EP1308610B1 - Method and device for controlling a cooling system of an internal combustion engine - Google Patents

Description

The invention relates to a method and a device for controlling a cooling system of an internal combustion engine, hereinafter also referred to as an engine, according to the preamble of patent claim 1 and of patent claim 11.

Such a device and such a method is known for example from WO 99/01650 A. In this case, it is decided in dependence on various parameters, in which order and at what time the control of various components of the cooling system, such. As a coolant pump, a thermostat, a blind and a fan is switched on.

Thus, such a cooling system also includes a coolant pump which directs coolant through an internal combustion engine to cool it.

From the prior art it is known that a coolant pump can be connected for example via a V-belt with the crankshaft of an internal combustion engine, so that it is driven with the engine.

With regard to the prior art, DE 195 08 104 C2 furthermore discloses a method for regulating a cooling circuit of an internal combustion engine in which a distinction is made between a warm-up phase, an operating phase and a tail. The warm-up and operation phase is determined with the engine running based on the coolant temperature at the engine outlet, which is compared with a coolant temperature limit for the warm-up phase. If the value is undershot, it is detected on the warm-up phase and on reaching or exceeding the value on the operating phase. In the warm-up phase, the engine is initially not cooled until it has reached a coolant start temperature. After reaching this initial temperature, however, a blower generated by an air flow is passed through a radiator module and the coolant flow generated by the coolant pump in response to a differential temperature setpoint of the coolant between engine inlet and outlet regulated. A required for the control differential temperature actual value is determined by the heat flow from the engine into the coolant. The heat flow is in turn calculated from the instantaneous coolant flow, the instantaneous engine load and the engine speed. The speed of the coolant pump changes with the change in heat flow, so that short-term engine load and speed changes do not affect the operation of the coolant pump. As soon as the Temperature limit for the warm-up phase is reached, the so-called. Operating phase begins. Therein, the control of the coolant pump and the blower takes place as a function of the differential temperature setpoint and a temperature setpoint of the coolant at the engine outlet. The temperature setpoint is determined via a corresponding characteristic map for a given engine temperature. In the trailing phase in which the engine is off, the engine is further cooled when the coolant temperature exceeds a predetermined temperature limit. This method has the disadvantage that the controlled variable used is the temperature or the difference between different temperatures in the cooling system. Such temperatures in the cooling circuit are sluggish and ultimately only effects of the engine or vehicle operating point.

EP 0 952 315 A1 discloses a control system for minimizing the consumption of electrical energy in a cooling system of an internal combustion engine. Based on the engine temperature detected by sensors, vehicle speed and ambient temperature, a control unit controls a fan and an electric pump for cooling the internal combustion engine. By means of the values detected by the sensors, an operating point is determined on the basis of a characteristic diagram in order to discharge a certain amount of heat energy from the engine, which indicates an optimum ratio of the sum of the energy supplied to the fan and the pump. The control system has the disadvantage that several sensors are necessary to detect certain parameters of which depends on the engine is cooled. In addition to the costs associated with each sensor, there is also a risk of failure of the same. It is also true that with temperature measuring the accuracy of measurement can be reduced by external influences and so a control based on the temperature is limited.

The object of the invention is to provide a method and a device for controlling a cooling system of an internal combustion engine, wherein a reliable cooling is made possible.

This object is achieved by a method with the features specified in claim 1 or a device having the features specified in claim 12.

The invention is based on the basic idea of variably regulating the cooling system and the variably drivable coolant pump connected thereto as a function of an amount of fuel supplied to the engine. With the invention, the power of the coolant pump over a range between preferably zero to a maximum pump power (l / h) can be set either continuously or in a plurality of stages variable. Characterized in that the amount of fuel supplied to the engine is related to the heating of the engine, the control of the coolant pump and thus the cooling of the engine can be carried out in advance and on the basis of the currently consumed fuel. The function of the heat input of the engine into the coolant to fuel mass flow is largely similar for all combustion concepts. This has the advantage that the cooling system or the coolant pump can be regulated according to causer sizes and not alone as known from the prior art, by temperatures in the cooling circuit are sluggish and also only effects of an engine or vehicle operating point. Another advantage is that a cooling control principle without interference-prone sensors or Temperaturmeßstellen is possible and these sensors or Temperaturmeßstellen may only be needed in the following operating cases and that warm-up, hot idle or Heißabstellen.

Advantageous embodiments and further developments are shown in the subclaims.

According to the invention, the sum of the amount of fuel supplied since the ignition of the engine Σm ' _{KS is} compared with a so-called target fuel amount m _Soll . If the setpoint is undershot, as is the case, for example, during the cold start of the engine, no cooling of the engine by the cooling system takes place initially, unless with a volume flow requested for other requirements in the cooling system, for example for a heater. This has the Advantage that the warm-up phase of the engine can be shortened and the fuel consumption can be reduced, in contrast to engines in which the coolant pump is connected to the crankshaft. In these engines, the coolant pump is automatically driven to start the engine, so that the engine is cooled before it has warmed up.

If the sum of the supplied amount of fuel Σm ' _KS exceeds the predetermined setpoint m _setpoint , then cooling takes place by switching on the coolant pump. The power of the coolant pump is determined as a function of at least one of the following parameters, such as engine speed nMot, engine load, ambient temperature and / or an average over a predetermined time interval (eg 30 seconds) of the fuel quantity m ' _KS . By a temporal averaging of the coolant pump speed is achieved that pressure threshold loads can be avoided, resulting in a lower load on the cooling system and the coolant pump such as a water pump.

Preferably, the cooling system and the coolant pump are additionally regulated as a function of the coolant temperature. For this purpose, in addition to the comparison of the supplied fuel quantity, the instantaneous temperature of the coolant T _{Mot is} compared with a _desired coolant temperature T _Soll . If the setpoint T _{set point is} exceeded, the motor is cooled by the cooling system, the power of the coolant pump being determined as described above as a function of the engine speed nMot, the engine load, the outside temperature and / or an average value of the fuel quantity m ' _KS can. This has the advantage that the operating point of the coolant pump can continue to be variably adjusted depending on certain parameters such as the outside temperature or the load. This operation is particularly advantageous during hot running and hot shutdown of the engine.

Additionally or alternatively, the cooling system and the coolant pump can be regulated as a function of the engine oil temperature. For this purpose, in addition to the comparison of the supplied fuel quantity, the coolant temperature, the instantaneous engine oil temperature T _{Oil is} compared with a _target engine oil temperature T _Soll . Will the Setpoint T _target is not reached, there is no cooling by the coolant pump unless a requested other needs in the cooling system flow rate, for example, a heater. Furthermore, the cooling sets in as soon as the engine oil _target temperature T _{Soll is} exceeded. The power of the coolant pump is determined as a function of the engine speed nMot, the engine load, the outside temperature and / or an average value of the fuel quantity m ' _KS .

Since not only the coolant pump but also the operation of additional devices such as an air conditioner, a separate heater or an automatic transmission draws and / or supplies heat to the engine, the control of the cooling system is preferably in addition depending on the connection or the heat input of such a device. In this case, the power of the coolant pump is preferably determined as a function of a Zuschaltgrad example of the heater. An advantage is that the pump is operated according to the requirements of the additional equipment, although this would not be necessary for the cooling of the engine. This is for example to supply the heating or cooling of the automatic transmission, e.g. idle the case. This may eliminate an additional water pump for heating. According to the Zuschaltgrad the heater, for example, of approximately 100%, the power of the coolant pump is increased accordingly, so that they can pump a portion of the coolant to the heat exchanger of the heater. If no heating is switched on, the previously determined power of the coolant pump is maintained.

Furthermore, the control system compares a first coolant temperature threshold with the current coolant temperature T _Mot . If the threshold is exceeded, the coolant pump is operated at least within a predetermined time interval with a predetermined power, so that the engine is further cooled. This has the advantage that the engine is sufficiently cooled even in hot running or additional heating by the ambient temperature.

In order to enable a reliable cooling when the engine is switched off after a high load, it is determined whether the engine is switched off. Exceeds the Coolant temperature while a second coolant temperature threshold, the coolant pump is operated at a predetermined power within a predetermined time interval and the engine is cooled. This has the advantage that the engine is further cooled and so temperature peaks in the engine after stopping the engine can be prevented after high load. The duration of the overrun is dependent on the temperature exceeding the setpoint, whereby a defined duration may not be exceeded (discharge of the battery). When falling below the second coolant temperature threshold, there is no further cooling by the cooling system.

If it is determined that the engine is in operation, the control loop is closed and again a calculation of the pump power based on the amount of fuel supplied to achieve a continuous cooling of the engine.

• Figur 1 ein Ablaufdiagramm für ein bevorzugtes Regelverfahren gemäß der Erfindung.

An embodiment of the invention will be described with reference to the following drawings. It shows:

• Figure 1 is a flow chart for a preferred control method according to the invention.

In the control method according to the invention shown in Figure 1 is first determined whether the engine is in operation. In this case, the sum of the amount of fuel since the ignition of the engine Σm ' _{KS is} compared with a predetermined target value m _set the amount of fuel. In a further query, the instantaneous temperature of the coolant T _{Mot is} compared with a setpoint temperature T _{Soll of} the coolant.

If one of the values falls below the corresponding desired value, ie if the sum of the fuel since the ignition of the engine is still insufficient to heat the engine to operating temperature or if the engine has not yet reached the required operating temperature, then the coolant pump is not initially operated except with a volume flow requested for other needs in the cooling system for example for a heater. As a result, a dissipation of heat from the engine is prevented, thus achieving a rapid warm-up of the engine. In the case where one of the setpoints is exceeded, the cooling starts. For this purpose, the power of the coolant pump is determined as a function of an average value of the fuel quantity in a specific time interval (for example 30 seconds), the engine speed and / or the engine load. Other parameters such as the operating parameters of the cooling system are also conceivable here.

As already mentioned above, the coolant pump can be operated when a volume flow for other needs in the cooling system is required, for example for a heater. The regulation of the power of the coolant pump depending on the switched-on heating has priority over the control depending on whether the setpoint values for the fuel quantity or the coolant temperature are under or exceeded.

For this purpose, it is determined in a further step, whether a heater is switched on and regulated depending on the performance of the coolant pump. When the heating system is switched on, it removes heat from the engine, in which at least part of the heated coolant is pumped to the heater where it is discharged to the vehicle interior via a heat exchanger. Depending on the degree of connection of the heating, the power of the coolant pump is regulated accordingly. If the heating is switched on to approximately 100%, the pumping capacity is correspondingly increased to a value of, for example, V'pump = 2200 l / h. If the heater is only switched on to 40%, the pumping capacity of the coolant pump is correspondingly lower and amounts, for example, to V'pump = 1500 l / h. In the event that the heater is not switched on, the previously determined pump power der- coolant pump remains unchanged. This embodiment of the invention has the particular advantage that under certain circumstances, no separate pump for the heating circuit is required. In addition to the heating, in addition or as an alternative, other elements which, when switched on or switched on, extract heat from a motor and / or supply it to control the coolant pump can be used. This can be done in a comparable manner as in the heating on the Zuschaltgrad or the heat input (loss).

In a further step, it is determined whether the coolant exceeds a first, upper coolant temperature threshold (e.g., 115 ° C), for example, by hot idling. If this is the case, then, when the pumping power of the coolant pump is below a predetermined value sufficient for the cooling, the pumping power is increased to this predetermined value and further cooled in a predetermined time interval. If the threshold value is undershot, the power of the coolant pump remains unchanged.

In a next step, it is determined whether the engine is still in operation. In this case, the loop closes, by recalculating the pump power based on the amount of fuel supplied to ensure continuous cooling of the engine.

With the engine shut down, it is monitored whether a second, lower coolant temperature threshold (e.g., 100 ° C) is exceeded by the coolant to provide reliable cooling when the engine is shut down after a high load (hot shutdown). In this case, the coolant pump cools the engine at a predetermined power in a predetermined time interval of preferably 60-300 seconds. If the second coolant temperature threshold is exceeded, no further cooling takes place.

By taking into account special cases such as hot shutdown, a cold start with or without heating and hot idling, the aim is to meet the requirements of the heating and component temperatures, as well as to minimize heat transfer by suppressing forced convection and thus faster component heating to obtain. The absolute temperature level of the cooling system is still regulated by a thermostat. This can be designed as a conventional thermostat with a Dehnstoffelement (heated as map thermostat or unheated) or as an electric actuator. As a coolant pump, an electrically operated coolant pump is preferably used, which has its own drive. As a coolant is preferably used cooling water. All values for pump power, temperatures and time intervals given here are only examples.

Claims (20)

1. A method for controlling a cooling system of an internal combustion engine, wherein the capacity of a coolant pump can be controlled as a function of a quantity of fuel supplied to the internal combustion engine, characterised in that a desired quantity of fuel m_desired is specified, which is compared with the sum of the quantity of fuel since the ignition of the internal combustion engine Σm'_KS and wherein no cooling takes place by means of the coolant pump when the desired value m_desired is fallen below and wherein the coolant pump is operated at an adjustable capacity when the desired value is exceeded.
2. A method according to claim 1, characterised in that the coolant pump is controlled as a function of the temperature of the coolant T_eng, wherein a desired temperature of the coolant T_desired is specified, which is compared with the temperature of the coolant T_eng and wherein no cooling takes place by means of the coolant pump when the desired value T_desired is fallen below and wherein the coolant pump is operated at an adjustable capacity when the desired value is exceeded.
3. A method according to claim 1 or claim 2, characterised in that the coolant pump is controlled as a function of the temperature of the engine oil T_oil, wherein a desired engine oil temperature is specified, which is compared with the temperature of the engine oil T_oil and wherein no cooling takes place by means of the coolant pump when the desired value is fallen below and wherein the coolant pump is operated at an adjustable capacity when the desired valued is exceeded.
4. A method according to any one of the preceding claims, characterised in that the adjustable capacity of the coolant pump is determined by at least one of the parameters such as the average value of the fuel quantity m'_KS over a predetermined time interval, the rotational engine speed, the engine load and/or the outside temperature.
5. A method according to any one of the preceding claims, characterised in that the capacity of the coolant pump is controlled as a function of the connection of an additional mechanism, which can withdraw heat from the internal combustion engine and/or supply it thereto, this control of the capacity of the coolant pump having priority.
6. A method according to claim 5, characterised in that this mechanism is a heater and/or an air conditioning system and/or an automatic transmission.
7. A method according to claim 6, characterised in that the capacity of the coolant pump can be adjusted depending on the degree of connection of the heater, the capacity preferably being at least 2200 l/h at a degree of connection of 100%.
8. A method according to claim 6 or claim 7, characterised in that the capacity of the coolant pump can be adjusted depending on the heat feeding of the automatic transmission, the pump capacity being added to the pump capacity required to cool the internal combustion engine.
9. A method according to any one of the preceding claims, characterised in that when the coolant exceeds a first coolant temperature threshold value of 115°C, for example, the coolant pump is operated at a predetermined capacity of preferably about 2000 1/h at least within a predetermined time interval.
10. A method according to any one of the preceding claims, characterised in that when the engine is switched off and the coolant temperature exceeds a second coolant temperature threshold value of 100°C, for example, the coolant pump is operated at a predetermined capacity of preferably about 1500 l/h within a predetermined time interval.
11. A device for controlling a cooling system of an internal combustion engine with a control mechanism for controlling the capacity of a coolant pump as a function of a quantity of fuel supplied to the internal combustion engine, characterised in that the control mechanism controls the coolant pump in such a way that no cooling takes place when a sum of the quantity of fuel since the ignition of the internal combustion engine Σm'_KS falls below a predetermined desired quantity of fuel m_desired, and operates the coolant pump at an adjustable capacity when the desired value is exceeded.
12. A device according to claim 10 or claim 11, characterised in that the control mechanism controls the coolant pump in such a way that no cooling takes place when the temperature of the coolant T_eng falls below a predetermined desired temperature of the coolant T_desired, and operates the coolant pump at an adjustable capacity when the desired value is exceeded.
13. A device according to any one of claims 10 to 12, characterised in that the control mechanism controls the coolant pump in such a way that no cooling takes place when the temperature of the engine oil T_oil falls below a predetermined desired engine oil temperature and operates the coolant pump at an adjustable capacity when the desired value is exceeded.
14. A device according to claim 11, 12 or 13, characterised in that the adjustable capacity of the coolant pump is dependent on at least one of the parameters, such as the average value of the quantity of fuel m'_ks over a predetermined time interval, the rotational engine speed, the engine load and/or the outside temperature.
15. A device according to any one of claims 10 to 14, characterised in that the control mechanism controls the capacity of the coolant pump as a function of the connection of an additional mechanism, which can withdraw heat from the internal combustion engine and/or supply it thereto, this control of the capacity of the coolant pump being carried out with priority by the control mechanism.
16. A device according to claim 15, characterised in that this mechanism is a heater and/or an air conditioning system and/or an automatic transmission.
17. A device according to claim 15 or claim 16, characterised in that the control mechanism controls the capacity of the coolant pump depending upon the degree of connection and/or heat feeding of the mechanism.
18. A device according to claim 15 or claim 16, characterised in that the control mechanism controls the capacity of the coolant pump so that it can be switched on for a certain time interval depending upon the degree of connection of the mechanism.
19. A device according to any one of claims 10 to 18, characterised in that the control mechanism operates the coolant pump at a predetermined capacity at least within a predetermined time interval when the coolant temperature exceeds a first coolant temperature threshold value.
20. A device according to any one of claims 10 to 18, characterised in that the control mechanism operates the coolant pump at a predetermined capacity within a predetermined time interval when the engine is switched off and the coolant temperature exceeds a second coolant temperature threshold value.

Images