FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10; RULE 13)
"TWO STAGE DUAL MASS FLYWHEEL WITH LOCK-UP MECHANISM
FOR AUTOMOTIVE VEHICLE"
MAHINDRA & MAHINDRA LIMITED
AN INDIAN COMPANY,
R&D CENTER, AUTOMOTIVE SECTOR,
89, M.I.D.C., SATPUR,
NASHIK-422 007,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES AND ASCERTAINS THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF THE INVENTION:-
The present invention is related to vehicle systems. More particularly, the invention relates to a device for damping vibrations, in particular between an engine and a drive train of a vehicle, forming a so-called dual-mass flywheel.
BACKGROUND OF THE PRESENT INVENTION:-
The present invention is based on a dual mass flywheel with springs as energy storage device which has an inherent concern pertaining to the resonance phenomena encountered during the starting and stopping. During the resonance very high torque levels are observed on the primary mass. This results in extreme oscillation of the energy transfer device which happens to be the flange with the arms/wings. This finally results in extreme oscillation of the energy storage device which is a spring damper arrangement. During this zone the springs undergo sudden shock/fatigue loading and also excessive oscillation results in wear of the springs rubbing against the guide rails and the additional force coming into action due to the centrifugal force.
The similar setup and arrangements have been described as shown in Patent number: 6416417 issued in 2000, Patent number: 5575183 in 1996. But all these suffer from the resonance issue on which lot of work is being done. DMF especially with annular spring dampening arrangement suffers the excessive vibration/oscillation which is an inherent property of DMF. Leading suppliers of DMF like Luk & Valeo are working extensively on methods to reduce the impact.
Different methodologies have been applied by different manufacturers and inventors to minimize the impact of the resonance phenomena. But all these methodologies are able to solve the issue only partly and no concrete solution for the phenomena during stopping is available. The present invention is based on a dual mass flywheel with springs employs a clutch

lockup mechanism which can be internal clutch or external locking or both above stated mechanism together to eliminate the resonance phenomenon.
OBJECT INVENTION:-
It is object invention to provide holding means to the primary mass flywheel
and secondary mass flywheel of automotive vehicle during cranking and
stopping for damping vibration.
It is another object of invention to provide externa! holding mechanism to the
primary mass flywheel and secondary mass flywheel of automotive vehicle
during cranking and stopping for damping vibration.
It is also another object of invention to provide internal holding mechanism
to the primary mass flywheel and secondary mass flywheel of automotive
vehicle during cranking and stopping for damping vibration.
It is also one more object of invention to provide efficient holding means
with combination of external holding mechanism and internal holding
mechanism to the primary mass flywheel and secondary mass flywheel of
automotive vehicle during cranking and stopping for damping vibration.
STATEMENT OF INVENTION:-
Accordingly the invention provides a two stage dual mass flywheel with lockup mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the action by the external locking mechanism consisting one or more clamps of cantilever with fixed end on the ring gear and free end carrying a mass tightly resting on the friction lining on the secondary mass flywheel.
According to another embodiment the invention provides a two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc

Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the action by the internal locking mechanism consisting of a flange mounted on secondary mass wheel flywheel with the arc wings/arm is modified at the center to incorporate one or more centrifugal clutches with at frictional surface facing the center with an internal arrangement is so made that the clamps at standstill are in tight contact with the frictional lining on the primary mass flywheel with an arrangement such that there is no free play at stand still position of the DMF. According to second embodiment the invention provides a two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the action by the internal locking mechanism consisting of a flange mounted on primary mass flywheel with the arc wings/arm is modified at the center to incorporate one or more centrifugal clutches with at frictional surface facing the center with an internal arrangement is so made that the clamps at standstill are in tight contact with the frictional lining on the secondary mass flywheel with an arrangement such that there is no free play at stand still position of the DMF. According to third embodiment the invention provides a two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the combined action by the external locking mechanism and by internal locking mechanism

BRIEF DESCRIPTION OF THE FIGURES:-
Figure 1 shows the constructional details of the general Dual Mass Flywheel used on automotive vehicle.
Figure 2 shows frequency phenomenon occuring during normal driving range.
Figure 3 shows the resonance phenomena during the startup of a Diesel engine of a vehicle.
Figure 4 represents the mathematical model which clearly shows the primary mass inertia and ICE (Crankshaft) inertia which constitutes the Primary Inertia and the secondary mass inertia along with the clutch constitutes the secondary inertia.
Figure 5 shows a further simplified model of Fig. 4.
Figure 6A to 6D illustrates the details of external mechanisms for primary mass flywheel and secondary mass fly wheel lock up during cranking and stopping.
Figures 7A to 7D illustrates the details of internal mechanism for primary mass flywheel and secondary mass flywheel lock up during cranking and stopping.
DESCRIPTION OF THE PRESENT INVENTION:-
The invention particularly relates to a dual mass flywheel, comprised of a primary mass, which can be connected to the output shaft of an engine, and to a secondary mass, which can be connected to the input component of a transmission, which are positioned relative to each other in a concentric and axial manner, and which can be rotated relative to each other, at least within

limits, against the effect of a damping device with energy accumulators, in particular compression coil springs. The energy accumulators can be received in an annular chamber, preferably formed by the components of the primary mass and including a viscous medium, and can comprise the components forming the chamber, and the other mass can carry loading sections for the energy accumulators.
Such torque transfer devices provided as dual-mass flywheels have typically proved useful in automobiles from medium size up, in particular in connection with diesel engines. In smaller vehicles, however, these devices have not become widely popular yet, in spite of their advantages, due to the comparatively high cost.
The general Dual Mass Flywheel construction is shown in figure 1. The standard dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F).
The primary mass flywheel is the inertia element associated with the engine side and the secondary mass flywheel is the inertia element associated with the transmission. In short it can be said that the dual mass flywheel is a flywheel which has been split into two and a torsional damping arrangement has been incorporated into between the two.
A Dual Mass Flywheel shifts the resonance frequency from the lower rpm level which lies near the idle speed range in a vehicle to a region which is never encountered during the normal driving range (Fig 2). The resonance is shifted to a lower rpm level region which is much below the idle speed and never encountered. This resonance region is only encountered during the starts and stops of the vehicle and ensures excellent vibration damping.
This ensures the control of rattling of gears in the transmission which can be a serious discomfort to the customer especially in vehicles which are Monocoque structure based or with a three shaft transmission.

As dual mass flywheel shifts the resonance frequency to a lower rpm range which is sub idle region, it is encountered only during every starts and stop of the engine. Even though the band is narrow and quickly run through, startability and DMF tuning during start and stop is a big challenge. This is critical as during the resonance phenomena very high torque levels are observed at the flywheel and these subjects the flange and springs for large angular travel. This subjects sudden shock loading of the springs as well as high frictional wear of the springs due to the additive normal force acting on the springs due to the rotational motion of the DMF. In Fig 3 we can clearly see the resonance phenomena during the startup of a 2.2 lit Diesel engine. In a scenario where today most of the auto manufacturers are looking at the Auto Start Stop Feature, this Dual Mass Flywheel is a big concern. The simple reason is the number of times resonance is encountered goes up exponentially which poses a bigger threat to the Dual Mass Flywheel.
Figure 4 represents the mathematical model which clearly shows the primary mass inertia and ICE (Crankshaft) inertia which constitutes the Primary Inertia and the secondary mass inertia along with the clutch constitutes the secondary inertia.
A further simplified model is shown in the figure 5. Here the primary mass inertia is denoted by Jp and the secondary mass inertia by Js. Jp and Js together constitutes the overall inertia mass. C2 and C3 are the stiffness constants associated with the DMF & Driveline side respectively.
Natural frequency of a system is given by f = (2n)-1√ (C/J)
, where C stands for the system stiffness and J stands for the mass inertia.
In this case C =C2+C3 and J = Jp+Js
Here due to DMF the C2 decreases hence the natural frequency is brought
low.

There are various methodologies which can theoretically be employed to tackle this issue and some have been already practically been employed to address the issue.
The first method which is deployed is to run through the resonance zone with higher speed and acceleration during the cranking which would result in minimal resonance zone experience. This is being practically realized by many OEMs. But the cost impact for the development of the reinforced starter to take up the back reaction and accelerate the ICE quickly is high. Off the shelf product are costlier compared to the existing starter motors available in the market. In addition to the component cost there is an impact on the fueling in some cases as there needs a change in the EMS software to increase the fueling to support the acceleration required. And such modification can control only the starting resonance behavior and no control over the stopping behavior.
The second method deployed relates to additive friction. Damping dissipates the energy of the vibrations. Damping in the DMF can be realized by different types of friction. Types of friction that exist in the DMF are:
• Friction of the arc springs with the DMF
• Friction of other parts of the DMF with are in contact and slide
• Controlled Additive friction is a type of friction that can be deliberately added to the DMF to damp the resonance amplitudes and is realized by what is called a friction control plate (FCP).
FCP only provides the DMF with extra friction for large relative rotations of the DMF inertias. This is done because friction of the DMF is a characteristic that is desired during start, during normal driving conditions the vibrations of the DMF stay within the free angle of the FCP. This is the only proven/ best solution available in the market today to tackle the starting behavior with DMF. But FCP could obstruct during the spring compression at higher accelerations. Secondly the resonance in the free play zone still exists and the resonance in totality remains in a smaller magnitude.

Another possibility is to shift the resonance band to a lower frequency scale. This is a theoretical concept in which we increase the primary mass of the flywheel to higher mass which will increase the over all inertia. This will reduce the overall engine irregularity. But the problem is higher primary inertia will make the engine response to load conditions slow which is not desirable.
Another option is to make the secondary mass lower which would help in reducing the peaks of the resonance amplitudes. But again the problem faced is that if the secondary mass is made too light the resonance will shift to the higher rpm which will be too close or would be in the driving range; hence DMF loses its function.
In this proposal the attempt is to arrest the resonance in such a way that it does not come in way during the starts or during the normal driving range. The idea is to lock the Primary & Secondary masses during the cranking and stopping process. During the stopping and starting of engine, the spring operation is arrested due to primary and secondary mass lock up. This results in DMF becoming a SMF during starting. During the phase when DMF becomes SMF the resonance frequency gets shifted to the higher engine rpm (-1000-1500rpm). So during starting period we have a SMF and during idling and running phases we have a DMF.
In this proposal we have two mechanisms by which the above said will be
achieved. The two mechanisms are optional depending upon the integration
challenges and constraints. For better results in systems both can be
deployed together. The two mechanisms are,
• The External Locking Mechanism of DMF as illustrated in figures
6 A to 6D Figure 6A shows primary mass flywheel with ring gear. A clamp made of cantilever with one end is fixed to the said ring gear and other end is resting on the friction lining on the secondary mass fly wheel. The clamp other end is firmly resting on the said friction lining. More particularly the fixed end of the

cantilever is hinged. When the said primary mass flywheel rotated above set rpm the other end will move away by the centrifugal force. Thus initially both primary mass fly wheel and secondary mass flywheel combined and after rotation above the set rpm get separated. The same features are illustrated in figures 6B ,6C and 6 D.
• The Internal Locking Mechanism of DMF as illustrated in figures 7A to 7D Figure 7 A shows the modification done to flange. A radially centrifugal clutch, consisting of a radial biased clutch pad, is provided to the said flange, The said flange is mounted on the secondary mass fly wheel with the clutch pad resting on the friction lining on the bearing; of primary mass fly wheel. Initially both primary mass fly wheel and secondary mass flywheel held together due to clutch pad firmly resting on the primary mass flywheel friction lined bearing more particularly the clutch pad is biased with a radial spring. When the said flywheels rotated after attaining speed above set rpm clutch pad move away from the friction lining and separating both flywheels to function individually.
These features are illustrated in figures 7B, 7C, and 7D. It is possible to connect flange to primary mass flywheel and friction lining on the secondary mass flywheel bearing.
To get improved result the combination of the said external mechanism and internal mechanism is the option.
The number of clamps in the external mechanism is worked out as per the requirement.
The number radial centrifugal clutches is as per the requirements. In the former system the ring gear is having a modification of having a clamp on it which has been integrated onto the ring gear by suitable mechanism. The clamp is a cantilever with the fixed end on the ring gear and the free end carrying a small mass 'm' The secondary mass flywheel has a machined groove on the surface (not shown in the fig), into which a friction lining is incorporated. DMF when assembled with ring gear has the free end of the clamp tightly resting of the friction surface on the secondary mass flywheel. The arrangement is such that there is no free play at stand still position of the DMF. The number of clamps required on the ring gear will depend upon the

detailed calculations which are not presented in the proposal and will vary from application to application on platforms.
Now as the clamps are holding the two masses firmly the DMF will not have the relative play between the primary mass and the secondary masses hence will act as a SMF with mass J = Jp+Js
Now as the engine cranks up during the resonance band of conventional DMF there will be no relative displacement of the two masses and hence the resonance zone is run through without any effect on the DMF. Now as the DMF reaches near the near idle speed, the centrifugal force acting on the masses pull the clamps in a radially outward direction, this would result in the release of secondary mass flywheel. This happens as the centrifugal force which is acting on the mass at the end of the clamp in radially outward direction is a function of rotational velocity, mass attached and the radial distance from the center. The last two quantities are fixed and the velocity is changing in an exponential manner with a power of 2. The centrifugal force variation over the startup of the DMF with an attached clamp with a mass of 200gm is plotted in the figure. Similarly during the stopping of the engine, as the engine rpm falls down below the idle range, the centrifugal force becomes lower and the stiffness force of the clamp pulls the clamp back in position and hence results in the lockup of the primary mass and the secondary mass during the engine shutdown. This again results in avoiding the resonance phenomena.
In the later system with internal locking mechanism, the Bearing tower is modified to incorporate a friction lining on it which is not shown in the figure. The flange with the arc wings/arm is modified at the center to incorporate a centrifugal clutch with at frictional surface facing the center. The number of clamps depends upon the application and has not been shown in the proposal. It is assumed to be a clamp clutch. The internal arrangement is so made that the clamps at standstill are in tight contact with the frictional lining on the primary mass flywheel. The above arrangement is such that there is no free play at stand still position of the DMF.

Now as the clamps are holding the two masses firmly the DMF will not have the relative play between the primary mass and the secondary masses hence will act as a SMF with mass J = Jp+Js
Now as the engine cranks up during the resonance band of conventional DMF there will be no relative displacement of the two masses and hence the resonance zone is run through without any effect on the DMF. Now as the DMF reaches near the near idle speed, the centrifugal force acting on the masses pull the clamps in a radially outward direction, this would result in the release of primary mass flywheel. This happens as the centrifugal force which is acting on the mass at the end of the clamp in radially outward direction is a function of rotational velocity, mass attached and the radial distance from the center. The last two quantities are fixed and the velocity is changing in an exponential manner with a power of 2. The centrifugal force variation over the startup of the DMF with an attached clamp with a mass of 200gm is plotted in the figure. Similarly during the stopping of the engine, as the engine rpm falls down below the idle range, the centrifugal force becomes lower and the stiffness force of the clamp pulls the clamp back in position and hence results in the lockup of the primary mass and the secondary mass during the engine shutdown. This again results in avoiding the resonance phenomena. The arrangement can be reversed to have the clutch on the primary mass and to have the friction lining on the secondary mass.
Since, during the startup/ cranking period (0-700rpm) the dual masses (primary and secondary) are locked up, there is a shift of the resonance frequency to higher rpm (1000-1500rpm). So during the startup the resonance zone is not encountered and hence excellent starting behavior without resonance & torque loss is experienced.
Since during the engine stops/ switched off process (800-Orpm) the dual masses (primary and secondary are locked up due to reduced centrifugal force there is a shift of the resonance frequency to higher rpm (1000-1500rpm). So during the stopping the resonance zone is not encountered and hence excellent engine stop can be experienced.

Since the resonance frequency run through during the startup is now eliminated; hence the design of springs (arc spring) is not constrained. In this system we can lower the stiffness of springs to the most optimized limits.
Spring Stiffness= Max Moment Engine /Deflection
Hence the need of multiple or parallel springs can be minimized as the
springs set with the least stiffness need not be included
Use of lower stiffness spring with less mass will enable further lowering of the resonance frequency, resulting in much better vibration isolation
This modification will help to use of lower weight spring material. The use low weight material will reduce the centrifugal force acting on the springs and hence will help in reducing the frictional wear of the surfaces and spring. As the rpm increases the spring's experiences radial centrifugal force, from the plot in the figure 12 we can see that there is a varying stiffness of the arc spring due the centrifugal force. This proposal will help in reducing the spring weight as lower stiffness material enables lower mass.
ADVANTAGES OF THE INVENTION:-
• Excellent Starting behavior of DMF during engine start.
• Improved stopping behavior of DMF during engine stop.
• Scope of spring material and further optimization of spring increased.
• Superior vibration isolation.
• Lower fuel consumption during starts.
• Cost saving as no reinforcement of starter required
• Reduced frictional wear of the guide surfaces and springs.

WE CLAIM:-
1. A two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the action by the external locking mechanism consisting one or more clamps of cantilever with fixed end on the ring gear and free end carrying a mass tightly resting on the friction lining on the secondary mass flywheel.
2. A two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Fiange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the action by the internal locking mechanism consisting of a flange mounted on secondary mass wheel flywheel with the arc wings/arm is modified at the center to incorporate one or more centrifugal clutches with at frictional surface facing the center with an internal arrangement is so made that the clamps at standstill are in tight contact with the frictional lining on the primary mass flywheel with an arrangement such that there is no free play at stand stil! position of the DMF.
3. A two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the action by the internal locking mechanism consisting of a flange mounted on primary mass flywheel with the arc wings/arm is modified at the center to incorporate one or more centrifugal clutches with at frictional

surface facing the center with an internal arrangement is so made that the clamps at standstill are in tight contact with the frictional lining on the secondary mass flywheel with an arrangement such that there is no free play at stand still position of the DMF.
4. A two stage dual mass flywheel with lock-up mechanism for automotive vehicle comprising a dual mass flywheel consists of a Primary mass (A), Main Bearing (B), Arc Springs/Energy Storage device(C), Flange (D), Primary Cover (E) and the Secondary Mass (F) characterized in that the said primary and secondary masses during cranking and stopping the said spring operation is arrested due to primary and secondary mass lock up by the combined action by the external locking mechanism as claimed in claim 1 and by internal locking mechanism as claimed in claim 2 or claim 3.
5. A two stage dual mass flywheel as claimed in claim 1 wherein the said cantilever one end fixed to the said primary mass flywheel is hinged.
6. A two stage dual mass flywheel as claimed in claims 2 and 3 the said centrifugal clutch consists of a clutch pad biased with radial spring.