1. Field of the Invention
The present invention relates to a fluid control device which performs fluid control.
2. Description of the Related Art
International Publication No. 2008/069264 discloses a conventional fluid pump (see FIGS. 1A to 1E). FIG. 1A to FIG. 1E show operations of the conventional fluid pump in a tertiary mode. The fluid pump, as shown in FIG. 1A, includes a pump body 10; a vibrating plate 20 in which the outer peripheral portion thereof is attached to the pump body 10; a piezoelectric element 23 attached to the central portion of the vibrating plate 20; a first opening 11 formed on a portion of the pump body 10 that faces the approximately central portion of the vibrating plate 20; and a second opening 12 formed on either one of a region intermediate between the central portion and the outer peripheral portion of the vibrating plate 20 or a portion of the pump body 10 that faces the intermediate region.
The vibrating plate 20 is made of metal. The piezoelectric element 23 has a size so as to cover the first opening 11 and a size so as not to reach the second opening 12.
In the above mentioned fluid pump, by applying voltage having a predetermined frequency to the piezoelectric element 23, a portion of the vibrating plate 20 that faces the first opening 11 and a portion of the vibrating plate 20 that faces the second opening 12 are bent and deformed in opposite directions, as shown in FIG. 1A to FIG. 1E. This causes the fluid pump to draw fluid from one of the first opening 11 and the second opening 12 and to discharge the fluid from the other opening.
The above mentioned fluid pump, as is shown in FIG. 1A with a conventional structure, has a simple structure, and thus the thickness of the fluid pump can be made thinner. Such a fluid pump is used, for example, as an air transport pump of a fuel cell system.
At the same time, electronic equipment and apparatuses into which the fluid pump is incorporated have tended to be miniaturized. Therefore, it is necessary to further miniaturize the fluid pump without reducing the pump performance (the discharge flow rate and the discharge pressure) of the fluid pump.
However, the performance of the fluid pump decreases as the fluid pump becomes smaller. Therefore, there are limitations to miniaturizing the fluid pump having the conventional structure while maintaining the pump performance.
Accordingly, the inventors of the present invention have devised a fluid pump having a structure shown in FIG. 2.
FIG. 2 is a sectional view showing a configuration of a main portion of the fluid pump. The fluid pump 901 is provided with a flexible plate 35, a vibrating plate unit 38, and a piezoelectric element 32, and is provided with a structure in which the components are layered in that order.
The vibrating plate unit 38 includes a vibrating plate 31, a frame plate 33, and a link portion 34. The vibrating plate unit 38 is formed of metal. In addition, the piezoelectric element 32 and the vibrating plate 31 bonded to the piezoelectric element 32 constitute an actuator 30. The vibrating plate 31 has the frame plate 33 provided therearound. The vibrating plate 31 is linked to the frame plate 33 by the link portion 34. A ventilation hole 35A is formed in the center of the flexible plate 35. Moreover, the frame plate 33 is fixed to the end of the flexible plate 35 by an adhesive agent layer 37. For this reason, the vibrating plate 31 and the link portion 34 are supported by the frame plate 33 in a position spaced away from the flexible plate 35 by a distance equal to the thickness of the adhesive agent layer 37. The link portion 34 has an elastic structure having the elasticity of a small spring constant.
Therefore, the vibrating plate 31 is flexibly and elastically supported at two points against the frame plate 33 by two link portions 34. For this reason, the bending vibration of the vibrating plate 31 generated by expansion and contraction of the piezoelectric element 32 cannot be blocked at all. In other words, the fluid pump 901 has a structure in which the peripheral portion of the actuator 30 is not substantially fixed. Accordingly, there will be a reduction in the loss caused by the bending vibration of the actuator 30.
Consequently, since the flexible plate 35 vibrates with driving of the actuator 30, the amplitude of vibration of the fluid pump 901 is effectively increased. This allows the fluid pump 901 to produce a high discharge pressure and a large discharge flow rate despite the small size and low profile design thereof.
However, in the fluid pump 901, when the frame plate 33 and the flexible plate 35 are fixed by an adhesive agent, an excess amount of the adhesive agent may possibly flow into a gap between the link portion 34 and the flexible plate 35 from the adhesive agent layer 37. Due to this, there is a possibility that the link portion 34 and the flexible plate 35 adhere to each other and block the vibration of the actuator 30.
In addition, although a distance between the vibrating plate 31 and the flexible plate 35 is determined by a thickness of the adhesive agent layer 37, it is extremely difficult to accurately and consistently achieve an exact distance determined by the applied amount of the adhesive agent. For this reason, in the fluid pump 901, a distance between the vibrating plate 31 and the flexible plate 35 that affects the pressure-flow rate characteristics of the fluid pump 901 cannot be accurately and consistently defined. Thus, the fluid pump 901 has a problem that the pressure-flow rate characteristics of the fluid pump 901 fluctuate with each fluid pump 901.