Tool center-of-gravity position measuring device and tool changing device

Abstract

This tool center-of-gravity position measuring device comprises: a tool holding member disposed so as to be able to hold a tool and be rotatable about a rotation axis; a tool weight measurement unit that measures the weight of the tool held by the tool holding member; a torque measurement unit that measures rotation torque of the tool holding member about the rotation axis, the rotation torque being generated by gravity acting on the tool holding member and the tool held by the tool holding member; a center-of-gravity position calculation unit that calculates a center-of-gravity position representing the position of the center of gravity of the tool as a distance from a predetermined reference position, on the basis of the weight of the tool measured by the tool weight measurement unit and the rotation torque measured by the torque measurement unit; and an output unit that outputs the center-of-gravity position calculated by the center-of-gravity position calculation unit.

Description

Tool center of gravity position measuring device and tool changer

[0001] The present disclosure relates to a tool center of gravity position measuring device and a tool changer.

[0002] In a machine tool, it may be desirable to adjust the speed at which the tool is moved according to the weight and center of gravity position of the tool. As an example, when holding a tool by a taper shank or the like, if the tool is swung so that the tip of the tool faces outward and the central axis of the tool is tilted, the tool may fall off due to the centrifugal force acting on the tool. Therefore, it is preferable to limit the swing speed according to the weight and center of gravity position of the tool so as to suppress the centrifugal force acting on the tool.

[0003] The tool may be composed of a combination of a holder and a cutting tool, and it is difficult for the user to calculate and input the center of gravity position of each tool. Therefore, a device for estimating the center of gravity position based on the shape data of the tool has also been proposed (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 8-118180

[0005] Even if the means for estimating the center of gravity position as in Patent Document 1 is adopted, the shape data of the tool is not always obtained, so the center of gravity position of the tool may not be estimated. Therefore, a technique that can directly measure the center of gravity position of the tool without acquiring information from the outside is desired.

[0006] A tool exchange measurement device according to an aspect of the present disclosure includes a tool holding member that can hold a tool and is disposed so as to be rotatable about a rotation axis, a tool weight measurement unit that measures the weight of the tool held by the tool holding member, a torque measurement unit that measures the rotational torque of the tool holding member about the rotation axis generated by the gravity acting on the tool holding member and the tool held by the tool holding member, a center of gravity position calculation unit that calculates a center of gravity position representing the position of the center of gravity of the tool as a distance from a predetermined reference position based on the weight of the tool measured by the tool weight measurement unit and the rotational torque measured by the torque measurement unit, and an output unit that outputs the center of gravity position calculated by the center of gravity position calculation unit.

[0007] This is a schematic diagram showing the configuration of a tool center of gravity position measuring device according to one embodiment of the present disclosure. This is a schematic diagram showing the configuration of a tool changing device equipped with the tool center of gravity position measuring device of Figure 1.

[0008] Embodiments of the present disclosure will be described below with reference to the drawings. Figure 1 is a schematic diagram showing the configuration of a tool center of gravity position measuring device 1 according to one embodiment of the present disclosure. The tool center of gravity position measuring device 1 is a device for measuring the position of the center of gravity G of a tool 100. The tool 100 may be composed of a cutting tool 110 such as a drill or mill and a holder 120 that holds the cutting tool 110. The holder 120 may have a shank portion 121 that fits onto the spindle (not shown) of a machine tool, a flange portion 122 that abuts against the end face of the spindle, and a holding portion 123 that holds the cutting tool 110.

[0009] The tool center of gravity position measuring device 1 comprises a measuring mechanism 10 and a calculation device 20. The measuring mechanism 10 comprises a pivot shaft 11, a tool holding member 12, a pivot member 13, a base support member 14, a first sensor 15, and a second sensor 16. The calculation device 20 comprises a tool weight measuring unit 21, a torque measuring unit 22, a center of gravity position calculation unit 23, an output unit 24, and a notification unit 25. Note that each component of the measuring mechanism 10 is a mechanical component that can be physically distinguished from one another, whereas each component of the calculation device 20 is a classification of the functions of the calculation device 20 and does not necessarily have to be clearly distinguishable from one another. The calculation device 20 may be implemented by one or more computer devices that have memory, a processor, an input / output interface, etc., and execute an appropriate program, or it may be configured integrally with a computer device that is installed for other purposes.

[0010] The pivot shaft 11 is positioned horizontally at least when measuring the center of gravity of the tool 100, and pivotally supports the tool holding member 12 so that it can rotate. A single pivot shaft 11 may be arranged to pass through the tool holding member 12, or a pair of pivot shafts 11 may be arranged on both sides of the tool holding member 12. The pivot shaft 11 may be integrated with the tool holding member 12 or the pivot member 13.

[0011] The tool holding member 12 is held so as to be rotatable around the pivot axis 11. The tool holding member 12 preferably has an opening formed at one end into which the tool 100 is inserted, and is configured to hold the tool 100 so that its axis is approximately horizontal when measuring the center of gravity of the tool 100. The tool holding member 12 preferably has been held so as to be rotatable by the pivot axis 11 near one end in the horizontal direction when measuring the center of gravity of the tool 100, and is configured so that the tool 100 is inserted into the other end face in the horizontal direction. The structure of the tool holding member 12 for holding the tool is such that the shank conforming to the standard of the tool 100 fits into it.

[0012] The pivot member 13 rotatably supports the tool holding member 12 via the pivot shaft 11. The pivot member 13 also holds the second sensor 16 together with the tool holding member 12. For this reason, the pivot member 13 can be formed to extend along the tool holding member 12 in the axial direction of the tool 100.

[0013] The base support member 14 holds the pivot member 13 via the first sensor 15, and consequently the pivot shaft 11, the tool holding member 12, the second sensor 16, and the tool 100 held by the tool holding member 12.

[0014] The first sensor 15 detects the force acting between the base support member 14 and the pivot member 13. In other words, the first sensor 15 detects the total weight of the pivot member 13, the pivot shaft 11 held by the pivot member 13, the tool holding member 12, the second sensor 16, and the tool 100 held by the tool holding member 12. The first sensor 15 can be made up of a well-known sensor such as a load cell.

[0015] The second sensor 16 detects a physical quantity that can be converted into the rotational torque of the tool holding member 12 relative to the pivot member 13, typically the force component of the torque. The second sensor 16 may be disposed on or near the pivot shaft 11, but it is preferable to dispose of it near the end of the tool holding member 12 opposite to the pivot shaft 11 in order to calculate the torque with high accuracy. The second sensor 16 can be made up of a well-known sensor such as a load cell.

[0016] The tool weight measurement unit 21 measures the weight Me of the tool 100 held by the tool holding member 12 using the first sensor 15. Specifically, the tool weight measurement unit 21 derives the weight of the tool 100 as the difference between the value detected by the first sensor 15 when the tool holding member 12 is holding the tool 100 and the value detected by the first sensor 15 when the tool holding member 12 is not holding the tool 100. The value detected by the first sensor 15 when the tool holding member 12 is not holding the tool 100 does not need to be acquired each time the weight of the tool 100 is measured, and may be a value stored during calibration or the like.

[0017] The torque measurement unit 22 uses the second sensor 16 to measure the rotational torque Tw of the tool holding member 12 around the pivot axis 11, which is generated by gravity acting on the tool holding member 12 and the tool 100 held by the tool holding member 12. Specifically, the torque measurement unit 22 calculates the rotational torque Tw of the tool holding member 12, including the tool 100, based on the positional relationship between the pivot axis 11 and the second sensor 16 and the detected value (force) of the second sensor 16. In the illustrated example, if the horizontal distance between the pivot axis 11 and the second sensor 16 is Ls and the detected value of the second sensor 16 is Fw, then the rotational torque Tw of the tool holding member 12, including the tool 100, is calculated as Tw = Ls・Fw.

[0018] The center of gravity position calculation unit 23 calculates the center of gravity position of the tool 100, expressed as a distance D from a predetermined reference position Po, based on the weight Me of the tool 100 measured by the tool weight measurement unit 21 and the rotational torque Tw measured by the torque measurement unit 22. The reference position Po is preferably the center of the contact surface between the flange portion 122 of the tool 100 and the tool holding member 12, so that the center of gravity G can be identified when the tool 100 is held by another device. More specifically, the center of gravity position calculation unit 23 may be configured to calculate the distance Le of the center of gravity G of the tool 100 from the rotation axis 11 by dividing the difference between the rotational torque Tw1 of the tool holding member 12 when the tool holding member 12 is holding the tool 100 and the rotational torque Tw2 of the tool holding member 12 when the tool holding member 12 is not holding the tool 100 by the force acting due to the weight of the tool 100. In other words, the distance Le can be calculated as Le = {(Tw1 - Tw0) / Me・g}, where g is the acceleration due to gravity. The center of gravity position calculation unit 23 calculates the distance D of the center of gravity G of the tool 100 from the reference position Po by subtracting the distance from the pivot axis 11 to the reference position Po from the distance Le of the center of gravity G of the tool 100 from the pivot axis 11.

[0019] The output unit 24 outputs the distance D. Specifically, the output unit 24 may display the distance D as text information on a display device, or it may transmit the distance D as a data signal to other devices such as tool changers or machine tools.

[0020] The notification unit 25 provides notification when the center of gravity position D exceeds a predetermined threshold. Possible notification methods include text display on a display device, lamp illumination, buzzer sounding, voice message output, and signal output to other devices. The notification unit 25 may also provide notification via other devices, such as a tool changer or machine tool.

[0021] The tool center of gravity position measuring device 1 can measure the center of gravity of the tool 100 without acquiring information about the tool 100 from an external source, and can therefore be used to reliably prevent the tool 100 from falling off due to centrifugal force in tool changing devices, machine tools, etc.

[0022] Next, Figure 2 shows a tool changing device 200 equipped with a tool center of gravity position measuring device 1. The tool changing device 200 is one embodiment of the tool changing device according to the present disclosure. The tool changing device 200 is a device for changing the tool 100 that is mounted on the spindle 301 of a machine tool 300.

[0023] The tool changer 200 includes a tool magazine 210 capable of holding a plurality of tools 100 that can be mounted on the spindle 301 of the machine tool 300, a transfer device 220 that exchanges a tool 100 mounted on the spindle 301 with a tool 100 held in the tool magazine 210 from among the plurality of tools 100, and a tool changer control device 230 that controls the operation of the tool magazine 210 and the transfer device 220.

[0024] The tool magazine 210 comprises a plurality of storage compartments 211, each holding one tool 100, and a tool center of gravity position measuring device 1. The tool magazine 210 is positioned at an exchange position (e.g., the lower end) where the tool 100 is selectively exchanged between the storage compartment 211 or the tool center of gravity position measuring device 1 and the transfer device 220. The tool magazine 210 may have a well-known configuration, such as a disc with a plurality of storage compartments 211 on its outer circumference, or an endless loop-shaped chain in which the plurality of storage compartments 211 and the tool center of gravity position measuring device 1 are arranged at equal intervals. The storage compartments 211 may have a well-known configuration. In this embodiment, the tool magazine 210 is arranged so that the storage compartments 211 and the tool center of gravity position measuring device 1 can rotate 90° between a state in which the axis of the tool 100 held at the exchange position is vertical and a state in which it is horizontal. In other words, in the tool magazine 210, the tool center of gravity position measuring device 1 receives the tool 100 vertically from the transfer device 220, and measures the center of gravity position of the tool 100 with the axis of the tool 100 approximately horizontal.

[0025] The transfer device 220 may be configured to include a pair of holding members 221 that are each capable of holding any one of the tools 100 and are capable of transferring one of the multiple tools between any one of the storage units 211 and the spindle 301, which are located at the exchange position among the multiple storage units 211; a rotational drive mechanism 222 that rotates the holding members 221 horizontally so that they are selectively facing the spindle 301 or the tool magazine 210; and a lifting drive mechanism 223 that moves the rotational drive mechanism 222 up and down together with the holding members 221. The transfer device 220 may be configured so that the timing of the transfer or receipt of the tool 100 by one of the holding members 221 between the spindle 301 and one of the tool magazine 210 is different from the timing of the transfer or receipt of the tool 100 by the other of the holding member 221 between the spindle 301 and the other of the tool magazine 210. For example, the system can be configured to transfer the tool 100 between the holding member 221 and the tool magazine 210 by raising and lowering the holding member 221 relative to the tool magazine 210, and to transfer the tool 100 between the holding member 221 and the spindle 301 by commanding the machine tool 300 to raise and lower the spindle 301.

[0026] The exchange control device 230 may be implemented by one or more computer devices having memory, a processor, input / output interfaces, etc., and executing an appropriate control program. The exchange control device 230 may be integrated with the calculation device 20 of the tool center of gravity position measuring device 1, or it may be integrated with other control devices such as the control device of the machine tool 300.

[0027] The tool changer 200, when a user stores a new tool 100 in the storage compartment 211 of the tool magazine 210, transfers the tool 100 to the transfer device 220, measures the distance D from the reference position Po of the tool 100 to its center of gravity G using the tool center of gravity position measuring device 1, and then returns the tool 100 to its original storage compartment 211. This allows the operating speed of the tool changer 200 when changing the tool 100 attached to the spindle 301 of the machine tool 300 to be set to the maximum speed that prevents the tool 100 from falling off due to excessive speed, thereby shortening the machining cycle time.

[0028] The following additional information is disclosed regarding the above embodiments and modifications. (Note 1) The tool center of gravity position measuring device (1) comprises a tool holding member (12) that is capable of holding a tool (100) and is rotatable about a pivot axis (11); a tool weight measuring unit (21) that measures the weight of the tool (100) held by the tool holding member (12); a torque measuring unit (22) that measures the rotational torque of the tool holding member (12) about the pivot axis (11) caused by gravity acting on the tool holding member (12) and the tool (100) held by the tool holding member (12); a center of gravity position calculation unit (23) that calculates the center of gravity position of the tool (100) as a distance from a predetermined reference position based on the weight of the tool (100) measured by the tool weight measuring unit (21) and the rotational torque measured by the torque measuring unit (22); and an output unit (24) that outputs the center of gravity position calculated by the center of gravity position calculation unit (23).

[0029] (Note 2) The tool center of gravity position measuring device (1) of Note 1 further comprises a pivot member that rotatably supports the tool holding member (12) via a pivot shaft (11), a base support member that holds the pivot member, a first sensor that detects the force acting between the pivot member and the base support member, and a second sensor that detects the force acting between the tool holding member (12) and the pivot member. The tool weight measuring unit (21) derives the weight of the tool (100) as the difference between the value detected by the first sensor when the tool holding member (12) is holding the tool (100) and the value detected by the first sensor when the tool holding member (12) is not holding the tool (100). The torque measuring unit (22) may calculate the rotational torque of the tool holding member (12) based on the positional relationship between the pivot shaft (11) and the second sensor and the value detected by the second sensor.

[0030] (Note 3) The tool center of gravity position measuring device (1) described in Notes 1 and 2 may further include a notification unit that provides notification when the center of gravity position exceeds a predetermined threshold.

[0031] (Note 4) The tool changing device (200) is equipped with the tool center of gravity position measuring device (1) described in Notes 1 to 3.

[0032] 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.

[0033] For example, in the tool center of gravity position measuring device according to this disclosure, the notification unit is not an essential component. Furthermore, the tool changing device according to this disclosure may include a tool center of gravity position measuring device disposed independently of the tool magazine, or it may include multiple tool center of gravity position measuring devices that are also used as storage units in the tool magazine.

[0034] 1 Tool center of gravity position measuring device 10 Measuring mechanism 11 Rotary shaft 12 Tool holding member 13 Pivot member 14 Base support member 15 First sensor 16 Second sensor 20 Calculation unit 21 Tool weight measuring unit 22 Torque measuring unit 23 Center of gravity position calculation unit 24 Output unit 25 Notification unit 100 Tool 110 Cutting tool 120 Holder 121 Shank part 122 Flange part 123 Holding part 200 Tool changer 210 Tool magazine 211 Storage unit 220 Transfer device 221 Holding member 222 Rotation drive mechanism 223 Lifting drive mechanism 230 Exchange control device 300 Machine tool 301 Spindle

Claims

1. A tool center of gravity position measuring device comprising: a tool holding member capable of holding a tool and rotatably disposed around a pivot axis; a tool weight measuring unit for measuring the weight of the tool held by the tool holding member; a torque measuring unit for measuring the rotational torque of the tool holding member around the pivot axis, generated by gravity acting on the tool holding member and the tool held by the tool holding member; a center of gravity position calculation unit for calculating a center of gravity position that expresses the position of the center of gravity of the tool as a distance from a predetermined reference position, based on the weight of the tool measured by the tool weight measuring unit and the rotational torque measured by the torque measuring unit; and an output unit for outputting the center of gravity position calculated by the center of gravity position calculation unit.

2. The tool center of gravity position measuring device according to claim 1, further comprising: a pivot member that rotatably supports the tool holding member via the pivot shaft; a base support member that holds the pivot member; a first sensor that detects the force acting between the pivot member and the base support member; and a second sensor that detects the force acting between the tool holding member and the pivot member, wherein the tool weight measuring unit derives the weight of the tool as the difference between the value detected by the first sensor when the tool holding member is holding the tool and the value detected by the first sensor when the tool holding member is not holding the tool; and the torque measuring unit calculates the rotation torque of the tool holding member based on the positional relationship between the pivot shaft and the second sensor and the value detected by the second sensor.

3. The tool center of gravity position measuring device according to claim 1 or 2, further comprising a notification unit that provides notification when the center of gravity position exceeds a predetermined threshold.

4. A tool changing device comprising a tool center of gravity position measuring device according to any one of claims 1 to 3.

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