JPH0461289B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a load detection device that can detect loads with high accuracy.

[Conventional technology]

Detecting the load applied to each mechanical component constituting a machine is important in achieving desired control of the machine.

Conventionally, as a load detection device used for detecting such a load, Japanese Utility Model Application Publication No. 57-46842,
The technology described in Japanese Patent Application Laid-open No. 50-97376 (hereinafter referred to as
(referred to as "Prior Art 1 and Prior Art 2").

In prior art 1, a shear pin type loadzel is provided as a load detection device for detecting the force acting between brackets constituting a force transmission member.
This shear pin type load cell consists of a load-bearing part that is placed between brackets and forms a columnar body that receives a load, and an insertion member that is inserted into a hole formed along the axial direction of this load-bearing part. .
This insertion member has a connecting part that connects with the load-bearing part at both ends and a central position, has a fixing part integrally with these connecting parts and has a dimension smaller than the dimension of the connecting part, and has a fixing part at the central position. One each is provided between a certain fixed part and a fixed part on one end side, and one each between a fixed part in the center position and a fixed part on the other end side, and the load-bearing part is It has a deformation sensitive part, that is, a sensor part, which deforms in response to the applied load and expands the strain. A strain gauge is attached to the sensor section.

In this prior art 1, when a load is applied to the joint portion located at the center of the load-bearing portion, the entire portion between the joint portions located at both ends deflects uniformly. The deflection at this time is the deflection due to bending,
This is a combination of deflection due to shear force. This deflection is magnified in the sensor section, detected by the strain gauge, and output as a signal. The applied load is calculated based on the signal value and the relational expression of deflection.

Furthermore, in Prior Art 2, a columnar body connecting a pair of bosses constituting a force transmission member and another boss arranged between these bosses, that is, a measuring pin is attached to both ends of the measuring pin and its axis. Two holes are formed in the center direction, and each of these holes is provided with an insertion member, that is, a load converter. The entire load transducer is formed in the shape of a bolt, has a hole passing through it along its axial direction, and has a deformation-sensitive part that deforms in response to the load, that is, an annular part, between the connecting part that connects to the measuring pin. It has a groove, and a strain gauge is attached to the inner peripheral surface corresponding to the annular groove.

In this prior art 2, although the load converter does not have a strain magnification function, the load converter uniformly bends and deforms in accordance with the load applied to the measurement pin, similar to the above-mentioned prior art 1. A signal corresponding to the deflection due to bending is output from the strain gauge, and the load applied to the measurement pin is determined according to that signal.

[Problem to be solved by the invention]

By the way, in both of the above-mentioned prior arts 1 and 2, the load is determined based on strain including strain due to bending deformation. In general, the magnitude of strain due to bending deformation varies depending on the location of the point of application of the load, as the form of bending deformation changes. It is not suitable for detecting loads in force transmitting members that change. For example, in Prior Art 1, if the point of application of the load is located at a position shifted from the center position, a bending strain component of a magnitude different from the strain due to bending deformation when the point of application of the load is at the center position is the strain. The load value is detected by the gauge and is therefore different from the load value when the load application point is at the center position. This is related to conventional technology 2.
The same applies to

As described above, in the conventional techniques 1 and 2 described above, when detecting a load in a force transmission member where the point of application of the load, that is, the position at which the load is applied, can fluctuate, the error in the detected value is large. , there is a problem that the load detection accuracy decreases.

The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to provide a load detection device that can determine the value of the load without being affected by changes in the point of application of the load. It is in.

[Means to solve the problem]

To achieve this objective, the present invention provides a columnar body disposed between force transmission members to receive a load, a hole formed at a neutral axis for bending deformation of this columnar body, and a columnar body inserted into the hole and provided at both ends. has a connecting portion that connects with the columnar body, a fixing portion that is connected to these bonding portions and has a dimension smaller than that of the bonding portion, and a fixing portion provided between these fixing portions that connects the columnar body with the columnar body. An insertion member having a deformation-sensitive portion that deforms in response to a load applied to the body to expand strain and whose axis of symmetry substantially coincides with the neutral axis; a signal conversion means for converting into a signal and extracting only a strain component due to shear deformation of the columnar body, and within a region formed by mutually opposing end surfaces provided at a portion where the force transmission member contacts the columnar body. The insertion member is arranged such that the mutually opposing end surfaces of the coupling portion are located at the ends of the coupling portion.

[Effect]

In the present invention, as described above, the symmetry axis of the deformation sensitive part is configured to coincide with the neutral axis with respect to the bending deformation of the columnar body, so that the strain in the deformation sensitive part caused by bending deformation is basically reduced. It is minute, and the fixed part and deformation sensitive part are located between the end faces of the force transmitting member, and the fixed part and deformation sensitive part do not come into contact with the columnar body and are not subjected to direct force. Therefore, a stable and relatively large strain magnification rate can be obtained regardless of changes in the position of the point of application of the load.Furthermore, only the strain component due to shear deformation is extracted by the signal deformation means, and the strain component due to this shear deformation is Since the structure is configured so that the load can be calculated according to the load, it is possible to prevent the strain component due to bending deformation from being involved in the calculation to calculate the load. Even if the magnitude of strain due to deformation changes, the value of the load can be determined without being affected by the change.

〔Example〕

Hereinafter, the load detection device of the present invention will be explained based on the drawings.

FIG. 1 is a side view including a cross section showing one embodiment of the present invention, FIG. 2 is a perspective view showing an insertion member provided in this embodiment, and FIG. 3 is a load detection device generated in the load detection device shown in FIG. FIG. 4 is an explanatory diagram illustrating a mode of modification, and is a wiring diagram of a strain gauge provided in this embodiment.

In FIG. 1, 1 and 2 are force transmission members, that is, mechanical components, and 3 is these mechanical components 1,
This is a load detection device of the present invention which also serves as a pin connecting two. This load detection device 3 is inserted into, for example, a cylindrical columnar body 4, two holes 5 and 6 having a circular cross section formed at a neutral axis with respect to bending deformation of this columnar body 4, and these holes 5 and 6, for example. Insert members 7 and 8 made of metal are provided. In addition, the insertion member 7
is arranged between one arm of the machine component 1 and the machine component 2, that is, in one force transmission path, and the insert member 8 is arranged between the other arm of the machine component 1 and the machine component 2. , i.e., in a force transmission path different from the above-mentioned force transmission path. As shown in FIG. 2, the insert member 7 is
Column-shaped coupling parts 9 and 10 having approximately the same diameter as the hole 5 are provided at both ends to be coupled to the columnar body 4.
A fixed part 9a having a diameter smaller than the diameter of
10a, and includes a thin plate-shaped deformation sensitive part 11 in the center that deforms in response to the load applied to the columnar body 4 and magnifies strain. Similarly, insert member 8
It also has coupling parts 12, 13, fixing parts 12a, 13a, and deformation sensitive part 14. As illustrated in FIG. 3, the area between the inner end surfaces of the coupling parts 9 and 10 of the insertion member 7 indicated by the distance
The coupling parts 9, 10 of this insertion part 7 are fixed, so as to be included in the area between the end face of the machine component 1 designated L' and the end face of the arm of the machine component 2 opposite this end face. parts 9a, 10a, deformation sensitive part 11
and the length of the hole 5 are set. The deformation sensitive parts 11 and 14 described above have their symmetry axes substantially aligned with the neutral axis for bending deformation, and magnify strain to a size corresponding to their length, that is, the distance between the fixed parts. In addition, the coupling parts 9, 10, 12, 13 of the insertion members 7, 8 are as follows:
It is coupled to the columnar body 4 by shrink fitting, welding, tightening with a tapered screw, fixing with an adhesive, or the like.

Reference numerals 15 and 16 are signal conversion means, such as strain gauges, for converting the amount of deformation of the deformation sensitive section 11 into a signal, and these strain gauges 15 and 16 are perpendicular to each other on the deformation sensitive section 11 and
at an angle of approximately 45° with the axial direction of the columnar body 4.
It is pasted so that it is located symmetrically in the vertical direction in the drawing with respect to the axis of the. Although not shown in FIGS. 1 to 3, a strain gauge 17 is installed in a direction perpendicular to the strain gauge 16 on the back side of the position where the strain gauge 16 of the deformation sensitive section 11 is attached.
In addition, a strain gauge 1 is attached to the back side of the position where the strain gauge 15 of the deformation sensitive part 11 is attached.
A strain gauge 18 is attached in a direction perpendicular to 5. That is, these strain gauges 15 and 1
6, and the strain gauges 17 and 18 are the columnar body 4
They are arranged at symmetrical positions with respect to the central axis for bending deformation.

Similarly, 19 and 20 are strain gauges attached to the deformation sensitive section 14, and although not shown in FIGS. 1 to 3, strain gauges 20 and 19 of the deformation sensitive section 14 are attached. Strain gauges 21 and 22 are attached to the back side of each position. These strain gauges 15-18 and strain gauges 19-22 constitute a bridge illustrated in FIG. 4. In Figure 4, ei
represents the input voltage, e ₁ represents the power voltage from the strain gauges 15 to 18, and e ₂ represents the power voltage from the strain gauges 19 to 22. 23 and 24 are strain gauges 15 to 18, or strain gauge 19, respectively.
These lead wires 23 and 24 are connected to the joints 9 and 1 of the insertion members 7 and 8.
It is inserted into passages 25a, 25b, and 26 formed in holes 0 and 13, and guided to the outside of the columnar body 4 through a hole 5 and a hole 50 that communicates the hole 5 and hole 6.

51 and 52 are covers that close both ends of the columnar body 4. Also, inside the bar 51 are lead wires 23,
A hole 53 is formed through which the holder 24 can be inserted. 54
is a connector to which lead wires 23 and 24 are connected,
It is supported by a cover 51. i.e. cover 5
1 also serves as a support member that supports the connector 54. Numerals 55 and 56 are bolts that fasten the covers 51 and 52 to the columnar body 4, respectively, and 57, 58, and 59 are O-rings that seal the inside of the load detection device 3.

Incidentally, FIG. 5 is a block diagram showing an example of a device connected to the load detection device 3 shown in FIG. 1.
In FIG. 5, 27 is an arithmetic device, for example, a microcomputer, and an input device 28 into which the output voltages e ₁ and e ₂ of the strain gauges 15 to 18 and 19 to 22 are input, and the output of the strain gauges. A storage device 29 that stores the correlation between the voltages e ₁ and e ₂ and the magnitude of the force; a CPU (central processing unit) 30 that performs logical judgments, calculations, etc. in accordance with the signals input to the input device 28; It consists of an output device 31 that outputs the results obtained by this CPU 30. Further, 32 is a display device connected to the output device 31 and consisting of a display or the like. These arithmetic device 27 and display device 32 constitute a signal processing means for processing the signal output by the load detection device 3. In general, this type of signal processing means is not limited to that shown in FIG. 5, and may take various forms.

In the embodiment configured as described above, suppose an unknown force is applied to the mechanical component 1 as shown in FIG.
Suppose that unknown forces W ₁ and W ₂ act on W ₃ and mechanical component 2, respectively (W ₃ =W ₁ +W ₂ ). At this time, for example, in the case of the side illustrated in _FIG . 4, a deformation amount δ within the range of distance L is generated. This deformation of the columnar body 4 and therefore the insertion member 7 in the range of distance L
The amount of deformation δ causes deformation due to the shear force shown in FIG. 6a and deformation due to the bending moment shown in FIG. 6b.

In this case, in the columnar body 4, the amount of deformation δ during the distance L
occurs between the length dimension d in the deformation sensitive parts 11 and 14. That is, as shown in FIG. 3, for example, the dimensions of the fixing parts 9a, 10a are set smaller than the diameter dimensions of the coupling parts 9, 10 of the insertion member 7. The hole 5 is kept away from the wall surface, and therefore does not undergo deformation due to receiving force from the wall surface of the hole 5.
Only the deformation sensitive portion 11 deforms well. At this time, a strain magnification factor of (L/d) is obtained, and since the force W ₁ does not directly act on the fixed parts 9a, 10a and the deformation sensitive parts 11, 14, the change in the point of application of the force W ₁ Regardless of the situation, the expansion rate does not change and a stable strain expansion rate can be obtained. Note that the same applies to the insertion member 8.

In the case of deformation due to shear force, the same
As shown in figure a, strain gauges 15, 19, 1
7, 21 are stretched, strain gauges 16, 20, 1
8, 22 will shrink. Since these strain gauges 15 to 18 and 19 to 22 constitute a bridge as shown in Fig. 4, e ₁ and e ₂ corresponding to the shear forces, that is, the forces W ₁ and W ₂ are output. Ru. At this time, uniform shear strain is generated on the surface of the deformation sensitive part 11. Therefore, there is no difference in output depending on where the gauge is attached. However, the orientation of the gauge is 45°
If it deviates from the angle, the output will change, but even in that case, the output is the cosine of the deviated angle, so if the deviation is only a few degrees, only extremely small output fluctuations will occur. In this way, there is almost no output change due to an error in the gage attachment position, so it is easy to make the rated outputs of the left and right detection sections and a large number of detectors the same. Further, since the surface of the deformation sensitive section 11 has a uniform shear strain, it can be used even with a strain gauge having a long gauge length, and there are almost no restrictions on the size of the strain gauge used.

Note that since the deformation sensitive parts 11 and 14 are arranged along the neutral axis of bending deformation, the strain caused by the deformation due to the bending moment is extremely small. Furthermore, since the bridge is configured as shown in FIG. 4, when deformed by this bending moment, the strain gauges 15, 19, 18, and 22 stretch as shown in FIG. 6b, and the strain gauge 17 , 21, 16, and 20 are contracted, and therefore the expansion and contraction are canceled, and in the end, no signal is output due to deformation due to the bending moment. In other words, a specific point parallel to the deformation sensitive part 11 is not affected by any deformation caused by the bending moment, that is, is not affected by any change in the position of the point of application where the forces W ₁ and _W 2 are applied. Only the shear strain component in the direction can be detected,
The forces W ₁ and W ₂ can be determined by calculation based on this shear strain component. In this way, in this embodiment, stable detection values with small detection errors can be obtained even if the positions of the loads W ₁ and W ₂ change, and the forces W ₁ and W ₂ can be detected with high precision. Can be done. In addition, since the deformation sensitive parts 11 and 14 are formed in a thin plate shape, the joint parts 9 and 14 at both ends,
10, the deformation of the entire load transmitting section is concentrated in the deformation sensitive sections 11 and 14, the strain becomes large, and sufficient detection sensitivity can be ensured.

Note that the output voltages e ₁ and e ₂ outputted from the strain gauges 15 to 18 and 19 to 22 are, for example,
Processed in the device shown in the figure, a force W ₁ corresponding to the output voltage e ₁ and a force W ₂ corresponding to the output voltage e ₂ are determined, and if necessary, W ₁ +W ₂ in the CPU 30
The force W ₃ obtained by calculating = W ₃ is obtained,
These W ₁ , W ₂ or W ₃ are the arithmetic unit 27
is output from the output device 31 to the display device 32 and displayed on the display device 32.

Further, in the above embodiment, since the holes 5 and 6 into which the insertion members 7 and 8 are inserted are formed at the neutral axis with respect to the bending deformation of the columnar body 4, the holes 5 and 6 are
The decrease in the strength of the columnar body 4 caused by this can be suppressed to an almost negligible level. In other words, when the columnar body 4 receives a force, the maximum stress generated in the columnar body 4 is usually expressed as bending stress, so it is appropriate to evaluate the strength of the columnar body 4 by this bending stress, and this bending stress is generally 3 of the diameter of the columnar body 4
It becomes larger corresponding to the power. Therefore, the columnar body 4
In this first embodiment, in which the outer diameter dimension, that is, the diameter of can.

In addition, in this embodiment, the strain gauge 15
18, 19 to 22 are arranged in a closed state inside the columnar body 4 by the joints 9, 10 or the joints 12, 13 of the insertion members 7, 8, so that the outside of the columnar body 4 is closed. Foreign object strain gauge 1
5-18, 19-22 can be completely prevented.

In this embodiment, as shown in FIG. 1, an insertion member 7 is provided in the force transmission path between the right arm of the member 2 and the member 1; An insertion member 8 is provided in the force transmission path between the For example, the position of the point of action is at the center of the columnar body 4, or at 1/1 of the total length from the right end
If the position is determined in advance, such as in position 3, the insertion member may be provided only for one transmission route instead of providing the insertion member for each transmission route as described above. The desired load can be detected even if the

FIG. 7 is a perspective view showing another example of the insertion member provided in this embodiment.

In place of the insertion members 7 and 8 shown in FIGS. 1 and 2 described above, an insertion member 33 shown in FIG. 7 may be provided. Insertion member 33 shown in FIG.
are provided with connecting portions 34, 35 at both ends to be connected to the columnar body 4, and are connected to these connecting portions 34, 35, and have a fixed portion 34a, which has a diameter smaller than the diameter of the connecting portions 34, 35. 35a, and a deformation sensitive section 38 in the center consisting of thin sections 36 and 37 that are connected to these fixing sections 34a and 35a and arranged parallel to each other. In addition, the thin part 3
6 and 37 are formed by square holes 39. Also, 4
0 is a passage formed in the joint 34 through which a lead wire connected to the strain gauge can be inserted. Insertion member 3 having deformation sensitive portion 38 configured in this way
3 can also detect only the shearing force in the direction parallel to the thin-walled portions 36 and 37.

FIGS. 8a to 8e are explanatory diagrams showing other examples of the thin wall portion constituting the deformation sensitive portion 38 of the insertion member 33 shown in FIG. 7. FIGS.

Such a thin wall portion is not limited to the pair of flat thin wall portions 36 and 37 formed to sandwich a square hole as shown in FIG.
A thin part 41 formed by sandwiching a square hole with curved corners as shown in FIG. 8a, a thin part 42 formed by sandwiching an octagonal hole as shown in FIG. A thin wall portion 43 formed across a round hole as shown in FIG. The thin wall portion 45 may be formed between two round holes and a passage connecting the round holes. In particular, the thin parts 43, 44, 45 formed by the holes shown in FIGS. 8c, d, and e are easy to manufacture.

In the above-described embodiments, a strain gauge is used as an example of the signal conversion means, but the present invention is not limited to this, and the signal conversion means may be configured by a differential transformer, a magnetic sensor, a piezoelectric element, etc. You can also.

Moreover, although the columnar body 4 is formed in a cylindrical shape in the above example, the present invention is not limited to this, and the columnar body 4 can take various shapes including a prismatic shape.

〔Effect of the invention〕

Since the load detection device of the present invention is configured as described above, it is possible to basically minimize the strain in the deformation sensitive part that occurs due to bending deformation, and it can also be used to However, a stable and relatively large strain magnification rate can be obtained, and unlike conventional methods, the strain component due to bending deformation is not involved in the calculation for calculating the load, so the position of the point of application of the load does not fluctuate. Even if the magnitude of strain due to bending deformation changes, the value of the load can be determined without being affected by it. Therefore, it is possible to determine the value of the load without being affected by it. This has the effect of reducing errors and achieving higher load detection accuracy than conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a side view including a cross section showing one embodiment of the load detection device of the present invention, FIG. 2 is a perspective view showing an insertion member provided in this embodiment, and FIG.
An explanatory diagram illustrating the mode of deformation that occurs in the load detection device shown in the figure, FIG. 4 is a wiring diagram of the strain gauge provided in this embodiment, and FIG. 5 is a device connected to the load detection device shown in FIG. 1. A block diagram showing an example, FIGS. 6a and 6b are explanatory diagrams illustrating the basic form of deformation occurring in the load detection device shown in FIG. 1, and FIG. 6a is an explanatory diagram showing deformation due to shearing force. FIG. 6b is an explanatory diagram showing deformation due to bending moment, FIG. 7 is a perspective view showing another example of the insertion member provided in the embodiment shown in FIG. 1, and FIGS.
FIG. 7e is an explanatory view showing another example of the thin wall portion constituting the deformation sensitive portion of the insertion member shown in FIG. 7; 3... Load detection device, 4... Column body, 5, 6,
50, 53... hole, 7, 8, 33... insertion member,
9, 10, 12, 13, 34, 35... joint part,
11, 14, 38...deformation sensitive section, 15, 16,
17, 18, 19, 20, 21, 22...Strain gauge (signal conversion means), 23, 24... Lead wire, 25a, 25b, 26, 40... Passage, 3
6, 37, 41, 42, 43, 44, 45... Thin wall part, 51, 52... Cover, 54... Connector, 55, 56... Bolt, 57, 58, 59...
...O-ring.

Claims (1)

[Claims] 1. A columnar body placed between force transmission members to receive a load, a hole formed at a neutral axis for bending deformation of the columnar body, and a columnar body inserted into the hole and having the above columnar body at both ends. It has joint parts to be joined, and has a fixed part connected to these joint parts and having dimensions smaller than the dimensions of the joint part, and is provided between these fixed parts and applies a load to the columnar body. an insert member having a deformation sensitive part whose symmetry axis is substantially coincident with the neutral axis, and converting the amount of deformation of the deformation sensitive part of the insert member into a signal; a signal conversion means for extracting only the strain component due to shear deformation of the columnar body, and the coupling portion is provided in a region formed by mutually opposing end surfaces provided at a portion where the force transmission member contacts the columnar body. A load detection device characterized in that the insertion member is arranged such that each of the mutually opposing end faces of the insertion member is located. 2. The load detection device according to claim 1, wherein the deformation sensitive portion has a signal converting means disposed in a pair of thin portions that face each other and are arranged in parallel with respect to the deformation direction of the columnar body. 3. The load detection device according to claim 1, wherein the signal conversion means is a strain gauge. 4. The load detection device according to claim 3, wherein the coupling portion has a passage through which a lead wire connected to the strain gauge can be inserted. 5. The load detection device according to claim 4, wherein the columnar body has a support member that supports a connector to which a lead wire is connected.