JPS623630A - Load detecting vibrator - Google Patents

Abstract

PURPOSE:To improve the working accuracy and the detection accuracy to enhance the mass productivity by working a metallic plate having a prescribed thickness in one direction to constitute a solid part and a vibrating part in one body and providing a through hole near the part connected to this vibrating part and absorbing the bending stress acting upon the vibrating part by a thin part formed with said through hole. CONSTITUTION:Both end parts of thin plate-shaped chords 1a and 1b constituting an oscillating body 1 are connected by connecting parts 5 to constitute an oscillator body 6. This vibrator body 6 is supported by thin plate-shaped supporting parts 7 and 7a extending from connecting parts 5, A through hole 8a parallel with the plate surfaces of supporting parts 7 and 7 and those of chords 1a and 1b is formed on each fixed part 8, and thin parts 8b and 8b are provided, and fixed parts 8 and supporting parts 7 are connected through them. Since the vibrator body 1, supporting parts 7, fixed parts 8, and through holes 8a are worked in the same direction, the working accuracy is improved, and deformation and working stress for working are not generated, and the detection accuracy as a load detecting means is improved, and the mass productivity is improved because there are no complicated reattaching works.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a load detection vibrator used as a load detection means of a scale.

"Prior Art" Generally, one end of a rod-shaped vibrating body is attached to a base, and a compressive force (
It is known that when a compressive force (or tensile force) is applied, a predetermined relationship exists between this compressive force (or tensile force) and the natural frequency of the vibrating body. therefore,
By providing the vibrating body with an excitation means that makes the vibrating body resonate and a detection means that detects the vibration frequency of the vibrating body,
A load detection means for detecting a load acting on the vibrating body can be configured.

In this case, it is known that the Q value of the vibrating body must be increased in order to achieve high precision measurement in the load detecting means as described above.

Furthermore, in general, the weighing pan of a scale is made to be larger than the object to be weighed, so that the weighing pan can accommodate the object to be weighed. For this reason, the object to be weighed is not necessarily placed on the center of the weighing pan, and the center of gravity is not necessarily placed on the center of the weighing pan.

In reality, the object to be weighed is often placed at a position offset from the center of the weighing pan and weighed with an unbalanced load. Therefore, when using the above-mentioned vibrating body as a weight detection means, in order to prevent the bending moment due to unbalanced load from being applied directly to the vibrating body, a mechanism such as a donkey pal is used to detect only the vertical tension (compression) component. It must be configured so that it is transmitted to the vibrating body. However, at this time, strictly speaking, the vibrating body is subjected to bending stress due to the slight inclination of the mechanism, and for high-precision measurement, it is necessary to apply a uniform axial force to the vibrating body due to the influence of this bending stress. First, the Q value decreases and the measurement accuracy is impaired. Also, when fixing the vibrating body to the mechanical part of the scale,
A similar effect is caused by the occurrence of bending stress due to misalignment of the central axis due to assembly errors in the mechanical parts.

Here, as this type of load detection means, a tuning fork vibrator as shown in FIG. 1O, proposed in Japanese Patent Publication No. 59-6369, is known.

In this figure, l is a vibrating body consisting of strings 1a and Ib,
Reference numeral 3.3 denotes a connecting portion that connects each end of the strings 1a and lb, and the vibrating body 1 and the connecting portion 3.3 constitute the vibrator main body 2. Reference numeral 4 indicates a fixing part in which a through hole 4a is formed, F indicates a connecting part that connects the fixing part 4 and the coupling part 3, and plate-shaped flexures Fa and Fb are perpendicular to each other.
It is composed of.

By providing the flexures Fa and Fb, the four corner loads of the weighing pan described above and the bending stress generated in the fixed part 4 due to attachment to a base etc. are prevented from being transmitted to the vibrating body 1, and the vibrating body l The transmission of vibration between the base and the base etc. is insulated.

"Problems to be Solved by the Invention" By the way, although the conventional tuning fork vibrator shown in Fig. 10 can reduce vibration energy loss and increase efficiency, it still has the following problems. was there.

That is, in the process of manufacturing a tuning fork vibrator from raw materials, wire-cut electric discharge machining is most suitable because there are many thin parts and the shape is very easily deformed.

However, in wire-cut electrical discharge machining, after forming the portion that will become the flexure Fb from the raw material, the raw material must be rotated 90 degrees to form other portions, or vice versa. As a result, after machining one of the thin parts, rotating it 90 degrees and reinstalling it does not result in dimensional accuracy, and the holding method is also difficult, often resulting in deformation, which reduces the measurement accuracy of the tuning fork vibrator. This will result in damage to the In addition, since the processing process is extremely complicated, it lacks mass productivity and increases manufacturing costs.

Furthermore, the shape of the fixing part 4 of the tuning fork vibrator is limited; for example, it is not possible to configure the fixing part 4 to be U-shaped or L-shaped, with the end extending to the side of the vibrating body l. , due to the need to form a flexure Fb,
It's impossible.

Note that instead of wire-cut electrical discharge machining, it is possible to use an end mill to cut the flexures, but in this case, it is not only extremely difficult to make the thickness of the flexures Fa and Fb 0.1 to 0.2 mm, but also deformation due to grinding. This is not a very preferable method because of the adverse effects caused by heat.

This invention was made in view of the above-mentioned circumstances, and can improve machining accuracy, eliminate deformation and machining stress,
In addition, the detection accuracy as a load detection means has been improved, and processing from the same direction eliminates the complicated mounting and changing work, increasing mass production. The object of the present invention is to provide a vibrator with a structure in which no signal is transmitted to the vibrator body.

"Means for Solving the Problems" The present invention provides a load detection vibrator comprising a pair of fixed parts and a vibrating part formed between each of these fixed parts.
The fixed part and the vibrating part are integrally formed by processing a metal plate having a predetermined thickness from one direction, and a penetration is formed in the same direction as the processing direction in the vicinity of the part of the fixed part connected to the vibrating part. It is characterized in that a hole is provided and a thin wall portion formed by the through hole absorbs bending stress acting on the vibrating portion.

"Effect" Machining accuracy is improved by machining from the same direction, so
There is no deformation or machining stress, which improves the detection accuracy as a means of detecting burr loads, and machining from the same direction eliminates the need for complicated attachment changes, which improves mass production. Bending stress caused by the error is no longer transmitted to the vibrating part.

Embodiment J An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of a tuning fork vibrator according to a first embodiment of the present invention.

In this figure, each thin plate-shaped string 1a that constitutes the vibrating body I is shown.
, Ib are connected by a connecting portion 5, thereby forming a vibrator main body 6.

The vibrator main body 6 includes a thin plate-shaped support portion 7 extending from the coupling portion 5 .
Supported by 7. On the other hand, reference numeral 8 is a fixed part that is attached to the base and the load transmission member that transmits the load to be detected. Parallel long hole-shaped through hole 8a
are formed respectively. As a result, the thin parts 8b, 8b
are provided, and the fixed part 8 and the support part 7 are connected via these thin parts 8b and 8b. In addition, the fixed part 8 includes
Attachment holes 8c and 8c for attachment are formed parallel to the through hole 8a, respectively.

According to the above-mentioned configuration, the strings 1a, lb, the support portion 7, the through hole 8a, the fixing portion 8, etc. can all be processed from the same direction, and the 90mm
A process such as rotation is required. This improves processing accuracy, eliminates deformation and processing stress, and improves detection accuracy as a load detection means.

Furthermore, machining from the same direction eliminates the complicated work of changing attachments, increasing mass productivity. Furthermore, Figure 2 (
As shown in b) and (b), when the thin parts 8b and 8b are twisted or bent, bending stress in either direction becomes difficult to be transmitted to the support part 7. Therefore, vibrations are transmitted through the support part 7. Since the stress is uniformly transmitted to the child body 6, there is less chance of a decrease in the Q value.
Regarding vibration insulation between the oscillator body 6 and the oscillator body 6, the provision of the thin parts 8b and 8b effectively reduces vibration energy loss more than the conventional tuning fork oscillator shown in FIG. 1O. be able to.

Here, to describe the thin parts 8b in more detail, bending stress is generated in the support part 7 due to the four corner loads and the deviation of the center line due to assembly error of the mechanism part during fixation. For example, in the case shown in FIG. 3, the bending stress happens to be a bending stress in the plane direction of the support part 7, and the support part 7 bends in response to this bending stress and absorbs this bending stress. The vibrator main body 6 is not affected. However, in many cases, the stress is not in the direction of bending the support part 7, but one side of the cross section perpendicular to the axial direction of the support part 7 receives strong stress, and the other side receives weak stress. In this case, the non-uniform stress of the support portion 7 is similarly transmitted to the vibrator main body 6, resulting in vibration in a non-uniform stress state, making it impossible to obtain a clear resonance point.

That is, the Q value decreases and the load detection accuracy decreases. The same thing can be said about tightening with bolts depending on force. Furthermore, as shown in FIG. 10, even in a tuning fork vibrator provided with flexures Pa and Fb, in response to bending stress in the plane direction of flexures Fa and Fb, flexures Fa and Fb can bend and absorb the bending stress. ,
For example, if a bending stress is applied to these at an angle of 45 degrees, uneven internal stress will occur in each flexure Fa and Fb, and the vibrating body l will be affected by this, resulting in a decrease in the Q value. becomes.

On the other hand, in the vibrator according to the first embodiment described above, the through hole 8a is provided, and the fixed part 8 and the supporting part 7 are connected by the thin parts 8b, 8b formed thereby. In response to the bending stress and tightening, the thin wall portions 8b, 8b twist or bend to absorb the stress, and the vibrator body 6 is not affected.

Next, modifications of each part of the first embodiment described above will be explained. FIG. 4(A) shows each string 1a constituting the vibrating body 1,
A case is shown in which thick portions 11a and 1 lb are provided in each of the lbs. Further, FIG. 4(b) shows a case in which the vibrating body l is constituted by a single thin plate between a pair of fixed parts 8.8. Moreover, FIGS. 5(A) to 5(N) show various modifications of the shape of the through hole 8a formed in the fixing part 8.

Next, the configuration of a scale to which the vibrator according to the first embodiment described above is applied will be explained with reference to FIGS. 6(a) and 6(b).

In Figure 6 (a) and (b), 15 has four legs 16
．． 16. A fixing member 17 is attached to the lower surface of the base 15, and the vibrator 2 according to the first embodiment described above is attached to the fixing member 17.
The fixing part 8 on the lower side of 0 is tightened and fixed by bolts 21 and 21. Further, both proximal end portions of the T-shaped lower link 24 are attached to the lower surface of the base I5 via a pair of thin sheet metal blades 25a, 25a. The side ends are swingable in the vertical direction.

On the other hand, on the upper surface of the base 15, there is a plate 26 parallel to this upper surface.
are the screw members 27, 27 and the nut 28.

28. Both proximal ends of a T-shaped upper link 29 having the same shape as the lower link 24 are attached to this plate body 26 via a pair of sheet metal blades 25b, 25b, so that the upper link 29 The tip side end portion of is swingable in the vertical direction. The lower and upper ends of the main metal 30 are attached to the swingable tip end portions of the lower link 24 and the upper link 29, respectively, via a sheet metal blade 25c and a sheet metal blade 25d.
A weighing pan 31 is attached to the upper end of the weighing pan 31 via a fitting 37. Further, a lever 32 is arranged between the upper surface of the base 15 and the plate 26, and this lever 32 is attached to the base 15 via a pair of sheet metal blades 25e, 25e.
It is swingable about the sheet metal blades 25e, 25e as fulcrums. One end of the lever 32 protrudes from an opening 30a formed in the main metal 30, and connects to the main metal 3 via a thin ribbon 33.
0, while the upper fixing portion 8 of the tuning fork vibrator 20 is fastened to the other end of the lever 32 by bolts 34 and 34.

In addition, in the figure, the reference numeral 35 is a vibration isolating material.

The structure of the above-mentioned scale is shown in FIG. 7 in a simplified manner.

That is, the base 15 (the path shown), the lower link 24 and the upper link 2 are interconnected by the sheet metal blades 25a to 25d.
9 and the main metal 30 constitute a donkey pal mechanism, and when an object to be weighed is placed on the weighing pan 31, the main metal 30 moves downward and the ribbon 33 moves downward. Accordingly, the lever 32 serves as a fulcrum for the sheet metal blade 25e.
In other words, one end of the lever 32 is pulled down and the other end of the lever 32 is pulled up, thereby applying a tensile force corresponding to the weight of the object to be weighed to the tuning fork vibrator 2o. act.

In this case, the tuning fork vibrator 20 is provided with an excitation means (the path shown in the figure) that makes the tuning fork vibrator 20 resonate, and a detection means (the path shown) that detects the vibration frequency of the tuning fork vibrator 20. , the weight of the object to be weighed is measured.

Note that, instead of the sheet metal blades 25a to 25e, a donkey pal type strain body having concave strain generating portions near both ends of the upper and lower sides of a parallelogram may be used.

Next, a second embodiment of the present invention will be described with reference to FIGS. 8(a) and 8(b). Figure 8 (a) and (b)
The difference from the first embodiment described above is that the fixing part 8
is U-shaped or L-shaped, and each end of the fixing portion 8 is formed parallel to the vibrator body 6 and extending to the sides of the vibrator body 6. And mounting holes 8c, 8
c... are formed at each end of the fixing part 8 in the central part of the vibrator main body 6 along an imaginary line S perpendicular thereto.

According to these configurations, it is possible to further reduce vibration energy loss than in the first embodiment described above. That is, if the shapes of the strings 1a and 1b are exactly symmetrical with respect to the central axis in the longitudinal direction of the tuning fork vibrator 6, the strings 1a and 1b will vibrate symmetrically, and in this case, the strings 1a and 1b will vibrate symmetrically. The bending moments generated in the joint 5 due to vibration cancel each other out.

However, in reality, it is difficult to form the shapes of the strings 1a and 1b accurately symmetrically, and therefore, the bending moment Mx (8th (see figure (a)) occurs alternately, and the fixed part 8
A minute couple of forces centered on the imaginary point K acts on . Therefore, as in the first embodiment described above, if the distance between the mounting holes 8c and 8c of the fixing part 8 is narrow as shown by e in FIG. As a result, the vibration energy of the vibrator main body 6 becomes a minute repetitive movement between the fixed part 8 and the member to which this fixed part 8 is attached, and between the fixed part 8 and the mounting bolt. It gets consumed. On the other hand, as in the second embodiment described above, the attachment hole 8c of the fixing part 8.

When the distance between 8c and 8c is wide as shown by L in FIG. 8(a), the couple acting on the fixed part 8 becomes smaller, and the amount of loss of vibration energy due to minute repeated movements is reduced.

In addition, in the second embodiment described above, since the mass of the fixing part 8 itself is large compared to the first embodiment, the force Fx alternately generated by the bending moment Mx and the vibration of the vibrator body 6 (See FIG. 8(a)) is strengthened, and therefore, it is possible to effectively insulate vibrational energy from being lost to the outside.

Furthermore, according to the second embodiment described above, when the outer circumferential temperature changes and the vibrator body 6 expands and contracts along its longitudinal direction, the end of the fixing part 8 moves in the longitudinal direction of the vibrator body 6. Since it expands and contracts along the vibrator body 6 and in the opposite direction to the vibrator main body 6,
These expansion and contraction amounts cancel each other out, so that the positions of the mounting holes 8c, 8c, . . . are always maintained on the virtual line S even if the outer peripheral temperature changes. Therefore, when the vibrator according to the second embodiment described above is applied to the scales shown in FIGS. 6(a) and 6(b), changes in the span and zero point of the scale due to changes in the peripheral temperature are extremely small. be able to.

Here, changes in the span and zero point of the scale due to changes in the peripheral temperature will be explained with reference to FIG. 9.

First, the tuning fork vibrator 20 and the ribbon 33 are made of steel material with the same coefficient of thermal expansion, and the base 15 (the path shown), the lower link 24, the upper link 29, and the main metal 30 are made of aluminum material with the same coefficient of thermal expansion. Configure. Further, when the lengths of the tuning fork vibrator 20 and the ribbon 33 are both Qts, and the outer circumferential temperature rises by a predetermined temperature, the tuning fork vibrator 20 and the ribbon 33 become Δ.

Assume that the lever 32 expands by ΔQ and the fulcrum of the lever 32 moves upward by ΔQ. In this case, the base 15, the lower link 24
, the upper link 29 and the main metal 30 are made of the same material, so the parallel relationship between the opposing sides does not collapse when viewed as a donkey pal mechanism. Then, when the peripheral temperature rises, each component becomes in the state shown by the dashed line in the figure due to thermal expansion, and the position of the weighing pan 31 moves upward. In this case, if each of the sheet metal blades 25a to 25e is constituted by a bearing, for example, the tension acting on the tuning fork vibrator 20 does not change, and therefore the span and zero point of the scale do not change. However, since the bearing has a certain amount of play, which impedes measurement accuracy, the sheet metal blade 25a~
It is advantageous to use 25e, in this case, sheet metal blade 25a ~
25e must be thick enough to withstand impact. And each sheet metal blade 25a~
When the plate thickness of 25e is thick, each sheet metal blade 25a~
25e, a reaction force is generated in the direction of lowering the weighing pan 31, and this reaction force acts in the direction of pulling the tuning fork vibrator 20. As a result, the tension acting on the tuning fork vibrator 20 changes, causing the scale to move downward. The span and zero point will change.

In other words, changes in the span and zero point of the scale configured as described above due to changes in the peripheral temperature occur due to the effect of expansion and contraction of the tuning fork vibrator 20 itself and the reaction force of each of the sheet metal blades 25a to 25e. Therefore, by using the tuning fork vibrator shown in Figures 8 (a) and (b), changes in the span and zero point of the scale caused by the expansion and contraction of the tuning fork vibrator can be removed, and furthermore, , the ribbon 33 is made of a material with a thermal expansion coefficient close to that of the aluminum material constituting the base 15, and by making the ribbon 33 expand and contract by the same amount as the rise Δg of the fulcrum of the lever 32, the outer periphery A highly accurate scale that is almost unaffected by temperature changes can be constructed.

Note that by constructing the vibrator according to the first embodiment described above from a constant elastic material and subjecting it to a prescribed heat treatment, the resonant frequency of the vibrator itself can be changed, and when the outer peripheral temperature changes, the vibrator This cancels out changes in the natural frequency caused by expansion and contraction of the vibrator, thereby making it possible to minimize the influence of changes in the outer peripheral temperature on the vibrator.

"Effects of the Invention" As explained above, according to the present invention, a load detection vibrator comprising a pair of fixed parts and a vibrating part formed between these fixed parts has a predetermined thickness. The fixing part and the vibrating part are formed integrally by processing a metal plate from one direction, and a through hole is provided in the same direction as the machining direction in the vicinity of a part of the fixing part that connects with the vibrating part. Since the thin portion formed by the through hole absorbs the bending stress acting on the vibrating portion, the following effects can be achieved.

■Since the vibrating part, support part, fixing part, and through-hole can all be machined in the same direction, machining accuracy is improved, and there is no deformation or machining stress during machining, making it suitable for detection as a load detection means. Accuracy can be improved, and there is no need for complicated attachment and change work, making it possible to increase mass productivity.

■By twisting or bending the thin wall part, bending stress in either direction becomes difficult to transmit to the vibrating part.
Transmission of vibration between the fixed part and the vibrating part is insulated, and loss of vibration energy can be reduced.

■Since the thin wall part has a buffering effect, it has a high tolerance to external shocks, and there is extremely little risk of breakage.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a vibrator according to a first embodiment of the present invention, FIGS. 2A and 2B are perspective views for explaining the operation of the same embodiment, and FIG. Figures 4(a) and 4(b) are diagrams for explaining the operation when the through hole 8a is not formed in the embodiment, and FIGS. 5(A) to 5(N) are perspective views showing configurations of modified examples of the through hole 8a of the same embodiment;
Figures (a) and (b) are a plan view and partially cutaway front view showing the configuration of a scale to which the same embodiment is applied, and Figure 7 is a simplified basic configuration diagram of the scale shown in Figure 6. , FIGS. 8(a) and 8(b) are front views showing the configuration of the vibrator according to the second embodiment of the present invention, and FIG. 9 shows the expansion and contraction of various parts of the scale shown in FIG. 6 due to changes in the outer peripheral temperature. FIG. 1O, which is a diagram for explaining the situation, is a perspective view showing the configuration of a conventional vibrator. 1... vibrating body, la, lb... string, 5...
...Coupling part, 6...Resonator body, 7...
・Supporting part, 8...Fixing part, 8a...Thin hole, 8b...Thin wall part, 8c...Mounting hole. Figure 1 Figure 2 r Figure 8 Figure 5 Figure 7 Sl Figure 9 Figure 8

Claims (1)

[Claims] 1) A load detection vibrator consisting of a pair of fixed parts and a vibrating part formed between these fixed parts, in which a metal plate having a predetermined thickness is processed from one direction. The fixing part and the vibrating part are integrally configured, and the fixing part includes:
A through hole extending in the same direction as the processing direction is provided near a portion connected to the vibrating portion, and a thin wall portion formed by the through hole absorbs bending stress acting on the vibrating portion. Vibrator for load detection. 2) The load detecting vibrator according to claim 1, wherein the vibrating section is composed of one thin plate. 3) The vibrating section includes a pair of thin plate-shaped strings, a connecting part that connects both ends of each of the strings, and a thin plate-shaped support part that connects each of the connecting parts and each of the fixed parts. A load detection vibrator according to claim 1, characterized in that it is constructed by: