Contents: General information 🠛 Description of the system operation 🠛 Governing bodies 🠛 Speed limiter 🠛
General information
The cars are equipped with the following systems:
- speed control, which allows the driver to maintain the speed selected by the driver. This function can be switched off at any time by pressing the brake pedal or one of the system switches.
- speed limit, which allows the driver to set a maximum speed. If it is exceeded, pressing the accelerator pedal does not increase the speed of the car. The selected speed can be increased at any time by pressing the accelerator pedal past the resistance point.
Fig. 7.92. Block diagram of the speed control and limitation system: 1 – speed limiter switch (regulator); 2 – switches on the steering wheel; 3 – accelerator pedal; 4 – instrument panel; 5 – clutch travel sensor (if it is installed); 6 – brake light switch; 7 – central electronic switching unit in the passenger compartment; 8 – ABS ECU; 9 – Injection system control unit
The functions "Cruise control" and "Speed limitation" are controlled by the injection system ECU. This unit exchanges information with the ABS ECU, UCH, and AT ECU (if it is installed) and the instrument panel. The injection system ECU implements the specified values by issuing control commands to the throttle valve unit with a servo drive or by regulating the supply of diesel fuel.
Note: Flashing of the indicator light on the instrument panel indicates that the set speed cannot be maintained (for example, when driving downhill).
Description of the system operation
The UCH sends the information "brake pedal pressed" (signal from the closing contact of the brake light switch).
The ABS control unit sends information about the vehicle speed.
Automatic transmission control unit (if there is one) sends information about the engaged gear.
The selected speed value is displayed on the instrument panel (for adjustable or limited) and the symbol of the enabled function (three-color signal lamp).
Each time these functions are activated, the trip computer display switches to the corresponding page.
Note: There is no malfunction indicator lamp for the cruise control and speed limiter functions.
Governing bodies
The three-position switch enables the speed controller or speed limiter to be turned on and off.
The switches on the steering wheel are used to change the set speed, cancel the function or recall the speed value from memory.
The accelerator pedal position sensor and brake light switch are shared with the injection system.
The clutch pedal travel sensor is designed specifically for the cruise control function. This sensor can also be used by the injection system.
Note: The vehicle is equipped with two clutch pedal position sensors: for starting the vehicle from a standstill (pedal end of stroke sensor) and for the speed control system (pedal start sensor).
Note: The accelerator pedal has a safety switch at the end of its travel.
Injection system ECU.
The injection system ECU receives via the multiplex network:
- information about the speed of the car (from ABS ECU);
- signal from the brake light switch closing contact (from the UCHBS);
- information about the gear engaged (from the automatic transmission control unit, if installed).
The injection system ECU sends via the multiplex network:
- set value of adjustable or limited speed on the instrument panel;
- signal to turn on a constant or flashing light of a two-color signal lamp on the instrument panel;
- control commands to the throttle valve unit with servo drive or to the diesel fuel supply regulator;
- information about automatic transmission gear shifting (if it is installed).
The injection system ECU receives the following information via wired communication:
- from the accelerator pedal position sensor;
- from the brake light switch (has two contacts: normally open and normally closed);
- from the clutch pedal travel sensor (if there is one);
- three-position switch signal;
- from the controls on the steering wheel.
Speed limiter
Conditions of inclusion:
- switch in the "speed limiter" position (30 km/h - minimum speed, 200 km/h - maximum speed);
- pressing the "+", "–" or "R" switches.
Shutdown conditions:
- sharp pressing of the accelerator pedal (with overcoming the point of resistance);
- switch in the "off" position;
- pressing the switch "0";
- injection system ECU intervention (in case of malfunction or exceeding the maximum permissible speed).
Note: Flashing of the indicator light on the instrument panel indicates to the driver that maintaining the set speed is not possible.