JP2018109524A - Method for measuring flexural rigidity of bead part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring the flexural rigidity of a bead part, capable of digitizing the flexural rigidity of the bead part to improve the accuracy of evaluation of rim assemblability.SOLUTION: A method for measuring the flexural rigidity of a bead part comprises: the step K1 of maintaining two positions Px facing each other in a first tire diameter direction on the inner surface Si of an upper bead part Tb by a bead support plate 7 and the step K2 of gradually loading a load W at two positions Py facing each other in a second tire diameter direction on the outer surface So of the upper side bead part Tb by a load action plate 8 to displace the two positions. The flexural rigidity of the bead part is required on the basis of the measurement data of the load W and the amount δ of displacement.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for measuring the bending stiffness of a bead portion that can be suitably used for evaluating the rim assembly property of a tire.

  When assembling the tire rim (including attaching to the rim and removing from the rim), the bead portion is partially deformed in the radial direction and the tire axial direction, and the bead portion is pulled out to the outside of the rim flange; In addition, it is necessary to draw the inside of the rim flange. This operation is usually performed by a rim assembly machine such as a tire changer.

  However, when the rigidity of the bead portion is very high, there is a possibility that the deformation becomes difficult and the rim assembling work becomes difficult.

  Therefore, when developing a tire, it is required to evaluate the rim assembly property of the developed tire as an index. Conventionally, a bead fastening force has been adopted as an index for evaluating rim assembly. This bead fastening force can be measured, for example, by a measuring device described in Patent Documents 1 and 2 below.

  However, as described above, when the rim is assembled, the bead portion is deformed in the radial direction and the tire axial direction, so that the bead fastening force alone is not sufficient as an index for evaluating the rim assembling property. Moreover, as a result of the inventors' research, it has been found that the rim assembly property is more influenced by the bending rigidity of the bead portion than by the bead fastening force.

Japanese Patent Laid-Open No. 01-313729 Japanese Patent Laid-Open No. 03-148036

  Therefore, an object of the present invention is to provide a method for measuring the bending rigidity of a bead part that can easily quantify the bending rigidity of the bead part and can improve the accuracy of evaluation of the rim assembly property.

The present invention uses a bead support plate extending in the first tire diametrical direction, and places two positions Px opposite to each other in the first tire diametrical direction on the inner surface in the tire axial direction of the upper bead portion in a horizontally placed tire. Tire holding process,
A load acting plate extending in a second tire diameter direction orthogonal to the first tire diameter direction is used, the outer surface in the tire axial direction of the upper bead portion held by the bead support plate, and the second tire diameter direction A load loading step of gradually displacing the two positions Py inward in the tire axial direction by pressing the opposite two positions Py inward in the tire axial direction and gradually applying a load;
And a measurement process for measuring the load and the displacement amount in the load application process,
The bending rigidity of the bead portion is obtained based on the measurement data of the load and the displacement amount.

  In the bending rigidity measurement of the bead part according to the present invention, it is preferable that the bending rigidity of the bead part is obtained from the slope of the load-displacement curve based on the measurement data.

  In the bending stiffness measurement of the bead portion according to the present invention, the bead support plate is mounted on an installation stand rising from a base surface, and the tire is placed on the bead support plate in a non-contact manner with the base surface. It is preferable.

  In the bending rigidity measurement of the bead portion according to the present invention, the upper surface of the bead support plate forms a flat surface, and the lower surface of the load acting plate passes through a step portion between the pressing surface portions that press the two positions Py. It is preferable to have a central surface portion that is recessed upward.

  In the bending rigidity measurement of the bead portion according to the present invention, the lower surface of the load acting plate forms a flat surface, and the upper surface of the bead support plate has a stepped portion between the holding surface portions on which the two positions Px are placed. It is preferable to have a central surface portion that is recessed downward through the center.

  Since the present invention is configured as described above, the upper bead portion can be easily bent and deformed in the tire axial direction between the adjacent positions Px and Py in the circumferential direction, and the measurement data of the load and the displacement amount at that time can be used. Based on this, the bending rigidity of the bead portion can be quantified.

  The digitized bending rigidity of the bead portion can be suitably used as an index for evaluating the rim assembly property.

  In the tire, the inner surface in the tire axial direction of the upper bead portion is placed on the bead support plate. Therefore, even when held at the two positions Px, the tire can be stably held. In addition, since the tire can be held without contacting other than the bead support plate, the adverse effect on the bending deformation of the bead portion can be eliminated, and the measurement accuracy can be improved.

It is a side view which shows the tire holding process in the bending rigidity measuring method of the bead part of this invention with the measuring apparatus which enforces it. It is a perspective view which shows a load loading process notionally. (A), (B) is the top view and sectional drawing which show a load loading process notionally. It is an expanded sectional view which shows the outer end part of a load action board. It is a graph which shows an example of the load-displacement curve based on measurement data. It is a perspective view which shows the other example of a bead support plate and a load action board.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 shows an example of a measuring apparatus 1 for carrying out the method for measuring the bending stiffness of a bead portion according to the present invention.

  As shown in FIG. 1, the measuring apparatus 1 of this example includes a tire holder 2, a load applying tool 3, and a measuring means (not shown). The tire holder 2 holds the tire T in a flat position. The load loader 3 gradually applies a load W in the tire axial direction to the tire T held by the tire holder 2. The measuring means measures the load W loaded by the load loader 3 and the displacement amount δ in the tire axial direction due thereto.

  The tire holder 2 of this example includes, for example, an installation base 6 that rises from a base surface 5 that is a table of a compression tester, and a bead support plate 7 that is attached to the upper end of the installation base 6.

  As shown in FIGS. 1 and 2, the bead support plate 7 has a plate shape extending in the first tire diameter direction Fx, which is an arbitrary tire diameter direction. This bead support plate 7 places and holds two positions Px and Px facing each other in the first tire diameter direction Fx, of the inner surface Si in the tire axial direction of the upper bead portion Tb of the tire T in a flat position. In this held state, the height of the installation base 6 is set so that the tire T does not come into contact with the base surface 5. 2 and 3, the upper bead portion Tb is drawn in a ring shape for the sake of simplicity.

  In such a tire holder 2, since the center of gravity of the tire T is below the holding position, the tire T can be stabilized even when held at the two positions Px. Further, since the tire T is not in contact with anything other than the bead support plate 7, the adverse effect on the bending deformation of the bead portion can be eliminated.

  The load application tool 3 includes a load application plate 8 that applies a load W to the inner side in the tire axial direction on the upper bead portion Tb. In this example, the load acting plate 8 is supported by a lifting platform (not shown) in the compression tester.

  The load acting plate 8 has a plate shape extending in the second tire diameter direction Fy perpendicular to the first tire diameter direction Fx. Then, by lowering the load acting plate 8, the two positions Py and Py facing each other in the second tire diameter direction Fy in the tire axial direction outer surface So of the upper bead portion Tb are pressed inward in the tire axial direction, and the load W is increased. Load gradually. As a result, the two positions Py can be gradually displaced inward in the tire axial direction.

  Here, the load acting plate 8 has a lower surface 8S between a height position where the lower surface 8S starts to contact the upper bead portion Tb and a height position where the lower surface 8S contacts the upper surface 7S of the bead support plate 7. Can be displaced. In this example, in order to secure a larger maximum displacement amount δ, as shown in FIG. 2, the upper surface 7S of the bead support plate 7 is made flat and the lower surface 8S of the load acting plate 8 is formed with a stepped surface. ing.

  Specifically, the lower surface 8S of the load acting plate 8 includes a pressing surface portion 8So that presses the two positions Py and Py, and a central surface portion 8Si that is arranged via a step D therebetween. The center surface portion 8Si is formed so as to be recessed above the pressing surface portion 8So. As a result, the maximum displacement amount δ can be increased by the level difference D as compared with the case where the lower surface 8S is a flat surface.

  For the same purpose, as shown in FIG. 6, the lower surface 8S of the load acting plate 8 can be a flat surface, and the upper surface 7S of the bead support plate 7 can be formed with a stepped surface. In this case, the upper surface 7S of the bead support plate 7 has a holding surface portion 7So on which the two positions Px and Px are placed, and a central surface portion 7Si disposed through a step D therebetween. The central surface portion 7Si is formed to be recessed below the holding surface portion 7So. As a result, the maximum displacement amount δ can be increased by the level difference D as compared with the case where the upper surface 7S is a flat surface.

  Note that the lower surface 8S of the load acting plate 8 is a stepped surface in which the central surface portion 8Si is recessed above the pressing surface portion 8So, and the upper surface 7S of the bead support plate 7 is more than the holding surface portion 7So. It is also possible to use a stepped surface that is recessed downward.

  The maximum displacement δ is preferably 80 mm or more, and this value corresponds to the displacement when the bead portion is displaced in the tire axial direction when the rim is assembled.

  It is important for the load acting plate 8 not to contact the sidewall portion Ts of the tire T when the upper bead portion Tb is pressed in order to increase the measurement accuracy of the bending rigidity of the bead portion. Therefore, it is preferable to set the length of the load acting plate 8 to be equal to or smaller than the rim maximum outer diameter including the rim flange in the normal rim.

  As shown in FIG. 4, it is also preferable that the lower surface 8S and the outer end of the load acting plate 8 are formed as a curved surface 8Se that approximates the shape of the rim flange in the regular rim. At this time, since the curved surface 8Se contacts the outer surface So of the upper bead portion Tb, contact with the sidewall portion Ts can be prevented. When the curved surface 8Se is formed, the length of the load acting plate 8 can be set larger than the rim maximum outer diameter.

  The bead support plate 7 is preferably longer than the load acting plate 8 in order to securely hold the tire T.

  Next, the measuring means measures the load W applied by the load applying tool 3 and the displacement amount δ in the tire axial direction at the two positions Py. Although it is not particularly defined as the measurement of the load W, a load sensor such as an existing load cell can be used in the compression tester. Further, as a measurement of the displacement amount δ, an existing distance sensor such as a rotary encoder can be used in a compression tester that measures the amount of descending of the lifting platform.

  Further, the measuring apparatus 1 of this example includes arithmetic means such as a CPU (central processing unit) for obtaining the bending rigidity of the bead portion based on the measurement data of the load W and the displacement amount δ obtained by the measuring means.

  Next, a method for measuring the bending rigidity of the bead portion will be described. This measurement method includes a tire holding step K1 (shown in FIG. 1), a load application step K2 (shown in FIGS. 2 and 3), a measurement step (not shown), and a calculation step (not shown).

  As shown in FIG. 1, in the tire holding step K <b> 1, the two positions Px and Px of the inner surface Si of the upper bead portion Tb are placed and held on the bead support plate 7.

  As shown in FIGS. 2 and 3, in the load application step K <b> 2, the two positions Py and Py of the outer surface So of the upper bead portion Tb are pressed against the inner side in the tire axial direction by the load action plate 8, and the load W is gradually increased. To load. As a result, the two positions Py are gradually displaced inward in the tire axial direction.

  In the measurement process, the load W and the displacement amount δ in the load application process K2 are sequentially measured. As shown in FIG. 3 (A), the upper bead portion Tb is in contact with the positions 7E on both side ends of the bead support plate 7 and the positions 8E on both side ends of the load acting plate 8 when a load is applied. That is, the annular bead portion has a load configuration that bends at 8 positions. When a load W is applied, as shown in FIG. 3B, each load at the 8 positions is W / 4.

  In the calculation step, the bending stiffness of the bead portion is obtained based on the measurement data of the load W and the displacement amount δ. Specifically, as shown in FIG. 5, the bending rigidity of the bead portion is obtained from the slope of the load-displacement curve Y obtained based on the measurement data. In this example, the load-displacement curve Y is shown as a regression curve obtained by performing regression analysis on the measurement data.

  As described above, it is preferable to secure the maximum displacement δ at 80 mm or more by making the lower surface 8S of the load acting plate 8 and / or the upper surface 7S of the bead support plate 7 into a stepped surface. However, when it is difficult to secure 80 mm or more, the width of the load acting plate 8 and the bead support plate 7 is widened, and the distance between the positions 7E and 8E (shown in FIG. 3A) is reduced to the bead portion. It is preferable to increase the burden. In FIG. 3A, for convenience, (interval between positions 7E and 7E) = (interval between positions 8E and 8E) <(interval between positions 7E and 8E), 7E, 7E) = (Distance between positions 7E, 8E) = (Distance between positions 8E, 8E).

  The bending rigidity of the bead portion thus obtained has a large correlation with the rim assemblability as compared with the bead fastening force, and can be suitably used as an index for evaluating the rim assemblage.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  1 and 2, and based on the method for measuring the bending rigidity of the bead portion of the present invention, tire A having excellent rim assemblability (no damage during rim assembling) and tire B having inferior rim assemblability ( The bending stiffness of the bead portion was measured against damage when the rim was assembled.

  Each of the tires A and B has a tire size of 206 / 65R16. As shown in FIG. 2, the lower surface 8S of the load acting plate 8 is a stepped surface, so that the maximum displacement δ is secured to 80 mm. ing. The distance between the positions 7E and 7E, the distance between the positions 7E and 8E, and the distance between the positions 8E and 8E are equal to each other.

  FIG. 5 shows a load-displacement curve Y based on the data of the load W and the displacement amount δ obtained by the load loading process. The bending rigidity of the bead portion in each tire A and B was determined as the slope (unit: N / mm) of the load-displacement curve Y between the displacement amount 10 mm and the displacement amount 30 mm. The results are shown in Table 1.

  As a comparison, the bead fastening force of the tires A and B was measured, and the results are shown in Table 1. The bead tightening force is based on Patent Document 2, and a plurality of tightening jaws arranged in the circumferential direction are displaced radially outwardly inside the bead portion, and the compressive force received from the bead portion at that time is measured. doing.

  As shown in the examples, the tire A having excellent rim assemblability has a larger bending rigidity at the bead portion than the tire B having inferior rim assembling properties. Can be confirmed. On the other hand, as shown in the comparative example, it can be confirmed that the rim assembly property and the bead fastening force are not matched.

5 Base surface 6 Installation base 7 Bead support plate 7Si Central surface portion 7So Holding surface portion 7S Upper surface 8 Load acting plate 8Si Central surface portion 8So Pressing surface portion 8So
8S Lower surface D Step Fx Tire diameter direction Fy Tire diameter direction K1 Tire holding process K2 Load application process Si Tire axial inner surface So Tire axial outer surface Tb Upper bead portion T Tire

Claims (5)

A tire that uses a bead support plate extending in the first tire diameter direction and places and holds two positions Px facing the inner surface in the tire axial direction of the upper bead portion and the first tire diameter direction in a horizontally placed tire. Holding process,
A load acting plate extending in a second tire diameter direction orthogonal to the first tire diameter direction is used, the outer surface in the tire axial direction of the upper bead portion held by the bead support plate, and the second tire diameter direction A load loading step of gradually displacing the two positions Py inward in the tire axial direction by pressing the opposite two positions Py inward in the tire axial direction and gradually applying a load;
And a measurement process for measuring the load and the displacement amount in the load application process,
A method for measuring the bending stiffness of a bead portion, wherein the bending stiffness of the bead portion is obtained based on measurement data of the load and the amount of displacement.   2. The method for measuring the bending stiffness of a bead portion according to claim 1, wherein the bending stiffness of the bead portion is obtained from an inclination of a load-displacement curve based on the measurement data.   3. The bead support plate is mounted on an installation stand rising from a base surface, and the tire is placed on the bead support plate in a non-contact manner with the base surface. Of measuring the bending stiffness of the bead part of the machine. The upper surface of the bead support plate forms a plane,
The bead portion according to any one of claims 1 to 3, wherein a bottom surface of the load acting plate has a central surface portion that is recessed upward through a step between pressing surface portions that press the two positions Py. Bending stiffness measurement method. The lower surface of the load acting plate forms a plane,
The upper surface of the bead support plate has a central surface portion that is recessed downward through a step between the holding surface portions on which the two positions Px are placed. Bending stiffness measurement method.

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