JP4193531B2 - Lapping machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lapping equipment which (sometimes hereinafter referred to as simply the film) by a film lapping (hereinafter simply lapping) wrapping film abrasive with the machined surface of the workpiece.
[0002]
[Prior art]
For example, when finishing a workpiece having an arc-shaped outer peripheral surface such as a cam lobe portion or journal portion of a camshaft or a journal portion or pin portion of a crankshaft, a lapping film recently provided with abrasive grains on one side Wrapping process.
[0003]
In this lapping process, the work surface of the work is covered with a lapping film, the film is pressed with a shoe from the back, and the work is processed on the abrasive surface of the film while rotating the work in a state where the film is pressed against the work (for example, , See Patent Document 1).
[0004]
The shoe used in such lapping is classified into a convex shoe and a concave shoe from the shape of its tip. Since the convex shoe is held in a fixed position and its tip is a convex arc, it is in line contact with the arc-shaped outer peripheral surface of the workpiece via a film, but so to speak. On the other hand, the concave shoe is rotatably held at the center of the shaft that supports the concave shoe, and has a concave tip portion that comes into contact with the processing surface at a plurality of positions via the film. Although the tip of the concave shoe is concave (concave), the contact surface itself with the workpiece is a convex arc, so the arc-shaped outer peripheral surface of the workpiece is through a film. Line contact at two points.
[0005]
When this concave shoe is used to wrap a workpiece having a non-circular cross section, such as the cam lobe portion of the camshaft, the concave shoe swings the neck as the workpiece rotates. While rotating, the abrasive grain surface of the wrapping film is pressed against the processing surface. Therefore, the point at which the lapping process proceeds by contacting the abrasive grain surface and the processed surface, that is, the lapping process point changes as the workpiece rotates.
[0006]
Since the work is rotating, at the lapping point, a force directed in the direction of feeding the lapping film acts on the film. In order to prevent the film from being fed against this force, a predetermined tension is applied to the entire film during the lapping process.
[0007]
In the present specification, the contact of the shoe indirectly with the outer peripheral surface of the workpiece via the film is abbreviated as “contact”.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-237116 (see FIGS. 1 and 2)
[0009]
[Problems to be solved by the invention]
However, when the force toward the film feeding direction becomes larger than the applied tension, a so-called film entrainment phenomenon occurs. The film entrainment phenomenon is a phenomenon in which the film is stirred into the recessed portion at the tip of the recessed shoe and stays in the recessed portion without being fed out thereafter. When the film entrainment phenomenon occurs, there is a problem that it becomes impossible to maintain an appropriate lapping process.
[0010]
The present invention has been made to solve the problems associated with the above-described prior art, and has an object to provide a lapping apparatus capable of preventing a film entrainment phenomenon and maintaining an appropriate lapping process. To do.
[0011]
[Means for Solving the Problems]
The object of the present invention is achieved by the following means.
[0012]
Recessed opposite the said working surface with pressing the lapping film which abrasive grains provided the workpiece to be rotated has an arc-shaped working surface of the cross-section non-circular on one surface of the thin meat substrate A shoe for lapping processing composed of a concave shoe having a concave tip ,
A lapping machine comprising: a shaft for rotatably holding the shoe;
The concave tip portion of the shoe has a contact surface including two convex arc portions that form a recess facing the processing surface and a concave bottom portion that connects the ends of the two convex arc portions. Then, by forming the concave bottom portion in a cross-sectional shape having a radius dimension (R2) smaller than the radius dimension (r3) of the portion having the smallest curvature radius on the processed surface, the contact surface is formed of the wrapping film. The one surface is pressed against the processing surface to form two lapping processing points spaced apart from each other regardless of the rotational position of the workpiece,
The abutment surface has an angle formed by tangents at two contact points where each of the two convex arc portions contacts the other surface of the wrapping film in order to form the lapping point. Regardless of the rotational position, it is formed into a cross-sectional shape that always forms an angle larger than 90 degrees ,
The round dimension (R1) of the convex arc portion is
(1/2) × Ps ≦ R1 ≦ Ps
Here, Ps: Pitch dimension of the shoe (width dimension of the concave tip in a plane perpendicular to the rotation axis of the workpiece)
A lapping apparatus characterized by satisfying the following relationship .
[0013]
【The invention's effect】
According to the lapping apparatus according to the present invention, when lapping a workpiece having an arc-shaped machining surface with a non-circular cross section, the relationship between the workpiece shape and the shoe shape becomes appropriate, and the wrapping film is entangled. to prevent a phenomenon This will allow for some maintaining the proper lapping, further, the relationship between the radius dimension of the workpiece shape and a convex arc portion becomes appropriate, to improve the surface roughness of the processing surface There is an effect that it becomes possible .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
1 is a schematic configuration diagram illustrating a lapping apparatus 1 according to the present invention, FIG. 2 is a schematic cross-sectional view illustrating a closed state of upper and lower arms 22 and 23 provided in the lapping apparatus 1 so as to be freely opened and closed, and FIG. FIG. 4 is a schematic sectional view showing the open state of the upper and lower arms 22 and 23, FIG. 4 is a diagram showing a shoe 70 for lapping according to the present embodiment, and FIGS. 5A and 5B are sectional views of the shoe 70. It is a figure where it uses for description of a shape. In FIG. 5A, only the upper shoe 70 is shown. FIG. 9A is a perspective view showing an example of the camshaft 60 as the workpiece W to be lapped, and FIG. 9B is a diagram for explaining each part in the cam lobe portion 61 of the camshaft 60. is there. For convenience of explanation, the axial direction of the camshaft 60 (left-right direction in FIG. 1) is defined as the X direction, and the horizontal direction orthogonal to the X direction (direction orthogonal to the paper surface in FIG. 1) is defined as the Y direction. The vertical direction (vertical direction in FIG. 1) perpendicular to the X direction is defined as the Z direction.
[0016]
The lapping apparatus 1 will be briefly described with reference to FIGS. 1 to 4. A lapping film 11 in which abrasive grains are provided on one surface of a non-stretchable and deformable thin substrate, and a back surface of the lapping film 11. , A wrapping shoe 70 that presses the abrasive grain surface (corresponding to one surface) of the wrapping film 11 against the workpiece W, a rotational drive unit 40 that rotationally drives the workpiece W, the workpiece W, and the wrapping film And an oscillation unit 50 for providing oscillation along the axial direction of the workpiece W to at least one of the workpieces 11, and the wrapping film 11 is pressed against the processing surface 65 of the rotating workpiece W to perform wrapping processing. . The shoe 70 is formed of a concave shoe having a concave tip portion 71 that is held so as to be rotatable about a predetermined axis and is recessed facing the processing surface 65 (see FIG. 4). The shoe 70 according to the present embodiment is suitably used for lapping a workpiece W having an arcuate machining surface 65 with a non-circular cross section. As this type of workpiece W, as shown in FIG. 9A, a camshaft 60 can be cited, and the outer peripheral surface of the cam lobe portion 61 in this camshaft 60 becomes a processing surface 65 to be lapped. Corresponding to the position of the cam lobe 61, a plurality of pairs of upper and lower arms 22 and 23 are arranged (see FIG. 1).
[0017]
In addition, the “circular shape with a non-circular cross section” in the present specification refers to an arc shape intended to make the radius from the rotation center to one part different from the radius to the other part, an elliptical shape, It should be understood that an egg shape like the cam lobe portion 61 shown in the figure is included, and that the outer shape is circular but the center of rotation is eccentric from the center of the circle.
[0018]
Hereinafter, the lapping apparatus 1 will be described in detail.
[0019]
Referring to FIG. 1, the rotary drive unit 40 includes a head stock 42 that rotatably supports a main shaft 41, a chuck 43 that is connected to the tip of the main shaft 41 and grips one end of a camshaft 60, and a belt attached to the main shaft 41. And a tail stock 46 including a center 45 that supports the other end of the camshaft 60. The camshaft 60 is rotationally driven by the rotation of the main shaft motor M1 being transmitted through the belt 44 and the main shaft 41. By changing the rotation speed of the spindle motor M1, the work rotation speed is set to a desired speed. A rotary encoder S1 that detects the rotational position of the workpiece W during machining is attached to the main shaft 41. Each of the head stock 42 and the tail stock 46 is provided on tables 47 and 48 that are slidable along the Y direction, and these tables 47 and 48 are arranged on a table 49 that is slidable along the X direction. ing. In order to set the camshaft 60 between the headstock 42 and the tailstock 46, or to move the camshaft 60 to the processing position, the respective tables 47, 48, 49 are moved.
[0020]
The oscillation unit 50 includes an eccentric rotator 51 that contacts the end surface of the table 49, and an oscillation motor M <b> 2 that rotationally drives the eccentric rotator 51. The oscillation unit 50 includes an elastic means 52 such as a spring for biasing a resilient force that presses the table 49 toward the eccentric rotator 51 so that the end surface of the table 49 and the eccentric rotator 51 are always in contact with each other. Is provided. By changing the rotation speed of the oscillation motor M2, the oscillation speed is set to a desired speed (for example, 10 Hz). The oscillation amplitude is determined based on the amount of eccentricity of the eccentric rotating body 51 with respect to the axis of the oscillation motor M2. The amount of eccentricity is about 1 mm, and the amplitude of oscillation is about 2 mm. The eccentric amount of the eccentric rotating body 51 can be adjusted by known means such as changing the number of inserted adjustment plates (not shown). A rotary encoder S <b> 2 that detects the rotational position of the eccentric rotator 51 is attached to the shaft of the eccentric rotator 51. 1 is a controller that controls the operation of the lapping apparatus 1.
[0021]
Although there are various types of the wrapping film 11, in this embodiment, the base material is made of a highly non-stretchable material, for example, a polyester having a plate thickness of about 25 μm to 130 μm. In this case, a large number of abrasive grains (specifically, made of aluminum oxide, silicon carbide, diamond, etc.) having a particle diameter of about several μm to 200 μm are attached by an adhesive. The abrasive grains may be bonded to the entire surface of the substrate, or may be formed by intermittently forming a non-abrasive grain region having a predetermined width. In order to prevent the shoe 70 from slipping, the other surface of the base material is back-coated with a resistance material (not shown) made of rubber, synthetic resin, or the like, or in some cases, slip-resistant.
[0022]
With reference to FIGS. 2 and 3, the wrapping film 11 is pulled out from the supply reel 15 and attached to a pair of first guide rollers R <b> 1 provided at the tip of the upper arm 22 and an inner position of the upper arm 22. The second guide roller R2, the third guide roller R3 attached to the inner position of the lower arm 23, the pair of fourth guide rollers R4 provided at the tip of the lower arm 23, etc. It is wound on a take-up reel 16. A motor M3 is connected to the take-up reel 16. When the motor M3 is operated and the take-up reel 16 is rotated, the wrapping film 11 is sequentially fed out from the supply reel 15. In order to detect the feed amount of the wrapping film 11, a rotary encoder S3 for detecting the rotation amount is attached to the shaft of the take-up reel 16. A lock device (not shown) is provided in the vicinity of the supply reel 15 and the take-up reel 16, and a predetermined tension is applied to the entire film 11 by the operation of the lock device.
[0023]
The paired upper arm 22 and lower arm 23 are rotatably provided via a support pin 24 so that the tip portion where the shoe 70 is disposed can be opened and closed relatively in the Z direction. One end of a fluid pressure cylinder 25 that is operated by hydraulic pressure or air pressure is pin-connected to the rear end portion of the upper arm 22, and the tip of a piston rod 26 is pin-connected to the rear end portion of the lower arm 23. When the piston rod 26 is extended from the contracted state, the upper and lower arms 22 and 23 are pivoted about the support pins 24 in the direction in which the tip ends are closed, and are in the closed state shown in FIG. On the other hand, when the piston rod 26 is contracted from the extended state, the upper and lower arms 22 and 23 are rotated in the direction in which the distal ends are opened, and are in the open state shown in FIG. The upper and lower arms 22 and 23 are rotated together with the wrapping film 11, the shoe 70 comes into contact with the cam lobe portion 61 via the wrapping film 11 by the closing rotation, and the cam lobe portion 61 and the shoe 70 are rotated by the opening rotation. Release contact.
[0024]
The shoe 70 is rotatably held by the shoe case 28 via a swing pin 29 as a predetermined shaft. The shoe case 28 is housed in a recess 27 formed at the tip of the upper and lower arms 22 and 23 so as to be movable forward and backward with respect to the workpiece W. The shoe case 28 moves while its outer surface is guided by the inner surface of the recess 27. A work clamping spring 33 made of a compression coil spring is disposed on the back surface of the shoe case 28. The shoe 70 is urged by the elastic force of the work clamping spring 33 and is pressed against the processing surface 65 via the wrapping film 11. The upper and lower swing pins 29 are positioned on a line passing through the axis O of the camshaft 60 so that the shoe pressing force acts on the film 11 efficiently.
[0025]
As shown in FIG. 9 (B), the cam lobe portion 61 is continuous with a base portion d that forms a base circle, a top portion a that defines the lift of the cam, and both sides of the top portion a. Event parts b1 and b2 that start to close, and a plurality of parts of ramp parts c1 and c2 that approach the event parts b1 and b2 from the base part d are provided. When the machining surface 65 has a non-circular cross section like the cam lobe portion 61, the radius from the axis O (rotation center) of the cam lobe portion 61 to the machining surface 65 changes for each part, and the end of the base portion d is reached. From the top to the top part a. Further, the radius of curvature of the base portion d is constant, but the event portions b1 and b2 are substantially linear, so the curvature radius is very large, and the top portion a has a relatively small curvature radius.
[0026]
FIG. 10 is a schematic diagram showing a situation in which the entrainment phenomenon C of the film 11 occurs when the cam lobe portion 61 is lapped using the shoe 170 according to the proportionality not considering the relationship with the shape of the workpiece W. is there.
[0027]
The entrainment phenomenon C of the film 11 occurs when the force of feeding the wrapping film 11 generated by the rotation of the cam lobe portion 61 becomes larger than the tension applied to the film 11 by the locking device. The contact surface pressure at each part of the cam lobe portion 61 is highest at the top portion a, and the peripheral speed is also highest at the top portion a. For this reason, when the top part a is processed, the wrapping film 11 is easily bitten into the recessed part 170a at the tip of the concave shoe 170, and the entrainment phenomenon C of the film 11 occurs remarkably. When the entrainment phenomenon C of the film 11 occurs, an appropriate lapping process cannot be maintained.
[0028]
In the conventional shoe 170, the relationship between the workpiece shape and the shoe shape of the concave shoe 170 is not considered at all in order to prevent the entanglement phenomenon C of the film 11 which adversely affects the processing quality. In order to prevent the entanglement phenomenon C of the film 11, measures such as increasing the clamping force of the film 11 by the locking device or reducing the work rotation speed are taken. However, increasing the film clamping force leads to an increase in the size of the locking device, and if the work rotation speed is decreased, there is a problem that a long time is required for lapping when the work rotation speed is decreased.
[0029]
Accordingly, the inventors of the present invention have found that if the relationship between the workpiece shape and the shoe shape of the concave shoe is appropriate, the entrainment phenomenon C of the film 11 can be prevented, and a suitable shoe 70 for lapping processing is obtained. It came to complete.
[0030]
As shown in FIGS. 4 and 5A and 5B, the shoe 70 according to the present embodiment is held rotatably about a predetermined axis (swing pin 29) and faces the processing surface 65. It comprises a concave shoe having a concave tip 71 that is recessed. The concave tip portion 71 forms at least two lapping points A1 and A2 spaced apart from each other by pressing the abrasive grain surface 11a (one surface) of the wrapping film 11 against the processing surface 65 regardless of the rotational position of the workpiece W. A contact surface 72 is provided. The contact surface 72 includes two convex arc portions 73 that form a recess facing the processing surface 65, and a concave bottom portion 74 that connects the ends of the two convex arc portions 73. The radius dimension of the convex arc portion 73 is represented as “R1”, and the radius dimension of the concave bottom portion 74 is represented as “R2”. The contact surface 72 is formed by tangents T1 and T2 at at least two contact points B1 and B2 that are in contact with the back surface 11b (other surface) of the wrapping film 11 to form the wrapping points A1 and A2. Regardless of the rotational position of the workpiece W, the angle θ is always formed in a cross-sectional shape that forms an angle larger than 90 degrees (see FIG. 5A). Since the cam lobe portion 61 is supported at four points by the upper and lower shoes 70, the cam lobe portion 61 can be stably rotated.
[0031]
The concave bottom 74 is preferably formed in a cross-sectional shape having a radius R2 that is smaller than the radius R3 of the portion having the smallest curvature radius on the processed surface 65 (see FIG. 5B). In the present embodiment, the portion having the smallest radius of curvature corresponds to the tip of the top portion a of the cam lobe portion 61.
[0032]
For convenience of explanation, hereinafter, the points on the contact surface 72 that contact the back surface 11b of the wrapping film 11 are also referred to as pressing points B1 and B2. Strictly speaking, the lapping points A1 and A2 and the pressing points B1 and B2 are surface contacts having a certain extent rather than point contacts, but in the present specification and drawings, they are in contact. The center of the region along the rotational direction of the cam lobe portion 61 is shown as a contact point. The dimension Ps shown in FIG. 4 indicates the pitch dimension of the shoe 70, which will be described later. The pitch dimension Ps is a width dimension of the concave tip portion 71 in a plane orthogonal to the rotation axis of the workpiece W.
[0033]
When designing the shape of the shoe 70 with the shape of the cam lobe portion 61 to be processed, even if the radius R1 of the convex arc portion 73 is the same, the position for setting the center point OR1 of R1 Is changed, the value of the angle θ formed by the tangents T1 and T2 at the pressing points B1 and B2 can be changed.
[0034]
Therefore, when the contact surface 72 of the shoe 70 is formed in a cross-sectional shape in which the angle θ always forms an angle larger than 90 degrees regardless of the rotational position of the cam lobe portion 61, the angle θ is the rotational position of the cam lobe portion 61. Regardless of whether the film 11 is formed in a cross-sectional shape that always forms an angle of 90 degrees or less, an experiment was conducted to investigate the occurrence of the entanglement phenomenon C of the film 11 and the surface roughness. In addition, experiments were performed by changing the radius R1 of the convex arc portion 73 and the radius R2 of the concave bottom 74.
[0035]
FIG. 6A is a chart showing experimental conditions and results, and FIG. 6B is a graph showing experimental results.
[0036]
The shoe used in the experimental conditions (1) and (2) is a concave shoe. The radius dimension R1 of the convex arc portion 73 is 14.3 mm and 20.0 mm, respectively, and the radius dimension R2 of the concave bottom portion 74 is the radius dimension r3 of the tip of the top portion a that is the smallest radius of curvature in the processed surface 65. Smaller than. The concave tip 71 has a contact surface 72 that forms two lapping points A1 and A2 regardless of the rotational position of the cam lobe 61. Further, the contact surface 72 is formed in a cross-sectional shape in which the angle θ formed between the tangents T1 and T2 at the pressing points B1 and B2 is always larger than 90 degrees regardless of the rotational position of the cam lobe portion 61.
[0037]
The shoe used in the experimental condition (3) is also a concave shoe. The radius R1 of the convex arc 73 is 14.3 mm, and the radius R2 of the concave bottom 74 is smaller than the radius r3 at the tip of the top portion a. The concave tip 71 has a contact surface 72 that forms two lapping points A1 and A2 regardless of the rotational position of the cam lobe 61. However, unlike the experimental conditions (1) and (2), the contact surface 72 is formed in a cross-sectional shape in which the angle θ always forms an angle of 90 degrees or less regardless of the rotational position of the cam lobe portion 61.
[0038]
The shoe used in the experimental condition (4) is also a concave shoe. Although the radius R1 of the convex arc portion 73 is 20.0 mm, unlike the experimental condition (2), the radius R2 of the concave bottom 74 is larger than the radius r3 of the top end a. For this reason, the contact surface 72 of the concave tip 71 forms two lapping points A1 and A2 when processing a portion other than the top portion a, but when the top portion a is processed, Therefore, only one lapping point is formed. The cross-sectional shape of the abutting surface 72 is such that when the portion other than the top portion a is processed, the angle θ is larger than 90 degrees.
[0039]
Unlike the experimental conditions (1) to (4), the shoe used in the experimental condition (5) is a convex shoe. The radius R1 of the convex arc portion forming the outer periphery of the convex shoe was 20.0 mm. Since it is a convex shoe, there is always one lapping point.
[0040]
With reference to FIG. 6 (B), under the experimental condition (3), the entrainment phenomenon C of the film 11 did not occur or was unstable. When the film 11 is not entrained, the required surface roughness is obtained, but when the film 11 is entrained, the pre-processed surface remains, and the required surface roughness cannot be obtained. It was.
[0041]
Under the experimental condition (4), the film 11 was not entrapped, but by setting the rounded dimension R2 of the concave bottom 74> the rounded dimension r3 of the top part a tip, the tip of the top part a was per point. As a result, the required surface roughness could not be stably obtained.
[0042]
Under the experimental condition (5), since a convex shoe having one lapping point is always used, the number of working abrasive grains involved in lapping is smaller than when two lapping points are formed. Cut in half. For this reason, the required surface roughness could not be stably obtained with the same processing time.
[0043]
On the other hand, under the experimental conditions (1) and (2), the angle θ> 90 degrees formed by the tangents T1 and T2 at the pressing points B1 and B2 is always satisfied regardless of the rotational position of the cam lobe 61. Therefore, a stable state in which the entrainment phenomenon C of the film 11 does not occur was obtained. Further, since the radius dimension R2 of the concave bottom portion 74 is smaller than the radius dimension r3 of the top portion a, the top end of the top portion a does not contact the bottom of the concave bottom portion 74. The lapping points A1 and A2 of the points are surely formed. For this reason, the required surface roughness can be stably obtained also in the top part a.
[0044]
Next, the regulation of the radius R1 of the convex arc portion 73 from the viewpoint of improving the surface roughness will be considered.
[0045]
In order to obtain a good surface roughness of the processed surface 65 in a short time under constant processing conditions (workpiece rotation speed, shoe pressing force, etc.), the contact area of the wrapping film 11 with respect to the processed surface 65 is set. It is necessary to increase the number of working abrasive grains per unit time and increase the amount of lapping work.
[0046]
In the conventional shoe, the relationship between the workpiece shape and the radius R1 of the convex arc portion 73 is not considered at all in order to improve the surface roughness of the processed surface 65.
[0047]
As described above, the cross-sectional shape of the contact surface 72 of the shoe 70, particularly the convex arc portion 73, is always the angle θ formed by the tangents T1 and T2 at the pressing points B1 and B2 regardless of the rotational position of the cam lobe portion 61. The angle is set to form an angle larger than 90 degrees. In the present embodiment, in addition to the above conditions, the radius R1 of the convex arc portion 73 is
(1/2) × Ps ≦ R1 ≦ Ps
Here, Ps: pitch dimension of the shoe 70 (width dimension of the concave tip portion 71 in a plane orthogonal to the rotation axis of the workpiece W)
To satisfy the relationship.
[0048]
An experiment was conducted to investigate the influence of the radius R1 of the convex arc portion 73 on the surface roughness. In the experiment, a concave shoe having a pitch dimension Ps of 28.6 mm and a round dimension R1 of the convex arc portion 73 of 6.0 mm, 14.3 mm, 28.6 mm, and 36.0 mm was used. The R1 / Ps of the shoe are about 0.21, 0.50, 1.0, and about 1.3, respectively. Regardless of the rotational position of the cam lobe portion 61, the center point OR1 of each R dimension R1 is set so as to always satisfy the angle θ> 90 degrees. FIGS. 7A and 7B show a shoe shape when the radius R1 of the convex arc 73 is small (6.0 mm), and when the radius R1 of the convex arc 73 is large (36.0 mm). It is a conceptual diagram which shows the shoe shape of.
[0049]
FIG. 8 is a graph showing experimental results.
[0050]
Referring to FIG. 8, the required surface roughness is stable in a shoe with R1 = 6.0 mm (R1 / Ps = about 0.21) and R1 = 36.0 mm (R1 / Ps = about 1.3). I couldn't get it.
[0051]
If the radius R1 of the convex arc portion 73 is too small (see FIG. 7A), the contact area between the wrapping film 11 and the processed surface 65 is extremely reduced. As a result, the number of working abrasive grains decreases, the amount of lapping work decreases, and the surface roughness deteriorates.
[0052]
Further, when the rounded dimension R1 of the convex arc portion 73 is large (see FIG. 7B), the contact area itself between the film 11 and the processing surface 65 at the lapping processing points A1 and A2 increases. However, when R1 is increased, as indicated by reference numeral Z in FIG. 7B, the distance from the top portion a to the base portion d of the rotating cam lobe portion 61 contacts the wrapping film 11, that is, the wrapping processing point A1, The distance that A2 is displaced becomes shorter. As a result, the number of working abrasive grains is reduced, the amount of lapping work is reduced, and clogging of the film 11 is likely to proceed, and the surface roughness is deteriorated.
[0053]
On the other hand, in the shoe of R1 = 14.3 mm (R1 / Ps = 0.50) and R1 = 28.6 mm (R1 / Ps = 1.0), the contact area of the wrapping film 11 with respect to the processed surface 65 is preferable. The number of working abrasive grains per unit time with respect to the processed surface 65 increases, and the distance Z at which the wrapping processing points A1 and A2 are displaced is secured, so that the clogging of the film 11 is difficult to proceed. As a result, the required surface roughness could be obtained stably and in a short time.
[0054]
From the above experimental results, it was found that the radius R1 of the convex arc portion 73 should be set to 11 mm ≦ R1 ≦ 32 mm in order to satisfy the required surface roughness. More preferably, it has been found that 14.3 mm ≦ R1 ≦ 28.6 mm, that is, (1/2) × Ps ≦ R1 ≦ Ps.
[0055]
Next, the operation of this embodiment will be described.
[0056]
First, the cam shaft 60 is supported between the head stock 42 and the tail stock 46, and the upper and lower arms 22 and 23 are moved to the position of the cam lobe 61. At this time, the fluid pressure cylinder 25 contracts the piston rod 26 and holds the upper arm 22 and the lower arm 23 in the open position. Thereafter, the fluid pressure cylinder 25 is operated to extend the piston rod 26 and rotate in a direction to close the upper and lower arms 22 and 23. By this closing rotation, the wrapping film 11 is set on the processing surface 65 of the cam lobe portion 61.
[0057]
While the upper and lower arms 22 and 23 are opened and rotated, the motor M3 is operated to rotate the take-up reel 16. The wrapping film 11 moves by a predetermined amount, and a new abrasive grain surface is set on the processing surface 65. Thereafter, when a lock device provided in the vicinity of the supply reel 15 is locked and the take-up reel 16 is rotated, a predetermined tension is applied to the wrapping film 11. Next, when the locking device in the vicinity of the take-up reel 16 is locked, the wrapping film 11 is given a tension and is not loosened.
[0058]
When the cam lobe portion 61 is clamped, the elastic force of the work W clamp spring 33 is urged to press the shoe 70 toward the cam lobe portion 61, and the abrasive surface of the wrapping film 11 is pressed against the processing surface 65.
[0059]
Then, when the oscillation unit 50 is operated to give the camshaft 60 oscillation in the axial direction, the rotation drive unit 40 is operated to rotate the camshaft 60 about the axis, and the shoe 70 holding the shoe 70 is held. The processing surface 65 is lapped while the case 28 moves forward and backward in the recess 27 following the rotation of the cam lobe 61.
[0060]
The camshaft 60 has a number of cam lobe portions 61, and lapping is performed on these cam lobe portions 61 all at once. When the lapping process is completed, the fluid pressure cylinder 25 is operated to contract the piston rod 26, and the upper and lower arms 22 and 23 are rotated in the opening direction, so that the camshaft 60 can be taken out. If another camshaft 60 is set after the camshaft 60 is taken out, the same lapping process can be started.
[0061]
During this lapping process, the relationship between the work shape and the shoe shape of the concave shoe 70 is set to an appropriate one, so that a stable state in which the entanglement phenomenon C of the film 11 does not occur is obtained, and the required surface roughness is reduced. It can be stably obtained over the entire circumference of the processed surface 65. Furthermore, since the relationship between the rounded dimension R1 of the convex arc portion 73 and the pitch dimension Ps of the shoe 70 is also defined, the surface roughness of the processed surface 65 can be obtained even better and in a short time.
[0062]
As described above, according to the shoe 70 for lapping according to the embodiment, one thin-walled substrate is provided for the workpiece W having the arcuate processing surface 65 having a non-circular cross section and being driven to rotate. A lapping film shoe 70 that presses a lapping film 11 having abrasive grains on its surface, and is held in a pivotable manner about a rocking pin 29 and recessed toward the machining surface 65 and recessed. The concave tip portion 71 includes at least two lapping processing points A1 and A2 that are spaced apart from each other by pressing one surface of the wrapping film 11 against the processing surface 65. Regardless, it has an abutment surface 72 to be formed, and the abutment surface 72 has at least two contact points that come into contact with the other surface of the wrapping film 11 to form wrapping points A1 and A2. 1, the angle θ formed between the tangents T1 and T2 between the tangents T1 and T2 is formed in a cross-sectional shape that always forms an angle larger than 90 degrees regardless of the rotation position of the workpiece W, so that the relationship between the workpiece shape and the shoe shape is As a result, the film 11 can be prevented from entraining phenomenon C and appropriate lapping can be maintained, and the required surface roughness can be stably obtained. Further, it is not necessary to increase the clamping force of the film more than necessary, and it is possible to reduce the size of the lock device and the like, and it is possible to reduce the load of the film winding motor M3.
[0063]
The contact surface 72 includes two convex arc portions 73 that form a recess facing the processing surface 65, and a concave bottom portion 74 that connects ends of the two convex arc portions 73. Is formed in a cross-sectional shape having a radius R2 that is smaller than the radius R3 of the portion having the smallest curvature radius on the machining surface 65, so that at least two lapping machining points A1 and A2 are at the rotational position of the workpiece W. Regardless of this, the required surface roughness can be stably obtained over the entire circumference of the processed surface 65.
[0064]
Further, the radius R1 of the convex arc portion 73 is
(1/2) × Ps ≦ R1 ≦ Ps
Here, Ps: pitch dimension of the shoe 70 (width dimension of the concave tip portion 71 in a plane orthogonal to the rotation axis of the workpiece W)
As a result, the contact area of the wrapping film 11 with respect to the processed surface 65 is suitably widened, and the distance Z at which the wrapping processing points A1 and A2 are displaced is secured, so that the clogging of the film 11 is difficult to proceed. The required surface roughness can be obtained stably and in a short time.
[0065]
In addition, since the processed surface 65 of the workpiece W is the outer peripheral surface of the cam lobe portion 61 in the camshaft, the relationship between the cam lobe portion 61 shape and the shoe shape becomes appropriate, preventing the entrainment phenomenon C of the film 11 and the cam lobe. A suitable lapping process can be performed on the portion 61.
[0066]
Further, the processing surface 65 of the workpiece W is the outer peripheral surface of the cam lobe portion 61 in the camshaft, and the portion having the smallest curvature radius is the tip of the top portion a of the cam lobe portion 61, so at least two lapping processes are performed. Since the points A1 and A2 are formed also in the top portion a, the required surface roughness can be stably obtained even in the top portion a.
[0067]
Further, since the wrapping film 11 is non-stretchable and deformable, by using the shoe 70, a suitable wrapping process is performed on the workpiece W having the arcuate processing surface 65 having a non-circular cross section. Can be done.
[0068]
(Modification example)
The machining surface 65 of the workpiece W is not limited to the cam lobe portion 61 of the camshaft 60. Needless to say, the machining surface 65 can be applied to other various workpieces W as long as it has the arcuate machining surface 65 having a non-circular cross section. Nor.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a lapping apparatus according to the present invention.
FIG. 2 is a schematic cross-sectional view showing a closed state of upper and lower arms provided in a lapping apparatus so as to be freely opened and closed.
FIG. 3 is a schematic cross-sectional view showing an open state of upper and lower arms.
FIG. 4 is a view showing a shoe for lapping according to the present embodiment.
FIGS. 5A and 5B are views for explaining a cross-sectional shape of a shoe.
FIG. 6A is a chart showing experimental conditions and results regarding the presence / absence of film entanglement and surface roughness, and FIG. 6B is a graph showing experimental results.
FIGS. 7A and 7B are conceptual diagrams showing a shoe shape when the radius of the convex arc portion is small and a shoe shape when the radius of the convex arc portion is large, respectively.
FIG. 8 is a graph showing experimental results regarding the influence of the rounded dimension of the convex arc portion on the surface roughness.
FIG. 9A is a perspective view showing an example of a camshaft as a workpiece to be lapped, and FIG. 9B is a diagram for explaining each part in a cam lobe portion of the camshaft.
FIG. 10 is a schematic view showing a situation in which a film entanglement phenomenon occurs when a cam lobe portion is lapped using a proportional shoe that does not consider the relationship with the shape of a workpiece.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lapping processing apparatus 11 ... Lapping film 11a ... Abrasive grain surface (one surface)
11b ... Back side (other side)
29 ... Oscillating pin (predetermined axis)
40 ... Rotation drive unit 50 ... Oscillation unit 60 ... Camshaft (work W)
61 ... Cam lobe 65 ... Working surface 70 ... Shoe 71 ... Concave tip 72 ... Abutting surface 73 ... Convex arc part 74 ... Concave bottom a ... Top part A1, A2 of the cam lobe part ... Lapping points B1, B2 ... Pressing Point (Contact point on the contact surface that contacts the other surface of the wrapping film)
Ps ... Shoe pitch dimension R1 ... Round dimension R2 of the convex arc part ... Rd dimension r3 of the concave bottom part ... R dimension T1, T2 of the part having the smallest radius of curvature in the processed surface (tip of the top part of the cam lobe part) ... Pressing Tangent line at point θ ... An angle W between tangents at the pressing point ... Workpiece

Claims (4)

Recessed opposite the said working surface with pressing the lapping film which abrasive grains provided the workpiece to be rotated has an arc-shaped working surface of the cross-section non-circular on one surface of the thin meat substrate A shoe for lapping processing composed of a concave shoe having a concave tip ,
A lapping machine comprising: a shaft for rotatably holding the shoe;
The concave tip portion of the shoe has a contact surface including two convex arc portions that form a recess facing the processing surface and a concave bottom portion that connects the ends of the two convex arc portions. Then, by forming the concave bottom portion in a cross-sectional shape having a radius dimension (R2) smaller than the radius dimension (r3) of the portion having the smallest curvature radius on the processed surface, the contact surface is formed of the wrapping film. The one surface is pressed against the processing surface to form two lapping processing points spaced apart from each other regardless of the rotational position of the workpiece,
The abutment surface has an angle formed by tangents at two contact points where each of the two convex arc portions contacts the other surface of the wrapping film in order to form the lapping point. Regardless of the rotational position, it is formed into a cross-sectional shape that always forms an angle larger than 90 degrees ,
The round dimension (R1) of the convex arc portion is
(1/2) × Ps ≦ R1 ≦ Ps
Here, Ps: Pitch dimension of the shoe (width dimension of the concave tip in a plane perpendicular to the rotation axis of the workpiece)
A lapping apparatus characterized by satisfying the following relationship . The lapping apparatus according to claim 1, wherein the processing surface of the workpiece is an outer peripheral surface of a cam lobe portion of a camshaft. The processing surface of the workpiece is an outer peripheral surface of a cam lobe portion in the camshaft,
  The lapping apparatus according to claim 1, wherein the portion having the smallest radius of curvature is a tip of a top portion of the cam lobe portion. The lapping apparatus according to claim 1, wherein the lapping film is non-stretchable and deformable.

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