JPH05155313A - Defogger control device - Google Patents

Abstract

PURPOSE:To rapidly remove the dew condensation on a glass surface which blurs the eyesight and also prevent its recurrence by a simple system constitution without obstructing the visibility through the glass. CONSTITUTION:A hot wire type heater is arranged into a glass. A defogger control device which removes dew condensation on the glass surface by energizing this hot wire type heater in duty control mode is made so that the duty- factor of energizing current supplied to it may be kept in the first preset value during the primary predetermined hours T1 after starting the energization, in the second preset value alpha which is less than the first one in the secondary predetermined hours T2 and, thereafter, the energization may be continued with the third preset value beta which the second preset one alpha is reduced to.

Description

Detailed Description of the Invention

[0001]

This invention relates to a defogger control device,
In particular, the present invention relates to a defogger control device suitable for removing fog on a window glass of a vehicle.

[0002]

2. Description of the Related Art As conventional defogger control devices, Japanese Patent Laid-Open Nos. 58-76345 and 60-88662 are available.
Those described in JP-A No. 60-244656 and JP-A No. 60-244656 are known. For example, JP-A-60-886
The defogger control device disclosed in Japanese Patent No. 62 is provided with a hot wire heater on the window glass, and the duty of the hot wire heater is controlled. Then, the duty factor of the current supplied to the hot wire heater is increased when the degree of fog is high and is decreased when the degree of fog is low.

[0003]

However, in this conventional defogger control device, since the duty factor is changed according to the degree of fogging of the window glass, it is necessary to attach the dew condensation sensor to the window glass. However, there was a problem that the system became complicated and part of the view was blocked. The present invention has been made in view of the above problems, does not hinder the visibility with a simple system, and can quickly remove fogging, and can also prevent recurrence of fogging,
Another object of the present invention is to provide a defogger control device for a vehicle that can save power.

[0004]

In order to achieve the above object, the present invention provides a defogger control for removing fogging of glass by providing a hot wire heater on the glass and controlling duty of energizing the hot wire heater. In the apparatus, the duty factor of the current supplied to the hot-wire heater is maintained at a first predetermined value for a first predetermined time from the start of energization, and a second predetermined time subsequent to the first predetermined time is set to the above-mentioned value. A second predetermined value smaller than the first predetermined value is held, and after the second predetermined time, the current is reduced to a third predetermined value smaller than the second predetermined value to continue energization.

[0005]

In the defogger control apparatus of the present invention, the duty factor is set to the first predetermined value which is relatively large during the first predetermined time, so that the temperature of the glass rapidly rises to the saturation temperature, and this temperature becomes the second temperature. Is held for a predetermined period of time to remove the fog during this period, after which the duty factor is maintained at a third predetermined value, which is relatively small, and the temperature of the glass is kept at a predetermined temperature to prevent it from becoming cloudy again. Then, after the cloudiness is removed, it is sufficient to energize with a small duty factor, and no wasted power is wasted.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a defogger control device according to an embodiment of the present invention, and FIG. 1 is a block diagram of a control system,
FIG. 2 is a flowchart showing the control process, and FIG. 3 is a timing chart for explaining the operation.

In FIG. 1, reference numeral 11 is a hot wire type heater provided on a rear window glass of a vehicle. One end of the hot wire type heater 11 is a power source + such as a battery and the other end is grounded via a switch element 12 (- ) Has been. The hot-wire heater 11 is well known in the above-mentioned publications, etc., and is embedded or attached to the rear window glass and generates heat when energized.

The switch element 12 is composed of a semiconductor element, for example, a field effect transistor (FET), and has a source / drain between the hot wire type heater 11 and the ground (-).
Further, the gate is connected to the chopping control circuit 13. A pulse width modulated (PWM) drive signal is input to the gate of the switch element 12, and the switch element 12 is turned on / off according to the duty factor of the drive signal to heat the heater 1.
1 is chopper driven. As is well known, the hot wire heater 1
A discontinuous current is applied to 1 and this discontinuous current has a duty factor according to the duty factor of the drive signal.

The chopping control circuit 13 includes a gate drive circuit, a booster circuit, a microcomputer and the like, and is connected to the operation switch 14. Operation switch 1
4 is composed of a switch that can be manually operated by the driver, and has a high level H actuation signal (FIG.
a)) is output. As shown in FIG. 3, the chopping control circuit 13 operates from the operation switch 14 to the high level H.
The drive signal is output during the period T0 during which the operation signal of is output, and the drive signal has a duty factor of 100% in the first period T1, α% in the subsequent period T2, and β% smaller than α (hereinafter, duty factor). The symbol% for the factor is omitted). However, the above period T1
Is the time until the temperature of the hot wire heater 11 converges to the saturation temperature, and the period (T1 + T2) is defined as the time until the fog is completely removed according to the specifications of the window glass, and α is less than 100. , Β is smaller than α,
These α and β satisfy the following formula. 0 <β <α <100

In the defogger control device of this embodiment, a series of processes shown in the flow chart of FIG. 2 is executed by the microcomputer of the duty control circuit 13 or the like to control the heat generation amount of the hot wire type heater 11, that is, the energization.

As shown in the figure, first, at step P1, it is determined whether or not the operation switch 14 is in the ON operation state.
That is, it is determined whether or not the operation signal is at the high level H. In step P1, if the operation switch 14 is in the ON state, a drive signal having a duty factor of 100 is output to the switch element 12 in step P2. Then, in the subsequent step P3, it is determined whether or not the predetermined time T1 has elapsed, and the process of step P2 is performed until the predetermined time T1 has elapsed. Therefore, as shown in FIG. 3, in the first period T1, the duty factor of the drive signal is 100 (FIG. 3B), the heat generation amount of the hot wire heater 11 is large, and the temperature of the window glass rises (FIG. 3C). , The fogging of the window glass is promptly removed (Fig. 6 (d)).

Next, when the predetermined time T1 has elapsed, the duty factor of the drive signal is changed to α in step P4, and it is determined in step P5 whether or not the predetermined time (T1 + T2) has elapsed, and this predetermined time (T1 + T2). ), The step P4 is executed to maintain the duty factor at α which is a value smaller than 100. Therefore, the temperature of the window glass is maintained at a relatively high temperature θ1 in the period T2 (FIG. 3c), and the fogging of the window glass is reliably removed.

After that, when a predetermined time (T1 + T2) has elapsed, the duty factor of the drive signal is changed to β in step P6, and then it is determined in step P7 whether or not the operation switch 14 has been turned off, and the operation is performed. The duty factor is maintained at β until the switch 14 is turned off.
Therefore, until the operation switch 14 is turned off,
That is, a small amount of power corresponding to the duty factor β is supplied until the operation signal shifts to the low level (FIG. 3b),
The temperature of the window glass is maintained at a relatively low temperature θ2 (Fig. 3c). Therefore, it is possible to obtain a good field of view without the clouding of the window glass again. In this period, the duty factor of the drive signal is relatively small and the power consumption of the hot wire heater 11 is small, so that power saving can be achieved.

Incidentally, although needless to say, when the operation switch 14 is turned off during the period T1 or the period (T1 + T2), the output of the drive signal to the switch element 12 is stopped. Therefore, the power supply to the hot wire heater 11 is also stopped.

[0015]

As described above, according to the defogger control apparatus according to the present invention, a relatively large amount of electric power is supplied to the hot wire heater at the beginning of energization to remove the fog from the glass and the fog is removed. After that, since the weak electric power that can keep the glass at a relatively low temperature is continued, it is possible to quickly remove the fogging of the glass at the start of energization, that is, when the operation switch is operated, and while saving power. It is possible to reliably prevent the glass from re-occurring with fogging, simplify the system configuration, and do not block the view.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a defogger control device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control process of the defogger control device.

FIG. 3 is a timing chart for explaining the operation of the defogger control device.

[Explanation of symbols]

 11 ... Hot wire type heater, 12 ... Switch element, 13 ... Chopping control circuit, 14 ... Operation switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Hirakawa 1-4-1 Chuo, Wako, Saitama Prefecture

Claims (1)

[Claims] 1. A defogger control apparatus for removing fogging of glass by providing a hot wire heater on glass and controlling the energization of the hot wire heater to control the duty factor of the energizing current to the hot wire heater. The first predetermined time is maintained at the first predetermined value from the start of energization.
For a second predetermined time period following the predetermined time period, the second predetermined value smaller than the first predetermined value is maintained, and then the current is reduced to a third predetermined value smaller than the second predetermined value to turn on the power. A defogger control device characterized by being continued.