Patent Grant
7033245
1. Field of the Invention
The present invention relates to a lapping apparatus and a lapping method for film-lapping (hereinafter simply called “lapping”) a pre-machined surface of a work by a lapping film (hereinafter simply and occasionally called “film”) provided with abrasive grains.
2. Description of the Related Art
There has been recently conducted lapping by a lapping film having one surface provided with abrasive grains, in case of finishing a work having a cross-sectionally arcuate outer peripheral surface, such as pin portions and journal portions of a crankshaft or cam-lobe portions and journal portions of a camshaft.
Such lapping is conducted by covering a pre-machined surface of a work by a lapping film, and by machining the work by an abrasive-grained surface of the film while rotating the work in a state where the film is pressed from its back surface by a shoe toward the work. In addition to a mechanism for pressing a shoe toward a work via film, lapping apparatus has a mechanism for rotationally driving the work, and an oscillation mechanism for applying oscillation in an axial direction of the work to at least one of the work and lapping film (see FIG. 1 and FIG. 2 of Japanese Patent Application Laid-Open No. 7-237116).
Works include one having a pre-machined surface formed with an open holed portion. For example, pin portions and journal portions of a crankshaft are formed with lubricant holes as holed portions penetrating the crankshaft in a direction perpendicular to the axial direction of the crankshaft, respectively. Such lubricant holes are to preferably have mouth-base edges in cross-sectionally rounded shapes, respectively, so as not to damage the engaged components (such as bearing metal).
Thus, mouth-base edges of lubricant holes have been conventionally formed with rounded portions, by conducting additional machining for pressing abrasive-grained surfaces of lapping films to mouth bases of lubricant holes of a work by so-called soft shoes, after once lapping the work by pressing abrasive-grained surfaces of lapping films to the pre-machined surfaces of the work by so-called hard shoes, respectively.
However, because such machining by the hard shoes is conducted independently of the machining by the soft shoes, it is required to prepare a lapping apparatus having hard shoes and another lapping apparatus having soft shoes, thereby deteriorating a machining efficiency and requiring a relatively longer machining time. Further, the increased number of equipments causes increased equipment cost, machining cost and the like.
Moreover, since the machining by soft shoes is conducted after improving shape accuracies (such as circularity and straightness) of pre-machined surfaces by machining based on hard shoes, the shape accuracies of the pre-machined surfaces may be considerably deteriorated due to the machining by the soft shoes.
Furthermore, the lapping films may excessively bite into the mouth-base edges of lubricant holes upon machining by soft shoes, thereby possibly and exemplarily causing separation of abrasive grains.
Meantime, in the conventional lapping apparatus, the shoe pressing force, work rotational speed and oscillation speed are kept constant during lapping.
Relatedly and in case of a work having a pre-machined surface in a cross-sectionally non-circular shape, radii from the axis (center of rotation) to the pre-machined surface are different region by region. For example, each cam-lobe portion of a camshaft is provided with a plurality of regions exemplarily including a base region establishing a base circle (reference circle), a top region defining a lift of the cam, and event regions extending from the base region to the top region, such that the radius from the axis of the work becomes longer from the end of the base region toward the top region.
Since circumferential speeds vary proportionally to radii when angular velocities are constant, the contact time per unit circumferential length of the outer peripheral surface as the pre-machined surface of the work with a film becomes different region by region when the rotational speed of the work is constant. In this situation, also the contact surface pressure of the film against the pre-machined surface becomes different region by region.
This leads to non-uniform machined amounts per unit circumferential length at the pre-machined surface of the cam-lobe portion, thereby resultingly causing a problem of non-uniform surface roughness of the pre-machined surface. Particularly, the surface roughness of the event regions becomes larger than that of the top region and base region. Since these event regions are important ones for exemplarily starting to open and close valves of an engine, larger surface roughness may possibly obstruct a smooth operation of the valves.
The present invention has been carried out to solve the problems accompanying to the above-mentioned related art. Therefore, it is an object of the present invention to provide a lapping apparatus and a lapping method capable of rapidly machining even a work having a pre-machined surface formed with an open holed portion such as a lubricant hole, of fully restricting increase of machining cost and deterioration of shape accuracy (such as circularity and straightness), and of reducing separation of abrasive grains from a lapping film.
It is another object of the present invention to provide a lapping apparatus and a lapping method capable of uniformalizing machined amounts per unit circumferential length at a pre-machined surface of a work, thereby equalizing the surface roughness of the pre-machined surface.
The first aspect of the present invention provides a lapping apparatus lapping a work having a pre-machined surface, comprising: a lapping film which includes a thin substrate having a surface provided with abrasive grains; a shoe disposed at a back surface side of the lapping film; a shoe driving unit which drives the shoe toward the work in order to press the abrasive-grained surface of the lapping film to the pre-machined surface of the work; a rotational driving unit which drives the work rotationally; a detecting unit which detects the position of the rotating work in the rotating direction; and a controlling unit which controls the pressing force of the shoe driving unit so as to drive the shoe correspondingly to the position of the work in the rotating direction during machining.
The second aspect of the present invention provides a lapping method for lapping a work having a pre-machined surface while rotationally driving the work in a state where an abrasive-grained surface of a lapping film is pressed to the pre-machined surface by a shoe, comprising: detecting a rotational position of the rotating work; and controlling the pressing force of the shoe correspondingly to the position of the work in the rotating direction during machining.
The third aspect of the present invention provides a lapping apparatus lapping a work having a pre-machined surface, comprising: a lapping film which includes a thin substrate having a surface provided with abrasive grains; a shoe disposed at a back surface side of the lapping film; shoe driving means for driving the shoe toward the work in order to press the abrasive-grained surface of the lapping film to the pre-machined surface of the work; rotational driving means for driving the work rotationally; detecting means for detecting the position of the rotating work in the rotating direction; and controlling means for controlling the pressing force of the shoe driving means so as to drive the shoe correspondingly to the position of the work in the rotating direction during machining.
The invention will now be described with reference to the accompanying drawings wherein;
There will be explained hereinafter embodiments of the present invention with reference to the drawings.
Generally, with reference to
The lapping apparatus 1 will be described hereinafter in detail.
Referring to
The oscillation unit 50 includes an eccentric rotor 51 abutting on an end surface of the table 49, and an oscillation motor M2 for rotationally driving the eccentric rotor 51. The oscillation unit 50 is provided with an elastic unit 52 such as a spring for applying a reactive elastic force for pressing the table 49 toward the eccentric rotor 51 so as to normally abut the eccentric rotor 51 onto the end surface of the table 49. Changing the rotational speed of the oscillation motor M2 causes an oscillation speed Vo to be set at a desired speed (such as 10 Hz). The amplitude of the oscillation is determined based on an eccentricity amount of the eccentric rotor 51 relative to the axis of the oscillation motor M2. This eccentricity amount is about 1 mm, and the amplitude of the oscillation is about 2 mm. Note, the eccentricity amount of the eccentric rotor 51 is adjustable, by a technique such as a variable number of inserted adjusting plates (not shown). The eccentric rotor 51 has a shaft attached with a rotary encoder S2 for detecting the rotational position of the eccentric rotor 51.
While various types of lapping films 11 are existent, the lapping film 11 in this embodiment is constituted of: a substrate comprising a material having an extremely inextensible property such as polyester having a thickness of 25 μm to 130 μm; and numerous abrasive grains (concretely, aluminum oxide, silicon carbide, diamond and the like) having particle sizes on the order of several μm to 200 μm, attached to one surface of the substrate by an adhesive. The abrasive grains may be adhered the one surface of the substrate over the whole thereof, or leaving intermittently defined areas of predetermined widths having no abrasive grains thereon. For avoiding slippage relative to the first and second shoes 71, 72, the other surface of the substrate is applied with a back coating comprising a resistive material (not shown) such as rubber or synthetic resin, or applied with an antislipping treatment as the case may be.
Referring to
The coupled upper arm 22 and lower arm 23 of each pair are pivotably disposed via supporting pins 24, respectively, such that the tip ends of these arms arranged with the first shoes 71 and second shoe 72 are relatively openable and closable in the Z direction. The upper arm 22 has a rear end portion pin-coupled with one end of a fluid pressure cylinder 25 such as operated by oil pressure or air pressure, and the lower arm 23 has a rear end portion pin-coupled with a tip end of a piston rod 26. Expanding the piston rod 26 from its contracted state pivots the upper and lower arms 22, 23 in directions for closing the tip end portions of these arms around the supporting pins 24, respectively, into the closed state shown in
In the illustrated embodiment, the first shoes 71 comprise hard shoes and the second shoe 72 comprises a soft shoe. Each hard shoe 71 is formed of a hard material such as grindstone or steel. Each lapping film 11 is backed up by the hard shoes 71 and the abrasive-grained surface of the lapping film 11 is pressed to the pre-machined surface 65, thereby finishing the pre-machined surface 65 as a cylinder surface with a higher shape accuracy (such as circularity and straightness). Meantime, the soft shoe 72 is formed of a material such as urethane, which is softer than the hard shoe 71 and is elastically deformable. The soft shoe 72 is elastically deformed, and contacts with the pre-machined surface 65 through a relatively wide area, actually via film 11. Although the soft shoe 72 has a lower ability to correct the work shape than the hard shoes 71, this soft shoe has a superior function for reducing the surface roughness of the pre-machined surface 65. In the first embodiment, this soft shoe 72 is used to form a rounded portion 68 at each mouth-base edge 67a (see
While the shoes are classified into concave shoes and convex shoes, each hard shoe 71 is a concave one having a concave tip end portion and each soft shoe 72 is formed into a convex one having a convex tip end portion. The soft shoe 72 of this embodiment is preferably one specifically used to form the rounded portion 68 at the mouth-base edge 67a, such as a convex shoe having a spherical shape.
The hard shoes 71 are plurally attached to shoe cases 73 having inner peripheral surfaces opposing to the pre-machined surface 65, respectively. In the illustrated embodiment, two hard shoes are attached to each of upper and lower shoe cases 73. The shoe cases 73 are housed in concaves 27 formed at the tip end portions of the upper and lower arms 22, 23, respectively, in a manner capable of advancing and retracting relative to the work W. Each shoe case 73 is moved while its outer surface is guided by an inner surface of the associated concave 27. Further, each shoe case 73 has a back surface arranged with a work clamping spring 74 comprising a compression coil spring. The hard shoes 71 are applied with reactive elastic forces of the work clamping springs 74 and pressed to the pre-machined surface 65 via lapping film 11, respectively.
As shown in
As conceptually shown in
The dimensions of the eccentric cam 31 such as cam lift and base circle diameter are determined based on the moving distance of the rod 76, i.e., the moving distance of the soft shoe 72, the pressing force of the soft shoe 72, and the like. Further, the position of center of rotation of the eccentric cam 31 is made adjustable in the X direction in the applicable figure, so that the pressing force of the soft shoe 72 can be adjusted even by using the same eccentric cam 31.
Referring to
It is ideal that the timing for driving the soft shoe 72 from its inoperative position to its operative position is only a moment where the rotating crankshaft 62 has just reached the reference position. However, since the crankshaft 62 is normally rotated, simply driving the soft shoe 72 to its operative position only at the moment where the crankshaft 62 has reached the reference position, may fail to uniformly machine the entire circumference of the mouth base 67 of the lubricant hole 66 even with a slight synchronous discrepancy between the rotation of the crankshaft 62 and the movement of the soft shoe 72. As such, it is desirable to drive the soft shoe 72 to its operative position before the crankshaft 62 reaches the reference position, and to hold the soft shoe 72 at the operative position even after the crankshaft 62 has reached the reference position.
The lapping for the mouth base 67 is effected while the soft shoe 72 contacts with the mouth base 67. This makes it enough for the soft shoe 72 to be driven to its operative position, only within a rotational angle range of the crankshaft 62 where a certain portion of the mouth base 67 is allowed to contact the soft shoe 72 in this operative position. It is assumed here that the leading portion of the mouth base 67 in the rotating direction abuts onto the soft shoe 72 at a rotational angle of θ=−α° before the crankshaft 62 reaches the reference position (θ=0°) as shown in
Nonetheless, the lapping to be performed by pressing the lapping film 11 by the soft shoe 72 is preferably delimited to the mouth base 67 itself of the lubricant hole 66 and the vicinity of the mouth base 67. This is to prevent the shape accuracy (such as circularity and straightness) of the pre-machined surface 65 from being deteriorated due to machining by the soft shoe 72. It is thus desirable to drive the soft shoe 72 to its operative position, within a range narrower than the above range (2α°). As conceptually shown in
In the lapping apparatus 1 of this embodiment, the rotational position of the crankshaft 62 is detected by the rotary encoder S1 in order to detect the position of each lubricant hole 66 of the rotating crankshaft 62, and the operation of the associated driving unit 30 is controlled to drive the associated soft shoe 72 to its operative position or inoperative position correspondingly to the position of the associated lubricant hole 66 during machining, so that the lapping to be performed by pressing the lapping film 11 by the soft shoe 72 is delimited to the vicinity of the mouth base 67 of the lubricant hole 66.
The above control will be explained with reference to
Referring to
The changing control of positions of the soft shoes 72 is conducted by controlling the operations of the shoe driving units 30 including the eccentric cams 31 and motors M4, such that the soft shoes 72 are brought into and out of the associated mouth bases 67 synchronizedly with the positions of the lubricant holes 66, respectively.
Concretely, the controller 100 outputs controlling signals to the motors M4 for controlling rotations thereof, such that the top region of each applicable eccentric cam 31 abuts on the rear end of each associated rod 76 when the rotating crankshaft 62 has reached the applicable reference position (θ=0°). This causes each soft shoe 72 to reach its operative position in order to press the abrasive-grained surface of the associated lapping film 11 to the associated mouth base 67, thereby forming the rounded portion 68 at the mouth-base edge 67a. The radius of each rounded portion 68 is exemplarily on the order of 10 μm to 20 μm.
There will be explained hereinafter an operation of this embodiment.
Firstly, the crankshaft 62 is supported between the headstock 42 and tailstock 46, and the upper and lower arms 22, 23 are moved to positions of the pin portions 63 and journal portions 64, respectively. At this time, the fluid pressure cylinders 25 have contracted the associated piston rods 26 in order to hold the associated upper arms 22 and lower arms 23 at the opened positions, respectively. Thereafter, the fluid pressure cylinders 25 are operated to expand the associated piston rods 26, thereby pivoting the upper and lower arms 22, 23 in the closing directions, respectively. These closing pivotal movements cause the lapping films 11 to be set on the pre-machined surfaces 65, respectively.
While the upper and lower arms 22, 23 are pivoted and closed, the motors M3 are operated to rotate the wind-up reels 16, respectively. The lapping films 11 are fed by predetermined amounts so that unused abrasive-grained surfaces are set onto the pre-machined surfaces 65, respectively. Thereafter, the wind-up reels 16 are rotated after locking the feeding reels 15 by the locking devices near them, so that the lapping films 11 are applied with predetermined tensions. Next, the wind-up reels 16 are locked by the locking devices near them, thereby bringing the lapping films 11 into states applied with tensions without any slack.
Further, upon clamping the crankshaft 62, the hard shoes 71 are applied with the reactive elastic forces of the associated work clamping springs 74 and pressed to the pre-machined surfaces 65, respectively.
Moreover, the crankshaft 62 is rotated around its axis by operating the rotational driving unit 40 while applying oscillation to the crankshaft 62 along the axial direction thereof by operating the oscillation unit 50, so that the abrasive-grained surfaces of lapping films 11 are pressed to the pre-machined surfaces 65 by the hard shoes 71, respectively, thereby lapping the pre-machined surfaces 65 throughout the whole thereof. The machining for the whole of the pre-machined surfaces 65 is conducted by the hard shoes 71, thereby improving the machining efficiency.
During this machining, the controller 100 controls the operations of the shoe driving units 30 to synchronize the movements of the soft shoes 72 with the rotation of the crankshaft 62. The rotary encoder S1 detects the rotational position of the crankshaft 62, and the controller 100 decides the positions of the lubricant holes 66 based on the rotational position of the crankshaft 62 so as to variably control the positions of the soft shoes 72 to the operative positions or inoperative positions correspondingly to the positions of the associated lubricant holes 66 during machining, respectively. Namely, the controller 100 controls the operations of the motors M4 to rotate the eccentric cams 31 such that the top region of each applicable eccentric cam 31 abuts on the rear end of each associated rod 76 when the rotating crankshaft 62 has reached the applicable reference position (θ=0°).
This causes each soft shoe 72 to reach its operative position in order to press the abrasive-grained surface of the associated lapping film 11 to the associated mouth base 67, thereby forming the rounded portion 68 at the mouth-base edge 67a.
During the lapping, the crankshaft 62 is forwardly rotated by a predetermined number of revolutions (such as 5 revolutions), and thereafter rearwardly rotated by the same number of revolutions. Changing the rotating direction eliminates clogging due to lapping films 11, maintains the due performance, and causes the entire circumferences of the mouth bases 67 to be uniformly machined.
In this way, the machining for the entire circumferences of the pre-machined surfaces 65 by the hard shoes 71 and the machining for the mouth bases 67 by the soft shoes 72 are conducted by the single set of lapping apparatus, thereby enabling to improve the machining efficiency and to shorten the time required for the machining. Further, the number of equipments is not increased, thereby also allowing to restrict an increase of equipment cost and machining cost.
Moreover, the lapping to be conducted by pressing the lapping film 11 by the associated soft shoe 72 is delimited to the vicinity of the mouth base 67 of the associated lubricant hole 66, thereby excluding a risk that the shape accuracy (such as circularity and straightness) of each pre-machined surface 65 is deteriorated due to machining by the soft shoe 72. Further, since the machining by the hard shoes 71 for improving the shape accuracy (such as circularity and straightness) of each pre-machined surface 65 and the machining by the associated soft shoe 72 for forming the rounded portion 68 at the mouth-base edge 67a are conducted in the same process, the function by the hard shoes 71 for correcting the work shape is to be also effected to those sites having been machined by the soft shoe 72. Also from this standpoint, there is no risk that the shape accuracy of each pre-machined surface 65 is deteriorated due to the machining by the associated soft shoe 72.
In case of a comparative example where additional machining for pressing an abrasive-grained surface of a lapping film to the mouth base 67 by a soft shoe is conducted after machining by hard shoes, the lapping film excessively bites into the mouth-base edge 67a upon machining by the soft shoe, thereby exemplarily causing separation of abrasive grains.
Contrary, since the lapping by the soft shoe 72 is delimited to the vicinity of the mouth base 67 of each lubricant hole 66, the lapping film 11 does not excessively bite into the mouth-base edge 67a, thereby reducing separation of abrasive grains from the lapping film 11 and reducing the number of locations of separation.
While the crankshaft 62 has many pin portions 63 and journal portions 64, the lapping is simultaneously conducted for these pin portions 63 and journal portions 64. Upon completing the lapping, the fluid pressure cylinders 25 are operated to contract the associated piston rods 26 in order to pivot the upper and lower arms 22, 23 in the opening directions, respectively, into states where the crankshaft 62 can be taken out of them. After taking out the crankshaft 62, another crankshaft 62 is set, thereby enabling to start the same lapping.
As described above, the lapping apparatus 1 according to the first embodiment includes: the lapping films 11; the first shoes 71 for pressing the abrasive-grained surfaces of the lapping films 11 to the pre-machined surfaces 65, respectively; the second shoes 72 for pressing the abrasive-grained surfaces of the lapping films 11 to the mouth bases 67 of the lubricant holes 66 as the holed portions, respectively; the shoe driving units 30 for driving the second shoes 72 between the operative positions where the second shoes 72 are pressed to the mouth bases 67 of the lubricant holes 66, respectively, and the inoperative positions where the second shoes 72 are separated away from the mouth bases 67 of the lubricant holes 66, respectively; the rotational driving unit 40 for rotationally driving the work W; the rotary encoder S1 for detecting the rotational position of the work W in order to detect the positions of lubricant holes 66 of the rotating work W; and the controller 100 for controlling the operation of the shoe driving units 30 so that the second shoes 72 are driven to the operative positions or inoperative positions correspondingly to the positions of the lubricant holes 66 during machining, respectively. Further, the lapping to be conducted by pressing the lapping films 11 by the second shoes 72 is delimited to the vicinity of the mouth bases 67 of the lubricant holes 66. Thereby, the lapping apparatus 1 according to the first embodiment exhibits such an effect that even a work W having pre-machined surfaces 65 formed with opened lubricant holes 66 can be rapidly machined while enabling to fully restrict increase of machining cost and deterioration of shape accuracy (such as circularity and straightness), and to reduce separation of abrasive grains from the lapping films 11 as well as the number of locations of separation.
Further, since the first shoes 71 comprise hard shoes and the second shoes 72 comprise soft shoes, the machining by the hard shoes 71 for improving the shape accuracy (such as circularity and straightness) of each pre-machined surface 65 and the machining by the associated soft shoe 72 for forming the rounded portion 68 at the mouth-base edge 67a are conducted in the same process, so that the function by the hard shoes 71 for correcting the work shape is to be also effected to those sites having been machined by the soft shoe 72. Thus, there is no risk that the shape accuracy of each pre-machined surface 65 is deteriorated due to the machining by the associated soft shoe 72.
Moreover, the holed portions exemplarily comprise the lubricant holes 66, so that the pre-machined surfaces 65 of pin portions 63, journal portions 64 and the like of the crankshaft 62 having such lubricant holes 66 can be preferably lapped.
Furthermore, the lapping film 11 is inextensible and deformable, thereby allowing the work W to be preferably lapped.
The lapping apparatus 1 of this embodiment embodies a lapping method for lapping a work W having pre-machined surfaces 65 formed with opened lubricant holes 66 while rotationally driving the work W in a state where the abrasive-grained surfaces of the lapping films 11 are pressed to the pre-machined surfaces 65 by the first shoes 71, respectively, comprising the steps of: detecting positions of the lubricant holes 66 of the rotating work W, by the rotary encoder S1; and driving, the second shoes 72 for pressing the abrasive-grained surfaces of the lapping films 11 to the mouth bases 67 of the lubricant holes 66, to the operative positions pressed to the mouth bases 67 of the lubricant holes 66 or to the inoperative positions separated away from the mouth bases 67 of the lubricant holes 66 correspondingly to the positions of the lubricant holes 66 during machining, respectively, such that the lapping to be conducted by pressing the lapping films 11 by the second shoes 72 is delimited to the vicinity of the mouth bases 67 of the lubricant holes 66. Thereby, the lapping apparatus 1 of this embodiment exhibits such an effect that even a work W having pre-machined surfaces 65 formed with opened lubricant holes 66 can be rapidly machined while enabling to fully restrict increase of machining cost and deterioration of shape accuracy (such as circularity and straightness), and to reduce separation of abrasive grains from a lapping film as well as the number of locations of separation.
As shown in
As shown in
Each first shoe member 81 is formed of a hard material such as grindstone or steel, so as to constitute a hard shoe. Contrary, each second shoe member 82 is formed of a material such as urethane resin which is softer than the first shoe member 81 and elastically deformable, so as to constitute a soft shoe.
The surface of each second shoe member 82 is protruded to the work W by a slight length (several μm) from the surface of the associated first shoe member 81. The optimum value of the protruded length of the second shoe member 82 is determined based on the hardness of the second shoe member 82 and the shoe pressing force.
Upon clamping the crankshaft 62 in the lapping apparatus 2 including the shoes 80 of such a constitution, both of the first shoe members 81 and second shoe members 82 are applied with reactive elastic forces of work clamping springs 74 and pressed to the pre-machined surfaces 65, respectively.
Moreover, the crankshaft 62 is rotated around its axis by operating the rotational driving unit 40 while applying oscillation to the crankshaft 62 along the axial direction thereof, so that the abrasive-grained surfaces of lapping films 11 are pressed to the pre-machined surfaces 65 by the first shoe members 81 constituting the hard shoes, respectively, thereby lapping the pre-machined surfaces 65 throughout the whole thereof. Further, the abrasive-grained surfaces of the lapping films 11 are pressed to the mouth bases 67 by the second shoe members 82 constituting the soft shoes, thereby forming the rounded portions 68 at the mouth-base edges 67a, respectively.
During the lapping, the crankshaft 62 is forwardly rotated by a predetermined number of revolutions (such as 5 revolutions), and thereafter rearwardly rotated by the same number of revolutions. Changing the rotating direction maintains the performance of the lapping films 11, and causes the entire circumferences of the mouth bases 67 to be uniformly machined.
Also in the second embodiment, the machining for the entire circumferences of the pre-machined surfaces 65 by the first shoe members 81, i.e., by the hard shoes and the machining for the mouth bases 67 by the second shoe members 82, i.e., by the soft shoes are conducted by the single set of lapping apparatus, thereby enabling to improve the machining efficiency and to shorten the time required for the machining, in this way. Further, the number of equipments is not increased, thereby also allowing to restrict an increase of equipment cost and machining cost.
It is additionally possible to replace shoes in an existing lapping apparatus by the shoes 80 of the second embodiment, thereby enabling to further restrict an increase of equipment cost, machining cost and the like as compared with the first embodiment.
Moreover, since the leftmost shoe 80 is constituted of the hard shoe such that the machining by the hard shoes for improving the shape accuracy (such as circularity and straightness) of each pre-machined surface 65 and the machining by the associated soft shoes for forming the rounded portion 68 at the mouth-base edge 67a are conducted in the same process, those regions of the pre-machined surface 65 which are once exerted with the machining by the soft shoes are subjected to the function for correcting the work shape based on the leftmost hard shoe. Thus, there is no risk that the shape accuracy of each pre-machined surface 65 is deteriorated due to the machining by the associated soft shoes.
Note, the second embodiment can be effectively applied to a work W the rounding amounts of the mouth-base edges 67a of which are smaller than those in the first embodiment.
The pre-machined surfaces 65 of the work W are never delimited to the pin portions 63, journal portions 64 or the like of the crankshaft 62, and can be applied to other various works W insofar as having a pre-machined surface 65 formed with an open holed portion 66.
Although the first embodiment has been exemplified in the configuration using the eccentric cams 31, motors M4 and the like as the shoe driving units 30, respectively, the first embodiment can be appropriately modified without limited thereto. For example, it is possible to drive the second shoes 72 to the operative positions or inoperative positions thereof, by actuators such as servomotors or fluid pressure cylinders to be operated by air pressure.
Further, although there has been shown a situation where each second shoe 72 is constituted of a soft shoe, it is possible to obtain the same effect even by a configuration in which the second shoe 72 is constituted of the same hard shoe as the first shoe 71 while the pressing force of the second shoe 72 is made weaker than that of the first shoe 71. The shoe pressing forces can be then adjusted, by adjusting the fluid pressure such as oil pressure or air pressure, or by adjusting the reactive elastic forces of springs, for example.
Moreover, the soft shoes 72 may be oscillated in the axial direction of the work.
While the leftmost shoe 80 in
There will be explained hereinafter a third embodiment of the present invention with reference to the drawings. Like reference numerals as used for components in the first embodiment are used to denote corresponding or identical components in the third embodiment, and the explanation thereof shall be omitted.
Generally, with reference to
Note, the term “cross-sectionally non-circular arcuate shape” used herein means an arcuate or elliptic shape in which a radius from a center of rotation of the shape to a part of an outer periphery of the shape is made different from other radii from the center of rotation to the other parts of the outer periphery of the shape, and it is to be understood that this term embraces an egg-like shape such as the illustrated cam-lobe portion 61 of course, as well as such a shape having a circular outer periphery in which the center of rotation of the shape is offset from the center of the circle.
There will be explained hereinafter the lapping apparatus 3 in detail.
Referring to
As shown in
Referring to
Pivotal movements of the upper and lower arms 22, 23 are conducted consonantly with the lapping films 11, such that the closing pivotal movements cause the associated shoes 21 to abut onto the applicable cam-lobe portion 61 via lapping film 11, and the opening pivotal movements release the abutment of the shoes 21 on the cam-lobe portion 61.
While the shoes 21 are classified into convex shoes and concave shoes, the shoes 21 in the illustrated embodiment are concave ones each having a concave tip end portion and each abutting on the pre-machined surface of the associated cam-lobe portion 61 at multiple locations (such as two locations) via film 11. While the tip end portion of each concave shoe 21 is concave, the abutting surfaces themselves of the shoe onto the work W are formed into cross-sectionally convex arcuate surfaces, respectively. Although via films 11, each concave shoe 21 contacts with the pre-machined surface of the cam-lobe portion 61, in a line contact manner at two locations. Each cam-lobe portion 61 are supported at four points by the upper and lower shoes 21, thereby enabling to stably rotate the cam-lobe portion 61. Note, also in this embodiment, the indirect abutment of the shoe 21 on the outer peripheral surface of the work W via film 11 is abbreviated to “contact”, and the area through which each shoe 21 abuts on the outer peripheral surface of the work W via lapping film 11 is abbreviated to “contact surface area”.
As also shown in
The shoe pressing units 330 are arranged at the tip end portions of the upper and lower arms 22, 23, respectively. As conceptually shown in
As shown in
As shown in
As shown in
If the work rotational speed Vw is made constant in case of lapping each cam-lobe portion 61 having such a shape, the contact time per unit circumferential length of the outer peripheral surface as the pre-machined surface of the cam-lobe portion with the film 11 becomes different region by region, as described above. Further, in the configuration where each neck-swingable concave shoe 21 is pressed to the associated cam-lobe portion 61, since the concave shoe 21 is neck swung and largely inclined while the concave shoe 21 contacts with the event region “b1”/“b2”, that component force of the applied shoe pressing force P, which acts in the normal direction of the contacting point between the concave shoe and the event region, becomes relatively small. Further, since the event regions “b1, b2” have extremely larger curvature radii, respectively, the contact surface areas of them relative to the shoe 21 become larger as compared with the other regions. Thus, the contact surface pressure of the film 11 is different region by region in such a situation, and particularly, the contact surface pressure is considerably lowered at the event regions “b1, b2”. This leads to an uneven machined amount of the pre-machined surface per unit circumferential length of the cam-lobe portion 61, thereby resultingly causing a possibility of increased surface roughness of the pre-machined surface, particularly of the event regions “b1, b2”.
In view of the above, the machined amount per unit circumferential length at the pre-machined surface of each cam-lobe portion 61 is uniformalized in the lapping apparatus 3 of this embodiment, by detecting the rotational position of the cam-lobe portion 61 by the associated rotary encoder S1 in order to variably control at least one of the shoe pressing force P, work rotational speed Vw and oscillation speed Vo, correspondingly to the rotational position of the cam-lobe portion 61 during machining.
The above control will be explained with reference to
As an expediency of explanation, the erected position of each cam-lobe portion 61 where the top region “a” and base region “d” thereof are positioned at the top and bottom, respectively, shown in
Referring to
The control for varying the shoe pressing forces P is as follows. As shown in
Concretely, the controller 100 outputs a controlling signal to the applicable pressing motor M4 so as to control the rotation of the pressing motor M4, such that the eccentric angle θe of the associated eccentric rotor 35 becomes 0° when the associated rotating cam-lobe portion 61 has reached its initial position, that the eccentric angle θe becomes 180° while the associated shoe 21 contacts with the event region “b1”/“b2” by the rotation of the cam-lobe portion 61, and that the eccentric angle θe becomes 360° when the cam-lobe portion 61 has further rotated and reached its reverse position. Each shoe pressing force P becomes the maximum when the associated eccentric angle θe becomes 180° (see
As shown in
Further, the control for varying the work rotational speed Vw is as follows. As shown in
Concretely, the controller 100 outputs a controlling signal to the main-shaft-aimed motor M1 so as to control the rotational speed of this main-shaft-aimed motor M1, such that the work rotational speed Vw becomes a normal speed when the applicable rotating cam-lobe portion 61 has reached its initial position, that the work rotational speed Vw becomes a reduced speed slower than the normal speed while the cam-lobe portion 61 has rotated and contacts with the event regions “b1, b2”, and that the work rotational speed Vw becomes the normal speed when the cam-lobe portion 61 has further rotated and reached its reverse position.
If the work rotational speed Vw is kept constant during lapping, the circumferential speed of the event region “b1”/“b2” becomes higher than the circumferential speed of the base region “d”, so that the contact time of the event region “b1”/“b2” with the film 11 becomes shorter than the contact time of the base region “d” with the film 11. Contrary, controlling the work rotational speed Vw in the above manner reduces the circumferential speed of the event region “b1”/“b2” upon machining the same, thereby prolonging the contact time of the event region “b1”/“b2” with the film 11. This corrects the non-uniformity of the machined amounts per unit circumferential length at the pre-machined surface of each cam-lobe portion 61, and restricts the increase of surface roughness of the pre-machined surface, particularly of the event regions “b1, b2”.
Note, the contact time of the top region “a” with the film 11 is not actively prolonged in the illustrated controlling configuration. This is because, the contact surface pressure of the top region “a” is inherently high (see
Moreover, the control for varying the oscillation speed Vo is as follows. As shown in
Concretely, the controller 100 outputs a controlling signal to the oscillation motor M2 so as to control the rotational speed of this oscillation motor M2, such that the oscillation speed Vo becomes a normal speed (such as 10 Hz) when the rotating cam-lobe portion 61 has reached its initial position, that the oscillation speed Vo becomes an increased speed faster than the normal speed while the cam-lobe portion 61 has rotated and contacts with the event regions “b1, b2”, and that the oscillation speed Vo becomes the normal speed when the cam-lobe portion 61 has further rotated and reached its reverse position.
If the oscillation speed Vo is kept constant during lapping, there is attained a fixed distance along which one piece of abrasive grain of the film 11 acts on the pre-machined surface per unit time. Contrary, controlling the oscillation speed Vo in the above manner prolongs the distance along which one piece of abrasive grain acts on the pre-machined surface at the event regions “b1, b2”, thereby increasing the number of abrasive grains effectively acting on the pre-machined surface per unit time, in order to increase the removed amount of the pre-machined surface per unit time. This corrects the non-uniformity of the machined amounts per unit circumferential length at the pre-machined surface of each cam-lobe portion 61, and restricts the increase of surface roughness of the pre-machined surface, particularly of the event regions “b1, b2”.
Note, the varying ratios of the shoe pressing forces P, work rotational speed Vw and oscillation speed Vo upon variably controlling them are not uniquely determined and are finally determined in a trial-and-error manner, because these varying ratios will vary such as depending on the work shape, the basic machining conditions (basic values of shoe pressing force, work rotational speed, and oscillation speed) and the required surface roughness.
There will be explained hereinafter an operation of this embodiment, taking a situation for variably controlling the shoe pressing force P, for example.
Firstly, the camshaft 60 is supported between the headstock 42 and tailstock 46, and the upper and lower arms 22, 23 are moved to positions of the cam-lobe portions 61, respectively. At this time, the fluid pressure cylinders 25 have contracted the associated piston rods 26 in order to hold the associated upper arms 22 and lower arms 23 at the opened positions, respectively. Thereafter, the fluid pressure cylinders 25 are operated to expand the associated piston rods 26, thereby pivoting the upper and lower arms 22, 23 in the closing directions, respectively. These closing pivotal movements cause the lapping films 11 to be set on the pre-machined surfaces of the cam-lobe portions 61, respectively.
While the upper and lower arms 22, 23 are pivoted and closed, the motors M3 are operated to rotate the wind-up reels 16, respectively. The lapping films 11 are fed by predetermined amounts so that unused abrasive-grained surfaces are set onto the pre-machined surfaces, respectively. Thereafter, the wind-up reels 16 are rotated after locking the feeding reels 15 by the locking devices near them, so that the lapping films 11 are applied with predetermined tensions. Next, the wind-up reels 16 are locked by the locking devices near them, thereby bringing the lapping films 11 into states applied with tensions without any slack.
In the state where each cam-lobe portion 61 is clamped, the eccentric rotor 35 of the applicable shoe pressing unit 330 is at the initial position thereof (eccentric angle θe=0°) and both of the associated shoes 21 are pressed by the reactive elastic forces of the work clamping springs 33, respectively. Both shoes 21 are thus pressed to the cam-lobe portion 61 by virtue of these reactive elastic forces, thereby pressing the abrasive-grained surface of the lapping film 11 to the pre-machined surface.
Moreover, the camshaft 60 is rotated around its axis by operating the rotational driving unit 40 while applying oscillation to the camshaft 60 along the axial direction thereof by operating the oscillation unit 50, so that the shoe cases 28 holding the shoes 21 advances and retracts within the concaves 27 in a manner to follow the rotation of the applicable cam-lobe portions 61, respectively, thereby lapping the pre-machined surfaces of the cam-lobe portions 61.
During this machining, the rotary encoder S1 detects the rotational positions of the cam-lobe portions 61, and the controller 100 variably controls the shoe pressing forces P correspondingly to the rotational positions of the cam-lobe portions 61 during machining, respectively. Namely, the operations of the applicable pressing motors M4 are controlled such that the eccentric angles θe of the eccentric rotors 35 become 180° while the associated shoes 21 contact the associated event regions “b1, b2”, thereby increasing the shoe pressing forces P upon machining the event regions “b1, b2” as compared with the shoe pressing forces P upon machining the other regions, respectively.
This increases the contact surface pressure at the event regions “b1, b2” (
While the camshaft 60 has many cam-lobe portions 61, the lapping is simultaneously conducted for these cam-lobe portions 61. Upon completing the lapping, the fluid pressure cylinders 25 are operated to contract the associated piston rods 26 in order to pivot the upper and lower arms 22, 23 in the opening directions, respectively, into states where the camshaft 60 can be taken out of them. After taking out the camshaft 60, another camshaft 60 is set, thereby enabling to start the same lapping.
In case of variably controlling the work rotational speed Vw instead of controlling the shoe pressing force P, the operation is as follows.
During lapping, the rotary encoder S1 detects the rotational positions of the cam-lobe portions 61 and the controller 100 variably controls the work rotational speed Vw correspondingly to the rotational positions of the cam-lobe portions 61 during machining, respectively. Namely, the operation of the main-shaft-aimed motor M1 is so controlled that the work rotational speed Vw becomes a lower speed while the shoes 21 contact with the associated event regions “b1, b2”, thereby reducing the work rotational speed Vw upon machining the event regions “b1, b2” as compared with the work rotational speed Vw upon machining the other regions (
This prolongs the contact time of the event regions “b1, b2” with the film 11, thereby resultingly uniformalizing the machined amounts per unit circumferential length at the pre-machined surface of each cam-lobe portion 61, in order to restrict an increase of the surface roughness of the event regions “b1, b2” so that the surface roughness is equalized.
In case of variably controlling the oscillation speed Vo instead of controlling the shoe pressing force P or work rotational speed Vw, the operation is as follows.
During lapping, the rotary encoder S1 detects the rotational positions of the cam-lobe portions 61 and the controller 100 variably controls the oscillation speed Vo correspondingly to the rotational positions of the cam-lobe portions 61 during machining, respectively. Namely, the operation of the oscillation motor M2 is so controlled that the oscillation speed Vo becomes a higher speed while the shoes 21 contact with the associated event regions “b1, b2”, thereby increasing the oscillation speed Vo upon machining the event regions “b1, b2” as compared with the oscillation speed Vo upon machining the other regions (
This increases the number of abrasive grains effectively acting on the event regions “b1, b2”, thereby resultingly uniformalizing the machined amounts per unit circumferential length at the pre-machined surface of each cam-lobe portion 61, in order to restrict an increase of the surface roughness of the event regions “b1, b2” so that the surface roughness is equalized.
As described above, the lapping apparatus 3 according to this embodiment includes: the lapping films 11; the shoes 21; the shoe pressing units 330 for pressing the shoes 21 toward the work W, thereby pressing the abrasive-grained surfaces of the lapping films 11 toward the work W, respectively; the rotational driving unit 40 for rotationally driving the work W; the oscillation unit 50 for applying oscillation to the work W along the axial direction thereof; the rotary encoder S1 for detecting the rotational position of the work W; and the controller 100 for variably controlling at least one of the shoe pressing forces P, work rotational speed Vw and oscillation speed Vo, correspondingly to the rotational position of the work W during machining; and the machined amounts per unit circumferential length at the pre-machined surface of the work W are uniformalized. Thereby the lapping apparatus 3 exhibits such an effect that even a work W having a pre-machined surface in a cross-sectionally non-circular arcuate shape can be equalized in terms of the surface roughness of the pre-machined surface. Further, the fact that the machined amounts per unit circumferential length at a pre-machined surface of a work W can be uniformalized does mean that no additional machining time is required to merely improve a machining quality such as a surface roughness at a specific site of the pre-machined surface. This enables to shorten the total machining time, not only in such a situation for increasing the shoe pressing forces P or oscillation speed Vo correspondingly to the rotational position of the work W, but also in a situation for controlling the work rotational speed Vw to slow down the same correspondingly to the rotational position of the work W.
Further, since the pre-machined surface of the work W is the outer peripheral surface of each cam-lobe portion 61 of the camshaft 60, there can be also exhibited such an effect that the machined amounts per unit circumferential length at the pre-machined surface of the cam-lobe portion 61 can be uniformalized to equalize the surface roughness of the pre-machined surface of the cam-lobe portion 61, thereby enabling to shorten the machining time of the cam-lobe portion 61.
Moreover, the shoe pressing units 330 include the adjusting units 331 for adjusting the shoe pressing forces P, respectively, and the controller 100 controls the operation of the adjusting units 331 such that the shoe pressing forces P upon machining the event regions “b1, b2” of the cam-lobe portions 61 become larger than shoe pressing forces P upon machining the other regions in order to increase the contact surface pressures at the event regions “b1, b2”. Thus, there can be resultingly obtained such an effect that the increase of surface roughness of the event regions “b1, b2” is restricted and the surface roughness of the pre-machined surfaces of the cam-lobe portions 61 is equalized.
Furthermore, the controller 100 controls the operation of the rotational driving unit 40 such that the work rotational speed Vw upon machining the event regions “b1, b2” of the cam-lobe portions 61 become slower than the work rotational speed Vw upon machining the other regions in order to prolong the contact times at the event regions “b1, b2” with the lapping film 11. Thus, there can be resultingly obtained such an effect that the increase of surface roughness of the event regions “b1, b2” is restricted and the surface roughness of the pre-machined surfaces of the cam-lobe portions 61 is equalized.
In addition, the controller 100 controls the operation of the oscillation unit 50 such that the oscillation speed Vo upon machining the event regions “b1, b2” of the cam-lobe portions 61 become faster than the oscillation speed Vo upon machining the other regions in order to increase the number of abrasive grains effectively acting on the event regions “b1, b2”. Thus, there can be resultingly obtained such an effect that the increase of surface roughness of the event regions “b1, b2” is restricted and the surface roughness of the pre-machined surfaces of the cam-lobe portions 61 is equalized.
Meantime, since the shoes 21 comprise concave shoes 21 held in a neck-swingable member and having concave tip end portions for abutting on the pre-machined surfaces of the work W at multiple locations via lapping films 11, there can be exhibited such an effect that the work W is stably rotated and stably lapped in order to improve the machining quality.
Further, the inextensible and deformable lapping films 11 enable to preferably lap the work W having the pre-machined surfaces in cross-sectionally non-circular arcuate shapes.
Moreover, the lapping apparatus 3 of this embodiment is to detect the rotational position of the work W by the rotary encoder S1 and to variably control at least one of the shoe pressing forces P, work rotational speed Vw and oscillation speed Vo correspondingly to the rotational position of the work W during machining in order to embody the lapping method for uniformalizing the machined amounts per unit circumferential length at the pre-machined surfaces of the work W. Thus, there can be exhibited such an effect that the surface roughness of the pre-machined surfaces is equalized even in the work W having the pre-machined surfaces in cross-sectionally non-circular arcuate shapes while enabling to shorten the total machining time.
Although there has been described the embodiment for variably controlling at least one of the shoe pressing forces P, work rotational speed Vw and oscillation speed Vo correspondingly to the rotational position of the work W during machining, the present invention is not limited thereto. For example, it is possible to adopt such a configuration for combining variable controls of: shoe pressing forces P and work rotational speed Vw; shoe pressing forces P and oscillation speed Vo; work rotational speed Vw and oscillation speed Vo; or all of shoe pressing forces P, work rotational speed Vw and oscillation speed Vo.
Further, the pre-machined surface of the work W is not delimited to the cam-lobe portion 61 of the camshaft 60, and other various works W are of course applicable insofar as having pre-machined surfaces in cross-sectionally non-circular arcuate shapes.
Although this embodiment has been exemplified in the configuration using the work clamping springs 33, eccentric rotors 35, pressing motors M4 and the like as the shoe pressing units 330 and the adjusting units 331 included therein, this embodiment can be appropriately modified without limited thereto. For example, it is possible to pressing the shoes 21 to the work W in order to press the abrasive-grained surfaces of the lapping film 11 toward the work W, by utilizing a fluid pressure cylinder such as operated by air pressure. In this case, the shoe pressing force P may be adjusted such as by adjusting the air pressure to be supplied to the fluid pressure cylinder or by turning on/off the air pressure by an electromagnetic valve.
Further, although the rotational driving unit 40 in the illustrated embodiment variably controls the work rotational speed Vw by varying the rotational speed of the main-shaft-aimed motor M1, it is possible to variably control the work rotational speed Vw by changing a gear ratio of a transmission arranged between an output shaft and a main shaft of the main-shaft-aimed motor M1.
Moreover, although the work W is applied with oscillation by applying oscillation to the table 49 in case of the oscillation unit 50 of the illustrated embodiment, it is possible to apply oscillation to the main shaft 41 supporting the work W. Further, it is not indispensable to apply oscillation to the work W, and it is possible to apply oscillation to the lapping film 11, or to both of the work W and lapping film 11.
Lastly, although the concave shoes 21 have been exemplarily described as shoes, the present invention is also applicable to a situation for using convex shoes having tip end portions in convex arc shapes.
The entire content of a Japanese Patent Applications No. P2003-34050 and No. P2003-34065 with a filing date of Feb. 12, 2003 is herein incorporated by reference.
Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above will occur to these skilled in the art, in light of the teachings. The scope of the invention is defined with reference to the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-034050 | Feb 2003 | JP | national |
| 2003-034065 | Feb 2003 | JP | national |
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| Number | Date | Country | |
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| 20040166767 A1 | Aug 2004 | US |
