Patent Application
20130298773
The present invention relates to a dust collection filter unit using a pleated filter for capturing dust, a projection image display device using the dust collection filter unit, and an air cleaner using the dust collection filter unit.
Conventionally, a projection image display device concentrates intense light from a light source onto image display elements such as a liquid crystal panel or a digital mirror device (DMD), modulates the concentrated light in accordance with the image signal, and enlarges and projects an image formed on the image display elements, to obtain a large screen. In the projection image display device, a large amount of heat generation occurs on the image display elements subjected to intense light, the light source, the device power supply, and the like, and they are thermally destroyed unless they are cooled properly. Therefore, the projection image display device is configured so as to cool the inside of the device by introducing external air to the inside of the device through a fan.
However, in this configuration, dust together with external air is introduced from the outside of the device to the inside of the device. Then, if the dust adheres to the image display elements or the vicinity of the light source, brightness reduction or color unevenness can occur. Therefore, in general, a dust collection filter for suppressing dust entry is provided at an air inlet. Such a dust collection filter is needed for not only the projection image display device but also other devices such as an air cleaner. As a dust collection filter, an urethane foam filter is generally used. The urethane foam filter can be reused by performing filter cleaning per several hundred hours of use. However, since the urethane foam filter is coarse, pollen or minute dust equal to or smaller than 1 μm cannot be captured.
Accordingly, in order to capture such minute dust, an electrostatic filter is employed. The electrostatic filter is a filter medium formed by an electrically charged chemical fiber and capable of capturing minute dust by using static electricity. The electrostatic filter is coarse, and therefore has a merit that pressure loss of passing air is small. However, in the electrostatic filter, the dust collection efficiency due to electric charge effect is reduced by dust adhesion with increase in usage time. In the electrostatic filter, dust can be removed by cleaning with water, but electric charge on the fiber surface is also lost, so that the dust collection efficiency reduces to an extremely low level. Therefore, there is a problem that the electrostatic filter cannot be reused and becomes a throwaway filter. In response to this problem, a renewable electrostatic filter is proposed (Patent Literature 1 and Patent Literature 2).
[PTL 1] Japanese Laid-Open Patent Publication No. H05-154318
[PTL 2] Japanese Laid-Open Patent Publication No. 2008-93501
In general, as a dust collection filter attached to an air inlet of a device such as a projection image display device or an air cleaner, a pleated filter is often employed in order to prolong a filter exchange period with a limited area. The pleated filter is a filter formed by zigzag folding a filter material. A conventional pleated filter has a hardness allowing its shape to be maintained by the single pleated filter alone, and for example, the outer circumference thereof is supported by a frame body.
On the other hand, the renewable electrostatic filter includes a cloth material (for example, unwoven cloth) composed of two or more kinds of different chemical fibers, and is recharged by friction between the chemical fibers. Therefore, in such an electrostatic filter, chemical fibers cannot be fixed, and therefore the electrostatic filter is flexible and its shape is likely to be deformed. In such an electrostatic filter, it is difficult to maintain the shape thereof by only the cloth material, and if the electrostatic filter is left for a while in a pleated shape, the shape is deformed. In particular, if cleaning work is conducted, deformation of the shape is significant.
Such deformation of shape can occur not only in the renewable electrostatic filter but also in the flexible pleated filter. In the conventional support structure which supports the outer circumference of the pleated filter, the shape of the flexible pleated filter is greatly deformed, and the deformation of the shape causes a problem that an area for capturing dust is reduced or an area to which dust adheres becomes partial.
Therefore, an object of the present invention is to provide a dust collection filter unit, a projection image display device using the dust collection filter unit, and an air cleaner using the dust collection filter unit, which can solve such a problem of shape deformation of the pleated filter.
In order to solve the above problem, a dust collection filter unit of the present invention includes: a pleated filter formed by folding a filter material; a frame body having a ventilation hole to which the pleated filter is attached; and support means provided on the ventilation hole and configured to support a plurality of folded portions of the pleated filter, thereby maintaining the shape of the pleated filter.
Typically, in the dust collection filter unit, the support means may include a plurality of support poles supported by the frame body and supporting the respective different folded portions. The folded portions of the pleated filter may be fixedly adhered to the support poles. The folded portions of the pleated filter may be embedded in the support poles. The outer circumferential portion of the pleated filter may be embedded in the frame body. The pleated filter may be embedded in the frame body and the support poles by insert molding upon molding of the frame body and the support poles.
The pleated filter may be configured to satisfy L/P≦3, where L is the height difference (the length in mountain-valley direction of the pleated filter) between mountain and valley in the case where each folded portion is mountain or valley, and P is the folding pitch between the adjacent folded portions on one surface side of the pleated filter.
The pleated filter may have: a filter portion on an air intake side where air enters, the filter portion being configured to capture dust; and a reinforcing net on an air discharge side where air for which dust has been eliminated by the filter portion is discharged, the reinforcing net being more difficult to sag than the filter portion and reinforcing the filter portion. A portion functioning as an electrostatic filter, of the pleated filter, may be composed of a mixed fiber including at least two kinds of synthetic fibers. The thickness of the pleated filter is 1 mm or more.
The support poles may be formed being integrated with the frame body. The plurality of support poles may be provided for some of the plurality of folded portions of the pleated filter. The support poles on an air inlet side of the pleated filter may be provided for every other folded portions on the air inlet side of the plurality of folded portions. Of the plurality of support poles, the number of supported poles supporting the folded portions on an air discharge side of the pleated filter may be less than the number of support poles supporting the folded portions on an air intake side of the pleated filter. The support poles may have concave portions formed thereon, the concave portions not supporting the pleated filter and each provided between portions supporting the folded portions of the pleated filter.
The dust collection filter unit may be provided on an air intake portion of a projection image display device. The dust collection filter unit may be provided on an air intake portion of an air cleaner.
According to the present invention, since the plurality of folded portions of the pleated filter are supported to maintain the shape of the pleated filter, it becomes possible to suppress reduction in the function of the pleated filter due to deformation of the shape.
By using this dust collection filter unit for a projection image display device, it becomes possible to suppress reduction in brightness and occurrence of color unevenness due to dust adhesion, with a high dust collection performance, over a long period. In addition, in the case of using a renewable electrostatic filter, it becomes possible to suppress maintenance cost by cleaning and renewing the filter even if clogging occurs by dust.
In the dust collection filter unit 100, the outer circumferential portion of the electrostatic filter 105 is embedded in the filter frame 106 by insert molding. In order to maintain the electrostatic filter 105 in a pleated shape (a folding shape of alternately making mountain and valley), the electrostatic filter 105 is inserted upon molding of the filter frame 106 so that the outer circumferential portion (peripheral portion) of the electrostatic filter 105 is embedded in resin of the filter frame 106. The insert molding is a molding method of molding the filter frame 106 by resin in the state in which the electrostatic filter 105 is inserted into the mold of the filter frame 106. The outer circumference of the electrostatic filter 105 is embedded in the filter frame 106 by insert molding, and as a result, no gap occurs at the outer circumferential portion of the ventilation hole of the filter frame 106. Therefore, air from the air intake portion 102 is prevented from reaching the air discharge portion 103 without passing through the electrostatic filter 105. The filter frame 106 is configured to be attachable to and detachable from the housing 101.
Owing to the above configuration, when external air taken in through the air intake portion 102 of the housing 101 is passed through the electrostatic filter 105 having a pleated shape by rotation of the axial flow fan 104, dust in the external air can be captured on the electrostatic filter 105. The air after dust has been thus removed is discharged from the air discharge portion 103 of the housing 101, whereby cleaned air can be provided. By configuring the electrostatic filter 105 as a pleated filter having a pleated shape as described above, the filter air passage area can be enlarged, and a time until clogging occurs due to the captured dust can be prolonged.
The support walls 107 are provided for all the folded portions (portions including the vertices of folding and the near portions). Some of the plurality of support walls 107 form air intake side support walls extending on the air intake side of the filter frame 106 along the air flowing direction, and the others form air discharge side support walls extending on the air discharge side of the filter frame 106 along the air flowing direction. In the air discharge side end portion of the air intake side support wall 107, the folded portion (valley folded portion in the case where the dust collection filter unit 100 is put with its air intake side facing upward as shown in
It is noted that the electrostatic filter 105 includes an unwoven cloth portion (filter portion) formed by a mixed fiber material of two kinds of different synthetic fibers, and a reinforcing net 108 for supporting the unwoven cloth portion. The reinforcing net 108 is integrated with the unwoven cloth portion so as to cover one surface of the unwoven cloth portion. The reinforcing net 108 is a net more difficult to sag than the unwoven cloth portion. By providing the reinforcing net 108, shape deformation of the electrostatic filter 105 is suppressed. In the electrostatic filter 105, the reinforcing net is positioned on the air discharge side of the unwoven cloth portion. It is noted that the number of the kinds of the synthetic fibers used for the electrostatic filter 105 may be three or more.
Here, in the case of a normal electrostatic filter, if the filter is cleaned when the ventilation performance is deteriorated due to accumulation of dust while dust is captured, the electrostatic force is also removed. Therefore, the electrostatic filter cannot be reused by cleaning, and after the ventilation performance of the electrostatic filter is deteriorated, the electrostatic filter is discarded. However, in the case of the electrostatic filter 105 according to the present embodiment 1, even if the electrostatic force is temporarily removed by cleaning, the electrostatic force is restored by friction between the two kinds of different synthetic fibers. That is, if the electrostatic filter 105 according to the present embodiment 1 is cleaned when the ventilation performance is deteriorated due to accumulation of dust while dust is captured, similarly, the electrostatic force is temporarily removed, but after the electrostatic filter 105 is dried, the electrostatic force is restored by causing friction between the different kinds of synthetic fibers, whereby dust collection performance can be obtained again.
It is noted that it is desirable to perform treatment such as kneading the electrostatic filter 105 in order to cause friction between the synthetic fibers. However, even by causing air passage in the state where the dust collection filter unit 100 is attached on the housing 101 again, friction occurs between the synthetic fibers by a certain degree of air movement, whereby the electrostatic force is restored. It is noted that in order to cause friction between the synthetic fibers by air movement, it is necessary to allow the synthetic fibers to move to some extent without fixing them. The electrostatic filter 105 is a flexible unwoven cloth, and therefore moves and swings along with the air passage. Therefore, the thickness thereof including the reinforcing net 108 for shape maintenance is 1 mm or more which is thicker than about 0.3 to 0.4 mm of a normal electrostatic filter. In addition, regarding the pitch of a conventional pleated filter, about 5 mm is most common irrespective of the depth. However, in the electrostatic filter 105 according to the present embodiment 1, even if the reinforcing net 108 is added for the above-described reason, the elasticity (toughness) is weak and the shape is unstable. Therefore, it is difficult to maintain the shape of the electrostatic filter 105. Accordingly, as shown in
If the value of L/P is large, the filter area becomes large relative to the ventilation hole (ventilation portion opening) of the filter frame 106. However, if L/P is too large, a portion near the folded portion of the electrostatic filter 105 contacts the support wall 107, whereby a dust collection capability reduced region arises in which dust collection capability is reduced.
A filter area enlargement factor A is represented by expression 1, a filter effectiveness factor B is represented by expression 2, and a filter effective enlargement factor C is represented by expression 3.
A=√{L
2+(P/2)2}/(P/2) Expression 1
B=(L−2×X)/L Expression 2
C=A×B Expression 3
It is desirable that the electrostatic filter 105 is overall judged by the filter effective enlargement factor with respect to the ventilation hole area and the filter effectiveness factor relevant to cost. In view of the function of the electrostatic filter 105, it is desirable that the filter effective enlargement factor is large, and in view of the cost, it is desirable that the filter effectiveness factor is large. Judging from a value D (D=B×C) obtained by multiplying the filter effective enlargement factor by the filter effectiveness factor, D greatly reduces if L/P is larger than 3. Thus, it is found that L/P≦3 is desirable. In addition, since D is maximized at L/P=2.5, 2≦L/P≦3 is further desirable.
In addition,
Further, the support poles 110 may be provided only for some of the plurality of folded portions of the electrostatic filter 105. For example, as shown in
In addition, regarding the plurality of support poles 110, the number of the support poles supporting the folded portions on the air discharge side of the electrostatic filter 105 may be equal to or less than the number of the support poles 110 supporting the folded portions on the air intake side of the electrostatic filter 105. The necessity of the support poles 110 largely depends on not performance but a factor of external appearance. Therefore, particularly, on the air intake side which is easily viewable from outside, the support poles 110 may be provided at every other mountain of the pleated shape, and on the air discharge side, the number of the support poles 110 may be less than on the air intake side. Thus, increase in the invalid region of the electrostatic filter 105 can be suppressed.
Thus, according to embodiment 1, since the shape of the electrostatic filter 105 is maintained by supporting the plurality of folded portions of the electrostatic filter 105 having a pleated shape, reduction in the function of the electrostatic filter 105 due to deformation of the shape can be suppressed. In addition, by forming the electrostatic filter 105 in a pleated shape, the air cleaner 155 for which maintenance management is easy can be provided.
In addition, the configuration of the dust collection filter unit 110 described above is also effective for a projection image display device 150 shown below. In addition, instead of the electrostatic filter 105, a flexible dust collection filter that captures dust by a mesh without using static electricity may be used.
In the projection image display device 150, light emitted from a light source 111 is caused to travel forward by a light reflection mirror 112, and then enters an optical unit 113. The light entering the optical unit 113 passes through dichroic mirrors 114 and 115 and total reflection mirrors 116, 117, and 118, thereby to be divided into color lights of red, green, and blue, and then the intensity of each light is modulated, in accordance with an input signal from outside (not shown), by entry side polarization plates 119R, 119G, and 119B, liquid crystal panels 120R, 120G, and 120B, and exit side polarization plates 121R, 121G, and 121B. These lights are synthesized onto one optical path by a synthesizing prism including dichroic reflection films 122R and 122B, and the synthesized light enters a projection lens 124. The projection lens 124 is designed and placed so that images on the liquid crystal panels 120R, 120G, and 120B can be enlarged and projected, through dust proof glass 126 attached on the opening of a housing 125, onto a screen (not shown) placed in front.
In the projection image display device 150, in order to perform black display, it is necessary to absorb light from the light source 111 by the entry side polarization plates 119R, 119G, and 119B and the exit side polarization plates 121R, 121G, and 121B, and as a result, high temperature occurs along with the absorption. On the other hand, since the polarization plates 119R, 119G, 119B, 121R, 121G, and 121B are mainly made of an organic material, the properties thereof are transformed unless they are cooled to an appropriate temperature. If the properties of the polarization plates 119R, 119G, 119B, 121R, 121G, and 121B are transformed, image control cannot be performed, leading to an unusable state. Besides these, inside the projection image display device 150, the bulb of the light source which can reach 1000 degree Celsius upon light emission, peripheral mechanism components, a power supply 127 for the light source or image display, also cause large self-heating. Therefore, the projection image display device 150 needs cooling means for ensuring the reliability.
In the present embodiment, by an air intake fan 128 which is a blower portion, external air (air with a relatively low temperature) is introduced to the inside of the housing 125 through an air inlet 129 provided on the side surface of the housing 125, a pre-filter 130, and the dust collection filter unit 100. The air forced by the air intake fan 128 contained in an air intake duct 132 is introduced into an optical unit duct 133 placed in close contact with the blow-off outlet of the fan. In the optical unit duct 133, an opening for blue, an opening for green, and an opening 134 for red are provided at positions under the entry side polarization plates 119R, 119G, and 119B, the liquid crystal panels 120R, 120G, and 120B, and the exit side polarization plates 121R, 121G, and 121B. The air introduced into the optical unit duct 133 is blown into the optical unit 113 through these openings. The air blown through these openings takes heat of the entry side polarization plates 119R, 119G, and 119B, the liquid crystal panels 120R, 120G, and 120B, and the exit side polarization plates 121R, 121G, and 121B, and thereafter, also takes heat of the light source 111, the peripheral mechanism components thereto, and the power supply 127 in the process of air drawing by an air discharge fan 135, and further, owing to the operation of a lamp sirocco fan 138.
Furthermore, since a light source drive circuit (not shown) and a video signal circuit (not shown) also generate heat, the thermal design of the projection image display device 150 is made such that these circuits are also cooled at the same time.
The air after reaching the air discharge fan 135 is blown off to the outside of the housing 125 through an air outlet 139 provided in the housing 125.
In the present embodiment 2, the pre-filter 130 is provided on the air intake side of the same dust collection filter unit 110 as that shown in embodiment 1. The pre-filter 130 itself is configured to be extremely unlikely to be clogged in order to prolong the clogging time, and a filter (for example, an extremely low pressure loss filter of 3M company) having a structure that an electrically charged film is made up into an extremely coarse honeycomb form, is used for the pre-filter 130. As shown in
Here, the filter frame 140 has a partition 141 at its center for increasing the strength. The inside of the filter frame 140 is divided into two rooms by the partition 141. In an electrostatic filter 142, support poles 143 are formed at the mountain-folded vertex portions of the pleated structure, at the same time as the molding of the filter frame 140. The electrostatic filter 142 is fixedly adhered to the support poles 143. By thus integrating the electrostatic filter 142 and the support poles 143, the electrostatic filter 142 is fixed and its pleated shape is maintained.
It is noted that as in embodiment 1, also the electrostatic filter 142 includes an unwoven cloth portion formed by a mixed fiber material of two kinds of different synthetic fibers, and a reinforcing net 144 for supporting the unwoven cloth portion. Also in the electrostatic filter 142, if the filter is cleaned when the ventilation performance is deteriorated due to accumulation of dust while dust is captured, the electrostatic force is temporarily removed, but after the electrostatic filter 142 is dried, the electrostatic force is restored by causing friction between the different kinds of synthetic fibers, whereby dust collection performance can be obtained again. Also regarding the restoration, as in embodiment 1, it is desirable to perform treatment such as kneading the electrostatic filter 142. However, even by causing air passage in the state where the dust collection filter unit 100 is attached on the housing 125 again, friction occurs between the fibers by air movement upon air intake, whereby the electrostatic force is restored. It is noted that in order to cause friction between the synthetic fibers by air movement, it is necessary to allow the synthetic fibers to move to some extent without fixing them. Therefore, the thickness thereof including the reinforcing net 144 for shape maintenance is 1 mm or more which is thicker than the thickness of a normal electrostatic filter. In addition, similarly to the description in
In addition, the reinforcing net 144 is placed on the air discharge side of the electrostatic filter 142. Thus, even if a fiber should be dropped off from the electrostatic filter 142, the fiber can be prevented from being drawn into the inside of the projection image display device 150.
As in embodiment 1, it is desirable that of the support pole 143, the support portion 109 integrated with the electrostatic filter 142 is as small as possible so that, of the electrostatic filter 142, the effective region functioning as a filter will not be reduced. In addition, naturally, it is also effective here to reduce an invalid region that cannot be used as a filter by forming a part of the support wall 143 into a concave portion so as to be away from the filter. Further, removal of some of the support poles 143 is also possible as shown in
The present invention can be used for manufacture, selling, and the like of a dust collection filter unit, a projection image display device using the dust collection filter unit, and an air cleaner using the dust collection filter unit.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-017544 | Jan 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/000542 | 1/27/2012 | WO | 00 | 7/24/2013 |
