184000312 - INTRODUCTION - EXTERNAL CONTROLS FOR GEARBOX ELECTROHYDRAULIC

ROBOTIZED GEARBOX

INTRODUCTION

The 1.4 16v versions is equipped with a C514 manual gearbox with an electrohydraulic control unit.The concept of the robotized control system on C514 gearboxes is designed to improve the performance of the manual mechanical transmission components. This system has been designed to automate the clutch and gear lever controls for a conventional manual gearbox using electro-hydraulic type power assistance.

This system:

  • 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 makes it possible to maintain 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 lever on the 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 located 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 components1, TCU (Transmission Control Unit)2, Electrohydraulic unit with electric pump3, Engine Management Control Unit4, Gear display and panel5, Eco/Normal auto 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 three solenoid valves (for which an electric pump and an accumulator provide the required hydraulic power) and a solenoid.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 engine control is governed by the gearbox control during gear changes.The interface 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.In terms of driving assistance it 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.Robotized gearbox system components
1, Gear selector lever on tunnel2, ECO/NORMAL button3, Transmission Control Unit4, Electrohydraulic unit5, Pump6, Reservoir7 - Gearbox main speed sensor8, Gear and Auto mode display9, Gearbox failure warning light10, General failure warning light11, Information display for driver12, Reversing switch (on hydraulic kit)

SYSTEM COMPONENTS

Gearbox components electrohydraulic kit

The electrohydraulic unit is positioned on the C514 gearbox as illustrated in the pictures below.Front view and panoramic view of C514 gearbox assembly and electrohydraulic kit
Side view (left driveshaft side) and rear view of C514 gearbox assembly and electrohydraulic kit

Electrohydraulic kit components

The electrohydraulic kit comes in one piece which includes three main components:

  • the mechanical gear control unit which interfaces directly with the gearbox via the opening in the casing which is the same as the type-approved manual version;
  • the solenoid valve unit transforms the hydraulic energy into mechanical energy by means of the interface of the engagement pistons with the control shaft;
  • the power unit comprising the electric pump and hydraulic reservoir.
The main units that make up the electrohydraulic kit fitted on the C514 gearbox are illustrated below.
1, Solenoid valve unit2, Electric pump and reservoir power unit3, Mechanical unitThe kit can be dismantled into three basic parts the upper part (valve unit) and the lower part (mechanical part) plus the hydraulic power unit (pump + reservoir).

Power unit

The power unit has the function of supplying hydraulic energy for the activation of the gear change and the clutch.The unit comprises an electric pump (electric motor and geared pump) and the fluid reservoir.
1, Electric pump2, Retaining bracket3, Reservoir4, High pressure supply pipe5, Low pressure return pipeThe line pressure operating range of the system is between 40 and 52 bar.The subsystem in question has the following technical specifications.Electric pump: nominal capacity 0.8 l/m with 13 [V] power supply at 50 [bar], oil temperature 60 [°C] e duty cycle 30%; it has the task of producing hydraulic energy.It is fastened directly to the gearbox securing bracket in three places. The electric pump consists of a geared pump of around 0.25cm3/rev, driven by means of a 12V direct current electric motor coupling through a relay controlled by the C.F.C228F.01 control unit.The electric pump is activated when the accumulated pressure is below 40 bar and it is switched off when the accumulated pressure 50 bar.The electric motor and the pump are fastened to one another through bolts by means of a flange.

The main technical specifications that the system must provide to guarantee correct operation are:

  • Hydraulic operating pressure of between 41 and 51 bar
  • Operating temperature between -30°C and + 125 °C
  • Starting should also be possible at temperatures of -30°C
  • The capacity of the pump is 0.8 l/m at 60 °C
  • The volume of the accumulator is 280 cm3 preloaded at 27 [bar] at 25 °C (an important figure because it determines the discharge time)
Electric pumpView of the electric pump
1, Electric connector2, Geared pump3, Electric motor4, Fixing points on the bracketMechanical geared pump
1, Engine connection coupling2, High pressure supply (semi-rigid supply pipe threaded connection)3, Intake from reservoir (direct connection to reservoir)Reservoir with filter: approx 0.5 l and filter with 150 micron output
1, Oil recovery connection2, Low pressure return connection3, Bracket connecting eyelet4, Electric motor connector support5, Pump connectionThe inset shows the level reading on the reservoir.

Hydraulic pipes:

  • 1 semi-rigid high pressure which connects the electric pump to the valve unit
  • 1 pre-moulded flexible rubber low pressure which connects the valve unit to the reservoir.
The connection between the reservoir and the pump is direct by means of a press-fitting with an O-ring seal.Bracket securing reservoir and electric pump to kit and gearbox.Hydraulic fluid: TUTELA CAR CS SPEED oil with "ATF Dexron III" additive (viscosity 1800 cPs at -40 [°C]; 6.5 cPs at 100 [°C])

Valve unit

This subsystem carries out the following functions:

  • Controls and implements the clutch position.
  • Controls the gear engagment/release and range selection.
  • Accumulates hydraulic power/energy for controlling the actuators.

The following components are involved in producing these functions:

  • Solenoid valve body
  • Clutch actuator (single-acting piston).
  • Flow rate proportional solenoid valve for controlling clutch actuator.
  • Gear engagement actuator (double-acting piston).
  • Two proportional pressure solenoid valves for controlling the engagement actuator: even gears proportional pressure solenoid valve (2 - 4 - Reverse) and odd gears proportional pressure solenoid valve (1 - 3 - 5).
  • Two potentiometric sensors for detecting the engagement position and clutch travel position
  • Accumulator
  • Linear pressure sensor (0-80 bar)
  • Single-acting valve.
Views of hydraulic unit
1, Accumulator2, Clutch travel potentiometer3, Engagement travel potentiometer4, Clutch lever control push rod5, Low pressure oil drain connection6, Pressure sensorRear view of hydraulic unit
1, Maximum valve2, High pressure supply pipe rapid connector3, Clutch capacity proportional solenoid valve (ev0)4, Even gears engagement proportional pressure solenoid valve (ev2)5, Odd gears engagement proportional pressure solenoid valve (ev1)6, Low pressure oil drain rubber pipe attachment7, Pressure sensor8, Earth point on kitView of hydraulic unit from below: the double-acting actuator (1) for the engagement with the control shaft attachment "fork" (2) should be noted.

Proportional pressure valves ev1 and ev2

The control the pressure of the fluid in the two double-acting gear engagement-release actuator chambers with two stable mechanical positions depending on the control combination (even gears, odd gears).They have a maximum capacity of 71/m with a pressure differential of 10 bar.The control current ranges from 0 to 2.5 A controlled directly by the C.F.C. 228F.01 control unit.The winding electrical resistance is 2.5 ohm ± 6% at 20°C.View of the valve unit from above
1, Odd gears engagement proportional pressure solenoid valve (ev1)2, Even gears engagement proportional pressure solenoid valve (ev2)3, Clutch capacity proportional solenoid valve (ev0)4, Accumulator5, Self-adjusting clutch push rod6, Pressure sensorElectrohydraulic control system prinicple diagram

Mechanial assembly

The mechanical assembly has the task of interfacing with the gearbox in order to engage or release the gears and change position. It is composed of:

  • Gear selection system ("S" cam)
  • Control shaft
  • Finger connected to the engagement pistons and gear retention system
  • Engagement finger
  • An on-off electromagnet for controlling the gear selection system
  • Reversing switch
  • Selection potentiometer.
View of mechanical assembly
1, S cam retaining chamber cover2, Position change cam lock on off electromagnet3, Reversing switch4, Engagement pistons connecting fingerThe mechanical system comprises a shaft which includes a control finger (1) and an interface element (2) for the pistons in the hydraulic unit; not rigidly secured to the shaft is a drum (3) (which contains two "S" shaped profiles and 3 splined housings) and a dead-bolt (4) which has the task of keeping the gearbox control fork pawls still and in line; both the elements (3) and (4) are kept in position by means of steel pins connected to the casting.View of mechanical assembly: the gearbox control finger (1), the piston interface element (2) and the dead-bolt (4) are highlighted
Diagrammatic view of mechanical assembly: the dead-bolt (4) and the drum (3) with the pins fastening it to the aluminium casing are indicated. The brake (5) and the spider (6) can be seen.
The operating principle is based on the transformation of the hydraulic piston linear motion into rotary motion or rototranslation of the shaft and consequently the rigid elements secured to it.

The purely rotary motion of the shaft (which corresponds to the release motion of a gear and the engagement of the gear in the same position) is produced by means of the following steps:

  • 1. one of the two hydraulic pistons moves with a translational motion
  • 2. the shaft is made to rotate by means of the connecting elemen
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