JPS5926867B2 - Dryer automatic control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control device for a dryer that dries damp clothes, etc., and in particular controls the temperature of outside air supplied to a drying room and the exhaust gas discharged contributing to drying. When the temperature difference between the outside air and the exhaust air increases and reaches the drying end value, the power supply circuit to the heating device is cut off, and after the power supply circuit to the heating device is cut off, the heating starts. The present invention relates to an automatic control device that supplies outside air to a drying chamber and shuts off a power supply circuit to an air blower when the object to be dried has been sufficiently cooled.

The present invention will be explained below in detail with reference to the drawings embodying the invention. In the drawings, reference numeral 1 indicates an outer casing of a dryer.

Reference numeral 2 denotes a drum rotatably supported around a horizontal axis within the outer casing, and forms a drying chamber in which clothes are stored.

Reference numeral 3 designates an opening provided on the front surface of the outer casing 1 for taking clothes in and out of the drum 2, and 4 designates a door that covers the opening in an openable and closable manner.

A motor 5 drives the drum 2 via a belt 6.

7 is an intake port provided on the front surface of the drum 2, and 8 is an exhaust port provided on the rear surface of the drum 2.

Reference numeral 9 denotes a hot air duct which contacts the front surface of the drum 2 to allow rotation of the drum 2 and communicates with the intake lower, and has a heating device 10 at its tip on the intake side.

The heating device is made of nichrome wire and a positive temperature resistance heating element (
PTCR), gas burner, etc. are used.

Reference numeral 11 denotes a fan casing that contacts the rear surface of the drum 2 to allow rotation of the drum 2 and communicates with the exhaust port 8, and has an exhaust duct 12 on the discharge side that connects to the outside of the outer casing.

13 is an intake fan installed inside the fan casing;
It is driven by a motor 5 via a belt.

14 is an outside air intake port for taking in outside air supplied into the drum via the heating device 10 and the hot air duct 9.

Figure 2 is an electrical circuit diagram, in which 15 is a power plug,
16 is a switch that moves to open and close the door 14.

17 is a relay coil, to which a self-holding contact 17a is connected in series.

Reference numeral 18 is a start switch connected in parallel with the self-holding contact 17a, and is closed only while the first push button is pressed.

19a is a normally closed relay contact connected to the heating device 10, and is controlled to open and close by the relay coil 19.

20a is a normally closed relay contact connected to the motor 5 and the relay coil 17, and is controlled to open and close by the relay coil 20.

The automatic detection circuit for the end of drying uses both ends AB of the motor 5 as a power source, and is provided with a full-wave rectifier 22 via a voltage drop transformer 21.

23 is a smoothing capacitor connected to the rectifier 22.

Reference numeral 24 denotes a thermistor, which is a heat sensitive element whose resistance value decreases as the outside air temperature rises, and is installed at a suitable location within the outer casing 1 near the outside air temperature.

26 and 27 are resistors, and 28 is a variable resistor for adjusting the degree of dryness. A thermistor 24 is inserted between the resistor 27 and the variable resistor 28, and these are connected to the positive side of the rectifier 22 in that order.

Reference numeral 25 denotes a posistor, which is a heat-sensitive body whose resistance value increases in response to a rise in exhaust gas temperature, and is installed in the exhaust duct 12.

The POSISTOR 25 is connected to the resistor 26 and the resistor 27 via the resistor 29.
It is connected to the connection point P with.

A Zener diode 30 is also connected to the connection point P.

31 is a differential amplifier that functions as a first comparator;
Its positive input terminal 31a is a diode 32 and a resistor 33.
The negative input terminal 31b is connected to the connection point S between the thermistor 24 and the variable resistor 28 via the resistor 34.

35 is a diode connected between the output terminal 31c and the positive input terminal 31a.

A resistor 36.37 is connected to the output terminal 31c, and a base terminal of a transistor 38 is connected to a connection point between the two resistors 36.37.

The relay coil 19 has one end connected to the rectifier 22 and the other end connected to the collector terminal of the transistor 38, and a diode 39 connected in parallel thereto.

40 is a differential amplifier that functions as a second comparator;
Its negative input terminal 40a is connected to the connection point Q through a resistor 41, and its positive input terminal 40b is connected to the connection point Q through a resistor 42 and two diodes 43 and 44.

45 is a capacitor, and 46 is a resistor connected in parallel with the capacitor, forming a time constant circuit.

The time constant circuit is connected to the connection point U between the two diodes 43,44.

A diode 47 is connected between the simultaneous constant circuit and the positive side of the rectifier 22, and forms a discharge circuit for the capacitor 45.

48 is a diode connected between the output terminal 40c of the differential amplifier 40 and the positive input terminal 40b.

Further, a resistor 49.50 is connected to the output terminal 40c, and the base terminal of the transistor 51 is connected to the connection point between the two resistors 49.50.

One end of the relay coil 20 is connected to a rectifier 22, the other end is connected to the collector terminal of a transistor 51, and a diode 52 is connected in parallel thereto.

Now, when the start switch 18 is closed with the door 4 closed and the door switch 16 closed, the relay coil 17 is energized, the contact 17a is closed, and the motor 5 and the heating device 10 are self-held. Powered by

As the exhaust temperature increases as the operation progresses as shown in the graph of FIG. 3, the resistance value of the exhaust temperature detecting POSISTOR 25 increases and the potential at point Q increases.

When the temperature difference between the outside air temperature Ta and the exhaust temperature Tb reaches the drying end value T1, the potential at that point Q, that is, the potential at the positive input terminal 31a of the differential amplifier, changes depending on the outside air temperature and the desired degree of dryness. The potential of the set point S becomes higher than the potential of the negative input terminal 31b, and the differential amplifier 31
outputs a positive potential signal.

The output makes the transistor 38 conductive, excites the relay coil 19, opens the relay contact 19a, and cuts off the electrical circuit of the heating device 10.

Further, the output of the differential amplifier 31 is applied to the positive input terminal 31a to raise the input potential to the positive input terminal 31a and maintain the output state.

Since the electric circuit of the motor 5 is not yet cut off, a cooling operation using only air blowing is started.

During the aforementioned heating operation, the potential signal at point Q is also input to the differential amplifier 40.

However, the positive input terminal 40b has a diode 43.
44, a potential signal corresponding to a potential lower by the forward drop potential, that is, a temperature Tc lower than the exhaust temperature Tb by T2 is input.

Since this potential signal is also charged or stored in the capacitor 45, its input state is maintained for the time constant of the capacitor 45 and the resistor 46.

The above time constant is set to be larger than the time t required for normal cooling operation.

Due to the cooling operation, the exhaust temperature decreases as shown in FIG. 3, and the potential input to point Q, that is, the negative input terminal 40a of the differential amplifier 40, also decreases accordingly.

When the potential input to the minus input terminal 40a becomes lower than the potential at the plus input terminal 40b (that is, the exhaust temperature drops by T2 and reaches Tc), the differential amplifier 40 outputs a signal with a plus potential. .

The output makes transistor 51 conductive, energizes relay coil 20, opens relay contact 20a, and cuts off the electric path between motor 5 and relay coil 17.

At the same time, capacitor 45 discharges through diode 47.

As a result, the dryer stops all operations.

In the above embodiment, the heating device is controlled by comparing the electric signals based on the outside air temperature and the exhaust gas temperature.
The heating device may be controlled by comparing the electrical signal based on the difference between the two temperatures with another reference electrical signal.

Furthermore, instead of controlling the motor by comparing changes in only the exhaust gas temperature, the motor may be controlled by comparing changes in the temperature difference.

Furthermore, not only a thermistor or a positor but also a thermocouple can be used to detect temperature.

As described above, in this invention, when the difference between the two temperatures increases and reaches a predetermined value, the heating device After that, compare the electrical signal based on the electrical signal at the time the power supply circuit to the heating device was cut off with the electrical signal when unheated outside air is being supplied to the drying room. When a predetermined relationship is reached, the power supply circuit to the blower is cut off, making it possible to reliably carry out cooling operation after heating operation, and to keep the material to be dried in a sufficiently cooled state. It is something that can be taken out.

[Brief explanation of drawings]

The drawings embody this invention, and FIG. 1 is a longitudinal sectional view of the dryer, FIG. 2 is an electric circuit diagram, and FIG. 3 is a graph showing changes in exhaust temperature. Signal explanation, 5: Motor, 10: Heating device, 24.25
: Heat sensitive body (thermistor, positor), 31: First device (comparator), 40: Comparator in second device, 45: Second
storage means in the device.

Claims (1)

[Scope of Claims] 1. In a dryer equipped with a blower device that supplies outside air heated by a heating device to a drying chamber that accommodates objects to be dried, and exhausts air that has contributed to drying from the same chamber, the outside air temperature and the exhaust temperature a heat sensitive body that detects the temperature of the heat sensitive body, and inputs the operation of the heat sensitive body as an electrical signal, and operates to cut off the power supply circuit to the heating device when the temperature difference between the outside air and the exhaust air increases and reaches a predetermined value. Compare the electrical signal based on the solid air electrical signal at the time when the power supply circuit to the heating device is cut off with the electrical signal when unheated outside air is being supplied to the drying chamber. and a second device that operates to cut off a power supply circuit to the blower device when a predetermined relationship is reached. 2. The first device generates an electrical signal based on outside temperature;
The automatic control device for a dryer according to claim 1, further comprising a comparator for comparing the electric signal based on the exhaust temperature. 3. The second device includes means for storing an electric signal based on the electric signal at the time when the power supply circuit to the heating device is cut off, and a comparison device for comparing the stored electric signal with a subsequent electric signal. 3. An automatic control device for a dryer according to claim 1 or 2, comprising a container.