BRIEF DESCRIPTION OF THE DRAWINGS
The following description and drawings set forth certain illustrative implementations of the invention in detail, which are indicative of several exemplary ways in which the principles of the invention may be carried out. The illustrated examples, however, are not exhaustive of the many possible embodiments of the invention. Other objects, advantages and novel features of the invention will be appreciated from the following detailed description of the invention when considered in conjunction with the drawings, in which:
FIG. 1 is a partial sectional top plan view illustrating an exemplary inductive hardening system with first and second bearing hardening stations, a TIR measurement station, and feedback control for adjusting one or more power, quench flow rate, or counter balance profiles used in the second hardening station according to a measured TIR value;
FIG. 2 is a side elevation view illustration of an exemplary crankshaft having four pin bearing surfaces to be hardened in the system of FIG. 1;
FIG. 3 is a partial sectional side elevation view illustrating a tunnel or corridor structure of the system of FIG. 1 with a window allowing an operator to observe a crankshaft bearing induction hardening process from a short distance;
FIG. 4 is a schematic diagram illustrating feedback control aspects of the controls for the second bearing hardening station in the system of FIG. 1;
FIG. 5 is a simplified schematic system diagram illustrating the sequence of bearing hardening and TIR measurement operations in the system of FIG. 1;
FIG. 6 is a graph illustrating an exemplary TIR acceptance value for the crankshaft of FIG. 2 defining an acceptable TIR range in which the system of FIG. 1 uses an unmodified second power, quench flow, and counter balance profiles or sets of profiles for hardening a second bearing or set of bearings, and a range above the acceptance limit in which the system selectively adjusts the second profiles or profile sets for processing the second bearing(s);
FIG. 7 is a simplified side elevation view illustrating the exemplary crankshaft undergoing TIR measurement using a set of five probes and associated linear transducers to determine a measured TIR value after hardening of an initial set of bearings;
FIG. 8 is a partial side elevation view illustrating an exemplary induction heating and quench system for hardening a crankshaft bearing in the system of FIG. 1; and
FIG. 9 is a flow diagram illustrating an exemplary method for bearing hardening in accordance with further aspects of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the figures, several embodiments or implementations of the present invention are hereinafter described in conjunction with the drawings, wherein like reference numerals are used to refer to like elements throughout. The invention provides methods and systems for selectively adjusting induction hardening power, quench flow, and/or counter balance profiles for a second bearing or group of bearings based upon a crankshaft TIR measured after hardening of a first bearing or bearings, and may be successfully implemented in the manufacture of crankshafts for automotive or other internal combustion engines having any number of centrifugal or orbiting pin bearings and any number of axial main bearings. Thus while illustrated and described hereinafter in the context of manufacturing an exemplary crankshaft with five axial main bearings and four off-axis pin bearings, the invention is generally applicable to production and processing of any number of different crankshaft designs. Furthermore, the invention finds utility in association with any form of inductive bearing hardening systems having induction heating components and quenching components, and may easily be automated to facilitate highly repeatable TIR results with reduced overall crankshaft distortion to reduce or eliminate straightening operations and production costs and to allow greater design flexibility with respect to crankshaft fatigue limits and weight.
Referring initially to FIGS. 1-3, a crankshaft bearing hardening system 10 is illustrated, which operates to control the TIR of processed crankshafts 12. Although illustrated hereinafter in the context of application to hardening pin bearings, the principles of the invention are also applicable to hardening main bearings or combinations of main and pin bearings, wherein the illustrated embodiments are merely examples. The exemplary system 10 includes first and second bearing hardening stations 20 and 30 having induction heating and quench systems 22 and 32 for processing first and second sets or groups of bearings, respectively, where the first and second groups may individually include as few as a single bearing. The system includes walls 60 defining the stations 20, 30 and separating the bearing hardening stations 20, 30 from an operator corridor 64. The protective wall 60 includes one or more windows 62 allowing an operator 14 to view processing of crankshafts 12 within one or both of the bearing hardening stations 20, 30 from a short distance 16 (FIG. 3) of about four feet or less in the illustrated embodiment. Each station 20, 30 is controlled for automated or manual operation via corresponding controls 24, 34, respectively, which may also be located within the corridor 64 opposite the process observation windows 62, thereby allowing an operator 14 to view the induction hardening processing of a crankshaft 12 at the corresponding station 20, 30 and to adjust the operation or view displayed information (not shown) associated with the station on the corresponding controls 24, 34. As best shown in FIG. 3, the exemplary second bearing hardening station 30 employs an induction heating and quenching apparatus 32 and a rotatable support for a crankshaft 12 undergoing induction hardening processing, where the window 62 provides an operator 14 with clear line-of-sight observation of the process in the second station 30. In this respect, the hardening system 10 provides the operator 14 with physical process proximity not heretofore available, while ensuring protection from the process environment and mitigating disruption of the processing itself. The corridor structure 64 and the walls 60 may extend beyond the portion shown in FIG. 1 wherein the system 10 may include other processing stations (not shown). For example, in one possible implementation, a main bearing hardening station could be provided before the first bearing hardening station 20, wherein the first station 20 is provided in one embodiment with crankshafts 12 having the main bearings pre-hardened, wherein one or more pin bearings are hardened in the first station 20.
FIG. 2 illustrates further details of the exemplary crankshaft 12, having five coaxial main bearings M1-M5 along a crankshaft axis 12a, as well as four centrifugal or off-axis pin bearings P1-P4 interspersed between the main bearings M1-M5. In general, the hardening processing is implemented to inductively heat and then quench harden the bearing surfaces of any of the pin bearings P1-P4 and/or main bearings M1-M5 according to required performance specifications for a given crankshaft design. The various aspects of the current invention are exemplified in the hardening of the pin bearings P1-P4 in this example, wherein the following description assumes that the main bearings have already been hardened by any suitable means, although this is not a requirement of the invention and the main bearings M1-M5 could alternatively be hardened at any suitable point in the crankshaft manufacturing process in the illustrated stations 20, 30, or in other stations (not shown) in any concurrent, prior, subsequent, or intervening process. One objective of the invention is advanced by the provision of crankshafts with hardened bearings P1-P4 and/or M1-M5 without the need for post-hardening straightening operations, although the invention may be employed in production processes that employ such straightening. In this regard, successful application of the various aspects of the invention can mitigate the amount of straightening needed for a given crankshaft 12 or eliminate the need to straighten some or all manufactured crankshafts 12 following the induction hardening processing. In this manner, the system 10 described herein can be advantageously employed in controlling the TIR of the crankshaft 12. Another important goal is the hardening of the crankshaft bearings, wherein the invention addresses both objectives concurrently to provide straight, undistorted crankshafts having the desired tempered hardness and other metallurgical characteristics for the individual cylindrical contact surfaces of the bearings. During processing in the illustrated hardening stations 20, 30, moreover, the pin bearing surfaces orbit about the crankshaft axis 12a as the crankshaft 12 is controllably rotated during induction heating, quench hardening, and automatic tempering of the individual bearing surfaces.
Referring now to FIGS. 1 and 7, the system 10 further includes a measurement or TIR station 40 with at least one probe 42 and a transducer 44 for measuring the TIR of the crankshaft 12 after processing in the first bearing hardening station 20. In this example, moreover, five probes 42a-42e are provided for engaging the rotating outer surfaces of the main bearings M1-M5, together with corresponding linear transducers 44a-44e, respectively, wherein the TIR station 40 includes a control element 42 that controllably rotates the measured crankshaft 12 about the axis 12a and receives signals from the transducers 44 in order to provide a crankshaft TIR value 40a to the controls 34 of the second bearing hardening station 30. In practice, the TIR controls 42 may derive the TIR value 40a using any suitable numeric technique, including without limitation averaging the readings from the transducers 44, taking the largest transducer value as the crankshaft TIR value 40a, etc.
As shown in FIG. 1, moreover, the exemplary system 10 can be essentially fully automated, with one or more robotic systems 50 for automatically transferring the crankshaft 12 from the first bearing hardening station 20 to the TIR station 40 after processing at the first station 20. The robot system 50 thereafter automatically transfers the crankshaft 12 from the TIR measurement station 40 to the second bearing hardening station 30 once the TIR has been measured. The first hardening station 20 includes induction heating and quench apparatus 22 for inductively heating and quench hardening and inductor counter balance force control apparatus to provide automatic tempering according to given first power, quench flow rate, and counter balance profile for each bearing P or M of a first set or group, which may include a single bearing or multiple bearings, wherein a group can be all pins P, all mains M, or combinations of pin and main bearings, or a single pin or main bearing. In this regard, the various aspects of the invention are generally applicable to any selected first and second bearings or groups thereof.
In one possible example, a first group is selected to include the inner-most pin bearings P2 and P3, wherein the induction hardening thereof tends to cause crankshaft distortion in a first direction. In this example, the remaining two pin bearings P1 and P4 (the outer pins) are hardened as a second group in the second station 30, where the hardening of this exemplary second group of bearings tends to distort the crankshaft 12 in a second generally opposite direction. Consequently, the hardening of the second group will tend to counteract the distortion effects caused by hardening the first group, whereby the overall pin hardening process is less likely to yield distorted crankshafts 12 that require extra straightening steps. Furthermore, the intervening TIR measurement at station 40 allows selective adjustment of the power, quench flow rate, and/or counter balance levels of the profile(s) used in the second station 30 so as to controllably affect the counter bending, whereby the invention can be used to tailor the final TIR to be within allowable tolerance limits while providing the desired tempering of the crankshaft bearing surfaces. Moreover, this concept can be extended to processing in more than two groups, with one or more intervening TIR measurements and correlated adjustment of post-measurement power, quench flow rate, and/or counter balance profiles.
Referring also to FIG. 5, the crankshaft 12 is provided (at “A” in FIG. 5) to the first bearing hardening station 20 with the main bearings M1-M5 already hardened. A first bearing or first set of bearings is then hardened via the induction heating and quench system 22 according to first power, quench flow, and counter balance profiles or sets of such profiles, which can be diagnostically determined. Following this first processing, the crankshaft 12 is automatically transferred to the TIR station 40 (path “B” in FIG. 5), at which the TIR of the crankshaft 12 is measured. Thereafter, the crankshaft is transferred (path “C”) to the second station 30 for controlled processing to harden a second (different) bearing or set of bearings. After the second bearing(s) have been hardened, the crankshaft 12 is removed from station 30 (path “D” in FIG. 5), and may optionally undergo a final TIR measurement. In this regard, the final TIR may be used to determine whether the processed crankshaft 12 is within allowable specifications for distortion, and whether subsequent straightening is needed. It will be appreciated that the robotic system 50 of FIG. 1 or multiple robots 50 may be programmed to perform the transfer operations illustrated in FIG. 5 such that the entire bearing hardening process is fully automated.
Referring now to FIG. 8, the induction heating and quench systems 22,32 in the first and second stations 20 and 30 include induction heating and quench systems 22 and 32, respectively, each of which provides at least one inductor structure 84 as depicted in FIG. 8 for hardening of a pin bearing P as it orbits around the shaft axis 12a at the center of the main bearings M in a direction indicated by arrow 94. The inductor structure 84 may be any suitable apparatus for performing induction heating and quenching, for example, as generally described in Griebel U.S. Pat. No. 5,451,749 incorporated herein by reference. In the exemplary implementation described herein, a first group of orbiting pin surfaces of pins P2 and P3 are hardened in the first station 20 and a second group is hardened in the second station 30 (P1 and P4), wherein hardening the two groups of bearings with intervening TIR measurement and selective profile adjustment facilitates holding the crankshaft TIR within a desired specification.
The nominal or default power, quench, and counter balance profiles used for the individual bearing hardening processes are preferably generated diagnostically to tailor the desired tempered metallurgical characteristics around the total circumference of each of the hardened bearing surfaces. As shown in FIG. 8, the heating and quenching systems include an inductor assembly for each treated bearing of the corresponding treated group, having a hollow, single turn arcuate conductor 90 with first and second portions 90a and 90b constructed in the form of laminations and extending in one embodiment over less than 180° of the outer surface of the treated bearing P, with cooling fluid being circulated through the conductor 90 via inlet and outlet lines 88a and 88b. Three shoes 92a, 92b, and 92c are provided to set the relative position of the conductor 90 with respect to the treated surface of the bearing, wherein the upper shoe 92b rides along the top of bearing surface and shoes 92a and 92c provide lateral alignment to maintain the desired induction heating gap between the bearing surface and the conductor 90. For a given crankshaft 12, the heating gap established by the shoes 92 is preferably designed to provide proper induction heating of the exemplary orbitally rotating pin bearing P in the areas opposite the laminations of the conductor portions 90a and 90b. For inductive heating of the bearing, electrical power is supplied to the conductor 90 via electrical wiring (not shown) coupled to a power source 80 through conduit 86.
The corresponding hardening station controls 24, 34 provide the necessary control signaling and/or messaging to coordinate and control the rotation of the shaft 12 and the corresponding lateral and vertical translation of the inductor structure 84, along with controlling the operation of the power source 80 and hence the inductive heating of the bearing, quench valve controls 82 for controlling the quench hardening of the treated bearing, and counter balance controls 83 to control counter balance force provided to the inductor structure 84. Quenching liquid is directed into the inductor assembly via liquid supply lines 96a and 96b under control of quench valve controls 82 and appropriate valves, supply lines, and nozzles (not shown) to propel the quench fluid against the bearing after the conductor 90 has inductively heated the surface thereof. In addition, the structure provides inlet and outlet fluid couplings 88a and 88b, respectively, to allow coolant liquid to flow through the hollow conductor 90, whereby both coolant and electrical power are directed to the inductor 90. Because the treated pin bearing P is off-axis with respect to the main bearing axis 12a in the illustrated example, the treatment system is operably mounted for controlled movement of the structure 84 in the X and Y directions by suitable means (not shown), such that as the pin bearing P orbits in the path direction indicated by arrow 94, the structure 84 follows the orbital pin bearing movement in concert with the support mechanism that rotates the crankshaft 12 about the main bearing axis 12a. In addition, the movable mounting structure supporting the inductor structure 84 preferably includes counter balancing apparatus operated according to the controls 83 to maintain the gapped relationship of the pin bearing P and the structure 84 via the shoes 92 without exerting undue force on the surface of the treated bearing P. Treatment apparatus for the axial main bearings M, of course, does not require such moving mounting structures, wherein a hardening station may be equipped with one or more moving inductor mountings for hardening pin bearings and/or one or more non-moving inductor mounts for treatment of main bearings.
The electrical power is provided to the conductor 90 for inductively heating the illustrated pin bearing P from the power source 80 to implement a power profile, such as a waveform current profile tailored to the desired thermal treatment, which in combination with the quenching, achieves the desired tempering of the treated bearing. In this regard, the power profile, quenching, and timing of the process are preferably controlled to provide automatic tempering of the treated bearing. In the first station 20, the heating and quench system 22 hardens at least a first bearing using a given first power profile, wherein multiple profiles can be used to harden multiple corresponding bearings if the first set includes more than one bearing.
The profiles, moreover, may be diagnostically generated prepatory to the full-scale manufacturing process into which the invention may be incorporated. One suitable diagnostic profiling technique is illustrated in co-pending U.S. patent application Ser. No. 11/555,789, filed on Nov. 2, 2006, owned by the assignee of the present invention, the entirety of which is hereby incorporated by reference as if fully set forth herein. In this example, a profile is created for the power level, quench fluid flow level, and counter balance force level at each 10° arcuate increment over the entire 360° span of the pin bearing P, and a separate set of such profiles is created for each treated bearing of the crankshaft 12. The profiles may be stored and used by the corresponding station controls 24, 34 in any suitable form or location, such as a look up table stored in memory internal to, or otherwise accessible by, the controls 24, 34, wherein the power source 80, quench valve controls 82, and counter balance controls 83 operate to set the levels of the applied power signals, the amount of quench fluid flow, and counter balance force based on the lookup table profile entries in concert with the rotation of the processed shaft 12. In this manner, the power, quench, and counter balance levels are set to the profiled values corresponding to the specific angular segments of the treated pin bearing P as the crankshaft 12 is rotated about axis 12a.
For diagnostically determining the nominal power, quench, and counter balance profiles, prior to a production run, a particular bearing surface is heated and quenched according to a default set of profiles, and the resulting hardened surface of the test shaft 12 is analyzed metallurgically in a laboratory to determine the metallurgical characteristics around the bearing surface. To the extent that the treated surface does not have the desired characteristics at all locations, one or more of the profiles are modified or adjusted. This process may be iterated one or more times for each bearing surface to derive a nominal set of profiles for production, which are thus diagnostically determined, and which are stored in or otherwise accessible by the controls 24, 34. In the illustrated example, therefore, the first station controls 24 will store diagnostically generated profiles for the inner pin bearings P2 and P3 of the first set, and the second station controls 34 will employ diagnostically generated profiles (selectively adjusted) for the set of outer pins P1 and P4.
Referring now to FIGS. 1, 4, and 6, with these diagnostically generated nominal profiles for the pin bearings P1-P4, the crankshaft 12 is provided initially to the first station 20, and the induction heating and quench system 22 thereof is operated according to the corresponding profiles to harden pins P2 and P3. The shaft 12 is then transferred by the robot system 50 to the TIR station 40, and the crankshaft TIR value 40a is measured and provided to the station 2 controls 34 (FIG. 4). The second pin hardening station 30 then selectively adjusts the power, quench flow, and/or counter balance profiles for the second set of pin bearings P1 and P4 according to the measured TIR value 40a, and the crankshaft 12 is transferred by the robot 50 to the second hardening station 30. FIG. 6 shows a graph 70 illustrating an exemplary TIR acceptance value for the crankshaft 12, which defines an acceptable TIR range in which the system 10 uses the unmodified, diagnostically determined power profiles for hardening the second set of pin bearings P1 and P4 at station 30, as well as a range above the acceptance limit in which the control system 34 selectively adjusts the second set of profiles for hardening P1 and P4 in the second station 30. In a preferred implementation, moreover, the control 34 adjusts one or more of the second set of profiles by an amount related to the degree to which the measured TIR value 40a exceeds the acceptance value. In this manner, the higher the amount of unacceptable bend resulting from the initial bearing hardening in the first station 10, the higher the amount of correction that is applied by adjusting the profile(s) used in the processing in the second station 30. In one possible implementation, the amount of adjustment is linearly related to (e.g., proportional to) the extent of the measured TIR beyond the acceptance value, although any suitable adjustment algorithm can be used which may be a fixed adjustment or the amount of adjustment may be related to the amount of error in the measured TIR.
FIG. 4 illustrates exemplary feedback control aspects of the second station controls 34, wherein the controls 34 receive the measured crankshaft TIR value 40a from the TIR station 40. While illustrated schematically in FIG. 4, the control, comparison, and adjustment functionality can be implemented in any suitable hardware, software, firmware, or combinations thereof. A comparator 34a (or software comparison function) determines whether the measured TIR value 40a exceeds the acceptance value 36, and provides the comparison result to an adjustment component 34b. The component 34b selectively adjusts the second profile set 34c (e.g., the diagnostically determined power, quench flow rate, and/or counter balance profiles for the second set of bearings P1 and P4 in the above described example) based on the measured TIR 40a, and provides the profile 34c (adjusted or not depending on the value 40a) to the induction heat power controller 34d for providing corresponding signals, messages, etc. to the induction heating and quench system 32 of the second station 30.
FIG. 9 illustrates an exemplary method 100 for hardening pin and/or main bearings of a crankshaft in accordance with certain aspects of the invention. Although the exemplary method 100 is illustrated and described below as a series of acts or events, it will be appreciated that the present invention is not limited by the illustrated ordering of such acts or events except as specifically set forth herein. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein, in accordance with the invention. In addition, not all illustrated steps may be required to implement a methodology in accordance with the present invention. Moreover, the methods of the invention may be carried out in conjunction with various systems, apparatus, and workpieces illustrated and described herein, as well as in association with other structures that are not illustrated or specifically discussed. At 120, a first set or group of bearings is hardened at a first station using a first set of predefined power and quench flow rate profiles, where the sets can include a single bearing and a single profile, or multiple bearings can be hardened at 120 using a set of corresponding profiles. Furthermore, if the hardened bearings are pin bearings, the hardening may also be done using corresponding counter balance profiles. At 130, a crankshaft TIR is determined (e.g., measured) after induction hardening the first bearing(s). Second power, quench flow rate, and/or counter balance profiles are then determined at least partially according to the measured crankshaft TIR. In the illustrated example, a determination is made at 140 as to whether the measured TIR is greater than an acceptance value. If not (NO at 140), no adjustments are made and the second group of bearings is hardened at 150 using a second group of predefined profiles (or a single unmodified set of profile to harden a single bearing). Thereafter at 180, a final TIR measurement may be made, although not a strict requirement of the invention, and the bearing hardening process is finished. If, however, the measured TIR is above the acceptance value (YES at 140), the second predefined power profile, quench flow rate profile, and/or counter balance profiles (or group of profiles) are adjusted at 160 according to the measured TIR value. Thereafter at 170, the second group of bearings is hardened at 170 using the adjusted or modified second group of power profiles (or a single adjusted set of profiles to harden a single bearing), followed by an optional final TIR measurement at 180 to complete the process.
The above examples are merely illustrative of several possible embodiments of various aspects of the present invention, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, systems, circuits, and the like), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component, such as hardware, software, or combinations thereof, which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the illustrated implementations of the invention. In addition, although a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.
Patent Application
20080041845
