RU2566208C2 - Injector for water solution of urea - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to the injector for the water solution of urea, it is used to inject the water solution of urea in the spent gases exhaust system of the vehicle. The injector (1) for the water solution of urea containing at least basic casing (2) with fitting (3) for the water solution of urea, valve (4) with valve drive (5), and separate feed pipe (6) for the water solution of urea, at that the feed pipe (6) at least partially goes through the basic casing (2).

EFFECT: assurance of reliable and long-life protection of the injector against damages as result of ice formation.

9 cl, 8 dwg

Description

The present invention relates to an injector for an aqueous solution of urea, with which an aqueous solution of urea can be introduced, first of all, into the exhaust system (exhaust) of an automobile. First of all, an injector is necessary for introducing a liquid aqueous urea solution in a precisely metered way into the exhaust gas of an internal combustion engine (ICE), then it becomes possible to carry out a selective catalytic reduction process (SCR) in the exhaust gas system in such a way that the nitrogen oxides contained in the exhaust gas can to be largely restored.

For this purpose, a large number of different injectors have already been proposed. However, there is a need for improvement, primarily with regard to the economical manufacture of this type of injector for the automotive industry. A particular problem encountered with previously known injectors is that the injectors must also remain operational under icing conditions. In this regard, it should be taken into account, first of all, that the urea aqueous solution contained in the injector can also freeze under normal vehicle operating conditions, and this leads to an increase in the volume of the urea aqueous solution. This increase in volume can periodically lead to blockage in the piping system, as well as to malfunctions or destruction of the injector parts due to high ice pressure. Another problem encountered in injectors of this type is that they are usually located on a hot exhaust pipe. This exposure to heat, which is sometimes significant, can also cause problems when feeding or dosing an aqueous urea solution. This is true, first of all, if gaseous urea supply is to be avoided where possible, or if the threshold temperature of the urea aqueous solution should not be exceeded during feeding. In this regard, it should be noted that the urea aqueous solution begins to evaporate already at a temperature of approximately 110 ° C, so that precisely controlled dosing of the urea aqueous solution can be difficult. Unwanted residues that are difficult to remove can also form and impede the flow of an aqueous urea solution into the exhaust gas. In this regard, the problem of cooling the injector often also arises.

Based on the foregoing, the aim of the present invention is to solve at least some of the problems mentioned with reference to the prior art. First of all, an injector for an aqueous urea solution should be proposed, which can be manufactured economically, is not sensitive to the ice pressure of an aqueous urea solution during freezing, and is sufficiently protected from high temperatures of the exhaust system.

These goals are achieved using the injector according to the characteristics of claim 1 of the claims. Other favorable injector configurations are proposed in the dependent claims. It should be noted that the features indicated in the formula separately can be combined with each other in any technologically possible way and illustrate additional configurations of the invention. The description, primarily in combination with the figures, illustrates the invention and shows additional options for its implementation.

The injector for an aqueous solution of urea contains at least a main body with a fitting for an aqueous solution of urea, a valve with a valve actuator, a separate feed tube for an aqueous solution of urea, at least partially extending through the main body, and at least one spring element, which biases the valve toward the main body.

An aqueous urea solution is sometimes called a reducing agent or a precursor of a reducing agent, since an aqueous solution of urea is converted to ammonia after thermolysis or hydrolysis and can then react with nitrogen oxides in the exhaust gas. In this example, a 32% aqueous urea solution, which, for example, is commercially available under the trade name AdBlue®, is used.

The main body, first of all, is a metal part, which can be constructed, on the one hand, with passages, surface recesses, contact surfaces for the valve and cooling system and with channels for supplying an aqueous urea solution. The main body, first of all, is an integral part that simultaneously serves as the base or support for the valve. Although, in principle, it is possible that the main body contains a plurality of valves and / or a plurality of fittings for an aqueous urea solution, a configuration with one valve and one fitting is still preferred. The fitting, in General, is made in the form of a passage in the main body. Since, in this regard, the main body is also at least partially in contact with the urea aqueous solution, the material for the main body and / or the coating on the contact surfaces open to the urea aqueous solution is made to be resistant to the urea aqueous solution . The fitting, first of all, is also made in such a way that conventional pipe connectors can be integrated or fixed on it.

Typically, the valve comprises a valve element in which inlet tubes and tubes for dosed flow are formed. In addition, a controllably actuated piston may be provided that can be actuated by the valve actuator, as necessary, so that the fitting, especially from the inlet tubes to the metered-flow tube, can open and close as necessary ( for example, depending on time). For this purpose, the valve may further comprise a plug connector for connecting the valve or valve actuator to the control unit (electrical or conductive signals), which initiates the operation of the valve, and thereby the injector, as necessary. It is particularly preferred if the valve and the valve actuator are made as far away as possible from the feed point of the urea aqueous solution, that is, first of all, on the side of the main body remote from the exhaust pipe. This gives, first of all, the position of the fitting for an aqueous solution of urea, which is therefore located between the exhaust pipe and the valve.

It is also contemplated that the injector has a separate feed tube for an aqueous urea solution that at least partially passes through the main body. Therefore, a separate supply tube is made, first of all, in such a way that it is a separate part, which is located, preferably completely, inside the main body. The feed tube is made primarily in the form of a small tube, first of all, a small tube passing in a straight line. Preferably, a metal feed tube is used, which consists primarily of material other than the material of the main body. In addition, it is preferable that the separate supply pipe is located mainly at a distance from the main body so that, first of all, the thermal conductivity between the separate supply pipe and the main body is minimized. Therefore, it is most preferred that at most 10% of the surface of the individual supply tube is in contact with the main body. The term "feed tube" primarily refers to the part of the pipe system for an aqueous urea solution, which is located downstream of the valve, primarily right at the place of supply to the exhaust system. Since, according to the above-described embodiment, the valve is preferably located on the side of the main body remote from the exhaust pipe, the supply pipe extends, for example, in the center through the entire main body.

This configuration of the injector alone leads to a significant improvement in relation to the problems detailed above. On the one hand, in this way, the valve can be protected from high temperatures of the exhaust system, but at the same time, the boiling of an aqueous urea solution in a separate feed tube is also reduced as a result of the low level of thermal conductivity to the main body.

In addition, the injector is provided with at least one spring element that biases the valve toward the main body. First of all, the purpose of the spring element is to reverse the stroke or movement of the valve relative to the main body, which occurred after the formation of ice. In addition, given the reservoir or the amount of urea aqueous solution stored therein, the spring element can be designed in such a way that in fact it only allows the valve to move relative to the reservoir when ice is formed. The spring element may be located primarily between the cover and the valve actuator, but it is also possible, for example, to fix the cover on the main body using fastening means, optionally, spring elements are provided between the cover and the main body or the fastening means. First of all, the spring elements can be made in the form of ring springs or spring washers.

The technical result achieved by the implementation of the invention is to provide reliable and durable protection of the injector from damage due to ice formation.

According to another improvement of the injector, it is also proposed that a separate supply tube terminates in the nozzle plate. This nozzle plate is preferably mounted opposite the valve at the end of a separate supply tube. First of all, a separate feed tube and nozzle plate form a separately detachable assembly. The nozzle plate is primarily distinguished by the fact that it is perforated by nozzle openings that spray an aqueous urea solution from the feed tube into the exhaust pipe at a predetermined angle of the jet. The angle of the jet can be adjusted, first of all, to ensure the configuration of the nozzle or spray cone produced by it. Preferably, the nozzle plate is made in the form of a disk, especially the space surrounding the separate feeding tube is limited when located in the injector, primarily located at a distance from the main body. In addition, the nozzle plate can be used to create a connection or mount on the injector, being located at a distance from a separate supply tube, so that it is possible to accurately orient the feed direction. A nozzle plate can also be provided with a material that has low thermal conductivity (for example, compared with the main body), is resistant to high temperatures (since it can come into contact with the exhaust gas), and is optionally made with a surface that repels an aqueous urea solution. That is, the nozzle plate is made primarily in the direction of the exhaust system in such a way that any remaining drops of an aqueous solution of urea on it can remain there only for a short time. This repellent coating primarily prevents (only) the partial evaporation of an aqueous urea solution and thus the formation of unwanted by-products or deposits. The outer surface of the nozzle plate preferably has a roughness of less than 0.2 mm and / or a titanium oxide coating.

According to yet another improvement of this injector, it is also proposed that the nozzle plate has at least a plurality of nozzle openings or forms a protruding end of the supply tube. It is particularly preferred that both of these features are implemented. Regarding the number of nozzle openings, it is preferable that at least two openings be provided, but so that their number does not exceed, for example, 5. It is most preferred that the nozzle openings are oriented or arranged so that jets of an aqueous urea solution leaving them intersected or collided with each other. In this way, a particularly favorable spray cone can be obtained. For example, nozzle holes are drilled through the nozzle plate in the form of microchannels, preferably by laser drilling.

In addition, it is preferable that when using the injector, the exhaust gas passes, where possible, in parallel past the nozzle plate (and nozzle holes). In order to remove, where possible, all the drops of an aqueous urea solution that are still held at the end of the dosing process, this area should protrude, that is, first of all, protrude as far as possible into the exhaust pipe. It is sufficient if the protrusion is very short, for example up to a maximum of 1 mm, especially even up to 0.5 mm or up to 0.2 mm. This short protrusion gives the advantage that the exposure of the injector to heat in the area of the nozzle plate is simultaneously reduced, first of all, for a separate supply tube connected to it.

In addition, it is considered particularly favorable if the main body also contains a cooling system that has an inlet and an outlet, as well as at least one cooling channel that extends through the main body and is partially penetrated by the supply tube. In other words, this means, first of all, that the main body contains passages that form the inlet for the cooler and the outlet for the cooler. It is particularly preferred that the cooling channel is formed concentrically in the supply pipe, i.e. in the form of an annular channel, especially along the predominant part of the individual supply pipe. Therefore, the cooling channel preferably extends in such a way that, starting from the inlet, it extends into the inner region of the main body, extends downward in the region between the supply tube and the outer wall or towards the side opposite the valve, there it is conducted in the region of the inlet or the nozzle plate is centered inward again to the feed axis, and then, at least partially, extends parallel to the feed axis and concentrically around the supply tube before the cooling channel finally extends to the outlet again shortly before it reaches the side with the valve. In this regard, the cooling system is designed primarily in such a way that a countercurrent heat exchanger is formed in the area of the supply tube, the cooler flowing to the valve and the introduced urea aqueous solution flowing from the valve. Most preferably, the cooling channel also extends to the nozzle plate, where, first of all, for a fresh, cold cooler, it is possible to flow around the entire area surrounding a separate supply tube.

In addition, it is also considered favorable if the main body forms a reservoir for an aqueous urea solution next to the valve, the valve being movably relative to this tank. First of all, the reservoir provides an urea solution for the valve. Thus, the reservoir is formed primarily between the valve and the main body. Most preferably, if the valve is at least partially located in the tank in such a way that the tank is limited by the main body, the valve and the sealing means, especially the sealing rings. The reservoir, which ultimately stores the urea aqueous solution for the valve during operation, is preferably annular, in particular the central annular segment conveys the injected portion of the urea aqueous solution in the direction of a separate feed tube. Since an aqueous urea solution is usually present in the indicated reservoir and can freeze at low temperatures, the urea aqueous solution expands in the indicated reservoir. To prevent damage to the injector, the valve is movably relative to the specified reservoir. This primarily means that the entire valve can be moved away from the main body, primarily along the feed axis. This movement, first of all, the stroke (for example, up to 2 mm, primarily more than 1 mm) is reversible, that is, when the urea aqueous solution melts again, the valve moves back to its normal position. Thus, it is also ensured that the same amount of an aqueous urea solution is always stored in the tank during operation.

In addition, it is advantageous if the main body forms a reservoir for an aqueous urea solution next to the valve, the valve comprising a plurality of inlet tubes that lead into the reservoir. It is preferable if a plurality of inlet tubes are formed, for example, with a uniform pitch in the direction along the circumference of the valve, that is, for example, one inlet tube every 120 °. A configuration with a plurality of inlet tubes gives the advantage that the injector can be used in a universal way relative to the final location relative to the exhaust system. Similarly, supply to the valve from the reservoir is also provided if the injector is subject, for example, to vibrations or the like during operation. Depending on the position of the filling level of the reservoir, this basically ensures that at least one of the plurality of inlet tubes is located in the region of the reservoir that currently provides the urea aqueous solution. This greatly increases versatility and improves metering accuracy during operation.

In addition, it is considered favorable if a base with a socket for the main body is provided, moreover, between the base and the main body in the region around the part of the supply tube an insulation is formed in the form of an air gap. First of all, the purpose of the base is to orient the main body relative to the exhaust pipe and securely fix it there. First of all, the base is also metal. The socket is configured, first of all, in such a way that the position of the main body is oriented at the base. The heat flux to the main body can be reduced, since a large area of the base is usually fixed to the hot exhaust system. For this reason, it is proposed that, first of all, the lower region of the main body facing the exhaust pipe is thermally disconnected. It is preferable here mainly to prevent unwanted heat flow from the exhaust pipe to the urea aqueous solution, on the one hand (to avoid boiling) and to prevent unwanted strong cooling of the exhaust pipe, on the other hand (to reduce the risk of deposits on the inside of the exhaust pipe). For this purpose, an annular or cup-shaped cavity is formed, first of all, by the base and the main body and forms an insulation in the form of an air gap. Thus, it is preferable, first of all, that the contact between the main body and the base was provided directly only on the side of the base, remote from the exhaust pipe. First of all, it is also preferable that only a linear contact or a repeating point contact is formed between the supply tube or nozzle plate and the base in the urea aqueous solution supply region. The gap between the base and the nozzle plate can optionally also be sealed with sealing means or a gasket located in the air gap.

According to another improvement of the injector, at least one gasket is provided in at least one insulation in the form of an air gap. The gasket is primarily used for precise orientation or simplified assembly of the base and main body relative to each other. This gasket can be made, for example, in the form of a washer, in the form of a metal seal, in the form of a spring element or the like. The gasket, first of all, has such a shape that the thermal conductivity from the base to the main body is negligible. First of all, materials are provided having low thermal conductivity and / or parts having a small contact area with the base and the main body. Most preferably, only one gasket is provided that forms a guide for the main body in the base seat.

In addition, it is also proposed that the fitting for an aqueous urea solution be made with a closed outlet. An injector of this type is usually installed downstream of the urea aqueous solution feed device. This means that the urea aqueous solution is stored under increased pressure, for example, under a pressure of 5 to 8 bar, in the connecting pipe from the supply device (for example, a pump) to the injector, and therefore in the fitting area in the main body. The goal of the outlet being closed is to relieve pressure in a predetermined position, for example, when an injector requires maintenance or replacement. First of all, the pressure on the volume of the urea aqueous solution under pressure in the injector can be relieved, and it can flow out through the outlet, at least partially. The output is made, first of all, in the form of a branch to the fitting and is closed with a stopper, for example, with a sealing screw.

The invention and the technical context will now be described in more detail with reference to the figures. It should be noted that the figures show particularly preferred embodiments of the invention, although the invention is not limited to them. Shown on:

Figure 1: external, partially exploded, view of the injector for an aqueous solution of urea,

Figure 2: sectional view of the injector for an aqueous solution,

Figure 3: sectional view of the main body and base assembly,

Figure 4: a component formed by a separate feed tube and nozzle plate,

Figure 5: detail of figure 4,

6: detail of the insulation in the form of an air gap between the base and the main body,

7: detail of the injector for an aqueous solution of urea with a closed outlet,

Fig. 8: automobile with an exhaust aftertreatment system comprising an injector for an aqueous urea solution.

Figure 1 is a partially exploded perspective view of a variant of the injector 1 for an aqueous urea solution. The adapter for pipe fittings 28 is shown by a dashed line on the right side of FIG. 1, the upwardly directed pipe fittings forming, for example, the supply and discharge of cooling water, and the central linear pipe fitting is a tube for an aqueous urea solution. These pipe fittings 28 can now be conveniently located on the main body 2 of the injector 1, for example, using screws, as shown in this example. Pipe fittings 28 for the cooling system lead into the inlet 11 or the outlet 12 provided for this purpose. The fitting 3 is formed in the main body 2 opposite the pipe fitting 28 for an aqueous solution of urea, primarily in the form of a passage. The main body is a molded part. To prevent solids from entering the injector 1, a filter 27 is also provided in the area of the fitting 3, and first of all, it contains a coarse filter (for example, with a mesh size of more than 100 microns) and a fine filter (for example, with a mesh size of less than 50 microns), that is, it consists of several layers. Consequently, an aqueous urea solution flows into injector 1 through this fitting 3 and filter 27.

A valve 4 is also shown above the main body 2, and in this example it is located under the cover 24. The cover 24, in which the valve 4 with the corresponding plug connector 26 is located, is displaced relative to the main body 2 by fixing means 25. Optionally, it is also possible to provide spring elements between the fastening means 25 and the cover 24 so that, first of all, when the valve 4 moves, the cover can optionally also make a compensating movement, especially in the form of a stroke, relative to the fastening means 25.

This component can now be inserted into the base 17, which is usually connected to the exhaust pipe. For this purpose, the base 17 contains an internal socket 18 so that the main body 2 is positioned with an exact fit and oriented along the circumference relative to the base 17.

Figure 2 shows an embodiment of an injector 1 for an aqueous urea solution. The fitting 3 for an aqueous urea solution is again shown on the right in FIG. 2. The direction of flow 30 of the aqueous urea solution through the injector 1 is also shown by black arrows. The filter 27, in turn, is shown in this fitting 3 and in this example is bent against the direction of flow 30, which is especially favorable since any incoming solid components are deposited in the outer edge region and therefore do not interfere with the flow in the center. Then the filtered aqueous urea solution flows further through the narrowed part of the channel to the valve 4. The main body 2 is configured so that a reservoir 14 is formed between the valve 4 penetrating the main body 2 and the end of the channel from the fitting 3 for the urea aqueous solution. The reservoir 14 in this example is substantially circular and is bounded or sealed inside and outside by the o-rings 35 (O-rings). Valve 4 comprises a plurality (namely, three) of inlet tubes 15 by which an aqueous urea solution can be sucked into the valve. The valve itself (with a valve flap or valve stem) is located above them and is actuated by the valve actuator 5. The control signals or power supply for the valve actuator 5 is supplied through a plug connector 26, which protrudes from the cover 24. Thus, the plug connector 26 is also significantly removed from the exhaust pipe and is therefore subject to slight heat. Now, if valve 4 is actuated, the inlet to the supply pipe 6 is opened in such a way that a predetermined amount of an aqueous urea solution can enter the supply pipe 6 until it again leaves the supply pipe 6 at the opposite end, first of all, into the exhaust gas flow of the internal combustion engine. A separate supply pipe 6 is flush with the valve 4 and is primarily surrounded by an internal O-ring 35. Optionally, a weld can be made between the separate supply pipe 6 and the main body 2 in the contact surface of the region 4 facing the valve.

Since the urea aqueous solution can now accumulate in the reservoir 14, there is a risk that, if the urea aqueous solution freezes, substantial pressure can occur. For this purpose, the valve 4 (together with the valve actuator 5) is made so that it is movable relative to the main body 2 and the cover 24. If the pressure inside the tank 14 increases, it is possible that the valve 4 and the valve actuator 5 will move, first of all , in the form of a stroke 22. Thus, the outer sealing ring 35 ensures that the tank 14 is still tight. Compensating movement or stroke 22 is made possible or is regulated by a spring element 16, with which the valve (together with the valve actuator 5) is displaced relative to the main body 2. If the pressure is too high as a result of ice formation, the valve 4 moves up, and if the urea is frozen in water again melts, and then the pressure decreases there, the spring element 16 again moves the valve 4 down.

The cooling system 10 is also shown in the lower region of the main body 2, with the cooler flow direction 29 in this example shown by white arrows. Thus, the cooler flows through an inlet (not shown here) into the interior of the main body 2 until it reaches the shown or visible part of the cooling channel 13. Referring to FIG. 2, the cooler flows downward, away from the supply tube 6, in the direction of the feed point or the hottest point for the urea water solution, where it deviates (in almost the opposite direction), and then flows back concentrically in the direction of valve 4 through the predominant part of a separate supply tube 6 in the form of a coating stream. Shortly before valve 4 is reached, the cooling channel 13 leaves the area around a separate supply tube 6 and extends further to an outlet (not shown). In this way, a countercurrent heat exchanger is formed inside the main body 2, regardless of the configuration of the rest of the injector, and ensures that the urea aqueous solution located in the supply pipe 6 is reliably cooled and that boiling of the urea aqueous solution is prevented. In order to ensure that this happens almost right up to the point of supply of the urea aqueous solution, the cooling channel 13 extends, first of all, to the nozzle plate 7, which forms the protruding end 9 of the injector 1. Therefore, even this part, which is subject to high temperatures, can be reliably chilled.

In addition, a base 17 is also shown here, wherein an insulation 20 in the form of an air gap is formed around the perimeter around the main body 2, as well as a separate supply tube 6. Therefore, on the one hand, a cooling jacket, and on the other hand, a shirt in the form of an air gap are provided around the supply tube 6 in the region 19 close to the feed point so that active and passive thermal insulation are provided in a circumferential direction concentrically to the supply tube 6.

Figure 3 is a cross-section through a device in which the main body is inserted into the base 17. First of all, Figure 3 is an enlarged view of the insulation 20 in the form of an air gap. It is seen that the main body 2 is actually only in a heat-conducting contact in the end region opposite the exhaust pipe. The insulation 20 in the form of an air gap and the concentric cooling channel 13 extend around the central axis 31 of the supply practically over the entire height of the base 17, but at least 70% or 80% of the height of the socket in the base 17. The insulation 20 in the form of an air gap is the strongest (for example, as a result of the large distance between the base 17 and the main body 2) where the base 17 is massive in the area of the exhaust pipe, since it is here that a high heat capacity is provided for the waste heat of the exhaust system. Thus, the insulation 20 in the form of an air gap is particularly pronounced in this area 19.

Figure 4 illustrates a component consisting of a separate feed tube 6 for an aqueous solution of urea and a nozzle plate 7 to be located near the supply point, that is, opposite the valve (not shown). A separate supply tube 6 may include an extension 18 in the region of the ends, for example, to compensate for positional tolerances. The volume 32 of the tube inside the supply tube 6 should be low, if possible, that is, first of all, a small cross section 33 of the tube should be obtained. For example, the volume 32 of the tube may be less than 100 mm or less than 60 mm. Thus, a separate nozzle plate 7 is formed at the end and rigidly connected (welded) to the supply pipe 6. The nozzle plate 7 contains a recess 19 around the contact area with the supply pipe 6, allowing the cooler to flow as close to the end of the supply pipe 6. First of all, thus, it is also possible to cool the nozzle holes 8 formed in the nozzle plate 7 at the end of the supply tube 6. An enlarged view of this part is shown in FIG.

Figure 5 shows the aforementioned detail of figure 4. It is seen that in front of the nozzle plate 7 contains a weld seam 37 connecting it to the end of the supply tube 6. The weld seam 37 can also be made by spot welding. The nozzle plate 7 is mounted flush with the end of the supply tube 6, and also completes the end of the supply tube in the direction along the circumference. Two nozzle openings 8 that extend obliquely to the power axis 31 are shown adjacent to the extension 38 shown in this example. The nozzle openings 8 are primarily configured in such a way that an angle 36 of the jet is obtained between them, which is preferably less than 20 °. The nozzle openings 8 are preferably oriented in such a way that the jets of the urea aqueous solution thus formed are connected after exiting the nozzle plate 7. A particularly effective spray pattern with very small drops of the urea aqueous solution can be obtained with colliding jets of this type, making it possible to achieve an improved distribution of the aqueous urea solution in the exhaust gas.

Figure 6 shows another detail of the injector 1 for an aqueous solution of urea. In this example, first of all, the insulation option 20 is again shown in the form of an air gap. Similarly, in order to ensure that the main body 2 is firmly located in the base 17, and with little movement, while the thermal conductivity from the base 17 to the main body 2 is simultaneously reduced, the insulation 20 in the form of an air gap is formed by the outlet 12. In this example, the gasket 21 is made in the form of a profiled metal part 39, which accommodates the main body 2 as a basket. A profiled metal part is, first of all, a type of spring element, which has such a shape that it forms only linear contacts 10 with the main body 2 or nozzle plate 7, on the one hand, and the base 17, on the other hand. Line contacts 10 enable orientation of the main body 2 or nozzle plate 7 relative to the base 17, but they do not overcome significant thermal conductivity through the shaped metal part 39.

Fig.7 is another cross section of the injector for an aqueous solution of urea, in this example only the lower partial region is shown. A separate supply tube 6 penetrating the main body 2 is shown in the center with the nozzle plate 7. In this example, the insulation 20 in the form of an air gap is also achieved by a washer 34 as a gasket. Washer 34 may be formed by a thermal insulator and / or sealing material in the direction of the exhaust pipe. Thus, a corresponding air gap insulation 20 can be obtained between the nozzle plate 7 and the base 17 to the feeding point where the nozzle plate 7 penetrates the base 17. Thus, the air gap insulation 20 can also be saved when the main body 2 and the base 17 is assembled using fasteners 25.

An outlet 23 is also shown on the right side of FIG. 7, which enables communication with the fitting 3 in the main body 2 for an aqueous urea solution. The outlet 23 can be closed by a plug 41, primarily with a screw. The plug 41 may be removed for dismantling or servicing the injector in such a way that the volume of the aqueous urea solution in the fitting 3 can be removed through this outlet 23.

On Fig shows a particularly preferred area of application of the injector 1 for an aqueous solution of urea. A car 50 with an internal combustion engine 42, for example a diesel engine, is shown schematically. The exhaust gas generated in the internal combustion engine is transported to the exhaust gas exhaust system 43, which contains at least one exhaust pipe 44. For the SCR process, the reducing agent (in this example, ammonia) is first introduced into the exhaust gas, and then the mixture is fed through the exhaust gas treatment device 45, primarily catalytic converter The nitrogen oxides contained in the exhaust gas can then be subjected to catalytic conversion in the exhaust gas treatment device 45 at an appropriate exhaust gas temperature and with a selective dosage of an aqueous urea solution in the exhaust gas upstream of the exhaust gas treatment device 45. The ammonia required for this process is obtained from an aqueous urea solution by thermolysis and / or hydrolysis, in the presence of exhaust gas. In turn, this solution is fed through the injector as needed. The urea aqueous solution can be stored, for example, in the reservoir 46 and can be transported to the injector 1 through a supply device 47, comprising, first of all, a pump. The operation of the feeding device 47 and / or injector 1 can be controlled as necessary by a superior control unit. It can take into account test data relating to the composition of the exhaust gas, the temperature of the exhaust gas and / or the state of the internal combustion engine. This control unit can also be part of the engine management system.

Thus, the invention discloses a practical, accurately dosing and frost-resistant injector, which can be manufactured in an economical way.

LIST OF REFERENCE NUMBERS one Injector 2 Main body 3 Fitting four Valve 5 Valve actuator 6 Feed tube 7 Nozzle plate 8 Nozzle hole 9 the end 10 Cooling system eleven Inlet 12 Outlet 13 Cooling channel fourteen Storage tank fifteen Intake pipes 16 Spring element 17 Base eighteen Nest 19 Region twenty Air gap insulation 21 Gasket 22 Move 23 Exit 24 Cap 25 Fasteners 26 Plug connector 27 Filter 28 Pipe fittings 29th Cooler flow direction thirty Flow direction 31 Power axis 32 Tube volume 33 Tube cross section 34 Washer 35 O-ring 36 Jet angle 37 Weld 38 Expansion 39 Profiled metal part 40 Line contact 41 Bung 42 two 43 Exhaust system 44 Exhaust pipe 45 Exhaust gas treatment device 46 Tank 47 Feed device 48 Connecting tube 49 Deepening fifty Car

Claims (9)

1. An injector (1) for an aqueous solution of urea, comprising at least a main body (2) with a fitting (3) for an aqueous solution of urea, a valve (4) with an actuator (5), a separate feed tube (6) for an urea aqueous solution at least partially extending through the main body (2), and at least one spring element (16) that biases the valve (4) to the main body (2). 2. The injector (1) according to claim 1, in which a separate feed tube (6) ends in the nozzle plate (7). 3. The injector (1) according to claim 2, wherein the nozzle plate (7) has at least a plurality of nozzle openings (8) or forms a protruding end (9) of the supply tube (6). 4. The injector (1) according to claim 1 or 2, in which the main body (2) further comprises a cooling system (10) comprising an inlet (11) and an outlet (12), as well as at least one channel (13 ) cooling, which extends through the main body (2) and is partially penetrated by the supply tube (6). 5. The injector (1) according to claim 1 or 2, in which the main body (2) forms a reservoir (14) for an aqueous urea solution next to the valve (4), and the valve (4) is mounted movably relative to the reservoir (14). 6. The injector (1) according to claim 1 or 2, in which the main body (2) forms a reservoir (14) for an aqueous urea solution next to the valve (4), wherein the valve (4) contains a plurality of inlet tubes (15), which lead into the tank (14). 7. The injector (1) according to claim 1 or 2, in which a base (17) is provided with a socket (18) for the main body (2), and between the base (17) and the main body (2) in the region (19) around part of the feed tube (6), insulation (20) is formed in the form of an air gap. 8. The injector (1) according to claim 7, wherein at least one gasket (21) is provided in the insulation (20) in the form of an air gap. 9. The injector (1) according to claim 1 or 2, in which the fitting (3) for the urea aqueous solution is made with a closed outlet (23).

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