JP4317837B2 - Vehicle rollover resistance evaluation method and vehicle rollover resistance evaluation device - Google Patents

Description

  The present invention relates to a vehicle rollover resistance evaluation method and a vehicle rollover resistance evaluation apparatus for a vehicle that evaluate the rollover resistance performance of a vehicle such as a passenger car, a truck, or a bus.

At present, the rollover resistance of vehicles has been regarded as important, and high rollover resistance (performance in which a vehicle does not roll over as much as possible) has been required as tire performance. In addition to the weight of the vehicle body and the tire performance, for example, the performance of the suspension and the like has a complex influence on the rollover resistance of the vehicle. In order to accurately evaluate the rollover resistance of each individual vehicle, it is necessary to actually drive the vehicle under a specific traveling condition and use the actual behavior data of each individual vehicle obtained at this time. As such a method for actually running the vehicle and evaluating the rollover resistance performance of the vehicle, the Fishhoe test method, the elk test (double lane change), and the like are known. In such a known anti-overturning performance test method, generally, the wheel lift of the turning inner wheel when each vehicle is turned under the same running condition is measured, and the turning inner wheel floats at the same time (the wheel lifts up). ) The traveling speed is used as an index representing the rollover resistance performance of each vehicle. Such a vehicle rollover resistance evaluation method is described in Non-Patent Document 1, for example.
Garrick J. Forkenbrock and two others, “A Demonstration of the Dynamic Tests Developed for NHTSA's NCAP Rollover Rating System-Phase VIII of NHTSA's Light Vehicle Rollover Research Program”, [online], August 2004, National Highway Traffic Safety Administration, [2005 June 2 search], Internet <URL: http://www-nrd.nhtsa.dot.gov/vrtc/ca/capubs/RolloverPhaseVIIIReport_NCAPdemo081104.pdf>

In such a conventional rollover resistance evaluation method for a vehicle, for example, in a state in which a rollover prevention device called an outrigger is mounted on the vehicle, the vehicle is turned at a relatively high speed, and the turning inner wheel of the vehicle is actually set. The two wheels are lifted at the same time (refer to the flowchart shown in P49-52 of Non-Patent Document 1 above, actually “Two-Wheel Lift”). In this way, the minimum speed at which the two turning inner wheels of the vehicle are lifted simultaneously is used as an index for evaluating the anti-overturn performance of the vehicle. However, such a rollover prevention device is expensive, and there is a problem that the cost for testing increases. In addition, for example, it was not possible to know the degree of lifting of the two wheels with high accuracy only by confirming the lifting of the wheels by visual inspection or the like, and the state of the wheels immediately before and after the lifting of the wheels, I could not know the speed of the machine with high accuracy. In fact, when the vehicle is driven at a speed at which the two turning inner wheels of the vehicle are lifted at the same time, the vehicle behavior changes suddenly, and even if the rollover prevention device is installed, the vehicle rolls over in the test. There was also a danger of end. If the vehicle rolls over, there is a risk that the test road surface on which the vehicle travels and the test vehicle itself are damaged, and further, the test driver who drives the vehicle is injured. In general, the test road surface is specially paved according to the purpose of the test, and the test becomes impossible when the pavement is damaged. For this reason, once the vehicle overturns, it is necessary to repair the damaged portion, and this repair requires a large amount of cost and time. In addition, since the rollover prevention device (outrigger) as described above is very expensive, the test cost is high. Furthermore, when the rollover prevention device is mounted on a vehicle, vehicle characteristics (vehicle center of gravity, vehicle moment of inertia, etc.) change, and it is difficult to evaluate the rollover resistance performance of the vehicle alone. .
Therefore, the present invention provides a vehicle rollover resistance evaluation method and a vehicle rollover resistance evaluation apparatus that can safely and accurately evaluate the rollover resistance performance of a single vehicle without mounting an expensive rollover prevention device. The purpose is to provide.

  In order to solve the above-mentioned problems, the present invention is a method for evaluating the rollover resistance of a vehicle provided with at least four or more wheels, the regulation of the traveling speed of the vehicle being changeable, A condition setting step for setting a traveling condition of the vehicle including a traveling course for turning on a road surface; and defining the traveling speed of the vehicle to travel the vehicle under the traveling condition; For at least one of the wheels on the turning inner wheel side, wheel information representing the magnitude of the load applied to the wheel from the road surface is obtained in time series, and a time series in the wheel information obtaining step. In the wheel information acquired in the above, the extraction step for extracting the wheel information minimum value at which the load is minimum, and the traveling speed of the vehicle are repeatedly changed. A repetition step of causing the vehicle to travel at a further travel speed and performing the wheel information acquisition step and the extraction step; a travel speed of the vehicle in the repetition step; and the wheel information minimum value at each travel speed. A regression equation deriving step for deriving a regression equation for the traveling speed of the minimum value of the wheel information, and when the vehicle travels under the traveling condition based on the derived regression equation, An anti-overturning limit speed calculating step for calculating a minimum traveling speed among the rising traveling speeds, and an evaluation step for evaluating the anti-overturning performance of the vehicle based on the minimum traveling speed calculated in the anti-overturning limit speed calculating step. And when the vehicle speed of the vehicle is repeatedly changed, the step of repeating the vehicle travels before the change. Compared each time to provide 耐転 covering performance evaluation method for a vehicle, characterized in that to increase the traveling speed after the change.

  When the vehicle is driven under the driving conditions set in the condition setting step, a safe driving speed at which the vehicle does not roll over is known in advance, and the vehicle driving is repeatedly changed in the repeating step. It is preferable that all the speeds are set to be equal to or less than the safe traveling speed.

When the vehicle is driven under the driving conditions set in the condition setting step, a safe driving speed at which the vehicle does not roll over is known in advance, and when the wheel information acquisition step is first performed The specified vehicle travel speed is set to be equal to or less than the safe travel speed,
In the repetition step, the minimum value wheel information acquired by executing the wheel information acquisition step and the extraction step is set in advance, and a set value of the wheel information indicating a state where the wheel is sufficiently grounded When it becomes less, it is also preferable not to implement the wheel information acquisition step and the extraction step thereafter.

  The wheel is a tire assembly in which a tire is mounted on a rim, and the wheel information acquisition step includes, as the wheel information, information on a contact length with a road surface of the tire surface during traveling of the vehicle. It is preferable to obtain

  Moreover, it is preferable that the information on the contact length is obtained from acceleration information obtained by measuring the acceleration of the tread portion of the tire of the wheel while the vehicle is running.

  The wheel may be a tire assembly in which a tire is mounted on a rim, and the wheel information acquisition step may acquire, as the wheel information, information on a tire deflection amount of the wheel during the traveling of the vehicle. Also preferred.

  The present invention is also an apparatus for evaluating the rollover resistance performance of a vehicle provided with at least four wheels or more, and includes a preset travel course for causing the vehicle to turn on a road surface. When the vehicle is driven under vehicle driving conditions, wheel information representing the magnitude of the load applied to the wheels from the road surface is acquired in time series for at least one of the plurality of wheels of the vehicle. Wheel information acquisition means, extraction means for extracting the wheel information minimum value when the load is minimized among the wheel information acquired in time series in the wheel information acquisition means, and the traveling speed of the vehicle Storage means for repeatedly storing the wheel information minimum values when the vehicle is driven at the changed traveling speed under the traveling conditions each time the vehicle is changed repeatedly; The wheel information minimum value at each travel speed stored in the storage means is read out, and the vehicle information and the wheel information minimum value at each travel speed are used to calculate the wheel information minimum value with respect to the travel speed. Based on a regression equation deriving unit for deriving a regression equation and the derived regression equation, a resistance value for calculating a minimum traveling speed among the speeds at which the wheels are lifted when the vehicle is traveling under the traveling condition. Rollover limit speed calculating means, and evaluation means for evaluating the rollover resistance performance of the vehicle based on the minimum traveling speed calculated by the rollover limit speed calculating means. An evaluation device is also provided.

  According to the vehicle rollover resistance evaluation method and the vehicle rollover resistance evaluation device of the present invention, the rollover resistance performance of a vehicle can be evaluated safely and with high accuracy at low cost.

DESCRIPTION OF EMBODIMENTS Hereinafter, a vehicle rollover resistance evaluation method and a vehicle rollover resistance evaluation apparatus according to the present invention will be described in detail on the basis of preferred embodiments shown in the accompanying drawings.
FIG. 1 is a schematic configuration diagram illustrating a vehicle rollover resistance evaluation system 10 (system 10), which is an example of a vehicle rollover resistance evaluation apparatus according to the present invention. The system 10 uses the vehicle 12 shown in FIG. 1 as a measurement target vehicle and measures the rollover resistance performance of the vehicle 12. The system 10 is provided in a vehicle 12 provided with four wheels 14a to 14d. The system 10 includes sensor units 16a to 16d provided on four wheels 14a to 14d and an evaluation device 20, respectively. The evaluation device 20 receives the radio signals transmitted from the sensor units 16a to 16d, and determines the contact length of each wheel from the deformation acceleration information of each wheel (the length of the contact area between the wheel and the road surface along the circumferential direction of the wheel). ) And the rollover resistance of the vehicle to be measured is evaluated based on the calculated contact length. The evaluation device 20 includes a display 36 that displays and outputs the calculation results and evaluation results of the evaluation device 20. The system 10 (the sensor unit 16, the evaluation device 20, and the display 36) can be removed from the vehicle 12, and can be installed in various vehicles different from the vehicle 12. The system 10 calculates an evaluation value that represents the ground contact state of the wheels of the vehicle with which the system 10 is grounded (measurement target vehicle) while the vehicle is traveling. Based on this evaluation value, the rollover resistance performance of the vehicle to be measured is evaluated.

  The anti-overturning performance of a vehicle is the performance of difficulty in overturning the vehicle. When different vehicles are driven under the same driving conditions (conditions where the driving course, driving speed, etc. are the same), a vehicle with better rollover resistance is more difficult to roll over than a vehicle with poor rollover resistance. Less likely). The vehicle overturning refers to a state in which one of the left and right wheels of the vehicle is lifted and the vehicle rolls over or falls. In a normal driving state (for example, a state where the vehicle is traveling straight on a paved road at a constant speed), the load applied to each wheel from the road surface (ground contact load) is substantially equal (the load applied to each road surface from the vehicle wheel is It can be said that it is almost equal. When the vehicle rolls over, the ground load applied to the wheel on either the left or right side of the vehicle gradually decreases and becomes less than 0 (zero), and the wheel is lifted. Here, it is known that the contact length of the wheel to the road surface increases as the size of the contact load increases, and the contact length of the wheel represents the size of the load applied from the wheel to the road surface. I can say that. As the wheel gradually lifts while the vehicle is running, the ground contact length of the wheel gradually decreases. When the wheel is lifted, the ground contact length of the wheel becomes 0 (zero) or less. The ground contact length of the wheel during traveling of the vehicle thus represents the behavior when the vehicle rolls over. The rollover resistance evaluation system 10 evaluates the rollover resistance of the vehicle 12 that is the vehicle to be measured based on such information on the contact length of the wheels.

  FIG. 2 is a block diagram illustrating a configuration of the evaluation device 20 of the system 10. The evaluation device 20 illustrated in FIG. 2 includes a receiver 3, an amplifier (AMP) 4, a contact length calculation unit 21, an evaluation unit 70, a CPU 23, and a memory 27. The evaluation device 20 is a computer in which each means (each part to be described later) of the contact length calculation means 21 and the evaluation part 70 function by executing a program stored in the memory 27 by the CPU 23. The evaluation unit 70 calculates the contact length with the road surface of the rolling tire 1 by using the acceleration measurement data in the tread portion of the tire 1 constituting the wheel 14 (any one of the wheels 14a to 14d). The rollover resistance performance of the vehicle 12 is evaluated based on the contact length. The acceleration measurement data used here is data transmitted from the transmission unit 16 provided on the wheel 14. The transmission unit 16 includes an acceleration sensor 2 and a transmitter 15 fixed to the inner peripheral surface of the hollow area of the tire (see FIG. 2), and acceleration measurement data is detected by the acceleration sensor 2 and the wheel 14 Is transmitted from the transmitter 15 of the transmission unit 16 provided to the receiver 3. The transmitted measurement data is amplified by the amplifier 4 and then acquired by the contact length calculation means 21.

  For example, the acceleration sensor 2 may be provided with a transmission function without providing the transmitter 15. In this case, the acceleration data measured by the acceleration sensor 2 may be transmitted from the acceleration sensor 2 itself to the receiver 3. Each transmitter 15 provided in each of the wheels 14a to 14d has identification information (ID) that enables identification of each, and the transmitter 15 measures the acceleration measured by the corresponding acceleration sensor. An ID is transmitted together with the data.

As the acceleration sensor 2, for example, a semiconductor acceleration sensor disclosed in Japanese Patent Application No. 2003-134727 filed earlier by the applicant of the present application is exemplified. Specifically, the semiconductor acceleration sensor includes a Si wafer having a diaphragm formed in the outer peripheral frame portion of the Si wafer, and a pedestal for fixing the outer peripheral frame portion, and a weight is provided at the center of one surface of the diaphragm. And a plurality of piezoresistors are formed on the diaphragm. When acceleration is applied to the semiconductor acceleration sensor, the diaphragm is deformed, and the resistance value of the piezoresistor changes due to the deformation. A bridge circuit is formed so that this change can be detected as acceleration information.
By fixing this acceleration sensor to the tire inner peripheral surface, the acceleration acting on the tread portion during tire rotation can be measured.
In addition to this, the acceleration sensor 2 may be an acceleration pickup using a piezoelectric element, or a strain gauge type acceleration pickup combined with a strain gauge.

  FIGS. 3A and 3B are views for explaining the installation position of the acceleration sensor 2 on the tire 1 in the present embodiment, and FIG. 3A shows a state where the wheels 14 of the vehicle 12 are grounded to the road surface. It is a schematic diagram, (b) shows a schematic cross-sectional view of the tire 1 in the state shown in (a). The lift of the wheel 14 from the road surface is mostly caused by roll resonance induced in the vehicle 12. During the rolling behavior of the vehicle 12 when the wheel 14 is lifted, the ground camber angle of the wheel 14 on the turning inner wheel side becomes a large negative ground camber angle. For this reason, when the tire 1 of the wheel 14 on the turning inner wheel side is lifted from the road surface, the tire 1 is gradually lifted from the outside of the vehicle 12, and the vicinity of the shoulder portion inside the vehicle 12 is finally lifted. In order to measure the contact length of the wheel 14, an acceleration sensor is provided as much as possible inside the vehicle 12 in the contact area of the tire 1, and the acceleration of the inside as much as possible of the vehicle 12 (the rolling tire 1 It is preferable to measure acceleration generated by receiving external force from the road surface. For this reason, it is preferable that the arrangement position of the acceleration sensor 2 is inside the vehicle 12 rather than the equator plane of the tire 1 (indicated by E in FIG. 3B). When the ground contact width of the tire 1 in a state where the vehicle 12 is stopped is W, the position of the acceleration sensor 2 is 0.2 W from the equator plane (passing the center position in the ground contact width W). The equatorial plane passing through a point spaced inward of the vehicle by 0.5 W from the first plane (indicated by F in FIG. 3B) parallel to the equatorial plane passing through It is more preferable that they are disposed within a range (a range indicated by diagonal lines in FIG. 3B) reaching a second plane (indicated by G in FIG. 3B) parallel to the horizontal plane.

  In the present embodiment, one acceleration sensor 2 is fixed to the tire inner peripheral surface. However, in the present invention, as shown in FIGS. 4A to 4D, the acceleration sensor 2 has a tire cross-section. It may be arranged in various parts, and the number of acceleration sensors 2 is not limited. For example, as shown in FIG. 4 (a), it may be arranged on the inner liner part of the tire, or as shown in FIG. 4 (b), it may be arranged on the upper part of the belt ply layer of the tire. In addition, as shown in FIG. 4C, it may be arranged inside the tire tread. Further, as shown in FIG. 4D, a plurality of acceleration sensors 2 may be arranged in the tire width direction over the entire region corresponding to the above-described tire contact width W. As shown in FIG. 4D, by arranging a plurality of acceleration sensors 2 in the width direction of the tire, in the lifting behavior of the wheels that gradually rise from the outside of the vehicle 12 to the vicinity of the shoulder portion inside the vehicle 12. Information on changes in the contact length of each part of the tire can be acquired in time series in the tire width direction.

  The contact length calculation means 21 to which the acceleration measurement data amplified by the amplifier 4 is supplied includes a data acquisition unit 22, a signal processing unit 24, a deformation amount calculation unit 26, and a contact length calculation unit 28. The data acquisition unit 22 is a part that acquires, as input data, acceleration measurement data for at least one rotation of the tire amplified by the amplifier 4. Data supplied from the amplifier 4 is analog data, which is sampled at a predetermined sampling frequency and converted into digital data. In addition, the data acquisition part 22 is based on the above-mentioned ID transmitted from each transmitter 15, and the measurement data of the acceleration transmitted from each wheel is the measurement data of the tire acceleration of which wheel (wheels 14a to 14a). Which wheel of the wheels 14d is determined). Thereafter, the processes performed by the signal processing unit 24, the deformation amount calculating unit 26, the contact length calculating unit 28, and the evaluating unit 70 are performed in parallel for the measurement data of the tires of the respective wheels.

  The signal processing unit 24 is a part that extracts time-series data of acceleration based on tire deformation from digitized acceleration measurement data. The signal processing unit 24 smoothes the acceleration measurement data, calculates an approximate curve for the smoothed signal to obtain the background component 1, and smoothes the background component 1 By removing from the acceleration measurement data, time series data of acceleration based on tire deformation is extracted. Specific processing will be described later.

  The deformation amount calculation unit 26 is a part that calculates the deformation amount of the tire by obtaining displacement data by performing second-order time integration on the time-series data of acceleration based on the extracted tire deformation. Second-order integration with respect to time is performed on time series data of acceleration based on tire deformation, and then an approximate curve is calculated for the data obtained by second-order integration to obtain background component 2, and this background The amount of deformation of the tire is calculated by removing component 2 from the displacement data obtained by second-order integration. Further, after that, a second-order differential with respect to time is performed on the calculated tire deformation amount data to obtain acceleration data corresponding to the tire deformation amount, that is, the acceleration based on the tire deformation not including the noise component. Calculate time-series data. Specific processing will be described later.

  The contact length calculation unit 28 is a part that calculates the contact length of each tire of the wheels 14a to 14d from the calculated tire deformation amount and time series data of acceleration based on the tire deformation. Information on the calculated contact length of each tire is output to the evaluation unit 70.

  The evaluation unit 70 evaluates the rollover resistance performance of the vehicle 12 based on the contact length of each wheel calculated by the contact length calculation means 21. Specifically, when the vehicle 12 is driven and the vehicle traveling speed is changed, for example, when a well-known elk test is repeatedly performed, the time series ground contact length of the turning inner wheel side wheel at each vehicle traveling speed is set. calculate. Then, the regression formula to the vehicle speed of the ground contact length of the turning inner wheel side is obtained, and from this regression formula, the minimum speed when the ground contact length of both wheels on the turning inner wheel side becomes zero (the wheel is lifted) (Limit speed) is calculated and output. The evaluation system 10 outputs this rollover resistance limit speed as an evaluation result. In the present invention, the rollover limit speed itself is not limited to output as an evaluation result. For example, the rollover resistance performance of the vehicle may be classified into levels by comparing the calculated rollover resistance limit speed with a predetermined numerical range. The evaluation result by the evaluation unit 70 is displayed on the display 36, for example.

  In the vehicle rollover resistance evaluation method according to the present invention, the wheels from which the wheel information is acquired are not limited to the two wheels on the turning inner wheel side when the vehicle is turning under the set traveling conditions. Preferably, it is preferable to acquire wheel information for all wheels deployed in the vehicle. Note that the wheel from which the wheel information is acquired may be only one of a plurality of wheels arranged in the vehicle. When acquiring wheel information from only one wheel, it is preferable that the wheel from which the wheel information is acquired is a wheel that is most likely to cause wheel lifting among the wheels on the turning inner wheel side, which has been determined in advance through experiments, simulations, and the like.

  FIG. 5 is a flowchart of a vehicle rollover resistance evaluation method performed in such a system 10. In the example shown in FIG. 5, the vehicle traveling speed is gradually increased from low speed to high speed, for example, a known elk test is repeatedly performed, and the ground contact length of the turning inner wheel side at each vehicle traveling speed is determined. By calculating the minimum running speed (rollover resistance limit speed) when both of the ground contact lengths of the two wheels on the turning inner wheel side become zero (wheels lift), the minimum running speed of the vehicle is calculated. Evaluate rollover resistance. First, travel conditions are set (step S100). As the traveling conditions, specific conditions that are not changed, such as the traveling course and the content of the driving operation performed on the vehicle by the driver during traveling, are set, and various vehicle speed conditions to be changed are set. As conditions for the vehicle speed, first, a condition for the travel speed when the vehicle 12 is traveled (initial speed condition) is set, and a travel speed change width when the travel speed is changed is also set. As the initial speed condition, a sufficiently low speed (for example, 10 km / h, etc.), which is confirmed in advance through experiments and calculations and does not lift the wheel even when the vehicle 12 travels under the above travel condition, is set. The Further, the travel speed change width is set to 4 km / h or less, for example. This travel speed change width is the width of the travel speed of the vehicle (usually 5 mph, that is, about 8 km / h) in the conventional vehicle rollover resistance evaluation method that is actually performed by overturning the vehicle (causing two-wheel lift). It is sufficiently smaller than

  In the vehicle rollover resistance evaluation method according to the present embodiment, the traveling speed condition of the vehicle is changed by gradually increasing the speed from low speed to high speed, and the vehicle is driven each time the change is made. At this time, if the wheel information acquired by running the vehicle is less than a predetermined set value, the running speed is not further increased and the vehicle is not run. In the vehicle rollover resistance evaluation method of the present invention, the vehicle is first run under the initial speed condition set at a sufficiently low speed, and then the speed condition is repeatedly changed with a sufficiently small fluctuation range. Then, when the vehicle travels every time the change is made and the acquired wheel information becomes less than a predetermined set value, the travel speed is not further increased and the vehicle is not traveled. For this reason, even if the vehicle speed is changed repeatedly and the vehicle is driven each time the vehicle is changed, the vehicle always travels at a sufficiently low speed so as not to overturn. For this reason, in the vehicle rollover resistance evaluation method of the present invention, the vehicle does not roll over and is safe. For this reason, it is not necessary to provide a rollover prevention device such as an outrigger that is expensive and changes the vehicle characteristics in preparation for rollover of the vehicle. According to the vehicle rollover resistance evaluation method of the present invention, the rollover resistance performance of a vehicle can be evaluated safely and with high accuracy at low cost.

  When such driving conditions are set, first, an initial speed condition corresponding to the driving condition is set (step S102), and the vehicle 12 is driven under the set initial speed condition (step S104). Then, the ground contact length of the time-series wheel (tire) is calculated for each wheel 14 (at least two wheels on the turning inner wheel side) while the vehicle is traveling. The calculation of the contact length (steps S106 to S120) will be described in detail below.

  First, the acceleration measurement data of each wheel amplified by the amplifier 4 is supplied to the data acquisition unit 22 and sampled at a predetermined sampling frequency to acquire digitized measurement data (step S106). At this time, as described above, the data acquisition unit 22 is based on the above-mentioned ID transmitted from each transmitter 15, and the acceleration measurement data transmitted from each wheel is the measurement data of the acceleration of the tire of which wheel. It is determined whether there is any wheel (wheel 14a to wheel 14d). The subsequent processes are performed in parallel for the measurement data of the tires of the wheels.

  Next, the acquired measurement data is supplied to the signal processing unit 24, and first, smoothing processing using a filter is performed (step S108). As shown in FIG. 6A, since the measurement data supplied to the signal processing unit 24 contains a lot of noise components, the smoothing process makes the data smooth as shown in FIG. 6B. For example, a digital filter having a predetermined frequency as a cutoff frequency is used as the filter. The cut-off frequency varies depending on the rolling speed and noise components. For example, when the rolling speed is 60 (km / hour), the cut-off frequency is set to 0.5 to 2 (kHz). In addition, a smoothing process may be performed using a moving average process, a trend model, or the like instead of the digital filter.

In the time-series graph shown in FIG. 6B, the horizontal axis is the time axis, and at the same time, the circumferential position of the tire is represented by θ (degrees). The circumferential position θ (degrees) of the tire is an angle with reference to a point O (see FIG. 2) facing the center position (θ = 180 degrees) of the ground contact surface of the tire as shown in FIG. Such a circumferential position θ (degrees) is, for example, a relative position between the circumferential position of the mark and the circumferential position of the acceleration sensor 2 by detecting a mark on the tire by a mark detection unit (not shown). From the relationship, the circumferential position θ (degree) of the rolling tire can be determined. Further, in the time-series graph, with reference to the position of the minimum value, this position may be set as the center position (θ = 180 degrees) of the contact surface, and the circumferential position θ (degree) of the rolling tire may be determined.
In FIG. 6B, the center position of the contact surface corresponds to θ = 180 degrees, 540 degrees, and 900 degrees, and FIG. 6B shows measurement data of acceleration for approximately three laps of the tire.

Next, the background component 1 is calculated from the acceleration measurement data subjected to the smoothing process (step S110).
The background component 1 of radial acceleration includes an acceleration component and centrifugal acceleration component of centrifugal force (centripetal force) during rolling of the tire (note that these components are also included in the background component of circumferential acceleration). In FIG. 6C, the waveform of the background component 1 is indicated by a dotted line. This background component 1 is a region on the circumference excluding a range of angles from 0 to less than 90 degrees in absolute value, with the center position θ = 180 degrees, 540 degrees, and 900 degrees of the ground plane as the center. Area) to approximate the acceleration measurement data.

  More specifically, the area on the circumference of the tire is divided into a first area including the road surface contact area and a second area other than this, and the first area is larger than θ = 90 degrees and less than 270 degrees. , More than 450 degrees and less than 720 degrees, more than 810 degrees and less than 980 degrees, and θ = 0 to 90 degrees and 270 degrees to 360 degrees, 360 degrees to 450 degrees and 630 as the second area An area of from 720 degrees to 720 degrees, from 720 degrees to 810 degrees, and from 980 degrees to 1070 degrees is defined. The background component 1 uses a plurality of circumferential positions (time corresponding to θ or θ) in the second region as nodes, and a predetermined function group, for example, a cubic spline function, The first approximate curve is calculated by the least square method for the data of the first region and the second region. The node means a constraint condition on the horizontal axis that defines the local curvature (flexibility) of the spline function. In the example of FIG. 6B, the position indicated by “Δ” in FIG. 6B, that is, θ = 10, 30, 50, 70, 90, 270, 290, 310, 330, 350, 370, 390. , 410, 430, 450, 630, 650, 670, 690, 710, 730, 750, 770, 790, 810, 990, 1010, 1030, 1050, 1070 degrees.

By performing function approximation on the data shown in FIG. 6B with a cubic spline function having the above nodes, an approximate curve indicated by a dotted line in FIG. 6C is calculated. When performing function approximation, there are no nodes in the first region, function approximation is performed using only a plurality of nodes in the second region, and a weighting factor is used in the least square method performed in function approximation. As for this weighting factor, when the weighting factor of the second region is 1, the weighting factor of the first region is set to 0.01 and processing is performed. When the background component 1 is calculated in this way, the first weighting factor is made smaller than the second weighting factor and no node is defined in the first region. This is because calculation is performed from acceleration measurement data in the second region. In the second region, the deformation due to the contact of the tread portion is small and the deformation changes smoothly on the circumference. Therefore, the acceleration component during rolling of the tire is dominated by the acceleration component of the centrifugal force (centripetal force) and the gravitational acceleration component. It is. On the other hand, in the first region, the tread portion of the tire changes greatly and rapidly based on the ground deformation. For this reason, the change of the acceleration component based on the ground deformation becomes larger than the change of the acceleration component and the gravity acceleration component of the centrifugal force (centripetal force) based on the rotation of the tire. That is, the acceleration measurement data in the second region is roughly the acceleration component and the gravity acceleration component of the centrifugal force (centripetal force) during rolling of the tire, and mainly uses the acceleration measurement data in the second region. By calculating the first approximate curve, it is possible to accurately estimate the acceleration component and the gravitational acceleration component of the centrifugal force (centripetal force) during the rolling of the tire not only in the second region but also in the first region. .
In FIG. 6 (c), the first range is an angle range from 0 to less than 90 degrees in absolute value around the ground contact center position (θ = 180, 540, 900 degrees). The region 1 may be in the range of an angle of at least 0 and less than 60 degrees in absolute value from the ground contact center position.

  Next, the acceleration component based on the rotation of the tire and the gravitational acceleration component are removed from the measurement data by subtracting the first approximate curve representing the calculated background component 1 from the acceleration measurement data processed in step S102. (Step S112). FIG. 6D shows time-series data of acceleration after removal. Thereby, the component of acceleration based on the ground deformation of the tread portion of the tire can be extracted.

Next, the calculated time series data of acceleration based on ground deformation is subjected to second-order time integration in the deformation amount calculation unit 26 to generate displacement data (step S114).
Since acceleration data to be integrated usually includes a noise component, if second-order integration is performed, the noise component is also integrated at the same time, and high-precision displacement data cannot be obtained. FIG. 7A shows the result of second-order integration of the time series data of the acceleration of FIG. 6D with respect to time. As shown in FIG. 7A, it can be seen that the displacement increases with time. This is because the time series data of acceleration to be integrated includes a noise component and is integrated by integration. In general, when the amount of deformation or displacement of a point of interest in a tread portion of a tire that rolls in a steady state is observed, a periodic change is shown with the rotation period of the tire as a unit. Therefore, it is usually not possible for the displacement to increase with time.
Therefore, the following processing is performed on the displacement data so that the displacement data obtained by performing the second-order time integration shows a periodic change in units of the tire rotation cycle.

That is, the noise component included in the displacement data is calculated as the background component 2 in the same manner as the method for calculating the background component 1 in step S110 (step S116).
More specifically, the region on the circumference of the tire is divided into a third region including a contact region with the road surface and a fourth region other than this, and the third region is larger than θ = 90 degrees 270. Below 4 degrees, greater than 450 degrees and less than 720 degrees, more than 810 degrees and less than 980 degrees, and the fourth area is θ = 0 to 90 degrees and 270 degrees to 360 degrees, 360 degrees to 450 degrees And 630 degrees to 720 degrees, 720 degrees to 810 degrees, and 980 degrees to 1070 degrees. The background component 2 uses the plurality of circumferential positions (the time corresponding to θ or θ) in the fourth region as nodes, and uses a predetermined function group to set the third region and the fourth region. It calculates | requires by calculating a 2nd approximation curve with the least squares method with respect to the data of an area | region. Note that the third region may be a region that matches the first region described above, or may be a different region. The fourth region may be a region that matches the second region described above, or may be a different region. As described above, the node means a constraint condition on the horizontal axis that defines the local curvature (flexibility) of the spline function. In FIG. 7B, a second approximate curve representing the background component 2 is indicated by a dotted line. In the example of FIG. 7B, the position indicated by “Δ” in FIG. 7B, that is, θ = 10, 30, 50, 70, 90, 270, 290, 310, 330, 350, 370, 390. , 410, 430, 450, 630, 650, 670, 690, 710, 730, 750, 770, 790, 810, 990, 1010, 1030, 1050, 1070 degrees.

A second approximate curve indicated by a dotted line in FIG. 7B is calculated by performing function approximation on the displacement data shown in FIG. 7A with a cubic spline function passing through the data points of the nodes. Is done. When performing function approximation, there is no node in the third region, function approximation is performed using only a plurality of nodes in the fourth region, and the weighting factor of the fourth region used in the least square method performed in function approximation is used. The processing is performed with 1 being set to 1, and the weighting factor of the third region being set to 0.01. When the background component 2 is calculated in this way, the reason why the first weighting factor is reduced and no node is defined in the third region is that the background component 2 is calculated mainly using displacement data in the fourth region. It is to do. In the fourth region, the deformation due to the ground contact of the tread portion is small and the deformation changes smoothly on the circumference, so the amount of deformation of the tire is small on the circumference and the change is also extremely small. On the other hand, in the third region, the tread portion of the tire is greatly displaced and rapidly changes based on the ground deformation. For this reason, the amount of deformation based on ground deformation is large and rapidly changes on the circumference. That is, the deformation amount of the tread portion in the fourth region is substantially constant as compared with the third deformation amount. Thus, by calculating the second approximate curve mainly using the displacement data obtained by the second-order integration of the fourth area, the third area including not only the fourth area but also the ground contact area with the road surface is obtained. The amount of deformation during rolling of the tire in the region can be obtained with high accuracy.
In FIG. 7B, the second approximate curve calculated mainly using the displacement data of the fourth region is indicated by a dotted line. In the fourth region, the second approximate curve substantially coincides with the displacement data (solid line).

Then, the approximate curve calculated as the background component 2 is subtracted from the displacement data calculated in step S110, and the distribution of the deformation amount based on the ground deformation of the tread portion is calculated (step S118).
FIG. 7C shows the distribution of deformation based on the ground deformation of the tread portion, which is calculated by subtracting the second approximate curve (dotted line) from the displacement signal (solid line) shown in FIG. 7B. Yes. FIG. 7C shows a distribution of deformation amounts for three rotations (three times of ground contact) when a predetermined measurement position on the tread portion is rotated around the circumference and displaced. It can be seen that the amount of deformation changes with each contact. The deformation amount calculated by such a method coincides with the deformation amount when the simulation is performed using the tire finite element model with high accuracy.

  Then, the deformation amount of the tread portion in which the noise component is removed from the acceleration shown in FIG. 6 (d) by performing second order differentiation with respect to time with respect to the time series data of the deformation amount in the tread portion shown in FIG. 7 (c). , That is, time series data of acceleration not including noise components (see FIG. 8A described later) based on the ground deformation of the tread portion is calculated (step S120).

Then, the contact length calculation unit 28 calculates the contact length (step S122). FIG. 8A shows a method for obtaining the grounding area and the grounding length. First, in the time series data of acceleration not including a noise component based on the ground deformation of the tire tread portion extracted in step S114, two points where the acceleration changes rapidly and crosses 0 are obtained. Next, the positions in the displacement data corresponding to the two obtained points are obtained, and these positions are set as the positions of the front end and the rear end as shown in FIG. The portion where the time series data of acceleration changes greatly in this way can be defined as the ground contact front end and the ground back end when the tread portion rotates and comes into the ground region, or when it comes out of the ground region. This is because the tire deforms rapidly. Further, it is possible to clearly determine the position where the time series data of acceleration crosses zero.
Note that the lower graph in FIG. 8A is a graph written by changing from a polar coordinate system expressed in the radial direction and circumferential direction of the tire to an orthogonal coordinate system expressed in the vertical direction and the front-rear direction of the tire. It is a graph which shows the deformation | transformation shape of the tire which has existed and deform | transformed by the grounding. On this graph, the contact length can be evaluated by determining the positions of the front end and the rear end.
The contact length calculated by such a method coincides with the contact length accurately when a simulation is performed using a finite element model of a tire.

Further, instead of the method shown in FIG. 8A, the ground region and the ground length can be obtained by the method shown in FIG. 8B. Specifically, FIG. 8B shows a standardization by dividing the position in the front-rear direction of the tire by the outer diameter R of the tread portion of the tire when the ground contact center position of the tire is the origin. It is the graph which expressed the deformation | transformation shape of the tire by dividing the position of an up-down direction by the outer diameter R, and normalizing. As shown in FIG. 8 (b), in the deformed shape of the tire, the position crossing a straight line separated by a certain distance δ from the lowest point in the vertical direction corresponds to the standardized position corresponding to the front end of contact and the rear end of the contact Standardized position. By obtaining the normalized positions and multiplying them by the outer diameter R, the positions of the front contact end and the rear contact end can be determined, whereby the contact area and the contact length of the tire can be determined. The fixed distance δ used for determining the front end position and the rear end position is preferably in the range of 0.001 to 0.005, for example. In addition, the position where the square value of the distance when the tread portion is separated upward from the lowest point crosses a predetermined value can be defined as the ground contact front end and the ground contact rear end. For example, the predetermined value is in the range of 0.00002 (cm ² ) to 0.00005 (cm ² ), and preferably 0.00004 (cm ² ) is used. It has been confirmed that the measurement results obtained by variously examining the contact length by changing the load applied to the stationary tire (load corresponding to the contact load) and the result of the contact length obtained by the above method show extremely high correlation. . Thus, the calculated contact length corresponds to a load (contact load) applied from the tire to the road surface. If the correlation between the measurement result of the contact length and the contact load, which is known in advance, is used, it is possible to convert the determined contact length into the contact load applied to the tire. FIG. 9 shows an example of the contact area and contact length obtained by the above method. A thick line portion in FIG. 9 indicates a grounding region.

  FIG. 10 shows the time change of the tire ground contact length calculated by the method shown in FIG. 8A when the traveling vehicle 12 performs the double lane change traveling. FIG. 5 is a graph showing each when tire B is mounted. FIG. Here, the double lane change traveling is the same as a test method called so-called elk test, in which the vehicle 12 turns in the forward direction (forward turning) while avoiding an obstacle while traveling straight ahead at a predetermined speed, and then in the reverse direction. The vehicle 12 is turned (reversely turned) to return to the original lane again. That is, the driver of the vehicle 12 travels straight at a predetermined speed in accordance with predetermined conditions (for example, a so-called VDA-ELK test or a test standard defined in “ISO-3888-2”), After turning a predetermined angle in one direction (forward direction) for a fixed time, the steering is returned by a predetermined angle in the reverse direction in a short time. FIG. 8A shows the tire 1 calculated from the acceleration of the tire (measurement target tire) of one wheel (front wheel) on the inner wheel side in the reverse turn when the vehicle 12 is subjected to the double lane change traveling. The contact length for each rotation is shown in time series.

  As shown in FIG. 10, the contact length of the measurement target tire shows a similar change in the case where both the tire A and the tire B are mounted. That is, when the vehicle turns in the forward direction, the contact length of the measurement target tire corresponding to the turning outer wheel of the forward turn increases due to the influence of the center of gravity of the vehicle 12 due to the centrifugal force. If a sudden reverse turn is performed in this state, roll resonance is induced in the vehicle 12, and the center of gravity of the vehicle 12 moves to the outside of the reverse turn at once. As a result, the contact load applied to the road surface from the measurement target tire corresponding to the turning inner wheel in the reverse turn is reduced, and further, the measurement target tire is lifted to the axle supporting the wheel including the measurement target tire. From the surface. In the example illustrated in FIG. 10, when the tire A is mounted, the wheel is lifted with respect to the measurement target tire (the wheel on which the vehicle 12 is mounted). According to the vehicle rollover resistance evaluation method of the present invention, when different tires are mounted on the same vehicle, the rollover performance of different tires can be comparatively evaluated by turning under the same traveling conditions. The contact length calculation unit 28 calculates the contact length for each rotation of the tire continuously for each tire 14a to 14d while the vehicle 12 is traveling.

  Next, the evaluation unit 70 extracts the minimum contact length during traveling from the calculated time-series contact length, and associates the value of the minimum contact length with the vehicle traveling speed set in step S102. Store in the memory 23. At this time, the evaluation unit 70 converts the extracted value of the minimum contact length into the value of the tire contact load based on the correlation, and stores the value of the contact load obtained by the conversion ( Step S124). As described with reference to FIG. 10, the ground load (corresponding to the ground contact length) on the reverse turning inner wheel side becomes the lowest at the timing when the center of gravity of the vehicle 12 greatly moves outward due to the reverse turning. The evaluation unit 70 stores the ground loads on the front and rear wheels on the reverse turning inner wheel side at such timing in the memory 27 in association with the vehicle traveling speed. A series of processes from the setting of the travel conditions (step S102) to the storage of the contact load (step S124) until the minimum contact load converted from the minimum contact length extracted in step S124 is less than a predetermined set value ( This is repeated (until the determination result in step S126 becomes YES). The predetermined set value is preferably, for example, a value of 70 to 80% of the minimum ground load obtained by running the vehicle 12 under the initial running conditions.

  As described above, by repeating the processing from step S102 to step S124, the memory 23 travels in the memory 23 when the minimum ground contact load and the minimum ground load are calculated under a plurality of travel speed conditions. The speed is stored. FIG. 11 is a graph showing the correspondence relationship between the vehicle traveling speed calculated in this way and the lowest ground contact load on the front wheel on the reverse turning inner wheel side. The evaluation unit 70 can also create such a graph and display it on the display 36. As shown in FIG. 11, the minimum grounding load on the reverse turning inner wheel side becomes smaller as the vehicle traveling speed increases, and the wheel on the reverse turning inner wheel side becomes easier to lift as the vehicle traveling speed increases. I understand. Such measurement results are consistent with actual vehicle behavior.

  In the evaluation unit 70, from the correspondence relationship with the traveling speed of the vehicle 12 when the plurality of minimum ground loads and the respective minimum ground loads stored in the memory 32 are calculated, the minimum of the wheel on the reverse turning inner wheel side is determined. A regression equation of the ground load to the vehicle traveling speed (a regression equation representing a regression curve indicated by a broken line in FIG. 11) is obtained. The regression curve may be a quadratic function derived using the least square method or a function derived using a Kalman filter. The type of regression curve is not particularly limited. The evaluation unit 70 obtains the regression equation for each of the front and rear wheels on the reverse turning inner wheel side of the vehicle 12 (step S128). And from this regression equation, the vehicle traveling speed when the minimum grounding load of both the front and rear wheels on the reverse turning inner ring side of the vehicle 12 becomes 0 (zero) is derived. Such a minimum wheel lifting speed is calculated for both the front and rear wheels on the reverse turning inner ring side, and the speed at which both the front and rear wheels are lifted is calculated as the anti-overturn limit speed (step S130). The evaluation unit 70 displays and outputs the rollover resistance limit speed derived as described above as an evaluation result on the display 36 (step S132). At this time, a graph showing the correspondence between the vehicle traveling speed and the minimum ground contact load of the tire as shown in FIG. 11 may be output as necessary.

According to the rollover resistance evaluation method of the present invention, the ground contact length representing the load applied to the wheel on the reverse turning inner ring side is accurately measured for each wheel without actually raising the wheel of the vehicle to be measured. To calculate. Based on such information, the lifting behavior of the wheel on the reverse turning inner wheel side under each traveling speed condition can be accurately grasped without actually lifting the wheel of the vehicle to be measured. As a result, the rollover limit speed limit under specific traveling conditions that quantitatively represents the rollover resistance performance of the vehicle to be measured can be derived safely and with high accuracy.
The rollover resistance evaluation method of the present invention is performed as described above.

  In the present invention, the vehicle is configured by providing wheels. When the wheels provided in the same vehicle body are replaced with different wheels, the vehicle after the wheel replacement and the vehicle before the wheel replacement can be regarded as different vehicles. That is, in the present invention, even when only the wheels arranged in the same vehicle body are changed, different vehicles are configured before and after the wheel change. If the vehicle rollover resistance evaluation method is applied to each vehicle configured by changing only the wheels, the difference in the rollover resistance evaluation results depends on the difference in the wheels of each vehicle. become. That is, the evaluation result obtained in this way shows the rollover resistance performance of each wheel. If it does in this way, it is also possible to evaluate the rollover-resistant performance of a wheel using the evaluation result by the rollover-resistant performance evaluation result of the present invention.

  Note that the wheel information representing the contact load applied to the wheels of the vehicle that is turning is acquired in the rollover resistance evaluation method of the present invention is not limited to the contact length. The wheel information acquired in the present invention may be information representing the tire ground contact load. For example, the load applied to the ground contact surface of the tire may be directly measured and used as wheel information. Alternatively, for example, the load applied to the tire axle may be measured and this axial load may be used as the wheel information. Also, for example, as shown in FIG. 12, a laser displacement meter 82 is attached to the rim portion of the wheel, and the distance between the rim and the tire is measured using the laser displacement meter 82, and obtained from the measured distance information. The amount of tire deflection may be used as wheel information. Further, for example, as shown in FIG. 13, a load sensor 84 is installed at a joint portion of the suspension supporting the axle for supporting the tire with the vehicle, and the vehicle is attached to the tire through the suspension by the load sensor 84. The suspension load to be applied may be measured, and this suspension load may be used as wheel information representing the ground contact load of the tire. Further, a measurement value of a suspension stroke that represents the magnitude of the suspension load that the vehicle applies to the tire via the suspension may be used as the wheel information. In the present invention, the wheel information indicating the contact length of the wheel is not particularly limited.

  As described above, the vehicle rollover resistance evaluation method and the vehicle rollover resistance evaluation device according to the present invention have been described in detail. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. Of course, improvements and changes may be made.

It is a schematic block diagram explaining the vehicle rollover resistance evaluation system which is an example of the vehicle rollover resistance evaluation apparatus of this invention. It is a block diagram which shows the structure of the evaluation apparatus with which the vehicle rollover resistance evaluation system shown in FIG. 1 was equipped. (A) And (b) is a figure explaining an example of the installation position to the tire of the acceleration sensor in this invention. (A)-(d) is a figure explaining the other example of the installation position to the tire of the acceleration sensor in this invention, respectively. It is an example of the flowchart of the vehicle rollover resistance evaluation method of this invention. (A)-(d) is a graph which shows the signal waveform obtained by the vehicle rollover-proof performance evaluation method of this invention. (A)-(c) is a graph which shows the signal waveform obtained by the vehicle rollover-proof performance evaluation method of this invention. (A) And (b) is a figure explaining the calculation method of the contact length in the vehicle rollover-proof performance evaluation method of this invention. It is a figure which shows an example of the contact length calculated by the vehicle rollover-proof performance evaluation method of this invention. It is a graph which shows an example of the time change of the tire contact length in specific driving conditions computed by the method shown in Drawing 8 (a). It is a graph which shows the correspondence of the vehicle running speed and the minimum grounding load of a tire produced | generated in the vehicle rollover resistance evaluation method of this invention. It is the schematic which shows the other example of the wheel information acquisition means of the vehicle roll-over resistance evaluation apparatus of this invention. It is the schematic which shows the other example of the wheel information acquisition means of the vehicle roll-over resistance evaluation apparatus of this invention.

Explanation of symbols

1 Tire 2 Acceleration Sensor 3 Receiver 4 Amplifier (AMP)
DESCRIPTION OF SYMBOLS 10 Vehicle overturning resistance evaluation system 12 Vehicle 14a-14d Wheel 15 Transmitter 16a-16d Sensor unit 20 Evaluation apparatus 21 Grounding length calculation means 22 Data acquisition part 23 CPU
24 signal processing unit 26 deformation amount calculation unit 27 memory 28 contact length calculation unit 36 display 70 evaluation unit 82 laser displacement meter 84 load sensor

Claims (7)

A method for evaluating the rollover resistance of a vehicle provided with at least four wheels,
A condition setting step for setting a traveling condition of the vehicle, including a traveling course that allows the vehicle to turn on a road surface, the regulation of the traveling speed of the vehicle being changeable;
The vehicle is driven under the traveling conditions by defining the traveling speed of the vehicle, and for at least one of the wheels on the turning inner wheel side of the vehicle, the magnitude of the load applied to the wheel from the road surface is set. Wheel information acquisition step for acquiring wheel information representing in time series; and
Of the wheel information acquired in time series in the wheel information acquisition step, an extraction step of extracting the wheel information minimum value at which the load is the minimum;
Repetitively changing the travel speed of the vehicle, each time the vehicle is driven at the changed travel speed, and performing the wheel information acquisition step and the extraction step;
A regression equation deriving step for deriving a regression equation for the traveling speed of the wheel information minimum value using the traveling speed of the vehicle in the repetition step and the wheel information minimum value at each traveling speed;
Based on the derived regression equation, the anti-rollover limit speed calculating step for calculating the minimum traveling speed among the traveling speeds at which the wheels are lifted when the vehicle is traveling under the traveling conditions;
An evaluation step for evaluating the anti-overturn performance of the vehicle based on the minimum traveling speed calculated in the anti-overturn limit speed calculating step;
The vehicle rollover resistance evaluation method according to claim 1, wherein when the travel speed of the vehicle is repeatedly changed, the repeat step increases the travel speed after the change compared to the travel speed of the vehicle before the change. When the vehicle is driven under the driving conditions set in the condition setting step, a safe driving speed at which the vehicle does not roll over is known in advance.
2. The vehicle rollover resistance evaluation method according to claim 1, wherein any of the travel speeds of the vehicle that are repeatedly changed in the repeat step is set to be equal to or less than the safe travel speed. When the vehicle is driven under the driving conditions set in the condition setting step, a safe driving speed at which the vehicle does not roll over is known in advance.
The vehicle traveling speed defined when the wheel information acquisition step is first performed is set to be equal to or less than the safe traveling speed,
In the repetition step, the minimum value wheel information acquired by executing the wheel information acquisition step and the extraction step is set in advance, and a set value of the wheel information indicating a state where the wheel is sufficiently grounded 3. The vehicle rollover resistance evaluation method according to claim 1, wherein the wheel information acquisition step and the extraction step are not performed after that. The wheel is a tire assembly in which a tire is mounted on a rim,
The vehicle according to any one of claims 1 to 3, wherein the wheel information acquisition step acquires, as the wheel information, information on a contact length with a road surface of the tire surface during travel of the vehicle. Of rollover resistance evaluation method.   5. The overturning resistance performance of a vehicle according to claim 4, wherein the information on the contact length is obtained from acceleration information obtained by measuring an acceleration of a tread portion of the tire of the wheel during traveling of the vehicle. Evaluation methods. The wheel is a tire assembly in which a tire is mounted on a rim,
4. The vehicle rollover resistance according to claim 1, wherein the wheel information acquisition step acquires, as the wheel information, information on a tire deflection amount of the wheel during travel of the vehicle. 5. Performance evaluation method. An apparatus for evaluating the rollover resistance of a vehicle provided with at least four wheels,
When the vehicle is driven under the driving conditions of the vehicle including a predetermined traveling course that allows the vehicle to turn on the road surface, at least one of the plurality of wheels of the vehicle, Wheel information acquisition means for acquiring, in time series, wheel information representing the magnitude of the load applied to the wheel from the road surface;
Of the wheel information acquired in time series in the wheel information acquisition means, an extraction means for extracting the wheel information minimum value when the load is minimum;
A memory for repeatedly storing the minimum wheel information for each time the vehicle is driven at the changed traveling speed under the traveling conditions, each time the traveling speed of the vehicle is changed repeatedly. Means,
The wheel information minimum value at each traveling speed stored in the storage means is read out, and the traveling speed of the wheel information minimum value is determined by using the traveling speed of the vehicle and the wheel information minimum value at each traveling speed. Regression equation deriving means for deriving a regression equation for
Based on the derived regression equation, a rollover limit speed calculation means for calculating a minimum running speed of the speeds at which the wheels are lifted when the vehicle is run under the running conditions;
An apparatus for evaluating rollover resistance of a vehicle, comprising: evaluation means for evaluating the rollover resistance performance of the vehicle based on the minimum traveling speed calculated by the rollover limit speed calculation means.

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