JP2004276121A - Roller burnishing method and burnishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller burnishing method and burnishing device, obtaining a desired surface roughness, and heightening the durability and working performance. <P>SOLUTION: In this roller burnishing method and device for finishing with a burnishing roller 3 pressed to a work 4 having a surface to be worked circular-arc in section, the surface to be worked of the work W is machined to be recessed at the center Wa by lapping, and then the projecting parts Wb at both end parts are burnished by the burnishing roller 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a roller burnishing method and apparatus for superfinishing an engine crankshaft and the like.
[0002]
[Prior art]
For example, a journal portion or a pin portion of a crankshaft of an automobile engine is subjected to a finishing process by a roller burnish after a lapping process, so that the surface is finished to a good surface roughness.
[0003]
In recent lapping processing, the surface of the work is covered with a wrapping film provided with abrasive grains on one surface, the outer surface of the wrapping film is pressed with a shoe, and the abrasive side of the wrapping film is pressed against the processing surface of the work, and in this state This is performed by polishing the surface of the work with the abrasive grain surface by rotating the work with (see Patent Document 1 and the like below).
[0004]
However, with such lapping alone, the surface roughness of the work may be insufficient, so the roller is pressed against the surface of the work, crushing the unevenness of the work surface, further reducing the work surface roughness, The surface properties of the work are improved (see Patent Document 2 below).
[0005]
[Patent Document 1]
JP-A-7-237116 (see FIGS. 1 and 2)
[Patent Document 2]
JP-A-6-190718 (paragraph number [0002], see FIG. 11)
[0006]
[Problems to be solved by the invention]
However, the conventional burnishing has a problem that processing is troublesome and the tool itself is expensive.
[0007]
For example, when a pin portion of a crankshaft is subjected to roller burnishing, the shaft end of the crankshaft is supported by a headstock and a tailstock, a pair of support rollers are applied from a direction perpendicular to the axis, and a burnish roller is applied from the opposite side of the support roller. And pressurized.
[0008]
In such a roller burnishing process, a fillet portion for tool escape is formed at an axial end portion of a pin portion of a crankshaft, so that an end portion near the fillet portion is crushed by the pressure of the burnishing roller. , So-called sagging occurs in the fillet portion side, and it is impossible to finish with good straightness.
[0009]
Therefore, in the conventional burnishing, in order to prevent such a dripping, the pressing force of the hydraulic cylinder for pressing the burnishing roller is controlled to be different between the vicinity of the fillet portion and the center portion, or the burnishing roller itself is controlled. The hardness is made different in the portion near the fillet portion than in the center portion of the work, so that the difference is transferred to the work.
[0010]
However, adjusting the pressure of the burnishing roller requires a troublesome control operation, which may reduce the productivity of the work.In addition, if the hardness of the burnishing roller itself is changed depending on the position, the forming of the roller is difficult. It is cumbersome and expensive.
[0011]
In addition, this roller burnishing process is to increase the surface roughness by pressing a burnishing roller over the entire surface of the shaft portion of the crankshaft. However, this process makes the surface roughness of the shaft portion too good, and When the surface roughness is extremely small, a necessary and sufficient oil reservoir is not formed on the sliding surface, so that an appropriate lubricating oil cannot be supplied, and there is a possibility that an oil film breaks, seizure or galling occurs.
[0012]
The present invention has been made in order to solve the problems associated with the above-described conventional technology, and has a work-side shape having a concave shape that is easy to perform a roller burnishing process. Roller burnishing method and processing that achieves the desired surface roughness by applying the processing, enables the supply of appropriate lubricating oil by using the middle concave portion as an oil sump, and thereby improves durability and operability. It is intended to provide a device.
[0013]
[Means for Solving the Problems]
The object of the present invention is achieved by the following means.
[0014]
(1) In a roller burnishing method in which a burnishing roller is pressed against a work having an arc-shaped work surface to finish the work, the work surface of the work is formed into a concave shape by lapping, and then the convex portions at both ends are burnished. A roller burnishing method that burnishes with rollers.
[0015]
(2) The roller burnishing method according to (1), wherein the burnishing process smoothes a projection in a cross section curve of the surface roughness of the projection.
[0016]
(3) The roller burnishing method according to (1) or (2), wherein the workpiece is a journal or a pin of a crankshaft having a fillet portion at both ends.
[0017]
(4) In a roller burnishing apparatus for finishing by pressing a burnishing roller against a work having an arc-shaped work surface, burnishing is performed by the burnishing roller on convex portions at both ends of the work, which are formed into a concave shape by lapping. Roller burnishing equipment.
[0018]
(5) The roller burnishing apparatus according to the above (4), wherein the burnishing process smoothes a projection in a surface roughness cross-sectional curve of the projection.
[0019]
(6) The roller burnishing apparatus according to (4) or (5), wherein the workpiece is a journal or a pin of a crankshaft having a fillet portion at both ends.
[0020]
【The invention's effect】
According to the first and fourth aspects of the present invention, the work surface of the workpiece is formed into a concave shape by lapping, and the convex portions at both ends are burnished. However, the state during processing can be maintained for a long period of time without causing so-called initial wear, and the durability is improved.
[0021]
In addition, since the convex portions at both ends are burnished, it is possible to finish with good straightness without causing sagging, and it is also possible to apply a compressive residual stress to both ends hit by the mating member. In addition, the strength of the product is improved, and there is no need to increase the diameter or the size unnecessarily, and the size and the weight can be reduced.
[0022]
Furthermore, since the burnishing portion is only at both ends, the burnishing process cost is small, the process can be performed in a short time, and the cost is extremely advantageous.
[0023]
According to the second and fifth aspects of the present invention, burnishing is performed on the protruding portion at the surface roughness cross-sectional curve of the protruding portion, so that a compressive residual stress can be applied to a predetermined region at an intended depth, and as a result, the strength of the product is reduced. As a result, it is possible to reduce the size and weight, and furthermore, it is possible to form an oil sump at both ends where the mating member contacts, thereby improving the durability. In particular, since the projecting portion is burnished, burnishing can be performed without an extremely large pressing force, and the occurrence of the sagging can be reliably prevented, and finishing can be performed with good straightness.
[0024]
According to the invention of claims 3 and 6, if the journal portion or the pin portion of the crankshaft having the fillet portions at both ends is a work, when a bearing or a connecting rod as a mating member is attached, the above-described prevention of sagging, Not only the strength improvement, miniaturization, weight reduction and processing advantage are further promoted, but also the concave central part becomes an oil reservoir, oil is supplied to both ends from here, lubricity and durability The properties are significantly improved.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 is a schematic configuration diagram showing a roller burnishing apparatus according to an embodiment of the present invention, and FIG. 2 is a side view of FIG. 1, in which the outline of a pin portion is exaggerated somewhat.
[0027]
In the present embodiment, the pin portion, which is the arc-shaped processing surface of the cross section of the crankshaft, is wrapped as a workpiece W, and after finishing it into a concave shape, the protrusions of the surface roughness cross-sectional curve at the protrusions generated at both ends are described above. Burnishing is performed by a burnishing roller.
[0028]
Here, in the present specification, the “convex portion” refers to a portion protruding from the middle concave portion generated on the surface of the work W, and the “protruded portion” protrudes in a zigzag surface roughness cross-sectional curve. Part.
[0029]
As shown in FIGS. 1 and 2, the roller burnishing apparatus 1 supports a shaft end of a wrapped crankshaft with a headstock and a tailstock (not shown), and a pair of support rollers 2 from a direction perpendicular to the axis. Is applied to the pin portion W of the crankshaft, and pressure is applied by the vanish roller 3 from the opposite side of the support roller 2. The burnishing roller 3 is supported by a bracket 4 and is connected to a pressure source 6 such as a fluid pressure or a motor via a holder 5. 5)).
[0030]
However, the burnishing roller 3 is also provided with a burnishing roller 3 ′ shown by a dashed line in the figure so that the convex portions Wb at both ends of the pin portion can be burnished at a time. Alternatively, since the pin portion W of the crankshaft, which is a work, is formed by forming the convex portions Wb at both ends of the concave portion Wa as described later in detail, the vanish roller 3 The length may be substantially the same as the length of the section W. In this way, only the two convex portions Wb are burnished at once without hitting the middle concave portion Wa. Regardless of which vanish roller 3 is used, the convex portion Wb is pressurized, so that dripping does not occur and does not enter the fillet portion Wf.
[0031]
The support roller 2 is supported by a support member 7 whose position is fixed.
[0032]
FIG. 3 is a schematic configuration diagram showing a lapping apparatus, and FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. The work W is subjected to lapping before burnishing, and an apparatus used for this lapping will be outlined.
[0033]
As shown in FIGS. 3 and 4, the lapping apparatus includes a wrapping film 10 in which abrasive grains are provided on one surface of a non-stretchable and deformable thin base material, and a shoe disposed on the back side of the wrapping film 10. 11, a shoe pressing means 12 for pressing the shoe 11 to press the abrasive surface of the wrapping film 10 against the pin portion W of the crankshaft, a rotation driving means 13 for rotating the crankshaft, and a crankshaft and wrapping film 10. And an oscillation means 14 for imparting an axial oscillation to at least one of them.
[0034]
In FIG. 3, reference numeral “M” denotes a motor, “15” denotes a rotary encoder that detects a rotational position of a workpiece W being processed, “16” denotes an eccentric rotating body, “17” denotes a resilient means such as a spring, and “18”. "" Is a table slidable along the X direction, "19" is a table slidable along the Y direction, and "C" is a control unit.
[0035]
In FIG. 4, the wrapping film 10 is pulled out from the supply reel 21 by rotating and pulling the take-up reel 20 by the motor M, guided by a number of film rollers R _{1 to} R ₉ , and wound around the take-up reel 20. Taken. A lock device (not shown) is provided near the supply reel 21 and the take-up reel 20, whereby a predetermined tension is applied to the entire film.
[0036]
The pressing arms 22 and 23 are rotatably provided about a support pin 25 by a fluid pressure cylinder 24. When the pressing arms 22 and 23 are closed, the wrapping film 10 also operates and covers the pin portion W of the crankshaft. It comes into contact with the processing surface of the pin portion W via the wrapping film 10.
[0037]
Next, a processing method will be described.
[0038]
<Wrapping process>
In general, a crankshaft of an automobile engine is machined, heat-treated, and ground. However, mere lapping does not provide a good surface roughness, and thus is subjected to lapping.
[0039]
In this lapping process, a lapping film 10 provided with abrasive grains on one surface is used, and the lapping film 10 is made of a non-stretchable base material, for example, a polyester having a plate thickness t of about 25 μm to 130 μm. A large number of abrasive grains (specifically, aluminum oxide, silicon carbide, diamond, etc.) having a particle size of about several μm to 200 μm are attached to one surface of the base material with an adhesive. As a result, a good surface roughness is obtained.
[0040]
In FIG. 4, first, in a state where both the pressing arms 11 and 12 are open, the lock device provided near the supply reel 21 is released, and the motor M is operated to rotate the take-up reel 20. After moving by a predetermined amount, a new abrasive grain surface is set on the processed surface of the work W.
[0041]
Then, when the lock device near the take-up reel 20 is locked, the wrapping film 10 is tensioned and stretched without slack.
[0042]
In this state, the crankshaft is set between the head stock 26 and the tail stock 27 as shown in FIG. After the setting, when the hydraulic cylinder 24 shown in FIG. 4 is operated, the two pressing arms 22 and 23 are closed and rotated, and the wrapping film 10 is set on the processing surface of the pin W of the crankshaft. At this time, the shoe pressing means 12 operates to press both shoes 11 against the processing surface of the pin portion W with a predetermined pressing force. If there are a plurality of processing surfaces such as the pin portions W of the crankshaft, the wrapping film 10 is set on each of the pin portions W.
[0043]
When the crankshaft is rotated about the axis by the motor M and the oscillation means 14 is operated, the processing surface of the pin portion W is wrapped by the abrasive grain surface of the wrapping film 1. Depending on the pin portion W, the pin portion W may be eccentrically rotated. However, both the pressing arms 22 and 23 swing by following the conventional method, and the lapping process is performed similarly.
[0044]
On the other hand, the oscillation means 14 drives the eccentric rotating body 16 to rotate by the motor M against the resilience of the resilient means 17, and oscillates the table 18 in the X direction to oscillate the crankshaft.
[0045]
Due to this oscillation, the distance of the pin portion W of the crankshaft in contact with the abrasive grains is increased, the number of working abrasive grains per unit time is increased, the processing time is reduced, and the processing efficiency is improved.
[0046]
During the lapping, processing chips are generated on the processing surface of the pin portion W and the wrapping film 10, and the processing chips are quickly removed by the lubricating liquid discharged from the lubricating means 30 (see FIG. 4).
[0047]
FIG. 5 is a diagram showing the surface shape of the workpiece after the lapping process, and FIG. 6 is a diagram showing the surface roughness of the pin portion after the lapping process. In these figures, the outer shape of the pin portion is somewhat exaggerated. Is shown.
[0048]
In this lapping process, since the band-shaped wrapping film 10 is processed in a state of covering the pin portion W, as shown in FIG. 5, the central portion of the pin portion W is cut off more than the other portions, and the dimension m It has been found that a middle concave portion Wa indicated by a circle is formed.
[0049]
This is because, when processing is performed in a state where the pin portion W is covered with the wrapping film 10, it is difficult for the lubricating liquid to enter the processing point from the outside, and the abrasive grains or chips that have fallen off the wrapping film 10 are not smoothly discharged. It is thought that they are gathered and processed by these.
[0050]
However, when formed in such a concave shape, if a mating member such as a bearing or a connecting rod is provided outside, the concave portion Wa can be used as an oil reservoir, and the surface roughness of the concave portion Wa Is in the state at the time of lapping, it also has a good oil holding ability.
[0051]
On the other hand, in order for the load acting on the pin portion W having the concave portion Wa to have a uniform distribution, it is necessary to increase the diameter of the pin portion W to increase the rigidity. It is difficult to reduce the weight of the pin portion W, that is, the component by making the component smaller and thinner. However, with regard to this uniform load distribution, when the convex portions Wb formed at both ends of the processing surface of the pin portion W are pressed and a compressive residual stress is applied thereto, the strength can be increased, and unnecessary parts can be increased. Does not increase in diameter.
[0052]
In particular, if the final step is lapping, the surface roughness cross-sectional curve of the pin portion W serving as the sliding surface has a surface property in which the protrusions T and the recesses R are substantially even as shown in FIG. Therefore, when a larger surface pressure is applied to the sliding surface of the pin portion W by the mating member, the protrusion portion T is deformed or worn, and the initial deformation amount and the initial wear amount are large, and an appropriate clearance is maintained. It may not be possible or the durability may be reduced. However, when the convex portion Wa is pressurized as described above and the convex portion T is smoothed, not only the diameter of the component can be prevented from being increased due to the improvement in strength, but also the durability is improved.
[0053]
<Bunishing process>
Therefore, in the present embodiment, burnishing is performed on the convex portion Wb. The shaft end of the wrapped crankshaft is supported by a headstock and a tailstock (not shown), and a pair of support rollers 2 are applied to a pin W of the crankshaft from a direction perpendicular to the axis to operate the pressure source 6. When the convex portion Wb of the pin portion W is pressed by the vanish roller 3 from the opposite side, the protrusion T of the convex portion Wa is crushed. In this case, since the protrusion T of the protrusion Wa is crushed, the above-described sagging does not occur, and it is possible to finish with a good straightness.
In addition, since the projection T is crushed, the surface has a smooth surface property, but has an oil reservoir here. Therefore, even if a mating member abuts at this end, sufficient lubrication can be achieved, and durability is improved.
[0054]
Further, since the projections T at both ends to which the counterpart member comes into contact are crushed, a compressive residual stress can be applied thereto, and the strength of the pin portion W is also improved. Therefore, there is no need to unnecessarily increase the diameter or size of the crankshaft, and the size and weight can be reduced.
[0055]
Such a burnishing process does not process the entire pin portion W but only the convex portions Wb at both ends. Therefore, the processing allowance is only l, which can be reduced and can be processed in a short time.
[0056]
However, if the surface roughness of the surface of the convex portion Wb is significantly reduced by burnishing, a necessary and sufficient oil reservoir may not be formed at this portion. It is preferable to set the degree of crushing.
[0057]
<Example>
As a roller burnishing tool, a commercially available hydraulic ball point tool manufactured by Ecorll was used. A crankshaft was provided between the headstock and tailstock of the lathe and rotated. First, the crankshaft was finished to 0.63 μmRa or less by grinding. Next, as a first-stage lapping step (rough lapping step), a lapping film having abrasive grains of about 30 μm was used to process the lapping film to 0.2 μmRa or less. The dimension m of the middle concave portion Wa was about 2 μm. Then, as a second lapping step (finishing lap step), a lapping film having abrasive grains of about 15 μm was used and processed to 0.1 μm Ra or less.
[0058]
On the other hand, when roller burnishing was performed, smoothing was difficult. The arithmetic average roughness (Ra) of 0.1 μm means that the surface roughness is about 1 μm, the surface roughness is fairly good, and the projections of the cross-sectional curve of the surface roughness are small and densely distributed. It is thought that there is.
[0059]
Therefore, the second-stage lapping step is abolished, and when the roller varnish is performed on the processed surface in the first-stage lapping step, the projection T of the surface roughness cross-sectional curve can be smoothed. Good results were obtained.
[0060]
The present invention is not limited to the above-described embodiment, but can be variously modified. For example, in the above-described embodiment, the case where the pin portion of the crankshaft is mainly processed has been described. However, not only this, but also the one having an arc-shaped processing surface having a non-circular cross-section such as a journal portion or the like. It can also be applied to workpieces that are not machined.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a side view of FIG.
FIG. 3 is a schematic configuration diagram showing a lapping apparatus.
FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;
FIG. 5 is a view showing a surface shape of a pin portion after a lapping process.
FIG. 6 is a diagram showing the surface roughness of a pin portion after lapping.
[Explanation of symbols]
3. Burnishing roller
10 ... wrapping film,
11 ... shoe,
T: Projection,
W: Work (pin part),
Wa: middle concave portion,
Wb: convex part,
Wf: Fillet part.

Claims (6)

In a roller burnishing method for finishing by pressing a burnishing roller against a work having a circular cross-section processed surface,
A roller burnishing method, wherein the work surface of the workpiece is formed into a concave shape by lapping, and then the convex portions at both ends are burnished by the burnishing roller. The method according to claim 1, wherein the burnishing includes smoothing a protrusion in a cross section curve of a surface roughness of the protrusion. The roller burnishing method according to claim 1, wherein the workpiece is a journal portion or a pin portion of a crankshaft having a fillet portion at both ends. In a roller burnishing apparatus that finishes by pressing a burnishing roller against a work having an arc-shaped machined surface,
A roller burnishing apparatus for performing burnishing by the burnishing roller on the convex portions at both ends of the work processed into a concave shape by lapping. The roller burnishing apparatus according to claim 4, wherein the burnishing process smoothes a protrusion in a cross section curve of a surface roughness of the protrusion. The roller burnishing apparatus according to claim 4, wherein the workpiece is a journal portion or a pin portion of a crankshaft having a fillet portion at both ends.

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