JPH0257956A - Raindrop sensor - Google Patents

Abstract

PURPOSE:To implement a raindrop sensor without causing erroneous detection by providing raindrop draining means which are arranged at a specified interval so as to cross the upper part of a detecting surface and drain the raindrop that is attached on the detecting surface and has a diameter larger than a specified size by capillarity. CONSTITUTION:The upper surface of a sensor chip 1 of a raindrop sensor S is a detecting surface 1a. Strips 4 each having a specified width W are provided at a small interval at the front upper part of the surface 1a. The strip 4 is constituted with stainless steel having the thickness of, e.g. about 0.3mm. The strip 4 is located directly over a detecting electrode 2 having the smaller width than the other part. The upper and lower ends of the strips 4 are linked together in a frame shape. The width W is made to be about 1.5mm based on the strength. A gap (d) between the strip 4 and the surface 1a is made to be about 0.2mm so as to provide capillarity. Among raindrops attached on the surface 1a, the raindrop L having the diameter larger than the interval between the strips 4 is sucked into the gap (d) owing to the capillarity of the gap (d) in contact with the raindrop beneath the strip 4 as shown with the continuous line. The raindrop descends along the slant surface 1a and drained downward.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a raindrop sensor that can be used for automatic operation control of vehicle wipers, and more particularly to a raindrop sensor that does not cause malfunctions due to raindrops remaining on its detection surface.

[Prior Art] If the amount of raindrops adhering to the windshield glass could be detected, it would be possible to automatically operate the wiper accordingly, which would be extremely convenient. So, for example,
No. 34354 discloses a raindrop sensor that utilizes the change in capacitance between electrodes due to the adhesion of raindrops, and
JP-A-62-138743 discloses a raindrop sensor that detects the change in capacitance between the electrodes and accurately detects newly deposited raindrops, regardless of dirt between the electrodes.

[Problems to be Solved by the Invention] By the way, such a raindrop sensor is not normally provided on a glass surface that is wiped by a wiper so as not to reduce the driver's visibility.
Even after the rain stops, raindrops remain on the detection surface for a while.

The remaining raindrops deform on the detection surface when they are affected by the wind and vibrations of the vehicle, but large-diameter raindrops have a large amount of deformation;
When the raindrop area increases due to deformation, the capacitance between the detection electrodes increases, causing a problem in that the raindrop sensor erroneously detects that a new raindrop has adhered and issues a command to wiper operation.

The present invention aims to solve the problem in view of the current situation, and aims to provide a raindrop sensor that does not cause false detection due to raindrops remaining on the detection surface.

[Means for Solving the Problems] The raindrop sensor of the present invention has a detection surface on which detection electrodes are formed facing each other at intervals, and the raindrops attached to the detection surface are reduced by the increased capacitance between the detection electrodes. It detects
Raindrop discharge means is provided at predetermined intervals across the detection surface and removes raindrops of a predetermined diameter or larger adhering to the detection surface by capillary action.

The raindrop discharge means is a band provided across the detection surface at a distance slightly larger than the predetermined diameter, and these bands are provided upwardly with a small gap from the detection surface. It is.

Further, the raindrop discharge means is a groove provided across the detection surface at a distance slightly larger than the predetermined diameter, and each of these grooves has a rectangular cross section at least at a bottom corner portion.

[Operation] In the raindrop sensor configured as described above, among the raindrops adhering to the detection surface, those having a predetermined diameter or more are promptly removed from the detection surface by the raindrop discharge means.

Raindrops smaller than the predetermined diameter remaining on the detection surface are deformed by the action of the wind, etc., but the area expansion due to deformation is small for these small raindrops, so the increase in capacitance between the detection electrodes at this time is difficult to detect. It will be much more efficient than the level.

In this way, even if the raindrops remaining on the detection surface after the rain is deformed, the sensor will not falsely detect new raindrops.

[First Embodiment] In FIG. 5, a raindrop sensor S is provided on the front bumper B of the vehicle, and details of the raindrop sensor S are shown in FIGS. 3 and 4.

The raindrop sensor S includes an open case 52 whose surface facing the front of the vehicle is inclined, and a cover 51 that covers the case except for the inclined surface.
The plate-shaped sensor chip 1 is supported and fixed on the inclined surface. The upper surface of the sensor chip 1 is a detection surface 1a, and a band 4 of a constant width is provided above and in front of the detection surface 1a with a small gap therebetween. The band 4 extends in the vertical direction along the slope, and its upper and lower ends are bent to form the case 52.
It is locked and fixed to the opening edge and front end surface. 1 and 2 show details of the sensor chip, in which these strips 4 are arranged in a plurality of stages at equal intervals in the left-right direction.

The sensor chip 1 has detection electrodes 2.3 formed of copper foil on a substrate 11 made of glass epoxy, ceramic, or resin, and these electrodes are covered with an insulating film 12 made of a coating or film material.
It is covered with

A large number of the electrodes 2.3 are formed in a strip shape and alternately spaced at equal intervals,
Lead electrodes 21. are connected at their upper and lower ends.
It is integrated into 31. When raindrops adhere to the detection surface 1a, the capacitance between the lead electrodes 21 and 31 changes. The formation pitch of the detection electrodes 2.3 is, for example, 1
．． 5m+n, and in this case, raindrops with a diameter of 1.5 mmφ or more can be effectively detected.

The lead electrode 21.31 is connected to a wiper control circuit 6, which controls the lead electrode 21.3.
detecting only the positive periodic variation of the oscillation output of the RC oscillation circuit 61 whose circuit element is a capacitance between 1 and 2;
It is comprised of a computer arithmetic circuit 62 which adds up the periodic changes and, when the added value exceeds a certain value, issues a wiper operation signal and clears the added value.

The RC oscillation circuit 61 is housed within the case 52. Further, the computer arithmetic circuit 62 is provided outside the case 52.

Thus, each time a raindrop adheres, the oscillation output cycle of the oscillation circuit 61 gradually increases, and even if raindrops flow on the detection surface 1a midway, regardless of this, adhesion of more than a certain amount of raindrops is detected. The wiper is activated.

Now, the band 4 arranged with a small gap above the detection surface 1a is made of stainless steel or resin, for example, about 0.3 mm thick, and the detection electrode 2 has a narrow width compared to others. It is located directly above. Each of the bands 4 is connected to each other at the upper and lower ends to form a frame shape, and the width W of the band 4 is approximately 1.5 mm from the viewpoint of strength. Then, the detection surface 1a
The gap d is 0.2M to exhibit effective capillary action.
It's to a certain extent.

Therefore, among the raindrops adhering to the detection surface 1a, the raindrops having a diameter larger than the interval between the belts 4 are
As shown by the solid line in the figure, it is sucked into the gap d by capillary action in the gap d under the band 4 that it contacts, descends on the inclined detection surface 1a along the gap d, and is discharged downward.

The reason why the detection electrode 2 below the band 4 is narrowed is to reduce the influence of raindrops that are drawn into the gap d and flow down on the detection.

In this embodiment, the distance 1 between the inner surfaces of the band 4 is five, as will be explained below. That is, assuming that the minimum detected raindrop diameter is <1.5 mmφ as described above, the periodic variation of the oscillation output when a raindrop of this size adheres is TA. On the other hand, by changing the interval between the strips 4, the detection surface 1
Examining the amount of periodic change when the raindrops remaining on top a change in area due to the wind of 1100 K/h, the 6th
As shown in the figure, when the interval between the bands 4 is set to 6 mm, the amount of change is about the same. This shows that if a raindrop close to 6ITImφ remains on the detection surface 1a, its deformation causes a false detection as a new raindrop adhesion.

Here, the interval between the strips 4 is 51TI! If TI is set, only raindrops with a diameter smaller than this will remain on the detection surface 1a after the rain (dashed line in Figure 1), so even if the raindrops are deformed, the amount of periodic change at this time will be equal to the above TA. This does not result in a false positive detection.

[Second Embodiment] FIG. 7 shows a second embodiment of the present invention, in which an insulating film 13 with a constant thickness of about 0.1 mm is formed on a substrate 11, and a film similar to that of the first embodiment is formed on the substrate 11. Detection electrode 2.3 and insulating film 12
is formed. Detection electrodes 2 are arranged at regular intervals on the detection surface 1a.
Grooves 14 are formed parallel to the grooves 14, each groove 14 has a rectangular cross section, the bottom surface reaches the substrate 11, and the depth is about 0.2 mm. The distance between the inner surfaces of the grooves is set to 1.

According to such a structure, raindrops L(
(solid line in the figure) enters the groove 14 and is discharged to the outside of the detection surface 1a due to capillary action at the bottom corner portion 141 of the rectangular cross section of the liquid groove 14. Therefore, only the raindrops L (dashed line in the figure) with a smaller diameter than the distance g remain on the detection surface 1a, so even if the raindrops are deformed by the running wind or the like, erroneous detection will not occur.

The width of the groove 14 is, for example, 0.5 mm, and the interval 1 is 5 mm.
It is M.

Note that the groove does not need to be rectangular as a whole as long as at least the corner portion is rectangular, and it may be a ■ groove or a U groove as long as the groove width is narrow and a drainage effect can be obtained by capillary phenomenon between the groove walls. .

[Effects of the Invention] As described above, the raindrop sensor of the present invention is provided with a raindrop discharge means that removes raindrops with a predetermined diameter or more adhering to the detection surface by capillary action, so that the raindrops remaining on the detection surface after the rain has stopped are removed. Since it is small and has a diameter equal to or less than the above-mentioned predetermined diameter, even if it is deformed by wind or vibration while driving, the increase in the capacitance between the detection electrodes is small, and it will not be mistakenly detected as new raindrop adhesion.

[Brief explanation of the drawing]

1 to 6 show a first embodiment of the present invention.
The figure is a partially enlarged cross-sectional view of the sensor chip, showing the I-I line in Figure 2.
2 is a partially enlarged plan view of the sensor chip with the insulating film removed, FIG. 3 is a front perspective view of the raindrop sensor, and FIG. 4 is a cross-sectional view thereof. 5 is a front perspective view of a vehicle equipped with a raindrop sensor, and FIG. 6 is a diagram showing periodic changes in oscillation output due to deformation of raindrops remaining on the detection surface for different band spacings. , FIG. 7 is a partially enlarged sectional view of a sensor chip showing a second embodiment of the present invention. 1...Sensor chip 11...Substrate 12.13...Insulating film 14...Groove 141...Corner portion 2.3...Detection electrode 4...Band 6...Wiper control Circuit B...Front bumper. L...Raindrop S...Raindrop sensor 1st session Fig. 5 Fig. 3 S Fig. 6 (1) Body spacing Fig. 7 (mm)

Claims (3)

[Claims] (1) In a raindrop sensor that has a detection surface on which detection electrodes are formed facing each other at intervals, and detects raindrops adhering to the detection surface based on the increased capacitance between the detection electrodes, A raindrop sensor comprising raindrop discharge means arranged at a predetermined interval and for removing raindrops of a predetermined diameter or larger adhering to a detection surface by capillary action. (2) The raindrop discharge means is a band provided across the detection surface at a distance slightly larger than the predetermined diameter, and the band is arranged upwardly with respect to the detection surface to form a small gap. The raindrop sensor according to claim 1, wherein the raindrop sensor is provided separately. (3) The raindrop discharge means is a groove provided across the detection surface at a distance slightly larger than the predetermined diameter, and each of these grooves has at least a bottom corner portion having a rectangular cross section. raindrop sensor.