EP0744539B1 - Cooling system with an electrically controlled actuator - Google Patents

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 Thermostat valve as an electrically adjustable actuator with which the temperature of the coolant in a warm-up mode, a mixed mode and a cooler mode is adjustable. Contains the thermostatic valve as an electrically controllable actuator an expansion element that is used to reduce the coolant temperature electrically is heated.

In this known cooling system, the thermostatic valve regulates the flow of the Coolant between the engine and the radiator such that during the warm-up operation, the coolant coming from the internal combustion engine in essentially bypassing the cooler through a short circuit Internal combustion engine flows back that during the mixed operation of the Internal coolant coming partially through the radiator and partially flows back through the short circuit to the internal combustion engine and that comes from the internal combustion engine during cooler operation Coolant 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 radiator compared to an opening cross section caused by the temperature of the coolant increased.

The electrically controllable actuator is electrically heated by a Control device by means of which the actual coolant temperature is recorded and with a predetermined target coolant temperature is compared. Is the recorded actual coolant temperature above the target coolant temperature is used to cool the Coolant turned on the electric heater while at a tst coolant temperature below the specified target coolant temperature, the electrical Heating of the electrically controllable actuator is switched off.

This known cooling system performs depending on the actual coolant temperature compared to the target coolant temperature, only a two-point control , which means that there are strong or overshoots can occur.

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

Furthermore, EP 0 557 113 A2 describes a cooling system with an electrically controllable one Actuator for influencing the coolant temperature of internal combustion engines in Motor vehicles known. Here, the target coolant temperature from one Map depending on various operating parameters. A correction value in the form of a gain factor is taken from a correction map, the difference between the coolant temperature in the radiator and the coolant temperature depends on the engine input. Otherwise concerns the EP 0 557 113 A2 merely the determination and setting of a specific target coolant temperature, not the strategy of achieving one already predetermined target coolant temperature.

It is an object of the invention to provide a cooling system of the type mentioned at the beginning improve that on the one hand undershoot or overshoot related to the given Desired coolant temperature is prevented and also the specified desired coolant temperature is achieved as quickly as possible.

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

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 controlling 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, for example, can be integrated in an electronic control device for controlling the cooling system and / or the internal combustion engine which is already present. 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 improved regulation. 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.

According to the invention, the term “characteristic diagram” is also intended to be a characteristic curve, a table and / or comprise a corresponding algorithm. Preferably an electronic one Control device provided in which the controller is integrated and in which the Maps, characteristic curves, tables and / or algorithms are stored.

The determination of the control parameters by means of a basic map under Consideration of at least one operating parameter and at least one Correction map taking into account the control difference enables to a very quick regulation by specifying a pre-control value by means of of the basic map and secondly a very precise regulation by the Specification of a correction value by means of the correction map, e.g. B. on the Reaction according to the input tax value. The basic map is taken into account preferably the actual coolant temperature and the engine speed. In the case of a PID controller or a PI controller, preference is given to both the I component as well as a correction map for the P component of the controller intended. These correction maps take into account at least the control difference, d. H. the difference between the actual coolant temperature and the specified one Target coolant temperature. Both in the basic map and in the / the Correction map / maps can still further operating parameters according to the invention be provided, 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 status of the air conditioning system and / or wind influences.

A further advantageous embodiment of the invention is the subject of claim 2.
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, other operating parameters can also be taken into account in addition to the values of the characteristic diagrams.

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

Another advantageous embodiment of the invention is the subject of the claim Third

The control signal size is preferably a pulse width modulated signal. hereby a very sensitive control of the actuator is possible, since usually at pulse width modulated signals as control signal size a resolution of at least 1% is common.

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 via a coolant Line connected to the input E of the internal combustion engine 1. On Another output of the actuator 3, shown here closed, is about a coolant-carrying line connected to the input of a cooler 2. The The output of the cooler 2 leads to the input E of the internal combustion engine 1.

For the closer functioning of the actuator 3 in the form of an electrically heatable Thermostat valve may be referred to DE 43 24 178 A1, for example.

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

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 will be introduced: 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. Via the first correction map K _K1 , a first correction value T _P is specified for the P component of the PID controller 4 and via the second correction map K _K2 a second correction value T _{I is} specified for the I component of the PID controller 4, 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: (T VSW + T P + T I ) U should / U 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, the actual coolant temperature T _{ist is} plotted against the 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 pilot control signal _value T _{VSW of} the basic characteristic _map K _{G is} used to determine the control signal _variable PWM. 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 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.

Thus, the exemplary embodiment according to the invention optimizes the rules created by depending on the information available a very quick and precise setting of the operating parameters predetermined target coolant temperature is possible.

However, the invention is not limited 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 every 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. an adjustment-proportional voltage signal or a frequency-modulated pulse.

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

Claims (3)

1. A cooling system comprising an electronic controller (4) for influencing the coolant temperature of internal combustion engines in motor vehicles, wherein the controller (4) is upstream of an electrically controllable actuator (3) and generates an actuator signal variable (PWM) at least in dependence on a variable (T_actual) influenced by the coolant temperature, for actuating the actuator in order to obtain a set coolant temperature (T_set), characterised in that the controller is a PID controller or a PI controller and a basic performance graph (K_G) for setting a pilot value (T_VSW) allowing for at least one operating parameter (n,T_actual) is preset in the controller and at least one collective performance graph (K_K1, K_K2) is stored for the purpose of setting at least one corrective value (T_P, T_I) for the P component and/or the I component of the controller (4) allowing for the controller difference (T_set - T_actual).
2. A cooling system according to claim 1, characterised in that the parameters of the controller (4) are determined by adding the values (T_VSW, T_p, T_I) of the basic performance graph (K_G) to the values of the corrective performance graph (K_K1, K_K2).
3. A cooling system according to claim 1 or 2, characterised in that the actuator signal variable (PWM) is a pulse-width modulated signal.

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