JPS63317727A - Weight sensor apparatus - Google Patents

Abstract

PURPOSE:To measure a weight accurately and electrically, by changing the relative position relation between a coil and a core with a shaft, which receives a load and can be displaced in the direction of a thrust, and changing the oscillating frequency of an oscillating circuit including said coil. CONSTITUTION:A material 40 to be measured such as food is mounted on a turntable 8. Then the weight of the material becomes a load for a shaft 3 in the direction of thrust. The load acts on a lower spring bearing 9. Plate springs 12 and 13 make elasticity to act on the load in the opposing direction in cooperation. The shaft is displaced to a balanced position. As a result, the relative position relation between a coil 20 and a core 21 is changed in proportion to the load in the direction of the thrust, i.e., the weight of the material 40 to be measured. Therefore, the self-inductance of the coil 20 is changed. As a result, the oscillating frequency of an oscillating circuit 18 is changed in correspondence with the change in self-inductance. Therefore, when the oscillating frequency (f) is identified, the weight of the material 40 to be measured can be indirectly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a weight sensor device that extracts a load in a thrust direction as a change in electrical output.

Prior Art Weight sensors of this type are incorporated into various electronic devices. For example, in order to prevent uneven heating, microwave ovens place food on a turntable inside the cooking chamber and heat the food while rotating the turntable at a constant speed during microwave irradiation. go. Of these,
Auto-sucking microwave ovens are equipped with a weight sensor that detects the weight of food on the turntable.
Based on the weight and type of food, an appropriate cooking program is selected and automatically executed.

By the way, for example, the device disclosed in Japanese Utility Model Application No. 61-114208 converts the weight of food into a load on a turntable, and transmits this load to a piezoelectric ceramic type weight sensor element. When detecting weight, a piezoelectric ceramic weight sensor generates a small amount of electric charge in proportion to the load, and sends this to a control system such as a microcomputer.

However, with the piezoelectric ceramic type weight sensor mentioned above, the piezoelectric ceramic element is susceptible to impact and there is a risk of breakage.In addition, since the generated electric charge is small, it is susceptible to noise such as hum and vibration, making accurate measurement difficult. Have difficulty.

Another type of sensor is a capacitive type sensor. The capacitive type requires a pair of parallel plates with a large area, and its electrical characteristics change greatly depending on humidity, making accurate measurement difficult.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide a highly accurate and small sensor device for detection.

Solution to the Invention Therefore, the present invention focuses on the change in the electrical characteristics of the coil, that is, the self-inductance, due to the relative position change between the coil and the core. By changing the relative positional relationship between the coil and the core using the displaceable shaft and changing the oscillation frequency of the oscillation circuit including this coil, the weight of the object to be measured is indirectly measured. Of course, the shaft is driven by the motor, and is supported together with the motor by a parallel spring mechanism so as to be movable in the thrust direction.

In this way, in the present invention, the weight of the object to be measured is converted into a change in relative position between the coil and the core, and then extracted as a change in the frequency of the oscillation circuit. is stabilized, and since the coil and core correspond in a non-contact state, there are no mechanical sliding parts or resistance during measurement, making it possible to detect the amount of ffl with high accuracy.

Structure of the Invention FIGS. 1 to 3 show the structure of a basic embodiment of the tUt sensor device of the present invention.

This weight sensor device 1 includes a driving motor 2 and a shaft 3 that is rotationally driven by the motor 2 and can be displaced in a thrust direction in response to a load from the weight of an object to be measured. The motor 2 and shaft 3 are incorporated into the casing 4.

That is, the motor 2 is fixed inside the casing 4 with the motor shaft 5 protruding, and transmits rotational force to the shaft 3 inside the casing 4 via a gear train 6 for deceleration. This shaft 3 is rotatably supported in the thrust direction by upper and lower bearings 7 on the casing 4 side, and supports a turntable 8 at its upper end, and supports a lower spring at its chamfered lower end. It is in contact with the upper surface of the receiver 9.

This spring receiver 9, together with the upper spring receiver 1O, holds the casing 4 between the plurality of setscrews 11.
is fixed to one end of the casing 4 by. These spring receivers 9.10 are fixed to one end of the pair of leaf springs '12.13 by fastening means such as caulking. These leaf springs 12, 13 have a rectangular outline, and are fixed at their proximal ends to a U-shaped support plate 14 by means of fixing such as caulking, and are attached to the support plate 14 and a plurality of attachments. The L-shaped installation is done by the plate 16 through the screw 15.
It is fixed at the rising part of.

In this way, the spring receiver 9.10, the leaf spring 12.13
The support plate 14 constitutes a parallel spring mechanism, with the shaft 3 movable in the thrust direction and the support plate 14 on the proximal end side being the fixed side. Usually these leaf springs12.13
When there is no load on the shaft 3 side, the mounting is parallel to the bottom side of the temporary 16, but when it receives a load in the thrust direction, it is elastic in the thrust direction. Displaced to. Note that this maximum displacement is regulated by the perforation 17 of the mounting plate 16.

On the other hand, this weight sensor device 1 includes an oscillation circuit 18 and a bumper circuit 19 as electrical parts.

As part of the oscillation circuit 18, a detection coil 2 is provided.
0, the spring receiver 9 and its attachment together with the core 21 are assembled in the temporary 16 part. That is, one coil 20 is made of a plastic coil bobbin 22, for example.
The spring receiver 9 is attached to the upper surface of the portion 23 and fixed by fitting into a hole 24 or the like. Note that this coil bobbin 22 is
It is open only on the lower side of the center position of the coil 20, and the upper surface is formed of the same material so as to be integrally closed. The core 21 is configured as a male screw made of magnetic material for position adjustment, and is inserted upward into the female screw 25 of the attachment Vi 16 so as to face the center portion of the coil 20. The coil 20 and the core 21 are electrically and magnetically coupled, and their electrical characteristics, that is, self-inductance, are proportionally changed by changing their relative positions.

Next, FIG. 4 illustrates the configuration of the electrical part. The oscillation circuit 18 is configured by combining a frequency adjustment volume 27, a capacitor 29, 30, and an inverting amplifier 28 between both ends of the coil 20 and the ground 26 for LC oscillation. The buffer circuit 19 includes a resistor 3 between the output side of the oscillation circuit 1 and the output terminal 35.
1.32 and an inverting amplifier 33.34.

Note that these circuit elements are incorporated into a circuit board 36, for example, attached to the side surface of the plate 16, and connected to the coil 20 by a lead wire 37.

Effect of the Invention An object to be measured 40 such as food is placed on the turntable 8.
When placed, its weight becomes a load in the thrust direction on the shaft 3, which acts on the lower spring receiver 9, so the leaf springs 12 and 13 work together to exert elasticity in a direction that counteracts the load. and displace it to a balanced position. At this time, the shaft 3 and the coil 20 are displaced in the direction in which the load is applied while maintaining a substantially parallel state.

As a result, the relative positional relationship between the coil 20 and the core 21 changes in proportion to the load in the thrust direction, that is, the weight of the object to be measured 40, so the self-inductance of the coil 20 changes. As a result, the oscillation circuit 18 changes its oscillation frequency according to the change in self-inductance.

The oscillation frequency r at this time is the self-inductance L1
Letting the capacitances of the capacitors 29 and 30 be C, C, respectively, it is given by the following equation.

As the coil 20 approaches the fixed core 21 and the coupling between them becomes deeper, the oscillation frequency f of the oscillation circuit 18 gradually decreases. Therefore, by identifying this oscillation frequency f, the weight of the object to be weighed 40 can be measured indirectly.

Next, FIG. 5 shows the temperature-frequency characteristics.

The coil 20 changes in the direction of decreasing the oscillation frequency f as the temperature rises. Furthermore, the elastic modulus of the leaf springs 12 and 13 changes more greatly as the temperature increases due to temperature changes and thermal expansion, so the oscillation frequency f also changes in the direction of decreasing. On the other hand, the oscillation circuit 18 itself changes the oscillation frequency f in a higher direction as the temperature rises in order to offset these characteristics. Therefore, as a whole, the output of the oscillation circuit 18, that is, the oscillation frequency f, has a flat characteristic as shown by the dotted line with respect to temperature changes. As a result, the oscillation frequency f changes as the weight or load changes.
It changes along a smooth curve sloping upward to the left as shown in FIG. Of course, such load-frequency characteristics can be modified to linearly change by using other function conversion means, software, or the like.

Another Embodiment of the Invention Next, FIG. 7 shows an example in which the coil 20 is provided upward, and the core 21 is fixed to the internal thread 39 of a fixed core receiver 38. The core receiver 38 is directly fixed to the upper surface of the plate 16, and also functions as a cover to prevent foreign matter from entering the center hole of the coil 20.

According to the above embodiment, the relationship between the coil 20 and the core 21 is opposite to that of the above embodiment, and the degree of coupling between the coils 20 and the core 21 becomes shallow depending on the load. As shown in FIG. 8, the characteristics change with a slope opposite to that of the previous example. The greater the deflection of the temporary springs 12 and 13, the higher the oscillation frequency f.
Even if no extreme correction is made on the oscillation circuit 18 side, the overall characteristics will remain flat.
As shown in FIG. 9, the frequency characteristics change with a slope opposite to that of the previous embodiment.

These characteristics are set by the user so as to take into account changes in the temperature of the usage environment and adjustment with the software on the correction side.

Next, in the embodiments shown in FIGS. 10 and 11, the upper spring receiver 10 is attached by attaching the coil 20 to the part 23 and forming a part of the lower spring receiver 9 into a recess by drawing. This is an example in which the lower end portion of the shaft 3 is brought into contact with the lower end portion of the shaft 3, and a recessed hole 41 is formed in the provisional 16 portion corresponding to this drawing portion, thereby reducing the thickness of the entire device. In addition to the side surface, the support body 14 can be attached to the temporary 16
They are also in contact with each other on the lower surface side, and are fixed at that portion with mounting screws 15. As a result, leaf spring 12.
The proximal end portion of No. 13 is supported with higher rigidity than in the previous embodiment.

Modifications of the Invention In all of the above embodiments, the coil 20 is fixed to the movable side part, and the corresponding core 21 is fixed to the fixed side part. However, the positions of both may be reversed.

Although the shaft 3 is in direct contact with the upper surface of the spring receiver 9 at its lower end, the part that receives this load may be brought into indirect contact with a plate-shaped member having a low coefficient of friction. good.

Effects of the Invention In the present invention, the thrust load is extracted as a change in the relative position between the coil and the core, and the weight is indirectly measured from the change in the electrical characteristics of the coil. Compared to conventional sensors, the device is small and can be constructed to be particularly thin, so it can be installed in small spaces such as electronic cookers, and changes in the coil's self-inductance are not electrically unstable like in capacitors. Also, since it is stable against electrical influences in the usage environment, it is possible to accurately detect weight even though it is an indirect measurement.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the weight sensor device of the present invention, FIG. 2 is a vertical sectional view thereof, FIG. 3 is a vertical sectional view seen from a different direction, FIG. 4 is a circuit diagram of the electrical part, and FIG. Figure 6 is a graph of temperature-frequency characteristics, Figure 6 is a graph of load-frequency characteristics, Figure 7 is a cutaway side view of the main part of another embodiment, and Figure 8 is temperature-frequency characteristics of another embodiment. 9 is a graph of load-frequency characteristics in another embodiment, FIG. 10 is a plan view of still another embodiment, and FIG. 11 is a partially cutaway side view. 1. Weight sensor device, 2. Motor, 3. Axis, 9
, lO... Spring holder, 12.13... Leaf spring, 14...
Support plate, 1B...Oscillation circuit, 19...Buffer circuit, 2
0...Coil, 21...Core, 40...Measured items such as food. Patent applicant: Santa Seiki Seisakusho Co., Ltd.
Patent Attorney Nakagawa Kunio Figure 7 jO/σJY 17 21 Figure 3, 40 JO'' Figure 4 Figure 5 6A Temperature - 471T
L - Figure 7 76 2'3 ゑ 7'7 8th, 2nd 9A Warmth, I - Load - 70th Prisoner Figure 71

Claims (1)

[Claims] It has a motor, a shaft that is driven by the motor and can be displaced in the thrust direction under load, a coil that forms part of an oscillation circuit, and a core that is inserted into the coil. A weight sensor device characterized in that the positional relationship between the coil and the core changes with displacement in the thrust direction, and the load is extracted as a change in the oscillation frequency of the oscillation circuit.