JP2877006B2 - Weight conversion method and cooking device using it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for converting the weight of a weight sensor used in a microwave oven or the like and a method for converting the weight of food during cooking. In particular, for many weight sensors,
The present invention relates to a method for efficiently and accurately giving a weight conversion formula.

[0002]

2. Description of the Related Art Conventionally, this type of weight sensor used in a cooking device has a structure as shown in FIG. 7 as described in Japanese Patent Application Laid-Open No. 1-267424. FIG. 4A is a plan view of the weight sensor, and FIG.
FIG. Two alumina substrates (0.63 mmt thick) of about 30 mm square (plate thickness 0.63 mmt)
2mm) Electrodes 3 and 4 are provided, and appropriate spacing (about 45μm)
And fixed at the peripheral portion 5 to form a capacitor and operate as a diaphragm having an effective diameter of about 24 mm. When a load (W) is applied to the center of the upper substrate 1, the upper substrate 1 is deformed into a concave shape, and the capacitance (C) formed by the electrodes 1 and 2 changes. This change is detected as a change in the oscillation frequency (F) by a detection circuit such as a CR oscillation circuit, and the load (W) is detected. Further, there is also a configuration as shown in FIG. FIG.
2 shows a plan view of the weight sensor, and FIG. 2B shows a cross-sectional view taken along line BB '. Circular (about 12 mm in diameter) electrodes 8 and 9 are provided in the center of two upper and lower alumina substrates 6 and 7, and annular (inner diameter 18 mm and outer diameter 22 mm) electrodes 10 and 11 are provided in the periphery thereof. At a suitable interval (approximately 45 μm),
Similarly, a circular capacitor fixed by the peripheral portion 12 and formed by an electrode in the center portion and an annular capacitor formed by the annular electrode in the peripheral portion are formed. The change in C) is detected by a detection circuit such as a CR oscillation circuit as a change in the oscillation frequency (F), and the capacitance (Cw) of the circular capacitor and the capacitance (Cr) of the annular capacitor are detected. Capacitance ratio (R = Cw / Cr)
Thus, the load (W) is detected from the above. FIG. 9 shows the relationship between the load (W), the capacitance (C), and the capacitance ratio (R). In the figure, the horizontal axis represents the load (W) applied to the weight sensor, and the vertical axis represents the characteristic value of the weight sensor, the capacitance (C), the solid line 13, the capacitance ratio (R), and the solid line 14. , And. The load (W) acting on the weight sensor is obtained by calculating the load (W) from these characteristic values (C or Rc), which are the outputs of the weight sensor, using a conversion formula consisting of a quadratic expression. I was

[0003]

However, in the configuration using the above-mentioned conversion formula composed of quadratic expressions, a wide load range cannot be converted with one conversion formula with high accuracy. For this reason, there have been problems such as the necessity of a plurality of conversion formulas and poor accuracy. In addition, there is another problem in that if a higher-order conversion formula is used to convert the weight, it takes a longer time to perform the conversion. For this reason, in a microwave oven with a fast cooking speed, it takes a long time to calculate a change in weight during cooking, and there is also a problem that it is difficult to automatically cook using a change in weight of food. Was.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a weight conversion method capable of converting a wide load range with high accuracy by one conversion formula. It is another object of the present invention to provide a method for calculating a change in weight of food during cooking in a short time. It is another object of the present invention to provide a heating cooker that can control cooking by changing the weight of a cooked food by using the weight conversion method of the present invention to convert the weight accurately, easily, and quickly. .

[0005]

In order to solve the above problems SUMMARY OF THE INVENTION The present onset Ming load conversion methods, characteristic values of the weight sensor (X)
And the weight value (W) is a cubic expression, W = F (X) = A (3)
・ X∧3 + A (2) ・ X∧2 + A (1) ・ X∧1 + A (0)
And two predetermined reference weight values (W0, W0
The difference (dX = X) between the characteristic values (X0, X1) of the weight sensor in 1)
1−X0) and the ratio (A (2) / A) of each coefficient value of the above cubic equation.
(3), A (1) / A (3)) using the correlation obtained in advance.
After the decision, the remaining two unknowns (A (3),
A (0)) is the characteristic at the two reference weight values (W0, W1).
The calculation is performed using the values (X0, X1) .

In a fourth load conversion method according to the present invention, weight conversion is performed using the output value of the weight sensor and the weight conversion formula for the first weight conversion, and the output value of the weight sensor is converted for the next weight conversion. The weight was converted using the change value and the differential coefficient of the weight conversion formula, and the configuration was adopted.

Further, in order to constitute a heating cooker for controlling the cooking by detecting a change in the weight of the food, the heating cooker according to the present invention is configured to determine the initial weight of the food before starting cooking or at the start of cooking. Detected by one of 1, 2, 3 methods,
The weight change of the food being cooked is converted from the differential coefficient of the weight conversion formula at the time of the initial weight calculation and the change value of the output value of the weight sensor.

[0008]

According to the present onset Akira configuration, weight conversion formula is 3-order equation
Because of the approximation , a wide range of load values can be converted by one conversion formula.

[0009] Also, the weight conversion equation is constituted by a cubic equation, and, using the characteristic values of the weight sensor in the two reference load value
To determine the respective coefficients of the weight conversion formula consisting of the cubic formula ,
Further, since the coefficient of the remaining cubic equation that passes through the two reference load values is determined, the cubic equation can be easily formed with high accuracy.
A weight conversion formula can be determined.

Further, according to this onset Ming configuration, the first terms of weight, and weight conversion by using the output values and weight conversion equation of the weight sensor, the weight conversion from the next, the weight sensor output Since the weight is converted using the change value of the value and the derivative of the weight conversion formula, the weight can be accurately converted in a short time even if a higher-order conversion formula is used.

Further, according to this onset Ming arrangement, since the initial weight value of the food being cooked, as well as in terms of accurately, the weight change of the food during cooking, can be converted quickly, cooking time Even when cooking is short, cooking can be controlled based on the change in weight of food, and automatic cooking can be realized.

[0012]

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

Embodiment 1 FIG. 1 shows a relationship between a characteristic value (capacitance ratio, R) and a load (W) for describing a weight conversion formula based on an embodiment of the present invention. The horizontal axis shows the characteristic value (capacitance ratio, R), and the vertical axis shows the load (W). Square (□) mark indicates the measured values, the solid line 15 the weight conversion equation cubic expression according to the present invention, the broken line 16 shows the weight conversion equation according to the prior quadratic equation. The weight conversion formula consisting of a cubic formula and the solid line 15 can cover a wide load range from 0 to 5 kg. If the broken line 16 is a conventional weight conversion formula composed of a quadratic formula, the error is large in a high load region of 3 kg or more when adjusted to a low load region. Therefore, in this case, a weight conversion formula consisting of a quadratic formula corresponding to the high load area is required (not shown in FIG. 1).

Therefore, when a predetermined reference load, for example, a zero point, is translated so as to coincide with the actually measured value,
It is understood that a wide load range can be converted by one weight conversion formula.

The above is described using mathematical expressions.
Assuming that the characteristic value is X (R) and the converted weight value is W (cal), a preset cubic equation is represented by (Equation 1).

[0016]

(Equation 1)

A (i) indicates a coefficient value in each order. When the constant term A (0) is corrected by the actually measured value and is set to A ′ (0) so that W (cal) = 0, that is, when translated, the equation (2) is obtained.
Becomes

[0018]

(Equation 2)

Here, X (0) indicates the characteristic value at the zero point.
Each coefficient A (3), A (2), A (1) is given in advance. This (Equation 2) shows a conversion equation consisting of a cubic equation that always passes through the zero point.

At this time, the weight conversion formula is given by (Equation 3).

[0021]

(Equation 3)

This (Equation 3) is a solid line 1 shown in FIG.
5 That is, a predetermined cubic expression is calculated by the up-down (Y-axis)
This is equivalent to translating in the direction.

[0023] Figure 3, shows the error that is measured with respect to about 1,000 weight sensor. The horizontal axis shows the load value W (kg), and the vertical axis shows the error (g). The solid line 19 and 20 shows the + 3 [sigma] and -3σ value of the error at each load. A broken line 21 indicates a region where the error is 3%. The figure shows that the conversion error is 3% or less over the entire region. This value indicates a level at which there is no practical problem when used in a cooker such as a microwave oven, and according to the present invention, a good approximation is shown over a wide load range.

The load conversion method of the present invention uses two reference load values.
Difference between sensor characteristic values (X0, X1) at (W0, W1), dX
= X1-X0, each coefficient value of weight conversion formula consisting of cubic formula
Is strongly correlated, as shown below.
It takes advantage of the fact that it is represented by a simple linear function.

For example , when mass-producing a large number of weight sensors,
When the weight conversion formula is given, the output values X0 and X1 of the weight sensor at two preset reference loads, for example, the zero point (W0) and the 1 kg point (W1) are actually measured, and the values are used. Using the relationship of the simple linear function shown in the above, each coefficient value ratio (A (2) / A (3)) and (A (1) / A (3)) of the cubic expression of each weight sensor are calculated. From the simple linear function (solid lines 22 and 23 in FIG. 4), the following (Equation 4) is obtained as a weight conversion formula.

[0026]

(Equation 4)

Here, X is the characteristic value of the weight sensor, (A (2)
/ A (3)) and (A (1) / A (3)) indicate the coefficient value ratio of the known cubic equation obtained from FIG. Therefore, the third order coefficient A (3)
And the constant term A (0) become unknown, and (Equation 4)
Can be easily determined from passing through the above two measured values and the reference load value.

FIG. 5 shows errors actually measured for about 1,000 weight sensors for which the weight conversion formula was determined in this way. The horizontal axis shows the load value W (kg), and the vertical axis shows the error (g).

The solid line 24 (○) represents the error of + 3σ for each load.
The solid line 25 (□) shows the -3σ value of the error at each load. A broken line 26 indicates a region where the error is 2%. From the figure, it can be seen that the conversion error is 2% or less over the entire area.

Since each coefficient value of the weight conversion formula is determined by a predetermined method according to the output value of the weight sensor under two reference loads, the conversion formula corresponding to each weight sensor over a wide load range. Which gives a better approximation,
A weight conversion value with a small conversion error was obtained.

(Example 2 ) The method of the present invention will be described below in order to reduce the conversion time required for weight conversion. Weight conversion formula consisting of polynomials, for example
For example, consider the case of a cubic equation. Assuming that a cubic equation for converting weight is given by the following equation 7,

[0032]

(Equation 5)

Here, (A3), (A2), (A1) and (A0) indicate the respective coefficient values of the cubic equation in terms of weight.

First, when converting the weight value from the output of the weight sensor, the output X1 of the weight sensor is substituted into (Equation 4) to obtain a converted weight value W (cal).

Thereafter, when the weight value is converted, assuming that the output value of the weight sensor is X2, a change value dX (= X2-X1) of the output value of the weight sensor is expressed by the following (Formula 6). The calculation is performed using the differential coefficient (dW / dX) of 5).

[0036]

(Equation 6)

By substituting X1 for X in (Equation 6), the differential coefficient (dW / dX) at X1 is obtained. In this case, the differential coefficient (dW / dX) is treated as one constant.

Therefore, the change weight value dW is given by the following simple expression (Equation 7).

[0039]

(Equation 7)

This (Equation 7) is a multiplication of two numerical values. Further, the converted weight value is obtained as the sum of the weight value W (cal) obtained first and dW.

That is, W = W (cal) + dW. As described above, when the weight value is first converted, the initial weight value is calculated over time using the characteristic value of the weight sensor and a higher-order approximation formula. The change in the weight value can be calculated by a simple multiplication process of the change amount of the characteristic value of the weight sensor and the differential coefficient. Therefore, when processing is performed by a microcomputer or the like, the calculation time is greatly reduced.

FIG. 6 shows an error comparison between the result calculated from the cubic equation and the result based on the differential coefficient described in this embodiment. In the figure, the horizontal axis shows the weight value changed from the initial weight value, and the vertical axis shows the error when converted using differential coefficients.
Solid lines 27, 28 and 29 have initial weight values of 50 g, respectively.
The results for 2 kg and 5 kg are shown. Even with the largest error of 5 kg, the error was 5 g or less. That is, when the initial weight value was 5 kg and the true weight change was 100 g, the error was 5 g or less. When applied to automatic cooking with a cooker such as a microwave oven, the level was practically no problem.

Example 3 A heating cooker such as a microwave oven is equipped with this type of weight sensor, and when cooking is controlled by a change in the weight of food, for example, when rice is cooked for warming, rice is cooked. As it is warmed, steam is generated from the rice and its weight is reduced. If you stop cooking when it becomes lighter, the rice will be warmed to a reasonably good temperature. At this time, since the progress of cooking in the microwave oven is very fast, it is necessary to quickly detect the weight of the food being cooked. Therefore, if a higher-order weight conversion value is used, the calculation takes a long time, so that a higher-order weight conversion formula with a small error may not be used. However, if the method using the differential coefficient described in the second embodiment can be used, the weight value can be converted in a short time. For this reason, the output value (X
Using s), the initial weight (Ws) of the food is converted into, for example, a higher-order (Equation 4). At this time, the slope Ks and the differential coefficient at the initial weight (Ws) in (Equation 4) are also obtained at the same time.

Assuming that Xt is a characteristic value of the weight sensor during cooking, the weight change dW is obtained by dW = Ks · (Xt−Xs). Note that (Xt-Xs) indicates a change in the characteristic value of the weight sensor.

As described above, even when a complicated higher-order weight conversion value is used, the weight change can be obtained by a simple multiplication linear equation as shown in the above equation. Therefore, the calculation time is short, and even in the case of quick cooking such as a microwave oven, cooking can be controlled using the weight change.

[0046]

As described above, the following effects can be obtained by the weight conversion method of the present invention and the cooking device using the method.

(1) Since a higher-order weight conversion formula consisting of a cubic formula is used, a load can be applied by one conversion formula over a wide load range.

( 2 ) A weight conversion formula corresponding to each weight sensor is provided in order to correct in accordance with each coefficient ratio of the higher-order conversion formula and the actually measured value based on the actually measured values at two reference points given in advance. Thus, a load can be applied more accurately with one conversion formula over a wide load range.

( 3 ) After the initial weight conversion, the weight change is converted using the differential coefficient of the conversion formula, so that the load can be converted in a relatively short time by a simple linear formula.

( 4 ) Since the conversion can be performed in a short time, cooking in a microwave oven or the like in which the cooking time is short can be controlled by changing the weight of the food.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of a weight sensor for explaining an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a weight sensor for explaining another embodiment of the present invention.

FIG. 3 is a diagram showing an error of a converted weight value according to the present invention.

FIG. 4 is a characteristic diagram of a weight sensor for explaining another embodiment of the present invention.

FIG. 5 is a diagram showing an error of a converted weight value according to the present invention.

FIG. 6 is a diagram showing a relationship between a changed weight value and an error according to the embodiment of the present invention.

7A is a plan view of a conventional weight sensor. FIG. 7B is a sectional view taken along line A-A 'of FIG.

8A is a plan view of a conventional weight sensor. FIG. 8B is a cross-sectional view taken along line B-B 'of FIG. 8A.

FIG. 9 is a characteristic diagram of a conventional weight sensor.

[Explanation of symbols]

 1, 2 Alumina substrate 3, 4 Electrode 5 Peripheral part 15 Tertiary weight conversion formula 16 Secondary weight conversion formula

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI G01G 19/52 G01D 3/02 N (72) Inventor Seiichi Yamashita 1006 Ojidoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference Document JP-A-1-267424 (JP, A) JP-A-63-151824 (JP, A) JP-A-1-302123 (JP, A) JP-A-63-1929 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G01G 3/00 G01G 23/01 G01G 23/37 G01G 19/52

Claims (3)

(57) [Claims] When mounting a weight sensor on a cooking device,
The relationship between the characteristic value (X) of the weight sensor and the weight value (W) is 3
The following equation, W = F (X) = A (3) · X∧3 + A (2) · X∧2 + A (1)
It is assumed that X∧1 + A (0) is approximated, and a predetermined 2
Characteristic value of the weight sensor at two reference weight values (W0, W1)
Using the difference (dX = X1-X0) of (X0, X1), the third order
The ratio (A (2) / A (3), A (1) / A (3)) of each coefficient value of the equation is obtained in advance.
After determining using the obtained correlation, the remaining
The two unknowns (A (3), A (0)) are calculated using the two reference weights.
Calculated using characteristic values (X0, X1) with quantity values (W0, W1)
Weight conversion method which is formed by. Wherein the initial weight value in terms of weight by using the output values and weight conversion equation of the weight sensor when the weight in terms of initial, change value of the output value of the weight sensor when the weight converted from the next (d X)
And a differential coefficient (dW / dX) of a weight conversion formula, and a weight conversion method in which a weight is calculated from the initial weight value and the changed weight value by calculating a changed weight value. 3. The method according to claim 1 , wherein an initial weight of the food before the start of cooking or at the start of the cooking is detected by the method of claim 1 , and a change in the weight of the food during the cooking is calculated by the fine conversion of the weight in the initial weight calculation. A heating cooker converted from a coefficient and a change in the output value of the weight sensor.