JP3387339B2 - Threading machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting machine, and more particularly to a workpiece having a fixed circular cross section (such as a steel pipe or a steel bar).
While turning the threading tool around the axis of
Supported by the support housing moved in the axial length direction
The present invention relates to a threading machine having a driven rotatable main shaft. 2. Description of the Related Art A typical example of a threading machine having a main shaft that can be driven and rotated is a work material in which an automatic opening / closing die head called a Runges type is attached to the tip of the main shaft and fixed. There is a so-called Rungis-type thread cutting machine that performs thread processing on the outer peripheral surface of the end portion. [0003] In the thread cutting by the above-mentioned Rungis type thread cutting machine, one process is completed by one reciprocating operation of the main shaft with respect to the workpiece. At this time, in order to maintain the accuracy of the machined screw correctly, the main shaft 1 must be moved at the time of the forward movement of the machined spindle with respect to the workpiece and at the time of machined screw cutting by the threading tool.
It is necessary to accurately secure the moving distance in the axial direction per rotation, in other words, the feed amount of the threading tool for one pitch of the screw to be machined. In addition, during reciprocating operation in which the machined screw is not cut by the threading tool, it is necessary to shorten the threading cycle by moving the spindle back and forth in the axial direction at the highest possible speed, thereby increasing productivity. The following methods A, B and C are well known as a spindle feed mechanism for that purpose. A: As seen in a general-purpose lathe, a main screw for main spindle feeding, which is screwed with a nut provided at a predetermined position in a non-rotatable state, and a main shaft that is driven to rotate, using a gear mechanism or the like. A mechanical tuning mechanism (see, for example, Japanese Utility Model Laid-Open No. 61-11738) in which the rotation of the main shaft is directly transmitted to the lead screw to drive the lead screw to rotate. B: As seen in an NC lathe, a lead screw for main shaft feeding, to which a nut provided at a predetermined position in a non-rotatable state is screwed, is driven to rotate using an independent drive source, and another drive is performed. An electric tuning mechanism for controlling the number of revolutions of the independent driving source based on the feed amount per one rotation of the main shaft driven to rotate by the source (for example, see Japanese Utility Model Application Laid-Open No. 63-172522). C: Instead of providing the above-mentioned tuning mechanisms A and B, by using a threading bit with an appropriate clearance angle, the threading bit itself is guided in accordance with the machined screw cut by itself. Self-tuning mechanism. However, among the above-mentioned tuning mechanisms, the self-tuning mechanism of C is not suitable for thread processing requiring a high-precision pitch. In addition, no effect is obtained from the viewpoint of shortening the processing cycle. On the other hand, the mechanical tuning mechanism of A and the electrical tuning mechanism of B can be applied to the Rungis type threading machine of the present invention, but their structures are as follows. FIG. 3 is a schematic view showing an example of a Rungis type threading machine using the mechanical tuning mechanism of the above A, and is a partially broken side view. In the drawing, reference numeral 1 denotes a bed provided with a guide rail 1a, 2 denotes a bed mounted on the bed 1,
The spindle support housing 3 that slides along a is a fluid pressure cylinder composed of normal hydraulic pressure for quickly moving the spindle support housing 2 toward and away from the fixed workpiece P. Reference numeral 4 denotes a shaft 4 which cannot be moved in the axial direction with respect to the main shaft support housing 2, but is rotatably supported at both ends by bearings 2a and 2a, and is provided at an intermediate portion in the axial direction. A gear 4a fitted and fixed is connected to a gear 6a provided on a rotating shaft of an electric motor 6 fixedly mounted on the spindle support housing 2 via an intermediate gear train 5, and is driven by a main shaft to rotate in a predetermined direction. is there. Further, a reference numeral 7 denotes a main shaft support housing 2 which is screwed with an openable and closable half nut 8 which is fixedly arranged at a predetermined position in a non-rotatable manner and which is closed. Further, the lead screw is a lead screw for feeding the spindle, which is fixed to the rear end of the spindle 4 for moving the spindle 4 closer to the workpiece P at a predetermined pitch. In the figure, reference numeral 9 denotes a Runge-type die head which automatically disposes a plurality (usually 4 to 6) of thread cutting tools 10 equally distributed on the same circumference on the front surface thereof in the radial direction. It can be moved to. Also, reference numeral 1
Reference numeral 1 denotes a high-speed feed limit detection sensor, and 12 denotes a high-speed return limit detection sensor, which are turned on by a striker 2b attached to the spindle support housing 2. Reference numeral 13 denotes a threading completion detection sensor which is attached to the spindle support housing 2 and is turned on by a striker 9a which is mounted on the die head 9 and automatically takes a posture shown by a thin line in the figure at the time of threading completion detection. It is supposed to work. In the threading machine constructed as above, the half nut 8 is opened and the electric motor 6 is driven to rotate the main shaft 4 so that the piston rod 3a of the hydraulic cylinder 3 is rotated. To move the spindle support housing 2, in other words, the spindle 4, to the workpiece P at a high speed until the high-speed feed limit detection sensor 11 is turned on. Next, the high-speed feed limit detecting sensor 11
Simultaneously with the N operation, the hydraulic circuit of the hydraulic cylinder 3 is switched so that pressure does not act on the hydraulic cylinder 3, the half nut 8 is closed and meshed with the lead screw 7, By giving a feed according to the screw pitch of the screw 7, predetermined thread cutting is performed. After the threading completion detecting sensor 13 is turned on and the half nut 8 is opened at the same time, the hydraulic circuit is switched to retract the piston rod 3a of the hydraulic cylinder 3 to detect the high-speed return limit. The spindle support housing 2, in other words, the spindle 4 is separated from the workpiece P at a high speed until the sensor 12 is turned on, thereby completing one cycle of thread cutting. However, in the threading machine to which such a mechanical tuning mechanism is applied, there is a problem that the quality of the machined screw is uniquely determined by the precision of the lead screw 7, and it is not possible to machine a screw of constant quality. This is because when the half nut 8 is opened and closed, the half nut 8 and the lead screw 7 come into shock contact with each other, causing wear to occur on both sides, and the screw accuracy of both becomes worse over time. When machining screws having different pitches, it is necessary not only to replace both the lead screw 7 and the half nut 8 each time, but also to machine screws having different diameters. Since it is necessary to adjust the screw cutting start position,
Each time, it is necessary to adjust the position of the high-speed feed limit detection sensor 11, and there is a problem that the operation rate of the threading machine is low. Further, since the wear of the half nut 8 and the lead screw 7 becomes more remarkable as the spindle 4 is rotated at a higher speed, it is difficult to reduce the cycle time by rotating the spindle 4 at a higher speed. There were also problems. On the other hand, FIG. 4 is a schematic view showing an example of a Rungis type thread cutting machine using the electric tuning mechanism of the above B, and is a partially cutaway side view. As shown in the figure, a Runges type threading machine using an electric tuning mechanism has an integral nut 80 mounted on the main shaft support housing 2 in a non-rotatable state in place of the half nut 8 described above. A lead screw 7 provided on the outside of the main shaft support housing 2 so as to be immovable in the axial direction is screwed into the integral nut 80, and the lead screw 7 is connected to an independent electric motor (usually a servomotor) 70. It is almost the same as the Rungis type threading machine using the mechanical tuning mechanism described above, except that it is driven to rotate and that it does not include the high-speed feed limit detection sensor 11. In the threading machine constructed as described above, the NC controller 14 controls the rotation of the electric motor 6 for driving the main shaft and the number of rotations thereof, and the rotation of the electric motor 70 for driving the lead screw. Reverse rotation drive and its rotation speed is N
C is controlled. Specifically, the electric motor 6 for driving the main spindle is driven and the electric motor 70 for driving the lead screw is rotated at a high speed, so that the main spindle support housing 2, in other words, the main spindle 4 is moved to the workpiece P at a high speed. Get closer. Next, when the spindle support housing 2, in other words, the spindle 4 reaches the high-speed feed limit position previously stored in the NC control device 14, the electric motor detected by the pulse generator 6 b attached to the electric motor 6. By controlling the number of revolutions of the electric motor 70 based on the number of revolutions of the motor 6, a thread having a predetermined pitch is thread-cut. At the same time when the threading completion detecting sensor 13 is turned on, the electric motor 70 is driven in reverse rotation at a high speed, and the spindle support housing 2, ie, the main shaft 4, is moved to the position where the high-speed return limit detecting sensor 12 is turned on. P
, One cycle of thread cutting is completed. In the threading machine to which the electric tuning mechanism is applied, as described above, the lead screw 7 is driven to rotate using the electric motor 70 different from the main shaft 4, so that the amount of movement in the axial direction per one rotation of the main shaft is obtained. Can be set arbitrarily, and there is an advantage that thread processing with various pitches is possible. The main shaft 4
Switching between high-speed feed and synchronous feed by the NC controller 1
4 can be performed based on a position command set and stored in advance. Therefore, there is no need to provide the high-speed feed limit detection sensor 11, and there is an advantage that the operation rate does not decrease due to the position adjustment. However, a threading machine adopting an electric tuning mechanism is, for example, a steel pipe specified by JIS and having an outer diameter in a wide range of 15 A to 100 A (10.5 to 114.3 mm). When performing thread cutting with only one threading machine on a workpiece to be processed, there is a problem that a highly accurate machined screw cannot be obtained. The reason is that the number of rotations of the electric motor 70 at the time of high-speed feeding when the spindle 4 approaches the workpiece P at a high speed in the early stage of threading (usually the maximum allowable rotation regardless of the outer diameter of the workpiece). ), And the ratio of the number of rotations to the number of rotations at the time of synchronized low-speed feeding during thread cutting is 10 at the maximum.
This is because the control accuracy of the electric motor 70 reaches the limit when the ratio exceeds 0: 1, and the tuning feed accuracy deteriorates. In particular, the above tendency is remarkable when machining a tapered screw with a large variation in cutting load, and a special thread cutting tool is used to obtain a high-precision machined screw, or some cutting load equalizing means is provided. Needed. In addition, an advanced NC control device is required, the threading machine becomes expensive, and the processing cost increases. In addition, as pointed out in the above-mentioned Japanese Utility Model Application Laid-Open No. 63-172522, the time between threading cycles is reduced. When the threading tool is polished by the method described above, there is also a problem that it is difficult to position a plurality of threading tools. SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object the following main problems of the threading machine employing the mechanical tuning mechanism.
It is an object of the present invention to provide a thread cutting machine which eliminates both (1) and (2) and the following main problems (3) to (5) of the thread cutting machine employing an electric tuning mechanism. (1) It is necessary to replace the lead screw and the half nut when changing the screw pitch, and to adjust the position of the high-speed feed limit detecting sensor when changing the diameter.
(2) High-precision and constant-quality machined screws cannot be obtained due to the impact contact wear between the lead screw and the half nut. (3) Feed synchronization accuracy is reduced due to fluctuations in cutting load. (4) It is difficult to align a plurality of threading tools with each other after polishing the threading tool between machining cycles. (5) An advanced NC controller is required, and the threading machine itself becomes expensive. As a result of various studies, the present inventor has adopted the following means to solve the above-mentioned disadvantages (1) to (5) of the conventional threading machine. The inventors have found that all of them can be eliminated, and have accomplished the present invention. That is, in order to eliminate the necessity of replacing the lead screw and the half nut at the time of changing the screw pitch, and to prevent the operating rate of the screw cutting machine from being reduced, the nut can be removed in the same manner as in the conventional screw cutting machine employing the electric tuning mechanism. Must be fixedly mounted on the spindle support and a lead screw to be screwed into the nut must be provided outside the spindle support housing. In order to minimize the abrasion of the lead screw, it is necessary to avoid the impact contact caused by opening and closing of the half nut, and for that purpose, an integral nut may be used instead of the half nut. The tuning of the main shaft and the change of the pitch need only be performed by gear-connecting the main shaft and the lead screw in such a manner that the gear ratio can be changed in the same manner as in a conventional threading machine employing a mechanical tuning mechanism. However, instead of directly connecting the main shaft and the lead screw with a gear, an integral nut is fixedly mounted rotatably on the main shaft support housing, and the integral nut and the main shaft are connected to an intermediate gear train provided with a brake and a clutch. By connecting an independent forward / reverse rotatable electric motor, specifically a servo motor, to the lead screw, the installation of the high-speed feed limit detection sensor can be omitted, and the workpiece material has a wide range of outer diameters. A high-precision screw can be machined irrespective of the rotational speed ratio between the main shaft rotation drive electric motor and the lead screw rotation drive electric motor at the time of thread machining. The gist of the present invention based on the above findings lies in the following thread cutter. While turning the threading tool (10) about the axis of the fixed workpiece (P) having a circular cross section ,
In the spindle support housing (2) rotatably be supported on the moving allowed is rotated in the axial length direction the main shaft (4) threading machine having a lead screw constituting the feed mechanism of the axial direction of the spindle (4) (7) is provided outside the spindle support housing (2) so as to be able to drive and rotate using an electric motor (70) different from the electric motor (6) for rotationally driving the spindle. Integral nut (80)
Thereby rotatably mounted relative to the spindle support housing (2), a main shaft (4) integral nut (80), the spindle
The gears are connected by an intermediate gear train (15) supported by a spindle support housing (2) having a brake (15a) and a clutch (15c) arranged in order from the support housing (2) side. Threading machine. Hereinafter, a thread cutting machine according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing an example of a Rungis type threading machine to which the above-mentioned contents of the present invention are applied, and is a partially broken side view. Note that the same parts as those of the Runges type threading machine using the conventional mechanical tuning mechanism and electric tuning mechanism are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in the figure, the threading machine of the present invention
As in the conventional Runge-type threading machine using the electric tuning mechanism shown in FIG.
An electric motor 70 including a servomotor is connected to the lead screw 7. On the other hand, the integral nut 80 screwed to the lead screw 7 has a gear 8
Reference numeral 0a is externally fitted and fixed, and is rotatably mounted on a bracket 2c fixed to the main shaft support housing 2 so as to be immovable in the axial direction. A shaft 4b is fixed to the rear end of the main shaft 4 so as to protrude therefrom, and a gear 4c is externally fitted to the tip of the shaft 4b so as not to rotate. The gear 80a and the gear 4c are
It is supported by the spindle support housing 2 and is gear-coupled from the side of the spindle support housing 2 with an intermediate gear train 15 in which a brake 15a, a gear 15b meshing with the gear 80a, a clutch 15c, and a gear 15d meshing with the gear 4c are arranged. Reference numeral 16 in the figure denotes a control device for issuing a forward / reverse rotation command to the electric motor 70 for driving the lead screw 7 to rotate. In the threading machine of the present invention configured as described above, at the time of thread cutting, first, the workpiece P is supplied to a predetermined position by an attached transport device (not shown) and fixed. On the other hand, the threading machine has its spindle support housing 2,
In other words, the high-speed return limit detection sensor 12 turns the spindle 4 ON.
In this state, the electric motor 6 is driven to drive the main shaft 4 to rotate continuously at a rotation speed corresponding to the screw specifications to be formed on the workpiece P. At the same time as the loading signal of the workpiece P,
The control device 16 issues a high-speed normal rotation command to the electric motor (servo motor) 70. At this time, the clutch 15c constituting the intermediate gear train 15 is opened, the brake 15a is closed, and the integral nut 80 is prevented from rotating. As a result, the spindle support housing 2, that is, the spindle 4, advances at a high speed toward the workpiece P with the rotation of the lead screw 7 irrespective of the rotation by the electric motor 6. At this time, the electric motor 70 composed of a servomotor automatically stops based on its own position information when reaching a preset number of rotations,
The spindle support housing 2, in other words, the spindle 4 is advanced at a high speed to a high-speed feed limit which is a screw cutting start position. Next, at the same time when the electric motor 70 is stopped,
The clutch 15c is closed, the brake 15a is opened, and the integral nut 80 is made rotatable. As a result, the spindle 4
Is transmitted to the gear 80a via the intermediate gear train 15 to rotate the integral nut 80, and accordingly, a predetermined feed corresponding to the rotation is given to the spindle support housing 2, in other words, the spindle 4. Therefore, a predetermined screw processing is performed on the workpiece P. At this time, if the gears 4c and 15d are replaced with gears having an appropriate gear ratio, screws having different pitches can be machined. Therefore, it is preferable that a plurality of gears 4c and 15d having different gear ratios are incorporated and can be switched by lever operation. Thereafter, the clutch 15c is opened and the brake 15
is switched to closed, and then, after the position information of the electric motor 70 is reset, a high-speed reverse rotation command is issued from the control device 16 to the electric motor 70, and the spindle support housing 2, in other words, the spindle 4, is retreated at high speed. Then, when the high-speed return limit detection sensor 12 is turned ON, the rotation of the electric motor 70 is stopped, and the high-speed feed limit position, which is the screw cutting start position, is reset in preparation for the next thread processing on the workpiece P. It is preferable that the lead screw 7 and the integral nut 80 are formed by forming a ball screw (round screw) with the least wear. Further, the electric motor 70 may be a normal electric motor instead of the servo motor. In this case, however, it is necessary to connect a pulse generator, a rotary encoder, or the like to the rotating shaft so that the high-speed feed limit detecting sensor does not need to be installed, so that the number of rotations can be detected. As described in detail above, in the threading machine of the present invention, the lead screw 7 is synchronized with the rotation of the main shaft 4 only during thread cutting, so that the conventional threading machine employing only the electric tuning mechanism is used. The disadvantages of the machine are the difficulty in aligning multiple cutting tools, the increase in the rotational speed ratio between the electric motors 6 and 70 when the outer diameter is changed, and the decrease in feed synchronization accuracy due to the change in cutting load when cutting taper screws. No worries at all. When the pitch is changed, it is not necessary to replace both the lead screw 7 and the integral nut 80, which is a drawback of the conventional threading machine employing only the mechanical tuning mechanism. It is only necessary to replace the gear 4c provided at the tip of the shaft 4b with a gear having a different gear ratio or to switch the gear 4c by operating a lever, and there is no need for troublesome setup change. [0051] Further, the electric motor 70 for driving rotation of the lead screw 7 is independently rotate drive the electric motor 6 for driving the rotation of the main shaft 4 in <br/> when driving only during high-speed feed at a high speed return it is to be able, because the permissible maximum may be driven at a rotational speed without receiving also restrictions whatever, with shortening of the processing cycle time Ru Hakare <br/> can return faster fast feed and fast, high-speed There is no need to install a feed limit detection sensor. Further, the control device 16 does not require an expensive device such as an NC control device, and may be an extremely simple device. Therefore, the cost of the threading machine can be reduced. Further, the lead screw 7 and the integral nut 80 are
By operating the brake 15b and the clutch 15c, the screw connection driving is performed in a non-impact state, and wear is suppressed to a minimum, so that a stable and high-precision screw can be machined. EXAMPLE A nominal diameter of 15 to 1 was used by using the threading machine of the present invention shown in FIG. 1 and the conventional threading machine shown in FIGS.
An external thread for a gas pipe was machined around the outer circumference of the steel pipe end of 00A. While examining the machining cycle time for each nominal diameter when using each threading machine, the thread machined by the threading machine of the present invention and the conventional threading machine employing only the electric tuning mechanism are used. The profile of the machined screws (all machined to a nominal diameter of 80A) was measured using a contracer. Of these results, the machining cycle time is shown in Table 1, and the profile is shown in FIG. [Table 1] As shown in Table 1, the processing cycle times of the conventional threading machine employing only the threading machine of the present invention and the electric tuning mechanism were almost the same. On the other hand, the machining cycle time in the case of the conventional threading machine employing only the mechanical tuning mechanism cannot rotate the main shaft 4 at the maximum speed due to the restriction on the opening / closing speed of the half nut 8 and the like. Because it was a bit long. The time required for the setup change when the nominal diameter is changed is less than one minute in the conventional threading machine employing only the threading machine of the present invention and the electric tuning mechanism, but only the mechanical tuning mechanism is used. The conventional threading machine employing the method required an extremely long time of about 2 hours. As shown in FIG. 2 (a), the profile of the thread processed by the threading machine of the present invention was normal. On the other hand, as shown in FIG. 2 (b), the profile of the screw machined by the conventional threading machine employing only the electric tuning mechanism has a variation in load during thread cutting and an alignment of the threading tool 10 with each other. Due to the imperfection, the tuning accuracy between the electric motors 6 and 70 was reduced, which was unsatisfactory. Although not shown, the profile of the thread processed by the conventional threading machine employing only the mechanical tuning mechanism was almost the same as that according to the threading machine of the present invention, and was normal. According to the threading machine of the present invention, the setup can be quickly changed when the pitch or the diameter is changed.
As a result, the operation rate of the threading machine can be improved. Further, not only the wear of the lead screw and the integral nut is small, but also there is no occurrence of spindle synchronization feed failure at the time of screw cutting due to a change in cutting load, so that a stable and high-precision screw can be machined for a long period of time. Furthermore, an expensive NC controller is not required,
The cost of the threading machine can be reduced, and the frequency of component replacement can be reduced, so that the tool unit consumption can be reduced, and the threading cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an example of a threading machine of the present invention, and is a partially broken side view. FIGS. 2A and 2B are diagrams showing the results of an embodiment, wherein FIG. 2A shows a profile of a screw machined by the threading machine of the present invention, and FIG. 2B shows a threading machine employing only a conventional electric tuning mechanism. It is a figure which shows the profile of the screw machined in FIG. FIG. 3 is a schematic view showing an example of a conventional threading machine employing only a mechanical tuning mechanism, and is a partially broken side view. FIG. 4 is a schematic view showing an example of a conventional threading machine employing only an electric tuning mechanism, and is a partially broken side view. [Description of Signs] 1: bed, 1a: rail, 2: spindle support housing, 2a: bearing, 2b: striker, 2c: bracket, 3: hydraulic cylinder, 3a: piston rod, 4: spindle, 4a: gear, 4b: shaft, 4c: gear, 5: intermediate gear train, 6: electric motor, 6a: gear, 6b: pulse generator, 7: lead screw, 8: half nut, 9: die head, 9a: striker 10: for thread cutting Bite, 11: High-speed feed limit detection sensor, 12: High-speed return limit detection sensor, 13: Threading completion detection sensor, 14: NC controller, 15: Intermediate gear train, 15a: Brake, 15b: Gear, 15c: Clutch, 15d : Gear, 16: control device, 70: electric motor, 80: integral nut, 80a: gear, P: workpiece.

Claims (1)

(57) [Claim 1] While rotating a threading tool (10) around the axis of a fixed workpiece (P) having a circular cross section ,
In the spindle support housing (2) rotatably be supported on the moving allowed is rotated in the axial length direction the main shaft (4) threading machine having a lead screw constituting the feed mechanism of the axial direction of the spindle (4) (7) is provided outside the spindle support housing (2) so as to be able to drive and rotate using an electric motor (70) different from the electric motor (6) for rotationally driving the spindle. Integral nut (80)
Thereby rotatably mounted relative to the spindle support housing (2), a main shaft (4) integral nut (80), the spindle
The gears are connected by an intermediate gear train (15) supported by a spindle support housing (2) having a brake (15a) and a clutch (15c) arranged in order from the support housing (2) side. Threading machine.