DEVICE FOR POST-TREATMENT OF WASTE GAS

Abstract

A device for exhaust-gas aftertreatment, including a delivery device 2 for delivering a liquid additive out of a tank 1, a pressure sensor 6, an exhaust line 5, a delivery line 3 leading from the delivery device 2 to the exhaust line 5, and an injection device 4 for introducing the delivered additive into the exhaust line 5. The pressure sensor 6 is arranged on the injection device 4.

Description

FIELD OF THE INVENTION

The invention relates to a device for exhaust-gas aftertreatment, including a delivery device for delivering a liquid additive out of a tank, a pressure sensor, an exhaust line, a delivery line leading from the delivery device to the exhaust line, and an injection device for introducing the delivered additive into the exhaust line.

BACKGROUND OF THE INVENTION

For optimum exhaust-gas aftertreatment, it is known for the additive to be injected in as accurately dosed a manner as possible into the exhaust line. The quantity to be injected is dependent on various parameters. Aside from the quantity, the pressure with which the additive is injected is also crucial, because the spray pattern of the additive injected into the exhaust line, and thus the distribution and mixing of the additive over the cross section of the exhaust line, are determined by means of the pressure. A pressure sensor is used to monitor the pressure. For this purpose, it is known for the pressure sensor to be arranged on the delivery device or to be integrated into a module that includes the delivery device. It is a disadvantage here that, during operation, the delivery device generates pressure pulses that are detected by the pressure sensor.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of providing a device for exhaust-gas aftertreatment which detects the pressure prevailing at the injection device as accurately as possible, wherein it is the intention for disturbing influences to be as far as possible reduced or eliminated.

According to the invention, the object is achieved in that the pressure sensor is arranged on the injection device. With the arrangement of the pressure sensor on the injection device, the pressure is measured in the immediate vicinity of the point that is crucial for an optimum injection of the liquid additive. Owing to the immediate proximity to the injection device, the pressure sensor is connected hydraulically rigidly to the injection device. Disturbing pressure pulses of the delivery device are eliminated by means of the great spatial separation thus realized. This is made possible in particular by means of the delivery line and the fluid column present therein, because damping is realized owing to the fluid characteristics. This effect, that has hitherto had an adverse effect on the pressure measurement, is now utilized in an advantageous manner owing to the new arrangement of the pressure sensor. It is thus made possible for the pressure pulses at the injector to be determined. Disturbing effects are virtually ruled out. This permits a rapid correction of the dosed quantity of the additive. Finally, the construction of the delivery module including the delivery device is also simplified. The structural space is likewise reduced, whereby the utilizable volume of a tank for the liquid additive is increased, if the delivery module is arranged in the tank.

The most significant advantage however consists in the fact that, owing to the arrangement and the determination of the pressure pulses at the injection device that is thus made possible, diagnosis of the injection device is also made possible, for example in order to be able to monitor every injection process. Since these deviations detected by the pressure sensor are often only small, it is made possible for the first time by means of the arrangement according to the invention to utilize these deviations for diagnostic purposes. For this purpose, the pressure characteristics of a fault-free injection device are determined in advance. If, during the operation of the device for exhaust-gas aftertreatment according to the invention, deviations in the pressure characteristics arise which go beyond tolerances to be defined, this may indicate impairments of the injection device. Such impairments may be deposits at the injection point via which the additive is injected into the exhaust line. This allows conclusions to be drawn regarding the spray pattern with which the additive is injected into the exhaust-gas flow. Conclusions may likewise be drawn regarding the quantity that is actually injected. Both the additive quantity and the spray pattern are crucial for the subsequent exhaust-gas aftertreatment, because the distribution of the additive in the exhaust gas is determined with the spray pattern, and the quantity determines the degree of exhaust-gas aftertreatment.

In one advantageous refinement, the arrangement of the pressure sensor on the housing of the injection device is achieved with little outlay. In particular, the housings of existing injection devices may thereby continue to be utilized, because the modifications are very small.

In a particularly simple refinement, the housing of the injection device has an opening into which the pressure sensor is inserted.

In another refinement, the pressure sensor is flange-mounted on the housing of the injection device, and a pressure connection to the pressure sensor exists via an opening in the housing.

In another advantageous refinement, protection of the pressure sensor against environmental influences is achieved in that the pressure sensor is arranged within the housing of the injection device.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be discussed in more detail on the basis of multiple exemplary embodiments. In the drawings:

FIG. 1 shows a device according to the invention for exhaust-gas aftertreatment;

FIG. 2 shows a first enlarged illustration of the injection device; and

FIG. 3 shown a second enlarged illustration of the injection device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

FIG. 1 schematically shows a device for exhaust-gas aftertreatment in a motor vehicle. A tank 1 for the liquid additive, in this case an aqueous urea solution, is arranged in the motor vehicle. By means of a delivery device 2, the urea solution is drawn in from the tank 1 and is delivered via a delivery line 3 to an injection device 4. The injection device 4 is arranged on an exhaust line 5 of the motor vehicle. By means of the injection device 4, the urea solution is injected into the exhaust line 5, where it mixes with the exhaust gas. To provide the urea solution to the exhaust-gas line 5 in adequate quantities in a manner dependent on the exhaust-gas flows that arise during the operation of the motor vehicle, the urea solution must be present at the injection device 4 at a particular pressure. The pressure is normally 5 to 7 bar. On the injection device 4, there is arranged a pressure sensor 6 which, owing to the immediate proximity, is connected hydraulically rigidly to the injection device 4. If urea solution is injected via the injection device 4, the pressure drop caused as a result is recorded directly and to the full extent by the pressure sensor 6.

FIG. 2 shows the injection device 4 arranged on the exhaust line 5 in an enlarged illustration. The pressure sensor 6 is flange-mounted on the housing 7 of the injection device 4. The pressure in the injection device 4 is directly detected by the pressure sensor 6 via an opening 8, and is fed as an electrical signal via a line 9 to a control unit (not illustrated).

In FIG. 3, the pressure sensor 6 is inserted into the opening 8 of the housing of the injection device 4, such that the pressure sensor is in direct and immediate contact with the additive and measures the pressure prevailing in the injection device 4.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims

1. A device for exhaust-gas aftertreatment, comprising: a delivery device for delivering a liquid additive out of a tank;a pressure sensor;an exhaust line;a delivery line leading from the delivery device to the exhaust line; andan injection device for introducing the delivered additive into the exhaust line;wherein the pressure sensor (6) is arranged on the injection device (4).

2. The device of claim 1, wherein the pressure sensor (6) is fastened to the housing (7) of the injection device (4).

3. The device of claim 2, the housing (7) of the injection device (4) further comprising an opening (8) into which the pressure sensor (6) is inserted.

4. The device of claim 2, wherein the pressure sensor (6) is flange-mounted on the housing (7) of the injection device (4).

5. The device of claim 4, further comprising: an opening in the housing; anda pressure connection to the pressure sensor;wherein the pressure connection to the pressure sensor (6) exists via the opening (8) in the housing (7).

6. The device of claim 1, wherein the pressure sensor (6) is arranged within the housing (7) of the injection device (4).