EP0744539A2 - Cooling system with an electrically controlled actuator - Google Patents

Abstract

The cooling circuit has an electrically-controlled setting element (3), for determining the temp of the cooling medium, preceded by an electronic regulator (4), providing a pulse width modulated setting signal for the setting element in dependence on the actual cooling medium temp (Tist), for obtaining a required cooling medium temp (Tsoll). The regulation parameters of the electronic regulator are determined from a basic characteristic curve, in combination with at least one correction characteristic curve.

Description

The invention relates to a cooling system with an electrically controllable actuator for influencing the coolant temperature of internal combustion engines in motor vehicles according to the preamble of claim 1.

Such a cooling system is known for example from DE 43 24 178 A1. This known cooling system for internal combustion engines has a cooler and a thermostatic valve as an electrically controllable actuator with which the temperature of the coolant can be controlled in a warm-up mode, a mixed mode and a cooler mode. The thermostatic valve as an electrically controllable actuator contains an expansion element which can be heated electrically to reduce the coolant temperature.

In this known cooling system, the thermostatic valve regulates the flow of the coolant between the internal combustion engine and the cooler in such a way that the coolant coming from the internal combustion engine flows back to the internal combustion engine essentially bypassing the cooler through a short circuit during warm-up operation, so that during the mixed operation that of the Internal coolant flows partially through the cooler and partially through the short circuit back to the internal combustion engine and that during cooler operation the coolant coming from the internal combustion engine essentially flows back through the cooler to the internal combustion engine. Due to the electrical heating of the electrically controllable actuator the opening cross section for the flow of the coolant to the cooler is increased compared to an opening cross section caused by the temperature of the coolant.

The electrically controllable actuator is electrically heated via a control device, by means of which the actual coolant temperature is detected and compared with a predetermined desired coolant temperature. If the detected actual coolant temperature is above the target coolant temperature, the electrical heating is switched on to cool the coolant, while when the actual coolant temperature is below the predetermined target coolant temperature, the electrical heating of the electrically controllable actuator is switched off.

This known cooling system, depending on the actual coolant temperature, only performs a two-point control in comparison with the target coolant temperature, so that strong undershoots or overshoots can occur with respect to the target coolant temperature to be achieved.

In addition, for example, from DE 44 03 713, which has not yet been published, a cooling system is known whose electrically controllable actuator for influencing the coolant temperature in internal combustion engines is an electrically controllable coolant feed pump. However, no control strategy has been described for this known cooling system, in particular with regard to the speed control of the coolant delivery pump.

It is an object of the invention to improve a cooling system of the type mentioned in such a way that, on the one hand, undershoots or overshoots are prevented in relation to the predetermined target coolant temperature and, moreover, the predetermined target coolant temperature is reached as quickly as possible.

This object is achieved by the characterizing features of patent claim 1.

According to the invention, the parameters of the controller are determined by means of a basic map and by means of at least one correction map.

It has been found in tests that a PID controller is particularly suitable for regulating the cooling system with an electronically or electrically controllable actuator for influencing the coolant temperature of internal combustion engines, in order to achieve the predetermined target coolant temperature as quickly as possible. Such a PID controller can be constructed either in an analog or digital manner and can be integrated, for example, in an electronic control device that is already present to control the cooling system and / or the internal combustion engine. In particular when using a digital PID controller, the outlay and the costs for a cooling system according to the invention are only small, despite the improved control. However, the regulator can also be another electronic regulator, e.g. B. a PI _n D _n - or a PI controller.

The controller is preferably designed in accordance with a physical model of the cooling process.
In addition, it is pointed out that the quantity influenced by the coolant temperature can also be the coolant temperature itself. The control signal variable can also be generated as a function of further operating parameters.

Kennfeld" soll erfindungsgemäß auch eine Kennlinie, eine Tabelle und/oder einen entsprechenden Algorithmus umfassen. Vorzugsweise ist ein elektronisches Steuergerät vorgesehen, in dem der Regler integriert ist und in dem die Kennfelder, Kennlinien, Tabellen und/oder Algorithmen abgespeichert sind.The term

According to the invention, the characteristic diagram should also include a characteristic curve, a table and / or a corresponding algorithm. An electronic control unit is preferably provided in which the controller is integrated and in which the characteristic diagrams, characteristic curves, tables and / or algorithms are stored.

The determination of the control parameters by means of a basic map and a correction map enables, on the one hand, very fast regulation by specifying a pilot control value by means of the basic map and, on the other hand, very precise regulation by specifying a correction value by means of the correction map, e.g. B. in response to the specification of the pre-control value.

An advantageous further development of the invention is the subject matter of patent claim 2.

According to the invention, the parameters of the controller are determined by means of a basic map taking into account at least one operating parameter and by means of determined at least one correction map taking into account the control difference.

The basic map according to the invention preferably takes into account the actual coolant temperature and the engine speed. In the case of a PID controller or a PI controller, a correction map is preferably provided for both the I component and the P component of the controller. These correction maps take into account at least the control difference, i. H. the difference between the actual coolant temperature and the specified target coolant temperature. According to the invention, further operating parameters can be provided both in the basic map and in the correction map (s), e.g. B. the current position of the actuator, the engine load, the vehicle electrical system voltage, the vehicle speed, the outside temperature, the switching state of the air conditioning system and / or wind influences.

A further advantageous embodiment of the invention is the subject of claim 3.
According to the invention, the values of the basic and correction maps are added to determine the parameters of the controller. To determine the parameters of the controller and thus the control signal size, additional operating parameters can also be taken into account in addition to the values of the characteristic diagrams.

These further developments according to the invention allow a very precise adaptation of the parameters of the controller to the current operating conditions of the vehicle.

A further advantageous embodiment of the invention is the subject of claim 4.
The control signal size is preferably a pulse width modulated signal. This enables a very sensitive control of the actuator, since a resolution of at least 1% is customary for pulse-width-modulated signals as the control signal variable.

Fig. 1

eine erfindungsgemäße Kühlanlage mit einem Regler, dessen Parameter durch ein Grundfeld und zwei Korrekturkennfelder bestimmt werden und

Fig. 2

den Verlauf der Kühlmitteltemperatur in Abhängigkeit von der Verwendung verschiedener Kennfelder.

In the drawing, an embodiment of the invention is shown. It shows

Fig. 1

a cooling system according to the invention with a controller, the parameters of which are determined by a basic field and two correction maps and

Fig. 2

the course of the coolant temperature depending on the use of different maps.

In Fig. 1, the output A of an internal combustion engine 1 leads via a coolant-carrying line to an input of the actuator 3 in the form of an electrically heatable thermostatic valve. An output of the actuator 3 is connected to the input E of the internal combustion engine 1 via a coolant-carrying line. At another output of the actuator 3, shown here closed, the input of a cooler 2 is connected via a coolant-carrying line. The output of the cooler 2 leads to the input E of the internal combustion engine 1.

For a more detailed function of the actuator 3 in the form of an electrically heatable thermostatic valve, reference is made, for example, to DE 43 24 178 A1.

In Fig. 1, the actuator 3 is shown in warm-up. During a warm-up, the coolant is returned from output A of internal combustion engine 1 in a kind of short circuit via actuator 3 to input E of internal combustion engine 1, bypassing cooler 2. After the coolant has been heated to the operating temperature, the actuator 3 is activated in such a way that the coolant is at least partially guided over the cooler 2 in mixed operation or in cooler operation. The more the actuator 3 is heated by the control signal PWM, the more the actuator 3 is shifted in the direction of the cooler operation; d. H. the right passage, shown here fully open, is closed more and more, while the left passage, shown here completely closed, is opened ever more.

The control signal PWM as a control signal variable is an output signal of the PID controller 4. The PID controller 4 can also be integrated in an electronic control unit. The PID controller 4 receives at least the actual coolant temperature T _ist as an input signal from the internal combustion engine 1. In addition, for example the following additional input signals to the PID controller 4 zoom out: The internal combustion engine speed n, the target coolant temperature T _set, the throttle angle DK, the vehicle speed v, the outside temperature T _A and / or the vehicle power supply battery U _b. Furthermore, three maps are stored in the PID controller 4. The basic map K _G gives z. As a function of the actual coolant temperature _T and the engine speed n, a pilot control value T _VSW before. A first correction value T _P is specified for the P component of the PID controller 4 via the first correction characteristic map K _K1 and a second correction value T _{I is} specified for the I component of the PID controller 4 via the second correction characteristic _map , the first Correction value T _P and the second correction value T _{I are determined} at least as a function of the control difference T _soll - T _ist . According to the invention, it is also possible to use only one correction map K _K1 or K _K2 if the accuracy of the controller is not so high.

The control signal size for controlling the actuator 3 is the pulse width modulated control signal PWM. According to the invention, the pulse-pause ratio of the control signal PWM preferably results from the following formula: $${\text{(T}}_{\text{VSW}}{\text{+ T}}_{\text{P}}{\text{+ T}}_{\text{I.}}{\text{) U}}_{\text{should}}{\text{/ U}}_{\text{b}}$$

In the exemplary determination of the driving signal PWM is a correction factor after the addition of the values of the basic (T _VSW) and correction maps (T _P, T _I) depending on the ratio of the target-vehicle electrical system voltage (U _soll) to the actual vehicle electrical system voltage (U _b ) provided. To determine the control signal PWM, other operating parameters such as. B. the throttle valve angle DK, the vehicle speed v and the outside temperature T _{a are also} taken into account.

In Fig. 2, the control quality is compared depending on the use of different maps to determine the control signal size PWM. 2 shows the actual coolant temperature T _ist over time t. In addition to the time t _{0 is} the predetermined desired coolant temperature T _set1 change to the target coolant temperature T _set2. The upper characteristic curve of the diagram shows the control behavior if only the PWM is used to determine the control signal variable _Pre- control _{signal value} T _{VSW of} the basic _map K _G is used. The middle course of the diagram in FIG. 2 shows the control behavior when using the basic map K _G and only one correction map K _K1 . The middle course of the diagram in FIG. 2, which results from an _{actuating signal variable} in which at least the values T _VSW and T _{P are} added, already shows a better control quality compared to the upper course. The lower curve of the diagram in FIG. 2, in which the values T _VSW , T _P and T _{I are} added to determine the control signal _variable PWM, shows the best control quality compared to the other curves in FIG. 2. On the one hand, the new target coolant temperature T _{soll2 is} reached as quickly as possible in the lower course and, on the other hand, in all three courses the use of the PID controller 4 _{according to the invention achieves} the newly specified target coolant temperature T _soll2 without _undershoot or overshoot.

A control optimization is thus created by the exemplary embodiment according to the invention, by means of which, depending on the information available about operating parameters, a very quick and precise setting of the predetermined target coolant temperature is possible.

However, the invention is not restricted to the exemplary embodiment mentioned. So instead of the thermostatic valve 3 or additionally as an electrically or electronically controllable actuator z. B. a coolant supply pump provided in the coolant circuit can be regulated according to the invention - or an electrically controllable coolant throttle valve. Basically, the invention covers each actuator that can be controlled electrically or electronically to influence the coolant temperature.
Furthermore, the control signal size does not necessarily have to be a pulse-width-modulated signal, but can also - according to the design of the actuator - be any suitable electrical signal, such as, for. B. a displacement-proportional voltage signal or a frequency-modulated pulse.

In addition, a variable influenced by the coolant temperature may be, for example, a different temperature instead of the coolant temperature itself, such as, for. B. that of a coolant-flowed component.

Claims (4)

Cooling system with an electrically controllable actuator for influencing the coolant temperature of internal combustion engines in motor vehicles and with an electronic controller (4) connected upstream of the actuator (3) and which depends at least on a variable influenced by the coolant temperature

the control signal size (PWM) to control the actuator (3) to reach a target coolant temperature

generated, characterized in that the parameters of the controller (4) are determined by means of a basic map (K _G ) and at least one correction map (K _K1 , K _K2 ). Cooling system according to claim 1, characterized in that the basic map (K

) taking into account at least one operating parameter

and the correction map (K

, K

) taking into account the control difference

be determined. Cooling system according to claim 1 or 2, characterized in that the values for determining the parameters of the controller (4)

T

, T

) the reason (K

) - and correction maps (K

, K

) can be added. Cooling system according to one of claims 1 to 3, characterized in that the control signal variable (PWM) is a pulse width modulated signal.

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