EP1497540A1

EP1497540A1 - Method for controlling and/or regulating a cooling system for an internal combustion engine of a motor vehicle

Info

Publication number: EP1497540A1
Application number: EP03746236A
Authority: EP
Inventors: Karsten Mann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-04-15
Filing date: 2003-04-11
Publication date: 2005-01-19
Anticipated expiration: 2023-04-11
Also published as: EP1497540B1; DE50310574D1; WO2003087552A1

Abstract

The invention relates to a method for controlling and/or regulating a cooling system for an internal combustion engine (1) of a motor vehicle. According to said method, a coolant is circulated by a coolant pump (5) and the coolant flows outside the internal combustion engine (1) at least through one radiator branch (3a, 7a, 7b, 8, 9) and one bypass branch (3b, 4a, 4b). The invention also relates to the control and/or regulation of a cooling system for an internal combustion engine (1) of a motor vehicle, comprising a coolant pump (5) for circulating a coolant and 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).

Description

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

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 cooler branch and a bypass branch through which coolant can flow outside the internal combustion engine.

A cooling circuit for an internal combustion engine of a motor vehicle includes in the

Usually 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 above the heat source depends on the heat input and the size of the coolant flow, while the absolute temperature of the coolant is determined by the heat input from the heat source, the heat dissipation via coolers in the circuit and the heat capacities of the materials.

At present, mechanical water pumps are used in motor cooling systems of motor vehicles, which are driven by the crankshaft of the engine via V-belts. The pumps are dimensioned so that even in the most critical operating conditions, For example, when driving uphill at high speed, high load and low vehicle speed, there is no impermissibly high engine temperature or temperature difference above the engine. The mixing ratio between the bypass branch and the cooler branch is set by an expansion-operated thermostatic valve depending on the coolant temperature. The thermostatic valve is dimensioned in such a way that there is no impermissibly high coolant temperature.

In order to achieve more efficient heat management in the cooling system of an internal combustion engine for a motor vehicle, there is, for. B. the possibility of a needs-based control or regulation of the engine cooling system with the aim of reducing fuel consumption and emissions or to comply with exhaust gas limit values and also to increase comfort. Critical limits of component loading must not be exceeded. A particularly critical component is z. B. the cylinder head temperature. These goals can be achieved by optimizing the coolant flow and load-dependent control of the engine temperature level.

An alternative that allows the coolant flow to be adjusted as required provides an electrically controllable water pump, which has the disadvantage, however, that on the one hand it is significantly more expensive than a mechanical water pump and on the other hand in pump systems with 12V voltage it does not have the required pumping capacity More can be realized.

From SAE Technical Paper Series 961813 by Jilian Yangg from 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 in exhaust gas and consumption values, the author proposes to throttle the coolant flow of the coolant pump. Two different versions are proposed for this. On the one hand, the author suggests that a throttle plate be inserted in the bypass branch of the cooling system. On the other hand, the author suggests installing a throttle valve directly at the pump outlet. In the first alternative, the coolant flow can be can be regulated by branch, while in the second alternative the total coolant flow of the cooling system can be regulated.

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, in which a coolant is circulated by a coolant pump, in which the coolant flows outside of the internal combustion engine at least through a cooler branch and through a bypass branch and in which control means and / or regulating means throttling a coolant flow through the cooler branch and of a coolant flow through the bypass branch is carried out independently of one another.

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

One measure provides that a desired temperature of the coolant is set by means of a predeterminable activation of the control and / or regulating means. Through this development, the method according to the invention is used to set a coolant target temperature in a particularly flexible manner.

Another development provides that a predeterminable total coolant flow is set by means of the control and / or regulating means. The method according to the invention also makes it possible for a predeterminable mixing ratio of the coolant flows through the cooler and bypass branch to be set independently of the boundary condition of the predetermined total coolant flow by means of the control and / or regulating means. In other words, it is possible to simultaneously set a specific total coolant flow and a mixing ratio of the coolant flows between the cooler and the bypass branches. (The mixing ratio is the manipulated variable 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, with a coolant pump for

Circulating a coolant and with at least one cooler branch and a bypass branch, through which coolant can flow outside the internal combustion engine, the control and / or regulating means being designed to independently throttle a coolant flow through the cooler branch and a coolant flow through the bypass branch.

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

Advantageous further developments of the method according to the invention or of the control and / or regulation according to the invention result from the dependent claims and from the following description.

drawing

Figure 1 shows a cooling system according to the prior art, Figure 2 shows a cooling system according to the invention, Figure 3a shows a first embodiment of a method according to the invention, Figure 3b shows the same exemplary embodiment in a different representation, Figure 4 shows a hydraulic network according to the invention and FIG. 5 shows an illustration for determining the desired hydraulic resistance in accordance with the invention.

The control 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 if the bypass and the cooler branches are decoupled from one another can be throttled. The throttling of the cooler branch and the bypass branch can be adjusted independently of one another to allow the mixing ratio of the coolant flows through the cooler branch and the bypass branch to be set flexibly. The coolant flow can be adjusted despite the operating point of the mechanical water pump, which is determined by the speed of the internal combustion engine, by changing the total hydraulic resistance of the system. The throttle valves are set in such a way that the desired mixing ratio between the cooler and the bypass branch as well as the desired total hydraulic resistance is set in the system, from which a desired total coolant flow of the cooling system results. A prerequisite for carrying out the method according to the invention is knowledge of the hydraulic resistances of the cooling circuit components and knowledge of the pump characteristic of the mechanical water pump.

Figure 1 shows an example of a conventional cooling system. According to FIG. 1, an internal combustion engine 1 has a coolant flowing through it. The coolant flows out of the internal combustion engine 1 via a line 2 and flows back into the internal combustion engine 1 via a three-way cooler valve 3, a bypass branch 4, a coolant pump 5 and a line 6. Furthermore, part of the coolant flows, starting from the Three-way cooler valve 3, via a line 7 to a cooler 8, from there via a line 9 and also via the coolant pump 5 and line 6 back to the internal combustion engine 1.

At another point, the coolant leaves the internal combustion engine 1 via a line 10 and flows from there via a heater 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 heating heat exchanger 13 and the line 14 form a heating branch.

FIG. 1 also shows three temperature sensors which record the temperatures at specific points in the cooling system. These are the temperature sensor 15 that the

Temperature detected 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 system 8.

Figure 2 shows a cooling system according to the invention. Those parts which correspond to the parts shown in FIG. 1 are each provided with the same reference numerals, and only the difference from FIG. 1 is discussed below. In contrast to Figure 1, the three-way cooler valve 3 shown there is replaced by two separate valves 3 a and 3 b. Here, a cooler valve 3 a is inserted into line 7, whereby line 7 is divided into two sub-lines 7 a and 7 b. In the line 4, a bypass valve 3 b was used, whereby the line 4 is divided into the parts 4a and 4b. The cooler valve 3, the sub-lines 7a, 7b, the cooler 8 and the line 9 form a cooler branch. The bypass valve 3 and the sub-lines 4a, 4b form a bypass branch.

By using two separate valves 3 a and 3 b according to the invention, the target mixing ratio and the total target coolant flow can be set. If necessary, it must be assumed that all other branches that short-circuit the coolant pump 5 can also be disconnected, such as the heating branch 10-14. On the determination of the target mixing ratio between the cooler branch 3, 7a, 7b, 8, 9 and the bypass branch 3b, 4a, 4b and on the determination of the

Total coolant flow through the entire cooling system is not further discussed in the context of this invention, since this is of no importance for the essence of the invention and this data can be determined in a separate thermal management process control.

FIG. 3 a shows a first exemplary embodiment of the method according to the invention. This shows schematically how the corresponding positions of the two valves 3a and 3b according to FIG. 2 are determined from the target mixing ratio and the total target coolant flow.

First, the operating point of the coolant pump 5 is determined as a function of the 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 map 31. This desired hydraulic system resistance R and a desired mixing ratio MV are the inputs of the second and third characteristic Fields 32, 33. The cooler valve 3a is activated from the second characteristic diagram 32 and the bypass valve 3b from the third characteristic diagram 33. Accordingly, signals are obtained from the two characteristic diagrams 32, 33, which correspond to the desired positions of the valves 3a, 3b.

The control of the valves 3 a and 3 b according to the invention is thus achieved by the corresponding connection of the three characteristic diagrams 31, 32, 33. Alternatively, two three-dimensional maps can be used instead of the three two-dimensional maps 31, 32, 33.

Figure 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 speed n of internal combustion engine 1 are recorded. Based on these input data, the total hydraulic resistance R of the cooling system is determined in a step 35 by means of the total target coolant flow Vp and the speed n.

This total hydraulic resistance R is transmitted to step 36, in which, based on the target mixing ratio MV and the total target coolant flow Vp, control variables for the cooler valve 3a and the bypass valve 3b are determined. In the final step 37, the cooler valve 3a and the bypass valve 3b are finally activated accordingly.

The first characteristic diagram 31 for determining the desired hydraulic resistance R and optionally the second and third characteristic diagrams 32, 33 can be generated automatically when the internal combustion engine is applied. Here, the characteristic diagram of the coolant pump 5 must be known, which specifies the pressure difference over the pump dependency of the coolant flow and the pump or internal combustion engine speed. Furthermore, the hydraulic resistances of the components should be known if necessary. In the case of the pump map, a hydraulic resistance can clearly be found for each pair of data from the coolant flow and speed. To determine the maps 32, 33 in the respective map depending on the desired

Mixing ratio and the desired hydraulic resistance the respective valve or. Throttle body position be stored. The data of the characteristic diagrams 32, 33 are strongly coupled to one another, since the mixing ratio and, depending on the working point, also the hydraulic resistance of the cooling system strongly depend on the valve position of each individual valve 3a, 3b or on the position of each throttle body. Assuming turbulent flow, the pressure drop is approximately proportional to the square of the coolant flow. Analogous to electrical engineering, a hydraulic equivalent resistance R of the cooling system can be determined for all valve positions using a hydraulic network, provided 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. 4. The individual resistances of the components add up to the total resistance analogously to an electrical circuit. This results in the system characteristic. The desired total coolant flow of the cooling system through the coolant pump 5 then results from the intersection of the pump characteristic curve with the system characteristic curve.

4 shows in detail: 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 cooler valve 3a and the hydraulic resistance 47 of the rest of the cooler branch 7a, 7b, 8, 9 without the cooler valve 3a. In this case, the hydraulic resistors 44, 45 of the bypass valve 3b and the remaining bypass branch 4a, 4b are connected in series. This series connection is in turn connected in parallel to the series connection of hydraulic resistor 46 of cooler valve 3 a and hydraulic resistor 47 of the remaining cooler branch 7a, 7, 8, 9. The parallel connection of hydraulic resistors 44, 45 on the one hand and 46, 47 on the other hand is in turn connected in series to the hydraulic resistance 43 of the cylinder head of the internal combustion engine 1. The series connection of the hydraulic resistors thus created is in turn connected in parallel to the hydraulic resistance 42 of the heating branch 10-14. The circuit of the hydraulic resistors 42-47 so far is in turn connected in series with the hydraulic resistor 41 of the internal combustion engine 1. Overall, the total hydraulic resistance of the cooling system results from the series and parallel connection of the hydraulic resistors 41-47 shown in FIG. In addition, from the parallel connection of the series connections of the hydraulic resistors 44, 45 and 46, 47, the ratio of the flow through the bypass and cooler branches 3b, 4a, 4b; 3 a, 7a, 7b, 8, 9 and thus the mixing ratio. Figure 5 shows characteristic curves for determining the desired hydraulic resistance. 5 shows coolant flows Vp on the horizontal axis, while pressure differences dp are shown on the vertical axis. Pump characteristics 51, 52, 53 are shown for the speeds nl, n2 and n3 (nl>n2> n3). Also shown is a system characteristic curve 54 which (in the case of turbulent flow) results from the multiplication of the hydraulic resistance R by the square of the coolant flow Vp. Mathematically, the system characteristic curve 54 thus represents a parabola, the pressure difference dp being a function of the square of the coolant flow Vp, the square of the coolant flow Vp being linked to the hydraulic resistance R as a factor.

As the hydraulic resistance R decreases, the slope of the system characteristic 54 thus becomes smaller and ultimately results in a system-related minimum hydraulic resistance R sys min, the dependence on the coolant flow Vp of which is given the reference number 55. If, on the other hand, the hydraulic resistance R increases, the system characteristic 54 increases, and the system characteristic 54 would shift further in the direction of the vertical axis. Knowing the current speed n of the internal combustion engine 1 and a desired total coolant flow Vp, it is thus possible to determine the desired system characteristic from the intersection of the coolant flow Vp sought with the corresponding pump characteristic 51-53, from which the sought hydraulic resistance R can be determined. For example, in the illustration according to FIG. 5, the intersection points 56, 57 and 58 are shown for the coolant flows Vpl, Vp2, Vp3 with the corresponding pump characteristic curve 51-53. The system characteristic curve 54 results from these intersection points 56-58, as a result of which the sought hydraulic resistance R can be inferred.

The method according to the invention shown can be integrated, for example, in a control unit of a motor vehicle, which additionally takes on the task of controlling internal combustion engine 1, for example. The functional relationships shown can include e.g. B. can be represented by corresponding mathematical functions, a multi-dimensional map or by several maps in the engine control unit. All in all, there is a particularly flexible and exact possibility of independently controlling coolant flows Vp and mixing ratios between cooler branch 3a, 7a, 7b, 8, 9 and bypass branch 3b, 4a, 4b, which enables simple, possibly computer-aided or automated applicability. The for the application The required data are easy to measure, but should also be known or made known as part of the cooling system dimensioning from the vehicle manufacturer or from the component supplier.

Claims

Expectations

1. A 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 outside the internal combustion engine (1) at least through a cooler branch (3a, 7a, 7b, 8, 9) and through a bypass branch

(3b, 4a, 4b) flows, characterized in that with control and / or regulating means a throttling of a coolant flow through the cooler branch (3a, 7a, 7b, 8, 9) and a coolant flow through the bypass branch (3 b, 4a, 4b) is carried out independently of one another.

2. The method according to claim 1, characterized in that a temperature of the coolant is set by means of a predeterminable control of the control and / or regulating means.

3. The method according to claim 1 or 2, characterized in that a predetermined total coolant flow (Vp) of the coolant is set by means of the control and / or regulating means.

4. The method according to claim 3, characterized in that by means of the control and / or regulating means by a predetermined mixing ratio of the coolant flows

Cooler and bypass branch (3a, 7a, 7b, 8, 9; 3b, 4a, 4b) is set.

5. The method according to 4, characterized in that at least from the predetermined mixing ratio, the predetermined total coolant flow (Vp) and a speed (n) of the internal combustion engine (1) and / or the coolant pump (5) and / or a position of the heating valve (11) Control variables for the control and / or regulating means are determined.

6. The method according to claim 5, characterized in that a total hydraulic resistance (R) of the cooling system is determined from the predeterminable total coolant flow (Vp) and the speed (s) of the internal combustion engine (1) and / or the coolant pump (5).

7. The method according to claim 5 or 6, characterized in that from characteristic maps (31, 32, 33) control variables for a cooler valve (3a) in the cooler branch (3a, 7a, 7b, 8, 9) and a bypass valve (3b) in the bypass branch (3b, 4a, 4b) can be determined.

8. The method according to claims 6 and 7, characterized in that the maps (31, 32, 33) are stored in a memory at least as a function of the predefinable mixing ratio and the total hydraulic resistance (R) of the cooling system.

9. The method according to claim 6, characterized in that a map (31, 32, 33) is stored in a memory for determining the total hydraulic resistance (R) of the cooling system. ,

10. Control and / or regulation of a cooling system of an internal combustion engine (1)

Motor vehicle, with a coolant pump (5) for circulating a coolant, with at least one cooler branch (3a, 7a, 7b, 8, 9) and a bypass branch (3b, 4a, 4b) through which the coolant can flow outside the internal combustion engine (1) , characterized in that control and / or regulating means for the independent throttling of a coolant flow through the cooler branch (3 a, 7a, 7b, 8, 9) and one

Coolant flow through the bypass branch (3b, 4a, 4b) are provided.