PNEUMATIC VEHICLE TIRE

Abstract

A pneumatic vehicle tire for commercial vehicles is provided wherein the wet traction properties are improved with simultaneously good rolling resistance properties. At least 120 transverse grooves are arranged in each of the central profile ribs over the entire circumference of the tire. The width (B1) of the transverse grooves in the central profile ribs is maximally 1.5 mm at a distance of 3.5 mm from the profile surface, and the width of each inner circumferential groove is maximally 4 mm at a distance of 3.5 mm from the profile surface.

Description

FIELD OF THE INVENTION

The invention relates to a pneumatic vehicle tire for commercial vehicles.

BACKGROUND OF THE INVENTION

A tire of the type stated at the outset is known from U.S. Pat. No. 5,535,798 B, for example. In order to achieve uniform abrasion of the tread, this tire is divided into circumferential ribs by four wide circumferential grooves running round in the circumferential direction, wherein a further, narrow circumferential groove running round in the circumferential direction is provided in each of the two circumferential ribs at the shoulders close to the edges of the tread. The wide circumferential grooves are bounded by groove flank surfaces which are provided with depressions that are the negative of three-sided pyramids, the points of which face the periphery of the tread.

In order to lower the rolling resistance of pneumatic vehicle tires, a large number of measures has already been proposed.

An improvement in the rolling resistance can often have negative effects on other important properties of the tire, for example, on the wet grip properties of the tire. The wet grip properties essentially affect the properties during braking on a wet underlying road surface.

SUMMARY OF THE INVENTION

It is an object of the invention to embody the tread of a pneumatic vehicle tire of the type described above in such a way that, while achieving good rolling resistance properties, the wet grip properties are simultaneously improved.

According to a feature of the invention, at least 120 transverse grooves are arranged in each of the central profile ribs over the entire circumference of the tire, wherein the width of the transverse grooves in the central profile ribs is no more than 1.5 mm at a distance of 3.5 mm from the profile surface, and wherein the width of each inner circumferential groove is no more than 4 mm at a distance of 3.5 mm from the profile surface.

One advantage of the vehicle tire according to the invention is that optimization of the profile gives the vehicle tire very good wet grip properties and, at the same time, the rolling resistance properties are likewise held at a very high level. The optimized and improved tire profile has been demonstrated by a large number of tests. The increased profiling, in accordance with the invention, of the tire profile through the large number of transverse grooves with the abovementioned dimensions has led essentially to better wet grip properties and, at the same time, the rolling resistance is likewise held at a high level. In the case of conventional profile optimizations, in contrast, greater profiling generally led to a significant deterioration in rolling resistance.

In another advantageous feature of the invention, provision is made for the transverse grooves in the central profile ribs to be arranged at an angle greater than 60° with reference to the circumferential direction.

By means of this alignment of the transverse grooves, optimum wet grip properties are achieved for the vehicle tire.

In another advantageous feature of the invention, provision is made for the difference in depth between the depth of the transverse grooves in the central profile ribs and the depth of the inner circumferential grooves to be no more than 2 mm.

As a result, the tire has a high starting and braking traction over its entire normal service life. One embodiment is shown in FIG. 2, which indicates the difference T5 in depth between the depth of the transverse grooves T2 and the depth of the inner circumferential grooves T3.

According to another advantageous feature of the invention, provision is made for the difference in depth between the depth of the inner circumferential grooves and the depth of the shoulder grooves to be no more than 2 mm.

As a result, the vehicle tire has particularly good wet grip properties over the entire normal service life.

One embodiment is shown by FIG. 2, which indicates the difference T6 in depth between the depth of the inner circumferential grooves T3 and the depth T4 of the shoulder grooves.

In another advantageous feature of the invention, provision is made for the depth of the transverse grooves in the central profile ribs to be 11 to 14 mm.

By virtue of this depth dimension, the properties mentioned are maintained over the entire normal service life of the vehicle tire.

According to another advantageous feature of the invention, provision is made for the depth of the inner circumferential grooves to be 9 to 14 mm and/or the depth of the shoulder grooves to be 9 to 14 mm.

According to still another advantageous feature of the invention, provision is made for the length of extent of the transverse grooves in the central profile ribs to be at least 80% of the total width of the central profile rib.

Good starting and braking traction for the vehicle tire is thereby ensured.

According to another advantageous feature of the invention, provision is made for the transverse grooves in the central profile ribs to be arranged in an arrow shape, wherein the arrow tip is formed by the central inner circumferential groove.

By means of this arrangement, particularly good wet handling properties of the vehicle tire are achieved.

According to another advantageous feature of the invention, provision is made for further transverse grooves to be arranged in the shoulder ribs.

The transverse grooves in the shoulder ribs increase the starting and braking traction of the vehicle tire.

In another advantageous feature of the invention, provision is made for the width of the central profile ribs to be in a range of from 25 to 55 mm, preferably in a range of between 35 and 45 mm.

In another advantageous feature of the invention, provision is made for the total groove volume of the circumferential grooves, shoulder grooves and transverse grooves in the tread to be between 1% and 10% of the gross volume of the tread, wherein the gross volume of the tread is based on the deepest groove in the tread.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawings wherein:

FIG. 1 shows a plan view of the tire profile according to the invention; and,

FIG. 2 shows a section through the tire profile in FIG. 1 at section line A-A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows the tread 1 of the pneumatic vehicle tire according to the invention for commercial vehicles.

Only a partial segment of the tire profile is depicted in the figure. The tire profile comprises a left-hand shoulder rib 2, a right-hand shoulder rib 3 and central profile ribs 4 to 7. The profile ribs represent the positive of the tire profile. These profile ribs are separated in circumferential direction 19 by the two shoulder grooves 8 and 12 and by the inner circumferential grooves 9 to 11.

The ribs are divided in radial direction 32 of the tread 1 by transverse grooves 13 to 16 in the central profile ribs and by transverse grooves 17 and 18 in the shoulder ribs 2 and 3. Transverse grooves 13 to 16 can have different widths. In this embodiment, transverse grooves 13 and 15 have a width of about 0.5 mm. Transverse grooves 14 and 16, in contrast, have a width of about 1.5 mm. Transverse grooves 13 to 16 extend in the central profile ribs 4 to 7 over the entire width thereof. The angle 20 between the circumferential direction 19 and the alignment of transverse grooves 13 and 14 is in a range of less than 60°. Moreover, transverse grooves 13 and 14 and transverse grooves 15 and 16 are arranged in an arrow shape, wherein the arrow tip is formed by the inner circumferential groove 10. In this embodiment, the shoulder ribs 2 and 3 likewise have transverse grooves 17, 18, 24 and 25.

Transverse grooves 24 and 25 are wider than transverse grooves 17 and 18. Recesses 27 can be arranged laterally on the shoulder ribs 2 and 3, these recesses being connected to transverse groove 17. In the central profile ribs 4 to 7, the number of transverse grooves 13, 14, 15 and 16 in each central profile rib is at least 120 in number over the entire circumference of the tire. Very good wet grip properties are achieved by means of this large number of transverse grooves. The inner circumferential grooves 9, 10 and 11 have a width 21 which is in a range of from 1 mm to 4 mm. The width 22 of the shoulder grooves 8 and 12 is in a range of from 1 mm to 15 mm. The width 23 of the inner profile ribs 4, 5, 6 and 7 is between 25 mm and 55 mm.

In some parts of the profile at the profile block surface, there are chamfers 26, which extend into the shoulder grooves 8 and 12. The groove volume is the sum of the circumferential grooves, shoulder grooves and transverse grooves in the tread 1. The groove volume represents the volume of the profile negative. The corresponding gross volume of the tread is based on the deepest groove in the tread 1. At the deepest point in the tire profile, an imaginary line is drawn in a horizontal direction, wherein the gross volume is formed by the upper part of the tread. In the embodiment in FIG. 1, the shoulder grooves 8 and 12 have a zigzag pattern. The wet grip properties are optimized by this zigzag pattern. It is likewise possible for the shoulder grooves 8 and 12 to run in a completely straight line, like the inner circumferential grooves 9 to 11.

FIG. 2 shows a section A-A through the tire profile in FIG. 1. It is essentially the depth of transverse groove 14 which is illustrated by this view. The depth T2 of the transverse groove is preferably 11 mm to 14 mm. The width B1 of the transverse groove is no more than 1.5 mm, wherein this width is measured at a depth T1 of 3.5 mm. The depth dimensions are in each case based on the profile surface 29. The depth T3 of the inner circumferential grooves is preferably between 9 mm and 14 mm. The depth T4 of the shoulder groove is preferably between 9 and 14 mm. Dashed line 30 represents the depth level of the lower edge of the inner circumferential grooves. Dashed line 31 shows the depth level of the lower edge of the shoulder grooves. Depth T5 indicates the maximum difference between the depth T2 of the transverse grooves and the depth T3 of the inner circumferential groove. Depth T5 is preferably less than 2 mm. Depth T6 indicates the maximum difference between the depth of the inner circumferential grooves and the depth of the shoulder grooves. Depth T6 is no more than 2 mm.

Table 1 shows test results obtained with the vehicle tire according to the invention. This table shows the test results for five different tire profiles. One surprising finding of the test results is that test tires E3 are provided with a relatively large number of transverse grooves, which do not lead to any deterioration in rolling resistance. On test tire E3, the number of transverse grooves is 140, which are distributed uniformly over the circumference of the central profile ribs. At the same time, the values for wet adhesion during braking and starting are increased by about 5%. The value for rolling resistance is abbreviated with the letters RR and is about 100% for all the reference tires. The values for wet adhesion during braking and starting are given in the last row.

The surprising finding is that adding transverse grooves in the central profile ribs does not lead to any deterioration in rolling resistance if the inner circumferential grooves used have a width of 3.5 mm and the transverse grooves have a maximum width of 1.5 mm. This finding is demonstrated by the test results in Table 1. It is surprising since, in previous test series with tires that have wider inner grooves, adding transverse grooves in the central ribs led to a significant deterioration in rolling resistance, as the test results in Table 5 show. Also surprising is the fact that, based on a tire with 4 circumferential grooves with narrow inner grooves, adding a fifth narrow circumferential groove did not lead to any deterioration in rolling resistance, whatever the width of the shoulder grooves. This is shown by the test results in Table 2. In previous tests, adding wider circumferential grooves led to the deterioration in rolling resistance, as shown by the test results in Table 3.

	TABLE 1
	Ref. 2	B1	E1	E2	E3
Circumferential	Groove width,	3 mm	3 mm	3 mm	3 mm	3 mm
shoulder grooves	groove base
	Groove width 1.5 mm	7.5 mm	7.5 mm	7.5 mm	7.5 mm	7.5 mm
	below tread surface
	Number of shoulder	2	2	2	2	2
	grooves
Circumferential	Groove width,	2 mm	2 mm	2 mm	2 mm	2 mm
inner grooves	groove base
	Groove width 1.5 mm	3.5 mm	3.5 mm	3.5 mm	3.5 mm	3.5 mm
	below tread surface
	Number of inner	2	3	3	3	3
	grooves
	Width of transverse	0.5 mm	0.5 mm	0.5 mm	0.5 mm	0.5 mm
	grooves
	Number of transverse	100	100	40	120	140
	grooves
	RR (drum test as	100%	100%	100%	100%	100%
	per ISO 28580)
	Wet adhesion, cornering	100%	102%	102%	102%	102%
	(assessment by a
	standardized internal
	vehicle test)
	Wet adhesion, braking/	100%	100%	99%	102%	105%
	starting (assessment by
	standardized internal
	vehicle test)

	TABLE 2
	Ref. 1	F1
	Circumferential	Groove width,	12 mm	12 mm
	shoulder grooves	groove base
		Groove width 1.5 mm	18 mm	18 mm
		below tread
		surface
		Number of	2	2
		shoulder grooves
	Circumferential	Groove width,	12 mm	12 mm
	inner grooves	groove base
		Groove width 1.5 mm	18 mm	18 mm
		below tread
		surface
		Number of inner	2	3
		grooves
		Width of	0.5 mm	0.5 mm
		transverse
		grooves
		Number of	100	100
		transverse
		grooves
		RR (drum test as	100%	103%
		per ISO 28580)

	TABLE 3
	Ref. 1	A1
	Circumferential	Groove width,	12 mm	12 mm
	shoulder grooves	groove base
		Groove width 1.5 mm	18 mm	18 mm
		below tread
		surface
		Number of	2	2
		shoulder grooves
	Circumferential	Groove width,	2 mm	2 mm
	inner grooves	groove base
		Groove width 1.5 mm	3.5 mm	3.5 mm
		below tread
		surface
		Number of inner	2	3
		grooves
		Width of	0.5 mm	0.5 mm
		transverse
		grooves
		Number of	100	100
		transverse
		grooves
		RR (drum test as	100%	100%
		per ISO 28580)

	TABLE 4
	Ref. 3	C1	C2	C3	C4
Circumferential	Groove width,	12 mm	12 mm	12 mm	12 mm	12 mm
shoulder grooves	groove base
	Groove width 1.5 mm	18 mm	18 mm	18 mm	18 mm	18 mm
	below tread surface
	Number of shoulder	2	2	2	2	2
	grooves
Circumferential	Groove width,	12 mm	12 mm	12 mm	12 mm	12 mm
inner grooves	groove base
	Groove width 1.5 mm	18 mm	18 mm	18 mm	18 mm	18 mm
	below tread surface
	Number of inner	2	2	2	2	2
	grooves
	Width of transverse	0.5 mm	2 mm	5 mm	8 mm	12 mm
	grooves
	Number of transverse	100	100	100	100	100
	grooves
	RR (drum test as	100%	104%	109%	112%	114%
	per ISO 28580)

	TABLE 5
	Ref. 4	D1	D2	D3	D4
Shoulder grooves	Groove width,	12 mm	12 mm	12 mm	12 mm	12 mm
	groove base
	Groove width 1.5 mm	18 mm	18 mm	18 mm	18 mm	18 mm
	below tread surface
	Number of shoulder	2	2	2	2	2
	grooves
Inner grooves	Groove width,	12 mm	12 mm	12 mm	12 mm	12 mm
	groove base
	Groove width 1.5 mm	18 mm	18 mm	18 mm	18 mm	18 mm
	below tread surface
	Number of inner	2	2	2	2	2
	grooves
	Width of transverse	0.5 mm	0.5 mm	0.5 mm	0.5 mm	0.5 mm
	grooves
	Number of transverse	100	40	50	75	140
	grooves
	RR (drum test as	100%	106%	105%	102%	96%
	per ISO 28580)

It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS

• 1 tread
• 2 left-hand shoulder rib
• 3 right-hand shoulder rib
• 4 central profile rib
• 5 central profile rib
• 6 central profile rib
• 7 central profile rib
• 8 shoulder groove
• 9 inner circumferential groove
• 10 central inner circumferential groove
• 11 inner circumferential groove
• 12 shoulder groove
• 13 transverse grooves in the central profile ribs (about 0.5 mm wide)
• 14 transverse grooves in the central profile ribs (about 1.5 mm wide)
• 15 transverse grooves in the central profile ribs (about 0.5 mm wide)
• 16 transverse grooves in the central profile ribs (about 1.5 mm wide)
• 17 narrow transverse grooves in the shoulder ribs
• 18 narrow transverse grooves in the shoulder ribs
• 19 circumferential direction of the tire
• 20 angle between alignment of the transverse groove and the circumferential direction
• 21 width of the inner circumferential grooves
• 22 width of the shoulder grooves
• 23 width of the inner profile ribs
• 24 wide transverse grooves in the shoulder ribs
• 25 wide transverse grooves in the shoulder ribs
• 26 chamfers on the profile block surface
• 27 recess on the shoulder rib
• 28 recess on the transverse groove
• 29 profile surface
• 30 depth level of the lower edge of the inner circumferential grooves
• 31 depth level of the lower edge of the shoulder grooves
• 32 radial direction
• B1 width of the transverse groove at distance T1 from the profile surface
• T1 depth at which the width of the transverse groove is measured
• T2 depth of the transverse groove
• T3 depth of the inner circumferential groove
• T4 depth of the shoulder groove
• T5 maximum difference between the depth of the transverse groove and the depth of the inner circumferential groove
• T6 maximum difference between the depth of the inner circumferential groove and the depth of the shoulder groove

Claims

1. A pneumatic vehicle tire for utility vehicles defining a profile surface, a circumferential direction and a tire circumference, the pneumatic vehicle tire comprising: a tread defining a first shoulder groove and a second shoulder groove and a first, second and third inner circumferential grooves;a first side wall and a second side wall;a plurality of central profile ribs;a first shoulder rib and a second shoulder rib;said profile ribs, said shoulder ribs, said inner circumferential grooves and said shoulder grooves being aligned and arranged approximately in the circumferential direction of the tire circumference;at least 120 transverse grooves arranged over the entire tire circumference in each of said central profile ribs;said transverse grooves each having a width (B1) of at most 1.5 mm at a distance of 3.5 mm from the profile surface in each of said central profile ribs; and,each of said inner circumferential grooves having a width of at most 4 mm at a distance of 3.5 mm from the profile surface.

2. The pneumatic vehicle tire of claim 1, wherein said transverse grooves in said central profile ribs are arranged at an angle of greater than 60° with respect to the circumferential direction.

3. The pneumatic vehicle tire of claim 1, wherein: said transverse grooves have a depth (T2);said inner circumferential grooves have a depth (T3); and,said depth (T2) and said depth (T3) having a depth difference (T5) of at most 2 mm.

4. The pneumatic vehicle tire of claim 1, wherein: said inner circumferential grooves have a depth (T3);said shoulder grooves have a depth (T4); and,said depth (T3) and said depth (T4) having a depth difference (T6) of at most 2 mm.

5. The pneumatic vehicle tire of claim 1, wherein said transverse grooves in said central profile ribs have a depth (T2) lying in the range of 11 to 14 mm.

6. The pneumatic vehicle tire of claim 1, wherein: said inner circumferential grooves have a depth (T3);said shoulder grooves have a depth (T2); and,at least one of said depth (T2) and said depth (T3) lies in a range of 9 to 14 mm.

7. The pneumatic vehicle tire of claim 1, wherein: each of said central profile ribs have a total width; and,each of said transverse grooves extend over at least 80% of said total width of respective ones of said central profile ribs.

8. The pneumatic vehicle tire of claim 1, wherein: said transverse grooves are arranged in an arrow shaped manner with an arrow tip;said second circumferential groove is a middle inner circumferential groove; and,said arrow tip is formed by said middle inner circumferential groove.

9. The pneumatic vehicle tire of claim 1, wherein said shoulder ribs have further transverse grooves arranged therein.

10. The pneumatic vehicle tire of claim 1, wherein said central profile ribs have a width lying in the range of 25 to 55 mm.

11. The pneumatic vehicle tire of claim 1, wherein said central profile ribs have a width lying in the range of 35 to 45 mm.

12. The pneumatic vehicle tire of claim 1, wherein: said first, second and third circumferential grooves, said first and second shoulder grooves and said transverse grooves define a total groove volume;said tread having a gross volume based on the deepest of said first circumferential groove, said second circumferential groove, said third circumferential groove, said first shoulder groove, said second shoulder groove, and said transverse grooves; and,said total groove volume lies in a range between 1% and 10% of said gross volume.