US20080085204A1

US20080085204A1 - Scroll compressor with titanium Oldham coupling

Info

Publication number: US20080085204A1
Application number: US11/544,403
Authority: US
Inventors: Alexander Lifson
Original assignee: Scroll Technologies LLC
Current assignee: Danfoss Scroll Technologies LLC
Priority date: 2006-10-06
Filing date: 2006-10-06
Publication date: 2008-04-10

Abstract

A scroll compressor includes an Oldham coupling which prevents the orbiting scroll member from rotating when driven by a rotating shaft. The Oldham coupling is formed of titanium or titanium alloy, thus increasing the strength of the Oldham coupling while minimizing its weight. Reduced coupling weight minimizes unnecessary scroll compressor vibration.

Description

BACKGROUND OF THE INVENTION

This application relates to a scroll compressor wherein the Oldham coupling is manufactured of titanium or titanium alloy.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In typical scroll compressors, a first scroll member has a base and a generally spiral wrap extending from its base. A second scroll member has a base and a generally spiral wrap extending from its base. The second scroll member is driven to orbit by a rotating shaft. An eccentric pin on the shaft extends into a slider block which is received within a boss on a rear face of the second scroll member. An anti-rotation coupling, known as an Oldham coupling, ensures that the second scroll member orbits relative to the first scroll member as driven by the rotating shaft. As the second scroll member orbits relative to the first, compression chambers defined between the wraps of the first and second scroll member decrease in size to compress the refrigerant.
In the prior art, the Oldham couplings have typically been formed of aluminum, and have often broke. This problem was especially pronounced in larger scroll compressors, and in particular during flooded start operation. Under such flooded starts, the force transmitted to the coupling by the orbiting scroll can be substantially higher than during normal operation, causing the Oldham coupling to break.
To overcome this problem, it has been proposed in the past, for example, to use cast iron to form the Oldham coupling. However, a cast iron Oldham coupling would be unduly heavy and cause excessive vibration, as the Oldham coupling is an element of a scroll compressor that cannot be fully balanced (such as for example using counterweights). A cast iron coupling would weigh roughly two and a half times as much as an aluminum coupling of the same size.
Titanium and titanium alloys have been utilized extensively in aerospace applications, and are beginning to find their way in some specialized automotive applications, where weight of the part is of concern. Examples, of some of the automotive applications include: turbocharger wheels, suspension springs, etc. However, titanium or its alloys have not been proposed for Oldham couplings for scroll compressors.

SUMMARY OF THE INVENTION

In a disclosed embodiment of this invention, an Oldham coupling is formed of titanium or titanium alloy. By utilizing titanium or titanium alloy, sufficient strength is provided for the Oldham coupling without the additional weight, as would be found utilizing cast iron.
Titanium is about 60% as dense as cast iron. As an example, titanium has a density of approximately 4500 kg/m²versus 7800 kg/m³for cast iron. In addition, the strength of titanium is superior to both aluminum and cast iron.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of a scroll compressor incorporating the present invention.

FIG. 1B is a schematic of an alternative system.

FIG. 2A is a view of an Oldham coupling according to the present invention.

FIG. 2B is another view along line 2B-2B of FIG. 2A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A compressor 20 is illustrated in FIG. 1A having an orbiting scroll 22 orbiting relative to a non-orbiting scroll 24. As shown in the example a motor 26 drives a rotating shaft 28. However, as shown in FIG. 1B, the compressor assembly 104, as known, can be driven directly by an engine 100 shaft through appropriate coupling mechanisms that would couple the engine shaft rotation to the compressor shaft. The engine shaft can be coupled to the compressor rotating shaft, for example, by means of a coupling, gearbox, or belt drive 102. The electric motor is normally an induction motor type. The motor speed can additionally be varied by means of variable speed drive.
An eccentric pin 29 at the top of the shaft extends into a slider block 31. The slider block 31 is received within a boss 33 on a rear face of an orbiting scroll 22. As is known, when the rotating shaft 28 rotates, the eccentric pin 29 moves within the slider block 31. The orbiting scroll 22 is supported on a crankcase 30. An Oldham coupling 32 ensures that when the rotating shaft 29 drives the orbiting scroll 22 it will be constrained to orbiting movement, and will not rotate. The structure and operation of the Oldham coupling 32 is as known in the art.
As shown in FIGS. 2A and 2B, the Oldham coupling 32 includes a generally ring shaped portion 34, and keys 36. The keys fit into slots to constrain the orbiting scroll to orbit rather than rotate.
In the present invention, the Oldham coupling 32 is formed of titanium or titanium alloy. As mentioned above the titanium or titanium alloy material provides additional strength and resistance to breakage as compared to other more conventional materials such as for example aluminum or cast iron. Pure titanium has good mechanical properties, however titanium is often alloyed. Most commonly, small amounts of aluminum and vanadium are added, however, other stabilizing materials, as provided below, can also be used. Such alloys have very high tensile strength and toughness. Titanium alloys that can be used as potential candidates for the Oldham Coupling, normally would fall into three main classes: alpha, beta, and alpha-beta phase that includes most of the titanium alloys now in use. Typical stabilizing materials include: aluminum, gallium, germanium, carbon, oxygen and nitrogen for alpha stabilizers; and chromium, cobalt, copper, iron, manganese molybdenum, nickel niobium silicon, tantalum, vanadium for beta stabilizers. Alpha-phase titanium is more ductile and beta-phase titanium is stronger but more brittle. Alpha-beta-phase titanium falls somewhere between both. One of the most common alloys currently in use is Ti-6Al-4V. A table, in addition to pure titanium, showing typical alfa, alfa-beta, and beta alloys that can be used for an Oldham coupling is shown below.


Alpha alloys	Alpha + Beta alloys	Beta alloys

Ti—2.5Cu	Ti—6Al—4V	Ti—13V—11Cr—3Al
Ti—5Al—2.5Sn	Ti—6Al—6V—2Sn	Ti—8Mo—8V—2Fe—3Al
Ti—8Al—1V—1Mo	Ti—6Al—2Sn—2Zr—2Cr—2Mo	Ti—10V—2Fe—3Al
Ti—6242	Ti—3Al—2.5V	Ti—15—3
Ti—6Al—2Nb—1Ta—0.8Mo	Ti—8Al—1Mo—1V
Ti—5Al—5Sn—2Zr—2Mo

It should be noted that the titanium coupling can be delivered first as cast titanium parts, before performing final machining operation. It is clear from this statement and from the drawings that the entirety of the Oldham coupling is formed of the titanium. However, the invention would extend to the use of titanium to form the majority of the Oldham coupling body.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

1. A scroll compressor comprising:

a first scroll member having a base and a generally spiral wrap extending from its base;

a second scroll member having a base and a generally spiral wrap extending from its base;

said second scroll member being caused to orbit by a rotating driveshaft; and

an Oldham coupling constraining said second scroll member to orbital movement when driven by said rotating driveshaft, said Oldham coupling being formed such that a majority of its body is formed of a titanium material.

2. The scroll compressor as set forth in claim 1, wherein titanium material is a pure titanium

3. The scroll compressor as set forth in claim 1, wherein titanium material is a titanium alloy

4. The scroll compressor as set in claim 3, wherein said titanium alloy is selected from the titanium alpha alloys.

5. The scroll compressor as set in claim 3, wherein said titanium alloy is selected from the titanium beta alloys.

6. The scroll compressor as set in claim 3, wherein said titanium alloy is selected from the titanium alpha-beta alloys.

7. The scroll compressor as set forth in claim 1, wherein said rotating driveshaft is driven by an electric motor

8. The scroll compressor as set forth in claim 1, wherein an engine drives said rotating driveshaft

9. The scroll compressor as set forth in claim 1, wherein said driveshaft includes an eccentric pin, said eccentric pin being received within a slider block, said slider block being received within a boss extending from a rear face extending from said second scroll member.

10. The scroll compressor as set forth in claim 1, wherein the entirety of the Oldham coupling is formed of a titanium material.

11. The scroll compressor as set forth in claim 11, wherein the Oldham coupling is cast of the titanium material.