The invention relates to a method and a device for driving
a fan motor.
The fan motor
is preferably used in cooling systems
for motor vehicles
used. After the fan after-run time
to be able to determine the shutdown of the engine optimally is
the energy input is recorded in the internal combustion engine. From the
Energy input just before the engine was turned off
and from the specific fan characteristic
will be the fan runtime
calculated, which is necessary to a subsequent overheating of the internal combustion engine
for fan motors
in motor vehicles have been around for a long time
known. The previously known follow-up controls work
either temperature or time dependent. For temperature-dependent follow-up controls
the coolant temperature is monitored with a temperature sensor
and when crossing
a critical temperature value is the tracking control of the fan motor
activated and the cooling circuit
with an electric coolant pump
set in motion. time-dependent
Follow-up controls work with timers. The timer determines
here the length of the
An overview of the above-mentioned prior art is in the German patent DE 3424 580 C1
contain. In the German patent specification, a cooling system is described, which is provided with an electrically operated fan and a tracking control. The tracking control operates either temperature- or time-dependent. In the cooling system, a second, electrically driven coolant pump is included, which is also controlled by the tracking control and which maintains the coolant flow during the tracking control.
Follow-up controls for
have the disadvantage of being independent of the actual one
Load condition and thus also independent of a possible overheating of the
Engage the engine. They therefore also set in when overheating
the engine at all
given is. time-dependent
Fan run controls
always use and temperature-dependent fan follow-up controls can for
Use this example only because of a high ambient temperature
a high coolant temperature
reverse case, if, for example, immediately before canceling the
Internal combustion engine, the engine was driven in the full load range, can
It takes several minutes for the engine to overheat
Temperature increase at the temperature sensor of the fan overrun noticeable. This
until the onset of the fan tracking control
temperature-sensitive microelectronic components in the motor vehicle
already too late
Task according to the invention
It was therefore a fan tracking control
to develop superfluous fan overclock times
avoids and recognizes the other hand, the risk of a delayed increase in temperature
and through timely countermeasures
prevents the temperature increase.
Task is solved
with a method and a device according to the independent claims. Further
preferred embodiments of
Invention are in the subclaims
and in the embodiments
with a fan following control,
to calculate the needed
Fan run time
considered the energy input into the internal combustion engine. From the integral value
the energy input into the internal combustion engine before the internal combustion engine
has been switched off, and the current operating data and environmental data
the internal combustion engine can with known fan characteristics the required
Fan run time
be calculated. By comparing the energy input in the internal combustion engine
with the cooling power
of the cooling system via a
certain period before the engine was turned off, too
be predicted whether a fan wake
will be necessary or not. A re-heating is always there
then be procured, if before the engine is turned off the energy input
in the engine clearly over
the currently applied cooling capacity
of the system. In the opposite case one becomes on one
in certain circumstances
can do without,
or you will the fan follow-up time
in prior art systems.
With the invention mainly the following advantages are achieved:
The invention allows the Lüfternachlaufzeit optimally adapted to the load condition of the engine immediately before switching off. Thus, superfluous fan follow-up times are avoided and it is possible to predict the afterheating effects to be attended, which would only become noticeable due to the thermal inertia of the cooling system with a time delay, and overheating can be counteracted in good time by increased cooling capacities.
In an advantageous embodiment of the invention, the energy input into the combustion engine determined from the air mass flow as a measure of the degree of filling of the combustion cylinder and the speed of the internal combustion engine. This embodiment has the advantage that the necessary measured values for the degree of filling and the rotational speed of the internal combustion engine can be taken from established engine control units. Known engine control units, which determine the degree of filling and the speed of the combustion cylinder and the internal combustion engine are, for example, the electronic engine control units from Bosch. These systems are offered and used under the name Motronic. These systems are described, for example, in "Kraftfahrisches Taschenbuch" / Bosch - 23. Updated Edition - Braunschweig: Viehweg, 1999, pages 498-507 Further alternative operating data for calculating the energy input are the induced torque, the induced power or, in particular, for diesel engines This alternative operating data is also provided by engine control units.
a further advantageous embodiment of the invention is in
Driving tests with a test vehicle from the signals of the engine control
a motor-specific air mass-speed-dependent temperature map
determined. This embodiment
has in practice the advantage that you in the field
the series vehicles only once with a representative
Determine this engine-specific air mass-speed-dependent temperature map
must and this engine specific air mass-speed-dependent temperature map
then in all other production vehicles of the same type and the same
Equipment taken as the test carrier
The engine-specific air mass-speed-dependent temperature characteristic can be
then in each individual series vehicle for determining the Lüfternachlaufzeit
a further advantageous embodiment of the invention is the
Duration of fan runtime through
temporal integration of those energy entries in the internal combustion engine
calculated in the air mass speed-dependent temperature map above
of a critical reference value. By the temporal integration
short-term charges that have no material effect on
have residual heating, be averaged out. By the
of a critical reference value also to be determined experimentally can be those
of the internal combustion engine, which do not require Lüftternachlauf out
the calculation of the fan trailing time
be taken out.
a further advantageous embodiment of the invention takes place
the temporal integration of the energy inputs in each case over a predetermined time interval.
The integration result is stored here at intervals.
The number of integration intervals that are recorded is
limited in this case. For example, for the last five minutes each
five integration intervals
each one minute in length
recorded and stored. The operation of the internal combustion engine takes
become the stored interval-specific integration results
This is the load state in the last five minutes,
before the internal combustion engine was switched off. This
spares a too extensive
Data retention for
the calculation of the fan overrun
is not necessary.
a further advantageous embodiment of the invention includes
the air mass speed dependent
Temperature map a family of characteristics of several temperature-critical
Components in the vehicle. Thus, the fan following can not only on
a temperature-critical component, but it can also
in the calculation of the fan trailing time
the temperatures of several critical components flow. This
has the advantage that, for example, local irregularities
in the heating in the engine compartment of a motor vehicle in the calculation
the fan runtime
can be. Critical temperature
Components that are, for example, in a heat sink, the
not heated at short-term heating of the engine, can at
the calculation of the fan lag time is disregarded
The invention will be explained in more detail below with reference to FIGS.
1 A cooling system of an internal combustion engine with a map-controlled logic for controlling an electric fan motor,
2 Schematically the follow-up calculation for the fan motor from the operating data of the engine control unit,
3 An interval-specific integration scheme for the calculation of the fan tracking control,
4 A functional scheme for averaging the interval-specific integration results,
5 an experimentally determined more Component air mass-speed-dependent temperature characteristic for the calculation of the fan wake time,
6 a from the map of 5 extracted reduced characteristic map in which by means of a limit value all uncritical temperature measuring points for the fan follow-up time were extracted.
1 schematically shows a typical cooling system for a six-cylinder internal combustion engine 1 , In addition to the internal combustion engine are in the cooling system, a vehicle radiator 2 and a heater core 3 integrated. The cooling capacity of the vehicle radiator can with an electrically driven fan 4 to be influenced. To regulate the fan power is the electric motor of the fan with a control unit 5 regulated. From the vehicle radiator is by means of the flow line 6 cooled coolant removed and with the coolant pump 7 in the cooling pipes 8th for feeding the cooling channels, not shown, for the combustion cylinder 9 fed. From the combustion cylinders 9 The heated coolant is returned via return lines 10 to a three-way thermostat 11 guided. Depending on the position of the valves in the three-way thermostat 11 the coolant from the internal combustion engine passes through the radiator return 12 back into the vehicle radiator or over the radiator short circuit 13 and the coolant pump 7 back to the cooling pipes 8th of the internal combustion engine.
Depending on the position of the valves in the three-way thermostat 11 If necessary, the cooling system can be operated in a manner known per se in short-circuit operation, in mixed operation, or in the large cooling circuit. The heating heat exchanger 3 is via a temperature-controlled shut-off valve 14 connected to the high-temperature branch of the cooling system in the internal combustion engine. The flow rate after opening the shut-off valve 14 through the heater core can be used to regulate the heating power with an additional electric coolant pump 15 and a clocked shut-off valve 16 be regulated.
The temperature level of the coolant in the internal combustion engine is in this case by the control unit 5 sensor-controlled. This follows in a conventional manner by actuating the control valves in the three-way thermostat 11 how about control of the electric fan 4 , if a Fahrwindkühlung is no longer sufficient.
an above-described sensor-controlled cooling system for internal combustion engines in motor vehicles
Satisfactory performance can be achieved while driving. After switching off
of the internal combustion engine can
for temperature sensitive
Components in the engine compartment of a motor vehicle then critical situations
arise when stored in the engine heat through
a standstill of the coolant
no longer be dissipated
It has therefore been provided in the past radiator tracking systems. This
Cooler up systems
worked, as described above, time-dependent or temperature-dependent. at
Therefore working systems always had to be in the past
which was usually far too long. But also
Systems had the disadvantage that the temperature sensors, which are usually
the temperature profile of the coolant
measure, the heating of the internal combustion engine only with a considerable
Could determine time delay. The time delay results here
from the thermal inertia of the
System. The effect of a delayed post-heating after switching off
of the internal combustion engine is particularly large, if, for example, the internal combustion engine over a long time
was driven in the partial load range and only in the last minutes
before stopping the engine, the engine was raised to full load.
In this scenario, a temperature-controlled cooling system works
still in the partial load range, while
the engine was fully fired just before switching off. In the engine
is a big one then
included, which still dissipated
must become. As a temperature-controlled tracking system also this
previously described scenario, you had to go to local overheating
in the internal combustion engine to prevent, the temperature threshold for the start
keep the tracking control very low. There was no way
Forecasting how much energy would still be dissipated and therefore had to
a detected increase in the coolant temperature
always go out of the worst case. That also means that in the vast majority
of the cases
the temperature-controlled tracking control starts too often and too long.
At this point, the invention begins.
Therefore, according to the invention with the control unit 5 for the follow-up control of the fan 4 the calculation of the follow-up time based on the energy input into the internal combustion engine in a sufficient period immediately before stopping the engine used. This is in the control unit 5 filed a motor-specific air mass speed-dependent temperature map. By monitoring the operating data of the internal combustion engine, for example by reading the operating data from the engine control system, the energy input into the internal combustion engine is determined by means of logic from the air mass-speed-dependent temperature characteristic map and from this a fan follow-up time is determined. For example, the energy input into the internal combustion engine for the last five minutes before stopping the engine can be logged, and from the energy input over the last a temporal integration is carried out for five minutes and this integration result is compared with an experimentally determined or model-based calculated reference value. If the integration result exceeds this reference value, then a fan overrun must be switched on. How long the fan has to follow depends on the size of the difference between the integration value and the reference value. These are essentially the control characteristic of the fan motor, the temperature of the ambient air and the current temperature of the coolant.
With all this data can be stored in a process computer of the control unit 5 According to thermodynamic laws, an energy balance of the internal combustion engine and the cooling system are performed and from this the required cooling capacity and thus the required follow-up time of the fan can be calculated.
On the calculation scheme is in 2 discussed in more detail. For the operating condition of the engine, the two reference variables speed and air mass flow are particularly relevant here. These two benchmarks are powered by state-of-the-art engine controls 17 provided in the form of digitized signals. The speed and the air mass here are the reference variables for that person energy that is introduced into the engine. A good overview of engine controls are the "Automotive Handbook" the company Bosch, as already cited above, on pages 498 to 507. The injected energy is a measure of the dissipated by a cooling energy and thus a measure of the required cooling capacity and the required overrun time of the fan.
However, it is preferable not to use the energy as the extensive quantity to be balanced for the determination of the fan following, but the estimated temperature of the motor as an intensive quantity to be determined. A calculation model aimed at the temperature of the internal combustion engine can be checked and improved more easily in practice by measuring runs. Temperature-intensive sizes can also be adapted more easily to specific motors by means of test drives. A calculation method which aims at the temperature of the internal combustion engine can thus be adapted to different engine variants. The adaptation takes place here with software implemented program modules 18 derived from the operating data of the engine control 17 the time-delayed temperature profile of the internal combustion engine 19 to calculate. In the program modules 18 is calculated from the operating data speed and Mass Air Flow (English for air mass flow) with the help of experimentally issued calculation equations the expected temperature profile of the internal combustion engine. The adaptation of the calculated temperature profile to the actual measured temperature profile takes place here via the tuning of the parameter values in the calculation equations of the program modules. Speed and air mass flow are the two most important reference variables for engine control and thus also for the calculation of the expected temperature curve of the internal combustion engine. This predicted temperature profile is with a correction term 20 , which is also implemented as a software program module adapted to the current environmental conditions of the internal combustion engine. The most important influencing factors from the ambient conditions are the air temperature, the temperature of the intake air, air pressure and humidity, current cooling capacity of the cooling system and, if appropriate, the position of the throttle valve of the internal combustion engine. The temperature profile corrected for the ambient conditions is provided with an integration stage 23 integrated in time in the form of a so-called moving average. At the integration level 23 will be related to the 3 discussed in more detail. The integration result from the integration stage 23 comes with another program module 24 for the final control of the fan motor 4 further processed. This is done with the program module 24 the integration result from the integration stage 23 with an experimentally determined reference value 22 compared and based on the fan characteristic 25 the required time fan after-run calculated. The determination of the reference value 22 takes place here experimentally and variant-specific for the vehicle in question. The reference value must be determined in such a way that it is ensured that the component with the greatest temperature sensitivity is certainly not damaged.
3 shows a logical flow chart for the integration level 23 , It is calculated a so-called moving average. The integration level 23 is preferably as a program module, so implemented by software. In a less preferred embodiment, the integration stage 23 However, also be implemented in terms of hardware with logical components. Moving average is understood to mean a time-moving average value formation in which the averaging is calculated in each case over a specified number of chronologically consecutive sub-averages, the sub-averages being recalculated and determined cyclically in chronological order. If, for example, one calculates the partial averages over the period of one minute and provides chronologically consecutive five partial averages, over which one then calculates an overall average, one obtains in each case the overall average over the last five minutes of the activated system. This average is updated and adjusted by cyclically overriding and recalculating the averages for the last five minutes of the activated system. Schematically, this process is in 3 represented as follows:
The corrected for the environmental conditions temperature profile is with a temporal integration element 26 The time division and the storage of the integration results from the integration intervals takes place by restarting the integration with a cyclic cascade after one minute, for example, and the integration result after one minute in each case in a memory area 27 is held. The duration of the interval lengths for the individual integration steps can in principle be chosen freely and is provided with a time constant or a delay element 28 established. The cyclic storage of the integration results from the integration intervals is preferably implemented by software in the form of a repeating loop. However, it is also possible to provide a hardware-based switching of the integration results to the memory areas. Both embodiments are in 3 schematically as a cascade 29 successive AND gates and an OR gate, with which, inter alia, the activation signal for the integration stage is fed, shown. The summary of in the storage areas 27 Partial results are recorded in a summation level 33 , which is preferably realized as a software program module. Less preferred is an embodiment of the summation stage 33 by hardware-implemented AND-terms 32 as it is for example in 3 is shown.
4 again shows a functional representation for calculating a total average. Here are the with the numbers 1 to 5 referred partial averages either by a software program or by a logical circuit summarized to an overall average. The individual partial averages are overwritten cyclically.
5 shows a measured value table obtained from driving tests. In the test vehicle here various temperature sensors were mounted, the oil temperature, the temperature of the Integralträgers, the temperature of the rack, the temperature of the steering sleeve, the temperature of the side shaft, the catalyst temperature and the temperature of the electronic injection system in dependence of the two variables air mass flow (MAF) and speed Eng-Spd have recorded and recorded.
The temperatures recorded in tabular form as a function of the two reference variables serve the program modules 18 out 2 as support points for the calculation of the temperature map 19 , Main task of the program modules 18 Here, the interpolation of the interpolation points, so that a continuous temperature map can be calculated. Table 1 5 clearly illustrates that different temperatures in the engine compartment of a motor vehicle can enter into the determination of the temperature map. Thus, not only a single locally occurring temperature can be secured with the Lüfternachlaufberechnung invention, but it can also be a temperature distribution or it can also locally different occurring temperatures of several components are hedged. That the program modules 18 for the calculation of the temperature map rely on experimentally obtained support points, also makes it possible to design the follower control according to the invention for the fan motor in a simple manner engine-specific or design variant-specific. For this purpose, the temperature fulcrums for the various vehicle variants or the different engine variants with a test vehicle are determined in a variant-specific or engine-specific manner, and these experimentally recorded temperature fulcrums are determined in the program modules 18 read in as interpolation points. The fan following the invention can thus be easily adapted to different vehicle variants.
6 shows a further Table 2, in which the temperature bases from Table 1 from 5 have already been evaluated for a critical reference temperature. Listed in Table 2 in the horizontal direction of the air mass flow and in the vertical direction, the engine speed. The table values themselves contain the temperature values for the rack, as determined from the test results of the 5 were measured. An evaluation of the temperature distribution 5 In fact, it has shown that the temperature of the toothed rack as a function of the two reference variables air mass flow and engine speed is the temperature whose temperature level most likely leads to damage. Therefore, the rack temperature for determining a reference temperature, as in 2 is most suitable for the calculation of the fan runtime. The temperature values of the toothed rack from Table 1 were normalized by a factor of 1000 and entered in Table 2. For the mathematical treatment of the temperature values, a re-normalization is not an essential part of the invention. With knowledge of the design conditions on the rack had to exceed a dimensionless reference value for the temperature from 109 respectively 0,109 as in 6 to be considered critical. These are the ones in 6 Bolded temperature readings. For the in 5 associated operating states of the internal combustion engine is therefore to provide a tracking control for the fan motor. These are in this embodiment also shown with bold operating states for air mass flow and engine speed from the table in 5 , For the remaining operating conditions of the internal combustion engine can be dispensed with a Lüfternachlauf.