JP2007502380A - How to start a thermostat - Google Patents

Abstract

  The present invention relates to a cooling system in which the pulse width activation for an operating element for a thermostat valve is closed loop controlled in an adaptive manner. In a pre-defined and stored basic adaptation mode, by taking into account the current ambient temperature, the desired temperature level in the refrigerant circuit is reached as quickly as possible, and three different temperature levels depend on the load conditions and ambient conditions. It is provided as a variable for setting the refrigerant temperature. When the currently required refrigerant temperature is reached for the first time after starting the engine, the closed loop control is switched to precision adaptation and the currently set refrigerant temperature is kept as constant as possible depending on the desired temperature and the external temperature. Kept. When the desired temperature of the refrigerant achieved by closed loop control changes due to a change in engine load conditions, the newly required temperature level is set by fine adaptation. The method has the advantage that when the vehicle is started, the currently set refrigerant temperature can be achieved immediately with the basic adaptive setting.

Description

  The invention relates to a method for starting a thermostat, in particular in a motor vehicle cooling system.

  Such a general type of cooling system and a method for operating such a general type of cooling system are known from US Pat. This cooling system is used to set two different refrigerant temperatures depending on the operating parameters specific to the vehicle. Influential operating parameters in this case are the vehicle speed, the load state of the internal combustion engine, and the intake air temperature. Depending on the aforementioned parameters, a control algorithm is used to determine at which temperature level the refrigerant should be set. In this case, the thermostat in the cooling circuit is actuated by a controller in which the control algorithm is implemented. The temperature levels provided are 90 degrees Celsius and 110 degrees Celsius.

  Known two-position controllers tend to oscillate in the level setting state and frequently switch the setting state. This problem occurs when the control algorithm adjusts to other temperature levels when the affecting variables and their evaluation are within the set range and there is a slight change in them. Furthermore, the known method reduces the external temperature, i.e. the ambient temperature, even if the ambient temperature fluctuates significantly and can have a significant effect on the engine temperature and the possible cooling power of the cooling system in extreme weather conditions. Do not consider.

  The problem of periodic fluctuation has already been identified in Patent Document 2. The proposed solution is optimal closed loop control. The proposal that has been made is to evaluate the system in response to and using a jump function to adapt to the control parameters in an optimal manner.

DE 4409547 Specification European Patent Application Publication No. 0744538A2

  Accordingly, it is an object of the present invention to provide a method for operating a thermostat that can avoid frequent switching of level setting conditions and that is improved with respect to adaptation to ambient conditions.

  This object is achieved by the features of claim 1. Preferred embodiments of the invention are described in the dependent claims and in the description of the embodiments.

  This solution is mainly achieved by the fact that the control of the pulse width for the operating element of the thermostat valve is controlled in a closed loop. The aim is to first reach the required temperature level in the refrigerant circuit as quickly as possible, with the basic settings determined and stored in view of the current ambient temperature. Depending on the load conditions and ambient conditions, the necessary variables for setting the refrigerant temperature are set at three different temperature levels. For the first time after start-up, when the required refrigerant temperature is reached, the closed-loop control is replaced with a precision adaptation. The refrigerant temperature to be set is kept as constant as possible by precise adaptation according to the desired temperature and the external temperature. When the desired temperature of the refrigerant to be achieved by closed loop control changes due to a change in engine load conditions, the newly required temperature level is set by fine adaptation. This has the advantage that when the vehicle is started, the refrigerant temperature to be set can be achieved immediately with the basic adaptive setting.

  If the refrigerant temperature set by the basic adaptation deviates from the desired temperature, fine adaptation is used to adjust this. The settings obtained by fine adaptation are in this case stored, for example, at regular intervals of 100 seconds, and the basic adaptation settings are overwritten by the new settings. In this way, the basic adaptation is matched to the currently prevailing ambient conditions and to the driving style of the car driver. In this case, the new settings are determined separately and stored for each of the three pre-specified temperature levels, specifically 80 ° C., 90 ° C., and 105 ° C. Thus, the basic adaptation has settings for a temperature level of 80 ° C., a temperature level of 90 ° C., and a temperature level of 105 ° C., respectively.

  In one preferred embodiment of the invention, the stored basic adaptive settings are matched to the ambient temperature by means of a correction function. This correction is made when the ambient temperature is changed by, for example, 8 degrees Celsius and a predetermined temperature interval, and when the automobile is stopped for a predetermined minimum time, such as 2 hours. Is always done. In this case, the correction is performed immediately when the vehicle is restarted even before the basic adaptation starts. Thus, if the ambient conditions have changed significantly, for example if the vehicle has been turned off overnight, the basic adaptation starts with the already corrected setting. As a result, it is not necessary to first find a new setting by fine adaptation. This advantage is important if, for example, the car is left off on a hot day and is driven again on a cold day the next day. In this case, for example, unlike the other adaptive closed-loop control systems in EP 0 745 538 A2, which uses the control parameters last used in the method according to the invention, the basic adaptation is the adaptation of the controlled control parameters. So there is no need to find new control parameters for new ambient conditions first.

  Further advantages of preset basic adaptations are obtained when using vehicles in different environmental areas. In this case, the cooling system of the vehicle can be matched to each environmental region in an optimum manner by basic adaptation adapted to each environmental region. Daily temperature fluctuations and variable engine load conditions are compensated by precision adaptation.

  In one preferred embodiment, the method according to the invention has a fallback level such that if two adaptation steps fail, control of the refrigerant is replaced by a proportional controller.

  A further advantage of the method according to the invention is seen that, unlike the prior art, three different temperature levels can be set for the refrigerant temperature. This has the advantage that the engine temperature can be matched more effectively to both ambient conditions and engine load conditions.

  Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 schematically shows a typical cooling system for a 6-cylinder internal combustion engine 1. In addition to the internal combustion engine, a radiator 2 and a heat exchanger 3 are integrated in the cooling system. The cooling power of the radiator is increased by the electric fan 4. In order to adjust the fan force, the motor of the fan is closed-loop controlled by the control unit 5. The cooled refrigerant is sent from the radiator by the feed pipe 6 and sent to the cooling line 8 by the refrigerant pump 7 in order to send a cooling line (not shown in detail) for the cylinder 9. The heated refrigerant passes from the cylinder 9 to the thermostat three-way valve 11 through the return line 10. Depending on the position of the valve in the thermostat three-way valve 11, the refrigerant returns from the internal combustion engine to the radiator via the radiator return pipe 12 or into the cooling line 8 of the internal combustion engine via the radiator bypass pipe 13 and the refrigerant pump 7. Return.

  In this case, the cooling system can be operated in a known manner, in bypass circuit operating mode, in mixed operating mode, or in radiator circuit operating mode, depending on the position of the thermostat three-way valve 11. is there. The heat exchanger 3 for heating is connected to a high-temperature branch path of the cooling system in the internal combustion engine by a temperature control cutoff valve 14. The flow rate through the heating heat exchanger after the shut-off valve 14 is opened is adjusted by an additional electric refrigerant pump 15 and a synchronous shut-off valve 16 to adjust the heating power.

  The operating elements for the valve of the thermostat three-way valve 11 are actuated here by the control unit 5. The control unit includes a logic element Logic in the form of a microcomputer unit. The control unit is preferably formed by a control unit of the engine electronics. The control algorithm outlined in FIGS. 2 and 3 is implemented in the form of a software program. In this case, the important operating data for adapting the control parameters are the actual refrigerant temperature, the desired refrigerant temperature, the outside air temperature, the PWM pulse occupancy for operating the valve, and the fault if the closed loop control system fails. Failure detection means for operating the back level, fail safe.

  FIG. 2 shows a simplified Matlab-Simulink display of the software architecture and a signal flow chart for determining the refrigerant temperature to be set according to the present invention. Input signals including intake air temperature 21, air mass flow rate 22, driver type classification 23, engine speed 24, fuel injection amount 25, and outside air temperature 26 are processed using a five-stage decision cascade. The refrigerant temperature 27 that is matched with the current operating parameters is then determined. Each stage of the decision cascade consists of an EDP (Electronic Data Processing) program for determining and calculating the set temperature as a function of program input variables. Individual software programs are hereinafter referred to as modules.

  In this case, the five-stage decision cascade is for engines with port injection: modules KE_ECT (for engine cooling temperature according to port injector (Kanaleinspritzer)), ECT_FTK (for engine cooling temperature according to driver type classification (Fahrertypklassifizierung)), ECT_AT (For engine cooling temperature according to intake air temperature (Ansauglufttemperatur)), ECT_VehSpd (for engine cooling temperature according to vehicle speed) and module ECT_ExtAir (for engine cooling temperature according to outside air temperature).

  In the direct injection type engine, the fuel amount is determined from the injection amount. In these engines, module DE_ECT (for Direkt Einspritzung “direct injection” engine cooling temperature) is used instead of module KE_ECT to calculate the first desired refrigerant temperature TMSoll1. The control algorithm includes both modules for port injectors and direct injectors on a standards basis. Which module is used is set by the program based on engine characteristics by operating one of the two modules. This selection is represented by switching element 28 in the signal flow diagram of FIG. This procedure has the advantage that a single control algorithm may be implemented for various types of mixture formation, and the algorithm can be set for each engine type.

  The first desired refrigerant temperature TMSoll1, calculated from the fuel input, depends on the engine load. That is, it is set to 105 degrees Celsius or 80 degrees Celsius depending on the engine speed EngSpd and the fuel amount. The first desired refrigerant temperature TMSoll1 is weighted according to the current classification FTK of the driver type from the engine controller, using the following module ECT_FTK, and is either 105 degrees Celsius or 80 degrees Celsius The refrigerant temperature is selected according to the driver type classification. A refrigerant temperature of 80 degrees Celsius is preferentially selected for the classification of those who prefer a sporty driving type. The result of this weighting is the second set refrigerant temperature TMSoll2.

  After the classification of the driver type, the intake air temperature is taken into account in the next stage of the decision cascade. This is done in module ECT_AT. The detection of the intake air temperature is used to detect a traffic jam condition. If it is detected that the vehicle is involved in a traffic jam, it is desirable to reduce the desired refrigerant temperature to 80 degrees Celsius or 90 degrees Celsius. This is done by reducing the refrigerant temperature to one of the two aforementioned values when the intake air temperature exceeds a reference value from a temperature interval of 40 degrees Celsius to 50 degrees Celsius. The result after considering the intake air temperature is the set refrigerant temperature TMSoll3.

  This determined refrigerant temperature TMSoll3 is evaluated in the decision cascade by the next module ECT_VehSpd using the current vehicle speed. When the vehicle speed exceeds a first reference value, for example 120 km / hour, the refrigerant temperature is set to 90 degrees Celsius, and when the vehicle speed exceeds a second reference value, for example 160 km / hour, the desired refrigerant temperature is 80 degrees Celsius. Set to

  In the final stage of the decision cascade, the desired refrigerant temperature TMSoll4, evaluated according to the vehicle speed, is evaluated and determined using the outside air temperature. In this way, the previously obtained desired refrigerant temperature is finally canceled out in extreme environmental conditions, such as extreme cold, and the desired refrigerant temperature TMSoll5 to be finally applied is determined. Is done. The refrigerant temperature TMSoll5 is defined in advance as a desired variable for the operating means of the fan 4 and the thermostat three-way valve 11. If the external temperature exceeds a first reference value, for example 12 degrees Celsius, the temperature is not lowered by the last stage of the decision cascade. In the case where the temperature is the first reference value, for example, the refrigerant set temperature of 90 degrees Celsius, when the outside air temperature falls below 12 degrees Celsius, the refrigerant set temperature is changed in accordance with the external temperature. When the external temperature further decreases, and when the external temperature decreases to a second reference value, for example, less than minus 15 degrees Celsius, the set temperature of the refrigerant is set to 105 degrees Celsius regardless of other influence variables.

  The desired refrigerant temperature TMSoll5 finally present after the fifth stage is determined by the fan 4 for a minimum time of, for example, 100 seconds, irrespective of the input signals 21, 22, 23, 24, 25, 26 and the vehicle speed. And a set value variable for operating the thermostat three-way valve 11. This holding function can be realized by using a delay means or a delay loop of a program, for example. In the signal flow diagram of FIG. 2, the determined function for maintaining the set temperature of the refrigerant is represented by the symbol of the timing delay means 29.

  The desired refrigerant temperature determined by the decision cascade of FIG. 2 is finally further processed by the adaptive open loop and closed loop control system shown in more detail in FIG. At the input end of the open loop control system, the basic adaptation for the desired refrigerant temperature TMSoll, for the actual refrigerant temperature TMist, for the outside temperature, for the basic adaptive open loop and closed loop control parameters to be read, for the GA Parameter Fallback level if the open-loop control system does not work correctly or fails because of one of the input signals is not available, for example, activation of GA, activation GA, precision adaptation, activation FA, etc. Signal values are provided for fail-safe operation. In FIG. 3, the signal input is represented by the symbols of the connection pins 31, 32, 33, 34, 35, 36, and 37, and is represented by corresponding signal values.

  The starting means for the thermostat 11 is also in the form of a software module 40 for basic adaptation, a software module 41 for precision adaptation, a software module 42 for pilot control of operating elements for the valve of the thermostat three-way valve 11, and a software module. A possible digital proportional controller 43.

  When the vehicle is started and the desired refrigerant temperature is less than 90 degrees Celsius, the basic adaptation is activated if the control unit 5 is connected to the voltage of the vehicle electrical system. Since the desired refrigerant temperature is used as a decision criterion for the operation of the basic adaptation, the inspection by the (German) technical monitoring body of the exhaust gas limits is not hindered. Precisely, since the engine temperature of 105 degrees Celsius, which is optimal for the exhaust gas level, is used for the exhaust gas test defined by the statute, the basic adaptation cannot be used to set the desired temperature, This is determined according to the algorithm of FIG. 2, which is less than 105 degrees Celsius. In other words, the thermostat three-way valve 11 is not activated by basic adaptation during the exhaust gas test. Moreover, the basic adaptation must be effective only during engine operation. If, for example, the basic adaptation is valid when the engine is in a stopped state, this allows adaptation in the form of the basic adaptation value GA_Parameter of the terminal 34 when self-adapting the basic adaptation mainly in prevailing ambient conditions. The value is broken.

  The GA_Parameter self-reset function may be executed, for example, by the sub-module GA_Reset of FIG. This submodule is integrated in the software module 40 for basic adaptation. The control deviation between the actual refrigerant temperature and the desired refrigerant temperature is also registered and integrated in this submodule. When the integral value exceeds a certain value, the basic adaptation is reset and the original control parameters are new control parameters calculated, for example, from the integrated temperature deviation and the temperature characteristic factor diagram of the pilot control means for starting the thermostat. To be replaced. At the start of the integral value, the actual temperature must once be within the range of the proportional controller 43. If the basic adaptive control parameters are not very good, resets are used to improve them. In addition, the basic adaptation is matched to different ambient conditions by resetting.

The correction coefficient TMGACorr for changing the controller parameter for basic adaptation is
TMGACorr = (Tmean-TMSoll) * TMGAGRad
(Here, TMGAGrad is measured in% / ° C.)
For example, the average integrated temperature Tmean of each desired temperature TMSoll of 80 ° C. or 90 ° C. and the characteristics of the pulse width control TMGAGRad for changing the cooling water temperature according to the pulse occupancy of the pulse width control Obtained from variables. The typical pulse width control used was a 3% increase in pulse occupancy for a 1 ° temperature decrease in the refrigerant circuit. The desired temperature value determined according to the algorithm of FIG. 2 can be used for TMSoll. The correction determined in this way is still a function of the ambient temperature.

  The dependence of the setting on the ambient temperature is taken into account by a further correction function integrated in the software module 40 for basic adaptation. For this reason, the outside air temperature is read as a digital value by the PIN 33. The influence of the outside temperature on the cooling power of the cooling system is taken into account by the correction characteristic factor diagram, the pulse occupancy of the pulse width control is selected accordingly, and this pulse occupancy compensates for the influence of the external temperature. For this compensation, for example, it may be necessary to consider the influence of the external temperature as a multiplicative correction coefficient for changing the cooling water temperature in accordance with the pulse occupation ratio TMGAGRad. The correction factor can then preferably be found in the aforementioned characteristic factor diagram according to the measured external temperature.

  After the controller is connected to the voltage of the vehicle electrical system, the basic adaptation is generally valid only once for the following driving cycle. In contrast, the fine adaptation 41 (FIG. 3) operates permanently and starts after the basic adaptation has reached the desired temperature of 80 ° C. or 90 ° C. for the first time and the basic adaptation has ended. For example, a threshold comparator (not shown) may establish when the desired temperature is reached and then communicates a corresponding start signal, Activation FA, to the input pin 36 of the fine adaptation means 41. Unlike basic adaptation, in the case of fine adaptation, correction is determined over time. The number of time components of the total operating time of the current fine adaptation phase, for example, where the actual temperature of the refrigerant deviates from the desired temperature is then recorded. Furthermore, the correction value TMFACorr is calculated in the fine adaptation means 41 and fed back to the basic adaptation means 40 in the control loop and used to correct the activation of the pilot control means 42.

  Finally, in the pilot control means 42, the predefined signal TMGA at the output of the basic adaptation means 40, whose signal contains correction information, is pulsed according to the characteristic curve of the operating element used in the thermostat three-way valve. Used to determine the correction of the width pulse occupancy, which correction is further superimposed on the controller output of the proportional controller 43. This superposition is represented in FIG. Process 30 finally outputs the pulse occupancy of the pulse width modulation used to manipulate the operating elements in the thermostat three-way valve.

  The closed-loop control system of FIG. 3 has the advantage that emergency functions can be provided in a very simple way, in particular by adaptive superposition of basic and fine adaptations on the output of the proportional controller 43. If the basic adaptation means or the fine adaptation means are not operating correctly, the two modules can be switched off in a simple manner by means of the corresponding signal, fail-safe represented on the terminal 37. The refrigerant temperature is then simply set by the proportional controller 43.

  Ambient conditions are taken into account by detecting the outside air temperature with a corresponding temperature sensor which supplies a temperature signal to the input of the terminal 33. The outside temperature measured in this way is taken into account by the software in the proportional controller 43, by the software in the basic adaptation means 40 and by the software in the fine adaptation means when determining controller settings and adaptations. . In the present specification, the temperature is considered using a computer according to a temperature characteristic factor diagram that considers the dependence of the cooling power on the external temperature. Therefore, the activation of the thermostat three-way valve can be set for the current ambient temperature. Thus, especially in the case of high external temperatures that would probably prevent reaching the desired refrigerant temperature of 80 ° C., the adaptation in the case of predefined impossible target values is meaningless, The adaptation can be deactivated.

1 is a schematic diagram showing a cooling system having the most important influence variable for the present invention. FIG. It is a simplified Matlab-Simlink diagram for determining the temperature level to be set. FIG. 2 is a simplified Matlab-Simlink diagram of an adaptive closed loop control system.

Claims (8)

A circuit bypassing the radiator (2) and a circuit passing through the radiator (2) can be switched by a closed loop temperature control by a valve in the thermostat, or a mixed operation with a predetermined mixing ratio is performed by the closed loop temperature control. You can select both circuits in the mode,
The operating unit of the valve in the thermostat (11) is activated by a control unit (5) and one of a plurality of possible refrigerant temperatures is set by opening and closing the valve in the thermostat. In a method for operating a thermostat (11) of a cooling circuit of an engine (1),
Closed-loop control for each pre-specified refrigerant temperature includes first and second closed-loop control stages;
The first closed-loop control stage in the form of a basic adaptation (40) with stored control parameters quickly sets a pre-designated refrigerant temperature;
After each reaching the current refrigerant temperature, the second closed-loop control step in the form of a fine adaptation (41) with variable control parameters keeps constant at the pre-specified next refrigerant temperature. how to.   The method of claim 1, wherein a new refrigerant temperature is set by fine adaptation when the pre-designated refrigerant temperature is changed.   The method according to claim 1 or 2, characterized in that the basic adaptation setting is corrected by the corrected fine adaptation setting.   3. A method according to claim 1 or 2, characterized in that the basic adaptive setting is matched to the ambient temperature when the vehicle is started.   If the vehicle is started when the ambient temperature has changed at least by a pre-designated temperature interval and the vehicle has not been operated for more than a pre-designated minimum time, the basic adaptation settings are adapted The method of claim 4.   The method according to claim 1, characterized in that the current refrigerant temperature (TMSoll) is selected from among three different refrigerant temperatures specified in advance depending on the load.   7. The method according to claim 1, wherein an outside temperature (33) is input into the closed-loop control system in the first and second closed-loop control phases.   8. A fault according to claim 1, characterized in that the basic adaptation (40) is deactivated and the closed-loop control of the refrigerant is replaced by a proportional controller (43) from a redundant fallback level. The method according to claim 1.

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