JPH027004B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a force generation mechanism used, for example, in a weighing machine, and particularly to a force generation mechanism that applies a force to a coil placed in a constant magnetic field by passing a current through the coil. This invention relates to a force generation mechanism that generates force.

[Conventional technology and problems]

FIG. 4 schematically shows a conventional force generation mechanism, which includes a main yoke 41, a center yoke 42,
It consists of a permanent magnet 43 and a coil 45 disposed in an air gap 44. It is assumed that the coil 45 is supported movably in the direction of arrow F. Permanent magnet 43
A constant magnetic flux flows into the center yoke 42, the air gap 44, and the main yoke 41 as shown by the solid arrow _B0 .

When a current I is passed through the coil 45, a force F=B ₀ I is generated in the direction of the arrow F along the length of the conductor (however, B ₀
is the magnetic flux density), and since the force F and the current I are proportional, the force F is measured from the value of the current I using this proportional relationship.

However, strictly speaking, force F and current I are not proportional. That is, when a current I is passed through the coil 45,
This itself generates a magnetic flux ΔB as shown by the dotted line. This magnetic flux △B is proportional to the current I, so △
If B=kI (k is a proportionality constant), then the magnetic flux density in the air gap 44 when the current I flows through the coil 45 becomes B=B ₀ +kI or B ₀ −kI. Therefore, strictly speaking, the force acting on the coil 45 is F=(B ₀ ±kI)Il.

In other words, F=B ₀ lI±klI ² , and 2 of the current I
A term proportional to the power appears, so it cannot be said that the force F is linearly proportional to the current I.

Therefore, a problem arises in that, for example, in a weighing machine, accurate weighing cannot be performed using the measuring method using this force generating mechanism.

[Object and structure of the invention]

The present invention was made in view of the above problems, and an object of the present invention is to provide a force generation mechanism that can measure force more precisely than before. According to the present invention, in the above configuration, a Hall element is connected in series to the coil, and the Hall element is disposed close to the coil in the magnetic field, and the voltage generated in the Hall element is This is achieved by a force generating mechanism characterized in that it measures the force generated in the coil.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A ram type weighing machine according to an embodiment of the present invention will be described below with reference to the drawings.

In the figure, the ramrod type weighing machine is indicated as 1 as a whole, and the ramrod, so-called pole 2, is supported at a fulcrum 4 on one support 3a of a frame 3, and a loading plate 6 is suspended via a fulcrum 5 at one end thereof. It's hanging. 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, yoke 12a, 12b, 12
c and the yoke 1 close to the coil 10 in the gap g.
The magnetic flux B ₀ from the permanent magnet 11 crosses the coil 10 as shown by the solid arrow, and flows through the yokes 12a, 12b,
It flows through 12c. When a direct current is applied to the coil 10 in a predetermined direction, a magnetic flux △B as shown by the dotted line flows through the coil 10, but the interaction between this current and the magnetic flux in the air gap g generates a downward force F, causing the operation. Pull the 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.

As shown in FIG. 3, the coil 10 and the Hall element 2
0 is connected in series to a variable DC power source 21, and the voltage generated in the Hall element 20 is configured to be measured by a voltage measuring device 22.

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,
Stopper screws 16 and 17 are screwed into these, respectively. 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, and the lower screw 17 determines the lower limit of rotation of the rod 2. The displacement width A, or the upper and lower limits of rotation, are the characteristics of the proximity switch 15, the distance between this switch 15 and the detected part 14 of the rod 2, the distance between the fulcrums 4 and 5, and the distance between the fulcrum 4 and the operating rod 8. It is determined by taking into account the distance between

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

Now, assuming 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. Along with this, coil 1 of actuator 7
0 from the variable DC power supply 21, and a downward force F acts on the 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 rotates clockwise, but the tip of the rod 2 collides with the lower end of the stopper screw 16, preventing further upward rotation. It will be done. Proximity switch 15 detects that rod 2 is above the balance position, which causes the current in coil 10 of actuator 7 to increase. 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. Conventionally, the weight of the object placed on the mounting plate 6 was measured from this value, but according to the present invention, the voltage V _H generated at this time in the Hall element 20 is sent to the voltage measuring device 22. By measuring this, the weight of the object to be measured can be determined.

That is, if current I is flowing through the coil 10, the magnetic flux density B in the air gap g at that time is B = B ₀ ±kI as described above (however, in this example, depending on the direction of the current, B ₀ −kI Become). Since the Hall element 20 is connected in series to the coil 10, the current value flowing through it is also I. Therefore, the voltage generated in the Hall element 20 is V _H =RI (B ₀ ±kI) (where R is a constant specific to this Hall element 20). On the other hand, the force F = (B ₀
±kI)Il (l is the total length of the coil 10), so
The relationship between F and _VH is as follows.

F=l/RV _H In other words, force F is linearly proportional to voltage V _H , so force F can be easily determined from voltage V _H. Since the Hall element 20 detects the actual magnetic flux density B in the air gap g, the force F and
In other words, the weight of the object to be measured can be determined.

The embodiments of the present invention have been described above, but of course the present invention is 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 proximity switch 15 was used to detect the position of the rod 2, but a differential transformer or a photoelectric switch may be used instead.

Further, 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 pole 2, but the load may be applied via another mechanism.

Furthermore, in the above embodiment, the shapes of the yokes 12a, 12b, and 12c in the load actuator 7 were different from those in FIG. 1 showing the conventional example, but of course,
The shape is not limited to this, and may be similar to the conventional example, for example.

Further, in the above embodiment, the permanent magnet 11 was used to provide a constant magnetic field, but a DC electromagnet may be used instead.

Further, in the above embodiment, the actuator 7 was applied to the weighing machine 1, but it can also be applied to other devices.

〔Effect of the invention〕

As described above, according to the force generation mechanism of the present invention, the magnitude of the acting force acting on the coil can be accurately detected from the voltage value generated in the Hall element.

[Brief explanation of drawings]

Fig. 1 is a side view of a ram-type weighing machine according to an embodiment of the present invention, Fig. 2 is a front view in the - line direction in Fig. 1, and Fig. 3 is a partially enlarged view showing the electrical wiring of the main part in Fig. 1. It is. FIG. 4 is a schematic diagram of a conventional force generating mechanism. In the figure, 7...load measuring actuator, 10...coil, 11...permanent magnet, 12a, 1
2b, 12c... Yoke, 20... Hall element, 22
...voltage measuring device.

Claims (1)

[Claims] 1. In a force generation mechanism that generates force by passing a current through a coil placed in a constant magnetic field, a Hall element is connected in series to the coil, and the Hall element is placed in the magnetic field. A force generating mechanism, characterized in that the force generating mechanism is arranged close to the coil and measures the force generated in the coil by the voltage generated in the Hall element.