Bearing setting process

Abstract

A method of setting a pre-load of a production bearing within a production power transmission device including pressing a test bearing including pre-load instrumentation onto a test power transmission device, detecting a vibration response of the test power transmission device with a sensor with a test controller determining a lower side limit of natural frequency based on a first vibration signal sent from the sensor, detecting a vibration response of the test power transmission device with the sensor with the test controller determining an upper side limit of natural frequency based on the second vibration signal sent from the sensor; and conveying the lower side limit of natural frequency and the upper side limit of natural frequency to a production controller and using them to set the pre-load in a production power transmission assembly.

Description

BEARING SETTING PROCESSBACKGROUND

[0001] The present invention relates to setting bearing pre-load in a power transmission device.

[0002] A correct setting (e.g., bearing pre-load or clearance) of bearings is important for bearing life performance and proper functioning of power transmissions of various types, including gearboxes. In the automotive industry among others for example, a variety of gearboxes may need to be built at high production rates. However, it is very challenging to achieve consistent and reliable bearing setting in complex power transmission and gearbox assemblies due to variations of part geometries. Currently, setting methods based on rolling torque or deflection are widely used. However, the consistency of these methods relies heavily on the experience and skill of the workers who perform the setting. A new setting method that can improve the setting consistency and accuracy is needed in the art.SUMMARY

[0003] In one aspect, the disclosure provides a method of setting pre-load of a production bearing within a production power transmission device. The method includes providing a test power transmission device including a test shaft. The test shaft defining a first rotational axis between a first end and a second end opposite the first end. The test shaft is arranged inside of a test transmission housing of the test power transmission device. A test bearing including pre-load instrumentation is pressed onto the shaft. The first end of the test shaft is positioned onto a press. While oscillating the test power transmission, the test shaft is actuated via the press along the first rotational axis under control of a test controller until the test controller receives a signal from the pre-load instrumentation that a targeted lower side limit of pre-load is reached. A test locking nut is tightened to the second end of the test shaft to hold the pre-load constant at the lower side limit. The press is retracted out of contact from the first end of the test shaft. The test power transmission device is struck with an impact element in response to input from the test controller, thereby causing a vibration response in the test power transmission device. The vibration response of the test power transmission device is detected with a sensor. The sensor sends a first vibration signal to the test controller. The test controller determines the lower sidelimit of natural frequency based on the first vibration signal. The press is extended to re-engage the first end of the test shaft. The test shaft is actuated via the press along the first rotational axis until the test controller receives signal from the instrumented bearing that a targeted upper side limit of pre-load is reached. The test locking nut is tightened to the second end of the test shaft to hold the pre-load constant at the upper side limit. The press is retracted out of contact from the first end of the test shaft. The test power transmission device is struck with the impact element in response to input from the test controller, thereby causing a vibration response in the test power transmission device. The vibration response of the test power transmission device is detected with the sensor. The sensor sends a second vibration signal to the test controller. The test controller determines the upper side limit of natural frequency based on the second vibration signal. The lower side limit of natural frequency and the upper side limit of natural frequency are conveyed to a production controller of a production pre-load setting apparatus on an assembly line. The production controller uses the lower side limit of natural frequency and the upper side limit of natural frequency to control the production pre-load setting apparatus to set the pre-load in a production power transmission assembly.

[0004] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a cross-sectional view of a testing apparatus for measuring pre-load of a test bearing in a gearbox housing and determining the target natural frequency range and the corresponding deflections of the gearbox at a given pre-load range.

[0006] FIG. 2 is a cross-sectional view of a production apparatus for setting pre-load of a production bearing in a gearbox housing using parameters determined in the testing process.

[0007] FIGS. 3A and 3B are a flowchart illustrating the steps for measuring pre-load of the test bearing and determining the ranges of natural frequency and deflection to be used in a production process, as seen in FIG. 1.

[0008] FIGS. 4A and 4B are a flowchart illustrating the steps for setting pre-load of the production bearing using the parameters determined in the testing process, as seen in FIG. 2.

[0009] FIG. 5 is a graph illustrating the relationship between pre-load of the test bearing and the natural frequency of the gearbox, as seen in FIG. 1.

[0010] FIG. 6 is a graph illustrating the relationship between pre-load of the test bearing and the deflection of the gearbox, as seen in FIG. 1.

[0011] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.DETAILED DESCRIPTION

[0012] FIG. 1 illustrates a testing apparatus 100a receiving a power transmission device 101a. In the illustrated embodiment, the power transmission device 101a is a gearbox having a gearbox housing 102a. In other embodiments, the power transmission device 101a may be one of varies types of transmission devices. The power transmission device or gearbox 101a includes a shaft 104a defining a rotational axis A between a first end 108a and a second end 112a of the shaft 104a opposite the first end 108a. A bearing 116a is pressed onto the shaft 104a to allow for rotation of the shaft 104a about the rotational axis A in the gearbox housing 102a. In the illustrated embodiment, the bearing 116a is a tapered roller bearing, but may be one of various other types of bearings. The testing apparatus 100a is centrally controlled by a controller 106a. The controller 106a instructs various components of the testing apparatus 100a, described in further detail later.

[0013] The bearing 116a includes an inner ring 120a, an array of rolling elements 124a, and an outer ring 128a. The inner ring 120a defines a bore to receive a portion of the shaft 104a. The bearing 116a is press-fit on the shaft 104a, thereby enabling the inner ring 120a to co-rotate with the shaft 104a. The rolling elements 124a are positioned between the inner ring 120a and the outer ring 128a and may be tapered rollers, or any other type of rolling elements that can be preloaded. The rolling elements 124a provide a rolling interface to reduce friction between theinner ring 120a and the outer ring 128a. The outer ring 128a is coupled to the gearbox housing 102a so that the outer ring 128a does not rotate with the inner ring 120a and the shaft 104a. In operation, an incorrect setting of the bearing 116a may cause undesirable noise, undesirable vibration, and pre-mature damage to the bearing 116a, thereby shortening the lifespan of the bearing 116a. Therefore, it may be desirable to accurately apply a prescribed amount of pre-load to the bearing 116a during installation, described in further detail later.

[0014] The second end 112a of the shaft 104a is received into an opening 132a in a yoke 136a at least partially positioned in the gearbox housing 102a. The yoke 136a is coupled to an intermediate support plate 140a at a point outside of the gearbox housing 102a. The intermediate support plate 140a is fastened to a fixture 144a by a first plurality of fasteners 148a. The fixture 144a is fastened to a support beam 152a by a second plurality of fasteners (not shown) through openings 156a on the fixture 144a. The testing apparatus 100a further includes a table 154a having an aperture 158a.

[0015] The testing apparatus 100a may be configured to selectively suspend the gearbox housing 102a from the support beam 152a via support members 160a. The support members 160a are actuated linearly by air cylinders or linear motors 164a in a direction perpendicular to the rotational axis A of the shaft 104a. The support members 160a include a lip 162a to engage the yoke 136a when instructed to by the controller 106a via a motor signal 166a, thereby providing hanging support to the gearbox housing 102a. When hanging support is provided by the support members 160a, an isolation layer 168ais positioned between the yoke 136a and the support members 160a, such that the gearbox 101a is structurally decoupled from the testing apparatus 100a during modal testing.

[0016] The testing apparatus 100a further includes a press 172a positioned in the aperture 158a. The press 172a can engage the first shaft end 108a directly, or as shown, an adapter 173a can be situated between the first shaft end 108a and a distal end of the press 172a. The adapter 173a is configured to transfer force from the press 172a to the first end 108a of the shaft 104a along the rotational axis A. The press 172a is in electrical communication with the controller 106a. As the controller 106a instructs the press 172a to actuate the shaft 104a along the rotational axis A, the yoke 136a compresses the inner ring 120a. As a result, a clearance between the innerring 120a and / or outer ring 128a and the rolling elements 124a is eliminated and the pre-load of the bearing 116a is increased. In the illustrated embodiment, the outer ring 128a of the bearing 116a includes an instrumentation device 180a (e.g., strain gauge) to detect the applied pre-load on the bearing 116a. In other embodiments, the inner ring 120a of the bearing 116a may include the instrumentation device 180a. The instrumentation device 180a communicates (i.e., sends) the pre-load of the bearing 116a to the controller 106a via a pre-load signal 184a. In other embodiments, the instrumentation device 180a may be positioned on an auxiliary bearing 186a positioned around the shaft 104a. In such an embodiment, a gear 178a including a shoulder 176a is positioned at the first end 108a of the shaft 104a. As the press 172a actuates the shaft 104a along the rotational axis A to enable the yoke 136a compress the inner ring 120a or a locking nut 182a is threaded to the second end 112a of the shaft 104a, the shoulder 176a engages an auxiliary inner ring 187a to apply pre-load to the auxiliary bearing 186a. In the illustrated construction, whether the instrumentation device 180a is on the bearing 116a or the auxiliary bearing 186a, the pre-load applied to the bearing 116a and the auxiliary bearing 186a is the same.

[0017] The testing apparatus 100a further includes a displacement sensor 199a capable of monitoring displacement of the shaft 104a. The displacement sensor 199a may be a linear variable differential transformer (i.e., LVDT) or any other type of displacement sensor. The displacement sensor 199a may be positioned physically above the second end 112a of the shaft 104a and may measure position of the second end 112a of the shaft 104a along its rotational axis A and relative to a “zero” or “home” position. Additionally, or alternatively, the displacement sensor 199a may be a built-in displacement sensor 199a of the press 172a that measures displacement of the shaft 104a along the rotational axis A relative to the press 172a itself. FIG. 1 illustrates such a built-in displacement sensor 199a in dashed lines. The displacement sensor 199a communicates sensed displacement along the rotational axis A to the controller 106a via a displacement signal 200a.

[0018] The testing apparatus 100a further includes a load cell 201a capable of monitoring compressive load applied to the bearing inner ring 120a, including the force overcoming the interference fit between the shaft 104a and the inner ring 120a and the pre-load applied to thebearing 1 16a. Before assembly, components of the bearing 116a, namely the inner ring 120a, rolling elements 124a, and outer ring 128a, may be relatively loosely held together, and may be movable relative to one another with a clearance gap (known as “slop” or “play”) between the components. A numerical distance of the clearance gap may differ from bearing to bearing. The load cell 201a illustrated in solid lines in FIG. 1 is positioned between the intermediate support plate 140a and the fixture 144a. Additionally or alternatively, the load cell 201a may be integrated with the press 172a. The load cell 201a illustrated in dashed lines in FIG. 1 is integrated with the press 172a. Other load cells 201a may be positioned at other locations in the testing apparatus 100a. The load cell 201a communicates (i.e., sends) sensed load compressing the bearing inner ring 120a to the controller 106a via a load signal 202a. Prior to the press 172a advancing the shaft 104a along the rotational axis A (i.e., inserting the shaft 104a through yoke 136a) to apply compressive force to the bearing inner ring 120a, the load signal 202a may reflect little to no sensed load. The load cell 201a may sense load compressing the bearing inner ring 120a, and the controller 106a may continuously or intermittently monitor for an increase of load. While the press 172a is advanced, the clearance gap is taken up, and the inner ring 120a, rolling elements 124a, and outer ring 128a are placed in contact with one another. When (i.e., once) the clearance gap is taken up, the controller 106a detects via the load signal 202a a sudden increase of load (called an inflection point) indicative of the clearance gap being eliminated and of contact between the inner ring 120a, rolling elements 124a, and outer ring 128a. The controller 106a marks the position of the shaft 104a when the clearance gap is taken up to be the aforementioned set the “zero” or “home” position of the displacement sensor 199a. As a result, the load cell 201a allows the testing apparatus 100a to account for variability of exact dimensions of the inner ring 120a, rolling elements 124a, and outer ring 128a and the clearance gap to set (and optionally save) a “zero” or “home” position of the displacement sensor 199a at a position corresponding with the inflection point. After the clearance gap is taken up, displacement of the shaft 104a along the longitudinal axis and deflection (i.e., axial deflection) of the gearbox 101a are numerically the same since any further displacement (i.e., advancement) of the shaft 104a corresponds with equal deflection (i.e., compression) of the gearbox 101a. Alternatively, the testing apparatus 100a can use the signal 184a from the instrumentation device 180a to determine the zero position of the displacement sensor 199a, which is the point when the signal 184a increases from zero to a positive value

[0019] The second end 112a of the shaft 104a includes threads to threadably receive the locking nut 182a to press against the yoke 136a, thereby holding constant pre-load applied to the bearing 116a. The locking nut 182a is fastened to the shaft 104a by a torque wrench (not shown) until the instrumentation device 180a indicates to the controller 106a that the pre-load of the bearing 116a has slightly increased. The amount of torque applied to the locking nut 182a by the torque wrench is detected and communicated to the controller 106a.

[0020] The gearbox housing 102a is oscillated during the pre-loading of the bearing 116a by an oscillator 188a. In the illustrated embodiment, the oscillator 188a is a device in communication with the controller 106a via an oscillation signal 190a to automatically oscillate the gearbox housing 102a. In other embodiments, an operator may manually oscillate the gearbox housing 102a.

[0021] As the pre-load of the bearing 116a increases, the structural stiffness of the bearing 116a, and therefore the gearbox 101a, also increases. After instructing the support members 160a to provide hanging support to the gearbox housing 102a, the controller 106a instructs the press 172a via a press signal 174a to retract from the first end 108a of the shaft 104a. The controller 106a then instructs an impact element 192a, positioned in the aperture 158a of the table 154a, via an impact signal 194a to strike the gearbox housing 102a with an impact force, thereby causing the gearbox 101a to vibrate. The impact force is measured by a force transducer 193a. The force transducer 193a is in communication with the controller 106a via an impact force signal 195a. In the illustrated embodiment, the vibration response of the second end 112a of the shaft 104a is detected by a sensor 196a with an unobstructed view of the shaft 104a. In other embodiments, the sensor 196a may be positioned on the shaft 104a. In other embodiments, the impact element 192a may strike the shaft 104a and then the sensor 196a may detect the vibration response of the gearbox housing 102a. In some constructions, the sensor 196a is a contactless laser doppler vibrometer. A laser doppler vibrometer is a two-beam laser interferometer that measures the difference, in frequency or phase, between an internal reference laser beam and a test laser beam. In other embodiments, the sensor 196a may be any contact sensor (e.g., accelerometer) to measure vibration. The sensor 196a communicates the detected vibration to the controller 106a via a vibration signal 198a. The controller 106a uses the detected vibration and impact force todetermine the natural frequency corresponding to the applied pre-load, according to known computational methods in the field.

[0022] An acceptable pre-load range for the bearing 116a is established by the manufacturers of the bearing 116a and the gearbox 101a. The acceptable pre-load range extends between a first value (lower side limit (LSL)) and a second value (upper side limit (USL)) higher than the first value. However, testing the pre-load directly during a production process may not be practical due to the instrumentation device 180a on the bearing 116a necessary to detect the pre-load. Since the pre-load applied to the bearing 116a is related to the natural frequency of the gearbox 101a, the testing apparatus 100a is used to determine a lower side limit (LSL) and an upper side limit (USL) of natural frequency based on the first value and the second value of pre-load, respectively. As noted further below, the LSL and / or USL of natural frequency as determined from the testing apparatus 100a can be used as a guide, in lieu of actual pre-load, in a production process with production parts where bearing pre-load is to be set to the acceptable pre-load range.

[0023] In operation, as seen in FIGS. 3 A and 3B, the shaft 104a is arranged inside of the gearbox housing 102a with the bearing 116a press-fit onto the shaft 104a. The first end 108a of the shaft 104a is positioned on the press 172a and the second end 112a is received into the opening 132a in the yoke 136a. The gearbox housing 102a is set into oscillation by the oscillator 188a while the controller 106a instructs the press 172a to load the shaft 104a along the rotational axis A, thereby compressing the inner ring 120a of the bearing 116a onto the shaft 104a. The pre-load applied to the bearing 116a increases until the controller 106a determines, via the preload signal 184a, that the bearing 116a has reached the first value. Data carried by the pre-load signal 184a and the displacement signal 200a are recorded and processed by the controller 106a to determine and optionally save the first deflection (DLSL, FIG. 6) corresponding to the lower side limit of the pre-load (LSLD). The gearbox housing 102a then stops oscillating. The locking nut 182a is then tightened to the second end 112a of the shaft 104a by a torque wrench until the controller 106a determines, via the pre-load signal 184a from the instrumentation device 180a to the controller 106a, that the pre-load originally applied by the press 172a is locked in by the locking nut 182a. This may be done by the controller 106a monitoring the pre-load signal 184aand stopping the tightening by the torque wrench immediately upon identifying that the locking nut 182a is beginning to apply pre-load.

[0024] A first amount of torque (LSLT) used to tighten the locking nut 182a by the torque wrench is communicated to the controller 106a and recorded for later use. The controller 106a instructs the linear motors 164a via the motor signal 166a to engage the yoke 136a with the support members 160a to provide hanging support. The press 172a is then retracted from the first end 108a of the shaft 104a. The controller 106a then instructs the impact element 192a via the impact signal 194a to strike the gearbox housing 102a, thereby causing the gearbox 101a to vibrate. The impact force applied to the gearbox housing 102a is detected by the force transducer 193a and sent to the controller 106a via the impact force signal 195a. The vibration response of the second end 112a of the shaft 104a is then detected by the sensor 196a and communicated to the controller 106a via the vibration signal 198a. The detected vibration and impact force are then used (in some embodiments, in combination) by the controller 106a to calculate the lower side limit of natural frequency (LSLNF). The press 172a is then extended to re-engage the first end 108a of the shaft 104a. The gearbox housing 102a is again set into oscillation via the oscillator 188a while the press 172a actuates the shaft 104a along the rotational axis A until the instrumented device 180a communicates to the controller 106a that the second value of pre-load (i.e., targeted upper side limit of pre-load) has been reached. The pre-load signal 184a and the displacement signal 174a are recorded and processed by the controller 106a to determine and optionally save the second deflection (DUSL, FIG. 6) corresponding to the upper side limit of the preload (USLD).

[0025] The gearbox housing 102a stops oscillating. The locking nut 182a is then re-tightened to the second end 112a of the shaft 104a until the controller 106a determines, via the pre-load signal 184a from the instrumentation device 180a to the controller 106a, that the pre-load originally applied by the press 172a is locked in by the locking nut 182a. A second amount of torque (USLT) used to tighten the locking nut 182a is communicated to the controller 106a and recorded for later use. The controller 106a then re-instructs the press 172a to retract out of contact with the first end 108a of the shaft 104a. The controller 106a again instructs the impact element 192a to strike the gearbox housing 102a, thereby causing the gearbox 101a to vibrate. The impact force applied to the gearbox housing 102a is detected by the force transducer 193aand sent to the controller 106a via the impact force signal 195a. The vibration response of the second end 112a of the shaft 104a is measured by the sensor 196a and communicated to the controller 106a via the vibration signal 198a. The detected vibration and the impact force at the second value of pre-load is then used by the controller 106a to calculate the upper side limit of natural frequency (USLNF).

[0026] As seen in FIG. 5, a relationship between the natural frequency of the gearbox 101a and the pre-load applied to the bearing 116a is determined. Optionally, additional natural frequencies corresponding to additional bearing pre-load settings, inside and / or outside the lower side and upper side limits, can be measured and recorded by the same process as described above or be interpolated using the relationship. This relationship is then conveyed to a controller 106b on a production pre-load setting apparatus 100b.

[0027] In sum, the load cell 201a may determine a zero position of the displacement sensor 199a when the bearing 116a clearance gap is taken up. The displacement sensor 199a may determine deflections (displacement relative to the zero position) corresponding to the lower side limit of pre-load (DLSL) (corresponding with targeted lower side limit of pre-load) and upper side limit of pre-load (DUSL) (corresponding with targeted upper side limit of pre-load), and the controller 106a may record first and second locking nut torques corresponding with the lower side limit and upper side limit, respectively, to hold the pre-load constant at the lower side limit (LSL) and upper side limit (LSL), respectively.

[0028] Various parameters (e.g., the lower side limit of natural frequency LSLNF, upper side limit of natural frequency USLNF, lower side limit of preload LSLD, upper side limit of preload USLD, locking nut torque corresponding with lower side limit LSLT, locking nut torque corresponding with upper side limit USLT, deflection at lower side limit DLSL, and deflection at upper side limit DUSL, as determined in the testing apparatus 100a) are conveyed to the controller 106b of the production pre-load setting apparatus 100b to function as input parameters to set the pre-load in the production bearing 116b. Different embodiments may convey different parameters to the production controller 106b, and the production controller 106b may utilize one or more of the parameters in the process of application of pre-load to the production bearing 116b.

[0029] Although illustrated and referred to herein as two controllers 106a, 106b, it is noted that the controllers 106a, 106b may optionally be implemented as two modules (e.g., two separate executable programs) within one common control unit. Alternatively, the controllers 106a, 106b may be two distinct controllers implemented by separate hardware components. Whether the hardware is the same or different, an algorithm of the first controller 106a can produce a file or specific outputs that can be inputted to the second controller 106b. In some constructions, the transfer of data from the first controller 106a to the second controller 106b is automated and occurs via signal communication between the controllers 106a, 106b. In other constructions, an operator may record outputs from the first controller 106a and then input them to the second controller 106b.

[0030] As seen in FIG. 6, a curve representing a relationship between preload of the bearing 116a in comparison to deflection of the gearboxlOla is determined. The curve is generated by processing the preload data from the instrumentation device 180a via the pre-load signal 184a and displacement data from the displacement sensor 199a via the displacement signal 200a. A zero value of displacement may correlate with the inflection point where the clearance gap is taken up. The curve is then input to the controller 106b to be used for bearing pre-load setting in production.

[0031] FIG. 2 illustrates the production pre-load setting apparatus 100b. The pre-load setting apparatus 100b may be a reproduction of the testing apparatus 100a in most respects. The production pre-load setting apparatus 100b receives a power transmission device 101b, which is a reproduction of the power transmission device 101a except for the absence of bearing pre-load instrumentation. In the illustrated embodiment, the power transmission device 101b is a gearbox, which may be implemented into a machine (i.e., vehicle, power tool, heavy machinery). In other embodiments, the power transmission device 101b may be one of varies types of transmission devices. The power transmission device or gearbox 101b includes a gearbox housing 102b that receives a shaft 104b. The shaft 104b defines a rotational axis B between a first end 108b and a second end 112b of the shaft 104b opposite the first end 108b. The shaft 104b is configured to be rotated inside of the gearbox housing 102b during operation by a mechanical input, such as a motor (not shown). A bearing 116b is pressed onto the shaft 104b to allow for rotation of the shaft 104b about the rotational axis B in the gearbox housing 102b. In the illustratedembodiment, the bearing 116b is a tapered roller bearing, but may also be one of various other type of bearing. The production pre-load setting apparatus 100b is centrally controlled by the controller 106b. The controller 106b instructs various components of the production pre-load setting apparatus 100b, described in further detail later.

[0032] The bearing 116b includes an inner ring 120b, rolling elements 124b, and an outer ring 128b. The inner ring 120b defines a bore to receive a portion of the shaft 104b. The bearing 116b is press-fit on the shaft 104b, thereby enabling the inner ring 120b to co-rotate with the shaft 104b. The rolling elements 124b are positioned between the inner ring 120b and the outer ring 128b and may be tapered rollers or any other type of rolling elements that can be preloaded. The outer ring 128b is coupled to the gearbox housing 102b so that the outer ring 128b does not rotate with the inner ring 120b and the shaft 104b. An auxiliary bearing 186b is also positioned around the shaft 104b. As noted above, the bearing 116b or the auxiliary bearing 186b do not include the instrumentation device 180a to detect the applied pre-load since the bearing 116b and the auxiliary bearing 186b are production parts that can go into service to support rotation of the shaft 104b for power transmission.

[0033] The second end 112b of the shaft 104b is received into an opening 132b in a yoke 136b at least partially positioned in the gearbox housing 102b. The yoke 136b is coupled to an intermediate support plate 140b at a point outside of the gearbox housing 102b. The intermediate support plate 140b is fastened to a fixture 144b by a first plurality of fasteners 148b. The fixture 144b is fastened to a support beam 152b by a second plurality of fasteners (not shown) through openings 156b on the fixture 144b. The production pre-load setting apparatus 100b further includes a table 154b having an aperture 158b.

[0034] The production pre-load setting apparatus 100b may be configured to selectively suspend the gearbox housing 102b from the support beam 152b via support members 160b. The support members 160b are actuated linearly by air cylinders or linear motors 164b in a direction perpendicular to the rotational axis B of the shaft 104b. The support members 160b include a lip 162b to engage the yoke 136b when instructed to by the controller 106b via a motor signal 166b, thereby providing hanging support to the gearbox housing 102b. When hanging support is provided by the support members 160b, an isolation layer 168bis used between the yoke 136band the support members 160b, such that the gearbox 101b is structurally decoupled from the test apparatus 100b for modal test. In other words, the support members 160b are prevented from clamping the yoke 136b.

[0035] The production pre-load setting apparatus 100b further includes a press 172b positioned in the aperture 158b. The press 172b can engage the first shaft end 108b directly, or as shown, an adapter 173b can be situated between the first shaft end 108b and a distal end of the press 172b. The adapter 173b is configured to transfer force from the press 172b to the first end 108b of the shaft 104b along the rotational axis B. The press 172b is in electrical communication with the controller 106b via a press signal 174b. As the controller 106b instructs the press 172b to actuate the shaft 104b along the rotational axis B, the yoke 136b compresses the inner ring 120b. As a result, a clearance between the inner ring 120b and / or outer ring 128b and the rolling elements 124b is eliminated and the pre-load of the bearing 116b is increased. In some embodiments, pre-load may also be applied to the auxiliary bearing 186b by a gear 178b, during preload of the bearing 116b. The gear 178b is positioned around the first end 108b of the shaft 104b and includes a shoulder 176b provided at the axial end of the gear 178b. As a locking nut 182b is threaded to the second end 112b of the shaft 104b by the torque wrench, the shoulder 176b engages the auxiliary inner ring 187b of the auxiliary bearing 186b to apply pre-load thereto. The locking nut 182b holds constant pre-load applied to the bearing 116b and auxiliary bearing 186b. In the illustrated construction, the pre-load applied to the bearing 116b and the auxiliary bearing 186b is the same.

[0036] The gearbox housing 102b is oscillated during the pre-loading of the bearing 116b by an oscillator 188b. In the illustrated embodiment, the oscillator 188b is a device in communication with the controller 106b via an oscillation signal 190b to automatically oscillate the gearbox housing 102b. In other embodiments, an operator can manually oscillate the gearbox housing 102b.

[0037] After instructing the support members 160b to provide hanging support, the controller 106b instructs the press 172b via the press signal 174b to retract from the first end 108b of the shaft 104b. The controller 106b then instructs an impact element 192b, positioned in the aperture 158b of the table 154b, via an impact signal 194b to strike the gearbox housing 102b, therebycausing the gearbox 101b to vibrate. The impact force is measured by a force transducer 193b and communicated to the controller 106b via an impact force signal 195b. The vibration response of the second end 112b of the shaft 104b is detected by a sensor 196b with an unobstructed view of the shaft 104b. In other embodiments, the impact element 192b may strike the shaft 104b and then the sensor 196b may detect the vibration response of the gearbox housing 102b. In the illustrated embodiment, the sensor 196b is a contactless laser doppler vibrometer. In other embodiments, the sensor 196b may be any contact sensor (e.g., accelerometer) to measure vibration. The vibration response is communicated to the controller 106b from the sensor 196b via a vibration signal 198b, which is used by the controller 106b along with the force signal 195b to determine the natural frequency of the gearbox 101b at the given pre-load, according to known computational methods in the field.

[0038] The controller 106b of the production pre-load setting apparatus 100b receives data (e.g., via an electronic file on a local network, via manual input, etc.) from the controller 106a of the testing apparatus 100a. After the testing apparatus 100a completes the testing process, the LSLNF, LSLD, LSLT, USLNF, USLD, and USLT are communicated from the controller 106a of the testing apparatus 100a to the controller 106b of the production pre-load setting apparatus 100b.

[0039] In operation, as seen in FIGS. 4A and 4B, the shaft 104b is arranged inside of the gearbox housing 102b with the bearing 116b press-fit onto the shaft 104b. The first end 108b of the shaft 104b is positioned on the press 172b and the second end 112b is received into the opening 132b in the yoke 136b. The gearbox housing 102b is set into oscillation while the controller 106b instructs the press 172b via the press signal 174b to load the shaft 104b along the rotational axis B, thereby compressing the inner ring 120b of the bearing 116b onto the shaft 104b. The controller 106b instructs the press 172b to stop actuating the shaft 104b when the controller 106b detects a sudden increase of load via the load signal 202b from the load cell 201b (e.g., at the inflection point). The displacement sensor 199a may be set to “zero” its measurements relative to this position. The controller 106b then instructs the press 172b to travel a displacement equal to the lower side limit of the pre-load LSLD, as indicated by the controller 106a of the testing apparatus 100a (i.e., corresponding with a targeted lower side limit of preload). The gearbox housing 102b then stops oscillating. The locking nut 182b is then tightened tothe second end 1 12b of the shaft 104b by the torque wrench with the first amount of torque LSLT previously recorded. The controller 106b instructs the linear motors 164b via the motor signal 166b to engage the yoke 136b with the support members 160b. The press 172b is then retracted, via instruction from the controller 106b, from the first end 108b of the shaft 104b. The controller 106b then instructs the impact element 192b to strike the gearbox housing 102b, thereby causing the gearbox 101b to vibrate. The impact force applied to the gearbox housing 102b is detected by the force transducer 193b and sent to the controller 106b via the impact force signal 195b. The vibration response of the second end 112b of the shaft 104b is detected by the sensor 196b and communicated to the controller 106b via the vibration signal 198b. The detected vibration and impact force are used by the controller 106b to calculate the natural frequency.

[0040] The controller 106b then determines if the natural frequency is within the lower side limit of natural frequency LSLNF and the upper side limit of natural frequency USLNF provided by the controller 106a of the testing apparatus 100a, as seen in FIG. 5. If the natural frequency is below the lower side limit of natural frequency LSLNF, the press 172b is extended to re-engage the first end 108b of the shaft 104b and move back to its last position. The controller 106b then instructs the press 172b to incrementally acuate (i.e., press forward) the shaft 104b, as illustrated in Equation (1), with S representing a calculated incremental amount of displacement of the shaft 104b and N representing the total number of increments set in the controller 106b, which can be application dependent.„ USLD—LSLD „ .5 = - - - Equation (1)The locking nut 182b is then tightened again by the torque wrench to torque T, as illustrated in Equation (2), witht(representing an initial amount of torque applied to the locking nut 182b, USLT representing the second amount of torque corresponding with the upper side limit USL, LSLT representing the first amount of torque corresponding with the lower side limit LSL„ N representing the total number of increments set in the controller 106b, and / representing the instantaneous iteration. . , Equation (2)The number of increments depends on geometry tolerances of the gearbox 101b and the bearing 116b and may be optimized via analysis of historical data or through deep machine learning. The controller 106b instructs retracting the press 172b, and then instructs the striking of the gearbox housing 102b with the impact element 192b. The impact force is detected by the force transducer 193b and sent to the controller 106b via the impact force signal 195b. The sensor 196b detects the vibration response of the second end 112b of the shaft 104b and communicates the vibration signal 198b to the controller 106b, which again calculates the natural frequency. If the natural frequency is still below the lower side limit of natural frequency, then the process described above repeats. If the natural frequency is within the lower side limit and the upper side limit of natural frequency, then the controller 106b indicates to an operator that the gearbox 101b may move down or be removed from the assembly line.

Claims

CLAIMSWhat is claimed is:

1. A method of setting pre-load of a production bearing within a production power transmission device, the method comprising: providing a test power transmission device including a test shaft, the test shaft defining a first rotational axis between a first end and a second end opposite the first end; arranging the test shaft inside of a test transmission housing of the test power transmission device; pressing a test bearing onto the shaft, the test bearing including pre-load instrumentation; positioning the first end of the test shaft onto a press; while oscillating the test power transmission, actuating the test shaft via the press along the first rotational axis under control of a test controller until the test controller receives a signal from the pre-load instrumentation that a targeted lower side limit of pre-load is reached; tightening a test locking nut to the second end of the test shaft to hold the pre-load constant at the lower side limit; retracting the press out of contact from the first end of the test shaft; striking the test power transmission device with an impact element in response to input from the test controller, thereby causing a vibration response in the test power transmission device; detecting the vibration response of the test power transmission device with a sensor, the sensor sending a first vibration signal to the test controller, the test controller determining the lower side limit of natural frequency based on the first vibration signal; extending the press to re-engage the first end of the test shaft; actuating the test shaft via the press along the first rotational axis until the test controller receives signal from the instrumented bearing that a targeted upper side limit of pre-load is reached; tightening the test locking nut to the second end of the test shaft to hold the pre-load constant at the upper side limit; retracting the press out of contact from the first end of the test shaft;striking the test power transmission device with the impact element in response to input from the test controller, thereby causing a vibration response in the test power transmission device, detecting the vibration response of the test power transmission device with the sensor, the sensor sending a second vibration signal to the test controller, the test controller determining the upper side limit of natural frequency based on the second vibration signal; and conveying the lower side limit of natural frequency and the upper side limit of natural frequency to a production controller of a production pre-load setting apparatus on an assembly line, the production controller using the lower side limit of natural frequency and the upper side limit of natural frequency to control the production pre-load setting apparatus and using them to set the pre-load in a production power transmission assembly.

2. The method according to claim 1, the method further comprising: providing the production power transmission assembly on the assembly line with: a production shaft, the production shaft defining a second rotational axis between a first end and a second end opposite the first end, the production shaft being a reproduction of the test shaft; arranging the production shaft inside of a production transmission housing that is a reproduction of the test transmission housing; pressing a production bearing onto the production shaft, the production bearing being a reproduction of the test bearing, without pre-load instrumentation; positioning the first end of the production shaft onto the press; while oscillating the production power transmission, actuating the production shaft via the press along the second rotational axis under control of the production controller; tightening a production locking nut to the second end of the production shaft, the production locking nut being a reproduction of the test locking nut; retracting the press out of contact from the first end of the production shaft; striking the production power transmission device with the impact element in response to input from the production controller, thereby causing a vibration response in the production power transmission device; detecting the vibration response of the production power transmission device with the sensor, the sensor sending a first production vibration signal to the production controller, theproduction controller determining a natural frequency based on the first production vibration signal; determining whether the natural frequency is within the lower side limit of natural frequency and the upper side limit of natural frequency using the production controller; selectively upon determining that the natural frequency is outside the lower side limit of natural frequency and the upper side limit of natural frequency, extending the press to re-engage the first end of the production shaft; actuating the production shaft via the press along the second rotational axis; tightening the production locking nut to the second end of the production shaft; striking the production power transmission device with the impact element after removing the press from the first end of the production shaft, thereby causing a vibration response in the production power transmission device; detecting the vibration response of the production power transmission device with the sensor, the sensor sending a second production vibration signal to the production controller, the production controller determining the natural frequency based on the second production vibration signal; removing the production transmission device from the assembly line when the production controller determines that the natural frequency is within the lower side limit of natural frequency and the upper side limit of natural frequency.

3. The method of claim 1, wherein, during steps of tightening the test locking nut, a torque wrench is applied until the test controller receives a pre-load signal from the pre-load instrumentation that the locking nut is beginning to apply pre-load, the method further comprising detecting a torque value of the torque wrench and sending the torque value to the test controller.

4. The method of claim 3, wherein the steps of tightening the production locking nut include tightening the production locking nut to a calculated torque using the torque value.

5. The method of claim 1, further comprising inserting the second end of the test shaft through an opening in a test yoke such that the test locking nut applies load through the test yoke to hold the pre-load constant on the test bearing.

6. The method of claim 5, further comprising providing hanging support to the test transmission housing by a plurality of supports engaged with the test yoke prior to striking the test transmission housing with the impact element.

7. The method of claim 6, further comprising actuating the plurality of supports in engagement with the test yoke via a plurality of linear motors under control of the test controller.

8. The method of claim 5, further comprising coupling the test yoke to a fixture, and positioning the sensor on the fixture.

9. The method of claim 1, further comprising providing the instrumented bearing with an inner ring and an outer ring, the inner ring in engagement with the test shaft, the outer ring in engagement with the test transmission housing and including the pre-load instrumentation to provide the signal to the test controller.

10. The method of claim 1, wherein the step of detecting the vibration response of the power transmission device with the sensor includes measuring a difference between an internal reference laser beam and a test laser beam with a laser doppler vibrometer.

11. The method of claim 1, wherein the test bearing is oscillated by oscillating the test transmission housing via a device in communication with the test controller to automatically oscillate the test transmission housing during the actuating of the test shaft via the press.

12. The method of claim 1, wherein during each step of striking the test power transmission device with an impact element, an impact force is measured by a force transducer and sent to the test controller, and the test controller uses the impact force in combination with the first and second vibration signals in determining the lower and upper side limits of natural frequency.

13. The method of claim 1, wherein the step of actuating the test shaft a first displacement via the press along the first rotational axis under control of the test controller occurs until the test controller receives the pre-load signal from the pre-load instrumentation that the targeted lower side limit of pre-load is reached, and wherein the step of actuating the test shaft via a second displacement the press along the first rotational axis under control of the test controller occurs until the test controller receives the pre-load signal from the pre-load instrumentation that a targeted upper side limit of pre-load is reached.

14. The method of claim 13, wherein the step of actuating the production shaft the first displacement via the press along the second rotational axis under control of the production controller, and wherein the step of actuating the production shaft via the press along the second rotational axis with a calculated incremental amount of displacement based on the first displacement and the second displacement.

15. The method of claim 2, wherein the test controller and the production controller are two distinct controllers implemented by separate hardware components.

16. The method of claim 2, wherein the test controller and the production controller are two modules within one control unit.

17. The method of claim 1, further comprising, while actuating the test shaft, monitoring via a load cell a load on the test bearing and determining whether a clearance gap of the test bearing has been taken up.

18. The method of claim 17, further comprising, while actuating the test shaft, monitoring displacement of the test shaft with a displacement sensor; setting a zero position of the displacement sensor in response to the load cell indicating the test bearing clearance gap has been taken up; andsaving a first displacement of the test shaft upon determining that the lower side limit of natural frequency is reached; saving a second displacement of the test shaft upon determining that the upper side limit of natural frequency is reached; and conveying the first displacement and second displacement to the production controller.

19. The method of claim 2, wherein while oscillating the production transmission, monitoring via a load cell a load on the production bearing and determining whether a clearance gap of the production bearing has been taken up.

20. The method of claim 19, wherein while oscillating the production transmission and once the clearance gap is taken up, actuating the production shaft a saved first displacement as communicated by the test controller to apply the lower side limit of pre-load to the production bearing.

21. The method of claim 1, further comprising determining deflection corresponding with at least one of a lower side limit of pre-load and an upper side limit of pre-load with a displacement sensor monitoring deflection of the test power transmission.

22. The method of claim 21, further comprising conveying the deflection corresponding with at least one of the lower side limit of pre-load and the upper side limit of pre-load as determined by the displacement sensor to the production controller of the production pre-load setting apparatus on the assembly line.

23. The method of claim 1, further comprising determining a locking nut torque corresponding with at least one of the lower side limit of pre-load and the upper side limit of preload and conveying the locking nut torque to the production controller of the production pre-load setting apparatus on the assembly line.

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