GB2287179A

GB2287179A - Wiper for motor vehicles

Info

Publication number: GB2287179A
Application number: GB9504949A
Authority: GB
Inventors: Tomoko Saitou; Haruhiko Iizuka
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1994-03-11
Filing date: 1995-03-10
Publication date: 1995-09-13
Anticipated expiration: 2015-03-10
Also published as: GB9504949D0; DE19508738A1; DE19508738C2; GB2287179B; JPH07246916A

Description

- 1 2287179 WIPER FOR WIPING WINDOW GLASS OF AUTOMOTIVE VEHICLES The

present invention relates to a wiping device, which is optimally applied to wipe off snow, rain,or the like from a windshield or a rear window for automobiles.

Figs. 11, 12, 13, 14, and 15 show a prior art automobile wiper which has been disclosed in Japanese Patent Provisional Publication No. 59-34963. The prior art wiper 1 is provided for wiping off snow or rain from a front window glass 3 serving as a windshield panel of the vehicle. Traditionally, the wiper 1 consists of a wiper motor and a wiper linkage. As seen in Figs. 11 and 12, the wiper linkage includes a wiper arm 5, a wiper blade 11, a wiper- blade holding fixture 9 mounted on the wiper arm 5 through a lever 7, and right and left pivot assemblies to which the wiper arms are attached. When the motor turns, the linkage is moved back and forth, thereby causing the pivots to turn back and forth so that the wiper blades sweep across the front windshield glass 3 to wipe it. As shown in Fig. 13, the wiper blade I I consists of a base section 13 which is supported by the wiperblade holding fixture 9, a lip section 17 with a comparatively thin t-i p end 19 which end is brought into sliding-contact with the windshield glass 3 to wipe off water or snow from the glass 3, and a neck section 15 through which the base section 13 and the lip section 17 are interconnected. As seen in Fig. 14, since a pushing force or pressure F is constantly applied to the wiper blade 11 during operation of the wiper, the pressure F causes a frictional force gF acting on the t,ip end 19 of the lip 17 in a direction opposing the relative motion of the wiper blade 11. The lip section 17 is slightly inclined with respect to the windshield glass 3 at a certain angle owing to the frictional force gF. The angle of inclination of the lip 17 to the windshield glass 3 can be defined as a contact angle 0 which is equivalent to an angle between the surface of the windshield glass 3 and the lip side wall contacting the windshield glass. Since the thickness of the lip section 17 is essentially uniform at the tip end 19, that is, the lip side walls forming the tip end 19 are parallel to each other, the lip contact angle 0 can be indicated as the angle between the lip side wall and the windshield glass. As seen in Fig. 16, the contact angle 0 may be defined to be equivalent to an angle between the surface of the windshield glass 3 and the central axial line (see the broken line indicated in Fig. 16) of the tip end 19 extending in the direction of the lateral cross-section of the wiper blade 11, because of the parallel arrangement of the lip side walls. The contact angle 0 will be hereinafter referred to as a "lip contact angle 0". During wiping, the lip section 17 removes water from the windshield glass 3, while sliding its tip end 19 at the lip contact angle 0 with respect to the windshield glass 3. As is generally known, water adhered onto the windshield glass 3 is not completely removed. Actually, the wiping operation is achieved in such a manner as to form a thin water film on a particular sectorial surface of the windshield glass 3 which make-s sliding contact with the tip end 19 of the lip 17. Such thin water film serves as a proper lubricant necessary to insure smooth sliding movement of the wiper blade relative to the windshield glass 3. To provide a proper thin water film on the windshield glass 3, Japanese Patent Provisional Publication No. 60-226343 discloses a structure of a wiper blade having an unsymmetrical lateral cross-section as shown in Fig. 16. The unsymmetrical cross-sectional structure of the wiper blade lla having an unsymmetrical base section 13a assures a wiper-blade wear totally balanced in both directions, namely a wiper-blade opening direction in which the wiper blade approaches to the upper portion of the windshield molding, and a wiper-blade closing direction in which the wiper blade approaches to the lower portion of the windshield molding. As a consequence, the balanced wiper-blade wear produces the previously-noted W uniform and thin water film on the windshield glass, thereby enhancing wiping performance. One skilled in the art took account of the above-mentioned wear balance of the wiper blade. However, in the conventional wiper blades, optimization of the lip contact angle 0 is not taken into account. Thus, in the event that the lip contact angle 0 reduces down to approximately 10 degree owing to changes in dynamic friction force gF creating at the interface between the windshield glass and the lip of the wiper blade during wiping, there is a possibility of an increase in unremoved water remaining on the windshield after wiping due to the undesirably reduced lip contact angle 0. Under a particular condition wherein undesired oil film still exists on the windshield glass or the surface of the windshield glass 3 is finished by commercial water repellent, the vehicle occupants would experience discomfort glare caused by one or more visible light beams resulting from excessive reflection or scattering of the light sources due to the oil film or the water repellent finish on the windshield glass 3 or a vehicle occupant's field of view would be disturbed by cloudy or opaque water film remaining unremoved on the windshield glass in the form of particles of water. In this case, the vehicle occupant feels discomfort.

Accordingly, it would be desirable to be able to provide an improved wiper for automotive vehicles which avoids the foregoing disadvantages of the prior art.

It would also be desirable to be able to provide an improved wiper for automotive vehicles which is capable of enhancing its wiping performance by way of optimization of the lip contact angle of the wiper blade.

The invention provides a wiping device comprises a wiper blade for sweeping across a windshield glass to wipe it, the wiper blade having a base which is supported by a wiper-blade holder turning back and forth to provide a wiping operation of the wiper - 4 blade and formed with an abutment surface opposing the windshield glass, a lip which is spaced apart from the abutment surface of the base by a predetermined aperture and formed with a tip end being in contact with the windshield glass and has a constant entire lip width in a wiping direction of the v;iper blade, and a neck which is located midway between the base and the lip to interconnect them. Also provided is means for maintaining a lip contact angle between the windshield glass and a side wall of the lip within a predetermined angle range of 30' < 8 < 550 during wiping.

The lip contact angle may be maintained by enhancing rigidity of the wiper blade. The rigidity of the wiper blade may be enhanced by a lip section having a preselected thickness greater than or equal to 0.7 mm at its tip end. The rigidity of the wiper blade may be enhanced by using a high-rigidity wiper blade coated with either nylon or molybdenum disulfide. The rigidity of the wiper blade may also be enhanced by using a high-rigidity wiper blade coated with nylon and molybdenum disulfide. Preferably, a coating process for the high-rigidity wiper blade is made to produce a surface layer of N-methoxymethylation nylon cross-linked to an outside surface of a molded base rubber material forming a wiper blade body, having a thickness in the range of 1 to 5 ym, the surface layer of N-methoxymethylation nylon containing 10 to 50% molybdenum disulfide powder. Alternatively, the rigidity of the wiper blade may be enhanced by using a high-rigidity wiper blade coated with nylon and graphite. In this case, a coating process for the high-rigidity wiper blade is preferably made to produce a surface layer of N-methoxymethylation nylon crosslinked to an outside surface of a molded base rubber material forming a wiper blade body, having a thickness in the range of 1 to 50)1m, the surface layer of N-methoxymethylation nylon containing 10 to 50% graphite powder. In the high-rigidity wiper blade having the surface layer of Nmethoxymethylation nylon containing 10 to 50% molybdenum disulfide powder or 10 to 50% graphite powder, it is preferable that a lip section of the high- rigidity wiper blade has a preselected thickness greater than or equal to 0.7 mm at its tip end. Additionally, the highrigidity wiper blade may preferably include a neck section having a preselected thickness less than or equal to 0.6 mm. Preferably, the thickness of the neck section is set to be within a range of 0.45 mm to 0.6 mm. BRIEF DESCRIEPTION OF THE DRAWINGS Fig. 1 is a lateral cross-sectional view illustrating a wiper blade incorporated in an automobile wiping device, according to the present invention, in a preferred embodiment.

Fig. 2 is an explanatory view showing the operation of the wiper blade of the embodiment at a lip contact angle 0.

Fig. 3A is an explanatory view showing the wiping operation of the lip section of the wiper blade of the embodiment.

Fig. 3B is an enlarged view showing the edge of the lip section as indicated by the circle A of Fig. 3A.

Fig 4 is a graph illustrating a relationship between the lip contact angle 0 and the pressure P, which pressure forces the wiper blade onto the windshield.

Fig. 5 is a graph illustrating a relationship between the lip contact angle 0 and criteria for evaluation of visibility.

Fig. 6 is a graph illustrating a relationship between a performance of reversion of the wiper blade and the lip contact angle 0.

Fig. 7 illustrates test results indicative of a relationship between a thickness t2 of a lip section of an uncoated wiper blade and its lip contact angle 0.

Fig. 8 illustrates test results indicative of a relationship between a thickness ti of a neck section of the uncoated wiper blade and its lip contact angle 0.

Fig. 9 illustrates test results indicative of a relationship between a thickness t2 of a lip section of a coated wiper blade and its lip contact angle 0.

Fig. 10 is a graph illustrating a relationship between the lip contact angle 0 and thickness of water film formed on the windshield after wiping.

Fig. 11 is a front view of the vehicle equipped with a prior art windshield wiper.

Fig. 12 is a perspective view illustrating a prior art wiper blade assembly.

Fig. 13 is a lateral cross-sectional view taken along line XIII - XIII of Fig. 12.

Fig. 14 is an explanatory view showing the operation of the prior art wiper blade.

Fig. 15 is an explanatory view of the lip contact angle 0 of the prior art wiper blade of Fig. 14.

Fig. 16 is a lateral cross-sectional view illustrating the other prior art wiper blade.

Referring now to the drawings, particularly to Figs. 1 and 2, a wiping device for automotive vehicles in accordance with the invention is exemplified in case of a windshield wiper for automotive vehicles. As seen in Fig. 1, the wiping device of the embodiment includes a wiper blade 21 suitable for wiping a windshield or a rear window. The basic construction of the wiper blade 21 is similar to that of the conventional wiper blade 11 as shown in Figs. 12 and 13. The wiper blade 21 includes a substantially H-shaped base section 23, a neck section 25, and a lip section 27. The base section 23 is supported by a substantially C-channel shaped wiper-blade holder or holding fixture 29. The wiper-blade holding fixture 29 is mounted on a wiper arm (not shown) constructing a wiper linkage (not shown).

In a conventional manner, the wiper-blade holding fixture 29 has a driven connection with a wiper drive motor such as an electrical motor. In the event that the motor turns, the wiperblade holding fixture 29 turns back and forth so as to provide the wiping operation of the wiper blade 21 across the windshield glass 3. The base section 23 is formed with a substantially flat abutment surface 31 facing the outside surface of the windshield glass 3. The H-shaped base section 23 consists of a rectangular portion 35 which is fitted into the C-channel shaped wiper-blade holding fixture 29 ' with a pair of slots 33, a hat-shaped portion 37, and an intermediate connecting portion 36 which interconnects the rectangular portion 35 and the hat-shaped portion 37. The hat-shaped portion 37 is formed with a pair of flanged portions 39a and 39b, respectively extending in its cross direction, namely in both directions of the width of the wiper blade 21. The cross direction of the wiper blade 21 is equivalent to the wiping direction. The previously-noted abutment surface 31 is formed as a bottom surface (viewing Fig. 1) of the hat shaped portion 37. On the other hand, the neck section 25 is arranged to interconnect the base section 23 and the lip section 27 and in addition to provide proper flexibility of the lip section 27 during wiping. The thickness of the neck section 25 is represented by ti in he cross direction of the wiper blade, while the height of the neck section 25 is represented by Li. The lip section 27 is formed with a substantially flat surface 41 opposing the abutment surface 31 of the hat-shaped portion 37 of the base section 23. The lip section 27 is also formed with a pair of raised portions 41a and 41b at two outside ends on the flat surface 41 of the lip section 27. The respective raised portions 41a and 41b are so dimensioned as to define a predetermined aperture L2 under a particular condition wherein the wiper blade 21 is not yet forced onto the windshield glass 3. The entire width of the lip section 27 is represented by B. The lip section 27 has the predetermined constant width t3 over the entire length of the wiper blade. The lip section 27 has a comparatively thin ti-p end 43 which is formed with an edge 45. The tip end 43 of the lip has a predetermined thickness t2 in the cross direction (wiping direction). The ti p end 43 of the lip has a pair of side walls 43a and 43b parallel to each other. The height of each side wall 43a and 43b is represented by L4. The distance between the flat abutment surface 31 and the bottom end (viewing Fig. 1) of the lip section 27 is represented by L3. The previously-noted construction of the wiper blade 21 of the wiping device of the embodiment is basically similar to that of the wiper blade 11 of the prior art windshield wiper. The wiper blade 21 assembled in the wiping device of the present invention is different from the prior art wiper blade 11 in that the wiper blade structure according to the present invention is designed to permanently maintain the lip contact angle 0 within a predetermined angle range of 300 _< 0:5 550 during wiping operation. The improved wiper blade structure comprises a high-rigidity wiper blade structure as compared with the prior art wiper blade. In order to obtain the above- noted high-rigidity wiper blade structure, i.e., to enhance the rigidity of the wiper blade, the wiper blade 21 of the embodiment is coated with nylon and/or molybdenum disulfide. The wiper blade 21 of the embodiment may be coated with nylon and graphite. As is generally known, a wiper blade is made of synthetic rubber or natural rubber. The wiper blade 21 of the embodiment is also made of synthetic rubber or natural rubber by way of extrus i on-mol ding. During extrusion-molding, a compounding ratio of several additive agents and several molding conditions, for example vulcanization speed, extrusion-molding speed, molding temperature, and the like, are preselected in a conventional manner, so as to insure proper flexibility of the wiper blade. Preferably, the coating process for the wiper blade 21 may be made to produce a surface layer of Nmethoxymethylation nylon, which is cross-linked to the outside surface of the molded base rubber material which forms a wiper blade body, having a thickness of 1 to 50 gm. Additionally, the N- methoxymethylation nylon coat of the wiper blade 21 of the embodiment also contains 10 to 50% molybdenum disulfide powder or 10 to 50% graphite powder,by weight. The coating process will be hereinbelow described in detail.

In the coating process for the wiper blade 21 of the embodiment, a rubber material such as synthetic rubber or natural rubber is first subjected to extrusion-molding.

Thereafter, for the purpose of producing a coated surface layer in thickness of I to 50 gm, the molded wiper-blade rubber material is coated with N-methoxymethylation nylon containing 10 to 50% molybdenum disulfide powder or 10 to 50% graphite powder, by weight, by way of cross-linking. Concretely, a preselected solute consisting of a cross-linking catalyst for N-methoxymethylation nylon and either one of molybdenum disulfide powder or graphite powder are dissolved in a preselected solvent consisting of liquid N-methoxymethylation nylon. The solution is applied partly to a designated portion, for example the outside surface of the lip section,of the molded wiper-blade rubber material. The solution may be applied to all surfaces of the molded wiper-blade rubber material. In this case, the molded wiper-blade rubber material itself may be dipped in the N-methoxymethylation nylon solution. Alternatively, all surfaces of the molded wiperblade rubber material may be coated by way of spray-coating. In caseswhere only the lip section 27 of the wiper blade is coated partly, the partial coating process may be performed by way of spray coating or brush coating. As previously described, the thickness of the coated surface layer of N-methoxymethylation nylon is adjusted within a range from 1 Lm to 50 gm. Finally, the N- methoxymethylation nylon containing 10 to 50% molybdenum disulfide powder or 10 to 50% graphite powder, by weight, which nylon is applied to the outside surface of the molded wiper-blade rubber material, can be cross- linked thereto by way of heating. As set forth above, the rigidity of the wiper blade 21 can be enhanced. Additionally, the coated surface layer of the wiper blade assures smooth sliding movement of the blade 21 on the windshield glass 3, owing to reduction of coefficient of dynamic friction between the two members 3 and 21 in contact, the reduction resulting from inherent characteristics of nylon. The N- methoxymethylation nylon coated wiper blade 21 exhibits high wear resistance and superior weather proofness. Aswill be appreciated, proper flexibility of the coated wiper blade 21 can be kept, since the thickness of the nylon coat is comparatively thin. Owing to inherent characteristics of molybdenum disulfide powder or graphite powder as well as those of Nmethoxymethylation nylon, the wiper blade 21 on the windshield 3 can slide more smoothly.

The improved wiper blade structure, according to which the lip contact angle 0 is maintained within a predetermined angle range of 300 <_ 0:5 550 during wiping operation, can be provided by suitably setting the thickness t2 of the lip section 27 in lieu of the previously-noted nylon coating process. Also, the improved wiper blade structure can be provided by suitably setting both the thickness t2 of the lip section 27 and the thickness ti of the neck section 25 in lieu of the nylon coating process. Preferably, the improved wiper blade structure can be provided by suitably setting both the thicknesses ti and t2 in addition to the nylon coating process. Particularly, the nylon coating process and setting of the thickness t2 of the t i:p end of the lip section 27 are very advantageous to enhance the rigidity of the wiper blade. The wiper blade made in accordance with the present invention is designed to satisfy two antinomical wiper-blade characteristics, namely prevention of discomfort glare or opaque water film and suppression of increase in sliding resistance (dynamic friction RF) of the blade, whereas hitherto the wiper blade structure was directed mainly to enhancement of removal performance of water drop adhered to the windshield glass. In addition to the previous ly-noted antinomical wiper-blade characteristics, the lip contact angle range of 300 to 550 of the improved wiper blade 21 of the present invention is designed to satisfy an acceptable reversion performance of the wiper blade during shifting one wiping direction to the other and to prevent beat noise occurring between the wiper blade and the windshield. This has been experimentally cmfirwd by the inventors of the present invention, on the basis of several test results as hereinafter detailed.

Referring now to Figs. 3A and 3B, there is shown the relationship between the lip contact angle 0 and the contact area S in which the tip end 43 of the lip section 27 touches the windshield glass 3. The inventors of the invention have discovered that the lip contact angle 0 correlates to thicknesses of the water film formed on the windshield glass 3 after wiping, as explained below. As seen in Fig. 2, assuming that the lip section 27 of the wiper blade 21 slides on the windshield glass 3 at a predetermined wiping speed V with a predetermined pushing force F, the pressure P applied to the windshield glass 3 is different depending on the magnitude of the pushing force F and the contact area S between the tip end 43 of the lip section 27 and the windshield glass 3. In case of the same pushing force F-. the smaller the contact area S, the higher the pressure P. That is, under the same pushing force F, the pressure P applied from the lip to the windshield is in inverse-proportion to the contact area S. As seen in Fig. 3B, assuming that the lip of the wiper blade 21 is forced uniformly onto the windshield 3 under the pressure P throughout the entire length of the wiper blade, the contact area S is considered to be proportion to the contact length L (= Ll + L2) of the lip ti-p end 43 in the wiping direction. (Note that the length Ll is not equal to the height Li of the neck section 25 of the wiper blade, and the length L2 is not equal to the predetermined aperture L2 defined between respective raised portion 41a and 41b and the abutment surface 31.) The contact length L can algorithmically be regarded as the contact area S.

As indicated by the phantom line of Fig. 3B, the lowermost triangular section containing a hypothetical edge point Q, is actually squeezed against the surface of the windshield glass 3. As appreciated from Fig. 3B, supposing that the contact length L is proportion to a distance X between the hypothetical edge point Q and the surface of the windshield glass 3, the contact length L can be represented by the following equation (1).

L=LI +L2 =X 1 +XtanO=Xx(l+tan 2 0) tan 0 tan 0 =XxA (A + tan20 tanO Assuming that the edge point Q of the lip is squeezed onto the windshield glass 3 by application of the pushing force F and thus the distance X is shifted from zero to a certain value XO, the pushing force IF is represented by the following equation (2):

X0 F= 1 Kx LdX X0 = t KxXxAdX (KxAX X02) (2) 2 where the character K denotes a spring constant of the wiper blade 21 made of rubber material.

Assuming that the contact length denoted by LO is regarded as the contact area in case of X = XO, the pressure P is expressed as P=_F jKxAxX02) LO 2LO . (K x A x X02) 2A x XO KxXO 2... (3) As appreciated from the above-indicated equation (3), under the same pushing force F, the pressure P is increased to the maximum, as the contact area (contact length) LO is reduced to the minimum.

XO and P are expressed from the equations (2) and (3), as follows:

X02 = 2E KxA XO = 1 2E V KXA P= K x XO (See the equation (3)) 2 _ KxF 2F 2A (since XO KxA =V KxF 0 (since A =... (4) 0 + 0) tan 0 As appreciated from the equation (4), the pressure P obtained at the lip contact angle 0 of 450 is considered to be a maximum pressure under the same pushing force F, as shown in Fig. 4. Thus, the thickness of the water film formed on the windshield after wiping, becomes reduced to the minimum with the lip contact angle 0 of 450.

Referring to Fig. 5, there is shown the relationship between the lip contact angle 6 and criteria for evaluation of visibility in case of both the conventional wiper blade and the improved wiper blade of the invention. The criteria for evaluation of visibility are indicated by five ranks. The criteria for evaluation of visibilityare defined such that the visibility is improved to the best visibility as the rank is increased from 1 to 5. Concretely, the rank "l" indicates a state of the lowest forward visibility; the rank "2" indicates a state wherein vehicle driving is impossible due to excessive discomfort glare or cloudy water film-, the rank "Y indicates a state wherein the vehicle occupant feels discomfort due to some glare, al'though vehicle driving is possible; the rank "4" indicates a state wherein slight glare exists partially on the windshield glass, altbough the slight glare does not affect vehicle driving at all; and the rank "Y' indicates a state of the best forward visibility because of less discomfort glare. As appreciated from the two plotted test results shown in the left-hand side of Fig. 5, in case of the prior art wiper blade of the lip contact angle 0 of approximately 200, the evaluation rank of the visibility is located substantially

14 - midway between the rank "Y and the rank "2". On the other hand, as appreciated from the three plotted test results shown in the right-hand side of Fig. 5, in case of the improved high-rigidity wiper blade 21 according to the present invention of the lip contact angle 0 of 300 or more, the rank of visibility is located among the rank "Y and the rank "4". That is, in case of the highrigidity wiper blade of the invention, the visibility is remarkably improved. Referring to Fig. 6, there are shown test results related to 10 the relationship between the reversion performance of the wiper blade 21 of the embodiment and the lip contact angle 0. In the axis of ordinates of Fig. 6, the reversion performance is indicated by reversible angles between the lip section 27 and the outside surface of the windshield glass 3 just before the wiper blade 15 reaches to its two reverse positions in both directions, namely the wiper opening direction and the wiper closing direction. The wider the region of the above-mentioned reversible angle, the better the reversion performance of the wiper blade. The wider region of the reversible angle means that the wiper blade is 20 reversible during shifting from one wiping direction to the other, even if the angle between the lip section and the windshield glass is relatively great just before each reverse position. As seen in Fig. 6, it will be appreciated that the reversion performance is remarkably lowered and thus the reverse motion of the lip section is so difficult when the lip contact angle 0 exceeds 550. In such a wiper blade of the lip contact angle exceedinj 5511, there are other problems such as occurrence of judder and beat noise. Based on the test results illustrated in Fig. 6, the lip contact angle 0 of the wiper blade 21 of the embodiment is 30 preselected to be a predetermined angle range of 300 to 550. The inventors of the invention investigated experimentally as to how the wiper-blade rigidity caused by the previously-noted nylon coating process, the thickness ti of the neck section 25, and the thickness t2 of the lip section 27 could affect the preselected 35 lip contact angle range of 300 to 550.

7 is - Fig. 7 shows p wiper-blade lip thickness (U) versus lip contact angle (0) characteristic in case of the uncoated wiper blade of the embodiment. Assuming that the lip thickness t2 of 0.65 mm is the reference lip thickness, the lip contact angle 0 is increased approximately to two times greater than the lip contact angle obtained at the reference lip thickness of 0.65 mm, when the lip thickness t2 is increased to two times the reference thickness of 0.65 mm. Within the range between the lip thickness of 1.3 mm (two times the reference thickness) and the lip thickness of 1.95 mm. (three times the reference thickness), the rate of change in the lip contact angle is comparatively small.

Fig. 9 shows a wiper-blade lip thickness versus lip contact angle characteristic in case of the coated wiper blade of the embodiment. As seen in Fig. 9, in the event that the lip thickness t2 is set at the reference lip thickness of 0.65 mm, the lip contact angle 0 is held at an angle of approximately 350. The lip contact angle 0 is increased approximately to 1.4 times greater than the lip contact angle obtained atthe reference thickness of 0.65 mm, when the lip thickness t2 is increased to two times the reference thickness. When the lip thickness t2 exceeds 1.3 mm (two times the reference thickness), the lip contact angle 0 gradually increases with a slightly greater rate of change as compared with the uncoated wiper blade shown in Fig. 7. In Figs. 7 and 9, the thickness of the neck section 25 is set at a preselected thickness of 0.45 mm. Based on the test results shown in Figs. 7 and 9, the thickness t2 of the tip end of the lip portion 27 is set to be greater than or equal to 0.7 mm, so as to insure the lip contact angle of 300 or more. In this case, since the thickness t2 of the lip section is set at a relatively large value as compared with the prior art wiper blade, this may facilitate the production of wiper blades. More preferably, the previously-described nylon coating process is executed to properly enhance the rigidity of the wiper blade, so as to insure the lip contact angle of 300 to 550.

Referring to Fig. 8, shows a wiper-blade neck thickness (ti) versus lip contact angle (0) characteristic in case of the uncoated wiper blade of the embodiment. Assuming that the neck thickness ti of 0. 45 mm is the reference neck thickness, when the neck thickness ti exceeds substantially 0.9 mm (two times the reference neck thickness) the wiper blade tends to generate beat noise by unstable wiping motion of the lip portion during wiping, because there is no abutment between the flat abutment surface 31 of the base section 23 and the raised portion 41a or 41b of the lip section 27. As compared with the change in the lip thickness t2, the change in the neck thickness ti has little effect on the change in the lip contact angle 0. Based on the test results shown in Fig. 8, the thickness ti of the neck portion 25 is set to be smaller than or equal to 0.6 mm, preferably to a range of 0.45 mm to 0.6 mm.

Referring to Fig. 10, there is shown the comparison results between the thickness of water film caused by the prior art wiper blade and the thickness of water film caused by the improved wiper blade of the present invention. The thickness of water film is detected by way of image processing for image signals generated from a video which is used to record reflection beam reflecting from the water film formed on the windshield just after wiping, while emitting light beam to the windshield glass 3. As seen in Fig. 10, in the wiper blade of the embodiment having a comparatively great lip contact angle of 300 or more, the detected thickness of water film is small (6 gm or less), as compared with the prior art wiper blade having a small lip contact angle of 100 to 200.

As will be appreciated from the above, in the wiper blade incorporated in the wiping device of the present invention, since the lip contact angle 0 is maintained within an angle range of 300 to 550 during wiping, the improved wiper blade can provide a smooth wiping operation while keeping the thickness of water film formed on the windshield to the minimum, thereby preventing discomfort glare or opaque water film. The improved wiper blade of the invention provides a satisfactory performance of reversion of the lip section at the respective reverse positions comparatively in the wiper opening direction and in the wiper closing -direction, owing to no occurrence of beat noise. Thus, the wiping device of the invention can provide good wiping performance, whereby the good visibility would bring a comfort driving condition to the vehicle occupants.

While the foregoing is a description of the preferred way of carrying out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope of this invention as defined by the following claims.

Claims

Claims:

1. A wiping device comprising a wiper blade having a lip with a tip end in contact with a windshield glass, the lip contact angle between the windshield glass and a sidewall of the lip being within the range 301 to 551 during wiping.

2. A wiping device as claimed in claim 1, wherein the wiper blade has a base which is supported by a wiper-blade holder and formed with an abutment surface opposing the windshield glass, the lip being spaced apart from the abutment surface and being connected to the base by a neck.

3. A wiping device as claimed in claim 2, wherein the tip end of the lip has a thickness of at least 0.7 mm.

4. A wiping device as claimed in claim 2 or 3, wherein at least the lip of the wiper blade has a coating comprising nylon and/or molybdenum disulfide.

5. A wiping device as claimed in claim 4, wherein the coating is in the form of a surface layer of N-methoxymethylation nylon cross-linked to an outside surface of a molded base rubber material forming a wiper blade body, the surface layer of N-met[.hoxymethylation nylon containing 10 to 50 wt.% molybdenum disulfide powder and having a thickness of 1 to 50)im.

6. A wiping device as claimed in claim 2 or 3, wherein at least the lip of the wiper blade has a coating comprising nylon and graphite.

7. A wiping device as claimed in claim 6, wherein the coating is in the form of a surface layer of N-methoxymethylation nylon cross-linked to an outside surface of a molded base rubber material forming a wiper blade body, the surface layer of N-methoxymethylation nylon containing 10 to 50 wt.% graphite powder and having a thickness of 1 to 50,um.

8. A wiping device as claimed in any of claims 2 to 7, wherein the neck has a thickness less than or equal to 0.6 mm.

- 19

9. A wiper device comprising:

a wiper blade for sweeping across a windshield glass to wipe it, the wiper blade having a base which is supported by a wiper-blade holder movable back and forth to provide a wiping operation of the wiper blade and which is formed with an abutment surface opposing the windshield glass, a lip which is spaced apart from the abutment surface of the base by a predetermined aperture and which is formed with a tip end in contact with the windshield glass and has a constant overall lip width in the wiping direction of the wiper blade, and a neck which is located midway between the base and the lip to interconnect them; and means for maintaining a lip contact angle, 9, between the windshield glass and a side wall of the lip within a predetermined angular range of 30 < 0 < 551 during wiping.

10. A wiping device as claimed in claim 9, wherein the means for maintaining the lip contact angle within the said angular range comprises means for enhancing rigidity of the wiper blade.

11. A wiping device as claimed in claim 10, wherein the said rigidity enhancing means includes a lip section having a preselected thickness greater than or equal to 0.7 mm at its tip end.

12. A wiping device as claimed in claim 10, wherein the said rigidity enhancing means includes a high-rigidity wiper blade coated with either nylon or molybdenum disulfide.

13. A wiping device as claimed in claim 10, wherein the said rigidity enhancing means includes a high-rigidity wiper blade coated with nylon and molybdenum disulfide.

14. A wiping device as claimed in claim 10, wherein the said rigidity enhancing means includes a high-rigidity wiper blade coated with nylon and graphite.

15. A wiping device as claimed in claim 13, wherein the coating process of the high-rigidity wiper blade is made to produce a surface layer of Nmethoxymethylation nylon 4 1 cross-linked to an outside surface of a molded base rubber material forming a wiper blade body, ranging in thickness from 1 to 50 ym, and containing 10 to 50% molybdenum powder.

16. A wiping device as claimed in claim 14, wherein the coating process of the high-rigidity wiper blade is made to produce a surface layer of Nmethoxymethylation nylon cross-linked to an outside surface of a molded base rubber material forming a wiper blade body, ranging in thickness from 1 to 50)im, and containing 10 to 50% graphite powder.

17. A wiping device as claimed in claim 15 or 16, wherein the highrigidity wiper blade includes a lip section having a preselected thickness greater than or equal to 0.7 mm at its tip end.

18. A wiping device as claimed in claim 17, wherein the high-rigidity wiper blade includes a neck section having a preselected thickness less than or equal to 0.6 mm.

19. A wiping device as claimed in claim 1, substantially as described with reference to Figures 1 to 10 of the accompanying drawings.

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