Design of a Diaphragm Spring Clutch

Design of a Diaphragm Spring Clutch

Tanmay Ajit Luniya

Department of Mechanical Engineering Rajarshi Shahu College of Engineering, Tathawade

Pune, India

Abstract Clutch is a very essential element in torque transmission process. The purpose of a clutch is to initiate motion in the automobile generally by transferring kinetic energy from another moving here which is the Engine. Clutches are designed to transfer maximum Torque form engine with Minimum Heat Generation. The present work deals with designing of (Ø310) Diaphragm Spring Clutch for a GVW of 8330kg with input parameters provided by the customer company.

Keywords Diaphragm Spring Clutch, Torque, Stress Generated, Clamp Loads, Heat Generated.

1. INTRODUCTION

   In the Automotive Power Transmission the Clutch is designed after the Engine and Gear Box characteristics is finalized. The Customer has provided Input data comprising of the Engine Parameters (i.e. Engine Power, Max Engine Torque, RPM and Number of Engine Cylinders), Gear Box Parameters (i.e. Gear Ratios and Final Reduction), Vehicle Dimensions(i.e. Clutch Housing Diameter and Vehicle Weight) to design the Single Plate Diaphragm type Clutch for Medium Duty Vehicle. During the Clutch Design is necessary to ensure that,

   1. The Contact surfaces develop the frictional force that may pick up and hold the load with reasonable low pressure between the contact surfaces.

   2. The Heat of friction should be rapidly dissipated and tendency to grab should be at minimum.

   3. The surface should be backed by the material stiff enough to ensure reasonable uniform distribution pressure.

   4. Suitable Friction material forming the contact surfaces is to be selected.

   5. Clutch should not require any external force to maintain contact and the projection parts must be guarded.

      Clutch Components are to be designed using these all the necessary parameters.

      Fig.1. Automotive Transmission System Layout.

2. WORKING OF CLUTCH

   The Diaphragm spring clutch uses a diaphragm or conical spring instead of coil spring to produce adequate pressure for engaging the clutch. The clutch cover is successfully secured to the engine flywheel. The pivot rings are held in clutch cover. The outer rim of the diaphragm spring is in contact with the pressure plate. In engaged position, the diaphragm spring keeps the pressure plate in firm contact with the flywheel.

   Fig.2. Working of Diaphragm Spring Clutch.

3. DESIGN DETAILS

   Sr. No.	Particulars	Specification
   1.	Vehicle : TD 3250 CR
   2.	GVW (kg)	8330
   3.	RAW (kg)	1710
   4	Tyre	3540
   5	Dy. Radius (m)	0.39
   6.	Engine	TD 3250 5CYL
   7	Engine Power (kW)	90
   8	Max Engine Torque Nm	320
   9	Max Engine RPM	2800
   10	Max Torque RPM	1800-2400
   11	Gear Box Ratios

   Sr. No.	Particulars	Specification
   1.	Vehicle : TD 3250 CR
   2.	GVW (kg)	8330
   3.	RAW (kg)	1710
   4	Tyre	3540
   5	Dy. Radius (m)	0.39
   6.	Engine	TD 3250 5CYL
   7	Engine Power (kW)	90
   8	Max Engine Torque Nm	320
   9	Max Engine RPM	2800
   10	Max Torque RPM	1800-2400
   11	Gear Box Ratios

   Table I: Input for Ø 310 Clutch Design for TD 3250

   	First	5.053
   	Second	2.601
   	Third	1.512
   	Fourth	1
   	Fifth	0.784
   	Reverse	4.756
   	Final Reduction	4.375
   12	Set Height	62
   13	Clutch Actuation	Hydraulic
   14	Pot Depth of Flywheel	Flat
   15	Clutch Mounting PCD	314
   16	Clutch Facing Inner Diameter (mm)	170
   17	Clutch Facing Outer Diameter (mm)	310

   Table III: Nomenclature and Symbols

   Sr. No.	Parameter	Symbols
   1	Gross Vehicle Weight	GVW
   2	Dynamic rolling radius	m
   3	Engine Torque	T
   4	Engine Speed	N
   5	Clutch Plate Inner Radius	Ri
   6	Clutch Plate Outer Radius	RO
   7	Coefficient of friction
   8	Outside diameter of clutch	D
   9	Inside diameter of clutch	Di
   10	Slip Torque	TS
   11	Clamp load	W
   12	Mean radius	Rm
   13	Diameter ratio	Dr
   14	Load on flat	Pflat
   15	Thickness of diaphragm spring	t
   16	Height of diaphragm spring	h
   17	Stress on diaphragm spring
   18	Deflection of spring
   19	Spring rate	K
   20	Working load	F
   21	Working stress
   22	Solid length of spring	LS
   23	Block load of spring	FB
   24	Block stress of spring
   25	Total torque	TT
   26	Total load	FT

   27	Wire diameter	d
   28	Outer diameter of spring		DO
   29	Mean diameter of spring	dm
   30	Modulus of rigidity	E
   31	Torsional radius	R
   32	Torsional angle
   33	No. of total coils of spring	n
   34	No. of active coils of spring	na
   35	Acceleration	A
   36	Force	F
   37	Velocity	V
   38	Slip time	ts
   39	Heat generated	q
   40	Specific heat	Q
   41	Thermal stress
   42	Outside diameter of casing
   43	Maximum diameter for bolt
   44	Spline diameter
   45	Maximum length required for spring
   46	Length of slot for 1st stage
   47	Outside diameter of hub
   48	Diameter of stop pin
   49	Outside diameter of diaphragm
   50	Outer diameter of slot
   51	Outside diameter of fulcrum
   52	Inside diameter of fulcrum
   53	Spring index	C
   54	Deflection Factor	K1 ,k2, k3
   55	Diaphragm angle	A

   • Material Selection: 50CrV4

     1. Clamp load (W) Calculation:

   • The given values as per problem statement are:

     • Max Engine Torque (T) = 320 Nm

     • Outer radius ) = 155mm

     • Inner radius (Ri) = 87.5mm

   • To find

     Clamp load

     Stresses at various points

   • Slip torque calculations:

     Max Engine Torque (T) = 320 Nm

     Assume Slip Torque (Ts) is 1.7 times T Therefore Ts = (T) * (1.7)

     = 320*1.7

     Ts =544 Nm

   • To calculate mean radius (Rm):

     Mean Radius (According to uniform Pressure Theory)

     Mean Radius (Rm)

     Rm=0.12438 m

     1. To calculate the clamp load (W):

        Slip Torque Ts= 2 * * W* Rm 544= 2*0.27*W*0.1136

        W = 900 Kg

        Clamp Load (W) = 825.63 kg

   • To determine the stresses induced in the diaphragm spring

   Input Parameters

   Thickness of diaphragm (t): 3.65mm

   Outside diameter of diaphragm (Da): 289mm Slot outer diameter (Di'): 240mm

   Diaphragm angle (A): 13.833º Height of diaphragm (h): 5.857mm

   Outer fulcrum diameter (Dap): 284.5mm Inner fulcrum diameter (Dip): 236mm Poisons ratio (µ): 0.27

   Modulus of elasticity (E): 20500kgf/mm2

   To determine:

   i

   i

   1. Actual Diameter (Di ) = (D )-(2 * S * Sin(A))

      =217 2(3 x sin (14))

      Di= 238.34 mm

   2. Diameter Ratio (Dr) =

      =

      Dr =1.2130

   3. Alpha () =

      =

      =

   4. Load on flat (Pflat) =

      =

   5. Load on flat with Pf )*

   = (818.07) *

   Pf=1025.3524 N

   3

   3

   1. Stress Calculations:

   Fig.3. Stresses on Diaphragm Spring Thickness as, t =3.65mm

   Consider Deflection h = 5.857mm

   Calculation of deflection factor k1, k2, k3

   1. =

   = 0.3050

   2. = *

   = 1.096

   3. = *

   = 1.0535

   1. Stress at point 5:

      * ) * (

      = -72.523 N/mm2

   2. Stress at point 1:

      = -146.7N/mm2

   3. Stress at Point 2:

      =13.364 N/mm2

      = 1014.8897 N

   4. Stress at Point 3:

      = 123.66N/mm2

   5. Stress at Point 4:

   = -7.536N/mm2

   Safe Stress = 0.8* UTS

   = 0.8 * 180

   Safe Stress = 144 N/mm2

   As the Max Stress, 138.914 N/mm2 < Safe Stress 144 N/mm2 our design is safe

   Factor of safety = Factor of Safety = 1.295

   3.2 Design of Damper Spring

   As per the given data of damper dimensions we find out the deflections, spring rate, stress and torque on the spring.

   Material for damper spring: Spring Steel as per AS 4454 1975 Grade2D

   Damper Torque Calculation:

   Assume that Damper Torque is 1.3 to 1.45 times engine torque

   Damper Torque= 1.4* Engine Torque

   = 1.4*320

   Damper Torque = 448 N

   Now we find out deflection to determine working load and spring rate for inner and outer springs

   Fig.4. Inner and Outer Damper Spring

   PARAMETER	UNIT	SPECIFICATION
   Wire Dia	Mm	4.5
   No. of Total Coils		5.5
   No. of Active Coils		3.5
   O. D.		23
   Material Grade		2D
   UTS	Kgf/mm2	185
   Mean Dia(dm)		18.5
   Length		28
   Modulus Of Rigidity (G)	Kg/mm2	7500
   Number of springs		8
   Engine Torque	Nm	320
   Torsion Angle	Degree	5.5
   Torsional Radius	Mm	53.3

   PARAMETER	UNIT	SPECIFICATION
   Wire Dia	Mm	4.5
   No. of Total Coils		5.5
   No. of Active Coils		3.5
   O. D.		23
   Material Grade		2D
   UTS	Kgf/mm2	185
   Mean Dia(dm)		18.5
   Length		28
   Modulus Of Rigidity (G)	Kg/mm2	7500
   Number of springs		8
   Engine Torque	Nm	320
   Torsion Angle	Degree	5.5
   Torsional Radius	Mm	53.3

   Table III: Input parameters for outer spring

   1. Calculation for outer spring

      1. Deflection () = Angle x radius(r)

      = x x 57.3

      = 4.9087 mm

      F =

      Working Load (F) = 85.1538kgf

      1. Spring rate (K) = = 17.35kg/mm

      2. Working Stress ) =

         = 44.022kgf/mm2

      3. Solid Length ) = (n) x (d)

         = (6.16 x 2.8)

         = 23.65 mm

      4. Spare Length ={Length – Solid Length} {Deflection}

         = 28 23.65 – 4.9087

         Spare Length= -0.563 mm

      5. Block Load ) = Block Length x K

         =78.386kgf

      6. Block Stress ( ) =

         =

         =38.97kgf/mm2

      7. Total Load ( ) = No. Of springs x Working Load

         =631.2034kgf

      8. Total Torque ) = Load x Torsional Radius x 9.81

      =631.234 x 53.3 x 9.81

      =417.69 Nm

   2. Calculations for Inner Spring

   Table IV Input parameters for Inner Spring

   PARAMETER	UNIT	SPECIFICATI ON
   Wire Dia		2.5
   No. of Total Coils		9.5
   No. of Active Coils		7.5
   O. D.		13.5
   Material Grade		2D

   UTS	Kgf/m m2	185
   Mean Dia (dm)		12
   Length		28
   Modulus Of Rigidity (G)	Kg/m m2	7500
   Number of springs		8
   Engine Torque	Nm	320
   Torsion Angle	Degre e	5.5
   Torsional Radius	Mm	53.3

   UTS	Kgf/m m2	185
   Mean Dia (dm)		12
   Length		28
   Modulus Of Rigidity (G)	Kg/m m2	7500
   Number of springs		8
   Engine Torque	Nm	320
   Torsion Angle	Degre e	5.5
   Torsional Radius	Mm	53.3

   1. Deflection () = Angle (in radian) x radius(r)

   = x x 57.3

   = 4.9087 mm

   F =

   Working Load (F) = 85.1538kgf

   1. Spring rate (K) = = 17.35kg/mm

   2. Working Stress ( )

      = 44.022kgf/mm2

   3. Solid Length ) = (n) x (d)

      = (6.16 x 2.8)

      = 23.65 mm

   4. Spare Length ={Length – Solid Length} {Deflection}

      = 28 23.65 – 4.9087

      Spare Length= -0.563 mm

   5. Block Load ) = Block Length x K

      =78.386kgf

   6. Block Stress ( ) =

      =

      =38.97kgf/mm2

   7. Total Load ( ) = No. Of springs x Working Load

      = 631.2034kgf

   8. Total Torque ) = Load x Torsional Radius x 9.81

   =631.2034 x 53.3 x 9.81

   = 417.69 Nm

   1. Calculations of Slip Time for 1st& 2ndGear :

      Table IV Input parameters for Slip Time Calculations

      S r. No.	Particulars	Specification
      1	Gradability (%)	15
      2	GVW (kg)	8330
      3	Dy. Radius (m)	0.339
      4	Max Engine Torque Nm	320
      5	Max Torque RPM	1400
      6	Gear Box Ratios
      	First	5.053
      	Second	2.601
      7	Differential ratio	4.375
      8	of transaxle )	85
      9	Road resistance constant (kg/ ton weight)	20

      1. Slip Time for 1st Gear:

         1. Consider 15 Gradability with Indian roads Tan = (

            = 0.148radian

         2. Force (F) =B- (

            Force (F) = 298.687kg

         3. Force = (mass) * (Accln) Accln =

            a = 0.35 m/s2

         4. Velocity(v)=( *( )

            = ( ) * ( )

            v= 2.393 m/s

         5. V = u + at (By Newtons Laws of motion) 2.393 = 0 + (1.7305) * )

         Slip time ) = 6.8175 sec

      2. Slip Time for 2ndGear:

   1. Force(F)=B- (

      F= 665.85kgf

   2. Force = (mass) * (Accln) Accln =

      a = 0.7842 m/s2

   3. Velocity(v)=(*

      = ) * )

      v = 6.6435 m/s

   4. V = u + at

   6.6435= 0 + (0.0910) * (t)

   = 8.4772 sec

   As the slip time value of 2nd gear is Large, vehicle will not start in 2nd gear.

   • Heat generated for 1st gear: q =

     =46.98kJ/s

   • Specific Heat for 1st gear (Q) = (q) * )

   = (46.98) * (6.8175)

   Q = 0.319 MJ

   Thermal stress ( ) =

   = 1.5508 J/mm2

   *Maximum permissible thermal stress is 2 J/mm2 As 2J/mm2 the Design is Safe.

4. CONCLUSION

   The Diaphragm type clutch is designed for TD 3250 as per the customer requirements. All the parts were modeled using CATIA and Finite Element Analysis in ANSYS is conducted to verify the results. All the results were found to be within the permissible limits. New designs of Diaphragm Spring have been suggested and should be considered for further investigation. Detailed study of manufacturing processes of Diaphragm spring was done and manufacturing process was suggested. All the parts were procured and assembled in the industry premises. Strict Quality Control and Inspection processes were devised and implemented on the clutch manufacturing.

5. FUTURE SCOPE

The Diaphragm spring Design can be optimized to reduce its weight. A modified design has been suggested, but further study and analysis needs to be done to checks its feasibility. The deflection of the Diaphragm clutch can be reduced by introducing a strap plate. However more study and research

needs to be conducted. Pin fin can be used to increase heat transfer rate and prevent the overheating of the clutch. Clutch housing can be provided with a window to enhance air circulation for heat dissipation.

ACKNOWLEDGMENT

I take this opportunity to express our gratitude towards my guide Prof. D.P.Borse, who helped me in times of difficulty. He remains a pragmatist with his untiring efforts, and his technical critique helped me complete this project. I also wish to express my sincere thanks to my Mother and Father who have been an invaluable source of guidance and motivation in writing this paper to the best of my potential. I am deeply grateful to our sponsor Jaya Hind Industries Ltd, our guide Mr. A.B.Mulani, Sr. Mgr R&D for providing us valuable guidance whenever required.

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