Dosing unit for exhaust gas treatment

Abstract

Dosing unit (3) of urea for exhaust gas treatment comprising: - an injector body (6) having at least one electromagnetic actuator, a pin, a nozzle, and an elastic element, - a supply connector (12) - a casing (7) radially external to the injector body (6) acting as a cooling jacket, - a cup element (10), integrally connected to the casing (7), in a distal position with respect to it, - an elastic ring (11) integrally connected to the injector body (6) and capable of expanding in a radially external direction, which ensures the correct axial force needed to lock the injector body, - a sealing gasket (13) to prevent the escape of exhaust gases and atomized urea towards the outside, whereas - the injector body (6) and the casing (7) define a first mechanical stop, - the elastic ring (11) and the cup element (10) define a second mechanical stop, in which the first and second mechanical stops ensure the axial positioning of the injector body (6) inside the casing (7).

Description

[0001] DOSING UNIT FOR EXHAUST GAS TREATMENT

[0002] D E S C R I PTI O N

[0003] Technical field of the invention

[0004] The present invention relates to a dosing unit for treating the exhaust gases of an internal combustion engine. The dosing unit may be, in particular, a urea dosing unit.

[0005] Background art

[0006] Injectors for internal combustion engines are well-known components both in the field of fuel systems for internal combustion engines and in the field of treatment of exhaust gases produced by internal combustion engines.

[0007] Typically, these injectors are operated by an electromagnetic actuator, using a solenoid that can be electrically energized to generate a magnetic field. This magnetic field induces the movement of a moving element that controls the opening or closing of one or more orifices in an injection nozzle. More specifically, the injector closes using a calibrated spring force, while opening occurs when the generated magnetic force prevails over the spring force.

[0008] In the case of an exhaust gas treatment injector, this component, also generally known as a dosing unit, is normally used to inject urea to promote the reduction of nitrogen oxides, a combustion residue, in a special reducing catalyst. The dosing unit is permanently connected to the engine's exhaust manifold, and the urea reaches the dosing unit from a special tank equipped with a pipe to which the dosing unit is connected via a supply connector.

[0009] With reference to Figure 1, which illustrates a dosing unit according to the prior art, the dosing unit 1 comprises an injector body 2 and a casing 4 that serves as a jacket to cool the urea from the heat coming from the exhaust manifold. A first cooling water supply conduit 8 and a second cooling water discharge conduit 9 are fluidly connected to the casing 7 (Fig. la). A mechanical constraint and a seal must be provided between the injector body 2 and the casing 4 to prevent the escape of exhaust gases and atomized urea.

[0010] According to the prior art (Fig. lb), the seal is ensured by a welded joint 5 made near the proximal end of the assembly comprising the injector body 2 and the casing 4.

[0011] The welded solution is impossible to disassemble, so in the event of a malfunction, the entire dosing unit must be replaced, not the individual component responsible for the malfunction. Furthermore, welding is a critical step in the process and requires a significant investment in the assembly line, an investment not suitable for projects with low production volumes.

[0012] Furthermore, the welded joint, under certain conditions, creates an unfavorable thermal bridge that could increase the temperature at the proximal end of the injector body. This portion of the injector body is a critical area and requires proper handling during operation of the dosing unit.

[0013] There is therefore a need to define a dosing unit in which the fixing of the injector body to the external casing is free from or at least minimizes the above-mentioned drawbacks.

[0014] Summary of the Invention

[0015] To substantially address the above-mentioned technical problems, one object of the present invention is to define a urea dosing unit in which the connection between the injector body and the casing is achieved by means of a press-fit connection, making it simple and cost-effective. This solution, by avoiding the need for a welded joint and ensuring a seal with a gasket, allows for the entire product to be disassembled. Furthermore, this solution improves the thermal behavior of the proximal end of the injector by avoiding a thermal bridge between the injector body and the casing.

[0016] Therefore, according to the present invention, a dosing unit is provided having the characteristics set forth in the independent claim, appended to this specification.

[0017] Further preferred and / or particularly advantageous embodiments of the invention are described according to the characteristics set forth in the appended dependent claims.

[0018] Brief Description of the Figures

[0019] The invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting embodiments, in which:

[0020] - Figure 1 is an axonometric view (Fig. la) and a partial cross-section (Fig. lb) of a urea dosing unit according to the prior art,

[0021] - Figure 2 shows a cross-section of a urea dosing unit according to a preferred embodiment of the invention,

[0022] - Figure 3 shows a partial cross-section and an enlarged scale of a first detail of Figure 2, and

[0023] - Figure 4 shows a partial cross-section and an enlarged scale of a second detail of Figure 2.

[0024] Detailed Description

[0025] By way of example and without limitation, the present invention will now be described with reference to Figures 2 to 4. The subject of the present invention is a dosing unit for treating the exhaust gases of internal combustion engines, more specifically, a urea dosing unit.

[0026] With reference to Figure 2, a urea dosing unit 3 is integrally connected to an exhaust manifold (of a known type and therefore not shown) by means of a fastening bushing (also of a known type and not shown).

[0027] It should be noted that the exhaust manifold and the fastening bushing are not part of the present invention.

[0028] Throughout this description and the claims, terms and expressions indicating positions such as "proximal" and "distal" refer to the distance from the exhaust manifold. Terms such as "radially internal" or "radially external" refer to an axisymmetric X-axis of the dosing unit 3.

[0029] With reference to Figure 2, the urea dosing unit 3 according to the present invention comprises:

[0030] - an injector body 6 comprising at least one electromagnetic actuator, a needle, a nozzle, and a spring element. These components are not shown in the figures as they are considered to be of a known type,

[0031] - a supply connector 12, connected to the injector body by means of a snap-fit connection, axially and proximal. The snap-fit connection of the supply connector to the injector body is the subject of a parallel patent application by the same Applicant and, therefore, is not part of the present invention;

[0032] - a casing 7 radially external to the injector body and serving as a cooling jacket. Coolant supply and discharge ducts, such as cooling water, are mounted to the casing 7, in a fluid connection and in a known manner. Casing 7 is necessary for the dosing units 3 because these dosing units are in close contact with the hot exhaust gases from the internal combustion engine.

[0033] According to the present invention and with reference also to Figures 3 and 4, the dosing unit 3 further comprises:

[0034] - a cup element 10, integrally connected to the casing 7, distal thereto. The cup element 10 comprises at least a proximal flanged portion 10a and a distal cylindrical portion 10b;

[0035] - an elastic ring 11 integrally connected to the injector body 6 and capable of expanding in a radially outward direction;

[0036] - a sealing gasket 13 to ensure the seal of the urea inside the injector body 6, preventing part of it from leaking into the casing 7 instead of being entirely injected into the exhaust manifold.

[0037] With these simple elements, it is possible to perform an assembly procedure of the injector body inside the casing, consisting of inserting the injector body into the casing by means of a single maneuver, that is, a push-fit. The correct positioning of the injector body is guaranteed by two mechanical stops, the first between the injector body 6 and the casing 7, the second between the elastic ring 11 and the cup element 10. The presence of the sealing gasket 13 allows the welded joint between the injector body and the refrigerant casing 7 to be avoided.

[0038] In greater detail, the correct and stable positioning of the injector body 6 within the casing 7 is ensured by:

[0039] - a first stop defined axially and proximal to the exhaust manifold between a flanged portion 6a of the injector body 6 and an annular projection 7a of the casing 7. This prevents the injector body 6 from sliding downwards more than necessary, axially and proximal, towards the exhaust manifold; and

[0040] - a second stop defined axially and distal to the exhaust manifold between the proximal flanged portion 10a of the cup element 10 and the elastic ring 11, integral with the injector body 6. This prevents the injector body 6 from protruding upwards, axially and distally, away from the exhaust manifold.

[0041] The operation of the elastic ring 11 is intuitive, similar to the operation of a Belleville or leaf spring: when the injector body is mounted inside the casing 7 and the cup element 10, the elastic ring 11 will be compressed by the cylindrical portion 10b of the cup element 10 and the injector body 6, creating an axial force that holds the latter in the correct position.

[0042] As already mentioned, the presence of the sealing gasket 13 prevents any welding between the injector body 6 and the refrigerant casing 7.

[0043] The sealing gasket is preferably a ring made of polytetrafluoroethylene (PTFE) filled with carbon fibers. This material is used in industry for high-temperature applications.

[0044] An example is the gasoline injection system in direct- injection internal combustion engines, where PTFE is used to ensure a seal between the injector and the engine housing.

[0045] The sealing gasket 13 is inserted between a proximal cylindrical portion 6b of the injector body 6 and an annular portion 7b of the casing 7, where the cylindrical portion 6b of the injector body 6 is radially internal to the annular portion 7b of the casing 7.

[0046] Preferably, the cylindrical portion 6b of the injector body 6 has a groove 6c to accommodate the sealing gasket 13 and a protuberance 6d to increase sealing efficiency.

[0047] Ultimately, the solution presented in this invention allows for:

[0048] - a simple assembly procedure consisting of inserting the injector body into the casing with a single movement, i.e., a press-fit connection. This eliminates the complex welding process;

[0049] - reduced investment in the assembly line;

[0050] - use of components, such as the sealing gasket, obtainable from the current production of other products;

[0051] - the ability to disassemble and work inside the dosing unit to replace a single component rather than the entire unit;

[0052] - consequently, an improvement in the repairability of the dosing unit.

[0053] In addition to the embodiment of the invention as described above, it should be understood that numerous other variations exist. It should also be understood that these embodiments are merely exemplary and do not limit the scope of the invention, its applications, or its possible configurations. Conversely, although the above description allows the skilled craftsman to implement the present invention according to at least one exemplary embodiment, it should be understood that many variations of the described components are possible without departing from the scope of the invention, as defined in the appended claims, which are interpreted literally and / or according to their legal equivalents.

Claims

C LA I M S1. Dosing unit (3) of urea or other reducing compound for the treatment of exhaust gases inside an exhaust manifold of an internal combustion engine, the dosing unit (3) comprising:- an injector body (6) comprising in turn at least one electromagnetic actuator, a pin, a nozzle and an elastic element,- a supply connector (12),- a casing (7) radially external to the injector body (6) acting as a cooling jacket,- the dosing unit (3) being characterized by the fact that it also comprises:- a cup element (10), integrally connected to the casing (7), in a distal position with respect to it,- an elastic ring (11) integrally connected to the injector body (6) and capable of expanding in a radially external direction so as to keep the injector body (6) locked in a correct position,- a sealing gasket (13) to prevent the escape of exhaust gases and of the urea nebulized outwards. and by the fact that:- the injector body (6) and the casing (7) define a first mechanical stop,- the elastic ring (11) and the cup element (10) define a second mechanical stop, in which the first and second mechanical stops ensure the axial positioning of the injector body (6) inside the casing (7).

2. Dosing unit (3) according to claim 1, wherein the first mechanical stop is defined in an axial and proximal direction with respect to the exhaust manifold between a flange portion (6a) of the injector body (6) and an annular projection (7a) of the casing (7).

3. Dosing unit (3) according to claim 1 or 2, wherein the cup element (10) comprises at least one flange portion (10a), proximal, and a cylindrical portion (10b), distal.

4. Dosing unit (3) according to claim 3, wherein the second stop is defined in an axial and distal direction with respect to the exhaust manifold between the flange portion (10a) of the cup element (10) and the elastic ring (11).

5. Dosing unit (3) according to anyone of the preceding claims, wherein the sealing gasket (13) is a ring made of polytetrafluoroethylene loaded with carbon fibers.

6. Dosing unit (3) according to anyone of the preceding claims, wherein the sealing gasket (13) is inserted between a cylindrical portion (6b) of the injector body (6), proximal, and an annular portion (7b) of the casing (7), proximal, wherein the cylindrical portion (6b) of the injector body (6) is radially internal to the annular portion (7b) of the casing (7).

7. Dosing unit (3) according to claim 6, wherein the cylindrical portion (6b) of the injector body (6) has a groove (6c) for positioning the sealing gasket (13).

8. Dosing unit (3) according to claim 6 or 7, wherein the cylindrical portion (6b) is provided with a protuberance to increase the efficiency of the seal.

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