JPS63237802A - Method and device for machining outer diameter of piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To attain simple and precise high-speed machining for a complicated piston external surface by causing a tool holder to advance or recede finely in a direction orthogonal with a main spindle and turn about the spindle, turning a workpiece at a speed higher than the rotational speed of the holder by a specific times and feeding a machining head toward the main spindle. CONSTITUTION:When a piston is machined, a column 2 is shifted on a bed 1 and the rotary main spindle 7' of a tool holder 7 and the rotary spindle 11' of a carriage bed 11 are finely dislocated. And the carriage bed 11 is turned at a speed 3/2 times the speed of the holder 7. Concurrently therewith, when a machining head 4 is moved toward the rotary spindle 11' for machining feed and the holder 7 is displaced for the spindle 7' with a servo motor 9, a distance between the cutting edge of a tool 8 and the main spindle 7' changes and furthermore the main spindle 7' is so controlled with the inclination mechanism of the head 4 as to make a fine inclination angle theta from a position parallel with the rotary spindle 11' match the machining feed, thereby proceeding with a machining process. In this case, the taper amount of a piston corresponds to a distance between the cutting edge of the tool 8 and the main spindle 7. The eccentricity of an ellipse is a deviation (q) between the main spindle 7' and the rotary spindle 11'. And the amount of addition is controlled by the inclination angle theta of the head 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for machining the outer diameter of a piston for an internal combustion engine and an apparatus for carrying out the method.

[Conventional technology]

Conventionally, one method for machining the outer circumferential surface of a piston is to attach the piston material to be machined and a master cam model prefabricated into the desired piston shape on the same main shaft.
So-called copying processing is used in which both are rotated in synchronization, the tip of the stylus is brought into contact with the surface of the master cam model, and the outer periphery of the piston material is machined with a cutting tool that moves in response to the movement of the stylus. has been done.

However, as will be explained in detail later, the shape of the piston to be machined is extremely complex, and in the copying process described above, a master cam model having this complex shape is manufactured in advance. This requires advanced technology using three-dimensional processing, which poses a problem in that it is not suitable for high-mix, low-volume production. Furthermore,
There is also the problem that when the number of revolutions during machining increases, the stylus bounces and separates from the surface of the master cam model, making accurate tracking impossible.

As a method to solve these problems, a method can be considered in which a numerical control device is used to move a cutting tool forward and backward toward the piston surface to be processed using a servo device while processing is performed. Although this method is currently possible at low speeds, it is currently not possible at high speeds. The reason for this is that a control signal is issued to the AC servo motor that controls the tool position based on the rotational position detection signal from the spindle encoder and the signal from the numerical control device, but at high speed rotation, the servo system lags. This may cause a phase shift and reduce the amount of cam on the piston, and if the servo system is controlled using an encoder feedback system, a delay may occur in the feedback system.

In order to solve these problems, the present inventor first filed a patent application in 1983.
No. 0-149946 discloses a novel method for machining the outer circumferential surface of a piston for an internal combustion engine, in which the outer peripheral surface of the piston is machined by rotating the workpiece and the tool around axes that intersect with each other at a slight angle in the same direction but at different speeds. A method and apparatus are disclosed.

That is, the processing method includes the steps of holding a tool capable of turning the outer circumferential surface of the workpiece so that it can move forward and backward by a minute distance in a direction perpendicular to the main axis, and adjusting the amount of expansion of the outer diameter of the workpiece in the 45° direction. a step of holding an additional amount adjuster capable of tilting at a minute angle with respect to a plane perpendicular to the main axis; a step of supporting a workpiece rotatably about an axis parallel to the main axis; The workpiece is moved forward and backward a minute distance in a direction perpendicular to the main axis, changes the inclination angle of the additional amount adjusting tool with respect to a plane perpendicular to the main axis, rotates the workpiece about the main axis, and rotates the workpiece about the one axis. The method is characterized by comprising the steps of rotating the tool at a speed of 372 times the rotational speed of the tool and feeding the tool in the direction of the main axis. A tool holder that is rotatably supported and holds a tool capable of turning the outer circumferential surface of a workpiece so that it can move forward and backward over a minute distance in a direction perpendicular to the spindle, and that can be tilted at a minute angle with respect to the spindle, and a tool holder. a device that is attached to the tool and controls the advance and retreat of the tool in a direction perpendicular to the main axis; a device that tilts the additional amount adjuster at a predetermined angle in a predetermined direction; a device that rotates the tool holder; and a device that rotates the tool holder. a workpiece table to which a body is attached, is rotatably supported around an axis parallel to the main axis, and is processed and fed in the direction of the main axis, and further eccentrically fed by a minute distance perpendicular to the main axis; and the above-mentioned object. Place the stand on 3/2 of the above tool holder.
It was characterized by consisting of a device that rotated the machine at a speed of .

However, in the above method and device, the addition amount adjusting device and the mechanism for tilting it at a predetermined angle are complicated, and there are practical difficulties in that they require high precision and high strength. was there.

[Problem that the invention seeks to solve]

The present invention has been made to solve the above problems, and its purpose is to solve the above problems.
To provide a method and device for machining the outer diameter of a piston for an internal combustion engine, which improves the machining method and device disclosed in No. 946, and can process the outer circumferential surface of a piston having a complicated shape accurately and at high speed using relatively simple means. It's about doing.

[Means for solving problems]

The above purpose is to hold a tool holder that is rotatably attached to the processing head so that it can move back and forth a minute distance in a direction perpendicular to the main axis of rotation, and to rotate the workpiece about an axis that is parallel to the main axis. a step of freely supporting the main shaft of the machining head with respect to the one axis; and a step of moving the tool holder forward and backward a very small distance in a direction perpendicular to the main shaft of rotation, and then tightening the main shaft. for an internal combustion engine, comprising the steps of rotating the workpiece about the one axis at a speed of 372 times the rotational speed of the tool holder, and further processing and feeding the processing head in the direction of the main axis. This can be achieved by a piston outer diameter machining method.

Further, the above method includes a column movably mounted on a bed, a machining head attached to the column so as to be movable up and down, a tool holder rotatably attached to the machining head, and a workpiece. a stage that is rotatably supported at a speed of 3/2 of the rotation speed of the tool holder; a column displacement mechanism that displaces the column on the bed in a direction perpendicular to the rotation axis of the workpiece; a machining head tilting mechanism that tilts the machining head at a slight angle on the column so that the main rotation axis of the tool holder is tilted at a slight angle with respect to the rotation axis of the workpiece; a machining head elevating mechanism that moves the tool holder up and down in the direction of the rotational axis of the body to perform machining feed; This can be carried out by a piston outer diameter machining device for an internal combustion engine equipped with the following.

[For production]

With the above configuration, an elliptical shape can be machined without frequently reciprocating the tool toward the workpiece, and the required complicated outer peripheral shape of the piston can be achieved by tilting the machining head itself at a minute angle. Since the method can be controlled and processed accurately, an excellent method and apparatus for machining the outer diameter of a piston for an internal combustion engine can be provided, which can perform accurate and high-speed machining using relatively simple means.

〔Example〕

Hereinafter, details of the configuration of the present invention will be explained with reference to the drawings.

FIG. 1 is a front view showing an embodiment of the processing apparatus according to the present invention used to carry out the method according to the present invention, FIG. 2 is a left side view thereof, and FIG. FIG. 4 is an explanatory diagram showing an example of the outer diameter profile of the piston to be manufactured by machining, and FIG. 5 is an axis-perpendicular cross-section of the piston shown in the figure. An explanatory diagram showing the profile, Figures 6 to 15 are explanatory diagrams showing step by step how the processing is performed by the apparatus shown in Figures 1 to 3, and Figure 16 is an explanatory diagram showing the processing performed by the apparatus shown in Figures 1 to 3. FIG. 3 is an explanatory diagram regarding the shape of an ellipse processed by the apparatus shown in the figure.

First, the final shape of the outer peripheral surface of the piston to be machined will be explained with reference to FIGS. 4 and 5.

The outer circumferential surface of the piston must be able to ensure good contact and sliding conditions with the inner circumferential surface of the cylinder during engine operation.In other words, when the piston becomes hot and thermally expands during engine operation, its axis-perpendicular cross section must be a perfect circle.

However, the temperature of the gas that the piston comes into contact with is uneven both in place and time, and fluctuates wildly, and its average value also differs from place to place, and the wall thickness of the piston varies locally. Furthermore, composite materials may be used or cooling cavities may be provided, so the amount of thermal expansion is not uniform.

In anticipation of such thermal expansion at high temperatures, the outer peripheral shape of the piston is usually made so that the cross section perpendicular to its axis is an ellipse at room temperature, and the diameter is smaller on the side closer to the piston head. It is manufactured in

FIG. 4 shows an example of the ideal profile of the piston outer diameter as described above.

That is, FIG. 4 shows the change in the outer diameter along the axial direction of the piston 100 shown in the left half of the figure, plotted enlarged on the right curve, and the curve 100a shows the change in the outer diameter of the piston 100 along the axial direction. The curve 100b shows the change in the outer diameter of the shaft in the axial direction of the piston, and the curve 100b shows the change in the outer diameter of the long axis in the axial direction of the piston.

As can be seen from this figure, the piston 100 has a barrel-shaped shape that is most bulging in the middle region of its skirt.

(Such a change in the piston diameter along the axial direction will be referred to as "Taber" in the following explanation.) Therefore, in the piston 100, as shown in FIG.
The difference α between the lengths of the major and minor axes of the ellipse in the cross section perpendicular to the axis also changes along the axial direction of the piston, that is, the eccentricity of the ellipse also gradually changes along the axial direction. is understood. This is also to accommodate changes in the amount of thermal expansion in response to changes in the piston wall thickness and temperature distribution.

Furthermore, ideally, the above ellipse is not a complete ellipse, but as shown in FIG.
In other words, the curve 100 shown by the two-dot chain line is arranged so that the radius slightly expands around the area 45° away from the apex of 00c.
It is desirable to have a shape like d. (This expansion amount β
is hereinafter referred to as the "additional amount". ) This is approximately equivalent to the known double ellipse, which is a combination of two ellipses with slightly different eccentricities.

As mentioned above, it is difficult to process a piston having such a complicated outer diameter at high speed using conventionally known methods or devices.

Hereinafter, a method for machining the above-mentioned piston outer circumferential surface using the apparatus according to the present invention shown in FIGS. 1 to 3 will be explained.

In Figures 1 to 3, 1 is the bed and 2 is the bed 1.
3 is a column displacement mechanism that moves the column 2 on the bed 1 in the left-right direction in FIG. 2; 4 is a processing head mounted on the column 2 so as to be able to rise and fall; 5 is the processing A lifting mechanism for the head 4, 6 a processing head tilting mechanism for tilting the processing hand 4 at a minute angle on the column 2, 7 a tool holder rotatably attached to the processing head 4, and 8 a tool such as a cutting tool. , 9 is a servo motor that advances and retreats the tool holder 7 by a minute distance in a direction perpendicular to its rotational axis via the ball screw table 0, 11 is a stage on which the workpiece 100 is attached, and 12 is the above-mentioned object. A processing table has a built-in rotation mechanism for rotating the table 11, and 13 is an operation panel used to set processing conditions and the like.

The axis of rotation of the stage 11 is indicated by a dotted line 11' in FIGS. 2 and 3, and the main axis of rotation of the tool holder 7 is indicated by a chain line 7'.

Note that the rotation of the tool holder 7, the rotation of the stage 11, and the rotation main shaft 7' of the tool holder 7, which is performed by driving the servo motor 9,
Advances and retreats toward the target, processing feed by raising and lowering the processing head 4,
The movement of the column 2 on the bed is collectively controlled by a numerical control device, which is not shown in the figure.

When performing machining, by moving the column 2 on the bed 1, the rotation main shaft 7' of the tool holder 7 and the rotation axis 11' of the workpiece table 11 are moved by a minute amount (see FIGS. 2 and 2). (Indicated by q in Fig. 3.) The workpiece stand 11 is rotated at a rotation speed 3/2 times the rotation speed of the tool holder 70 (for example, when the rotation speed of the tool holder 7 is 400° rpm, the workpiece stand 11 is in an eccentric state. ), and at the same time, the machining head 4 is slowly moved along the rotation axis 11' of the stage 11 to apply machining feed, and the servo motor 9 is activated. By displacing the tool holder 7 with respect to its rotating main shaft 7', the distance between the cutting edge of the tool 8 and the rotating main shaft 7' is changed, and furthermore, the tilting mechanism 6 of the machining head 4 is actuated to produce the state shown in FIG. Tool holder 7 as shown
Machining is carried out by controlling the slight inclination angle θ of the rotating main shaft 7' from a position parallel to the rotating shaft 11' of the stage 11 in accordance with the machining feed.

At this time, the amount of taper of the piston is controlled by the distance between the cutting edge of the tool 8 and the rotating main shaft 7' controlled by the servo motor 9, and the eccentricity of the ellipse is determined by the rotation of the tool holder 7 based on the position of the column 2 on the bed. Eccentricity between the main shaft 7' and the rotating shaft 11' of the stage 11! q, and the addition amount β
is controlled by the inclination angle θ of the processing head 4.

Hereinafter, the progress of one process will be explained with reference to FIGS. 6 to 15.

Now, the rotating main shaft 7' of the tool holder 7 and the rotating shaft 11 of the stage
' are set parallel to each other and their eccentricity is q, the tool holder 7 is 4000 rpra, and the stage 11 is 6000 rpra.
The rotating main shaft 7' of the tool holder 7 is rotated at rpm.
The explanation will be made assuming that the distance from to the cutting edge of the tool 8 is constant.

FIG. 6 shows a state in which the tool 8 is on the same plane as the plane containing the main shafts 7' and ll, and machining is started from this position. Further, at this time, the cutting edge of the tool 8 is assumed to be in contact with the surface of the piston 100 (indicated by point a in the figure).

If the number of rotations of the stage 11 is set to 3/2 times the number of rotations of the tool holder 7, the piston 100 will rotate 60' while the tool holder 7 rotates, for example, 40', as shown in FIG. The situation will be as shown. At this time, the position of the cutting edge of the tool is b
As a result, the area from point a to b, that is, the area of about 20° in terms of the center angle of the piston (main axes 71 and 11'
Since it is eccentric, it is not exactly 20 degrees) has been turned.

Similarly, the tool holder 7 is set at 40°, and the piston 100 is
The states in which the blades are rotated by 60° are sequentially shown in FIGS. 8 to 15, and the respective positions of the cutting edges are indicated by C to J.

FIG. 15 shows that the tool holder 7 has rotated 360' and the piston 100 has rotated 540' during this period, so that the half circumference of the piston 100 is rotated from point a to j.
It can be seen that it is processed into an elliptical shape along the .

Thereafter, in the same manner, the tool holder 7 is further rotated by 360° and the piston 100 is rotated by 540', and the remaining half circumference is machined to form a complete ellipse.

The above-mentioned elliptical machining is not possible by simply rotating either the piston 100 or the tool holder 7 with the main shafts 71 and 11' eccentric.
It is easily understood that this becomes possible only when both are rotated at a ratio of 3/2.

Furthermore, it should be noted that in the method according to the present invention, the above-mentioned elliptical machining can be performed while keeping the distance between the cutting edge of the tool 8 and the rotating main shaft 7' of the tool holder constant.

That is, since elliptical machining is performed without frequently reciprocating the tool toward the workpiece as in the past, accurate machining can be performed even when the tool holder 7 and piston 100 are rotated at high speed. This enables high-speed and high-precision machining.

Thus, changing the eccentricity q of the main shafts 7' and 11',
Alternatively, it is easily understood that by changing the distance between the main shaft 71 and the cutting edge of the tool 8, the shape of the ellipse to be machined, that is, the eccentricity can be changed. When machining the outer circumferential surface of the piston as shown in Fig. 4, the machining equipment shown in Figs. Thereafter, the servo motor 9 is operated to gradually displace the tool holder 7 to gradually increase the distance, thereby machining the taper so that the outer diameter of the piston gradually increases toward the bottom of the skirt. be.

In addition, the basic eccentricity of the ellipse to be machined is determined by adjusting the eccentricity q of the main shafts 71 and 111 at the start of machining, and the column displacement mechanism 3 is operated to move the column 2 in accordance with the machining feed. By gently advancing and retracting the stage toward the rotating shaft 111, it is possible to form a difference in length between the long and short axes (that is, a minute change in eccentricity) shown by α in FIG.

This will be explained with reference to FIG. The distance between the rotational spindle 7' of the tool holder 7 and the tip of the tool 8 is D, and the rotational spindle 7' of the tool holder 7 and the rotational axis 11' of the workpiece 100 is
If the amount of eccentricity is q (where 1) >> q), then the major axis of the ellipse to be machined will be 1) + q, and the minor axis will be D - q.

Here, when changing the short axis without changing the long axis, D'-
D+Δ, q'=q-Δ, and when changing the major axis without changing the minor axis, D'=D+Δ, q'
= q + Δ, and when changing the whole in a similar manner, D' = D + Δ and q' = q.

Therefore, when these are combined, it is possible to produce a desired barrel shape in which the eccentricity of the ellipse in the cross section perpendicular to the axis gradually changes along the axial direction. .

Therefore, the additional amount β (usually several tens of μm) shown in Figure 5
In the apparatus shown in FIGS. 1 and 2, the rotation main shaft 7' of the tool holder 7 is aligned with the rotation axis 1 of the workpiece.
The machining head 4 is tilted slightly N so that the machining head 4 is tilted at a slight angle θ with respect to 1'. That is,
Processing is performed with the processing head 4 tilted to a position of 7" as shown in FIG.
In the case of forming an additional amount of m, the objective can be achieved by setting the inclination angle θ to about 1° when the distance between the cutting edge of the tool 8 and the rotating main shaft 7' is 150 mm.

〔Effect of the invention〕

Since the present invention is constructed as described above, the present invention provides an excellent piston outer diameter for internal combustion engines that allows piston outer diameters having complicated shapes to be machined accurately and at high speed by relatively simple means. A processing method and apparatus are provided.

The configuration of the present invention is not limited to the embodiments described above, but includes all modified embodiments that can be easily conceived by a person skilled in the art from the above description within the scope of the purpose of the present invention. It is something.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the processing apparatus according to the present invention used to carry out the method according to the present invention, FIG. 2 is a left side view thereof, and FIG. FIG. 4 is an explanatory diagram showing an example of the outer diameter profile of the piston to be manufactured by machining, and FIG. 5 is an axis-perpendicular cross-section of the piston shown in the figure. An explanatory diagram showing the profile, Figures 6 to 15 are explanatory diagrams showing step by step how the processing is performed by the apparatus shown in Figures 1 to 3, and Figure 16 is an explanatory diagram showing the processing performed by the apparatus shown in Figures 1 to 3. FIG. 3 is an explanatory diagram regarding the shape of an ellipse processed by the apparatus shown in the figure. 1・・−・−・−・−−m−−−−−・−Bed 2
−−−−〜−−−−・・・・−・−・−−−−−One column 3−−−−−−−−−−−−−−・−−−m−・−・
・Column displacement mechanism 4-------・・----1------
−−〜−−−−−Processing head 5−・・・−・・・・・
・−・−・−Processing head lifting mechanism 6−−−−−・−
−−−−1・・−・・−−−−～・−Processing head tilting mechanism 7・・−・・−・−・−1−−・・−1−−−・−
・Tool holder 8--...-----11--
−−−Tool 9−−−−−−・−・−−−−−−1−
−−・・−Servo motor 10・−・−・−・・−−−−
−・−−−−・−・・Ball screw table 1i−
−−−−1−−・−−−−−−−−−−−−−−・−Processing table 12−−−−−−1−−−−−−・−・−Processing table 13−・・−−１−−−・−・−・−・・
・−Operation panel 100−～−−−−・−−−−−−−−・・
・--Workpiece patent applicant Izumi Jidosha Kogyo Co., Ltd. Agent (7524) Mogami Seita-part Workpiece

Claims (1)

[Claims] 1) Holding a tool holder rotatably attached to the processing head so as to be able to move forward and backward by a minute distance in a direction perpendicular to the main axis of rotation, and holding the workpiece on one axis parallel to the main axis. a step of tilting the main axis of the machining head at a minute angle with respect to the one axis; and moving the tool holder forward and backward a minute distance in a direction perpendicular to the main axis of rotation. rotating the workpiece around the main axis, rotating the workpiece around the one axis at a speed of 3/2 of the rotational speed of the tool holder, and further processing feeding the processing head in the direction of the main axis; A method for machining the outer diameter of a piston for an internal combustion engine. 2) A column movably mounted on a bed, a machining head attached to the column so as to be movable up and down, a tool holder rotatably attached to the machining head, and a workpiece being rotated by the tool holder. a workpiece stand rotatably supported at 3/2 of the speed; a column displacement mechanism for displacing the column on the bed in a direction perpendicular to the rotation axis of the workpiece; and rotation of the tool holder. a processing head tilting mechanism that tilts the processing head at a small angle on the column so that the main axis is inclined at a small angle with respect to the rotation axis of the workpiece; an internal combustion engine comprising: a machining head elevating mechanism that moves the tool holder up and down to perform machining feed; and a tool holder advance/retreat mechanism that holds the tool holder on the machining head so that it can move back and forth over a minute distance in a direction perpendicular to its rotational main axis. Engine piston outer diameter processing equipment.