The invention relates to the art of induction heating and quench hardening rotating bearing surfaces and more particularly to an apparatus and method for hardening the cylindrical bearing surfaces spaced axially along a crankshaft of the type used in an internal combustion engine. Bearing surfaces include the terminal fillets.
Induction heating for quench hardening the cylindrical bearing surfaces of a rotating crankshaft was pioneered by Park Ohio Industries many years ago. Now this technology is well developed and is the subject of many patents constituting background information to the present invention. Representative background technology is disclosed in Sorensen U.S. Pat. No. 4,123,644. An inductor for use in such an apparatus is described in Griebel U.S. Pat. No. 5,451,749. These two patents owned by assignee of the present application are incorporated by reference. Indeed, the inductor shown in Griebel U.S. Pat. No. 5,451,749 is generally the same type inductor as used in the apparatus and method of the present invention. Consequently, the inductor structure need not be described in further detail for understanding the induction heating and hardening concept of the invention. Other representative patents incorporated by reference herein are Storm U.S. Pat. No. 6,013,904; Loveless U.S. Pat. No. 6,274,857; Zahn U.S. Pat. No. 6,555,800; and, Schulte U.S. Pat. No. 6,638,379. The Schulte patent discloses an apparatus and method for inductively heating and then quench hardening a crankshaft of the type processed by the present invention; however, this patent is merely prior art of the type improved by the present invention. In this prior art patent, the distortion or total indicator run out (TIR) of the crankshaft is reduced by inductively heating and quench hardening the main bearings of the crankshaft after the orbiting pin bearing surfaces have been hardened. This procedure sequence has not proven satisfactory and requires substantial bending of the crankshaft after it is hardened, in an effort to reduce the TIR. Indeed, shaft distortion is usually corrected after hardening. This drastically reduces the strength of the crankshaft and increases the processing cost associated with the apparatus and method for hardening the axially spaced bearing surfaces.
The present invention recognizes the advantage of first inductively heating and quench hardening the main bearings, after which the orbital pin bearings are processed by first hardening one group of pin bearings and then hardening another group of pin bearings. Consequently, the apparatus and method of the present invention essentially inductively heats and quench hardens the main bearings and, then, inductively heats and quench hardens the two center orbital pin surfaces. A final station is used to inductively heat and quench harden the two outside orbital pin bearings. Hardening of one group of pin bearing causes distortion (TIR) in one direction and hardening of the next group causes a corrective distortion in the opposite direction. The pins in each group may vary when processing different crankshafts. By using the present invention, total indicator run out (TIR) of the main bearings after the whole crankshaft has been processed is less than 0.020 inches and preferably less than 0.015 inches. There is no need for successive straightening of the processed crankshaft.
This unique sequencing of the hardening procedure results in a straight crankshaft without subsequent straightening. Furthermore, the heating and quenching of each of the cylindrical bearing surfaces of a crankshaft is performed by a combination of a specific heating profile and a quenching procedure that produces an automatic tempering in the preferred embodiment. Automatic tempering is accomplished by quenching the surfaces to leave a controlled amount of heat energy to temper the hardened surfaces.
The second and fourth main bearing surfaces and all the pin surfaces employ a pulse quenching procedure where the amount of quenching liquid is controlled at arcuate increments of crankshaft rotation. In practicing the invention, the apparatus and method is created and adjusted by testing the metallurgy of the bearing surfaces. Then the heating profile is interactively modified until the desired metallurgical properties are obtained around the bearing surface. In accordance with this aspect of the invention, the heat profile for the bearing surfaces is interactively adjusted in a closed loop fashion at each of a small arcuate increment, in practice 10 degrees. The metallurgical characteristics of the surface are again tested and the heat profile is modified to provide a final profile having the desired metallurgical characteristics. In this fashion, the final heat profile use for production compensates for the power lag during the induction heating cycle of each cylindrical bearing surface. The final constructed profile is used to provide power at each arcuate increment. Another aspect of the invention is use of a pulsating quench for the bearing surfaces associated with the orbiting pins of the crankshaft. The pulsating quenching is preceded by a full quench flow to reduce the temperature of the rotating pin surface preparatory to pulse quenching to a temperature allowing automatic tempering of the heated, hardened surfaces. The heating profile that is constructed for production run of the pins changes the amount of heating of the pins when the heating is at top dead center or at bottom dead center. The unique combination of use of a constructed power profile and pulse quenching is employed to produce the desired metallurgical characteristics of the several axially spaced pins on the crankshaft. This set-up is then used for the production run of the apparatus for hardening the bearing surfaces. Thus, this unique procedure for hardening the pins utilizing a constructed heat profile and a pulsed quenching procedure to leave a certain amount of heat energy. Then a soaking operation provides the desired tempered metallurgical characteristics. At the same time, the sequence for processing the bearing surfaces results in a relatively straight crankshaft requiring no subsequent straightening operation.
The term “cylindrical surface” used to describe the invention includes the fillets on axial ends of the actual surfaces. Thus, the surfaces and associated fillets are hardened by using the present invention.
In accordance with the primary aspect of the invention, there is provided an apparatus for hardening the concentric main bearing surfaces and the orbiting pin bearing surfaces of a crankshaft for an internal combustion engine. The apparatus comprises a somewhat standard inductor for encircling each of the surfaces to be hardened over at least a portion of the surface, preferably over substantially less than 180 degrees of the surface, and riding on the surface to maintain an induction heating gap. Such inductor is shown in Griebel U.S. Pat. No. 5,451,749. The inductor is connected to a high frequency power source having a power controller to cause the power source to direct a given power to the inductor. The power is controlled at the different rotational positions of the crankshaft. Furthermore, the inductor includes a quench chamber or quenching head with outlet orifices directing quenching liquid toward the surface encircled by the inductor. A supply of quenching liquid with a flow controller is used to direct a given quantity of quench liquid to the chamber and through the orifices against the surface after the surface has been heated by the inductor using the constructed heat profile. The amount of quenching liquid is controlled at different rotational positions of the crankshaft during the quenching cycle. The heat profile is performed repeatedly over each 360 degrees of rotation, whereas the quench flow is controlled at arcuate increments during the total quench cycle A counter balancing mechanism is employed with a counter balanced controller to control the riding force of the inductor against a surface encircled by the inductor. This is important when heating or quenching a pin surface. When processing a main surface the counter balance does not vary. A master controller is used for creating output signals to control the level of power by the power controller (to follow the constructed profile) and the amount of liquid flow by the flow controller for each of the surfaces encircled by the inductor. The power and quench flow is controlled at rotational positions in arcuate increments of less than 30 degrees and more particularly less than 20 degrees. In practice the increments are about 10 degrees. In summary, the power level is controlled during each arcuate increment which is less than 30 degrees and preferably about 10 degrees. The liquid flow during the quench hardening cycle is also changed by a flow controller operated in accordance with signals created at each of the arcuate increments. In accordance with another feature, at each of the arcuate increments the master controller creates signals for controlling the counter balancing for each of the surfaces. The force of the inductor riding against the rotating surface is in the range of 15-30 pounds.
A primary aspect of the invention is to heat and then quench the cylindrical surface and fillets while leaving sufficient heat energy to allow automatic tempering of the surface and its fillets.
In accordance with another aspect of the invention, the quenching of the inner main bearings and each of the pin bearings involves a pulsed flow of quenching liquid. For the pin bearings, the quenching cycle is divided into a continuous flow portion and a pulsed flow portion. The pulsed flow is coordinated with the top dead center and bottom dead center of the orbiting pin surfaces. Both the main bearing surfaces and the pin bearing surfaces are not fully quenched. Residual heat energy in the quenched bearing surfaces allows tempering of the hardened surfaces without requirement of a subsequent tempering operation.
In accordance with still a further aspect of the present invention, the sequence of hardening the various cylindrical bearing surfaces is unique. In general, the invention provides for controlled sequencing and adaptation of hardening of multiple bearing sets such that the hardening process for one bearing set compensates for, or counteracts, distortion caused by hardening of an earlier set, where the sets can be one or more bearings, and either set can include main bearings, pin bearings, or both. The controlled sequencing aspects of the invention may be successfully employed to control or limit final distortion of the crankshaft after all bearing surfaces have been hardened. In one possible implementation, a first station inductively heats and quench hardens the main bearing surfaces. This procedure provides a given total indicator run out in a known first direction. A second station is then used to inductively heat and quench harden certain pin bearings, such as pins 2 and 3. This procedure has a known, previously determined distortion in the same direction as the main bearing surfaces, where the distortions caused by the main bearing hardening and the hardening of the first set of pin bearings can be determined in any suitable manner, such as through empirical experiments, measurements of a continuing process, SPC, SQC, or other data gathering technique, or through design calculations or combinations thereof. In this example, a third station is used to harden a second set of pins, such as pins 1 and 4, in a manner to provide run out in the direction opposite to the determined run out of the first two stations. Thus, the hardening procedure for pins 1 and 4 counteract distortion caused by the hardening of the main bearings and the surfaces of pins 2 and 3. This action drives the crankshaft toward a straight position with a total indicator run out within a preset level, such as less than 0.020 and preferably less than 0.015 inches. Distortions at the first and second stations are in the same direction, while the distortion in the third station is in the opposite direction. This action eliminates the necessity for subsequent straightening of the crankshaft as shown in Shult U.S. Pat. No. 6,638,379. This compensatory effect of the final hardening can be accomplished through selection of the constituent bearings hardened in each station, alone or in combination with adaptive adjustment of the later hardening process based on an intervening TIR measurement of the initial distortion in the first direction. In one embodiment, measurement of the total indicator read-out after the second station allows the heating profile for use on the third station to be adjusted to bring the total run out of the crankshaft into the desired specification.
Still a further aspect of the present invention is the provision of an apparatus for hardening the orbital pin bearing surfaces of a crankshaft for an internal combustion engine. This apparatus has an orbital inductor to heat the pins, an orbital quench head with a supply of quenching liquid having a flow controller to direct a given quantity of quench liquid to the head and against the heated pin surface and a device for controlling the flow controller during a rotational quenching cycle. The quenching flow is generally continuous for at least 360 degrees rotation of the crankshaft and then is pulsed to harden the surface while leaving sufficient internal heat for slight tempering of the hardened surface. This automatic tempering is determined by a diagnostic procedure before the production run of a given crankshaft is started.
Yet another aspect of the present invention is the provision of an apparatus for hardening the orbital, successive pin bearing surfaces 1, 2, 3 and 4 of a crankshaft for an internal combustion engine. The crankshaft has previously hardened main bearing surfaces. The novel apparatus includes a mechanism for measuring the TIR of the main bearing surfaces after a first group of the pin surfaces is hardened, a circuit for determining the relationship of the measured TIR and a desired value of TIR and then a circuit for adjusting the heating power for the second group of pins to move the TIR toward the desired value. In this aspect of the invention, the desired TIR is less than 0.015 inches, the first group of pins comprises pins 2 and 3 and the second group of pins comprises pins 1 and 4.
Yet another aspect of the invention is the provision of an apparatus for inductively heating and quench hardening the bearing surfaces of a crankshaft for an internal combustion engine. The apparatus includes a memory device with a data table indexed during each arcuate increment of rotation of the crankshaft. The data table contains a series of output signals for the heating power for the heating cycle for each of the surfaces. The series of signals over the cycle defines a heating profile. A device indexes the table each arcuate increment of the crankshaft rotation. The arcuate increments are less than 30 degrees and more particularly less than 20 degrees. In practice the increments are about 10 degrees.
Still a further aspect of the present invention is the provision of a method for hardening the concentric main bearing surfaces and orbital pin bearing surfaces of a crankshaft for an internal combustion engine rotatable about a common center axis of the main bearing surfaces. This method involves encircling each one of the surfaces to be hardened with an inductor, preferably extending over substantially less than 180 degrees of the surface, and riding on the surface, connecting the inductor to a high frequency power source with a power controller to cause the power source to direct a given power to the inductor at given rotational heating positions of the crankshaft, providing a quench head to direct liquid toward the surface encircled by the inductor, controlling the flow of a quenching liquid to the head after the surface has been heated by the inductor, counter balancing the inductor for controlling the riding force of the inductor against the surface encircled by the inductor and controlling the power controller and the flow controller for each of the surfaces encircled by the inductor and at rotatable positions in arcuate increments of less than 30 degrees. This method is further practiced by controlling the counter balancing for each inductor at the same rotational increments. The counter balancing provides a riding force in the general range of 15-30 pounds. At the inductors for the pin bearing surfaces the quench flow is continuous over a given number of rotational increments amounting to at least 360 degrees of rotation of the crankshaft and then is pulsed to complete the quenching cycle.
Another aspect of the present invention is the provision of a method for hardening the concentric main bearing surfaces and orbital pin surfaces of a crankshaft for an internal combustion engine. The method comprises providing a first multi-surface hardening station, simultaneously induction heating of the main bearing surfaces in the first station, and then quench hardening all of the main bearing surfaces simultaneously. A second multi-surface hardening station is used for inductively heating and quench hardening pins 2 and 3, while a third multi-surface hardening station is used for inductively and quench hardening pins 1 and 4. In this manner, the natural shift of TIR during the first two stations is overcome by adjusting the heat for hardening of pins 1 and 4 in the third processing station.
Yet another aspect of the invention is a method for hardening the orbital pin bearing surfaces of a crankshaft for an internal combustion engine. The method comprises providing an orbital inductor to heat each of the pins, providing an orbital quenching head with a supply of quenching liquid with a controller to direct flow with a given quantity of quench liquid to the head and against the heated pin surface and controlling the flow during a quenching cycle. The quenching cycle involves generally continuous liquid flow for at least 360 degrees rotation of the crankshaft and then pulsed flow to harden the surface. Sufficient internal heat is retained for slight tempering of the hardened surface.
Another aspect of the present invention is a method for hardening orbital successive pin bearing surfaces 1, 2, 3 and 4 of a crankshaft for an internal combustion engine, the crankshaft having hardened main bearing surfaces. The method includes measuring the TIR of the main bearing surfaces after a first group of the pin surfaces are hardened, determining the relationship of the measured TIR and a desired value of TIR and then adjusting the heating power for the second group of pins to move the TIR toward the desired value. The first group of pins comprises pins 2 and 3 whereas the second group of pins comprises pins 1 and 4.
Still a further aspect of the present invention is a method for inductively heating and quench hardening the bearing surfaces of a crankshaft for an internal combustion engine. The method includes providing a memory device with a data table indexed during each arcuate increment of rotation of the crankshaft, wherein the data table contains a series of output signals for the heating power for the heating cycle of each surface. The series of signals over the heating cycle defines a heating profile for each rotation of the bearing surface. The method involves indexing the table each arcuate segment of the crankshaft rotation. Furthermore, the method includes changing the profile based upon the final tempered hardness of the surface over the heating cycle before the profile is used for the final production run.
Still a further aspect of the invention is the provision of an apparatus for hardening the concentric main bearing surfaces and orbital pin bearing surfaces of a crankshaft for an internal combustion engine, which apparatus comprises an inductor for encircling each one of the surfaces to be hardened over substantially less than a 180° of the surface and riding on the surface. The inductors are connected to a high frequency power source with a power controller to cause the power source to direct a given power to the inductor. A supply of quenching liquid is provide with a flow controller to direct a given quantity of quench liquid against the surface after the surface has been heated by the inductor. A counter balancing mechanism, with a counter balanced controller, is used for controlling the riding force of the inductor against the encircling inductor. A master controller MC causes the power source 100 to continuously heat main bearing surfaces 1, 3 and 5 and pulse heat main bearing surfaces 2 and 4.
A broad aspect of the present invention is the provision of an apparatus for hardening the cylindrical surface of a pin bearing of a crankshaft, which apparatus comprises means for developing a heat cycle profile with power levels at arcuate increments, an inductor for encircling the surface, preferably over substantially less than 180 degrees of the surface, a high frequency power source with a controller to implement the profile repeatedly during the successive rotations of the crankshaft to heat the surface. A quench head is used for directing quenching liquid against the surface after it has been heated. The quench head has a flow controller for directing quenching liquid through the head in a first continuous flow and then in a pulsed flow to quench the heated surface. This is accomplished in a manner to leave sufficient heat energy to automatically temper the surfaces and, thus, the associated fillets to a desired metallurgical condition around the pins.
Another broad aspect of the invention is related to hardening techniques for crankshaft bearing surfaces, including induction hardening a first bearing, which can be a pin bearing or a main bearing, using a first power profile, and measuring a crankshaft TIR after induction hardening the first bearing. The method further includes determining a second power profile at least partially according to the measured crankshaft TIR, and induction hardening a second bearing, whether a pin or main bearing, using the second power profile.
The invention is applicable to crank shafts of configurations different from the crankshaft shown in
The primary object of the present invention is the provision of an apparatus and method for hardening the axially spaced bearings of a crankshaft, which apparatus and method produces a crankshaft with a low TIR without subsequent processing.
Another object of the present invention is the provision of an apparatus and method, as defined above, which apparatus and method is controlled to produce the desired metallurgical characteristics around the cylindrical bearing surfaces utilizing an automatic tempering procedure instead of a subsequent tempering operation.
Still a further object of the present invention is the provision of an apparatus and method, as defined above, which apparatus and method adjust the heat during short arcuate increments. The same short arcuate increments are sensed and then used to adjust the quenching flow and/or the counter balancing position or force. In practice, the arcuate increments are less than 20 degrees and are preferably about 10 degrees. In this manner, the lag time of the power source can be identified and compensated for by changing the arcuate position of the defined heating profile before the profile is used for the production run.
Another object of the invention is an apparatus and method of induction heating and quench hardening the surfaces of the bearing of various crank shafts by controlling the heating and quenching at arcuate increments of less than 30 degrees and preferably less than 20 degrees. In practice the increments are about 10 degrees.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.
The present invention relates to an apparatus and method for hardening the axially spaced bearing surfaces of a crankshaft for a multi-cylinder internal combustion engine, such as crankshaft A for an eight cylinder engine as shown in
While the following embodiments are illustrated and described in the context of induction hardening the exemplary crankshaft A having 5 main and 4 interspersed pin bearings, the invention finds utility in association with induction hardening of any type of crankshaft having any number of pin and main bearings, wherein the invention is not limited to the illustrated embodiments. Moreover, the invention contemplates hardening of individual bearings or groups of bearings, which can be accomplished using two or more such sets, and the broad aspects of the invention are not limited to the number of groups in the illustrated examples, or the constituent members of the exemplary groups or sets described herein.
In the illustrated examples, the crankshaft bearing surfaces are inductively heated and then quench hardened with the objective of providing a straight, undistorted crankshaft with metallurgical characteristics for the individual cylindrical bearing surfaces constituting a tempered hardness. Representative crankshaft A includes axially spaced, cylindrical bearing surfaces 10, 12, 14, 16 and 18 for concentric main bearings M1, M2, M3, M4 and M5 and coaxial with axis x of the crankshaft. In accordance with standard design, shaft A includes cylindrical bearing surfaces 20, 22, 24 and 26 for pin bearings P1, P2, P3 and P4, respectively. The pin bearing surfaces orbit about axis x as shaft A is rotated during induction heating, quench hardening and automatic tempering of each of the individual bearing surfaces. As will be explained later, the main bearing surfaces are hardened in a first station. In this first station the inner main bearings M2, M3, M4 can be supported by steady rest devices 32, 34 and 36; however, these devices are optional and are not necessarily employed in the hardening of the main bearings in the first station used in performing the method of the present invention. The steady rests contact the lower portion of the inner bearing surfaces 12, 14 and 16 to support these rotating surfaces by using reactive support platform 40. The first station for hardening the concentric cylindrical surfaces constituting the main bearings is followed by a second station for hardening a first group of orbiting pin surfaces and a third station for hardening a second group of the cylindrical pin surfaces. The use of two separate stations for hardening the pin bearings facilitates an aspect of the invention capable of producing a crankshaft with a total indicator run out (TIR) within a prescribed specification, such as less than 0.015 inches. The novel procedure of hardening the main bearings first and then two separate groups of pin bearings allows the TIR to be held within the desired specification. Furthermore, the apparatus and method of the present invention uses diagnostic setup procedures shown in
Each of the bearing surfaces is inductively heated and then quench hardened by an inductor assembly having the structure generally described in Griebel U.S. Pat. No. 5,451,749. This type of inductor assembly is schematically illustrated as inductor B shown in
The apparatus and method for hardening the axially spaced cylindrical bearing surfaces of crankshaft A is performed by installation 200 schematically illustrated in
An aspect of the invention is hardening a first group of pin bearings and then measuring the run out. Thereafter, a second group of pin bearings is hardened. If the run out after hardening the first group of pin bearings is in an area indicating that subsequent normal hardening will not bring the crankshaft back into specification, the subsequent group of pin bearings is hardened using more or less power to move the run out into specification. This procedure is an important feature of the present invention. The first group of pin bearings comprises the inner pin bearings and the second group comprises the external pin bearings. Although a first station is illustrated, as previously mentioned, the main bearings may be hardened in two groups before crankshaft A is transferred to station 204.
After the main bearings have been inductively heated, they are quench hardened to a temperature allowing a certain amount of automatic tempering. To accomplish the desired metallurgical characteristics and the desired run out, the quenching procedure for each main bearing surface is controlled over an arcuate increment of 10 degrees of a quench cycle amounting to several revolutions of the crankshaft. The increments are less than 30 degrees and preferably less than 20 degrees. The quench hardening protocol is disclosed in
The pin bearings are quench hardened in stations 202, 204 of
The apparatus and method of the present invention controls the extent of final run out for crankshaft A by first hardening main bearings either in two separate stations or, preferably, in a single station 202. By a procedure set forth in
Another aspect of the invention provides methods for induction hardening internal combustion engine crankshaft bearing surfaces using tuned profiles for angularly incremented provision of power, quenching fluid, and inductor counter balancing as the treated crankshaft is rotated about the main bearing axis, by which an induction hardening process can be tailored to achieve a desired post-hardening metallurgy. This technique involves induction hardening one or more test crank shafts using initial profiles for power, quenching fluid flow rate, and/or inductor counterbalancing force which measuring various actual process values, such as applied inductor voltages, currents, quench flow rates, etc. at each associated control increment, and thereafter measuring one or more post-hardening crankshaft characteristics, such as hardened surface metallurgy, crankshaft TIR, and/or markings on the counter balance apparatus (e.g., shoe markings). One or more of the power, quench flow, and/or counter balance profiles are then adjusted according to one or more of the measured process profiles and/or crankshaft characteristics, and thereafter further crank shafts are hardened using the adjusted profiles. The process may be repeated any number of times to establish an optimized set of profiles for use in production hardening to achieve the desired metallurgical characteristics of a tempered hardened surface without requiring subsequent heat treatment of the bearing surfaces. One example is illustrated in
The heat or power profile are repeated over 360° of rotation and are monitored for changing each arcuate increment, which is less than 30° and more particularly less than 20°. In practice the increments are about 10°. This is shown for one pin in
The signal levels of heating, as well as adjusted quenching and counter balance, for the pin bearings are provided in the table shown in
The general system of the present invention for each hardening station used in installation 200 of
This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 60/821,412, filed Aug. 4, 2006, entitled APPARATUS AND METHOD FOR HARDENING BEARING SURFACES OF A CRANKSHAFT, the entirety of which is hereby incorporated by reference.
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Number | Date | Country | |
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20080041844 A1 | Feb 2008 | US |
Number | Date | Country | |
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60821412 | Aug 2006 | US |