JPH0814995A - Electronic balance - Google Patents

Abstract

PURPOSE:To provide an electronic balance which can be controlled more stably than the conventional example even in a bad environment or even if the sample to be measured is a dynamic sample without deteriorating the responsiveness and stability during the ordinary use of the balance in a good environment. CONSTITUTION:A mechanical electromagnetic damper which can be changed in braking force is constituted by fixing a conductive member 20 to the movable section of an electronic balance and positioning the member 20 in a magnetic field formed perpendicularly to the moving direction of the member 20 when the member is moved by the displacement of the movable section of the balance, and then, providing a circuit means which can change the magnitude of an oscillating current resulting from the movement of the member 20 in the magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic force balance type electronic balance.

[0002]

2. Description of the Related Art Generally, in an electromagnetic force balance type electronic balance, a coil (force coil) is fixed to a movable part such as a lever which is displaced by the load of a load to be measured, and the coil is arranged in a static magnetic field. The electromagnetic force generated by passing a current therethrough is opposed to the load to be measured, the current flowing through the coil is controlled so that the two are balanced, and the magnitude of the load to be measured is obtained from the coil current in the balanced state.

The current flowing through the coil is feedback-controlled so that the displacement of the movable part is detected by a displacement sensor and a current according to the detection result flows through the coil. That is, the coil current is controlled by the servo mechanism that maintains the displacement of the movable portion at zero.

In an electronic balance having such a servo mechanism, normally, the output of the displacement sensor is PID (proportional, integral, and derivative) calculated by a PID control circuit, and then fed back to a coil as a current signal, so that each calculation is performed. It is considered that the response and stability of the system can be obtained by appropriately setting the constants and the like.

[0005]

By the way, in the control using the PID control circuit, as described above, by optimally setting the respective arithmetic constants and the like, it is possible to operate as designed in a normal environment under a good environment. Although the desired responsiveness and stability can be obtained, the responsiveness and stability of the system are inherently contradictory performances, and PI is assumed assuming normal use.
Due to the fact that each constant of the D control circuit is set, it is apparently stable when conventionally used in an environment with large vibration or when measuring the weight of a dynamic sample such as an animal. Is missing, and the weighing display value fluctuates drastically.

The present invention has been made in view of the above circumstances, and can be used in a vibrating adverse environment or in animals without damaging the responsiveness and stability under normal use conditions in a favorable environment. An object of the present invention is to provide an electronic balance that can perform more stable control than a conventional electronic balance even when performing measurement, and can suppress fluctuations in the measured display value even in such a case. .

[0007]

A structure for achieving the above object will be described with reference to FIG. 1 which is an embodiment drawing, and an electronic balance of the present invention is displaced by a load W to be measured. By fixing the coil 5 to the movable part (lever 2, etc.),
The electromagnetic force generated by arranging the coil 5 in a static magnetic field and passing an electric current through it is opposed to the load W to be measured, and the magnitude of the load W to be measured is calculated from the current flowing through the coil 5 in a state where these two are balanced. In a balance for determining the height, a conductive member 20 fixed to a movable portion, magnetic field generation means (for example, a magnetic circuit 6) that generates a magnetic field in a direction orthogonal to the moving direction of the conductive member 20 due to displacement of the movable portion, Circuit means (for example, variable resistor 22) that can change the magnitude of the induced current generated by the movement of the conductive member 20 in the magnetic field.
It is characterized by having.

Here, the magnetic field generating means can be provided separately from the case where it is also used as the magnetic circuit 6 of the electromagnetic force generating device originally possessed by the electronic balance as shown in FIG.

Further, as illustrated in FIG. 3, a bobbinless coil 200 can be used as the conductive member 20, and in this case, the bobbinless coil 200 has the same static magnetic field as the electromagnetic force generating coil 5 ( It is desirable to wind coaxially in the magnetic field space M).

[0010]

According to the present invention, in addition to the electrical response and stability of the system being electrically obtained by the PID control circuit, a mechanical electromagnetic damper is provided and the braking force of the damper is made variable. It is intended to obtain more stable control.

That is, when the conductive member 20 moves in a magnetic field, an induced current flows through the conductive member 20, but the direction of the current is such that an electromagnetic force is generated to prevent the movement. Becomes That is, the conductive member 20 constitutes an electromagnetic damper in cooperation with the magnetic field generated by the magnetic field generating means 6 and has a function of reinforcing the electrical differential operation of the PID control circuit.

When the magnitude of the induced current generated in the conductive member 20 is changed, the effect of the electromagnetic damper is changed, and the conductive member 20, the magnetic field generating means 6,
The circuit means 22 as a whole constitutes an electromagnetic damper having a variable braking force.

During normal use in a favorable environment, the circuit means 22 cuts off or reduces the induced current flowing through the conductive member 20 to obtain the same responsiveness and stability as a conventional electronic balance. At the same time, when used in an environment where there is a large amount of vibration, if the braking force by the electromagnetic damper is increased by increasing the induced current flowing through the conductive member 20 by the circuit means 22, the system can be used even in such use. Stability is obtained.

The bobbinless coil 2 is used as the conductive member 20.
00, and if the bobbinless coil 200 is coaxially wound and arranged in a static magnetic field (magnetic field space M) in which the coil 5 for electromagnetic force generation is placed, the bobbinless coil is mechanically substantially Only 200 need be added, which is most advantageous in terms of cost.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural view (A) and an AA cross-sectional view (B) showing a mechanical view and a block diagram of an electric circuit structure of an embodiment of the present invention.

A plate 3 for applying a load W to be measured is provided at one end of a lever 2 rotatable about a fulcrum 1. Further, on the opposite side of the lever 2 with the fulcrum 1 in between, a coil 5 wound in a cylindrical shape around the vertical axis is fixed via a support member 4. The coil 5 is placed in the static magnetic field formed by the magnetic circuit 6.

The magnetic circuit 6 includes a south pole and a north pole as shown.
A permanent magnet 61 arranged so that the poles are located above and below,
An inner peripheral surface of the yoke 62 is configured by a yoke 62 having a bottomed cylindrical shape and a lower end surface of the permanent magnet 61 fixed to the bottom surface thereof, and a columnar or disk-shaped pole piece 63 fixed to the upper end surface of the permanent magnet 61. A static magnetic field is formed in the cylindrical space between the pole piece 63 and the outer peripheral surface of the pole piece 63. The coil 5 is arranged in the cylindrical magnetic field space M in a state of being wound so as to be orthogonal to the direction of the magnetic field, and these constitute a balanced electromagnetic force generator as described below. .

A displacement sensor 7 is arranged at the tip of the lever 2 and the displacement sensor 7 detects the displacement of the lever 2. The output of the displacement sensor 7 is introduced into the PID control circuit 9 via the amplifier 8. After the displacement detection result of the lever 2 is PID-calculated by the PID control circuit 9,
It is converted into an electric current and passed through the coil 5. An electromagnetic force is generated by the current flowing through the coil 5 in the magnetic field, and the electromagnetic force is transmitted to the lever 2 via the coil 5. With this configuration, a current flows through the coil 5 such that the measured load W and the electromagnetic force are balanced and the displacement of the lever 2 becomes zero, and the current has a magnitude proportional to the measured load W. .

The current flowing through the coil 5 is converted into a voltage signal by the measuring resistor 10 and then digitized by the A / D converter 11 to be loaded into the microcomputer 12 as load data. Microcomputer 12
Then, the magnitude of the load to be measured W is calculated from this load data and the device constants such as the strength of the magnetic field by the magnetic circuit 6, the number of turns and the length of the coil 5, the lever ratio of the lever 2, and the like. The value is displayed on the display 13 as a value.

A cylindrical conductive member 20 is fixed to the support member 4 provided on the lever 2 coaxially with the coil 5, and the conductive member 20 is placed in the magnetic field space M together with the coil 5. Has been inserted. The conductive member 20 is formed with slits 21 extending from the upper end to the lower end along the cylindrical generatrix, and the slits 21 cut the cylindrical loop of the conductive member 20. Both ends of the loop of the conductive member 20 cut by the slit 21 are connected to each other by a variable resistor 22. The variable resistor 22 can change its resistance value from substantially 0 (a conductive state of the loop) to ∞ (an insulated state of the loop).

In the above-described embodiment of the present invention, when the movable part including the lever 2 is displaced, the conductive member 20 moves to the magnetic field space M.
Inside it moves in a direction perpendicular to the direction of the magnetic field. By this movement, if the loop of the conductive member 20 is connected, an induced current flows in the loop. The direction of this induced current is a direction in which an electromagnetic force that prevents the movement of the conductive member 20 is generated, and a mechanical electromagnetic damper is configured to apply a braking force to the movable portion.

When the resistance value of the variable resistor 22 is set to ∞, no induction current flows through the conductive member 20, so that the braking force by the mechanical electromagnetic damper does not act on the movable portion.
On the other hand, when the resistance value of the variable resistor 22 is set to 0, a large induced current flows through the conductive member 20, and a large braking force is exerted by the mechanical electromagnetic damper when the movable part is displaced. However, in this case, the responsiveness of the system decreases. After all, the relationship between the resistance value of the variable resistor 22 and the responsiveness and stability of the system is as shown in FIG.

Therefore, when the embodiment of the present invention is normally used in a favorable environment free from disturbance such as vibration, the variable resistor 22 is used.
By setting the resistance value of to ∞ or a considerably large value,
The electric braking force mainly by the differential element of the PID control circuit 9 acts on the system, and the system is controlled with the responsiveness and stability equivalent to those of the conventional ordinary electronic balance.

On the other hand, the resistance value of the variable resistor 22 is set to 0 or a considerably small value when used in an environment with large vibration or when measuring a dynamic sample such as weighing an animal.
As a result, in addition to the electric braking force by the PID control circuit 9, a large braking force by the mechanical electromagnetic damper acts on the system, and a large stability can be obtained although the response is reduced, The fluctuation of the displayed value is suppressed.

Here, in the above embodiment, the conductive member 2 is used.
Although 0 is provided separately from the coil 5, the conductive member 20 may be shared with the winding frame of the coil 5. That is, while forming the winding frame of the coil 5 with a conductive material,
A slit 21 similar to the above may be formed on the winding frame, and a variable resistor 22 may be interposed. In this case, there is an advantage in that the width of the cylindrical void forming the magnetic field space M can be made equal to that of a conventional ordinary electronic balance without particularly widening it.

Next, another embodiment of the present invention will be described. FIG. 3 is a configuration diagram showing the mechanism diagram and a block diagram of the electrical circuit configuration of the main part together. It should be noted that, in FIG. 3, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description of these members will be omitted in the following description.

The feature of this example is that instead of the cylindrical conductive member 20 having the slit 21 shown in the previous example,
The point is that the bobbinless coil 200 is used. Then, the bobbinless coil 200 for the electromagnetic damper is wound coaxially with the coil 5 for generating the electromagnetic force, that is, the force coil 5, and these are wound in the magnetic field space M created by the magnetic circuit 6 similar to the previous example. It is located in. Further, both ends of the bobbinless coil 200 for the electromagnetic damper are connected to the variable resistor 2 as in the previous example.
2 are connected to each other.

In this example, the force coil 5 is also a bobbinless coil, and two bobbinless coils are double-wound and fixed to the lever 2 via the support member 4 and arranged in the cylindrical magnetic field space M. are doing.

Also in the embodiment of FIG. 3, the bobbinless coil 200 moves in the magnetic field space M in the direction orthogonal to the direction of the magnetic field when the movable part including the lever 2 is displaced, and both ends of the bobbinless coil 200 are moved. If they are connected to each other, an induced current flows in a direction in which an electromagnetic force that blocks the movement of the bobbinless coil 200 is generated, and a braking force can be applied to the movable portion. This braking force becomes maximum when the resistance value of the variable resistor 22 is set to 0, and
In the state where the resistance value of the variable resistor 22 is ∞, the induction current does not flow in the bobbinless coil 200 and the braking force does not work,
The relationship between the resistance value of the variable resistor 22 and the responsiveness and stability of the system is as shown in FIG. 2 as in the previous example.

In this embodiment, the points to be particularly noted are the coils 5 for generating the balanced electromagnetic force and the electromagnetic damper.
And 200 are respectively arranged as double bobbin-less windings and arranged in the magnetic field space M. Therefore, mechanically, a coil is simply added to an ordinary electronic balance without manufacturing special parts. It is only necessary to additionally wind, and it is possible to obtain an electronic balance that can perform stable measurement at extremely low cost even in an environment with vibration.

In each of the above embodiments, the slit 21
Both ends of the conductive member 20 are connected via the variable resistance 22 via, or both ends of the bobbinless coil 200 are connected via the variable resistance 22, and the resistance value is continuously changed from 0 to ∞. However, instead of the variable resistor 22, a switch for switching the conductive member 20 or the loop of the bobbinless coil 200 to conductive / non-conductive may be provided.

Further, in each of the above-mentioned embodiments, the magnetic circuit 6 of the balanced electromagnetic force generator originally possessed by the electronic balance is provided.
An example is shown in which the conductive member 20 or the bobbinless coil 200 is arranged in the magnetic field created by the device, and the magnetic field for the mechanical electromagnetic damper and the magnetic field for generating the balanced electromagnetic force are combined.
The present invention is not limited to this, and in addition to the magnetic circuit 6 for generating the balanced electromagnetic force, a magnetic circuit dedicated to the mechanical electromagnetic damper is provided at an arbitrary position, and the lever 2 is provided in the magnetic circuit. A dedicated support member may be mounted so that a conductive member or coil similar to the example of FIG.

As an embodiment of the present invention, the slit 21 of the conductive member 20 or the variable resistor 22 or switch for short-circuiting both ends of the bobbinless coil 200 as described above is automatically operated to make the system It is possible to employ a configuration in which the mechanical electromagnetic damper does not work when the response is in a transient state, and the electromagnetic damper works when the steady state is reached. In this case, as shown in the block diagram of the main circuit configuration in FIG. 4, the output of the displacement sensor 7 is introduced into the comparator 23, and the displacement detection output exceeds a preset range around 0, That is, the switching element 24 is opened in the transient state (or the resistance value of the variable resistor is set to near ∞), the electromagnetic damper is not effective, and the switching element 24 is closed when the displacement detection output is within the above range. (Or set the resistance value of the variable resistor to near 0) to make the electromagnetic damper effective. According to this configuration, the response of the measured display value when the load W to be measured is placed on the pan 3 becomes quick, and it becomes possible to perform extremely stable display after the variation of the measured display value has subsided.

[0034]

As described above, according to the present invention,
Attach a conductive member to the moving part of the balance of electromagnetic force balance,
The conductive member is arranged in a magnetic field in a direction orthogonal to the moving direction of the conductive member due to the displacement of the movable part to form a mechanical electromagnetic damper, and the conductive member moves in this magnetic field. By providing a circuit means for controlling the induced current generated by, it is possible to change the braking force of the electromagnetic damper, by increasing the braking force of the electromagnetic damper as needed, by using, It is possible to perform stable control even when used in environments with large vibrations or when measuring dynamic samples.
Compared with the conventional electronic balance that relies only on the electrical control of the system by the D control circuit, it can be used more flexibly and widely.

If a bobbinless coil is adopted as the conductive member and it is coaxially wound with a coil for generating an electromagnetic force and placed in a static magnetic field for generating an electromagnetic force, the above-mentioned effects are obtained. Can be achieved at a very low cost.

[Brief description of drawings]

FIG. 1 is a configuration diagram (A) showing a mechanism diagram of an embodiment of the present invention and a block diagram of an electric circuit configuration together, and a sectional view (A) taken along the line AA.

FIG. 2 is a graph showing the relationship between the resistance value of the variable resistor 22 according to the embodiment of the present invention and the responsiveness and stability of the system.

3A and 3B are a structural view (A) and a cross-sectional view taken along line BB of FIG. 3B, which shows a mechanical view of another embodiment of the present invention and a block diagram of an electric circuit structure of a main portion.

FIG. 4 is a block diagram of a circuit configuration of a main part of still another embodiment of the present invention.

[Explanation of symbols]

 1 fulcrum 2 lever 3 dish 4 support member 5 coil 6 magnetic circuit 61 permanent magnet 62 yoke 63 pole piece 7 displacement sensor 9 PID control circuit 12 microcomputer 20 conductive member 21 slit 22 variable resistance M magnetic field space 200 bobbinless coil

Claims (2)

[Claims] 1. A coil is fixed to a movable part which is displaced by the load of the load to be measured, and the coil is placed in a static magnetic field so that an electromagnetic force generated by passing a current through the coil opposes the load to be measured. Then, in the balance in which the magnitude of the load to be measured is obtained from the current flowing through the coil in these balanced states, the conductive member fixed to the movable part and the moving direction of the conductive member due to the displacement of the movable part An electronic balance comprising magnetic field generating means for generating magnetic fields in orthogonal directions and circuit means for controlling an induced current generated by the movement of the conductive member in the magnetic field. 2. The electrically conductive member is a bobbinless coil, and the bobbinless coil is wound in the static magnetic field coaxially with a coil for generating an electromagnetic force that should oppose the load to be measured. The electronic balance according to claim 1, wherein: