JPH02183134A - Axial force detector for screw link tightening means - Google Patents

Abstract

PURPOSE:To enable improvement in detection sensitivity and accuracy of an axial force by detecting the axial force loaded on a shaft-shaped section with a tightening of a screw linking means with a strain gauge. CONSTITUTION:When flange sections 5 and 6 are tightened by turning a nut 4, a tension works on a shaft section 1 downward in the drawing and a axial force introducing section 2 receives an axial force. As a support part 8 is supported with the flange section 6, the axial force introducing section 2 alone is displaced downward eventually causing a strain gauge section 2 to deform. That is, in the deformation, strain gauges 10 and 13 on the side of a top surface 7a and strain gauges 15 and 16 on the side of an undersurface 7b extend while strain gauges 110 and 12 on the side of the top surface 7a and strain gauges 14 and 17 on the side of the underside 7b contract separately. Then, in the strain gauges 10-17, the contraction thereof means a decrease in a resistance value and the extension means an increase in the resistance value. Thus, an axial force can be detected by a deformation of the strain gauge section 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an axial force detector for a screw-coupled tightening means, and more particularly, the present invention relates to an axial force detector for a screw-coupled tightening means, and more particularly, the present invention relates to an axial force detector for a screw-coupled tightening means, which has a shaft-shaped portion on one side. The present invention relates to an axial force detector for a screw-coupled tightening means that detects the axial force generated in the shaft-like part when tightening the screw.

[Conventional technology]

2. Description of the Related Art Screw connection and tightening means such as bolts and nuts are widely used to connect two or more members or elements constituting a structure or mechanism. And the bolt.

When tightened, the bolt deforms within the elastic limit in response to the tightening force, so by attaching a strain gauge to the bolt, it becomes possible to detect the tightening force (axial force) of the bolt.

One of the conventional bolt axial force detectors is, for example, Japanese Patent Application Laid-open No. 62
There is a technique described in Japanese Patent No.-194430.

That is, a circular hole is formed in the center of the bolt, reaching a predetermined depth from the head toward the inside of the shaft of the bolt.

Some devices detect axial force by gluing a strain gauge to the inner circumferential surface of this circular hole.

In addition, in a technique different from the technique described in JP-A No. 62-194430 mentioned above, a washer-type load transducer with a strain gauge glued to the outer peripheral surface of a washer-like washer is attached to the head of the bolt (the head of the bolt). If the bolt does not have a bolt, it is inserted between the bolt (nut) and the member to be tightened (for example, a flange), and the compressive force applied between the head of the bolt and the flange when the bolt is tightened. There is one in which the axial force is determined by deforming a washer type load transducer and detecting this deformation using the strain gauge.

[Problem to be solved by the invention]

In the former conventional example described above, it is extremely difficult to bond and fix the strain gauge because the diameter of the circular hole is small.
In particular, there was a problem that the mounting position in the depth direction of the circular hole was not constant. Therefore, there is a problem that high measurement accuracy cannot be expected.Furthermore, since generally only one strain gauge can be glued together, the output is small, and a bridge cannot be constructed with strain gauges, so interference due to unbalanced loads and lateral loads can be prevented. There were problems such as the inability to adopt a circuit configuration for compensation and the inability to incorporate circuits for performing other characteristic compensation.

In addition, in the latter conventional example, the compressive force corresponds to the tensile force of the bolt, so the washer type load converter (
Although there is an advantage in that the axial force of the bolt can be easily determined by detecting the strain generated in the load sensor (hereinafter referred to as the "load sensor"), there are cases where the load sensor is tilted relative to the bolt.

There is a problem in that the load distribution on the contact surface that contacts the flange of the load sensor becomes uneven, that is, so-called uneven contact occurs, resulting in an error.

In addition, the above load sensor is used in place of a normal washer, but since it is inevitably thicker than a normal washer, consideration must be given to the length of the bolt, and it is expected that the bolt will not be long enough. When tightening with a torque wrench, you have to prepare bolts of sufficient length in advance, resulting in poor workability. There was a risk of it being destroyed.

For these reasons, when assembling a large tank, etc., when tightening the entire body with a large number of bolts, the axial force of these bolts becomes uneven. Accidents may occur, such as internal filling fluid leaking or bolts breaking due to over-tightening.

The present invention has been made in view of the above-mentioned circumstances, and its objectives are to enable strain gauges to be attached to predetermined positions accurately, reliably, and easily, to have high detection sensitivity and precision;
Another object of the present invention is to provide an axial force detector for a screw-connected tightening means that is unlikely to cause lead wire breakage or peeling of a strain gauge connected to the lead wire during tightening work.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides a screw-joint tightening means that detects the axial force generated in the shaft-like part when the screw-joint tightening means has a shaft-like part on the - side and tightens a member to be tightened. In the axial force detector, the above-mentioned shaft-shaped part is integrally connected to or connected to the central part with high rigidity to receive the above-mentioned axial force, and the above-mentioned A thin strain-generating portion connected in a radial direction substantially perpendicular to the shaft-like portion and a highly rigid external shape connected to surround the outer periphery of the strain-generating portion and supported in contact with the member to be tightened are regular hexagons. It comprises a square support part and a strain gauge attached to at least one surface of the strain generating part, and the strain gauge detects the axial force applied to the shaft part by tightening the screw coupling means. It is characterized by being configured as follows.

[Function] Since the present invention is configured as described above, as a function thereof, when a member to be tightened is tightened by a screw coupling means having a shaft-like portion, the axial force applied to the shaft-like portion is The axial force is transmitted from the axial force introduction section to the axial force introduction section, and the strain generating section that connects the axial force introduction section and the support section is bent. This deflection causes compression and expansion in at least one plane of the strain-generating portion, so by attaching a strain gauge to the area where these compressions and expansions occur, an electrical signal corresponding to the axial force can be detected. The strain generating part according to the present invention has a radial shape perpendicular to the support part and the axial force introducing part, and can easily and reliably attach a strain gauge to an accurate position, and can also reduce shear strain. The structure allows a strain gauge to be attached for detection, which improves detection accuracy.

【Example〕

Embodiments and examples of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a partially cutaway front view showing the overall configuration of an axial force detector of a screw connection tightening means according to the present invention.

In Fig. 1, reference numeral 1 indicates a bolt shaft (hereinafter referred to as "
2 is a highly rigid axial force introduction part connected to the base end of the shaft part 1, and 3 is a male thread part screwed on the outer periphery over a predetermined length from the tip of the shaft part 1. , 4 is a nut screwed into this male threaded portion 3, 5 and 6 are flange portions as members to be tightened having mounting holes 5a and 6a through which the shaft portion 1 passes through at predetermined positions, and 7 is a nut having an upper surface 7a and a lower surface 7b. A thin strain-generating portion 8 is connected to surround the outer periphery of the strain-generating portion 7, and is connected (or extended) from the axial force introducing portion 2 in a radial direction substantially perpendicular to the shaft portion 1. The supporting portion has a thick, rigid outer shape having a contact surface 8a that contacts the flange portion 6, and has a regular hexagonal shape. A support portion 8 whose outer shape is a regular hexagon,
The strain generating portion 7 and the axial force introduction portion 2 constitute a head 9, the head 9 and the shaft portion 1 constitute a bolt, and the bolt and the nut 4 form a set of threaded connections using screws. It constitutes a tightening means.

10 to 17 are upper and lower surfaces 7a of the strain-generating portion 7;

Of these, 10 to 1 are strain gauges attached to 7b.
3 is attached to the upper surface 7a, and 14 to 17 are attached to the lower surface 7b.Moreover, strain gauges 10, 14°13.
, 12, 15, and 16 are respectively attached at positions extremely close to the axial force introduction part 2.

In the following drawings, the same parts as in FIG. 1 are designated by the same reference numerals.

2 to 5 are plan views showing configurations of modified examples in which only the shape of the head of the axial force detector shown in FIG. 3 shows the head of the second modification, FIG. 4 shows the head of the third modification, and FIG. 5 shows the head of the fourth modification. ing.

In FIG. 2, reference numerals 18 and 19 are parts constituting the support portion 8, each having a regular hexagonal outer shape.

The strain-generating portion 7 is formed to have a sufficiently thinner thickness in the axial direction than the portions 18 and 19. Reference numeral 20 denotes a substantially semicircular through hole formed between the portions 18 and 19 to form the strain-generating portion 7. The overall planar shape of the head 9 is formed into a symmetrical hexagonal shape with the axial force introduction part 2 as the center, and the strain generating part 7 forms a so-called - character-shaped beam 21.

In FIG. 3, reference numerals 22 to 25 indicate through holes 26 and 2, which are bored at approximately symmetrical positions left and right and up and down with the axial force introduction part 2 as the center.
Reference numeral 7 denotes a vertical beam and a horizontal beam that are left between adjacent through holes among these through holes 22 to 25, and form so-called cross-shaped beams each having a strain-generating portion 7. . The overall planar shape of the head 9 is a regular hexagon.

Further, strain gauges 28° and 29 are attached to the longitudinal beam 26, and strain gauges 30° and 31 are attached to the horizontal beam 27, respectively, at positions where the bending stress is maximum.

In FIG. 4, reference numeral 32 indicates through holes drilled at equal angular intervals at predetermined radius positions around the axial force introducing portion 2, and reference numeral 33 indicates strain generating portions 7 formed radially between these through holes 32. The overall planar shape of the head 9 is a regular hexagon. Also.

34 is a strain gauge attached to the spoke-shaped beam 33 at a position where the bending stress is maximum.

FIG. 5 is a plan view of the third modification, and FIG. 6 is a plan view of the third modification.

FIG. 2 is a front center vertical cross-sectional view showing the overall configuration.

In FIG. 5 and FIG. 6, 35 is an axial force introduction part, 36
Reference numeral 37 indicates a shaft portion of the bolt, 37 indicates a strain-generating portion, and 38 indicates a support portion having a regular hexagonal outer shape and a smooth contact surface 38a. 39 is a member to be tightened, for example, a flange portion, 40
-43 and 44-47 are strain gauges attached to the upper and lower surfaces of the strain generating part 37, respectively, corresponding to the strain gauges 10-17 of the first riA. Furthermore, 48 and 5
4 is a vertical beam and a horizontal beam that constitute the strain-generating portion 37, and 50, 51, 52, and 53 are strain gauges attached to the vertical beam 48.

In addition, in order to detect shear strain, a strain gauge 58a is used.
, 58b are attached to predetermined positions on the side surface of the strain-generating portion 57, as shown in FIG. In addition, in FIG. 7, 55 is an axial force introduction part, and 56 is a bolt shaft part.

FIG. 8 is an explanatory diagram in which a part of FIG. 1 is omitted and exaggerated in order to explain the operation.

In FIG. 8, 59 is an arrow indicating the direction of the axial force.

Figure 9 shows the strain gauge 1 shown in Figures 1 and 8.
FIG. 2 is a circuit diagram showing an example in which a bridge is configured by 0 to 17;

In FIG. 9, 60 and 61 are bridge electric WA (I
i@ (not shown), 62 and 63 are output terminals, and 6
4 is a first side where both ends of a series branch consisting of strain gauges 11 and 12 are connected to an input end 60 and an output end 62, respectively, and both ends of a series branch consisting of strain gauges 10 and 13 are connected to an output end 62 and an output end 62, respectively. a second side connected to the input end 61; a third side where both ends of the series branch of the strain gauge 14.17 are connected to the input end 61 and the output end 63, respectively;
Both ends of the series branches of the strain gauges 15 and 16 are Wheatstone bridges (hereinafter simply referred to as "r bridges") consisting of a fourth side connected to an output end 63 and an input end 60, respectively.

FIG. 10 is an explanatory diagram with a part of FIG. 1 omitted to explain the operation when no axial force acts in the vertical direction.

In FIG. 10, 65 is the planned position of the center of the shaft portion 1;
In the figure, the center of the shaft portion 1 is moved to the planned position 6 due to some force.
5 is shown tilted at a predetermined angle, but for purposes of explanation, it is the opposite.

It can also be applied when the axis 1 is vertical and the head 9 is inclined.

Next, the operation of this embodiment configured as described above will be explained using the first embodiment (FIGS. 1 and 2) as a representative.

When the nut 4 in Fig. 1 is turned to tighten the flange parts 5 and 6, a tensile force acts on the male threaded part 3, that is, on the shaft part 1 in the direction shown by the arrow 59 in Fig. 8, and an axial force is introduced. Part 2 receives an axial force in the direction of arrow 59. On the other hand, since the support section 8 is supported by the flange section 6, only the axial force introduction section 2 is displaced downward, and as a result, the strain generating section 7 is deformed as shown.

That is, the strain gauges 10, 13 on the upper surface 7a side and the strain gauges 15, 16 on the lower surface 7b side extend in the directions shown by the small arrows, while conversely, the strain gauges 11.16 on the upper surface 7a side expand. 12 and the strain gauges 14 and 17 on the lower surface 7b are compressed and deformed in the directions indicated by the small arrows, respectively.

Now, in the strain gauges 10 to 17, compression means a decrease in resistance value, and expansion means an increase in resistance value, so the change in resistance value on each side of the bridge 64 in FIG. The resistance value of both strain gauges 11 and 12 decreased,
The strain gauges 10.13 on the second side both increase, the strain gauges 14.17 on the third side both decrease, and the strain gauges 15.16 on the fourth side both increase. In other words, the axial force can be detected based on the amount of deformation of the strain generating portion 7.

Now, referring to FIG. 10, the function of removing errors when the shaft portion 1 is tilted due to an unbalanced load or a lateral load, for example, will be explained.

As shown in FIG. 10, it is assumed that the shaft portion 1 is inclined by a predetermined angle with respect to the planned position 65 due to some lateral load. In this case, the strain-generating portion 7 deforms as follows. In other words, the strain gauges 11 and 13 on the upper surface 7a side and the lower surface 7
The strain gauges 14, 16 on the b side are each expanded, and conversely, the strain gauges 10.12 on the upper surface 7b side and the strain gauges 15, 17 on the lower surface 7b side are each deformed in a compressing direction. Therefore, in the bridge 64 shown in FIG.
The resistance values of strain gauges (for example, 11 and 12) that are combined in series on all sides from the 1st side to the 4th side increase and decrease each other, and the output due to the above slope is generated within each side. Since it acts to erase the voltage, the voltage vO does not change as a result.

Therefore, even if an axial force is applied in the direction of the arrow 59 shown in Fig. 8 with the shaft portion 1 tilted as shown in Fig. 10, the correct axial force can be detected without being affected by the inclination. be. Although FIG. 10 shows the case where the shaft portion 1 is tilted, the same applies even when the head 9 is tilted.

Also, in the head 9 shown in FIGS. 3, 4, and 5, which were not explained, the only difference is the shape of the strain-generating portion 7,
Since you can think of it in a similar way, I will omit the explanation.

As described above, according to this embodiment, when the head 9 of the embodiment is removed from the flange portions 5 and 6 (state before joining), both ends of the upper and lower ends in the figure are open, respectively.
Since the upper and lower surfaces of the strain generating parts 7 and 37 are formed as flat surfaces that are easily visible, strain gauges (for example, 10
-17) The attachment work is easy, and therefore it can be attached at an accurate position, resulting in an advantage that the detection accuracy is dramatically improved compared to the conventional one.

In addition, as mentioned above, since the upper end faces of the axial force introduction parts 2 and 35 in the head 9 are open in the figure, connecting means such as lead wire connectors can be provided here to facilitate tightening work. In some cases, it is possible to disconnect the connection wires from external equipment, which has the advantage of preventing disconnection of the connection wires (lead wires), peeling off of the strain gauge, and damage to the strain gauge, as well as improving work efficiency. be.

In addition, since the head 9 can be made larger than at least the shaft of the bolt, the area to which it can be attached becomes wider. Gauge (e.g. 10-17)
Because it can be attached.

Detection sensitivity is increased, and bridge 6 is further improved with strain gauges.
4 can be configured, it becomes possible to perform various electrical processing such as, for example, removing the influence of the inclination of the shaft part 1 or the head part 9,
Overall, there is an advantage that detection accuracy is improved.

Also, compared to the conventional example (especially washer type), the support part 8.38 has a regular hexagonal outer shape corresponding to the outer periphery of the washer type.
Since the rigidity of the head 9 can be made sufficiently large, the head 9 itself will not be deformed, and at least there is an advantage that uneven contact will not occur due to this deformation. In addition, washer-type sensors have the disadvantage of large variations in sensor output when the axial height is low, but the sensor in this example has a stable output and high detection accuracy even though it is thin. There is an advantage.

Further, as described above, the shape of the head 9 can be made large, and the contact surfaces 8a and 38a can be easily machined, so there is an advantage that high flatness can be obtained.

Although not shown in Fig. 1, it is of course possible to insert various combinations of spring washers, plain washers, etc. between the nut 4 and the flange portion 5, and the changes may be affected by the changes in conditions due to the above combinations. It has the advantage that it can be tightened with approximately the same axial force without being affected.

Further, the bolt consisting of the head 9 and the shaft portion 1 of the example is as follows:
Each type can be used as a normal bolt, and special consideration may be required for the length of the bolt, as in the case of conventional bolts (especially washer type bolts).

Eliminates the hassle of preparing bolts of appropriate length in advance.1
This has the advantage of improving workability.

It should be noted that the present invention is not limited to the embodiments described and illustrated above, but can be modified in various ways without departing from the spirit thereof.

For example, the head 9 of the first embodiment is the first. As shown in the second, third, and fourth modifications, the through holes 20, 22 to 25
．． 32, the strain-generating portions 7.37 are continuous between the axial force introduction portions 2, 35 and the support portions 8, 38 having regular hexagonal outer shapes. It may also have a so-called diaphragm shape.

Further, the configuration of each side of the bridge 64 is not limited to the example shown in FIG. 9, and may be changed as appropriate depending on the number of strain gauges, attachment positions, etc.

In addition, in the above embodiment, the strain gauge is placed on the upper surface 7a,
Although an example has been shown in which the adhesive is attached to both sides, 37a and the lower surface 7b, 37b, it is of course possible to attach it to only one of the surfaces.

(Effects of the Invention) As described in detail above, according to the present invention, the axial force generated when the member to be tightened is tightened with the screw-coupled tightening means can be absorbed by the axial force introducing portion with high rigidity and the support with high rigidity. The axial force is detected by converting it into the amount of deformation of the thin strain-generating part connected between the two parts, and detecting this deformation with the strain gauge. It can be attached reliably and easily, significantly improving detection accuracy and sensitivity, and there is no risk of breakage of the lead wire or peeling of the strain gauge connected to the lead wire during tightening work. Therefore, it is possible to provide an axial force detector for a screw-coupled tightening means with extremely good workability.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the entire structure of a first embodiment of an axial force detector for a screw-coupled tightening means according to the present invention in a nearly cutaway manner, and FIGS. 2 to 5 are all similar to FIG. 1. FIG. 2 is a diagram showing various modifications of the head of the axial force detector of the first embodiment shown in FIG.
FIG. 3 shows a second head whose strain-generating portions are composed of approximately cross-shaped beams, FIG. 4 shows a third head whose strain-generating portions are composed of spoke-shaped beams, and FIG. a fourth head whose strain-generating portion is a cross-shaped beam;
FIG. 6 is a front center vertical cross-sectional view partially omitting the entire configuration of a modified example of the fourth head in which the strain-generating portion is a cross-shaped beam, and FIG. 7 is a detection of shear strain in the strain-generating portion. The fifth form of
FIG. 8 is an explanatory view showing a part of FIG. 1 omitted and exaggerated in order to explain the present invention in detail, and FIG. 61.36 A circuit diagram showing an example in which a bridge is constructed using the strain gauges shown in FIGS. ,56...
... Bolt shaft part, 2.35.55 ... Axial force introduction part, 13 ... Male thread part, 4
... Nut, 5.6, 39 ... Flange part, 7.37, 57 ... Strain part. 8.38...Support part with regular hexagonal outer shape, 8a
, 38a... contact surface, 9... head of bolt. lO~17.28~31, 34.40~4750~53
, 58a, 58b...Strain gauge. 20.22~25,32...Through hole, 33...
...spoked beam, 60.61 ...input end. 62.63...Output end, 6"4...Wheatstone bridge, 65...
...The planned position of the center. Figure J2 Patent applicant: Kyowa Denka Co., Ltd. Figure 7a Figure 7a Figure 6

Claims (1)

[Claims] (1) In the axial force detector of the screw-coupled tightening means that detects the axial force generated in the shaft-like portion when the screw-coupling tightening means having a shaft-like portion on one side tightens the member to be tightened, the central portion has a large rigidity. an axial force introduction part to which the shaft part is integrally connected or integrally connected to receive the axial force; and an axial force introduction part which is connected to the shaft part in a radial direction substantially perpendicular to the shaft part. a thin strain-generating portion; a supporting portion having a regular hexagonal outer shape with high rigidity that is connected to surround the outer periphery of the strain-generating portion and supported in contact with the member to be tightened; and at least one of the strain-generating portions. and a strain gauge affixed to a surface thereof, and is configured such that the strain gauge detects an axial force applied to the shaft-like part by tightening the screw joint means. Axial force detector.