Sequential Transmission

8/10/2019 Sequential Transmission

http://slidepdf.com/reader/full/sequential-transmission 1/18

ADITHYA SHANKER

SEQUENTIAL TRANSMISSION



Introduction

If you have read the report on the manual transmission by MR ABHISHEK KUMAR JHA, then you

understand the inner workings of a typical manual transmission, and you know why manual

transmissions use the standard "H" pattern in the shifter.

If you have ever ridden a motorcycle, you know that the manual transmission in a motorcycle is

nothing like this. On a motorcycle, you shift gears by clicking a lever up or down with your toe. It is a

much faster way to shift. This type of transmission is called a sequential gearbox or asequential

manual transmission.

It turns out that most race cars use sequential gearboxes as well. A sequential gearbox gives the

driver several important advantages that are very useful in a race car. We will discuss these

advantages later in the report.

In this report, you will learn how a sequential manual transmission works and why this type of

transmission is now appearing on so many high-performance vehicles.

ORIGIN OF SEQUENTIAL TRANSMISSION

Central to its function has been the move from a H-gate to sequential gear selection, for with this it

is much easier to provide powered control of the actual selection mechanism. In the modern boxthis normally takes the form of a drum, with a pathway machined into it, whose axis is parallel to

that of the actual gear shafts. Depending on the type of system fitted to the car, as the driver pulls at

his steering wheel paddles, an actuator will be operated either by pneumatic, hydraulic, or fully

electric means, which will in turn move a peg or lever that engages in the track of the drum, and so

rotates it. As it does so it will sequentially pick up conventional selector forks that will move face

dogs into engagement with the next gear.

The historical ancestor of the concept – in the racing world – is the gearbox designed for the Cisitalia

GP car for which Porsche was responsible, immediately post war. This was never raced, but in 1956 a

similar system was adopted for the first single seater Lotus, the front engine type 12 Formula Twocar. For his first tentative steps into single seater racing, Chapman boldly commissioned a bespoke

unit that was typically somewhat in advance of anything else available ‘off the shelf’ at the time – of

which there was precious little in any case. It was, in effect, a scaled up motorcycle unit, with five

forward speeds occupying no more than 80 mm in length, and an all up weight of just 22,5 kg. Shaft

centres were 99 mm with a further 30 mm step up available from a hypoid final drive. In its original

form the manually operated unit was fully sequential. One set of gears was permanently splined to

the pinion shaft and the other free to rotate about the first motion shaft. Rather than using a

rotating drum, selection was by a sliding sleeve that sat over the first motion shaft. On this was

formed a six sided spline which engaged with similar splines formed on the inner annulus of each

http://auto.howstuffworks.com/gear.htm

http://auto.howstuffworks.com/gear.htm



gear. Bronze spacers between each gear formed a neutral position, with the cockpit lever always

returning to the same, central, neutral position after down- or up-changes.

The ‘box was notoriously variable in its reliability, gaining the nome de plume of ‘Lotus Queerbox’

something that has been put down variously over the years to poor lubrication, undersized gears,

and reuse of out of life parts in what was still an organisation that existed on the margins of viability.

By 1961, when it was replaced by a ZF unit, it had been adapted for mid-engine use, the final drive

had been changed to a spiral form after lubrication issues with the hypoid, and the change had been

modified so that the lever now migrated as gears were selected, two racks being required in the

system to achieve this.

But Chapman never completely gave up on his original transmission concept. In 1974, by which time

Formula One Lotus’s were using the same dog clutch H-shift Hewland FG400 gearboxes as everyone

else, he introduced a change system operated by a button on the gearlever, thus deleting the use of

a conventional clutch pedal for all but starting. The idea was to speed up changes and reduce the

time spent in freewheel, at the same time allowing the drivers to left foot brake. Even then this was

recognised as a potentially faster way around the lap, but the system was driven by the starter

motor with the conventional clutch release operated electrically from this, and instead of clutches

gear shifting the end result was more often a series of burnt out motors and electrical short circuits

that killed the engine.

Still he pursued his two pedal philosophy and in 1978 reintroduced a version of the ‘queerbox’.

Instead of using splines, engagement was now by ball bearings thrust into position with each gear by

a bobbin running inside the input shaft. Ground effect aerodynamics were just beginning to be

applied to the type 78 and 79 and clutchless, two pedal control, by which pitch change under

acceleration and deceleration could be more closely controlled, suddenly opened up a whole new

relevance for the technology...

Sequential gearboxes - what, why and how? A Brief Overview of the

Mechanism

If you've ever watched motorsports you'll have noticed that the drivers don't have an "H" gate for

their gearstick. They either jam the stick back and forth or use paddle-shifters behind the steering

wheel. The paddle-shifters do the same job as the gearstick movement in this case, only using

electronics to move the shifter. So what's going on in a sequential gearbox? Actually it's quite

simple. A sequential gearbox is just like a manual gearbox but the selector system is different. The

manual gearbox example at the top of the page showed a series of selector forks which were moved

by the physical position of the gearstick. In a sequential box, those selector forks are connected to a

single shaft that has corkscrew-type grooves in it. The collar that fits around this selection shaft has a

ballbearing in it which sits in a recess in the collar as well as in one of the corkscrew grooves.



When the gearstick is moved forwards or backwards, the selector shaft is mechanically turned by

some number of degrees. That twisting motion rotates the corkscrew groove which in turn interacts

with the ballbearings and the selector fork collars, forcing them to slide back and forth. Each click of

the gearstick rotates the shaft another number of degrees and all the selector forks change position

in one go. That's why it's called a sequential gearbox - the gears are always selected in sequence.

You can't jump from first to third, you have to go via second. Often, sequential gearboxes have a

"double-click for neutral" option and when you do this, it disengages the clutch and rotates the

selector shaft back around to the neutral position, just before first gear. So why design and use a

sequential gearbox? Well for a start it's a simpler design than a fully-manual gearbox with less

moving parts. For racing drivers it makes for much quicker gearchanges - bang the gearstick andyou're up a gear nearly instantly.

SEQUENTIAL TRANSIMISSION MECHANISM

We have seen the mechanism of manual transmission. It offers a basic understanding of the

mechanisms inside a manual transmission. The five-speed manual transmission is fairly standard on

cars today. It looks something like this internally:



There are three forks controlled by three rods that are engaged by the shift lever. Looking at the shift

rods from the top, they look like this in neutral, reverse, first and second gear:

The "H" pattern allows you to move the shift rod between the control rods for the three forks and

move the rods back and forth.

A sequential manual transmission works the same way. There is still a set of gear selector forks that

move collars that engage gears. The only difference is the way the control rods are manipulated. The

"H" pattern is eliminated and replaced with a different motion.

In a race car, the motion of the shift lever is either "push forward" to up-shift or "pull backward" to

downshift. If you are in a gear and you want to go to a higher gear (e.g. from 2nd to 3rd), you push

the shift lever forward. To go from 3rd to 4th, you push the lever forward again. To go from 4th to

5th, you press it forward again. It is the same motion every time. To drop back down a gear, say from

5th to 4th, you pull the lever backward. In European mass-produced automobiles, the shift lever

moves forward and backward to shift into higher and lower gears, respectively. In Formula One cars,

there are actually two paddles on the sides of the steering wheel, instead of a shift lever. The left

paddle up-shifts, while the right paddle downshifts. On a motorcycle, you do the same thing, but

instead of moving a lever back and forth with your hand, you move a lever up and down with your

foot.

What these motions are doing is rotating a ratcheting drum. The drum looks like this:



You can see that there are grooves cut into the drum. These grooves can do one of two things:

If the drum is located away from the transmission's gears, the grooves control standard control rods.

If the drum is located next to the gears, the grooves directly move the gear selector fork, and no

control rods are needed. This seems to be the more common technique because it has fewer parts

and is more compact.

So, when you move the lever, it rotates the drum one increment (for example, 50 degrees). This

rotation causes the rods or forks to move according to the grooves in the drum, changing the gears.

SEQUENTIAL MANUAL TRANSMISSION IN CARS

The sequential manual transmission contains a Hydraulic Power Unit(HPU) assembly, Gear Shift

Actuator (GSA), electronic throttle, dedicated shift lever, transmission control ECU and sensors, in

addition to the conventional transaxle.

The following are the various components of a sequential manual transmission in a car:

a. Hydraulic Power Unitb. Gear Shift Actuator

c. Shift Lever

d. Shift Lever switches

e. Transmission Control ECU

f. ECM

g. System Warning Light

h. Gear Position Indicator

i. Stop Light Switch

j. Shift Lock Solenoid



Transmission Control Unit

The Transmission Control ECU controls the hydraulic power unit and the gear shift actuator assembly

to engage or disengage the clutch and shift the gears based on signals from the ECM, sensors, and

switches. Additionally, the Transmission Control ECU requests the ECM to control the ETCS_i throttlecontrol motor during gear changes.

Hydraulic Power Unit (HPU)

The Hydraulic Power Unit (HPU) assembly generates hydraulic pressure for the shift operating

system and the clutch release cylinder. It is located in the engine compartment and mounted to the

vehicle body. The pump draws the sequential M/T fluid from the reservoir tank and provides high

pressure to the accumulator. The pressure sensor monitors accumulator pressure and provides input

to the transmission control ECU. The hydraulic power unit is connected to the gear shift actuator

through three high_pressure hoses.

Gear Shift Actuator (GSA)

The Gear Shift Actuator (GSA) assembly engages or disengages the clutch and selects gears based on

signals from the transmission control ECU. It is mounted to the side of the transaxle case, and

attaches to the shift and select lever shaft. The actuator clutch cable attaches to the transaxles

clutch release fork.

The select solenoid valve provides hydraulic pressure to move the select shaft. The select shaft

positions the shift inner lever and shift fork lock over the shift fork heads of the transaxle shift and

select assembly. The shift solenoid valve provides hydraulic pressure to rotate the select shaft thatmoves the shift inner lever to engage the desired gear. The clutch solenoid valve provides hydraulic

pressure to the clutch release cylinder and moves the clutch cable to engage or disengage the clutch.

The gear shift actuator houses three sensors that monitor the shift stroke and select stroke of the

shift and select lever shaft assembly as well as the clutch stroke. These sensors provide input to the

ECU on the clutch and select shaft positions.

Gear Shift Actuator Link Fixing Plate

The gear shift actuator link fixing plate SST is required to keep the shift actuator link in a neutral

position whenever the gear shift actuator is removed or a new unit is installed. Failure to use the SST

may result in the inability to shift the transmission.

Shift Lever

The sequential manual transmission uses a control_by_wire type shift mechanism that detects the

movement of the shift lever based on the combination of four switches; this shift mechanism is

integrated into the shift lever position sensor. The three ranges are R for reverse, N for neutral and S

for sequential range. Shift lever position is maintained by spring_loaded detents, which provide shift

feedback to the driver.



Shift Lever Switches

The shift position and the movement of the shift lever are detected through the combination of the

four switches integrated into the shift lever position sensor. Switch positions are determined by the

shift lever arm and the two position sensor links. The operating conditions of the switches are

detected and the signals are sent to the transmission control ECU.

Steering Wheel Shift Switches

Steering wheel switches (optional equipment) are available and are located on the steering wheel.

Two switches are located on each steering wheel spoke; the two facing the driver provide for

downshifts and the two switches facing away from the driver provide for upshifts.

Stop Light Switch

The stop light switch detects when the brake pedal is applied. The ECM must see the brake pedal

signal before it allows the engine to start.

Transmission Revolution Sensor

The transmission revolution sensor detects input shaft speed so the ECU can disengage the clutch

when shaft speed reaches a predetermined speed threshold. The ECU matches input shaft and

engine speed when shifting with the pedal released.

Gear Position Indicator

The gear position indicator is located in the combination meter and shows the gear position of the

transmission. The indicator blinks if the shift lever position and the gear position becomemismatched.

System Warning Light

The System Warning Light activates to alert the driver when the transmission control ECU detects a

malfunction in the sequential manual transmission.

Courtesy Light Switch

The courtesy light switch is located on the driver's door to indicate the driver's entry to the vehicle.

This input to the ECU starts the HPU to build hydraulic pressure for actuator operation.

Throttle Control (ETCS-i)

Throttle position is determined by the accelerator pedal position sensor input and the ECM. The

throttle opening is controlled by the ECM's signal to the throttle motor. The ECM matches engine

speed to the transmission input shaft speed for proper gear engagement.

Shift Lock Mechanism

A shift lock mechanism locks the shift lever when the ignition switch is turned to OFF or ACC. Since

there is no mechanical linkage, this mechanism prevents the shift lever position and thetransmission gear position from becoming mismatched.



The shift lock mechanism contains:

Shift lock solenoid

Stopper plate

Lock plate (integrated with No. 2 lever)

The lock plate and No. 2 lever move in unison with the shift lever when shifting between ranges. The

lock plate has holes for R, N, and S, so that it can be locked in any range. When the ignition is

switched OFF the stopper plate rotates due to the movement of the shift lock solenoid, causing the

protrusion on the plate to engage with the hole in the lock plate.

Shift Lock Solenoid

The shift lock solenoid locks the movement of the shift lever when the ignition switch is turned to

OFF or ACC and prevents the lever position and gear position from becoming mismatched.

Sequential Transmission in Motorcycle



A simple transmission

A motorcycle engine can create an enormous amount of power, which must be delivered to the

wheels of the vehicle in a controllable way. The motorcycle transmission delivers power to the rear

wheel through a series of structures that include the gearset, the clutch and the drive system.

Gearset

A gearset is a set of gears that enable a rider to move from a complete stop to a cruising

speed. Transmissionson motorcycles typically have four to six gears, although small bikes may have

as few as two. The gears are engaged by shifting a lever, which moves shifting forks inside the

transmission. Most manual motorcycle gearboxes have "constant mesh" gears which are always

mated but may rotate freely on a shaft until locked by a toothed sliding collar or "dog clutch". Since

the gears are always rotating and can only be accessed sequentially ,synchromesh is not generally

needed. To save space, both shafts may contain a mixture of fixed and free-spinning gears, with

some gears built into the sliding parts.

Clutch

The job of a clutch is to engage and disengage power from the engine crankshaft to the

transmission. Without the clutch, the only way to stop the wheels from turning would be to turn off

the engine -- an impractical solution in any kind of motorized vehicle. The clutch is a series of spring-

loaded plates that, when pressed together, connect the transmission to the crankshaft. When a rider

wants to shift gears, he uses the clutch to disconnect the transmission from the crankshaft. Once the

new gear is selected, he uses the clutch to reestablish the connection.

The belt drive on a Buell Lightning

DriveSystems

There are three basic ways to transmit engine power to the rear wheel of a motorcycle: chain, beltor shaft. Chain final-drive systems are by far the most common. In this system, a sprocket mounted

http://auto.howstuffworks.com/clutch.htm

http://science.howstuffworks.com/gear.htm

http://auto.howstuffworks.com/transmission.htm

http://en.wikipedia.org/wiki/Manual_transmission#Dog_clutch

http://en.wikipedia.org/wiki/Synchromesh

http://en.wikipedia.org/wiki/Synchromesh

http://en.wikipedia.org/wiki/Manual_transmission#Dog_clutch

http://auto.howstuffworks.com/transmission.htm

http://science.howstuffworks.com/gear.htm

http://auto.howstuffworks.com/clutch.htm



to the output shaft (i.e., the shaft in the transmission) is connected to a sprocket attached to the

rear wheel of the motorcycle by a metal chain. When the transmission turns the smaller front

sprocket, power is transmitted along the chain to the larger rear sprocket, which then turns the rear

wheel. This type of system must be lubricated and adjusted, and the chain stretches and the

sprockets wear, requiring periodic replacements.

The Friction Drive

The friction drive is another transmission found in some motorcycles. A friction drive is a type

of continuously variable transmission, or CVT, in which the variation in gear ratios comes about as a

disc connected to the engine (the driving disc) rotates across the face of a second disc connected to

the rear wheel (the driven disc). By varying the radius of the contact point between the two disc

surfaces, different gears can be achieved. Continuously variable transmissions have a long history of

use in motorized vehicles, with variable friction transmissions appearing in motorcycles in the early

1900s.

Belt drives are an alternative to chain drives. Early motorcycles often used leather belts, which could

be tensioned to give traction using a spring-loaded pulley and hand lever. Leather belts often

slipped, especially in wet weather, so they were abandoned for other materials and designs. By the

1980s, advances in materials made belt final-drive systems viable again. Today's belts are made of

cogged rubber and operate much the same way as metal chains. Unlike metal chains, they don't

require lubrication or cleaning solvents.

Shaft final-drives are sometimes used. This system transmits power to the rear wheel via a drive

shaft. Shaft drives are popular because they are convenient and don't require as much maintenance

as chain-based systems. However, shaft drives are heavier and sometimes cause unwanted motion,called shaft jacking, in the rear of the motorcycle.

The other components that make a motorcycle a motorcycle are part of the chassis.

Sequential Transmission in Formula One Race Cars

"Simple" gearbox is not in use in racing any more. Only most basic racing categories are using it. InFormula 1 this kind of gearbox is not in use more than 20 years. Sequential gearbox is stuff of

the day in our sport, take rally, DTM, Formula 1, almost all open wheel classes, WTCC, Indy, truck

racing... Sequential transmissions usually use the rotation of a drum to switch gears.

http://auto.howstuffworks.com/cvt.htm

http://www.formula1-dictionary.net/seamless_gearbox.html


http://auto.howstuffworks.com/cvt.htm



Ferrari 640 with Mansel driving

Ferrari 640 was the first F1 car using a semiautomatic sequential gearbox 1989 in the Brasilian GP.

Car was driven by Nigel Mensel.

John Bernard, in this time Ferrari technical director, proposed this innovation 1988, and was

accepted and adopted for first time in 1989. Idea was to speed up gear change to maximum, and get

rid of clutch pedal. First idea in time of development was to have one lever on right hand side of the

driver, on the place of "old" "H" gear shift lever. Driver will move this lever only backward and

forward to go trough gears. During development period Bernard got better idea. He put two buttons

on each side of the steering wheel to prevent driver to move hands from the steering

wheel. Later, they change this idea to two paddles behind a wheel. They added third, clutch paddle

little bit offset and smaller then first two. Left side paddle was used for downshift, and right paddle

for up shift. Clutch paddle was smaller because this one is in use only during the start, stop and in

some emergency situations. During normal race clutch was operated automatically, together with

gear change forks with help of electronically controlled electrohydraulic system.

Paddles behind a wheel

http://www.formula1-dictionary.net/steering_wheel.html







Ferrari 640 steering wheel with innovative paddles behind the wheel

Selector drum of an modern sequential gearbox

Honda RA106 Formula 1 Gear Selector Barrel



For many years it was the convention on F1 cars to locate the gear clusters behind the differential,

for ease of access in order to change gear ratios, although this compromised weight

distribution and aerodynamic performance. The current trend, with the gear clusters at the front

(engine) end of the gearbox, means that the gearbox must be removed to change the gear ratios.

The gear cluster (input shaft and output shaft) is mounted in a removable cassette, which can be

removed once the gearbox/rear suspension/wing assembly has been removed from the rear of

the car. The input shaft and output shaft each carry seven gears, and each pair of gears (one on the

input shaft and one on the output shaft) is carefully selected to give the required gear ratio.

The FIA from 2011 regulations stipulate

that each car is allowed 30 pairs of gear

ratios from which to choose during the

entire season, and these 30 ratios must

be declared to the FIA before the first

race of the season. The 2010 FIA

regulations stipulated that all gears

must be manufactured from steel, with

a minimum weight (0.6kg) for gear pairs,

and a minimum thickness (12mm) for

each gear. All cars must be fitted with a

reverse gear to comply with the FIA

regulations, and reverse is operated

using a button on the steering wheel

which engages an intermediate gear

between the gearbox input and outputshafts to reverse the direction of

rotation of the output shaft.

FIA technical rules allow gearbox's with

4 to 7 forward speed and one reverse

gear. Reverse gear is mandated. The driver initiates gear changes using paddles, and electro-

hydraulics perform the actual change as well as throttle and clutch control.

Since the Ferrari 640 F1 showed the performance benefits of semi-automatic gearboxes back in

1989, all F1 teams adopted that idea. Development has been astonishing: they've become smaller,

lighter (because of the use of advanced materials, particularly in the gears and casing). And, most

importantly, they become faster. Talking about "old" F1 sequential gearbox (two or three years ago),

they become so fast that "normal" person can't understand and can't believe if that is possible.

Complete gear change happened in 10-15 millisecond.

In this time:

1. Driver gives a command to up or downshift.

2. Electronic control system check position of the clutch, engine speed and wheelspeed

(using different sensors in engine and differential)

Inside Formula 1 gearbox, the gear

clusters are mounted in a removable

cassette. Much easier to work with.

http://www.formula1-dictionary.net/weight_balance.html


http://www.formula1-dictionary.net/engine.html



http://www.formula1-dictionary.net/suspension.html

http://www.formula1-dictionary.net/wings.html


http://www.formula1-dictionary.net/fia.html


http://www.formula1-dictionary.net/wheels.html




http://www.formula1-dictionary.net/fia.html


http://www.formula1-dictionary.net/suspension.html






3. Initiating clutch opening (electronics give a signal to electrohydraulic system to operate

solenoid valve, valve open and release high pressure oil into hydraulic piston, piston push

clutch discs to open position)

4. Changing the gear. Disengaging old one and then engaging new, selected gear. (electronic

give a signal to electrohydraulic system to operate solenoid valves to operate gear selector

forks and to adjust proper gear to desired position)

5. ECU is checking new proper position of gears, and comparing this data with engine and

wheels speed in this instant (using different sensors in motor and differential. If driver select

wrong speed, gear change will not be done)

6. Closing the clutch if item 5 is OK (electronic give a signal to electrohydraulic system to close

solenoid valve and to release hydraulic oil from piston and to close the clutch)

7. If item 5 is not OK, electronic control system will try to engage proper gear, or to return to

originally engaged gear.

All this checking is necessary because of high speed of the system. If anything goes wrong during

gear change process, anything, we can see white smoke behind car or blocked rear wheels and spin.

2008 Honda Formula 1 Gear Selector Hub

But only in the last few years we can see some very serious, inventive thinking been applied to

developing a step change in the way gearboxes work. This 10-15 milliseconds explained before, for

them is to much of lost time. They want something better and faster. F1 engineer are never satisfied

(that's why they are F1 engineers), and they started to think about seamless gearshift.

Despite the systems having been in use for several years, there is still little information coming from

the teams on how they work. What is known is that the systems retain the conventional two-shaft

gearbox and single clutch. A double clutch would provide a seamless shift, but this is banned under

the current rules. No F1 engineer wants to talk about that. Every team has his own way to do the

job.

http://www.formula1-dictionary.net/ecu.html




http://www.formula1-dictionary.net/ecu.html



Nearly all race transmissions use the sequential shift approach. The drum is rotated manually by a

lever in the cockpit, or it is rotated by solenoids, pneumatics or hydraulics that are activated

electronically. In the electronic case, the driver has a pair of paddle switches on the steering wheel

to control the mechanism and never has to move his/her hands from the steering wheel.

Because of the advantages of the sequential approach, this type of transmission is starting to appear

on cars in the high-end tuner market. A sequential manual transmission is not to be confused with a

"tiptronic" sort of automatic transmission. The tiptronic system may duplicate the shift lever motion

of a sequential gearbox. However, because a tiptronic transmission is an automatic transmission at

its core, it still has the torque converter and usually does not shift as quickly.

http://auto.howstuffworks.com/automatic-transmission.htm

http://auto.howstuffworks.com/torque-converter.htm



http://auto.howstuffworks.com/automatic-transmission.htm



REFERENCES

http://en.wikipedia.org/wiki/Sequential_manual_transmission

http://auto.howstuffworks.com/sequential-gearbox1.htm

https://www.highpowermedia.com/RET-Monitor/3545/sequential-gearbox-origins

http://www.formula1-dictionary.net/gearbox.html

http://www.ariclim.com/files/mr2spyder/SMT.pdf

http://auto.howstuffworks.com/motorcycle6.htm



















Sequential Transmission

Documents

Transcript of Sequential Transmission