JP2010162628A - Method for machining scroll member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for machining a scroll member allowing realizing a long service life of an end mill by performing highly accurate machining and speeding up the machining at a lower cost. <P>SOLUTION: This scroll member in a scroll compressor is end-milled by using a multi-edge end mill 11 having 10 to 16 sheets of outer peripheral cutting edges. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention provides a scroll member processing method in which a scroll member in a scroll compressor is end-milled using an end mill, and in particular, achieves higher accuracy and higher speed at a lower cost, thereby realizing a longer life of the end mill. The present invention relates to a method for processing a scroll member.

An end mill used for processing a scroll member in a scroll compressor is a kind of cutting tool, and is a tool similar to a generally well-known drill.
FIG. 12 shows a bottom view and a side view of a commonly used end mill. As shown in FIG. 12, the end mill 21 has an outer peripheral blade 22 that is a cutting edge on the outer periphery of a main body that is a shaft body, and a bottom blade 23 that is a cutting edge on the bottom surface of the main body. Then, the workpiece is scraped off by the up / down / left / right feed movement.
It is a multi-functional tool that can be used to machine shoulders, outer circumferences, grooves, curved surfaces, and holes with a single end mill, and is also used for machining scroll members.
In this end milling, as one of means for realizing higher accuracy, there is an increase in the number of cutting edges. When the number of cutting edges is increased, the number of cutting edges acting on the workpiece is increased, the cutting width per sheet is reduced, and processing is performed such that fine cutting is performed, and the processing surface is improved.

However, if the number of cutting edges is increased, the distance between the adjacent cutting edges of the end mill becomes narrower, the chip pocket, which is a space where chips are discharged, decreases, chip discharge becomes worse, and machining is in progress. In some cases, chips may become clogged, resulting in marked deterioration of the machined surface or damage to the end mill. For this reason, it is not necessary to increase the number of cutting edges as much as possible, and the number of cutting edges must be determined in consideration of the dischargeability of chips.
For the above reasons, in general commercial products, end mills with 2 to 8 cutting edges that cover a wide range from roughing to finishing are generally used.

In general end mill processing of a scroll member, coolant (cooling water, oil) is supplied for cooling the end mill and improving chip discharge.
The end milling of the scroll member is deep groove processing, which is a process in which the scroll member becomes a barrier against the intrusion of the coolant and the coolant is not sufficiently supplied to the cutting point.
And if the coolant supply shortage occurs at the end mill edge, the frictional heat of the cutting edge due to cutting cannot be suppressed, and the chipping and normal wear of the cutting edge due to the generation and missing of the constituent edge increase significantly, and the chips This will lead to deterioration of the accuracy of the machined surface and damage to the end mill.
That is, in the end mill processing of the scroll member, it is important to suppress the processing heat such as the frictional heat and improve the chip discharging property.
Therefore, as a conventional technology to satisfy these requirements, a coolant supply hole can be provided in the end mill, and the coolant can be forcedly lubricated from the end mill, enabling better coolant supply to the end mill cutting point. In addition, there is one for the purpose of ensuring cutting accuracy in the scroll member and extending the life of the end mill (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 7-9232 (first page, FIG. 1) JP-A-7-2465 (first page, FIG. 1)

The above-described conventional technology enables a good coolant supply to the end mill cutting point by opening a coolant conduction hole in the end mill and forcibly lubricating the coolant from the end mill, ensuring the cutting accuracy of the scroll member and the end mill. However, by making a conduction hole in the end mill, the rigidity of the end mill itself becomes weak, and a coolant hole must also be made in the spindle system on the equipment side. Since the specification had to be changed, there were problems such as high costs.
Further, in order to realize a high-precision processed surface of the scroll member, the number of processing steps is increased as compared with the conventional processes such as roughing, intermediate finishing, and finishing. Therefore, the number of tools used increases and the tool cost increases. The tool cost for the orbiting scroll and the fixed scroll, which are scroll members having a high-precision machining surface, occupies about 50% of the total tool cost for the scroll compressor. Further, the processing time is greatly increased due to the increase in the number of processes.

As described above, in the processing of the scroll member of the scroll compressor, it has been a problem how to suppress a great tool cost and processing time.
In recent years, attention has been focused on how to increase the processing accuracy of element parts and eliminate loss such as leakage of compressed gas as a performance improvement of compressors, and it is the most important in scroll compressors. At present, there is a demand for further improvement in processing accuracy of the scroll member, which is a critical part.

  The present invention has been made to solve the above-described problems, and is a scroll member machining method that can achieve high-precision machining, high-speed machining, and long life of an end mill at a lower cost. The purpose is to obtain.

  The processing method of the scroll member according to the present invention is such that the scroll member in the scroll compressor is end-milled using a multi-blade end mill having 10 to 16 outer peripheral cutting edges.

In the scroll member processing method according to the present invention, the scroll member in the scroll compressor is end milled using a multi-blade end mill having 10 to 16 outer peripheral cutting edges. Can improve the accuracy of the machined surface in the processing of scroll members, leading to reduced leakage of compressed gas and sliding friction from the compression chamber, improving the performance of the compressor, and chipping and wear of the end mill edge. This reduces the life of the end mill and increases the processing speed, which can greatly reduce the processing time spent on the scroll member of the scroll compressor and greatly improve productivity. There is an effect that can be performed.
Moreover, simply changing the end mill to a multi-blade end mill does not change equipment specifications or introduce new equipment, so it can produce benefits at a lower cost.

Sectional drawing which shows the structure of the scroll compressor with which the processing method of the scroll member of embodiment of this invention is implemented. The perspective view which shows the mode of a process by the processing method of the scroll member. Sectional drawing which shows the mode of the process by the processing method of the scroll member. The bottom view and side view of a multiblade end mill used for the processing method of the scroll member. The graph which shows the processing test result of a multiblade end mill. Explanatory drawing which shows the ideal process cross-sectional shape of the work material in 1 rotation of the end mill of 6 blades and 12 blades with rotation speed and feed rate constant. Explanatory drawing which shows the ideal process cross-sectional shape of the workpiece in 1 rotation of a 6 blade and 12 blade (feed 2 times) end mill with constant rotation speed. The graph which shows the relationship of the price with respect to the blade diameter of an end mill. The graph which shows an example of the relationship between the blade diameter of an end mill, and the number of processes leading to a lifetime. The graph which shows the relationship between the blade diameter of an end mill, and the cost per processing number. Explanatory drawing which shows the relationship between the twist angle of an end mill, and the component force of cutting resistance. The bottom view and side view of a general end mill.

Embodiment.
1 is a cross-sectional view showing a structure of a scroll compressor in which a scroll member processing method according to an embodiment of the present invention is implemented, FIG. 2 is a perspective view showing a state of processing by the scroll member processing method, and FIG. FIG. 4 is a bottom view and a side view of a multi-blade end mill used in the scroll member machining method, and FIG. 5 shows a machining test result of the multi-blade end mill. Graph, FIG. 6 is an explanatory view showing an ideal machining cross-sectional shape of a work material in one rotation of a 6-blade and 12-blade end mill at a constant rotation speed and feed rate, and FIG. FIG. 8 is a graph showing the relationship between the end mill blade diameter and the price, and FIG. 9 is the end mill blade. Shows the relationship between diameter and life Graph, Figure 10 is a graph, Figure 11 shows the cost relationship edge diameter and the processing number per end mill is an explanatory view showing the relationship between the component force of the torsion angle and the cutting resistance of the end mill.

First, a scroll compressor in which a method for processing a scroll member according to an embodiment of the present invention is described.
The scroll compressor is an apparatus used for refrigeration / air conditioning equipment and the like, as shown in FIG. The refrigerating machine oil 3 for lubricating and sealing the compression mechanism sliding portion is stored at the bottom.
In this scroll compressor, a low-pressure intake gas enters a compression chamber 7 formed by plate-like spiral teeth of a fixed scroll 5 and an orbiting scroll 6 from an intake pipe 4. The orbiting scroll 6 driven by the crankshaft 8 connected to the motor 2 performs an eccentric turning motion and reduces the volume of the compression chamber 7. By this compression step, the suction gas becomes high pressure and is discharged from the discharge port 9 of the fixed scroll 5, fills the sealed container 1 with a high pressure atmosphere, and is eventually discharged from the discharge pipe 10 to the outside of the compressor.

For such a scroll compressor, leakage of compressed gas and sliding friction in the compression chamber 7 directly lead to a decrease in the performance and reliability of the compressor. Therefore, the orbiting scroll 6 and the fixed scroll 5 constituting the compression chamber 7 are used. These scroll members are required to have very high dimensional accuracy and machined surface shape.
Further, as shown in FIGS. 2 and 3, coolant (cooling water, oil) 12 is supplied to cool the end mill 11 and improve chip discharge performance, and performs deep groove processing, and is a scroll member. For example, the orbiting scroll 6 serves as a barrier against the intrusion of the coolant 12 and is a process in which the coolant 12 is not sufficiently supplied to the cutting point. Similarly, the fixed scroll 5, which is a scroll member, is processed so that the coolant 12 is not sufficiently supplied to the cutting point.

Next, the structure of the end mill used for the processing method of the scroll member of embodiment of this invention is demonstrated based on FIG.
As shown in FIG. 4A, the end mill is a multi-blade end mill 11 having 12 outer peripheral cutting edges and a blade diameter of 11 mm.
4A, the bottom surface of the multi-blade end mill 11 has a shallow hole with a diameter of 5 mm and a depth of 1 mm in the center, and the shallow hole portion has no cutting edge.
Normally, when trying to form many cutting edges on the bottom of a small-diameter end mill, the distance between adjacent blades becomes narrower, and the distance between the blades becomes narrower as it gets closer to the center. Therefore, it cannot be formed well with the size of the conventional grindstone.
However, by drilling this shallow hole, it was possible to form as many as 12 outer peripheral cutting edges even with a conventional size grindstone and a small diameter of 11 mm.
In this way, the 12-blade multi-blade end mill 11 has a blade diameter of 11 mm, a hole with a diameter of 5 mm and a depth of 1 mm in the center of the bottom, a twist angle θ ₁ of 46 °, and a rake angle of the outer peripheral cutting edge. θ ₂ is set to 4 °, the second clearance angle θ ₃ is set to 6 °, the rake angle θ ₄ of the bottom cutting edge is set to 1.5 °, and the second clearance angle θ ₅ is set to 7 ° (FIG. ), See (b)).

The graph of FIG. 5 shows the result of the machining test of the 12-blade multi-blade end mill 11.
The work material is a rocking scroll 6 of FC250, which is a cast iron product, rotating at 3000 rpm, feed rate 2200 mm / min, cutting (axial direction) 19.2 mm, cutting (perpendicular to the axis) 0.15 mm, 1 piece The hit cutting length was 1000 mm in total on the inner and outer groove surfaces of the scroll member, and 2,000 of them were processed.
Here, the horizontal axis represents the number of processes, and the vertical axis represents the straightness value, which is an evaluation item of how the processed surface is uneven.
For comparison, the result of a machining test in a conventional 6-flute end mill is also shown. This 6-flute end mill has substantially the same specifications except for the blade diameter of 11 mm and the twist angle of 45 °, and the number of the 12-flute end mill and cutting edge of the present invention.

As can be seen from FIG. 5, in the first product, the 12-flute has a straightness of 4 μm and the 6-flute has 7 μm, and the 12-flute which is a multi-blade end mill 11 improves machining accuracy by approximately 40% compared to the 6-flute. Is shown.
Also, if the end mill life reaches 10μm, 6 blades can process up to 2000, but 12 blades can process up to 4000, and the end mill has a long life. It turns out that it is improving by 2 times by doing.
This is because the amount of cutting per blade decreases as the number of cutting edges increases. That is, since the cutting resistance applied to one blade and the generated processing heat are reduced, chipping and normal wear of the cutting edge due to generation and lack of the constituent cutting edge are suppressed, and the tool life can be extended.

FIG. 6 shows an ideal machining section of the work material in one rotation of a 6-blade and 12-blade end mill at a constant rotation speed and feed rate.
In this way, as the number of cutting edges increases, the number of times the cutting edge strikes increases, and as shown in FIG. 6, the larger the number of times the cutting edge strikes, the smaller the unevenness of the machining surface and the better the machining surface shape. become.
Further, as shown in FIG. 7, even if the rotational speed is kept constant in a 12-flute end mill and the feed is doubled, the same machining surface shape as that of a 6-flute can be theoretically obtained. That is, the feed can be increased as the number of blades increases.

The processing method of the scroll member of the present invention is to perform end milling using the multi-blade end mill 11 in which the number of cutting edges is increased as compared with the conventional end mill for processing the scroll member.
As described above, if the number of cutting edges is excessively increased, the chip pockets are decreased, and there is a concern that the chip dischargeability is deteriorated.
However, in the finishing process of the scroll member, since the cutting width of the multi-blade end mill 11 is as small as 0.5 mm or less, only small swarf is generated, and it is not necessary to consider the chip discharging property so much. The cutting edge can be made into 12 multi-blade.

FIG. 8 is a graph showing the relationship between the end mill blade diameter and the price. As shown in the graph of FIG. 8, the price of the end mill requires a larger material as the blade diameter increases, and the processing cost increases, so the price increases in a quadratic curve.
In addition, as the blade diameter becomes smaller, both the material cost and the processing cost can be reduced. However, if the blade diameter becomes smaller than a certain value, the price will not drop much because it is less demanding.

FIG. 9 is a graph showing an example of the relationship between the blade diameter of the end mill and the number of machining operations leading to the life. As shown in the graph of FIG. 9, generally, as the diameter of the blade increases, the rigidity of the end mill increases and the number of cutting edges can be increased, so that the lifetime increases in a quadratic curve.
However, conversely, when the diameter is about 5 mm or less, the number of blades is limited, and the service life becomes flat.
FIG. 10 shows the cost of the tool of the end mill shown in FIG. 8 divided by the life shown in FIG. 9, that is, the tool cost per machined. The cost is the cheapest when the blade diameter is around 11 mm. It aims at further cost reduction in this range.

Also, as shown in FIG. 11, when the twist angle of the end mill is increased, the feed component force, which is one of the component forces of the cutting resistance, is reduced, and the feed rate can be increased by that amount, thereby enabling more efficient machining. However, if it becomes too large, the axial component force will become strong, and in cutting thin workpieces, the force that lifts the workpiece upwards will work, so chatter vibration will be induced and the end mill will be easily removed from the holder. End up.
Therefore, the present invention aims at higher efficiency and aims at a twist angle of 40 ° to 50 ° capable of achieving both accuracy and reliability.

The multi-blade end mill 11 used in the first embodiment has a blade diameter of 11 mm, a hole having a diameter of 5 mm and a depth of 1 mm in the center of the bottom, 12 outer peripheral cutting edges, and a twist angle θ _1. Is 46 °, the rake angle θ ₂ of the outer peripheral cutting edge is 4 °, the second clearance angle θ ₃ is 6 °, the rake angle θ ₄ of the bottom cutting edge is 1.5 °, and the second clearance angle θ ₅ is 7 °. Although it is set, the multi-blade end mill 11 has a blade diameter of 8 to 15 mm, a shallow hole with a diameter of 4 to 8 mm in the center of the bottom surface, and the number of outer peripheral cutting edges is 10 to 16 and twisted. The angle θ ₁ is 40 ° to 50 °, the rake angle θ ₂ of the outer peripheral cutting edge is 2 ° to 10 °, the second clearance angle θ ₃ is 6 ° to 8 °, and the rake angle θ of the bottom cutting edge ₄ having a range of 1 ° to 4 ° and a second clearance angle θ _{5 in} the range of 6 ° to 8 ° has substantially the same effect as the 12-blade multi-blade end mill 11.

  DESCRIPTION OF SYMBOLS 1 Airtight container, 2 motor, 3 refrigerator oil, 4 suction pipe, 5 fixed scroll, 6 rocking scroll, 7 compression chamber, 8 crankshaft, 9 discharge port, 10 discharge pipe, 11 multiblade end mill.

Claims (2)

  A scroll member processing method, wherein a scroll member in a scroll compressor is end milled using a multi-blade end mill having 10 to 16 outer peripheral cutting edges.   2. The scroll member according to claim 1, wherein the multi-blade end mill has a shallow hole with a diameter of 8 mm to 15 mm, a diameter of 4 mm to 8 mm in the center of the bottom surface, and a twist angle of 40 ° to 50 °. Processing method.

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