JP3189674B2 - Tire pressure determination 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 judging device and, more particularly, to a device for estimating tire pressure and judging whether or not it is abnormal.

[0002]

2. Description of the Related Art Wheel speed is used in a vehicle control device for controlling the motion of a vehicle by controlling the motion state of the wheel, for example, the slip ratio of the wheel and the braking / driving force. further,
It is also used in a wheel characteristic detecting device that detects a characteristic of a wheel such as a tire pressure of the wheel.

Conventionally, a tire pressure warning device has been developed which estimates the tire pressure of each wheel using the wheel speed or rotational angular speed of each of the four wheels, and issues, for example, an alarm when the tire pressure of any of the wheels drops. Have been. For example,
In Japanese Patent Application Laid-Open No. 6-92115, the rotational angular velocities F1, F2, F3, and F4 of each of the four wheels are obtained, and the sum F1 + F4 of the rotational angles of a pair of diagonal wheels and the rotation of a pair of other diagonal wheels are determined. The ratio dF to the sum of angular velocities F2 + F3 = (F1
+ F4) / (F2 + F3) as the dynamic load radius ratio,
When the ratio dF is not 1, it is detected that the air pressure of one of the tires has decreased.

[0004]

In the conventional apparatus, the rotation detection pulse of each wheel is counted for a predetermined time in order to obtain the rotational angular velocity of each wheel. Further, since the dynamic load radius ratio dF is easily affected by steering and acceleration / deceleration, in order to improve the accuracy, counting is performed until the count value of the rotation detection pulse of each wheel increases. That is, a long time count is performed. Further, the dynamic load radius ratio dF is obtained from the count values F1, F2, F3, F4 of the rotation detection pulses as the rotational angular velocities of the respective wheels.

Accordingly, the sum of the rotational angular velocities (F1 + F4),
(F2 + F3) each have a large value, that is, a large number of bits, and C is used to divide the sum of these rotational angular velocities.
There is a problem that the load on the PU increases. Usually, this CPU is often the CPU of a vehicle control device that controls the motion of the vehicle. In this case, the load increases by obtaining the dynamic load radius ratio dF, so that the control process executed by the CPU is delayed. The problem arises.

The present invention has been made in view of the above points, and obtains a deviation of a count value of a wheel speed pulse of each wheel from a predetermined value, and obtains an approximate value of a dynamic load radius ratio by adding or subtracting the deviation. To provide a tire pressure determination device in which the number of bits of data when calculating an approximate value of the dynamic load radius ratio can be reduced by performing the determination of the air pressure, can be calculated only by addition and subtraction, and the calculation load is small. With the goal.

[0007]

According to the first aspect of the present invention, as shown in FIG. 1, a wheel speed detecting means M1 for detecting rotation of each wheel of a vehicle to generate a wheel speed pulse; by counting the number of pulses for each wheel, when the wheel speed pulse number of the particular wheel has a number of pulses greater than a predetermined value, obtains the difference between the number of pulses of the wheel speed pulse number and the predetermined value of the respective wheels ,
Deviation calculating means M2 for adding the difference a predetermined number of times to obtain a first deviation for each wheel; a first deviation for the left front wheel and a first deviation for the right front wheel;
, A first deviation of the left rear wheel and a first deviation of the right rear wheel.
An approximate value calculating means M3 for obtaining a second deviation, which is a difference from the deviation, as an approximate value of the dynamic load radius ratio, and when the approximate value of the dynamic load radius ratio is out of a predetermined range centered on zero. ,
Determining means M4 for determining that the tire pressure of one of the wheels is abnormal.

As described above, by using the first deviation between the wheel speed pulse number of each wheel and the pulse number of a predetermined value , each wheel
The first deviation has a small value and a small number of bits,
Further, since the approximate value of the dynamic load radius ratio can be obtained only by performing the addition and subtraction of the first deviation of each wheel, the calculation load is reduced.

[0009]

FIG. 2 is a schematic diagram showing an embodiment of the apparatus according to the present invention. In the figure, the left and right front wheels 11, 12 and the left and right rear wheels 13, 14 are provided with wheel speed sensors 21, 22, 23, 24 as wheel speed detecting means M1, respectively. The wheel speed pulses detected for each of the four wheels are supplied to an electronic control circuit (ECU) 25. An alarm 30 is connected to the ECU 25.

As shown in FIG. 3, the ECU 25 includes a central processing unit (CPU) 40 and a read only memory (ROM) 4.
2 and a random access memory (R
AM) 44, an input port circuit 46, an output port circuit 48, and an electric erasable programmable read only memory (EEPRO) which is a nonvolatile memory.
M) 50, which are connected to each other by a bidirectional bus 52. The alarm 30 is connected to the output port circuit 48.

The input port circuit 46 includes a wheel speed sensor 21
24 to 24 are input. The principle of the present invention will be described. The count values of the wheel speed pulses of the four wheels are Pfr, Pfl, Prr, and Prl. Here, when the predetermined value Q is used, the following equation is established.

Pfr = n · Q + Δfr Pfl = n · Q + Δfl Prr = n · Q + Δrr Pfl = n · Q + Δrl where the difference S between the left-right difference between the front wheels and the right-left difference between the rear wheels is equivalent to the dynamic load radius ratio k, That is, it is an approximate value and is represented by the following equation.

S = n · Q · k = (Pfr−Pfl) − (Prr−Prl) = (Δfr−Δfl) − (Δrr−Δrl) The tire pressure of each of the four wheels is normal, and the tire radius of each wheel is substantially equal. if the same Δfr-Δfl ≒ 0 Δrr-Δ r l ≒ 0 , and becomes the S ≒ 0. Further, for example, if either the left or right of the front wheel is punctured and the radius of the tire is reduced, Δfr−Δfl = a Δrr−Δrl = 0, and S = a (≠ 0). If all four wheels are at normal pressure, Δfr, Δfl, Δrr, and Δrl each take a value near zero.

FIG. 4 shows a flowchart of the tire pressure warning process executed by the CPU 40. This process is, for example, an interrupt process executed by interruption every 6 msec. In the figure, in step S10, a cycle counter (cycle Coun
ter) is determined to be less than a predetermined value n (n is, for example, 16), and if the cycle counter <n, the process proceeds to step S12. The cycle counter is reset to zero at the start of the main routine. In step S12, it is determined whether or not the value of the pulse counter pfr is less than a predetermined value Q. If pfr <Q, the process proceeds to step S14.

The counter pfr is a 15-bit counter for counting the wheel speed pulses of the right front wheel, and similarly, the 15-bit counters pfl, prr, pr
For each of the left front wheel, the right rear wheel, and the left rear wheel, the wheel speed pulses are counted. The predetermined value Q is 30,000, for example.

In step S14, counters nfr, nfl, nr which count the wheel speed pulses of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel generated after the previous processing of FIG.
The respective values of r and nrl are calculated by the following equations using counters pfr and pf
Integration is performed for each of l, prr, and prl.

Pfr = pfr + nfr pfl = pfl + nfl prr = prr + nrr prl = prl + nrl After this integration, counters nfr and nf are obtained in step S16.
Each of l, nrr, and nrl is reset to zero and the processing cycle ends.

After repeating steps S10 to S16,
If pfr ≧ Q in step S12, step S12
Proceed to 18. Here, other counters pfl, prr, p
rl are also near Q, and in step S18 as the deviation calculating means M2, pfr, pfl, pr are calculated by the following equations.
deviations r and prl from Q and Δfr, Δfl, Δrr,
Integrate Δrl.

Δfr = Δfr + (pfr−Q) Δfl = Δfl + (pfl−Q) Δrr = Δrr + (prr−Q) Δrl = Δrl + (prl−Q) Next, in step S20, the cycle counter is incremented by one, and the counter is incremented by one. pfr, pfl, prr, pr
1 is reset to zero, and the processing cycle ends. After this step S18, S20 is repeated n times, becomes cycle counter ≧ n in step S10, step S2
Proceed to 2. This means that the occurrence of the right front wheel of the wheel speed pulse is 480
At some point beyond 000 pulses, the process proceeds to step S22.

In step S22, a judgment flag judge
Is reset to 0, and in the next step S24, the dynamic load radius ratio (Δfr−Δfl−Δrr + Δr) is calculated from the integrated deviation of the four wheels.
1) is determined, and it is determined whether or not this exceeds a threshold value K.
If K <Δfr−Δfl−Δrr + Δrl, the determination flag judge is set to 1 in step S26, and the process proceeds to step S28, where K ≧ Δfr−Δfl−Δrr + Δrl.
In the case of, the process proceeds directly to step S28.

In step S28, a dynamic load radius ratio (.DELTA.fr-.DELTA.fl-.DELTA.rr + .DELTA.rl) is obtained from the integrated deviation of the four wheels, and it is determined whether or not this is less than a threshold value -K. −K> Δf
If r−Δfl−Δrr + Δrl, the determination flag judge is set to 1 in step S30, and step S32 is performed.
The process proceeds to step S32 if −K ≦ Δfr−Δfl−Δrr + Δrl. Step S2 above
4 to S30 correspond to the approximate value calculation means M3 and the determination means M4.

In step S32, a judgment flag judge
Is determined to be 1 or not, and if judge = 1, the process proceeds to step S34, a puncture warning is issued from the alarm device 30, and the process proceeds to step S36. If judge ≠ 1, the process proceeds directly to step S36. That is, the dynamic load radius ratio (Δfr−Δ
When fl−Δrr + Δrl) is in the range from K to −K, since the wheel speeds of the four wheels are substantially the same, no puncture is issued and no puncture warning is issued, and the dynamic load radius ratio exceeds K. Or less than -K, a puncture warning is issued assuming that the tire air pressure of one of the wheels is reduced, the tire radius is reduced, and more wheel speed pulses are output than the other wheels.

At step S36, the integrated deviations Δfr, Δ
Each of fl, Δrr, and Δrl is reset to zero, then the cycle counter is reset to zero in step S38, and each of the counters pfr, pfl, prr, and prl is reset to zero, and the processing cycle ends.

As described above, the count values pfr, pfl, prr, and prl of the wheel speed pulses of each wheel and the predetermined value Q
By calculating the deviations .DELTA.fr, .DELTA.fl, .DELTA.rr, and .DELTA.rl, the deviations .DELTA.fr, .DELTA.fl, .DELTA.rr, and .DELTA.rl of the respective wheels are small, the number of bits is reduced, and the addition and subtraction of the deviation of each wheel (S = .DELTA.fr) −Δfl−Δrr−Δrl)
, An approximate value S of the dynamic load radius ratio can be obtained, so that the calculation load is reduced. This allows the CPU
40 can execute other processes without delay as much as the load is reduced.

[0025]

As described above, the first aspect of the present invention provides
A wheel speed detecting means for detecting the rotation of each wheel of the vehicle to generate a wheel speed pulse, and counting the wheel speed pulse for each wheel, so that the wheel speed pulse number of a specific wheel is equal to or more than a predetermined value pulse number. when it became obtains a difference between the number of pulses of the wheel speed pulse number and the predetermined value for each wheel, first and said difference by adding a predetermined times 1
Deviation calculating means for calculating a deviation of each wheel, and a first deviation of the left front wheel.
And the difference between the first deviation of the right front wheel and the first deviation of the left rear wheel.
Center and the approximate value calculating means for determining a second deviation which is a difference between the difference between the first deviation of the deviation and the right rear wheel as an approximation of the dynamic load radius ratio, the approximate value of the dynamic load radii ratio zero And determining means for determining that the tire pressure of any one of the wheels is abnormal when the pressure is out of the predetermined range.

As described above, by using the first deviation between the wheel speed pulse number of each wheel and the predetermined number of pulse numbers , each wheel
The first deviation has a small value and a small number of bits,
Further, since the approximate value of the dynamic load radius ratio can be obtained only by performing the addition and subtraction of the first deviation of each wheel, the calculation load is reduced.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a schematic configuration diagram of the present invention.

FIG. 3 is a block diagram of an ECU.

FIG. 4 is a flowchart of a tire pressure warning process.

[Explanation of symbols]

 11-14 wheels 21-24 wheel speed sensor 25 ECU 30 alarm M1 wheel speed detecting means M2 deviation detecting means M3 determining means

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 23/00-23/06

Claims (1)

(57) [Claims] 1. A wheel speed detecting means for detecting rotation of each wheel of a vehicle to generate a wheel speed pulse, and counting the number of wheel speed pulses for each wheel to determine a specific wheel. when the wheel speed pulse number reaches the number of pulses greater than a predetermined value, the number of pulses of the predetermined value and the wheel speed pulse number of each wheel
A difference calculating means for obtaining a difference and adding the difference a predetermined number of times to obtain a first deviation for each wheel ; a difference between a first deviation of the left front wheel and a first deviation of the right front wheel;
The difference between the first deviation of the rear wheel and the first deviation of the right rear wheel
An approximate value calculating means for obtaining a certain second deviation as an approximate value of the dynamic load radius ratio; and when the approximate value of the dynamic load radius ratio is out of a predetermined range centered on zero, the tire pressure of one of the wheels is A tire pressure judging device comprising: judging means for judging an abnormality.