JP2829520B2 - Wiper control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a wiper control device for an automobile by detecting rainfall.

[Prior art]

As a conventional wiper control device of this type, for example, a device that uses a piezoelectric element as a raindrop detection sensor and measures the number of collisions of raindrops is known, and a wiper mechanism is provided every time a predetermined number of collisions are detected. The driving is performed, and an operation almost in proportion to the amount of rainfall can be obtained from an intermittent operation during light rain to a continuous operation during heavy rain.

However, when raindrops having a size smaller than the detection sensitivity of the piezoelectric element, such as drizzle, are raining, the output of the raindrop detection sensor is naturally obtained. As a result, it is impossible to detect rainfall, and as shown by the detection curve D in FIG. 4, a dead zone Z is generated below a certain raindrop size, and the wiper is produced despite the impaired visibility. This causes a problem that the mechanism does not operate, and causes a practical problem.

[Means for Solving the Problems]

The present invention, as a specific means for solving the above-mentioned conventional problems, calculates the amount of rainfall by differentiating the output of the raindrop detection sensor, which varies according to the amount of raindrop attached, by a differentiation circuit of the control unit. In the wiper control device that drives the wiper mechanism based on the result, the control unit stores a first storage unit that stores an output of the raindrop detection sensor at the time of starting operation as a reference value, and the first storage unit that corresponds to an invisible state of the window glass. A second memory for storing the output of the raindrop detection sensor as an absolute reference value
A memory for comparing the output of the raindrop sensor with the reference value and the absolute reference value and the output of the raindrop detection sensor; and a drive for driving the wiper mechanism by an output of the differentiation circuit or the arithmetic unit. A circuit for driving the wiper mechanism when the output of the raindrop sensor changes by a predetermined amount from the reference value, and also drives the wiper mechanism when the output changes by a predetermined amount from the absolute reference value. And a wiper control device capable of responding to any rainfall state by providing a wiper control device, wherein the output of the raindrop sensor at the end of driving the wiper mechanism is similarly replaced with the reference value. The present invention solves the above-mentioned conventional problems.

【Example】

Next, the present invention will be described in detail based on an embodiment shown in the drawings. In FIG. 1, reference numeral 1 denotes a raindrop detection sensor,
This raindrop detection sensor 1 is provided with a light emitting element 1b such as an LED via a detection unit 1a formed of a transparent member having a relatively high refractive index.
And a light-receiving element 1c such as a photodiode. When no raindrop R is attached to the detection unit 1a, a predetermined amount of light from the light-emitting element is internally reflected on a contact surface with the atmosphere, and a predetermined amount of light is emitted from the light-receiving element. 1c, a predetermined output is obtained, but the attachment of the raindrop R causes light leakage from the contact surface, and the amount of light reaching the light receiving element 1c decreases according to the amount of the attachment of the raindrop R. . Since the output of the raindrop detection sensor 1 decreases in accordance with the amount of adhesion as described above, the amount of adhesion per time, that is, the amount of rainfall can be known by differentiating this output by the control unit 2, and the present invention In the automatic wiper control method, a differential circuit 2a is provided in the control unit 2, and when the output from the differential circuit 2a is equal to or more than a predetermined value, the wiper mechanism 3 is operated by the drive circuit 2b. Further, in the present invention, the control unit 2 can be rewritten.
For example, a first storage unit 2c such as a RAM element is provided, and when the power is turned on to the raindrop detection sensor 1 and the control unit 2, for example, at the start of operation of an automobile, the raindrop detection sensor 1 at the time when the operation is started is started. The output value is stored and held as a reference value, and this reference and a subsequent change in the output of the raindrop detection sensor 1 are compared by an arithmetic unit 2d such as a microcomputer. When the change amount reaches a predetermined value on the decreasing side, the differentiation is performed. The wiper mechanism 3 is driven regardless of whether or not there is an output from the circuit 2a. In this drive, for example, the wiper mechanism 3 is driven a predetermined number of times. When this drive is completed, the first storage unit 2c
Is rewritten to the output value of the raindrop detection sensor 1 at the time when the driving is completed. Thereafter, the rewritten value is adopted as a new reference value and is provided for a change in the output value of the raindrop detection sensor 1 thereafter. It will be. At the same time, the control unit 2 is provided with a non-rewritable second storage unit 2e such as a ROM element.
In 2e, the same value as the output from the raindrop detection sensor 1 corresponding to the invisible state of the window glass, that is, the state where the field of view through the window glass cannot be secured, is stored as an absolute reference value. When the output of the raindrop detection sensor 1 is lower than the predetermined value,
The wiper mechanism 3 is driven by 2d irrespective of the result from the differentiating circuit 2a or the first storage unit 2c. Next, the operation of the present invention will be described with reference to the output from the raindrop detection sensor 1 shown in FIG. 2 and the flowchart of the operation shown in FIG. The point indicated by ON on the time axis in FIG. 2 is the power-on by the ignition key corresponding to the start of driving of the car, and
This corresponds to step S00 in the flowchart in the figure. At this time, in the example shown in the drawing, it is already in a rainfall state, and water droplets have already adhered to the windshield surface so as to impair the visibility.
S01) The output from the raindrop detection sensor 1 (the curve indicated by the symbol B) falls below the absolute reference value (point A on the output axis) preset in the second storage unit 2e. In the comparison between the absolute reference value A and the sensor output B (step S02), a result of A> B is obtained (step S03), and the driving of the wiper mechanism 3 is performed (step S31). The provision of the second storage unit 2e has an operation capable of coping with a state that has already occurred at the start of operation or the like. When the driving of the wiper mechanism 3 is completed (step S33), the field of view is restored, and the control unit 2 transmits the raindrop detection sensor 1 (C in FIG. 2) at that time.
) Is stored in the first storage unit 2c. At this time, if the rainfall state is drizzle, the output change of the raindrop detection sensor 1 is very slow as shown in the figure, and even if this change is differentiated by the differentiating circuit 2a, no output is obtained. Therefore, the wiper mechanism 3 is not driven, and the field of view is surely impaired. Here, the reference value C in the first storage unit 2c and the output from the raindrop detection sensor 1 are calculated by the calculation unit 2d (step S07), and a predetermined condition such as a 75% reduction of the reference value C is used. In other words, when the condition of κB <C is satisfied, the wiper mechanism 3 is driven to secure the field of view, and at the time of completion, the output from the raindrop detection sensor 1 at that time (point in FIG. 2). C ′) is stored as a new reference value in the first storage unit 2c. In a normal rainfall state, the output from the raindrop detection sensor 1 changes rapidly, so that a sufficient differential output can be obtained through the differentiating circuit 2a (steps S09 and S10). The wiper mechanism 3 is driven. It should be noted that the stroke shown in steps S04 to S06 in FIG.
Is not performed, thereby preventing the initial reference value from being stored.
If <B, the reference value is set (step S04). If it is set, the process proceeds to the next step (step S07), and if it is not set, it is set (step S06).

【The invention's effect】

As described above, according to the present invention, the output of the first raindrop detection sensor is stored in the first storage unit as a reference value, compared with the output of the subsequent raindrop detection sensor, and when a predetermined change occurs, the wiper mechanism is activated. By driving it,
It is also possible to cope with a rainfall state that changes slowly such as drizzle and cannot be detected by the differentiating circuit, and further stores an absolute reference value in the second storage unit, even when the output of the raindrop sensor falls below this value. By driving the wiper mechanism, it is possible to cope with a situation where visibility is already impaired by rainfall at the start of traveling, and it is possible to cope with any state by adopting this control method This makes it possible to provide a simple wiper control device, and has an outstanding effect in improving practicality. In addition, by using the output of the raindrop sensor at that time as a reference value, for example, aging of the sensor element, or can also escape from fluctuation factors such as temperature characteristics, durability,
It also has the effect of being excellent in reliability.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a wiper control device according to the present invention, FIG. 2 is a graph showing the operation of the same embodiment by the output of a raindrop sensor, and FIG. 3 is a flowchart showing the procedure of the same control method. FIG. 4 is a graph showing the detection state of the conventional example. 1 raindrop sensor 1a detection unit 1b light-emitting element 1c light-receiving element 2 control unit 2a differential circuit 2b drive circuit 2c first storage unit 2d arithmetic unit 2e Second storage unit 3 Wiper mechanism

Continuing from the front page (72) Inventor Eoki Noro 1-4-1, Chuo, Wako-shi, Saitama Pref. In Honda R & D Co., Ltd. (72) Inventor Shigeru Kimura 41-924 Sakuradai, Midori-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Toru Tanabe 1937-28 Kanaicho, Machida-shi, Tokyo (72) Inventor Osamu Matsumoto 1-35-1, Oshidate-cho, Fuchu-shi, Tokyo (72) Inventor Atsuhiro Takita 2-17-8, Edanami, Midori-ku, Yokohama, Kanagawa 56) References JP-A-59-100034 (JP, A) JP-A-61-76946 (JP, A) JP-A-60-252045 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) B60S 1/08

Claims (1)

(57) [Claims] 1. A wiper control device for differentiating an output of a raindrop detection sensor, which varies according to the amount of raindrops deposited, by a differentiation circuit of a control unit to calculate a rainfall amount, and driving a wiper mechanism based on a result of the calculation. A controller configured to store the output of the raindrop detection sensor at the start of operation as a reference value, a first storage unit that stores an output of the raindrop detection sensor corresponding to an invisible state of the window glass as an absolute reference value. 2
A memory for comparing the output of the raindrop sensor with the reference value and the absolute reference value and the output of the raindrop detection sensor; and a drive for driving the wiper mechanism by an output of the differentiation circuit or the arithmetic unit. A circuit for driving the wiper mechanism when the output of the raindrop sensor changes by a predetermined amount from the reference value, and also drives the wiper mechanism when the output changes by a predetermined amount from the absolute reference value. A wiper control device that replaces the output of the raindrop sensor at the end of driving the wiper mechanism with the reference value.