JP2005104205A - Tire state determining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve determination accuracy in a tire state determining device for determining a tire state based on a rotation state amount of the wheel, in a vehicle having the wheel formed by mounting the tire to the wheel. <P>SOLUTION: A threshold value TH to be compared with a calculation value of the uniformity Gn of the tire to determine whether the tire is abnormal is changed based on a relation between the temperature Tt detected by a sensor about the tread side of the tire and the temperature Tr detected by another sensor about the rim side of the tire. The threshold value TH is changed to a threshold value THT for the tread side when the temperature Tt is higher (S4), or to a threshold value THR for the rim side when the temperature Tr is higher (S5). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire state determination device that determines the state of a tire based on the amount of rotational state of the wheel in a vehicle in which the wheel is configured by mounting the tire on a wheel. The present invention relates to a technique for improving accuracy.

2. Description of the Related Art There is already known a tire state determination device that determines the state of a tire based on the amount of rotation state of the wheel in a vehicle in which a wheel configured by mounting the tire on a wheel is mounted. In general, the tire state determination device includes: (a) a rotation state amount sensor that detects a rotation state amount of a wheel; and (b) a rotation state amount detected by the rotation state amount sensor and a reference value. It is comprised so that the determination device which determines whether it is abnormal can be included (for example, refer patent document 1).
JP-A-8-132831

  In the conventional tire state determination device described in Patent Document 1, the detected value of the rotational state amount of the wheel is compared with a single reference value that is a fixed value, and the tire is abnormal based on the comparison result. It is determined whether or not there is.

  On the other hand, the inventor conducted research to develop a technique for accurately judging tire abnormality by using this type of tire condition judging device, and as a result, obtained the following knowledge.

  For example, a phenomenon of abnormal tire deformation may occur. When abnormal deformation of the tire occurs, a change appears in the rotational state amount of the wheel prior to that. That is, a change appears in the rotational state quantity of the wheel as a predictive phenomenon of abnormal tire deformation. Accordingly, if a change in the rotational state amount of the wheel is detected, abnormal deformation of the tire can be predicted.

  When abnormal deformation of the tire occurs, there are a mode in which the abnormal deformation occurs from the outer peripheral side portion of the tire and a mode in which the abnormal deformation occurs from the inner peripheral side portion. Then, the present inventor has noticed the fact that if the occurrence location of the abnormal deformation is different, the change appearing in the rotational state quantity as a predictive phenomenon is different prior to the abnormal deformation.

  Based on such knowledge, the present invention provides a tire state determination device that determines the state of a tire based on the rotational state amount of the wheel in a vehicle in which the wheel is configured by mounting the tire on the wheel. An object is to improve the accuracy of the determination.

  The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is given a number, and is described in a form that cites other section numbers as necessary. This is to facilitate understanding of some of the technical features that the present invention can employ and combinations thereof, and the technical features that can be employed by the present invention and combinations thereof are limited to the following embodiments. Should not be interpreted. That is, although not described in the following embodiments, it should be construed that it is not impeded to appropriately extract and employ the technical features described in the present specification as the technical features of the present invention.

Further, describing each section in the form of quoting the numbers of the other sections does not necessarily prevent the technical features described in each section from being separated from the technical features described in the other sections. It should not be construed as meaning, but it should be construed that the technical features described in each section can be appropriately made independent depending on their properties.
(1) A tire state determination device that determines a state of a tire based on a rotation state amount of a wheel in a vehicle in which a wheel is configured by mounting a tire in which air is sealed under pressure. And
A rotational state amount sensor for detecting a rotational state amount of the wheel;
A determination device for determining whether or not the tire is abnormal by comparing a detected value of a rotational state quantity by the rotational state quantity sensor with a reference value, wherein the tire abnormality is an outer peripheral side portion of the tire A tire condition determination device including: a device that changes the reference value depending on whether it occurs on the inner peripheral side or the inner peripheral side portion.

  In this device, the reference value to be compared with the detected value of the rotational state amount of the wheel in order to determine whether or not the tire is abnormal is the difference in the portion where the abnormality occurs in the tire, that is, abnormal Is changed depending on whether it occurs on the outer peripheral side or the inner peripheral side of the tire.

  Therefore, according to this apparatus, although the change that appears in the rotational state amount of the wheel varies depending on whether the abnormality occurs on the outer peripheral side or the inner peripheral side of the tire, early detection of the tire abnormality is detected. And it becomes easy to make compatible the prevention of the misjudgment by which it is judged that the tire which should be judged to be normal originally is abnormal.

  More specifically, the change appearing in the rotational state amount of the wheel differs depending on whether the abnormality occurs on the outer peripheral side or the inner peripheral side of the tire. Therefore, when the only reference value that is a fixed value is used, in order to prioritize early detection of tire abnormality, the influence of the abnormality occurrence point on the rotational state amount of the outer peripheral side and the inner peripheral side is small. If the reference value is set so that the abnormality is detected even in the case of the direction, the influence of the occurrence location of the abnormality on the rotational state quantity is greater on the outer peripheral side and the inner peripheral side. The sensitivity of abnormality determination will be too sensitive. As a result, there is a possibility that a tire that should be determined to be normal is erroneously determined to be abnormal.

  On the other hand, in order to prioritize prevention of misjudgment, a standard is set so that an abnormality is detected only when the location where the abnormality occurs is the one that has a greater influence on the rotational state quantity between the outer peripheral side and the inner peripheral side. When the value is set, the sensitivity of abnormality determination becomes too insensitive when the abnormality occurrence location has a smaller influence on the rotation state amount between the outer peripheral side portion and the inner peripheral side portion. As a result, it becomes difficult to detect tire abnormality at an early stage.

  On the other hand, according to the apparatus according to this section, the reference value is changed depending on the location of the tire where the abnormality occurs (location where the occurrence of the abnormality is expected). It is easy to achieve both prevention of determination.

  In order to “change the reference value” in this section, a plurality of different reference values are prepared in advance, and one of these reference values is selected as a value to be compared with the detected value of the rotational state quantity. It is possible to adopt a mode or a mode in which the size of one reference value is changed and the reference value having the changed size and the detected value of the rotational state quantity are compared with each other. .

In this section, “tire abnormality” can be interpreted to mean, for example, an abnormality that appears in the tire prior to abnormal deformation of the tire, or can be interpreted to mean that abnormal deformation. When the former interpretation is adopted, abnormal deformation of the tire can be predicted.
(2) Furthermore,
A first sensor for detecting a state quantity of the outer peripheral side portion;
A second sensor that detects a state quantity of the inner peripheral side portion, and the determination unit determines the reference value based on a relationship between the state quantities detected by the first sensor and the second sensor. The tire state determination device according to item (1), including first changing means for changing.

  If the relationship between the state quantity of the outer peripheral side portion and the state quantity of the inner peripheral side portion of the tire is found, an abnormality is about to occur in either the outer peripheral side portion or the inner peripheral side portion. It is possible to distinguish whether the cause of the change appearing in the rotational state quantity is an abnormality on the outer peripheral side or an abnormality on the inner peripheral side.

  For example, the degree that the state quantity of the outer peripheral side indicates that the abnormality may occur in the outer peripheral side is higher than the degree that the state quantity of the inner peripheral side indicates that the abnormality may occur in the inner peripheral side. In this case, it is possible to specify that the cause of the change appearing in the rotational state quantity of the wheel is an abnormality on the outer peripheral side.

Based on such knowledge, in the apparatus according to this section, the state quantity detected by the first sensor for the outer peripheral side part of the tire and the state quantity detected by the second sensor for the inner peripheral side part Based on the relationship, the reference value is changed.
(3) In the item (2), the first sensor and the second sensor respectively detect at least one of temperature and strain of the corresponding one of the outer peripheral side portion and the inner peripheral side portion as the state quantity. The tire condition determination device described.

  One of the causes of tire abnormality is tire heat generation. One cause of the tire heat generation is repeated bending of the tire. The amount of heat generated by the tire due to repeated bending increases as the bending increases, that is, as the tire distortion increases.

  Therefore, if at least one of the temperature and strain of the tire is detected and referred to for each of the outer peripheral side portion and the inner peripheral side portion, it is easy to predict a location where an abnormality occurs in the tire.

Based on such knowledge, in the apparatus according to this section, at least one of temperature and strain is detected for each of the outer peripheral side portion and the inner peripheral side portion.
(4) Of the tires, the first changing means has a large state quantity detected by the corresponding one of the first sensor and the second sensor among the outer peripheral side part and the inner peripheral side part. The tire condition determination device according to (3), wherein the reference value is changed as an abnormality occurs.

  In the apparatus according to the above item (3), it is possible to assume that there is a high possibility that a tire abnormality will occur in the outer peripheral side portion and the inner peripheral side portion of the tire that have a large state quantity. . If this assumption is adopted, if the reference value is changed so that the outer peripheral side portion and the inner peripheral side portion of the tire have a large state quantity, the abnormality of the tire is regarded as the occurrence location of the abnormality. It becomes possible to detect appropriately in the relationship.

Based on such knowledge, in the apparatus according to this section, the state quantity detected by the corresponding one of the first sensor and the second sensor among the outer peripheral side portion and the inner peripheral side portion is large. The reference value is changed as a tire abnormality occurs.
(5) The tire state determination device according to any one of (1) to (4), wherein the determination unit includes a second change unit that changes the reference value based on a pressure level of the tire.

  To determine which of the tires is likely to cause an abnormality on the outer peripheral side or inner peripheral side, the state quantity is detected for each of the outer peripheral side and the inner peripheral side and compared with each other. This can be determined by referring to the tire pressure level.

  For example, according to the inventor's research, when the tire air pressure is not so low and the rigidity of the inner peripheral side portion is not insufficient, the outer peripheral side portion is more bent than the inner peripheral side portion. It is easy to generate. On the other hand, when the tire air pressure is considerably low and the rigidity of the inner peripheral side portion is insufficient, the inner peripheral side portion is more likely to bend repeatedly than the outer peripheral side portion. There is a tendency that abnormalities such as exfoliation and breakage of tire rubber occur due to heat generation or the like in a portion where the bending is repeatedly generated between the outer peripheral side portion and the inner peripheral side portion.

In this way, there is a certain relationship between the height of the tire air pressure and the location of the tire where bending is repeated and the location where an abnormality occurs in the tire. In such an apparatus, the reference value is changed based on the height of tire air pressure.
(6) The tire state determination device according to any one of (1) to (5), wherein the rotational state quantity is a physical quantity representing a uniformity of the tire.

  Between the presence / absence of a tire abnormality and the tire uniformity, a relationship is established that if a tire abnormality occurs, the tire uniformity decreases. Accordingly, if attention is paid to the uniformity of the tire, it is possible to detect the abnormality of the tire.

Based on such knowledge, in the apparatus according to this section, the rotational state quantity of the wheel referred to in order to detect the abnormality of the tire is a physical quantity representing the tire uniformity.
(7) The rotational state quantity is a physical quantity that represents a vibration generated in the tire based on a change in rigidity of the tire in a circumferential direction of the tire, according to any one of (1) to (5). Tire condition judging device.

As an example of the “physical quantity” in this section, for example, there is “Uniformity” in the section (6).
(8) The tire state determination device according to (6) or (7), wherein the rotation state amount is a rotation speed of the wheel.
(9) A tire that has an outer peripheral side portion and an inner peripheral side portion and is used by being mounted on a vehicle, and a sensor that detects a state quantity is embedded in each of the outer peripheral side portion and the inner peripheral side portion. Tires.

  According to this tire, a tire suitable for implementing the device according to any one of the items (1) to (8) is provided.

  Hereinafter, some of more specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view of a tire condition determination device (hereinafter simply referred to as “determination device”) according to the first embodiment of the present invention. This determination device is mounted on a vehicle including left and right front wheels 10 and 10 and left and right rear wheels 10 and 10. The determination device includes a portion mounted on the tire for detecting the state quantity of the tire, and a portion mounted on the vehicle body for acquiring information on the state quantity of the tire by wireless communication with the part. ing. These parts will be described in detail later.

  As shown in FIG. 2, each wheel 10 is configured by attaching a tire 12 to a wheel 24 (or rim). In each wheel 10, the tire 12 and the wheel 24 are mounted in an airtight manner, and an air chamber 26 is formed between them. The air is sealed in the air chamber 26 under pressure, whereby the elasticity of the tire 12 is realized.

  The tire 12 extends in the circumferential direction of the tire 12 with a generally C-shaped cross section. The tire 12 is classified into a tread portion 30, a pair of shoulder portions 32, a pair of sidewall portions 34, and a pair of bead portions 36.

  The tread portion 30 is a portion of the tire 12 that is in contact with the road surface during traveling of the vehicle. In the present embodiment, two steel belts 40 and 40 that both extend in the circumferential direction of the tire 12 are embedded.

  Each shoulder portion 32 is a portion of the tire 12 that hits the boundary between the tread portion 30 and the sidewall portion 34, and is also a portion that repeatedly undergoes bending in a vertical plane that includes the rotation axis of the tire 12 during traveling of the vehicle. Both sides 48, 48 of each steel belt 40 are positioned on the pair of shoulder portions 32. A carcass 50 is embedded in the tread portion 30, the shoulder portion 32, and the sidewall portion 34.

  The bead portion 36 is a portion of the tire 12 that is attached to the wheel 24. In the present embodiment, the bead wire 52 is embedded along one circumference that is coaxial with the tire 12, and the bead wire 52 is placed inside. A carcass 50 is embedded so as to be folded when viewed.

  The tire 12 is divided into a tread side portion that is an example of an outer peripheral side portion and a rim side portion that is an example of an inner peripheral side portion. An example of the tread side portion is the tread portion 30 and the shoulder portion 32, and an example of the rim side portion is the bead portion 36.

  As shown in FIG. 2, the determination device detects a first temperature sensor unit 60 for detecting a temperature that is an example of a state quantity of the tread side portion, and a temperature that is an example of a state quantity of the rim side portion. The second temperature sensor unit 62 is provided in a state embedded in the tire 12.

  As shown in FIG. 3, the 1st temperature sensor unit 60 is comprised so that the 1st temperature sensor 64 and the 1st transponder 66 as a wheel side communication apparatus may be included. Similarly, the 2nd temperature sensor unit 62 is comprised so that the 2nd temperature sensor 68 and the 2nd transponder 70 as a wheel side communication apparatus may be included. In each temperature sensor unit 60, 62, the output signal of each temperature sensor 64, 68 is supplied to each transponder 66, 70. As shown in FIG. 2, the first temperature sensor unit 60 is disposed in the tread portion 30 (or the shoulder portion 32 is acceptable), and the second temperature sensor unit 62 is disposed in the bead portion 36.

  The transponders 66 and 70 are communication devices of a type that transmits a signal in response to a radio signal from the outside without using a power supply itself. Therefore, as shown in FIG. 2, the vehicle body side communication device 74 is installed in the vehicle body 72 at a position close to the locus drawn by the transponders 66 and 70 while the vehicle is traveling. The vehicle body side communication device 74 has at least a function of supplying energy (for example, electromagnetic energy) for driving the transponders 66 and 70 in a non-contact state to the transponders 66 and 70 and a signal generated by the transponders 66 and 70. And a function to receive.

  As shown in FIG. 2, the vehicle body side communicator 74 is located on the rim side and a first communication unit 76 that communicates with the first transponder 66 corresponding to the first temperature sensor 64 located on the tread side. A second communication unit 78 that communicates with the second transponder 70 corresponding to the second temperature sensor 68 is provided. Accordingly, communication is performed for each of the temperature sensors 64 and 68 so that the temperature on the tread side and the temperature on the rim side are distinguished from each other and received by the vehicle body side communication device 74.

  As shown in FIG. 1, a determination device 80 is connected to the vehicle body side communication device 74. The determination device 80 is configured mainly by a computer 82. As is well known, the computer 82 is configured by connecting a CPU 84, a ROM 86, and a RAM 88 to each other via a bus 90 as shown in FIG. 4. Various programs such as a tire condition determination program conceptually shown in the flowchart of FIG. 6 are stored in the ROM 86 in advance. The CPU 84 reads a necessary program from the ROM 86, and executes the read program while appropriately using the RAM 88.

  As shown in FIG. 1, a vehicle equipped with this determination device includes a wheel speed sensor 100 for each wheel 10. As is well known, each wheel speed sensor 100 is a sensor that detects the angular speed of each wheel 10 as the wheel speed at a fixed position of the vehicle body 92. Specifically, the wheel speed sensor 100 is an electromagnetic pickup, and outputs a voltage signal that periodically changes according to the passage of a large number of teeth formed on the outer periphery of a rotor (not shown) that rotates with the wheel 10. In the present embodiment, the total number of teeth is selected to be 48.

  As shown in FIG. 5, each wheel speed sensor 100 is connected to the determiner 80 via a waveform shaper (not shown). The waveform shaper is provided to generate a pulsed voltage signal (hereinafter simply referred to as “pulse signal”) by shaping the output signal of each wheel speed sensor 100. One pulse signal is generated from the wheel speed sensor 100 each time one tooth is detected by the wheel speed sensor 100.

  The determiner 80 determines whether each wheel 10 is abnormal with respect to the tire 12 by paying attention to the magnitude of the rotational fluctuation of each wheel 10 based on the output signal of each wheel speed sensor 100. In the present embodiment, since the abnormality of the tire 12 is used as a term meaning an abnormality that occurs in the tire 12 prior to the abnormal deformation that occurs in the tire 12, It is possible to predict the deformation and notify the driver.

  As shown in FIG. 5, the vehicle body side communication device 74 is also connected to the determination device 80, and the alarm device 110 is also connected. This alarm device 110 is activated to notify the driver of the vehicle when the condition of the tire 12 is abnormal. The alarm device 110 can display necessary information visually or audibly.

  Here, the tire condition determination program will be described with reference to FIG.

  In this tire condition determination program, whether each wheel 10 is abnormal with respect to the tire 12 by paying attention to the magnitude of the rotational fluctuation of each wheel 10 based on the output signal of each wheel speed sensor 100 for each wheel 10. It is determined whether or not. In the present embodiment, the magnitude of the rotational fluctuation of each wheel 10 is expressed by a physical quantity called uniformity Gn (n: degree) of the tire 12.

  In the present embodiment, the uniformity Gn is calculated so as to increase as the rotational fluctuation of the tire 12 increases based on the output signal of the wheel speed sensor 100. This calculation will be described in detail later. Therefore, in the present embodiment, the physical quantity called uniformity Gn is defined as having a change characteristic that is opposite to the change characteristic that the term uniformity means in the first place.

  In the tire condition determination program, it is further determined whether or not the calculated uniformity Gn is greater than the threshold value TH, that is, whether or not the rotational fluctuation amount of the tire 12 is greater than an allowable value. Whether the tire 12 is abnormal is determined.

  By the way, the present inventor has simulated the load rotation state of several similar tires mounted on the same vehicle, so that abnormal deformation occurs in the tread side portion of a certain tire, and the same type of tire. The state in which abnormal deformation occurs in the rim side portion was reproduced. At that time, it was observed that the value of the secondary uniformity G2 of each tire changed with time t.

  FIG. 7 is a graph showing the temporal transition of the value of the secondary uniformity G2 from the start of load rotation of a certain tire until the occurrence of abnormal deformation at the tread side. FIG. 8 is a graph showing the temporal transition of the value of the secondary uniformity G2 from the start of load rotation of the same type of tire to the occurrence of abnormal deformation at the rim side.

  Both temporal transitions are common to each other in that the value of the secondary uniformity G2 increases rapidly immediately before the occurrence of abnormal deformation, but the time when a significant change occurs in the secondary uniformity G2 ( The value of the secondary uniformity G2 in the solid line with the arrow in FIGS. 7 and 8 is also the value of the secondary uniformity G2 at the time when the peak is shown (indicated by the broken line with the arrow in FIGS. 7 and 8). It is also clear that the value is greater when abnormal deformation occurs on the tread side than when it occurs on the rim side.

  Therefore, in order to accurately determine whether or not the tire 12 is abnormal by comparing the uniformity Gn of the tire 12 and the threshold value TH (that is, whether or not the tire 12 may shift to abnormal deformation) It is desirable to distinguish between whether the abnormality occurs on the tread side or the rim side and to change the threshold value TH accordingly.

  Based on such knowledge, in this tire condition determination program, when an abnormality is expected to occur on the tread side, the calculated value and threshold value of the uniformity Gn (for example, the second-order uniformity component) When THT is compared with each other, but an abnormality is expected to occur on the side of the rim, the computed value of uniformity Gn and the threshold value THR that are smaller than the threshold value THT are compared with each other. Is done.

  Further, in this tire condition determination program, the tread side temperature Tt is detected by the first temperature sensor 64, and the rim side temperature Tr is detected by the second temperature sensor 68. And when the detected value of temperature Tt is higher than the detected value of temperature Tr, it is estimated that possibility that abnormality will generate | occur | produce in the tread side part is high. On the other hand, when the detected value of the temperature Tt is not higher than the detected value of the temperature Tr, it is expected that an abnormality is likely to occur on the rim side.

  In addition, in this embodiment, in order to determine whether there is a possibility that an abnormality may occur in either the tread side portion or the rim side portion, the temperature Tt on the tread side portion and the rim side portion are determined. Although the temperatures Tr are simply compared, the comparison can be performed according to other methods.

  For example, the margin of the actual temperature of the tread side relative to the limit temperature, which is the temperature immediately before the occurrence of an abnormality on the tread side, and the abnormality on the rim side of the actual temperature of the rim side begin to occur. It is possible to carry out the present invention in a mode in which the margin with respect to the limit temperature, which is the immediately preceding temperature, is compared with each other.

  In this aspect, for example, when the former margin is lower than the latter margin, the threshold value TH is set to the threshold value THT for the tread side, and conversely, the latter margin is set to the former margin. The threshold value TH can be set to the threshold value THR for the rim side when it is lower than the degree.

  The tire condition determination program in the present embodiment has been schematically described above, but will be specifically described below with reference to the flowchart of FIG.

  The tire condition determination program is repeatedly executed by the computer 82 for each tire 12. At the time of each execution, first, in step S1 (hereinafter, simply expressed as “S1”, the same applies to other steps), the first communication unit 76 receives the first tire 12 from the first transponder 66 for the current tire 12. Based on the signal, the tread side temperature Tt is detected.

  Next, in S <b> 2, the rim side temperature Tr is detected for the same tire 12 based on the signal received by the second communication unit 78 from the second transponder 70.

  Subsequently, in S3, it is determined whether or not the detected value of the tread side temperature Tt is higher than the detected value of the rim side temperature Tr. If it is assumed that the detected value of the tread side temperature Tt is higher this time, the determination is YES, and in S4, the threshold value TH is the tread side threshold value THT (the higher threshold value). Set to On the other hand, this time, if it is assumed that the detected value of the rim side temperature Tr is higher, the determination in S3 is NO, and in S5, the threshold value TH is lower than the rim side threshold value THR (lower). Threshold).

  In any case, thereafter, in S6, the above-described uniformity Gn is calculated for the current tire 12.

  The details of S6 are conceptually shown in the flowchart of FIG. 9 as a uniformity calculation routine.

  In this uniformity calculation routine, first, in S101, each of the plurality of actual teeth in the rotor described above or each of a plurality of groups in which the actual teeth are grouped in the circumferential direction of the rotor is apparently represented. Each time a pulse signal is output from the wheel speed sensor 100, the edge generation timing t (i) of each pulse signal is detected.

  In addition, in this embodiment, in this embodiment, the rotor has 48 actual teeth, and these actual teeth are classified into 8 groups. Each group is defined such that six actual teeth belonging to it constitute one apparent tooth. Therefore, in this embodiment, the rotor is handled so as to have eight apparent teeth.

  Next, in S102, as the period of the latest pulse signal of the current edge generation time t (i) from the previous edge generation time t (i-1), that is, the individual time interval Tw (i). Calculated.

  In addition, if it adds, the fluctuation | variation for one rotation of the tire of the period of each pulse signal means the rotation fluctuation signal of the tire 12, and when it is acquired on condition that the tire 12 is not normal, The rotation fluctuation signal means a combination of a basic fluctuation component that depends on factors other than the tire 12 and a fluctuation component that depends on the tire 12.

  Subsequently, in S103, in order to extract the fluctuation component depending on the tire 12, the deviation W of the calculated individual time interval Tw (i) from each individual time interval Tw (i) in the basic fluctuation component. (I) is calculated. Each individual time interval Tw (i) in the basic fluctuation component is calculated, for example, as an average value Ta (i) of a plurality of individual time intervals Tw (i) continuous with each other. An example of an expression to be used for calculating the average value Ta (i) is shown in the expression (1) of FIG.

In this embodiment, the deviation W (i) is basically a divided value obtained by dividing the difference between the average value Ta (i) and the current individual time interval Tw (i) by the average value Ta (i). Is used to calculate. However, the deviation W (i) is calculated by taking the above-mentioned division value into consideration in consideration of the previous deviation W (i-8) (deviation calculated for the same tooth before one rotation of the wheel) in the presence of the sensitivity coefficient K. It can be used for calculation. An example of an expression to be used for that purpose is shown in Expression (2) in FIG. However, the calculation is, for example,
W (i) = Tw (i) / Ta (i)
Can be performed using the following equation.

  Thereafter, in S104 of FIG. 9, the n-order sine wave component An of the signal representing the temporal variation of the individual time interval Tw is defined in association with the latest one rotation of the tire. An example of an equation for the definition is shown in equation (3) in FIG.

  Subsequently, in S105 of FIG. 9, an n-order cosine wave component Bn in the signal representing the temporal variation of the individual time interval Tw is defined in association with the latest one rotation of the tire. An example of an equation for this definition is shown in equation (4) in FIG.

  Thereafter, in S106 of FIG. 9, the cumulative value of the nth-order deviation W (i) is calculated as the uniformity Gn (cumulative deviation) in association with the latest rotation of the tire. The uniformity Gn corresponds to the sum of the areas of the n-order sine wave component An and the n-order cosine wave component Bn. An example of an equation for calculating the uniformity Gn is shown in Equation (5) in FIG.

  Thus, one execution of this uniformity calculation routine is completed.

  Subsequently, in S7 of FIG. 6, it is determined whether or not the calculated uniformity Gn is greater than a threshold value TH. If it is larger, the determination is YES, and it is determined in S8 that the current wheel 10 is abnormal with respect to the tire 12, and in S9, the alarm device 110 is turned on to notify the driver of this. Thus, one execution of the tire abnormality determination program is completed.

  On the other hand, if the calculated uniformity Gn is not greater than the threshold value TH, the determination in S7 of FIG. 9 is NO, and it is determined in S10 that the current wheel 10 is normal with respect to the tire 12. In step S11, the alarm device 110 is turned off to notify the driver of the fact. Thus, one execution of the tire abnormality determination program is completed.

  As is apparent from the above description, in the present embodiment, the wheel speed sensor 100 constitutes an example of the “rotation state quantity sensor” in the item (1) or (6), and the first temperature sensor 64 is An example of the “first sensor” in the item (2) or (3) is configured, and the second temperature sensor 68 is an example of the “second sensor” in the item (2) or (3). The threshold value TH constitutes an example of the “reference value” in the item (1).

  Furthermore, in the present embodiment, the portion of the computer 82 that executes S1 to S5 in FIG. 6 constitutes an example of the “first changing means” in the above item (2) or (4).

  Next, a second embodiment of the present invention will be described. However, since this embodiment has many elements in common with the first embodiment, and only the elements relating to the tire condition determination program are different, only the different elements will be described in detail, and the common elements are denoted by the same reference numerals. Or the detailed description is abbreviate | omitted by quoting using a name.

  In 1st Embodiment, the state quantity called temperature is detected separately about the tread side part and rim side part of the tire 12, and it is determined whether the tire 12 is abnormal based on the relationship between both regarding temperature. The threshold value TH used for determination is changed.

  On the other hand, in this embodiment, the threshold value TH is changed based on the height of the air pressure P of the tire 12. Specifically, when the air pressure P is higher than the threshold value Pth, it is assumed that there is a high possibility that an abnormality will occur in the tread side portion, and the threshold value TH is the tread side threshold value THT (the higher one). Threshold). On the other hand, if the air pressure P is not higher than the threshold value Pth, it is assumed that there is a high possibility that an abnormality will occur toward the rim side portion, and the threshold value TH is lower than the rim side threshold value THR Threshold).

  FIG. 11 conceptually shows the contents of a tire condition determination program executed by the computer 82 of the determiner 80 of the tire condition determination apparatus according to the present embodiment in a flowchart. The tire condition determination program is different from the tire condition determination program in the first embodiment only in the method of setting the threshold value TH, and the other points are common, and therefore only the differences will be described in detail.

  In the tire condition determination program, first, the air pressure P is detected for the current tire 12 in S31. This detection can be performed using, for example, a sensor that is mounted on the tire 12 and directly detects the air pressure P, or can be detected indirectly on the vehicle body 92 side. According to an example of the indirectly detecting method, the air pressure P is estimated by referring to the output signal of the wheel speed sensor 100.

  Next, in S32, it is determined whether or not the detected air pressure P is higher than a threshold value Pth. If it is assumed that it is high this time, the determination is YES, and the threshold value TH is set to the tread side threshold value THT in S33. On the other hand, this time, assuming that the detected air pressure P is not higher than the threshold value Pth, the determination in S32 is NO, and in S34, the threshold value TH is changed to the rim side threshold value THR. Is set.

  Thereafter, S35 to S40 are executed in the same manner as S6 to S11 in FIG. 6, and one execution of the tire condition determination program is completed.

  The present inventor has studied the relationship between the repeated bending stress generated in the tire 12 during traveling of the vehicle and the air pressure P. As a result, the relationship between the case where the repeated bending stress is generated on the tread side and the rim. I inferred that it was different from the case of the side.

  Specifically, as shown in the graph of FIG. 12, in the region where the air pressure P is not so insufficient, the tread side portion has a larger bending stress and abnormal deformation occurs in the tread side portion. Whereas the possibility is high, in the region where the air pressure P is considerably insufficient, the bending stress on the rim side portion is larger repeatedly, and there is a high possibility that abnormal deformation will occur on the rim side portion.

  According to this reasoning, a region higher than the threshold value Pth in the change range of the air pressure P is set as a region where the tread side threshold value THT is used, whereas it is equal to or less than the threshold value Pth. It is desirable to set the region to a region where the rim side threshold value THR is used.

  Based on such knowledge, in the present embodiment, the threshold value TH is changed based on the height of the air pressure P of the tire 12.

  As is clear from the above description, in the present embodiment, the portion of the computer 82 that executes S31 to S34 in FIG. 11 constitutes an example of the “second changing means” in the above item (5). is there.

  As described above, some of the embodiments of the present invention have been described in detail with reference to the drawings. However, these are merely examples, and those skilled in the art, including the aspect described in the section of [Means for Solving the Problems], described above. It is possible to implement the present invention in other forms in which various modifications and improvements are made based on the knowledge.

It is a top view which shows systematically the tire state determination apparatus according to 1st Embodiment of this invention. It is sectional drawing which shows a part of wheel 10 in FIG. FIG. 3 is a block diagram for explaining each configuration of a first temperature sensor unit 60 and a second temperature sensor unit 62 in FIG. 2. FIG. 2 is a block diagram conceptually showing the configuration of a computer 82 in FIG. 1. It is a block diagram which shows the hardware constitutions of the part mounted in the vehicle body side among the tire state determination apparatuses shown in FIG. 5 is a flowchart conceptually showing the contents of a tire condition determination program in FIG. 3 is a graph showing a temporal transition of secondary uniformity G2 in a process in which abnormal deformation occurs on the tread side portion of the tire 12 in FIG. 2. 3 is a graph showing a temporal transition of secondary uniformity G2 in a process in which abnormal deformation occurs on the rim side portion of tire 12 in FIG. 7 is a flowchart conceptually showing details of S6 in FIG. 6 as a uniformity calculation routine. It is a figure for demonstrating the calculation in the uniformity calculation routine shown in FIG. 9 by a type | formula. It is a flowchart which represents conceptually the content of the tire condition determination program performed by the computer of the determination device of the tire condition determination apparatus according to 2nd Embodiment of this invention. 3 is a graph for explaining how the repeated bending stresses generated on the tread side and the rim side of the tire 12 in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wheel 12 Tire 30 Tread part 36 Bead part 64 1st temperature sensor 68 2nd temperature sensor 80 Judgment device 82 Computer 100 Wheel speed sensor

Claims (6)

A tire state determination device that determines a state of the tire based on a rotation state amount of a wheel in a vehicle in which a wheel configured by mounting a tire in which air is sealed under pressure is mounted on the wheel,
A rotational state amount sensor for detecting a rotational state amount of the wheel;
A determination device for determining whether or not the tire is abnormal by comparing a detected value of a rotational state quantity by the rotational state quantity sensor with a reference value, wherein the tire abnormality is an outer peripheral side portion of the tire A tire condition determination device including: a device that changes the reference value depending on whether it occurs on the inner peripheral side or the inner peripheral side portion. further,
A first sensor for detecting a state quantity of the outer peripheral side portion;
A second sensor that detects a state quantity of the inner peripheral side portion, and the determination unit determines the reference value based on a relationship between the state quantities detected by the first sensor and the second sensor. The tire state determination device according to claim 1, comprising first changing means for changing.   The tire condition according to claim 2, wherein the first sensor and the second sensor respectively detect at least one of temperature and strain of the corresponding one of the outer peripheral side part and the inner peripheral side part as the state quantity. Judgment device.   An abnormality of the tire occurs when the first change means has a large state quantity detected by the corresponding one of the first sensor and the second sensor, of the outer peripheral side and the inner peripheral side. The tire state determination device according to claim 3, wherein the reference value is changed.   The tire condition determination device according to any one of claims 1 to 4, wherein the determination unit includes a second changing unit that changes the reference value based on a pressure level of the tire. The tire state determination device according to any one of claims 1 to 5, wherein the rotational state quantity is a physical quantity representing uniformity of the tire.

Images