JPS5912590A - High frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in the intermittent mechanism of the primary current of a transformer that applies high voltage to a magnetron for high frequency oscillation. For example, the primary-side disconnection device in a turntable-type high-frequency heating device uses a motor as the driving force for rotation of the turntable, and when rotating the food table using a transmission shaft that passes through the bottom wall of the heating chamber, the motor is Rotating at a commercial frequency increases the number of revolutions, and it is inconvenient to connect directly to a food table, so some devices have been implemented by attaching an on/off switch to the deceleration mechanism to reduce the speed to about 1 Orpm. Most of the switches use small so-called microswitches (push button type), and in order to turn on and off the main circuit of the microwave oven, an electrical rating of 12 to 1 eA is required. For this reason, this microswitch has a snap-action mechanism with a built-in reversing spring, and it is necessary to ensure sufficient pressure between the contacts to ensure durability even when a large current is turned on and off. Figure 1 shows this microswitch M.
It shows the change in pressure between the contacts when the S push button is moved. Normally closed contact of micro switch MS (N
Normally C1ose: When considering the NC) side, when the 3 vane push button is pressed, the contact pressure decreases), the reversal spring reverses around zero (point A), and the contact opens. At the moment of reversal, the contact pressure increases from 0 to d grams.

As the push button is pressed further, the contact pressure increases.

It is known that in the case of an AC power supply and a transformer load circuit, such as a microwave oven, an inrush current of about 10 times the steady current occurs when the switch is turned on, but when the pressure between the contacts drops below a certain level, It is easy to generate an arc current, which results in the inconvenience of welding between the contacts and shortening the contact life, but by using such a reversing mechanism, the area where the contact pressure is low is reduced. For large current microswitches, the pressure between the contacts immediately after reversal is required to be large, and for this reason, the operating force (○F) and return force (RF) must also be large, and the operating noise during reversal must be large. Along with this, the microswitch will inevitably become larger compared to a low current microswitch. When this is externally attached to the cam for operating the microswitch provided in the speed reduction mechanism of the turntable rotation motor, as shown in the circuit diagram shown in Figure 2, 1
The on/off switch on the next side repeats ON and OFF at all times while the magnetron cooling fan motor is in operation, regardless of the setting of the strength changeover switch. The impact noise caused by the reversal of the built-in spring and the operation of the push button was loud and harsh, which was inconvenient for use in a quiet kitchen.

As mentioned above, microswitches become unstable in terms of durability when the contact pressure between the contacts is low, so the time it takes for a switch to change from on or off using a cam to off or on is faster. is preferable, and therefore a mechanism for instantly releasing the push button when the switch is turned off can be considered, but it goes without saying that in such a case, the impact noise will further increase. In addition, since it is installed near the heating chamber, there is little air movement around the on/off switch due to the overall structure, and the heat generated by intermittent high-current energization is less likely to be radiated to the outside. This was not desirable in terms of the durability and life of the springs, etc.

Purpose of the Invention The present invention solves the above-mentioned drawbacks of the conventional switch.The operating noise of the primary on/off switch is low, so the user does not feel uncomfortable or anxious, and the cooling effect is good, so the temperature rise can be suppressed. The purpose is to realize a microwave oven equipped with a strength switching device that has excellent durability and safety.

Structure of the Invention In order to achieve the above-mentioned object, the present invention includes a food mounting table rotatably installed on the bottom of a heating chamber, a motor for rotationally driving the food mounting table via a deceleration means, and a first stage of the deceleration means. Belt transmission is used, a worm gear is used in the second and subsequent stages, and a microswitch for switching on and off the primary current of a transformer that applies high voltage to the magnetron and a plurality of reduction gears are installed in the housing housing the worm gear. The microswitch is arranged in a position where it directly receives the flow of cooling air from a magnetron cooling fan that supplies high-frequency energy to the heating chamber, and has a low-noise, highly durable output switching device. A heating device can be provided.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 1 is the main body of the heating chamber device, and 2 is a heating chamber provided within the main body 1, at least the bottom plate portion of which is made of a non-magnetic metal material. 3 is a door that covers the front opening of the heating chamber 2 so that it can be opened and closed; 4 is a magnetronon that supplies high-frequency energy into the heating chamber 2; and 7/djM is a food mounting table that is rotatably installed at the inner bottom of the heating chamber 2. A permanent magnet 9 supported by a holder 8 made of non-magnetic metal is provided on the lower surface, and a roller 1o is rotatably provided. 11 is food 12
The saucer 13 containing the heating chamber is a rotating body that also functions as a pulley and is rotatably mounted on a shaft 14 fixed at the center of the outside bottom of the heating chamber.
The upper surface is equipped with a driving magnet 15 corresponding to the permanent magnet 9, and is also equipped with a roller 16 that comes into contact with the bottom surface outside the heating chamber. 17 is a magnetron cooling fan motor;
18 is a worm gear that converts the rotational force of the motor 17 into 9g, and pulleys 21 and 22 are provided on each shaft 19 and 20.
A belt 26 is placed between the pulley 25 provided on the transmission rod 24 and the rotating body 13 to transmit the rotational force of the motor 17 to the rotating body 13. When the rotating body 13 having the driving magnet 16 rotates, the food mounting table 7 having the permanent magnet 9 rotates following this rotation.

27 is a micro switch for disconnecting the primary side, and worm 18
It is attached to a gear box 28 that houses the.

FIGS. 4(A) and 4(B) are external views of the gearbox, in which the vicinity of the terminal of the on/off switch 27 is exposed for wiring. Figure 6 (A+, (B) shows gearbox 2
FIG. 8 is a partial cross-sectional view showing the internal configuration of FIG. In CB+ of the same figure, the worm gear 18, which has received the rotation of the fan motor (not shown), transmits the rotation to the worm gear 29, and since it is fixed with the pin 3o, the transmission rod 24 rotates. A boo IJ-26 is provided at the bottom of the transmission rod (third
(see figure), move the food table inside the refrigerator via the belt. At the same time, the transmission rod 24 has a D-shaped tip (see FIG. 6 [Al)], and a spur tooth work glove 31 is fixedly attached thereto. The gear box 28 is made of resin with excellent heat resistance, wear resistance, oil resistance, etc. in terms of shape and function, and the shaft 32 on which the reduction gear slides is also integrally molded. In this example, the intermittent switch is on for 12 seconds and off for 18 seconds, so the transmission rod has a rotation speed of 600 rotations per minute, so the combination of gears has a rotation speed of 2760 (, rpm).
) = 1725 reductions/speeds are required. The spur gear 32 is not combined with a gear dog 33 that freely moves around the shaft 32, and the gear dog 33 is a two-stage gear, large and small. Combining 34. The middle gear 34 also has a two-stage shape, and the small teeth combine with a cam gear (hereinafter referred to as a cam) 35 that freely rotates around the shaft 32 to move the cam.

A lever 36 made of resilient metal is provided near the cam 35 and is rotatably supported by the gear box. The cam 36 rotates twice per minute, and the convex portion of the cam 36 pushes the lever 36 while rotating, and the tip of the lever pushes the push button 37 of the intermittent switch 27. cam 36
As the rotation progresses, the push button 37 is completely pushed in by the lever 36, and the switch 27 is activated. This operation is performed twice every minute. Reference numeral 38 denotes a lid that covers the upper part of the gear box 28 and is fixed to the gear box 28 by screws 39 in alignment with the on/off switch 27.

As shown in FIG. 3, the gear box assembly operating with such a configuration is installed at a position where it is constantly supplied with cold outside air sent out from a fan 40 assembled to a fan motor.

FIG. 6 is a graph showing the difference in the temperature rise value of the contact points when air is supplied by the fan 40 and when there is no air at all. The difference between these two lines shows that the cooling effect of the wind is large.If the actual usage time is 30 minutes, it can be seen that there is a big difference in the temperature reached between the two.

Effects of the Invention As described above, according to the present invention, since the intermittent microswitch is built into the gear box, the sound when the microswitch is operated and the impact noise of various parts when the push button is released can be suppressed. In addition, the wind from the magnetron cooling fan cools the area near the terminals of the on/off switch, so even when operating for a long time, the temperature of the contact area remains low, ensuring durability and safety. Also, while the on/off switch is operating, the sound source is in the wind flow, so
The wind noise/flowing sound and the impact sound from the switch cancel each other out, and as a result, the sound from the switch is alleviated.
It started to feel quite small. In addition, because the gearbox has components such as microsinches, gears, cams, and levers built-in, the grease used to keep each part warm and to muffle noise between gears is durable and of high quality. Long-term stability can also be guaranteed. In addition, since there is no need for a direct connection to the turntable motor, the dimensions below the bottom of the cooking cabinet can be reduced, making the entire product more compact, providing durability and safety for users. Since the abnormal noise is also small, it is possible to provide a high-frequency heating device that does not cause anxiety.

11 Beno

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between contact contact force, operating force, and stroke of a conventional snap-action microswitch, Fig. 2 is a circuit diagram of a conventional high-frequency heating device, and Fig. 3 is an embodiment of the present invention. Fig. 4 is a side cross-sectional view of a high-frequency heating device, which is a partially cutaway side view of Fig. 4 (B) of the same device, and Fig. 6 is a characteristic showing changes in temperature rise of the on/off switch of the same device. Fig. 2: heating chamber, 4: magnetron,
7... Food placing table, 27... Primary side intermittent micro switch, 28... Gear box, 36... Gear with cam, 40... ····fan. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 211ffl Figure 4 Figure 5

Claims (1)

[Claims] A food placing table rotatably installed on the bottom of the heating chamber, a motor for rotationally driving the food placing table via a deceleration means, a belt transmission as the first stage of the deceleration means, and a worm gear in the second and subsequent stages. The housing housing the worm gear is equipped with a microswitch for intermittent primary current of a transformer that applies high voltage to the magnetron, and a plurality of deceleration gears. The high-frequency heating device is configured to be placed in a position that directly receives the flow of cooling air from the magnetron cooling fan that supplies the magnetron.