JP3045957B2 - Tire pressure drop warning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a decrease in air pressure of each tire of a four-wheeled vehicle and generating an alarm.

[0002]

2. Description of the Related Art In recent years, a device for detecting a decrease in tire air pressure has been developed as one of safety devices for four-wheeled vehicles such as passenger cars and trucks, and some of them have been put to practical use. The importance of the low air pressure alarm device has been recognized and developed mainly for the following reasons. When the air pressure is low, the increase in the deflection increases the temperature of the tire, decreases the strength of the polymer material used for the tire, and leads to a burst of the tire. However, if the tire pressure drops, the driver does not notice it.

A method for detecting a decrease in air pressure in the air pressure decrease alarm device includes, for example, four tires W ₁ ,
W ₂ , W ₃ , W ₄ (Note that the tires W ₁ , W ₂ correspond to the front left and right wheels, respectively, and the tires W ₃ , W ₄ correspond to the rear left and right wheels, respectively. Tire W
_i ". ), Each of the rotational angular velocities F ₁ , F ₂ , F ₃ , F ₄
(Hereinafter, when collectively referred to as “rotational angular velocity F _i ”)
There is a method based on the difference.

[0004] According to this method, the rotational angular velocity F _i of the tires W _i, for example on the basis of the signal outputted from the wheel speed sensor mounted on the tire W _i, is detected for each predetermined sampling period [Delta] T. This rotational angular velocity F _i is calculated by dividing the dynamic load radius of each tire W _i (the apparent rolling radius of the tire calculated by dividing the distance traveled by the vehicle during one rotation of each tire during the running of the tire by 2π). ) Are the same when the vehicle is traveling straight.

However, the dynamic load radius of the tire W _i is, for example, varies with changes in the pressure of the tire W _i. When the pneumatic pressure of the tire W _i is reduced, the dynamic load radius becomes smaller than that in the normal internal pressure. Accordingly, the rotational angular velocities F _i of the tires W _i is faster than at a normal internal pressure, it is possible to detect decrease in tire air-pressure W _i by the difference in the rotational angular velocity F _i. The following shows the determination expression for detecting decrease in tire air-pressure W _i (JP 63-305011
And JP-A-4-212609).

[0006] D = 2 _{[(F 1 + F 4) -} (F 2 + F 3) ] _{/ (F 1 + F 2 +} F 3 + F 4) (1) e.g. is the same all if the dynamic load radii of the tires W _i , The rotational angular velocities F _i are all the same (F
₁ = F ₂ = F ₃ = F ₄ ), and the judgment value D is 0. Therefore, threshold _values D _TH1 and D _TH2 (D _TH1 , D _TH2 > 0) are set, and if the determination formula of D <−D _TH1 or D> D _TH2 is satisfied, there is a tire W _i with reduced air pressure. If the determination formula is not satisfied, it is determined that there is no tire W _i having a decreased air pressure. Then, when it is determined that there is a tire W _i with a decreased air pressure, an alarm is generated using a display device or a speaker.

However, in the air pressure drop detection processing during actual running, when the longitudinal acceleration or the lateral acceleration of the vehicle is large,
For example, at the time of rapid acceleration, when a load such as traveling on a curve moves to the front, rear, left and right of the vehicle, the drive tires may lock or spin. Locking and idling do not always occur evenly on the left and right sides of the driving tires, so the rotation speed of each driving tire is different. As a result, D ≠ 0, and an erroneous determination of pressure reduction is performed. Therefore, a technique for removing data corresponding to the rotational angular velocity Fi is _disclosed in, for example, Japanese Utility Model Publication No.
No. 11,844.

Japanese Utility Model Publication No. Hei 4-11844 discloses
In technology, tire W_iIs idle or locked
If you think that, the angular velocity calculated at that time
Degree F _iTo remove the tire W_iAir pressure is low
Is detected. More specifically, before
Left and right tires W₁, W_TwoOr rear left and right tires W_Three, W_Fourof
Each rotational angular velocity F₁, F_TwoOr F_Three, F_FourRatio F₁/
F_TwoOr F_Three/ F_FourAre out of the specified range.
When turned off, tire W_iHas locked or slipped on one wheel
And the rotational angular velocity F_iDay of
Is removed.

[0009]

By the way, in the technique for detecting a decrease in tire air pressure, the ratios F ₁ / F ₂ , F ₃ /
Since only the rotational angular velocity F _i calculated when both F ₄ are determined to be out of the predetermined range are excluded, FIG.
As shown in 5, the vehicle is on the opposite side, so one side is bad (for example, unpaved road shoulder such as grass or sand, or a snow-covered part on the side of the road)
When the vehicle is running on a rough road, and the road is slipping little by little because the rough road is slippery, the ratio F ₁ / F ₂ or F ₃
/ F ₄ only when judged by, during running of the one-sided rough road because normally does not satisfy the conditions, thereby issuing an erroneous determination value. Therefore, there is a disadvantage that inappropriate travel data is adopted for the decompression determination and a false alarm is issued.

Therefore, as in the above-mentioned technology disclosed in Japanese Utility Model Publication No. 4-1844, the right / left wheel ratio F ₁ /
F ₂ and F ₃ / F ₄ is can not accurately determine only determines or outside a predetermined range. An object of the present invention is to accurately determine a state of traveling on a one-sided rough road,
An object of the present invention is to provide a tire pressure drop warning device that prohibits determination of a decrease in tire pressure and that can reliably detect a decrease in tire pressure.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, a tire pressure drop warning device according to the present invention comprises a time differential value of a front-rear wheel ratio of a rotational angular velocity of a left tire and a rotational differential velocity of a right tire. Calculating means for obtaining the time differential value of the front and rear wheel ratio and the left and right difference or the right and left ratio of the time differential value of the front and rear wheel ratio, and based on the left and right difference or the right and left ratio of the front and rear wheel ratio obtained by the calculating means. And a one-sided bad road running determining means for determining running conditions having different road conditions on the left and right, and prohibiting the determination by the air pressure drop determining means when it is determined that the running conditions have different road conditions on the left and right. (Claim 1).

According to this configuration, when the vehicle travels on a road in which the left and right states are different, the front-to-back ratio of the rotational angular speed of the tire on one side is stronger than the front-rear ratio of the rotational angular speed of the tire on the other side. Fluctuates and the time derivative appears large,
It is possible to determine running conditions in which road conditions are different between the left and right. When it is determined that the road conditions are different between the left and right road conditions, the rotation of the four tires may be unbalanced and a false alarm may be generated. False alarms can be prevented from occurring. The reason for taking the left-right difference or the right-left ratio of the front-rear wheel ratio is to cancel the influence of acceleration / deceleration.

[0013] The one-sided rough road traveling judging means makes a difference between the left and right road conditions based on the result of integrating the left-right difference or the left-right ratio of the time derivative of the front-rear wheel ratio obtained by the calculating means. The driving condition may be determined (claim 2). Since the integration processing is performed, it is possible to eliminate an unstable state in which the traveling condition in which the road condition differs between the left and right is temporarily determined or not determined.

The one-sided rough road traveling determining means determines that the value obtained by integrating the left-right difference or the right-left ratio of the time derivative of the front-rear wheel ratio obtained by the calculating means exceeds a predetermined threshold value t _1. While the vehicle is running, it is determined that the road conditions are different between the left and right road conditions, and the left / right difference or left / right ratio of the time derivative of the front / rear wheel ratio is below a predetermined threshold value t ₂ (t ₂ <t ₁ ). In some cases, the value obtained by performing the integration processing may be regarded as being lower than a predetermined threshold value t ₁ , that is, it may be determined that the road condition is the same on the left and right (claim 3). . Even after the vehicle has shifted from the running condition in which the road condition is different between the left and right to the normal running condition, the value subjected to the integration process may not be easily attenuated. Therefore, the comparison with the left-right difference or right ratio with a predetermined threshold value t ₂ of the time differential value of the front and rear wheel ratio (t ₂ <t _1), when less than a predetermined threshold value t ₂ the road in right and left It is determined that the running conditions are the same. Then, the value subjected to the integration process is forcibly cleared. As a result, the vehicle can be quickly changed to a state in which the determination by the air pressure drop determination unit can be performed immediately after the vehicle shifts from the running condition in which the road condition differs between the left and right to the normal running condition.

The one-sided rough road traveling determining means determines whether the left-right difference or the left-right ratio of the time derivative of the front-rear wheel ratio calculated by the calculating means exceeds a predetermined threshold value t _1. And when the left / right difference or the left / right ratio of the time derivative of the front / rear wheel ratio falls below a predetermined threshold value t ₂ (t ₂ <t ₁ ), the time of the front / rear wheel ratio is determined. The left / right difference or left / right ratio of the differential value is a predetermined threshold value t
_The driving condition may be regarded as being lower than ₁ , that is, the driving condition may be determined such that the road condition is the same on the left and right (claim 4). In this case, when the left and right difference or the right ratio exceeds a predetermined threshold value t ₁ of the time differential value of the front and rear wheels ratio, determines the running condition of different road conditions in the left and right, road conditions the vehicle is on the left and right The determination is continued even after the transition from the different driving condition to the normal driving condition. Therefore, this is equivalent to performing an integration process with an infinite time constant. Then, the comparison with the left-right difference or right ratio with a predetermined threshold value t ₂ of the time differential value of the front and rear wheel ratio (t ₂ <t _1), when less than a predetermined threshold value t ₂ the road in right and left It is determined that the running conditions are the same. Then, the prohibition of the judgment by the air pressure drop judging means is released. by this,
After the vehicle shifts from the running condition in which the road condition is different between the left and right to the normal running condition, the vehicle can be quickly changed to a state in which the determination by the air pressure drop determining means can be performed.

A tire pressure drop warning device according to a fifth aspect of the present invention calculates a front-rear wheel ratio of a rotational angular velocity of a left tire and a front-rear wheel ratio of a rotational angular velocity of a right tire, and calculates a right-left difference or a right-left wheel ratio. A calculating means for calculating a time differential value of the left / right ratio, and a one-sided bad determining a running condition in which road conditions are different on the left and right based on a left / right difference in front / rear wheel ratio or a time differential value of the right / left ratio obtained by the calculating means. A road travel determining means is provided, and when it is determined that the driving conditions are different between the left and right road conditions, the determination by the air pressure drop determining means is prohibited.

In this configuration, the same operation and effect can be obtained only by differentiating the step of performing the time differentiation from the first aspect of the present invention. The tire pressure drop warning device according to the sixth, seventh and eighth aspects has the same operation as that of the tire pressure drop warning device according to the second, third and fourth aspects, except that the stage of time differentiation is different. The effect can be achieved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of the tire pressure drop warning device. The tire pressure drop warning device is provided for each tire W ₁ , W
₂ , a wheel speed sensor 1 of a conventionally known configuration provided in association with W ₃ , W ₄ , respectively, and the output of the wheel speed sensor 1 is provided to a control unit 2. The control unit 2 includes an initialization switch 3 operated by a driver, and a display 4 on which tires with reduced air pressure are displayed.
Is connected.

FIG. 2 is a block diagram showing an electrical configuration of the tire pressure drop warning device. The control unit 2 is composed of a microcomputer, and the hardware configuration of the control unit 2 includes I / O necessary for transmitting and receiving signals to and from an external device.
O interface 2a, CP as the center of arithmetic processing
U2b, a ROM 2c in which a control operation program of the CPU 2b is stored, and a RAM 2d in which data or the like is temporarily written when the CPU 2b performs a control operation, or the written data is read out. . RAM2d
To, as described later, the rotational angular velocity for the area for storing a valid rotational angular velocities F _i for the initial correction processing, 1
A speed area for storing the speed of the vehicle before the cycle, a distance area for storing the travel distance of the vehicle, and the like are provided.

The wheel speed sensor 1 is, specifically, a tire W
_i has a sensor rotor having a plurality of (for example, 49 or 98) teeth inside the wheel, and a pulse signal (hereinafter referred to as “wheel speed pulse”) generated in accordance with the number of teeth when the sensor rotor rotates. ").
The CPU 2b, based on the output wheel speed pulse,
For each predetermined sampling period ΔT, each tire W ₁ , W
₂ , W ₃ , W ₄ rotational angular velocities F ₁ , F ₂ , F ₃ , F ₄ ,
And to calculate the front and rear wheels ratio _{F 1 / F 3, F 2} / F 4.

The CPU 2b determines the rotational angular velocity F_iBased on
And tire W_iSpeed V_iIs detected. Each tire W₁,
W_Two, W_Three, W_FourIf all radii are R, the velocity V_i
Is V_i= R × F_i (2) can be obtained. The CPU 2b further controls the vehicle
It is determined whether the vehicle is traveling on a line. When the vehicle runs straight
Whether or not the front left and right tire W₁, W_TwoAnd left and right
Tire W_Three, W _FourOf each rotational angular velocity F_iIs the difference or ratio of
Both are based on whether a specified value is exceeded with the same sign.
Judgment, if both do not exceed a certain specified value with the same sign
In this case, it is determined that the vehicle is traveling straight. <Air pressure drop detection processing> (1) General processing Tire W_iThe air pressure drop detection process is based on the following equation (3).
It is done.

D = 2 [(F ₁ + F ₄ ) − (F ₂ + F ₃ )] / (F ₁ + F ₂ + F ₃ + F ₄ ) (3) In the present embodiment, the D value calculated thereby is as follows:
If equation (4) is satisfied, it is determined that the air pressure has dropped (see FIG. 3). D <D _TH1 or D> D _TH2 (4) where D _TH1 and D _TH2 are predetermined constants.

[0023] In this embodiment, not only informed only that there is a tire whose air pressure has dropped to a driver, alarm of the air pressure of any tire W _i can be informed whether has dropped to the driver The method is adopted. The method in (3), if D> 0, if the tire is a W ₁ or W ₄ D <0 whose air pressure has dropped, the tire whose air pressure has dropped is W ₂ or W ₃ First specify. Further, when the vehicle is running straight, if F ₁ > F ₂ , the tire with reduced air pressure is W ₁ F ₁ <F ₂ , and if F ₁ > F ₂ , the tire with reduced air pressure is W ₂ F _3> If F _4, the tire air pressure is decreased if W ₃ F ₃ <F _4, tires are identified as W ₄ whose air pressure has dropped.

After specifying the tire W _i having a reduced air pressure in this manner, the result is displayed on the display 4 shown in FIG.
Output to and display. The display mode of the display device 4, for example four display lamps air pressure corresponding to the tire has dropped out of the tire W ₁ to _W-4 is to be turned. When the tire cannot be specified, the four display lamps are turned on at the same time. Accordingly, the air pressure of any tire W _i can be recognized simply by glance whether degraded. (2) Processing Considering One-Way Rough Road Running Next, processing that considers one-side rough road running related to the present invention will be described.

In the above-described process for detecting a decrease in air pressure, the vehicle
Normal internal pressure when traveling on a slippery road on only one side
Even if the D value exceeds the threshold, an alarm occurs
May be. Changes in wheel speed of each wheel with actual data
Is as shown in FIG. Figure 4 shows a normal road surface
A, bad road on both sides (gravel road) B, bad road on one side (shoulder on one side)
Of each wheel when driving on C)
It is the graph which plotted the measurement data of the turning angle velocity. same
Looking at the figure, when running on a paved road, A is the rotational angular velocity
Degree F _iIs almost the same for all four wheels,
B is the rotational angular velocity F_i, The center of fluctuation is almost equal for all four wheels
New, but fluctuating. Wheel speed on this both sided rough road
Fluctuations are caused by fluctuations in road surface irregularities and road surface slipperiness.
It is thought to occur. However, when driving on a bad road on one side,
C is the rotational angular velocity F of the wheels on the pavement side_iHaho
The rotational angular velocity F of the driving wheels on the rough road_iWa
It fluctuates violently on the plus side than the rotational speed on the
Rotational angular velocity F of the side driven wheel_iFluctuates strongly on the negative side
ing. The rotational angular velocities of drive wheels and driven wheels on rough roads are paved
Positive and negative respectively compared to the roadside rotational angular velocity
The major shift to the side is that the rough road side is grassy
Because it is very slippery, the drive wheels tend to idle,
This is because the driven wheels tend to brake. Also on the bad road side
The rotational angular velocities of both the driven and driven wheels fluctuate drastically
The reason for this is that the road surface is uneven and the road surface is slippery.
It is thought to be due to movement.

When the D value is calculated on the basis of such data, it is supposed that D ≒ 0 at the normal internal pressure, but only the rough road side is very slippery. The D value becomes abnormally large and exceeds the alarm threshold. In order to prevent false alarms, the condition of one-sided rough road running is detected, and the D value is determined at this time (see (3) and (4) above).
Expression) must be prohibited. Rotational angular velocity F _i of the tires of the person who is slipping is because not reflect the internal tire pressure.

Here, a normal road surface A, rough roads on both sides (gravel roads, etc.) B, rough roads on one side (such as when one side runs over a road shoulder)
FIG. 6 shows the relationship between the front and rear wheel ratio of the rotational angular velocity when traveling on C. When running on a paved road A
Are almost equal in both front and rear wheel ratios. In the case B running on a bad road on both sides, both front and rear wheel ratios fluctuate drastically. However, when traveling on a bad road on one side, C:
The front and rear wheel ratio on the pavement road side is almost constant, but only the rough front and rear wheel ratio fluctuates sharply. When the vehicle is running on a rough road on only one side, it is not possible to correctly detect a decrease in tire air pressure due to slippage of the wheels on the rough road side, but the front-rear wheel ratio on the rough road fluctuates sharply as described above. Is also generated at the same time, so that it is possible to detect a one-sided rough road condition by using this. Therefore, if the detection of a decrease in tire air pressure is not performed when one-sided rough road traveling is detected, it is possible to prevent an erroneous alarm from being generated.

Hereinafter, the air pressure drop detection performed in this embodiment will be described.
The output processing will be described with reference to a flowchart (FIG. 7).
I do. First, the front and rear wheel ratio F₁/ F_ThreeTo C_LAnd the front and rear wheels
Ratio F_Two/ F_FourTo C_RI will write. The CPU 2b
Calculated every predetermined sampling period ΔT (for example, 1 second)
Each tire W₁, W_Two, W_Three, W_FourOf rotational angular velocity
Front and rear wheel ratio C_L= F₁/ F_Three, C _R= F_Two/ F_FourIs calculated
(Step S1), C_L, C_RBased on the previous
Front and rear wheel ratio C calculated one cycle ago_L', C_R'And the difference C_L
-C_L', C_R-C_R'(Step S2). This
Is referred to as the "differential front / rear wheel ratio" δ in this specification.
C_L, ΔC_RI mean. That is, δC_L= C_L-C_L′ (5) δC_R= C_R-C_R′ (6) The differential front / rear wheel ratio is determined by determining the degree of fluctuation of the front / rear wheel ratio.
Because I want to know.

FIG. 8 is a graph showing the time transition of the differential front / rear wheel ratio. When running on a pavement road (A), the differential front / rear wheel ratio changes smoothly and is the same for both wheels. On the other hand, when traveling on one side of a rough road (C), the differential front and rear wheel ratio on the pavement road side changes smoothly, but the differential front and rear wheel ratio on the rough road side fluctuates sharply. The CPU 2b calculates δC _L
ΔC _R , that is, the difference between the left and right differential front and rear wheel ratios, and takes the absolute value (step S3).

Sub (δC) = | δC _L −δC _R | (7) The reason for obtaining the left / right difference is to remove the influence of the fluctuation of the front / rear wheel ratio during acceleration / deceleration. The CPU 2b plots the absolute value sub (δC) of the left / right difference of the differential front / rear wheel ratio and obtains the envelope of the time change.

FIG. 9 shows the absolute value su of the left / right difference of the differential front / rear wheel ratio.
FIG. 6 is a graph showing the time transition of b (δC), and when running on a paved road (A), the differential front and rear wheel ratios cancel each other out, and sub (δC) is almost 0, but one-sided bad. When the vehicle is traveling on the road (C), the differential front and rear wheel ratio cannot be canceled on the left and right, and is changing drastically. Therefore, the envelope appears significantly.

The value of the envelope will be written as env (δC). env (δC) is obtained as follows.
The previous env (δC) is compared with the current sub (δC) (step S5), and if sub (δC) ≧ env (δC) × α, env (δC) = sub (δC) ( Step S7).

If sub (δC) <env (δC) × α, then env (δC) = env (δC) × α (step S6). α is an attenuation constant, for example, a value of about 0.99.

In this way, the value env (δC) of the envelope (the output value of the integrating circuit having a constant time constant) can be obtained. The value env (δC) of this envelope is set as a one-sided rough road traveling determination value. The reason why the value of the envelope is adopted as described above is as follows. When the idle rotation of the wheel on one side of a rough road continues for multiple cycles, the difference between the front and rear wheel ratio itself is a large value, but the value of sub (δC) is a differential value, so the value may be small. This is because if the determination is made only based on the left / right difference sub (δC) of the ratio, it is erroneously determined that the vehicle is traveling normally.

The CPU 2b has a one-sided rough road running determination value env
(ΔC) is compared with a fixed threshold value t ₁ (step S
8), if the one-sided rough road running judgment value env (.delta.C) exceeds a certain threshold t _1, determines that the one-sided rough road running (step S10), and stops the air pressure reduction detection processing of the tire. If one-sided rough road running judgment value env (.delta.C) does not exceed a certain threshold t _1, determines that the ordinary road traveling in (step S9), and performs the pressure drop detecting process of the tire.

Since the damping constant α is set to a value close to 1, the one-sided rough road running determination value env (δC) is not easily attenuated even when the one-sided rough road running ends and the vehicle enters normal running. The state exceeding the value t ₁ may last for several minutes. During that period, tire pressure drop detection cannot be performed, but considering the purpose of tire pressure drop detection,
It is determined that no significant adverse effects will occur even if detection is not performed for a certain period of time.

However, it is also possible to adopt an embodiment in which a decrease in tire air pressure can be promptly detected when normal driving is completed after one-sided rough road driving is completed. According to this embodiment, the left-right difference sub (δ)
I always check C). One-sided bad road running judgment value e
Even when nv (δC) does not attenuate easily, sub
If (δC) continues to be small, it is determined that the vehicle is traveling on a normal road, and the processing for detecting a decrease in tire air pressure is started.

FIG. 10 shows a pneumatic pressure according to this embodiment.
It is a flowchart of a fall detection process. Along this line
Explain the front and rear wheel ratio C_L, C_RCalculation, differential front and rear wheels
Ratio δC _L, ΔC_RCalculation of the left and right difference of the differential front and rear wheel ratio
The calculation of the absolute value sub (δC) is performed by the flowchart of FIG.
Has the same content as

Next, a normal road surface determination based on sub (δC) is performed (steps S41-S45). Step S
At 41, it is determined whether or not sub (δC) is equal to or less than a predetermined threshold value t ₂ . If sub (δC) is equal to or smaller than the predetermined threshold value t ₂ , the count value CNT is incremented by one (step S43), and it is determined whether or not the count value CNT is greater than a predetermined number of times M (step S44). If so, the one-sided rough road running determination value env (δC) is set to 0 (step S45). If sub (δC) is equal to or greater than the predetermined threshold value t ₂ , the count value CNT is cleared to 0, and the process proceeds to step S5.

The predetermined threshold value t ₂ can be set even when the one-sided rough road traveling judgment value env (δC) does not readily attenuate.
If sub (δC) continues to be small, this is a threshold value for determining that the vehicle is traveling on a normal road surface and entering a process for detecting a decrease in tire air pressure, which is a threshold value for a one-sided rough road traveling determination value env (δC). it is a value smaller than t _1. The predetermined number M times
This is the number of times that the state in which sub (δC) is smaller than the threshold value t ₂ continues until it is determined that the vehicle is traveling on a normal road surface. Therefore, even if the sub (δC) accidentally falls below the threshold value t ₂ due to the influence of noise or the like, e is only therefor.
nv (δC) never becomes 0.

Even when the vehicle is traveling on a normal road surface, sub (δC) may temporarily exceed the threshold value t ₁ due to partial irregularity of the road surface. Again, e
Since nv (δC) is not easily attenuated, the process of detecting a decrease in tire air pressure may be hindered. Even in this case, if the state where sub (δC) is small as described above continues, there is an advantage that it is possible to determine that the vehicle is traveling on a normal road surface and to start the processing for detecting a decrease in tire air pressure.

At steps S5, S6 and S7, the value of the envelope env (δC)
, And in steps S8, S9, and S10,
By comparing the value env (δC) of the envelope with the threshold value t ₁ , it is determined whether the vehicle is traveling on a one-sided rough road or traveling on a normal road surface. The processing according to the flowchart of FIG.
(ΔC) and sub (δC) will be described with reference to a graph (FIG. 11) representing a time transition, and FIG.
The process according to the flowchart of FIG. 0 will be described with reference to a graph (FIG. 12) showing the time transition of env (δC) and sub (δC).

According to FIG. 11, at time X, sub (δC)
Even if the value of env (δC) decreases, the time Y at which env (δC) becomes lower than the threshold value t ₁ is much earlier than the time X. According to FIG. 12, since a process of comparing sub (δC) with a predetermined threshold value t ₂ is added, at the time X, sub (δC) is added.
If C) decreases and sub (δC) continues to fall below the predetermined threshold value t ₂ M times, env (δC) is forcibly set to 0.
I will. Therefore, even if the vehicle shifts from one-sided rough road traveling to normal road traveling, the vehicle can immediately follow this.

In the above embodiment, the attenuation constant α <
Although it was 1, it is also possible to take α = 1 (it is known that α is closer to 1 is better to reliably exclude one-sided rough road traveling data). In this case, su
b and (δC) exceeds the threshold t _1, env (δC)
Does not decay spontaneously, so it is not possible to return to the tire pressure drop detection processing forever. Therefore, as shown in the flowchart of FIG. 13, if the sub (δC) continues to be lower than the predetermined threshold value t ₂ M times, it is determined that the vehicle is traveling on a normal road surface (step S46). Therefore,
Even if the vehicle shifts from one-sided rough road running to normal road running, the vehicle can quickly follow this. When sub (δC) exceeds the predetermined threshold value t ₂ and exceeds the predetermined threshold value t ₁ , it is determined that the vehicle is traveling on a one-sided rough road (step S4).
8). sub (δC) exceeds a predetermined threshold value t ₂ ,
And to hold the decision if below a predetermined threshold value t _1. According to this embodiment, it is not necessary to calculate env (δC), so that there is an advantage that the algorithm is simplified and the memory can be saved.

FIG. 14 is a graph showing the contents of the processing according to the flowchart of FIG. According to this graph, at time X, sub (δC) decreases, and sub (δC)
There fall below a predetermined threshold value t ₂ if continued M times, it is determined that the ordinary road travel in releasing the pressure drop determination prohibition of the tire. Therefore, even if the vehicle shifts from one-sided rough road traveling to normal road traveling, the vehicle can immediately follow this.

Finally, various modifications will be described. In the above embodiment, the CPU 2b calculates the left-right difference of the differential front-rear wheel ratio, but may calculate the left-right ratio. Further, in the embodiment of the differential front and rear wheel ratio .delta.C _L, from seeking .delta.C _R, the difference between .delta.C _L and .delta.C _R, that is, had sought laterality differential front and rear wheels ratio, reverse the order After calculating the left-right difference between the front and rear wheel ratios, the difference between the previous cycle and the current cycle may be calculated.

In the above-described embodiment, the value of the envelope is used as the one-sided rough road running determination value. Alternatively, a moving average value over several cycles is obtained to obtain the one-sided rough road running determination value. It may be. Also, during a predetermined time, sub
The number of times (δC) exceeds the threshold value may be counted, and this count value may be used as a one-sided rough road traveling determination value.

[0048]

As described above, according to the tire pressure drop warning device according to the first or fifth aspect, when the vehicle travels on a road in which the left and right states are different, the traveling conditions in which the left and right road conditions are different are determined. When it is determined that the driving conditions are different between the left and right road conditions, by prohibiting the determination by the air pressure reduction determining means, it is possible to prevent the occurrence of a false alarm due to the unbalance of the tire rotation of the four wheels, A decrease in tire air pressure can be reliably detected.

According to the second or sixth aspect of the present invention, the running condition in which the left and right road conditions are different is determined based on the result of the integration processing, so that the left and right road conditions are different. Even when the driving conditions are temporarily judged or not, the judgment by the air pressure drop judging means can be prohibited without being influenced by the influence and when the vehicle is traveling on a road in which the left and right states are different. According to the tire pressure drop warning device according to any one of claims 3, 4, 7 and 8, which can more surely detect a drop in tire pressure, the vehicle can travel normally from running conditions where road conditions differ between left and right. After shifting to the condition, the state can be immediately changed to a state where the determination by the air pressure reduction determining means can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a tire pressure drop warning device.

FIG. 2 is a block diagram showing an electrical configuration of the tire pressure drop warning device.

FIG. 3 is a graph showing a method for determining a decrease in air pressure based on a D value.

Fig. 4 Running on a paved road (A), running on a bad road on both sides (B), and running on a bad road on one side
It is the graph showing the change of the wheel speed of each wheel of (C).

FIG. 5 is a graph showing that the D value becomes an abnormally large value on one side of a rough road and exceeds a warning threshold value.

FIG. 6: Running on a paved road (A), running on a bad road on both sides (B), and running on a bad road on one side
FIG. 4C is a graph showing a change in the front-rear wheel ratio of the rotational angular velocity of each wheel of FIG.

FIG. 7 is a flowchart illustrating an air pressure drop detection process.

FIG. 8 is a graph showing the time transition of the differential front-rear wheel ratio when traveling on a paved road (A) and traveling on one side of a bad road (C).

FIG. 9 is a graph showing a time transition of the absolute value of the left / right difference in the differential front / rear wheel ratio when traveling on a paved road (A) and traveling on a bad road on one side (C).

FIG. 10 is a flowchart showing a process for detecting a decrease in air pressure.

FIG. 11 is a graph showing time transitions of env (δC) and sub (δC).

FIG. 12 is a graph showing time transitions of env (δC) and sub (δC).

FIG. 13 is a flowchart showing an air pressure drop detection process according to another embodiment.

FIG. 14 is a graph showing a time transition of sub (δC).

FIG. 15 shows a rough road (eg, grass,
It is a figure which shows the state which runs on unpaved road shoulders, such as sand, or the snow part of a roadside).

[Explanation of symbols]

1 the wheel speed sensor 2 control unit 2a I / O interface 2b CPU 2c ROM 2d RAM 4 indicator _{W 1, W 2, W 3} , W 4 each tire F ₁ of a four-wheel _{vehicle, F 2, F 3, F} 4 rotates angular velocity

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroto Horie 41-1, Shimizu, Uozumi-cho, Akashi-shi, Hyogo (56) References JP-A-5-213019 (JP, A) JP-A-59-160605 (JP, A) A) JP-A-6-92114 (JP, A) JP-A-63-305011 (JP, A) JP-A-4-212609 (JP, A) JP-A-7-40717 (JP, A) JP-A-7 -40718 (JP, A) JP-A-7-40719 (JP, A) JP-A-7-40720 (JP, A) JP-A-8-169217 (JP, A) JP-A-7-149123 (JP, A JP-A-7-144518 (JP, A) JP-A-8-1556537 (JP, A) JP-A-7-125510 (JP, A) JP-A-6-3444734 (JP, A) 74008 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 23/06-23/08 G01L 17/00 G01P 3/56

Claims (8)

(57) [Claims] 1. A rotational angular velocity calculating means for calculating a rotational angular velocity of a tire provided in a four-wheeled vehicle, and based on the rotational angular velocity calculated by the rotational angular velocity calculating means, whether or not the tire pressure is reduced. A tire pressure decrease alarm device comprising: a pressure decrease judgment device for judging whether the pressure is low, and an alarm generation device for generating / stopping a predetermined alarm in accordance with a result of the judgment by the pressure decrease judgment device. Time derivative of the front and rear wheel ratio of
Calculating means for determining the time differential value of the front-rear wheel ratio of the rotational angular velocity of the right tire and the left-right difference or the right-left ratio of the time differential value of the front-rear wheel ratio; and the front-rear wheel ratio calculated by the calculating means. A one-sided rough road running determining means for determining running conditions with different road conditions on the left and right based on the left / right difference or the left / right ratio, and determining a decrease in air pressure when it is determined that the running conditions have different road conditions on the left and right. A tire pressure drop warning device for prohibiting determination by means. 2. The one-sided rough road running determining means is configured to perform an integration process on a left-right difference or a left-right ratio of a time differential value of a front-rear wheel ratio obtained by the calculating means, and to perform a road condition on the left and right sides. 2. The method according to claim 1, wherein different driving conditions are determined.
The tire pressure drop warning device as described in the above. 3. The one-sided rough road traveling determining means determines that a value obtained by performing an integration process on a left-right difference or a left-right ratio of a time differential value of a front-rear wheel ratio obtained by the calculating means is a predetermined threshold value t ₁ . While it is exceeded, it is determined that the driving condition is different between the left and right road conditions, and the left / right difference or the left / right ratio of the time differential value of the front / rear wheel ratio is greater than a predetermined threshold value t ₂ (t ₂ <t ₁ ). The tire pressure drop warning device according to claim 1, wherein when the vehicle speed falls below the threshold value, it is determined that the vehicle is running under the same road condition. Wherein said one-sided rough road determining means, when the left and right difference or the right ratio of the time differential value of the front and rear wheel ratio obtained by said calculating means exceeds a predetermined threshold value t _1, the left and right When it is determined that the driving condition is different from the road condition, and when the left / right difference or the left / right ratio of the time differential value of the front / rear wheel ratio falls below a predetermined threshold value t ₂ (t ₂ <t ₁ ), the left and right road conditions are determined. The tire pressure drop warning device according to claim 1, wherein it is determined that the running conditions are the same. 5. A rotational angular velocity calculating means for calculating a rotational angular velocity of a tire provided in a four-wheeled vehicle, and based on the rotational angular velocity calculated by the rotational angular velocity calculating means, whether or not the tire pressure is reduced. A tire pressure decrease alarm device comprising: a pressure decrease judgment device for judging whether the pressure is low, and an alarm generation device for generating / stopping a predetermined alarm in accordance with a result of the judgment by the pressure decrease judgment device. And the front and rear wheel ratio of the rotational angular velocity of the right tire, respectively,
Calculating means for calculating a left-right difference of the front-rear wheel ratio or a time differential value of the left-right ratio; and a left-right road state difference based on the left-right difference of the front-rear wheel ratio or the time differential value of the right-left ratio obtained by the calculating means. Tire pressure decrease warning device, comprising: one-sided rough road traveling determination means for determining a traveling condition; prohibiting the determination by the air pressure reduction determining means when it is determined that the traveling condition is different between the left and right road conditions. . 6. The one-sided rough road traveling determining means, based on the result of integrating the left-right difference of the front-rear wheel ratio or the time differential value of the left-right ratio obtained by the calculating means, determines whether the road condition is left or right. 6. A different driving condition is determined.
The tire pressure drop warning device as described in the above. 7. The one-sided rough road traveling determining means determines that a value obtained by performing an integration process on the left-right difference of the front-rear wheel ratio or the time differential value of the left-right ratio obtained by the calculating means is a predetermined threshold value t ₁ . While it is exceeded, it is determined that the road conditions are different between the left and right road conditions, and the left-right difference in the front-rear wheel ratio or the time derivative of the left-right ratio exceeds a predetermined threshold value t ₂ (t ₂ <t ₁ ). The tire pressure drop warning device according to claim 5, wherein when the vehicle speed falls below the predetermined value, it is determined that the vehicle is running under the same road condition. Wherein said one-sided rough road determining means, when the time differential value of the difference between right and left or right and left ratio of the front and rear wheels ratio obtained by said calculating means exceeds a predetermined threshold value t _1, the left and right When it is determined that the driving condition is different from the road condition, and when the time difference of the left / right difference or the left / right ratio falls below a predetermined threshold value t ₂ (t ₂ <t ₁ ), the left and right road conditions are determined. The tire pressure drop warning device according to claim 5, wherein it is determined that the running conditions are the same.