JPH067076B2 - Load detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a load detection device for detecting loads applied to various objects.

BACKGROUND OF THE INVENTION Detecting loads (forces and moments) applied to an object or a specific portion of an object is essential in many fields. As a load detecting device for detecting such a load, an excellent load detecting device including a parallel flexural beam structure or a radial flexural beam structure, or both,
It is proposed by JP-A-60-62497. This publication discloses various types of load detecting devices using the parallel flexible beam structure and the radial flexible beam structure. One type of load detecting device will be described with reference to FIG.

FIG. 4 is a partially cutaway perspective view of a conventional load detecting device.
In the figure, X, Y, and Z indicate coordinate axes. 22 is a columnar body,
Overhangs 22a, 22b, 22c, 22d are formed in the columnar body 22, a through hole 23 is formed in the center, and a through hole reaching the through hole 23 is formed between adjacent adjacent overhangs. As a result, thin portions 24a, 24a '... 24d, 24d' are formed. Strain gauges 25a to 25h 'are provided at the center of the upper and lower surfaces of each thin portion. 26a, 26
b, 26c, 26d are through holes formed in the Z-axis direction at the respective overhang portions 22a, 22b, 22c, 22d, and the thin portions 15a, 15a '... 15d, are formed by these through holes 26a-22d. 15
d'is formed. A strain gauge 17c is provided at the center of each thin portion. Opposite overhang 22
The upper portions of b and 22d are connected by the upper annular portion 16a,
The lower portions of the other opposing protruding portions 22a and 22c are lower annular bodies.
It is connected by 16b. There is a considerable gap between the upper annular body 16a and the upper surfaces of the overhanging portions 22a and 22c, and between the lower annular body 16b and the lower surfaces of the overhanging portions 22b and 22d.

In this configuration, the force F _Z in the Z-axis direction, the moment about the X-axis, and the Y-axis is exerted between the upper annular body 16a and the lower annular body 16b.
When M _X and M _Y are created, the thin-walled portions 24a and 24 of the cross-shaped parallel flexural beam structure portion composed of the through holes communicating with the through holes 23 are formed.
a '......... 24d, 24d' is deformed in the corresponding thin portion. Further, the forces F _X and F _Y in the X-axis and Y-axis directions and the moment M _Z about the Z-axis between the upper annular body 16a and the lower annular body 16b.
Is applied, a change occurs in the corresponding thin-walled portion of the guiding insides 15a, 15a '... 15d, 15d' of the parallel flexible beam structure formed in each overhang. These deformations are detected by the strain gauge of the corresponding portion, and the respective forces and moments are detected by forming an appropriate bridge circuit with each strain gauge. The deformation of each thin portion, the bridging circuit, and the like are described in detail in the publication.
After all, this load detection device can detect six load components of a force acting in the X-axis, Y-axis, and Z-axis directions, and a moment acting around the X-axis, Y-axis, and Z-axis.

By the way, in the load detecting device as described above using the parallel flexural beam structure and the radial flexural beam structure, of course, higher output sensitivity is required. In order to increase the output sensitivity, it is necessary to increase the stress of the parallel flexural beam structure and the radial flexural beam structure when the rated load is applied. However, when the stress is increased in this way, if an overload exceeding a certain limit, for example, a large load of several times the rated load acts, the stress value in the flexible beam becomes excessive and plastic deformation occurs in that part. Or it will be damaged. Then, the action of such an excessive load is not only the load to be detected actually becomes excessive, but also the machine to which the load detecting device is attached, the erroneous operation of the device, the handling error such as dropping the load detecting device itself, etc. It is also caused by.

[Object of the Invention]

The present invention has been made in view of such circumstances, and an object thereof is to provide a load detection device capable of preventing performance deterioration and damage even when an excessive load acts.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention comprises a rigid block having a flexible portion and two rigid bodies connected to different predetermined portions of the rigid block, and a load acting between these two rigid portions is In the load detection device for detecting, at least one of the two rigid body parts, and the protruding member is fixed to one of the rigid body blocks other than the predetermined portion, a hole is formed in the other, and the protruding member is inserted into the hole, A predetermined gap is formed between the projecting member and the inner wall of the hole, and when the load is an overload of a certain value or more exceeding the rated load, the projecting member and the inner wall of the hole are in contact with each other. To do.

Example of Invention

 Hereinafter, the present invention will be described based on the illustrated embodiments.

FIG. 1 is a perspective view of a load detecting device according to an embodiment of the present invention. In the figure, the same parts as those shown in FIG. 30a and 30c are overhangs, respectively
Stoppers 30b and 30d (not shown) formed between 22a and 22c and the upper annular body 16a are projecting portions, respectively.
It is a stopper formed between 22b and 22d and the lower annular body 16b. Since the stoppers 30a, 30b, 30c, 30d have the same configuration, only the configuration of the stopper 30a will be described below.

Reference numeral 31a is a pin fixing portion formed on the projecting portion 22a. The pin fixing portion 31a includes thin portions 15a and 15a 'and an upper annular body 16a.
The upper annular body 16a is formed at substantially the same height as the upper annular body 16a. 32a is the upper annular body 16a,
It is a through hole formed in a portion facing the pin fixing portion 31a. A pin 33a is fixed to the pin fixing portion 31a and is inserted into the through hole 32a. The construction of such a stopper 30a is shown in more detail in FIG.

FIG. 2 is a sectional view of the stopper 30a portion shown in FIG. In the figure, the same parts as those shown in FIG. 1 are designated by the same reference numerals. The pin 33a is fixed to the pin fixing portion 31a through the through hole 32a by an appropriate means such as press fitting. There is a defined clearance g between the pin 33a and the inner wall of the through hole 32a.

Now, in the upper annular body 16a, the downward force in the Z-axis direction in FIGS.
When F _Z acts, this force F _Z acts on the columnar body 22 via the overhanging portions 22b and 22d. Therefore, the thin portions 24a, 24a '...
……… 24d and 24d ′ are deformed according to this force. This deformation is detected by a strain gauge (not shown) of each thin portion, and a bridge circuit constituted by these strain gauges can obtain a signal proportional to the force F _Z. During this operation, the upper annular body 16a is displaced downward in the drawing due to the deformation of each thin portion of the columnar body 22. For this reason,
The clearance g between the pin 33a and the upper inner wall of the through hole 32a becomes smaller, and the clearance g with the lower inner wall becomes larger.

By the way, when an excessive downward force F _Z acts on the upper annular body 16a for some reason, the displacement amount of the upper annular body 16a becomes extremely large, and the clearance g between the pin 33a and the upper inner wall of the through hole 32a becomes 0. And both abut. on the other hand,
The overhanging portion 22a on which the pin fixing portion 31a is formed is the lower annular body 16
Since it is connected to b, the force for further displacing the upper annular body 16a, that is, the force for further deforming each thin portion of the columnar body 22 is the pin 33a and the pin fixing portion 31.
It is transmitted to the lower annular body 16b via a and the protruding portion 22a.
Similar operations occur for the other stoppers 30b, 30c, 32d. As a result, even if an excessive force F _Z is applied to the upper annular body 16a, each thin-walled portion of the columnar body 22a is not deformed by a predetermined amount or more, is not plastically deformed or damaged, and is completely protected. It In this case, the upper and lower clearances g in the figure are generated when the rated force F _Z acts in the state where no load is applied (the values of the upper and lower clearances g are equal in this state). Is selected as a predetermined multiple of the displacement amount. This multiple value is determined mainly based on the characteristics of the thin portion.

In the above description, the case where the force F _Z acts was described, but even when the forces F _X and F _Y and the moments M _X , M _Y , and M _Z act, each thin-walled part is protected by the operation according to the above. To be done. The stoppers having a protection function against each load are summarized as follows. That is, for the force F _X , the stoppers 30a, 30
c, Stoppers 30b, 30d for force F _Y , Stoppers 30a, 30b, 30c, 30d for force F _Z , Stoppers 30a, 30c for moment M _X , Stoppers for moment M _Y Stopper 30 for 30b, 30d and moment M _Z
Each of a, 30b, 30c, and 30d has a protective function.

As described above, in this embodiment, since the stopper is configured between each overhanging portion and the upper and lower annular bodies, even if a load equal to or more than a predetermined multiple of the rated load is applied, a load larger than that is applied to each thin portion. Does not act, and it is possible to prevent plastic deformation and damage of the thin portion due to an excessive load. Further, since the fixing hole of the pin fixing portion and the through hole are concentric holes, processing is easy.

FIG. 3 is a sectional view of a part of a load detecting device according to another embodiment of the present invention. In the figure, the same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted. Third
The figure is a cross-sectional view of the same portion as that shown in FIG. This embodiment differs from the previous embodiment in the configuration of the upper annular body 16a, the lower annular body 16b, and the stopper. The upper annular body 16 is divided into a lower portion 16a ₁ and an upper portion 16a ₂ . 42a ₁ is a cylindrical hole formed in a portion of the lower portion 16a ₁ facing the overhanging portion 22a, and 42a ₂ is a hole communicating with the hole 42a ₁ . 43a ₁ is a pin fixed to the overhanging portion 22a, and 43a ₂ is a flange portion of the head of the pin 43a ₁ . The pin 43a ₁ is inserted into the hole 42a ₂ , and
The flange portion 43a ₂ is located in the hole 42a ₁ . After the pin 43a ₁ having the flange portion 43a ₂ is fixed to the overhanging portion 22a in the illustrated state, the upper portion 16a ₂ of the upper annular body 16a is fixed to the lower portion 16a ₁ with a bolt (not shown). In this state, the flange portion 43a ₂ of the lower surface and the hole 42a ₁ of the bottom surface, and are respectively allowed to exist is a clearance g between the lower surface of the flange portion 43a ₂ of the top surface and the top 16a _2. Lower ring 16b
Is similarly divided into an upper part 16b ₁ and a lower part 16b _2, and the stop 40
After the flanged pins b and 40d (not shown) are fixed, the lower portion 16b ₂ is fixed to the upper portion 16b ₁ by the bolt 44.

The operation of this embodiment is similar to that of the previous embodiment. That is,
For example, when the force F _Z acts on the upper annular body 16a, the flange portion
The clearance g between the upper surface of 43a _{2 and} the lower surface of the upper portion 16a ₂ is reduced. Then, when a larger force F _Z is applied, the clearance g becomes 0 and the upper surface and the upper portion of the flange portion 43a ₂ are
The lower surface of 16a ₂ comes into contact, and the force F _Z beyond that is directly transmitted to the lower annular body 16b without passing through each thin portion. The same applies to other loads, and the stoppers that operate are the same as in the previous embodiment.

As described above, in this embodiment, since the stopper is configured between each overhanging portion and the upper and lower annular bodies, not only the same effect as the previous embodiment is achieved but also the clearance is provided by providing the flange portion on the pin. Can be easily adjusted.

In the description of the above embodiment, the load detecting device for detecting the force and the moment about each of the X-axis, the Y-axis, and the Z-axis has been described as an example, but the present invention is not limited to this, and the rigid block has a thin wall. Any material having a part can be applied. Further, the number of stoppers can be determined corresponding to the load to be detected.

[Brief description of drawings]

1 is a partially broken perspective view of a load detecting device according to an embodiment of the present invention, FIG. 2 is a sectional view of a stopper portion shown in FIG. 1,
FIG. 3 is a sectional view of a stopper portion of a load detecting device according to another embodiment of the present invention, and FIG. 4 is a partially cutaway perspective view of a conventional load detecting device. 15a to 15d ', 24a to 24d' ... thin portion, 16a ... upper annular body, 16b ... lower annular body, 22 ... columnar body, 22a-22d ...
… Overhang, 30a to 30d, 40a… Stopper, 31a… Pin fixing part, 32a… Through hole, 33a, 43a ₁ … Pin, 42
a ₁ , 42a ₂ ...... hole, 43a ₂ ...... flange part.

Continuation of the front page (72) Takami Kusagi, 650 Jinrachi-cho, Tsuchiura-shi, Ibaraki Prefecture Tsuchiura factory, Hitachi Construction Machinery Co., Ltd. (56) References JP 61-57825 (JP, A) JP 60- 62497 (JP, A) JP 58-8863 (JP, A) Actual development 61-193344 (JP, U) JP 45-76199 (JP, B1)

Claims (6)

[Claims] 1. A load detection device for detecting a load acting between two rigid bodies, the rigid block having a flexure portion and two rigid bodies connected at different predetermined points of the rigid block. A projecting member fixed to at least one of the two rigid body portions and one of the rigid body blocks other than the predetermined location, and the projecting member formed on the other side is inserted with a predetermined gap. A load detection device characterized in that a hole is provided. 2. The load detection device according to claim 1, wherein the rigid block is provided with two sets of projecting portions forming a substantially cross shape. 3. The load output device according to claim 2, wherein the projecting portions of each set are connected to one and the other of the two rigid body portions, respectively. 4. The load detection device according to claim 1, wherein the protruding member is a pin. 5. The load detection device according to claim 1, wherein the protruding member is a pin with a flange. 6. The predetermined gap according to claim 1, wherein the predetermined gap has a size such that contact between the projecting member and the hole occurs when the load is equal to or more than a predetermined value exceeding a rated value. A load detection device characterized by being set.