JPS6323490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a load detection mechanism for reliably and precisely measuring loads using a top scale scale or the like.

In general, a condition required for a load detection mechanism is that it can faithfully measure only the force in the measurement direction, and even if a force is applied in a direction perpendicular to the measurement direction, the resistance of the mechanism is strong and will not affect the measured value. First, especially in the case of a top-pan weighing scale, it is necessary to prevent so-called four-corner errors from occurring in response to an eccentric load applied to a position offset from the center of the weighing pan.

A typical example of a conventionally used load detection mechanism for a top-pan scale is shown in FIG. In FIG. 1, a weighing pan (not shown) is placed on top of a pan support rod 1, and gravity acting in the Z-axis direction is applied to this mechanism as a measurement load. The plate support rod 1 is further extended downward as a load shaft 2, and its lower end 3 is connected to a load cell 5 on a substrate 4. As the load cell 5, an appropriate load transducer with relatively small change is generally used, such as a strain gauge type, an electromagnetic force balance type, a piezoelectric element, a tuning fork vibrator, a vibrating string, a gyroscope, a variable capacitance element, etc. There are two more on board 4.
Book columns 6, 7 are installed, and these columns 6, 7 and the load shaft 2 are connected to two V-shaped arms 8, which are arranged vertically in parallel and form a roberval mechanism.
9 are supported, the V-shaped bases 8a, 9a of these arms 8, 9 are connected to the load axis 2, the tips 8 of the branches
b, 8c, 9b, and 9c are fixed to the columns 6 and 7, respectively, and a reinforcing bar 1 is installed between the upper ends of the columns 6 and 7.
0 is attached. The V-shaped arms 8, 9 themselves are made to have sufficient rigidity, but there are flexible parts 11a, 11b, 11c, 12a, 12b, 12 near their bases and outer ends.
c are provided, and the bending at these parts is relatively free.

To explain the operation of this conventional mechanism using FIG. 2, the link mechanism has flexures 11a, 11b, 1
By forming a parallelogram consisting of four points 2a and 12b and selecting the positions of flexures 11b and 12b as fixed points, the displacement allowed for the weighing pan 13 and load shaft 2 attached to the movable flexures 11a and 12a is determined. is limited to circular motion as shown by the arrow. When the load W is biased in the X direction from the center of the weighing pan 13 as shown in the figure, compressive force and tensile force act on arms 8 and 9 in the arm direction due to the biased load, but both If they are parallel, even if they are not horizontal, the vertical component of the compressive force and the vertical component of the tensile force cancel each other out, so only the force acting in the axial direction, that is, the vertical direction, is transmitted to the load shaft 2. is well known.

However, in the conventional detection mechanism shown in FIG. 1, the load shaft 2 moves in an arc while maintaining its vertical position, so that the load shaft 2 is displaced in the vertical direction and at the same time is also slightly displaced in the horizontal direction. Load cell 5
An undesirable force in the direction of the water level is also added to the surface, causing measurement errors. Therefore, not only can a load cell with a large displacement amount or a linear motion displacement transducer such as a differential transformer not be used, but even if a load cell with a small displacement amount is used, the impact force when the load W is applied is It is not allowed to interpose a spring or damper with a large displacement between the load shaft 2 and the load cell 5 for the purpose of absorbing and alleviating overload, and as a result, there is a risk that the load cell 5 may be damaged.

In order to solve the above-mentioned drawbacks of the prior art, the present applicant proposed a load detection mechanism in which the load shaft 2 moves not in a circular arc but in a linear motion in Japanese Patent Application No. 57-205284 (Japanese Patent Application Laid-Open No. 59-94016). As proposed earlier, load axis 2
In addition to the drawbacks of linear motion and simultaneous rotational motion around the load axis 2, there was also the problem that machining of some parts was difficult.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and because the load axis performs complete linear motion, it is possible to use a load cell with a large displacement or a linear motion displacement transducer, and to We provide a load detection mechanism that can freely include a spring for shock mitigation, has strong resistance to horizontal unbalanced loads, is less prone to four-corner errors, and is easy to work with. It's about doing.

The gist of the specific invention to achieve the above purpose is:
A peeled metal block having parallelogram sides and having a thin flex at both ends of each side, with slits cut in the cross-sectional direction, and having one common vertical axis side. , forming a double link mechanism consisting of a movable side link mechanism and a fixed side link mechanism each having the remaining sides independently, and the movable side link mechanism has a side opposite to the common vertical axis side as a load axis. The fixed side link mechanism is characterized in that the side opposite to the common vertical axis side is fixedly attached near the load axis side.

In relation to the specific invention, the gist of the present invention for achieving the above object is to have each side of a parallelogram,
A stripped metal block with thin flexure near both ends of each side, with slits in the cross-sectional direction, one common vertical axis, and each remaining side independently. At least two sets of double link mechanisms consisting of a movable side link mechanism and a fixed side link mechanism are arranged at approximately equal angles around the load center axis, and the movable side link mechanism is located on the side opposite to the common vertical axis side. The side is the load axis side, and the link mechanism on the fixed side has the side opposite to the common vertical axis side fixedly attached near the load axis side, and the movement of the load center axis is controlled by the load axis side. The load is transmitted to the shaft side, and the load shaft side moves linearly in the direction of the load center axis.

The present invention will be explained in detail based on the embodiment shown in FIG. 3 and below. In addition, in these drawings,
The same reference numerals as in FIGS. 1 and 2 indicate the same members.

FIG. 3 is a diagram showing the basic principle of the present invention, and as shown, the link mechanism forms two parallelograms of the same size with six flexures 15 to 20 as vertices. The first link mechanism is a flexure 15,1
Horizontal arms 21, 2 with 6, 19, 20 as vertices
2 and a vertical link 23, the vertical link 2
The position of the flexures 15, 16 on the opposite side from 3 is fixed, and the point that these flexures 15, 16 are located near the load shaft 2 is greatly different from the conventional mechanism shown in FIG. The second link mechanism is composed of horizontal arms 24, 25 and a vertical link 23 with flexures 17, 18, 19, 20 at the apex, and the flexures 19, 20 and the vertical link 23 are in principle shared with the first link mechanism. , a load shaft 2 is attached to the flexures 17, 18 on the opposite side of the vertical link 23.

In such a basic configuration of the present invention, the load W
is applied to the weighing pan 13, if the rotational resistance of each of the flexures 15 to 20 is equal, the load shaft 2 will move linearly in the vertical direction, and if the flexure has good spring characteristics, it will move linearly as it is. A spring scale of the shape is obtained. Furthermore, as shown in FIG. 1, the load shaft 2 can be connected to the load cell 5, or the movement can be transmitted to a linear motion displacement transducer.

Even if the rotational drag of each flexure is not equal to each other due to machining errors, if two sets of double link mechanisms shown in FIG. 3 are installed on the west side of the load shaft 2, as shown in FIG. always moves in a straight line. When the mechanism of the present invention is configured with two sets of double link mechanisms in this way, it is clearly more advantageous than the conventional mechanism in terms of eliminating errors at the four corners. for example,
FIG. 5 is a diagram of the principle mechanism in which four link mechanisms are arranged symmetrically, but the state in which they all deviate from the parallelogram due to manufacturing errors is exaggerated for the sake of explanation. If the weighing pan 13 and the load shaft 2 deviate from the parallelogram by this much, it is impossible to move smoothly, and in reality, only a very small deviation due to machining error is assumed, and the problem of four corner errors is We will consider this.

When a load W is applied to the end of the weighing pan 13 as shown in FIG. 5, a tension or compression force acts on each arm of the link mechanism due to the force that tends to tilt the load shaft 2, and the reaction force Forces F1, F1'F2, and F2' in the arm direction act on the load shaft 2 at the flexures 17, 17', 18, and 18', respectively. When considering the conventional mechanism shown in FIG. 2 in comparison with FIG. 4 or FIG. However, this mechanism does not necessarily require this condition. The reason for this is that when arms 24 and 25 are not parallel, the vertical component force of F1 and the vertical component force of F2 are not equal in magnitude, so they do not cancel each other out, but because they are symmetrically constructed, The vertical component force of F1′ and the vertical component force of F1′ are equal in magnitude and opposite in direction, so they cancel each other out, and similarly, the vertical component force of F2 and
Since the vertical component of F2' is also canceled out, the reaction forces F1, F2 of the tensile force and compressive force of each arm based on the unbalanced load,
The vertical component forces of F1' and F2' do not act on the load axis 2 as a whole and do not cause any four corner errors.

Although it is desirable to have a symmetrical structure in this way, the load detection mechanism according to the present invention can also be configured even if an asymmetrical shape is adopted in which the left and right arms have different lengths, for example, as shown in FIG. Can be done.
However, the matters explained with reference to FIG. 5 regarding the elimination of four corner errors do not hold true as they are, and the condition that the arms 24 and 25 and 24' and 25' corresponding to the upper and lower sides are parallel to each other is required.

Figure 7 shows an example of the structure of a basic double link mechanism on one side only, which corresponds to Figure 3, and includes two parallel links in the cross-sectional direction of a parallelogram-shaped metal block with an integral structure with the inside stripped out. A central movable link mechanism 31 and fixed link mechanisms 32, 32 on both sides thereof are provided.
In this case, in order to equalize the rotational drag of each flexure, the width b of the movable link mechanism 31 is desirably selected to be twice the width a of each fixed link mechanism 32. Here slit 30,30
are cut so that one side of the parallelogram is common and the remaining sides are separated from each other.
A plate support rod 33 is provided in a part of the movable link mechanism 31, and the vertical shaft sides 34 of the fixed link mechanisms 32, 32 on both sides thereof are fixed to a fixed member (not shown) and are substantially fixed. It is designed to function as an integral part of the component.

If this is compared with the mechanism in FIG. 3, the vertical axis side 35 that is common to the movable link mechanism 31 and the fixed link mechanisms 32, 32 corresponds to the vertical link 23,
A load shaft side 36 on which the plate receiving rod 33 of the movable link mechanism 31 is provided corresponds to the vertical shaft 2. Furthermore,
The upper sides 37, 37 of the fixed side link mechanisms 32, 32 correspond to the horizontal arm 21, and the lower sides 38, 38 correspond to the horizontal arm 22, respectively. The upper side 39 of the movable side link mechanism 31 corresponds to the horizontal arm 24, and the lower side 40 corresponds to the horizontal arm. 25 respectively. The thin wall portions 41 near both ends of each side have flexures 15 to 20
corresponds to

Since the double link mechanism of this configuration is manufactured based on an integral metal block, it has the advantage of being resistant to horizontal forces and torsion, and that it is easy to obtain parallelism on each side. Then, as shown in FIG. 8, when a load W is applied to the load shaft side 36 via the plate support rod 33, the load shaft side 36 becomes almost straight with respect to the vertical axis sides 34, 34 of the fixed side parallelogram. If this displacement is measured by a converter such as a load cell or a differential transformer, the load can be accurately measured.

Figure 9 shows one slit 30 in the center of the thickness direction instead of the two slits in the mechanism of Figure 7.
The mechanism principle and operating functions are the same as those shown in FIGS. 3 and 7.

In addition, in the embodiments shown in FIGS. 7 and 9, if the rotational drag of each flexure 41 is not equal to each other,
Strictly speaking, there may be arcuate motion in addition to linear motion on the load shaft side 36, but this can be prevented by combining two sets of double link mechanisms as shown in FIG. In this embodiment, slits 30, 30 are formed in a metal block having two cut-out parts, and the double link mechanism shown in FIG. 7 is provided symmetrically. . Then, the load shaft side 3 of the fixed side link mechanism 32, 32
4, 34 and the load axis side 3 of the movable link mechanism 31
6 is commonly used in the left and right double link mechanisms, and is the same in principle as the mechanism shown in FIG. 4.

In the descriptions so far, the double link mechanism formed by two parallelogram links on each side sharing the vertical link 23 remains as one set, or one set on the left and right
For the sake of convenience, the present invention has been described in such a manner that two sets in total are arranged almost symmetrically, but if three or more sets are arranged radially around the load axis, it is possible to eliminate errors at the four corners and It is further advantageous that the influence of undesirable interfering external forces in the direction perpendicular to the direction can be eliminated.

FIGS. 11a and 11b show three sets of double link mechanisms, excluding the plate support rod 33 shown in FIG. are fixed on a short cylindrical base 42, and the load shaft sides 36 of the movable link mechanism 31 are fixed to each other by a connecting plate 44 provided with a plate support rod 43 at the upper part. A groove 45 is provided for escape from the descent of the side 36. The operation in this case is almost the same as in the above case, but it is particularly superior in that it has a large resistance against disturbing forces from any horizontal direction.

The features of the load detection mechanism according to the present invention explained above can be summarized as follows.

(1) If the rotational drag of each flexure is equal, leave one set of double link mechanism; even if they are not equal, if two or more sets are used, the load axis side 3 becomes the load axis
6 performs linear motion, so it is possible to use a linearly linked displacement transducer such as a load cell with a large displacement or a differential transformer, and displacement in a direction perpendicular to the load direction, which is unfavorable for measurement, can be transmitted to the load cell. Highly accurate load detection is possible.

(2) Since the displacement of the load axis can be large, by interposing a buffer spring or damper between the load axis side 36 and the load cell, damage to the load cell due to impact load can be prevented when the displacement of the load cell is small. Furthermore, by providing a mechanical stopper against displacement of the load shaft side 36 during overload, it is possible to extremely easily prevent overload from being applied to the load cell.

(3) If the parallelogram double link mechanism is arranged axially symmetrically, the upper and lower sides 39
Even if the lower side 40 or the upper side 37 and the lower side 38 are not sufficiently parallel, a four-corner error will not occur.

(4) It has high strength against undesirable horizontal forces applied to the load axis side, which is the load axis, and especially if three or more sets of double link mechanisms are used, it becomes extremely strong in any direction, so it is resistant to impact forces. In addition, there is no risk of breakage, and there is little error in the four corners due to unbalanced loads. Applications where the unbalanced loads in a particular direction are large can be handled by appropriately selecting the length of each side.

(5) In the conventional mechanism, as illustrated in Fig. 1, the entire detection mechanism including the load cell 5 is attached to the substrate 4 with a large planar area, so the substrate 4 may be distorted due to large loads or uneven loads. However, in the present invention, as shown in FIG. 11, the detection mechanism is entirely supported by a base 42 with an extremely small plane area, so even if the bottom plate of the scale is distorted, measurement errors will not occur. Therefore, the detection mechanism can be housed in a thin, lightweight, and inexpensive case.

Although the above-mentioned advantages are mainly applied to a top-pan weigher, the load detection mechanism according to the present invention also has the following advantages and adaptability to other devices.

(6) If the load axis side 36 is set horizontally, it can be used as a horizontal vibration acceleration or force detection type inclinometer or a horizontal load meter, and the disturbing component force in the direction perpendicular to the load axis side 36 is large. However, only accelerations and forces applied in the axial direction are accurately detected.

(7) In addition to detecting displacement and force, it can also be used as a contactless and frictionless linear motion mechanism that is not directly related to measurement.

For many years, the Roberval mechanism shown in Figures 1 and 2 has been used almost without exception in all types of balances, including not only electronic scales but also mechanical spring scales and balances. As described above, the load detection mechanism according to the present invention has many outstanding advantages not found in conventional mechanisms, and has made an extremely large contribution to the progress and development of scales and load cells.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional load detector, Figure 2 is a diagram of its basic principle, Figure 3 and the following diagrams show a load detection mechanism according to the present invention, and Figures 3 and 4 are diagrams of its basic principle. , Fig. 5 and Fig. 6 are explanatory diagrams regarding the elimination of four corner errors, Fig. 7 is a perspective view of a specific embodiment, Fig. 8 is an explanatory diagram of its operating state, and Fig. 9 and Fig. 10 are illustrations of other examples. FIG. 11a is a plan view of still another embodiment, and FIG. 11b is a side view thereof. Code 2 is the load axis, 5 is the load cell, 15-20
is a flexure, 21, 22, 24, 25 are horizontal arms, 23 is a vertical link, 30 is a slit, 31
32 is a movable link mechanism, 32 is a fixed link mechanism,
33, 43 are plate support rods, 34, 35 are vertical axis sides, 3
6 is a load axis side, 37 and 39 are upper sides, 38 and 40 are lower sides, 41 is a flexure, 42 is a base, and 44 is a connecting plate.

Claims (1)

[Scope of Claims] 1. A peeled-out metal block having parallelogram sides and having thin flexure near both ends of each side, with slits made in its cross-sectional direction, 1
forming a double link mechanism consisting of a movable side link mechanism and a fixed side link mechanism each having a common vertical axis side and the remaining sides independently, and the movable side link mechanism is connected to the common vertical axis side. The side opposite to the side is the load axis side, and the link mechanism on the fixed side has the side opposite to the common vertical axis side fixedly attached near the load axis side. Load detection mechanism. 2. The load detection mechanism according to claim 1, wherein the slits are two parallel lines, the link mechanism at the center is on the movable side, and the link mechanisms on both sides are on the fixed side. 3. Load detection according to claim 1, wherein the slit is provided in the center in the thickness direction, and the link mechanism on one side separated by the slit is the movable side, and the link mechanism on the other side is the fixed side. mechanism. 4. A stripped metal block with parallelogram-like sides and a thin flexure near both ends of each side is made with a slit in its cross-sectional direction, and 1
At least two sets of double link mechanisms, each consisting of a movable side link mechanism and a fixed side link mechanism, each having a common vertical axis side and the remaining sides independently, are arranged at approximately equal angles around the load center axis. The link mechanism on the movable side has the side opposite to the common vertical axis side as the load axis side, and the link mechanism on the fixed side has the side opposite to the common vertical axis side as the load axis side. Load detection characterized in that it is fixedly attached near a side, the movement of the load center axis is transmitted to the load axis side, and the load axis side moves linearly in the direction of the load center axis. mechanism.