JP6634780B2 - Tire contact stress measurement method - Google Patents

Description

  The present invention relates to a method for measuring a ground contact stress of a running tire.

  The measurement of the contact stress on the contact surface of a tire running on a road surface is important for evaluating the contact characteristics of the tire. An example of such a method for measuring the contact stress of a tire is disclosed in JP-A-2014-21012.

  In this measurement method, stress is measured by a three-component force sensor at each measurement point in a predetermined range in the circumferential direction of the tire, and a contact pressure distribution and a shear force distribution are obtained. On the other hand, the tire is not in contact with the road surface of the drum at one point in the circumferential direction. The tires are in contact with each other in a plane having a range in the tire circumferential direction and axial direction (ground plane). Therefore, even at one point on the tread surface of the tire, it takes time from the start of contact with the ground (called "contact with the ground") to the departure from the contact with the ground (called "out of contact with the ground"). Normally, the stress value at each measurement point changes with time from entering the ground to leaving the ground.

JP 2014-21012 A

  However, the measurement method disclosed in the above publication only measures the change over time for points on the tread surface, but it is not enough to observe the stress distribution of the entire contact surface at a specific point in time. I have not even taught. Therefore, in this measurement method, it is considered that the maximum value or the average value has to be adopted as the stress value at the measurement target point. In this case, an accurate contact pressure and its distribution cannot be obtained. In addition, the measurement points by the three-component sensor are random in a predetermined range in the tire circumferential direction. Some points may not be measured and others may have multiple measurements.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for measuring the contact surface stress distribution of the entire contact surface at a specific point in time.

The method for measuring the tire contact surface stress according to the present invention,
A method for measuring a tire contact surface stress using a test device having a cylindrical drive drum,
The test device includes a rotation angle detector that detects a rotation angle of the tire, a tire stress measurement device installed on a road surface of the drum, and a rotation angle detector that detects a rotation angle of the drum.
While repeating the rotation of the tire and the axial movement of the tire, the time series data of the stress from the point of contact with the road surface to the point of contact with the road surface at each position determined from the axial position and the rotation angle of the tire is calculated for the tire and the drum. A time-series data obtaining step to be obtained in correspondence with the rotation angle of
From the time-series data of each of a plurality of specified measurement points set in the circumferential direction at the same axial position, a stress within a contact length range including any one of the plurality of specified measurement points as a reference measurement point. Contact length data acquisition step of obtaining the contact length data of the tire and the drum in correspondence with the rotation angle of the drum,
A representative contact length data selecting step of selecting one contact length data as representative contact length data from all contact length data obtained in the contact length data obtaining step;
A measurement center setting step of setting a measurement center in the circumferential direction to the representative contact length data selected in the representative contact length data selection step;
Acquisition of ground plane data to obtain ground plane data by specifying the ground plane data that includes the measurement center in the same angle position in the representative ground plane data among other ground plane data different in axial position from the representative ground plane data Steps.

Preferably, in the contact length data obtaining step,
Within the time-series data at each of the plurality of prescribed measurement points close to the reference measurement point, the ground contact length data of the stress is selected by selecting the stress at the time corresponding to the separation distance of the prescribed measurement point from the reference measurement point. obtain.

  Preferably, in the representative contact length data selecting step, the contact length data selected as the representative contact length data is the contact length data having the largest contact length among all the contact length data.

  Preferably, the method further includes a stress display step of displaying the stress in the ground plane obtained in the ground plane data acquisition step together with color information corresponding to the stress value.

  According to the present invention, the ground stress can be measured more accurately by taking into account the temporal change of the stress value at the measurement point on the tire surface.

FIG. 1 is a partial cross-sectional front view schematically showing a test apparatus used for a method for measuring a tire contact surface stress according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of the driving drum and the tire in the test apparatus of FIG. 1 as viewed along the line II-II. FIG. 3 is a graph showing time-series stress measurement data at one point in the tire circumferential direction. FIG. 4 is a graph showing a procedure for obtaining a stress distribution along a tire contact length at a temporary point from time-series data of stresses at a plurality of points in the tire circumferential direction. ) Is a graph showing time-series data of stresses at a plurality of points, and FIG. 4E is a graph showing a stress distribution (contact length data) along the contact length of the tire at one point. FIG. 5 is a diagram schematically showing a grid on which the stress distribution on the ground contact surface of the tire is recorded. FIG. 6 is a graph showing three stresses at one point on the grid shown in FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[Test equipment]
FIG. 1 shows an inside drum type test apparatus 2 used for executing the method for measuring a tire contact surface stress according to the present embodiment. The test apparatus is not limited to the inside drum type, and an outside drum type test apparatus may be employed. The test device 2 includes a tire support device 4 that rotatably supports the tire T, and a drive drum (hereinafter, simply referred to as a drum) 6 that can rotationally drive the tire T. The drum 6 is rotatably supported by a drum support device 8. The drum supporting device 8 includes a rotation driving device (drum driving device) 10 for rotating the drum 6. The rotation speed of the drum driving device 10 can be controlled. The drum 6 has a bottomed cylindrical shape.

  The tire T supported by the tire support device 4 is inserted into the inside of the drum 6 from the opening 18 side of the drum 6. The center axis of the drum 6 and the center axis of the tire T both extend in the horizontal direction. The tire support device 4 can be separated from and approached to the drum 6 in the center axis direction. The tire support device 4 includes a rotation driving device (tire driving device) 12 for driving the tire T to rotate. The rotation speed of the tire driving device 12 can be controlled. By the tire driving device 12, the tire T can rotate without depending on the drum 6. The tire support device 4 also has a braking function of bringing the tire T into a free rotation state and accelerating, decelerating, and stopping the rotation. Each of the above-described rotation driving devices 10 and 12 includes a rotation speed control unit.

  The tire support device 4 includes a lifting device 14. The tire T is moved up and down by the lifting device 14. The lifting device 14 causes the tire T to move away from and close to the road surface 16 of the drum 6. The lifting device 14 can press the tire T against the road surface 16 with an arbitrary load. The lifting device 14 includes a load control unit that controls a load applied to the tire T. When the tire T is pressed against the road surface 16 in a freely rotatable (free rolling) state and the drum 6 rotates, the tire T rotates followingly. When the tire T is pressed against the road surface 16 and driven to rotate while the drum 6 is rotatable, the drum 6 is driven to rotate.

  It is preferable that the inner diameter of the road surface 16 be an integral multiple (for example, three times) of the outer diameter of the tire T or a size close thereto. With such a configuration, as described later, it is possible to efficiently collect data required for measuring the tire contact surface stress.

  The tire support device 4 includes an axis angle control unit that can incline or incline the direction of the center axis of the supported tire T with respect to the center axis of the drum 6 by an arbitrary angle. With this axis angle control means, an arbitrary camber angle and an arbitrary slip angle can be set for the tire T.

  A three-component force sensor 20 as a tire stress measuring device is embedded at at least one location on the road surface 16 of the drum 6. The three-component force sensor 20 is disposed such that its detection part is in contact with the surface of the tire T. For easy understanding of the measurement target of the three-component sensor, the tire axial direction (width direction) is defined as the X-axis direction, the tire circumferential direction is defined as the Y-axis direction, and the tire radial direction is defined as the Z-axis direction. The three-component force sensor 20 detects the shear stress τx in the tire axial direction, the shear stress τy in the tire circumferential direction, and the normal stress in the tire radial direction (referred to as a ground contact pressure) at one position on the tread surface of the tire T. σ can be measured simultaneously.

  On the drum support shaft 8a of the drum support device 8, a rotary encoder (hereinafter, referred to as a drum encoder) 22 as a drum rotation angle detector is installed. A rotary encoder (hereinafter, referred to as a tire encoder) 24 as a tire rotation angle detector is installed on a tire support shaft 4 a of the tire support device 4.

  The test device 2 is provided with a processing device 26 for processing measurement data by the three-component sensor 20 and data detected by the encoders 22 and 24. The processing device 26 includes a CPU, a memory, and the like, and is also connected to an operation panel (not shown).

[Measurement step]
The position of the tire T is adjusted with respect to the drum 6. As the position adjustment, first, the axial position adjustment is performed so that the three-component force sensor 20 is located at a certain position within the width of the tire T. For example, the adjustment is performed so that the three-component force sensor 20 is located substantially at the center of the width of the tire T.

  The tire T and the drum 6 are driven to rotate. Along with the rotation of the tire T and the drum 6, the rotation angle of the drum 6 is detected by the drum encoder 22 from a certain point as a start point. Further, the rotation angle of the tire T is detected by the tire encoder 24 from the start time. The stress measurement may be started from this start point.

  As shown in FIG. 2, with the rotation of the tire T and the drum 6, a position on the tread surface of the tire T, for example, a point A contacts the three-component force sensor 20 and then leaves, that is, the LS with the ground contact. From the ground out LE. This point A is the measurement point A. At the same time, in the processing device 26, the measured values of the three stresses are associated with the rotation angles of the tire T and the drum 6 from the start point. The rotation angle is associated with a certain position on the tire circumference at a certain point in time and a certain position on the drum circumference with respect to all positions on the tire circumference and all positions on the drum circumference. Can be specified (addressed). The three stresses are measured in synchronization with the rotation angle information of the tire T. The measurement data of the three consecutive stresses at the point A is time-series data at the point A.

  The point in time at which a certain position on the tread surface of the tire T comes into contact with the road surface 16 of the drum 6 is referred to as ground contact LS, and the point at which the tire T separates from the road surface 16 is referred to as ground contact LE. Therefore, the time from when the point A comes into contact with the three-component force sensor 20 until it separates is referred to as a ground contact LS to a ground contact LE. The grounded LS corresponds to a point in time when any one of the three stresses occurs at the measurement position, and the grounded out LE corresponds to a point in time when all three stresses have disappeared.

  FIG. 3 is a graph showing the time-series data at the point A. The horizontal axis of this graph represents the elapsed time and also represents the rotation angle position. The vertical axis illustrates the ground contact pressure σ of the three stresses. The shear stress τx in the tire axial direction and the shear stress τy in the tire circumferential direction are similarly recorded, and can be shown in a graph similar to FIG.

  By rotating the tire T and the drum 6 a plurality of times, time-series data is obtained for each of a plurality of different measurement points (for example, points B, C, D,...) In the tire circumferential direction. These time series data are similar to the time series data at point A shown in FIG.

  When the measurement is completed by rotating the tire T a predetermined number of times, the tire T is automatically moved (laterally moved) in the axial direction with respect to the drum 6. The lateral movement distance may be set at equal intervals obtained by dividing the tire width by a predetermined number. The above measurement is automatically performed for each lateral movement. Lateral movement and measurement are automatically repeated. For each lateral movement, measurement data (time-series data) from the ground contact LS to the ground contact LE for each of a plurality of measurement points (for example, each point of A, B, C, D...) On the tread surface is obtained. can get. The measurement data obtained at a plurality of positions in the axial direction is specified as the measurement data obtained at the axial position. The above is the time series data acquisition step.

[Processing step]
In the processing step, the stress distribution on the ground contact surface at a certain point in time is obtained from the time-series data of many points on the tread surface obtained in the measurement step. Time series data of three stresses at a number of measurement points (A, B, C, D, etc.) along a circumferential direction at a certain axial position is input to the processing device 26. Since the tire T and the drum 6 rotate a plurality of times, a plurality of time-series data at a certain point (for example, point A) often exist. Here, it is assumed that adjacent measurement points (A, B, C, D, etc.) are separated by a small angle. There is no data of other measurement points (B, C, D, etc.) in the time-series data at a certain point (for example, point A).

  The points A, B, C, D,... There are measurement points A, B, C, D,... Along the circumferential direction at each position on the axial direction. The circumferential position of each of these points is the same even if the axial position changes. At one axial position, A, B, C, D... Are points, but when viewed from the entire tire tread surface, they can be said to be not the points but the axial lines A, B, C, D. .

  Further, time-series data of each measurement point (A, B, C, D...) Obtained while the tire T is sequentially moved laterally in the axial direction is input to the processing device 26. As described above, when the inner diameter of the road surface 16 is an integral multiple of the outer diameter of the tire T or a size close thereto, time-series data at positions close to each other in the tire circumferential direction is sequentially obtained. That is, the measurement points A, B, C, D,... Are close to each other.

  Hereinafter, a method of obtaining the stress distribution in the ground contact surface at a certain point in time performed in the processing device 26 will be described. It should be noted that the length from the ground contact LS to the ground contact LE at the point A shown in FIGS. 2 and 3 passes over time and cannot be said to be the ground contact length. Here, the contact length refers to the circumferential length of the contact surface.

  First, with reference to FIG. 4, a method for obtaining a circumferential stress distribution (contact length data) at an arbitrary position in the axial direction at a certain point in time will be described. One of the time-series data at point A is selected from among many time-series data measured at a certain axial position on the tread surface. Points A, B, C, D, etc., are referred to as defined measurement points. One of these specified measurement points, for example, point A is selected as a reference measurement point. One of the points B, C, D, etc. may be selected as the reference measurement point. The points such as A, B, C, and D are circumferential positions on the tire tread surface. An arbitrary one of the time series data of the selected reference measurement point A from the ground contact LS to the ground contact LE is set as a reference time. For example, as shown in FIG. 4A, the point of time of A.LS at which the reference measurement point A enters the ground is defined as this reference point a. Time points sequentially separated from the reference time point a by a predetermined small angle in the circumferential direction are specified as specified time points b, c, d,.

  4 (a) to 4 (d) show time-series data. The ground contact of the prescribed measurement point B is indicated by a reference B · LS, and the ground contact thereof is indicated by a reference B · LE. The ground contact of the prescribed measurement point C is indicated by the symbol C · LS, and the ground contact thereof is indicated by the symbol C · LE. The ground contact of the specified measurement point D is indicated by the symbol D · LS, and the ground contact thereof is indicated by the symbol D · LE. FIG. 4E shows contact length data described later. The horizontal axis in FIGS. 4A to 4D represents time, but also corresponds to the rotation angle. The horizontal axis in FIG. 4E represents the distance, but also corresponds to the rotation angle. The vertical axis in each figure indicates the contact pressure. As shown in FIGS. 4 (a) to 4 (d), from a large number of measurement data, the reference time point a and the specified time points b, c, d,... Of each of the above measurement points A, B, C, D.・ Extract stress data in. In FIG. 4, at the time of rotation of the tire and the drum 6, point B precedes point A, point C precedes point B, and point D precedes point C.

  In FIG. 4A, the reference time point a and the specified time points b, c, d,... Are the time points at which the point A has moved from the landing A.LS to the landing A.LE. 4B), the point B has moved from the grounded B.LS to the grounded B.LE in both cases, and in FIG. 4C, the point C has been moved from the grounded C.LS to the grounded C.LS in FIG. 4D. In FIG. 4D, the point D is a point at which the point D has moved from the ground-in D.LS to the ground-out D.LE. In addition, the measurement point corresponds to the reference time and the specified time. For example, in the time-series data of the point A shown in FIG. 4A, the reference time point a and the specified time points b, c, d,... Correspond to the measurement points A, B, C, D,. are doing. In other words, the angle between a and b matches the angle between AB, the angle between bc matches the angle between BC, and the angle between cd matches the angle between CD. The time points a, b, c, d,... May be time points spaced at equal intervals. This interval is set to be equal to or greater than the resolution of the encoder.

  First, time-series data of points A, B, C, D,... Are selected. Next, as to the reference time point a, stress data at the time point at which the point A is at the reference time point a (at the time of A / LS with ground contact) is selected from the time-series data at the point A (FIG. 4A). At the time point b, stress data when the point B is at a time point (angular position) corresponding to the specified time point b is selected from the time-series data at the point B (FIG. 4B). Next, as to the time point c, stress data when the point C is at a time point (angular position) corresponding to the specified time point c is selected from the time-series data at the point C (FIG. 4C). Similarly, at the time point d, the stress data when the point D is at the time point (angular position) corresponding to the specified time point d is selected from the time point data of the point D (FIG. 4D). The same applies hereinafter. The data at the point where the stress value becomes zero is not adopted. Only the data in the ground plane, that is, the data of the points A, B, C, D,.

  Thereby, as shown in FIG. 4 (e), the grounding length (the circumferential length of the grounding surface) including the reference measurement point A at the position of the grounded A · LS at the certain axial position, and Stress data within the range of the contact length is recorded in correspondence with the rotation angle. This is referred to as contact length data as described above.

  As described above, when the selected stress data is made to correspond to the position, as shown in FIG. 4E, the stress distribution along the circumferential direction at the arbitrary position in the axial direction at the one-time point (ground contact) Long data). From FIG. 4E, the ground contact length and the stress distribution within the range of the ground contact length at one position in the axial direction become clear. From this contact length data, it can be seen that the contact surface pressure is lower at the front end and the rear end in the circumferential direction than at the center.

  For each of the prescribed measurement points (B, C, D,...) In the circumferential direction of the tire T, the ground contact length data can be obtained in the same manner as described above. Circumferential length and stress distribution of the ground contact surface including point B at the point of contact B · LS (contact length data at point B), circumferential length of the contact surface including point C at the contact point C · LS And the stress distribution (contact length data at the point C), the circumferential length of the contact surface including the point D in the contact point D · LS, and the stress distribution (contact length data at the point D). it can.

  In this way, the measurement points of the three-component force sensor 20 are arranged at predetermined intervals in a predetermined range in the circumferential direction, instead of being random as in the technique disclosed in the above-mentioned prior art document. sell. In addition, accurate data can be obtained in consideration of the fact that the stress value at a certain point changes with time.

  Next, the same processing as shown in FIG. 4 is performed on measurement data at different axial positions obtained by laterally moving the tire T in the axial direction. That is, at all the positions in the axial direction, the contact length data at the point A, the contact length data at the point B, the contact length data at the point C, the contact length data at the point D,... Can be As described above, ground contact length data at many points in the circumferential direction can be obtained over the entire width of the contact area of the tire tread surface. The above is the contact length data acquisition step.

  As shown in FIG. 5, data having the largest contact length ML is selected from all these contact length data. The maximum contact length ML determines the range of the stress distribution data. For this purpose, the maximum contact length data having the maximum contact length ML is selected from the total contact length data as the representative contact length data. This is the representative ground length data selection step.

  The measurement center MC is set within the range of the maximum contact length ML as a representative of the total contact length data. The measurement center MC is a circumferential position within the range of the maximum contact length ML at the axial position where the maximum contact length ML exists. The measurement center MC corresponds to the rotation angle. The measurement center MC can be specified by the rotation angle from the above-described start point. The measurement center MC is an arbitrary point in the circumferential direction of the tire tread surface, and is constant along the tire axial direction. Therefore, the measurement center MC is indicated by a line (dashed line) in FIG. For example, if the above-mentioned point A exists in the maximum contact length ML, the point A may be designated as the measurement center MC. This is the measurement center setting step.

  When the point A is designated as the measurement center MC, the contact length data D1, D2, D3... Where the measurement center MC is at the point A are collected. That is, from the data of all the positions W whose axial position is different from the maximum contact length ML, the contact length data D1, D2, D3... Where the point A is located at the same rotation angle position as the measurement center MC are selected. Is done. Thereby, it is possible to obtain the shape of the contact surface and the stress distribution of the entire contact surface. The contact surface shape and the stress distribution of the entire contact surface in FIG. 5 obtained in this manner are not a collection of data of different circumferential portions of the tire T. The shape of the ground contact surface and the stress distribution thereof are data of many different axial positions, all of which are data whose circumferential positions are substantially matched. The ground plane shape and its stress distribution indicate the ground plane shape and its stress distribution as close as possible to the actual ground plane. This is the ground plane data acquisition step.

  It is preferable that the reference time point a and the specified time points b, c, d,... Are specified within the range of ± 15 ° of the point A in the above-described contact length data obtaining step. The reason why the data extraction range is set within the range of ± 15 ° from the reference measurement point A is that the range can sufficiently cover the contact length. There is no need to use other data, which saves time and reduces the load on the processing device.

  When an arbitrary point P is designated in the stress distribution of the entire ground contact surface shown in FIG. 5, as shown in FIG. 6, the shear stress τx in the tire circumferential direction at this point P (FIG. 6A) , The shear stress τy in the tire axial direction (FIG. 6B) and the contact pressure σ (FIG. 6C) become clear.

  In the method described above, only the data of one contact surface specified based on the maximum contact length is obtained. However, the present invention is not limited to this, and it is also easy to determine the shape of the contact surface and the stress distribution of the entire contact surface based on a non-maximum contact length.

  The stress values arranged on the XY plane grid in the ground plane as shown in FIG. 5 can be replaced with color information (color, brightness, etc.) and displayed. For example, the color is changed according to the magnitude of the stress value. The brightness is changed according to the magnitude of the stress value. The color information can be switched to any of the contact pressure, the circumferential shear stress, and the axial shear stress.

  The tire contact surface stress measuring method according to the present invention is applicable to evaluation of contact characteristics of various tires and the like.

2 ... Testing device 4 ... Tire support device 4a ... Tire support shaft 6 ... Drum 8 ... Drum support device 8a ... Drum support shaft 10 ... Drum drive device 12 ... Tire driving device 14 ... Lifting device 16 ... Road surface 18 ... Opening 20 ... 3 component force sensor 22 ... Drum encoder 24 ... Tire encoder 26 ... Processing device LS ... Grounding In LE: Ground contact MC: Measurement center ML: Maximum ground length T: Tire

Claims (3)

A method for measuring a tire contact surface stress using a test device having a cylindrical drive drum,
The test device includes a rotation angle detector that detects a rotation angle of the tire, a tire stress measurement device installed on a road surface of the drum, and a rotation angle detector that detects a rotation angle of the drum.
While repeating the rotation of the tire and the axial movement of the tire, the time series data of the stress from the point of contact with the road surface to the point of contact with the road surface at each position determined from the axial position and the rotation angle of the tire is calculated for the tire and the drum. A time-series data obtaining step to be obtained in correspondence with the rotation angle of
On the circumferential direction of the tire, a plurality of specified measurement points having the same axial position are set, and any one of the specified measurement points is selected as a reference measurement point. An arbitrary angular position from the touchdown to the touchdown is set as a reference time point, and for each specified measurement point within the range of the tire contact length from the reference measurement point, the angle position corresponding to the reference time point in the time-series data, The specified position is an angular position separated by an angle corresponding to the angle between the specified measurement point and the reference measurement point, the stress data at the reference time in the time series data of the reference measurement point, and each specified measurement point when extracts stress data of the specified point in the sequence data, creates a stress data from the reference measurement point at a particular point in time within the contact length, the angle of rotation of the tire and drum A contact length data acquisition step of obtaining the contact length data in correspondence with,
A representative contact length data selecting step of selecting one contact length data as representative contact length data from all contact length data obtained in the contact length data obtaining step;
A measurement center setting step of setting a measurement center in the circumferential direction to the representative contact length data selected in the representative contact length data selection step;
Acquisition of ground plane data to obtain ground plane data by specifying the ground plane data that includes the measurement center in the same angle position in the representative ground plane data among other ground plane data different in axial position from the representative ground plane data Measuring the tire tread stress. In the representative contact length data selection step,
The method according to claim 1, wherein the contact length data selected as the representative contact length data is the contact length data having the largest contact length among all the contact length data. 3. The ground plane stress measuring method according to claim 1, further comprising a stress displaying step of displaying the stress in the ground plane obtained in the ground plane data acquiring step together with color information corresponding to the stress value.

Images