Patent Application
20080304983
The present application claims priority to Japanese Patent Application JP2007-152411 filed in the Japanese Patent Office on Jun. 8, 2007, the entire contents of which being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a diaphragm air pump which vibrates a diaphragm in a reciprocating manner to obtain a pump action.
2. Description of the Related Art
The disclosure examines a method in which a piezoelectric air pump using a piezoelectric vibrator is used for cooling a heat generating source (for example, CPU) of a notebook PC, for example.
The piezoelectric vibrator has an amplitude of several tens to several hundreds μm order. As a piezoelectric vibrator vibrates in a variable volume chamber, the volume of the chamber is sufficiently reduced such that jet gas (air) can be transferred, and the heated air around the heat generating source is moved by the gas flow such that the heat generating source is cooled.
The piezoelectric vibrator is constructed by stacking a piezoelectric body on at least one of the top and bottom surfaces of a shim (conductive thin metal plate). The thickness of the piezoelectric vibrator can be reduced into less than 1 mm as a whole. Further, the variable volume chamber formed over and under the piezoelectric vibrator has such a small volume as to supply and discharge compressive air through the vibration of the piezoelectric vibrator. Therefore, the thickness of a piezoelectric gas jetting device can be significantly reduced in such a manner that the device is used for cooling such an apparatus as a notebook PC having a small space. Such a gas jetting device is disclosed in Japanese Patent Unexamined Publication No. 2005-256834 and U.S. Pat. Nos. 6,801,430 and 6,123,145.
In the piezoelectric air pump, a ring-shaped seal member formed of an elastic material is provided on the top and bottom surfaces of the piezoelectric vibrator, in order to secure an air-tight structure of the piezoelectric vibrator (diaphragm). That is, the ring-shaped seal member is interposed between the top periphery of the diaphragm and an upper housing and between the bottom periphery of the diaphragm and a lower housing, respectively. It has been considered to be essential that the ring-shaped seal member is provided on both the top and bottom surfaces of the diaphragm. However, according to the analysis of the present inventors, a diaphragm air pump in which liquid leak does not need to be considered may not have a ring-shaped seal member provided on both the top and bottom surfaces. By improving a seal structure, air seal can be realized by a single ring-shaped seal member.
A diaphragm air pump includes a diaphragm and upper and lower housings that interpose the diaphragm such that a variable volume chamber is formed over and under the diaphragm. The diaphragm air pump vibrates the diaphragm to obtain a pump operation, and the variable volume chambers provided on the top and bottom of the diaphragm, respectively, can be air-sealed by one ring-shaped elastic seal member.
In the diaphragm air pump, a circular concave portion into which the diaphragm that is circular in plan view is fitted is formed in any one of the upper and lower housings, a ring-shaped groove for housing a seal member is formed in the other, the ring-shaped groove having inner and outer diameters which are set across the circular concave portion, and a ring-shaped elastic seal member which is compressively deformed across the periphery of the diaphragm by the upper and lower housings is housed in the ring-shaped groove.
The diaphragm may be a piezoelectric vibrator.
The piezoelectric vibrator 10 is a unimorph-type piezoelectric vibrator which includes a shim 11 and a piezoelectric body 12 stacked on one surface of the shim 11 (
The lower housing 30 has a stepped circular concave portion 31 formed therein. The stepped circular concave portion 31 is composed of a small-diameter circular concave portion 32, in which the piezoelectric body 12 is positioned in a non-contact manner, and a large-diameter circular concave portion 33 into which the shim 11 is fitted. The large-diameter circular concave portion 33 is formed on the small-diameter circular concave portion 32 such that the concave portions are concentric with each other. The depth and thickness of the large-diameter circular concave portion 33 correspond to the diameter and thickness of the shim 11. When the shim 11 is fitted into the large-circular concave portion 33, the surface of the shim 11 becomes flush with a peripheral abutting surface 34 of the lower housing 30. The depth of the small-diameter circular concave portion 32 is set in such a manner that when the piezoelectric vibrator 10 (shim 11) is fitted into the stepped circular concave portion 31 (large-diameter circular concave portion 33), a lower variable volume chamber 35 with a minute space is formed between the piezoelectric body 12 and the bottom of the small-diameter circular concave portion 32. As such, only the shim 11 of the piezoelectric vibrator 10 is interposed between the upper and lower housings, and the piezoelectric body 12 is positioned so as not to come in contact with the housing. Therefore, the deformation (vibration) of the piezoelectric vibrator 10 is easily performed, which makes it possible to increase the amplitude of vibration.
Meanwhile, the upper housing 20 has a circular concave portion 21 and a ring-shaped groove 22 concentric with the circular concave portion 21. The outer diameter D of the ring-shaped groove 22 is set to be larger than the outer diameter of the large-diameter circular concave portion 33, and the inner diameter d of the ring-shaped groove 22 is set to be smaller than the outer diameter of the large-diameter circular concave portion 33. That is, the inner and outer diameters of the ring-shaped groove 22 are set across the largest-diameter portion (edge) of the large-diameter circular concave portion 33. The depth of the circular concave portion 21 is set in such a manner that when the peripheral abutting surface 23 of the upper housing 20 is abutted on the peripheral abutting surface 34 of the lower housing 30, an upper variable volume chamber 24 with a minute space is formed between the shim 11 of the piezoelectric vibrator 10 fitted into the stepped circular concave portion 31 and the bottom of the circular concave portion 21.
The ring-shaped elastic seal member 40 is inserted into the ring-shaped groove 22 of the upper housing 20. The inner and outer diameters of the ring-shaped elastic seal member 40 correspond to those of the ring-shaped groove 22 and are set across the outer-diameter edge of the shim 11 of the piezoelectric vibrator 10. Further, the depth of the ring-shaped groove 22 and the thickness of the ring-shaped elastic seal member 40 are set in such a manner that when the peripheral abutting surface 23 of the upper housing 20 and the peripheral abutting surface 34 of the lower housing 30 are abutted so as to be fastened through a fastening screw 27, the ring-shaped elastic seal member 40 is compressed 20-30%. The ring-shaped elastic seal member 40 has a rectangular cross-section in a free state. However, the ring-shaped elastic seal member 40 may have a circular cross-section, an oval cross-section, or an elliptical cross-section.
The upper and lower housings 20 and 30 have upper and lower supply/discharge holes 26 and 36, respectively, through which the upper and lower variable volume chambers 24 and 35 communicate with the outside. The upper and lower supply/discharge holes 26 and 36 extend between the bottom surface of the upper and lower variable volume chambers 24 and 35 and the side surface of the upper and lower housings 20 and 30. The volume (cross-sectional area) of the upper and lower variable volume chamber 24 and 35 is determined in such a manner that the suction and discharge of air accompanied by the vibration of the piezoelectric vibrator 10 is performed as impulsively as possible and a compression ratio increases. Further, the opening ends of the upper and lower supply/discharge holes 26 and 36 on the side surface of the piezoelectric air pump 100 are disposed in a zigzag shape such that the positions thereof do not coincide with each other in the vertical direction. The upper and lower supply/discharge holes 26 and 36 can be connected to suitable pipes so as to be opened in arbitrary positions.
As an index indicating what size the present piezoelectric air pump 100 has, a specific dimensional example is described as follows.
Upper housing 20 (Lower housing 30)=Square Of 35 mm in length of about one
Total thickness of upper and lower housings 20 and 30=3 mm
Thickness of shim 11=0.2 mm
Thickness of piezoelectric body 12=0.2 mm
Gap between circular concave portion 21 and shim 11 in free state (Depth of upper variable volume chamber 24)=0.15 mm
Gap between small-diameter concave portion 32 and piezoelectric body 12 in free state (Depth of lower variable chamber 35)=0.15 mm
Amplitude of piezoelectric vibrator 10=0.15 to 0.2 mm
In the above-described piezoelectric air pump 100, as an alternating electric field is applied to the top and bottom surfaces of the piezoelectric body 12 through the feed line 13, the piezoelectric vibrator 10 vibrates in such a manner that the amplitude of the central portion thereof that is circular in plan view becomes the greatest. Then, in a stroke where the volume of the upper variable volume chamber 24 (lower variable volume chamber 35) expands, the air is sucked into the upper variable volume chamber 24 (lower variable volume chamber 35) from the upper supply/discharge hole 26 (lower supply/discharge hole 36). In a stroke where the volume of the upper variable volume chamber 24 (lower variable volume chamber 35) contracts, the air is discharged into the upper supply/discharge hole 26 (lower supply/discharge hole 36) from the upper variable volume chamber 24 (lower variable volume chamber 35). The volumes (cross-sectional areas) of the upper variable volume chamber 24 (lower variable volume chamber 35) and the upper supply/discharge hole 26 (lower supply/discharge hole 36) are determined in such a manner that the suction and discharge of air is performed as impulsively as possible. Therefore, the movement of the air occurs in the vicinities of the opening end of the upper supply/discharge hole 26 (lower supply/discharge hole 36), which makes it possible to obtain a cooling operation.
In the above-described embodiment, the terms of ‘upper’ and ‘lower’ have been used for convenience of description. However, the terms do not indicate the upper and lower relationship when the piezoelectric air pump 100 is used.
In the above-described embodiment, a unimorph-type piezoelectric vibrator is used as the piezoelectric vibrator 10. However, a bimorph-type piezoelectric vibrator may be used, in which a piezoelectric body is provided on the top and bottom surfaces of a shim and of which the amplitude is large. Further, the present invention can be applied to an air pump using a diaphragm, in addition to a piezoelectric vibrator.
In the diaphragm pump according to the embodiment of the invention, a circular concave portion to which a diaphragm that is circular in plan view is fitted is formed in any one of upper and lower housings, and a ring-shaped groove for housing a seal member is formed in the other one, the ring-shaped groove having inner and outer diameters which are set across the circular concave portion. Further, a ring-shaped elastic seal member, which is compressively deformed across the periphery of the diaphragm by the upper and lower housings, is housed in the ring-shaped groove for housing the seal member. Therefore, variable volume chambers provided on the top and bottom of the diaphragm, respectively, can be air-sealed by one ring-shaped elastic seal member.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims of the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-152411 | Jun 2007 | JP | national |
