The invention relates to a delivery unit for delivering a liquid additive in a motor vehicle, which delivery unit has a temperature sensor. A delivery unit of said type is for example suitable for delivering liquid reducing agent into an exhaust-gas treatment device of an internal combustion engine.

In the automotive field in particular, exhaust-gas treatment devices for purifying the exhaust gases of internal combustion engines are widely used into which a liquid additive is supplied for the conversion of certain pollutant constituents in the exhaust gas. As liquid additive, use is particularly frequently made of a reducing agent by means of which nitrogen oxide compounds in the exhaust gas can be reduced in an effective manner. In exhaust-gas aftertreatment devices of said type, the method of selective catalytic reduction (SCR) is implemented. As reducing agent, use is generally made of a urea- water solution which can be converted into ammonia within the exhaust gas in the exhaust-gas treatment device or outside the exhaust gas in a reactor provided especially for the purpose. In the case of the conversion within the exhaust gas, there is often arranged in the exhaust-gas treatment device a hydrolysis catalytic converter which catalyses the conversion of urea into ammonia. Nitrogen oxide compounds in the exhaust gas react with the ammonia to form non-harmful nitrogen, water and carbon dioxide. To assist said reaction, a catalytic converter (an SCR catalytic converter) is generally also provided in the exhaust-gas treatment device. Urea-water solution as additive for exhaust-gas purification in motor vehicles is available for example under the trade name AdBlue®. AdBlue® is a urea-water solution with a urea fraction of 32.5 per cent.

To deliver liquid additive into the exhaust-gas treatment device of a motor vehicle, a delivery unit is generally required by means of which the additive can be pumped out of a tank and supplied to the exhaust-gas treatment device. Various aspects must be considered in the design of such delivery units. One important aspect is that commonly used liquid additives (for example also the described reducing agent) can freeze. The 32.5 per cent urea-water solution AdBlue®, for example, freezes at -11°C. In the case of motor vehicles, such low temperatures may arise in particular during long standstill periods in winter. Furthermore, it must be considered that the viscosity of liquid additives may vary with the temperature of the additive. Furthermore, it must be considered that the energy required for evaporating a liquid additive varies depending on how high the outlet temperature of the liquid additive in the delivery unit is.

Furthermore, a delivery unit for delivering a liquid additive into an exhaust-gas treatment device of a motor vehicle should be as cheap as possible and have as precisely settable a delivery rate as possible. In a motor vehicle, such a delivery unit constitutes an additional delivery system in addition to the fuel supply, and should therefore entail as little additional costs as possible. An overdosing and/or underdosing of liquid additive into the exhaust-gas treatment device can be avoided by means of a precisely settable delivery rate. Taking this as a starting point, it is an object of the present invention to solve or at least alleviate the technical problems highlighted in connection with the prior art. It is sought in particular to propose a particularly advantageous delivery unit for delivering a liquid additive. Said objects are achieved by means of a delivery unit according to the features of Claim 1 and also by means of a method according to the features of Claim 9. Further advantageous refinements of the invention are specified in the dependent claims. The features specified individually in the claims may be combined with one another in any desired technologically meaningful way and may be supplemented by explanatory facts from the description, with further design variants of the invention being specified. Accordingly, there is proposed a delivery unit for delivering a liquid additive in a motor vehicle, having at least one temperature sensor by means of which a temperature can be measured in a contactless manner at at least one measurement point in the delivery unit, wherein the temperature sensor and the measurement point have a spacing to one another and a radiation channel which is free from fixtures exists between the temperature sensor and the measurement point.

Here, a delivery unit means in particular a device which, at a suction point, can extract or suck liquid additive out of a tank for storing the liquid additive, and which discharges the liquid additive at a discharge point. The delivery unit is preferably also designed to build up a delivery pressure at the discharge point or in the line system downstream thereof. The delivery unit can be operated such that the delivery pressure of the liquid additive at the discharge point always attains a certain pressure independently of how much liquid additive is demanded or discharged at the discharge point. The pump of the delivery unit may then be referred to as a "pressure-increasing pump". It is also possible for the delivery unit to be designed to discharge precisely a certain predefined quantity of liquid additive at the discharge point. The pump of the delivery unit is then preferably a "dosing pump" which, as it delivers, simultaneously performs a dosing action.

A motor vehicle may be for example a passenger motor vehicle, a heavy goods vehicle or else a ship or a rail vehicle. The liquid additive is preferably a reducing agent for exhaust-gas purification, and particularly preferably urea-water solution.

A temperature sensor which can measure a temperature at a measurement point in a contactless manner (contactless temperature sensor) is in particular not in material contact with the measurement point at which the temperature measurement is carried out. The measurement point is preferably formed by a surface or an outer surface of a component of the delivery unit. The measurement point is preferably composed of a material which can emit and/or reflect radiation comprising information regarding the temperature at the measurement point.

Information regarding the temperature at the measurement point is transported from the measurement point to the temperature sensor by non-material transmission. In particular, there is no exchange of heat between the measurement point and the temperature sensor by thermal conduction and/or by convection, which is of significance for the measurement of the temperature by means of the temperature sensor.

With regard to the transmission of the information regarding the temperature by radiation, there are two different possible concepts for the temperature sensor which may be used in the described delivery unit. In the first concept, the temperature sensor measures the radiation which is emitted passively from the measurement point, and determines the temperature from said radiation. Such radiation is for example the heat radiation emitted by any body on account of its temperature. The wavelength of said radiation is dependent on the temperature. It is therefore possible for the temperature sensor to determine the temperature at the measurement point on the basis of the wavelength of the radiation. In the second concept, the temperature sensor emits radiation which is reflected by the measurement point and strikes the temperature sensor again. At the measurement point, the radiation emitted by the temperature sensor is modified in such a way that the temperature measurement takes place on the basis of the reflected beam which strikes the sensor again. For this sensor concept, the modification of the radiation at the measurement point has a temperature dependency. For example, the wavelength of the radiation can be changed at the measurement point, wherein said change differs depending on what the temperature is at the measurement point. It is also possible for the radiation to be reflected at the measurement point at an angle which is temperature-dependent. Depending on the temperature of the measurement point, the radiation can then strike the temperature sensor again at a different point, and in this way the temperature sensor can identify the temperature at the measurement point.

To ensure that the transmission of the information between the measurement point and the temperature sensor is possible, the radiation channel is provided between the measurement point and the temperature sensor. The radiation channel is free from fixtures. This means in particular that, between the temperature sensor and the measurement point, no material is provided which prevents the transport of the information regarding the temperature (in particular the radiation) between the measurement point and the temperature sensor. It is possible for the intermediate space between the temperature sensor and the measurement point to be filled with air or some other gas. The air or the gas is then permeable to the information regarding the temperature (or the radiation).

The air or the gas preferably furthermore does not perform any (considerable, appreciable) heat transport function in the sense of heat conduction or convection from the measurement point to the temperature sensor, by means of which the information regarding the temperature at the measurement point passes to the temperature sensor.

That the radiation channel is free from fixtures means in particular that no impermeable fixtures are arranged between the measurement point and the temperature sensor. Permeable components or permeable fixtures may be arranged in said radiation channel. Said permeable components or permeable fixtures however do not block the radiation channel. Such components may for example be produced from special filter foils and provided for protecting the temperature sensor. The radiation channel is preferably rectilinear. This means in particular that the radiation channel has no bends or curves, but rather forms, from the measurement point to the temperature sensor, a rectilinear connection which is free from fixtures.

In special embodiments of the delivery unit, it is possible for the radiation channel to have bends. Means for deflecting the information regarding the temperature (or the radiation) are then preferably provided. For example, in the region in which the radiation must bend, there may be arranged a type of mirror by means of which the information regarding the temperature (or the radiation) is deflected.

The described problems, such as the risk of freezing of liquid additive, the temperature influence on the viscosity of liquid additive, and/or the temperature dependency of the energy quantity required for evaporating liquid additive, can be at least partially solved by means of a temperature sensor in the delivery unit.

By means of a temperature sensor in the delivery unit, it is also possible to improve the delivery accuracy of a delivery unit. The temperature of the delivery unit may have a cross-influence on the amount of liquid additive delivered by the delivery unit and on the delivery rate of the delivery unit. For example, an increased temperature can cause the power losses of a delivery unit to rise, as a result of which the delivery rate is reduced. It may also be the case that the viscosity of the liquid additive falls with increasing temperature. In this way, the energy expenditure for delivery is reduced, and the delivery rate of the delivery unit rises with increasing temperature. The temperature may have other influences on the delivery rate (and in particular also on the accuracy of the delivery rate).

The temperature of the delivery unit can be determined by means of a temperature sensor. With the knowledge of said temperature, the described cross-influences can be at least partially taken into consideration, and the delivery accuracy can be improved. By means of a temperature sensor, the heating of the delivery unit (or else of certain components of the delivery unit, such as for example a pump) can be monitored, in order to initiate measures for lowering the temperature of the components if appropriate. For example, if the temperature of a component exceeds a critical temperature, the delivery unit may even be deactivated in order to prevent damage to the component. It is also possible for the delivery rate of the delivery unit to merely be reduced in order to lower the temperature of the delivery unit or of the component.

With the described contactless temperature sensor, monitoring of the temperature of components of the delivery unit can be realized in a particularly simple and cheap manner. There is no need for direct contact between the temperature sensor and the component being monitored. It is thereby possible in particular to dispense with electrical lines to the temperature sensor on the monitored component.

The delivery unit is particularly advantageous if the temperature sensor is an infra-red sensor.

An infra-red sensor can identify infra-red radiation. An infra-red sensor as a temperature sensor is preferably designed so as to receive infra-red radiation from the measurement point. The infra-red radiation emitted from the measurement point comprises information regarding the temperature of the infra-red point. The frequency of infra-red radiation emitted by a body is dependent on the temperature of the measurement point. In this way, information regarding a temperature of the measurement point can be gained on the basis of the infra-red radiation. An infra-red sensor of said type enables a particularly advantageous embodiment of the described delivery unit with a contactless temperature sensor. The delivery unit is also advantageous if the measurement point and the temperature sensor are arranged with a spacing of at least 2 cm [centimetres] to one another. The spacing may preferably also be more than 3 cm or particularly preferably even more than 5 cm. The spacing is preferably not greater than 20 cm.

In this way, it is possible from one position in the delivery unit to measure a temperature at a remote position (the measurement point) in the delivery unit. The temperature may thus be arranged for example in the vicinity of the further electronic components of the delivery unit, whereas the measurement point is situated on a component of the delivery unit which delivers liquid additive. The temperature measurement at the measurement point can thus be utilized to gain information regarding the temperature of the liquid additive in the delivery unit. Connecting lines between the temperature sensor and further electronic components can thus be dispensed with. The outlay for the assembly of the delivery unit is also reduced considerably. Mounting a connecting line from a temperature sensor on a component of the delivery unit to a further electronic component (for example a control unit) is generally cumbersome and can be avoided by means of the described delivery unit with a contactless temperature sensor.

The delivery unit is furthermore advantageous if a plurality of temperature sensors, by means of which temperature sensors temperatures can be measured at different measurement points in the delivery unit, are arranged on a common sensor support.

The temperature sensors are preferably arranged on a common structure. It is for example possible for a plurality of temperature sensors to be mounted on a common (printed) circuit board. Each of said temperature sensors is then designed to measure a temperature at an associated measurement point. From each individual temperature sensor to each individual measurement point there preferably exists in each case one radiation channel which is free from fixtures and via which the temperature at the measurement point can be measured. The individual measurement points are preferably spaced apart from one another, such that the radiation channels may extend in different directions proceeding from the sensor support.

Such an arrangement makes it possible for the temperature sensors to be arranged very close to one another, such that the information from the temperature sensors can be processed very easily by further electronic components in order to monitor the temperature at very different locations in the delivery unit simultaneously in a simple manner.

The delivery unit is furthermore advantageous if temperatures at different measurement points can be monitored by means of one temperature sensor. It is preferable for the different measurement points to be spaced apart from one another, and for in each case one radiation channel which is free from fixtures to exist between the (single) temperature sensor and the different measurement points. The temperature sensor is preferably designed such that it can be switched between the different measurement points, such that it receives information regarding the temperature (or in particular radiation) from different measurement points at different times. For example, the temperature sensor may have a cover which opens up in each case only one radiation channel to one certain measurement point, and which for example can be moved or deformed in order to cover in each case some of the existing radiation channels to some of the measurement points provided, and to open up a particular radiation channel to a particular measurement point. It is also possible for a movable temperature sensor to be used which is directed alternately to the different measurement points and which thus determines alternately the temperatures prevailing at each of said measurement points. In this way, the temperature at different measurement points in the delivery unit can be monitored using only one temperature sensor.

The delivery unit is furthermore advantageous if the delivery unit has at least one heating apparatus for heating additive which is present in the delivery unit.

A heating apparatus may be for example a line through which a liquid for heating the delivery unit flows. The liquid may be for example the coolant of an internal combustion engine. The heating apparatus may also be an electrical heating apparatus which has for example a PTC heating element.

It is particularly advantageous for the delivery unit to have a heating apparatus because, in particular in the case of delivery units with a heating apparatus, monitoring of the temperature of the delivery unit is necessary in order to monitor the result of the operation of the heating apparatus.

The delivery unit is furthermore advantageous if it has a pump for delivering the additive and at least one measurement point is arranged on an outer surface of the pump.

A pump may be for example an electrically driven pump which has a rotary drive or a linear drive. In the case of a pump with a linear drive, an electric drive typically acts directly on a pump piston, which executes a delivery movement such that the pump delivers the liquid additive. In the case of a pump with a rotary drive, a mechanical transmission element such as a connecting rod is typically provided which converts the rotational movement of the pump drive into a linear movement of the pump piston or of a pump diaphragm. The pump piston or the pump diaphragm then performs a delivery movement which leads to the delivery of the additive. A pump normally exhibits power losses. Not all of the electrical energy imparted for driving the pump is actually also absorbed and/or transferred to the liquid additive in the form of a pressure increase and volume delivery of the liquid additive (in the form of the delivery rate). The energy which is not transferred constitutes a power loss, and typically leads to heating of the pump. In this way, a significant increase in the temperature of the pump can arise in particular in the case of pumps with a linear drive. Such an increase in the temperature can be monitored in a contactless manner by means of the temperature sensor of the delivery unit if a measurement point is arranged on an outer surface of the pump. In this way, an undesired temperature increase or damage to the pump as a result of the temperature increase can be avoided because suitable countermeasures for reducing the temperature of the pump can be implemented in good time. Such countermeasures may include for example a partial shut-down of the pump, a reduction in the delivery rate of the pump or even a complete shut-down of the pump.

In pumps with a linear drive, power losses are particularly high. On the other hand, pumps with a linear drive are particularly cheap, and are therefore often used for delivery units for liquid additive. The particularly cheap solution described here for a delivery unit with a temperature sensor for monitoring the temperature of the pump is therefore particularly advantageous in the case of a delivery unit with a pump with a linear drive.

A further component of a delivery unit whose temperature can be monitored by means of a contactless temperature sensor may be for example a portion of a delivery duct for the liquid additive. The measurement point may then be arranged on an outer surface of a line which forms the delivery duct. The temperature sensor may then be used in particular also for measuring the temperature of the liquid additive in the portion of the delivery duct. This functions particularly well if the line which forms the delivery duct in the portion is of thin- walled design with high thermal conductivity, and the temperature of the liquid additive is transferred quickly to the outside (or the measurement point) through the thin- walled line.

Further components whose temperature can be monitored by means of a contactless temperature sensor are for example valves, electronic components and/or the housing of the delivery unit. The measurement point is then preferably arranged in each case on the surface of the respective component.

A contactless temperature sensor for monitoring the temperature of the housing is particularly advantageous if the delivery unit is arranged in a tank for the liquid additive. It is then possible to utilize the temperature of the housing to determine a temperature of the liquid additive in the tank. For this purpose, it is particularly advantageous if the housing is of thin design with particularly high thermal conductivity in the region of the measurement point, in order that the temperature of the liquid additive is transferred particularly effectively to the measurement point.

The delivery unit is furthermore advantageous if the delivery unit has a panel for fastening electronic components, wherein the temperature sensor is fastened to the panel. The panel may be for example an electronic printed circuit board on which, aside from the temperature sensor, there are also arranged further electronic components such as for example processors of a control unit and/or memory chips of a control unit. The panel with electronic components and the temperature sensor may be installed in a housing of the delivery unit as one component during the assembly of the delivery unit. Special application of a temperature sensor for measuring a temperature in the delivery unit is then no longer necessary. If appropriate, it is necessary merely for the described radiation channel from the panel or from the temperature sensor arranged on the panel to the desired measurement point to be free from fixtures. This is realized by means of one-off design measures implemented during the design of the delivery unit, and requires no special assembly steps during the assembly of the delivery unit. This permits particularly simple and cheap assembly of the delivery unit.

Also described within the context of the invention is a method for checking the operating state of a delivery unit by means of which a liquid additive can be delivered, wherein a contactless temperature measurement is carried out at at least one measurement point in the delivery unit, and the temperature of the additive in a delivery duct of the delivery unit can be inferred from the temperature measured at the measurement point.

The method is suitable in particular for being carried out with a delivery unit as described. The contactless temperature measurement takes place preferably by means of a suitable temperature sensor through a radiation channel which is free from fixtures. The described further features of the delivery unit may be transferred to the method. Said method makes it possible to determine the temperature of the liquid additive in the delivery unit using a particularly simple and cheap temperature sensor. The determination of the temperature of the liquid additive from the temperature measured at the measurement point is preferably carried out by means of a calculation within an electronic component or within an electronic component of a control unit of the delivery unit.

The advantages and special embodiment features of the method may be transferred to the delivery unit. Also specified is a motor vehicle having an internal combustion engine, an exhaust-gas treatment device for purifying the exhaust gases of the internal combustion engine, and a delivery unit for delivering a liquid additive into the exhaust-gas treatment device. The motor vehicle preferably has a tank in which the liquid additive is stored and from which the delivery unit can extract the liquid additive. Also preferably provided is a feed device by means of which the liquid additive delivered by the delivery unit can be fed to the exhaust-gas treatment device. The additive is preferably a reducing agent by means of which the SCR process can be implemented in the exhaust-gas treatment device. The tank, the delivery unit and the feed device are preferably connected to one another via a line for the liquid additive.

The delivery unit of the motor vehicle is preferably also suitable for carrying out the described method.

The invention and the technical field will be explained in more detail below on the basis of the figures. The figures show particularly preferred exemplary embodiments, to which the invention is however not restricted. In particular, note that the figures and in particular the illustrated proportions are merely schematic. In the figures: Fig. 1 : shows a first design variant of a delivery unit,

Fig. 2: shows a second design variant of a delivery unit, and Fig. 3 : shows a motor vehicle having a described delivery unit.

Figures 1 and 2 illustrate two different design variants of a delivery unit 1. The delivery unit 1 has, in each case, a housing 18 through which runs a delivery duct 19 for delivering the liquid additive. The delivery duct 19 preferably runs in each case from a suction point (not illustrated) for the extraction or suction of liquid additive, out of a tank, and to a discharge point at which the liquid additive is provided. The liquid additive is preferably reducing agent or urea-water solution. The delivery duct 19 illustrated in figure 1 and figure 2 can be extended, proceeding from the illustration in the figures, in each case to the suction point and to the discharge point by line portions. Said line portions need not be a constituent part of the delivery unit 1 but may rather be formed for example by hoses. There is preferably provided in the delivery duct 19 a pump 10 by means of which the liquid additive can be pumped through the delivery duct 19. The delivery unit 1 preferably also has a heating apparatus 9. The delivery unit 1 preferably additionally has a sensor support 8 which is for example a constituent part of a panel 12 on which further electronic components 13 of the delivery unit 1 are also mounted. As per figure 1, a temperature sensor 3 is arranged on the sensor support 8. A radiation channel 6 leads from the temperature sensor 3 to a measurement point 4 on a component 20 of the delivery unit. Radiation can pass from the measurement point 4 to the temperature sensor 3 through the radiation channel 6. The temperature sensor 3 can determine the temperature at the measurement point 4 by means of said radiation. The radiation channel 6 is free from fixtures 7, such that the path for the radiation from the measurement point 4 to the temperature sensor 3 is free.

In figure 1, the pump 10 is illustrated as component 20, and the measurement point 4 is situated on an outer surface 11 of the pump 10.

Figure 2 shows a design variant in which two temperature sensors 3 are arranged on the sensor support 8, which temperature sensors have in each case a separate radiation channel 6 through which radiation can pass in each case from a separate measurement point 4 to the respective temperature sensor 3. Here, too, the radiation channels 6 are free from fixtures 7. Here, too, the measurement points 4 are situated on components 20 of the delivery unit 1. By way of example, it is also the case in figure 2 that the pump 10 of the delivery unit is illustrated as a component 20, wherein the measurement point 4 is arranged on the outer surface 11 of the pump 10. The further component 20 may for example be a valve.

Figure 3 shows a motor vehicle 2 having an internal combustion engine 14 and having an exhaust-gas treatment device 15 for the purification of the exhaust gases of the internal combustion engine 14. Arranged on the exhaust-gas treatment device 15 is a feed device 17 which receives liquid additive from a delivery unit 1 which is arranged on a tank 16 for the liquid additive. List of reference symbols

1 Delivery unit

2 Motor vehicle

3 Temperature sensor

4 Measurement point

5 Spacing

6 Radiation channel

7 Fixtures

8 Sensor support

9 Heating apparatus

10 Pump

11 Outer surface

12 Panel

13 Electronic component

14 Internal combustion engine

15 Exhaust-gas treatment device

16 Tank

17 Feed device

18 Housing

19 Delivery duct

20 Component