A method for detecting the gripping force of a machine tool chuck, and a method for setting the tightening amount of a chuck.

Abstract

To provide a technique cable of appropriately controlling a chuck gripping force.SOLUTION: A machine tool comprises a main spindle equipped with a chuck for gripping a workpiece. A chuck gripping force with respect to the workpiece in a closed state is acquired on the basis of the size of a difference between first time from issuing of a control signal of a closed operation from the control unit to an opening / closing mechanism to detection of the opened state of the chuck by a sensor and second time from issuance of the control signal from the control signal during an opening / closing period to detection of the closed state of the chuck by the sensor when the opening / closing mechanism closes the chuck so as to change from the opened state to the closed state.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for detecting the gripping force of a chuck in a machine tool.

Background Art

[0002] In a machine tool that processes a workpiece by rotating a spindle gripping the workpiece and moving a processing tool forward and backward relative to the rotating workpiece, proper gripping of the workpiece by the chuck (gripping jaws is an important factor for machining accuracy. Patent Document 1 discloses that the relationship between the tightening amount achieved by rotation of a spindle motor from when the chuck is brought into contact with the workpiece until a predetermined gripping force is generated and the gripping force of the chuck is obtained in advance, and the gripping force of the chuck is controlled by controlling the rotation angle of the spindle motor.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] As described above, it is not easy to directly measure the gripping force of a chuck, and a method of estimating the gripping force from the control amount of the mechanism that operates the chuck is generally employed. However, in many cases, the relationship between the control amount and the gripping force is not always constant due to various factors such as progress of wear of the chuck and changes in lubrication conditions.

[0005] An object of the present invention is to provide a technology that enables appropriate control of chuck gripping force.

Means for Solving the Problem

[0006] To achieve the above object, the machine tool of the present invention comprises: a spindle provided with a chuck for gripping a workpiece; The chuck is provided with an opening and closing mechanism that operates the chuck to either a closed state for gripping a workpiece or an open state for attaching and detaching a workpiece. The chuck Open Whether or not it is in that state A first sensor that detects and , before The chuck is the aforementioned closed In what state or not Check to know 2nd Sensors and, A control unit that controls the opening and closing mechanism, In a machine tool equipped with, When the opening / closing mechanism closes the chuck from the open state to the closed state, the control unit issues a control signal for the closing operation to the opening / closing mechanism and then determines that the chuck is no longer in the open state. 1 The first time until the sensor detects, and the control unit's opening and closing. mechanism The system will issue the control signal and then indicate that the chuck has entered the closed state. 2nd The system is characterized by comprising an acquisition means for acquiring the gripping force of the chuck on the workpiece in the closed state, based on the magnitude of the difference between the second time until the sensor detects the workpiece and the current time.

[0007] Furthermore, in order to achieve the above objective, the method for detecting the gripping force of the chuck of the present invention is as follows: A method for detecting the gripping force of a chuck on a workpiece when the chuck, which is attached to the spindle of a machine tool, grips the workpiece, The opening and closing mechanism performs a first step of closing the chuck from an open state, which allows the workpiece to be attached and detached, to a closed state, which grips the workpiece. In the first step, the control unit issues a control signal for the closing operation to the opening / closing mechanism, and then the chuck is no longer in the open state. 1 The first time until the sensor detects the action, and the time from when the control unit issues the control signal to the opening / closing mechanism until the chuck is in the closed state. 2ndThe second step involves obtaining the second time until the sensor detects something, and the second step involves obtaining the second time. A third step of obtaining the gripping force based on the correlation between the magnitude of the difference between the first time and the second time, the amount of clamping the chuck to the workpiece in the closed state adjusted by the adjustment mechanism, and the gripping force. It is characterized by including.

[0008] Furthermore, in order to achieve the above objective, the method for setting the tightening amount of the chuck according to the present invention is: A method for setting the amount of clamping of a chuck on a workpiece when the chuck, which is attached to the spindle of a machine tool, grips the workpiece, The adjustment mechanism adjusts the amount of clamping the chuck to the workpiece in the closed state, where the chuck grips the workpiece, to a first clamping amount. Then, the opening and closing mechanism moves the chuck from an open state, where the workpiece can be attached and detached, to the closed state in a first step. In the first step, the control unit issues a control signal for the closing operation to the opening / closing mechanism, and then the chuck is no longer in the open state. 1 The first time until the sensor detects the action, and the time from when the control unit issues the control signal to the opening / closing mechanism until the chuck is in the closed state. 2nd The second step involves obtaining the second time until the sensor detects something, and the second step involves obtaining the second time. A third step of obtaining a second tightening amount that yields the desired gripping force, based on the correlation between the magnitude of the difference between the first time and the second time, the amount of tightening of the chuck on the workpiece in the closed state adjusted by the adjustment mechanism, and the gripping force of the chuck on the workpiece in the closed state. A fourth step involves adjusting the tightening amount to the second tightening amount obtained in the third step using the adjustment mechanism, It is characterized by including. [Effects of the Invention]

[0009] According to the present invention, appropriate control of chuck gripping force can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] [Figure 1] It is a schematic diagram of a machine tool provided with a workpiece recovery device according to an embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view of the main configuration around a spindle. [Figure 3] It is a schematic cross-sectional view of the main configuration around a spindle. [Figure 4] It is a schematic cross-sectional view of the configuration around a chuck jaw, a bobbin, and a chuck holder. [Figure 5] It is a schematic cross-sectional view of the configuration around a chuck jaw, a bobbin, and a chuck holder. [Figure 6] It is a timing chart of chuck close signals and sensor reaction timings. [Figure 7] It is a graph showing the relationship between the tightening amount of an adjustment nut (nut angle) and the B-A period. [Figure 8] It is a block diagram schematically showing an example of the configuration of a machine tool according to the present embodiment. [Figure 9] It is a diagram showing an example of the functional configuration of a control unit. [Figure 10] It is a flowchart for creating gripping force correlation data. [Figure 11] It is a flowchart for gripping force detection. [Figure 12] It is a timing chart of chuck open signals and sensor reaction timings. [Figure 13] It is a flowchart for gripping force correction. MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments described below are merely illustrative of preferred configurations of the present invention, and the scope of the present invention is not limited to these configurations This invention is not limited to these. Furthermore, the hardware and software configurations of the device, manufacturing conditions, the functions, materials, shapes, and relative arrangements of the components described below are not intended to limit the scope of the present invention to those unless specifically stated otherwise. In principle, the same reference numeral is used for identical components to avoid repeated explanations.

[0012] (Examples) Figure 1 is a schematic diagram illustrating the configuration of a machine tool 1 according to an embodiment of the present invention. The machine tool 1 shown in Figure 1 is a so-called automatic lathe device that rotates a workpiece W, such as a long bar, and brings a cutting tool (machining tool) into contact with it to perform cutting (turning).

[0013] The machine tool 1 generally comprises a spindle mechanism 100 and a tool post 300 arranged on a base 2. The spindle mechanism 100 has a spindle 101. The rotation axis direction of the spindle 101 is defined as the Z-axis direction, and among the directions perpendicular to the axis direction, the direction parallel to the vertical direction is defined as the X-axis direction, and the direction parallel to the horizontal direction is defined as the Y-axis direction. Figure 1 is a schematic diagram showing the configuration of the machine tool 1 in the Y-axis direction.

[0014] The spindle mechanism 100 includes a headstock 102 that rotatably supports the spindle 101, and a drive mechanism 103 for moving the headstock 102 on the base 2 in the Z-axis direction. As the drive mechanism, for example, a ball screw drive mechanism consisting of a motor as a drive source, a ball screw, a guide rail, etc. may be used. Furthermore, the spindle mechanism 100 may also include a drive mechanism for moving the headstock 102 not only in the Z-axis direction, but also in the Y-axis direction and the X-axis direction. The headstock 102 is equipped with, for example, a built-in motor (not shown), and is configured to rotate the spindle 101 with its rotational driving force.

[0015] The spindle 101 has a hollow structure with a workpiece holding hole for holding or gripping a workpiece W, and is equipped with a chuck, chuck sleeve, guide bush, etc., for gripping the workpiece W (aligning the axis and restricting axial movement). The workpiece W is inserted and fed axially into the workpiece holding hole from the spindle rear end opening of the workpiece holding hole, and is gripped by the chuck at a predetermined insertion position. The portion of the workpiece W exposed from the spindle tip opening of the workpiece holding hole is the portion that is turned by a cutting tool 301 supported on the tool post 300. The guide bush, which is not shown above, is provided, for example, at the spindle tip opening of the workpiece holding hole, and holds the position of the workpiece W near the opening of the workpiece holding hole. The workpiece W support structure by the guide bush may be a separate structure from the spindle mechanism 100.

[0016] As will be explained in more detail later, the chuck and chuck sleeve shown in Figure 1 are configured such that the chuck sleeve is joined to the chuck from the rear via a tapered surface in the axial direction, while the chuck's movement in the axial direction is restricted. The chuck sleeve attempts to move in the axial direction by receiving a force from an air cylinder (not shown in Figure 1), thereby acting a force on the chuck that includes a component force in the direction toward the axis, generating a clamping force on the chuck that closes the slit provided in the chuck. This creates a state in which the workpiece W is gripped.

[0017] The tool post 300 is equipped with multiple cutting tools 301 that can be selected according to the type of machining to be performed. The tool post 300 is configured to move forward and backward in the X-axis direction relative to the workpiece W by a drive mechanism (not shown), and the desired cutting (turning) operation is performed on the workpiece W by bringing one of the selected cutting tools 301 into contact with the workpiece W.

[0018] The machine tool 1 includes a control unit 200 which is composed of a computer having a processor such as a CPU (Central Processing Unit) and memory. The control unit 200 includes the spindle mechanism 100, the tool post 300, a workpiece supply unit (not shown), and actuators 60 and display units 70 which will be described later. It controls the various operations of each component that makes up the machine tool 1.

[0019] Figures 2 and 3 are schematic cross-sectional views showing enlarged views of the main components around the spindle 101, respectively. Figure 2 shows the configuration of each part when the collet chuck 41 is closed, i.e., when it is gripping the workpiece W. Figure 3 shows the configuration of each part when the collet chuck 41 is open, i.e., when the workpiece W is detachable from the spindle 101. Figures 4 and 5 are schematic cross-sectional views showing enlarged views of the configuration around the chuck jaws 47, bobbin 48, and chuck holder 50, respectively. Figure 4 shows the configuration of each part when the chuck jaws 47 are in the closed position, i.e., when the collet chuck 41 is gripping the workpiece W. Figure 5 shows the configuration of each part when the chuck jaws 47 are in the open position, i.e., when the workpiece W is detachable from the collet chuck 41.

[0020] As shown in Figures 2 and 3, the spindle 101 is rotatably mounted to the headstock 102 via bearing devices 121, 122, and 123. The collet chuck 41 is mounted on the axial end of the spindle 101. The collet chuck 41 comprises a hollow cylindrical body 411 capable of receiving a workpiece W inside, and a gripping portion 412 provided on the end of the cylindrical body 411 in the direction of the central axis L (longitudinal direction).

[0021] The gripping portion 412 has a so-called slotted structure, and the central axis L The internal diameter dimension, which is set as a reference, is configured to be elastically changeable. That is, the gripping portion 412 is provided with a slit 413 that extends axially for a predetermined length from its front end face toward the rear end. The slit 413 is formed to cut out the gripping portion 412 radially with respect to the central axis L, and multiple slits are provided, for example, at equal intervals in the circumferential direction around the central axis L. Between these multiple slits 413 is the central axis L A longitudinal split piece 414 is formed that is capable of displacement in the radial direction with respect to its center. Each longitudinal split piece 414 is configured in a leaf spring shape that is elastically deformable in the radial direction, with its base end as a fulcrum.

[0022] The central axis of each vertical section 414 L The facing inner surfaces are each concave curved surfaces, and by working together, they form a substantially cylindrical workpiece gripping surface 415 in the gripping portion 412. In addition, the outer surface of each longitudinal slit 414 includes an inclined surface that is tilted with respect to the axial direction, and by working together, each inclined surface forms a tapered force-receiving surface 416 that gradually widens in diameter towards the axial end. Furthermore, the central axis is located axially towards the end of the force-receiving surface 416 of each longitudinal slit 414. L A shoulder surface 417 extending vertically in the opposite direction is formed.

[0023] The multiple longitudinal sections 414, when subjected to radially inward external forces via the force-receiving surfaces 416, elastically flex, reducing the diameter of the workpiece gripping surfaces 415 until they are in close contact with the workpiece W, thereby firmly and securely gripping the workpiece W. When the radial pressure on the gripping section 412 is released, each longitudinal section 414 elastically returns to its original position, expanding the diameter of the workpiece gripping surfaces 415, and releasing the workpiece W from the gripping section 412.

[0024] A cap nut 42 is attached to the tip of the workpiece holding hole of the spindle 101. The cap nut 42 has an end face facing the rear end in the axial direction and a locking surface 421 that abuts the shoulder surface 417 of the collet chuck 41 in the axial direction. In addition, a chuck sleeve 43 is assembled to the workpiece holding hole of the spindle 101 as a second working member, sandwiching the collet chuck 41 between itself and the cap nut 42.

[0025] The chuck sleeve 43 is a hollow cylindrical body capable of receiving the workpiece W and the collet chuck 41 surrounding it. The chuck sleeve 43 has a force-applying surface 431 on its inner surface that acts on the force-receiving surface 416 of the collet chuck 41, and a compression coil spring 44 is assembled thereto as an elastic member that applies an axial biasing force to the collet chuck 41. The chuck sleeve 43 has a spring receiving surface 432, and compresses the compression coil spring 44 in the axial direction between the spring receiving surface 432 and the axial rear end surface of the collet chuck 41. Due to the biasing force of this compression coil spring 44, the collet chuck 41 is pressed axially against the cap nut 42, with its shoulder surface 417 contacting the locking surface 421.

[0026] The force-applying surface 431 is a tapered surface that gradually widens in diameter towards the axial end, and relative to the force-receiving surface 416, along the central axis. L The direction along the axis and the central axis L These are opposing surfaces that contact each other in the radial direction with respect to the center. The force-applying surface 431 applies an inward radial force to the force-receiving surface 416, causing the gripping portion 412 of the collet chuck 41 to perform the gripping operation of the workpiece W, as described above.

[0027] In the workpiece holding hole of the main spindle 101, a chuck opening / closing sleeve 45 and a balance sleeve 46, which are hollow cylindrical bodies capable of receiving a workpiece W inside, are assembled to the axial rear end of the chuck sleeve 43. The chuck sleeve 43, the chuck opening / closing sleeve 45 and the balance sleeve 46 are arranged in series in this order axially and engage with each other in the axial direction, and are configured to be integrally displaceable in the axial direction as a second working member. The axial rear end of the balance sleeve 46 is provided with an actuated surface 461 that receives the operating force.

[0028] The spindle 101 is provided with a chuck jaw 47 as a first working member for applying an operating force to the actuated surface 461 of the balance sleeve 46. The chuck jaw 47 is located along the central axis. L lap For example, multiple chuck jaws are provided at equal intervals. Each chuck jaw 47 has an action portion 471 that abuts the work surface 461 in the axial direction, and is located relative to the spindle 101 along the central axis. L Multiple units are configured to rotate around a rotation axis 472 that is aligned with the tangential direction of a central virtual circle. The chuck jaws 47 are integrally supported by the chuck holder 50 and are assembled to the spindle 101 via the chuck holder 50.

[0029] The chuck jaws 47 rotate so that they can assume a closed position in which the working portion 471 moves forward in the axial direction, and an open position in which the working portion 471 is retracted to the rear in the axial direction. The chuck jaws 47 have a worked portion 473 that receives the driving force for the above-mentioned change in position. A bobbin 48, which acts as a linear motion member that applies driving force to the worked portion 473, is mounted on the cylindrical wall of the spindle 101 so as to be displaceable in the axial direction. Specifically, the bobbin 48 is configured as part of a bearing device 123 that is displaceable in the axial direction relative to the spindle 101. The bearing device 123 is displaced in the axial direction relative to the spindle 101 by the driving force from the actuator 60, which is a driving means. The axial displacement of the bearing device 123 causes the bobbin 48 to assume an working position that causes the chuck jaws 47 to assume a closed position, and to assume an open position that causes the chuck jaws 47 to assume an open position. Non It is configured to be movable between the operating position and the other position.

[0030] The bobbin 48 has an action portion 481 which is a substantially conical outer surface that extends so as to gradually decrease in diameter toward the axial rear end. When the bobbin 48 is in the action position, the chuck jaws 47 have their actuated portion 473 in contact with the action portion 481, and the chuck jaws 47 ride up onto the bobbin 48, and the rotation during the riding-up process takes the closed position. Non When in the operating position, the actuated part 473 is separated from the actuated part 481 and contacts the outer surface of the main spindle 101, the chuck jaws 47 are not in contact with the bobbin 48, and the rotation during the process of lowering from the bobbin 48 takes the open position.

[0031] The actuator 60 comprises an air cylinder 61 and an arm 62 that connects the rod 610 of the air cylinder 61 to the bearing device 123. The arm 62 is mounted to the headstock 102 so as to be rotatable about a rotation axis 622, and is rotatably connected to the rod 610 via a rotation axis 621, and rotatably connected to the bearing device 123 via a rotation axis 623. The components are connected. The rod 610 of the air cylinder 61 reciprocates along the central axis L, and the arm 62 rotates around the rotating shaft 622 due to the reciprocating motion of the rod 610. For example, the rotating shaft 623 connecting the bearing device 123 and the arm 62 is configured to be displaceable in the longitudinal direction of the arm 62, and as the arm 62 rotates, it is displaced in the longitudinal direction of the arm while also being displaced along the central axis L. As a result, the bearing device 123 is displaced axially on the main shaft 101, and the axial relative position of the bobbin 48 with respect to the chuck jaws 47 changes.

[0032] When the chuck jaws 47 change from the open position to the closed position, the working part 471 presses the actuated surface 461 axially forward, and the balance sleeve 46, chuck opening / closing sleeve 45, and chuck sleeve 43 are sequentially pressed axially forward. As a result, a radially inward force is applied from the force-applying surface 431 of the chuck sleeve 43 to the force-receiving surface 416 of the collet chuck 41, increasing the amount of clamping the collet chuck 41 on the workpiece W, resulting in a closed state in which the workpiece W is firmly and securely gripped.

[0033] When the chuck jaws 47 change from a closed position to an open position, the working part 471 retracts axially backward, and the biasing force of the compression coil spring 44 sequentially presses the chuck sleeve 43, chuck opening / closing sleeve 45, and balance sleeve 46 axially backward. As a result, the radially inward force from the force-applying surface 431 of the chuck sleeve 43 to the force-receiving surface 416 of the collet chuck 41 is released, reducing the amount of clamping the collet chuck 41 on the workpiece W, and the collet chuck 41 becomes open, allowing for easy attachment and detachment of the workpiece W.

[0034] The air cylinder 61 is equipped with a chuck open position sensor 71 and a chuck closed position sensor 72. closed Position sensor 7 2 The rod 610 is configured to react when the stroke of the rod is in the retracted position (Figure 2) which moves the bobbin 48 to the working position. Open Position sensor 7 1 The system is configured to react when the stroke of the rod 610 is in the extended position (Figure 3) which moves the bobbin 48 to the non-operating position. Examples of the configurations of sensors 71 and 72 include optical sensors that detect marks provided on the rod 610, but conventionally known sensors may be used as appropriate.

[0035] As shown in Figures 4 and 5, an adjustment nut 51 is screwed onto the cylindrical wall of the spindle 101 at the axial rear end of the chuck holder 50. The chuck holder 50 is mounted so as to be axially slidable on the outer surface of the spindle 101 by a guide mechanism (not shown) provided on the cylindrical wall of the spindle 101. The adjustment nut 51 abuts against the chuck holder 50 in the axial direction against the biasing force of the compression coil spring 44, which is applied via the chuck sleeve 43, chuck opening / closing sleeve 45, balance sleeve 46, chuck jaws 47, and chuck holder 50. The adjustment nut 51 is configured so that its axial position relative to the spindle 101 can be adjusted by tightening or loosening it relative to the spindle 101. Therefore, by adjusting the axial position of the adjustment nut 51, the axial position of the chuck holder 50, i.e., the axial position of the chuck jaws 47, can be adjusted. By adjusting the axial position of the chuck jaws 47 (adjusting the tightening amount of the adjustment nut 51), it is possible to adjust the amount of pressure the collet chuck 41 applies to the workpiece W when it is closed.

[0036] Here, the inventors of the present invention, through diligent research, have found that differences in the tightening amount (nut angle) of the adjustment nut 51 result in differences in the timing of the reaction of the chuck open position sensor 71 and the timing of the reaction of the chuck closed position sensor 72.

[0037] Chuck closed Position sensor 7 2 The device outputs an ON signal when the rod 610 is in the retracted position (or when it exceeds a predetermined retraction reference position), and outputs an OFF signal when the rod 610 moves away from the retracted position due to the stroke (or does not reach the retraction reference position). Similarly, the chuck Open Position sensor 7 1 The device outputs an ON signal when the rod 610 is in the extended position (or when it exceeds a predetermined extended reference position), and outputs an OFF signal when the rod 610 moves away from the extended position due to the stroke (or does not reach the extended reference position). During the stroke of the rod 610, there is a transient period in which neither the chuck open position sensor 71 nor the chuck closed position sensor 72 reacts (both output an OFF signal). The length of this transient period changes depending on the amount the adjustment nut 51 is tightened.

[0038] Figure 6 is a timing chart showing the timing at which the control unit 200 issues a chuck closing signal to the actuator 60, and the respective response timings of the chuck open position sensor 71 and the chuck closed position sensor 72. When the actuator 60 closes the collet chuck 41 from the open state to the closed state, let A be the period (first time) from when the control unit 200 issues a closing control signal to the actuator 60 until the output of the chuck open position sensor 71 switches from ON to OFF. Also, let B be the period (second time) from when the control unit 200 issues a closing control signal to the actuator 60 until the output of the chuck closed position sensor 72 switches from OFF to ON. Then, a transient period of BA (difference time) occurs.

[0039] During period A, that is, the period until the output of the chuck open position sensor 71 switches from ON to OFF, the detection timing is approximately constant regardless of the tightening amount of the adjustment nut 51, as this is a position where no load is applied during chuck operation. In contrast, during period B, that is, the period until the output of the chuck closed position sensor 72 switches from OFF to ON, this is a period during which a load is applied during chuck operation, so the detection timing will shift depending on the tightening amount of the adjustment nut 51. Therefore, the magnitude of the transient period BA will change.

[0040] Figure 7 is a graph showing an example of how the BA period changes when the tightening amount (nut angle) of the adjustment nut 51 is changed. As shown in Figure 7, when the nut angle was changed to 30°, 60°, 90°, 120°, and 150°, the BA period was plotted as 0.068, 0.075, 0.082, 0.088, and 0.102, respectively. From these results, it can be seen that there is a roughly linear relationship between the tightening amount of the adjustment nut 51 and the BA period.

[0041] The gripping force is typically adjusted by first determining a reference point for the angle (axial position) of the adjustment nut 51, and then adjusting the tightening angle from that reference point to set the desired gripping force. A conventional method for determining the reference point is to adjust the axial position of the adjustment nut 51 so that, for example, the tip of the worked part 473 abuts against the working part 481 while the chuck jaws 47 are not riding on the bobbin 48, and then use the nut angle at this point as the reference angle. However, it is difficult to set such a reference point uniquely and consistently. In contrast, as in this embodiment, by setting the adjustment amount of the adjustment nut 51 (tightening amount of the collet chuck 41) in correspondence with the time difference of the sensor detection timing, it becomes easy to grasp the gripping force regardless of how the reference point is set.

[0042] Figure 8 is a block diagram schematically showing an example of the configuration of a machine tool according to this embodiment.

[0043] The control unit 200 has a configuration similar to that of a typical computer. The control unit 200 has a CPU (Central Processing Unit) 201, ROM (Read Only Memory) 202, RAM (Random Access Memory) 203, and an input / output interface 204. The control unit 200 also has an input section 81 and an output section It has a section 82. These are interconnected by a bus. Various sensors, including a chuck open position sensor 71 and a chuck closed position sensor 72, are connected to the bus via an input / output interface 204, and signals from these sensors are input to the control unit 200. On the other hand, actuators that drive the spindle mechanism 100 and the tool post 300, and actuator 60 that performs the opening and closing operation of the collet chuck 41 are connected to the bus via the input / output interface 204, and control signals are sent from the control unit 200 to these devices.

[0044] The CPU 201 controls the machine tool 1 and performs various information processing calculations. The ROM 202 and RAM 203, which serve as memory devices, store the operating system (OS), various programs, various tables, etc. Each component is controlled through the execution of the program. This allows the control unit 200 to realize functions that meet the predetermined purpose. The control unit 200 may be a single computer or a system of multiple computers working together.

[0045] The input unit 81 is a means for receiving input operations performed by the user, and includes, for example, a touch panel, mouse, keyboard, or microphone. The output unit 82 is a means for presenting information to the user, and may include, for example, an LCD (Liquid Crystal Display), EL (Electroluminescence) panel, speaker, lamp, etc. Note that the input unit 81 and the output unit 82 may be configured as a single touch panel display.

[0046] Figure 9 shows an example of the functional configuration of the control unit 200. The control unit 200 includes a machining control unit 211, a gripping force acquisition unit 212, and a gripping force correction unit 213 as functional components. The machining control unit 211, the gripping force acquisition unit 212, and the gripping force correction unit 213 are functional components provided, for example, by the CPU 201 of the control unit 200 executing various programs stored in the ROM 202 and RAM 203.

[0047] The machining control unit 211 controls the machine tool 1 during machining of the workpiece W. The machining control unit 211 fastens the workpiece W with the collet chuck 41, rotates the spindle 101, and further controls the movement of the cutting tool 301 on the tool post 300 to cut the workpiece W, for example. Known techniques can be used for this machining control of the workpiece W by the machining control unit 211.

[0048] The gripping force acquisition unit 212 acquires the gripping force on the workpiece W when the collet chuck 41 is in the closed state, based on the magnitude of the BA period described above. The acquisition of the gripping force is based on the correlation between the BA period and the nut tightening amount described above. That is, the BA period and the nut tightening amount (adjustment amount by the adjustment nut 51) are linearly correlated with each other, and the nut tightening amount is linearly correlated with the amount the collet chuck 41 tightens on the workpiece W when it is in the closed state. As the gripping force corresponding to the nut tightening amount, for example, multiple specific numerical values ​​in kilograms of force (kgf) may be acquired in advance, for example by attaching a torque sensor to the collet chuck 41 in an experiment and detecting it, and the gripping force may be calculated and acquired from the above linear relationship based on multiple measured values. As notification of the gripping force to the user, in addition to presenting specific numerical values, the nut tightening amount may be divided into stages according to a predetermined numerical range, and a level display may be used to indicate the strength level of the gripping force for each stage.

[0049] Figure 10 is a flowchart showing the creation of gripping force correlation data by the gripping force acquisition unit. It is preferable to create the gripping force correlation data during the preparation and adjustment stage before starting actual product processing. In other words, the workpiece W used in this process may be a spare workpiece W rather than the workpiece W that will be processed as the actual product.

[0050] First, the control unit 200 sends a chuck closing operation signal to the actuator 60, causing the collet chuck 41 to close and grip the workpiece W (S101). At this time, the control unit 200 acquires two periods: period A, from the issuance of the closing operation control signal until the chuck open position sensor 71 detects that the collet chuck 41 is no longer in the open state; and period B, from the issuance of the closing operation control signal until the chuck closed position sensor 72 detects that the collet chuck 41 is in the closed state (S102, S103). The control unit 200 stores the acquired periods A and B, and the resulting BA period, in a storage means.

[0051] If the necessary number of period A and B data points have been obtained to acquire the correlation between the BA period and the nut tightening amount (gripping force) required for gripping force acquisition (S104, YES), then correlation data between the BA period and gripping force is created (S107). If the number of period A and B data points is insufficient (S104, NO), data acquisition is performed again. That is, the collet chuck 41 is opened (S105), the angle of the adjustment nut 51 is changed, and the position of the chuck jaws 47 is changed (S106). The adjustment amount of the adjustment nut 51 may be changed manually by the user, or if automatic adjustment is possible, it may be changed by the device. Repeat steps S101 to S106 until the necessary data is obtained.

[0052] Figure 11 is a flowchart for detecting the chuck gripping force using the gripping force data obtained in Figure 10. This gripping force detection can be performed during the adjustment stage before processing the actual product, or during the processing of the actual product, similar to Figure 10.

[0053] The control unit 200 sends a chuck closing operation signal to the actuator 60, causing the collet chuck 41 to close and grip the workpiece W (S201). At this time, the angle of the adjustment nut 51, which is adjusted in advance, may be set to an angle that has a predetermined margin over the actual machining angle. In other words, the amount of tightening of the collet chuck 41 adjusted by the adjustment nut 51 here is a temporary tightening amount (first tightening amount) to obtain the optimal tightening amount (second tightening amount). Then, the period A from the issuance of the closing operation control signal until the chuck open position sensor 71 detects that the collet chuck 41 is no longer in the open state, and the period B from the issuance of the closing operation control signal until the chuck closed position sensor 72 detects that the collet chuck 41 has become closed are obtained (S202, S203). Then, the BA period obtained from the acquired periods A and B is compared with the correlation with the gripping force obtained in Figure 10 (gripping force data), or calculated based on the correlation, and the corresponding gripping force is obtained (S204). The acquired gripping force is then notified to the user via the output unit 82 as a notification means (S205).

[0054] As a result of the above process, the user who has been notified of the gripping force can, based on the notified gripping force, adjust the adjustment nut 51 to achieve the desired gripping force if necessary. Re Adjustments can be made. In addition, when notifying the user in S205, the correlation between the nut adjustment amount and the gripping force may also be displayed. Alternatively, if the desired gripping force has been input in advance via the input unit 81, the nut adjustment amount (second tightening amount) required to obtain the desired gripping force may be acquired in S204 and presented to the user in S205.

[0055] The gripping force correction unit 213 corrects the correlation between the acquired BA period and the gripping force (gripping force data). As described above, period A is basically a position where there is no load (the load does not change significantly) during chuck operation, and the detection timing is approximately constant regardless of the tightening amount of the adjustment nut 51. However, for example, in the case of long-term use, it may fluctuate due to changes in the state of the air supply pressure of the air cylinder 61 and the lubrication oil state between the chuck jaws 47 and the bobbin 48. For example, if the air supply pressure of the air cylinder 61 drops from the standard 0.5 MPa to 0.4 MPa, time A will be extended, and consequently, period B will also be extended. It is preferable to correct the gripping force data to respond to such changes in the device behavior over time. Therefore, in this embodiment, the opening operation is performed. The time difference in the timing of sensor detection when synchronized ( DC The delay time (coefficient) is obtained from the change over time (period), and the deviation time (BA period) in the closing operation is corrected.

[0056] Figure 12 is a timing chart showing the timing at which the control unit 200 issued a chuck open signal to the actuator 60, and the respective reaction timings of the chuck open position sensor 71 and the chuck closed position sensor 72. The actuator 60 moves the collet chuck 41 from the closed state to the open state. Open When the system is in operation, let C be the period (third time) from when the control unit 200 issues an open control signal to the actuator 60 until the output of the chuck closed position sensor 72 switches from ON to OFF. Also, let D be the period (fourth time) from when the control unit 200 issues an open control signal to the actuator 60 until the output of the chuck open position sensor 71 switches from OFF to ON. Then, a transient period of DC (difference time) occurs.

[0057] As mentioned above, the DC period, which is a transitional period, may vary due to changes in the device's behavior over time. Therefore, by comparing the DC period in a new state with the DC period in a state where the device has been in operation for a certain period (i.e., a state where wear and tear have progressed), a coefficient (delay time) for correcting the gripping force data can be obtained. By correcting the gripping force data using this coefficient, it becomes possible to obtain a more optimal gripping force.

[0058] Figure 13 is a flowchart showing the correction of gripping force correlation data by the gripping force acquisition unit. This operation is performed when the device has been used for a predetermined number of times, after the device has created reference gripping force correlation data in its new state, and the gripping force correlation data is reacquired.

[0059] First, the control unit 200 sends a chuck open operation signal to the actuator 60, causing the collet chuck 41 to open and release the workpiece W (S301). At this time, the control unit 200 acquires the period C from the time the open operation control signal is sent until the chuck closed position sensor 72 detects that the collet chuck 41 is no longer in the closed state, and the period D from the time the open operation control signal is sent until the chuck open position sensor 71 detects that the collet chuck 41 is in the open state (S302, S303). The control unit 200 stores the acquired periods C and D, and the DC period acquired by them, in the storage means.

[0060] If the necessary number of period C and D data points have been obtained to obtain the correlation between the DC period and the nut tightening amount (gripping force) required for gripping force acquisition (S304, YES), then correlation data between the DC period and gripping force is created (S307). If the number of period C and D data points is insufficient (S304, NO), data acquisition is performed again. That is, the angle of the adjustment nut 51 is changed to change the position of the chuck jaws 47 (S305), the collet chuck 41 is closed (S306), and the workpiece W is gripped again. The adjustment amount of the adjustment nut 51 may be changed manually by the user, or if automatic adjustment is possible, it may be changed by the device. Steps S301 to S306 are repeated until the necessary data is obtained.

[0061] The latest gripping force data (C', D') obtained through the above process is compared with the reference gripping force data (C, D) acquired at the beginning of use to obtain the delay time (coefficient). DC The gripping force data corresponding to the period is corrected (S308). For example, the BA in the latest gripping force data is corrected using C' / C=α as a coefficient (α(BA)). By using the gripping force data corrected in this way, it becomes possible to set a more appropriate gripping force that reflects the changes in the device over time.

[0062] As described above, according to this embodiment, by setting the adjustment amount of the adjustment nut 51 (tightening amount of the collet chuck 41) in correspondence with the time difference of the sensor detection timing, the setting of the reference point can be adjusted accordingly. This allows for the setting of the optimal gripping force. In other words, it becomes possible to appropriately control the gripping force of the chuck, thereby improving machining accuracy.

[0063] Furthermore, according to this embodiment, the gripping force of the chuck, which is difficult to obtain (quantify) directly, can be obtained more appropriately using the device configuration that is conventionally provided by the machine tool, without requiring the addition of a separate device configuration, and it can also be quantified.

[0064] It should be noted that the specific configurations of the spindle mechanism, chuck opening and closing mechanisms such as the collector chuck, chuck sleeve, and chuck jaws, actuators for operating these mechanisms, and opening / closing sensors shown in this embodiment are merely examples. In other words, other conventionally known configurations may be adopted as appropriate. [Explanation of Symbols]

[0065] 1...Machine tool, 100...Spindle mechanism, 101...Spindle, 102...Headstock, 103...Drive mechanism, 2...Base, 200...Control unit, 300...Tool post, 301...Cutting tool, 41...Collet chuck, 43...Chuck sleeve, 44...Compression coil spring, 45...Chuck opening / closing sleeve, 46...Balance sleeve, 47...Chuck jaws, 48...Bobbin, 60...Actuator, W...Workpiece

Claims

1. A spindle equipped with a chuck for gripping the workpiece, The chuck is provided with an opening and closing mechanism that operates the chuck to either a closed state for gripping a workpiece or an open state for attaching and detaching a workpiece. A first sensor for detecting whether the chuck is in the open state, A second sensor for detecting whether the chuck is in the closed state, A control unit that controls the opening and closing mechanism, A machine tool comprising an adjustment mechanism capable of adjusting the amount of clamping the chuck to the workpiece in the closed state, A storage means that stores the correlation between the magnitude of the difference between a first time, when the control unit issues a control signal for the closing operation to the opening / closing mechanism to close the chuck from the open state to the closed state, and a second time, when the control unit issues the control signal to the opening / closing mechanism to close the chuck from the open state to the closed state, and the tightening amount, when the opening / closing mechanism closes the chuck from the open state to the closed state, and the tightening amount. A machine tool characterized by comprising: an opening / closing mechanism that causes the chuck to perform the closing operation during machining of a workpiece and acquires the difference, and an acquisition means that acquires the gripping force of the chuck on the workpiece in the closed state based on the tightening amount acquired from the acquired difference and the correlation.

2. The machine tool according to claim 1, further comprising a correction means for correcting the correlation relationship based on the change over time of the magnitude of a second difference between a third time, from when the control unit issues a control signal for the opening operation to the opening / closing mechanism when the chuck moves from the closed state to the open state, until the second sensor detects that the chuck is no longer in the closed state, and a fourth time, from when the control unit issues the control signal to the opening / closing mechanism until the first sensor detects that the chuck has entered the open state.

3. The machine tool according to claim 1, further comprising a notification means for notifying an external party of information including the gripping force.

4. The opening and closing mechanism is A first operating member is provided on the main shaft so that the chuck can assume a closed position that acts on the chuck to bring it to the closed state, and an open position that acts on the chuck to bring it to the open state. A second working member whose relative position to the first working member in the rotational axis direction of the main spindle is displaceable, the second working member provided on the main spindle, such that it can take a closed position in which it acts on the first working member to put the first working member in the closed position, and an open position in which it acts on the first working member to put the first working member in the open position, A driving means including an air cylinder for moving the second operating member between the closed position and the open position, The machine tool according to claim 1, characterized by comprising the following:

5. The machine tool according to claim 4, characterized in that the adjustment mechanism can change the amount of tightening of the chuck by changing the position of the first working member with respect to the main spindle in the direction of the rotation axis.

6. The first sensor detects whether the driving means is in a state where the second operating member is in the open position, The machine tool according to claim 5, characterized in that the second sensor detects whether or not the driving means is in a state where the second working member is in the closed position.

7. A method for detecting the gripping force of a chuck on a workpiece when the chuck, which is attached to the spindle of a machine tool, grips the workpiece, The opening and closing mechanism performs a first step of closing the chuck from an open state, which allows the workpiece to be attached and detached, to a closed state, which grips the workpiece. In the first step, a second step is to obtain a first time from when the control unit issues a control signal for the closing operation to the opening / closing mechanism until the first sensor detects that the chuck is no longer in the open state, and a second time from when the control unit issues the control signal to the opening / closing mechanism until the second sensor detects that the chuck is in the closed state. A third step involves obtaining a correlation between the magnitude of the difference between the first time and the second time, the amount of clamping the chuck to the workpiece in the closed state adjusted by the adjustment mechanism, and the gripping force, during non-processing periods when no processing is performed on the workpiece. A fourth step in which, during the machining process on the workpiece, the opening and closing mechanism causes the chuck to perform the closing operation and obtains the difference, and the gripping force is obtained based on the tightening amount obtained from the obtained difference and the correlation, A method for detecting the gripping force of a chuck, characterized by including [a specific element].

8. The opening and closing mechanism performs a fifth step of opening the chuck from the closed state to the open state, In the fifth step, a sixth step is to obtain a third time from when the control unit issues the control signal for the opening operation to the opening / closing mechanism until the second sensor detects that the chuck is no longer in the closed state, and a fourth time from when the control unit issues the control signal to the opening / closing mechanism until the first sensor detects that the chuck is in the open state. A seventh step to correct the correlation based on the change over time in the magnitude of the difference between the third time and the fourth time when the fifth and sixth steps are repeated. 、 The method for detecting the gripping force of a chuck according to claim 7, further comprising the above.

9. A method for setting the amount of clamping of a chuck on a workpiece when the chuck, which is attached to the spindle of a machine tool, grips the workpiece, The adjustment mechanism adjusts the amount of clamping the chuck to the workpiece in the closed state, where the chuck grips the workpiece, to a first clamping amount. Then, the opening and closing mechanism moves the chuck from an open state, where the workpiece can be attached and detached, to the closed state in a first step. In the first step, a second step is to obtain a first time from when the control unit issues a control signal for the closing operation to the opening / closing mechanism until the first sensor detects that the chuck is no longer in the open state, and a second time from when the control unit issues the control signal to the opening / closing mechanism until the second sensor detects that the chuck is in the closed state. A third step involves obtaining a correlation between the magnitude of the difference between the first time and the second time, the amount of clamping the chuck to the workpiece in the closed state adjusted by the adjustment mechanism, and the gripping force of the chuck to the workpiece in the closed state, during a non-processing period when no processing is performed on the workpiece. In the process of machining a workpiece, the opening and closing mechanism causes the chuck to perform the closing operation to obtain the difference, and a fourth step is to obtain a second tightening amount that can obtain the desired gripping force based on the tightening amount obtained from the obtained difference and the correlation, A fifth step in which the tightening amount is adjusted by the adjustment mechanism to the second tightening amount obtained in the fourth step, A method for setting the tightening amount of a chuck, characterized by including the following.

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