DRIVE DEVICE FOR A MOTOR VEHICLE AND METHOD OF OPERATING SUCH A DRIVE DEVICE

Abstract

A drive device for a motor vehicle includes an exhaust pipe and a secondary air device having a first secondary air path which feeds into the exhaust gas pip. Disposed in the first secondary air path is a secondary air pump and a secondary air valve. To compensate, for example, fluctuations in the supply voltage of the secondary air pump, provision is made for arrangement in the secondary air path of a Laval nozzle which can be placed downstream of the secondary air valve.

Claims

What is claimed is:

1. A drive device for a motor vehicle, comprising: an exhaust pipe; a secondary air device having a first secondary air path which feeds into the exhaust pipe; a secondary air pump disposed in the first secondary air path; a secondary air valve disposed in the first secondary air path; and at least one Laval nozzle formed in the first secondary air path.

2. The drive device of claim 1, wherein the first secondary air path has a secondary air line, said Laval nozzle being arranged in a secondary air line upstream of the secondary air pump or downstream of the secondary air pump.

3. The drive device of claim 1, wherein the Laval nozzle is integrated in the secondary air pump or in the secondary air valve.

4. The drive device of claim 2, further comprising a line connection device provided in the secondary air line, said Laval nozzle being arranged in the line connection device.

5. The drive device of claim 4, wherein the line connection device is a quick-action coupling.

6. The drive device of claim 1, further comprising an internal combustion engine including a cylinder head, said secondary air path including a secondary air channel which is formed in the cylinder head, said Laval nozzle being disposed in the secondary air channel.

7. The drive device of claim 1, wherein the secondary air device includes a second secondary air path branching off the first secondary air path downstream of the secondary air pump and provided in the exhaust pipe or a further exhaust pipe, and further comprising a further secondary air valve disposed in the second secondary air path.

8. The drive device of claim 7, further comprising a further Laval nozzle formed in the second secondary air path.

9. The drive device of claim 7, further comprising an internal combustion having first and second cylinder banks, one of the exhaust pipes being associated to one of the first and second cylinder banks, and the other of the exhaust pipes being associated to the other one of the first and second cylinder banks.

10. The drive device of claim 8, wherein a secondary air mass flow flowing through at least one member selected from the group consisting of the Laval nozzle and the further Laval nozzle corresponds to a choked mass flow of the member during normal operation of the drive device.

11. The drive device of claim 8, wherein a secondary air mass flow flowing through at least one member selected from the group consisting of the Laval nozzle and the further Laval nozzle corresponds to a choked mass flow of the member during normal operation of the secondary air pump.

12. The drive device of claim 10, wherein the secondary air device is configured such that the secondary air mass flow corresponds to the choked mass flow, even when an actual supply voltage of the secondary air pump deviates from a desired supply voltage.

13. A method of operating a drive device for a motor vehicle, comprising conducting a flow of secondary air through a Laval nozzle in a secondary air path before entering an exhaust pipe to compensate fluctuation in a supply voltage of a secondary air pump in the secondary air path.

14. The method of claim 13, further comprising configuring the Laval nozzle such that its choked mass flow corresponds to a secondary air mass flow introduced at a maximum into exhaust flowing in the exhaust pipe.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0029] Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which the sole FIG. 1 is a schematic illustration of a drive device for a motor vehicle in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] The depicted embodiment is to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figure may not necessarily be to scale. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

[0031] Turning now to FIG. 1, there is shown a schematic illustration of a drive device according to the present invention, generally designated by reference numeral 1, for use in a motor vehicle. The drive device 1 includes an internal combustion engine 2, which has, by way of example, two cylinder banks 3, 4. It is to be understood that the principles described in the following description with respect to an internal combustion engine having two cylinder banks are generally applicable to an internal combustion engine having only a single cylinder bank for example.

[0032] Each of the cylinder banks 3, 4 includes several cylinders 5 which can be supplied via fresh gas lines 6 with fresh gas, e.g. fresh air or a mixture of fresh air and exhaust gas. During operation of the internal combustion engine 2, exhaust is produced inside the cylinders 5 which is carried away via exhaust pipes 7. The exhaust pipes 7 may be part of exhaust manifolds 8, with each of the cylinder banks 3, 4 being operatively connected to such an exhaust manifold 8. The exhaust manifolds 8 can be integrated, at least in part, in cylinder heads of the cylinder banks 3, 4, respectively.

[0033] The drive device 1 includes a secondary air device 9, by which secondary air can be introduced into the exhaust of the internal combustion engine 2. For this purpose, the secondary air device 9 has a secondary air path 10 which is associated to the cylinder bank 3. A further secondary air path 11 is associated to the cylinder bank 4. The secondary air path 10 includes a secondary air pump 12 and a secondary air valve 13. The secondary air path 11 branches off the secondary air path 10 downstream of the secondary air pump 12, e.g. at branch point 14. Using the secondary air pump 12, air, e.g. fresh air, can be drawn in, as indicated by arrow 15. The secondary air pump 12 conveys air in the direction of the secondary air valve 13, i.e. initially in the direction of branch point 14. A further secondary air valve 16 is provided in terms of flow in parallel relation to the secondary air valve 13 and arranged in the secondary air path 11.

[0034] The secondary air valves 13, 16 can each be constructed as a proportional valve, or, as an alternative, as discretely switching valve.

[0035] Provided downstream of the secondary air valve 13 and secondary air valve 16 are respective secondary air channels 17 which are integrated, at least in part, in the cylinder heads of the cylinder banks 3, 4, respectively, and form part of the secondary air paths 10, 11, respectively. Of course, the secondary air paths 10, 11 may also be configured completely outside of the cylinder heads and sized to stretch up to the exhaust lines 7 or exhaust manifolds 8.

[0036] To compensate, for example, fluctuations in the supply voltage of the secondary air pump 12, provision is made for arrangement of a Laval nozzle 18 in the secondary air path 10 and/or a Laval nozzle 19 in the secondary air path 11. For example, the Laval nozzle 18 is arranged downstream of the secondary air valve 13, and the Laval nozzle 19 is arranged downstream of the secondary air valve 16. Other dispositions of the Laval nozzles 18, 19 are, of course, also conceivable,

[0037] The Laval nozzles 18, 19 can be configured such that their choked mass flow corresponds to the secondary air mass flow, which should be introduced at a maximum into the exhaust that flows in the exhaust pipes 7. Advantageously, the secondary air pump 12 is adjusted such as to generate across the Laval nozzles 18, 19 a pressure ratio which is slightly greater than the pressure ratio, at which the Lava! nozzles 18, 19 choke. In this way, fluctuations of the supply voltage of the secondary air pump 12 and thus of the pressure ratio across the respective Laval nozzles 18, 19 can be compensated downwards.

[0038] While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.