Seating checking method and seating checking device for machine tool

Abstract

To provide a seating checking method and a seating checking device for a machine tool capable of automatically, precisely and easily checking that a detachable object such as a tool, a pallet, and a workpiece is seated on a seating surface without biting a foreign object.SOLUTION: A seating checking method for checking whether a toolholder 14 is in close contact with seating surfaces ES1 and ES2 of a tool clamp device 16 of a machine tool 10 includes: mounting the toolholder 14 with predetermined seating checking clamp force smaller than specified clamp force for mounting the toolholder 14 by the tool clamp device 16 when the machine tool 10 is operated; detecting a seating state between the seating surfaces ES1 and ES2 and the toolholder 14 when the toolholder 14 is mounted with the seating checking clamp force; and determining whether a detection result of the seating state is good.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and device for confirming seating of a machine tool. [Background technology]

[0002] In automating machining, it is desirable to automatically detect whether detachable objects, such as tool holders and work pallets, attached to and detached from machine tools are properly clamped to the machine tool. Patent Document 1 discloses a tool attachment confirmation device that eliminates air leaks for tool attachment confirmation, enabling tool attachment confirmation. However, in machine tools that use spindle tools, if a foreign object, such as a chip with a thickness of 10 μm to 30 μm, is sandwiched between the spindle and the tool and the tool is clamped with a predetermined clamping force, the gap disappears due to elastic deformation of the foreign object and the tool holder and spindle member around the foreign object. Therefore, when attempting to confirm seating by, for example, flowing air through the seating surface and measuring the pressure and flow rate with an air-type seating sensor, the pressure in the air flow path where the gap has disappeared increases or the flow rate drops to zero, making it difficult to determine whether the detachable object is properly clamped or whether a small foreign object has been trapped.

[0003] In relation to this, Patent Document 2 discloses a tool clamping device that can grasp a decrease in tool clamping force due to deterioration of the biasing member over time by compressing a disc spring in the unclamping direction with a second pressure that is lower than the first pressure used during normal unclamping and detecting the magnitude of the compression. However, it does not disclose detecting foreign matter caught in the tool seating surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-259906 [Patent Document 2] Japanese Patent Application Publication No. 2019-14017 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, accurate detection of small foreign objects trapped inside the tool requires the use of an expensive sensor or the measurement of the rotational runout accuracy of the tool attached to the spindle each time the tool is replaced, but this is not practical for general-purpose machine tools. In view of the above circumstances, the present invention aims to provide a machine tool seating confirmation method and device that can automatically, precisely, and easily confirm that removable objects such as tools, pallets, and workpieces are seated on the seating surfaces without getting caught in the foreign objects. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a method for confirming the presence or absence of a detachable object in close contact with the seating surface of a mounting / detachment mechanism of a machine tool, the method comprising: mounting the detachable object with a predetermined seating confirmation clamping force that is smaller than a specified clamping force for the mounting mechanism to mount the detachable object when the machine tool is operating; detecting the seating state between the seating surface and the detachable object when the detachable object is mounted with the seating confirmation clamping force; and judging whether the detection result of the seating state is good or bad.

[0007] According to one aspect of the present invention, there is provided a seating confirmation device for a machine tool that confirms whether an object is in close contact with the seating surface of a mounting / detaching mechanism of the machine tool, the device comprising: a mounting / detaching mechanism that, when the machine tool is operating, can switch between at least two clamping forces: a specified clamping force for the mounting mechanism to mount the object, and a predetermined seating confirmation clamping force that is smaller than the specified clamping force; a seating detector that detects the seating state between the seating surface and the object; and a control unit that sets the clamping force of the mounting / detaching mechanism to the seating confirmation clamping force in order to detect the seating state using the seating detector, and judges whether the detection result of the seating state is good or bad. [Effects of the Invention]

[0008] According to one aspect of the present invention, a machine tool seating confirmation method can accurately detect the seating state between the seating surface and the detachable object by attaching the detachable object with a seating confirmation clamping force that is smaller than the specified clamping force when the machine tool is operating. If a small foreign object is trapped on the seating surface, the specified clamping force would eliminate a gap due to elastic deformation of the foreign object, the detachable object around the foreign object, and the seating surface member. However, the seating confirmation clamping force results in small elastic deformation, leaving a gap. If the seating state is good with the seating confirmation clamping force, the presence of a trapped foreign object can be detected, and the specified clamping force can be used to safely and accurately machine the workpiece. This allows automatic, precise, and simple confirmation of whether a detachable object, such as a tool, pallet, or workpiece, is seated on the seating surface and whether a foreign object is trapped.

[0009] According to one aspect of the present invention, a machine tool seating confirmation device includes an attachment / detachment mechanism that can switch between at least two clamping forces: a specified clamping force for the attachment / detachment mechanism to attach an object when the machine tool is operating, and a predetermined seating confirmation clamping force that is smaller than the specified clamping force. The device also includes a seating detector for detecting the seating state between the seating surface and the object, and a control unit that sets the clamping force of the attachment / detachment mechanism to the seating confirmation clamping force so that the seating state can be detected by the seating detector. This allows the object to be attached with a seating confirmation clamping force smaller than the specified clamping force, allowing for accurate detection of the seating state between the seating surface and the object. If a small foreign object is trapped on the seating surface, a gap will disappear due to elastic deformation of the foreign object, the object around the foreign object, and the seating surface member, but a gap will remain due to small elastic deformation when the seating confirmation clamping force is used. If the seating condition is good with the seating confirmation clamping force, it is possible to detect the presence of a foreign object, and the workpiece can be machined safely and accurately with the specified clamping force. This allows the seating confirmation device to automatically, precisely, and easily confirm whether or not a removable object such as a tool, pallet, or workpiece is seated on the seating surface and whether or not a foreign object is caught in it. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side cross-sectional view of a seating confirmation device for a machine tool according to a first embodiment. [Figure 2] FIG. 2 is a block diagram of the machine tool seating confirmation device according to the first embodiment. [Figure 3] FIG. 3 shows a flowchart of seating confirmation according to the first embodiment. [Figure 4] FIG. 4 shows a side view of a seating confirmation device for a machine tool according to the second embodiment. [Figure 5] FIG. 5 is a side cross-sectional view of a seating confirmation device for a machine tool according to the second embodiment. [Figure 6] FIG. 6 is a side cross-sectional view of a seating confirmation device for a machine tool according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a seating confirmation device for a machine tool according to an embodiment will be described with reference to the accompanying drawings. Similar or corresponding elements are given the same reference numerals, and duplicated explanations will be omitted. For ease of understanding, the scale of the drawings may be changed.

[0012] (First embodiment) FIG. 1 shows a schematic side cross-sectional view of a spindle unit 12 serving as a seating confirmation device for a machine tool 10 according to a first embodiment. The spindle unit 12 is equipped with a tool clamping device 16 serving as an attachment / detachment mechanism for attaching and detaching a tool holder 14 serving as a detachable object. The spindle unit 12 has a spindle head 12a serving as a housing and a spindle 12b rotatably disposed within the spindle head 12a. The spindle 12b is held within the spindle head 12a via a bearing 18, and is configured to be rotatable relative to the spindle head 12a. A built-in motor 20 is incorporated at the portion where the spindle head 12a and the spindle 12b face each other, and this drives the spindle 12b to mechanically rotate it.

[0013] The spindle unit 12 is configured to rotate the tool TL and the tool holder 14 by mounting a tool TL attached to the spindle 12b, and perform cutting or other processing using the tool TL. The tool holder 14 is formed with a flange portion 30 that seats on a first seating surface ES1 on the tip side of the spindle 12b, and a hollow, tapered shank portion 32 that extends along the longitudinal direction of the spindle 12b from the flange portion 30 toward the rear end of the spindle 12b so as to gradually reduce in diameter. Furthermore, an engagement portion 32a is formed at the rear end of the shank portion 32, which extends along the inner periphery of the shank portion 32 and protrudes radially inward of the spindle 12b.

[0014] The tool clamping device 16 includes a rod-shaped draw bar 22 disposed at the center of the spindle 12b so as to be movable within the spindle 12b along the longitudinal direction. The draw bar 22 has a recessed portion 26 formed at its tip end, i.e., the side where the tool TL and tool holder 14 are attached, so that the outer diameter is smaller than that of the remaining portion of the draw bar 22. Furthermore, a plurality of collets 28 are arranged cylindrically on the outer periphery of the recessed portion 26 so that the tip end can expand and contract in the radial direction. The draw bar 22 and the collets 28 are configured to be independently movable within the spindle 12b. Furthermore, the longitudinal tip end of the collet 28 is formed so that the outer diameter is larger than that of the remaining portion.

[0015] When the tool holder 14 is attached to the spindle 12b by a tool changer (not shown), the draw bar 22 is first moved toward the tip end by the unclamping piston 40, which will be described later. The tip end of the collet 28 is then retracted into the recess 26 by a biasing means (not shown), and its outer diameter becomes smaller than the inner diameter of the engaging portion 32a. The tool holder 14 is inserted into the tapered hole 12C of the spindle 12b until the rear end surface of the flange portion 30 of the tool holder 14 abuts against the first seating surface ES1 at the tip end of the spindle 12b. When the unclamping piston 40 then moves rearward, the draw bar 22 moves rearward due to the biasing force of the disc spring 34, which will be described later. As a result, the drawbar tip portion 24, which has a large outer diameter, presses the tip side of the collet 28 from the inside radially outward, expanding the diameter, and engages with the engaging portion 32a, pulling the tool holder 14 rearward. At the same time, the shank portion 32 expands in diameter and abuts against the second seating surface ES2, which is the inner surface of the tapered bore 12c of the spindle 12b. This restrains, or clamps, the tool holder 14 to the spindle 12b on two surfaces, the axial direction and the radial direction. Here, a two-face contact type tool holder, typified by a so-called HSK shank, will be described as an example, but the present invention is not limited to this, and a single-face contact type tool holder, typified by a so-called BT shank, may also be used. In this case, there is no first seating surface ES1 between the flange of the tool holder and the front end face of the spindle, and only a second seating surface ES2 between the shank of the tool holder and the tapered hole of the spindle. Therefore, it goes without saying that the spindle tip side of the tip-side flow passage 50b is blocked and air is discharged only from the branch flow passage 54.

[0016] Furthermore, a disc spring 34 is disposed on the longitudinal rear end side of the spindle 12b, and a lock nut 36 disposed on the rear end side of the disc spring 34 restricts movement of the draw bar 22 toward the rear end side of the lock nut 36. The disc spring 34 is configured to bias the draw bar 22 from the front end side toward the rear end side, i.e., in the direction of retracting the draw bar 22 into the spindle 12b. This allows the shank portion 32 to retract the tool holder 14, which is engaged with the collet 28, toward the spindle 12b, and the tool holder 14 can be stably clamped to the spindle 12b.

[0017] An unclamping cylinder 38 for releasing the clamping of the tool holder 14 is disposed on the rear end side of the spindle unit 12. An unclamping piston 40 configured to be hydraulically operable is disposed inside the unclamping cylinder 38. The unclamping piston 40 is configured to be movable along the longitudinal direction of the spindle 12b and the draw bar 22, and is configured to come into contact with and press the rear end of the draw bar 22 when it moves toward the front end side of the spindle 12b. A piston body 40a of the unclamping piston 40 divides the interior of the unclamping cylinder 38 into a front end side and a rear end side, forming a front chamber 44 and a rear chamber 42.

[0018] The front chamber 44 and the rear chamber 42 are configured to be connected to a hydraulic pressure source 64 or an oil tank 66 via a switchable first solenoid valve 60. The first solenoid valve 60 is configured to be switchable between three modes. Among these, in a forward mode 60a, oil in the front chamber 44 is allowed to flow out to the oil tank 66, and hydraulic pressure can be applied to the rear chamber 42. In this manner, by reducing the hydraulic pressure in the front chamber 44 and increasing the hydraulic pressure in the rear chamber 42, the piston body 40a can be moved toward the draw bar 22, and the draw bar 22 can be pressed toward the tip side. Furthermore, in a reverse mode 60c, oil in the rear chamber 42 is allowed to flow out to the oil tank 66, and hydraulic pressure can be applied to the front chamber 44. In this manner, by reducing the hydraulic pressure in the rear chamber 42 and increasing the hydraulic pressure in the front chamber 44, the piston body 40a can be moved rearward and separated from the draw bar 22. Furthermore, in a neutral mode 60b, hydraulic pressure can be prevented from being applied to the unclamping piston 40.

[0019] In the forward mode 60a, when the piston body 40a is moved toward the draw bar 22 and the draw bar 22 is pressed toward the tip side, the draw bar tip portion 24 that had been pressed into the collet 28 moves toward the tip side of the spindle 12b. In response to this, the tip side of the collet 28 moves into the recessed portion 26 and, since it is no longer pressed by the draw bar tip portion 24, its diameter is reduced by the biasing means. This releases the engagement between the collet 28 and the engaging portion 32a of the shank portion 32, and the tool holder 14 is released from the lock on the spindle 12b, i.e., the tool holder 14 is unclamped.

[0020] A proportional electromagnetic control valve 62 is connected between the hydraulic source 64 and the unclamping piston 40. The proportional electromagnetic control valve 62 is configured so that the opening of a relief valve can be changed according to the current applied to a solenoid, thereby adjusting the hydraulic pressure applied to the unclamping piston 40. The hydraulic pressure can be switched between two levels: high pressure (e.g., 7 MPa) and low pressure (e.g., 2 MPa). Here, the high hydraulic pressure (7 MPa in this embodiment) applied to the rear chamber 42 of the unclamping piston 40 corresponds to the unclamping force for unclamping the tool holder 14. The predetermined clamping force required to completely attach the tool holder 14 to the spindle 12b corresponds to this unclamping force. Note that a dual-pressure valve that switches between high pressure and low pressure may be used instead of the proportional electromagnetic control valve 62.

[0021] The low hydraulic pressure (2 MPa in this embodiment) applied to the rear chamber 42 of the unclamping piston 40 is set to a pressure smaller than the unclamping force, which is not sufficient to completely unclamp the tool holder 14. Therefore, when the unclamping piston 40 presses the draw bar 22 with this low pressure, a state occurs in which the tool holder 14 is loosely clamped to the spindle 12b. This state is hereinafter referred to as the intermediate clamping state. Furthermore, a clamping force smaller than the predetermined clamping force that causes this intermediate clamping state is referred to as the seating confirmation clamping force. Furthermore, in the neutral mode 60b, no hydraulic pressure is applied to the unclamping piston 40, so the unclamping piston 40 remains stationary without pressing the draw bar 22.

[0022] Although the hydraulic pressure can be switched between two levels in the following description, the present invention is not limited to this, and the hydraulic pressure may be switched between multiple levels in order to check the seating confirmation in more detail depending on the intended use of the machine tool. Also, here, the high pressure and low pressure of the hydraulic pressure corresponding to the default clamping force and seating confirmation clamping force are set to 7 MPa and 2 MPa, respectively, but these default clamping forces and seating confirmation clamping forces can be set as appropriate depending on the dimensions and intended use of the machine tool.

[0023] A tubular air flow path 48 extending along the longitudinal direction of the main shaft 12b is formed inside the unclamping piston 40. The air flow path 48 is connected to an air supply source 58, and air supplied from the air supply source 58 can flow inside the air flow path 48. An air-type seating sensor 46 is disposed (connected) between the air flow path 48 and the air supply source 58, and can detect the pressure or flow rate of the air flowing in from the air supply source 58.

[0024] A spindle-side passage 50 is formed inside the spindle 12b. The passage 50 is connected to the air passage 48 when the unclamping piston 40 contacts (presses) the draw bar 22 to allow air to flow from the rear end of the draw bar 22 to the first seating surface ES1 of the spindle 12b. The spindle-side passage 50 has a tubular rear-end-side passage 50a extending longitudinally from the rear end of the draw bar 22 with which the unclamping piston 40 contacts (presses) the draw bar 22, and a tubular front-end-side passage 50b formed radially outward of the draw bar 22 to connect with the rear-end-side passage 50a and extend to the first seating surface ES1. Furthermore, an adjustment portion 52 having a length along the longitudinal direction of the draw bar 22 is formed in the spindle-side passage 50 at a portion on the draw bar 22 side where the rear-end-side passage 50a and the front-end-side passage 50b are connected. Therefore, even if the positional relationship between rear end side passage 50a and front end side passage 50b changes as draw bar 22 moves within spindle 12b for clamping or unclamping, the connection between them is maintained, allowing air to flow from rear end side passage 50a to front end side passage 50b. Also, spindle side passage 50 is formed with a branch passage 54 that branches off from front end side passage 50b and allows air to flow to second seating surface ES2.

[0025] The air seating sensor 46 and the air flow path 48 are connected to an air supply source 58 via a switchable second solenoid valve 56. The second solenoid valve 56 is configured to be switchable between two modes. In the air discharge mode 56a, air discharged (sent) from the air supply source 58 can be made to flow to the first seating surface ES1 and the second seating surface ES2 via the air flow path 48 and the spindle-side flow path 50. This allows chips and dust around the first seating surface ES1 and the second seating surface ES2 to be blown away and the first seating surface ES1 and the second seating surface ES2 to be cleaned before the tool holder 14 is attached. Furthermore, when cleaning or checking the seating state (described later) is not being performed, the second solenoid valve 56 is switched to an air suction mode 56b, and the air flow path 48 is opened to atmospheric pressure via an exhaust pipe 56c.

[0026] The air seating sensor 46 and air supply source 58 provided in the machine tool 10 also function as a seating detector for the spindle unit 12. Specifically, when the tool holder 14 is fully attached to the spindle 12b, the flange portion 30 comes into close contact with the first seating surface ES1 and the second seating surface ES2. As a result, the tip of the tip-side flow passage 50b is blocked by the flange portion 30, and the branch flow passage 54 is blocked by the shank portion 32, i.e., the two passages are sealed. In this state, if the second solenoid valve 56 is set to the air discharge mode 56a and air is allowed to flow from the air supply source 58 to the first seating surface ES1 and the second seating surface ES2, once the air has sufficiently spread throughout the spindle-side flow passage 50, air will no longer flow through the spindle-side flow passage 50, and the air seating sensor 46 will detect a high pressure or a low flow rate.

[0027] Furthermore, when the tool holder 14 is not attached to the spindle 12b (clamped state without a tool) or when the tool holder 14 is attached to the spindle 12b in an intermediate clamped state with a foreign object sandwiched therein, the tip-side flow path 50b and / or the branch flow path 54 are not blocked, and the air that has flowed in flows out from the tip of the tip-side flow path 50b. As a result, air continues to flow through the spindle-side flow path 50, and the air seating sensor 46 detects a low pressure or a high flow rate. This allows the spindle unit 12 to determine, from the pressure or flow rate detected by the air seating sensor 46, whether the tool holder 14 is in a clamped state in which it is fully attached to the spindle 12b, an intermediate clamped state in which no foreign object is sandwiched, a clamped state in which no tool is attached to the spindle 12b, or an intermediate clamped state in which a foreign object is sandwiched.

[0028] On the other hand, chips generated during machining may remain around the first seating surface ES1. When attempting to mount the tool holder 14 on the spindle 12b in this state, the chips may become trapped (squeezed) between the flange portion 30 and the first seating surface ES1 or between the shank portion 32 and the second seating surface ES2. If the foreign object trapped between the seating surfaces ES1 and ES2 is small, the default clamping force eliminates any gap due to the elastic deformation of the foreign object, the detachable objects around the foreign object, and the seating surface components. However, the seating confirmation clamping force reduces the elastic deformation, creating a gap at the tip of the tip-side flow path 50b or the branch flow path 54. Therefore, the air seating sensor 46 may detect a low pressure or a high flow rate even in the intermediate clamping state. Note that multiple air seating sensors 46 are circumferentially arranged around the tip-side flow path 50b and the branch flow path 54 to prevent erroneous detection. As will be described later, the spindle unit 12 is configured to set a first threshold value for the pressure or flow rate that may occur in the air seating sensor 46 when chips are trapped in this manner, and to determine that chips are trapped between the flange portion 30 and the seating surface ES1 and / or between the shank portion 32 and the second seating surface ES2 when the pressure detected by the air seating sensor 46 is below the first threshold value or when the detected flow rate is above the first threshold value in the intermediate clamp state. Furthermore, the spindle unit 12 determines that the tool holder 14 is properly seated when the pressure detected by the air seating sensor 46 exceeds the first threshold value or the detected flow rate is below the first threshold value.

[0029] Furthermore, the air seating sensor 46 and the air supply source 58 can distinguish and determine whether small chips are trapped in the tool holder 14 in the intermediate clamping state or whether the tool holder 14 is not attached to the spindle 12b. Specifically, the spindle unit 12 sets the pressure or flow rate that the air seating sensor 46 can detect when no tool holder 14 is attached to the spindle 12b as a second threshold value, and can determine that nothing is attached to the spindle 12b (no-tool clamping state) when the pressure detected by the air seating sensor 46 is below the second threshold value or when the detected flow rate is above the second threshold value. In this way, the spindle unit 12 can detect the presence or absence of chips that would prevent the tool holder 14 from being attached to the spindle 12b and further determine the presence or absence of the tool holder 14 and whether it is properly seated by measuring the air pressure or flow rate.

[0030] The first threshold value may be determined based on the pressure or flow rate detected by the air-type seating sensor 46 when air is allowed to flow in a state where, for example, a shim (thickness gauge) or the like having a predetermined thickness (10 μm, 20 μm, 30 μm, etc.) is placed as a simulated chip on the first seating surface ES1 and / or the second seating surface ES2 of the spindle 12b and sandwiched between the flange portion 30 of the tool holder 14 and the first seating surface ES1. Alternatively, the pressure or flow rate may be detected (measured) for multiple types of tool holders 14 and shims of multiple thicknesses, and the first threshold value may be set for each tool or object to be machined based on the results of these measurements.

[0031] 2 shows a block diagram of a seating confirmation device for a machine tool. The machine tool 10 is equipped with a machine control device 70 for controlling the machine tool 10. The machine control device 70 is configured to include a seating confirmation control unit 72 as a control unit for controlling seating confirmation of the spindle device 12. The machine control device 70 also includes a spindle control unit 78 that is electrically connected to the spindle device 12, unclamping piston 40, air-type seating sensor 46, first solenoid valve 60, second solenoid valve 56, and proportional solenoid control valve 62 and controls these in conjunction with the seating confirmation control unit 72. The machine control device 70 also includes a tool change control unit 80 for controlling the attachment, i.e., mounting and removal, of the tool holder 14.

[0032] The machine control device 70 is also configured for general purposes so that it can simultaneously or by switching the connection of devices other than the spindle device 12 incorporating the tool clamping device 16. For example, it is configured to be able to control a table device 100 incorporating a pallet clamping device 106 (see FIGS. 4 and 5) and a workpiece mounting table 150 having a workpiece clamper 156 (see FIG. 6). For this reason, the machine control device 70 is equipped with a table control unit 82 for controlling the table device 100 and a workpiece exchange control unit 84 for controlling the workpiece mounting table 150. Furthermore, it is equipped with an other control unit 86 for controlling devices other than those mentioned above.

[0033] The seating confirmation control unit 72 has a determination unit 74 for determining the seating state of the tool holder 14, and a memory unit 76 for storing (recording) first and second threshold values, which are threshold values ​​of the air seating sensor 46 for determining the seating state and are set according to the specifications of the spindle unit 12. The determination unit 74 is electrically connected to the spindle control unit 78, and is configured to determine the seating state by comparing the pressure or flow rate detected by the air seating sensor 46 with the first and second threshold values. Furthermore, if the comparison of the pressure or flow rate with the first threshold value determines that the seating state is poor due to, for example, trapped chips, the determination unit 74 sends a command to the spindle control unit 78 to clean the first seating surface ES1 and the second seating surface ES2, as will be described later. The spindle control unit 78, which has received the command, operates the unclamping piston 40 to connect it to the draw bar 22, unclamps the tool holder 14, and operates the air supply source 58 to send air into the air flow path 48 and the spindle-side flow path 50, thereby controlling the cleaning of the first seating surface ES1 and the second seating surface ES2.

[0034] Furthermore, the determination unit 74 is also electrically connected to the tool change control unit 80. Therefore, if the determination unit 74 determines that the tool holder 14 is properly seated on the spindle 12b, it transmits a signal notifying the tool change control unit 80 of this fact. Upon receiving the signal, the tool change control unit 80 terminates the tool changing operation. On the other hand, if the determination unit 74 determines that the tool holder 14 is not properly seated on the spindle 12b, it transmits a signal notifying the tool change control unit 80 of this fact. Upon receiving the signal, the tool change control unit 80 re-attaches the tool holder 14 or a new, replaced tool holder 14 to the spindle 12b, and operates the machine tool 10 to clean the seating surface by discharging air from the air supply source.

[0035] Furthermore, the machine control device 70 is equipped with an operation panel 90 that allows the user of the machine tool 10 to operate the machine control device 70, and a numerical control unit 88 that transmits commands to check the seating state input by the user from the operation panel 90 to the determination unit. The numerical control unit 88 not only commands the timing of this seating state check, but also issues all operational commands for the machine tool 10 using numerical information. Furthermore, the operation panel 90 is equipped with a display unit 92 that visualizes the seating state determination results for the user. This allows the user to easily understand the seating state of the tool holder 14.

[0036] The effects of the spindle unit 12 of the machine tool 10 according to this embodiment will be described below through the description of the flowchart for seating confirmation shown in FIG.

[0037] When the replacement of the tool TL and the tool holder 14 is started (step S10), the process proceeds to step S20, where the determination unit 74 of the seating confirmation control unit 72 operates the machine tool 10 via the spindle control unit 78 to start attaching (inserting) the tool holder 14 to the spindle 12b. Subsequently, the process proceeds to step S30, where the spindle control unit 78 operates the air supply source 58 to send air into the air flow path 48 and the spindle-side flow path 50, thereby cleaning the first seating surface ES1 and the second seating surface ES2. When the cleaning is completed, the process proceeds to step S40, where the determination unit 74 starts the work of determining the seating state.

[0038] When the work of determining the seating state starts, the process proceeds to step S50, where the determination unit 74 operates the machine tool 10 to push the tool holder 14 into the spindle 12b with a predetermined clamping force, i.e., attempts to fully attach the tool holder 14. When this pushing is completed, the process proceeds to step S60, where the determination unit 74 operates the unclamping piston 40 via the spindle control unit 78 to press the draw bar 22 to a seating confirmation clamping force. This results in an intermediate clamping state.

[0039] When the draw bar 22 is in the intermediate clamp state, the process proceeds to step S70, where the determination unit 74 activates the air supply source 58 via the spindle control unit 78 to send air to the first seating surface ES1 and the second seating surface ES2, and detects (measures) the pressure or flow rate with the air seating sensor 46. When the pressure or flow rate is detected by the air seating sensor 46, the process proceeds to step S80, where the determination unit 74 compares the pressure or flow rate with a first threshold value and a second threshold value to determine the seating state, and the process proceeds to step S90, where the determination result of the seating state is displayed on the display unit 92.

[0040] If it is determined in step S80 that the seating condition is poor, that is, that chips are trapped, the process proceeds to step S100, where the determination unit 74 actuates the unclamping piston 40 via the spindle control unit 78 to press the draw bar 22 with high pressure. This presses the draw bar 22 to enter the unclamped state. Once the tool holder 14 enters the unclamped state and is unclamped, the process proceeds to step S110, where the determination unit 74 actuates the air supply source 58 via the spindle control unit 78 to send air to the first seating surface ES1 and the second seating surface ES2, thereby cleaning them. After cleaning, the process proceeds to step S30, where the seating condition is determined again (steps S30 to S80). If the seating condition remains poor even after cleaning has been performed a predetermined number of times, the process proceeds from step S110 to step S120, where the machine tool 10 issues an alarm indicating that the seating condition is poor.

[0041] On the other hand, if it is determined in step S80 that the seating condition is good, i.e., that no chips are trapped, the process proceeds to step S130, where the determination unit 74 operates the machine tool 10 again to retract the unclamping piston 40 and attach the tool holder 14 to the spindle 12b with a predetermined clamping force. Once the attachment of the tool holder 14 is complete, the process proceeds to step S140, where the determination unit 74 activates the air supply source 58 via the spindle control unit 78 to stop the air supply. Furthermore, the process proceeds to step S150, where the determination unit 74 performs the replacement operation of the tool TL and the tool holder 14 by the machine tool 10 via the tool replacement control unit 80. Once the replacement operation of the tool TL and the tool holder 14 is completed, the process proceeds to step S160, where the machine tool 10 starts machining.

[0042] According to the spindle unit 12 of the machine tool 10 according to this embodiment, the spindle unit 12 is provided with a tool clamping device 16 that can switch between at least two clamping forces: a specified clamping force for mounting the tool holder 14 when the machine tool 10 is in operation, and a predetermined seating confirmation clamping force that is smaller than the specified clamping force. The spindle unit 12 also has an air-type seating sensor 46 and an air supply source 58 as seating detectors for detecting the seating state between the first seating surface ES1 and the second seating surface ES2 and the tool holder 14. The spindle unit 12 also has a seating confirmation control unit 72 that sets the clamping force of the tool clamping device 16 to a seating confirmation clamping force in order to detect the seating state using the air-type seating sensor 46.

[0043] In machine tool 10, small chips generated during machining may remain around first seating surface ES1 and second seating surface ES2, and when attempting to attach tool holder 14 to spindle 12b in this state, the small chips may become caught (sandwiched) between flange portion 30 and seating surface ES1 and / or between shank portion 32 and second seating surface ES2. When the trapped chips are compressed with a predetermined clamping force, the tip of tip-side flow passage 50b and / or branch flow passage 54 may become blocked, as if the chips were not trapped at all. This may cause air-type seating sensor 46 to detect a high pressure or a low flow rate, even though tool holder 14 is not fully attached to spindle 12b.

[0044] Therefore, in the spindle unit 12 of the machine tool 10 according to this embodiment, the pressure or flow rate that may occur in the air seating sensor 46 when a chip is trapped is set as the first threshold value. The seating confirmation clamping force causes small elastic deformation, which may cause a gap at the tip of the tip-side flow path 50b or the branch flow path 54. Therefore, in the intermediate clamping state, if the pressure detected by the air seating sensor 46 is below the first threshold value or if the detected flow rate exceeds the first threshold value, it can be determined that a small chip is trapped between the flange portion 30 and the seating surface ES1 and / or between the shank portion 32 and the second seating surface ES2. Furthermore, if the pressure detected by the air seating sensor 46 exceeds the first threshold value or if the detected flow rate is below the first threshold value, the spindle unit 12 can determine that the tool holder 14 is properly seated.

[0045] Furthermore, with the spindle unit 12 of the machine tool 10 according to this embodiment, when it is determined that the seating of the tool holder 14 is poor, it can distinguish whether this determination result indicates that the tool holder 14 is not properly attached to the spindle 12b due to chips being trapped in the intermediate clamping state, or whether it indicates a so-called tool-less clamping state in which the draw bar 22 has retracted to the clamping position without the tool holder 14 being attached to the spindle 12b. Specifically, the spindle unit 12 sets the pressure or flow rate that can be detected by the air seating sensor 46 when no tool holder 14 is attached to the spindle 12b as the second threshold value, and when it is determined that the seating of the tool holder 14 is poor using the first threshold value, it can determine that nothing is attached to the spindle 12b when the pressure detected by the air seating sensor 46 is below the second threshold value or the detected flow rate is above the second threshold value. Although this explanation is not detailed in the flowchart of FIG. 3, in the seating determination in step S80, the detection value of the air seating sensor 46 is compared with a second threshold value to determine the tool-less clamped state, and the result is displayed on the display unit 92 in step S90. In the tool-less clamped state, steps S100, S110, and S120 for cleaning the first seating surface ES1 and the second seating surface ES2 are not performed. In this way, by measuring the air pressure or flow rate in the intermediate clamped state with the air seating sensor 46, the spindle unit 12 can detect the presence or absence of chips that would hinder the attachment of the tool holder 14 to the spindle 12b and determine the presence or absence of the tool holder 14 and whether it is properly seated. Experiments have shown that quicker detection can be achieved by temporarily retracting the draw bar 22 with a predetermined clamping force in step S50 and then establishing the intermediate clamped state (step S60) and detecting with the air seating sensor 46. Although the flow of this embodiment includes step S50, the flow is not limited to this, and may not include step S50.

[0046] As explained above, according to the spindle device 12 of the machine tool 10 and the seating confirmation method of this embodiment, it is possible to automatically, precisely, and simply confirm that a removable object such as the tool holder 14 is seated on the seating surface ES1 without getting any foreign matter caught in it.

[0047] (Variation) While the draw bar 22 has been described here as being moved by being pressed by the unclamping piston 40 and hydraulic source 64, the present invention is not limited to this and may be moved by other means, such as a servo motor and a ball nut. The servo motor rotates the ball nut to drive the screw shaft corresponding to the unclamping piston in the axial direction. This allows the draw bar to move back and forth, creating a clamped state and an unclamped state. Furthermore, adjusting the current value of the servo motor allows an intermediate clamped state to be created. While the first embodiment uses a common air cleaning circuit and seating confirmation air circuit, the present invention is not limited to this and separate air circuits may be used.

[0048] In addition, although the air-type seating sensor 46 is used to detect whether or not chips are trapped here, the present invention is not limited to this. The presence or absence of trapped chips may be determined by measuring the distance (gap) between the flange portion of the tool holder and the seating surface in the intermediate clamping state, for example, using a position sensor or the like.

[0049] (Second embodiment) The seating confirmation device according to the second embodiment will be described below. Elements similar to or corresponding to those in the first embodiment will be given the same reference numerals, and duplicated descriptions will be omitted.

[0050] FIG. 4 shows a schematic side view of a machine tool 10 equipped with a table device 100 as a seating confirmation device. The table device 100 is configured to clamp a work pallet 102 as a detachable object to which a workpiece W to be machined is attached, and is equipped with a pallet clamping device 106 as an attachment / detachment mechanism fixed to the upper surface of the table 104. The pallet clamping devices 106 are arranged at the four corners of the table 104, which is rectangular in plan view, and locating cones 108 are respectively arranged above the pallet clamping devices 106. Locating bushes 110 are respectively arranged at the four corners of the lower side of the work pallet 102 in positions corresponding to the locating cones 108. The work pallet 102 is positioned and fixed on the table 104 when the locating bushes 110 engage with the locating cones 108 and are clamped by the pallet clamping device 106.

[0051] 5, a cylindrical pull stud 112 is fixed to the work pallet 102, passing through the center of the locating bush 110 and extending along the thickness direction (vertical direction) of the work pallet 102. The pull stud 112 has a stud shank 112a extending along the vertical direction, and a stud head 112b that is generally truncated cone-shaped and formed at the lower end of the stud shank 112a so that the diameter of its cross section along the radial direction is larger than that of the stud shank 112a. The pull stud 112 further has a stud engaging portion 112c formed at the connection between the stud shank 112a and the stud head 112b, and whose cross-sectional shape in elevation view is generally the same as the outer circumferential shape of the ball 124 so that the surface of the ball 124 (described later) can abut against it.

[0052] The pallet clamping device 106 includes a cylinder 114 formed in a cylindrical shape that extends vertically, and a collet 116 disposed in the center of the cylinder 114 and having a cylindrical collet shank 116a that also extends vertically. The collet shank 116a extends above the cylinder 114, with a locating cone 108 disposed to cover its upper side. The locating cone 108 and collet 116 are open at the top, i.e., are through-molded, so that the pull stud 112 can be inserted from above, and are disposed on the cylinder 114 so as to be coaxial with the pull stud 112. The inner diameter of the cylindrical collet shank 116a is slightly larger than the outer diameter of the stud head 112b to allow insertion of the pull stud 112. A piston 116b, which is disk-shaped in plan view, is formed below the collet shank 116a.

[0053] The collet shank 116a also has ball holes 116c formed at its upper end along the radial direction of the collet shank 116a, which are circular in side view. The ball holes 116c are formed at multiple locations along the circumferential direction of the collet shank 116a, and each has an inner diameter slightly larger than the outer diameter of the ball 124 to allow the ball 124 to fit therein. To attach the work pallet 102 to the pallet clamping device 106, the piston 116b of the collet 116 is first raised by hydraulic pressure from the hydraulic source 64 (described later) until the height of the ball 124 is aligned with the height of the recess 108a formed on the inner diameter side of the locating cone 108. Next, when the pull stud 112 is inserted into the collet shank 116a, the stud head 112b abuts against the ball 124, causing the ball 124 to retract into the recess 108a. When the stud head 112b passes the ball 124 and moves downward, the tapered hole 110a of the locating bushing 110 comes into contact with the locating cone 108 and stops. For this reason, the seating surface ES3 in this embodiment is the tapered outer diameter surface of the locating cone 108. Note that on the inner peripheral side of the collet shank 116a, there is disposed a shaft member 118 that extends in the vertical direction and has a lid portion 118a at its upper end. On the lower side of the lid portion 118a, there is disposed a lid spring 120 that is arranged along the shaft member 118 and that biases the lid portion 118a upward relative to the collet 116.

[0054] When work pallet 102 is placed on table 100, shaft member 118 is pressed down by pull stud 112 as shown in Figure 5. On the other hand, when work pallet 102 is not on table 100, lid portion 118a is raised to the upper end surface position of collet 116 by the biasing force of lid spring 120, preventing foreign matter such as chips from entering inside collet 116.

[0055] When the first solenoid valve 60 is switched to the clamping mode 60e, oil from the hydraulic power source 64 is supplied to the upper chamber 130, the collet 116 is lowered, and the ball 124 moves radially inward from the recessed portion 108a. The ball 124 engages with the stud head 112b of the pull stud 112, pressing the tapered hole portion 110a of the locating bushing 110 against the seating surface ES3. This action occurs simultaneously between the four locating cones 108 and the locating bushings 110, clamping the work pallet 102 to the table device 100. At this time, the oil in the lower chamber 132 is recovered in the oil tank 66. When the first solenoid valve 60 is switched to the unclamping mode 60d, oil is supplied to the lower chamber 132, and the oil in the upper chamber 130 is recovered in the oil tank 66. Therefore, the collet 116 is raised, and the ball 124 is retracted into the recessed portion 108a, as described above. This unclamping operation is performed simultaneously at all four locations (four corners), and a pallet changing device (not shown) lifts the work pallet 102 to perform the pallet change. During the pallet change operation, air is supplied from the air supply source 58 to the chamber 122 below the collet 116, passes through a gap inside the collet 116, and is discharged from the top of the collet 116 into the inside of the locating bush 110, cleaning the inner surface of the tapered hole portion 110a and the outer peripheral surface of the locating cone 108. At this time, the second solenoid valve 56 is set to air discharge mode 56a, and when the pallet change operation is completed, it is switched to air suction mode 56b, the circuit is opened to atmospheric pressure, and cleaning is completed.

[0056] The pallet clamping device 106 can create an intermediate clamped state by using a proportional electromagnetic control valve 62 installed midway through the hydraulic circuit to reduce the hydraulic pressure below the hydraulic pressure during clamping. The pallet clamping device 106 also has an air-type seating sensor 46 in the cleaning air circuit, which can detect the air pressure or flow rate in the intermediate clamped state, just like the first embodiment.

[0057] According to the table device 100 of the machine tool 10 of this embodiment, the pressure or flow rate that can be generated in the air seating sensor 46 when chips are caught on the seating surface ES3 is set as a first threshold value, and when the pressure detected by the air seating sensor 46 in the intermediate clamp state is below the first threshold value or when the detected flow rate is above the first threshold value, it can be determined that chips are caught between the locating bush 110 and the seating surface ES3. Furthermore, when the pressure detected by the air seating sensor 46 exceeds the first threshold value or the detected flow rate is below the first threshold value, the table device 100 can determine that the workpiece pallet 102 is properly seated.

[0058] As explained above, the table device 100 and seating confirmation method of the machine tool 10 according to this embodiment can automatically, precisely, and simply confirm that a removable object such as a work pallet 102 is seated on the seating surface ES3 without getting any foreign matter caught in it.

[0059] (Third embodiment) The seating confirmation device according to the third embodiment will be described below. Elements similar to or corresponding to those in the first and second embodiments will be given the same reference numerals, and redundant description will be omitted.

[0060] 6 is a schematic side view of machine tool 10 equipped with a workpiece mounting table 150 serving as a seating confirmation device. Workpiece mounting table 150 includes a tombstone 152 on which a workpiece W, which is a removable object to be machined, is placed (placed), and a plurality of workpiece clampers 156, which are fixed to the upper surface of tombstone 152 and serve as a mounting / removal mechanism configured to clamp workpiece W. Workpiece mounting table 150 also includes a hydraulic cylinder 154 that is connected to hydraulic power source 64 and oil tank 66 via proportional electromagnetic control valve 62 and drives workpiece clamper 156. Workpiece clamper 156 includes a clamp shaft 156a that is configured to be movable up and down and rotatable horizontally by hydraulic cylinder 154, and a clamp plate 156b that is connected to the upper end of clamp shaft 156a and clamps workpiece W. The work clamper 156 is configured to clamp the workpiece W by rotating the clamp shaft 156a and pivoting the clamp plate 156b above the workpiece W, and to unclamp the workpiece W by moving the clamp plate 156b away from the upper side of the workpiece W. An intermediate clamped state can be created by adjusting the pressure that presses the clamp shaft 156a downward by the hydraulic cylinder 154 to a predetermined pressure that is lower than the pressure during clamping. Furthermore, by lowering the clamp shaft 156a from the intermediate clamped state and pressing the clamp plate 156b against the workpiece W, a clamped state can be created in which the workpiece is clamped between the tombstone 152 and the clamp plate 156b.

[0061] The workpiece mounting table 150 is equipped with an air flow path 158 that extends downward along the thickness direction of the tombstone 152 from a seating surface ES4 where the workpiece W abuts against the upper surface of the tombstone 152, and the air flow path 158 is connected to an air supply source 58 via a switchable second solenoid valve 56. The second solenoid valve 56 is configured to be switchable between two modes, and in the air discharge mode 56a, air discharged (sent) from the air supply source 58 passes through the air flow path 158 and flows to the seating surface ES4. This makes it possible to check whether chips are trapped on the seating surface ES4 in the intermediate clamping state, as in the first embodiment.

[0062] With the workpiece mounting table 150 of the machine tool 10 according to this embodiment, the pressure or flow rate that can be generated in the air seating sensor 46 when chips are caught between the workpiece W and the upper surface of the tombstone 152 is set as a first threshold value, and when the pressure detected by the air seating sensor 46 in the intermediate clamp state is below the first threshold value or when the detected flow rate is above the first threshold value, it can be determined that chips are caught between the workpiece W and the upper surface of the tombstone 152. Furthermore, the workpiece mounting table 150 can determine that the workpiece W is properly seated when the pressure detected by the air seating sensor 46 exceeds the first threshold value or the detected flow rate is below the first threshold value.

[0063] As explained above, the workpiece mounting table 150 and seating confirmation method of the machine tool 10 according to this embodiment can automatically, precisely, and simply confirm that a removable object such as the workpiece W is seated on the seating surface ES4 without getting any foreign matter caught in it.

[0064] Although the embodiments of the seating confirmation device 12, 100, 150 and the seating confirmation method for the machine tool 10 have been described above, the present invention is not limited to the above-described embodiments. In addition to the above, it is believed that a person skilled in the art would understand that various modifications of the above-described embodiments are possible. [Explanation of symbols]

[0065] 10 Machine tools 12 Spindle device (seating confirmation device) 14 Tool holder (detachable) 16 Tool clamping device (detachable mechanism) 46 Air-type seating sensor (seat detector) 58 Air supply source (seating detector) 72 Seat confirmation control unit (control unit) 100 Table device (seating confirmation device) 102 Work pallet (detachable) 106 Pallet clamp device (detachable mechanism) 150 Workpiece mounting table (seating confirmation device) 156 Work clamper (detachable mechanism) ES1 First seating surface ES2 Second seating surface ES3 seating surface ES4 seating surface W work (detachable items)

Claims

1. A method for checking the seating of a machine tool, which checks whether an attachment or detachment object is in close contact with a seating surface of a mounting mechanism of a machine tool, comprising: attaching the detachable object with a predetermined seating confirmation clamping force that is smaller than a specified clamping force for the attachment / detachment mechanism to attach the detachable object when the machine tool is operating; detecting a seating state between the seating surface and the detachable object when the detachable object is attached by the seating confirmation clamp force; determining whether the detection result of the seating state is good or bad; A method for confirming seating of a machine tool, comprising:

2. 2. The method for confirming seating of a machine tool according to claim 1, wherein the combination of the attachment / detachment mechanism and the detachable object is any one of a tool clamping device and a tool holder built into a spindle device, a pallet clamping device and a pallet built into a table device, and a work clamper and a work placed on a work mounting table.

3. 2. The seating confirmation method for a machine tool according to claim 1, wherein, when the detachable object is attached with the seating confirmation clamp force, determining whether the detection result of the seating state is good or bad includes making a determination by comparing a detection value of an air-type seating sensor provided in the middle of an air flow path opening to the seating surface of the attachment / detachment mechanism with a preset first threshold value.

4. 4. A method for confirming seating of a machine tool according to claim 3, further comprising: comparing the detection value of the air seating sensor with the first threshold value set in advance; and, if it is determined that seating is poor, further comparing the detection value of the air seating sensor with the second threshold value set in advance to determine whether or not the detachable object is present.

5. A machine tool seating confirmation device that confirms whether an attachment or detachment object is in close contact with a seating surface of a machine tool attachment / detachment mechanism, an attachment / detachment mechanism that can switch between at least two clamping forces: a specified clamping force for the attachment / detachment mechanism to attach the detachable object when the machine tool is in operation, and a predetermined seating confirmation clamping force that is smaller than the specified clamping force; a seating detector for detecting a seating state between the seating surface and the detachable object; a control unit that sets the clamping force of the attachment / detachment mechanism to the seating confirmation clamping force in order to detect the seating state by the seating detector, and determines whether the detection result of the seating state is good or bad; A machine tool seating confirmation device comprising:

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