JPH026335Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to electronic scales.

[Conventional technology and problems]

Conventionally, this type of scale uses a permanent magnet that is connected to a ram that is rotatably supported on a fulcrum, in order to apply a load to be measured on one end of the ram and a load for balancing the ram on the other end. , an actuator is known which is equipped with a load measuring actuator consisting of a moving coil, generates a force in the vertical direction by the interaction between the current flowing through the moving coil and the magnetic flux from the permanent magnet, and balances the ramrod by the magnetic force. It is being

However, if the ambient temperature is always constant, there is no problem, but if it fluctuates, the magnitude of the force generated will also change even if the current flowing through the coil is constant. In other words, even if the load to be measured is the same, the measured value will change if the ambient temperature changes.

[Problem that the invention attempts to solve]

The present invention was developed based on the fact that the temperature characteristics of permanent magnets are greatly involved in the fluctuations in the above-mentioned measured values, and the present invention aims to provide an electronic scale that can obtain accurate measured values even when the ambient temperature fluctuates greatly. That is.

[Means for solving problems]

The above problem is solved by applying a load to be measured to one end of the ram which is rotatably supported on a fulcrum, and applying a load to balance the ram to the other end, and using a permanent magnet, a moving coil, etc. In an electronic scale, the electronic scale is equipped with a load measuring actuator consisting of a load measuring actuator, which generates a force in the vertical direction through the interaction between the current flowing through the movable coil and the magnetic flux from the permanent magnet, and balances the hammer rod by the force,
The problem is solved by an electronic scale characterized in that a constant temperature generating means is disposed close to the permanent magnet and is surrounded by a heat insulating material.

[Effect]

Even if the ambient temperature fluctuates, the permanent magnet is kept at a constant temperature, so its magnetic flux density is constant, and the load can be accurately measured by the current flowing through the moving coil.

〔Example〕

Hereinafter, an electronic scale according to an embodiment of the present invention will be described with reference to the drawings.

In the figure, the electronic scale is indicated as 1 as a whole, and a rod, so-called a rod 2, is supported at a fulcrum 4 on one support 3a of a frame 3, and a mounting plate 6 is suspended from one end thereof via a fulcrum 5. ing. Also,
At the other end, the actuating rod 8 of the load-measuring actuator 7 is pivotally mounted.

In addition to the above-mentioned actuating rod 8, the load measuring actuator 7 includes a bobbin 9 and a coil 1 wound around the bobbin 9.
0, permanent magnet 11, magnetic pole member 11 fixed to it
a, consists of yokes 12a, 12b, and 12c, and the magnetic flux from the permanent magnet 11 crosses the coil 10 as shown by the arrow, and flows through the yokes 12a, 12c, and 12c.
flows. When the coil 10 is energized with a direct current in a predetermined direction, the interaction between this current and the magnetic flux generates a downward force F, which pulls the actuating rod 8 downward as shown by the arrow. By controlling the magnitude of the current applied to the coil 10, this force F is adjusted and balanced with the weight of the object to be measured placed on the placing plate 6.

According to the present invention, an electric heating coil 20 is disposed close to the permanent magnet 11, and a heat retaining cylinder 30 made of a heat insulating material, for example, ceramic, is disposed around this coil. The heat generation temperature of the electric heating coil 20 is measured by, for example, a thermocouple (not shown), and the current flowing through the coil 20 is adjusted so as to reach a predetermined temperature. Therefore, the permanent magnet 11 is heated to this predetermined temperature, and is stably maintained at the predetermined temperature by the heat insulating tube 30 without being affected by the ambient temperature. A thermostat may be used instead of a thermocouple.

A stopper mounting block 13 is fixed on the other support column 3b of the frame 3, and the tip of the rod 2 is inserted through a through hole 13a formed in the stopper mounting block 13.
The detected portion (metal) 14 formed at the tip faces the proximity switch 15 at a predetermined distance when the rod 2 is in a balanced state as shown.

Screw holes 13b and 13c are formed above and below the through hole 13a of the stopper mounting block 13, and these are provided with stopper screws 16 and 17, respectively.
is screwed on. The displacement width A of the rod 2 is determined by adjusting the screws 16 and 17. That is, the upper screw 16 determines the upper limit of rotation of the rod 2,
The lower limit of rotation of the rod 2 is determined by the screw 17 on the lower side. The displacement width A, or the upper and lower limits of rotation, are the characteristics of the proximity switch 15, and this switch 15 and rod 2.
It is determined by taking into account the distance between the fulcrums 4 and 5, the distance between the fulcrums 4 and 5, the distance between the fulcrums 4 and the actuating rod 8, and the like.

The embodiment of the present invention is configured as described above,
Next, this action, effect, etc. will be explained.

The figure shows the balanced state of the rod 2, but normally it rotates clockwise or counterclockwise around the fulcrum 4, and the tip of the rod 2 lightly touches either screw 16 or 17. It is in a stable condition. Now, suppose that the object to be measured is placed on the mounting plate 6.
The rod 2 rotates clockwise in the figure around the fulcrum 4. Proximity switch 15 detects this, current flows through coil 10 of actuator 7, and downward force F acts on actuating rod 8. That is, the rod 2 is rotated counterclockwise around the fulcrum 4.

When the object to be measured is placed on the mounting plate 6, the rod 2 attempts to rotate significantly clockwise, but the tip of the rod 2 collides with the lower end of the stopper screw 16, preventing further upward rotation. movement is suppressed. Proximity switch 1
5 detects that the rod 2 is above the balance position, and as a result, the coil 1 of the actuator 7
0 current is increased. The force F acting on the actuating rod 8 increases, and the rotational force of the rod 2 in the counterclockwise direction increases. That is, the rod 2 increases the rotational force toward the balance position.

When the rod 2 rotates downward beyond the balance position, the proximity switch 15 detects this,
The current flowing through the coil 10 of the actuator 7 is reduced. In this way, when the rod 2 assumes a balanced state as shown in the figure, the current flowing through the coil 10 is kept at a constant value. From this value, the weight of the object placed on the placing plate 6 is measured.

The present embodiment operates as described above, and has the following effects.

That is, according to this embodiment, the permanent magnet 11 is heated to a predetermined temperature by the electric heating coil 20, and is stably maintained at the predetermined temperature by the heat retaining cylinder 30 even if the ambient temperature fluctuates. Therefore, the current value-load of the coil 10 can be accurately calibrated in consideration of the characteristics of the permanent magnet 11 at a predetermined temperature.

Although the embodiments of the present invention have been described above, the present invention is of course not limited thereto, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, the mounting plate 6 suspended from the fulcrum 5 was used to load the weight of the object to be measured on the rod 2, but the load may be applied via another mechanism. .

Further, in the above embodiments, the permanent magnet 11 is rod-shaped, but the shape is not limited to this, and the present invention is also applicable to a horseshoe shape, for example.

Further, in the above embodiments, a thermocouple was used as the heat measuring means, but a thermistor may be used instead, or a cooling means may be used instead of the heating means.

[Effect of idea]

As described above, according to the electronic scale of the present invention, the accuracy of weighing can be improved almost without being affected by the ambient temperature.

[Brief explanation of drawings]

FIG. 1 is a side view of an electronic scale according to an embodiment of the present invention, and FIG. 2 is a front view in the - line direction in FIG. In the figure, 7... Load measuring actuator, 11... Permanent magnet, 20... Electric heating coil, 3
0...Thermos cylinder.

Claims (1)

[Scope of utility model registration request] A load measuring actuator consisting of a permanent magnet and a moving coil is coupled to apply a load to be measured to one end of a ram which is rotatably supported on a fulcrum and to apply a load for balancing the ram to the other end. In the electronic scale, the electric scale generates a force in the vertical direction through the interaction of the current flowing through the moving coil and the magnetic flux from the permanent magnet, and the force balances the hammer rod, wherein a constant temperature is generated in the permanent magnet. An electronic scale characterized by having means arranged close to each other and surrounded by a heat insulating material.