U.S. patent application number 11/778131 was filed with the patent office on 2009-01-22 for asynchronous non-constant-pitch spiral scroll-type fluid displacement machine.
Invention is credited to Zhihuang DAI, Zhengzhi ZHAN.
Application Number | 20090022613 11/778131 |
Document ID | / |
Family ID | 40264981 |
Filed Date | 2009-01-22 |
United States Patent
Application |
20090022613 |
Kind Code |
A1 |
DAI; Zhihuang ; et
al. |
January 22, 2009 |
Asynchronous non-constant-pitch spiral scroll-type fluid
displacement machine
Abstract
A scroll-type spiral fluid displacement machine having at least
one pair of interfitting scroll elements. The scroll vanes of the
scroll elements are constructed upon a base line spiral defined by
the equation: L=K.sub.0.phi..sup.K1e.sup.-.phi./.sup.K2 where L is
the distance from the spiral's origin to any point on the spiral
curve, .phi. is the angular displacement of the spiral, K.sub.0 is
a constant greater than 1, K.sub.1, is a constant greater than 1,
and K.sub.2 is a constant greater than 10.
Inventors: |
DAI; Zhihuang; (Chicago,
IL) ; ZHAN; Zhengzhi; (Westmont, IL) |
Correspondence
Address: |
LADAS & PARRY LLP
224 SOUTH MICHIGAN AVENUE, SUITE 1600
CHICAGO
IL
60604
US
|
Family ID: |
40264981 |
Appl. No.: |
11/778131 |
Filed: |
July 16, 2007 |
Current U.S.
Class: |
418/55.2 ;
418/55.3 |
Current CPC
Class: |
F04C 18/0269
20130101 |
Class at
Publication: |
418/55.2 ;
418/55.3 |
International
Class: |
F04C 18/063 20060101
F04C018/063 |
Claims
1. A scroll-type fluid displacement device comprising: a first
scroll and a second scroll, each scroll having an end plate from
which a spiral projects transversely from the end plate; said first
scroll and said second scroll being opposingly arranged to interfit
said spirals; said spirals being opposingly symmetrical about a
central axis; a base line for each spiral be defined by the
equation: L=K.sub.0.phi..sup.K1e.sup.-.phi./.sup.K2 wherein L is
the distance from said central axis to any point on the base line
curve, .phi. is the angular displacement of the base line curve,
K.sub.o is a constant greater than 1, K.sub.1 is a constant greater
than 1, and K.sub.2 is a constant greater than 10.
2. The device according to claim 1 further comprising an orbital
movement generating mechanism that moves at least one of the
scrolls so that said first scroll moves in a non-rotating orbital
path perpendicular to said central axis, relative to said second
scroll.
3. The device according to claim 1 further comprising a housing to
which one of said scrolls is rigidly affixed.
4. The device according to claim 2 wherein said orbital movement
generating mechanism is a rotationally driven crankshaft.
5. The device according to claim 1 further comprising a third
scroll and a fourth scroll that are defined and interfit in the
same manner as said first and second scrolls; wherein said first
and third scrolls are rigidly affixed to a housing; and wherein
said second and fourth scrolls are driven in a non-rotating orbital
path perpendicular their respective central axes, relative to said
first and third scrolls.
6. The device according to claim 5 wherein the central axes of said
second and fourth scrolls are parallel; wherein said second and
fourth scrolls are driven in the same direction on their respective
orbital paths and at an angular phase difference of 180
degrees.
7. The device according to claim 5 wherein said second and fourth
scrolls share a common central axis.
8. A method of designing scroll elements for a scroll-type fluid
displacement device, the steps comprising: designing a base line
spiral for first and second scroll elements, the base line spiral
being defined by the equation:
L=K.sub.0.phi..sup.K1e.sup.-.phi./.sup.K2 wherein L is the distance
from a central axis to any point on the base line curve, .phi. is
the angular displacement of the base line curve, K.sub.o is a
constant greater than 1, K.sub.1, is a constant greater than 1, and
K.sub.2 is a constant greater than 10; designing inner and outer
spirals to define spiral walls that create fluid pockets having a
desired change in volume when said first and second scroll elements
are fit and orbitally rotated together in the scroll-type fluid
displacement device.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This application relates generally to a spiral scroll-type
fluid displacement machine and more particularly to an asynchronous
non-constant pitch spiral scroll-type fluid displacement
machine.
[0003] 2. Description of the Related Art
[0004] Generally, a conventional spiral scroll-type fluid
displacement machine is formed with a pair of scroll elements
(i.e., an orbiting scroll element and a fixed scroll element) each
having spiral vanes that are fitted together in a certain
predetermined way to intake fluid such as air or water through an
intake port. The interfitting spiral vanes create one or more fluid
pockets and trap the fluid inside the pocket(s) by moving the
orbiting scroll element in a predetermined manner. The fluid pocket
moves toward an outlet port while maintaining pressure in the
pocket by continuously moving the orbiting scroll element within
the interfitted fixed scroll element. The pressurized fluid is
discharged though an outlet port.
[0005] U.S. Pat. No. 801,182 (Creux) describes a conventional
spiral scroll-type machine. A typical spiral scroll-type machine
includes a pair of scroll elements where one scroll element is
termed a fixed scroll and the other one is termed an orbiting
scroll. Either the fixed or orbiting scroll comprises a spiral vane
or a curled up wrap connected to an end plate in such a manner that
the spiral vane is perpendicular to the planar surface of the end
plate. The projecting spiral vanes or wraps of the fixed and
orbiting scrolls interfit to form a plurality of line contacts
between them, and thus at least one pair of fluid pockets is
formed. The fixed scroll is stationary and does not move. The
orbiting scroll does not rotate by revolving around its center.
Rather the movement of the orbiting scroll is an orbiting motion.
That is, the non-rotating orbiting scroll is moved in an orbit
(generally circular in shape) formed around the center of the fixed
scroll. With such orbiting motion, the line contacts between the
spiral vanes of the fixed and orbiting scrolls move along the
curved surfaces of spiral wraps, thereby creating fluid pockets and
possibly changing the volume of (and thus the pressure in) the
fluid pockets. The volume can be increased or decreased depending
on the orbiting direction of the orbiting scroll, or the geometry
of the spiral vane structure. Therefore, a spiral scroll type
machine can compress or expand fluids for pumping action.
[0006] FIGS. 10A-10D show simplified cross-sectional views of
interfitted spiral vanes of the fixed and orbiting scroll elements
in a spiral scroll-type fluid displacement machine for generally
illustrating the concept of the moving pair of spiral vanes moving
fluid. Referring to FIG. 10A, a fluid is sucked into one of the
outer openings of the interfitted spiral vanes. Only a single
intake of fluid into a fluid pocket is shown for ease of
illustration and understanding. As the orbiting scroll progresses
along its orbital path, the fluid inlet is closed to create a fluid
pocket as shown in FIG. 10B. FIG. 10C shows a complete revolution
of the orbiting scroll from FIG. 10A, showing the progression of
the fluid pocket toward the center of the interfitted spiral vanes.
FIG. 10D shows another complete revolution of the orbiting scroll
showing the progression of the fluid pocket to the center of the
interfitted spiral vanes where the fluid is discharged.
[0007] In the past decade, the rapid development of the computer
and the availability of high-precision CNC machines propelled a
marvelous progress in this field. This type of fluid displacement
machine demonstrates the following advantages:
1. High efficiency--mainly because the process of
suction-compression-discharge occurs continuously and the expansion
of remaining fluid into suction pocket does not exist, thereby
offering a higher volume efficiency. 2. Torque varies in a
relatively small range during a full rotation. Vibration is kept at
the low level, as is the noise. 3. The structure is simple and
compact.
[0008] The scroll-type compressor has gained increasing popularity
and taken more and more market share, which used to be occupied by
other types of compressors (such as the reciprocating-type
compressor and rotary-type compressor, among others), especially
for small-size compressors ranging in power from 0.5 to 15
kilowatts. Scroll-type fluid displacement machines are being widely
used in some industries such as for air-conditioning and medical
equipment. In order to meet the requirements for broader industry
applications, it is desired to further optimize the design of these
types of machines.
[0009] Although this design concept of scroll-type fluid
displacement machines appeared as early as the beginning of
twentieth century, its development was hindered due the difficulty
to optimize its design and the requirement for high precision
machining. A lot of effort is now being invested to improve the
performance and reliability of scroll-type fluid displacement
machines. Some are focusing on developing dual scroll compressors
to enlarge capacity and achieve higher energy efficiency (as in
U.S. Pat. Nos. 5,258,046 and 5,556,269). Some are emphasizing the
axial and/or radial compliant mechanism (as in U.S. Pat. Nos.
4,846,639, 6,461,131, and 6,695,600). Some are focusing on a
coating treatment on the spiral surface in order to prevent seizure
or friction and provide good lubrication between scroll wraps. Some
are trying to provide a better rotation preventive device (as in
U.S. Pat. No. 6,752,606). Designing scroll vanes to improve the
performance of compressor is one of various key areas. Some are
focusing on the central portion of spiral surface (as in U.S. Pat.
No. 5,513,967). Some are stressing on finding an appropriate scroll
curve to increase the volume ratio (as in U.S. Pat. No. 5,458,471),
or minimize the machine size (as in U.S. Pat. No. 5,318,424), or
for special requirements (as in U.S. Pat. No. 5,547,353).
[0010] However, the conventional scroll-type fluid displacement
machines have problems in that the fluid pressure distribution and
the fluid pressure variation during operation are not optimized
such that the conventional scroll-type fluid displacement machines
have the shortcomings less-than-optimal efficiency, and relatively
high noise and vibration, all of which contributes to decreased
durability of the machines.
SUMMARY OF THE INVENTION
[0011] With the aid of sophisticated computer-based real-time
measurement systems and advanced computer fluid dynamics analysis,
it was found that fluid pressure distribution and variation during
the operation of scroll-type fluid displacement machines is key to
the design of a new fluid displacement machine structure, and to
choose an appropriate curve for scroll wraps. The present fluid
displacement machine overcomes the general shortcomings of current
machines and manifest inherent advantages such as high efficiency,
low noise, low vibration and enhanced durability. With such
consideration and using an optimization technique, the present
invention uses a single, continuous curve as the base line for
constructing scroll vanes.
[0012] The scroll vanes of the present invention are constructed
based upon a base line spiral defined by the equation:
L=K.sub.0.phi..sup.K1e.sup.-.phi./.sup.K2
Wherein L is the distance from the origin to any point on the
spiral curve, .phi. is the angular displacement of the spiral,
K.sub.o is a constant greater than 1, K.sub.1 is a constant greater
than 1, and K.sub.2 is a constant greater than 10.
[0013] The fluid displacement machine according to a preferred
embodiment of the present invention comprises two pairs of scroll
elements, where each element is made up of a fixed scroll and an
orbiting scroll. These two pairs of scroll elements are separate
and mounted in a back-to-back manner. The scroll wraps of the two
orbiting scrolls are symmetric with respect to the central axis of
a driving shaft. So are the scroll vanes of two fixed scrolls. Two
pairs of scrolls are offset by a phase difference of 180 degrees.
These two orbiting scrolls share the same orbiting circle.
[0014] The scroll elements can be mounted on two separate
crankshafts, of which the eccentric parts are positioned opposite
radially. The two crankshafts are then linked with a rigid coupling
such that the rotation force can be transmitted to the second
crankshaft through the first one. The fluid displacement machine
has two inlets and two outlets. The inflowing fluid will be divided
and may be compressed or expanded through either pair of scrolls
simultaneously. The discharged fluid from each outlet is then
merged together to export.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view of scroll-type fluid
displacement machine in accordance with a preferred embodiment of
the present invention.
[0016] FIG. 2 is an exploded perspective view showing two orbiting
scrolls, two fixed scrolls, two crankshafts and one rigid coupling
in the arrangement shown in FIG. 1.
[0017] FIG. 3 is a side view of the assembly of two crankshafts and
one rigid coupling in accordance with a preferred embodiment of the
present invention.
[0018] FIG. 4 is a diagram showing the relative position of
eccentric parts of the two crankshafts in accordance with a
preferred embodiment of the present invention.
[0019] FIG. 5 is a diagram showing the relative position of spiral
wraps of two orbiting scrolls machine in accordance with an
embodiment of the present invention.
[0020] FIG. 6 is a diagram showing an example of a spiral curve
which defines the shapes of spiral wraps of the scrolls in
accordance with the present invention.
[0021] FIG. 7 is a cross-sectional view of spiral wrap of an
orbiting scroll used in a single-scroll compressor in accordance
with a preferred embodiment of the present invention.
[0022] FIG. 8 is a cross-sectional view of spiral wraps for an
orbiting scroll used in a dual-scroll compressor in accordance with
a preferred embodiment of the present invention.
[0023] FIG. 9 is a cross-sectional showing the mating of an
orbiting scroll with a fixed scroll which are used in a dual-scroll
compressor in accordance with an embodiment of the present
invention.
[0024] FIGS. 10A-10D depict cross-sectional views of mating spiral
wraps showing the progression of a fluid pocket as the orbiting
scroll is rotated along its orbiting path.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Referring to FIG. 1, the first fixed scroll 1 has its spiral
wrap that interfits the spiral wrap of the first orbiting scroll 2.
The concentric part of crankshaft 4 passes through the center hole
of fixed scroll 1 and is supported by bearing 5 while the eccentric
part of crankshaft 4 goes through the center hole of orbiting
scroll 2 and is supported by bearing 3. The second fixed scroll 8
has its spiral wrap that interfits the spiral wrap of the first
orbiting scroll 9. The concentric part of crankshaft 10 passes
through the center hole of fixed scroll 8 and is supported by
bearing 5 while the eccentric part of crankshaft 10 goes through
the center hole of orbiting scroll 9 and is supported by bearing 3.
The rigid coupling 6 connects crankshaft 4 and crankshaft 10. The
fixed scroll 1 and fixed scroll 8 are affixed to the housing 7. The
rotating force is transmitted to the end of crankshaft 10 so that
the crankshaft 10 drives the orbiting scroll 9 to produce relative
orbiting motion. Meanwhile, the force is transmitted to crankshaft
4 through rigid coupling 6 to produce relative orbiting motion. A
rotation preventive device includes part 11, 12, 13, and 14, and
prevents rotational movement of the orbiting scrolls 2 and 9.
[0026] The orbital movement generating mechanism for this preferred
embodiment comprises two crankshafts 4 and 10 connected by the
rigid coupling 6. However, the orbital movement generating
mechanism could comprise a single crankshaft or any other means for
producing non-rotating relative orbital movement between the
orbital and fixed scrolls. It is noted that, none of the scrolls
necessarily needs to be fixed as long as relative orbital movement
between mating scrolls is achieved through some means.
[0027] FIG. 2 is an exploded perspective view showing the two
orbiting scrolls 2 and 9, two fixed scrolls 1 and 8, two
crankshafts 4 and 10 and one rigid coupling 6.
[0028] As shown in FIG. 3, the crankshaft 4 and crankshaft 10 are
connected by rigid coupling 6. The eccentric part 4a of crankshaft
4 and the eccentric part 10a of crankshaft 10 preferably share the
same diameter and length. The eccentric distance of 4a is
preferably equal to that of 10a.
[0029] FIG. 4 is a diagram representing the relative positioning of
the crankshafts 4 and 10 described in FIG. 3. C0 represents the
cross-section of the thickest concentric part of crankshaft 4. C1
represents the cross-section of the eccentric part 4a of crankshaft
4 while C2 is the cross section of the eccentric part 10a of
crankshaft 10.
[0030] C3 represents the orbiting circle along which the center of
C1 and the center of C2 travel. The orbiting scroll 2 is mounted on
eccentric part 4a and the orbiting scroll 9 is mounted on eccentric
part 10a, so these two orbiting scrolls share the same orbiting
circle. When connecting crankshaft 4 and crankshaft 10, it is
preferred that the centers of the eccentric parts 4a and 10a of
both crankshafts 4 and 10 are located radially oppositely with
respect to the circle C3. Such an arrangement simplifies the
balancing of the machine. As shown in FIG. 4, the center of C1, O1,
is located at the top of C3 while the center of C2, O2, is located
at the very bottom of C3. When crankshaft 4 is rotating in a
counter-clockwise direction, the circle C1 representing the
eccentric part 4a orbits along the circle C3 from the top of C3
counter-clockwise, and the circle C2 representing the eccentric
part 10a orbits along the circle C3 from the bottom of C3. During
the rotation cycle, eccentric parts 4a and 10a always remain at
radially opposite positions.
[0031] FIG. 5 depicts the relative overlapping positioning of the
spiral wraps of two orbiting scrolls 2 and 9. The rotating axis of
the concentric part of crankshaft 4 goes through point O. As shown
in FIG. 5, orbiting scrolls 2 and 9 are symmetric around the point
O. Therefore, the mass distribution of orbiting scroll 2 and that
of orbiting scroll 9 would normally also be symmetric around the
point O, if the orbiting scrolls are both uniformly made of the
same material. The need for balance weight to balance the orbiting
scroll is thus eliminated.
[0032] The scroll-type fluid displacement machine in accordance
with present invention preferably comprises two inlets and two
outlets. Referring back to FIG. 1, there are inlets. 1a and 8a, and
there are outlets 1b and 8b. The inflowing fluid is divided and fed
into the two inlets 1a and 8a, processed in the two pairs of
scrolls, discharged through each outlet 1b and 8b, and merged
together to export.
[0033] The non-constant-pitch spiral curve shown in FIG. 6 is used
as the base line to define the spiral vanes of the orbiting
scrolls. The defining equation for such a spiral curve is:
L=K.sub.0.phi..sup.K1e.sup.-.phi./.sup.K2
where
[0034] L: the distance from the origin to any point on the spiral
curve;
[0035] .phi.: the angular displacement of the spiral curve
[0036] K.sub.0: a real number greater 1, (K.sub.0>1)
[0037] K.sub.1: a real number greater 1, (K.sub.1>1)
[0038] K.sub.2: a real number greater 10, K.sub.2>10
[0039] The strategy to select an appropriate spiral curve is:
[0040] 1. To obtain a high volume ratio. The ratio of the
displacement (V.sub.s) to the final compression volume (V.sub.e) is
required to be high enough to meet the requirement according the
application of the scroll-type fluid displacement machine.
[0041] 2. To use a single, continuous, smoothly changing curve to
define the scroll wraps for its entire length. It is required that
the change of the volume of the fluid pocket formed between two
scrolls be smooth and continuous in order to increase or decrease
the fluid pressure smoothly and avoid shock.
[0042] 3. When the former two conditions are satisfied, it is
desired to have a spiral curve, which defines a faster change of
volume of the fluid pocket. In so doing, the full cycle of
suction-processing-discharge is shortened. Energy efficiency can be
also enhanced.
[0043] The particular curve shown in FIG. 6 is defined by the
equation:
L=2.phi..sup.1.5e.sup.-.phi./100
[0044] It is important to note that this particular curve is just a
member of a family of curves that are described by the equation. In
practice, the consideration of performance requirements including
power, physical properties of fluid and pressure ratio, will be
included in the design of the curve. All these requirements must be
met with the highest priority. Then the curve will be optimized to
enable the fluid displacement machine to achieve its optimum
performance in terms of its fluid dynamics. The result of
optimization is the best combination of three parameters: K.sub.0,
K.sub.1 and K.sub.2. The intended machine will be improved in the
following aspects: increased operating efficiency, reduced
vibration, reduced noise and increased durability.
[0045] The proposed curve can be used to construct a scroll vane
for a single-scroll fluid displacement machine as well as
dual-scroll fluid displacement machine. A typical method is
employed to construct the scroll vanes for a single-scroll fluid
displacement machine. FIG. 7 shows the constructed cross-section of
an orbiting scroll 20. The scroll vane of the corresponding fixed
scroll 22 is symmetric to the vane of the orbiting scroll around
the origin.
[0046] The proposed curve can be also adopted in the design of
dual-scroll fluid displacement machine. A typical dual-scroll fluid
displacement machine has a crankshaft which goes through the fixed
scroll 22 and the orbiting scroll 20. In order to allow the
eccentric part of the crankshaft to pass through the central
portion of orbiting scroll 20, the spiral scrolls must start from
some angular offset, such as is depicted in FIGS. 8 and 9 where an
angular offset of 141.degree. in the second turn counting from the
center. FIG. 8 depicts the cross-section of spiral wraps of
orbiting scroll 20. The dimensions 4.35 mm, 5.79 mm, and 5.16 are
shown in FIG. 8 as an example of one embodiment for one optimum
case; nevertheless, it should be clearly understood that the
present invention is not just limited to the dimensions shown in
FIG. 8. Other optimum dimensions satisfying the equation
L=K.sub.0.phi..sup.K1e.sup.-.phi./.sup.K2 besides those shown in
FIG. 8 are also possible. The mating between the orbiting scroll 20
and the fixed scroll 22 is shown in FIG. 9.
[0047] It will be clear that the present invention is well adapted
to attain the ends and advantages mentioned as well as those
inherent therein. While various embodiments including the presently
preferred one has been described for purposes of this disclosure,
various changes and modifications may be made, which are well
within the scope of the present invention. Numerous other changes
may be made which will readily suggest themselves to those skilled
in the art and which are encompassed in the spirit of the invention
disclosed and as defined in the appended claims.
* * * * *