Windowpane defogging device for a motor vehicle and windowpane defogging method using the same

1. A windowpane defogging device for a motor vehicle which, upon generation of a fog on a windowpane, comes into a defogging mode to remove the fog generated on the windowpane, comprising:

a relative humidity detecting unit configured to detect a windowpane relative humidity of a driver seat view field region of the windowpane and a windowpane relative humidity of a passenger seat view field region of the windowpane, the driver seat view field region comprising a left portion of the windowpane before a driver seat, the passenger seat view field region comprising a right portion of the windowpane before a front passenger seat;

a driver seat occupancy sensor and a front passenger seat occupancy sensor to detect occupancy or non-occupancy of the driver seat and the front passenger seat, respectively; and

a control unit configured to enter the defogging mode when at least one of the windowpane relative humidity of the driver seat view field region and the windowpane relative humidity of the passenger seat view field region inputted from the relative humidity detecting unit is greater than a predetermined reference humidity; and

wherein the control unit, in the defogging mode, causes an air condition system to discharge a cold air toward the windowpane;

wherein the relative humidity detecting unit further comprises:

a first temperature sensing unit configured to sense a windowpane temperature of the driver seat view field region;

a second temperature sensing unit configured to sense a windowpane temperature of the passenger seat view field region;

a humidity sensing unit configured to sense a humidity of the windowpane; and

a microcomputer configured to calculate the windowpane relative humidity of the driver seat view field region and the windowpane relative humidity of the passenger seat view field region by processing the windowpane temperature of the driver seat view field region, the windowpane temperature of the passenger seat view field region and the humidity of the windowpane using a calculation program stored in advance;

wherein each of the first temperature sensing unit and the second temperature sensing unit has a non-contact-type structure;

wherein the first temperature sensing unit comprises a thermopile infrared ray sensor installed in a position spaced apart from the windowpane and configured to detect a windowpane temperature distribution of the driver seat view field region by picking up an image of a windowpane portion corresponding to the driver seat view field region and an infrared ray temperature analyzing program configured to extract a lowest temperature of the driver seat view field region from the windowpane temperature distribution of the driver seat view field region;

wherein the second temperature sensing unit comprises a thermopile infrared ray sensor installed in a position spaced apart from the windowpane and configured to detect a windowpane temperature distribution of the passenger seat view field region by picking up an image of a windowpane portion corresponding to the passenger seat view field region and an infrared ray temperature analyzing program configured to extract a lowest temperature of the passenger seat view field region from the windowpane temperature distribution of the passenger seat view field region;

wherein the microcomputer is configured to calculate the windowpane relative humidity of the driver seat view field region and the windowpane relative humidity of the passenger seat view field region based on the lowest temperature of the driver seat view field region and the lowest temperature of the passenger seat view field region; and wherein, when only one of the driver seat and the front passenger seat is detected as taken by a user, the control unit is configured to determine the generation or non-generation of the fog on the windowpane based on only the windowpane relative humidity of the driver seat view field region or the passenger seat view field region corresponding to the driver seat or the front passenger seat taken by the user, while excluding the windowpane relative humidity of the driver seat view field region or the passenger seat view field region corresponding to the driver seat or the front passenger seat not taken by the user.

2. The windowpane defogging device of claim 1 , wherein, when both the driver seat and the front passenger seat are detected as taken by users, the control unit is configured to determine the generation or non-generation of the fog on the windowpane based on the larger of the windowpane relative humidity of the driver seat view field region and the windowpane relative humidity of the passenger seat view field region.

3. The windowpane defogging device of claim 1 , wherein the thermopile infrared ray sensor of the first temperature sensing unit is installed to face toward a central section of the driver seat view field region, and the thermopile infrared ray sensor of the second temperature sensing unit is installed to face toward a central section of the passenger seat view field region.

4. The windowpane defogging device of claim 3 , wherein the first temperature sensing unit, the second temperature sensing unit and the humidity sensing unit of the relative humidity detecting unit are fixedly secured to a room mirror spaced apart from the windowpane and existing within a vehicle room.

5. A windowpane defogging method which, upon generation of a fog on a windowpane, comes into a defogging mode to remove the fog generated on the windowpane, comprising:

a) a step of detecting, by a first temperature sensor, a second temperature sensor and a humidity sensor of a relative humidity detector, a windowpane temperature of a driver seat view field region of the windowpane, a windowpane temperature of a passenger seat view field region of the windowpane and a humidity of the windowpane, respectively, the driver seat view field region comprising a left portion of the windowpane before a driver seat, the passenger seat view field region comprising a right portion of the windowpane before a front passenger seat;

b) a step of calculating, by a microcomputer of the relative humidity detector, a windowpane relative humidity of the driver seat view field region and a windowpane relative humidity of the passenger seat view field region, respectively, by processing the windowpane temperature of the driver seat view field region, the windowpane temperature of the passenger seat view field region and the humidity of the windowpane;

c) a step of determining, by a controller, whether at least one of the windowpane relative humidity of the driver seat view field region and the windowpane relative humidity of the passenger seat view field region is equal to or higher than a predetermined reference humidity; and

d) a step of, when at least one of the windowpane relative humidity of the driver seat view field region and the windowpane relative humidity of the passenger seat view field region is equal to or higher than the predetermined reference humidity, entering, by the controller, the defogging mode to discharge a cold air toward the windowpane; and

wherein a temperature of a coldest section of the driver seat view field region and a temperature of a coldest section of the passenger seat view field region are detected in the step a);

wherein the step a) comprises:

a-1) picking up an image of a windowpane portion corresponding to the driver seat view field region and an image of a windowpane portion corresponding to the passenger seat view field region in a position spaced apart from the windowpane;

a-2) detecting a windowpane temperature distribution of the driver seat view field region and a windowpane temperature distribution of the passenger seat view field region using the image of the windowpane portion corresponding to the driver seat view field region and the image of the windowpane portion corresponding to the passenger seat view field region; and

a-3) extracting the temperature of the coldest section of the driver seat view field region and the temperature of the coldest section of the passenger seat view field region from the windowpane temperature distribution of the driver seat view field region and the windowpane temperature distribution of the passenger seat view field region;

wherein the step c) comprises:

c-1) a step of determining, by a driver seat occupancy sensor and a front passenger seat occupancy sensor, whether the driver seat or the front passenger seat is taken by a user; and

c-2) a step of determining, by the controller, whether the windowpane relative humidity of the driver seat view field region or the passenger seat view field region corresponding to the driver seat or the front passenger seat taken by the user is equal to or higher than the predetermined reference humidity, while excluding the windowpane relative humidity of the driver seat view field region or the passenger seat view field region corresponding to the driver seat or the passenger seat not taken by the user.