EP0664383B1 - Cooling system for an internal combustion engine - Google Patents

Description

The invention relates to a cooling system for an internal combustion engine of a motor vehicle with a radiator and a thermostatic valve that controls the temperature of the coolant in a warm-up mode, a mixed mode and a cooler operation is controllable, the thermostatic valve contains an expansion element to reduce the coolant temperature is electrically heated.

The thermostatic valve regulates the flow of the coolant between the internal combustion engine and the radiator such that during the warm-up operation that of the internal combustion engine coming coolants essentially bypassing the cooler through a short circuit to Internal combustion engine flows back that during mixed operation the coolant coming from the internal combustion engine partly through the cooler and partly through flows back through the short circuit to the internal combustion engine and that during the cooler operation that of the internal combustion engine coming coolant essentially through flows back through the radiator to the internal combustion engine.

The electrical heating of the expansion element is used for Enlarging the opening cross section towards the radiator one by the temperature of the coolant in the area opening of the thermostatic valve.

A cooling system according to the preamble of the claim is known for example from DE 30 18 682 A1. At this known cooling system is in an expansion element an electric heating resistor of a thermostatic valve arranged, the electrical energy through a stationary held working piston can be fed through. The feed the electrical energy takes place via a control device, the coolant temperature regulated by the thermostatic valve better than a normal thermostatic valve to be able to keep constant. For this, the Actual coolant temperature measured and with a predetermined upper and with a predetermined lower temperature value compared. If the upper temperature value is reached, so the heating resistor with electrical energy supplied so that the thermostatic valve opens further, by an increased cooling capacity and thus a lowering of the Actual coolant temperature can be reached. The actual coolant temperature drops then below the lower temperature value, so the supply of electrical energy to that Heating resistor interrupted so that the expansion element is cooled by the colder coolant. This will make the Valve cross section reduced again, so that the actual coolant temperature rises again. These rules games will be constantly repeated to maintain a coolant temperature in the Maintain a range of, for example, 95 ° C as constant as possible.

DE 37 05 232 A1 describes a temperature control device known in the place of a conventional thermostatic valve with an expansion element by means of a Servomotor adjustable valve is provided. At this Known temperature control device is the servomotor to adjust the valve depending on one Sensor controlled that the coolant temperature in a line connected to the internal combustion engine. Of the The sensor is also equipped with a heating device. The heating device is dependent on map sizes of the internal combustion engine can be switched on and off. In this known temperature control device can accordingly by heating the sensor higher than the real one Coolant temperature can be faked to an increased To achieve cooling of the coolant. Such Temperature control device is constructively special complex and therefore costly.

In the as yet unpublished German patent application P 43 24 178 is also a cooling system for one Internal combustion engine of a motor vehicle mentioned above Type described in which the expansion element such is designed so that the coolant temperature without heating of the expansion element in warm-up mode and / or in mixed operation to an upper limit temperature settles. There is a control unit in this cooling system provided, depending on the detected operating and / or Environmental variables of the combustion engine heating the Expansion element releases if necessary to the mode of operation the cooling system from warm-up mode or from mixed mode the upper working limit temperature towards mixed operation or cooling operation against the upper working limit temperature lower coolant temperature relocate. Because the expansion element in this cooling system of the thermostatic valve depending on the detected operating and / or environmental variables of the internal combustion engine, is used to control the heating of the expansion element an electronic control unit is required in of the detected operating and / or environmental variables of the internal combustion engine processed in a suitable manner and Control of the heating of the expansion element used will.

The invention has for its object a cooling system of the type mentioned at the outset, as simple as possible, that the operation of the internal combustion engine with respect optimized fuel consumption and emissions can be without in the event of an increased power requirement the performance of the internal combustion engine is reduced is.

This task is performed according to the characterizing part of the claim 1 solved.

The upper working limit temperature is preferably the same the most economical operating temperature of the internal combustion engine and is slightly smaller than the maximum permissible operating temperature of the internal combustion engine. Preferably is the upper working limit temperature 100 ° C, especially at approx. 105 ° C. The maximum allowable Operating temperature is the highest possible temperature, with that the internal combustion engine in normal operation for longer Time can be operated without problems. This will even if the electrical heating of the expansion element fails damage to the internal combustion engine prevented. The maximum permissible operating temperature is usually between 105 ° C and 120 ° C.

If the expansion element is not heated electrically, there is only one opening cross-section to the radiator depending on the coolant temperature of the internal combustion engine. This opening cross section causes the coolant temperature to adjust to defined upper working limit temperature. It will Expansion element, e.g. B. by selecting an appropriate temperature-dependent material and a suitable one constructive design, designed so that the defined upper working limit temperature of the opening cross section the cooler is not yet maximum, d. H. no pure cooler operation is achieved. So is by additional Heating the expansion element another Enlargement of the opening cross-section and thus one Relocation towards cooler operation possible.

In addition, it should be noted that the opening cross section towards the radiator and the opening cross section to the the cooler immediate short circuit changed in opposite directions will.

Through the cooling system according to the invention, in normal operation, d. H. not with increased performance requirements, such as e.g. B. in full load operation of the internal combustion engine or at Ascent of the engine driven by the internal combustion engine Motor vehicle, the highest possible operating temperature of the internal combustion engine reached. Here is for example due to lower friction the power consumption of the Internal combustion engine lower, which increases fuel consumption lower and improve the exhaust gas composition leaves. However, when the operating state of the internal combustion engine due to increased performance requirements lower coolant temperature level required, quickly to be able to switch to this coolant temperature level a temperature switch is provided according to the invention, which depends on the on or near the radiator outlet detected coolant temperature electrical energy feeds the heatable expansion element in the sense that increased cooling capacity by opening the Thermostatic valve is obtained and thus a reduced Coolant temperature is reached quickly. Too high Coolant or internal combustion engine temperatures at elevated Performance requirement would be reduced Degree of filling and thus a reduced performance of the Lead internal combustion engine.

The advantage of the cooling system according to the invention over that in the as yet unpublished German patent application P 43 24 178 cooling system described exists in that depending on different Performance requirements for the internal combustion engine various Coolant temperature levels using a simple temperature switch without a technically complex and expensive electronic Control unit can be reached. So the Cooling system according to the invention in particular for an internal combustion engine for motor vehicles of the lower Price segment. Another advantage of the invention Cooling system is that on the elaborate and cost-intensive recording of company and environmental parameters of the internal combustion engine can be dispensed with.

The expansion element can be heated, for example time-controlled after a certain predetermined time be switched off again.

In the invention a two-point switch is provided as a temperature switch, whose upper switching point is in the range of 55 ° C to 75 ° C, preferably at 65 ° C and its lower Switching point minimum 5 ° C and maximum 50 ° C below the upper switching point. With this configuration the Invention is the heating of the expansion element again turned off when on or near the radiator outlet detected coolant temperature the lower switching point of the two-point switch.

In the following the invention is based on an embodiment explained in more detail.

Fig. 1

eine erfindungsgemäße Kühlanlage für eine Brennkraftmaschine in schematischer Darstellung und

Fig. 2 oben

einen mit der erfindungsgemäßen Kühlanlage gewonnenen Verlauf der Kühlmitteltemperatur am Ausgang des Kühlers der Brennkraftmaschine sowie

unten

den dazugehörigen Heizspannungsverlauf für die Beheizung des Dehnstoffelementes des Thermostatventiles der erfindungsgemäßen Kühlanlage.

Show it

Fig. 1

a cooling system according to the invention for an internal combustion engine in a schematic representation and

Fig. 2 above

a course of the coolant temperature obtained with the cooling system according to the invention at the outlet of the cooler of the internal combustion engine and

below

the associated heating voltage curve for heating the expansion element of the thermostatic valve of the cooling system according to the invention.

The cooling system shown in Fig. 1 for an internal combustion engine 1 comprises a radiator 2. Between the internal combustion engine 1 and the cooler 2 is a coolant pump 3 arranged having a flow of the coolant in the Arrows shown direction generated. From the coolant outlet 4 of the internal combustion engine 1 leads a flow line 5 to the coolant inlet 6 of the radiator 2. From the coolant outlet or output 7 of the cooler 2 leads to Coolant inlet 8 of the internal combustion engine 1 has a return line 9. In the return line 9 is a thermostatic valve 10 with an expansion element, not shown here arranged. It is also in the return line 9 a temperature switch in the form of a two-point switch 11 provided. The two-point switch 11 controls the heating of the expansion element of the thermostatic valve 10 depending on the at or near the radiator outlet 7 detected coolant temperature by a electrical heating voltage U to a heating element of the expansion element of the thermostatic valve 10 is applied. The thermostatic valve 10 is also via a short-circuit line 12 connected to the flow line 5.

The cooling system essentially works in three operating modes. In a first mode of operation, the so-called warm-up mode, especially after the cold start of the internal combustion engine 1, the thermostatic valve 10 is set so that the coolant coming from the internal combustion engine 1 Flow over the short-circuit line 12 essentially is completely returned to the internal combustion engine 1. In a second mode of operation, the cooling system works in the Mixed operation, d. H. that coming from the internal combustion engine 1 Coolant runs partly through the cooler 2 and partly via the short-circuit line 12 back to the internal combustion engine 1. In a third mode of operation Cooling system in cooler mode, d. H. that of the internal combustion engine 10 coming coolant will be essentially complete through the radiator 2 to the internal combustion engine 1 returned.

The cooling system can be operated by heating the Expansion element of the thermostatic valve 10 by control via an electrical line 13 through which the Thermostatic valve 10 with the two-point switch 11 electrically connected, adjusted in the direction of cooler operation or switched completely to cooler operation will. This reduces the temperature level of the Coolant compared to that with an operation without Heating of the expansion element reached the temperature level. Then the heating of the expansion element of the thermostatic valve 10 by activation by the Two-point switch 11 via the electrical line 13 again interrupted, so the cooler coolant cools the expansion element of the thermostatic valve 10 until it assumes a regulated end position in mixed operation, so that the coolant temperature returns to a final temperature is raised. The regulated final temperature in Mixed operation is at the upper working limit temperature fixed.

The supply of the thermostatic valve 10 with electrical Energy is generated by the two-point temperature switch 11 via the electrical line 13 depending on the at or in the vicinity of the cooler outlet 7 detected coolant temperature controlled. Because the coolant temperature at or near the radiator outlet 7 in a very good approximation Shows the load state of the internal combustion engine 1, this coolant temperature is suitable at or near the cooler outlet 7 is very good for controlling the heating of the expansion element of the thermostatic valve 10. This is the basis for the control of the heating of the Expansion element of the thermostatic valve in constructive very simple and therefore very inexpensive way a simple temperature switch, preferably one Two-point temperature switch can be done. It is with it not required, different company and / or environmental sizes of the internal combustion engine 1 to detect and in an expensive electronic control unit for control heating of the expansion element of the thermostatic valve 10 to process.

In Fig. 2 above is the coolant temperature in a diagram T over time t at full load of the internal combustion engine 1 (Fig. 1) shown as it is by means of the invention Cooling system can be reached. The expansion element the thermostatic valve 10 (Fig. 1) is for example due to the composition of the expansion material designed upper working limit temperature, for example here a cooling temperature of approx. 105 ° C in the regulated Mixed operation corresponds. This coolant temperature of approx. 105 ° C is only possible in partial load operation of the internal combustion engine, where it is appropriate is, by reducing friction, fuel consumption to reduce and at the same time the exhaust gas composition to improve. Basically, the coolant temperature to optimize consumption always as hot as possible but with performance requirements in the full load range as cool as possible to improve cylinder filling be.

The expansion element of the thermostatic valve 10 is designed so that the possible adjustment path of the thermostatic valve or the maximum possible opening cross section is not yet set at about 105 ° C. Thus, at full load of the internal combustion engine, the expansion element of the thermostatic valve 10 (FIG. 1) can be heated in such a way that a maximum opening cross-section to the cooler is set in order to reduce the coolant temperature as quickly as possible, thereby completely switching to cooler operation. The full load operation is detected in the cooling system according to the invention by the temperature switch in the form of the two-point switch 11 (FIG. 1). If, due to a heavy load on the internal combustion engine, the coolant temperature at or in the vicinity of the radiator outlet 7 (FIG. 1), as shown in FIG. 2 above at point A, exceeds the critical upper temperature threshold of 65 ° C. and thus the upper switching point, we will Shown in FIG. 2 below, at time t _1, the heating voltage U for heating the expansion element of the thermostatic valve 10 is applied to the heating element of the expansion element until the temperature of the coolant at or near the cooler outlet 7 (FIG. 1) is the one shown in FIG 2. The lower temperature threshold of 60 ° C. shown above and thus the lower switching point of the temperature switch 11 are reached. Then, as shown in FIG. 2 below, the heating of the expansion element of the thermostatic valve 10 (FIG. 1) is interrupted again at the time t ₂ , ie after a period of time Δ t. This has the consequence that the coolant temperature at or in the vicinity of the radiator outlet 7 (FIG. 1) slowly rises again until the upper temperature threshold of 65 ° C. is reached again, and the time switch 11 (FIG. 1) when it reaches it Upper switching point, the voltage U is again applied to the heating element for heating the expansion element of the thermostatic valve 10 (FIG. 1).

The cooling system according to the invention is based on the knowledge that that the coolant temperature at or near the Output 7 of the cooler 2 in a very good approximation represents for the load of the internal combustion engine 1. This finding is in the cooling system according to the invention used in that on or in the immediate vicinity the output 7 of the cooler 2, a temperature switch in Form of a two-point switch 11 is provided, which load-dependent heating of the expansion element of the Thermostat valves 10 in full load operation of the internal combustion engine 1 controls. With this simple type of control heating of the expansion element of the thermostatic valve 10 can rely on the cost-intensive recording of the operating and environmental variables of the internal combustion engine 1 and also dispenses with an expensive electronic control unit will. The cooling system according to the invention is suitable therefore especially for motor vehicles of the lower Price segment.

Claims (1)

1. A cooling system for an engine of a motor vehicle comprising a radiator and a thermostat valve by means of which the temperature of the coolant is adjustable in warming-up operation, mixed operation and radiator operation, wherein the thermostat valve contains an expandable-material element which can be electrically heated to reduce the coolant temperature,
   characterised in that the expandable-material element is designed so that the coolant temperature is set at an upper limiting working temperature during mixed operation without heating the expandable-material element and a temperature switch (11) is provided and, in dependence on the coolant temperature (T) measured at or near the radiator outlet (7), releases the heating of the expandable-material element when required in order to displace the mode of operation of the cooling system towards radiator operation, wherein the temperature switch (11) is a two-point switch having an upper switching point in the range from 55°C to 75°C, preferably at about 65°C and a lower switching point not less than 5°C and not more than 50°C below the upper switching point.

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