JP2527308B2 - Weighing device that prevents the influence of air flow - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electromagnetic parallel type high resolution weighing device, and more particularly to a weighing device configured to prevent deterioration of weighing accuracy due to convection of air generated inside the device. .

[Conventional technology]

As an electromagnetic balance type high-resolution weighing device, there is a weighing device called an electronic balance. The basic structure of this device is that the weighing pan on which the weighing object is placed, the arm for transmitting the weight applied to the weighing pan, the load transmitted through this arm, and the conversion of this load into an electric signal. It consists of a weighing mechanism. Furthermore, a display unit is connected to the weighing mechanism unit, and the load measured by an appropriate display means such as a liquid crystal is displayed by the signal output from the weighing mechanism unit.

 FIG. 2 shows a specific configuration of the electronic balance described above.

Reference numeral 1 is an electronic balance main body, 2 is a weighing chamber that constitutes a part of the main body, and normally the weighing chamber 2 is configured as a glass case.

The load of the object to be measured placed on the weighing pan 3 in the weighing chamber 2 is stored in the mechanism chamber 17 via the pin 6 arranged through the floor 5 of the weighing chamber 2 and the arm 4 having the pin 6. It is transmitted to the Roberval mechanism 16. The Roberval mechanism 16 includes an upper sub-bar 7, a lower sub-bar 8 parallel to the upper sub-bar 7, a floating frame 9,
It is a parallelogram composed of leaf springs 10a, 10b, 10c and 10d connecting these. The arm is connected to the Roberval mechanism 16. A beam 12 swings around a fulcrum 13, one end of which is connected to the floating frame 9 of the Roberval mechanism 16 and the other end of which is connected to the electromagnetic portion 14.

In the above structure, the load of the weighing object reaches the beam 12 through the arm 4, the Roberval mechanism 16 and the leaf spring 11, the displacement of the beam 12 is detected by a sensor (not shown), and this displacement signal is detected by the servo mechanism. Amplified by (not shown), the output current is supplied to the electromagnetic section 14 to balance the beam 12 against the load. Since the generated force in the electromagnetic unit is proportional to the electric power supplied to the electromagnetic unit, this electric power is output as a voltage and displayed on the display unit 15 as the load of the weighing object.

The electronic balance with the above configuration has very high weighing accuracy,
On the other hand, there is a problem in that this accuracy is high and it is easily affected by the outside. In particular, the influence of the air flow on the weighing pan is great, and the air flow causes the weighing pan to oscillate, which causes a problem that the load display becomes inaccurate or unstable. For this reason, the weighing unit is covered with glass as described above to temporarily shut off the outside air as a weighing chamber to prevent the influence of the flow of the outside air. However, when the weighing accuracy of the device is improved, not only the flow of outside air but also a very slight flow of air inside the device has an influence on the weighing accuracy, and some countermeasures have been proposed.

[Problems to be solved by the invention]

First, even if the tightness of the weighing device itself is improved, it is unavoidable that air convection occurs due to the temperature difference inside the device. In particular, since the electric circuit of the mechanism chamber generates heat when energized, the temperature of the mechanism chamber is generally higher than that of the weighing chamber.

Here, in order to transfer the load of the object to be weighed to the weighing mechanism, the weighing dish 3 in the weighing chamber 2 and the weighing mechanism in the mechanism chamber 17 are mechanically connected, and therefore the floor 5 of the weighing chamber 2 is connected. Is formed with an opening 5a for inserting the pin 6. However, by forming this opening, the air in the mechanism chamber having a high temperature flows into the weighing chamber 2 through this opening 5a. Therefore, the air rising through the opening stirs up the weighing dish 3, making it difficult to measure the load accurately. In order to reduce the flow of air, it is necessary to make the inner diameter of the opening 5a as close as possible to the outer diameter of the pin 6 and reduce the gap between the opening 5a and the pin 6. However, if the opening 5a and the pin 6 come into contact with each other, accurate measurement cannot be performed. Therefore, including the swinging amount of the arm 4 when the weighing object is placed,
The inner diameter of the opening 5a cannot be made too small, and there is naturally a limit to the prevention of air flow.

In order to solve the above problems, several kinds of configurations have been proposed in the past.

As one of the configurations, there is Japanese Patent Laid-Open No. 153223/1982. In this configuration, a lower plate (airflow protection plate) is fixedly installed in the lower part of the weighing pan, a sleeve is formed in the center of the lower plate, and a shaft (pin) for transmitting the load is inserted into the sleeve. At the same time, by making the outer diameter of the shaft body close to the inner diameter of the sleeve, the gap between the sleeve and the shaft body is made smaller, thereby increasing the ventilation resistance of this gap, and further, the floor formed around the sleeve and its surroundings. The gap with the surface opening is increased, and the ventilation resistance of the floor opening is reduced. As a result, most of the airflow from the mechanism chamber rises on the outer peripheral portion of the sleeve having a small airflow resistance, and the ascending airflow hits the lower tray fixed to the floor surface. For this reason, the weighing pan itself is rarely hit by an upward flow, and high weighing accuracy is guaranteed.

However, in this configuration, it is necessary to make the gap between the sleeve and the shaft body as small as possible. Therefore, when the weighing object is placed away from the center of the weighing pan, the shaft body may be moved even by a slight inclination of the weighing pan. And the inner wall surface of the sleeve come into contact with each other, and as a result, as described above, there is a possibility that an accurate load cannot be transmitted to the mechanism portion. Even if the sleeve is eliminated and only the opening for inserting the shaft is formed in the lower plate arranged close to the weighing pan, it is necessary to minimize the gap between the opening and the shaft body. Therefore, if the weighing pan is tilted, the shaft body still comes into contact with the opening. In other words, since the center of swing of the shaft due to uneven distribution of the weighing object on the weighing pan is at the connecting part between the shaft and the mechanism part or the beam which is the lower end of the shaft, the lower plate is located close to the weighing pan. In the structure, a slight displacement of the shaft causes the upper part of the shaft, which has a large displacement, to come into contact with the opening. Further, in order to suppress the swing, a very strong shaft body must be used, and it becomes necessary to significantly strengthen the connection structure between the shaft body and the mechanism part or the beam.

 Next, in addition to the above-mentioned configuration, there is Jitsukai Sho 59-21735.

This structure is intended to simplify the means for preventing the effect of rising airflow. In other words, while the above-mentioned configuration uses the lower tray to protect the weighing dish from upward airflow, this configuration is covered by the weighing dish on the surface (floor surface) separating the weighing chamber and the mechanism chamber. By forming a plurality of openings in a portion other than the region where the rising air flows, it is possible to prevent the ascending air current from directly hitting the weighing pan. This configuration is very simple and can suppress an increase in the manufacturing cost of the device, but has the following problems.

In other words, because of its structure, the opening must always be formed in a region other than the area covered by the weighing pan. After that, it easily falls into the lower mechanism room. That is, the opening for the rising air flow is preferably formed in the lower part of the weighing pan, without considering the influence of the air flow on the weighing pan and only considering the fall of the weighing object into the mechanism chamber. By the way, if the opening is formed at this position, the weighing dish itself functions as a cover for preventing the falling of the weighing object.

Further, in order to prevent the outflow of air from the opening 5a, a method of forming an air vent opening 17a in the mechanism chamber 17 has been attempted. In this method, the temperature-elevated air rises in the mechanism chamber and flows out from the opening 17a, but the outflowing air is sucked into the mechanism chamber 17 from the opening 5a of the weighing chamber, and this time, a downward flow of air around the weighing dish. The result is that the weighing pan 3 eventually becomes agitated by the air flow.

Although various methods have been proposed as described above, all of them have advantages and disadvantages and are not the fundamental solution to the problem.

[Means for solving problems]

Since all of the above-mentioned solutions are based on the premise that the load transmission mechanism connected to the weighing pan is located in the lower part of the weighing chamber, an opening for inserting the load transmission mechanism is always formed on the floor surface of the weighing mass chamber. , Air flows through this opening, and the weighing pan located above the opening is affected by this air flow, albeit to varying degrees.

The present invention is configured in view of this point, based on the recognition that the fundamental problem can not be solved as long as there is an opening for the load transmission mechanism insertion on the floor of the weighing chamber, the floor of the weighing chamber A feature of the weighing device is that the configuration of inserting the load transmitting mechanism is abolished, and the side of the weighing chamber is inserted to arrange the load transmitting mechanism.

[Action]

Since the present invention eliminates the configuration of arranging the load transmission mechanism by inserting the floor surface of the weighing chamber as described above, and the configuration of arranging the load transmission mechanism by inserting the side wall of the weighing chamber, the load transmission mechanism insertion portion is The weighing dish is not affected by the flow of the passing air, and the weighing accuracy can be greatly improved.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

Reference numeral 1 is an electronic balance main body, 2 is a weighing chamber constituting a part of the main body, and the weighing chamber 2 is usually configured as a glass case as in the conventional configuration.

Reference numeral 16 is a Roberval mechanism arranged in a mechanism chamber 17, and this Roberval mechanism 16 includes an upper sub-bar 7, a lower sub-bar 8 parallel to the upper sub-bar 7, a floating frame 9, and a leaf spring 10a connecting them. , 10b, 10c, 10d are parallelograms. The arm 4 is connected to this Roberval mechanism (directly, the floating frame 9). However, unlike the conventional configuration, the arm 4 is not located in a part of the mechanism chamber below the weighing chamber 2, but is located above the floor 5 of the weighing chamber 2 and protrudes into the chamber 2. .

That is, specifically, one end of the arm 4 is connected to the floating frame 9 of the Roberval mechanism 16, and the other end thereof is projected into the weighing chamber 2 through the opening 18a of the partition wall 18 partitioning the weighing chamber 2 and the mechanism chamber 17. are doing. That is, the arm 4 is arranged so as to be positioned substantially parallel to the floor 5 of the weighing chamber 2, and the floor 5 itself does not form any opening. The weighing dish 3 is arranged on the arm 4 in this state.

In the above configuration, the load of the weighing object placed on the weighing dish 3 reaches the arm 4, the Roberval mechanism 16, and the beam 12,
This beam displacement sensor (not shown) as in the prior art
Detected by, the displacement signal is amplified by a servo mechanism (not shown), and an output current is supplied to the electromagnetic section 14 to balance the beam 12. As described above, since the force generated in the electromagnetic section is proportional to the electric power supplied to the electromagnetic section, this electric power is output as a voltage and displayed on the display unit 15 as the load of the weighing object.

In the above operation, the air in the mechanism chamber 17 tries to flow into the cooler weighing chamber 2, and the flow of the air passes through the opening 18a which is the only part connecting the weighing chamber 2 and the mechanism chamber 17 with each other. It will be. This will be described by taking the flow of air flowing into the weighing chamber 2 as an example.
It goes up so as not to affect the weighing pan 3. Therefore, the weight can be measured with extremely high accuracy. Further, when an opening for venting air is formed on the side of the mechanism chamber 17, air flows from the weighing chamber 2 to the mechanism chamber 17 through the opening 18a.
However, in this case as well, the air flows along the partition wall 18, so that the influence on the weighing pan 3 can be ignored.

〔effect〕

As described above, the present invention eliminates the configuration in which the load transfer mechanism is arranged by inserting it through the floor of the weighing chamber, and the load transmission mechanism is arranged through the side wall (partition wall) of the weighing chamber. Therefore, the weighing pan is not affected by the flow of air passing through the load transmission mechanism insertion portion, and the weighing accuracy can be greatly improved.

Further, since the floor surface of the weighing chamber is formed airtight and has no opening, the weighing object does not enter the mechanism chamber even if the weighing object is accidentally dropped.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an electromagnetic balance type weighing device showing an embodiment of the present invention, and FIG. 2 is a vertical sectional view of a conventional electromagnetic balance type weighing device. 1 ... Weighing device main body, 2 ... Weighing chamber 3 ... Saucepan, 4 ... Arm 5 ... Weighing chamber floor, 16 ... Roberval mechanism 17 ... Mechanism room, 18 ... Partition wall

Claims (1)

(57) [Claims] 1. A load of a weighing object placed on a pan located in the weighing chamber, where the weighing chamber and the mechanism chamber are adjacent to each other via a partition wall formed in a substantially vertical direction, and a mechanism connected via an arm connected to the tray. In the apparatus configured to be transmitted to the weighing mechanism in the room, the floor of the weighing chamber is formed airtight, the arm is arranged substantially parallel to the floor above the airtight floor, and the saucer is provided at one end. It is provided, and the other end is inserted through the partition wall and connected to the weighing mechanism in the mechanism chamber, and the flowing air due to the temperature difference between the weighing chamber and the mechanism chamber moves along the partition wall through the insertion portion of the arm. The weighing device prevents the influence of the air flow, which is characterized in that the flowing air is prevented from hitting the pan.