Patent Description:
There is known a technique for ascertaining a state of a cutting tool by measuring a physical quantity of the cutting tool by a sensor during machining by the cutting tool (for example, <CIT> (PTL <NUM>), <CIT> (PTL <NUM>), <CIT> (PTL <NUM>), <CIT> (PTL <NUM>), <CIT> (PTL <NUM>), Utility Model Registration No. <CIT> (PTL <NUM>), <CIT> (PTL <NUM>), <CIT> (PTL <NUM>), <CIT> (PTL <NUM>) and <CIT> (PTL <NUM>)). <CIT> relates to a force measurement module, tool-holder and robot arm end equipped with such a force measurement module, which forms the basis of the preamble of appended claim <NUM>.

A cutting tool according to the present disclosure includes a shaft extending along a rotation axis and having a first end portion and a second end portion, and a sensor device disposed in such a manner as to surround a portion of the shaft in a longitudinal direction of the shaft. The cutting tool is configured to cut a workpiece by rotating around the rotation axis of the shaft. The sensor device includes a sensor module including a plurality of first sensors configured to detect a first physical quantity of the shaft, a substrate electrically connected to the first sensors, and a wireless communication unit electrically connected to the substrate and configured to transmit a signal including information of the first physical quantity detected by the first sensors to outside and a housing accommodating the sensor module. A region of the shaft surrounded by the sensor device includes a first region having a shape of a 4n-sided polygon when viewed from a direction in which the rotation axis extends. The n is a natural number of two or more. When viewed from the direction in which the rotation axis extends, the plurality of first sensors are arranged on at least two of outer peripheral surfaces of the first region, each of the outer peripheral surfaces of the first region corresponding to one of sides of the 4n-sided polygon, perpendicular lines of the at least two outer peripheral surfaces passing through the rotation axis and intersecting each other at <NUM> degrees.

From the viewpoint of ascertaining the state of the cutting tool in detail during machining, it is required to obtain more useful data by the sensor. It is an object of the present disclosure to provide a cutting tool in which more useful data can be obtained by the sensor.

According to the cutting tool of the present disclosure, more useful data can be obtained by the sensor.

First, embodiments of the present disclosure will be listed and explained. A cutting tool of the present disclosure includes a shaft extending along a rotation axis and having a first end portion and a second end portion, and a sensor device disposed in such a manner as to surround a portion of the shaft in a longitudinal direction of the shaft. The cutting tool is configured to cut a workpiece by rotating around the rotation axis of the shaft. The sensor device includes a sensor module including a plurality of first sensors configured to detect a first physical quantity of the shaft, a substrate electrically connected to the first sensors, and a wireless communication unit electrically connected to the substrate and configured to transmit a signal including information of the first physical quantity detected by the first sensors to outside and a housing accommodating the sensor module. A region of the shaft surrounded by the sensor device includes a first region having a shape of a 4n-sided polygon when viewed from a direction in which the rotation axis extends. The n is a natural number of two or more. When viewed from the direction in which the rotation axis extends, the plurality of first sensors are arranged on at least two of outer peripheral surfaces of the first region, each of the outer peripheral surfaces of the first region corresponding to one of sides of the 4n-sided polygon, perpendicular lines of the at least two outer peripheral surfaces passing through the rotation axis and intersecting each other at <NUM> degrees.

In the cutting tool of the present disclosure, a region of the shaft surrounded by the sensor device includes a first region having a shape of a 4n-sided polygon (n is a natural number of two or more) when viewed from a direction in which the rotation axis extends. A plurality of first sensors configured to detect the same physical quantity (first physical quantity) are arranged on at least two of outer peripheral surface of the first region each corresponding to one of sides of the 4n-sided polygon, perpendicular lines of the at least two outer peripheral surfaces passing through the rotation axis and intersecting each other at <NUM> degrees. In this way, sensors detecting the same physical quantity are arranged with a phase difference of <NUM> degrees in rotation about the rotation axis. As a result, the first physical quantity in the plane perpendicular to the rotation axis may be appropriately ascertained. The physical quantity ascertained in this way is useful for ascertaining the state of the cutting tool during machining. As described above, according to the cutting tool of the present disclosure, more useful data can be obtained by the sensor.

In the cutting tool, when viewed from the direction in which the rotation axis extends, angles formed by perpendicular lines of pairs of the outer peripheral surfaces of the first region, the perpendicular lines passing through the rotation axis, and each of the pairs corresponding to respective of the sides of the 4n-sided polygon that are adjacent to each other in a circumferential direction, are equal to each other. In this way, it becomes easy to ensure the symmetry of the outer peripheral surface of the first region where the sensor can be arranged with respect to the rotation axis.

In the cutting tool, the substrate may be disposed in such a manner as to extend along the outer peripheral surfaces of the first region corresponding to a plurality of sides of a 4n-sided polygon when viewed from the direction in which the rotation axis extends. In this way, it is easy to prevent the substrate module from moving relative to the shaft. As a result, the accuracy of the physical quantity obtained from the first sensor is increased.

In the cutting tool, a first recess may be formed in an outer peripheral surface of the shaft. Each of the first sensors may be accommodated in the first recess. In this way, this facilitates the arrangement of the first sensor.

In the cutting tool, the first sensors may be strain sensors. The sensor arrangement of the present disclosure is suitable for measuring strain.

In the cutting tool, a second recess may be formed in an outer peripheral surface of the shaft. Each of the first sensors may be arranged in such a manner as to straddle the second recess. In a case where the first sensor is a strain sensor, by arranging the first sensor so as to straddle the second recess as described above, strain can be easily measured with high accuracy.

In the cutting tool, the first sensors may be strain sensors. An outer peripheral surface of the shaft may have a first recess and a second recess, the second recess being deeper than the first recess and overlapping the first recess. Each of the first sensors may be arranged in such a manner as to straddle the second recess and accommodated in the first recess. With this configuration, the first sensor can be easily arranged and the strain can be easily measured with high accuracy by the first sensor.

In the above cutting tool, the second recess may be a groove extending in a circumferential direction of the shaft. The first recess may extend in direction perpendicular to the second recess. With this configuration, the first sensor can be easily arranged and the strain can be more easily measured with high accuracy by the first sensor.

In the cutting tool, the first sensor may be acceleration sensors. The sensor arrangement of the present disclosure is suitable for measuring acceleration.

In the cutting tool, the sensor module may further include a plurality of second sensors configured to detect a second physical quantity of the shaft different from the first physical quantity of the shaft. The substrate may be electrically connected to the second sensors. The wireless communication unit may be electrically connected to the substrate and configured to transmit a signal including information of the second physical quantity detected by the second sensors to outside.

As described above, by arranged the second sensor that detects the second physical quantity different from the first physical quantity, two types of physical quantities can be ascertained at the same time. As a result, the sensor can obtain more useful data for ascertaining the state of the cutting tool during machining.

In the above cutting tool, the first sensors may be strain sensors configured to detect strain as the first physical quantity. The second sensors may be acceleration sensors configured to detect acceleration as the second physical quantity. In this way, the strain and acceleration of the cutting tool can be ascertained simultaneously.

In the cutting tool, the first sensors and the second sensors may be arranged on the outer peripheral surfaces of the first region, and the outer peripheral surfaces on which the first sensors are arranged correspond to the sides of the 4n-sided polygon different from the sides of the 4n-sided polygon that the outer peripheral surfaces on which the second sensors are arranged. In this way, this facilitates the arrangement of the sensor.

In the above cutting tool, the sensor module further may include a wiring line connected to the first sensor. The wiring line may be configured to connect the first sensors to the substrate with slack in the wiring line. As described above, the first sensor can be easily arranged without adjusting the length of the wiring line by allowing the wiring line of the first sensor to have slack.

In the cutting tool, the sensor module may further include an AD converter disposed on the substrate. In a fourth region that may be different from a second region in which the wireless communication unit is placed and a third region in which the AD converter is placed, a thickness of the substrate is smaller than a thickness of the substrate in the second region and smaller than a thickness of the substrate in the third region, the substrate being bent in the fourth region. With this configuration, it is possible to facilitate deformation of the substrate for installation while preventing the wireless communication unit and the AD converter, which are relatively large components, from being peeled off due to deformation of the substrate.

In the above cutting tool, the substrate may be a rigid substrate. A groove may be formed in the fourth region of the substrate, the groove connecting both ends of the substrate in the direction in which the rotation axis extends. With this configuration, it becomes easy to make the thickness of the fourth region smaller than the thicknesses of the second region and the third region.

In the cutting tool, the substrate may include a main body being a flexible substrate and reinforcing plates disposed in the second region and the third region, each of the reinforcing plates having a Young's modulus higher than a Young's modulus of the main body. With this configuration, it becomes easy to make the thickness of the fourth region smaller than the thickness of the second region and the third region.

Embodiments of a cutting tool according to the present disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

<FIG> is a schematic perspective view showing the structure of a cutting tool. First, the structure of the cutting tool will be schematically described with reference to <FIG>. A cutting tool <NUM> according to the present embodiment includes a shaft <NUM> and a sensor device <NUM>. Shaft <NUM> extends along a rotation axis A from a first end portion 10A to a second end portion 10B. Sensor device <NUM> is arranged to surround a portion of the longitudinal direction of shaft <NUM>. In shaft <NUM>, a plurality of recesses <NUM> (four recesses <NUM> in this case) which are open in first end portion 10A and the outer peripheral surface are formed at equal intervals in the circumferential direction. A cutting insert <NUM> is attached to the wall defining recess <NUM>. A workpiece (not shown) may be machined by rotating cutting tool <NUM> around rotation axis A to bring cutting insert <NUM> into contact with the workpiece. That is, cutting tool <NUM> is a cutting tool that cuts a workpiece by rotating around rotation axis A of shaft <NUM>.

Details of each part of the cutting tool will now be described. <FIG> is a schematic perspective view showing the structure of the shaft viewed from second end portion 10B. <FIG> is a schematic perspective view showing the structure of the shaft viewed from first end portion 10A. <FIG> is a schematic plan view showing the structure of the shaft viewed from the first end portion in the rotation axis direction. <FIG> is a schematic plan view showing the structure of the shaft viewed from the second end portion in the rotation axis direction. <FIG> is a schematic plan view showing the structure of the shaft viewed in a direction perpendicular to the axial direction. <FIG> is a schematic cross-sectional view showing a cross section taken along line VII-VII of <FIG>. The structure of shaft <NUM> will be described with reference to <FIG>.

Referring to <FIG> and <FIG>, shaft <NUM> includes a main body <NUM> and an increased-diameter portion <NUM> as a first region. Main body <NUM> has a cylindrical shape. Rotation axis A coincides with the central axis of main body <NUM>. Increased-diameter portion <NUM> is a portion having a larger diameter than main body <NUM>. Although the position of increased-diameter portion <NUM> in the longitudinal direction of main body <NUM> is not particularly limited, in the present embodiment, increased-diameter portion <NUM> is disposed at the central portion in the longitudinal direction of main body <NUM>. Increased-diameter portion <NUM> is disposed in a region of shaft <NUM> which is surrounded by sensor device <NUM>.

Referring to <FIG>, as described above, cutting insert <NUM> is attached to the wall surface defining recess <NUM> of shaft <NUM>. Cutting insert <NUM> is fixed to shaft <NUM> by inserting and tightening a screw <NUM> into a screw hole formed in cutting insert <NUM>.

Referring to <FIG>, increased-diameter portion <NUM> has a shape of an octagonal prism. Referring to <FIG> and <FIG>, increased-diameter portion <NUM> has an octagonal shape when viewed from a direction in which the rotation axis A extends. More specifically, increased-diameter portion <NUM> has, in a cross-section perpendicular to rotation axis A, the shape of an octagon obtained by removing four isosceles right triangles with the same shape from each of the four corners of a square. Rotation axis A passes through the center of gravity of the octagon. This octagonal shape is the same in the direction in which rotation axis A extends. A central axis of main body <NUM> and a central axis of increased-diameter portion <NUM> coincide with each other. Here, the central axis of increased-diameter portion <NUM> means a straight line passing through the center of gravity of the octagon.

Referring to <FIG> and <FIG>, when viewed in the direction in which the rotation axis A extends, the octagon is formed by an outer peripheral surface 12A corresponding to a long side and an outer peripheral surface 12B corresponding to a short side shorter than the long side. The long sides and the short side are alternately arranged. Angles θ formed by perpendicular lines LA and LB of pairs of outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> are equal to each other, perpendicular lines LA and LB passing through rotation axis A, and each of the pairs corresponding to two of the sides of the octagon that are adjacent to each other in the circumferential direction. Specifically, angle θ is <NUM> degrees. Note that the shape of the octagon is not limited to the shape described above, and the lengths of outer peripheral surface 12A and outer peripheral surface 12B may be the same when viewed in the direction in which the rotation axis A extends.

Referring to <FIG>, a first recess <NUM>, extending in the direction in which rotation axis A extends, is formed in each outer peripheral surface 12B. A bottom surface 16A defining first recess <NUM> is planar. First recess <NUM> is disposed at a position crossing perpendicular line LB. First recess <NUM> extends through outer peripheral surface 12B in the direction in which rotation axis A extends. A second recess <NUM>, extending in the circumferential direction of increased-diameter portion <NUM>, is formed in outer peripheral surfaces 12A, 12B of increased-diameter portion <NUM>. Second recess <NUM> is formed so as to overlap first recess <NUM>. Second recess <NUM> intersects (is orthogonal to) first recess <NUM>. Second recess <NUM> is formed over the entire circumference of outer peripheral surfaces 12A, 12B of increased-diameter portion <NUM>. That is, second recess <NUM> is formed in an annular shape.

Referring to <FIG> and <FIG>, a depth d<NUM> of second recess <NUM> is greater than a depth d<NUM> of first recess <NUM>. A first small-diameter portion 11A having a smaller diameter than other portions is formed at a boundary portion near first end portion 10A between main body <NUM> and increased-diameter portion <NUM>. A second small-diameter portion 11B having a smaller diameter than other portions is formed at a boundary portion near second end portion 10B between main body <NUM> and increased-diameter portion <NUM>. A through hole 10C penetrating through shaft <NUM> in the direction in which rotation axis A extends is formed in shaft <NUM>. Through hole 10C extends to include rotation axis A.

Next, the structure of sensor device <NUM> will be described with reference to <FIG>. Referring to <FIG>, sensor device <NUM> includes a sensor module <NUM> and a housing <NUM> for accommodating sensor module <NUM>. Sensor module <NUM> includes a plurality of strain sensors <NUM> as a plurality of first sensors, a substrate <NUM> electrically connected to strain sensors <NUM>, and a wireless communication unit <NUM> (see <FIG>) electrically connected to substrate <NUM>. Strain sensor <NUM> detects strain as a first physical quantity of shaft <NUM>. Wireless communication unit <NUM> transmits a signal including information on the strain detected by strain sensor <NUM> to the outside.

Referring to <FIG>, strain sensor <NUM> constitutes a strain sensor component <NUM>. Strain sensor component <NUM> includes strain sensor <NUM> and a wiring line <NUM> which is connected to strain sensor <NUM> and has a connector <NUM> at its tip. Wiring line <NUM> has a belt-like shape. Strain sensor <NUM> is arranged near one end of wiring line <NUM>. Connector <NUM> is disposed at the other end of wiring line <NUM>.

Referring to <FIG>, substrate <NUM> constitutes a substrate module <NUM>. Substrate <NUM> includes a substrate main body made of an insulator such as resin and a circuit pattern (not shown) made of a conductor such as copper formed on the surface of the substrate main body. Substrate module <NUM> includes substrate <NUM>, wireless communication unit <NUM>, acceleration sensors <NUM> as second sensors, sockets <NUM>, and an AD converter <NUM>. Wireless communication unit <NUM>, acceleration sensors <NUM>, sockets <NUM>, and AD converter <NUM> are disposed on one main surface of substrate <NUM> and are electrically connected to substrate <NUM> (the circuit pattern of substrate <NUM>). Acceleration sensors <NUM> detects an acceleration as a second physical quantity of shaft <NUM>. A plurality of acceleration sensors <NUM> are arranged on substrate <NUM>. Wireless communication unit <NUM> is electrically connected to acceleration sensor <NUM> via substrate <NUM>. Wireless communication unit <NUM> transmits a signal including information on the acceleration of shaft <NUM> detected by acceleration sensors <NUM> to the outside.

Substrate <NUM> is a rigid substrate. Substrate <NUM> has a belt-like shape. Substrate <NUM> includes a first area <NUM>, a second area <NUM>, a third area <NUM>, a fourth area <NUM>, a fifth area <NUM>, a sixth area <NUM>, a seventh area <NUM>, and an eighth area <NUM>. First area <NUM> to eighth area <NUM> are arranged in this order in the longitudinal direction of substrate <NUM>. Wireless communication unit <NUM> and acceleration sensor <NUM> are mounted on first area <NUM>. Sockets <NUM> are mounted on second area <NUM>. Acceleration sensor <NUM> are mounted on third area <NUM>. Socket <NUM> is mounted in fourth area <NUM>. Acceleration sensor <NUM> and AD converter <NUM> are mounted in fifth area <NUM>. Socket <NUM> is mounted on sixth area <NUM>. Acceleration sensor <NUM> is mounted in seventh area <NUM>. Socket <NUM> is mounted in eighth area <NUM>.

A bendable region 49A having a smaller thickness than other portions is formed between first area <NUM> to eighth area <NUM> adjacent to each other. Bendable region 49A is a groove connecting both ends of substrate <NUM> in a width direction (a direction perpendicular to a longitudinal direction). First area <NUM> is a second area in which wireless communication unit <NUM> is mounted. Fifth area <NUM> is a third area in which AD converter <NUM> is mounted. Bendable region 49A is a fourth region having a smaller thickness than the second region and the third region. The lengths of first area <NUM>, third area <NUM>, fifth area <NUM> and seventh area <NUM> in the longitudinal direction of substrate <NUM> correspond to the length of outer peripheral surface 12A which is the long side of the octagon when increased-diameter portion <NUM> is viewed from the direction in which rotation axis A extends. The lengths of second area <NUM>, fourth area <NUM>, sixth area <NUM> and eighth area <NUM> in the longitudinal direction of substrate <NUM> correspond to the length of outer peripheral surface 12B which is the short side of the octagon when increased-diameter portion <NUM> is viewed from the direction in which rotation axis A extends.

Next, the arrangement of strain sensor component <NUM> and substrate module <NUM> on shaft <NUM> will be described. Strain sensor component <NUM> is arranged such that strain sensor <NUM> spans second recess <NUM> and strain sensor <NUM> is accommodated in first recess <NUM> (see <FIG>, <FIG>, <FIG>, etc.). Strain sensor component <NUM> is arranged on each of four outer peripheral surfaces 12B. As a result, when viewed from the direction in which rotation axis A extends, strain sensor <NUM> is arranged on each of all outer peripheral surfaces 12B (outer peripheral surfaces corresponding to the short sides) of increased-diameter portion <NUM>, each of outer peripheral surfaces of increased-diameter portion <NUM> corresponding to one side of the octagon, perpendicular lines LB passing through rotation axis A and intersecting each other at <NUM> degrees.

Referring to <FIG> and <FIG>, substrate module <NUM> is wound around increased-diameter portion <NUM> such that the main surface of substrate <NUM> is in contact with outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM>, the main surface being opposite to the surface on which wireless communication unit <NUM>, acceleration sensors <NUM>, sockets <NUM>, AD converter <NUM>, and the like are mounted. At this time, first area <NUM>, third area <NUM>, fifth area <NUM>, and seventh area <NUM> are arranged on outer peripheral surface 12A, and second area <NUM>, fourth area <NUM>, sixth area <NUM>, and eighth area <NUM> are arranged on outer peripheral surface 12B. Substrate <NUM> is bent at bendable region 49A which is a groove connecting both ends in the direction in which rotation axis A extends (a groove connecting both ends in the width direction).

As a result, when viewed from a direction in which rotation axis A extends, substrate <NUM> is disposed along outer peripheral surfaces 12A, 12B of increased-diameter portion <NUM>. Sockets <NUM> are disposed on substrate <NUM> disposed on outer peripheral surface 12B. Connector <NUM> disposed at the end of wiring line <NUM> connected to strain sensor <NUM> is connected to socket <NUM>. Thus, substrate <NUM> and strain sensor <NUM> are electrically connected to each other. As shown in <FIG>, wiring line <NUM> straddle substrate <NUM> in the width direction (direction in which rotation axis A extends). Wiring line <NUM> is warped in an arch shape. In other words, wiring line <NUM> connects strain sensor <NUM> and socket <NUM> with slack.

Acceleration sensor <NUM> is arranged on first area <NUM>, third area <NUM>, fifth area <NUM>, and seventh area <NUM> of substrate <NUM>. Therefore, when substrate module <NUM> is installed in increased-diameter portion <NUM> as described above, acceleration sensor <NUM> is arranged on each of all outer peripheral surfaces 12A (outer peripheral surfaces corresponding to the long sides) of increased-diameter portion <NUM>, each of outer peripheral surfaces of increased-diameter portion <NUM> corresponding to one side of the octagon, perpendicular lines LA passing through rotation axis A and intersecting each other at <NUM> degrees when viewed from the direction in which rotation axis A extends. That is, strain sensor <NUM> and acceleration sensor <NUM> are arranged on outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> corresponding to the respective sides of the octagon different from each other.

Referring to <FIG>, in the present embodiment, acceleration sensors <NUM> are arranged at a central portion in a short side direction of substrate <NUM> having a rectangular planar shape. As a result, referring to <FIG> and <FIG>, in the direction in which rotation axis A extends, acceleration sensors <NUM> and strain sensor <NUM> are arranged at the same position. In this way, the axial length required for arrangement of the sensor can be reduced. As a result, sensor device <NUM> can be reduced in size. Here, referring to <FIG> and <FIG>, the state in which "acceleration sensors <NUM> and strain sensor <NUM> are arranged at the same position in the direction in which rotation axis A extends" means that a measurement range a of acceleration sensor <NUM> (specifically, the range in which the electrical resistance wiring line for detecting acceleration is arranged) and a measurement range b of strain sensor <NUM> (specifically, the range in which the electrical resistance wiring line for detecting strain is arranged) at least partially overlap in the direction in which rotation axis A extends. The positional relationship between acceleration sensors <NUM> and strain sensor <NUM> in the direction in which rotation axis A extends may be changed in consideration of the ease of detection of acceleration and strain. For example, in the direction in which rotation axis A extends, strain sensor <NUM> may be arranged at a position farther from first end portion 10A (a position farther from cutting insert <NUM> ; around an upper part in <FIG>) than acceleration sensor <NUM>. The strain of shaft <NUM> caused by the cutting process increases further away from the cutting insert. The acceleration of shaft <NUM> caused by the cutting process is greater at a position closer to the cutting insert. Therefore, by employing such an arrangement, the sensitivity of detection of strain and acceleration by strain sensor <NUM> and acceleration sensor <NUM> is improved. On the other hand, in the direction in which rotation axis A extends, strain sensor <NUM> may be arranged at a position closer to first end portion 10A than acceleration sensor <NUM> (a position closer to cutting insert <NUM> ; around a lower part in <FIG>). When shaft <NUM> is long, the strain of shaft <NUM> at the position where strain sensor <NUM> is arranged may be too large in the above arrangement. In such a case, by disposing strain sensor <NUM> at a position closer to first end portion 10A than acceleration sensor <NUM>, it is possible to set the magnitude of the strain at the position where strain sensor <NUM> is arranged within a range in which strain sensor <NUM> easily detects the strain.

Referring to <FIG> and <FIG>, in the present embodiment, strain sensor <NUM> includes a temperature sensor. That is, in the present embodiment, a sensor in which strain sensor <NUM> and the temperature sensor are integrated is employed as strain sensor <NUM>. The temperature sensor does not necessarily have to be integrated with strain sensor <NUM>, and may be a separate body. In this case, referring to <FIG>, the temperature sensor is arranged at the same position as strain sensor <NUM> in the direction in which rotation axis A extends. More specifically, referring to <FIG> and <FIG>, the temperature sensor is arranged at an arbitrary position in an annular region of outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> corresponding to measurement range b of strain sensor <NUM> in the direction in which rotation axis A extends (a band-like region of outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> whose width coincides with measurement range b). The temperature sensor is not essential in the cutting tool of the present disclosure, but may be employed to detect the temperature of the location where strain sensor <NUM> is arranged or the region corresponding to measurement range b of strain sensor <NUM> in outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM>. Based on the temperature detected by the temperature sensor, the thermal strain at the location where strain sensor <NUM> is arranged or the region corresponding to measurement range b of strain sensor <NUM> in outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> may be calculated. Thermal strain is the product of temperature change and coefficient of linear expansion. By correcting the strain detected by strain sensor <NUM> based on the thermal strain, the strain caused by the cutting can be more accurately ascertained.

Next, the installation of housing <NUM> on shaft <NUM> will be described. Referring to <FIG> and <FIG>, housing <NUM> includes a housing main body <NUM>, a first fixing member <NUM>, a second fixing member <NUM>, and a lid <NUM>. As shown in <FIG>, housing main body <NUM> includes a disk-shaped bottom wall portion <NUM> having a through hole 61A at the center thereof, and a side wall portion <NUM> rising from the outer peripheral surface of bottom wall portion <NUM> and having a cylindrical shape. In bottom wall portion <NUM>, a plurality of screw holes <NUM> (here, eight crew holes <NUM>) penetrating bottom wall portion <NUM> in the thickness direction are formed at equal intervals in the circumferential direction. Housing main body <NUM> is made of a metal, for example. Examples of the metal that can be employed include aluminum alloy and iron alloy (steel such as stainless steel).

Referring to <FIG>, first fixing member <NUM> has a shape of an annular flat plate divided into two. First fixing member <NUM> is formed with a plurality of screw holes <NUM> (here, eight screw holes <NUM> in total in first fixing member <NUM> divided into two in this case) at equal intervals in the circumferential direction so as to correspond to screw holes <NUM> of bottom wall portion <NUM> of housing main body <NUM>. An inner peripheral surface 63A of first fixing member <NUM> has a shape corresponding to first small-diameter portion 11A of shaft <NUM>. When two first fixing members <NUM> are assembled into an annular shape, the diameter of inner peripheral surface 63A is equal to or slightly larger than the diameter of first small-diameter portion 11A. First fixing member <NUM> is made of a metal, for example. Examples of the metal that can be employed include an aluminum alloy and an iron alloy (steel such as stainless steel).

Referring to <FIG>, second fixing member <NUM> is a part having a flat circular arc shape. In this embodiment, housing <NUM> includes two second fixing members <NUM>. An inner peripheral surface 65A of each second fixing member <NUM> has a shape corresponding to a part of the planar shape of the outer peripheral surface of increased-diameter portion <NUM>, i.e. a shape corresponding to a part of an octagon. A plurality of screw holes <NUM> (here, two screw holes <NUM> for each second fixing member <NUM>) so as to correspond to screw holes <NUM> of bottom wall portion <NUM> of housing main body <NUM> and screw holes <NUM> of first fixing member <NUM>. The material constituting second fixing member <NUM> is resin, for example.

Referring to <FIG>, lid (upper wall portion) <NUM> has a disk-like shape having a through hole 22A in the center thereof. Lid <NUM> is made of, for example, resin.

Housing <NUM> may be installed in a state in which strain sensor component <NUM> and substrate module <NUM> are installed on shaft <NUM>. Referring to <FIG>, housing main body <NUM> is disposed such that main body <NUM> of shaft <NUM> penetrating through hole 61A of bottom wall portion <NUM> of housing main body <NUM>. In a state in which first fixing member <NUM> is disposed on bottom wall portion <NUM>, first fixing member <NUM> is fitted into first small-diameter portion 11A such that inner peripheral surface 63A is in contact with the bottom wall of first small-diameter portion 11A of main body <NUM>. In a state in which second fixing member <NUM> is disposed on first fixing member <NUM> such that inner peripheral surface 65A is in contact with outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM>. Then, housing main body <NUM>, first fixing member <NUM> and second fixing member <NUM> are fixed to each other by a screw passing through screw hole <NUM> of second fixing member <NUM> and screw hole <NUM> of first fixing member <NUM> and reaching screw hole <NUM> of bottom wall portion <NUM>. At this time, since the inner diameter of first fixing member <NUM> corresponds to the outer diameter of first small-diameter portion 11A, the central axis of housing main body <NUM> coincides with rotation axis A. In addition, since inner peripheral surface 65A of second fixing member <NUM> has a shape corresponding to a part of the planar shape of the outer peripheral surface of increased-diameter portion <NUM> (a shape corresponding to a part of an octagon), housing main body <NUM> is prevented from rotating in the circumferential direction relative to shaft <NUM>. Lid (upper wall portion) <NUM> is fixed to increased-diameter portion <NUM> by a screw or the like, for example, in a state of being placed on an end surface of side wall portion <NUM> and an end surface of increased-diameter portion <NUM>. In this way, housing <NUM> is fixed to shaft <NUM> in a state where sensor module <NUM> is accommodated therein.

During operation of cutting tool <NUM>, cutting tool <NUM> rotates about rotation axis A. As cutting insert <NUM> comes into contact with the workpiece, the workpiece is machined. At this time, strain and acceleration of shaft <NUM> are detected by strain sensor <NUM> and acceleration sensor <NUM>, respectively. The strain and acceleration information, which is an analog signal, is converted into a digital signal by AD converter <NUM>, and then transmitted to the outside by wireless communication unit <NUM>. Here, since lid (upper wall portion) <NUM> of housing <NUM> is made of resin, wireless communication unit <NUM> can transmit a signal to the outside through lid (upper wall portion) <NUM>. This signal is externally received and analyzed to ascertain the state of shaft <NUM> in a plane perpendicular to the rotation axis.

In cutting tool <NUM> according to the present embodiment, the region of shaft <NUM> surrounded by sensor device <NUM> includes increased-diameter portion <NUM> having an octagonal shape when viewed from the direction in which rotation axis A extends. A plurality of strain sensors <NUM> for detecting strain are arranged on outer peripheral surfaces 12B of increased-diameter portion <NUM>, each of outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> corresponding to one side of the octagon, perpendicular lines LB passing through rotation axis A and intersecting each other at <NUM> degrees. In this way, the sensors for detecting strain are arranged with a phase difference of <NUM> degrees in the rotation around rotation axis A. As a result, it is possible to appropriately ascertain the strain in the plane perpendicular to rotation axis A. The strain ascertained in this way is useful for ascertaining the state of cutting tool <NUM> during machining. As described above, cutting tool <NUM> of the present embodiment is a cutting tool capable of obtaining more useful data by the sensor.

In the present embodiment, when viewed from the direction in which rotation axis A extends, the angles formed by perpendicular lines LA and LB of pairs of outer peripheral surfaces 12A and 12B of the increased-diameter portion <NUM> are equal to each other, perpendicular lines LA and LB passing through rotation axis A, and each of the pairs corresponding to two sides of the octagon that are adjacent to each other in the circumferential direction. As a result, the symmetry of outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> on which strain sensor <NUM> is arranged with respect to rotation axis A is increased.

In the present embodiment, substrate <NUM> is disposed along outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> when viewed from the direction in which rotation axis A extends. This makes it difficult for substrate module <NUM> to move relative to shaft <NUM>. As a result, the accuracy of information obtained from strain sensor <NUM> is increased.

In the present embodiment, first recess <NUM> is formed in outer peripheral surface 12B of increased-diameter portion <NUM>. Strain sensor <NUM> is accommodated in first recess <NUM>. This facilitates the arrangement of strain sensor <NUM>.

Further, in the present embodiment, second recess <NUM> is formed in outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM>. Strain sensor <NUM> is arranged in such a manner as to straddle second recess <NUM>. This makes it easy to measure the strain with high accuracy.

Further, in the present embodiment, second recess <NUM> is deeper than first recess <NUM> and overlaps with first recess <NUM>. Thus, strain sensor <NUM> can be easily arranged and the strain can be easily measured with high accuracy by strain sensor <NUM>.

Further, in the present embodiment, second recess <NUM> is a groove extending in the circumferential direction of increased-diameter portion <NUM>. The first recess extends in a direction perpendicular to the second recess. Thus, strain sensor <NUM> can be further easily arranged and the strain can be easily measured with high accuracy by strain sensor <NUM>.

Further, in the present embodiment, sensor module <NUM> includes a plurality of acceleration sensors <NUM> for detecting the acceleration of the shaft. Thus, two kinds of physical quantities of strain and acceleration can be ascertained at the same time.

Further, in the present embodiment, strain sensor <NUM> and acceleration sensor <NUM> are arranged on outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> corresponding to the respective sides of the octagon different from each other. Although it is possible to arrange strain sensor <NUM> and acceleration sensor <NUM> on same outer peripheral surfaces 12A and 12B, it is easy to arrange the sensors by arranging them on different surfaces.

Further, in the present embodiment, wiring line <NUM> constituting strain sensor component <NUM> connects the strain sensor and socket <NUM> with slack. This makes it easy to arrangel strain sensor <NUM> without adjusting the length of wiring line <NUM>.

Further, in the present embodiment, substrate <NUM> is bent in bendable region 49A having a smaller thickness than first area <NUM> on which wireless communication unit <NUM> is mounted and fifth area <NUM> on which AD converter <NUM> is mounted. Accordingly, substrate <NUM> can be easily deformed for installation while preventing wireless communication unit <NUM> and AD converter <NUM>, which are relatively large components, from being peeled off or the like due to deformation of substrate <NUM>.

Further, in the present embodiment, substrate <NUM> is a rigid substrate. A groove connecting both ends in the direction in which rotation axis A extends is formed in bendable region 49A of substrate <NUM>. Thus, bendable region 49A can be easily formed.

Instead of substrate <NUM> of the above-described embodiment which is a rigid substrate, substrate <NUM> of a modified example described below may be employed. Referring to <FIG>, substrate <NUM> of the present modification includes a main body 49B which is a flexible substrate, and a reinforcing plate <NUM> which is disposed at least in first area <NUM> and fifth area <NUM> as a second area and a third area and has a Young's modulus larger than that of main body 49B. In the present modification, reinforcing plates <NUM> are disposed in first area <NUM>, third area <NUM>, fifth area <NUM>, and seventh area <NUM>. As described above, by employing main body 49B which is a flexible substrate and reinforcing only a necessary portion with reinforcing plate <NUM>, it is possible to obtain the same effect as that of the above-described embodiment.

In the above-described embodiment, the two types of sensors, i.e., strain sensor <NUM> and acceleration sensor <NUM>, are employed as the first sensor and the second sensor, respectively. However, for example, acceleration sensor <NUM> as the second sensor may be omitted. In addition, strain sensor <NUM> may be omitted and only acceleration sensor <NUM> may be employed. That is, the first sensor may be an acceleration sensor. Further, a sensor that detects a physical quantity other than strain and acceleration may be employed instead of one or both of strain sensor <NUM> and acceleration sensor <NUM>, or may be employed in addition to them.

In the above-described embodiment, the end mill has been described as an example of the cutting tool of the present disclosure, but the cutting tool of the present disclosure is not limited thereto. The cutting tool of the present disclosure may be, for example, a drill, a milling cutter, a boring, a reamer, a tap, etc..

In the above-described embodiment, increased-diameter portion <NUM> of shaft <NUM> disposed in the region surrounded by sensor device <NUM> has an octagonal shape when viewed from the direction in which rotation axis A extends. However, the planar shape of the increased-diameter portion may be a 4n-sided polygon (n is a natural number of <NUM> or more), and may be, for example, a dodecagon, a hexadecagon, or an icosagon.

In the above-described embodiment, strain sensor <NUM> is arranged on each of all of outer peripheral surfaces 12B (four surfaces) of increased-diameter portion <NUM>, each of outer peripheral surfaces 12A and 12B of increased-diameter portion <NUM> corresponding to one side of the octagon, the perpendicular lines of outer peripheral surfaces 12B passing through rotation axis A and intersecting each other at <NUM> degrees. Strain sensor <NUM> may be arranged on at least two surfaces. More generally, a strain sensor is arranged on each of a set of a total of two outer peripheral surfaces, which are a first outer peripheral surface and a second outer peripheral surface of which perpendicular lines pass through the rotation axis and intersect each other at <NUM> degrees, or arranged on each of a set of outer peripheral surfaces, which are the two outer peripheral surfaces and a third outer peripheral surface, the perpendicular line of the third outer peripheral surface passing through the rotation axis and intersecting the perpendicular line of the first outer peripheral surface at <NUM> degrees. By arranging strain sensors on the first outer peripheral surface and the second outer peripheral surface of which perpendicular lines pass through the rotation axis and intersect each other at <NUM> degrees, information on the magnitude and the direction of a load acting in a plane perpendicular to the rotation axis can be obtained. Further, by arranging a strain sensor on the third outer peripheral surface, the influence of the load parallel to the rotation axis can be removed, and the information on the magnitude and the direction of the load acting in the plane perpendicular to the rotation axis can be obtained more accurately. There may be more than one set of outer peripheral surfaces. For example, when there are two sets of outer peripheral surfaces, a strain sensor may be arranged on each set of outer peripheral surfaces including two outer peripheral surfaces or three outer peripheral surfaces. That is, the strain sensors may be arranged on a maximum of six outer peripheral surfaces. There is no angle limit between the two sets of outer peripheral surfaces.

In the above-described embodiment, first fixing member <NUM> and second fixing member <NUM> are separate members. However, first fixing member <NUM> and second fixing member <NUM> may be integrated. In this case, first fixing member <NUM> and second fixing member <NUM> may be an integral metal member.

Next, other embodiments of the present disclosure will be described. <FIG> is a schematic perspective view showing the construction of a cutting tool in accordance with another embodiment. Referring to <FIG>, cutting tool <NUM> of the present embodiment basically has the same structure as cutting tool <NUM> of the above-described embodiment described based on <FIG>, operates in the same manner, and achieves the same effects. However, cutting tool <NUM> of the present embodiment differs from the above-described embodiment mainly in the structure of shaft <NUM>.

Specifically, referring to <FIG>, shaft <NUM> of the present embodiment includes a annular first projecting portion 10D and a annular second projecting portion 10E projecting in a radial direction (a direction perpendicular to rotation axis A) in a region closer to second end portion 10B than to sensor device <NUM>. Second projecting portion 10E is disposed close to second end portion 10B side than first projecting portion 10D. In the direction in which rotation axis A extends, the region between first projecting portion 10D and second projecting portion 10E of shaft <NUM> is a groove portion <NUM>. A region opposite to first projecting portion 10D when viewed from second projecting portion 10E is a tapered portion 10F having a diameter decreasing toward the second end portion. That is, shaft <NUM> of the present embodiment includes tapered portion 10F having a truncated cone shape.

When cutting tool <NUM> according to the present embodiment is in use, tapered portion 10F is inserted into a recess formed in a spindle of a machine tool, whereby cutting tool <NUM> is held by the spindle of the machine tool. The shapes of tapered portion 10F, first projecting portion 10D, and second projecting portion 10E can be appropriately selected in accordance with the tool holding mechanism provided in the spindle of the machine tool.

It should be understood that the embodiments disclosed herein are illustrative in all respects and are not restrictive in any respect. The scope of the present invention is defined not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claim 1:
A cutting tool (<NUM>) comprising:
a shaft (<NUM>) extending along a rotation axis (A) and having a first end portion (10A) and a second end portion (10B); and
a sensor device (<NUM>),
wherein the cutting tool (<NUM>) is configured to cut a workpiece by rotating around the rotation axis (A) of the shaft (<NUM>),
wherein the sensor device (<NUM>) includes
a sensor module (<NUM>) including a plurality of first sensors configured to detect a first physical quantity of the shaft (<NUM>) and a substrate (<NUM>) electrically connected to the first sensors,
characterised in that the sensor device (<NUM>) is disposed in such a manner as to surround a portion of the shaft (<NUM>) in a longitudinal direction of the shaft (<NUM>), and the sensor module (<NUM>) further includes a wireless communication unit (<NUM>) electrically connected to the substrate (<NUM>) and configured to transmit a signal including information of the first physical quantity detected by the first sensors to outside and
a housing (<NUM>) accommodating the sensor module (<NUM>),
wherein a region of the shaft (<NUM>) surrounded by the sensor device (<NUM>) includes a first region having a shape of a 4n-sided polygon when viewed from a direction in which the rotation axis (A) extends,
wherein the n is a natural number of two or more, and
wherein, when viewed from the direction in which the rotation axis (A) extends, the plurality of first sensors are arranged on at least two of outer peripheral surfaces (12A, 12B) of the first region, each of outer peripheral surfaces (12A, 12B) of the first region corresponding to one of sides of the 4n-sided polygon, perpendicular lines (LA, LB) of the at least two outer peripheral surfaces (12A, 12B) passing through the rotation axis (A) and intersecting each other at <NUM> degrees.