U.S. patent application number 11/600889 was filed with the patent office on 2007-05-24 for raindrop sensor.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Jun Tarui.
Application Number | 20070114369 11/600889 |
Document ID | / |
Family ID | 38037888 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070114369 |
Kind Code |
A1 |
Tarui; Jun |
May 24, 2007 |
RAINDROP SENSOR
Abstract
A raindrop sensor for sensing water attached to a second surface
of a transparent body includes a light emitting element, a light
guide body, a light receiving element, and an abnormality
determining device. The light emitting element is provided in a
first surface side of the transparent body for emitting light
toward the transparent body. The light guide body is mounted on a
first surface of the transparent body for guiding the light. The
light receiving element is provided in first surface side of the
transparent body for receiving the reflected light, which is
reflected by the second surface of the transparent body. The light
receiving element outputs a signal based on an amount of the
reflected light received. The abnormality determining device
determines an abnormality of the light guide body by comparing a
value indicated by the signal with an index value.
Inventors: |
Tarui; Jun; (Kariya-city,
JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
38037888 |
Appl. No.: |
11/600889 |
Filed: |
November 17, 2006 |
Current U.S.
Class: |
250/227.25 |
Current CPC
Class: |
G01N 21/274 20130101;
G01N 21/552 20130101; G02B 6/002 20130101 |
Class at
Publication: |
250/227.25 |
International
Class: |
G02B 6/42 20060101
G02B006/42 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2005 |
JP |
2005-336128 |
Claims
1. A raindrop sensor, which is provided in a first surface side of
a transparent body for sensing water attached to a second surface
of the transparent body, the raindrop sensor comprising: a light
emitting element that is provided in the first surface side of the
transparent body for emitting light toward the transparent body; a
light guide body that is mounted on a first surface of the
transparent body, wherein: the light guide body guides the light,
which is emitted by the light emitting element, to the transparent
body; and the light guide body guides the light, which is reflected
by the transparent body, to the first surface side of the
transparent body; a light receiving element that is provided in the
first surface side of the transparent body for receiving the
reflected light, which is reflected by the second surface of the
transparent body, the light receiving element outputting a signal
based on an amount of the reflected light received by the light
receiving element; and an abnormality determining device that
determines an abnormality of the light guide body by comparing a
value indicated by the signal outputted by the light receiving
element with an index value.
2. The raindrop sensor according to claim 1, wherein the light
receiving element is a first light receiving element that outputs a
first signal based on the amount of the reflected light received by
the first light receiving element, the raindrop sensor further
comprising a second light receiving element that is provided in the
first surface side of the transparent body for receiving the
reflected light, which is reflected by the second surface of the
transparent body, wherein: the second light receiving element
outputs a second signal based on the amount of the reflected light
received by the second light receiving element; the light guide
body includes: a first light passage that guides the light emitted
by the light emitting element to the transparent body and guides
the reflected light, which is reflected by the transparent body,
toward the first light receiving element; and a second light
passage that guides the light emitted by the light emitting element
to the transparent body and guides the reflected light, which is
reflected by the transparent body, toward the second light
receiving element; the abnormality determining device computes one
of the followings: a ratio of a first value indicated by the first
signal to a second value indicated by the second signal; and a
difference between the first value and the second value; and the
abnormality determining device determines the abnormality of the
light guide body by comparing the computed one of the ratio and the
difference with the index value.
3. The raindrop sensor according to claim 2, wherein: the first
light receiving element is provided apart from the light emitting
element by a first distance; the second light receiving element is
provided apart from the light emitting element by a second
distance, which is different from the first distance; and the light
guide body includes a diverging portion that diverges the light
emitted by the light emitting element into a first input light,
which travels through the first light passage, and a second input
light, which travels through the second light passage.
4. The raindrop sensor according to claim 2, wherein the light
emitting element is a first light emitting element that emits the
light, which travels through the first light passage, the raindrop
sensor further comprising a second light emitting element that is
provided in the first surface side of the transparent body for
emitting the light, which travels through the second light passage,
wherein: the first light emitting element is provided apart from
one of the first and second light receiving elements by a first
distance; and the second light emitting element is provided apart
from the one of the first and second light receiving elements by a
second distance, which is different from the first distance.
5. The raindrop sensor according to claim 1, wherein the light
emitting element is a first light emitting element that emits the
light, the raindrop sensor further comprising a second light
emitting element that is provided in the first surface side of the
transparent body for emitting the light toward the transparent
body, wherein: the light guide body includes: a first light passage
that guides the light, which is emitted by the first light emitting
element, to the transparent body and guides the reflected light,
which is reflected by the transparent body, toward the light
receiving element; and a second light passage that guides the
light, which is emitted by the second light emitting element, to
the transparent body and guides the reflected light, which is
reflected by the transparent body, toward the light receiving
element; the first light emitting element is provided apart from
the light receiving elements by a first distance; the second light
emitting element is provided apart from the light receiving
elements by a second distance, which is different from the first
distance; and the light guide body further includes a converging
portion that converges the light, which travels through the first
light passage, to the light receiving element, and converges the
light, which travels through the second light passage, to the light
receiving element.
6. The raindrop sensor according to claim 2, wherein: the light
guide body includes a prism portion and a silicone portion, which
is held between an end surface of the prism portion and the first
surface of the transparent body; the light, which travels through
the first light passage, is reflected by the second surface of the
transparent body, and the reflected light is guided toward the
first light receiving element through the first light passage; the
light, which travels through the second light passage, is reflected
by the second surface of the transparent body, and the reflected
light is guided toward the second light receiving element through
the second light passage; and the light guide body further includes
a third light passage that guides the light, which is emitted by
the light emitting element, to the end surface of the prism portion
and guides the reflected light, which is reflected by the end
surface of the prism portion, toward the first light receiving
element.
7. The raindrop sensor according to claim 4, wherein: the light
guide body includes a prism portion and a silicone portion, which
is held between an end surface of the prism portion and the first
surface of the transparent body; the light, which is emitted by the
first light emitting element and travels through the first light
passage, is reflected by the second surface of the transparent
body, the reflected light being guided toward the fist light
receiving element through the first light passage; the light, which
is emitted by the second light emitting element and travels through
the second light passage, is reflected by the second surface of the
transparent body, the reflected light being guided toward the
second light receiving element through the second light passage;
and the light guide body includes a third light passage that guides
the light emitted by the second light emitting element to the end
surface of the prism portion and guides the reflected light, which
is reflected by the end surface of the prism portion, toward the
first light receiving element.
8. The raindrop sensor according to claim 5, wherein: the light
guide body includes a prism portion and a silicone portion, which
is held between an end surface of the prism portion and the first
surface of the transparent body; the light, which is emitted by the
first light emitting element and travels through the first light
passage, is reflected by the second surface of the transparent
body, the reflected light being guided toward the light receiving
element through the first light passage; the light, which is
emitted by the second light emitting element and travels through
the second light passage, is reflected by the second surface of the
transparent body, the reflected light being guided toward the light
receiving element through the second light passage; and the light
guide body includes a third light passage that guides the light,
which is emitted by the first light emitting element, to the end
surface of the prism portion and guides the reflected light, which
is reflected by the end surface of the prism portion, toward the
light receiving element.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2005-336128 filed on Nov.
21, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a raindrop sensor, and more
particularly to a raindrop sensor, which is preferably applied to,
for example, a wiper controller for a vehicle.
[0004] 2. Description of Related Art
[0005] Japanese Unexamined Patent Publication No. 2001-66246
corresponding to U.S. Pat. No. 6,507,015 discloses a raindrop
sensor, which is mounted on an inner surface of a windshield and
senses raindrops attached to an outer surface of the windshield.
The raindrop sensor includes a light emitting element, a light
guide body, and a light receiving element. The light emitting
element emits light in a direction from the inner surface to the
outer surface. The light guide body guides the light to the outer
surface, and also guides a reflected light, which is reflected by
the outer surface, toward the inner surface side. The light
receiving element receives the light from the light guide body, and
generates a signal according to an amount of the received light.
The raindrop sensor compares an amount of the light received in a
clear whether condition with a current amount of the light
currently received in order to determine whether moisture, such as
raindrops, is attached to the outer surface or not.
[0006] Also, Japanese Unexamined Patent Publication No.
2001-521158T corresponding to U.S. Pat. No. 5,898,183 discloses a
raindrop sensor, which includes a light guide body having a prism
body and a flexible interlayer. In the raindrop sensor, a silicone
sheet, for example, serves as the interlayer, which is held between
the windshield and the prism body. Thus, this limits an air layer
from forming between the prism body and the windshield such that
the light, which travels through the prism body, can be guided to
the outer surface of the windshield.
[0007] However, in assembly of the raindrop sensor to the inner
surface, when the prism body is attached to the inner surface
directly without the interlayer, the air layer is formed between
the prism body and the inner surface. Then, the light, which
travels through the prism body, may not reach the windshield, but
may reflects off the end face of the prism body. Thus, the raindrop
may not be detected because the light emitted by the light emitting
element does not sufficiently reach the outer surface of the
windshield.
[0008] To deal with the above disadvantages, in a factory for
attaching the raindrop sensor, an operator checks whether the
silicone sheet, which is a part of the light guide body, is
appropriately attached or not by visual examination. However,
because this silicone sheet is provided at the back of the raindrop
sensor and thus the silicone sheet is behind a cover thereof, it is
often difficult for the operator to check by the visual
examination.
SUMMARY OF THE INVENTION
[0009] The present invention is made in view of the above
disadvantages. Thus, it is an objective of the present invention to
address at least one of the above disadvantages.
[0010] To achieve the objective of the present invention, there is
provided a raindrop sensor, which is provided in a first surface
side of a transparent body for sensing water attached to a second
surface of the transparent body, the raindrop sensor including a
light emitting element, a light guide body, a light receiving
element, and an abnormality determining device. The light emitting
element is provided in the first surface side of the transparent
body for emitting light toward the transparent body. The light
guide body is mounted on a first surface of the transparent body.
The light guide body guides the light, which is emitted by the
light emitting element, to the transparent body. The light guide
body guides the light, which is reflected by the transparent body,
to the first surface side of the transparent body. The light
receiving element is provided in the first surface side of the
transparent body for receiving the reflected light, which is
reflected by the second surface of the transparent body, and the
light receiving element outputs a signal based on an amount of the
reflected light received by the light receiving element. The
abnormality determining device determines an abnormality of the
light guide body by comparing a value indicated by the signal
outputted by the light receiving element with an index value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention, together with additional objectives, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0012] FIG. 1 is a side view of a raindrop sensor according to a
first embodiment of the present invention;
[0013] FIG. 2 is a plan view of a prism shown in FIG. 1;
[0014] FIG. 3 is a side view of the raindrop sensor, which is
mounted on a windshield without a silicone sheet, according to the
first embodiment;
[0015] FIG. 4 is a flow chart showing a process for determining an
abnormal state of a light guide body of the raindrop sensor
according to the first embodiment;
[0016] FIG. 5 is a side view of a raindrop sensor, which is mounted
on the windshield without the silicone sheet, according to a second
embodiment; and
[0017] FIG. 6 is a side view of a raindrop sensor according to a
third embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Embodiment
[0018] The first embodiment of the present invention will be
described with reference to accompanying drawings. A raindrop
sensor shown in FIG. 1 is, for example, applied to a wiper
controller that controls a wiper (not shown) provided to an outer
surface of a front windshield (transparent body) 80 of a vehicle.
The wiper is controlled by the wiper controller based on a sensing
output from a raindrop sensor 1, and slides within a wipe range on
an outer surface (second surface) 82 of the windshield 80.
[0019] The raindrop sensor 1 is provided from an inner surface 81
side (first surface side) of the windshield 80 according to the
wiping range. That is, the raindrop sensor 1 is provided in a space
defined adjacent to an inner surface (first surface) 81 of the
windshield 80. The raindrop sensor 1 optically senses raindrops,
which drop on the wipe range of the windshield 80, to output a
signal to the wiper controller.
[0020] FIG. 1 is a side view of the raindrop sensor 1 of the
present embodiment. FIG. 2 is a plan view of the raindrop sensor 1
shown in FIG. 1 viewed from above a light guide body 50 of the
raindrop sensor 1. FIG. 1 is a side view of raindrop sensor 1 shown
in FIG. 2. As shown in FIG. 1, the raindrop sensor 1 includes the
light guide body 1, light emitting elements 20, a first light
receiving element 30, a second light receiving element 40, a
computing element 121, a storing element 122, a circuit substrate
120, and a cover 10. Here, the light guide body 50 includes a prism
60 and a silicone sheet 70.
[0021] The prism 60 is made of a transparent resin, and is provided
on the inner surface 81 of the windshield 80 through the silicone
sheet 70. The prism 60 guides light emitted by the light emitting
elements 20 to the windshield 80. Then, the light reflected by the
outer surface 82 of the windshield 80 is guided by the prism 60 to
the first and second light receiving element 30, 40. A structure of
the prism 60 will be described later.
[0022] Here, the silicone sheet 70 is of a flexible material, and
is provided between the prism 60 and the windshield 80 such that an
air layer is limited from forming therebetween. A refraction index
of the silicone sheet 70 is nearly equal to that of the windshield
80 such that the light traveling from the prism 60 can be guided to
the windshield 80 without deterioration. Also, the light reflected
by the outer surface 82 of the windshield 80 can be returned to the
prism 60 without deterioration.
[0023] Then, the structure of the prism 60 will be detailed with
reference to FIGS. 1, 2. The prism 60 has a generally rectangular
shape when viewed from above. A longitudinal direction parallel to
a long side of the prism 60 is named as a long side direction. A
traverse direction parallel to a short side of the prism 60 is
named as a short side direction. The prism 60 includes first input
side lens portions 63, second input side lens portions 64, a first
output side lens portion 65, a second output side lens portion 66,
and a body 61.
[0024] Each of the first input side lens portions 63 collimates the
light emitted by a corresponding one of the light emitting elements
20 such that the collimated light is applied to a predetermined
raindrop sensing range 140. Thus, the first input side lens portion
63 is formed relative to the light emitting element 20 such that an
optical axis of the first input side lens portion 63 corresponds to
a light emitting part of the corresponding light emitting element
20. As shown in FIG. 2, the first input side lens portions 63 are
arranged relative to each other in the short side direction at an
end portion of the body 61 in the long side direction. The
collimated light collimated by each first input side lens portion
63 is named as a first input light 101 (indicated as a chain line
in FIG. 1).
[0025] Reflecting portions 67 are formed at the end portion of the
body 61 to reflect the first input light 101 toward the windshield
80. The reflecting portions 67 are arranged relative to each other
in the short side direction similar to the first input side lens
portions 63. As shown in FIG. 1, the first input light 101 firstly
travels toward an end face of the prism 60, at which the reflecting
portions 67 are formed, and then travels toward the windshield 80
after reflected by the corresponding reflecting portion 67.
[0026] The second input side lens portions 64 are formed at a
position away from the first input side lens portions 63 in the
long side direction. Each of the second input side lens portions 64
collimates the light emitted by a corresponding light emitting
element 20 such that the collimated light is applied to another
predetermined raindrop sensing range 150. Thus, the second input
side lens portion 64 is formed relative to the corresponding light
emitting element 20 such that a focus of the second input side lens
portion 64 corresponds to a light emitting part of the
corresponding light emitting element 20. As shown in FIG. 2, the
second input side lens portions 63 are arranged relative to each
other in the short side direction on the body 61. The collimated
light collimated by each second input side lens portion 64 is named
as a second input light 111 (indicated as a chain double-dashed
line in FIG. 1). The second input light 111 travels toward the
windshield 80 generally parallel to the first input light 101 in
the long side direction.
[0027] Both the first input side lens portion 63 and the second
input side lens portion 64 are formed on the body 61 such that an
optical axis of each of the lens portions 63, 64 corresponds to the
light emitting part of the light emitting element 20. Thus, the
light applied from the light emitting element 20 can be diverged
into the first input light 101 and the second input light 111. The
structures of the first and second input side lens portions 63, 64
correspond to a diverging portion of the present invention. Thus,
each light emitting element 20 is associated with the first input
light 101 and the second input light 111. As a result, the number
of the light emitting elements 20 can be reduced relative to the
number of the input lights (the first input light 101 and the
second input light 111), and therefore, the raindrop sensor 1 is
limited from increasing in size.
[0028] As shown in FIG. 1, the first and second input lights 101,
111 reach the raindrop sensing ranges 140, 150, respectively,
through the silicone sheet 70 by predetermined input angles. Then,
the first and second input lights 101, 111 are reflected by the
raindrop sensing range 140, 150 to again travel toward the prism
60. The light reflected by the sensing range 140 is named as a
first reflected light 102 (indicated as a chain line in FIG. 1) and
the light reflected by the sensing range 150 is named as a second
reflected light 112 (indicated as a chain double-dashed line in
FIG.1).
[0029] In contrast, the first output side lens portion 65 is formed
at a position away from the second input side lens portions 64 in
the long side direction toward another end of the body 61 as shown
in FIG. 1. The first output side lens portion 65 converges the
first reflected light 102 such that the first light receiving
element 30 can receive the first reflected light 102.
[0030] The second output side lens portion 66 is formed at a
position away from the first output side lens portion 65 in the
long side direction toward the anther end of the body 61. The
second output side lens portion 66 converges the second reflected
light 112 such that the second light receiving element 40 can
receive the second reflected light 112. A step portion 66a is
formed on a generally center of the second output side lens portion
66 on its surface as shown in FIG. 1. A surface shape of the second
output side lens portion 66 is not detailed here because a similar
lens portion, which is similar to the second output side lens
portion 66 of the present embodiment, is disclosed in Japanese
Unexamined Patent Publication No. 2001-66246. The prism 60 can be
reduced in height because the prism 60 includes a lens shape of the
second output side lens portion 66 having the step portion 66a.
[0031] A light passage, through which the first input light 101 and
the first reflected light 102 travel, corresponds to a first light
passage of the present invention. Also, another light passage,
through which the second input light 111 and the second reflected
light 112 travel, corresponds to a second light passage of the
present invention.
[0032] The first and second input side lens portions 63, 64, the
reflecting portions 67, and the first and second output side lens
portions 65, 66 may be integrally formed with the body 61. Also,
the above portions 63 to 67 may be separately formed from the body
61 and then, the above portions 63 to 67 may be attached to the
surface of the body 61.
[0033] The circuit substrate 120, which is fixed to the cover 10,
is provided above the prism 60. The light emitting elements 20, the
first light receiving element 30, the second light receiving
element 40, a computing element 121, and the storing element 122.
The computing element 121 receives signals according to amounts of
the light received by the first and second light receiving elements
30, 40 to compute amounts of the raindrops attached to the raindrop
sensing ranges 140, 150. Also, the computing element 121 receives
the above signals to determine the abnormal state of the light
guide body 50. The storing element 122 stores index values used
when the computing element 121 determines the abnormality of the
light guide body 50.
[0034] Each of the light emitting element 20 is provided on the
circuit substrate 120 such that the light emitting part of the
light emitting element 20 corresponds to an intersection of the
optical axes of both the first and second input side lens portions
63, 64. Two first input side lens portions 63 are arranged relative
to each other in the short side direction. Also, two second input
side lens portions 64 are arranged relative to each other in the
short side direction. Thus, two light emitting elements 20 are
required to correspond to the first and second input side lens
portions 63, 64. The light emitting elements 20 are also arranged
side by side in the short side direction (see FIG. 2).
[0035] The first light receiving element 30 is provided to the
circuit substrate 120 such that a light receiving part of the first
light receiving element 30 corresponds to a convergent point of the
light outputted from the fist output side lens portion 65. The
second light receiving element 40 is provided to the circuit
substrate 120 such that a light receiving part of the second light
receiving element 40 corresponds to a convergent point of the light
outputted from the second output side lens portion 66. The second
light receiving element 40 is located away from the first light
receiving element 30 in the long side direction. In other words,
the first and second light receiving elements 30, 40 are provided
on the circuit substrate 120 relative to the corresponding light
emitting element 20 such that a distance between the first light
receiving element 30 and the light emitting element 20 is different
from a distance between the second light receiving element 40 and
the light emitting element 20. That is, the first light receiving
element 30 is provided apart from the light emitting element 20 by
a first distance, and the second light receiving element 40 is
provided apart from the light emitting element 20 by a second
distance, which is different from the first distance.
[0036] The computing element 121 is constituted by, for example, a
known CPU, and receives signals, which corresponds to the amounts
of light received by the first and second light receiving elements
30, 40. Then, the computing element 121 computes the amount of
raindrops attached to the raindrop sensing ranges 140, 150.
Specifically, the computing element 121 compares the signals
received in a non-raindrop state with the current signals currently
received to sense the raindrops. Here, in the non-raindrop state,
the raindrops are not attached on the raindrop sensing ranges 140,
150.
[0037] Also, the computing element 121 determines the abnormal
state of the light guide body 50 by comparing the signals with the
index values stored in the storing element 122. Determining process
for determining the abnormal state will be specifically described
later. Here, the storing element 122 includes, for example, a known
EEPROM, a known RAM, and a known ROM.
[0038] The computing element 121 and the storing element 122 may be
provided externally to the raindrop sensor 1 instead of being
provided on the circuit substrate 120. Also, the raindrop sensor 1
is not limited to be used for an automobile, but may be used for
various vehicles, ships, and air planes.
[0039] Next, the determining process for determining the abnormal
state of the light guide body 50 will be described with reference
to FIGS. 3, 4. FIG. 4 is a flow chart showing a process for
determining the abnormal state of the light guide body 50. At step
SI, the computing element 121 receives the signals from the first
and second light receiving elements 30, 40. Here, each signal
corresponds to the amount of the light received by the
corresponding light receiving element. At step S2, the computing
element 121 computes the amounts of the light received by the first
and second light receiving elements 30, 40 based on the above
signals inputted at step S1.
[0040] Next, the computing element 121 computes a ratio of the
light amounts received by the first and second light receiving
elements 30, 40. Specifically, the ratio of the light amounts is
computed by dividing the amount of the light received by the first
light receiving element 30 by the amount of the light received by
the second light receiving element 40.
[0041] Next, the computing element 121 determines at step S4 to
step S8 whether the light guide body 50 is under the abnormal state
or not. Before describing the processes shown at and after step S4,
the abnormal state of the light guide body 50 will be described
with reference to FIG. 3. Here, the abnormal state is, for example,
a mounting state of the raindrop sensor 1 on the windshield 80
without the silicone sheet 70 (i.e., the mounting state of the
raindrop sensor 1 with the silicone sheet 70 missed). Thus, the
light passage in the prism 60 and the light received by the first
and second light receiving elements 30, 40 under this mounting
state will be described.
[0042] FIG. 3 is the side view of the raindrop sensor 1, which is
mounted on the windshield 80 without the silicone sheet 70. The
structure of components of the raindrop sensor 1 in FIG. 3 is the
same as that in FIG. 1 except that the raindrop sensor 1 in FIG. 3
does not includes the silicone sheet 70. Differences between
mounting structure shown in FIG. 1 and that shown in FIG. 3 will be
mainly described.
[0043] As shown in FIG. 3, the prism 60 directly contacts the inner
surface 81 of the windshield 80 without the silicone sheet 70.
Thus, the air layer 130 is formed between an end surface 62 of the
body 61 of the prism 60 and the inner surface 81 because there is
no silicone sheet 70.
[0044] When the light is emitted by the light emitting element 20
under this state, the first and second input lights 110, 111 are
formed at the first and second input side lens portions 63, 64.
These first and second input lights 101, 111, however, cannot reach
the outer surface 82 of the windshield 80 but are reflected by the
end surface 62 of the body 61 because of the air layer 130. The
reflected lights are named as a first abnormal reflected light 103
and a second abnormal reflected light 113.
[0045] Because the first and second abnormal reflected lights 103,
113 are reflected at different positions from the first and second
reflected lights 102, 112, the passages of the abnormal reflected
lights 103, 113 are different from those of the reflected lights
102, 112. As shown in FIG. 3, the first abnormal reflected light
103 does not reach either of the output side lens portions 65, 66,
and is outputted through a surface of the body 61. In contrast, the
second abnormal reflected light 113 reaches the first output side
lens portion 65, and is converged to the first light receiving
element 30 as shown in FIG. 3. A light passage, through which the
second input light 111 and the second abnormal reflecting light 113
travel, corresponds to a third light passage of the present
invention.
[0046] Therefore, when the raindrop sensor 1 is mounted without the
silicone sheet 70, the light emitted by the light emitting element
20 can be received only by the first light receiving element 30 but
not received by the second light receiving element 40. In the
present embodiment, each of lens portions 63 to 66 of the prism 60,
the reflecting portion 67 are designed, and also the light emitting
elements 20, the light receiving elements 30, 40 are positioned
such that the first and second light receiving elements 30, 40 can
receive the same amount of light when the light guide body 50 is
under a normal state (i.e., not the abnormal state). Also, the
above portions and elements are designed and positioned such that
either one of the first and second light receiving elements 30, 40
can receive the light emitted by the light emitting elements 20
when the light guide body 50 is under the abnormal state (e.g.,
mounting the raindrop sensor 1 without the silicone sheet 70).
[0047] From here, a specific example of the determining process for
determining the abnormality of the light guide body 50 will be
described. At step S4, the computing element 121 reads Rmax, which
is one of the index values stored in the storing element 122, to
compare Rmax with the ratio of the light amounts computed at step
S3. Rmax is a maximum value of the ratio of the light amounts when
the light guide body 50 is under the normal state. When the ratio
of the light amounts (light amount ratio) is equal to or larger
than Rmax, control continues with step S7, where the computing
element 121 stores in the storing element 122 information that the
light guide body 50 is mounted on the windshield 80 without the
silicone sheet 70. Then, the process ends. When the light amount
ratio is less than Rmax, control of the computing element 121
continues with step S5.
[0048] At step S5, the computing element 121 reads Rmin, which is
another one of the index values stored in the storing element 122,
to compare Rmin with the light amount ratio computed at step S3.
Rmin is a minimum value of the light amount ratio when the light
guide body 50 is under the normal state. When the light amount
ratio is equal to or larger than Rmin, control of the computing
element 121 continues with step S6, where the computing element 121
stores in the storing element 122 information that the light guide
body 50 is not under the abnormal state (i.e., the light guide body
50 is under the normal state). Then, the process ends. When the
light amount ratio is less than Rmin, the computing element 121
stores in the storing element 122 information that the light guide
body 50 is under the abnormal state by some reasons. The, the
process ends. The above step S4 to step S8 corresponds to an
abnormality determining device of the present invention.
[0049] Then, the state information of the light guide body 50
stored in the storing element 122 is reported to drivers, repair
people, and quality control managers in factories through a
diagnosis system (not shown).
[0050] In the present embodiment, the amount of lights received by
the first and second light receiving elements 30, 40 are compared
with the index values prestored in the storing element 122 to
detect the abnormal state of the light guide body 50. Thus, the
visual examination is not employed to detect the abnormal state.
Here, the abnormal state is for example the state where the
raindrop sensor 1 is mounted without the silicone sheet 70.
[0051] Also, in the present embodiment, the ratio of the amounts of
light received by the first and second light receiving elements 30,
40 is compared with the index values prestored in the storing
element 122 to detect the abnormal state of the light guide body
50. Thus, the abnormal state of the light guide body 50 can be
detected independently from the change of light emitting property
of the light emitting element 20 according to a change of ambient
temperature. Also, the abnormal state can be detected independently
from different light transmittances of different windshields
80.
[0052] In the present embodiment, the light amount ratio is used to
determine the abnormal state. However, a difference between the
amount of light received by the first light receiving element 30
and that received by the second light receiving element 40 may be
used to determine the abnormal state.
[0053] Advantages of using the light amount ratio for detecting the
abnormal state of the light guide body 50 will be described in
detail. The light emitting property of the light emitting element
20 may change according to the change of the surrounding
temperature. Also, the light transmittance of the windshield 80 is
different for each different type of the vehicle. When the light
emitting property changes, the amount of the light emitted by the
light emitting element 20 varies. This results in that the amounts
of the light received by the light receiving elements 30, 40 may
also vary. Also, when the light transmittance is different, the
amounts of the light received by the light receiving elements 30,
40 may also vary.
[0054] Therefore, if the index value stored in the storing element
122 were a normal value measured under a certain temperature with
the windshield 80 of a certain light transmittance, the abnormal
state might not be correctly detected when the temperature changes
from the certain temperature or the windshield 80 of the different
type is used as described above.
[0055] In contrast, in the present embodiment, the abnormal state
can be detected without the above disadvantages because the light
amount ratio of the first and second light receiving elements 30,
40 is used.
Second Embodiment
[0056] Next, the second embodiment of the present invention will be
described with reference to FIG. 5. Similar components to those in
the first embodiment will be indicated by the same numerals.
Characteristic points, which are different from the first
embodiment, will be mainly described. FIG. 5 is a side view of a
raindrop sensor 1a of the second embodiment. FIG. 5 shows a
mounting state of the raindrop sensor 1a on the windshield 80
without the silicone sheet 70 similar to FIG. 3.
[0057] Locations of light emitting elements and light receiving
elements relative to the light guide body 50 of the raindrop sensor
la of the present embodiment are changed from the locations of
those of the raindrop sensor 1 of the first embodiment shown in
FIG. 1 (i.e., locations of the light emitting elements are switched
with the locations of the light receiving elements). Specifically,
a first light emitting element 21 and a second light emitting
element 22 are provided on a right side in FIG. 5. Light receiving
elements 31 are provided on a left side in FIG. 5.
[0058] Lens portions corresponding to the first and second output
side lens portions 65, 66 of the first embodiment are named as
first and second input side lens portions 63a, 64a. Lens portions
corresponding to the first and second input side lens portions 63,
64 of the first embodiment are named as first and second output
side lens portions 65a, 66b.
[0059] The first and second output side lens portions 65a, 66b can
converge the lights that travel through the body 61. Thus, the
first and second output side lens portions 65a, 66b correspond to a
converging portion of the present invention. Thus, each light
receiving element 31 is associated with the corresponding first and
second light emitting element 21, 22. As a result, the number of
the light receiving elements 31 can be reduced relative to the
number of the light emitting elements, and therefore, the raindrop
sensor 1 is limited from increasing in size.
[0060] In a structure, where the mounting positions of the light
emitting elements are switched with the mounting positions of the
light receiving elements, the light receiving elements 31 only
receive the light from the first light emitting element 21 if the
raindrop sensor 1a is mounted without the silicone sheet 70 as
shown in FIG. 5. Thus, the computing element 121 compares the
amounts of light received by the light receiving elements 31 with
an index value stored in the storing element 122 to determine the
abnormal state of the light guide body 50.
Third Embodiment
[0061] Next, the third embodiment of the present invention will be
described with reference to FIG. 6. Similar components to those in
the first embodiment will be indicated by the same numerals.
Characteristic points, which are different from the first
embodiment, will be mainly described. FIG. 6 is a side view of a
raindrop sensor lb of the third embodiment.
[0062] The raindrop sensor 1b of the present embodiment includes
first light emitting elements 23 and second light emitting elements
24. The light emitted by each of the first light emitting elements
23 is inputted into a corresponding one of first input side lens
portions 63b, and the light emitted by each of the second light
emitting elements 24 is inputted into the corresponding one of the
second input side lens portions 64. The above structure is
different from the structure of the first embodiment.
[0063] Also in the above structure, the amounts of light received
by the first and second light receiving elements 30, 40 change due
to changes of light passages similar to the first and second
embodiment when the raindrop sensor 1b is mounted without the
silicone sheet 70. When the process shown in FIG. 4 is executed,
the abnormal state of the light guide body 50 can be
determined.
[0064] Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader terms is
therefore not limited to the specific details, representative
apparatus, and illustrative examples shown and described.
* * * * *