JPH07125511A - Tire air pressure alarm device - Google Patents

Abstract

PURPOSE:To realize a cheap and high-precision device to be stabilized to vibration by comparing outputs of fluid pressure sensors of a shock cushioning fluid pressure means of respective wheels with each other and providing a calculating means for issuing alarm with respect to the wheel showing abnormal change. CONSTITUTION:Fluid pressures of shock cushioning fluid pressure means 2 provided on supporting mechanisms of respective wheels 1 are input as an electric signal into a program control circuit 4 by respective pressure sensor 3. When the frequency that the signal of the pressure sensor 3 of only one wheel 1 exceeds the threshold value is low in excess of the specific ratio, this program control circuit 4 issues the alarm to an alarm means 5. Accordingly, tire air pressure can be detected at high precision, and it can be detected all the time and the tire pressure is always kept normal, and fuel consumption can be decreased, moreover the tire life can be lenghened with a cheap device structure without being affected by vibration.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used in automobiles. The present invention is used in a vehicle equipped with a pneumatic tire. The present invention relates to a device for issuing an alarm to a driver's seat when tire air pressure is abnormal.

[0002]

2. Description of the Related Art A tire pressure is generally inspected by connecting a pressure gauge to an air injection valve of the tire when the vehicle is stopped. An appropriate warning is given to the tire pressure when the vehicle is running. The device is not widely used although some methods are known. If the tire air pressure drops significantly during running, running resistance increases. It is desirable for the driver to notice the decrease in tire pressure at the initial stage. However, under the present circumstances, the driver often feels that the steering wheel has become heavier and the tire pressure is considerably lowered, and the driver often notices it.

A technique described in Japanese Utility Model Laid-Open No. 1-147706 is known as a first device for monitoring the tire air pressure of a vehicle when the vehicle is running and giving an alarm when the air pressure is abnormal. This is because a pressure sensor that outputs an electric signal is provided to the air injection valve of the tire, and a weak electromagnetic wave that is modulated by the output signal of this pressure sensor is generated. Is to be transmitted. When the air pressure shows an abnormal value, an alarm is generated in the driver's seat to prompt the driver to check.

As a second device using another principle, there is a technique disclosed in Japanese Patent Application Laid-Open No. 4-212609. This is because each wheel is equipped with a rotation sensor, and if there is a relative deviation in the output of this rotation sensor, the air pressure of the wheel with a large number of revolutions will decrease on average and the diameter of the wheel will be substantially smaller. As a matter of fact, an abnormality in tire air pressure for the wheel is warned.

[0005]

In the first device, it is necessary to equip the tire with a sensor for detecting the air pressure and an electric circuit for modulating an electromagnetic wave according to the sensor output, and a signal indicating the tire air pressure. Since the electromagnetic waves are modulated and transmitted as electromagnetic waves, a receiving and demodulating device for weak electromagnetic wave signals and a device for transmitting electric energy to the sensor side must be installed on the vehicle side. These are inevitably expensive, and are still not always sufficient to be mounted and stably operated in a vehicle with large vibration.

The second device can only be used in vehicles equipped with an automatic braking system. Providing a device for detecting the rotational state of each wheel very accurately in a vehicle not equipped with an automatic braking system is too expensive for a device which is used only for tire pressure warning.

The present invention has been made under such a background, and provides a tire pressure warning device which is relatively inexpensive, stable even in the presence of vibration, and high in detection accuracy. With the goal.

[0008]

SUMMARY OF THE INVENTION The apparatus of the present invention uses a fluid pressure (pneumatic pressure or hydraulic pressure) for a wheel support mechanism, specifically, a shock absorber, a suspension spring, and the like, when the fluid pressure is used. The pressure or its variation is detected for each wheel, the fluid pressures of the wheels are compared, and only one unique wheel is warned as an abnormality in tire air pressure.

That is, according to the present invention, a plurality of pressure sensors for detecting the fluid pressure of fluid pressure means provided in the support mechanism of each wheel for absorbing the impact as electric signals are compared with each output of the plurality of pressure sensors. And a calculating means for warning a tire pressure abnormality of a wheel exhibiting a peculiar change.

A threshold value is set for the output value or the change value of the output value of each pressure sensor, and the number of times that the threshold value is exceeded for each constant traveling distance exceeds a predetermined ratio for only one wheel and the frequency is low. Sometimes it is desirable to have means for issuing an alarm for that wheel, said pressure sensor being shared with a sensor for the input signal of the device controlling the fluid pressure.

The fluid pressure means can use the shock detection signal of the existing device for a vehicle already equipped with a device for electrically controlling the operating condition of the shock absorber.

[0012]

The pressure sensor provided on the support mechanism of each wheel detects the change in the fluid pressure of the fluid pressure means for absorbing the impact and sends it as an electric signal. The program control circuit takes in this electric signal and sends an alarm signal to the alarm means to generate an alarm when there is a wheel that shows a peculiar change in comparison with a predetermined threshold value. Whether or not the vehicle is abnormal is determined by utilizing the property that the wheel with low air pressure absorbs the impact due to the road surface irregularities. For example, it is assumed that there is an abnormality when the number of times the value becomes equal to or less than the threshold value set for each constant traveling distance is unique to one wheel.

This device can be constructed at a relatively low cost, and since the fluid pressure is the object of detection, it can be detected in a stable state even if there is vibration, and highly accurate detection can be performed. In addition, it is possible to detect while driving, therefore
Since the occurrence of an abnormality can be immediately dealt with, the running stability can be improved. Furthermore, since the air pressure is always maintained normal, fuel consumption can be reduced and the life of the tire can be extended.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a structure of a main part of an embodiment of the present invention, and FIG. 2 is a sectional view showing a structure of a fluid pressure means provided with a pressure sensor in the embodiment of the present invention.

In the embodiment of the present invention, a plurality of pressure sensors 3 for detecting the fluid pressure of the fluid pressure means 2 provided on the support mechanism of each wheel 1 for absorbing the impact as electric signals, and the plurality of pressure sensors 3 are used. And a program control circuit 4 including a calculation means 4a for warning tire pressure abnormality of the wheel 1 showing a peculiar change by comparing each output, and the calculation means 4a further outputs the output value of each pressure sensor 3 or the output value. A threshold value is set for the change value, and when the number of times the threshold value is exceeded for each constant mileage exceeds one wheel 1 at a predetermined rate and the frequency is low, an alarm means 5 is provided for issuing an alarm for the wheel 1. The pressure sensor 3 is also used as a sensor for the input signal of the device for controlling the fluid pressure.

As shown in FIG. 2, the fluid pressure means 2 has an inner cylinder 22 having a one-way valve 21 fixed at its lower end inserted into an outer cylinder 23, and is vertically movable inside the inner cylinder 22. The main valve 24, the first piston rod 25 attached to the main valve 24, and the first piston rod 25 is inserted with its short diameter portion vertically movable, and the pressure sensor 3 is attached to the tip of the long diameter portion. A fixed plunger 26 and a second piston rod 27 connected and fixed to the first piston rod are arranged.

Inside the inner cylinder 22, there are formed fluid chambers A and B which are separated by a main valve 24 and which are completely sealed. The pressure sensor 3 is connected to the program control circuit 4 via a lead wire 6.

Next, the operation of the embodiment of the present invention thus constructed will be described.

First, the normal operation of the fluid pressure means 2 will be described. Since the upper end of the fluid pressure means 2 is fixed to the body side and the lower end is fixed to the axle side, when the axle side moves up and down due to a change in the road surface, the position of the main valve 24 in the inner cylinder 22 is relatively fixed. By moving vertically, the spatial volumes of the fluid chamber A and the fluid chamber B change. At this time, the shock is absorbed by the resistance when the fluid moves from the chamber A to the chamber B or from the chamber B to the chamber A.

For example, when a force is applied from the axle side in the direction shown by the solid line arrow in FIG. 2, the inner cylinder 22 pressurizes the fluid in the fluid chamber B and pushes up the second valve 24d to raise the second orifice 2
4b is closed. On the other hand, when the fluid in the pressurized fluid chamber B passes through the first orifice 24a and pushes up the first valve 24c to flow into the fluid chamber A, when the pressures in the fluid chambers A and B become the same value. Fluid movement stops.

When the body side is lifted and receives a force in the direction indicated by the broken line arrow, the main valve 24 is moved to the fluid chamber A.
The fluid inside is pressurized to push down the first valve 24c and close the first orifice 24a. On the other hand, the pressurized fluid chamber A
The fluid inside passes through the second orifice 24b and the second valve 24.
d is pushed down to flow into the fluid chamber B, and similarly, the fluid chamber A
When the pressures in B and B reach the same value, the movement of fluid stops.

By such an operation, the impact from the axle side or the body side is absorbed. The one-way valve 21 is provided for returning the fluid leaked from the inside of the inner cylinder 22 with the passage of time.

Here, the detection operation of the pressure sensor 3 in the embodiment of the present invention will be described.

In the embodiment of the present invention, as shown in FIG. 2, the pressure sensor 3 is attached to the tip of the long diameter portion of the plunger 26, and the plunger 2 is inserted into the first piston rod 25.
Since the fluid passage 25a to which the fluid pressure in the fluid chamber B is applied is provided on the end face of the minor diameter portion of 6, the fluid chamber by the normal operation described above when a force is applied in the direction of the solid line arrow shown in FIG. With the movement of the fluid from B to the fluid chamber A, the fluid pressure at that time is applied from the fluid passage 25a to the short diameter portion of the plunger 26. Plunger 26 with fluid pressure
Pressurizes the pressure sensor 3. The pressure sensor 3 detects and outputs the pressure as an electric signal.

Further, when a force is applied in the direction of the broken line arrow shown in FIG.
The fluid pressure at that time is applied from the fluid passage 25a to the short diameter portion of the plunger 26 with the movement of the fluid to the. Similarly, the plunger 26 to which the fluid pressure is applied pressurizes the pressure sensor 3, and the pressure sensor 3 detects and outputs the pressure as an electric signal.

A feature of the present invention is that a threshold value is set for the output value of each pressure sensor 3 or a change value thereof, and it is judged how the change is with respect to the threshold value, and a peculiar change is made. The purpose is to give an alarm when there is an abnormality in the tire pressure.

FIG. 3A is a diagram showing a waveform detected by a pressure sensor in the embodiment of the present invention on a relatively rough road. Despite that three of the four wheels are in the state of FIG. 3 (a), when one wheel has the detection waveform shown in FIG. 3 (b), it indicates that the air pressure of the one wheel is abnormal. . In this way, the pressure sensor 3 can accurately detect the change in vibration due to the change in the road surface.

FIG. 4 is a flow chart showing the flow of control operation in the embodiment of the present invention.

The program control circuit 4 clears the memory, inputs the damping force of each tire, and determines whether or not the vehicle has traveled a certain distance. If the vehicle has not traveled for a certain distance, the same processing is repeated. If the vehicle has traveled for a certain distance, the number of times that the arithmetic means 4a exceeds the threshold value set for the output value of the pressure sensor 3 or the change value of the output value is only one wheel. It is determined whether or not there is one, and when only one wheel exceeds the predetermined ratio and the frequency is low, it is determined that the air pressure is low and the vibration is absorbed, and an alarm is issued for that wheel. If there are relatively extremely infrequent tires, return the process.

[0030]

As described above, according to the present invention, the tire air pressure can be detected with high accuracy without being affected by vibration with a relatively inexpensive device configuration. Further, since it is possible to always detect even during traveling, it is possible to immediately respond to the occurrence of an abnormality, and there is an effect that traveling stability can be improved. Further, since the tire air pressure is always maintained normal, the fuel consumption can be reduced and the tire life can be extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a fluid pressure means provided with a pressure sensor according to an embodiment of the present invention.

FIG. 3A is a diagram showing a detected waveform on a relatively rough road by the pressure sensor in the embodiment of the present invention, and FIG. 3B is a diagram showing a detected waveform on a relatively smooth road.

FIG. 4 is a flowchart showing a flow of control operation in the embodiment of the present invention.

[Explanation of symbols]

 1 Wheel 2 Fluid Pressure Means 3 Pressure Sensor 4 Program Control Circuit 4a Computing Means 5 Alarm Means 6 Lead Wire 21 One Way Valve 22 Inner Cylinder 23 Outer Cylinder 24 Main Valve 24a First Orifice 24b Second Orifice 24c First Valve 24d Second Valve 25 first piston rod 25a fluid passage 26 plunger 27 second piston rod

Claims (3)

[Claims] 1. A plurality of pressure sensors for detecting the fluid pressure of a fluid pressure means provided in a support mechanism of each wheel for absorbing a shock as electric signals, and outputs of the plurality of pressure sensors are compared with each other to make a unique change. And a calculating means for warning a tire pressure abnormality of a wheel indicating the tire pressure warning device. 2. The calculation means sets a threshold value for the output value of each pressure sensor or a change value of the output value, and the number of times the threshold value is exceeded for each constant mileage exceeds the predetermined ratio for only one wheel. The tire pressure warning device according to claim 1, further comprising means for generating an alarm for the wheel when the tire pressure is low. 3. The tire pressure warning device according to claim 1, wherein the pressure sensor is also used as a sensor for an input signal of a device for controlling a fluid pressure.