JP2005186830A - Tire abnormality detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire abnormality detection device capable of detecting local abnormality of a tire with high reliability. <P>SOLUTION: The tire abnormality detection device 10 comprises a torque sensor 1 which is used for the output control of a vehicular electric power steering device 20 to detect the steering torque from a steering wheel 12 applied against the steering load torque from a steered wheel, and a signal processing means 2 to extract the vibration composition attributable to the local abnormality of the tire mounted on the steered wheel included in the steering load torque from the output signal of the torque sensor 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire abnormality detection device that detects a local abnormality of a running tire, and particularly relates to a tire having a highly reliable detection performance.

  As a device for detecting local abnormalities of running tires, for example, signs of failure such as separation, it is attached to a wheel and rotates around its central axis, and the physical quantity at a predetermined position is periodically changed by the rotation. A rotating body that is attached to an axle that pivotally supports the wheel, a sensor that continuously detects the physical quantity and outputs a signal corresponding to the physical quantity, and a period of rotation of the rotating body from the output signal of the sensor There is known a tire abnormality detection device including signal processing means for extracting a vibration component caused by a local abnormality of a tire superimposed on a typical component (see, for example, Patent Document 1), and a rotating body and a sensor. As an example, there is a combination of a gear pulser that constitutes an ABS signal generator and a wheel sensor that detects a change in magnetic field accompanying rotation of the gear pulser.

The signal processing means is configured to extract a change in the physical quantity due to vibration of the rotating body caused by a local abnormality of the tire superimposed on a periodic change in physical quantity due to the rotation of the rotating body. This utilizes the fact that a vibrational change appears in the rotation of the rotating body due to a mechanical abnormality. However, in practice, this change is slight, especially when extracting this change by comparing with the adjacent wheels of the same vehicle, or by comparing with the state of the tires of the own wheels that are not abnormal. However, there is a problem that the detection is very delicate and the reliability of abnormality detection is low and not practical.
JP 2003-146036 A

  The present invention has been made in view of such problems, and an object of the present invention is to provide a tire abnormality detection device that can detect a local abnormality of a tire with high reliability.

  <1> is used for output control of the electric power steering device for a vehicle, and a torque sensor for detecting a steering torque from a steering wheel acting against a steering load torque from a steering wheel, and an output signal of the torque sensor And a signal processing means for extracting a vibration component included in the steering load torque due to a local abnormality of the tire mounted on the steering wheel.

  <2> is the means for extracting the rotation correlation signal correlated with the rotation of the wheel from the output signal of the sensor using the adaptive digital filter from the sensor output signal in <1>; Is a tire abnormality detecting device comprising an abnormality determining means for determining a local abnormality of the tire.

  According to the invention of <1>, since the signal processing means for extracting the vibration component caused by the local abnormality of the tire is provided from the output signal of the torque sensor, the portion that causes the local abnormality of the tire is grounded to the road surface. This abnormality causes the steering load torque to fluctuate greatly, and the signal processing means is configured to extract only this torque fluctuation from the torque detected by the torque sensor, so that the local abnormality of the tire is highly reliable. Can be detected.

  According to the invention of <2>, the signal processing means uses an adaptive digital filter to extract only the rotation correlation signal correlated with the wheel rotation from the output signal of the sensor, and based on this rotation correlation signal, the tire Therefore, irregular vibrations caused by road surface conditions and driving conditions can be excluded, and the reliability in detecting tire abnormality can be improved.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the configuration of the tire abnormality detection device of this embodiment. The tire abnormality detection device 10 is based on the output from the torque sensor 1, the signal processing means 2 that extracts the vibration component due to the local abnormality of the tire from the output signal of the torque sensor 1, and the output from the signal processing means 2. And a display alarm device 3 for displaying an abnormality of the tire and generating an alarm. The torque sensor 1 detects the direction and magnitude of torsion of the torsion bar 9 generated according to the magnitude of the steering torque Tr2 from the steering wheel 12 acting opposite to the steering load torque Tr1 from the steering wheels FR and FL. It is configured as follows.

  The torque sensor 1 is used for output control of the vehicular electric power steering apparatus 20. The power steering apparatus 20 includes a steering wheel 12 operated by a driver and a steering coupled to the steering wheel 12. The shaft 8 includes a pinion gear 34 provided at the tip of the steering shaft 8 and a rack shaft 35 that meshes with the pinion gear 34 by a rack gear portion 35a and extends in the left-right direction of the vehicle. Tie rods 36 are coupled to both ends of the rack shaft 35, and the tie rods 36 are pivotally provided around the king pins 38 and are coupled to knuckle arms 37 that support the left and right steering wheels FL, FR.

  With this configuration, when the steering wheel 12 is operated and the steering shaft 8 is rotated in the power steering device 20, this rotation is converted into a linear motion along the left-right direction of the vehicle by the pinion gear 34 and the rack shaft 35. This linear motion is converted into rotation around the king pin 38 of the knuckle arm 37, whereby the front left and right wheels FL, FR are steered.

  The steering shaft 8 is divided into an input shaft 8a that transmits the steering torque from the steering wheel 12, and an output shaft 8b that transmits the steering load torque from the side of the pinion 34, that is, the steering wheels FR and FL. These are connected by a torsion bar 9. A steering assist force from the electric motor 7 is applied to the output shaft 8b via the electromagnetic clutch 31 and the speed reducer 13.

  The magnitude of the steering assist force is adjusted by controlling the voltage applied to the motor 7, and the motor 7 is controlled by the steering control means 5. The steering control means 5 determines the applied voltage to the motor 7 based on the output signal of the steering angle sensor 6 that detects the steering angle of the steering wheel 12 and the output signal of the torque sensor 1, and thereby the steering angle and A steering assist force according to the steering torque is applied to the steering wheels FR and FL.

  FIG. 2 is a graph showing the change over time of the torque detected by the torque sensor 1, with the magnitude of the detected torque on the vertical axis and the elapsed time on the horizontal axis. When there is no local abnormality in any of the tires of the steering wheels FR and FL when the vehicle is traveling straight ahead, a torque time change CV1 as shown in FIG. As shown in FIG. 2 (b), when an antecedent of abnormality such as tread separation occurs locally in one of the tires of FR and FL, as shown in FIG. 2 (b), when the tire portion corresponding to this abnormality contacts the road surface. Torque fluctuation Ta is superimposed on CV1 and detected as torque time change CV2. Here, the torque fluctuation Ta appears once per tire rotation, and the time interval between adjacent Tas is the time Tt required for one tire rotation.

  Next, the signal processing means 2 for extracting the vibration component resulting from the local abnormality of the tire from the output signal of the torque sensor 1 will be described. FIG. 3 is a block diagram showing the configuration of the signal processing means 2. The signal processing means 2 is a sensor output capturing means 15 that captures the output signal of the torque sensor 1, and the wheel rotation from the output signal of the torque sensor 1. The rotation correlation signal extraction means 16 for extracting the rotation correlation signal correlated with the rotation correlation signal and the presence / absence of a tire local abnormality are determined from the rotation correlation signal. It comprises an abnormality determination means 18 for outputting.

  Here, the rotation correlation signal extraction means 16 may use an adaptive digital filter as shown below. For example, refer to FIG. 4 showing the processing of the rotation correlation signal extraction means 16 in a block diagram. I will explain. The rotation correlation signal extraction means 16 inputs the digital signal X (i) acquired by the sensor output acquisition means 15 and supplies the input signal (reference signal R (i) to the adaptive digital filter 23 via the comparator 24. And the signal obtained by delaying the input signal through the delay circuit 22 (directly supplied to the adaptive digital filter 23) are calculated in the adaptive digital filter 23 in real time, and output as the output signal Y (i). A signal correlated in period is output. Therefore, the output signal Y (i) can be obtained as a signal (periodic signal) correlated with the rotation of the wheel. The obtained output signal Y (i) is input to the tire local abnormality signal extraction means 17.

  The delay time in the delay circuit 22 is preferably equal to or less than the time interval of one rotation of the wheel, but even if it is a time interval of two or more rotations, or a time interval that is slightly different from the time of one rotation, Due to the characteristics of the adaptive digital filter 23, there is no problem in obtaining a periodic component synchronized with the rotation by calculation. Further, even when the time interval of one rotation of the wheel changes depending on the number of rotations (running speed), it can be dealt with by appropriately setting the sampling frequency and tap length of the adaptive digital filter 23. It can also be realized by previously setting three stages of delay time, low speed, medium speed, and high speed, and changing the delay time of the delay circuit 22 in three stages according to the speed. Of course, it is also conceivable to always measure the speed of the vehicle and change the delay time of the delay circuit 22 in real time according to the speed.

  As the adaptive digital filter 23, a conventionally known configuration can be used. In the example shown in FIG. 4, the reference signal R (i) composed of the digital data X (i) measured by the sensor output capturing means 15 and the output Y (i) of the adaptive digital filter are output by the comparator 24. The difference between the two is calculated to obtain the error signal E (i). Therefore, the error signal E (i) can be obtained as a signal (random signal) that is irrelevant to the rotation of the wheel, for example, that contributes to the road surface or the vehicle body. The obtained error signal E (i) is fed back to the coefficient changing unit of the adaptive digital filter 23, and the coefficient of the adaptive digital filter 23 is dynamically changed in accordance with the error signal E (i). 23 optimization is planned. As a method for optimizing the error signal E (i) by feeding it back to the coefficient changing unit of the adaptive digital filter 23, the LMS (least mean square) method, Newton method, A plunging method can be used.

  As an example of the rotation correlation signal extraction means 16, as shown in FIG. 4, a delay circuit 22 is provided between the input portion of the digital signal X (i) from the sensor output acquisition means 15 and the adaptive digital filter 23. In addition to the example, as shown in FIG. 4, a delay circuit 22 is provided between the input portion of the digital signal X (i) from the sensor output capturing means 15 and the comparator 24, and the reference signal R (i) is provided. Even if it is delayed, the same effects as those shown in FIG. 4 can be obtained.

  The determination of the presence / absence of a tire local abnormality from the rotation correlation signal can be performed, for example, as follows. The vibration detected by the torque sensor 1 is a superposition of vibrations of various frequencies, but the frequency that changes due to a local abnormality of the tire corresponds to the natural frequency of the wheel, and is local to the tire. Since the amplitude at this natural frequency differs depending on whether or not an abnormality has occurred, the amplitude at the natural frequency of each wheel in the state where there is no local abnormality is stored for each wheel. Then, it may be determined that an abnormality has occurred when a change larger than a predetermined threshold appears with respect to the normal amplitude.

An output signal from the torque sensor 1 constituting the vehicle steering device 20 during actual vehicle traveling, and a rotation correlation signal extracted from this signal using the rotation correlation signal extracting means 16 are illustrated below. The conditions relating to signal capture are as follows.
(1) Travel conditions: straight travel (2) travel speed: 60 km / h
(3) Driving road surface: smooth asphalt dry road surface (4) Test tire: A tire with a tread separation formed in a part of the tread in the circumferential direction, mounted on one of the steered wheels, and an abnormal tire model It was.

  The signal processing means 2 is configured as described above, and in particular, the rotational correlation signal extraction means 16 is configured by using the adaptive digital filter 23.

  FIG. 6 shows an output signal from the torque sensor 1 when the test tire is mounted, and FIG. 7 shows an output signal of the rotation correlation signal extraction means 16 corresponding to this, and a local abnormality is used instead of the test tire. FIG. 8 shows an output signal of the rotation correlation signal extracting means 16 when a tire without a tire is mounted. Each of these figures is a graph showing the frequency distribution with the horizontal axis representing the frequency and the vertical axis representing the amplitude expressed in decibels.

  Comparing FIG. 7 to FIG. 6, it can be seen that in the rotational correlation signal, a ripple-like distribution having a random frequency that is not correlated with the rotation of the tire is removed from the frequency distribution shown in FIG.

  Further, when FIG. 7 is compared with FIG. 8, the rotation correlation signal when a tire having a local abnormality is attached has a frequency corresponding to the natural frequency of this wheel as compared with that when a normal tire is attached. When the amplitude at 90 Hz and 220 Hz is large and the amplitude of at least one of the frequencies 90 Hz and 220 Hz is larger than a predetermined value, it can be determined that there is a tire local abnormality, and the frequency 90 Hz is taken as an example. When an amplitude of 90 dB abnormality is detected, it can be determined that there is an abnormality.

  As shown in the above embodiment, it can be understood that a local abnormality of the tire can be determined by processing the output signal from the torque sensor 1 by the signal processing device 2.

It is a conceptual diagram which shows the structure of the tire abnormality detection apparatus of embodiment which concerns on this invention. It is a graph showing the time change of the torque detected by a torque sensor. It is a block diagram which shows the structure of a signal processing means. It is a block diagram which shows the process of a rotation correlation signal extraction means. It is a block diagram which shows the other aspect of a rotation correlation signal extraction means. It is a graph which shows the output signal from torque sensor 1 when mounting a tire with a local abnormality. It is a graph which shows the rotation correlation signal which processed the signal of FIG. 6 with the rotation correlation signal extraction means 16. It is a graph which shows a rotation correlation signal when a normal tire is mounted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Torque sensor 2 Signal processing means 3 Display alarm device 5 Steering control means 6 Steering angle sensor 7 Electric motor 8 Steering shaft 8a Input shaft 8b Output shaft 9 Torsion bar 10 Tire abnormality detection device 12 Steering wheel 13 Reducer 15 Sensor output capture Means 16 Rotation correlation signal extraction means 18 Abnormality judgment means 20 Vehicle electric power steering device 22 Delay circuit 23 Adaptive digital filter 31 Electromagnetic clutch 34 Pinion gear 35 Rack shaft 35a Rack gear portion 36 Tie rod 37 Knuckle arm 38 Kingpin FL, FR Steering wheel

Claims (2)

  A torque sensor that is used for output control of an electric power steering device for a vehicle and that detects a steering torque from a steering wheel that acts against a steering load torque from a steered wheel, and an output signal from the torque sensor, the steering load A tire abnormality detection apparatus comprising signal processing means for extracting a vibration component included in a torque and caused by a local abnormality of a tire mounted on a steered wheel. The signal processing means extracts from the sensor output signal only a rotational correlation signal correlated with wheel rotation using an adaptive digital filter, and an abnormality for determining a local abnormality of the tire from the rotational correlation signal The tire abnormality detection device according to claim 1, comprising a determination unit.

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