Working machinery

Abstract

The present invention makes it possible to detect not only the presence or absence of a tool with respect to a main spindle but also a misclamped state of the tool, without increasing the number of sensors to be attached to a machine tool. Provided is a machine tool with an interchangeable tool clamped to a main spindle, the machine tool comprising: a drawbar which is biased backward by a biasing member and which clamps the tool to the main spindle by moving backward and unclamps the tool from the main spindle by moving forward; an interlocked part which is connected to the drawbar and interlocked with the forward and backward movement of the drawbar; an arm that pushes the interlocked part forward to move the drawbar forward against the biasing member; a proximity sensor which is fixed to either the arm or the part, and the output of which switches on / off depending on the distance between the arm and the part; and a determination unit that determines the clamp state of the tool on the basis of the on / off state of the proximity sensor.

Description

Technical Field

[0001] The present disclosure relates to a machine tool.

Background Art

[0002] Conventionally, a machine tool that clamps a tool arranged at a predetermined position and releases the clamped tool as needed to replace it with another tool is known. The machine tool includes a drawbar that is provided inside a spindle so as to be movable back and forth, and an arm that pushes the drawbar forward when exchanging tools. The drawbar is biased rearward by a spring inside the spindle, and when the drawbar is pushed forward by the arm, the spring extends to unclamp the tool, and when the forward pushing of the arm is released, the drawbar moves rearward by the biasing force of the spring to clamp the tool.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When automatically exchanging tools, in order to avoid the machine tool performing a machining operation in a state without a tool due to a failure in tool exchange or the like, the expansion and contraction state of the drawbar is monitored, and it is detected that the tool is clamped to the spindle. The expansion and contraction state of the drawbar is indirectly detected by one sensor provided in a position fixed with respect to the spindle.

[0005] However, when monitoring the extension and retraction state of the drawbar with a single sensor, it can detect the presence or absence of a tool, but it cannot detect misclamping conditions, such as when an object gets caught between the spindle and the tool while the tool is clamped. In this case, a separate sensor is required to detect misclamping conditions, and two or more sensors must be installed on the machine tool to monitor the extension and retraction state of the drawbar.

[0006] Therefore, it is desirable to be able to detect not only the presence or absence of a tool on the spindle, but also the misclamping status of the tool, without increasing the number of sensors attached to the machine tool. [Means for solving the problem]

[0007] The machine tool of this disclosure is a machine tool in which a tool to be clamped to a spindle can be replaced, and comprises: a drawbar that is biased rearward by a biasing member, clamps the tool to the spindle by moving rearward, and unclams the tool to the spindle by moving forward; an interlocking component connected to the drawbar and linked to the forward and backward movement of the drawbar; an arm that pushes the interlocking component to move the drawbar forward against the biasing member; a proximity sensor fixed to either the arm or the interlocking component, the output of which switches on / off depending on the distance between the arm and the interlocking component; and a determination unit that determines the clamping state of the tool based on the on / off state of the proximity sensor. [Brief explanation of the drawing]

[0008] [Figure 1] This is a partial side view of the machine tool of this embodiment. [Figure 2] This is a partial cross-sectional view showing the clamping state of the tool in the machine tool of this embodiment. [Figure 3] This is a partial cross-sectional view showing the unclamped state of the tool in the machine tool of this embodiment. [Figure 4] This is a magnified perspective view showing the interlocking components in the machine tool of this embodiment. [Figure 5] This is a front view of the interlocking components in the machine tool of this embodiment, as seen from direction A in Figure 4. [Figure 6] This is a functional block diagram illustrating the configuration of the control device for the machine tool of this embodiment. [Figure 7A] This diagram illustrates the state of the machine tool in this embodiment without a tool. [Figure 7B] This diagram illustrates the clamping state of the tool in the machine tool of this embodiment. [Figure 7C] This diagram illustrates the unclamped state of the tool in the machine tool of this embodiment. [Figure 8] This diagram illustrates the on / off state of the proximity sensor when the tool has been replaced correctly in the machine tool of this embodiment. [Figure 9] This diagram illustrates the on / off state of the proximity sensor when the tool is not changed properly in the machine tool of this embodiment. [Figure 10] This is a flowchart showing the determination process in the machine tool of this embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In Figure 1, the machine tool 1 includes a column 2, a spindle head 3, a spindle 4, a drawbar 5, an air injection unit 6, an arm 7, an automatic tool changer 8, a proximity sensor 9, and a control device 10 (see Figure 7). The machine tool 1 is, for example, a machining center.

[0010] Column 2 is a support column of the machine tool 1 that extends substantially perpendicular to the worktable (not shown). As shown in Figures 2 and 3, column 2 has a translation shaft 21 located inside it. The translation shaft 21 extends vertically inside column 2. The translation shaft 21 is made of, for example, a ball screw. The translation shaft 21 rotates around its axis by the drive of a translation shaft motor 20, which is a servo motor provided at the upper end of column 2.

[0011] The spindle head 3 is supported on the column 2 so as to be movable in the vertical direction. The spindle head 3 extends from the column 2 in a direction substantially perpendicular to the direction of extension of the column 2. The tip of the spindle head 3 furthest from the column 2 supports the spindle 4, which will be described later. The base end of the spindle head 3, which is close to the column 2, is connected to the translation axis 21 of the column 2. More specifically, the base end of the spindle head 3 is connected to a nut member 22 that screws onto the translation axis 21, as shown in Figures 2 and 3. When the translation axis 21 rotates due to the drive of the translation axis motor 20, the nut member 22 moves up and down along the translation axis 21. As a result, the spindle head 3 connected to the nut member 22 moves up and down along the column 2, causing the spindle 4 to move up and down.

[0012] The spindle 4 is provided at the tip of the spindle head 3 so as to extend vertically. The spindle 4 is formed in a substantially cylindrical shape with a hollow portion 41 that runs along the vertical direction. The spindle 4 is rotatable around an axis that extends vertically by the drive of the spindle motor 40 shown in Figures 2 and 3. This allows the machine tool 1 to rotate a tool 80 clamped to the spindle 4 and machine a workpiece (not shown). The workpiece is mounted on a turntable (not shown) having a rotation axis 200 (see Figure 6). The spindle 4 has a conical tool housing portion 42 at its lower end, the hollow portion 41 which widens in diameter downwards. The tool housing portion 42 accommodates the conical portion 82 at the upper end of the tool 80. The spindle 4 has a space 43 between the hollow portion 41 and the tool housing portion 42, which is formed to have a larger diameter than the inner diameter of the hollow portion 41. The hollow portion 41 of the main shaft 4 is provided with a cylindrical support portion 44 at its upper end to support the drawbar 5, which will be described later.

[0013] The drawbar 5 is disposed within the hollow portion 41 of the main shaft 4 and is provided so as to be movable back and forth within the main shaft 4. Here, the front and rear of the drawbar 5 are defined as follows. The "front" of the drawbar 5 is the side where the tool 80 is disposed with respect to the drawbar 5. The "rear" of the drawbar 5 is the side opposite to the side where the tool 80 is disposed with respect to the drawbar 5. In the illustrated embodiment, the front and rear of the drawbar 5 correspond to the lower and upper in the drawing, respectively. Therefore, in the following description, regarding the moving direction and the biasing direction of the drawbar 5, the "front" is expressed as "lower" and the "rear" is expressed as "upper". As shown in FIG. 2, the drawbar 5 includes a drawbar main body 51, a tool gripping portion 52, and a biasing member 53.

[0014] The drawbar main body 51 extends in the vertical direction along the hollow portion 41 of the main shaft 4. The drawbar main body 51 is housed above the tool housing portion 42 within the hollow portion 41 of the main shaft 4. The outer diameter of the drawbar main body 51 is smaller than the inner diameter of the hollow portion 41 of the main shaft 4. Therefore, a gap is formed between the inner surface of the hollow portion 41 of the main shaft 4 and the outer surface of the drawbar main body 51. The upper end portion of the drawbar main body 51 is inserted into the support portion 44 of the main shaft 4 so as to be movable up and down. The drawbar main body 51 has an air flow path 511 that extends vertically along the central axis (see FIGS. 7A, 7B, and 7C).

[0015] The tool gripping portion 52 is integrally provided at the lower end portion of the drawbar main body 51. The tool gripping portion 52 is formed to have a larger diameter than the outer diameter of the drawbar main body 51. The tool gripping portion 52 has a recess 521 that opens downward and houses a pull stud 81 provided at the upper end of the tool 80. A plurality of balls 522 are arranged in the circumferential direction on the circumferential surface of the lower end portion of the tool gripping portion 52 that constitutes the outer peripheral wall of the recess 521. The plurality of balls 522 are provided so as to be movable in the radial direction of the tool gripping portion 52 by being loosely attached to the tool gripping portion 52. The lower end of the air flow path 511 of the drawbar main body 51 communicates with the recess 521 of the tool gripping portion 52.

[0016] The biasing member 53 is disposed in the gap between the inner surface of the hollow portion 41 of the main shaft 4 and the outer surface of the drawbar body 51. The biasing member 53 is, for example, a coil spring. The biasing member 53 is provided so as to constantly bias the drawbar body 51 upward with respect to the support portion 44 of the main shaft 4.

[0017] The air injection portion 6 is connected to the upper end portion of the drawbar 5. The air injection portion 6 is composed of a metal cylinder and is arranged coaxially with the drawbar 5. As shown in FIGS. 7A, 7B, and 7C, an air injection flow path 61 is provided inside the air injection portion 6. One end of the air injection flow path 61 communicates with the upper end of the air flow path 511 of the drawbar body 51. The air injection portion 6 is connected to an air supply source (not shown), and supplies the air supplied from the air supply source to the air flow path 511 of the drawbar body 51 through the air injection flow path 61. The air supplied to the drawbar body 51 is jetted into the recess 521 of the tool gripping portion 52. Thereby, the cleaning of the contaminants adhering to the recess 521 of the drawbar body 51 and the conical portion 82 of the tool 80 is performed.

[0018] The air injection portion 6 also functions as a component to be pressed by the arm 7 described later when the tool 80 is replaced by the drawbar 5. The air injection portion 6 is arranged above the main shaft 4 and is connected to the upper end portion of the drawbar body 51. Therefore, the air injection portion 6 is an interlocking component that interlocks with the vertical movement of the drawbar 5. The air injection portion 6 is formed to have a larger diameter than the main shaft 4. The upper end surface 62 of the air injection portion 6 is a flat annular surface. The upper end surface 62 of the air injection portion 6 is a surface to be pressed by the arm 7 described later.

[0019] The arm 7 includes an arm body 71, a rotation shaft 72, a cam follower 63, and a pressing operation portion 74.

[0020] The arm body 71 is rotatably supported on the upper part of the spindle head 3 by a pivot shaft 72. The pivot shaft 72 extends in a direction perpendicular to the extension direction of the column 2 and perpendicular to the extension direction of the spindle head 3. The arm body 71 is formed in a substantially L-shape, having a first arm portion 711 that extends from the pivot shaft 72 along the spindle head 3 toward the spindle 4, and a second arm portion 712 that extends upward from the pivot shaft 72. The arm body 71 is rotatable around the pivot shaft 72 in clockwise and counterclockwise directions as shown in Figures 1 to 3.

[0021] The cam follower 73 is provided at the tip of the first arm portion 711 of the arm body 71. The cam follower 73 is made of, for example, a cylindrical body. The cam follower 73 is rotatably mounted on a pivot shaft 731 which is arranged parallel to the pivot shaft 72.

[0022] The push-button operation section 74 is provided at the tip of the second arm section 712 of the arm body 71. As shown in Figures 4 and 5, the push-button operation section 74 has a pair of arms 741 that are arranged to sandwich the air injection section 6 from both radial sides. As shown in Figure 5, cylindrical push members 742 are attached to the opposing inner surfaces of the pair of arms 741. The central axes of the push members 742 extend in opposing directions and are positioned at the same height from the upper end surface 62 of the air injection section 6. The outer circumferential surface 742a of the push member 742 is positioned to face the upper end surface 62 of the air injection section 6. At the fixed position of the arm 7, which is moving upward due to the biasing force of the biasing member 53, as shown in Figure 5, the push member 742 of the push-button operation section 74 is not in contact with the upper end surface 62 of the air injection section 6. At this time, the push member 742 is located above the upper end surface 62 of the air injection section 6, separated by a distance D.

[0023] As shown in Figures 1 to 3, a cam 23 is attached to the upper end of the column 2, which is above the spindle head 3. The cam 23 is positioned to protrude from the column 2 towards the spindle 4. The cam 23 is composed of a plate-shaped member that extends along the extension direction of the column 2. The cam 23 has an inclined surface 231 at its lower end that slopes upward toward the tip of the spindle head 3, and a flat surface 232 that extends linearly vertically from the upper end of the inclined surface 231. The inclined surface 231 and the flat surface 232 form the cam surface of the cam 23, continuously extending vertically. The cam follower 73 of the arm 7 is slidably positioned on the cam 23 as the spindle head 3 moves up and down.

[0024] When the cam follower 73 of arm 7 is in contact with the inclined surface 231 of cam 23, as shown in Figures 1 and 2, arm 7 rotates counterclockwise, positioning the push-button 74 at its highest point. When the cam follower 73 of arm 7 is in contact with the plane 232 of cam 23, as shown in Figure 3, arm 7 rotates clockwise, positioning the push-button 74 at its lowest point. This rotation of arm 7 causes the push-button member 742 of the push-button 74 to move toward and away from the upper end surface 62 of the air injection section 6.

[0025] The automatic tool changer (ATC) 8 is a disc-shaped device that holds multiple tools 80. The automatic tool changer 8 is rotatably mounted on the machine tool 1 so that the tool attached to the spindle 4 can be changed to the desired tool 80 depending on the operation. However, the automatic tool changer 8 does not necessarily have to be provided on the machine tool 1. The tool 80 has a pull stud 81 at its upper end that is housed in a recess 521 of the tool gripping portion 52 of the drawbar 5, and a conical portion 82 provided below the pull stud 81. The conical portion 82 has a shape that matches the inner surface shape of the tool housing portion 42 of the spindle 4.

[0026] The proximity sensor 9 is a non-contact sensor that detects the approach of an object. The proximity sensor 9 has a coil that generates a high-frequency magnetic field, and when the object to be detected approaches the magnetic field, it detects the change in impedance caused by the induced current flowing through the object. When the change in impedance detected by the approaching object reaches a predetermined threshold, the proximity sensor 9 outputs an ON / OFF signal to the control device 10 (see Figure 6).

[0027] In this embodiment, the proximity sensor 9 is fixed to the push-button 74 of the arm 7. Specifically, as shown in Figures 4 and 5, an L-shaped bracket 743 is attached to one arm portion 741 of the push-button 74 of the arm 7. The proximity sensor 9 is attached to the bracket 743 and moves up and down together with the push-button 74 of the arm 7. The proximity sensor 9 is positioned above the upper end surface 62 of the air injection section 6 so as to face the upper end surface 62 when attached to the bracket 743. The lower surface of the proximity sensor 9 is positioned at the same location as the lower end of the push member 742 of the push-button 74 and is spaced above the upper end surface 62 of the air injection section 6. The proximity sensor 9 detects whether the upper end surface 62 of the air injection section 6 has approached a predetermined distance, using the upper end surface 62 of the air injection section 6 as the detection object.

[0028] The proximity sensor 9 may output an ON signal when the upper end surface 62 of the air injection section 6 approaches a predetermined distance, or it may output an OFF signal when the upper end surface 62 of the air injection section 6 approaches a predetermined distance. In this embodiment, the case in which the proximity sensor 9 outputs an ON signal when it is a predetermined distance away from the upper end surface 62 of the air injection section 6 and outputs an OFF signal when it approaches a predetermined distance away from the upper end surface 62 of the air injection section 6 will be described. In this embodiment, the predetermined distance is set to the distance D between the proximity sensor 9 and the upper end surface 62 of the air injection section 6 when the arm 7 is positioned in a fixed position. Therefore, the proximity sensor 9 is configured to be ON when it is farther away from the upper end surface 62 of the air injection section 6 than the distance D, and OFF when it approaches the upper end surface 62 of the air injection section 6 to a distance D or less.

[0029] Figure 6 shows a functional block diagram of the control device 10. The control device 10 includes a control unit 101, a determination unit 102, an acquisition unit 103, and a storage unit 104. The control device 10 may be installed in the machine tool 1, or it may be installed in a numerical control device (not shown) that controls the operation of the machine tool 1.

[0030] The control unit 101 controls various processes performed by the control device 10. Specifically, the control unit 101 controls the driving of the automatic tool changer 8, the translation axis motor 20, and the spindle motor 40 in order to perform clamping and unramping operations on the tool 80 in the machine tool 1.

[0031] The determination unit 102 compares the detected value of the on / off state switching timing sent from the proximity sensor 9 with the normal value of the on / off state switching timing preset in the storage unit 104. Based on the comparison result, the determination unit 102 determines whether there is a clamping abnormality in the tool 80 and an abnormality in the proximity sensor 9. The determination unit 102 also determines whether a tool change is in progress by monitoring the signal that the control unit 101 uses to control the automatic tool changer 8. Furthermore, the determination unit 102 determines whether the amount of movement of the arm 7 is normal based on the amount of movement of the arm 7 obtained by the means 12 for acquiring the amount of arm movement, which will be described later.

[0032] The acquisition unit 103 acquires the ON / OFF signal from the proximity sensor 9 and outputs it to the determination unit 102.

[0033] The memory unit 104 stores the normal timing for the switching of the on / off state of the proximity sensor 9, which is used to determine clamp abnormalities.

[0034] In Figure 6, the display unit 11 is configured, for example, as a liquid crystal display device. The display unit 11 is connected to the control device 10 and displays various data sent from the control device 10 on the screen.

[0035] In Figure 6, the means 12 for acquiring the amount of arm movement is, for example, an encoder provided on the pivot axis 72 of the arm 7. The means 12 for acquiring the amount of arm movement detects when the arm 7 has started to rotate normally from its fixed position for clamping and unclamping the tool 80 and when the arm 7 has returned normally to its fixed position by acquiring the amount of arm movement of the arm 7. Whether the amount of arm movement of the arm 7 is normal can be determined by comparing the amount of rotation of the arm 7 detected by the encoder with a normal value of the amount of rotation that is preset in the storage unit 104. For example, if the amount of rotation of the arm 7 is within a predetermined threshold relative to the normal value, the determination unit 102 determines that the amount of arm movement of the arm 7 is normal. The means 12 for acquiring the amount of arm movement outputs the detection result to the acquisition unit 103.

[0036] The main part of the control device 10 is comprised of a processor. The control device 10, consisting of the processor, non-volatilely stores control programs executed by the processor and data processed by the control device 10 in a memory that functions as a storage unit 104. The memory is composed of a magnetic storage device, a semiconductor storage element such as flash ROM (Read Only Memory), or other types of non-volatile storage devices. The memory may also include RAM (Random Access Memory) which constitutes the work area of ​​the processor. The functions of the control unit 101, determination unit 102, and acquisition unit 103 of the control device 10 are realized by the processor executing predetermined software (programs, applications) stored in the memory, for example.

[0037] Next, the positions of the drawbar 5 and air injection port 6 when the tool 80 is clamped and unclamped, and the on / off state of the proximity sensor 9 will be explained with reference to Figures 7A to 7C.

[0038] Figure 7A shows the state where the tool 80 is not attached to the spindle 4. In this state, the arm 7 is positioned in its fixed position. That is, the arm 7 has the pressing member 742 of the pressing operation section 74 positioned at its uppermost position. The drawbar 5 is moved to its uppermost position by the upward biasing force of the biasing member 53. The upper end surface 62 of the air injection section 6, which is linked to the drawbar 5, is positioned at position P0. This position P0 is equal to distance D, which is a predetermined distance at which the on / off state of the proximity sensor 9 switches. Therefore, the proximity sensor 9 is in the off state.

[0039] Figure 7B shows the state in which the tool 80 is properly clamped to the spindle 4. The drawbar 5 moves upward due to the biasing force of the biasing member 53, and clamps the tool 80 by gripping the pull stud 81 of the tool 80, which is housed in the recess 521 of the tool gripping portion 52, with the multiple balls 522. The upward movement of the drawbar 5 is restricted by the conical portion 82 of the tool 80 contacting the inner circumferential surface of the tool housing portion 42 of the spindle 4. The upper end surface 62 of the air injection portion 6 is positioned at position P1, which is lower than position P0. Therefore, when the arm 7 returns to its fixed position, the proximity sensor 9 is ON. In other words, the fact that the proximity sensor 9 is ON when the arm 7 is in its fixed position indicates that the tool 80 is clamped to the spindle 4.

[0040] Figure 7C shows the state during attachment and detachment of the tool 80. The pressing member 742 of the pressing operation part 74 of the arm 7 pushes down the upper end surface 62 of the air injection part 6, causing the drawbar 5 to move to its lowest position against the biasing force of the biasing member 53. As a result, the multiple balls 522 provided on the tool gripping part 52 are positioned in the space 43 of the spindle 4. The multiple balls 522 move radially outward from the tool gripping part 52, and the tool 80 becomes unclamped. Since the upper end surface 62 of the air injection part 6 is positioned at position P2, which is lower than position P1, the proximity sensor 9 is ON when the arm 7 returns to its original position.

[0041] The on / off state of the proximity sensor 9 when the tool 80 is clamped and unclamped will be further explained with reference to Figures 8 and 9. In Figures 8 and 9, the dashed lines indicate the region where the proximity sensor 9 is ON, and the solid lines indicate the region where the proximity sensor 9 is OFF.

[0042] First, with reference to Figure 8, let's explain the case where the tool 80 is properly clamped. When the tool 80 is not attached (as shown in Figure 7A), the arm 7 is positioned in a fixed position (timing T0). At this time, the upper end surface 62 of the air injection section 6 is positioned at position P0. Therefore, the proximity sensor 9 is in the ON state and outputs an ON signal to the control device 10.

[0043] Subsequently, as the pressing operation part 74 of the arm 7 moves downward to clamp the tool 80, the pressing member 742 pushes down the upper end surface 62 of the air injection part 6 until it is positioned at position P2, as shown in Figure 7C. During the pushing operation, the proximity sensor 9 switches to the off state at timing T1 when it approaches the upper end surface 62 of the air injection part 6 at a distance D or less.

[0044] When the tool 80 is transferred from the automatic tool changer 8 to the drawbar 5 and the tool 80 is properly clamped, the upper end surface 62 of the air injection section 6 is positioned at position P1, as shown in Figure 7B. This position P1 is lower than position P0. Therefore, as the arm 7 rotates toward its fixed position, the proximity sensor 9 switches back to the ON state at timing T2 when it moves beyond a distance D from the upper end surface 62 of the air injection section 6.

[0045] Thus, when the tool 80 is properly clamped to the spindle 4 by the drawbar 5, it takes time T1-T2 from the timing T1 when the proximity sensor 9 switches from the ON state to the OFF state to the timing T2 when it switches back to the ON state.

[0046] In contrast, when clamping the tool 80, if, for example, foreign matter gets caught between the conical portion 82 of the tool 80 and the tool housing portion 42, the tool 80 will be in a half-clamped state and will not be properly clamped. In this case, even if the arm 7 returns to its fixed position and the drawbar 5 moves upward due to the biasing force of the biasing member 53, the upper end surface 62 of the air injection portion 6 will not return to the normal clamping position P1 shown in Figure 7B. Because the upward movement of the drawbar 5 is hindered by the foreign matter getting caught, the upper end surface 62 of the air injection portion 6 is positioned below position P1. As a result, in the process of the arm 7 returning to its fixed position, the proximity sensor 9 moves away from the upper end surface 62 of the air injection portion 6 by a distance D earlier than expected. Therefore, as shown in Figure 9, the time T1-T3 required from the timing T1 when the proximity sensor 9 switches from the ON state to the OFF state to the timing T3 when it switches back to the ON state is shorter than the normal time T1-T2 shown in Figure 8.

[0047] The above time intervals T1-T2, which represent the timing when the tool 80 is clamped correctly, are stored as normal values ​​in the storage unit 104 of the control device 10. The determination unit 102 detects the timing of the on / off signal switching output from the proximity sensor 9 during a tool change operation and compares it with the above time intervals T1-T2 stored as normal values ​​in the storage unit 104. If the determination unit 102 determines that the detected value is smaller than the normal value by a predetermined threshold, it determines that a clamping abnormality of the tool 80 due to misclamping has occurred.

[0048] Furthermore, during tool changing operations, the push-button operation section 74 of the arm 7 pushes down the upper end surface 62 of the air injection section 6, causing the proximity sensor 9 to approach the upper end surface 62 and always turn off. Therefore, if the proximity sensor 9 does not switch to the off state during tool changing operations, it can be determined that an abnormality such as a malfunction has occurred in the proximity sensor 9. The determination unit 102 determines whether or not an abnormality has occurred in the proximity sensor 9 by determining whether or not the proximity sensor 9 switched to the off state during tool changing operations.

[0049] Next, with reference to the flowchart in Figure 10, one embodiment of the process for determining whether there is a clamp abnormality in the control device 10 and whether there is movement of the proximity sensor 9 will be described.

[0050] First, after the machine tool 1 starts operating, the determination unit 102 of the control device 10 determines whether the control unit 101 is controlling the automatic tool changer 8 (step ST1). Based on this, the determination unit 102 determines whether the machine tool 1 is in the process of changing tools (step ST2).

[0051] In step ST2, if the determination unit 102 determines that the machine tool 1 is not changing tools (step ST2: NO), the determination unit 102 determines the presence or absence of the tool 80 on the spindle 4 from the signal of the proximity sensor 9 acquired by the acquisition unit 103 (step ST3). That is, when the spindle 4 is clamping the tool 80, as shown in Figure 7B, the upper end surface 62 of the air injection unit 6 is positioned at position P1, so the proximity sensor 9 is ON. The determination unit 102 determines whether the tool 80 is clamped on the spindle 4 from the state of the proximity sensor 9 acquired from the acquisition unit 103 (step ST4). In step ST4, if the determination unit 102 determines that the tool 80 is clamped on the spindle 4 (step ST4: YES), the determination unit 102 determines that the machining operation of the machine tool 1 is possible, outputs a signal to that effect to the control unit 101, and terminates the determination process.

[0052] In step ST4, if the determination unit 102 determines that the tool 80 is not clamped to the spindle 4 (step ST4: NO), the determination unit 102 outputs a signal indicating no tool to the control unit 101. As a result, the control unit 101 controls the spindle 4, translation axis 21, and rotation axis 200 to stop (step ST5). Subsequently, the control unit 101 displays a warning on the display unit 11 indicating no tool (step ST6).

[0053] In step ST2 described above, if the determination unit 102 determines that the machine tool 1 is undergoing a tool change (step ST2: YES), it acquires an on / off signal from the proximity sensor 9 from the acquisition unit 103 (step ST7). During a tool change, the proximity sensor 9 always approaches the upper end surface 62 of the air injection unit 6 and outputs an off signal. Therefore, during a tool change, the determination unit 102 monitors the signal from the proximity sensor 9 acquired from the acquisition unit 103 and determines whether or not there was an off signal from the proximity sensor 9 (step ST8).

[0054] In step ST8, if the determination unit 102 determines that there is an OFF signal from the proximity sensor 9 (step ST8: YES), the determination unit 102 monitors the amount of movement of the arm 7 obtained from the means 12 that acquires the amount of arm movement by the acquisition unit 103, and the switching timing of the on / off state of the proximity sensor 9, and determines whether these are normal (step ST9). That is, the determination unit 102 determines whether the amount of movement of the arm 7 obtained from the means 12 that acquires the amount of arm movement falls within the range of normal values ​​set in the storage unit 104, and whether the detected value of the timing of the switching of the on / off state of the proximity sensor 9 falls within the range of normal values ​​set in the storage unit 104 (step ST10).

[0055] In step ST10, if the determination unit 102 determines that both the amount of movement of the arm 7 and the switching timing of the proximity sensor 9 are normal (step ST10: YES), the determination unit 102 determines that the tool 80 has been replaced normally and that the machining operation of the machine tool 1 can be performed, outputs a signal to the control unit 101 to that effect, and terminates the determination process.

[0056] If, for example, during tool change, foreign matter gets caught between the tool housing 42 of the spindle 4 and the conical portion 82 of the tool 80, preventing the tool 80 from being properly clamped, or if the cam follower 73 of the arm 7 does not slide properly against the cam 23, resulting in an abnormal amount of movement of the arm 7, then in step ST10, the determination unit 102 determines that at least one of the amount of movement of the arm 7 or the switching timing of the proximity sensor 9 is abnormal (step ST10: NO). As a result, the determination unit 102 determines that the tool 80 is not properly clamped and outputs a signal to the control unit 101 to that effect.

[0057] When the control unit 101 receives a signal from the determination unit 102 indicating that the tool 80 is not properly clamped, it stops the spindle 4, translation axis 21, and rotation axis 200 after the tool change operation is complete (step ST11). Subsequently, the control unit 101 displays a warning on the display unit 11 indicating that the tool 80 is not properly clamped (step ST12).

[0058] In step ST8 described above, if the determination unit 102 determines that there is no OFF signal from the proximity sensor 9 (step ST8: NO), it determines that the proximity sensor 9 did not come within a predetermined distance of the upper end surface 62 of the air injection section 6 during tool change. Therefore, the determination unit 102 outputs a signal to the control unit 101 indicating that an abnormality has occurred in the proximity sensor 9 due to a malfunction or the like. As a result, the control unit 101 displays a warning on the display unit 11 indicating the abnormality of the proximity sensor 9.

[0059] In the above embodiment, the proximity sensor 9 is fixed to the push operation part 74 of the arm 7 and configured to switch on / off depending on the distance from the upper end surface 62 of the air injection part 6. However, the proximity sensor 9 may also be fixed to the air injection part 6 and configured to switch on / off depending on the distance from the push operation part 74 of the arm 7.

[0060] The machine tool 1 can detect the presence or absence of the tool 80 on the spindle 4, as well as the misclamping state of the tool 80, using a single proximity sensor 9 fixed to the arm 7. Therefore, without increasing the number of sensors attached to the machine tool 1, it is possible to detect not only the presence or absence of the tool 80 on the spindle 4, but also the misclamping state of the tool 80.

[0061] The determination unit 102 of the machine tool 1 determines whether or not there is a clamping abnormality in the tool 80 simply by comparing the detected value of the switching timing of the on / off state of the proximity sensor 9 with a normal value. There is no need to perform complex calculations based on the sensor's detected value. Therefore, the circuit configuration for determining clamping abnormalities is simplified.

[0062] The determination unit 102 of the machine tool 1 determines whether or not there is an abnormality in the proximity sensor 9 based on the on / off state of the proximity sensor 9 during tool change, so there is no need to provide a separate configuration for detecting abnormalities in the proximity sensor 9. Therefore, the circuit configuration for detecting abnormalities in the proximity sensor 9 is simplified.

[0063] The following additional information is disclosed regarding the above embodiments and modifications. (Note 1) The machine tool (1) is a machine tool (1) capable of automatically changing the tool (80) that is clamped to the spindle (4), and comprises a drawbar (5) which is biased upward by a biasing member (53) and clamps the tool (80) to the spindle (4) by moving upward and unclams the tool (80) to the spindle (4) by moving downward; an interlocking part (6) which is connected to the drawbar (5) and is linked to the up and down movement of the drawbar (5); an arm (7) which pushes down the interlocking part (6) to move the drawbar (5) downward against the biasing member (53); a proximity sensor (9) which is fixed to either the arm (7) or the interlocking part (6) and whose output switches on / off depending on the distance between the arm (7) and the interlocking part (6); and a determination unit (102) which determines the clamping state of the tool (80) based on the on / off state of the proximity sensor (9).

[0064] (Note 2) In the machine tool 1 described in Appendix 1, a storage unit (104) is provided to store a normal value for the timing of the switching of the on / off state of the proximity sensor (9) during tool change operation. The determination unit (102) determines whether or not there is a clamping abnormality of the tool (80) based on the comparison result between the detected value of the switching timing of the on / off state of the proximity sensor (9) and the normal value stored in the storage unit (104).

[0065] (Note 3) In the machine tool 1 described in Appendix 1 or Appendix 2, the determination unit (102) determines whether or not there is an abnormality in the proximity sensor (9) based on the on / off state of the proximity sensor (9) during tool change.

[0066] Although the present disclosure has been described in detail above, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the present disclosure or from the spirit of the present disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0067] 1 Machine tools 4 spindle 5 Drawbacks 6. Air injection section (connecting part) 7 Arms 9. Proximity Sensor 80 Tools 53. Biasing member 102 Judgment section 104 Storage section

Claims

1. A machine tool in which the tool clamped to the spindle can be replaced, A drawbar that is biased rearward by a biasing member, clamps the tool to the spindle by moving rearward, and unclams the tool to the spindle by moving forward, A connecting component connected to the drawbar and linked to the forward and backward movement of the drawbar, An arm that pushes the interlocking component forward in order to move the drawbar forward against the biasing member, A proximity sensor fixed to either the arm or the interlocking component, whose output switches on / off depending on the distance between the arm and the interlocking component, A determination unit that determines the clamping state of the tool based on the on / off state of the proximity sensor, A machine tool equipped with the following features.

2. The system includes a storage unit that stores the normal timing of the switching between the on and off states of the proximity sensor during the tool changing operation. The machine tool according to claim 1, wherein the determination unit determines whether or not there is a clamping abnormality in the tool based on the result of comparing the detected value of the timing of the switching of the on / off state of the proximity sensor with the normal value stored in the storage unit.

3. The machine tool according to claim 1 or 2, wherein the determination unit determines whether or not there is an abnormality in the proximity sensor based on the on / off state of the proximity sensor during tool replacement.

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