Clamping mechanism, clamping device, and machine tool

Abstract

To not only switch between clamping / unclamping but also control a torque at clamping so as to detect clamp failure.SOLUTION: When a foreign material DS is sandwiched between a tapered face 220 of a spindle 200 and a tapered face 502 of a tool holder 500, a slide amount becomes smaller than at clamping even when a drawbar 300 is rotated by a drawbar drive control mechanism 600 as indicated by figure 4(B). The slide amount corresponds with a rotation amount of the drawbar 300, and further corresponds with a rotation amount of a stepping motor 610, and is detected by a clamp failure detecting part 632. When the slide amount is equal to or less than a prescribed value, it is determined that the foreign material DS is sandwiched, and a clamp torque of the tool holder 500 is insufficient.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to improvements in a clamp mechanism for holding tools and the like, a clamp device, and machine tools such as machining centers using the same.

Background Art

[0002] As a conventional clamp device, for example, there is a "tool clamp device" described in Patent Document 1 below. In addition to disc springs, a biasing coil spring is provided around the drawbar in the main spindle, and a temporary holding cylinder is provided at the rear of the unclamping cylinder at the rear of the main spindle. The coil spring operates to pull and bias the drawbar with a weak force to prevent the tool from falling off when the drawbar pull-in biasing by the disc spring is released by the operation of the unclamping cylinder. In addition, the temporary holding cylinder locks the drawbar that has moved forward when the tool is pulled out at that position, so that the drawbar does not move backward under the action of the coil spring until the next tool is inserted.

[0003] In the "unclamping device" described in Patent Document 2 below, when the plunger pin is pressed during unclamping, the drawbar moves downward by the booster mechanism composed of the tapered surface and the balls, the tool holder is pushed out, and the close contact state between the tapered surface and the tool holder is released. In the temporary holding mechanism, since the balls return to the groove by the temporary holding spring, the drawbar moves upward, the tool holder also returns upward, and its tapered surface comes into contact with the tapered surface on the spindle side again to return to the original position.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0005] Incidentally, while it is ideal for the tapered surface of the spindle and the tapered surface of the tool holder to be in close contact, if machining debris or other materials get trapped for any reason, the contact force between the tapered surfaces will decrease, and there is a risk that the tool holder will not be held properly. In the background technology described above, only the clamping and unclamping operation of the tool holder is performed, and it is not possible to determine whether the tool holder is being clamped properly. Furthermore, since disc springs and coil springs are used, maintenance is required according to their deterioration. In addition, there is the inconvenience that shock is applied to the bearing between the spindle and the drawbar when switching between clamping and unclamping.

[0006] The present invention focuses on these points and aims to provide a clamping mechanism, clamping device, and machine tools utilizing them, which not only switch between clamping and unclamping but can also detect clamping failures, simplify maintenance, and furthermore do not cause impact to bearings. [Means for solving the problem]

[0007] The clamping mechanism of the present invention comprises a spindle with a clamping surface formed at its tip that contacts the clamping portion of the object to be clamped, a collet for clamping the object to be clamped within the spindle, and a drawbar for driving the collet. The collet comprises a first member having a screw mechanism between it and the drawbar, and a second member having clamping claws that move in accordance with the forward and backward movement of the first member in the main axis direction and engage with the clamping portion of the object to be clamped, and is equipped with a temporary holding mechanism that temporarily holds the first member with respect to the spindle in an unclamped state. The method is characterized in that when the drawbar is rotated, the collet moves forward and backward by the screw mechanism, thereby clamping and unclamping the object to be clamped. The object to be clamped is, for example, a tool holder, and the tool holder is clamped by engaging the clamping portion of the tool holder from the inside or outside.

[0008] According to one of the main forms, the temporary holding mechanism includes a ball and The ball A spring that presses against it and around the main shaft Leave some space between themMultiple collets are provided, and a groove is formed around the entire circumference of the outer surface of the first member of the collet, and the ball is pressed into this groove by the spring to temporarily hold the object. In another embodiment, a movable means is provided that allows the drawbar to move in the direction of pulling out the object to be clamped so that the clamping claws open when the object to be clamped is removed from the collet.

[0009] In another embodiment, the clamping claws engage with the clamping portion of the object to be clamped and the spindle, respectively, during clamping. Furthermore, when the object to be clamped is removed from the collet, the clamping claws open. In the direction of pulling out the clamped object The invention is characterized by providing a movable means that allows the drawbar to move.

[0010] Furthermore, according to other forms, The object to be clamped is a tool holder, the clamping surface is formed on the inside of the spindle, a clamping groove is formed on the inside of the tool holder, an unclamping groove is formed on the outside of the first member, and clamping claws are formed on the outside of the second member. When unclamped, the clamping claws of the second member are disengaged from the clamping groove of the tool holder, and when clamped, the clamping claws of the second member engage with the clamping groove of the tool holder, thereby locking the tool holder from the inside. This is characterized by the fact that, in another embodiment, the clamping claws are biased toward the rotation center of the spindle by a biasing means. In yet another embodiment, the clamping portion of the object to be clamped and the clamping surface of the spindle are tapered surfaces.

[0011] The clamping device of the present invention is characterized by comprising a drawbar rotation drive mechanism for rotationally driving a drawbar in any of the clamping mechanisms described above, and a clamping defect detection means for detecting a clamping defect by the collet based on the amount of rotation of the drawbar. The machine tool of the present invention is characterized by comprising any of the clamping mechanisms or clamping devices described above. The above and other objects, features, and advantages of the present invention will become clear from the following detailed description and accompanying drawings. [Effects of the Invention]

[0012] According to the present invention, since the clamping and unclamping of the object to be clamped by the collet is performed by the screw mechanism between the draw bar and the collet, clamping failure can be detected, no countersunk screws or coil springs are required, maintenance can be simplified, and furthermore, since no bearing is used between the spindle and the draw bar, there is no impact effect on the bearing during switching between clamping and unclamping. Brief Description of the Drawings

[0013] [Figure 1] It is a main cross-sectional view in the spindle direction showing Embodiment 1 of the present invention. [Figure 2] It is a cross-sectional view showing an enlarged main part of the above embodiment and a perspective view showing main components of the collet. [Figure 3] It is a diagram showing the state during temporary holding and clamping in the above embodiment. [Figure 4] It is a diagram showing the state during unclamping and at the time of clamping failure in the above embodiment. [Figure 5] It is a main cross-sectional view in the spindle direction showing Embodiment 2 of the present invention. [Figure 6] It is a main cross-sectional view in the spindle direction showing Embodiment 3 of the present invention. [Figure 7] It is a main cross-sectional view in the spindle direction showing Embodiment 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Hereinafter, the best mode for carrying out the present invention will be described in detail based on the embodiments. EXAMPLES

[0015] Figure 1 shows a cross-section of the clamping device of the present embodiment along the main axis direction. This figure shows a state where the tool holder 500 is pulled out from the clamping mechanism 100. When the main part of this figure is enlarged, it becomes as shown in Figure 2(A). In these figures, the clamping mechanism 100 is provided with a spindle 200 penetrating inside an outer housing 110. Bearings 112 are appropriately provided between the housing 110 and the spindle 200, whereby the spindle 200 is rotatably supported relative to the housing 110. A draw bar 300 penetrates through the spindle 200, and a collet 400 for clamping the tool holder 500 is provided at the tip of the draw bar 300.

[0016] Among the above, the spindle 200 is configured to be rotationally driven around the main axis by a drive source not shown. A movable groove 210 is provided on the inner side of its rear end (the right side in the figure), into which the projection 310 of the draw bar 300 is fitted. This movable groove 210 enables the movement of the projection 310 in the axial direction (the left-right direction in the figure) when the tool holder 500 is pulled out, and further enables the axial movement of the draw bar 300.

[0017] A tapered surface 220 is formed at the tip of the spindle 200 (the left side in the figure), which comes into contact with the tapered surface 502 of the tool holder 500. In addition, a clamping groove 230 is provided on the collet side of the tapered surface 220 of the spindle 200, so that the tip of the component of the collet 400 is caught as will be described later. Further, a temporary holding mechanism 240 composed of balls 242, a spring 244, and a spring retainer 246 is provided at the depth of the clamping groove 230 of the spindle 200, whereby temporary holding of the collet 400 is performed. A plurality of the temporary holding mechanisms 240 are provided at appropriate intervals around the main shaft.

[0018] Next, the collet 400 is mainly composed of a slide body 410 and a retaining ring 420. Of these, the slide body 410 has a cylindrical portion 412 into which the tip of the drawbar 300 fits, and a cylindrical portion 414 that fixes the retaining ring 420. On the outside of the cylindrical portion 412, a groove 416 is provided around its entire circumference into which the ball 242 of the temporary holding mechanism 240 described above fits, and on the inside of the cylindrical portion 412, a screw mechanism 430 is provided between it and the tip of the drawbar 300. On the other hand, one end of the retaining ring 420 is fitted into the reduced diameter portion of the cylindrical portion 414 of the slide body 410 and fixed in place.

[0019] On the other hand, as shown in Figure 2(B), the retaining ring 420 has a clamping claw 422 at its left end. That is, the left opening portion of the retaining ring 420 is bent outward, and multiple slits 424 (three in the illustrated example) are formed in the axial direction. This allows the clamping claw 422 to swing radially to open and close. A locking projection 426 is provided on the rear side (right side of the figure) of the retaining ring 420, which slides within the groove 232 of the drawbar 300 or catches on the side of the groove.

[0020] The tool holder 500 has a tip (left side in Figure 1) to which a suitable tool (not shown) can be attached, and the opposite side has a tapered surface 502 and a pull stud. Do A 504 is provided. These configurations are publicly known.

[0021] On the other hand, as shown in Figure 1, a drawbar drive control mechanism 600 is provided at the rear end (right side of the figure) of the drawbar 300. The drawbar drive control mechanism 600 uses a stepping motor 610 as a drive source, and its rotational drive is adjusted to an appropriate rotational speed by a gear mechanism or belt mechanism before being transmitted to the drawbar 300 via a clutch 620. The rotational drive of the stepping motor 610 is controlled by a drawbar control device 630, and the amount of rotation of the stepping motor 610, i.e., the amount of slide, is detected by a clamp failure detection unit 632.

[0022] Next, the rotation of the drawbar 300 and the basic operation of the collet 400 will be explained. When the drawbar drive control mechanism 600 is rotated, the collet 400 slides axially due to the screw mechanism 430 at its tip. That is, the slide body 410 and the retaining ring 420 slide in the direction of the main axis. When the retaining ring 420 slides toward the tip, the clamping claws 422 on its tip side catch on the clamping groove 230 of the spindle 200, and the retaining ring 420 opens (see Figures 1 and 2). Conversely, when the retaining ring 420 slides toward the rear end, the clamping claws 422 on its tip side disengage from the clamping groove 230 of the spindle 200, and the retaining ring 420 closes (see Figure 3, which will be described later). The amount of slide of the collet 400 at this time corresponds to the amount of rotation of the stepping motor 610, and is therefore detected by the clamp failure detection unit 632 of the drawbar control device 630. Furthermore, when the tool holder 500 is withdrawn, the drawbar 300 is made possible by the projection 310 on the rear end and the movable groove 210 on the spindle 200 side.

[0023] Next, the operation of this embodiment will be explained with reference to Figures 3 and 4. <Temporary Holding> From the state shown in Figures 1 and 2 above, when the tool holder 500 is inserted through the tip opening of the spindle 200 as indicated by arrow F3A in Figure 3(A), the pull stud of the tool holder 500 Do 504 strikes the tip of the sliding body 410 of collet 400, pushing collet 400 and drawbar 300 backward. This causes the clamping jaws 422 of the retaining ring 420 of collet 400 to close, and the pull stud Do As 504 is locked and gripped, the ball 242 of the temporary holding mechanism 240 fits into the groove 416 on the outer circumference of the slide body 410, and the tool holder 500 is temporarily held in place. Meanwhile, the tapered surface 502 of the tool holder 500 contacts the tapered surface 220 of the spindle 200. The drawbar 300 retracts until the projection 310 on its rear side hits the right side of the movable groove 210 of the spindle 200 (see arrow P3A).

[0024] <Clamping> Next, in this state, as shown by arrow F3B in Figure 3(B), when the drawbar 300 is rotated by the drawbar drive control mechanism 600, the tip of the drawbar 300 and the inside of the slide body 410 of the collet 400 are connected by a screw mechanism 430, so the drawbar 300 will fit into the slide body 410 as shown by arrow F3C. Then, when the projection 310 on the rear side of the drawbar 300 hits the left side of the movable groove 210 of the spindle 200, the movement of the drawbar 300 in the direction of arrow F3C stops (see arrow P3B).

[0025] Meanwhile, the rotation of the drawbar 300 causes the collet 400 to be pulled in the direction of arrow F3D. As a result, the clamping jaws 422 of the collet 400 pull the pull stud Do The 504 is gripped more firmly, changing from a temporary holding state to a clamped (fixed) state. In this state, the projection 310 at the rear end of the drawbar 300 is in contact with the left side of the movable groove 210 of the spindle 200, so even if you try to pull out the tool holder 500, the drawbar 300 and collet 400 will not move, and the clamping jaws 422 will not open. Therefore, the tool holder 500 remains clamped.

[0026] Then, when the drawbar drive control mechanism 600 is turned OFF and the spindle 200 is rotated, the spindle 200, drawbar 300, and tool holder 500 rotate together relative to the housing 110 (see Figure 1), and machining is performed by the tool attached to the tool holder 500.

[0027] <Unclamping> Next, when removing the tool holder 500, the drawbar drive control mechanism 600 rotates the drawbar 300 in the opposite direction to the previous rotation, F4A, as shown in Figure 4(A). Then, the tip of the drawbar 300 and the screw mechanism 430 inside the slide body 410 of the collet 400 slide in the direction of arrow F4B so that the drawbar 300 separates from the slide body 410, thereby changing from a clamped state to an unclamped or temporarily held state.

[0028] In this state, the projection 310 at the rear end of the drawbar 300 is in contact with the right side of the movable groove 210 of the spindle 200 (see arrow P4A). Therefore, when the tool holder 500 is pulled out in the direction of arrow F4C, the drawbar 300 and collet 400 can move, the clamping jaws 422 open, and the tool holder 500 is removed as shown in Figure 1.

[0029] <Clamping failure> Incidentally, foreign matter DS such as cutting chips may get stuck between the spindle 200 and the tool holder 500, for example, between the tapered surface 220 of the spindle 200 and the tapered surface 502 of the tool holder 500. In this case, even if the drawbar 300 is rotated by the drawbar drive control mechanism 600, the clamping torque by the collet 400 may be insufficient.

[0030] As described above, under normal circumstances, when clamped, the projection 310 on the rear side of the drawbar 300 contacts the left side of the movable groove 210 of the spindle 200, as shown by the arrow P3B in Figure 3(B). However, the amount of sliding of the drawbar 300 is slightly different from when it is clamped.

[0031] In contrast, in this embodiment, the sliding of the drawbar 300 is performed by rotation via a screw mechanism 430 between it and the collet 400, and the amount of rotation of the drawbar 300 is detected by the clamping failure detection unit 632. When the amount of rotation of the drawbar 300 deviates from a predetermined value and exceeds an allowable value due to reasons such as foreign matter DS getting caught, it can be determined that the clamping torque of the tool holder 500 is insufficient. In response, the drawbar control device 630 performs control such as issuing a warning or stopping the rotation of the spindle 200. [Examples]

[0032] Next, Embodiment 2 of the present invention will be described with reference to Figure 5. Note that components identical to or corresponding to those in Embodiment 1 described above are denoted by the same reference numerals with letters, and their descriptions are omitted (the same applies to Embodiments 3 and below). Figure (A) shows the clamped state, and Figure (B) shows the unclamped state. This embodiment has the same basic structure and operation as Embodiment 1, but the slide body 410A of the collet 400A is longer, the drawbar 300A is shorter, and the screw mechanism 430A is provided on the rear end. Furthermore, the slide body 410A of the collet 400A and the retaining ring 420A have different shapes, and a rotation-preventing pin 241A is provided in relation to the pin groove 247A of the slide body 410A, along with the temporary holding mechanism 240A.

[0033] <Clamping> When the drawbar 300A is rotated by the drawbar drive control mechanism 600A, the screw mechanism 430A causes the drawbar 300A to engage with the slide body 410A. Then, when the projection 310A on the rear side of the drawbar 300A hits the left side of the movable groove 210A of the spindle 200A, the movement of the drawbar 300A stops and the slide body 410A of the collet 400A is retracted. As a result, as shown in Figure (A), the clamping claws 422A of the collet 400A pull the stud. Do The 504A is gripped more firmly, changing from a temporary holding state to a clamped (fixed) state. In this state, the projection 310A at the rear end of the drawbar 300A is in contact with the left side of the movable groove 210A of the spindle 200A. Therefore, even if you try to pull out the tool holder 500A, the drawbar 300A and collet 400A will not move, and the clamping jaws 422A will not open. Consequently, the tool holder 500A remains clamped.

[0034] <Unclamping> Next, when removing the tool holder 500A, the drawbar drive control mechanism 600A rotates the drawbar 300A in the opposite direction to the previous rotation, as shown in Figure 5(A). Then, the screw mechanism 430A slides the drawbar 300A away from the slide body 410A, thereby changing from the clamped state to the unclamped or temporarily held state. In this state, the projection 310A at the rear end of the drawbar 300A is in contact with the right side of the movable groove 210A of the spindle 200A. Therefore, when the tool holder 500A is pulled out, the drawbar 300A and collet 400A can move, the clamping claws 422A open, and the tool holder 500A can be removed. [Examples]

[0035] Next, Embodiment 3 of the present invention will be described with reference to Figure 6. Figure 6(A) shows the state when clamping is complete, and Figure 6(B) shows the state when unclamping is complete. Figure 6(C) shows a schematic cross-section viewed in the direction of the arrow along the line #6-#6 in Figure 6(B). In the above embodiment, the tool holder 500A was clamped by locking it with the collet 400A from the outside, but in this embodiment, the tool holder 500B is clamped with the collet 400B from the inside. That is, a tapered surface 220B is provided on the inside of the tip of the spindle 200B, and the tapered surface 502B of the tool holder 500B is in contact with this. Also, in this embodiment, the projection 310B on the rear end side of the drawbar 300B is sandwiched on the spindle 200B side. Therefore, the drawbar 300 rotates relative to the spindle 200B but does not slide.

[0036] The collet 400B consists of a nearly cylindrical slide body 410B and an outer retaining ring 420B, and the tool holder 500B is clamped by the movement of the clamping claw 422B at its tip. A screw mechanism 430B is provided on the outside of the tip of the drawbar 300B and on the inside of the slide body 410B of the collet 400B, so that when the drawbar 300B rotates, the slide body 410B slides in the direction of the main axis.

[0037] The rear of the tool holder 500B described above is cylindrical, and a clamp groove 506B is provided on its inside. On the other hand, an unclamping groove 418B is provided on the outer circumference of the slide body 410B. The retaining ring 420B has a clamping claw 422B on its front side and is held by the spindle 200B on its rear side. The clamping claw 422B, like the clamping claw 422 shown in Figure 2(B), expands from a contracted state to engage with the clamp groove 506B of the tool holder 500B. A pin groove 247B is provided on the rear end of the slide body 410B, and the slide body 410B is prevented from rotating by a pin 241B.

[0038] <Clamping> With the tool holder 500B inserted into the tip of the spindle 200B, the drawbar 300B is rotated by the drawbar drive control mechanism 600B, causing the slide body 410B to slide backward as shown in Figure (A) by the screw mechanism 430B. Then, the clamping claws 422B expand in diameter along the unclamping groove 418B of the slide body 410B and contact and lock against the side surface 507B of the clamping groove 506B of the tool holder 500B. As a result, the tool holder 500B is clamped.

[0039] <Unclamping> Next, when removing the tool holder 500B, the drawbar drive control mechanism 600B rotates the drawbar 300B in the opposite direction to the previous rotation. As a result, as shown in Figure 6(B), the screw mechanism 430B pushes the slide body 410B forward. This causes the clamping claw 422B, which is engaged with the side surface 507B of the clamping groove 506B of the tool holder 500B, to retract and return to its original position, and enter the unclamping groove 418B of the slide body 410B. This causes the clamping claw 422B to disengage from the clamping groove 506B of the tool holder 500B, changing it from a clamped state to an unclamped or temporarily held state. Then, when the tool holder 500B is pulled, it can be removed from the spindle 200B. [Examples]

[0040] Next, with reference to Figure 7, Embodiment 4 of the present invention will be described. Figure 7(A) shows the state when clamping is complete, and Figure 7(B) shows the state when unclamping is complete. Figure 7(C) shows a schematic cross-section viewed in the direction of the arrow along the line #7-#7 in Figure 7(B). In this embodiment, as in the previous embodiment, the tool holder 500C is clamped from the inside with the collet 400C. In this embodiment, the projection 310C on the rear end side of the drawbar 300C is sandwiched on the spindle 200C side. Therefore, the drawbar 300C rotates relative to the spindle 200C but does not slide.

[0041] The collet 400C consists of a nearly cylindrical slide body 410C and an outer retaining ring 420C, and the tool holder 500C is clamped by the movement of the clamping claw 422C at its tip. A screw mechanism 430C is provided on the outside of the tip of the drawbar 300C and on the inside of the slide body 410C of the collet 400C, so that when the drawbar 300C rotates, the slide body 410C slides in the direction of the main axis.

[0042] The retaining ring 420C is provided with spring fixing pins 450C. In the illustrated example, as shown in Figure (C), three spring fixing pins 450C are provided at 120-degree intervals when viewed in a cross-section perpendicular to the main spindle. On the other hand, an unclamping groove 418C is provided on the outside of the slide body 410C, extending from the spring fixing pins 450C toward the clamping claws 422C, and an unclamping spring 428C extends from the spring fixing pins 450C toward the clamping claws 422C within this unclamping groove 418C. The unclamping spring 428C biases the clamping claws 422C toward the main spindle or the center of rotation. This is the same as the clamping claws in the above-described embodiment being in the direction of diameter reduction. The unclamping groove 418C is provided with an inclined surface 419C, which causes the clamping claws 422C to be pushed outward against the spring force of the unclamping spring 428C.

[0043] <Clamping> With the tool holder 500C inserted into the tip of the spindle 200C, the drawbar 300C is rotated by the drawbar drive control mechanism 600C. The screw mechanism 430C pulls in the slide body 410C, causing it to slide backward as shown in Figure (A). As a result, the clamping claws 422C strike the inclined surface 419C of the unclamping groove 418C of the slide body 410C and are pushed outward. Consequently, the tip of the clamping claws 422C enters the clamping groove 506C of the tool holder 500C and locks into place by striking its side surface 507C. This clamps the tool holder 500C.

[0044] <Unclamping> Next, when removing the tool holder 500C, the drawbar 300C is rotated in the opposite direction to the previous rotation by the drawbar drive control mechanism 600C, as shown in Figure (B). This causes the slide body 410C to be pushed forward by the screw mechanism 430C. As a result, the clamping claw 422C is pulled back towards the unclamping groove 418C by the action of the unclamping spring 428C. This disengages the tip of the clamping claw 422C from the clamping groove 506C of the tool holder 500C, changing it from a clamped state to an unclamped state. Therefore, the tool holder 500C can be pulled out from the spindle 200C.

[0045] As described above, the following effects can be obtained according to Examples 1 to 4. a. By using a screw mechanism to perform clamping and unclamping with a collet, and without using hydraulics, there is no so-called vibration, and powerful cutting operations can be performed well. In addition, since the load on the motor that drives the screw mechanism is only during clamping and unclamping, the screw life is also extended. b. Since clamping and unclamping are performed by a servo motor, torque control during clamping, detection of foreign object jamming, and detection of clamping failures can be performed. For example, when the jamming is "0.005", depending on the taper angle, it can be 7 times, and in combination with the screw lead, the servo motor's position can be detected. c. Because it does not use disc springs or coil springs, spring breakage and imbalances can be avoided, and maintenance of these is unnecessary. d. There is no bearing between the spindle and the drawbar, and therefore no load is placed on the bearing. Consequently, there is no impact on the bearing from the clamping and unclamping switching. e. By temporarily holding the tool holder during unclamping and completing the structure at the spindle section, including the reaction force, it does not affect the bearings between the spindle and the housing. f, Applicable to various collets.

[0046] <Other Embodiments> The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, the following are also included. (1) The shapes and dimensions of the parts shown in the above embodiment are examples only, and the design can be modified to perform similar functions. For example, mechanical elements such as temporary holding mechanisms, pins, and keys may be provided as needed. (2) In the above embodiment, a stepping motor 610 was used to detect a clamping failure from the amount of slide of the drawbar that drives the collet 400, but this does not prevent using a normal motor to perform only clamping and unclamping. (3) The clamping mechanism 100 of the present invention is suitable for, for example, the replacement of tool holders in an ATC (Automatic Tool Changer) of a machining center, but it can be applied to various clamping mechanisms. Therefore, the object to be clamped is not limited to tool holders. (4) In the above embodiment, a screw mechanism 430 is provided between the outer circumferential surface of the drawbar 300 and the inner circumferential surface of the slide body 410. However, the screw mechanism 430 may be provided in the opposite way, between the inner circumferential surface of the drawbar 300 and the outer circumferential surface of the slide body 410. [Industrial applicability]

[0047] According to the present invention, a screw mechanism between the drawbar and the collet is used to clamp and unclam the object to be clamped by the collet. This allows for the detection of clamping failures, eliminates the need for countersunk screws or coil screws, simplifies maintenance, and eliminates the impact on the bearings during clamping and unclamping, making it suitable for ATCs in machining centers and the like. [Explanation of symbols]

[0048] 100: Clamping mechanism 110: Cabinet 112: Bearing 200, 200A~200C: Spindle 210,210A: Movable groove 220, 220B: Tapered surface 230: Clamp groove 232: Groove 240, 240A: Temporary holding mechanism 241A, 241B: Pins 242: Ball 244: Spring 246: Spring retainer 247A, 247B: Pin groove 300, 300A~300C: Drawbar 310,310A~310C:Protrusion 400, 400A~400C: Collet 410, 410A~410C: Slide body 412: Cylindrical section 414: Cylindrical section 416: Groove 418B, 418C: Anchor groove 419C: Inclined surface 420, 420A~420C: Retaining ring 422, 422A~422C: Clamping claws 424: Slit 426: Locking protrusion 428C: Ankle clamp spring 430, 430A~430C: Screw mechanism 450C: Spring retaining pin 500, 500A~500C: Tool holder 502, 502B: Tapered surface 504, 504A: Pull stud Do 506B, 506C: Clamp groove 507B, 507C: Side 600, 600A~600C: Drawbar drive control mechanism 610: Stepping motor 620: Clutch 630: Drawbar control device 632: Clamp failure detection unit DS: Foreign object

Claims

1. A spindle with a clamping surface formed at its tip that contacts the clamping portion of the object to be clamped. Within the spindle, a collet for clamping the object to be clamped, A drawbar that drives the collet, It is equipped with, The aforementioned collet is A first member having a screw mechanism between it and the drawbar, A second member having clamping claws that move in accordance with the forward and backward movement of the first member in the main axis direction and engage with the clamping portion of the object to be clamped, It is composed of, The device is equipped with a temporary holding mechanism that temporarily holds the first member in an unclamped state relative to the spindle, A clamping mechanism characterized in that when the drawbar is rotated, the collet moves forward and backward by the screw mechanism, thereby clamping and unclamping the object to be clamped.

2. The object to be clamped is a tool holder, The clamping mechanism according to claim 1, characterized in that the tool holder is clamped by locking the clamp portion of the tool holder from the inside or the outside.

3. The temporary holding mechanism is, Multiple balls and springs that press against the balls are provided around the main shaft at intervals. A groove is formed around the entire circumference of the outer side of the first member of the collet. The clamping mechanism according to claim 1, characterized in that the ball is pressed into the groove by the spring to temporarily hold it in place.

4. The clamping mechanism according to claim 1, characterized in that a movable means is provided that allows the drawbar to move in the direction of pulling out the clamped object so that the clamping claws open when the clamped object is removed from the collet.

5. The clamping mechanism according to claim 1, characterized in that, when clamping, the clamping claws engage with the clamping portion of the object to be clamped and the spindle, respectively.

6. The clamping mechanism according to claim 5, characterized in that a movable means is provided that allows the drawbar to move in the direction of pulling out the clamped object so that the clamping claws open when the clamped object is removed from the collet.

7. The object to be clamped is a tool holder, The clamping surface is formed on the inside of the spindle, A clamp groove is formed on the inside of the tool holder. An unclamping groove is formed on the outer side of the first member. Clamp claws are formed on the outer surface of the second member. The clamping mechanism according to claim 1, characterized in that when unclamped, the clamping claws of the second member are disengaged from the clamping groove of the tool holder, and when clamped, the clamping claws of the second member engage with the clamping groove of the tool holder, thereby locking the tool holder from the inside.

8. The clamping mechanism according to claim 7, characterized in that the clamping claws are biased toward the rotation center of the spindle by a biasing means.

9. The clamping mechanism according to any one of claims 1 to 8, characterized in that the clamping portion of the object to be clamped and the clamping surface of the spindle are tapered surfaces.

10. A machine tool characterized by comprising a clamping mechanism according to any one of claims 1 to 8.

11. The clamping mechanism according to any one of claims 1 to 8 is equipped with a drawbar rotation drive mechanism for rotationally driving the drawbar, A clamping device characterized by comprising a clamping defect detection means for detecting a clamping defect by the collet based on the amount of rotation of the drawbar. 。

12. A machine tool characterized by being equipped with the clamping device described in claim 11.

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