JP2008162392A - Method and device for estimating tire ground contact state, tire and vehicular control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for estimating a tire ground contact state and its device capable of estimating the tire ground contact state during traveling with a simple constitution, high in followability to the change in a road surface, a tire used for estimating the ground contact state of the tire, and a vehicular control device. <P>SOLUTION: An acceleration sensor 11 is embedded in a block 23B in the vicinity of an equatorial part of a tire with the detection direction in the tire rotational direction. The vibration waveform in the tire rotational direction of the block 23B at the kick-out is extracted from the detected output of the acceleration sensor 11, and the ground contact state of the tire in traveling is estimated based on the magnitude of the peak value G on the positive side of the vibration waveform. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for estimating a ground contact state of a running tire, and a tire used for estimating a tire ground contact state.

In order to improve the running stability of an automobile, it is required to accurately estimate the friction coefficient between the tire and the road surface (road surface friction coefficient) or the ground contact state of the tire and feed it back to the vehicle control. If the road surface friction coefficient and the ground contact state of the tire can be estimated in advance, for example, more advanced control of the ABS brake or the like can be performed before the risk avoidance operation such as braking / driving or steering, and safety is further improved. Expected to increase.
As a method of estimating the road surface friction coefficient, for example, after detecting the wheel speed and detecting the wheel speed fluctuation Δω when receiving the disturbance ΔT from the detected wheel speed signal ω, the road surface friction coefficient Δω is satisfied. The transfer function of the wheel is identified by the least square method, the gradient of the road surface μ is estimated, and the braking force of the vehicle is determined from the relationship between the gradient of the road surface μ, the braking force of the vehicle obtained in advance, and the gradient of the road surface μ. And estimating the slope of the road surface μ when the slip ratio is zero from the braking force and the slope of the road surface μ (see, for example, Patent Document 1), or as shown in FIG. A sensing block 52H having a height higher than the tread surface and a sensing block 52L having a height lower than that of the tread surface are formed on the tire tread portion 51 of the tire 50, and the sensing blocks 52H and 52L are respectively provided on side surfaces parallel to the tire circumferential direction. Strain gauges 53H and 53L are attached, and the road surface friction coefficient is determined from the difference between the strain levels detected by the two strain gauges 53H and 53L, and a map indicating the relationship between the previously determined strain level difference and the road surface friction coefficient. And the like have been proposed (see, for example, Patent Document 2).
JP 2002-160620 A JP 2002-36836 A

However, in the method of estimating the slope of the road surface μ when the slip ratio is zero from the slope of the road surface μ obtained based on the wheel speed and the estimated braking force of the vehicle, the force generated between the tire and the road surface Since there is no information, the estimation time is required, and there is a limit to the followability to the road surface change.
Further, in the method of estimating the road surface friction coefficient from the difference in strain level detected by the strain gauges 53H and 53L attached to the sensing blocks 52H and 52L having different heights, the road surface friction coefficient is good. Although μ can be estimated with high accuracy, it is necessary to change the tread pattern and mold in order to form blocks 52H and 52L having a height different from the height of the tread surface in the tire tread portion 51. There was a problem that it took time and effort to manufacture.

  The present invention has been made in view of the conventional problems, and is capable of accurately estimating the ground contact state of a running tire with a simple configuration and having a high follow-up property to a road surface change. Another object of the present invention is to provide a tire and a vehicle control device used for estimating the ground contact state of the tire and the device.

The invention according to claim 1 of the present application is a method for estimating a ground contact state of a running tire, and a slip state of the block in the tire rotation direction on a block defined by a groove formed on a surface of the tire tread. A sensor for detecting the tire is attached, and the ground contact state of the tire is estimated based on the detected slip state of the block.
According to a second aspect of the present invention, in the tire ground contact state estimating method according to the first aspect, an acceleration sensor for measuring vibration in the tire rotating direction of the block is attached to the inside of the block or the side surface of the block. The vibration waveform at the time of kicking out the block is extracted from the output of the acceleration sensor, and the slip state is detected based on the extracted vibration waveform.
According to a third aspect of the present invention, in the tire ground contact state estimating method according to the second aspect, the ground contact state of the tire is estimated from the magnitude of the positive peak value of the vibration waveform at the time of kicking out. It is.

The invention according to claim 4 is an apparatus for estimating a ground contact state of a running tire, and is arranged in a block defined by a groove formed on a surface of a tire tread or on a side surface of the block. A slip state detecting means for detecting a slip state of the block in the tire rotation direction, and a tire contact state estimation for estimating a ground contact state of the tire on the basis of the tire rotation direction slip state of the block detected by the slip state detecting means Means.
The invention according to claim 5 is the tire ground contact state estimating device according to claim 4, wherein the slip state detecting means is attached to the inside of the block or to the side surface of the block. A vibration waveform extracting means for extracting from the output of the acceleration sensor a vibration waveform at the time of kicking out the block depending on the slip state of the block in the tire rotation direction. The ground contact state of the tire is estimated based on the extracted vibration waveform at the time of kicking out.
The invention according to claim 6 is the tire ground contact state estimation device according to claim 5, wherein the tire ground contact state estimation means is preset with a positive peak value of the extracted vibration waveform. When a threshold value is exceeded, it is provided with the determination means which determines that the road surface to which a tire contacts is a low μ road.
According to a seventh aspect of the present invention, in the tire ground contact state estimating device according to any of the fourth to sixth aspects, the acceleration sensor is attached to a block near the equator portion of the tire.

The invention according to claim 8 is a tire in which a block partitioned by a groove is formed on a surface of a tire tread, and a slip state in the tire rotation direction of the block is detected inside the block or on the surface of the block. It is characterized in that a sensor is arranged.
The invention according to claim 9 is the tire according to claim 8, in which the tire ground contact state estimation device according to any one of claims 4 to 7 is mounted.
The invention according to claim 10 is an apparatus for controlling the traveling state of the vehicle, and includes the tire ground contact state estimation device according to any one of claims 4 to 7 and the tire ground contact state estimation device. Control means for controlling the running state of the vehicle based on the estimated ground contact state of the tire is provided.

According to the present invention, a sensor that detects a slip state in the tire rotation direction of the block, such as an acceleration sensor, is attached to the block defined by the groove formed on the surface of the tire tread, and the slip of the detected block is detected. Since the ground contact state of the tire is estimated based on the state, it is possible to accurately estimate the ground contact state of the running tire with a simple configuration, and it is possible to ensure the followability to the road surface change.
At this time, the vibration waveform at the time of kicking out the block is extracted by the sensor, and the slip state of the block is detected based on the magnitude of the extracted vibration waveform, particularly the positive peak value of the vibration waveform. By doing so, it is possible to reliably grasp the slip state.
Further, if the sensor is attached to a block in the vicinity of the equator of the tire, the ground contact state of the tire can be surely grasped, so that the estimation accuracy can be further improved.
Further, if the running state of the vehicle is controlled based on the estimated tire contact state, the safety of the vehicle can be further improved.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing a configuration of a tire ground contact state estimation device 10 according to the best mode. In FIG. 1, reference numeral 11 denotes an acceleration attached to the tire block for measuring vibration in the tire rotation direction of the block. A sensor, 12 is a vibration waveform extracting means for extracting the vibration waveform of the block from the detection signal of the acceleration sensor, and 13 is a positive peak value that appears after the negative peak of the extracted vibration waveform. Peak value detecting means 14 for performing tire contact state estimation means for estimating the contact state of the running tire based on the detected positive peak value. The vibration waveform extracting means 12, the peak value detecting means 13, and the tire ground contact state estimating means 14 constitute a calculation unit 15 of the tire ground contact state estimating device 10.
In this example, as shown in FIG. 2, the detection direction of the acceleration sensor 11 in the block 23 </ b> B near the equator of the tire among the blocks 23 defined by the grooves 22 formed on the surface of the tire tread 21. Are embedded so as to be in the tire rotation direction, and vibration in the tire rotation direction of the block 23B is detected.
The position at which the acceleration sensor 11 is embedded is preferably on the kicking side with respect to the center in the circumferential direction of the block 23B. Further, the distance L from the rear end portion on the block kicking side is the block groove depth H. It is desirable that the distance is within a range. When the acceleration sensor 11 is embedded on the stepping-in side of the block, when the sensor position of the block 23B moves away from the grounding surface, the remaining portion of the block 23B is still grounded, so that it is not easily affected by slippage. On the other hand, as shown in this example, when the block is embedded on the kick-out side of the block, the kick-out side is finally separated from the grounding surface and is susceptible to slipping. This is because appears more clearly.
Examples of the acceleration sensor 11 include a piezoelectric acceleration sensor, a semiconductor strain gauge acceleration sensor, and the like, but it is preferable to use a piezoelectric type that is small and excellent in frequency characteristics.
Further, the installation location of the calculation unit 15 may be in the groove 22 or may be provided on a substrate integrated with the acceleration sensor 11 and embedded in the block 23B. Or you may make it install in the tire inner surface side or wheel part which is not shown in figure, and connect this with the acceleration sensor 11 with a cable etc.

Next, the tire ground contact state estimating method according to the best mode will be described.
First, the acceleration sensor 11 measures the vibration of the block 23B in the tire rotation direction, and sends the data to the vibration waveform extraction means 12 to extract the vibration waveform when the block 23B is kicked out.
FIG. 3 is a vibration waveform obtained when a vehicle equipped with the tire ground contact state estimating device 10 of the present invention is driven on a dry asphalt road surface (road surface μ≈0.9), and FIG. 4 is a road surface having a low road surface friction coefficient. This is a vibration waveform obtained when the vehicle travels on (road surface μ≈0.2).
In the contact surface, as shown in FIG. 5, the blocks 23 and 23B increase in the amount of deformation toward the kick-out, but since the deformation is released at the time of kick-out, the blocks 23 and 23B vibrate in the circumferential direction (tire rotation direction). This vibration appears as a negative peak (pickout peak) of the vibration waveform shown in FIGS.
When the road surface friction coefficient μ of the road on which the tire is traveling is high, the blocks 23 and 23B are constrained to the road surface 30 until immediately before kicking the block, but when the road surface friction coefficient μ is low, the restriction is small. Therefore, the blocks 23 and 23B enter the sliding region on the way from stepping to kicking out, and the blocks 23 and 23B start to slide. As a result, the vibrations of the blocks 23 and 23B also become larger than when the road surface friction coefficient μ is high. This difference appears as the difference between the vibration waveforms shown in FIG. 3 and FIG.
Specifically, when the road surface friction coefficient μ is high, not only the amplitude of the vibration waveform after kicking is small, but also the acceleration waveform changes only on the negative side. On the other hand, when the road surface friction coefficient μ decreases, the amplitude of the vibration waveform increases and the acceleration waveform also changes to the positive side. This positive peak appears after the negative peak of the vibration waveform.
As shown in FIG. 4, the positive peak value G is higher than the acceleration level G ₀ in the ground contact surface on the dry asphalt road surface shown in FIG. The peak value G on the positive side is detected from the vibration waveform when the block 23B is kicked out and is extracted by the vibration waveform extracting means 12, and the tire ground contact state estimating means 14 detects the positive peak value G in advance. By comparing with the set threshold value K, the size of the road surface friction coefficient μ, that is, the ground contact state of the tire 20 during traveling can be estimated. Specifically, as shown in FIG. 4, when the positive peak value G exceeds the threshold value K, it is estimated that the ground contact state of the tire 20 is slippery. On the other hand, as shown in FIG. 3, when there is no positive peak or when there is a positive peak value G, if the peak value G is equal to or less than the threshold value K, it is estimated that the slip is difficult.

As described above, in the best mode, the acceleration sensor 11 is embedded in the block 23B near the equator of the tire so that the detection direction is the tire rotation direction, and the acceleration sensor 11 is kicked from the detection output of the acceleration sensor 11. Since the vibration waveform in the tire rotation direction of the block 23B is extracted and the ground contact state of the running tire is estimated based on the magnitude of the positive peak value G of this vibration waveform, the configuration is simple. It is possible to accurately estimate the ground contact state of the tire while the vehicle is traveling, and to ensure followability to a road surface change.
Further, since the ground contact state of the tire estimated in this example is an estimation of whether or not the tire is slippery, the ground contact state of the tire reflects the grip state of the tire. Therefore, the tire ground contact state estimation device 10 of the present invention can also be used as a tire grip state estimation device.
Further, since the mechanism of the present invention is directly related to the force with which the road surface restrains the tread, for example, it can be applied to the case where the effective road surface friction coefficient is reduced due to road surface inclusions such as sand and water. .
Further, since the tire ground contact state estimation device 10 of the present invention can estimate the grip state of the tire, based on the tire ground contact state estimation device 10 of the present invention and the tire ground contact state estimated by the tire ground contact state estimation device 10, If a vehicle control device including a control unit that controls the running state of the vehicle is configured to control the running state of the vehicle, the safety of the vehicle can be further improved.

In the best mode described above, the positive peak value G that appears after the negative peak that occurs when the block is kicked out is detected to estimate the ground contact state of the tire. Since the value itself also reflects the slip state, the ground contact state of the tire may be estimated from the negative peak value.
In the above example, the acceleration sensor 11 is embedded in the block 23B so that the detection direction is the tire rotation direction. However, as shown in FIG. The same effect can be obtained by attaching to the side surface 23a on the kick-out side of 23B. In this case, however, it is needless to say that the sensor needs to be mounted so that the detection direction is the tire rotation direction.

今回の試験では誤答はなく、アスファルト路面では７７回の判定のすべてが、摩擦係数の低い路面では８２回の判定のすべてが正しい結果を示した。
これにより、ブロックのタイヤ回転方向の滑り状態からタイヤの接地状態を精度よく推定できることが確認された。 A vehicle equipped with a tire in which an acceleration sensor is embedded in the block so that the detection direction is the tire rotation direction is moved from an asphalt road surface (road surface μ≈1) to a road surface with a friction coefficient μ equivalent to 0.2 at a speed of 60 km / h. The vibration waveform of the block was obtained on each road surface, and the presence or absence of a positive peak that appeared when the vibration waveform was kicked out was examined to determine whether the tire was slippery or not. The vibration waveform on the asphalt road surface (road surface μ≈1) is the same as that shown in FIG. 3, and the vibration waveform on the road surface with a low friction coefficient (road surface μ≈0.2) is the same as that shown in FIG.
In this embodiment, since the acceleration sensor is attached to only one place on the circumference, the above determination is made for each rotation of the tire, and the accuracy rate of the determination results for a plurality of times is obtained.
In addition, since the frequency | count determined by the road surface differs, it described together also about the number of determination opportunities.

There were no errors in this test, and all 77 judgments were correct on asphalt road surfaces, and all 82 judgments were correct on road surfaces with a low coefficient of friction.
Thereby, it was confirmed that the ground contact state of the tire can be accurately estimated from the slip state of the block in the tire rotation direction.

  As described above, according to the present invention, it is possible to accurately estimate the ground contact state of a running tire with a simple configuration and to ensure followability with respect to a road surface change. Can be improved.

It is a functional block diagram which shows the structure of the tire ground-contact-state estimation apparatus which concerns on the best form of this invention. It is a figure which shows the attachment state of an acceleration sensor. It is a figure which shows the vibration waveform of the block at the time of dry asphalt road running. It is a figure which shows the vibration waveform of a block when drive | working the road surface with a low road surface friction coefficient. It is a schematic diagram which shows the deformation | transformation state of the block at the time of tire rolling. It is a figure which shows the other example of the attachment state of an acceleration sensor. It is a figure which shows the estimation method of the conventional road surface friction coefficient.

Explanation of symbols

10 tire ground contact state estimation device, 11 acceleration sensor, 12 vibration waveform extraction means,
13 peak value detection means, 14 tire ground contact state estimation means, 15 calculation unit,
21 tire tread, 22 groove, 23, 23B block, 23a kick-out side surface.

Claims (10)

  A sensor for detecting a slipping state of the block in the tire rotation direction is attached to a block defined by a groove formed on the surface of the tire tread, and the grounding state of the running tire is based on the detected slipping state of the block. A method for estimating a tire ground contact state, wherein the tire contact state is estimated.   An acceleration sensor for measuring the vibration in the tire rotation direction of the block is attached to the inside of the block or the side surface of the block, and the vibration waveform at the time of kicking out the block is extracted from the output of the acceleration sensor. 2. The tire ground contact state estimating method according to claim 1, wherein the slip state is detected based on the vibration waveform.   3. The tire according to claim 2, wherein the ground contact state of the tire is estimated from the magnitude of the positive peak value that appears after the negative peak of the vibration waveform at the time of kicking out. Grounding state estimation method.   A slip state detecting means for detecting a slip state in the tire rotating direction of the block arranged in a block defined by a groove formed on the surface of the tire tread or on the side surface of the block, and detected by the slip state detecting means A tire ground contact state estimation device, comprising: a tire ground contact state estimation unit that estimates a tire ground contact state based on the slip state of the block.   The slip state detecting means is composed of an acceleration sensor that is attached to the inside of the block or on the side surface of the block and measures vibration in the tire rotation direction of the block, and from the output of the acceleration sensor, the tire rotation of the block A vibration waveform extracting means for extracting a vibration waveform at the time of kicking out the block depending on a sliding state in the direction is provided, and the ground contact state of the tire is estimated based on the extracted vibration waveform at the time of kicking out. The tire ground contact state estimation device according to claim 4.   The tire ground contact state estimation means reduces the road surface on which the tire contacts when the positive peak value that appears after the negative peak of the extracted vibration waveform exceeds a preset threshold value. 6. The tire ground contact state estimating device according to claim 5, further comprising determination means for determining that the road is a μ road.   The tire ground contact state estimation device according to any one of claims 4 to 6, wherein the acceleration sensor is attached to a block near the equator of the tire.   A tire in which a block partitioned by a groove is formed on the surface of the tire tread, and a sensor for detecting a slip state in the tire rotation direction of the block is disposed inside the block or on the surface of the block. A characteristic tire.   The tire according to claim 8, comprising the tire ground contact state estimation device according to any one of claims 4 to 7.   A tire ground contact state estimation device according to any one of claims 4 to 7 and a control means for controlling the running state of the vehicle based on the tire ground contact state estimated by the tire ground contact state estimation device. A vehicle control device.

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