JP2001222065A - Electronic apparatus having cooling fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic apparatus having a cooling fan capable of preventing the generation of sounds by the cooling fan. SOLUTION: The cooling fan 31 is disposed in the middle within a air sending pipeline (duct) 32. The pipeline 32 introduces air sucked from the outside of the apparatus by the cooling fan 31 to liquid crystal panels 21, 22 and 23 which are heat generating sections. A first resonance chamber 35 and a first resonance silencer consisting of through-holes 32a, etc., are constituted on the air suction side of the cooling fan 31. A second resonance chamber 36 and a second resonance silencer 32 consisting of through-holes 32a, etc., are constituted on the air blow-off side of the cooling fan 31. The sounds generated in the air sending pipeline 32 by the cooling fan 31 enter the inside of the resonance chamber 35 and 36 from the through-holes 32a, etc., and the energy of the sound is lost by the resonance, and the sounds are silenced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device provided with a cooling fan for cooling a heat generating portion in the device. Examples of this type of electronic device include a liquid crystal projector used for a high-definition theater for business use, a conference presentation, or an exhibition demonstration.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing the internal structure of a conventional liquid crystal projector. Light emitted from a light source 51 such as a halogen lamp or a metal halide lamp is light-modulated by passing through a liquid crystal panel 52 to become image light, and is enlarged and projected on a screen 54 by a projection lens 53.

The liquid crystal panel 52 includes an incident-side polarizing plate, a panel portion in which liquid crystal is sealed between a pair of glass substrates (on which pixel electrodes and an alignment film are formed), and an output-side polarizing plate. Become. The incident-side polarizing plate applies linear polarized light in a predetermined direction to the panel unit, and transmits linear polarized light in a vibration direction parallel to its transmission axis, but absorbs linear polarized light in an orthogonal vibration direction. The incident side polarizing plate generates heat and rises in temperature due to the absorbed light energy. When the temperature of the incident-side polarizing plate exceeds its allowable temperature, the polarizing plate changes its color and its polarization performance deteriorates. For this reason, in the liquid crystal projector, the liquid crystal panel is cooled by the cooling fan 55 so that the temperature of the polarizing plate does not exceed the allowable temperature.

[0004] The cooling fan 55 is attached to a motor (not shown). When the cooling fan 55 is rotated by the motor, air outside the device is sucked into the device from the air inlet 56, and the sucked air flows into the chassis 57 on which the liquid crystal panel 52 is mounted from the outlet opening 57a. Is blown in. In order to prevent the sucked air from escaping to the outside, the space between the air inlet 56 and the cooling fan 55 and the space between the cooling fan 55 and the suction opening 57 are covered with a peripheral wall 58 to form an air duct. are doing.

[0005]

When the cooling fan 55 is rotated, a fan noise is generated, and the fan noise increases as the cooling capacity is increased. On the other hand, liquid crystal projectors are often used in presentations in which product explanations and the like are performed using a projection screen. There was a problem that the fan sound was felt as noise because this presentation was performed in a quiet room.

In view of the above circumstances, an object of the present invention is to provide an electronic device provided with a cooling fan which can minimize the generation of noise by the cooling fan.

[0007]

According to another aspect of the present invention, there is provided an electronic apparatus including a cooling fan for cooling a heat generating portion in the apparatus. A blower duct that guides air sucked from outside the device to the heat generating section, a through hole formed in a wall surface of the blower pipe, and a resonance chamber communicated with the through hole. Features.

With the above structure, the sound generated in the air duct by the cooling fan enters the resonance chamber through the through hole, and the energy of the sound is lost by the resonance phenomenon.
Muting is performed.

The cooling fan is provided substantially in the middle of the air duct, and a first resonance silencer including a first resonance chamber and a first through hole is provided on an air suction side of the cooling fan. A second resonance muffler including a second resonance chamber and a second through hole may be provided on the air blowing side of the fan.

According to this, the sound generated on the air suction side of the cooling fan is mainly silenced by the first resonance silencer, and the sound generated on the air blowing side of the cooling fan is mainly silenced by the second resonance silencer. Will be done. In these two resonance silencers, the volume of the resonance chamber and the like can be set independently, so there is a difference between the frequency of the sound generated on the air suction side of the cooling fan and the frequency of the sound generated on the air blowing side of the cooling fan. Even in such a case, an optimal silencing design can be achieved.

The apparatus may further comprise means for detecting a range of the generated sound, and a mechanism for changing an element related to a resonance frequency according to the range. With such a configuration, it is possible to cope with a variation in generated sound for each product. Further, it is possible to reduce the cost by mass production by using a common resonance type silencer for the equipment of each specification.

[0012]

(Embodiment 1) Hereinafter, a liquid crystal projector according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing an optical system of a three-panel liquid crystal projector of this embodiment, FIG. 2 is an internal structural diagram of the liquid crystal projector, and FIG. 3 is an explanatory diagram for explaining components of a resonance muffler. is there.

In FIG. 1, white light emitted from a light source 10 such as a halogen lamp or a metal halide lamp is guided to a first dichroic mirror 12 after only visible light is transmitted through a filter 11.

The first dichroic mirror 12 transmits light in the red wavelength band and reflects light in the cyan (green + blue) wavelength band. The light in the red wavelength band transmitted through the first dichroic mirror 12 is reflected by the total reflection mirror 13, the optical path is changed, and the light is guided to the transmissive liquid crystal panel 21 for red light. Modulated. On the other hand, light in the cyan wavelength band reflected by the first dichroic mirror 12 is guided to the second dichroic mirror 14.

The second dichroic mirror 14 transmits light in the blue wavelength band and reflects light in the green wavelength band. The light in the green wavelength band reflected by the second dichroic mirror 14 is guided to a transmissive liquid crystal panel 22 for green light,
Light is modulated by transmitting the light. The light in the blue wavelength band transmitted through the second dichroic mirror 14 is guided to the transmissive liquid crystal panel 23 for blue light through the total reflection mirrors 15 and 16, and is light-modulated by transmitting the liquid crystal panel 23.

The modulated light (image light of each color) obtained through the liquid crystal panels 21, 22, 23 is applied to the dichroic prism 17
Are combined into a color image light. This color image light is enlarged and projected by the projection lens 18 in the projection mechanism, and is projected and displayed on the screen 19.

Each of the liquid crystal panels 21, 22 and 23 has a panel section in which liquid crystal is sealed between the incident side polarizing plates 21a, 22a and 23a and a pair of glass substrates (on which pixel electrodes and alignment films are formed). 21b, 22b, and 23b, and emission-side polarizing plates 21c, 22c, and 23c. The incident-side polarizing plates 21a, 22a, and 23a absorb unnecessary polarized light and transmit necessary polarized light. Due to the absorption of unnecessary polarized light, the incident-side polarizing plates 21a, 22a, and 23a generate heat and rise in temperature. In order to prevent this temperature rise, the liquid crystal projector is provided with a cooling fan 31 (see FIG. 2).

As shown in FIG. 2, the cooling fan 31 is provided in the middle of an air duct 32. The blower duct 32 guides the air sucked from outside the device by the cooling fan 31 to the liquid crystal panels 21, 22, and 23, which are heat generating parts. That is, the cooling fan 31 is driven by a motor (not shown).
Is rotated, air outside the machine is sucked into the air duct 32 from the air inlet 33, and the sucked air passes through the air duct 32 and from the blowout opening 34 a to the liquid crystal panel 2.
It is blown into the chassis 34 on which the components 1, 22, 23 are mounted. The liquid crystal panels 21, 22, and 23 are cooled by the wind blown into the chassis.

A first resonance chamber 35 is provided outside the peripheral wall of the air duct 32 between the cooling fan 31 and the air inlet 33 so as to surround the air duct 32. Further, a second resonance chamber 36 is provided outside the peripheral wall of the blower duct 32 between the blower fan 31 and the blowout opening 34 a so as to surround the blower duct 32. The first and second resonance chambers 35 and 36 communicate with the inside of the air duct 32 through through holes 32 a formed in the peripheral wall of the air duct 32. The first resonance chamber 35 and the through-holes 32 a connecting the resonance chamber 35 to the air duct 32 constitute a first resonance type silencer on the air suction side of the cooling fan 31. Further, the second resonance chamber 36 and the through holes 32 a communicating the resonance chamber 36 with the air duct 32 constitute a second resonance type silencer on the air blowing side of the cooling fan 31.

The sound absorbing material 3 is located on the inner side of the peripheral wall of the air duct 32 where the through holes 32a are not formed.
7 ... is pasted. This sound absorbing material 37 is made of a porous material such as glass wool, for example, and is designed to absorb sounds in the mid-high range that are difficult to absorb with the above-described resonance type silencer.

FIG. 3 shows elements relating to the resonance frequency and elements relating to the sound reduction in the resonance type silencer.
Factors related to the resonance frequency include the volume V of the resonance chamber,
There are the area So of the through hole, the number n thereof, and the length of the through hole (plate thickness of the air duct). The cross-sectional area S of the air duct (duct) is related to the sound reduction. The resonance frequency is represented by the following first equation, and the volume reduction TL of the sound (frequency f) to be silenced is represented by the following third equation. The meaning of each symbol in these formulas is shown below. C: Sound velocity Co: Conductivity (see the second formula below) fr: Resonance frequency (Hz) V: Volume of resonance chamber (m3) n: Number of through holes f: Frequency of sound to be silenced S: Duct cut Area (m2) So: Area of through-hole (m2) t: Length of through-hole (plate thickness of duct) (m)

[0022]

(Equation 1)

The sound generated in the air duct 32 by the cooling fan 31 is transmitted from the through holes 32a to the resonance chambers 35 and 36.
The sound energy is lost due to the resonance phenomenon, and the sound is muted. In particular, in this embodiment,
The noise generated on the air suction side of the cooling fan 31 is mainly silenced by the first resonance type silencer, and the noise generated on the air blowing side of the cooling fan 31 is mainly silenced by the second resonance type silencer. Become. In these two resonance silencers, the volume of the resonance chamber and the like can be set independently, so that the frequency of the sound generated on the air suction side of the cooling fan 31 and the frequency of the sound generated on the air blowing side of the cooling fan 31 are different. Even in the case where a difference occurs, an optimal silencing design can be achieved.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to FIG. In order to avoid redundancy due to duplication of description, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

A bottle-shaped first resonance chamber 41 is provided outside the peripheral wall of the air duct 32 between the cooling fan 31 and the air inlet 33. A bottle-shaped second resonance chamber 42 is provided outside the peripheral wall of the blower duct 32 between the blower fan 31 and the blowout opening 34a. The first and second resonance chambers 41 and 42 communicate with the inside of the air duct 32 by through holes 32 b and 32 c formed in the peripheral wall of the air duct 32. The first resonance chamber 41 and the through hole 32b constitute a first resonance type silencer on the air suction side of the cooling fan 31. Also, the second resonance chamber 4
2 and the through-hole 32c constitute a second resonance type silencer on the air blowing side of the cooling fan 31.

The bottom portion 41a of the bottle-shaped first resonance chamber 41
The bottom portion 42a of the second resonance chamber 42 is movably provided. The resonance chamber 4 is moved by moving the bottoms 41a and 42a.
The volumes of 1, 42 can each be varied. Bottom 4
1a and 42a are moved by an actuator 43 such as a motor.

The air duct 3 on the air suction side of the cooling fan 31
2, a first sound range detecting means 44 is provided.
The sound range information of the sound generated in the air duct 32 on the air suction side is supplied to the muffling control unit 46. In addition, the second sound range detecting means 4 is provided in the air duct 32 on the air blowing side of the cooling fan 31.
5 is provided, and supplies the sound range information of the sound generated in the air duct 32 on the air blowing side to the sound deadening control unit 46.

The muffling control unit 46 includes sound range detecting means 44 and 4.
The actuator 43 for moving the bottom 41a and the actuator 43 for moving the bottom 42a are respectively controlled based on the range information from No. 5. For example, among the received sound range information, a frequency of the highest level sound is detected, a resonance chamber volume V for silencing the sound of this frequency is calculated, and a control signal for realizing the resonance chamber volume, for example, If the actuator 43 is a stepping motor, a pulse signal to be given to the motor is generated and output.

With such a configuration, the volume of the resonance chamber can be changed according to the generated sound, so that it is possible to cope with the variation in the generated sound for each product. Further, it is possible to reduce the cost by mass production by using a common resonance type silencer for the equipment of each specification.

In the above example, the volume changing mechanism is provided for the bottle-shaped resonance chamber. However, the volume changing mechanism can be realized also in the donut-shaped resonance chamber shown in the first embodiment. Also, the volume of the resonance chamber was changed to correspond to the frequency of the generated sound, but other elements related to the resonance frequency, such as the area and the number of through holes formed in the air duct, were changed. Is also good. In addition, the first
A configuration in which a volume changing mechanism is provided on one side of the second resonance type silencer and not provided on the other side may be employed. Further, a configuration in which only one of the first and second resonance silencers is provided may be employed. In this case, since the sound generated on the air suction side has a large effect, it is desirable to provide the air suction side. Further, the resonance chamber may be formed so as to surround the entire air duct from the air suction side to the air discharge side. Further, in the above embodiments, the liquid crystal projector is exemplified, but the present invention can be applied to other electronic devices having a cooling fan.

[0031]

As described above, according to the present invention, there is an effect that generation of noise by the cooling fan can be prevented as much as possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an optical system of a liquid crystal projector according to an embodiment of the present invention.

FIG. 2 is an internal structural diagram showing a liquid crystal panel cooling system of the liquid crystal projector according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing elements related to a resonance frequency and elements related to sound volume reduction in a resonance type silencer.

FIG. 4 is an internal structural diagram showing a liquid crystal panel cooling system of a liquid crystal projector according to a second embodiment of the present invention.

FIG. 5 is an internal structural diagram showing a liquid crystal panel cooling system of a conventional liquid crystal projector.

[Explanation of symbols]

 21, 22, 23 Liquid crystal panel 31 Cooling fan 32 Ventilation duct (duct) 32a Through hole 32b Through hole 32c Through hole 33 Air inlet 34 Chassis 34a Air outlet 35 First resonance chamber 36 Second resonance chamber 37 Sound absorbing material 41 First resonance chamber 42 Second resonance chamber 46 Noise reduction control unit

Claims (4)

[Claims] 1. An electronic device having a cooling fan for cooling a heat-generating portion in a device, wherein: a blower duct for guiding air sucked from outside the device by the cooling fan to the heat-generating portion; An electronic device comprising a cooling fan, comprising: a through-hole formed in a wall surface; and a resonance chamber communicated with the through-hole. 2. An electronic apparatus comprising the cooling fan according to claim 1, wherein the cooling fan is provided substantially in the middle of the air duct, and a first resonance chamber and an air suction side are provided on an air suction side of the cooling fan. A first resonance silencer comprising a first through-hole is formed, and a second resonance muffler comprising a second resonance chamber and a second through-hole is formed on the air blowing side of the cooling fan. Electronic equipment with a cooling fan. 3. An electronic device provided with the cooling fan according to claim 1, wherein a means for detecting a sound range of a generated sound and a mechanism for changing an element related to a resonance frequency according to the sound range. And an electronic device provided with a cooling fan. 4. An electronic device comprising the cooling fan according to claim 1, wherein said heat generating portion is a liquid crystal panel.