Machine tool

Abstract

Provided is a machine tool that prevents a tool spindle unit from turning when the machine tool is stopped. A machine tool 1 comprises: a brake disk 651; a brake piston 652 movable in a direction to be brought into contact with and separated from the brake disk 651; a hydraulic device 653 that moves the brake piston 652 to change the state between a turning prevention state in which a tool spindle unit 7 is prevented from turning and a turning permission state in which the tool spindle unit 7 is permitted to turn, and maintains the changed state; and a biasing member 654 that presses the brake member 652 against the brake disk 651 to prevent the tool spindle unit 7 from turning when the hydraulic device 653 is stopped.

Description

machine tools

[0001] The present invention relates to a machine tool equipped with a swiveling tool spindle unit.

[0002] There is known a machine tool in which a tool such as a drill or an end mill is attached to a swiveling tool spindle unit and the tool spindle unit is moved in multiple axial directions to machine a workpiece (see, for example, Patent Document 1). The machine tool described in Patent Document 1 is equipped with a brake mechanism that prevents the tool spindle unit from rotating due to a machining load while machining a workpiece. This brake mechanism prevents the tool spindle unit from rotating by a brake member that moves hydraulically.

[0003] Patent No. 4311705

[0004] However, because the brake mechanism described in Patent Document 1 moves the brake member with hydraulic pressure, when the machine tool stops due to an emergency stop or when the power is turned off, the hydraulic pressure disappears, the brake function is lost, and the tool spindle unit becomes free to rotate. If the tool spindle unit rotates due to its own weight or the like, there is a risk that the tool spindle unit or a tool attached to the tool spindle will interfere with the workpiece or other components of the machine tool, damaging those components or the workpiece.

[0005] In view of the above circumstances, an object of the present invention is to provide a machine tool that prevents a tool spindle unit from rotating when the machine tool stops.

[0006] The machine tool of the present invention that solves the above-mentioned problems is a machine tool equipped with a swiveling tool spindle unit, comprising: a brake disc; a brake member that is movable in a direction toward and away from the brake disc; a brake drive device that moves the brake member to change the state between a swiveling prevented state in which swiveling of the tool spindle unit is prevented and a swiveling permitted state in which swiveling of the tool spindle unit is permitted, and maintains the changed state; and a biasing member that moves the brake member toward the brake disc when the brake drive device is stopped, thereby preventing swiveling of the tool spindle unit.

[0007] According to this machine tool, when the power supply to the machine tool is cut off and the brake drive device stops, the biasing member can prevent the tool spindle unit from rotating.

[0008] Here, the tool spindle unit may have a center of gravity eccentric to the swivel central axis. The brake disc may rotate together with the tool spindle unit. The brake member may press the brake disc against a non-swiveling portion to sandwich the brake disc between the non-swiveling portion. The brake drive device may move the brake member by fluid pressure. The biasing member may prevent the tool spindle unit from rotating when the fluid pressure drops below a predetermined value. The brake drive device may establish the swivel-permitted state by moving the brake member in a direction away from the brake disc against the biasing force of the biasing member.

[0009] In this machine tool, the brake member may be cylindrical, and the biasing members may be arranged on the same circumference at equal intervals around the brake member to bias the brake member toward the brake disc.

[0010] This prevents the brake piston from tilting relative to the direction of movement when the brake piston is moved by the biasing member, which would hinder the movement of the brake piston. Also, uneven contact between the brake piston and the brake disc is eliminated, which prevents uneven wear of the brake piston and the brake disc.

[0011] Furthermore, in this machine tool, the brake member moves away from the brake disc to enter the swing-permitting state when fluid is supplied to a first pressure chamber and the fluid in the second pressure chamber is recovered, and moves toward the brake disc to enter the swing-blocking state when fluid is supplied to the second pressure chamber and the fluid in the first pressure chamber is recovered; the brake drive device has an electromagnetic valve that switches the supply destination of the fluid from one of the first pressure chamber and the second pressure chamber to the other, and simultaneously switches the recovery destination of the fluid from the other of the first pressure chamber and the second pressure chamber to one; and when the brake drive device is stopped, the electromagnetic valve may supply the fluid to the second pressure chamber and recover the fluid to the first pressure chamber.

[0012] This prevents the fluid from interfering with the movement of the brake member caused by the biasing member.

[0013] According to the present invention, it is possible to provide a machine tool that prevents the tool spindle unit from turning when the machine tool stops.

[0014] 1 is a perspective view showing the main internal configuration of a machine tool according to this embodiment. 2 is a cross-sectional view of the B-axis drive mechanism and tool spindle unit shown in FIG. 1. 3 is a hydraulic circuit diagram schematically showing the external cylinder, brake disc, brake piston, and hydraulic device that moves the brake piston shown in FIG. 2. 4 is a hydraulic circuit diagram similar to FIG. 3, but schematically showing the external cylinder, brake disc, brake piston, and hydraulic device in a swing-permitted state. 5 is a cross-sectional view similar to FIG. 2, showing the B-axis drive mechanism and tool spindle unit in a swing-permitted state. 6(a) is a cross-sectional view taken along line A-A in FIG. 2, and 6(b) is a perspective view of a flange on which a biasing member is arranged.

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] FIG. 1 is a perspective view showing the main internal configuration of a machine tool 1 according to this embodiment.

[0017] As shown in Figure 1, machine tool 1 is a CNC (Computerized Numerical Control) lathe in which a tool spindle turret 2 is movably mounted on a base 9. The operation of this tool spindle turret 2 is controlled by a control device (not shown). The control device operates machine tool 1 in accordance with an NC program stored in a storage device and operations performed using an operating unit (not shown).

[0018] Although not shown in FIG. 1 , the leg 9 also carries a headstock 8 (see FIG. 2 ) that rotatably holds a spindle 81 (see FIG. 2 ). The headstock 8 moves in the Z-axis direction together with the spindle 81 in response to a signal from the control device. The Z-axis direction is horizontal, and in FIG. 1 , it is the direction connecting the lower left and upper right. FIG. 1 also shows a spindle guide 91 that guides the movement of the headstock 8 in the Z-axis direction. This spindle guide 91 is fixed to the leg 9. The spindle 81 releasably grips a rod-shaped workpiece W (see FIG. 2 ) and rotates together with the gripped workpiece W around the axis of the spindle 81 in response to a signal from the control device. Note that the axes of the spindle 81 and the workpiece W both run in the Z-axis direction. The leg 9 also carries an opposing headstock (not shown) that rotatably holds an opposing spindle. This opposing spindle has a configuration similar to the spindle 81 and is positioned opposite the spindle 81. The workpiece W that has been machined by the spindle 81 is transferred to the counter spindle and gripped by the counter spindle.

[0019] The leg 9 is also provided with a Z-axis linear guide 92, a Z-axis ball screw 93, and a Z-axis motor 94. Two Z-axis linear guides 92 are provided spaced apart in the Y-axis direction. The Y-axis direction is horizontal and perpendicular to the Z-axis direction. The two Z-axis linear guides 92 extend in the Z-axis direction and are each fixed to the leg 9.

[0020] A Z-axis ball screw 93 also extends in the Z-axis direction and is rotatably held by the leg 9. A Z-axis motor 94 is connected to one end of the Z-axis ball screw 93. The Z-axis motor 94 is driven by a signal from the control device, causing the Z-axis ball screw 93 to rotate.

[0021] The tool spindle turret 2 has a Z-axis moving carriage 3, a Y-axis moving carriage 4, an X-axis moving carriage 5, a B-axis drive mechanism 6, and a tool spindle unit 7. The Z-axis moving carriage 3 moves in the Z-axis direction together with the Y-axis moving carriage 4, the X-axis moving carriage 5, the B-axis drive mechanism 6, and the tool spindle unit 7 by rotation of a Z-axis ball screw 93. The Z-axis moving carriage 3 is provided with a Y-axis linear guide 31, a Y-axis motor 32, and a Y-axis ball screw (not shown).

[0022] Two Y-axis linear guides 31 are provided spaced apart in the Z-axis direction. Fig. 1 shows one of the two Y-axis linear guides 31. The two Y-axis linear guides 31 extend in the Y-axis direction and are each fixed to the Z-axis movable table 3.

[0023] The Y-axis ball screw also extends in the Y-axis direction and is rotatably held by the Z-axis moving stage 3. One end of the Y-axis ball screw is connected to a Y-axis motor 32. The Y-axis motor 32 is driven by a signal from the control device, causing the Y-axis ball screw to rotate.

[0024] The Y-axis moving table 4 moves in the Y-axis direction together with the X-axis moving table 5, the B-axis drive mechanism 6, and the tool spindle unit 7 by rotation of the Y-axis ball screw. The Y-axis moving table 4 is provided with an X-axis linear guide 41, an X-axis ball screw 42, and an X-axis motor 43.

[0025] Two X-axis linear guides 41 are provided spaced apart in the Z-axis direction. The two X-axis linear guides 41 extend in the X-axis direction and are each fixed to the Y-axis movable stage 4. The X-axis direction is the vertical direction.

[0026] The X-axis ball screw 42 also extends in the X-axis direction and is rotatably held by the Y-axis moving table 4. An X-axis motor 43 is connected to one end of the X-axis ball screw 42. The X-axis motor 43 is driven by a signal from the control device, causing the X-axis ball screw 42 to rotate.

[0027] The X-axis moving table 5 moves in the X-axis direction together with the B-axis drive mechanism 6 and the tool spindle unit 7 by rotation of the X-axis ball screw 42 .

[0028] The B-axis drive mechanism 6 is a mechanism that rotates the tool spindle unit 7 around the Y-axis direction as the center of rotation and maintains the rotated state. The direction of rotation around the Y-axis direction as the center of rotation is the B-axis direction. The B-axis drive mechanism 6 and the tool spindle unit 7 will be described in detail later.

[0029] Figure 2 is a cross-sectional view of the B-axis drive mechanism 6 and the tool spindle unit 7 shown in Figure 1. Figure 2 shows the B-axis drive mechanism 6 and the tool spindle unit 7 cut along a vertical plane passing through the swivel center line C1 of the tool spindle unit 7. Note that in the cross-sectional view of this embodiment, no hatching is used to indicate the cut surface.

[0030] 2 , the tool spindle unit 7 has a spindle housing 71, a tool spindle 72, a tool spindle motor 73, and a tool spindle rotation detector 74. The spindle housing 71 is an outer shell part connected to the pivot shaft 62 of the B-axis drive mechanism 6. The tool spindle 72, the tool spindle motor 73, and the tool spindle rotation detector 74 are disposed inside the spindle housing 71.

[0031] The tool spindle 72 is a part that rotates around the tool spindle center line C2 as the center of rotation, and is rotatably supported by bearings on the spindle housing 71. A tool T, such as a drill or end mill, for machining a workpiece W is replaceably attached to the tip of the tool spindle 72. Figure 2 shows the tool T attached to the tool spindle 72.

[0032] The tool spindle motor 73 is a built-in motor that rotates the tool spindle 72. The drive of the tool spindle motor 73 is controlled by a control device. When the tool spindle motor 73 is driven, the tool spindle 72 rotates together with the tool T. The workpiece W held by the spindle 81 can be machined into any shape by moving the tool spindle 72 in each axial direction and by rotating the tool spindle 72 about the B axis.

[0033] The tool spindle rotation detector 74 is a sensor that detects the rotation of the tool spindle 72. The detection result of the tool spindle rotation detector 74 is transmitted to the control device.

[0034] The B-axis drive mechanism 6 has an outer cylinder 61, a rotating shaft 62, a B-axis motor 63, a rotating angle detector 64, and a brake mechanism 65. The outer cylinder 61 is fixed to the X-axis movable table 5. The rotating shaft 62, the B-axis motor 63, the rotating angle detector 64, and the brake mechanism 65 are disposed inside the outer cylinder 61, except for a hydraulic device 653, which will be described later.

[0035] The pivot shaft 62 is an axis that pivots about a pivot center line C1. The central portion of the pivot shaft 62 is hollow, and an inner cylinder 66 is disposed in the central portion, through which wiring (not shown) passes for transmitting and receiving signals to and from the tool spindle unit 7 and for supplying power. This inner cylinder 66 and the aforementioned outer cylinder 61 are fixed to the X-axis movable table 5 and are non-rotating parts that do not pivot together with the pivot shaft 62. The pivot shaft 62 is rotatably supported by the outer cylinder 61 via bearings. The tool spindle unit 7 is fixed to the tip of the pivot shaft 62, and when the pivot shaft 62 pivots, the tool spindle unit 7 also pivots.

[0036] The B-axis motor 63 is a built-in motor that rotates the pivot shaft 62. The B-axis motor 63 is composed of a rotor 631 that rotates together with the pivot shaft 62 and a stator 632 fixed to the outer cylinder 61. The driving of the B-axis motor 63 is controlled by a control device. When the B-axis motor 63 is driven, the tool spindle unit 7 rotates.

[0037] The rotation angle detector 64 is an absolute sensor that detects the rotation angle of the rotation shaft 62. The detection result of the rotation angle detector 64 is sent to the control device.

[0038] The brake mechanism 65 has a brake disc 651, a brake piston 652, a hydraulic device 653 (see FIG. 3), and a biasing member 654. The brake mechanism 65 functions as a brake against the rotation of the pivot shaft 62 and the tool spindle unit 7. FIG. 2 shows a rotation prevented state in which the brake mechanism 65 prevents the rotation of the pivot shaft 62 and the tool spindle unit 7.

[0039] The brake disc 651 has a thin, disk-like shape with its inner peripheral portion fixed to the pivot shaft 62. The outer peripheral portion of the brake disc 651 protrudes radially outward beyond the pivot shaft 62. When the pivot shaft 62 pivots, the brake disc 651 pivots together with the pivot shaft 62. The outer peripheral portion of the brake disc 651 is sandwiched between the outer cylinder 61 and the brake piston 652, thereby preventing the brake disc 651 from pivoting.

[0040] The brake piston 652 is a cylindrical piston held in the outer cylinder 61 so as to be slidable in the Y-axis direction, which is the direction in which the brake piston 652 approaches and moves away from the brake disc 651. This brake piston 652 corresponds to an example of a brake member. The inner circumferential surface of the brake piston 652 faces the outer circumferential surface of the rotating shaft 62 with a very small gap between them. A groove is formed in the outer circumferential surface of the brake piston 652 along the circumferential direction. An annular seal member 6521 is attached to this groove. This seal member 6521 is sandwiched between the bottom of the groove of the brake piston 652 and the inner circumferential surface of the outer cylinder 61.

[0041] A first pressure chamber 653A and a second pressure chamber 653B are formed between the outer peripheral surface of the brake piston 652 and the inner peripheral surface of the outer cylinder 61. Oil, which serves as a driving source for moving the brake piston 652, is supplied to the first pressure chamber 653A. The first pressure chamber 653A is a space formed closer to the brake disc 651 than the second pressure chamber 653B, and is formed to the left of the second pressure chamber 653B in FIG. 2. Hereinafter, the left side in FIG. 2 may be referred to as the "advance side," and the right side in FIG. 2 may be referred to as the "retract side." The above-mentioned seal member 6521 is disposed between the first pressure chamber 653A and the second pressure chamber 653B. When oil is supplied to the first pressure chamber 653A, the brake piston 652 slides in the retraction direction. When oil is supplied to the second pressure chamber 653B, the brake piston 652 slides in the advance direction. When the brake piston 652 moves in the advance direction, the brake piston 652 presses against the brake disc 651, causing the brake disc 651 to elastically deform. 2, the brake disc 651 is sandwiched between the brake piston 652 and the outer cylinder 61. This prevents the rotation of the pivot shaft 62 to which the brake disc 651 is fixed, resulting in a rotation-blocked state.

[0042] The hydraulic device 653 is a device that supplies oil at a predetermined pressure to one of the first pressure chamber 653A and the second pressure chamber 653B and recovers the oil from the other. The hydraulic device 653 maintains the pressure (hydraulic pressure) of the supplied oil until the oil supply destination is switched to the other of the first pressure chamber 653A and the second pressure chamber 653B. By switching the oil supply destination using the hydraulic device 653, the brake piston 652 moves in a direction toward and away from the brake disc 651. This hydraulic device 653 corresponds to an example of a brake drive device.

[0043] The biasing member 654 is a plurality of compression springs arranged on a flange 661 fixed to the rear end of the outer cylinder 61. The biasing member 654 constantly biases the brake piston 652 in the advancing direction. The biasing force of the biasing member 654 is weaker than the load applied by the hydraulic device 653 to move the brake piston 652, being no more than 1 / 10 of the load. The hydraulic device 653 and the biasing member 654 will be described in detail later.

[0044] FIG. 3 is a hydraulic circuit diagram that schematically shows the outer cylinder 61, brake disc 651, brake piston 652, and hydraulic device 653 that moves brake piston 652 shown in FIG.

[0045] 3, the hydraulic device 653 includes a tank 6530, a hydraulic pump 6531, a check valve 6532, and a solenoid valve 6533. The tank 6530 is a tank in which oil used in the hydraulic device 653 is stored.

[0046] The hydraulic pump 6531 is a pump that sucks up oil stored in the tank 6530. The operation of the hydraulic pump 6531 is controlled by a control device, and when driven, it pumps out oil at a predetermined pressure.

[0047] The check valve 6532 is a so-called check valve, which prevents the discharged oil from flowing backward and also serves to maintain the pressure of the discharged oil downstream of the check valve 6532. The check valve 6532 may be omitted. In that case, the hydraulic pressure is maintained by controlling the operation of the hydraulic pump 6531 so that the oil is always discharged at a predetermined pressure.

[0048] The solenoid valve 6533 is an electromagnetic switching valve that switches the supply destination and recovery destination of the oil sent from the hydraulic pump 6531 in response to a switching signal from the control device. As a result, the hydraulic device 653 supplies oil at a predetermined pressure to one of the first pressure chamber 653A and the second pressure chamber 653B, and recovers the oil in the other chamber into the tank 6530.

[0049] FIG. 3 shows the hydraulic device 653 supplying oil to the second pressure chamber 653B and recovering the oil that was in the first pressure chamber 653A. As a result, the brake piston 652 moves forward, preventing the rotation of the pivot shaft 62 and the tool spindle unit 7, resulting in a rotation-blocked state. Note that in FIG. 3 , the outer cylinder 61, the brake disc 651, and the brake piston 652 are shown separated from each other to make them easier to see. However, in reality, oil is supplied to the second pressure chamber 653B and the oil in the first pressure chamber 653A is recovered, so that the brake disc 651 is sandwiched between the outer cylinder 61 and the brake piston 652 as shown in FIG. 2 . The pressure (hydraulic pressure) of the oil supplied to the second pressure chamber 653B is maintained, thereby maintaining the rotation-blocked state. By setting the rotation prevention state, it is possible to prevent the tool spindle unit 7 from rotating due to the machining load generated when machining the workpiece W (see FIG. 2).

[0050] The solenoid valve 6533 has a valve spring 6533A inside. When the hydraulic device 653 stops and the power supply to the solenoid valve 6533 is cut off due to, for example, an emergency stop or the power being turned off and the machine tool 1 is stopped, the action of the valve spring 6533A causes the oil to be supplied to the second pressure chamber 653B and the oil to be recovered to the first pressure chamber 653A, as shown in Fig. 3. That is, Fig. 3 shows the solenoid valve 6533 when the solenoid valve is controlled by the control device to be in a rotation-blocked state and when the machine tool 1 is stopped due to an emergency stop or the power being turned off.

[0051] FIG. 4 is a hydraulic circuit diagram similar to FIG. 3, which schematically shows the outer cylinder 61, the brake disc 651, the brake piston 652, and the hydraulic device 653 in the turning permitted state.

[0052] When the tool spindle unit 7 is rotated, the control device moves the solenoid valve 6533 to the right in Fig. 3 relative to the state shown in Fig. 3. As a result, as shown in Fig. 4, the oil is supplied to the first pressure chamber 653A and recovered from the second pressure chamber 653B. The hydraulic pump 6531 is then driven to supply oil to the first pressure chamber 653A and recover the oil pushed out from the second pressure chamber 653B, causing the brake piston 652 to move backward, and the state changes to a rotation permitted state in which rotation of the rotation shaft 62 and the tool spindle unit 7 is permitted. After the state changes to the rotation permitted state, the pressure of the oil supplied to the first pressure chamber 653A is maintained, thereby maintaining the rotation permitted state until the machine tool 1 is stopped by an emergency stop or power OFF, or until the solenoid valve 6533 returns to the state shown in Fig. 3 in response to a command from the control device.

[0053] FIG. 5 is a cross-sectional view similar to FIG. 2, showing the B-axis drive mechanism 6 and the tool spindle unit 7 in the rotation-permitted state.

[0054] As shown in FIG. 5 , in the rotation-permitted state, oil is supplied to the first pressure chamber 653A, pushing the brake piston 652 to the right in FIG. 5 and moving it backward against the biasing member 654. As the brake piston 652 moves backward, it moves away from the brake disc 651 in the Y-axis direction. Furthermore, the elastic deformation of the brake disc 651 is released, creating a small gap in the Y-axis direction between the brake disc 651 and the outer cylinder 61. This allows the brake disc 651, the swivel shaft 62, and the tool spindle unit 7 to rotate freely. By driving the B-axis motor 63 in this rotation-permitted state, the tool spindle unit 7 can be rotated at any desired angle. FIG. 6( a ) is a cross-sectional view taken along line A-A in FIG. 2 , and FIG. 6( b ) is a perspective view of the flange 661 on which the biasing member 654 is disposed.

[0055] As shown in Figures 6(a) and 6(b), the flange 661 fixed to the rear end of the outer cylinder 61 (see Figure 2) is composed of a large diameter portion 6611 screwed to the outer cylinder 61 and a small diameter portion 6612 protruding on the advancing side with its protruding surface facing the retracting end face of the brake piston 652 (see Figure 2). The small diameter portion 6612 has a plurality of recesses 661A formed on the same circumference at equal intervals in the circumferential direction. In this embodiment, the recesses 661A are formed at 24 locations at 15-degree intervals on the circumference of a circle centered on the turning center line C1.

[0056] As shown in FIG. 6A , a biasing member 654 is inserted into each recess 661A. That is, in this embodiment, the biasing members 654 are arranged at 15-degree intervals on a circle centered on the turning centerline C1. One end of the biasing member 654 presses against the bottom of the recess 661A, and the other end presses against the retreating end face of the brake piston 652 (see FIG. 2 ), thereby constantly biasing the brake piston 652 in the advance direction. The angular intervals at which the biasing members 654 are arranged and the number of biasing members 654 may be any number. However, it is preferable that there are multiple biasing members 654, and that the angular intervals are uniform. This prevents the brake piston 652 from tilting relative to the direction of movement and becoming unable to move when the brake piston 652 is moved by the biasing force of the biasing member 654. In addition, since the brake piston 652 and the brake disc 651 (see FIG. 2) are pressed evenly in the circumferential direction, they do not come into uneven contact, and uneven wear of the brake disc 651, brake piston 652, and outer cylinder 61 (see FIG. 2) can be prevented.

[0057] According to the machine tool 1 of the present embodiment described above, the biasing member 654 constantly biases the brake piston 652 in the advancing direction, so that when the machine tool 1 stops in the swing blocked state due to an emergency stop or when the power is turned off, the brake piston 652 continues to press the brake disc 651, maintaining the swing blocked state. When the machine tool 1 stops in the swing permitted state or during a state change between the swing blocked state and the swing permitted state, the biasing member 654 moves the brake piston 652 in the advancing direction, so that the moved brake piston 652 presses the brake disc 651, changing the state to the swing blocked state. In other words, when the machine tool 1 stops and the power supply to the hydraulic device 653 is cut off, causing the hydraulic device 653 to stop, the swing blocked state can be maintained or changed to the swing blocked state without power, thereby maintaining the attitude (swing angle) of the tool spindle unit 7. This prevents the tool spindle unit 7 from rotating due to its own weight or the like even when the machine tool 1 is stopped, and prevents the tool T attached to the tool spindle unit 7 or the tool spindle 72 from interfering with the workpiece W or other components of the machine tool 1 and damaging those components or the workpiece W.

[0058] Here, when the biasing member 654 moves the brake piston 652 in the advancing direction, if the hydraulic pump 6531 supplies oil to the first pressure chamber 653A and recovers it from the second pressure chamber 653B, the pressure of the oil in the first pressure chamber 653A may interfere with the movement of the brake piston 652. In contrast, in this embodiment, when the power supply to the solenoid valve 6533 is interrupted, the action of the valve spring 6533A causes the oil to be recovered to the first pressure chamber 653A as shown in FIG. 3 . Therefore, when the brake piston 652 is moved in the advancing direction by the biasing member 654, the oil in the first pressure chamber 653A is easily pushed out and flows out toward the tank 6530. Therefore, the movement of the brake piston 652 in the advancing direction is not obstructed by the oil in the first pressure chamber 653A.

[0059] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, in this embodiment, a CNC lathe has been described as an example of the machine tool 1. However, the present invention may also be applied to other machine tools 1 equipped with a rotating tool spindle, such as a machining center. Furthermore, the machine tool 1 may be equipped with a guide bush that guides the tip of the workpiece W gripped by the spindle 81 so that the tip can slide in the Z-axis direction. Furthermore, a tool post on which a tool T, such as a cutting tool, is mounted may be provided in addition to the tool spindle 72. The counter spindle may be omitted. In addition, while the brake mechanism 65 using hydraulic pressure as a driving source has been described as an example, a mechanism using other fluid pressure, such as air pressure, as a driving source may also be used, or a mechanism using electricity as a driving source may also be used.

[0060] It should be noted that even if a constituent element is included only in the description of each of the modified examples described above, that constituent element may be applied to other modified examples.

[0061] 1 Machine tool 7 Tool spindle unit 651 Brake disc 652 Brake piston (brake member) 653 Hydraulic device (brake drive device) 654 Biasing member

Claims

1. A machine tool equipped with a swiveling tool spindle unit, comprising: a brake disc; a brake member movable toward and away from said brake disc; a brake drive device that moves said brake member to change the state between a swiveling prevented state in which swiveling of said tool spindle unit is prevented and a swiveling permitted state in which swiveling of said tool spindle unit is permitted, and maintains the changed state; and a biasing member that moves said brake member toward said brake disc when said brake drive device is stopped, thereby preventing swiveling of said tool spindle unit.

2. A machine tool according to claim 1, characterized in that the brake member is cylindrical, and the biasing members are arranged in multiple numbers on the same circumference at equal intervals around the brake member to bias the brake member toward the brake disc.

3. A machine tool according to claim 1 or 2, characterized in that the brake member moves away from the brake disc to enter the swing-permitting state when fluid is supplied to the first pressure chamber and the fluid in the second pressure chamber is recovered, and moves towards the brake disc to enter the swing-blocking state when fluid is supplied to the second pressure chamber and the fluid in the first pressure chamber is recovered, the brake drive device having an electromagnetic valve that switches the supply destination of the fluid from one of the first pressure chamber and the second pressure chamber to the other, and simultaneously switches the recovery destination of the fluid from the other of the first pressure chamber and the second pressure chamber to one, when the brake drive device is stopped, the electromagnetic valve that supplies the fluid to the second pressure chamber and recovers the fluid to the first pressure chamber.

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