EP1497540B1 - Method for controlling and/or regulating a cooling system for an internal combustion engine of a motor vehicle - Google Patents

Description

State of the art

The invention relates to a method for controlling and / or regulating a cooling system of an internal combustion engine of a motor vehicle, in which a coolant is circulated by a coolant pump and in which the coolant flows outside the internal combustion engine at least through a cooler branch and through a bypass branch.

The invention further relates to a control and / or regulation of a cooling system of an internal combustion engine of a motor vehicle, with a coolant pump for circulating a coolant and with at least one radiator branch and a bypass branch, can flow through the coolant outside of the internal combustion engine.

To a cooling circuit for an internal combustion engine of a motor vehicle usually include a heat source to be cooled (the internal combustion engine), which is cooled by means of a coolant by free or forced convection. The temperature difference across the heat source is dependent on the heat input and the size of the coolant flow, while the absolute temperature of the coolant is determined by the heat input of the heat source, the heat removal via recirculating coolers and the heat capacities of the materials.

Currently motor water cooling systems of motor vehicles use mechanical water pumps which are driven via V-belts by the crankshaft of the engine. The pumps are in this case dimensioned such that even in the most critical operating states, For example, when driving uphill at high speed, high load and low vehicle speed, no unacceptably high engine temperature or temperature difference across the engine arises. The mixing ratio between the bypass branch and the radiator branch is adjusted by means of a worm-operated thermostatic valve as a function of the coolant temperature. The thermostatic valve is dimensioned so that no inadmissibly high coolant temperature is established.

In order to achieve a more efficient thermal management in the cooling system of an internal combustion engine for a motor vehicle, z. B. the possibility of a demand-driven control or regulation of the engine cooling system with the aim to reduce fuel consumption and emissions or to comply with emission limits and also to increase comfort. At the same time, critical limits of the component load must not be exceeded. A particularly critical component here is z. B. the cylinder head temperature. These goals can be achieved by optimizing the coolant flow and load-dependent control of the temperature level of the engine.

An alternative that allows a needs-based adjustment of the coolant flow, provides an electrically controllable water pump, but has the disadvantage that it is significantly more expensive than a mechanical water pump and partly in today's electrical systems with 12V voltage partly the required pump power not without Further feasible.

From the SAE Technical Paper Series 961813 by Jilian Yangg of the Ford Motor Co. entitled "Coolant Pump Throttling - A Simple Method to Improve the Control Over SI Engine Cooling System" by the International Off-Highway & Powerplant Congress & Exposition, Indianapolis , Indiana, August 26-28, 1996, a cooling system for an internal combustion engine of a motor vehicle has become known, in which the pump is designed as a mechanically driven coolant pump. With the aim of improved heating of the combustion chambers after a cold start and an improvement of exhaust gas and consumption values, the author proposes to throttle the coolant flow of the coolant pump. For this purpose, two different embodiments are proposed. On the one hand, the author proposes to use an orifice plate in the bypass branch of the cooling system. On the other hand, the author proposes to install a throttle valve directly on the pump outlet. In the first alternative, the coolant flow in the bypass branch be regulated, while in the second alternative, the total coolant flow of the cooling system can be controlled.

From the DE 40 33 261 A1 is already an internal combustion engine with a coolant line therein, which is traversed by a liquid coolant, known, wherein the coolant line is associated with at least one aid to reduce the coolant mass flow, according to claim 1 or 8, the first part.

The invention has for its object to provide a flexible control and / or regulation of the coolant flows in a cooling system of an internal combustion engine of a motor vehicle.

Advantages of the invention

The object is achieved by a method for controlling and / or regulating a cooling system of an internal combustion engine of a motor vehicle, according to claim 1.

Due to the independent control and / or regulation of the coolant flows through the radiator branch and through the bypass branch, the coolant flows can be given in a particularly flexible manner in the method according to the invention. In particular, it is possible over conventional cooling circuit systems to not only completely interrupt the cooler branch after a cold start in order to achieve faster heating of the internal combustion engine, but additionally the coolant flow through the bypass branch can be throttled in order to achieve even faster heating of the internal combustion engine.

One measure provides that a desired temperature of the coolant is set by means of a presettable actuation of the control and / or regulating means. By this development, the inventive method used to set a coolant target temperature in a particularly flexible manner.

Another development provides that by means of the control and / or regulating means a predeterminable total coolant flow is set.

The method according to the invention furthermore makes it possible, independently of the boundary condition of the predetermined total coolant flow, to set a specifiable mixing ratio of the coolant flows through the radiator and bypass branch by means of the control and / or regulating means. In other words, it is possible to simultaneously set a certain total coolant flow and a mixing ratio of the coolant flows between the radiator and the bypass branch. (The mixing ratio is the control value for motor temperature control).

The object is further achieved by a control and / or regulation of a cooling system of an internal combustion engine of a motor vehicle, having the features according to claim 8.

The control and / or regulation according to the invention has the same advantages as the method according to the invention.

Advantageous developments of the method and the control and / or regulation according to the invention will be apparent from the dependent claims and from the following description.

drawing

• FIG. 1 shows a cooling system according to the prior art, FIG. 2 shows a cooling system according to the invention, FIG. 3a shows a first embodiment of a method according to the invention, FIG. 3b shows the same embodiment in another representation, FIG. 4 shows a hydraulic network according to the invention and FIG. 5 shows a representation for determining the desired hydraulic resistance according to the invention.
• The regulation of the coolant flow (volume flow) and the temperature level in a cooling system of the internal combustion engine is also possible with a conventional mechanical water pump when the bypass and the radiator branch are decoupled from each other can be throttled. Due to the independently possible throttling of the radiator and the bypass branch, the mixing ratio of the coolant flows through the radiator and the bypass branch can be set flexibly. The coolant flow can be adjusted despite the operating point of the mechanical water pump set by the engine speed by changing the overall hydraulic resistance of the system. In this case, the throttle valves are adjusted such that the desired mixing ratio between the cooler and the bypass branch and the desired total hydraulic resistance is set in the system, from which results in a desired total coolant flow of the cooling system. A prerequisite for carrying out the method according to the invention is the knowledge of the hydraulic resistances of the cooling circuit components and the knowledge of the pump characteristic of the mechanical water pump.

FIG. 1 shows an example of a conventional cooling system. Corresponding FIG. 1 an internal combustion engine 1 is traversed by a coolant. The coolant flows out via a line 2 from the internal combustion engine 1 and flows through a three-way radiator valve 3, via a bypass branch 4, a coolant pump 5 and a line 6 back into the internal combustion engine 1. Furthermore, a portion of the coolant, starting from the three-way radiator valve 3, over a line 7 to a radiator 8, from there via a line 9 and also via the coolant pump 5 and line 6 back to the internal combustion engine. 1

Elsewhere, the coolant leaves the internal combustion engine 1 via a line 10 and flows from there via a heating valve 11, a line 12, a heating heat exchanger 13, a line 14, the coolant pump 5 and line 6 back to the internal combustion engine 1. The line 10, the Heating valve 11, the line 12, the Heizungswärmübertrager 13 and the line 14 form a heating branch.

In FIG. 1 Furthermore, three temperature sensors are shown, which detect the temperatures at certain points of the cooling system. These are the temperature sensor 15, which detects the temperature in line 2, the temperature sensor 16, which detects the temperature in line 6, and the temperature sensor 17, which detects the temperature in line 9. The temperature sensor 15 thus detects the temperature at an output of the internal combustion engine 1. The temperature sensor 16 thus detects the temperature at an input of the Internal combustion engine 1, The temperature sensor 17 thus detects the temperature of the coolant at an outlet of the radiator fan 8.

FIG. 2 shows a cooling system according to the invention. Here are those parts with the in FIG. 1 parts shown correspond in each case with the same reference numerals and it will only be the difference to FIG. 1 received. In contrast to FIG. 1 the three-way radiator valve 3 shown there is replaced by two separate valves 3a and 3b. In this case, a cooler valve 3a is inserted into the line 7, whereby the line 7 is divided into two sub-lines 7a and 7b. Into the conduit 4, a bypass valve 3b has been inserted, whereby the conduit 4 is divided into the parts 4a and 4b. The cooler valve 3, the partial lines 7a, 7b, the radiator 8 and the line 9 form a cooler branch. The bypass valve 3 and the sub-lines 4a, 4b form a bypass branch.

By the use according to the invention of two separate valves 3a and 3b, the desired mixing ratio and the total nominal coolant flow can be set. If necessary, it must be assumed in this case that all the other branches short-circuiting the coolant pump 5 can likewise be disconnected, for example the heating branch 10-14. On the determination of the desired mixing ratio between the radiator branch 3, 7a, 7b, 8, 9 and the bypass branch 3b, 4a, 4b as well as on the determination of the total coolant flow through the entire cooling system is not discussed in the context of this invention, since this is not relevant to the essence of the invention and this data can be determined in a separate thermal management process management.

FIG. 3a shows a first embodiment of the method according to the invention. Here, it is shown schematically how from the desired mixing ratio and the total target coolant flow, the corresponding positions of the two valves 3a and 3b after FIG. 2 be determined.

First, the operating point of the coolant pump 5 is determined as a function of the rotational speed n of the internal combustion engine 1, and the desired hydraulic system resistance R is determined as a function of the total target coolant flow Vp by means of a first characteristic map 31. This desired hydraulic system resistance R and a desired mixing ratio MV are the inputs of the second and third maps 32, 33. From the second map 32 out the cooling valve 3a and from the third map 33 out the bypass valve 3b is driven. Accordingly, signals are obtained from the two characteristic diagrams 32, 33 which correspond to the desired positions of the valves 3a, 3b.

By the corresponding interconnection of the three maps 31, 32, 33 so the erfmdungsgemäße actuation of the valves 3a and 3b is achieved. Alternatively, two three-dimensional maps can be used instead of the three two-dimensional maps 31, 32, 33.

FIG. 3b shows the same embodiment in a different representation. In a first step 34, the input variables setpoint mixing ratio MV, total setpoint coolant flow Vp and rotational speed n of the internal combustion engine 1 are detected. Based on these input data, the hydraulic total resistance R of the cooling system is determined in a step 35 by means of the total target coolant flow Vp and the rotational speed n. This total hydraulic resistance R is transmitted to step 36, wherein, based on the desired mixing ratio MV and the total target refrigerant flow Vp drive quantities for the cooling valve 3a and the bypass valve 3b are determined. Finally, in the final step 37, the radiator valve 3a and the bypass valve 3b are activated accordingly.

The first map 31 for determining the desired hydraulic resistance R and optionally the second and third maps 32, 33 can be generated automatically during the application of the internal combustion engine. Here, the map of the coolant pump 5 must be known, which indicates the pressure difference across the pump dependence of the coolant flow and the pump or engine speed. Furthermore, if necessary, the hydraulic resistances of the components should be known. In the case of the pump map, a hydraulic resistance can be clearly found for each data pair of coolant flow and speed. To determine the maps 32, 33, the respective valve or throttle body position must be stored in the respective map depending on the desired mixing ratio and the desired hydraulic resistance. The data of the maps 32, 33 are strongly coupled with each other, since the mixing ratio and, depending on the operating point, and the hydraulic resistance of the cooling system strongly depends on the valve position of each valve 3a, 3b or of the position of each throttle body. Under the assumption of turbulent flow, the pressure drop is approximately proportional to the square of the coolant flow. For all valve positions, a hydraulic equivalent resistance R of the cooling system can be determined by means of a hydraulic network analogous to electrical engineering, as long as the hydraulic resistances of the components and the resistance characteristics of the valves 3a, 3b are known.

An example of such a hydraulic network according to the invention is shown in FIG. The individual resistances of the components add up analogously to an electrical circuit for total resistance. This results in the system characteristic. The sought total coolant flow of the cooling system through the coolant pump 5 then results from the intersection of the pump curve with the system curve.

In detail are in FIG. 4 illustrated: the hydraulic resistance 41 of the internal combustion engine 1, the hydraulic resistance 42 of the heating branch 10-14, the hydraulic resistance 43 of a cylinder head, not shown in detail, contained in the internal combustion engine 1, the hydraulic resistance 44 of the bypass valve 3b, the hydraulic resistance 45 of the bypass branch 4a, 4b without the bypass valve 3b, the hydraulic resistance 46 of the radiator valve 3a and the hydraulic resistance 47 of the remaining radiator branch 7a, 7b, 8, 9 without the radiator valve 3a. Here, the hydraulic resistors 44, 45 of the bypass valve 3b and the remaining bypass branch 4a, 4b are connected in series. This series circuit is in turn connected in parallel to the series circuit of hydraulic resistance 46 of the radiator valve 3a and hydraulic resistor 47 of the remaining radiator branch 7a, 7, 8, 9. The parallel connection of the hydraulic resistors 44, 45 on the one hand and 46, 47 on the other hand, in turn connected in series hydraulic resistance 43 of the cylinder head of the internal combustion engine 1. The thus resulting series connection of the hydraulic resistors is in turn connected in parallel to the hydraulic resistance 42 of the heating branch 10-14. The hitherto present circuit of the hydraulic resistors 42-47 is in turn connected in series with the hydraulic resistance 41 of the internal combustion engine 1. Overall, resulting from the in FIG. 4 shown series and parallel connection of the hydraulic resistors 41-47 of the hydraulic total resistance of the cooling system. In addition, it follows from the parallel connection of the series circuits of the hydraulic resistors 44, 45 and 46, 4 7, the ratio of the flow through the bypass and radiator branch 3b, 4a, 4b; 3a, 7a, 7b, 8, 9 and thus the mixing ratio.

FIG. 5 shows characteristics to determine the desired hydraulic resistance. In FIG. 5 On the horizontal axis coolant flows Vp are shown, while on the vertical axis pressure differences dp are shown. For the rotational speeds n1, n2 and n3 (n1>n2> n3) pump characteristics 51, 52, 53 are respectively shown. Also shown is a system characteristic curve 54 which results (in the case of turbulent flow) from the multiplication of the hydraulic resistance R by the square of the coolant flow Vp. Thus, mathematically, the system characteristic 54 represents a parabola, where the pressure difference dp is a function of the square of the refrigerant flow Vp, where the square of the refrigerant flow Vp is linked to the hydraulic resistance R as a factor.

With decreasing hydraulic resistance R, the slope of the system characteristic curve 54 thus becomes smaller and finally results in a system-dependent minimum hydraulic resistance R sys min, the dependence of which on the coolant flow Vp is provided with the reference number 55. If, on the other hand, the hydraulic resistance R increases, the system characteristic curve 54 will increase in size, and the system characteristic curve 54 would continue to shift in the direction of the vertical axis. Knowing the current speed n of the internal combustion engine 1 and a desired total desired coolant flow Vp can thus be determined from the intersection of the sought coolant flow Vp with the corresponding pump curve 51-53 the desired system characteristic, from which the sought hydraulic resistance R can be determined. For example, in the illustration after FIG. 5 for the coolant flows Vp1, Vp2, Vp3 the points of intersection 56, 57 and 58 are shown with the respective corresponding pump characteristic 51-53. Through these intersections 56-58 results in the system characteristic 54, which can be deduced the sought hydraulic resistance R.

The illustrated method according to the invention can be integrated, for example, in a control unit of a motor vehicle, which additionally assumes, for example, the task of controlling the internal combustion engine 1. The functional relationships shown may, for. B. be represented by corresponding mathematical functions, a multi-dimensional map or by multiple maps in the engine control unit. Overall, a particularly flexible and exact possibility of independent control of coolant flows Vp and mixing ratios between cooler branch 3a, 7a, 7b, 8, 9 and bypass branch 3b, 4a, 4b, whereby a simple, possibly computer-aided or automated applicability is given. The for the application required data are easily measurable, but should also be known or made known in the context of cooling system dimensioning by the vehicle manufacturer or by the component supplier.

Claims (8)

1. Method for controlling and/or regulating a cooling system of an internal combustion engine (1) of a motor vehicle, a coolant being circulated by a coolant pump (5) and the coolant flowing outside the internal combustion engine (1) at least through a radiator branch (3a, 7a, 7b, 8, 9) and through a bypass branch (3b, 4a, 4b),

   - throttling of a coolant flow through the radiator branch (3a, 7a, 7b, 8, 9) and of a coolant flow through the bypass channel (3b, 4a, 4b) being carried out independently of one another by way of control and/or regulating means,

   characterized

   - in that a predefinable overall coolant flow (Vp) of the coolant is set by means of the control and/or regulating means,

   - in that a predefinable mixing ratio of the coolant flows through the radiator and bypass branch (3a, 7a, 7b, 8, 9; 3b, 4a, 4b) is set by means of the control and/or regulating means,

   - in that a hydraulic overall resistance (R) of the cooling system is determined proceeding from the predefinable overall coolant flow V_p, the predefinable mixing ratio (MV) and the rotational speed (n) of the internal combustion engine (1),

   - and actuating variables are determined for the radiator valve (3a, 7a, 7b, 8) and the bypass valve (3b, 4a, 4b).
2. Method according to Claim 1, characterized in that a temperature of the coolant is set by means of predefinable actuation of the control and/or regulating means.
3. Method according to at least one of the preceding claims, characterized in that actuating variables for the control and/or regulating means are determined at least from the predefinable mixing ratio, the predefinable overall coolant flow (V_p) and a rotational speed (n) of the internal combustion engine (1) and/or the coolant pump (5) and/or a position of the heating valve (11).
4. Method according to Claim 3, characterized in that a hydraulic overall resistance (R) of the cooling system is determined from the predefinable overall coolant flow (V_p) and the rotational speed (n) of the internal combustion engine (1) and/or the coolant pump (5).
5. Method according to Claim 3 or 4, characterized in that actuating variables for a radiator valve (3a) in the radiator branch (3a, 7a, 7b, 8, 9) and a bypass valve (3b) in the bypass branch (3b, 4a, 4b) are determined from characteristic diagrams (31, 32, 33).
6. Method according to Claims 4 and 5, characterized in that the characteristic diagrams (31, 32, 33) are stored in a memory at least as a function of the predefinable mixing ratio and the hydraulic overall resistance (R) of the cooling system.
7. Method according to Claim 4, characterized in that a characteristic diagram (31, 32, 33) is stored in a memory in order to determine the hydraulic overall resistance (R) of the cooling system.
8. Control and/or regulation of a cooling system of an internal combustion engine (1) of a motor vehicle, having a coolant pump (5) for circulating a coolant, having at least one radiator branch (3a, 7a, 7b, 8, 9) and one bypass branch (3b, 4a, 4b), through which the coolant can flow outside the internal combustion engine (1),

   - throttling of a coolant flow through the radiator branch (3a, 7a, 7b, 8, 9) and of a coolant flow through the bypass channel (3b, 4a, 4b) being carried out independently of one another by way of control and/or regulating means, characterized in that

   - a predefinable overall coolant flow (Vp) of the coolant is set by means of the control and/or regulating means,

   - a predefinable mixing ratio of the coolant flows through the radiator and bypass branch (3a, 7a, 7b, 8, 9; 3b, 4a, 4b) is set by means of the control and/or regulating means,

   - in that a hydraulic overall resistance (R) of the cooling system is determined proceeding from the predefinable overall coolant flow Vp, the predefinable mixing ratio (MV) and the rotational speed (n) of the internal combustion engine (1),

   - and actuating variables are determined for the radiator valve (3a, 7a, 7b, 8) and the bypass valve (3b, 4a, 4b).

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