JP5540352B2 - Screw rotor machining method - Google Patents

Description

The present invention relates to a scan clew rotor machining method, in particular, it relates away clew rotor machining method to process a screw rotor having unequal lead unequal inclination angle.

  Generally, as a screw-type vacuum pump, a gas working chamber is configured by a pair of male and female screw rotors that mesh with each other and a stator that houses both screw rotors, and a gas intake air is connected to one end and the other end of the working chamber. A device provided with a mouth and a discharge port is known.

  As a screw rotor used in a screw-type vacuum pump, attention has been paid to a screw rotor having an unequal lead unequal inclination angle so that the twist angle continuously changes with the progress of the twist.

  Further, there is a demand for inexpensive and large-scale supply of a screw-type vacuum pump having a screw rotor having such unequal lead and unequal inclination angles. Conventionally, cutting is performed using a rotary tool such as an end mill. As a result, it took about 7 days to process one rotor.

  Moreover, in cutting using a rotary tool such as an end mill, there are problems that it is difficult to remove shaving residue, the tool is easy to break and wears out, and the machining accuracy becomes unstable. It was difficult.

  In addition, as a conventional processing device for a screw rotor having an equal lead angle, the spindle driving device that rotationally drives the workpiece spindle, the tool post to which the tool for machining the workpiece is attached, and the tool post perpendicular to the workpiece spindle A turret driving device for driving in any direction, a spindle control device and a numerical control device for controlling the turret driving device, and a switchable operation with the spindle driving device to rotate the spindle of the workpiece. 2. Description of the Related Art A machining apparatus provided with a spindle driving device is known (for example, see Patent Document 1).

  In addition, as a conventional screw processing machine for processing a screw rotor having an unequal lead and an unequal inclination angle, a cutter axis for rotating the rotary blade at a position where the rotary blade can contact the screw lead, and a tool rest on which the cutter axis is installed, A ω-axis that rotates the workpiece, which is a screw generating material, a Y-axis that moves the tool post and the workpiece relative to each other in the normal direction from the center of the workpiece, and a tool post in the axial direction of the workpiece A screw processing machine having an X axis for moving the workpiece and the workpiece relative to each other and a θ axis for changing the screw lead angle by turning the tool post on which the cutter axis is installed, and capable of simultaneously controlling at least the ω axis and the X axis. It is known (for example, refer to Patent Document 2).

  In a specific processing method using this screw processing machine, two processing steps using different blades, that is, rough processing by a general rotary blade (grinding stone) having substantially the same shape as the groove cross section of the screw rotor, The screw rotor is processed in two processing stages of finishing with a rotating cutter (grinding stone) having a small thickness.

  Moreover, as a conventional screw type vacuum pump equipped with a screw rotor having unequal lead unequal inclination angles, the shape of the vertical cross section with respect to the shaft is the same, and the same diameter from the suction end to the discharge end along the axial direction. It has a certain number of winding screws, and the screw is a non-uniform lead suction end side screw part where the lead gradually becomes dense from the suction end toward the discharge end side, and an equal lead whose lead is close to the suction end side screw part. There is known a screw-type vacuum pump comprising a discharge end side screw portion and a suction end side screw portion and a discharge end side screw portion formed separately from each other (for example, Patent Documents). 3).

JP-A-8-197331 Japanese Patent Laid-Open No. 10-311288 JP 11-270485 A

  However, the conventional screw rotor processing apparatus described in Patent Document 1 does not cause a problem when processing a screw rotor having an inclined angle such as an equal lead, but means for adjusting the rake angle between the cutting tool and the workpiece. Therefore, when machining a screw rotor with an unequal lead unequal inclination angle, the cutting tool cannot be brought into contact with the workpiece at an appropriate rake angle, and the unequal lead unequal inclination angle There is a problem that it is difficult to process a screw rotor having a high accuracy.

  In addition, in the conventional screw processing machine described in Patent Document 2, the tool rest on which the tool shaft is installed has a θ axis that changes the screw lead angle, so that the tool rest is centered on the θ axis. Although it is possible to form a rough outer shape of a screw rotor having unequal lead and unequal inclination angles by turning, it is possible to increase the twist of the screw teeth of the screw rotor using a single rotary blade (milling machine). In order to machine the screw rotor with high accuracy, two machining stages, rough machining and finishing machining, are required, and a large machining load and machining time are required. It was.

  Further, the conventional screw type vacuum pump described in Patent Document 3 is obtained by machining the suction lead side screw portion having a rough lead and the dense discharge end side screw portion of the lead into separate bodies with appropriate blades. In this case, the connection work between the suction end side screw portion and the discharge end side screw portion is still overcome. As a method for processing a screw rotor having an unequal lead unequal inclination angle that continuously changes as the torsion progresses, any solution is presented. It was not a thing.

Therefore, the present invention solves the conventional problems. That is, the object of the present invention is to avoid unequal lead inaccurate at a low cost and in a short time without requiring a large processing burden. it is possible to process a large amount of screw rotors having equal tilt angle, it is to provide the possibility to be absent clew rotor machining method to inexpensively and mass supply of a screw-type vacuum pump.

In the screw rotor machining method of the present invention, a workpiece is attached to a spindle that is rotatably supported around a C axis on a spindle stock, while a Z axis parallel to the C axis and a cutting direction with respect to the workpiece are defined. A tool for cutting can be rotated about an A axis parallel to the X axis on a tool table that is movable along an X axis for performing movement and a Y axis that is orthogonal to the X and Z axes. Mounting, rotating the workpiece about the C axis, while numerically controlling the position of the tool along the X, Y, and Z axes, and the rotation angle about the A axis, The above-described problems are solved by processing a screw rotor having an unequal lead unequal inclination angle from a workpiece .

  According to the present invention, it is possible to process a large amount of screw rotors having highly accurate unequal lead unequal inclination angles at a low cost and in a short time without requiring a great processing burden. Pumps can be supplied inexpensively and in large quantities.

It is a vertical top view which shows the screw type vacuum pump which is one Example of this invention. It is a vertical front view which shows a screw type vacuum pump. It is a perspective view which shows the meshing state of a pair of male and female screw rotors. It is a perspective view which shows a screw rotor. It is a top view which shows the meshing state of a pair of male and female screw rotors. It is explanatory drawing which shows the tooth trace shape of a screw rotor. It is a whole perspective view which shows the machine tool for screw rotor processing. It is a whole perspective view which shows the casing of the machine tool for screw rotor processing with a dotted line. It is a perspective view which shows the state which made the tool contact | abut the workpiece. It is the elements on larger scale which show the machine tool for screw rotor processing centering on a three-dimensional measuring means. It is a perspective view which shows the screw rotor which is a modification of this invention. It is explanatory drawing which shows the tooth trace shape of the screw rotor which is a modification of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, as shown in FIGS. 1 and 2, the screw-type vacuum pump 100 includes a stator 110 having a discharge port 111 and an intake port 112 and a pair of male and female screws disposed in mesh with each other in the stator 110. The rotors 120a and 120b, the bearing unit 130 attached to the stator 110 and bearing both ends of the rotor rotation shaft 121 of the screw rotor 120, and the rotation of the pair of screw rotors 120 attached to one end of the rotor rotation shaft 121 are synchronized. And a shaft seal 150 that prevents the lubricating oil supplied to the timing gear 140 and the bearing portion 130 from entering the gas working chamber.

  As shown in FIGS. 3 to 6, each screw rotor 120a, 120b includes an equal lead portion 122 disposed on the discharge port 111 side of the stator 110 and an unequal lead portion disposed on the intake port 112 side of the stator 110. 123, respectively.

  As shown in FIG. 6 and the like, the equal lead portion 122 is formed with an equal lead equal inclination angle and has straight tooth traces.

  Further, as shown in FIG. 6 and the like, the unequal lead portion 123 is formed so that the lead and the inclination angle gradually decrease from the intake port 112 side to the discharge port 111 side, and has curved tooth traces. ing.

  The tooth traces of the equal lead portion 122 and the unequal lead portion 123 are connected tangentially as shown in FIG.

  In the unequal lead portion 123, the cross-sectional shape perpendicular to the axis also changes.

  Thus, each screw rotor 120a, 120b is designed to obtain a large exhaust speed regardless of the molecular weight by increasing the intake conductance on the intake port 112 side.

  The mutual spacing between the screw teeth 124a and 124b of the pair of male and female screw rotors 120a and 120b, that is, the meshing gap, is independent of changes in the lead and inclination angle of the screw rotor 120, as shown in FIGS. Further, it is formed so as to be always constant from the intake port 112 side to the discharge port 111 side.

  As shown in FIGS. 7 to 9, the screw rotor machining machine tool 200 includes a spindle 211 that holds a workpiece W, a spindle base 210 that rotatably supports the spindle 211, a spindle base 210, and a spindle 211. The tool base 220 that is movable with respect to the tool base 220, the C axis that rotates the spindle 211 with respect to the spindle base 210, and the tool 221 for the workpiece W that is orthogonal to the C axis. On the line that intersects the C-axis perpendicular to the X-axis and the Z-axis, and the X-axis that defines the cutting direction, the Z-axis that moves the tool table 220 perpendicular to the X-axis and parallel to the C-axis Depending on the Y axis to be moved, the B axis when the tool table 220 and the tool 221 are turned to form an undercut in the cross section perpendicular to the axis of the screw rotor 120, and the lead angle of the screw rotor 120 The A axis for adjusting the rake angle of the tool 221 relative to the workpiece W by rotating the tool 221 with respect to the tool base 220, the rotation of the spindle 211, the movement of the tool base 220, and the rotation of the tool 221 are numerically controlled and synchronized. And a numerical control means 230 for making it possible.

  That is, as shown in FIGS. 7 to 9, the main shaft 211 is designed to rotate around the C axis that coincides with the main shaft 211 with respect to the main shaft 210.

  Further, as shown in FIGS. 7 to 9, the tool table 220 is designed to be movable along the X axis, the Y axis, and the Z axis, and is designed so that the B axis can pivot about the Y axis. ing.

  As shown in FIGS. 7 to 9, the tool 221 is designed to have an A-axis so as to rotate with respect to the tool table 220 about the X-axis that coincides with the axis of the tool 221.

  Then, as shown in FIGS. 8 and 10, the screw rotor machining machine tool 200 is a three-dimensional measuring means including a measurement probe that generates a measurement value by measuring the shape of the screw rotor 120 during or after machining. 240, a numerical value comparison means 250 that generates a correction value by comparing the measured value with the three-dimensional model of the screw rotor, and a correction value output means 260 that outputs the correction value to the numerical control means 230. I have.

  In the present embodiment, the numerical value comparison means 250 and the correction value output means 260 are constituted by a personal computer terminal connected to the screw rotor machining machine tool 200 as shown in FIG. The machine 200 itself may be provided with the numerical value comparison means 250 and the correction value output means 260.

  Next, a screw rotor processing method for processing the screw rotor 120 using the screw rotor processing machine tool 200 will be described.

  First, when machining the equal lead portion 122 formed at the same lead equal inclination angle of the screw rotor 120, the X axis, the Y axis, the Z axis, the C axis, and the B axis are used, that is, the X axis. A first tool moving step of moving the tool table 220 and the tool 221 along the Y axis and the Z axis, a first spindle rotating step of rotating the spindle 211 around the C axis, and a tool around the B axis. The first undercut forming process in the case of forming the undercut in the cross section perpendicular to the axis of the screw rotor 120 by turning the table 220 and the tool 221 is executed by numerical control by the numerical control means 230.

  The first tool moving step, the first main spindle rotating step, and the forming step for forming the first undercut are performed simultaneously or individually according to the shape of the equal lead portion 122.

  Next, when machining the unequal lead portion 123 formed with the unequal lead unequal inclination angle of the screw rotor 120, the X axis, the Y axis, the Z axis, the C axis, the B axis, and the A axis are A second tool moving step of moving the tool table 220 and the tool 221 along the X axis, the Y axis, and the Z axis, and a second spindle rotating step of rotating the main shaft 211 around the C axis. , The second undercut forming step when the tool table 220 and the tool 221 are turned around the B axis to form an undercut in the cross section perpendicular to the axis of the screw rotor 120, and the tool according to the lead angle of the screw rotor 120 An angle adjusting step of adjusting the rake angle of the tool 221 with respect to the workpiece W by rotating the A axis about the X axis with respect to the table 220 and performing numerical control by the numerical control means 230 is executed. That.

  The second tool moving step, the second main spindle rotating step, the forming step when forming the second undercut, and the angle adjusting step are performed simultaneously or individually according to the shape of the unequal lead portion 123. Executed.

  When cutting the tooth surface 125 of the screw rotor 120, the rake angle, clearance angle, blade angle, etc. between the tool 221 and the rake surface (machined surface) of the workpiece W are calculated to obtain the workpiece W The tool 121 is brought into contact with an appropriate rake angle.

  Further, when cutting the tooth bottom 126 of the screw rotor 120, the tooth tip 221 a of the tool 221 is made parallel to the C axis and brought into contact with the workpiece W.

  Then, during or after the processing of the screw rotor 120, a measuring step for measuring the shape during or after the processing using the three-dimensional measuring means 240 comprising a measuring probe and generating a measured value, A comparison step of comparing the three-dimensional model of the screw rotor 120 and generating a correction value using the numerical value comparison means 250, and an output step of outputting the correction value to the numerical control means 230 using the correction value output means 260 Perform further.

  By performing these steps once or a plurality of times during or after the processing of the screw rotor 120, the processing accuracy of the screw rotor 120 can be improved.

  In the present embodiment thus obtained, the tool table 220 and the tool 221 are turned to form a B axis that forms an undercut in the cross section perpendicular to the axis of the screw rotor 120, and the tool table according to the lead angle of the screw rotor 120. By providing the A axis for adjusting the rake angle of the tool 221 with respect to the workpiece W by rotating the tool 221 with respect to 220, it is possible to reduce the cost at a low cost without requiring tool change during the machining. It is possible to process a large amount of the screw rotor 120 having highly accurate unequal lead unequal inclination angles over time, and to supply a large amount of the screw type vacuum pump 100 at a low cost.

  Then, by processing the screw rotor 120 with high accuracy in this way, when the screw rotor 120 is disposed in the screw type vacuum pump 100 as a pair of male and female, the meshing clearance of the screw teeth 124 from the inlet 112 side. Since it becomes always constant toward the discharge port 111 side, the compression ratio of the screw type vacuum pump 100 can be remarkably improved.

  Next, a modified example of the screw rotor will be described with reference to FIGS.

  Here, the configuration of the modification other than the screw rotor 320, that is, the configuration of the screw type vacuum pump 100 and the screw rotor machining machine tool 200 is exactly the same as that of the above-described embodiment. The screw type vacuum pump 100 and the screw rotor machining machine tool 200 shown in FIG.

  Therefore, the same reference numerals are assigned to the screw type vacuum pump 100 and the screw rotor machining machine tool 200, and description thereof will be omitted.

  The screw rotor 320 of this modification is installed in a pair of males and females in the stator 110 of the screw type vacuum pump 100.

  As shown in FIG. 11, each screw rotor 320 includes an equal lead portion 322 disposed on the discharge port 111 side of the stator 110, an equal lead portion 327 disposed on the intake port 112 side of the stator 110, and these equal leads. The non-uniform lead portion 323 is disposed between the portion 322 and the equal lead portion 327.

  As shown in FIGS. 11 and 12, the lead and inclination angle of the equal lead portion 327 are set larger than the lead and inclination angle of the equal lead portion 322.

  As shown in FIGS. 11 and 12, the equal lead portion 322 is formed with an equal lead equal inclination angle and has straight tooth traces.

  Further, as shown in FIGS. 11 and 12, etc., the unequal lead portion 323 is formed so that the lead and the inclination angle gradually decrease from the intake port 112 side to the discharge port 111 side. have.

  Further, as shown in FIGS. 11 and 12, the equal lead portion 327 is formed with an equal lead equal inclination angle and has straight tooth traces.

  The tooth traces of the equal lead portion 322, the unequal lead portion 323, and the equal lead portion 327 are connected tangentially as shown in FIGS.

  In the unequal lead portion 323, the cross-sectional shape perpendicular to the axis also changes.

  Thus, the screw rotor 320 is designed to obtain a large exhaust speed regardless of the molecular weight by increasing the intake conductance on the intake port 112 side.

  The mutual distance between the screw teeth 324 of the pair of male and female screw rotors 320, that is, the meshing gap, is always constant from the intake port 112 side to the discharge port 111 side regardless of changes in the lead and inclination angle of the screw rotor 320. It is formed as follows.

  Next, the processing method of the screw rotor 320 of this modification is demonstrated.

  Here, the processing method of the equal lead portion 322 and the unequal lead portion 323 of the screw rotor 320 according to this modification is the same as the processing method of the equal lead portion 122 and the unequal lead portion 123 of the screw rotor 120 described above. Therefore, the description thereof is omitted.

  Below, only the processing method regarding the equal lead part 327 which is the difference with the screw rotor 320 and the screw rotor 120 is demonstrated.

  The processing method of the equal lead portion 327 of the screw rotor 320 of this modification is the same as that of the equal lead portion 322 except for the lead and the inclination angle.

  That is, when machining the equal lead portion 327 formed at an equal lead equal inclination angle, the X axis, Y axis, Z axis, C axis, and B axis are used, and the X axis, Y axis, and Z axis are used. A first tool moving step for moving the tool table 220 and the tool 221 along the first axis, a first main shaft rotating step for rotating the main shaft 211 about the C axis, and a tool table 220 and the tool 221 about the B axis. The first undercut forming process in the case of forming the undercut in the cross section perpendicular to the axis of the screw rotor 120 by turning is executed by numerical control by the numerical control means 230.

  The first tool moving step, the first spindle rotating step, and the forming step in the case of forming the first undercut are executed simultaneously or individually according to the shape of the equal lead portion 327.

DESCRIPTION OF SYMBOLS 100 ... Screw type vacuum pump 110 ... Stator 111 ... Discharge port 112 ... Intake port 120, 320 ... Screw rotor 121 ... Rotor rotating shaft 122, 322 ... Equal lead part 123 323 ... Unequal lead parts 124, 324 ... Screw teeth 125 ... Tooth surfaces 126, 326 ... Tooth bottoms
327 ・ ・ ・ Equal lead part 130 ・ ・ ・ Bearing part 140 ・ ・ ・ Timing gear 150 ・ ・ ・ Shaft seal part 200 ・ ・ ・ Machine tool for screw rotor processing 210 ・ ・ ・ Spindle table 211 ・ ・ ・ Spindle 220 ・ ・Tool table 221 ... Tool 230 ... Numerical control means 240 ... Three-dimensional measurement means 250 ... Numerical comparison means 260 ... Correction value output means W ... Workpiece

Claims (2)

While the work piece is attached to the spindle supported rotatably around the C axis on the spindle stock,
For cutting work, a Z-axis parallel to the C-axis, an X-axis for defining a cutting direction with respect to the workpiece, and a tool table movable along the Y-axis orthogonal to the X-axis and the Z-axis The tool is attached so as to be rotatable around an A axis parallel to the X axis,
While rotating the workpiece about the C axis, numerically controlling the position of the tool along the X, Y, and Z axes and the rotation angle about the A axis, the workpiece A screw rotor processing method for processing a screw rotor having an unequal lead unequal inclination angle from an object ,
A screw rotor machining method , wherein the tool rest is further configured to be pivotable about the Y axis, and the pivot angle of the tool about the Y axis is numerically controlled . The machining shape of the workpiece during or after machining is measured to generate a measurement value, and the measurement value is compared with the three-dimensional model data of the screw rotor to be machined to generate a correction value. screw rotor machining method according to claim 1, characterized in that the numerically controlled rotation of the tool post of the movement and the tool based on the value.

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