JP4261309B2 - Vehicle tire type determination method - Google Patents

Description

  The present invention relates to a vehicle tire type determination device and method, and more particularly to determination of whether a tire in a wheel is a studless tire or a non-studless tire.

  In recent years, in vehicle control such as traction control, braking force control, or torque distribution control, when calculating the control parameters, the road surface friction coefficient and the grip state between the wheel and the road surface are improved in order to improve the calculation accuracy. Referenced. When such a vehicle is controlled, it is important to accurately determine the state of the road surface on which the vehicle is traveling in order to improve the control accuracy. However, even in the case of traveling on the same road surface, there is a problem that an erroneous determination occurs in the road surface determination when the type of tire in the wheel is different. Therefore, it is necessary to determine the type of tire as a premise for performing road surface determination.

For example, Patent Document 1 discloses a tire identification method for identifying a tire type based on a ratio (front-rear wheel ratio) between a rotation speed of a front wheel and a rotation speed of a rear wheel and an acceleration in the front-rear direction of the vehicle. It is disclosed. In this identification method, the front and rear wheel ratios are sequentially determined for each predetermined acceleration for tires whose types are known in advance, the function created based on these data, the vehicle front and rear wheel ratio and the current value of acceleration, The tire type is identified by comparing.
JP 09-188114 A

  The value specified from the running tire (for example, front / rear wheel ratio) not only reflects the tendency of the tire, but also changes in the state of the tire (for example, the rear wheel The effect of changes in the radius of movement is also reflected. Therefore, even if the tire-specific tendency is obtained in advance as a function, the value specified from the running tire does not appropriately correspond to the function, which may lead to erroneous determination of the tire type.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress erroneous determination in tire type determination.

  In order to solve this problem, the second invention provides a vehicle tire type determination method. This vehicle tire type determination method is based on the detection results of a plurality of sensors that respectively detect the wheel speeds of a plurality of wheels provided in the vehicle, and calculates the difference between the slip ratio of the front wheels and the slip ratio of the rear wheels. The first step of calculating as a difference and the change in the dynamic radius of the rear wheel based on the dynamic radius of the front wheel are estimated, and the tire determination that is the determination criterion for the type of tire in the wheel based on the estimated change A second step of variably setting the value, and a third step of determining the tire type by comparing the slip rate difference with the tire determination value.

  Here, in the second invention, the second step includes a first region which is a frequent region of the slip rate difference when the studless tire is mounted in the frequency distribution of the slip rate difference measured in advance, and a non-studless A reference value determined based on a distribution difference with the second region, which is a frequent region of slip rate differences when a tire is mounted, is a step of setting a tire determination value, and the third step is When the slip rate difference is a value on the first region side of the tire determination value, the tire type is determined as a studless tire, and when the slip rate difference is a value on the second region side of the tire determination value, Preferably, the step is to determine the type of tire as a non-studless tire.

  In the second invention, in the second step, in the state where the tire type is determined to be a non-studless tire, the slip rate difference is an average of the frequency distribution of the slip rate difference when the non-studless tire is mounted. A step of changing the tire determination value to a predetermined value on the first region side relative to the reference value when the value changes to the first region side from a predetermined threshold value set in advance with reference to the value Furthermore, it is preferable to include. In this case, the second step is a case where the slip rate difference that has changed to the first region side from the threshold value has changed to the second region side from the threshold value, or travels at a speed equal to or higher than the determination speed. Preferably, the method further includes a step of changing the changed tire determination value to a reference value when the determined time reaches the determination time.

  In the second invention, the wheel type determination method further includes a fourth step of detecting the temperature of the front wheel and the temperature of the rear wheel. By monitoring the temperature of the detected front wheel and the detected temperature of the rear wheel in a state where the tire is determined to be a studless tire, the temperature of the front wheel is equal to or higher than a predetermined value and between the front wheel and the rear wheel. When the temperature difference is equal to or greater than a predetermined value, it is preferable to include a step of changing the tire determination value to a predetermined value closer to the first region than the reference value. Alternatively, in the second step, when the operation signal of the radiator fan is detected in a state where the tire type is determined to be a non-studless tire, the tire determination value is set to the first region from the reference value. It is preferable that the method further includes a step of changing to a predetermined value on the side.

Further, in the second invention, the second step is, if it is determined that the type gas studless tires, it is preferable that the step of setting fixedly a tire judgment value to the reference value.

  According to the present invention, a change in the dynamic radius of the rear wheel is estimated based on the dynamic radius of the front wheel, and a tire determination value that is a criterion for determining the tire type is variably set based on the estimated change. The In the case where there is a difference in the dynamic radii between the front and rear wheels, the tendency of the difference in slip rate changes. Therefore, if this tire determination value is fixedly set, erroneous determination is likely to occur. Therefore, in the present invention, the difference in the dynamic radii generated in the front and rear wheels is estimated, and the tire determination value is variably set based on this. Thereby, the erroneous determination of the tire type can be suppressed.

First, the concept of tire type determination will be described prior to the description of the system configuration and system processing of the tire type determination device 1 according to the present embodiment. FIG. 1 is a diagram showing the frequency distribution of the slip rate difference Sfr related to the wheels. In FIG. 1, the broken line indicates the frequency distribution of the slip rate difference Sfr when traveling on a flat road with the studless tire mounted, and the solid line indicates the slip when traveling on the uneven road with the non-studless tire mounted. The frequency distribution of the rate difference Sfr is shown. Here, the non-studless tire is a tire harder than a studless tire, which is suitable for driving on a dry dry road, and includes, for example, a summer tire and an all-season tire (hereinafter referred to as a non-studless tire). Simply called "summer tires"). The “slip rate difference Sfr” means a difference between the slip rate Sf of the front wheel and the slip rate Sr of the rear wheel (see Formula 1).
(Formula 1)
Sfr = Sf-Sr

The slip ratio S relating to a certain wheel means the ratio between the difference between the wheel speed v and the vehicle body speed Vb and the vehicle body speed Vb, and is defined such that the value is positive. This slip ratio S is uniquely calculated by the basic formula shown in Formula 2. In addition, when the units of the wheel speed v corresponding to the peripheral speed of the wheel and the vehicle body speed Vb are different (for example, rpm, km / h), it is necessary to unify the units in advance to either one.
(Formula 2)
S = (v−Vb) / Vb (or S = (Vb−v) / Vb)

When the left and right front wheels and the left and right rear wheels are regarded as one wheel, the front wheel speed is defined as vf, and the rear wheel speed is defined as vr, Formula 1 is based on Formula 2 and Formula 3 shown below: Can be rewritten.
(Formula 3)
Sfr = (vf-vr) / Vb

  As can be seen from FIG. 1, when the summer tire is mounted, the frequent region of the slip rate difference Sfr is on the left side with respect to a certain reference value C1, that is, the side where the value of the slip rate difference Sfr is smaller than the reference value C1. . On the other hand, when the studless tire is mounted, the frequent region of the slip rate difference Sfr is on the right side with respect to the reference value C1, that is, on the side where the value of the slip rate Sfr is larger than the reference value C1. According to experiments and simulations, when the brake pedal is depressed and the longitudinal deceleration Gx of the vehicle is within a predetermined range (0.2 G to 0.3 G), the frequency distribution characteristics as shown in FIG. Is obtained. In the case where the deceleration Gx is smaller than 0.2 G, there is almost no distributional difference between the slip rate difference Sfr related to the studless tire and the slip rate difference Sfr related to the summer tire. On the other hand, in the case where the deceleration Gx is larger than 0.3 G, the slip ratio difference Sfr regarding the studless tire becomes relatively large, and it is difficult to obtain a frequency distribution characteristic that can clearly identify the type of the tire.

  Therefore, the wheel slip rate difference Sfr is monitored when the brake pedal is depressed and a condition in which the deceleration Gx is in the range of 0.2 G to 0.3 G (hereinafter referred to as “execution condition”) is satisfied. Then, based on the distributional difference between the frequent region related to the summer tire (solid line in FIG. 1) and the frequent region related to the studless tire (broken line in FIG. 1), the tire determination value Cvari set to an appropriate value, and monitoring The calculated slip rate difference Sfr is compared. The tire type is a summer tire or a studless tire by determining whether or not the slip rate difference Sfr is larger than the tire judgment value Cvari after referring to the frequent area for each type of tire. It can be determined whether there is. According to experiments and simulations, the tire determination value Cvari can be set to a reference value C1 (generally 0.006) corresponding to the boundary between both regions under the execution conditions described above.

  When comparing the tire determination value Cvari and the slip rate difference Sfr, the value of the slip rate difference Sr at a certain moment can be used as the slip rate difference Sfr. However, since the instantaneous value easily includes the influence of noise or the like, an average value, a mode value, a sum total, or the like may be used as a value indicating a tendency with time of the slip rate difference Sfr in a predetermined time. In the present embodiment, even values such as the average value, the mode value, and the sum are included in the concept of the slip rate difference Sfr to be compared with the tire determination value Cvari. For example, the average value Sfra The following will be described using.

  By the way, in a state where the dynamic radius of the rear wheel is changed with the dynamic radius of the front wheel as a reference, the frequent region of the slip rate difference Sfr when the summer tire is mounted shows a characteristic different from that in the normal state. Such a change, that is, a difference in the dynamic radius between the front and rear wheels, is caused by a temperature difference between the front wheels and the rear wheels or a difference in air pressure between the front wheels and the rear wheels. In this embodiment, the description of the concept of tire determination is continued assuming a dynamic radius difference caused by the temperature difference between the front and rear wheels, but the concept is the same for the dynamic radius difference caused by the air pressure difference between the front and rear wheels. Since there is, explanation here is omitted. In this specification, the term “change in the dynamic radius of the rear wheel based on the dynamic radius of the front wheel (the difference in the dynamic radius of the front and rear wheels)” refers to the front and rear which are set in advance as the specifications of the driver itself or the vehicle. It means that the moving radius of the wheel shifts due to the temperature difference or the air pressure difference between the front and rear wheels. Therefore, in a vehicle in which the initial setting is performed so that a difference in the dynamic radius occurs between the front and rear wheels, the deviation of the dynamic radius of the front and rear wheels from this initial state is referred to as “based on the dynamic radius of the front wheels. The change in the dynamic radius of the rear wheel (the difference in the dynamic radius of the front and rear wheels) ”.

  The reason why the temperature difference occurs between the front and rear wheels is the warm air flowing into the tire house from the engine compartment or the heat generated by the brake while traveling on a long downhill road when the radiator fan is operated. In these cases, the temperature of the front wheels rises above the temperature of the rear wheels due to warm air that has flowed in or heat generated in the brakes of the front wheels. In particular, such a tendency becomes remarkable in a vehicle that is stopped when the radiator fan is operated. When the vehicle resumes running from this state, the wheel speed difference between the front and rear wheels increases due to the difference in the radius of the front and rear wheels. . Therefore, when the summer tire is mounted, the value of the slip ratio difference Sfr becomes relatively large, and the frequent area related to the summer tire tends to shift toward the frequent area of the studless tire as compared with that in the normal time. . In particular, when the temperature of the front wheels is about 40 ° C. or more and the temperature difference between the front and rear wheels is about 10 ° C. or more, the frequent region related to the summer tire tends to shift to the frequent region side of the studless tire.

  FIG. 2 is a distribution diagram showing a change in the frequency distribution of the slip ratio difference Sfr regarding the summer tire when a difference in dynamic radius occurs between the front and rear wheels. In the same figure, the frequency distribution related to the normal summer tire corresponding to FIG. 1 is shown by a one-dot chain line, and the frequency distribution related to the summer tire when a difference in dynamic radius occurs between the front and rear wheels is shown by a solid line. When there is no difference in dynamic radius between the front and rear wheels, the average slip ratio difference Sfr for the summer tire is approximately 0.002, whereas when there is a difference in dynamic radius between the front and rear wheels, the difference in the slip ratio regarding the summer tire. The average value of Sfr is approximately 0.006. Therefore, when there is a difference in the dynamic radius between the front and rear wheels, the slip rate difference Sfr may be larger than the reference value C1 even though the summer tire is mounted. May be misidentified as a studless tire.

  Therefore, in anticipation of such a change in the slip rate difference Sfra, the current value of the slip rate difference Sfra is based on the average value (0.002) of the frequency distribution (solid line in FIG. 1) of the slip rate difference Sfr related to the summer tire. It is determined whether or not there is a difference in dynamic radius between the front and rear wheels by determining whether or not the threshold has changed to a frequent appearance region side with respect to the studless tire from a predetermined threshold value set in advance. As a result of experiments and simulations, this threshold can be set to approximately 0.004. When it is determined that there is a difference in the dynamic radius between the front and rear wheels, the tire determination value Cvari is determined from the reference value C1 on the frequent region side of the studless tire with respect to the reference value C1 (change value C2). Change to This change value C2 is a value corresponding to the boundary between the two based on the distribution difference between the frequent region related to the summer tire (solid line in FIG. 2) and the frequent region related to the studless tire (broken line in FIG. 2). 0.008). Thereby, in a case where a summer tire is mounted and a difference in dynamic radii is generated between the front and rear wheels, it is difficult to determine that the tire type is a studless tire, and thus erroneous determination of the tire type can be suppressed.

The case where it is effective to set the tire judgment value Cvari to the change value C2 is a case where a difference in dynamic radii has occurred in the front and rear wheels. It is necessary to return the determination value Cvari to the reference value C1. Therefore, in the present embodiment, when the following condition 1 or 2 is satisfied, the tire determination value Cvari is changed from the change value C2 to the reference value C1.
Condition 1: In a vehicle having execution conditions, the average value Sfra of the slip rate difference Sfr is 0.004 or less.
Based on this condition 1, it is determined that there is no dynamic radius difference between the front and rear wheels by not satisfying the condition for determining that there is a dynamic radius difference between the front and rear wheels.
Condition 2: The time during which the vehicle is traveling at a determination speed (for example, 50 km / h) or more reaches a determination time (for example, 5 minutes).
In the case where the condition 2 is satisfied, even if a temperature difference occurs between the front and rear wheels at the beginning, the front wheel temperature and the rear wheel temperature act in a balanced direction. Judge that it is not.

  In cases where studless tires are mounted, problems due to the difference in the radius of movement of the front and rear wheels are unlikely to occur. Therefore, the reference value C1 is fixedly set as the tire determination value Cvari when performing the determination on the summer tire in the state where the studless tire is mounted.

  The tire type determination device will be described based on the concept of tire determination. FIG. 3 is a block diagram of the vehicle tire type determination device according to the present embodiment. The tire type determination device 1 is a device that determines the type of tire that the vehicle is wearing. In the present embodiment, the tire type is a studless tire or a summer that is a form of a non-studless tire. Determine if it is a tire. As the tire type determination device 1, a microcomputer composed of a CPU, a RAM, a ROM, an input / output interface, and the like can be used. The microcomputer performs various calculations related to determination of the tire type by software processing according to a control program stored in the ROM.

  Information necessary when the tire type determination device 1 determines the tire type includes detection signals from the wheel speed sensors 2 to 5 and the brake switch 6. The wheel speed sensors 2 to 5 are sensors for detecting the peripheral speed (hereinafter referred to as “wheel speed”) of a wheel provided in the vehicle, and the left front wheel speed sensor 2 detects the wheel speed vfl of the right front wheel. The right front wheel speed sensor 3 detects the wheel speed vfr of the right front wheel. The left rear wheel speed sensor 4 detects the wheel speed vrl of the left rear wheel, and the right rear wheel speed sensor 5 detects the wheel speed vrr of the right rear wheel. These wheel speed sensors 2 to 5 detect, for example, the rotation of gears attached to the centers of the corresponding wheels by magnetic sensors, and detect the rotation state of the wheels, thereby detecting detection signals corresponding to the wheel speeds. Output. The brake switch 6 is a sensor that detects whether or not the brake pedal is depressed, and outputs an on signal when the brake pedal is depressed, and outputs an off signal when the brake pedal is not depressed. To do.

  When the microcomputer for determining the tire type is functionally grasped, it includes a filter processing unit 7, a slip rate difference calculation unit 8, a deceleration calculation unit 9, an average value calculation unit 10, a setting unit 11, and a tire determination unit 12. The filter processing unit 7 performs filter processing on each of detection signals corresponding to the wheel speeds vfl to vrr of the wheels detected by the wheel speed sensors 2 to 5. The slip rate difference calculation unit 8 calculates the vehicle body speed Vb based on each detection signal subjected to the filtering process, that is, the wheel speeds vfl to vrr of each wheel, and the vehicle body speed Vb and the wheel speed vfl of each wheel. Based on ~ vrr, the slip ratios Sf and Sr of the front and rear wheels are calculated. Then, based on these slip rates Sf and Sr, the slip rate difference Sfr between the front and rear wheels is calculated. On the other hand, the deceleration calculation unit 9 calculates the vehicle deceleration Gx based on the change in the vehicle body speed Vb per predetermined time. The average value calculation unit 10 calculates an average value Sfra indicating a tendency over time of the slip rate difference Sfr calculated within a predetermined time. Based on the calculated average value Sfra, the setting unit 11 estimates a change in the moving radius of the tire in the front and rear wheels, and determines a tire determination that is a criterion for determining the type of tire according to the estimated change in the moving radius. The value Cvari is set to be variable. The tire determination unit 12 determines the type of tire by comparing the calculated average value Sfra and the tire determination value Cvari.

  Hereinafter, the tire type determination process will be described. The tire type determination process is executed by the microcomputer at predetermined intervals, and each execution cycle proceeds in the order of setting the tire determination value Cvari and determining the tire type using the set tire determination value Cvari. FIG. 4 is a flowchart showing details of the determination threshold value Cvari setting process. First, detection signals vfl to vrr are read from the wheel speed sensors 2 to 5 (step 10), and filter processing is performed on the read detection signals vfl to vrr (step 11). Usually, the detection signals output from the wheel speed sensors 2 to 5 include noise and the like. For this reason, for example, low-pass filter processing is performed on these detection signals to remove high-frequency noise and the like in each detection signal.

  In step 12, the wheel speed vf of the front wheel, the wheel speed vr of the rear wheel, and the vehicle body speed Vb are calculated. The wheel speed vf of the front wheel is uniquely specified by calculating the average value of the detected wheel speeds vfl and vfr of the left and right front wheels. Similarly, the wheel speed vr of the rear wheel is uniquely specified by calculating the average value of the detected wheel speeds vrl and vrr of the left and right rear wheels. On the other hand, the vehicle body speed Vb is uniquely calculated by calculating the average value of the wheel speed vf of the front wheel and the wheel speed vr of the rear wheel, that is, the average value of the wheel speeds vfl to vrr of each wheel. The vehicle body speed Vb is specified by calculating the average value of the wheel speeds of the left and right wheels in a wheel (driven wheel) different from the driving wheel, in addition to calculating the average value of the wheel speeds vfl to vrr of each wheel. May be. Then, in step 13, as shown in the above-described equation 3, the front wheel slip ratio difference Sfr, which is the difference between the front wheel slip ratio Sf and the rear wheel slip ratio Sr, is calculated.

  In step 14 following step 13, it is determined whether or not an execution condition that defines an operation condition suitable for calculating the average value Sfra of the calculated slip rate difference Sfr is satisfied. As described in the concept description of the tire type, this execution condition is that the vehicle deceleration Gx is within a predetermined range (0.2 G to 0.3 G) and that the output signal of the brake switch 6 is an ON signal. And are applicable. The vehicle deceleration Gx can be determined based on the value calculated by the deceleration calculation unit 9. If an affirmative determination is made in step 14, that is, if the execution condition is satisfied, the process proceeds to step 15. On the other hand, if a negative determination is made in step 14, that is, if the execution condition is not satisfied, the processing after step 15 is skipped and the routine is exited.

  In step 15, the calculated slip rate difference Sfr is stored in time series at predetermined addresses in the RAM of the microcomputer. Then, a plurality of slip rate differences Sfr calculated within a predetermined time (for example, 1 second) are read from the RAM, and an average value Sfra of these slip rate differences Sfr is calculated (step 16).

  In step 17 following step 16, it is determined whether or not the vehicle is stopped. When the vehicle is stopped, the temperature of the front wheels tends to rise more easily than the temperature of the rear wheels, and the frequent occurrence region of the slip rate difference Sfr related to the summer tire tends to shift to a relatively larger direction than that in the normal state. is there. In this case, an erroneous determination may occur in the tire type determination. Therefore, it is necessary to change the tire determination value Cvari to an appropriate value to reduce the occurrence of an erroneous determination. Therefore, in this step 17, it is determined whether or not the situation is such that a difference in dynamic radius can occur between the front and rear wheels due to the temperature difference between the wheels, such as when the vehicle is stopped. The determination as to whether or not the vehicle is stopped can be made based on the vehicle body speed Vb. If a negative determination is made in step 18, that is, if the vehicle is traveling, the routine is exited. On the other hand, if an affirmative determination is made in step 17, that is, if the vehicle is stopped, the process proceeds to step 18.

  In step 18, it is determined whether or not the current tire type is determined to be a summer tire. The tire type is determined to be either a summer tire or a studless tire by performing a tire type determination process described later once or more. Note that if the tire type determination process has never been performed, either one of the types is alternatively selected.

If an affirmative determination is made in step 18, that is, if the tire type is determined to be a summer tire, the process proceeds to step 19. In step 19, the tire determination value Cvari is variably set according to any of patterns 1 to 5 shown below. The tire determination value Cvari is initially set to the reference value C1.
(1) When the current value of the tire judgment value Cvari is the reference value C1
Pattern 1: When the average value Sfra is greater than 0.004 Cvari ← Changed value C2
Pattern 2: When the average value Sfra is 0.004 or less Cvari ← Reference value C1
(2) When the current value of the tire judgment value Cvari is the change value C2
Pattern 3: When the average value Sfra is greater than 0.004 Cvari ← Changed value C2
Pattern 4: When the average value Sfra is 0.004 or less Cvari ← Reference value C1
Pattern 5: When the vehicle speed of 50 km / h has elapsed for more than 5 minutes Cvari ← Reference value C1

  On the other hand, if a negative determination is made in step 18, that is, if the tire type is determined to be a studless tire, the process proceeds to step 20. In step 20, the tire determination value Cvari is fixedly set to the reference value C1.

  FIG. 5 is a flowchart showing details of the tire type determination process. When the tire determination value Cvari is set, first, in step 21, it is determined whether or not an execution condition is satisfied. This execution condition is the same as the execution condition in the tire determination value Cvari setting process. If a negative determination is made in step 21, the routine is exited. On the other hand, if an affirmative determination is made in step 21, the process proceeds to step 22.

  In step 22, it is determined whether or not the average value Sfra of the slip rate difference Sfr is larger than the tire determination value Cvari. As the average value Sfra in step 22, the value calculated in the setting processing of the tire determination value Cvari can be used as it is. However, on the assumption that this step 22 is performed, the average value Sfra is newly calculated. Also good. If an affirmative determination is made in step 22, that is, if the average value Sfra is greater than the tire determination value Cvari, the process proceeds to step 23, where the tire type is determined to be a studless tire. On the other hand, if a negative determination is made in step 22, that is, if the average value Sfra is equal to or less than the tire determination value Cvari, the process proceeds to step 24, where the tire type is determined to be a summer tire.

  In step 25, the determined tire type is output and the routine is exited. The output tire type is input to, for example, the road surface determination device 13 that determines the state of the road surface and the tire, and is used as information for determining the road surface state by the road surface determination device 13.

  As described above, according to the present embodiment, in the case where the execution condition is satisfied, the average value Sfra of the slip rate difference Sfr is monitored, and when the average value Sfra exceeds about 0.004, the tire determination is performed. The value Cvari is changed from the reference value C1 to the change value C2. In the case where there is a difference in the dynamic radii between the front and rear wheels, the tendency of the slip rate difference Sfr changes. Therefore, if the tire determination value Cvari is fixedly set, erroneous determination is likely to occur. However, the threshold value setting corresponding to the tendency of the slip rate difference Sfr is made by estimating the difference in the radius of the radii generated in the front and rear wheels and changing the tire judgment value Cvari from the reference value C1 to the change value C2 based on this. It can be performed. Thereby, in a case where a summer tire is mounted and a difference in dynamic radii is generated between the front and rear wheels, it is difficult for the tire type to be erroneously determined as a studless tire, and thus erroneous determination of the tire type can be suppressed.

  When the difference in the dynamic radius between the front and rear wheels is caused by the temperature difference between the front and rear wheels, the front wheel temperature and the rear wheel temperature may be detected. In this case, the setting unit 11 monitors the detected front wheel temperature and rear wheel temperature when the tire determination unit 12 determines that the tire type is a summer tire. When it is determined that the front wheel temperature is equal to or higher than a predetermined value (for example, 40 ° C. or higher) and the temperature difference between the front and rear wheels is equal to or higher than a predetermined value (for example, 10 ° C. or higher), the tire determination value Cvari is The reference value C1 is changed to a predetermined value (changed value) C2 on the frequent appearance region side (broken line in FIG. 1) regarding the studless tire. A well-known non-contact thermometer (for example, radiation thermometer) etc. can be used for the temperature of the front and rear wheels. In addition, assuming that the temperature difference between the front and rear wheels frequently occurs when the radiator fan is activated, the tire judgment value Cvari is changed from the reference value C1 to the change value C2 when the operation signal of the radiator fan is detected. Also good.

The figure which showed frequency distribution of slip rate difference Sfr regarding the wheel Distribution diagram showing changes in frequency distribution of slip rate difference Sfr for summer tires when dynamic radius difference occurs between front and rear wheels The block block diagram of the tire classification determination apparatus of the vehicle concerning this embodiment The flowchart which shows the detail of the setting process of determination threshold value Cvari Flow chart showing details of tire type determination process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire classification determination apparatus 2 Left front wheel speed sensor 3 Right front wheel speed sensor 4 Left rear wheel speed sensor 5 Right rear wheel speed sensor 6 Brake switch 7 Filter processing part 8 Slip rate difference calculation part 9 Deceleration calculation part 10 Average value calculation unit 11 Setting unit 12 Tire determination unit 13 Road surface determination device

Claims (7)

In the vehicle tire type determination method,
A first step of calculating a difference between the slip rate of the front wheel and the slip rate of the rear wheel as a slip rate difference based on detection results of a plurality of sensors that respectively detect wheel speeds of a plurality of wheels provided on the vehicle; ,
A change in the dynamic radius of the rear wheel based on the dynamic radius of the front wheel is estimated, and a tire determination value that is a determination criterion for the type of tire in the wheel is variably set based on the estimated change. A second step;
A vehicle tire type determination method comprising: a third step of determining the tire type by comparing the slip rate difference with the tire determination value. In the frequency distribution of the slip rate difference measured in advance, the second step includes a first region that is a frequent region of the slip rate difference when a studless tire is mounted, and a case where a non-studless tire is mounted. Including a step of setting, as the tire determination value, a reference value determined based on a distribution difference with the second region, which is a frequent region of the slip rate difference,
In the third step, when the slip rate difference is a value closer to the first region than the tire determination value, the tire type is determined to be a studless tire, and the slip rate difference is determined to be the tire determination value. 2. The vehicle tire type determination method according to claim 1, further comprising a step of determining that the tire type is a non-studless tire when the value is on the second region side.   In the second step, in the state where the tire type is determined to be the non-studless tire, the slip rate difference is an average value of the frequency distribution of the slip rate difference when the non-studless tire is mounted. When it changes to the first region side from a predetermined threshold value set in advance as a reference, the tire determination value is changed to a predetermined value on the first region side from the reference value. The vehicle tire type determination method according to claim 2, further comprising a step.   In the second step, the slip rate difference that has changed to the first region side from the threshold value has changed to the second region side from the threshold value, or a determination speed or more. 4. The vehicle tire type determination according to claim 3, further comprising a step of changing the changed tire determination value to the reference value when a time during which the vehicle is traveling reaches a determination time. 5. Method. And further comprising a fourth step of detecting the temperature of the front wheel and the temperature of the rear wheel,
In the second step, when the tire type is determined to be the non-studless tire, the temperature of the front wheel is equal to or higher than a predetermined value, and a temperature difference between the front wheel and the rear wheel is predetermined. 3. The vehicle tire type according to claim 2, further comprising a step of changing the tire determination value to a predetermined value closer to the first region than the reference value when the tire determination value is equal to or greater than a value. Judgment method.   In the state where the tire type is determined to be the non-studless tire, and the second step detects the activation signal of the radiator fan, the tire determination value is set to be greater than the reference value. The vehicle tire type determination method according to claim 2, further comprising a step of changing to a predetermined value on the first region side. The second step, if the type of the tire is determined before kiss studless tire according to claim 2, characterized in that said tire judgment value is a step of setting fixedly to the reference value To 6. The vehicle tire type determining method according to any one of items 1 to 6.

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