JP3403087B2 - Electromagnetic cooker - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic cooker for heating a cooking object by causing a cooking vessel to generate heat by induction heating, and in particular, to a component of an electric circuit. The present invention relates to a method for adjusting variation in heating power and switching element protection voltage caused by variation. 2. Description of the Related Art FIG.
FIG. 4 is a circuit block diagram of a conventional rice cooker shown in FIG. In this case, the method of adjusting the variation is such that the heating power applied to the pot (3) is adjusted so that the output of the input current detecting means (7) becomes constant. (D) The output of the input current detecting means (7) is compared with the output of the input current detecting means (8). When the output of the input current detecting means (7) is larger than the reference value, the on-pulse time is shortened and flows into the inverter circuit. Current, that is, the power consumed by the pan (3), and when the output of the input current detection means (7) is smaller than the reference value, the reverse operation is performed on the control means (11). In this prior art, the reference value of the reference value storage means is fixed. Since the voltage across the switching element does not exceed the limit of the element, the on-pulse time is limited in the same manner as described above so that the output of the element voltage detecting means does not exceed a certain level. Control method. However, the outputs from the input current detecting means (7) and the element voltage detecting means (9) are output from the structural parts constituting the main body, the input current detecting means (7), the element voltage detecting circuit (9), and the like. If there is some variation depending on the components that make up the control circuit, and if there is no adjustment means, the heating power and element protection voltage of each rice cooker will have characteristics that deviate from the design intention, and this is the original purpose. Precise control of the heating coil will not be possible. Conventionally, as a method of adjusting this variation, two semi-fixed resistors are used as shown in FIGS. 5A and 5B, and each is operated to operate the input current detecting means and the element voltage detecting means. It was common to adjust the sensitivity. As described above, in the prior art, in order to adjust this variation, a semi-fixed resistor for sensitivity adjustment is provided in each of the input current detecting means and the element voltage detecting means. Each was adjusted by mechanically changing the resistance value. A specific adjustment operation will be described with reference to FIG.
The stabilizing AC power supply (40) is connected to the cooker body (42) via the ammeter (41). First, adjust the semi-fixed resistor for sensitivity adjustment of the element voltage detection means to the maximum sensitivity so that it will not be controlled by high power when the power of the rice cooker is energized beforehand in the non-energized state. Keep it to a minimum. Next, the power supply voltage is adjusted to an appropriate voltage, a pan, which is an appropriate load, is set in the main body, and power is supplied to the electromagnetic cooker so that the rated output state to be adjusted is set. Next, when the sensitivity is reduced by operating the semi-fixed resistor for adjusting the element voltage sensitivity, the indicated value of the ammeter (41) is increased so that the power value corresponds to the voltage suitable for element protection. I do. [0009] This is adjusted so as to exhibit power higher by a fixed value than the rated power adjusted by the power control means. Next, when the sensitivity is increased by opening the sensitivity adjustment semi-fixed resistor for the input current, the indicated value of the ammeter (41) decreases, and the adjustment is completed by operating the target current to the target rated power. . As described above, in the conventional example, it is necessary to adjust the two semi-fixed resistors twice each one time. However, in such a method, it is necessary to provide a small hole or the like for allowing the semi-fixed resistor to be operated from outside, as shown in FIG. Also, care must be taken to prevent intrusion of water and dust, and a special jig (43) and a measuring instrument (41) are required for the adjustment operation. Further, since the semi-fixed resistor has a mechanical sliding portion, there is a defect that the adjustment is wrong due to a change with time, vibration, and mischief of a contact portion. The present invention eliminates the use of a semi-fixed resistor for sensitivity adjustment for adjustment, and provides a highly reliable adjustment means for an electromagnetic cooker in which variations are adjusted by a simple external input operation. It is. The present invention provides a cooking vessel made of a magnetic material, a heating coil for inductively heating the cooking vessel, an inverter circuit for supplying a high-frequency current to the heating coil, and an input current for detecting an input current to the inverter circuit. Detecting means, a switching element for switching a high-frequency current to the heating coil, element voltage detecting means for detecting a voltage applied to the switching element, an input current serving as a control reference for the heating coil, and an element of the switching element Reference value storage means for storing a reference value of voltage, comparison means for comparing reference values of the input current detection means and element voltage detection means, and on-time of the switching element in accordance with an output of the comparison means. Power control means, input means operated externally, and a reference value of an input current which is increased or decreased according to the output of the input means. The output value of the input means has an adjustment means for storing the reference value of the input current at that time and the output value of the switching element voltage detection circuit as a reference value in the reference value storage means, and when the adjustment means is in an unadjusted state, The central value of the variation of the output of the input current detecting means caused by the variation of the circuit components is stored in the reference value storing means in advance to a value lower than the rated value by a predetermined value. Further, when the adjusting means is in the non-adjusted state, the central value of the variation of the output of the input current detecting means, which is caused by the variation of the circuit components, is reduced by a predetermined value from the rated value. This is stored in advance in the reference value storage means. Embodiments of the present invention will be described with reference to the drawings. 1 is a circuit block diagram of an electric rice cooker which is an embodiment of the electromagnetic cooker of the present invention, FIG. 2 is a plan view of an operation panel, FIG. 3 is a characteristic diagram of a switching element voltage,
FIG. 4 is a flowchart showing the operation. (1) is a heating coil, (2) is a switching element of the heating coil, and (3) is a cooking vessel made of a magnetic material (hereinafter, referred to as a heating vessel) that generates heat by eddy current generated by an inverter current applied to the heating coil. And the cooked food is heated. (4) is an inverter circuit,
(5) is an AC power supply, (6) is a current transformer for capturing the heating power applied to the heating coil (1) in the form of a current,
(7) is an input current detecting means for detecting a current by the current transformer, and (8) is an input current detecting means (7).
Input current comparison means for comparing the output (c) of FIG. 5 with the input current reference value (d) of FIG. 5 stored in the reference value storage means (12) described later. (9) is the switching element (2).
Element voltage detecting means for detecting a voltage between the emitter (E) and the collector (C) of the IGBT, and (10) an output (a) of the element voltage detecting means (9) and a reference value storing means (1)
The element voltage comparison means (11) for comparing the element voltage reference value (b) of FIG. 5 stored in 2) with the input current comparison means (8) and the output of the element voltage comparison means (10). A power control means for controlling the switching element (2); a reference value storage means (12) made of a semiconductor such as a nonvolatile memory, for example; an input current serving as a reference for controlling the heating coil (1) and the switching element (2); Is stored. The heating power applied to the heating coil (1) is obtained by comparing the output (c) of the input current detection means (7) with the input current reference value (d) of the reference value storage means (12). The power control means (11) is controlled so as to decrease the output when the former is large and to increase the output when the former is small. The voltage between the emitter (E) and the collector (C) of the switching element (2) is detected by the element voltage detecting means (9), and the element voltage reference value (b) of the reference value storing means (12). ) Is compared with a reference value obtained by adding a predetermined value to the element voltage comparison means (8), and the control means (11) is controlled so as to decrease the output when the former is large and to increase the output when the former is small. As for the outputs of the input current comparing means (8) and the element voltage comparing means (10), when one of them is trying to lower the output, the one with the larger signal to lower the output takes precedence. When the signal is to be raised, arbitration is performed by the control means (11) so that the smaller the signal to be raised is given priority. FIG. 2 is a plan view of the operation panel, which is configured so that a current time, a reserved time, and a menu can be displayed on the liquid crystal display (20). (21) is a rice cooker key for instructing the start of rice cooker.
An ED (22) is displayed, (23) is an off key for stopping rice cooking and other operations, (24) is a warming key for starting warming, and an LED (25) indicates that warming is being performed.
(26) is a menu key for selecting a menu for cooking rice,
(27) is a reservation key for selecting reserved rice cooking using a timer.
Displayed in 8). (29) and (30) are an hour key and a minute key for changing the current time and the reserved time of the reserved rice cooking. Next, the operation of the program will be described with reference to FIG. First, in the rice cooker of the present invention, when the power is turned on for the first time, the contents stored in the reference value storage means (12) are checked, and when it is determined that nothing has been written yet (S
1) Write a predetermined input current target value and element voltage target value as default values to the reference value storage means (15) (S2). This default value is a target value when the variation of the components is all the standard value (Type) of the switching element voltage shown in the characteristic diagram of FIG. By doing so, the intended operation state can be achieved with a minimum correction value for individual variations in the rice cooker. If the default value is set to a value lower than the target value when the variation of the components is all the standard value (Type), the correction amount increases, but if the storage means is destroyed, However, it is possible to suppress the probability that the power varies or the protection voltage increases. Although the rice cooker of the present invention is not described in detail, the rice cooker key (21), the warming key (24) or the reservation key (2)
7) An operation mode (adjustment means) dedicated to adjustment is prepared separately from a mode (operation means) for operating the normal rice cooking function by operating the same rice cooking procedure. In this operation mode, the rice cooker key (21) is
When the button is kept pressed for two seconds (S3), a transition is made from the mode for executing the normal rice cooking function to the operation mode of the adjustment state for executing the operation mode exclusively for adjustment (adjustment means) (14: adjustment switching means). In this case, the rice cooking key (21) is an input means (e) for outputting an output signal (e) for executing an operation mode (adjustment means) dedicated to adjustment together with the hour key (29) and the minute key (30) as shown in FIG. 13). In the operation mode dedicated to adjustment, the default value written in the reference value storage means (12) is transferred to the control target (S4), and induction heating is performed according to the contents of the control reference value (S5). In the adjustment-only operation mode, the rated output to be adjusted is controlled to the input current reference value read from the reference value storage means (12). The input current reference value and a signal which is too large, too small or appropriate from the input means are received, and the target value is decreased by one step (S6), increased by one step (S7), and the control target is decreased. Reference value storage means (1
The operation of writing in 2) is performed (S8). In the present invention, the input signals are assigned to key inputs such that the hour key (29) is too large (S9), the minute key is too small (S10), and the reservation key is appropriate (S11). . When there is an appropriate input (S11), not only the operation (S8) of writing the control target into the reference value storage means (12), but also the output of the element voltage detection means (9) is stored in the reference value storage means (12). (S12), or exits from the adjustment mode to the normal rice cooking operation mode (S13). At this time, as the element voltage reference value stored in the reference value storage means, the element voltage at the time of output of the rated power is stored. As shown in FIG. 3, a specific adjusting method is to connect the stabilizing power source (40) of AC to the rice cooker (42) via the ammeter (41) as in the conventional adjusting operation. Constitute. Then, the rice cooker (21) on the operation panel of the rice cooker (42) is pressed for 3 seconds to make a transition to a special operation state in which adjustment is performed. In this state, the default control reference value is written in the storage means as described in the above-mentioned initial operation, and control is performed according to the target. Next, the hour, minute, and reservation keys (29), (3) are set so that the indicated value of the ammeter (41) becomes a predetermined current.
Adjustment is performed by operating (0) and (27). The device protection operation will be described with reference to the device voltage characteristic diagram of FIG. When the rice cooker of the present invention performs a normal heating operation, the output of the element voltage detecting means (9) is a predetermined value corresponding to the element voltage reference value at the rated output stored in the reference value storing means (12). It has been mentioned above that it is controlled by the added value. This predetermined value is a predetermined value that exhibits the same power as the “constant value higher power” described in the conventional example of adjusting the rated power. In the characteristic diagram, the element voltage at the time of rated power (h)
It is intended to control with a control target element voltage (R) which is higher than the element voltage (H) and a predetermined value is added. The control target element voltage (R) is an actual element limit voltage (N). The above-mentioned predetermined value is a value obtained by adding a predetermined value (a), (b) or (c) to (A), (I) or (U) obtained at the time of rated power output. It turns out that it becomes. Since (a), (b) or (c) can be approximated by a constant calculation, there is no need to adjust only the element voltage control reference value, and a constant calculation is performed on the output of the element voltage detection means at the rated output. Can be obtained by things. In this embodiment, the input means is performed by a key. However, when the operation panel name is not attached, a connector is provided so that electrical communication can be performed between the robot and the rice cooker. Instead of the mechanical operation of the operation, the adjustment may be performed only by completely electric communication processing. The adjustment by communication is a method which cannot be realized by the conventional adjustment method using a semi-fixed resistor, and shows the superiority of the possibility of the present invention. As described above, the present invention relates to an input current detecting means for detecting an input current to an inverter circuit, a switching element of a heating coil, an element voltage detecting means of a switching element, and the heating coil. A reference value storage means for storing an input current serving as a control reference and a reference value of an element voltage of the switching element; a comparison means for comparing reference values of the input current detection means and the element voltage detection means; and Power control means for controlling the on-time of the switching element according to the output, input means operated externally, and a reference value for the input current which is increased or decreased according to the output of the input means, and the output from the input means at that time Having an adjusting means for storing the reference value of the input current and the output value of the switching element voltage detection circuit in the reference value storage means as a reference value. Therefore, without using mechanical parts such as semi-fixed resistors, the characteristics including the variations of the components constituting the main body and the variations of the input current detection circuit and the element voltage detection circuit are stored in the storage means and adjusted. can do. In particular, it is possible to provide a safer product with no change over time in the circuit, no tampering, no opening for adjustment, and no change. In addition, as in the prior art, the semi-fixed resistor has a limited mounting position so that it can be operated from the outside, and the wiring tends to be long, so that there was a problem in reliability. . Further, since the output of the element voltage detecting means is controlled by a reference value obtained by adding a predetermined value to the element voltage reference value stored in the reference value storing means, it is possible to accurately perform the target control. it can. Further, there is provided an operating means for executing a function as a cooking appliance, and an adjustment switching means for switching an adjusting means to an adjustment state which is different from the operation for executing the function as a cooking appliance, wherein the operating means is used as the input means. Since the diversion can be performed, the adjustment operation can be performed by a simple key input from the outside instead of the rotation operation of the semi-fixed resistor, so that the adjustment is easy. By using the operating means of the adjusting means also as the input means, a special tool such as a driver is not required, so that the serviceability is improved and the user is not inconvenienced. Then, the center value of the variation of the output of the input current detecting means, which is caused by the variation of the circuit components when the adjusting means is in the non-adjusted state, is stored in advance in the reference value storing means at a value lower than the rated value by a predetermined value. As a result, the target control can be accurately performed by storing the control state including the variation unique to the main body. In addition, since a non-volatile memory is used for the reference value storage means, a structure for adjustment is not required, and it is resistant to aging and vibration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit block diagram of an electric rice cooker which is an embodiment of the electromagnetic cooker of the present invention. FIG. 2 is a plan view of the operation panel. FIG. 3 is a characteristic diagram of a switching element voltage. FIG. 4 is a flowchart showing the same operation. FIG. 5 is a circuit block diagram according to the related art. FIG. 6 is an explanatory view showing an operation procedure of adjustment according to a conventional technique. [Description of Signs] 1 heating coil 2 switching element 3 cooking vessel 4 inverter circuit 7 input current detection means 8 input current comparison means (comparison means) 9 element voltage detection means 10 element voltage comparison means (comparison means) 11 heating control means 12 Reference value storage means 13 Input means 14 Adjustment switching means 21 Cooking rice key (operation means, adjustment means)

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuo Tanigawa 3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori Sanyo Electric Co., Ltd. (72) Inventor Akio Arinaka 3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tori Tori Sanyo Electric Co., Ltd. (72) Inventor Yuji Saito 3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori Sanyo Electric Co., Ltd. (56) References JP-A-8-66302 (JP, A) JP-A-9 -245948 (JP, A) JP-A-2-270292 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A47J 27/00 103 A47J 27/00 104 A47J 27/00 109 H05B 6/12

Claims (1)

(57) [Claims 1] A cooking container made of a magnetic material, a heating coil for inductively heating the cooking container, an inverter circuit for supplying a high-frequency current to the heating coil, Input current detecting means for detecting an input current, a switching element for switching a high-frequency current to the heating coil, element voltage detecting means for detecting a voltage applied to the switching element, and an input serving as a control reference for the heating coil Reference value storage means for storing a current and a reference value of the element voltage of the switching element; comparison means for comparing the reference values of the input current detection means and the element voltage detection means; and the switching in response to an output of the comparison means. Power control means for controlling the on-time of the element, input means for externally operating,
The reference value of the input current is increased or decreased according to the output of the input means, and the reference value of the input current at that time and the output value of the switching element voltage detection circuit are stored in the reference value storage means as a reference value by the output from the input means. Adjusting means for adjusting the circuit components when the adjusting means is in an unadjusted state.
Of the output of the input current detection means
Set the variation center value to a value lower than the rated value by a predetermined value.
An electromagnetic cooker characterized by being stored in an initial reference value storage means .