JP2553637B2 - Microwave oven with bread kneading function - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rotation speed control of an electric motor, and more particularly to a turntable driving motor provided in a microwave oven with a bread kneading function.

Conventional Technology Conventional technology will be described with reference to FIG. FIG. 11 (a) is a structural diagram in the case of heating food by high frequency. The food 2 placed on the plate 1 is heated at high frequency by the high frequency output from the magnetron 3. At this time, the plate 1 and the food 2 are rotated in the heating chamber 5 by the rotation of the turntable 4, so that they can be heated uniformly. The rotation speed at this time is 5 to 6 rpm. The turntable 4 is connected to a rotating shaft 7 of a motor 6 at the bottom of the heating chamber 5, and is configured to follow the rotation of the motor 6. FIG. 11 (b) is a structural diagram when kneading bread. Kneading the bread ingredients 9 in the bread case 8
Knead using 10, the kneading rod 10 is connected with the kneading shaft 11 that penetrates the hole at the bottom of the heating chamber 5, and the kneading shaft 11
Is rotated according to the rotation of the motor 14 by the pulley 12 and the belt 13, and the kneading rod 10 in the pan case 8 is rotated. The rotation speed at this time is about 300 rpm, and the turntable 4
60 times faster than the number of revolutions.

Problems to be Solved by the Invention However, the conventional structure has the following problems. First, there must be a large hole for penetrating the bottom of the heating chamber into two shafts, the shaft 7 to which the turntable 4 is attached and the kneading shaft 11 to which the kneading rod 10 is attached. Therefore, a complicated mechanism such as a choke structure must be provided at the bottom of the heating chamber, resulting in an increase in the outer shape of the entire cooking device, particularly in height, which does not meet the recent demand for space saving. Secondly, a dedicated motor is required for each of high-frequency heating and bread kneading, which is disadvantageous in terms of space saving and cost merit. Thirdly, since it is necessary to control two motors individually, two control circuits are required, and since the number of semiconductor components is increased due to the increase in complexity, the reliability of the system is reduced and the two control systems are required. The cost was high as much as it was, and users could not use cheap products.

The present invention solves such a conventional problem, and an object of the present invention is to provide a user with a cheap, space-saving and highly reliable microwave oven with a bread kneading function.

Means for Solving the Problems In order to achieve the above-mentioned object, a microwave oven with a bread kneading function of the present invention includes a single motor, a rotation speed detecting means for detecting the rotation speed of the motor, and a control rotation of the motor. Selection means for selecting either one of the low speed rotation speed of about 1/60 compared to the steady rotation speed, a start key for inputting a cooking start command, and a multi-step output setting means for the motor When the low speed rotation control is performed, the control unit starts rotating the motor with a power input of the lowest step at the time of input of a start key, and the rotation speed detecting means causes the motor to rotate at regular intervals. If the rotation speed is low due to the low speed rotation, the power input is increased step by step, and the power to the motor is exceeded when the preset forward and backward low rotation speed is exceeded. Stop to higher force setting, and configured to secure the subsequent power setting in the previous power setting that exceeds the low-speed rotation speed.

Action The microwave oven with a pan-kneading function of the present invention, which is composed of one motor and one shaft, eliminates the need for the conventional complicated choke structure, and saves a considerable amount of space, including the fact that one motor can be eliminated. Can be expected. In addition, the cost is low and the number of parts of the control unit can be reduced, so that the reliability is much higher than the conventional one.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 (a) is a sectional structural view of a microwave oven with a kneading bread according to the present invention. Rotate the motor 17 to the pulley 12
And convey to shaft 18 by belt 13. When heating food at a high frequency, the turntable 4 shown in FIG. 2 (b) is attached to the shaft 18, and when kneading bread ingredients, the kneading rod 10 shown in FIG. 2 (c) is attached to the shaft 18. The food in the heating chamber 5 is heated by the magnetron 3 at high frequency, and is electrically heated by the upper heater 15 and the lower heater 16. Further, reference numeral 32 is a rotation speed detecting means for detecting the rotation speed of the motor 17 by a combination of the disk 34 having a slit and the photo interrupter 35.

Fig. 3 shows the front operation part of the microwave oven with bread kneading according to the present invention. The user selects the "bread" key 19 when making bread, sets the ingredients and equipment for making bread and presses the "start" key. When you press 21, the bread kneading operation starts first. On the other hand, when performing high frequency heating, the "range" key
Select 20 and set the heating time with the timer knob 22, put the food in the heating chamber and press the "Start" key 21 to start high frequency heating. Further, by using the "cancel" key 23, it is possible to instruct to cancel the setting of the category or the cooking time or stop the cooking.

FIG. 4 is an electric circuit diagram of a control unit of the oven for baking bread according to the present invention. Capacitor motor 17 by outputting the pan connector (hereinafter referred to as microcomputer) during the microcomputer 26 the output port O _3, O ₄ alternately 50 / 60Hz power phase gate signal synchronized with the signal directional thyristor 27 - 28 Repeat forward and reverse. This will be described with reference to the timing chart of FIG. 4th AC 100V signal
The power supply signal conversion circuit 31 shown in the figure converts the DC waveform and outputs the H output from O ₃ during forward rotation and O ₄ during inversion at the zero-cross timing read from the I ₀ port of the microcomputer 26. 17 can be forward / reverse. At this time, almost 100% of the electric power is applied to the capacitor motor 17, so when kneading the capacitor motor
The 17 rotates at 1800 rpm (at 60 Hz). Pulley 1 in Figure 2
Due to the 2 ratio, the number of rotations of the shaft 18 is then 1/6, ie, 300 rpm. Next, motor control during high frequency heating will be described. Since foods and containers containing foods are placed on the turntable 4 in FIG. 2, it is necessary to rotate the turntable 4 at a considerably lower rotation speed (about 5 to 6 rpm) than 300 rpm when kneading the bread. . Therefore, 5 to 6 rpm is realized by supplying a low power to the condenser motor 17. This will be described with reference to the timing chart of FIG. The microcomputer 26 of FIG. 4 converts the signal of AC100V into the power signal conversion circuit 31.
It is converted into a DC waveform by and is read at the I ₀ port, but in order to make the energization to the capacitor motor 17 low power, it is energized for a half cycle and then not energized for a constant cycle (in FIG. 6, half cycle 4
One), repeat this all the time. Hereinafter, this is referred to as pulse extraction control. As a result, the power input to the capacitor motor 17 drops to about 20%, but in order to further reduce the power, the timing of outputting the gate signal to the phase directional thyristor 27, that is, the H signal of the O ₃ output of the microcomputer 26 is set. It is intentionally delayed by several tens of degrees instead of near the zero crossing of the power supply phase. The conduction angle control (hereinafter referred to as phase control) to the condenser motor 17 can be set in about 20 steps in 9 steps (FIG. 7). By combining this phase control and pulse extraction control, it is possible to perform fine control with low power to the capacitor motor 17. However, for the condenser motor 17, since the low power input is about 10% of the normal input, the torque is originally insufficient, and load (food weight) fluctuations and AC10
The rotation speed of the turntable easily fluctuates due to fluctuations in 0V voltage, fluctuations in belt tension and temperature, fluctuations in the position on which food is placed (known as unbalanced load).

On the other hand, when the condenser motor 17 is controlled at an ultra-low speed of about 5 to 6 rpm by the combined control of the phase control and the pulse extraction control as described above, the relationship between the power input to the condenser motor 17 and the rotation speed is as shown in FIG. It has the characteristics shown in the graph. For example, under condition A, when the AC100V voltage drops to 85V and the weight of food, that is, the load is 500g, and the power is gradually increased from 0, the turntable rotation speed is once 5 rpm.
It stabilizes in the A1 range, and when the power is further increased, the rotation speed suddenly becomes 60 rpm, which is unusable as a turntable on which food is placed. Even when the conditions are changed such as the conditions B and C, there is a stable region such as B1 and C1 of about 4 to 6 rpm. This shows the same characteristics even when the temperature, the strength of the belt tension, and the eccentric load are changed in addition to the change of the AC100V voltage and the load. That is, there is a stable region at 4 to 6 rpm. Therefore, this stable region is called the first stable rotational speed region. This 4 to 6 rpm is the optimum turntable rotation speed during high frequency heating. Since the rotation speed ratio (pulley ratio) between the turntable and the condenser motor is 1: 6, the turntable has 4 to 6 rpm.
At that time, the condenser motor is at 24 to 36 rpm.

Therefore, the number of rotations of the condenser motor 17 is detected by the combination of the disk 34 with slits and the photo interrupter 35 in FIG. 2 and the power input to the motor is optimized according to the conditions, so that the first The configuration is such that the motor can be controlled in the stable rotation speed range. That is, the fourth
In the figure, the microcomputer 26 enables the photo interrupter 35 to detect the number of revolutions of the condenser motor 17, so that the condenser motor 17 can be driven with a power according to an unbalanced load during high-frequency heating, voltage / load / temperature variation, and belt tension variation. Can be operated, and the turntable can be rotationally controlled at 4 to 6 rpm which is the first stable rotational speed region.

On the other hand, in FIG. 4, the rotation speed detection input of the condenser motor 17 input to the I ₁ port of the microcomputer 26 is the turntable 4 of FIG. 2 when the turntable is to be rotated at 5 to 6 rpm by high frequency heating. Play and pulley 12 for mating with shaft 18
Backlash of the belt and the belt 13, and the condenser motor 17
The frequency fluctuates considerably due to the rotation irregularity of itself (which occurs when trying to rotate at low speed with low power). This is shown in FIG. Moreover, the speed response of the capacitor motor 17 is also poor. That is, it takes 1 to 2 seconds to change the power input to the condenser motor 17 and respond to near the constant rotation speed. Further, in FIG. 2, this microwave oven is provided with a saucer 1 placed on a turntable 4, and the weight of the food 2 placed on the saucer 1 is measured. The weight sensor 36 for detecting the weight of the food 2 is provided at the lower part of the shaft 18 according to the movement of the food 2. By detecting the weight of the food 2, the optimum cooking of the food 2 is realized. are doing. In order to reduce the error due to the mechanical catching of the shaft 18 and the error due to the position where the food 2 is placed when detecting the weight, the turntable 4 is set to 1 when the user inputs a cooking start command. The weight is detected while rotating from / 4 cycle to 1/2 cycle, and heating is started after the weight is detected.
Therefore, in order to detect the weight and start heating as soon as possible after inputting the start command, it is necessary to quickly start the rotation of the turntable to a predetermined rotation speed (about 5 to 6 rpm). On the other hand, when trying to control the rotation speed of the capacitor motor 17 at an ultra-low speed, the I ₁ port input of the microcomputer 26 in FIG. 4 is counted at a relatively long time interval due to the poor response of the capacitor motor 17, and based on this count (That is, feedback), it is necessary to gradually change the power input setting to the condenser motor 17 to control the change to the predetermined rotation speed.

Therefore, in order to satisfy the above contradictory contents, the control is performed as shown in FIG. That is, after the start command is input from the user, power 16 which is a relatively large output is supplied to the capacitor motor for t ₁ hours (for example, 0.5 seconds) to start the rotation of the capacitor motor, and then t ₂ hours (for example, 1.5). A relatively short time t ₃ (for example, 0.5 seconds) in order to provide a rest period (a period for stabilizing the rotation) with a relatively low power of 2 seconds) and then to quickly start the rotation of the capacitor motor to the minimum allowable rotation speed. Each time the power setting is increased by several steps, the microcomputer detects the rotation speed of the condenser motor obtained from the rotation speed detection means every t ₃ hours, and when it reaches the minimum allowable rotation speed of 3 rpm (power 6). in turn will raise slowly power setting by one step every relatively long time t ₄ as compared to t ₃ (eg 2 seconds), the power setting upon reaching a predetermined rotational speed 4-6 rotation A constant (power 10 in the graph of FIG. 10 (b)). In other words, since the weight detection is performed quickly after the start, the rotation of the condenser motor is started in a short time unit, the rotation speed that does not interfere with the weight detection and the rotation speed that does not cause uneven heating in cooking performance 3 rpm. Where
The power input to the capacitor motor is set for each long time unit. FIG. 10 (a) is a graph showing changes in the number of revolutions converted based on the number of pulses read by the microcomputer at regular intervals. Since it exceeded 3 rpm at 4 seconds from the start, the power is increased by one step every 2 seconds.
When it goes up, the target rotation speed exceeds 6 rpm at 14 seconds after the start when the power becomes 11. Thus power
With a power of 10 lower than that of 11, the load (weight of food, etc.) at this time is fixed thereafter, that is, controlled in the first stable rotation speed range. The following evaluation is a table showing the setting of the pulse extraction ratio and the conduction angle at each power stage.

A flow chart of these operations (control method) is shown in FIG. As shown in the figure, start cooking (step
In (101), determine whether it is high frequency heating, bread kneading, or other cooking such as oven heating, and (steps 102, 10
3) If there is any other heating, the motor will not rotate (step 10
4) If the bread is kneaded, the motor is rotated at full power until the end of kneading (steps 105 to 107). If it is high frequency heating, first input the high power 16 steps to the condenser motor for t ₁ hour, and ( Step 108,109), then input low power 2 for t ₂ hours (step 110,111), then 3
The power is increased by one step every t ₃ hours until the rpm is exceeded (steps 112 to 114), and after the rpm is exceeded, the rotational speed is judged every t ₄ hours (about 2 seconds) until the rpm is exceeded 1 The power is gradually increased step by step (steps 115 to 117).
When the speed exceeds 6 rpm, the power is set to one level lower (step 118), and the cooking is continued until the cooking is completed.
That is, the power is set and fixed so as to be in the first stable rotation speed region of the condenser motor, and the turntable is driven at the first stable rotation speed (step 119). With the heating cooker, the following effects can be obtained.

(1) Since one motor and one shaft can satisfy both the rotation at the time of pan kneading and the rotation of the turntable, it is complicated to prevent radio wave leakage from the hole through the shaft penetrating the bottom of the heating chamber. The need for a choke structure is no longer necessary, and it is possible to expect considerable space savings in addition to being able to originally use two motors.

(2) It is possible to achieve stable rotation of the turntable at 4 to 6 rpm during high-frequency heating while satisfying 300 rpm for kneading with one motor, which is extremely cost-effective.

(3) Since there is only one motor, only one control circuit is required for the motor, so the number of parts such as semiconductors used in the control circuit can be reduced, which increases the reliability of the control system (reduces failure). The motor drive can be realized with a low-cost control circuit.

(4) Since the rotation of the turntable quickly rises to a predetermined number of revolutions after the start of cooking, even in a cooker having a built-in weight sensor and a means for detecting the weight of food, the weight can be measured quickly after the start and the cooking time can be reduced. The cooking efficiency can be improved because the heating can be controlled according to the weight of the food.

(5) Since the rotation of the turntable rises to the specified number of rotations quickly after starting cooking, when heating a small amount of food, the heating time is short, but high frequency heating with less heating unevenness is realized by taking advantage of the turntable. it can.

(6) In a single motor, despite the fluctuation of AC100V power supply voltage, temperature, load, belt tension, and unbalanced load, the rotation speed is stable at an ultra-low speed of about 1/60 of the steady speed. It became possible to control.

[Brief description of drawings]

FIG. 1 is a control flowchart of an electric motor according to an embodiment of the present invention, and FIGS. 2A to 2C are cross-sectional views of a microwave oven provided with the electric motor according to an embodiment of the present invention and perspective views of parts. 3, FIG. 3 is a front view of the operation unit, FIG. 4 is a circuit diagram of the control unit, FIG. 5 is a timing chart showing motor control at the time of bread kneading, and FIG. 6 is motor control at the time of high frequency heating. 7 is an explanatory view showing the method of phase control of the motor, FIG. 8 is a graph showing the relationship between the power input to the motor and the number of revolutions during ultra-low speed operation, and FIG. 9 is Microcomputer I ₁ input waveform (feedback output circuit waveform) diagram, Fig. 10 (a) is a characteristic diagram showing the change in the number of revolutions of the motor from the high frequency heating start, and Fig. 10 (b) is the motor from the start Explanatory diagram showing changes in input power setting to the 11 (a) and 11 (b) are sectional views of a conventional microwave oven. 1 ... saucer, 2 ... food, 3 ... magnetron, 4 ...
… Turntable, 5 …… Heating room, ………… Kneading rod, 17
...... Capacitor motor, 18 …… Axis, 26 …… Microcomputer, 31
...... Power supply signal conversion circuit, 32 …… Rotation speed detection means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuaki Soi, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Katsunori Harima, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial (72) Inventor Akihisa Takano 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshio Mimoto 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56 ) References JP-A-59-34233 (JP, A)

Claims (1)

(57) [Claims] 1. A single motor, a rotation speed detecting means for detecting the rotation speed of the motor, and a steady rotation speed of the control rotation speed of the motor and about 1/60 of the steady rotation speed. The control unit is provided with a selection unit for selecting one of low speed rotation, a start key for inputting a cooking start command, and a control unit having a multi-stage output setting unit for the motor. At the same time, start the motor with a low power input of the lowest step along with the input of the start key,
When the rotation speed of the motor is input from the rotation speed detecting means at regular intervals and the rotation speed is lower than the low speed rotation speed, the power input is increased step by step until the preset low speed rotation speed is exceeded. Then, the microwave oven with a bread kneading function is configured such that the setting of the power input to the motor is stopped to be increased, and the power setting is fixed at one previous power setting exceeding the low speed rotation number.