EP1718850A1

EP1718850A1 - Method and device for controlling the coolant circuit of an internal combustion engine

Info

Publication number: EP1718850A1
Application number: EP05700532A
Authority: EP
Inventors: Isabelle Gentil-Kreienkamp; Joerg Grothe; Dirk Schoeneberg; Franz Lukas; Rainer Mayer
Original assignee: Robert Bosch GmbH; Audi AG
Current assignee: Robert Bosch GmbH; Audi AG
Priority date: 2004-02-19
Filing date: 2005-01-10
Publication date: 2006-11-08
Also published as: DE102004008170A1; JP4658971B2; JP2007522388A; DE102004008170B4; WO2005080766A1

Abstract

The invention relates to a method and a device for controlling the coolant circuit of an internal combustion engine, said control being achieved by means of a predetermined target temperature. For the warm-up phase, a warm-up target temperature (Tsw), which is higher than the target temperature (Ts), is used temporarily.

Description

Method and device for controlling the cooling circuit of an internal combustion engine

State of the art

The invention relates to a method and a device for controlling the cooling circuit of an internal combustion engine according to the type of the independent claims. Cooling circuits of internal combustion engines are usually regulated to a predetermined target temperatures.

Advantages of the invention

In contrast, the method according to the invention and the device according to the invention have the advantage that an improved warm-up of the internal combustion engine is achieved. In particular, faster heating of the internal combustion engine is ensured during the warm-up operation.

Further developments and improvements result from the features of the dependent claims. The warm-up target temperature is expediently chosen between the target temperature and the boiling point of the coolant in the cooling circuit. The temperature of the internal combustion engine that is present immediately after the internal combustion engine starts can be used to identify the warm-up operation. When the warm-up temperature is reached, the cooling circuit is activated by activating a corresponding control valve or a pump. The volume flow should be slowly increased with a given dependency by the Opening of the valve and / or the pump performance of the pump can be influenced. After reaching the warm-up target temperature, a transition target temperature can also be specified. These measures are used to ensure a smooth, non-overshoot transition to the target temperature after the warm-up target temperature has been reached.

drawings

Embodiments of the invention are shown in the following drawings and explained in more detail in the following description.

Show it

FIG. 1 shows a schematic view of a cooling circuit of an internal combustion engine,

Figure 2 shows the temperature profile with a conventional temperature control in

Warm-up,

Figure 3 shows the temperature profile during warm-up according to the invention and

Figure 4 individual process steps of the inventive method.

description

The cooling circuit of an internal combustion engine is shown schematically in FIG. The internal combustion engine has an engine block 1 with cylinders 2 arranged therein. The engine block 1 is flowed through by a coolant, which is supplied from an inlet 3 and is led away from an outlet 4. The coolant in the engine block 1 is fed back to the engine block 1 through the drain 4 either directly via the bypass 10 or a schematically indicated cooler 5 through an inlet 3. Depending on the coolant temperature, the thermostat 11 (or alternatively an electronic mixing valve) determines the branch through which the coolant flows. If the coolant is too hot, the heat generated in the cylinders 2 during the combustion of fuel is transported through the coolant into the cooler 5 and released there into ambient air or the like. The coolant thus cooled is then transported back into the engine block 1 through the inlet 3. In the outlet 4, a throttle valve 6 and a pump 7 are also provided in the inlet 3. The connection between the engine block 1 and the radiator 5 can be closed, throttled or interrupted by the valve 6. The pump 7 Coolant is set in motion to transport it in the cooling circuit. The valve 6 and the pump 7 are controlled by a control unit 8 via lines, not shown here. The control unit 8 also receives information about the engine temperature, for example from the engine temperature sensor 9, which is arranged on the engine block 1. This engine temperature sensor 9 can also be provided at another suitable location, for example in the outlet 4.

FIG. 2 shows the temperature profile in a conventional method for controlling the cooling circuit. Time t is plotted against temperature T. The internal combustion engine is started at time tO. This leads relatively quickly to an increase in the temperature in the engine block up to the time t1, at which the target temperature Ts is reached. At this point in time, the controller 8 then opens the valve 6 and activates the pump 7. This target temperature Ts is the temperature that is sought when the internal combustion engine is in continuous operation. Whenever this temperature is reached, the thermostat is opened, i.e. H. hot coolant is removed from the engine block 1, pumped through the radiator 5 and thereby cooled, and then fed back to the engine block 1 at a lower temperature. Reliable cooling of the engine block 1 is achieved in this way. When the internal combustion engine has reached this target temperature Ts for the first time at the time t1, the valve 6 is opened and the pump 7 is activated. Since there is still very cold cooling medium in the cooler 5 and also in the lines 3, 4 and 10, this first activation of the cooling circuit is associated with a sharp temperature drop in the engine temperature. There is therefore a very significant drop in temperature between times t1 and t2, i. H. the internal combustion engine is operated again below the optimal target temperature Ts. Only after the comparatively long time between t2 and t3 does the temperature in the engine block 1 again reach the temperature value Ts. However, the activation of the cooling circuit, which then occurs again, does not then lead to such sharp temperature drops since the cooling medium in the cooler 5 and the lines 3 and 4 have already reached a certain temperature.

FIG. 3 shows the method for controlling the cooling circuit which is improved according to the invention. The internal combustion engine starts at time t0, and the time course of the heating up to time t1 corresponds to the course as has already been described for FIG. For the purpose of warming up, however, an initial activation of the cooling circuit is not at temperature Ts, but at one higher warm-up target temperature Tsw provided. A certain excess of the temperature in engine block 1 is thus accepted during warm-up. It is only at time t4, ie later than in FIG. 2, and at the higher temperature Tsw that the cooling circuit is activated for the first time by slowly opening valve 6 and switching on pump 7. This measure alone, ie by permitting a higher warm-up target temperature Tsw, thus achieves an improved warm-up. Even if the temperature profile after time t4 would then correspond to the temperature profile as it corresponds in FIG. 2 between times t1 to t3, overall a better adaptation of the engine temperature to the desired target temperature Ts is achieved. As an additional measure, however, it is also provided that the control of the opening of the valve and / or the pump power takes into account the fact that the cooler 5 and the lines 3, 4 contain coolant which has a very low temperature due to the warm-up operation. For this reason, the mass flow rate is limited by the cooling system by the opening of the valve ^■ 6 and / or the pump power to be adjusted of the pump to the temperature conditions. In particular, the valve is opened slowly with a predetermined time constant or the output of the pump is slowly increased. The temperature curve shown in FIG. 3 between times t4 and t5 is thus achieved, which has a significantly lower cooling compared to the intervals t1 and t2 according to FIG. A significantly slower approach to the target temperature t5 is achieved in this way. In addition to slowly opening the valve or increasing the pump output, this can also be achieved by specifying a transition setpoint temperature after time t4, which changes with a specified time dependency from the setpoint warm-up temperature to the setpoint temperature. I

As can be seen immediately by comparing FIGS. 2 and 3, the method according to the invention, as shown in FIG. 3, ensures that the temperature in engine block 1 when the internal combustion engine is warming up after the desired temperature of the cooling system has been reached for the first time does not collapse as much. The warm-up of the internal combustion engine is thus improved by better achieving the control quality, ie the approximation to the target temperature in engine block 1 over the course of time. The resulting short-term exceeding of the target temperature is not critical since, due to the very cool coolant in the cooler 5, an increased cooling capacity is available in this phase and thus the target warm-up temperature Tsw is exceeded in a range that would be harmful to the engine. can be safely prevented. Due to this increased cooling capacity, the safety margin of the desired warm-up temperature from a possibly harmful engine temperature can be significantly reduced during the warm-up phase.

In FIG. 4, the method according to the invention is shown again schematically on the basis of a process sequence. In block 100, the method for controlling the cooling circuit is started when the internal combustion engine starts. This is followed by query block 101 by reading in the engine temperature and deciding whether it is a cold start. This can easily be done by querying whether the motor temperature is less than 30 ° C. If this is not the case, ie there is no cold start, then step 102 follows step 101. If it is determined in step 101 that there is a cold start (y), step 101 follows step 103 In step 103 the valve 6 is closed, the pump 7 is switched off and the control temperature, ie the temperature at which the valve and pump are activated, is set to the value of the warm-up target temperature. Step 103 is followed by step 104, in which a query is made as to whether the temperature of engine block 1 exceeds the warm-up temperature. If this is not the case (s), step 104 follows step 104 again. However, if query 104 reveals that the temperature of engine block 1 exceeds the warm-up temperature, step 104 follows step 105 Step is the activation of the cooling circuit, whereby the opening of the valve and the performance of the pump are influenced depending on the time. This measure ensures that the complete volume flow through the cooling circuit is not immediately permitted, but only a reduced volume flow initially, so that there is no rapid cooling, as is the case with conventional systems. This time function takes into account the fact that the coolant in the cooler 5 is still at a very low temperature. Furthermore, the control temperature is set to the value of a transition setpoint temperature which has a value between the warmup setpoint temperature and the setpoint temperature. These two measures can also be used individually, if necessary, since both measures are suitable for limiting the temperature drop too quickly in this warm-up phase. However, both measures are preferably used at the same time, since the approach to the target temperature can be set particularly precisely in this way. Step 105 is then followed by step 106, in which it is checked whether the temperature of engine block 1 has reached the target temperature. If this is not yet the case (s), step 106 follows step 106 again. If this is the case, however, ie if the temperature of engine block 1 has reached the desired temperature, step 106 follows step 106 The normal operating control of the cooling circuit then takes place in step 102, ie the setpoint temperature is used as the control temperature and the valve 6 and the pump 7 are controlled with the usual data designed for normal operation. This normal regulation can then also provide different target temperatures or different characteristics for the actuation of valve 6 or pump 7 for different operating states.

Claims

Expectations

1. A method for controlling the cooling circuit of an internal combustion engine, the cooling circuit having a predetermined target temperature (Ts), characterized in that a warm-up target temperature (Tsw) is provided for a warm-up of the internal combustion engine, which is higher than the target temperature (Ts).

2. The method according to claim 1, characterized in that the warm-up target temperature (Tsw) between the target temperature (Ts) and a boiling point of a coolant in the cooling circuit (3, 4, 5) is selected.

3. The method according to any one of the preceding claims, characterized in that the warm-up is detected by the temperature of the internal combustion engine is below a predetermined value after the start of the internal combustion engine. I

4. The method according to any one of the preceding claims, characterized in that a throttle valve (6) and a pump (7) of the cooling circuit (3, 4, 5) are activated when the target warm-up temperature (Tsw) is reached.

5. The method according to claim 4, characterized in that the activation of the opening of the valve (6) and / or the pumping capacity of the pump (7) are increased with a predetermined time dependency.

6. The method according to any one of the preceding claims, characterized in that after reaching the desired warm-up temperature (Tsw) for the cooling circuit Transition target temperature is specified, which changes with a predetermined time dependency from the warm-up target temperature (Tsw) to the target temperature (Ts).

7. Device for controlling the cooling circuit of an internal combustion engine, which controls a cooling circuit (3, 4, 5) of the internal combustion engine with a predetermined target temperature (Ts), characterized in that a warm-up target temperature (Tsw) is used for the warm-up, which is higher than the target temperature (Ts).