Machine tool

Abstract

To provide a machine tool capable of preventing a tool spindle unit from swinging when the machine tool has stopped.SOLUTION: A machine tool 1 comprises: a brake disc 651; a brake piston 652 that is movable in a direction toward and away from the brake disc 651; a hydraulic device 653 that, by moving the brake piston 652, changes a state between a swing-inhibition state in which swinging of a tool spindle unit 7 is inhibited and a swing-allowance state in which swinging of the tool spindle unit 7 is allowed, and maintains the changed state; and a biasing member 654 that, when the hydraulic device 653 is stopped, presses the brake piston 652 against the brake disc 651 to prevent swinging of the tool spindle unit 7.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[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 the machining load while machining the workpiece. This brake mechanism prevents the tool spindle unit from rotating by a brake member that moves hydraulically. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4311705 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because the brake mechanism described in Patent Document 1 moves the brake member using 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 other reasons, 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. [Means for solving the problem]

[0006] The machine tool of the present invention, which solves the above problems, comprises: In a machine tool having a swiveling tool spindle unit, Brake discs and a brake member 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 rotation prevented state in which rotation of the tool spindle unit is prevented and a rotation permitted state in which rotation 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 the tool spindle unit from turning.

[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 enter 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 is cylindrical, The biasing members may be arranged in plurality on the same circumference at equal intervals in the circumferential direction of the brake member, and 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] In addition, in this machine tool, When fluid is supplied to a first pressure chamber and the fluid is collected from a second pressure chamber, the brake member moves away from the brake disc to enter the turning-permitted state, and when fluid is supplied to the second pressure chamber and the fluid is collected from the first pressure chamber, the brake member moves toward the brake disc to enter the turning-prevented state, the brake drive device has an electromagnetic valve that switches a supply destination of the fluid from one of the first pressure chamber and the second pressure chamber to the other, and simultaneously switches a recovery destination of the fluid from the other of the first pressure chamber and the second pressure chamber to one of the first pressure chamber and the second pressure chamber, The solenoid valve may supply the fluid to the second pressure chamber and recover the fluid from the first pressure chamber when the brake drive device is stopped.

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

[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. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a perspective view showing a main internal configuration of a machine tool according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the B-axis drive mechanism and the tool spindle unit shown in FIG. 1. [Figure 3] 3 is a hydraulic circuit diagram schematically showing the outer cylinder, brake disc, brake piston, and hydraulic device that moves the brake piston shown in FIG. 2.

[0023] FIG. [Figure 4] FIG. 4 is a hydraulic circuit diagram similar to FIG. 3, showing a schematic diagram of an outer cylinder, a brake disc, a brake piston, and a hydraulic device in a turning-permitted state. [Figure 5] FIG. 3 is a cross-sectional view similar to FIG. 2 showing the B-axis drive mechanism and the tool spindle unit in a rotation-permitted state. [Figure 6] 3(a) is a cross-sectional view taken along the line AA in FIG. 2, and FIG. 3(b) is a perspective view of a flange on which a biasing member is disposed. DETAILED DESCRIPTION OF THE INVENTION

[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 with a tool spindle turret 2 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 extends from the lower left to the upper right in FIG. 1. 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. After the workpiece W has been machined by the main spindle 81, it is transferred to the counter spindle and gripped by the counter spindle.

[0019] In addition, the leg 9 is 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 a horizontal direction that is 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 movable carriage 3, a Y-axis movable carriage 4, an X-axis movable carriage 5, a B-axis drive mechanism 6, and a tool spindle unit 7. The Z-axis movable carriage 3 moves in the Z-axis direction together with the Y-axis movable carriage 4, the X-axis movable 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 movable 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 stage 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 stage 4 moves in the Y-axis direction together with the X-axis moving stage 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 stage 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 movable stage 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 about the Y-axis direction as the center of rotation and maintains the rotated state. The direction of rotation about the Y-axis direction as the center of rotation is the B-axis. The B-axis drive mechanism 6 and the tool spindle unit 7 will be described in detail later.

[0029] Fig. 2 is a cross-sectional view of the B-axis drive mechanism 6 and the tool spindle unit 7 shown in Fig. 1. Fig. 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 the cross-sectional view of this embodiment does not include hatching 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 rotating 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 arranged inside the spindle housing 71.

[0031] The tool spindle 72 is a part that rotates around the tool spindle center line C2 as its 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 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 sent 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 rotating shaft 62. The B-axis motor 63 is composed of a rotor 631 that rotates together with the rotating 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 is 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 advancing side, and the right side in FIG. 2 may be referred to as the retreating 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 toward the retreating side. When oil is supplied to the second pressure chamber 653B, the brake piston 652 slides toward the advancing side. When the brake piston 652 moves toward the advancing side, 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 by the hydraulic device 653, the brake piston 652 moves in a direction toward or 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 1 / 10 or less. 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, the brake disc 651, the brake piston 652, and the hydraulic device 653 that moves the brake piston 652, all of which are shown in FIG.

[0045] 3, the hydraulic device 653 has 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 draws 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 of the oil sent from the hydraulic pump 6531 and the recovery destination of the oil 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 a state in which oil is supplied to the second pressure chamber 653B by the hydraulic device 653 and the oil that was in the first pressure chamber 653A is recovered. As a result, the brake piston 652 moves to the advancing side, and a rotation-blocked state is established in which rotation of the pivot shaft 62 and the tool spindle unit 7 is blocked. 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 that occurs when machining the workpiece W (see FIG. 2).

[0050] Solenoid valve 6533 has a valve spring 6533A inside. When hydraulic device 653 stops and power supply to solenoid valve 6533 is cut off due to, for example, a stop of machine tool 1 caused by an emergency stop or power being turned off, valve spring 6533A acts to supply oil to second pressure chamber 653B and recover oil to first pressure chamber 653A, as shown in Fig. 3. That is, Fig. 3 shows solenoid valve 6533 when the solenoid valve is controlled by the control device to enter a rotation-blocked state and when machine tool 1 is stopped due to an emergency stop or 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 collected from the second pressure chamber 653B. The hydraulic pump 6531 is then driven to supply oil to the first pressure chamber 653A and collect 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, and the rotation permitted state is maintained until the machine tool 1 is stopped by an emergency stop or by turning off the power, 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 swing-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 between the brake disc 651 and the outer cylinder 61 in the Y-axis direction. This allows the brake disc 651, the swing shaft 62, and the tool spindle unit 7 to swing freely. By driving the B-axis motor 63 in this swing-permitted state, the tool spindle unit 7 can be set to any swing angle. FIG. 6(a) is a cross-sectional view taken along line AA 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 to the advancing side with its protruding surface facing the retreating end face of the brake piston 652 (see Figure 2). A plurality of recesses 661A are formed on the small diameter portion 6612 at equal intervals in the circumferential direction on the same circle. 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. 6(a), 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 center line 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 advancing direction. The angular intervals at which the biasing members 654 are arranged and the number of biasing members 654 may be any number, but 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 moving direction 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 contact with one side, which prevents uneven wear of the brake disc 651, brake piston 652, and outer cylinder 61 (see FIG. 2).

[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, and the swing blocked state is maintained. 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, even when the machine tool 1 stops, 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 obstruct 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 moves 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. Additionally, 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. [Explanation of symbols]

[0061] 1 Machine tools 7 Tool spindle unit 651 Brake disc 652 Brake piston (brake member) 653 Hydraulic system (brake drive system) 654 biasing member

Claims

1. In a machine tool having a swiveling tool spindle unit, Brake discs and a brake member 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 rotation prevented state in which rotation of the tool spindle unit is prevented and a rotation permitted state in which rotation of the tool spindle unit is permitted, and maintains the changed state; a biasing member that moves the brake member toward the brake disc when the brake drive device is stopped, thereby preventing the tool spindle unit from turning.

2. The brake member is cylindrical, 2. The machine tool according to claim 1, wherein the biasing members are arranged in a plurality on the same circumference at equal intervals around the circumferential direction of the brake member to bias the brake member toward the brake disc.

3. When fluid is supplied to a first pressure chamber and the fluid is collected from a second pressure chamber, the brake member moves away from the brake disc to enter the turning-permitted state, and when fluid is supplied to the second pressure chamber and the fluid is collected from the first pressure chamber, the brake member moves toward the brake disc to enter the turning-prevented state, the brake drive device has an electromagnetic valve that switches a supply destination of the fluid from one of the first pressure chamber and the second pressure chamber to the other, and simultaneously switches a recovery destination of the fluid from the other of the first pressure chamber and the second pressure chamber to one of the first pressure chamber and the second pressure chamber, 3. The machine tool according to claim 1, wherein the solenoid valve supplies the fluid to the second pressure chamber and recovers the fluid to the first pressure chamber when the brake drive device is stopped.

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