Projection display device

1. A projection display device that enlarges and projects an image formed by a display element through a projection lens onto a screen, the display device comprising:

a suction fan that draws air from outside of the device through an inlet into the device and blows the cooling air to the display element;

a dustproof filter that is arranged in the vicinity of the inlet and removes dust and a foreign material from the drawn air;

an air guide path that guides, to the display element, the cooling air blown by the suction fan;

an air velocity detector that is arranged in the air guide path and detects the velocity of the cooling air that flows in the air guide path; and

a controller that determines, on the basis of the value detected by the air velocity detector, whether or not the dustproof filter is clogged;

wherein the air velocity detector includes a reference temperature sensor that measures the temperature of the cooling air that flows in the air guide path, a heat generating element that generates a predetermined amount of heat, and a heater-vicinity temperature sensor that measures the temperature of air in the vicinity of the heat generating element that will be increased due to heat transfer generated by the heat generating element,

the reference temperature sensor, the heat generating element and the heater-vicinity temperature sensor of the air velocity detector are arranged, within a flow path for the cooling air at the air guide path, in order of the reference temperature sensor, the heat generating element, and the heater-vicinity temperature sensor from the suction fan side, and

the air velocity detector detects the velocity of the cooling air on the basis of a difference between the temperature measured by the reference temperature sensor and the temperature measured by the heater-vicinity temperature sensor.

2. The projection display device according to claim 1 , wherein

the air velocity detector is located on a side surface of the air guide path but in the vicinity of an outlet of the suction fan.

3. The projection display device according to claim 2 , wherein

the air guide path includes a wide portion having a width that is larger than the width of the outlet of the suction fan, and

at least the heat generating element and the heater-vicinity temperature sensor are arranged on the wide portion of the air guide path among the sensors and the element that are included in the air velocity detector.

4. The projection display device according to claim 1 , wherein

the air velocity detector compares the difference between the temperature measured by the reference temperature sensor and the temperature measured by the heater-vicinity temperature sensor with a reference temperature difference and calculates a reduction rate of the velocity of the cooling air on the basis of an increase rate of the difference between the measured temperatures, and

the controller determines that the dustproof filter is clogged when the reduction rate calculated by the air velocity detector is equal to or lower than a predetermined value.

5. The projection display device according to claim 1 , wherein

the air velocity detector is arranged so that a plurality of the heat generating elements and the heater-vicinity temperature sensor are mounted on a common substrate and do not overlap each other in a direction in which the cooling air flows while the heat generating elements surround the heater-vicinity temperature sensor.

6. The projection display device according to claim 1 , wherein

the controller controls rotational speed of the suction fan on the basis of the temperature measured by the reference temperature sensor that is included in the air velocity detector.

7. The projection display device according to claim 1 , wherein

when the controller determines that the dustproof filter is clogged, the controller causes an alarm prompting cleaning of the dustproof filter to be displayed on the screen and causes a light source to be turned off, the light source being used in order to enlarge and project the image.

8. A projection display device that enlarges and projects an image formed by a display element through a projection lens, the display device comprising:

a dustproof filter through which air that is drawn from outside of the device through an inlet into the device passes;

a suction fan that blows, to the display element, the cooling air that has passed through the dustproof filter;

an air guide path that guides, to the display element, the cooling air blown by the suction fan;

a reference temperature sensor that measures the temperature of the cooling air that flows in the air guide path;

a heat generating element that is arranged in the air guide path and generates a predetermined amount of heat;

a heater-vicinity temperature sensor that is arranged in the air guide path and measures the temperature of air in the vicinity of the heat generating element; and

a controller that prevents the display element from being excessively heated;

wherein:

the reference temperature sensor, the heat generating element and the heater-vicinity temperature sensor of the air velocity detector are arranged, within a flow path for the cooling air at the air guide path, in order of the reference temperature sensor, the heat generating element, and the heater-vicinity temperature sensor from the suction fan side, and

when a difference between the temperature measured by the reference temperature sensor and the temperature measured by the heater-vicinity temperature sensor is equal to or larger than a predetermined value, the controller causes an alarm prompting cleaning of the dustproof filter to be displayed and causes a light source to be turned off, the light source being used in order to enlarge and project the image.

9. A projection display device that enlarges and projects an image formed by a liquid crystal panel through a projection lens onto a screen, the display device comprising:

a suction fan that draws air from outside of the device through an inlet into the device and blows the cooling air to the liquid crystal panel;

a dustproof filter that is arranged in the vicinity of the inlet and removes dust and a foreign material from the drawn air;

a first air guide path that guides, to the suction fan, the air that has passed through the dustproof filter;

a second air guide path that guides, to the liquid crystal panel, the cooling air blown by the suction fan;

a reference temperature sensor that measures the temperature of the cooling air that flows in the second air guide path;

a heat generating element that is arranged in the second air guide path and generates a predetermined amount of heat;

a heater-vicinity temperature sensor that measures the temperature of air in the vicinity of the heat generating element; and

a controller that determines whether or not the dustproof filter is clogged;

wherein:

the reference temperature sensor, the heat generating element and the heater-vicinity temperature sensor of the air velocity detector are arranged, within a flow path for the cooling air at the second air guide path, in order of the reference temperature sensor, the heat generating element, and the heater-vicinity temperature sensor from the suction fan side, and

the reference temperature sensor is mounted on a first substrate that is fixed to a side surface of the second air guide path but in the vicinity of an outlet of the suction fan,

the heat generating element and the heater-vicinity temperature sensor are mounted on a second substrate that is fixed to the side surface of the second air guide path but on a downstream side of the first substrate, and

the controller determines that the dustproof filter is clogged when a difference between the temperature measured by the reference temperature sensor and the temperature measured by the heater-vicinity temperature sensor is equal to or larger than a predetermined value.

10. The projection display device according to claim 9 , wherein

the second air guide path includes a wide portion having a width that is larger than the width of the outlet of the suction fan, and

the second substrate is arranged on the wide portion of the second air guide path.