JP2001203067A - Heater with control circuit for mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain reduction of power consumption. SOLUTION: A switch element 21 is connected in series with the heater 11 which is installed in the mirror of an automobile to remove frost and dew and a control circuit 22 outputs an on/off signal to the switch element 21. The control circuit 22 comprises a timer circuit 23, which outputs 'on' signal to the switch element 21 for a prescribed time after power input, and an on/off circuit 24, which is operated by a time-out output of the timer circuit 23 and outputs repeatedly 'on'/'off' signal to the switch element 21. Unnecessary power consumption after removing frost and dew is eliminated by the operation of the on-off circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater mounted on a mirror such as a side mirror mounted outside a vehicle.

[0002]

2. Description of the Related Art Some mirrors of this type which are exposed to the outside air are equipped with a heater for removing frost and dew adhering to the mirror surface and ensuring a good visibility. The structure is such that a heater is attached to the back and the surface temperature of the mirror is raised to quickly remove frost and dew. FIG. 4 shows an example of a conventional structure of such a heater. In this example, as a heater, a PT whose electric resistance value sharply increases with a rise in temperature is used.
A heater (PTC heater) 11 having C (positive temperature coefficient) characteristics is used, and a thermostat 12 is attached.
Is controlled by turning the thermostat 12 on and off. In the figure, 13 indicates a power supply, and 14 indicates a power switch.

In such a heater 11, in order to evaporate the dew on the mirror surface in a short time and secure a view,
It is necessary to raise the mirror surface temperature to at least about 60 ° C. From this point, the set temperature (upper limit) of the thermostat 12 is set to, for example, 60 ° C. By setting the upper limit of the mirror surface temperature to such a temperature,
It is also possible to prevent a person from being burned or a mirror from being broken. 5A and 5B show the relationship between the elapsed time after power-on of the heater 11 shown in FIG. 4 and power consumption, and FIG. 5A shows that the ambient temperature (outside air) is 25.
5C shows the case where the ambient temperature is -30 ° C. FIG. 5C shows the relationship between the elapsed time and the heater temperature shown corresponding to FIGS. 5A and 5B.

When the power switch 14 is turned on and the power is turned on, the maximum current flows through the heater 11, and then the PTC
The current gradually decreases due to the characteristics, and the power consumption gradually decreases. When the ambient temperature is 25 ° C., the heater temperature reaches the set temperature (upper limit) of the thermostat, and at that time, the thermostat is turned off, and the heater temperature decreases.
Then, when the heater temperature reaches the thermostat set temperature (lower limit), the thermostat is turned on again, and current flows through the heater. By repeating the on / off operation of the thermostat in this manner, the heater temperature decreases as shown in FIG.
And the power consumption changes as shown in FIG. 5A.

On the other hand, when the ambient temperature is -30.degree.
As shown in C, the heater temperature is saturated and does not reach the set temperature (upper limit) of the thermostat, so that the thermostat is always on. Therefore, a current always flows through the heater, and the power consumption is maintained at a constant value as shown in FIG. 5B.

[0006]

By the way, in order to melt the frost adhering to the mirror in a short time and to secure the visibility,
Although it is necessary to raise the mirror surface temperature to about 30 ° C. as shown in FIG. 5C, once the visibility is secured, it is sufficient to keep the temperature at which frost does not form again, that is, 30 ° C. is not required. In addition, in order to evaporate the dew attached to the mirror surface in a short time and to secure the visibility, it is necessary to raise the mirror surface temperature to about 60 ° C. as described above. 5-1 from outside air so as not to dew again
It is sufficient to keep the temperature about 0 ° C. higher, and it is considered that 60 ° C. is not necessary.

[0007] In this respect, it can be said that the conventional heater having the temperature characteristic shown in FIG. 5C consumes more power than necessary, and particularly when the heater is used at a low temperature (when defrosting), the power is extremely large. Had become something. An object of the present invention is to provide a mirror heater that suppresses unnecessary power consumption after removing frost and dew, and can greatly reduce power consumption.

[0008]

According to the first aspect of the present invention, there is provided a heater with a control circuit for a mirror mounted on the outside of an automobile, comprising: a heater disposed on the mirror; and a switch connected in series with the heater. And a control circuit that outputs an on / off signal to the switch element. The control circuit outputs a turn-on signal to the switch element for a predetermined time after power-on, and a time-out of the timer circuit. An on / off circuit that is operated by an output and repeatedly outputs an on / off signal to the switch element.

According to a second aspect of the present invention, in the first aspect of the present invention, the heater comprises a PTC heater.

[0010]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention. In this example, a switch element 21 is provided in series with the heater 11, and an on / off signal is output from the control circuit 22 to the switch element 21 so that the switch element 21 is on / off controlled. Are turned on and off. The heater 11 is a PTC heater in this example, and is attached to the back of the mirror.

The control circuit 22 includes a timer circuit 23 and an on / off circuit 24. The timer circuit 23 is started when the power switch 14 is turned on and the power is turned on. ), The switch element 21
To output an ON signal. The on / off circuit 24 is activated by the time-out output of the timer circuit 23, and the switch element 2
1 repeatedly outputs an on / off signal at predetermined time intervals. 2A to 2C are timing charts showing the operation of the timer circuit 23, the on / off circuit 24, and the switch element 21 described above.

Next, the relationship between the elapsed time and the power consumption of the heater 11 having the configuration shown in FIG. 1 after the power is turned on and the relationship between the elapsed time and the heater temperature will be described with reference to FIGS. 3A to 3C. 3A to 3C respectively correspond to FIGS. 5A to 5C which show the characteristics of a conventional heater provided with a thermostat. First, the ambient temperature (outside air) is 2
The case of 5 ° C. will be described. When the power switch 14 is turned on and the power is turned on, the timer circuit 23 starts and the maximum current flows through the heater 11. Thereafter, the power consumption gradually decreases as shown in FIG. 3A due to the PTC characteristics. The heater temperature rises as shown in FIG. 3C and approaches the saturation temperature (maximum temperature reached) due to the PTC characteristics.

When the set time of the timer circuit 23 elapses,
The circuit is switched to the on / off circuit 24, and the power supply to the heater 11 is repeatedly turned on and off at predetermined time intervals. By selecting the ON / OFF cycle or ON time to a required value, the heater temperature can be reduced as shown in FIG. 3C, that is, the minimum necessary temperature (for example, 35 ° C.) at which dew does not come back again. Degree) can be stabilized. The power consumption at this time is as shown in FIG. 3A.

On the other hand, even when the ambient temperature is -30.degree. C., the ON / OFF circuit 24
As a result, the heater temperature decreases as shown in FIG. 3C, and the heater temperature can be stabilized at the minimum necessary temperature without frost again. The set time of the timer circuit 23 is set to the time required for the heater to rise to the temperature required for dew and defrost. The broken lines in FIGS. 3A and 3B show the average values of the power consumption during the operation of the on / off circuit 24, respectively, and the power consumption after removing the dew and frost is reduced as compared with FIGS. 5A and 5B. When the defrosting is used at a low temperature (-30 ° C.), the decrease is remarkable.

In this example, a PTC is used as the heater 11.
Since the heater is used, the power consumption slightly increases as the heater temperature decreases due to the operation of the ON / OFF circuit 24. However, if the OFF time is subtracted, the power consumption is reduced as shown in FIGS. 5A and 5B as described above. Power is reduced. In the above example, as the heater 11, a PTC heater is used in which the temperature rises at a stretch when energized, and the electric resistance value increases sharply as the temperature approaches the maximum attained temperature, thereby suppressing power consumption. It is also possible to use a metal heater that does not have any. In this case, the effect of reducing power consumption can be similarly obtained.

[0016]

As described above, according to the present invention, unnecessary frost and dew on the mirror surface are removed.
That is, wasteful power consumption can be eliminated, and power consumption can be significantly reduced as compared with the conventional case. In this respect, it is possible to realize an easy heater that has a small load on the battery of the vehicle.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

2A is a time chart showing the operation of the timer circuit in FIG. 1, B is a time chart showing the operation of the on / off circuit in FIG. 1, and C is a time chart showing the operation of the switch element in FIG.

FIGS. 3A and 3B are diagrams showing changes over time in the power consumption of the heater in FIG. 1; A corresponds to a case where the ambient temperature is 25 ° C .; B corresponds to a case where the ambient temperature is −30 ° C .; FIG. 5 is a diagram showing a change over time in the heater temperature.

FIG. 4 is a view for explaining a conventional heater structure.

5A and 5B are diagrams showing changes over time of the power consumption of the heater in FIG. 4; A corresponds to the case where the ambient temperature is 25 ° C .; B corresponds to the case where the ambient temperature is −30 ° C .; FIG. 5 is a diagram showing a change over time in the heater temperature.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shunsuke Sekiguchi 2-268, Aobudai, Zama-shi, Kanagawa F-term in the Kanagawa Plant, Tokyo Cosmos Electric Co., Ltd. (Reference) 3K058 AA81 BA00 CA62 CB02 CB27 3K092 PP20 QA05 QB21 UA01 UA02 VV33 VV40

Claims (2)

[Claims] 1. A heater with a control circuit for a mirror mounted outside a vehicle, comprising: a heater disposed on the mirror; a switch element connected in series with the heater; and an on / off signal to the switch element. A control circuit that outputs an ON signal to the switch element for a predetermined time after power-on, and is operated by a time-out output of the timer circuit to turn on the switch element. A heater with a control circuit for a mirror, comprising: an on / off circuit that repeatedly outputs an off signal. 2. The heater with a control circuit for a mirror according to claim 1, wherein the heater comprises a PTC heater.