JP2016049611A - Fastening structure of tool holder and spindle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fastening structure of a tool holder and a spindle capable of ensuring both of static stiffness and attenuation performance to a certain degree, and resolving the chattering of a cutting tool.SOLUTION: A fastening structure of a tool holder and a spindle includes: a tool holder (20) which has a cutting tool gripping portion (21), a collar portion (22), and a tapered shank portion (23); a spindle (10) which has a tip end surface (12) opposite to a rear end surface (22a) of the collar portion, and a tapered hole (13) extending from the tip end surface to a rear side in an axial direction to receive the tapered shank portion; draw-in mechanisms (51 and 52) which draw in the tool holder toward the rear side in the axial direction; and pre-load applying mechanism (60) which applies a pre-load Ftoward the tip end side on the tool holder for improving attenuation performance, when the tool holder is drawn in till a draw-in margin between the rear end surface (22a) and the tip end surface (12) of the collar portion is eliminated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fastening structure in which a tool holder for grasping a cutting tool is mounted on a spindle of a machine tool such as a machining center with an automatic tool changer.

  As a fastening structure between the tool holder and the main shaft, for example, a two-surface constraining type disclosed in Japanese Patent Laid-Open No. 5-285715 (Patent Document 1) is widely known. The fastening structure of Patent Document 1 is a flat annular flange formed in the flange portion of the tool holder while fitting a tapered taper shank portion formed in the rear end region of the tool holder into a tapered hole in the center of the spindle end. The two-surface restraint is realized by abutting the end surface of the part against the flat surface at the peripheral edge of the spindle.

JP-A-5-285715

  Since the spindle of the machine tool rotates at a high speed and the workpiece is cut with a cutting tool attached to the tip of the spindle, it is necessary to consider that chatter of the cutting tool does not occur during the cutting. As a cutting theory, chatter is considered to correlate with the static rigidity of the fastening structure and the damping performance of the fastening structure. In short, in the fastening structure of the tool holder and the spindle, chatter of the cutting tool cannot be effectively prevented if the damping performance is low even if the static rigidity is high. On the other hand, even if the damping performance is high, if the static rigidity is low, the processing accuracy may be reduced. Therefore, it is desirable to secure both static rigidity and damping performance to some extent.

  In the conventional two-surface constraining type fastening structure, since the tool holder is fastened with two surfaces of a taper and a flat surface, the combined surface pressure of the taper and the flat surface can be increased to increase the static rigidity. Low and chatter may be a problem.

  An object of the present invention is to provide a fastening structure of a tool holder and a main shaft that can secure both static rigidity and damping performance to some extent and can eliminate chatter of a cutting tool in view of the above situation. .

  For this purpose, the fastening structure between the tool holder and the spindle according to the present invention is a tapered tool extending from the rear end surface of the cutting tool grasping portion located in the tip region, the collar portion located in the intermediate region, and the collar portion toward the rear in the axial direction. A tool holder having a taper shank portion, a tip surface facing the rear end surface of the collar portion, a main shaft having a tapered hole extending from the tip surface toward the rear in the axial direction and receiving the taper shank portion, and the tool holder facing the rear in the axial direction. A retraction mechanism that retracts the tool holder, and a preload imparting mechanism that applies a preload toward the front end side to the tool holder in order to increase the damping performance when the tool holder is retracted until the retraction margin between the rear end surface and the front end surface of the collar portion is eliminated. Is provided.

  According to the present invention, in the fastening structure of the tool holder and the main shaft that draws the tool holder with a strong pulling force and realizes the two-surface constrained state of the tapered surface and the flat surface, the preload applying mechanism is applied to the tool holder in the distal direction. Since the preload is applied, the combined surface pressure of the tapered surface and the flat surface is lower than the conventional one. Therefore, the damping performance of the fastening structure can be enhanced as compared with the fastening structure of the conventional tool holder and the main shaft. In addition, the static rigidity of the fastening structure can be secured to some extent by pulling the tool holder with a strong force as in the prior art. Therefore, both static rigidity and damping performance can be ensured, and chatter can be eliminated.

  As one embodiment of the present invention, the preload applying mechanism includes an elastic member, and applies a preload to the tool holder by the elastic force of the elastic member. According to this embodiment, the preload can be obtained with a simple mechanical configuration. Examples of the elastic member include a disc spring and a coil spring. In addition, a disc spring, a coil spring, etc. have friction damping property alone.

  Although the position of the elastic member is not particularly limited, as a preferred embodiment of the present invention, the elastic member is disposed between the rear end surface of the tool holder and the opposing surface of the main shaft facing the rear end surface. According to this embodiment, a preload can be applied to the tapered shank portion. Therefore, the center of the preload can be aligned with the center line of the tool holder. The opposing surface of the main shaft may be formed on the main shaft main body, or may be formed on a component attached to the main shaft main body.

  As another embodiment, the preload applying mechanism applies a preload to the tool holder by a fluid pressure such as a hydraulic pressure or a pneumatic pressure. According to this embodiment, the preload can be adjusted to a desired magnitude by increasing or decreasing the fluid pressure. Note that the fluid pressure itself has friction damping properties.

  As a preferred embodiment of the present invention, the preload applying mechanism may include a preload adjusting unit that adjusts the magnitude of the preload. According to this embodiment, the size of the preload is set in advance corresponding to the content of the cutting process such as the shape of the workpiece, the type of the cutting tool, the feeding direction of the cutting tool, and the cutting feed, and the tool is fastened to the spindle The preload may be adjusted when changing the holder. Thereby, it becomes possible to set a suitable damping performance in the content of each cutting process.

  As a preferred embodiment of the present invention, the preload adjusting unit may automatically adjust the size of the preload corresponding to the content of the cutting process. According to this embodiment, the work burden on the operator is reduced. As another embodiment, the operator manually adjusts the magnitude of the preload by operating the preload adjusting unit.

  ADVANTAGE OF THE INVENTION According to this invention, attenuation | damping performance can be improved rather than the conventional two-surface restraint type fastening structure. Therefore, chatter can be eliminated.

1 is an overall view showing a fastening structure between a tool holder and a spindle according to an embodiment of the present invention. It is a general view which shows the fastening structure of the embodiment, Comprising: The state which left the drawing allowance is shown. It is a general view which shows the fastening structure of the tool holder and main shaft which become other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 are general views showing a fastening structure between a tool holder and a spindle according to an embodiment of the present invention, in which a machine tool side is shown in a sectional view and a tool holder side is shown in a side view. FIG. 1 shows a two-surface constrained state in which the tapered surfaces and the flat surfaces are brought into close contact with each other, and FIG. 2 shows a state in which the tapered surfaces are brought into close contact with each other and a drawing allowance is left between the flat surfaces. The tool holder 20 is a tapered taper extending from the cutting tool grasping portion 21 located in the tip region, the collar 22 located in the intermediate region, and the rear end surface of the collar toward the rear in the axial direction (sometimes simply referred to as rear). A shank portion 23 is provided.

  The cutting tool grasping unit 21 grasps various types of cutting tools 30 such as an end mill and a drill in a detachable manner. The cutting tool grasping unit 21 grasps the cutting tool 30 with high accuracy and strength along the center line of the tool holder 20. The collar portion 22 is gripped by a manipulator during automatic tool change. The taper shank portion 23 extends along the center line of the tool holder 20, and a pull stud 40 is securely fixed to the rear end of the taper shank portion 23 in advance. The pull stud 40 that is tightly screwed into the central hole of the taper shank portion 23 includes a flange portion 43, a small-diameter shaft portion 41 that protrudes rearward from the flange portion 43, and a large diameter formed at the tip of the shaft portion 41. End 42. Since the flange portion 43 is in close contact with the rear end of the taper shank portion 23 and integrated with the tool holder 20, the rear end surface 43 a of the flange portion 43 is referred to as the rear end surface 43 a of the tool holder 20 in the following description.

  The spindle 10 of the machine tool is rotatably supported by a spindle head (not shown) via a ball bearing 17 disposed on the outer periphery of the spindle 10. The main shaft 10 includes a front end portion 10a and a rear end portion 10b. The front end portion 10a and the rear end portion 10b are assembled in the axial direction of the main shaft and fastened and fixed by bolts 10c. Then, the rear end of the tapered hole 13 formed in the front end portion 10a is connected to the front end of the intermediate hole 14 formed in the rear end portion 10b. The taper hole 13 extends rearward from the front end surface 12 of the main shaft 10 along the axis O of the main shaft 10 and becomes thinner toward the rear. The intermediate hole 14 extends with a constant inner diameter along the axis O of the main shaft 10 and is connected to the rear end of the tapered hole 13. A rear hole 16 further extends rearward from the bottom of the intermediate hole 14.

  The rear hole 16 has a smaller diameter than the intermediate hole 14, and extends from the bottom of the intermediate hole 14 along the axis O of the main shaft 10 with a constant inner diameter. The bottom of the intermediate hole 14 is an annular flat surface and is perpendicular to the axis O. When the taper shank portion 23 of the tool holder 20 is inserted into the taper hole 13, the hole bottom of the intermediate hole 14 faces the flat rear end face 43a of the tool holder 20. Therefore, in the following description, the hole bottom of the intermediate hole 14 is opposed. Called surface 15. However, the facing surface 15 does not need to be strictly opposed to the rear end surface 43a of the tool holder 20. For example, the inner periphery of the facing surface 15 may be larger than the outer periphery of the rear end surface 43a. In short, the facing surface 15 that faces forward (referring to the front end side direction of the axis O) may be arranged more rearward in the axial direction than the rear end surface 43a that faces backward. As will be described in detail later, a preload applying mechanism 60 is provided between the rear end surface 43a of the tool holder 20 and the opposing surface 15 on the main shaft 10 side.

  In this case, the inner peripheral surface of the intermediate hole 14, the annular facing surface 15, and the inner peripheral surface of the rear hole 16 may be configured by a continuous main shaft of one member, but in the present embodiment, the main shaft 10 is configured. It consists of two members. Specifically, the intermediate hole 14 formed in the rear end portion 10b of the main shaft 10 extends rearward from the rear end of the tapered hole 13, and a cylindrical sleeve 65 passes through the intermediate hole 14 from the rear. Is done. The sleeve 65 is a main shaft component attached to the main shaft 10. The front end surface of the sleeve 65 constitutes the facing surface 15. The inner peripheral surface of the sleeve 65 constitutes the rear hole 16. The sleeve 65 is basically fixed so as not to move in the axial direction, but its axial position can be adjusted. The position adjustment of the sleeve 65 will be described in detail later.

  The machine tool includes a retracting mechanism for retracting the tool holder toward the rear in the axial direction. The retracting mechanism includes a cylindrical collet 51 and a draw bar 52 connected to the rear end of the collet 51, and the collet 51 and the draw bar 52 are disposed in the rear hole 16, that is, the sleeve 65. With the tapered shank portion 23 inserted into the tapered hole 13, the shaft portion 41 of the pull stud 40 passes through the central hole 64 of the preload applying mechanism 60, and the end portion 42 of the pull stud 40 is positioned in the rear hole 16. The end 42 is connected to the tip of the collet 51.

  The preload applying mechanism 60 disposed in the intermediate hole 14 includes at least one disc spring 61, an annular disk 62, and a snap ring 63. The disc spring 61 is a ring-shaped elastic steel plate with a central hole 64 and is formed in a round plate shape. A plurality of disc springs 61 according to the present embodiment are stacked along the axis O, and exhibit elastic force in the axial direction. The number of disc springs 61 can be arbitrarily selected. Further, in this embodiment, a backward-facing disc spring 61 whose outer peripheral edge faces rearward and a forward-facing disc spring 61 whose outer peripheral edge faces front are mixed, but the orientation of the disc spring 61 is not limited to this embodiment. Absent. For example, although not shown in the figure, all the disc springs may be laminated forward. Or you may laminate | stack all the disc springs backward. In any case, the axially rearmost disc spring 61 contacts the facing surface 15. In addition, the foremost disk spring 61 in the axial direction is in contact with the rear end face of the flat annular disk 62. The inner diameter of the annular disc 62 is larger than that of the pull stud 40 and smaller than the rear end surface 43a of the tool holder 20. Therefore, the front end surface of the annular disc 62 is in contact with the rear end surface 43a of the tool holder 20. A snap ring 63 is disposed in front of the annular disk 62. The snap ring 63 is locked in an annular groove formed on the inner peripheral surface of the intermediate hole 14 and prevents the annular disk 62 from slipping forward.

  A method for fastening the spindle 10 and the tool holder 20 will be described.

  First, referring to FIG. 2, the taper shank portion 23 of the tool holder 20 is inserted into the tapered hole 13 of the main shaft 10, and the shaft portion 41 of the pull stud 40 protruding from the rear end surface 43 a of the tool holder 20 is placed in the center of the preload applying mechanism 60. The end portion 42 of the pull stud 40 is connected to the collet 51 of the retracting mechanism through the hole 64. The draw bar 52 of the retracting mechanism retracts the tool holder 20 rearward in the axial direction with a backward light force F1 indicated by an arrow. The light pull-in force F1 causes the taper outer surface of the taper shank portion 23 to be in close contact with the taper inner surface of the taper hole 13 while leaving a pull-in allowance D1 between the rear end surface 22a of the flange portion and the tip surface 12 of the main shaft 10. . The pull-in allowance D1 is a slight gap of 0.01 to 0.03 mm. At this time, one surface is restricted by the tapered surface, and the preload applying mechanism 60 applies a slight preload to the rear end surface 43a of the tool holder 20 or does not apply any preload at all.

When the draw bar 52 continues to pull the tool holder 20 backward with a strong force F2 (F2> F1), the pull-in allowance D1 decreases and the collar rear end surface 22a comes into close contact with the front end surface 12 of the main shaft 10 as shown in FIG. . As a result, the two-surface constraint by the tapered surface and the flat surface is realized. At this time, the disc spring 61 of the preload applying mechanism 60 is compressed by the same amount as the retracting allowance D1. The preload applying mechanism 60, in order to enhance the damping performance of the fastening structure of the tool holder 20 and the main shaft 10, gives a positive preload F _p on the rear end face 43a of the tool holder 20 as shown by arrows in FIG. 1. When the drawing force of the draw bar 52 in a two-face restraint state and F _2, coupling surface pressure acting on the tapered surface and the flat surface becomes F ₂ -F _p.

According to the present embodiment, the total combined surface pressure acting on the tapered surface and the flat surface can be made smaller by the preload F _p than in the prior art. As described above, since the combined surface pressure of the tapered surface and the flat surface can be made lower than that of the conventional two-surface constraint type, the damping performance can be made higher than that of the conventional two-surface constraint type. Moreover, according to the present embodiment, the pull force F2 strongly conventional street, it is possible to secure the static rigidity of the fastening portion of the spindle and the tool holder to some extent by the pre-load F _p to appropriate size. Therefore, both static rigidity and damping performance can be ensured and chatter of the cutting tool 30 can be eliminated.

  Moreover, according to this embodiment, the elastic force of the disc spring 61 can be adjusted with the sleeve 65 as a preload adjustment part. Specifically, when the axial position of the sleeve 65 is adjusted and the opposing surface 15 is fixed at the forward α position, the disc spring 61 moves forward and applies a large preload to the rear end surface 43 a of the tool holder 20. On the other hand, when the axial direction position of the sleeve 65 is adjusted and the opposing surface 15 is fixed at the rear β position, the disc spring 61 moves backward to apply a small preload to the rear end surface 43a.

  Therefore, the size of the preload is set in advance corresponding to the content of the cutting process such as the shape of the workpiece, the type of the cutting tool, the feeding direction of the cutting tool, and the cutting feed, and is fastened to the spindle 10 by the automatic tool changer. When changing the tool holder 20, the size of the preload may be automatically adjusted. Thereby, it becomes possible to set a suitable damping performance in the content of each cutting process, and it is possible to provide an automatic control system for a machine tool equipped with an intelligence function.

  As a position adjustment mechanism of the sleeve 65, for example, a male screw is engraved on the outer periphery of the sleeve 65, a female screw is engraved on the inner peripheral surface of the main shaft 10, the sleeve 65 is screwed to the main shaft 10, and the sleeve 65 is rotated. To move forward and backward in the axial direction. Alternatively, the sleeve 65 is slidable with respect to the inner peripheral surface of the main shaft 10, and the sleeve 65 is moved back and forth in the axial direction by an actuator attached to the rear end of the main shaft 10.

  Alternatively, simple preload adjustment can be performed by changing the number of disc springs 61 and the standard instead of the preload adjustment by the sleeve 65.

  When the tool holder 20 fastened to the main shaft 10 is manually replaced without depending on the automatic tool changer, a manual draw bolt is prepared instead of the pull stud 40, the collet 51, and the draw bar 52, and the draw bolt is prepared. It is good to fix the front-end | tip of this to the female screw hole of the taper shank part 23 by screwing.

  Next, another embodiment of the present invention will be described. FIG. 3 is an overall view showing another embodiment of the present invention, and shows a two-plane restraint state. Regarding the other embodiments, the same reference numerals are given to the configurations common to the above-described embodiments, and the description thereof will be omitted, and different configurations will be described below. In another embodiment, the preload applying mechanism 60 applies a preload to the tool holder 20 by fluid pressure such as hydraulic pressure.

  The preload applying mechanism 60 shown in FIG. 3 has an annular piston 66, an annular fluid pressure chamber 67, and a fluid pressure supply path 68. The piston 66 is an annular body having a central hole 64, and includes a cylindrical portion 66c and a flange portion 66f that extends radially inward and outward from the tip of the cylindrical portion 66c. The central hole 64 of the piston 66 receives the pull stud 40. The outer periphery of the flange portion 66 f is slidable in the axial direction along the inner peripheral surface of the intermediate hole 14. The outer periphery of the cylindrical portion 66 c is slidable in the axial direction along the inner peripheral surface of the rear hole 16. The tip of the rear hole 16 is connected to the intermediate hole 14 having a larger diameter than the rear hole 16. A flat annular step surface 18 directed forward is formed at the boundary between the rear hole 16 and the intermediate hole 14. Thereby, the annular step surface 18, the cylindrical portion 66 c, the flange portion 66 f, and the inner peripheral surface of the intermediate hole 14 form an annular fluid pressure chamber 67. The fluid pressure chamber 67 is connected to a fluid pressure supply path 68 formed inside the wall of the main shaft 10, and fluid pressure is supplied from the fluid pressure supply path 68.

Flat tip surface 66a of the piston 66 is in contact with the rear end surface 43a of the tool holder 20, provide a positive preload _{F p} to the tool holder 20. This preload F _p can be controlled by adjusting the fluid pressure in the fluid pressure chamber 67.

Also in the embodiment shown in FIG. 3, the preload F _p can be adjusted using the fluid pressure source that supplies the fluid pressure to the fluid pressure supply path 68 as a preload adjusting unit. Therefore the shape of the workpiece, the type of cutting tool, the feeding direction of the cutting tool, may be adjusted to preload F _p corresponding to the contents of the machining such as cutting feed. Therefore, also by the embodiment shown in FIG. 3, the damping performance of the fastening structure of the tool holder 20 and the main shaft 10 can be adjusted.

  Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The fastening structure between the tool holder and the spindle according to the present invention is advantageously used in a machine tool.

10 main shaft, 12 tip surface of main shaft, 13 taper hole,
14 intermediate hole, 15 opposite surface, 16 rear hole,
17 ball bearing, 18 annular stepped surface,
20 tool holder, 21 cutting tool grasping part, 22 collar part,
22a buttock rear end surface, 23 taper shank,
30 cutting tools, 40 pull studs, 43 flanges,
43a Rear end surface of tool holder, 51 Collet of retracting mechanism,
52 drawbar draw-in mechanism, 60 preloading mechanism,
61 disc spring, 62 annular disc, 63 snap ring,
64 center hole, 65 sleeve, 66 piston,
Piston tip surface 66a, 67 fluid pressure chamber,
68 Fluid pressure supply path, D1 pull-in allowance, O axis.

For this purpose, the fastening structure between the tool holder and the spindle according to the present invention is a tapered tool extending from the rear end surface of the cutting tool grasping portion located in the tip region, the collar portion located in the intermediate region, and the collar portion toward the rear in the axial direction. A tool holder having a taper shank portion, a tip surface facing the rear end surface of the flange portion , a taper hole extending axially rearward from the tip surface, and receiving the taper shank portion, with the taper shank portion inserted into the taper hole A retraction mechanism that retracts the tool holder toward the rear in the axial direction, and when the tool holder is retracted until the retraction mechanism eliminates the retraction margin between the rear end surface and the front end surface of the flange, the tool holder is and a main shaft having a preload applying mechanism for giving a preload toward the distal end side.

Although the position of the elastic member is not particularly limited, as a preferred embodiment of the present invention, the tool holder includes a pulls dud that is attached and fixed to the rear end surface of the tapered shank portion and is integrated with the tapered shank portion. A retraction mechanism having a shaft portion that is screwed into the female screw hole of the taper shank portion and whose rear end side protrudes from the rear end surface of the taper shank portion, and a flange portion that is formed on the shaft portion and closely contacts the rear end surface of the taper shank portion. draws the tool holder coupled with the shaft portion of the pull stud, the elastic member, and the rear end surface of the flange portion of the pull stud is disposed in the hole behind the tapered hole of the spindle facing the rear end surface of the flange portion of the pull stud It arrange | positions between opposing surfaces. According to this embodiment, a preload can be applied to the tapered shank portion. Therefore, the center of the preload can be aligned with the center line of the tool holder. The opposing surface of the main shaft may be formed on the main shaft main body, or may be formed on a component attached to the main shaft main body.

Claims (6)

A tool holder having a cutting tool grasping portion located in a tip region, a collar portion located in an intermediate region, and a tapered taper shank portion extending axially rearward from the rear end surface of the collar portion;
A front end surface facing the rear end surface of the flange portion, a main shaft having a tapered hole extending from the front end surface toward the rear in the axial direction and receiving the tapered shank portion;
A retraction mechanism for retracting the tool holder toward the rear in the axial direction;
A tool provided with a preload applying mechanism for applying a preload toward the tip side to the tool holder in order to enhance the damping performance when the tool holder is pulled in until the drawing allowance between the rear end surface of the flange and the tip surface is eliminated. Fastening structure of holder and spindle.   The fastening structure of the tool holder and the main shaft according to claim 1, wherein the preload applying mechanism includes an elastic member, and applies a preload to the tool holder by an elastic force of the elastic member.   2. The fastening structure between the tool holder and the main shaft according to claim 1, wherein the elastic member is disposed between a rear end surface of the tool holder and a facing surface of the main shaft facing the rear end surface.   The fastening structure between the tool holder and the main shaft according to claim 1, wherein the preload applying mechanism applies a preload to the tool holder by fluid pressure.   The said preload provision mechanism is a fastening structure of the tool holder and main shaft in any one of Claims 1-4 containing the preload adjustment part which adjusts the magnitude | size of a preload.   6. The fastening structure between a tool holder and a spindle according to claim 5, wherein the preload adjusting section automatically adjusts the size of the preload according to the content of the cutting process.

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