Calibrating apparatus of tire testing machine and calibrating method of tire testing machine

A calibrating apparatus of a tire testing machine of the present invention calibrates force components along a lateral direction of a load cell on a tire testing machine provided with a rotary drum and the load cell mounted to a shaft portion of the rotary drum and capable of measuring force applied to the rotary drum, and has a hook member hooked on an outer peripheral edge of the rotary drum, a linear body, one end side of which is connected to the hook member, a load applying member connected to the other end side of the linear body and capable of generating a reference load toward a downward direction, and a pulley device around which the linear body is wound to convert the downward force by the load applying member into an upward force on one end side of the linear body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a calibrating apparatus of a tire testing machine and a calibrating method of the tire testing machine.

2. Description of the Related Art

The tire testing machine for measuring uniformity or the like of a tire is usually provided with a load measuring means, such as a load cell. In the case of a rotary drum having shaft portions in a vertical direction, the load cell is disposed at each of the upper and lower shaft portions one by one. These load cells have a configuration capable of measuring both the vertical load and the horizontal load applied to the rotary drum.

Since the load cells have the configuration capable of measuring both the horizontal load and the vertical load, when calibrating the load cells of the tire testing machine, it is necessary to evaluate whether the measurement results corresponding to a reference load are measured by the load cells, by applying the reference load to the rotary drum in the horizontal direction (a radial direction) and the vertical direction (a lateral direction).

For example, JP 2012-167962 A discloses calibrating the load cells, by attaching a weight having the reference load to the rotary drum via a wire or the like, and by applying the reference load to the rotary drum in the horizontal direction (radial direction) via the wire, when calibrating the load cells.

SUMMARY OF THE INVENTION

The above-described related art discloses “ . . . calibration in the vertical direction of the latter can be performed by directly placing the weight as a reference load on the drum” as well as applying the reference load to the rotary drum in the horizontal direction, but does not disclose a specific aspect thereof.

In addition, in the actual tire test, power in the lateral direction is generated in an upward direction as well as in a downward direction. For that reason, in order to accurately calibrate the load cell, it is necessary to perform the calibration by actually applying the upward force to the rotary drum, but in this respect, the above-described related art does not disclose the specific aspect thereof.

If the calibration is performed using the output values of the load cells obtained in the calibration which applies the load in the downward direction in place of the calibration of the upward force, since the upward force is not actually applied to the load cells in such a calibration, there is a possibility that the output value is not correct, which lacks the accuracy of the calibration.

For example, even if the calibrating method disclosed in JP 2012-167962 A or a calibrating method conceivable from the matters disclosed in JP 2012-167962 A is applied to the load cells that are normal when measuring the downward force, but are abnormal when measuring the upward force, it is not possible to confirm the abnormality as long as the calibration is performed by applying the downward load, and it is not possible to perform the accurate calibration.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a calibrating apparatus and a calibrating method of the tire testing machine capable of accurately performing the calibration of the rotary drum in the lateral direction, by actually applying the upward force to the rotary drum, when performing the calibration of the rotary drum in the lateral direction.

In order to solve the above-described problems, the calibrating apparatus of the tire testing machine of the present invention has the following technical means.

That is, according to the present invention, there is provided a calibrating apparatus that performs calibration of force components along a lateral direction of the load cell on a tire testing machine provided with a cylindrical rotary drum that is rotatably mounted around a shaft portion oriented in a vertical direction, and a load cell that is mounted to the shaft portion of the rotary drum and capable of measuring force applied to the rotary drum, wherein the calibrating apparatus has a hook member that is hooked on an outer peripheral edge of the rotary drum; a linear body, one end side of which is connected to the hook member; a load applying member that is connected to the other end side of the linear body and capable of generating a reference load for calibrating the load cell toward a downward direction; and a pulley device around which the linear body is wound to convert the downward force applied to the other end side of the linear body by the load applying member into an upward force on the hook member side of the linear body.

Preferably, the load applying member may have a weight stacking unit mounted to a leading end of the linear body, and a plurality of weight members that can be stacked on the weight stacking unit.

Preferably, the weight members may be formed in a disc-shaped object, a part of the weight members may be recessed toward a center portion from an outer diameter portion, and the recessed portion may be formed as an insertion hole.

Preferably, handles may be mounted to the outer diameter portion of the weight member.

Preferably, a force measurer capable of measuring the upward force applied to the hook member may be disposed on the linear body between the hook member and the pulley device.

Preferably, a strip-shaped long body formed by a strip-shaped long plate member may be disposed between one end of the linear body extending from the hook member via the pulley device and the load applying member.

Further, according to the calibrating method of the tire testing machine of the present invention, when performing the calibration of the force components along the lateral direction of the load cell using the above-described calibrating apparatus of the tire testing machine, by performing a gradual increase process of adding one weight member stacked on the weight stacking unit to measure the upward force applied to the hook member by the load cell each time, and a gradual decrease process of decreasing one weight member stacked on the weight stacking unit to measure the upward force applied to the hook member by the load cell each time, the load cell is calibrated based on the plurality of measured values of the upward force obtained in the gradual increase process and the gradual decrease process.

According to the calibrating apparatus and the calibrating method of the tire testing machine of the present invention, when performing the calibration of the rotary drum in the lateral direction, by actually applying the upward force to the rotary drum, it is possible to accurately perform the calibration of the rotary drum in the lateral direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Hereinafter, an embodiment of a calibrating apparatus2of a tire testing machine1and a calibrating method of the present invention will be described in detail with reference to the drawings.

FIG. 1schematically illustrates the calibrating apparatus2of the first embodiment.

As illustrated inFIG. 1, the calibrating apparatus2of the first embodiment is configured to perform the calibration of force components along the lateral direction of a load cell5on the tire testing machine1having a cylindrical rotary drum4that is rotatably mounted around a drum shaft3(shaft portion) oriented in the vertical direction, and a load cell5that is mounted to the drum shaft3of the rotary drum4and capable of measuring force acting on the rotary drum4.

First, the tire testing machine1provided with the calibrating apparatus2of the first embodiment will be described below.

The tire testing machine1has a configuration in which the rotary drum4is horizontally moved and pressed against the tire fixed to a spindle6to measure force and moment generated in the rotary drum4when pressed against the tire.

Specifically, the spindle6provided in the tire testing machine1is a rod-shaped member that is disposed to direct the axis in the vertical direction, and is freely rotatable about an axis oriented in the vertical direction. Further, rims7configured to fix the tire so as to be interposed therebetween are provided in the spindle6, and by rotating the spindle6while fixing the tire by the rims7, it is possible to rotate the tire about the axis oriented in the vertical direction. The rims7are mounted to a vertically movable beam member, and when the beam member moves down, the rims7come into close contact with a projecting portion of the top of the spindle6facing the rims7, and it is possible to fix the tire to be interposed therebetween.

Further, the rotary drum4has a cylindrical drum main body8, and a drum shaft3penetrating the center of the drum main body8along the vertical direction. A bearing (not illustrated) is provided between the drum main body8and the drum shaft3, and the rotary drum4is supported by the drum shaft3so as to be freely rotatable about the axis oriented in the vertical direction. On the outer peripheral surface of the rotary drum4, a simulated road surface9is formed, and the tire that is a test target can come into contact with the simulated road surface9. Further, the upper and lower ends of the drum shaft3are mounted to a support frame10having a center formed in a recessed shape when viewed from the front, via a load cell5to be described later using a fastening pin11. Specifically, the upper end of the drum shaft3protrudes upward from the upper surface of the drum main body8, and the upper load cell5is mounted to the protruding end of the drum shaft3protruding upward. Furthermore, the lower end of the drum shaft3protrudes downward from the lower surface of the drum main body8, and the lower load cell5is mounted to the protruding end of the drum shaft3protruding downward.

The load cells5(force measurers) provided at upper and lower positions of the drum shaft3are capable of measuring force (radial direction force) that acts in a direction in which the rotary drum4comes close to or is away from the spindle6, and force (lateral direction force) acting in the vertical direction.

The support frame10that supports the rotary drum4is provided with a slide mechanism12that moves the support frame10forward and backward with respect to the base in the horizontal direction. The slide mechanism12has a rail member13capable of guiding the support frame10along a horizontal direction, and a screw jack member14that is provided on the side of the support frame10to push and pull the support frame10in the horizontal direction, and when the support frame10pushed and pulled by the screw jack member14moves along a laying direction of the rail member13, it is possible to press the outer peripheral surface (simulated road surface9) of the rotary drum4against the tire mounted on the spindle6, or pull the outer peripheral surface apart from the tire. In addition, as the rail member13, for example, it is possible to adopt a linear motion guide or the like.

However, the calibrating apparatus2of the present invention is configured to calibrate the force components along the lateral direction of the load cell5on the above-described tire testing machine1, and has a hook member15hooked on the outer peripheral edge of the rotary drum4, a linear body16, one end side of which is connected to the hook member15, a load applying member17that is connected to the other end side of the linear body16and capable of generating the reference load for calibrating the load cell5toward the downward direction, and a pulley device18around which the linear body16is wound to convert the downward force applied to the other end side of the linear body16by the load applying member17into the upward force on one end side of the linear body16.

Each of the hook member15, the linear body16, the load applying member17, and the pulley device18forming the calibrating apparatus2of the present invention will be described.

As illustrated inFIG. 1, the hook member15is a member that is bent in a U-shape when viewed in the front view, and is hooked on the outer peripheral edge of the rotary drum4. Specifically, the rotary drum4is formed of a cylindrical plate member or the like, the upper edge of the outer periphery of the cylindrical rotary drum4projects upward in the form of eaves, and the lower edge thereof projects downward in the form of eaves. Therefore, the above-described hook member15is hooked so that the bent portion is hooked on the lower edge of the outer periphery (outer peripheral surface). This enables the upward force generated by the load applying member17and transmitted via the pulley device18and the linear body16to be applied to the lower edge of the outer periphery (outer peripheral surface) of the rotary drum4.

The linear body16is a string-shaped (linear) long member that does not break even by applying the maximum load generated by the load applying member17, and a wire rope is used here. As the linear body16, a rope, a sling or the like formed of metal, such as steel or stainless steel, and a synthetic fiber, such as nylon and aramid is used. The above-described hook member15is connected to one end side of the linear body16, and the load applying member17is connected to the other end side of the linear body16. A portion between one end side and the other end side of the linear body16is wound around the pulley device18.

The load applying member17has a weight stacking unit19mounted to the leading end of the linear body16, and a plurality of weight members20capable of being stacked on the weight stacking unit19.

Specifically, the weight stacking unit19is a plate-like member disposed along the horizontal direction, and the upper surface of the weight stacking unit19is formed to be able to place the weight members20in a stacked form. Further, the other end side of the above-described linear body16is connected to the weight stacking unit19such that the weight of the weight member20stacked on the weight stacking unit19is applied to the linear body16.

Further, as illustrated inFIG. 2, the weight member20is formed in a substantially disc shape, for example, using metal such as steel, a insertion hole21through which the linear body16can be inserted is formed at the center thereof in a slit shape, that is, so that a part is recessed to the central portion from the outer diameter portion of the disc-shaped weight member20. Further, two handles25are mounted to the outer diameter portion of the weight member20to interpose the insertion hole21. Thus, the weight member20is configured to be easily stacked or detached by adding the weight stacking unit19in a suspended state. In addition, force generated per each weight member20is about 50 N to 100 N.

With such a configuration, when vertically stacking the plurality of weight members20, in the load applying member17, the plurality of weight members20are mounted on the upper portion of the weight stacking unit19so as not to fall out so that the insertion holes21provided at the center of the stacked weight members20are arranged in the vertical direction, and the linear body16passes through the insertion holes21arranged in the vertical direction.

Furthermore, the weight of the weight member20is set to the reference weight in advance, and by changing the number of the weight members20stacked on the weight stacking unit19, it is possible to adjust the upward force applied to the hook member15. If it is possible to adjust the downward force applied to the other end side of the linear body16in this way, it is also possible to change the upward force applied to the hook member15provided on one end side of the linear body16, thereby performing the calibration of the load cell5, while changing the applied load.

The pulley device18is a fixed pulley mounted at a position higher than the rotary drum4, such as a ceiling and a beam of the production building, in a suspended shape, and is configured such that the position of the pulley does not move up and down.

Specifically, the pulley device18has a bracket22, and a disc-shaped sheave23mounted to the bracket22so as to be rotatable about an axis oriented in the horizontal direction. The bracket22is mounted to the beam member provided with the rim7. As mentioned above, the beam member is configured to be movable up and down as described above, but when practicing the method of calibrating the load cell5in the lateral direction, the beam member is fixed at the upper position.

A groove or the like, around which the linear body16can be wound, is formed on the outer peripheral surface of the sheave23along the circumferential direction. By providing the pulley device18, it is possible to convert the downward force applied to the other end side of the linear body16by the load applying member17into the upward force on one end side of the linear body16(in other words, the hook member15) and transmit the upward force to the rotary drum4.

Next, the method of calibrating the load cell5in the lateral direction using the above-described calibrating apparatus2, in other words, the method of calibrating the load cell5of the present invention will be described in detail.

First, before performing the calibration procedure of the load cell5, a portion bent in a U-shape of the hook member15is hooked on the lower edge of the outer peripheral surface of the rotary drum4as preparation of the calibrating apparatus2. One end side of the linear body16is connected to the hook member15. Moreover, a halfway side in the longitudinal direction of the linear body16is wound around the sheave23of the pulley device18, and the weight stacking unit19of the load applying member17is mounted to the other end side of the linear body16.

When the preparation of the calibrating apparatus2is completed in this manner, a single weight member20is placed on the above-described weight stacking unit19. Then, weight of the single weight member20stacked on the weight stacking unit19is applied to the other end side of the linear body16as a downward force, the direction of force is converted by the pulley device18, and the upward force is applied to one end side of the linear body16. In this way, the upward force measured by the load cell5is first measured when there is one weight member20.

Next, the number of the weight member20stacked on the weight stacking unit19increases one by one to measure the upward force applied to the hook member15by the load cell5each time the number of weight member20increases by one. In this way, a gradual increase process of alternately repeating the addition of the weight member20and the measurement of force in the load cell5as described above is carried out continuously, until the maximum number of weight members20stacked on the weight stacking unit19is obtained.

After the maximum number of the weight members20stacked on the weight stacking unit19is obtained, the upward force is measured, while reducing the number of the weight member20. That is, the number of the weight members20stacked on the weight stacking unit19decreases one by one to measure the upward force applied to the hook member15by the load cell5each time the number of weight member20decreases by one. In this way, the gradual decrease process of alternately repeating the decrease of the weight member20from the weight stacking unit19, and the measurement of force is continuously carried out, until the number of the weight member20stacked on the weights stacking unit19becomes zero again.

Next, the load cell5is calibrated based on the plurality of measured values of upward force obtained in the above-described gradual increase process and gradual decrease process. That is, the values measured by the load cell5in the gradual increase process and the gradual decrease process are plotted with respect to the load applied to the load applying member17calculated from the number of the weight member20, and the gain straight line of the load cell5nearest to the value of the reference load cell5is calculated by least squares method, thereby calibrating the load cell5to achieve the gain straight line.

The specific calibration procedure may be performed in the following order of (1) to (8).

(2) One weight member20(reference weight) is placed. The output value of the load cell5is recorded.

(3) One weight member20is added. The output value of the load cell5is recorded.

(4) Similarly, the weight member20is added, and the value of the load cell5is recorded each time.

(5) The procedure of (4) is performed up to the maximum stacking amount (the maximum number) of the weight member20. The above is the gradual increase process.

(6) The weight member20is next removed in order. The value of the load cell5is recorded each time.

(7) The procedure of (6) is repeated until there is no weight member20. The above is the gradual decrease process.

(8) The calibration is performed by the output value of the load cell5with respect to the load due to the weight member20thus obtained.

If the above-described calibration procedure is performed, it is possible to determine the output value of the load cell5with respect to the reference weight load, that is, the gain straight line, and it is possible to calibrate the load cell5.

In addition, the gain straight line is calculated by connecting the measured value when there is no load (in the case of minimum load) and the measured value when the weight member20is applied to the maximum stacking (in the case of maximum load), only the difference from the gain straight line is recorded between the maximum and minimum values, and it is possible to calibrate the load cell5using the recorded difference load and the gain straight line.

If the above-described calibrating apparatus2is used, since calibration of the load cell5is performed, while actually applying the upward force to rotary drum4, it is possible to more accurately calibrate the load in the lateral direction. Further, in such a calibrating apparatus2, when there is an abnormality in the load cell5when measuring the upward force, it is possible to immediately find the abnormality, thereby more reliably maintaining the accuracy of the load cell5.

Second Embodiment

Next, the calibrating apparatus2of the tire testing machine1of the second embodiment will be described.

As illustrated inFIG. 3, in the calibrating apparatus2of the second embodiment, in the linear body16between the hook member15and the pulley device18, a force measurer capable of measuring the upward force applied to the hook member15is disposed.

That is, the calibrating apparatus2of the second embodiment is provided with a second load cell24(force measurer) in the linear body16between the hook member15and the pulley device18, apart from the load cell5to be calibrated, provided in the rotary drum4. The second load cell24is able to exactly measure the upward force applied to the hook member15, in other words, the upward force applied to the linear body16.

The provision of the second load cell24is for the following reasons.

That is, between the sheave23of the pulley device18and the linear body16, the frictional force is generated more or less, and even if the reference load is applied to the other end side of the linear body16, only the load, from which the generated frictional force is subtracted, is applied to one end side interposing the pulley device18. Therefore, there is a possibility that the measured value measured by the load cell5for calibration does not strictly correspond to the reference load. Of course, in many cases, since the above-described frictional force is very small, it is also possible to calibrate the load cell5without regard to the friction force, but in order to perform the more accurate calibration, it is preferred to directly measure the load applied to one end side of the linear body16, that is, the hook member15.

Therefore, as illustrated inFIG. 4, in the calibrating apparatus2of the second embodiment, by providing the second load cell24in the linear body16between the hook member15and the pulley device18to actually measure the upward force applied to the linear body16, the calibration accuracy of the load cell5is further enhanced.

Specifically, when performing the gradual increase process and the gradual decrease process in the calibrating apparatus2of the second embodiment, if the load measured by the second load cell24is measured each time the weight member20is added or reduced and the gain straight line is calculated using the load measured by the second load cell24and the load measured by the load cell5, more accurate calibration can be performed.

Third Embodiment

Next, a calibrating apparatus2of a tire testing machine1of a third embodiment will be described.

As illustrated inFIG. 5, in the calibrating apparatus2of the third embodiment, a strip-shaped long body26is disposed between one end of the linear body16extending from the hook member15via the pulley device18and the load applying member17.

As illustrated inFIG. 6, the strip-shaped long body26is formed by a strip-shaped long plate member (such as a metal plate) as its name. The strip-shaped long member26is able to prevent the load applying member17from rotating, consequently to prevent the rotation of the weight member20, and to stabilize the load in a shorter time. As illustrated inFIG. 7, the strip-shaped long body26can also be used in the downward calibration.

It should be understood that the embodiments disclosed herein are illustrative in all respects but not restrictive. In particular, in the embodiment disclosed herein, matters which are not explicitly disclosed, for example, the operating conditions and working conditions, various parameters, dimensions, weights, and volumes of the compositions and the like do not depart from the scope usually performed by those skilled in the art, and values that can be easily assumed by those skilled in the art are adopted.