JP3339749B2 - Tire pressure abnormality judgment 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 pressure abnormality judging device for judging whether or not a tire air pressure of a vehicle is abnormally low, and more particularly to a technique for achieving both the accuracy of the judgment and the quick response. It is about.

[0002]

2. Description of the Related Art The above-described tire pressure abnormality judging device generally detects a tire pressure itself of a vehicle or an air pressure related quantity which is a physical quantity related thereto, and when the detection result satisfies a predetermined low pressure judging condition, the tire pressure is judged. Is determined to be abnormally low.

[0003] One conventional example thereof is described in Japanese Patent Application Laid-Open No. 3-50006. This is because the rotational speed difference between the left and right wheels is detected, the rotational speed difference between the left and right wheels is detected as a tire pressure related amount, and the rotational speed difference is not 0 and the rotational speed difference exists between the left and right wheels. A tire pressure abnormality determination device that determines that the air pressure of one of the left and right wheels is abnormally low when a low pressure determination condition of continuing for a predetermined time or more is satisfied.

[0004]

In this conventional apparatus for judging a tire air pressure abnormality, in order to ensure the accuracy of the judgment of a decrease in the air pressure, the air pressure immediately drops abnormally even if a rotational speed difference occurs between the right and left wheels. It is determined that the air pressure has dropped abnormally only when the time during which the rotational speed difference between the left and right wheels continues to occur reaches the set value. Further, since the tire pressure abnormality determination apparatus adopts the premise that the possibility of the air pressure drop is always the same, the low pressure determination condition, that is, the time during which the rotational speed difference between the left and right wheels continues to occur, is determined. The time to reach is fixed.

[0005] However, the likelihood of air pressure drop is not always the same. For example, if the air inside the tire is left untouched even if there is no damage to the tire, it will naturally pass through the rubber of the tire and leak little by little, or it will leak little by little from the small gap between the tire and the wheel There is a phenomenon referred to as a natural leak, and the possibility that the air pressure is reduced increases as the use period of the tire, the running time, and the like increase due to the natural leak. For this reason, in the conventional tire pressure abnormality determination device, the determination of the pressure decrease is always performed under the same low pressure determination condition regardless of whether the possibility of the decrease in the pressure is high. High and cannot be detected quickly enough in situations where it is desirable to detect the fact of low air pressure as quickly as possible.

[0006] In short, the conventional tire air pressure abnormality judging device has a problem that the accuracy of the air pressure drop judgment and the quick response cannot be sufficiently satisfied at the same time. It is an object of the present invention to make it possible to achieve both the accuracy and the quick response of the air pressure drop determination by estimating the possibility of the air pressure drop and changing the low pressure determination condition according to the probability of the possibility. It is a thing.

[0007]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention detects an air pressure related amount of a tire of a vehicle, and when the detection result satisfies a predetermined low pressure determination condition, the air pressure becomes abnormal. The tire pressure abnormality determination device that determines that the pressure is low, (a) an air pressure drop possibility estimating unit that estimates the likelihood that the air pressure has dropped based on the usage history of the tire, and (b) the low pressure determination condition A low-pressure determination condition changing unit that changes to a condition that is more easily satisfied when the air pressure drop possibility estimating unit estimates that the possibility that the air pressure is low is high is low. It is characterized by having.

It should be noted that the "pneumatic pressure-related amount" does not mean that the pneumatic pressure itself is excluded, but of course includes the pneumatic pressure itself.

[0009]

The amount of decrease in tire air pressure due to natural leakage can be estimated to some extent based on the history of use of the tire, which means that the possibility of air pressure decrease can be estimated from the history of use of the tire. . Therefore, if the air pressure drop determination is performed in consideration of the information based on the estimation, it is possible to sufficiently achieve both the accuracy of the determination and the quick response.

[0010] Based on such knowledge, in the tire pressure abnormality determination apparatus according to the present invention, the air pressure drop possibility estimating unit estimates the high possibility that the air pressure has dropped based on the use history of the tire. Then, the low pressure determination condition changing unit
The low pressure determination condition is changed to a condition that is more easily satisfied when the air pressure drop possibility estimating unit estimates that there is a high possibility that the air pressure has dropped, when the possibility is estimated to be low. That is, even if the detection result is the same, the low-pressure determination condition is changed so that when the possibility of the air pressure drop is high, the air pressure is determined to be abnormally low more easily than when the possibility is low.

[0011]

Therefore, according to the present invention, since the low pressure determination condition is changed so as to adapt to the change in the possibility of the air pressure drop, the fact that the air pressure has dropped in the situation where the possibility of the air pressure drop is high can be further improved. The detection can be performed quickly, and the effect of sufficiently satisfying both the accuracy of the determination of the decrease in air pressure and the quick response can be obtained.

[0012]

Preferred embodiments of the present invention are listed below. (1) The invention according to claim 1, wherein the air pressure drop possibility estimating unit determines at least a running distance of the vehicle from a time when air is sealed in the tire or a time when the tire is replaced with a use history of the tire. And a tire pressure abnormality determination device that estimates that the longer the acquired traveling time is, the higher the possibility that the air pressure is lowered.

(2) The invention according to claim 1, wherein the air pressure drop possibility estimating unit determines at least an elapsed time from when the tire is filled with air or when the tire is replaced (if only the running time is exceeded). Tire stoppage time) as a tire use history, and estimates that the longer the acquired elapsed time is, the higher the possibility that the air pressure is decreasing is.

(3) The invention according to (1) or (2), wherein the air pressure drop possibility estimating unit determines when the air is sealed in the tire or when the tire is replaced based on the operation of the operating member by the driver. A tire pressure abnormality determining device for detecting a time when the tire pressure is detected.

(4) The invention according to (1) or (2), wherein the air pressure drop possibility estimating unit determines whether or not the rate of increase of the detected value of the air pressure related amount while the vehicle is stopped exceeds a reference value. A tire pressure abnormality judging device for judging whether or not the tire is currently filled with air or when the tire has been replaced, when it is determined that the tire pressure has been exceeded.

(5) The tire pressure abnormality judging device according to claim 1, wherein the tire pressure abnormality judging device judges that the air pressure is abnormally low when the detected value of the air pressure related amount becomes equal to or less than a reference value. The tire pressure abnormality determination device, wherein the unit changes the reference value to be larger when it is estimated that the possibility that the air pressure has decreased is high, when the possibility is estimated to be low. .

(6) The tire pressure abnormality determination method according to the first aspect of the present invention, wherein when the number of times that the detected value of the air pressure related amount exceeds the reference value exceeds the reference number, the tire pressure is determined to be abnormally low. In the apparatus, the low-pressure determination condition changing unit includes:
A tire pressure abnormality determination device that changes the reference number to be smaller when it is estimated that there is a high possibility that the air pressure has decreased, than when it is estimated that the possibility is low.

(7) The tire pressure abnormality according to claim 1, wherein the tire pressure is determined to be abnormally low when the time during which the detected value of the air pressure related amount continues to be equal to or more than the reference value exceeds the reference time. In the determination device, the low-pressure determination condition changing unit changes the reference time to be shorter when it is estimated that the possibility that the air pressure is decreasing is high when the possibility is estimated to be low. A tire pressure abnormality determination device.

(8) The invention according to claims 1, (1) to (7), wherein the tire pressure is directly detected by a pressure sensor and a transmitter mounted on the tire side, and a signal corresponding to the tire pressure is generated. In addition, the tire pressure is detected by the method of receiving the signal from the transmitter by the receiver attached to the vehicle body and converting it into tire pressure (signal transmission between the tire and the vehicle is magnetically coupled or radio wave). Judgment device.

(9) The invention according to claims 1, (1) to (7), wherein a detecting section for detecting not the tire pressure itself but a physical quantity related thereto, and a tire based on a detection value by the detecting section. A tire air pressure abnormality determining device including: an estimating unit that estimates air pressure; and a determining unit that determines whether the air pressure is abnormally low based on a relationship between an estimated value of the estimating unit and the low pressure determination condition.

(10) The invention according to (9), wherein the detecting section detects the wheel motion state quantity as the related physical quantity, and the estimating section detects the wheel motion state detected by the detecting section. A tire pressure abnormality determining apparatus for estimating that the tire pressure is estimated to be lower as the frequency is lower among the plurality of frequency components whose intensity is substantially maximum within a set frequency range.

(11) The invention according to (9), wherein the detecting section detects the motion state amount of the wheel as the related physical quantity, and the estimating section includes at least wheel information related to tire pressure. From a wheel information basic value that is a basic value of the wheel motion state amount detected by the detection unit, a disturbance observer that detects a disturbance to the wheel, and based on the detected disturbance, wheel information that is an actual value of the wheel information. A tire pressure abnormality determining device having a wheel information change amount estimating unit for estimating a change amount of an actual value from a wheel information base value.

Here, the "wheel motion state quantity" can be selected from, for example, the rotational speed, rotational angular speed, vertical speed, vertical acceleration, longitudinal speed, longitudinal acceleration, and the like of the wheel.

In the "wheel information related to tire pressure", for example, a spring constant and a damper coefficient of a tire can be selected.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to several embodiments shown in the drawings. In FIG. 2, 10 is a rotor,
Reference numeral 12 denotes an electromagnetic pickup. The rotor 10 rotates together with the wheels 14 shown in FIG. 3, and has a number of teeth 16 on the outer circumference. The electromagnetic pickup 12 generates a voltage that changes periodically as the teeth 16 pass.
This voltage is shaped into a rectangular wave by the waveform shaper 18,
It is supplied to the I / O port 22 of the computer 20. There are four wheels 14, and all the electromagnetic pickups 12 provided on them are connected to a computer 20 via a waveform shaper 18, but only one set is typically shown in FIG.

The wheel 14 is, as shown in FIG.
4 is a tire-equipped wheel having a tire 26 mounted on the outer periphery thereof. As shown in FIG. 4, it is considered that a rim side portion 28 and a belt side portion 30 that are relatively rotatable are connected by a torsion spring 32. Can be. Since the rotor 10 is mounted so as to rotate integrally with the wheel 24, the electromagnetic pickup 12 detects the angular velocity of the rim side portion 28 strictly.

As shown in FIG. 2, the computer 20 has a CPU 40 as a processing device and a ROM as a first storage device.
1 and a RAM 44 as a second storage device, and a control program (not shown) is stored in the ROM 42 so that the rim side rotation speed calculator 4 shown in FIG.
5. This computer 20 is connected to another computer 47. This computer 47
Is a CPU 48 as a processing device, as shown in FIG.
ROM 49 as a first storage device, RAM 50 as a second storage device, and I / O port 5 as an input / output device
9 and a routine for determining a tire air pressure abnormality shown in the flowchart of FIG.
1 stores a disturbance observer 52, a parameter identification unit 53 (correlation calculation unit 56, normalization unit 58 and air pressure) shown in FIG. The change amount calculation unit 60) and the abnormality determination unit 62 are configured.

As shown in FIG. 2, a display device 66 for notifying the driver of the result of the judgment made by the abnormality judging section 62 is connected to the I / O port 51 of the computer 47. Display device 6
Reference numeral 6 denotes a liquid crystal display in this embodiment, but it is also possible to use another display device such as a lamp that lights or blinks, and various types of notification devices including a voice notification device that notifies the driver by voice. Can be adopted. The I / O port 51 of the computer 47 further includes a drive /
A driving / braking torque detecting device 68 for detecting a braking torque by a strain gauge or the like attached to the shaft of the wheel 24.
Is connected. Further, a clock 70 and a traveling distance calculating device 72 are also connected. The clock 70 is a digital type that electrically measures and displays the current time, and the mileage calculating device 72 is a digital type that electrically calculates and displays the mileage from the start of vehicle running to the present. is there.

The disturbance observer 52 is configured based on the model of the wheel 14 shown in FIG. Hereinafter, the configuration of the disturbance observer 52 will be described. Wheel 14
If the rim side portion 28 of the inertia moment J _R and the belt side portion 30 of the inertia moment J _{B that} can be relatively rotated are modeled as being connected by a torsion spring 32 having a spring constant K, (1) to (3) Is established, which constitutes a linear system. _JR ω _R ′ = −Kθ _RB + T ₁ (1) J _B ω _B ′ = Kθ _RB −T _d (2) θ _RB ′ = ω _R −ω _B (3) , Ω _R : angular velocity of rim side 28 ω _R ': angular acceleration of rim side 28 ω _B : angular velocity of belt side 30 ω _B ': angular acceleration of belt side 30 θ _RB : rim side 28 and belt Torsion angle with side 30 T ₁ : Driving / braking torque detected by driving / braking torque detecting device 68 T _d : Disturbance torque from road surface

Although a damper actually exists between the rim side portion 28 and the belt side portion 30, its influence is relatively small, and therefore its existence is ignored in this embodiment.

If the above state equation is expressed using a vector and a matrix, the following equation (4) is obtained.

[0032]

(Equation 1)

Here, the air pressure of the tire 26 changes, and the spring constant of the torsion spring 32 changes from the normal value K to K + ΔK.
The state equation of the wheel 14 when the state is changed to the equation (5).

[0034]

(Equation 2)

That is, a change in the spring constant K by ΔK is equivalent to a disturbance represented by the last term on the right side of the equation (6) being applied to the normal tire 26. Since this disturbance includes information on the change amount ΔK of the spring constant K, and the spring constant K changes according to the air pressure of the tire 26,
By estimating the disturbance, the amount of change in the tire air pressure can be detected. The disturbance observer is used for the estimation of the disturbance. If the torque _Td from the road surface is also treated as a disturbance, the disturbance w to be estimated is expressed by the following equation (6).

[0036]

(Equation 3)

However, theoretically, only one element of the disturbance [w] can be estimated, so that the second element w ₂ is estimated. By defining the disturbance w ₂ in (7), for the state equation of the wheel 14 is made as a (8), constitute a disturbance observer based on the equation (8). w ₂ = (− 1 / J _B ) T _d + (ΔK / J _B ) θ _RB (7)

[0038]

(Equation 4)

The disturbance observer estimates a disturbance as one of the state variables of the system. Therefore, (7) for inclusion in the state of the disturbance w ₂ system equation to approximate the disturbance dynamics to be estimated by equation (9). w ₂ ′ = 0 (9) This means that the continuously changing disturbance is approximated stepwise (zero order approximation) as shown in FIG. 5, and the disturbance estimation speed of the disturbance observer 52 is estimated. This approximation is well tolerated if it is fast enough compared to the change in disturbance to be made. From equation (9), if the disturbance w ₂ is included in the state of the system, an extended system of equation (10) is configured.

[0040]

(Equation 5)

In the equation (10), [ω _B θ _RB w ₂ ] ^T cannot be detected. Therefore, if the disturbance observer 52 is configured based on this system,
The disturbance w ₂ and the state variables ω _B and θ _RB that cannot be measured originally can be estimated. For simplicity of description, the vectors and matrices in equation (10) are decomposed and expressed as follows.

[0042]

(Equation 6)

At this time, the state [z] = [ω _B θ _RB w
₂ ] The configuration of the minimum dimension observer for estimating ^T is expressed by equation (11). [Z _p ′] = [A ₂₁ ] [x _a ] + [A ₂₂ ] [z _p ] + [B ₂ ] [u] + [G] ｛[x _a ′] − ([A ₁₁ ] [x _a ] + [A ₁₂ ] [z _p ] + [B ₁ ] [u])｝ = ([A ₂₁ ] − [G] [A ₁₁ ]) [x _a ] + ([A ₂₂ ] − [G] [ _{A 12]) [z p]} + [G] [x a '] + ([B 2] - [G] [B 1]) [u] ··· (11) However, [z _p]: [z ] [Z _p ']: Rate of change of the estimated value [z _p ] [G]: gain that determines the estimated speed of the disturbance observer 52 This equation is represented by a block diagram as shown in FIG. In the figure, [I] is a unit matrix, and s is a Laplace operator. If the error [e] between the true value [z] and the estimated value [z _p ] is [e] = [z] − [z _p ], and the rate of change of the error [e] is [e ′]. , (12) are obtained. [E '] = ([A 22] - [G] [A 12]) [e] ··· (12) which represents the estimated property of the disturbance observer 52, the matrix ([A _22] - [G [A ₁₂ ]) is the pole of the disturbance observer 52. Therefore, the estimated speed of the disturbance observer 52 increases as the eigenvalue moves away from the origin on the left half surface of the s-plane. The observer gain [G] may be determined so as to achieve a desired estimated speed.

The disturbance observer 5 configured as described above
2, the torsion spring 3 receives the angular velocity ω _R calculated in consideration of the tire radius R from the rotation speed v of the wheel 14 calculated in the rim side rotation speed calculation unit 45.
When the spring constant K of No. 2 changes by ΔK, the disturbance w ₂ represented by the equation (7) is estimated, and the disturbance estimated value w _2p is obtained.
Along with the disturbance, the angular velocity ω _B of the belt side portion 30 that cannot be detected and the torsion angle θ _RB between the rim side portion and the belt side portion are also estimated, and estimated values ω _Bp and θ _RBp are obtained, respectively.

The rotational speed v of the wheel 14 is calculated based on the peripheral speed.
(Wheel 1 from the road surface with the tire deformed by the load
Distance to the center of the tire 4), which is
It depends on the air pressure. Therefore, a normal radius R when the air pressure is normal is used initially. However, if a change in the air pressure of the tire 26 is found by a process described later, the air pressure is obtained from a tire diameter table stored in the ROM 42 in advance. The tire radius R corresponding to the change is read and used.

Using the disturbance w _2p and the torsion angle θ _RBp , a correlation operation is performed in a correlation operation unit 56, and a normalization unit 58
, The change in the spring constant K of the torsion spring 32 is obtained.

The acquisition of the change in the spring constant K of the torsion spring 32 will be described with reference to the flowchart of FIG. In the initial setting of S21, the integer i is reset to 1, and
(7) the cross-correlation C (w _2p, θ _RBp) between the estimated value w _2p and torsion angle estimate theta _RBp of the disturbance w ₂ expressed by the equation estimated torsion angle value theta _RBp of the autocorrelation C (theta _RBp, θ _RBp ) is reset to 0. The contents of the cross-correlation memory and the auto-correlation memory of the RAM 50 are set to zero.

Subsequently, at step S22, the current estimated disturbance value w
_{2p (i)} and the estimated torsion angle θ _{RBp (i)} are read and S
At 23, the product of the disturbance estimation value w _{2p (i)} and the torsion angle estimation value θ _{RBp (i)} is calculated and added to the cross-correlation C (w _2p , θ _RBp ). However, when S23 is first executed, the cross-correlation C (w _2p , θ _RBp ) is 0, and therefore, the estimated disturbance w _{2p (i)} and the estimated torsion angle θ _{RBp (i) are} stored in the cross-correlation memory. Is merely stored. Similarly, the square of the estimated torsion angle θ _{RBp (i)} is calculated in _S24 and added to the autocorrelation C (θ _RBp , θ _RBp ) in the autocorrelation memory.

In S25, it is determined whether or not the integer i has become equal to or greater than a predetermined reference value M. Since the determination is initially NO, the integer i is increased by 1 in S26,
S22 to S24 are executed again. When this execution is repeated M times, the determination in S25 becomes YES, and the cross-correlation C
(W _2p , θ _RBp ) and autocorrelation C (θ _RBp ,
One calculation of θ _RBp ) ends.

As described above, the cross-correlation C (w _2p , θ _RBp ) and the autocorrelation C (θ _RBp , θ
_RBp ) is obtained, the L _K value is obtained by the normalizing section 58 by the equation (13), and is stored in the L _K value memory of the RAM 50. L _k = C (w _2p , θ _RBp ) / C (θ _RBp , θ _RBp ) (13) The L _K value is expressed by equation (14) based on equation (7). L _k = (− 1 / J _B ) C ₀ + ΔK / J _B (14) where C ₀ is C (T _dp , θ _RBp ) / C (θ _RBp , θ
_RBp ), which is independent of the change in the spring constant K, and can be compensated for by _obtaining the tire pressure in a normal state in advance. Also, C (T
_dp , θ _RBp ) is the estimated value of the disturbance torque T _d and the torsion angle θ _RB
Represents the cross-correlation with the estimated value.

In the air pressure change amount calculating section 60, L_K
L stored in value memory_K= C (w_2p, Θ_RBp) /
C (θ_RBp, Θ_RBp), The air pressure P of the tire 26
Of the actual value from the normal value is determined. L
_KThe relationship between the value and the change amount ΔP is used as a tire pressure table.
Is stored in the ROM 49 in advance, and L _K
The air pressure change amount ΔP corresponding to the value is determined.

In the abnormality judging section 62, the calculated current change amount ΔP is compared with a negative reference value ΔP ₀ , and the judgment that the change amount ΔP is smaller than the reference value ΔP ₀ is continuously made N times. When it is repeated, it is determined that the air pressure of the tire 26 is abnormally low, and the driver is notified by the display device 66 to that effect. Even if it is once determined that the change amount ΔP is smaller than the reference value ΔP _0, it is not immediately determined that the air pressure is abnormally low. If the air pressure is abnormally low only when the reference value is repeated N times continuously. The determination is made in order to avoid erroneous determination due to the estimation error of the change amount ΔP. However, the reference value N is not a fixed value but a variable value. Paying attention to the fact that the possibility that the air pressure is decreasing is not always the same, it is a variable value that decreases as the possibility that the air pressure decreases is high, so that the air pressure decrease can be detected quickly It is possible.

The possibility of reduced air pressure generally depends on the tire 26
Increases as the elapsed time T from when air is sealed in the vehicle increases, and increases as the traveling distance L of the vehicle increases. Therefore, the abnormality determination unit 62 determines the reference value N based on at least one of the elapsed time T and the travel distance L.
Is determined, and a reference value determination routine shown in FIG. 9 is provided for this reference value determination.

The disturbance observer 52, the correlation calculator 56, the normalizer 58, and the air pressure change calculator 60 shown in FIG.
Each function of the abnormality determination unit 62 has been described individually. Hereinafter, the operation of all the components will be described based on the flowchart of FIG. 7 and the flowchart of FIG.

In the tire pressure abnormality determination routine of FIG. 7, first, in S101, the integer n is reset to 0. Next, in S102, the disturbance observer 52
Are initialized. Subsequently, in S103, the rotational speed v is read from the computer 20, and then, in S104, the disturbance w ₂ and the torsion angle θ _RB are respectively estimated by using a disturbance observer based on the read rotational speed v. That is, the disturbance observer 52 is configured by the part of the computer 47 that executes S104. Further, in S105, an L _K value is calculated by the correlation calculation and normalization, and a variation ΔP of the air pressure P is calculated based on the L _K value. In other words, the part of the computer 47 that executes S105 constitutes the correlation operation unit 56, the normalization unit 58, and the air pressure change amount operation unit 60.

When the vehicle speed is sufficiently close to 0 because the key switch of the vehicle is ON but the vehicle is substantially stopped, the estimation by the disturbance observer 52 is prohibited. The current value of the change amount ΔP is fixed to the previous value, whereby the change amount ΔP can be obtained even when the rotation speed v is sufficiently close to zero.

Thereafter, in S106, it is determined whether the variation ΔP is smaller than the negative reference value ΔP ₀ , that is, whether the air pressure P is abnormally low. If the change amount ΔP is not smaller than the reference value ΔP ₀ , the determination is NO, and
S107 command to reset the integer n to zero is issued in, whereas, YES next determination when the change amount [Delta] P is the reference value [Delta] P ₀ is less than, in S108, the integer n is 1
Increased.

In any case, thereafter, the latest reference value N is read from the RAM 50 in S109. The reference value N is determined in advance by execution of a reference value determination routine described in detail later, and is stored in the RAM 50. Subsequently, in S110, it is determined whether or not the value of the integer n, that is, the number of times that it is determined that the change amount ΔP is smaller than the reference value ΔP ₀ is larger than the reference value N. If it is not larger than the reference value N, the determination is NO, and it is determined that the air pressure P is not abnormally low this time, and the process returns to S103,
On the other hand, if the value is larger than the reference value N, the determination becomes YES, and in S111, it is determined that the air pressure P is abnormally low this time, and the driver is notified by the display device 66 to that effect. In this case, the process returns to S101. That is, in the present embodiment, the "low pressure determination condition" according to the first aspect of the present invention is that the number n of times that the change amount ΔP is continuously determined to be smaller than the reference value ΔP ₀ becomes larger than the reference value N.

In the reference value determination routine of FIG. 9, first, in S151, it is determined whether or not a series of natural leaks of the tire 26 has started. The time when the air is sealed in the tire 26 by a human or the time when the tire 26 is replaced with another is the start of a series of natural leaks of the tire 26. At this time, the driver operates the operating member 74 (FIG. 2).
) Is input to the computer 47 to indicate that the current time is the start of a series of natural leaks. That is, in S151, it is ultimately determined whether or not the operating member 74 has been operated by the driver.

The determination as to whether or not the present time is the start of a series of natural leaks can be made automatically without depending on the driver's operation. For example, it is not a device that can detect a change in air pressure only during rotation of the wheel 14 as in the present embodiment, but detects a change in air pressure regardless of whether the wheel 14 is rotating, such as a radio wave type. In a device that can
If an increase in air pressure is detected, it is assumed that the increase is due to the filling of the air pressure by a human or a tire change.If the increase in the air pressure is detected, it is automatically determined that a series of natural leaks has started. It becomes possible to determine.

In this case, if it is assumed that the operation member 74 has been operated, the determination becomes YES, and the flow shifts to steps from S152.

In S152, the current time t _C is read from the clock 70, and in S153, it is set as the reference time t _S. Further, in S154, the elapsed time T from the reference time t _S to the present time is set to 0. Thereafter, in S155, the current distance L _C is read from the traveling distance calculation device 72, and in S156, it is set as the reference distance L _S. Further, in S157, the travel distance L traveled by the vehicle from the time when the vehicle traveled the reference distance L _S to the current time is set to 0.

Thereafter, in S158, a reference value N is determined based on at least one of the elapsed time T and the travel distance L. The reference value N is, for example, a relationship between the elapsed time T and the reference value N, and as shown in a graph of FIG. 10, for example, a relationship in which the reference value N decreases as the elapsed time T increases (stored in the ROM 49). ), The elapsed time T
Or the travel distance L alone. Furthermore, the provisional value of the reference value N determined from the elapsed time T and the reference value N determined from the traveling distance L
The final value of the reference value N can also be determined by comprehensively using the provisional value. For example, the final value can be determined as an average value of two temporary values, the final value can be determined as the larger one of the two temporary values, or the final value can be determined as the smaller one. The reference value N determined as described above
Are stored in the RAM 50.

That is, the elapsed time T and the traveling distance L are acquired as the use history of the tire 26, and the reference value N is decreased as the elapsed time T or the traveling distance L increases. Since the air pressure is determined to be abnormally low, the low pressure determination condition is eventually relaxed as the elapsed time T or the traveling distance L increases.

Thereafter, returning to S151, if it is determined whether or not the operation of the operation member 74 is performed, the determination is NO if it is assumed that the operation is not performed this time, and the process proceeds to S159 and subsequent steps.

In S159, the current time t _C is read from the clock 70, and then in S160, the elapsed time T is calculated by subtracting the reference time t _S from the current time t _C. Further, in S161,
The current distance L _C is read from the mileage calculating device 72,
Subsequently, in S162, the travel distance L is calculated by subtracting the reference distance L _S from the current distance L _C. Thereafter, the flow shifts to S158, where the reference value N is determined in the same manner as in the above case. After that, the process returns to S151.

That is, the part of the computer 47 that executes the steps S106 to S111 of the tire air pressure abnormality determination routine and the part that executes the reference value determination routine cooperate with each other to form the abnormality determination unit 62 shown in FIG. It is.

As is clear from the above description, in the present embodiment, the computer 47 of S151 to S151 of FIG.
The part that executes S157 and S159 to S162 constitutes the “pneumatic pressure drop possibility estimating unit” according to the first aspect of the present invention in cooperation with the timepiece 70, the traveling distance calculating device 72, and the operating member 74. Of these, the part that executes S158 in the figure constitutes a “low-pressure determination condition changing unit”.

Next, the present invention will be specifically described based on another embodiment. Unlike the previous embodiment, the tire air pressure abnormality determination apparatus according to the present embodiment does not detect the air pressure using a disturbance observer, but detects the intensity within a set frequency range among a plurality of frequency components of the rotational speed v. Detects air pressure by taking advantage of the fact that is substantially maximal, but the frequency is lower at lower air pressures. Therefore, in the present embodiment, as shown in FIG. 11, the computer 47 causes the disturbance observer 52, the correlation operation unit 54, and the normalization unit 56 in the previous embodiment.
A frequency analysis unit 82, a resonance point detection unit 84, and an air pressure calculation unit 86 are provided instead of the air pressure change amount calculation unit 58. However, this embodiment has some parts in common with the previous embodiment, and the common parts are denoted by the same reference numerals, and description thereof is omitted.

The frequency analysis unit 82 acquires the frequency characteristics of the rotation speed signal fetched from the computer 20 by the FFT (fast Fourier transform) method. The resonance point detection unit 84 resonates the frequency of the plurality of frequency components of the rotational speed signal, of which the intensity is substantially maximum within the set frequency range, based on the analysis result of the frequency characteristic supplied from the frequency analysis unit 82. It is detected as a frequency f ₀ (resonance point). The air pressure calculation unit 86 calculates the resonance frequency f
_The air pressure P is calculated using the relationship that the air pressure P is lower as ₀ is lower.

The frequency analyzer 82 and the resonance point detector 8
4 and the air pressure calculation unit 86 are configured such that various control programs including a tire air pressure abnormality determination routine shown in the flowchart of FIG. 12 are stored in the ROM 49 of the computer 47 together with the abnormality determination unit 88. . Hereinafter, the contents of the tire air pressure abnormality determination routine will be described, but portions common to the previous embodiment will be briefly described.

In this routine, first, in S201, the operation of the operation member 74, that is, the tire 26
It is determined whether or not there has been a natural leak start instruction operation for instructing the start of a series of natural leaks. If there is no natural leak start instruction operation, the determination is NO, and immediately S203
However, if there has been a natural leak start instruction operation, the determination is YES, and in S202, the current time t _C is read from the clock 70 as necessary information, which is set as the reference time t _S, and , And then S
Move to 203.

In any case, in S203, the current time t _C is read from the clock 70, and the reference time t _S is read from the RAM 50. By subtracting the reference time t _S from the current time t _C , natural leakage occurs. The elapsed time T from the last time the start instruction operation was performed is calculated. continue,
In S204, the calculated elapsed time T is equal to the maximum time T.
_It is determined whether or not _MAX has been exceeded. Air pressure P is believed to decrease with increasing elapsed time T as represented by the graph of FIG. 13, for example by natural leakage, the air pressure P when the elapsed time T becomes the maximum time T _MAX is abnormally lowered by natural leakage It is considered that the vehicle has entered the area determined to have been made. Therefore, in this embodiment, when the elapsed time T has exceeded the maximum time T _MAX is adapted to the air pressure P is determined to be abnormally low in immediately S218 without estimation of the air pressure P which will be described later. Therefore, the elapsed time T
Is longer than the maximum time T _MAX , an air pressure abnormality warning can be performed without estimating the air pressure P. Therefore, in a state where the device related to the estimation cannot operate (for example, due to a device failure or the like). In this case, a special effect that an abnormal air pressure warning can be obtained is obtained.

On the other hand, the elapsed time T is equal to the maximum time T _MAX
If not, the determination in S204 is NO, and S2
Go to step 05 or lower. In S205, the reference values M and N are respectively determined based on the calculated elapsed time T. These reference values M and N are determined so as to decrease as the elapsed time T increases, as shown in the graphs of FIGS.

Subsequently, in S206, the rotation speed v is read from the computer 20 and stored in the rotation speed memory of the RAM 50. Thereafter, in S207, a frequency analysis of the rotation speed signal is performed based on the plurality of rotation speeds v stored in the rotation speed memory. The relationship between the frequency and the gain is calculated. Then, S2
In 08, an integer m representing the number of times the frequency analysis has been performed
Is increased by one. Note that the integer m is initialized to 0 when the execution of this routine starts. Thereafter, in S209, it is determined whether or not the integer m is larger than the reference value M. This time, if it is assumed that the value is not larger than the reference value M, the determination is NO, and the process returns to S201.

If the integer m becomes larger than the reference value M as a result of repeating the execution of S201 to S209 many times, S2
The determination at 09 is YES, the integer m is initialized to 0 in preparation for the subsequent series of frequency analysis in S210, and then the averaging process is performed on the frequency analysis result in S211. The average value of the gain is obtained for each frequency based on the results of the frequency analysis performed a plurality of times.

Subsequently, in S212, a smoothing process for smoothing a graph represented by the average frequency analysis result, which is a relationship between the frequency and the average gain, is performed. For example, the gain Y _i of the i-th frequency is
The average values of the gains y _i−1 , y _i , and y _{i + 1} before the smoothing processing from the (i−1) th to the (i + 1) th are set. That is, a smoothing process is performed on the average frequency analysis result in accordance with the rule represented by the following formula: _Yi = ( _yi-1 + _yi + _{yi + 1} ) / 3. Note that the number of gains before the smoothing process used in the averaging process is not limited to three, but may be any number.

That is, S20 of the computer 47
The part that executes steps 6 to S209 and S210 to S212 constitutes the frequency analysis unit 82 shown in FIG.

Thereafter, in S213, based on the result of the average frequency analysis after the smoothing process, the frequency at which the gain (which is an example of a unit for describing the “strength” of the signal) is substantially maximum within the set frequency range. Is the resonance frequency f ₀
Is detected as That is, the portion of the computer 47 that executes S213 constitutes the resonance point detecting section 84 shown in FIG.

Subsequently, in S214, based on the detected resonance frequency f ₀ , the current air pressure P is calculated in accordance with the relationship between the resonance frequency f ₀ and the air pressure P, which is stored in the ROM 49 in advance. That is, the part of the computer 47 that executes S214 constitutes the air pressure calculation unit 86 shown in FIG. Further, in this S214, whether the air pressure P is lower than the reference value P ₀ is determined. This time, if it is assumed that the value is equal to or more than the reference value P ₀ , the determination is NO, and in S 215,
An integer n representing the number of times that the air pressure P is continuously determined to be lower than the reference value P ₀ is initialized to 0, while this time the air pressure P
Is lower than the reference value P _{0, the} determination is YES, and the integer n is incremented by 1 in S216.

In any case, it is determined in S217 whether the integer n is larger than the reference value N. If it is assumed that the air pressure P is not greater than the reference value N this time, the determination becomes NO, and the process immediately returns to S201. However, if it is assumed that the air pressure P is larger than the reference value N this time, the determination becomes YES. It is determined to be low, and the driver is notified by the display device 66 to that effect. Then, S2
Return to 01. That is, in this embodiment, the air pressure P
It is an example of the "low-pressure determination condition" in the invention of claim 1 that the number n of times that is determined to be lower than the reference value P ₀ is larger than the reference value N.

That is, the computer 47 performs steps S201 to S205 and S21 of the tire pressure abnormality determination routine.
The part that performs steps S218 to S218 constitutes the abnormality determination unit 88 shown in FIG.

As is apparent from the above description, in this embodiment, it is presumed that the longer the elapsed time T, the higher the possibility that the air pressure has decreased. According to the result, one resonance frequency f ₀ is determined. Number of frequency analysis required to acquire M
Is reduced, and the number N of the air pressures P to be compared with the reference value P ₀ until it is determined that the air pressure is abnormally low.
Is reduced. Therefore, according to the present embodiment, the higher the possibility that the air pressure is reduced, the shorter the sampling frequency of the resonance frequency f _{0, and} thus the air pressure P, and the more the low pressure determination condition related to the determination of the air pressure abnormality is relaxed. , The number of resonance frequencies f ₀ obtained from the time when the abnormal decrease in air pressure actually occurs until the time when the abnormal decrease is detected is also the air pressure P
Is also reduced, and as a result, an effect that an abnormal decrease in air pressure can be detected at an early stage is obtained.

As is apparent from the above description, in the present embodiment, the computer 47 of S201 in FIG.
Step S203 is performed by the clock 70 and the operating member 7.
4 together with the “pneumatic pressure drop possibility estimating unit” in the first aspect of the present invention, and the part of the computer 47 that executes S205 in FIG. It is.

Although the present invention has been specifically described based on two embodiments, the present invention can be implemented in other embodiments.

For example, in each of the two embodiments, the natural leakage amount factor, which determines the natural leakage amount of the air pressure, which is the elapsed time T or the traveling distance L, and each of the reference values M and N are directly related. The reference values M and N are immediately determined from the natural leak amount factor. For example, the natural leak amount at each time is predicted from the natural leak amount factor,
The present invention can be implemented such that the reference values M and N are determined from the predicted natural leakage amount.

That is, if it is assumed that the air pressure decreases only due to natural leakage, the change with time in the air pressure is shown in FIG.
3 is a graph, and this graph can be approximately expressed by the following equation, for example.

[0088]

(Equation 7)

Where P _N : air pressure due to natural pressure reduction characteristics P P _int : initial value of air pressure P _N (value at start of natural leak) κ ₁ , κ ₂ : constant T: elapsed time (from start of natural leak) L: Traveling distance (increment from the start of natural leakage)

Therefore, while using this equation, the temporal change of the air pressure caused only by the natural leak and the natural leak amount of the air pressure are predicted, the relationship between the natural leak amount and each of the reference values M and N is determined in advance. If stored in the ROM 49, the present invention can be implemented by determining the reference values M and N from the amount of natural leakage.

In the above equation, “constants κ ₁ , κ ₂ ”
May be a fixed value, for example, a variable value that changes according to the type of tire (for example, tire manufacturer, size, etc.), and an operating member operated by a driver to indicate the type of tire is provided. It is desirable to change the constants κ ₁ and κ ₂ according to the operation in order to improve the prediction accuracy of the air pressure P.

The air pressure P _N can also be obtained approximately using, for example, the following equation.

[0093]

(Equation 8)

Where tmp: air temperature in tire tmp ₀ : initial value of air temperature in tire (value at the start of natural leakage)

Here, "air temperature in tire tmp"
Can be estimated, for example, as the sum of the outside air temperature and the temperature rise caused by the rotation of the wheels 14, and in this case, the outside air temperature can be obtained from an outside air temperature sensor of a vehicle air conditioner or an engine control device. On the other hand, the rotational energy of the wheel 14 can be obtained from the rotational speed v of the wheel 14. That is, for example,

[0096]

(Equation 9)

The tire air temperature tmp can be obtained by using the following equation. Where: ：: outside air temperature κ ₃ , κ ₄ : constant (can be changed depending on the type of tire)

Although not specifically exemplified, the present invention can be implemented in various improved and modified aspects.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a tire air pressure abnormality determining apparatus according to one embodiment of the present invention.

FIG. 2 is a configuration block diagram of the tire pressure abnormality determination device.

FIG. 3 is a cross-sectional view showing a part of a wheel for which a disturbance is detected in the tire pressure abnormality determination device.

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

FIG. 5 is a graph for explaining approximation of disturbance dynamics in the tire pressure abnormality determination apparatus.

FIG. 6 is a block diagram illustrating a configuration of a disturbance observer in the tire pressure abnormality determination apparatus.

FIG. 7 is a flowchart showing a control program stored in a ROM of a computer 47 which is a component of the tire pressure abnormality determination apparatus.

FIG. 8 is a flowchart illustrating details of S105 in FIG. 7;

FIG. 9 is a flowchart showing another control program stored in the ROM of the computer 47, which is one component of the tire pressure abnormality determination apparatus.

FIG. 10 is a graph for explaining characteristics of a reference value N in the control program of FIG. 9;

FIG. 11 is a functional block diagram of a tire air pressure abnormality determining apparatus according to another embodiment of the present invention.

FIG. 12 is a flowchart showing a control program stored in a ROM of a computer 47, which is a component of the tire pressure abnormality determination device.

FIG. 13 is a graph for explaining how the air pressure of a tire decreases due to natural leakage.

FIG. 14 is a graph for explaining characteristics of a reference value M in the control program of FIG.

FIG. 15 is a graph for explaining characteristics of a reference value N in the control program of FIG.

[Explanation of symbols]

 Reference Signs List 10 rotor 12 electromagnetic pickup 14 wheels (wheels with tires) 20, 47 computer 24 wheels 26 tires 28 rim side 30 belt side 32 torsion spring 62, 88 abnormality determination unit 70 clock 72 mileage calculating device 74 operating member

Continued on the front page (72) Inventor Hiroyuki Kawai 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hiroyoshi Kojima 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Invention Person Koji Umeno 41 Toyota Chuo R & D Laboratories Co., Ltd. at 41, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture (72) Inventor Katsuhiro Asano 41 Toyoda Central R & D Lab. (72) Inventor Noboshi Onoki 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture, Japan Denso Co., Ltd. (72) Inventor Yuichi Inoue 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Nihon Denso Co., Ltd. (56) References JP-A-6-297923 (JP, A) JP-A-3-50006 (JP, A) International publication 93/2877 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 23 / 00-23/06

Claims (5)

(57) [Claims] 1. A tire pressure abnormality determining apparatus for detecting an air pressure related amount of a tire of a vehicle, and determining that the air pressure is abnormally low when a result of the detection satisfies a predetermined low pressure determination condition. An air pressure drop possibility estimating unit that estimates the likelihood that the air pressure has dropped based on the history that influences the natural leak of air in the tire, and the low pressure determination condition, A low-pressure determination condition changing unit that changes to a condition that is more easily satisfied when the air pressure drop possibility estimating unit estimates that the possibility that the air pressure is low is high is high; A tire pressure abnormality determination device, characterized in that: 2. The method according to claim 2, wherein the air pressure drop possibility estimating unit uses at least one of a traveling distance and an elapsed time of the vehicle since the time when air is sealed in the tire or when the tire is replaced. The tire pressure abnormality determination device according to claim 1, wherein the tire pressure abnormality determination device is configured to acquire as a history and estimate that the longer the acquired usage history is, the higher the possibility that the air pressure is lowered. 3. The air pressure drop possibility estimating unit determines whether or not the rate of increase of the detected value of the air pressure related amount during a stop of the vehicle exceeds a reference value. The tire pressure abnormality determination device according to claim 2, wherein it is determined that air has been sealed in the tire or the tire has been replaced. 4. A detecting unit for detecting a motion state amount of a wheel on which the tire is mounted as the air pressure related amount, and at least (a) estimating the air pressure based on a detected value by the detecting unit. A disturbance observer for detecting a disturbance to the wheel from a wheel information basic value which is a basic value of the wheel information related to the air pressure and a wheel motion state amount detected by the detection unit; and (b) a detected disturbance. An estimating unit having a wheel information change amount estimating unit for estimating a change amount of the wheel information actual value, which is an actual value of the wheel information, from the wheel information base value; and an estimated value obtained by the estimating unit and the low pressure. The ear air pressure abnormality determination device according to any one of claims 1 to 3, further comprising: a determination unit configured to determine whether the air pressure is abnormally low based on a relationship with a determination condition. 5. A method for detecting an air pressure related amount of a tire of a vehicle,
In the tire pressure abnormality determination device that determines whether the air pressure is abnormally low based on the relationship between the detection result and the reference value, the natural leakage amount at each time from the natural leakage amount factor of the air in the tire is determined. Predicted, the reference value based on the predicted amount of natural leakage, the larger the predicted amount of natural leakage
Easily, the air pressure is abnormally low based on the detection result.
A tire pressure abnormality determination device that determines to determine that the tire pressure is abnormal.