JP2008001017A - Residual rubber thickness correcting method of buff processing base tire for regenerated tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a residual rubber thickness correcting method of a buff processing base tire for a regenerated tire capable of sufficiently removing the irregularity of a residual rubber thickness in the peripheral direction of a tire in a short time regardless of the presence of the axial shift between the tire and the rim combined therewith after the buff processing to a regenerating tire is performed by rotating the rim-combined tire. <P>SOLUTION: The thickness distribution in the peripheral direction of the tire of the residual rubber 4 present on the outer peripheral side of a belt 3 of the buff processing base tire 1 to which buff processing is applied while the required shaven-off thickness (a) in the thickest part Gmax of the residual rubber thickness is calculated. Subsequently, a rasp 6 is advanced to the thickest part Gmax of the residual rubber thickness of the fixed base tire 1 while rotated to be displaced and the residual rubber 4 is shaven off by the required shaven-off thickness (a) over the whole width of the base tire. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  This invention is for a retread tire that has a buffed base tire that has a sufficiently uniform thickness over the entire circumference of the tire under a high work efficiency. The present invention relates to a method for correcting the remaining rubber thickness of a buffed base tire.

  The rehabilitation method for the production of rehabilitated tires is a so-called hot rehabilitation method in which unvulcanized tread rubber is adhered and arranged on a base tire, and the unvulcanized tread rubber is vulcanized and molded in a flow mold, A pre-cured tread that has been vulcanized and molded in advance in a belt shape is placed on the base tire, and this pre-cured tread is roughly divided into a so-called cold retreading method in which the pre-cured tread is vulcanized and bonded to the base tire in a vulcanizing can In any of these rehabilitation methods, the tire to be rehabilitated can be buffed by cutting, grinding, etc., and the old tread rubber of the tire can be scraped off at least to the extent that the pattern grooves completely disappear. I need it.

  In this case, in the hot retreading method, the unvulcanized tread rubber is vulcanized and molded in the vulcanization mold with the peripheral surface being restrained, so the thickness of the remaining rubber existing on the outer peripheral side of the belt of the old tread rubber However, in the cold rehabilitation method in which a pre-cured tread that has been pre-cured and molded is stuck on the base tire, the remaining rubber thickness on the belt outer peripheral side must be strictly controlled. It is essential to ensure the uniformity and other performance of retreaded tires.

Therefore, in order to make the remaining rubber thickness on the outer peripheral side of the belt sufficiently uniform over the entire circumference of the base tire, as described in Patent Document 1, from the outer peripheral surface of the base tire that has been buffed, The thickness of the remaining rubber on the side is measured by an eddy current sensor, the belt circumference is calculated from the outer circumference of the base tire and the residual rubber thickness, and from this belt circumference, the target outer circumference of the base tire is determined, And based on this target outer periphery length, the technique which further scrapes off the peripheral surface of the base tire after a buff process and makes it a final base tire is proposed.
JP 2002-86586 A

  However, with this proposed technology, it is necessary to buff a tire for rehabilitation twice while rotating the tire, so it takes time to make it the final tire. In order to remove the variation in the remaining rubber thickness in the circumferential direction of the tire and improve the quality of the retreaded tire, remove the rim once from the tire before the second buffing, After that, it is necessary to remove the misalignment between the tire and the rim by reassembling the rim on the tire, but the misalignment between them can be completely removed even after reassembling the rim. There is another problem that the variation in the thickness of the remaining rubber cannot be removed sufficiently unless there is a guarantee of the rim. There is also a problem that it takes.

  The present invention has been made to solve such problems of the proposed technology, and the object of the present invention is to perform a first buffing process on a retread tire with a rim assembled tire. In the same way as in the proposed technology, the remaining rubber thickness variation in the circumferential direction of the tire is reduced for a short time regardless of whether there is misalignment between the tire and the rim attached to the tire. It is an object of the present invention to provide a method for correcting the remaining rubber thickness of a buffed tire for a retread tire, which can be sufficiently removed.

The method of correcting the residual rubber thickness of the buffed base tire for retread tires according to the present invention is the residual rubber existing on the outer peripheral side of the belt of the retreaded base tire subjected to buffing in order to produce the final base tire. The thickness distribution in the tire circumferential direction is determined under the action of an appropriate measuring means, and the required scraped thickness at the thickest portion of the remaining rubber thickness, for example, the difference between the maximum value and the minimum value of the remaining rubber thickness. Then, a rotating grinding means having a cutting or grinding surface such as a file, a grindstone, a brush or the like is moved forward and displaced with respect to the thickest portion of the residual rubber of the fixed base tire under the rotation thereof. The rubber is scraped over the entire width of the base tire by the required scraping thickness.
Here, when there is a specification for the residual rubber thickness of the final base tire, for example, when the average value of the tire residual rubber thickness over the entire circumference is larger than the specification value, the difference is determined as the required scraping thickness. You can also

  More preferably, in this case, as described above, after the remaining rubber of the thickest portion of the remaining rubber is scraped by the required scraping thickness, the remaining rubber of each portion adjacent to the scraped portion in the tire circumferential direction is removed. Then, scraping is performed over half the thickness of the required scraped portion, thereby making the change in the remaining rubber thickness in the tire circumferential direction sufficiently smooth.

  Here, the half-thickness scraping is performed by, for example, positioning the center of the width of the rotary grinding means, that is, the center of the length corresponding to the scraping edge of the first scraping portion, or the center of rotation. This can be done by positioning it in correspondence with the shaving edge of the first shaving part.

  In order to make the remaining rubber thickness change more smoothly in the tire circumferential direction, an uncut portion adjacent to the tire circumferential direction of the cut portion as described above, which is half the required cut thickness, For example, it is preferable that the center of rotation or the center of rotation of the rotary grinding means is positioned corresponding to the shaving edge and scraped over a quarter of the required shaving thickness.

  By the way, in the tire circumferential direction, it is preferable that the number of scraped portions while reducing the shaved thickness is increased as the initial required scraped thickness is thick, and the remaining rubber existing on the outer peripheral side of the belt is in the tire circumferential direction. The thickness distribution is preferably determined by measuring the remaining rubber thickness using an eddy current sensor.

  In the method for correcting the remaining rubber thickness of the buffed base tire for retread tire according to the present invention, the buffing was performed based on the distribution of the remaining rubber thickness obtained in advance and the required scraped thickness at the portion where the remaining rubber thickness is the thickest. With the rim assembly tire fixed, the rotation grinding means is used to scrape off the thickest part of the remaining rubber by the required scraping thickness, so that there is a misalignment between the rim and the tire. Regardless of this, it is possible to reduce the amount of variation in the thickness of the remaining rubber in the tire circumferential direction appropriately and reliably in a short time, and to equalize the remaining rubber thickness over the entire circumference.

  In this case, after scraping off the remaining rubber of the thickest portion of the remaining rubber as described above, when scraping the adjacent portion of the scraped portion over half the above-mentioned required scraping thickness, the remaining rubber thickness The change in the tire circumferential direction can be made sufficiently smooth, which is more effective when the adjacent portion of the half-thickened portion is cut over a quarter of the required thickness. It is.

  It should be noted that the number of scraped parts in the tire circumferential direction while halving the scraped thickness is increased as the required scraped thickness at the initial thickest part of the rubber is increased. It is preferable for reducing the change in rubber thickness.

  By the way, when determining the thickness distribution of the remaining rubber in the tire circumferential direction, when measuring the remaining rubber thickness with an eddy current sensor, at least when the outermost belt layer is made of steel cord, A high-frequency current is caused to flow in the detection coil of the eddy current sensor that is capable of relative displacement in the direction to induce a magnetic flux there, and an eddy current is generated in the belt layer due to the change in the magnetic flux, and is induced by the eddy current. The magnetic flux acting on the detection coil is caused to cause an impedance change, and the residual rubber thickness signal is extracted from the impedance change of the detection coil as a voltage. Therefore, nondestructive measurement can be performed easily and sufficiently accurately.

  In order to measure the thickness of the remaining rubber, an ultrasonic distance sensor can be used instead of the eddy current sensor.

  FIG. 1 is a schematic side view and a schematic plan view showing an embodiment of a method according to the present invention. In FIG. 1, reference numeral 1 denotes a buffing process in which a pattern groove completely disappears in a tread portion of a retreading tire. The reference numeral 2 denotes a base tire for a retread tire which has been previously applied, and 2 denotes a rim assembled to the base tire 1, and 3 denotes a belt.

  Here, first, the thickness distribution in the tire circumferential direction of the remaining rubber 4 existing on the outer peripheral side of the belt 3 is arranged, for example, by arranging the eddy current sensor 5 on the peripheral surface of the base tire 1, and the eddy current sensor 5 and the base tire. The residual rubber thickness of each part of the tire is determined by measuring the tire in the required position as described above by the relative displacement in the circumferential direction with respect to 1.

After that, for example, the difference between the maximum value and the minimum value of the remaining rubber thickness in the obtained thickness distribution is set as the required scraping thickness a at the thickest portion Gmax of the remaining rubber thickness.
On the other hand, when there is a specification in the residual rubber thickness of the final base tire, a value obtained by subtracting the specification value from the average value of the residual rubber thickness can be used as the required scraping thickness a.

  On the other hand, as shown in the figure, a rotating grinding means having a rotation center line extending in a direction orthogonal to the center axis line of the base tire 1, for example, a rotation center extending in the vertical direction with respect to the base tire axis line extending in the horizontal direction. As an example of rotational grinding means having a line, a rasp 6 having a constant outer diameter is prepared over the entire width w, and this rasp 6 is rotated with respect to the thickest portion Gmax of the residual rubber thickness of the fixed base tire 1. The remaining rubber 4 of the base tire 1 is scraped off by the required scraping thickness a, and the rasp 6 is also displaced in the width direction of the base tire 1 at the advance limit position. Then, a flat scraped surface 7 that covers the entire width of the base tire 1 is formed in the portion Gmax where the remaining rubber thickness of the base tire 1 is the thickest, as indicated by a virtual line in the figure.

  When the remaining rubber thickness is corrected in this manner, the remaining rubber 4 of the thickest portion Gmax of the remaining rubber 4 is as expected regardless of whether there is a misalignment between the base tire and the rim. Thus, the thickness of the remaining rubber 4 can be made sufficiently uniform over the entire circumference of the base tire 1.

  Further, when the remaining rubber 4 is scraped in this way, for example, the time required for buffing in advance is 3.2 minutes, and the time required for this partial scraping is 0.8 minutes. When the buffing is performed for the second time after detaching the rim after the first buffing while rotating the tire as described above, the total In addition to the time required for processing of 3.2 minutes, it takes 1 minute to detach the rim, which takes a total of 7.4 minutes. The time can be shortened by 44%.

  Here, in the present invention, more preferably, the respective portions adjacent to the tire circumferential direction of the scraping surface 7 formed as described above, for example, the center of the width of the rasp 6 is positioned at each scraping surface edge, The rasp 6 is scraped over a / 2, which is half the thickness of the previous scraping thickness a, to reduce the fluctuation in the tire circumferential direction in the remaining rubber thickness.

  In addition, according to this, not only the flat scraped surface 7 but also a polygonal scraped surface becomes obvious, for example, between the base tire and the precure tread on its peripheral surface. When the interposed cushion rubber layer is formed directly on the peripheral surface of the base tire by extrusion from an extrusion die, the outer peripheral surface of the cushion rubber layer absorbs each flat surface. Since it will be formed in an arc shape, it will not cause any special problems in the subsequent molding machine operation or the quality of the product retreaded tire. This is almost the same when a cushion rubber sheet that has been pre-extruded is pasted around the base tire to form a cushion rubber layer, and each flat surface is effectively relaxed by pasting the cushion rubber sheet. can do.

  More preferably, the uncut portion adjacent to the tire circumferential direction of the cut portion having the half thickness a / 2 as described above is cut off over the thickness of a / 4 by, for example, the rasp 6 arranged in the same manner as described above. Thus, the variation of the remaining rubber thickness is further reduced.

  By the way, it is preferable to increase the chamfer-like chamfered portions as described above in the tire circumferential direction as the required chamfered thickness a obtained as described above increases.

  In addition, in the place shown in FIG. 1, although the rotation center of the rasp 6 is arranged in a posture extending in a direction perpendicular to the central axis of the base tire 1, the rotation center of the rasp 6 is It is also possible to extend in parallel with the central axis of the tire 1, and even in this case, a concave curved surface becomes apparent on the scraped surface of the remaining rubber 4 by selecting a large outer diameter of the rasp 6. In addition, by setting the width of the rasp 6, in other words, the length in the axial direction, to be long, the rasp 6 can be moved forward and displaced with respect to the thickest portion Gmax of the remaining rubber. The required scraping over the full width of the base tire can be completed.

  By the way, in any of these cases, the rasp is advanced and displaced in the radial direction of the base tire having a fixed position, so that the residual rubber of the base tire is scraped off as expected as expected. be able to.

  For example, the amount of scraping required for carrying out the method for correcting the remaining rubber thickness can be specified as follows, for example.

  The variation R (= Gmax−Gmin) in the tire circumferential direction of the remaining rubber thickness of the original base tire subjected to the buffing process generally has a distribution characteristic as shown in FIG. Here, assuming that the average value of the thickness variation R for the plurality of tires is 0.8 mm and the standard deviation (σ) is 0.25, the required scraped thickness is 0.5 mm. Considering the above case, there are two tires having a thickness variation R exceeding 1.0 mm, and two tires with a variation R of 1.5 mm or more appear with a probability of about 2%. Then, when the thickness variation is larger than the standard value, the required scraped thickness is “thickness exceeding standard value + 0.5 (mm)”.

  Also, here, when the remaining rubber is scraped off from the base tire as shown in FIG. 1, the relationship between the required scraping thickness and the required rasp width for the base tire having a radius of 500 mm is shown in FIG. As shown in the graph, according to this, when the required scraping thickness is 1 mm, by setting the rasp width to 70 mm, it is possible to perform the required scraping of the base tire by a single scraping process. When the shaving thickness is 2 mm, it is understood that the remaining rubber can be shaved off by a single process by setting the rasp width to 100 mm.

  And as for specific shaving with respect to a base tire, if the required shaving thickness in the thickest part of the remaining rubber is up to about 1 mm, for example, as described in claim 2, the tire shaving is performed at three locations in the tire circumferential direction. When the thickness exceeds 1 mm, as shown in claim 3, the unevenness of the remaining rubber thickness is sufficiently reduced by performing grinding at five locations in the tire circumferential direction, and a flat scraped surface. However, it is possible to effectively eliminate the influence on the quality of the subsequent molding machine work and the product retreaded tire.

  For example, when the required scraping thickness is 0.5 mm and scraping is performed at three locations in the tire circumferential direction, the first scraping of the thickest part of the remaining rubber is performed with a depth of 0.5 mm and a scraping width of 45 mm. Next, the above-described effects can be brought about by performing the second and third cuts on the portion adjacent to the cut-off portion by a depth of 0.25 mm and a cut-off width of 32 mm.

  As described above, when the remaining rubber thickness of the base tire after buffing is corrected to make the final base tire, FIG. 4 shows the variation in the residual rubber thickness of the final base tire and the unbalance of the final base tire. As is clear from the graph showing the relative relationship with the amount, the unbalance amount of the final tire can be reduced by reducing the variation in the thickness of the remaining rubber in the final tire.

  Further, according to this method, the residual rubber thickness distribution of the buffed base tire 1 is automatically measured, for example, by the eddy current sensor 5 that relatively displaces on the peripheral surface of the base tire, and the residual rubber thickness By providing a final base tire by buffing in advance and partially correcting the remaining rubber thickness under a system that can determine the thickest portion Gmax of the tire and the required scraped thickness of the portion, As described above, the variation in the remaining rubber thickness of the final tire can be sufficiently reduced in a total processing time of 4 minutes. On the other hand, as in the proposed technology, two buffing operations are performed while rotating the rim-assembled tires, and the rim is detached between the first buffing operation and the second buffing operation. In this case, it takes a total of 7.4 minutes, and the effect of misalignment between the rim and the base tire cannot be removed sufficiently, and there remains a problem in machining accuracy. Become.

It is an approximate line side view and an approximate line top view showing an embodiment of a method concerning this invention. It is a graph which shows the thickness distribution characteristic of residual rubber. It is a graph which shows the relationship between the required scraping thickness of a remaining rubber, and required rasp width. It is a graph which shows the relationship between the dispersion | variation in the remaining rubber thickness of the last stand tire, and the unbalance amount of the last stand tire.

Explanation of symbols

1 tire 2 rim 3 belt 4 remaining rubber 5 eddy current sensor 6 rasp 7 scraping surface Gmax thickest part of the remaining tire thickness a required scraping thickness w total rasp width

Claims (5)

  While calculating the thickness distribution in the tire circumferential direction of the residual rubber existing on the outer peripheral side of the belt of the retread tire that has been buffed, the required scraped thickness at the thickest part of the residual rubber thickness is determined, Next, the rotating grinding means is moved forward and displaced with respect to the thickest portion of the remaining tire thickness of the fixed base tire under its rotation, and the remaining rubber is made by the required scraping thickness over the entire width of the base tire. A method for correcting the remaining rubber thickness of buffed tires for retreaded tires.   After removing the remaining rubber of the thickest portion of the remaining rubber by the required scraping thickness, scraping off the remaining rubber of each portion adjacent to the tire circumferential direction of the scraped portion over half the required scraping thickness, The method for correcting the remaining rubber thickness of the buffed base tire for retread tire according to claim 1.   The method for correcting the remaining rubber thickness of a buffed tire for a retread tire according to claim 2, wherein an uncut portion adjacent to the tire circumferential direction of the cut portion having a half thickness is cut over a thickness of 1/4 of the required cut thickness.   The method for correcting the remaining rubber thickness of the buffed tire for rehabilitated tire according to claim 2 or 3, wherein the thicker the required scraping thickness, the greater the number of scraping points in the tire circumferential direction.   The residual rubber thickness of the buffed base tire for retreaded tires according to any one of claims 1 to 4, wherein the thickness distribution in the tire circumferential direction of the residual rubber existing on the outer peripheral side of the belt is obtained by measuring the residual rubber thickness by an eddy current sensor. How to fix.

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