Patent Description:
Scroll machines generally include a class of positive fluid displacement apparatuses which use orbiting involute spiral wraps formed on facing parallel plates to compress, expand, or pump a fluid. Scroll machines specifically are directed to scroll-type apparatuses wherein radially compliant means permit actual moving line contact between the flank surfaces of intermeshing wrap elements. Scroll compressors may use several bolts to connect a fixed scroll to an upper main frame of the scroll compressor. The fixed scroll bolts add material cost to the bill of materials, require holes to be drilled and tapped in the scroll and frame, and require cycle time to install on the assembly line. Additionally, use of fixed scroll bolts increase the overall diameter of the compressor due to the diameter of the individual bolts and the minimum required wall thickness adjacent to the bolt holes. Although many designs for scroll machines exist, improved designs and assembly methods to enable easier and faster assembly while reducing costs and quantity of components are desirable.

<CIT> describes a non-orbiting scroll having a structure which interfits with a plurality of crankcase towers. The plurality of crankcase towers are circumferentially spaced by gaps, and the non-orbiting scroll has tabs which extend into the gaps. The crankcase towers optionally fit into grooves in the non-orbiting scroll. The crankcase towers and the grooves on the non-orbiting scroll properly position the non-orbiting scroll and the crankcase relative to each other. The tabs extending into the gaps between the crankcase towers prevent the ingress of welding material into a compressor housing.

For purposes of reducing cost, complexity and diameter of scroll compressor designs, it is desirable to eliminate the fixed scroll bolts used in attaching the fixed scroll to the upper frame.

In a scroll compressor, the joint between the fixed scroll and the upper frame is created by machining matching tapered radially contacting surfaces on each part which, when twisted together, pulls the fixed scroll axially toward the frame, locking it in place. Machining matching, as used in this description, includes machining a contact surface on a first part and machining a surface on a second part, the machining surfaces being designed to correspond or match when mated with each other. In addition, a pressure dome, located above the fixed scroll, clamps the scroll tight against the frame at initial assembly. When the compressor is running, discharge gas pressure acts on the dome to further clamp the fixed scroll in place with sufficient force that fixed scroll bolts may be eliminated, decreasing the overall diameter, weight and cost of the compressor.

References are made to the accompanying drawings that form a part of this disclosure and which illustrate embodiments in which the systems and methods described in this specification can be practiced.

A scroll machine (e.g., a scroll compressor or the like) can include a pair of scroll members which orbit relative to each other to compress a working fluid such as, but not limited to, air or a refrigerant. The scroll compressor includes a first, stationary (non-orbiting) scroll member having a base and a generally spiral wrap extending from the base, and a second, orbiting scroll member having a base and a generally spiral wrap extending from the base. The spiral wraps of the first and second scroll members are intermeshed, creating a series of compression chambers. The scroll compressor also includes a frame to which the stationary scroll is typically fixed via bolts. Embodiments described in this specification are directed to systems and methods for securing the stationary scroll member to the frame in a boltless connection. A boltless connection, which may utilize an intermediate cap to bias the stationary scroll to the frame, can be relatively cheaper and simpler to manufacture than a bolted connection. Further, in an embodiment, the boltless connection can reduce a radial footprint of the scroll compressor.

A scroll machine is generally denoted by reference numeral <NUM>. In the preferred embodiment, the scroll machine <NUM> is a refrigerant fluid compressor. It will be understood that a scroll machine in accordance with the description in this specification can also be configured for use as a pump or for expanding a gaseous fluid.

Scroll compressor <NUM> includes a hermetic shell <NUM> that encloses substantially all the operating mechanism of the device. A frame <NUM> supports the operating mechanism.

<FIG> shows a prior art scroll compressor <NUM>. The scroll compressor <NUM> includes an electric motor <NUM> inside the hermetic shell <NUM>. The electric motor <NUM> includes a stator <NUM> and a rotor <NUM>. The stator <NUM> can be press fit or interference fit to the hermetic shell <NUM>. The rotor <NUM> may typically be press-fit or otherwise assembled to a drive shaft <NUM>. The drive shaft <NUM> extends along a longitudinal axis <NUM> of the scroll compressor <NUM>. The drive shaft <NUM> and the rotor <NUM> may be supported and centered within the frame <NUM> and the stator <NUM> by a lower drive shaft main bearing <NUM> and an upper drive shaft main bearing <NUM>. The drive shaft main bearings <NUM> and <NUM> may be of the plain sleeve bearing type, according to an embodiment.

A drive crank pin <NUM> can be formed on an upper end 27a of the drive shaft <NUM>. The drive crank pin <NUM> can be radially displaced from and parallel to the longitudinal axis <NUM> of the drive shaft <NUM>. The drive crank pin <NUM> connects the drive shaft <NUM> to an orbiting scroll plate <NUM> through a bearing <NUM>. Rotation of the drive shaft <NUM> and the crank pin <NUM> can thereby draw the scroll plate <NUM> around in an orbital path having a radius equal to the displacement of the center of drive pin <NUM> from the longitudinal axis <NUM> of the drive shaft <NUM>. The principles by which scroll machines such as compressor <NUM> operate are well known to those skilled in the art and have been explained in numerous prior art U. patents, as for example, <CIT>.

Axial force may be applied to a lower surface of the orbiting scroll plate <NUM> by a thrust bearing <NUM>. A face of the thrust bearing <NUM> can be machined into a top surface of the frame <NUM>.

Orbiting scroll plate <NUM> is constrained to orbit in a circular path relative to a stationary or fixed scroll plate <NUM> by means of an Oldham coupling <NUM>. The orbiting and stationary scroll plates <NUM> and <NUM>, respectively, include involute wrap elements <NUM> on their facing surfaces. The involute wrap elements <NUM> define moving pockets of fluid (e.g., a working fluid being compressed) by means of moving line contacts as scroll plate <NUM> orbits relative to the stationary scroll plate <NUM>. The relative orbital motion of the scroll plates <NUM> and <NUM> causes these pockets of fluid to experience a change in volume and pressure as the fluid moves radially inward toward the center of the plates <NUM>, <NUM>. Thus, fluid entering the scroll compressor <NUM> through an inlet port <NUM> in the hermetic shell <NUM> can cool the rotor <NUM> and the stator <NUM>, be compressed by the orbital motion of the scroll plate <NUM>, and discharged from the hermetic shell <NUM> through the outlet port <NUM> that is in fluid communication with the center of the stationary scroll plate <NUM>.

Prior art compressors include bolts <NUM> clamping the scroll plate <NUM> to the frame <NUM>. Bolt holes <NUM> in both the fixed scroll plate <NUM> and the frame <NUM> accommodate the bolts <NUM>. The bolts <NUM> and the bolt holes <NUM> can increase the diameter of the scroll compressor <NUM> and increase machining requirements, assembly time, and/or component costs.

<FIG> and <FIG> are cross-sectional views of a scroll compressor <NUM> including a boltless connection clamping the scroll plate to the frame, according to an embodiment. Aspects of the scroll compressor <NUM> can be the same as or similar to aspects of the scroll compressor <NUM>. For simplicity of this specification, common features are labeled with like reference numbers and are not described in additional detail. In an embodiment, a twist lock mechanism can provide a feature to implement the boltless design. In an embodiment, the twist lock mechanism can simplify an assembly of the scroll compressor <NUM> and can enable assembly without the use of bolts to clamp the non-orbiting scroll plate <NUM> to the frame <NUM> of the scroll compressor <NUM>. The frame <NUM> is secured (e.g., via a press-fit, interference fit, etc.) in a middle shell <NUM> of the scroll compressor <NUM> and can abut against a top edge <NUM> of the shell <NUM>.

<FIG> is a perspective view of the frame <NUM>, according to an embodiment. As shown in <FIG>, the frame <NUM> has a plurality of frame extensions 53which are machined to create a contact surface <NUM>. In an embodiment, the contact surface <NUM> can be a flat axial contact surface. The frame extensions <NUM> may alternatively be referred to as the legs <NUM>. In the illustrated embodiment, four frame extensions <NUM> are shown. It will be appreciated that other numbers of frame extensions <NUM>, such as three or five or even two, can be provided. The frame extensions <NUM> include an axially extending interlock mechanism <NUM>. The axially extending interlock mechanism <NUM> can be formed, for example, by machining the frame <NUM> to create contact surfaces <NUM> on the frame extensions <NUM>. In an embodiment, the contact surfaces <NUM> can be inwardly facing, tapered radial contact surfaces <NUM>. In an embodiment, the contact surfaces <NUM> may be at or about parallel to the axis <NUM>. An undercut <NUM> can be machined at an intersection of a contact surface <NUM> and the contact surface <NUM> to minimize stress in the frame extensions <NUM> when assembled. In an embodiment, the contact surface <NUM> may be an axial contact surface.

<FIG> is an isometric view of the fixed scroll <NUM> including a plurality of fixed scroll extensions <NUM> extending radially from the axis <NUM>, according to an embodiment. The fixed scroll extensions <NUM> include an axially extending interlock mechanism <NUM> adapted to engage the frame interlock mechanisms <NUM> upon radial rotation of the fixed scroll <NUM>. In one embodiment, the fixed scroll <NUM> includes four cast bosses <NUM> on an involute side of the fixed scroll <NUM>. In an embodiment, the four cast bosses <NUM> can be semi-circular cast bosses. An arc length of the bosses <NUM> is slightly greater than that of the frame extensions <NUM>. The fixed scroll bosses <NUM> can be machined to create an axial contact surface <NUM> and an outwardly facing, tapered radial contact surface <NUM>. A radius of the fixed scroll contact surface <NUM> may be slightly larger than the radius of the contact surface <NUM> so as to be fitted between the frame <NUM> and the fixed scroll <NUM> when assembled. In an embodiment, the fit can be an interference fit or the like. In an embodiment, an angle of the contact surfaces <NUM> on the frame legs <NUM> is selected to match an angle of the contact surfaces <NUM> on the fixed scroll <NUM>. The bosses <NUM> include a transitional engagement region <NUM> which can be milled into the radial surface. In an embodiment, the transitional engagement region <NUM> can have a slightly smaller radius than the contact surface <NUM> and can transition into the contact surface <NUM>. The fixed scroll <NUM> can include a plurality of guides <NUM>. The guides <NUM> can, for example, provide alignment assistance when assembling the scroll compressor <NUM>.

When assembling the fixed scroll <NUM> onto the frame <NUM>, as can be seen in <FIG>, the bosses <NUM> can be first positioned, or clocked, between the frame extensions <NUM> with approximately <NUM>° spacing. The fixed scroll <NUM> can rest on the axial contact surfaces <NUM> prior to final assembly. The transitional engagement region <NUM> on the bosses <NUM> can slip inside the contact surfaces <NUM> of the frame <NUM> to pilot the scroll and ensure it is centered. To complete the fixed scroll assembly, the fixed scroll <NUM> can be rotated about axis <NUM> with respect to the frame <NUM> approximately <NUM>° until cast anti-rotation stop surface <NUM> on the frame <NUM> contacts a mating machined anti-rotation stop surface <NUM> of the fixed scroll <NUM>. An amount of rotation may depend, for example, on a length of the inter-meshing contact surfaces <NUM>, <NUM> and the number of frame extensions <NUM>. During operation of the scroll compressor <NUM>, the torque on the fixed scroll <NUM> due to gas pressures in the involute pockets can maintain the fixed scroll <NUM> securely against the anti-rotation stop on the frame <NUM>, preventing the fixed scroll <NUM> from twisting loose.

Thus at least one of the frame interlock mechanisms <NUM> has contact surfaces <NUM>, <NUM> having a radial and an axial slope, at least one of the fixed scroll support interlock mechanisms <NUM> has contact surfaces <NUM>, <NUM> having a radial and an axial slope, and the contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> can engage the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> upon radial rotation. The radial slope ranges between <NUM> and <NUM> degrees, and preferably ranges between <NUM> and <NUM> degrees from the vertical. In an embodiment, the contact surfaces <NUM>, <NUM> or the contact surfaces <NUM>, <NUM> can also be collectively referred to as engagement surfaces.

The contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> and the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> are non-planar, such that the non-planar contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> and the non-planar contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> are arced about the axis <NUM>.

Because the contact surfaces <NUM>, <NUM> are tapered and fitted together, when the fixed scroll <NUM> is assembled, a component of the contact forces acts in a downward direction <NUM> and pulls the fixed scroll <NUM> tight against the frame <NUM>. Structural analysis of one embodiment shows that at or about <NUM> (<NUM> lb. ) the axial load can be generated with at or about. <NUM>" radial interference fit in the tapered joints and a taper angle of at or about <NUM>° from vertical.

As shown in <FIG> and <FIG>, a drawn steel intermediate cap <NUM> is assembled over the fixed scroll <NUM> and stops against the scroll backside, contacting over an annular region <NUM>. A radial lip seal <NUM> between the neck of the intermediate cap <NUM> and the fixed scroll <NUM> separates the high pressure discharge <NUM> and low pressure suction <NUM> sides of the compressor <NUM>. When making the intermediate cap weld <NUM>, an external axial force is first applied through the upper cap <NUM> to deflect the outside diameter of the intermediate cap <NUM> downward in direction <NUM> and further clamp the fixed scroll <NUM> against the frame <NUM>. The diameter of the contact band between the cap <NUM> and the fixed scroll <NUM> is sized so that a line of action of contact forces are generally centered on the width of the frame legs <NUM>, ensuring that no bending moment is applied to the fixed scroll <NUM> in order to keep scroll distortion to a minimum. The intermediate cap <NUM>, when joined to the upper cap <NUM> and sealed to the fixed scroll with seal <NUM>, creates a discharge pressure region through which gas flows after exiting the fixed scroll port/center and prior to flowing thru the outlet port <NUM>.

The intermediate cap <NUM> is designed with a flat annular section near the outer diameter where it joins the skirt of the cap <NUM> in a near <NUM>° bend <NUM>. So constructed, the cap <NUM> is not stiff in the axial direction and, when the compressor <NUM> is running, the majority of the pressure forces acting on the cap <NUM> are bore against the fixed scroll <NUM>, adding further to the clamp loads keeping the fixed scroll <NUM> in place.

One embodiment includes at least three fixed scroll support extensions <NUM> and at least three frame extensions <NUM>.

In an embodiment, the scroll compressor includes an orbital scroll plate <NUM> having an attached involute wrap element <NUM> in intermeshed relationship with the wrap <NUM> of the fixed scroll <NUM>. The contact surfaces <NUM>, <NUM> of the frame interlock mechanism and the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism are arced about the axis, engagement of the frame interlock mechanism <NUM> with the fixed scroll support interlock mechanism <NUM> biases the frame <NUM> and the fixed scroll <NUM> axially towards each other, and the radial slope ranges between <NUM> and <NUM> degrees.

The intermediate cap <NUM> can be assembled over the fixed scroll <NUM> on a side of the fixed scroll support axially removed from the frame <NUM>, the intermediate cap <NUM> contacting an annular region <NUM> of the fixed scroll <NUM> to bias the fixed scroll <NUM> against the frame <NUM>.

At least one of the frame interlock mechanisms <NUM> has contact surfaces <NUM>, <NUM> having a radially varying diameter, and the contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> contacts the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> upon radial rotation.

A person of skill in the art will recognize that the arrangement can be reversed or inverted. In these variations, the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> has one of a fixed radial diameter, an increasing radial diameter, or a decreasing radial diameter; the radially varying diameter of the frame interlock mechanism <NUM> is either an increasing radial diameter or a decreasing radial diameter. Similarly, the fixed scroll support interlock mechanism <NUM> has contact surfaces <NUM>, <NUM> having a radially varying diameter, and the contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> contacts the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> upon radial rotation. Variations include the contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> has one of a fixed radial diameter, an increasing radial diameter, or a decreasing radial diameter, and the radially varying diameter of the fixed scroll support interlock mechanism <NUM> is either an increasing radial diameter or a decreasing radial diameter.

A person of skill in the art will recognize that the diameters of the contact surfaces can be varied, such that the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> has one of a fixed axial diameter, an increasing axial diameter, or a decreasing axial diameter, and the axially varying diameter of the frame interlock mechanism <NUM> is either an increasing axial diameter or a decreasing axial diameter.

The scroll compressor <NUM> can be assembled according to the following:.

The method of assembly may also include:.

Engaging the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> with the contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> upon radial rotation can be planar, or the contact surfaces <NUM>, <NUM> of the frame interlock mechanism <NUM> and the contact surfaces <NUM>, <NUM> of the fixed scroll support interlock mechanism <NUM> can be non-planar and arced about the axis <NUM>.

A method of biasing a scroll compressor assembly together without bolts or the like includes : (a) providing a frame <NUM> including a plurality of frame extensions <NUM> extending radially from an axis <NUM> and an axially extending interlock mechanism <NUM> on each frame extension; (b) providing a fixed scroll support <NUM> including a fixed scroll wrap <NUM>, a plurality of extensions <NUM> extending radially from the axis <NUM> and an axially extending interlock mechanism <NUM> on each fixed scroll support extension <NUM>; (c) providing an orbital scroll plate <NUM> having an attached involute wrap element <NUM> in intermeshed relationship with the fixed scroll wrap <NUM>; and (d) engaging the frame interlock mechanism <NUM> with the fixed scroll support interlock mechanism <NUM> to provide a first pressure biasing the frame <NUM> and the fixed scroll support axially towards each other.

In an embodiment, the method can further include: (e) providing an intermediate cap <NUM> assembled over the fixed scroll <NUM> on a side of the fixed scroll support axially removed from the frame <NUM>; and (f) contacting an annular region <NUM> of the fixed scroll support with the intermediate cap <NUM> and to provide a second pressure biasing the fixed scroll <NUM> against the frame <NUM>.

In an embodiment, the method can further include: (g) operating the scroll compressor <NUM> assembly to provide a third pressure on a discharge side <NUM> of the intermediate cap <NUM> biasing the fixed scroll <NUM> against the frame <NUM>.

It should be noted that the above description is for a frame and scroll design that has four legs and bosses, respectively. This arrangement can provide for optimal packaging of the orbiting scroll and Oldham coupling (not shown). It will be appreciated that the twist lock feature can also work with a "three-legged" design or with a multi-legged design. Further, the direction of the tapered radial contact surfaces can be switched. For example, the contact surface on the frame could face radially outward and the contact surface on the fixed scroll could face radially inward. The angle on the tapered surfaces, however, is preferably set in a dovetail arrangement so that when the surfaces are engaged the fixed scroll is pulled toward the frame.

Claim 1:
A scroll compressor (<NUM>), comprising:
a shell (<NUM>);
a frame (<NUM>) aligned about a longitudinal axis (<NUM>) of the scroll compressor, the frame being fitted into the shell, wherein the frame includes a plurality of frame extensions (<NUM>) including axially extending frame interlock mechanisms (<NUM>);
a fixed scroll (<NUM>) having a fixed scroll wrap (<NUM>) and a fixed scroll support, wherein the fixed scroll support is aligned about the longitudinal axis and is secured to the frame in a boltless connection, wherein the fixed scroll support includes a plurality of fixed scroll support extensions (<NUM>) including axially extending fixed scroll support interlock mechanisms (<NUM>) configured to engage the frame interlock mechanisms; and
an intermediate cap (<NUM>) engaging with a surface of the fixed scroll support on an opposite side of the fixed scroll wrap, the intermediate cap being secured to the shell and contacting an annular region (<NUM>) of the fixed scroll support to bias the fixed scroll against the frame.