JP2000065631A - Weight detection means and heating device using it the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arbitrarily set the level of a load by detecting the load continuously with a simple configuration and to prevent an excessive weight exceeding a certain weigh from being applied to a piezoelectric body for protection regarding a weight detection means using the piezoelectric body, and a heating device using the weight detection means. SOLUTION: A weight detection means judges a load being applied to a piezoelectric body 1 according to an electrical signal that is outputted from a second electrode 3 by inputting an electrical signal to first electrode 2 on the piezoelectric body 1 so that it can detect a load continuously, can set one end of a load conversion means 8 as a support 9 and the other as an operation point 10 for transferring the load to the piezoelectric body 1, and can provide a force point 11 for receiving a load 7 between both of them, thus changing to the most effective load level according the position of the force point 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weight detecting means for detecting a weight based on a load applied to a piezoelectric element, and a heating device for controlling the heating means in accordance with the weight of an object to be heated detected by the weight detecting means.

[0002]

2. Description of the Related Art First, IEEE Transaction on Electron Dev
Ices, vol. ED-26, No. 5, p815 to p817, 1979 (hereinafter referred to as Reference 1) proposed a bimorph-type pressure detector. This is to detect the contact position with the piezoelectric film. One end of the piezoelectric film itself is supported in a cantilever shape, and a contact position is detected by monitoring an output signal at an appropriate frequency.

[0003] Also, Japanese Patent Application Laid-Open No. 8-62068 (hereinafter referred to as
Reference 2) discloses a pressure detection device that detects distribution of fine peaks and valleys such as fingerprints. Scanning is performed by arranging a large number of scanning electrodes on a matrix on the front and back surfaces of the piezoelectric film, and detecting the distribution of peaks and valleys of the fingerprint when touched by a finger.

Japanese Patent Application Laid-Open No. 7-5025 (hereinafter referred to as Reference Document 3) discloses a load measuring circuit for detecting the weight of food in a microwave oven with a piezoelectric sensor. Since the roller ring passes over the piezoelectric sensor and applies a load with the rotation of the mounting table, an electric charge corresponding to the magnitude of the instantaneous pressure change is generated, and eventually an output corresponding to the load is obtained.

[0005]

However, the pressure detecting device of Reference 1 can detect the presence or absence of a contact with the piezoelectric film and the contact position, but cannot detect the magnitude of the load due to the contact of the object. Had the problem of not being able to do so.

Further, in the pressure detecting device of Reference 2, the number of pressure detection points of the piezoelectric sensor can detect only whether the peak of the fingerprint pattern is in contact with the valley. That is, the method detects the presence or absence of contact of an object at each point, and has a problem that the magnitude of the load cannot be detected.

In the load measuring circuit of Reference 3, the load can be measured by detecting the charge generated according to the magnitude of the instantaneous pressure change. However, in order to give an instantaneous pressure change, it is necessary to switch between a moment when a load is applied and a moment when no load is applied, that is, there is a problem that chopping is required. In addition, when chopping, there is a problem that the load cannot be monitored continuously.

Conventionally, when the application, that is, the range of the load to be detected is changed, the sensitivity is optimized by changing the configuration of the piezoelectric body itself or the detection circuit, and the same configuration is generally used. There was a problem that it was difficult to do.

Conventionally, when a large load exceeding the range to be detected is applied, if the load exceeds the strength of the piezoelectric body, it may lead to destruction, or even without destruction, the characteristics of the piezoelectric substance may change and the weight may be incorrect. There is a problem that there is a risk of detection.

[0010]

In order to solve the above-mentioned problems, the present invention provides a piezoelectric body, load converting means for converting the magnitude of a load and transmitting the load to the piezoelectric body, and a plurality of electrodes on the piezoelectric body. Input means for inputting an electric signal to the first electrode; and
Determining means for determining a load applied to the piezoelectric body by an electric signal output from the electrode, the load converting means having one end as a fulcrum and the other end as an action point for transmitting a load to the piezoelectric body, It has a point of force that receives a load between the two.

According to the above invention, an electric signal is input to the first electrode on the piezoelectric body, and the determination means determines the load based on a change in the electric signal from the second electrode on the piezoelectric body due to the load. Since the load can be continuously detected with a simple configuration, one end is set as a fulcrum, the other end is set as an action point for transmitting a load to the piezoelectric body, and a force point receiving the load is provided between the two. Since the magnitude of the load is converted by the load converting means and then transmitted to the piezoelectric body, the level of the load applied to the piezoelectric body can be set arbitrarily.

A piezoelectric body, a plurality of electrodes on the piezoelectric body, input means for inputting an electric signal to the first electrode,
A determination means for determining a load applied to the piezoelectric body by an electric signal output from the electrode, and a stopper for protecting the piezoelectric body from being applied with an excess of a certain weight.

According to the above invention, an electric signal is input to the first electrode on the piezoelectric body, and the determination means determines the load based on the fact that the electric signal from the second electrode on the piezoelectric body changes with the load. The load can be detected continuously with a simple configuration, and the stopper protects the piezoelectric body from overload exceeding a certain weight. Change is unlikely to occur,
The reliability of weight detection can be improved.

[0014]

According to a first aspect of the present invention, there is provided a weight detecting means, comprising: a piezoelectric body; a load converting means for converting the magnitude of a load to be transmitted to the piezoelectric body; and a plurality of electrodes on the piezoelectric body. And input means for inputting an electrical signal to the first electrode, and determining means for determining a load on the piezoelectric body based on the electrical signal output from the second electrode, wherein the load converting means has one end Is used as a fulcrum, the other end is used as an action point for transmitting a load to the piezoelectric body, and a force point for receiving the load is provided between the two.

Then, an electric signal is input to the first electrode on the piezoelectric body, and the determination means determines the load based on the fact that the electric signal from the second electrode on the piezoelectric body changes with the load. With a simple configuration, the load can be continuously detected, and one end is used as a fulcrum, and the other end is used as an operating point for transmitting a load to the piezoelectric body, and a load converting means having a load point between the two ends, Since the magnitude of the load is transmitted to the piezoelectric body after being converted, the level of the load applied to the piezoelectric body can be arbitrarily set.

In the weight detecting means according to the second aspect of the present invention, the position of the force point can be changed.

Since the load applied to the piezoelectric body can be changed depending on the position of the point of force, the sensitivity can be selected.

According to a third aspect of the present invention, there is provided a weight detecting means, comprising: a piezoelectric body; a plurality of electrodes on the piezoelectric body; an input means for inputting an electric signal to the first electrode; A determination means for determining a load applied to the piezoelectric body based on the applied electric signal; and a stopper for protecting the piezoelectric body from excessive load exceeding a certain weight.

According to a fourth aspect of the present invention, there is provided a weight detecting means having a load transmitting means for transmitting a load to the piezoelectric body, wherein when a load exceeding a certain weight is applied to the load transmitting means, the load transmitting means is provided with a stopper. The position is regulated by this so that the piezoelectric body does not cover the piezoelectric body.

Then, an electric signal is input to the first electrode on the piezoelectric body, and the determining means determines the load based on the fact that the electric signal from the second electrode on the piezoelectric body changes with the load. , The load can be detected continuously with a simple configuration, and the stopper protects the piezoelectric body from overload exceeding a certain weight, so that the piezoelectric body is unlikely to be damaged by the overload or change in the characteristics of the piezoelectric body. The reliability of weight detection can be improved.

According to a fifth aspect of the present invention, there is provided a heating device for heating an object to be heated, weight detecting means for detecting the weight of the object to be heated, and heating means for detecting the weight of the object to be heated based on the weight detected by the weight detecting means. .

Then, heating can be performed according to the weight of the object to be heated.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic structural view of a weight detecting means according to Embodiment 1 of the present invention.

In FIG. 1, a piezoelectric ceramic 1 is used as a piezoelectric body, and electrodes 2, 3, and 4 are formed on both surfaces. The input means 5 is for inputting an AC electric signal between the input electrode 2 and the ground electrode 4 and is input in a frequency band close to the natural frequency of the piezoelectric ceramics 1. The judging means 6 extracts an electric signal having the same frequency as that of the input from between the output electrode 3 and the ground electrode 4, and judges the load applied to the piezoelectric ceramics 1. Incidentally, the load applied to the piezoelectric ceramic 1 is not the actual load 7 but the level is lowered by the load converting means 8. The load converting means 8 of the present embodiment has a fulcrum 9 at one end,
Action point 1 for transmitting load to multiple ends of piezoelectric ceramics 1
0, a force point 11 receiving the actual load 7 is provided, and the load applied to the piezoelectric ceramic 1 can be changed depending on the position of the force point 11. Load 7 applied to power point 11
Most of the load is applied to the piezoelectric ceramics 1 when the power point 11 is on the action point 10 depending on the position of the power point 11, but when the power point 11 is on the fulcrum 9, most of the load is not applied to the piezoelectric ceramics 1. Therefore, the output point from the electrode 3 can be changed by selecting the power point 11 at the optimum position according to the application (use range of the load). Reference numeral 12 denotes protection means for protecting the piezoelectric ceramics 1, which may be a cushion for dispersing a load, a rigid body for increasing strength, or a combination thereof. Further, the piezoelectric ceramics 1 is fixed on a table 13 via protection means 12.

FIGS. 2 to 4 are characteristic diagrams for explaining the principle of obtaining an output corresponding to a load from the piezoelectric ceramic 1.

FIG. 2 shows the frequency characteristics of the piezoelectric ceramic 1 when the frequency is changed while the load is constant and the input voltage of the input means 5 is constant (for example, 1 V). According to the natural frequency of the piezoelectric ceramic 1 under a load, f1, f1
There is a resonance point at the frequency f2. As experimental values, the load was 905 g, f1 was 44 kHz, the output voltage was 5.64 v, and f2
Was 115 kHz and the output voltage was 2.48 V. It can be seen that it is better to select f1 as the input frequency in order to maximize the sensitivity.

FIG. 3 shows the results when the load is changed (load m1 <m2
<M3) is a frequency characteristic. The characteristic of the load m1 is L1,
The characteristic of m2 is L2, and the characteristic of m3 is L3. Load m1
When an input is input at f1 close to the resonance frequency at the time of (characteristic L1), the output V1 at the load m1 (characteristic L1) and the load m2
An output V2 at (characteristic L2) and an output V3 at load m3 (characteristic L3) are obtained.

FIG. 4 is a characteristic diagram in which the load of FIG. 3 is plotted on the horizontal axis and the output changes with respect to the load. In this case, the sensitivity is good (V1≫V2) at a light load (m1 to m2), but is poor (V2 ≒ V3) at a large load (m2 to m3).

However, this is because the input was input at f1 close to the resonance frequency at the time of the load m1. If an input is made near the resonance frequency at the time of load m3 in FIG.
It can easily be imagined that it will be a curve that rises to the right and is different. This may be selected depending on whether the sensitivity is required for a lighter one or for a heavier one.

Although the characteristics largely depend on the characteristics of the piezoelectric body itself, the linearity of FIG. 4 can be improved by changing the steepness of the resonance characteristics shown in FIGS. 2 and 3 according to the range of the load to be measured. It is possible.

FIGS. 5 and 6 show how the characteristics change depending on the position of the force point of the load converting means 8. FIG.
FIG. 5 is a characteristic diagram showing an output with respect to the weight (a relative value when the output at the load m1 is set to V0), and FIG. 6 is a configuration diagram showing the position of the force point. Even if the load 7 is the same, the power points are 11a and 11
The characteristics at b and 11c change to La, Lb and Lc, respectively. First, since the power point 11a is close to the point of action 10, most of the load 7 is applied to the piezoelectric body 1, the deviation of the resonance frequency with respect to the change of the load is large, and the output change amount (m0-m4) at m1-m3. Becomes larger. Next, emphasis 11
Since c is close to the fulcrum 9, most of the load 7 is not applied to the piezoelectric body 1, the deviation of the resonance frequency with respect to the change of the load is small, and the output change amount (V0-V6) at m1 to m3 is small.

The power point 11b is located between the two, and the shift of the resonance frequency with respect to the change in the load is also in the middle of the two, and the variation (V0-V8) of the output at m1 to m3 is also between the two.

Further, the sensitivity to weight La, L
The characteristics of b and Lc will be described. In the case of La, the sensitivity under a light load is high, and the sensitivity under a large load is low. That is, the output change (V0-V4) between m1 and m2 in FIG.
The output change (V4-V4 ≒ 0) between 2 and m3 is extremely small. Therefore, if the load range is m1 to m3, it is inappropriate as a weight detecting means because of low sensitivity under a large load. On the other hand, in the case of Lc, the sensitivity under a light load is low, and the sensitivity under a large load is high. That is, the output change (V0-V5) between m1 and m2 in FIG. 5 is small, and the output change (V5-V6) between m2 and m3 is large. Therefore, the load range is m1
If it is m3, it is unsuitable as a weight detecting means due to low sensitivity under light load. In the case of Lb, the sensitivity under a light load is equal to the sensitivity under a large load. That is, the output change (V0-V7) between m1 and m2 in FIG.
The output change (V7-V8) during 3 is the same. Therefore, if the load range is m1 to m3, the sensitivity is stable from a light load to a large load, and it is the most suitable as the weight detecting means.

According to this embodiment, since the position of the force point of the load converting means 8 can be changed, the load applied to the piezoelectric body can be converted to an appropriate level, and the sensitivity within the load range can be stabilized. . According to the present embodiment, the sensitivity can be changed without changing the piezoelectric body itself.

It should be noted that, without being limited to the present embodiment, it is conceivable that the sensitivity under a light load is important or the sensitivity under a large load is important depending on the application. In this case, the sensitivity can be increased in any important load range.

(Embodiment 2) FIG. 7 is a schematic structural view of a weight detecting means according to Embodiment 2 of the present invention. The components having the same reference numerals as those in the first embodiment have the same structure, and the description will be omitted.

A load transmitting means 16 comprising a plate 14 for receiving the load 7 and a projection 15 for transmitting a load to the piezoelectric body 1 is configured to be able to move up and down in a slit 18 provided in a support 17. In the case of a load within the detection range, the plate 14 descends in the slit 18, and the projection 15
Pressing 9 transfers the load 7 to the piezoelectric body 1. The rigid body 19 transmits a load to the piezoelectric body 1 and also serves to reinforce the piezoelectric body 1. On the other hand, when an excessive load exceeding the detection range is applied as the load 7, the position of the plate 14 is restricted by the stopper 20 at the lower end of the slit 18. Therefore, the overload is not transmitted to the rigid body 19 and is not applied to the piezoelectric body 1.

According to this embodiment, breakage of the piezoelectric body and change in the characteristics of the piezoelectric body due to overload hardly occur, and the reliability of weight detection can be improved.

FIG. 8 is a configuration diagram of a main part in this embodiment.
The configuration of the electrodes on the piezoelectric body 1 and the lead wires for input and output are shown.
Electrodes are formed on both sides of the disc-shaped piezoelectric ceramic 1, an input electrode 2 is formed in the center of the front surface, an output electrode 3 is formed around the surface, and the entire back surface is used as a ground electrode. . Lead wires 21, 22, and 23 are protruded from the respective electrodes. An electric signal is input between the lead wires 21 and 23, and an electric signal is output from between the lead wires 22 and 23.

According to this embodiment, the thickness of the piezoelectric body 1 can be reduced. FIG. 9 is a block diagram of the present embodiment. In particular, input and output circuits and signal processing will be described. First, the input means 5 inputs an electric signal of a reference frequency between the electrodes 2 and 4 on the piezoelectric body 1. The piezoelectric body 1 vibrates while receiving an actual load 7, and outputs the vibration as an electric signal from the electrodes 3 and 4. This output is processed in an output processing circuit 24. Since the piezoelectric body 1 has a high impedance, the impedance is converted by an impedance conversion circuit 25, and the same frequency component as the input is input by a filter circuit 26 to remove a noise component. Rectifier circuit 27
And the peak value is taken out by the peak hold circuit 28. The weight is determined by the determination means 6 based on this signal. In the determination means 6, the analog output is converted into a digital value by the AD conversion means 29, and the correlation between the signal and the actual weight is stored in advance. Comparison with the value of the storage means 30
By calculating, the actual weight can be detected. The comparison operation means 31 plays this role, and it is also possible to control external devices and other means 32 based on the detected weight. Further, it is easy to configure the input means 5 and the output processing circuit 24 as the input / output circuit 33 on the same substrate.

According to this embodiment, the weight can be detected using the piezoelectric body 1 with a simple configuration.

Actually, other configurations (for example, replacing a hardware circuit with a software program, inserting an amplifier circuit in the middle, etc.) are also conceivable.
It is not limited to this embodiment.

(Embodiment 3) FIG. 10 is a schematic structural view of a heating apparatus using weight detecting means in Embodiment 3 of the present invention. Those having the same reference numerals as the first and second embodiments have the same structure,
Description is omitted. The heating device of FIG. 10 is a microwave oven that heats the food 34 by microwaves, detects the weight of the food 34, and performs appropriate heating by changing the heating time according to the weight. The food 34 is placed on a plate 35 and rotated in conjunction with the rotation of the turntable 36. The turntable 36 is rotated by transmitting a rotational force by a shaft 38 of a motor 37. Here, the shaft 38 also penetrates the lower part of the motor 37 and plays a role of transmitting a load to the load converting means 8. Thus, the load converted by the load converting means 8 is transmitted from the point of application 10 to the load transmitting means 39 and transmitted to the piezoelectric body 1. Parts for weight detection are
It is attached to the bottom surface of the heating chamber 41 by an attachment plate 40. Regarding the output processing, the weight is determined by the determination means 6,
By controlling the power supply 43 by the heating control means 42 based on the determined weight, the microwave emission from the magnetron 44 is controlled. Specifically, the optimum heating time t when the determination weight is m is experimentally obtained in advance and stored in a memory, and when the time t has elapsed from the start of heating, the heating control means 42 43 may be turned off.

According to the present embodiment, the weight of the food is detected to control the microwave radiation from the magnetron.
Appropriate heating can be performed according to the food, and automation can be achieved. In particular, since the input / output characteristics at a frequency near the natural frequency of the piezoelectric body are used, the weight can be detected without an instantaneous change (chopping) of the load.

In this embodiment, microwave heating has been described as a heating means. However, radiation heating or induction heating may be used, and any heating means or sequence whose heating time or sequence is to be changed depending on the weight of the load can be widely applied.

Further, even if there is no heating means, a control device for feeding back the weight of the load, for example, a device for notifying and displaying whether the load has become lighter or heavier than a certain weight can be considered. You may consider controlling the means.

[0048]

As is apparent from the above description, according to the weight detecting means of the present invention and the cooking device using the same,
The following effects can be obtained.

(1) An electric signal is input to the first electrode on the piezoelectric body, and the judging means judges the load based on the fact that the electric signal from the second electrode on the piezoelectric body changes due to the load. Therefore, the load can be continuously detected with a simple configuration. Therefore, the load can be continuously monitored. In addition, a small change in load can be detected without missing.

(2) Since the magnitude of the load is transmitted to the piezoelectric body after being converted, the level of the load applied to the piezoelectric body can be arbitrarily set. Therefore, the same piezoelectric body can be used for applications having different load ranges, and versatility is improved.

(3) Since the load applied to the piezoelectric body can be changed depending on the position of the force point, the sensitivity can be selected. Therefore, the sensitivity can be weighted according to the required accuracy of the load.

(4) Since the stopper protects the piezoelectric body from overload exceeding a certain weight, the piezoelectric body is unlikely to be destroyed by the overload or change in the characteristics of the piezoelectric body, and the reliability of weight detection can be improved.

(5) Since the position of the load transmitting means is regulated by the stopper, an excessive load exceeding a certain weight is not applied to the piezoelectric body, so that the load can be easily and reliably prevented.

(6) Since the heating means is controlled based on the weight detected by the weight detecting means, appropriate heating can be performed according to the weight of the object to be heated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a weight detection unit according to a first embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of the weight detecting means.

FIG. 3 is a frequency characteristic diagram in which a load of the weight detecting means is used as a parameter.

FIG. 4 is a diagram showing load characteristics of the weight detecting means.

FIG. 5 is a load characteristic diagram in which the position of a force point of the weight detection means is used as a parameter.

FIG. 6 is a configuration diagram of a main part of the weight detecting means.

FIG. 7 is a schematic configuration diagram of a weight detection unit according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a main part of a piezoelectric body of the weight detection unit.

FIG. 9 is a configuration diagram of a signal processing circuit of the weight detection unit.

FIG. 10 is a schematic configuration diagram of a heating device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic (piezoelectric material) 2 Input electrode (1st electrode) 3 Output electrode (2nd electrode) 5 Input means 6 Judgment means 7 Load 8 Load conversion means 9 Support point 10 Application point 11, 11a, 11b, 11c Force point 16, 39 Load transmitting means 20 Stopper

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Biao Nagai 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (Reference) 3L086 AA01 CB03 DA18 DA23

Claims (5)

[Claims] 1. A piezoelectric body, load converting means for converting the magnitude of a load and transmitting the load to the piezoelectric body, a plurality of electrodes on the piezoelectric body, and input means for inputting an electric signal to the first electrode. ,No. 2
Determining means for determining a load applied to the piezoelectric body by an electric signal output from the electrode, the load converting means having one end as a fulcrum and the other end as an action point for transmitting a load to the piezoelectric body, Weight detection means configured to have a force point between them to receive a load. 2. The weight detecting means according to claim 1, wherein the position of the force point can be changed. 3. A piezoelectric body, a plurality of electrodes on the piezoelectric body,
Input means for inputting an electrical signal to the first electrode, determining means for determining a load applied to the piezoelectric body based on an electrical signal output from the second electrode, and protection so that an excess of a certain weight is not applied to the piezoelectric body Weight detecting means provided with a stopper that performs the operation. 4. A load transmitting means for transmitting a load to a piezoelectric body, wherein when a load exceeding a certain weight is applied to the load transmitting means, the position of the load transmitting means is regulated by a stopper, whereby the piezoelectric body is controlled. 4. The weight detecting means according to claim 3, wherein said weight detecting means does not cover the surface. 5. A heating means for heating an object to be heated, a weight detecting means for detecting a weight of the object to be heated, and a weight detected by the weight detecting means. A heating device having a control means for controlling the heating means by means of the heating means.