Exhaust Gas Turbocharger

The present invention relates to an exhaust gas turbocharger, especially with pulse turbocharging for vehicle engines and with a corresponding multi-duct or multi-channel spiral housing of the exhaust gas turbine, whose inlet channels are combined only directly ahead of a turbine rotor at the periphery thereof.

With the supercharging of vehicle engines by means of a turbocharger, it has proven as appropriate by reason of the large rotational speed range of the engines, to provide a control of the exhaust gas turbocharger. It has also proved advantageous for that purpose to provide a turbine by-pass because the operational behavior of the supercharged engine can be favorably influenced therewith.

Furthermore, multi-channel exhaust gas installations are used in order to realize a pulse turbocharging whose advantages are unquestionable for the vehicle engine. Two-channel or two-duct turbine housings are used therefor as a rule because they enable nearly undisturbed charging changes of the individual cylinders without significant reaction or feed-back from one exhaust gas connection onto the other.

It is also known to utilize with diesel engines the external exhaust gas recirculation for the reduction of the nitrogen oxides in the exhaust gas.

It is necessary in connection therewith to provide, in addition to the turbine by-pass, a further bifurcation for the exhaust gas return up to the rotor inlet of the turbines. This encounters enormous difficulties in particular with multi-channel or multi-ducted exhaust gas installations since a mutual influencing of the exhaust gas channels by the exhaust gas feedback valves or by-pass valves is to be avoided in every case.

It is the aim of the present invention to avoid in multi-channel or multi-ducted spiral housings an influencing of the individual exhaust gas connections by a particular valve arrangement.

The underlying problems are solved by the present invention in that, within an area in which the rotor back surface and the periphery of the turbine rotor form a circumferential circular edge, an annular gap is provided, through which a part of the exhaust gas flows out of the spiral housing of the exhaust gas turbine into an annular channel arranged at the rotor back surface, from which a feedback line branches off to the charging air channel of the compressor and a by-pass line by-passing the turbine to the turbine exhaust gas line. For the control of a ratio of the exhaust gas partial streams, according to another feature of the present invention, a turbine by-pass diaphragm-valve controlled by the supercharging or exhaust gas pressure may be arranged in the turbine by-pass line, and an exhaust gas recirculation valve may be arranged in the exhaust gas return line which is controlled in dependence on engine-specific magnitudes, for example, in dependence on the mean effective pressure or charging pressure as well as the rotational speed. Furthermore, a throttle valve may be arranged in the turbine exhaust gas line which is also controlled in dependence on magnitudes of the engine. By actuating this throttle valve which is arranged in the exhaust gas stream downstream of the turbine rotor, the rate of exhaust gas return flow can be controlled. This throttle valve is intended to bring about at low loads of the engine an ever-increasing throttling of the exhaust gas stream in the turbine exhaust gas line and therewith a higher exhaust gas counter-pressure, as a result of which the rate of return flow of the exhaust gas is increased.

For purposes of controlling the exhaust gas quantity ratio in the turbine by-pass line, the diaphragm-valve installed therein is controlled in such a manner that it is closed at low load and is increasingly opened at higher load, approximately from 1/3 to full load.

The exhaust gas recirculation valve in the exhaust gas return line, in contrast thereto, is so controlled that it is opened at low load and is increasingly closed at higher load until it is fully closed at a load which corresponds to about 2/3 of the full load.

The control of the valve may take place mechanically, electrically, electronically, pneumatically or hydraulically.

Such housings with this type of an annular gap may also be used without an exhaust gas return, if so desired.

Accordingly, it is an object of the present invention to provide an exhaust gas turbocharger which avoids by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in an exhaust gas turbocharger for vehicle engines which avoids mutual interference from the respective exhaust gas connections of the individual engine cylinders.

A further object of the present invention resides in an exhaust gas turbocharger which permits pulse turbocharging of vehicle engines, yet requires only a simple control that can be readily realized by simple means.

A still further object of the present invention resides in an exhaust gas turbocharger for vehicle engines which optimizes the operation at different loads and different rotational speeds without problems of mutual interference from the respective cylinders of the engine.

These and further objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one embodiment in accordance with the present invention, and wherein:

FIG. 1 is an elevational view illustrating the contours of an exhaust gas turbocharger in accordance with the present invention which is shown in axial cross section within the area of the exhaust gas turbine; and

FIG. 2 is a schematic diagram of a system of compressor and turbine of an exhaust gas turbocharger with the associated lines according to the present invention.

Referring now to the drawing wherein like reference numerals are used throughout the two views to designate like parts, in the exhaust gas turbocharger illustrated in the drawing, the turbine rotor 1 of an exhaust gas turbine generally designated by reference numeral 2 is connected with the rotor (not shown) of a compressor 3 by a common shaft 4. The exhaust gas turbine 2 includes a two-channel or two-duct spiral housing 5 with a first inlet channel 6 and with a second inlet channel 7. The inlet channels 6 and 7 combine shortly before reaching the periphery 8 of a turbine rotor 1. Within an area in which a rotor back-surface 9 and the periphery 8 of the turbine rotor 1 form a circumferential circular edge 11, an annular gap 12 is provided through which a part of the exhaust gas flows from the spiral housing 5 into an annular channel 13 arranged at the rotor back-surface 9, from which an exhaust return line 14 leads to the supercharging air channel 15, which conducts air sucked-in and compressed by the compressor 3 by way of an air suction channel 16 to the suction line of the engine. An exhaust gas recirculation valve 17 is located in the exhaust gas return line 14 which is opened at the engine operating points, at which an external exhaust gas feedback is permissive for combustion reasons. This is primarily the case at low and medium loads.

The annular gap and the annular channel may also begin, under certain circumstances, in the spiral housing 5 of the turbine 2 at that place, at which the turbine rotor 1 passes over from the periphery 8 into the area 23 of smaller outside diameters.

Additionally, a by-pass line 18 branches off from the annular channel 13, which by-passes the exhaust gas turbine 2 and which terminates in a turbine exhaust gas line 19. A turbine by-pass valve 21 is disposed in the by-pass line 18, which is controlled, for example, by the supercharging or exhaust gas pressure. The turbine by-pass valve 21 is opened essentially at middle and high loads.

A throttle valve 22 is disposed in the turbine exhaust gas line 19 downstream of the discharge of the by-pass line 18, which is controlled by the load input of the engine. The rate of exhaust gas return flow can additionally be influenced by this control valve 22. The valve 22 makes it possible to establish, at low loads of the engine, a higher exhaust gas counter-pressure and therewith higher rates of exhaust gas recirculation.

The control of the valves can be realized electrically, electronically, pneumatically, hydraulically or mechanically.

While I have shown and described only one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all changes and modifications as are encompassed by the scope of the appended claims.