JP4580221B2 - Tread radius measuring jig - Google Patents

Description

  The present invention relates to a tread radius measurement jig, and more specifically, measures a radius of curvature in a width direction of a tread surface of a pneumatic tire.

  The radius of curvature (radius) in the width direction of the tread surface of the pneumatic tire has a great influence on the performance of the tire. Therefore, if an error occurs in the radius of curvature in the same type of tire, the tire performance cannot be made uniform. Therefore, in all tires, the radius of curvature is measured after manufacturing to prevent a large error.

  As a method of measuring the radius of curvature of the tire tread surface in the width direction, the present applicant provides a measuring method using a profiling device in Japanese Patent Laid-Open No. 3-226615 (Patent Document 1). The measurement method includes measuring the X position and the Y position of the tire outer peripheral surface in a non-contact manner by the X detection means and the Y detection means, with the X axis as the axis of the tire and the Y axis as the axis orthogonal to the X axis. The measured value is divided into a plurality of parts of the tire based on a predetermined reference value (value indicating the width and position of the tread surface), and the radius of curvature (radius) of the divided part is obtained using the divided data. Is obtained by a circular equation.

With the measurement method provided in Patent Document 1, it is possible to measure the radius of curvature with extremely high accuracy, but it takes time and effort to set and input the reference value, and measures the radius of curvature of a large number of tires. There is a problem that it is difficult to do.
JP-A-3-226615

  The present invention has been made in view of the above problems, and is intended to enable efficient measurement of the curvature radius in the width direction of the tread surface of a pneumatic tire using a simple jig while maintaining measurement accuracy. It is an issue.

In order to solve the above-mentioned problem, the present invention is a three-point tread radius measuring jig for measuring a curvature radius in a width direction of a tread surface of a pneumatic tire,
A horizontal support piece disposed in the width direction of the tire;
Both side legs that are suspended from both sides of the horizontal support piece and are brought into contact with both sides in the width direction of the tread surface;
A central elevating leg that hangs up and down in a state of being biased downward from the horizontal support piece at the midpoint of the both side legs, and makes contact with the center of the tread surface;
A groove filler that is attached to the lower ends of the central lifting leg and the both side legs and inserted into the groove of the tread surface;
A displacement meter for detecting the vertical displacement of the central lifting leg,
A camber which is a vertical distance between the both side legs and the center lifting leg detected by the displacement meter in a state where the lower end sides of the both side legs and the center lifting leg are pressed against the tread surface. When the amount is A, the base amount which is the distance in the horizontal direction between the central lifting leg and one of the both side legs is B, and the radius of curvature of the tread surface in the tire width direction is R,
R = (A ² + B ² ) / 2A
The tread radius measuring jig is characterized in that the radius of curvature of the tread surface can be calculated.

According to the above configuration, the tread radius measuring jig is provided with the three legs of the central elevating leg part and the both side leg parts spaced on a straight line, and when measuring the curvature radius in the width direction of the tread surface, these three parts are provided. Since the points are arranged on a straight line in the width direction of the tread surface and are in contact with the tread surface, the tread radius measuring jig does not tilt in the width direction of the tread surface. As a result, the accuracy of the camber amount A, which is the distance in the vertical direction between the both side legs and the central lifting leg detected by the displacement meter, can be increased, and the curvature radius R in the width direction of the tread surface of the pneumatic tire can be accurately determined. It can be calculated well.
Furthermore, the radius of curvature R can be calculated simply by bringing the central lifting leg and both side legs of the tread radius measuring jig into contact with the required portions of the tread surface, and the tire profile is measured as in the conventional example. Compared to the case of calculating the radius of curvature, the radius of curvature R can be calculated efficiently without complicated initial setting.

Specifically, the tread radius measurement jig has a displacement meter above the central lifting leg, and connects the displacement portion protruding downward from the lower end of the displacement meter and the upper end of the central lifting leg. . The displacement portion is attached to a displacement meter so as to be movable up and down, and its position is displaced toward the inside of the displacement meter by external pressure, and the amount of displacement is measured by the displacement meter. Therefore, at the time of radius measurement, the upper end of the central lifting leg pushed up against the tread surface presses the displacement part of the displacement gauge upward, and the amount of vertical displacement of the central lifting leg is measured by the amount of pressing. ing.
Moreover, the displacement part is urged | biased below with the spring etc., and the center raising / lowering leg part connected with this displacement part is also urged | biased below. The central elevating leg is set so that the lower end surface of the central elevating leg and the lower ends of the both side legs are at the same height in a biased state.

When the displacement meter is a digital dial gauge, the vertical displacement of the central lifting leg is displayed on the digital display unit, and the measurer can easily know the vertical displacement of the central lifting leg.
Further, a calculation for calculating a radius of curvature R by means of inputting a base amount B which is a horizontal distance between the central lifting leg and one of the both side legs, and the input base amount B and the camber amount A detected by the measurement. If a means is provided and the calculation result is displayed on the display unit of the displacement meter, the value of the curvature radius R can be obtained together with the measurement of the camber amount A, and the measurement work of the curvature radius R can be performed efficiently. it can.
The input unit and the calculation unit may be provided integrally with the displacement meter, or may be provided separately from the displacement meter and connected to the displacement meter, the input unit, and the calculation unit, respectively. Good.

The center in the width direction of the tread surface with which the lower end of the central lifting leg abuts, that is, the equator line is close to the horizontal plane, and the tread surface is substantially symmetric in the width direction around the equator line. The lower end of the central lifting leg may be a horizontal plane. On the other hand, the position away from the equator line in the width direction of the tread surface generally has a high curvature, so both leg portions that abut on this position have a sharpened bottom end, such as an inverted conical shape, and the tread surface. Point contact is preferred.
In addition, if both side legs can be attached to and detached from the horizontal support piece, and the distance from the central lifting leg can be changed and attached to any position, the radius of curvature can be set regardless of the width of the tread surface. It can be measured and versatility can be improved .

A specific method for measuring the radius of curvature R using the tread radius measurement jig is as follows. First, the groove exists on the tread surface, and the groove filler inserted into the grooves at the lower ends of the central lifting leg and the both side legs is provided. Install.
The mounting on both sides leg from the central elevator leg at a position equidistant respectively (based weight B), with the lower end surface of the central lifting legs downward so that the height and the same height as the lower end of both side legs bias To do.
Next, the length direction of the horizontal support piece is made to coincide with the width direction of the tread surface, the central lifting leg is positioned on the equator line of the tread surface, and the tread radius measuring jig is attached to the groove filling material at the lower ends of the both side legs. It is lowered until the filling into the groove of the door red surface. At this time, the central lifting leg rises relative to the both side legs. This amount of increase, that is, the camber amount A is detected by a displacement meter, and the radius of curvature R in the width direction of the tread surface is calculated by the above formula.

A tape-like contact piece having required rigidity and flexibility is attached to the lower end surface of the central lifting leg portion and extends to the lower ends of the both side leg portions, and the both side leg portions and the central lifting leg portion are through the tape-shaped contact piece may be configured to be contact with the tread surface. Also,
Protruding in the orthogonal direction from the horizontal support piece, a second support piece arranged in the equator direction of the tire is provided, and both supporting leg portions that are in contact with the tread surface from both sides of the second support piece are provided. It is preferable to provide.

According to the above construction, since at the time of measurement does both side leg portions and a central elevator leg groove filling material of the lower end of the direct contact with the tread surface, there is no risk of damaging the bets red surface.

In addition, since both side legs for support are provided on both sides of the central lifting leg in the equator direction, it is possible to prevent the tread radius measuring jig from being inclined in the equator direction of the tread surface, and the camber with higher accuracy. By detecting the amount A, an accurate radius of curvature R can be calculated.
Moreover, it can confirm visually that the center raising / lowering leg part is arrange | positioned on the equator line by the 2nd support piece extended in an equator direction, and the position shift to the tread surface width direction of a center raising / lowering leg part is prevented. Can do.

As described above, attach the groove filling material to insert into the groove before Symbol tread surface in the central lifting leg end and the bottom of the two side legs. The front Symbol central lifting leg, it is preferable if you have installed a pre Symbol tape-shaped contact piece under end of each side leg is configured to attach to the lower surface of the tape-like contact piece.

  According to the above configuration, since the groove filling material is fitted into the grooves facing both the side legs and the central lifting leg to fill the groove, the both side legs and the central lifting leg do not enter the groove, The accuracy of the radius of curvature R to be measured is not lowered.

  It is preferable that the central elevating leg portion, the both side leg portions and the tape-shaped contact piece are made of metal, while a magnet is attached to the groove filling material so as to be detachably attached.

According to the above configuration, since it is possible to attach an appropriate groove filler according to the presence / absence of a groove facing the central elevating leg part and both side leg parts and the groove shape, it is possible to cope with the radius measurement of various tires, and the tread. The versatility of the radius measurement jig can be enhanced.
For example, if there is no groove at the position facing the central lifting leg and both side legs, it is not necessary to attach a groove filler. If there is a groove, a groove filler suitable for the shape of the groove is inserted via a magnet. Just install it.

The groove filling material is required rigidity, elasticity, flexibility having, for example, formed from materials such as kneading natural rubber, comb-shaped member in which an incision from the lower end, the elasticity of the groove shape and similar or the same shape It is preferably made of a hollow material or an elastic solid material.

  According to the above configuration, since the groove filling material is made of elastic material, or the groove filling material is given elasticity by cutting or hollowing, the groove filling material depends on the shape of the groove. The radius of curvature R can be accurately measured by deforming and fitting into grooves of different shapes. Since these groove filling materials can be deformed in accordance with the shape of the groove, they can cope with various groove shapes and can enhance versatility.

  The groove filling material is preferably made of a resin material or metal material having rigidity, is fitted into the inserted groove, and has a height substantially equal to the depth of the groove.

According to the above configuration, since the height of the groove filler is substantially the same as the depth of the groove to be inserted, the groove filler is fitted into the groove, so that the groove has no groove on the tread surface. Thus, a more accurate radius of curvature can be measured.
Further, when the groove filling material has a shape substantially similar to the groove shape, the tread radius measuring jig can be positioned at an appropriate position by inserting the groove filling material into the groove.

It is preferable that the groove filling material is attached to the lower surface of the tape-shaped contact piece at the lower end of the central lifting leg and is filled in a groove located at the center in the width direction of the tread surface.
Many tires have a wide groove on the equator line, which is the center of the tread surface in the width direction. In such a case, when the tread radius measurement jig is pushed downward, the central lifting leg is taped. There is a risk of entering the groove together with the contact piece. Thus, if the central lifting leg enters the groove, the accurate camber amount A cannot be measured. Therefore, as described above, when there is a large groove at a position facing the central lifting leg, it is preferable to attach a groove filler to the lower surface of the tape contact piece at the lower end of the central lifting leg.

As described above, according to the present invention, the horizontal support piece arranged in the width direction of the tread surface is provided with three points, that is, the central lifting leg portion and the both side leg portions, and the curvature radius in the width direction of the tread surface is set. At the time of measurement, these three points are brought into contact with the straight line in the width direction of the tread surface, so that the tread radius measurement jig does not tilt in the width direction of the tread surface. As a result, the accuracy of the camber amount A, which is the vertical distance between the both side legs and the central lifting leg detected by the displacement meter, can be increased, and the curvature radius R in the width direction of the tread surface of the pneumatic tire can be accurately set. Can be calculated.
Further, the radius of curvature R can be calculated simply by bringing the central lifting leg and both side legs of the tread radius measuring jig into contact with the required portions of the tread surface, and the tire profile is measured and the curvature is measured as in the conventional example. The curvature radius R can be calculated more efficiently than in the case of calculating the radius.

  In addition, if both side legs for support are provided on both sides of the central lifting leg in the equator direction, it is possible to prevent the tread radius measuring jig from being inclined in the circumferential direction of the tread surface. , And an accurate radius of curvature R can be calculated.

Further, the lower end of the central lifting leg and bilateral legs against toward the groove provided in the preparative red face, attach the groove filling material to be inserted into the groove, the groove filling material on both sides leg and the central elevation Since the groove is filled by being fitted in the groove facing the leg part, the both side leg parts and the central lifting leg part do not enter the groove, and the accuracy of the curvature radius to be measured is not lowered.

Embodiments of the present invention will be described with reference to the drawings.
1 through 4 show a reference implementation of the invention, the tread radius measurement jig 10, the pneumatic tire 20 of curvature in the width direction of the tread surface 21 (hereinafter, referred to as tire 20) radius (radius) R is measured.

  As shown in FIG. 1, the horizontal support piece 11 of the radius measurement jig 10 is provided at the center in the length direction so as to be able to move up and down in a state where a central lifting leg 12 is biased downward. At the same time, both leg portions 13A and 13B are suspended from both sides.

  As shown in FIGS. 1 and 3, a displacement gauge 14 for detecting the vertical displacement of the central lifting leg 12 is provided above the central lifting leg 12, and is directed downward from the lower end of the displacement gauge 14. The projecting displacement part 14a is projected downward through a through hole 11a drilled in the center of the horizontal support piece 11, and the lower end of the displacement part 14a is connected to the upper end 12a of the central lifting leg 12. The displacement portion 14a is attached to the displacement meter 14 so as to be movable up and down while being urged downward by an urging means (not shown) provided in the displacement meter 14, and accordingly, the displacement portion 14a is attached to the displacement portion 14a. The connected central lifting leg 12 is also suspended from the horizontal support piece 11 so as to be lifted and lowered while being biased downward. The lower end surface 12b of the central elevating leg portion 12 is a horizontal plane and is a surface that is brought into contact with the tread surface 21 on the equator line at the time of radius measurement.

Further, a tape-like contact piece 15 made of a metal material or a resin material having required rigidity and flexibility is attached to the lower end surface 12b of the central elevating leg portion 12, and the tape-like contact piece 15 is attached to the lower end surface 12b. It extends to the lower end of both leg portions 13A.
The tape-like contact piece 15 is attached only to the lower end surface 12b of the central lifting leg 12 and is not bonded to the lower ends of the both side legs 13A, 13B.

  The both-side leg portions 13A and 13B are composed of an inverted conical leg portion main body 13a and a thin-shaft screw portion 13b protruding from the large-diameter end of the leg main portion 13a. The threaded portion 13b is passed through the mounting hole 11b formed in the horizontal support piece 11 from below, and the nut N is screwed into the threaded portion 13b projecting upward from the mounting hole 11b and tightened. 13B is detachably attached to the horizontal support piece 11. Further, the mounting holes 11b provided in the horizontal support piece 11 are elongated holes extending from the vicinity of both ends in the length direction to the vicinity of the through hole 11a provided in the center, and the both side legs 13A and 13B are provided to the horizontal support 11 It can be attached to any position in the length direction.

  As described above, the central lifting leg 12 is biased downward, and the lower end surface 12b of the central lifting leg 12 and the lower ends 13a-1 of the both side legs 13A and 13B are normal at times other than radius measurement. The height of the central elevating leg 12 is set in advance so that and become the same height. Therefore, when the central lifting leg 12 and the both side legs 13 are brought into contact with the tread surface 21 of the tire 20, the vertical displacement amount of the central lifting leg 12 detected by the displacement meter 14 is below the central lifting leg 12. This corresponds to the camber amount A that is the distance in the vertical direction between the end surface 12b and the lower ends 13a-1 of the both side leg portions 13A, 13B.

  Further, the tread radius measurement jig 10 is provided with a second support piece 16 that is orthogonal to the horizontal support piece 11 and extends in the horizontal direction, and both supporting leg portions from both sides of the second support piece 16. 17 is suspended. The supporting side legs 17 include a flat plate portion 17a at the lower end, a support bar 17b protruding upward from the upper end of the flat plate portion 17a, a large diameter portion 17c to be brought into contact with the lower surface of the second support piece 16, It consists of a thin-shaft threaded portion 17d at the upper end. The threaded portion 17d is passed through the mounting hole 16a formed in the second support piece 16 from below, and the nut N is screwed into the threaded portion 17d protruding upward from the mounting hole 16a and tightened. The leg 17 is detachably attached to the second support piece 16. The mounting holes 16a provided in the second support piece 16 are elongated holes extending from the vicinity of both ends in the length direction to the vicinity of the center, and the supporting both side legs 17 are arranged in the length direction of the second support piece 16. It can be attached to any position.

On the second support piece 16, two elevating part support rods 18 that support an elevating part 41, which will be described later, are erected upward. A spring 19 for urging is wound around the lower outer peripheral surface of the elevating part support bar 18 and the upper side of the elevating part support bar 18 is passed through the through hole 40a of the connecting member 40 to raise and lower the connecting member 40. The lifting part support rod 18 is freely attached.
The connecting member 40 extends in a vertical direction at a side position of the lifting / lowering support rod 18, and a mounting piece 14 c protruding from the back side of the display portion 14 b of the displacement meter 14 is bolted and fixed to the upper end. The horizontal support piece 11 is fixed by bolting. Therefore, the horizontal support piece 11 and the displacement meter 14 are attached to the elevating part support bar 18 so as to be movable up and down while being biased upward by the spring 19 via the connecting member 40. As described above, the horizontal support piece 11 and the displacement meter 14 are connected by the connecting member 40, and the connecting member 40, the horizontal support piece 11, the displacement meter 14, the central lifting / lowering leg portion 12, and the both side leg portions 13, 41 is formed.

Further, the tread radius measuring jig 10 includes a tip 13a-1 corresponding to the center point of the horizontal support piece 11 of the central lifting leg 12 in the length direction and the center point of either one of the both foot portions 13A (13B). An input means (not shown) for inputting a base amount B, which is a horizontal distance between the camber amount A, and a calculating means (not shown) for calculating a radius of curvature R from the camber amount A and the base amount B. 14 is provided. An equation R = (A ² + B ² ) / 2A for calculating the curvature radius R is input to the calculation means, and the curvature radius R is calculated from the camber amount A detected by the displacement meter 14 and the base amount B input in advance. Can be calculated.
The formula R = (A ² + B ² ) / 2A is obtained by the following method. That is, as shown in FIG. 4, the center point of the virtual circle C partially including the curve in the width direction of the tread surface 21 to be measured is O, the contact point between the tread surface 21 and the both side legs 13 is P1, and the tread. A contact point between the surface 21 and the central lifting leg 12 is P2, and a right triangle is formed by straight lines OP1 and OP2 and a perpendicular line from P1 to the straight line OP2. In the right triangle, R ² = (R−A) ² + B ² is established, and the formula R = (A ² + B ² ) / 2A is obtained.
The input means and the calculation means may be provided in a calculation device different from the displacement meter 14 and connected to the displacement meter 14. Further, without providing the input means and the calculation means, the measurer may calculate the curvature radius R by applying the camber amount A and the base amount B detected by the displacement meter 14 to the above equation.

Next, a method for measuring the curvature radius R in the width direction of the tread surface 21 of the tire 20 using the tread radius measurement jig 10 will be described.
First, the side legs 13A and 13B are attached to the required positions of the horizontal support piece 11. Both leg portions 13A and 13B are attached at positions equidistant from the central lifting leg portion 12, respectively.
Next, the base amount B, which is the distance in the horizontal direction between the central lifting leg 12 and the side legs 13, is input to the input means.
Next, the heights of the lower end 13a-1 of the both side legs 13 and the lower end surface 12b of the central lifting leg 12 are set to the same height, and the camber amount A of the displacement meter 14 at this time is set to 0 as a reference value. Keep it.

Next, the length direction of the horizontal support piece 11 is made to coincide with the width direction of the tread surface 21, and the central lifting leg 12 is placed on the equator line which is the center of the tread surface in the width direction. At this time, the lower end surface of the flat plate portion 17a of the supporting both side leg portions 17 is in contact with the tread surface 21 on both sides of the tread surface 21 in the equator direction, and the central elevating leg portion 12 is inclined in the equator direction of the tread surface 21. Without contacting the tread surface 21 in the vertical direction.
Next, the lower end 13 a-1 of the both side legs 13 is connected via the tape-shaped contact piece 15 to the elevating part 41 composed of the connecting member 40, the horizontal support piece 11, the displacement meter 14, the central elevating leg part 12 and the both side legs 13. It is lowered until it comes into contact with the tread surface 21. At this time, the central elevating leg 12 does not descend because it is in contact with the tread surface 21, rises relative to the both side legs 13, and presses the displacement part 14 a of the displacement meter 14 upward.
Finally, the lowering of the elevating part 41 is stopped when the central elevating leg part 12 and the both side leg parts 13A, 13B abut on the tread surface 21 via the tape-like abutting piece 15. At this time, the camber amount A is detected by the displacement meter 14, and the curvature radius R in the width direction of the tread surface 21 is calculated by the calculating means.

According to the above configuration, the central lifting leg 12 and the both side legs 13A and 13B are provided at intervals in the width direction of the tread surface, and these three points are in contact with the tread surface, respectively. 10 does not incline in the width direction of the tread surface 21, and the accuracy of the camber amount A to be detected can be increased. Thereby, the radius of curvature R in the width direction of the tread surface 21 of the tire 20 can be accurately calculated.
In addition, since both supporting leg portions 17 are provided on both sides of the central elevating leg portion 12 in the equator direction, the radius measuring jig 10 is prevented from being inclined in the equator direction of the tread surface 21, and the camber is accurately provided. By detecting the amount A, an accurate radius of curvature R can be calculated.
Further, as described above, the radius of curvature R can be calculated simply by bringing the central lifting leg 12 and the both side legs 13A and 13B of the radius measurement jig 10 into contact with the tread surface 21, and the tire as in the conventional example. The curvature radius R can be calculated more efficiently than the case where the curvature radius is calculated by measuring the profile.

5 and 6 show an implementation form of the present invention.
The radius measurement jig 10 ′ of this embodiment is suitably used for measuring the radius of curvature R of the tread surface in which the groove 22 is provided on the equator line.
Specifically, on the lower surface side of the metal tape-like contact piece 15 ′, the groove filler 30 is disposed at a position facing the central lifting leg 12 ′ via a magnet 33 bonded to the groove filler 30. Removably attached.

The groove filler 30 is made of an elastic material such as unvulcanized rubber and has a trapezoidal shape in which the vertical cross section of the outer shape decreases in the downward direction as shown in FIG. It is almost the same as the size. The lower end surface of the groove filler 30 is provided with elasticity by providing a plurality of cut portions 32 and can be deformed depending on the shape of the groove. Furthermore, as shown in FIG. 5B, if the cut width is increased and the lower end side is formed in a comb-teeth shape, even greater elasticity can be imparted. In this embodiment, the width of the upper end of the groove filler 30 is 11 mm, the width of the lower end is 5 mm, and the height is 7 mm.
In addition, as shown in FIG. 5C, elasticity may be imparted by providing a hollow portion 31 in the center of the groove filler 30.
When an elastic material having a high elastic force is used, as shown in FIG. 5 (D), a solid groove filling material 30 in which neither a hollow portion nor a cut portion is provided may be used. In the case of the groove filler shown in FIGS. 5C and 5D, the shape of the groove filler is similar to or the same as the groove shape into which the groove filler is inserted.

Tread radius measurement jig 10 'of the present embodiment the measuring method of the radius of curvature R of the tread surface 21 using, the reference is substantially similar to the measuring method of implementation form, radius measurement jig 10' of the tire 20 When placing on the tread surface 21, first, as shown in FIG. 6, the groove filler 30 is buried in the groove 22 on the equator line. In this state, similarly to the reference implementation form lowers the tread radius measurement jig 10 ', by detecting the camber quantity A, and calculates the radius of curvature R.
Incidentally, other configurations and other method of measuring radius measurement jig is omitted because the same reference implementation form.

According to the configuration, even if the grooves 2 2 is provided on the equator line of the tread surface 21, by burying the groove filling material 30 in the groove 2 2, central lifting leg 12 'enter into the grooves 2 2 Therefore, the camber amount A can be detected with high accuracy, and the accurate radius of curvature R of the tread surface 21 can be calculated.
In addition, the groove filling material 30 is formed of an elastic material, and the hollow portion 31 is provided, or the cut portion 32 is provided on the lower end surface to provide elasticity, so that various grooves having different sizes and shapes can be provided. It becomes possible to be buried, and versatility can be improved.
In this embodiment, the groove filling material 30 is attached to the tape-like contact piece 15 ′ via a magnet. However, the groove filling material 30 is adhered to the tape-like contact piece 15 ′ using an adhesive or the like. May be.
Further, in this embodiment, the groove filler 30 is attached at a position facing the central lifting leg 12 ′ , but grooves are provided at positions facing the both side legs 13 A ′ and 13 B ′ of the tread surface 21. If you are the both side leg portions 13A ', 13B' Ru fitted with a groove filling material 30 to the position facing.

7, the shows a modification of the implementation form, formed of a resin material or metal material having a rigidity groove filling material 30 ', with a shape that is fitted into the groove 22 to be inserted, the height Is substantially the same as the depth H of the groove 22. The groove depth H is the depth from the top of the virtual curve L of the tread surface 21 to the groove bottom surface 22a when there is no groove 22. Thereby, the camber amount A with higher accuracy can be detected, and the accurate radius of curvature R can be calculated.
Further, not only the height of the groove filling material 30 ′ and the depth of the groove 22 are made substantially the same, but if the shape of the groove filling material 30 ′ is made substantially the same as the shape of the groove 22 at the measurement position, the groove filling material. By fitting 30 ′ into the groove 22, the tread radius measuring jig 10 ′ can be easily positioned with respect to the tread surface 21.

It is a rear view of the radius measuring jig reference implementation of the invention. It is a top view (upper side is a front side) of a radius measurement jig. It is a left view of a radius measurement jig. It is drawing which shows the state which is measuring the curvature radius of the tread surface of a tire using a radius measurement jig | tool. (A) ~ (D) are views illustrating the groove filling material provided on the radius measurement jig implementation form of the present invention. Wherein a drawing showing a state of measuring the radius of curvature of the tread surface of the tire with a radius measurement jig implementation forms. Wherein is a view showing a modified example of the implementation form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radius measurement jig | tool 11 Horizontal support piece 12 Center raising / lowering leg part 12b Lower end surface 13A, 13B Both-sides leg part 13a-1 Lower end 14 Displacement meter 15 Tape-like contact piece 16 Second support piece 17 Supporting both side leg part 20 Air Entered tire 21 Tread surface 22 Groove 30 Groove filler 31 Hollow part 32 Cut part

Claims (7)

A three-point tread radius measurement jig for measuring a radius of curvature in the width direction of a tread surface of a pneumatic tire,
A horizontal support piece disposed in the width direction of the tire;
Both side legs that are suspended from both sides of the horizontal support piece and are brought into contact with both sides in the width direction of the tread surface;
A central elevating leg that hangs up and down in a state of being biased downward from the horizontal support piece at the midpoint of the both side legs, and makes contact with the center of the tread surface;
A groove filler that is attached to the lower ends of the central lifting leg and the both side legs and inserted into the groove of the tread surface;
A displacement meter for detecting the vertical displacement of the central lifting leg,
A camber which is a vertical distance between the both side legs and the central lifting leg detected by the displacement meter in a state where the lower end sides of the both side legs and the central lifting leg are pressed against the tread surface. When the amount is A, the base amount which is the distance in the horizontal direction between the central lifting leg and one of the both side legs is B, and the radius of curvature of the tread surface in the tire width direction is R,
R = (A ² + B ² ) / 2A
The tread radius measuring jig is characterized in that the radius of curvature of the tread surface can be calculated. A tape-like contact piece having required rigidity and flexibility is attached to the lower end surface of the central lifting leg portion and extends to the lower ends of the both side leg portions, and the both side leg portions and the central lifting leg portion are It is configured to be in contact with the tread surface through a tape-shaped contact piece, and
The tread radius measurement jig according to claim 1, wherein the groove filler is attached to a lower surface of the tape-shaped contact piece . Protruding in the orthogonal direction from the horizontal support piece, a second support piece arranged in the equator direction of the tire is provided, and both supporting leg portions that are in contact with the tread surface from both sides of the second support piece are provided. tread radius measuring jig according to claim 1 or claim 2 is provided. The central lifting leg, while the both side leg portions and the tape-shaped contact piece is made of metal, the groove a magnet is attached to the filler, removably attached to constitute a capable and has claim 1 or claim 2 tread radius measuring jig according to. The groove filling material is required rigidity, elasticity, flexibility and formed of a material having a comb-tooth-like material in which incisions the lower end, an elastic hollow material or in the elastic solid material of the groove shape and similar or the same shape It becomes claims 1 to tread radius measuring jig according to claim 4. The groove filling material is formed of a resin material or metal material having a rigidity, the inserted claims 1 to have a depth and substantially the same height of the groove with a shape that is fitted into the groove 4 The tread radius measuring jig described in 1. Wherein the groove filling material attached to the lower surface of the tape-shaped contact piece of the lower end of the central lifting leg, claims 2 to are intended to be filled in a groove located in the center of the width direction of the tread surface 6 The tread radius measuring jig according to any one of the above.

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