JP3303681B2 - 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 warning device, and more particularly to a device for estimating tire pressure, judging whether or not the tire pressure is abnormal, and issuing a warning when the tire pressure 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,
Japanese Patent Application Laid-Open No. Hei 6-278421 discloses that the wheel speed (wheel rotation speed) of each of four wheels of a vehicle is detected, a deviation value and an undetermined coefficient are obtained from the wheel speeds of the four wheels, and the deviation value has a predetermined width. It is disclosed that the abnormality of any one of the four wheels is detected by comparing with the deviation value.

[0004]

In the conventional apparatus, in order to obtain the wheel speed of each of the four wheels, the rotation detection pulse of each wheel is counted for a predetermined time. However, when the vehicle turns by steering, a wheel speed difference occurs between the inner wheel side and the outer wheel side of the turn. The steering amount of the vehicle is small when the vehicle speed is high, and the steering amount is large when the vehicle speed is low.

For this reason, when the vehicle speed is lower than when the vehicle speed is high, it is necessary to take a long time until the count number of the rotation detection pulse of each wheel becomes large to some extent so as not to be affected by turning or acceleration / deceleration. Also, since the number of rotation detection pulses in a predetermined time increases as the vehicle speed increases, it takes time to perform accurate tire pressure abnormality detection at a low speed, and high-precision abnormality detection cannot be performed in a short time. There was a problem.

The present invention has been made in view of the above points, and a large decrease in tire air pressure is detected at an early stage by setting a plurality of predetermined values serving as a trigger for calculating a dynamic load radius ratio. It is an object of the present invention to provide a tire pressure abnormality alarm device that can detect over time and perform an error alarm with high accuracy without error.

[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; Calculating means for calculating a dynamic load radius ratio based on a count value of each wheel when a pulse value is counted for each wheel and a count value of an arbitrary wheel becomes a predetermined value; A warning means for issuing a warning that the tire pressure of any of the wheels is abnormal when the ratio is out of a predetermined range corresponding to the predetermined value. Multiple different values
It has a setting means M4 is set to either the same count value of the arbitrary wheel with any of a plurality of different predetermined values
Calculating the dynamic load radius ratio when a predetermined plurality of different
The value of the above-mentioned
The predetermined range corresponding to the predetermined value where the
Compare with the calculated dynamic load radius ratio, and
Configured to issued the warning when it is.

[0008] As described above, the predetermined value is determined by any of a plurality of different values.
When the count value of an arbitrary wheel becomes one of a plurality of different predetermined values, the dynamic load radius ratio is calculated, and the dynamic load radius ratio falls within a predetermined range corresponding to the predetermined value. The tire pressure abnormality determination is performed depending on whether the tire pressure is large or small. Therefore, by setting the predetermined value to a small value, it is possible to detect a sudden decrease (large decrease) in the tire pressure at an early stage. Slow drops (small drops) can be detected over time.

According to a second aspect of the present invention, in the tire pressure warning device according to the first aspect, the setting means sets the predetermined value to a plurality of different values in accordance with a lapse of time from the start of the vehicle.
Change to one of the following values: For this reason, immediately after the start, the predetermined value is set to a small value, and a large decrease in the tire air pressure that greatly affects driving can be detected early, and thereafter, the predetermined value is set to a large value, and a small decrease in the tire pressure can be detected over time.

[0010]

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. By the way, assuming that the wheel speed pulse numbers of the front left wheel, front right wheel, rear left wheel, and rear right wheel are CFL, CFR, CRL, and CRR, the dynamic load radius ratio M is expressed by the following equation.

[0013]

(Equation 1)

The above CL is a predetermined value, and CFL is CL
When it becomes the same as the above, the calculation of the equation (1) is performed to determine the dynamic load radius ratio M. When a small value CL1 is selected as the predetermined value CL, the variation width W1 of the dynamic load radius ratio M increases, and CL
If a medium value CL2 is selected, the variation width W2 of M
Is medium, and if a large value CL3 is selected as CL, the variation width W3 of M becomes small. This is because the influence of turning and acceleration / deceleration becomes relatively small as the predetermined value CL increases. FIG. 4 shows, for example, the measurement times L1, L2, L3 when the predetermined value CL at a vehicle speed of 40 km / h is CL1, CL2, CL3, respectively, and the variation widths W1, W2, W
3 is shown.

When the measurement time is L1 and is short, the variation width of the dynamic load radius ratio M is as large as W1, so that the tire can be distinguished from the tire pressure Pa by the dynamic load radius ratio M as shown in FIG. The air pressure is Pd (Pd <Pa).
In addition, when the measurement time is L2 and is medium, the variation width of the dynamic load radius ratio M is medium and W2, so that it is distinguished from the tire pressure Pa by the dynamic load radius ratio M as shown in FIG. Possible tire pressure is Pc (Pd <Pc <Pa)
It is. Further, when the measurement time is L3 and the length is long, the variation width of the dynamic load radius ratio M is small. Therefore, as shown in FIG. Pb (Pc <Pb <Pa).

The values E1, E2, and E3 of the dynamic load radius ratios shown in FIGS. 5A, 5B, and 5C are the center values at the tire pressure Pa, and E1H, E2H, E3.
H is the maximum value of the variation width (dynamic load radius ratio),
Each of E1L, E2L, and E3L is the minimum value of the variation width (dynamic load radius ratio).

FIG. 6 is a flowchart of a first embodiment of the tire pressure warning process executed by the CPU 40. This process is an interrupt process executed by interruption every predetermined time such as 6 msec. In the figure, in a step S10, it is determined whether or not the value of the register CFL1 is smaller than a predetermined value CL1.
If FL1 <CL1, the process proceeds to step S12, and CFL1
If ≧ CL1, the process proceeds to step S14. Here, the predetermined value C
L1 is, for example, the number of wheel speed pulses obtained at time L1 at a vehicle speed of 40 km / h. In step S12, the wheel speed sensors 21, 22, 2
Wheel speed pulse numbers Δfl, Δf detected at 3, 24, respectively
r, Δrl, Δrr are stored in registers CFL1, CFR, respectively.
1, CRL1 and CRR1 are added. Register CF
L1, CFR1, CRL1, and CRR1 are registers that hold the added values of the wheel speed pulses of the front left wheel, front right wheel, rear left wheel, and rear right wheel, respectively, and are reset to zero when the engine is started.

In step S14, a dynamic load radius ratio M1 is calculated by the following equation.

[0019]

(Equation 2)

Next, it is determined whether or not the dynamic load radius ratio M1 is in the range of a predetermined value M1L to M1H, and M1L> M1 or M1
If M1H is out of the range, the tire air pressure of one of the wheels is decreased, the tire radius is reduced, and it is determined that more wheel speed pulses are output than the other wheels.
Proceed to 8 to issue a tire pressure abnormality alarm, and step S19
Proceed to. If M1L <M1 <M1H is within the range, it is determined that the tire air pressure is normal, and the process proceeds to step S19.
In step S19, the registers CFL1, CFR1, CR
L1 and CRR1 are each reset to zero, and thereafter, the process proceeds to step S20.

In step S20, it is determined whether or not the value of the register CFL2 is less than a predetermined value CL2, and CFL2 <CL2
If CFL2 ≧ CL2, the process proceeds to step S22. Here, the predetermined value CL2 is, for example, the number of wheel speed pulses obtained at time L2 at a vehicle speed of 40 km / h. In step S12, the wheel speed pulse numbers Δfl, Δfr, Δrl, Δ detected by the wheel speed sensors 21, 22, 23, 24 during the period from the previous interrupt to the current interrupt.
rr are stored in registers CFL2, CFR2, CRL2, and C, respectively.
Add to each of RR2. Register CFL2, CFR2,
CRL2 and CRR2 are registers for holding the added values of the respective wheel speed pulses of the front left wheel, front right wheel, rear left wheel and rear right wheel, and are reset to zero when the engine is started.

In step S24, the dynamic load radius ratio M2 is calculated by the following equation.

[0023]

(Equation 3)

Next, it is determined whether or not the dynamic load radius ratio M2 is within a range of a predetermined value M2L to M2H, and M2L> M2 or M2L.
If M2H is out of the range, the tire air pressure of one of the wheels is reduced, the tire radius is reduced, and it is determined that more wheel speed pulses are output than the other wheels.
Proceed to 8 to issue a tire pressure abnormality alarm, and step S29
Proceed to. If M2L <M2 <M2H is within the range, it is determined that the tire pressure is normal, and the process proceeds to step S29.
In step S29, the registers CFL2, CFR2, CR
L2 and CRR2 are each reset to zero, and thereafter, the process proceeds to step S30.

In step S30, it is determined whether or not the value of the register CFL3 is less than a predetermined value CL3, and CFL3 <CL3
If CFL3 ≧ CL3, the process proceeds to step S34. Here, the predetermined value CL3 is, for example, the number of wheel speed pulses obtained at time L3 at a vehicle speed of 40 km / h. In step S32, the wheel speed pulse numbers Δfl, Δfr, Δrl, Δ detected by the wheel speed sensors 21, 22, 23, 24 during the period from the previous interrupt to the current interrupt.
rr is stored in each of the registers CFL3, CFR3, CRL3, C
Add to each of RR3. Register CFL3, CFR3
CRL3 and CRR3 are registers for holding the added values of the wheel speed pulses of the front left wheel, front right wheel, rear left wheel and rear right wheel, respectively, and are reset to zero when the engine is started.

In step S34, the dynamic load radius ratio M3 is calculated by the following equation.

[0027]

(Equation 4)

Next, it is determined whether or not the dynamic load radius ratio M3 is within a range of a predetermined value M3L to M3H, and M3L> M3 or M3L.
If M3H is out of the range, it is determined that the tire air pressure of one of the wheels is reduced, the radius of the tire is reduced, and that more wheel speed pulses are output than the other wheels.
Proceed to 8 to issue a tire pressure abnormality alarm, and step S39
Proceed to. If M3L <M3 <M3H is within the range, it is determined that the tire pressure is normal, and the process proceeds to step S39.
In step S39, the registers CFL1, CFR1, CR
L1 and CRR1 are each reset to zero, and the post-processing ends.

The above steps S10 to S14, S19,
S20 to S24, S29, S30 to S34, and S39 correspond to the calculating means M2, and correspond to steps S16, S26, and S36.
Corresponds to the alarm means M3, and corresponds to steps S10, S20, S
Reference numeral 30 corresponds to the setting means M4.

The case where the tire air pressure of any one of the four wheels at a constant vehicle speed gradually decreases from Pa to Pb as shown in FIG. 7A due to spontaneous leakage or the like will be described. FIG.
FIG. 2B is an enlarged view of FIG. When the tire pressure becomes equal to or lower than Pb within the measurement time L3 from the time t0, an alarm is issued at the start of the next measurement time L3 as shown at a high level in FIG.

On the other hand, if the tire air pressure does not fall below Pc (Pc <Pb) during the measurement time L2, it is indistinguishable from Pa. Therefore, as shown in FIG. It cannot be emitted. If the tire pressure does not fall below Pd (Pd <Pb) even during the measurement time L1, it cannot be distinguished from Pa, so that it does not go to a high level as shown in FIG.

A case where the tire pressure of any one of the four wheels at a constant vehicle speed sharply decreases from Pa to Pb due to puncture or the like as shown in FIG. 8A will be described. FIG.
FIG. 2B is an enlarged view of FIG. Time t10
If the tire air pressure becomes equal to or less than Pd within the measurement time L1 from the start, an alarm is issued as shown at a high level in FIG.

On the other hand, in the measurement time L2, the start time t1 of the next measurement time L2 when the tire pressure becomes equal to or less than Pc.
At 2, the high level is set as shown in FIG. Also at the measurement time L3, at the start time t13 of the next measurement time L3 at which the tire pressure becomes equal to or lower than Pb, the level becomes high as shown in FIG.

That is, when there is a sudden decrease in tire air pressure, an alarm is issued within a short measurement time L1. Note that the measurement times L1, L2, and L3 correspond to the wheel speed pulse numbers CL1, CL2, and CL3, respectively, and the wheel speed pulse number is equivalent to the travel distance. Is also good.

In the first embodiment, the wheel speed pulse number is C
Although the determination of the tire pressure abnormality of each of L1, CL2, and CL3 is performed in parallel, in the following second embodiment, the determination of the tire pressure abnormality with the wheel speed pulse number CL1 is performed first, and then the wheel speed pulse number CL2 is determined. The tire pressure abnormality of
After that, the tire pressure abnormality determination for the wheel speed pulse number CL3 is performed.

FIG. 9 shows a flowchart of a second embodiment of the tire pressure warning process executed by the CPU 40. This process is an interrupt process executed by interruption every predetermined time such as 6 msec. In the figure, at step S50, the value of a timer T that measures time from the start of the engine is a predetermined value T1 + T2.
Is determined, the process proceeds to step S55 if T ≦ T1 + T2, and proceeds to step S80 if T> T1 + T2. In step S55, it is determined whether or not the value of the timer T exceeds a predetermined value T1. If T ≦ T1, the process proceeds to step S60, and if T> T1, the process proceeds to step S60.
Go to 70. In step S60, it is determined whether or not the value of the register CFL3 is less than a predetermined value CL3, and CFL3 <CL3
If CFL3 ≧ CL3, the process proceeds to step S34. Here, the predetermined value CL3 is, for example, the number of wheel speed pulses obtained at time L3 at a vehicle speed of 40 km / h. In step S62, the number of wheel speed pulses Δfl, Δfr, Δrl, Δ detected by the wheel speed sensors 21, 22, 23, 24 during the period from the previous interrupt to the current interrupt.
rr is stored in each of the registers CFL3, CFR3, CRL3, C
Add to each of RR3. Register CFL3, CFR3
CRL3 and CRR3 are registers for holding the added values of the wheel speed pulses of the front left wheel, front right wheel, rear left wheel and rear right wheel, respectively, and are reset to zero when the engine is started.

In step S64, the dynamic load radius ratio M3 is calculated by the following equation.

[0038]

(Equation 5)

Next, it is determined whether or not the dynamic load radius ratio M3 is within a range from a predetermined value M3L to M3H, and M3L> M3 or M3L.
If> M3H is out of the range, it is determined that the tire air pressure of one of the wheels has decreased and the tire radius has decreased, and that more wheel speed pulses have been output than the other wheels.
Proceeding to 8, a tire pressure abnormality alarm is issued and step S69
Proceed to. If M3L <M3 <M3H is within the range, it is determined that the tire pressure is normal, and the process proceeds to step S69.
In step S69, the registers CFL3, CFR3, CR
Each of L3 and CRR3 is reset to zero, and the process ends.

In step S70, it is determined whether or not the value of the register CFL2 is less than a predetermined value CL2, and CFL2 <CL2
If CFL2 ≧ CL2, the process proceeds to step S74. Here, the predetermined value CL2 is, for example, the number of wheel speed pulses obtained at time L2 at a vehicle speed of 40 km / h. In step S72, the number of wheel speed pulses Δfl, Δfr, Δrl, Δ detected by the wheel speed sensors 21, 22, 23, 24 during the period from the previous interrupt to the current interrupt.
rr are stored in registers CFL2, CFR2, CRL2, and C, respectively.
Add to each of RR2. Register CFL2, CFR2,
CRL2 and CRR2 are registers for holding the added values of the respective wheel speed pulses of the front left wheel, front right wheel, rear left wheel and rear right wheel, and are reset to zero when the engine is started.

In step S74, the dynamic load radius ratio M2 is calculated by the following equation.

[0042]

(Equation 6)

Next, it is determined whether or not the dynamic load radius ratio M2 is within a range of a predetermined value M1L to M2H, and M2L> M2 or M2L.
If> M2H is out of the range, it is determined that the tire radius of one of the wheels has decreased due to a decrease in the tire air pressure of one of the wheels, and that more wheel speed pulses have been output than the other wheels.
Proceed to 8 to issue a tire pressure abnormality alarm, and step S79
Proceed to. If M2L <M2 <M2H is within the range, it is determined that the tire pressure is normal, and the process proceeds to step S79.
In step S79, the registers CFL2, CFR2, CR
Each of L2 and CRR2 is reset to zero, and the post-processing ends.

In step S80, it is determined whether or not the value of the register CFL1 is less than a predetermined value CL1, and CFL1 <CL1
If CFL1 ≧ CL1, the process proceeds to step S84. Here, the predetermined value CL1 is, for example, the number of wheel speed pulses obtained at time L1 at a vehicle speed of 40 km / h. In step S82, the wheel speed pulse numbers Δfl, Δfr, Δrl, Δ detected by the wheel speed sensors 21, 22, 23, 24 during the period from the previous interrupt to the current interrupt.
rr are stored in registers CFL1, CFR1, CRL1, C
Add to each of RR1. Registers CFL1, CFR1,
CRL1 and CRR1 are registers for holding the added value of the wheel speed pulse of each of the front left wheel, front right wheel, rear left wheel, and rear right wheel, and are reset to zero when the engine is started.

In step S84, the dynamic load radius ratio M1 is calculated by the following equation.

[0046]

(Equation 7)

Next, it is determined whether or not the dynamic load radius ratio M1 is within a range of a predetermined value M1L to M1H, and M1L> M1 or M1L.
If> M1H is out of the range, it is determined that the tire air pressure of one of the wheels has decreased and the tire radius has decreased, and that more wheel speed pulses have been output than the other wheels.
Proceed to 8 to issue a tire pressure abnormality alarm, and step S89
Proceed to. If M1L <M1 <M1H is within the range, it is determined that the tire pressure is normal, and the process proceeds to step S89.
In step S89, the registers CFL1, CFR1, CR
L1 and CRR1 are each reset to zero, and the post-processing ends.

As shown in FIG. 10A, the tire pressure of one of the four wheels at a constant speed is reduced due to natural leakage or the like.
From Pb to Pb will be described. FIG. 10B is an enlarged view of FIG. If the tire pressure has become equal to or less than Pd within the measurement time L1 within a time period corresponding to the predetermined value T1 from the start of the engine (time t20), the timing (E) at the start of the next measurement time L1 (t21).
An alarm is issued as shown at a high level.

Thereafter, after a lapse of the time corresponding to the predetermined value T1, the measurement time L is elapsed until the time corresponding to the predetermined value T1 + T2 elapses.
2, the tire pressure abnormality is determined, and the next measurement time L2
At the start time t22, an alarm is issued as shown at a high level in FIG. Further, after a lapse of the predetermined time T1 + T2, a tire pressure abnormality determination is made at the measurement time L3, and an alarm is issued at a start time t23 of the next measurement time L3 as shown by a high level in FIG. In this embodiment, a short measurement time L1 is used immediately after starting the engine, which is required to detect a large decrease in tire air pressure such as a puncture in a short time, and then the measurement times are sequentially increased to L2 and L3. To detect a slow decrease in tire pressure.

[0050]

According to the first aspect of the present invention, since the predetermined value is set to one of a plurality of different values, the count value of an arbitrary wheel becomes one of a plurality of different predetermined values. When the dynamic load radius ratio is calculated, the tire pressure abnormality determination is performed based on whether the dynamic load radius ratio is within or outside a predetermined range according to a predetermined value. A small decrease (large decrease) can be detected early, and a slow decrease (small decrease) in tire air pressure can be detected over time by setting the predetermined value to a large value.

[0051]

According to the second aspect of the present invention, immediately after the start, the predetermined value is set to a small value to detect a large decrease in tire air pressure which has a great effect on driving at an early stage. Can be detected over time.

[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 diagram for explaining the principle of the present invention.

FIG. 5 is a diagram for explaining the principle of the present invention.

FIG. 6 is a flowchart of a tire pressure warning process.

FIG. 7 is a diagram for explaining the principle of the present invention.

FIG. 8 is a diagram for explaining the principle of the present invention.

FIG. 9 is a flowchart of a tire pressure warning process.

FIG. 10 is a diagram for explaining the principle of the present invention.

[Explanation of symbols]

 11-14 wheels 21-24 wheel speed sensor 25 ECU 30 alarm device M1 wheel speed detecting device M2 calculating device M3 warning device M4 setting device

Claims (2)

(57) [Claims] 1. A wheel speed detecting means for detecting a rotation of each wheel of a vehicle to generate a wheel speed pulse, and counting the wheel speed pulse for each wheel so that a count value of an arbitrary wheel becomes a predetermined value. Calculating means for calculating a dynamic load radius ratio based on the count value of each wheel, and when the calculated dynamic load radius ratio is out of a predetermined range according to the predetermined value, a tire of one of the wheels A warning means for issuing a warning when the air pressure is abnormal, comprising: changing a predetermined value of the calculating means to one of a plurality of different values.
Further to have a setting means for setting, to calculate the dynamic load radius ratio when it becomes the same as any of the predetermined value different from the count value of the arbitrary wheel of plural,
Different predetermined ranges corresponding to different predetermined values of
Of the above-mentioned count values correspond to the predetermined value
Compare the constant range with the calculated dynamic load radius ratio,
Serial tire pressure warning system, characterized by being configured to calling an alarm when a predetermined range. 2. The tire pressure warning device according to claim 1, wherein the setting unit changes the predetermined value to one of a plurality of different values according to a lapse of time from a start of the vehicle. Tire pressure warning device.