation as generated from the graph depicted in FIGURE 12

Time (min) Constant pulley ratio Variable pulley ratio
0 29.295 29.0875
30 3.87975 3.22811
60 0.810998 2.26679
90 0.0255565 1.45188
120 10.1398 7.4753
• The evaporator air exit temperature is improved by 2°C to 3°C.
Table2: simulation data showing values of pulley ratio (engine pulley diameter/ compressor pulley diameter) with respect to time duration of operation as generated from the graph depicted in FIGURE 13

Time (min) Constant pulley ratio Variable pulley ratio
0 65 65
30 29.4488 28.9662
60 24.0979 24.5782
90 24.2492 23.7912
120 29.7716 27.7671
• No compressor tripping is observed that indicates removal of thermistors and is successfully implemented.
TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The technical advancements offered by the present disclosure include the realization of:

• a clutch mechanism for compressors that provides flexibility in RPM (revolution per minute) of compressors;
• a clutch mechanism for compressors that can be integrated with all types of compressors;
• a clutch mechanism for compressors that is simple in design;
• a clutch mechanism for compressors that improves low RPM cooling performance;
• a clutch mechanism for compressors that eliminates use of thermistor;
• a clutch mechanism for compressors that provides relatively better durability performance;
• a clutch mechanism for compressors that eliminates use of magnetic clutches in compressors; and
• a clutch mechanism for compressors that makes compressor RPM independent of engine RPM.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall

within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
Wherever a range of values is specified, a value up to 10% below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure.
The foregoing description of the specific embodiment 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 embodiment 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 embodiment. 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 embodiment herein have been described in terms of preferred embodiment, those skilled in the art will recognize that the embodiment herein can be practiced with modification within the spirit and scope of the embodiment as described herein.

WE CLAIM:
1. A clutch mechanism for a compressor of a vehicle air conditioning system:
• an axis shaft adapted to derive drive from an engine of the vehicle, said axis shaft functionally coupled to the compressor and adapted to drive the compressor; and
• a variable diameter pulley assembly mounted on said axis shaft and adapted to dynamically transmit drive from said engine to the compressor via a flexible drive by utilizing variable pulley ratios, said variable diameter pulley assembly comprising:
o an expandable, resilient, continuous sleeve element supported on said axis shaft and adapted to support said flexible drive; and
o a radially expanding sub-system mounted on said axis shaft and co-axially disposed within said expandable, resilient, continuous sleeve element, said radially expanding sub-system adapted to move between a retracted normal configuration during engine idling and a radially expanded configuration during high engine speeds, wherein at high engine speeds centrifugal forces acting on said radially expanding sub-system urges said radially expanding sub-system towards said expandable, resilient, continuous sleeve to expand said expandable, resilient, continuous sleeve radially outwards, thereby enabling said variable diameter pulley to rotate at lesser rpm during high engine speeds than during engine idling when improved cooling is required.
2. The clutch mechanism as claimed in claim 1, wherein radially expanding subsystem comprising:

• a first disc mounted on said axis shaft and axially movable thereon, said first disc having first internal guides configured thereon;
• a second disc securely mounted on said axis shaft and having second internal guides configured thereon, wherein said second internal guides are complimentary to said first internal guides;
• a spring element disposed between said first disc and second disc and adapted to maintain pre-determined gap there-between; and
• a centrifugally actuated urging mechanism comprising:
o an expansion ring configured of a plurality of arcuate elements adapted to move relative to each other to change dimension of said expansion ring, said expansion ring mounted on said axis shaft and co-axially disposed within said expandable, resilient, continuous sleeve element; and
o a plurality of ball elements disposed between said first and second discs and adapted to move radially outwardly due to centrifugal forces acting thereon, each ball element disposed and guided between adjacent first and second internal guides of the first and second discs respectively, further each ball element connected to a corresponding arcuate element of said expansion ring via a linkage to change dimension of said expansion ring and facilitate urging said expansion ring towards said expandable, resilient, continuous sleeve element to expand said expandable, resilient, continuous sleeve radially outwards.
3. The clutch mechanism as claimed in claim 2, wherein said ball elements are of metallic material.

4. The clutch mechanism as claimed in claim 2 further comprises a plurality of keys for mounting said first disc and said second disc on said axis shaft.
5. The clutch mechanism as claimed in claim 1, wherein said expandable, resilient, continuous sleeve element is of rubber material.
6. The clutch mechanism as claimed in claim 1, wherein said flexible drive adapted to maintain three point contact with said expandable, resilient, continuous sleeve element.