JPH01306347A - Device for removing water droplets - Google Patents

Abstract

PURPOSE:To contrive to remove water droplets with little electric power consumed by supporting a plate member such as an on-vehicle mirror and the like in such a way as to be freely vibrated, propergating the vibration of a piezo-electric element to the plate member, which is mounted on the back of the plate member at its center, and thereby deflecting the whole of the plate member repeatedly. CONSTITUTION:A plate member 11 such as an on-vehicle mirror and the like is supported in such a way as to be freely vibrated, and a piezo-electric element 20 is mounted on the back face 11a of it at its center. The piezo-electric element 20 is composed of an electrostrictive element, electrodes and of lead wires, and when it is energized, it is extended and contracted so that it starts vibrating. Vibration caused by the piezo-electric element is propagated to the plate member such as the mirror and the like. When current to be supplied is selected, standing waves which is uniform all over the mirror and have great amplitude are developed. In this case, high kinetic energy is imparted to water droplets attached to the reflection surface 11b so that they are removed while being dropped down by gravity or being atomized. By this constitution, attached water droplets can be effectively removed with little electric power consumed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an apparatus for removing water droplets attached to a plate-shaped member such as a reflective mirror of a vehicle.

(Prior Art) A conventional device of this type is disclosed in Japanese Patent Application Laid-Open No. 59-8548 (see FIG. 11). This device has a plate member 1 (mirror) of a vehicle reflector and a vibrator 2.
is fixed, and the vibrator 2 is vibrated by the oscillation circuit 3 in order to remove water droplets attached to the plate-shaped member.

When the plate-like member 1 vibrates, if water droplets adhere to the reflective surface of the plate-like member 1, the water droplets are excited by the plate-like member's 10 vibrations and become atomized.

(Problem to be Solved by the Invention) In order to uniformly remove water droplets attached to the plate-shaped member, it is necessary to vibrate the entire plate-shaped member evenly. In the conventional device, the size of the vibrator is approximately the same as the plate-like portion 10A in order to vibrate the entire plate-like member evenly.

By the way, general vibrators have a problem in that as the shape of the vibrator becomes larger, the vibrator does not vibrate uniformly. For this reason, if the size of the vibrator is set to be approximately the same size as the plate-like member, the vibrator will not vibrate uniformly, causing unnecessary vibrations in the plate-like member (27, the problem of increased power consumption). There is a point.

The present invention was made to solve the problems of the conventional devices, and a common technical problem is to uniformly vibrate a plate member and reduce power consumption.

(Structure of the Invention) (Means for Solving the Problem) In order to achieve the technical problem described in iii, the present invention fixes a vibrator to a part of a plate-like member fixed to be vibrating freely, An oscillation circuit was connected to the vibrator, and the plate member was repeatedly bent by the vibrator.

Further, a frequency variable means is provided to change the oscillation frequency of the oscillation circuit.

(Function) According to the technical means mentioned in t7 above, the plate member is repeatedly bent by the vibrator. This bending excites vibrations in the plate member. The vibrations excited at this time propagate throughout the plate-like member.1. As a result, uniform standing waves are generated throughout the plate member.

Water droplets generated on the plate-shaped member are removed by standing waves generated uniformly over the entire plate-shaped member.

According to the technical means reached i11, power consumption is reduced because unnecessary vibrations are not generated in the plate member. Also,
Power consumption is also reduced by making the vibrator smaller.

Further, according to the above-mentioned technical means, the wavelength of the standing wave generated in the plate member is changed by the frequency variable means, so that the antinode of the standing wave generated in the plate member is moved. Therefore, water droplets adhering to all parts of the plate-like member can be evenly removed.

(Example) Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a plan view of a vehicle side mirror using the water droplet removing device of this embodiment. In addition, Figure 2 shows A-A in Figure 1.
FIG. Furthermore, FIG. 3 is a plan view depicting electrodes 21 and 22 of the piezoelectric vibrator 20.

Almost at the center of the mirror 11 is a disk-shaped piezoelectric vibrator 20.
is fixed with adhesive. The piezoelectric vibrator 20 is
Electrodes 21 and 22 are integrally formed on both end surfaces of the electrostrictive element 23. A lead wire 31 is connected to the electrode 21, and a lead wire 31 is connected to the electrode 22.
A lead wire 32 is soldered to each. When power is input to the lead wires 31 and 32, the piezoelectric vibrator 2o
It expands or contracts in the horizontal direction (vertical direction in the second figure) and the radial direction (horizontal direction in the second figure).

By the way, it is known that general piezoelectric vibrators have a navy effect in which they expand and contract in the same direction as the direction of the applied electric field, and a transverse effect in which they expand and contract in the direction perpendicular to the direction of the applied electric field. There is. Regarding the piezoelectric vibrator 20 used in this embodiment, it is characterized in that the resonance frequency due to the transverse effect is lower than the resonance frequency due to the joint effect. Therefore, in the device of this embodiment, the mirror 11 is caused to bend by using the transverse effect. However, it may be preferable to utilize the longitudinal effect for some mirrors with a high resonance frequency or for some mirrors that cannot withstand large amounts of expansion and contraction.

This will be explained with reference to FIG. 4a. Connect the power supply to the lead wire 31 (
1) When the (-) terminal of the power source is connected to the lead wire 32, the piezoelectric vibrator 20 contracts in the radial direction due to the transverse effect. At this time, a strong contraction force acts on the back surface 11a of the mirror 11, causing the mirror 11 to bend.

This will be explained with reference to Fig. 4b. Contrary to the case in Figure 4a, connect the (=) terminal of the power supply to lead wire 31, and
When the (1) terminal of the power supply is connected to the piezoelectric vibrator 20, the piezoelectric vibrator 20 expands in the radial direction due to the transverse effect. At this time, mirror]
A strong stretching force acts on the back surface 11a of mirror 11, causing mirror 11 to bend in the opposite direction to that shown in FIG. 4a.

This will be explained with reference to FIG. 4c. When an oscillation circuit 40 is connected to the piezoelectric vibrator 20 and AC power is applied to the piezoelectric vibrator 20, the mirror 11 is repeatedly bent. When the frequency of the AC power is selected to be around an integral multiple of the lowest resonant frequency of the mirror 11, the mirror 11 resonates, and a standing wave that is uniform and large in amplitude is generated throughout the mirror 11. This standing wave causes the reflecting surface 1'lb of the mirror 11 to move at high speed. At this time, the water droplets adhering to the reflective surface 11b are given high kinetic energy by the mirror 11, and drop due to gravity,
The light is atomized and removed from the reflective surface 11b of the mirror 11.

Note that the piezoelectric vibrator 20 also has a unique resonance frequency that is determined by the shape of the piezoelectric vibrator 20, so when manufacturing the device of this embodiment, the shape of the piezoelectric vibrator 20 is adjusted to match the resonance frequency of the mirror 11. It is good to consider and decide. In this embodiment, in order to utilize the resonance frequency of the mirror 11 existing in the frequency range of 70 (kHz) to 80 (kHz), a piezoelectric vibrator 20 with a unique resonance frequency of about 70 (kHz) to 80 (kHz) is used. ing. However, since there are many natural vibrations of the mirror 11 ranging from low frequencies to high frequencies, other frequencies may be used.

- As an example, the electrical characteristics of the piezoelectric vibrator 20 of the device of this embodiment are shown in FIG. The electrical characteristics shown in Figure 5 are for a general vehicle sight mirror (Habo 160) currently on the market.
mm) x90 (marked rectangle) with a diameter of 30 mm at the center of gravity.
(mm), and a disk-shaped piezoelectric vibrator 20 with a thickness of 2.8 (n++n) was fixed. The resonant frequency of the piezoelectric vibrator 20 having this shape is approximately 70 [kHz]. Furthermore, the resonant frequency of the mirror 11 is 70 (kHz).
There are some in the frequency range of ~801:kl(z). From this graph, 73(kl(zl~80 (kHz
It can be seen that the impedance of the piezoelectric vibrator 20 fluctuates at z). That is, it can be seen that in the combined system of the resonant system of the mirror 11 and the resonant system of the piezoelectric vibrator 20 used in the measurement, the resonant frequency exists in the range of 73 (kl) to 80 (kHz). 1.8 (w
), the moving speed of the reflective surface 11b of the mirror 11 is approximately 300 m at the center of the piezoelectric vibrator 20.
m/s) or more, approximately 1000 (
M/s) or more.

As a result of many experiments, it has been confirmed that even if the fixed position of the piezoelectric vibrator 20 is changed, there is almost no change in the vibration generated in the mirror 11. Therefore, in the device of this embodiment,
If the piezoelectric vibrator 20 is fixed to a part of the mirror 11, almost the same vibration can be obtained as when the mirror 11 is fixed to the center of gravity.

Furthermore, in the device of this embodiment, the piezoelectric vibrator 20 has a disk shape. The piezoelectric vibrator 20 does not particularly need to be disk-shaped. However, when a disk-shaped piezoelectric vibrator 20 is used, continuous bending occurs in the mirror 11 surrounding the outer periphery of the piezoelectric vibrator 20 as the piezoelectric vibrator 20 expands and contracts in the radial direction.

Therefore, by using the disc-shaped piezoelectric vibrator 20, uniform vibration can be generated in the entire mirror 11 by the single piezoelectric vibrator 20.

FIG. 6 shows the distribution of vibration amplitude at a certain moment in the mirror 11 of the device of this embodiment. From this distribution diagram, it can be seen that the antinodes and nodes of the standing wave are distributed almost uniformly over the entire surface of the mirror 11 with the piezoelectric vibrator 20 at the center. Reflective surface i of mirror 11
The water droplets adhering to tb are atomized at the position where the velocity of movement is maximum, that is, at the antinode of the standing wave. Therefore, in the device of this embodiment, water droplets are removed from the entire surface of the reflective surface 11b of the mirror 11, even though the piezoelectric vibrator 20 is smaller than the size of the mirror 11.

By the way, at the position where the motion speed is minimum, that is, at the node of the standing wave, it takes more time to atomize water droplets than at the antinode of the standing wave. Therefore, when the mirror 11 starts to vibrate, minute water droplets remain at the nodes of the standing wave.
The appearance is upward, and the reflective surface 11b of the mirror 11 appears cloudy. This fogging is removed by continuing to vibrate the mirror 11 for a suitably short period of time. However, it is preferable that such clouding not occur. Further, if the mirror 11 is continuously vibrated to remove fogging, energy is wasted at the antinodes of the standing waves.

Therefore, in the present embodiment, a special oscillation circuit 40 moves the antinode and node of the standing wave generated in the mirror 11 to prevent the mirror 11 from fogging up.

The oscillation circuit 40 of the device of this embodiment will be explained below with reference to FIG. The oscillation circuit 40 includes a microcomputer 41, a power supply circuit 42, an input circuit 113, a D/A converter 44, and a voltage controlled oscillation circuit 451. and a vibrator drive circuit 46.

The power supply circuit 42 is connected to a battery 47, and the oscillation circuit 4
Supply power to each circuit of 0. Further, a star l-switch 4 is connected to the input circuit 43. The start switch 48 is fixed at a position within the vehicle interior where it can be easily operated.

When the start switch 48 is turned on, the oscillation circuit 40 supplies AC power to the piezoelectric vibrator 20.

The frequency of the AC power supplied to the piezoelectric vibrator 20 is determined by the voltage controlled oscillation circuit 45.

The voltage controlled oscillation circuit 45 is controlled by the microcoscipulator 41 via the D/A converter 44.

A vibrator drive circuit 46 is connected between the voltage controlled oscillation circuit 45 and the piezoelectric vibrator 20. A strobe signal 49 from the microcomputer is input to the drive circuit 46 . The drive circuit 46 supplies AC power to the piezoelectric vibrator 20 only when the strobe signal 49 is on.

The oscillation frequency of the oscillation circuit 40 is determined by the microcomputer 41.
It is possible to make various changes depending on the program stored in the . Microphone 10 is shown in Figures 8, 9, and 10.
An example of a program executed on the computer 41 is shown below.
According to the program shown in FIG. 8, the oscillation circuit 40
, the different resonance frequencies of the mirror 12 are randomly switched and output. According to the program shown in FIG. 9, different resonance frequencies of the mirror 12 are sequentially switched and outputted from the oscillation circuit 40. Furthermore, according to the program shown in FIG.
A frequency that continuously varies from 0 to within a predetermined range centered around one resonance frequency of the mirror 12 is output.

First, the program shown in FIG. 8 will be explained. When the power supply circuit 42 is connected to the battery 47, the process of step S1 is executed. In step S1, initial settings necessary for subsequent processing are performed, and the strobe signal 49 is set to OFF.

In step S2, it is determined whether the start switch 48 is on. If the switch 48 is off, the process of step S3 is executed and the strobe signal 49 is turned off. Conversely, when the switch 48 is on, the processes of steps 84 to S7 are executed, and the piezoelectric vibrator 2
0 is made to vibrate.

In step S4, a random number is assigned to flag n. Here, the random number takes a value of either 1"' or 21Z113". In step S5, the map shown in Table 1 is referred to, and a numerical value corresponding to the value of flag n is assigned to flag f. The value of the flag [corresponds to the oscillation frequency of the voltage-controlled oscillation circuit 45. Note that all the oscillation frequencies of the voltage-controlled oscillation circuit 45 are the resonance frequencies of the mirror 12.

In step S6, the value of the flag r set in step S5 is output to the D/A converter 44, and the voltage controlled oscillation circuit 45 oscillates at a frequency determined by a random number. In step S7, the strobe signal is turned on, and AC power is supplied from the drive circuit 46 to the piezoelectric vibrator 20. In step S8, execution of the process is suspended for a predetermined period of time.

The above program causes the oscillation circuit 4o to randomly switch the different resonance frequencies of the mirror 12 at predetermined time intervals substantially determined in step S8 while the start switch 18 is on. Output.

Next, the program shown in FIG. 9 will be explained. In the program of FIG. 9, snap S4 of the program shown in FIG. 8 is step Sll, step S12. It has been replaced with S13. Through the processing of steps 811 to S13, the value of the flag n is sequentially switched in the following order: ``BI'SU2PA→PA3''→"l"). Accordingly, the program of FIG. 9 causes the oscillation circuit 4o to sequentially adjust the different resonant frequencies of the mirror 12 at predetermined time intervals substantially determined by step S8 while the start switch 48 is on. It is switched and output.

Finally, the program shown in FIG. 10 will be explained. In the program of FIG. 10, step S4 of the program shown in FIG. S5 is step 321. S22, S23. S24
It has been exchanged with. Through the processing in steps 321 to S24, the value of the flag f fluctuates within a predetermined range around the predetermined value f1. Here, in the device of this embodiment, the predetermined value f1 is set to 74(kl(z:1), that is, 85''), so the value of the flag f ranges from '75' to '95'.
Therefore, according to the program shown in FIG. 64 (kHz) to 8 centered around one resonance frequency of 12 (14CkHz)
A frequency that continuously fluctuates within the range of 4(kl(z:)) is output.

According to the programs shown in FIGS. 8, 9, and 10 described above, the oscillation frequency of the oscillation circuit 40 changes.

When the oscillation frequency of the oscillation circuit 40 changes, the length of the standing wave generated on the mirror 12 changes.
The antinodes and nodes of the standing wave generated in 1 move. Therefore, the kinetic energy on the mirror 12 can be distributed almost uniformly.

As a result, water droplets adhering to the entire surface of the mirror 12 can be atomized almost simultaneously, and fogging can be prevented. Furthermore, wastage of energy that occurs when removing fogging is also prevented. Therefore, the durability of the mirror 12 and the piezoelectric vibrator 20 can be improved by minimizing the heat generation of the piezoelectric vibrator 20.

Furthermore, according to the programs shown in FIGS. 8, 9, and 10, the oscillation frequency of the piezoelectric vibrator 20 is set outside the audible frequency range. Therefore, no unpleasant audible sound is generated from the mirror 11.

Furthermore, according to the program shown in FIG. 10, the oscillation frequency of the oscillation circuit 40 fluctuates around the resonance frequency of the mirror II. Therefore, even if the resonant frequency of the mirror 11 changes due to various causes, the mirror 11 can be reliably resonated.

In the device of this embodiment, since the mirror 11 is not vibrated at a constant frequency, strong vibrations in the resonance state can be prevented. Therefore, excessive displacement of the mirror II is prevented, and the stress applied to the mirror 11 can be kept to a minimum. Therefore, it is also possible to prevent the mirror 11 from being bent due to the applied stress.

〔Effect of the invention〕

According to the present invention, water droplets adhering to the plate-shaped portion [E] can be removed using a small amount of water.

Furthermore, since the vibrator only needs to be fixed to a part of the plate-like member, the vibrator is smaller than the plate-like member.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a vehicle side mirror depicting an embodiment of the present invention. FIG. 2 is an A-Alli plane view of FIG. 1. FIG. 3 is a plan view depicting electrodes of a piezoelectric vibrator according to an embodiment of the present invention. Figures 4a, 4b, and 1c are explanatory sections showing the operation of an embodiment of the present invention. FIG. 5 is a graph showing the electrical characteristics of the piezoelectric oscillator of the device according to an embodiment of the present invention. FIG. 6 is a distribution diagram showing the distribution of vibration amplitude that occurs at a certain moment in an apparatus according to an embodiment of the present invention. FIG. 7 is a block diagram depicting an oscillation circuit of an apparatus according to an embodiment of the present invention. FIGS. 8, 9, and 10 are flowcharts 1 depicting a program executed by the oscillation circuit of an apparatus according to an embodiment of the present invention.
・It is. FIG. 11 is an explanatory diagram depicting a conventional water droplet removing device. DESCRIPTION OF SYMBOLS 11...Mirror (plate-shaped member), 11a...Back surface, 11b...Reflection surface, 20...Piezoelectric vibrator (vibrator), 21.22...1 cover, 23...
Electrostrictive element, 31.32...-Lead wire, 40... Oscillation circuit. 4I...Microcomputer (frequency variable means).

Claims (6)

[Claims] (1) A plate-like member fixed so as to be able to freely vibrate, a vibrator fixed to a part of the plate-like member and bending the plate-like member, and a vibrator connected to the vibrator and caused by the vibrator A water droplet removal device comprising: an oscillation circuit that repeatedly bends a member; and a frequency variable means that changes the oscillation frequency of the oscillation circuit. (2) The water droplet removing device according to claim (1), wherein the vibrator is disk-shaped. (3) The water droplet removing device according to claim (1), wherein the plate member is bent using a transverse effect of the vibrator. (4) The water droplet removing device according to claim (1), wherein the oscillation circuit is caused to oscillate at a resonance frequency of the plate-like member. (5) The water droplet removing device according to claim (1), wherein the oscillation circuit vibrates at a frequency other than an audible frequency. (6) The water droplet removing device according to claim (1), wherein the resonant frequency of the vibrator and the resonant frequency of the plate member are made to match.