JP7394733B2 - Holding force sensor - Google Patents

Description

The present invention relates to a holding force sensor.

In machining, a rotatable chuck grips a workpiece, and the rotating workpiece is brought into contact with a fixed tool to perform cutting or the like. Alternatively, a tool is held by a rotatable chuck and brought into contact with a fixed workpiece to perform drilling or the like.

Here, in order to measure the gripping force of the chuck, it has been proposed to attach a strain gauge to the outer cylinder of the chuck (Patent Document 1).

JP2016-140940

In Patent Document 1, since the strain gauge is attached to the chuck, which is a rotating body, the environmental load on the strain gauge is large. That is, strain gauges are exposed to high-speed rotation and vibration, and are also exposed to cutting oil. Therefore, the accuracy of the strain gauge may be impaired.

An object of the present invention is to provide a holding force sensor that can more easily measure the holding force of a chuck and has high measurement reliability.

According to the first aspect of the invention,
A holding force sensor that is gripped by a chuck and measures the holding force of the chuck,
The base part and
a plurality of flexure-generating bodies disposed on one side of the base portion, each of which is cantilever-supported by the base portion and has a free end;
a strain gauge attached to at least one of the plurality of strain-generating bodies,
In order to measure the holding force, a holding force sensor is provided in which the free ends of the plurality of strain-generating bodies are integrally gripped by the chuck rather than the strain gauges.

In the holding force sensor according to the first aspect, each of the plurality of strain-generating bodies is placed closer to the free end than the strain gauge to be abutted by the chuck in order to grip the holding force sensor. The holding force sensor may have a sensor center axis that coincides with the center axis of the chuck when held by the chuck, and the abutted portion may have a sensor center axis that coincides with the sensor center axis when the holding force sensor is gripped by the chuck. It may be located on a virtual circle centered on .

In the holding force sensor of the first aspect, the contact portions of the plurality of strain-generating bodies may be provided at equal intervals along the virtual circle.

In the holding force sensor of the first aspect, each of the plurality of strain-generating bodies may have an alignment surface that comes into contact with a tip of the chuck when the holding force sensor grips the chuck, and A positioning surface may extend in a plane perpendicular to the sensor central axis on a side closer to the strain gauge than the abutted portion.

In the holding force sensor of the first aspect, the abutted portion of each of the plurality of strain-generating bodies may be a curved surface extending along a virtual circle centered on the sensor central axis.

In the holding force sensor of the first aspect, each of the plurality of strain-generating bodies has a first curved surface that curves in an arc around the sensor central axis, and a radius of curvature smaller than the first curved surface around the sensor central axis. and a connecting surface extending in a plane orthogonal to the sensor central axis to connect the first curved surface and the second curved surface, and at least one of the plurality of flexure-generating bodies. The strain gauge may be attached to the first curved surface, and the second curved surface of each of the plurality of strain bodies may have the abutted portion.

In the holding force sensor of the first aspect, the plurality of strain-generating bodies may be adjacent to each other via a slit or a gap, and a wiring extending from the strain gauge passes through the slit or the gap to the base portion. It may be extended.

In the holding force sensor of the first aspect, the thickness of the plurality of strain-generating bodies may be smaller at a position where the strain gauge is attached than at other positions.

The holding force sensor of the first aspect may further include a temperature compensation strain gauge attached to the base portion.

In the holding force sensor of the first aspect, the plurality of strain bodies may be at least two strain bodies.

In the holding force sensor of the first aspect, the strain gauge may be attached to each of the plurality of strain bodies.

The holding force sensor of the present invention can more easily measure the holding force of a chuck and has high measurement reliability.

FIG. 1 is a perspective view of the holding force sensor unit of the first embodiment. FIG. 2(a) is a cross-sectional view of the holding force sensor taken along line IIa-IIa in FIG. FIG. 2(b) is a side view of the holding force sensor, viewed in the direction of the central axis of the holding force sensor. FIG. 3 is a front view of the ring adapter, viewed in the direction of the central axis of the ring adapter. FIG. 4 is a perspective view of a holding force sensor and a collet chuck that holds the holding force sensor. FIG. 5(a) is an explanatory diagram showing how the collet chuck directly grips the holding force sensor. FIG. 5(b) is an explanatory diagram showing how the collet chuck grips the holding force sensor via the ring adapter. FIG. 6(a) is a cross-sectional view showing how the collet chuck directly grips the holding force sensor. FIG. 6(b) is a cross-sectional view showing how the collet chuck grips the holding force sensor via the ring adapter. In both figures, the position of the cross section is the same as in FIG. 2(a). FIG. 7 is a perspective view of a modified holding force sensor and a diaphragm chuck that holds the holding force sensor. FIG. 8 is a perspective view of a holding force sensor according to the second embodiment. FIG. 9(a) is a cross-sectional view of the holding force sensor taken along line IXa-IXa in FIG. FIG. 9(b) is a side view of the holding force sensor, viewed in the direction of the central axis of the holding force sensor. FIG. 10A is an explanatory diagram showing how the collet chuck grips the outer surface of the fourth fan-shaped plate portion of the holding force sensor. FIG. 10(b) is an explanatory diagram showing how the collet chuck grips the outer surface of the third fan-shaped plate portion of the holding force sensor. FIG. 11A is a cross-sectional view showing how the collet chuck grips the outer surface of the fourth fan-shaped plate portion of the holding force sensor. FIG. 11(b) is a sectional view showing how the collet chuck grips the outer surface of the third fan-shaped plate portion of the holding force sensor. In both figures, the position of the cross section is the same as in FIG. 9(a).

<First embodiment>
The holding force sensor unit (gripping force sensor unit) 1000 of the first embodiment will be described using an example in which the holding force (gripping force) of the collet chuck 2000 (FIG. 4) is measured using the holding force sensor unit 1000. In the description, reference is made to FIGS. 1-6.

As shown in FIG. 1, the holding force sensor unit 1000 includes a holding force sensor 100 and a ring adapter (annular adapter) 500 that is detachably attached to the holding force sensor 100. The holding force sensor 100 has a substantially cylindrical shape with a central axis (sensor central axis) _X100 . Ring adapter 500 is annular with a central axis X ₅₀₀ . The ring adapter 500 is coaxially attached to the holding force sensor 100.

In the following description, the direction in which the central axis X ₁₀₀ extends will be referred to as the axial direction of the holding force sensor 100, and the side where the ring adapter 500 is attached to the holding force sensor 100 will be referred to as the front side in the axial direction. The radial direction centered on the axial direction is called the radial direction of the holding force sensor 100, and the direction around the axial direction is called the circumferential direction of the holding force sensor 100.

In the following description, the direction in which the central axis X ₅₀₀ extends will be referred to as the axial direction of the ring adapter 500, and the side facing the holding force sensor 100 when attached to the holding force sensor 100 will be referred to as the rear side in the axial direction. The radial direction centered on the axial direction is called the radial direction of the ring adapter 500, and the direction around the axial direction is called the circumferential direction of the ring adapter 500.

As shown in FIGS. 1, 2(a), and 2(b), the holding force sensor 100 includes a base portion 11, a strain generating portion 12, and three measurement strain gauges G attached to the strain generating portion 12. and three temperature compensation strain gauges CG attached to the base part 11. The base portion 11 and the strain-generating portion 12 may be integrally formed of metal (for example, stainless steel) or the like.

The base portion 11 is a portion that serves as the foundation of the holding force sensor 100, and is a portion that does not undergo deformation (strain) when measuring the holding force of the chuck to be measured. The base portion 11 includes a disk portion 111 and a ridge portion 112.

The disk portion 111 is disk-shaped and has a front surface 111f and a rear surface 111r. A circular through hole 111h extending axially about the central axis _X100 is provided in the radial center of the disk portion 111.

The ridge portion 112 stands up rearward from the rear surface 111r of the disk portion 111. The ridge portion 112 extends over the entire circumferential area near the outer periphery of the rear surface 111r. In the first embodiment, the height (axial dimension) of the ridge portion 112 is approximately equal to the thickness (axial dimension) of the disk portion 111.

The strain-generating portion 12 is a portion supported by the base portion 11, and is a portion that exhibits deformation (strain) in accordance with the magnitude of the holding force when measuring the holding force of the chuck to be measured.

Roughly, as shown in FIGS. 1, 2(a) and 2(b), the strain-generating portion 12 connects two cylinders with different diameters coaxially along the axial direction, and connects them in the circumferential direction. It has a shape divided into three parts.

Specifically, the strain-generating portion 12 includes a first strain-generating body F1, a second strain-generating body F2, and a third strain-generating body F3 along the circumferential direction. The first strain body F1, the second strain body F2, and the third strain body F3 have the same shape.

Each of the first to third strain bodies F1 to F3 includes a large diameter curved plate portion 120, a connecting portion 121, and a small diameter curved plate portion 122.

The large diameter curved plate portion 120 is a curved plate that is curved in an arc shape around the central axis _X100 . A rear end (fixed end) 120Er of the large diameter curved plate portion 120 is fixedly supported by the front surface 111f of the disk portion 111 of the base portion 11.

A recess R is provided in the circumferential center of the outer surface (first curved surface) 120o of the large diameter curved plate portion 120. The bottom surface Rb of the recess R is a flat surface perpendicular to the radial direction.

The connecting portion 121 is a fan-shaped flat plate that extends radially along the radial direction. At the outer end 121Eo of the connecting portion 121, a front end 120Ef of the large diameter curved plate portion 120 is fixed to the rear surface 121r of the connecting portion 121. Note that in this specification and the present invention, a "sector shape" refers not only to a shape surrounded by a circular arc and a radius passing through both ends thereof, but also to a shape surrounded by a concentric large-diameter arc and a small-diameter arc and a radius passing through their both ends. It also includes a shape (a shape obtained by cutting out a portion of a circular ring in the circumferential direction).

The small diameter curved plate portion 122 is a curved plate that is curved in an arc shape around the central axis _X100 . The rear end 122Er of the small diameter curved plate portion 122 is fixed to the front surface 121f of the connecting portion 121 at the inner end 121Ei of the connecting portion 121.

Each of the first to third strain bodies F1 to F3 has the above configuration. The first strain body F1 to the third strain body F3 are each a cantilever-shaped strain body with the rear end 120Er of the large diameter curved plate portion 120 as a fixed end and the front end 122Ef of the small diameter curved plate portion 122 as a free end. It is.

Between the first strain body F1 and the second strain body F2, between the second strain body F2 and the third strain body F3, and between the third strain body F3 and the first strain body F1. A slit SL is defined between them. Each of the slits SL extends along the axial direction from the front end 122Ef of the small diameter curved plate portion 122 to the vicinity of the rear end 120Er of the large diameter curved plate portion 120.

As shown in FIG. 1, in the first embodiment, the rear end of the slit SL is located in front of the rear end 120Er of the large diameter curved plate portion 120, and the large diameter of the first to third strain bodies F1 to F3 is The radius curved plate portions 120 are connected in the circumferential direction near the rear end 120Er. However, the present invention is not limited to this, and the position of the rear end of the slit SL and the position of the rear end 120Er of the large diameter curved plate portion 120 in the axial direction may be the same.

The large diameter curved plate portions 120 of the first strain body F1 to the third strain body F3 are adjacent to each other along the circumferential direction. Each of the large-diameter curved plate portions 120 of the first to third strain-generating bodies F1 to F3 can also be regarded as part of a virtual large-diameter cylinder whose central axis is the central axis _X100 . The outer surface 120o of the large diameter curved plate portion 120 extends along the outer peripheral surface of the virtual large diameter cylinder. That is, the outer surface 120o of the large-diameter curved plate portion 120 of the first to third strain-generating bodies F1 to F3 is a curved surface extending along a large-diameter virtual circle centered on the central axis _X100 .

The connecting portions 121 of the first strain body F1 to the third strain body F3 are adjacent to each other along the circumferential direction. Each of the connecting portions 121 of the first to third strain bodies F1 to F3 can also be regarded as part of a virtual disk whose central axis is the central axis _X100 . The front surface 121f of the connecting portion 121 extends along the front surface of the virtual disk. That is, the front surface 121f of the connecting portion 121 of the first strain body F1 to the third strain body F3 is a flat surface extending along a plane orthogonal to the central axis _X100 .

The front surface 121f of the connecting portion 121 of the first strain body F1 to the third strain body F3 functions as a positioning surface against which the tip of the chuck and/or the rear surface of the ring adapter 500 comes into contact (details will be described later).

The small diameter curved plate portions 122 of the first strain body F1 to the third strain body F3 are adjacent to each other along the circumferential direction. Each of the small-diameter curved plate portions 122 of the first to third strain-generating bodies F1 to F3 can also be regarded as part of a virtual small-diameter cylinder whose central axis is the central axis _X100 . The outer surface (second curved surface) 122o of the small diameter curved plate portion 122 extends along the outer peripheral surface of the virtual small diameter cylinder. That is, the outer surface 122o of the small-diameter curved plate portion 122 of the first to third strain-generating bodies F1 to F3 is a curved surface extending along a small-diameter virtual circle centered on the central axis _X100 . The diameter of the small-diameter virtual circle is smaller than the diameter of the large-diameter virtual circle (the surface along which the outer surface 120o of the large-diameter curved plate portion 120 lies).

When attaching the ring adapter 500, the outer surface (second curved surface) 122o of the small diameter curved plate portion 122 of the first strain body F1 to the third strain body F3 is brought into contact with the inner circumferential surface of the ring adapter 500, and the chuck When the holding force sensor 100 is directly gripped, it functions as a contact surface against which the chuck comes into contact (details will be described later).

The three measurement strain gauges G are each attached to the bottom surface Rb of the recess R in the large-diameter curved plate portion 120 of the first to third flexure elements F1 to F3. Although the structure of the measuring strain gauge G is arbitrary, as an example, a strain gauge having four strain sensing elements may be used.

The three temperature compensation strain gauges CG are attached to the rear surface 111r of the disk portion 111 of the base portion 11 at equal intervals in the circumferential direction. Although the structure of the temperature compensation strain gauge CG is arbitrary, the same strain gauge as the measurement strain gauge G can be used.

One of the three measurement strain gauges G, one of the three temperature compensation strain gauges CG, and two fixed resistors (not shown) are connected by a wiring W (Fig. 1) to form a Wheatstone bridge circuit. There is. That is, the holding force sensor 100 includes three Wheatstone bridge circuits configured by three measurement strain gauges G, three temperature compensation strain gauges CG, and six fixed resistors (not shown). The wiring W extending from the measurement strain gauge G passes through the slit SL.

Each of the three Wheatstone bridge circuits is used to measure the load applied to the first to third strain bodies F1 to F3. Since each of the three Wheatstone bridge circuits includes one temperature-compensating strain gauge CG, temperature errors are suppressed. The calculation unit that calculates the load value based on the fixed resistance and the output of the Wheatstone bridge circuit may be provided externally or may be provided in the base portion 11.

The ring adapter 500 is configured such that the lower limit of the grippable range of the chuck to be measured (the range of the diameter of the workpiece/tool that the chuck can grip) is a small-diameter virtual circle along which the outer surface 122o of the second curved plate portion 122 of the holding force sensor 100 extends. This is an adapter placed between the chuck and the holding force sensor 100 when the chuck is larger than the diameter and cannot directly grip the holding force sensor 100.

As shown in FIG. 3, the ring adapter 500 has an annular shape in which three main body parts 501 are connected by three elastic connecting parts 502.

The three main body parts 501 are parts that are disposed between the jaws of the chuck and the first to third strain bodies F1 to F3 of the holding force sensor 100 and transmit the holding force of the chuck to the holding force sensor 100. be. Each of the three main body parts 501 is formed of a material having a high elastic modulus, such as metal (for example, SU material or SUS material).

The three main body parts 501 have the same configuration. Each of the three main body parts 501 has a shape in which a prism is curved into an arc along its central axis.

Each of the three main body parts 501 has a front surface 501f, a rear surface 501r (FIG. 1), an inner surface 501i, an outer surface 501o, and a pair of side surfaces 501s. The front surface 501f and the rear surface 501r have the same shape, and are fan-shaped when viewed in the axial direction. The inner surface 501i and the outer surface 501o are each curved surfaces extending along the circumferential direction. Each of the pair of side surfaces 501s is approximately rectangular. The radius of curvature of the inner surface 501i is equal to the radius of curvature of the outer surface 122o of the small diameter curved plate portion 122 of the first to third strain bodies F1 to F3 of the holding force sensor 100.

The three elastic connecting portions 502 are portions that connect the three main body portions 501 so as to be relatively movable. Each of the three elastic connecting portions 502 is formed of a material with a low elastic modulus such as resin (for example, rubber such as NBR).

The three elastic connecting parts 502 have the same configuration. Each of the three elastic connecting portions 502 has a shape in which a prismatic column is curved into an arc along its central axis.

Each of the three elastic connections 502 has a front surface 502f, a rear surface 502r (FIG. 1), an inner surface 502i, an outer surface 502o, and a pair of side surfaces 502s. The front surface 502f and the rear surface 502r have the same shape, and are fan-shaped when viewed in the axial direction. The inner surface 502i and the outer surface 502o are each curved surfaces extending along the circumferential direction. Each of the pair of side surfaces 502s is approximately rectangular.

A pair of side surfaces 502s of the elastic coupling section 502 are fixed to side surfaces 501s of the main body section 501 located on both sides of the elastic coupling section 502 in the circumferential direction, respectively. The main body portion 501 and the elastic connecting portion 502 may be fixed using adhesive, for example.

The holding force of the collet chuck 2000 is measured using the holding force sensor unit 1000 as follows.

The collet chuck 2000 has a main body M and three claws N, as shown in FIG. Each of the three claws N is a curved plate curved in the circumferential direction centered on the central axis X ₂₀₀₀ of the collet chuck 2000. The collet chuck ₂₀₀₀ moves the three jaws N in a radial direction (radial direction) centered on the central axis )do. Specifically, the object to be held is, for example, a workpiece or a tool.

First, if the lower limit of the grippable range of the collet chuck 2000 (range of diameters of workpieces/tools that the chuck can grip) is smaller than the diameter of the small-diameter virtual circle along which the outer surface 122o of the second curved plate portion 122 of the holding force sensor 100 follows. I will explain about it. In this case, the collet chuck 2000 can directly grip the holding force sensor 100, so the ring adapter 500 is not used.

When measuring the holding force of the collet chuck 2000, as shown in FIG. Insert the small diameter curved plate portion 122.

At this time, alignment is made so that the central axis X 100 of the holding force sensor ₁₀₀ is parallel to the central axis X ₂₀₀₀ of the collet chuck 2000. This positioning is performed by aligning the front surface Nf of the jaw N of the collet chuck 2000 (the surface facing the holding force sensor 100, FIG. 6(a)) with the first to third strain bodies F1 to F3 of the holding force sensor 100. This can be easily done by bringing it into contact with the front surface (alignment surface) 121f of the connecting portion 121 (FIG. 6(a)).

Further, the position of the holding force sensor 100 in the circumferential direction can be adjusted so that each of the three claws N of the collet chuck 2000 is located at a small diameter bend of any one of the first strain body F1 to the third strain body F3 of the holding force sensor 100. It is adjusted so that it contacts only the outer surface (abutted surface, second curved surface) 122o of the plate portion 122 (FIG. 5(a)).

When the collet chuck 2000 is operated with the holding force sensor 100 inserted and the three claws N are moved inward in the radial direction, the inner surfaces Ni of the three claws N move between the first strain body F1 and the third strain body F3. The collet chuck 2000 grips the first strain body F1 to the third strain body F3 as one body (collectively) (FIG. 5(a), FIG. 6(a)). )). In this state, the central axis X ₁₀₀ of the holding force sensor 100 coincides with the central axis X ₂₀₀₀ of the collet chuck 2000. In this specification and the present invention, the term "the central axis of the chuck and the central axis of the holding force sensor coincide" refers not only to the case where they completely coincide, but also to the case where they almost coincide but still maintain measurement accuracy. This also includes cases where there is a slight deviation within the range obtained.

After that, when the three claws N of the collet chuck 2000 are further moved radially inward, the free end sides of the first strain body F1 to the third strain body F3 are pressed radially inward, and the first strain body F1 - Strain occurs in the third flexure element F3.

A load (holding) is applied to the first flexure element F1 by a claw N in contact with the first flexure element F1 via a Wheatstone bridge including a measuring strain gauge G attached to the first flexure element F1. force) can be found. Similarly, the claws N that are in contact with the second and third strain bodies F2 and F3 are transmitted through the Wheatstone bridge including the measuring strain gauge G attached to the second and third strain bodies F2 and F3. The magnitude of the load (holding force) applied to the second and third strain bodies F2 and F3 can be determined.

The holding force (gripping force) of the collet chuck 2000 can be calculated from the sum of the loads applied to the first to third strain bodies F1 to F3. Further, the balance of the holding force by each jaw of the collet chuck 2000 can be determined based on the balance of the loads applied to the first to third strain bodies F1 to F3. It can be seen that if the magnitudes of the loads applied to the first to third strain bodies F1 to F3 are the same, the collet chuck 2000 can hold the workpiece or tool in a well-balanced manner in the circumferential direction. On the other hand, if there are variations in the magnitude of the loads applied to the first to third flexure elements F1 to F3, it can be seen that there are variations in the holding force of the three jaws N of the collet chuck 2000.

Next, a case will be described in which the lower limit of the grippable range of the collet chuck 2000 is larger than the diameter of the small-diameter virtual circle along which the outer surface 122o of the second curved plate portion 122 of the holding force sensor 100 follows. In this case, the holding force sensor 100 cannot be directly gripped by the collet chuck 2000, so the ring adapter 500 is used.

When measuring the holding force of the collet chuck 2000, as shown in FIG. 5(b) and FIG. A ring adapter 500 is placed around the portion 122. As described above, the radius of curvature of the inner surface 501i of the main body portion 501 of the ring adapter 500 is equal to the radius of curvature of the outer surface 122o of the small diameter curved plate portion 122. Therefore, the ring adapter 500 is attached to the holding force sensor 100, the inner surface 501i of the main body part 501 of the ring adapter 500 is brought into contact with the outer surface 122o of the small diameter curved plate part 122, and the rear surface 501r of the main body part 501 of the ring adapter 500 is When the ring adapter 500 is brought into contact with the front surface (alignment surface) 121f of the connecting plate portion 121 of the flexure element F1 to the third flexure element F3, the center axis X ₅₀₀ of the ring adapter 500 coincides with the center axis X ₁₀₀ of the holding force sensor 100. do.

Furthermore, the position of the ring adapter 500 in the circumferential direction is such that each of the three main body parts 501 of the ring adapter 500 has a small diameter curve of any one of the first strain body F1 to the third strain body F3 of the holding force sensor 100. Adjust so that it contacts only the plate portion 122.

Next, the small diameter curved plate portions 122 of the first to third strain bodies F1 to F3 of the holding force sensor 100 and the ring adapter 500 are inserted inside the three jaws N of the collet chuck 2000. At this time, alignment is made so that the central axis X 100 of the holding force sensor ₁₀₀ is parallel to the central axis X ₂₀₀₀ of the collet chuck 2000. This positioning is performed by bringing the front surface Nf of the claw N of the collet chuck 2000 into contact with the front surface (alignment surface) 121f of the connecting portion 121 of the first strain body F1 to the third strain body F3 of the holding force sensor 100. This can be easily done (FIG. 6(b)). In the first embodiment, since the radial dimension of the main body 501 of the ring adapter 500 is smaller than the radial dimension of the front surface 121f of the connecting portion 121, even when the ring adapter 500 is attached to the holding force sensor 100, the front surface 121f Alignment can be performed using

Further, the positions of the holding force sensor 100 and the ring adapter 500 in the circumferential direction are adjusted so that each of the three claws N of the collet chuck 2000 contacts only the outer surface 501o of the main body 501 of any one of the ring adapters 500. (Figure 5(b)).

When the collet chuck 2000 is operated with the holding force sensor 100 and the ring adapter 500 inserted and the three claws N are moved inward in the radial direction, the inner surfaces Ni of the three claws N are attached to the three main body parts 501 of the ring adapter 500. The collet chuck 2000 grips the first flexure element F1 to the third flexure element F3 as one body (collectively) via the ring adapter 500 (FIGS. 5(b) and 6). (b)). In this state, the central axis X ₁₀₀ of the holding force sensor 100 coincides with the central axis X ₂₀₀₀ of the collet chuck 2000.

After that, when the three jaws N of the collet chuck 2000 are further moved radially inward, the free end sides of the first strain body F1 to the third strain body F3 are moved radially inward via the main body 501 of the ring adapter 500. , and strain is generated in the first to third strain-generating bodies F1 to F3. The three main body parts 501 of the ring adapter 500 are connected via elastic connection parts 502 so as to be relatively movable. Therefore, the three main bodies 501 move radially inward substantially independently of each other in accordance with the movement of the claws N of the collet chuck 2000.

As a result, the holding force of the collet chuck 2000 can be calculated in the same way as when the ring adapter 500 is not used, and the balance of the holding force by each jaw of the collet chuck 2000 can be grasped.

The effects of the holding force sensor 100 and the holding force sensor unit 1000 of the first embodiment are summarized below.

In the holding force sensor 100 of the first embodiment, a measuring strain gauge G is provided in the holding force sensor 100 which is separate from the chuck. Therefore, the holding force of the chuck can be easily measured by simply gripping the holding force sensor 100 with the chuck. In addition, measurement reliability is higher than when a measurement strain gauge is provided on a chuck that is a rotating body and may be exposed to cutting oil or the like.

The holding force sensor 100 of the first embodiment has a first strain body F1, a second strain body F2, and a third strain body F3, and the three claws N of the collet chuck 2000 are connected to the first strain body F1, a second strain body F2, and a third strain body F3. The load due to the three claws N is measured independently by making the body F1, the second strain body F2, and the third strain body F3 come into contact with each other. Therefore, it is possible to measure not only the holding force of the chuck as a whole, but also the balance of the holding force of the chuck in the circumferential direction. When performing high-precision finishing on a workpiece, it is important to hold the workpiece in a well-balanced manner in the circumferential direction. Therefore, it is advantageous to be able to measure the circumferential balance of the holding force of the chuck.

In the holding force sensor 100 of the first embodiment, the measurement strain gauge G is attached to the large diameter curved plate portions 120 of the first strain body F1, the second strain body F2, and the third strain body F3. . Therefore, the sensitivity of load measurement can be adjusted simply by adjusting the thickness of the large diameter curved plate portion 120. For example, by simply reducing the thickness of the large-diameter curved plate portion 120, a highly sensitive holding force sensor that can be used for measuring the holding force of a chuck for precision finishing can be easily obtained.

The holding force sensor 100 of the first embodiment has an alignment surface formed by the front surface 121f of the connecting portion 121 of the first strain body F1 to the third strain body F3. Therefore, when the holding force sensor 100 is gripped by the chuck, the holding force sensor 100 can be easily adjusted to an appropriate posture in which the central axis X ₁₀₀ of the holding force sensor 100 is parallel to the central axis of the chuck.

The holding force sensor unit 1000 of the first embodiment includes a ring adapter 500. Therefore, by using the ring adapter 500 according to the grippable range of the chuck to be measured, it is possible to measure the holding force of many types of chucks having different grippable ranges.

In the holding force sensor unit 1000 of the first embodiment, the following modification may also be used.

Although the holding force sensor 100 of the first embodiment has three strain bodies arranged in the circumferential direction, the present invention is not limited thereto. The number of strain bodies that the holding force sensor 100 has may be any number greater than or equal to 2, and may be, for example, 5, 8, 11, or the like. More specifically, for example, the structure is the same as that of the first flexure element F1 to the third flexure element F3 except that the circumferential dimension is larger than that of the first flexure element F1 to third flexure element F3. Two strain-generating bodies may be arranged in the circumferential direction. Alternatively, a strain body having the same structure as the first strain body F1 to third strain body F3 except that the circumferential dimension is smaller than the first strain body F1 to third strain body F3. Four or more may be arranged in the circumferential direction. An arbitrary number of strain bodies may be arranged at equal intervals in the circumferential direction. The circumferential balance of the holding force of the chuck can be well measured when the number of flexure elements is 3 or more, and it can be better measured when the number of flexure elements is 4 or more. .

The holding force sensor unit 100 having n strain bodies (n is an integer of 2 or more) can be suitably used for a chuck having n jaws. FIG. 7 shows how the holding force of a diaphragm chuck 2001 having eight jaws is measured using the holding force sensor 101 having eight strain bodies.

In the holding force sensor 100 of the first embodiment, each of the first strain body F1 to the third strain body F3 has a large diameter curved plate portion 120, a connecting portion 121, and a small diameter curved plate portion 122. is not limited. The strain-generating body included in the strain-generating portion 12 of the holding force sensor 100 can be cantilever-supported by the base portion 11 and may have any shape having a free end.

Specifically, for example, a shape may be adopted in which the axial dimension of the large diameter curved plate portion 120 is increased and the connecting portion 121 and the small diameter curved plate portion 122 are removed. In this case, the front end 120Ef of the large diameter curved plate portion 120 becomes a free end, and the outer surface 120o near the front end 120Ef functions as a contact surface against which the jaws of the chuck come into contact.

The strain-generating body of the strain-generating portion 12 may be a beam-shaped strain-generating body in which a square bar or a round bar is cantilever-supported by the base portion 11 . In this case, the radially outer surface near the free end of the beam-like strain body becomes the abutted surface.

The abutted surface does not necessarily have to be a curved surface along a virtual circle centered on the central axis X ₁₀₀ of the holding force sensor 100, and may have any form depending on the shape of the strain body. For example, in an embodiment in which each rod includes a beam-shaped strain body supported in a cantilever manner, the contact surface is a flat surface extending perpendicularly to the radial direction. That is, the abutted surface may be in any form that can be abutted by the jaws of the chuck to be measured.

Regardless of the shape of the strain body, the contact surfaces may be located at equal distances from the central axis X ₁₀₀ of the holding force sensor 100. That is, the contact surfaces of each of the plurality of strain-generating bodies may be located on a virtual circle centered on the central axis X ₁₀₀ of the holding force sensor 100. For example, if the abutted surface is a flat surface and a part or center of the abutted surface is on a virtual circle, the abutted surface can be considered to be on a virtual circle. As a result, the jaws of the chuck to be measured come into even contact with the plurality of contact surfaces, improving measurement accuracy.

Note that the chuck claws are generally arranged at equal intervals around the central axis of the chuck. Therefore, the contact surfaces of the plurality of strain-generating bodies of the holding force sensor 100 may also be arranged at equal intervals along a virtual circle centered on the central axis X ₁₀₀ of the holding force sensor 100.

Regardless of the shape of the strain body, the thickness of the strain body in the radial direction in the area where the measurement strain gauge G is attached should be smaller than the thickness in other areas of the strain body. Accordingly, the sensitivity of holding force measurement can be increased.

In the holding force sensor 100 of the first embodiment, the measurement strain gauges G are attached to each of the first strain body F1 to the third strain body F3, but the present invention is not limited to this. It is also possible to use an embodiment in which the measurement strain gauge G is attached to at least one of the first to third strain bodies F1 to F3. Similarly, in the holding force sensor 100 having n strain bodies (n is an integer of 2 or more), a strain gauge G may be attached to at least one strain body. In this case as well, the strength of the gripping force can be determined easily and with high reliability.

In the holding force sensor 100 of the first embodiment, the temperature compensation strain gauge CG may be omitted.

Although the ring adapter 500 of the first embodiment uses a curved columnar elastic connection portion 502 made of resin such as rubber, the present invention is not limited to this. For example, a coil spring can also be used as the elastic connection portion 502.

Note that, as described above, the chuck claws are generally arranged at equal intervals around the central axis of the chuck. Therefore, the main body portions 501 of the ring adapter 500 may also be provided at equal intervals in the circumferential direction.

The ring adapter 500 of the first embodiment may have a C-ring shape with a portion removed in the circumferential direction. In this case, the C annular ring adapter 500 may be constructed of only the C annular main body portion 501. Alternatively, the C-shaped ring adapter 500 may be configured with a plurality of main body portions 501 and one or more elastic connection portions 502.

<Second embodiment>
The holding force sensor (gripping force sensor) 200 of the second embodiment will be described using an example in which the holding force (gripping force) of the collet chuck 2000 (FIG. 4) is measured using the holding force sensor 200. In the description, reference is made to FIGS. 8-11.

As shown in FIGS. 8, 9(a), and 9(b), the holding force sensor 200 includes an annular base portion ₂₁ having a center axis (sensor center axis) It mainly includes three measurement strain gauges G attached to the strain part 22 and three temperature compensation strain gauges CG attached to the base part 21. The base portion 21 and the strain-generating portion 22 may be integrally formed of metal (for example, stainless steel) or the like.

In the following description, the direction in which the central axis X ₂₀₀ extends will be referred to as the axial direction of the holding force sensor 200, and the side where the strain generating part 22 is located will be referred to as the front side, and the side where the base part 21 will be located will be referred to as the rear side. The radial direction centered on the axial direction is called the radial direction of the holding force sensor 200, and the direction around the axial direction is called the circumferential direction of the holding force sensor 200.

The base portion 21 is a portion that serves as the foundation of the holding force sensor 200, and is a portion that does not undergo deformation (strain) when measuring the holding force of the object to be measured.

The base portion 21 is annular and has a front surface 21f and a rear surface 21r. A circular through hole 21h extending axially about the central axis X ₂₀₀ is provided in the radial center of the base portion 21.

The strain-generating portion 22 is a portion supported by the base portion 21, and is a portion that exhibits deformation (strain) in accordance with the magnitude of the holding force when measuring the holding force of the object to be measured.

Roughly speaking, as shown in FIGS. 8, 9(a) and 9(b), the strain-generating portion 22 connects four cylinders having different outer diameters coaxially along the central axis X ₂₀₀ . It has a shape in which it is divided into six parts in the circumferential direction and a total of three parts are removed from every other part.

Specifically, the strain-generating portion 22 includes a first strain-generating body FF1, a second strain-generating body FF2, and a third strain-generating body FF3 along the circumferential direction. The first strain body FF1, the second strain body FF2, and the third strain body FF have the same shape.

Each of the first flexural body FF1 to the third flexural body FF3 includes a large-diameter curved plate portion 220, a first fan-shaped plate portion 221, a second fan-shaped plate portion 222, a third fan-shaped plate portion 223, and a fourth fan-shaped plate portion. 224.

The large-diameter curved plate portion 220 is a curved plate that is curved about the central axis X ₂₀₀ . A rear end 220Er of the large diameter curved plate portion 220 is fixed to the front surface 21f of the base portion 21.

A recess R is provided in the circumferential center of the outer surface 220o of the large diameter curved plate portion 220. The bottom surface Rb of the recess R is a flat surface perpendicular to the radial direction.

The first fan-shaped plate part 221, the second fan-shaped plate part 222, the third fan-shaped plate part 223, and the fourth fan-shaped plate part 224 are each fan-shaped flat plates that extend radially along the radial direction. The outer diameters of the first fan-shaped plate portion 221, the second fan-shaped plate portion 222, the third fan-shaped plate portion 223, and the fourth fan-shaped plate portion 224 decrease in this order. On the other hand, the inner diameters of the first fan-shaped plate part 221, the second fan-shaped plate part 222, the third fan-shaped plate part 223, and the fourth fan-shaped plate part 224 are equal to each other.

A front end 220Ef of the large-diameter curved plate portion 220 is fixed to the rear surface 221r of the first fan-shaped plate portion 221 along the outer surface 221o of the first fan-shaped plate portion 221.

The outer diameter (radius) of the first fan-shaped plate portion 221 is equal to the radius of curvature of the outer surface 220o of the large diameter curved plate portion 220. That is, the outer surface 221o of the first fan-shaped plate section 221 and the outer surface 220o of the large-diameter curved plate section 220 are connected without any step, forming a series of curved surfaces.

The rear surface of the second fan-shaped plate section 222 is fixed to the front surface 221f of the first fan-shaped plate section 221. The second fan-shaped plate portion 222 and the first fan-shaped plate portion 221 are aligned so that both end surfaces in the circumferential direction are flush with each other, and the inner circumferential side surfaces are flush with each other. In this state, the outer surface 222o of the second fan-shaped plate section 222 and the outer surface 221o of the first fan-shaped plate section 221 extend coaxially about the central axis _X200 .

The rear surface of the third fan-shaped plate section 223 is fixed to the front surface 222f of the second fan-shaped plate section 222. The third fan-shaped plate portion 223 and the second fan-shaped plate portion 222 are aligned so that both end surfaces in the circumferential direction are flush with each other, and the inner circumferential side surfaces are flush with each other. In this state, the outer surface 223o of the third fan-shaped plate section 222 and the outer surface 222o of the second fan-shaped plate section 222 extend coaxially about the central axis _X200 .

The rear surface of the fourth fan-shaped plate section 224 is fixed to the front surface 223f of the third fan-shaped plate section 223. The fourth fan-shaped plate portion 224 and the third fan-shaped plate portion 223 are aligned so that both end surfaces in the circumferential direction are flush with each other, and their inner peripheral surfaces are flush with each other. In this state, the outer surface 224o of the fourth fan-shaped plate section 224 and the outer surface 223o of the third fan-shaped plate section 223 extend coaxially about the central axis _X200 .

The large diameter curved plate portions 220 of the first to third strain bodies FF1 to FF3 are arranged at equal intervals along the circumferential direction. Each of the large diameter curved plate portions 220 of the first to third strain bodies FF1 to FF3 can also be regarded as part of a virtual large diameter cylinder having the central axis X ₂₀₀ as its central axis. The outer surface 220o of the large diameter curved plate portion 220 extends along the outer peripheral surface of the virtual large diameter cylinder. That is, the outer surface 220o of the large-diameter curved plate portion 220 of the first to third strain-generating bodies FF1 to FF3 is a curved surface extending along a large-diameter virtual circle centered on the central axis _X200 .

The first fan-shaped plate portion 221, the second fan-shaped plate portion 222, the third fan-shaped plate portion 223, and the fourth fan-shaped plate portion 224 of the first strain body FF1 to the third strain body FF3 are arranged along the circumferential direction. They are placed at equal intervals. The first fan-shaped plate portions 221 of the first to third strain bodies FF1 to FF3 can also be considered as part of a first virtual disk whose central axis is the central axis _X200 . Similarly, the second fan-shaped plate portion 222, the third fan-shaped plate portion 223, and the fourth fan-shaped plate portion 224 of the first strain body FF1 to the third strain body FF3 are connected to the second fan-shaped plate portion 222, the third fan-shaped plate portion 223, and the fourth fan-shaped plate portion ₂₂₄ of It can also be considered as part of a virtual disk, a third virtual disk, and a fourth virtual disk.

That is, the outer surface 221o of the first fan-shaped plate part 221, the outer surface 222o of the second fan-shaped plate part 222, the outer surface 223o of the third fan-shaped plate part 223, and the outer surface 224o of the fourth fan-shaped plate part 224 each have a central axis X _200. It is a curved surface extending along a first virtual circle, a second virtual circle, a third virtual circle, and a fourth virtual circle that are centered. The diameters of the first virtual circle, the second virtual circle, the third virtual circle, and the fourth virtual circle become smaller in this order.

The outer surface 222o of the second fan-shaped plate portion 222, the outer surface 223o of the third fan-shaped plate portion 223, and the outer surface 224o of the fourth fan-shaped plate portion 224 of the first strain body FF1 to the third strain body FF3 are each held by a chuck. It functions as a contact surface against which the chuck contacts when gripping the force sensor 200 (details will be described later).

Further, the front surface 221f of the first fan-shaped plate section 221, the front surface 222f of the second fan-shaped plate section 222, and the front surface 223f of the third fan-shaped plate section 223 are each flat surfaces extending along a plane orthogonal to the central axis _X200 . be.

The front surface 221f of the first fan-shaped plate section 221, the front surface 222f of the second fan-shaped plate section 222, and the front surface 223f of the third fan-shaped plate section 223 of the first flexure element FF1 to the third flexure element FF3 are the tip of the chuck, respectively. functions as a positioning surface against which is abutted (details will be described later).

The three measurement strain gauges G are attached to the bottom surface Rb of the recess R in the large diameter curved plate portions 220 of the first to third strain bodies FF1 to FF3. Although the structure of the measuring strain gauge G is arbitrary, as an example, a strain gauge having four strain sensing elements may be used.

The three temperature compensation strain gauges CG are attached to the rear surface 21r of the base portion 21 at equal intervals in the circumferential direction. Although the structure of the temperature compensation strain gauge CG is arbitrary, the same strain gauge as the measurement strain gauge G can be used.

Similar to the holding force sensor 100 of the first embodiment, three Wheatstone bridges are configured using three measurement strain gauges G, three temperature compensation strain gauges CG, and six fixed resistors (not shown). There is. The wiring W (FIG. 8) extending from the measurement strain gauge G passes through the gap between the first strain body FF1 to the third strain body FF3.

Each of the three Wheatstone bridge circuits is used to measure the load applied to the first to third strain bodies FF1 to FF3. A calculation unit that calculates the load value based on the fixed resistance and the output of the Wheatstone bridge circuit may be provided externally, or may be provided in the base portion 21.

The holding force of the collet chuck 2000 (FIG. 4) is measured using the holding force sensor 200 as follows.

When measuring the holding force of the collet chuck 2000 using the holding force sensor 200, the first to third strain bodies FF1 to FF3 of the holding force sensor 200 are placed inside the three claws N of the collet chuck 2000. Insert. The grippable range of the collet chuck 2000 (the workpiece/tool that the chuck can grip The optimum position according to the diameter range of the collet chuck 2000 is held by the claws N of the collet chuck 2000.

First, the grippable range of the collet chuck 2000 is the fourth virtual disk of the holding force sensor 200 (that is, the virtual disk including the fourth fan-shaped plate portion 224 of the first strain body FF1 to the third strain body FF3). , the fourth fan-shaped plate portions 224 of the first to third strain bodies FF1 to FF3 are inserted inside the three jaws N of the collet chuck 2000.

At this time, alignment is made so that the central axis X 200 of the holding force sensor ₂₀₀ is parallel to the central axis X ₂₀₀₀ of the collet chuck 2000. This positioning is performed by bringing the front surface Nf of the claw N of the collet chuck 2000 into contact with the front surface (alignment surface) 223f of the third fan-shaped plate portion 223 of the first strain body FF1 to third strain body FF3. This can be easily done (FIG. 11(a)).

Further, each of the three claws N of the collet chuck 2000 adjusts the position of the holding force sensor 200 in the circumferential direction to the fourth position of any one of the first to third strain bodies FF1 to FF3 of the holding force sensor 200 It is adjusted so that it contacts only the outer surface (abutted surface) 224o of the fan-shaped plate portion 224 (FIG. 10(a)).

The grippable range of the collet chuck 2000 is outside the third virtual disk of the holding force sensor 200 (that is, the virtual disk including the third fan-shaped plate portion 223 of the first strain body FF1 to the third strain body FF3). If the diameter is included, the fourth fan-shaped plate portion 224 and the third fan-shaped plate portion 223 of the first to third strain elements FF1 to FF3 are inserted inside the three claws N of the collet chuck 2000.

At this time, in order to align the central axis X ₂₀₀ of the holding force sensor 200 and the central axis X 2000 of the collet chuck ₂₀₀₀ , the front surface of the second fan-shaped plate portion 222 of the first strain body FF1 to third strain body FF3 is (Alignment surface) 222f is used (FIG. 11(b)).

Furthermore, each of the three claws N of the collet chuck 2000 can adjust the position of the holding force sensor 200 in the circumferential direction to the third position of any one of the first to third strain bodies FF1 to FF3 of the holding force sensor 200. It is adjusted so that it contacts only the outer surface (abutted surface) 223o of the fan-shaped plate portion 223 (FIG. 10(b)).

The graspable range of the collet chuck 2000 is outside the second virtual disk of the holding force sensor 200 (that is, the virtual disk including the third fan-shaped plate portion 223 of the first strain body FF1 to the third strain body FF3). If the diameter is included, the fourth fan-shaped plate portion 224, the third fan-shaped plate portion 223, and the second fan-shaped plate portion of the first strain body FF1 to the third strain body FF3 are placed inside the three jaws N of the collet chuck 2000. 222 is inserted.

At this time, in order to align the central axis X ₂₀₀ of the holding force sensor 200 and the central axis X ₂₀₀₀ of the collet chuck 2000, it is necessary to (Alignment surface) 221f is used. Further, each of the three claws N of the collet chuck 2000 adjusts the circumferential position of the holding force sensor 200 to the second position of any one of the first strain body FF1 to the third strain body FF3 of the holding force sensor 200. It is adjusted so that it contacts only the outer surface (abutted surface) 222o of the fan-shaped plate portion 222.

When the collet chuck 2000 is operated with the holding force sensor 200 inserted and the three claws N are moved inward in the radial direction, the inner surfaces Ni of the three claws N are moved between the first strain body FF1 and the third strain body FF3. The collet chuck 2000 contacts the outer surface 224o of the fourth fan-shaped plate portion 224 (or the outer surface 223o of the third fan-shaped plate portion 223, or the outer surface 222o of the second fan-shaped plate portion 222), and the collet chuck 2000 The strain body FF3 is held as one (collectively) (FIG. 10(a), FIG. 10(b), FIG. 11(a), FIG. 11(b)). In this state, the central axis X ₂₀₀ of the holding force sensor 200 coincides with the central axis X ₂₀₀₀ of the collet chuck 2000.

After that, when the three claws N of the collet chuck 2000 are further moved radially inward, the free end sides of the first strain body FF1 to third strain body FF3 are pressed radially inward, and the first strain body FF1 - Strain occurs in the third strain body FF3. Thereby, similarly to the holding force sensor 100 of the first embodiment, it is possible to calculate the holding force of the collet chuck 2000 and measure the balance of the holding forces by the respective claws of the collet chuck 2000.

The effects of the holding force sensor 200 of the second embodiment are summarized below.

In the holding force sensor 200 of the second embodiment, each of the first strain body FF1 to the third strain body FF3 has a second fan-shaped plate portion 222 to a fourth fan-shaped plate portion 224 having mutually different outer diameters, Depending on the grippable range of the chuck to be measured, the object to be measured is attached to one of the outer surface 222o of the second fan-shaped plate 222, the outer surface 223o of the third fan-shaped plate 223, and the outer surface 224o of the fourth fan-shaped plate 224. The chuck can be brought into contact with it. Therefore, it is possible to measure the holding force of many types of chucks with different grippable ranges.

The holding force sensor 200 of the second embodiment has a front surface 221f of the first fan-shaped plate portion 221 of the first strain body FF1 to third strain body FF3, a front surface 222f of the second fan-shaped plate portion 222, and a third fan-shaped plate. It has an alignment surface constituted by the front surface 223f of the portion 223. Therefore, when the holding force sensor 200 is gripped by the chuck, the holding force sensor 200 can be easily adjusted to an appropriate posture in which the central axis X ₂₀₀ of the holding force sensor 200 is parallel to the central axis of the chuck.

Like the holding force sensor 100 of the first embodiment, the holding force sensor 200 of the second embodiment is easy to measure, has high measurement reliability, and measures not only the holding force of the entire chuck but also the circumferential direction. The balance of the holding force of the chuck can also be measured.

Similar to the holding force sensor 100 of the first embodiment, the holding force sensor 200 of the second embodiment can increase the sensitivity of load measurement simply by reducing the thickness of the large diameter curved plate portion 220, and has a precision finish. It is possible to easily obtain a highly sensitive holding force sensor that can be used to measure the holding force of a chuck for use.

In the holding force sensor 200 of the second embodiment, the following modification may also be used.

Although the holding force sensor 200 of the second embodiment has three strain-generating bodies arranged in the circumferential direction, the present invention is not limited thereto. The number of strain bodies that the holding force sensor 200 has may be any number greater than or equal to two, and may be, for example, five, nine, eleven, or the like. More specifically, for example, the structure is the same as that of the first strain body FF1 to third strain body FF3 except that the circumferential dimension is larger than that of the first strain body FF1 to third strain body FF3. Two strain-generating bodies may be arranged in the circumferential direction. Alternatively, a strain body having the same structure as the first strain body FF1 to third strain body FF3 except that the circumferential dimension is smaller than the first strain body FF1 to third strain body FF3. Four or more may be arranged in the circumferential direction. An arbitrary number of strain bodies may be arranged at equal intervals in the circumferential direction.

The holding force sensor 200 having n strain bodies (n is an integer of 2 or more) can be suitably used for a chuck having n jaws.

In the holding force sensor 200 of the second embodiment, the first strain body FF1 to the third strain body FF3 each have a large-diameter curved plate portion 220 and a first fan-shaped plate portion 221 to a fourth fan-shaped plate portion 224. However, it is not limited to this. The strain-generating body of the strain-generating portion 22 of the holding force sensor 200 is cantilever-supported by the base portion 21, has a free end, and is an abutted portion on a first virtual circle centered on the central axis X ₂₀₀ . , and an abutted part located on a second imaginary circle centered on the central axis X ₂₀₀ and having a smaller diameter than the first imaginary circle on the free end side of the abutted part.

Specifically, for example, a shape in which the fourth fan-shaped plate portion 224 is removed from the first to third strain bodies FF1 to FF3 of the second embodiment may be adopted. In this case, the front surface 223f of the third fan-shaped plate 223 becomes a free end, and the outer surface 223o of the third fan-shaped plate 223 and the outer surface 222o of the second fan-shaped plate 222 become abutted surfaces.

The strain-generating body of the strain-generating portion 22 is a substantially Z-shaped member made by bending a square bar or round bar twice at right angles, or a step-shaped member made by bending a square bar or round bar at right angles multiple times. It may be supported in a cantilever manner by the base portion 21. In this case, the radially outer surface near the free end functions as the contact surface on the smallest virtual circle, and the radially outer surface in the area on the fixed end side across the stepped portion functions as the next smallest virtual circle. Functions as the upper abutted surface. The front surface of the step functions as an alignment surface.

The first strain body FF1 to the third strain body FF3 of the strain body 22 of the second embodiment have three abutted portions located on three virtual circles having different diameters, It is not limited to this. The number of contact surfaces provided along the axial direction of the strain body and located on virtual circles having mutually different diameters may be any number greater than or equal to two. The greater the number of contact surfaces that the strain body has, the more versatile the holding force sensor is.

In order to increase the number of abutted surfaces, for example, the front surface of the fourth fan-shaped plate part 224 of the first flexure element FF1 to the third flexure element FF3 is made to have a larger number of surfaces than the fourth fan-shaped plate part 224. Connect the rear surface of the fan-shaped plate portion with a small outer diameter. As a result, the outer surface of the fan-shaped plate portion becomes an abutted surface located on an imaginary circle centered on the central axis X ₂₀₀ and having a smaller diameter than the fourth imaginary circle.

The abutted surface does not necessarily have to be a curved surface along a virtual circle centered on the central axis X ₂₀₀ of the holding force sensor 200, and may have any form depending on the shape of the strain body. For example, in an embodiment in which each rod is provided with a strain-generating body having a bent shape, the abutted surface is a flat surface extending perpendicularly to the radial direction. That is, the abutted surface may be in any form that can be abutted by the jaws of the chuck to be measured. For example, if the abutted surface is a flat surface and a part or center of the abutted surface is on a virtual circle, the abutted surface can be considered to be on a virtual circle.

Note that, as described above, the chuck claws are generally arranged at equal intervals around the central axis of the chuck. Therefore, the contact surfaces of the plurality of strain bodies of the holding force sensor 200 may also be arranged at equal intervals along a virtual circle centered on the central axis X ₂₀₀ of the holding force sensor 200.

Regardless of the shape of the strain body, the thickness of the strain body in the radial direction in the area where the measurement strain gauge G is attached should be smaller than the thickness in other areas of the strain body. Accordingly, the sensitivity of holding force measurement can be increased.

In the holding force sensor 200 of the second embodiment, the measurement strain gauges G are attached to each of the first to third strain bodies FF1 to FF3, but the present invention is not limited to this. It is also possible to use an embodiment in which the measurement strain gauge G is attached to at least one of the first to third strain bodies FF1 to FF3. Similarly, in the holding force sensor 200 having n strain bodies (n is an integer of 2 or more), a strain gauge G may be attached to at least one strain body. In this case as well, the strength of the gripping force can be determined easily and with high reliability.

In the holding force sensor 200 of the second embodiment, the temperature compensation strain gauge CG may be omitted.

Each of the above embodiments may be applied in combination as long as there is no contradiction with each other. For example, a holding force sensor unit may be configured by combining the holding force sensor 200 of the second embodiment and the ring adapter 500 of the first embodiment.

In the above description, collet chucks and diaphragm chucks are mentioned as examples of chucks, but chucks are not limited to these. For example, it may be a scroll chuck.

As long as the characteristics of the present invention are maintained, the present invention is not limited to the above embodiments, and other forms that can be considered within the scope of the technical idea of the present invention are also included within the scope of the present invention. .

11, 21 Base part, 21, 22 Strain generating part, 100, 200 Holding force sensor, 1000 Holding force sensor unit, 2000 Collet chuck, 2001 Diaphragm chuck, F1, F2, F3, FF1, FF2, FF3 Strain body, G Strain gauge for measurement, CG Strain gauge for temperature compensation

Claims (10)

A holding force sensor that is gripped by a chuck and measures the holding force of the chuck,
The base part and
a plurality of flexure-generating bodies disposed on one side of the base portion, each of which is cantilever-supported by the base portion and has a free end;
a strain gauge attached to at least one of the plurality of strain-generating bodies,
In order to measure the holding force, the holding force sensor is a holding force sensor in which the free end side of the plurality of flexure generating bodies is held as one body by the chuck rather than the strain gauge,
Each of the plurality of strain-generating bodies has an abutted part, which is abutted by the chuck in order to grasp the holding force sensor, on the free end side of the strain gauge;
The holding force sensor has a sensor center axis that coincides with the center axis of the chuck when held by the chuck,
The abutted portion is located on a virtual circle centered on the sensor central axis,
Each of the plurality of strain-generating bodies has an alignment surface that comes into contact with the tip of the chuck when the chuck grips the holding force sensor , and the alignment surface has a strain that is lower than the abutted portion. A holding force sensor extending in a plane perpendicular to the sensor center axis on the gauge side. Each of the plurality of strain bodies has a first curved surface that curves in an arc around the sensor central axis, a second curved surface that curves in an arc around the sensor central axis with a smaller radius of curvature than the first curved surface, and a connecting surface extending in a plane perpendicular to the sensor central axis and connecting the first curved surface and the second curved surface;
The strain gauge is attached to a first curved surface of at least one of the plurality of strain bodies,
The holding force sensor according to claim 1, wherein the second curved surface of each of the plurality of strain bodies has the abutted portion. A holding force sensor that is gripped by a chuck and measures the holding force of the chuck,
The base part and
a plurality of flexure-generating bodies disposed on one side of the base portion, each of which is cantilever-supported by the base portion and has a free end;
a strain gauge attached to at least one of the plurality of strain-generating bodies,
a holding force sensor in which the free ends of the plurality of flexure generating bodies are integrally gripped by the chuck in order to measure the holding force;
Each of the plurality of strain-generating bodies has an abutted portion, which is abutted by the chuck in order to grip the holding force sensor, on the free end side of the strain gauge;
The holding force sensor has a sensor center axis that coincides with the center axis of the chuck when held by the chuck,
The abutted portion is located on a virtual circle centered on the sensor central axis,
Each of the plurality of strain bodies has a first curved surface that curves in an arc around the sensor central axis, a second curved surface that curves in an arc around the sensor central axis with a radius of curvature smaller than the first curved surface, and a connecting surface extending in a plane perpendicular to the sensor central axis and connecting the first curved surface and the second curved surface;
The strain gauge is attached to a first curved surface of at least one of the plurality of strain bodies,
A holding force sensor in which a second curved surface of each of the plurality of strain bodies has the abutted portion. The holding force sensor according to claim 1 , wherein the contact portions of the plurality of strain-generating bodies are provided at equal intervals along the virtual circle. The holding force sensor according to any one of claims 1 to 4, wherein the abutted portion of each of the plurality of strain-generating bodies is a curved surface extending along a virtual circle centered on the sensor central axis. The plurality of strain-generating bodies are adjacent to each other via a slit or a gap,
The holding force sensor according to any one of claims 1 to 5 , wherein a wiring extending from the strain gauge extends to the base portion through the slit or the gap. The holding force sensor according to any one of claims 1 to 6 , wherein the thickness of the plurality of strain-generating bodies is smaller at a position where the strain gauge is attached than at other positions. The holding force sensor according to any one of claims 1 to 7 , further comprising a temperature compensation strain gauge attached to the base portion. The holding force sensor according to any one of claims 1 to 8 , wherein the plurality of flexure elements are at least two flexure elements. The holding force sensor according to any one of claims 1 to 9 , wherein the strain gauge is attached to each of the plurality of strain bodies.

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