JP3286005B2 - Tire pressure 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 a tire pressure alarm device.

[0002]

2. Description of the Related Art According to a result of a survey, it has been found that the defective rate of tire maintenance of a vehicle running on a highway is unexpectedly higher than that of other power systems and the like. And is the first place, followed by tire groove shortage and abnormal tire wear. In addition, many drivers experienced punctures while driving high-speed vehicles,
The fear at that time also works, and there is an increasing demand to equip the vehicle with a tire pressure alarm device or a device equivalent to the tire pressure alarm device. If the tire pressure alarm device can be installed at low cost, the vehicle currently in use There is also a request to add additional equipment. On the other hand, a system for detecting the air pressure of each tire of a vehicle including a lorry is provided on the vehicle side, and a system that detects the air pressure of the rotating tire in real time via a slip ring, a radio wave, electromagnetic induction means, or the like is known. This system is known, and attempts have been made by the system to inform a driver of a tire pressure abnormality due to a puncture or the like.

In recent years, with the reduction in the cost of electronic components, passenger cars equipped with a four-wheel ABS device and a TRC (traction control) device have become quite popular. When such a four-wheel ABS device or the like is provided, a tire rotation detector for detecting the number of rotations of the tire is separately provided, and a control system constituted by each brake and a brake hydraulic differential device is provided. It is configured so as to be appropriately controlled according to the behavior of the vehicle. Then, as disclosed in Japanese Patent Application Laid-Open No. Sho 63-305011, the tire rotation numbers are summed diagonally, and it is determined whether the difference between the two sets of diagonal total values and the difference between the rotation numbers of the tires is equal to or greater than a predetermined value. A detection method has been proposed in which a determination is made and a tire air pressure abnormality is detected.

[0004]

However, according to the above-mentioned system for detecting the air pressure of each tire of a four-wheel passenger car in real time, the tire air pressure is directly detected, so that the system has an advantage of high reliability. However, since the air pressure information is transmitted to the vehicle via a slip ring, radio waves, electromagnetic induction means, and the like, the whole device is disadvantageously large and expensive, and has a problem of poor practicality.

[0005] Under such circumstances, in order to configure a tire air pressure warning device without additionally mounting extra hardware-related parts, a tire rotation detector already provided in a vehicle equipped with the above-described four-wheel ABS device or the like is used. The above-mentioned proposal which makes effective use of the detection of the tire rotation speed will come to mind.

That is, if a puncture or the like occurs in a specific tire during straight running and the air pressure decreases drastically, only the outer diameter of the punctured tire becomes smaller than that of other normal tires. The tire rotation speed will increase compared to a normal tire (since a small diameter tire rotates more to travel the same distance). This makes use of the principle that allows detection of punctured or tires with reduced air pressure.

Therefore, it is sufficient that the difference between the tire rotational speeds is determined on the tire pressure alarm device side. For this determination, the tire rotational speeds of at least four wheels are always determined individually. , And high-speed processing must be performed, which complicates control. Therefore, some processing is required. From this, the difference between the tire rotation numbers on the diagonal line is added, the difference between them is obtained, and a deviation value obtained by dividing the average value by twice the obtained value is obtained. By performing the comparison, it is conceivable to determine a tire pressure abnormality when the value exceeds the predetermined value.

However, when the comparison with the comparison value is performed, it may not be possible to determine the tire pressure abnormality because the deviation value is not stable. That is, accurate comparison may not be possible due to noise factors caused by variously changing road conditions, vehicle running conditions, and the like.

Accordingly, the tire pressure warning device of the present invention has been made in view of the above-mentioned problems, and an object of the invention is to provide a method for judging a difference in tire rotation speed on the tire pressure warning device side. An object of the present invention is to accurately detect an abnormality in tire air pressure without being affected by various noise generation factors generated during running.

[0010]

Means for Solving the Problems and

In order to solve the above-mentioned problems and achieve the object, the present invention has the following arrangement. That is, by the wheel speed sensor
Using the detected wheel speeds of the four wheels, a deviation value obtained from a predetermined arithmetic expression based on the rotation difference of the four tires is obtained as a positive or negative value, and then compared with a deviation width having a predetermined width. judging means for judging abnormal air pressure of the tire by performing within a predetermined time width, a tire pressure warning system comprising comprising a warning means to notify the determination result, the determination hand
The step has a range in which the positive or negative value exceeds the deviation width.
If the integral value is equal to or greater than a predetermined value within the predetermined time width, it is determined that the air pressure is abnormal.

[0011]

[0012]

[0013]

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic plan view of a tire pressure warning device according to an embodiment. In this drawing, a vehicle 20 is equipped with a four-wheel ABS device to a TRC device and the like.

For this purpose, the front, rear, left and right tires 1, 2, 3,
The 4 and the rotational speed detector 7 are provided individually for detecting the tire rotation speed F _n, tire rotation required for the control of a known ABS device (anti-lock braking system) and TRC (traction control) The numbers F ₁ , F
₂ , F ₃ , and F ₄ can be provided to the control device 11. The control device 11 also includes a warning lamp 10 for notifying a driver or the like of an abnormal condition of the tire pressure, and a propeller connected to the engine 5 for driving the rear tires 3 and 4 via the rear differential device 8. and it is configured so that the information of the rotational speed V _M of the shaft 6 is inputted.

As is well known, the emergency tire 9 has a smaller width and diameter than a normal tire so as not to occupy the trunk space as much as possible, and is used for emergency when the tire is punctured. is there.

In the above configuration, the tire rotation speed F ₁ ,
In order to simplify the difference between F ₂ , F ₃ , and F ₄ by the control device 11, the deviation value D in FIG.
It is to obtain the undetermined coefficient C _x of (b). That is, the tire 1 and 3 in the diagonal indicated by the continuous lines in FIGS. 1, a set of tire rotation speed F _n between the tire 2 and 4 in the diagonal lines indicated by the broken line after adding separately , F ₁ + F ₃ are multiplied by an undetermined coefficient C _x and then divided by a value obtained by doubling the average tire rotation number F _n to obtain a deviation value D.

[0018] has a basic determination process that the abnormality detection of the tire air pressure by comparing the thus deviate width with a predetermined width, which will be described later with resulting deviation value D and D _S, the High-speed processing of tire pressure abnormality judgment by comparison (by reducing the number of processing steps in the control device)
In addition, the hardware configuration in the control device 11 can be minimized, thereby realizing a low cost.

The undetermined coefficient C _{x in} FIG. 2B is F ₁
It is obtained by dividing + F ₃ by F ₂ + F ₄ and is used to return the deviation value D to the initial state. Normally, at the start of driving of a vehicle, not all tires have the same condition, and the air pressures are usually different from each other. Also, immediately after tire replacement after puncture repair, or after replacement with emergency tires with a small outside diameter, or when the vehicle speed is insufficient, all tires are not under the same conditions, The difference between the numbers cannot be accurately determined on the tire pressure warning device side. Therefore, before calculating the deviation value D, an undetermined coefficient _Cx is obtained and then F ₁ + F
By multiplying ₃ , the correction for tire replacement etc. after puncture repair is performed.

[0020] Thus, if all the tire is normal, undetermined coefficient C _x becomes a value close to "1", it does not give much of an effect on the deviation value D. However, for example, when the tire 1 is a emergency tire 9, while the "1" value less than the fact that F ₁ is increased, the air pressure of the other tires 2, 3 and 4 is abnormally low, undetermined values of the coefficients C _x to generate a warning (warning) as described below as a determination condition not met in the case of extremely deviates from "1".

Next, FIG. 3 is a flow chart schematically showing the manner in which an abnormality in the tire air pressure is determined from the difference in the number of rotations of the tire. Each of the flow charts to be described later is appropriately interrupted with respect to the flow chart in FIG. It is configured as follows. In the figure, when the process is started, step S1
, The process start, tire rotation speed data, and the like are input as appropriate, and the flow advances to step S2 to determine whether the flag 1 is set. In this step S2,
When the flag 1 is set, the process proceeds to step S3 to determine whether or not the determination condition is satisfied by determining that the above-mentioned undetermined coefficient _Cx is not an abnormal value. When it is determined that the determination condition is satisfied, the process proceeds to step S4, and the tire air pressure is determined. On the other hand, if the flag 1 is not set in step S2, the process proceeds to step S5 and returns.

FIG. 4 is a flow chart for judging the satisfaction of the judgment condition. More specifically, FIG. 4 shows an example of the operation of initializing the above-mentioned undetermined coefficient _CX and generating a warning after detecting an abnormality of the undetermined coefficient _CX. Is shown. In FIG. 4, when the process for determining the satisfaction of the determination condition is started, in step S11, the process start, tire rotation speed data and the like are appropriately input, the process proceeds to step S12, and the initial state in which the determination start switch SW is turned on. Is determined (when a manual switch is provided in the driver's seat). Alternatively, in step S10 surrounded by a broken line, after the deviation value D changes extremely, after the ignition switch is turned on,
Alternatively, after the diagnostic terminal of the self-diagnosis terminal is in the initial state, an initial state signal is automatically output to perform an initial state in which the determination condition is satisfied, and the process proceeds to step S13.

In this step S13, it is provided near the driver's seat.
Warning lamp 10 lights up and the tire pressure
While letting the driver know that preparations are complete,
A flag 0 is set to prohibit the judgment. Next,
Proceed to step S14 to determine the undetermined coefficient C _x Vehicle is constant to get
It is determined whether or not the vehicle is in the traveling state, and the undetermined coefficient C
_x When it is determined that can be obtained, step S15
The undetermined coefficient C is calculated according to the equation (b) of FIG._x Is calculated. Continued
In step S16, the obtained undetermined coefficient C_x Is "1"
It is difficult to judge whether it is an appropriate value that does not deviate greatly.
If the value is an appropriate value, the process proceeds to step S21,
Previous undecided coefficient C_x If is stored, this value
rewrite. If it is not stored, a new registration
Record. By executing the above steps, the undetermined coefficient C_x 
Is registered, and the deviation value D is calculated in consideration of the initial state.
It becomes possible. Therefore, the process proceeds to step S22, and the initial
Set the status switch to "zero" and set the warning lamp 1
0 is turned off and the air pressure judgment is started, while the main flow in FIG.
Set flag 1 in rocha-that.

On the other hand, in step S16, for example,
Immediately after only one tire has traveled on the large road depression, and the undetermined coefficient C _x is uncertain greatly deviating from “1”, it is determined in step S17 whether or not such an uncertain state exists. After that, step S1 is performed again.
4 and execute the following steps. In step S17, when it is determined that the undetermined coefficient C _x is not indefinite but largely deviates from “1” of the undetermined coefficient C _x and is an unsuitable value, the warning lamp 10 becomes noticeable because the tire pressure is abnormal. Flashes to alert the driver. Thereafter, the process proceeds to step S20, and the initial state switch is set to "zero". Further, in step S18, it is determined to be appropriate values not deviate from the "1" of undetermined coefficients C _x, performing the steps after the process returns to step S14.

As described above, for example, even when the emergency tire is mounted or immediately after the tire replacement, the tire pressure abnormality can be accurately determined from the difference in the tire rotation speed, while immediately after the start of operation. By evaluating the undetermined coefficient _Cx as described above, it is possible to easily inform the driver of the tire pressure abnormality, so that sufficient measures can be taken before entering the expressway, for example, and safety can be further secured. In the above, an example of the control flow until immediately after the start of driving has been described. Next, when the vehicle is running, the deviation D obtained from the above equation (the equation of FIG. 2A) has a predetermined width. A determination process for detecting an abnormality in tire air pressure by comparing with the deviation width D _S will be described.

[0026] (a) in FIG. 5, a deviation between the width D _S on the vertical axis,
FIG. 9 is a diagram showing a state in which a deviation value D is within a normal range, with time t on the horizontal axis. FIG. 5B is a diagram showing a state where the deviation value D is in an abnormal state. Then, (a) in FIG. 6 is a state deviation width D _S gradually increases in proportion to the vehicle speed A, also (b) in FIG. 6 by direct proportion to the deviation width D _S halfway the tire temperature rise B Temperature FIG. 10 is a diagram showing a state in which B ｀ is increased and is not changed thereafter.

First, in FIG. 5A, the deviation value D is positive when the value of F ₁ + F ₃ is larger than the value of F ₂ + F ₄ as described above, and when the value is the opposite, Since it becomes negative, the deviation width D _{S in the} range (shown by a dashed line) between the positive D _S1 and the negative D _S1 in the figure becomes the tire pressure normal range, and the deviation value D obtained after the vehicle runs normally. As shown by the solid line and the dashed line in the figure, it is determined that the state is normal when the determination is made within the predetermined period T.

On the other hand, in FIG. 5B, the range in which the deviation value D is sandwiched between the above-mentioned positive D _S1 and negative D _S1 (shown by a dashed line) is shifted upward or downward within a predetermined period T. If so, the tire pressure abnormality is determined. That is, in FIG. 5 (b), if the integrated value 範 囲 D of the range exceeding the positive value D _S1 of the deviation value D exceeds a predetermined value within a predetermined period T, it is determined that the tire pressure is abnormal, and the deviation value D
It is also determined that the tire air pressure is abnormal even if the positive _DS1 suddenly exceeds the negative _DS1 after exceeding the negative _DS1 .

Next, in each drawing of FIG. 5, the positive / negative deviation width D _S2 indicated by the broken line gradually increases in proportion to the increase of the vehicle speed A, as shown in FIG. Like that. Thus by varying the deviation width D _S in accordance with the vehicle speed A, thereby eliminating negative effects due to securing the deviation width D _S. That is, as the vehicle speed A increases, the deviation value D tends to increase, and the damage at the time of occurrence of puncture increases. Therefore, the deviation width D _S2 is set to be larger than the deviation width D _S1. Try to make it less.

Also, as shown in FIG. 6B, by gradually increasing the temperature to a temperature B ｀ in direct proportion to the tire temperature rise B, and setting the deviation width D _S2 so as not to change thereafter.
It is possible to make a determination in consideration of a rise in tire air pressure due to a rise in temperature. Here, parameters other than the vehicle speed A and the tire temperature B shown in FIG. 6 include a load determined by the number of occupants and the like, a value detected by a vehicle height sensor of the active suspension, and a degree of turning. There are yaw turning moment values to be detected, front and rear G, left and right G, and the like.

As described above, without fixing the deviation width D _S , by appropriately changing the deviation width D _S2 in consideration of various factors, it is possible to determine the tire air pressure according to the running state of the vehicle. Can be performed.

Next, FIG. 7 is a tire air pressure determination Furocha <br/> over the windows, and the air pressure determination is started after it is detected that there is no abnormality in the undetermined coefficients C _x above, step S30
The determination timer is started, and the flag "4" is set. Proceeds to step S31 after this, since when the deviation value D found by the above equation is of whether more positive deviation width D _s determined large runs is abnormal, the process proceeds to step S32, the flag 2 It is determined whether or not is set. If 2 is set , the process proceeds to step S33, where the value S _k is set to a value obtained by adding ₁ to the previous value S _k−1 , and then the process proceeds to step S35, where the flag is set. Is set to “2”. Further, in step S32, if the flag 2 is not set, the flow proceeds to step S35 to set the value S _k to zero. In step S35, the process proceeds to step S41 to determine whether a predetermined time (cycle) T has elapsed.

On the other hand, in step S31, the deviation value D
There When it is determined that the positive deviation value D _s is smaller than is the subsequently deviation value D proceeds to step S36 of whether less negative deviation D _s judgment. In this step S36,
Although deviation D that is determined at the moment of least determination if it is determined that the negative deviation D _s is smaller than is abnormal,
Since there may be a simple noise factor, the process proceeds to step S37 to wait for a sufficient time for determination to determine whether or not "3" is set in the flag. If "3" is set in the flag in step S37,
Proceeding to step S38, the value ΣS _{k is changed} to the previous value ΣS _k-1 by 1
And then proceeds to step S41 to set the time T
Wait for the passage of.

On the other hand, if it is determined in step S37 that "3" is not set in the flag, step S39 is executed.
In the flag "3" is set, followed by the value [sigma] s _k is set to "zero" at step S40, waits for the lapse of time T the procedure proceeds to step S41. Time T
When the time has elapsed, the process proceeds to step S42, while returning to step S31 until the time T has elapsed. In step S42, "4" is set in the flag, and the determination result based on the series of steps described above is prepared for determination.
Proceeding to 3, if it is determined that the value S _k or the value ΣS _k exceeds a predetermined value, a tire pressure abnormality is determined in step S44. If it is determined that the value is not more than the predetermined value, the process returns.

If it is determined in step S44 that the tire pressure is abnormal, the process proceeds to step S45, in which a warning lamp is turned on, and in the case of a vehicle equipped with an ABS device, automatic control is performed so as to control the braking operation to a safe side. I do. Similarly, in the case of a vehicle equipped with a TRC device and a vehicle equipped with a 4WS device, the control is automatically performed so as to be on the safe side, and the control is continued until the tires return to a normal state.

By performing the control as described above, in the case where the detection of the tire rotation speed is effectively used, it is possible to accurately determine a tire air pressure abnormality by removing a noise factor in particular.

Next, FIG. 8 is a flow chart of the puncture sensing, when the deviation value D is out larger than the deviation width D _S as indicated by a broken line in FIG. 5 (b), the tire Since the puncture state is caused by a sudden decrease in air pressure, this puncture determination is performed. In FIG. 8, when the process is started, in step S50,
Absolute value comparison is of the deviation value D and the deviation width D _S, if the deviation value D is larger than the absolute value of the deviation width D _S proceeds to step S52 waits for the lapse of time T the procedure proceeds to step S51. In this step S52, steps S50 and S51
If even after execution determination whether or not there is in the running predetermined U number of times, still the deviation value D is determined to be larger than the absolute value of the deviation width D _S is step S53
And a puncture determination is made. As a result, while the warning lamp is turned on, in the case of the vehicle equipped with the ABS device, the brake operation is automatically controlled to be controlled to the safe side. Similarly, in the case of a vehicle equipped with a TRC device and a vehicle equipped with a 4WS device, the control is automatically performed so as to be on the safe side, and the control is continued until the tires return to a normal state. By performing the puncture determination as described above, the puncture determination can be accurately performed by determining the air pressure abnormality occurring within the predetermined time T so as not to make an erroneous determination.

According to each of the flowcharts described above, the driver can judge whether or not the tire pressure is abnormal by turning on the warning lamp, and the driver has sufficient practicality. Is not specified, and it is more preferable that it can be specified. Therefore,
In order to identify a tire having an abnormal air pressure and to notify the driver of the abnormality, processing by a flowchart for identifying an abnormal tire in FIG. 9 is performed, and each warning lamp shown in FIG. 10 is displayed.

Therefore, the processing for identifying the abnormal tire is started.
Then, the process proceeds to step S60 in FIG.
, The deviation value D obtained by using the equation (a) in FIG.
Value and deviation width D_s Are compared, and F₁ + F_Three F than the value of
_Two + F_Four Is larger and the deviation value D is a negative deviation width D_s Yo
If it is determined that the difference is greater than _Two 
+ F_Four Tire 2, 4 which shows the rotation of the tire
It is determined that a puncture has occurred due to an abnormality.

Subsequently, in step S65,
The rotation speed and the engine speed of the tire 4 driven through the differential device 8
Gin rotation speed V_M And the value of the final reduction ratio multiplied by the tire
Number of rotations F of 4_Four Is performed, and the rotation speed F of the tire 4 is
_Four Is the engine speed V _M If greater than tie
In step S67, it is determined that the yam 4 is in a punctured state.
After making a determination, the process proceeds to step S68. This step S68
Now, the display as shown in FIG.
Tire 4 is in a punctured state for a bad driver
To inform. On the other hand, in step S65, the tire 4
Of rotation F_Four Is the engine speed V_M Smaller place
In step S6, it is determined that the tire 2 is in a punctured state.
7 and proceed to step S68 to display similarly
I do.

In step S60, the deviation value D
Value and deviation width D_s Are compared, and F ₁ + F_Three Than the value of
F_Two + F_Four Is smaller, and the deviation value D is a negative deviation width D._s 
If it is determined that it is greater than
Difference value D and positive deviation width D_s And the deviation value D is positive
Difference width D_s If it is determined that it is larger than
Go ahead, F₁ + F_Three One of tires 1 and 3 showing rotation
Judge that there is a puncture due to an abnormality in one of the tires
You. On the other hand, in step S61, the deviation value D
Width D_s If the difference is smaller than
Because there is, the process proceeds to step S62 and the system failure
Is output and the flag is set to “X” to return to the normal flow.
Attribute.

Subsequent to step S63, the rotational speed of the tire 3 driven via the differential gear 8 and the engine rotational speed V _M
And the value obtained by multiplying the final reduction ratio by the rotation speed F _{3 of the} tire ₃
Comparison is performed in the case is greater than the engine speed V _M towards the rotational speed F ₃ of the tire 3 is determined in step S67 that the tire 3 is in a punctured state, the process proceeds to step S68, with respect to the driver To inform that the tire 3 is in a punctured state. On the other hand, in step S66, the that tire 1 is in the puncture state when more speed F ₃ of the tire 3 the engine speed V _M and smaller than determined in step S67, the step S68
Proceed to and display similarly.

Next, FIG. 10 (a) is an energization diagram of the first embodiment of the warning lamp display, (b) is a display example according to the second embodiment, and (c) is a display example according to the third embodiment. And (d) are schematic diagrams showing display examples according to the fourth embodiment. First, in FIG. 10A, the tire 1 or 3 punctured by the above-described flow chart in FIG.
Is specified, the warning lamp display is displayed once at predetermined time intervals as shown in the figure to notify the driver that the tire 1 is in a punctured state. When the tire 3 is punctured, three times are displayed at predetermined time intervals,
Notify puncture status. Thereafter, similarly, two or four flashes are performed to notify the punctured tire. With such a display method, a punctured tire can be displayed by providing only one warning lamp 10 used as described above in the flowchart of FIG.

FIG. 10B shows an example in which a punctured tire is displayed using a so-called 7-segment display. 10 (c) shows the tire 1 as F
L, tire 2 FR, tire 3 RR, tire 4 RL
This is an example in which a punctured tire is directly displayed by printing and displaying on a display panel, and arranging lamps on the back surface of the display panel. FIG. 10 (d) shows an example in which pictographs are printed and displayed, lamps are provided on the back of the display panel, and punctured tires are directly displayed.

By specifying and displaying a punctured tire as described above, for example, when a puncture occurs, it is not necessary to go outside the vehicle and check the punctured tire.

In each of the embodiments described above, the rotation speed obtained from the rotation detector 7 is used in order to detect a difference in tire rotation speed. However, the present invention is not limited to this. There is a method of judging from the distance and the like, which can be appropriately selected.

[0047]

As described above, according to the present invention, when the difference in the number of rotations of the tire is determined on the side of the tire air pressure warning device, the accuracy can be improved without being affected by various noise generation factors generated when the vehicle is running. Abnormal tire pressure can be detected well.

[Brief description of the drawings]

FIG. 1 is a schematic configuration plan view of a tire pressure alarm device.

Figure 2 is a diagram showing an equation for determining the deviation value and undetermined coefficients, is a diagram illustrating the drawing, the equation for (b) are undetermined coefficients C _X indicating the equation for (a) the deviation value D .

FIG. 3 is a flowchart schematically showing a state in which a tire air pressure abnormality is determined from a difference in tire rotation speed.

FIG. 4 is a flowchart for determining whether a tire pressure determination condition is satisfied.

[5] is a comparison view of the deviation value D and the deviation width D _S,
(A) is a diagram showing the deviation width D _S on the vertical axis and time t on the horizontal axis, showing that the deviation value D is within a normal range, and (b) is a diagram showing that the deviation value D is in an abnormal state. FIG.

6 is a corresponding view of the deviation width D _S and the vehicle state,
(A) is a state deviation width D _S gradually increases in proportion to the vehicle speed A, also (b) in FIG. 6 increases the deviation width D _S to `temperature B by direct proportion halfway to the tire temperature rise B It is a figure showing a state that is not changed thereafter.

FIG. 7 is a determination flowchart based on the diagram shown in FIG. 5 (b).

FIG. 8 is a flowchart for puncture determination.

FIG. 9 is a puncture-specific flow chart.

10A and 10B show an embodiment of an alarm device, wherein FIG. 10A is an energization diagram of a first embodiment in which a warning lamp is displayed, and FIG.
FIG. 14 is a schematic diagram illustrating a display example according to an embodiment, (c) is a schematic diagram illustrating a display example according to a third embodiment, and (d) is a schematic diagram illustrating a display example according to a fourth embodiment.

[Explanation of symbols]

1, 2, 3, 4 ... tire, 6 ... propeller shaft, 7 ... rotation speed detector, 8 ... differential device, 9 ... emergency tire, 10 ... warning lamp, 11 ... control device, D ... deviation value, D _sn ... deviation width, C _X ... undetermined coefficients, F _n ... number of tire revolutions, V _M ... engine speed, T ... duration (period), a ... vehicle speed is B ... tire temperature.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-305011 (JP, A) JP-A-4-212610 (JP, A) JP-A-63-258226 (JP, A) JP-A-5-205 116512 (JP, A) JP-A-3-50006 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 23/00-23/08

Claims (1)

(57) [Claims] 1. A four-wheeled vehicle detected by a wheel speed sensor
Using the wheel speed, a deviation value obtained from a predetermined arithmetic expression based on the rotation difference of the four tires is obtained as a positive or negative value, and a comparison with a deviation width having a predetermined width is performed within a predetermined time width. A tire pressure alarm device comprising: a determination unit that determines a tire air pressure abnormality, and a warning unit that notifies the determination result, wherein the determination unit determines that the positive or negative value indicates the deviation width. A tire air pressure alarm device, wherein an abnormality in air pressure is determined when an integrated value in a range exceeding a predetermined value within the predetermined time width.