DE102005045499A1 - Coolant circuit for internal combustion engine and method for its control, comprise use of threshold values for coolant temperature - Google Patents

Abstract

The coolant circuit (1) comprises a thermostat (7), sensors for the determination of the temperature (18,19,20) of the coolant at the outlet of the radiator (KAT) or the engine (MAT) and a control device (8) opening and closing the valve (7). The environmental temperature is additionally determined by the temperature sensors (18,19,20). The temperature at the engine outlet (MAT) and/or the outlet of the radiator (KAT) is compared with predetermined upper and lower threshold values by the control device (8) and the thermostat (7) opened or closed as required. An independent claim is given for a method for the control of the coolant circuit.

Description

The The invention relates to a coolant circuit according to the generic term the claims 1 or 2 and a method for controlling a coolant flow through a coolant circuit an internal combustion engine according to the preamble the claims 10 or 11.

Coolant circuits for internal combustion engines Of motor vehicles are usually designed so that they are next to a cooler branch with a stream of wind cooler a bypass branch, through which the coolant after the start of the Internal combustion engine to be passed bypassing the radiator can order for a faster warming the internal combustion engine and thus during cold start or warm-up for lower pollutant emissions and lower fuel consumption. For controlling of the coolant flow through the cooler branch or the bypass branch is in the cooler branch usually a thermostatic valve provided at low coolant temperatures is closed and open is when the coolant temperature exceeds a predetermined value. When opening the thermostatic valve hits the hot, from the internal combustion engine in the cooler flowing cooling water on the cold radiator pipes, have the ambient temperature. This will be there in particular causes high local temperature differences at low ambient temperatures, which in turn leads to thermal stress in the radiator pipes to lead. A resulting different length expansion of individual radiator tubes may be the worst Case cracks in the radiator have as a consequence. The same problems are especially with coolant circuits with a controllable thermostatic valve to watch where the internal combustion engine to avoid heat loss and to increase the efficiency at partial load with higher cooling water temperatures operated, which favor the occurrence of thermal stresses.

From the DE 196 21 674 C2 a coolant circuit for an internal combustion engine of the aforementioned type with a controllable thermostatic valve is already known, with which the amount of coolant flowing through the radiator is controlled. The coolant circuit there still contains an additional heat storage branch, which is opened or closed by a control unit in dependence on the coolant temperature.

The Coolant temperature can there when entering the internal combustion engine or at the exit be determined from the same.

Next discloses the DE 103 16 017 A1 a method for controlling and / or regulating a cooling system of an internal combustion engine, wherein the mixing ratio between a radiator branch and a bypass branch of the cooling system is adjusted by an expansion-operated thermostatic valve in dependence on the coolant temperature. The coolant temperature is measured there both at the entrance to the engine and at the exit from the same.

From the DE 103 11 188 A1 Furthermore, a method and a device for demand-driven cooling of internal combustion engines is known in which a thermostat between a bypass branch and a cooler branch of a coolant circuit opens the cooler branch more and more from a certain operating temperature and thereby keeps the coolant inlet temperature to the engine approximately constant.

outgoing This is the object of the invention, an optimized Control strategy for a Map cooling with a coolant circuit the to provide the type mentioned above, with no harm the thermodynamic benefits thermal stresses in the cooler and in the internal combustion engine and thus in particular the burden of cooler minimize.

These Task is done according to a first variant of the invention achieved in that the ambient temperature as well as the engine outlet temperature and the radiator outlet temperature of the refrigerant be measured so that the measured engine outlet temperature with one set as a function of the measured ambient temperature Lower and / or upper limit the engine outlet temperature and / or the measured radiator outlet temperature with a fixed as a function of the measured ambient temperature Lower limit of the radiator outlet temperature be compared, and that the thermostatic valve is opened or closed if at least one of these limits is exceeded or is fallen short of.

A second variant of the invention, on the other hand, provides that only the ambient temperature is measured, while the engine exhaust temperature (MAT) and coolant exit temperature (KAT) are calculated or predicted from temperature models, for example, by calculating or predicting the calculated or predicted engine exit temperature (MAT) the lower and / or upper limits of the engine outlet temperature (MAT) and / or the calculated or predicted radiator outlet temperature (KAT) with one as a function of the measured ambient temperature lower limit of the radiator outlet temperature (KAT) determined in the measured ambient temperature, and that the thermostatic valve ( 7 ) is opened or closed if at least one of these limits is exceeded or fallen short of.

Around to allow a stable regulation and to avoid fluttering of the thermostatic valve when the measured or calculated engine entry or engine exit temperature respective upper or lower limit alternating at short intervals from above and from below are used for the specified upper and lower Lower limits also hysteresis bands provided, that is different switching points when approaching from above or below to the respective border.

A preferred embodiment of the invention provides that the at Start of the engine closed thermostatic valve from the controller open when the lower limit of the engine outlet temperature is one exceeded predetermined temperature becomes.

In the subsequent Warm-up phase of the engine is the thermostatic valve according to a further preferred embodiment of the invention closed when the lower limit of the engine outlet temperature is exceeded, and will be opened again, when the upper limit of the engine outlet temperature is exceeded becomes.

A Yet another preferred embodiment of the invention provides that the thermostatic valve is open is when either the lower limit of the radiator outlet temperature falls below or exceeded the upper limit of the engine outlet temperature becomes.

If due to a driving style, an extreme ambient temperature or Like the lower limits of the radiator outlet temperature and the engine outlet temperature simultaneously over a predetermined period of time be fallen below, the thermostatic valve is closed properly and only open again, when the lower limit of the engine outlet temperature by a predetermined Temperature exceeded becomes.

As in known maps regulations, the thermostatic valve is also dependent on from the speed and the load of the internal combustion engine according to maps controlled in which the dependency the engine exit temperature of the engine speed and the engine load considered is.

in the The following is the invention with reference to an illustrated in the drawing embodiment explained in more detail. It demonstrate:

1 a schematic representation of a coolant circuit of an internal combustion engine;

2 a representation of coolant temperature limits as a function of the ambient temperature at an engine load of less than, for example, 60% of full load;

3 a representation of coolant temperature limits as a function of the ambient temperature at an engine load of more than, for example, 60% of full load.

The In 1 illustrated coolant circuit 1 an internal combustion engine 2 of a motor vehicle is flowed through in a known manner by a coolant, usually cooling water. The at 3 from the internal combustion engine 2 Exiting heated coolant flows through a pipe 4 in a cooler branch 5 or a bypass branch 6 , wherein the amount of the through the cooler branch 5 or the bypass branch 6 directed coolant by means of a controllable thermostatic valve 7 is changed as needed. The thermostatic valve 7 is from a control unit 8th controlled, for example, an engine control unit of the motor vehicle. The radiator branch 5 includes one with a blower 9 provided by ambient air flowed cooler 10 from which the cooled coolant passes through a pipe 11 to the internal combustion engine 2 flows back into it at 12 re-enters. The bypass branch 6 flows, bypassing the radiator 10 also in the line 11 , The coolant circuit 1 further includes a heating branch 13 with a heating valve 14 and one with a fan 15 provided heating heat exchanger 16 for heating a passenger compartment of the vehicle by opening the heating valve 14 with hot, at 23 out of the engine 2 exiting coolant can be applied. After passing through the heating branch 13 The coolant is also at 12 in the internal combustion engine 2 returned. Before entering the internal combustion engine 2 the coolant flows through a coolant pump 17 , which is used to circulate the coolant through the coolant circuit 1 serves. The coolant circuit 1 also contains two temperature sensors 18 and 19 of which one 18 between the internal combustion engine 2 and the thermostatic valve 7 is arranged and at 3 the engine outlet temperature MAT measures, that is the temperature of the engine 2 escaping hot coolant while the other 19 behind the radiator 10 is arranged and at 24 the radiator outlet temperature KAT measures, that is the temperature of the radiator 10 exiting cooled coolant. The two temperature sensors 18 and 19 , another, anywhere, for example, near the radiator 10 , vehicle mounted temperature sensor 20 to Measurement of the ambient temperature and the adjustable thermostatic valve 7 are via signal lines 21 with the control unit 8th connected.

The thermostatic valve 7 is at the start of the internal combustion engine 2 closed for faster heating of the cold engine 2 to ensure lower pollutant emissions and lower fuel consumption. If at the end of the starting phase of the engine 2 the thermostatic valve 7 is opened, this flows out of the engine 2 escaping coolant into the radiator 10 what at a high engine outlet temperature MAT when the coolant hits the ambient temperature having individual radiator tubes 22 the radiator 10 due to the large temperature difference to significant local thermal stresses and a different linear expansion of individual radiator tubes 22 in the cooler 10 lead and in the worst case cracks in the radiator 10 can result. The same applies if the thermostatic valve 7 is opened after the internal combustion engine 2 previously by closing the thermostatic valve 7 operated at partial load with higher coolant temperatures to avoid heat loss and increase its efficiency.

As a remedy, an optimized control strategy is now described, with the thermal stresses in the radiator 10 and thus the burden of the radiator 10 without compromising on the thermodynamic benefits of the system. To carry out this optimized control strategy, the engine outlet temperature MAT of the engine 2 Upper limits and lower limits and for the radiator outlet temperature KAT lower limits depending on the respective ambient temperature set and these limits in the control unit 8th stored in the form of maps, of which in 2 and 3 two are shown by way of example. The maps are in later operation of the internal combustion engine 2 together with those from the temperature sensors 18 . 19 and 20 measured actual temperatures of the engine outlet temperature MAT, the radiator outlet temperature KAT and the ambient temperature for controlling the thermostatic valve 7 used. In this case, the dependence of the engine outlet temperature MAT of the engine load and the engine speed is taken into account by different maps, as in 2 and 3 for an engine load of less than 60% of full load or more than 60% of full load exemplified.

As can be seen from the exemplary illustration in 2 It can be seen, increase at an engine load of less than 60% of full load both the upper limit and the lower limit of the engine outlet temperature MAT and the lower limit of the radiator outlet temperature with increasing ambient temperature, but they have a slightly different profile over the ambient temperature. As a result, the differences between the upper limit of the engine exit temperature MAT, the lower limit of the engine exit temperature MAT, and the lower limit of the radiator exit temperature KAT also vary with the ambient temperature.

As from the also exemplary representation in 3 can be seen, however, have at an engine load of more than 60% of the full load, the upper limit of the engine outlet temperature MAT and the lower limit of the radiator outlet temperature KAT a substantially independent of the ambient temperature constant course, while the lower limit of the engine outlet temperature MAT between -25 ° C and + 20 ° C recorded a slight increase, but smaller than the corresponding increase in 2 is. Next are in 3 the absolute values of the upper limit of the engine outlet temperature MAT, the lower limit of the engine outlet temperature MAT and the lower limit of the radiator outlet temperature KAT are slightly lower than in 2 and the difference between the upper and lower limits of the engine outlet temperature MAT on the one hand and the lower limit of the radiator outlet temperature KAT on the other hand, slightly lower.

ever as required the upper and lower limits of the engine outlet temperature MAT and the Lower limit of the radiator outlet temperature KAT also changed course have the ambient temperature.

During operation of the motor vehicle, the control unit compares 8th that of the temperature sensor 18 measured respective actual engine outlet temperature MAT or that of the temperature sensor 19 measured respective actual radiator outlet temperature KAT with the upper and / or lower limit of the engine outlet temperature MAT or with the lower limit of the radiator outlet temperature KAT, in the associated map of the instantaneous engine load and engine speed for that of the temperature sensor 20 measured actual ambient temperature are stored and changes the setting of the thermostatic valve 7 if any of the following conditions are met:
If, for example, in a starting phase of the internal combustion engine 2 the lower limit of the engine outlet temperature MAT is exceeded by a predetermined temperature value, the thermostatic valve 7 opened, since this means the end of the start phase.

When in a warm-up phase of the internal combustion engine 2 the lower limit of the engine outlet temperature MAT is undershot, the thermostatic valve 7 closed and the coolant through the bypass branch 6 to increase the engine temperature faster. If at the end of the warm-up phase exceeds the upper limit of the engine outlet temperature MAT, the thermostatic valve 7 re-opened to a portion of the coolant through the radiator branch 5 to lead.

When driving the motor vehicle, ie in normal operation of the internal combustion engine 2 , is the thermostatic valve 7 only open if either the lower limit of the radiator outlet temperature KAT is exceeded or the upper limit of the engine outlet temperature MAT is exceeded.

If, due to the driving mode or an extreme ambient temperature, the lower limit of the engine outlet temperature MAT and the lower limit of the radiator outlet temperature KAT are simultaneously undershot for a predetermined period of time, for example a few seconds, the thermostatic valve becomes 7 closed until the lower limit of the engine outlet temperature MAT is exceeded by a predetermined temperature value.

Around to enable a stable regulation for the Upper and lower limits of the engine outlet temperature MAT as well for the Lower limits of the radiator outlet temperature KAT also hysteresis bands provided, i. slightly different switching points when approaching these boundaries from above or from below.

1

Coolant circuit

2

internal combustion engine

3

Coolant outlet

4

Coolant line

5

cooler branch

6

bypass branch

7

thermostatic valve

8th

control unit

9

fan

10

cooler

11

Coolant line

12

Coolant inlet

13

Heating branch

14

Heating valve

15

fan

16

HeizungswärKATauscher

17

Coolant pump

18

temperature sensor

19

temperature sensor

20

temperature sensor

21

signal lines

22

cooler tubes

23

Coolant outlet Heating branch

MAT

Motor outlet temperature

KAT

Cooler outlet temperature

24

Radiator outlet

Claims (18)

Coolant circuit for an internal combustion engine, with a flow of the coolant through a radiator controlling adjustable thermostat valve, a temperature measuring device for measuring a radiator outlet temperature or engine outlet temperature of the coolant, and a control device for opening and closing of the thermostatic valve in dependence on the temperature measured by the temperature measuring device temperature, characterized characterized in that the temperature measuring device measures the ambient temperature and the engine outlet temperature (MAT) and the radiator outlet temperature (KAT) of the coolant, and that the control device ( 8th ) compares the measured engine exit temperature (MAT) with a lower and / or upper engine exhaust temperature limit (MAT) and / or the measured radiator exit temperature (KAT) with a lower radiator outlet temperature (KAT) limit determined as a function of the measured ambient temperature and the thermostatic valve ( 7 ) opens or closes if at least one of these limits is exceeded or fallen short of. Coolant circuit for an internal combustion engine, comprising a controllable thermostatic valve controlling the flow of coolant through a radiator and a control device for opening or closing the thermostatic valve, characterized in that the control device ( 8th ) compares a calculated engine exit temperature (MAT) with a lower and / or upper engine exhaust temperature limit (MAT) determined as a function of the measured ambient temperature and / or a calculated radiator exit temperature (KAT) with a lower limit radiator exit temperature (KAT) determined as a function of the measured ambient temperature and the thermostatic valve ( 7 ) opens or closes if at least one of these limits is exceeded or fallen short of. Coolant circuit according to claim 1 or 2, characterized in that the control device ( 8th ) at the start of the internal combustion engine ( 2 ) closed thermostatic valve ( 7 ) opens when the lower limit of the engine outlet temperature (MAT) is exceeded by a predetermined temperature. Coolant circuit according to one of claims 1 to 3, characterized in that the control device ( 8th ) the thermostatic valve ( 7 ) in a warm-up phase of the internal combustion engine ( 2 ) closes when the lower limit of the engine outlet temperature (MAT) is exceeded. Coolant circuit according to claim 4, characterized in that the control device ( 8th ) the thermostatic valve ( 7 ) in the warm-up phase again opens when the upper limit of the engine outlet temperature (MAT) is exceeded. Coolant circuit according to one of the preceding claims, characterized in that the control device ( 8th ) the thermostatic valve ( 7 ) when driving, when either the lower limit of the radiator outlet temperature (CAT) is exceeded or the upper limit of the engine outlet temperature (MAT) is exceeded. Coolant circuit according to one of the preceding claims, characterized in that the control device ( 8th ) the thermostatic valve ( 7 ) closes when at the same time the lower limits of the radiator outlet temperature (KAT) and the engine outlet temperature (MAT) are exceeded for a predetermined period of time. Coolant circuit according to claim 7, characterized in that the control device ( 8th ) the thermostatic valve ( 7 ) closes until the lower limit of the engine outlet temperature (MAT) is exceeded by a predetermined temperature. Coolant circuit according to one of the preceding claims, characterized in that the control device ( 8th ) when opening and closing the thermostatic valve ( 7 ) the dependence of the engine outlet temperature (MAT) on the speed and the load of the internal combustion engine ( 2 ) taken into account by a map control. A method for controlling a coolant flow through a coolant circuit of an internal combustion engine with a radiator and a controllable thermostatic valve, characterized in that the ambient temperature and the engine outlet temperature (MAT) and the radiator outlet temperature (KAT) of the coolant are measured that the measured engine outlet temperature (MAT) with a and / or upper limit of engine outlet temperature (MAT) and / or measured radiator outlet temperature (KAT) with a lower limit of radiator outlet temperature (KAT) determined as a function of the ambient temperature measured, and that the thermostatic valve ( 7 ) is opened or closed if at least one of these limits is exceeded or fallen short of. Method for controlling a coolant flow through a coolant circuit of an internal combustion engine with a radiator and a controllable thermostatic valve, characterized in that the ambient temperature is measured, that the engine outlet temperature (MAT) and the radiator outlet temperature (KAT) of the coolant are calculated or predicted that the calculated or predicted engine exit temperature (MAT) with a lower and / or upper engine exhaust temperature limit (MAT) and / or the calculated or predicted radiator exit temperature (KAT) with a lower radiator exit temperature (KAT) lower ambient air temperature limit be compared and that the thermostatic valve ( 7 ) is opened or closed if at least one of these limits is exceeded or fallen short of. A method according to claim 10 or 11, characterized in that the thermostatic valve ( 7 ) at the start of the internal combustion engine ( 2 ) is closed and is opened when the lower limit of the engine outlet temperature (MAT) is exceeded by a predetermined value. Method according to one of claims 10 to 12, characterized in that the thermostatic valve ( 7 ) in a warm-up phase of the internal combustion engine ( 2 ) is closed when the lower limit of the motor outlet temperature (MAT) is exceeded. A method according to claim 13, characterized in that the thermostatic valve ( 7 ) in the warm-up phase of the internal combustion engine ( 2 ) is reopened when the upper limit of the engine outlet temperature (MAT) is exceeded. Method according to one of claims 10 to 14, characterized in that the thermostatic valve ( 7 ) is opened while driving, if either the lower limit of the radiator outlet temperature (CAT) is undershot or the upper limit of the engine outlet temperature (MAT) is exceeded. Method according to one of claims 10 to 15, characterized in that the thermostatic valve ( 7 ) is closed, if at the same time the lower limits of the radiator outlet temperature (KAT) and the engine outlet temperature (MAT) are exceeded for a predetermined period of time. Method according to claim 16, characterized in that that the thermostatic valve is kept closed until the lower limit of the engine exit temperature (MAT) by a predetermined Temperature exceeded becomes. Method according to one of claims 10 to 17, characterized in that when opening and closing the thermostatic valve ( 7 ) the dependence of the engine outlet temperature (MAT) on the speed and the load of the internal combustion engine ( 2 ) is taken into account by a map control.