JPH0310958Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application The present invention relates to a protection device for clothes dryers, and in particular, to a protection device for electronic control devices of electric dryers that control the completion of drying using a microcomputer and a power semiconductor. be.

BACKGROUND ART Conventionally, a control device for a clothes dryer for drying household clothes has been equipped with a control device that detects drying of clothes and automatically shuts down the drying process.

As shown in FIG. 2, such a household clothes dryer has a structure in which a housing 1 holds a drum 2 for storing clothes, and hot air is sent into the drum 2 to dry the clothes. . Further, a lid is attached to the clothes input port 3, and for safety reasons, the rotation of the drum 2 is stopped when the lid is opened or closed. 4 is a main switch operated by the user, and 5 is a start button.

FIG. 3 is a block diagram of a conventional electronic control device, in which an alternating current voltage is applied from an alternating current power supply 6 to a load circuit consisting of a heater 7 and a motor 8 via a control device 10. Further, the control device 10 is connected to a temperature detection device 15 provided inside the drum 2 via a lead wire. One terminal of the AC power source 6 is normally grounded, and the casing 1 of the dryer is made of an iron plate and is provided with a ground terminal.

Problems to be solved by the invention However, in the above configuration, the control device 10:
Three-terminal thyristors with bidirectional control poles (hereinafter referred to as triax) 12 and 13 that control the heater 7 or motor 8 are directly connected to the signal circuit 11 and its control terminal (hereinafter referred to as gate terminal), and the signal circuit 11 is connected to the ground. , and is connected to the AC power source with low impedance, so if the lead wire 14 or the temperature detection device 15 connected to the control device 10 is grounded, a large current will flow from the AC power source 6 to the control device 10. There was a risk that the control device 10 would catch fire.

In order to prevent the risk of ground faults, it is possible to electrically isolate the control circuit from the AC power supply using a transformer, but this has the problem of requiring a large and expensive component called a transformer. Ta.

The present invention eliminates the above-mentioned drawbacks and provides a dryer protection device that is inexpensive and prevents fire from occurring even in the event of a ground fault.

Means for Solving the Problems In order to solve the above problems, the dryer protection device of the present invention is powered by an AC power source whose one end is grounded. a control section for the heater and motor;
The temperature detection section is supplied with power from an AC power supply via the control section, and a protection section is connected in series between the control section and the temperature detection section.

Effect: With the above configuration, even if the temperature detection section is grounded and a large current attempts to flow to the control section, the protection section will block it. Moreover, this makes it possible to connect the control section directly to the power source, resulting in low cost.

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

Reference numeral 6 denotes an AC power source that applies power voltage to the control device 17 via the power switch 4. Control device 17
The sensor detects the temperature of a signal circuit 11 including an integrated circuit such as a microprocessor, a heater control triac 12 and a motor control triac 13, which are electrically opened and closed according to drive signals from the signal circuit 11, and an exhaust duct. Temperature detection device 15
, and resistors 16a and 16b connected in series to the temperature detection device 15. Signal circuit 11 connects the gate terminals of triacs 12 and 13 and T ₁
It is directly connected to the terminal, and triax 12, 13
Since the T ₁ terminal of is connected to the AC power supply 6,
As a result, the signal circuit 11 is connected to the AC power source 6 through low impedance, and has approximately the same potential. The heater 7 is connected to the _T2 terminal of the heater control triac 12, and the other terminal of the heater 7 is
T Connected to the terminal of the other power line opposite the power line of the ₁ terminal. Similarly, the motor 8 is connected to the _T2 terminal side of the motor control triax 13. In order to make the triacs 12 and 13 conductive, it is only necessary to flow a gate current of about 10 to 50 mA from the _T1 terminal to the gate terminal, and the signal circuit 11
are connected to the _T1 terminal and the gate terminal, respectively.

On the other hand, the temperature detection device 15 is bonded to a part of an iron plate of an exhaust hole through which exhaust air is discharged from the drum, and the iron plate serves as a so-called heat receiving plate to detect the exhaust temperature. However, the heat receiving plate and thermistor 1
5 and the lead wire 14 may also be grounded due to accidents such as scratches on the lead wire coating, and the AC power supply 6
There is a possibility that a large current flows from the signal circuit 11 to the ground through the signal circuit 11 and the lead wire 14. However, in the event that a large current flows to the ground, the resistors 16a and 16b will melt, thereby preventing a fire. Here, the resistances 16a and 16b are from several ohms to several ohms.
It uses a 10Ω fuse resistor and becomes open when an overcurrent flows. When fuses are used in place of the resistors 16a and 16b, it is difficult to cut the fuses with a small amount of current, so using resistors is reliable.

Effects of the invention As described above, according to the invention, even if a large current attempts to flow due to a ground fault in the control unit having a signal circuit directly connected to the triax through the lead wire, the protection unit prevents the flow of a large current. Accidents in which the device or lead wire catches fire can be prevented. Therefore, the control section can be directly connected to the power source, and an inexpensive control section for a dryer can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control device for a dryer which is an embodiment of the present invention, FIG. 2 is an external view of the dryer, and FIG. 3 is a block diagram of a conventional control device. 6... AC power supply, 7... Heater, 8... Motor, 15... Temperature detection device, 17... Control device.

Claims (1)

[Scope of utility model registration request] an AC power supply having at least one terminal grounded; a control unit connected to the AC power supply; a load circuit including a heater and a motor controlled by the control unit; and power supplied from the AC power supply via the control unit. A protection device for a dryer, comprising a temperature detection section for detecting exhaust gas temperature, etc., and an overcurrent protection section connected in series with the temperature detection section.