JP2000205155A - Scroll lap processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish good processing accuracy, shorten the time of processing, and suppress the production costs by deciding the optimum end mill feeding speed for the part processed in accordance with the radius of curvature in a scroll lap processing method with varying radius of curvature. SOLUTION: Processing of the outer side face 1b of a scroll lap 1a is conducted with the feeding speeds of end mills 2 and 3 decreased in compliance with decrease in the radius of curvature R of the outer side face 1b so that the surface roughness in the end mill moving direction determined by the radius of curvature R of the outer side face 1b, the radius of end mill, and its feeding speed becomes constant, while processing of the inner side face 1c of the lap 1a is conducted while the feeding speeds of the end mills 2 and 3 are decreased in compliance with the decrease in the radius of curvature R of the inner side face 1c in reverse proportion to the maximum contacting length of the inner side face 1c with the end mills 2 and 3 decided by the radius of curvature R of the inner side face 1c, the radius of end mill, and its feeding speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to inner and outer surfaces and bottom surfaces of orbiting scrolls and fixed scrolls forming a compression chamber of a scroll compressor used for a room air conditioner, a vacuum pump, a car air conditioner, an air compressor and the like. And a method of processing a scroll wrap for processing

[0002]

2. Description of the Related Art Regarding a processing method for finishing a scroll wrap having an involute curve shape with an end mill,
JP-A-4-284509, JP-A-7-16423
There are methods described in, for example, Japanese Patent Application Laid-Open Publication No. 1 (1995) -207, which controls the feed speed of an end mill according to the radius of curvature of an involute curve. This will be described with reference to FIG. 11 in the case where the wrap of the orbiting scroll is finished with an end mill.

First, a processing method described in Japanese Patent Application Laid-Open No. 4-284509 will be described. FIG. 11A shows a method of processing the outer surface 11 a of the scroll wrap by the end mill 12. The end mill 12 is moved and processed so as to form the outer surface 11a, and the feed speed of the end mill at this time is controlled so as to be a constant value F at a contact point between the end mill 12 and the outer surface 11a. In order to obtain this constant value F,
An NC machine tool (not shown) changes the feed speed at the center of the end mill 12 according to the radius of curvature R.

Next, a processing method described in Japanese Patent Application Laid-Open No. 7-164231 will be described. FIG. 11B shows a method of processing the inner side surface 11 b by the end mill 12. In the processing of the inner side surface 11b, the cutting arc length S of the end mill 12 remarkably changes due to the radius of curvature of the inner side surface 11b. The smaller the radius of curvature R, the longer the cutting arc length S, and the longer the cutting arc length S, the greater the cutting resistance acting on the end mill 12. In particular, the increase in the cutting arc length S becomes remarkable at the central portion where the radius of curvature R of the inner side surface 11b becomes small, and the cutting resistance also increases remarkably. This increase in cutting resistance causes deterioration of machining accuracy. Therefore, to prevent an increase in cutting force,
The feed speed of the end mill 12 is changed so as to decrease as the cutting arc length S increases.

[0005]

In the above-mentioned method of processing a scroll wrap, the following points have not been considered in the method of controlling the feed speed of the end mill.

The first point is that when processing is performed with the end mill feed speed at the cutting point being constant, the surface roughness of the processed surface changes as the radius of curvature of the lap decreases.
In particular, this was a phenomenon in which the surface roughness was significantly deteriorated in a portion where the radius of curvature of the outer surface was small.

Next, in the method of controlling the feed rate of the end mill corresponding to the cutting arc length determined by the radius of curvature and the radius of the end mill, the feed amount of the end mill is considered in determining the length of the end mill in contact. I didn't. In finish machining with a very small depth of cut, the feed amount of the end mill also affects the length that the end mill contacts.
In particular, there has been a phenomenon in which the influence of the end mill feed amount becomes remarkable in the processing of the center portion of the inner surface where the length of contact with the end mill increases. For this reason, the cutting resistance has increased at the center portion of the inner surface, and the accuracy of the curved shape has deteriorated.

[0008] The second point is that end mills usually have cutting edges on the side and bottom surfaces, and can process both the side surface alone and the side surface and the bottom surface at the same time. It was done.

As described above, the method of controlling the feed rate of the end mill and the processing method are an inefficient operation in which processing experiments are repeated by trial and error.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scroll wrap capable of finishing the inner and outer surfaces and the bottom surface of the orbiting scroll and the fixed scroll forming the compression chamber of the scroll compressor with high precision and efficiency. Is to provide a law.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an end mill for processing a scroll wrap having a thickness and a height, wherein a wrap having an involute curve stands upright from a mirror surface. Processing is performed by decreasing the feed speed of the end mill in accordance with the decrease in the radius of curvature of the outer surface so that the surface roughness in the end mill moving direction determined by the radius of curvature of the outer surface, the end mill radius, and the end mill feed speed is constant. On the inner surface of the wrap, the radius of curvature of the inner surface decreases so as to be inversely proportional to the maximum contact length between the inner surface and the end mill determined by the radius of curvature of the inner surface, the end mill radius, and the end mill feed speed. And reducing the feed rate of the end mill in accordance with the above.

[0012] The object of the present invention is to provide an end mill for processing a scroll wrap having a thickness and a height, wherein a wrap having an involute curve stands upright from a mirror surface, wherein an outer surface of the wrap has a radius of curvature of the outer surface. And reducing the feed rate of the end mill in accordance with a decrease in the radius of curvature of the outer surface so that the surface roughness in the end mill moving direction determined by the end mill radius and the end mill feed rate is substantially constant, and processing the wrap. On the inner surface, the radius of curvature of the inner surface is reduced in proportion to the increase in the maximum contact length between the inner surface and the end mill, which is determined by the radius of curvature of the inner surface, the end mill radius, and the end mill feed rate. Processing by reducing the feed rate of the end mill
Achieved by:

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. An embodiment of a machining method according to the present invention will be described with reference to FIGS. Even when a pair of fixed scrolls is to be processed, the processing method is the same, except that the spiral direction of the scroll wrap is opposite.

1 (a), 1 (b) and 1 (c) are explanatory diagrams showing the movement path of the end mill, FIG. 2 is a diagram showing an involute curve, and FIGS. 3 (a) and 3 (b) show the formation of the surface roughness of the cylindrical outer surface. FIG. 4, FIG. 4 shows the formation of the surface roughness of the inner surface of the cylinder, FIG. 5 shows the change in the surface roughness, FIG. 6 shows the maximum contact length of the outer surface of the cylinder, and FIG. Diagram showing the maximum contact length of the inner surface,
FIG. 8 is a diagram showing a change in the maximum contact length, and FIG.
(B) is a diagram showing an example of an end mill feed speed, and FIG.
(A), (b) is a figure which shows the processing situation of the inner or outer surface or bottom surface of the scroll wrap of an end mill.

In FIGS. 1 (a), 1 (b) and 1 (c), reference numeral 1 denotes a revolving scroll, 1a denotes a wrap, 1b denotes an outer surface, 1c denotes an inner surface, 1d denotes a bottom surface, 1f denotes an outer surface processing start point, and 1g denotes an outer surface. The side processing end point, 1h is the inner surface processing start point, 1i is the inner surface processing end point, 1j is the bottom processing start point, 1k is the bottom processing end point, 2 is the end mill for side processing, and 3 is the end mill for bottom processing. .

3, 6 and 7, 4 is a cylindrical surface, and in FIGS. 10 (a) and 10 (b), 2a is an outer peripheral blade, 2b
Denotes a bottom blade, 3a denotes an outer peripheral blade, and 3b denotes a bottom blade. First,
The trajectory of the end mill will be described with reference to FIGS. In the wrap 1a of the orbiting scroll 1 shown in (a), the side milling end mill is moved from the outer surface processing start point 1f of the outer surface 1b toward the center toward the outer surface processing end point 1g.

Next, the side milling end mill 2 shown in (b) is folded back at the center portion, and moved from the inner surface milling start point 1h to the inner line milling end point 1i in the outer circumferential direction. Subsequently, the center of the bottom milling end mill 3 shown in (c) is moved from the processing start point 1j of the bottom surface 1d to the bottom surface processing end point. The diameter of the bottom milling end mill 3 is smaller than the groove width of the wrap 1a, and does not contact the outer side surface 1b and the inner side surface 1c.

The outer surface 1b, the inner surface 1c and the bottom surface 1d are finished by a series of movements of the end mills 2 and 3 described above. In the above embodiment, the outer surface 1b, the inner surface 1c, and the bottom surface 1d are processed in this order, but the combination of this order may be other. Although the side milling end mill 2 and the bottom milling end mill 3 are shown separately, they do not prevent the same end mill.

Here, referring to FIG. 2 to FIG.
A method for determining the feed speed of the end mill in the processing of the inner surface 1b and the inner surface 1c will be described. FIG. 2 shows the scroll wrap 1
3 shows an involute curve defining a. In the figure, the point (X, Y) on the involute curve is represented by the following formula 1 when A is a base circle radius, θ is an expansion angle, and α is a phase angle.
It is represented by

[0020]

(Equation 1)

The radius of curvature R at the expansion angle θ is expressed by the following equation (2).

[0022]

(Equation 2)

As shown in Equation 2, the radius of curvature R of the involute curve changes in proportion to the opening angle θ. Among the changes in the processing accuracy under the condition in which the radius of curvature R changes, the change in the surface roughness will be described with reference to FIGS.

FIGS. 3A and 3B show the formation of surface roughness on the outer surface. 2 on the side end mill 2 to be machined
Taking an example of a single-blade end mill, the sectional shape shown in FIG. This end mill 2 has two cutting edges A (1), A
There is (2), and cutting is performed by moving while rotating. By the rotation, the cutting edge A reaches the position of the cutting edge A (2).
The distance the end mill 2 moves while (1) is rotating is referred to as one-blade feed and is indicated by F. The feed speed of the end mill 2 is determined by the product of the feed F of one blade, the number of blades, and the rotation speed of the end mill 2.

Hereinafter, the indication of the end mill 2 is simply indicated by a circle. In (b), the side end mill 2 having a radius W is moving so as to machine the outer periphery of the cylindrical surface 4 having a radius of curvature R. The center of the side end mill 2 after processing the center of the side end mill 2 by one feed F from point P is defined as point Q.
The feed F of one blade is set equal to the length of the arc BC. Here, a portion surrounded by three circles, that is, circles 1, 2, and 3 is an uncut portion after the cylindrical surface 4 having the curvature radius R is processed by the side end mill 2 having the radius W. The maximum height T is the theoretical surface roughness of the cylindrical surface 4 having the radius of curvature R. The scroll wrap 1a (see FIG. 1) is an involute curve in which the radius of curvature changes continuously. However, in practice, the feed F of one blade of the side end mill 2 is very small. As far as focusing on one section,
It can be approximated by an arc. In addition, U is an allowance (cutting allowance).

The theoretical surface roughness T is the length of the line segment DE, and is a value obtained by subtracting the lengths of the line segments GH and DG from the line segment HE, and is determined by the following equation (3). On the other hand, FIG.
When the theoretical surface roughness T for processing the inner surface of the cylinder 4 having the radius of curvature R in the arrangement shown in FIG.
Here, in Equations 3 and 4, the radius W of the side end mill 2 is 4 mm, the feed F of one blade is 0.3 mm, and the radius of curvature R is obtained in a range of 2 mm to 50 mm. Then, it becomes as shown in FIG.

In the figure, on the outer surface, the theoretical surface roughness T increases in accordance with the decrease in the radius of curvature R. For example, for a theoretical surface roughness of 3.0 μm at a position with a radius of curvature of 50 mm, the radius of curvature is

[0028]

(Equation 3)

[0029]

(Equation 4)

The theoretical surface roughness at the position of 2 mm is 8.5 μm, which is 2.8 times larger. On the other hand, on the inner side surface 1c, the theoretical surface roughness T decreases as the radius of curvature R decreases. For example,
While the theoretical surface roughness at a position with a radius of curvature of 50 mm is 2.6 μm, the surface roughness at a position with a radius of curvature of 5 mm is 0.6 μm and 23 μm.
% To be good.

As described above, if machining is performed with the feed F of one blade being constant, a problem occurs in that the theoretical surface roughness T becomes extremely large at a part of the center having a small radius of curvature R on the outer surface 1b of the scroll wrap 1a. Becomes

Therefore, in order to prevent the surface roughness at the center of the outer surface 1b from deteriorating, the theoretical surface roughness T in Equation 3 may be set to a constant value at an expected value. F solves Equation 3 with respect to F, and becomes Equation 5 below.

[0033]

(Equation 5)

If the feed F of one blade of the end mill corresponding to the radius of curvature R is determined by the above formula 5, the surface roughness of the outer side surface 1b can be kept constant.

Next, the phenomenon that the maximum contact length of the end mill changes will be described with reference to FIGS.

First, the outer side surface 1b will be described with reference to FIG. 6 having an arrangement similar to that of FIG. In the figure, the arc DCI is the maximum contact length of one blade in the cross section of the side end mill 2 and is represented by S.

The maximum contact length S is given by:

[0038]

(Equation 6)

If ∠OQD is γ and ∠OQI is δ, β is the sum of γ and δ.

[0040]

(Equation 7)

## EQU1 ## Therefore, the maximum contact length S in the processing of the inner side surface 1c can be determined by substituting Equation 7 into Equation 6.

Further, in the arrangement of FIG. 7 similar to FIG. 4, the maximum contact length S on the inner side surface 1c can be calculated by the same method as that obtained by the above-mentioned equation (7), where ΔDQI is β.

[0043]

(Equation 8)

[0044]

(Equation 9)

Is as follows. Thus, the maximum contact length S in the processing of the inner side surface 1c can be determined by obtaining β from Expression 9 and substituting β into Expression 8.

Here, the above-mentioned equations (6), (7), (8),
Using Equation 9, the maximum contact length S is determined in a range of a radius of curvature R of 2 to 50 mm with a radius W of the side end mill 2 of 4 mm and a feed F of one blade of 0.3 mm. Become like

According to the embodiment shown in FIG. 8, the change in the maximum contact length S is relatively small with respect to the change in the radius of curvature R on the outer side surface 1b, while the center portion with a small radius of curvature R on the inner side surface 1c. Shows a phenomenon that the maximum contact length S becomes extremely large. The maximum contact length S at the center of the inner surface 1c
The rapid increase in the cutting force leads to a sudden increase in the cutting resistance, which promotes the deformation of the end mill 2 and deteriorates the processing accuracy, particularly the shape accuracy.

In order to avoid this phenomenon, in processing the inner surface 1c, the feed F of one blade for processing the outermost peripheral portion is set to F (ma
x) and the maximum contact length S (min) at this time is:
The feed F is obtained according to the change in the radius of curvature R according to the following equation (10).

[0049]

(Equation 10)

From the above equation (10), it is possible to appropriately decrease the feed F of one blade of the end mill 2 in accordance with the increase of the maximum contact length S, and the cutting resistance increases at the central portion where the radius of curvature R is small, so that the accuracy is increased. Can be prevented from deteriorating.

The method of changing the feed F of one blade of the end mill 2 on the outer surface 1b from the above equation (5) and the method of changing the feed F of one blade of the end mill 2 on the inner surface 1c from the above equation (10) are plotted. Then, FIG. 9A,
(B). As an example condition, the radius W of the side end mill 2 is 4 mm, the feed F of one blade at the maximum portion of the radius of curvature R is 0.3 mm, and the radius of curvature R is 2 to 50 mm.

By changing the feed speed instruction value of the processing device (not shown) according to the deceleration patterns shown in FIGS. 9A and 9B, it is possible to control the feed speed of the end mill appropriately.

Next, the working condition of the inner and outer surfaces 1b, 1c or the bottom surface 1d of the scroll wrap 1a of the end mill 2 will be described with reference to FIG.

When finishing the outer side surface 1b and the inner side surface 1c, as shown in FIG.
, But not the bottom blade 2c (ie, non-contact). The optimal one-blade feed for finishing the outer side surface 1b and the inner side surface 1c does not consider the processing of the bottom surface 1d.

Therefore, the outer surface 1b is formed by the above-described method.
When finishing the inner side surface 1c, it is not possible to select the optimum conditions for finishing the bottom surface 1d. So, bottom 1
It is advisable to finish d in a separate step. in this case,
The fact that the bottom edge 2c of the side end mill 2 is in contact causes a bad effect and only causes vibration, but does not bring a significant situation. Therefore, the bottom blade 2c does not contact,
Finish outer surface 1b and inner surface 1c.

The bottom surface 1d is finished using only the bottom blade 3b without contacting the side blade 3a of the bottom end mill 3 as shown in FIG. Optimal conditions can be set for finishing the bottom surface 1d.

As described above, the outer surface 1b and the inner surface 1
c, by individually finishing the bottom surface 1d, processing can be performed under optimum conditions specific to each of them.

[0058]

According to the present invention, in the processing of a scroll wrap having a variable radius of curvature, the optimum feed rate of the end mill for the processing portion can be determined according to the radius of curvature, and good processing accuracy can be obtained. Further, since the feed speed of the end mill can be optimized, the processing time can be shortened, and therefore, the production cost of the scroll compressor can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a moving path of an end mill according to a method of processing a scroll wrap according to the present invention.

FIG. 2 is an explanatory diagram showing an involute curve.

FIG. 3 is an explanatory view showing the formation of surface roughness on the outer surface of a cylinder.

FIG. 4 is an explanatory diagram showing the formation of surface roughness on the inner surface of a cylinder.

FIG. 5 is a diagram showing a change in surface roughness.

FIG. 6 is an explanatory view showing a maximum contact length of a cylindrical outer surface.

FIG. 7 is an explanatory view showing the maximum contact length of the inner surface of the cylinder.

FIG. 8 is a diagram showing a change in a maximum contact length.

FIG. 9 is a diagram illustrating an example of a feed speed of an end mill.

FIG. 10 is an explanatory view showing contact of an end mill.

FIG. 11 is an explanatory view showing a moving path of an end mill in a conventional scroll wrap processing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... orbiting scroll 1a ... scroll wrap 1b ... outer surface 1c ... inner surface 1d ... bottom surface 1f ... outer surface processing start point 1g ... outer surface processing end point 1h ... inner surface processing start point 1i ... outer surface processing end point 1j ... bottom surface Processing start point 1k Bottom processing end point 2 Side processing end mill 2a Peripheral blade 2b Bottom blade 3 Bottom processing end mill 3a Peripheral blade 3b Bottom blade 4 Cylinder F Feeding one blade R Curvature radius T Theoretical surface roughness U: removal allowance W: radius of end mill

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuya Kato 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside of Hitachi, Ltd. Hitachi, Ltd.Cooling Division (72) Inventor Minoru Tateno 800, Oda-machi, Ohira-machi, Shimotsuga-gun, Tochigi Prefecture F-term (Ref.) 3C022 AA04 AA09 AA10 EE05 EE17 KK03 KK06 KK23 KK25 3H039 BB07 CC02 CC03 CC05

Claims (4)

[Claims] 1. A method for processing a scroll wrap having a thickness and a height, wherein a wrap having an involute curve is upright from a mirror surface by an end mill, wherein a radius of curvature and an end mill radius of the outer surface are provided on an outer surface of the wrap. In order to keep the surface roughness in the end mill moving direction determined by the end mill feed speed and the end mill feed speed constant, the feed speed of the end mill is reduced in accordance with the decrease in the radius of curvature of the outer surface, and processing is performed. The feed of the end mill according to the decrease of the radius of curvature of the inner surface so as to be inversely proportional to the maximum contact length between the inner surface and the end mill determined by the radius of curvature of the inner surface, the end mill radius and the end mill feed speed. A scroll wrap processing method characterized by processing at a reduced speed. 2. The scroll wrap according to claim 1, wherein the end mill is kept out of contact with the bottom surface of the scroll wrap, and the outer surface or the inner surface of the scroll wrap is machined using the outer peripheral edge of the end mill. Processing method. 3. The scroll wrap according to claim 1, wherein the end mill is not in contact with the outer surface and the inner surface of the scroll wrap, and the bottom surface of the scroll wrap is machined using the bottom blade of the end mill. Processing method. 4. A processing method for processing a scroll wrap having a thickness and a height and having a wrap formed of an involute curve standing upright from a mirror surface by an end mill, wherein an outer surface of the wrap has a radius of curvature and an end mill radius of the outer surface. And reducing the feed speed of the end mill in accordance with the decrease in the radius of curvature of the outer surface so that the surface roughness in the end mill moving direction determined by the end mill feed speed is substantially constant. In accordance with the decrease in the radius of curvature of the inner surface so as to be substantially inversely proportional to the increase in the maximum contact length between the inner surface and the end mill determined by the radius of curvature of the inner surface, the end mill radius and the end mill feed rate. A scroll wrap processing method characterized by processing by reducing the feed speed of an end mill.