JPH069331Y2 - Electronic balance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an electromagnetic force balance type electronic balance, and more specifically, a pulsed current (pulse duty ratio) is applied to a coil in a magnetic circuit by applying a pulsed current. (Including also) to control the electromagnetic force generated by changing, to an electronic balance of the system to balance with the load to be measured.

<Prior art> An electromagnetic force balance type electronic balance generally has a coil placed in a static magnetic field created by an electromagnetic circuit and an electric current is generated in the coil to generate the electromagnetic force, which is balanced with the load. The current flowing is controlled so that the magnitude of the load is detected from the magnitude of the current.

In such an electronic balance, the magnitude of the current flowing through the coil changes depending on the magnitude of the load, so the amount of heat generated by the coil changes depending on the magnitude of the load, and the temperature change based on this changes the strength of the static magnetic field. There is a problem that the balance sensitivity changes due to changes.

In order to solve this problem, the current flowing in the coil is pulsed in alternating positive and negative pulses, and the pulse width is changed to control the generated electromagnetic force while keeping the absolute value of the current flowing in the coil constant. A method has been proposed (Japanese Patent Laid-Open No. 56-157).
No. 821) has been put to practical use.

By the way, in an electronic balance that generates a balanced electromagnetic force by applying a pulsed current to a coil, a sound with a pulse current frequency as a fundamental frequency is generated from the electromagnetic force generator, and When the balance mechanism is supported on a balance base such as a balance base or a housing via a rigid support such as a metal strut, the balance base may resonate and reach a considerably large sound pressure.

Therefore, as shown in FIG. 3, the balance mechanism A is conventionally used.
Is supported on the balance base D via a plurality of elastic bodies C, C ... Of rubber or the like.

<Problems to be Solved by the Invention> In the conventional supporting method shown in FIG.
The generation of sound cannot be suppressed unless the elastic coefficient of ... Is considerably reduced, and therefore, when the load to be measured acts on the balance mechanism A, the elastic bodies C, C .. If the balance mechanism A tilts due to this deformation, the measured value becomes inaccurate, and therefore, in order to suppress the tilt due to this deformation, the span L between the elastic bodies C and C is reduced.
Is required to be considerably long. If the span L is lengthened, the balance mechanism A will be easily bent when the balance base D is elastically deformed by an external force. The deflection of the balance mechanism A not only makes the rest point of the balance unstable, but also causes the sensitivity to be disturbed. The conventional supporting method shown in FIG. 3 can only take measures to increase the overall rigidity of the balance base D to reduce its deformation, which causes a cost increase.

An object of the present invention is to provide an electronic balance that does not generate noise even when a pulse current is passed through a coil of an electromagnetic force generator, and that does not cause flexure in the balance mechanism due to external force without increasing the rigidity of the base body of the balance. Especially.

<Means for Solving Problems> A structure for achieving the above object will be described with reference to a basic conceptual diagram shown in FIG. 1. The present invention provides an electromagnetic force generating device, a load receiving portion, and these. The most rigid part of the balance mechanism a including a mechanism for connecting the above is connected to a high-rigidity member b disposed below the balance mechanism a, and the high-rigidity member b is respectively set to have a low elastic modulus and a high elasticity. It is characterized by being supported on the balance base body d via a plurality of supports c, c ... Having a damping coefficient and distributed in a predetermined positional relationship.

<Operation> The sound generated from the electromagnetic force generator of the balance mechanism a is
As in the conventional case, the support c having a low elastic modulus and a high damping coefficient
c ... is not transmitted to the balance base d, etc., and does not resonate. Even if the span between the supports c and c is increased to suppress the inclination of the balance mechanism a due to the measurement load, the balance mechanism a is not directly supported by the supports c and c, and therefore the balance base body d is elastically deformed by an external force. However, the balance mechanism a does not bend.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a view showing the internal structure of the embodiment of the present invention.

The electromagnetic force generator 1 includes a permanent magnet 11 and a pole piece 12.
The movable coil 14 is arranged in the magnetic field formed by the magnetic circuit constituted by the yoke 13 and the pulse current is passed through the movable coil 14.

A fixed column 3 is fixed to the electromagnetic force generator 1 via a spacer 2, and one end of parallel elastic beams 4a and 4b is attached to both upper and lower ends of the fixed column 3. The other ends of the elastic beams 4a and 4b are attached to the upper and lower ends of a movable column 5 having a load receiving portion 51 that is engaged with a lightweight dish (not shown). The fixed column 3, the elastic beams 4a and 4b, and the movable column 5 constitute a Roberval mechanism, and the load receiving portion 5
The displacement of the movable column 3 due to the measured load acting on 1 is restricted only in the vertical direction.

One end of a lever 6 supported by an elastic fulcrum 61 is fixed to the movable column 5 via a flexible body 62, and the other end of the lever 6 is fixed to the movable coil 14 of the electromagnetic force generator 1. There is. As a result, the load to be measured applied to the load receiving portion 51 acts to displace the movable coil 14. Then, the pulse width of the pulse current flowing through the movable coil 14 is controlled so that this displacement becomes zero, and the measured load is obtained from the pulse width in the equilibrium state.

By the way, in the balance mechanism as described above, on the lower surface of the yoke 13 of the electromagnetic force generator 1, which is the most rigid part, a highly rigid flat plate-shaped intermediate member 7 is provided through the metal columns 71, 71. Fixed to the upper surface of. As the material of the high-rigidity intermediate member 7, in addition to metals, materials having high rigidity and excellent damping characteristics such as non-metal porous materials and wood can be used. A composite material in which metal materials are stacked can be used.

The intermediate member 7 has a plurality of elastic supports 8, 8 ... Distributed at a sufficient distance from each other on its lower surface so that the balance mechanism is not tilted by the load to be measured acting on the load receiving portion 51. And is supported by a base body 9 such as a base or a housing. This elastic support 8,8
A rubber or the like having a low elastic coefficient and a high damping coefficient is suitable for.

In the above embodiment, the sound from the electromagnetic force generator 1 generated by passing the pulsed current is the elastic supports 8, 8 ...
Is attenuated by ... and the base body 9 and the like do not resonate.
Here, if a material having excellent damping characteristics such as the above-mentioned non-metallic porous material or composite material is used for the intermediate member 7, the damping effect is further enhanced.

When the base body 9 is elastically deformed, the force due to the deformation acts on the intermediate member 7 via the elastic supports 8, 8 ..., However, since the intermediate member 7 is made of a highly rigid material, it is difficult to deform, and Even if this intermediate member 7 is deformed, the balance mechanism has a relatively short span at its most rigid portion by the metal columns 71, 71.
Since it is connected to the balance, the balance mechanism is less likely to bend.

<Effects of the Invention> As described above, according to the present invention, the balance mechanism is temporarily connected to the high-rigidity member at its most rigid part, and the high-rigidity member has a low elastic coefficient and a high damping coefficient. In addition, since it is supported on the balance base through a plurality of supports that are distributed appropriately, the high-frequency sound caused by the pulse current is not attenuated and resonated as in the conventional case, and the measured object is not measured. Even if the support body is arranged in a wide span so that the support mechanism does not tilt due to the deformation of the support body due to the load, the balance mechanism does not bend due to the elastic deformation of the balance base body due to an external force.

As a result, it is possible to obtain an electronic balance in which the generation of sound is extremely small, the inclination of the balance mechanism due to the load to be measured is small, and the balance mechanism is not always deflected by an external force and the rest point is always stable and the sensitivity is not easily changed.

Further, according to the structure of the present invention, external vibrations are hard to be transmitted to the balance mechanism, and in combination with the above-mentioned quiescent point and stability of sensitivity, especially for a high-sensitivity electronic balance with a minimum reading limit. It is valid.

[Brief description of drawings]

 FIG. 1 is a basic conceptual diagram showing the configuration of the present invention, FIG. 2 is a diagram showing an internal structure of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional method of supporting an electronic balance. 1 ... Electromagnetic force generator 11 ... Permanent magnet 12 ... Pole piece 13 ... Yoke 14 ... Movable coil 3 ... Fixed column 4a, 4b ... Elastic beam 5 ... Movable column 51 ... Load receiving part 6 …… Lever 61 …… Elastic fulcrum 7 …… High rigidity intermediate member 71 …… Metal column 8 …… Elastic support 9 …… Base body

Claims (3)

[Scope of utility model registration request] Claim: What is claimed is: 1. A pulsed current is applied to a coil in a magnetic circuit, the pulse width is changed to control the generated electromagnetic force, and the electromagnetic force is balanced with the load acting on the load receiving portion. In the balance that measures the load, the most rigid part of the balance mechanism including the electromagnetic force generating device consisting of the magnetic circuit and the coil, the load receiving part, and the mechanism connecting them is located below the balance mechanism. The high-rigidity member is coupled to the arranged high-rigidity member, and each of the high-rigidity members has a low elastic coefficient and a high damping coefficient, and through a plurality of supports distributed in a predetermined positional relationship. An electronic balance, which is supported by a base of the balance. 2. An electronic balance according to claim 1, wherein the high-rigidity member is made of a material having a high damping coefficient. 3. The electronic balance according to claim 1, wherein a yoke forming the magnetic circuit is connected to the high-rigidity member.