JPH0748407Y2 - Tire pressure alarm device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a tire pressure warning device, and more particularly to a tire pressure warning device for warning a tire abnormal pressure drop or puncture.

[Prior Art] If the air pressure of a tire (hereinafter, referred to as tire pressure) is abnormally lowered, not only the maneuverability is deteriorated, but also a standing wave phenomenon occurs during high speed running, which is very dangerous.

Conventionally, such a tire pressure abnormality is detected by a tire pressure warning system shown in FIG. 4 (“Toyota Technology”, June 1986, Vol. 36, No. 1, page 61, FIG. 9). ). It has a built-in pressure switch in each wheel, and the output of the pressure switch is transmitted by transmitters 24, 25, 26, 27 attached to each wheel, and this transmission signal is transmitted to an antenna 28.
The signal is sent to the receiver 29 via the, and an alarm is issued based on the transmitted signal.

In the system of FIG. 4, since the pressure switch is built in the tire, the mounting itself is difficult and the tire tube is easily damaged. Further, the tire pressure varies depending on the temperature difference such as in summer and winter, which makes it difficult to adjust the pressure switch.

On the other hand, when the tire is flat or the tire force is abnormally reduced, the dynamic radius of gyration becomes smaller and the rotational speed becomes relatively higher. Utilizing this phenomenon, there is known a device that detects an abnormality in the relative rotation speed by a rotation speed sensor attached to each wheel, and issues an alarm to a traveling driver without incorporating a pressure switch.

Such a device, for example, as disclosed in JP-A-59-206212, compares the rotation speed ratio of each wheel with a limit value, and the comparison result is determined to be a tire pressure imbalance. When the vehicle speed is slow, it is highly probable that the vehicle is traveling on a curve, and even if the tire pressure is the same, it is likely that there will be a difference in the number of rotations, and the vehicle speed will be low. The influence of the curve is eliminated by increasing the allowable range of the rotational speed ratio.

However, the above-mentioned device which is intended to prevent malfunction during traveling on a curve has the following problems. First, when obtaining the average number of revolutions, if the count distance is set long, the malfunction can be prevented to some extent. However, for example, in the section where there are many curves in one direction, the malfunction cannot be avoided even if the distance is set long. If the count distance is set too long, the responsiveness of the alarm will deteriorate. Next, if the permissible range of the rotational speed ratio is increased as the vehicle speed becomes lower, stochastic malfunctions may certainly decrease, but in reality, the tire pressure will be abnormal during straight running when the vehicle speed is slow. Even if the drop occurs, the abnormality cannot be detected. Further, as in the case of curve running, the wheel rotation speed ratio fluctuates due to the idling or braking of the drive wheels on a temporarily low friction road, etc. However, the above-mentioned device does not take measures against it.

Therefore, by eliminating from the driving conditions of the vehicle a condition that causes a rotation difference in each wheel even if the tire pressure is normal, the above problems are solved, malfunction of the alarm is prevented, and reliability is improved. A tire pressure warning device was provided. This is disclosed in Japanese Utility Model Laid-Open No. 62-74008 of the present applicant and has a structure shown in FIG. Each wheel 20, 21, 2
Rotation speed sensors 1, 2, 3, 4 that detect the rotation speed of 2, 23
And a steering wheel angle sensor 30 for detecting the steering wheel angle of the wheels. These sensors are connected to a calculation unit 31 for obtaining the rotation speed ratio of each wheel. The calculation unit 31 outputs an operation signal to the alarm unit 32. Here, the sensors shown in FIG. 6 are used as the rotation speed sensors 1, 2, 3, and 4. Magnetic poles are provided on a magnetizing disk 33 attached to the wheels 20 to 23, and a coil 35 is wound around a fixed core 34 so as to face the magnetic teeth. Since the magnetizing disk 33 also rotates with the rotation of the wheel, the core is regenerated every time the magnetic pole teeth pass in front of the core 34.
The magnetic flux passing through 34 changes, and the pulse current is detected corresponding to the number of magnetic pole teeth passing through the coil 35. The rotation speed of the wheel can be detected from the number of pulses.

Further, as the steering wheel angle sensor 30, the sensor shown in FIG. 7 is used. The steering wheel 36 is fitted on an upper portion of a steering shaft 37 supported by a column tube 38. Ring electrodes 39 and 40 are arranged on the upper end surface of the column tube 38, and brushes 42 and 43 are attached to the lower end portion of the steering wheel 36 facing the upper end surface of the column tube 38, and the brushes 42 and 43 are electrodes. When the switch 47 is turned on by sliding on 39 and 40, the in-vehicle battery 45
The horn 46 is energized from. As the steering wheel angle sensor 30, a conductor 41 is provided inside the electrode 40 at a position where the wheel is straight, that is, at a position corresponding to 0 °, and a brush 44 that can contact the conductor 41 is provided at the lower end of the steering wheel 36. Brush 41
Is electrically connected to the brush 42, the rotation of the steering wheel 36 causes the brush 44 to move and slide on the conductor 41. Is output. At this time, the steering wheel angle is zero, which means that the vehicle is traveling straight.

When the arithmetic unit 31 first determines from the detection signal of the steering wheel angle sensor 30 that the vehicle is traveling straight instead of traveling in a curve, it detects the rotational speeds N _1i , N _2i , N _{3i of the} wheels 20 to 23. , N _4i
Is read and the rotation speed ratios N _1i / N _2i and N _3i / N _4i of the left and right wheels are obtained. Next, this rotation speed ratio is the judgment value A and its inverse value 1 / A.
If this does not fit within the range with (for example, N _2i / N _1i is taken into account), it is determined that the wheel is temporarily idling or locked and excluded, and if it falls within the above range, Whether or not the integrated rotational speed ratios ΣN1i / ΣN2i, ΣN3i / ΣN4i obtained by integrating the rotational speed ratios for a certain period of time fall within the range defined by another judgment value B and its inverse value 1 / B. If it does not fall within this range, it is judged as a real abnormal decrease in tire pressure or a flat condition and an alarm unit
It outputs an alarm signal to 32.

[Problems to be solved by the invention]

In the tire pressure alarm device shown in FIG. 5, the above-mentioned judgment value compared with the additional rotation speed ratio is the tire effective diameter r ₁ when the tire pressure is normal, and the puncture time if the tire pressure is normal. Must be set to a value larger than the ratio r ₁ / r ₂ of the effective diameter r ₂ of the tires. This judgment value can detect one-sided clutch (lock) and slip (idle) during braking. When braking, only one wheel is rarely locked and often falls within the above judgment value. Therefore, useless calculation is performed and only the left / right wheel ratio is used. When it became, it was not possible to judge.

In addition, the road surface is usually uneven even during straight running (when the brake pedal is not depressed). Therefore, even if the tire pressure is normal, only one wheel may run longer. In such a case, the tire pressure warning device described above has a problem that the added rotation speed ratio does not fall within the determination value, and the tire pressure is erroneously determined to be abnormal.

Therefore, the object of the present invention is to exclude from the driving conditions of a vehicle a condition that causes a rotation difference of each wheel even if the tire pressure is normal, and to accurately detect which of the wheels has an abnormal tire pressure. It is to provide a tire pressure alarm device that can do this.

[Means for solving problems]

As means for solving the above-mentioned problems, in the tire pressure warning device according to the present invention, the brakes are depressed by the rotation speed detecting means of each wheel, the steering wheel angle sensor and the brake switch during straight running. When the vehicle height sensor detects that the road is flat and has no unevenness, the rotation speeds are integrated and the tires of the wheels when the ratio of the rotation speed of each wheel to the average rotation speed of all wheels is at least 1 or more. And a calculating means for determining that the pressure is decreasing and outputting an alarm signal to the alarm means.

[Action]

In the present invention, the output of the steering wheel angle sensor detects that the vehicle is traveling straight, and the output of the brake switch detects that the brake is not stepped on and the output of the vehicle height sensor detects that the road surface is not uneven. , Exclude running conditions in which the tire pressure is normal but the rotation speed of each wheel varies. Then, the rotation speed of each wheel at that time is detected and integrated by the output of the rotation speed detection means, the rotation speed of each wheel and the average rotation speed of all the wheels are compared, and if the ratio is at least greater than 1, the tire When it is judged that the pressure has decreased, an alarm signal is output to the alarm means to issue an alarm.
Thereby, the tire pressure abnormality of any wheel can be detected.

〔Example〕

An embodiment of the tire pressure warning device according to the present invention will be described below.

FIG. 1 shows a system block in an embodiment of the present invention. Reference numerals 1, 2, 3, 4 are rotation speed sensors as rotation speed detection means provided for every four wheels, and 5 is a steering wheel angle sensor. , 6 is a brake switch, 7, 8, 9, and 10 are vehicle height sensors, 11 is an input processing circuit 12, a central processing unit (CP).
U) 13, a controller comprising a memory 14 and an output processing circuit 15 as an arithmetic means, and 16 an alarm display device as an alarm means.

Here, the arrangements of the rotation speed sensors 1, 2, 3, 4 and the steering wheel angle sensor 5 are the same as those shown in FIG. 5, and the rotation speed sensor is the one shown in FIG. As the sensor 5, the one shown in FIG. 7 can be used.

Further, the vehicle height sensors 7, 8, 9 and 10 are provided for every four wheels, and the one having the structure schematically shown in FIG. 3 (a) can be used. That is, the axle 18 is suspended on the chassis 17 via the spring 19, and the sensors 7 to 10 are arranged in or near the spring 19. As shown in FIG. 3 (b), the variation of the vehicle height H is output from the sensors 7 to 10 according to the expansion and contraction of the spring 19, and this output signal is digitalized by the A / D converter in the input processing circuit 12. And is input to the CPU 13.

The brake switch 6 may be a switch whether or not the brake pedal is depressed, and an "H" level signal is obtained when the brake pedal is depressed.

Next, the operation of the tire pressure warning device shown in this embodiment will be described with reference to the program flow chart of the controller 11 shown in FIG.

First, each rotation speed sensor 1 provided for every four wheels,
Signal output of 2, 3 and 4 for Δt seconds, for example 0.05 to 0.20
Read only [s]. At this time, the rotation speeds P ₁ , P ₂ ,
P ₃ and P ₄ are equivalent to the number of pulses of each output of the sensors 1 to 4, and are counted by the pulse counter in the input processing circuit 12 and sent to the CPU 13. The CPU 13 stores the rotational speeds P ₁ , P ₂ , P ₃ , P ₄ of each wheel in the memory 14 and calculates the average value = (P ₁ + P ₂ + P ₃ + P ₄ ) / 4 (step
S1).

Here, first, it is preferable to exclude the low speed traveling state.
Since the average value is proportional to the vehicle speed, it is compared with the set value P ₀ . The set value P ₀ is, for example, a converted value corresponding to 50 km / h,
If it is less than or equal to the set value P ₀ , the process is terminated, and if it is more than this, the process proceeds to the next step (step S2).

When the brake pedal is pressed, the rotation speed of each wheel is affected. Therefore, the brake switch 6 detects whether or not the brake pedal is pressed, and if the sensor output is "L".
If it is at the level, it is determined that the brake is depressed, and the process is terminated. If the brake is not depressed at the "H" level, the process proceeds to the next step (step S3).

Next, in order to exclude the number of rotations of the wheel when traveling on a curve, when it is judged that the vehicle is in a traveling condition on a curve from the detected angle signal of the steering wheel angle sensor 5 (when an "L" level signal is received), the processing is terminated and the vehicle travels straight ahead. When it is determined that the vehicle is in the state ("H" level signal is received, that is, steering wheel angle θ = 0), the process proceeds to the next step (step S4).

Further, the vehicle height sensors 7, 8, 9 and 10 detect the vehicle height variation of each wheel. Each output signal fluctuates around the average vehicle height as shown in FIG. Large variations in vehicle height affect the rotation speed of the wheels and must be excluded. As shown in the figure, if there is a portion that greatly fluctuates in Δt seconds, it is determined that the road surface is not a flat road and there is unevenness, and the average vehicle height from the vehicle height sensor outputs H ₁ , H ₂ , H ₃ , H ₄ = (H ₁ + H ₂ + H ₃ + H ₄ )
/ 4 is calculated by the CPU 13, and it is determined whether or not H ₁ , H ₂ , H ₃ , and H ₄ each have an amplitude variation of ΔH or more with respect to the average vehicle height. If any one of H ₁ , H ₂ , H ₃ , and H ₄ has an amplitude of ΔH or more, the process is terminated, and if it is within ΔH, the process proceeds to the next step (steps S5 and S6).

Here, when the processing is to be ended in steps S2 to S6, the rotational speeds P ₁ , P ₂ , P ₃ , P ₄ of the wheels read in step S1 and stored in the memory 14 are erased, and the running condition is From the above, the case where the wheel rotation speed is affected despite the normal tire pressure is excluded.

In this way, in order to improve the detection accuracy under the running conditions, the rotation speed count time T (for example, 10 to 20
[S]) is subdivided, the number of rotations is read for Δt seconds, N times are integrated, and the results are averaged. For each wheel, the total average rotation speed ▲ ▼ = (P _1s + P _2s + P _3s + P _4s ) / 4 is calculated from the rotation speeds P _1s , P _2s , P _3s , and P _4s N times for T seconds (step S7). ).

After that, the total average rotation speed ▲ ▼ is multiplied by a predetermined value γ (γ> 1) to _obtain γ · of the rotation speeds P _1s , P _2s , P _3s , and P _4s of each wheel.
▲ ▼ Determine if there is anything larger. γ
The wheel determined to be larger than ▲ ▼ (the ratio to ▲ ▼ is larger than γ) has a higher rotation speed than the other wheels.
That is, the dynamic radius has become small, and it is determined that the tire pressure is abnormally reduced or punctured (step S8). It should be noted that this γ is a value of at least 1 or more.

When the CPU 13 determines in step S8 that the tire pressure has decreased,
An alarm signal is held in a latch circuit (not shown) in the output processing circuit 15, and the alarm display device 16 displays which wheel the tire pressure is decreasing or is flat (step S9).

[Effect of device]

As described above, in the present invention, from the driving conditions of the vehicle,
Excludes conditions that cause a difference in rotation between the wheels even if the tire pressure is normal by detecting that the vehicle is traveling straight ahead, that the brakes are not operating, and that the wheels are on a flat road that does not vibrate abnormally. Since the alarm is issued when the ratio between the average wheel rotation speed and the average value of all wheel speeds exceeds at least 1, it is possible to prevent malfunction during curve running, idling, or braking, and to truly reduce abnormal tire pressure or puncture. It is possible to reliably warn the driver of the occurrence of the occurrence in a short time, and there is an effect that reliability is significantly improved.

As a result, the tire can be prevented from being damaged due to the occurrence of the standing wave phenomenon during high-speed traveling, and the driver can drive safely.

[Brief description of drawings]

FIG. 1 is a system block diagram showing an embodiment of a tire pressure warning device according to the present invention, FIG. 2 is a flow chart diagram of a program executed by a controller used in the present invention, and FIG. ) And (b) are respectively a mounting structure diagram of a vehicle height sensor used in the present invention and a graph diagram showing its output signal, and FIGS. 4 and 5 are diagrams for showing a conventional tire pressure warning device, FIG. 6 is a view showing a conventionally used rotation speed sensor, and FIG. 7 is a view showing a conventionally used steering wheel angle sensor. In FIG. 1, 1, 2, 3 and 4 are rotation speed sensors, 5
Is a steering wheel angle sensor, 6 is a brake switch, 7, 8 and
9 and 10 are vehicle height sensors, 11 is an input processing circuit 12, a CPU 13,
Controller composed of memory 14 and output processing circuit 15, 16
Indicates an alarm display device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. When the number of revolutions of each wheel, the steering wheel angle sensor and the brake switch detect that the vehicle is not stepping on the brake during straight running and the vehicle height sensor detects that the road is flat. A calculation for accumulating the number of revolutions and determining that the tire pressure of each wheel is decreasing when the ratio of the number of revolutions of each wheel to the average number of revolutions of all wheels is greater than 1 and outputting an alarm signal to an alarm means. A tire pressure warning device comprising: