JP3473147B2 - Screw rotor processing apparatus and processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a screw rotor used in a compressor or a vacuum pump, and a processing apparatus for processing the rotor.

[0002]

2. Description of the Related Art Conventionally, in the processing of a screw rotor having a screw groove, a hobbing process using a milling machine using a cutting tool of a general shape that fits with the groove shape and a hobbing process using a hob cutter are widely used. It was done. Furthermore, as a method of processing the groove shape by reciprocating cutting,
Grooving is known in which grooving is performed on a flat surface using a shaper. Such screw groove processing is described in JP-A-53-116596, JP-A-3-161216, and JP-B-51-14723.

[0003]

In the machining with the general-purpose cutting tool described in the above-mentioned prior art, the processed groove shape depends on the shape of the cutting tool, and feedback correction cannot be performed. Therefore, it is necessary to change the cutting tool when changing the groove shape. Then, in the processing using the shaped tool, the cutting resistance becomes extremely large, and the maximum cutting feed rate is limited to about 200 mm / min. This is a general-purpose lathe with a rapid feed rate of 10 ~
It was only 1 to 2% at 20 m / min, which was a major obstacle to the realization of high-speed machining.

Further, in grooving using a shaping machine, only grooving on a flat surface is possible, and it is difficult to machine a complicated shape such as a screw groove. In addition, since this processing method is cutting in only one direction, there is a problem in that a blank feed occurs when the cutting tool moves in the backward direction and the processing time becomes long.

An object of the present invention is to solve the problem that the machining speed is lowered due to the cutting resistance, which occurs in machining using a shaping tool or a hob cutter, and to provide a machining method of a screw groove and a screw rotor with good machining efficiency. To provide. Another object of the present invention is to provide a processing apparatus capable of processing a complicated screw groove and screw rotor while ensuring high-speed cutting performance of the NC lathe.

Still another object of the present invention is to provide a screw rotor at low cost by high speed cutting. Another object of the present invention is to provide a screw rotor, a processing apparatus therefor, and a processing method at low cost while ensuring the processing accuracy. Another object of the present invention is to provide an inexpensive processing apparatus and processing method that can easily correct the shape of the screw groove. Another object of the invention is to provide a screw groove processing apparatus and method in which the tool cost is reduced by using a general-purpose blade.

[0007]

In order to achieve the above object, a spindle drive device for rotationally driving a spindle of a work, a tool post for mounting a cutting tool for machining the work, and a tool post perpendicular to the spindle of the work. In a screw rotor processing apparatus including a tool rest driving device driven in a direction, and a numerical control device controlling the main spindle driving device and the tool rest driving device, the main shaft driving device is switchably operated, and a second spindle drive for rotating the spindle of the workpiece is provided, the cutting tool has two bytes opposing or contradictory, the two bytes which are mounted at predetermined intervals in the main axis of the workpiece Is.

[0008]

[0009]

[0010]

Further, the blade tool attached to the tool rest is moved in the main axis direction of the work in synchronization with the rotation of the work, and the screw rotor having a plurality of teeth twisted in the main axis direction is N-shaped.
In a method for processing a screw rotor formed by using a C lathe, the work is rotated in a forward direction, and one of the plurality of teeth is used by using one of two cutting tools provided opposite or opposite to the cutting tool. After cutting the tooth flank of the tooth from one end to the other end in the axial direction, the workpiece is rotated in the reverse direction and the tooth face of the tooth adjacent to the tooth face is machined from the other end to the one end in the axial direction by using the other bite. By making it possible to perform reciprocal cutting, the above object is achieved. ◆ And preferably,
Screw teeth are formed by repeating the reciprocating cutting a plurality of times for one tooth.

[0012]

[0013]

In the screw rotor, grooves or lobes axially twisted are formed in the male rotor and the female rotor. In the grooving, a general-purpose NC milling machine is used for processing with a forming tool, or a dedicated hobbing machine is used for processing with a hob cutter, but it is difficult to correct the tooth profile or the like. Therefore, one tooth profile is divided into a plurality of tooth profile parts, and each part is reciprocally cut at high speed by two blade tools provided facing each other to form a screw groove. According to this, although the number of machining steps is increased, the reciprocating cutting of the minute tooth profile portion can be performed at high speed a plurality of times, and as a whole, the machining time can be reduced as compared with the cutting by the profile tooth profile,
The production efficiency of the screw rotor is improved. Further, when a screw rotor is used, thermal deformation occurs due to the difference in operating temperature between the inlet side and the outlet side, but it is sufficient to record the machining locus on the NC tape in consideration of the amount of these deformations.
The screw rotor can be processed with high accuracy. Further, as the machining progresses, the tool wears. However, if the NC tape is prepared in consideration of the wear amount of the tool, the working including the influence of the tool wear can be performed. Furthermore, different groove shapes and numbers of teeth can be easily handled by simply changing the program, and can easily be processed in a high-mix low-volume production site. Further, the modification of the tooth profile during the machining and the feedback machining while measuring the tooth profile can be easily executed by modifying the program of the NC controller.

By disposing the processing blades so as not to interfere with each other, reciprocating processing can be performed by the NC lathe. As a result, the work can be machined regardless of the movement of the work or the reciprocating motion of the cutting tool, so that the idling time can be omitted and the machining time can be shortened.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a method for processing a screw rotor according to the present invention, the details of which will be described later. 2 to 4 show an example of a screw compressor device incorporating a screw rotor. Screw compressors or screw vacuum pumps are used in chemical plants, refrigerators, semiconductor manufacturing equipment and the like. FIG. 2 shows a cross section perpendicular to the axis of the screw compressor, and the screw compressor 1 includes a casing 2, a male rotor 3, and a female rotor 5. The casing 2 is formed with a bore 6 which is a working space in which the male rotor 3 and the female rotor 5 are housed. The bore 6 has a male rotor side bore wall 8 and a female rotor side wall 8 which are circular in cross section and are parallel to each other. It is divided into side bore walls 9.

The male rotor 3 and the female rotor 5 have a bore wall 8,
Rotate in the directions of arrows K and L at the center of 9, respectively. The male rotor 3 has five lobes 11 interposed between the five grooves 10.
The female rotor 5 is a helical tooth composed of six lobes 13 interposed between the six grooves 12.
The lobes 11, 13 mesh with each other at the intersection of the bore walls 8, 9.

In the casing 2, a high pressure port 15 communicating with the bore walls 8 and 9 at an intersection of the bore walls 8 and 9, a discharge chamber 16 communicating with the high pressure port 15, and a gas sent from the outside. A suction chamber 18 for sucking and feeding into the bore walls 8, 9 through a low pressure port (not shown), and water jackets 19, 20 arranged adjacent to the bore walls 8, 9 for cooling the bore walls 8, 9 are formed, respectively. Has been done. And bore 6
The high-pressure gas compressed inside by the male rotor 3 and the female rotor 5 is sent to the line through the discharge chamber 16.

Since a high pressure is applied to the screw rotor of such a screw compressor or thermal deformation occurs, it is necessary to process the rotor shape with high precision. Had a tooth formation.

On the other hand, in FIGS. 3 and 4 in which the screw rotor is used as the vacuum pump, the screw vacuum pump 4 is used.
0 is a casing 41, a male rotor 43, and a female rotor 4
5, a shaft sealing device 46, and a slinger 48.
The casing 41 includes a main casing 49, a discharge side casing 50, and an end cover 51. Both ends of the male rotor 43 and the female rotor 45 are rotatably supported by bearings 52 and 53. The male timing gear 55 and the female timing gear 56, which are respectively attached to the discharge side, hold a minute gap and mesh with each other to rotate. ing. A compression working chamber 57 is formed between the male rotor 43, the female rotor 45, the main casing 49 , and the discharge side casing 50.

The shaft sealing device 46 seals the oil supplied to the bearings 52 and 53 and the timing gears 55 and 56. The slinger 48 splashes the oil in the oil sump 58 formed by the end cover 51 and a part of the main casing 49, and supplies the oil to the bearing 52. The main casing 49 has a suction port 59 and a discharge side casing 50.
The discharge port 60 is formed in each of them. The male timing gear 55 meshes with the pull gear 61, and the pull gear 6
1 is directly connected to an electric motor (not shown).

Also in the screw vacuum pump constructed as described above, in order to minimize leakage from the outer peripheral portion of the screw rotor and the casing, it is necessary to form the screw rotor tooth profile with high accuracy. Therefore, the conventional tooth profile has been used to machine the tooth profile of the rotor with high accuracy. However, since machining with this full-shape tooth profile requires a large number of machining steps, a machining method with improved productivity is required. In order to solve this problem, we have developed lathe processing using a high-rigidity NC lathe instead of the conventionally used milling and hobbing. An apparatus for improving the efficiency of this processing is shown in FIGS.

FIG. 5 shows an example of a screw rotor machining apparatus according to the present invention. A schematic front view of a high-rigidity NC lathe, FIG. 6 is a side view thereof, and FIG. 7 is a machining method of the present invention. 7 is a schematic diagram of a rotary drive system of the lathe shown in FIG. In the high-rigidity lathe 99, a control board 88 is placed on the base 100, and the control board 88 controls the lathe 99 based on an input command from the operation board 87. And lathe 99
Is provided with a chuck 92 that holds the work 71 by the action of the chuck cylinder 81 and a centering table 83 that is used for centering the work 71 together with the chuck, and the chuck 92 side rotates the work 71. Is connected to the main shaft (C-axis) motors 82a and 82b. On the other hand, the tool bit is attached to the tool post 84,
The axial feed motor 89 changes the depth of cut into the workpiece 71, and the Z-axis moves in the horizontal direction, that is, in the Z-axis direction.
Horizontal movement of the tool rest 84 is executed from the shaft feed motor 85 via a ball screw (not shown).

FIG. 7 shows details of the drive system of the high-rigidity lathe 99 thus constructed. This lathe also has a function of a general-purpose lathe, and in normal processing, the work 71 attached to the chuck 92 is rotationally driven by the spindle motor 82b via the belt drive system 95 attached to the main spindle motor 82b. It The other end of the work 71 is centered and positioned by the tail stock provided on the centering base 83 as described above.

By the way, in the machining such as the screw groove machining having a large tool load, the drive torque is too small to use the ordinary spindle motor 82b, and the sufficient machining efficiency cannot be obtained. Therefore, in carrying out the present invention, a C-axis motor 82a is additionally installed in addition to the spindle motor 82b, and the output of the C-axis motor 82a is transmitted to the work 71 via a reduction gear. The clutch 94 is used by switching the output of the spindle motor 82b.

Next, details of an embodiment of the processing method using the NC lathe will be described below. FIG. 1 shows a work 71 and a tool 76,
In the case of a male rotor, the work 71 has a lobe formed in a four-threaded or five-threaded shape. On the other hand, in the case of the female rotor, the groove is formed with five or six grooves and a helix angle matching the twist of the male rotor. Figure 1
The groove processing of the row is shown. The tool table moves in the axial direction 74 or 75 in synchronization with the rotation 73 of the work 71 driven by the C-axis motor. By the way, when the tool base moves in the 74 direction, the cutting tool 76 attached to the tip of the tool attachment 93 shown in FIG. 11 processes one side surface of the groove. And
When processing is completed from one end to the other end of the work 71, the rotation direction of the work 71 becomes the opposite direction, and accordingly, the moving direction of the tool base becomes the direction of 75. Then, the other side surface of the groove is processed by the tool 77. That is, as shown in FIG. 8, the bites 76 and 77 are attached to the tool attachment 93 so as to face each other in the axial direction, and
It is set at a position deviated from the direction perpendicular to the axis. This situation will be described with reference to FIG. Grooves having steps are formed in the bite setting spacer 95, and the grooves are separated by a predetermined bite interval 70a. Further, the steps between the grooves are formed by a predetermined step 70b, and by using the spacer formed in this way, the tool can be set at a predetermined position of the tool attachment.
For example, the interval 70a is set to 10 mm and the step 70b is set to 5 mm to process the rotor of the screw refrigerator.

In the processing of the screw rotor having the six grooves shown in FIG. 10, the cutting depth of the cutting tool is changed so that the tooth profile 79 shown in FIG. 11 is created. That, A of FIG. 11 at one end of the workpiece 71
The cutting depth and the circumferential position are set at the R position, the Z-axis position of the cutting tool and the rotation of the work are synchronized so that a predetermined twist angle is obtained, and the machining up to the opposite end is completed (forward machining). Next, a bit different from the one used previously is set at the position AL point, which has moved in the circumferential direction by the amount corresponding to the width of one groove minus the width of the tooth. Then, the work 71 is rotated in the reverse direction, and in synchronization with this reverse rotation, the tooth surface is processed so that the cutting tool returns to the above-mentioned one end (reverse processing).

Next, at one end, the position of the cutting tool is moved from the AL position of the previous processing to the BL position, and the same forward processing as above is performed. Next, at the opposite end, a bit different from that used for the forward machining is moved from the AR position to the BR position and set, and the same re-machining as above is performed. This is repeated until the predetermined tooth profile 79 is obtained. The trajectory 78 of the tool center at this time is a curve substantially parallel to the tooth surface. Note that this FIG.
For simplicity, the tip shape of the cutting tool is represented by a round tool with a round shape, but it goes without saying that a round piece tool and a diamond tool can be used if necessary. However, when using these cutting tools, it is necessary to mount the two cutting tools 76 and 77 so as not to interfere with each other. Further, in the above-described embodiment, in the forward machining and the backward machining, the distance between the pair of cutting tools is kept constant, and the circumferential position and the cutting depth are changed between the forward machining and the backward machining.
The tool attachment may be configured so that the interval itself between the pair of cutting tools can be changed during reciprocating processing. In this way, the screw tooth profile can be created more easily. Of course, the two tools are mounted in the tool fixture so that they fit within a width much smaller than the maximum width of the groove.
Further, although the cutting tools are provided so as to face each other in this embodiment, they may be mounted so as to be opposite to each other.
The material of the screw rotor includes ductile cast iron, stainless steel and the like.

FIG. 12 shows the forming process of the screw rotor according to the present invention. Work piece 71, which is the material of the female rotor 12
In order to form a single groove on the top, groove processing is performed up to the positions corresponding to points CL and CR in FIG. 11 (FIG. 11A). By repeating the procedure described above, processing of one groove is completed ((b) of the same figure). Then, the work is rotated by the pitch of the number of teeth and the same processing is repeated, so that the female rotor is finally created ((c) in the same figure).

Next, an example in which the screw rotor is concretely processed by using the processing apparatus configured as described above will be described below. The theoretical maximum torque of the C-axis motor 82a is about 80.
N · m, and the twist angle of the screw groove in the work 71 is 57.3 °. Further, the number of screw grooves is 6, and the total number of times of cutting N per groove is N = 53. The diameter D of the workpiece 71 is D = 112 mm, and the rotor lobe length L, which is the axial length of the portion where the screw groove is formed, is L = 156 mm. Cutting feed rate (C
The combined speed of the shaft and the Z-axis) was set to 20 m / min for high-speed processing. As a result, the time required for machining all screw grooves was significantly reduced from the conventional 20 minutes to 10 minutes.

FIG. 13 shows a flow chart of processing at this time. First, a cutting tool required for machining is selected from a round cutting tool, a round cutting tool, a diamond cutting tool, etc., and cutting tools Pn are set to cutting tools 76 and 77.
Next, the NC controller controls the movement amounts of the C axis and the Z axis. In this embodiment, 302.934 ° in the C-axis direction.
NC so that it moves 190 mm in the Z-axis direction while rotating.
It is controlled by the control device. When both the reciprocating processing is completed, the cutting tool is moved to the cutting start point Pn + 1 at the next tooth profile position on the same groove. When the machining for one groove is completed (when the number of reciprocating cuttings N reaches 53 times), move the cutting tool to the position moved by the groove pitch in the circumferential direction (position moved 60 ° with respect to Pn), and The processing is repeated, and when the processing of all 6 grooves is completed, the entire processing is completed.

When it is necessary to correct the tooth profile from the theoretical curved surface due to thermal deformation or the like, modification processing can be easily performed by changing the program of the numerical controller. Needless to say, a highly accurate tooth profile can be automatically formed by considering in advance the correction of the machining path due to wear of the cutting tool in the program.

[0032]

As described above, the present invention has the following effects. ◆ Since a spindle drive is provided on a general-purpose NC lathe via a clutch mechanism, it is possible to perform high-speed machining of screw rotors with complicated shapes in addition to ordinary turning. Further, since the blade is driven in synchronization with the rotation of the main shaft, it is possible to process a twisted groove shape having a constant or variable twist angle. Furthermore, since two blades are provided facing each other or in the opposite direction, reciprocating machining is possible and the machining efficiency is improved. Further, since the cutting tools are arranged at positions where they do not interfere with each other, different tooth surfaces can be easily machined in reciprocating machining, and machining efficiency is improved. Further, since the cutting tool may be a general-purpose cutting tool, the cost of the cutting tool is low.

Further, in the groove processing of the screw rotor, since the tooth profile is machined a plurality of times so as to be composed of a plurality of curves or straight lines, the cutting resistance per one time is reduced and high speed machining becomes possible. Then, the increase in the number of times of cutting can be compensated by increasing the cutting feed rate, and the processing time can be shortened as a whole.

Further, since the programming is carried out by the numerical control device, it is possible to perform not only highly accurate machining but also machining considering the deviation from the theoretical curved surface due to wear of the tool or thermal deformation. Further, machining of rotors having different numbers of teeth can be easily performed only by changing the program.

[0035]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a processing method of a screw rotor.

FIG. 2 is a cross-sectional view of a screw compressor.

FIG. 3 is a vertical top view of a screw vacuum pump.

FIG. 4 is a vertical sectional front view of a screw vacuum pump.

FIG. 5 is a front view of a high-rigidity NC lathe according to an embodiment of the present invention.

FIG. 6 is a side view of a high-rigidity NC lathe according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of a drive system of a high-rigidity NC lathe according to an embodiment of the present invention.

FIG. 8 is a partial perspective view of a bite fitting.

FIG. 9 is a vertical cross-sectional view of a jig for bite setting.

FIG. 10 is a perspective view of a female rotor.

FIG. 11 is a diagram showing a procedure for creating a tooth surface shape.

FIG. 12 is a view showing a procedure for creating a female rotor from a work.

FIG. 13 is a flowchart for implementing the present invention.

[Explanation of symbols]

1 ... Screw compressor, 3 ... Male rotor, 5 ... Female rotor, 10 ... Groove, 11 ... Lobe, 12 ... Groove, 13
...... Lobe, 40 ...... Screw vacuum pump, 46 ......
Shaft seal device, 52, 53 ... Bearing, 55, 56 ... Timing gear, 70a ... Gap, 70b ... Axis deviation, 71 ...
... Work, 72 ... Machining groove, 73 ... Work rotation direction, 74, 75 ... Work Z-axis movement direction, 76, 77
…… Bite, 78 …… Chip, 79 …… Tooth surface shape, 82
a, 82b ... C-axis motor, 83 ... tailstock, 84 ...
… Turret, 85… Z-axis feed motor, 87… Operation panel,
88 ... control panel, 89 ... tool feed motor, 92 ... chuck, 94 ... clutch device.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohiko Makino 390 Muramatsu, Shimizu-shi, Shizuoka Hitachi Shimizu Engineering Co., Ltd. (72) Inventor Masao Tomioka 390, Muramatsu, Shimizu-shi Hitachi, Ltd. (56) References JP-A-2-180523 (JP, A) JP-A-60-90601 (JP, A) JP-A-5-187373 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23F 15/08 B23F 9/04 B23F 21/04 B23B 5/00 B23B 5/46 B23B 5/48 B23B 29/24

Claims (4)

(57) [Claims] 1. A spindle drive device for rotatably driving a spindle of a work, and a tool post for mounting a cutting tool for machining the work,
In a screw rotor processing apparatus including a tool rest driving device that drives this tool rest in a direction perpendicular to a work spindle, and a numerical controller that controls the spindle drive device and the tool rest drive device, the spindle drive and switchably operated, the second spindle drive for rotating the spindle of the workpiece is provided, the cutting tool has two bytes opposing or contradictory, the 2
One byte processing device, for a screw rotor, characterized in that mounted at predetermined intervals in the main axis of the workpiece. 2. An NC lathe device for turning a work according to an NC program, comprising a spindle drive device for rotationally driving the work, a tool rest for mounting a cutting tool for turning the work, and a tool rest mounted on the tool rest. A tool post driving device that changes the cutting depth of the cutting tool and a Z-axis drive device that drives the tool post in the spindle direction of the work are provided, and a second spindle drive device that can be switched and used with the spindle drive device is provided. And a controller for synchronizing the rotational driving of the second spindle driving device and the linear driving of the Z-axis driving device in the spindle direction, wherein the cutting tool has two bites facing or contradictory to each other. The NC lathe device in which the cutting tools are attached at a predetermined interval in the main axis direction of the work. 3. A screw rotor for forming a screw rotor having a plurality of teeth twisted in the main-axis direction by using an NC lathe by moving a tool attached to a tool post in the main-axis direction of the work in synchronization with rotation of the work. In the machining method described above, the workpiece is rotated in the forward direction, and the tooth surface of one of the plurality of teeth is rotated from one end in the axial direction by using one of two cutting tools provided facing or opposite to the cutting tool. After cutting to the other end, the workpiece is rotated in the reverse direction so that the tooth surface of the tooth adjacent to the tooth surface is machined from the other end to the one end in the axial direction by using the other bit, thereby enabling reciprocal cutting. A method for processing a screw rotor, characterized by. 4. The method of processing a screw rotor according to claim 3, wherein screw teeth are formed by repeating the reciprocating cutting a plurality of times for one tooth.