JPH0332884Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a damper device that controls ventilation into the heating chamber of a microwave oven, and in particular, a damper device that opens and closes the damper by utilizing the shape change of a shape memory alloy coil spring. Regarding.

<Prior art> A damper spring made of shape memory alloy formed into a spring shape and used as a damper spring to drive a damper that opens and closes the opening of the heating chamber of a microwave oven has already been commercialized. The damper lid is closed by the urging force that returns to its original memorized shape by generating heat, but since shape memory alloys have very low resistance, it is necessary to apply a large current to generate heat.

However, if you apply 100V, it will generate too much heat and melt, so you can use a step-down transformer to lower the voltage and apply it, or use a positive temperature coefficient thermistor (PTC).
The solution was to connect thermistors (called thermistors) in series.

An example of the former will be described below based on the drawings. 3 and 4 are a schematic side sectional view and a schematic cross-sectional view of a hot air circulation type microwave oven showing an embodiment of the present invention, and FIG. 5 is a damper as seen from the direction of arrow A in FIG. 3. FIG. 6 is an exploded view of the main parts of the damper.

In the figure, reference numeral 1 denotes a hot air circulation type microwave oven consisting of a hot air circulation fan 4 disposed on the back side 3 of the heating chamber 2 and a heater 5 attached around the fan 4, and 6 denotes the heating chamber 2. 7 is a control panel on which keys for various operations are arranged. 8 is magnetron 9 and high voltage transformer 1
This is a cooling fan that cools electrical components such as 0. 1
Reference numeral 1 denotes an air introduction hole having a large number of small holes formed in the side wall surface 2' of the heating chamber 2, and a damper assembly 12 that covers the entire area of the air introduction hole 11 is connected to the heating chamber 2 by a damper mounting screw 13. Fixed. The external shape of the damper assembly 12 is a substantially triangular prism with three sides a, b, and c and a height h.
Rotating around the damper shaft 15, the opening 14 is opened in the rectangular opening 14 with side a and height h,
A protruding piece 17 of the damper lid 16 is attached to the damper lid 16 and is provided on the damper shaft 15.
As shown in FIG. 4, a bias spring 19 is attached between the damper assembly 12 and the protruding piece 18 of the damper assembly 12, which always biases the opening 14 in the direction of opening. Reference numeral 20 denotes an L-shaped angle fixed to the damper lid 16, and the terminal 22 fixing one end of the shape memory alloy coil spring 21 is held between insulating spacers 23 and 24 so as to be rotatable. A screw hole (not shown) into which a stepped screw 25 is screwed is provided. Reference numeral 26 denotes an angle formed integrally with the damper assembly main body 12, and is connected by insulating spacers 24 and 28 so that the terminal 27, which fixes the other end of the shape memory alloy coil spring 21, can rotate freely. A screw hole (not shown) into which the stepped screw 25 to be clamped is screwed is provided. The terminals 22 and 27 are caulked to electrically and mechanically fix the shape memory alloy coil spring 21, and an AC
A ground wire 30 and a lead wire 29 that supply power of about 3V and 3A are connected, and the ground wire 3
0 is connected to a ground terminal 31 attached to the damper assembly main body 12.

32 is a resin-molded first duct disposed around the outer periphery of the damper assembly 12, and a resin-molded second duct 33 which integrally holds and fixes the cooling fan 8 and cooling fan motor 8'. and the rear plate 1' of the hot air circulation type microwave oven 1. 34 is a ventilation path formed by the first duct 32 and the second duct 33;
The air passing through this ventilation path 34 is supplied to the rear plate 1'.
The air is discharged indoors through an exhaust louver 35 formed at the upper part of the air.

Although not shown, the lead wire 29 and the ground wire 30 are connected to the secondary winding side of the step-down transformer.

Next, an overview of the operation of the hot air circulation microwave oven having the above configuration will be explained.

First, when performing microwave heating, the magnetron 9, high voltage transformer 10, etc. are activated to irradiate the heating chamber 2 with microwaves, and the cooling fan 8
rotates, and the intake louver 36 formed around the high voltage transformer 10 as shown by arrow B in FIG.
The cooling air sucked through the exhaust louvers 35 passes through the ventilation path 34 and is discharged indoors from the exhaust louvers 35. On the other hand, during microwave heating, the lead wire 29 is connected to the secondary winding of the step-down transformer (not shown).
Since the shape memory alloy coil spring 21 is not connected to the side, the current supply to the shape memory alloy coil spring 21 is stopped.

Therefore, since the coil spring 21 made of shape memory alloy is not in a high temperature state, no biasing force is generated as a spring, and the damper lid 16 is moved in the direction of opening the opening 14 by the elastic force of the bias spring 19 described above. is maintained. Therefore, the cooling air that has passed through the opening 14 enters the heating chamber 2 through the air introduction hole 10, and serves to discharge gaseous components such as steam and gas generated from the food being heated to the indoor side.

Next, when heating the heater by stopping power to the magnetron and starting power to the heater,
AC is supplied from the lead wire 29 and ground wire 30, which are connected in parallel to the secondary winding (not shown) of the step-down transformer.
As power of about 3V and 3A is supplied to the shape memory alloy coil spring 21, the shape memory alloy generates heat, reaches a predetermined temperature within a short time, and quickly returns to its original shape with a biasing force in a high temperature state. Then, the damper lid 16 is rotated about the damper shaft 15 in the closing direction against the elastic force of the bias spring 19. Therefore, since the opening 14 is blocked, no cooling air is supplied into the heating chamber 2, so that the heating chamber is not cooled. In particular, it is possible to efficiently raise the temperature immediately after the start of hot air circulation cooking, in which heat from a heater is forcibly circulated within the heating chamber.

By the way, when the shape memory alloy 21 is directly energized and raised to a predetermined temperature, it maintains the memorized original state and functions as a spring, but even when the energization is stopped, other electrical components Due to the heat generated, it returns to its original shape slightly,
During microwave heating, the damper lid 16 may rotate and the opening area may decrease; however, the damper lid 16,
A damper assembly 12 made of a shape memory alloy coil spring 21 is connected to a first duct 32 and a second duct 33.
Since it is installed inside the ventilation path 34 surrounded by
During microwave heating, which requires the damper lid 16 to be open at all times, the cooling air always hits the shape memory alloy coil spring 21 in the same state, which has the effect of keeping the shape memory alloy coil spring 21 at a relatively low temperature. . Therefore, the temperature of the shape memory alloy coil spring 21 does not rise during microwave heating, and a stable state can be maintained without generating unnecessary biasing force.

<Problems to be solved by the present invention> However, a step-down transformer is required if the voltage is lowered and applied using a step-down transformer, and a step-down transformer is required if the PTC thermistor is connected in series. A current control PTC thermistor must be used to heat the small damper spring to an appropriate temperature, and as the initial (inrush) current of the PTC thermistor is large, a large current relay is required, which increases costs. There were flaws.

Further, the conventional damper device has a disadvantage in that its structure is not compact.

<Means for solving the problem> In a microwave oven damper device that opens and closes a damper by changing the shape of a coil spring made of a shape memory alloy, a positive temperature characteristic thermistor that indirectly heats the coil spring made of a shape memory alloy is attached to the coil spring. Placed in a hollow part.

<Operation> Since the shape memory alloy coil spring is heated by the indirect heating of the positive temperature coefficient thermistor disposed in the hollow part of the coil spring, the initial (rush) current is small, and a small current relay is not required. can be used. Furthermore, since the positive temperature characteristic thermistor is disposed in the hollow portion of the coil spring, the structure of the damper device becomes compact.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a diagram corresponding to FIG. 5 of the conventional example, and FIG. 2 is a sectional view of the shape memory alloy coil spring portion as seen from the direction of arrow C in FIG. Incidentally, the same or equivalent parts as in the conventional example are given the same reference numerals, and the explanation thereof will be omitted.

21' in Fig. 2 is a shape memory alloy coil spring;
37 is a positive temperature characteristic thermistor (hereinafter referred to as a PTC thermistor), 38 is an outer electrode piece for the PTC thermistor, and 39 is a fixing of the PTC thermistor 37 and fixing of the outer electrode piece 38 and one end of the shape memory alloy coil spring 21'. The fixing plate also serves as a fixing plate, 40 is the inner electrode piece of the PTC thermistor, 41 is the inner electrode rod for the PTC thermistor, and the nut 43 is connected through the insulating plate 42.
It is attached to the damper spring support plate 44. 4
5 is a screw for fixing the fixing plate 39 to the damper spring support plate 44, and 48 and 49 are lead wires for supplying electricity to the PTC thermistor 37, which are connected to the control circuit to be energized when the heater is heated.

In FIG. 1, 46 is a protrusion for hooking the coil spring 21' provided on the damper lid 16, and 47 is a screw for attaching the damper spring support plate 44 to the main body of the damper assembly 12. Since the coil spring 21' will not operate smoothly unless the angle of the PTC thermistor 37 is changed depending on the opening angle of the damper lid 16, the damper spring support plate 44 is designed to rotate freely.

The operation of the damper device having the above configuration is the same as that of the conventional example, so it will not be described here. However, by disposing the indirect heating PTC thermistor 37 in the hollow part of the shaped alloy coil spring 21', the coil spring 21' Since the temperature rises quickly and the self-temperature control ability does not exceed a predetermined temperature, deterioration of the characteristics of the shaped alloy coil spring 21' can be prevented, and costs can be reduced by eliminating step-down transformers and adopting low-current relays. It can be measured.

<Effects> The present invention can reduce costs and make the damper device more compact, and since the temperature of the shaped alloy coil spring does not exceed a predetermined temperature, deterioration of the characteristics of the coil spring can be prevented.

[Brief explanation of the drawing]

Figure 1 is a bottom view of the damper device of the present invention, Figure 2 is a bottom view of the damper device of the present invention;
The figure is a sectional view taken in the direction of arrow C in Fig. 1, Figs. 3 and 4 are side sectional views of main parts of the microwave oven, and top sectional views of main parts.
Figure 5 is a conventional bottom view seen from direction A in Figure 3;
FIG. 6 is an exploded perspective view of a conventional damper device. Code, 12: Damper assembly, 16: Damper lid, 21': Shape memory alloy coil spring, 37:
Positive temperature characteristic thermistor (PTC thermistor).

Claims (1)

[Claim for Utility Model Registration] In a damper device for a microwave oven that opens and closes a damper by changing the shape of a coil spring made of a shape memory alloy, a positive temperature characteristic thermistor that indirectly heats the coil spring made of a shape memory alloy is installed in the hollow part of the coil spring. A damper device for a microwave oven, characterized in that the damper device is arranged in a microwave oven.