DE2621905C2 - - Google Patents

Description

The invention relates to a tread for pneumatic vehicle tires with the features the preamble of claim 1.

A tread with these features is e.g. B. from FR-PS 15 48 673 known (cf. there in particular FIG. 6). This publication sees such a profile design before that the road grip improves and a strong driving noise avoided becomes. For this, the crosswise to the wide, continuous, circumferential zigzag-shaped profile grooves, extending grooves that form in front are designed inclined to the circumferential direction. The flanks The inclination of the profile blocks delimiting these transverse grooves can be straight, spherical be curved or polygonal and extends over the entire flank height (cf. in the FR-PS Figures 4a to 4d).

In contrast to the subject of FR-PS 15 48 673, it is about present invention not to improve the road grip and the Avoiding strong driving noises, but questions about the wear and tear of the profile. The invention is based on the observation that with strongly structured Tread pattern, which is essentially determined by individual block elements a particularly heavy wear on the outer edges of the profile blocks  ment occur. Above all, it was observed that these edges Mainly used on the rear edge in the direction of travel of the car a profile block element occurs. Continuous in the circumferential direction However, this type of wear occurs only substantially to a lesser degree. It was further observed that these edges usage overlays the general tread wear of the tire. The increased Kan Wear is evident from the block elements when driving effective torques caused by contact of the profile element with the road surface to bend or twist the block element to lead. The block elements are bent obliquely backwards into in relation to the direction of travel of the vehicle. The block elements take theirs normal position in the profile at the moment when the Contact friction between block element and road surface is over, that Block element therefore leaves the uprising area. The block elements are thus in addition to the usual rolling motion while driving one Subjected to bending deformation. This bending deformation on a block element occurs only during a fraction of each revolution of the tire and corresponds to a slip of the area trailing in the direction of rotation of the tire of the block element. This subsequent area of the block element is countered pressed the road surface with a compressive force that is less than that Pushing force with which the front area of the block element against the street is pressed. The localized and preferred wear at the rear Edge area of the stud therefore stems from slippage during the Action of the lower contact pressure.

In this context, it should be noted that the edges on the Sides of the block elements and ribs are subject to considerable wear that is even greater than the wear described above  running block edges. The wear on the side edges is caused by the lateral deformation of the profile elements during the passage of curves on the one hand and on the other hand while driving straight ahead due to the profile Tire curvature and due to the flexibility of the tread material conditionally.

The invention has for its object the normal profile wear Tire overlapping wear on the edge areas of the tread block elements simple way to significantly reduce the life of the tire to increase the profile significantly.

This object is achieved by the teaching of claim 1.

In order to reduce the profile wear it is known from DE-AS 16 80 347 a profile with essentially narrow, continuous in the circumferential direction To provide profile grooves of predetermined cross-sectional shape, which at Can make contact with the road under the uprising pressure so that the profile elements more or less rigidly on both sides of the profile grooves can support others. These narrow in the circumferential direction Profile grooves are extended in the shape of a club near their base and open into the Tread in an outward V-shaped extension, so that the narrow Grooves in the tread itself are considerably wider. The drainage of the profile takes place by means of a wide central profile groove running in the circumferential direction, on both sides of each two narrow profile grooves of the type described are provided. In this known profile training, the general Wear of the profile by increasing the tread rubber compound corresponding to the reduction in the width of the circumferential Counteracted grooves. The aim of this measure is:  Finding that the wear of the profile is less, the more rigid the Can support profile elements in the contact area of the tread.

From DE-OS 20 29 844 it is also known in the circumferential direction going zigzag-shaped profile ribs and accordingly these ribs separating profile grooves in the slope of the flank of these profile grooves To change circumferential direction in a predetermined, repetitive manner. The starting point is an essentially U-shaped circumferential groove compared to their width at the level of the tread less floor space in the direction is shifted laterally across the circumference and at the kink points of the zigzag shaped course is shifted towards the inner edge of the kink. The principle of solution, which the person skilled in the art can see from this publication, consists of changing the slope of the flank depending on the abrasion that in the area of increased abrasion the rubber mass in the area of the tread gets bigger.

From US-PS 37 68 535 a tread pattern is known in which it is goes, the profile grooves under all circumstances, including under pressure from the riot to keep open in the contact area. For this purpose, the normal U-shaped cross-sectional shape of the profile groove while increasing the rubber mass a V-shaped cross-sectional shape with different slope passed over. When designing the profile, it is assumed that that when the profile grooves close, the grip and grip of the profile To suffer. A not preferred solution is in US Pat. No. 3,768,535 seen a slight rounding of the edges of the profile groove. Wear pro Bleme of the profile are practically not up for discussion in US Pat. No. 3,768,535.

In contrast, the present invention is concerned with the solution of a  special wear problem, namely a certain edge wear, the overlaps the general profile wear. Surprisingly, has shown that by reducing the rubber mass to those in the tread lying boundary edges of all profile block elements, d. H. so by one correct weakness of the profile of the mentioned edge wear can be effectively countered. Despite deliberate weakening of the profile a tire with a noticeably longer tread life. While with a normal tire, the edge wear continues, if the profile block edges wear their sharp edge character have already lost, surprisingly, it turns out that by the manuf according to the bevelling of all edges the pronounced edge wear in the uses much smaller dimensions and progresses much more slowly.

The subclaims contain advantageous developments of the teaching of the An saying 1.

The invention is described below with the aid of schematic drawings Embodiments explained in more detail. It shows

Figure 1 is a schematic plan view of a portion of the surface of a tread, the figure showing the usual wear pattern of conventional tread block elements.

Fig. 2 in cutting a plane perpendicular to the wheel axle section of a conventional tire in contact with a road surface, the section being taken along about the equatorial plane of the tire;

Fig. 3 is a view similar to Figure 2, wherein the deformation of the tread block elements is shown during the rolling of the tire.

Fig. 4 is a representation similar to Figure 2 on a larger scale, the figure showing the wear process when using the tire with a single predetermined running direction.

FIG. 5 in a representation similar to FIG. 4, the wear of the boundary edges of a conventional tire when the tire is used alternately in opposite running directions;

Fig. 6 one step along different sectional planes 6-6 of Fig. 8 by a tire with a tread according to the invention,

Fig. 7 in a similar representation as Fig. 6, but with a modified embodiment of the edge bevel of the profile block elements and

Fig. 8 in plan view of a tread portion with tread block elements and longitudinal ribs, which are designed according to the invention.

From Fig. 1, a schematic plan view of results on a portion of the tread 1 of a conventional tire. This tread is profiled and comprises a plurality of profile block elements 3, 5 and 7 , which are independent of one another and separated by profile grooves 9 and 11 . Furthermore, a profile block element 13 of a different outline shape is also shown in FIG. 1. The tread usually includes one or more, in the circumferential direction continuous longitudinal ribs, which are not shown in Fig. 1.

The rolling direction of the tread is indicated by the words "forwards" and "backwards". The wear pattern of the tread block elements in relation to the type of wear that is under discussion here, and which is caused by the rolling in the forward direction of the tire, is shown at the rear boundary edge of the tread elements at 3 a , 5 a , 7 a and 13 a . With regard to the block element 13 , the wear pattern is also shown at 13 b , which is obtained when the direction of roll is reversed. Such a reversal of the rolling direction can occur, for example, if the tires are mounted on the opposite side of the vehicle for the purpose of periodic inspection.

FIGS. 2 to 5 each show a schematic cross section of a part of the tire with a sectional view along the central equatorial plane of the tire, the causes and the type of occurrence of the abovementioned wear being described. In FIG. 2, the profile block elements 15, 17, 19, 21, 23 and 25 shown, separated by grooves 27, 29, 31, 33 and 35 from each other. Fig. 2 illustrates the tire tread in case of contact with a road surface 37.. The tire is in contact with the ground without being subject to a rotary movement. Under these conditions it can be seen that the grooves 27, 29, 31 and 33 are not deformed and the area or portion of the tread which is in contact with the road surface 37 has practically the same outline shape as those areas of the tire tread that are not in contact with the ground. The only exception to this is, of course, only the area that has flattened slightly due to the load due to the ground contact.

FIG. 3 shows the same tread section as FIG. 2, with the exception that the tread section according to FIG. 3 is shown in a representation which corresponds to the position and shape of the tread block elements during the rotation of the tire. It can thus be seen that the block elements 17, 19 and 21 are deformed, so that the grooves 29 and 31 no longer run radially with respect to the tire, but are inclined with respect to the radius. This means that the open area of the groove, which borders on the road surface, is shifted in the forward direction, while the bottom of the groove is shifted backwards. It can also be seen that the groove 35 , which was previously in the contact area 37 and has now been released, has returned to its normal, ie radial position, while the grooves 27 and 33 are in an intermediate state of deformation. The groove 27 approaches the state of greatest deformation, while the groove 33 is already changed from this state in the direction of the normal shape.

The deformation of the tread block elements is caused by the force shown at F in Fig. 3, which is the result of a torque between the tire edge and the tread. The torque is a function of the elasticity of the tread rubber material and the adhesion between the tread and the road surface 37 . Judging from the shape of the tread block member 19 , which is in the deformed state, and goes over to the shape of the tread block member 25 , which is in the normal position, it is clear that each tread block member in addition to the general rolling motion Sliding movement is subject, which affects the front and rear portions of the block element differently. The result is that the localized wear, referred to above, occurs at the rear portion 21 a of each block member 21 and is caused by the fact that this portion is subjected to less compression than the front portion 21 b of the block element 21 as soon as the aforementioned sliding movement occurs.

FIG. 4 shows a tread section corresponding to FIGS. 2 and 3, namely after prolonged use when driving forward. It can be seen that the profile block elements 17, 19 and 21 show a sawtooth-like profile with asymmetrical wear of the block elements. This means that the rear Be boundary edges of the block elements 17, 19 and 21 , as indicated at 17 a , 19 a and 21 a , are subject to heavy wear, while the front edges are not or only slightly worn.

Fig. 5 shows the tread portion of Fig. 4 after the tire has been used in the rotating directions. From the figure it can be seen that in this case the profile block elements show a generally symmetrical Abnut profile by the edges 19 a and 19 b , z. B. the block element 19 experienced virtually identical wear. It has been found that the type of edge wear as shown in Figs. 4 and 5, once it begins, continues indefinitely without stabilizing.

On the other hand, it was found that when the boundary edges of the tread block elements and longitudinal ribs are beveled in terms of production, as will be explained below with reference to FIGS . 6 to 8, the type of edge wear does not occur in the first place and therefore the service life of the tread becomes significantly longer. The tread wear is shifted more towards the central area of the tread block elements, so that a uniform wear of the tread occurs.

It was also found that the optimal profile of the bevels one Curve corresponds which is a function of several parameters. One this parameter refers to the way in which the vehicle be  is driven on which the tire is mounted. It is therefore not possible to use one specify the optimal profile for all tires for all possible purposes. It values can therefore only be specified for the bevels that are within of predetermined limits. Should be within the specified ranges the profiles used are determined so that they are less complex Constructions require, and especially those in which the Tire forming requirements and their difficulties are taken into account are.

In FIG. 6, the profile is shown in dashed cross-sectional lines, which results from cuts along the different cutting lines 6-6 of FIG. 8. This is a portion of the tread shown in FIG. 8, and the cross-sectional line in FIG. 8 can either be placed along a plane parallel to the central equatorial plane of the tire or parallel to one of the tread grooves of the tread. In the embodiment according to FIG. 6, the profile block elements 39, 41 and 43 have beveled boundary edges. The radial depth of the bevel is denoted by D and its width in the tread is denoted by W. L denotes the dimension of the profile block elements measured in the same direction as the width W , while Z means the grooves depth. In Fig. 6, the lugs 39, 41 and 43 separating grooves with 45 and 47 and the bevels in turn each with 49, 51, 53 and 55 be distinguished. In this embodiment, the bevels 49, 51, 53 and 55 are straight or flat and the grooves 45 and 47 are inclined with respect to the tread and the radial central plane. It has been found that the desired reduction in wear of the boundary edges of the tread block elements is obtained when the width W of the bevel is between about 0.15 L and about 0.5 L and the depth D is between about 0.2 Z and about 0 , 4 Z lies. Values in which the width W of the bevel is between approximately 0.18 L and approximately 0.26 L and the depth D between approximately 0.26 Z and approximately 0.34 Z are preferred.

A modified embodiment is shown in Fig. 7. This differs from that of Fig. 6 in that the bevels 49, 51 and 53 and 55 of the boundary edges of the block elements as shown at 57, 59, 61 and 63 , rounded or curved instead of flat or are just trained. The profile of the bevels in the exemplary embodiment according to FIG. 7 is that of an arc of a circle with a radius of curvature which is indicated at R. In this exemplary embodiment, the radius R is equal to the dimension L of the tread block element 5 in the tread 65 . The length L is measured perpendicular to the course of the bevelled boundary edges. As can be seen from Fig. 7, the equality of the radius of curvature R of the bevel with the width L means that the width W of the bevels 57, 59, 61 and 63 is equal to half the width L. It can be, for example, in the profile block element 41, the radius of curvature R of each of the bevels 59 and 61 also smaller than L / 2, so that the block element 41 has a flat section which is in the plane 65 between the two bevels 59 and 61 .

In the exemplary embodiment according to FIG. 7, the radius of curvature R of the bevels was preferably chosen between approximately 0.8 L and approximately 1.2 L , in particular between approximately 0.95 L and approximately 1.05 L. In this case, regardless of the size of the selected radius of curvature R , the width W of the bevel in the direction of L should in any case be between about 0.15 L and about 0.5 L and the depth D of the bevel between about 0.2 Z. and be about 0.4 z .

In FIG. 8 is a top view is shown of a portion of a running surface 69. The line XY indicates the central equatorial plane of the tire, of which the tread 69 represents a part. The tread 69 comprises a plurality of tread block elements, which are indicated at 71, 73, 75 and 77 and which are separated from one another by tread grooves 79 and 81 . The tread 69 further has a plurality of longitudinal ribs running continuously in the circumferential direction, of which a rib 83 is shown. The rib 83 is separated from the block elements 71 to 77 by wide, continuous, circumferential, zigzag-shaped pro filnuten 85 and 87 .

As has already been indicated above, the lateral edges 86, 88, 90 and 92 of the tread block elements and the edges of the longitudinal ribs are also subject to wear of the type in question here. All boundary edges of the block elements and the longitudinal ribs lying in the tread are therefore beveled , namely both the front and rear as well as the lateral edges. Each of these bevels is labeled 89 . It is evident that each of the bevels 89 must correspond to the relationships previously indicated. This means that the width W of each of the bevels must be between approximately 0.15 L and approximately 0.5 L and the depth D of each of the bevels must be between approximately 0.2 Z and approximately 0.4 Z. You can be either flat or curved.

Claims (3)

1.Tread for pneumatic vehicle tires with a tread pattern and profile block elements, which consists of several circumferentially oriented profile block rows and, if necessary continuous, zigzag-shaped profile grooves are separated, which are connected to one another by wide profile grooves running transversely to the circumferential direction, characterized in that all the boundary edges of each profile block element ( 39, 41, 43, 71, 73, 75, 77 ) or all the longitudinal ribs ( 83 ) are chamfered, the radial depth D of the chamfer between 0.2 times and 0.4 times the groove depth Z determined according to the position and the width W of the chamfer in the tread between 0.15 times and 0.5 times the dimension L of the profile block elements measured in the same direction s lies. 2. Tread according to claim 1, characterized in that the width W of the bevel between 0.18 times and 0.26 times the dimension L measured in the same direction of the tread block element and its radial depth D between 0.26 times and 0.34 times the groove depth Z is. 3. Tread according to claim 1, characterized in that the convex radius of curvature is the radius of curvature between 0.8 times and 1.2 times the dimension L.