The present invention relates to a method of and an apparatus for machining (processing) a crankshaft to burnish a shank of the crankshaft for vehicle engines or the like, and a crankshaft burnishing roller for burnishing a shank of a crankshaft by rollingly pressing an outer surface of the shank of the crankshaft.
Heretofore, it is known to burnish a shank of a crankshaft for engines for increased productivity and improved surface properties of the shank.
For example, Patent Document 1 discloses a technical idea for making the machining surface pressure of the burnishing roller applied from a burnishing roller to a shank lower at both ends of the burnishing roller than at the center thereof in order to prevent both ends of the shank of the crankshaft from being rounded.
Patent Document 1 discloses a roller burnishing apparatus for burnishing a crankshaft with a burnishing roller, the apparatus including a pair of support rollers by which a shank of the crankshaft is rotatably supported, a burnishing roller having a dimension substantially identical to the width of the shank, and a backup roller for engaging the burnishing roller to press the burnishing roller in rolling contact with the shank.
Patent Document 2 discloses a roller burnishing method and apparatus for burnishing a workpiece having a centrally concave shape that can easily be burnished with a roller. Convex regions of the workpiece are burnished to desired surface roughness by an ordinary burnishing roller, whereas the central concave region is used as an oil reservoir to allow itself to be supplied appropriately with lubricating oil for increased durability and operability.
The burnishing apparatus disclosed in Patent Document 2 comprises a pair of support rollers by which a pin of a crankshaft is rotatably supported, a support member supporting the support rollers, a burnishing roller for pressing the pin of the crankshaft remotely from the support rollers, and a bracket by which the burnishing roller is rotatably supported.
Patent Document 3 reveals a roller burnishing tool including a tool shank base of circular cross section which has a plurality of ridges disposed on an outer surface thereof. At least one of the ridges has side edges extending across a generatrix along the circumferential direction of the tool base. Each of the ridges is shaped such that the sum of the widths of the ridges as measured in the axial direction of the tool base remains essentially the same at any circumferential positions on the tool base.
According to the technical ideas disclosed in Patent Documents 1, 2, fillets for clearing the tool are formed at the axial ends of the shank of the crankshaft. The ends near the fillets are compressed when they are pressed by the burnishing roller to prevent round corners from being formed. The technical ideas disclosed in Patent Documents 1, 2 are based on the premise of a crankshaft with fillets.
If a shank of a crankshaft free of fillets is burnished by a burnishing roller as is the case with the present invention, then since it is not necessary to take into account the formation of round corners, it is requested that the conventional machining method be simplified to improve surface properties of the shank.
The burnishing apparatus disclosed in Patent Documents 1, 2 are complex in structure and highly costly to manufacture because they need a plurality of components including the pair of support rollers (support members), the backup roller, etc.
The roller burnishing tool disclosed in Patent Document 3 is advantageous in that if a shank (a surface be burnished) of a crankshaft has an oil hole defined therein, for example, then when the shank is burnished, the ridges of the roller burnishing tool tend to fall into the oil hole, damaging the surrounding edge of the opening of the oil hole.
Patent Document 1: Japanese Laid-Open Patent Publication No. 06-190718
Patent Document 2: Japanese Laid-Open Patent Publication No. 2004-276121
Patent Document 3: Japanese Laid-Open Patent Publication No. 04-115866
It is a general object of the present invention to provide an apparatus for machining a crankshaft to improve surface properties of a shank of the crankshaft which is free of fillets.
A major object of the present invention is to provide a method of machining a crankshaft to improve surface properties of a shank of the crankshaft which is free of fillets.
Another object of the present invention is to provide an apparatus for machining a crankshaft, the apparatus being simplified in structure and less costly to manufacture.
Still another object of the present invention is to provide a crankshaft burnishing roller for improving surface properties of a shank of a crankshaft which is free of fillets and for appropriately burnishing the shank even if an oil hole is defined therein.
According to the present invention, a pair of burnishing rollers, each substantially disk-shaped, is placed in opposite relation to each other across a shank of a crankshaft therebetween, and when the crankshaft is rotated about its own axis, the shank of the crankshaft is gripped and rollingly pressed by outer circumferential surfaces of the burnishing rollers.
According to the present invention, therefore, the shank has surface properties improved by a machining method which is simpler than heretofore. As a result, the surface properties of the shank of the crankshaft which is free of fillets are improved, and a crankshaft machining apparatus is simplified in structure and less costly to manufacture.
According to the present invention, furthermore, the burnishing rollers for rollingly pressing the shank of the crankshaft have outer circumferential surfaces having a plurality of ridges having respective crests axially spaced at equal intervals, and the crests of adjacent two of the ridges are spaced from each other by a distance which is greater than the inside diameter of an oil hole. Therefore, even if the oil hole is present in a region to be burnished, the ridges do not fall into the oil hole, and the surrounding edge of the oil hole is not damaged.
According to the present invention, therefore, the surface properties of the shank of the crankshaft which is free of fillets are improved, and even if the oil hole is present in the region to be burnished, the shank can appropriately be burnished.
In
The crankshaft machining apparatus 10 is mounted on the turret (or rotary tool base) of a turret lathe (or a machining center) which is controlled by a numerical control system, not shown. The crankshaft machining apparatus 10 comprises first and second adapters 12a, 12b displaceable in the directions of three axes X, Y, Z which are perpendicular to each other, a pair of burnishing rollers 16a, 16b rotatably supported respectively on rotational shafts 14 of the first and second adapters 12a, 12b, and first and second holding mechanisms 22a, 22b for engaging respective both axial ends of a crankshaft 18 (hereinafter referred to as workpiece 18) and holding the workpiece 18 such that the workpiece 18 can be rotated about its own axis by a rotary drive source M.
The burnishing rollers 16a, 16b are disposed in mutually opposite relation to each other linearly perpendicular to the axis of the workpiece 18 across a shank 24, which is a region to be burnished, of the workpiece 18 (see
Each burnishing roller 16a (16b) is of a substantially disk-like identical shape and has an outer circumferential surface 20 shaped like a single flat web. As shown in
The round corner 26 of each burnishing roller 16a (16b) may have a radius r2 of curvature smaller than a radius r1 of curvature of round corners 48 (to be described later) on the both axial ends of the shank 24 as the region to be burnished (r1>r2).
The first and second adapters 12a, 12b comprise respective slide members 32 displaceable in the direction indicated by the arrow A in unison with the burnishing rollers 16a, 16b against the spring forces of pressure control springs (to be described below), not shown, a pair of respective guide rods 34a, 34b for guiding the slide members 32, pressure control springs, not shown, for biasing the slide members 32 toward the workpiece 18, and respective knobs 36 for adjusting the spring forces of the pressure control springs (see
When the operator grips the knobs 36 and turn the knobs 36 in certain directions, the pressure control springs are set to an initial set load (a preloading pressure, to be described later).
As shown in
The adapters 12a, 12b may be of either the type in which the burnishing roller 16a (16b) is cantilevered on one side (see
The crankshaft machining apparatus 10 according to the present embodiment is basically constructed as described above. Operation and advantages of the crankshaft machining apparatus 10 will be described below.
First, a process of manufacturing the crankshaft 18 will briefly be described below.
After a forged blank is machined on a lathe, oil holes are bored in the blank, for example, and then the shank 24 is burnished (plastically machined) by the burnishing rollers 16a, 16b of the crankshaft machining apparatus 10 which grip the shank 24 and are pressed in rolling contact with the shank 24. Then, the workpiece is heat-treated by gas nitriding (GSN) or high-frequency heating (HFQ) or the like, after which the workpiece is finished and finally inspected into a product.
As described above, the burnishing process based on the roll-pressing operation of the crankshaft machining apparatus 10 is performed as a process preceding the heat-treatment (GSN or HFQ) on the crankshaft.
Operation of the crankshaft machining apparatus 10 will be described below.
After the workpiece 18 is set and rotatably supported on the first and second holding mechanisms 22a, 22b, the knobs 36 are turned to adjust the spring forces of the non-illustrated pressure control springs to set the preloading pressure to a prescribed value. The preloading pressure refers to a pressing force applied to the shank 24 when the shank 24 as the region to be burnished is gripped and pressed by the burnishing rollers 16a, 16b that are disposed in mutually opposite relation to each other. Stated otherwise, the preloading pressure refers to a machining surface pressure which the shank 24 receives from the burnishing rollers 16a, 16b. The preloading pressure may be set to a level depending on the surface roughness which is required of the crankshaft 18.
It is assumed that when the burnishing rollers 16a, 16b are in their initial positions, they are spaced from each other by a predetermined distance radially from the shank 24 of the workpiece 18 and are waiting in opposite positions which are spaced a predetermined distance linearly perpendicular to the axis of the workpiece 18.
After the above preparatory stage, the rotary drive source M is energized to rotate the workpiece 18 about its own axis at a predetermined angular velocity. Then, based on a control signal from the non-illustrated numerical control system, the first and second adapters 12a, 12b are displaced toward the workpiece 18 in respective directions toward each other, and an axial central area of the shank 24 is gripped by the burnishing rollers 16a, 16b.
Since the workpiece 18 is rotating about its own axis, the burnishing rollers 16a, 16b are caused to rotate in respective opposite directions by the rotating workpiece 18. The shank 24 is burnished by the rotating burnishing rollers 16a, 16a as the outer circumferential surfaces 20 thereof rollingly press the surface to be burnished of the shank 24. According to the burnishing process, small surface irregularities, not shown, on the outer surface of the shank 24 are flattened to provide good surface roughness.
When the burnishing rollers 16a, 16b contact the shank 24, they should be brought into oblique contact with the surface to be burnished of the shank 24 (see
After the burnishing rollers 16a, 16b are linearly positioned across the shank 24 therebetween and start rollingly pressing the shank 24, one of the burnishing rollers 16a (16b) and the other burnishing roller 16b (16a) are caused to slide in respective opposite directions (directions away from each other parallel to the axis of the crankshaft 18) to rollingly press the region to be burnished of the shank 24.
As described above, after the central area of the region to be burnished is gripped by the burnishing rollers 16a, 16b, the burnishing rollers 16a, 16b are displaced in respective directions away from each other to burnish the region to be burnished. Consequently, the burnishing time is shortened for higher efficiency.
Since the burnishing rollers 16a, 16b are caused to slide in respective opposite directions, the round corners 48 on the both axial ends of the shank 24 as the region to be burnished can also appropriately be rollingly pressed by the round corners 26 of the burnishing rollers 16a, 16b (see
The shank as the region to be burnished comprises pins and journals of the crankshaft 18.
As shown in
According to the present embodiment, the burnishing rollers 16a, 16b are disposed in mutually opposite relation to each other across the shank 24 of the crankshaft 18, and while the crankshaft 18 is rotating, the shank 24 of the crankshaft 18 is burnished by being gripped and rollingly pressed by the burnishing rollers 16a, 16b. Consequently, the surface properties of the shank 24 of the crankshaft 18 which is free of fillets are improved, and the crankshaft machining apparatus is simplified in structure and less costly to manufacture.
The crankshaft machining apparatus 110 includes a pair of burnishing rollers 116a, 116b rotatably supported on the respective rotational shafts 14 of the first and second adapters 12a, 12b which are displaceable in the directions of three axes X, Y, Z which are perpendicular to each other.
The burnishing rollers 116a, 116b are disposed in mutually opposite relation to each other linearly perpendicular to the axis of the workpiece 18 across the shank 24, which is a region to be burnished, of the workpiece 18 (see
Each burnishing roller 116a (116b) is of a substantially disk-like identical shape and has an outer circumferential surface for rollingly pressing the shank 24. The outer circumferential surface of each burnishing roller 116a (116b) has first through fourth ridges 120a through 120d having respective crests spaced at equal intervals along the axis of the burnishing roller (see
The number of the ridges is not limited to four. Rather, the outer circumferential surface of each burnishing roller 116a (116b) may have at least three ridges. The outer surface of each of the first through fourth ridges 120a through 120d for contacting the shank 24 of the crankshaft 18 has a round corner 28 having an arcuate cross-sectional shape. The round corner 28 has a radius r2 of curvature which is smaller than the radius r1 of curvature of the round corners 48 on the both axial ends of the shank 24 (see
The adapters may be of either the type in which the burnishing roller 116a (116b) is cantilevered on one side (see
The crankshaft machining apparatus 110 incorporating the burnishing rollers 116a, 116b according to the present embodiment is basically constructed as described above. Operation and advantages of the crankshaft machining apparatus 110 will be described below.
After a predetermined preparatory process, the rotary drive source M is energized to rotate the workpiece 18 about its own axis at a predetermined angular velocity. Then, based on a control signal from the non-illustrated numerical control system, the first and second adapters 12a, 12b are displaced toward the workpiece 18 in respective directions toward each other, and an axial central area of the shank 24 is gripped by the burnishing rollers 116a, 116b.
Since the workpiece 18 is rotating about its own axis, the burnishing rollers 116a, 116b are caused to rotate in respective opposite directions by the rotating workpiece 18. The shank 24 is burnished by the rotating burnishing rollers 116a, 116a as the first through fourth ridges 120a through 120d on the outer circumferential surfaces 20 thereof rollingly press the surface to be burnished of the shank 24. According to the burnishing process, small surface irregularities, not shown, on the outer surface of the shank 24 are flattened to provide good surface roughness.
When the outer circumferential surfaces of the burnishing rollers 116a, 116b contact the shank 24, they should be brought into oblique contact with the surface to be burnished of the shank 24 (see
After the burnishing rollers 16a, 16b are linearly positioned across the shank 24 therebetween and start rollingly pressing the shank 24, one of the burnishing rollers 116a (116b) and the other burnishing roller 116b (116a) are caused to slide in respective opposite directions (directions away from each other parallel to the axis of the crankshaft 18) to rollingly press the region to be burnished of the shank 24.
As described above, after the central area of the region to be burnished is gripped by the burnishing rollers 116a, 116b, the burnishing rollers 116a, 116b are displaced in respective directions away from each other to burnish the region to be burnished. Consequently, the burnishing time is shortened for higher efficiency.
Since the burnishing rollers 116a, 116b are caused to slide in respective opposite directions, the round corners 48 on the both axial ends of the shank 24 as the region to be burnished can also appropriately be rollingly pressed by the round corners 28 of the first ridges 120a (or the fourth ridges 120d) of the burnishing rollers 116a, 116b (see
As shown in
According to the present embodiment, the burnishing rollers 116a, 116b are disposed in mutually opposite relation to each other across the shank 24 of the crankshaft 18, and while the crankshaft 18 is rotating, the shank 24 of the crankshaft 18 is burnished by being gripped and rollingly pressed by the burnishing rollers 116a, 116b. Consequently, the surface properties of the shank 24 of the crankshaft 18 which is free of fillets are improved, and the crankshaft machining apparatus is simplified in structure and less costly to manufacture.
According to the present embodiment, furthermore, the first through fourth ridges 120a through 120d having the respective crests spaced at equal intervals along the axis of the burnishing roller 116a are disposed on the outer circumferential surface of the burnishing roller 116a (116b), and the distance S by which the crests of adjacent two of the first through fourth ridges 120a through 120d are spaced is greater than the inside diameter T of the oil hole 126. Therefore, even if the oil hole 126 is present in the region to be burnished, the first through fourth ridges 120a through 120d do not fall into the oil hole 126, and the surrounding edge of the oil hole 126 is not damaged.
According to the present embodiment, consequently, even if the oil hole 126 is present in the region to be burnished, the region to be burnished can appropriately be burnished to provide good surface roughness.
Number | Date | Country | Kind |
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2005-175184 | Jun 2005 | JP | national |
2005-175190 | Jun 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/312048 | 6/15/2006 | WO | 00 | 12/14/2007 |