Automobile Gearbox BY GAURANG PRAJAPATI 1 The word

Automobile Gearbox • BY: GAURANG PRAJAPATI 1

The word “Transmission” • The word transmission means the mechanism that transmits the power from the engine crank shaft to the rear wheels. 2

Function of Transmission • Provide a means to vary torque ration between the engine and the road wheels as required. • Provides a neutral position. • A means to back the car by reversing the direction of rotation of the drive is also provided by the transmission. 3

Gear Ratio The gear ratio, or velocity ratio, between a pair of gear wheels is in inverse ratio to the number of teeth on each. 4

Gear Ratio Thus, NB/NA = DA/DB= n. A/n. B NB = NA (n. A/n. B) 5

Gear Ratio Where: NA= rev per min of gear A, n. A = number of teeth on A NB = rev per min of gear B, n. B = number of teeth on B DA = Diameter of gear A DB = Diameter of gear B 6

Types of Gearbox • Sliding mesh gearbox • Constant mesh gearbox • Synchromesh gearbox • Epicyclic Gearbox 7

Sliding mesh type gearbox 1. Constant mesh gears. 2. Primary shaft (Clutch shaft) 3. Spigot bearing. 4. Main shaft. 5. Lay shaft (counter shaft) 8

Sliding mesh type gearbox Primary shaft • This shaft transmits the drive from the clutch to the gearbox. • At the end, the shaft is supported by a spigot bearing positioned close to the splines on to which the clutch driven plate is connected. 9

Sliding mesh type gearbox Primary shaft • The main load on this shaft is taken by a bearing; normally a sealed radial ball type, positioned close to an input gear called a constant mesh pinion. 10

Sliding mesh type gearbox Primary shaft • The gear is so named because it is always in mesh with a larger gear • Small driving gear is called a pinion and a large gear a wheel. 11

Sliding mesh type gearbox Layshaft • This shaft, which is normally fixed to the gearbox casing, supports the various-sized driving pinions of the layshaft gear cluster 12

Sliding mesh type gearbox Main Shaft • This splined output shaft carries spur gearwheels that slide along the shaft to engage with the appropriate lay shaft gears. • At the ‘front’ end, the main shaft is supported by a spigot bearing situated in the centre of the constant mesh pinion. 13

Sliding mesh type gearbox Main Shaft • A heavy duty radial ball bearing is fitted at the other end to take the force of the gears as the attempt to move apart. 14

Sliding mesh type gearbox • The power comes from the engine to the clutch shaft and thence to the clutch gear which is always in mesh with a gear on the lay shaft. • All the gears on the lay shaft are fixed to it and as such they are all the time rotating when the engine is running and clutch is engaged. 15

Sliding mesh type gearbox Gear position 16

Sliding mesh type gearbox Neutral • All main shaft gearwheels are positioned so that they do not touch the layshaft gears. • A drive is taken to the layshaft, but the mainshaft will not be turned in neutral position 17

First gear 18

Second 19

Third 20

Top 21

Reverse 22

Disadvantage of Sliding mesh Gearbox • Gear noise due to the type of gear. • The difficulty of obtaining a smooth, quit and quick change of gear without the great skill and judgment. 23

Selector Mechanism • A fork is used to slide a gearwheel along the main shaft in order to select the appropriate gear. • It is mounted on its own rod and links the driver’s gear stick to the sliding gearbox. 24

Selector Mechanism 25

Selector Detent • It holds the gears and selectors in position and so prevent gear engagement or disengagement due to vibration. • The figure shows a typical arrangement suitable for a layout having the selector fork locked to the rod 26

Interlock Mechanism 27

Interlock Mechanism • Prevents two gears engaging simultaneously • If this occurs the gearbox will lock up and shaft rotation will be impossible. 28

Power take-off arrangement • In addition to the mechanism use for driving a vehicle along a road, a power supply is often required for operating external items of auxiliary equipment. • A light truck having a tipping mechanism is one example, but the most varied application of power takeoff units is associated with specialized off-road vehicles 29

Power take-off arrangement 30

Constant mesh gearbox • All the gear are in constant mesh with the corresponding gears on the layshaft. The gears on the splined main shaft are free • The dog clutch are provided which are free to slide on the main shaft. • The gears on the lay shaft are fixed. 31

Constant mesh gearbox 32

Constant mesh gearbox • When the left dog clutch is slid to left by means of the selector mechanism, it’s teeth are engaged with those on the clutch gear we get the direct gear. 33

Constant mesh gearbox • The same dog clutch when slid to right makes contact with the second gear and second gear is obtained. • Similarly movement of the right dog clutch to the left result in low gear and towards right in reverse gear. 34

Double Declutching with Constant mesh Gearbox • For the smooth engagement of the dog clutches it is necessary that the speed of the clutch shaft, layshaft and main shaft gear must be equal. • Therefore to obtain lower gear, the speed of clutch shaft, layshaft and the main shaft gear must be increased. • By Double declutching this can be done. 35

Double Declutching with Constant mesh Gearbox • The clutch is disengaged and the gear is brought to neutral. • Then the clutch is engaged and accelerator pedal pressed to increased the speed of the main shaft gears. 36

Double Declutching with Constant mesh Gearbox • After this the clutch is again disengaged and the gear moved to required lower gear and the clutch is again engaged. • As the clutch is disengaged twice in this process, it is called double declutching 37

Advantage of Constant mesh Gearbox compared to Sliding mesh Gearbox • As the gear remain always in mesh, it is no longer necessary to use straight spur gear. Instead helical gear is used which are quieter running. 38

Advantage of Constant mesh Gearbox compared to Sliding mesh Gearbox • Wear of dog teeth on engaging and disengaging is reduced because here all the teeth of the dog clutches are involved compared to only two or three teeth in the case of sliding gears. 39

Synchromesh Gearbox • Similar to constant mesh type, because all the gears on the main shaft are in constant mesh with corresponding gears on the layshaft. • The gears on the main shaft are free to rotate on it and that on the layshaft are fixed to it. 40

Synchromesh Gearbox • Avoids the necessity of double declutching. • The parts which ultimately are to be engaged are first brought into frictional contact which equalizes their speed, after which these may be engaged smoothly. 41

Synchromesh Gearbox 42

Synchromesh Gearbox • A : engine shaft. • Gears B, C, D, E are free on the main shaft and always mesh with corresponding gears on lay shaft. • Members F 1 and F 2 are free to slide on splines on the mainshaft. • G 1 and G 2 are ring shaped members having internal teeth fit onto the external teeth on members F 1 and F 2 respectively. 43

Synchromesh Gearbox • K 1 and K 2 are dog teeth on B and D respectively fit onto the teeth of G 1 and G 2. • S 1 and S 2 are the forks. • T 1 and T 2 are the ball supported by springs. • M 1, M 2, N 1, N 2, P 1, P 2, R 1, R 2 are the frictional surfaces. 44

Synchromesh Gearbox • T 1 and T 2 tend to prevent sliding of members G 1(G 2) on F 1(F 2). • When force applied on G 1(G 2) through forks S 1(S 2) exceeds a certain value, the balls are overcome and member G 1(G 2) slides over F 1(F 2). • There are usually six of these balls symmetrically paced circumferentially in one synchromesh device. 45

Engagement of direct gear in Synchromesh Gearbox Cones M 1 and M 2 mate to equalize speeds. 46 Member G 1 pushed further to engage with dog k 1

Engagement of direct gear in Synchromesh Gearbox • For direct gear, member G 1 and hence member F 1 is slid towards left till cones M 1 and M 2 rub and friction makes their speed equal. • Further pushing the member G 1 to left cause it to override the balls and get engaged with dogs k 1. • So the drive to the mainshaft is direct from B via F 1 and the splines. 47

Engagement of direct gear in Synchromesh Gearbox • Similarly for the second gear the members F 1 and G 1 are slid to the right so that finally the internal teeth on G 1 are engaged with L 1. • Then the drive to mainshaft will be from B via U 1, U 2, C, F 1 and splines. • For first gear, G 2 and F 2 are moved towards left • The drive will be from B via U 1, U 3, D, F 2 and splines to the main shaft. 48

Engagement of direct gear in Synchromesh Gearbox • For reverse, G 2 and F 2 are slid towards right. • In this case the drive will be from B via U 1, U 4, U 5, E, F 2 and splines to the main shaft. 49

It’s too simple to Understand 50

Selector Mechanism with gear lever on top of the transmision 51

Selector Mechanism with gear lever on top of the transmision • There are forks mounted on the sleeves on three separate selector rods which are supported in the gearbox casing. • Each selector sleeve can slide on its rod. • There are slots on the selector rods and the sleeves are provided with spring loaded balls to avoid unwanted engagement of the gears. 52

Selector Mechanism with gear lever on top of the transmision • These balls resist the movement of the forks until some force is applied to the gear lever to overcome their resistance. • Grooves are provided on the gear bosses where the selector forks can fit in. • Transverse motion of the gear lever selects the forks which is to be engaged and the longitudinal movement then slides the forks and its gear to engage the selected gear. 53

Selector Mechanism with gear lever on top of the transmision • Various gear position are marked on the gear lever knob itself. 54

Epicyclic Gearbox PLANET SUN GEAR RING GEAR 55

Epicyclic Gearbox • An epicyclic gearbox consists of two, three or even four epicyclic or planetary gear sets. • A simple gear set has a sun gear, about which planets turns round. • These planet gears are carried by a carrier and a shaft and are also in mesh with a ring gear. 56

How The Gears Move The white band with blue bars behind the planets represents the planet carrier. 57

Principle of Algebraic Method “ The gear ratio of a pair of mating gear wheels with respect to the link carrying the axes of the gears is always the same whether the link carrying axes is fixed or moving. ” 58

Speed Ratio C B A • Here gears B and C mating with each other and connected by means of arm A. • So according to principle Speed of the gear B w. r. t arm A = - TC Speed of the gear B w. r. t arm A TB 59

Controls in Epicyclic Gearbox • There are two controls i. e. the brake and the clutch. • The brake is in the form of a band that surrounds a drum attached to the gear (in case of sun gear) or the outer surface of the gear itself (in case of ring gear). • The clutch used is of multiplate type. 60

Controls in Epicyclic Gearbox • Both the brake and the clutch are applied by the fluid pressure. • These are selected by hydraulic shift valves which are usually located at the bottom of the gearbox. 61

Advantage of Epicyclic Gearbox • All gear are in constant mesh and to engage any desire gear one simply has to apply the particular brake or the clutch. • For this, the drive from the engine need not to be disconnected as in case of ordinary gearbox. • Thus gear changing operation becomes very easy with an epicyclic gearbox. 62

ZF-Ecomid GEARBOX 63

Some Technical Data Model 9 S 75 Input torque max Nm 770 900 13. 6 9. 56 Forward gear 8. 91 -1. 00 6. 47 -0. 73 Reverse gear 11. 74 8. 53 Crawler Ratios Speedometer Mechanical 1. 556 Electronic Installation Shift system Shift actuation Z=6 Flange mounted on engine; installation potion horizontal to the left or vertical Four-speed section Crawler / reverse gear with dog clutch engagement, all other gears synchronized. Range change group Synchronized. Four speed section Mechanical with turning shaft control with double H or superimposed H shift pattern Range change group Double H: changes are carried out and controlled automatically. Superimposed H: changeover using preselector switch on shift lever. Weight (approx. Kg) Approx. 125 kg weight without additional equipment Oil volume horizontal/ vertical position. Approx 10. 5 dm 3 / 9. 5 dm 3 Oil grade According to relevant ZF list of lubricants, TE-ML 02 64

ZF-Ecomid Gearbox • ZF-Ecomid transmission consist of a 4 -speed section with crawler and reverse gear. • The transmission is of countershaft type. • The rear mounted planetary range change group double the number of ratios in 4 -speed section. 65

ZF-Ecomid Gearbox • Together with crawler, this equips with 9 forward gears. • Gears 1 -4 from the low range and gears 5 -8 from the high in the range-change group 66

4 -speed section: • Synchronized, Reverse gear and crawler with constant mesh. • Mechanical shift operation. • Double-H shifting or super-imposed H shifting Range-Change group: • Synchronized • Automatic changeover in transition from gate 3/4 to gate 5/6 and vice versa (pneumatic) with double H shift pattern. • Changeover with preselector switch on shift lever with super imposed H shift pattern 67

Shift Actuation 1. Range Change Group Double H Shift Mechanism 2. Range Change Group Superimposed H Shift Mechanism 68

Selector patent-1 Selector patent-2 Superimposed H shift pattern Selector patent-1 69 Selector patent-2 Double H Pattern

Double H Shift Mechanism • This shift mechanism divided into 5 adjacent gates. • There is spring loaded neutral position in both gates 3/4 and 5/6. 70

Double H Shift Mechanism • Different strengths of spring detent enable the driver to navigate effectively through the transmission shift pattern. • The pneumatic selection feature operates automatically when changing from gate 3/4 to 5/6 or back again. 71

Superimposed H Shift Mechanism • The shift mechanism divided into 3 adjacent gates. • There is spring loaded Neutral position in gates 3/4 and 7/8. 72

Superimposed H Shift Mechanism • The pneumatic selection feature operated via the preselection switch on the shift lever when changing from gate 3/4 to gate 5/6 or back again. 73

Shifting of Transmission • ZF-Ecomid transmissions are synchromesh transmission. • A synchromesh transmission is one which enables all gears to rotate in the same direction at synchronous speeds. • This system makes process quicker and more reliable. 74

Shifting of Transmission • There isn’t any problem of double declutching during up shifts. • No intermediate throttle application and no double declutching when shifting down, even when driving downhill and in difficult situations. 75

Transmission Shift Pattern 1. Double H Shift Pattern. 2. Superimposed H Shift pattern. 76

Double H Shift Pattern 7 • The double H shift pattern has what is known as neutral position in R gates 3/4 (low range ) and 5/6 (High Range). 5 3 1 N N 6 4 2 C 77 8

Double H Shift Pattern • To select gates 1/2 or 7/8, move the selector level against spring force in the relevant direction and hold against this force when selecting. • The selector lever jumps back to the neutral when released from mid-position of the gate. 78

Double H Shift Pattern • Gate 3/4 and 5/6 are separated by a more powerful spring detent. • During this gate change, an automatic changeover is performed in the range change group. • The gate for reverse gear is protected by a pawl stop and requires more force to be applied. 79

Double H Shift Pattern • The different level of spring force provided good orientation within the shift pattern , i. e. the gates can be located with reliable certainty. 80

Superimposed H Shift Pattern 7 • The superimposed H shift pattern has a spring loaded return to neutral (idling) in the 3/4 (low range change group) and 7/8 (high range change group) gates. 5 N 3 1 R 8 N 6 4 2 81 C

Superimposed H Shift Pattern • To select gates 1/2 or 5/6, move the selector lever jumps against spring force in the relevant direction and hold against this spring force when selecting. • The selector level jumps back to the neutral when released from the midposition of the gate. 82

Superimposed H Shift Pattern • The reverse gear is secured by means of a bolt detent and additional force has to be exerted to select it. 83

Gear Selection • Move the selector rapidly without too much force. This is important when the transmission oil is still cold. • When selecting gear, hold the selector lever against the pressure point until the synchronizing process is complete and the gear has engaged properly. 84

Gear Selection • For Double H Change out of the ¾ gate into 5/6 gate or vice versa by briefly striking the shift lever with your palm of your hand swiftly moving the shift lever into the gear required without exerting too much force. 85

Gear Selection Down Shifting Gate 86 change Up Shifting

Gear Selection • For superimposed H if someone wants to shift from 4 th gear into the 5 th gear in the basic transmission then he 1. must Preselect high ratio (high range group) on selector switch 2. Disengage the clutch pedal 3. Shift into neutral – at which point the range change group starts to change over. 4. Select gate ½. 5. Shift the basic transmission into 1 st gear – the range change group will by now have shifted into high ratio 6. Engage the clutch 7. Leave preselector switch in the selected range group 87

Bleeding the Transmission Why? ? ? • The transmission oil heats up during travel. • This results in formation of excess pressure which is continuously removed via a bleed valve 88

PART IDENTIFICATION ZF-GEARBOX 89

Slave cylinder Oil line Air line 90

Z-bracket Gear shifting bracket Bush 91

Neutral Gear sensor Reverse gear sensor 92

Speedometer Sensor 93

Crawler gear sensor 94

Gear Shifting Bracket 95

Oil Drain Plug 96

THANK YOU 97