Patent Description:
Various circular members (circular members and annular members) such as bead members and cylindrical rubber members are used in the manufacture of a rubber product such as a tire. The inner circumferential length of such a circular member has a preset setting value designated by the design. However, due to a manufacturing error or the like, the actual inner circumferential length of the circular member may differ from the preset setting value. In a case where this deviation is within a tolerance range, there is no problem. However, in a case where this deviation is outside of this tolerance range, the rubber product manufactured using the circular member may have quality problems. Thus, the inner circumferential length of the circular member needs to be measured and determined.

In the related art, various measuring devices for the inner circumferential length of an annular bead member have been proposed (for example, see Patent Documents <NUM> and <NUM>). In the device described in Patent Document <NUM>, a cylindrical measurement support including two semicylindrical sections is disposed on the inner side of a bead member. In measuring the inner circumferential length of the bead member, the sections are moved away from each other and the outer circumferential surfaces of the sections are put in close contact with the inner circumferential surface of the bead member. The separation distance between the sections at this time and the circumferential length around the outer circumferential surfaces of the sections are used to measure the inner circumferential length of the bead member. However, because the outer circumferential surfaces of the sections are put in close contact with the inner circumferential surface of the bead member, force pushing to expand the diameter of the bead member is applied. This may cause deformation. Thus, this is not advantageous in improving the accuracy in measuring the inner circumferential length.

In the device described in Patent Document <NUM>, a roller is directly brought into contact and pushed against an inner circumferential surface of a bead member. The roller is rolled along the inner circumferential surface of the bead member for one rotation in the circumferential direction. The number of times the roller rotated is used to measure the inner circumferential length of the bead member. However, because the roller directly comes into contact and pushes against the inner circumferential surface of the bead member, deformation may occur. Thus, this is not advantageous in improving the accuracy in measuring the inner circumferential length.

<CIT> discloses a circumferential length measurement method for a tire wherein a laser sensor is rotated along the inner circumference of the tire.

An object of the present invention is to provide an inner circumferential length measurement method for a circular member capable of accurately measuring an inner circumferential length without applying an unnecessary load of the circular member.

To achieve the object described above, an inner circumferential length measurement method for a circular member according to claim <NUM> is provided.

According to an embodiment of the present invention, the inner circumferential length of the circular member placed flat in an unrestrained state on the support is measured using the two-dimensional sensor without the two-dimensional sensor coming into contact with the circular member. Thus, an unnecessary load is not applied to the circular member, and thus deformation thought obligatory does not occur. This is advantageous in measuring the inner circumferential length of the circular member with high accuracy.

An inner circumferential length measurement method for a circular member according to embodiments of the present invention will be described in detail below with reference to embodiments illustrated in the drawings.

An inner circumferential length measurement method for a circular member according to an embodiment of the present invention uses an inner circumferential length measuring device <NUM> (referred to as measuring device <NUM> below) for a circular member illustrated in <FIG> and <FIG>. In an embodiment of the present invention, the inner circumferential length can be measured for various circular members <NUM> (circular members and annular members) such as bead members and cylindrical rubber members used in a rubber product such as a tire. In <FIG>, the circular member <NUM> is indicated by a two-dot chain line. When measuring, a single circular member <NUM> is set in the measuring device <NUM>.

The measuring device <NUM> includes a support <NUM> on which the circular member <NUM> to be measured is placed, a two-dimensional sensor <NUM> disposed allowing for movement independent of the support <NUM>, a rotation driving mechanism 10a configured to rotate the two-dimensional sensor <NUM>, and a calculation unit <NUM> configured to receive measurement data from the two-dimensional sensor <NUM>. As the calculation unit <NUM>, various kinds of computers can be used.

The circular member <NUM> is placed flat in an unrestrained state on the horizontally orientated support <NUM>. "Unrestrained state" is a state in which no external forces other than those relating gravitational forces (empty weight) are acting upon the circular member <NUM>. In this embodiment, the support <NUM> includes a plurality of sections <NUM> divided in the circumferential direction. Each section <NUM> includes on an upper surface a protrusion-like support portion <NUM> that projects upward. The circular member <NUM> is placed flat in an unrestrained state on the protrusion-like support portions <NUM>. The protrusion-like support portion <NUM> extends in a rod-like manner in the radial direction of the circular member <NUM>.

The support <NUM> may be formed as an undivided single plate body instead of including the sections <NUM>. The number of protrusion-like support portions <NUM> is at least three, with a suitable number ranging from three to twelve, for example.

The support <NUM> is attached to a frame <NUM>. The frame <NUM> includes a base frame 2a and a movable frame 2b, and the movable frame 2b is connected to the base frame 2a at one end in a manner allowing for rotation. The movable frame 2b is able to be raised off the base frame 2a via a raising mechanism <NUM>. For example, as illustrated in <FIG>, the movable frame 2b is raised a predetermined angle range from a horizontal state to a vertical state, taking an upright state. Accordingly, the support <NUM> also can be raised from a horizontal state to an upright state. A hydraulic cylinder or the like can be used as the raising mechanism <NUM>.

A plurality of projection portions <NUM> are provided on the surface of the support <NUM> spaced from one another, the projection portions <NUM> projecting from the surface. The projection portions <NUM> are moved via a retracting mechanism 7a allowing them to retract from the surface of the support <NUM>. An air cylinder, a hydraulic cylinder, and the like can be used as the retracting mechanism 7a. Two projection portions <NUM> work as a set, and the space between and position of the projection portions <NUM> of a set in a plan view is set based on the inner diameter of the circular member <NUM> to be measured.

The two-dimensional sensor <NUM>, in a plan view, is disposed in a central portion of the support <NUM> and disposed inward of the circular member <NUM> placed flat on the support <NUM>. The two-dimensional sensor <NUM> is capable of movement in the radial direction of the circular member <NUM> via a horizontal movement mechanism 10b. This allows the two-dimensional sensor <NUM> disposed facing an inner circumferential surface 12a of the circular member <NUM> placed flat to be moved in the direction toward the inner circumferential surface 12a and away from the inner circumferential surface 12a.

The two-dimensional sensor <NUM> and the horizontal movement mechanism 10b, in a plan view, are disposed at a predetermined position on the support <NUM> (for example, the center of the support <NUM>) and are supported by a rotation shaft <NUM> configured to extend and retract vertically. The rotation shaft <NUM> is driven in rotation by the rotation driving mechanism 10a about the axial center thereof. Accordingly, the two-dimensional sensor <NUM> is driven in rotation about the rotation shaft <NUM>.

A laser sensor can be used as the two-dimensional sensor <NUM>. The two-dimensional sensor <NUM> is configured to measure a separation distance d from the two-dimensional sensor <NUM> to the inner circumferential surface 12a in a non-contact state with the circular member <NUM> by reflecting a laser beam of the inner circumferential surface 12a and receiving the reflected laser beam. The two-dimensional sensor <NUM> is configured to measure the separation distance d from the two-dimensional sensor <NUM> and the inner circumferential surface 12a in the range irradiated by radiating a laser beam not at one point of the inner circumferential surface 12a but in a single instance radiating a lengthwise area.

The separation distance d measured by the two-dimensional sensor <NUM> is entered into the calculation unit <NUM>. Additionally, a distance w from the position of the rotation shaft <NUM> (axial center) to the two-dimensional sensor <NUM> in a plan view is entered into the calculation unit <NUM>.

The process of measuring an inner circumferential length L of the circular member <NUM> using the measuring device <NUM> will be described below.

To place the circular member <NUM> flat on the support <NUM>, firstly, the support <NUM> is put in an upright state at a predetermined angle as illustrated in <FIG>. Then, two of the projection portions <NUM> chosen based on the inner diameter of the circular member <NUM> are made to project from the surface of the support <NUM>. The inclination angle of the support <NUM> in an upright state with respect to the horizontal ranges from <NUM>° to <NUM>°.

Next, the circular member <NUM> is placed on the support <NUM> with the inner circumferential surface 12a of the circular member <NUM> engaging with the two projection portions <NUM> projecting from the surface of the support <NUM>. Accordingly, the circular member <NUM> is put in a state in which the inner circumferential surface 12a is supported by the two projection portions <NUM> and a lower surface 12b is supported by the protrusion-like support portions <NUM>. A crane or the like can be used to place large-sized circular members <NUM>.

Next, as illustrated in <FIG>, the support <NUM> is lowered to a horizontal state by the raising mechanism <NUM>. Thereafter, the projection portions <NUM> are retracted under the surface of the support <NUM>. This puts the circular member <NUM> flat on the support <NUM> in an unrestrained state.

By placing the circular member <NUM> on the support <NUM> in an upright state in such a manner, large-sized and heavy circular member <NUM> can be placed on the support <NUM> in a relatively small space. The inner diameter of the circular member <NUM> measured as the inner circumferential length L is not particularly limited in the present invention, and, for example, the inner diameter in embodiments of the present invention can range from <NUM> to <NUM>. By the inner circumferential surface of the circular member <NUM> engaging with the two projection portions <NUM> on the support <NUM> in an upright state, the circular member <NUM> can be positioned on the support <NUM>.

Additionally, when the support <NUM> in an upright state is brought to a horizontal state, the circular member <NUM> is placed flat, positioned at a desired position with respect to the support <NUM>. Accordingly, the positions of the projection portions <NUM> are set on the support <NUM> at positions in a plan view where the circular member <NUM> can be positioned at desired position when placed flat. For example, the positions of the projection portions <NUM> are set on the support <NUM> at positions in a plan view such that the position of the center of the circle of the circular member <NUM> when placed flat is in a range equal to or less than <NUM> out from the position of the rotation shaft <NUM>. Additionally, a suitable space between the projection portions <NUM> is ensured, as when the space in a plan view between the two projection portions <NUM> that work as a set is too small, the support <NUM> in an upright state is unsuitable to stably hold the circular member <NUM>.

With different circular members <NUM> of different inner diameters, the positions of the projection portions <NUM> can change so that the circular member <NUM> is positioned at a desired position when placed flat. For example, the two projection portions <NUM> are preferably set at suitable positions and a suitable space in a plan view to correspond to each size of the inner diameters of the circular members <NUM>. In this embodiment, by the positions of and space between the two projection portions <NUM> in a plan view being suitably set, circular members <NUM> of different inner diameter sizes can be set with the center of their circle when placed flat substantially coinciding with the position of the rotation shaft <NUM>. This allows various circular members <NUM> of various inner diameter sizes to be accurately position at a desired position on the support <NUM> and placed flat, granting high versatility.

Next, the two-dimensional sensor <NUM> that faces the inner circumferential surface 12a of the circular member <NUM> is moved as necessary by the horizontal movement mechanism 10b toward the inner circumferential surface 12a and is stopped at a predetermined measurement position. In other words, the two-dimensional sensor <NUM> is moved such that the inner circumferential surface 12a is in a range enabling measurement by the two-dimensional sensor <NUM>. Accordingly, in a case where the inner circumferential surface 12a of the circular member <NUM> placed flat in an unrestrained state on the support <NUM> is in a range of the two-dimensional sensor <NUM> at its initial position enabling measurement, there is no need to move the two-dimensional sensor <NUM> via the horizontal movement mechanism 10b. The horizontal movement mechanism 10b allows the two-dimensional sensor <NUM> to be easily set in a range enabling measurement of various circular members <NUM> of various inner diameter sizes.

Next, as illustrated in <FIG> and <FIG>, the two-dimensional sensor <NUM> positioned at a predetermined measurement position is rotated about the rotation shaft <NUM>, the separation distance d from the two-dimensional sensor <NUM> to the inner circumferential surface 12a is measured, and the separation distances d for the entire circumference of the circular member <NUM> is measured. The measured separation distances d are entered into the calculation unit <NUM>. The distance w in a plan view from the rotation shaft <NUM> to the two-dimensional sensor <NUM> at a predetermined measurement position can be determined, and this distance w is also entered into the calculation unit <NUM>. Accordingly, a distance (w + d) from the axial center of the rotation shaft <NUM> to the inner circumferential surface 12a in a plan view can be determined for the entire circumference of the circular member <NUM>.

The angle the two-dimensional sensor <NUM> rotates about the rotation shaft <NUM> between measuring the separation distance d at one position to measuring the separation distance d at the next position is a minute angle A (rad). For example, the minute angle A is approximately 2n/<NUM> (rad).

One example of the many possible methods of calculating the inner circumferential length L of the circular member <NUM> will be described below. As illustrated in <FIG>, adopting the axial center of the rotation shaft <NUM> as the origin point, a discretionary position P1 (X, Y) on the inner circumferential surface 12a of the circular member <NUM> that is detected by the two-dimensional sensor <NUM> and a position P2 (x, y) that is the position P detected next are specified. The distance from the axial center of the rotation shaft <NUM> to the position P1 in a plan view is w + d1 and the distance from the axial center of the rotation shaft <NUM> to the position P2 is w + d2. The rotational angle from a reference point C to a position P1 is θ, and the coordinates for the position P1 (X, Y) are X = (w + d1)cosθ, and Y = (w + d1)sinθ. The coordinates for the position P2 (x, y) are x = (w + d2)cosθ(θ + A), and y = (w + d2)sinθ(θ + A). The coordinates of the reference point C, the rotational angle θ, the minute angle A, the distance (w + d1) and (w + d2) can be determined, thus the coordinates of the position P1 (X, Y) and the position P2 (x, y) can be found. A minute inner circumferential length L1 for the minute angle A can be approximated to L1 = {(X - x)<NUM> + (Y - y)<NUM>}<NUM>/<NUM>. The calculation unit <NUM> calculates the inner circumferential length L by adding together the minute inner circumferential lengths L1 for the entire circumference of the circular member <NUM>. Note that in <FIG>, the angle is illustrated larger than the actual angle for the sake of describing the minute angle A.

The two-dimensional sensor <NUM> in one instance radiates laser beams in a predetermined lengthwise range in the vertical direction and measures the separation distance d from the two-dimensional sensor <NUM> and the inner circumferential surface 12a in the irradiated range. As the separation distance d obtained when calculating the inner circumferential length L, for example, the separation distance d at a discretionary position in the vertical direction, such as the separation distance d at a center position of the inner circumferential surface 12a in the vertical direction, and the separation distance d at a predetermined position in the vertical direction, can be used.

According to the embodiment described above, the inner circumferential length L of the circular member <NUM> placed flat in an unrestrained state on the support <NUM> is measured using the two-dimensional sensor <NUM> in a non-contact state with the circular member <NUM>. Thus, an unnecessary load is not applied to the circular member <NUM>, and thus deformation thought obligatory does not occur. This is advantageous in measuring the inner circumferential length L of the circular member <NUM> with high accuracy.

In this embodiment, the surface of an adjacent portion of the support <NUM> adjacent to the circular member <NUM> placed flat on the support <NUM> in an unrestrained state includes a low reflection surface 6a configured to diffuse reflect the laser beam radiated from the two-dimensional sensor <NUM>. Specifically, the upper surface and the inner circumferential end surface of the protrusion-like support portion <NUM> are low reflection surfaces 6a blast treated to form minute ridges/grooves in the surface. In this way, a laser beam that hits the upper surface or the inner circumferential end surface of the protrusion-like support portion <NUM> is diffuse reflected and is not received by the two-dimensional sensor <NUM>. Thus, in a configuration in which the two-dimensional sensor <NUM> is configured to radiate a laser beam in an area rather than at a single point, measurement noise when measuring the separation distance d can be reduced.

The projection portions <NUM> are retracted below the surface of the support <NUM> when the two-dimensional sensor <NUM> measures the separation distance d. Thus, the projection portions <NUM> do not block the laser beam radiated from the two-dimensional sensor <NUM>.

Additionally, the circular member <NUM> is supported by the protrusion-like support portions <NUM>, making it easy to align the measurement center of the two-dimensional sensor <NUM> and the center of the inner circumferential surface 12a of the circular member <NUM> in the vertical direction. Furthermore, the inner circumferential surface 12a is suspended at the portions where the circular member <NUM> is not supported by the protrusion-like support portions <NUM>. Thus, the adjacent portions of the support <NUM> adjacent to the inner circumferential surface 12a are kept to a minimum. This is advantageous in reducing measurement noise when measuring the separation distance d via the two-dimensional sensor <NUM>.

Claim 1:
An inner circumferential length measurement method for a circular member (<NUM>), comprising the steps of:
disposing a two-dimensional sensor (<NUM>) at a predetermined measurement position on an inner side of the circular member (<NUM>) placed flat in an unrestrained state on a support (<NUM>), such that the two-dimensional sensor (<NUM>) faces an inner circumferential surface (12a) of the circular member (<NUM>) in a non-contact state;
rotating the two-dimensional sensor (<NUM>) about a predetermined position on the inner side of the circular member (<NUM>);
measuring a separation distance from the two-dimensional sensor (<NUM>) to the inner circumferential surface (12a) around an entire circumference of the circular member (<NUM>); and
calculating an inner circumferential length of the circular member (<NUM>) via a calculation unit (<NUM>) using the separation distance measured and a distance from the predetermined position to the two-dimensional sensor (<NUM>) in a plan view,
characterized in that
the support (<NUM>) is raisable from a horizontal state to an upright state and a surface of the support (<NUM>) is provided with projection portions (<NUM>) spaced from one another, the projection portions (<NUM>) projecting from the surface;
the circular member (<NUM>) is placed flat in an unrestrained state on the support (<NUM>) by, in a case where the support (<NUM>) is in an upright state, engaging the inner circumferential surface (12a) of the circular member (<NUM>) with two of the projection portions (<NUM>) to place the circular member (<NUM>) on the support (<NUM>) and putting the support (<NUM>) in a horizontal state;
the projection portions (<NUM>) are retractable from the surface of the support (<NUM>); and
the projection portions (<NUM>) are retracted below the surface of the support (<NUM>) after the circular member (<NUM>) is placed flat on the support (<NUM>).