Turbocharger with recessed compressor wheel to reduce turbocharger oil leakage

Abstract

Turbocharger (10), which includes: a compressor section (12) comprising a compressor housing (14) with an air inlet (16) and a compressor air outlet (18) and a compressor wheel (20) in the compressor housing (14); a turbine section (24) comprising a turbine housing (26) with an exhaust gas inlet (28) and a turbine exhaust gas outlet (32) and a turbine wheel (34) in the turbine housing (26), wherein the turbine wheel (34) is driven by the compressor wheel (20), wherein the exhaust gas inlet (28) is configured to be connected to an exhaust duct of the engine, and the turbine exhaust gas outlet (32) is configured to be connected to an exhaust system; wherein the compressor housing (14) includes a diffuser (37) with a recess (38) which receives the compressor wheel (20), wherein the recess (38) has a side wall with an upper edge (50) and the compressor wheel (20) has a base plate with a top (20a) which is located below the upper edge (50) of the side wall of the recess (38) in the diffuser (37); characterized by the fact that the turbocharger (10) in the recess (38) in the diffuser (37) further comprises a compressor backplate (40) which is opposite the baseplate of the compressor wheel (20); wherein the turbocharger (10) further comprises a pressure relief channel in the compressor backplate (40) which contains a check valve (52).

Description

INTRODUCTION

[0001] The present invention relates to a turbocharger and in particular to a turbocharger according to the preamble of claim 1, as is essentially known from DE 10 2014 106 849 A1 or US 2012 / 0 003 081 A1.

[0002] Further prior art can also be found in the documents US 2 835 203 A, EP 0 961 033 A1 and DE 10 2019 104 499 A1.

[0003] A boost throttle valve is used in engines to mitigate intercooler icing and facilitate fuel tank emptying in large gasoline tanks. The use of this boost throttle valve results in a negative pressure being exerted on the compressor side of the ring seal between the turbocharger compressor housing and the bearing housing, causing oil to leak from the bearing housing into the compressor housing.

[0004] The design of a standard turbocharger has the compressor wheel flush with the edge / geometry of the compressor backplate diffuser, resulting in ambient or higher air pressure behind the compressor wheel that increases with turbocharger speed. This causes gases bypassing the compressor sealing rings to flow from the compressor housing into the bearing housing and into the engine crankcase. However, the negative pressure created by the pre-compressor throttle causes a pressure behind the compressor wheel that is lower than the crankcase pressure, particularly at low compressor wheel speeds where the pressure created by the wheel is not large enough to cancel the negative pressure created by the pre-compressor throttle. If the air pressure behind the compressor wheel is lower than that in the bearing housing (i.e., in the crankcase of the engine), engine oil leaks past the compressor seals into the compressor housing, where it is ultimately absorbed by the engine or leaks out of the intercooler duct system.

[0005] The invention is based on the object of providing a turbocharger in which the described oil leakage problem is less apparent. SUMMARY

[0006] This problem is solved with a turbocharger which is characterized by the features of claim 1.

[0007] Recessing the compressor wheel in the compressor backplate utilizes the boost pressure generated by the compressor wheel to increase the pressure on the compressor side of the ring seal, thereby mitigating oil leakage. A special geometry near the diffuser reduces the required wheel recess height.

[0008] The novel shape of the compressor backplate and its interaction with the compressor wheel is optimized to maximize the pressure behind the compressor wheel while minimizing the impact on compressor efficiency. The check valve aspect of the design is also unique in that it would limit the maximum pressure behind the compressor wheel to prevent any overloading of the turbocharger thrust bearing.

[0009] According to a further aspect, a pressure relief channel is connected to the recess in the diffuser.

[0010] The check valve can be used to limit the maximum pressure that would be generated behind the wheel to reduce the risk of overloading the turbocharger thrust bearing.

[0011] According to yet another aspect, the turbine wheel is drive-connected to the compressor wheel by a shaft.

[0012] Further areas of applicability of the present invention will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are provided for illustrative purposes only. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be more fully understood from the detailed description and the accompanying drawings, in which: Fig. 1 is a cross-sectional view of a turbocharger according to the principles of the present invention; and Fig. 2 a detailed cross-sectional view of the compressor section of the Fig. 1 shown turbocharger.

[0014] In the drawings, reference symbols may be used multiple times to identify similar and / or identical elements. DETAILED DESCRIPTION

[0015] In Fig. 1, a turbocharger 10 includes a compressor section 12 having a compressor housing 14 with an air inlet 16 and a compressor air outlet 18 configured to communicate with an intake manifold of an engine. A compressor wheel 20 is located within the compressor housing 14. A turbine section 24 includes a turbine housing 26 having an exhaust inlet 28 connected to an exhaust outlet of an engine exhaust manifold and a turbine exhaust outlet configured to communicate with an exhaust system of the vehicle. A turbine wheel 34 is located within the turbine housing 26 and is drivingly connected to the compressor wheel 20 by a turbocharger shaft 36. In operation, the exhaust inlet 28 of the turbine section 24 receives engine exhaust, which drives the turbine wheel 34.The turbine wheel 34 drives the turbocharger shaft 36 and the compressor wheel 20, which compresses the intake air, which is then fed to the intake manifold of the engine.

[0016] In Fig. 2, the compressor housing 14 includes a diffuser 37 with a recess 38 that accommodates the compressor wheel 20. The compressor wheel 20 is disposed against a compressor backplate 40. The compressor backplate 40 is arranged around a slinger 42, which is disposed against a thrust bearing 44. The turbocharger shaft 36 is connected to the compressor wheel 20 and the slinger 42 and is rotatably supported by journal bearings 46. According to the embodiment shown, lubricating oil is supplied through an oil passage 48, which lubricates the journal bearing 46 and the thrust bearing 44.

[0017] According to the present invention, the recess 38 in the diffuser 37 includes an upper edge 50. By the term "upper," it is meant that the compressor wheel 20 has a top surface 20a that is recessed relative to the upper edge 50, wherein the compressor wheel 20 has a conical convex surface 20b that is received in a concave conical recess of the compressor backplate 40. The compressor section 12 utilizes the boost pressure generated by the compressor wheel to increase the backpressure on the compressor side of the ring seals 51a, 51b, which mitigates oil leakage.

[0018] A one-way check valve 52 and a pressure relief passage 54 may be used to limit the maximum pressure that would be generated behind the compressor wheel 20 to reduce the risk of overloading the turbocharger thrust bearing 44. The check valve 52 may include a ball 52a, a spring 52b, and a threaded retainer 52c. Alternatively, other forms of check valves, such as, but not limited to, a diaphragm valve and a duckbill valve, may be used. An O-ring seal 56 may seal the passage between the compressor housing 14 and the diffuser 37.

[0019] The recessed surface 20a of the compressor wheel 20 and its interaction with the relatively higher rim 50 of the diffuser 37 is optimized to maximize the pressure behind the compressor wheel 20 while minimizing the impact on compressor efficiency. The check valve 52 is also unique in that it limits the maximum pressure behind the compressor wheel 20 to prevent any overloading of the turbocharger thrust bearing.

[0020] The turbocharger of the present invention reduces oil leakage through the turbocharger compressor seal ring when using the engine's boost throttle. The unique geometry of the compressor backplate, combined with the compressor wheel setback, allows for a more favorable pressure differential across the compressor seal, while the check valve can limit the maximum pressure behind the wheel during operation at higher turbocharger speeds, thereby limiting the load requirements on the turbocharger thrust bearing.

[0021] Recessing the compressor wheel within the compressor backplate makes it more likely that the airflow generated by the wheel will strike the edge of the compressor backplate. The sharp edge of the unique geometry of the recess increases the effectiveness of this, with the combination of these redirecting a portion of the compressed air behind the wheel. This creates a more favorable pressure differential across the compressor ring seal compared to a standard design and helps reduce oil leakage into the engine. These features are passive; at high compressor wheel speeds, large volumes of air would be redirected behind the compressor wheel, increasing the pressure beyond what a standard turbocharger bearing would be designed for.According to this scenario, the check valve 52, which connects to the volume behind the compressor wheel 20, is activated by the high differential pressure (the pressure pushes the valve open), allowing some of the pressure to be released before the bearing 44 is damaged.

[0022] The recessed compressor wheel design allows for a wider operating range for the pre-compressor throttle valve concept during scavenging. A wider operating range allows for a larger scavenging volume, allowing the use of a larger fuel tank in the vehicle. Limiting oil leakage and subsequent consumption by the engine also benefits the exhaust aftertreatment system, reducing the likelihood of pre-ignition or exhaust smoke. It also reduces overall engine oil consumption.

Claims

[1] Turbocharger (10) comprising: a compressor section (12) having a compressor housing (14) with an air inlet (16) and a compressor air outlet (18) and a compressor wheel (20) in the compressor housing (14); a turbine section (24) having a turbine housing (26) with an exhaust gas inlet (28) and a turbine exhaust gas outlet (32) and a turbine wheel (34) in the turbine housing (26), the turbine wheel (34) being drivingly connected to the compressor wheel (20), the exhaust gas inlet (28) being configured to be connected to an exhaust passage of the engine, and the turbine exhaust gas outlet (32) being configured to be connected to an exhaust system; wherein the compressor housing (14) includes a diffuser (37) with a recess (38) which receives the compressor wheel (20), the recess (38) having a side wall with an upper edge (50) and the compressor wheel (20) having a base plate with an upper surface (20a) which is located below the upper edge (50) of the side wall of the recess (38) in the diffuser (37); characterized by , that the turbocharger (10) in the recess (38) in the diffuser (37) further comprises a compressor back plate (40) which is opposite the base plate of the compressor wheel (20); wherein the turbocharger (10) further comprises a pressure relief channel in the compressor back plate (40) containing a check valve (52). [2] The turbocharger (10) of claim 1, further comprising a pressure relief channel (54) communicating with the recess (38) in the diffuser (37). [3] Turbocharger (10) according to claim 1, wherein the turbine wheel (34) is drivingly connected to the compressor wheel (20) by a shaft (36). [4] Turbocharger (10) according to claim 1, wherein the check valve (52) includes a ball and spring check valve. [5] Turbocharger (10) according to claim 1, wherein the pressure relief channel (54) further extends through the diffuser (37).

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