Raindrop detecting method and apparatus having temperature-dependent characteristic compensation

• US 6,686,992 B2
• Filed: 05/21/2001
• Issued: 02/03/2004
• Est. Priority Date: 06/09/2000
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ishikawa, Junichi, Terakura, Osamu, Wakabayashi, Shinji, Kurahashi, Akira
• Primary Examiner(s): Pvo, Kevin
• Assistant Examiner(s): Sohn, Seung C.
• Application Number:
  US09/860,641
• Publication Number:
  US 20010050766A1
• Time in Patent Office: 988 Days
• Field of Search: 356/72, 356/73, 356/335, 356/336, 356/337, 250/573-575, 250/214.R, 250/227.25, 250/205, 250/208.1, 250/564, 250/565
• US Class Current: 356/72
• CPC Class Codes: B60S 1/0818 including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like
• CPC Class Codes: B60S 1/0833 Optical rain sensor
• CPC Class Codes: B60S 1/0866 including a temperature sensor heating devices for windshield B60H

Abstract

A raindrop detecting apparatus has a temperature sensor, an EEPROM, a processor and a raindrop sensor. A temperature characteristic data is defined by a first temperature data of the temperature sensor and a first output data of the raindrop sensor produced at a first temperature condition, and stored in the EEPROM. The processor updates a raindrop detection threshold by using the stored characteristic data, a second temperature data and a second output data produced at a second temperature, when an engine is started under no-raindrop condition. The processor compares an output data of the raindrop sensor with the raindrop detection threshold to detect a raindrop, while converting at least one of the characteristic data and the output data in correspondence with a temperature data produced at a raindrop detection time.

Claims

1. A raindrop detecting method comprising:

storing a characteristic data of a raindrop sensor as a comparison reference, all of the characteristic data being indicative of a temperature-dependent output characteristic of the raindrop sensor under a no-raindrop condition; and

detecting a raindrop by comparing an output data of the raindrop sensor produced from time to time and the stored characteristic data.

2. The raindrop detecting method according to claim 1, further comprising:

updating the stored characteristic data in accordance with varying conditions of the raindrop sensor.

3. The raindrop detecting method according to claim 2, further comprising:

converting the stored characteristic data to a data which corresponds to a temperature at which the output data is produced, so that the detecting of the raindrop involves detecting the raindrop based on a deviation of the output data from the converted characteristic data.

4. The raindrop detecting method according to claim 1, further comprising:

determining the temperature-dependent output characteristic from a plurality of initial output data of the raindrop sensor produced under a no-raindrop condition before the raindrop sensor is installed in a vehicle; and

converting the latest stored characteristic data under a no-raindrop condition and the current output data based on the determined temperature-dependent output characteristic, so that the detecting of the raindrop involves comparing two data of the latest stored characteristic data and the current output data to detect the raindrop under a same temperature condition.

5. The raindrop detecting method according to claim 4, further comprising:

updating the stored characteristic data in accordance with another output data of the raindrop sensor each time an engine of the vehicle is started or at a predetennined period.

6. The raindrop detecting method according to claim 5,

wherein updating the stored characteristic data is executed only under a no-raindrop condition on the raindrop sensor.

7. The raindrop detecting method according to claim 1,

wherein reading, before the raindrop sensor is installed on a vehicle, a plurality of initial output data of the raindrop sensor and a plurality of initial temperature data indicative of temperatures at which the initial output data are produced;

and

calculating a rate of change in the initial output data with respect to temperature, so that storing the characteristic data involves storing the calculated rate as a part of the characteristic data.

8. The raindrop detecting method according to claim 7,

storing, when the raindrop sensor is installed on the vehicle, another output data of the raindrop sensor and another temperature data indicative of a temperature at which the another output data is produced as another part of the characteristic data.

9. The raindrop detecting method according to claim 8, further comprising:

updating, each time an engine of the vehicle is started, the stored another output data of the raindrop sensor and the stored another temperature data by a further output data of the raindrop sensor and a further temperature indicative of a temperature at which the further output data is produced.

10. The raindrop detecting method according to claim 9,

wherein the updating includes further updating the stored output data and the stored temperature data by the output data and the temperature data which are used in the detecting of the raindrop.

11. The raindrop detecting method according to claim 1, wherein the stored characteristic data is stored before shipment of the raindrop sensor.

12. The raindrop detecting method according to claim 1, wherein the stored characteristic data is stored after shipment of the raindrop sensor.

13. A raindrop detecting apparatus comprising:

a raindrop sensor disposed to sense a raindrop and produce an output data indicative of the sensed raindrop;

a temperature sensor disposed to sense a temperature around the raindrop sensor and produce a temperature data indicative of the sensed temperature;

a memory for storing all of the characteristic data as a comparison reference that includes the temperature data and the output data corresponding to the temperature data, which are produced under a no-raindrop condition; and

a processor for detecting a raindrop by comparing a current output data of the raindrop sensor produced from time to time with the latest stored characteristic data.

14. The raindrop detecting apparatus according to claim 13,

wherein the stored characteristic data includes an output rate data indicative of an output rate of the output data of the raindrop sensor relative to a reference output data of the raindrop sensor produced at a reference temperature.

15. The raindrop detecting apparatus according to claim 14,

wherein a temperature-dependent output rate data is calculated by a plurality of temperature data of the temperature sensor and a plurality of output data of the raindrop sensor produced at temperatures of the plurality of temperature data.

16. The raindrop detecting apparatus according to claim 15,

wherein the output rate data is stored in the memory before installation of the raindrop sensor.

17. The raindrop detecting apparatus according to claim 16,

wherein the stored characteristic data is updated to a second temperature data of the temperature sensor and a second output data of the raindrop sensor produced in correspondence with the second temperature data;

and

the second temperature data and the second output data are produced and updated after the temperature sensor and the raindrop sensor are installed in a vehicle.

18. The raindrop detecting apparatus according to claim 16,

a no-raindrop detection criterion setting part for setting a no-raindrop detecting output level at a certain temperature from the stored temperature-dependent output rate data, a second temperature data of the temperature sensor produced under a no-raindrop condition and a second output data of the raindrop sensor produced in correspondence with the temperature data under a no-raindrop condition;

and

a raindrop detecting part for detecting a raindrop by converting a current output data of the raindrop sensor to an output data at a certain temperature in order to compare with a no-raindrop detecting output level for comparison under a same temperature condition.

19. The raindrop detecting apparatus according to claim 13, wherein the memory stores the stored characteristic data before shipment of the raindrop detecting apparatus.

20. The raindrop detecting apparatus according to claim 13, wherein the memory stores the stored characteristic data after shipment of the raindrop detecting apparatus.

21. A raindrop detecting method comprising:

storing a characteristic data, an output data of a raindrop sensor, and a temperature data of a temperature sensor, wherein all of the characteristic data indicates a temperature-dependent characteristic of the raindrop sensor, the output data is produced under a no-raindrop condition and the temperature data is produced at the same time as the output data;

converting an output data of the raindrop sensor produced from time to time into converted output data and the stored output data produced under a no-raindrop condition into convened stored output data so that the output data and the stored output data are compared under a same temperature condition; and

detecting a raindrop by comparing the converted output data and the converted stored output data;

wherein said converting is based on a temperature data produced at the same time as the output data, the stored temperature data and the stored characteristic data.

22. The raindrop detecting method according to claim 21,

wherein detecting the raindrop further includes:

calculating a ratio of the converted output data and the converted stored output data; and

determining the raindrop to adhere to the raindrop sensor when the ratio is below 1.0 and a predetermined ratio.

23. The raindrop detecting method according to claim 22,

wherein the predetermined ratio changes in accordance with a temperature difference between the temperature data and the stored temperature data.

24. The raindrop detecting method according to claim 21,

wherein detecting the raindrop further includes:

calculating a ratio of the converted output data and the converted stored output data;

determining no raindrop to adhere to the raindrop sensor when the ratio is equal to and above 1.0; and

updating the stored output and the stored temperature data by the output data and the temperature data.

25. The raindrop detecting method according to claim 21,

wherein the stored output data and the stored temperature data are initially stored in such a manner that an initial output data and an initial temperature data are produced at primary energization of the raindrop and temperature sensors after shipment of the raindrop and temperature sensors so that the initial output and temperature data are stored as an initially stored output data and an initially stored temperature data.

26. The raindrop detecting method according to claim 25,

wherein detecting the raindrop further includes:

calculating a ratio of the converted output data and the converted stored output data;

determining no raindrop to adhere to the raindrop sensor when the ratio is equal to and above 1.0; and

updating the stored output data and the stored temperature data by the output data and the temperature data after the initially stored output data and the initially stored temperature data are stored.

27. The raindrop detecting method according to claim 21,

wherein the stored characteristic data is initially stored in such a manner that a plurality of output data of the raindrop sensor at different temperatures are produced just after shipment of the raindrop sensor so that an output ratio data is stored as an initial characteristic data, the output ratio data being produced by a rate of the plurality of output data at different temperatures to a reference output data produced at a predetermined temperature.

28. The raindrop detecting method according to claim 27,

wherein the predetermined temperature is 25°

C.

29. The raindrop detecting method according to claim 28,

wherein detecting the raindrop further includes:

calculating a ratio of the converted output data and the converted stored output data;

determining no raindrop to adhere to the raindrop sensor when the ratio is equal to and above 1.0;

updating the stored output data and the stored temperature data by the output data and the temperature data; and

updating the stored output ratio data by a ratio of the output data to the reference output data at 25°

C.

30. The raindrop detecting method according to claim 21,

wherein the stored characteristic data is initially stored in such a manner that an output ratio data is estimated from a predetermined temperature-dependent characteristic of a raindrop sensor so that the output ratio data is stored as an initial characteristic data, and

wherein the output ratio data is a rate of a plurality of output data at different temperatures to an output data at a predetermined temperature.

31. A raindrop detecting apparatus comprising:

a raindrop sensor disposed to sense a raindrop and produce an output data indicative of the sensed raindrop;

a temperature sensor disposed to sense a temperature around the raindrop sensor and produce a temperature data indicative of the sensed temperature;

a memory for storing a characteristic data, an output data of a raindrop sensor, a temperature data of a temperature sensor, wherein all of the characteristic data indicates a temperature-dependent characteristic of the raindrop sensor, the output data is produced under a no-raindrop condition and the temperature data is also produced at the same time as the output data; and

a processor for converting an output data produced from time to time into converted output data and the stored output data produced under a no-raindrop condition into converted stored output data so that the output data and the stored data are compared under a same temperature condition, and for detecting a raindrop by comparing the convened output data and the converted stored output data,

wherein the converting is based on a temperature data produced at the same time as the output data, the stored temperature data and the stored characteristic data.