JP2007278711A - Raindrop sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the height of a lens in a raindrop sensor for optically detecting the raindrops adhered to a wind shield. <P>SOLUTION: The raindrop sensor includes a plurality of light emitting elements 1, one light detecting element 2 for detecting the lights emitted from the light emitting elements 1, a plurality of lenses 5 on an emission side for converting the lights emitted by the light emitting elements 1 to parallel light to totally reflect the parallel light by the outside surface of the wind shield 8 and a lens 6 on a detection side for condensing the parallel light totally reflected by the wind shield 8 to the light detecting element 2. The lens 5 on the emission side and the lens 6 on the light detection side are integrally formed into a shape wherein a convex lens is divided into many parts in a concentric circular state and the curved surface parts of the divided parts are arranged on a plane and the optical axes of them are inclined at an angle below a critical angle so as to totally reflect the parallel light by the outside surface of the wind shield 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a raindrop sensor, and more particularly to a raindrop sensor that is attached to an inner surface of a windshield of a vehicle or the like and optically detects raindrops attached to the outer surface of the windshield.

  Some vehicles are equipped with an auto wiper device that automatically detects a raindrop adhering to a windshield when it rains and automatically activates the wiper. As a raindrop sensor employed in such an auto wiper device, a type of detecting raindrops adhering to the windshield as a change in capacitance (for example, see Patent Document 1) and a type of optically detecting (for example, Patent Document) 2).

  A raindrop sensor that detects raindrops optically is configured so that light emitted from the light emitting element toward the windshield is totally reflected by the outer surface of the windshield and enters the light receiving element. This utilizes the fact that the amount of light reflected on the outer surface of the windshield differs depending on whether or not there is adhesion. That is, since the glass and raindrops constituting the windshield have substantially the same refractive index, the light incident on the windshield from the light emitting element is totally reflected on the outer side if the raindrops are attached to the outer side. Without going straight to the raindrop, the amount of light reflected by the windshield and directed to the light receiving element is reduced. Therefore, if the amount of light received by the light receiving element decreases, the raindrop sensor can determine that there are raindrops on the windshield.

The raindrop sensor basically refracts the light emitted from the light emitting element at an incident angle such that the obliquely arranged plano-convex lens totally reflects the outer surface of the windshield and reflects it on the outer surface of the windshield. Another plano-convex lens condenses the emitted light on the light receiving element. In particular, the raindrop sensor described in Patent Document 2 has a structure in which the shape of a prism main body in which a plano-convex lens is divided into two to form a lens is reduced. As a result, the raindrop sensor can be downsized while ensuring a wide raindrop detection region.
JP 2000-75052 A Japanese Patent No. 35673838

  Since such a raindrop sensor is mounted in a state protruding from the inside of a windshield on the front side of a vehicle or the like, further downsizing is desired so that the height is low and does not hinder the field of view. In the conventional raindrop sensor, one plano-convex lens is divided into two as a lens arranged obliquely according to the incident angle and the emission angle with respect to the windshield and shifted in the optical axis direction. There is a problem that it is difficult to lower.

  The present invention has been made in view of these points, and an object thereof is to provide a raindrop sensor capable of reducing the height of a lens.

  In the present invention, in order to solve the above problems, in a raindrop sensor that optically detects raindrops attached to a windshield, a plurality of light emitting elements that emit light toward the windshield, and light reflected by the windshield One light-receiving element that receives light, a plurality of light-emitting side lenses that convert the light emitted by the light-emitting element into parallel light and totally reflect it on the outer surface of the windshield, and receive the parallel light that is totally reflected by the windshield A light-receiving side lens that focuses light onto the element, and the light-emitting side lens and the light-receiving side lens are integrally formed in a shape in which convex lenses are divided into multiple portions and their curved surface portions are arranged on a plane, and The raindrop sensor is characterized by having an optical axis inclined below a critical angle.

  According to such a raindrop sensor, the light-emitting side lens and the light-receiving side lens are integrally formed in a shape in which the convex lens is divided into multiple parts and the curved surface portions thereof are arranged on a plane. can do.

  In the raindrop sensor of the present invention, the light-emitting side lens and the light-receiving side lens are integrally formed in a shape in which convex lenses are divided into multiple parts and their curved surfaces are arranged on a plane, so that the lens height can be lowered. There is an advantage that it can be reduced in size.

In addition, since the light-emitting side lens and the light-receiving side lens that are integrally formed do not have portions with extremely different thicknesses, when resin molding is performed, it is possible to manufacture parts that are not inferior.
Further, the provision of the calibration means eliminates the need for the wiping operation by the windshield wiper, which was necessary before the raindrop detection was started by the auto wiper device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a configuration of a raindrop sensor according to a first embodiment of the present invention, and FIG.

  This raindrop sensor has a plurality of light emitting elements 1 that emit light such as infrared light, in the illustrated example, and a single light receiving element 2 that receives the light, and these components handle raindrop detection. It is mounted on the wiring board 3 together with the circuit components to be performed.

  A prism 4 is arranged to face the surface on which the light emitting element 1 and the light receiving element are mounted. The prism 4 has four light-emitting side lenses 5 corresponding to the four light-emitting elements 1 and one light-receiving side lens 6 corresponding to the single light-receiving element 2, and is adjacent to each other as shown in FIG. Has been placed. In this prism 4, the light-emitting side lens 5 and the light-receiving side lens 6 are integrally formed of a transparent resin, and like a so-called Fresnel lens, the convex lens is divided into multiple concentric circles, and the curved surface portions of the divided segments However, the optical axis is not perpendicular to the plane, but inclined in the direction equal to the incident angle to the windshield 8. The prism 4 is bonded to the inner side surface of the windshield 8 through the adhesive layer 7, and is entirely covered with a case 9 except for the prism 4, and covered with a lid 10 from the back.

  The light emitting side lens 5 has an optical axis such that the incident angle of light emitted from the light emitting element 1 with respect to the outer surface of the windshield 8 is less than a critical angle (45 degrees). The axis is also set so as to incline below the critical angle with respect to the outer surface of the windshield 8.

  In the raindrop sensor configured as described above, the light emitted from each light emitting element 1 reaches the corresponding light emitting side lens 5 where it is converted into parallel light and incident on the windshield 8, and the outside of the windshield 8. Proceed toward the four detection areas on the side. Light incident at an incident angle less than the critical angle in each detection region is totally reflected on the outer surface of the windshield 8. The totally reflected light is received by the light receiving side lens 6, condensed here, and incident on the light receiving element 2.

  Here, when it is not raining, the light emitted from the light emitting element 1 and entering the light emitting side lens 5 is totally reflected by the outer surface of the windshield 8 and enters the light receiving element 2 through the light receiving side lens 6. Therefore, the amount of light received by the light receiving element 2 is large.

  On the other hand, when it rains, raindrops adhere to the detection area on the outer surface of the windshield 8, so that all the light emitted from the light emitting element 1 and entering the light emitting side lens 5 is generated on the outer surface of the windshield 8. Without reflection, at least a part of the windshield 8 goes straight through the raindrop as it is, and diverges from the outer surface of the raindrop to the outside. For this reason, the amount of light incident on the light receiving element 2 is reduced by the amount that is not totally reflected at the portion where raindrops adhere.

  Therefore, by sequentially measuring the amount of light incident on the light receiving element 2 and observing the change in the amount of received light, it is possible to detect the attachment of raindrops on the outer surface of the windshield 8 and automatically activate the wiper of the vehicle. It is possible to perform such control.

  By the way, in this raindrop sensor, on the light emitting side, the four light emitting elements 1 are caused to emit light simultaneously or sequentially at a predetermined cycle, for example, and on the light receiving side, the light receiving element 2 receives light according to the timing of light emission. A change in the amount of received light is determined by comparing the amount of light received this time with the amount of light received during the previous light emission. However, since there is no data to compare for the amount of light received when the light is first emitted, generally, when performing raindrop detection, the wiper is operated and the outer surface of the windshield 8 is wiped off so that raindrops are attached. The change in the amount of received light is determined on the basis of the amount of received light in the absence state. Therefore, when the auto wiper device is activated and the detection of raindrops is started, it is necessary to make an initial setting of the amount of light received, which is the basis for such judgment, and for this purpose, the wiper must be operated regardless of whether there is rainfall. I have to let it. Next, a raindrop sensor that eliminates the need for such a wiper operation before the start of raindrop detection will be described.

  FIG. 3 is a cross-sectional view showing a configuration of a raindrop sensor according to the second embodiment of the present invention, and FIG. 4 is a plan view showing a main part of the raindrop sensor. 3 and 4, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  This raindrop sensor includes calibration means for calibrating the amount of light received by the light receiving element 2 in the raindrop sensor according to the first embodiment. The calibration means includes a calibration light-emitting element 11 disposed on the opposite side of the light-emitting element 1 across the light-receiving element 2, a light-emitting side lens 12 disposed between the light-emitting element 11 and the light-receiving element 2, and light reception. A side lens 13 and a pseudo windshield 14 simulating the windshield 8 are provided.

  The light-emitting side lens 12 and the light-receiving side lens 13 for calibration are formed integrally with the light-emitting side lens 5 and the light-receiving side lens 6 for measurement with a transparent resin, and the pseudo windshield 14 is formed of the light-emitting side lens 5 and the light-receiving side lens. 6 is formed by forming a plane parallel to the windshield 8 on the side of the windshield 8. The windshield 8 side of the pseudo windshield 14 is a hermetically sealed space 15, and the space 15 is filled with a vacuum or dry air. As a result, even if the temperature in the passenger compartment to which the raindrop sensor is attached becomes low, condensation does not occur on the space 15 side surface of the pseudo windshield 14.

  In the raindrop sensor configured as described above, the calibration light emitting element 11 emits light before the detection of the raindrop is started. The light is first converted into parallel light by the light emitting side lens 12, totally reflected by the pseudo windshield 14, condensed by the light receiving side lens 13, and received by the light receiving element 2. At this time, since the surface of the pseudo windshield 14 on the space 15 side is always clean, the light receiving element 2 can stably obtain a reference received light amount.

  FIG. 5 is a sectional view showing the structure of a raindrop sensor according to the third embodiment of the present invention. In FIG. 5, the same components as those shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this raindrop sensor, the light receiving element 2 can function as a sun sensor with respect to the raindrop sensor according to the second embodiment. The sun sensor detects the amount of solar radiation hitting the vehicle, and the detected data is used to control the air conditioner.

  According to this raindrop sensor, the concave lens 16 is formed on the surface of the prism 4 facing the light receiving element 2, and the convex lens 17 is disposed on the same axis as the concave lens 16 so as to be fitted to the prism 4. The concave lens 16 and the convex lens 17 are separated from each other, and a sealed space 18 is formed therebetween.

  In such a raindrop sensor, the function as a raindrop sensor is exactly the same as that of the raindrop sensor according to the second embodiment. That is, as this raindrop sensor, the calibration means operates before starting the detection of raindrops, and thereafter, for example, the light emitting element 1 emits light for a predetermined short period with a predetermined period, and the light receiving element 2 is synchronized with the light emitting element 1. Is received, and it is determined whether or not raindrops have adhered to the windshield 8 by observing the change in the amount of received light. As described above, the light-emitting element 1 and the light-receiving element 2 perform light emission and light reception intermittently, but do nothing during other idle periods.

  In this raindrop sensor, the light receiving element 2 is caused to function as a sun sensor during an idle period as the raindrop sensor. That is, the concave lens 16 takes in light from the outside of the windshield 8 at a wide angle to make it parallel light, and the parallel light is condensed by the convex lens 17 on the light receiving element 2. The light outside the vehicle is also incident on the light receiving element 2 even when functioning as a raindrop sensor, but is substantially smaller than the power of the light emitted from the light emitting element 1 and thus is substantially disturbed. Even if sunlight is directly incident and a large disturbance occurs, the raindrop sensor does not erroneously detect because it is sunny and there is no need to detect raindrops.

It is sectional drawing which shows the structure of the raindrop sensor which concerns on the 1st Embodiment of this invention. It is a top view which shows the principal part of a raindrop sensor. It is sectional drawing which shows the structure of the raindrop sensor which concerns on the 2nd Embodiment of this invention. It is a top view which shows the principal part of a raindrop sensor. It is sectional drawing which shows the structure of the raindrop sensor which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 3 Wiring board 4 Prism 5 Light emitting side lens 6 Light receiving side lens 7 Adhesive layer 8 Windshield 9 Case 10 Lid 11 Light emitting element 12 Light emitting side lens 13 Light receiving side lens 14 Pseudo windshield 15 Space 16 Concave lens 17 Convex lens 18 space

Claims (4)

In the raindrop sensor that optically detects raindrops attached to the windshield,
A plurality of light emitting elements that emit light toward the windshield;
One light receiving element for receiving the light reflected by the windshield;
A plurality of light-emitting side lenses that convert the light emitted by the light-emitting element into parallel light and totally reflect the light on the outer surface of the windshield;
One light-receiving side lens for condensing the parallel light totally reflected by the windshield onto the light-receiving element;
With
The light emitting side lens and the light receiving side lens are integrally formed in a shape in which a convex lens is divided into multiple parts and their curved surface portions are arranged on a flat surface, and have an optical axis that is tilted below a critical angle. A raindrop sensor.   The raindrop sensor according to claim 1, wherein the light emitting side lens and the light receiving side lens are integrally formed of a transparent resin.   A light emitting element for calibration, a pseudo windshield that simulates the windshield, a light emitting side lens for calibration that causes the light emitted by the light emitting element for calibration to be parallel light and totally reflected on the outer surface of the pseudo windshield, A calibration light receiving lens for condensing the parallel light totally reflected by the pseudo windshield onto the light receiving element, the pseudo windshield, the calibration light emitting side lens, and the calibration light receiving side lens, The raindrop sensor according to claim 1, wherein the raindrop sensor is formed integrally with the light emitting side lens and the light receiving side lens. A concave lens that is arranged at a position facing the light receiving element and that takes light at a wide angle from the outside of the windshield, and a convex lens that is arranged on the same axis as the concave lens and collects the light taken by the concave lens on the light receiving element The raindrop sensor according to claim 1, wherein the concave lens is formed integrally with the light emitting side lens and the light receiving side lens.

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