JPH0629761B2 - Electronic balance - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic balance for weighing an article.

[Prior Art] Generally, such an electronic balance has a roberval mechanism called a parallel guide for keeping the tray of an article horizontal and a displacement of the height of the tray as seen in Japanese Utility Model Publication No. 55-164519. It is configured by combining a lever mechanism or the like that acts as a lever for transmitting the force to the load sensor.

[Problems to be Solved by the Invention] Each of these mechanisms is configured by being fixed to a frame by an elastic member or by connecting each mechanism so that a predetermined movement is possible. The elastic member for fixing and connecting this mechanism is made of a different material from each mechanism,
Screwing, caulking or bonding is performed on each mechanism.

Therefore, when the ambient temperature changes, the fixed portion and the connecting portion of the above mechanism are distorted between the connected portions due to the difference in the thermal expansion coefficient of the materials. As a result, there is a problem that the weight measurement result causes a temperature drift and accurate measurement cannot be performed.

Further, there has been a problem that it is necessary to create and assemble each mechanism and many parts for fixing these, which requires a lot of manufacturing man-hours.

In view of the above problems, it is an object of the present invention to provide an electronic balance that can reduce the number of manufacturing steps and can perform accurate measurement.

[Means for Solving the Problems] Therefore, according to the present invention, a movable part that is displaced together with a tray on which an article is placed, a Roberval mechanism for translating the movable part, and a displacement of the movable part are transmitted to a load sensor. The lever and the connecting part of each part are integrated by boring one base material, and the part that connects the lever mechanism and the movable part is flexibly bent at a right angle to the longitudinal direction of the Roberval mechanism. A thin portion is provided.

[Operation] Since it is not necessary to individually create and assemble each part mechanism,
Since the number of manufacturing steps is reduced and the connecting parts of each part mechanism are made of the same material, there is no distortion due to temperature change, and when placing an object on a plate, Even if the object is placed at a right angle, the thin part absorbs the inclination, the lever does not bend, and the displacement is accurately transmitted to the load sensor at the tip of the lever. Weight can be measured.

[Examples] Examples of the present invention will be described in detail below.

FIG. 1 is an external perspective view showing a mechanical portion of an electronic balance according to an embodiment of the present invention, and FIG. 2 is a side sectional view thereof. In these figures, the mechanism 1 is a rectangular parallelepiped, for example, an aluminum alloy that is hollowed out in a certain shape from the side to form each part having various functions, and the support 2a fixed to the base frame 2 is formed. It is fixed by screws 3 to.

A plate-like Roberval part is provided at the upper end and the lower end of this mechanism 1.
4,5 are respectively formed, and narrowed portions 4a, 5b, 5a, 5b are respectively formed at both ends of each Roberval portion 4,5.

A lever 6 supported by a narrowed portion 6a serving as a fulcrum is formed below the roberval portion 4, and a force coil 7 is fixed below the lever 6 on the support body 2a side.
The force coil 7 is hollowed around, and a magnet having a yoke 8a and a pole piece 8b fixed in its cavity.
8 is fixed.

The other end of the lever 6 is connected to the movable part 10 by a connecting part 9 having narrowed parts 9a and 9b formed at both ends.

A thin portion 9c is formed at a portion of the connecting portion 9 corresponding to the center of the Roberval portions 4 and 5 as shown in FIG.

A catch rod 11 is screwed onto the upper end of the movable part 10.
A plate 12 is fixed to the.

Although not shown, a zero position sensor that uses a photosensor or the like to detect the displacement is attached to the end portion of the lever 6 on the force coil 7 side.

The electronic balance of the present embodiment is composed of the above-mentioned mechanical section and a control circuit (not shown). With this configuration, when the electronic balance is used, the dish to be weighed is placed on the dish 12.

Due to this load, the movable part 10 tends to be displaced downward. At this time, since the upper surface and the lower surface of the movable portion 10 are supported by the Roberval portions 4 and 5, the movable portion 10 is displaced while maintaining the horizontal state of the dish 12.

The downward displacement of the movable portion 10 is transmitted to one end of the lever 6 by the connecting portion 9, and the lever 6 has its end portion on the force coil 7 side displaced upward with the narrowed portion 6a as a fulcrum. The upward displacement of the end portion of the lever 6 is detected by the zero position sensor. The control circuit energizes the force coil 7 with a current that makes the displacement zero due to the attraction between the force coil 7 and the magnet 8.

As a result, the force coil 7 is energized with a current proportional to the load of the article placed on the tray 12. Here, the applied current value is converted to weight (grams),
It is displayed on a display unit (not shown).

By the way, in FIG. 2, if the articles are unevenly placed on the front end portion on the plate 12 or on the opposite side, the load amount may be uneven and the Roberval parts 4 and 5 may not be able to keep the plate 12 horizontal.
In this case, the fixed portion 10 is inclined, but the connecting portion 9 is thin.
It can be bent by c, and does not distort the lever 6.

If the lever 6 is distorted, correct weight cannot be measured, but
The thin portion 9c formed in the connecting portion 9 maintains the normal state of the lever 6 even if the fixed portion 10 is tilted, and correct measurement can be performed.

Further, when so-called eccentricity error occurs in the measurement result when the position of placing the article on the plate 12 is biased, the narrowed portions 4a, 4b, 5a, 5b of the Roberval parts 4 and 5 are ground with a file. The parallelism can be adjusted by changing the center point as the substantial fulcrum, and the position error can be adjusted.

In addition, it may be difficult to form the narrowed portions 4a, 4b, 5a, 5b, 9a, 9b, 6a sufficiently thin due to processing restrictions.
The mechanical sensitivity is reduced for displacement of 10, but the position of the fixed part 10 is always controlled to a constant height.When the zero method measurement is performed, the influence of the elastic force of that part can be almost eliminated. It has the advantage of starting.

As described above, in the present embodiment, by hollowing out the rectangular parallelepiped metal base material, the Roberval parts 4 and 5, the lever 6 and other parts are formed, and the constriction part is formed in the connecting part of each part to form each part. It enables a certain movement. Since the entire mechanism is made of the same material in this way, even if the ambient temperature changes, the connected portion will not be distorted as in the conventional case. As a result, there is no temperature drift in the weight measurement result, and accurate measurement can be performed. Moreover, since each of the above-mentioned parts can be formed only by hollowing out the metal material, it is not necessary to individually create each part or assemble many of those parts as in the conventional case, and the number of manufacturing steps can be reduced.

In the above embodiment, the load sensor is constituted by the zero position sensor, the force coil 7 and the magnet 8. However, as shown in FIGS. 4 and 5, the arm 13 is provided at the end of the lever 6. Fix the load sensor 14 that detects the force or displacement of the arm and screw 15 to the end of the mechanism 1.
You may make it attach by a, 15b. in this case,
The bottom of the mechanism body 1 is fixed to the base frame 2 with screws 16. The load sensor 14 is not limited to an electromagnetic type, and various types of sensors such as a tuning fork type, a string vibration type, a capacitance type, or an inductance type can be used. According to this structure, the mechanism portion is formed to be short, the same operational effect as described above can be obtained, and the attachment adjustment of the load sensor 14 is facilitated.

Further, in each of the above embodiments, the lever 6 is formed between the roberval portions 4 and 5, but the lever 6 may of course be formed above or below the roberval portions 4 and 5. In a large-capacity balance, the lever may have a plurality of stages as in the conventional case.

[Effects of the Invention] As described above, according to the present invention, since the entire mechanism is formed by hollowing out one base material, the number of manufacturing steps is smaller than that in the conventional method in which each part of the mechanism is individually created and assembled. In addition to being reduced, since each part of the mechanism is composed of the same material, distortion of the mechanism connection part due to environmental temperature change is eliminated, temperature drift of the measurement result is also eliminated, not only can accurate load measurement be performed, Accurate measurement can be performed even with an eccentric load, and further improvement in measurement accuracy is satisfied.

[Brief description of drawings]

FIG. 1 is a perspective view of a mechanism of an electronic balance according to an embodiment of the present invention, FIG. 2 is a side sectional view thereof, FIG. 3 is a perspective view of a connecting portion, and FIG. 4 is related to another embodiment. FIG. 5 is a perspective view of the mechanism of the electronic balance, and FIG. 5 is a side view thereof. 1 …… Mechanism body, 2 …… Base frame, 2a …… Support body, 3,15
a, 15b, 16 …… Screw, 4,5 …… Roberval part, 4a, 4b, 5a, 5
b, 6a, 9a, 9b …… Constriction part, 6 …… Lever, 7 …… Force coil, 8 …… Magnet, 8a …… Yoke, 8b …… Pole piece, 9 …… Coupling part, 9c …… Thin wall part , 10 …… Movable part, 1
1 …… Roller, 12 …… Plate, 13 …… Arm, 14 …… Load sensor.

Claims (2)

[Claims] 1. A movable part to which a dish on which an article is placed is fixed, a Roberval mechanism for moving the movable part in parallel in a vertical direction, a lever mechanism for transmitting a displacement of the movable part to a load sensor, and a load sensor. In an electronic balance equipped with a display device for displaying the detected weight, the movable part, the Roberval mechanism, the lever mechanism and their respective connecting parts are integrally formed by boring one base material. , The Roberval mechanism is composed of two parallel plates having one end fixed to the upper and lower parts of the movable part and the other end fixed, while the lever mechanism is arranged between the parallel plates. At the central position of the two parallel plates of the connecting portion that connects the movable portion and the lever mechanism, there is a thin-walled portion that allows the connecting portion to bend in a direction perpendicular to the longitudinal direction of the parallel plate. Electronic balance, characterized in that the form was. 2. The weight sensor according to claim 1, wherein the weight sensor includes a zero position sensor for detecting a displacement of an end portion of the lever mechanism, and a coil for reducing the displacement of the end portion to zero. An electronic balance comprising a magnet and a drive unit.