JP4194931B2 - Spindle tool fixing device - Google Patents

Description

  The present invention relates to a tool fixing device provided with a gas spring for fixing a tool or a tool holder to a spindle of a machine tool.

  Conventionally, many spindle tool fixing devices include a collet capable of gripping a base end portion of a tool or a tool holder attached to a distal end portion of the spindle, a draw bar disposed inside the spindle, and the draw bar and the collet. , A first drive means for driving the draw bar toward the main shaft base end side, and a second drive means for driving the draw bar toward the front end side of the main shaft. The collet can be switched between a non-operating position where the tip is widened and an operating position which is slightly closer to the main shaft proximal side than the non-operating position and the tip is depressed, and the collet is located in the non-operating position. In this state, the tool or the tool holder is attached to and detached from the tip portion of the main shaft.

  When the draw bar is driven to the main shaft base end side by the first driving means with the tool or the tool holder attached to the front end portion of the main shaft, the collet is switched to the operating position via the coupling mechanism. The collet grips the base end portion of the tool or tool holder and pulls it toward the main shaft base end side, and the tool or tool holder is firmly pressed and fixed to the tool holding portion of the main shaft. On the other hand, when the draw bar is driven to the main shaft tip side by the second driving means from this state, the collet is switched to the non-operating position via the coupling mechanism, and the tool or the tool holder is released from the main shaft.

  By the way, as the first driving means, conventionally, a spring member such as a disc spring that urges the draw bar toward the main shaft proximal side is well known. However, due to manufacturing errors and deterioration of the spring member, there is a problem that it is difficult to urge the draw bar with a stable and strong spring force. Therefore, the applicant of the present application uses a gas spring as the first driving means. An applied tool fixing device has been proposed and put into practical use (Patent Documents 1 to 3, etc.).

  In the tool fixing device of Patent Document 1, a gas spring is provided at the base end side portion of the main shaft. More specifically, a gas working chamber in which a base end-open cylindrical hole is formed inside the base end side portion of the main shaft, a piston is mounted in the cylindrical hole, and compressed gas is accommodated in the main end of the main shaft of the piston in the cylindrical hole. The lid member is attached to the base end portion of the main shaft, and the cylindrical hole is closed. The piston is integrally formed with a cylindrical portion that extends in the axial direction of the main shaft, and both end portions of the cylindrical portion are slidably fitted into the main shaft and the lid member, and the piston and the cylindrical portion are fixed with a draw bar passing therethrough. Has been.

In the tool fixing device disclosed in Patent Document 2, a gas spring including a cylinder member, a piston, and a gas working chamber is incorporated into a cylindrical hole formed in a base end open shape inside a base end side portion of the main shaft. And the draw bar is fixed in a state of penetrating through the cylindrical portion.
In the tool fixing device of Patent Document 3, a cylinder member, a piston, and a gas spring including a gas working chamber are all disposed outside the base end of the main shaft and fixed to the main shaft, and a draw bar is formed on a cylindrical portion integral with the piston and piston. Is fixed in a penetrating state.

Japanese Patent Laid-Open No. 2000-5907 JP 2001-246507 A JP 2001-87910 A

  When a gas spring that urges the draw bar toward the main shaft base end is applied to the tool fixing device for the main shaft, if a gas leak occurs from the gas working chamber, the gas pressure in the gas working chamber decreases, and the draw bar moves to the main shaft base side. The urging force that urges to decreases. Although the gas working chamber can be filled with compressed gas, it is difficult to frequently perform the gas filling operation. However, there is no way to gradually cause a gas leak from the gas working chamber. Therefore, it is necessary to minimize the decrease in the gas pressure (biasing force to the draw bar) in the gas working chamber when a gas leak occurs from the gas working chamber. For this purpose, the volume of the gas working chamber should be as large as possible. do it.

  However, as in Patent Document 1, when the gas spring is provided inside the main shaft, the size of the gas spring is restricted by the size (length / thickness) of the main shaft and the internal configuration, and a piston is installed in the main shaft. Therefore, there is a limit to increasing the gas working chamber to suppress a decrease in gas pressure when the gas leakage occurs. As in Patent Document 2, when a gas spring is incorporated in the main shaft, the gas working chamber is made larger than in Patent Document 1 to suppress a decrease in gas pressure when the gas leakage occurs. Is difficult.

  Further, as in Patent Documents 1 and 2, since the piston is disposed inside the main shaft, the piston diameter, that is, the pressure receiving area is limited by the size (diameter) of the main shaft, and the piston pressure receiving area is also increased. There is a limit. Therefore, if the gas pressure in the gas working chamber is increased to generate a predetermined large urging force for urging the draw bar, gas leakage is likely to occur from the gas working chamber, and compressed gas filling work into the gas working chamber is also possible. Will also be difficult.

  In the tool fixing device disclosed in Patent Document 3, it is difficult to increase the volume of the gas working chamber because the entire gas spring is disposed outside the base end of the main shaft and fixed to the main shaft. Further, the main shaft is not effectively used for disposing the gas spring. As a result, the length of the main shaft can be shortened, but it is very difficult because the gas spring, which is considerably large and heavy, needs to be firmly and accurately assembled to the main shaft rotating at high speed.

An object of the present invention is to increase the volume of a gas working chamber and a gas storage chamber (including both of them, appropriately referred to as a gas chamber) for storing a compressed gas of a gas spring in a tool fixing device for a spindle, The gas pressure in the gas working chamber (the urging force to the draw bar) should be kept as small as possible when the gas leaks from the chamber, and the pressure receiving area of the piston is increased to reduce the gas pressure of the compressed gas in the gas working chamber. It made lower than conventionally, Rukoto to generate a predetermined large urging force of urging the draw bar, to prevent as much as possible gas leakage from the gas chamber, to simplify the compressed gas filling work into the gas chamber, Etc.

A tool fixing device for a spindle according to claim 1 is a collet capable of gripping a base end portion of a tool or a tool holder attached to a tip portion of a spindle of a machine tool, a draw bar disposed inside the spindle, and the draw bar In the main body tool fixing device, the gas spring is a cylinder projecting outside the base end of the main shaft. The main body tool fixing device includes a coupling mechanism that interlocks the collet and the collet, and a gas spring that pulls and biases the draw bar toward the main shaft base end. A cylinder main body having a member fixed to the main shaft, a piston mounted inside the cylinder main body and integrally connected to the draw bar, and formed on the main shaft side with respect to the piston in the cylinder member; The gas working chamber accommodated, the gas accommodating chamber formed inside the proximal end portion of the main shaft and containing compressed gas, and the gas working chamber and the gas accommodating chamber are connected to each other. And a communicating passage which is characterized in that encapsulating the oil to obtain a sealing function to the gas storage chamber.

  In this tool fixing device, for example, the collet is composed of a plurality of collet divided bodies, a non-operating position where the tip is widened, and an operating position where the tip is narrowed slightly closer to the main shaft base end side than the non-operating position. It is supported by the main shaft so that it can be switched over. A tool or a tool holder is attached to and detached from the tip portion of the spindle while the draw bar is driven toward the tip of the spindle and the collet is in the non-operating position.

  When the draw bar is pulled by the gas spring with the tool or tool holder attached to the tip of the spindle, the collet is switched to the operating position via the coupling mechanism. The base end portion of the tool or tool holder is gripped and pulled toward the main shaft base end side, and the tool or tool holder is strongly pressed and fixed to the tool holding portion of the main shaft. On the other hand, from this state, for example, when the draw bar is driven to the front end side of the main shaft by a hydraulic cylinder provided outside the main shaft, the collet is switched to the non-operating position via the coupling mechanism, and the tool or tool holder is moved. Unfixed from the spindle.

  In the gas spring, a cylinder body having a cylinder member protruding outside the base end of the main shaft is fixed to the main shaft, and a piston integrally connected to the draw bar is mounted inside the cylinder main body, and the piston in the cylinder member On the other hand, a gas working chamber is formed on the main shaft side (with respect to the piston in the cylinder member). Due to the gas pressure of the compressed gas accommodated in the gas working chamber, the draw bar is urged together with the piston toward the main shaft base end side.

In addition to the gas working chamber in the piston member, a gas containing chamber containing compressed gas is formed in the proximal end portion of the main shaft, and the gas working chamber and the gas containing chamber are communicated with each other by a communication passage. . Therefore, the overall volume of the gas working chamber and the gas storage chamber of the gas spring can be increased without substantially being restricted by the size (length / thickness) of the main shaft and the internal configuration. By increasing the diameter, that is, the diameter of the piston, the pressure receiving area of the piston on which the gas pressure of the compressed gas in the gas working chamber acts can be increased. In addition, oil for obtaining a sealing function can be sealed in the gas storage chamber to prevent gas leakage from the gas storage chamber as much as possible.

  According to a second aspect of the present invention, there is provided the main shaft tool fixing device according to the first aspect, wherein the piston is integrally formed with the draw bar, and the base end portion of the draw bar protrudes from the cylinder body to the opposite side of the main shaft. It is. Since the piston is integrally formed with the draw bar, the number of parts is reduced and the configuration is simplified. Since the base end portion of the draw bar protrudes from the cylinder main body to the opposite side of the main shaft, the draw bar can be driven to the main shaft front end side by pushing the base end portion of the draw bar to the main shaft front end side.

  According to a third aspect of the present invention, there is provided the tool fixing device for the main shaft according to the first or second aspect of the invention, wherein the gas storage chamber is formed by a large portion of a cylindrical hole formed in a base end open shape inside the base end side portion of the main shaft. An annular member for partitioning the distal end side end of the gas storage chamber is attached to the distal end side of the cylindrical hole at the distal end side of the cylindrical hole, and an annular member integral with the cylinder body is attached to the proximal end portion of the cylindrical hole. The partition member is mounted.

  Since the gas storage chamber is formed by a large portion of the cylindrical hole formed in the base end open portion inside the base end side portion of the main shaft, the gas storage chamber is simply configured. An annular member for partitioning the distal end of the gas storage chamber is attached to the inner end of the cylindrical hole on the distal end side, and an annular partition member integral with the cylinder body is attached to the proximal end of the cylindrical hole. A gas storage chamber is formed between the annular member and the annular partition member in the hole. Since the annular partition member is integral with the cylinder body, the cylinder body is fixed to the main shaft by mounting the annular partition member on the proximal end portion of the cylindrical hole.

According to a fourth aspect of the present invention, there is provided the tool fixing device for the main shaft according to any one of the first to third aspects, wherein the cylinder member of the cylinder body has an outer diameter equal to or larger than the outer diameter of the main shaft. It has a volume at least 5 times the volume of the gas working chamber. Since the cylinder member of the cylinder body has an outer diameter that is equal to or greater than the outer diameter of the main shaft, the pressure receiving area of the piston on which the gas pressure of the compressed gas acts in the gas working chamber is larger than that of the main shaft equipped with a piston. . Gas storage chamber, for example, since at least 5 times the volume of the volume of the gas actuating chamber, that Ki out to increase the overall volume of the gas chamber.

  According to a fifth aspect of the present invention, there is provided the tool fixing device for the main shaft according to any one of the first to fourth aspects, wherein a gas filling passage for filling the gas storage chamber with the compressed gas is formed on the main shaft. It is. A gas filling passage is simply constructed.

A tool fixing device for a main shaft according to claim 6 is the hydraulic cylinder according to any one of the first to fifth aspects, wherein the base end portion of the draw bar is pressed and driven to the front end side of the main shaft when releasing the bias by the gas spring. Is provided. The base end portion of the draw bar is pressed and driven to the tip end side of the main shaft by the hydraulic cylinder, and the bias to the draw bar by the gas spring is released, so that the tool or the tool holder fixed to the main shaft can be released from the main shaft.

According to the tool fixing device of the main shaft of claim 1, the base end portion of the tool or tool holder attached to the front end portion of the main shaft of the machine tool is obtained by pulling and biasing the draw bar toward the main shaft base end side by the gas spring. It can be gripped by a collet, and the tool or tool holder can be pulled toward the base end side of the main shaft and firmly pressed and fixed to the tool holding portion of the main shaft. In the gas spring, a cylinder body having a cylinder member protruding outside the base end of the main shaft is fixed to the main shaft, and separately from the gas working chamber in the piston member, a gas storage chamber is formed in the base end side portion of the main shaft, Since these gas working chambers and gas storage chambers are connected by a communication passage, the gas working chamber and the gas storage chamber (including both of them) are hardly affected by the size (length / thickness) of the main shaft and the internal configuration. As a result, the overall volume of the gas chamber can be increased as appropriate, so that the gas pressure in the gas working chamber (the urging force to the draw bar) can be reduced as much as possible when a gas leak from the gas chamber occurs. It can be kept small. Further, since the cylinder member is provided so as to protrude outside the base end of the main shaft, the diameter of the cylinder member, that is, the diameter of the piston is increased, and the pressure receiving area of the piston on which the gas pressure of the compressed gas in the gas working chamber acts Thus, the gas pressure of the compressed gas in the gas working chamber can be made lower than before, and a predetermined large urging force for urging the draw bar can be generated, and the gas from the gas working chamber can be generated. Leakage can be prevented as much as possible, and compressed gas filling work into the gas chamber can be simplified. Moreover, since the oil for obtaining the sealing function is enclosed in the gas storage chamber, gas leakage from the gas storage chamber can be prevented as much as possible.

  According to the tool fixing device for the main shaft according to claim 2, since the piston is integrally formed with the draw bar, the number of parts can be reduced and the configuration can be simplified, and the base end portion of the draw bar is opposite to the main shaft from the cylinder body. The base of the draw bar is pushed toward the tip of the spindle, the draw bar is driven toward the tip of the spindle, the collet is switched to the non-operation position, and the tool or tool holder is attached to or detached from the tip of the spindle. Can do.

  According to the tool fixing device for a main shaft of claim 3, the gas storage chamber is formed by a large part of the cylindrical hole formed in the base end open shape inside the base end side portion of the main shaft. An annular member for partitioning the distal end of the gas storage chamber can be easily installed at the distal end of the cylindrical hole, and an annular partition integral with the cylinder body can be installed at the proximal end of the cylindrical hole. Since the member is mounted, the gas storage chamber can be reliably formed between the annular member and the annular partition member in the cylindrical hole. Since the annular partition member is integrated with the cylinder body, the cylinder body can be fixed to the main shaft by attaching the annular partition member to the base end portion of the cylindrical hole, and the overall number of parts is reduced. Can be simplified.

  According to the main shaft tool fixing device of claim 4, the cylinder member of the cylinder body has an outer diameter equal to or larger than the outer diameter of the main shaft, so that the compressed gas in the gas working chamber is compared with the one in which the piston is mounted inside the main shaft. The pressure receiving area of the piston on which the gas pressure acts can be increased, and the gas storage chamber has a volume that is at least five times the volume of the gas working chamber, so that the overall volume of the gas chamber can be increased. Therefore, since the volume of the gas working chamber can be reduced, the cylinder body can be reduced in size.

  According to the tool fixing device of the main shaft of claim 5, since the gas filling passage for filling the gas storage chamber with the compressed gas is formed in the main shaft, the gas storage chamber can be easily and surely filled with the compressed gas. Also, the gas filling passage can be configured simply.

According to the spindle tool fixing device of the sixth aspect of the present invention, the hydraulic cylinder that pushes and drives the base end portion of the draw bar toward the tip end side of the main shaft when releasing the bias by the gas spring is provided. It is possible to reliably press and drive the end portion toward the front end side of the main shaft to release the bias to the draw bar by the gas spring, and to reliably release the tool or the tool holder fixed to the main shaft from the main shaft.

  The spindle tool fixing device of the present embodiment includes a collet that can grip a base end portion of a tool or a tool holder that is attached to a tip portion of a spindle of a machine tool, a draw bar disposed inside the spindle, and the draw bar. And a collet, and a gas spring that pulls and urges the draw bar toward the main shaft base end. The gas spring has a cylinder member that protrudes outside the base end of the main shaft. A cylinder body fixed to the main shaft, a piston mounted inside the cylinder main body and integrally connected to the draw bar, and a gas working chamber formed on the main shaft side with respect to the piston in the cylinder member and containing compressed gas And a gas storage chamber that is formed inside the base end side portion of the main shaft and that stores compressed gas, and a communication passage that communicates the gas working chamber and the gas storage chamber.

  As shown in FIG. 1, a spindle unit 1 of a machine tool includes a spindle 2, a housing 3 on which a drive motor (not shown) that rotates the spindle 2 is mounted, and a tool holder 5 that holds a tool 5a on the spindle 2. And a tool fixing device 4 for fixing the tool so as to be unlockable. In addition, the lower part of FIG. 1 is demonstrated as a downward direction. The main shaft 2 is arranged in the vertical direction, and the distal end side is the lower side and the proximal end side is the upper side.

  A tapered holder holding portion 2a whose diameter increases toward the distal end side is formed at the distal end portion of the main shaft 2, and a tapered shank portion formed on the proximal end portion of the tool holder 5 is formed on the holder holding portion 2a. 5b is engaged. In this spindle unit 1, the tool holders 5 of a plurality of exchangeable spindles 5a have the same configuration. The main shaft 2 is inserted in the housing 3 so that the tip side portion of the main shaft 2 is rotatably supported by the housing 3 via a bearing (not shown), and the base end side portion of the main shaft 2 is integrated with the housing 3 or A separate support member 10 is rotatably supported via bearings 11 and 12.

  Inside the main shaft 2, the holder holding part 2 a and the accommodation hole 2 b connected to the upper end of the holder holding part 2 a are formed in series. The tool holder 5 includes the shank portion 5b, a small diameter shaft portion 5c and an engaged portion 5d formed at the proximal end portion of the shank portion 5b, and an automatic tool formed at the distal end side of the shank portion 5b. A large-diameter gripping part 5e is gripped by an exchange device (not shown). When the tool holder 5 is attached to the tip end portion of the main shaft 2, the shank portion 5b engages with the holder holding portion 2a in a substantially close contact state, and the engaged portion 5d enters the accommodation hole 2b. The collet 20 accommodated in the accommodation hole 2b can grip the joint portion 5d.

The tool fixing device 4 will be described.
As shown in FIGS. 1 to 4, the tool fixing device 4 includes a collet 20 capable of gripping an engaged portion 5 d at a base end portion of a tool holder 5 attached to a distal end portion of the main shaft 2, and the inside of the main shaft 2. , A connecting mechanism 22 that interlocks and connects the draw bar 21 and the collet 20, a gas spring 23 that pulls and urges the draw bar 21 toward the main shaft base end (upper side), and the draw bar 21 at the front end of the main shaft. And a hydraulic cylinder 24 that is pressed to the side (lower side).

  Here, the accommodation hole 2a formed in the main shaft 2 is formed in a substantially lower half of the main shaft 2 on the upper side of the holder holding portion 2a. Further, the main shaft 2 is formed with a partition mounting hole 2c that is continuous with the upper end of the accommodation hole 2a, and a cylindrical hole 2d that is continuous with the upper end of the partition mounting hole 2c. The cylindrical hole 2d is a hole formed in the base end side portion of the main shaft 2 so as to be open to the base end, and the main shaft 2 has, in order from the lower end, a holder holding portion 2a, an accommodation hole 2b, a partition mounting hole 2c, Cylindrical holes 2d are formed in series and vertically through the main shaft 2.

  As shown in FIGS. 1 to 3, the collet 20 is disposed at the inner lower portion of the cylindrical member 15 fixedly mounted in the accommodation hole 2b, and has a non-operating position (see FIG. 3) with its tip widened. It is supported by the cylindrical member 15 so as to be switchable over an operating position (see FIG. 2) that is slightly above the non-operating position and has its tip narrowed. The collet 20 includes a plurality of collet divided bodies 30 arranged side by side in the circumferential direction. For example, four collet divided bodies 30 are arranged at equal intervals in the circumferential direction.

  Each collet divided body 30 has a substantially arc-shaped cross section, and at the tip of the collet divided body 30 is a gripping part that protrudes radially inward and can be engaged with the engaged part 5d of the tool holder 5 from below. 30a and a protruding portion 30b protruding outward in the radial direction are formed. An inner overhang 30c projecting radially inward and an outer overhang 30d projecting radially outward are formed at the base end of the collet split body 30, and the lower inner surface of the inner overhang 30c A first inclined surface 41 having an arc-shaped cross section that increases in diameter toward the side is formed, and a second inclined surface 42 having an arc-shaped cross section that decreases in diameter toward the lower side is formed on the lower outer surface of the outer projecting portion 30d. Yes.

A small diameter portion 21c at the tip of the draw bar 21 is disposed on the inner side of the collet 20, and a lower portion of the cylindrical member 15 is disposed on the outer side. The small diameter portion 21c has an inner side corresponding to each collet divided body 30. A third inclined surface 43 having an arcuate cross-section that is increased in diameter toward the lower side where the first inclined surface 41 of the overhanging portion 30c can be engaged in surface contact is formed, and a radial direction is formed on the inner surface of the cylindrical member 15. A recess 15a that is recessed outwardly and engageable with the outer overhanging portion 30d is formed, and a lower side that can engage with the second inclined surface 42 of the outer overhanging portion 30d in a surface contact manner is formed at the lower end of the recess 15a. A fourth inclined surface 44 having a circular arc cross-section with a smaller diameter is formed. In addition, the 1st-4th inclined surfaces 41-44 are contained in the below-mentioned force increase mechanism 40. As shown in FIG.

  As shown in FIGS. 1 to 3, the draw bar 21 is disposed in the vertical direction so that its axis coincides with the axis of the main shaft 2, and most of the draw bar 21 is accommodated inside the main shaft 2. Is located inside the collet 20 inside the accommodation hole 2 b, and the base end portion protrudes toward the base end side of the main shaft 2. The draw bar 21 has a first draw bar member 21a at the distal end side portion and a second draw bar member 21b at the proximal end side portion, and a proximal end portion of the first draw bar member 21a inside the cylindrical member 15 (accommodating hole 2b). The leading end of the second draw bar member 21b is screwed and connected.

  The first draw bar member 21a includes a small-diameter portion 21c at the distal end portion and a large-diameter portion 21d at the proximal end portion. A tapered shaft portion 21e is formed at the central portion in the vertical direction of the small diameter portion 21c, and the third inclined surface 43 is formed on the outer surface of the tapered shaft portion 21e. The large-diameter portion 21d is slidably fitted into the upper portion of the concave portion 15a of the cylindrical member 15, and the large-diameter portion 21d is formed with a mounting hole 21f that is closed by the distal end portion of the second draw bar member 21b. .

  A piston member 35 having a passage 35a and a compression coil spring 36 that elastically urges the piston member 35 downward are attached to the attachment hole 21f. A through hole 21g is formed in the lower portion of the mounting hole 21f of the draw bar 21, and a pipe member 37 is slidably fitted into the through hole 21g, and an upper end portion of the pipe member 37 is screwed and connected to the piston member 35. The interior of the pipe member 37 communicates with the passage 35a. On the distal end side of the tube member 37, a flange portion 37a is formed on which the engaged portion 5d of the tool holder 35 can come into contact from below.

  The second draw bar member 21 b extends upward from the accommodation hole 2 b and penetrates the gas spring 23, and an upper end portion of the second draw bar member 21 b protrudes above the cylinder member 50 that protrudes outside the base end of the main shaft 2. ing. A passage 21h is formed in the second draw bar member 21b, and the cooling water supplied to the passage 21h is led out to the tool holder 5 side through the passage 21h, the mounting hole 21f, the passage 35a, and the inside of the pipe member 37. The

  As shown in FIGS. 1 to 3, the coupling mechanism 22 includes a concave portion 15 a formed in the cylindrical member 15 mounted in the accommodation hole 2 b, an inner overhang portion 30 c formed on the base end portion of the collet 20, and an outer side. It has a projecting portion 30d, a tapered shaft portion 21e formed on the small diameter portion 21c of the draw bar 21, and the like, and includes a force-intensifying mechanism 40 having these first to fourth inclined surfaces 41 to 44. The force-increasing mechanism 40 increases the urging force (driving force) that urges the draw bar 21 toward the main shaft proximal side by the gas spring 23 and transmits it to the collet 20, and the collet 20 is moved toward the main shaft proximal side by the strong force. It is configured to drive.

  In the coupling mechanism 22 including the force-increasing mechanism 40, as shown in FIG. 3, when the draw bar 21 is located at the lower limit position, the collet 20 is switched to the non-operating position. The outer projecting portion 30d is engaged with the lower inner surface of the concave portion 15a of the cylindrical member 15, and the projecting portion 30b of the tip end portion of the collet 20 is substantially engaged with the lower end portion of the cylindrical member 15 to the inner surface of the receiving hole 2b. In the approached state, the grip portion 30a at the distal end portion spreads, and the engaged portion 5d of the tool holder 5 can pass therethrough.

  From this state, when the draw bar 21 is driven to the main shaft proximal side by the urging force of the gas spring 23, first, the draw bar 21 is engaged by the engagement of the first inclined surface 41 of the collet 20 and the third inclined surface 43 of the draw bar 21. The collet 20 moves to the main shaft proximal end side. Thereafter, when the second inclined surface 42 of the collet 20 is engaged with the fourth inclined surface 44 of the cylindrical member 15, the collet 20 is switched to the operating position, and the force-increasing mechanism 40 functions.

  That is, as shown in FIG. 2, the outer projecting portion 30 d of the base end portion of the collet 20 engages with the concave portion 15 a of the cylindrical member 15, and the protruding portion 30 b of the distal end portion of the collet 20 is formed on the inner surface of the cylindrical member 15. In the engaged state, the grip portion 30 a at the tip is squeezed, and the engaged portion 5 d of the tool holder 5 is gripped. Then, due to the engagement between the first inclined surface 41 and the third inclined surface 43 and the engagement between the second inclined surface 42 and the fourth inclined surface 44, the tensile biasing force of the draw bar 21 by the gas spring 23 is increased. Is transmitted to the collet 20.

  As a result, the collet 20 is driven strongly toward the main shaft base end side, and the shank portion 5b of the tool holder 5 pulled by the collet 20 toward the main shaft base end side is strongly pressed against the holder holding portion 2a of the main shaft 2 to be in close contact therewith. The tool holder 5 is firmly fixed to the main shaft 2 by engaging with each other. From this state, when the draw bar 21 moves to the lower limit position, the collet 20 is switched to the inoperative position, and the tool holder 5 can be removed.

The gas spring 23 will be described in detail.
As shown in FIG. 1 and FIG. 4, the gas spring 23 includes a cylinder body 51 that has a cylinder member 50 that protrudes to the outside (upper side) of the main shaft 2, and is fixed to the main shaft 2. A piston 52 mounted and integrally connected to the draw bar 21, a gas working chamber 53 formed on the main shaft 2 side (lower side) with respect to the piston 52 in the cylinder member 50 and containing the compressed gas G, and a main shaft 2, a gas storage chamber 54 in which the compressed gas G is stored, and a communication passage 55 that communicates the gas working chamber 53 and the gas storage chamber 54.

  The gas storage chamber 54 is formed by a large portion of the cylindrical hole 2 d formed in the base end open portion inside the base end side portion of the main shaft 2. An annular member 56 for partitioning the distal end side end of the gas storage chamber 54 is attached to the distal end side (lower side) of the cylindrical hole 2d and attached to the proximal end portion (upper end portion) of the cylindrical hole 2d. Is provided with an annular partition member 57 integral with the cylinder body 51. In the present embodiment, the annular partition member 57 is formed integrally with the cylinder member 50.

  The annular member 56 is fitted into the central portion of the main shaft 2 in the longitudinal direction, and an O-ring 60 that seals between the main shaft 2 and the annular member 56 is attached to the annular member 56. An insertion hole 56a is formed in the annular member 56, and the draw bar 21 is inserted into the insertion hole 56a so as to be movable up and down. In the insertion hole 56 a, a cylindrical dry bearing 61, an annular rod seal 62 that seals between the draw bar 21 and the annular member 56, and an annular wiper 63 are attached to the annular member 56.

  The annular partition member 57 is screwed into the base end portion of the main shaft 2 so as to be fitted inside, and an O-ring 65 that seals between the main shaft 2 and the annular partition member 57 is attached to the annular partition member 57. An insertion hole 57a is formed in the annular partition member 57, and the draw bar 21 is inserted into the insertion hole 57a so as to be movable up and down. In the insertion hole 57a, a cylindrical dry bearing 66 and an annular wiper 67 are attached to the annular partition member 57. In the cylindrical hole 2 d, a portion surrounded by the main shaft 2, the annular member 56, the annular partition member 57, and the draw bar 21 is formed in the gas storage chamber 54. The gas storage chamber 54 is configured, for example, such that its vertical length A is about four times the diameter B.

  A gas filling passage 58 for filling the gas storage chamber 54 with the compressed gas G is formed in the main shaft 2. The gas filling passage 58 extends upward from the lower end of the main shaft 2 and is connected to the gas storage chamber 54 in the vicinity of the annular partition member 56. A check valve 59 is attached to the lower end portion of the gas filling passage 58, and a predetermined compressed gas filling device (not shown) is connected to the check valve 59 so that the gas storage chamber 54 is connected to the gas filling passage 58. Can be filled with the compressed gas G.

  In the gas storage chamber 54, oil L for obtaining a sealing function is sealed in the gas storage chamber 54. The oil L is sealed in an amount sufficient to fill at least the upper side of the hole of the gas filling passage 58 facing the gas storage chamber 54 when the rotation of the main shaft 2 is stopped, and the main shaft 2 and the annular member 56 are filled with the oil L. During this, the space between the annular member 56 and the draw bar 21 is reliably sealed, and the hole of the gas filling passage 58 facing the gas storage chamber 54 is securely sealed.

  The cylinder body 51 includes a cylinder member 50 having an outer diameter equal to or larger than the outer diameter of the main shaft 2 and a partition member 70 connected to the upper end portion of the cylinder member 50 by a plurality of bolts 70a. As described above, the cylinder body 2 is fixed to the main shaft 2 by mounting the annular partition member 57 integral with the cylinder main body 51 in the cylindrical hole 2 d of the main shaft 2. An insertion hole 70 a is formed in the partition member 70, and the draw bar 21 is inserted into the insertion hole 70 a so as to be movable up and down, and a base end portion of the draw bar 21 protrudes from the cylinder body 51 to the opposite side (upper side) from the main shaft 2. . An annular rod seal 71 that seals between the draw bar 21 and the partition member 70 is attached to the partition member 70.

  An annular piston seal 72 that seals between the cylinder member 50 and the piston 52 is attached to the piston 52. The gas working chamber 53 is formed in a portion surrounded by the cylinder body 51, the piston 52, and the draw bar 21 on the lower side of the piston 52. The gas working chamber 53 and the gas storage chamber 54 are provided in the annular partition member 57 and the cylinder body 51. A communication passage 55 that communicates with each other is formed. The communication passage 55 is composed of one or a plurality of passages oriented in the vertical direction.

  The gas working chamber 53 has a maximum vertical length C (vertical length when the piston 52 is located at the upper limit position) of about ½ of the diameter D, and the maximum vertical length C is the vertical length of the gas storage chamber 54. The diameter D is configured to be about 1/6 of the length A, and the diameter D is configured to be larger than the diameter of the gas storage chamber 54. In this way, the gas storage chamber 54 has, for example, a volume that is at least five times the volume of the gas working chamber 53, specifically about 5.1 times the volume.

  For example, the cylinder member 50 is formed with a hole 73a that allows the gas working chamber 53 to communicate with the outside, and a plug 73 is attached to the hole 73a. By loosening the plug 73, the compressed gas in the gas working chamber 53 is provided. G can be discharged to the outside. A breathing hole 74 is formed in the cylinder body 51 and the partition member 70, and a vent plug 75 is attached to the breathing hole 74.

  The hydraulic cylinder 24 is disposed in a downward posture on the upper side of the draw bar 21. The hydraulic cylinder 24 is connected to a hydraulic pressure supply device (not shown). When hydraulic pressure is supplied from the hydraulic pressure supply device, the piston rod 24a of the hydraulic cylinder 24 is driven to advance, and the piston rod 24a causes the draw bar to move. The base end portion of 21 is pressed and driven toward the distal end side of the main shaft, and the biasing force by the gas spring 23 is released.

Next, functions and effects of the tool fixing device 4 will be described.
The collet 20 is switched between a non-operating position where the tip is widened (see FIG. 3) and an operating position (see FIG. 2) where the tip is narrowed away from the non-actuated position. The tool holder 5 is attached to and detached from the tip portion of the spindle 2 in a state where the draw bar 21 is driven to the tip end side of the spindle by the hydraulic cylinder 24 and the collet 20 is located at the non-operation position.

  When the driving of the draw bar 21 by the hydraulic cylinder 24 is stopped in a state where the tool holder 5 is mounted on the tip portion of the main shaft 2, the draw bar 21 is pulled toward the main shaft base side by the gas spring 23, as shown in FIG. The collet 20 is switched to the operating position by the connecting mechanism 22, and the collet 20 grips the non-engaging portion 5 d of the tool holder 5 and pulls it toward the main shaft base end side. At this time, the driving force is increased by the force-increasing mechanism 40, and the collet 20 and the tool holder 5 are drawn by the strong driving force, and the tool holder 5 is strongly pressed and fixed to the main shaft 2.

  On the other hand, when the hydraulic cylinder 24 is driven from the state where the tool holder 5 is fixed to the main shaft 2, the draw bar 21 is driven to the front end side of the main shaft by the hydraulic cylinder 24, and the collet 20 is switched to the non-operating position. The tool holder 5 can be unlocked.

  In the gas spring 23, a cylinder main body 51 having a cylinder member 50 protruding outside the base end of the main shaft 2 is fixed to the main shaft 2, and a piston 52 integrally connected to the draw bar 21 is inside the cylinder main body 51. A gas working chamber 53 is formed on the main shaft 2 side with respect to the piston 52 in the cylinder member 50. The draw bar 21 is urged together with the piston 52 toward the proximal end of the main shaft by the gas pressure of the compressed gas G accommodated in the gas operation chamber 53.

  In this way, the draw bar 21 is pulled and urged toward the base end side of the main shaft by the gas spring 23, whereby the engaged portion 5d of the tool holder 5 attached to the tip portion of the main shaft 2 is gripped by the collet 20, and the tool holder 5 can be pulled in to the base end side of the main shaft, and can be firmly pressed and fixed to the tool holding portion 2a of the main shaft 2.

  In the gas spring 23, a cylinder body 51 having a cylinder member 50 protruding outside the base end of the main shaft 2 is fixed to the main shaft 2, and a base end side portion of the main shaft 2 is separated from the gas working chamber 53 in the piston member 50. Since the gas storage chamber 54 is formed and the gas working chamber 53 and the gas storage chamber 54 are communicated with each other through the communication passage 55, there is almost no restriction due to the size (length / thickness) of the main shaft 2 or the internal configuration. The volume of the gas chambers 53 and 54 of the gas working chamber 53 and the gas storage chamber 54 can be increased, so that gas leakage from the gas chambers 53 and 54 occurs in the gas working chamber 53. The decrease in gas pressure (the urging force to the draw bar 21) can be minimized.

  Further, since the cylinder member 50 is provided so as to protrude outside the base end of the main shaft 2, the diameter of the cylinder member 50, that is, the diameter of the piston 52 is increased, and the gas pressure of the compressed gas G in the gas working chamber 53 is increased. The pressure receiving area of the piston 52 on which the pressure acts can be increased, whereby the gas pressure of the compressed gas G in the gas working chamber 53 is made lower than before, and a predetermined large biasing force for biasing the draw bar 21 is obtained. It can be generated, gas leakage from the gas chambers 53 and 54 can be prevented as much as possible, and compressed gas filling work to the gas chambers 53 and 54 can be simplified.

  Since the piston 52 is integrally formed with the draw bar 21, the number of parts can be reduced and the configuration can be simplified. Since the base end portion of the draw bar 21 protrudes from the cylinder body 51 to the opposite side of the main shaft 2, the draw bar The tool holder 5 can be attached to and detached from the distal end portion of the spindle 2 by pushing the proximal end portion 21 toward the distal end side of the spindle, driving the draw bar 21 toward the distal end side of the spindle, and switching the collet 20 to the inoperative position.

  Since the gas storage chamber 54 is formed by a large portion of the cylindrical hole 2d formed in the base end open portion inside the base end side portion of the main shaft 2, the gas storage chamber 54 can be easily configured, and the cylinder An annular member 56 for partitioning the distal end side end of the gas storage chamber 54 is attached to the rear end portion on the distal end side of the hole 2d, and an annular partition member 57 integral with the cylinder body 51 is attached to the proximal end portion of the cylindrical hole 2d. Therefore, the gas storage chamber 54 can be reliably formed between the annular member 56 and the annular partition member 57 in the cylindrical hole 2d. Since the annular partition member 57 is integral with the cylinder body 51, the cylinder body 51 can be fixed to the main shaft 2 by attaching the annular partition member 57 to the proximal end portion of the cylindrical hole 2d. The configuration can be simplified by reducing the number of parts.

  Since the cylinder member 50 of the cylinder body 51 has an outer diameter equal to or larger than the outer diameter of the main shaft 2, the gas pressure of the compressed gas G in the gas working chamber 53 acts as compared with the main shaft 2 having a piston mounted therein. The pressure receiving area of the piston 52 can be increased, and the gas storage chamber 54 has, for example, a volume that is at least five times the volume of the gas working chamber 53. Therefore, the entire volume of the gas chambers 53, 54 is increased. Therefore, since the volume of the gas working chamber 53 can be reduced, the cylinder body 51 can be reduced in size.

  Since the gas filling passage 58 for filling the gas containing chamber 54 with the compressed gas G is formed in the main shaft 2, the gas containing chamber 54 can be filled with the compressed gas G easily and surely, and the gas filling passage 54 can be filled. 58 can also be configured easily. Since the oil L for obtaining the sealing function is sealed in the gas storage chamber 57, gas leakage from the gas storage chamber 54 can be prevented as much as possible. Since the hydraulic cylinder 24 is provided to push the base end portion of the draw bar 21 toward the main shaft tip side when releasing the urging by the gas spring 23, the hydraulic cylinder 24 ensures the base end portion of the draw bar 21 toward the main shaft tip side. The tool holder 5 fixed to the main shaft 2 can be reliably released from the main shaft 2 by releasing the urging of the gas spring 23 to the draw bar 21.

Next, modified examples in which various modifications are made to the above embodiment will be described. However, the same components as those in the above embodiment are given the same reference numerals and the description thereof is omitted as appropriate.
1] The number of the collet divided bodies 30 of the collet 20 is not limited to four, and may be appropriately changed according to various conditions such as the diameter of the main shaft 2 and the strength of the pulling force of the draw bar 21.
2] In the above embodiment, the tool holder 5 holding the tool 5a is gripped by the collet 20 and the tool 5a is fixed to the main shaft 2. However, the tool 5a is directly gripped by the collet 20. May be.

3] In the connecting mechanism 22 that interlocks and connects the draw bar 21 and the collet 20, and the force-increasing mechanism 40 included in the connecting mechanism 22, various configurations other than the configuration applied in the above embodiment may be applied.
4] The cylinder body 51 and the annular partition member 57 are formed as separate members.
The annular partition member 57 may be fixed and integrated.

5] The draw bar 21 and the piston 52 may be configured as separate members, and the draw bar 21 and the piston 52 may be integrally connected.
6] The cylindrical member 15 mounted in the accommodation hole 2b of the main shaft 2 may be omitted. In this case, a concave portion 15a, a fourth inclined surface 44, and the like are formed in the inner surface portion of the housing hole 2b of the main shaft.

7] Depending on the size (length and thickness) of the main shaft 2 and the internal configuration, the sizes of the gas working chamber 53 and the gas storage chamber 54 can be appropriately changed. For example, in the above-described embodiment, the gas storage chamber 54 has a volume that is at least five times the volume of the gas working chamber 35, but may have a volume that is less than five times. Further, the cylinder member 50 may have an outer diameter less than the outer diameter of the main shaft 2.
8] Other than the above, the present invention can be implemented with modifications other than the above modifications without departing from the spirit of the present invention.

It is a longitudinal cross-sectional view of the main shaft unit according to the embodiment of the present invention. It is a longitudinal cross-sectional view of the lower part of a spindle unit (tool fixed state). It is a longitudinal cross-sectional view of the lower part of a spindle unit (tool fixed release state). It is a longitudinal cross-sectional view of the gas spring of a spindle unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main shaft unit 2 Main shaft 2d Cylindrical hole 4 Tool fixing device 5 Tool holder 5a Tool 20 Collet 21 Draw bar 22 Connecting mechanism 23 Gas spring 24 Hydraulic cylinder 40 Booster mechanism 50 Cylinder member 51 Cylinder main body 52 Piston 53 Gas working chamber 54 Gas storage chamber 55 Communication passage 56 Annular member 57 Annular partition member 58 Gas filling passage G Compressed gas L Oil

Claims (6)

A collet capable of gripping the base end of a tool or tool holder attached to the distal end portion of the spindle of the machine tool, a draw bar disposed inside the spindle, and a coupling mechanism for interlockingly connecting the draw bar and the collet; In the spindle tool fixing device comprising a gas spring that pulls and urges the draw bar toward the spindle proximal end,
The gas spring is
A cylinder body having a cylinder member protruding outside the base end of the main shaft and fixed to the main shaft;
A piston mounted inside the cylinder body and integrally connected to the draw bar;
A gas working chamber formed on the main shaft side with respect to the piston in the cylinder member and containing compressed gas;
A gas storage chamber formed inside the proximal end portion of the main shaft and containing compressed gas;
A communication passage communicating the gas working chamber and the gas storage chamber ,
A tool fixing device for a spindle, wherein oil for obtaining a sealing function is sealed in the gas storage chamber .   2. The spindle tool fixing device according to claim 1, wherein the piston is integrally formed with the draw bar, and a base end portion of the draw bar protrudes from the cylinder body to the opposite side of the spindle.   The gas storage chamber is formed by a large portion of a cylindrical hole formed in a base end open shape inside the base end side portion of the main shaft, and a gas storage chamber is formed at the back end portion of the cylindrical hole at the distal end side. The main shaft according to claim 1 or 2, wherein an annular member for partitioning a distal end side end portion is attached, and an annular partition member integral with the cylinder body is attached to a proximal end portion of the cylindrical hole. Tool fixing device.   The cylinder member of the said cylinder main body has an outer diameter more than the outer diameter of a main axis | shaft, The said gas storage chamber has a volume at least 5 times or more of the volume of a gas working chamber, The Claim 1 characterized by the above-mentioned. The spindle tool fixing device according to any one of the above.   5. The spindle tool fixing device according to claim 1, wherein a gas filling passage for filling the gas storage chamber with compressed gas is formed on the spindle. The spindle tool fixing according to any one of claims 1 to 5 , further comprising a hydraulic cylinder that presses and drives the base end portion of the draw bar toward the tip end side of the draw bar when releasing the bias by the gas spring. apparatus.

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