Exhaust gas turbocharger

An apparatus for turbocharging an internal combustion engine, and which is characterized by the ability to avoid excessive heat transfer to the bearings and any other heat sensitive components. In the preferred embodiment, the lubricating oil for the bearings in the turbocharger housing is directed through a passageway in the bearing shaft and is discharged onto the end wall of the bearing housing in a circular pattern, to thereby cool the end wall and minimize heat transfer from the turbine to the bearings in the housing. Also, the end wall of the bearing housing is spaced from the adjacent rear wall of the turbine housing to define a cooling air gap therebetween, and apertures are provided in the housing for permitting air to flow through the cooling gap to cool the opposing surfaces of the two adjacent walls and thereby minimize heat transfer therebetween. Still further, the turbocharger of the present invention may include an air duct for conveying a portion of the compressed air into the turbine housing, to thereby lower the temperature of the exhaust gases and thus also the temperature of the turbine.

Exhaust gas turbochargers are commonly employed in association with 
internal combustion engines, such as Diesel or Otto-cycle gasoline 
engines, for increasing the available horsepower thereof. Generally, such 
turbochargers comprise a turbine and centrifugal or rotary compressor 
mounted on a common shaft. The exhaust gases of the engine are utilized to 
rotate the turbine wheel, and thus the compressor wheel, and the rotary 
compressor acts to pressurize the air being delivered to the engine's 
combustion chambers. 
The rotational speed of such exhaust gas turbochargers often exceeds 
100,000 revolutions per minute, and for this reason, an oil lubricated 
bearing system is preferably used for mounting the common shaft for the 
exhaust gas turbine wheel and rotary compressor wheel. Temperatures of 
about 800 degrees C. occur in the exhaust gas turbine in the case of 
Diesel engines and above about 1,000 degrees C. in the case of Otto-cycle 
engines. The resulting heat flow from the turbine wheel and the housing to 
the adjacent bearing housing poses a significant problem, in that 
excessive temperatures can result in the destruction of the bearings, as 
well as in the decomposition of the lubricating oil. 
It is accordingly an object of the present invention to provide means for 
rotatably mounting an exhaust gas turbine or the like, and which avoids 
the overheating of heat sensitive components thereof. 
It is a more specific object of the present invention to provide a 
turbocharging apparatus of the described type which has provision for 
reducing heat transfer from the exhaust gas turbine wheel into the bearing 
housing, to thereby avoid damage to the bearings and oil of the 
lubrication system. 
These and other objects and advantages of the present invention are 
achieved in accordance with the present invention by the provision of an 
apparatus which comprises a bearing housing having an end wall with an 
opening therethrough, a shaft having a turbine wheel mounted thereon and 
including an internal passageway which defines an inlet and a radially 
directed outlet, means rotatably mounting the shaft in the bearing 
housing, and means for conducting lubricating oil to the inlet of the 
shaft passageway during rotation of the shaft and so that the oil exits 
radially from the passageway outlet and contacts the surface of the end 
wall of the bearing housing in a circular pattern to thereby cool the 
same. Preferably, the means mounting the shaft in the bearing housing 
includes a pair of oil lubricated rotary bearings mounted in axially 
spaced relation on the shaft, and the inlet of the shaft passageway is 
disposed intermediate the rotary bearings, so that the lubricating oil 
flows through the bearings and then into the inlet of the passageway on 
the shaft. 
As another specific aspect of the present invention, there is provided a 
turbocharging apparatus wherein the bearing housing has an end wall which 
is spaced from the adjacent rear wall of the turbine housing to define an 
annular cooling gap therebetween, and apertures are provided in the 
housing for permitting air to flow through the cooling gap to cool the 
opposing surfaces of the end wall and rear wall and thereby minimize heat 
transfer therebetween. Preferably, the apertures to the cooling gap are 
positioned to permit ambient air to move through the cooling gap by 
natural convection during operation of the apparatus. Further, the end 
wall of the bearing housing and/or the rear wall of the turbine housing 
may be coated with or formed from a suitable heat-insulating material, to 
further thermally insulate the bearings from the high temperatures of the 
turbine wheel. Also, the end of the shaft to which the turbine wheel is 
affixed may have a coaxial passage which serves to minimize the thermal 
bridge, and in one embodiment of the present invention, this passage is 
evacuated to provide thermally insulating space. 
As still another aspect of the present invention, the turbocharger may 
include an air duct for conveying a portion of the air compressed in the 
compressor housing into the turbine housing, to thereby lower the 
temperature of the exhaust gases and cool the turbine wheel during 
operation of the apparatus.

Referring now specifically to the drawings, there is disclosed in FIG. 1 an 
exhaust gas turbocharger which embodies the features of the present 
invention, and which is composed of a turbine housing 1, a bearing housing 
2, and a compressor housing 3. The bearing housing 2 includes an end wall 
at one end thereof, which is composed of the radial flange 4 and end wall 
portion 20. Also, the end wall includes a centrally disposed circular 
opening 47 therethrough. The bearing housing 2 further includes a pair of 
spaced apart integral bushes 29 and 30, which define circular openings 
which are axially aligned with the opening 47 in the end wall. 
The turbine housing 1 is mounted on the flange 4 of the bearing housing, 
and includes a rear wall 19 which also has an opening 48 therethrough. The 
compressor housing 3 includes a wall section 5 which is fixed to the 
bearing housing 2 in the recess 6, and the wall section 5 includes an 
opening 49 therethrough which is coaxially aligned with the bushes 29, 30 
and opening 47. 
The turbocharger further comprises a bearing shaft 7 rotatably mounted in 
the bearing housing, and having one end extending through the opening 47 
of the end wall and the opening 48 of the rear wall. Preferably, the shaft 
7 is sealed in the opening 47 by conventional means (not shown) to prevent 
the passage of a liquid and for the purposes to become apparent. An 
exhaust gas turbine wheel 14 comprising a hub 15 and blades 16 is affixed 
to this end of the shaft, as by welding, and is operatively disposed in 
the turbine housing 1. The other end of the shaft extends through the 
opening 49 in the wall section 5, and mounts a rotary compressor wheel 17 
having blades 18 in the compressor housing 3. The shaft 7 is rotatably 
mounted in the bushes 29 and 30 by a pair of oil lubricated sleeve 
bearings 8, 9 and a sleeve 31 is coaxially disposed about the shaft in 
radially spaced relation, and extends between the bearings to define an 
annular chamber 27 therebetween. 
A thrust bearing is mounted on the end of the shaft 7 within the bearing 
housing, and comprises spaced rings 50, 51 of relatively large diameter, 
and an intermediate sleeve (not numbered) of smaller diameter. An axial 
bearing holding disc 33 is fixed between the bearing housing 2 and wall 
section 5 of the compressor housing, and the disc 33 extends within the 
groove defined between the spaced rings 50, 51, and is spaced from the 
intermediate sleeve to form an annular gap 32. The rings 50, 51 and disc 
33 are axially dimensioned so that lubricating oil may be forced between 
the opposing surfaces to form a lubricating film in the manner hereinafter 
further described. To complete the mounting of the shaft 7 in the 
turbocharger, there is provided a conventional sealing ring within the 
opening 49 of the wall section 5 for sealing the shaft 7 and to prevent 
losses from the lubricating system into the housing of the rotary 
compressor 17. 
As best seen in FIG. 1, the shaft 7 has an enlarged diameter portion 52 at 
the end to which the hub 15 of the turbine wheel 14 is affixed, and the 
shaft further includes an internal passageway which defines a radially 
directed inlet 25 at a medial point along its length, a radially directed 
outlet 26 adjacent the end to which the hub 15 of the turbine wheel 14 is 
affixed, and an axial segment 24 interconnecting the inlet and outlet. The 
inlet 25 is disposed intermediate the bearings 8, 9 and communicates with 
the annular chamber 27, and the outlet 26 is disposed adjacent the inside 
of the end wall portion 20 of the bearing housing. The outlet 26 is also 
disposed on the enlarged diameter portion 52 of the shaft, and thus it 
terminates at a point radially beyond the inlet 25 of the passageway. 
Also, the enlarged diameter portion 52 of the shaft is hollow to define an 
enclosed chamber 28, which communicates with the passageways of the shaft. 
In the embodiment of FIG. 2 however, the chamber 28a terminates short 
before the passageway in the shaft, and it is sealed and evacuated, to 
thereby provide a thermally insulating space. In this regard, the 
evacuation of the chamber 28a may for example be accomplished by the 
electron beam welding of the shaft to the turbine wheel 14 under vacuum 
conditions and so as to form an encircling, sealing seam. In either 
embodiment, it will be seen that the chamber 28(or 28a), together with the 
axial segment 24 of the passageway, serve to minimize the thermal bridge, 
and thus the thermal conduction, from the turbine wheel 14 to bearings 8, 
9. 
The turbocharger of the present invention further comprises duct means for 
conducting pressurized lubricating oil from the lubrication system of the 
associated internal combustion engine, to the rotary bearings 8, 9, and 
then into and through the passageway in the shaft 7. By this arrangement, 
the oil is caused to exit radially from the outlet 26 and so as to contact 
the inside surface of the end wall in a circular pattern to thereby cool 
the same. The oil then flows by gravity over the inside surface of the end 
wall and downwardly through the opening 13 of the housing to the oil sump 
of the internal combustion engine. The circular pattern of the sprayed oil 
assures that the cooling oil will wet substantially the full surface area 
of the wall portion 20 (which is immediately adjacent the hot turbine 
wheel) with a continuous stream of oil to thereby maximize the cooling 
effect. Also, in the embodiment of FIG. 1, the fact that the passageway 
communicates with the chamber 28 permits this oil to contact a significant 
area of the warmest portion of the shaft, to thereby facilitate the 
cooling thereof. 
As illustrated herein, the above described duct means comprises an oil 
inlet passage 10 in the bearing housing 2 which communicates via an axial 
passage (not numbered) to the individual passages 11, 12 which lead to the 
bearings 8, 9 respectively. The oil issues from both sides of the bearings 
8, 9, with a portion entering the annular chamber 27 and the remainder 
flowing out through the opening 13. The oil which enters the chamber 27 is 
drawn through the passageway of the shaft, in part by the siphoning or 
centrifugal pump effect resulting from the fact that the outlet 26 is 
disposed radially further from the axis of the shaft than is the inlet 25. 
The oil duct means also includes a passage 53 in the disc 33 for conveying 
the pressurized oil directly to the gap 32 of the thrust bearing. The oil 
issuing from the thrust bearing also exits through the outlet opening 13. 
As a further aspect of the present invention, the end wall of the bearing 
housing 2 is opposed to and spaced from the turbine housing rear wall 19 
over substantially its full area to define an annular cooling gap 21 
therebetween. In addition, a plurality of apertures 22, 23 are provided in 
the flange 4 of the bearing housing end wall, with the aperture 22 being 
disposed at the bottom of the cooling gap and the aperture 23 being 
disposed at the top thereof. By this positioning of the apertures 22, 23, 
ambient air is permitted to move through the cooling gap by natural or 
free convection during operation of the apparatus. Thus the gap 21 not 
only functions as an insulating space, but it also serves to actively cool 
the walls by reason of the air moving therethrough. 
It will also be noted that the rear wall 19 of the turbine housing includes 
a frusto-conical peripheral portion which is inclined at an angle of about 
45 degrees with respect to the axis of the shaft 7, and which extends in a 
direction toward the bearing housing, to thereby facilitate the transfer 
of heat from the rear wall 19 to the air passing through the cooling gap 
21. The rear wall 19 of the turbine housing, and/or the end wall of the 
bearing housing, may be coated with or formed from a suitable conventional 
insulating material, to further thermally insulate the internal components 
of the bearing housing from the heat of the turbine wheel and turbine 
housing. 
FIG. 3 illustrates another aspect of the present invention, and wherein 
means are provided for conveying a portion of the air compressed in the 
compressor housing into the turbine housing, to thereby lower the 
temperature of the exhaust gases and cool the turbine during operation of 
the apparatus. As illustrated, there is provided a compressor housing 34 
and an exhaust gas turbine housing 35, together with a shaft 7 which 
interconnects the compressor and turbine in the manner described above. 
The compressor housing 34 has an air inlet 38 and an air outlet 36 which 
leads to the combustion chambers of the engine. The turbine housing 35 has 
an exhaust gas inlet 37 coming from the engine, as well as an outlet 39 
leading to the exhaust. Also, there is provided a by-pass line 43 by which 
a portion of the exhaust gases may be caused to by-pass the turbocharger, 
and a control device 40 is provided for selectively opening and closing 
the line 43. More particularly, the outlet 36 of the compressor housing 
communicates with a pressure gauge 41 by means of which a by-pass valve 42 
in the line 43 is opened or controlled. By this arrangement, the by-pass 
line 43 is progressively opened as the speed of the turbocharger 
increases. This pressure control device 40 is known in the prior art, and 
is not per se a part of the present invention. 
The turbocharger illustrated in FIG. 3 further comprises a cooling air duct 
44 having an inlet end 45 disposed in the outlet 36 of the compressor 
housing, and an outlet end 46 disposed in the exhaust gas inlet 37 of the 
turbine housing. Since the static pressure on the outlet side of the 
compressor is usually approximately equal to or less than the static 
pressure at the inlet side of the exhaust gas turbine, means are provided 
for insuring that cooling air will flow through the duct 44 under all 
operating conditions. In particular, the inlet end 45 of the duct 44 is 
directed toward the air flowing outwardly through the compressor housing 
outlet, and so that the resulting dynamic pressure tends to convey the air 
through the duct. Also, the exhaust gas inlet of the turbine housing 
includes a restricted passage or Venturi forming a reduced pressure zone 
47, and the outlet end 46 of the duct is disposed in alignment with the 
movement of the exhaust gas and in the reduced pressure zone. As will be 
apparent, the reduced pressure around the outlet 46 serves to draw the air 
from the compressor through the duct 44. 
In the drawings and specification, there has been set forth a preferred 
embodiment of the invention, and although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation.