JPS61193954A - Raindrop detector - Google Patents

Abstract

PURPOSE:To perform accurate raindrop detection, by installing a heating unit on a diaphragm of a raindrop detector. CONSTITUTION:The voltage produced in a piezoelectric element 1 is led out via cable 9 after being amplified by an integrated circuit 10 and a condenser 11 on a circuit board 8. Thereupon, DC voltage to be obtained of rectifying the signal led out the calbe 9 is measured whereby a quantity of raindrops colliding with a diaphragm 2 is detected. At this time, this diaphragm 2 is heated by a hot wire 5 through which snow on the diaphragm 2 is dissolved and removed so that vibration is in no case hindered by fallen snow.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a raindrop detection device that detects the amount of raindrops using vibrations caused by falling raindrops.

(Prior art) In wipers for vehicles, it is known that the operating speed of the wiper can be adjusted, or that when there is light rain or drizzle, the wiper operates once, stops for, for example, 5 seconds, and then operates again in so-called intermittent operation. (Refer to Japanese Patent Application Laid-open No. 112852/1983). Furthermore, recently, wipers have been adopted that control the operating speed and intermittent time according to the amount of raindrops. It is installed on the top panel 7, etc., and is detected by converting vibrations generated when raindrops collide with this diaphragm into electrical signals.

(Problem to be Solved by the Invention) In a raindrop detection device that detects the vibration of the diaphragm due to the collision of raindrops, if there is snow on the diaphragm, the diaphragm cannot vibrate freely and the detection characteristics change. This may cause a detection imbalance, which may cause the wiper to operate at an inappropriate operating speed or intermittently for the amount of rainfall, or may become inoperable.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and the object thereof is to provide a raindrop detection device that detects the amount of raindrops using vibrations caused by falling raindrops, in which the detection characteristics change due to snow accumulation. The purpose is to prevent detection imbalances.

(Structure of the Invention) In order to achieve the above object, the present invention has a configuration in which a heating element is disposed on or near a diaphragm for detecting vibrations caused by raindrops to melt accumulated snow.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 shows an embodiment of a raindrop detection device according to the present invention.

A piezoelectric element 1 made of crystals such as barium titanate or Rochelle salt is attached to a diaphragm 2. The diaphragm 2 is held on the upper surface of a case 3 via a damper 4 made of rubber or the like, and a hot wire 5 is printed on the back surface of the damper 4. FIG. 2 is a schematic view of the diaphragm 2 viewed from inside the case 3 to show the positional relationship among the piezoelectric element 1, the hot wire 5, and the damper 4. The piezoelectric element 1 and the hot wire 5 are connected to a circuit board 8 via lead wires 6 and 7, respectively. The hot wire 5 is connected to a switch that operates in conjunction with the wiper switch via a circuit board 8 and a cable 9, and is configured such that a current flows through the hot wire 5 even if the wiper switch is in either the LOW HIGH AUTO position. Here, LOW is a mode in which the operating speed of the wiper is low, HIGH is a high mode, and AUTO is a mode in which the operating speed or intermittent time is automatically adjusted according to the amount of rain detected by this raindrop detection device. The reason why current is passed through the hot wire 5 even in Low or old GH is that
This is to enable normal raindrop detection immediately even when switching from to AUTO.

The voltage generated in the piezoelectric element 1 is amplified by the IC 10 on the circuit board 8, the capacitor 11, etc., and then led out via the cable 9. The voltage generated in the piezoelectric element 1 corresponds to the vibration generated in the diaphragm 2 due to the collision of raindrops. Therefore, the amount of raindrops hitting the diaphragm 2 is detected by measuring the DC voltage obtained by rectifying the signal derived from the cable 9, and the wiper operating speed and intermittent time are controlled based on this detection result. ing.

With the above configuration, the diaphragm 2 is heated by the hot wire 5,
Since the snow on the diaphragm 2 is melted and removed, the vibration is no longer hindered by the snow.

FIG. 3 shows another embodiment of the raindrop detection device according to the present invention, in which the same components as in FIG. 1 are denoted by the same reference numerals.

In the embodiment shown in FIG. 1, current always flows through the hot wire 5 while the wiper switch is on, and the temperature may become higher than necessary. Therefore, in this embodiment, a thermistor 12 is provided within the case 3 as a heat-sensitive element. In this way, when the inside of the case 3 becomes high temperature, the lowering of the resistance value of the thermistor 12 is used to limit the current flowing through the hot wire 5, thereby reducing the temperature inside the case 3 and the diaphragm 2. The heating wire 5 is energized only when the temperature is below a predetermined temperature (for example, 4° C.).

FIG. 4 shows still another embodiment of the raindrop detection device according to the present invention, and the same parts in FIG. 1 as in FIG. 1 are given the same reference numerals.

In this embodiment, P CT (Positive Temperature
ureCoefficient) element 13 is provided. The PCT element 13 is wired in place of the hot wire 5 shown in FIG. 1, and when a voltage is applied to the PCT element 13, it self-heats, and as shown in FIG.
'C) or above, the resistance value rises rapidly, which limits the current and suppresses the temperature rise.

Therefore, the predetermined temperature is selected to be, for example, 4°C, and the inside of the case 3 and the diaphragm 2 are kept at a constant temperature of 4°C.

(Effects of the Invention) As explained above, in the present invention, a heating element is provided on or near the diaphragm for detecting the amount of raindrops by using vibrations caused by falling raindrops, and a heating element is provided on or near the diaphragm to melt snow. Therefore, even during snowfall, the detection characteristics of the amount of raindrops do not change or become undetectable, allowing accurate raindrop detection.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the raindrop detection device according to the present invention. FIG. 2 is a schematic plan view of a portion of FIG. FIG. 4 is a sectional view showing another embodiment of the raindrop detection device according to the present invention, and FIG. 5 is a characteristic diagram of a PCT element. 1.Piezoelectric element, 2.Fist diaphragm, 3.Case, 4.
Damper, 5Φ/heat wire, 12... thermistor, 13...
PCT device patent applicant Nissan Motor Co., Ltd. agent Patent attorney Hiroo Suzuki Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A raindrop detection device that detects the amount of raindrops using vibrations caused by falling raindrops, characterized in that a heating element is provided on or near a diaphragm for detecting the vibrations.