JPH0436280B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention can be applied to air intake devices for indoor temperature sensors in air conditioners, computer cooling devices, convection devices in ovens, defrosting devices for refrigerators, etc. This invention relates to a piezoelectric fan device.

(Prior art) Conventionally, the structure of this type of piezoelectric fan device is as follows:
For example, as shown in Fig. 1, the casing 1
A piezoelectric fan 2 is housed inside the fan 2, and the diaphragm 20 of the fan 2 is vibrated as shown by the broken line in the figure by applying an alternating voltage to guide air into the casing 1 from the suction port 1a as shown by the arrow. It is discharged to the outside from the outlet 1b.

When the air inside the casing 1 of the fan device having the above structure was visualized using the Schiereren method, the following was discovered.

That is, as the diaphragm 20 of the piezoelectric fan 2 moves, a vortex is formed and the vortex is emitted obliquely forward, a cycle repeated. When observing this in detail, as shown in FIG. 2, as the diaphragm 20 moves, the air in the area surrounded by the broken line
Casing 1 is pushed diagonally forward while being pushed by
The liquid collides with the wall surface and is discharged (flow B in the figure).
On the other hand, the vibration causes a pressure difference between the front and back sides of the diaphragm 20 in the vibration direction, and a separation vortex A is formed that goes around the tip of the diaphragm and leaks to the back side of the diaphragm. Also, even on the front side of the diaphragm,
By the above-mentioned collision of the airflows or by the next vibrational movement of the diaphragm 20, that is, by the vibrational movement in the opposite direction,
A backflow C to the suction side is generated.

As described above, the conventional structure causes collision of airflows, generation of separated vortices, and backflow toward the suction port, resulting in a decrease in the discharge air volume.

Therefore, the inventor of the present invention has found that the main cause of the reduction in air volume due to the above-mentioned mechanism is the structure of the discharge port in the casing.

(Objective of the Invention) The present invention provides the above-mentioned collision of air, generation of separated vortices,
It is an object of the present invention to provide a piezoelectric fan device that can suppress a decrease in discharge air volume caused by a backflow phenomenon and efficiently guide airflow to a discharge port.

(Structure of the Invention) In order to achieve the above object, the piezoelectric fan device of the present invention includes a piezoelectric fan having a flat plate shape that utilizes the vibration motion of a piezoelectric bimorph element; and a casing having a discharge port at the other end, and the discharge ports are independently set so as to branch corresponding to the front and back sides of the piezoelectric fan in relation to the housing position of the voltage fan. The axial direction of the opening is set at a predetermined spread angle with respect to the suction direction from the suction port.

More specifically, it is desirable that the spread angles of the opening axes of the discharge ports set on each of the front and back sides be symmetrical with respect to the piezoelectric fan when not vibrating, for example, from 120° to 180°.

Further, it is desirable that the tip position of the piezoelectric fan is set with a predetermined clearance with respect to the branch portion of each discharge port.

(Actions and Effects of the Invention) As described above, the piezoelectric fan device of the present invention has the following features:
The discharge port is branched to the front and back sides of the piezoelectric fan, and the axial direction of the opening has a predetermined spread angle with respect to the suction direction.
It is possible to suppress the decrease in the discharge air volume due to the collision of the air flow with the wall surface or the backflow phenomenon caused by the collision. In addition, the branch points of the discharge ports set on the front side and the back side of the piezoelectric fan are set in relation to the housing position of the piezoelectric fan, so
By setting the clearance between the branch point and the tip of the fan, it is also possible to suppress a decrease in air volume caused by the generation of separated vortices.

As described above, according to the present invention, it is possible to suppress the decrease in the discharge air volume caused by the above-mentioned collision of air flows, generation of separated vortices, and backflow phenomenon, and it is possible to efficiently guide the air flow to the discharge port. The excellent effect of being able to do this is produced.

(Example) The present invention will now be described in detail with reference to Examples.
First, the structure of the piezoelectric fan will be explained with reference to FIG. In the figure, numerals 21 and 22 are piezoelectric elements, both of which are made of semiconductor porcelain made of lead zirconate titanate, and electrodes 23, 24, 25, and 26 are formed on both surfaces by printing, plating, or vapor deposition methods. It is formed into a thin film. The material is Ag, Ni, Al, etc.

A reinforcing plate/diaphragm 20 made of a metal such as Kovar whose coefficient of thermal expansion is close to that of the piezoelectric elements 21 and 22 is sandwiched between the piezoelectric elements 21 and 22. It is fixed by gluing or soldering. The right side of the diaphragm 20 in the figure protrudes dimensionally long from the piezoelectric elements 21 and 22, and vibrates at this protrusion. A lead wire 27 is connected to the left side.

Further, the electrodes 23 and 26 of the piezoelectric elements 21 and 22 are sandwiched between electrode plates 28 made of an electrically conductive metal such as copper.

One of the piezoelectric elements 21 is polarized in the direction of the arrow X in the figure, and the other piezoelectric element 22 is also polarized in the X direction.

By applying an alternating voltage between the diaphragm 20 and the electrode plate 28, the tip of the diaphragm 20 vibrates in the direction of arrow A in FIG.

Next, a schematic structural diagram of a fan device incorporating the piezoelectric fan having the above structure will be shown and explained. Fourth
In the example of the present invention shown in the figure, the discharge port 1b of the casing 1 for accommodating the piezoelectric fan is set in a Y-shape.
To explain in more detail, the discharge port 1b is divided into two in the vibration direction of the diaphragm 20 of the piezoelectric fan 2 (in the direction of the dashed line in the figure).

By adopting such a discharge port structure,
The flow that goes around the diaphragm 20, the flow that collides with the wall surface of the casing 1, and the back flow are eliminated, and the discharge port 1b
It is possible to significantly increase the amount of air from the

Specific experimental data regarding this point is shown in FIG. 5, and will be explained. First, to clarify the specifications of the sample used in the experiment, the length a of the diaphragm 20 (see Figure 3, the same below) is 22.5 mm, and its thickness is
55 μm, and the length b of each piezoelectric element 21 and 22 is
22.5mm, each of which has a thickness of 0.2mm. Also,
The inner flow path of the casing 1 in Fig. 4 has a width c of 20 mm.
Length d is 100mm, height is 25mm, width e of discharge port 1b
is 11mm and the height is 25mm.

In the above specifications, the two discharge ports 1b in FIG.
The air volume was measured under the conditions of a resonance frequency of 135 Hz and an applied voltage of 140 Vp-p by changing the spread angle θ (deg) of the diaphragm 20 and the tip clearance X (mm) of the diaphragm 20. Figure 5 shows the results.

According to FIG. 5, it can be seen that the spread angle θ of the discharge port 1b is preferably in the range of 120° to 180°, although it depends on the clearance X. It is considered that when the spread angle is small, the air volume is low and the impact of the air flow colliding with the casing 1 is large. Further, the clearance X is desirably about 1 mm to 7 mm, and it is considered that if the distance is too large (clearance X is large), the air volume decreases because the flow path of the separated vortex that goes around the diaphragm increases.

By the way, the structure shown in Figure 1 (piezoelectric fan 2)
(The specifications, casing flow path dimensions, and discharge port dimensions are the same as those explained in Figures 3 and 4), the air volume is 1.6.
m ³ /h, which is extremely low.

According to the inventor's experiments, the most desirable discharge port structure is a T-shaped structure in which θ is 180° as shown in FIG. 6, and the clearance X is 4 mm. With this structure, we were able to increase the air volume by about 60% compared to the one shown in Figure 1.

FIG. 7 shows still another embodiment of the present invention, in which the spread angle θ is slightly larger than 180°. According to this Fig. 7, the discharge port 1
It is possible to increase the air volume compared to b.

Next, the structure of an air introduction fan device for a vehicle interior temperature sensor of an automobile automatic air conditioner using the piezoelectric fan device according to the present invention will be described below.

FIG. 8 is a sectional view seen from above, in which the box 3 and panel 4 are separated and integrated by fitting. Inside the box 3, an auto air conditioner control circuit board, a piezoelectric fan 2, and a piezoelectric fan driving circuit are incorporated. The piezoelectric fan 2 is housed in a casing 1, and the upstream side of the casing 1 communicates with a duct 5. This duct 5 communicates with the outside via a suction grille 4a of the panel 4. Further, the downstream side of the casing 1 communicates with the outside via a discharge grille 3a provided on the side surface of the box 3. Note that the downstream side of the casing 1 communicates with the outside via a discharge grille 3a provided on the side surface of the box 3. Note that a vehicle interior temperature sensor 6 is installed at the connection between the casing 1 and the duct 5.

The above-mentioned suction grill 4a and suction duct 5 are connected to a panel 4 on which an operation switch section 7 and a temperature display section 8 are provided.
The terminal of the sensor 6 is fixed to the auto air conditioner control circuit board 8 (FIG. 10).
The temperature sensing part is installed inside the duct 5. Then, other components are attached to the box 3 side,
When the box 3 and panel 4 are integrated, the casing 1 of the piezoelectric fan 2 is assembled so as to sandwich the gasket 9 of the sensor 6. A control device having such a configuration is installed in the center of a vehicle's instrument panel.

The piezoelectric elements 21 and 22 of the piezoelectric fan 2 are provided with an electrode plate 28 as shown in FIG. 3, which is shown in a perspective view as shown in FIG. 11. This piezoelectric fan 2 is fitted into a groove of an insulating mounting portion 10 integrally formed on the casing 1. As shown in FIG. 12, this casing 1 is attached to a box 3 with screws 13 via a cover 11 and cushion rubber 12 on its upper part. In addition, there is a cushion rubber 1 between screw 13 and box 3.
4 is interposed. With this configuration, vibrations of the piezoelectric fan 2 can be prevented from leaking to the outside via the box 3.

In the above configuration, the electrode plate 28 and the lead wire 2
7, the piezoelectric fan 12 vibrates, and the air inside the vehicle reaches the inside of the duct 5 through the suction grille 4a, passes through the temperature sensing part of the sensor 6, and enters the casing 1. to go into. Subsequently, the air is again discharged into the vehicle interior through the T-shaped bent discharge grille 3a and returned.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a conventional example, Fig. 2 is a cross-sectional view used to explain the problems of the conventional example in Fig. 1, and Fig. 3 shows a detailed structure of a piezoelectric fan used in an embodiment of the present invention. 4 is a sectional view showing one embodiment of the present invention, FIG. 5 is a characteristic diagram for explaining the effects of the present invention, and FIGS. 6 and 7 show other embodiments of the present invention. 8 is a sectional view showing an application example of the present invention, FIG. 9 is a front view of FIG. 8, FIG. 10 is a sectional view taken along line A-A in FIG. 8, and FIG. 11 is a piezoelectric FIG. 12 is a perspective view showing the support structure of the fan, and FIG. 12 is a sectional view showing the mounting structure between the casing and the box shown in FIG. 1...Casing, 1a...Suction port, 1b...Discharge port, 2...Piezoelectric fan.

Claims (1)

[Claims] 1. A piezoelectric fan having a flat plate shape that utilizes the vibration motion of a piezoelectric bimorph element;
and a casing having a discharge port at the other end, and the discharge port is independently set so as to branch corresponding to the front and back sides of the plate surface of the piezoelectric fan in relation to the accommodation position of the voltage fan. A piezoelectric fan device, characterized in that the axial direction of the opening is set at a predetermined spread angle with respect to the suction direction from the suction port. 2. Claim 1, wherein the spread angle of the opening axes of the discharge ports set on each of the front and back sides is set in a range of about 120° to about 180° symmetrically with respect to the piezoelectric fan when the front and back are not vibrating. The piezoelectric fan device described in . 3. The piezoelectric fan device according to claim 1 or 2, wherein a tip position of the piezoelectric fan is set with a predetermined clearance with respect to a branch portion of each of the discharge ports.