Raindrop quantity sensing apparatus and wiper control system having the same

• US 7,733,049 B2
• Filed: 07/19/2007
• Issued: 06/08/2010
• Est. Priority Date: 08/03/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Hiramoto, Satoru, Morishita, Taiji
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): Luo; David S
• Application Number:
  US11/826,897
• Publication Number:
  US 20080030159A1
• Time in Patent Office: 1,055 Days
• Field of Search: 318/483, 702/3, 731/702.1, 731/701.7
• US Class Current: 318/483
• CPC Class Codes: B60S 1/0818 including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like

Abstract

A change computing arrangement computing an amount of change in a measured value of a measurement signal of a raindrop sensor in a raindrop quantity sensing execution time period that is a time period, during which a wiper blade moves outside of a sensing range of the raindrop sensor. A difference computing arrangement computes a difference between a predetermined reference value and an initial measured value of the measurement signal of the raindrop sensor. A determining arrangement determines the quantity of raindrops on the windshield based on the amount of change, which is computed by the change computing arrangement, and the difference, which is computed by the difference computing arrangement.

Claims

1. A raindrop quantity sensing apparatus comprising:

a raindrop sensor that outputs a measurement signal, which corresponds to a quantity of raindrops in a predetermined area in a wiping range of a wiper blade on a windshield;

a change computing means for computing an amount of change in a measured value of the measurement signal of the raindrop sensor in a raindrop quantity sensing execution time period, wherein the change computing means sets a time period, during which the wiper blade moves in a sensing range of the raindrop sensor, as a raindrop quantity sensing prohibited time period, and the change computing means sets a time period, during which the wiper blade moves outside of the sensing range, as a raindrop quantity sensing execution time period;

a difference computing means for computing a difference between a predetermined reference value and an initial measured value of the measurement signal of the raindrop sensor, wherein the initial measured value of the measurement signal of the raindrop sensor is measured at a beginning of the raindrop quantity sensing execution time period; and

a determining means for determining the quantity of raindrops on the windshield based on the amount of change, which is computed by the change computing means, and the difference, which is computed by the difference computing means;

wherein the determining means determines the quantity of raindrops on the windshield based on;

an increasing tendency or decreasing tendency of the amount of change, which is computed by the change computing means; and

an increasing tendency or decreasing tendency of the difference, which is computed by the difference computing means.

2. The raindrop quantity sensing apparatus according to claim 1, wherein a measured value of the measurement signal of the raindrop sensor, which is outputted from the raindrop sensor when no raindrop is present in the sensing range, is set as the predetermined reference value.

3. The raindrop quantity sensing apparatus according to claim 1, further comprising a renewing means for renewing the predetermined reference value when no raindrop is present in the sensing range.

4. A wiper control system comprising:

the raindrop quantity sensing apparatus recited in claim 1;

a wiper motor that drives the wiper blade; and

a wiper control means for controlling a wiping operation of the wiper blade according to the quantity of raindrops on the windshield, which is determined by the raindrop quantity sensing apparatus.

5. A raindrop quantity sensing apparatus comprising:

a raindrop sensor that outputs a measurement signal, which corresponds to a quantity of raindrops in a predetermined area in a wiping range of a wiper blade on a windshield;

a change computing means for computing an amount of change in a measured value of the measurement signal of the raindrop sensor in a raindrop quantity sensing execution time period, wherein the change computing means sets a time period, during which the wiper blade moves in a sensing range of the raindrop sensor, as a raindrop quantity sensing prohibited time period, and the change computing means sets a time period, during which the wiper blade moves outside of the sensing range, as a raindrop quantity sensing execution time period;

a difference computing means for computing a difference between a predetermined reference value and an initial measured value of the measurement signal of the raindrop sensor, wherein the initial measured value of the measurement signal of the raindrop sensor is measured at a beginning of the raindrop quantity sensing execution time period; and

a determining means for determining the quantity of raindrops on the windshield based on the amount of change, which is computed by the change computing means, and the difference, which is computed by the difference computing means;

wherein a measured value of the measurement signal of the raindrop sensor, which is outputted from the raindrop sensor when no raindrop is present in the sensing range, is set as the predetermined reference value;

the determining means determines that the quantity of raindrops on the windshield is an extremely large quantity, which is greater than a predetermined quantity, when the following two conditions are both satisfied;

the amount of change, which is computed by the change computing means, shows a decreasing tendency; and

the difference, which is computed by the difference computing means, shows an increasing tendency.

6. The raindrop quantity sensing apparatus according to claim 5, wherein a quantity of raindrops, which corresponds to a lower limit value of the measurement signal that is suppliable from the raindrop sensor, is set as the predetermined quantity.

7. A wiper control system comprising:

the raindrop quantity sensing apparatus recited in claim 5;

a wiper motor that drives the wiper blade; and

a wiper control means for controlling a wiping operation of the wiper blade according to the quantity of raindrops on the windshield, which is determined by the raindrop quantity sensing apparatus.

8. A raindrop quantity sensing apparatus comprising:

a raindrop sensor that outputs a measurement signal, which corresponds to a quantity of raindrops in a predetermined area in a wiping range of a wiper blade on a windshield;

a change computing means for computing an amount of change in a measured value of the measurement signal of the raindrop sensor in a raindrop quantity sensing execution time period, wherein the change computing means sets a time period, during which the wiper blade moves in a sensing range of the raindrop sensor, as a raindrop quantity sensing prohibited time period, and the change computing means sets a time period, during which the wiper blade moves outside of the sensing range, as a raindrop quantity sensing execution time period;

a difference computing means for computing a difference between a predetermined reference value and an initial measured value of the measurement signal of the raindrop sensor, wherein the initial measured value of the measurement signal of the raindrop sensor is measured at a beginning of the raindrop quantity sensing execution time period; and

a determining means for determining the quantity of raindrops on the windshield based on the amount of change, which is computed by the change computing means, and the difference, which is computed by the difference computing means;

wherein a measured value of the measurement signal of the raindrop sensor, which is outputted from the raindrop sensor when no raindrop is present in the sensing range, is set as the predetermined reference value;

the determining means determines that the quantity of raindrops on the windshield is increased when the amount of change, which is computed by the change computing means, shows an increasing tendency;

the determining means determines that the quantity of raindrops on the windshield is decreased when the following two conditions are both satisfied;

the amount of change, which is computed by the change computing means, shows a decreasing tendency; and

the difference, which is computed by the difference computing means, shows a decreasing tendency; and

the determining means determines that the quantity of raindrops on the windshield is an extremely large quantity, which is greater than a predetermined quantity, when the following two conditions are both satisfied;

the amount of change, which is computed by the change computing means, shows a decreasing tendency; and

the difference, which is computed by the difference computing means, shows an increasing tendency.

9. A wiper control system comprising:

the raindrop quantity sensing apparatus recited in claim 8;

a wiper motor that drives the wiper blade; and

a wiper control means for controlling a wiping operation of the wiper blade according to the quantity of raindrops on the windshield, which is determined by the raindrop quantity sensing apparatus.

10. A raindrop quantity sensing apparatus comprising:

a raindrop sensor that outputs a measurement signal, which corresponds to a quantity of raindrops in a predetermined area in a wiping range of a wiper blade on a windshield;

a change computing means for computing an amount of change in a measured value of the measurement signal of the raindrop sensor in a raindrop quantity sensing execution time period, wherein the change computing means sets a time period, during which the wiper blade moves in a sensing range of the raindrop sensor, as a raindrop quantity sensing prohibited time period, and the change computing means sets a time period, during which the wiper blade moves outside of the sensing range, as a raindrop quantity sensing execution time period;

a difference computing means for computing a difference between a predetermined reference value and an initial measured value of the measurement signal of the raindrop sensor, wherein the initial measured value of the measurement signal of the raindrop sensor is measured at a beginning of the raindrop quantity sensing execution time period;

a determining means for determining the quantity of raindrops on the windshield based on the amount of change, which is computed by the change computing means, and the difference, which is computed by the difference computing means;

a temperature sensing means for sensing a temperature of the raindrop sensor;

a storage means for storing information of a temperature characteristic of the measurement signal outputted from the raindrop sensor; and

a temperature compensating means for performing temperature compensation of at least one the predetermined reference value, an initial measured value of the measurement signal of the raindrop sensor and a last measured value of the measurement signal of the raindrop sensor based on the temperature, which is measured with the temperature sensing means, and the information of the temperature characteristic stored in the storage means, so that the at least one of the predetermined reference value, the initial measured value of the measurement signal of the raindrop sensor and the last measured value of the measurement signal of the raindrop sensor is corrected to a corresponding value that is supposed to be achieved at a common temperature of the raindrop sensor that is common to a temperature of the raindrop sensor, which is measured by the temperature sensing means at a time of measuring the rest of the predetermined reference value, the initial measured value of the measurement signal of the raindrop sensor and the last measured value of the measurement signal of the raindrop sensor, wherein the initial measured value of the measurement signal of the raindrop sensor is measured at the beginning of the raindrop quantity sensing execution time period, and the last measured value of the measurement signal of the raindrop sensor is measured at an end of the raindrop quantity sensing execution time period.

11. The raindrop quantity sensing apparatus according to claim 10, wherein:

the information of the temperature characteristic, which is stored in the storage means, includes a plurality of gradients of the measurement signal of the raindrop sensor, which are obtained at a plurality of predetermined temperature ranges, respectively, upon linear approximation of the measurement signal of the raindrop sensor at each of the plurality of predetermined temperature ranges; and

the temperature compensating means corrects the at least one of the predetermined reference value, the initial measured value of the measurement signal of the raindrop sensor and the last measured value of the measurement signal of the raindrop sensor based on;

a difference between the temperature, which is measured with the temperature sensing means, and the common temperature; and

the temperature gradient of each of the plurality of predetermined temperature ranges.

12. The raindrop quantity sensing apparatus according to claim 10, wherein the temperature compensating means corrects the at least one of the predetermined reference value, the initial measured value of the measurement signal and the last measured value of the measurement signal when an amount of change in the temperature, which is measured with the temperature sensing means, becomes greater than a predetermined amount.

13. A wiper control system comprising:

the raindrop quantity sensing apparatus recited in claim 10;

a wiper motor that drives the wiper blade; and

a wiper control means for controlling a wiping operation of the wiper blade according to the quantity of raindrops on the windshield, which is determined by the raindrop quantity sensing apparatus.