JP2007153034A - Tire abrasion state judging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire abrasion state judging device capable of judging abrasion in high precision in simple constitution. <P>SOLUTION: A judging part of the tire abrasion state judging device provides actual acceleration generated in the tire circumferential direction by an acceleration sensor 18 when a rotating tire 14 grounds. Additionally, it provides abrasion causing threshold value to be a standard for abrasion judgement set against standard acceleration generated in the tire circumferential direction from a memory part when the tire in a non-abrasion state grounds. The abrasion state of the tire is judged by comparing the detected actual acceleration and the abrasion causing threshold value with each other in accordance with at least either one of size of an output value of the acceleration, changing gradient of the output value and a peak interval in acceleration increase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire wear state determination device, and more particularly to an improvement in a tire wear state determination device that performs highly accurate tire wear determination.

Tires are one of the most important parts of vehicles that require wear management. Tire wear also affects running stability, braking performance, fuel consumption, and the like. Therefore, it is desirable to monitor the tire wear state frequently. Thus, techniques for determining the tire wear state have been proposed. For example, Patent Document 1 discloses a technique in which a processor monitors wear on a tire ground contact surface based on acceleration in a radial direction and a lateral direction of a tire. In this technique, the resonance frequency in the range of 30 to 60 Hz is determined by performing fast Fourier transform of acceleration in the radial direction and lateral direction. A system is disclosed in which the determined resonance frequency is compared with a reference resonance frequency indicating that there is no wear, and when there is a resonance frequency displacement, it is determined that there is wear. Moreover, as a technique for estimating the state of the tire, there is, for example, Patent Document 2. This technique includes tire input detection means for detecting input from the road surface, and detects the peak of vibration that occurs when the tire tread portion enters and exits the contact portion with the road surface. In this estimation method, a time difference between vibration peaks is obtained, and a contact length index or a contact length ratio of the tire block portion is obtained. Further, the lateral force generated in the tire is estimated from the contact length ratio, or the contact load applied to the tire is estimated.
JP 2001-215175 A JP 2005-205956 A

  However, the technique of Patent Document 1 has a problem that the value of the resonance frequency based on the acceleration of the tire is easily affected by disturbance. For example, the resonance frequency based on acceleration is easily changed by a slight change in tire air pressure, and there is a problem that the reliability of wear determination is lowered. Further, the frequency analysis using the fast Fourier transform has a problem that the processing load is high and the system becomes complicated, resulting in an increase in system cost. Further, in the technique of Patent Document 2, there is no disclosure regarding tire wear estimation.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a tire wear state determination device that can determine with high accuracy that wear exceeding a predetermined value has occurred with an easy configuration. is there.

  In order to solve the above problems, in one aspect of the present invention, when a rotating tire is grounded, an acting force sensor that acquires an actual acceleration generated by an acting force acting on the tire, and a rotating non-wearing tire The storage means for storing the reference information related to the reference acceleration generated by the acting force acting on the tire when the vehicle contacts the ground, the acquired actual acceleration and the reference information are compared, and at least the magnitude or output of the acceleration output value Determining means for determining the wear state of the tire based on any one of the change gradient of the value or the peak interval when the acceleration increases.

  When the tire is rotating, the force acting on the tire changes when the pedal starts to come into contact with the road surface, when it completely touches, or when it is kicked away from the road surface. The force changes, and the generated acceleration changes accordingly. This change in acceleration differs depending on whether the tire has no wear or not. In other words, when tire wear occurs, the tire tread, which is the contact portion, becomes thinner and the tire radius is substantially reduced.Therefore, the rise and fall timing of acceleration at the time of stepping on, contacting, and kicking is worn. This is faster than a tire with a large radius, that is, a tire with a large radius, so the gradient of change in acceleration becomes steep. Further, when attention is paid to a certain portion of the tire, the time for grounding is shortened. That is, the peak interval when acceleration is increased is shortened. Furthermore, since the apparent rigidity of the tire is increased by reducing the thickness of the tire tread portion, the peak value of acceleration is increased as compared with the case where there is no wear. Therefore, the comparison between the detected actual acceleration and the reference information related to the reference acceleration when there is no wear is performed by comparing at least one of the output value of the acceleration in the tire circumferential direction, the change gradient of the output value, or the peak interval when the acceleration is increased. By carrying out the above, it is possible to determine whether or not wear of a predetermined value or more has occurred in the tire. According to this aspect, highly accurate wear determination can be realized with a simple system.

  In the above aspect, the reference information may be a wear occurrence threshold value for determining the degree of tire wear set with respect to the reference acceleration. According to this aspect, it is possible to easily and quickly determine when tire wear has occurred. In the above aspect, the reference information may be a transition pattern of the reference acceleration. According to these aspects, it is possible to easily and quickly carry out the determination when wear of a predetermined value or more occurs in the tire.

  In the above aspect, the determination unit may correct either the actual acceleration or the reference information based on a speed at the time of acquiring the actual acceleration. The acting force acting on the tire varies depending on the speed (vehicle speed or wheel speed). Also, the tire contact time changes. That is, the acceleration changes depending on the speed, and the comparison reference between the actual acceleration and the reference information is different. Therefore, it is possible to perform highly reliable wear determination by correcting either the actual acceleration or the reference information based on the speed and matching the comparison reference. When correcting the actual acceleration, it is only necessary to prepare one pattern of the reference information, so that the storage unit can be downsized. Further, when the basic information is corrected, the same basic information can be used once corrected, so that the correction process is simplified.

  In the above aspect, the determination unit may correct either the actual acceleration or the reference information based on a load acting on the tire when the actual acceleration is acquired. For example, the force acting on the tire changes depending on whether the vehicle load is small or large, and the acceleration changes accordingly. And the comparison reference | standard of real acceleration and reference | standard information will differ. Therefore, it is possible to perform highly reliable wear determination by correcting either the actual acceleration or the reference information based on the load acting on the tire and matching the comparison reference. When correcting the actual acceleration, it is only necessary to prepare one pattern of the reference information, so that the storage means can be reduced in size. Further, when the basic information is corrected, the same basic information can be used once corrected, so that the correction process is simplified.

  In the above aspect, the determination unit may correct either the actual acceleration or the reference information based on the tire pressure at the time of acquiring the actual acceleration. Since the acting force acting on the tire changes depending on the tire air pressure, the acceleration changes accordingly. As a result, the comparison reference between the actual acceleration and the reference information is different. For example, if the tire pressure is higher than the recommended value, the stiffness of the tire will be high, so the response of the tire acceleration will be sensitive and will be greater than the actual acceleration. Conversely, when the tire pressure is lower than the recommended value, the stiffness of the tire is low, and the response of the tire acceleration becomes slow, resulting in a value smaller than the actual acceleration. Therefore, it is possible to determine wear with high reliability by correcting either the actual acceleration or the reference information in accordance with the tire air pressure and matching the comparison reference. Further, since the shape of the tire itself is deformed when the tire air pressure changes, the wear determination considering the tire deformation can be performed by performing correction based on the tire air pressure. When correcting the actual acceleration, it is only necessary to prepare one pattern of the reference information, so that the storage means can be reduced in size. Further, when the basic information is corrected, the same basic information can be used once corrected, so that the correction process is simplified.

  In the above aspect, the determination unit may correct either the actual acceleration or the reference information based on the temperature of the tire tread portion when the actual acceleration is acquired. When the temperature of the tire changes, the tire stiffness changes, so that the comparison reference between the actual acceleration and the reference information is different. That is, when the tire temperature is low, the tire becomes stiff and the rigidity becomes high. Conversely, when the temperature of the tire is high, the tire becomes soft and the tire rigidity decreases. When the tire stiffness is high, the response of the tire acceleration becomes sensitive, and the value is larger than the actual acceleration. Conversely, when the tire stiffness is low, the response of the tire acceleration becomes slow, and a value smaller than the actual acceleration is obtained. Therefore, it is possible to determine wear with high reliability by correcting either the actual acceleration or the reference information according to the tire temperature and matching the comparison reference. Further, since the shape of the tire itself is deformed when the tire temperature changes, the wear determination considering the tire deformation can be performed by performing correction based on the tire temperature. Furthermore, when correcting the actual acceleration, it is only necessary to prepare one pattern of the reference information, so that the storage means can be reduced in size. Further, when the basic information is corrected, the same basic information can be used once corrected, so that the correction process is simplified.

  In the above aspect, the determination unit may determine whether or not to execute determination based on a steering state when the actual acceleration is acquired. When the tire is traveling straight and when the vehicle is steered and a lateral force is generated, the acting force acting on the tire changes and the acceleration changes. That is, the acceleration changes due to factors other than wear. Therefore, for example, by comparing the actual acceleration with the reference information in a straight traveling state that is not affected by the lateral force, highly reliable wear determination can be performed efficiently. It is also possible to correct the actual acceleration and the reference information acquired based on the steering state, and it is possible to perform wear determination during turning.

  In the above aspect, the acting force sensor may detect acceleration after mounting a non-wearing tire on a vehicle, and store information based on the acceleration in the storage means as reference information. . According to this aspect, for example, it is possible to acquire reference information of a non-wearing tire when the tire is replaced. As a result, even when a non-wearing tire is newly mounted, the wear determination can be performed based on the optimum reference information.

  Further, in the above aspect, a plurality of the acting force sensors are arranged in the tire width direction, and the determination means determines uneven wear in the tire width direction based on a comparison between the actual acceleration for each tire width direction and the reference information. Can also be implemented. Depending on the running state of the vehicle and the characteristics of the vehicle, the tire may cause uneven wear such as internal or external decrease. Thus, by performing wear determination at a plurality of positions in the width direction of the tire, uneven wear of the tire can be easily determined.

  In the above aspect, the storage unit stores a limit value at the time of tire wear limit as the reference information, and the determination unit estimates a current tire wear level using the limit value and the actual acceleration. May be. According to this aspect, the driver can grasp the current tire wear progress state, and can provide the driver with information such as the tire replacement time.

  According to the tire wear state determination device of the present invention, it is possible to determine the occurrence of tire wear exceeding a predetermined value with high accuracy with an easy configuration.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  In the tire wear state determination apparatus according to the present embodiment, the acting force acting on the tire that is rotating on the ground changes depending on the tire wear state. As a result, the magnitude of the output value of acceleration, the gradient of acceleration change, the peak We focus on changes in value intervals. That is, the actual acceleration acquired during actual vehicle travel is compared with basic information relating to reference acceleration prepared in advance, and it is determined whether or not tire wear of a predetermined value or more has occurred.

  FIG. 1 is a schematic configuration diagram of a vehicle 10 equipped with the tire wear state determination device of the present embodiment. In addition, in FIG. 1, the structure which is not related to a tire wear condition determination apparatus is abbreviate | omitting illustration. The vehicle 10 is equipped with wheels 12 on which various sensors are mounted at the front wheel position and the rear wheel position. The wheel 12 includes a tire 14 and a wheel 16 that supports the tire 14 and is connected to the axle of the vehicle 10. Although details of the tire 14 will be described later, for example, a plurality of acceleration sensors 18 that detect acceleration in the circumferential direction of the tire 14 that is basic information for determining the wear state of the tire 14 inside the tire tread portion, and the tire A temperature sensor 20 for detecting the temperature of the tread portion is disposed. Further, the wheel 16 includes a pressure sensor 22 that detects a pressure in the space between the tire 14 and the wheel 16, that is, a tire air pressure, a detected value of the air pressure sensor 22, a detection by the acceleration sensor 18, the temperature sensor 20, and the like. For example, a transmitter 26 that wirelessly transmits the value to the ECU 24 on the vehicle 10 side is disposed. In addition, since the transmission interval of the information transmitted to the ECU 24 varies depending on the type, a dedicated transmission unit may be provided for each sensor.

  In addition to the information transmitted from the transmission unit 26, the ECU 24 acquires information from the load sensor 28, the vehicle speed sensor 30, the steering angle sensor 32, and the like disposed on the suspension that supports the wheels 12.

  When paying attention to a certain part of the tire 14, the grounding and separation are repeated by rotating. And the acting force which acts on the circumferential direction of the tire 14 changes between grounding and separation. That is, the acceleration generated in the circumferential direction of the tire 14 changes. Further, when the air pressure of the tire 14 changes, the shape of the tire 14 changes and the rigidity changes. That is, when the tire air pressure increases and the rigidity of the tire 14 increases, the acceleration acting in the circumferential direction of the tire 14 reacts sensitively. On the other hand, when the rigidity is lowered, the response of acceleration in the tire circumferential direction becomes slow. That is, the acceleration in the circumferential direction of the tire 14 that is the basis for wear determination changes even though the tire 14 has not undergone a substantial change in the wear state. Therefore, the ECU 24 acquires tire pressure information from the air pressure sensor 22 as correction information at the time of wear determination. Similarly, when the temperature of the tire 14 is changed, the shape of the tire 14 is changed and a change in hardness is generated, so that the rigidity is changed and the acceleration is changed. Therefore, the ECU 24 acquires temperature information of the tire tread portion 14a from the temperature sensor 20 as correction information at the time of wear determination.

  Furthermore, one of the factors that change the rigidity of the tire 14 is a load acting on the tire 14. That is, when the load acting on the tire 14 is increased, the tire 14 is deformed so as to be crushed, so that the internal pressure is increased, the rigidity of the tire 14 as a whole is increased, and the circumferential direction of the tire 14 that is the basis for wear determination is increased. The acceleration changes. Therefore, the ECU 24 acquires load information added to the tire 14 as correction information at the time of wear determination from the load sensor 28. Further, when the speed of the vehicle 10 changes, the acceleration detected by the acceleration sensor 18 changes. For example, as the speed increases, the force acting when the tire 14 contacts the ground increases, and the acceleration generated in the tire circumferential direction also increases. In addition, the interval between stepping on and kicking out becomes narrow. Therefore, the ECU 24 acquires the speed information of the tire 14 from the vehicle speed sensor 30 as correction information at the time of wear determination. Note that the wheel speed may be used as the speed information of the tire 14. Further, the force acting when the tire 14 contacts the ground is different between when the tire 14 is in a straight traveling state and when the tire 14 is steered and turning. When the tire 14 is turning, the tire 14 is deformed under the influence of lateral force or the like, and the rigidity is changed in the same manner as described above. Stiffness changes due to turning change continuously and frequently. For this reason, it is desirable that the wear determination be performed during straight traveling with little change in rigidity due to external force. Therefore, the ECU 24 acquires information from the steering angle sensor 32 in order to determine whether or not to perform wear determination. It is possible to correct the acceleration generated based on the steering state, and it is also possible to carry out wear determination during turning.

  FIG. 2 is an explanatory diagram for explaining an arrangement state of the acceleration sensor 18 in the tire 14. A plurality of acceleration sensors 18 are desirably arranged in the tire width direction inside the tire tread portion 14 a of the tire 14. In the example of FIG. 2, an example in which four are arranged is shown. The number of the acceleration sensors 18 arranged in the tire width direction is arbitrary, but it is desirable that the acceleration sensors 18 be arranged over the entire width of the tire. It is desirable to determine the wear state at each of the inner part, the central part, and the outer part. By disposing the acceleration sensor 18 in this way, it is possible to determine the uneven wear in the width direction of the tire 14 such as an internal decrease in which the inner side of the tire 14 is greatly worn or an external decrease in which the outer side is largely worn. In addition, it is desirable that the acceleration sensor 18 is disposed immediately below the convex portion between the grooves of the tire tread portion 14a so that a change in acceleration due to wear of the convex portion is detected sensitively. When one acceleration sensor 18 is arranged at the center, the wear determination of the tire 14 as a whole is performed. Further, even if the acceleration sensor 18 is disposed only on the inner side and the outer side of the tire 14, the tire 14 is subjected to the determination of the partial wear in the width direction of the tire 14 and the process of calculating the average value of the inner wear and the outer wear. Overall wear can be judged. In the case of FIG. 2, an example is shown in which two acceleration sensors 18 are arranged at the center to improve the accuracy of acceleration detection at the center of the tire 14. In this case, the average of the output values of the two acceleration sensors 18 may be obtained to determine the wear. The central acceleration sensor 18 may be one.

  It is desirable to arrange the acceleration sensor 18 at a plurality of positions in the circumferential direction of the tire 14 as well as in the width direction of the tire 14. For example, they can be arranged at intervals of 120 °. When the tire is running normally, it can be considered that the wear of the tire 14 occurs almost uniformly over the entire circumference. However, when a large amount of wear occurs in a part of the tire 14 due to sudden braking or the like, it is necessary to perform wear determination based on that part. In this case, by disposing a plurality of acceleration sensors 18 in the circumferential direction of the tire 14, more detailed acceleration can be detected, occurrence of wear can be detected in detail, and reliable wear determination can be performed. . Since the temperature of the tire tread portion 14a can be regarded as being substantially uniform over the entire circumference of the tire 14, it is sufficient that at least one tire tread portion 14a is disposed at an arbitrary position in the tire tread portion 14a. Further, if the temperature sensor 20 and the acceleration sensor 18 are arranged relatively close to each other, the measurement result of the temperature sensor 20 can be reflected in the measurement result of the acceleration sensor 18. A plurality of temperature sensors 20 may be arranged to acquire the temperature distribution inside the tire 14 and reflected in the detection result of the acceleration sensor 18.

  The detection results of the acceleration sensor 18 and the temperature sensor 20 are not shown in the figure, but are provided to the transmission unit 26 via, for example, a signal line and wirelessly transmitted to the ECU 24 on the vehicle 10 side. In the case of FIG. 2, the transmission unit 26 and the air pressure sensor 22 are integrated, and each information is transmitted to the ECU 24 using the transmission unit 26 at a predetermined timing. The transmitting unit 26 may include a memory, and may be configured to transmit collectively when a predetermined amount of information is accumulated.

  FIG. 3 shows a functional block diagram of the ECU 24. The ECU 24 is data used when determining the wear state of the tire 14 and the receiving unit 34 that receives information from the transmission unit 26, and is generated in the tire circumferential direction when the rotating non-wearing tire 14 contacts the ground. Information obtained from the load sensor 28, the vehicle speed sensor 30, the steering angle sensor 32, and the like. And a determination unit 38 that performs wear determination based on the reference information regarding the basic acceleration obtained from the storage unit 36. The reference information related to the reference acceleration includes, for example, a wear occurrence threshold value that determines how much the acceleration pattern changes with respect to the reference acceleration that occurs during non-wearing and is determined to be worn. This wear occurrence threshold value can be set, for example, for the magnitude of the output value of acceleration, the change gradient of the output value, the peak interval when the acceleration increases, and the like. These wear occurrence threshold values may be used alone for wear determination, or may be used in combination. The storage unit 36 can store in advance reference information related to reference acceleration in the tire circumferential direction in a non-wearing state for each tire 14. The reference information regarding the basic reference acceleration can be stored at the time of dealer shipment. As another method, when the tire 14 in a non-wearing state is mounted, the acceleration sensor 18 is used to actually detect the acceleration pattern, and the value is used as a reference acceleration, and the actually detected acceleration is used as a reference. A predetermined wear occurrence threshold value may be set. Normally, the information of the acceleration sensor 18 acquired by the reception unit 34 is provided to the determination unit 38 as it is. However, when the tire 14 in an unworn state is mounted and the reference acceleration is acquired using the acceleration sensor 18. Is converted to reference information from the acceleration acquired via the information processing unit 41 and provided to the storage unit 36. Therefore, in this embodiment, the switching unit 40 is provided between the reception unit 34 and the determination unit 38, and the acceleration information acquired by the reception unit 34 is stored in the storage unit 36 or the determination unit 38 via the information processing unit 41. It is configured to provide to either. Note that, as a wear determination method, the determination may be performed by comparing the pattern of the actual acceleration and the pattern of the reference acceleration. In this case, the information processing unit 41 can be deleted in the ECU 24.

  The result of determining the wear of the tire 14 by the determination unit 38 can be displayed on the result presentation unit 42 provided in the driver's seat of the vehicle 10 or the like. The result presentation unit 42 may be configured with, for example, an LED or a display and visually present the wear state to the driver. Moreover, you may make it show to a driver with a warning sound or a voice message using a speaker etc.

  The wear determination procedure of the tire wear state determination apparatus configured as described above will be described with reference to the flowcharts of FIGS. 4 and 5.

  FIG. 4 illustrates a pattern of acceleration generated in the tire circumferential direction when the rotating tire 14 contacts the ground. When the tire 14 rotates and a portion where the acceleration sensor 18 is disposed approaches the road surface G, the tire 14 starts to receive a force from the road surface G, and the tire 14 starts to be compressed and deformed. As a result, as shown by the solid line in the graph of FIG. 4, as the tire 14 approaches the stepping point A where the tire 14 steps on the road surface G, a compressive force acts on the tire tread portion 14a. As a result, the tire 14 starts to receive a positive acceleration in the circumferential direction, the compression deformation becomes maximum at the stepping point A, and the circumferential acceleration reaches a positive peak A1. Thereafter, since the tire tread portion 14a rotates while kicking the road surface G, the tire tread portion 14a receives a force extending along the road surface G in the left-right direction in the drawing. As a result, a tensile force in the circumferential direction acts on the tire tread portion 14a, and the tire 14 receives a negative acceleration in the circumferential direction. And while the part in which the acceleration sensor 18 is disposed in the tire 14 is in contact with the ground (part B), the acceleration in the tire circumferential direction changes in the reverse direction from the peak A1. Further, when the rotation of the tire 14 proceeds and approaches the kicking point C, the frictional force between the road surface G and the tire tread portion 14a starts to decrease. As a result, the tire 14 begins to return to its shape due to its own elasticity. Then, the acceleration in the negative direction starts to increase and reaches the negative peak C1 at the kicking point C. And if the corresponding part of the tire 14 in which the acceleration sensor 18 is arrange | positioned leaves | separates from the road surface G, the negative acceleration which increased will fall, and it will approach zero.

  Such a pattern of acceleration in the circumferential direction of the tire 14 is unique to the tire 14 and changes when the state of the tire itself or the state of use of the tire changes. Therefore, even in the same tire, the shape of the acceleration pattern in the unworn state is different from the shape of the acceleration pattern in the worn state. In the present embodiment, an acceleration pattern in an unworn state is measured in advance to obtain a basic acceleration pattern M, and basic information about the basic acceleration pattern M is stored in the storage unit 36. As described above, the basic information includes, for example, a wear occurrence threshold value that determines how much the acceleration pattern changes with respect to a reference acceleration that occurs during non-wearing. The wear occurrence threshold is set, for example, with respect to the magnitude of the output value of acceleration, the change gradient of the output value, the peak interval when the acceleration increases, and the like. As described above, the basic information regarding the basic acceleration pattern M can be stored in advance for each tire 14 by a dealer or the like. Further, the acceleration at the time of non-wearing measured using the acceleration sensor 18 after the tire 14 is mounted is set as a reference acceleration, and the information processing unit 41 automatically sets a wear occurrence threshold value obtained by applying a predetermined offset to the reference acceleration. It may be set and stored in the storage unit 36.

  By the way, when the tire 14 is worn, that is, when the tire tread portion 14a is thin, the rigidity of the tire 14 is increased and the deformation of the tire tread portion 14a becomes sensitive. Therefore, as shown by the broken line in FIG. 4, the acceleration change gradient becomes steep and the magnitude of the output value, that is, the peak values A2 and C2 increase. Further, since the radius of the tire 14 is substantially reduced, the ground contact area of the tire 14 is reduced, so that the peak interval when the acceleration is increased, that is, the peak A2-C2 is narrower than the peak A1-C1.

  As described above, when the tire 14 is worn, the circumferential acceleration pattern of the tire 14 changes in a certain direction as shown in FIG. The determination unit 38 determines the actual acceleration acquired using the acceleration sensor 18 while the vehicle 10 is traveling, the magnitude of the output value of the acceleration stored in the storage unit 36, the gradient of change in the output value, the peak interval when the acceleration increases, and the like. It is possible to determine whether or not the tire 14 has a degree of wear that is desirably recognized by the driver or the vehicle, based on whether or not the wear occurrence threshold is exceeded. When the reference acceleration pattern M is stored as reference information in the storage unit 36, the determination unit 38 acquires the current actual acceleration pattern P using the acceleration sensor 18 while the vehicle 10 is traveling, When the reference acceleration pattern M is acquired from the storage unit 36 and compared, and the actual acceleration pattern P is shifted in a predetermined direction (leftward in FIG. 4), the tire 14 is worn. May be determined. In this case, when the shift amount of the actual acceleration pattern P with respect to the reference acceleration pattern M is greater than or equal to a predetermined amount, it can be determined that wear of a predetermined value or more has occurred.

  The flowchart of FIG. 5 shows a processing procedure using the wear occurrence threshold in the determination unit 38. First, the tire wear state determination device according to the present embodiment is started, for example, when an ignition switch is turned on. Based on the information from the vehicle speed sensor 30, the ECU 24 determines whether or not the vehicle speed is a predetermined value or less, for example, 10 km / h or less (Y or N in S100). When the vehicle speed (wheel speed) is high, the time during which the tire tread portion 14a on which the acceleration sensor 18 is disposed is grounded on the rotating tire 14 is shortened, making it difficult to detect a clear change in acceleration as shown in FIG. become. Therefore, the wear determination is performed by selecting a timing at which acceleration / deceleration is not performed so as not to be very high speed and to affect the acceleration in the circumferential direction of the tire. Therefore, when the vehicle speed exceeds a predetermined value, for example, 10 km / h (N in S100), the wear determination process is terminated. When the current vehicle speed is slower than a predetermined value, for example, 10 km / h (Y in S100), the ECU 24 determines whether the tire 14 is in a substantially straight traveling state based on information from the steering angle sensor 32, for example, Then, it is determined whether or not the steering angle is 1 degree or less (Y or N in S102). As described above, when the tire 14 is steered, a lateral force or the like acts on the tire 14, and the tire 14 is deformed to change its rigidity. Therefore, in the present embodiment, the wear determination is performed by selecting a timing at which the tire 14 is in a straight traveling state that is not affected by a lateral force or the like. Therefore, when the steering angle is a predetermined value, for example, 1 degree or more (N in S102), the wear determination process is terminated.

  The determination unit 38 of the ECU 24 starts detection of actual acceleration via the acceleration sensor 18 when the vehicle speed is, for example, 10 km / h and the vehicle 10 is traveling substantially straight (Y in S102). That is, as shown in FIG. 4, the tire tread portion 14a in which the acceleration sensor 18 is disposed steps on and acquires actual acceleration including a period during which kicking is started (S104). This acceleration detection is performed, for example, at a 1/1000 second period. The actual acceleration of the same portion of the tire 14 can be obtained by calculating the data for a plurality of times and performing an averaging process since the same data can be obtained once per rotation of the tire 14 if the detection conditions such as the vehicle speed are the same. The actual acceleration used for the determination may be used. As described above, the operating power of the system can be reduced by performing the data communication using the transmission unit 26 and the reception unit 34 and acquiring the acceleration data only when the conditions regarding the vehicle speed and the steering angle are met. Note that the acquisition of acceleration data may always be performed.

  Then, when the actual acceleration can be acquired, the determination unit 38 acquires a wear occurrence threshold included in the basic acceleration reference information of the determination target tire 14 from the storage unit 36 (S106). Further, as described above, the determination unit 38 acquires information from the temperature sensor 20, the air pressure sensor 22, the load sensor 28, the vehicle speed sensor 30, and the like in addition to the acceleration information from the acceleration sensor 18. The detection conditions at the time of acceleration detection are acquired. Accordingly, the acquired actual acceleration detection condition is compared with the basic acceleration measurement condition, and it is determined whether or not acceleration correction is necessary (Y or N in S108).

  When the determination unit 38 determines that the actual acceleration detection condition and the basic acceleration measurement condition are substantially the same (N in S108), the determination unit 38 determines whether the actual acceleration and the basic acceleration wear occurrence threshold values are the same. Is compared (S110), and it is determined whether or not the tire 14 is worn beyond a predetermined value (S112). In the wear determination, for example, when the magnitude of the output value of the actual acceleration exceeds the wear occurrence threshold related to the magnitude of the output value, it is determined that the tire 14 currently in use is worn. Further, when the change gradient of the output value of the actual acceleration exceeds the wear occurrence threshold related to the change gradient, it is determined that the currently used tire 14 is worn. Further, when the peak interval when the acceleration of the actual acceleration increases exceeds the wear occurrence threshold related to the peak interval, it is determined that the currently used tire 14 is worn. The determination unit 38 may perform any one of the determinations to determine whether the tire 14 is worn or may combine several determinations to improve the reliability of the determination. When the wear determination is completed, the ECU 24 performs a result process corresponding to the determination result (S114). If the tire 14 does not wear more than a predetermined value, no presentation process is required. Further, the “no wear notification (including wear within an allowable range)” may be performed via an LED, a display, a speaker, or the like. Thereafter, the operation of the present tire wear state determination device is terminated, and the tire wear state determination device at the next timing is prepared for starting. Note that the tire wear state determination device may be continuously started a plurality of times. Wear determination accuracy can be further improved by performing the determination a plurality of times. Alternatively, it may be performed every time the ignition switch is turned on, that is, every time the vehicle 10 is started. Also, in addition to the ignition switch ON information, the timer count information and the cumulative travel distance information are added to the starting condition of the tire wear state determination device, and the tire wear state determination device A start may occur.

  If the tire 14 is worn beyond a predetermined value, a wear warning notification is provided to the driver via the LED, display, speaker, etc., and the process is terminated. In this case, it is possible to present a message that recommends tire confirmation or immediate replacement. In addition, a signal for controlling the engine and the brake can be provided to the ECU of the vehicle 10 so that no slip or the like occurs.

  On the other hand, when the determination unit 38 determines in S108 that the actual acceleration detection condition is different from the basic acceleration measurement condition (Y in S108), the determination unit 38 determines whether the actual acceleration or the basic information is related to the different conditions. One of them is corrected (S116). For example, when the tire air pressure at the time of detecting the actual acceleration is higher than the tire air pressure at the time of measuring the basic acceleration, the rigidity of the tire 14 is increased, and the acceleration value is shifted on the wear side. Therefore, correction based on the difference in tire air pressure is performed. When the actual acceleration is corrected, the wear determination can be performed using the wear occurrence threshold stored in the storage unit 36. Further, when the basic information is corrected, the wear determination can be performed using new reference information, that is, a new wear occurrence threshold. The reference acceleration pattern (transition pattern) M may be corrected based on the difference in detection conditions. As a result of this correction, the wear determination of the tire 14 can be performed with high accuracy. This correction may be performed for either the actual acceleration or the basic information. However, if the tire wear state determination is continuously performed, the same basic information can be used once the basic information is corrected. The correction process is simplified. Further, when correcting the actual acceleration, it is only necessary to prepare one pattern of the reference information, so that the storage unit 36 can be reduced in size. After the correction, the process proceeds to S110 and the above-described process is executed.

  Similarly, even if the speed condition, load condition, and temperature condition are different between the actual acceleration detection condition and the basic acceleration measurement condition, the actual acceleration or reference information is corrected, and the comparison process is performed. Wear judgment is possible. Of course, when a plurality of conditions are different when the basic information is corrected, the conditions are corrected simultaneously. The correction amount under each condition may be performed using a dedicated correction map.

  As described above, in the tire wear state determination device according to the present embodiment, the wear state of the tire 14 is obtained by simply comparing the actual acceleration in the circumferential direction of the tire 14 with the wear occurrence threshold value of the reference acceleration of the tire in the non-wear state. Can be determined with high accuracy.

  In addition, when a plurality of acceleration sensors 18 are arranged in the width direction of the tire 14 as illustrated in FIG. 2, it is possible to perform wear determination on the inside, the center, and the outside of the tire 14. Therefore, it is possible to easily determine the uneven wear of the tire 14.

  By the way, in the case of tire wear, if it is possible to provide information on how much current wear is, i.e., how much replacement is necessary, the maintenance and safety of the vehicle 10 can be improved. Can contribute.

  Therefore, in the tire wear state determination apparatus according to the present embodiment, as shown in FIG. 6, the storage unit 36 is indicated by a one-dot chain line in addition to the reference acceleration pattern M indicated by a solid line for the determination target tire 14. A limit acceleration pattern N at the time of wear limit is stored. The determination unit 38 determines which area the actual acceleration pattern P indicated by the broken line is shifted within the range formed by the reference acceleration pattern M and the limit acceleration pattern N, thereby determining the tire to be determined. It can be estimated to what percentage of the wear limit 14 wear has progressed, ie the wear level. Further, it is possible to estimate the next tire replacement time based on the travel distance from the replacement of the tire 14. In the case of FIG. 6, an acceleration pattern is shown for easy understanding. However, as described above, the determination of occurrence of wear and the determination that the wear limit has been reached are based on the reference acceleration pattern M. The wear estimation can be performed by comparing the actual threshold value with the corresponding threshold value corresponding to the wear occurrence threshold value and the limit acceleration pattern N.

  As described above, the tire wear state determination apparatus according to the present embodiment can not only detect the presence / absence of wear of the tire 14 but also estimate the wear level and the replacement time of the tire 14 with a simple configuration.

  In the above-described embodiment, an example has been described in which the acceleration sensor 18 that detects the acceleration in the circumferential direction of the tire 14 is disposed as the acting force sensor on the tire 14 to directly detect the acceleration. You may arrange | position the distortion sensor which detects the distortion of the circumferential direction. In this case, the distortion waveform Q output from the distortion sensor is as shown in FIG. The first peak in the compression direction of the distortion output appears immediately before the stepping point A. After that, a peak on the pulling side appears at the ground contact portion. Then, immediately after passing the kick point C, the compression side peak appears again. By differentiating the distortion waveform Q, it can be converted into an acceleration waveform similar to that in FIG. Thereafter, as in the above-described embodiment, it is possible to determine the wear state of the tire 14 by comparing the actual acceleration based on the measured strain and the wear occurrence threshold value or comparing the pattern with the actual acceleration and the pattern with the reference acceleration. it can.

  In the embodiment described above, the presence or absence of wear of the tire 14 is determined by comparing the actual acceleration based on the acting force acting in the circumferential direction of the tire 14 and the reference information. In other embodiments described below, the presence or absence of wear of the tire 14 is determined using a change in acceleration generated in the radial direction of the tire 14.

  FIG. 8 illustrates a pattern of acceleration generated in the tire radial direction when the rotating tire 14 contacts the ground. When the tire 14 rotates and a portion where the acceleration sensor 18 is disposed approaches the road surface G, the tire 14 starts to receive a force from the road surface G, and the tire 14 starts to be compressed and deformed. As a result, as shown by the solid line in the graph of FIG. 8, as the tire 14 approaches the stepping point A where the tire 14 steps into the road surface G, a compressive force acts on the tire tread portion 14a. As a result, the tire 14 starts to receive a positive acceleration in the radial direction, the compression deformation becomes maximum immediately before the stepping point A, and the radial acceleration reaches the first positive peak A1. Thereafter, since the tire tread portion 14a rotates while kicking the road surface G, the tire tread portion 14a receives a force that extends in the left-right direction in the drawing along the road surface G. As a result, a tensile force in the circumferential direction acts on the tire tread portion 14a, and the tire 14 receives a negative acceleration in the radial direction. The acceleration in the tire radial direction reaches a negative peak B1 in the vicinity of the approximate center (symbol B) of the contact width of the tire 14. Further, as the rotation of the tire 14 proceeds, the frictional force between the road surface G and the tire tread portion 14a starts to decrease. As a result, the tire 14 begins to return to its shape due to its own elasticity, and shifts from the extended state to the compressed state. That is, positive acceleration starts to occur again. Then, immediately after the kicking point C, the second positive peak C1 is reached. And if the corresponding part of the tire 14 in which the acceleration sensor 18 is arrange | positioned leaves | separates from the road surface G, a positive acceleration will reduce and will approach zero.

  Such an acceleration pattern in the radial direction of the tire 14 is unique to the tire 14 and changes when the state of the tire itself or the use state of the tire changes. Therefore, even in the same tire, the shape of the acceleration pattern in the unworn state is different from the shape of the acceleration pattern in the worn state. In the present embodiment, an acceleration pattern in a non-wearing state is measured in advance to obtain a basic acceleration pattern M, and basic information regarding the basic acceleration is stored in the storage unit 36. As described above, the basic information includes, for example, a wear occurrence threshold value that determines how much the acceleration pattern changes with respect to a reference acceleration that occurs during non-wearing. The wear occurrence threshold is set, for example, with respect to the magnitude of the output value of acceleration, the change gradient of the output value, the peak interval when the acceleration increases, and the like.

  Regarding the acceleration in the radial direction of the tire 14, when the tire 14 is worn, that is, when the tire tread portion 14 a is thin, the rigidity of the tire 14 is increased and the deformation of the tire tread portion 14 a is sensitive. Become. Therefore, as shown by the broken line in FIG. 8, the acceleration change gradient becomes steep and the magnitude of the output value, that is, the peak values A2, B2, and C2 increase. Further, since the radius of the tire 14 is substantially reduced, the ground contact area of the tire 14 is reduced, and the peak interval when the acceleration is increased, that is, the peak A2-C2 is narrower than the peak A1-C1.

  As described above, when the tire 14 is worn, the acceleration pattern in the radial direction of the tire 14 changes in a certain direction as shown in FIG. The determination unit 38 determines the actual acceleration acquired using the acceleration sensor 18 while the vehicle 10 is traveling, the magnitude of the output value of the acceleration stored in the storage unit 36, the gradient of change in the output value, the peak interval when the acceleration increases, and the like. It is possible to determine whether or not the tire 14 has a degree of wear that is desirably recognized by the driver or the vehicle, based on whether or not the wear occurrence threshold is exceeded. When the reference acceleration pattern M is stored as reference information in the storage unit 36, the determination unit 38 acquires the current actual acceleration pattern P using the acceleration sensor 18 while the vehicle 10 is traveling, When the reference acceleration pattern M is acquired from the storage unit 36 and compared, and the actual acceleration pattern P is shifted in a predetermined direction (leftward in FIG. 8), the tire 14 is worn. May be determined. In this case, when the shift amount of the actual acceleration pattern P with respect to the reference acceleration pattern M is greater than or equal to a predetermined amount, it can be determined that wear of a predetermined value or more has occurred. Further, as described with reference to FIG. 6, the wear occurrence threshold value or wear limit acceleration pattern related to the limit acceleration at the time of wear limit is stored in the storage unit 36 for the radial acceleration, thereby detecting the presence or absence of wear. In addition, the wear level and the replacement time of the tire 14 can be estimated.

  In addition, the system configuration shown in the present embodiment is an example, and when a rotating tire is grounded, an acting force sensor that acquires an actual acceleration generated by an acting force acting on the tire and a rotating non-wearing tire are provided. The storage means for storing the reference information related to the reference acceleration generated by the acting force acting on the tire when contacting the ground, the acquired actual acceleration and the reference information are compared, and at least the magnitude of the output value of the acceleration or the output value Other configurations can be arbitrarily changed as long as the configuration includes a determination unit that determines a wear state of a tire based on any one of a change gradient or a peak interval at the time of acceleration increase. The same effect can be obtained.

  In the present embodiment, the example in which the wear occurrence threshold value and the wear limit threshold value are set in advance as fixed values has been shown, but it is desirable to change them based on the characteristics of the tire 14 to be used. However, it is desirable that the threshold value be changed by a specialist such as a dealer of the vehicle 10 or a tire seller.

It is explanatory drawing explaining the structural concept of the vehicle carrying the tire wear condition determination apparatus which concerns on this embodiment. It is explanatory drawing explaining arrangement | positioning of the acceleration sensor and temperature sensor in the tire wear state determination apparatus which concerns on this embodiment. It is a functional block diagram of ECU of the tire abrasion state determination apparatus which concerns on this embodiment. It is explanatory drawing explaining the comparison of the pattern of the real acceleration of the circumferential direction of a tire used for the wear determination of the tire wear state determination apparatus which concerns on this embodiment, and the pattern of a basic acceleration. It is a flowchart explaining the wear determination procedure based on the acceleration of the tire peripheral direction of the tire wear state determination apparatus which concerns on this embodiment. It is explanatory drawing explaining that a wear level can be estimated using the pattern of a reference acceleration and the pattern of a limit acceleration in the tire wear state determination apparatus which concerns on this embodiment. It is explanatory drawing explaining the output waveform at the time of using the distortion sensor which detects distortion to a tire peripheral direction as an action force sensor in the tire wear state determination apparatus which concerns on this embodiment. It is explanatory drawing explaining the comparison of the pattern of the real acceleration of the radial direction of a tire used for the wear determination of the tire wear state determination apparatus which concerns on this embodiment, and the pattern of a basic acceleration.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Vehicle, 12 Wheel, 14 Tire, 14a Tire tread part, 16 Wheel, 18 Acceleration sensor, 20 Temperature sensor, 22 Air pressure sensor, 24 ECU, 26 Transmission part, 28 Load sensor, 30 Vehicle speed sensor, 32 Steering angle sensor, 34 Receiving unit, 36 storage unit, 38 determination unit, 40 switching unit, 42 result presentation unit, M reference acceleration pattern, P actual acceleration pattern.

Claims (11)

An acting force sensor for acquiring an actual acceleration generated by an acting force acting on the tire when the rotating tire contacts the ground;
Storage means for storing reference information relating to reference acceleration generated by an acting force acting on the tire when the rotating non-wearing tire contacts the ground;
Judgment that compares the acquired actual acceleration with the reference information and determines the tire wear state based on at least one of the magnitude of the output value of acceleration, the change gradient of the output value, or the peak interval when the acceleration increases. Means,
A tire wear state determination device comprising:   The tire wear state determination device according to claim 1, wherein the reference information is a wear occurrence threshold value for determining the degree of tire wear set with respect to the reference acceleration.   The tire wear state determination device according to claim 1, wherein the reference information is a transition pattern of the reference acceleration.   The said determination means correct | amends any one of the said actual acceleration or reference | standard information based on the speed at the time of acquisition of the said actual acceleration, The Claim 1 characterized by the above-mentioned. Tire wear state determination device.   The said determination means correct | amends any one of the said actual acceleration or reference | standard information based on the load which acts on a tire at the time of acquisition of the said actual acceleration, The any one of Claims 1-4 characterized by the above-mentioned. The tire wear state determination device according to 1.   The said determination means correct | amends any one of the said actual acceleration or reference | standard information based on the tire pressure at the time of acquisition of the said actual acceleration, The Claim 1 characterized by the above-mentioned. Tire wear state determination device.   The said determination means correct | amends any one of the said real acceleration or reference | standard information based on the temperature of the tire tread part at the time of the acquisition of the said real acceleration. The tire wear state determination device according to item.   The tire wear state determination device according to any one of claims 1 to 7, wherein the determination unit determines whether or not to execute determination based on a steering state when the actual acceleration is acquired.   The said action force sensor detects acceleration after mounting a non-wearing tire on a vehicle, and memorize | stores the information based on this acceleration in the said memory | storage means as reference information. The tire wear state determination device according to any one of claims 8 to 9.   A plurality of the acting force sensors are arranged in the tire width direction, and the determination means performs a partial wear determination in the tire width direction based on a comparison between the actual acceleration for each tire width direction and the reference information. The tire wear state determination device according to any one of claims 1 to 9.   The storage means stores, as the reference information, a limit value at the time of tire wear limit, and the determination means estimates a current tire wear level using the limit value and actual acceleration. The tire wear state determination device according to any one of claims 2 to 10.

Images