Hệ Thống Lái Trợ Lực Tay Lái ĐiệnThủy Lực Electrically Powered Hydraulic Steering EPHS

Electrically Powered Hydraulic Steering EPHS SP34_13 The new EPHS (Electrically Powered Hydraulic Steering) system manufactured by TRW Chassis Systems is used for the first time within the Group in the ŠKODA FABIA The new steering system, while retaining the excellent steering properties of the conventional hydraulic power steering, offers a wide range of advantages This system is used in the ŠKODA FABIA on models fitted with 14” and 15” running gear It is available as a left-hand drive and righthand drive version Advantages of the electrically powered hydraulic steering are: Improvement in comfort, easier operation when parking and manoeuvring, while offering a taught steering at high speeds (safety factor) Fuel savings, as the energy consumption is based on demand - irrespective of the operating state of the internal combustion engine In this self-study programme we wish to familiarise you with the design and operation of this steering system and provide you with initial information regarding service GB Contents System Overview Engine-Pump Unit Power Steering Control Unit Power Steering Sensor Power Steering Gear 10 Service 12 Self-Diagnosis 14 Function Diagram 15 Service Service xxxxxxxxxxxxxxxx FABIA xxxxxxxxxxxxxxxx FABIA XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX Service Service Service Service Service xxxxxxxxxxxxxxxx FABIA XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX xxxxxxxxxxxxxxxx FABIA XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX xxxxxxxxxxxxxxxx FABIA XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX xxxxxxxxxxxxxxxx FABIA XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX Service xxxxxxxxxxxxxxxx FABIA XXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXX You will find notes on inspection and maintenance, setting and repair instructions in the Workshop Manual GB System Overview Power steering sensor G250 Steering gear Reservoir Gear pump SP34_17 Power steering control unit J500 Pump motor The system pressure which is required for the steering force assistance, is produced by a hydraulic pump In the conventional power steering system, familiar, for example, from the FELICIA and OCTAVIA, this pump is driven directly by the vehicle engine In other words, part of the power output of the engine is therefore required for driving the pump Engine speed is at its lowest, however, at the moment at which the greatest servo assistance is required for the steering - in other words when parking or manoeuvring Consequently, the pump capacity must be designed for such cases When the engine is operating at higher revs, the pump capacity which is not required, is dumped over a bypass In the new steering system, the hydraulics continue assisting the human steering effort, but the hydraulic pump - a gear pump - is driven in this case by an electric motor, and is therefore mechanically separate from the vehicle engine The electrically powered hydraulic steering system is similar to a conventional one The hydraulic control is also basically identical A new feature is that the steering servo assistance depends on the steering angle That is why a steering angle sensor is provided additionally above the steering housing, to detect the steering angle rate and transmit this information to the electronic control The steering angle information flows along a sensor cable directly to the control unit In addition, the vehicle speed is detected in the control unit for analysis This information flows over the CAN bus The overview on the page opposite shows the system design GB System overview, schematic diagram Note: The system overview is not the electrical connection diagram Refer to the function diagram for this information Vehicle speed sender Engine control unit Control unit in dash panel insert J285 Servotronic warning lamp K92 Gear pump CAN Pressure limiting valve Engine speed signal Hydraulic fluid reservoir CAN Non-return valve Vehicle speed signal Signal of steering angle rate CAN Power steering sensor G250 Power steering control unit J500 Power steering terminal +30 Power steering terminal +15 Earth – M Pump motor SP34_05 Technical data System pressure max 10 ± 0.4 MPa (100 ± bar) Power demand max 70 A Volume flow at max pressure and corresponding steering angle rate l/min Power demand in standby mode 2.5 A Volume flow at 0˚ steering angle l/min max i.e at v > km/h, Q < l/min Operational readiness –40 to 100˚C GB System Overview Average power consumption in [watts] Advantages of the electrically powered hydraulic steering 600 500 400 300 200 100 SP34_16 Standard power steering EPHS Driving on motorway Driving on main road Driving in town In comparison to the traditional conventional power steering system, as used in the FELICIA and OCTAVIA, the newly developed electrically powered hydraulic steering offers a wide range of benefits: – Energy savings of as much as 85 % – Enhanced environmental compatibility as a result of reduced energy demand and energy input, as well as a smaller volume of oil in hydraulic system – – Realistic driving cycles produce fuel savings of about 0.2 ltr./100 km in comparison with a conventional system When driving only on motorways, a conventional power steering system produces a high power loss at the bypass valve because of the high engine revs, in other words the power steering pump supplies an excess volume flow at low steering angle rates and high engine speeds The new electrically powered hydraulic steering system offers the greatest savings as a result of the low steering angle rate when driving on fast roads and from the fact that the volume flow is matched to the vehicle speed Even driving in towns, it is still possible to achieve significant savings (refer to chart) Improvement in active safety as the steering is easier to operate when parking, while taught at high speeds GB Engine-Pump Unit The motor-pump unit The motor-pump unit is a self-contained component A special bracket for the motor-pump unit is bolted to the longitudinal member, in the left of the engine compartment, between bumper and wheelhouse The motor-pump unit is flexibly mounted in rubber bushings on the bracket and surrounded by a noise-absorbing encapsulation SP34_18 Screw cap The motor-pump unit combines the following components: – the hydraulic unit with gear pump, pressure limiting valve and electric motor, – the reservoir for the hydraulic fluid, – the power steering control unit Reservoir Return-flow connection The motor-pump unit requires no maintenance It is lubricated internally by the hydraulic fluid It cannot be dismantled and no provision is made for repairs A pressure line connects the pump to the power steering gear Gear pump Pressure hose connection The return-flow line of the hydraulic fluid merges into the reservoir Rubber bushing Power steering control unit Electric motor GB SP34_14 Power Steering Control Unit The power steering control unit J500 is part of the engine-pump unit Incoming signals – – – Engine speed (internal combustion engine) Vehicle speed Steering angle rate Task Converting the signals for powering the gear pump in line with the steering angle rate and vehicle speed CAN C H1 H2 Extended functions – – SP34_23 Temperature protection for power steering Reactivate protection after faults Self-diagnosis The control unit detects faults during operation and stores these in a permanent memory Pump function Ignition Vehicle engine Pump Steering servo assistance on running running present off not running, vehicle speed = not running none Vehicle speed Steering angle rate Delivery Steering servo assistance low e.g parking high high high (light steering) high e.g motorway low low low (taught steering) Steering servo assistance GB Power Steering Sensor Task The power steering sensor G250 is located at the top in the steering gear and surrounds the input shaft of the steering gear It detects the steering wheel angle and computes the steering angle rate It is not an absolute angle sensor (steering wheel angle proportional to steering wheel lock)! Analysis of signal SP34_19 The signal is required in the power steering control unit in order to detect steering movements The greater the steering angle rate, the greater is the pump speed and thus the volume flow (ignoring the vehicle speed) Substitute function If the sensor fails, the power steering moves into a programmed emergency mode The steering function is assured The steering is slightly heavier to operate Self-diagnosis Power steering sensor SP34_08 Input shaft The sensor is integrated in the self-diagnosis The power steering control unit stores malfunctions of the sensor 30 30 15 15 In the function 02 - Interrogating fault memory it is possible to detect – short circuit to earth – open/short circuit to positive – faults CAN L CAN L CAN H CAN H S CAN J500 Electrical circuit G250 J500 CAN +31 + Power steering sensor Power steering control unit 15 + M - G250 31 31 SP34_10 GB Power Steering Gear Initial position Vehicle running straightahead Engine running Pump motor running Gear pump delivering Operating principle The pressurized oil flows from the gear pump along the pressure line to the hydraulic control unit in the mechanical steering gear SP34_03 Power steering sensor b Return flow c Feed from gear pump Non-return valve d Note: From a hydraulic aspect, the function positions of “right lock” and “left lock” are similar to the familiar power steering Read more on this in SSP 14 10 a In the same way as in the conventional power steering system, there is a torsion bar in the hydraulic control unit which is connected at the one side to the rotary slide, and on the other side to the drive pinion and to the control sleeve GB Torsion bar Rotary slide Control sleeve b to power cylinder on left d from pump a c to power cylinder on right Return flow SP34_07 Hydraulic control unit - schematic diagram SP34_04 When driving straightahead, the torsion bar holds the rotary slide and control sleeve in the Neutral position The power steering sensor does not detect any steering angle The hydraulic fluid flows practically pressureless through the hydraulic control unit along the return-flow line and back to the reservoir GB 11 Service Service The electrically powered hydraulic steering is maintenance-free No new special tools are required No provision is made for repair work on the power steering gear or on the motor-pump unit The causes for problems can be detected by carrying out the pressure and leak test, as well as self-diagnosis If a problem exists, the power steering gear or the motor-pump unit should be replaced The following parts of the steering gear may be replaced: Track rod end, track rod, boot, clamp, spring strap clamp, seal (sealing power steering gear to body), clamp, rubber insert and power steering sensor G250 SP28_04 Note: When replacing the track rod ends, pay attention to the marking by means of letters on the end Left track rod end If correctly installed, the track rod end must be angled to the rear and the stud of the track rod end facing up Carry out a check of chassis alignment Right track rod end SP34_15 The following parts may be replaced at the motor-pump unit: Bracket, rubber bush, noise encapsulation and screw cap with dipstick Reactivate protection The motor-pump unit features a reactivate protection after a fault, failure or a crash The reactivate protection can be cancelled by switching the ignition off and starting the engine again 12 If the unit has overheated, wait, if necessary, 15 minutes to allow it to cool down If it is not possible to cancel the reactivate protection by starting the engine after this waiting time, there is a fault in the vehicle electrical system, or the motor-pump unit is faulty In such cases, carry out self-diagnosis GB Power steering gear Pressure line and return-flow line When reconnecting the pressure line or return-flow line, replace the existing seals and clamps Return-flow line Note: Each time the pressure line is disconnected at the power steering gear, the banjo bolt and non-return valve should be replaced On no account use the banjo bolt without a non-return valve Fit only a genuine replacement part Avoid stresses and bends in the hydraulic lines SP34_20 Pressure line Banjo bolt with non-return valve Subframe Inspecting hydraulic fluid level The hydraulic fluid level can be inspected with the aid of the dipstick at the screw cap of the reservoir – When hydraulic fluid is cold: in area of lower marking – When hydraulic fluid is warm (from engine temperature of about 50 ˚C): approximately in the middle between bottom and top markings top marking bottom marking SP34_22 Screw cap with dipstick Hydraulic fluid reservoir Note: Detailed information on the service aspect can be found in the Workshop Manual Running Gear and in the Inspection and Maintenance binder GB SP34_21 13 Self-Diagnosis The system Diagnosis communication flows over the CAN The gateway converts the signals from CAN to the K cable Self-diagnosis relates to the electrical and electronic parts of the power steering system The control unit detects faults during operation and stores these in a permanent memory This information is also retained even if there is no battery voltage Sporadic faults are not stored in the permanent memory Servotronic warning lamp K92 The warning lamp After the ignition is switched on, the Servotronic warning lamp -K92- comes on An internal check cycle is completed during this period If the warning lamp does not go out after the engine is started and after completion of the check cycle, this indicates that faults may be stored Faults may be defects in the electrical system SP34_06 The self-diagnosis It is necessary to switch on the ignition first in order to initiate self-diagnosis Self-diagnosis can be performed with the vehicle system tester V.A.G 1552, the fault reader V.A.G 1551 or the vehicle diagnosis, measuring and information system VAS 5051 It is initiated with the address word 44 - Power steering Available functions 01 02 05 06 07 08 - 14 Interrogating control unit version Interrogating fault memory Erasing fault memory Ending output Coding control unit Reading measured value block SP33_73 GB Function Diagram 30 30 15 15 CAN L CAN L CAN H CAN H S K92 J519 J533 CAN J500 CAN 15 + M +31 + J J285 - +15 G250 G22 31 31 SP34_09 The function diagram provides a simplified representation of the linkages of the system components of the “electrically powered hydraulic steering” with other system components of the vehicle Communication takes place in this case over the drive CAN Legend G22 G250 J… J285 J500 J519 J533 K92 S Vehicle speed sender Power steering sensor Engine control unit Dash panel insert control unit Power steering control unit Vehicle electrical system control unit Gateway Servotronic warning lamp Fuse Positive Note: The function diagram is not a current flow diagram Negative Output signal Input signal CAN (output and input signals) GB 15 ... vehicle engine The electrically powered hydraulic steering system is similar to a conventional one The hydraulic control is also basically identical A new feature is that the steering servo assistance... revs, in other words the power steering pump supplies an excess volume flow at low steering angle rates and high engine speeds The new electrically powered hydraulic steering system offers the greatest... speed Steering angle rate Delivery Steering servo assistance low e.g parking high high high (light steering) high e.g motorway low low low (taught steering) Steering servo assistance GB Power Steering