Spindle device, machine tool equipped with spindle device, and balancing machine

Abstract

The invention provides a main shaft device and a machine tool equipped with the main shaft device. The main shaft device can clamp inner and outer positions of a multifunctional holder through a driving unit. In the main shaft device, a holder is used by being attached to the front end of a main shaft, the holder has a first clamped part and a second clamped part which are arranged in two layers, and a first pull rod (8) and a second pull rod (9) are arranged in series in a main shaft tube in an overlapping manner. When the first pull rod (8) is pushed by the cushion block (17) to move forwards, the first pull rod (8) and the acting force of the first belleville spring assembly (10) are confronted and move forwards, the first clamping mechanism is released, then the second pull rod (7) and the acting force of the second belleville spring assembly (11) are confronted and move forwards, and the second clamping mechanism is also released. And along with the retreating of the cushion block (17), the first clamping mechanism of the first pull rod (8) and the second clamping mechanism of the second pull rod (9) act under the acting force of the first belleville spring assembly (10) and the second belleville spring assembly (11).

Description

Technical Field

[0001] The present invention relates to a spindle device, a machine tool equipped with the spindle device, a balancing machine, etc. The spindle device is used by installing a tool or workpiece holder on the front end of the spindle. The tool or workpiece holder has a first clamped portion and a second clamped portion arranged in a double layer on the inside and outside at its base side. Background Art

[0002] The inventor of the present invention has developed a multifunctional holder installed on the spindle of a machine tool as a holder that can be used to install both tools and workpieces. While developing the holder, a holder holding mechanism when the above-mentioned holder is installed on the spindle, a spindle device having such a holder holding mechanism, etc. are also developed. As a prior art that discloses the above-mentioned technology, as shown in Patent Document 1. In the spindle device of Patent Document 1, a separate clamping structure for installing the above-mentioned multifunctional holder is provided. Specifically, as shown in FIG. 2, for example, a structure having the following components is adopted: an outer gripping mechanism (composed of an outer pull rod 85, an outer ball 92a, etc.) for clamping (holding) the holder itself, and an inner gripping mechanism (composed of an inner pull rod 84, an inner ball 92b, etc.) for clamping the head of a movable traction stud of a chuck mechanism that opens and closes the holder. In other words, it is a mechanism for clamping a multifunctional holder having a double-layer clamped portion on the inside and outside. Then, the outer tie rod 85 and the inner tie rod 84 are respectively advanced and retreated by two cylinder devices (double-layer push-pull mechanism 9a) arranged on the upper part of the main shaft to perform a clamping operation. Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2010-284768 Summary of the invention Technical issues to be solved by the invention

[0004] However, in order to clamp the two clamped parts, the two cylinder devices are arranged on the main spindle device as described above, respectively. This structure will cause the main spindle device to be large and heavy, and will cause high costs due to the need for multiple cylinder devices. In addition, since the actions of the two cylinder devices must be controlled, the operation will become complicated. In addition, maintenance will also become inconvenient. Therefore, a mechanism is required for clamping both the inner side and the outer side of the above-mentioned retainer using only one pushing unit such as a cylinder device. The object of the present invention is to solve the above-mentioned technical problems and to provide a spindle device capable of clamping two locations inside and outside a multifunctional holder by driving a single pushing unit, a machine tool equipped with the spindle device, and a balancing machine. Technical solutions for solving technical problems

[0005] In a first method for solving the above-mentioned technical problem, a spindle device is provided, which installs a holder for a tool or a workpiece on the front end of the spindle for use, and the holder has a first clamped portion and a second clamped portion arranged in a double layer on the inner side and the outer side at its base side. The spindle device is characterized in that it includes a first pull rod and a second pull rod, and the first pull rod has a first clamping mechanism on the front end side for clamping the first clamped portion of the holder, and the second pull rod has a second clamping mechanism on the front end side for clamping the second clamped portion of the holder, and the first pull rod and the second pull rod are connected to each other. The pull rods are arranged in series in the above-mentioned main shaft tube and can move forward and backward. The above-mentioned first pull rod is configured to be pressed in the forward direction by the pushing unit, thereby opposing the force generated by the first force-applying unit and moving forward. The above-mentioned second pull rod is configured to be directly or indirectly pushed by the above-mentioned first pull rod as the above-mentioned first pull rod moves forward, thereby opposing the force generated by the second force-applying unit and moving forward. The above-mentioned first pull rod that moves forward with the help of the above-mentioned pushing unit has the above-mentioned first clamping mechanism released at a specified forward and backward position, and the above-mentioned second clamping mechanism of the above-mentioned second pull rod that is pushed by the above-mentioned first pull rod is also released. As the pressing force generated by the pushing unit is released, the first pull rod and the second pull rod in the specified forward and backward positions are respectively retreated toward the base direction of the spindle cylinder by the forces of the first force unit and the second force unit, and the first clamping mechanism of the first pull rod and the second clamping mechanism of the second pull rod are actuated. In this way, the first clamping mechanism and the second clamping mechanism can be released only by the push of the pushing unit. In addition, by retreating the pushing unit, the first force unit and the second force unit can be actuated only by the forces of the first force unit and the second force unit, so that the two clamped parts of the retaining member can be clamped, and the loosening structure becomes simple, which is conducive to the miniaturization and low cost of the spindle device.

[0006] The "first pull rod" has a first clamping mechanism on the front end side for clamping the first clamped part of the holder. The front end side refers to the front end side of the spindle. The configuration position of the first clamped part of the holder is determined according to the relationship with the second clamped part, and can be on the inside or on the outside. The "second rod" has a second clamping mechanism at the front end side for clamping the second clamped portion of the retainer. The second rod is in a relationship of directly or indirectly pushing the first rod as the first rod advances. The first rod and the second rod are arranged in series and may also overlap partially. The "pushing unit" may include a pressing member such as a hydraulic cylinder device, a cylinder device, or a cylinder (piston) driven by an electric motor device. The pushing unit (pressing member) may be connected to the first tie rod or not. When not connected, it is only in contact for pushing, so it will not become a load when the main shaft rotates. When the pushing unit presses the first pull rod to move the first pull rod forward, the "first force applying unit" is compressed as the first pull rod moves forward, and a force exists inside. By releasing the pressing force from the pushing unit, the first pull rod is moved back toward the main shaft cylinder base by the force. The first force applying unit preferably has a certain degree of force inside at the beginning, and is preferably configured to always push the first pull rod toward the main shaft cylinder base by using the force. In the "second force-applying unit", when the first rod is pushed forward by the pushing unit and the second rod also moves forward, the second rod is compressed and a force exists inside. By releasing the pressing force from the pushing unit, the second rod is moved back toward the spindle tube base by the force. The second force-applying unit preferably has a certain degree of force inside at the beginning, and is preferably configured to always push the second rod toward the spindle tube base by using this force. When the first force applying unit and the second force applying unit are spring devices, for example, they may be coil springs, disc springs, leaf springs, etc. Cylinder devices or hydraulic cylinder devices may also be used. The "clamped portion" needs to be a shape that can be clamped (grasped) by the clamping mechanism. The clamped portion preferably has, for example, a protruding portion, or a shape into which a member on the clamping side is embedded. This is because the clamped portion interferes with the clamping mechanism and prevents the retainer from moving in the removal direction. The "clamping mechanism" preferably has a structure of an interference body that advances and retreats in the radial direction of the main shaft relative to the clamped part. Moreover, it is preferred that the interference body appears and disappears in the passage through which the clamped part is inserted to clamp the clamped part. The shape of the interference body is preferably ball-shaped, cylindrical, or barrel-shaped. Alternatively, the interference body can be set to move forward and backward in the radial direction of the main shaft, such as a collet, by swinging around the axis. Since “the second rod is pushed indirectly or directly by the first rod”, the first rod and the second rod may be in contact and pushed, or may be pushed via other components.

[0007] The "holder" has a first clamped portion and a second clamped portion arranged in double layers on the inner and outer sides at its base side. It is preferably a multifunctional holder with high versatility that can be used for both tools and workpieces. Even if it has a first clamped portion and a second clamped portion, it can also be a holder specific to a tool, for example. If there are two clamping parts of the first clamped portion and the second clamped portion, the tensile force of the holder is increased, making it particularly suitable for high-load cutting. In the above case, it does not function as a multifunctional holder but as a tool holder. In the case of a multifunctional holder, various processing tools such as milling cutters, drills, end mills, drills, and reamers, which are used as tools, such as ATC (Automatic Tool Change) equipped in a machining center, can be clamped by the chuck mechanism and installed on the front end side for use. In the case of a workpiece, the workpiece is directly or indirectly clamped and installed on the front end side by the chuck mechanism, and the workpiece can be processed by a CNC machine tool, for example. The chuck mechanism also includes a clamping mechanism. For example, the first clamped portion is formed on a rod member such as a traction stud, and the first clamped portion is pushed and pulled, so that the chuck mechanism is opened and closed. Preferably, the second clamped portion is formed on a mounting portion installed in the mounting hole of the holder, and the holder is installed on the front end of the spindle cylinder through the second clamped portion.

[0008] Furthermore, as a second aspect, the pushing unit retreats to a position where it does not contact the first pull rod when the first pull rod is not pressed. Therefore, when the first clamping mechanism and the second clamping mechanism of the second pull rod are operated to clamp the holder, the pushing unit does not become a load on the spindle cylinder side, so that energy consumption and rotation unevenness when the spindle rotates can be reduced. Furthermore, as a third aspect, a force obtained when the second force applying means applies force is greater than a force obtained when the first force applying means applies force. Therefore, when the first clamping mechanism and the second pull rod are released by the pushing of the pushing unit and the pushing force generated by the pushing unit is released, the second clamping mechanism of the second pull rod is first actuated by the force of the second force applying unit, and then the first clamping mechanism of the first pull rod is actuated with a time difference. Furthermore, as a fourth aspect, when the first tie rod retreats from the predetermined advance / retract position, the first clamping mechanism of the first tie rod is actuated after the second clamping mechanism of the second tie rod is actuated. By arranging the first clamp mechanism to be operated after the second clamp mechanism is operated with a time difference in this manner, it is possible to prevent erroneous mounting of the holder. In the third and fourth modes, since a two-stage clamping action can be performed, for example, the retaining member is correctly installed on the spindle device and clamped by the second clamping mechanism, and then the first clamping mechanism clamps the head of the movable traction stud, it is not easy to cause problems such as clamping the traction stud in a tilted state before the retaining member is correctly installed on the spindle device or the first clamping mechanism does not operate smoothly.

[0009] Furthermore, as a fifth aspect, the first tie rod includes an outer peripheral surface that contacts the inner peripheral surface of the second tie rod, and is guided by the inner peripheral surface and the outer peripheral surface to slide forward and backward. Thus, during the relative advance and retreat operation of the two parties, such as when the first tie rod advances and retreats or when the first tie rod is pushed and advanced and retreated by the first tie rod, the central axes can be aligned and moved without chattering. Furthermore, as a sixth aspect, the first clamp mechanism and the second clamp mechanism are arranged at positions offset in a front-rear direction, and the second clamp mechanism is arranged closer to the front end of the spindle than the first clamp mechanism. This makes it easy to cope with a situation where the positions of the first clamped portion and the second clamped portion of the retainer are offset in the front-rear direction, and since the first clamping mechanism and the second clamping mechanism are not in the same position, interference between the two will not occur.

[0010] In addition, as a seventh method, the above-mentioned first clamping mechanism has an interference body that advances and retreats in the radial direction of the above-mentioned main shaft. When the above-mentioned first pull rod is arranged in the above-mentioned first advance and retreat position, the above-mentioned interference body that clamps the above-mentioned first clamped part is located facing the storage part formed on the inner circumferential surface of the above-mentioned second pull rod, so that the above-mentioned first clamping mechanism is released. This is a specific configuration of a release structure for releasing the first clamping mechanism from the clamped state. Thus, the clamped state in which the first clamping mechanism clamps the first clamped portion of the holder can be released (released). In addition, as an eighth mode, the above-mentioned second clamping mechanism has an interference body that advances and retreats in the radial direction of the above-mentioned main shaft. When the above-mentioned first pull rod is arranged in the above-mentioned first advance and retreat position, the above-mentioned interference body that clamps the above-mentioned second clamped part is in a position in contact with the storage part surface formed on the inner circumferential surface of the above-mentioned main shaft cylinder, so that the above-mentioned second clamping mechanism is released. This is a specific configuration of a structure for releasing the clamped state of the second clamp mechanism. In this way, the clamped state of the second clamped portion of the holder by the second clamp mechanism can be released (released). Here, the interference body advances radially to clamp the clamped portion, and the retainer is installed by maintaining the clamped state. It is preferred to have a clamping portion that prevents the retainer from moving in the removal direction. As the interference body that advances and retreats radially, a ball or a chuck or a split claw such as the above can be configured.

[0011] Furthermore, as a ninth aspect, the holder is mounted on a holder mounting hole formed at a front end of the spindle cylinder. That is, the holder is mounted on the holder mounting hole of the spindle device, and its first clamped portion and second clamped portion are clamped by the first clamp mechanism and the second clamp mechanism. In addition, as a tenth method, the above-mentioned retaining member for the workpiece is configured as follows: the above-mentioned retaining member for the workpiece is configured as follows: the above-mentioned first clamped portion is formed by a rod member that can move forward and backward, and when the above-mentioned second clamping mechanism applies action to the above-mentioned retaining member installed on the above-mentioned main shaft front end, the above-mentioned rod member is pulled out through the above-mentioned first clamped portion, so that the above-mentioned workpiece in a loose state is clamped, and the above-mentioned first pull rod is advanced, so that the above-mentioned rod member is pushed back and the above-mentioned workpiece in a clamped state is loosened. Thus, the rod member can be advanced and retreated by the first tie rod while the second clamping mechanism is operated to clamp the workpiece holder, so the workpiece can be clamped and released only by the first clamping mechanism of the first tie rod. The rod member is, for example, a draw stud or a draw bolt. Furthermore, as an eleventh aspect, the first urging means and the second urging means are compression spring devices, and urge the first tension rod and the second tension rod in a backward direction. By using the compression spring device in this way, it is possible to contribute to weight reduction and compactness of the biasing unit for biasing the first and second tension rods in the backward direction. Furthermore, a twelfth aspect is a machine tool equipped with the spindle device described in any one of the first to eleventh aspects. Furthermore, a thirteenth aspect is a balancing machine equipped with the spindle device described in any one of the first to eleventh aspects. The machine tool may be, for example, a numerically controlled machine tool, a machining center, or even a numerically controlled machine tool with an ATC. In the machining center, it is preferably used as a spindle device of an ATC (automatic tool changer). The inventions of the first to thirteenth aspects described above can be combined arbitrarily. In particular, it is preferable to combine the structure of the first aspect with at least one structure of the inventions of the first to thirteenth aspects. Any constituent element of the inventions of the first to thirteenth aspects can also be combined with other constituent elements. Effects of the Invention

[0012] In the above invention, the first clamping mechanism and the second clamping mechanism can be released only by pushing the pushing unit. In addition, by making the pushing unit retreat, the first clamping mechanism and the second clamping mechanism can be operated only by the action of the first force applying unit and the second force applying unit, and the structure of clamping and releasing the two clamped parts of the retainer becomes simple, which is conducive to the miniaturization and low cost of the spindle device. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a partially broken longitudinal sectional view of the spindle unit according to the first embodiment. Figure 2A This is a longitudinal sectional view of the main part of the spindle device of the spindle unit according to the first embodiment, illustrating a state in which the first tie rod and the second tie rod are fully retracted without the first tie rod being pressed by the spacer. Figure 2B This is a longitudinal sectional view of the main part of the spindle device for explaining a state in which the first tie rod is pressed by the spacer and only the first tie rod has moved downward in the spindle device of the spindle unit according to the first embodiment. Figure 2C This is a longitudinal sectional view of the main part of the spindle device of the spindle unit according to the first embodiment, illustrating a state in which the first tie rod is not pressed by the spacer and the first tie rod and the second tie rod are moved most downward. Figure 2D Is to hold the retainer relative to Figure 2C A longitudinal sectional view of the main parts of the device for explaining a state in which a spindle unit is in the process of being installed or removed from a spindle device. Figure 2E This is a longitudinal sectional view of the main part of the device, illustrating a state in which a spacer in a pressed state is slightly lifted in the spindle device of the spindle unit of the first embodiment and only the second pull rod moves upward to clamp the flange portion of the retainer (a state in which the second clamping mechanism has been actuated). Figure 2F This is a longitudinal sectional view of the main part of the device, illustrating a state in which the spacer in the pressed state in the spindle device of the spindle unit of the first embodiment is completely disengaged and the first pull rod and the second pull rod move in two directions and are clamped by the raised portion and the flange portion of the retaining member respectively (a state in which both the first clamping mechanism and the second clamping mechanism are in operation). Figure 3A This is a longitudinal sectional view of the main part of the device, illustrating a state in which the spacer in the pressed state in the spindle device of the spindle unit of the first embodiment is completely disengaged, the first pull rod and the second pull rod move in both directions, and the raised portion and the flange portion of the retaining member are clamped respectively (a state in which both the first clamping mechanism and the second clamping mechanism are in operation). Figure 3BThis is an enlarged explanatory diagram for explaining a state in which the first pull rod is largely retracted to pull the draw stud out of the holder while the protrusion and flange of the holder are clamped around the clamp mechanism of the spindle device of the spindle unit of the first embodiment. Figure 4A This is an enlarged explanatory diagram for explaining a state in which the first and second tie rods advance to a position where the inner and outer balls are locked and cannot move out of or into the clamp mechanism of the spindle device of the spindle unit according to the first embodiment. Figure 4B This is an enlarged explanatory diagram for explaining a state in which the balls inside and outside the first and second tie rods advance to positions where they can freely appear and retract around the clamp mechanism of the spindle device of the spindle unit of the first embodiment. Figure 4C The invention relates to a spindle unit of the first embodiment, and the spindle unit has a clamping mechanism around the spindle device. Figure 4B An enlarged illustration showing a state in which both the raised portion and the flange portion of a retaining member that is being installed or removed are not clamped. Figure 4D The second tie rod is arranged around the clamping mechanism of the spindle device of the spindle unit of the first embodiment. Figure 4C An enlarged explanatory diagram illustrating a state in which the flange portion of the retainer is clamped while the retainer is retracted. Figure 4E The first tie rod is arranged around the clamping mechanism of the spindle device of the spindle unit of the first embodiment. Figure 4D An enlarged explanatory diagram illustrating a state in which the protrusion and flange of the retainer are clamped while the retainer is retracted. Figure 5 It is a partially enlarged stereoscopic view of the front end of the first pull rod. Figure 6 (a) is a front view of the chuck holder in the chuck open state, Figure 6 (b) is a bottom view of the chuck holder in the chuck open state. Figure 7 (a) is a front view of the chuck holder in the chuck closed state, Figure 7 (b) is a bottom view of the chuck holder in the chuck closed state. Figure 8 It is a partially broken longitudinal sectional view of the spindle unit according to the second embodiment. Fig. 9 (a) is a front view of the tool chuck holder, Fig. 9 (b) is a longitudinal sectional view of the tool chuck holder. Fig.10 This is an explanatory diagram schematically explaining the outline of the balancing machine according to the third embodiment. DETAILED DESCRIPTION

[0014] Hereinafter, embodiments will be described with reference to the drawings. <Implementation Method 1> like Figure 1 As shown, the main components of the spindle unit 1 as an automatic tool changing device include a spindle device 2, a bearing unit 4 surrounded by a housing 3 arranged around the spindle device 2, a spindle rotating mechanism 5, and a cylinder device 6. First, the outline of the spindle unit 1 is described. In the following description, it is assumed that the spindle device 2 is arranged in the vertical direction in the spindle unit 1, and the front end side of the spindle device 2 is the lower side. The spindle unit 1 is supported by a spindle frame not shown. like Figure 1 and Figure 2A-2F As shown, the alloy spindle device 2 has a roughly cylindrical spindle cylinder 7. The spindle cylinder 7 has a passage connected in the up-down direction and the outer peripheral shape is a perfect circle. A first tie rod 8 and a second tie rod 9 are accommodated in the spindle cylinder 7. Between the first tie rod 8 and the spindle cylinder 7, a first disc spring assembly 10 as a first force applying unit is arranged. Between the second tie rod 9 and the spindle cylinder 7, a second disc spring assembly 11 as a second force applying unit is arranged.

[0015] The spindle device 2 is surrounded by a bearing unit 4. The bearing unit 4 is a portion of the spindle unit 1 that rotatably supports the spindle device 2. An inner cylinder portion 4A of the bearing unit 4 is fixed to the spindle device 2 and is formed to rotate together with the spindle device 2. An outer cylinder portion 4B of the bearing unit 4 is fixed to the housing 3 side and is formed to be a non-rotating portion. The housing 3 is supported by a spindle frame (not shown). The first pulley 12 constituting the spindle rotating mechanism 5 is fixedly mounted on the outer periphery of the first cylinder portion 7A at the upper part of the spindle cylinder 7. The second pulley 13 is supported by a bearing fixed to the spindle frame side (not shown) at a side position separated from the first pulley 12. A drive belt 14 for driving transmission is wound around the outer peripheries of the first pulley 12 and the second pulley 13. The output shaft 15a of the motor device 15 is coaxially connected to the second pulley 13. The motor device 15 is supported on the spindle frame side (not shown). A cylinder device 6 is arranged at the upper position of the main shaft cylinder 7. The cylinder device 6 is supported by the main shaft frame side (not shown). The cylinder device 6 allows a piston rod 6a driven by an air compressor (not shown) to advance and retreat. The piston rod 6a is arranged to be retracted downward and a cylindrical spacer 17 is connected to the front end of the piston rod 6a.

[0016] Next, the spindle device 2 will be described in more detail. like Figure 1 , Figure 2A-2FAs shown, a spindle cover 18 is connected to the front end side of the spindle cylinder 7. The spindle cover 18 is a cylindrical body that is connected in the up and down directions and has a circular cross-section. The spindle cover 18 is fixed in a state of being inserted into the front end of the spindle cylinder 7. The spindle cylinder 7 has three areas with different inner diameter sizes, and from the top are the first cylinder portion 7A, the second cylinder portion 7B, and the third cylinder portion 7C. The spindle cylinder 7 is constructed so that the inner diameter increases in the above order. A retainer mounting hole 19 in a frustum-shaped shape whose diameter increases toward the bottom is formed on the inner circumference of the spindle cover 18. The spindle cover 18 and the spindle cylinder 7 together constitute a frame 20 of the spindle device 2. In the internal space of the frame 20 , the first tie rod 8 and the second tie rod 9 are arranged in series so as to partially overlap. A fixing ring 21 is fixedly mounted in the second cylinder portion 7B of the spindle cylinder 7. A passage 23 is formed at the center of the fixing ring 21 so as to communicate in the up-down direction. The first pull rod 8 is formed to have a circular shape in the cross-sectional shape and is composed of three parts with different diameters. That is, the first pull rod 8 has a first large diameter portion 8A, a small diameter portion 8B and a second large diameter portion 8C, the small diameter portion 8B is adjacent to the first large diameter portion 8A and extends downward (forward) and has a smaller diameter, and the second large diameter portion 8C is connected to the front end side of the small diameter portion 8B and has the largest diameter. The front end of the second large diameter portion 8C is formed as a cylindrical portion 8D, and the cylindrical portion 8D is formed into a cylindrical shape with the same outer shape as the second large diameter portion 8C. The internal space of the cylindrical portion 8D is located at the rear end side of the traction stud 55 of the chuck holder 51 described later and is located to clamp the raised portion 56. A cooling liquid passage 24 connected up and down is formed at the axial position of the first pull rod 8. A first disc spring assembly 10 is disposed around the first large diameter portion 8A of the first tie rod 8. The first disc spring assembly 10 is disposed between the first large diameter portion 8A and the main shaft cylinder 7, and is disposed to be clamped in a state where a force is applied between a nut 25 fixed to the upper end of the first large diameter portion 8A and a fixing ring 21 in the up-down direction. The second tie rod 9 is also configured to have a circular cross-sectional shape. The second tie rod 9 has a cylindrical main body 9A, a flange portion 9B formed to protrude toward the outer circumference at a position close to the upper portion of the main body 9A, a partition wall 9C located between the main body 9A and the flange portion 9B, and a ring portion 9D protruding upward in a ring shape. A passage 26 is formed in the partition wall 9C. The lower portion of the second rod 9 near the main body 9A is housed in the spindle cover 18 and is in close contact with the inner circumferential surface 18a, and the outer periphery of the flange portion 9B is in close contact with the second barrel portion 7B of the spindle barrel 7. With the above-mentioned close contact structure, the second rod 9 can be guided when it slides linearly in the up and down directions. The internal space near the front end of the main body 9A is in a position to house the flange portion 57 of the chuck holder 51 described later and clamp the reduced diameter portion 58. A second disc spring assembly 11 is disposed around the main body 9A of the second tie rod 9. The second disc spring assembly 11 is disposed between the main body 9A and the spindle cylinder 7, and is disposed so as to be clamped in a state where a force is applied between the flange portion 9B and the spindle cover 18 in the up-down direction. A pin 27 for preventing the second tie rod 9 from rotating in the circumferential direction is disposed between the second tie rod 9 and the fixing ring 21. A key 28 is mounted at the front end of the retainer mounting hole 19, and the key 28 is used to engage with the side of the chuck retainer 51 when the chuck retainer 51 is mounted on the spindle device 2 to prevent the chuck retainer 51 from rotating in the circumferential direction.

[0018] The arrangement state of the first tie rod 8 and the second tie rod 9 having the above-described structure with respect to the frame 20 will be described. The second rod 9 is configured to be able to slide in the cylindrical frame 20, and is also configured to be cylindrical to accommodate the first rod 8 and allow the first rod 8 to slide. The first rod 8 is accommodated in the second rod 9 near the bottom so as to be able to slide. In other words, the frame 20, the first rod 8 and the second rod 9 constitute a double-layer sliding mechanism with inner and outer overlaps. In the first tie rod 8, the portion of the first large diameter portion 8A close to the lower end is accommodated in the ring portion 9D on the second tie rod 9 side, the small diameter portion 8B communicates with the passage 26 of the partition wall 9C on the second tie rod 9 side, and the second large diameter portion 8C is arranged in the main body 9A on the second tie rod 9 side. The components are arranged in a close contact state, and can guide the first tie rod 8 when it slides linearly in the up and down direction. In the first tie rod 8, the lower end of the first large diameter portion 8A abuts against the upper surface of the partition wall 9C on the side of the second tie rod 9, thereby limiting the further downward movement of the first tie rod 8. The above position is set to the lowest position, and further upward movement is limited by the upper end of the second large diameter portion 8C abutting against the lower surface of the partition wall 9C on the upper side. In the second tie rod 9, the upper surface of the flange portion 9B abuts against the lower surface 28 of the second cylinder portion 7B of the spindle cylinder 7, thereby limiting the further upward movement of the second tie rod 9. In addition, in the second tie rod 9, the front end of the main body 9A abuts against the shelf portion 29 protruding inwardly from the inner circumference of the spindle cover 18, thereby limiting the further downward movement of the second tie rod 9. The front end of the cylindrical portion 8D of the first tie rod 8 is always arranged at a position retreated from the front end of the second tie rod 9.

[0019] Next, according to Figure 2A-2F , Figure 4A-4E as well as Figure 5 , the clamping mechanism of the first pull rod 8 and the second pull rod 9 is described. The first pull rod 8 clamps a draw stud 55 side of the chuck holder 51 to be described later, and the second pull rod 9 clamps a mounting portion 53 side of the chuck holder 51 to be described later. like Figure 5As shown, a plurality of first through holes 31 are formed in the cylindrical portion 8D of the first tie rod 8 at predetermined intervals in the circumferential direction. Each first through hole 31 has a circular opening portion that connects the radial inside and outside of the cylindrical portion 8D of the first tie rod 8. Each first through hole 31 is configured such that the diameter of the inner opening portion is smaller than the diameter of the outer opening portion and the inner wall is formed in a tapered shape. A first ball 32 is accommodated in each first through hole 31. The diameter of the first ball 32 is configured to be larger than the diameter of the inner opening portion of the first through hole 31 and smaller than the diameter of the outer opening portion. Second through holes 33 are formed at predetermined intervals in the circumferential direction near the front end of the second tie rod 9. The structure of the second through holes 33 is the same as that of the first through holes 31 and is omitted. In addition, a second ball 34 is accommodated in each second through hole 33. The structure and operation of the second ball 34 are the same as those of the first ball 32 and their detailed description is omitted.

[0020] First recesses 35 are formed on the inner side of the main body 9A of the second tie rod 9 at positions above the second through hole 33 at predetermined intervals in the circumferential direction. The first recess 35 is formed in a circular opening shape and has the same diameter as the opening diameter of the outer side of the first through hole 31. The first recess 35 is configured such that when the first ball 32 enters the innermost side of the first through hole 31 ( Figure 4A , Figure 4E In other words, when the first recess 35 is aligned with the first through hole 31, the first ball 32 retreats to the outside, and when it is immersed in the innermost part of the first recess 35, the first ball 32 does not protrude from the surface (flush plane) of the first tie rod 8. The wall surface of the first recess 35 is formed into a tapered shape that is easy to enter and exit the first through hole 31. The first recess 35 is aligned with the first through hole 31 according to the relative positional relationship between the first pull rod 8 and the second pull rod 9. If the first recess 35 is aligned with the first through hole 31, the first ball 32 is in a loose fit state, and can therefore retreat to the outside and be in a loose state. On the other hand, in the absence of alignment, the first ball 3 cannot move inward or outward and is held in a clamped state with the front end side slightly protruding toward the inside of the first through hole 31. In this embodiment, clamping refers to the pressing of the traction stud 55 of the chuck holder 51 and the axial portion of the mounting portion 53 by a plurality of first balls 32 from around them.

[0021] Second recesses 37 are formed at predetermined intervals in the circumferential direction on the lower inner peripheral surface 7 a of the spindle cylinder 7 and in the vicinity of the base side of the holder mounting hole 19 . The second recess 37 is configured to have a larger diameter than the second through hole 37 in order to prevent the second tie rod 9 from interfering with the main shaft cylinder 7. In addition, when the second recess 37 is aligned with the second through hole 33, the second ball 34 is the last to retreat, and when it is immersed in the second recess 37, the second ball 34 does not protrude from the surface (flush plane) of the second tie rod 9, which is the same as the first tie rod 8 side. The wall surface of the second recess 37 is formed in a tapered shape that is easy to enter and exit the second through hole 33. The second recess 37 is arranged at a predetermined forward and backward position by the second pull rod 9 so as to be aligned with the second through hole 33. As described above, in the aligned state, the second ball 34 is in a loose fit state, and thus can be withdrawn to the outside, and is in a loose state. On the other hand, in the case of misalignment, the second ball 34 is held in a clamped state while the front end side is slightly protruding, and cannot move inward or outward. A first clamping mechanism is formed between the first tie rod 8 and the second tie rod 9 by means of the first through hole 31 , the first ball 32 , the first recess 35 and the like. The second through hole 33 , the second ball 34 , the second recess 37 and the like form a second clamping mechanism between the main shaft cylinder 7 and the second tie rod 9 .

[0022] The spindle unit 1 configured as described above is mounted on a bed plate (not shown) in a machining center, and processes a workpiece under the control of a computer device (not shown).

[0023] In this embodiment, Figure 6 (a), (b) and Figure 7 The chuck holder 51 with three claws shown in (a) and (b) is set to be mounted on the holder mounting hole 19 of the spindle device 2. The chuck holder 51 is composed of a holder body 52 that accommodates a chuck mechanism (not shown) and a mounting portion 53 for mounting on the spindle device 2. The mounting portion 53 is a conical protrusion formed integrally with the holder body 52. ​​The outer peripheral shape of the mounting portion 53 corresponds to the inner peripheral shape of the holder mounting hole 19. Three claws 54 are movably mounted on the holder body 52. Figure 6 The states (a) and (b) are states where the claw portion 54 is opened to the maximum. Figure 7 The states (a) and (b) are states where the claw portion 54 is closed to the maximum (stuck state). The pull stud 55 protrudes from the rear end of the mounting portion 53. The pull stud 55 is connected to the chuck mechanism in the retainer body 52 as a rod member, and the claw portion 54 is changed from the open state to the closed state by advancing the pull stud 55 backward (pulling it out). The front end of the pull stud 55 is integrally formed with a protrusion 56 of a substantially ellipsoidal shape that protrudes outward as a locking portion. The front end of the mounting portion 53 is integrally formed with a flange portion 57 that protrudes outward in a disc shape as a locking portion. A reduced diameter portion 58 is formed between the mounting portion 53 adjacent to the flange portion 57 and the flange portion 57 as a locking portion. The reduced diameter portion 58 is a portion that is formed into a collar shape over the entire circumference of a discontinuous recess relative to the continuous tapered shape of the mounting portion 53. The flange portion 57 is arranged on the inner side of the retainer mounting hole 19 when the chuck retainer 51 is mounted to the retainer mounting hole 19 (in a state where the tapered surfaces are in close contact with each other).

[0024] Next, according to Figure 2A-2F , Figure 4A-4E The clamping and loosening actions of the chuck holder 51 with respect to the spindle device 2 in the spindle unit 1 are described below. The state of the chuck holder 51 when the chuck holder 51 is mounted on the spindle device 2 is Figure 6 The claws 54 of (a) and (b) are in the state where they are opened to the maximum, that is, the default state. A. Figure 2A and Figure 4A The first pull rod 8 is pushed to the top by the force of the first disc spring assembly 10, and the second pull rod 9 is pushed to the top by the force of the second disc spring assembly 11. The first clamping mechanism and the second clamping mechanism are both released. The above-mentioned advance and retreat position is regarded as the initial advance and retreat position of the first pull rod 8. Figure 2A In the above, the initial forward and backward position is set as S1, and the end position of the first tie rod 8 is used as a reference. In addition, the end position of the first tie rod 8 is determined by a proximity sensor (not shown). The state of the first disc spring assembly 10 applying force to the first tie rod 8 and the state of the first disc spring assembly 10 applying force to the first tie rod 8 are described in more detail. The first disc spring assembly 10 presses the nut 25 with the fixing ring 21 as a reference. Then, the first tie rod 8 is pushed upward by the nut 25. The first tie rod 8 abuts against the ring portion 9C through the upper end of the second large diameter portion 8C, so that the further upward movement of the first tie rod 8 is restricted. In addition, the second disc spring assembly 11 presses the flange portion 9B with the main shaft cover 18 as a reference. Then, the second tie rod 9 is pushed upward by the flange portion 9B. The flange portion 9B abuts against the lower surface 28 of the second cylinder portion 7B, so that the further upward movement of the flange portion 9B is restricted. At this time, if Figure 4AAs shown, the first ball 32 in the first through hole 31 is locked in a clamping position where it is not allowed to move in the direction of the first recess 35. The second ball 34 in the second through hole 33 is also locked in a clamping position where it is not allowed to move in the direction of the second recess 37. That is, in the above state, the chuck holder 51 is in a state where the first ball 32 and the second ball 34 interfere with each other and cannot be connected.

[0025] B. Next, the spacer 17 at the front end of the piston rod 6a of the cylinder device 6 is moved downward by a predetermined control action, and the first tie rod 8 is pressed downward. The downward movement of the spacer 17 counteracts the force generated by the first disc spring assembly 10 that pushes the first tie rod 8 upward, and the first tie rod 8 moves downward. Figure 2A The S1 position is Figure 2B At this time, since the spring force of the second disc spring assembly 11 is stronger than that of the first disc spring assembly 10, the second disc spring assembly 11 will not be compressed when the first disc spring assembly 10 is compressed due to the downward movement of the cushion block 17. In other words, only the first pull rod 8 moves downward, while the second pull rod 9 does not move downward and stays at this position. Figure 2B The first pull rod 8 is in a loose state where the first ball 32 in the first through hole 31 is allowed to move toward the first recess 35. On the other hand, the second ball 34 in the second through hole 33 is still in a clamped position where it is locked and not allowed to move toward the second recess 37.

[0026] C. If the cushion block 17 moves further downward, the second tie rod 9 is pressed downward by the first tie rod 8 that moves downward to the maximum at the stage when the first disc spring assembly 10 is compressed to the maximum or the force generated by the compression is greater than the force of the second disc spring assembly 11. In the above stage, the downward movement of the cushion block 17 counteracts the force generated by the second disc spring assembly 11 that pushes the second tie rod 9 upward, and the second tie rod 9 moves downward. Figure 2C This is a state where the first tie rod 8 has moved to the S3 position which is lower than S1 and S2, and the second tie rod 9 is in a state where it has moved most downward. At this time, if Figure 4B As shown, the first ball 32 in the first through hole 31 is allowed to move toward the first recess 35 and is in the released position. The second ball 34 in the second through hole 33 is also allowed to move toward the second recess 37 and is in the released position. That is, the chuck holder 51 is in a connectable state.

[0027] D. Figure 2DAs shown, in the state C., the chuck holder 51 is installed in the holder installation hole 19 of the spindle device 2 through a predetermined control action. Figure 4C As shown, even if the mounting portion 53 and the traction stud 55 advance further than the retainer mounting hole 19, the raised portion 56 of the traction stud 55 and the flange portion 57 of the mounting portion 53 will not interfere with the first ball 32 (second ball 34) and hinder their advancement. E. After the chuck holder 51 is installed in the holder installation hole 19 of the spindle device 2, the cushion block 17 is moved upward by a predetermined control action. Figure 2E As shown, as the weight is released, the strong force of the compressed second disc spring assembly 11 is released, and the second pull rod 9 is pushed upward again. Assume that the position at this time is S4 which is higher than S3. As the second pull rod 9 moves upward, the reduced diameter portion 58 at the rear end of the mounting portion 53 of the chuck holder 51 is clamped by the second clamping mechanism (by the second ball 34). However, in the above stage, since the cushion block 17 is in the middle of moving upward, the first pull rod 8 has not yet moved ( Figure 4D status).

[0028] F. Figure 2E As shown, if the pad 17 moves further upward, the strong force of the compressed first disc spring assembly 10 is released as the weight is released, and the first pull rod 8 is pushed upward again. As a result, the first pull rod 8 relatively retreats, so the first recess 35 moves, and the traction stud 55 (the reduced diameter corner part at the root of the raised part 56) of the chuck holder 51 is also clamped by the first clamping mechanism (by the first ball 32). In this way, when the first clamping mechanism is in operation and the pulling stud 55 is clamped, the first pull rod 8 is then pushed upward (that is, moved back upward) (actually at the moment when the cushion block 17 moves upward), so that the pulling stud 55 is pulled out backward (upward), and the claw 54 of the chuck holder 51 is closed. At this time, the position of the first pull rod 8 is S5 which is higher than S4. Since the chuck holder 54 is clamped, S5 is at a lower position than S1. Figure 2F In the Figure 6 In the state of (a) and (b), it is assumed that the workpiece not shown is clamped and the claw portion 54 has moved slightly. Therefore, the claw portion 54 is different from Figure 7 As in (a) and (b), it is not closed.

[0029] GF shows that the workpiece is not clamped, i.e. Figure 7 (a) and (b) show the action when the claw 54 moves greatly. Figure 3A As shown, Figure 2FIn comparison, the pulling amount of the pulling stud 55 is larger, so the first pull rod 8 is arranged at the S6 position which is upward from S4 ( Figure 3B status). On the contrary, when the chuck holder 51 is removed from the state where the chuck holder 51 is installed on the spindle device 2, the control is reversed to the above: the spacer 17 is moved forward (downward) and reaches A. from F. (G.) in sequence. In the above, in order to explain each stage of movement, the first tie rod 8 and the second tie rod 9 are shown to move separately, but since the movement of the spacer 17, the release of the force of the first disc spring assembly 10 and the second disc spring assembly 11, etc. are all instantaneous, the movement of the first clamping mechanism and the second clamping mechanism when the chuck holder 51 is actually installed is performed almost simultaneously.

[0030] With the above-described structure, the spindle unit 1 according to the first embodiment can achieve the following effects. (1) In order to clamp the chuck holder 51 having a double-layer clamped portion having an inner side and an outer side (and a front and a rear side), the clamping can be performed by driving only one cylinder device 6 as a pushing unit. Since this can be achieved by only one cylinder device 6, the spindle unit 1 and the spindle device 2 can be miniaturized and lightweight. (2) Since the mechanism is such that the second tie rod 9 is actuated via the first tie rod 8 only by the advance and retreat of the pad 17 connected to the piston rod 21, and the first tie rod 8 advances and retreats via the first disc spring assembly 10, and the second tie rod 9 advances and retreats via the second disc spring assembly 11, the structure is simple and failure is not likely to occur. (3) The pull stud 55 of the chuck holder 51 can be clamped by the first clamping mechanism and pulled upward (rearward) only by the biasing force of the first disc spring assembly 10 , thereby contributing to the miniaturization and weight reduction of the spindle device 2 . (4) Since the first tie rod 8 and the second tie rod 9 are arranged in series and partially overlap each other, the overall length and overall width of the spindle device 2 can be reduced in size. (5) During the clamping action, the mounting portion 53 of the chuck holder 51 is first clamped by the second clamping mechanism of the second pull rod 9, and then the traction stud 55 of the chuck holder 51 is clamped by the first clamping mechanism of the first pull rod 8. The clamping actions are performed with a time difference. Therefore, the chuck holder 51 can be reliably fixed to the holder mounting hole 19, and it is not easy to cause erroneous clamping of the traction stud 55, such as the traction stud 55 moving or vibrating and the second ball 34 not being clamped at the specified position. (6) Since the spacer 17 retreats and does not come into contact with the first drawbar 8 when the chuck holder 51 is clamped, it does not become a load on the cylinder device 6 when the spindle device 2 is subsequently rotated, thereby reducing energy consumption and rotation unevenness during rotation. (7) Since the spindle device 2 does not become a load on the cylinder device 6 and can rotate at high speed, it is not only suitable for processing by, for example, a CNC machine tool but also suitable for processing by a machining center, and a machine tool that can be arbitrarily converted and has no restrictions can be provided.

[0031] <Implementation Method 2> Embodiment 2 is a modification of Embodiment 1 and is an example in which the motor device 15 and the pulleys 12 and 13 are not used as the spindle rotating mechanism 5 for rotating the spindle device 2. In addition, it is an example in which the spacer 17 is not used as an element for pushing the first tie rod 8. For components having the same functions as those in Embodiment 1, the same symbols are used and their detailed description is omitted. like Figure 8 As shown, the spindle unit 71 of the second embodiment includes a spindle motor device, not shown, as a spindle rotation mechanism, and a coupling 72 connected to the spindle motor device is directly connected to the spindle cylinder 7 of the spindle device 2. In this way, the rotational force from the coupling 72 is transmitted to the spindle device 2. A cylinder device 73 is arranged at the upper position of the spindle unit 71 in a manner of surrounding the spindle cylinder 7. The cylinder device 73 is fixed to the side of the housing 3 and is formed as a non-rotating part. In the cylinder device 73, a piston 74 as a pushing unit is arranged in a manner of being able to move forward and backward in the vertical direction. The piston 74 includes a first port 75 and a second port 76 for introducing the working oil supplied by a hydraulic pump, not shown, which is formed on the side of the cylinder device 73. The piston 74 slides in the vertical direction according to the supply of working oil from the hydraulic pump device to the cylinder device 73. A pressing pin 78 is connected to the upper end of the first tie rod 8 so as to be perpendicular to the axial direction of the first tie rod 8. Slide blocks 79 are fixed to both ends of the pressing pin 78.

[0032] In the above-mentioned structure, the upper surface of the slider 79 is pressed against the bottom surface of the piston 74, so that the first tie rod 8 moves downward against the force of the first disc spring assembly 10 through the pressing pin 78. At the stage where the first disc spring assembly 10 is maximally compressed by the piston 74 or the force generated by the compression is greater than the force of the second disc spring assembly 11, the second tie rod 9 is pressed downward by the first tie rod 8 that moves maximally downward. Then, after the chuck holder 51 is stored in the holder mounting hole, the hydraulic pressure of the cylinder device 73 is controlled to make the piston 74 rise and disengage from the slider 79, so that the first clamping mechanism and the second clamping mechanism can be operated with a time difference. In the above-mentioned spindle unit 71, the same effect as the spindle unit 1 of the above-mentioned embodiment 1 can also be achieved.

[0033] <Implementation Method 3> The third embodiment is an example in which the spindle device 2 is applied to a balancing machine instead of an automatic tool changer. Components having the same functions as those in the first embodiment are given the same reference numerals and detailed description thereof is omitted. like Fig.10 As shown in the description, the main component constituting the balancing machine 80, that is, the spindle device 2, is placed on the base 81 in a manner that is different from the above-mentioned embodiments 1 and 2 and is reversed from top to bottom. The cylinder device 6 and the cushion block 17 that push the first pull rod 8 are arranged below the base 81. The motor device 15, the pulleys 12, 13 and the transmission belt 14 are accommodated in the base 81. A vibration sensor 82 for detecting the vibration of the spindle device 2 is arranged on the base 81. A rotary encoder 83 is provided on the output shaft 15a of the motor device 15, and the rotation position of the spindle device 2 is detected. A first measuring device 84 for measuring the balance of the chuck holder 51 installed on the spindle device 2 is installed. A second measuring device 85 for measuring the balance of the product is installed at the upper position of the first measuring device 84. The balancing machine 80 of the above-mentioned structure calculates and computes the position where the unbalanced state (not shown) occurs based on the information of the vibration sensor 82 and the rotary encoder 83 through a computer device. Then, the balance of the chuck holder 51 is obtained by reducing the position (or conversely loading the weight). At this time, if the spindle device 2 is used, it is suitable as a balancing machine 80 that can easily install and remove the chuck holder 51 and can reduce the uneven rotation of the spindle device 2.

[0034] The above-mentioned embodiments are only recorded as specific embodiments for illustrating the principle and concept of the present invention. That is, the present invention is not limited to the above-mentioned embodiments. The present invention can also be embodied as, for example, the following modified forms. In the above embodiment, the chuck holder 51 having a chuck function is used as an example to be clamped, but other holders may be installed in the spindle device 2. For example, Fig. 9 As shown in (a) and (b) of the drawings, a tool holder 60 may also be used. The tool holder 60 includes a holder body 61 and a mounting portion 62. The base of a tool not shown is fixed to a mounting hole 61a in the holder body 61. A stud 63 protrudes from the rear end of the mounting portion 62. The stud 63 is a structure that does not move forward or backward. A protruding portion 64 of a roughly ellipsoidal shape that protrudes outward as a snap-fitting portion is integrally formed at the front end of the stud 63. A flange portion 65 that protrudes outward in a circular plate shape as a snap-fitting portion is integrally formed at the front end of the mounting portion 62. A reduced diameter portion 69 that serves as a snap-fitting portion is formed between the mounting portion 62 adjacent to the flange portion 65 and the flange portion 65. In the above-mentioned tool holder 60, the shapes of the mounting portion 62 and the stud 63 are configured to be the same as the mounting portion 53 of the chuck holder 51 and the traction stud 55 in a state that does not move forward or backward. Since such a tool holder 60 can also be mounted on the spindle device 2 at two clamped positions as described above, the tool holder 60 can be firmly mounted on the spindle device 2 from the inside and outside and from the front and back.

[0035] The cylinder devices 6, 73 may be either hydraulic or pneumatic. Other spring devices may be used as a mechanism or device for urging the first tie rod 8 and the second tie rod 9. In addition, a cylinder device may be used as the urging device. As the motor device 15, a multi-phase AC, for example, a six-phase AC servo motor may be used, or other motors or a DC motor device may be used instead of an AC motor. In the above, the first ball 32 and the second ball 34 are used as an example as the interference body of the clamping mechanism that advances and retreats in the radial direction. Alternatively, a clamping mechanism that is provided with a chuck or a split claw and advances and retreats while shaking in the radial direction may be used. The present invention is not limited to the structures described in the above-mentioned embodiments. The constituent elements of the above-mentioned embodiments and variants may be arbitrarily selected and combined. In addition, any constituent element of each embodiment and variant and any constituent element described in the solution of the present invention or any constituent element described in the solution embodying the present invention may be arbitrarily combined. For the above-mentioned combination, it is also hoped that these rights can be obtained by modifying the present application or applying for a divisional application. In addition, it is also hoped that these rights can be obtained by changing the application to an appearance application, thereby obtaining the overall appearance or partial appearance. The drawings depict the entire device with solid lines, but the drawings include not only the overall appearance, but also the partial appearance of the local parts of the relevant device. For example, the drawings include certain parts of the device as partial appearance, and certain parts of the device as partial appearance that are not related to the components. The local part of the device can also be a local component of the device, or a part of the component. Explanation of symbols

[0036] 2...spindle device, 6...cylinder device as a pushing unit, 8...first pull rod, 9...second pull rod, 10...disc spring assembly as a first force applying unit, 11...disc spring assembly as a second force applying unit, 51...chuck holder as a retaining member, 60...tool holder as a retaining member, 56...a raised portion as a first clamped portion, 58...a reduced diameter portion as a second clamped portion, 73...cylinder device as a pushing unit.

Claims

1. A spindle device, which is used by mounting a holder for a tool or a workpiece on the front end of the spindle, wherein the holder has a first clamped portion and a second clamped portion arranged in double layers on the inner side and the outer side at its base side, wherein the spindle device is characterized in that: The first pull rod and the second pull rod are provided, wherein the first pull rod has a first clamping mechanism at the front end side for clamping the first clamped portion of the holder, and the second pull rod has a second clamping mechanism at the front end side for clamping the second clamped portion of the holder, and the first pull rod and the second pull rod are arranged in series in the main shaft tube so as to be able to move forward and backward. The first pull rod is configured to be pressed in the forward direction by the pushing unit, thereby resisting the force generated by the first force applying unit and moving forward, and the second pull rod is configured to be directly or indirectly pushed by the first pull rod as the first pull rod moves forward, thereby resisting the force generated by the second force applying unit and moving forward, The first tie rod advanced by the pushing unit is released from the first clamping mechanism at a predetermined advancing and retreating position, and the second clamping mechanism of the second tie rod pushed by the first tie rod is also released. As the pressing force generated by the pushing unit is released, the first pull rod and the second pull rod in the specified advance and retreat positions are retreated toward the base of the main shaft cylinder by the forces of the first force applying unit and the second force applying unit, respectively, and the first clamping mechanism of the first pull rod and the second clamping mechanism of the second pull rod are activated.

2. The spindle device according to claim 1, characterized in that: The pushing unit retreats to a position not in contact with the first pull rod when the first pull rod is not pressed.

3. The spindle device according to claim 1 or 2, characterized in that: The force obtained when the second force applying unit applies force is greater than the force obtained when the first force applying unit applies force.

4. The spindle device according to claim 1 or 2, characterized in that: When the first tie rod retreats from the predetermined advance / retract position, the first clamping mechanism of the first tie rod is actuated after the second clamping mechanism of the second tie rod is actuated.

5. The spindle device according to claim 1 or 2, characterized in that: The first tie rod includes an outer peripheral surface that contacts the inner peripheral surface of the second tie rod, and is guided by the inner peripheral surface and the outer peripheral surface to slide forward and backward.

6. The spindle device according to claim 1 or 2, characterized in that: The first clamp mechanism and the second clamp mechanism are arranged at positions offset from each other in the front-rear direction.

7. The spindle device according to claim 1 or 2, characterized in that: The first clamping mechanism has an interference body that advances and retreats radially of the main shaft. When the first pull rod is arranged in the first advance and retreat position, the interference body that clamps the first clamped part is located facing the storage part formed on the inner circumferential surface of the second pull rod, so that the first clamping mechanism is released.

8. The spindle device according to claim 8, characterized in that: The second clamping mechanism has an interference body that advances and retreats radially of the main shaft. When the first pull rod is arranged in the first advance and retreat position, the interference body that clamps the second clamped part is located facing the storage part formed on the inner circumferential surface of the main shaft tube, so that the second clamping mechanism is released.

9. The spindle device according to claim 1 or 2, characterized in that: The retainer is mounted in a retainer mounting hole formed at the front end of the spindle cylinder.

10. The spindle device according to claim 1 or 2, characterized in that: The retaining member for the workpiece is constructed as follows: the first clamped portion is formed by a rod member that can move forward and backward, and when the second clamping mechanism applies action to the retaining member installed on the front end of the spindle, the rod member is pulled out through the first clamped portion, so that the workpiece in a loose state is clamped, and the first pull rod is advanced, so that the rod member is pushed back and the workpiece in a clamped state is loosened.

11. The spindle device according to claim 1 or 2, characterized in that: The first force applying unit and the second force applying unit are compression spring devices, and apply force to the first pull rod and the second pull rod in a backward direction.

12. A machine tool, characterized in that: The main spindle device according to claim 1 or 2 is mounted thereon.

13. A balancing machine, characterized in that: The main spindle device according to claim 1 or 2 is mounted thereon.

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