Patent Application
20100146942
This applications claims priority to German application 10 2008 062 479.9, which was filed Dec. 16, 2008.
To purify exhaust gases, vehicle exhaust systems have inserts, for example catalytic converters or diesel particulate filters having catalytic converters connected upstream. Particulate filters require regeneration at regular intervals. To reach the high temperatures that are required for the regeneration, in most cases the particulate filter has an oxidation catalytic converter connected upstream thereof in which the temperature of the exhaust gas is raised. For regeneration it is known to introduce vapor upstream of the particulate filter, the vapor acting as a regeneration agent.
However, oxidation catalytic converters become active only as of a particular temperature, which is not reached during a cold start and in the starting phase of the engine. Increased pollutant values are known to occur in this phase.
It is the object of the present invention to provide an exhaust system which operates effectively in the warm-up phase of the engine as well. In particular, the exhaust system according to the invention is intended to allow a regeneration of the diesel particulate filter at lower temperatures.
According to the invention, an exhaust system of an internal combustion engine, comprises a channel, an insert for purifying exhaust gas within the channel, a mixing chamber arranged upstream of the insert, a vaporizer device vaporizing an oxidizable liquid and introducing generated oxidizable vapor into the mixing chamber, and an ignition device protruding at least partly into the mixing chamber. The exhaust gas flows along the channel through the insert and the mixing chamber. The mixing chamber includes at least one permeable wall and is arranged on a channel wall and protrudes radially into an interior of the exhaust system. The vaporizer device includes a glow element which is heatable in such a way that an auto-ignition of oxidizable vapor occurs on a surface of the glow element.
The combination of the vaporizer device with the ignition device necessitates no additional ignition elements, which reduces the manufacturing expenditure. Since the oxidizable liquid is ignited directly during or immediately upon the vaporizing process, a reliable ignition is additionally ensured.
Furthermore, the invention provides an exhaust system of an internal combustion engine, comprising a channel, an insert for purifying exhaust gas within the channel, a mixing chamber arranged upstream of the insert, a vaporizer device vaporizing an oxidizable liquid and introducing generated oxidizable vapor into the mixing chamber, and an ignition device protruding at least partly into the mixing chamber. The exhaust gas flows along the channel through the insert and the mixing chamber. The mixing chamber includes at least one permeable wall and is arranged on a channel wall and protrudes radially into an interior of the exhaust system. The ignition device includes at least one ignition electrode producing an ignition spark for ignition of the oxidizable vapor.
The oxidizable liquid or a mixture of the vaporized oxidizable liquid and exhaust gas is ignited still inside the mixing chamber before the oxidizable vapor is fed into the exhaust gas channel or into the insert. An ignition spark reliably ensures an ignition of the oxidizable vapor.
The ignition electrodes may be arranged, for example, on a channel wall section which is located radially opposite to the mixing chamber. In this way, the ignition electrodes are arranged outside the mixing chamber and merely protrude into the mixing chamber. This means that the electrodes can be manufactured separately and are so compact as to be positionable in the region of the vaporizer device.
The electrodes employed in this embodiment may be, for example, spark plugs as are commonly used in the automotive sector, which results in reduced manufacturing expenditure and production costs.
In one example, openings are provided on the channel wall of the exhaust system, with the spark plugs protruding through the openings and into the gas guiding channel. The spark plugs may be secured to rims of the openings, for example by a thread provided in each opening or by separate fastening elements. In this way, the spark plugs may be installed or replaced in a simple manner.
To produce a larger or longer ignition spark, the ignition spark may also be produced between two electrodes. This allows the size or length of the ignition spark to be ensured and varied to achieve an improved and reliable ignition effect.
In addition, the arrangement of the electrodes in the mixing chamber allows the ignition spark to be ideally oriented relative to an inflow direction of the oxidizable liquid, so that a more effective ignition occurs. In one example, the electrodes are arranged such that the ignition spark is oriented substantially transversely or perpendicularly to the inflow direction of the oxidizable liquid into the mixing chamber.
In one example, an electronic controller is provided for the ignition device and/or the vaporizer device. The electronic controller on the vaporizer device allows both the amount of the oxidizable liquid and also the temperature of the vaporizer device to be regulated, so that consumption of the oxidizable liquid can be controlled. In addition, an electronic controller for the ignition device permits a generation of an ignition spark as needed, so that the exhaust system can be operated more effectively.
The electronic controller drives the ignition device and/or the vaporizer device depending on the temperature and/or the exhaust gas flow, for example. The amount of the oxidizable vapor can be regulated such that the exhaust gas temperature is maintained in a temperature range that is ideal for the regeneration of the insert. When the temperature in the gas guiding channel is sufficiently high, the electronic controller can reduce the supply of the oxidizable vapor and, where required, suspend the ignition of the oxidizable vapor or, in case the temperature is too low, can supply the oxidizable vapor and/or activate the ignition. The exhaust gas flow may likewise be made use of as an indicator for the electronic controller, since a higher exhaust gas flow occurs in the case of higher speeds and higher exhaust gas temperatures resulting therefrom.
The electronic controller controls more particularly the quantity of the vapor introduced into the mixing chamber as a function of the temperature and/or the exhaust gas flow. The quantity of the oxidizable vapor allows the combustion in the exhaust system and, hence, the exhaust gas temperature to be controlled especially effectively, so that the ideal temperatures for a regeneration are always reached in the exhaust gas flow.
In one example, the vaporizer device includes a glow element, in particular a glow plug, which terminates in the region of, or in, the mixing chamber. The glow element produces the high temperatures that are necessary for a vaporization of the oxidizable liquid.
In one example, the glow element can be heated to different temperatures. The glow element can be heated to a first temperature level which ensures a vaporization of the liquid, and a second temperature level which leads to an auto-ignition of the vapor. As a result, only one component is required for vaporizing the liquid and for igniting the vapor.
The insert of the exhaust system includes a diesel particulate filter, and an oxidation catalytic converter, for example, is arranged in the flow direction upstream of the diesel particulate filter. The catalytic converter may also be dispensed with; in that case, the particulate filter would be burnt free upon ignition of the vapor.
The vaporized liquid may, for example, be a fuel, in particular a diesel fuel.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
The wall of the pipe 2 constitutes a channel wall 12 of the exhaust system 10, which in its interior defines a gas guiding channel 14.
Provided upstream of the diesel particulate filter 4 is a vaporizer device 16 and, optionally, an ignition device 18 which is likewise arranged in the region of the vaporizer device 16 in the gas guiding direction.
As can be seen in section according to
Arranged in the gas guiding channel 14 is a mixing chamber 20 which is defined by a cylindrical wall 22 which is fastened to the channel wall 12 and has openings 23 on its entire peripheral surface, so that the exhaust gas can flow through the mixing chamber (see in particular
The ignition device 18 is fastened to a wall section of the channel wall 12 radially opposite to the mixing chamber 20 and has a free end that protrudes into the mixing chamber 20, as does the vaporizer device 16.
The vaporizer device 16 has a glow element 24 and a feed line 26 through which an oxidizable liquid is fed to the glow element 24. The oxidizable liquid is vaporized by the glow element 24 and reaches the mixing chamber 20 in an axial inflow direction E.
In the mixing chamber 20 the vaporized liquid is mixed with the exhaust gas flowing through. At a sufficiently high temperature, the oxidizable vapor burns with the residual oxygen contained in the exhaust gas and thus raises the temperature of the exhaust gas, so that the oxidation catalytic converter 8 that is arranged downstream of the vaporizer device 16 in the flow direction is heated to the operating temperature.
An ignition of the oxidizable liquid or of the oxidizable vapor may be effected by the ignition device 18 protruding into the mixing chamber 20. The ignition device 18 has two spark plugs 28 in this example, which each protrude into the mixing chamber 20 by an electrode 30. The spark plugs 28 are each secured in an opening 32 in the channel wall 12 and each protrude into the mixing chamber 20 by an electrode 30. When the catalytic converter is heated up, an ignition spark Z, which is oriented transversely to an inflow direction E, will be generated between the electrodes 30. The ignition spark ignites the oxidizable vapor or the mixture consisting of oxidizable vapor and exhaust gas.
Activation of the ignition device 18 may be effected here by an electronic controller which checks, for example, a temperature of the exhaust gas and, when the temperature is not sufficient for a regeneration, drives the ignition device 18, so that the ignition spark Z is produced. The controlling process may, however, be effected also as a function of other measured variables, such as, e.g., the exhaust gas flow. But embodiments without an electronic controller are also conceivable.
Provision is further made for the vaporizer device 16 to have a controller which regulates the supply of the oxidizable liquid as a function of the exhaust gas temperature, for example. The controller may likewise regulate the temperature of the glow element 24 and in this way control the vaporizing quantity of the oxidizable liquid.
The spark plugs 28 of the ignition device 18 are each arranged in an opening 32 and each protrude into the mixing chamber 20 by an electrode 30. This allows the spark plugs 28 to be quickly replaced. But the spark plugs 28 may also be arranged on the exhaust system 10 in any other way.
Instead of the spark plugs 28 shown here, other electrodes 30 may also be used. In particular, it is also possible to provide only one spark plug 28 having two electrodes 30.
The electrodes 30 may protrude into the mixing chamber 20 in any desired manner to produce an ignition spark Z. In particular, the ignition spark Z need not be oriented transversely to the inflow direction E of the oxidizable liquid.
The ignition device 18 need not necessarily be arranged on a section of the channel wall 12 located radially opposite to the mixing chamber 20. The ignition device 18 may be arranged on the exhaust system 10 in any desired way. In particular, it is conceivable for the ignition device 18 to be arranged on, or integrated in, the vaporizer device 16.
The shape and the size of the mixing chamber 20 may likewise be varied as desired, just as the openings 23 on the wall 22 of the mixing chamber may be varies. More particularly, the mixing chamber 20 need not be of a cylindrical design.
Rather than by the ignition device 18, the ignition of the oxidizable vapor may also be effected by the vaporizer device 16. In this case, the ignition will be effected by the glow element 24, which is heatable to such an extent that an auto-ignition of the oxidizable vapor occurs on its surface. To this end, the glow element 24 is heated to different temperature levels, for example, on the one hand for the vaporization and, on the other hand, for vaporization and subsequent auto-ignition of the vapor/gas mixture at the end of the glow element 24. In this embodiment, the ignition devices 18 may optionally be dispensed with.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 062 479.9 | Dec 2008 | DE | national |
