Method of regenerating an exhaust gas purification filter, and vaporizer

Abstract

A method of regenerating an exhaust gas purification filter, in particular for internal combustion engines, uses a vaporized liquid that is to be introduced into the exhaust gas flow. A surface temperature of a heating element in a vaporizer chamber is limited to a maximum of 700 to 750 C.

Claims

1. A method of regenerating an exhaust gas purification filter of an internal combustion engine using a vaporized liquid to be introduced into an exhaust gas flow, comprising by the steps of: providing at least one heating element positioned in a vaporizer chamber, wherein the at least one heating element includes at least one heating coil; feeding a liquid into the vaporizer chamber; heating up and vaporizing the liquid with the at least one heating element; controlling a surface temperature of the at least one heating element, in an operating condition, within a range of 700 C. to 750 C.; supplying energy to the at least one heating element as a function of an amount of liquid present in the vaporizer chamber and/or of liquid mass flow delivered through the vaporizer chamber; and heating up and vaporizing the liquid without igniting the liquid.

2. The method according to claim 1, wherein the liquid is fuel.

3. The method according to 1, wherein the at least one heating element is a glow plug that is within the vaporizer chamber, and wherein the vaporizer chamber is downstream from the internal combustion engine and upstream of the exhaust gas purification filter.

4. The method according to claim 1, including controlling an amount of energy supplied to the at least one heating element with pulse width modulation.

5. The method according to claim 1, including switching the liquid mass flow introduced into the vaporizer chamber between preset fixed values.

6. The method according to claim 1, including dividing the vaporizer chamber into a liquid section and a vapor section, and configuring the at least one heating element to have an outer surface that makes more energy available in the liquid section than in the vapor section.

7. The method according to claim 1, wherein the at least one heating element includes a control coil connected upstream of the heating coil.

8. The method according to claim 7, wherein the control coil changes resistance at a specific temperature.

9. The method according to claim 7, including connecting an electronic controller to the control coil with at least one electrical connection such that the electronic controller controls the control coil to vary resistance in relation to the temperature.

10. The method according to claim 7, wherein the heating element further comprises a second heating coil downstream of the control coil, and wherein the control coil is configured to have different resistances as a function of temperature.

11. The method according to claim 1, wherein the at least one electrical heating element includes a plurality of heating wires which are adapted to be driven differently for controlling the surface temperature.

12. A method of regenerating an exhaust gas purification filter of an internal combustion engine using a vaporized liquid to be introduced into an exhaust gas flow, comprising by the steps of: providing at least one electric heating element positioned in a vaporizer chamber, wherein the at least one electric heating element includes at least one heating coil; feeding a liquid into the vaporizer chamber; heating up and vaporizing the liquid with the at least one electric heating element; controlling a surface temperature of the at least one electric heating element, in an operating condition, within a range of 700 C. to 750 C., controlling the at least one electric heating element based on an amount of liquid supplied to the vaporizer chamber by a pump; and heating up and vaporizing the liquid without igniting the liquid.

13. A vaporizer of a vehicle exhaust gas purification device comprising: a vaporizer chamber that receives a liquid; at least one electrical heating element positioned in the vaporizer chamber to heat the liquid; a controller configured to control surface temperature of the at least one electrical heating element within a range of 700 C. to 750 C.; the controller configured to supply energy to the at least one heating element as a function of an amount of liquid present in the vaporizer chamber and/or of liquid mass flow delivered through the vaporizer chamber; and the controller configured to heat up and vaporize the liquid without igniting the liquid.

14. The vaporizer according to claim 13, wherein the controller comprises an electronic controller which includes at least one electrical connection to the at least one electrical heating element.

15. The vaporizer according to claim 13, wherein the at least one electrical heating element includes at least one heating coil and a control coil connected upstream of the heating coil.

16. The vaporizer according to claim 15, wherein the control coil is configured to have different resistances as a function of temperature.

17. The vaporizer according to claim 13, wherein the vaporizer chamber is subdivided into a liquid section and a vapor section, and wherein the at least one electrical heating element has an outer surface that makes more energy available in the liquid section than in the vapor section.

18. The vaporizer according to claim 13, wherein the at least one electrical heating element includes a plurality of heating wires which are adapted to be driven differently for controlling the surface temperature.

19. The vaporizer according to claim 13, wherein the at least one electrical heating element is a glow plug that is within the vaporizer chamber, and wherein the vaporizer chamber is downstream from an internal combustion engine and upstream of the vehicle exhaust gas purification device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will be apparent from the description below and from the accompanying drawings, to which reference is made and in which:

(2) FIG. 1 shows a schematic view of a vehicle exhaust system which has an exhaust gas purification device that is regenerated in accordance with the method according to the invention and that is fitted with the vaporizer according to the invention;

(3) FIG. 2a shows a schematic cross-sectional view of a vaporizer according to the invention;

(4) FIG. 2b shows a schematic circuit engineering drawing of the heating element of FIG. 2a; and

(5) FIG. 3 shows a second embodiment of the vaporizer according to the invention.

DETAILED DESCRIPTION

(6) FIG. 1 schematically illustrates an exhaust system 10 of an internal combustion engine 12 which, more particularly, is a diesel engine or a gasoline direct injection engine. The exhaust system 10 includes an exhaust pipe 14 which accommodates a particulate filter 16 having an oxidation catalytic converter 18 connected upstream.

(7) Arranged upstream of the oxidation catalytic converter 18 is a vaporizer 20 which includes a vaporizer chamber 22 into which one or more heating elements 24, 26 protrude.

(8) According to the embodiment shown, the heating elements 24, 26 are electric heating elements which are connected to a controller 28.

(9) The one or more heating elements 24, 26 are preferably adapted to be driven individually by the controller 28.

(10) In the illustrated embodiment, the heating elements 24, 26 are operated electrically and are symbolically shown as coils for function's sake only.

(11) A pipe 30 feeds an oxidizable liquid, more specifically fuel, into the vaporizer chamber 22.

(12) The liquid is heated up and vaporized in the vaporizer chamber 22, the vapor then being supplied to the exhaust gas flow via a pipe 32 and a nozzle 34 protruding into the exhaust pipe 14 in regeneration phases of the filter 16.

(13) FIG. 2a illustrates one possible embodiment of the electric heating element 24, 26. The heating element 24, 26 includes a glow plug that is surrounded by a housing 36. The glow plug is provided with an electrical connection 38 leading to the controller 28.

(14) The liquid supplied stands in the vaporizer chamber 22 up to a specific variable level 40. Above the level 40, the chamber 22 is filled with vapor that flows via the opening 42 to the feeding pipe 32.

(15) The glow plug includes one or more coils, where a plurality of coils forms a plurality of heating elements 24, 26. Alternatively or additionally, a plurality of such heating elements 24, 26 may, of course, also project into a common vaporizer chamber 22.

(16) FIG. 2b shows a circuit engineering illustration of the heating element 24, 26, which includes a first heating coil 45, a subsequent control coil 46, and another, second heating coil 48 subsequent thereto.

(17) In order to prevent an outer surface 44 from coking caused by the vaporizing liquid, the temperature on the surface 44 of the heating element 24, 26 is limited to a maximum value of 700 to 750 C. Below this limiting value, either no coking will occur at all (below approximately 700 C.), or only very little coking will occur (above approximately 700 C. up to a maximum of 750 C.).

(18) To limit this surface temperature, several options are available, only some of which will be presented below. The presented versions may, of course, be combined with each other as desired and with other variants that are not presented, in order to reach the aim of not exceeding the maximum temperature.

(19) For example, the controller 28 may be coupled to a flow sensor 50 (see FIG. 1), which leads into the supply pipe 30 and determines the mass flow of the liquid. As an alternative, it is, of course, also conceivable that a pump 52 used for delivering the liquid into the vaporizer chamber 22 is coupled to the controller 28, so that in this case, too, the amount of liquid supplied to the vaporizer chamber 22 is known. The electrical energy supplied could also be determined using a characteristic map which takes the amount of liquid into account, for example.

(20) A further embodiment makes provision that a measuring element is arranged in the vaporizer chamber 22, which is used for determining the amount of liquid in the vaporizer chamber 22.

(21) The resistance of the electric heating element 24, 26 may, of course, also be used for determining the temperature.

(22) In the embodiment according to FIG. 2b, the control coil 46 is configured in such a way that it has different resistances as a function of the temperature. For instance, the control coil can change its resistance relatively abruptly at a particular temperature, so that the subsequent heating coil 48 receives less heat energy. This allows the temperature at the surface of the heating element to be controlled in an open loop or even in a closed loop.

(23) Depending on the liquid mass flow and/or the amount of liquid contained in the vaporizer chamber 22, the one or more heating elements 24, 26 or heating coils 45, 48, for example, is/are supplied with a greater or smaller amount of energy to bring the temperature on the outer surface 44 as close as possible to the maximum temperature, which is fixed to be between 700 C. and 750 C., or up to the maximum temperature while not exceeding it.

(24) The energy supplied may be controlled by pulse width modulation, for example.

(25) Alternatively or additionally, it is also feasible to allow the liquid mass flow to be switched between preset, fixed values. This allows the surface temperature to be influenced since in case of too high a temperature, it can be abruptly reduced by a liquid surge.

(26) In addition, it is possible for the mass flow to be switched between different, preset values, and it is also possible to assign amounts of electrical energy to these values. For instance, tables may be stored here, which assign to a mass flow a value for the amounts of energy supplied to the heating element or elements 24, 26.

(27) For example, in the case of large amounts of liquid, both heating elements 24 or 26 can be fully connected; or in the case of very small amounts of liquid, only one heating element 24 or 26 can be connected. As already emphasized above, a glow plug may, of course, also include a plurality of separately switchable heating coils, each of which is considered a respective drivable heating element.

(28) As shown in FIG. 2a, the vaporizer chamber 22 is subdivided into a lower liquid section and an upper vapor section, with the heating element or elements 24, 26 being arranged and designed in such a way that on their outer surface 44 they make more energy available in the liquid section than in the vapor section.

(29) The embodiment according to FIG. 3 substantially corresponds to the one illustrated in FIG. 2, so that only the differences will be discussed below.

(30) In this embodiment, two heating elements 24, 26 in the form of two glow plugs are provided, which are drivable individually and project into the shared vaporizer chamber 22. Each of the two heating elements may include one or more heating coils that are drivable separately or jointly, so that two, three or more different stages of heat energy levels are available, where required.

(31) The generation of vapor is not performed constantly, but only in so-called regeneration phases, so that the heating devices 24, 26 start to operate only in these phases, and liquid is supplied to the vaporizer chamber 22 only in these phases.

(32) The oxidizable liquid provides for an increase in the temperature of the exhaust gas in the oxidation catalytic converter 18, so that the particulates are burnt in the exhaust gas purification filter 16.

(33) 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.