U.S. patent application number 11/625936 was filed with the patent office on 2008-07-24 for supercharger with heat insulated gear case.
Invention is credited to Gregory P. Prior.
Application Number | 20080175739 11/625936 |
Document ID | / |
Family ID | 39641404 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080175739 |
Kind Code |
A1 |
Prior; Gregory P. |
July 24, 2008 |
SUPERCHARGER WITH HEAT INSULATED GEAR CASE
Abstract
A positive displacement supercharger includes a housing having a
rotor cavity. A pair of positive displacement rotors are oppositely
rotatable in the rotor cavity and have interleaved helical lobes
forming rotor chambers operative to carry air axially from an inlet
end to an outlet end of the cavity. A gear case adjacent the rotor
cavity is drivably connected with and supports the rotors, the gear
case including a bearing housing having an end surface facing the
rotor cavity and the outlet ends of the rotors. A heat insulating
material is applied to the end surface of the bearing housing and
is effective to reduce heat flow between the rotor cavity and the
end surface of the bearing housing to effectively reduce
lubricating oil temperatures in the gear case. The insulating
material may be a ceramic plate fixed to the bearing housing end
surface.
Inventors: |
Prior; Gregory P.;
(Birmingham, MI) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21, P O BOX 300
DETROIT
MI
48265-3000
US
|
Family ID: |
39641404 |
Appl. No.: |
11/625936 |
Filed: |
January 23, 2007 |
Current U.S.
Class: |
418/83 ; 418/179;
418/201.1; 418/206.3 |
Current CPC
Class: |
F04C 18/16 20130101;
F04C 18/086 20130101; F04C 18/126 20130101; F05C 2251/04 20130101;
F04C 29/02 20130101; F05C 2203/08 20130101 |
Class at
Publication: |
418/83 ; 418/179;
418/201.1; 418/206.3 |
International
Class: |
F01C 21/06 20060101
F01C021/06; F01C 1/16 20060101 F01C001/16; F01C 1/24 20060101
F01C001/24 |
Claims
1. A positive displacement supercharger comprising: a housing
including a rotor cavity having a surrounding cavity wall; a pair
of positive displacement rotors oppositely rotatable in the rotor
cavity and having interleaved helical lobes forming rotor chambers
operative to carry air axially from an inlet end of the cavity to
an outlet end of the cavity; a gear case received within the rotor
cavity and drivably connected with and supporting the rotors at
outlet ends thereof, the gear case including a bearing housing
having an end surface facing the rotor cavity and the outlet ends
of the rotors; and a heat insulating material applied to the end
surface of the bearing housing and effective to reduce heat flow
between the rotor cavity, with the rotors and compressed air
therein, and the end surface of the bearing housing to effectively
limit lubricating oil temperatures in the gear case.
2. A supercharger as in claim 1 wherein the heat insulating
material is a ceramic.
3. A supercharger as in claim 2 wherein the ceramic is formed as a
preformed plate.
4. A supercharger as in claim 3 wherein the ceramic plate is
secured to the end surface of the bearing housing by mechanical
fasteners.
5. A supercharger as in claim 3 wherein the ceramic plate is
secured to the end surface of the bearing housing by an adhesive.
Description
TECHNICAL FIELD
[0001] This invention relates to positive displacement compressors
or superchargers, such as roots type or screw compressors utilized
for automotive engine superchargers and other purposes.
BACKGROUND OF THE INVENTION
[0002] It is known in the art to utilize positive displacement
compressors having lobed rotors for supercharging internal
combustion engines and for providing compressed air for other
purposes. Such a compressor used as an automotive supercharger may
include a housing having a rotor cavity in which a pair of parallel
rotors having interleaved lobes rotate to compress air drawn into
one end of the housing and discharged through an opening in the
cavity wall near an opposite end of the housing. The rotors may be
belt driven by the engine through a pulley connected directly, or
through a gear train, to the pair of rotors.
[0003] Roots type and screw type compressors used on original
equipment automotive engines are made with a bearing housing
between the rotors and the supercharger gear case. This bearing
housing is made of aluminum on some commercial superchargers. The
aluminum rotors have their compressed air outlet ends rotatably
mounted adjacent the bearing housing and are supported and driven
through rotor drive stubs extending into the gear case The bearing
housing and gear case are sealed by a front cover to form a drive
assembly provided with a permanent charge of oil for lubricating
the gears and bearings. The gear case has no positive cooling other
than ram air in an automotive installation.
[0004] Boost operation of the supercharger increases the air
temperature at the outlet ends of the rotors next to the bearing
plate with the highest temperatures reached at maximum engine
speeds. The boosted air heats the gear case oil by forced
convection/conduction through the aluminum bearing plate At high
boost levels, this can lead to unacceptable gear case temperatures
at continued high speeds and loads. This in turn may require speed
limits or boost trim to prevent gear case oil damage or seal damage
that can lead to catastrophic supercharger damage.
[0005] Dynamometer tests of a supercharger have shown that the gear
case heats up very rapidly at high speeds without supplementary
cooling of the gear case. This problem is limited in some vehicle
installations because continuous maximum speed operation is not
possible for most vehicle installations. However, with less under
hood air flow and/or higher continuous speeds, the gear case
temperatures could exceed design limits. Methods and means are
desired for limiting supercharger gear case oil temperatures during
severe operating conditions.
SUMMARY OF THE INVENTION
[0006] The present invention results from consideration of both
practical and low cost means for limiting gear case oil
temperatures of a positive displacement supercharger.
[0007] Since high temperature of the compressed air at the
discharge end of the compressor rotor cavity appears to be a main
source of heat flow to the gear case oil, the present invention is
designed to reduce the rate of heat flow between the rotor cavity
and the gear case oil of a supercharger.
[0008] The heat flow may be reduced by applying a suitable
insulating material between the rotor cavity and the associated
bearing housing of the supercharger.
[0009] In a selected embodiment, the insulating material is a
ceramic suitable for high temperature applications.
[0010] In accordance with the invention, a heat resistant
insulating ceramic material may be applied to a face of the
aluminum bearing housing that faces toward the rotor cavity and the
rotors operative therein. The ceramic material may be in the form
of a preformed plate having substantial strength for operation
adjacent the rotor cavity and the ends of the rotors. The plate may
be secured to the bearing housing by any suitable means including,
for example, adhesives or mechanical fasteners.
[0011] If desired, other forms of heat insulation may be applied in
any suitable manner to the cavity facing face of the bearing
housing. Alternatively, or in addition, other forms of insulation
or insulators may be applied between the rotors and extensions
thereof into the gear case to further reduce heat transmission to
the gear case oil.
[0012] These and other features and advantages of the invention
will be more fully understood from the following description of
certain specific embodiments of the invention taken together with
the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an exterior pictorial view of an exemplary helical
rotor supercharger according to the invention;
[0014] FIG. 2 is a partial cross-sectional plan view showing the
insulated interior of a supercharger similar to that of FIG. 1.
[0015] FIG. 3 is an interior pictorial view of the supercharger of
FIG. 2 with the bearing housing omitted to show the insulating
plate; and
[0016] FIG. 4 is a face view of the insulating plate.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
[0017] Referring first to FIG. 1 of the drawings in detail, numeral
10 generally indicates a positive displacement helical lobed
compressor or supercharger according to the invention. Supercharger
10 includes a rotor housing 12 having an internal rotor cavity 14
defined by a surrounding wall 16 and front and rear end walls 18,
20 respectively. A generally rectangular inlet opening 22 in a
lower portion of the rear end wall 20 communicates an inlet end 23
of the cavity 14 with a source of inlet air, not shown. A generally
V-shaped outlet opening 24 extends through the surrounding wall 16
adjacent the front end wall 18 of the housing and communicates an
outlet end 25 of the cavity 14 with a pressure charging air system,
not shown.
[0018] Within the cavity 14 there are rotatably mounted a pair of
supercharger rotors 26, 28 having lobes 30, 32 with opposite helix
angles, as is best shown in FIG. 2. The lobes 30, 32 of the rotors
are interleaved in assembly to define with the housing helical
rotor chambers 34.
[0019] The rotors form a rotor assembly 36 having inlet and outlet
ends 38, 40. The rotor assembly 36 is belt driven through a pulley,
not shown, connected with a drive gear case 42 to form a drive and
rotor assembly 44.
[0020] The gear case 42 includes a front cover 46 and a bearing
housing 48 enclosing a timing gear train 50 and bearings 52, which
drive and support the outlet end 40 of the rotor assembly 36.
Bearing housing 48 includes an inner end surface 54 facing the
rotor cavity 14 and the rotor assembly outlet end 40 The rotors are
of the helical Roots type, although a screw type supercharger
having air compressing screw type rotors could be used if desired.
The rotor chambers 34 carry charging air from the inlet end 23 to
the outlet end 25 of the rotor cavity 14.
[0021] In accordance with the invention, the inner end surface 54
of the bearing housing 48 is covered with a suitable insulating
material, such as a temperature resistant ceramic, preferably in
the form of a preformed ceramic plate 56, best shown in FIGS. 3 and
4. It is formed with an outer periphery 58 configured to cover the
inner end surface 54 of the bearing housing (not shown in FIG. 3)
with openings 60 for the rotor drive shafts, not numbered. The
plate may be fixed to the end surface 54 of the bearing housing 48
by any suitable means, such as high temperature adhesives or
mechanical fasteners. Alternatively, other forms of insulation
could be applied in place of or in addition to the described
ceramic plate.
[0022] In operation, the supercharger 10 draws air into the inlet
end 23 of the rotor cavity 14 and carries it to the outlet end 25
of the rotor cavity where it is discharged at a higher pressure and
temperature. As the rotor speed is increased to a maximum, the air
outlet temperature is raised to a limit, which, if conducted into
the gear case 42 through the aluminum material of the bearing
housing 48, could overheat the lubricating oil in the gear case and
possibly damage the oil and oil seals, not shown. However, the
addition of the ceramic plate 56, or other insulation, on the inner
end surface 54 of the bearing housing 48 substantially reduces the
conduction of heat into the gear case 42 and reduces the operating
temperature of the oil in the gear case. This protects the gear
case against excessive oil temperatures and may allow supercharger
operation at higher speeds and loads than have been acceptable.
[0023] While the invention has been described by reference to
certain preferred embodiments, it should be understood that
numerous changes could be made within the spirit and scope of the
inventive concepts described. Accordingly, it is intended that the
invention not be limited to the disclosed embodiments, but that it
have the full scope permitted by the language of the following
claims.
* * * * *