Machine tool

Abstract

The invention provides a machine tool which can export clamping force of a clamping part with low cost and high precision. This machine tool is provided with: a first spindle (4) having a collet chuck (41) for clamping a workpiece (W1); a first headstock (3) that rotatably supports the first spindle (4); a cylinder (33) that generates a driving force that changes the state of the collet chuck (41) between a clamping state in which the collet chuck (41) clamps the workpiece (W1) and a clamping release state in which the clamping of the workpiece (W1) is released; a non-rotation transmission member (34) that transmits the driving force received from the cylinder (33); a rotation transmission member (45) that rotates together with the first main shaft (4) and transmits the driving force received from the non-rotation transmission member (34) to the collet chuck (41); a strain detection mechanism (46) that is attached to the non-rotation transmission member (34) and detects strain of the non-rotation transmission member (34) generated when the driving force is transmitted from the cylinder (33) to the collet chuck (41); and a derivation unit (23) that derives the clamping force of the collet chuck (41) on the basis of the detection result of the strain detection mechanism (46).

Description

Technical Field

[0001] This invention relates to a machine tool for machining a workpiece held by a spindle. Background Technology

[0002] A machine tool for machining a rod-shaped workpiece held by a freely rotating spindle is known (see, for example, Patent Document 1, etc.). The spindle of this machine tool is rotatably supported by a spindle table. A clamping section is provided in the spindle, which changes state between a clamped state holding the workpiece and a clamped-out state releasing the workpiece from the clamp. The clamping section is actuated by an actuator fixed to the spindle table. In the machine tool of Patent Document 1, by driving the actuator to swing a shifter lever, the jaw assembly tilts as the shifter moves. Then, as the jaw assembly tilts, the push sleeve and chuck sleeve move along the axis of the spindle, thereby causing the clamping section to clamp or release the workpiece.

[0003] In addition, the spindle is generally equipped with an adjusting nut as an adjustment mechanism for adjusting the clamping force of the workpiece. This adjusting nut is mounted on the spindle body in a manner that allows it to rotate relative to the spindle body. By rotating the adjusting nut relative to the spindle body's axis, its position is displaced, thus changing the workpiece clamping force. During a so-called "adjustment" operation, when machining workpieces with different diameters or materials compared to previously machined workpieces, the machine operator inserts the next workpiece to be machined into the clamping part and adjusts the clamping force by rotating the adjusting nut relative to the spindle body. Then, the operator manually actuates the shift lever used to move the shifter, estimating the clamping force of the clamping part based on the force required for this actuation. After repeatedly rotating the adjusting nut and estimating the clamping force, the operator fixes the adjusting nut to the spindle body at the position where the desired clamping force is achieved.

[0004] [Background Technical Documents]

[0005] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-97075 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] However, conventional adjustment methods rely on operator feel to estimate clamping force, resulting in low accuracy. Furthermore, the clamping force can change over time or years after adjustment, due to factors such as wear or thermal displacement of mechanisms like shifters or claw components between the actuator and the clamping unit, and deterioration of rubber pads. Therefore, there is a concern that the adjusted clamping force may differ from the estimated clamping force at the time of adjustment, but this difference cannot be detected. As a countermeasure, installing a load sensor or similar measuring mechanism on the clamping unit to detect the clamping force is considered. However, obtaining the detection results from a measuring mechanism mounted on the rotating spindle requires expensive devices such as slip rings. Furthermore, due to the high-speed rotation of the spindle, noise is generated in the sliding parts between the spindle and non-rotating parts like slip rings, leading to a decrease in the reliability of the detection signal.

[0009] The present invention was made in view of the aforementioned problems, and aims to provide a machine tool that can generate the clamping force of the clamping part with high precision and inexpensive construction.

[0010] [Technical means to solve the problem]

[0011] The machine tool of the present invention, which solves the aforementioned problem, is characterized by comprising:

[0012] The spindle has a clamping part for holding the workpiece;

[0013] The spindle table supports the spindle in a manner that allows it to rotate freely.

[0014] An actuator, mounted on the spindle table, generates a driving force that causes the clamping part to change state between a clamping state that clamps the workpiece and a clamping release state that releases the workpiece from the clamp.

[0015] A non-rotational transmission component, mounted on the spindle table, transmits the driving force received from the actuator;

[0016] The rotary transmission component rotates together with the main shaft and transmits the driving force received from the non-rotary transmission component to the clamping part;

[0017] A strain detection mechanism, installed on the non-rotational transmission component, detects the strain of the non-rotational transmission component generated when the driving force is transmitted from the actuator to the clamping part; and

[0018] The output section, based on the detection results of the strain detection mechanism, outputs the clamping force of the clamping section.

[0019] According to this machine tool, since the clamping force of the clamping part is derived based on the strain generated when the driving force is transmitted from the actuator to the clamping part, the clamping force of the clamping part can be derived with high accuracy, and there will be no errors caused by the operator. Furthermore, since this machine tool can derive the clamping force of the clamping part whenever a workpiece clamping action (a state change action from the clamping release state to the clamping state) is performed between machining operations when using an NC program for continuous machining, it is possible to identify changes that occur over time or over years. In addition, since the strain detection mechanism is mounted on the non-rotational transmission component, the detection results of the strain detection mechanism can be communicated using an inexpensive communication mechanism. Therefore, compared to the case where the measuring mechanism is mounted on the rotary transmission component, the machine tool of the present invention can achieve a more cost-effective configuration.

[0020] Here, the clamping part can also be a collet chuck. The non-rotational transmission component can also transmit the driving force from the actuator to the rotary transmission component. The rotary transmission component can also be mounted on the spindle. The output part can also output the clamping force of the clamping part in the clamping state based on the strain generated by the non-rotational transmission component during the change of state from the clamping release state to the clamping state.

[0021] In this machine tool,

[0022] The rotary transmission component includes: a claw component capable of changing its posture between a first posture in which the clamping part is in the clamping state and a second posture in which the clamping part is in the clamping release state; and a shifter capable of changing its position between a first position in the first posture and a second position in the second posture by moving it in the axial direction of the spindle.

[0023] The non-rotational transmission component has a shift lever that moves the shifter in the direction of the axis.

[0024] The strain detection mechanism can also detect the strain of the gear shift lever.

[0025] Because the shift lever is located downstream of the drive force transmission path in the non-rotational transmission component, it is less susceptible to interference compared to components located upstream of the drive force transmission path. Therefore, the clamping force of the clamping part can be derived with higher accuracy.

[0026] Here, the claw component can also change its posture by rotating within a specified angle range. Furthermore, the claw component can rotate around an orthogonal direction orthogonal to the axis of the main shaft (rotation center axis direction). The shift lever can also swing around a swing center axis by the driving force generated by the actuator.

[0027] In this machine tool,

[0028] The strain detection mechanism can also detect the strain at the location between the force-bearing part and the action part. The force-bearing part is the part where the shift lever receives the driving force from the actuator, and the action part is the part where the reaction force received by the shift lever from the shifter takes effect when the driving force received by the shift lever is transmitted to the shifter.

[0029] By doing so, the strain generated by the shift lever when transmitting the driving force from the actuator can be detected with high precision.

[0030] In addition, in this machine tool,

[0031] The gear shift lever swings freely around its swing center axis, and this swinging motion causes the gear shifter to move towards the axis.

[0032] The strain detection mechanism can also detect the strain on the side of the shift lever formed in a manner parallel to the axis of the swing center.

[0033] In doing so, the strain generated when the driving force from the actuator is transmitted can also be detected with high precision by the strain detection mechanism.

[0034] In addition, in this machine tool,

[0035] The gear shift lever swings freely around its swing center axis, and this swinging motion causes the gear shifter to move towards the axis.

[0036] The strain detection mechanism can also detect the strain at the following location: the location whose distance from the axis of the swing center is shorter than its distance from the force-bearing location and the action location.

[0037] Since the strain generated by the shift lever when transmitting the driving force from the actuator is greater near the swing center axis than near the force-bearing part or the action part, the strain can be detected with high precision by shortening the distance from the swing center axis.

[0038] Here, the axis of the swing center can also be located between the force-bearing part and the action part.

[0039] Furthermore, in this machine tool,

[0040] The derivation section can also derive the clamping force of the clamping section based on the maximum value of the strain of the non-rotational transmission component during the process of the state changing from the clamping release state to the clamping state as detected by the strain detection mechanism.

[0041] Since there is a correlation between the maximum strain detected by the strain detection mechanism and the clamping force of the clamping part, the clamping force of the clamping part can be derived with high accuracy based on the maximum strain.

[0042] [Invention Effects]

[0043] According to the present invention, a machine tool with an inexpensive structure that can accurately output the clamping force of the clamping part can be provided. Attached Figure Description

[0044] Figure 1 This is a top view that simply shows the internal structure of the NC lathe in this embodiment.

[0045] Figure 2 It is Figure 1 The three-dimensional sectional view obtained by cutting off a portion of the first spindle stage and the first spindle shown.

[0046] Figure 3 It is Figure 1 The first spindle table and the first spindle shown are sectional views obtained by cutting them with a horizontal plane passing through the axis of the first spindle and viewed from above.

[0047] Figure 4 yes Figure 3 An enlarged view of the first spindle and the rotary transmission component shown.

[0048] Figure 5 It is Figure 1 The first spindle stage shown is cut off to represent a perspective sectional view of a portion of the non-rotational transmission component and a portion of the rotational transmission component.

[0049] Figure 6 It is Figure 5 The three-dimensional sectional view is obtained by cutting a portion of the shift lever along its extension direction.

[0050] Figure 7 It is from the rear end side of the spindle. Figure 5 The diagram was obtained by observing the gear shift lever shown.

[0051] Figure 8 yes Figure 1 The control block diagram of the NC lathe is shown.

[0052] Figure 9 It means Figure 1 The graph shown is an example of the strain of the shift lever detected by the strain detection mechanism when the state of the first spindle changes from the clamped-off state to the clamped state.

[0053] Figure 10 It means Figure 1 The flowchart shows the automatic adjustment action of the clamping force in the first spindle.

[0054] Figure 11 (a) in the text represents Figure 5 The diagram shows the relationship between the force received by the gear shift lever and the position of its swing center. Figure 11 (b) in the diagram is a schematic diagram showing the gear shift lever in the variation example and the relationship between the force received by the gear shift lever in the variation example and the position of the swing center. Detailed Implementation

[0055] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, an example of applying the present invention to a Swiss-type NC (Numerical Control) lathe will be used for explanation. That is, the NC lathe described below is equivalent to an example of a machine tool.

[0056] Figure 1 This is a top view that simply shows the internal structure of the NC lathe 1 of this embodiment.

[0057] like Figure 1 As shown, the NC lathe 1 is internally equipped with a control device 2, a first spindle head 3, a first spindle 4, a guide sleeve 5, a first tool post 6, a second spindle head 7, a second spindle 8, and a second tool post 9. The control device 2 is a computer that operates the first spindle head 3, first spindle 4, first tool post 6, second spindle head 7, second spindle 8, and second tool post 9 according to an NC program. In addition to operating the NC lathe 1 using an NC program, commands can also be directly transmitted from the operation unit 11 (see reference 11). Figure 8 The input is sent to the control device 2 to make the NC lathe 1 move.

[0058] The first spindle stage 3 moves along the Z1 axis along with the first spindle 4, based on signals from the control device 2. The Z1 axis is horizontal. Figure 1 The center represents the left-right direction. The first spindle 4 is rotatably supported on the first spindle table 3. Furthermore, a first spindle motor 31 (see reference) is provided between the first spindle table 3 and the first spindle 4. Figure 2The first spindle motor 31 receives a signal from the control device 2 and rotates, thereby causing the first spindle 4 to rotate about the first axis CL1. The first axis CL1 is an example of an axis. The direction of the first axis CL1 is consistent with the direction of the Z1 axis.

[0059] The first spindle 4 changes state between a clamping state where it holds a long, rod-shaped workpiece W1 inserted into it and a clamping-release state where it releases the workpiece W1 from the clamp. This first spindle 4 is equivalent to an example of a spindle. As the first spindle 4 rotates, the workpiece W1 held by the first spindle 4 rotates together with the first spindle 4 about the first axis CL1. The configuration of the first spindle stage 3 and the first spindle 4 will be described in detail below.

[0060] The guide sleeve 5 is fixed inside the NC lathe 1. The guide sleeve 5 supports the front end portion of the workpiece W1 protruding from the first spindle 4, allowing it to slide freely along the Z1 axis. The portion of the guide sleeve 5 supporting the workpiece W1 can rotate synchronously with the first spindle 4 around the first axis CL1. That is, the first axis CL1 is also the axis of rotation of the portion of the workpiece W1 supported by the guide sleeve 5. Because of the guide sleeve 5, deflection of the workpiece W1 during machining is suppressed, thus enabling high-precision machining of particularly slender workpieces W1.

[0061] The first tool post 6 is capable of moving along the X1 axis (orthogonal to the Z1 axis and oriented horizontally) and the Y1 axis (oriented vertically). The first tool post 6 moves along the X1 and Y1 axes upon receiving signals from the control device 2. Figure 1 In the middle, the vertical direction is the X1 axis direction, and the direction orthogonal to the paper plane is the Y1 axis direction. The first tool holder 6 is equipped with the first spindle tool T1 for machining the workpiece W1. Figure 1 The diagram shows a first spindle tool T1 mounted in the first tool post 6. Several types of first spindle tools T1, including turning tools for external diameter machining and turning tools for cutting, are mounted side-by-side along the Y1 axis in the first tool post 6. By moving the first tool post 6 along the Y1 axis, any one of these first spindle tools T1 can be selected. Then, by moving the first tool post 6 along the X1 axis, the selected first spindle tool T1 is inserted into the workpiece W1 held by the first spindle 4 to machine the workpiece W1.

[0062] The second spindle stage 7 moves along the X2 and Z2 axes together with the second spindle 8 according to signals from the control device 2. The X2 axis is the same direction as the X1 axis, and the Z2 axis is the same direction as the Z1 axis. The second spindle stage 7 is equipped with a second spindle motor (not shown) such as a built-in motor. This second spindle motor rotates upon receiving signals from the control device 2, thereby causing the second spindle 8 to rotate around a second axis CL2. This second axis CL2 is also an example of an axis. The direction of the second axis CL2 is consistent with the Z2 axis.

[0063] The second spindle 8 receives workpiece W2, which has been machined using the first spindle 4 and cut off by a cutting tool. The second spindle 8 changes state between a clamping state holding the cut-off workpiece W2 delivered from the first spindle 4 and a clamping-release state releasing the clamped workpiece W2. This second spindle 8 is also an example of a spindle. As the second spindle 8 rotates, the cut-off workpiece W2, held by the second spindle 8, rotates together with the second spindle 8 around the second axis CL2.

[0064] The second tool post 9 moves in the Y2 axis direction according to the signal from the control device 2. This Y2 axis direction is the same as the Y1 axis direction, that is, the perpendicular direction. The second tool post 9 is equipped with a plurality of second spindle tools T2 for machining the workpiece W2 that has been cut and held by the second spindle 8. Figure 1 The image shows a second spindle tool T2 mounted in the second tool post 9. The second tool post 9 can hold various types of second spindle tools T2, such as drills or end mills. Figure 1 Although not explicitly stated, the second spindle tool T2 can be mounted side-by-side not only along the X2 axis but also along the Y2 axis. By moving the second spindle head 7 along the X2 axis and the second tool post 9 along the Y2 axis, any of these various types of second spindle tools T2 can be selected. Then, by moving the second spindle head 7 along the Z2 axis, the cut-off end portion of the workpiece W2, held by the second spindle 8, is machined.

[0065] Figure 2 It is Figure 1 The perspective sectional view obtained by cutting off a portion of the first spindle stage 3 and the first spindle 4 shown. Figure 2 The text shows that... Figure 2 The first spindle stage 3 and the first spindle 4, after the 90-degree portion near the upper front side has been cut off. Additionally, in the accompanying drawings used to describe this embodiment, besides the following... Figure 6Apart from the cross-section of the gear shift lever 341, no additional shading lines indicating the cross-section are added.

[0066] like Figure 2 As shown, the first spindle stage 3 includes a first spindle stage body 30, a first spindle motor 31, and a bearing 32. The first spindle stage body 30 is the base component of the first spindle stage 3 and is a moving object that moves along the Z1 axis direction via a Z1 axis motor (not shown). The first spindle motor 31 is a built-in motor installed in the first spindle stage body 30. The bearing 32 supports the first spindle 4 in a manner that allows it to rotate freely. As described above, by rotating the first spindle motor 31, the first spindle 4 is rotated about the first axis CL1 via the bearing 32.

[0067] Furthermore, a cylinder 33 is installed in the first spindle stage 3. More specifically, a non-rotational transmission component 34 is installed in the first spindle stage 3. This non-rotational transmission component 34 includes a piston rod 340, a shift lever 341, a rocker arm shaft 342, a connecting pin 343, an actuating shaft 344, and an actuating bearing 345. The configuration of these cylinders 33 and the non-rotational transmission component 34 will be described in detail below.

[0068] The first spindle 4 includes a spindle body 40, a spring collet 41, and a spindle cap 42. Furthermore, a rotational transmission component 45 is installed in the first spindle. The rotational transmission component 45 includes a shifter 452, a jaw component 453, a push sleeve 454, a helical spring 455, a chuck sleeve 456, and an adjusting nut 457. This rotational transmission component 45 transmits the driving force received from the non-rotational transmission component 34 to the spring collet 41, causing the spring collet 41 to either reduce or expand its diameter. The spindle body 40 is the base component of the first spindle 4 and is a cylindrical body extending in the Z1 axis direction. The spring collet 41, the spindle cap 42, and the rotational transmission component 45 rotate together with the spindle body 40 about the first axis CL1 as the center of rotation.

[0069] Figure 3 It is Figure 1 The first spindle stage 3 and the first spindle 4 shown are sectional views obtained by cutting them through a horizontal plane passing through the first axis CL1 and viewing them from above. Furthermore, Figure 4 yes Figure 3 An enlarged view of the first main shaft 4 and the rotary transmission component 45 shown. In these... Figure 3 and Figure 4 In the diagram, the first spindle stage 3 and the first spindle 4 are represented by solid lines in the clamped-out state. Furthermore, in... Figure 3 and Figure 4 In the diagram, the left side becomes the rear end side of the first main axis 4, and the right side becomes the front end side of the first main axis 4. Furthermore, the directions towards the front end and the rear end are consistent with the Z1 axis direction.

[0070] like Figure 4 As shown, the spring collet 41 is configured to expand and contract in the radial direction orthogonal to the first axis CL1. This spring collet 41 is an example of a clamping part. The outer peripheral surface 41a of the front end of the spring collet 41 has an inclined surface with a larger diameter closer to the front end. A total of three slots are formed in the spring collet 41, which are continuous structures extending from the front end to a hole formed near the center in the Z1 axis direction, and the three slots are arranged at 120° intervals along the circumferential direction. Through these holes and slots, the front end side of the spring collet 41, in particular, can expand and contract in the radial direction. Figure 3 and Figure 4 In the diagram, solid lines represent the expanded diameter of the spring collet 41. Furthermore, in... Figure 4 In the diagram, a double-dotted line is used to indicate the reduction in diameter of the spring collet 41. By reducing the diameter of the spring collet 41, the first spindle 4 is put into a clamping state, and by expanding the diameter of the spring collet 41, the first spindle 4 is put into a clamping-out state.

[0071] The spindle end cap 42 is disposed at the foremost end of the first spindle 4. The spindle end cap 42 is cup-shaped, and a circular end cap through hole extending through the Z1 axis is formed in the center portion. By contacting the front end face of the spring collet 41 with the portion corresponding to the bottom of the cup shape, the spindle end cap 42 restricts the movement of the spring collet 41 towards the front end. The spring collet 41 is pressed against the spindle end cap 42 by the helical spring 455. The spindle end cap 42 is fixed to the spindle body 40 by engaging the female thread portion formed on the inner side of its cup-shaped edge with the male thread portion formed on the front end portion of the spindle body 40.

[0072] The shifter 452 is disposed on the outer side of the spindle body 40. The shifter 452 is generally cylindrical and is mounted on the spindle body 40 in a manner that allows it to slide along the Z1 axis through sliding contact between its inner circumferential surface and the outer circumferential surface of the spindle body 40. Figure 4 As shown, a cam surface 452a and a groove 452b are formed on the outer peripheral surface of the shifter 452. The cam surface 452a, counting from the rear end of the first main shaft 4, sequentially includes a small-diameter surface 452a1 with a fixed outer diameter, a changing-diameter surface 452a2 with a gradually increasing outer diameter, and a large-diameter surface 452a3 with a fixed outer diameter. This shifter 452 is connected via a cylinder 33 (see reference). Figure 2 Driven by the driving force of the cylinder 33, it slides along the Z1 axis. The action of the cylinder 33 is controlled by the control device 2 (see reference). Figure 1 Controlled by ) Figure 3 and Figure 4 In the diagram, a solid line indicates that the shifter 452 is located on the front end closest to the main shaft 4. Furthermore, in... Figure 4In the diagram, a double-dotted line is used to indicate the position of the shifter 452 closest to the rear end of the first main shaft 4. The position of the shifter 452 indicated by the double-dotted line is the first position, and the position of the shifter 452 indicated by the solid line is the second position.

[0073] Two claw components 453 are mounted on the main shaft body 40. The claw components 453 are capable of rotating within a specified angle range around the claw shaft 4531. A claw front end portion 453b is formed at the front end of the claw component 453, which functions as a cam follower in contact with the cam surface 452a of the shifter 452. As the shifter 452 slides, the claw front end portion 453b moves closer to or further away from the first axis CL1 along the cam surface 452a, thereby causing the claw component 453 to rotate around the claw shaft 4531 as its rotation center. A sleeve pushing portion 453a is formed in the claw component 453, which contacts the rear end of the pushing sleeve 454.

[0074] The push sleeve 454 is a cylinder disposed inside the main shaft body 40, and its front end contacts the rear end portion of the chuck sleeve 456. As the shifter 452 moves along the Z1 axis, the push sleeve 454 and the chuck sleeve 456 move in the opposite direction to the shifter 452. Specifically, as the shifter 452 slides toward the rear end of the first main shaft 4, the front end portion 453b of the pawl member 453 is pushed upward by the cam surface 452a of the shifter 452 and moves in a direction away from the first axis CL1. In this way, Figure 4 The upper claw component 453 rotates counterclockwise around the claw axis 4531 as the rotation center. Figure 4 The lower claw component 453 rotates clockwise, and the push sleeve 454 and chuck sleeve 456 are pushed towards the front end of the first spindle 4 by the sleeve push part 453a of the claw component 453. Figure 4 In the diagram, a double-dotted line is used to indicate the situation where the front end portion 453b of the claw component 453 is far away from the first axis CL1. The posture of the claw component 453 represented by the double-dotted line is the first posture, and the posture of the claw component 453 represented by the solid line is the second posture.

[0075] During the upward pushing of the cam surface 452a of the shifter 452 by the claw tip portion 453b, at the instant the contact point between the claw tip portion 453b and the cam surface 452a reaches the intersection point of the changing surface 452a2 and the large diameter surface 452a3, the spring collet 41 changes to its maximum diameter reduction state, and the first main shaft 4 changes to a clamping state. Furthermore, at that instant, the spring collet 41 is released from the cylinder 33 (reference...) Figure 3 The force transmitted to the spring collet 41 becomes maximum. At workpiece W1 (reference...) Figure 1When the workpiece is located within the spring collet 41, the force is related to the clamping force of the spring collet 41 on the workpiece W1; the greater the force, the greater the clamping force. Furthermore, when the contact point between the jaw tip 453b and the cam surface 452a exceeds the intersection of the changing surface 452a2 and the major diameter surface 452a3 and is located on the major diameter surface 452a3, the first spindle 4 maintains the clamping state.

[0076] Conversely, as the shifter 452 slides towards the front end of the first main shaft 4, the front end portion 453b of the pawl member 453 moves along the cam surface 452a of the shifter 452 in a direction closer to the first axis CL1. In this way, Figure 4 The upper claw component 453 rotates clockwise around the claw axis 4531. Figure 4 The lower jaw component 453 rotates counterclockwise, pushing the sleeve 454 and chuck sleeve 456 towards the rear end of the first spindle 4. Furthermore, the spring collet 41 becomes an expanded diameter state. Figure 4 In the diagram, solid lines are used to represent the situation where the upper claw component 453 rotates clockwise and the lower claw component 453 rotates counterclockwise.

[0077] While the helical spring 455 continuously pushes the chuck sleeve 456 toward the rear end, it also continuously pushes the spring collet 41 toward the front end. In this way, the chuck sleeve 456 pushes the push sleeve 454 toward the rear end, and the rear end of the push sleeve 454 pushes the sleeve push portion 453a toward the rear end.

[0078] The inner circumferential surface 456a of the front end of the chuck sleeve 456 is an inclined surface whose diameter increases as it approaches the front end. Figure 3 and Figure 4 In the clamping release state, indicated by the solid line, since the chuck sleeve 456 is located on the rear end side, there is almost no force exerted by the inner circumferential surface 456a of the front end of the chuck sleeve 456 pushing the outer circumferential surface 41a of the front end of the spring collet 41 radially inward. The front end of the spring collet 41 expands in diameter due to its own elasticity. On the other hand, in Figure 3 and Figure 4 In the clamping state indicated by the double-dotted line, since the chuck sleeve 456 is located on the front end side, the inner circumferential surface 456a of the front end of the chuck sleeve 456 pushes the outer circumferential surface 41a of the front end of the spring collet 41 radially inward, thereby reducing the diameter of the front end side of the spring collet 41.

[0079] An adjusting nut 457 is disposed at the rear end of the first spindle 4. This adjusting nut 457 is an example of an adjusting mechanism. A female thread is formed on the inner side of the adjusting nut 457, which engages with a male thread formed at the rear end of the spindle body 40. By rotating in the direction that tightens the adjusting nut 457, the jaw member 453, the push sleeve 454, and the chuck sleeve 456 move together with the adjusting nut 457 toward the front end of the first spindle 4. As a result, the inner diameter of the spring collet 41 in the clamping state becomes relatively smaller, and the clamping force of the first spindle 4 on the workpiece W1 increases. On the other hand, by rotating in the direction that loosens the adjusting nut 457, the jaw member 453, the push sleeve 454, and the chuck sleeve 456 move together with the adjusting nut 457 toward the rear end of the first spindle 4. As a result, the inner diameter of the spring collet 41 in the clamping state becomes relatively larger, and the clamping force of the first spindle 4 on the workpiece W1 decreases.

[0080] Viewed from the rear end of the first spindle 4 towards the front end, the adjusting nut 457 presents a C-shape with a notch extending radially. The width of this notch can be changed using a fixing screw (not shown). After adjusting the clamping force using the adjusting nut 457, the notch is narrowed using the fixing screw, thereby fixing the adjusting nut 457 to the spindle body 40 in the adjusted position. Furthermore, a nut rotation inhibiting device (not shown) is also installed in the first spindle table 3, which inhibits the rotation of the adjusting nut 457. With the screw that narrows the notch of the adjusting nut 457 loosened and the nut rotation inhibiting device preventing the rotation of the adjusting nut 457, the adjusting nut 457 can be positioned at the desired rotation angle relative to the first spindle 4 by rotating the first spindle 4 at a specified angle. In other words, the clamping force of the workpiece W1 on the first spindle 4 can be automatically adjusted by the rotation inhibiting device and the rotation of the first spindle 4. Alternatively, the clamping force of the workpiece W1 on the first spindle 4 can be adjusted using an adjustment mechanism other than the adjusting nut 457.

[0081] like Figure 3 As shown, cylinder 33 includes a cylinder barrel 321 and a piston 322. This cylinder 33 is an example of an actuator. Alternatively, a hydraulic cylinder or a motor, such as a hydraulic cylinder, can be used instead of cylinder 33. The cylinder barrel 321 is the housing of cylinder 33 and is cylindrical. Piston 322 is in contact with the inner circumferential surface of cylinder barrel 321 and is arranged within cylinder barrel 321 in a manner that allows it to move in one direction and the other. This piston 322 is driven by air supplied to cylinder 33 and moves within cylinder barrel 321 towards the rear end and the front end. Figure 3 The image shows the piston 322 positioned closest to the rear end.

[0082] Figure 5 It is Figure 1 The first spindle stage 3 shown is cut off to represent a portion of the non-rotational transmission component 34 and a portion of the rotational transmission component 45 in a perspective sectional view. Furthermore, Figure 6 It is Figure 5 The perspective sectional view is obtained by cutting a portion of the shift lever 341 along its extending direction. Additionally, in Figure 6 In the diagram, the cross-section of the gear shift lever 341 is represented by an additional shading line.

[0083] As described above, the non-rotational transmission component 34 includes a piston rod 340, a shift lever 341, a rocker arm shaft 342, a connecting pin 343, and an actuating shaft 344 (see reference). Figure 6 ), and the function bearing 345 (reference) Figure 6 The piston rod 340 has one end fixed to the piston 322 (see reference). Figure 3 A rod-shaped object. (e.g.) Figure 5 As shown, the other end of the piston rod 340 is connected to the shift lever 341 via a connecting pin 343. The piston rod 340 is driven by the piston 322, changing state between a forward state (advancing from the cylinder 321 to the rear end) and a backward state (retracting to the front end). In other words, the driving force of the cylinder 33 is transmitted to the piston rod 340, thus functioning as the forward and backward movement of the piston rod 340.

[0084] The shift lever 341 swings freely around the rocker arm shaft 342 fixed to the first main shaft body 30. That is, the center line of the rocker arm shaft 342 becomes the axis of swing of the shift lever 341. A connecting pin 343 is fixed to one end of the shift lever 341. One end of the shift lever 341 is connected to the other end of the piston rod 340 via the connecting pin 343 in a freely rotatable manner. In this way, the driving force of the cylinder 33 is transmitted to the shift lever 341 via the connecting pin 343. The contact portion of the shift lever 341 with the connecting pin 343 becomes the force-receiving portion of the shift lever 341 that receives the driving force from the cylinder 33.

[0085] like Figure 6As shown, an actuating shaft 344 is fixed to the other end of the shift lever 341, and an actuating bearing 345 is installed in the actuating shaft 344. The actuating bearing 345 is fitted into the groove 452b of the shifter 452. In this way, the driving force transmitted from the cylinder 33 to the shift lever 341 via the connecting pin 343 is transmitted to the shifter 452. That is, the shift lever 341 is oscillated by driving the cylinder 33, and with this oscillation, the shifter 452 slides along the Z1 axis. The center line of the actuating shaft 344 coincides with the center line of the actuating bearing 345. When the shift lever 341 transmits the driving force to the shifter 452, the shift lever 341 is subjected to a reaction force from the shifter 452 via the actuating bearing 345 and the actuating shaft 344. The part of the shift lever 341 that contacts the actuating shaft 344 is called the actuating part. The distance from the center line of the rocker arm shaft 342 (which serves as the swing center line of the rocker arm 341) to the center line of the connecting pin 343 is longer than the distance from the center line of the rocker arm shaft 342 to the center line of the actuating shaft 344. Therefore, the shift lever 341 is equivalent to an example of a force-multiplying mechanism (lever mechanism) that amplifies the driving force transmitted from the piston rod 340 and then transmits that driving force to the shifter 452. The non-rotational transmission component 34 and the rotational transmission component 45 described above are examples of transmitting driving force from the cylinder 33 to the collet 41 (see reference). Figure 3 The driving force transmission mechanism.

[0086] Figure 7 It is from the rear end side of the spindle. Figure 5 The diagram was obtained by observing the gear shift lever 341 shown. Additionally, in Figure 7 In the diagram, double-dotted lines are used to represent the first main shaft 4, piston rod 340, gear shifter 452, push sleeve 454, and cylinder 33.

[0087] like Figure 7 As shown, the shift lever 341, viewed from the rear end, is roughly U-shaped. The actuating shaft 344 and the actuating bearing 345 are symmetrical about the horizontal direction and are respectively positioned at the other end of the shift lever 341 that divides it into upper and lower parts. Furthermore, at the rear end of the shift lever 341 ( Figure 7 A strain detection mechanism 46 is mounted on the side of the paper (near the front). Alternatively, the strain detection mechanism 46 can also be mounted on the front end of the shift lever 341. Figure 7 The middle side is the back side of the paper.

[0088] The strain detection mechanism 46 is a strain gauge, which measures the strain generated on the shift lever 341 when the driving force of the cylinder 33 is transmitted from the cylinder 33 to the spring collet 41. A signal line 461 is connected to the strain detection mechanism 46. The strain signal detected by the strain detection mechanism 46 is sent to the control device 2 (reference) via the signal line 461. Figure 1 ).

[0089] The strain detection mechanism 46 detects the strain of the shift lever 341 generated at the mounting location of the strain detection mechanism 46. From the Z1 axis direction ( Figure 7 When observing (in the direction perpendicular to the paper), the strain detection mechanism 46 is installed at a position coinciding with the center line of the rocker arm shaft 342. The strain detection mechanism 46 is preferably positioned between the contact point between the shift lever 341 and the connecting pin 343, and between the contact point between the rocker arm 341 and the actuating shaft 344. The contact point between the shift lever 341 and the connecting pin 343 is the force-bearing part of the shift lever 341 that receives the driving force, while the contact point between the rocker arm 341 and the actuating shaft 344 is the action part of the shift lever 341 that receives the reaction force from the shifter 452. By positioning the strain detection mechanism 46 between the force-bearing part and the action part, the strain generated by the shift lever 341 when it receives the driving force from the cylinder 33 can be detected with high precision. Furthermore, as described in this embodiment, in the configuration where the center line of the rocker arm shaft 342 is located between the force-bearing part and the action part, the strain detection mechanism 46 is more preferably installed at a location where the distance from the center line of the rocker arm shaft 342 is shorter than the distance from both the force-bearing part and the action part, and even more preferably installed at a location coinciding with the center line of the rocker arm shaft 342. This is because, since the strain generated near the center line of the rocker arm shaft 342 is greatest when the shift lever 341 receives the driving force from the cylinder 33, by shortening the distance from the center line of the rocker arm shaft 342, the strain detection mechanism 46 can detect the strain with higher accuracy.

[0090] Furthermore, the strain detection mechanism 46 is preferably mounted on the side of the shift lever 341, which is formed parallel to the center line of the rocker arm shaft 342. A neutral surface exists at the center of the shift lever 341 in the thickness direction (Z1 axis direction), and this neutral surface is a surface that will not expand or contract even when the shift lever 341 receives a driving force from the cylinder 33. The reason for mounting the strain detection mechanism 46 on the side of the shift lever 341 is that the strain is greatest on the side separated from this neutral surface; therefore, by mounting the strain detection mechanism 46 on this side, the strain detection mechanism 46 can detect strain with high precision. In other words, the strain detection mechanism 46 can also be preferably mounted on a side parallel to the neutral surface of the shift lever 341.

[0091] Figure 8 yes Figure 1 The control block diagram of NC lathe 1 is shown below. Additionally... Figure 8 Although only the control configuration that is particularly relevant to this embodiment is shown, the control device 2 performs control over all the constituent devices of the NC lathe 1.

[0092] like Figure 8 As shown, the NC lathe 1 includes an operation unit 11 and a display unit 12 as an interface with the operator. The operation unit 11 is an input device for operating the NC lathe 1. The operation unit 11 includes multiple buttons or keys for input operations performed by the operator of the NC lathe 1. Alternatively, the operation unit 11 may be a touch panel integrated with the display unit 12. The display unit 12 is a display that shows various information related to the NC lathe 1, including the NC program, various settings, error messages, and the export results from the export unit 23 described below.

[0093] The control device 2 includes a timer 21, a storage mechanism 22, and a discharge unit 23. The timer 21 is used to measure the time elapsed since the start of the measurement. For example, the timer 21 measures the time elapsed since the NC lathe 1 was powered on, or the time elapsed since the start of the specified action.

[0094] The storage mechanism 22 stores control programs, NC programs, and various information, including non-volatile memory and volatile memory. In addition, the storage mechanism 22 has a strain-clamping force information storage unit 221, an adjusting nut-clamping force information storage unit 222, and a maximum strain storage unit 223.

[0095] The strain-clamping force information storage unit 221 stores the relationship between the magnitude of the strain detected by the strain detection mechanism 46 and the clamping force of the spring collet 41. The adjusting nut-clamping force information storage unit 222 stores the relationship between the rotation angle of the adjusting nut 457 and the clamping force of the spring collet 41. The maximum strain storage unit 223 stores the maximum strain, which is the maximum value of the strain detected by the strain detection mechanism 46 during the period from the issuance of the clamping command (closing command) of the spring collet 41 until a predetermined time has elapsed. Furthermore, the predetermined time is set to a sufficient time so that after the clamping command of the spring collet 41 is issued to the first spindle 4 in the clamping release state, its state is sufficient to change to the clamping state. The timer 21 measures whether the predetermined time has elapsed. Although this predetermined time is set by the manufacturer of the NC lathe 1, it can also be changed through operator input. Additionally, it can also be... Figure 3 The cylinder 33 shown is equipped with a sensor to detect when the piston 322 or piston rod 340 reaches the stroke end, and the time until the sensor sends an arrival signal is used instead of the specified time.

[0096] Figure 9 It means Figure 1 The graph shown is an example of the strain of the shift lever 341 detected by the strain detection mechanism 46 when the state of the first spindle 4 changes from the clamped-off state to the clamped state. See below for reference. Figure 4 and Figure 9 For use Figure 8 The action of deriving the clamping force of the spring collet 41 will be explained.

[0097] If a clamping command is issued to the first spindle 4, which is in the clamped-out state, then the cylinder 33 is driven under the control of the control device 2. In this way, the driving force of the cylinder 33 is transmitted to the shift lever 341 (see reference). Figure 3 When the shift lever 341 swings, the shifter 452 moves to the rear end. Then, the front end portion 453b of the pawl member 453 is pushed upward by the cam surface 452a of the shifter 452. At this time, due to the reaction force from the shifter 452 side generated by the moving resistance of the shifter 452 and the driving force from the cylinder 33, strain is generated in the shift lever 341, which should be as follows. Figure 9 As shown, the strain detected by the variable detection mechanism 46 continuously increases. When the contact point between the front end portion 453b of the jaw and the cam surface 452a reaches the intersection point of the variable surface 452a2 and the large diameter surface 452a3, the strain of the shift lever 341 reaches its maximum strain. When the front end portion 453b of the jaw exceeds this intersection point, the strain of the shift lever 341 begins to decrease. As described above, at the instant the contact point between the front end portion 453b of the jaw and the cam surface 452a reaches this intersection point, the spring collet 41 changes to its maximum diameter reduction state, and the first main shaft 4 changes to a clamping state.

[0098] After receiving the strain detected by the strain detection mechanism 46, the control device 2 performs the following processing, for example, every tens of μ seconds. The control device 2 stores the strain detected first after issuing a clamping command to the first spindle 4 in the clamped-out state in the maximum strain storage unit 223. Then, it compares the strain stored in the maximum strain storage unit 223 with the strain detected by the strain detection mechanism 46. If the current strain is greater, the strain value stored in the maximum strain storage unit 223 is overwritten. On the other hand, if the strain detected by the strain detection mechanism 46 is less than the strain stored in the maximum strain storage unit 223, the strain value stored in the maximum strain storage unit 223 remains unchanged. By repeatedly performing this processing until a predetermined time has elapsed after issuing a clamping command to the first spindle 4, the maximum strain is stored in the maximum strain storage unit 223. Furthermore, since the strain detected by the strain detection mechanism 46 is less than the strain stored in the maximum strain storage unit 223, it is highly likely that the strain stored in the maximum strain storage unit 223 at that time is the maximum strain. Therefore, the control device 2 can stop processing without waiting for the specified time to pass. This reduces the load on the control device 2.

[0099] After storing the maximum strain in the maximum strain storage unit 223, the derivation unit 23, based on the strain-clamping force relationship stored in the strain-clamping force information storage unit 221, derives the spring collet 41's position relative to the workpiece W1 (reference) based on the maximum strain stored in the maximum strain storage unit 223. Figure 1 The clamping force is then determined by the output unit 23. The output unit 23 then displays the value of the output clamping force on the display unit 12. Regarding the operation of the output unit 23, it is executed not only during debugging operations but also during continuous machining processes where the same operation is repeatedly performed using the NC program. The output unit 23 is executed whenever the state of the first spindle 4 needs to be changed to the clamping state. Normally, this state change occurs between machining operations in a continuous machining process. However, the output unit 23 may be executed only during debugging operations or only during continuous machining. Furthermore, the operator can choose whether to execute the output unit 23 during debugging operations and continuous machining operations respectively.

[0100] Next, the operation of automatically adjusting the clamping force during the debugging process will be explained.

[0101] Figure 10 It means Figure 1 The flowchart shows the automatic adjustment operation of the clamping force in the first spindle 4. Additionally, this... Figure 10 The automatic adjustment action shown is performed under the control of the control device 2.

[0102] Before the automatic adjustment operation, the operator of the NC lathe 1 uses the operating unit 11 to input the required clamping force into the control device 2. Furthermore, the operator of the NC lathe 1 uses the operating unit 11 to put the first spindle 4 in the clamped-out state and inserts the workpiece W1 into the spring collet 41. Then, the fixing screw (not shown) that secures the adjusting nut 457 to the first spindle 4 is loosened, allowing the adjusting nut 457 to rotate relative to the first spindle 4. After these preparatory operations are completed, the automatic clamping force adjustment operation is performed.

[0103] like Figure 10As shown, after automatic adjustment begins, the control device 2 activates the nut rotation inhibition device (not shown), causing the first spindle 4 to rotate and return the adjusting nut 457 to its initial position. This initial position is where the clamping force of the spring collet 41 is at its weakest. Next, based on the relationship between the rotation angle of the adjusting nut 457 and the clamping force of the spring collet 41 stored in the adjusting nut-clamping force information storage unit 222, the rotation angle of the adjusting nut 457 at which the pre-input required clamping force is achieved is extracted, and the first spindle 4 and the adjusting nut 457 rotate relative to each other only by this rotation angle (step S11). Alternatively, the current rotation angle of the adjusting nut 457 can be pre-stored in the storage mechanism 22, causing the adjusting nut 457 to rotate by the difference between its current rotation angle and the rotation angle at which the required clamping force is achieved.

[0104] Next, the control device 2 issues a clamping command to the first spindle 4, and while performing the process of storing the strain detected by the strain detection mechanism 46 in the maximum strain storage unit 223, changes the state of the first spindle 4 from the clamping release state to the clamping state (step S12).

[0105] After the state change is completed, the derivation unit 23 derives the clamping force of the spring collet 41 on the workpiece W1 based on the maximum strain obtained in the state change performed in step S12 and the relationship between strain and clamping force stored in the strain-clamping force information storage unit 221 (step S13).

[0106] Then, the output unit 23 determines whether the output clamping force is consistent with the required clamping force input by the operator (step S14). If it is determined that they are inconsistent in step S14, then based on the relationship between the rotation angle of the adjusting nut 457 and the clamping force of the spring collet 41 stored in the adjusting nut-clamping force information storage unit 222, the additional rotation angle required for the adjusting nut 457 is calculated. This additional rotation angle is to ensure that there is no difference between the clamping force output in step S13 and the required clamping force (step S15).

[0107] Then, the control device 2 rotates the first spindle 4 and the adjusting nut 457 relative to each other only by the additional rotation angle calculated in step S15 after the first spindle 4 is in the clamped release state (step S16). After completing step S16, the control device returns to step S12 and performs the operation stored in the maximum strain storage unit 223 while changing the state of the first spindle 4 back to the clamped state.

[0108] On the other hand, if the determination in step S14 is consistent, the action of the nut rotation prohibition device is released, and the automatic adjustment action ends. Thereafter, in order to maintain the required clamping force, the operator of the NC lathe 1 tightens the fixing screw (not shown) to ensure that the adjusting nut 457 does not rotate relative to the first spindle 4.

[0109] According to the NC lathe 1 of this embodiment described above, since the clamping force of the spring collet 41 is derived based on the detection results of the strain detection mechanism 46 mounted on the non-rotational transmission component 34, the detection results of the strain detection mechanism 46 can be sent to the control device 2 with a less expensive configuration compared to the case where the strain detection mechanism 46 is mounted on the rotational transmission component 45. Furthermore, since the clamping force of the spring collet 41 is derived based on the detection results of the strain detection mechanism 46, errors caused by the operator are eliminated, and the clamping force of the spring collet 41 can be derived with high accuracy. Moreover, since the clamping force can be derived not only during debugging operations but also whenever the workpiece W1 is clamped during continuous machining using the NC program, it is possible to identify changes in the clamping force due to time-related or year-related variations.

[0110] Furthermore, since the strain detection mechanism 46 is mounted on the shift lever 341 located downstream of the drive force transmission path in the non-rotational transmission component 34, it is less affected by interference such as clearance or frictional resistance between components compared to the case where the strain detection mechanism 46 is mounted upstream of the transmission path. Therefore, the clamping force of the spring collet 41 can be derived with higher accuracy.

[0111] Furthermore, by deriving the clamping force of the spring collet 41 based on the maximum strain, which is the maximum value of the strain detected by the strain detection mechanism 46, the influence of errors or noise caused by each change of state from the clamping release state to the clamping state is suppressed, and the clamping force of the spring collet 41 can be derived with higher accuracy.

[0112] The above description, based on the configuration of the first spindle head 3 and the first spindle 4, explains the configuration of the clamping force of the collet 41 in the NC lathe 1 of this embodiment. However, the drive force transmission mechanism from the drive source to the collet in the second spindle head 7 and the second spindle 8 also adopts the same configuration as that in the first spindle head 3 and the first spindle 4. Therefore, the description is omitted. However, the second spindle head 7 and the second spindle 8 can also derive the clamping force of the collet with low cost and high accuracy based on the detection results of the strain detection mechanism mounted on the non-rotational transmission component. In addition, the workpiece W2 that has been cut in the second spindle 8 is an example of a workpiece.

[0113] Next, the shift lever 341 and its variations described above will be further explained. In the following description, for components with the same names as those described above, the same symbols as those used above will be attached, and repeated descriptions will sometimes be omitted.

[0114] Figure 11 (a) in the text represents Figure 5 The diagram shows the relationship between the force received by the gear shift lever 341 and the position of its swing center. Figure 11 (b) is a schematic diagram showing the gear shift lever 341 in the variation example and the relationship between the force received by the gear shift lever 341 and the position of the swing center.

[0115] like Figure 11 As shown in (a) of this embodiment, in the shift lever 341, the swing center axis, which serves as the rocker arm shaft 342 and the axis center line of the rocker arm shaft 342, is located at the point where the shift lever 341 originates from the cylinder 33 (reference). Figure 3 The force-receiving part that receives driving force via the connecting pin 343 and the shift lever 341 from the shifter 452 (reference) Figure 3 The action parts that receive the reaction force via the action shaft 344. Furthermore, as described above, the strain detection mechanism 46 is installed from the Z1 axis direction (… Figure 11 The part that coincides with the swing center axis when projected orthographically in the left-right direction (Z1 direction). By placing the strain detection mechanism 46 between the force-bearing part and the action part, the strain generated by the shift lever 341 when it receives an external force can be detected with high precision. Furthermore, by placing the strain detection mechanism 46 on the side of the shift lever 341, close to the swing center axis, strain can be detected with even higher precision. However, since in this embodiment the strain detection mechanism 46 is installed at the part that coincides with the swing center axis when projected orthographically from the Z1 axis direction, strain can be detected with even higher precision. Additionally, Figure 11 (a) and Figure 11 The force-bearing and action-acting parts shown in (b) are the parts of the shift lever 341 that receive force when the state of the first main shaft 4 changes from the clamping release state to the clamping state.

[0116] like Figure 11As shown in (b), in the modified shift lever 341, the rocker arm shaft 342 and the swing center axis are not located between the force-bearing part and the action part, but rather outside of both. In this modified example, the strain detection mechanism 46 is also installed on the side of the shift lever 341, between the force-bearing part and the action part. In this modified example, the strain generated between the force-bearing part and the action part is also large when the state of the first main shaft 4 changes from the clamping release state to the clamping state. Therefore, the installation position of the strain detection mechanism 46 can be any position, as long as it is between the force-bearing part and the action part. However, since the strain generated is particularly large, especially on the side of the shift lever 341, and at a distance equidistant from both the force-bearing part and the action part, the strain detection mechanism 46 is installed at this location in this modified example.

[0117] The present invention can be varied within the scope of the claims without being limited to the described embodiments or variations. For example, although the description of this embodiment shows an example of applying the invention to a so-called Swiss-type NC lathe 1 equipped with guide sleeve 5, the invention can also be applied to lathes or other machine tools such as machining centers that do not have guide sleeve 5. Furthermore, the second spindle head 7, the second spindle 8, and the second tool post 9 can be omitted. Further, the strain detection mechanism 46 can be installed at any position on the non-rotational transmission component 34, as long as it is a non-rotational transmission component 34. However, as described above, by installing the strain detection mechanism 46 on the shift lever 341, the clamping force of the collet 41 can be derived with higher accuracy.

[0118] Furthermore, the constituent elements individually included in the descriptions of the variations above may also be applied to other variations.

[0119] [Symbol Explanation]

[0120] 1: NC lathe (machine tool)

[0121] 4: First spindle (main spindle)

[0122] 3: First spindle table (spindle table)

[0123] 23: Export Section

[0124] 33: Cylinder (Actuator)

[0125] 34: Non-rotational transmission components

[0126] 41: Spring collet (clamping part)

[0127] 45: Rotary transmission component

[0128] 46: Strain Testing Agency

[0129] W1: Workpiece.

Claims

1. A machine tool, characterized in that, have: The spindle has a clamping part for holding the workpiece; The spindle table supports the spindle in a manner that allows it to rotate freely. An actuator, mounted on the spindle table, generates a driving force that causes the clamping part to change state between a clamping state that clamps the workpiece and a clamping release state that releases the workpiece from the clamp. A non-rotational transmission component, mounted on the spindle table, transmits the driving force received from the actuator; The rotary transmission component rotates together with the main shaft and transmits the driving force received from the non-rotary transmission component to the clamping part; A strain detection mechanism is installed on the non-rotational transmission component to detect the strain of the non-rotational transmission component generated when the driving force is transmitted from the actuator to the clamping part; and The output section, based on the detection results of the strain detection mechanism, outputs the clamping force of the clamping section.

2. The machine tool according to claim 1, characterized in that, The rotary transmission component includes a claw component capable of changing its posture between a first posture that places the clamping part in the clamping state and a second posture that places the clamping part in the clamping release state. The shifter, by moving in the direction of the axis of the main shaft, is able to change position between a first position in the first posture and a second position in the second posture; The non-rotational transmission component has a shift lever that moves the shifter in the direction of the axis. The strain detection mechanism detects the strain of the gear shift lever.

3. The machine tool according to claim 2, characterized in that, The strain detection mechanism detects the strain at the location between the stress point and the action point. The stress point is the part of the shift lever that receives the driving force from the actuator, and the action point is the part where the reaction force received by the shift lever from the shifter occurs when the driving force received by the shift lever is transmitted to the shifter.

4. The machine tool according to claim 3, characterized in that, The gear shift lever swings freely around its swing center axis, and this swinging motion causes the gear shifter to move towards the axis. The strain detection mechanism detects the strain on the side of the shift lever, which is formed parallel to the axis of the swing center.

5. The machine tool according to claim 3, characterized in that, The gear shift lever swings freely around its swing center axis, and this swinging motion causes the gear shifter to move towards the axis. The strain detection mechanism detects the strain at locations where the distance from the axis of the swing center is less than the distance from the force-bearing part and the action part.

6. The machine tool according to any one of claims 1 to 5, characterized in that, The derivation section derives the clamping force of the clamping section based on the maximum strain of the non-rotational transmission component during the process of the state changing from the clamping release state to the clamping state as detected by the strain detection mechanism.

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