DE102014225966A1 - Impeller housing with a bypass valve device for exhaust gas turbocharger and turbocharger - Google Patents

Abstract

The invention relates to an impeller housing (109, 111) with a bypass valve device (112, 113) for an exhaust gas turbocharger (101) and to an exhaust gas turbocharger (101) with at least one such impeller housing. In this case, the impeller housing (109, 111) consists of a light metal material and has at least one bearing insert (15, 16) with respect to the light metal material of the impeller housing (109, 111) increased wear resistance. The impeller housing (109, 111) can be, for example, a turbine housing (109) or a compressor housing (109) and is characterized in that the bearing insert (15, 16) is produced by means of a cohesive connection (20) produced in a friction-stir welding process. with the impeller housing (109, 111) is in communication.

Description

The invention relates to an impeller housing for an exhaust gas turbocharger, wherein the impeller housing has a bypass valve device with a valve flap, which cooperates with a valve seat and is mounted by means of valve-bearing components in the impeller housing.

Exhaust gas turbochargers are increasingly used to increase performance in automotive internal combustion engines. This happens more often with the aim of reducing the internal combustion engine with the same or even increased performance in size and weight while reducing consumption and thus the CO ₂ emissions, in view of increasingly stringent legal requirements in this regard. The operating principle is to use the energy contained in the exhaust gas flow to increase the pressure in the intake tract of the engine and thus to better fill the combustion chamber with air-oxygen and thus to be able to convert more fuel, gasoline or diesel, per combustion process, ie to increase the performance of the internal combustion engine.

An exhaust gas turbocharger has for this purpose a turbine arranged in the exhaust gas line of the internal combustion engine with a turbine runner driven by the exhaust gas flow and a compressor arranged in the intake tract with a compressor runner building up the pressure. Turbine impeller and compressor impeller are rotatably secured to the opposite ends of a rotor shaft, which is rotatably mounted in a bearing assembly disposed between the turbine and compressor. Thus, with the aid of the exhaust gas mass flow, the turbine wheel and, in turn, the compressor wheel are driven via the rotor shaft and the exhaust gas energy is thus used to build up pressure in the intake tract.

Turbines and compressors are turbomachines and have due to the physical laws each dependent on size and design optimum operating range is characterized by the mass flow rate, the pressure ratio and the rotational speed of the respective impeller.

In contrast, the operation of an internal combustion engine in a motor vehicle is characterized by dynamic changes of the load and the operating range.

In order to be able to adapt the operating range of the exhaust gas turbocharger to changing operating ranges of the internal combustion engine and thus to ensure a desired response as far as possible without noticeable delays (turbo lag), exhaust gas turbochargers are equipped with so-called variable turbine geometries and with bypass ducts to be opened in the turbine housing and compressor housing via valve flaps.

A corresponding bypass channel device on the turbine side is referred to as a wastegate valve. The wastegate valve connects the exhaust passage in the flow direction in front of the turbine runner with the exhaust passage behind the turbine runner. The wastegate valve can be opened or closed via a closing device, for example a valve flap. At low speed and correspondingly small exhaust gas mass flow of the internal combustion engine, the wastegate valve is closed and the entire exhaust gas mass flow is passed through the turbine runner. This ensures a sufficient speed of the turbine and compressor impeller and thus a sufficient pressure build-up of the compressor even at low speed of the engine. At high speed and correspondingly large exhaust gas mass flow of the internal combustion engine, the wastegate valve is then opened and passed at least part of the exhaust gas mass flow past the turbine impeller directly into the exhaust area in the flow direction behind the turbine wheel to the speed of the turbine and compressor impeller and the pressure ratio of turbine and Keep compressor within the desired working range of the exhaust gas turbocharger.

A corresponding bypass channel device on the compressor side is referred to as a thrust-recirculation valve. The thrust recirculation valve connects the fresh air intake duct in the flow direction in front of the compressor impeller with the compressed air duct in the flow direction after the compressor impeller. In operating ranges of the internal combustion engine in which the internal combustion engine draws in and consumes so much compressed air that the compressor does not generate too high an overpressure increase in the intake tract of the internal combustion engine, the thrust recirculation valve remains closed. However, if the overpressure in the intake tract of the internal combustion engine increases too much, which is the case, for example, when the throttle valve is closed abruptly at high rpm, there is a risk that the so-called compressor pumping will occur, which would be detrimental to the mechanics due to the associated vibrations of the turbocharger and therefore should be avoided. In this case, the thrust recirculation valve is opened and the excess pressure in the intake tract of the internal combustion engine is reduced by the return flow of compressed air from the compressed air duct into the fresh air intake duct of the exhaust gas turbocharger.

Such an exhaust gas turbocharger 101 in the prior art is shown in schematic sectional view in 1 shown and includes an exhaust gas turbine 102 , a compressor 103 and a bearing housing 104 , The exhaust gas turbine 102 is with one Wastegate valve 112 in the turbine housing 109 equipped and the exhaust gas mass flow AM through the exhaust gas turbine 102 is indicated by arrows. The compressor 103 has a push-circulating valve 113 in the compressor housing 111 on and the fresh air mass flow FM through the compressor 103 is also indicated by arrows. turbine housing 109 and compressor housing 111 are similar in their basic structure, each take an impeller, the turbine wheel 108 and the compressor impeller 110 , and are also considered below under the generic term impeller housing together.

The so-called rotor unit of the exhaust gas turbocharger 101 consists of the turbine wheel 108 , the compressor impeller 110 as well as the rotor shaft 107 , The rotor unit rotates in operation around the rotor axis 107a the rotor shaft 107 , the axial direction of the rotor shaft 107 is represented by the drawn center line. The rotor unit is with its rotor shaft 107 by means of two radial bearings 105 and 106 stored. The radial bearings 105 . 106 be via a lubricant supply 104a supplied with lubricant.

As a closing device for opening and closing of said bypass valve means, such as the wastegate valves 112 and the thrust recirculation valves 113 , flap valves are used in a known manner. Examples are the in 1 shown conventional flap valves, which are each operated with a crank arm actuator to the bypass channels 5 depending on the operating requirements of the exhaust gas turbocharger 101 open or close.

How out 2 by way of example with reference to the illustrated cut-open turbine housing with wastegate valve 112 it can be seen, the crank arm actuator has a in the interior of the turbine housing 109 arranged crank arm 8th on, on which the plate-shaped valve flap 7 is appropriate. The valve flap 7 is in the closed state of the wastegate valve 112 sealing on the valve seat 6 on and thus closes the bypass channel.

The to the crank arm 8th subsequent crank spindle 9 penetrates the turbine housing 109 and is rotatable in the turbine housing wall about its axis in a bearing bush 16 stored. Outside the turbine housing 109 is an operating lever 11 on the crank spindle 9 attached, in turn, an Betätigungsaktuator 12 attacks. A push-circulating air valve in the compressor housing 111 can in principle have the same or a similar structure.

Such flap valves are in the mass flow of the exhaust gas or the intake air of the internal combustion engine and are exposed to fluctuating pressure and temperature conditions. This applies in particular to the wastegate valve 112 to which temperatures up to 1200 ° C may be exposed. Furthermore, high demands are placed on the tightness of the valve devices and their wear resistance. This applies both to the valve seat 6 as well as on the implementation and storage of the crank spindle in the turbine housing 109 respectively compressor housing 111 to. This requires in particular a flat, tight resting of the valve flap on the valve seat surface in the closed state and the application of correspondingly high closing forces, as well as narrow gaps in the bearing of the crank spindle.

Such or similar designs of bypass valves are also in the documents, for example DE 10 2008 011 416 A1 and DE 10 2011 089 777 A1 disclosed.

Due to the above-mentioned loads and operating conditions, increased wear between the valve flap and valve seat surface and in the bearing of the crank spindle can be adjusted. Increased wear is to be expected especially if, for reasons of weight saving, the respective housing areas of the exhaust gas turbocharger consist of a light metal, for example an aluminum alloy. For this reason, as a valve seat, for example, a separate valve seat ring and used for the storage of the crank spindle a bearing bush in the respective housing, which consist of a material of higher wear resistance. However, this requires an increased processing and assembly costs and an increased number of parts. Such a wastegate valve device with an inserted valve seat ring is made, for example DE 10 2010 062 403 A1 known.

For example, aluminum alloy impeller housings incorporate valve seat inserts and steel bushings. These are for example pressed in the respective receiving seat in the housing, shrunk, cast, screwed or caulked. The pressing, shrinking, screwing as well as the caulking is a compromise on strength of the connection and can, especially in thermal cycling, to loosening or even to loosen the connection and thus lead to a massive machine damage. In addition, an increased effort in the component preparation manufacturing and assembly process is required. Pouring also leads to a complex process in the production of the mold and the casting of the housing blank. Conventional welding methods such as electron beam welding, laser welding or plasma welding are either not suitable to combine the mentioned different materials or lead by the generation of residual stresses and embrittlement of the metal structure to cracking and corrosion during operation.

The present invention is therefore an object of the invention to provide an impeller housing with a corresponding bypass valve for an exhaust gas turbocharger and a corresponding exhaust gas turbocharger, which increased wear resistance of the bypass valve with respect to the valve seat surfaces and the crank spindle bearing through the use of bearing bush and valve seat ring and at the same time avoid the mentioned disadvantages of the above-mentioned conventional joining methods.

This object is achieved by an impeller housing with the features according to claim 1 and an exhaust gas turbocharger according to the independent independent claim. Advantageous training and further developments, the features of which can be used individually or in combination with each other, are the subject of the dependent claims.

The impeller housing according to the invention has a bypass valve device and is provided for an exhaust gas turbocharger. In this case, the impeller housing consists of a light metal material and has at least one bearing insert with respect to the light metal material of the impeller housing increased wear resistance. The impeller housing is characterized in particular in that the bearing insert is connected to the impeller housing by means of a cohesive connection produced in a friction-stir welding process and is thus fastened therein and fixed in its intended position.

The exhaust gas turbocharger according to the invention is intended for an internal combustion engine, in particular for a reciprocating engine, and is characterized in that it has at least one impeller housing, which may be a compressor housing or a turbine housing and the above features of the impeller housing, if necessary in combination with the in the subclaims specified additional features.

The friction-stir welding method is in itself already for example from EP 0 615 480 B1 Known as "friction stir butt welding" or "butt welding", it allows a variety of different workpieces to be connected by means of a "non-consumable" probe. The representation in 3 should illustrate the process. This will be the probe tip 31 a largely unconsumable friction-welding probe 30 with a probe contact force F in the by a blunt bump 21 formed gap between the materials to be joined with the friction-welding probe 30 at a certain speed ω around its own probe longitudinal axis 32 turns to generate frictional heat. The probe tip 31 is completely immersed in the gap until the friction-welding probe 30 with its probe face 33 rests on the workpiece surface. Upon sufficient heating, a layer of plasticized material is formed around the probe, consisting largely of the two materials to be bonded, such that upon slow traversing of the rotating probe about a probe advance S, along the bond line or blunt joint 21 and perpendicular to the longitudinal axis of the friction-welding probe 32 , the plastified material is "stirred" along the connecting line with each other. During the cooling of the plasticized material, with respect to the probe feed path S behind the probe tip 31 , The plasticized material forms a cohesive connection 20 along the dull push 21 and thus connects the components in the desired manner with each other. The cross-sectional area of the cohesive connection is dependent on the geometry of the probe tip of the friction-welding probe, which may, for example, have a cone shape with a rounded tip.

The advantage of this method is mainly that different materials are virtually connected in a hot forming process, with no special seam preparation is required and no additional materials are needed. Furthermore, the process is carried out in temperature ranges below the melting temperature of the material to be joined, whereby unfavorable material structure changes and residual stresses in the connection region are largely avoidable.

The impeller housing according to the invention and the corresponding exhaust gas turbocharger have the advantage that for the respective impeller housing, turbine housing and / or compressor housing, a lighter weight light metal material can be used to save weight, whereby a high wear resistance is ensured by appropriate bearing inserts for a bypass valve device. In addition, a permanent and firm positioning and fixing of the bearing inserts in the impeller housing given while avoiding residual stresses and unfavorable material changes in the connecting areas.

An embodiment of the impeller housing is characterized in that the bearing insert is embedded in a corresponding recess of the impeller housing, wherein a flat bearing surface is formed by an end face of the bearing insert and an immediately adjacent region of the impeller housing and by a lateral surface of the bearing insert with the immediately adjacent region the recess of the impeller housing, formed at least in a region adjacent to the flat support surface area, a blunt shock is. This allows a plane resting the probe end face of the friction-welding probe, thus preventing the escape of material from the Verbindungsnahtbereich and results in a particularly clean and uniform connection seam.

A further embodiment of the impeller housing according to the invention is characterized in that the cohesive connection produced in the friction-stir welding process is formed as a circumferential, continuous connecting seam in the region and along the blunt joint. The connecting seam area thus has maximum length and can withstand high mechanical and thermal stresses. Alternatively, the connecting seam can also be embodied as individual mutually separate connecting seam sections. With less high loads to be sustained, time and energy can thus be saved in the production process of the connecting seam.

In an advantageous embodiment of the impeller housing, the light metal material of the respective impeller housing is an aluminum-containing material or an aluminum alloy. This significantly reduces the weight of the impeller housing and facilitates machining of the workpiece in the factory.

A further embodiment of the impeller housing according to the invention has as bearing insert at least one valve seat ring or a bearing bush. The valve seat ring ensures increased wear resistance and thus in the long term a tight closing of the respective valve and thus a reduced leakage mass flow.

In a further embodiment of the impeller housing, at least one bearing insert, that is to say a valve seat ring or a bearing bush or both, is produced from a steel material. This increases the wear resistance due to the material properties.

The impeller housing according to the invention may be a turbine housing or a compressor housing of an exhaust gas turbocharger. However, both the turbine housing and the compressor housing of an exhaust-gas turbocharger may also be designed in the manner of the impeller housing according to the invention. As a result, the exhaust gas turbocharger is given a longer service life or better efficiency over the service life.

If the impeller housing is a turbine housing, then the bypass valve device is a wastegate valve device and in the case of a compressor housing, the valve device is a thrust recirculation valve device.

Embodiments and developments of the invention will be explained in more detail below with reference to the drawings in the drawing.

Show it:

1 an exhaust gas turbocharger according to the prior art, with the essential components, in a simplified schematic sectional view;

2 a perspective view of an exhaust gas turbocharger with a cut turbine housing with a wastegate valve, according to the prior art;

3 a simplified representation of the friction stir welding process;

4 a sectional view of a valve seat of a valve impeller housing according to the invention with inserted and connected by means of friction stir welding valve seat ring; and

5 a sectional view of a storage area of an impeller housing according to the invention with inserted and connected by friction-stir welding bearing bushing.

Function and naming equal parts are denoted by the same reference numerals in the figures.

The 1 to 3 serve to explain the state of the art and have already been described above in this context.

4 shows in a sectional view a bypass channel 5 in a wheel housing 109 . 111 , in the area of the valve seat 6 with a recessed bearing insert, here a valve seat ring 15 , Is the impeller housing a turbine housing 109 this corresponds to the bypass channel 5 a wastegate channel 5 , Is the impeller housing a compressor housing 111 this corresponds to the bypass channel 5 a thrust recirculation channel 5 ,

The valve seat ring 15 has in this example a square cross-sectional area and is formed in a paragraph formed as a corresponding recess at the upper edge of the bypass channel 5 the impeller shell, such as a turbine housing 109 , taken in. Through the frontal area 18 of the valve seat ring 15 and an immediately adjacent, the valve seat ring circumferentially surrounding area 19 of the impeller housing 109 . 111 is a flat bearing surface 22 educated.

Through the lateral surface of the valve seat ring 15 , so its cylindrical outer contour, is with the immediately adjacent region of the corresponding recess, so the cylindrical inner contour of the paragraph-shaped recess at the upper end of the bypass channel 5 of the impeller housing 109 . 111 in the on the flat bearing surface 22 adjacent area, a dull push 21 formed, which can be seen in the right half of the drawing in the sectional plane. The flat bearing surface 22 , which extends on both sides of the blunt thrust is a plan resting the face 33 the friction-welding probe 30 around the probe tip 31 allow and therefore extends on both sides of the blunt shock at least over half the diameter of the end face 33 the friction-welding probe 30 ,

In the left half of the picture, in the area of the blunt joint, the cohesive connection produced in the friction-stir welding process 20 between the material of the impeller housing 109 . 111 and the valve seat ring 15 to recognize in the cutting plane. The cohesive connection is in the left half of the 4 as continuous along the blunt joint circumferential seam 23 executed. By contrast, in the right-hand half of the figure, the cohesive connection is exemplary in individual mutually separate connecting seam sections 24 along the dull push 21 trained, in similar form as in the well-known "spot welding". The cross-sectional area of the cohesive connection 20 depends on the geometry of the probe tip 31 the friction-welding probe 30 which may, for example, have a conical shape with a rounded tip.

In contrast to a made of light metal, in particular an aluminum alloy impeller housing 109 . 111 the valve seat ring can be made of a steel material with greater hardness and toughness, so better wear resistance.

Furthermore, in 4 the friction-welding probe 30 , which at a certain speed ω around their own probe longitudinal axis 32 rotates, and the probe feed S (in the case of a continuous circumferential seam 23 ). Accordingly, the rotating friction-welding probe 30 initially along its probe longitudinal axis 32 , in the drawing down, moves until the probe tip 31 in the blunt push 21 formed gap is completely immersed and the friction-welding probe 30 with its probe face 33 Plan on the flat support surface 22 rests. Subsequently, the rotating friction-welding probe 30 perpendicular to its probe longitudinal axis 32 at a certain feed rate along the course of the blunt impact 21 move between the workpieces and so the connection seam 23 , educated.

5 shows one in an impeller housing 109 , 111 recessed bushing 16 , The bearing bush 16 has in this example a circumferential bushing collar 17 at one end (in the drawing above), which forms a shoulder at the upper end of the lateral surface of the bearing bush and the end face 18 the bearing bush radially enlarged.

This bushing collar 17 is in a trained as a paragraph corresponding recess at the top of the impeller housing wall penetrating receiving bore of the impeller housing, such as a turbine housing 109 or a compressor housing 111 , taken in. Through the frontal area 18 the bearing bush 16 and an immediately adjacent, the collar of the bearing bush 16 surrounding surrounding flat area 19 of the impeller housing 109 . 111 is a flat bearing surface 22 educated.

Through the cylindrical outer surface of the bush collar 17 is with the immediately adjacent region of the corresponding recess, so the cylindrical inner contour of the paragraph-shaped recess at the upper end of the receiving bore of the impeller housing 109 . 111 in the on the flat bearing surface 22 adjacent area, a dull push 21 formed, which can be seen in the right half of the drawing in the sectional plane. The flat bearing surface 22 that are on both sides of the blunt push 21 should extend a plane resting the end face 33 the friction-welding probe 30 around the probe tip 31 allow and therefore extends on both sides of the blunt shock at least over half the diameter of the end face 33 the friction-welding probe 30 ,

In the left half of the picture 5 is in the area of the butt 21 the cohesive connection produced in the friction-stir welding process 20 between the material of the impeller housing 109 . 111 and to recognize the bearing bush in the cutting plane. The cohesive connection is in the left half of the 4 as continuous along the blunt joint circumferential seam 23 executed. In the right half of the picture is the connecting seam 23 not continued to the course of the blunt impact 21 to make recognizable. Also in the case of the bearing bush 16 For example, the cohesive connection can be made into individual mutually separate connecting seam sections along the butt joint 21 be formed (not shown here).

In contrast to a made of light metal, in particular an aluminum alloy impeller housing 109 . 111 can be made of a steel material with greater hardness and toughness, so better wear resistance, or even made of a sintered material of the bearing bush.

Summarized in brief again, the invention relates to an impeller housing with a bypass valve device for an exhaust gas turbocharger and an exhaust gas turbocharger with at least one such impeller housing. In this case, the impeller housing consists of a light metal material and has at least one bearing insert, for example a valve seat ring and / or a bearing bush, with respect to the light metal material of the impeller housing increased wear resistance. The impeller housing may be, for example, a turbine housing or a compressor housing of an exhaust gas turbocharger and is characterized in that the respective bearing insert is connected to the impeller housing by means of a cohesive connection produced in a friction stir welding process.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008011416 A1 [0015]
• DE 102011089777 A1 [0015]
• DE 102010062403 A1 [0016]
• EP 0615480 B1 [0022]

Claims (9)

Impeller housing ( 109 . 111 ) with a bypass valve device ( 112 . 113 ) for an exhaust gas turbocharger ( 101 ), whereby the impeller housing ( 109 . 111 ) consists of a light metal material and at least one bearing insert ( 15 . 16 ) with respect to the light metal material of the impeller housing ( 109 . 111 ) has increased wear resistance, characterized in that the bearing insert ( 15 . 16 ) by means of a cohesive connection produced in a friction-stir welding process ( 20 ) with the impeller housing ( 109 . 111 ). Impeller housing ( 109 . 111 ) according to claim 1, characterized in that the bearing insert ( 15 . 16 ) in a corresponding recess of the impeller housing ( 109 . 111 ) is embedded, wherein by an end face ( 18 ) of the bearing insert ( 15 . 16 ) and an immediately adjacent area ( 19 ) of the impeller housing ( 109 . 111 ) a flat bearing surface ( 22 ) is formed and by a lateral surface of the bearing insert ( 15 . 16 ) with the immediately adjacent region of the recess of the impeller housing ( 109 . 111 ), at least in one to the flat bearing surface ( 22 ) adjacent area, a blunt bump ( 21 ) is trained. Impeller housing ( 109 . 111 ) according to claim 2, characterized in that the cohesive connection produced in the friction-stir welding process ( 20 ) as a circumferential, continuous connection seam ( 23 ) or as individual mutually separate connecting seam sections ( 24 ) in the area and along the blunt thrust ( 21 ) is trained. Impeller housing ( 109 . 111 ) according to one of claims 1 to 3, characterized in that the light metal material of the respective impeller housing ( 109 . 111 ) is an aluminum-containing material or an aluminum alloy. Impeller housing ( 109 . 111 ) according to one of claims 1 to 4, characterized in that at least one bearing insert a valve seat ring ( 15 ) or a bearing bush ( 16 ). Impeller housing ( 109 . 111 ) according to one of claims 1 to 5, characterized in that at least one bearing insert consists of a steel material. Impeller housing ( 109 . 111 ) according to one of claims 1 to 6, characterized in that the impeller housing ( 109 . 111 ) a turbine housing ( 109 ) or a compressor housing ( 111 ) is an exhaust gas turbocharger. Impeller housing ( 109 . 111 ) according to claim 7, characterized in that the bypass valve device ( 112 . 113 ) a wastegate valve device ( 112 ) in the turbine housing ( 109 ) or a push-circulating valve device ( 113 ) in the compressor housing ( 111 ). Exhaust gas turbocharger ( 101 ) for an internal combustion engine, with at least one impeller housing ( 109 . 111 ) according to one of claims 1 to 8.

Images