Field

[001] This application relates to noise and vibration damping mechanisms. The application provides a method and bearing assembly for damping noise emanating from a bearing and for reducing vibration and noise in the installed assembly.

Background

[002] Supercharger rotors can be supported in the case by bearings. Bearings are supported in the case by way of press fit. Typically, the housing and bearing are made of different materials (i.e. aluminum and steel). Due to differing materials, it is common to see a housing cause additional stress on the bearing, especially at cold temperatures. These stresses can cause a reduction in the inner diameter (also known as under-roller diameter) of the bearing. One method to mitigate this issue and prevent seizure of the supercharger rotors is to add additional clearance between the rotor shafts and bearing. Clearance between the rotor shaft and bearing is a source of noise, and is amplified at hot temperatures, when clearances expand. An additional source of noise is present at cold temperatures, when bearing needles are seen to skid when impacted by the shaft, due to the thicker grease within the bearing.

Summary

[003] The methods and devices disclosed herein overcome the above disadvantages and improves the art by way of swaging a constrained layer material to a bearing.

[004] A bearing assembly comprises a bearing, which includes an outer ring. The bearing assembly further comprises a swage can surrounding the outer ring of the bearing, and a constrained layer material located between the swage can and the outer ring. The swage can is swaged against the constrained layer material thereby compressing the constrained layer material against the outer ring.

[005] The swaging process can compress the constrained layer material without significantly compressing the outer ring. This avoids compression of the rollers within the bearing assembly. [006] A supercharger assembly comprises a housing, a gear box, a first shaft and a second shaft located in the housing, a first rotor attached to the first shaft, a second rotor attached to the second shaft, and a first bearing assembly located on the first shaft. The first rotor is located between the first bearing assembly and the gear box. The first bearing assembly comprises a bearing comprising an outer ring, a swage can surrounding the outer ring of the bearing, and a constrained layer material located between the swage can and the outer ring. The swage can is swaged against the constrained layer material thereby compressing the constrained layer material against the outer ring.

[007] A method of assembling a bearing assembly comprises placing a constrained layer material around an outer ring of a bearing, placing a swage can over the constrained layer material, and swaging the swage can onto the constrained layer material. The swaging compresses the constrained layer material against the outer ring of the bearing.

[008] Additional objects and advantages will be set forth in part in the

description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

[009] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention.

Detailed Description

[010] Reference will now be made in detail to the examples, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Directional references such as "left" and "right" are for ease of reference to the figures.

[01 1 ] When an automobile is operating in low temperatures, such as

between -40 to 0 degrees centigrade, the bearing supporting the rotor shaft squeals. The condition occurs most frequently during start-up and when the supercharger is lightly loaded or providing no boost. It is thought that the squealing is caused in part by skidding needles or by the bearing race within the bearing.

[012] Adjusting the tolerances and clearances between the shaft and bearing can remove noise to a limited extent. Reducing clearances will reduce noise, but the device is limited in the amount of clearance it can reduce by the clearance available at the minimum operating temperature. If there is not sufficient clearance available at minimum operating temperature, seizure of the supercharger will occur.

[013] In a similar manner, the housing expands when the temperature rises. The housing can expand at a greater rate than the bearing. For example, the housing can be made of aluminum, and the bearing assemblies can be made of steel. The rate of heat expansion and contraction differ between the housing and the bearing assembly. This greater rate of expansion can affect the press fit on the bearing, which will then affect the clearance between the bearing rollers and shaft. However, it is desirable to use the different materials for the advantages offered. For example, it is possible to select among materials that are durable enough to withstand the forces, pressures, and heat experienced during operation of a supercharger. The material can also be selected differently between the housing and bearing because of the ability to machine or form the components in a predictable manner. Therefore, it is desirable to find a way to use different housing and bearing assembly materials, yet minimize squealing and other noises caused by the dissimilar material attributes.

[014] Tolerances or other gaps can be another source of noise and vibration because the gap allows greater room for the shaft to move within the bearing. This results not only in unwanted noise and vibration, but it can also cause the rotor to lose its true position. The rotor can move both axially and radially within the housing.

[015] It is desired to damp the impacts from the shaft to the bearing near its source, improving the user experience. This is accomplished by abutting a constrained layer material next to the rotor bearing. A swage can is applied around the constrained layer material to radially compress the layer to the bearing to form a bearing assembly. After the swage can, constrained layer material, and bearing are swaged together, the bearing assembly becomes a single, integral part. With the swage can pressed against the constrained layer material, which is pressed against the bearing, all three parts are securely connected. The constrained layer material, swaged in this manner, permits damping of the impacts from the shaft onto the bearing.

[016] Figure 1 shows a perspective view of bearing assembly 100. Bearing assembly 100 comprises a bearing 1 10, a constrained layer material 120, and a swage can 130. Constrained layer material 120 fits over outer ring 1 1 1 of bearing 1 10.

[017] The bearing 1 10, constrained layer material 120, and swage can 130 of Figure 1 are fixed together using a swaging process. Figure 2 illustrates such a process. Bearing 1 10, constrained layer material 120, and swage can 130 can be assembled in their free state before being swaged.

[018] The constrained layer material can be, for example, a sheet of NVH damping material manufactured by Trelleborg AB using the RUBORE® process, or QUIET STEEL® manufactured by Material Sciences Corporation, or their equivalents. For example, the constrained layer material can be RDDL6 47 41 , RDDL6 49 01 , RPN50 09 01 , RPN04 01 , RPN50 00 01 , RDD50 04 01 , or RDD50 09 01 manufactured by Trelleborg AB. The constrained layer material can comprise an isolating rubber, a damping rubber, a rubber that both isolates and damps, or a combination of rubbers. The constrained layer damping material comprises multiple layers, such that a sheet material of rubber-steel-rubber is swaged around the bearing assembly. The

constrained layer material can comprise a viscoelastic polymer material between layers of metal. Ordinarily, such a constrained layer material is draped over the assembly, such as the supercharger housing, or clipped in place around the engine compartment of a vehicle. But, this noise reduction strategy differs from the prior art because the constrained layer material is not clipped in place or draped. A much smaller piece of constrained layer material is swaged to a bearing assembly. This disclosure mounts the constrained layer material in a new way, places the constrained layer material closer to a noise source, and implements the constrained layer material for new purposes, including deformation, expansion, and contraction purposes as discussed herein.

[019] The constrained layer damping material differs from prior art soft rubbers such as natural rubber, foams, neoprene rubbers, felts, or fabrics in that the constrained layer can provide better performance in a bearing assembly. For example, conventional soft rubbers compress too much under loads experienced during operation of a supercharger. The constrained layer material also differs from prior art materials because it is a multi-layer material that can be on the order of 1 mm in total thickness, whereas prior art materials are more thickly applied or applied as a single layer of material. And, some of the prior art materials cannot be swaged and maintain their intended function. For example, prior art felts and fabrics cannot perform their wicking functions when swaged. Thus, the application of a constrained layer material to a bearing assembly differs from the prior art damping materials.

[020] During standard operation of the supercharger, the rotor shaft will impact the bearing, its force being a function of the amount of clearance between the rotor shaft and the bearing (under-roller clearance). A soft rubber used in this application would allow excessive deflection of the rotor shaft as the rubber absorbs the impacts. Deviation from the true position of the shaft in excess amounts could cause adverse effects on the supercharger, including failure of the supercharger by contact of the rotors. When including both rubber and steel layers, a constrained layer damping material can better resist the deformation caused by the shrinking bore. This protects the bearing and it's internal components from unwanted forces and strains.

[021 ] Constrained layer damping materials can work well when possessing a compressibility between the range of 14-22 micrometers at 100 bar. The materials can possess a compressibility between the range of 18-29 micrometers at 160 bar. For example, a constrained layer damping material can have a compressibility of 14 micrometers at 100 bar and 17 micrometers at 160 bar. Another example, a constrained layer material can have a compressibility of 20 micrometers at 100 bar and 24

micrometers at 160 bar. For another example, the constrained layer damping material can have a compressibility of 17 micrometers at 100 bar and 20 micrometers at 160 bar. Other combinations of compressibility are possible along the range.

[022] Because the constrained layer absorbs the deformation experienced during installation, less compressive forces act on the bearing. When using a bearing assembly with constrained layers swaged over a bearing, the diameter of the inner ring (also known as under roller) is no longer reduced when installing the bearing assembly into the shaft bore of a supercharger. This arrangement also reduces the load

experienced when the aluminum housing shrinks at cold temperatures because the constrained layer absorbs the compression. This allows one to reduce the clearances between the shaft and the inner ring. Smaller clearances result in quieter operation of the supercharger assembly.

[023] Cold squeal is a noise heard when the supercharger operates at cold temperatures, for example, at temperatures less than zero (0) degrees centigrade. Constrained layers can eliminate the cold squeal heard at temperatures between minus forty (-40) and zero (0) degrees Centigrade. Cold squeal is mitigated with the constrained layer material in two ways. First, it allows for a reduced under-roller clearance, lowering the impact forces of the shaft onto the bearing. Second, it allows isolation of the bearing from the housing, allowing the vibration and noise outputted from the skidding needles to not be transmitted to the housing.

[024] Constrained layers also possess ideal elasticity to both absorb

deformation when the housing, including the shaft bore around the bearing, shrinks and to apply spring forces to maintain the fit between the bearing assembly and the shaft bore. That is, the constrained layer can be compressed in cold temperatures without transferring pressure to the roller elements 413 of the bearing. In a supercharger application, these properties serve to limit gear rattle noise, as well as general vibration caused from the impact of the shaft onto the bearing, across a large temperature operating range.

[025] As shown in Figure 1 , constrained layer 120 is inserted between bearing 1 10 and swage can 130. The constrained layer 120 can be, for example roll-formed to the bearing 1 10, or a section can be otherwise applied to the bearing outer ring 41 1 . Swaging the constrained layer 120 around a bearing 1 10 improves the durability of the bearing assembly 100. The constrained layer 120 is compressed during the swaging process, but the compression is not transferred to the roller elements 413. Swaging therefore inures benefits that are not possible via prior art applications of a soft rubber coating around the bearing.

[026] Figure 2 shows a swage assembly 200 where a press fixture 203 pushes the bearing assembly 201 through a swage die 202 in the direction D toward exit 205. Because the bore of the swage die narrows from entrance 204 to exit 205, bearing assembly 201 compresses as it travels through swage die 202. [027] A method for assembling the bearing assembly 100 is shown in Figure 8. The method assembles a bearing in step S800. The bearing can comprise outer ring 41 1 and roller elements 413. A cage or inner ring 412 can seat the roller elements 413 depending upon whether the bearing 1 10 is a needle roller bearing, ball bearing, etc. The bearing 1 10 can also be of the "cageless" variety.

[028] In step S801 , the constrained layer material 420 surrounds the outer ring 41 1 . This can be done, for example, by slip-rolling the constrained layer material to the bearing 1 10, or by roll-forming the constrained layer material and wrapping it around the bearing 1 10, among other techniques.

[029] In step S802, a swage can 430 is placed around the constrained layer material 420 and the swage can 430 is swaged. The constrained layer material 420 can be preloaded via this step, without applying significant preload pressure to the bearing 1 10.

[030] The swaging process compresses swage can 230 against constrained layer material 220. Swage can 230 can be made of steel. The steel swage can 230 thus narrows in diameter and the constrained layer material 220 absorbs this deformation, becoming pre-loaded. A one to two percent decrease in diameter of the swage can 230 can be sufficient deformation to pre-load the swage assembly 200. Pre-load forces exist in the radial direction where the surface of swage can 230 contacts the surface of constrained layer material 220. Frictional forces keep these two materials fixed together to resist axial forces. The preload and material properties of the constrained layer prevents shearing of the constrained layer, especially those occurring when the bearing assembly is pressed into the housing bearing bore, as happens with prior art damping materials. In a supercharger application, the constrained layer material 420 is able to resist the axial and radial forces exerted by the shaft 740, 741 , and is better able to keep proper alignment of the rotors 730, 731 .

[031 ] As above, the ability of the constrained layer to absorb deformation, such as the thermal expansion deformation seen at cold temperatures, prevents transfer of deformation to the roller elements 413, and thus a reduction in under-roller clearance.. The constrained layer absorbs thermal expansion, particularly in cold conditions, when the housing bore is adding additional stress to the bearing. Since changes in bearing under-roller diameter due to temperature are no longer of concern, the constrained layer allows for a reduction in nominal under-roller clearance. This allows the shaft to experience less radial play. Other preloading forces, such as that provided by optional spring 700, can act on the bearing assembly in the axial direction to serve another purpose. In a supercharger application, the spring 700 preloads the bearing assembly to reduce chatter between lobes 730, 731 .

[032] Constrained layer material 220 also presses against the outer ring 21 1 of bearing 210. This creates frictional forces where the surfaces of constrained layer material 220 contacts outer ring 21 1 . Because constrained layer material 220 absorbs the deformation caused by the compressed swage can, bearing 210 does not deform significantly due to the compression of swage can 230. Thus, there are no detrimental forces acting against rollers 213 or inner ring 212 of bearing 210. The swaging process therefore has no detrimental effect on the durability or lifespan of the bearing assembly. These statements also serve true when functioning in cold temperatures in excess of - 40°C and deformation is seen due to thermal expansion coefficient difference of the housing and bearing.

[033] By swaging the swage can 230 with constrained layer material 220 and bearing 210, the bearing assembly can be used as a single part. Swaging the bearing assembly also prevents the constrained layer material from tearing when installing the components into a supercharger housing. This significantly improves the effectiveness of the constrained layer 120, while not negatively impacting the life of bearing assembly 1 10 and the supercharger.

[034] The bearing assembly can be press-fit into a housing of a supercharger. Also, one can press-fit a shaft into the bearing assembly. Press-fitting the shaft into the bearing assembly can occur before or after press-fitting the bearing assembly into the housing of the supercharger.

[035] The bearing assembly can be used, for example, at the support side of the housing to permit rotation of the rotor shaft, which can be powered by an input shaft and other torque transfer mechanisms at the other side of the housing.

[036] In addition to eliminating or reducing the squeal noise near its source, the constrained layer material provides shear damping for the rotors. And, the constrained layer allows for a reduction in bearing clearances between the bearing and the shaft because the diameter of the inner ring of the bearing is no longer reduced from compression during installation, nor is it reduced from compression caused by thermal expansion of the housing.

[037] Additional benefits inure from the bearing assembly use. For example, it is possible to avoid compressing the outer ring of the bearing because the bearing is not directly press-fit inside the rotor bore. Instead, the swage can is press-fit against the rotor bore and the constrained layer can deform along with the swage can instead of the bearing outer diameter. This permits a reduction of bearing clearances, which further reduces squealing by the bearing. It is also possible to reduce clearances for thermal expansion, because the constrained layer can deform during thermal expansion and contract without exerting detrimental forces against either the bearing or the swage can, further reducing noise at the bearing. Furthermore, the constrained layer reduces vibrations induced from impacts by the rotor shaft on the bearing. Using the constrained layer-damped bearing thus improves operability of the rotors and reduces clearances within the main housing through the vibration damping of the rotor shaft.

[038] Figure 3 shows an example of a bearing arrangement 300 with bearing assembly 303 installed into shaft bore 302 of a supercharger housing 301 . Bearing bore 302 is located at the inlet side 340 of the supercharger housing 301 , away from the pulley side.

[039] Bearing assembly 303 can be press-fit into bearing bore 302 such that an interference fit exists where swage can 330 contacts the surface of shaft bore 302. This interference fit can further compress swage can 330 against constrained layer material 320. Constrained layer material 320 can absorb deflection caused by this interference fit, thus, preventing outer ring 31 1 of bearing 310 from deforming, thereby eliminating compression loads acting against roller 313 and inner ring 312.

[040] When housing 301 expands due to thermal expansion, shaft bore 302 can move away from swage can 330. Constrained layer 320 can be selected such that it expands due to the lessening of compression forces caused by swage can 330. During thermal expansion of swage can 330, constrained layer 320 can expand because the compression force lessens. During this expansion, constrained layer does not lose contact with either swage can 330 or outer ring 31 1. Because constrained layer expands in such a way, no gap exists between swage can 330 and outer ring 31 1 . In this arrangement, constrained layer always fills the space between swage can 330 and outer ring 31 1 of bearing 310. Using a Trelleborg AG RUBORE® process material for constrained layer 320 is advantageous, because these materials have multiple layers of very thin rubber. This is advantageous because rubber by nature is naturally

incompressible. Having thin layers means there is little material to squeeze out of the assembly when compressed. The Trelleborg AG RUBORE is also advantageous due to its textured cross-hatch pattern. This allows for natural gaps where the rubber can fill in when compressed. Constrained layer materials are also more durable than stand-alone soft rubbers. Constrained layer materials better withstand shear forces, which prevents shaft motion in the bore.

[041 ] Swage can 330 need not be made of steel. Swage can 330 can be made from the same material as housing 301 . For example, swage can 330 and housing 301 can both be made from aluminum. This way swage can 330 and housing 301 expand at the same rate, thus, the interference fit between swage can 330 and shaft bore 302 can remain constant during thermal expansion or contraction.

[042] Swage can 330 can be made from a different material than housing 301 . One might select a different material because it makes the manufacturing or the swaging process easier or more effective. When swage can 330 is made from a different material than housing 301 , one can select a constrained layer 320 that accounts for the different rates of thermal expansion. For example, the thickness and elasticity of constrained layer 320 can be selected to absorb any deformation to the swage can 330 caused by thermal contraction. This can be an especially important consideration when designing a supercharger that operates in cold (for example, -40 degrees Centigrade) environments.

[043] Figure 4 shows a bearing arrangement 400 with a shaft 440 located inside of bearing assembly 403. Bearing assembly 403 is located in bearing bore 402. Shaft 440 can be press-fit into bearing 410 if the application is a ball bearing.

[044] If slip-fit into bearing 410, shaft 440 must have small clearances between the inner ring 412 of bearing 410 and the surface of shaft 440, otherwise, noise can occur if the shaft impacts bearing 410. Also, shaft 440 can move away from its true position if the clearances are too large.

[045] Using bearing assembly 403 with a constrained layer material 420 and a swage can 430 allows one to reduce or eliminate the clearance between shaft 440 and inner ring 412 of bearing 410. When housing 401 cools, it contracts and presses against bearing assembly 403, causing swage can 430 to shrink. Constrained layer material 420, however, can absorb this deflection, preventing outer ring 41 1 from pressing against internal roller 413, which would press against inner ring 412. Without

constrained layer material 420, these compressive forces and deformation can cause inner ring 412 to press against shaft 440, resulting in creep.

[046] Creep is deformation over time. If deformed, shaft 440 can lose its dynamic stability, rotating out of balance. This deformation can also cause shaft 440 to vibrate and lose its true position even at normal operating temperatures because the damage caused by creep can be permanent.

[047] Shaft 440 is connected to a rotor, thus, when shaft 440 loses its position, the rotor also loses its position. This can reduce the performance of the rotor and even cause damage.

[048] Providing a single layer of constrained layer material can produce many advantages to the bearing assembly. But the bearing assembly is not limited to a single layer of constrained layer material, and other material layer additions are possible. The constrained layer material can comprise more than one layer of material, and at least one metal layer with at least one synthetic material or rubber compound. Other examples place a synthetic material between two metal layers, or place one metal layer between two synthetic layers, or place two layers of synthetic material with two layers of metal. The metal layer can be selected, for example, from carbon steel, galvanized steel, cold-rolled steel, EG, GA, hot-dip, or stainless steels, aluminum, etc. The synthetic material can be selected from, for example, an elastomeric damping material, a viscoelastic polymer, a highly saturated nitrile (HSN) halogenated acrylonitrile butadiene (HNBR), a hydrogenated acrylonitrite butadiene, nitrile rubber, isolating rubber, or damping rubber. Layers of other materials, for example, can include rust prevention material, cold pressure adhesive, hot pressure adhesive, plastic protective material, reinforced rubber, silicone, among many other materials. The constrained layer is compact and can range in thickness from, for example, 0.6-1 .3 millimeters. The thickness can increase by a fraction of a millimeter when a plastic protective layer is included. And, these materials can be swaged together as illustrated in Figure 2.

[049] Each layer could serve its own purpose or complement the other layers. For example, one can use a first elastomeric damping material to damp certain frequencies while using a second layer, of the same or a different elastomeric damping material, to damp other frequencies. One can use an isolating rubber to add hardness. One can use a more elastic rubber to absorb deformation or provide more spring force. The rust protection layer can prevent internal components from oxidizing, such as the metal layer internal to the constrained layer material. A silicone layer can be selected to separate dissimilar metals, thus, preventing oxidation due to contact between two dissimilar metals.

[050] Figure 5 shows a cross-section of an assembly of layers 500 of damping material. First layer 501 can be a damping material 220. Second layer 502 can be steel. And, third layer 503 can be an isolating rubber. In this arrangement, first layer 501 can damp vibrations and absorb deformation when the housing compresses against the bearing assembly during thermal contraction. Second layer 502 can reinforce the strength of the assembly of layers 500, while third layer 503 increases the frictional forces holding the bearing assembly against the swage can.

[051 ] Figure 6 shows a cross-section of another assembly of layers 600, comprising a first layer 601 , a second layer 602, a third layer 603, and a fourth layer 604. First layer 601 can be an isolating rubber, pressed against a steel second layer 602. Third layer 603 can be a layer of rust prevention material, protecting second layer 602 and other bearing assembly components. Fourth layer 604 can be a cold pressure adhesive or a layer for plastic protection. This layer can abut the surface of the swage can. Of course, the order of layers, number of layers, and types of layers can be selected to fit the needs of the bearing assembly. Exemplary layer materials include a rust prevention compound, a cold pressure adhesive, a plastic protection material, an isolating rubber, carbon steel, galvanized steel, a silicone material, and an elastomeric damping material. The layers can be assembled via the Trelleborg AG RUBORE process, or another process that assembles a constrained layer material.

[052] Figure 7 shows a supercharger assembly 710 with a housing 720. Two rotors 730, 731 attached to shafts 740, 741 are located inside housing 720. Shafts 740, 741 are driven by gears located inside gear box 750, which is operatively connected to a power source, for example, an engine. Rotors 730, 731 turn in opposite directions at same rotational speed. Rotors 730, 731 pull air into the supercharger assembly and push the air into an engine. Away from the gear box 750 along axes A,B, bearing assemblies 760, 761 are located inside shaft bores 722, 723. The bearing assemblies 760, 761 can be preloaded via optional springs 700.

[053] Bearing assemblies 760, 761 can include a swaged constrained layer, giving bearing assemblies excellent damping capability. The bearing assemblies 760, 761 can include any of the features described and shown in Figures 1 -6. Because assemblies 760, 761 can include a swaged constrained layer, they can absorb compression forces and deformation experienced when housing 720 presses against bearing assemblies 760, 761 .

[054] Exemplary supercharging devices include Roots and non-Roots type, such as centrifugal or twin screw superchargers. And, while a supercharger has been shown and described, other devices can benefit from the swage-formed bearing assembly. For example, propellers, alternators, compressors, pulleys, pumps, motors, and fans can benefit from a swage-formed bearing assembly. Roller elements 413 can be, for example, any one of ball bearings, roller bearings, needle bearings, and magnetic bearings, among others.

[055] Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims.