JPH07164231A - Machining method for scroll volute - Google Patents

Abstract

PURPOSE:To reduce cutting force and increase shape accuracy, by reducing the feeding speed of a tool to machine a work piece in accordance with the increase ratio of the length of the cutting arc of tool decided from the radius of an end mill and the curvature of an involute curve. CONSTITUTION:When the outer and inner wall faces of a scroll wrap 1 are processed by an end mill tool 2 to make an involute curve, after the locus of tool has been calculated from the data regarding to the preparation of tool locus, in which an appropriate distribution of the tool-feeding speed is automatically input by a tape or the like, by use of a NC device, an equivalent radius of curvature of the tool locus for the time when the outer and inner wall faces of the scroll wrap are processed is calculated. The previously input tool-feeding speed is made 100% and the tool-feeding speed is gradually made 100% as the equivalent radius of curvature increases. Ans also, the feeding speed is appropriately distributed in accordance with the feeding speed operation function gradually delaying the speed as the equivalent radius of curvature increases to numerically control the driving motor for the processing table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scroll processing method suitable for highly accurately processing the spiral shape of a scroll wrap portion which is a protruding portion of a male scroll and a female scroll of a scroll compressor.

[0002]

2. Description of the Related Art As a method of processing the outer wall surface and the inner wall surface of the wrap portion of the male scroll and the female scroll which form the compression chamber of the scroll compressor, for example, Japanese Patent Laid-Open No. 63-239388 and Japanese Patent Laid-Open No. 3389388 As described in JP-A-35911, machining the outer and inner wall surfaces of a scroll wrap with the same end mill tool, bending rigidity in a direction perpendicular to the side wall surface of the scroll wrap portion, and bending of an end mill which is a machining tool. Attempts have been made to improve the squareness by setting the rigidity to be almost the same. In these conventional techniques, due to the change of the contact arc length of the scroll lap involute curve and the diameter of the end mill, the cutting force is temporarily changed, and the shape accuracy of the outer and inner wall surfaces of the involute curve is not considered to be deteriorated. .

[0003]

When the involute curves on the outer and inner wall surfaces of the scroll wrap according to the present invention are machined by an end mill, the shape accuracy becomes poor in a region where the radius of curvature of the involute curve at the center of the scroll is small. . The purpose is to improve the shape accuracy of the outer and inner wall surfaces of the scroll wrap. In the region where the radius of curvature of the involute curve at the center of the scroll is small, the cutting arc length of the tool and the work becomes long, the cutting force increases, and the shape accuracy after machining deteriorates. In order to reduce the cutting force at the center of the scroll, therefore, it is necessary to reduce the tool feed speed or the depth of cut to prevent the shape accuracy from deteriorating. The method of appropriately distributing the position of the tool locus of the scroll wrap portion, the tool feed speed, and the depth of cut is unknown, and NC data was created by trial and error and trial machining was performed. The problems to be solved by the present invention are the creation of NC data by trial and error and the omission of the trial processing step, and the improvement of the shape accuracy of the scroll wrap portion.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for machining the outer wall surface and the inner wall surface of a scroll wrap portion by NC control using an end mill tool, and in accordance with the radius of curvature of the involute curve of the scroll wrap portion, the end mill. Corresponding to changes in the cutting arc length of the tool, by slowing down the tool feed speed at the machining point where the cutting arc length becomes longer,
The shape accuracy of the involute curve can be improved.

Further, instead of the means for changing the tool feed speed, the machining allowance is preliminarily set so that the cutting depth of the tool changes from the cutting arc length of the tool and the workpiece corresponding to the pre-calculated tool locus. The shape accuracy of the scroll wrap portion can be improved by finishing the work at an almost constant tool feed speed.

[0006]

The present invention relates to a method of cutting an outer wall surface and an inner wall surface of a scroll wrap portion by using an end mill tool with an NC-controlled tool locus. The tool path of the end mill is given by an involute curve, a radius of curvature equivalent to the involute curve is calculated, and from this radius of curvature and the radius of the tool, an equivalent radius of curvature of the tool converted as a linear shape is calculated, After that, the cutting arc length between the tool and the workpiece can be calculated from the equivalent radius of curvature and the cutting amount of the tool. The tool feed rate corresponding to the tool trajectory of the involute curve is NC by the method of obtaining the equivalent radius of curvature of the tool.
Highly accurate shape accuracy can be obtained by automatically performing arithmetic processing in the control device, distributing an appropriate tool feed speed corresponding to the tool trajectory, and processing the scroll wrap portion with the end mill.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIGS. 4 is an external perspective view of the scroll processing machine, FIG. 3 is a perspective view showing a scroll vortex-shaped processing portion of FIG. 4, and FIG. 1 is a tool locus when processing the involute curve of the scroll of FIG. 2 is an explanatory diagram showing FIG.
FIG. 6 is an explanatory diagram in which the cutting arc length of the end mill and the workpiece changes when the involute curve of 1 is cut by the end mill to machine.

The processing machine shown in FIG. 4 has substantially the same structure as a general horizontal axis machining center, and an N-type machine is installed on the bed 9.
An X-axis table 4, a Y-axis table 6, a Z-axis table 8 and a rotary table 5 which are movable by a positioning input from the C control device are arranged. On the rotary table 5, a male scroll, which is the workpiece 1, is fixed by a chuck 10. An end mill 2 is fixed to the tip of the rotating shaft of the main shaft 3 so as to face the workpiece 1. The motion system of the processing machine shown in FIG.
X-axis table 4 for linearly moving the tool feed in the horizontal direction, a rotary table 5 for rotationally moving the workpiece 8, a Y-axis table 6 for linearly moving the rotary table 5 in the vertical direction, and an X-axis for the Y-axis table 6. A linear movement is possible in a direction perpendicular to the movement direction of the table 4, and both are configured so that they can be positioned according to an input signal from an NC control device (not shown).

In this embodiment, by using the processing machine having the structure shown in FIG. 4, the outer side of the scroll wrap shown in FIG.
The present invention relates to an NC control method when the inner wall surface is cut by the end mill 2. Next, FIG. 1 shows a tool locus of the end mill 2 when processing the outer and inner wall surfaces of the scroll wrap portion into an involute curve shape. The end mill 2 moves to the central portion along the outer wall surface of the scroll wrap, folds back the central portion, moves along the inner wall surface, and takes a tool locus to reach the machining end point. At this time, FIG. 2 shows the magnitude of the cutting arc length when the end mill 2 moving along the outer wall surface and the inner wall surface is machined with a cutting depth t. When the end mill 2 having the radius r is machined along the outer wall surface having the radius of curvature Ro with the depth of cut t, the contact arc length between the tool and the workpiece, that is, the cutting arc length Lo is given by the following equation. The equivalent radius of curvature of the tool here is R _EO .

[0010] Further, when the end mill 2 having the radius r is machined with the depth of cut t along the inner wall surface having the radius of curvature Ri, the cutting arc length Li between the tool and the workpiece is given by the following equation. The equivalent radius of curvature of the tool here is R _Ei .

[0011] In Expression 2 and Expression 4, the end mill 2 having the same radius r
When cutting is performed with the same depth of cut t, the respective equivalent curvature radii R _EO and R _Ei when the radii of curvature Ro and Ri of the outer wall surface and the inner wall surface are equal to R _EO <r <R _Ei Become. As a result, from Expression 1 and Expression 3, the cutting arc length Lo of the outer wall surface and the cutting arc length Li of the inner wall surface are Lo <Li, and the cutting arc length Li of the inner wall surface increases.

5 and 6 show the results calculated by using the formulas 1 to 4 in the example of the male scroll of the scroll compressor. FIG. 5 shows the radius of curvature when the tool loci of the involute curves of the outer wall surface and the inner wall surface of the male scroll are interpolated by an arc, and the equivalent radius of curvature corresponding to this FIG. 5 is shown in FIG. From FIG. 6, when machining the inner wall surface of the central portion of the scroll wrap, it becomes as large as about 7 times the other equivalent radius of curvature R _Ei . That is, when processing is performed using an end mill having a diameter of 10 mm, the cutting arc length at the center of the scroll wrap is the same as that when processing is performed using an end mill having a diameter of 70 mm. With this 7 times cutting arc length, the cutting force also increases about 7 times, and the shape accuracy of the inner wall surface of the scroll deteriorates from 2 μm to 15 μm at the same tool feed speed. As a means to reduce the cutting force at the center of this scroll wrap,
Generally, it has been attempted to reduce the feed rate of the tool or reduce the depth of cut. However, it is unclear how to properly distribute the position of the tool path and the tool feed speed or the depth of cut when machining the scroll wrap portion without deteriorating the shape accuracy, and input NC data by trial and error and try. I was working.

Therefore, in this embodiment, N having the configuration shown in FIG.
With the C control device, it is possible to automatically perform appropriate distribution of the tool feed speed. After calculating the tool trajectory from the data related to the tool trajectory creation input with tape, etc., calculate the equivalent radius of curvature of the tool trajectory when machining the outer wall surface and the inner wall surface of the scroll wrap part, and enter the pre-entered tool With the feed rate set to 100%, appropriate distribution is performed according to the tool feed rate calculation function that slows the temporary tool feed rate as the equivalent radius of curvature increases, and the table drive motor of the processing machine is NC controlled. .

Further, instead of changing the tool feed speed,
Similar effects can be obtained by changing the tool cutting amount. That is, this is a method of reducing the amount of tool cutting in advance at the time of intermediate finishing as the equivalent radius of curvature of the tool path increases. As a result, the side wall surface of the scroll wrap portion can be machined with the tool feed speed kept substantially constant.

[0015]

According to the present invention, the tool feed speed and the depth of cut are distributed by the conventional trial and error, the complicated work input as NC data is eliminated, and the proper tool feed is automatically performed from the tool trajectory data. By distributing the speed and the depth of cut, the setup time for work such as trial machining can be greatly reduced. In addition, the shape accuracy of the scroll wrap is 15
There is an effect that the performance of the scroll compressor can be improved by increasing the thickness from μm to 2 μm.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a tool locus of an end mill when processing an outer wall surface and an inner wall surface of a scroll wrap.

FIG. 2 is an explanatory diagram of equivalent radii of curvature of a tool and a workpiece on outer and inner wall surfaces.

FIG. 3 is a perspective view of a scroll vortex-shaped processing portion.

FIG. 4 is an external perspective view of a scroll processing machine.

FIG. 5 is a diagram showing an example of calculation of a radius of curvature by circular interpolation of an involute curve.

FIG. 6 is a diagram showing an example of calculating an equivalent radius of curvature when processing an involute curve.

FIG. 7 is a configuration diagram of an NC control device that corrects a tool feed speed.

[Explanation of symbols]

 1 ... Workpiece, 2 ... End mill, 3 ... Spindle, 4 ... X-axis table, 5 ... Rotary table, 6 ... Y-axis table, 7 ... Column, 8 ... Z-axis table, 9 ... Bed, 10 ... Chuck, 11 ... nail.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Yamanaka 800 Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Prefecture Living Equipment Division, Hitachi Ltd.

Claims (3)

[Claims] 1. An outer side of a scroll wrap comprising an end plate and a spiral wrap provided on one surface of the end plate and having a thickness and a height, the main part of the wrap portion being formed by an involute curve. In the method of machining the wall surface and the inner side surface with the end mill tool, it is necessary to reduce the feed rate of the tool according to the increase rate of the cutting arc length of the tool determined by the radius of the end mill and the curvature of the involute curve. Characteristic scroll vortex processing method. 2. The one-side machining allowance from 5 μm to 200 so that the length of the cutting arc of the tool determined by the radius of the end mill and the curvature of the involute curve is constant.
A method for processing a scroll vortex, characterized in that finishing processing is performed by changing the thickness in the range of μm. 3. The one-side machining allowance is 5 μm so that the length of the cutting arc of the tool determined by the radius of the end mill and the curvature of the involute curve is constant.
A method for machining a scroll vortex, which is characterized by varying in the range of m to 200 μm and reducing the feed rate of the tool so that the cutting force becomes constant even if the tool wears.