Projector Lamp Cooling Control for Thermal Stress Reduction
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Solution Overview
Problem
Existing projecting type image display apparatuses face challenges in prolonging the lifespan of ultra-high pressure mercury lamps due to rapid temperature changes when turned off, leading to distortion and potential failure, as conventional cooling methods either shorten the lamp's lifetime or fail to adequately slow down the cooling process.
Innovation Solution
A method is introduced where the electric power to the lamp is gradually reduced to 80% of the normal power and then cut off, while simultaneously increasing the rotations of the lamp cooling fan, and then stopping it almost simultaneously with power cutoff, to create a gentle temperature gradient and reduce thermal stress on the quartz glass bulb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the lamp is turned off by cutting power immediately, then the cooling speed is fast, but the temperature difference between inner and outer surfaces causes distortion and reduces reliability
Solution Approach 1:
The cooling fan is activated in advance before the lamp power is cut off, and continues running for a predetermined period after power cutoff. This preliminary and extended cooling action ensures that the bulb cools down gradually and uniformly, preventing thermal distortion and cracking while maintaining fast overall cooling speed.
Solution Approach 2:
The cooling fan operates continuously through the transition period from lamp on to lamp off, maintaining uninterrupted cooling flow. This continuous cooling action prevents sudden temperature changes that would cause thermal shock to the quartz glass bulb, thereby extending lamp lifetime without sacrificing cooling efficiency.
2Speed
If the cooling fan is stopped when the lamp is turned off, then the cooling speed decreases, but the calorific power is significantly reduced and cooling speed cannot be decreased enough
Solution Approach 1:
The cooling fan is activated in advance before the lamp power is cut off, and continues running for a predetermined period after power cutoff. This preliminary and extended cooling action ensures that the bulb cools down gradually and uniformly, preventing thermal distortion and cracking while maintaining fast overall cooling speed.
Solution Approach 2:
The cooling fan operates continuously through the transition period from lamp on to lamp off, maintaining uninterrupted cooling flow. This continuous cooling action prevents sudden temperature changes that would cause thermal shock to the quartz glass bulb, thereby extending lamp lifetime without sacrificing cooling efficiency.
3Reliability
If electric power is lowered significantly when turning off the lamp, then the cooling gradient becomes gentle, but adhesion of electrode materials to bulb tube wall or extinction occurs, shortening lamp lifetime
Solution Approach 1:
The cooling fan is activated in advance before the lamp power is cut off, and continues running for a predetermined period after power cutoff. This preliminary and extended cooling action ensures that the bulb cools down gradually and uniformly, preventing thermal distortion and cracking while maintaining fast overall cooling speed.
Solution Approach 2:
The cooling fan operates continuously through the transition period from lamp on to lamp off, maintaining uninterrupted cooling flow. This continuous cooling action prevents sudden temperature changes that would cause thermal shock to the quartz glass bulb, thereby extending lamp lifetime without sacrificing cooling efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively elongates the lamp's lifetime by reducing the probability of breakage and distortion, as demonstrated by reliability tests showing reduced failure rates compared to conventional methods.
Implementation Method 1
it is important to cool the temperature of the interior of the bulb to an adequate temperature by flowing a cold air thereon from the outside
Implementation Method 2
a temperature difference between an inner surface and an outer surface of the bulb causes a difference in time of arrival at a point of distortion of the quartz glass, whereby a distortion is generated within the quartz glass
Data Source
AI summary
An image display apparatus including a light source; a light source control unit configured to control electric power to be supplied to the light source; a light source cooling unit configured to cool the light source; a cooling control unit configured to control the light source cooling unit; an image display device; an illumination optical system configured to introduce light from the light source to the image display device, and a projecting optical system configured to project light modulated by the image display device. When the light source control unit receives a turn-off command, the light source control unit first lowers electric power to be supplied to the light source to a predetermined electric power lower than normal electric power to be supplied when the lamp is on, and then blocks the supply of the electric power to the light source, thereby turning the light source off.