EP2739833B1 - Coolant circuit for an internal combustion engine and method for operating a coolant circuit - Google Patents

Description

The invention relates to a coolant circuit for an internal combustion engine, wherein the coolant between the internal combustion engine and a heat sink in dependence of a switchable valve, which is closed in the initial state at a cold start of the internal combustion engine, can circulate, and a method for operating a coolant circuit.

Such coolant circuits are used, in particular in vehicle construction, to cool the coolant heated by the internal combustion engine by circulating it via the heat sink. As a result, the internal combustion engine is protected against damage due to overheating. To reduce the friction of the internal combustion engine in terms of efficiency improvement, a rapid warming of the internal combustion engine and, accordingly, the coolant is desirable in a cold start of the engine. For this reason, a valve that is switched to a closed state can prevent coolant circulation until sufficient heating has been achieved.

The determination of the time to open the valve takes place according to the prior art as a function of the exceeding of a torque or speed threshold by the internal combustion engine. That's how it shows DE 100 45 613 A1 a method for coolant temperature control of an engine cooling, wherein the coolant temperature is regulated in dependence on a load and / or a rotational speed of the internal combustion engine. This However, often leads to premature opening of the valve at low coolant temperatures, which efficiency losses must be taken into account.

The DE 101 54 091 A1 describes a method and a device for controlling a cooling system of an internal combustion engine, wherein the power of a coolant pump in dependence on a fuel quantity supplied to the internal combustion engine is controllable. However, the amount of fuel is not readily suitable as a control variable for controlling a cooling system, since in particular takes place at a cold start of the internal combustion engine regularly no stoichiometric conversion of the fuel.

The object of the present invention is therefore to provide a coolant circuit for an internal combustion engine, and a method for operating a coolant circuit, which enables an efficiency-optimized cold start of the internal combustion engine.

This object is solved by the features of patent claims 1 and 5, respectively.

Coolant circuit for an internal combustion engine, wherein the coolant between the internal combustion engine and a heat sink in response to a switchable valve, which is closed in the initial state at a cold start of the internal combustion engine, circulate and wherein the valve depending on an emitted from the internal combustion engine exhaust gas mass flow in an at least partially open Subsequent state is switchable, wherein a control device determines an integral of the exhaust gas mass flow after the time and switches on exceeding a Integralschwellwertes the valve in the subsequent state.

By making the opening of the valve after the cold start dependent on the emitted exhaust gas mass flow, the optimal time for ending the rapid heating of the internal combustion engine can be very accurately determined. The integral value of the exhaust gas mass flow over time reflects the actual entry of heat energy into the coolant. If the integral value exceeds a previously defined integral threshold value, the valve is opened completely or step by step. As a result, local overheating of the internal combustion engine (so-called "hot spots") is effectively prevented on the one hand and, on the other hand, the fastest possible achievement of low friction power is achieved. A cold start in this context can be understood to mean a startup of the internal combustion engine in which the coolant temperature approximately corresponds to the temperature of the ambient air. As a heat sink, a conventional air-liquid heat exchanger is suitable, which forms a circuit via a hosing with the internal combustion engine. Coolant pumps, for example centrifugal pumps, are suitable for the forced circulation of the coolant. The valve is preferably designed as a heatable map thermostat or is actuated by pneumatic or electromechanical.

In a preferred embodiment of the coolant circuit, the control device determines the exhaust gas mass flow from an injection quantity of a fuel. The control device is preferably designed as a control unit for the internal combustion engine and measures in this function, inter alia, the amount of fuel to be injected. From the amount of fuel inevitably derived from the combustion exhaust gas mass flow is derived, which is dissipated by the exhaust system.

In a preferred embodiment of the coolant circuit, the control device determines the injection quantity per unit time. Particularly advantageous is the subdivision of the injection process in the smallest possible time units for more accurate determination of the injection quantity.

In a preferred embodiment of the coolant circuit, the valve is part of a coolant pump or is formed by the coolant pump. The valve may be integrated in the coolant pump or formed by a switchable coolant pump. This can save components and space.

• Schalten eines geschlossenen Ausgangszustandes des Ventils bei einem Kaltstart der Brennkraftmaschine;
• Kontinuierliches Erfassen eines von der Brennkraftmaschine emittierten Abgasmassenstroms ab dem Kaltstart;
• Schalten des Ventils in einen zumindest teilweise geöffneten Folgezustand in Abhängigkeit des Abgasmassenstroms, wobei ein Integral des Abgasmassenstroms nach der Zeit gebildet und bei Überschreiten eines Integralschwellwertes der Folgezustand geschaltet wird.

A method for operating a coolant circuit for an internal combustion engine, wherein the coolant can circulate between the internal combustion engine and a heat sink in dependence on a switchable valve, comprises the following steps:

• Switching a closed output state of the valve at a cold start of the internal combustion engine;
• Continuously detecting an exhaust gas mass flow emitted by the internal combustion engine from the cold start;
• Switching of the valve in an at least partially open sequence state as a function of the exhaust gas mass flow, wherein an integral of the exhaust gas mass flow is formed after the time and is switched when exceeding a Integralschwellwertes the subsequent state.

When carrying out the method according to the invention, the advantages already mentioned for the coolant circuit also result.

Further details and features of the invention will become apparent from the following description of a preferred embodiment with reference to the drawings.

• Figur 1 eine schematische Ansicht eines Kühlmittelkreislaufs für eine Brennkraftmaschine;
• Figur 2 ein Diagrammdarstellung des Abgasmassenstroms über die Zeit.

Show:

• FIG. 1 a schematic view of a refrigerant circuit for an internal combustion engine;
• FIG. 2 a diagram of the exhaust gas mass flow over time.

According to Fig. 1 has a coolant circuit 1 for an internal combustion engine 2, a heat sink 3. The heat sink 3 is flowed through on the one hand with ambient air and on the other hand with coolant. Due to the heat exchange taking place, the coolant circulating in the coolant circuit 1 cools down. The coolant circulation is generated by a coolant pump 5, wherein a switchable valve 4 can prevent the coolant circulation. The internal combustion engine 2 has a plurality of combustion chambers 2 c, in which fuel is burned, whereby the internal combustion engine 2 heats up. The resulting heat can be dissipated by the coolant to the heat sink 3. The fuel is either injected into the intake 2 a or directly into the combustion chambers 2 c and then mixed with the intake air. The spent fuel-air mixture is discharged through the exhaust system 2b. A control device 6 detects the injection quantity of the fuel per unit time and determines therefrom the exhaust gas mass flow through the exhaust system 2b. The control device 6 forms an integral of the exhaust gas mass flow over time, as shown in FIG Fig. 2 is shown. In a cold start of the internal combustion engine 2, so the startup at a coolant temperature which corresponds approximately to the ambient temperature, the valve 4 is in its closed initial state and there is no coolant circulation. The control device 6 starts simultaneously with a continuous calculation of the integral value and causes at least partial opening of the valve 4 as soon as the integral value exceeds a defined integral threshold value.

According to the Fig. 2 the integral value is formed by detecting the emitted exhaust gas mass flow per unit time t _x and continuously integrating it until the integral threshold value is exceeded.

List of reference numbers:

t _x

time unit

1

Coolant circuit

2

Internal combustion engine

2a

Intake

2 B

exhaust system

2c

combustion chamber

3

heat sink

4

Valve

5

Coolant pump

6

control device

Claims (5)

1. Coolant circuit (1) for an internal combustion engine (2), wherein the coolant can circulate between the internal combustion engine (2) and a heat sink (3) in dependence on a switchable valve (4), which is closed in the initial state on cold starting of the internal combustion engine (2), characterised in that in dependence on an exhaust gas mass flow emitted by the internal combustion engine (2) the valve (4) can be switched to an at least partially opened subsequent state, wherein a control device (6) determines an integral of the exhaust gas mass flow as a function of time and on exceeding of the integral threshold value switches the value (4) to the next state.
2. Coolant circuit according to claim 1 characterised in that the control device (6) determines the exhaust gas mass flow from an injected quantity of a fuel.
3. Coolant circuit according to claim 2 characterised in that the control device (6) determines the injected quantity per unit of time.
4. Coolant circuit according to any one of claims 1 to 3 characterised in that the valve (4) is part of a coolant pump (5) or is formed by the coolant pump (5).
5. Method of operating a coolant circuit (1) for an internal combustion engine (2), wherein the coolant can circulate between the internal combustion engine (2) and a heat sink (3) in dependence on a switchable valve (4), comprising the following steps:

   - setting a closed initial state of the valve (4) during a cold start of the internal combustion engine (2);

   - continuously recording of an exhaust gas mass flow emitted by the internal combustion engine (2) as of the cold start;

   - switching the valve (4) to an at least partially open subsequent state in dependence on the exhaust mass flow, wherein an integral the exhaust gas mass flow as a function of time is determined and on exceeding an integral threshold value the valve is switched to the next state.

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