JP3518575B2 - Tire pressure estimation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire air pressure estimating device for estimating the air pressure of a tire mounted on each wheel based on the rotation state of the wheel.

[0002]

2. Description of the Related Art Conventionally, based on the wheel speed of each wheel,
There has been proposed a tire air pressure estimation device that estimates the air pressure of a tire mounted on each wheel. For example, JP-A-6-3
Japanese Patent No. 28919 discloses a tire air pressure estimation device that extracts a tire resonance frequency component from a detection signal of a wheel speed sensor and estimates a tire air pressure state from the resonance frequency component. In addition, since the tire air pressure-resonance frequency characteristics change according to the type of tire, a selection switch is provided to select the type of tire installed, and after the tire is replaced, the driver operates the selection switch. Then, the type of the mounted tire is set. In this way, the tire type is preliminarily set by the driver, and thus the tire air pressure state estimation process according to the tire type is executed.

[0003]

However, when the tire type is set by operating the selection switch as described above, the type of tire to be mounted may be different between the front wheel and the rear wheel. Therefore, the selection switch on the front wheel side and the rear wheel are different. It is necessary to separately provide the selection switch on the side. Therefore, not only the number of switches increases, but also the setting operation becomes complicated. Further, the setting operation must be executed after the tires are replaced, and if the setting is forgotten or an incorrect setting is made, there is a possibility that the accurate estimation process of the tire air pressure state cannot be executed.

The present invention has been made to solve such a problem, and an object thereof is to make an optimum estimation without requiring any operation by a driver even when tires are replaced. It is to provide a tire pressure estimation device that can perform processing.

[0005]

Therefore, a tire air pressure estimating device according to a first aspect of the present invention is a tire air pressure estimating device that estimates the air pressure of a tire mounted on a wheel. Which has a plurality of observers for estimating the air pressure of the tire mounted on each wheel and a rotation state detecting means for outputting a detection signal corresponding to the selected tire, and selecting one of the observers according to the mounted tire. Means, the tire pressure estimation means for estimating the air pressure of the tire mounted on each wheel based on the detection signal by the observer selected by the selection means, and the tire mounted on any specific wheel of each wheel And an air pressure detecting means for detecting the air pressure of the tire, and the selecting means is the estimated air pressure and the air pressure estimated by the tire air pressure estimating means. On the basis of the detected air pressure that has been detected by the detecting means, and selects one of the observer.

Since the selecting means selects the observer based on the estimated air pressure and the detected air pressure, the optimum observer can be selected without requiring the driver's operation.

A tire air pressure estimating device according to a second aspect of the invention is a tire air pressure estimating device that estimates the air pressure of a tire mounted on a wheel, detects the rotation state of each wheel,
It has a rotation state detecting means for outputting a detection signal according to the rotation state and a plurality of observers for estimating the air pressure of the tire mounted on each wheel, and selects one of the observers according to the mounted tire. And a tire air pressure estimating means for estimating the air pressure of a tire attached to each wheel based on a detection signal by the observer selected by the selecting means, and attached to any one of the specific wheels. And a pneumatic pressure detecting means for detecting the pneumatic pressure of the tire, and the selecting means, when the pneumatic pressure detected by the pneumatic pressure detecting means is within a predetermined range, the resonance frequency of the tire included in the detection signal. It is characterized by selecting one of the observers based on.

The detection signal includes a resonance frequency unique to each tire, and this resonance frequency changes depending on the tire air pressure. Therefore, the selection means determines that the tire air pressure is normal when the air pressure detected by the air pressure detection means is within a predetermined range, and selects an optimum observer based on the resonance frequency included in the detection signal at this time. select.

According to a third aspect of the present invention, there is provided the tire pressure estimating device according to the first or second aspect, in which the air pressure estimating means of each tire is based on the detected air pressure of the tire mounted on a specific wheel and the estimated air pressure of this tire. It comprises a correction means for correcting the estimated air pressure.

Since the correcting means corrects the estimated air pressure of each tire based on the detected air pressure of the tire directly detected, it is possible to estimate the air pressure with high accuracy.

According to a fourth aspect of the present invention, there is provided a tire air pressure estimating device in which the air pressure detecting means of the first or second aspect is composed of a pressure sensor having a predetermined threshold value at which the sensor output changes before and after the air pressure detecting means.

The air pressure detecting means is not a linear sensor,
By using a pressure sensor having a predetermined threshold value at which the sensor output changes, power saving and simplification of the sensor can be achieved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
Description will be given with reference to the accompanying drawings.

FIG. 1 schematically shows the construction of a tire air pressure estimating device according to this embodiment. Wheel speed sensors 10 as rotation state detecting means for detecting the rotation states of the respective wheels are provided on the front, rear, left and right wheels FL, FR, RL, RR mounted on the respective wheels.

The wheel speed sensor 10 is, as shown in FIG.
The rotor 11 includes a gear-shaped rotor 11 made of a magnetic material and a pickup coil 12, and the rotor 11 includes wheels FL and F.
It rotates together with R, RL, and RR, and tooth portions 13 having a constant pitch are formed around it. The pickup coil 12 generates a voltage that periodically changes as the tooth portion 13 of the rotor 11 passes. Then, this voltage is shaped into a rectangular wave by the waveform shaper 14 and output.

Each wheel FL is provided with an air pressure sensor 20 as an air pressure detecting means for directly detecting the air pressure of the tire mounted on the wheel FL. The air pressure sensor 20 has two threshold values whose sensor output changes before and after the air pressure sensor 20. As shown in FIG. 5A, the two threshold values Sh and Sl are set so that normal tire air pressure (normal pressure) exists between the threshold value Sh and the threshold value Sl. The detection results are (a), (b),
Any of the three detection states (2-bit information) of (c) is output. For example, if the detection result is (b),
It can be seen that the measured tire pressure is within a predetermined range that is considered normal pressure.

The threshold values Sh and Sl are set as shown in FIG.
As shown in (b), it is also possible to set such that the center value between the normal pressure and the alarm pressure exists between the threshold value Sh and the threshold value Sl. In this case, the detection result is (d),
If there are three detection states of (e) and (f) and the detection result is (d), it can be seen that the measured tire air pressure is within a predetermined range considered to be normal pressure.

The detection signals of the wheel speed sensor 10 and the air pressure sensor 20 are given to the tire air pressure estimating device 30. The tire pressure estimation device 30 includes a plurality of observers according to the tire type, and the wheel speed sensor 1 can be detected by any one of the observers selected as described below.
0 and the detection signals of the air pressure sensor 20 based on each wheel F
Estimate the air pressure of the tires attached to L, FR, RL, and RR. Then, when the tire pressure attached to any of the wheels is lowered, an alarm process is performed to notify the driver of the tire pressure drop, such as activating the warning device 40 to turn on a warning lamp.

Next, the operation of the tire air pressure estimating device 30 will be briefly described with reference to the flowchart of FIG.

First, in step 102 (hereinafter "step" is referred to as "S"), the detection signals of the wheel speed sensor 10 and the air pressure sensor 20 are read, and in step S104, the read detection signals of the wheel speed sensor 10 are also read. Then, the wheel speed of each wheel FL, FR, RL, RR is calculated.

In the subsequent S106, the wheels FL, FR, RL, RR are set based on the wheel speeds calculated by the observer preset according to the tires currently mounted.
Estimate the air pressure of the tire mounted on the. The observer selection processing will be described in detail later.

Here, a plurality of provided observers (disturbance observers) will be schematically described. Each observer is constructed based on the wheel model shown in FIG. 4, and the wheel is treated as a linear system in which the rim side portion 1 and the belt side portion 2 are connected by a torsion spring 3 having a spring constant K. ing. When the tire air pressure changes, the spring constant K of the torsion spring 3 changes and is reflected as a disturbance in this linear system. Therefore, the tire pressure is estimated by estimating the disturbance using the method of the disturbance observer (Japanese Patent Laid-Open No. 8-34215).
No.). Thus, in S106, the wheels FL,
Estimate the air pressure of tires mounted on FR, RL, and RR.

In subsequent S108, the estimated air pressures estimated for the respective tires in S106 are set to Pfl, Pfr, Prl, P.
rr is corrected using the air pressure A detected by the air pressure sensor 20. That is, since the wheel to which the air pressure sensor 20 is attached is the wheel FL, the correction coefficient Kp is set to Kp = A / Pfl based on the estimated air pressure Pfl of the tire attached to the wheel FL and the detected air pressure A. Then, this correction coefficient Kp is used as the estimated air pressure Pfl, Pfr, P of each tire.
The estimated air pressure is corrected by multiplying rl and Prr.
As described above, the estimated air pressure is corrected based on the value directly detected by the air pressure sensor 20, so that a more accurate estimated air pressure can be obtained.

In subsequent S110, it is determined whether or not the estimated air pressure of each tire corrected in S108 is less than or equal to the determination reference value Ps. When the estimated air pressures of all the tires are larger than the determination reference value Ps, it is determined that the air pressures of all the tires are normal, and the estimated air pressures of any of the tires are the determination reference value Ps.
In the case of s or less, the alarm device 40 performs an alarm process indicating that the tire pressure of the corresponding wheel is abnormal.

The tire air pressure estimating device 30 continuously executes the estimation processing and the determination processing in this manner to monitor the air pressure state of the tire during traveling.

Next, the selection process for selecting the observer used in S106 will be described with reference to the flowchart of FIG.

First, in S202, the air pressure sensor 2
The detected air pressure of 0 and the estimated air pressure estimated in S106 are read. In subsequent S204, based on the read detected air pressure and estimated air pressure, it is determined whether or not detected air pressure-α> estimated air pressure. Note that “α” is a value indicating the accuracy range of the observer. When the determination in S204 is affirmative (“Yes” in S204), the detected air pressure is −
From α> estimated air pressure, the estimated air pressure by the currently selected observer is estimated to be a small value that exceeds the range of accuracy range α than the actually detected detected air pressure. In this case, In S206, the observer whose peak value is on the higher frequency side than the present is temporarily selected,
This routine ends.

On the other hand, if the determination in S204 is negative ("No" in S204), the process proceeds to S208. S20
At 8, it is determined whether or not detected air pressure + α <estimated air pressure, based on the read detected air pressure and estimated air pressure. If the determination in S208 is affirmative, (S2
08: “Yes”), the estimated air pressure by the currently selected observer is estimated to be a value larger than the actually detected detected air pressure from the detected air pressure + α <estimated air pressure, which exceeds the range of the accuracy range α. Will be
In this case, the process proceeds to S210, the observer whose peak value is on the lower frequency side than the present is temporarily selected, and this routine is ended.

After passing through S206 and S210 in this way, the processing from S202 onward is repeated again, but the estimated air pressure read in S202 in the next routine is the estimated air pressure by the observer temporarily selected in the previous routine. , S based on this new estimated air pressure value
The processing after 204 is repeated.

Then, the judgment process proceeds, and if the judgment in S208 is negative ("No" in S208), S21
Go to 2. In the situation of proceeding to S212, the detected air pressure −α ≦
Estimated air pressure ≦ detected air pressure + α, and the estimated air pressure by the currently selected observer is within the range of accuracy range α with respect to the actually detected detected air pressure. That is, the current observer is the optimum observer according to the currently installed tire, and the current observer is main-selected and set as the observer used in the tire air pressure estimation processing to be performed in S106.

At S106, the tire pressure is estimated by the observer thus selected.

The observer selection process can also be carried out as follows.

The detection signal of the wheel speed sensor 10 contains the vibration frequency component of the tire. When the output distribution of the detection signal is subjected to frequency analysis, a peak value is shown at the resonance frequency peculiar to each tire. Varies with tire pressure. Therefore, if the resonance frequency in a normal tire pressure state is obtained in advance for each tire type and the resonance frequency of the tire is detected under normal tire pressure, the tire type, that is, the optimum observer according to the tire type is selected. can do. Further, the plurality of observers described above are provided with bandpass filters corresponding to the respective observers, and in the above-described linear system of the disturbance observer system, a set of bandpass filters and observers is uniquely determined. Therefore, in the observer selection processing, a set of bandpass filter and observer (disturbance observer) is selected in accordance with the tire mounted.

The observer selection processing will be described below with reference to the flowchart of FIG.

First, in S302, it is determined whether or not the ignition switch is turned on. When the ignition switch is turned on, the process proceeds to S304, the detection result of the air pressure sensor 20 is read, and it is determined whether or not the detected air pressure is normal pressure. . For example, the threshold value of the air pressure sensor 20 is shown in FIG.
When the setting is as shown in (b), it is determined whether or not the detection state of the air pressure sensor 20 is (d). S
When it is determined in 304 that the detected state of the air pressure sensor 20 is not (d) (not normal pressure), the process proceeds to S306, the detected tire air pressure is stored in the low pressure state, and this routine is executed. To finish.

When it is determined in S304 that the detection state of the air pressure sensor 20 is (d) (normal pressure),
In step S308, the determination result for the past T seconds is read, and it is determined whether or not the air pressure detected by the pressure sensor 20 has a low pressure state for the past T seconds. If there is no low pressure state in the past T seconds, this routine is ended.

If it is determined in S308 that the low pressure state has been present in the past T seconds, it can be determined that the low pressure state has been recovered because the current detected air pressure of the air pressure sensor 20 is the normal pressure. That is, it is determined that tire replacement or the like has been performed, and the process proceeds to the observer initialization routine in S400.

FIG. 8 shows the initialization routine. In this initialization routine, a set of band pass filter and observer (disturbance observer) is selected.
The tire air pressure estimation device 30 includes band pass filters 1 to 1.
3 and the observers 1 to 3 corresponding thereto will be described as an example.

First, the detection signal of the wheel speed sensor 10 is given to the band pass filters 1 to 3 and the output thereof is examined. S4
The root mean square of the output of the band pass filter 1 is calculated in 02, the root mean square of the output of the band pass filter 2 is calculated in S404, and the root mean square of the output of the band pass filter 3 is calculated in S406.

When the bandpass filters 1 to 3 have the frequency characteristics shown in FIG. 9, assuming that the frequency response of the wheel speed detected by the wheel speed sensor 10 has the distribution shown in the upper part of FIG. The root mean square of the output of the bandpass filter including the peak value (resonance point) of the frequency distribution becomes the largest. Therefore, in S408, the root mean squares of the filter outputs calculated in S402 to S406 are compared, and the bandpass filter having the maximum calculation result is selected. In the example of FIG. 9, the bandpass filter 2 is selected. Then, in subsequent S410, an observer corresponding to this bandpass filter 2 is selected.

The observer can be selected in this way, and in S106 described above, the tire pressure is estimated by the observer thus selected.

Among the embodiments described above, the flowchart of FIG. 7 exemplifies the case where the observer selection process is started at the timing when the air pressure state returns to the normal pressure based on the detection result of the air pressure sensor 20. However, for example, the observer selection process can be started at the timing when the ignition switch is turned on under the condition that the pressure detected by the air pressure sensor 20 is the normal pressure.

Although the air pressure sensor 20 is exemplified by a sensor having two threshold values, a pressure sensor having one threshold value and outputting two detection states may be used. In this case, the threshold value S is the normal pressure of the tire and the accuracy (variation width) of the observer method ± 2Q.
On the other hand, the normal pressure is set to be −Q ≦ S ≦ normal pressure.

[0044]

As described above, according to the tire air pressure estimating device of each claim, the air pressure of the tire mounted on any one of the wheels is detected by the air pressure detecting means, and Since it was decided to use the detection result to select the observer by the selection means, even if tires were replaced, the optimum observer according to the tire type could be selected without requiring any operation by the driver. It is possible to select, and it is possible to continue to carry out the optimum estimation process even after the tire is replaced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a tire air pressure estimating device according to an embodiment.

FIG. 2 is an explanatory diagram schematically showing the configuration of a wheel speed sensor.

FIG. 3 is a flowchart showing a tire pressure estimation process.

FIG. 4 is a diagram showing a dynamic model of a wheel.

5 (a) and 5 (b) are explanatory views showing threshold values set by an air pressure sensor.

FIG. 6 is a flowchart showing a process of selecting an observer.

FIG. 7 is a flowchart showing a process of selecting an observer.

FIG. 8 is a flowchart showing an initialization routine in the flowchart of FIG.

FIG. 9 is an explanatory diagram showing a relationship between a frequency response of a wheel speed input to each bandpass filter, a frequency characteristic of each filter, and a filter output.

[Explanation of symbols]

FL, FR, RL, RR ... Wheels, 10 ... Wheel speed sensor,
20 ... Air pressure sensor, 30 ... Tire pressure estimation device, 4
0 ... Alarm device.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-8-230422 (JP, A) JP-A-7-329526 (JP, A) JP-A-5-221208 (JP, A) JP-A-6- 328919 (JP, A) JP-A-6-115328 (JP, A) JP-A-10-217724 (JP, A) JP-A-8-34215 (JP, A) JP-A-9-39524 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 23/06 B60C 23/02

Claims (4)

(57) [Claims] 1. A tire air pressure estimating device for estimating air pressure of a tire mounted on a wheel, comprising: a rotation state detecting means for detecting a rotation state of each wheel and outputting a detection signal according to the rotation state; Having a plurality of observers for estimating the air pressure of the mounted tires, selecting means for selecting one of the observers according to the mounted tires, by the observer selected by the selecting means, the detection signal, A tire air pressure estimating means for estimating the air pressure of a tire originally attached to each wheel, and an air pressure detecting means provided on a tire attached to any one of the wheels, and detecting an air pressure of the tire. The selection means is based on the estimated air pressure estimated by the tire air pressure estimation means and the detected air pressure detected by the air pressure detection means. There are, tire air pressure estimating apparatus characterized by selecting one of the observer. 2. A tire air pressure estimating device for estimating the air pressure of a tire mounted on a wheel, comprising: a rotation state detecting means for detecting a rotation state of each wheel and outputting a detection signal according to the rotation state; Having a plurality of observers for estimating the air pressure of the mounted tires, selecting means for selecting one of the observers according to the mounted tires, by the observer selected by the selecting means, the detection signal, A tire air pressure estimating means for estimating the air pressure of a tire originally attached to each wheel, and an air pressure detecting means provided on a tire attached to any one of the wheels, and detecting an air pressure of the tire. The selection means, when the detected air pressure of the air pressure detection means is within a predetermined range, the resonance frequency of the tire included in the detection signal. DOO, the tire air pressure estimating apparatus characterized by selecting one of the observer. 3. The air pressure estimating means comprises a correcting means for correcting the estimated air pressure of each tire based on the detected air pressure of the tire mounted on the specific wheel and the estimated air pressure of the tire. 2. The tire pressure estimation device according to 2. 4. The tire air pressure estimating device according to claim 1, wherein the air pressure detecting means is a pressure sensor having a predetermined threshold value at which a sensor output changes before and after the air pressure detecting means.