Rpm control power take-off - function

W07.15-1279-79

4 Engine CAN bus

5 Vehicle CAN bus

A3 Drive control (FR) control unit

A6 MR/PLN control unit

A22 PSM control unit

B1 Foot throttle actuator

P2 Instrument

S2 Engine control/permanent brake operating lever

S23 PTO 1 indicator switch

S64 PTO 1 switch

S65 PTO 2 switch

S66 PTO 3 switch

S79 PTO 2 indicator switch

S80 PTO 3 indicator switch

S108 Switch, ADR

Y6 Cylinder 1 unit pump

A Vehicles with code (ED5) parameterizable special module (PSM),
code (EM7) parameterizable special module with body CAN bus or
code (EM8) parameterizable special module with body and trailer CAN bus

B Vehicles without
code (ED5) parameterizable special module (PSM),
code (EM7) parameterizable special module with body CAN bus or
code (EM8) parameterizable special module with body and trailer CAN bus

Y7 Cylinder 2 unit pump

Y8 Cylinder 3 unit pump

Y9 Cylinder 4 unit pump

Y10 Cylinder 5 unit pump

Y11 Cylinder 6 unit pump

Y12 Cylinder 7
unit pump - only for engine 542.9

Y13 Cylinder 8
unit pump - only for engine 542.9

Y46 PTO 1 solenoid valve

Y47 PTO 2 solenoid valve

Y48 PTO 3 solenoid valve

Z1 CAN star point cab dash support

a) up to 31.12.1999

b) from 01.01.2000

General information

Various types of regulator are stored in the MR/PLN control unit (A6) for rpm control of the power take-off or the power take-offs (according to the vehicle equipment).

These can be called up differently when switching on a power take-off according to the area of use of the vehicle and according to how the parameters for the power take-off functions are set in the drive control (FR) control unit (A3) or in PSM control unit (A22).

Here the variable speed governor (RQV, speed droop �0) is the most often used type of regulator.

Starting requirements such as "Parking brake on" or "Transmission in neutral", the engine speed range (min. engine speed, max. engine speed) or the torque limitation are, in addition to a variety of other parameter, also parameterizable in the drive control (FR) control unit (A3) or parameterizable special module control unit (A22).

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1 Regulation of the working speed
Regulation of the working speed takes place as soon as the engine control (MR) receives an appropriate request from the drive control (FR) control unit (A3) or from the parameterizable special module control unit (A22).
Here it mainly takes account of the parameters set in the drive control (FR) control unit (A3) in as far as these are not crossfaded by the parameterizable special module control unit (A22).

This last point means that for vehicles with the code (ED5) parameterizable special module (PSM), code (EM7) parameterizable special module with body CAN bus or code (EM8) parameterizable special module with body and trailer CAN bus, only the parameters in the parameterizable special module control unit (A22) will be taken account of, irrespective of which parameters are set in the drive control (FR) control unit (A3).

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As mentioned above, various types of regulator are programmed into the engine control (MR) to regulate the working speed. These can be allocated individually to the switches power take-off 1 (S64), power take-off 2 (S65) and power take-off 3 (S66) so that regulator selection when switching on a power take-off exclusively depends on the parameterization.
Apart from selection of the appropriate type of regulator by the drive control (FR) control unit (A3) or the parameterizable special module control unit (A22), other parameters such as the minimum rotational speed, maximum rotational speed etc. are sent to the engine CAN bus (4) from where they are made available to the MR/PLN control unit (A6).

 For vehicles with code (ED5) parameterizable special module (PSM), code (EM7) parameterizable special module with body CAN bus or code (EM8) parameterizable special module with body and trailer CAN bus, the drive control (FR) control unit (A3) acts as a GateWay.
This means that it passes on information from the parameterizable special module control unit (A22) unchanged to the engine control (MR).

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The MR/PLN control unit (A6) uses this information in end effect to select the performance map stored for the requested type of regulator and regulates the working speed according to the set parameters through appropriate control of the fuel delivery quantity.
Parallel to this it also regulates the start of injection in order to keep the pollutant emission as low as possible.

One separate task of regulating the working speed is taken on by the "working speed control" switch (S108).
This allows the constant rotational speed function to be switched on which means that the engine control (MR) regulates a specific parameterized engine speed and maintains this constant, irrespective of load.
The applied positions of the "working speed control" switch (S108) are detected by the parameterizable special module control unit (A22). If the "working speed control" switch (S108) is actuated the parameterizable special module control unit (A22) demands a constant rotational speed using appropriate messages which are transmitted over the
vehicle CAN bus (5) to the drive control (FR) control unit (A3) and from there over the engine CAN bus (4) to the MR/PLN control unit (A6).

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 Before the engine control (MR) regulates the working speed, the power take-off must be fully engaged. This can be recognized by the fact that the indicator lamps in the switches light up and an appropriate indication appears in the display of the instrument (P2).

2 Changing the working speed
For a given vehicle equipment and parameterization for the power take-off functions it is possible to alter the working speed with the accelerator pedal, that is over the foot throttle actuator (B1), with the operating lever engine control/permanent brake (S2) or automatically with the "working speed control" switch (S108) in as far as the maximum working speed is not exceeded and the engine does not go below the minimum working speed:

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2.1 Changing the working speed with the accelerator pedal over the foot throttle actuator (B1)

2.1.1 Detecting the regulating specification

2.1.1.1 Vehicles without code (ED5) parameterizable special module (PSM), code (EM7) parameterizable special module with body CAN bus or code (EM8) parameterizable special module with body and trailer CAN bus:

If the accelerator pedal and therefore the foot throttle actuator (B1) is actuated, the drive control (FR) control unit (A3) compares the requested working speed with both the current and the maximum permissible working speed. This is assuming that a maximum working speed has been parameterized.

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If the maximum permissible working speed is not exceeded, a request is sent to increase the working speed which is transmitted over the
engine CAN bus (4) to the MR/PLN control unit (A6).

2.1.1.2 Vehicles with code (ED5) parameterizable special module (PSM), code (EM7) parameterizable special module with body CAN bus or code (EM8) parameterizable special module with body and trailer CAN bus:

If the accelerator pedal and therefore the foot throttle actuator (B1) is actuated, the drive control (FR) control unit (A3) alters the regulating specification for the working speed and transmits this over the vehicle CAN bus (5) to the parameterizable special module control unit (A22). Here the desired working speed is compared both the current and the maximum permissible working speed.

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This is assuming that a maximum working speed has been parameterized.

If the maximum permissible working speed is not exceeded, a request is sent to increase the working speed which is first transmitted over the vehicle CAN bus (5) to the drive control (FR) control unit (A3) and from there over the engine CAN bus (4) to the MR/PLN control unit (A6).

2.1.2 Implementation of the regulating specification

The MR/PLN control unit (A6) increases the working speed through appropriate control of the fuel delivery quantity to the desired value and holds it constant.

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2.2 Changing the working speed with the operating lever engine control/permanent brake (S2)

2.2.1 Detecting the regulating specification

2.2.1.1 Vehicles without code (ED5) parameterizable special module (PSM), code (EM7) parameterizable special module with body CAN bus or code (EM8) parameterizable special module with body and trailer CAN bus:

The position of the operating lever for engine control/permanent brake (S2) is pressed or pulled into causes the drive control (FR) control unit (A3) to alter the regulating specification for the working speed and to transmit this over the engine CAN bus (4) to the MR/PLN control unit (A6).

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It does, however, first compare the requested working speed with the current, the maximum permissible as well as the minimum permissible working speed.
One prerequisite for this is, however, that both the maximum permissible and the minimum permissible working speed is parameterized.

Only if the maximum permissible working speed is not exceeded or the working speed does not go below the minimum permissible figure does an appropriate request to increase or decrease the working speed get issued.

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2.2.1.2 Vehicles with code (ED5) parameterizable special module (PSM), code (EM7) parameterizable special module with body CAN bus or code (EM8) parameterizable special module with body and trailer CAN bus:

The position the operating lever for engine control/permanent brake (S2) is pressed or pulled into causes the drive control (FR)
control unit
(A3) to alter the regulating specification for the working speed and to transmit this over the engine CAN bus (5) to the MR/PLN control unit (A22). Here the requested working speed is compared with the current, the maximum

permissible and the minimum permissible working speed. One prerequisite for this is, however, that both the maximum permissible and the minimum permissible working speed is parameterized.

If the maximum permissible working speed is not exceeded and the working speed does not go below the lowest permissible, then an appropriate request to increase or decrease the working speed get issued, first over the vehicle CAN bus (5) to the drive control (FR) control unit (A3) and from there over the engine CAN bus (4) to the MR/PLN control unit (A6).

W54.25-1088-71

2.2.2 Implementation of the regulating specification

The MR/PLN control unit (A6) receives the new regulating specification and implements the requested rotational speed through controlling the fuel delivery quantity as follows:

Operating lever for engine control/permanent brake (S2)

 press shortly into position (1):
The current working speed increases in increments of 20 rpm.

 hold in position (1):
The current working speed increases up to a maximum of 750 rpm.

 press shortly into position (2):
The current working speed decreases in increments of 20 rpm.

 hold in position (2):
The current working speed decreases down to a minimum of 550 rpm.

 press shortly into position (3):
The parameterized working speed is regulated to again.