JPH07181090A - Load sensor board and load sensor - Google Patents

Abstract

PURPOSE:To obtain a highly accurate high strength load sensor having simple structure by embedding a disc incorporating a strain gauge into a structural body, e.g. a pin, and then recovering the surface completely. CONSTITUTION:A stainless steel disc 10 is provided with four small holes 21-24 symmetrically to axes L1, L2 intersecting perpendicularly at the center O0 of the disc. Thin film strain gauges 31-34 are patterned on the axes L1, L2 between the adjacent small holes while being insulated from the disc 10 with the direction of sensitivity being matched with the axes L1, L2. Electrodes 41-44 for bridging the gauges 31-34 are patterned in other regions. The small holes 21-24 prevent concentration of of stress and since elongating/contracting parts are provided radially between the small holes 21-24, the anisotropy of stress becomes conspicuous and since the board is made of a plate, the load is converted immediately into stress thus enhancing the accuracy in measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a high strength, a high measurement accuracy,
And a load sensor substrate having a simple structure and a load sensor.

[0002]

2. Description of the Related Art Measurement of loads applied to mechanical structural members is important for design and control. A bridge using a strain gauge is usually used for the measurement. Most strain gauges have a line gauge or foil gauge installed on one side (or both sides) of a flexible resin substrate and adhesive applied to the other side, and the adhesive side is used as the member to be measured. Attach and use.

For example, a pin-type load sensor for measuring a load applied between members connected to a pin is one in which a strain gauge is incorporated in a pin, and the following ones are known. (1) A pin with a recess on the outer surface and a strain gauge attached inside the recess (2) A pin with a strain gauge attached on the inner surface (3) A recess on both end faces of the pin A member in which a strain gauge is attached to the sensitive section is inserted and further plugged (see, for example, JP-A-61-145426).

The load measurement by the pin type load sensor is
Shear strain caused by the load applied to the pin is received by the resistance change of the strain gauge, and the output voltage of the bridge due to this resistance change is converted into the load. Therefore, the strain gauge is usually attached with its sensitivity direction aligned with the principal stress direction based on the shearing force.

[0005]

By the way, the load sensor for measuring the load applied to the mechanical structural member is not only high in measurement accuracy but also high in strength itself, as can be seen from the above-mentioned pin type load sensor. is important. However, the conventional pin type load sensor has the following problems.

In the pin type load sensor of (1), since the concave portion serves as a stress concentration portion, the pin strength is low. In order to increase the strength of this, it is sufficient to make the pin diameter thick, but if this is done, the measurement accuracy will decrease. Also, since the strain gauge is exposed, it is easy to install, but the strain gauge is easily peeled off and damaged, resulting in a short life.

The pin type load sensor of (2) has a high strength as the cylinder thickness is increased, but the measurement accuracy is lowered. Further, since the strain gauge is mounted inside the cylinder, it is difficult to mount it, and it is easy to peel off if it is not as thick as the pin type load sensor of the above (1), so that the life is short.

The pin type load sensor of (3) has high strength and high measurement accuracy, but has a large number of parts such as an insertion member and a plug, and has a complicated structure.

It is an object of the present invention to provide a load sensor substrate and a load sensor having high strength, high measurement accuracy and a simple structure, paying attention to the above problems of the prior art.

[0010]

In order to achieve the above object, the load sensor according to the first aspect of the present invention comprises a disk, in which a strain gauge is incorporated, embedded in a structure such as a pin, and the surface thereof is completely restored. It is characterized by that.

The load sensor according to the second aspect of the invention is characterized in that, in the load sensor according to the first aspect of the invention, the surface is hardened after being restored.

The load sensor of the third invention is characterized in that, in the load sensor of the first invention or the second invention, the amplifier board 70 is mounted in the vicinity of the sensor portion.

A load sensor substrate according to a fourth aspect of the present invention is characterized in that a circular plate is provided with notched holes having a gentle shape, and a strain gauge is installed in a gap between the holes. .

A load sensor substrate according to a fifth aspect of the present invention is characterized in that, in the load sensor substrate according to the fourth aspect of the present invention, the disc is made of stainless steel, and the thin film strain gauge is installed on the disc.

The load sensor substrate according to the sixth aspect of the present invention will be described with reference to FIGS. 1A and 1B. In the metal disc 10, an orthogonal axis L1 with the disc center Oo as an intersection point. ,
Four small holes 20 which are line-symmetrical to L2 are provided, and the orthogonal directions L1 and L2 between the adjacent small holes 20 are insulated from the disc 10 and the sensitivity direction is the orthogonal axes L1 and L2 directions. The strain gauge 30 is installed.

Although not shown, the load sensor substrate according to the seventh aspect of the present invention is a metal cross-shaped plate in which the end faces of the intersections are gently formed and the lengthwise surface is insulated from the cross-shaped plate. In addition, the strain gauge 30 having the sensitivity direction set to the longitudinal direction of the longitudinal portion may be installed.

The load sensor of the eighth invention is shown in FIG.
Referring to (a), (b) and FIGS. 3 (a) to (c), the pin 30 for connecting the members 400 and 500 with a pin.
0, a concave portion 320 is provided in a portion P where a shearing force is generated based on the load F applied between the members 400 and 500, and the load sensor substrate according to claim 6 or 7 is provided in the concave portion 320 when the sensitivity direction is the It is fixed so as to have a principal stress direction based on the shearing force, and is further plugged with a plug 330 so as to be integrated with the pin 300.
It is characterized in that a lead hole 310 for guiding the lead wire 60 of the strain gauge 30 toward the outside of 0 is provided.

[0018]

The operation of the load sensor substrate and the load sensor will be described collectively. When the load F is applied between the members 400 and 500, the portion P of the pin 300 corresponding to the joint position of these members.
Shear force is generated in the. Then, a principal stress in the orthogonal direction is generated in the portion P. On the other hand, whether the load sensor substrate is a disc or a cross, the strain gauges 30 are installed so that their sensitivity directions are orthogonal to each other. Therefore, such a load sensor substrate is attached to the pin 300 so that the sensitivity direction of the strain gauge 30 matches the principal stress direction. By doing so, the load F can be measured with high accuracy. However, if it is left as it is, the pin strength does not change, but since the strain gauge 30 is exposed, the life becomes short. Therefore, a concave portion 320 is provided in the portion P, and the load sensor substrate is first fixed in the concave portion 320 by welding or the like, and then the plug 330 is integrated with the pin 300. The lead wire 60 from the strain gauge 30 is guided to the lead hole 310 provided from the inside of the recess 320 toward the outside of the pin 300. As described above, according to the load sensor, the load sensor substrate and the load sensor have high strength, high measurement accuracy, and a simple structure.

[0019]

EXAMPLE An example of the load sensor substrate 100 is shown in FIG. As shown in FIGS. 1 (a) to 1 (c), the stainless steel disk 10 has orthogonal axes L 1 and L with the disk center Oo as an intersection.
2 are line-symmetric to each other (in other words, 9 at center Oo
4 small holes 20 (21 to 24) that are phased by 0 degrees and are point objects)
Is provided. And the small holes (21 and 2) adjacent to each other
2, 22 and 23; 23 and 24;
(31 to 34) are patterned respectively. Electrodes 40 (41 to 44) for bridge connection between the thin film strain gauges 30 (31 to 34) are patterned in the other region.

The small holes 20 are holes for preventing stress concentration. The small hole 20 is ideally circular, but may be any shape as long as it can prevent stress concentration, and may be any shape that is gentle, such as a long hole, a half hole, or a rice ball-shaped hole. If the shape is gentle, the circular plate 10 may be used instead of the circular plate 10, for example, a substantially cross-shaped plate in which the end faces of the intersecting portions are gently formed.

Thin film strain gauge 30 (31-34) and electrode 4
The bridge pattern with 0 (41 to 44) is, for example, as shown in FIG.
It is an all bridge shown in (e). As shown in FIG. 1D, this patterning is performed by, for example, Si on the disk 10.
An insulating film 51 made of O2, a strain gauge 30 made of a semiconductor thin film by vapor deposition, and a thin film electrode 40 made by vapor deposition of aluminum
And a protective film 52 made of SiNx are laminated in this order. In FIG. 1 (e), the symbol e indicates the voltage applied to the bridge, and the symbol E indicates the output voltage of the bridge. Lead wires 60 (61 to 64) are provided on each of the electrodes 40 (41 to 44).
Are soldered respectively.

As another embodiment, although not shown, the number of strain gauges 30 and the number of electrodes 40 depend on the application of the load sensor substrate 100 (that is, shearing force, vertical force, twisting force (twisting force). When measuring, it can be said that it is more like a torque sensor than a load sensor) and for each measurement purpose) such as tolerance, double-sided installation, single-sided installation, external resistance, all bridges
Various arrangements can be made for each configuration such as half bridge, series bridge, parallel bridge, and contents of computer processing. Next, the effect of the embodiment will be described.

(1) The measurement accuracy is improved for the following reasons. (A) Since the circular plate 10 is provided with four small holes 20, and in the case of a substantially cross-shaped plate or the like, the intersecting portion has a gentle shape,
Stress concentration is unlikely to occur. Therefore, the measurement accuracy is improved. (B) Since the radial direction between the small holes 20 serves as a stretchable portion, stress anisotropy becomes remarkable. Therefore, the measurement accuracy is improved. (C) Since the substrate is a plate, the load immediately changes to strain. Therefore, the measurement accuracy is improved. (D) Since the circular plate 10 and the substantially cross-shaped plate are made of metal, the strain gauge 30 and the electrode 40 can be thinned. Such a thin film strain gauge has measurement accuracy several times higher than that of a line gauge or a night gauge. The strain gauge 30 is not limited to the thin film strain gauge, and may be a line gauge or a foil gauge.

(2) If the strain gauge 30 is made thin, the load sensor substrate can be downsized. Further, unlike the line gauge and the night gauge, the thin film gauge has resistance to external vibration and mechanical damage. As described above, the strain gauge 30
Is not limited to the thin film strain gauge, and may be a line gauge or a foil gauge.

(3) Since the circular plate 10 and the substantially cruciform plate are made of metal, the load sensor substrate 100 can be directly fixed to a measured object such as a pin or a steel plate by welding or cold fitting.

Next, the load sensor substrate 10 according to the above embodiment.
An example of the load sensor using 0 will be described with a pin-type load sensor for measuring the load F applied between the members 400 and 500 connected to each other by a pin.

The first embodiment is shown in FIG. Pin 300 is S
The C member is a cantilever support in which the fixed member 400 and the rotating member 500 are pin-connected. The pin 300 is shown in FIG.
As shown in (a) and (b), a load F in a substantially constant direction is applied downward in the drawing. Then, in the portion P (the joint between the members 400 and 500) where the shearing force is generated based on the load F, one of the above-described embodiments is provided so that the sensitivity direction of the strain gauge 30 matches the principal stress direction based on the shearing force. 100 g of the load sensor substrate is embedded and fixed.

At the part P, as shown in FIG.
A stepped counterbore (hereinafter referred to as a recess 320) is provided, and as shown in FIG. 3B, the load sensor substrate 100 g is fixed to the bottom of the second step 322 by welding the outer periphery. Then, as shown in FIG. 3C, a blind plug 330 made of SC material is fitted into the first stage 323 and welded on the outer circumference. The blind plug 330 is induction hardened together with the surface of the pin 300 to provide a surface hardened layer 350, and is then polished. Therefore, there is no difference in appearance from ordinary pins. It should be noted that the bottom of the third stage 311 is shown in FIG.
As shown in (a) to (c), a sub lead hole 311 communicating with the chamber 313 storing the amplifier substrate 70 via the main lead hole 312 is provided.
Pin type load sensor 100g via (311, 312)
The lead wires 60 (61 to 64) are connected to the amplifier substrate 70. The lead wire from the amplifier board 70 is connected to an external calculator (not shown), and the load F is calculated by this calculator.

The recess 320 is not limited to three stages as described above, but may be multiple cuts, two stages, one stage, or a tapered hole. Also, a recess may be provided on the back surface of the blind plug 330, the outer periphery of the load sensor substrate 100g may be welded and fixed in the recess, and the blind plug 330 may be fitted into the recess 320 of the pin 300 and welded to the outer periphery (such a case). Configurations are also included in the scope of the claims). Further, in FIG. 2A, the sub lead hole 311 is dug vertically to the pin 300, but it is preferable to be dug obliquely in view of the strength of the pin 300. The bridge of the first embodiment is shown in FIG.
Connect as shown in (c).

The second embodiment is shown in FIG. Pin 300 is
The load sensor substrates 100b, 100c, 10 are provided at both left and right portions P1 and P2 in FIG.
0f and 100g are buried and fixed in the manner shown in FIG. That is, the load sensor boards 100b, 1
One 00c is buried in the front and back of the drawing. On the other hand, at the position P2, the load sensor boards 100f and 100g are provided.
In the same manner as the above, one is embedded in each of the front and back of the drawing.
The bridge example of the second embodiment will be described with reference to the bridge 20 of FIG.
The circuit does not include the circuits 3, 204 and the amplifier board 72.

A third embodiment is shown in FIG. As shown in FIG. 5A, the two-sided support is the same as in the second embodiment. However, a load sensor substrate 100c is embedded on the front side of the portion P1 in the drawing, and a load sensor substrate 100f is embedded on the rear side of the portion P2 in the drawing. A first example of the bridge of the third embodiment is shown in FIG. 6 (b), and a second example is shown in (c). In each of these bridge examples, each load sensor substrate 100c,
A 100f bridge is connected in parallel to average both outputs.

A fourth embodiment is shown in FIG. This pin 300
Also, as shown in FIGS. 6 (a) and 6 (b), both ends are supported as in the second and third embodiments. Eight load sensor substrates 100a to 100h are embedded and fixed in the left and right portions P1 and P2 in the drawing where a shearing force is generated, in the same manner as shown in FIG. That is, the load sensor substrate 100 is provided at the portion P1.
One a to 100d is embedded and fixed on the upper and lower sides in the drawing. On the other hand, at the position P2, the load sensor substrate 1
00e to 100h are embedded in the front and back sides in the drawing, respectively.

FIG. 7C shows an example of the bridge of the fourth embodiment. FIG. 7A is a schematic diagram of FIG. 6B. Figure 7
(B1) to (b8) are the strain gauges 30 of the eight load sensor substrates 100a to 100h embedded and fixed in FIG. 7 (a).
Is.

The operation and effect of the fourth embodiment will be described with reference to FIG. 8 in comparison with the first and second embodiments.

FIG. 8A shows two load sensor substrates 1
00b and 100c are embedded and fixed so that the center Oo of the disk coincides with the bending neutral plane Co of the pin 300 based on the load F, and each strain gauge 30 is at a position rotated by 45 degrees from the neutral plane Co. There is. For example, when the load F (vehicle body weight) direction with respect to the pin is constant, such as a mounting pin of a suspension cylinder of a dump truck,
Since the bending neutral plane Co is also constant, the number of load sensor substrates may be one (that is, the first embodiment). Specifically, since the strain gauges 30 are arranged symmetrically with respect to the bending neutral plane Co, the counter load F of the neutral plane Co based on the load F.
This is because the bridge can be configured so that the tensile stresses generated on the side of the neutral plane C are canceled by each other and the compressive stress generated on the side of the load F of the neutral plane Co is canceled by the load F. Therefore, only the principal stress generated by the shearing force due to the load F can be detected. Thereby, the load F can be measured with high accuracy.

However, when the direction of the load F with respect to the pin changes, as in the case of a swivel and a boom of a hydraulic excavator, a boom and an arm, or an arm and a bucket, for example, as shown in FIG.
As shown in (b), the load sensor boards 100b, 100
The position Co of c is the true bending neutral plane C1 based on the load F.
From the angle of rotation θ. Therefore, the load F cannot be accurately measured with only one load sensor substrate 100 as in the first embodiment. However,
When the directional fluctuation of the load F is not so large and the measurement error due to this is within the allowable range, as shown in FIG. 8A (that is, as in the second and third embodiments), Each strain gauge 30 of the two load sensor substrates 100b and 100c
To cancel the tensile stresses due to bending based on the load F,
In addition, it is necessary to use a bridge that cancels the compressive stresses. In this way, although there is an error, only the shear force due to the load F can be measured. It should be noted that the error is inconvenient as the direction change of the load F becomes larger (that is, the larger θ in the figure shows), the smaller the measured value becomes. Therefore, for example, 15% (−30 ° <θ <+30 in advance
This is suitable when the use with an error of () is within the allowable range.

That is, the fourth embodiment is similar to the second embodiment and the third embodiment.
In the embodiment, it is suitable when the change in the direction of the load F cannot be ignored as a measurement error or when accurate measurement is desired. As shown in FIG. 8C, the load sensor substrate 100
In c and 100b, the principal stress based on the cos θ of the shear force due to the load F is measured. On the other hand, the load sensor substrate 100
In a and 100b, the main stress based on the shearing force sin θ is measured. Therefore, as shown in the bridge of FIG. 7C, the load F can be accurately output by calculating both outputs E1 and E2 by the microcomputer 600. still,
Even in this case, as shown in the bridge of FIG. 7C, the bridge needs to be a bridge that cancels tensile stresses due to bending based on the load F and cancels compressive stresses. That is, according to the fourth embodiment, the load F can be measured with high accuracy regardless of the change in the direction of the load F.

As an example of the fourth embodiment, the change in the direction of the load F can be dealt with by using only two load sensor substrates. In FIGS. 6A and 6B, for example, load sensor boards 100a and 100b on the left side in the figure, load sensor boards 100e and 100g on the right side in the figure, and load sensor boards 100a and 100g on the left and right sides in the figure, The load sensor includes two load sensor substrates that are 90 degrees in phase.

Another embodiment will be described. In the above embodiment, the same number of load sensor substrates 100 are embedded on the left and right sides of the drawing,
If the load is equal on the left and right (F1 = F2), it is sufficient to embed only one side. The number of left and right load sensor substrates 100 may be different depending on the purpose accuracy. In the second and fourth embodiments, two bridges (201 and 202, 2
03 and 204) are connected in series and have the same polarity to form an addition type, but as described above, a parallel bridge, a series, an AC / DC power supply bridge, or the like can be appropriately prepared depending on the purpose.

Another embodiment will be described. In the pin type load sensor of the above embodiment, the load sensor substrate 100 is mounted on the member 40.
It was placed at the seam of 0,500 (parts P1, P2),
Actually, these parts P1 and P2 are usually extremely narrow. In such a case, for example, a load sensor substrate as shown below and a load sensor in which the load sensor substrate is arranged are preferably used. (1) As shown in FIG. 9A, only the strain gauges 33c, 34c, 33f, 34f on the left side of the load sensor boards 100c, 100f on the left and right sides of the figure are the parts P1, P.
Both load sensor boards 100c, 100f
To the right in the figure. (2) As shown in FIG. 9B, the load sensor substrate 100c is moved to the right side in the figure so that only the strain gauges 33c and 34c on the left side of the load sensor substrate 100c on the left side in the figure are located at the region P1. On the contrary, the load sensor board 10 on the right side of the drawing
Only the strain gauges 31f and 32f on the right side of 0f in the figure have the part P.
The load sensor substrate 100f is moved to the left side in the drawing so as to be 2. (3) As shown in FIG. 9C, the load sensor substrate 100c is moved to the left side in the drawing so that only the strain gauges 31c and 32c on the right side of the load sensor substrate 100c on the left side in the drawing are the portions P1. On the contrary, the load sensor board 10 on the right side of the drawing
Only the strain gauges 33f and 34f on the left side of 0f in the figure have a portion P.
The load sensor substrate 100f is moved to the right side in the drawing so as to be 2.

[0041]

As described above, according to the load sensor substrate according to the present invention, whether it is four small holes or an intersection where the end faces are gentle, they alleviate stress concentration.
Further, since it is a plate material, distortion due to load is likely to appear, so that the measurement accuracy becomes high. Further, since it is made of metal, the strain gauge can be a thin film strain gauge that has high measurement accuracy and can be easily downsized. Further, it can be easily fixed to a metal object to be measured by welding, cold fitting, or the like.

On the other hand, according to the load sensor of the present invention, the sensitivity direction of the load sensor substrate is aligned with the principal stress direction based on the shearing force in the recess provided in the portion where the shearing force is generated by the load. Since it is provided, the load can be measured with high sensitivity and high accuracy. Moreover, since the load sensor substrate is embedded, the strength of the pin or the like is not significantly reduced. In addition, since the strain gauge is not exposed, it has a long life. The parts used are only the plugs such as pins and the load sensor substrate, and are simple.

[Brief description of drawings]

FIG. 1 is an example of a load sensor substrate, (a),
(B) is a front view, (c) is a sectional view taken along the line A-A of (b),
(D) is a BB sectional view of (b), and (e) is a bridge.

FIG. 2 is a first embodiment of the load sensor, (a) is a side sectional view, (b) is an assembled front view, and (c) is a bridge.

FIG. 3 is a procedure diagram for embedding and fixing the load sensor substrate in the load sensor, where (a) is a first step, (b) is a second step,
(C) is a figure which shows the final process.

4A and 4B show a second embodiment of the load sensor, wherein FIG. 4A is a side sectional view and FIG. 4B is an assembled front sectional view.

FIG. 5 is a third embodiment of the load sensor, (a) is a front view, and (b) and (c) are bridges.

FIG. 6 is a fourth embodiment of the load sensor, (a) is a side view and (b) is an assembled front sectional view.

FIG. 7 is a bridge of a fourth embodiment of the load sensor,
(A) is a layout view of the load sensor substrate, (b1) to (b8)
Is a diagram of a strain sensor on each load sensor substrate, and a bridge in (c).

8A and 8B are views for explaining the action and effect of the fourth embodiment of the load sensor, where FIG. 8A is a constant load direction, FIG. 8B is a load direction change, and FIG. It is a figure which shows composition.

FIG. 9 is a diagram of another embodiment of the load sensor, (a) of FIG.
FIG. 6 is a diagram in which two load sensor substrates are moved to one side, (b) is a type in which two load sensor substrates are moved to the inside, and (c) is a diagram in which two load sensor substrates are moved to the outside.

[Explanation of symbols]

100 ... Load sensor substrate, 10 ... Disc, L1, L2 ... Orthogonal axis, 20 (21-24) ... Small hole, 30 (31-34)
... Strain gauge, 40 (41-44) ... Electrode, 60 (61-
64) ... lead wire, 300 ... pin, 310 ... lead hole,
320 ... Recessed portion, 330 ... Stopper, 400, 500 ... Member, C
… Pin center (pin axis center), Co… Pin bending neutral plane,
Oo ... Disk center, F ... Load, P (P1, P2) ... Shear force generation site.

Claims (8)

[Claims] 1. A load sensor, wherein a disk having a strain gauge incorporated therein is embedded in a structure such as a pin, and the surface of the disk is completely restored. 2. The load sensor according to claim 1, wherein the load sensor is surface-hardened after being restored. 3. The load sensor according to claim 1, wherein an amplifier board is mounted near the sensor section. 4. A load sensor substrate comprising a circular plate having cutout holes having a gentle shape, and a strain gauge being installed in a gap between the holes. 5. The load sensor substrate according to claim 4, wherein the circular plate is made of stainless steel, and the thin film strain gauge is installed on the circular plate. 6. A metal disk (10), wherein the disk center (O
4) which are line-symmetric with respect to the orthogonal axes (L1, L2) whose intersection is o)
Two small holes (20) are provided, and on the orthogonal axes (L1, L2) between adjacent small holes (20), insulated from the disc (10) and the sensitivity direction is the orthogonal axes (L1, L2). A load sensor substrate comprising a strain gauge (30) oriented in a direction. 7. In a metal cross-shaped plate, the end face of the intersection is gently formed, and the surface of the longitudinal portion is insulated from the cross-shaped plate, and the sensitivity direction is the longitudinal direction of this longitudinal portion. A load sensor substrate comprising a strain gauge (30) installed. 8. A pin (3) for connecting pins between members (400, 500).
In (00), a recess (320) is provided in the part (P) where shearing force is generated based on the load (F) applied between the members (400,500),
The load sensor substrate according to claim 6 or 7 is fixed in the concave portion (320) so that the sensitivity direction thereof is the main stress direction based on the shearing force, and further, the pin (300) is fixed with a stopper (330). Plug the plug (1) into the recess (320) and
00) A load sensor characterized by being provided with a lead hole (310) for guiding the lead wire (60) of the strain gauge (30) to the outside.