JPH01191028A - Force sensor - Google Patents

Abstract

PURPOSE:To work a through hole and a cut part which form a deformation part for strain generation in the same direction by forming the though hole and cut part so that the through direction of the through hole and the cutting direction of the cut part meet each other. CONSTITUTION:When a hand fitted to the tactual sensor 11 is strained in an X direction, the stress is transmitted to the base part 13 of a sensor main body 12. Then 1st thin parts 17 formed at 2nd and 4th projection parts 14b and 14d positioned at right angles to the X direction are strained more than other thin parts. The X-directional stress is therefore detected by eight 1st strain gauges 19 in total which are stuck on the 1st thin parts 22 of the 2nd and 4th projection parts 14b and 14d. When the hand is strained in a Y direction, 1st thin parts 17 formed at 1st and 3rd thin projection parts 14a and 14c are strained, which is detected by eight 1st strain gauges 19 in total.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention can be used, for example, in robots, NC processing machines, etc.
The present invention relates to a force sensor used for contacting a work object and detecting its reaction force.

(Prior art) For example, when assembling parts using a robot,
Unless the parts are precisely positioned by the robot's hand, assembly work cannot be carried out smoothly. That is, when the assembly work by the robot is, for example, the work of fitting a bottle into a hole, if the positions of the bottle and the hole are even slightly misaligned, the bottle may not be able to be fitted into the hole.

Therefore, in order to eliminate such problems, a force sensor is installed on the arm of the robot, and this force sensor measures the stress in a total of six directions, including the X, Y, and Z directions, and the rotational moment in each of these directions. The assembly work is performed while controlling the posture of the arm using the detection signal.

Conventionally, there is a force sensor as shown in FIG. 11 as the above-mentioned force sensor. That is, a prismatic mounting portion 3 having a mounting hole 2 is arranged in the internal space of the hollow sensor body 1 . One end of a bar 4 is connected to each outer circumferential side of the mounting portion 3, and the other end of the bar 4 is connected to the inner circumferential surface of the sensor main body 1, thereby integrally connecting the sensor main body 1 and the mounting portion 3. Join. Further, a strain gauge 5 is attached to each of the four bars 4. By connecting the sensor main body 1 to the arm of the robot and attaching a finger to the mounting part 3, when assembling the parts gripped by the finger, X, Y, and
The stress in the Z direction is detected by strain gauges 5 provided on each bar 4.

Then, the posture of the arm is controlled by the detection signal, so that the parts can be assembled with high precision.

However, according to a force sensor with such a structure,
The strength of the connection between the robot arm and the finger, that is, the strength of the robot arm, is largely influenced by the rigidity of the bar 4 for attaching the mounting portion 3 to the sensor body 1. However, if the rigidity of the bar 4 is increased in order to improve the strength of the robot's arm, the stress applied to the fingers when assembling the parts makes it difficult for the bar 4 to deform, resulting in a decrease in the sensitivity of detecting that stress. occurs.

On the other hand, if the bar 4 is made less rigid so that it is easily deformed by stress in order to increase the stress detection sensitivity of the bar 4, sufficient strength of the robot arm cannot be obtained.

For this reason, when attaching it to an object such as a robot arm to detect the stress applied to it,
There has been a strong desire for a force sensor that does not impair the mechanical strength of the object to be attached and is capable of sensitively detecting stress applied to the portion to be attached.

A device that meets this demand has already been proposed (Japanese Patent Application No. 307656/1983). This prior example is constructed as shown in FIGS. 8 to 10.

That is, this force sensor 11 includes a sensor body 12. This sensor body 12 includes a base 13 and a base 1
It is composed of four first to fourth convex portions 14a to 14d that protrude from the outer circumferential surface of No. 3 at intervals of 90 degrees in the circumferential direction. A first through hole 15 having a rectangular cross section is bored through each of the protrusions 1/18 to 14d in the thickness direction thereof. The base 13 is provided with a mounting hole 13a that penetrates in the thickness direction in the center thereof, and a mounting hole 13a that penetrates in the radial direction at a position offset by 45 degrees in the circumferential direction from each of the protrusions 14a to 14d. A pair of second through holes 16 are bored. Therefore, the first thin portions 17 are formed on both side surfaces of each of the convex portions 148 to 14d by the first through holes 15, and the first thin portions 17 are formed on the upper and lower end surfaces of the base 13 by the second through holes 16, respectively. 4 second thin walls i'1l1
18 are formed. Then, the first thin portion 17
and the second thin wall portion 18 each constitute a deformable portion that deforms in response to a load in a specific direction.

First thin wall portion 1 of each of the above-mentioned convex portions 14a to 14d
A pair of first strain gauges 19 are attached to the outer surface of the strain gauge 7 . That is, four first strain gauges 19 are attached to one convex portion 14, and a total of 16 strain gauges are provided.

Further, a pair of second strain gauges 21 is attached to each second thin wall portion 18 of the base 13, and a total of 16 second strain gauges 21 are provided. Each of the first strain gauges 19 is configured to detect strain occurring in the first thin wall portion 17, and the second strain gauge 21 is configured to detect strain occurring in the second thin wall portion 18. Note that each convex portion 148 to 14d1. ::The four Q-shaped strain gauges 19 and the four second strain gauges 21 provided on the opposing second thin parts 18 of the base 13 form a bridge circuit, thereby forming a detection means. ing. Therefore, the symmetry of the structure of the sensor main body 12 is created so that distortion can be detected in a well-balanced manner. That is, after noise is removed from the electrical signal from the bridge circuit, it is amplified by an amplifier to a level that can be processed by a computer. This amplified signal is A/D converted and digitally encoded, and by applying a conversion matrix to this, the strain signal is converted into a six-axis force signal.

A first coupling member 22 is provided on one end surface side of the sensor main body 12.
is provided, and a second coupling member 23 is provided on the other end surface side. The first coupling member 22 is connected to the sensor main body 1.
The four convex portions 148 to 14 of No. 2 (the end surfaces of the second convex portion 14b and the fourth convex portion 14d of No. 1 along the Y direction are integrally connected with sufficient strength, and the remaining portions along the X direction A first slit 24 is formed between the end faces of the first convex portion 14a and the third convex portion 14C to maintain a sufficient distance therebetween.

The second coupling member 23 has a first convex portion 14 along the X direction.
a and the third convex portion 14c, and the remaining two second convex portions 14b and the fourth convex portion
A second slit 25 is formed between the end face and the convex portion 14d to maintain a sufficient distance therebetween. The force sensor 11 configured in this way is connected to the first coupling member 2.
2 to an arm of a robot (not shown), and a hand of the robot (also not shown) is attached to the mounting hole 13a of the base 13.

Next, the operation of the force sensor 11 will be explained.

First, when stress in the X direction is applied to a hand (not shown) attached to this force sensor 11, the stress is applied to the sensor body 1.
It is transmitted to the base 13 of 2. Then, the second. Fourth convex portions 14b, 14d
A larger distortion occurs in the first thin wall portion 17 formed in the first thin wall portion than in the other thin wall portions. Therefore, the stress in the X direction is the second. The first thin portions 22 of the fourth convex portions 14b and 14d
A total of eight first strain gauges 19 attached to the strain gauges 19 are used for detection.

Further, when stress in the Y direction is applied to a hand (not shown), the stress is transmitted to the base 13 of the sensor body 12. Then, Y
The first one located in the direction perpendicular to the stress in the direction. The first thin portions 17 formed on the third convex portions 14a and 14c are distorted more than the other thin portions. Therefore, the stress in the Y direction is applied to the 1° strain gauges 1, which are attached to the first thin portions 17 of the third convex portions 14a and 14c.
can be detected by one.

Furthermore, when a stress in the Z direction is applied to the hand (not shown) attached to the mounting hole 13a of the force sensor 11, the sensor main body 12 has its base 13 and the four convex portions 14a to 14d 7
Try to displace in the opposite direction. therefore,
The second thin wall portion 18 located in the direction orthogonal to the stress in the Z direction is distorted more than the other thin wall portions. Therefore, the stress in seven directions can be detected by the second strain gauge 21 attached to the second thin section 18.

On the other hand, when moments around the X direction and around the X direction are applied to the force sensor 11, the first
The second thin-walled portion 18 is more easily deformed than the thin-walled portion 17 of the second thin-walled portion 17 . In other words, since the second thin part 18 is located in a direction perpendicular to the moments in the X and Y directions, it is more easily deformed than the first thin part 17. Therefore, the second thin part 1
Moments around the X direction and the Y direction can be detected by a total of 16 second strain gauges 21 attached to the second strain gauges 8 . Further, when a moment in seven directions is applied to the sensor body 12, the first thin part 17 located in a direction perpendicular to the moment in the Z direction is more easily deformed than the second thin part 18. Therefore, a total of 16 first strain gauges 1 attached to the first thin part 17
9 makes it possible to detect moments around seven directions.

By the way, in the force sensor 11 having the above structure, the first
Moments in the X, Y, and The first thin part 17 or the second thin part 18 is formed to be easily deformed. Therefore, each direction applied to the force sensor 11 and moments around those directions can be detected with high sensitivity.

In addition, in response to stress in the X direction applied to the force sensor 11, the first sensor located parallel to the X direction. Third convex portions 14a, 14
The first thin part 17 of 0 has sufficient rigidity, and the second thin part 17 located parallel to the Y direction has sufficient rigidity to withstand stress in the Y direction. The first thin portions 17 formed on the fourth convex portions 14b and 14d exhibit sufficient rigidity. Furthermore, with respect to stress in the Z direction, the first thin portions 18 formed in each of the convex portions 148 to 14d are located parallel to the direction of the stress, so that they exhibit sufficient rigidity. Furthermore, the first thin part 17 exhibits sufficient rigidity for [-ment around the X and Y directions,
The second thin portion 18 exhibits sufficient rigidity against moments around the Z direction. Therefore, such a force sensor 11 has sufficient rigidity against the X, Y, and Z directions and moments around each of these directions.

As described above, according to this force sensor 11, X, Y
, the stress in the Z direction and the moment around each of these directions are applied to the first thin section 1 located in a direction perpendicular to the stress.
7 or the second thin walled portion 18 can be detected with good sensitivity, and at this time, the thin walled portion located in the direction parallel to the force exhibits sufficient rigidity.

Therefore, according to such a force sensor 11, it is possible to improve both sensitivity and rigidity, which were conventionally contradictory factors.

(Problems to be Solved by the Invention) Although the force sensor 11 described above can obtain excellent effects,
There are the following problems. That is, the force sensor 1
1, a pair of first through holes 15.degree. 15 orthogonal to each other and a plurality of second through holes 16. ...must be drilled. To drill the first through holes 15, 15, the machining positions are changed two to four times from the eight directions in FIG. 10, and the second through holes 16. In order to drill holes, the positions are changed from eight directions in FIG. 10 and the process is carried out.

In other words, two different machining directions A and B are required.

For this reason, the machining setup was troublesome and required a lot of machining time.

The present invention has been made in view of the above-mentioned problems.The purpose of the present invention is to form a deformed portion in one machining direction, simplify the setup of the machining, and shorten the machining time. The objective is to provide a force sensor that can improve productivity.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a force sensor for detecting the reaction force when it comes into contact with a sensing object. a sensor body consisting of a plurality of protrusions protruding from the outer peripheral surface of the sensor body at intervals in the circumferential direction; A through hole that forms a deformed portion for strain generation in the side wall portion that has become thin, and a thin wall portion that is formed in at least one of the convex portion and the base portion in a direction in which the through hole passes through. It consists of a notch forming a deformable part for generating strain, and a detection means for detecting the strain generated in each of the deformable parts for generating strain and converting it into an electric signal.

Therefore, the through holes and notches for forming each of the deformed parts for generating strain can be formed from the same direction.

Therefore, the preparation for the above-mentioned machining can be carried out in the cylinder, and the machining time can be shortened.

(Example) The first and fourth are force sensing sensors 9 as an example of the present invention.
-11. Since the basic IM structure of this force sensor 11 has already been explained based on FIGS. 8 to 10, the same parts are given the same reference numerals and detailed explanation thereof will be omitted.

In this embodiment, the second through hole 1 provided in the base 13 is
6 is eliminated, and in its place, a notch 26 is formed in each of the protrusions 14a to 14d. Each notch 2
6 is in the same direction as the (first) through hole 15, that is, each convex portion 14
8 to 14d are cut in the thickness direction. In other words,
The cutout portions 26 are formed by cutting them from below in the direction in which the through hole 15 passes through. Therefore, each of the notches 26 can be formed by machining from the bottom to the top in the same manner as the through hole 15. As this processing direction, for example, a wire electrolytic method can be considered.

Further, each through hole 15 is arranged closer to the proximal end of the protrusions 14a to 14d, whereas each notch 26 is arranged closer to the protruding tip side of the protrusions 148 to 1/I (l). The first thin portions 17 formed by forming the through holes 15 in the same manner as described above constitute deformable portions that deform under load in a specific direction. A pair of first strain gauges 19 are affixed to the outer surfaces of the thin-walled portions 17, respectively.

Further, by forming the cutout portion 26, a second thin portion 27 is formed in the upper portion as shown in FIG. The second thin portion 27 also constitutes a deformable portion that deforms under load in a specific direction. Each of the second thin portions 27
A second strain gauge 21 is attached to the outer surface of each. That is, in the present invention, the second thin portion 27 is formed by forming the cutout portion 26 in the convex portions 14a to 14d instead of the second through hole 16.

Note that the tips of each of the protrusions 14a to 14d are integrally connected to the first coupling member 22 or the second coupling member 23, respectively. This is done via a thin-walled connecting portion 36 that is freely deformable.

Therefore, the stress applied to the first and second thin portions 17.27 is not inhibited here.

Therefore, the force sensor 11 is configured to apply strain to the force sensor 11 by detecting the strain occurring in each thin wall portion 17.2.7 of the force sensor 11 with each strain gauge 19.21 in the same manner as described above. X.

Stresses in the Y and Z directions and rotational moment in each of these directions can be detected.

Further, in this embodiment, mechanical stopper mechanisms as shown in FIG. 1 are attached to four locations of 0PQR shown in FIG. 2. That is, the headed bolts 30 are screwed to the displacement side ends of each of the protrusions 14a to 14b close to the first coupling member 22 or the second coupling member 23, respectively. Also, there is a clearance 'V!' between the end surface 31 facing the coupling member 22.23 and the coupling member 22.23. is formed. Further, each bolt 30 has a corresponding coupling member 2
2.23 is inserted into a round hole 32 which extends through the hole 2.23. This mating hole 32 is the first hole portion 3 through which the shaft 33 of the bolt 30 is passed.
2a and a second hole portion 32b through which the head 34 of the bolt 30 is passed.
It consists of A clearance y2 is formed between the head 34 of the bolt 30 and the bottom end surface of the second hole portion 32b. Further, a clearance y3 is formed between the head 34 of the bolt 30 and the inner peripheral surface of the second hole portion 32b.

r

If such a mechanical stopper mechanism is installed, even if an excessive external force is applied to a deformed part that is sensitive to external force and causes strain, the mechanical stopper will move and prevent the excessive external force from being applied. do.

Therefore, damage to the force sensor 11 can be prevented, residual strain will not be caused in the deformed portion, and the reliability of accurate detection can be increased.

Note that the clearance y2 can be arbitrarily set by adjusting the screwing of the bolt 30.

Further, the cliff face y3 can be adjusted by replacing the bolt 30.

In the above embodiment, the bolt 30 having a round head 34 is used, and the hole 32 through which it passes is round.
The structure can be used in common without providing separate mechanical stoppers for each direction, and the structure can be simplified.

In addition, through holes 15 and notches 2 provided in the convex portions 14a to 14d
Alternatively, the positions of the holes 15 and 6 may be exchanged to arrange the through holes 15 on the outside and the notches 26 on the inside, as shown in FIG. 5 or 6.

Furthermore, as shown in FIG. 5, the through hole 15 may be formed in an oval shape, or as shown in FIG. 6, it may be formed in a shape in which two circular holes are communicated through a slit portion. Moreover, FIG. 7 shows a modification in which the bottom surface of the notch 26 is formed into a circular shape.

Further, the notch portion 26 may be formed by cutting out from above, contrary to the case of the above embodiment. In this case, the second thin portion 18 is formed on the lower surface side of the convex portions 14a to 14d.

Furthermore, in the present invention, the notch 26 may be formed in the base 13 of the sensor body 12. Also,
While the notches 26 are formed in the protrusions 14a to 14d, the through holes 15 may be formed in the base 13.

[Effects of the Invention] As explained above, in the force sensing sensor of the present invention, the penetration direction of the through hole and the notch portion for forming each strain generation deformation portion are made to coincide with the notch direction. The notches can be formed by processing from the same direction. Therefore, machining setup is simple, machining time can be shortened, and productivity can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the vicinity of a mechanical stopper of a force sensor according to an embodiment of the present invention, FIG. 2 is a perspective view of a force sensor according to the same embodiment, and FIG. 3 is a bottom view of a force sensor according to the same embodiment. figure,
4 is a sectional view taken along the line X-X in FIG. 3, and FIGS. 5 to 7 are perspective views of the convex portion showing different modifications, respectively.
, FIG. 8 is a cross-sectional view of the force sensor of the prior example, FIG. 9 is a perspective view of the same prior force sensor, and FIG. 10 is a partially cutaway perspective view of the same prior force sensor. FIG. 11 is a perspective view of a conventionally known force sensor. 11...force sensor, 12...sensor body, 13.
...Base, 14...Convex part, 15...Through hole, 17.2
7... Thin wall part (deformed part), 19.21... Strain gauge (detection means), 26... Notch part. Applicant's agent Patent attorney Takehiko Suzue 1X2I! l Figure 3 b Figure 4 Figure 5 Figure 6! ! 1 Figure 8

Claims (1)

[Claims] A force sensor for detecting a reaction force when it comes into contact with a sensing object, which includes a sensor body comprising a base and a plurality of protrusions protruding from the outer peripheral surface of the base at intervals in the circumferential direction; A through hole is formed in at least one of the convex part and the base in the thickness direction thereof and forms a deformed part for generating strain in the thin side wall part; A notch is formed in a thin wall shape in the direction through which the through hole passes, and the thin wall portion forms a deformed part for generating strain, and the strain generated in each of the deformed parts for generating strain is detected. A force sensor comprising a detection means for converting into an electric signal.