JP6506647B2 - Measurement method of tire contact characteristics - Google Patents

Description

  The present invention relates to a method of measuring the contact characteristics of a running tire.

  The measurement of the contact characteristics of a tire traveling on a road surface is important in evaluating various performances of the tire. An example of such a measuring method of the grounding characteristic of a tire is indicated by JP, 2011-203207, A.

  In this measurement method, a drum test apparatus provided with a three-component force sensor is used. In this measurement method, the tire and the drum are rotated while the tire whose contact characteristics are to be measured is displaced in the rotational axis direction of the drum, and the contact pressure and the shear stress are simultaneously measured. The tire is rotated a number of times so that the three component force sensor contacts the contact area of the tire many times.

  As shown in FIGS. 6 and 7, normally, the contact position P1 (FIG. 6) with the three component force sensor 20 in the circumferential direction of the tire 50 and thereafter, the drum 6 makes one rotation and the three component force sensor 20 The contact position P2 (FIG. 7) in the circumferential direction of the tire when returning to the contact portion of the tire 50 is a different position on the circumference of the tire 50. At this time, the tire 50 rotates a plurality of times. Thereafter, again, the position P1 coincides with the three component force sensor (FIG. 6). Therefore, in order to effectively distribute the measurement points within the set measurement range, the tire 50 needs to pass the position of the three-component force sensor 20 many times by rolling many times. The circumferential contact length of the tire 50 is approximately 150 mm. In terms of the phase of the tire 50, many measurement points need to be distributed within a range near 15 °.

  However, depending on the combination of tire diameter, load, internal pressure and rotational speed, and drum diameter, circumferential position (phase) or circumferential direction that can not contact with the three component force sensor even if the tire is rotated for many rotations A range (phase width) occurs. As a specific example, in the case of a tire with a dynamic load radius of 300 mm and a drum with a radius of 1000 mm, theoretically, the contact of the tire tread surface with the three component force sensor is every 120 ° center angle of the tire Limited to The above-mentioned dynamic load radius refers to a value obtained by dividing the distance advanced per one rotation of the tire by 2π when the tire is rotated in a loaded state. In addition, the phase interval of the tire that can be measured (the pitch in the circumferential direction between measurement points) is determined by the combination of the tire diameter, load, internal pressure, rotational speed, etc. and the drum diameter described above. It can not be set to the interval etc.).

  Japanese Patent Application Laid-Open No. 2005-265748 discloses an example of a method of measuring the contact stress of a tire. In this measurement method, a contact portion measurement device having a flat fixed road surface is used. In this measurement method, the tire is moved while rolling on a fixed road surface. In this measurement method, first, a position to be measured on the tire tread surface is designated. Then, based on the data obtained by the preliminary traveling, the rolling start position of the tire is adjusted and determined so that the designated position contacts the three component force sensor. In order to measure different positions, it is necessary to once return the tire to the start position and adjust the position. In this method, measurement of a plurality of positions can not be performed continuously, which requires a large number of man-hours.

JP, 2011-203207, A JP 2005-265748 A

  In the measurement method disclosed in Japanese Patent Application Laid-Open No. 2014-021012, measurement points on the tire tread surface can not be set arbitrarily. The measurement method disclosed in Japanese Patent Application Laid-Open No. 2005-265748 can not continuously measure a plurality of positions.

  An object of the present invention is to provide a method of measuring a contact characteristic which can arbitrarily change measurement points on the tire surface during rolling of the tire.

The method for measuring the contact characteristics of a tire according to the present invention is
A method of measuring the contact characteristics of a tire using a test apparatus comprising a cylindrical drive drum, comprising:
The test apparatus includes a rotation angle detector that detects a rotation angle of a tire, and a measuring device installed on the surface of the drum that can measure tire stress.
A grounding characteristic acquiring step of measuring the stress of the tire in correspondence with the rotation angle by the measuring device while rotating the tire in a state of being in contact with the driving drum;
The step of acquiring the ground contact characteristic includes, if necessary, a phase change step of changing the phase of the rotating tire.

Preferably, the precondition for changing the phase in the phase change step is that the position of the same phase of the tire is measured a plurality of times in the contact characteristic acquisition step, and the same phase is expressed by
360 ° × circumferential length of the above measuring instrument 周 tire circumferential length × 2 × 0.7
Defined as less than or equal to the value obtained by

  Preferably, in the phase change step, the dynamic load radius of the tire is changed for a necessary time in order to change the phase of the tire.

  Preferably, in the phase change step, in order to change the dynamic load radius of the tire, a load for the drum loaded on the tire, a velocity of the tire, an internal pressure of the tire, a camber angle of the tire, and the tire and the drum At least one item of the rotation speed ratio is changed.

  Preferably, a change in a dynamic load radius of the tire when at least one of the load, the tire speed, the tire internal pressure, the camber angle, and the rotational speed ratio is changed in the phase change step. Measuring the dynamic load radius change.

  According to the present invention, the measurement points on the tire surface can be arbitrarily changed during rolling of the tire. Therefore, it is also easy to obtain stress distribution within the measurement range set arbitrarily for the tire, and efficient measurement of the tire contact characteristics is possible.

FIG. 1 is a partial cross-sectional front view schematically showing a test apparatus used in the method for measuring the contact characteristics of a tire according to an embodiment of the present invention. FIG. 2 is a perspective view showing an example of a contact surface of a tire against a road surface of a drive drum in the test apparatus of FIG. FIG. 3 is a perspective view showing a measurement range set on the tread surface of the tire. FIG. 4 is a front view of the tire and the drum for illustrating the range of the same phase of the tire. FIG. 5 is a front view showing an example of the ground contact state after the phase of the tire rolling on the drum road surface is changed. FIG. 6 is a front view showing a contact state before the phase of the tire rolling on the drum road surface is changed. FIG. 7 is a front view showing another example of the contact state after the phase of the tire rolling on the drum road surface is changed.

  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 device 2 used to execute the method of measuring the tire ground contact characteristics according to the present embodiment. The invention is not limited to the inside drum type, and an outside drum type testing device may be employed. The test apparatus 2 includes a tire support device 4 rotatably supporting a tire 50, and a drive drum (hereinafter simply referred to as a drum) 6 capable of rotationally driving the tire 50. The drum 6 is rotatably supported by the drum support device 8. The drum support device 8 includes a rotation drive device (drum drive device) 10 for rotating the drum 6. The drum drive 10 can control the rotational speed. The drum 6 has a bottomed cylindrical shape.

  The tire 50 supported by the tire support device 4 is inserted into the drum 6 from the opening 18 side of the drum 6. The central axis of the drum 6 and the central axis of the tire 50 both extend in the horizontal direction. The tire support device 4 can be separated and approached with respect to the drum 6 in the central axial direction. The tire support device 4 includes a rotational drive device (tire drive device) 12 for rotationally driving the tire 50. The tire drive device 12 can control the rotational speed. The tire drive device 12 allows the tire 50 to rotate without relying on the drum 6. The tire support device 4 also has a braking function of freely rotating the tire 50 and accelerating, decelerating, and stopping the rotation. Each of the above-described rotary drive devices 10 and 12 includes rotational speed control means.

  The tire support device 4 is provided with a lifting device 14. The lifting device 14 moves the tire 50 up and down. The lifting device 14 separates and approaches the tire 50 from the road surface 16 of the drum 6. The lifting device 14 can press the tire 50 against the road surface 16 with an arbitrary load. The lifting device 14 includes load control means for controlling the load applied to the tire 50. When the tire 50 is pressed against the road surface 16 in a rotatable (free rolling) state, and the drum 6 is rotated, the tire 50 is driven to rotate. When the tire 50 is pressed against the road surface 16 and rotationally driven while the drum 6 is rotatable, the drum 6 is also driven to rotate.

  The tire support device 4 is provided with axial angle control means capable of making the direction of the central axis of the supported tire 50 be inclined or parallel to the central axis of the drum 6 at an arbitrary angle. The camber angle and the slip angle can be set to the tire 50 by the axial angle control means.

  A three-component force sensor 20 as a tire stress measuring device is embedded in at least one location of the road surface 16. The three-component sensor 20 is disposed such that its detection portion is in contact with the surface of the tire 50. For easy understanding of the measurement target of the three component force sensor, the tire axial direction (width direction) is taken as the X axis direction, the tire circumferential direction as the Y axis direction, and the tire radial direction as the Z axis direction. The three-component force sensor 20 detects shear stress τx in the axial direction of the tire, shear stress τy in the circumferential direction of the tire, and vertical stress (contact pressure) σ in the radial direction of the tire at one position on the tread surface of the tire 50 , 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. On a tire support shaft 4 a of the tire support device 4, a rotary encoder (hereinafter referred to as a tire encoder) 24 as a tire rotation angle detector is installed.

  The test apparatus 2 is provided with a processing unit 26 for processing measurement data by the three-component force sensor 20 and detection data by the two encoders 22 and 24. The processing device 26 includes a CPU, a memory and the like, and is also connected to an operation panel and the like (not shown). An operation instruction can be issued from the processing device 26 to each drive device, measuring device, and the like by a program input from the operation panel.

  The contact characteristics of the tire 50 are measured using this test device 2. As an operation of acquiring the contact characteristics of the tire 50, as described later, "a preliminary measurement step of dynamic load radius change", "measurement step" and "phase change step" are performed in that order. Here, the “measurement step” will be described below.

[Measuring step]
In the measurement step, the tire 50 is attached to the test device 2 and traveled according to the set measurement conditions. Then, while traveling, the three stresses of the tread surface of the tire 50 that is in contact with the drum 6 are measured. At the same time, in the processing device 26, the measured values of these three stresses are associated with the tire 50 rotation angle. The above measurement conditions include the load for the drum 6 applied to the tire 50, the traveling speed of the tire 50, the internal pressure of the tire 50, the camber angle of the tire 50, the slip angle of the tire 50, and the tire 50 and the drum 6 It is the ratio of the rotational speed etc.

  The aim of this measurement step is to comprehensively measure the inside of the contact surface LA of the tire 50 with respect to the road surface 16 of the drum 6 shown in FIG. As shown in FIG. 3, a predetermined measurement range MA covering the contact surface LA is set on the tire tread surface, and actual measurement points are distributed substantially equally in the measurement range MA. The central angle α and the circumferential position of this measurement range MA are specified. For this purpose, the point (the above measurement point) in contact with the three-component force sensor 20 on the tire tread surface can not be left as it is.

  Therefore, when stress measurement is performed by rolling the tire 50 under predetermined measurement conditions, if the same phase of the tire is repeatedly detected, the tire phase is only a small amount and for a short time in the phase changing step described later. Only change. This phase can be said to be a rotation angle based on a certain position. Then, the original measurement conditions of the tire 50 are immediately returned. This is a phase change step described later. Measurement is resumed after the phase is changed. This phase change and measurement is repeated as necessary. This makes it possible to efficiently measure for any tire phase.

  The measurement steps are described in detail below. First, the tire 50 having a predetermined internal pressure is adjusted in position with respect to the road surface 16 on the inner periphery of the drum 6. First, the three-component force sensor 20 is adjusted to be positioned at a certain position within the width of the tire 50. This is the axial position adjustment. For example, the three-component force sensor 20 is adjusted to be positioned approximately at the center of the width of the tire. The tire 50 is loaded with a predetermined load on the road surface 16. Furthermore, a predetermined camber angle and / or slip angle is set for the tire 50.

  The tire 50 and the drum 6 are rotationally driven at a predetermined rotational speed. The travel speed of the tire 50 is preferably 30 km / h to 200 km / h. As the traveling speed is higher, the necessary change time T of the dynamic load radius becomes shorter in the phase changing step described later. If the traveling speed exceeds 200 km / h, the necessary change time T of the dynamic load radius becomes too short, which may make control difficult. On the other hand, if the traveling speed is less than 30 km / h, it may take too long to change the dynamic load radius. As the tire 50 and the drum 6 rotate, the rotational angle of the drum 6 is detected by the drum encoder 22 based on a certain point in time. The tire encoder 24 detects the rotation angle of the tire 50 from the reference time point. The above-mentioned stresses τx, τy, σ are acquired in the processing unit 26 in correspondence with the rotation angle of the tire 50. That is, the addresses of the circumferential direction are attached to the measured stress.

  When the tire 50 is rotated a predetermined number of times and measurement is finished, the tire 50 is automatically moved (laterally moved) relative 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. Since the central angle α and the circumferential position of the measurement range MA are specified, the measurement point after lateral movement is automatically set to the same circumferential position as the measurement point before movement. Lateral movement and measurement are repeated automatically. The measurement data obtained at a plurality of positions in the axial direction are each specified as measurement data obtained at the axial position. In this manner, the stress measurement is also covered in the width direction of the tire 50, and is distributed substantially equally in the measurement range MA.

[Phase change step]
If measurement of the same phase of the tire 50 is repeatedly detected while the measurement is continued in the measurement step, the phase is changed. In the present embodiment, “repeatedly detected” means that the measurement of the same phase is detected two to three times. Assuming that the measurement of the same phase of the tire 50 is detected two to three times, the center angle of the tire is 0 °, 120 °, 240 °, applying the example of the tire with a dynamic load radius of 300 mm and the drum with a radius of 1000 mm. It means that the measurement of each position is repeated 2 to 3 times. Such a tire can not cover all the measurements in the contact surface.

In a real tire, it would be rare for the detection of the completely same phase to be repeatedly detected. Here, this same phase is defined as being equal to or less than the value obtained by the following equation (1) in the processing device 26.
360 ° x SL TL TL ÷ 2 x 70% (1)
here,
SL: Circumferential length of force sensor 20,
TL: circumferential length of tire Also, “360 ° × SL ÷ TL” in the equation (1) is a tire central angle θ corresponding to the length SL of the three-component force sensor 20 shown in FIG. 4 in the drum circumferential direction. is there. When the tire center angle formed by the same measurement points on the tire circumference is equal to or smaller than the above-mentioned equation (1), these measurement points are regarded as having the same phase. Specifically, in FIG. 6, the difference between the angular position of the contact position P1 which first contacts the three-component force sensor 20 and the angular position when the contact position P1 again contacts the three-component force sensor 20 is If the above equation (1) or less, these measurement points are regarded as having the same phase.

  The phase change is performed by changing the dynamic load radius of the tire 50 in a pulse manner. Immediately after shifting the phase by a short phase change, the dynamic load radius is returned to the state of the original measurement condition and the measurement is restarted. When the dynamic load radius is increased, the measurement point is shifted rearward looking at the tire traveling direction. When the dynamic load radius is decreased, the measurement point is shifted forward from the point before the increase by looking at the tire running direction from before the increase. The longer the dynamic load radius is changed, the larger the amount of phase shift.

  The position of the measurement point on the tire circumference is grasped by both encoders 22 and 24. In the processing unit 26, the time to change the dynamic load radius is determined so as to be changed from this position by the desired phase width. The desired modified phase width (phase to be shifted) is the phase interval to be measured, for example 1 °.

The determination of the time T for changing the dynamic load radius is made as follows. The relationship between the phase A to be shifted and the time T for changing the dynamic load radius is expressed by the following equation (2). The time required to change the desired phase width is determined by equation (2).
T = π ÷ 180 ° × DLc × DLm ÷ (DLc−DLm) ÷ Vc × A (2)
here,
T: Dynamic load radius required change time (seconds)
DLc: Dynamic load radius after change (mm)
DLm: Dynamic load radius (mm) before change (under measurement conditions)
Vc: Travel speed when the dynamic load radius is changed to shift the phase (mm / sec)
A: Phase you want to slip (°)

The way of deriving the equation (2) is as follows. By changing the dynamic load radius, the phase B ° shifted by one rotation of the tire 50 can be obtained by the following equation (3).
B = (2πDLc-2πDLm) ÷ 2πDLm × 360 ° (3)

The required number of revolutions C of the tire after the dynamic load radius change corresponding to the phase A to be shifted is obtained by the following equation (4).
C = A ÷ B (4)

Further, the required change time T of the dynamic load radius is expressed by the following equation (5).
T = 2πDLc × C ÷ Vc (5)
Here, “2πDLc × C” in the equation (5) is the traveling distance after the change of the dynamic load radius. The equation (2) is obtained by substituting the equations (4) and (3) into the equation (5).

  For the phase A to be shifted, a pulse input of a dynamic load radius change instruction is automatically performed for the necessary time T obtained by the equation (2). This process causes a desired phase shift. After the required time T has elapsed, the dynamic load radius under the original measurement conditions is automatically returned. Thus, as shown in FIG. 5, the contact position P1 (FIG. 6) with the three component sensor 20 does not match the three component force sensor after multiple rotations of the tire 50, and the different position P2 is three Contact the force sensor. The different position P2 is shifted from the initial contact position P1 by a desired phase (for example, 1 °). In other words, the previous contact position P1 (FIG. 6) is shifted from the previous position of the three component force sensor by a desired phase (FIG. 5) this time. In this way, measurements with desired phase spacing are performed. In FIG. 5, the phase shift is drawn at 1 ° or more for easy understanding. After the above processing, when the same phase is repeatedly detected again, the pulse input of the dynamic load radius change instruction and the restart of measurement are repeated. Of course, this phase change step is also carried out as needed in measurements that are moved in the axial direction of the tire and repeated.

  Hereinafter, a method of changing the dynamic load radius of the tire 50 will be described. In order to change the dynamic load radius, the load for the drum 6 applied to the tire 50, the speed of the tire 50, the internal pressure of the tire 50, the camber angle of the tire 50, and the rotational speed ratio between the tire 50 and the drum 6; Among the plurality of elements, at least one element is changed. For example, an increase in tire internal pressure, an increase in tire running speed, and an increase in camber angle all result in an increase in dynamic load radius. On the other hand, an increase in tire load causes a decrease in dynamic load radius. Also, an increase in the tire rotational speed / drum rotational speed ratio results in a decrease in the dynamic load radius, and a reduction in this ratio results in an increase in the dynamic load radius.

[Primary measurement step of dynamic load radius change]
In the above phase change step, in order to select an appropriate change time of the dynamic load radius, change of each of the above-mentioned elements (speed of tire, load, internal pressure, camber angle, rotational speed ratio of tire to drum) and It is necessary to grasp the relationship with the change of dynamic load radius quantitatively. For this purpose, prior to the measuring step, a preliminary measurement of the dynamic load radius change is performed. In the preliminary measurement step of the dynamic load radius change, the relationship with the dynamic load radius is grasped while changing the value of each of the plurality of elements in multiple stages.

  Specifically, multiple regression analysis that optimizes the coefficients of each explanatory variable using the dynamic load radius as a target variable and each of the above-described elements as an explanatory variable based on the basic data obtained by preliminary measurement in the processing apparatus 26 Is done. According to the multiple regression equation obtained by this analysis, an optional element is selected for changing the dynamic load radius within the tolerance of the test apparatus 2.

  Whether the measurement performed through the “preliminary measurement step of dynamic load radius change”, “measurement step” and “phase change step” described above covers the desired measurement range MA in the processing apparatus 26 Is confirmed. If there is an unmeasured point, the "measurement step" and the "phase change step" are resumed. If the unmeasured point is not confirmed, the measurement ends.

  Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be interpreted in a limited manner based on the description of the examples.

Example 1
As Example 1, a pneumatic tire was prepared. The size of this tire was 225 / 55R17. The contact characteristics of this tire were measured using the above-mentioned test device 2. The dynamic load radius under the measurement conditions of this tire was 336 mm. The internal diameter (diameter of the road surface) of the drum 6 of the test device 2 was 5 m. The phase of the tire necessary for forming the contact surface, that is, the circumferential angle range α of the measurement range MA was 15 °. The phase interval to be measured was set to 1 °.
The measurement conditions of this tire were as follows.
Internal pressure: 250 kPa
Load when driving: 4.12 kN
Camber angle: 0 °
Driving speed: 80km / h

When the measurement is carried out under the above conditions, a phase shift of 158.6 ° occurs every rotation of the drum 6. For this reason, as for the tire phase in the measurement range from 0 ° to 15 °, four identical phases are detected every 84 revolutions. That is, there is a tire phase that can not be measured. Therefore, the tire phase was changed during the measurement.
The phase change input of this tire was as follows.
Load load: (From 4.12kN) Change to 4.00kN Change input time: 0.7 seconds Frequency of change input: 85 times during one rotation of drum

The multiple regression equation of the dynamic load radius adopted in the phase change was the following equation (6).
DR = -0.9993 W + 0.023 V + 338.27711 (6)
here,
DR: Dynamic load radius (mm)
W: Load load (kN)
V: Running speed of tire (km / h)

Example 2
As Example 2, a pneumatic tire was prepared. The tire phase was also changed during this measurement for this tire. The measurement conditions and phase change input contents of the tire of this Example 2 are as shown in Table 1.
The phase change input of this tire was as follows.
Travel speed: (from 80 km / h) Change to 82 km / h Time of change input: 1.9 seconds The configuration and conditions other than those described in Table 1 above were the same as the tire of Example 1.

Comparative Example 1
As a comparative example 1, a pneumatic tire was prepared. As shown in Table 1, in the measurement of this tire, no tire phase change was performed. Other configurations and conditions were the same as the tire of Example 1.

[Evaluation of measurement of grounding characteristics]
The results of the ground contact characteristic measurement for the tires of Examples 1 and 2 and Comparative Example 1 are shown in Table 1. The time required for the measurement was 240 seconds in each case, and the number of rotations of the drum was 340 revolutions. For each of the tires of Example 1 and Example 2, the measurement range with a center angle of 15 ° could be measured at an interval of 1 °. The phases that can be measured are indicated by ○ in Table 1. On the other hand, in the tire of Comparative Example 1, as apparent from Table 1, there were many phases which could not be measured within the measurement range of the central angle of 15 °. The phases that could not be measured are shown in Table 1 by-marks. The superiority of the present invention is clear from the evaluation results.

  The method for measuring the ground contact characteristics of a tire according to the present invention is applicable to the evaluation of the ground contact characteristics of various tires.

2 Test 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 drive device 14 ··· Lifting device 16 · · · Road surface 18 · · · 20 · · · 20 minutes force sensor 22 · · · drum encoder 24 · · · tire encoder 26 · · · processing unit 50 · · · tire LA · · · Ground surface MA · · · · Measurement range

Claims (4)

A method of measuring the contact characteristics of a tire using a test apparatus comprising a cylindrical drive drum, comprising:
The test apparatus includes a rotation angle detector that detects a rotation angle of a tire, and a measuring device installed on the surface of the drum that can measure tire stress.
A grounding characteristic acquiring step of measuring the stress of the tire in correspondence with the rotation angle by the measuring device while rotating the tire in a state of being in contact with the driving drum;
In this ground characteristic acquisition step, if necessary, looking contains a phase change step of changing the tire phase during rotation,
In the above phase change step, a dynamic load radius of a tire is changed for a necessary time in order to change a phase of the tire . In the phase change step, in order to change the dynamic load radius of the tire, the load for the drum loaded on the tire, the speed of the tire, the internal pressure of the tire, the camber angle of the tire, and the rotational speed ratio between the tire and the drum of, changing at least one item, the measurement method of the ground characteristics of claim 1. The change of the dynamic load radius of the tire when at least one of the load, the tire speed, the tire internal pressure, the camber angle, and the rotational speed ratio is changed in the phase change step is measured. The method of measuring a grounding characteristic according to claim 2 , comprising a preliminary measurement step of dynamic load radius change. A method of measuring the contact characteristics of a tire using a test apparatus comprising a cylindrical drive drum, comprising:
The test apparatus includes a rotation angle detector that detects a rotation angle of a tire, and a measuring device installed on the surface of the drum that can measure tire stress.
A grounding characteristic acquiring step of measuring the stress of the tire in correspondence with the rotation angle by the measuring device while rotating the tire in a state of being in contact with the driving drum;
In the step of acquiring the ground contact characteristic, as required, a phase change step of changing the phase of the rotating tire,
The precondition for changing the phase in the phase change step is that the position of the same phase of the tire is measured a plurality of times in the contact characteristic acquisition step, and the same phase is expressed by the following equation:
360 ° × circumferential length of the above measuring instrument 周 tire circumferential length × 2 × 0.7
A method of measuring the contact characteristics of a tire , defined as being less than or equal to the value obtained by

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