JP2011020198A - U shaft driving structure of machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To connect two rotating elements without receiving restriction of a phase in a circumferential direction when connecting them to transmit rotational force of a spindle to a U shaft tool unit. <P>SOLUTION: A machine tool has the U shaft tool unit 7 mounted on a tool holder 6 and includes a chucking means 14 allowing a pull stud 11 and a draw bar 12 to be integrally engaged with each other irrespective of the phase in the circumferential direction and the spindle 5 for detachably fixing the tool holder 6. The pull stud 11 is rotatably journaled to the tool holder 6, the draw bar 12 is rotatably journaled to the spindle 5, a servo motor 25 for a U shaft that rotates the draw bar 12 is arranged, and the rotational force of the draw bar 12 is transmitted to the U shaft tool unit 7 through the pull stud 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a U-axis drive structure in a machine tool such as a machining center.

  As a device that cuts and feeds a tool in a direction that intersects the spindle rotation center (hereinafter referred to as a U-axis tool unit), a type that has a mechanism that converts the rotational force around the spindle rotation center into a force that intersects the spindle rotation center As a conventional example of a structure for driving and transmitting the rotational force to the U-axis tool unit, the one described in Patent Document 1 can be cited.

  If the reference of the same literature is attached | subjected and demonstrated, in patent document 1, the drawbar will be formed in hollow and the connecting shaft 22 rotated by the servomotor 28 will be inserted in the inside, and this connecting shaft 22 will be u-axis tool. A technique is described in which when advancing to the unit 15 side, the groove 35 and the projection 36 are coupled to the u-axis drive shaft 13 so as to be integrally rotatable by a fitting method. The rotation of the u-axis drive shaft 13 is converted into the cutting feed of the tool 12 by the gear train 14 and the like in the u-axis tool unit 15.

Japanese Patent No. 3793107

  According to the technique described in Patent Document 1, it is necessary to match the circumferential phase of the coupling shaft 22 and the u-axis drive shaft 13 to a predetermined phase when fitting the groove 35 and the protrusion 36. As described in paragraph [0017] of this document, it is necessary to take measures to always stop the connecting shaft 22 at a predetermined rotational position using a numerical control device.

  In addition, the structure requires a driving source such as the connecting shaft 22 and the cylinder mechanism 44 for moving the connecting shaft 22 back and forth, so that the number of parts increases and the manufacturing cost tends to increase. Furthermore, since the technique of Patent Document 1 has a structure in which the draw bar is formed hollow as described above and the connecting shaft 22 is inserted through the hollow, the connecting shaft 22 has to be a small-diameter shaft member, and is twisted. There is a risk that the rigidity will be lowered and the cutting feed accuracy will be affected.

  The present invention has been created to solve such a problem. In connecting the two rotating elements to transmit the rotational force around the spindle rotation center to the U-axis tool unit, the circumferential direction is It is an object of the present invention to provide a U-axis drive structure for a machine tool that can be connected without being limited in phase and can easily solve the problems of an increase in the number of parts and a decrease in rigidity of a drive transmission member.

  In order to solve the above-described problems, the present invention provides a tool holder having a U-axis tool unit that converts a rotational force around a spindle rotation center into a force in a direction intersecting the spindle rotation center to cut and feed the tool, In the machine tool comprising: a chucking means for integrally engaging the drawbar and the draw bar regardless of the circumferential phase; and a main shaft for detachably fixing the tool holder, the pull stud is rotated on the tool holder. The draw bar is rotatably mounted on the main shaft, and a draw bar rotation drive source for rotating the draw bar is provided, and the rotational force of the draw bar is transmitted to the U-axis tool unit via the pull stud. By doing so, the tool is cut and fed.

  The present invention utilizes a pull stud and a draw bar as two rotating elements to be connected when driving the rotational force around the center of rotation of the spindle to the U-axis tool unit, and the pull stud is rotatably mounted on the tool holder. At the same time, the draw bar is rotatably mounted on the main shaft, and the rotational force of the draw bar is transmitted to the U-axis tool unit via the pull stud integrated by the chucking means.

  Since the chucking means is configured to integrally engage the pull stud and the draw bar irrespective of the phase in the circumferential direction, unlike the fitting method of the groove and the protrusion described in Patent Document 1, There is no restriction on the phase of the direction.

  In addition, the draw bar that originally has only the function of attaching / detaching the tool holder to / from the main shaft also serves as the drive transmission function of the rotational force to the U-axis tool unit side, and it is necessary to separately provide the connecting shaft described in Patent Document 1 There is no. Of course, since the pull-in operation of the draw bar is directly connected to the pull stud and the draw bar, a driving source such as a cylinder mechanism for moving the connecting shaft back and forth described in Patent Document 1 is not required. Since the draw bar is used as the drive transmission member, the problem of lowering the rigidity of the drive transmission member as in the case where the hollow portion is provided and the connecting shaft is inserted does not occur.

  In the present invention, the chucking means may be a steel ball chucking mechanism in which a plurality of steel balls move toward the spindle rotation center and engage with the pull stud as the draw bar is pulled, and the pull stud Is mounted on the tool holder via a bearing.

  Since the steel ball chucking mechanism is excellent in the engagement force between the draw bar and the pull stud, it is suitable as a means for integrating the two. In addition, when the draw bar is pulled, a thrust load is applied to the rotation support portion of the pull stud in the tool holder. By pulling the pull stud on the tool holder via the bearing, the thrust load is absorbed and the pull stud is smooth. Rotation function can be secured.

  According to the present invention, the machine tool is a machining center, and instead of the tool holder, a BT holder having a structure in which a pull stud is integrally provided so as not to rotate with respect to the holder is attached to the spindle by the chucking means. It can be attached to.

  BT holders for tools that do not have a U-axis mechanism such as drills, millers, reamers, and end mills, that is, existing general-purpose BT holders that have a structure in which a pull stud is integrally provided so as not to rotate with respect to the holder. In the case of mounting, according to the technique of the cited document 1, it is necessary to move the connecting shaft. However, according to the present invention, the mounting can be performed only by the operation of the chucking means. I don't need it.

  The present invention utilizes a pull stud and a draw bar as two rotating elements to be connected when driving the rotational force around the spindle rotation center to the U-axis tool unit. Regardless of the connection. Therefore, according to the present invention, the phase matching technique described in Patent Document 1, that is, means for controlling the rotation stop position of the rotating element to match the phase is not required. Further, according to the present invention, since the draw bar has a drive transmission function of the rotational force to the U-axis tool unit side, a dedicated drive transmission member and a drive source for the connection are not required, and the number of parts can be increased. Can be suppressed. Further, since the draw bar is used as the drive transmission member, the problem of the rigidity of the drive transmission member does not occur. Even when an existing general-purpose BT holder is mounted on the spindle, it can be mounted only by the operation of the chucking means.

It is a sectional side view of a machining center to which the present invention is applied. It is a sectional side view around a chucking means, (a), (b) shows the non-engagement state and engagement state of a draw bar and a pull stud, respectively.

  In FIG. 1, a machining center 1 includes a spindle 5 that is supported by a frame 2 via a plurality of bearings 3 and that is rotated by a built-in spindle motor 4. The spindle motor 4 is composed of a servo motor, for example. A tool holder 6 is detachably fixed to the tip of the spindle 5 by close contact between the shank surfaces, and the rotational force around the spindle rotation center P is applied to the tool holder 6 in a direction intersecting the spindle rotation center P. A U-axis tool unit 7 for converting and cutting and feeding the tool T is mounted.

  The U-axis tool unit 7 has a rotation input shaft 8 that is integrally connected to a pull stud 11 in the tool holder 6. As will be described later, when the pull stud 11 rotates, the rotation input shaft 8 also rotates together, and the rotational force is output to the rotation output shaft 10 via the speed reduction mechanism 9. The rotational force of the rotary output shaft 10 is converted into a force that cuts and feeds the tool T in the direction intersecting the spindle rotation center P by a gear mechanism such as a rack and pinion or a motion force conversion mechanism (not shown) such as a cam mechanism. The A detailed description of the athletic force conversion mechanism will be omitted because it is out of the spirit of the present invention.

  Inside the main shaft 5, a draw bar 12 that is constantly urged to the pull-in side (right side in FIG. 1) by a flat spring 13 is inserted, and a chucking means 14 for chucking the pull stud 11 is assembled at the tip of the draw bar 12. Yes. The chucking means 14 is a BT holder (not shown) of a tool that does not have a U-axis mechanism such as a drill, a milling cutter, a reamer, and an end mill, that is, a pull stud is integrally provided so as not to rotate with respect to the holder. The configuration is basically the same as a conventional chucking means for mounting a general-purpose BT holder having a configuration on a main shaft. However, as will be described later, the pull stud 11, the draw bar 12, and the ring member 19 rotate relative to the main shaft 5.

  The chucking means 14 has a function of integrally engaging the pull stud 11 and the draw bar 12 regardless of the phase in the circumferential direction. In this embodiment, as shown in FIG. Accordingly, the steel ball chucking mechanism is configured such that the plurality of steel balls 15 move toward the main shaft rotation center P and engage with the pull stud 11. The draw bar 12 is formed in a cylindrical shape around the end of the pull stud 11 to accommodate the end of the pull stud 11, and a plurality of steel ball storage holes 17 are formed in the cylindrical wall portion 16 along the circumferential direction. A steel ball 15 is stored in the ball storage hole 17 so as to be movable in the radial direction. In order to prevent the steel balls 15 from falling off, the inner surface of the steel ball housing hole 17 is formed as an inclined surface that decreases in diameter toward the spindle rotation center P. A ring member 19 is formed between the inner surface of the main shaft 5 and the cylindrical wall portion 16. The ring member 19 is formed with a thin wall near the front end and a positioning groove 18 formed on the inner circumferential surface of the middle thick wall portion. .

  When the draw bar 12 is in the forward position, the steel ball 12 is positioned on the thin portion side of the ring member 19 as shown in FIG. 2A, and the pull stud 11 and the draw bar 12 are in a disengaged state. Then, when the draw bar 12 is drawn to the right side in the drawing, the steel ball 15 moves toward the main spindle rotation center P in a manner of climbing from the thin portion to the thick portion, and is fitted into the positioning groove 18. At this time, each steel ball 15 presses the inclined surface 11a of the pull stud 11 and the inclined surface of the steel ball storage hole 17 of the draw bar 12 toward the main shaft rotation center P. Therefore, the steel ball 15, the pull stud 11, and the draw bar are pressed. 12, a large frictional force is generated between each of the ring members 19, the pull stud 11 and the draw bar 12 are engaged, and the tool holder 6 is fixed to the spindle 5 by the close contact between the shank surfaces. Since the ring member 19 and the main shaft 5 are not in the engaged state, the draw bar 12 is freely rotatable with respect to the main shaft 5 in the clamped state (chucking state).

  In the above configuration, the present invention is configured such that the pull stud 11 is rotatably mounted on the tool holder 6 and the draw bar 12 is rotatably mounted on the main shaft 5, and the rotational force of the draw bar 12 is transmitted via the pull stud 11. The main feature is that the tool T is cut and fed by transmitting to the shaft tool unit 7.

  The pull stud 11 is supported on the tool holder 6 via a bearing 20. Since a relatively large thrust load is applied to the bearing 20 by the drawing of the draw bar 12, an angular ball bearing or a deep groove ball bearing is suitable as the bearing 20.

  As shown in FIG. 1, a cylindrical first flat spring receiver 22 is attached around the rear end of the main shaft 5 via a bearing 21. The front end of the flat spring 13 is supported by the first flat spring receiver 22, and the rear end is supported by a second flat spring receiver 23 that is fitted and fixed near the rear end of the draw bar 12. The draw bar 12 is rotatably supported by the inner peripheral surface of the first flat spring receiver 22 and the inner peripheral surface of the main shaft 5.

  The rear end of the draw bar 12 is connected to a U-axis motor 25 as a draw bar rotation drive source via a joint 24. The U-axis motor 25 is composed of a servo motor, for example. The U-axis motor 25 is mounted on the guide rail 26 so as to be movable in the axial direction (Z-axis direction) of the main shaft 5, and by moving the draw bar 12 back and forth in the Z-axis direction by a draw bar drive device (not shown), The U-axis motor 25 also moves forward and backward together. The drawbar drive device may be a known device such as one using hydraulic pressure, and a detailed description thereof will be omitted because it is out of the spirit of the present invention.

  The U-axis drive structure of the present invention is configured as described above. When the draw bar 12 is pulled, the steel ball chucking mechanism is activated and the pull stud 11 is integrally connected to the draw bar 12 regardless of the phase in the circumferential direction. The Then, at the time of machining accompanied by U-axis cutting, the rotational speed of the U-axis motor 25 is set higher than the rotational speed of the main shaft motor 4 so that a predetermined speed difference is generated between them. The rotation of the U-axis motor 25 causes the draw bar 12, the spring spring 13, the ring member 19, and the pull stud 11 to rotate together, and the rotation input shaft 8 also rotates together. It is cut and fed in a direction orthogonal to the rotation center P.

  At the time of machining with the U-axis cutting depth fixed, the spindle motor 4 and the U-axis motor 25 are synchronized, and both are set to the same rotation speed. In the case of a tool without a U-axis mechanism, that is, when the above-mentioned general-purpose BT holder is mounted, the spindle motor 4 and the U-axis motor 25 are synchronized, or the U-axis motor 25 is It may be configured such that only the main shaft motor 4 is driven to be turned off and the U-axis motor 25 is rotated.

  As described above, in the machine tool such as the machining center 1 having the chucking means 14 that integrally engages the pull stud 11 and the draw bar 12 regardless of the circumferential phase, the pull stud 11 is rotated to the tool holder 6. The draw bar 12 is rotatably mounted on the main shaft 5 while being freely mounted, and a draw bar rotation drive source (U-axis motor 25) for rotating the draw bar 12 is provided, and the rotational force of the draw bar 12 is supplied via the pull stud 11. If the configuration is such that the tool T is cut and fed by transmitting to the U-axis tool unit 7, the pull stud 11 and the draw bar 12 are connected without being limited by the circumferential phase due to the interposition of the chucking means 14. To do. Thereby, the means for controlling the rotation stop position of the rotating element described in Patent Document 1 is not required.

  Further, since the draw bar 12 has a function of transmitting the rotational force to the U-axis tool unit 7 side, a dedicated drive transmission member and a drive source for connecting the same are not required, and an increase in the number of parts is suppressed. It is done. Furthermore, since the draw bar 12 is used as the drive transmission member, there is no problem of lowering the rigidity of the drive transmission member as in the case where the hollow portion is provided and the connecting shaft is inserted.

  Then, as in this embodiment, the machine tool is a machining center, and the pull stud rotates with respect to the holder instead of the tool holder 6 having a U-axis mechanism and the pull stud 11 rotatably mounted on the shaft. If a BT holder having a structure integrally provided cannot be mounted on the spindle 5 by the chucking means 14, the BT holder can be mounted only by the operation of the chucking means 14 as in the case of mounting the tool holder 6. It becomes possible.

  The best mode of the present invention has been described above. In the embodiment described above, the chucking means 14 is a steel ball chucking mechanism. However, the pull stud 11 and the draw bar 12 have a function of being integrally engaged regardless of the phase in the circumferential direction by pulling the draw bar 12. Any other chucking mechanism such as a collet chucking mechanism may be used as long as a predetermined engagement force can be obtained. Further, the spindle motor 4 may be other than the built-in type, and may be other than the servo motor. The U-axis motor 25 may be other than the servo motor. In addition, various design changes can be made without departing from the spirit of the present invention.

1 Machining center (machine tool)
4 Spindle motor 5 Spindle 6 Tool holder 7 U-axis tool unit 11 Pull stud 12 Draw bar 13 Sarah spring 14 Chucking means 15 Steel ball 25 U-axis motor (draw bar rotation drive source)
P Spindle center of rotation T Tool

Claims (3)

A U-axis tool unit that converts a rotational force around the spindle rotation center into a force in a direction crossing the spindle rotation center to cut and feed the tool is mounted on the tool holder,
In a machine tool comprising: chucking means for integrally engaging a pull stud and a draw bar regardless of the circumferential phase; and a spindle for detachably fixing the tool holder.
The pull stud is rotatably mounted on the tool holder and the draw bar is rotatably mounted on the main shaft,
Providing a draw bar rotation drive source for rotating the draw bar;
A U-axis drive structure for a machine tool, wherein the tool is cut and fed by transmitting the rotational force of the draw bar to the U-axis tool unit via the pull stud. The chucking means is a steel ball chucking mechanism configured to engage a pull stud by moving a plurality of steel balls toward the spindle rotation center as the draw bar is retracted,
The U-axis drive structure for a machine tool according to claim 1, wherein the pull stud is mounted on the tool holder via a bearing. The machine tool is a machining center,
The BT holder having a structure in which a pull stud is integrally provided so as not to rotate with respect to the holder can be attached to the main shaft by the chucking means instead of the tool holder. Item 3. A U-axis drive structure for a machine tool according to Item 2.

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