Electric gas flow heater and vehicle

Abstract

An electric gas flow heater has a grid-like heating element through which exhaust gas can flow axially, and which forms an electrical resistance heating. The grid-like heating element includes radially successive layers of band-like material, wherein the layers, in an axial view of the heating element, are bent in an undulating manner and include valleys and peaks. The layers that are located between the radially outermost layer and the radially innermost layer are attached by their peaks and valleys to the respectively radially adjacent layer, so that flow-through openings are formed between the layers. The wavelengths of the layers are increasing radially outwards.

Claims

1. An electric gas flow heater, comprising: a grid-like heating element through which gas can flow axially and which forms an electrical resistance heating, and wherein the grid-like heating element includes radially successive layers of band-like material, wherein the radially successive layers, in an axial view of the grid-like heating element, are bent in an undulating manner and include valleys and peaks, wherein the radially successive layers that are located between a radially outermost layer and a radially innermost layer are attached by the peaks and the valleys to radially adjacent layers, so that flow-through openings are formed between the radially successive layers, and wherein wavelengths of the radially successive layers increase radially outwards.

2. The electric gas flow heater according to claim 1, wherein each valley and each peak of a layer of the radially successive layers lie on a radial straight line on which the valley or the peak of the layer adjacent radially inside and radially outside is located.

3. The electric gas flow heater according to claim 1, wherein each radially successive layer is formed by a separate band.

4. The electric gas flow heater according to claim 1, wherein the radially successive layers are formed by band sections of a single continuous wound band lying on top of each other.

5. The electric gas flow heater according to claim 1, wherein the radially successive layers are connected to each other by a current-conducting attachment.

6. The electric gas flow heater according to claim 1, wherein the radially outermost layer is surrounded by a terminating ring, to which the radially outermost layer is attached.

7. The electric gas flow heater according to claim 1, wherein a prefabricated disk or prefabricated ring around which the radially successive layers extend and to which the radially innermost layer is attached is provided in a center.

8. The electric gas flow heater according to claim 1, wherein in addition to the valleys and the peaks, at least one band forms at least one layer of the radially successive layers and has indentations and protrusions an amplitude of which is smaller than an amplitude between neighboring valleys and peaks and/or which extend only over part of a width of the at least one band.

9. The electric gas flow heater according to claim 1, wherein within a layer of the radially successive layers, a radial thickness of the layer is the same.

10. The electric gas flow heater according to claim 9, wherein the radially successive layers have equal radial thicknesses in comparison to each other.

11. The electric gas flow heater according to claim 1, wherein the electric gas flow heater is positioned upstream of an exhaust gas purification device and constitutes a unit therewith.

12. A vehicle comprising: an internal combustion engine and the electric gas flow heater according to claim 1 by which exhaust gas of the vehicle is heated.

13. The electric gas flow heater according to claim 1, wherein each radially successive layer surrounds a center of the grid-like heating element.

14. The electric gas flow heater according to claim 13, wherein the radially outermost layer extends completely around the radially innermost layer.

15. The electric gas flow heater according to claim 1, including a radially inner disk or a radially inner ring, and wherein the radially innermost layer immediately surrounds the radially inner disk or the radially inner ring.

16. The electric gas flow heater according to claim 15, wherein each radially successive layer has an undulating shape formed by alternating valleys and peaks, and wherein the radially innermost layer is attached to the radially inner disk or the radially inner ring exclusively at the valleys.

17. The electric gas flow heater according to claim 15, including a radially outer terminating ring that surrounds the radially outermost layer, and wherein the radially outermost layer is attached to the radially outer terminating ring exclusively at the peaks.

18. The electric gas flow heater according to claim 1, including a radially outer terminating ring that completely surrounds the radially outermost layer, and wherein the radially outermost layer is attached to the radially outer terminating ring at a plurality of discrete points that are circumferentially spaced apart from each other.

19. The electric gas flow heater according to claim 18, wherein the radially outermost layer completely surrounds the radially innermost layer, and including a radially inner disk or a radially inner ring that is completely surrounded by the radially innermost layer, and wherein the radially innermost layer is attached to the radially inner disk or the radially inner ring at a plurality of discrete points that are circumferentially spaced apart from each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic longitudinal section of a vehicle with an exhaust duct, an electric gas flow heater according to the disclosure, and an exhaust gas purification device;

(2) FIG. 2 shows a top view of the electric gas flow heater according to the disclosure as shown in FIG. 1;

(3) FIG. 3 shows a schematic detail view of the electric gas flow heater according to the disclosure as shown in FIG. 2;

(4) FIG. 4 shows a schematic, simplified top view of a first embodiment of the electric gas flow heater according to the disclosure as shown in FIG. 2; and

(5) FIG. 5 shows a schematic, simplified top view of a second embodiment of the electric gas flow heater according to the disclosure as shown in FIG. 2.

DETAILED DESCRIPTION

(6) As already discussed above, the electric gas flow heater can be used for various purposes in which a gas is to be heated.

(7) In the following, only the use of the electric gas flow heater to heat an exhaust gas of the vehicle will be described in greater detail.

(8) FIG. 1 shows a vehicle 10 having an internal combustion engine 12 and an exhaust line in which a purification unit 14 is accommodated. The purification unit 14 is defined by an outer housing 16 and includes an exhaust gas purification device 18 and an exhaust gas flow heater 20.

(9) The exhaust gas purification device 18 is, for example, a catalytic converter.

(10) In the embodiment illustrated here, the exhaust gas flow heater 20 is arranged spaced apart from and upstream of the exhaust gas purification device 18 in the exhaust gas flow direction 22.

(11) The exhaust gas flow heater 20 may, however, also abut against the exhaust gas purification device 18 so that they are in contact and, accordingly, there is no distance between the exhaust gas flow heater 20 and the exhaust gas purification device 18. In other words, the exhaust gas flow heater 20 may be positioned immediately upstream of the exhaust gas purification device 18.

(12) In the embodiment shown herein, the exhaust gas flow heater 20 and the exhaust gas purification device 18 are each attached to the outer housing 16 and constitute a pre-assembled unit therewith.

(13) Alternatively, the exhaust gas flow heater 20 may also be mounted directly to the exhaust gas purification device 18, for example in a separate, additional housing of the exhaust gas purification device 18.

(14) FIG. 2 shows the exhaust gas flow heater 20 as viewed in the exhaust gas flow direction 22. The exhaust gas flow heater 20 comprises a heating element 24, a radially inner disk or radially inner ring 26, and a radially outer terminating ring 28.

(15) The heating element 24 has at least one band-like material or band B that is formed as a type of elongated and electrically conductive sheet.

(16) In particular, the band B is an elongated metal sheet such as, for example, a stainless steel sheet.

(17) The band B is arranged with its longitudinal edge circumferentially around the ring 26, and the width of the band B is oriented in the exhaust gas flow direction 22. The width has previously also been referred to as the axial height. Accordingly, in FIG. 2, only a side surface of a longitudinal edge of the band B is visible, this side surface being defined by a length of the longitudinal edge and a band thickness.

(18) The band thickness may be the same over the entire band or may vary.

(19) In FIG. 3, a detail of the exhaust gas flow heater 20 is shown in detail in a simplified form.

(20) The heating element 24 is arranged in a plurality of layers S1 to S6 between the two rings 26, 28, only a few layers being depicted here in order to simplify the drawing.

(21) Here, the radially innermost, first layer S1 is attached to the radially inner ring 26 and the radially outermost, last layer S6 is attached to the radially outer ring 28, in particular in a current-conducting manner, for example by soldering, welding or gluing.

(22) Each layer S1-S6 may be formed here by its own separate band B1 to B6 (see FIG. 4) or by a single continuous band B1 (see FIG. 5).

(23) The band B1 or bands B1-B6 each have an undulating shape, forming valleys 30 and peaks 32.

(24) Within a layer S1-S6, a radial thickness D and an axial height, as viewed in the direction of flow, are substantially the same.

(25) In particular, all layers S1-S6 have substantially equal radial thicknesses and/or axial heights when compared to each other.

(26) Alternatively, the layers S1-S6 may have different radial thicknesses and/or axial heights when compared to each other.

(27) Furthermore, the band width as measured in the axial direction is always constant throughout all layers S1-S6.

(28) The band B1 or the bands B1-B6 may have smallish indentations 36 and opposing protrusions 38 to increase the surface area of the band B1 or the bands B1-B6, which are preferably produced by impressions in band B1 or in the bands B1-B6 before creating the valleys and peaks by bending.

(29) These indentations 36 and protrusions 38, which are optionally provided in addition to the valleys 30 and peaks 32, have an amplitude which is much smaller, in particular smaller by a factor of 4, than the amplitude between neighboring valleys 30 and peaks 32, and/or extend only over part of the width of the band B1 or the bands B1-B6.

(30) Accordingly, the indentations 36 and protrusions 38 do not form valleys 30 and peaks 32.

(31) The layers S, which are each radially adjacent to each other, are attached to each other by their valleys 30 and peaks 32 in a current-conducting manner.

(32) The first layer S1 is attached to the ring 26 exclusively by its valleys 30 and the last layer S6 is attached to the terminating ring 28 exclusively by its peaks 32, in particular in a current-conducting manner. As regards the other layers S2 to S5, the valleys 30 are attached to the peaks 32 of the radially inner layer S in the region of the peaks 32 in a current-conducting manner, and the peaks 32 are attached to the valleys 30 of the radially outer layer S in the region of the valleys 30 in a current-conducting manner.

(33) The attachment, in particular current-conducting attachment, is effected, for example, by soldering, welding or gluing.

(34) In the embodiment shown, the radially neighboring layers S are attached to each other in such a way that each valley 30/each peak 32 lies on a radial straight line G on which a peak 32/a valley 30 of the radially inwardly adjacent layer S and a valley 30/a peak 32 of the radially outwardly adjacent layer S are located.

(35) In a different embodiment, the valleys 30/peaks 32 of a layer S may abut the peaks 32/valleys 30 of the adjacent layers S slightly offset from the peaks 32/valleys 30 of the adjacent layers S.

(36) Flow-through openings 34 are formed between the layers S1-S6 by the arrangement described above, through which the exhaust gas can flow.

(37) To heat the exhaust gas flowing through the flow-through openings 34, a current is applied to the band B1 or the bands B1-B6 of the heating element 24.

(38) The current can be distributed uniformly over the entire heating element via the connection points along the straight line G between the radially innermost layer S1 and the inner ring 26, between the radially outermost layer S6 and the terminating ring 28, and between the individual layers S1-S6.

(39) It may be provided here that the ring 26 and the terminating ring 28 are also made of an electrically conductive material.

(40) When current flows, the band B1 or bands B1-B6 heat up, which causes the exhaust gas flowing through the flow-through openings 34 to also heat up.

(41) Accordingly, the heating element 24 forms an electrical resistance heating.

(42) FIGS. 4 and 5 illustrate a first and a second embodiment of the heating element 24. For reasons of clarity, not all of the radial straight lines G are drawn in these figures.

(43) In the first embodiment, the individual layers S1-S6 are each formed by an individual, separate band B1 to B6. Therefore, here the number of layers S1-S6 corresponds to the number of bands B1-B6.

(44) The bands B1-B6 are arranged concentrically with each other here. The features described so far with reference to FIGS. 2 and 3 are provided here as well.

(45) In contrast, in the second embodiment the individual layers S1-S6 are formed by a single continuous band B1.

(46) Here, starting from the radially inner ring 26, the band B1 extends in ring-like layers radially outwards to the terminating ring 28. In other words, the layers S1-S6 are formed by band sections of the wound band B1 lying on top of each other, wherein the band B1 “jumps” to the next layer by an angled portion 40 after a circulation through 360 degrees. In FIG. 5, two angled portions 40 are provided with reference numbers.

(47) In both embodiments, the attachment points of the valleys 30 and peaks 32 of two radially neighboring layers S each lie on the straight lines G.

(48) This requires that the number of valleys 30 and peaks 32 of neighboring layers S be exactly equal. In particular, the number of valleys 30 and peaks 32 of all layers S1-S6 is exactly equal.

(49) The radius and circumference of a layer S increases as the radial distance from the radially inner ring 26 increases; the radial layer thickness, or thickness D for short, remains constant.

(50) To ensure that the number of valleys 30 and peaks 32 of all layers S, and thus also of neighboring layers S, is the same, the wavelength of a band B1, B1-B6 increases as the radial distance from the radially inner ring 26 increases.

(51) As an alternative, in other embodiments, the valleys 30/peaks 32 of a layer S may abut the peaks 32/valleys 30 of the adjacent layers S slightly offset from the peaks 32/valleys 30 of the adjacent layers S. In this case, the number of valleys 30 and peaks 32 of neighboring layers S need not be exactly the same.

(52) Although various embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.