Method for detecting chucking force of machine tool, chuck, and method for setting tightening amount of chuck

Abstract

Provided is a technology that can appropriately control chuck clamping force. A machine tool has a spindle that has a chuck for clamping a workpiece, and a difference in size between a first time and a second time when the chuck is caused to change from an open state to a closed state by the chuck performing a closing operation based on an opening / closing unit, the first time being a time from when a control section sends a closing operation control signal to the opening / closing unit until a first sensor detects that the chuck is no longer in the open state, and the second time being a time from when the control section sends the control signal to the opening / closing unit until a second sensor detects that the chuck is in the closed state, and a clamping force of the chuck on the workpiece in the closed state is obtained.

Description

Technical Field

[0001] This invention relates to a method for detecting the clamping force of a chuck in a machine tool. Background Technology

[0002] In machine tools that rotate a spindle holding a workpiece and move a machining tool forward and backward relative to the rotating workpiece, the proper clamping of the workpiece by the chuck (clamping jaws) is a crucial factor affecting working accuracy. Patent Document 1 discloses a scheme that pre-calculates the relationship between the clamping amount generated by the rotation of the spindle motor from the moment the chuck contacts the workpiece until a specified clamping force is generated and the clamping force of the chuck, and controls the clamping force of the chuck by controlling the rotation angle of the spindle motor.

[0003] (Existing technical literature)

[0004] (Patent Documents)

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-096409 Summary of the Invention

[0006] (The problem the invention aims to solve)

[0007] As mentioned above, the clamping force of a chuck is difficult to measure directly. Therefore, a method is used to determine the clamping force of the chuck based on the control quantity of the unit that causes the chuck to move. However, in many cases, the relationship between the control quantity and the clamping force is not necessarily constant due to various factors such as the progression of chuck wear and changes in lubrication conditions.

[0008] The purpose of this invention is to provide a technique for properly controlling the clamping force of a chuck.

[0009] (The measures taken to solve the problem)

[0010] To achieve the above objectives, the machine tool of the present invention comprises:

[0011] The spindle has a chuck for holding the workpiece.

[0012] An opening and closing unit that actuates the chuck to place the chuck in either a closed state that holds the workpiece or an open state that allows the workpiece to be detached.

[0013] A first sensor detects whether the chuck is in the open state;

[0014] A second sensor detects whether the chuck is in the closed state; and

[0015] The control unit controls the opening and closing unit.

[0016] The machine tool includes an acquisition component that acquires the clamping force of the chuck on the workpiece in the closed state based on the difference between a first time and a second time when the chuck changes from the open state to the closed state by performing a closing action on the chuck by the opening and closing unit. The first time is the time from when the control unit sends the control signal for the closing action to the opening and closing unit until the first sensor detects that the chuck is no longer in the open state, and the second time is the time from when the control unit sends the control signal to the opening and closing unit until the second sensor detects that the chuck has become closed.

[0017] Furthermore, in order to achieve the above objectives, the chuck clamping force detection method of the present invention is a method for detecting the clamping force of the chuck on the workpiece when the chuck of the machine tool spindle clamps the workpiece.

[0018] The detection method includes:

[0019] In the first step, the opening and closing unit causes the chuck to close, so that the chuck changes from an open state that allows the workpiece to be detached and assembled to a closed state that holds the workpiece.

[0020] The second step involves acquiring the first time from the moment the control signal for the closing action is sent from the control unit to the opening / closing unit in the first step until the first sensor detects that the chuck is no longer in the open state, and the second time from the moment the control signal is sent from the control unit to the opening / closing unit until the second sensor detects that the chuck has become in the closed state; and

[0021] The third step involves obtaining the clamping force based on the relationship between the difference between the first and second times, the clamping amount of the chuck in the closed state adjusted by the adjustment unit, and the clamping force.

[0022] Furthermore, in order to achieve the above objectives, the chuck tightening amount setting method of the present invention is a method for setting the chuck tightening amount on the workpiece when the chuck of the machine tool spindle clamps the workpiece.

[0023] The setting method includes:

[0024] In the first step, when the clamping amount of the chuck to the workpiece is adjusted to a first clamping amount by the adjustment unit in the closed state of the chuck holding the workpiece, the opening and closing unit causes the chuck to close, so that the chuck changes from the open state that can detach and install the workpiece to the closed state.

[0025] The second step involves obtaining the first time from the start of the control signal sent by the control unit to the opening / closing unit for the closing action in the first step until the first sensor detects that the chuck is no longer in the open state, and the second time from the start of the control unit sending the control signal to the opening / closing unit until the second sensor detects that the chuck has become in the closed state.

[0026] The third step involves obtaining a second tightening amount to achieve the desired clamping force, based on the relationship between the difference between the first and second times, the tightening amount of the chuck on the workpiece in the closed state adjusted by the adjustment unit, and the clamping force of the chuck on the workpiece in the closed state.

[0027] In the fourth step, the fastening amount is adjusted by the adjustment unit to the second fastening amount obtained in the third step.

[0028] (The effect of the invention)

[0029] According to the present invention, the chuck clamping force can be properly controlled. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a machine tool equipped with a workpiece recycling device according to an embodiment of the present invention.

[0031] Figure 2 A schematic sectional view of the main structure around the main axis.

[0032] Figure 3 A schematic sectional view of the main structure around the main axis.

[0033] Figure 4 This is a schematic cross-sectional view of the chuck jaws, barrel, and the structure surrounding the chuck holder.

[0034] Figure 5 This is a schematic cross-sectional view of the chuck jaws, barrel, and the structure surrounding the chuck holder.

[0035] Figure 6 This is a timing diagram showing the chuck closing signal and the sensor's response timing.

[0036] Figure 7 A diagram showing the relationship between adjusting the tightening amount of the nut (nut angle) and the BA period.

[0037] Figure 8 A block diagram illustrating an example of the structure of the machine tool involved in this embodiment.

[0038] Figure 9 This diagram illustrates an example of the functional structure of the control unit.

[0039] Figure 10 A flowchart for creating data related to clamping force.

[0040] Figure 11 This is a flowchart for detecting clamping force.

[0041] Figure 12 This is a timing diagram showing the chuck open signal and the sensor response timing.

[0042] Figure 13 This is a flowchart for correcting the clamping force. Detailed Implementation

[0043] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. However, the embodiments described below are merely illustrative examples of preferred structures of the present invention and are not intended to limit the scope of the invention to these structures. Furthermore, unless otherwise stated, the hardware and software structures of the apparatus, manufacturing conditions, functions, materials, shapes, relative configurations, etc., of the structural components described below are not intended to limit the scope of the present invention. In addition, in principle, the same reference numerals are given to the same components, and repeated descriptions are omitted.

[0044] (Example)

[0045] Figure 1 A schematic diagram illustrating the structure of the machine tool 1 according to an embodiment of the present invention is provided. Figure 1 The machine tool 1 shown is a so-called automatic lathe, which is a device that rotates a workpiece W, such as a long bar, and brings a cutting tool (machining tool) into contact with the workpiece W to perform cutting (turning).

[0046] Machine tool 1 generally includes: a spindle unit 100 and a tool post 300 mounted on a base 2. The spindle unit 100 has a spindle 101. The direction of the rotation axis of the spindle 101 is set as the Z-axis direction, the direction that is parallel to the vertical direction among the directions orthogonal to the axis direction is set as the X-axis direction, and the direction that is parallel to the horizontal direction among the directions orthogonal to the axis direction is set as the Y-axis direction. Figure 1 This is a schematic diagram of the structure of machine tool 1 when viewed in the Y-axis direction.

[0047] The spindle unit 100 includes a spindle housing 102 that rotatably supports the spindle 101, and a drive unit 103 for moving the spindle housing 102 on the base 2 along the Z-axis. As the drive unit, a ball screw drive unit, consisting of an electric motor, a ball screw, and a guide rail as the drive source, can be used, for example. Furthermore, the spindle unit 100 may also include a drive unit that moves the spindle housing 102 not only along the Z-axis but also along the Y-axis and X-axis. The spindle 102, for example, includes a built-in motor (not shown) and is configured to rotate and drive the spindle 101 using the rotational driving force of the built-in motor.

[0048] The spindle 101 has a hollow structure and includes a chuck, chuck sleeve, guide bush, etc., for clamping the workpiece W (axis-aligned and axial movement restricted). The hollow structure has a workpiece holding hole for holding or clamping the workpiece W. The workpiece W is inserted into the spindle through the spindle's rear end opening along the axial direction, supplied into the workpiece holding hole, and clamped by the chuck at a predetermined insertion position. The portion of the workpiece W exposed from the spindle's front end opening of the workpiece holding hole becomes the portion subjected to turning by the cutting tool 301 supported on the tool holder 300. The guide bush (not shown) is provided, for example, at the spindle's front end opening of the workpiece holding hole and maintains the workpiece W's posture near the opening of the workpiece holding hole. Furthermore, the support structure for the workpiece W, constituted by the guide bush, can be a structure independent of the spindle unit 100.

[0049] exist Figure 1 The chuck and chuck sleeve, not shown in the diagram, have the following structure: the chuck sleeve engages from the rear via a conical surface along the axial direction with a chuck whose movement in the axial direction is restricted; details will be described later. Figure 1 The cylinder (not shown) exerts force to move along the axial direction, thereby applying a force to the chuck, including a component force in the direction of the axis, and generating a clamping force in the chuck that closes the gap provided in the chuck. This creates a state in which the workpiece W is clamped.

[0050] The tool holder 300 is equipped with multiple cutting tools 301 that can be selectively prepared according to the type of machining target. The tool holder 300 is configured to move back and forth along the X-axis relative to the workpiece W under the action of a drive unit (not shown), so that a selected cutting tool 301 contacts the workpiece W and performs the desired cutting machining (turning machining) on ​​the workpiece W.

[0051] Machine tool 1 includes a control unit 200, which is configured as a computer having a processor such as a CPU (central processing unit) and memory. The control unit 200 controls various operations of the components of machine tool 1, such as spindle unit 100, tool post 300, workpiece supply unit (not shown), actuator 60 (described later), and display unit 70.

[0052] Figure 2 , Figure 3 These are schematic cross-sectional views showing the main structures around the main shaft 101 in an enlarged manner. Figure 2 The structure of each part is shown when the collet chuck 41 is closed (i.e., when the workpiece W is clamped). Figure 3 The structure of each part is shown when the chuck 41 is in the open state (i.e., the state in which the workpiece W can be attached and detached relative to the spindle 101). Figure 4 , Figure 5 These are schematic cross-sectional views showing the main structures around the chuck jaw 47, bobbin 48, and chuck holder 50, enlarged respectively. Figure 4 The structure of each part is shown in the closed position of the chuck jaw 47 (i.e., the closed state in which the chuck jaw 41 clamps the workpiece W). Figure 5 The structure of each part is shown in the state where the chuck jaws 47 are open (i.e., the open state in which the workpiece W can be attached and detached relative to the chuck jaws 41).

[0053] like Figure 2 , Figure 3 As shown, the spindle 101 is rotatably assembled to the spindle housing 102 via bearing devices 121, 122, and 123. A chuck 41 is assembled to the front end of the spindle 101 along its axial direction. The chuck 41 includes a hollow cylindrical body 411 capable of housing a workpiece W, and a clamping portion 412 located at the front end of the cylindrical body 411 along its central axis L (length direction).

[0054] The clamping portion 412 has a so-called slot structure and is configured to elastically change its inner diameter dimension relative to the central axis L. Specifically, the clamping portion 412 is provided with a slit 413 extending a predetermined length from its front end face toward its rear end face along the axial direction. The slits 413 are formed to radially cut through the clamping portion 412 relative to the central axis L, and a plurality of slits 413 are provided at equal intervals around the central axis L in the circumferential direction. Between these slits 413 are longitudinally segmented pieces 414 capable of radial displacement centered on the central axis L. Each longitudinally segmented piece 414 is configured as a leaf spring capable of elastically deforming along the aforementioned radial direction with its base end as a fulcrum.

[0055] Each longitudinal segment 414 has a concave curved surface facing the central axis L, which cooperates with each other to form a cylindrical workpiece clamping surface 415 in the clamping part 412. Furthermore, the outer surface of each longitudinal segment 414 includes an inclined surface that is inclined relative to the axial direction, and these inclined surfaces cooperate with each other to form a conical force-bearing surface 416 whose diameter gradually increases towards the front end in the axial direction. Additionally, a shoulder surface 417 extending perpendicularly to the central axis L is formed on each longitudinal segment 414 at a position closer to the front end in the axial direction than the force-bearing surface 416.

[0056] Multiple longitudinal segmented pieces 414 apply an external force toward the radially inward side through the force-bearing surface 416, thereby causing elastic deflection and reducing the diameter of the workpiece clamping surface 415 until it comes into close contact with the workpiece W, thus firmly and permanently clamping the workpiece W. If the radial pressure on the clamping part 412 is released, each longitudinal segmented piece 414 elastically recovers and the diameter of the workpiece clamping surface 415 expands, thereby freeing the workpiece W from the clamping part 412.

[0057] A cap nut 42 is installed at the front end of the workpiece holding hole of the spindle 101. The cap nut 42 has a locking surface 421, which is an end face facing the rear end in the axial direction and abuts against the shoulder surface 417 of the chuck 41 in the axial direction. In addition, the chuck sleeve 43, which serves as a second working component in the workpiece holding hole of the spindle 101, is assembled such that a spring chuck 41 is sandwiched between the cap nut 42 and the spring chuck 43.

[0058] The chuck sleeve 43 is a hollow cylindrical body capable of housing the workpiece W and the jaw chuck 41 surrounding the workpiece W. The chuck sleeve 43 has an inner surface with a force-applying surface 431 that applies force to the force-bearing surface 416 of the jaw chuck 41, and is equipped with a compression coil spring 44 as an elastic component that applies a force in the axial direction to the jaw chuck 41. The chuck sleeve 43 has a spring-bearing surface 432, and the compression coil spring 44 is compressed along the axial direction between the spring-bearing surface 432 and the rear end face of the jaw chuck 41. Under the applied force of the compression coil spring 44, the shoulder surface 417 of the jaw chuck 41 abuts against the locking surface 421, and the jaw chuck 41 presses against the cap nut 42 along the axial direction.

[0059] The force-applying surface 431 is a conical surface whose diameter gradually increases towards the front end in the axial direction, and it abuts against the force-receiving surface 416 in both the axial direction along the central axis L and the radial direction centered on the central axis L. The force-applying surface 431 applies a radially inward force to the force-receiving surface 416, thereby performing the action of the clamping part 412 of the chuck 41 clamping the workpiece W as described above.

[0060] In the workpiece holding hole of the spindle 101, a chuck opening / closing sleeve 45 and a balancing sleeve 46, which are hollow cylindrical bodies capable of accommodating the workpiece W, are provided at the rear end of the chuck sleeve 43 in the axial direction. The chuck sleeve 43, the chuck opening / closing sleeve 45, and the balancing sleeve 46 are configured to be arranged in series along the axial direction, joined together in the axial direction, and integrally displaced along the axial direction as a second working component. The rear end of the balancing sleeve 46 in the axial direction has an applied surface 461 that bears the applied force.

[0061] The spindle 101 is provided with chuck jaws 47 as first working components, which are used to apply force to the working surface 461 of the balancing sleeve 46. Multiple chuck jaws 47 are arranged at equal intervals around the central axis L. Each chuck jaw 47 has a working portion 471 that abuts against the working surface 461 along the axial direction and is configured to rotate relative to the spindle 101 about a rotation axis 472, which is an axis along the tangent direction of an imaginary circle centered on the central axis L. Multiple chuck jaws 47 are integrally supported by a chuck holder 50, which is mounted to the spindle 101.

[0062] The chuck jaw 47 rotates in a closed position where the actuating part 471 advances forward along the axial direction and in an open position where the actuating part 471 retracts backward along the axial direction. The chuck jaw 47 has an actuated part 473 that bears the driving force for achieving the aforementioned positional changes. A tube 48, serving as a direct-drive actuating member that applies the driving force to the actuated part 473, is mounted on the cylindrical wall of the main shaft 101, enabling displacement along the axial direction. Specifically, the tube 48 is configured as part of a bearing assembly 123 capable of displacement relative to the main shaft 101 along the axial direction. The bearing assembly 123 is displaced relative to the main shaft 101 along the axial direction under the action of a driving force from the actuator 60, which is a drive unit. Under the axial displacement of the bearing assembly 123, the tube 48 can move between an operating position where the chuck jaw 47 is in a closed position and a non-operating position where the chuck jaw 47 is in an open position.

[0063] The bobbin 48 has an actuating portion 481, which is a slightly conical outer peripheral surface extending toward the rear end in the axial direction, with its diameter gradually decreasing. When the bobbin 48 is in the actuating position, the chuck jaws 47 are in a state where the actuated portion 473 contacts the actuating portion 481 and is mounted on the bobbin 48, and are closed by rotation during the mounting process. Furthermore, when the bobbin 48 is in the non-actuating position, the actuated portion 473 separates from the actuating portion 481 and contacts the outer peripheral surface of the spindle 101, so that the chuck jaws 47 are not in contact with the bobbin 48, and are opened by rotation during the descent of the bobbin 48.

[0064] The actuator 60 includes a cylinder 61 and an arm 62 connecting the cylinder 61 and the bearing assembly 123. The arm 62 is mounted on the spindle housing 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 to the bearing assembly 123 via a rotation axis 623. The rod 610 of the cylinder 61 reciprocates along the central axis L, and the arm 62 rotates about the rotation axis 622 due to the reciprocating motion of the rod 610. For example, the rotation axis 623 connecting the bearing assembly 123 and the arm 62 is configured to be displaceable along the length of the arm 62, and simultaneously displaced along the central axis L while rotating the arm 62. As a result, the bearing assembly 123 displaces along the axial direction on the spindle 101, and the relative position of the cylinder 48 with respect to the chuck jaws 47 changes in the axial direction.

[0065] If the chuck jaws 47 change from an open to a closed position, the actuating part 471 presses the acting surface 461 forward in the axial direction, and the balancing sleeve 46, chuck opening / closing sleeve 45, and chuck sleeve 43 are pressed forward in sequence in the axial direction. As a result, a force in the radially inward direction is applied from the force-applying surface 431 of the chuck sleeve 43 to the force-receiving surface 416 of the jaw chuck 41, thereby increasing the clamping amount of the jaw chuck 41 on the workpiece W and achieving a closed state in which the workpiece W is firmly and fixedly clamped.

[0066] If the chuck jaws 47 change from a closed position to an open position, the actuating part 471 retracts backward in the axial direction. The chuck sleeve 43, chuck opening and closing sleeve 45, and balance sleeve 46 are pressed backward in the axial direction in sequence under the force applied by the compression coil spring 44. As a result, the force from the force-applying surface 431 of the chuck sleeve 43 to the force-receiving surface 416 of the jaw chuck 41 in the radially inward direction is released, thereby reducing the tightening amount of the jaw chuck 41 on the workpiece W and making the workpiece W free to be installed and removed from the jaw chuck 41.

[0067] Cylinder 61 is equipped with a chuck open position sensor 71 and a chuck closed position sensor 72. The chuck closed position sensor 72 is configured such that when the stroke of rod 610 is in the retracted position that moves the bobbin 48 to the operating position... Figure 2 A reaction occurs when the chuck open position sensor 71 is in the extended position that moves the barrel 48 to the non-operating position during the stroke of the lever 610. Figure 3 A reaction occurs when the sensor 71 or 72 is applied. Examples of sensors that can be used to detect a mark set on the rod 610 include optical sensors, but existing known sensors may also be used appropriately.

[0068] like Figure 4 , Figure 5 As shown, an adjusting nut 51 is screwed onto the cylindrical wall of the spindle 101 at the rear end of the chuck holder 50 in the axial direction. The chuck holder 50 is configured to move along the axial direction on the outer circumferential surface of the spindle 101 via a guide unit (not shown) provided on the cylindrical wall of the spindle 101. The adjusting nut 51 abuts against the chuck holder 50 in the axial direction against the force applied by the compression coil spring 44 via the chuck sleeve 43, chuck opening / closing sleeve 45, balance sleeve 46, chuck jaws 47, and chuck holder 50. The adjusting nut 51 is configured to adjust its position relative to the axial direction of the spindle 101 by tightening or loosening it relative to the spindle 101. Therefore, by adjusting the position of the adjusting nut 51 in the axial direction, the position of the chuck holder 50 in the axial direction, i.e., the position of the chuck jaws 47 in the axial direction, can be adjusted. The tightness of the chuck 41 on the workpiece W in the closed state can be adjusted by adjusting the position of the chuck jaw 47 along its axis (adjusting the tightness of the adjusting nut 51).

[0069] Here, the inventors of the present invention have discovered through careful study that different tightening amounts (nut angles) of the adjusting nut 51 will result in different differences between 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.

[0070] When lever 610 is in the retracted position (or, beyond the specified retracted reference position), chuck closed position sensor 72 outputs an ON signal; when lever 610 deviates from the retracted position due to its travel (or, does not reach the retracted reference position), chuck closed position sensor 72 outputs an OFF signal. Similarly, when lever 610 is in the extended position (or, beyond the specified extended reference position), chuck open position sensor 71 outputs an ON signal; when lever 610 deviates from the extended position due to its travel (or, does not reach the extended reference position), chuck open position sensor 71 outputs an OFF signal. Therefore, during the travel of lever 610, there is a transition period during which neither chuck open position sensor 71 nor chuck closed position sensor 72 reacts (both output OFF signals). The length of this transition period varies depending on the tightening amount of adjusting nut 51.

[0071] Figure 6This diagram illustrates the timing of the control unit 200 issuing a chuck closing signal to the actuator 60, and the respective response times of the chuck open position sensor 71 and the chuck closed position sensor 72. When the actuator 60 causes the jaw chuck 41 to close, changing it from an open to a closed state, the period from when the control unit 200 issues the closing control signal to the actuator 60 until the output of the chuck open position sensor 71 switches from open (ON) to closed (OFF) (first time) is defined as A. Furthermore, if the period from when the control unit 200 issues the closing control signal to the actuator 60 until the output of the chuck closed position sensor 72 switches from closed (OFF) to open (ON) (second time) is defined as B, then a transition period BA (differential time) is generated.

[0072] During period A, i.e., until the output of the chuck open position sensor 71 switches from ON to OFF, the chuck is in a position where no load is applied during operation, and therefore the detection timing is approximately constant regardless of the tightness of the adjusting nut 51. In contrast, during period B, i.e., until the output of the chuck closed position sensor 72 switches from OFF to ON, the chuck operates under load, and therefore the detection timing will deviate depending on the tightness of the adjusting nut 51. Therefore, the length of period BA, which is the transition period, will vary.

[0073] Figure 7 A graph illustrating an example of the change during the BA period when the tightening amount (nut angle) of adjusting nut 51 is changed. (See graph for example.) Figure 7 As shown, when the nut angle changes to 30°, 60°, 90°, 120°, and 150°, the BA period is plotted as 0.068, 0.075, 0.082, 0.088, and 0.102, respectively. Based on these results, it can be seen that the tightening amount of adjusting nut 51 and the BA period have a roughly linear relationship.

[0074] Regarding the adjustment of the clamping force, a reference point for the angle (position in the axial direction) of the adjusting nut 51 is usually determined first, and then the tightening angle relative to that reference point is adjusted, thereby setting the desired clamping force. As a conventional method for determining the reference point, for example, one method involves adjusting the axial position of the adjusting nut 51 so that the front end of the applied part 473 touches the actuating part 481 when the chuck jaws 47 are not engaged with the cylinder 48, and setting the nut angle at this point as the reference angle. However, it is difficult to achieve a unique and consistently constant setting of such a reference point. In contrast, as in this embodiment, the adjustment amount of the adjusting nut 51 (the tightening amount of the chuck jaws 41) is set in relation to the time difference of the sensor detection timing, thereby making it easier to control the clamping force regardless of the reference point setting.

[0075] Figure 8 A block diagram illustrating an example of the structure of the machine tool involved in this embodiment.

[0076] The control unit 200 has a typical computer structure. The control unit 200 includes: a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, and an input / output interface 204. Furthermore, the control unit 200 has an input section 81 and an output section 82. These components are interconnected via a bus. Various sensors, including a chuck open position sensor 71 and a chuck closed position sensor 72, are connected to the bus via the input / output interface 204, and signals from these sensors are input to the control unit 200. On the other hand, the bus is also connected via the input / output interface 204 to actuators that drive the spindle unit 100 and the tool holder 300, and actuators 60 that perform the opening and closing actions of the chuck 41, and control signals are sent from the control unit 200 to these devices.

[0077] CPU 201 controls machine tool 1 and performs various information processing calculations. ROM 202 and RAM 203, serving as storage components, store the operating system (OS), various programs, and various worksheets. Each structural unit is controlled by executing the stored programs. Thus, control unit 200 achieves its intended function. Furthermore, control unit 200 can be a single computer or a component consisting of multiple computers working together.

[0078] Input unit 81 is a component that receives input operations from the user, such as a touch panel, mouse, keyboard, or microphone. Output unit 82 is a component that displays information to the user, and may include, for example, an LCD (Liquid Crystal Display), an EL (Electroluminescence) panel, a speaker, or a lamp. Furthermore, input unit 81 and output unit 82 can also be configured as a single touchscreen display.

[0079] Figure 9This diagram illustrates an example of the functional structure of the control unit 200. The control unit 200 includes, as functional components, a machining control unit 211, a clamping force acquisition unit 212, and a clamping force correction unit 213. The machining control unit 211, the clamping force acquisition unit 212, and the clamping force correction unit 213 are functional components provided by causing, for example, the CPU 201 of the control unit 200 to execute various programs stored in the ROM 202 and the RAM 203.

[0080] The machining control unit 211 controls the machine tool 1 when machining the workpiece W. The machining control unit 211 controls the workpiece W to be cut, for example, by securing the workpiece W to the chuck 41, rotating the spindle 101, and moving the cutting tool 301 of the tool holder 300, thereby cutting the workpiece W. The machining control of the workpiece W using this machining control unit 211 can employ known techniques.

[0081] The clamping force acquisition unit 212 acquires the clamping force of the jaw chuck 41 on the workpiece W in the closed state based on the magnitude of the aforementioned BA period. The clamping force is acquired based on the correlation between the aforementioned BA period and the nut tightening amount. That is, the aforementioned BA period and the nut tightening amount (based on the adjustment amount of the adjusting nut 51) are linearly correlated with each other, and the nut tightening amount is linearly correlated with the tightening amount of the jaw chuck 41 on the workpiece W in the closed state. For example, multiple specific values ​​in kilogram-force (kgf) can be obtained in advance by installing a torque sensor on the jaw chuck 41 in an experiment, and the clamping force corresponding to the nut tightening amount can be calculated / acquired based on multiple measured values ​​and according to the aforementioned linear relationship. As a notification to the user regarding the clamping force, in addition to indicating the specific numerical value, the nut tightening amount can be divided into multiple stages according to a specified numerical range, and a level display of the clamping force strength can be shown for each stage.

[0082] Figure 10 This is a flowchart illustrating the creation of clamping force-related data based on the clamping force acquisition unit. It is preferable to create the clamping force-related data during the preparation and adjustment phase before actual product processing begins. That is, the workpiece W used in this process can be a pre-prepared workpiece W, rather than the workpiece W to be processed as the actual product.

[0083] First, the control unit 200 sends a chuck closing action signal to the actuator 60, causing the chuck jaws 41 to close and grip the workpiece W (S101). Then, the control unit 200 acquires the period A from the issuance of the closing action control signal until the chuck open position sensor 71 detects that the chuck jaws 41 are no longer in the open state, and the period B from the issuance of the closing action control signal until the chuck closed position sensor 72 detects that the chuck jaws 41 are in the closed state (S102, S103). The control unit 200 stores the acquired periods A and B, and the period BA acquired through periods A and B, in the storage unit.

[0084] If the required amount of data for periods A and B, which are necessary for obtaining the clamping force, and the relationship between the BA period and the nut tightening amount (clamping force), has been obtained (S104, "Yes"), then the data on the relationship between the BA period and the clamping force is generated (S107). If the amount of data for periods A and B is insufficient (S104, "No"), the data is obtained again. That is, the chuck 41 is opened (S105), the angle of the adjusting nut 51 is changed, and the position of the chuck jaw 47 is changed (S106). The adjustment amount of the adjusting nut 51 can be changed manually by the user, or it can be changed on the device side if automatic adjustment is possible. Repeat S101 to S106 until all the required data is obtained.

[0085] Figure 11 For use through Figure 10 A flowchart for chuck clamping force detection to obtain clamping force data. This clamping force detection can be combined with... Figure 10 Similarly, it can be carried out during the adjustment stage before the actual product is processed, or it can be carried out during the actual product processing.

[0086] The control unit 200 sends a chuck closing action signal to the actuator 60, causing the jaw chuck 41 to close and grip the workpiece W (S201). At this time, the angle of the pre-adjusted adjusting nut 51 can be set to an angle with a specified margin compared to the actual machining angle. That is, here, the tightening amount of the jaw chuck 41 adjusted by the adjusting nut 51 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 action control signal until the chuck open position sensor 71 detects that the jaw chuck 41 is no longer in the open state and the period B from the issuance of the closing action control signal until the chuck close position sensor 72 detects that the jaw chuck 41 is in the closed state are obtained (S202, S203). Then, the period BA obtained based on the obtained periods A and B is compared with the period in the machining process. Figure 10The clamping force is obtained by comparing it with the correlation data (clamping force data) obtained in the previous step or by calculating based on the correlation data (S204). Then, the obtained clamping force is notified to the user through the output unit 82, which is a notification unit (S205).

[0087] Through the above processing, the user who has been notified of the clamping force can readjust the adjusting nut 51 to the desired clamping force when needed, based on the notified clamping force. Furthermore, when notifying the user in S205, the relationship between the nut adjustment amount and the clamping force can be displayed simultaneously. Alternatively, if the desired clamping force has been pre-input via the input unit 81, the nut adjustment amount (second tightening amount) necessary to obtain the desired clamping force can be obtained in S204 and displayed to the user in S205.

[0088] The clamping force correction unit 213 corrects the correlation (clamping force data) between the acquired BA period and the clamping force. As described above, period A is the position where no load is applied during chuck operation (the load does not change significantly), and the detection timing is approximately constant regardless of the tightening amount of the adjusting nut 51. However, for example, in cases of long-term use, changes may occur due to variations in the state of the gas supply pressure of cylinder 61, the state of the lubricating oil between chuck jaws 47 and barrel 48, etc. For example, if the gas supply pressure of cylinder 61 drops from the standard 0.5 MPa to 0.4 MPa, time A will be prolonged, and period B will also be prolonged. To cope with such changes in device operation over time, it is preferable to correct the clamping force. Therefore, in this embodiment, the delay time (coefficient) during the closing operation is corrected by obtaining the offset time (DC period) of the sensor detection timing during the closing operation, which varies over time.

[0089] Figure 12 To illustrate the timing of the control unit 200 issuing the chuck open signal to the actuator 60 and the respective response times of the chuck open position sensor 71 and the chuck closed position sensor 72, a timing diagram is provided. The period from the time the actuator 60 performs the opening action on the jaw chuck 41, causing it to change from a closed to an open state, from the time the control unit 200 issues the opening action control signal to the actuator 60 until the output of the chuck closed position sensor 72 switches from ON to OFF (third time) is defined as C. Furthermore, if the period from the time the control unit 200 issues the opening action control signal to the actuator 60 until the output of the chuck open position sensor 71 switches from OFF to ON (fourth time) is defined as D, a DC period (differential time) is generated as the transition period.

[0090] As mentioned above, the DC period, which serves as the transition period, can change due to variations in device operation over time. Therefore, by comparing the DC period in the new product state with the DC period in a state where the device has been operated to a certain extent (i.e., a state where wear has occurred), a coefficient (delay time) for correcting the clamping force data can be obtained. By correcting the clamping force data using this coefficient, the optimal clamping force can be obtained.

[0091] Figure 13 This is a flowchart illustrating the calibration of clamping force-related data performed by the clamping force acquisition unit. After creating baseline clamping force-related data for a device in a new state, this action is performed whenever the device has completed a predetermined number of operations, and clamping force-related data is acquired again.

[0092] First, the control unit 200 sends a chuck opening signal to the actuator 60, causing the chuck jaws 41 to open and release the workpiece W (S301). Then, the control unit 200 acquires the period C from the issuance of the opening control signal until the chuck closed position sensor 72 detects that the chuck jaws 41 are no longer closed, and the period D from the issuance of the opening control signal until the chuck open position sensor 71 detects that the chuck jaws 41 are now open (S302, S303). The control unit 200 stores the acquired periods C and D, and the DC period acquired through periods C and D, in a storage unit.

[0093] If the required data for the clamping force and the relationship between the DC period and the nut tightening amount (clamping force) have been obtained (S304, "Yes"), then the data on the relationship between the DC period and the clamping force is generated (S307). If the data for the DC period and the clamping force is insufficient (S304, "No"), the data is obtained again. That is, after changing the angle of the adjusting nut 51 to change the position of the chuck jaw 47 (S305), the chuck jaw 41 is closed (S306) and the workpiece W is gripped again. The adjustment amount of the adjusting nut 51 can be changed manually by the user, or it can be changed on the device side if it can be adjusted automatically. Repeat S301 to S306 until all the required data are obtained.

[0094] The latest clamping force data (C', D') obtained from the above processing is compared with the reference clamping force data (C, D) obtained at the beginning of use to obtain the delay time (coefficient), and the clamping force data corresponding to the DC period is corrected (S308). For example, C' / C=α is used as a coefficient to correct BA in the latest clamping force data (α(BA)). In this way, by using the corrected clamping force data, a more appropriate clamping force setting that reflects the time change of the device can be achieved.

[0095] As described above, according to this embodiment, the adjustment amount of the adjusting nut 51 (the tightening amount of the chuck 41) is set in relation to the time difference of the sensor detection timing. Therefore, regardless of the reference point setting, the optimal clamping force can be achieved. That is, the clamping force of the chuck can be properly controlled, thereby improving machining accuracy.

[0096] Furthermore, according to this embodiment, no additional device structure is required. The clamping force of the chuck, which is difficult to obtain directly (numerically), can be obtained more appropriately using the device structure that the machine tool itself has, thus enabling digitalization.

[0097] Furthermore, the specific structures of the spindle unit, chuck jaws, chuck sleeve, chuck jaws, chuck opening and closing unit, actuator for actuating the unit, and opening / closing sensor shown in this embodiment are merely examples. That is, other existing and known structures may also be appropriately employed.

[0098] (Explanation of reference numerals in the attached diagram)

[0099] 1: Machine tool; 100: Spindle unit; 101: Spindle; 102: Spindle box;

[0100] 103: Drive unit; 2: Base; 200: Control unit; 300: Tool holder;

[0101] 301: Cutting tool; 41: Jaw chuck; 43: Chuck sleeve;

[0102] 44: Compression coil spring; 45: Chuck opening and closing sleeve; 46: Balance sleeve;

[0103] 47: Chuck jaws; 48: Spool; 60: Actuator; W: Workpiece.

Claims

1. A machine tool comprising: The spindle has a chuck for holding the workpiece. An opening and closing unit that actuates the chuck to place the chuck in either a closed state that holds the workpiece or an open state that allows the workpiece to be detached. A first sensor detects whether the chuck is in the open state; A second sensor detects whether the chuck is in the closed state; and The control unit, which controls the opening and closing unit, is characterized in that... The machine tool includes an acquisition component that acquires the clamping force of the chuck on the workpiece in the closed state based on the difference between a first time and a second time when the chuck changes from the open state to the closed state by performing a closing action on the chuck in the opening and closing unit. The first time is the time from when the control unit sends the control signal for the closing action to the opening and closing unit until the first sensor detects that the chuck is no longer in the open state, and the second time is the time from when the control unit sends the control signal to the opening and closing unit until the second sensor detects that the chuck has become the closed state.

2. The machine tool according to claim 1, wherein, The machine tool also features: The adjustment unit is capable of adjusting the clamping amount of the chuck on the workpiece in the closed state; and A storage component that stores the magnitude of the difference and the relationship between the fastening amount and the clamping force.

3. The machine tool according to claim 2, wherein, The machine tool further includes: a correction component that corrects the correlation based on the change over time of a second difference between a third time and a fourth time when the chuck changes from the closed state to the open state by the opening / closing unit performing an opening action, wherein the third time is the time from when the control unit sends the control signal for the opening action to the opening / closing unit until the second sensor detects that the chuck is no longer in the closed state, and the fourth time is the time from when the control unit sends the control signal to the opening / closing unit until the first sensor detects that the chuck has become the open state.

4. The machine tool according to claim 1, wherein, The machine tool also includes a notification component that notifies the outside of information including the clamping force.

5. The machine tool according to claim 2, wherein, The opening / closing unit includes: The first actuating component is disposed on the main shaft and is capable of acting on the chuck to make the chuck into the closed state and acting on the chuck to make the chuck into the open state. The second action component is disposed on the main shaft and is capable of displacing the relative position of the main shaft with respect to the first action component in the direction of the rotation axis, thereby enabling the action component to be in the closed position of the closed posture and to be in the open position of the open posture. as well as A drive unit, including a cylinder, moves the second actuating component between the open position and the closed position.

6. The machine tool according to claim 5, wherein, The adjustment unit changes the clamping amount of the chuck by changing the position of the first actuating component relative to the spindle in the direction of the rotation axis.

7. The machine tool according to claim 6, wherein, The first sensor detects whether the driving unit is in the open position where the second active component is in the open position. The second sensor detects whether the driving unit is in the closed position where the second active component is in the closed position.

8. A method for detecting the clamping force of a chuck, comprising detecting the clamping force of the chuck on a workpiece when the chuck of a machine tool spindle clamps the workpiece, characterized in that, The detection method includes: In the first step, the opening and closing unit causes the chuck to close, so that the chuck changes from an open state that allows the workpiece to be detached and assembled to a closed state that holds the workpiece. The second step involves acquiring the first time from the moment the control signal for the closing action is sent from the control unit to the opening / closing unit in the first step until the first sensor detects that the chuck is no longer in the open state, and the second time from the moment the control signal is sent from the control unit to the opening / closing unit until the second sensor detects that the chuck has become in the closed state; and The third step involves obtaining the clamping force based on the relationship between the difference between the first and second times, the clamping amount of the chuck in the closed state adjusted by the adjustment unit, and the clamping force.

9. The method for detecting the clamping force of a chuck according to claim 8, wherein, The detection method further includes: In the fourth step, the opening and closing unit causes the chuck to open, thus changing the chuck from the closed state to the open state. The fifth step involves obtaining the third time from the start of the control signal sent from the control unit to the opening / closing unit in the fourth step until the second sensor detects that the chuck is no longer in the closed state, and the fourth time from the start of the control signal sent from the control unit to the opening / closing unit until the first sensor detects that the chuck has become open; and The sixth step involves correcting the correlation based on the change over time in the magnitude of the difference between the third time and the fourth time when repeating the fourth and fifth steps.

10. A method for setting the clamping amount of a chuck, which is a method for setting the clamping amount of the chuck on the workpiece when the chuck of a machine tool spindle clamps the workpiece, characterized in that, The setting method includes: In the first step, when the clamping amount of the chuck to the workpiece is adjusted to the first clamping amount by the adjustment unit in the closed state of the chuck holding the workpiece, the opening and closing unit causes the chuck to close, so that the chuck changes from the open state that can detach and install the workpiece to the closed state. The second step involves obtaining the first time from the start of the control signal sent by the control unit to the opening / closing unit for the closing action in the first step until the first sensor detects that the chuck is no longer in the open state, and the second time from the start of the control unit sending the control signal to the opening / closing unit until the second sensor detects that the chuck has become in the closed state. The third step involves obtaining a second tightening amount to achieve the desired clamping force, based on the relationship between the difference between the first and second times, the tightening amount of the chuck on the workpiece in the closed state adjusted by the adjustment unit, and the clamping force of the chuck on the workpiece in the closed state. In the fourth step, the fastening amount is adjusted by the adjustment unit to the second fastening amount obtained in the third step.

Images