DE102020206336A1 - System and method for temperature control of a metering valve - Google Patents

Abstract

The invention relates to a system for regulating the temperature of a metering module (1) which is arranged on an exhaust line (2) of an internal combustion engine with a main coolant circuit. The system comprises a heat exchange body (13) which is arranged around and / or in the metering module (1), a coolant inlet (3) which is connected to the cold side of the main coolant circuit and to the heat exchange body (13), a coolant return (4), which is connected to the heat exchanger body (13) and the hot side of the main coolant circuit. A heating element (31) is provided, which is arranged in the coolant inlet (3).

Description

The present invention relates to a system for regulating the temperature of a metering valve in a conveying and metering system. The invention also relates to a method for regulating the temperature of the metering valve. The invention also relates to a computer program that executes each step of the method when it runs on a computing device, as well as a machine-readable storage medium that stores the computer program. Finally, the invention relates to an electronic control device which is set up to carry out the method according to the invention.

State of the art

There are known conveyor and metering systems with a metering module. For example, the DE 103 46 220 A1 a delivery and metering system emerges in which a 32.5% urea-water solution is metered into the exhaust system of an internal combustion engine by means of the metering module as part of an SCR process (Selective Catalytic Reduction). The dosing module has an optimal operating temperature for dosing. The dosing module is typically fastened in the exhaust line via a flange connection, so that the dosing module and the exhaust line are thermally coupled. The exhaust gas in the exhaust system is typically very hot during operation and gives off heat to the metering tip of the metering module that protrudes into the exhaust system. If the temperature of the dosing module is too high, for example above 175 ° C to 250 ° C, there is a risk of solid deposits of the HWL in the dosing module. It is known to connect the metering module to the main coolant circuit of the internal combustion engine so that the metering module is cooled by means of the coolant. Coolant circuits for internal combustion engines are already well known. However, too much cooling is not wanted either. Typical temperatures of the metering module in the exhaust gas for metering are in a range between 100 ° C and 670 ° C. This means that the dosing modules are also operated at temperatures that are outside an optimal temperature range for dosing.

Disclosure of the invention

A system for regulating the temperature of a metering module, which is arranged on an exhaust gas line of an internal combustion engine, is proposed. The internal combustion engine has a main coolant circuit which is set up to cool the internal combustion engine. The temperature and the flow rate of the coolant in the main coolant circuit are regulated in such a way that the temperature of the internal combustion engine is in an optimal operating range. A heat exchange body is provided which is arranged around the metering module and / or in the metering module and is in thermal contact with it. The system comprises a coolant inlet which is connected on the one hand to the cold side of the main coolant circuit and on the other hand to the heat exchanger body. The section of the cooling circuit in which the coolant comes from the radiator at a low temperature before it has reached the internal combustion engine is referred to as the cold side of the main coolant circuit. In particular, the coolant inlet is connected to a line on the cold side of the main coolant circuit via a three-way valve. In addition, the system includes a coolant return, which is connected on the one hand to the heat exchanger body and on the other hand to the hot side of the main coolant circuit. The section of the cooling circuit in which the coolant comes out of the internal combustion engine at an elevated temperature and has not reached the radiator is referred to as the hot side of the main coolant circuit.

The coolant from the cold side of the main coolant circuit flows through the coolant inlet to the heat exchanger body. Depending on the application (see below), the coolant in the heat exchanger body absorbs heat from the dosing module or transfers heat to the dosing module. The coolant then flows through the coolant return to the hot side of the main coolant circuit and is transported away. The coolant inlet, the heat exchanger body and the coolant return are referred to as the secondary coolant circuit.

The main coolant circuit is controlled or regulated in such a way that the coolant circulating in it is designed for an optimal operating temperature of the internal combustion engine. The coolant that flows from the main coolant circuit to the heat exchanger is therefore not set to an optimal temperature range of the metering module for metering and can therefore be too cold.

The system for temperature regulation comprises a heating element which is arranged in the coolant inlet. The heating element heats the coolant flowing to the heat exchanger body so that the metering module is operated in the optimal temperature range for metering. As a result, the temperature of the coolant in the secondary coolant circuit can be increased and thus adjusted independently of the main coolant circuit.

In addition, the system for temperature regulation can comprise a pump which is arranged in the coolant inlet. The pump can be arranged upstream of the heating element. The pump conveys the coolant from the main coolant circuit through the secondary coolant circuit with an adjustable by the pump Flow rate. Greater cooling can be achieved with a high flow rate. As a result, the temperature of the coolant in the secondary coolant circuit can be reduced and thus adjusted largely independently of the main coolant circuit. In addition, by adjusting the flow rate, the amount of coolant to be heated by the heating element can also be adjusted so that the heating element is not overloaded. Typically, the coolant in the main coolant circuit is always cold enough to cool the metering module. The temperature of the main coolant circuit is normally monitored. An alarm is issued before the coolant reaches a critical temperature at which the dosing module can no longer cool.

The system can comprise a temperature sensor which is arranged in the coolant inlet upstream of the heat exchanger body and downstream of the heating element and measures the temperature of the coolant there. Additionally or alternatively, the system can comprise a mass flow sensor which is arranged in the coolant inlet upstream of the heat exchanger body and downstream of the pump and measures the mass flow of the coolant there. The temperature sensor and the mass flow sensor in the coolant inlet can be used to determine the influence of the coolant on the temperature of the metering module. The measured temperature and the measured mass flow rate of the coolant can be used to determine the temperature of the metering module. A model can be used for this.

The system can optionally include a temperature sensor which is arranged in the exhaust gas line upstream of the metering module and measures the temperature of the exhaust gas there. Additionally or alternatively, the system can include a mass flow sensor, which is arranged in the exhaust line upstream of the metering module and there measures the mass flow of the exhaust gas. The temperature of the exhaust gas and / or the mass flow of the exhaust gas preferably flow into the regulation below. Existing sensors in the exhaust line upstream of the metering module can be used for the temperature sensor and / or the mass flow sensor.

In addition, a method for regulating the temperature in a partial volume at the metering tip protruding into the exhaust system is proposed for the above-mentioned metering module, which is arranged on an exhaust gas line of an internal combustion engine. The metering module has a heat exchanger body and is connected to a main coolant circuit of the internal combustion engine via a coolant inlet. The above-mentioned heating element and the above-mentioned pump are arranged in the coolant inlet. For each dosing module there is an optimal temperature range in this partial volume at the dosing tip, in which dosing proceeds as best as possible. The optimal temperature range is, for example, over 140 ° C and is limited at the top by specifications for component protection of the dosing module. The specifications for component protection relate to components within the dosing module, especially the dosing valve. The temperature relevant for component protection depends not only on the temperature at the dosing tip, but also on the heat transfer between the dosing tip and the relevant component in the dosing module, which is dependent on the respective dosing module, and on the dimensions of the secondary coolant circuit. The relationship can preferably be determined experimentally in advance and stored, for example, in characteristic diagrams.

In order to determine the temperature in the partial volume at the dosing tip, the measured temperature and the measured mass flow of the coolant through the coolant inlet are used. A model can be used to determine the temperature in the partial volume. In addition, the heat given off by the exhaust gas to the partial volume can be taken into account and ultimately included in the regulation of the temperature in the partial volume.

If the temperature in the partial volume is below a lower threshold, the heating element is activated in order to heat the coolant in the coolant inlet. The lower threshold is preferably 140 ° C. And, if the temperature in the partial volume is above the upper threshold, the pump in the coolant inlet is activated in order to increase the coolant mass flow through the coolant inlet. As described above, the upper threshold for each dosing module is selected according to the specifications of the component protection for the dosing valve. The maximum permissible temperature for the metering valve is 120 ° C to 140 ° C. The upper threshold can in particular be stored in characteristic diagrams that were determined experimentally in advance. The temperature of the coolant in the main coolant circuit is typically always below the lower threshold, so that the metering module is always more cooled by the higher coolant mass flow. The coolant is preferably heated to a temperature between 75 ° C. and 90 ° C. by the heating element.

As a result, the temperature in the partial volume at the metering tip of the metering module can be maintained in a temperature range that is optimal for metering, regardless of the regulation of the main coolant circuit.

The regulation can be carried out differently in different operating states When the internal combustion engine is started, the temperature of the metering valve is normally below the lower threshold. If the temperature of the metering module is below approx. 140 ° C, it can happen that the metered reducing agent solution forms a liquid wall film on the inside of the exhaust system and does not evaporate immediately. The heating element can be activated in order to heat the coolant. With a cold start of the internal combustion engine and a low ambient temperature, a quick readiness for dosing can be achieved.

In normal operation of the internal combustion engine, in which the internal combustion engine is operated in a medium or lower power range, the temperature of the coolant taken from the main coolant circuit is typically too low to operate the metering module in the optimal temperature range for metering. The heating element can be activated in order to heat the coolant. As a result, the coolant of the main coolant circuit, which is typically too cold, can be heated independently of the regulation of the main coolant circuit.

In a power mode of the internal combustion engine, in which the internal combustion engine is operated in an upper power range, the pump in the coolant inlet can be activated in order to increase the mass flow of the coolant. The coolant is preferably not heated by the heating element. This achieves strong cooling, which is necessary for power operation.

When the internal combustion engine is switched off, the pump can be activated to continue to deliver coolant through the coolant inlet to the heat exchanger body of the metering module. As a result, the metering module is further cooled down even after the internal combustion engine has been switched off, so that damage due to the hot exhaust gas, which may still be in the exhaust system, can be prevented.

The computer program is set up to carry out every step of the method, in particular if it is carried out on a computing device or control device. It enables the implementation of the method in a conventional electronic control unit without having to make structural changes to it. For this purpose, it is stored on the machine-readable storage medium.

By uploading the computer program to a conventional electronic control device, the electronic control device is obtained, which is set up to regulate the temperature of the dosing module.

Figure list

• 1 zeigt eine schematische Darstellung eines Dosiermoduls an einem Abgasstrang und eines Ausführungsbeispiels des erfindungsgemäßen Systems zur Regelung der Temperatur des Dosiermoduls.
• 2 zeigt eine schematische Darstellung eines Ausführungsbeispiels der erfindungsgemäßen Regelung.

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

• 1 shows a schematic representation of a metering module on an exhaust gas line and an exemplary embodiment of the system according to the invention for regulating the temperature of the metering module.
• 2 shows a schematic representation of an exemplary embodiment of the control system according to the invention.

Embodiments of the invention

1 shows a schematic representation of a dosing module 1 an SCR system, which is attached to an exhaust system 2 an internal combustion engine, not shown, of a motor vehicle. The dosing module 1 has a metering valve 11 on, which is a reducing agent solution, which is provided by a conveyor system (not shown), via a dosing tip 12th in the exhaust system 2 dosed. The dosing tip 12th is by means of a flange connection with the exhaust system 2 connected and is in thermal contact with the exhaust gas coming from the internal combustion engine through the exhaust system 2 flows. At the dosing tip 12th a partial volume A is shown. The temperature T _{A of} this partial volume A is of interest for metering. If the temperature T _{A is} too low, for example below 140 ° C., the reducing agent solution metered in can form a liquid wall film on the inside of the exhaust gas line due to insufficient evaporation 2 form. If the local exposure to the reducing agent is too high, _{solid deposits of the reducing agent solution can occur at a temperature T A of} the partial volume A in a range from 175 ° C. to 250 ° C. An optimal temperature range Ts for the metering is, for example, above 140 ° C and is determined by specifications for component protection for the metering valve upwards 11 limited. A temperature T _I in the metering valve 11 is limited by the requirements for component protection, z. B. to 120 ° C - 140 ° C. The temperature T _{I of} the metering valve 11 depends on the temperature T _A of sub-area A, the heat transfer between the dosing tip 12th and the dosing valve 11 and the dimensions of the coolant inlet 3 away.

In addition, in 1 an embodiment of the system according to the invention for regulating the temperature of the metering module 1 shown. The dosing module 1 has a heat exchanger body 13th inside the dosing module 1 is arranged and the metering valve 11 including the dosing tip 12th surrounds and is in thermal contact with them. The system for regulating the temperature of the Dosing module 1 has a coolant inlet 3 and a coolant return 4th on which the heat exchanger body 13th connect to a main coolant circuit. The main coolant circuit is connected to the internal combustion engine and is used to cool it. The flow rate and the temperature of the coolant in the main coolant circuit are regulated in such a way that the operating temperature of the internal combustion engine is in an optimal range. The coolant in the line 5 the cold side comes from a cooler (not shown) and therefore has a low temperature; It is therefore also referred to as cool coolant in the following. The coolant in the line 6th the hot side comes from the internal combustion engine and flows to the cooler and therefore has a higher temperature.

The coolant supply 3 is via a three-way valve 51 with one line 5 connected to the cold side of the main coolant circuit. The cool coolant flows out of the line 5 the cold side in the heat exchanger body 13th of the dosing module 1 where it absorbs or gives off heat depending on the application (see below). The three-way valve 51 points to the coolant inlet 3 open a check valve, so that the coolant from the coolant inlet cannot flow back into the main coolant circuit. The coolant return 4th is via a three-way valve 61 with one line 6th connected to the hot side of the main cooling circuit. Coolant, which the heat exchanger body 13th in the dosing module 1 has flowed through, is via the coolant return 4th reintegrated into the main coolant circuit and transported to the cooler. The three-way valve 61 points to the coolant return 4th open a check valve.

In the coolant supply 3 is a heating element 31 provided, which the coolant in the coolant inlet 3 can heat up before the heat exchanger body 13th achieved. There is also a pump 32 provided in the coolant inlet, which the mass flow ṁ _k of through the coolant inlet 3 can adjust the pumped coolant. In one embodiment, the is by the pump 32 determined mass flow ṁ _{k of} the coolant from a speed-dependent pump characteristic. In one embodiment shown here is a flow sensor 33 downstream of the pump 32 provided, which measures the mass flow ṁ _{k of} the coolant. There is also a temperature sensor 34 downstream of the heating element 31 arranged, which _{measures the temperature T K of} the coolant. The heating element 31 , the pump 32 and the sensors 33 , 34 are with an electronic control unit 7th tied together. With the heating element 31 and the pump 32 can regulate the temperature T _A of sub-area A on the control unit 7th be performed. Such a scheme is in conjunction with 2 described below.

In the exhaust system 2 are upstream of the dosing module 1 further sensors 21 , 22nd arranged, on the one hand, a temperature sensor 21 , which measures the temperature T _{E of} the exhaust gas, and a mass flow sensor 22nd , which measures the mass flow ṁ _{E of} the exhaust gas. The two sensors 21 , 22nd are also connected to the control unit. For the two sensors 21 , 22nd in the exhaust system 2 can also be in the exhaust system 2 existing sensors can be used.

2 shows a schematic representation of a regulation according to an embodiment of the method according to the invention. An optimal temperature range T _S of sub-range A for metering in is specified. This is above 140 ° C, for example, and is increased by specifications for component protection in the dosing module 1 existing dosing valve 11 limited. The upper threshold for the optimal temperature range Ts is set in advance for the dosing module used 1 experimentally from the relationship to the temperature T _{I of} the metering valve 11 determined and stored in characteristic maps that are accessed during the control. The current temperature T _A of sub-area A is compared with the optimal temperature range Ts. The determination of the current temperature T _A is described further below. If the current temperature T _A of sub-range A deviates from the optimum temperature range Ts, the difference is sent to a controller 100 passed on. The regulator 100 controls an actuator 101 , which is a power P _{H of} the heating element 31 and a speed n _{P of} the pump 32 . The heating element 31 and the pump 32 as well as the heat exchanger body 13th are part of the controlled system 102 . If the current temperature T _{A of} the partial volume A is below the optimal temperature range Ts, the power P _{H of} the heating element 31 increases, whereby the coolant is heated and finally the temperature T _{A of} the partial volume A is increased. If the current temperature T _{A of} the partial volume A is above the optimal temperature range T _S , the speed n _{P of} the pump 32 increases, whereby the mass flow ṁ _{k of} the coolant increases and finally the temperature T _{A of} the partial volume A is reduced. The heat Q _E , which is given off by the exhaust gas to the partial volume, flows into the control as a disturbance variable. _{The heat Q E} given off by the exhaust gas can be derived from the temperature T _{E of} the exhaust gas, which is determined by the temperature sensor 21 is measured, and the mass flow ṁ _{E of} the exhaust gas, which is measured by the mass flow sensor 22nd is measured, determined.

The temperature T _{A of} the partial volume A is determined by the temperature T _{K of} the coolant in the coolant inlet 3 by means of the temperature sensor 34 and the mass flow ṁ _{k of} the coolant through the coolant inlet 3 measured 110. Alternatively, the mass flow ṁ _{k of} the coolant can also be determined from the above-mentioned pump characteristic. Eventually becomes a model 111 used to to deduce the temperature T _{A of} the partial volume A from the measured temperature T _K and the measured mass flow ṁ _{k of the coolant.}

• Bei einem Kaltstart der Verbrennungsmaschine gibt das Abgas keine oder nur wenig Wärme Q_E ab und die Temperatur T_A des Teilvolumens A liegt im Bereich der Umgebungstemperatur. Das Heizelement 31 wird angesteuert, um das Kühlmittel auf ca. 75°C - 90°C zu erwärmen, sodass eine möglichst schnelle Aufheizung erfolgt und die Temperatur T_A des Teilvolumens A über 140°C liegt.

Special operating states and the preferred controls are described below:

• During a cold start of the internal combustion engine, the exhaust gas gives off little or no heat Q _E and the temperature T _{A of} the partial volume A is in the range of the ambient temperature. The heating element 31 is activated in order to heat the coolant to approx. 75 ° C - 90 ° C, so that heating takes place as quickly as possible and the temperature T _A of partial volume A is above 140 ° C.

In normal operation of the internal combustion engine, in which the internal combustion engine is operated in a medium or lower power range, the heating element is 31 controlled to heat the coolant to approx. 75 ° C - 90 ° C. Together with the heat Q _{E of} the exhaust gas, the temperature T _A at the partial volume A is approx. 150 ° C. If the temperature T _{K of} the coolant is already high enough, the heating element will 31 not controlled.

In a power mode of the internal combustion engine, in which the internal combustion engine is operated in an upper power range, the heating element is 31 not activated and the coolant is not heated. It becomes the pump 32 controlled to increase the mass flow ṁ _{K of} the coolant and thus _{lower the temperature T A of} the partial volume A.

When the internal combustion engine is switched off, the pump is turned off 32 still controlled to coolant through the coolant inlet 3 to the heat exchanger body 13th of the dosing module 1 to promote. The temperature T _{A of} the partial volume is thus kept low even after the internal combustion engine has been switched off.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 10346220 A1 [0002]

Claims (13)

System for temperature control of a metering module (1), which is arranged on an exhaust line (2) of an internal combustion engine with a main coolant circuit, comprising: a heat exchanger body (13) which is arranged around and / or in the metering module (1); a coolant inlet (3) which is connected to the cold side of the main coolant circuit and to the heat exchanger body (13); and a coolant return (4) which is connected to the heat exchanger body (13) and the hot side of the main coolant circuit, characterized by a heating element (31) which is arranged in the coolant inlet (3). System according to Claim 1 , characterized by a pump (32) which is arranged in the coolant inlet (3). System according to Claim 1 or 2 , characterized by a temperature sensor (34) and / or a mass flow sensor (33) which are arranged in the coolant inlet (3) upstream of the heat exchanger body (13). System according to Claims 1 until 3 , characterized by a temperature sensor (21) and / or a mass flow sensor (22) which are arranged in the exhaust line (2) upstream of the metering module (1). Method for regulating the temperature (T _A ) of a metering module (1), which is arranged on an exhaust line (2) of an internal combustion engine, in a partial volume (A) on the metering tip (12) of the metering module (1) protruding into the exhaust line (2) ), wherein the metering module (1) is connected to a main coolant circuit of the internal combustion engine via a coolant inlet (3) and a heating element (31) and a pump (32) are arranged in the coolant inlet (3), characterized in that - when the temperature (T _A ) is below a lower threshold, the heating element (31) heats the coolant in the coolant inlet (3); and - if the temperature (T _A ) is above an upper threshold, the pump (32) increases the coolant mass flow (ṁ _k ) through the coolant inlet (3). Procedure according to Claim 5 , characterized in that the heat (Q _E ) given off by the exhaust gas to the partial volume (A) at the metering tip (12) of the metering module (1) is included in the regulation. Method according to one of the Claims 5 or 6th , characterized in that when the internal combustion engine is started, the heating element (31) heats the coolant. Method according to one of the Claims 5 or 6th , characterized in that during normal operation of the internal combustion engine, the heating element (31) heats the coolant. Method according to one of the Claims 5 or 6th , characterized in that when the internal combustion engine is operating the heating element (31) does not heat the coolant. Method according to one of the Claims 5 or 6th , characterized in that when the internal combustion engine is switched off, the pump (32) continues to deliver coolant to the metering module (1). Computer program which is set up, each step of the method according to one of the Claims 5 until 10 perform. Machine-readable storage medium on which a computer program is based Claim 11 is stored. Electronic control device (7) which is set up to use a method according to one of the Claims 5 until 10 to regulate a temperature (T _A ) of a metering module (1).

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