Method and device to assess the wear of a windshield wiper unit

Patent metadata

Field	Value
Publication number	US-9539984-B2
Application number	US-201214118750-A
Country	US
Kind code	B2
Filing date	May 15, 2012
Priority date	May 20, 2011
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

Method to estimate the wear state of wiper blades ( 5 ) of a vehicle windshield wiper unit ( 1 ), said windshield wiper unit ( 1 ) comprising: at least one wiper blade ( 5 ) configured to wipe a windshield surface (S) when activated, at least one motor ( 7 ) configured to activate the at least one wiper blade ( 5 ), a controller ( 9 ) configured to control the at least one motor ( 7 ), comprising the steps: deriving a friction coefficient (B) between the at least one wiper blade ( 5 ) and the windshield surface (S), using the derived friction coefficient (B) to determine the wetness of the windshield surface (S), if the windshield surface (S) is dry, using the derived friction coefficient (B) to estimate the wear state of the at least one wiper blade ( 5 ).

First claim

The invention claimed is:

1. A method to estimate the wear state of wiper blades of a vehicle windshield wiper unit, said windshield wiper unit comprising:
at least one wiper blade configured to wipe a windshield surface when activated,
at least one motor configured to activate the at least one wiper blade at a wiping speed, and
a controller configured to control the at least one motor,
said method comprising:
deriving a friction coefficient between the at least one wiper blade and the windshield surface;
comparing the derived friction coefficient to a first predetermined threshold value, to determine the wetness of the windshield surface; and
when the windshield surface is dry, comparing the derived friction coefficient to a second predetermined threshold value to estimate the wear state of the at least one wiper blade.

2. The method as claimed in claim 1 , wherein the at least one motor has a power consumption, said method further comprising dividing the power consumption by a size factor of the windshield wiping unit.

3. The method as claimed in claim 1 , the method further comprising dividing the derived friction coefficient by the size factor of the windshield wiping unit.

4. The method as claimed in claim 2 , the windshield wiping unit wiping the windshield surface at a wipe angle and comprising at least one wiper arm, and at least one wiper blade, wherein said windshield wiping unit presents a size factor comprising the wipe angle, the length of the at least one wiper arm and the length of the at least one wiper blade.

5. The method as claimed in claim 2 , the method further comprising determining the first predetermined threshold value with a test windshield wiping unit, said determination comprising:
wetting the test windshield surface,
measuring the power consumption of the at least one test motor,
determining the wiping speed of the at least one test wiper blade,
using the measured power consumption and wiping speed to deduce a reference wet friction coefficient of the wet windshield surface,
using the reference wet friction coefficient to determine the first predetermined threshold value,
said determination further comprising a step of dividing the power consumption or the first predetermined threshold value by the size factor of the test wiper unit.

6. The method as claimed in claim 2 , further comprising determining the second predetermined threshold value with the test windshield wiping unit, said determination comprising:
measuring the power consumption of the at least one test motor on dry test windshield surface,
determining the wiping speed of the at least one test wiper blade on dry test windshield surface,
using the measured power consumption and determined wiping speed to derive the friction coefficient,
monitoring the over time wiping performance and the corresponding friction coefficient to determine the second predetermined threshold value,
said determination further comprising a step of dividing the power consumption or the friction coefficient by the size factor of the test wiping unit.

7. The method as claimed in claim 1 , the controller being connected to a windshield washing unit, wherein the first predetermined threshold value is determined using a calibration, the calibration comprising:
wetting the windshield surface by activating the windshield washing unit,
measuring the power consumption of the at least one motor during a certain number of cycles done by the at least one wiper blade,
using the measured power consumption to deduce a reference wet friction coefficient of the wet windshield surface,
using the reference wet friction coefficient to determine the first predetermined threshold value.

8. The method as claimed in claim 7 , wherein the first predetermined threshold value is a multiple of the reference wet friction coefficient, at least four times the reference wet friction coefficient.

9. The method as claimed in claim 1 , wherein the second predetermined threshold value, is determined using a calibration, the calibration comprising:
measuring the power consumption of the at least one motor on dry windshield surface,
determining the wiping speed of the at least one wiper blade on dry windshield surface,
using the measured power consumption and determined wiping speed to derive an initial dry friction coefficient of the dry windshield surface,
using said initial dry friction coefficient to determine the second predetermined threshold value.

10. The method as claimed in claim 9 , wherein the second predetermined threshold value is a multiple of said corresponding friction coefficient or said initial dry friction coefficient.

11. The method as claimed in claim 1 , further comprising generating a signal when the at least one wiper blade is estimated worn.

12. The method as claimed in claim 1 , further comprising storing the derived friction coefficient values and restoring them.

13. A windshield wiper unit comprising:
at least one wiper blade configured to wipe a windshield surface when activated;
at least one motor configured to activate the at least one wiper blade; and
a controller configured to:
control the at least one motor,
derive a friction coefficient between the at least one wiper blade and the windshield surface,
compare the derived friction coefficient to a first predetermined threshold value, to determine the wetness of the windshield surface, and
if the windshield surface is dry, compare the derived friction coefficient to a second predetermined threshold value, in order to estimate the wear state of the at least one wiper blade.

14. The windshield wiper unit as claimed in claim 13 , wherein the controller comprises means for performing a calibration of the first predetermined threshold value and of the second predetermined threshold value.

15. The windshield wiper unit as claimed in claim 13 , wherein the controller comprises means to generate an alert signal when the at least one wiper blade is estimated worn.

16. The windshield wiper unit as claimed in claim 13 , wherein the controller comprises means for storing the values of the derived friction coefficient and restoring them.

Assignees

• Dias Dominique
• Valeo Systemes Dessuyage

Inventors

• Dias Dominique

Classifications

• G01M5/0033

  by determining damage, crack or wear · CPC title

• B60S1/0818 Primary

  including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like · CPC title

• H02P3/02

  Details {of stopping control} · CPC title

• B60S1/0859

  Other types of detection of rain, e.g. by measuring friction or rain drop impact · CPC title

• G01N19/02

  Measuring coefficient of friction between materials {(testing of tyres G01M17/02; determinations of friction coefficient used in vehicle braking or traction control systems B60T8/172)} · CPC title