199001750 - INTRODUCTION - EXT. CONTROLS FOR GEAR SELECTION ELECTROHYDRAULIC

INTRODUCTION

The MTA robotized transmission system (Mechanical Transmission Automatized) for the M20 (6 speed) gearbox fitted on the 1.3 Multijet 90 CV version is designed to improve the performance of the manual transmission components.The system means that the driver does not have to control the clutch pedal and the gear lever affording them the pleasure of driving that comes from the direct control of the transmission.It also improves driving safety through a direct control of driver errors.The system basically consists of a manual transmission, with a dry, single plate clutch and manual gearbox with synchromesh with hydraulic power assistance.Neither the clutch nor the gearbox has been modified for the installation of the hydraulic actuators designed to control the clutch travel and the gear engagement/selection movements.

INTRODUCTION

The MTA system for the M20 gearbox has the following main specifications:- Improves the performance of the manual mechanical transmission components.- Saves the driver having to control the clutch pedal and the conventional gear lever.- Improves safe driving by means of a control that prevents driver errors and the incorrect operation of the transmission system.- Offers the driver a more advanced vehicle interface.- It is a hydraulic power assistance system for the gearbox and the clutch that maintains all the advantages of a dry clutch and a manual gearbox (weight, strength and reliability, low energy consumption).- It is simple to use and makes driving less tiring, especially town driving.- It ensures comfortable or sports gear changes thanks to the advanced power assistance logics.- There is no clutch pedal in the passenger compartment and the gear lever has been replaced with "Up/Down/Neutral/Reverse" controls on a joystick on the centre tunnel.- Automatic management of the gearbox can be enabled (by the driver) in AUTO mode with two different logics (ECO/NORMAL).There are two system operating modes for the robotized gearbox:- SEMIAUTOMATIC Mode (MANUAL): the driver engages the gears using the lever on the tunnel.- AUTOMATIC Mode (AUTO): the electronic system manages the decision to change gear in accordance with two strategies, the first dictated by driving comfort (NORMAL) and the second with the aim of reducing consumption (ECO).

General diagram showing main robotized gearbox system components

1. TCU (Transmission Control Unit)2. Electrohydraulic unit with electric pump3. Engine management control unit4. Gear display and panel5. Eco logic selection button6. Brake pedal (with dual switch)7. Gear and Auto mode selector lever8. Accelerator pedal (Drive by Wire)The power assisted system consists of an electrohydraulic unit (2) fitted directly on the gearbox casing which manages the following gearbox movements by means of two actuators:- the gear selection and engagement movement (double acting actuator)- the control of the clutch opening.The electrohydraulic unit is controlled by four solenoid valves (for which an electric pump and an accumulator provide the required hydraulic power).Having identified the driver''s requests from the position of the lever, an electronic control unit (1) manages the gear change independently, controlling the clutch, gearbox and engine torque directly.The synergy between the gearbox and the engine improves the performance of the system considerably and frees the driver from any need to synchronize clutch-accelerator movements during gear changes which can be carried out with the accelerator fully depressed.The system inhibits requests for incorrect gear changes and prevents the engine from cutting out or going outside of revs.In terms of driving assistance the system also ensures the immediate availability of first gear when the vehicle stops and the automatic changing up through the gears in the case of strong deceleration.The indication of the gear engaged is shown on a display in the instrument panel, in the same way as the signalling of faults or critical driving conditions for the vehicle or the transmission components with a series of warning or failure messages for the system together with the general failure or transmission failure warning lights.

ARRANGEMENT OF THE COMPONENTS ON THE GEARBOX

The electrohydraulic unit is positioned as follows on the M20 gearbox.1. Power unit2. Solenoid unit3. TCU4. Clutch actuator

ELECTROHYDRAULIC UNIT COMPONENTS

The electrohydraulic unit comes in one piece which includes three main components:- the power unit (1) comprising the electric pump, accumulator and reservoir;- the solenoid valve unit (2) which transforms the hydraulic energy into mechanical energy by means of the interface of the engagement pistons with the control shaft;- the gear control mechanical unit (3) which interfaces directly with the gearbox through the opening in the actual casing;- the clutch actuator (4) comprising the master cylinder and reservoir.

Power unit

The power unit supplies hydraulic energy for the activation of both the gear engagement/selection and the clutch master cylinder. The unit includes an electric pump (1) and a fluid reservoir (2). There is also a semi-rigid high pressure pipe (3) that connects the pressure accumulator (4) with the soleniod valve assembly and a low pressure pipe (5) that connects the valve assembly to the reservoir.The system operates at a line pressure that varies between 36.5 and 46 bar in normal conditions. In the Recovery condition, the system can work at a pressure of 75 bar.The electric pump is activated when the pressure goes below 36.5 bar and is deactivated when the circuit pressure reaches 46 bar.

Solenoid unit

The solenoid valve unit has the following functions:- it controls and manages the position of the clutch- it controls and manages the gear selection and engagement.The components used for activating these functions are shown in the diagram.1. Flow rate proportional solenoid valve for controlling the clutch (EV0)2. Pressure proportional solenoid valve for even gear engagement (R - 2 - 4 - 6) (EV2)3. Pressure proportional solenoid valve for odd gear engagement (1 - 3 - 5) (EV1)4. On-Off solenoid valve for range selection (EV3)5. Linear pressure sensor (0-70 bar)6. Hall effect sensor for engagement position7. Hall effect sensor for selection position8. Earth points for TCU electronic management control unit

Clutch actuator

Operation1. Clutch position potentiometer2. Clutch fluid reservoir3. Fluid outlet for clutch coaxial actuator (inside the bellhousing)4. Fluid inlet from solenoid valve assemblyThe clutch master cylinder comprises a cylinder in which a piston (4) slides forming three chambers: in the first chamber (5) the pressurized fluid arrives from the hydraulic unit via solenoid valve EV0; the second (6) and third (7) chambers come into contact with the flow of clutch fluid which, depending on the thrust the fluid receives from the first chamber, produces the thrust on the clutch control coaxial actuator. The advantage of this solution lies in the fact that the same clutch control coaxial actuator is used as on the manual gearbox.1. Pressurized fluid inlet/outlet - hydraulic unit2. Clutch fluid inlet3. Pressurized clutch fluid outlet4. Piston5. Chamber 16. Chamber 27. Chamber 38. Clutch closed9. Clutch open

Mechanical unit

The mechanical unit consists of a gear selector for choosing the suitable gear and then managing both the gear engagement and selection.Composition1. Control shaft2. Gear control finger3. "S" cam4. Latch5. Selection centering ballThe selector consists of a control shaft (1) which includes a double selection finger (2). The latter is capable of managing both the gear selection in the same range and that in other ranges.The latch device (4) is capable of rotary movement to alter the selection from a lower range to a higher one and viceversa. The drum with the double "S" slot (3) makes it possible to create a rotation, through the thrust of the fluid, following a movement of the selection finger. This forces the finger to change the selection range.This operating principle is based on the conversion of the hydraulic piston linear motion into the translation-rotatry movement of the shaft and consequently the components connected to it.OperationThe translation movement of the shaft (which corresponds to the gear change in the same range) is implemented by two simple shifts:- with the activation of solenoid valve EV1 or EV2, the hydraulic piston moves in a linear fashion in one direction only- with solenoid valve EV1 the odd gears (1 - 3 - 5) are engaged and with solenoid valve EV2 the even gears are engaged (R - 2 - 4 - 6).The movement which allows the change of the "gear branch" is activated with three shifts:- the hydraulic brake is activated (solenoid valve EV3 is pressurized and the drum is locked)- when one of the two chambers produced by the piston in the hydraulic cylinder is pressurized and moves in a linear fashion, the latch is forced to follow the "S" profile of the drum; in this way the shaft and therefore the selection finger is forced to follow a "translation - rotary - translation" movement which allows a change of both gear engagement and gear branch selection.- the correct position for the branch is maintained thanks to the centering ball which acts on a surface with four channels which correspond to the four gear branches.

Electronic control unit tcu

The control unit is located directly on the solenoid valve assembly and is connected, by means of two connections, to the engine wiring and to the gearbox hydraulic system wiring.

If the control unit is removed-refitted, in order not to damage the contact plates between the actual control unit and the solenoid valves it is advisable to use the special tool mentioned in the specific procedure.

Pin outCONNECTOR A (vehicle side)1. Not connected2. Driver''s door switch signal3. Vbat for TCU4. Reversing lights output signal5. Vbat for electric pump6. Not connected7. Selector lever position 38. Not connected9. Brake pedal signal10. TCU activation signal (key-on: +15)11. Selector lever position 212. Selector lever position 113. Selector lever earth14. Not connected15. Not connected16. Selector lever position 417. ECO switch18. Not connected19. CAN L (high speed)20. CAN L (high speed)21. Not connected22. CAN H (high speed)23. CAN H (high speed)from 24. to 28. Not connectedCONNECTOR B (system side)1. Pump motor control2. Not connected3. Gearbox speed sensor (-)4. Engagement sensor and selection sensor power supply (+5V)5. Engagement position signal6. Engagement and selection position sensor reference earth7. Not connected8. Gearbox speed sensor (+)9. Clutch position sensor power supply (+5V)10. Clutch position signal11. Clutch earth reference12. Selection position signalInput signalsThe system uses the following signals arriving from other vehicle systems for the operating logics:- specific sensors from the robotized gearbox- clutch rpm sensor (the reading is taken from the main gearbox shaft)- position sensor for: clutch, engagement and selection- individual signals coming from other vehicle systems- engine rpm (signal coming from the engine management control unit via the C-CAN)- brake pedal switch (two signals: one discreet - pin 9 vehicle connector, the other via the C-CAN)- driver''s door open switch (discreet)- key-on (stable position and starting discreet).The following other signals arrive from other systems via the CAN:- accelerator pedal position- engine torque, vehicle speed, engine temperature, etc.Output signalsThe reversing lights activation signal is no longer managed by a switch but is activated directly by the MTA control unit at pin 4 of the vehicle connector.User interfaceThe user interfaces with the system via the following controls:- accelerator pedal via the CAN from the engine management node- brake pedal, via two signals: one discreet, the other via the C-CAN- gear change or selection mode request via the multistable lever- ECO mode (the signal is given by a switch connected directly to the MTA control unit).The system supports the driver in the following way via the multifunction display:- display of gear engaged (via CAN)- "AUTO" mode selection (via CAN)- mode in use: "ECO" (through the display of the letter "E")- system failures (through a dedicated warning light coming on via the CAN)- acoustic signal from the instrument panel buzzer: connected via the CAN, it warns the driver of a critical vehicle/system situation.

The display shows the current gear during operation in AUTO mode.

OPERATING LOGICS

Operation of the system

Hydraulic circuit pressurizationIf the pressure is below the minimum operating level, the pressurization of the hydraulic circuit takes place in two different ways:- if the driver''s door is opened the system automatically pressurizes the hydraulic circuit to allow a gear change, if requested, without waiting for the circuit to be charged (fixed pump activation time;- with the ignition key in the OFF position: the control unit receives a power supply (and will continue to do so until the ignition key is turned OFF and the engine speed and vehicle speed are zero).The system electric pump also receives a power supply to pressurize the system when the pressure reaches the minimum value of around 36.5 bar.

... DATA ERROR - CROPPED TEXT | Ошибка данных - Текст обрезан ...