Wiper blade rubber, method for manufacturing the same, and method for inspecting the same.

Abstract

The wiper blade rubber (10) has a contact sliding portion (121) that contacts and slides against the surface of another component. The skewness Ssk of the contact sliding portion (121) is 0 or greater and 0.4 or less.

Description

Technical Field

[0001] The present invention relates to a wiper blade rubber, a method for manufacturing the same, and a method for inspecting the same.

Background Art

[0002] A technique for surface modification by chlorination treatment on the surface of a wiper blade rubber is known. For example, Patent Documents 1 and 2 disclose wiper blades that have been chlorinated and have a chlorine concentration on the surface of 1.0 mass% or more and 2.5 mass% or less.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The present invention is a wiper blade rubber having a contact sliding portion that contacts and slides on the surface of another member, wherein the skewness Ssk of the contact sliding portion is 0 or more and 0.4 or less.

[0005] The present invention is a method for manufacturing a wiper blade rubber, which includes a step of immersing a molded body formed of a crosslinked rubber composition for manufacturing a wiper blade rubber in an aqueous chlorination treatment solution to perform chlorination treatment, wherein the effective chlorine concentration of the aqueous chlorination treatment solution is 30 ppm or more and 600 ppm or less.

[0006] The present invention is a method for inspecting a wiper blade rubber having a contact sliding portion that contacts and slides on the surface of another member, which includes obtaining the skewness Ssk of the contact sliding portion and determining that it is qualified when it is 0 or more and 0.4 or less.

Brief Description of the Drawings

[0007] [Figure 1] This is a perspective view of a piece of wiper blade rubber according to Embodiment 1. [Figure 2A] This is a first explanatory diagram of a method for manufacturing a wiper blade rubber according to Embodiment 1. [Figure 2B] This is a second explanatory diagram of the method for manufacturing a wiper blade rubber according to Embodiment 1. [Figure 3] This is a perspective view of one piece of wiper blade rubber according to Embodiment 2. [Figure 4] This is an explanatory diagram of the method for manufacturing a wiper blade rubber according to Embodiment 2. [Modes for carrying out the invention]

[0008] The embodiments will be described in detail below.

[0009] (Embodiment 1) Figure 1 shows a wiper blade rubber 10 according to Embodiment 1.

[0010] The wiper blade rubber 10 according to Embodiment 1 is a generally flat, elongated rubber component. In this wiper blade rubber 10, a mounting and holding portion 11 is provided on one side in the width direction, a lip portion 12 is provided on the other side in the width direction, and a neck portion 13 is provided to connect the mounting and holding portion 11 and the lip portion 12.

[0011] The wiper blade rubber 10 according to Embodiment 1 has a mounting and holding portion 11 that is attached to and held by a vertebra of a wiper drive unit provided, for example, on the lower side of the windshield of an automobile. When the wiper drive unit is driven, the lip portion 12 of the wiper blade rubber 10 tilts with the neck portion 13 as a pivot point, and the surface of the elongated sheet-like tip portion 121 of the lip portion 12 contacts and slides against the surface of the windshield, thereby wiping away rain and other debris. Therefore, the surface of the sheet-like tip portion 121 of the lip portion 12 constitutes a contact sliding portion with respect to other members.

[0012] The wiper blade rubber 10 according to Embodiment 1 is formed from a crosslinked rubber composition containing a rubber component and a rubber compounding agent.

[0013] Examples of rubber components include natural rubber (NR), chloroprene rubber (CR), ethylene propylene diene rubber (EPDM), and styrene butadiene rubber (SBR). Examples of CR include sulfur-modified type, mercaptan-modified type, and xanthogene-modified type. The rubber component preferably contains one or more of these, and a blended rubber containing NR and CR is more preferable from the viewpoint of obtaining excellent wiping and sliding properties, as described later. When the rubber component is a blended rubber containing NR and CR, the mass ratio of the NR content to the CR content in the rubber component is preferably greater than 35 / 65, more preferably 40 / 60 or more, preferably 70 / 30 or less, and more preferably 65 / 35 or less, from the same viewpoint. From the same viewpoint, the NR content in the rubber component is preferably greater than the CR content.

[0014] Examples of rubber compounding agents include carbon black, vulcanization accelerators, processing aids, vulcanization accelerators, and antioxidants.

[0015] Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Examples of furnace black include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of thermal black include FT and MT. It is preferable that the carbon black contains one or more of these. The carbon black content in the crosslinked rubber composition is, for example, 20 parts by mass or more and 40 parts by mass or less per 100 parts by mass of rubber component. In this application, the content in the crosslinked rubber composition refers to the amount of the crosslinked rubber composition blended into the uncrosslinked rubber composition before crosslinking.

[0016] Examples of vulcanization accelerators include metal oxides, metal carbonates, fatty acids, and derivatives of fatty acids. Examples of metal oxides include zinc oxide (zinc oxide) and magnesium oxide. The vulcanization accelerator preferably contains one or more of these, and from the viewpoint of obtaining excellent wiping and sliding properties, it is more preferable to contain a metal oxide, even more preferable to contain zinc oxide and / or magnesium oxide, and even more preferable to contain both zinc oxide and magnesium oxide. When the rubber component contains CR and the vulcanization accelerator contains a metal oxide, the metal oxide also acts as a crosslinking agent for CR. The content of the vulcanization accelerator in the crosslinked rubber composition is, for example, 3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0017] Examples of processing aids include stearic acid, polyethylene wax, and metal salts of fatty acids. The processing aid preferably contains one or more of these, and more preferably contains stearic acid from the viewpoint of obtaining excellent wiping and sliding properties. The content of the processing aid in the crosslinked rubber composition is, for example, 0.5 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the rubber component.

[0018] Examples of vulcanization accelerators include sulfenamide-based vulcanization accelerators, thiourea-based vulcanization accelerators, aldehyde-ammonia-based vulcanization accelerators, aldehyde-amine-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. It is preferable that the vulcanization accelerator contains one or more of these. The content of the vulcanization accelerator in the crosslinked rubber composition is, for example, 2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the rubber component.

[0019] Examples of the anti-aging agent include p-phenylenediamine-based anti-aging agents, diphenylamine-based anti-aging agents, amine-ketone-based anti-aging agents, monophenol-based anti-aging agents, bisphenol-based anti-aging agents, polyphenol-based anti-aging agents, benzimidazole-based anti-aging agents, dithiocarbamate-based anti-aging agents, phosphite-based anti-aging agents, organic thioacid-based anti-aging agents, and the like. The anti-aging agent may contain one or more of these. The content of the anti-aging agent in the crosslinked rubber composition is, for example, 2 parts by mass or more and 6 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0020] From the viewpoint of obtaining excellent wiping properties and sliding properties, it is preferable that sulfur is used as a crosslinking agent for crosslinking the crosslinked rubber composition. In this case, the compounding amount of sulfur in the uncrosslinked rubber composition is, for example, 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the rubber component. Note that an organic peroxide may be used as a crosslinking agent for crosslinking the crosslinked rubber composition.

[0021] The wiper blade rubber 10 according to Embodiment 1 is subjected to a wet chlorination treatment using an aqueous chlorination treatment solution having a low effective chlorine concentration as described below. The surface of the sheet-like tip portion 121 of the lip portion 12 constituting the contact sliding portion with other members has a skewness Ssk (degree of bias), which is the distortion of the contour curved surface in surface roughness, of 0 or more and 0.4 or less by this wet chlorination treatment. This skewness Ssk is determined based on ISO25178-2 and is also defined in JIS B0681-2. In the present application, the skewness Ssk of the contact sliding portion is the average value of the values at five locations of the contact sliding portion. Examples of the device for obtaining the skewness Ssk include the digital microscope VHX-Xl manufactured by Keyence Corporation.

[0022] According to the wiper blade rubber 10 according to Embodiment 1, since the skewness Ssk of the surface of the sheet-like tip portion 121 of the lip portion 12 constituting the contact sliding portion is 0 or more and 0.4 or less, excellent wiping performance and sliding performance can be obtained. The skewness Ssk of the surface of the sheet-like tip portion 121 of the lip portion 12 is preferably 0.01 or more and 0.3 or less, more preferably 0.1 or more and 0.25 or less, from the viewpoint of obtaining excellent wiping performance and sliding performance. Further, in the product inspection of the wiper blade rubber 10, if an inspection is performed to obtain the skewness Ssk of the surface of the sheet-like tip portion 121 of the lip portion 12 constituting the contact sliding portion and determine that it is 0 or more and 0.4 or less as qualified, excellent wiping performance and sliding performance can be guaranteed thereby.

[0023] The chlorine addition amount by chlorination treatment on the surface of the sheet-like tip portion 121 of the lip portion 12 is preferably 0.1% by mass or more and 3.5% by mass or less, more preferably 0.5% by mass or more and 2.0% by mass or less, still more preferably 0.8% by mass or more and 1.2% by mass or less, from the viewpoint of obtaining excellent wiping performance and sliding performance. In the present application, this chlorine addition amount is obtained by measuring the chlorine element concentration in all the elements on the surface of the lip portion 12 by elemental analysis by fluorescent X-ray analysis of the surface of the sheet-like tip portion 121 of the lip portion 12, and measuring the chlorine element concentration in the same manner as a control for the unchlorinated product, and taking the difference obtained by subtracting the chlorine element concentration of the latter from the chlorine element concentration of the former.

[0024] Next, a manufacturing method of the wiper blade rubber 10 according to Embodiment 1 will be described.

[0025] First, an uncrosslinked rubber composition is prepared by mixing a rubber compounding agent with a rubber component and kneading it. By molding and crosslinking this uncrosslinked rubber composition, a tandem molded body 20 formed from a crosslinked rubber composition for wiper blade rubber manufacturing is produced, as shown in Figure 2A. This tandem molded body 20 has a shape in which the sheet-like tip portions 121 of the lip portions 12 of a pair of wiper blade rubbers 10 are butted together and joined. Examples of molding methods for the tandem molded body 20 include press molding, extrusion molding, injection molding, and transfer molding.

[0026] Next, the tandem molded body 20 is immersed in a chlorinated aqueous solution with a low effective chlorine concentration to perform chlorination treatment. Examples of chlorinated aqueous solutions include aqueous solutions of hypochlorous acid and / or hypochlorites (e.g., calcium hypochlorite or sodium hypochlorite) to which an acid such as hydrochloric acid is added to lower the pH and generate chlorine. From the viewpoint of obtaining excellent wiping and sliding properties, the effective chlorine concentration of the chlorinated aqueous solution is preferably 30 ppm to 600 ppm, more preferably 80 ppm to 500 ppm, and even more preferably 100 ppm to 200 ppm. From the same viewpoint, the pH of the chlorinated aqueous solution is preferably 1.5 to 2.4, more preferably 1.8 to 2.3.

[0027] Next, after removing the tandem molded body 20 from the chlorinated aqueous solution, the tandem molded body 20 is immersed in washing water and washed in order to effectively stop the chlorination reaction.

[0028] Next, after removing the tandem molded body 20 from the washing water, the tandem molded body 20 is immersed in hot water with a higher temperature than the washing water for further washing.

[0029] Then, after removing the tandem molded body 20 from the hot water and drying it, the center of the tandem molded body 20 is cut as shown in Figure 2B to obtain a pair of wiper blade rubbers 10.

[0030] (Embodiment 2) Figure 3 shows a wiper blade rubber 10 according to Embodiment 2. Parts with the same names as those in Embodiment 1 are denoted by the same reference numerals as those in Embodiment 1.

[0031] In the wiper blade rubber 10 according to Embodiment 2, both sides of the sheet-like tip portion 121 of the lip portion 12 are covered with a graphite coating layer 14. Therefore, the surface of the graphite coating layer 14 contacts and slides against the surface of the windshield, thereby wiping away rain and other debris. Thus, the surface of the graphite coating layer 14 constitutes a contact sliding portion with other components.

[0032] The graphite coating layer 14 is composed of a thin film layer in which graphite is bonded via a binder. The thickness of the graphite coating layer 14 is, for example, 3 μm to 7 μm.

[0033] Examples of graphite include natural graphite and artificial graphite. Examples of natural graphite include flaky graphite, lumpy graphite, and earthy graphite. The graphite preferably contains one or more of these types, and more preferably contains flaky graphite from the viewpoint of obtaining excellent wiping properties and durability. The particle size of the graphite is, for example, 2 μm to 8 μm.

[0034] Examples of binders include thermosetting resins, thermoplastic resins, and photocurable resins. Examples of thermosetting resins include thermosetting polyurethane resins, silicone resins, epoxy resins, phenolic resins, urea resins, and melamine resins. Examples of thermoplastic resins include polyethylene resins, polypropylene resins, polyamide resins, polyester resins, and thermoplastic polyurethane resins. Examples of photocurable resins include epoxy compounds and urethane compounds to which acrylic acid has been added. From the viewpoint of obtaining excellent wipeability and durability, the binder is preferably a thermosetting resin, and more preferably a thermosetting polyurethane resin.

[0035] The mass ratio of the graphite content in the graphite coating layer 14 to the binder content is, for example, 0.5 or more and less than 1.5.

[0036] The surface of the sheet-like tip portion 121 of the lip portion 12, which is the base of the graphite coating layer 14, is subjected to the same chlorination treatment as in Embodiment 1. Since the thickness of the graphite coating layer 14 is very thin, the surface properties formed on the surface of the sheet-like tip portion 121 of the lip portion 12 by the chlorination treatment are generally reflected on the surface of the graphite coating layer 14. As a result, the skewness Ssk of the surface of the graphite coating layer 14 constituting the contact sliding portion is 0 to 0.4, preferably 0.01 to 0.3, and more preferably 0.1 to 0.25, from the viewpoint of obtaining excellent wiping and sliding properties.

[0037] When manufacturing the wiper blade rubber 10 according to Embodiment 2, as shown in Figure 4, a graphite coat layer 14 is formed by coating and solidifying a coating agent on each of the surfaces on both sides of the joint between the sheet-like tip portions 121 of the lip portion 12 in the tandem molded body 20.

[0038] The coating agent contains solid components including graphite and a binder before solidification, and an organic solvent for dissolving or dispersing these solid components. The solid component concentration of the coating agent is, for example, 3% by mass or more and 30% by mass or less. Examples of organic solvents include aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, alcohol-based solvents, ketone-based solvents, and ester-based solvents. Examples of aromatic hydrocarbon solvents include benzene, toluene, and xylene. Examples of aliphatic hydrocarbon solvents include n-hexane, isohexane, cyclohexane, n-octane, isooctane, decane, and dodecane. Examples of alcohol-based solvents include methanol, ethanol, and isopropanol. Examples of ketone-based solvents include methyl ethyl ketone and methyl isobutyl ketone. Examples of ester-based solvents include ethyl acetate and isobutyl acetate. It is preferable that the organic solvent contains one or more of these. A coating method for the coating agent is, for example, spray coating using a spray nozzle.

[0039] The other configurations and effects are the same as those of Embodiment 1.

[0040] (Other embodiments) In embodiments 1 and 2 described above, the wiper blade rubber 10 is primarily for automobiles, but it is not limited to this, and any wiper blade rubber used in other wiper systems may be used.

[0041] In embodiments 1 and 2 described above, the tandem molded body 20 is subjected to chlorination treatment, but the invention is not limited to this, and a configuration in which a single molded body having the same shape as the wiper blade rubber 10 is subjected to chlorination treatment may also be used. [Examples]

[0042] (Wiper blade rubber) Wiper blade rubbers for Examples 1 to 5 and Comparative Example 1, with the same configuration as Embodiment 1 described above, were manufactured. Wiper blade rubbers for Examples 6 to 10 and Comparative Example 2, with the same configuration as Embodiment 2 described above, were also manufactured. The respective configurations are shown in Tables 1 and 2.

[0043] <Example 1> A blend of rubber mixed in a mass ratio of NR / CR = 60 / 40 was used as the rubber component. To 100 parts by mass of this rubber component, 30 parts by mass of FEF, 5 parts by mass of zinc oxide, 1 part by mass of magnesium oxide, 1 part by mass of stearic acid, 3 parts by mass of process oil, 2 parts by mass of vulcanization accelerator, 4 parts by mass of antioxidant, and 2 parts by mass of sulfur were added and kneaded to prepare an uncrosslinked rubber composition. A tandem molded body was produced by press molding and crosslinking using this uncrosslinked rubber composition, and the tandem molded body was subjected to a wet chlorination treatment.

[0044] Specifically, in the chlorination treatment, the tandem molded body was first immersed in a chlorination treatment aqueous solution. The chlorination treatment aqueous solution used was one in which chlorine was generated by adding hydrochloric acid to an aqueous solution of calcium hypochlorite to lower the pH to 2.2. The effective chlorine concentration in the chlorination treatment aqueous solution was set to 50 ppm.

[0045] Next, the tandem molded body was removed from the chlorinated aqueous solution and then immersed in washing water for cleaning. Subsequently, the tandem molded body was removed from the washing water and then immersed in hot water, which was hotter than the washing water, for further cleaning. The tandem molded body, removed from the hot water, was placed in an oven to dry.

[0046] Then, the tandem molded body was divided into two to obtain a pair of wiper blade rubbers. This was designated as Example 1.

[0047] <Examples 2-5 and Comparative Example 1> Example 2 was obtained in the same manner as in Example 1, except that the effective chlorine concentration in the chlorinated aqueous solution was set to 90 ppm.

[0048] Example 3 was obtained in the same manner as in Example 1, except that the effective chlorine concentration in the chlorinated aqueous solution was set to 145 ppm.

[0049] Example 4 was obtained in the same manner as in Example 1, except that the effective chlorine concentration in the chlorinated aqueous solution was set to 170 ppm.

[0050] Example 5 was a wiper blade rubber obtained in the same manner as in Example 1, except that the effective chlorine concentration in the chlorinated aqueous solution was set to 310 ppm.

[0051] Comparative Example 1 was a wiper blade rubber obtained in the same manner as in Example 1, except that the effective chlorine concentration in the chlorinated aqueous solution was set to 680 ppm.

[0052] <Examples 6-10 and Comparative Example 2> Wiper blade rubbers obtained in the same manner as in Examples 1-5 and Comparative Example 1, except that the surfaces on both sides of the sheet-like tip of the lip portion were coated with a graphite coating layer, were designated as Examples 6-10 and Comparative Example 2, respectively. For the formation of the graphite coating layer, a coating agent containing graphite as a solid lubricant and thermosetting polyurethane resin as a binder was used. The thickness of the graphite coating layer was adjusted to 2.0 μm.

[0053] [Table 1]

[0054] [Table 2]

[0055] (Test methods and results) The following tests were performed on the wiper blade rubbers of Examples 1-10 and Comparative Examples 1-2. The results are shown in Tables 1 and 2.

[0056] <Sskewness> For each of the wiper blade rubbers of Examples 1-10 and Comparative Examples 1-2, a Keyence VHX-X1 digital microscope was used to examine five locations on the surface of the tip of the lip portion at a magnification of 1000x, measuring 45000 μm. 2 Images were taken of the region, the skewness Ssk was calculated from each of these images, and the average value of the skewness Ssk at five locations was calculated.

[0057] <Static friction coefficient> For each of the wiper blade rubbers from Examples 1-10 and Comparative Examples 1-2, a 100 mm long test piece was cut out. The mounting and holding portion of the test piece was attached to a long, slender fixing jig. The fixing jig with the test piece attached was then positioned on a rotatable glass disc with a diameter of 400 mm, which had been treated with a water-repellent agent, so that the test piece extended radially and the tip of the lip portion of the test piece was in contact with the disc. A vertical load of 1.57 N was applied to the fixing jig to press the tip of the lip portion of the test piece against the glass disc. Water was sprayed onto the glass disc to wet it, and the glass disc was rotated so that the speed at the center of the test piece was 1.0 m / s, allowing the test piece to slide on the glass disc. At this time, the frictional force was measured using a load cell attached to the fixing jig. The maximum frictional force at the start of movement was defined as the static frictional force, and the static friction coefficient was calculated by dividing this by the vertical load of 1.57 N.

[0058] <Amount of chlorine added> For each of the wiper blade rubber test specimens from Examples 1-10 and Comparative Examples 1-2, a 35mm square rubber sheet with a thickness of 2mm was prepared using the same process. Elemental analysis using X-ray fluorescence analysis was performed to measure the chlorine concentration of all elements. Similarly, the chlorine concentration was measured for a rubber sheet test specimen that had not undergone chlorination treatment, serving as a control. The difference between the chlorine concentration of the former and the chlorine concentration of the latter was calculated as the amount of chlorine added.

[0059] <Wipeability and sliding properties> Each wiper blade rubber from Examples 1-10 and Comparative Examples 1-2 was mounted on an actual vehicle. Water was sprayed onto the windshield to wet it, and the wiper drive motor was activated to wipe the water off the windshield with the wiper blade rubber. The wiping performance was evaluated as follows: no streaks or unwiped areas were observed (rated A), streaks or unwiped areas were observed (rated B), and both streaks and unwiped areas were observed (rated C). Regarding sliding performance, no chatter was observed (rated A), slight chatter was observed (rated B), and significant chatter was observed (rated C). [Industrial applicability]

[0060] The present invention is useful in the technical field of wiper blade rubber, methods for manufacturing the same, and methods for inspecting the same. [Explanation of Symbols]

[0061] 10 Wiper Blade Rubber 11 Mounting and holding part 12 Lip section 121 Sheet-like tip portion (contact sliding portion) 13. Neck section 14. Graphite coating layer (contact sliding part) 20 Tandem molded body

Claims

1. A wiper blade rubber having a contact sliding portion that contacts and slides against the surface of another component, A wiper blade rubber having a skewness Ssk of 0 or more and 0.4 or less in the contact sliding portion.

2. In the wiper blade rubber described in claim 1, The contact sliding portion is a wiper blade rubber whose surface is made of a cross-linked rubber composition that has been subjected to chlorine treatment.

3. In the wiper blade rubber described in claim 2, A wiper blade rubber in which the amount of chlorine added by the chlorination treatment in the contact sliding portion is 0.1% by mass or more and 3.5% by mass or less.

4. In the wiper blade rubber described in claim 2, A wiper blade rubber in which the rubber component of the crosslinked rubber composition is a blend rubber containing natural rubber and chloroprene rubber.

5. In the wiper blade rubber described in claim 4, A wiper blade rubber in which the content of natural rubber in the rubber component is greater than the content of chloroprene rubber.

6. In the wiper blade rubber described in claim 2, The aforementioned crosslinked rubber composition is a wiper blade rubber in which sulfur is used as a crosslinking agent.

7. In the wiper blade rubber described in claim 1, The contact sliding portion is a wiper blade rubber whose surface is covered with a graphite coating layer that has been treated with a chlorine-treated crosslinked rubber composition.

8. A method for manufacturing wiper blade rubber, comprising the step of immersing a molded body formed from a crosslinked rubber composition for manufacturing wiper blade rubber in a chlorinated aqueous solution to perform a chlorinated treatment, A method for manufacturing wiper blade rubber, wherein the effective chlorine concentration of the chlorinated aqueous solution is 30 ppm or more and 600 ppm or less.

9. In the method for manufacturing a wiper blade rubber as described in claim 8, A method for producing wiper blade rubber, wherein the chlorinated aqueous solution is an aqueous solution obtained by adding an acid to an aqueous solution of hypochlorous acid and / or a hypochlorite salt.

10. In the method for manufacturing a wiper blade rubber as described in claim 8, A method for manufacturing wiper blade rubber, wherein the pH of the chlorinated aqueous solution is 1.5 or higher and 2.4 or lower.

11. In the method for manufacturing a wiper blade rubber as described in claim 8, A method for manufacturing a wiper blade rubber, comprising: removing the molded body from the chlorinated aqueous solution; immersing the molded body in washing water for cleaning; and subsequently removing the molded body from the washing water; and then immersing the molded body in hot water with a temperature higher than that of the washing water for further cleaning.

12. A method for inspecting a wiper blade rubber having a contact sliding portion that slides in contact with the surface of another component, A method for inspecting a wiper blade rubber, which involves determining the skewness Ssk of the contact sliding portion and determining that it is acceptable if it is between 0 and 0.4.

Images