JPS6349633A - Weight sensor added heat cooker - Google Patents

Abstract

PURPOSE:To prevent the measuring error of weight due to the change of temperature as well as an offset error due to the contamination or the like of a food, by a method wherein the weight is reset to a new zero point of weight when a weight, detected by a weight sensor circuit, is continuously within a predetermined range and minute weight change, less than a predetermined time and the predetermined amount. CONSTITUTION:When the ambient temperature of a weight sensor element 26 and an interface circuit 8 is risen, the frequency of the output signal of the circuit 8 is changed by the temperature drift thereof. When heating for cooking is effected, the food is put on at a temperature A, however, the weight is higher than the upper limit Wphig allowable for resetting, therefore, the function of resetting is not operated thereafter even when a minute fluctuation of the weight is continued between temper A and B for a predetermined time. According to this method, a measuring error due to a temperature drift is generated between the temperatures A and B, however, the phenomenon of mistaken resetting of the change of the weight, which is due to the evaporation of moisture in the food upon heating, will never be generated. When cooking is finished at the point B and the food is taken out, an error weight Werr due to the temperature drift generated between the temperatures A and B remains. However, when the weight-Werr is lower than the weight Wphi, the weight is reset to a new zero weight point after a predetermined time has elapsed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat cooker with a weight sensor that detects the weight of food and realizes optimal cooking corresponding to the weight.

BACKGROUND OF THE INVENTION In a general heat cooker with a weight sensor, the temperature of the atmosphere in the sensor section and the detection circuit that detects the output from the sensor changes depending on the heat source during cooking. An even bigger factor is the change in temperature throughout the four seasons, which varies by region or installation environment, but is extremely large, ranging from 0 to 36 degrees Celsius. Due to this temperature change, the output value of the sensor and detection circuit inevitably changes due to temperature drift. In order to compensate for this temperature, it has been very common to use a temperature-sensitive resistance element such as a thermistor.

Problems to be Solved by the Invention However, in the case of such temperature compensation, it is impossible to compensate for the tolerance of the temperature characteristics of the temperature drift of the sensor element itself and the components of the electronic circuit that constitute the detection circuit. Can not. In other words, 11 parts people and 29 people and 5 people...
..., An, and the tolerance for each temperature change is A1±d11 people2±d2. A3±d3+・・・・・・
, mn±dn, the total temperature characteristic person tota
l is Atota1= (person 1+A2+person s −...+An)
±m digits = 17, and even if -(person 1 + person 2 + person 3 ・
・・・・・・Temperature compensation is performed by selecting a temperature sensing element with the opposite temperature characteristic of 10 people n).Even if ±m=,,,,,a
The A- variation will still exist. In this regard, it was necessary to select components with a small temperature tolerance for temperature drift for each component, which was a huge problem in terms of cost. However, even if parts were selected, it was impossible to completely eliminate this variation.

In addition, there have been other problems such as food or water remaining on the food plate due to boiling over during continuous cooking, and food sticking to the food plate over time, causing the zero point of the weight to shift.

The present invention solves these conventional problems, and eliminates weight measurement errors caused by temperature changes and offset errors caused by food stains, etc., and provides a zero point correction function that is optimal for a heating cooker. It is.

Means for Solving the Problems The heat cooker with a weight sensor according to the present invention detects the problem when the weight detected by the weight sensor and the weight sensor circuit that processes its output signal is less than a predetermined weight and a minute weight change continues for a predetermined time. The weight is reset to a new Og weight point.

action The weight sensor-added heat cooker of the present invention is suitable for cooking and heating.

If the offset component caused by a change in temperature or residual food is less than a predetermined weight, the reset operation is limited to when a minute weight change continues for a certain period of time within the predetermined weight range. There is no phenomenon of erroneously resetting the transient state during loading or unloading, and only the desired offset component can be reliably reset.

EXAMPLE Hereinafter, a weight sensor-added heat cooker according to an example of the present invention will be described with reference to the drawings. FIG. 3 is a perspective view from the front of the weight sensor-added heat cooker, and FIG. 4 is a simplified configuration diagram showing the overall simple configuration.

1 is a door that can be opened and closed to place food, 2 is a key power section for selecting any cooking category and start/end of cooking, 3 is food, 4 is a heating chamber for storing food, 5 is a turntable that can be rotated to place food and heat it uniformly; 7 is a weight detection unit that converts the load of the food 3 transmitted to the shaft 6 of the turntable 6 into capacitance; be. The capacitance output by the weight detection section 7 is converted by the interface circuit 8 into a frequency, which is a physical quantity that can be analyzed by the microcomputer 9. The microcomputer 9 has various functions, including a main control function that controls the entire system of the main body, a counter function that detects the frequency of the signal from the interface circuit 8, a function that calculates weight from the detected frequency, and A/D conversion. Performs a variety of functions and tasks in a timely manner.

13 is a high-frequency oscillation tube magnetron that supplies high-frequency energy into the heating chamber 4; 14 is a high-voltage direct 5FF for driving the magnetron; a magnetron drive circuit that generates voltage; and 15 is a commercial power source.

Microcomputer 9 turns relay 12'i ON, OFF
The output of the magnetron 13 is controlled to adjust the degree of heating of the food 3.

FIG. 5 is a sectional view from the side of the heat cooker with weight detection function, and FIG. 6 is a partial sectional view of the weight detection section from the front of the apparatus. The load of the food 3 is concentrated in the thrust direction of the shaft 6 through the shaft 6 by the action of a donkey pal mechanism, which will be described later. This is a technique already known in the field of weighing. Donkey pal mechanism 16
Parallel holding bracket 17, donkey pal mechanism mounting bracket 18
, the movable metal fittings 19 and the movable fittings 19 are connected to each other with an appropriate clearance by a donkey pal connecting shaft 20 so that the connected parts can slide smoothly. A metal fitting 18 for mounting the donkey pal mechanism is fixed to the bottom of the heating chamber 4 as shown in the figure. Therefore, the movable metal fitting 19 can freely move in the vertical direction. A shaft 6 passes through the movable fitting 19 that can move in the vertical direction, and a part of the movable fitting 19 (the attached bearing is attached to the base 2
For the purpose of rotating the turntable 5 and eliminating uneven heating, a gearman 23 attached to the turntable motor 22 rotates a gear B24 attached to the shaft e. The table 5 is configured to rotate. The load transmitted vertically by the action of the donkey pal mechanism 16 is applied to the stopper 35 when an excessive weight is applied to the pressure point 2a fixed to the surface of the weight sensor element 26 via the damper spring 26. hits the mount base 31 and protects the sensor. Next, the structure and principle of the weight sensor element 26 will be described. Electrodes 29 formed on the surfaces of a pair of ceramic substrates 28 by screen printing or the like are opposed to each other at a minute interval by electrode spacers 30 made of glass or the like. and is fixed to the sensor base 31. Weighted points 27
The applied load causes the upper ceramic substrate 29 to bend and the distance between the electrodes 29 changes, so the distance between the electrodes changes depending on the magnitude of the food load, and the capacitance changes as an electrical property. become. This change in capacitance is led out to the external interface circuit 8 by the lead wire 32. Note that 33 is a metal sensor cover for reducing the influence of capacitance fluctuation due to externally floating capacitance. The load detected as capacitance in this manner is converted by the interface circuit 8 into a frequency, which is an electrical quantity that can be detected by the microcomputer 9. FIG. 7 shows a circuit diagram of the interface circuit 8. The configuration is an unstable multivibrator circuit consisting of an integrator circuit of operational amplifier OP1 and a comparator circuit of operational amplifier OP2.

Assume that the output of the comparator circuit is now at the 'H' level.Then, the output of the zener diode ZD is transmitted through the resistor R6.
1, current is supplied to Zn2, Zener diode Z
At D1, the voltage of the mermaid becomes a constant voltage vH. The voltage is applied to resistors R3, R4, and VRl.

The signal R is input to the inverting terminal of the operational amplifier OP1.

The output of this operational amplifier OP1 is negatively fed back by a capacitor consisting of a sensor element, and the inverting terminal is imaginary short-circuited to the non-inverting terminal connected to the ground potential. Therefore, when the operational amplifier OP2 outputs "H", the resistor RK becomes the resistor R3.
, VRl.

A constant current determined by R4 and R flows, and the potential at point B continues to fall. When the potential at point 0 reaches the ground potential, the comparator circuit is inverted and the output of operational amplifier OP2 is inverted and becomes L''. Then, a constant current flows through the resistor R in the opposite direction, repeating the same operation, and the mermaid generates a rectangular wave signal whose frequency is variable depending on the capacitance of C.Furthermore, this signal is passed through the resistor R6゜R6 and the switching transistor Tr.
+ ) The diode D1 for reverse voltage protection of the transistor converts the signal level to the microcomputer signal level and inputs it. The oscillation frequency f of the interface circuit is expressed by the L'" output of the comparator and the H output of the comparator. Therefore, the oscillation frequency changes due to a change in the capacitance of the weight sensor element 26 due to the food load. Figure 8 shows the relationship between the weight of the food and the capacitance of the sensor element, b shows the relationship between the capacitance of the sensor element and the oscillation frequency of the interface circuit 8, and C shows the relationship between the weight of the food and the oscillation frequency of the interface circuit 8. Show relationships.

C is weight W1 Frequency f, iL, and C are constants, w=a
The relational expression is f+c. Next, how this device calculates the weight will be explained according to the flowchart of FIG. 9. The microcomputer 9 has a built-in free-running counter that is operated by an external signal clock regardless of the work of the internal K and CPH.

This function is becoming very common as an optional function of microcontrollers as sensors are increasingly used. The free running counter here is a frequency counter that counts signals from the interface circuit 8 and detects the frequency.

Next, the algorithm will be explained. First, when the frequency counter is initialized and activated, the frequency counter starts operating by an external signal and stops after a second interval. The value of the frequency counter at this time is the frequency of the signal, and after being loaded into the calculation register X, the weight W is calculated by executing the calculation of w=ax+c. If the weight W is within the range of the predetermined weight -Wφg to +Wφg, the timer register is incremented, and if it is outside the range, it is reset. Therefore, the weight W of this timer counter is -W
It continues to be incremented as long as it continues to exist within the range of φg≦W≦Wφg, and at the nth time, by performing the c-w operation and setting it as a new C, the state at that time is changed to a state of zero weight. do. Next, the effects of this algorithm in actual use will be explained using FIG.

As shown in Fig. a, when cooking is performed, the temperature of the atmosphere around the sensor element 26 and the interface circuit 8 gradually rises. Due to the accompanying temperature drift, the frequency of the output signal of the interface circuit 8 changes as shown in Figure b, and as a result, a phenomenon appears as if a weight change had occurred, as shown in Figure 0. And after tnn is W
ng will drift to the zero point, and an error in Wng will occur when measuring the weight at that point.However, in the present invention, when the weight less than a predetermined weight changes slightly for a predetermined time, forced KIJ Because it is configured to be set, almost no errors occur.

Other examples will be explained using FIG. 2. Assume that heating by cooking is performed as shown in Figure a.

Although the food is placed at point λ, the weight is greater than the upper limit Wφg of the weight that is allowed to be reset, so the reset function will not work thereafter even if slight fluctuations continue for a predetermined period of time between temperatures A and B. As a result, a measurement error due to temperature drift occurs between A and B, but the phenomenon of erroneously resetting the weight change due to evaporation of moisture during heating of the food does not occur.

When the cooking ends at point B and the food is taken out, an error weight W6rr due to the temperature drift that occurs between A and B remains. However, if -Welrr is less than or equal to Wφ, it is reset after a predetermined period of time has elapsed and becomes a new zero weight point. The significance of the predetermined time here will be described. Assume now that the food plate 5 is not actually placed on it. The cook places food on the food plate 5 and places them on the placing table 34. This operation is likely to occur frequently. However, since it is impossible for the device to be placed in synchronization with the activation of the frequency counter shown in Figure 9, it is inevitably placed during an interval of t seconds, and the data for that period is transiently detected as less than the actual weight. Resulting in. There is a strong possibility that this transient weight will fall within the above-mentioned predetermined weight range, and if the transient weight value is reset without taking some duration into consideration, the reset amount will result in an error. Therefore, since errors are expected to occur frequently in this usage method, it is necessary to confirm whether or not to reset by confirming that a slight change in the acquisition time of at least 1 to 2 pieces of data has continued. It turns out that doing so is very meaningful in terms of eliminating such errors.

With the configuration described above, temperature drifts caused by environmental temperature changes such as changes in air temperature are successively corrected and zero.
No point deviation occurs. In addition, the error due to temperature drift that occurs during cooking is reset and returns to zero after a while after the food is taken out, so it is completely immune to the influence of temperature drift that occurs in heating cookers. No very reliable weight sensor can be provided.

Effects of the Invention As described above, the weight sensor-added heat cooker of the present invention resets the weight to a new zero weight point when the weight detected by the weight sensor circuit is within a predetermined range and a minute weight change continues for a predetermined time. Therefore, there is no problem of temperature drift occurring due to temperature changes throughout the seasons, causing the zero point to shift. Furthermore, even if the temperature rises rapidly near the weight sensor during cooking, the temperature returns to zero instantaneously from the moment the cooked food is taken out, so no problems occur even when the food is used continuously. In particular, in the past, it has been common to place weight sensors and their peripheral circuits in locations away from heat sources and where they are less likely to be affected by temperature. Because of this, it can be placed relatively close to the heat source and the heating chamber, making it possible to design the overall size of the main unit more compactly, which has great advantages not only in terms of temperature reliability but also in terms of appearance.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram showing the temperature compensation function of a weight sensor-added heat cooker according to an embodiment of the present invention, Fig. 2 is a principle diagram showing the temperature compensation function, and Fig. 3 is a principle diagram showing the temperature compensation function of the weight sensor-added heat cooker according to an embodiment of the present invention. FIG. 4 is a perspective view from the front of the cooking device; FIG. 4 is a simplified block diagram showing the structure of the weight sensor-added heat cooking device of the present invention;
The figure is a sectional view from the side of the weight sensor-added heat cooker of the present invention, FIG. 6 is a sectional view from the front near the weight detection part of the weight sensor-added heat cooker of the present invention, and FIG. 7 is a sectional view of the weight sensor-added heat cooker of the present invention. A circuit diagram of the interface circuit of the weight sensor-added heat cooker, FIG. 8 is a principle explanatory diagram showing the weight detection principle of the weight sensor-added heat cooker of the present invention, and FIG. 9 is a circuit diagram of the interface circuit of the weight sensor-added heat cooker of the present invention. It is a flowchart which shows the algorithm of frequency detection in a computer. 7... Weight detection unit, 8... Interface circuit, 9... Microcomputer. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 1 ridge) Shoulder; 7 number change emperor! Figure 2 Figure 3 Figure 5 Figure 6 Ward

Claims (1)

[Claims] a heating chamber; a heating means for heating food in the heating chamber;
A weight sensor that detects the weight of food; a weight sensor circuit that processes the output signal of the weight sensor to calculate the weight; and a control circuit that controls the heating means in accordance with the weight detected by the weight sensor circuit and performs automatic heating. Weight sensor-added heat cooking, comprising: a weight sensor circuit configured to reset the weight to a new zero weight point when the weight detected by the weight sensor circuit is within a predetermined range and a minute weight change of less than a predetermined amount continues for a predetermined time. vessel.