JP4232017B2 - Drawbar position detection mechanism for machine tools - Google Patents

Description

  The present invention relates to a draw bar position detection mechanism that detects the position of a draw bar that performs clamping and unclamping of a tool on a spindle end in a machine tool such as a machining center.

  In this specification and claims, the side on which the tool of the spindle is attached, that is, the left side of FIG. 1 is the front side, and the opposite side is the back side.

  A machine tool such as a machining center is arranged so that a tool is attached to the tip of a hollow spindle, and the spindle can be moved in the axial direction relative to the spindle, and the tool is clamped and unclamped to the front end of the spindle by moving in the axial direction. The main shaft unit includes a draw bar to be performed, an urging means for urging the draw bar in the clamping direction, and a draw bar driving means arranged behind the draw bar and moving the draw bar in the unclamping direction.

  In such a machine tool, it is necessary to check whether the tool is correctly mounted and clamped on the spindle, and a mechanism for checking whether the tool is mounted by detecting the position of the draw bar is considered. Yes.

  The conventional drawbar position detection mechanism is arranged at a position in front of the drawbar driving means, a disk member fixed to a portion protruding rearward from the main shaft of the drawbar, and a disk member disposed on a fixed portion of the main shaft unit. A first proximity switch that faces a part of the outer peripheral surface, and a second proximity switch that is arranged at a fixed portion of the spindle unit behind the first proximity switch and faces a part of the outer peripheral surface of the disk member. What is provided is known (for example, refer to Patent Document 1).

However, in the conventional draw bar position detection mechanism, the disk member is fixed to a portion protruding rearward from the main shaft at the rear end portion of the draw bar at a position in front of the draw bar driving means, and at a position separated in the front-rear direction. In order to arrange the two proximity switches, it is necessary to make the protruding length of the rear end portion of the draw bar from the main shaft relatively long, resulting in a problem that the main shaft unit becomes relatively long. In addition, because the rear end of the draw bar is relatively long and protrudes from the main shaft, the draw bar vibrates when the main shaft rotates, and the rotation balance changes when the main shaft rotation speed changes, hindering speedup of the main shaft and high processing accuracy. become.
JP-A-10-80841

  SUMMARY OF THE INVENTION An object of the present invention is to provide a drawbar position detection mechanism for a machine tool that solves the above-described problems and that can shorten the spindle unit, increase the speed of the spindle, and increase the accuracy of machining.

  The drawbar position detecting mechanism for a machine tool according to the first aspect of the present invention is arranged so that a tool is attached to the tip of the hollow main shaft, the main shaft is movable in the axial direction with respect to the main shaft, and the main shaft tip is moved by the axial movement. In a machine tool comprising a draw bar for clamping and unclamping the tool, an urging means provided in the main shaft and urging the draw bar in the clamping direction, and a draw bar driving means for moving the draw bar in the unclamping direction, A mechanism for detecting the position of the draw bar, wherein the draw bar driving means includes a hollow pressing member that presses the draw bar in the unclamping direction against the urging force of the urging means. Drawbar movement detection part that moves relative to the pressing member by movement in the clamping direction and unclamping direction, and drawbar movement detection In which a displacement sensor for detecting the movement position of the part is provided.

  The drawbar position detection mechanism of the machine tool according to the invention of claim 2 is the invention according to claim 1, wherein a coolant introduction member having a coolant introduction hole communicating with a coolant passage formed in the drawbar is fixed to the rear end portion of the drawbar. The draw bar movement detection part is connected to the coolant introduction hole of the coolant introduction member and the coolant supply hole leading to the coolant supply source is formed, and the draw bar movement detection part is urged forward by the urging member, thereby detecting the draw bar movement. It is preferable that the front end of the portion is always in contact with the rear end of the coolant introduction member so that the coolant supply hole and the coolant introduction hole communicate with each other.

  According to the draw bar position detection mechanism of the first aspect of the invention, the draw bar driving means includes the hollow pressing member that presses the draw bar in the unclamping direction against the urging force of the urging means. A drawbar movement detecting portion that moves relative to the pressing member by movement of the drawbar in the clamping direction and unclamping direction, and a displacement sensor that detects the movement position of the drawbar movement detecting portion, so that the rear end portion of the drawbar The projecting length from the main shaft can be shortened compared to the conventional one, and the main shaft unit can be shortened. In addition, since the protrusion length of the rear end of the draw bar from the main shaft is shorter than that of the conventional one, the vibration of the draw bar during main shaft rotation is suppressed, and the change in the rotation balance when the main shaft speed changes is small. Thus, the spindle can be sped up and machining can be performed with high accuracy.

  According to the draw bar position detecting mechanism of the invention of claim 2, since the position of the draw bar can be detected by using the device for supplying the coolant to the coolant passage formed in the draw bar, the number of parts can be reduced. . In addition, since the protrusion length from the main shaft of the rear end portion of the draw bar is shorter than the conventional one, the vibration of the draw bar is suppressed and the vibration of the coolant introduction member is also suppressed. Coolant leakage from the coolant introduction member can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows the overall configuration of the main spindle unit with a tool clamped at the front end of the main spindle. 2 to 4 show main parts of the spindle unit in different states, FIG. 2 shows a state in which the tool is clamped at the front end of the spindle, FIG. 3 shows a state in which the tool is unclamped, and FIG. The state where the draw bar has moved in the clamping direction is shown.

  As shown in FIG. 1, the spindle unit (1) includes a fixed housing (2) fixed to a spindle head (not shown) such as a machining center, and a hollow spindle (3) arranged in the fixed housing (2). And. The front portion and the rear portion of the main shaft (3) are rotatably supported by the fixed housing (2) by rolling bearings (4) and (5), respectively. Here, there are a plurality of rolling bearings (4) that support the front part of the main shaft (3), and there is only one rolling bearing (5) that supports the rear part. As the rolling bearing (4) that supports the front portion of the main shaft (3), a bearing that receives a radial load and at least one thrust load, such as an angular ball bearing, is used. As the rolling bearing (5) that supports the rear portion of the main shaft (3), for example, a cylindrical roller bearing that receives a radial load is used.

  A built-in type electric motor (6) for rotating the main shaft (3) is provided in a portion between the front bearing (4) and the rear bearing (5) in the fixed housing (2). The electric motor (6) includes a rotor (7) provided on the outer periphery of the main shaft (3) and a stator (8) provided on the inner periphery of the housing (2) around the motor (6).

  At the front end of the main shaft (3), a tapered hole (3a) is formed into which the taper shank (9a) of the tool holder (9) holding a tool (not shown) is fitted, and the rear end of the tapered hole (3a) and the main shaft (3) A first hole portion (11) having an inner diameter substantially equal to the small end diameter of the tapered hole (3a) between the rear end opening and a second hole portion having a smaller diameter than the first hole portion (11). A third hole portion (13) having a larger diameter than (12) and the first hole portion (11) is formed in order from the front. A collet relief portion (14) having a diameter larger than that of the first hole portion (11) is formed at a boundary portion between the tapered hole (3a) and the first hole portion (11). A forward-facing step (15) is formed at the boundary between the first hole (11) and the second hole (12), and the boundary between the second hole (12) and the third hole (13). A rearward-facing step 16 is formed.

  A pull stud (9b) is provided at the rear end of the taper shank (9a) of the tool holder (9), and a coolant passage (not shown) is formed through the tool holder (9) in the front-rear direction. ing.

  In the holes (11), (12), and (13) of the main shaft (3), the draw bar (17) extending in the front-rear direction is coaxial with the main shaft (3) so that it does not rotate but can move in the axial direction. Has been placed. The rear end portion of the draw bar (17) protrudes slightly rearward from the main shaft (3). A first flange (17a) for holding the collet and a second flange (17b) for guiding are formed at the front end and a part slightly behind the front end of the draw bar (17), respectively. The first flange (17a) is located at the front part in the first hole part (11), and the second flange (17b) is located at the rear part in the first hole part (11). A large-diameter portion (17c) for guiding is formed at the rear end of the draw bar (17), the large-diameter portion (17c) is at the rear end in the third hole (13), and a part is from the main shaft (3). Is also arranged to protrude rearward. A coolant passage (18) penetrating the draw bar (17) in the axial direction is formed at the center of the draw bar (17). A large-diameter portion is formed at the front end portion of the coolant passage (18), and a coolant passage member (20) is inserted into the large-diameter portion so as to be movable in the front-rear direction, and is always urged forward by a spring (not shown). In the coolant passage member (20), a coolant passage (not shown) communicating with the coolant passage (18) is formed penetrating in the front-rear direction.

  The front end portion of the coolant introduction member (19) is screwed into the rear end portion of the coolant passage (18) of the draw bar (17), thereby fixing the coolant introduction member (19) to the rear end portion of the draw bar (17). . An adhesion member (21) made of a ceramic having wear resistance is fixed to the rear end face of the coolant introduction member (19). The coolant introduction member (19) is formed with a coolant introduction hole (22) that passes through the coolant introduction member (19) in the front-rear direction and communicates with the coolant passage (18) of the draw bar (17). Further, an outward flange (19a) (see FIG. 2) is integrally formed at the intermediate portion in the front-rear direction of the coolant introduction member (19).

  The small diameter part of the rear end of the collet (23) holding the pull stud (9b) of the tool holder (9) is located between the first flange (17a) and the second flange (17b) of the draw bar (17). The collet (23) is also moved back and forth by the back and forth movement of the draw bar (17). A tool holding part (23a) is formed at the front end of the collet (23). The inner diameter of the tool holding part (23a) is smaller than the rear part, and the outer diameter of the tool holding part (23a) is larger than the rear part. When the drawbar (17) is moved to the rear clamping position, the tool holder (23a) of the collet (23) enters the first hole (11) and is held with its inner diameter reduced. The pull stud (9b) at the rear end of the tool holder (9) is held by the tool holder (23a). When the draw bar (17) moves to the front unclamping position, the tool holding part (23a) of the collet (23) matches the collet relief part (14), and the tool holding part (23a) can be expanded. Therefore, the pull stud (9b) of the tool holder (9) is released.

  The collars (24) for spring bearings are slidably fitted back and forth at the front and rear ends of the portion of the draw bar (17) located in front of the large diameter part (17c) and in the third hole (13). A plurality of disc springs (25) serving as biasing means for biasing the draw bar (17) rearward (clamping direction) are fitted between the collars (24). The disc spring (25) pushes the front collar (24) against the rearward stepped part (16) and the rear collar (24) against the front end face of the large diameter part (17c), and the drawbar (17) to the rear. Energize.

  The rear end of the fixed housing (2) extends to the rear of the rear end of the draw bar (17), and the draw bar (17) is moved forward (unclamped) to the rear end of the fixed housing (2). A draw bar driving device (26) which is a draw bar driving means to be moved is provided.

  The drawbar drive device (26) has a cylinder tube (27) fixed so as to protrude rearward at the rear end of the fixed housing (2), and passes through the cylinder tube (27) so as to be movable in the front-rear direction. And a cylindrical pressing member (28) for pressing the draw bar (17) forward. An inward flange (27a) (see FIG. 2) is formed on each of the front and rear ends of the cylinder tube (27), and the inner peripheral surface of the inward flange (27a) is pressed through the seal member (28). It comes in close sliding contact with the outer peripheral surface. An annular piston portion (28a) (see FIG. 2) is integrally formed on the outer peripheral surface of the portion of the pressing member (28) existing in the cylinder tube (27). The outer peripheral surface of the piston portion (28a) is in close sliding contact with the inner peripheral surface of the cylinder tube (27) via a seal member. Also, the thickness of the piston part (28a) in the front-rear direction is smaller than the distance between the inward flanges (27a) at the front and rear ends of the cylinder tube (27) so that it can move in the front-rear direction in the cylinder tube (27). The pressure oil chambers (29) and (31) are formed on both the front and rear sides of the piston portion (28a). Both pressure oil chambers (29) and (31) are connected to a pressure oil source (33) through a switching valve (32).

  As shown in FIGS. 2 to 4, an annular pressing portion (28 b) protruding inward is integrally formed at the front end of the pressing member (28). The inner diameter of the pressing portion (28b) is larger than the outer diameter of the outward flange (19a) of the coolant introduction member (19). A columnar body (34) is closely fitted to the rear part of the pressing member (28). A coolant supply hole (35) is formed penetratingly in the front-rear direction at the center of the cylindrical body (34). The front part of the coolant supply hole (35) of the cylindrical body (34) has a larger diameter than the rear part. The sleeve (36) is fixed to the columnar body (34) while being inserted into the large diameter portion (35a) of the coolant supply hole (35). An outward flange (36a) is integrally formed at a portion protruding forward from the cylindrical body (34) at the front end of the sleeve (36), and the outward flange (36a) is integrally formed with the cylindrical body (34). It is in contact with the front end face. The columnar body (34) and the sleeve (36) constitute a fixed portion. The cylindrical body (34) has a through hole (37) (38) extending in the front-rear direction on the radially outer portion of the coolant supply hole (35) and the outward flange (36a) of the sleeve (36). The displacement sensor (39) is inserted into the through holes (37) and (38) from the rear. The movable contact (39a) of the displacement sensor (39) projects forward from the through hole (38) of the outward flange (36a) of the sleeve (36). The displacement sensor (39) is connected to an NC control device (not shown).

  A rear portion of the detection member (42), which is a draw bar movement detection portion, is inserted into the sleeve (36) so as to be movable in the front-rear direction. A coolant supply hole (43) is formed in the detection member (42) so as to penetrate in the front-rear direction. On the front end surface of the detection member (42), a contact member (44) made of ceramics having wear resistance capable of being in close contact with the contact member (21) of the coolant introduction member (19) is fixed. The coolant introduced from a coolant supply source (not shown) is supplied to the coolant passage (18) of the draw bar (17) by the coolant introduction member (19), the cylindrical body (34), the sleeve (36), and the detection member (42). A coolant supply device for supplying is configured.

  An outward flange (42a) is integrally formed at a portion of the detection member (42) protruding forward from the sleeve (36). The outer diameter of the outward flange (42a) is such that the contact (39a) of the displacement sensor (39) contacts the rear surface of the outward flange (42a). The male screw member (45) is passed from the front to the outward flange (42a) at a position displaced in the circumferential direction from the displacement sensor (39), and the tip of the male screw member (45) is the sleeve (36). Is formed on the front surface of the outward flange (36a) and is screwed into the screw hole (46). A compression coil spring (47) (biasing member) is mounted around the part of the male thread member (45) located between the two outward flanges (36a) (42a), and the detection member (42) is always in front The close contact member (44) is in close contact with the close contact member (21) of the coolant introduction member (19), and as a result, the coolant supply hole (43) of the detection member (42) is attached to the coolant introduction member (19). It leads to the coolant introduction hole (22).

  FIG. 2 shows a state in which the tool mounted on the front end of the spindle (3) is clamped by the automatic tool changer.

  In this case, the taper shank (9a) of the tool holder (9) fits in the taper hole (3a) of the main shaft (3), and the draw bar (17) is urged rearward by the disc spring (25) to pull the stud. (9b) is grabbed by collet (23). The front end surface of the coolant passage member (20) of the draw bar (17) contacts the rear end surface of the pull stud (9b), and the coolant passage of the tool holder (9) and the coolant passage (18) of the draw bar (17) are connected. The coolant passes through the coolant passage member (20). The switching valve (32) is switched to the clamp position, and the pressure oil is supplied to the front oil chamber (29) of the cylinder tube (27) of the drawbar drive device (26), whereby the pressing member (28) is pressed. (28b) is in a retracted position spaced rearward from the draw bar (17). The detection member (42) is biased by the spring (47) and moves forward, and the contact member (44) is in close contact with the contact member (21) of the coolant introduction member (19). In addition, the contact (39a) of the displacement sensor (39) advances to the foremost normal clamp position, thereby detecting that the draw bar (17) is in the clamp position and outputting the signal to the NC controller. . Then, the NC control device determines that the machining is possible, moves the spindle unit (1) to the machining position, and starts machining. The coolant supplied from the coolant supply source includes the coolant supply hole (35) of the cylindrical body (34), the sleeve (36), the coolant supply hole (43) of the detection member (42), the coolant introduction member (19 ) Through the coolant introduction hole (22) and the coolant passage (18) of the draw bar (17) and into the coolant passage of the pull stud (9b) and tool holder (9) to be supplied to the tool. Yes.

  FIG. 3 shows a state in which the tool is unclamped.

  In this case, the switching valve (32) is switched to the unclamping position, and pressure oil is supplied to the rear oil chamber (31) of the cylinder tube (27) of the drawbar drive device (26), so that the pressing member (28) is The draw bar (17) is pushed forward (unclamping direction) against the urging force of the disc spring (25) by the pressing part (28b), and the collet (23) moves to the unclamping position at the front end. Then, the pull stud (9b) of the tool holder (9) is unclamped. At this time, the detection member (42) is pushed rearward by the coolant introduction member (19) and moves backward against the biasing force of the spring (47), and as a result, the contact (39a) of the displacement sensor (39) ) Retreats to the rearmost unclamping position, whereby it is detected that the draw bar (17) is in the unclamping position, and the signal is output to the NC controller. Then, the NC control device determines that the tool can be changed, and removes the used tool from the front end of the spindle (3) by the automatic tool changer and attaches the next tool to the front end of the spindle (3).

  FIG. 4 shows a state where the draw bar (17) is moved in the clamping direction in a state where the tool is not mounted on the front end of the main spindle (3) by the automatic tool changer.

  In this case, the switching valve (32) is switched to the clamp position, and the pressure oil is supplied to the front oil chamber (29) of the cylinder tube (27) of the drawbar drive device (26), whereby the pressing member (28) Is in a retracted position in which the pressing portion (28b) is spaced rearward from the draw bar (17). The draw bar (17) is moved rearward by the disc spring (25) to a position where the second flange (17b) contacts the forward stepped portion (15) of the main shaft (3). The detection member (42) is moved backward from the normal clamp position against the biasing force of the spring (47) by the coolant introduction member (19), and as a result, the contact (39a) of the displacement sensor (39) is normal clamp. The position is retracted to the abnormal clamp position between the normal clamp position and the unclamp position, whereby it is detected that the draw bar (17) is in the abnormal clamp position, and the signal is output to the NC controller. Then, the NC control device determines that the tool is not clamped at the front end of the spindle (3), and issues an alarm.

It is a longitudinal cross-sectional view which shows the whole spindle unit structure in the state where the draw bar moved in the clamping direction and the tool was clamped at the spindle front end. It is a longitudinal cross-sectional view which shows the principal part of the spindle unit in a state where the draw bar moves in the clamping direction and the tool is clamped at the spindle front end. FIG. 3 is a view corresponding to FIG. 2 showing a state where the tool is unclamped. It is a figure equivalent to FIG. 2 which shows the state which the draw bar moved to the clamp direction, without a tool existing.

Explanation of symbols

(3): Spindle
(17): Drawbar
(18): Coolant passage
(19): Coolant introduction member
(22): Coolant introduction hole
(25): Disc spring (biasing means)
(26): Drawbar drive device (drawbar drive means)
(28): Pressing member
(42): Detection member (drawbar movement detection part)
(43): Coolant supply hole
(47): Compression coil spring (biasing member)

Claims (2)

A hollow main shaft to which a tool is attached at the tip, a draw bar arranged in the main shaft so as to be movable in the axial direction relative to the main shaft, and a tool for clamping and unclamping the tool to the tip of the main shaft by movement in the axial direction; A mechanism for detecting the position of the draw bar in a machine tool provided with a biasing means for biasing the draw bar in the clamping direction and a draw bar driving means for moving the draw bar in the unclamping direction,
The draw bar driving means has a hollow pressing member that presses the draw bar in the unclamping direction against the urging force of the urging means, and the pressing member moves in the pressing member by moving the draw bar in the clamping direction and the unclamping direction. A drawbar position detection mechanism for a machine tool, provided with a drawbar movement detection portion that moves relative to the position and a displacement sensor that detects a movement position of the drawbar movement detection portion. A coolant introduction member having a coolant introduction hole that leads to a coolant passage formed in the draw bar is fixed to a rear end portion of the draw bar, and a draw bar movement detection portion leads to a coolant introduction hole of the coolant introduction member and also leads to a coolant supply source. The coolant supply hole is formed, and the draw bar movement detection part is urged forward by the urging member, so that the front end of the draw bar movement detection part is always in contact with the rear end of the coolant introduction member and the coolant supply hole and the coolant introduction hole The drawbar position detecting mechanism for a machine tool according to claim 1, wherein

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