Function description - RA3000TPM0006X(30-0006)
Electronic accelerator (EA)
Block diagram
Function
The following functions are integrated in the EA control module:
- Idle speed control
- Cruise control
- Electrical/electronic throttle control (electronic accelerator)
In conjunction with the mechanical components, all control processes as well as the mechanical positioning movements are performed by components of the electrics/ electronics. The EA control module receives unfused voltage when the ignition is switched on from the base module or overvoltage protection relay.
The cruise control switch receives unfused voltage from terminal 15 (ignition).
Using the control module input signals (refer to block diagram), the output signal which the position controller, monitoring system and the data bus (CAN) receive is calculated in the "specified value selection" control module. The specified value signal is compared with the actual value signal in the "position controller" control module. In the event of deviations, the throttle valve position is adapted to the specified value (accelerator pedal position).
In so doing, the output stage for the actuator motor is actuated via the "approval/ disconnection " system which is downstream of the monitoring system.
At the same time, the output stage is also actuated by the safety relay. Only if the signal is available from both systems is the actuator motor actuated and thus the position of the throttle valve determined.
ASR control
If the specified value input (deflection of the accelerator pedal) is greater than the drive moment which can be transmitted to the road, this means the wheels will spin (slip). This slip is detected by the ABS/ASR control module and signalled to the EA control module as a signal (throttle valve reduction) via the data bus (CAN). In order to achieve an immediate reduction in torque, this signal is transmitted simultaneously to the DI control module and the ignition timing is briefly retarded.
The drive moment is reduced in the event of excess throttle opening until the slip at the drive wheel falls below a set value.
In the event of excessive drive moment at the driving wheels (ASR control) the helical spring in the spring capsule of the actuator permits adjustment of the throttle valve contrary to the throttle pedal position.
EBR control
The EBR (engine braking regulation) is effective under the following conditions:
- Vehicle speed > 20 km/h to 120 km/h.
- No ASR control
- Opening angle of the throttle valve < 20° (set by the driver's foot).
If, when the accelerator pedal is released or during a downshift (e.g. manual) slip occurs at the drive wheels, this is also detected by the ABS/ASR control module. The throttle valve is briefly opened (approx. 450 ms) so that no further slip occurs at the rear wheels. This increases directional stability.
When the ignition is switched on, the EA system and the integrated idle speed control is operative. The control module detects the accelerator pedal position via the specified value potentiometer in the EA actuator, on the engine 120 the actuator for the right cylinder bank, located on the left. The position of the throttle valve is signalled by the actual value potentiometer in the EA actuator.
Accelerator pedal not operated
When the accelerator pedal is not operated, the idle safety contact is "closed" and the synchronous safety contact is "open". Both safety contacts and their signals are continuously checked by the monitoring system in the EA control module. The control module of the LH-SFI or HFM-SFI injection is actuated by the output signal of the monitoring system. As a result the actuation of the injection valves is guaranteed over the entire speed range via the safety fuel shut-off. In the absence of a signal, e.g. when both safety contacts are detected as open (mechanical or high contact resistance at the contact), the LH-SFI or HFM-SFI control module actuates the injection valves so that an engine speed of only approx. 1200 rpm is reached with the quantity of fuel.
When the accelerator pedal is not operated, the position of the throttle valve is also determined as a function of the instantaneous coolant temperature before starting.
Throttle control
The throttle linkage is connected to the throttle by means of a loose connection via the drive lever and the internal spring capsule.
On the engine 120, the EA actuator is "not" connected to the throttle linkage or the left cylinder bank (located on the right of the engine).
The throttle valve is adjusted here only by means of electric/electronic actuation.
Emergency running system
(refer to chapter on Individual Functions)
Fault memory
(refer to chapter on Individual Functions)
Information is continuously exchanged between the ABS/ASR, LH-SFI or HFM-SFI, EA control modules and the DI/KSS ignition control module and the Diagnostic module (
only) via the data bus (CAN). The data bus is also checked by the monitoring system.
Accelerator pedal operated
By operating the accelerator pedal, the control movement is transmitted to the specified value potentiometer in the actuator via the floor-type accelerator pedal, bowden cable and throttle linkage. Depending on the accelerator pedal position, an appropriate voltage signal is input to the EA control module by the specified value potentiometer.
The slip signal at the drive wheels is signalled to the EA control module via the data bus (CAN). In ASR mode, the torque is reduced by closing the throttle until no further slip occurs.
In EBR mode the torque is increased by briefly opening the throttle (approx. 450 ms) until no further slip occurs.
Overall, the throttle valve can be adjusted between idle and full throttle or closed in the direction of idle by ASR or briefly opened slightly by EBR using the EA system. The opening angle for idle control is limited by the EA control module over the entire adjustment range of the throttle valve (idle to full throttle stop).
Cruise control (CC)
The following signals are processed in the cruise control section of the EA control module for the parameters of cruise control control:
- Push-button switch
- Engine speed
- Speed of left front and rear wheel (Model 124, engine 104 HFM-SI, left front wheel and hall sensor signal, speedometer)
- Throttle valve position
- Selector lever position
- Stop lamp switch
- Clutch switch (MT only)
The cruise control function can only be activated by operating the switch (S40) at a speed above 40 km/h. The cruise control switches off if the brake or clutch pedal are operated.
To maintain directional stability, the speed signal from the left rear wheel is measured in addition to the speed signal of the left front wheel. On Model 124, engine 104, signal of the left front wheel and the hall sensor signal from the speedometer.
When the cruise control is switched off, the return of the throttle valve to the specified value of the accelerator pedal is monitored by the safety circuit in the electronic accelerator control module.
If, for example, when the stop lamp switch is defective, the vehicle decelerates > 1.5 m/s 2 , the deceleration is recorded by the computer and the actuator closes the throttle valve at the highest speed possible.
When the cruise control is set, the position controller in the EA control module receive an appropriate input signal. As a result the position of the throttle valve is specified, recorded by the actual value potentiometer of the throttle valve and signalled to the EA control module. If the driver requires a higher speed via the accelerator pedal, the cruise control remains inoperative.
If ASR detects drive slip during cruise control mode, the reduction of engine output (lower speed) has priority over cruise control mode. If ASR operates for more than 0.5 ms, cruise control is switched off. In this case the system has to be reactivated via the switch if further cruise control mode is required.
Monitoring and limp-home systems
If the max. differential speed between the left front wheel and the left rear wheel (EA) is exceeded for more than 0.5 s, the cruise control is switched off by the CC/ISC control module.
The synchronous safety contact must be bridged by means of the switching transistor in cruise control mode. Inadmissible acceleration is now detected by monitoring the speed and acceleration plausibilities, and the cruise control is switched off.
Maximum differential speed
up to 149 km/h 3 km/h
above 150 km/h 5 km/h
Fault memory
(refer to chapter on individual functions)
Cruise control/idle speed control (CC/ISC)
Block diagram
Function
The following functions are integrated in the CC/ISC control module
- Cruise control
- Idle speed control
The Cruise control function can only be activated at a speed above 40 km/h by operating the switch. The cruise control switches off if the brake or clutch pedal are operated. To maintain vehicle stability, the speed signal from the rear axle and, in vehicles with electronic traction support (ETS), that of the left rear wheel is measured in addition to the speed signal of the left front wheel.
If the differential speed between the front and rear wheel is too high, cruise control is switched off after 0.5 s .
Maximum differential speed
up to 149 km/h 3 km/h
above 150 km/h 5 km/h
If, for example, a stop lamp switch is defective and the vehicle decelerates > 1.5 m/s2, the deceleration is recorded by the computer and the actuator closes the throttle valve at the highest positioning rate possible.
When the cruise control is switched on, the control module input signals (refer to block diagram) are used to calculate the output signal which the position controller, the monitoring system and the data bus (CAN) receive in the "specified value selection" control module.
In so doing, the output stage for the actuator motor is actuated via the approval/disconnection system which is downstream of the monitoring system
The position is fed back by the drive actual value potentiometer and the throttle valve actual value potentiometer.
If the driver requires a higher speed via the accelerator pedal when the cruise control is switched on, the cruise control remains inoperative.
The idle speed contact and the safety contact are located in the CC/ISC actuator. Normally the contact is always closed. The idle speed contact is closed when the accelerator pedal is not operated and opened when the throttle is opened.
Normally (when driving) the safety contact is always closed. If it is "open", in the event of a fault, (e.g. due to an inadmissible throttle opening), the "safety fuel shut-off" is triggered by the injection system control module and the engine speed is limited to approx 1200 rpm.
In cruise control mode the safety contact is bridged by means of the switching transistor. Inadmissible acceleration is detected by monitoring the speed and acceleration plausibilities and the cruise control is switched off.
Fault memory
(refer to chapter on individual functions)
Idle speed control
(refer to chapter on idle speed control)
Idle speed control (ISC)
Block diagram for ISC with separate control module
(engine 104, Model 140 only without EA or CC/ISC)
Function
When the ignition is switched on, the idle speed control system is operative. Before starting, the position of the throttle valve for idle is specified via the actuator motor depending on the coolant temperature.
Depending on the input signals shown, refer to block diagram, an output signal is transmitted to the specified value selection in the idle speed control module. It evaluates the idle speed signal in conjunction with other adjacent signals. The position controller and the data bus (CAN) is actuated by the output signals. The signals are checked by the monitoring system and the output stage actuated via the approval/ disconnection system.
The ISC control module compares the actual and specified engine speed and determines the required position of the throttle valve via the actuator motor. The position of the throttle valve is recorded by the actual value potentiometer in the actuator and signalled to the ISC control module.
The adjustment range of the throttle valve for idle adjustment (e.g. opening angle) is limited to max. 10° by the control module.
Support of idle speed control by the ignition system
If there is an engine speed control deviation, the idle speed control is supported by varying the ignition timing. Idle speeds with and without gear engagement vary. They are determined according to the selector lever position and the coolant temperature via the EA, CC/ISC or ISC control module.
Engine speed increase or stabilization
a) Speed stabilization on engines with A/C compressor
When the A/C compressor cuts in, the EA, CC/ ISC or ISC control module receives a cut-in signal. The control module processes the applied voltage and transmits an appropriate signal to the specified value selection. The cross-section of the opening becomes larger before the A/C compressor cuts in so that the idle speed remains almost constant in the process.
b) Speed stabilization on vehicles with automatic transmission (AT)
The signal is evaluated when the drive position is engaged. This results in a changeover of characteristics. This signal is then passed on to the specified value selection. In this way, the throttle valve is opened to a varying extent due to the characteristic in force when the accelerator pedal is deflected. A gentle progression is thus achieved for each selector lever position.
c) Increasing engine speed to generate heat
In order to bring the catalytic convertor more quickly to operating temperature, the speed is increased for approx. 20 seconds after each starting operation when coolant temperatures are below +20°C and a recognized idle speed signal and selector lever position P/N.
| Engine | Temperature | Time | Engine speed |
|---|---|---|---|
| M 104 | < + 20°C | approx. 20 seconds | 1100 ± 100/rpm |
| M 119 | +20°C -+ 30°C | approx. 20 seconds | 1000 ± 100/rpm |
| M 120 | +20°C - + 30°C | approx. 20 seconds | 850 + 100 -50 |
d) Speed increase on engines with diode matrix
(Model 140, engine 119, 120 LH-SFI only)
In order to achieve a higher charge current at idle speed, the engine speed is increased from 550 rpm to 650 rpm under certain conditions.
The control module receives a signal via the diode matrix when auxiliary appliances are switched on.
The idle speed increase is activated when drive stage D, 3, 2 and 1 is engaged when an engine speed of 900 rpm is exceeded and one or more of the following appliances are switched on:
- Dipped beam (except in the case of day-driving light)
- Blower on stage 3 or higher in the case of automatic heater control
- Heated rear window Automatic air
- window
- Automatic air conditioning
- Left and right auxiliary fans
- Front or rear seat heating on stage 2
The idle speed increase is switched off when dry stages P, R or N are engaged and a coolant temperature of ≥ 110°C.
| Engine speed | Generator speed | Charge current |
|---|---|---|
| 550/rpm | 1595/rpm | 47 A |
| 650/rpm | 1885/rpm | 65 A |
| 2180/rpm | 6300/rpm | 120 A |
e) Idle speed increase dependent on battery voltage
(Models 129 and 202 with engine 104)
In order to increase the charge current of the generator, the idle speed is increased to approx. 650 rpm under the following operating conditions:
- Battery voltage <12.3 V
- Selector lever position "D"
- Coolant temperature 40 -110°C
If these conditions are met, the idle speed remains at the increased level after exceeding 900 rpm when the engine speed reduces.
Detection and adaptation of mechanical end stop of throttle valve
The control module detects and adapts the end stop (idle speed stop) when the ignition is switched on. The time for this is approx. 45 s. The detection is effected by the throttle valve being drawn onto the end stop by the actuator motor integrated in the actuator.
The throttle valve position is recorded by the actual value potentiometer, transmitted to the control module and stored there.
The control module then calculates from these values the position of the throttle valve for idle speed.