TORSION DAMPING MECHANISM FOR A SUPERCHARGER
TECHNICAL FIELD
The present invention relates to a torsion damping mechanism for a
supercharger or rotary blower, including a torsion damping mechanism (e.g., "isolator") for
reducing audible noise from the supercharger or blower, and especially from the timing gears.
BACKGROUND
Although the present invention may be used advantageously on many different
types of blowers, regardless of the manner of input drive to the blower, the present invention
is especially adapted for use with a Roots-type rotary blower that is driven by an internal
combustion engine. In a typical internal combustion engine used commercially for on-
highway vehicles, the torque output of the engine is not perfectly smooth and constant, but
instead, is generated in response to a series of individual, discrete combustion cycles.
A typical Roots-type blower transfers volumes of air from the inlet port to the
outlet port, whereas a screw compressor actually achieves internal compression of the air
before delivering it to the outlet port. However, for purposes of the present invention, the
blower, or compressor, generally includes a pair of rotors, which must be timed in
relationship to each other, and therefore, are driven by meshed timing gears. As is now well
known to those skilled in the blower art, the timing gears are potentially subject to conditions
such as gear rattle and bounce.
Rotary blowers of the type to which the present invention relates (e.g., either
Roots-type or screw compressor type) are also referred to as "superchargers," because they
are used to effectively supercharge the intake side of the engine. Typically, the input to an
engine supercharger is a pulley and belt drive arrangement that is configured and sized such
that, at any given engine speed, the amount of air being transferred into the intake manifold is
greater than the instantaneous displacement of the engine, thus increasing the air pressure
within the intake manifold, and increasing the power density of the engine.

Rotary blowers of either the Roots-type or the screw compressor type are
characterized by the potential to generate noise. For example, Roots-type blower noise may
be classified as either of two types. The first is solid borne noise caused by rotation of timing
gears and rotor shaft bearings subjected to fluctuating loads (the periodic firing pulses of the
engine). The noise, which may be produced by the meshed teeth of the timing gears during
unloaded (non-supercharging), low-speed operation is also referred to as "gear rattle." The
second type of noise is fluid bome noise caused by fluid flow characteristics, such as rapid
changes in the velocity of the fluid (i.e., the air being transferred by the supercharger). The
present invention is concerned primarily with the solid bome noise caused by the meshing of
the timing gears.
To minimize solid borne noise, torsion damping mechanisms (e.g., "isolators")
have been developed, which can minimize the "bounce" of the timing gears during times of
relatively low speed operation, when the blower rotors are not "under load." Such torsion
damping mechanisms are also referred to as "isolators" because part of their function is to
isolate the timing gears from the speed and torque fluctuations of the input to the
supercharger. A torsion damping mechanism or torsional isolator may have the opportunity
to create a noise referred to as clunk. Clunk noise is generated when the negative input
torque exceeds the isolator's negative torque capacity. The clunk noise includes the noise
generated by impacts within the mechanical components of the isolator and the impact of the
timing gear teeth to each other.
SUMMARY
A torsion damping mechanism for a rotary blower may be provided. The
torsion damping mechanism may be adapted to be rotatably interposed between a first drive
member for driving a first gear in constant mesh with a second gear and a second drive
member rotatably driven in a first rotational direction by torque from an engine. The torsion
dampening mechanism may comprise: an input hub driven by the second drive member and
adapted to engage a first end of a torsion spring; an output hub adapted to drive the first drive
member and to engage a second end of the torsion spring ; an intermediate hub fixed for
rotation with the first drive member; and a bearing member. The bearing member may have

an inner portion connected for rotation with the intermediate hub and an outer portion
connected for rotation with the output hub. The bearing member may be a one-way bearing
that permits torque to flow from the output hub into the intermediate hub and the first drive
member when the output hub is driven in a first rotational direction, and permits the output
hub to rotate relative to the intermediate hub with no substantial torque transfer therebetween
when the output hub is driven in a second rotational direction opposite the first rotational
direction. A rotary blower employing a torsion dampening mechanism may also be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described, by way of example, with
reference to the accompanying drawings, wherein:
FIG. 1 is a schematic illustration of an intake manifold assembly having a
positive displacement blower or supercharger for boosting intake pressure to an internal
combustion engine;
FIG. 2 A is a cross-sectional view of a torsion damping mechanism according to
an embodiment of the present invention;
FIG. 2B is an exploded view of a torsion damping mechanism according to an
embodiment of the present invention;
FIG. 3 is first perspective view of an input hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 4 is a second perspective view of an input hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 5 is a cross-sectional view of an input hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 6 is a perspective view of a torsion spring of the torsion damping
mechanism shown in FIGS. 2A-2B;

FIG. 7 is a first perspective view of an output hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 8 is a second perspective view of an output hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 9 is a cross-sectional view of an output hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 10 is a perspective view of an intermediate hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 11 is a cross-sectional view of an intermediate hub of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 12 is a cross-sectional view of a bearing of the torsion damping
mechanism shown in FIGS. 2A-2B;
FIG. 13 is s front view of a bearing of the torsion damping mechanism shown in
FIGS. 2A-2B.
DETAILED DESCRIPTION
Reference will now be made in detail to embodiments of the present invention,
examples of which are described herein and illustrated in the accompanying drawings. While
the invention will be described in conjunction with embodiments, it will be understood that
they are not intended to limit the invention to these embodiments. On the contrary, the
invention is intended to cover alternatives, modifications and equivalents, which may be
included within the spirit and scope of the invention as embodied by the appended claims.
Schematically illustrated in FIG. 1 is a portion of an internal combustion engine
10, which may be of a periodic combustion type, such as the Otto or Diesel cycle type. The
engine 10 may include a plurality of cylinders 12 and a reciprocating piston 14 disposed
within each cylinder to define an expandable combustion chamber 16. The engine 10 may

also include intake and exhaust manifold assemblies 18, 20 for respectively directing
combustion air to and from the combustion chambers 16 via intake and exhaust valves 22, 24,
The intake manifold assembly 18 may include a positive displacement blower
or supercharger 26 of the backflow or Roots-type. The blower 26 may have a housing and a
pair of rotors 28, 29 with meshed lobes 28a, 29a rotatably supported by the housing. The
rotors 28,29 may be fixed to rotor shafts that may also be rotatably supported by the housing.
The rotors 28, 29 may be fixed to the rotor shafts for rotation. The rotors 28, 29 may be
mechanically driven by engine crankshaft torque transmitted thereto in a known manner via a
drive belt (not shown). The mechanical drive may rotate the blower rotors 28, 29 at a fixed
ratio relative to crankshaft speed, such that the blower displacement is greater than the engine
displacement, thereby boosting or supercharging the air going to the engine combustion
chambers to increase engine power. Although a pair of rotors are described in detail, fewer
or more rotors may be utilized in other embodiments.
The illustrated blower 26 may include an inlet port 30 that receives an air or air-
fuel mixture charge from an intake duct or passage 32 and a discharge or outlet port 34
directing the charge to the intake valves 22 via a discharge duct or passage 36. The intake
and discharge ducts 32, 36 may be intercommunicated via a bypass duct or passage 38
connected at openings 32a, 36a in the intake and discharge ducts 32, 36, respectively. If the
engine 10 is of the Otto cycle type, a throttle valve 40 may control air or air-fuel mixture flow
into intake duct 32 from a source, such as ambient or atmospheric air, in a manner known in
the art.
Disposed within the bypass duct 38 may be a bypass valve 42, which may be
moved between open and closed positions by an actuator assembly 44 that may be responsive
to pressure in intake duct 32 via a line 46 and, therefore, operative to control supercharging
pressure in duct 36 as a function of engine power demand. When bypass valve 42 is in the
fully open position, the air pressure in discharge duct 36 is relatively low relative to the air
pressure in intake duct 32. When the valve 42 is fully closed, the air pressure in the discharge
duct is relatively high.

Referring to FIGS. 2A-2B, a portion of blower 26 is shown in detail. In the
illustrated configuration, blower 26 may include a housing assembly 48 (partially shown in
FIG. 2A), an input drive member 50, a torsion damping mechanism 52 according to an
embodiment of the present invention, and an output member 54 drivingly connected to the
rotors 28, 29 (not shown in FIG. 2A).
Input and output drive members 50, 54 may be rotatable relative to the housing
assembly 48. Input torque produced by the engine 10 may be received by the input drive
member 50 and may be routed through the torsion damping mechanism 52 into the output
drive member 54. A pulley 55 may be connected to an end of the input drive member 50.
Pulley 55 may be driven by the previously mentioned drive belt (not shown) which may
transmit engine torque to the blower 26. Input drive member 50 may be supported by
bearings 57, 59, and output drive member 54 may also be supported by bearings 61. The
output drive member 54 may be considered a first drive member, and the input drive member
50 may be considered a second drive member in accordance with an embodiment of the
invention. A first timing gear (not shown) of blower 26 may be connected to an end of the
output drive member 54 as is known in the art. The first timing gear (not shown) may be in
constant mesh with a second timing gear (not shown) of blower 26. The timing gears may be
press fit into the rotor shafts (not shown) as is known in the art and may be operative to
prevent contact of the lobes 28a, 29a of the rotors 28,29.
During non-supercharging, low engine speed or idle speed operation, the
meshed teeth of the blower timing gears may be substantially unloaded and may bounce or
clash back and forth against each other through the backlash therebetween. The bounce or
clash may produce an objectionable noise known as gear rattle and is believed to be caused
by torsionals in the supercharger drive torque provided by periodic combustion engines such
as engine 10. The resilient drive provided by torsion damping assembly 52 may reduce the
rattle noise below the audible range.
As shown in FIG. 2A, torsion damping mechanism 52 may be disposed for
rotation about the common axis a-a of the input and output drive members 50, 54. The input
drive member 50 may be fixed for rotation with an input hub 56. Referring now to FIGS. 3-

5, input hub 56 may be generally cylindrical in shape. Input hub 56 may include a
circumferentially extending flange 76. The input hub 56 (specifically, for example, the
circumferentially extending flange 76 of input hub 56) may include a first receiving groove
58 adapted to receive a first end 63 of a torsion spring 60. The circumferentially extending
flange 76 may include at least in part a scalloped edge 78. The input hub 56 may further
include a tapered cylindrical portion 80 that may extend from the end of the input 56 with the
circumferentially extending flange 76.
Referring again to FIGS. 2A-2B, a second end 65 of the torsion spring 60 may
be adapted to engage a second receiving groove 62 in an output hub 64. Referring now to
FIGS. 7-9, output hub 64 may be generally cylindrical in shape. Output hub 64 may include
a circumferentially extending flange 82. The output hub 64 (specifically, for example, the
circumferentially extending flange 82 of output hub 64) may include a second receiving
groove 62 adapted to receive a second end 64 of the torsion spring 60. The circumferentially
extending flange 82 may include at least in part a scalloped edge 84.
Referring now to FIG. 6, the axially extending, opposite ends or tangs 63, 65 of
torsion spring 60 may be received in grooves 58,62 and may be interconnected by a plurality
of helically wound coils. In an embodiment, the torsion spring 60 may include about eight
coils. Although eight coils is mentioned in detail, torsion spring 60 may include more or
fewer coils in other embodiments. In an embodiment, the helically wound coils may be
disposed about portions of the input and output hubs 56, 64. Torsion spring 60 may provide a
resilient drive between the input and output hubs 56, 64, which may attenuate and/or isolate
torque fluctuations or torque spikes in a first or positive rotational direction for preventing
audible gear tooth rattle of the timing gears during non-supercharging, low engine speed
modes of operation.
Torsion damping mechanism 52 may also include an intermediate hub 68.
Referring again to FIGS. 2A-2B, intermediate hub 68 may be fixed for rotation with output
drive member 54. Referring now to FIGS 10-11, intermediate hub 68 may be generally
cylindrical in shape. The intermediate hub 68 may include a circumferentially extending
flange 86 at a first end. The intermediate hub 68 may include a cylindrical portion 88 at a

second end of the intermediate hub 68 (e.g., opposite the first end of the intermediate hub 68
with the circumferentially extending flange 86). The cylindrical portion 88 may have a
smaller outer diameter than the outer diameter of the remainder of the intermediate hub 68.
Torsion damping mechanism 52 may also include a bearing member 70.
Referring now to FIGS. 2A-2B and 12-13, bearing member 70 may have an inner portion 72
connected for rotation with the intermediate hub 68 and an outer portion 74 connected for
rotation with the output hub 64. In an embodiment of the invention, bearing member 70 may
be a one-way bearing that may permit torque T (represented by arrows in FIG. 2A) to flow
from output hub 64 into intermediate hub 68 and output drive member 54 when output hub 64
is driven in a first rotational direction, and may permit output hub 64 to rotate relative to
intermediate hub 68 with no substantial torque transfer between the components (i.e.,
between output hub 64 and intermediate hub 68) when output hub 64 is driven in a second
rotational direction (e.g., opposite the first rotational direction). Since bearing member 70, by
virtue of its one-way operation, may prevent the transfer of torque between the input and
output hubs 56, 64 in the second or negative rotational direction, it may attenuate ore
eliminate torque spikes in the negative rotational direction for preventing audible clunk noise.
The foregoing descriptions of specific embodiments of the present invention
have been presented for purposes of illustration and description. They are not intended to be
exhaustive or to limit the invention to the precise forms disclosed, and various modifications
and variations are possible in light of the above teaching. The embodiments were chosen and
described in order to explain the principles of the invention and its practical application, to
thereby enable others skilled in the art to utilize the invention and various embodiments with
various modifications as are suited to the particular use contemplated. The invention has
been described in great detail in the foregoing specification, and it is believed that various
alterations and modifications of the invention will become apparent to those skilled in the art
from a reading and understanding of the specification. It is intended that all such alterations
and modifications are included in the invention, insofar as they come within the scope of the
appended claims. It is intended that the scope of the invention be defined by the claims
appended hereto and their equivalents.

WE CLAIM

1. A torsion damping mechanism (52) for a rotary blower (26) that is adapted to be
rotatably interposed between a first drive member (54) for driving a first gear in constant
mesh with a second gear and a second drive member (50) rotatably driven in a first rotational
direction by torque from an engine (10), the torsion damping mechanism (52) comprising:
an input hub (56) driven by the second drive member (50) and adapted to engage a
first end (63) of a torsion spring (60);
an output hub (64) adapted to drive the first drive member (54) and to engage a
second end (65) of said torsion spring (60);
an intermediate hub (68) fixed for rotation with the first drive member (54); and
a bearing member (70) having an inner portion (72) connected for rotation with the
intermediate hub (68) and an outer portion (74) connected for rotation with the output hub
(64), wherein the bearing member (70) is a one-way bearing that permits torque to flow from
the output hub (64) into the intermediate hub (68) and the first drive member (54) when the
output hub (64) is driven in a first rotational direction, and permits the output hub (64) to
rotate relative to the intermediate hub (68) with no substantial torque transfer therebetween
when the output hub (64) is driven in a second rotational direction opposite the first rotational
direction.
2. The torsion damping mechanism in accordance with claim 1, wherein the engine (10)
comprises a periodic combustion engine.
3. The torsion damping mechanism in accordance with claim 1, wherein the input hub
(56) is generally cylindrical.
4. The torsion damping mechanism in accordance with claim 3, wherein the input hub
(56) includes a circumferentially extending flange (76).

5. The torsion damping mechanism in accordance with claim 4, wherein the
circumferentially extending flange (76) includes a first receiving groove (58) adapted to
receive a first end (63) of said torsion spring (60).
6. The torsion damping mechanism in accordance with claim 4, wherein the
circumferentially extending flange (76) includes a scalloped edge (78).
7. The torsion damping mechanism in accordance with claim 4, wherein the input hub
(56) includes a tapered cylindrical portion (80) extending from the circumferentially
extending flange (76).
8. The torsion damping mechanism in accordance with claim 1, further comprising a
torsion spring (60), wherein said torsion spring (60) includes a plurality of helically wound
coils.
9. The torsion damping mechanism in accordance with claim 8, wherein the helically
wound coils are configured to be disposed about portions of the input hub (56) and the output
hub (64).
10. The torsion damping mechanism in accordance with claim 1, wherein the output hub
(64) is generally cylindrical.
11. The torsion damping mechanism in accordance with claim 1, wherein the output hub
(64) includes a circumferentially extending flange (82).
12. The torsion damping mechanism in accordance with claim 11, wherein the
circumferentially extending flange (82) includes a second receiving groove (62) adapted to
receive the second end (65) of said torsion spring (60).
13. The torsion damping mechanism in accordance with claim 11, wherein the
circumferentially extending flange (82) includes a scalloped edge (84).

14. The torsion damping mechanism in accordance with claim 1, wherein the intermediate
hub (68) is generally cylindrical.
15. The torsion damping mechanism in accordance with claim 14, wherein the
intermediate hub (68) includes a circumferentially extending flange (86).
16. The torsion damping mechanism in accordance with claim 15, wherein the
intermediate hub (68) includes a cylindrical portion (88) extending from an end of the
intermediate hub (68) that is opposite the circumferentially extending flange (86), the
cylindrical portion (88) having a smaller outer diameter than the remainder of the
intermediate hub (68).
17. The torsion damping mechanism in accordance with claim 1, wherein the first drive
member (54) is an output drive member.
18. The torsion damping mechanism in accordance with claim 1, wherein the second
drive member (50) is an input drive member.
19. A rotary blower including a housing (48); first and second rotors (28, 29) disposed in
the housing and having meshed lobes (28a, 29a) for transporting air from an inlet port (30) to
an outlet port (34); first and second shafts rotatably supported by the housing (48) and having
the first and second rotors (28, 29) fixed for rotation therewith; first and second timing gears
fixed for rotation with the first and second shafts for preventing contact of the meshed lobes
(28a, 29a); an input pulley (55) adapted to be rotatably driven about an axis; and a torsion
damping mechanism (52) operably associated with the input pulley (55), the torsion damping
mechanism (52) comprising:
a torsion spring (60);
an input hub (56) adapted to engage a first end (63) of the torsion spring (60);
an output hub (64) adapted to engage a second end (65) of the torsion spring (60);
an intermediate hub (68) disposed proximate the output hub (64); and

a bearing member (70) having an inner portion (72) connected for rotation with the
intermediate hub (68) and an outer portion (74) connected for rotation with the output hub
(64), wherein the bearing member (70) is a one-way bearing that permits torque to flow from
the output hub (64) into the intermediate hub (68) when the output hub (64) is driven in a first
rotational direction, and permits the output hub (64) to rotate relative to the intermediate hub
(68) with no substantial torque transfer therebetween when the output hub (64) is driven in a
second rotational direction opposite the first rotational direction.
20. A torsion damping mechanism (52) for a rotary blower (26) that is adapted to be
rotatably interposed between a first drive member (54) for driving a first gear in constant
mesh with a second gear and a second drive member (50) rotatably driven in a first rotational
direction by torque from an engine (10), the torsion damping mechanism (52) comprising:
an input hub (56) driven by the second drive member (50);
an output hub (64) adapted to drive the first drive member (54);
a means for providing a resilient drive between the input hub (56) and the output hub
(64);
an intermediate hub (68) fixed for rotation with the first drive member (54); and
a bearing member (70) having an inner portion (72) connected for rotation with the
intermediate hub (68) and an outer portion (74) connected for rotation with the output hub
(64), wherein the bearing member (70) is a one-way bearing that permits torque to flow from
the output hub (64) into the intermediate hub (68) and the first drive member (54) when the
output hub (64) is driven in a first rotational direction, and permits the output hub (64) to
rotate relative to the intermediate hub (68) with no substantial torque transfer therebetween
when the output hub (64) is driven in a second rotational direction opposite the first rotational
direction.

A torsion damping mechanism (52) for a rotary blower
(26) is provided that includes an input hub (56)
adapted to engage a first end (63) of a torsion spring
(60) and an output hub (64) adapted to engage a second
end (65) of the torsion spring (60). An intermediate
hub (68) is fixed for rotation with a first drive
member (54). A bearing member (70) includes an inner
portion (72) connected for rotation with the
intermediate hub (68) and an outer portion (74)
connected for rotation with the output hub (64). The
bearing member (70) may be a one-way bearing that
permits torque to flow from the output hub (64) into
the intermediate hub (68) and the first drive member
(54) when the output hub (64) is driven in a first
rotational direction, and permits the output hub (64)
to rotate relative to the intermediate hub (68) with no
substantial torque transfer there between when the
output hub (64) is driven in a second rotational
direction.