JP2015072172A - Tire steering stability evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire steering stability evaluation method.SOLUTION: A tire steering stability evaluation method includes: a step S1 of continuously performing left-right continuous steering which steers a steering wheel of a traveling four-wheeled vehicle with tires mounted thereon, from a neutral state to one of the left and right sides, steers it to the other side through the neutral state, and returns to the neutral state in one period, while changing the period, to obtain time-series data of a steering angle of the steering wheel; a step S2 of continuously measuring a steering torque applied to the steering wheel, to obtain time-series data of the steering torque; a step S3 of acquiring frequency data of the steering angle per steering torque, on the basis of the two pieces of time-series data; a step S4 of frequency-analyzing the time-series data of the steering angle per steering torque, to obtain a gain of frequency response characteristics; and a step S5 of evaluating tire steering stability on the basis of the gain in a preset frequency domain.

Description

  The present invention relates to a method for evaluating steering stability performance of a tire that can be approximated to sensory evaluation of a driver.

  Conventionally, a method for evaluating the steering stability performance of a tire has been proposed (see, for example, Patent Document 1 below). In this evaluation method, first, a four-wheeled vehicle equipped with a tire to be evaluated is run. Next, for example, the steering of the four-wheeled vehicle is steered to the left from the neutral state, and then steered to the right through the neutral state, and the steering pattern for returning to the neutral state again is performed as one cycle. This steering is performed, for example, by keeping the period constant, that is, maintaining a constant frequency (speed).

  Next, a physical quantity such as a lateral acceleration generated by the steering pattern is measured, and time-series data of the physical quantity is acquired. Based on the time series data, the steering stability performance of the tire is evaluated.

JP 2009-250766 A

  A driver driving a four-wheeled vehicle changes the steering speed of the steering wheel based on the traveling speed, the curvature of the curve, and the like. Therefore, in order to be closer to the sensory evaluation of the steering stability performance of the tire by the driver, the steering stability performance of the tire should be evaluated with respect to the steering speed of the steering wheel having a certain range.

  However, in the method of Patent Document 1, since the steering speed (frequency) is constant, there is a possibility that the steering stability performance of the tire cannot be correctly evaluated.

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a method for evaluating the steering stability of a tire that can be made closer to the sensory evaluation of the driver.

  The method for evaluating the steering stability performance of a tire according to the present invention is a method for evaluating the steering stability performance of a tire, wherein the four-wheeled vehicle on which the tire is mounted is caused to travel, and the handle of the four-wheeled vehicle is set in a neutral state. Steering from left to right after steering from left to right, then steering to the other left and right through the neutral state, and the left and right continuous steering with one cycle to return to the neutral state again while continuously changing the cycle Obtaining time series data of the steering angle of the steering wheel, continuously measuring the steering torque applied to the steering wheel, obtaining time series data of the steering torque, and the two time series Obtaining the frequency data of the steering angle per the steering torque based on the data, and analyzing the frequency data of the steering angle per the steering torque to obtain the gain of the frequency response characteristic And that step, based on the gain in the predetermined frequency region, characterized in that it comprises an evaluation step of evaluating the steering stability of the tire.

  In the method for evaluating steering stability performance of the tire according to the present invention, the frequency region is preferably 0.2 to 1.0 Hz.

  In the method for evaluating the steering stability performance of the tire according to the present invention, the evaluation step uses the gain at a first frequency selected from the frequency domain and a second frequency different from the first frequency. It is desirable to evaluate the steering stability performance based on the absolute value of the difference from the gain.

  In the method for evaluating the steering stability performance of the tire according to the present invention, the slip angle of the tire when the steering wheel is steered to the right from the neutral state is positive, and the slip angle when the steering wheel is steered to the left from the neutral state is negative. In this case, it is desirable that the left and right continuous steering give the tire a slip angle of -1.5 to 1.5 degrees.

  In the method for evaluating the steering stability performance of the tire according to the present invention, it is preferable that the left-right continuous steering is performed at a traveling speed of the four-wheeled vehicle of 60 to 120 km / h.

  The method for evaluating the steering stability of the tire according to the present invention is to drive a four-wheeled vehicle equipped with a tire, steer the handle of the four-wheeled vehicle from the neutral state to one of the left and right, and then pass through the neutral state. Steering to the other of the left and right and steering to return to the neutral state again is continuously performed with the left and right continuous steering while changing the cycle, and time-series data of the steering angle of the steering wheel is acquired. In the evaluation method of the present invention, the steering torque applied to the steering wheel is continuously measured, and time series data of the steering torque is acquired.

  Furthermore, in the present invention, based on the two time series data, the step of obtaining the time series data of the steering angle per steering torque, the frequency analysis of the time series data of the steering angle per steering torque, and the frequency response characteristics And a step of evaluating the steering stability performance of the tire based on a gain in a preset frequency region.

  As described above, in the evaluation method of the present invention, the gain is acquired not in the steering speed of the single steering wheel but in the preset frequency region. For example, by setting the frequency range to a steering speed (frequency) range that is frequently used in actual driving, it is possible to evaluate the steering stability performance of the tire closer to the sensory evaluation of the driver.

It is a flowchart which shows an example of the process sequence of the evaluation method of this embodiment. It is a flowchart which shows an example of the steering angle acquisition process of this embodiment. It is the graph which showed the relationship between a steering angle and time. It is the graph which showed the relationship between steering torque and time. It is the graph which showed the relationship between the steering angle per steering torque, and the frequency of a steering angle. It is the graph which showed the gain of the frequency response characteristic of the steering angle per steering torque. It is a graph which shows the relationship between the steering speed of the driver in actual driving | running | working, and its frequency.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The method for evaluating the steering stability of the tire according to the present embodiment (hereinafter sometimes simply referred to as “evaluation method”) is the same as that for the tire to be evaluated (hereinafter simply referred to as “tire”). This is a method for evaluating close to the sensory evaluation. In the evaluation method of the present embodiment, the evaluation target tire is mounted on a four-wheeled vehicle, and the steering stability performance is evaluated.

  FIG. 1 shows a specific processing procedure of the evaluation method of the present embodiment. In the evaluation method of the present embodiment, first, a four-wheeled vehicle equipped with tires is run to acquire time-series data of the steering angle of the steering wheel (steering angle acquisition step S1).

  FIG. 2 shows a specific processing procedure of the steering angle acquisition step S1 of the present embodiment. In the steering angle acquisition step S1 of the present embodiment, first, a tire to be evaluated is mounted on a four-wheeled vehicle (step S11). In the present embodiment, the evaluation target tire is mounted on all wheels of a four-wheeled vehicle by assembling the rim on a regular rim and filling the regular internal pressure. Further, for example, a load of about 45 to 70% of the normal load is applied to the tire.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, the standard rim for JATMA, “Design Rim” for TRA, or ETRTO If present, it means "Measuring Rim".

  “Regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA and the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA, If there is, “INFLATION PRESSURE” is set, but in the case of passenger car tires, it is set to 180 kPa.

  “Regular load” is the load specified by the standard for each tire. If JATMA, maximum load capacity, if TRA, maximum value described in table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, ETRTO If so, use "LOAD CAPACITY".

  Next, the steering pattern of the steering wheel is input to the automatic steering device (step S12). The automatic steering device automatically steers the steering wheel of a four-wheeled vehicle according to a steering pattern inputted in advance.

  As the steering pattern, for example, left and right continuous steering is set, in which the steering wheel is steered to the left from the neutral state, then steered to the right through the neutral state, and then returned to the neutral state for one cycle. In the left-right continuous steering, the steering wheel may be steered to the right from the neutral state, then steered to the left through the neutral state, and returned to the neutral state again for one cycle. In the steering pattern, the left and right continuous steering is continuously performed while changing the cycle (steering speed). In the steering pattern of the present embodiment, the period is gradually decreased with the passage of time (in this embodiment, the steering frequency is gradually increased in the range of 0.3 Hz to 2.0 Hz).

  Next, the four-wheeled vehicle is driven, and left and right continuous steering is continuously performed while changing the cycle, and time-series data of the steering angle of the steering wheel is acquired (step S13). In step S13, first, the four-wheeled vehicle is accelerated until a predetermined traveling speed is reached. Next, the left and right continuous steering is automatically performed by the automatic steering device according to the steering input pattern. While the left and right continuous steering is performed, the steering angle of the steering wheel is continuously measured. Based on the measurement result of the steering angle, a graph (time series data of the steering angle As) showing the relationship between the steering angle As and time shown in FIG. 3 is acquired.

  In the time-series data of the steering angle As shown in FIG. 3, the steering angle As continuously changes along a sine wave curve. A steering angle of 0 degrees indicates the position of the neutral steering wheel. Moreover, the positive steering angle has shown the state steered to the right from the neutral state. Further, the negative steering angle indicates a state in which the steering is steered to the left from the neutral state. The steering angle As is preferably measured using a steering force angle meter that can measure the steering angle of the steering wheel and the steering torque applied to the steering wheel. Further, in the present embodiment, the automatic steering device is exemplified in which the left and right continuous steering is automatically performed, but may be steered by the driver.

  Next, the steering torque applied to the steering wheel is measured, and time-series data of the steering torque is acquired (step S2). In step S2 of this embodiment, first, while the steering wheel is being automatically steered, the steering torque applied to the steering wheel is continuously measured by a steering force angle meter. Based on the measurement result of the steering torque, a graph (time series data of the steering torque Ts) showing the relationship between the steering torque Ts and time shown in FIG. 4 is acquired. In the time series data of the steering torque Ts, the positive steering torque Ts indicates the magnitude of the torque when steering from the neutral state to the right. The negative steering torque Ts indicates the magnitude of torque when steering from the neutral state to the left. Note that the power steering is turned off when acquiring the time-series data of the steering angle As and the time-series data of the steering torque Ts.

  Next, frequency data of the steering angle per steering torque is acquired based on the two time series data (step S3). In this step S3, first, time-series data of the steering angle As (shown in FIG. 3) and time-series data of the steering torque Ts (shown in FIG. 4) are Fourier-transformed, and the power calculated for each frequency. A graph showing the relationship between the steering angle (As / Ts) per steering torque shown in FIG. 5 and the frequency of the steering angle As shown in FIG. 5 (frequency of the steering angle (As / Ts) per steering torque) by dividing the spectrum. Data) is acquired.

  In the frequency data of the steering angle (As / Ts) per steering torque according to the present embodiment, when the steering angle As frequency is 0.3 Hz to 1.35 Hz, the steering angle As frequency increases as the steering angle As frequency increases. There is a tendency that the steering angle (As / Ts) gradually increases. This indicates that the driver tends to feel that steering of the steering wheel is lighter as the frequency of the steering angle As increases. On the other hand, when the frequency of the steering angle As is 1.35 Hz to 2.0 Hz, the steering angle per steering torque (As / Ts) tends to gradually decrease as the frequency of the steering angle As increases. This indicates that the driver tends to feel that the steering of the steering wheel is heavier as the frequency of the steering angle As increases.

  Next, the gain of the frequency response characteristic of the steering angle per steering torque is acquired (step S4). In step S4, frequency analysis (FFT processing) is performed on the frequency data of the steering angle (As / Ts) per steering torque shown in FIG. 5 based on each frequency of the steering angle As. Thereby, the gain of the frequency response characteristic of the steering angle (As / Ts) per steering torque shown in FIG. 6 is obtained.

  In step S4, the FFT processing is performed a plurality of times by shifting the window function in units of 2 seconds with respect to the frequency data of the steering angle per steering torque (As / Ts) shown in FIG. Therefore, it is desirable that the maximum value of the power spectrum of each frequency is the gain G of the steering angle (As / Ts) per steering torque of each frequency. This is because, for example, the influence of noise included in a specific frequency can be reduced and the calculation accuracy can be improved as compared with the case where FFT processing is performed on a wide frequency region by applying a single window function. .

  Next, the steering stability performance of the tire is evaluated based on a gain in a preset frequency region (evaluation step S5).

  In the frequency response characteristic gain shown in FIG. 6, for example, in a frequency region including a plurality of frequencies, the smaller the gain change of each frequency, the higher the linearity of the steering angle (As / Ts) with respect to the steering torque. ing. In this case, even if the driver changes the steering speed of the steering wheel, the weight of the steering wheel does not suddenly increase or decrease. For this reason, in the sensory evaluation of the driver, there is a tendency that the response of the steering wheel is good and the steering stability performance of the tire is excellent. Therefore, in the evaluation step S5 of the present embodiment, it is determined that the steering stability performance of the tire is better as the change in the gain of each frequency is smaller in the frequency domain.

  On the other hand, in the gain of the frequency response characteristic, for example, in the frequency domain, the greater the change in the gain of each frequency, the lower the linearity of the steering angle (As / Ts) with respect to the steering torque. In this case, when the driver changes the steering speed of the steering wheel, the weight of the steering wheel suddenly increases or decreases. For this reason, in the sensory evaluation of the driver, there is a tendency that the response of the steering wheel is poor and the steering stability performance of the tire is inferior. Therefore, in the evaluation step S5 of the present embodiment, it is determined that the steering stability performance of the tire is poorer as the gain change of each frequency is larger in the frequency domain.

  As described above, in the evaluation step S5, the gain of the frequency response characteristic is obtained, so that the steering stability performance of the tire can be evaluated in a manner close to the sensory evaluation of the driver. Therefore, in the evaluation method of the present invention, the evaluation of the steering stability performance of the tire closer to the sensory evaluation of the driver by setting the frequency region to a steering speed (frequency) range that is frequently used in actual driving, for example. Is possible.

  FIG. 7 shows a graph showing the relationship between the driver's steering speed (frequency) and the frequency in actual driving. As is clear from this graph, the steering speed (frequency) range frequently used in actual traveling is 0.2 Hz to 1.0 Hz. For this reason, the frequency region in which the steering stability performance of the tire of this embodiment is evaluated is preferably 0.2 Hz to 1.0 Hz. Thereby, in the evaluation step S5, the steering stability performance of the tire is evaluated based on the gain in the frequency region that is frequently used in actual driving. Therefore, in the evaluation step S5, the steering stability performance of the tire can be evaluated effectively close to the sensory evaluation of the driver.

  Note that if the lower limit value of the frequency region is less than 0.2, the steering stability performance of the tire may not be accurately evaluated because the frequency region is out of the frequency region that is frequently used in actual driving. Moreover, even if the upper limit value of the frequency domain exceeds 1.0, there is a risk that the frequency domain will be out of the frequency domain frequently used in actual driving. For this reason, the frequency region is more preferably 0.3 Hz or more, and more preferably 0.8 Hz or less.

  In addition, the evaluation step S5 determines the absolute value of the difference (Ga−Gb) between the gain Ga at the first frequency selected from the frequency domain and the gain Gb at the second frequency different from the first frequency. Based on this, it is desirable to evaluate the steering stability performance. Thereby, in the evaluation step S5, since a change in gain is quantitatively obtained in the frequency domain, it is possible to prevent variation in evaluation of the steering stability performance of the tire.

  The first frequency is preferably the minimum frequency in the frequency domain, and the second frequency is preferably the maximum frequency in the frequency domain. Thereby, in evaluation process S5, the steering stability performance of a tire is evaluated based on the difference (Ga-Gb) in the whole range of a frequency domain.

  In the evaluation step S5, it is desirable to determine that the steering stability performance is good when the absolute value of the difference (Ga−Gb) is 0.002 dB or less. When the absolute value of the difference (Ga−Gb) exceeds 0.002 dB, the gain change tends to increase, and the driver's sensory evaluation tends to be judged to have poor tire steering stability performance. For this reason, the absolute value of the difference (Ga−Gb) is more preferably 0.001 dB or less.

  The left and right continuous steering is desirably performed at a traveling speed of the four-wheeled vehicle of 60 to 120 km / h. If the traveling speed of the four-wheeled vehicle is less than 60 km / h, the steering torque applied to the steering wheel becomes small, and the difference in steering stability performance among the plurality of tires 1 to be evaluated can be clearly evaluated. May be difficult. Conversely, if the traveling speed of a four-wheeled vehicle exceeds 100 km / h, the speed at which the driver normally travels may be exceeded, which may make it difficult to evaluate the steering stability performance of the tire that is closer to the driver's sensory evaluation. Furthermore, if the traveling speed of the four-wheeled vehicle exceeds 100 km / h, the grip limit of the tire 1 may be reached and the steering torque may not be measured. From such a viewpoint, the traveling speed of the four-wheeled vehicle is more preferably 80 to 100 km / h.

  Further, the left and right continuous steering is performed when the tire slip angle when the steering wheel is steered to the right from the neutral state is positive and the slip angle when the steering wheel is steered from the neutral state to the left is negative. It is desirable to provide a slip angle in the range of 5 to 1.5 degrees. As a result, in this embodiment, for example, during high-speed driving, the gain of the frequency response characteristic is acquired within the range of steering normally performed by the driver, so the steering stability is evaluated close to the sensory evaluation of the driver. sell.

  Furthermore, in the evaluation method of the present embodiment, it is desirable that the evaluation method be performed on an understeered four-wheeled vehicle. When implemented in an oversteered four-wheeled vehicle, the steering direction of the steering wheel differs from the direction in which the vehicle moves, and therefore there is a possibility that the steering stability performance based on the response of the steering wheel cannot be fully evaluated.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In accordance with the processing procedure shown in FIGS. 1 and 2, the left and right continuous steering is continuously performed while changing the cycle, and the gain of the frequency response characteristic is acquired. And the steering stability performance of the tire was evaluated based on the gain of the frequency response characteristic (Examples 1 to 11).

For comparison, the left and right continuous steering was performed while maintaining a constant frequency (0.3 Hz), and the physical quantities (steering angle, steering torque, etc.) of the tire were measured. And the steering stability performance of the tire was evaluated from these physical quantities (Comparative Examples 1 and 2). The common specifications are as follows.
Tire size: 175 / 65R14
Rim size: 14 × 5J
Internal pressure: 230 kPa
load:
Front wheel: 2.75kN, rear wheel: 2.25kN (regular load: 4.66kN)
Automobile: Fit made by Honda Motor Co., Ltd. (displacement 1300cc)
Steering input: Steering by driver Steering force angle meter: Steering force angle meter (SFA-E-SA20) manufactured by Kyowa Denki Co., Ltd.

  And sensory evaluation (steering stability performance of a tire) by 10 drivers (evaluation experience: 1 to 10 years) is performed, and the sensory evaluation and evaluation results of Examples 1 to 11 and Comparative Examples 1 and 2 The match rate was calculated. The higher the match rate, the closer the evaluation method can be to the driver's sensory evaluation. The test results are shown in Table 1.

  As a result of the test, it was confirmed that the evaluation method of the example had a high matching rate with the sensory evaluation of the driver and could be close to the sensory evaluation of the driver.

S1 Step of acquiring time series data of steering angle of steering wheel S2 Step of acquiring time series data of steering torque S3 Step of acquiring time series data of steering angle per steering torque S4 Evaluation step of evaluating steering stability performance of tire

Claims (5)

A method for evaluating the steering stability performance of a tire,
A four-wheeled vehicle equipped with the tire is run, and the steering wheel of the four-wheeled vehicle is steered from the neutral state to one of the left and right, and then through the neutral state, steered to the other of the left and right, and again neutral. Continuously performing left and right continuous steering with one cycle of returning to the state while changing the cycle, and obtaining time-series data of the steering angle of the steering wheel;
Continuously measuring the steering torque applied to the steering wheel, and obtaining time series data of the steering torque;
Obtaining frequency data of the steering angle per steering torque based on the two time-series data;
Analyzing the frequency data of the steering angle per steering torque to obtain a gain of frequency response characteristics;
An evaluation step of evaluating the steering stability performance of the tire based on the gain in a preset frequency region.   The method for evaluating the steering stability performance of a tire according to claim 1, wherein the frequency region is 0.2 to 1.0 Hz.   The evaluation step is based on an absolute value of a difference between the gain at a first frequency selected from the frequency domain and the gain at a second frequency different from the first frequency. The method for evaluating the steering stability performance of a tire according to claim 1, wherein the stability performance is evaluated.   When the slip angle of the tire when the steering wheel is steered to the right from the neutral state is positive and the slip angle when the steering wheel is steered to the left from the neutral state is negative, the left and right continuous steering is −1 to the tire. The evaluation method of the steering stability performance of the tire according to any one of claims 1 to 3, wherein a slip angle of 5 to 1.5 degrees is given.   The tire steering stability evaluation method according to any one of claims 1 to 4, wherein the left and right continuous steering is performed at a traveling speed of the four-wheeled vehicle of 60 to 120 km / h.

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