JP2003154828A - Tire air pressure detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new detection method that can precisely detect tire air pressure in a vehicle speed range higher than the vehicle speed range in which a detection method conventionally proposed as an indirect detection method can precisely detect tire air pressure. SOLUTION: A vibration level in a specific frequency range of wheel speed signals as time-series data on wheel speed detected by a wheel speed sensor for detecting an angular velocity of a wheel as a wheel speed is detected as an objective vibration level, according to which tire air pressure is estimated. Whether the estimation of tire air pressure is effective or not is determined according to a vibration-characteristic related value related to characteristics of vibration in the specific frequency range of the wheel speed signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting tire air pressure in a vehicle, and in particular,
The present invention relates to a technique for indirectly detecting the air pressure of a tire based on the angular velocity of the tire.

[0002]

2. Description of the Related Art There is already a technique for detecting a tire pressure for the purpose of finding an abnormality in a tire of a vehicle while the vehicle is traveling. This technique is classified into a direct detection system and an indirect detection system from the viewpoint of a system for detecting tire pressure.

In the direct detection type, a pressure sensor (including a pressure switch) that detects tire air pressure and wirelessly transmits the detected value to the vehicle body side is used by being attached to the tire itself. The tire pressure is directly detected by the pressure sensor.

On the other hand, in the indirect detection type, a wheel speed sensor for detecting the angular speed of a wheel, which is constructed by mounting a tire on a wheel, is mounted on the vehicle body side and used. The tire pressure is indirectly detected by the wheel speed sensor.

By the way, in recent years, an anti-lock control function,
Vehicles equipped with a wheel force control function, such as a traction control function, that controls a wheel force that is a braking force or a driving force of a wheel so that the slip ratio of the wheel at the time of braking or driving becomes appropriate, are widely used. . In this type of vehicle, a wheel speed sensor is used to detect the slip rate of the wheels.

Therefore, in this type of vehicle, if it is allowed to detect the tire air pressure by the above-mentioned indirect detection type, the same wheel speed sensor is used for the tire air pressure detection and the wheel force control function. Can be used for both. Such use facilitates a reduction in the number of vehicle parts, and thus a reduction in vehicle weight and cost.

Some specific methods for detecting the tire air pressure by the indirect detection method have already been proposed.

One of them is a dynamic load radius method. In this method, if the tire pressure changes, the dynamic load radius of the tire changes, and as a result, the angular velocity of the tire,
That is, focusing on the phenomenon that the wheel speed detected by the wheel speed sensor also changes, the tire pressure is detected based on the wheel speed. A conventional example of this dynamic load radius method is described in Japanese Patent Laid-Open No. 8-164720.

Another method is a tire vibration method. In this method, attention is paid to the phenomenon that the characteristics of vibration of the tire change when the tire pressure changes, and the change is reflected in the wheel speed, and the tire pressure is detected based on the wheel speed.

This tire vibration method is classified into a resonance frequency method and a disturbance observer method.

In the resonance frequency system, paying attention to the phenomenon that the resonance frequency of the vibration of the tire changes when the tire pressure changes, the resonance frequency is detected based on the wheel speed, and the detected resonance frequency is The tire pressure is estimated based on the tire pressure. One conventional example of this resonance frequency method is described in Japanese Patent No. 2836652.

On the other hand, in the disturbance observer system, according to the modern control theory of disturbance observer, it is possible to estimate a change in tire air pressure as a disturbance to the tire, and based on the wheel speed, the tire air pressure is estimated. Is estimated. A conventional example of this disturbance observer system is described in Japanese Patent Laid-Open No. 2000-238516.

[0013]

DISCLOSURE OF THE INVENTION The present inventors evaluated the practicality of the above-mentioned various detection methods proposed so far with respect to the indirect detection method. As a result, it has been found that the detection accuracy when the tire pressure is detected by various detection methods has a characteristic that depends on the vehicle speed, which is the traveling speed of the vehicle.

Specifically, the tire vibration system has a characteristic that it is difficult to detect tire air pressure with high accuracy in a high vehicle speed region (for example, a vehicle speed region of about 80 to about 120 [km / h] or more). Have. On the other hand, the dynamic load radius method has a characteristic that the tire air pressure can be detected with high accuracy even in such a high vehicle speed range.

Regardless of whether it is an indirect detection type or a direct detection type, it is required to accurately detect the tire air pressure in the entire vehicle speed changeable region.

As described in Japanese Patent Application Laid-Open No. 9-2031, a hybrid system combining a tire vibration system and a dynamic load radius system has already been proposed in order to meet the demand. In this hybrid system, the tire vibration system is selected in the low speed region and the dynamic load radius system is selected in the higher vehicle speed region as the tire air pressure detection system.

When the variable range of the vehicle speed is divided into three regions, a low speed region, a medium speed region, and a high speed region, the hybrid system described above is such that the dynamic load radius system is selected in the medium speed region and the high speed region. It is possible to carry out.

However, the accuracy of tire pressure detection by the dynamic load radius method tends to decrease as the vehicle speed increases. Hereinafter, this will be specifically described.

When the vehicle speed increases, the rotation speed of the tire also increases, and the centrifugal force acting on the tread portion of the tire also increases accordingly. The centrifugal force acts as a force that causes the tread portion of the tire to bulge outward in the radial direction thereof, that is, as a lifting force, and the centrifugal force increases in proportion to the square of the rotational speed of the tire.

Therefore, as the vehicle speed increases, the tendency of the tread portion of the tire to lift increases. As a result, as the vehicle speed increases, the ratio of the lift amount of the tread portion to the apparent dynamic load radius of the tire also increases.

Further, in the dynamic load radius method, it is necessary to grasp the actual outer peripheral length of the tire while the vehicle is running, but it is difficult to grasp this directly, and the detected value of the vehicle speed (or Generally, the average value of the detected values of the wheel speeds of a plurality of wheels in the vehicle is used to indirectly grasp. At this time, it is necessary to assume a certain value or range for the slip ratio when the tire rolls on the road surface, but as the vehicle speed increases, the slip ratio of the tire tends to increase. If set on the basis of a region where the vehicle speed is low, will lose its validity in the region where the vehicle speed is high.

As is clear from the above description, when the dynamic load radius method is implemented, the vehicle speed range where the tire air pressure detection accuracy is high due to the increase in the lift tendency of the tire tread portion and the increase in the slip ratio. It tends to decrease in.

By the way, regardless of the type of the detection method, it is ideal that a sufficiently high detection accuracy can be realized with the same detection method over the entire range in which the vehicle speed can be changed without switching to another detection method. Is.

However, in reality, as described above, there is a possibility that the tire air pressure detection accuracy may fluctuate due to some circumstances.

In this case, whether or not the detection accuracy when the tire air pressure is detected by the detection method that is currently attracting attention is sufficiently high for practical use, that is, it is necessary to adopt that detection method from the viewpoint of the detection accuracy. It is desirable to judge whether it is appropriate.

Further, when it is determined that the detection method is appropriate from the viewpoint of detection accuracy, the tire pressure detected by the detection method is permitted and is not appropriate. If judged, it is desirable to prohibit.

Against the background of the circumstances described above, the present invention is
The object was to propose a new detection method that can accurately detect the tire pressure in a vehicle speed range that is faster than the vehicle speed range that can detect the tire pressure with high accuracy by the detection method that has been conventionally proposed as an indirect detection method. is there.

[0028]

MEANS FOR SOLVING THE PROBLEMS AND EFFECTS OF THE INVENTION The following aspects are obtained by the present invention. Each mode is divided into sections, numbers are attached to each section, and the numbers of other sections are referred to as necessary. This is for facilitating the understanding of some of the technical features described in the present specification and some of the combinations thereof, and the technical features described in the present specification and the combination thereof are as follows. It should not be construed as limiting. (1) A device that is provided in a vehicle in which a wheel configured by enclosing air under pressure inside a tire mounted on a wheel is supported by a vehicle body and that detects the air pressure of the tire by estimation. The wheel speed sensor that detects the angular speed of the wheel as the wheel speed, and the wheel speed signal that is the time-series data of the wheel speed detected by the wheel speed sensor, the vibration level in a specific frequency region as the vibration level of interest. Detecting, estimating the air pressure based on the detected vibration level of interest, based on the vibration characteristic-related value of the wheel speed signal, which is related to the characteristic of vibration in the specific frequency region, the estimation of the air pressure. A tire pressure detection device including an estimation device that determines whether the tire pressure is valid.

The vibration level of the wheel speed signal accurately reflects the tire pressure in a particular frequency range.

Based on such knowledge, in the device according to this section, the vibration level of the wheel speed signal in the specific frequency region is detected as the noticed vibration level, and the tire air pressure is detected based on the detected noticed vibration level. Is estimated. The method adopted for this estimation is a new method that should be called a vibration level method.

Generally, in a high speed vehicle speed range, resonance of a vehicle vibration element including a tire is less likely to occur than in a lower speed vehicle speed range. On the other hand, when the above-mentioned vibration level method is adopted, it is possible to estimate the tire pressure without using such resonance.

Therefore, according to the apparatus of this section, by adopting the above-mentioned vibration level method, it becomes easy to accurately estimate the tire pressure in the high speed vehicle speed range.

Further, in the device according to this section, it is effective to estimate the tire pressure by the above-mentioned vibration level method based on the vibration characteristic related value of the wheel speed signal related to the characteristic of the vibration in the above-mentioned specific frequency region. Is determined.

Therefore, according to this apparatus, the tire pressure estimation by the above-mentioned vibration level method is executed only when it is effective, or is executed regardless of whether the estimation is effective or not. The estimated value of the air pressure obtained by the above estimation can be used only when the estimation is valid.

Therefore, according to this device, it becomes easy to improve the reliability of the estimated value of the tire air pressure.

In this section and each of the following sections, "detection of air pressure" is interpreted to mean detecting an absolute value of air pressure, or a relative value (that is, a change amount) of a reference value of air pressure is detected. Can be interpreted as meaning that the air pressure is higher or lower than a reference value. This interpretation also applies to the term "pneumatic pressure estimation".

In this section and the following sections, the "vibration level" can be defined as a gain, for example. (2) The wheels include left and right wheels, and the wheel speed sensors are provided for the left and right wheels, respectively.
The estimation device detects the noticed vibration level for each of the left and right wheels, and based on the relationship between the detected left and right wheels of the noticed vibration level, is any of the left and right wheels abnormal with respect to the air pressure? The tire air pressure detection device according to item (1), which determines whether or not the tire pressure is detected.

According to this device, it is relatively determined between the left and right wheels whether or not one of the left and right wheels is abnormal with respect to the air pressure.

The "relationship between the left and right wheels at the noticeable vibration level" in this section can be defined as, for example, the difference between the left and right wheels at the noticeable vibration level or as a ratio. (3) The wheel is supported by the vehicle body via a suspension, and the specific frequency range is set within a range between a resonance frequency of vibration of the suspension and a resonance frequency of vibration of the tire. (1) or (2)
The tire pressure detection device according to item.

The frequency range in which the vibration level accurately reflects the tire pressure exists between the resonance frequency of suspension vibration and the resonance frequency of tire vibration.

Based on such knowledge, in the device according to the present section, the specific frequency range is set within the range between the resonance frequency of the vibration of the suspension and the resonance frequency of the vibration of the tire.

Therefore, according to this apparatus, it becomes easy to detect the vibration level of interest without being affected by the resonance of the suspension and the resonance of the tire as much as possible, and thus the estimation accuracy of the tire air pressure is improved. It will also be easy. (4) The vibration characteristic-related values have different values depending on whether the detected vibration level of interest is affected by the resonance of the vehicle vibration element including the tire as noise resonance or not. The tire air pressure detection device according to any one of (1) to (3), which is a physical quantity that changes as described above.

According to this device, the vibration characteristic-related value changes so that the vibration level of interest takes different values depending on whether the resonance of the vehicle vibration element is affected by noise resonance or not. It is a physical quantity.

Therefore, according to this apparatus, it becomes easy to accurately determine whether or not the estimation of the tire air pressure by the vibration level method is effective. (5) The vibration characteristic-related value includes at least one of a vehicle speed that is a traveling speed of the vehicle and the wheel speed as a vehicle speed-related value, and the estimation device sets the vehicle speed-related value to a first value.
The tire air pressure detection device according to item (4), including first determination means for determining that the estimation of the air pressure is valid when the vehicle speed is equal to or higher than a set vehicle speed related value.

Generally, when the vehicle speed and the wheel speed are high, the resonance of the vehicle vibration element is less likely to occur than when the vehicle speed and the wheel speed are low, and thus the noise resonance at the vibration level of interest is less likely to occur.

Based on such knowledge, in the device according to this section, when the vehicle speed-related value that is at least one of the vehicle speed that is the traveling speed of the vehicle and the wheel speed is equal to or greater than the first set vehicle speed-related value, It is determined that the tire pressure estimation by the vibration level method is effective. (6) The tire air pressure detection device according to item (4) or (5), wherein the vibration characteristic-related value includes a noise resonance characteristic value that directly represents the characteristic of the noise resonance.

There is a noise resonance characteristic value that directly represents the characteristic of the noise resonance. By using the noise resonance characteristic value, it is possible to determine whether or not the estimation of the tire air pressure by the vibration level method is effective.

Based on such knowledge, in the device according to this section, the vibration characteristic related value in the above (4) or (5) includes a noise resonance characteristic value that directly represents the characteristic of the noise resonance. It is said that. (7) The noise resonance characteristic value includes a degree of dispersion of a distribution regarding a frequency of occurrence of the resonance frequency of the noise resonance, and the estimation device determines the air pressure of the air pressure when the degree of dispersion is larger than a first set degree of dispersion. The tire air pressure detection device according to item (6), including second determination means for determining that the estimation is valid.

Generally, at the resonance frequency of the noise resonance,
The fact that the degree of dispersion of the frequency distribution is large (the resonance frequencies are dispersed) is stronger than the fact that the distribution is small (the resonance frequencies are concentrated), indicating that noise resonance does not occur significantly. Shows.

Based on such knowledge, in the device according to this section, when the distribution degree of the distribution of the resonance frequency of the noise resonance with respect to the occurrence frequency is larger than the first set dispersion degree, the tire pressure by the vibration level method is used. Is estimated to be valid.

The "scattering degree" in this section and the following sections, for example, is defined as the degree of dispersion, the standard deviation, the kurtosis, or the skewness with respect to the resonance frequency. Is possible. (8) When the noise resonance characteristic value includes the strength of the resonance frequency of the noise resonance and the estimation device has the strength equal to or lower than the first set strength, the estimation of the air pressure is determined to be effective. The tire air pressure detection device according to (6) or (7), including a third determination means.

In general, the fact that the intensity of the resonance frequency of the noise resonance is small is compared with the fact that it is large,
It strongly indicates that noise resonance does not occur remarkably.

Based on such knowledge, in the device according to this section, when the strength of the resonance frequency of noise resonance is equal to or lower than the first set strength, it is effective to estimate the tire pressure by the vibration level method. To be judged. (9) The vibration characteristic-related value includes a vibration level characteristic value that represents a characteristic that the vibration level of the wheel speed signal changes with the frequency within a monitoring frequency range set to include the specific frequency range (4). ) To (8), the tire pressure detecting device.

Generally, a vibration level characteristic value representing a characteristic that the vibration level of the wheel speed signal changes with the frequency within the monitoring frequency range set to include the specific frequency range is directly related to the characteristic of the noise resonance. It functions as an example of the noise resonance characteristic value represented by.

Based on such knowledge, in the device according to this section, the vibration characteristic related value as set forth in any one of (4) to (8) above is set so as to include the specific frequency region. In the monitoring frequency range, a vibration level characteristic value representing a characteristic that the vibration level of the wheel speed signal changes with the frequency is included. (10) The vibration level characteristic value includes a vibration level difference between peak values, which is a difference between two peak values of the vibration level of the wheel speed signal in the monitoring frequency region,
The estimating device includes fourth determining means for determining that the estimation of the air pressure is effective when the vibration level difference between peak values is smaller than the vibration level difference between set peak values (9).
The tire pressure detection device according to item.

When there are a plurality of vehicle vibration elements (for example, suspensions and tires) having a resonance frequency in the monitoring frequency region, the peak value of the vibration level of the wheel speed signal in the monitoring frequency region is a plurality of those vibration factors. There are more than the same number of vehicle vibration elements.

The phrase "the number of peak values is equal to or more than the number of vehicle vibration elements" is used to define the term peak value to include resonance points but not antiresonance points. If so, the number of peak values will be the same as the number of vehicle vibration elements, but if the term peak value is defined to include both resonance points and anti-resonance points, the number of peak values will be multiple. This is because there will be more than the same number of vehicle vibration elements.

On the other hand, comparing the case where at least one of the plurality of vehicle vibration elements resonates with the case where none of the vehicle vibration elements resonates, the former case is the latter case. In some cases, the difference between the plurality of peak values existing in the monitored frequency region tends to be large.

Therefore, the difference between the plurality of peak values existing in the monitored frequency region also functions as an example of the noise resonance characteristic value that directly represents the characteristic of the noise resonance.

Based on such knowledge, in the device according to this section, the vibration level difference between the peak values, which is the difference between the two peak values in the monitoring frequency region of the vibration level of the wheel speed signal, is the difference between the set peak values. If the difference is smaller than the vibration level difference, it is determined that the tire pressure estimation by the vibration level method is effective.

"Two peak values" in this section mean, for example, those two peak values in the case where there can be only two peak values in the monitoring frequency region, or the peaks in the monitoring frequency region. Any two peak values where there can be more than two values, two adjacent to each other
It may mean one peak value or a combination of the maximum peak value and the minimum peak value.

Further, "two peak values" in this section
Can be defined, for example, as representing two resonance points adjacent to each other or as one resonance point and one anti-resonance point adjacent to each other. (11) The estimation device has, as a method of estimating the air pressure, a vibration level method of estimating the air pressure based on the noticed vibration level and a method other than that, and a method different from those vibration level methods. Judging whether or not the estimation of the air pressure by the method is effective,
The tire air pressure detection device according to any one of (1) to (10), which determines a final detection value of the air pressure based on the result.

According to this apparatus, since the tire pressure is detected by the hybrid method in which the vibration level method and another method are combined, it is necessary to detect the tire pressure only by using the vibration level method. In comparison with the above, it becomes easy to detect the tire air pressure with sufficiently high accuracy in all vehicle environments.

Here, the "vehicle environment" includes, for example, vehicle speed and tire type. The type of tire is classified according to the use, performance, shape, etc. of the tire.

Depending on the application of the tire, for example, it is classified into a normal tire (also called a summer tire), a snow tire and the like. Further, depending on the presence or absence of the run flat performance that the tire can run even in a punctured state, it is classified into a run flat tire having the performance and a normal tire not having the performance. Further, depending on the size of the tire flatness defining the shape of the tire, it is classified into a flat tire having a high flatness and a normal tire having no flatness.

Therefore, according to the apparatus of the present section, it becomes easy to improve the robustness against changes in the vehicle environment such as changes in vehicle speed, differences in tire type, etc. with respect to the estimation accuracy of tire air pressure. (12) The estimation device, based on the environment of the vehicle,
In the high speed range of the vehicle speed, which is the traveling speed of the vehicle,
The estimated value of the air pressure by the vibration level method, in the low speed region, the estimated value of the air pressure by the other method is adopted preferentially over other estimated values to determine the final detected value of the air pressure. The tire air pressure detection device according to item (11).

As described in the above item (1), the vibration level method is a method in which it is easy to accurately estimate the tire pressure in a high vehicle speed range.

Based on such knowledge, in the device according to the present section, the entire variable range of the vehicle speed is divided into two regions suitable for each estimation of the tire air pressure by the vibration level method and another method, that is, , Is divided into a high speed region and a low speed region, and in the high speed region,
In the low-speed region, the estimated value by the vibration level method, the estimated value by another method is preferentially adopted over the other estimated values, and the final detected value of the tire air pressure is determined.

Therefore, according to this device, it becomes easy to detect the tire air pressure accurately regardless of the vehicle speed.

The term "vehicle environment" in this section and the following sections may be interpreted to include, for example, the running state of the vehicle, the rotational state of the tire, and the type of tire. Can be interpreted to include the vibration characteristics of the wheel speed signal, or to include the road surface condition.

The embodiment of the “estimation device” in this section is
The mode of estimating the tire pressure by using both the vibration level method and another method under the same vehicle speed is not excluded. (13) Regardless of the result of the determination whether the estimation of the air pressure by the vibration level method and another method is effective, the estimation device uses the vibration level method and a method different from the above. Estimated value for estimating the air pressure, respectively, among a plurality of estimated values obtained thereby, the one obtained by the method determined that the estimation of the air pressure is effective is selected as the final detected value of the air pressure The tire air pressure detection device according to (11) or (12), which performs selection. (14) The estimation device performs a method selection that selects one of the vibration level method and another method that is determined to be effective for the estimation of the air pressure, and the air pressure is selected according to the selected method. The tire air pressure detection device according to item (11) or (12), wherein the estimated value is determined as the final detected value of the air pressure. (15) The another method focuses on the phenomenon that the characteristics of vibration of the tire change if the air pressure changes, and the change is reflected in the wheel speed, and the air pressure is changed based on the wheel speed. Including the estimated tire vibration method (1
The tire air pressure detection device according to any one of 1) to (14).

According to this apparatus, it is easy to accurately estimate the tire air pressure so as to have high robustness against changes in the vehicle environment, by the hybrid method combining at least the vibration level method and the tire vibration method. Becomes (16) When the vehicle speed-related value that is at least one of the vehicle speed that is the traveling speed of the vehicle and the wheel speed is equal to or less than a second set vehicle speed-related value, the estimation device determines the air pressure of the tire vibration method. The tire air pressure detection device according to item (15), including fifth determination means for determining that the estimation is valid.

The tire vibration method is a method for estimating tire air pressure by positively utilizing the vibration of the tire. On the other hand, when the vehicle speed and the wheel speed are low, the tire vibration tends to be larger than when the vehicle speed and the wheel speed are high.

Based on those findings, the device according to this section was proposed. (17) The estimation device is effective in estimating the air pressure by the tire vibration method when the degree of dispersion of the distribution related to the occurrence frequency of the resonance frequency of the tire vibration is equal to or less than the second set dispersion degree. The tire air pressure detection device according to (15) or (16), including a sixth determination means for determination.

When the degree of dispersion of the distribution of the resonance frequency of the tire vibration is small (when the resonance frequencies are concentrated), it is larger than when it is large (when the resonance frequencies are dispersed). Vibration tends to be large.

Based on such knowledge, the device according to this section was proposed. (18) The estimating device includes a seventh determining unit that determines that the estimation of the air pressure by the tire vibration method is effective when the resonance frequency intensity of the tire vibration is within a set range (15). ) To (17), the tire air pressure detecting device according to any one of items.

When the intensity of the resonance frequency of the tire vibration is too small, there is a possibility that the tire vibration causes only a vibration of a magnitude that is not sufficient to accurately estimate the tire air pressure. On the other hand, if the intensity of the resonance frequency of the tire vibration is too large, there is a possibility that an abnormality has occurred, such as an abnormality in the detected value of the wheel speed, which prevents accurate estimation of the tire pressure by the tire vibration method. is there.

Based on such knowledge, in the device according to the present section, it is judged that the tire pressure estimation by the tire vibration method is effective when the intensity of the resonance frequency of the tire vibration is within the set range. It (19) The another method focuses on the phenomenon that the dynamic load radius of the tire changes and the wheel speed also changes when the air pressure changes, and the dynamic load that estimates the air pressure based on the wheel speed. The tire pressure detection device according to any one of (11) to (18), including a radius method.

According to this device, the tire pressure can be accurately detected by the hybrid method in which at least the vibration level method and the dynamic load radius method are combined so as to have high robustness against changes in the vehicle environment. It will be easy. (20) When the vehicle speed-related value that is at least one of the vehicle speed that is the traveling speed of the vehicle and the wheel speed is less than or equal to a third set vehicle speed-related value, the estimation device uses the pneumatic pressure based on the dynamic load radius method. The tire pressure detection device according to item (19), including an eighth determination means for determining that the estimation of is effective.

As described above, the accuracy of tire pressure estimation by the dynamic load radius method is due to an increase in the lift tendency of the tread portion of the tire and an increase in the slip ratio, and tends to decrease as the vehicle speed and the wheel speed increase. is there.

Based on such knowledge, the apparatus according to this section was proposed. (21) The estimation device determines that the estimation of the air pressure by the dynamic load radius method is effective when the change gradient of the wheel speed with respect to the vehicle speed that is the traveling speed of the vehicle is gentler than the set change gradient. The tire air pressure detection device according to (19) or (20), which includes a ninth determination means that:

In principle, in the dynamic load radius method,
The fact that the tire peripheral speed is equal to the product of the dynamic load radius of the tire and the wheel speed, that is, the angular velocity of the tire is utilized, but it is practically difficult to directly detect the tire peripheral speed.

Although it is possible to obtain the tire peripheral speed using the vehicle speed, the relationship between the tire peripheral speed and the vehicle speed changes depending on the slip ratio when the tire rolls on the road surface. However, the amount of change in tire peripheral speed per constant time and the amount of change in vehicle speed per constant time should essentially match each other.

On the other hand, under the condition that the dynamic load radius of the tire does not change with time, the ratio of the amount of change in tire peripheral speed per constant time to the amount of change in wheel speed per constant time is also changed with time. Should not change.

Therefore, by combining the above two facts, under the condition that the dynamic load radius of the tire does not change with time, the amount of change in vehicle speed per constant time and the change in wheel speed per constant time are combined. It is possible to induce the fact that the ratio with quantity also does not change over time.

This induced fact can be understood as the fact that the change gradient of the wheel speed with respect to the vehicle speed does not change with time under the condition that the dynamic load radius of the tire does not change with time. It is possible.

Therefore, the fact that the change gradient changes with time originally means that the dynamic load radius changes with time. However, the dynamic load radius changes with time, for example, at high speed. If it occurs during traveling, it is highly possible that the temporal change in the dynamic load radius is caused by an increase in the lift amount of the tread portion of the tire rather than a change in the tire air pressure.

Therefore, in the situation where the change gradient with time changes, the estimation accuracy of the tire air pressure by the dynamic load radius method is low.

Based on these findings, the apparatus according to the present section estimates the tire air pressure by the dynamic load radius method when the change gradient of the wheel speed with respect to the vehicle speed, which is the traveling speed of the vehicle, is gentler than the set change gradient. Is determined to be valid.

In addition, the characteristic technique described in this section can be implemented independently of the characteristic technique described in (19) or (20). (22) The estimation device is effective in estimating the air pressure by the dynamic load radius method when the slip ratio related value related to the slip ratio occurring in the wheel is equal to or less than the set slip ratio related value. The tire air pressure detection device according to any one of (19) to (21), including a tenth determination means for determining.

As described above, the estimation accuracy of the tire air pressure by the dynamic load radius method tends to be lower when the tire slip rate is higher than when it is low.

Based on such knowledge, in the device according to this section, when the slip ratio related value related to the slip ratio occurring in the wheel is equal to or less than the set slip ratio related value, the dynamic load radius method is used. The tire pressure estimation is determined to be valid.

An example of the "slip rate-related value" in this section is a drive slip rate-related value related to a slip rate that occurs on wheels (particularly drive wheels) when the vehicle is driven, and another example is braking of the vehicle. It is a braking slip rate related value related to the slip rate that sometimes occurs in the wheel.

An example of the drive slip ratio-related value can be data representing whether or not the drive wheels are in a drive state. When the wheel is in the driving state, the slip ratio of the wheel is generally large as compared with the case where the wheel is not in the driving state. This is because the represented data can function as the drive slip ratio related value.

Another example of the above-mentioned drive slip ratio-related value is
The data can be data representing the magnitude of the driving force acting on the driving wheels. (23) The another method focuses on the phenomenon that if the air pressure changes, the dynamic load radius of the tire changes, and the wheel speed also changes, and the dynamic load that estimates the air pressure based on the wheel speed. A radius vibration method and a tire vibration method that estimates the air pressure based on the wheel speed, focusing on the phenomenon that the characteristics of the tire vibration change if the air pressure changes, and that change is reflected in the wheel speed. The tire pressure detection device according to any one of (11) to (22), including:

According to this device, at least by the hybrid system in which the vibration level system, the tire vibration system, and the dynamic load radius system are combined, the tire pressure is accurately measured so as to have high robustness against changes in the vehicle environment. It becomes easy to detect. (24) An apparatus for detecting a tire air pressure by estimating the tire air pressure, which is provided in a vehicle in which a wheel configured by enclosing air under pressure in a tire mounted on a wheel is supported by a vehicle body. As a method of estimating the air pressure based on the wheel speed sensor that detects the angular speed of the wheel as the wheel speed and the wheel speed detected by the wheel speed sensor, (a) a time series of the detected wheel speed Detect the vibration level in a specific frequency range of the wheel speed signal that is the data as the vibration level of interest,
Focusing on the vibration level method of estimating the air pressure based on the detected vibration level of interest, and (b) the phenomenon that the dynamic load radius of the tire changes and the wheel speed also changes if the air pressure changes. A dynamic load radius method for estimating the air pressure based on the wheel speed, and (c) a phenomenon in which the tire vibration characteristics change if the air pressure changes, and the change is reflected in the wheel speed. A tire including a tire vibration method for estimating the air pressure based on the wheel speed, and an estimation device for estimating the air pressure by the vibration level method, the dynamic load radius method, and the tire vibration method. Air pressure detection device.

According to this device, at least by the hybrid system in which the vibration level system, the tire vibration system and the dynamic load radius system are combined, the tire pressure is accurately measured so as to have high robustness against changes in the vehicle environment. It becomes easy to detect. As described in the item (1), the vibration level method is a method that can easily estimate the tire pressure accurately in a high vehicle speed range. (25) The estimation device, based on the environment of the vehicle,
It is determined whether or not the estimation of the air pressure by the vibration level method, the dynamic load radius method, and the tire vibration method is effective, and based on the result, the final detected value of the air pressure is determined. The tire air pressure detection device according to the item (24). (26) Regardless of the result of the determination by the estimation device whether or not the estimation of the air pressure by the vibration level method, the dynamic load radius method, and the tire vibration method is effective,
The air pressure is estimated by each of the vibration level method, the dynamic load radius method, and the tire vibration method, and the estimation of the air pressure is obtained by the method determined to be effective among the plurality of estimated values obtained by the estimation. The tire air pressure detecting device according to the item (25), wherein an estimated value is selected by selecting a tire pressure as a final detected value of the air pressure. (27) The estimation device performs a method selection that selects one of the vibration level method, the dynamic load radius method, and the tire vibration method for which the estimation of the air pressure is determined to be effective, and the selection is performed. The tire air pressure detection device according to item (25), wherein the air pressure is estimated by the above method, and the estimated value is determined as a final detection value of the air pressure. (28) The estimation device, based on the environment of the vehicle,
In the high speed range of the vehicle speed, which is the traveling speed of the vehicle,
At least the estimated value of the air pressure by the vibration level method, in the medium speed region, at least the estimated value of the air pressure by the dynamic load radius method, in the low speed region, at least the estimated value of the air pressure by the tire vibration method other than This is adopted preferentially over the estimated value to determine the final detected value of the air pressure (24) to (27).
The tire air pressure detection device according to any one of items.

In this device, the entire variable range of the vehicle speed is three areas suitable for the estimation of the tire air pressure by the vibration level method, the dynamic load radius method, and the tire vibration method, that is, the high speed area and the middle area. When divided into a high speed region and a low speed region, at least in the high speed region, an estimated value by the vibration level method, in the medium speed region, at least an estimated value by the dynamic load radius method,
In the low speed range, at least the estimated value based on the tire vibration method is adopted in preference to other estimated values to determine the final detected value of the tire pressure.

Therefore, according to this device, it becomes easy to detect the tire air pressure accurately regardless of the vehicle speed.

The embodiment of the "estimation device" in this section is
It is not excluded that the tire pressure is estimated by using two or more methods of the vibration level method, the dynamic load radius method, and the tire vibration method under the same vehicle speed. (29) A device for detecting the air pressure of a tire by estimating the air pressure of the tire, which is provided in a vehicle in which a wheel configured by enclosing air under pressure inside a tire mounted on a wheel is supported by a vehicle body. As a method of estimating the air pressure based on the wheel speed sensor that detects the angular speed of the wheel as the wheel speed and the wheel speed detected by the wheel speed sensor, (a) a time series of the detected wheel speed Detect the vibration level in a specific frequency range of the wheel speed signal that is the data as the vibration level of interest,
A vibration level method of estimating the air pressure based on the detected vibration level of interest, and (b) if the air pressure changes, the characteristics of the tire vibration change, and the change is reflected in the wheel speed. A tire air pressure detection device that has a tire vibration method that focuses on a phenomenon and estimates the air pressure based on the wheel speed thereof, and that includes an estimation device that estimates the air pressure by the vibration level method and the tire vibration method. .

According to this apparatus, it is possible to accurately estimate the tire air pressure with a hybrid system combining at least the vibration level system and the tire vibration system so as to have high robustness against changes in the vehicle environment. Becomes As described in the item (1), the vibration level method is a method that can easily estimate the tire pressure accurately in a high vehicle speed range.

The apparatus according to this item is (1) to (1)
It is possible to implement by adopting the characteristic technique described in any one of the items 8). (30) The estimation device, based on the environment of the vehicle,
It is determined whether or not the estimation of the air pressure by the vibration level method and the tire vibration method is effective, and based on the result, the final detected value of the air pressure is determined (29). The tire pressure detection device described. (31) The estimation device, based on the environment of the vehicle,
In the high speed range of the vehicle speed, which is the traveling speed of the vehicle,
The estimated value of the air pressure by the vibration level method, in the low speed region, the estimated value of the air pressure by the tire vibration method is adopted preferentially over other estimated values to determine the final detected value of the air pressure. The tire air pressure detection device according to item (29) or (30).

In this device, the entire vehicle speed changeable region includes two regions suitable for the estimation of the tire air pressure by the vibration level system and the tire vibration system, that is, the high speed region and the low speed region. In addition, the estimated value by the vibration level method is adopted in the high speed area, and the estimated value by the tire vibration method is adopted in preference to the other estimated values in the low speed area. Is determined.

Therefore, according to this device, it becomes easy to detect the tire air pressure accurately regardless of the vehicle speed.

The embodiment of the “estimation device” in this section is
It does not exclude a mode in which the tire pressure is estimated by adopting both the vibration level method and the tire vibration method under the same vehicle speed. (32) A device for detecting the air pressure of the tire by estimating the tire pressure, which is provided in a vehicle in which a wheel configured by enclosing air under pressure inside a tire mounted on the wheel is supported by a vehicle body. Then, as a method for estimating the air pressure based on the wheel speed sensor that detects the angular velocity of the wheel as the wheel speed and the wheel speed detected by the wheel speed sensor, (a) a time series of the detected wheel speed Detect the vibration level in a specific frequency range of the wheel speed signal that is the data as the vibration level of interest,
Focusing on the vibration level method of estimating the air pressure based on the detected vibration level of interest, and (b) the phenomenon that the dynamic load radius of the tire changes and the wheel speed also changes if the air pressure changes. , A dynamic load radius method for estimating the air pressure based on the wheel speed, and
A tire air pressure detection device including an estimation device that estimates the air pressure by the vibration level method and the dynamic load radius method.

According to this apparatus, the tire pressure can be accurately estimated by the hybrid method in which at least the vibration level method and the dynamic load radius method are combined so as to have high robustness against changes in the vehicle environment. It will be easy. As described in the item (1), the vibration level method is a method that can easily estimate the tire pressure accurately in a high vehicle speed range.

The apparatus according to this item is (1) to (1) above.
It is possible to implement by implementing the characteristic technique described in any one of the items (0) and (19) to (22). (33) The estimation device is based on the environment of the vehicle,
It is determined whether or not the estimation of the air pressure by the vibration level method and the dynamic load radius method is effective, and the final detection value of the air pressure is determined based on the result (32). The tire pressure detection device according to. (34) The estimation device, based on the environment of the vehicle,
In the high speed range of the vehicle speed, which is the traveling speed of the vehicle,
The estimated value of the air pressure by the vibration level method, in the low speed region, the estimated value of the air pressure by the dynamic load radius method is adopted preferentially over other estimated values to determine the final detected value of the air pressure. The tire air pressure detection device according to item (32) or (33).

In this device, the entire vehicle speed changeable region includes two regions suitable for estimating the tire air pressure by the vibration level method and the dynamic load radius method, that is, a high speed area and a low speed area. In the high speed region, the estimated value by the vibration level method is adopted, and in the low speed region, the estimated value by the dynamic load radius method is adopted preferentially over other estimated values, and the final tire pressure is determined. The detected value is determined.

Therefore, according to this device, it becomes easy to detect the tire air pressure accurately regardless of the vehicle speed.

The embodiment of the “estimation device” in this section is
It is not excluded that tire pressure is estimated by adopting both the vibration level method and the dynamic load radius method under the same vehicle speed. (35) The tire air pressure according to any one of (1) to (34), further including a determination device that determines whether or not the tire is abnormal based on the air pressure detected by the tire air pressure detection device. Detection device. (36) The tire according to the paragraph (35), further including an alarm device that is activated to notify the driver of the vehicle when the determination device determines that the tire is abnormal. Air pressure detection device.

[0111]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, some more specific embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram conceptually showing the hardware structure of the tire abnormality determining apparatus according to the first embodiment of the present invention. This tire abnormality determination device is mounted on a vehicle.

The vehicle has wheels on the front, rear, left and right thereof. In Figure 1, "FL" is the left front wheel, "F"
“R” means the right front wheel, “RL” means the left rear wheel, and “RR” means the right rear wheel. The total number of wheels is four. As is well known, each wheel is configured by enclosing air under pressure inside a rubber tire mounted on a metal wheel.

As shown in FIG. 1, the tire abnormality determining device has a wheel speed sensor 10 for each wheel.
As is well known, each wheel speed sensor 10 is a sensor that detects the angular speed of each wheel as a wheel speed.
Specifically, the wheel speed sensor 10 is an electromagnetic pickup, and outputs a voltage signal that periodically changes according to passage of a large number of teeth formed on the outer circumference of a rotor that rotates together with the wheel.

The four wheel speed sensors 10 are shown in FIG.
As shown in, it is electrically connected to the determiner 20.
The determiner 20 is mainly composed of a computer 22, and determines whether or not there is a wheel having an abnormally low tire air pressure among a plurality of wheels based on the output signals of the four wheel speed sensors 10. It is a device.

Incidentally, in addition, in the following description,
The term tire anomaly is used as a term that means an abnormally low tire pressure.

FIG. 2 is a block diagram conceptually showing the hardware structure of the computer 22. As is well known, the computer 22 includes a CPU 30 (an example of a processor), a ROM 32 (an example of a memory), and an RA.
An M34 (an example of a memory) is connected to each other via a bus 36.

As shown in FIG. 2, various programs including a tire abnormality determination program, a vehicle speed estimation program, and a driving state detection program are stored in the ROM 32 in advance.

As is well known, the vehicle speed estimation program is a program executed to estimate the vehicle speed based on the plurality of wheel speeds respectively detected by the plurality of wheel speed sensors 10.

The drive state detection program is a program executed to detect whether or not the drive wheels driven by the power source among the plurality of wheels in the vehicle are in the drive state.

The tire abnormality determination program is a program executed to determine whether or not there is an abnormal tire among a plurality of tires in the vehicle. The tire abnormality determination program is configured to include a plurality of individual programs, as shown in FIG. Details of each individual program will be described later.

As shown in FIG. 1, an alarm device 40 is also connected to the judging device 20. The alarm 40 is activated to visually or audibly notify the driver of the vehicle that there is an abnormally low tire pressure among the wheels. When the alarm device 40 is configured to visually notify information, it can be configured as a dedicated lamp or as a multi-display that selectively displays a plurality of different information at the same display position. is there.

FIG. 3 is a block diagram showing the functions realized by the decision unit 20.

The determiner 20 is configured to include a portion for estimating the tire air pressure based on the output signal of the wheel speed sensor 10 and a portion for determining whether or not the estimated air pressure is abnormal. ing. As shown in FIG. 3, the former part includes a signal processing unit 60, an effectiveness determination unit 62,
The system selecting section 64 and the air pressure estimating section 66 are configured to include the air pressure determining section 68, while the latter portion is configured to include the air pressure determining section 68.

By the way, the judging device 20 has a tire vibration method, a dynamic load radius method, and a vibration level method as methods for estimating the air pressure. That is, the determiner 20
The air pressure is estimated by a hybrid method that combines these three methods.

As described above, in the tire vibration system, attention is paid to the phenomenon that the characteristics of tire vibration change when the air pressure changes, and the change is reflected in the wheel speed, and the air pressure is changed based on the wheel speed. This is an estimation method.

In this embodiment, the disturbance observer method is adopted as an example of the tire vibration method.

In this disturbance observer system, a tire model is assumed in which a rim side portion and a belt side portion that are relatively rotatable with respect to the wheel are connected to each other by at least a torsion spring. In this disturbance observer method, a motion system that describes the rotational motion of the wheel based on the tire model is further assumed. In that motion system, changes in the spring constant of the torsion spring with changes in air pressure are considered to be disturbances to the wheels.

In this disturbance observer system, the output signal of the wheel speed sensor 10 is used as a signal indicating the angular speed of the rim side portion. As a result, in this disturbance observer method, the disturbance is estimated as one of the state variables of the motion system, so that the air pressure is finally estimated. According to this disturbance observer method, the air pressure is estimated for each wheel.

On the other hand, the dynamic load radius method is a method of estimating the air pressure based on the wheel speed by paying attention to the phenomenon that the dynamic load radius of the tire changes and the wheel speed also changes when the air pressure changes. is there.

Although there are various methods for embodying the dynamic load radius method, they are embodied as follows in this embodiment. That is, when the individual wheel speed, which is the wheel speed of each wheel, matches the average wheel speed, which is the average value of the wheel speeds of all wheels in the vehicle, it is assumed that the air pressure of each individual wheel is equal to the standard air pressure. Then, the value obtained by dividing the average wheel speed by the individual wheel speed is calculated as the dynamic load radius ratio. Further, the product of the calculated dynamic load radius ratio and standard air pressure is estimated to be the air pressure of each individual wheel.

According to the vibration level method, the vibration level in the specific frequency region of the wheel speed signal, which is the time-series data of the wheel speed detected by the wheel speed sensor 10, is detected as the vibration level of interest, and the detected vibration of interest is detected. This is a method of estimating the air pressure based on the level.

FIG. 4 shows the frequency characteristic of the wheel speed signal,
Graphs are shown for the case where the air pressure is high and the case where the air pressure is low. In the figure, the vibration level of the wheel speed signal is represented as a gain.

Generally, in a vehicle, the resonance frequency of the rotational vibration of the tire is about 40 [Hz], and the resonance frequency of the longitudinal vibration of the suspension connecting the tire to the vehicle body is about 15 [Hz].

Here, the vibration level difference, which is the difference between the vibration levels when the air pressure is high and when the air pressure is low, is compared for the vicinity of the above resonance frequency and frequencies other than the resonance frequency.

In the vicinity of the resonance frequency, the actual resonance frequency when the air pressure is high shifts in an increasing direction with respect to the actual resonance frequency when the air pressure is low. The difference in the vibration level at the point markedly changes.

On the other hand, at frequencies other than the resonance frequency, even if the actual resonance frequency when the air pressure is high shifts in an increasing direction with respect to the actual resonance frequency when the air pressure is low, it is not the resonance frequency. The vibration level difference in frequency is maintained.

Therefore, between the resonance frequency of the suspension and the resonance frequency of the tire, a frequency range that does not include those resonance frequencies is selected as a specific frequency range, and it is irrelevant whether it is the left front wheel or the right rear wheel. However, assuming that the air pressure of the left and right wheels does not become abnormal at the same time, if the difference between the left and right wheels of the vibration level is detected as the vibration level left / right difference in that specific frequency range, the vibration level left / right difference Accordingly, it is possible to estimate the air pressure of the left and right wheels of which the air pressure is abnormal.

In the present embodiment, as shown in FIG. 4, the specific frequency region has a lower limit of 20 [Hz] and a lower limit of 30 [Hz].
It is selected as a region having an upper limit of [Hz].

Therefore, in this embodiment, the vibration level method is embodied as a method of estimating the air pressure without utilizing the resonance of the vehicle vibration element including the tire and the suspension.

FIG. 5 is a graph showing the temporal transition of the experimental value of the left-right difference of the vibration level, taking the case where the vehicle speed is 200 [km / h] and the left and right wheels are the left and right rear wheels as an example. Has been done.

In the figure, the temporal change of the experimental value of the left-right difference of the vibration level is 180 when the air pressure is at the left rear wheel RL.
[Pa] and 280 [Pa] at the right rear wheel RR (indicated by "RL180-RR280" in the figure)
When the air pressure is 230 [Pa] at the left rear wheel RL and 280 [Pa] at the right rear wheel RR (indicated by "RL230-RR280" in the figure), the air pressure is also right at the left rear wheel RL. 280 [P even in the rear wheel RR
a] (in the figure, "RL280-RR28
0 ").

As is clear from FIG. 5, the experimental value of the left-right difference in vibration level increases in accordance with the difference in air pressure between the left and right rear wheels. Therefore, regardless of whether it is the left and right front wheels or the left and right rear wheels, it is assumed that the air pressure for the left and right wheels will drop only for one of the wheels. It is verified that it is possible to estimate the amount of decrease in a certain tire pressure from the normal value.

As described above, in the determining device 20, the air pressure is estimated by the three methods. Therefore, the signal processing unit 60 outputs the output of the wheel speed sensor 10 as shown in FIG. A first signal processing for processing the signal for the tire vibration method, a second signal processing for processing for the dynamic load radius method, and a third signal processing for processing for the vibration level method are respectively executed. Is designed.

FIG. 6 shows the range in which the estimation of the air pressure by the tire vibration method, the dynamic load radius method, and the vibration level method is effective in relation to the vehicle speed. As shown in the figure, the tire vibration method can effectively estimate the air pressure in the low speed vehicle speed region, and the dynamic load radius method can effectively estimate the air pressure in the low speed and medium speed vehicle speed regions. According to the vibration level method, the air pressure can be effectively estimated in the medium speed and high speed vehicle speed regions.

Therefore, in the present embodiment, basically, at least the tire vibration method is used in the low vehicle speed range, at least the dynamic load radius method is used in the medium speed range, and at least the vibration level method is used in the high speed range. , The air pressure is estimated.

Further, in the present embodiment, whether or not the estimation of the air pressure by each method is effective is performed for each method and by referring to the vibration characteristic related value which is a physical quantity other than the vehicle speed.

Therefore, as shown in FIG. 3, the validity judging section 62 makes a first validity judgment for judging whether or not the estimation of the air pressure by the tire vibration method is effective, and the air pressure by the dynamic load radius method. It is designed to execute a second validity determination that determines whether the estimation is valid and a third validity determination that determines whether the estimation of the air pressure by the vibration level method is valid. . The effectiveness determination unit 62 makes these determinations by referring to the output signal of the signal processing unit 60, the vehicle speed, and the driving state of the wheels.

The air pressure estimating section 66, as shown in FIG.
Selected by the method selection unit 64 from the first air pressure estimation that estimates the air pressure by the tire vibration method, the second air pressure estimation that estimates the air pressure by the dynamic load radius method, and the third air pressure estimation that estimates the air pressure by the vibration level method. Designed to do what was done.

As shown in FIG. 3, the system selection unit 64 is effective in estimating the air pressure among the tire vibration system, the dynamic load radius system, and the vibration level system based on the determination result by the effectiveness determination unit 62. Select what is. The method selection unit 64 includes the first to third air pressure estimation units 66.
The air pressure estimation unit 66 is instructed to execute the air pressure estimation that estimates the air pressure by the selected method. The system selection unit 64 supplies the estimated value of the air pressure acquired by the air pressure estimation unit 66 according to the command to the air pressure determination unit 68 as the effective air pressure, that is, the final detected value of the air pressure.

The air pressure determination unit 68 determines whether or not there is a wheel whose air pressure is low, based on the supplied effective air pressure. If there is a wheel whose air pressure is low, the air pressure determination unit 68 notifies the driver of the vehicle of the fact via the alarm device 40.

In addition, in addition, in the graph of FIG. 5, the sign of the vibration level left / right difference is defined so that the direction in which the air pressure of the left rear wheel decreases is positive, and the direction in which the air pressure of the right rear wheel decreases is negative. ing.

In the first signal processing (disturbance observer method) in FIG. 3, the computer 22 executes the first signal processing program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. It is executed by being executed.

This first signal processing program is repeatedly executed for each wheel. At the time of each execution, first, in step S11 (hereinafter, simply referred to as “S11”; the same applies to other steps), a signal is fetched from the wheel speed sensor 10 related to the wheel to be executed this time.

Next, in S12, the wheel speed is calculated based on the fetched signal. Then, S13
At, the fluctuating frequency component is extracted from the wheel speed signal, which is time-series data indicating that the calculated wheel speed changes with time. Then, in S14, frequency analysis such as FFT is performed on the extracted fluctuating frequency component. This frequency analysis reveals how the vibration level of the fluctuating frequency component changes with frequency.

Thus, one execution of this first signal processing program is completed.

In the second signal processing (dynamic load radius method) in FIG. 3, the program name is displayed in FIG. 2 and the second signal processing program whose contents are conceptually shown in the flowchart in FIG. 8 is the computer 22. It is executed by being executed by.

This second signal processing program corresponds to the first
Similar to the signal processing program, it is repeatedly executed for each wheel. At the time of each execution, first, in S31, S
In the same manner as in 11, a signal is acquired from the wheel speed sensor 10 associated with the currently executed wheel.

Next, in S32, the wheel speed is calculated based on the fetched signal in the same manner as in S12. Then, in S33, similarly to S14, frequency analysis such as FFT is performed on the wheel speed signal which is the time series data of the calculated wheel speed. This frequency analysis reveals how the vibration level of the wheel speed signal changes with frequency.

Thus, one execution of this second signal processing program is completed.

In the third signal processing (vibration level method) in FIG. 3, the computer 22 executes the third signal processing program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. It is executed by being executed.

This third signal processing program is also repeatedly executed for each wheel. When executing each time, first, S5
In 1, in the same manner as in S11, a signal is fetched from the wheel speed sensor 10 related to the current execution target wheel.

Next, in S52, the wheel speed is calculated based on the received signal in the same manner as in S12.

Subsequently, in S53, a frequency component whose frequency is within the monitoring frequency region is extracted as a monitoring frequency component from the wheel speed signal which is the time-series data of the calculated wheel speed. In the present embodiment, the monitored frequency range is selected as a frequency range including the specific frequency range and further including the tire resonance frequency and the suspension resonance frequency.

Then, in S54, the frequency analysis such as FFT is performed on the extracted monitoring frequency component in the same manner as in S14. This frequency analysis reveals how the vibration level of the monitored frequency component changes with frequency. As a result, a characteristic is obtained in which the vibration level of the wheel speed signal changes with the frequency in the monitored frequency range.

As described above, one execution of the third signal processing program is completed.

In the first effectiveness judgment (tire vibration method) in FIG. 3, the program name is displayed in FIG. 2 and the contents are conceptually shown in the flow chart in FIG. 22 is performed by being performed.

This first effectiveness judgment program is repeatedly executed for each wheel. When executing each time, first, S
At 71, it is determined whether the current vehicle speed is less than or equal to the set vehicle speed H1. The set vehicle speed H1 can be set as a value within a range of about 80 to about 120 [km / h], for example.

If the current vehicle speed is less than or equal to the set vehicle speed H1,
The determination in S71 is YES, and in S76, it is determined that the estimation of the air pressure by the tire vibration method is effective. This is the end of the one-time execution of the first effectiveness determination program.

On the other hand, if the current vehicle speed is not equal to or lower than the set vehicle speed H1, the determination in S71 is NO and S7 is set.
Move to 2.

In S72, the degree of dispersion of the resonance frequency of the wheel speed signal is calculated.

Specifically, the resonance frequency of the wheel speed signal is detected based on the frequency analysis result found by the execution of the first signal processing program. The resonance frequencies are sequentially detected over time, and as a result, a plurality of resonance frequencies are finally detected. After that, a standard deviation of the detected plurality of resonance frequencies as a sample is calculated as the dispersion degree.

FIG. 11 shows a distribution of resonance frequencies when the resonance frequencies tend to concentrate and the degree of dispersion is small.
The distribution of the resonance frequency when the resonance frequency has a strong tendency to disperse and the degree of dispersion is large is conceptually illustrated in the graph. A small degree of dispersion means that a tire vibration method that positively utilizes tire vibration to estimate air pressure is effective, and conversely, a large degree of dispersion is not effective. means.

Upon completion of execution of S72,
In S73, it is determined whether the calculated dispersion degree is less than or equal to the set dispersion degree Σ. If it is less than or equal to the set scattering degree Σ, the determination is YES and S76.
In, it is determined that the estimation of the air pressure by the tire vibration method is effective. This is the end of the one-time execution of the first effectiveness determination program.

On the other hand, when the calculated dispersion degree is not less than the set dispersion degree Σ, the determination in S73 is N.
It becomes O, and in S74, whether or not the resonance intensity which is the intensity of the resonance frequency (for example, the intensity of the resonance frequency at which the occurrence frequency is the maximum) is within the setting range having the value A1 as the lower limit and the value A2 as the upper limit. Is determined.

FIG. 12 is a graph showing a state in which the resonance intensity changes with time, and therefore transitions between the lower limit value A1 or less, the setting range, and the upper limit value A2 or more. Has been done.

If the resonance intensity this time is within the set range, S
The determination of 74 is YES, and it is determined in S76 that the estimation of the air pressure by the tire vibration method is effective.
This is the end of the one-time execution of the first effectiveness determination program.

Since the condition regarding the vehicle speed, the condition regarding the scattering degree, and the condition regarding the resonance strength are not satisfied, S
When the determinations in S71, S73, and S74 are all NO, it is determined in S75 that the estimation of the air pressure by the tire vibration method is invalid. This is the first
One execution of the effectiveness determination program ends.

In the second effectiveness judgment (dynamic load radius method) in FIG. 3, the second effectiveness judgment program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. It is executed by being executed by the computer 22.

This second effectiveness judgment program is also repeatedly executed for each wheel. When executing each time, first, S
At 101, it is determined whether the current vehicle speed is less than or equal to the set vehicle speed H2. The set vehicle speed H2 is, for example, about 80.
It is possible to set it as a value within the range of about 180 [km / h].

If the current vehicle speed is equal to or lower than the set vehicle speed H2,
The determination in S101 is YES, and in S106, it is determined that the estimation of the air pressure by the dynamic load radius method is effective. This is the end of the one-time execution of the second effectiveness determination program.

On the other hand, if the current vehicle speed is not equal to or lower than the set vehicle speed H2, the determination in S101 is NO and S
Move to 102.

In S102, the gradient of change in wheel speed with respect to vehicle speed is calculated.

Specifically, the above-described change gradient is calculated by dividing the amount of change in wheel speed per constant time reflecting the dynamic load radius by the amount of change in vehicle speed per constant time.

FIG. 14 is a graph illustrating the manner in which the change gradient increases in the high vehicle speed region. Such an increase in the change gradient is rather than a change in air pressure.
It is highly possible that this occurred due to an increase in the lift amount of the tread portion of the tire.

When the execution of S102 is completed, thereafter, in S103, it is determined whether or not the calculated change gradient is smaller than the set change gradient G, that is, whether it is gentle. When it is smaller than the setting change gradient G, the determination in S103 is YES, and in S107, it is determined that the estimation of the air pressure by the dynamic load radius method is effective. This is the end of the one-time execution of the second effectiveness determination program.

On the other hand, when the calculated change gradient is not smaller than the set change gradient G, the determination in S103 is NO, and in S104, by referring to the execution result of the drive state detection program, this time It is determined whether or not the execution target wheel of is not in the driving state. If it is not in the driving state, the determination in S104 is YES and S107
In, it is determined that the estimation of the air pressure by the dynamic load radius method is effective. This is the end of the one-time execution of the second effectiveness determination program.

On the other hand, if the wheel to be executed this time is in the driving state, the determination in S104 is NO, and in S105, is it determined that the tire vibration method is invalid by executing the first effectiveness determination program? It is determined whether or not. If it is determined to be invalid, the determination in S105 is YES, and it is determined in S107 that the estimation of the air pressure by the dynamic load radius method is valid. This is the end of the one-time execution of the second effectiveness determination program.

On the other hand, the condition regarding the vehicle speed, the condition regarding the change gradient, the condition regarding the driving of the wheels, and the condition regarding the effectiveness of the tire vibration method are not satisfied.
101, S103 to S105 are all NO
If it is, it is determined in S106 that the estimation of the air pressure by the dynamic load radius method is invalid. Above,
The one-time execution of the second effectiveness determination program ends.

In the third effectiveness judgment (vibration level method) in FIG. 3, the program name is displayed in FIG. 2 and the contents are conceptually shown in the flow chart in FIG. 22 is performed by being performed.

This third effectiveness judgment program is also repeatedly executed for each wheel. When executing each time, first, S
At 131, it is determined whether the current vehicle speed is equal to or higher than the set vehicle speed H3. The set vehicle speed H3 can be set equal to the set vehicle speed H1 or the set vehicle speed H2, for example.

If the current vehicle speed is equal to or higher than the set vehicle speed H3,
The determination in S131 is YES, and in S139, it is determined that the estimation of the air pressure by the vibration level method is effective. With the above, the one-time execution of the third effectiveness determination program is completed.

In the example of this embodiment, the relationship between the set vehicle speed H3 and the above-mentioned set vehicle speeds H1 and H2 is that the set vehicle speed H2 is higher than the set vehicle speed H1 and the set vehicle speed H
3 is set equal to the set vehicle speed H2.

In this example, in the low speed region where the actual vehicle speed is equal to or lower than the set vehicle speed H1, the tire pressure estimation value by the tire vibration method and the estimation value by the dynamic load radius method (at least the estimation of the air pressure by the tire vibration method) are performed. Value ”) is preferentially adopted over the estimated value by the vibration level method.

Further, in this example, in the medium speed range in which the actual vehicle speed is higher than the set vehicle speed H1 and lower than the set vehicle speed H2, the estimated value of the tire pressure by the dynamic load radius method (“at least the dynamic load radius method” is used. “Estimated value of air pressure according to the example”) is preferentially adopted over the estimated value by the tire vibration method and the estimated value by the vibration level method.

Further, in this example, in the high speed region where the actual vehicle speed is equal to or higher than the set vehicle speed H3, the estimated value of the tire pressure by the vibration level method (an example of "at least the estimated value of air pressure by the vibration level method") is , The tire vibration method and dynamic load radius method are used with priority.

In another example of the present embodiment, the set vehicle speeds H1 to H3 are mutually related such that the set vehicle speed H2 is higher than the set vehicle speed H1 and the set vehicle speed H3 is the set vehicle speed H.
It is set equal to 1.

In this example, in the low speed region where the actual vehicle speed is equal to or lower than the set vehicle speed H1, the tire vibration pressure is estimated by the tire vibration method and the dynamic load radius method is estimated ("at least the tire vibration pressure is estimated. Value ”) is preferentially adopted over the estimated value by the vibration level method.

Further, in this example, in the medium speed range in which the actual vehicle speed is higher than the set vehicle speed H1 and lower than the set vehicle speed H2, the tire pressure is estimated by the dynamic load radius method and the estimated value by the vibration level method. (An example of "at least estimated value of air pressure by dynamic load radius method")
, Is preferentially adopted over the estimated value by the estimated value by the tire vibration method.

Further, in this example, in the high speed region where the actual vehicle speed is equal to or higher than the set vehicle speed H3, the estimated value of the tire pressure by the vibration level method (an example of "at least the estimated value of air pressure by the vibration level method") is , The tire vibration method and dynamic load radius method are used with priority.

If the current vehicle speed is not equal to or higher than the set vehicle speed H3, the determination at S131 in FIG. 15 is NO,
The process moves to S132.

In S132, the degree of dispersion of the resonance frequency of the monitoring frequency component is calculated in the same manner as in S72 of FIG. When the vibration level method is adopted, the resonance of the tire and the suspension causes noise resonance in the monitored frequency component, which becomes a factor of reducing the estimation accuracy of the air pressure. Therefore, the vibration level method should be judged to be effective when the resonance is small and the degree of dispersion is large, or when the resonance strength is small.

Thereafter, in S133, it is determined whether or not the calculated dispersion degree is larger than the set dispersion degree Σ. If it is larger than the set scattering degree Σ, the determination becomes YES, and it is determined in S139 that the estimation of the air pressure by the vibration level method is effective. Above,
The one-time execution of the third effectiveness determination program ends.

On the other hand, when the calculated dispersion degree is not larger than the set dispersion degree Σ, the determination in S133 is NO, and the process proceeds to S134.

In this step S134, the resonance intensity for the monitored frequency component is acquired in the same manner as in step S74 in FIG. 10, and it is further determined whether or not the acquired resonance intensity is equal to or less than the above-mentioned value A1. To be done. If the value is less than or equal to A1, the determination is YES and S13.
In 9, it is determined that the estimation of the air pressure by the vibration level method is effective. With the above, the one-time execution of the third effectiveness determination program is completed.

On the other hand, the obtained resonance strength is the value A1.
If not, the determination in S134 is NO,
The process moves to S135.

In S135, the lower antiresonance frequency (for example, 25 [Hz] as shown in FIG. 16 is referred to by referring to the frequency analysis result obtained by executing the third signal processing program in FIG. ) And the first peak value, which is the vibration level, and the upper resonance frequency (see, for example, FIG.
As shown in 6, the tire resonance frequency of 40 [H
z]) and the second peak value, which is the vibration level. After that, as shown in FIG. 16, the difference between the two peak values is calculated as the vibration level difference between the peak values. In the present embodiment, the first peak value is defined as the vibration level of a certain frequency between the resonance frequency of the suspension and the resonance frequency of the tire.

In addition, in addition to the above-mentioned lower anti-resonance frequency, the first peak value is replaced by the lower resonance frequency (for example,
As shown in FIG. 16, it is possible to obtain the vibration level at the resonance frequency of the suspension, which is 15 [Hz]. However, as described above, when the vibration level difference between the anti-resonance frequency and the resonance frequency adjacent to each other is acquired, the resonance level difference is obtained more than when it is acquired as the vibration level difference between the two resonance frequencies adjacent to each other. It is considered to be effective for accurately determining whether or not is occurring. This is because it is considered that in the former case, the vibration level difference changes more significantly depending on the presence or absence of resonance than in the latter case.

Thereafter, in S136, it is determined whether or not the calculated vibration level difference between peak values is smaller than the set vibration level difference D between peak values. When it is smaller than the set peak value vibration level difference D, the determination is YES, and in S139, it is determined that the estimation of the air pressure by the vibration level method is effective. With the above, the one-time execution of the third effectiveness determination program is completed.

On the other hand, when the calculated vibration level difference between peak values is not smaller than the set vibration level difference between peak values D, the determination in S136 is NO, and in S137, the second validity determining program is executed. It is determined whether the dynamic load radius method is determined to be invalid by executing. If it is determined to be invalid, the determination in S137 becomes YES, and in S139, it is determined that the estimation of the air pressure by the vibration level method is valid. With the above, the one-time execution of the third effectiveness determination program is completed.

On the other hand, since the condition regarding the vehicle speed, the condition regarding the degree of dispersion, the condition regarding the resonance strength, the condition regarding the vibration level difference between peak values, and the condition regarding the effectiveness of the dynamic load radius method are not satisfied, S131 , S1
When the determinations at 33, S134, S136, and S137 are all NO, it is determined at S138 that the estimation of the air pressure by the vibration level method is invalid.
With the above, the one-time execution of the third effectiveness determination program is completed.

In the first air pressure estimation (tire vibration method) in FIG. 3, the computer 22 executes the first air pressure estimation program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. It is executed by being executed.

This first air pressure estimation program is repeatedly executed for each wheel. When executing each time, first, S
At 151, the amount of change in the spring constant of the tire of the wheel to be executed this time is estimated based on the fluctuation frequency component extracted at S13 in FIG. 7 and by the above-described disturbance observer method.

Next, in S152, the tire air pressure is estimated according to the estimated change amount of the spring constant. The relationship between the amount of change in the spring constant and the tire air pressure is stored in the ROM 32 in advance, and the tire air pressure is estimated according to the relationship. This is the end of one execution of the first air pressure estimation program.

In the second air pressure estimation (dynamic load radius method) in FIG. 3, the program name is displayed in FIG. 2 and the second air pressure estimation program whose contents are conceptually shown in the flowchart in FIG. 18 is the computer 22. It is executed by being executed by.

This second air pressure estimation program is also repeatedly executed for each wheel. When executing each time, first, S
At 171, a reference vehicle speed is determined as the average wheel speed.

Next, in S172, the determined reference vehicle speed is divided by the wheel speed of the currently executed wheel to calculate the dynamic load radius ratio of the currently executed wheel.

Subsequently, in S173, the tire air pressure of the wheel to be executed this time is estimated by multiplying the calculated dynamic load radius ratio by the standard air pressure.

With the above, one execution of this second air pressure estimation program is completed.

In the third air pressure estimation (vibration level method) in FIG. 3, the computer 22 executes the third air pressure estimation program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. It is executed by being executed.

This third air pressure estimation program is also repeatedly executed for each wheel. When executing each time, first, S
At 191, the left and right front wheels and the left and right rear wheels to which the current execution target wheel belongs are determined as the current left and right wheels. Then, the vibration level left / right difference is calculated by referring to the frequency analysis result obtained by executing the third signal processing program in FIG. 9.

Specifically, first, the vibration level for each of the left and right wheels this time is acquired for a specific frequency component having a frequency within the specific frequency range. The acquired vibration level is the above-mentioned vibration level of interest. Next, the difference between the vibration level acquired for the left wheel and the corresponding vibration level acquired for the right wheel is calculated as the vibration level left / right difference for the left and right wheels.

Next, in S192, the air pressure of the low-pressure side wheel, which is the wheel with the lower air pressure of the left and right wheels this time, is estimated according to the calculated left-right difference in vibration level. The ROM 32 stores the relationship between the left-right difference in vibration level and the amount of decrease in air pressure from the standard air pressure in advance.
According to the relationship, the air pressure decrease amount corresponding to the left-right difference of the vibration level is estimated, and the air pressure of the low-pressure side wheel is estimated by subtracting the estimated air pressure decrease amount from the standard air pressure.

As described above, one execution of this third air pressure estimation program is completed.

The system selection unit 64 in FIG. 3 is operated by the computer 22 executing a system selection program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. To be

This system selection program is repeatedly executed for each wheel. When executing each time, first, S201
At the execution target wheel of this time, it is determined whether or not the tire vibration method is determined to be effective by executing the first effectiveness determination program. If it is not determined to be valid, the determination is NO, and immediately S
Move to 205.

On the other hand, if it is determined that the tire vibration method is effective, the determination in S201 is YES, and in S202, the tire vibration method is selected for the wheel to be executed this time.

Then, in S203, the first air pressure estimation program is executed, and thereby the air pressure is estimated by the tire vibration method.

Subsequently, in S204, the estimated air pressure is stored in the RAM 34 as the first effective air pressure. Then, it transfers to S205.

In S205, it is determined whether or not the dynamic load radius method has been determined to be effective by executing the second effectiveness determination program for the wheel to be executed this time. If it is not determined to be valid,
The determination becomes NO, and the process immediately shifts to S209.

On the other hand, if it is determined that the dynamic load radius method is effective, the determination in S205 is YES, and in S206, the dynamic load radius method is selected for the wheel to be executed this time.

Thereafter, in S207, the second air pressure estimation program is executed, and thereby the air pressure is estimated by the dynamic load radius method.

Subsequently, in S208, the estimated air pressure is stored in the RAM 34 as the second effective air pressure. Then, it transfers to S209.

In S209, it is determined whether or not the vibration level method is determined to be effective by executing the third effectiveness determination program for the wheel to be executed this time. If it is not determined to be valid,
When the determination is NO, the one-time execution of this system selection program ends immediately.

On the other hand, if it is determined that the vibration level method is effective, the determination in S209 is YES, and in S210, the vibration level method is selected for the wheel to be executed this time.

Thereafter, in S211, the third air pressure estimation program is executed, and thereby the air pressure is estimated by the vibration level method.

Subsequently, in S212, the estimated air pressure is stored in the RAM 34 as the third effective air pressure. This completes the one-time execution of this system selection program.

The air pressure determination unit 68 in FIG. 3 is operated by the computer 22 executing an air pressure determination program whose program name is displayed in FIG. 2 and whose contents are conceptually shown in the flowchart in FIG. To be

This air pressure determination program is repeatedly executed for each wheel. When executing each time, first, S23
1, it is determined whether or not a value lower than the threshold air pressure exists in at least one effective air pressure actually stored in the RAM 34 among the first to third effective air pressures for the wheel to be executed this time. To be done. The threshold air pressure is a reference value set in advance that it is appropriate to determine that the air pressure is abnormally low when the air pressure is lower than that.

If it is assumed that there is no value lower than the threshold air pressure in the at least one effective air pressure this time, the determination in S231 is NO, and the routine proceeds to S232.

In S232, it is determined that the air pressure is normal for the wheel to be executed this time. Then, in S233, a signal for turning off the alarm device 40 is output to the alarm device 40. Above,
One execution of this air pressure determination program ends.

On the other hand, this time, assuming that a value lower than the threshold air pressure exists in the at least one effective air pressure, the determination in S231 becomes YES, and S2
Move to 34.

In S234, it is determined that the air pressure of the wheel to be executed this time is low. Then, in S235, a signal for turning on the alarm device 40 is output to the alarm device 40. This is the end of one execution of this air pressure determination program.

As is apparent from the above description, in the present embodiment, the portion of the tire abnormality determining device excluding the alarm device 40 and the air pressure determining portion 68 is the "tire pressure detecting device" according to the above item (1). Of the determination unit 20.
The portion excluding the air pressure determination unit 68 constitutes an example of the “estimation device” in the same section, and the vehicle speed, the degree of dispersion, the resonance strength, and the vibration level difference between peak values are respectively the “vibration characteristic-related values” in the same section. It constitutes an example of ".

Further, in the present embodiment, the vehicle speed, the degree of dispersion, the resonance intensity, and the vibration level difference between peak values each constitute an example of the “vibration characteristic-related value” in the item (4). .

Further, in this embodiment, the vehicle speed constitutes an example of the "vehicle speed related value" in the above item (5), and the set vehicle speed H3 constitutes an example of the "first set vehicle speed related value" in the same item. The portion of the determiner 20 that executes S131 and S139 of FIG. 15 constitutes an example of the “first determining means” in the same section.

Furthermore, in the present embodiment, the degree of dispersion, the resonance strength, and the vibration level difference between peak values each constitute an example of the “noise resonance characteristic value” in the above item (6).

Furthermore, in the present embodiment, the set dispersion degree Σ constitutes an example of the “first set dispersion degree” in the above item (7), and the determination unit 20 of the determination unit S13 of FIG.
The part that executes 2, S133 and S139 constitutes an example of the "second determination means" in the same section.

Furthermore, in the present embodiment, the value A1 constitutes an example of the "first set strength" in the item (8), and the determination unit 20 includes S134 and S139 in FIG.
The part that executes is forming an example of the “third determining means” in the same section.

Further, in this embodiment, the vibration level difference between peak values constitutes one example of the "vibration level characteristic value" in the item (9).

Furthermore, in the present embodiment, the vibration level difference D between the set peak values constitutes an example of the “vibration level difference between the set peak values” in the above item (10), and the judging unit 20
The part that executes S135, S136, and S139 in FIG. 15 constitutes an example of the “fourth determination means” in the same section.

Further, in the present embodiment, the vehicle speed constitutes an example of the "vehicle speed related value" in the item (16),
The set vehicle speed H1 constitutes an example of the “second set vehicle speed-related value” in the same section, and the portion of the determiner 20 that executes S71 and S76 of FIG. 10 is an example of the “fifth determination unit” in the same section. It is composed.

Further, in the present embodiment, the set scattering degree Σ constitutes an example of the “second set scattering degree” in the above item (17), and S7 of FIG.
The part that executes 2, S73 and S76 constitutes an example of the "sixth determination means" in the same section.

Further, in this embodiment, the lower limit value A
The range defined by 1 and the upper limit A2 is (1
An example of the “setting range” in the item 8) is configured, and the judging device 2
The portion of 0 that executes S74 and S76 of FIG. 10 constitutes an example of the “seventh determination means” in the same section.

Further, in the present embodiment, the vehicle speed constitutes an example of the "vehicle speed related value" in the item (20),
The set vehicle speed H2 constitutes an example of the “third set vehicle speed-related value” in the same section, and the portion of the determiner 20 that executes S101 and S107 of FIG. 13 is an example of the “eighth determination section” in the same section. It is composed.

Furthermore, in the present embodiment, the setting change gradient G constitutes an example of the “setting change gradient” in the above item (21), and the determination unit 20 includes S102 and S1 of FIG.
The part that executes 03 and S107 constitutes an example of the “ninth determination means” in the same section.

Further, in the present embodiment, the case where the wheels are not in the driving state is "when the slip ratio related value is equal to or less than the set slip ratio related value" in the above item (22).
In the determination unit 20, the part that executes S105 and S107 of FIG.
That is, it constitutes an example of "determining means".

Further, in the present embodiment, the portion of the tire abnormality determining device excluding the alarm device 40 and the air pressure determining portion 68 is the "tire" relating to each of the above (24), (29) and (32). An example of the “air pressure detection device”, and the portion of the determination device 20 excluding the air pressure determination unit 68 is
It constitutes an example of the “estimation device” in the same section.

Further, in this embodiment, the decision unit 2
The part of 0 other than the air pressure determination part 68 is the same as the above (2
5), (27), (28), (30), (31), (3
"Estimator" in each of 3) and (34)
The vehicle speed, the degree of dispersion, the resonance intensity, and the vibration level difference between the peak values respectively constitute an example of the “vehicle environment” in the above section.

Next, a second embodiment of the present invention will be described.

In the first embodiment, the tire pressure is detected by the hybrid system in which the tire vibration system, the dynamic load radius system and the vibration level system are combined.

On the other hand, in this embodiment, as shown in FIG.
As shown in 2, the tire pressure is detected by the hybrid method in which the tire vibration method and the vibration level method are combined. The tire vibration method can effectively detect the tire pressure in the low and medium vehicle speed regions, and the vibration level method can effectively detect the tire pressure in the high vehicle speed region.

This embodiment is different from the first embodiment in that the part related to detecting the tire air pressure by the dynamic load radius method is omitted.

Therefore, in the present embodiment, the portion of the tire abnormality determining device excluding the alarm device 40 and the air pressure determining portion 68 constitutes an example of the "tire air pressure detecting device" according to the item (29), The portion of the determining device 20 excluding the air pressure determining portion 68 constitutes an example of the “estimating device” in the same section.

Further, in this embodiment, the decision unit 2
The part of 0 other than the air pressure determination part 68 is the above (30).
And an example of the "estimation device" in each of the items (31), and a vehicle speed, a degree of dispersion, a resonance intensity, and a vibration level difference between peak values respectively constitute an example of the "vehicle environment" in the same item. Is there.

Next, a third embodiment of the present invention will be described.

In the present embodiment, as shown in FIG. 23, the tire pressure is detected by the hybrid method in which the dynamic load radius method and the vibration level method are combined. The dynamic load radius method can effectively detect the tire pressure in the low and medium vehicle speed regions, and the vibration level method can effectively detect the tire pressure in the high vehicle speed region.

This embodiment is different from the first embodiment in that the parts related to detecting the tire air pressure by the tire vibration method are omitted.

Therefore, in the present embodiment, the portion of the tire abnormality determination device excluding the alarm device 40 and the air pressure determination portion 68 constitutes an example of the "tire pressure detection device" according to item (32) above. The portion of the determining device 20 excluding the air pressure determining portion 68 constitutes an example of the “estimating device” in the same section.

Further, in the present embodiment, the decision unit 2
The part of 0 other than the air pressure determination part 68 is the above (33).
And (34) constitutes an example of the “estimation device”, and the vehicle speed, the gradient of change, the wheel driving state, the degree of dispersion, the resonance intensity, and the vibration level difference between the peak values are respectively defined in the “vehicle environment”. It constitutes an example of ".

Some of the specific embodiments of the present invention have been described in detail above with reference to the drawings. However, these are merely examples, and the above-mentioned [Means for solving the problems and effects of the invention] column are described. It is possible to carry out the present invention in other modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in (1).

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing a hardware structure of a tire abnormality determination device according to a first embodiment of the present invention.

FIG. 2 is a block diagram conceptually showing the hardware structure of a computer 22 in the decision unit 20 in FIG.

FIG. 3 is a block diagram for explaining a function realized by a determiner 20 in FIG.

4 is a graph for explaining the principle of tire pressure estimation by a vibration level method in an air pressure estimation unit 66 in FIG.

FIG. 5 is a graph for explaining the adequacy of the technique for estimating the tire air pressure by the vibration level method.

FIG. 6 is a diagram conceptually showing how the tire pressure is detected by the determiner 20 in FIG. 1 by a hybrid method in which a tire vibration method, a dynamic load radius method, and a vibration level method are combined.

7 is a flowchart conceptually showing the contents of a first signal processing program executed to execute the first signal processing in FIG.

8 is a flowchart conceptually showing the content of a second signal processing program executed to execute the second signal processing in FIG.

9 is a flowchart conceptually showing the contents of a third signal processing program executed to execute the third signal processing in FIG.

10 is a flowchart conceptually showing the contents of a first effectiveness determination program executed to execute the first effectiveness determination in FIG.

11 is a graph for explaining the contents of S72 in FIG.

12 is a graph for explaining the contents of S74 in FIG.

FIG. 13 is a flowchart conceptually showing the contents of a second effectiveness determination program executed to execute the second effectiveness determination in FIG.

FIG. 14 is a graph for explaining the content of S102 in FIG.

FIG. 15 is a flowchart conceptually showing the contents of a third effectiveness determination program executed to execute the third effectiveness determination in FIG.

16 is a graph for explaining the contents of S135 in FIG.

FIG. 17 is a flowchart conceptually showing the contents of a first air pressure estimation program executed to execute the first air pressure estimation in FIG.

18 is a flowchart conceptually showing the contents of a second air pressure estimation program executed to execute the second air pressure estimation in FIG.

FIG. 19 is a flowchart conceptually showing the contents of a third air pressure estimation program executed to execute the third air pressure estimation in FIG.

20 is a flowchart conceptually showing the contents of a system selection program executed to operate the system selection unit 64 in FIG.

21 is a flowchart conceptually showing the contents of an air pressure determination program executed to operate the air pressure determination unit 68 in FIG.

FIG. 22 is a diagram for explaining how tire pressure is detected by the hybrid system in which the tire vibration system and the vibration level system are combined in the determiner 20 of the tire abnormality determination device according to the second embodiment of the present invention. is there.

FIG. 23 is a diagram for explaining how tire pressure is detected by a hybrid system in which a dynamic load radius method and a vibration level method are combined in the determiner 20 of the tire abnormality determination device according to the third embodiment of the present invention. Is.

[Explanation of symbols]

10 Wheel speed sensor 20 Judgment device 22 Computer 60 signal processor 62 Effectiveness judging section 64 system selection section 66 Air pressure estimation unit 68 Air pressure determination unit

Continued front page    (72) Inventor Hideki Ohashi             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Katsuhiro Asano             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Eiichi Ono             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Koji Umeno             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. F term (reference) 2F055 AA12 BB19 CC59 DD20 FF49                       GG31

Claims (29)

[Claims] 1. An apparatus for detecting a tire air pressure by estimating the tire air pressure, which is provided in a vehicle in which a wheel, which is configured by enclosing air under pressure inside a tire mounted on a wheel, is supported by a vehicle body, and which estimates the tire air pressure. The wheel speed sensor that detects the angular velocity of the wheel as the wheel speed, and the wheel speed signal that is the time-series data of the wheel speed detected by the wheel speed sensor, the vibration level in a specific frequency range is focused. Detected as a level, while estimating the air pressure based on the detected vibration level of interest, based on the vibration characteristic-related value of the wheel speed signal, which is related to the characteristic of vibration in the specific frequency region, the air pressure A tire pressure detection device including an estimation device that determines whether the estimation is valid. 2. The wheel includes left and right wheels, the wheel speed sensor is provided for each of the left and right wheels, and the estimation device detects the noticed vibration level for each of the left and right wheels and detects the noticed vibration level. The tire air pressure detection device according to claim 1, wherein it is determined whether or not any one of the left and right wheels is abnormal with respect to the air pressure based on the relationship between the left and right wheels of the noted vibration level. 3. The wheel is supported by the vehicle body via a suspension, and the specific frequency range is set within a range between a resonance frequency of vibration of the suspension and a resonance frequency of vibration of the tire. 3. The tire air pressure detection device according to claim 1 or 2, which is provided. 4. The vibration characteristic-related value is different between a state where the detected vibration level of interest is affected by resonance of a vehicle vibration element including the tire as a noise resonance and a state where it is not affected by the resonance. The tire air pressure detection device according to any one of claims 1 to 3, which is a physical quantity that changes so as to take a value. 5. The vibration characteristic related value includes at least one of a vehicle speed, which is a traveling speed of the vehicle, and the wheel speed as a vehicle speed related value, and the estimation device has the vehicle speed related value associated with a first set vehicle speed. The tire air pressure detection device according to claim 4, further comprising a first determination unit that determines that the estimation of the air pressure is valid when the value is equal to or more than a value. 6. The tire air pressure detection device according to claim 4, wherein the vibration characteristic-related value includes a noise resonance characteristic value that directly represents the characteristic of the noise resonance. 7. The noise resonance characteristic value includes a degree of dispersion of a distribution relating to a frequency of occurrence of the resonance frequency of the noise resonance, and the estimation device, when the degree of dispersion is larger than a first set degree of dispersion, The tire air pressure detection device according to claim 6, further comprising a second determination unit that determines that the estimation of the air pressure is valid. 8. The estimation of the air pressure is effective when the noise resonance characteristic value includes the intensity of the resonance frequency of the noise resonance and the estimation device has the intensity equal to or lower than a first set intensity. The tire air pressure detection device according to claim 6 or 7, which includes a third determination means for determination. 9. The vibration characteristic related value includes a vibration level characteristic value representing a characteristic in which a vibration level of the wheel speed signal changes with frequency within a monitoring frequency range set to include the specific frequency range. Claims 4 to 8
The tire air pressure detection device according to any one of 1. 10. The vibration level characteristic value includes a vibration level difference between peak values, which is a difference between two peak values of the vibration level of the wheel speed signal in the monitored frequency region, and the estimation device includes: The tire air pressure detection device according to claim 9, further comprising a fourth determination unit that determines that the estimation of the air pressure is valid when the difference in vibration level between peak values is smaller than the difference in vibration level between set peak values. 11. The vibration estimating method includes a vibration level method for estimating the air pressure based on the vibration level of interest and a method other than the vibration level method for estimating the air pressure. 11. The method according to claim 1, wherein it is determined whether or not the estimation of the air pressure by another method is effective, and the final detected value of the air pressure is determined based on the result. Tire pressure detection device. 12. The estimated value of the air pressure by the vibration level method in a high speed region of a vehicle speed, which is a traveling speed of the vehicle, based on the environment of the vehicle,
The tire air pressure detection according to claim 11, wherein in the low speed region, the estimated value of the air pressure by the other method is preferentially adopted over other estimated values to determine the final detected value of the air pressure. apparatus. 13. The another method focuses on a phenomenon that a characteristic of vibration of the tire changes when the air pressure changes, and the change is reflected in the wheel speed, and based on the wheel speed, The tire air pressure detection device according to claim 11 or 12, which includes a tire vibration method for estimating air pressure. 14. The tire vibration method according to claim 14, wherein the estimation device determines that a vehicle speed related value that is at least one of a vehicle speed that is a traveling speed of the vehicle and the wheel speed is equal to or less than a second set vehicle speed related value. The tire pressure detection device according to claim 13, further comprising a fifth determination unit that determines that the estimation of the air pressure is valid. 15. The estimation of the air pressure by the tire vibration method is effective when the estimation device has a dispersion degree of a distribution related to the occurrence frequency of the resonance frequency of the tire vibration is equal to or less than a second set dispersion degree. Sixth to judge that there is
The tire air pressure detection device according to claim 13 or 14, including a determination means. 16. The estimating device includes seventh determining means for determining that the estimation of the air pressure by the tire vibration method is effective when the resonance frequency intensity of the tire vibration is within a set range. The tire air pressure detection device according to any one of claims 13 to 15. 17. The another method focuses on the phenomenon that if the air pressure changes, the dynamic load radius of the tire changes and the wheel speed also changes, and the air pressure is estimated based on the wheel speed. 12. A dynamic load radius method is included.
17. The tire air pressure detection device according to any one of 1 to 16. 18. The dynamic load radius method is used by the estimation device when a vehicle speed related value that is at least one of a vehicle speed that is a traveling speed of the vehicle and the wheel speed is equal to or less than a third set vehicle speed related value. The tire pressure detection device according to claim 17, further comprising an eighth determination unit that determines that the estimation of the air pressure is valid. 19. The estimation of the air pressure by the dynamic load radius method is effective when the estimation device has a gradient of a change in the wheel speed with respect to a vehicle speed, which is a traveling speed of the vehicle, that is gentler than a preset change gradient. The tire air pressure detection device according to claim 17 or 18, which includes a ninth determination means for determining. 20. The estimation device is effective in estimating the air pressure by the dynamic load radius method when the slip ratio related value related to the slip ratio occurring in the wheel is equal to or less than a set slip ratio related value. 20. The tire air pressure detection device according to claim 17, further comprising a tenth determination means for determining that 21. An apparatus for detecting a tire air pressure by estimating the air pressure of the tire, which is provided in a vehicle in which a wheel configured by enclosing air under pressure inside a tire mounted on a wheel is supported by a vehicle body. A method for estimating the air pressure based on a wheel speed sensor that detects the angular speed of the wheel as a wheel speed, and a wheel speed signal that is time-series data of the wheel speed detected by the wheel speed sensor, a) a vibration level method in which a vibration level of the wheel speed signal in a specific frequency range is detected as a vibration level of interest and the air pressure is estimated based on the detected vibration level of interest; and (b) the air pressure changes. Focusing on the phenomenon that the dynamic load radius of the tire changes and the wheel speed also changes, the air pressure is estimated based on the wheel speed. Dynamic load radius method, and (c) focusing on the phenomenon that the characteristics of the tire vibration change if the air pressure changes, and the change is reflected in the wheel speed. And a tire vibration detecting method for estimating the air pressure according to the vibration level method, the dynamic load radius method, and the tire vibration method. 22. The estimating device respectively determines whether or not the estimation of the air pressure by the vibration level method, the dynamic load radius method, and the tire vibration method is effective based on the environment of the vehicle, and a result thereof is determined. 22. The tire air pressure detection device according to claim 21, wherein a final detection value of the air pressure is determined based on the above. 23. Based on the environment of the vehicle, the estimating device calculates at least an estimated value of the air pressure by the vibration level method in a high speed region of a vehicle speed which is a traveling speed of the vehicle, and in an intermediate speed region, The estimated value of the air pressure by the dynamic load radius method, in the low speed region, at least the estimated value of the air pressure by the tire vibration method is adopted preferentially over other estimated values to determine the final detected value of the air pressure. The tire air pressure detection device according to claim 21 or 22, which is provided. 24. An apparatus for detecting a tire air pressure by estimating the air pressure of the tire, which is provided in a vehicle in which a wheel configured by enclosing air under pressure in a tire mounted on a wheel is supported by a vehicle body. A method for estimating the air pressure based on a wheel speed sensor that detects an angular velocity of the wheel as a wheel speed and a wheel speed detected by the wheel speed sensor includes (a) A vibration level method of detecting a vibration level of a wheel speed signal, which is time-series data, in a specific frequency region as a vibration level of interest, and estimating the air pressure based on the detected vibration level of interest; and (b) the air pressure. Changes in the characteristics of the tire vibration, and the change is reflected in the wheel speed. And a tire vibration method for estimating the pneumatic Te, and the tire air pressure detecting device comprising an estimation unit for estimating the air pressure by the their vibration level mode and tire vibration method. 25. The estimating device determines whether or not the estimation of the air pressure by the vibration level method and the tire vibration method is effective based on the environment of the vehicle,
The tire air pressure detection device according to claim 24, which determines a final detection value of the air pressure based on the result. 26. The estimation device, based on the environment of the vehicle, estimates the air pressure by the vibration level method in a high speed region of a vehicle speed that is a traveling speed of the vehicle.
25. In the low speed range, the estimated value of the air pressure by the tire vibration method is preferentially adopted over other estimated values to determine the final detected value of the air pressure.
Or the tire air pressure detection device described in 25. 27. An apparatus for detecting the air pressure of a tire by estimating the air pressure of the tire, which is provided in a vehicle in which a wheel configured by enclosing air under pressure inside a tire mounted on the wheel is supported by a vehicle body. A method for estimating the air pressure based on a wheel speed sensor that detects an angular velocity of the wheel as a wheel speed and a wheel speed detected by the wheel speed sensor includes (a) A vibration level method of detecting a vibration level of a wheel speed signal, which is time-series data, in a specific frequency region as a vibration level of interest, and estimating the air pressure based on the detected vibration level of interest; and (b) the air pressure. The phenomenon that the dynamic load radius of the tire changes and the wheel speed also changes if changes in The and a dynamic load radius scheme for estimating and tire inflation pressure detecting apparatus comprising an estimating device for estimating the air pressure by the their vibration level mode and the dynamic load radius method. 28. The estimating device respectively determines whether or not the estimation of the air pressure by the vibration level method and the dynamic load radius method is effective based on the environment of the vehicle,
The tire air pressure detection device according to claim 27, wherein a final detection value of the air pressure is determined based on the result. 29. The estimation device, based on the environment of the vehicle, estimates the air pressure by the vibration level method in a high speed region of a vehicle speed which is a traveling speed of the vehicle.
28. In the low speed range, the estimated value of the air pressure by the dynamic load radius method is preferentially adopted over other estimated values to determine the final detected value of the air pressure.
Or the tire air pressure detection device according to item 28.