JP6878668B2 - Force sensor - Google Patents

Description

An embodiment of the present invention relates to a 6-axis force sensor used for, for example, a robot arm.

The force sensor is used, for example, in a robot arm or the like, and detects an external force and torque in the XYZ directions (see, for example, Patent Documents 1 and 2).

In the force sensor, the external force applied to the receiving body as the movable part is transmitted to, for example, the diaphragm part as the strain generating body, and the deformation of the diaphragm part is converted into an electric signal and detected.

Here, if an excessive external force is applied to the diaphragm portion, the deformation of the diaphragm portion exceeds the limit, and even after the external force is removed, the shape of the diaphragm portion is not restored to its original shape or the diaphragm portion is damaged. There is a risk.

Therefore, in order to protect the diaphragm portion from such an excessive external force, a protection mechanism such as a stopper that regulates the displacement of the receiving body is provided.

Japanese Unexamined Patent Publication No. 2010-8343 Special Fair 6-43937 Gazette

However, since the amount of displacement of the receiving body is extremely small, when trying to realize a highly sensitive force sensor in the 6-axis direction, the distance between the receiving body and the stopper (displacement until the protection mechanism functions). It is necessary to manage the amount) with extremely high accuracy in all of the 6 axial directions.

The present invention has been made in view of the above circumstances, and provides a force sensor capable of managing the distance between the receiving body and the stopper with high accuracy.

The force sensor according to the embodiment is fixed to a cylindrical main body, a cylindrical movable body that can move with respect to the main body, the main body, and the movable body, and is deformable according to the movement of the movable body. The strain body, the strain sensor provided on the strain generating body, at least three circular openings provided around the movable body at equal intervals, and the openings arranged inside each of the openings. It has a small first outside diameter than the diameter of the section, a first side surface that can be brought into contact with the inner surface of the opening, located outside in the said opening from the first side surface, a small second than the first outer diameter have a second outer diameter, and the stopper jig adjustment and a second side surface can be inserted between the inner surface of the opening, a fixing member for fixing the stopper to the body, the first or A gap having a predetermined distance is further provided between the inner surface of the stopper parallel to the second side surface and the fixing member, and the jig is inserted between the inner surface of the opening and the second side surface. When this is done, the stopper is configured to be movable by the distance of the gap.

The perspective view which shows the force sensor which concerns on 1st Embodiment. The exploded perspective view which shows the force sensor which concerns on 1st Embodiment. The plan view which shows the force sensor which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view showing a force sensor along IV-IV of FIG. The cross-sectional view for demonstrating the external force detection operation in the Z-axis direction. The plan view which shows the force sensor which attached the jig. FIG. 6 is a cross-sectional view showing a force sensor along VII-VII of FIG. The figure which shows the relationship between the displacement of a strain-causing body and a load when a load is applied in the Z direction. The cross-sectional view which shows the force sensor which concerns on 2nd Embodiment, and shows only the main part. FIG. 9 is an enlarged cross-sectional view showing a portion shown by A in FIG.

Hereinafter, embodiments will be described with reference to the drawings. In the following description, substantially the same functions and elements are designated by the same reference numerals and will be described as necessary. In addition, the drawings are schematic, and the relationship between the thickness and the plane dimensions and the ratio of the thickness of each layer may differ from the actual ones.

(First Embodiment)
[Constitution]
overall structure
The overall configuration of the force sensor according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a force sensor according to the first embodiment. FIG. 2 is an exploded perspective view showing a force sensor according to the first embodiment. The force sensor 10 according to the first embodiment will be described by taking as an example a 6-axis force sensor used for, for example, a robot arm or the like and for detecting a force and torque in the XYZ directions.

The force sensor 10 includes a cylindrical main body 11 and a cylindrical movable body 12 that can operate with respect to the main body 11. The main body 11 is fixed to the main body of the robot arm (not shown) by a plurality of mounting screws 19 penetrating the plurality of screw holes 19a formed in the bottom of the main body 11. The movable body 12 functions as a hand mounting plate for removing the hand portion of the robot arm (not shown) on the upper surface thereof.

The main body (base) 11 is a base member serving as the main body of the force sensor 10, and the movable body 12 is located in a 6-axis direction (X-axis) with respect to the main body 11 via a strain-causing body 16 capable of elastic deformation. It is operably attached in the direction, the Y-axis direction, the Z-axis direction, and the direction around each axis). That is, as shown in FIG. 2, the strain-causing body 16 is fixed to the main body 11 by the strain-causing body fixing screws 17 penetrating the plurality of screw holes 17a formed in the strain-causing body 16, and the plurality of screw holes. It is also fixed to the movable body 12 by the hand plate fixing screws 18 penetrating each of the 18a.

The surface of the strain-causing body 16 is arranged parallel to the surface formed by the X-axis and the Y-axis, and the line perpendicular to the center of the strain-causing body 16 coincides with the Z-axis. When an external force is applied to the movable body 12, the movable body 12 operates and the strain-causing body 16 is displaced. The strain generating body 16 is provided with a strain sensor described later, and the displacement of the strain generating body 16 is detected by the strain sensor.

For example, four circular openings 13 are provided at equal intervals on the peripheral surface of the movable body 12. That is, each opening 13 is arranged in the X-axis direction and the Y-axis direction. The number of openings 13 is not limited to four, and may be three or more. A stopper 14 is arranged inside each opening 13, and each stopper 14 is fixed to the main body 11 by a stopper mounting bolt 15.

The stopper 14 regulates the operating range of the movable body 12, and the outermost peripheral portion of the stopper 14 is provided with a first side surface 14a to which the inner surface of the opening 13 can come into contact. That is, the first side surface 14a is protected so that when the strain-causing body 16 is deformed due to the movement of the movable body 12, the inner surface of the opening 13 of the movable body 12 comes into contact with the first side surface 14a to prevent excessive deformation of the strain-causing body 16. Functions as a mechanism.

A substrate 20 is provided inside the main body 11 so as to face the strain generating body 16. The substrate 20 has a plurality of screw holes 21a and is fixed to the main body 11 by fixing screws 21 penetrating each screw hole 21a. A strain sensor provided on the strain generating body 16 is electrically connected to the substrate 20.

A cover 22 that closes the opening 11a is attached to the bottom of the main body 11. That is, the cover 22 has a plurality of screw holes 23a and is fixed to the main body 11 by the fixing screws 23 penetrating the screw holes 23a.

A wiring 25 for transmitting a detection signal to the outside is drawn out from the side surface of the main body 11. The wiring 25 is electrically connected to the substrate 20.

Planar configuration and cross-sectional configuration
The plane configuration and the cross-sectional configuration of the force sensor according to the first embodiment will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a plan view showing the force sensor 10. FIG. 4 is a cross-sectional view showing a force sensor 10 along IV-IV of FIG.

The strain sensor (not shown) described above is attached to a predetermined position on the surface of the strain generating body 16 and measures the displacement of each location of the strain generating body 16 to measure a force and torque in the 6-axis direction. To detect. The configuration and arrangement of the strain sensor are not particularly limited and can be deformed. Further, an FPC (Flexible printed circuits) 26 for electrically connecting the strain sensor on the surface of the strain generating body 16 and the substrate 20 is provided. The FPC 26 includes an insulating flexible film and a predetermined electric circuit wired to the film, and has a configuration capable of freely bending according to the movement of the movable body 12.

The stopper 14 has the above-mentioned first side surface 14a and the second side surface 14b. The first side surface 14a is located inside the movable body 12 with respect to the second side surface 14b, and has a first outer diameter R14a smaller than the diameter R13 of the opening 13 of the movable body 12. The second side surface 14b has a second outer diameter R14b smaller than the first outer diameter R14a. Therefore, the distance W14 between the first side surface 14b and the inner surface of the opening 13 is configured to be smaller than the distance W30 between the second side surface 14b and the inner surface of the opening 13 (W14 <W30). ). A gap corresponding to the distance W30 is also provided on the side surfaces of the movable body 12 and the main body 11, so that the movable body 12 can operate with respect to the main body 11. The distance W30 is, for example, about several mm.

Here, the distance (clearance) W14 between the first side surface 14a and the inner surface of the opening 13 is, for example, about 20 μm to 40 μm, and is therefore very narrow. Moreover, when the movable body 12 operates, it is necessary to manage this distance W14 with extremely high accuracy in order to prevent the strain generating body 16 from being damaged.

Further, as shown by enlarging the portion surrounded by the broken line in FIG. 4, in reality, a predetermined distance W15a is established between the inner side surface of the stopper 14 facing the first side surface 14a and the shaft of the fixing bolt 15. A gap is provided. Further, a predetermined gap having a distance W15b is also provided between the inner side surface of the stopper 14 parallel to the first and second side surfaces 14a and 14b and the side surface of the head of the fixing bolt 15. The distances W15a and W15b are, for example, about 0.2 mm. In the following description, the illustration of these gaps will be omitted.

In the present embodiment, a shim as an adjustment jig having an insertion portion having a thickness substantially the same as the distance W30 is inserted between the second side surface 14b and the inner surface of the opening 13. The stopper 14 is fixed to the main body 11 by the fixing bolt 15. By adjusting in this way, the stopper 14 can be moved by the distances W15a and 15b of the gap, so that the distance (clearance) between the inner surface of the opening 13 of the movable body 12 and the first side surface 14a of the stopper 14 ) W14 can be managed with high accuracy, a predetermined movable range of the movable body 12 with respect to the main body 11 can be secured, and the sensitivity of the force sensor 10 can be improved. The details will be described later.

[Detection operation]
The detection operation of the force sensor 10 having the above configuration will be described with reference to FIG. FIG. 5 is a cross-sectional view for explaining an external force detection operation in the Z-axis direction. Here, a case where the external force (load) FZ applied to the substantially central portion of the movable body 11 in the Z-axis direction is detected will be given as an example.

As shown in the figure, when an external force FZ is applied to a substantially central portion of the movable body 11 in the Z-axis direction, the movable body 11 moves downward along the Z-axis direction due to the external force FZ. Since the main body 11 is fixed and does not move by the external force FZ, the movable body 11 moves downward until the inner surface on the upper side of the opening 13 abuts on the first side surface 14a on the upper side of the stopper 14. Due to the above movement, the upper distance W14U becomes substantially 0, and the lower distance W14D increases to about twice as much as the initial state before the movement.

Therefore, the lower surface 12a of the movable body 12 pressurizes the upper surface of the strain generating body 16, and the pressed strain generating body 16 deforms. Since the deformation of the strain generating body 16 is limited to a predetermined range by the stopper 14, the strain generating body 16 is protected from destruction due to an excessive external force. The deformation of the strain generating body 16 is detected by the strain sensor 26 and converted into a detection signal as an electric signal. The detection signal is transmitted to the outside by the wiring 25 via the substrate 20, so that the external force FZ can be detected.

After that, when the application of the external force FZ to the movable body 12 is released, the strain-causing body 16 returns to its original shape due to elastic deformation.

Although the external force detection operation in the Z-axis direction is given as an example here, the same applies to other external force detection operations in the X-axis direction and the Y-axis direction. Further, since each torque detection operation in the X, Y, and Z axis directions is substantially the same as the external force detection operation, detailed description thereof will be omitted.

[Adjustment of clearance W14]
Next, the clearance adjustment will be described with reference to FIGS. 6 and 7.

As shown in FIGS. 6 and 7, the clearance is adjusted by attaching the shim 30 to the opening 13. 6 and 7 show a case where the shim 30 is attached to one opening 13, but it is preferable to make adjustments with the shim 30 attached to all four openings 13. In this case, the adjustment accuracy is further improved, and the adjustment work time can be shortened.

The shim 30 has a tubular insertion portion 30a, a knob portion 30b, and an opening 33.

The knob portion 30b has an outer diameter R30 larger than the diameter R13 of the opening 13.

The opening 33 penetrates the knob portion 30a, and a hexagon wrench (not shown) attached to the hexagonal hole provided in the head of the mounting bolt 15 can be inserted.

The insertion portion 30a has an outer diameter R13 substantially equal to the diameter of the opening 13 of the movable body 12, and the thickness of the insertion portion 30a is the distance W30 between the second side surface 14b of the stopper 14 and the inner surface of the opening 13. The thickness is set to be substantially the same as.

With the mounting bolt 15 loosened, as shown in FIG. 7, the insertion portion 30a of the shim 30 is inserted between the second side surface 14b of the stopper 14 and the inner surface of the opening 13. The outer diameter of the insertion portion 30a is substantially the same as the diameter R13 of the opening 13, and the inner diameter of the insertion portion 30a is substantially the same as the second outer diameter R14b of the second side surface 14b of the stopper 14. Therefore, with the insertion portion 30a of the shim 30 inserted into the opening 13, the axis C30 of the shim 30 and the axis C14 of the stopper 14 coincide with each other to form concentric circles. That is, in this state, since the stopper 14 can be moved by the distances W15a and 15b of the gap, the distance W14 between the first side surface 14a of the stopper 14 and the inner surface of the opening 13 is accurately set.

In this state, the stopper 14 is fixed to the main body 11 by inserting a hexagon wrench (not shown) from the opening 33 of the shim 30 and tightening the mounting bolt 15.

In this way, by inserting the insertion portion 30a having a thickness corresponding to the distance W30 between the second side surface 14b of the stopper 14 and the opening 13, the first side surface 14a of the stopper 14 and the inner surface of the opening 13 are formed. The clearance, which is the distance W14, can be accurately managed.

[Action effect]
According to the first embodiment, the stopper 14 has a first side surface 14a to which the inner surface of the opening 13 of the movable body 12 is in contact, and a second side surface 14b having an outer diameter smaller than that of the first side surface. At the time of adjusting 14, the insertion portion of the shim 30 having a thickness corresponding to the distance W30 between the second side surface 14b of the stopper 14 and the inner surface of the opening 13 and the distance W30 between the second side surface 14b and the inner surface of the opening 13. 30a is inserted. Therefore, when the axis C30 of the shim 30 and the axis C14 of the stopper 14 coincide with each other, the stopper 14 moves by the distances W15a and 15b of the gap, and the first side surface 14a of the stopper 14 and the opening 13 The distance W14 from the inner surface of the can be set accurately.

For example, when a load FZ is applied to the force sensor 10 according to the present embodiment in the Z direction, the relationship between the displacement [μm] of the strain generating body 16 and the detected load [N] is as shown in FIG. Shown. As shown in FIG. 8, the inclination (rising angle) of the characteristic line CL10 changes when the displacement in the Z direction is around 0.022 μm (inflection point). This indicates that the stopper 14 does not function and the strain generating body 16 is deformed from the state where the displacement is zero to the inflection point (D1), and after the inflection point (D2), the first side surface 14a of the stopper 14 is It shows that the stopper 14 is functioning because it comes into contact with the inner surface of the opening 13. After the inflection point (D2), the slope of the characteristic line CL10 increases, the strain-causing body 16 is less likely to be deformed, and it is clear that the clearance W14 can be set accurately. ..

Moreover, since it is only necessary to attach the shim 30 and tighten the mounting bolt 15 from the opening 33 of the shim 30 with the mounting bolt 15 loosened, the adjustment work is performed while reducing the error of the clearance W14 as much as possible. Can be facilitated.

Further, the first side surface 14a and the second side surface 14b of the stopper 14 can be formed by, for example, continuously cutting using the same process. Therefore, the dimensional control and inspection of the first side surface 14a and the second side surface 14b are easy.

Further, in the manufacturing process of the movable body 12, only the dimension of the diameter R13 of the opening 13 needs to be controlled, so that the dimension control and inspection are easy.

Further, the shim 30 can be formed by continuously cutting the outer surface and the inner surface of the insertion portion 30a, for example, by using the same process. Therefore, the dimensional control, inspection and concentricity of the shim 30 can be facilitated.

Moreover, the stopper 14 has a very simple shape and has a protective function in all six axial directions. Therefore, it is possible to provide the force sensor 10 having high sensitivity and advantageous in reducing the manufacturing cost.

(Second embodiment (an example having a tapered structure))
Next, the force sensor 10A according to the second embodiment will be described with reference to FIGS. 9 and 10. The second embodiment relates to an example in which the stopper 14 and the shim 30 have a tapered structure.

[Construction]
FIG. 9 is a cross-sectional view showing the force sensor 10A according to the second embodiment. FIG. 10 is a cross-sectional view showing a force sensor 10A in the vicinity of A in FIG. 9 in a state where a jig is used.

As shown in FIG. 9, in the second embodiment, the stopper 14 has a tapered structure in which the second side surface 14c is configured such that the second outer diameter R14c becomes smaller as the second side surface 14c is separated from the first side surface 14a. As shown in FIG. 10, the angle θ14 formed by the second side surface 14c of the stopper 14 and the horizontal plane is an acute angle.

Further, as shown in FIG. 10, the inner side surface of the insertion portion 30a of the shim 30 is formed so that the inner diameter thereof decreases as the distance from the first side surface 14a increases so as to match the taper structure of the stopper 14. Has a structure. The angle θ30 formed by the inner surface of the insertion portion 30a of the shim 30 and the horizontal plane is an acute angle.

Since other structures are substantially the same as those of the first embodiment, detailed description thereof will be omitted. Further, since the detection operation is substantially the same as that of the first embodiment, detailed description thereof will be omitted.

[Action effect]
According to the structure and operation of the force sensor 10A according to the second embodiment, at least the same effect as that of the first embodiment can be obtained.

Further, in the force sensor 10A according to the second embodiment, the second side surface 14c of the stopper 14 and the insertion portion 30a of the shim 30 have a tapered structure. Specifically, as shown in FIG. 9, the second side surface 14c of the stopper 14 and the inner side surface of the insertion portion 30a are configured such that the second outer diameter R14c and the inner diameter become smaller as the distance from the first side surface 14a increases. ..

As described above, since the second side surface 14c of the stopper 14 and the insertion portion 30a of the shim 30 have a tapered structure, the insertion portion 30a of the shim 30 can be easily inserted into the opening 13 when positioning the stopper 14. It is possible to do.

Moreover, since the second side surface 14c of the stopper 14 and the insertion portion 30a of the shim 30 have a tapered structure, the axes of the stopper 14 and the shim 30 can be reliably aligned with each other. Therefore, the distance W14 between the first side surface 14a and the inner surface of the opening 13 can be managed with higher accuracy as compared with the first embodiment.

(Modification example)
The present invention is not limited to the disclosure of the first and second embodiments, and it goes without saying that various modifications can be made as needed.

For example, in the present embodiment, the stopper 14 is fixed to the main body 11 by the mounting bolt 15, but the stopper 14 is not limited to this configuration. Specifically, in the first embodiment, the portion of the movable body 12 provided with the opening 13 is located outside the portion where the mounting bolt 15 of the main body 11 is screwed, but the portion is opened in the main body 11. A portion where the portion 13 is provided is provided, a portion where the mounting bolt 15 is screwed into the movable body 12 is provided, and a portion where the opening portion 13 provided in the main body 11 is provided is provided by the mounting bolt 15 provided on the movable body 12. It may be arranged outside the screwed portion, and the stopper 14 may be arranged in the opening 13 provided in the main body 11.

Further, the shim 30 is not limited to the inspection of the force sensors 10 and 10A, but may be used, for example, during maintenance after the force sensors 10 and 10A have been moved to some extent.

In addition, the present invention is not limited to each of the above embodiments as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by appropriately combining the plurality of components disclosed in each of the above embodiments. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

10, 10A ... Force sensor, 11 ... Main body, 12 ... Movable body, 13 ... Opening, 14 ... Stopper (protection mechanism), 15 ... Fixing member (stopper mounting bolt), 16 ... Distortion body, 26 ... Distortion sensor , 30 ... Jig (sim).

Claims (4)

Cylindrical body and
A cylindrical movable body that can operate with respect to the main body,
A strain-causing body that is fixed to the main body and the movable body and can be deformed according to the movement of the movable body.
The strain sensor provided on the strain-causing body and
At least three circular openings provided around the movable body at equal intervals,
Is disposed within each of said openings, it has a small first outside diameter than the diameter of the opening, a first side surface that can be brought into contact with the inner surface of the opening, in the inner opening than the first side surface located outside, and the first to have a smaller second outer diameter than the outer diameter, stopper having a second side capable jig insertion for adjustment between an inner surface of said opening,
A fixing member that fixes the stopper to the main body ,
A gap having a predetermined distance is further provided between the inner side surface of the stopper parallel to the first or second side surface and the fixing member.
A force sensor configured so that when the jig is inserted between the inner surface of the opening and the second side surface, the stopper can be moved by the distance of the gap. Cylindrical body and
A cylindrical movable body that can operate with respect to the main body,
A strain-causing body that is fixed to the main body and the movable body and can be deformed according to the movement of the movable body.
The strain sensor provided on the strain-causing body and
At least three circular openings provided around the main body at equal intervals,
Is disposed within each of said openings, it has a small first outside diameter than the diameter of the opening, a first side surface that can be brought into contact with the inner surface of the opening, in the inner opening than the first side surface A stopper located on the outside, having a second outer diameter smaller than the first outer diameter, and having a second side surface into which an adjustment jig can be inserted between the outer diameter and the inner surface of the opening.
A fixing member that fixes the stopper to the movable body ,
A gap having a predetermined distance is further provided between the inner side surface of the stopper facing the first or second side surface and the fixing member.
A force sensor configured so that when the jig is inserted between the inner surface of the opening and the second side surface, the stopper can be moved by the distance of the gap. The force sensor according to claim 1 or 2, wherein the second side surface has a smaller second outer diameter as the distance from the first side surface increases. The jig has an insertion portion that can be inserted between the inner surface of the opening and the second side surface.
The diameter of the inner surface of the insertion portion decreases as the distance from the first side surface increases.
The force sensor according to claim 3.

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