Patent Description:
Recent CFC-free commercial refrigerant compositions, such as R134A, are characterized as having lower density compared to previously-used CFC or HCFC refrigerants such as R12. Consequently, an air conditioning system must process a higher volume of a CFC-free refrigerant composition relative to CFC or HCFC refrigerant to provide a comparable amount of cooling capacity. To process higher volumes of refrigerant, the design of a gas compressor may be modified to process refrigerant at higher operating speeds and/or operate with higher efficiency.

Centrifugal compressors that make use of continuous dynamic compression offer at least several advantages over other compressor designs, such as reciprocating, rotary, scroll, and screw compressors that make use of positive displacement compression. Centrifugal compressors have numerous advantages over at least some positive displacement compressor designs, including lower vibration, higher efficiency, more compact structure and associated lower weight, and higher reliability and lower maintenance costs due to a smaller number of components vulnerable to wear. High-capacity cooling systems employing centrifugal compressors operate a driveshaft at high-rotational speeds to transmit power from the motor to the impeller to impart kinetic energy to the incoming refrigerant. To mitigate the challenges associated with the high-rotational speed driveshafts, centrifugal compressors typically require relatively tight tolerances and high manufacturing accuracy. Additionally, other types of mechanical systems, such as motors, pumps, and turbines etc., also operate driveshafts at high-rotational speeds. As known to those familiar with these types of rotating mechanical systems, loosening and misalignment of components mounted to the driveshaft may occur during operation creating unbalanced loads which result in vibrations, subjecting the driveshaft to cyclic stress loadings, resulting in decreased operational lifespans and premature failures, particularly premature failure of bearings and seals.

Centrifugal compressors include one or more bearing assemblies which support and maintain alignment of the driveshaft. In typical centrifugal compressors, components, such as the impeller and the thrust disk, are separately coupled to the driveshaft using friction fit connections, e.g., such as a press fit or a shrink fit. The driveshaft, impeller, and the thrust disk, rotating at high-rotational speeds, induce centrifugal forces which increase with increased rotational speed. The centrifugal force is directed radially, away from the axis of rotation, pulling the components outward away from the driveshaft, loosening the friction fit connections. Furthermore, the inertia of the components, particularly radial distribution of mass extending away from the axis of rotation contributes to the centrifugal force further loosening the friction connections with the driveshaft. The loosening of connections creates eccentric loads such that the center of mass of the mounted component is not coincident with the axis of rotation of the driveshaft. The effects of eccentric loading are further exaggerated at high-rotational speeds resulting in vibrations that increase wear and may result in increased system downtime.

The design of mounted components on the high-rotational speed driveshaft poses an on-going challenge of maintaining the friction fit connections between the driveshaft and the components. Furthermore, maintaining alignment of the center of gravity of the components coincident with the axis of rotation of the driveshaft during high-rotational operating speeds facilitates avoiding eccentric loads that lead to vibrations which may damage components of the centrifugal compressor. <CIT> discloses a compressor assembly having an insert screwed into an impeller bore, the insert having a threaded insert bore. The assembly also has a shaft having a threaded bore. A stud is theadedly engaged with the shaft threaded bore and with the insert threaded bore and allows the compressor impeller to be pulled or drawn into the compressor assembly during assembly. <CIT> concerns a centrifugal compressor in which an axial force applied from a shrink-fit impeller to a sleeve section is ensured even if the sleeve section is separated from a clamp surface in an axial direction of an attachment hole. <CIT> relates to optimizing a flow cooling the bearings and motor of a two stage vapor cycle compressor. A thrust disk is positioned between the second stage impeller and an electric motor. A tie rod holds the entire rotating assembly of the compressor including a rotor of the electric motor, the first stage impeller, the second stage impeller, and the thrust disk together.

This background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below, the invention being solely defined by the appended claims.

The present invention provides driveshaft assembly for a compressor, as defined in claim <NUM>. The driveshaft may be rotatably supported within a housing of the compressor.

The present invention correspondingly provides a method of assembling a compressor as defined in claim <NUM>.

Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination. However, the scope of the present invention is solely defined by the appended claims.

The following figures illustrate various aspects of the disclosure.

Referring to <FIG>, a compressor illustrated in the form of a two-stage refrigerant compressor is indicated generally at <NUM>. The compressor <NUM> generally includes a compressor housing <NUM> forming at least one sealed cavity within which each stage of refrigerant compression is accomplished. The compressor <NUM> includes a first refrigerant inlet <NUM> to introduce refrigerant vapor into the first compression stage, a first refrigerant exit <NUM>, a refrigerant transfer conduit <NUM> to transfer compressed refrigerant from the first compression stage to the second compression stage, a second refrigerant inlet <NUM> to introduce refrigerant vapor into the second compression stage (not labeled in <FIG>), and a second refrigerant exit <NUM>. The refrigerant transfer conduit <NUM> is operatively connected at opposite ends to the first refrigerant exit <NUM> and the second refrigerant inlet <NUM>, respectively. The second refrigerant exit <NUM> delivers compressed refrigerant from the second compression stage to a cooling system in which compressor <NUM> is incorporated. The refrigerant transfer conduit <NUM> may further include a refrigerant bleed <NUM> to add or remove refrigerant as needed at the compressor <NUM>.

Referring to <FIG>, the compressor housing <NUM> encloses a first compression stage <NUM> and a second compression stage <NUM> at opposite ends of the compressor <NUM>. The first compression stage <NUM> includes a first stage impeller <NUM> configured to impart kinetic energy to incoming refrigerant gas entering via the first refrigerant inlet <NUM>. The kinetic energy imparted to the refrigerant by the first stage impeller <NUM> is converted to increased refrigerant pressure (i.e. compression) as the refrigerant velocity is slowed upon transfer to a diffuser formed between a first stage inlet ring <NUM> and a portion of the outer compressor housing <NUM>. Similarly, the second compression stage <NUM> includes a second stage impeller <NUM> configured to add kinetic energy to refrigerant transferred from the first compression stage <NUM> entering via the second refrigerant inlet <NUM>. The kinetic energy imparted to the refrigerant by the second stage impeller <NUM> is converted to increased refrigerant pressure (i.e. compression) as the refrigerant velocity is slowed upon transfer to a diffuser formed between a second stage inlet ring <NUM> and a second portion of outer compressor housing <NUM>. Compressed refrigerant exits the second compression stage <NUM> via the second refrigerant exit <NUM> (not shown in <FIG>).

The first stage impeller <NUM> and second stage impeller <NUM> are connected at opposite ends of a driveshaft <NUM> that rotates about a driveshaft axis A<NUM>. The driveshaft extends from a driveshaft first end <NUM> to a driveshaft second end <NUM>, and is axisymmetric about the driveshaft axis A<NUM>. Additionally, the driveshaft axis A<NUM> extends through a center of gravity of the driveshaft <NUM>. The driveshaft <NUM> is operatively connected to a motor <NUM> positioned between the first stage impeller <NUM> and second stage impeller <NUM>, such that the motor <NUM> rotates the driveshaft <NUM> about the driveshaft axis A<NUM>. The first stage impeller <NUM> and the second stage impeller <NUM> are both coupled to the driveshaft <NUM> such that the first stage impeller <NUM> and second stage impeller <NUM> are rotated at a rotation speed selected to compress the refrigerant to a pre-selected pressure exiting the second refrigerant exit <NUM>. Any suitable motor may be incorporated into the compressor <NUM> including, but not limited to, an electrical motor.

In reference to <FIG>, driveshaft <NUM> includes a first shaft portion <NUM> having a first shaft portion radius R<NUM> and a second shaft portion <NUM> having a reduced diameter including a second shaft portion radius R<NUM>, less than the first shaft portion radius R<NUM>, i.e., the driveshaft <NUM> includes a step down feature proximate the driveshaft first end <NUM>, in proximity to the first stage impeller <NUM>. The first shaft portion <NUM> includes first end surface <NUM> and the second shaft portion <NUM> includes a second end surface <NUM>, distal to the first end surface <NUM>, disposed on the driveshaft first end <NUM>. The second shaft portion <NUM> includes a second shaft portion length L<NUM> extending between the first end surface <NUM> and the second end surface <NUM> along the driveshaft axis A<NUM>. The driveshaft <NUM> further includes a blind bore <NUM> that extends axially inward into the driveshaft <NUM> from the second end surface <NUM> to a bore length L<NUM> along the driveshaft axis A<NUM>. That is, the blind bore <NUM> is co-axial with the driveshaft axis A<NUM>. In some example embodiments, the bore length L<NUM> may be substantially the same length as the length of the second shaft portion L<NUM>. The bore <NUM> includes a radius R<NUM> extending from the driveshaft axis A<NUM> to a bore inner surface <NUM> that defines the boundary of the blind bore <NUM>. The bore radius R<NUM> is less than the second shaft portion radius R<NUM>, such that the second shaft portion <NUM> includes an annular wall having a thickness T<NUM> extending between the bore inner surface <NUM> and a second shaft portion outer surface <NUM>. The bore <NUM> further includes a tapered end <NUM> (<FIG>) and a threaded portion defined on the bore inner surface <NUM>.

In reference to <FIG>, a thrust bearing assembly <NUM> supports axial forces imparted to the driveshaft <NUM> during operation of the compressor (e.g., from thrust forces generated by first stage impeller <NUM> and/or second stage impeller <NUM>). The axial forces are directed generally parallel to the driveshaft axis A<NUM>. The thrust bearing assembly <NUM> may include any suitable bearing type, including for example and without limitation, roller-type bearings, fluid film bearings, air foil bearings, and combinations thereof. The thrust bearing assembly <NUM> includes a bearing bracket <NUM> that is coupled to the compressor housing <NUM>. The bearing bracket <NUM> includes a first plate 202a and a second plate 202b that are separated by a distance and disposed on axially opposite sides of a thrust disk <NUM> of the thrust bearing assembly <NUM>. The first and second plates 202a and 202b are annular in shape and include a center opening (not labeled) to receive at least a portion of the driveshaft <NUM> therein when the compressor <NUM> is assembled (as shown in <FIG>). The first and second plates 202a and 202b may be coupled to the compressor housing <NUM> using any suitable means including, for example and without limitation, press-fit connections and/or mechanical fasteners. Each of the first and second plates 202a and 202b may include an inner surface that faces the opposing first plate 202a or the second plate 202b to support and engage the bearings of the thrust bearing assembly <NUM>.

Referring to <FIG>, the thrust disk <NUM> includes a central hub <NUM> and an outer disk <NUM> extending radially outward from the hub <NUM>. The thrust disk <NUM>, specifically the hub <NUM> in the illustrated embodiment, defines a thrust disk bore <NUM> and includes a thrust disk bore surface <NUM> that defines the boundary of the thrust disk bore <NUM>. A thrust disk axis A<NUM> extends though the center of gravity of the thrust disk <NUM>, and the thrust disk <NUM> is axisymmetric about the thrust disk axis A<NUM>. The thrust disk bore <NUM> has a radius R<NUM> extending from the thrust disk axis A<NUM> to the thrust disk bore surface <NUM>. The second shaft portion <NUM> of the driveshaft <NUM> projects or extends through the thrust disk bore <NUM> such that the thrust disk axis A<NUM> and the driveshaft axis A<NUM> are coincident.

The thrust disk <NUM> is coupled to the driveshaft <NUM> by a friction or press fit connection. For example, the thrust disk bore surface <NUM> is in frictional engagement with the second shaft portion outer surface <NUM> and the outer disk <NUM> is in frictional engagement with the first end surface <NUM> of the driveshaft <NUM> such that rotation of the driveshaft <NUM> imparts rotation to the thrust disk <NUM>. The thrust disk bore surface <NUM> is in contact with the second shaft portion outer surface <NUM> with limited or no gaps or spaces. Additionally, the radius R<NUM> is sized such that there is interference between the thrust disk <NUM> and the driveshaft <NUM>. In example embodiments, components, such as the thrust disk <NUM> are coupled to the driveshaft <NUM>, using a press fit, also referred to as interference fit and/or a friction fit. Friction between mating surfaces of the two parts is generated after the two parts having interference are press fit assembled. Based on the amount of interference between thrust disk <NUM> and the driveshaft <NUM>, the thrust disk <NUM> may be assembled onto the driveshaft <NUM> using a hammer or hydraulic ram. In some cases, the components may be assembled using shrink fitting techniques. Shrink fitting techniques are performed by selective heating and/or cooling of the components to be coupled by a shrink fit. In some embodiments, for example, the thrust disk <NUM> is heated, causing expansion of the thrust disk bore <NUM> such that the second shaft portion <NUM> may be inserted and positioned within the expanded thrust disk bore <NUM>. Subsequently, the thrust disk bore <NUM> shrinks upon cooling of the thrust disk <NUM> and contracts around the second shaft portion <NUM>. In some embodiments, one or more alignment features or components may be used to assemble mating components, including for example and without limitation, an alignment pin, keyed features, or other features that are engaged between the thrust disk and the driveshaft.

The driveshaft <NUM>, the first stage impeller <NUM>, and the thrust disk <NUM> are part of a driveshaft assembly <NUM> of the compressor <NUM>. In the illustrated embodiment, the driveshaft assembly <NUM> also includes the second stage impeller <NUM>. The driveshaft assembly <NUM> may include additional or fewer components in other embodiments. In some embodiments, for example, the second stage impeller <NUM> may be coupled to the second end <NUM> of the driveshaft <NUM> by a thrust disk in the same manner as the first stage impeller <NUM>.

In reference again to <FIG>, the outer disk <NUM> includes a first disk surface <NUM> and an opposing second disk surface <NUM> spaced axially from the first disk surface <NUM> by a disk length L<NUM>. The hub <NUM> extends axially from the second disk surface <NUM> to a hub end surface <NUM> for a hub length L<NUM>. The overall length of the thrust disk <NUM> includes the disk length L<NUM> and the hub length L<NUM>. In some embodiments, the hub length L<NUM> is greater than the disk length L<NUM>. The outer disk <NUM> has a disk radius R<NUM> measured from the thrust disk axis A<NUM> to an outer circumferential surface <NUM> of the outer disk <NUM>. The hub <NUM> has a hub radius R<NUM> measured from the thrust disk axis A<NUM> to a radial outer surface <NUM> of the hub <NUM>. The outer disk <NUM> and the hub <NUM> are formed integrally - i.e., as a unitary member, such as by casting or additive manufacturing. In other embodiments, the outer disk <NUM> and the hub <NUM> may be formed separately and coupled together using any suitable means, for example, a welding connection.

The hub radius R<NUM> is less than the disk radius R<NUM>. In the illustrated embodiment, for example, the disk radius R<NUM> is about <NUM>-<NUM> times greater than the hub radius R<NUM>. In other embodiments, the disk radius R<NUM> may be greater than or less than <NUM>-<NUM> times greater than the hub radius R<NUM>. Additionally, the mass of the outer disk <NUM> is greater than the mass of the hub <NUM>. The centrifugal force is proportional to the mass and the radial distribution of mass. Accordingly, the centrifugal force generated on the outer disk <NUM> is greater than a centrifugal force generated on the hub <NUM> during high-speed rotation of driveshaft <NUM>. In some embodiments, the centrifugal force on the outer disk <NUM> is much greater than the centrifugal force on the hub <NUM>.

The radius R<NUM> of the thrust disk bore <NUM> is less than the first radius R<NUM> (<FIG>) of the first shaft portion <NUM>. At least a portion of the first disk surface <NUM> is in contact with the first end surface <NUM> of the first shaft portion <NUM>. Additionally, the outer disk radius R<NUM> is greater than the first shaft portion radius R<NUM> such that a portion of the outer disk <NUM> extends radially outward from the first shaft portion <NUM>. The thrust disk <NUM> is shaped such that the cross-section of the thrust disk <NUM> about a plane passing through the thrust disk axis A<NUM>, yields a generally "L-Shaped" profile arranged on each side of the second shaft portion <NUM>. The outer disk <NUM> extends away from the driveshaft <NUM>, such that at least a portion of the outer disk <NUM> is disposed between the first plate 202a and the second plate 202b of the bearing bracket <NUM>. The first disk surface <NUM> is disposed toward (i.e., facing) the first plate 202a and the second disk surface <NUM> is disposed toward (i.e., facing) the second plate 202b. Suitable bearings are supported by the first and second plate 202a, 202b and are rotationally engaged with the outer disk <NUM>, such that the outer disk <NUM> may rotate relative to the first plate 202a and the second plate 202b.

In reference to <FIG>, the first stage impeller <NUM> extends a length L<NUM> along an impeller axis A<NUM> between an impeller first end <NUM> and an impeller second end <NUM>. Impeller axis A<NUM> extends through the center of gravity of the impeller <NUM>. The impeller <NUM> is axisymmetric, i.e., symmetric about the impeller axis A<NUM>. The impeller <NUM> further includes a first impeller bore <NUM> extending axially into the impeller <NUM> from the impeller first end <NUM>, and a second impeller bore <NUM> extending axially into the impeller <NUM> from the impeller second end <NUM>. The first impeller bore <NUM> has a radius R<NUM>, and the second impeller bore <NUM> has a radius R<NUM>. The radius R<NUM> is greater than R<NUM>. The first impeller bore <NUM> and the second impeller bore <NUM> are arranged such that they collectively form an opening that passes entirely through the impeller <NUM> from the impeller second end <NUM> to the impeller first end <NUM>. The impeller <NUM> further includes a plurality of vanes and may include a shroud. The impeller <NUM> may include any suitable type of vanes that are employed to impart kinetic energy to incoming refrigerant.

The first impeller bore <NUM> includes an impeller inner surface <NUM> that defines the boundary of the first impeller bore <NUM>. The hub <NUM> of the thrust disk <NUM> is disposed within the first impeller bore <NUM> of the impeller <NUM>, such that the impeller axis A<NUM> is coincident with both the thrust disk axis A<NUM> and the driveshaft axis A<NUM>. The hub <NUM> is press fit within the first impeller bore <NUM> such that the outer surface <NUM> is frictionally connected with the impeller inner surface <NUM> with minimal gaps or spaces. In some example embodiments, the hub <NUM> may be frictionally connected with the first impeller bore <NUM> using shrink fitting techniques. Accordingly, rotation of the driveshaft <NUM> results in rotation of the thrust disk <NUM> and the impeller <NUM>. The thrust disk <NUM> transmits torque from the driveshaft <NUM> to the impeller <NUM> and, as such, the impeller <NUM> is not directly mounted to the driveshaft <NUM>. The thrust disk <NUM> and the impeller <NUM> are arranged relative to the driveshaft <NUM> such that the center of gravity of the thrust disk <NUM> and the impeller <NUM> are aligned with the driveshaft axis A<NUM>. In other words, the driveshaft axis A<NUM>, thrust disk axis A<NUM>, and the impeller axis A<NUM> are all co-axial. Furthermore, the assembly of the driveshaft <NUM>, the thrust disk <NUM>, and the impeller <NUM> is axisymmetric about the driveshaft axis A<NUM>.

Referring again to <FIG>, in some example embodiments, the hub <NUM> includes a first hub portion 216a extending from the outer disk <NUM>, and a second hub portion 216b extending from the first hub portion 216a. The first hub portion 216a includes a first outer surface 220a and a first inner surface 208a defining a first portion 206a of the thrust disk bore <NUM>. The first hub portion 216a has an inner hub radius (not shown) measured from the thrust disk axis A<NUM> to the first inner surface 208a and an outer radius (not shown) measured from the thrust disk axis A<NUM> to the first outer surface 220a. The second hub portion 216b includes a second outer surface 220b and a second inner surface 208b defining a second portion 206b of the thrust disk bore <NUM>. The second hub portion 216b includes an inner hub radius (not shown) measured from the thrust disk axis A<NUM> to the second inner surface 208b and an outer radius (not shown) measured from the thrust disk A<NUM> to the second outer surface 220b. The outer radius of the second hub portion 216b is less than the outer radius of the first hub portion 216a, such that there is a greater interference (i.e., a tighter fit) between the first outer surface 220a and the impeller inner surface <NUM> compared to the interference between the second outer surface 220b and impeller inner surface <NUM>. In some embodiments, there may be a clearance or gap C<NUM> between the second outer surface 220b and the impeller inner surface <NUM>. For example, the clearance C<NUM> may be between. <NUM> to <NUM> millimeters (mm). The second outer surface 220b of the second hub portion 216b may include threads that may facilitate removal of the thrust disk <NUM> from the driveshaft <NUM> during disassembly.

The inner radius of the second hub portion 216b may be smaller than the inner radius of the first hub portion 216a, such that the second inner surface 208b has greater interference (i.e., a tighter fit) with the driveshaft <NUM> compared with the interference between the first inner surface 208a and the driveshaft <NUM>. In some embodiments, there may be a clearance or gap C<NUM> between the first inner surface 208a and the driveshaft <NUM>. For example, the clearance C<NUM> between the first inner surface 208a and the driveshaft <NUM> may be between. <NUM> and <NUM> (mm).

Rotation of the driveshaft <NUM>, the thrust disk <NUM>, and the impeller <NUM> induce centrifugal forces directed in an outward radial direction, perpendicular to the driveshaft axis A<NUM>. The induced centrifugal forces increase with increased rotational speed squared. The centrifugal force is an inertial force that is proportional to the radial distribution of mass about the axis of rotation, i.e., the driveshaft axis A<NUM>. The outer disk <NUM> has a larger radius R<NUM> compared with the hub radius R<NUM> of the hub <NUM>. Accordingly, the outer disk <NUM> experiences a greater centrifugal force compared to the centrifugal force experienced by the hub <NUM>. The centrifugal force on the outer disk <NUM> pulls the outer disk <NUM> in a radial direction, perpendicular to the driveshaft axis A<NUM>, away from the driveshaft <NUM>. The centrifugal force on the outer disk <NUM> also exerts an outward radial force on the first hub portion 216a which is proximate to the outer disk <NUM>. The outward radial force exerted on the first hub portion 216a, causes the first outer surface 220a of the first hub portion 216a to exert a force against the impeller inner surface <NUM>, referred to as a first contact force F<NUM>, thereby increasing the frictional connection between the first outer surface 220a and the impeller inner surface <NUM>. The first contact force F<NUM> increases with increased rotational speed of the driveshaft <NUM>, and provides sufficient contact force to maintain the friction connection between the hub <NUM> and the impeller <NUM> and to maintain the alignment of the center of gravity of the impeller <NUM> and the center of gravity of the thrust disk <NUM> at high-rotational operation speeds.

The centrifugal force on the second hub portion 216b pulls the second hub portion 216b radially outward away from the driveshaft <NUM>. The centrifugal force on the outer disk <NUM> and the first hub portion 216a may cause the second hub portion 216b to flex, slightly, in a radially inward direction, towards the driveshaft <NUM>. In some embodiments, the friction fit between the second hub portion 216b and the driveshaft <NUM> may decrease with increased rotational speed of the driveshaft <NUM>. The contact force F<NUM> between the second inner surface 208b of the second hub portion 216b and the driveshaft <NUM> is sufficient to maintain the friction connection between the thrust disk <NUM> and the driveshaft <NUM> and the alignment of the center of gravity of thrust disk <NUM> with the driveshaft axis A<NUM> at normal operational speeds of the driveshaft <NUM>. In other words, as the rotational speed of the driveshaft <NUM> increases, the interference fit or connection between the thrust disk <NUM> and the driveshaft <NUM> may decrease slightly and the connection between the thrust disk <NUM> and the impeller <NUM> becomes stronger (i.e., tighter). The friction fit or connection between the thrust disk <NUM> and the driveshaft <NUM> prevents slipping or relative movement between the thrust disk <NUM> and the driveshaft <NUM>, and. enables the transfer of torque from the driveshaft <NUM> to the thrust disk <NUM> and, consequently, from the driveshaft <NUM> to the impeller <NUM>.

The impeller <NUM> further includes a screw <NUM> that extends through the second impeller bore <NUM> and the first impeller bore <NUM>, and into the blind bore <NUM> of the driveshaft <NUM>. The screw <NUM> includes a threaded portion having threads that are engaged with threads defined on the bore inner surface <NUM> (not shown). The screw <NUM> includes a head <NUM> that is engaged with the impeller second end <NUM>. When the screw <NUM> is tightened, the screw <NUM> compresses the impeller <NUM> against the thrust disk <NUM>, thereby facilitating transmission of torque from the thrust disk <NUM> to the impeller <NUM>. More specifically, the screw <NUM> forces the impeller first end <NUM> into contact with the second disk surface <NUM> of the thrust disk <NUM> thereby causing a portion of the outer disk <NUM> to be compressed between the impeller first end <NUM> and the first end surface <NUM> of the driveshaft <NUM>. Tightening of the screw <NUM> generates a clamping force on the thrust disk <NUM>. The threads of the screw <NUM> are arranged such that rotation of the driveshaft <NUM> does not loosen or unscrew the threads of the screw <NUM> with the threads of the blind bore <NUM>.

Accordingly, in the embodiments illustrated in this disclosure, the thrust disk <NUM>, the impeller <NUM>, and the driveshaft <NUM> are arranged such that the frictional connections or fits between the components are generally maintained at operational rotational speeds of the driveshaft <NUM>. The frictional fit between the driveshaft <NUM> and the thrust disk <NUM> may decrease slightly with increased rotational speed of the driveshaft <NUM>. The decrease in friction fit between the driveshaft <NUM> and the thrust disk <NUM> is not highly dependent on the rotational speed of the driveshaft <NUM>. Further, increases in the rotational speed of the driveshaft <NUM> may increase the frictional connection between the thrust disk <NUM> and the impeller <NUM>. More specifically, increases in the rotational speed of the driveshaft <NUM> increases the first contact force F<NUM> between the hub <NUM> and the impeller <NUM> and only slightly decreases the second contact force F<NUM> between the hub <NUM> and the driveshaft <NUM>. The first and second contact forces F<NUM>, F<NUM> are sufficient to maintain frictional connection between the assembled components. Furthermore, the assembly of the components is such that the center of gravity of the thrust disk <NUM> and the impeller <NUM> are coincident with the axis of rotation, limiting eccentric loading at high-rotational speeds.

Embodiments of the systems and methods described achieve superior results as compared to prior systems and methods associated with thrust bearing assemblies. The thrust disk, impeller, and driveshaft assembly facilitate maintaining alignment of the rotating components at high-rotational operating speeds consistent with compressor systems. The high-rotational operating speeds of the driveshaft increase friction fit connections between the thrust disk and the impeller, and maintain the friction fit connection between the thrust disk and the driveshaft. In some embodiments, the impeller is not directly coupled to the driveshaft, and torque is transmitted from the driveshaft to the impeller through the thrust disk. The improved friction fit connection maintains the alignment between the center of gravity of the thrust disk, the impeller, and the driveshaft with the axis of rotation. The disclosed assemblies are compatible with centrifugal compressors, which typically operate at high rotational speeds. The assembly of the components described herein may be incorporated into the design of any type of centrifugal compressors. Non-limiting examples of centrifugal compressors suitable for use with the disclosed system include single-stage, two-stage, and multi-stage centrifugal compressors. Additionally, the described assembly is well suited for other applications including other mechanical systems having components, such as an impeller and bearing assemblies coupled to a high-rotational speed driveshaft.

Unlike known bearing systems and impellers mounted to a driveshaft of compressor systems, the thrust disk, impeller, and driveshaft assembly described in this disclosure enables the alignment of the center of gravities of the components as well as maintaining of friction fit connections, regardless of the high-rotational operation speed of the driveshaft, both of which are important factors in the successful implementation of centrifugal compressors as discussed above. Furthermore, the high-rotational speeds serve to improve the friction fit between the thrust disk and the impeller, maintaining friction connections and preventing eccentric loads on the driveshaft. The described assembly may result in improved operational lifespan while reducing wear of components thereby lowering costs associated with repair and downtime of rotational machines. The assembly described provides enhanced features increasing the working life and durability of impeller, thrust disk, and driveshaft for use in the challenging operating environment of refrigerant compressors of HVAC systems.

Example embodiments of compressor systems and methods, such as refrigerant compressors, are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the system and methods may be used independently and separately from other components described herein. For example, the impeller and thrust disk described herein may be used in compressors other than refrigerant compressors, such as turbocharger compressors and the like.

When introducing elements of the present disclosure or the embodiment(s) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," "containing" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., "top", "bottom", "side", etc.) is for convenience of description and does not require any particular orientation of the item described.

Claim 1:
A driveshaft assembly for a compressor, the driveshaft assembly (<NUM>) comprising:
a driveshaft (<NUM>);
a thrust disk (<NUM>) coupled to the driveshaft and including an outer disk (<NUM>) and hub (<NUM>), wherein the hub (<NUM>) includes a hub outer surface (<NUM>), and wherein the thrust disk (<NUM>) defines a thrust disk bore (<NUM>) having a bore inner surface (<NUM>) in contact with the driveshaft (<NUM>); and
an impeller (<NUM>) coupled to the thrust disk (<NUM>), the impeller (<NUM>) including an impeller bore (<NUM>) having an inner surface (<NUM>);
wherein the hub (<NUM>) of the thrust disk (<NUM>) is disposed within the impeller bore (<NUM>), and wherein the hub outer surface (<NUM>) is in contact with the inner surface (<NUM>) of the impeller bore (<NUM>), and wherein a first contact force between the hub outer surface (<NUM>) and the inner surface (<NUM>) of the impeller bore (<NUM>) increases with increased rotational speed of the driveshaft (<NUM>) and wherein the bore inner surface (<NUM>) of the thrust disk bore (<NUM>) flexes radially inward toward the driveshaft (<NUM>) with increased rotational speed of the driveshaft creating a second contact force between the bore inner surface (<NUM>) of the thrust disk bore (<NUM>) and the driveshaft (<NUM>).