JP2009198274A - Pin-type load cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost, high-reliability pin-type load cell. <P>SOLUTION: This pin-type load cell 10 has holes 2, 3 formed in a region, including a center axis and is provided with a pin 1 to which load is applied, strain detection rods 4, 5 provided so as to touch the walls 2n, 3n of the holes 2, 3 with lines, sensors 6, 7 for strain measurement provided on the detection rods 4, 5 and having input/output wiring conductors 6h, 7h, and resins J1, J2 which are provided between the pin 1 and the detection rods 4, 5 and covers the sensors 6, 7 for strain measurement, and into which the inputting/outputting wiring conductors are inserted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pin type load cell that can detect a load applied to a machine part or the like with high accuracy.

As a technique for detecting the load or force received by each machine component constituting the machine, a pin in which the strain measurement sensors 106 and 107 shown in FIG. 12 are incorporated in the joint pin itself of the pivot shaft for coupling the components. A type load cell is known (see FIGS. 1 and 3 of Patent Document 1). FIG. 12 is a perspective view of a detection block 101 provided with measurement sensors 106 and 107 in a conventional pin type load cell.
The pin type load cell is a technique for detecting deformation of the pin 109, that is, a load applied to the machine, by the strain measuring sensors 106 and 107 installed in the detection block 101 inserted into the pin 109.

For example, a joint pin that connects a bucket and an arm of a hydraulic excavator is used as a pin-type load cell and used for excavation force measurement, work amount measurement, and the like.
Examples of the strain measuring sensors 106 and 107 include a metal resistance strain gauge that is widely used in general and a semiconductor strain sensor as disclosed in Patent Document 2. The semiconductor strain sensor uses an impurity diffusion resistor in which an impurity is introduced into a single crystal silicon substrate as a strain sensitive resistor, and has features such as high sensitivity, low drift, and built-in amplifier.
Japanese Patent Publication No. 4-50970 (FIG. 1, FIG. 2, FIG. 3, etc.) JP 2005-114443 A JP 10-38713 A (paragraph 0002, FIG. 2 etc.)

By the way, as a conventional pin type load cell, a structure in which a strain gauge is adhered to an inner wall of a hole provided in a neutral shaft of the pin 109 (see paragraph 0002 of FIG. 2 and FIG. 2), or a pin 109 shown in FIG. There is a structure in which a detection block 101 having strain gauges 106 and 107 bonded therein is inserted into the hole.
The technique of bonding the strain gauge to the inner wall of the hole of the former pin 109 requires that the strain gauge be bonded directly to the inner wall of the deep hole, which makes it difficult to manufacture and requires a special device, which increases the manufacturing cost. There's a problem.
On the other hand, in the latter technique of inserting the detection block 101 having a strain gauge bonded inside the hole of the pin 109, in order to transmit the deformation of the pin 109 to the detection block 101, the inner wall of the pin 109 and the surface of the detection block 101 are Has a structure that touches the surface.

Therefore, it is necessary to process the hole 101a for pulling out the wirings 106h and 107h of the strain gauges 106 and 107 to the outside and the depression 101b for installing the strain gauges 106 and 107 into the detection block 101. As in the former technique, Manufacturing costs increase.
In view of the above circumstances, the present invention is to provide an inexpensive and highly reliable pin type load cell.

The above-described object is achieved by arranging a strain detection detection rod, to which a strain measurement sensor is bonded, in contact with the inner wall of the pin by a line, and filling a resin in a gap between the pin and the detection rod.
That is, the pin type load cell of the present invention has a hole provided in a region including the central axis, a pin to which a load is applied, a strain detection rod provided so as to contact the inner wall of the hole with a line, and a strain detection rod And a strain measurement sensor having an input / output wiring, and a resin provided between the strain detection rod and the pin, covering the strain measurement sensor and through which the input / output wiring is inserted.

According to the present invention, since the detection rod is in contact with the inner wall of the pin with a line, the deformation of the pin can be transmitted from the contact portion between the detection rod and the pin to the detection rod as in the case of contact with the surface. Since the detection rod is in line contact with the pin, it is possible to secure a space for installing the sensor and its wiring between the line contact portions between the pin and the detection rod, and to install a hole and sensor for drawing the wiring from the sensor to the outside Therefore, a hollow structure is unnecessary and a simple structure can be obtained, and the cost can be reduced.
Further, by filling the gap between the pin and the detection rod with resin, entry of moisture from the outside and entry of foreign matter are prevented, and weather resistance is improved.

According to the present invention, an inexpensive and highly reliable pin type load cell can be realized.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
<< First Embodiment >>
FIG. 1A is a front view of the pin type load cell 10 of the first embodiment, and FIG. 1B is a right side view of the pin type load cell 1 shown in FIG. FIG. 1C is a left side view of the pin type load cell 10 shown in FIG. 1A, and FIG. 1D is a cross-sectional view of the pin type load cell 10 shown in FIG.
A pin type load cell 10 according to the first embodiment shown in FIG. 1 is applied as a joint pin to a machine having a mechanism for connecting machine parts by a joint pin, and measures a shearing force applied to the joint pin.

As an application example of the pin type load cell 10, for example, the pin type load cell 10 is applied to the joint pins 82 and 83 for connecting the bucket 81 and the arms 84 and 85 of the excavator shown in FIG. 3, or the robot hands 91a and 91b shown in FIG. Are applied to joint pins 92 and 93 for connecting the arm 94 to the arm 94.
3 and 4 are diagrams showing application examples of the pin type load cell 10.

  FIG. 3A shows a hydraulic excavator excavating bucket 81 and arms 81, 85 that support the bucket 81 via joint pins 82, 83 and control the rotational operation of the bucket 81 in the direction of the arrow. FIG. 3B is an enlarged view as viewed in the direction of the arrow B in the vicinity of the connecting portion between the bucket 81 and the arm 84 in FIG.

  Further, FIG. 4 shows the robots 91a and 91b and the hands 91a and 91b used in the construction site and factory, and supporting the hands 91a and 91b via the joint pins 92 and 93, and the gripping operation of the arrows 91a and 91b in the arrow direction. It is the side view which showed the arm 94 which controls operation | movement of hand rotation operation | movement.

  When the pin type load cell 10 shown in FIG. 1 is applied to a joint pin 82 (see FIG. 3B) of a hydraulic excavator, the pin type load cell 10 serves to connect the bucket 81 and the arm 84. As the arm 84 and the bucket 81 move upward and downward, the load 81 (the weight of soil or the like excavated by the bucket 81 and the bucket 81 in the pin type load cell 10 (joint pin 82) (in FIG. 3B) The arm 84 supporting the bucket 81 has an upward force F1 (indicated by the upward white arrow in FIG. 3B) that is balanced with the load F1. Therefore, an upward force F1 from the arm 84 is applied to the pin type load cell 10 (joint pin 82).

Therefore, the shear force generated in the joint pin 82, that is, the pin type load cell 10 by these forces F 1 can be measured by the sensors 6 and 7.
As shown in FIG. 1, the pin type load cell 10 includes a substantially cylindrical pin 1 and detection rods 4 and 5 that are inserted into the pin 1 and on which strain detection sensors 6 and 7 are installed. Has been.
The pin 1 of the pin type load cell 10 is manufactured using, for example, structural carbon steel (S45C), and has a substantially cylindrical shape as shown in FIGS. 1 (a), 1 (b), and 1 (c). Cylindrical outer peripheral grooves 1m1 and 1m2 having an outer shape and having a short diameter at a portion where sensors 6, 7 such as metal resistance strain gauges are embedded are provided.

As shown in FIG. 1 (a), FIG. 1 (b), and FIG. 1 (c), a round shaft is provided on both sides of the neutral shaft that is the central axis of the pin 1 and is the axis of bending deformation. Half through-holes 2 and 3 that are holes are formed from both end edges to the vicinity of the center portion.
As shown in FIGS. 1 (b), 1 (c), and 2, the detection rods 4 and 5 for strain detection inserted into the semi-through holes 2 and 3 of the round holes are respectively shown in FIG. 3 is an elongated prismatic rod-like member made of stainless steel or the like having a square cross section with a diagonal line having a dimension approximately equal to the inner diameter of the inner peripheral wall surfaces 2n and 3n. FIG. 2 is a perspective view showing the detection rod 4 to which the sensor 6 is attached and the detection rod 5 to which the sensor 7 is attached.

As shown in FIG. 2, a sensor 6 to which a voltage input / output wiring 6h is connected is attached to one surface of the detection rod 4 by using, for example, an epoxy-based adhesive. A sensor 7 to which a voltage input / output wiring 7h is connected is bonded to one surface of the bar 5 using, for example, an epoxy-based adhesive.
As shown in FIG. 1 (d), when the detection rods 4 and 5 for strain detection are inserted into the half through holes 2 and 3, respectively, the plane corresponding to the outer peripheral grooves 1m1 and 1m2 6 and 7 are bonded using, for example, an epoxy-based adhesive. From these sensors 6, 7, voltage input / output wirings 6 h, 7 h are drawn out of the pin type load cell 10.

Here, as the sensors 6 and 7, a metal resistance strain gauge, a semiconductor strain sensor, or the like can be applied. This semiconductor strain sensor has an impurity diffusion resistance in which an impurity is introduced into a single crystal silicon substrate as a strain sensitive resistor. It is used and has features such as high sensitivity, low drift, and built-in amplifier having an amplifier circuit inside. The low drift means that the output fluctuation with time is small and the output fluctuation with respect to the temperature change is small, that is, the time drift and the temperature drift are low.
As for the dimensions of the pin type load cell 10, for example, the diameter of the pin 1 is 8.5 cm, and its length is 25 cm.

As described above, the pin-type load cell 10 has a square diagonal line of the cross-section of the detection rods 4 and 5 for detecting strain, which is substantially equal to the inner diameters of the pin inner peripheral walls 2n and 3n of the semi-through holes 2 and 3. The detection rods 4 and 5 for strain detection are inserted into the half through holes 2 and 3 in contact with the pin inner peripheral wall surfaces 2n and 3n forming the half through holes 2 and 3 with lines.
Here, as shown in FIGS. 1A and 1B, when the detection rod 4 is inserted into the semi-through hole 2 of the pin 1, the contact portion 4 b that contacts the pin inner peripheral wall surface 2 n of the semi-through hole 2. The contact line 4b1 is the four sides of the prism (see FIG. 1 (b), FIG. 2), and the part that contacts these four sides is the part A or the sensor where at least the sensor 6 is present in the detection rod 4 shown in FIG. 6, two contact lines 4 b 1 of the contact portion 4 b of the detection rod 4 are parallel to the axis 1 o (see FIG. 1) of the pin 1.

Similarly, as shown in FIGS. 1A and 1C, when the detection rod 5 is inserted into the half through hole 3 of the pin 1, the contact portion 5 b that comes into contact with the pin inner peripheral wall surface 3 n of the half through hole 3. The contact line 5b1 is the four sides of the prism (see FIG. 1 (c), FIG. 2), and the site where these four sides are in contact is the site A or the sensor having at least the sensor 7 in the detection rod 5 shown in FIG. 7, and two contact lines 5 b 1 of the contact portion 5 b of the detection rod 5 are parallel to the axis 1 o (see FIG. 1) of the pin 1.
As shown in FIG. 1 (d), the sensors 6 and 7 are arranged on a plane that forms one side of the square cross section of each of the detection rods 4 and 5 inside the outer peripheral grooves 1m1 and 1m2 of the pin 1. 1 (b) and FIG. 1 (c), the detection rods 4, 5 and the pin inner peripheral wall surface 2n, Between 3n, contact portions 4b and 5b and gaps 4a and 5a are formed.

As shown in FIG. 1B, the sensor 6 is disposed in one gap 4a1 of the pin type load cell 10, and the wiring 6h of the sensor 6 extends to the outside. ), The sensor 7 is disposed in one gap 5a1 of the pin type load cell 10, and the wiring 7h of the sensor 7 extends to the outside.
As shown in FIG. 1 (b), the resin 6 is filled in the gap 4a between the pin 1 where the sensor 6 of the pin type load cell 10 and its wiring 6h extend to the outside and the detection rod 4. Further, as shown in FIG. 1 (c), a resin J2 is filled in the gap 5a between the pin 1 and the detection rod 5 where the sensor 7 and its wiring 7h of the pin type load cell 10 extend to the outside. Various resins can be appropriately selected as the resins J1 and J2, but an epoxy resin that is resistant to water and has little secular change is desirable.

In order to further strengthen the fixing of the detection rods 4 and 5 to the pin 1, the detection rods 4 and 5 are press-fitted into the half-through holes 2 and 3 of the pin 1, respectively, or the pin 1 is heated and expanded to a high temperature. It is possible to perform shrink fitting or the like for cooling after inserting the detection rods 4 and 5 into the pin 1.
As described above, when the pin type load cell 10 is applied to the joint pin 82 of the excavator shown in FIG. 3, the pin type load cell 10 serves to connect the bucket 81 and the arm 84. As shown in (b), when the arm 84 and the bucket 81 try to move up and down respectively, the load F1 of the weight of soil or the like excavated by the bucket 81 and the bucket 81 on the pin type load cell 10 (joint pin 82). (Indicated by a downward white arrow in FIG. 3B) is added downward, while the arm 84 supporting the bucket 81 has an upward force F1 (in FIG. 3B) that balances the load F1. Therefore, a force F1 from the arm 84 is applied upward to the pin type load cell 10 (joint pin 82).

Therefore, as shown in FIG. 3B, in the pin type load cell 10 which is the joint pin 82, the force F1 applied from the bucket 81 is applied downward to both sides supporting the bucket 81, and from the arm 84, The applied F1 is applied upward to the central portion that supports the arm 84.
As described above, the loads F1 and F1 are applied to the pins 1 of the pin type load cell 10 in the opposite directions, and the outer peripheral grooves 1m1 and 1m2 are subjected to shear deformation.
As shown in FIGS. 1 and 3 (b), sensors 6 and 7 are arranged in the vicinity of the pin neutral shaft in the outer peripheral grooves 1m1 and 1m2 of the pin 1, and distortion caused by this shear deformation is regarded as a change in electric resistance. To detect.

  As shown in FIGS. 1 (a), 1 (b), and 2, the contact line 4b1 of the contact portion 4b of the detection rod 4 contacting the pin inner peripheral wall surface 2n of the semi-through hole 2 of the pin 1 is a prismatic shape. The contact line 4b1 on the four sides of the contact portion 4b of the detection rod 4 is the axis of the pin 1 and has four sides and at least the part A where the sensor 6 is located on the detection rod 4 or the two parts B sandwiching the sensor 6 Since it is parallel to the core 1o (see FIG. 1), the shear deformation of the pin 1 is accurately transmitted to the sensor 6 of the detection rod 4, and the sensor 6 can accurately detect the shear deformation. .

  Similarly, as shown in FIGS. 1 (a), 1 (c), and 2, the contact line 5b1 of the contact portion 5b of the detection rod 5 contacting the pin inner peripheral wall surface 3n of the semi-through hole 3 of the pin 1 is a prism. Of the detection rod 5, at least the portion A where the sensor 7 is located or the two portions B sandwiching the sensor 7, and the contact lines 5b1 on the four sides of the contact portion 5b of the detection rod 5 are Since it is parallel to the shaft core 1o (see FIG. 1), the shear deformation of the pin 1 is accurately transmitted to the sensor 7 of the detection rod 5, and the sensor 7 can accurately detect the shear deformation. Yes.

Although the pin 1 causes bending deformation as well as shear deformation due to the load F1, the strain due to the bending deformation changes depending on the position of the load point. Therefore, in the pin type load cell 10, the strain due to the shear deformation is detected by the sensors 6 and 7. is doing.
FIG. 5 is an enlarged conceptual view of a portion C around the sensor 6 in the pin type load cell 10 serving as a rotation shaft in the bucket 81 and the arm 84 shown in FIG.
As shown in FIG. 5, the sensor 6 provided in the outer peripheral groove 1m1 of the pin 1 can detect the strains ε _x and ε _y due to shear deformation by being disposed at an inclination of 45 degrees with respect to the direction of the load F1. .

That is, in order to detect the strains ε _x and ε _y in the 45 degree direction generated by the shearing force F1 applied to the pin 1 by the sensor 6, the sensor 6 is arranged in a direction having sensitivity in that direction.
Note that the sensor 6 shown in FIG. 5 is configured to be able to detect distortions in the side direction of the outer shape of the square, that is, distortions ε _x and ε _y .
The sensor 7 provided in the outer peripheral groove 1m2 of the pin 1 is also arranged in the same manner.
An output signal obtained by detecting a change in resistance value caused by the strains ε _x and ε _y of the sensors 6 and 7 mounted in this way is transmitted to the control unit, and an arithmetic unit such as a microcomputer of the control unit is used. By calculating, from the output signal of the pin type load cell 10, the excavation force of the bucket 81 of the hydraulic excavator shown in FIG. 3A to which the pin type load cell 10 is applied, and the hands 91a and 91b of the work robot shown in FIG. A gripping force or the like can be obtained.

According to the said structure, when inserting the detection rods 4 and 5 in the half through-holes 2 and 3 of the pin 1, respectively, as shown in FIG.1 (b) and FIG.1 (c), the pin 1 and the detection rod 4 are shown. Therefore, the pin 1 is easily positioned on the neutral shaft.
Moreover, the deformation | transformation which arose in the pin 1 can be transmitted to the detection rods 4 and 5 via the contact parts 4b and 5b.
Further, since the pin-type load cell 10 is provided with the gaps 4a and 5a, the sensors 6 and 7 and the wirings 6h and 7h extending from the respective sensors 6 and 7 can be installed in the gaps 4a and 5a, thereby securing an installation space. it can. Therefore, it is not necessary to process the holes for drawing out the wires 6h and 7h and the recesses for arranging the sensors 6 and 7 in the detection rods 4 and 5 to secure a new installation space.

Thereby, the structure of the pin type load cell 10 can be simplified, and cost reduction can be achieved.
Further, the resin J1 can be easily injected onto the outer surface of the sensor 6 by the gap 4a between the pin 1 and the detection rod 4, and the resin J2 can be easily injected onto the outer surface of the sensor 7 by the gap 5a between the pin 1 and the detection rod 5. . The resins J1 and J2 reinforce the fixing of the detection rods 4 and 5 to the inner peripheral wall surfaces 2n and 3n of the pin 1, and the resin J1 and J2 are used to connect the pin type load cell 10 from the outside. Since the intrusion of moisture, the intrusion of dust and the like can be prevented and the influence of outside air can be blocked, the weather resistance of the sensors 6 and 7 is improved.

5 illustrates the case where the direction of the sensitivity for detecting the strain of the sensor 6 is inclined by 45 degrees with respect to the direction of the load F1, but the direction of the sensitivity for detecting the strain of the sensor 6 is the load F1. If the sensor 6 is arranged in a non-perpendicular direction, the shear force can be calculated using a trigonometric function. Therefore, if the direction of sensitivity of the sensor 6 and the direction of the load F1 are non-perpendicular, the sensor 6 is set to the load F1. The angle to be arranged is not limited to 45 degrees.
<< Modification of First Embodiment >>

FIG. 6 shows a pin type load cell 10 ′ according to a modification of the pin type load cell 10 of the first embodiment. FIG. 6 (a) shows a pin type load cell 10 ′ according to a modification of the first embodiment. FIG. 6B is a right side view of the pin type load cell 10 ′ shown in FIG. 6A, and FIG. 6C is a cross-sectional view taken along the line DD of FIG. 6B. It is.
In the pin type load cell 10 of the first embodiment, the semi-through holes 2 and 3 are drilled from both ends of the pin 1 to the center, and the detection rods 4 and 5 are inserted into the semi-through holes 2 and 3 from both ends of the pin 1. As shown in FIG. 6, the pin type load cell 10 ′, which is inserted in this way, has a semi-through hole 2 ′ drilled from one end side of the neutral shaft of the pin 1 ′. One detection rod 4 ′ provided with sensors 6 ′ and 7 ′ is inserted into the half through hole 2 ′.

  Here, the contact lines 4b1 ′ of the contact portion 4b ′ of the detection rod 4 ′ that contacts the pin inner peripheral wall surface 2n ′ of the semi-through hole 2 ′ of the pin 1 ′ are the four sides of the prism (see FIG. 6B). As in FIG. 2, at least the sensor 6 ′, 7 ′ in the detection bar 4 ′ is a part A ′ where the sensor 6 ′, 7 ′ is located, or two parts B ′ sandwiching the sensors 6 ′, 7 ′, and the detection bar 4 ′ The contact lines 4b1 ′ on the four sides of the contact portion 4b ′ are parallel to the axis 1o ′ (see FIG. 6) of the pin 1 ′.

Since the configuration other than this is the same as that of the first embodiment, components similar to those of the first embodiment are indicated by adding “(dash)” to the reference numerals of the first embodiment, and detailed description thereof is omitted. To do.
The modified pin type load cell 10 ′ is applied as a joint pin 82, 83 or the like for connecting the bucket 81 and the arms 84, 85 of the excavator shown in FIG.
Therefore, a pin fixing hole 1k ′ for inserting a fixing pin (not shown) for fixing the pin type load cell 10 ′ to the bucket 81 and the arm 84 etc. into the pin 1 ′ is provided on the other end side of the pin 1 ′. Perforated.

According to this modification, the detection rod 4 ′ is inserted on one side of the pin type load cell 10 ′, and the fixing hole 1k ′ for fixing to the detection target machine is formed on the other side of the pin type load cell 10 ′. Therefore, the pin type load cell 10 ′ can be easily fixed by inserting a fixing pin into the fixing hole 1k ′.
Moreover, since all the wiring 6h and 7h can be pulled out from one side of pin 1 ', it is easy to lay.
Further, even when the pin fixing hole 1k ′ is provided, the sensors 6 ′ and 7 ′ can be installed in the left and right groove portions 1m1 ′ and 1m2 ′.
In addition, the effect which the structure of other 1st Embodiment show | plays similarly is show | played.

<< Second Embodiment >>
Next, the pin type load cell 20 of 2nd Embodiment is demonstrated using FIG. 7A is a front view of the pin type load cell 20 of the second embodiment, and FIG. 7B is a cross-sectional view taken along line EE of FIG. 7A.
The pin type load cell 20 of the second embodiment is provided with a pair of sensors 26a and 26b facing each other with the detection rod 24 in between, and a pair of sensors 26c and 26d facing each other with the detection rod 24 in between. It is.

Since the configuration other than this is the same as that of the first embodiment, components similar to those of the first embodiment are denoted by the reference numeral of the first embodiment, and detailed description thereof is omitted. .
In the pin type load cell 20 of the second embodiment shown in FIG. 7 (a), as shown in FIG. 7 (b), the detection rod 24 is a square rod having a square cross-sectional shape, and the outer peripheral groove 21m1 of the pin 21. The sensors 26a and 26b are arranged to face each other on the four planes inside, and the sensors 26c and 26d are arranged to face each other.

  Here, as shown in FIGS. 7A and 7B, the contact line 24b1 of the contact portion 24b of the detection rod 24 that contacts the pin inner peripheral wall surface 22n of the semi-through hole 22 of the pin 21 has four sides of the prism. 2 (see FIG. 7B), and similarly to FIG. 2, at least the sensor 26a, 26b, 26c, 26d in the detection rod 24 or two parts sandwiching the sensors 26a, 26b, 26c, 26d The contact lines 24b1 on the four sides of the contact portion 24b of the detection rod 24 are parallel to the axis 21o of the pin 21 (see FIG. 7A).

Similarly, the detection rod 25 of the pin type load cell 20 is a long rectangular bar having a square cross-sectional shape, and a pair of sensors are respectively opposed to the four planes inside the outer peripheral groove 21m 2 of the pin 21. It is arranged.
Similarly to FIGS. 7 (a) and 7 (b), the contact line of the contact portion of the detection rod 25 that contacts the inner wall surface of the pin of the semi-through hole of the pin 21 is a rectangular column as in FIG. 7 (b). 2, and at least a part of the detection rod 25 where the sensor 27a,... Is located or two parts sandwiching the sensor 27a, and the contact of the four sides of the contact portion of the detection bar 25. The line is parallel to the axis 21o of the pin 21 (see FIG. 7A).

As shown in FIG. 7B, the sensors 26a and 26c are installed on the two orthogonal surfaces 24m1 and 24m2, and the sensors 26b and 26d are installed on the two orthogonal surfaces 24m3 and 24m4. Can be detected by the sensors 26a and 26b, the load in the α2 direction can be detected by the sensors 26c and 26d, and the loads in the two directions α1 and α2 can be detected separately.
From these two output results, the load direction and size in the cross section of the detection rod 24 can be calculated.

Further, as shown in FIG. 7C, which is an enlarged view of the F part in FIG. 7A, the sensors 26c and 26d are installed on the two opposing surfaces 24m2 and 24m4, so that bending deformation due to the bending M is caused. When this occurs, an output fluctuation (+) due to the bending M (+), that is, an extension strain occurs in the sensor 26c, and an output fluctuation (−) due to the bending M, that is, a contraction distortion occurs in the sensor 26d.
Therefore, adding the output result of the sensor 26c and the output result of the sensor 26d and dividing by 2 cancels the output fluctuation (+) of the sensor 26c and the output fluctuation (-) of the sensor 26d, which cause measurement errors. can do.
Similarly, since the sensors 26a and 26b are installed on the two opposite surfaces 24m1 and 24m3, output results due to bending deformation that cause measurement errors can be canceled by adding the respective output results.
The same applies to the detection rod 25 inside the outer peripheral groove 21m2 of the pin 21 because a pair of sensors are arranged on the four planes to face each other.

<< Third Embodiment >>
Next, the pin type load cell 30 of 3rd Embodiment is demonstrated using FIG. 8A is a front view of the pin type load cell 30 according to the third embodiment, and FIG. 8B is a cross-sectional view taken along the line GG of FIG. 8A. ) Is a cross-sectional view taken along the line GG of FIG. 8A in a modified form different from FIG.
As shown in FIGS. 1B and 7B, the detection rods 4 and 5 of the pin type load cell 10 of the first embodiment and the detection rods 24 and 25 of the pin type load cell 20 of the second embodiment are square. However, the detection rod may be in a shape that is in contact with the half through holes 2 and 3 provided in the pin 1 by a line, as in the pin type load cell 30 shown in FIG. A structure in which the polygonal detection rod 34 other than a square is in contact with the inner peripheral wall surface 32 n of the half through-hole 32 may be employed.

As shown in FIGS. 8A and 8B, the contact line 34b1 of the contact portion 34b of the detection rod 34 that contacts the pin inner peripheral wall surface 32n of the half through hole 32 of the pin 31 is each side of the polygonal column. In addition, as in FIG. 2, at least a part of the detection rod 34 where the sensor 36 is located or two parts sandwiching the sensor 36, and a contact line 34 b 1 on each side of the contact portion 34 b of the detection bar 34 is the axis of the pin 31. It is parallel to the core 31o (see FIG. 8A).
Similarly, as shown in FIGS. 8A and 8B, the contact line of the contact portion of the detection rod 35 that contacts the pin inner peripheral wall surface 33n of the half through hole 33 of the pin 31 is on each side of the polygonal column. In addition, as in FIG. 2, at least the part where the sensor 37 is present or the two parts sandwiching the sensor 37 in the detection bar 35, and the contact line on each side of the contact part of the detection bar 35 is the axis of the pin 31. It is parallel to 31o (see FIG. 8A).

Further, as shown in FIG. 8 (c), the detection rod 34 ′ having a circular cross section may be in contact with the inner peripheral wall surface 32n ′ of the semi-through hole 32 ′ having a square hole shape of the pin 31 ′. .
Here, as shown in FIGS. 8A and 8C, the contact line 34b1 ′ of the contact portion 34b ′ of the detection rod 34 ′ that contacts the pin inner peripheral wall surface 32n ′ of the half through hole 32 ′ of the pin 31 ′. Are four points facing each other as a pair of intersections between a diameter line perpendicularly intersecting the cross section of the detection rod 34 ′ shown in FIG. 8C and the outer peripheral surface of the detection rod 34 ′, and FIG. Similarly, at least the part where the sensor 36 ′ is located in the detection rod 34 ′ or two parts sandwiching the sensor 36 ′, and the contact line 34b1 ′ of the contact portion 34′b of the detection bar 34 ′ is the axis of the pin 31 ′. It is parallel to the core 31o ′ (see FIG. 8A).

As shown in FIG. 7 (b), the sensors are provided facing the sensors 36 and 36 '(see FIGS. 8 (b) and 8 (c)) to separate the loads in the two directions. Therefore, the output fluctuations caused by bending deformation that cause measurement errors can be canceled by adding the output results of the sensors provided opposite to each other.
Since the configuration other than this is the same as that of the first embodiment, components similar to those of the first embodiment have a sign of 30 in the sign of the first embodiment or '(dash) in the sign of the thirty place. A detailed description will be omitted.

<< Fourth Embodiment >>
Next, a pin type load cell (not shown) of the fourth embodiment will be described with reference to FIG. FIG. 9 is a perspective view of the pin type load cell detection rod 44 of the fourth embodiment.
The pin type load cell (not shown) of the fourth embodiment is provided with a cylindrical half-through hole in the pin as in the pin type load cell of the first to third embodiments (FIG. 1). (See (b), (c), (d)).
As shown in FIG. 9, the detection rod 44 inserted into the cylindrical half through-hole in the pin has a square cross-sectional shape, but the cross-sectional shape is not constant in the longitudinal direction, and the sensor 46 A thin stepped portion 46d is formed in the vicinity of the bonded portion.

  Here, when the detection rod 44 is inserted into the cylindrical half through hole of the pin, the contact lines 44b1 of the contact portion 44b of the detection rod 44 that contacts the inner peripheral wall surface of the pin are the four sides of the prism (see FIG. 9). 2, and at least two portions B sandwiching at least the sensor 46 in the detection rod 44, and the contact lines 44 b 1 on the four sides of the contact portion 44 b of the detection rod 44 are similar to those in FIG. Parallel to the axis of the pin

Since the configuration other than this is the same as that of the first embodiment, components similar to those of the first embodiment are denoted by the reference numeral of the first embodiment, and detailed description thereof is omitted. .
Since the stepped portion 46d has a narrower shape than the other portions of the detection rod 44, the section modulus of the stepped portion 46d is smaller than that of the other portion and is greatly deformed when a load is applied. Since the generated distortion, that is, the output can be amplified and measured, the measurement accuracy is improved.
In addition, if the diameter of the semi-through hole of the pin must be reduced for reasons such as reducing the strength reduction, the space between the inner peripheral wall surface of the pin and the detection rod becomes narrow, and the installation space for the sensor and sensor wiring is narrow. It may happen that the wiring cannot be installed.
On the other hand, the installation space of the sensor and its wiring can be secured by providing the stepped portion 46d.

<< Fifth Embodiment >>
Next, a pin type load cell (not shown) according to a fifth embodiment will be described with reference to FIGS. FIG. 10 is a perspective view of the detection rod 54 according to the fifth embodiment, and FIG. 11 is a perspective view of a detection rod 54 ′ according to a modification of the fifth embodiment.
In the pin type load cell of the fifth embodiment, a cylindrical half-through hole is formed in the pin as in the pin type load cell of the first to third embodiments (FIG. 1 (b), ( c), see (d)).
As shown in FIG. 10, the detection rod 54 of the pin type load cell of the fifth embodiment has a surface contact area 54 p from the one end surface 54 t 1 of the detection rod 54 to the vicinity of the sensor 56 with respect to the inner peripheral wall surface of the cylindrical pin. From the vicinity of the sensor 56 to the other end face 54t2 of the detection rod 54, a thin stepped portion that forms a prismatic line contact region 54s is formed.

  Here, when the detection rod 54 is inserted into the cylindrical half through-hole of the pin, the contact line 54b1 of the contact portion 54b in the line contact region 54s of the detection rod 54 that contacts the inner peripheral wall surface of the pin is a prismatic 4 2, and in the same manner as in FIG. 2, at least the part A having the sensor 56 in the line contact region 54 s of the detection bar 54 or the two parts B sandwiching the sensor 56, and the line of the detection bar 54 The contact lines 54b1 on the four sides of the contact portion 54b of the contact area 54s are parallel to the axis of the pin, as in FIG.

By making surface contact from one end face 54t1 of the detection rod 54 to the vicinity of the sensor 56, when the detection rod 54 is fixed by shrink fitting that heats and expands the pin to a high temperature, the surface contact region 54p of the detection rod 54 and the pin The contact area with the inner peripheral wall of the pin becomes larger, and the region where the detection rod 54 receives pressure from the inner peripheral wall surface of the pin is expanded and the fixing is strengthened than in the case of only the line contact.
In addition, since there is a line contact from the vicinity of the sensor 56 to the other end surface 54t2 of the detection rod 54, a space is generated between the inner peripheral wall surface of the pin and the line contact portions 54b and 54b. An installation space for the wiring 56h can be secured.

In the detection rod 54 ′ of the modified form of the fifth embodiment shown in FIG. 11, the outer peripheral surface of the detection rod 54 ′ is the same as the inner peripheral wall surface of the cylindrical pin similar to the first to third embodiments. Are not in contact with each other over the entire surface, but only a part of the cylindrical surfaces 54b1 ′, 54b2 ′, 54b3 ′, 54b4 ′ are in contact with each other.
Here, when the detection rod 54 ′ is inserted into the cylindrical half through-hole of the pin, the contact cylindrical surface 54b0 ′ of the contact portion of the detection rod 54 ′ that contacts the inner peripheral wall surface of the pin has four cylindrical cylinders. The surface 54b1 ′, 54b2 ′, 54b3 ′, 54b4 ′, and similarly to FIG. 2, at least the sensor 56 ′ of the detection rod 54 ′ or the two parts B ′ sandwiching the sensor 56 ′, And the four contact cylindrical surfaces 54b0 'of the detection rod 54' are parallel to the axis of the pin, as in FIG.

When the detection rod 54 ′ is fixed by shrink fitting by making surface contact with the inner peripheral wall surface of the pin at some cylindrical surfaces 54b1 ′, 54b2 ′, 54b3 ′, 54b4 ′ of the detection rod 54 ′, The contact area with the inner peripheral wall surface of the pin is increased, and the fixing is strengthened as compared with the case of only line contact. Further, since the surface of the detection rod is not in contact with the entire surface, an installation space for the sensor 56 ′ and its wiring 56h ′ can be secured between the inner peripheral wall surface of the pin and the detection rod 54 ′.
As described above, the first to fifth embodiments have been described. However, in the pin type load cell shown in the first to fifth embodiments, the detection rod is in contact with the inner peripheral wall surface of the pin by a line. The deformation of the pin can be transmitted to the detection rod from the contact portion between the detection rod and the pin.

In addition, since the detection rod is in line contact with the pin, a hole for drawing the wiring from the sensor to the outside and a recess for installing the sensor are unnecessary and a simple structure can be achieved, thereby reducing the cost.
In addition, by filling the gap between the inner peripheral wall surface of the pin and the detection rod with, for example, an epoxy resin that is resistant to moisture and has little secular change, entry of moisture from the outside and intrusion of foreign matter can be prevented. Will improve.
In addition, although the structure of Embodiment 1 to Embodiment 5 was demonstrated independently, it is also possible to comprise combining the structure of Embodiment 1 to Embodiment 5 suitably.

(a) is a front view of the pin type load cell of the first embodiment, (b) is a right side view of the pin type load cell shown in (a), and (c) is shown in (a). It is a left view of the pin type load cell shown, (d) is the sectional view on the AA line of the pin type load cell of (b) figure. It is a perspective view which shows the detection rod 4 to which the sensor 6 was attached, and the detection rod 5 to which the sensor 7 was attached. (a) is the side view which showed the bucket for excavation of a hydraulic shovel, and the arm which carries out operation | movement control of the rotation operation | movement of the excavation operation of the bucket in the arrow direction, (b) is the bucket of FIG. It is a B direction arrow enlarged view around the connection part of an arm. It is the side view which showed the hand of the work robot used in a construction site and a factory, and the arm which supports this hand via a joint pin, and controls the rotation operation | movement of the holding | grip operation | work of the arrow direction of a hand. FIG. 4 is an enlarged conceptual view of a portion C around a sensor in a pin-type load cell serving as a rotation axis of the bucket and arm shown in FIG. (a) is a front view of a pin type load cell of a modification of the first embodiment, (b) is a right side view of the pin type load cell shown in (a), and FIG. b) It is the DD sectional view taken on the line of a figure. (a) is a front view of the pin type load cell of 2nd Embodiment, (b) is EE sectional view taken on the line of (a), (c) is F section of (a) figure It is an enlarged view. (a) is a front view of a pin type load cell of a 3rd embodiment, (b) is a GG line sectional view of (a) figure, (c) is a (a) figure of a modification. It is a GG sectional view taken on the line. It is a perspective view of the detection rod of 4th Embodiment. It is a perspective view of the detection rod of 5th Embodiment. It is a perspective view of the detection rod of the modification of 5th Embodiment. It is a perspective view of the detection block which installed the sensor for measurement in the conventional pin type load cell.

Explanation of symbols

1, 1 ', 21, 31, 31' ... pins 2, 3, 2 ', 23, 32, 32' ... half-through holes (holes),
2n, 3n, 2n ', 23n, 32n, 32n' ... inner peripheral wall surface (inner wall),
4, 5, 24, 25, 34, 34 ', 44, 54, 54' ... detection rod (distortion detection rod)
6, 7, 6 ', 7', 26a, 26b, 26c, 26d, 36, 37, 46, 56, 56 '... Sensor (Sensor for strain measurement)
6h, 7h, 6h ′, 7h ′, 26h, 27h, 36h, 37h, 46h, 56h, 56h ′... Wiring (input / output wiring)
10, 10 ', 20, 30, 30' ... pin type load cell,
46d: Stepped portions 54b1 ', 54b2', 54b3 ', 54b4' ... Cylindrical surface 54p ... Surface contact area (cylindrical surface)
J1, J2, J1 ', J21, J31, J31' ... resin

Claims (9)

A pin having a hole provided in a region including the central axis, to which a load is applied;
A strain detection rod provided to contact the inner wall of the hole with a line;
A strain measuring sensor installed on the strain detecting rod and having input / output wiring;
A pin type load cell provided between the strain detection rod and the pin, and covering the strain measurement sensor and through which the input / output wiring is inserted. In claim 1,
The strain sensor is a strain gauge or a semiconductor strain sensor. In claim 1,
The pin-type load cell, wherein the strain measuring sensor is provided at a location where shear deformation of the strain detecting rod occurs. In claim 3,
The pin-type load cell is characterized in that the strain measuring sensor is installed with a direction of sensitivity for detecting strain inclined by 45 degrees with respect to a load applied to the strain detecting rod. In claim 1,
A cross-sectional shape of the strain detection rod is a polygonal shape or a circular shape. In claim 1,
The strain sensor is provided on at least one surface of the strain detection rod between the pin and the strain detection rod. In claim 1,
The strain detection rod is provided with the sensor unit for strain measurement, and is provided with a stepped portion that is narrower than other portions. In claim 1,
The strain detection rod is provided with a region in contact with a surface in addition to a region in contact with a line on an inner wall of the hole of the pin. In claim 1,
A pin type load cell, wherein the strain detection rod has a cylindrical surface partially in contact with an inner wall of the pin hole.

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