JP2005238928A - Tire state estimating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately estimate a state of a tire. <P>SOLUTION: The tire state estimating device 10 of a vehicle 1 is provided with an acceleration sensor 32 for detecting acceleration of the tire 20, a wheel speed sensor 50 for detecting a wheel speed of the tire 20, an ECU 80 for estimating abnormality of the tire 20 based on detected result of the sensors, an alarm part 82 for informing a driver of the estimated result, and a speed control part 84 for performing control such as decelerating a vehicle speed when the abnormality of the tire 20 is estimated. The ECU 80 varies estimation contents in accordance with the vehicle speed, a temperature of the tire 20, a deteriorated state of the tire 20, and a state of a road on which the vehicle travels. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for estimating the state of a tire, and more particularly to a tire state estimation device that estimates the state of a tire based on a detection result by a sensor provided in the tire.

It is known that when a mechanical failure occurs in a tire, the tire is deformed, and the uniformity (uniformity) of the tire is changed. There has been proposed a technique for predicting an abnormality of a tire by using this phenomenon to monitor a change in tire uniformity when the vehicle is traveling. For example, the wheel state detection device described in Patent Document 1 defines data having a value of 0 in an ideal uniform state as a tire uniformity component as an amount indicating tire uniformity, and is obtained by a wheel speed detection mechanism. The tire condition is determined by extracting the tire uniformity component from the rotation signal. Further, the tire abnormality detection device described in Patent Document 2 calculates a uniformity component from the pulse period of each pulse of the wheel speed signal of the tire, and predicts a tire abnormality based on a change in the uniformity component.
JP-A-8-132831 JP 2003-237330 A

  Each of the above-mentioned patent documents discloses a technique for determining an abnormality of a tire based on the rotation state of the tire. However, the rotation state of the tire is easily affected by road surface input, and is affected by road surface input during rough road driving. Even if the rotation state of the tire changes, and there is no abnormality in the tire, the uniformity component may change. Accordingly, there is a need for a technique that prevents erroneous determination due to the influence of road surface input and the like and estimates the tire state with higher accuracy.

  This invention is made | formed in view of such a condition, The objective is to provide the technique which estimates the state of a tire with sufficient precision.

  One embodiment of the present invention relates to a tire state estimation device. The tire state estimation device includes a detection unit that detects a tire state, and an estimation unit that estimates an abnormality of the tire based on a detection result of the detection unit. Accordingly, the estimated content is changed. Thereby, since it is possible to estimate the tire state based on the appropriate estimation contents according to the state of the vehicle, it is possible to prevent erroneous estimation and accurately estimate the tire state.

  The detection means may be an acceleration sensor that detects acceleration in the radial direction of the tire. The acceleration sensor may be provided in the tread rubber of the tire. The output of the acceleration sensor may be transmitted by a transmitter provided on the tire, received by a receiver provided on the vehicle body side, and transmitted to the estimating means. The transmitter may transmit the output of the sensor v at a predetermined timing, or may transmit the output of the sensor in response to an interrogation signal from the interrogator on the vehicle body side. The detection means may be a wheel speed sensor that detects the rotational speed of the tire. The vehicle state may be a traveling state of the vehicle, a road surface state during traveling, or a tire state.

  The estimation unit may change the estimation content according to a vehicle speed. When the vehicle is traveling at a low speed, there is a low possibility that an abnormality will occur in the tire and the safety problem is small. Therefore, the estimation may be stopped or the threshold for estimation may be relaxed. As a result, erroneous estimation can be prevented.

  The estimation means may change the estimation content according to whether or not a plurality of wheels are simultaneously estimated to be abnormal. Since it is unlikely that a plurality of wheels will cause an abnormality at the same time, if it is estimated that the plurality of wheels are abnormal at the same time, there is a high possibility that the abnormality is estimated due to the influence of road surface input or the like. Therefore, when it is estimated that a plurality of wheels are abnormal at the same time, it may be determined that there is no abnormality. As a result, erroneous estimation can be prevented.

  The estimation unit may change the estimation content according to a road surface state during traveling. For example, if it is determined that the vehicle is traveling on a rough road by analyzing the unsprung resonance frequency component of the acceleration signal detected by the acceleration sensor or analyzing the acceleration in the vertical direction, it is erroneous due to the influence of the road surface input. Since there is a possibility of estimation, the estimation may be stopped or the threshold for estimation may be relaxed. As a result, erroneous estimation can be prevented.

  The estimation means may change the estimation content according to the temperature of the tire. When the temperature of the tire is low, there is a low possibility that an abnormality will occur in the tire, so the estimation may be stopped or the threshold value for estimation may be changed. Further, in the case of a temperature range and a vehicle speed range where an abnormality is likely to occur in the tire, a wide threshold value for estimation may be set. As a result, erroneous estimation can be prevented.

  The estimation means may change the estimation content according to a deterioration state of the tire. The estimation means may estimate the tire deterioration state using various state quantities of the tire and change the estimation content according to the degree of deterioration progress. Thereby, the state of the tire can be accurately estimated.

  The estimation means may stop the estimation when the estimation content is changed. The estimation means may change a threshold used for estimation when the estimation content is changed. The abnormality of the tire may be a mechanical failure of the tire, and may be, for example, loose, cord break, tread peeling, or the like.

  According to the present invention, it is possible to accurately estimate the state of the tire.

(First embodiment)
FIG. 1 shows an overall configuration of a vehicle 1 including a tire state estimation device 10 according to a first embodiment. The vehicle 1 has four tires (hereinafter collectively referred to as a vehicle body 12, a tire 20a that is a right front wheel, a tire 20b that is a left front wheel, a tire 20c that is a right rear wheel, and a tire 20d that is a left rear wheel. And a tire condition estimating device 10 that estimates the condition of the tire 20. The tire state estimation device 10 is provided on the tire 20, and includes an acceleration sensor that detects the acceleration G in the radial direction of the tire 20, a wheel speed sensor that detects the rotational speed of the tire 20, and a tire 20 output from the acceleration sensor. An electronic control unit (hereinafter referred to as “ECU”) 80 which is an example of an estimation means for estimating an abnormality of the tire 20 based on the rotation speed of the tire 20 output from the acceleration or wheel speed sensor, and the ECU 80 When it is determined that there is an abnormality in the tire 20, an alarm unit 82 for transmitting the fact to the driver, and when the ECU 80 determines that there is an abnormality in the tire 20, control such as reducing the vehicle speed is performed. A speed control unit 84.

  Each of the tires 20a, 20b, 20c, and 20d includes acceleration sensors 32a, 32b, 32c, and 32d (hereinafter referred to as “acceleration sensor 32” when collectively referred to) and an interrogator provided on the vehicle body 12 side. Transponders 34a, 34b, 34c and 34d for transmitting information related to the acceleration G in the radial direction of the tire 20 detected by the acceleration sensor 32 to the vehicle body 12 in response to the interrogation signal (hereinafter collectively referred to as “transponder 34”). ) And transmission / reception antennas 36a, 36b, 36c, and 36d (hereinafter collectively referred to as “antenna 36”), respectively, acceleration sensor units 30a, 30b, 30c, and 30d (hereinafter collectively referred to as “general”). Is called "acceleration sensor unit 30") Eclipsed.

  The vehicle body 12 has interrogators 40a, 40b, 40c and 40d (hereinafter collectively referred to as "interrogators 40a", "40b", "40c" and "40d") which receive information related to acceleration by transmitting interrogation signals to transponders 34 provided on the respective tires 20a, 20b, 20c and 20d. "Interrogator 40"), transmission / reception antennas 42a, 42b, 42c and 42d (hereinafter referred to as "antenna 42" when collectively referred to) and the rotational speeds of tires 20a, 20b, 20c and 20d are detected. Wheel speed sensors 50a, 50b, 50c and 50d (hereinafter referred to as “wheel speed sensor 50” when collectively referred to), ECU 80, alarm unit 82, and speed control unit 84 are provided.

  As the wheel speed sensor 50, a known technique can be used, and for example, a wheel rotor that rotates with the wheel may be provided. The rotor is configured as a gear having a large number of, for example, 48 teeth formed at equal intervals around the rotor, and an electromagnetic pickup is fixedly provided in the vicinity of the outer periphery of the rotor. The electromagnetic pickup detects a change in the magnetic field accompanying the passage of the teeth of the rotor, and outputs one pulse signal each time one of the teeth passes.

  The acceleration G of the tire 20 received by the antenna 42 and the wheel speed pulse signal detected by the wheel speed sensor 50 are transmitted to the ECU 80. The interrogator 40 may transmit the interrogation signal in accordance with the wheel speed pulse signal output from the wheel speed sensor 50, or may transmit the interrogation signal at a predetermined sampling rate. It suffices if sensor values can be acquired at a sampling rate sufficient to estimate. In the example shown in FIG. 1, four interrogators 40 are provided for each tire 20, but there may be one interrogator 40 or a plurality of interrogators 40. In the example shown in FIG. 1, an example is shown in which acceleration is acquired by two-way communication. However, a transmitter is provided in place of the transponder 34, a receiver is provided in place of the interrogator 40, and acceleration is obtained by one-way communication. You may get it.

  The ECU 80 acquires the acceleration G in the radial direction of the tire 20 and estimates the presence / absence of an abnormality in the tire 20. The ECU 80 calculates the uniformity component of the tire 20 based on the wheel speed pulse signal supplied from the wheel speed sensor 50 as in the above-described Patent Document 1 or 2, and calculates the tire 20 from the level of the uniformity component or the amount of change thereof. Although an abnormality may be estimated, in the present embodiment, another estimation technique using the acceleration G is proposed. When a mechanical failure such as a cord cut, tread peeling, or looseness occurs in the tire 20, the symptom appears as a variation in RFV (Radial Force Variation). Since the fluctuation of RFV causes the vibration of the same mode, it is considered that the fluctuation of the acceleration signal detected by the acceleration sensor 32 is detected. Therefore, the ECU 80 acquires an acceleration signal from the acceleration sensor 32, extracts a frequency component that is predicted to generate RFV, and estimates an abnormality of the tire 20. Since the fluctuation of the RFV is directly analyzed by the acceleration, not the indirect information of the wheel speed, the estimation can be performed with higher accuracy. Further, the ECU 80 changes the determination contents based on the vehicle state such as the vehicle speed and the road surface state in order to reduce the occurrence of erroneous determination.

  When the ECU 80 estimates that the tire 20 is abnormal, the warning unit 82 warns the driver to that effect. When the ECU 80 estimates that there is an abnormality in the tire 20, the speed control unit 84 controls the vehicle speed to decrease, and if necessary, stops the vehicle. Thereby, safety is ensured.

FIG. 2 shows an installation example of the acceleration sensor 32. In the example shown in FIG. 2, the acceleration sensor unit 30 is embedded in the tread rubber 22 of the tire 20. Ground to have portions of the tire 20, since the bent by a load applied to the tire 20, the dynamic load radius r ₁ at the time of grounding is shorter than the dynamic load radius r ₂ at the non-grounded. Accordingly, the radial acceleration G = rω ² increases or decreases during one rotation of the tire 20 even when the tire 20 rotates at a constant speed. However, the ECU 80 considers the change in acceleration in advance. What is necessary is just to estimate 20 abnormalities. For example, the change in the acceleration G detected when the tire 20 is normal, such as when the tire 20 is replaced, is stored, and when the abnormality is estimated, the change amount of the normal acceleration G stored in advance is subtracted. Then, the acceleration signal may be corrected and used for estimation.

  FIG. 3 shows another installation example of the acceleration sensor 32. In the example shown in FIG. 3, the acceleration sensor unit 30 is provided inside the tire valve 24 of the tire 20. Also in this case, a change in acceleration may be stored in advance when the tire 20 is normal, and correction may be performed when the abnormality is estimated. In the case where a pressure sensor for direct TPMS is provided in the tire valve 24, a configuration for transmitting the detection result of the pressure sensor to the vehicle body side is used in order to transmit information on acceleration to the vehicle body side. May be. The acceleration sensor 32 may be provided at yet another position of the tire 20 or may be provided at a plurality of positions.

  FIG. 4 shows functional blocks of estimation means realized by the ECU 80. The estimation means includes an acceleration acquisition unit 90, a speed calculation unit 91, a band pass filter (BPF) 92, a level calculation unit 93, and an estimation unit 99. These configurations can be realized in hardware by a CPU, memory, or other LSI of an arbitrary computer, and can be realized in software by a program loaded in the memory. Those skilled in the art will understand that these functions can be realized in various forms by hardware only, software only, or a combination thereof.

  The acceleration acquisition unit 90 acquires the acceleration signal detected by the acceleration sensor 32 from the interrogator 40. The acceleration acquisition unit 90 may transmit the interrogation signal from the interrogator 40 in synchronization with the wheel speed pulse signal in order to acquire the acceleration signal with the same sampling number per rotation without depending on the wheel speed. The speed calculation unit 91 calculates the vehicle speed based on the wheel speed pulse signal supplied from the wheel speed sensor 50. The BPF 92 extracts frequency components that do not depend on the vehicle speed, such as unsprung resonance frequency components, from the acquired acceleration signal. The unsprung resonance frequency is generally around 20 Hz. The level calculation unit 93 uses a method such as fast Fourier transform from the acquired acceleration signal to generate a primary component that makes one cycle in one rotation, a secondary component that makes two cycles in one rotation,. The level of the Nth order component that is a cycle is calculated. As described above, the level calculation unit 93 stores the change amount of the acceleration signal at the normal time in advance, and subtracts the change amount of the acceleration signal at the normal time before calculating the level of the N-order component. Good.

  The estimation unit 99 estimates the presence / absence of abnormality of the tire 20 from the level of the N-order component of the acceleration signal calculated by the level calculation unit 93. The estimation unit 99 stores a threshold value in advance for each of the N-order components, compares the calculated level of the N-order component with the threshold value, and is abnormal if the threshold value is exceeded. It may be estimated. The estimation unit 99 may perform estimation using the level of any order component. In addition, when the estimation unit 99 uses a plurality of order components for estimation, it may estimate that one of them exceeds the threshold value, and a plurality of them may be estimated. You may estimate that it is abnormal when a threshold value is exceeded. The estimation unit 99 may perform estimation by weighting the order used for estimation. For example, estimation may be performed with emphasis on the primary component. The estimation unit 99 may estimate the abnormality of the tire 20 from the amount of change in the level of the Nth order component.

  When the vehicle speed calculated by the speed calculation unit 91 is lower than a predetermined threshold value, the estimation unit 99 is less likely to cause an abnormality of the tire 20 and has less safety problems. Alternatively, the threshold for abnormality estimation may be relaxed. When the level of the unsprung resonance frequency component extracted by the BPF 92 exceeds a predetermined threshold value, the estimation unit 99 determines that the vehicle is traveling on a rough road and the influence of the road surface input is large, and cancels the estimation. Alternatively, the threshold for abnormality estimation may be relaxed. When it is estimated that the plurality of wheels are abnormal at the same time as a result of estimation, the estimation unit 99 determines that the determination is erroneous due to the influence of road surface input, etc., discards the estimation result, and determines that it is normal. Also good. Thereby, erroneous estimation can be prevented and the accuracy of estimation can be improved.

  FIG. 5 is a flowchart showing a procedure of a method for estimating an abnormality of the tire 20 according to the present embodiment. First, the estimation unit 99 determines whether or not to estimate an abnormality of the tire 20 based on the vehicle speed calculated by the speed calculation unit 91 (S10). The estimation unit 99 does not estimate the abnormality of the tire 20 when the vehicle speed is in a low speed range where safety is a small problem (N in S10). As a result, it is possible to reduce a situation in which it is erroneously determined that an abnormality has occurred in the tire 20 due to the influence of vibration caused by input from the road surface. When the vehicle speed is equal to or higher than the predetermined monitoring speed (Y in S10), the acceleration signal detected by the acceleration sensor 32 is acquired by the acceleration acquisition unit 90 (S12), and the unsprung resonance frequency component is extracted from the acceleration signal by the BPF 92. (S14). The BPF 92 extracts a frequency component around 20 Hz, for example. The estimation unit 99 compares the unsprung resonance frequency component of each wheel with a predetermined threshold value (S16). When a frequency component that does not depend on the rotation of the tire 20 such as an unsprung resonance frequency component exceeds a predetermined threshold (Y in S16), it does not result from an abnormality of the tire 20 but originates from an input from the road surface. Therefore, the estimation unit 99 does not estimate the abnormality. The estimation unit 99 may stop the estimation of abnormality when the unsprung resonance frequency component exceeds the threshold value in all the wheels, or the threshold value in the one, two, or three-wheel tire 20 may be stopped. If it exceeds, estimation of abnormality may be stopped.

  When the level of the unsprung resonance frequency component is smaller than the predetermined threshold value (N in S16), the level calculation unit 93 uses the acquired acceleration signal to predict the generation of RFV from the first, second, third, and third. Next, the level of the frequency component is calculated (S18), and the estimation unit 99 compares the level of the N-order component of each wheel with a predetermined threshold (S20). When the level of the N-order component of each wheel is smaller than the threshold value (N in S20), the estimation unit 99 estimates that there is no abnormality in the tire 20, and ends the process. When the level of the Nth order component of a certain wheel exceeds the threshold value (Y in S20), when the level of the Nth order component simultaneously exceeds the predetermined threshold value in all the wheels (Y in S22), Since there is a low possibility that all the wheels will fail at the same time and there is a high possibility that it is due to road surface input or the like, the estimation unit 99 estimates that there is no abnormality in the tire 20 and ends the processing. The estimation unit 99 may estimate that there is no abnormality when the level of the N-order component of the acceleration signal exceeds the threshold value in all the wheels, and in the two- or three-wheel tire 20, the threshold value may be estimated. If it exceeds, you may estimate that it is not abnormal. When there is a tire 20 in which the level of the Nth order component exceeds the threshold value and it is not estimated that the level is not abnormal (N in S22), the estimation unit 99 sets the level of the Nth order component to the threshold value. It is estimated that an abnormality has occurred for the tires 20 that have exceeded (S24), the alarm unit 82 is commanded to issue a warning to the driver, and the speed control unit 84 is commanded to reduce the speed (S26).

  With the above configuration and operation, it is possible to accurately estimate an abnormality of the tire 20 at an initial stage that is not easily noticed by the driver, so that before developing into a failure that hinders safe driving of the vehicle. Appropriate measures can be taken. Further, when estimating the state of the tire 20, it is possible to appropriately change the estimation content according to the vehicle speed, the road surface condition, and the like, thereby improving the estimation accuracy.

(Second Embodiment)
FIG. 6 shows an overall configuration of the vehicle 1 including the tire state estimation device 10 according to the second embodiment. Compared to the configuration of the tire condition estimation device 10 of the first embodiment shown in FIG. 1, the tire condition estimation device 10 of the present embodiment has a temperature sensor instead of an acceleration sensor in each tire 20. Is provided. In FIG. 6, an example in which an abnormality of the tire 20 is estimated by calculating a tire uniformity component from a wheel speed pulse signal detected by the wheel speed sensor 50 using the technique described in Patent Document 1 or 2. As shown in the first embodiment, the acceleration sensor is omitted, but when the abnormality of the tire 20 is estimated using the acceleration signal as described in the first embodiment, the acceleration sensor is provided for each tire 20. 32 may be provided. Other configurations and operations are the same as those of the first embodiment, and the same reference numerals are given to the same configurations. In the following, differences from the first embodiment will be mainly described.

  Each of the tires 20a, 20b, 20c, and 20d includes temperature sensor units 38a, 38b, 38c, and 38d (including temperature sensors 37a, 37b, 37c, and 37d (hereinafter collectively referred to as “temperature sensors 37”)). Hereinafter, these are collectively referred to as “temperature sensor unit 38”. Each of the temperature sensor units 38 is provided with a transponder 34 and an antenna 36, and transmits the temperature of the tire 20 detected by the temperature sensor 37 to the vehicle body side. The installation position of the temperature sensor unit 38 may be the same as the installation position of the acceleration sensor unit 30 in the first embodiment shown in FIG. 2 or FIG. 3, or may be provided at any other position. . Information regarding the temperature of the tire 20 transmitted from the temperature sensor unit 38 is transmitted to the ECU 80 via the antenna 42 and the interrogator 40.

  In the present embodiment, the estimation means realized by the ECU 80 changes the estimation content according to the temperature of the tire 20. An abnormality occurs in the tire 20 in many cases when the temperature of the tire 20 is high during traveling at high speed. Therefore, in the present embodiment, estimation of abnormality of the tire 20 is started when the tire 20 becomes high temperature, and estimation is not performed when the tire 20 is low temperature. Thereby, erroneous estimation can be prevented and the accuracy of estimation can be improved.

  FIG. 7 shows functional blocks of the estimation means according to the present embodiment. The estimation means includes a speed calculation unit 91, a level calculation unit 93, a temperature calculation unit 94, an initial value calculation unit 95, and an estimation unit 99. These configurations can also be realized in various forms by hardware only, software only, or a combination thereof.

  The temperature calculation unit 94 acquires the detection result detected by the temperature sensor 37 and calculates the temperature of the tire 20. The level calculation unit 93 calculates an index for estimating the abnormality of the tire 20. The level calculation unit 93 may calculate the level of the tire uniformity component described in Patent Document 1 or 2, and when an acceleration sensor is mounted, the acceleration signal is the same as in the first embodiment. The level of the Nth-order component may be calculated. The initial value calculation unit 95 sets an initial value serving as a reference for calculating the amount of change in the index calculated by the level calculation unit 93 when the estimation unit 99 performs abnormality of the tire 20. The estimation unit 99 estimates whether the tire 20 is abnormal when the vehicle speed is equal to or higher than a predetermined threshold and the temperature is equal to or higher than the predetermined threshold. The estimation unit 99 compares the level calculated by the level calculation unit 93 with the initial value set by the initial value calculation unit 95, and when there is a fluctuation greater than a predetermined threshold value, the tire 20 It is estimated that an abnormality occurred. As in the first embodiment, the estimation unit 99 may estimate that an abnormality has occurred in the tire 20 when the level calculated by the level calculation unit 93 exceeds a predetermined threshold value. . Similarly to the first embodiment, a BPF for extracting an unsprung resonance frequency component may be provided, and the content of estimation may be changed based on the unsprung resonance frequency component.

  FIG. 8 is a diagram illustrating conditions for the estimation unit 99 to perform estimation. In the example of FIG. 8, when the vehicle speed is V0 (for example, 100 km / h) or higher and the temperature of the tire 20 is T0 (for example, 100 degrees Celsius) or higher, the abnormality of the tire 20 is estimated. . No estimation is performed in other speed ranges and temperature ranges.

FIG. 9 is a flowchart showing the procedure of the tire condition estimation method according to the present embodiment. First, the estimation unit 99 determines whether or not to estimate an abnormality of the tire 20 based on the vehicle speed calculated by the speed calculation unit 91 (S30). The estimation unit 99 does not estimate the abnormality of the tire 20 when the vehicle speed is, for example, 200 km / h or less, which is a low speed range where safety problems are small (N in S30). As a result, it is possible to reduce a situation in which it is erroneously determined that an abnormality has occurred in the tire 20 due to the influence of vibration caused by input from the road surface. When the vehicle speed is equal to or higher than the predetermined monitoring speed (Y in S30), the estimation unit 99 confirms whether or not the initial value is set by the initial value calculation unit 95 (S32). When the initial value is not set (N of S32), the level calculation unit 93 calculates the level Gn of the uniformity component based on the wheel speed pulse signal acquired from the wheel speed sensor 50 (S44), and the initial value calculation unit 95 sets the calculated Gn to the initial value Gn ₀ (S46). The initial value calculation unit 95 may set an initial value for each vehicle speed range or temperature range.

When the initial value has already been set (Y in S32), the estimation unit 99 determines whether to estimate the abnormality of the tire 20 based on the temperature of the tire 20 calculated by the temperature calculation unit 94 (S34). ). The estimation unit 99 does not estimate the abnormality of the tire 20 when the temperature of the tire 20 is, for example, a low temperature range where safety problems are small such as 100 degrees Celsius or less (N in S34). Thereby, erroneous determination can be prevented and the accuracy of estimation can be improved. When the temperature of the tire 20 is abnormal in the monitoring temperature (Y in S34), the level calculation unit 93 calculates the vibration level Gn (S36), and the estimation unit 99 is set to the calculated vibration level Gn. comparing the initial value Gn ₀ (S38). If the difference between Gn and Gn ₀ is greater than the predetermined threshold (Y in S38), the estimation unit 99 estimates that an abnormality has occurred in the tire 20 (S40), and the alarm unit 82 notifies the driver. In response to this, an instruction is issued to issue an alarm, and the speed controller 84 is instructed to reduce the speed (S42). If the difference between the Gn and Gn ₀ is smaller than a predetermined threshold value (S38 of N), the estimation unit 99 estimates that there is no abnormality in the tire 20, the process ends.

  With the above configuration and operation, when the state of the tire 20 is estimated, the estimation content can be appropriately changed according to the vehicle speed, the temperature of the tire 20, and the like, and the estimation accuracy can be improved.

(Third embodiment)
In the present embodiment, the estimation content in the estimation means realized by the ECU 80 is changed according to the deterioration state of the tire 20. When the variation in the level of the tire uniformity component increases, it is considered that the tire 20 has been deteriorated, and the possibility that an abnormality will occur in the tire 20 increases. Therefore, when it is determined that the deterioration of the tire 20 is progressing, the condition for estimating the abnormality of the tire 20 is expanded so that the occurrence of the abnormality of the tire 20 can be accurately detected. The configuration of the tire condition estimation device 10 of the present embodiment is the same as the configuration of the tire condition estimation device 10 of the second embodiment shown in FIG. In the following, differences from the second embodiment will be mainly described.

  FIG. 10 shows functional blocks of the estimation means according to the present embodiment. The estimation means includes a speed calculation unit 91, a level calculation unit 93, a temperature calculation unit 94, an initial value calculation unit 95, a level comparison unit 96, an estimation region update unit 97, and an estimation unit 99. These configurations can also be realized in various forms by hardware only, software only, or a combination thereof. The initial value calculation unit 95 sets an initial value of the uniformity level for each predetermined speed range. The level comparison unit 96 compares the uniformity level calculated by the level calculation unit 93 with the initial value for each speed range set by the initial value calculation unit 95, and the amount of change in the uniformity component level for each speed range Is calculated. Based on the level change calculated by the level comparison unit 96, the estimation region update unit 97 updates the temperature range and speed range in which the estimation unit 99 performs estimation.

  FIG. 11 shows an example of a change in uniformity level for each speed range. In the figure, black circles indicate initial values for each speed range, and white circles indicate uniformity levels observed after initial value setting. In the example shown in FIG. 11, for example, the uniformity level changes by 1 in the speed range from V1 to less than V2, and the uniformity level changes by 2 in the speed range from V2 to less than V3. The total change amount of the uniformity level at this time is 6. In the present embodiment, it is determined that the deterioration of the tire 20 is progressing as the total amount of change is larger. The estimation area update unit 97 determines the deterioration state of the tire 20 based on the total value of the changes, and changes the threshold value used by the estimation unit 99 for estimation.

  FIG. 12 shows an example of a table storing the correspondence between the level change amount and the estimated area. In the example of FIG. 12, for example, when the total value of the change amount of the uniformity level for each speed range is 0 to 2, the estimation region update unit 97 uses the speed range in which the estimation unit 99 estimates the state of the tire 20. Is “200 km / h or more”, and the temperature range is “100 ° C. or more”. In the example shown in FIG. 11, since the total value of the change amount of the uniformity level is “6”, the estimation area update unit 97 sets the speed range for estimation to “160 km / h or more” and the temperature range to “ Update to “80 ° C. or higher”.

  FIG. 13 shows a state where the estimated area is updated by the estimated area update unit 97. Initially, the region in which the estimation unit 99 performs estimation has a speed of 200 km / h or more and a temperature of 100 ° C. or more, but the estimation region update unit 97 allows the speed region to 160 km / h and the temperature region to 80 ° C. , Each estimation area is expanded. As the deterioration of the tire 20 progresses, it is possible to accurately detect the occurrence of an abnormality in the tire 20 by expanding the estimation region. As described above, according to the present embodiment, the degree of deterioration of the tire 20 can be accurately determined, and the condition for the estimation unit 99 to perform estimation can be set according to the degree of deterioration. Can be improved.

  FIG. 14 is a flowchart showing the procedure of the tire condition estimation method according to the present embodiment. FIG. 14 shows a procedure for changing the estimation content by the estimation unit 99 in accordance with the degree of deterioration of the tire 20, and thereafter, the tire state estimation method shown in FIG. 9 is executed. First, the estimation part 99 acquires a vehicle speed from the speed calculation part 91, and determines the present vehicle speed range (S50). If the current vehicle speed does not correspond to any vehicle speed range (N in S50), the process is terminated. When the estimation unit 99 determines the vehicle speed range (Y in S50), the initial value calculation unit 95 checks whether or not an initial value in the vehicle speed range is set (S52). When the initial value is not set (N in S52), the level calculation unit 93 calculates the level of the uniformity component based on the wheel speed pulse signal acquired from the wheel speed sensor 50 (S60), and the initial value calculation unit 95 sets the calculated level to the initial value of the vehicle speed range (S62).

  When the initial value in the current vehicle speed range has been set (Y in S52), the level calculation unit 93 calculates the vibration level (S54), and the level comparison unit 96 determines the calculated vibration level and the current vehicle speed. The level change amount is calculated by comparing with the initial value in the area (S56). The estimation area update unit 97 estimates the degree of deterioration of the tire 20 based on the level change amount, and updates the estimation condition by the estimation unit 99 according to the degree of deterioration (S58). When the estimation condition is updated, the initial value may be cleared.

  With the above configuration and operation, when the state of the tire 20 is estimated, the estimation content can be appropriately changed according to the deterioration state of the tire 20 to improve the estimation accuracy.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

It is a figure showing the whole vehicle composition provided with the tire state estimating device concerning a 1st embodiment. It is a figure which shows the example of installation of an acceleration sensor. It is a figure which shows the other example of installation of an acceleration sensor. It is a figure which shows the functional block of the estimation means implement | achieved by ECU. It is a flowchart which shows the procedure of the estimation method of the abnormality of the tire which concerns on 1st Embodiment. It is a figure which shows the whole structure of a vehicle provided with the tire state estimation apparatus which concerns on 2nd Embodiment. It is a figure which shows the functional block of the estimation means which concerns on 2nd Embodiment. It is a figure which shows the conditions which an estimation part estimates. It is a flowchart which shows the procedure of the estimation method of the tire state which concerns on 2nd Embodiment. It is a figure which shows the functional block of the estimation means which concerns on 3rd Embodiment. It is a figure which shows the example of a change of the uniformity level for every speed range. It is a figure which shows the example of the table which stored the response | compatibility with the amount of level changes, and an estimation area | region. It is a figure which shows a mode that the estimation area | region was updated by the estimation area | region update part. It is a flowchart which shows the procedure of the estimation method of the tire state which concerns on 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Vehicle, 10 Tire state estimation apparatus, 12 Car body, 20 Tire, 22 Tread rubber, 24 Tire valve, 30 Acceleration sensor unit, 32 Acceleration sensor, 34 Transponder, 36 Antenna, 37 Temperature sensor, 38 Temperature sensor unit, 40 Interrogator , 42 antenna, 50 wheel speed sensor, 82 alarm unit, 84 speed control unit, 90 acceleration acquisition unit, 91 speed calculation unit, 93 level calculation unit, 94 temperature calculation unit, 95 initial value calculation unit, 96 level comparison unit, 97 An estimation area update unit, 99 an estimation unit.

Claims (9)

Detection means for detecting the condition of the tire;
An estimation means for estimating an abnormality of the tire based on a detection result of the detection means,
The estimation means changes the estimation contents according to the state of the vehicle.   The tire state estimation device according to claim 1, wherein the estimation unit changes the estimation content according to a vehicle speed.   The tire state estimation device according to claim 1, wherein the estimation means changes the estimation content according to whether or not a plurality of wheels are simultaneously estimated to be abnormal.   The tire state estimation device according to claim 1, wherein the estimation unit changes the estimation content according to a road surface state during traveling.   The tire state estimation device according to claim 1, wherein the estimation unit changes the estimation content according to a temperature of the tire.   The tire state estimation device according to claim 1, wherein the estimation unit changes the estimation content according to a deterioration state of the tire.   The tire state estimation device according to any one of claims 1 to 6, wherein the estimation unit stops estimation when the estimation content is changed.   The tire state estimation device according to any one of claims 1 to 6, wherein when the estimation content is changed, the estimation unit changes a threshold value used for estimation.   The tire condition estimation device according to any one of claims 1 to 8, wherein the abnormality of the tire is a mechanical failure.

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