JPH0442163Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a tire pressure detection device (hereinafter referred to as tire pressure), and particularly relates to a tire pressure detection device that can continuously detect tire pressure.

<Prior art> Since the tire pressure of a vehicle has a great effect on the life of the tire and the ride comfort of the car, devices for adjusting the tire pressure (for example, Japanese Utility Model Application Publication No. 60-24604, etc.), telemeter systems, and resonance coils have been developed. Tire pressure detection devices such as the following method have been put into practical use.

The telemeter system consists of a microsensor (transmission element) attached to the inside of the rim of each wheel with a small pin to detect tire pressure, an annular antenna attached to the tire side to transmit a detection signal, and an annular antenna attached to the axle side to transmit a signal. There is a system that displays tire pressure in real time, consisting of a receiving antenna that receives the signal, a circuit that processes the signal received by the receiving antenna, and a device that displays the processed signal on the instrument panel. (See “MACHINE DESIGN” Feb.26.1987).

Further, in the resonance coil method, a resonance coil is provided on the wheel side and an oscillation coil is provided on the vehicle body side so as to face each other, and the oscillation coil is connected to a display in the vehicle interior via a coaxial cable and an oscillator. Furthermore, a pressure switch is installed in the resonance circuit, which opens when the tire pressure falls below the allowable lower limit. Therefore, there is a difference in the oscillator output when the pressure switch is closed and when it is open, and a lamp (indicator) is lit when the tire pressure decreases.

<Problems to be solved by the invention> By the way, in such conventional tire pressure detection devices, the telemeter type requires a power source for transmitting data using an antenna, making the system complex and expensive. It is.

On the other hand, with the resonant coil type, the structure is simple, but the resonant frequency does not change, so
Tire pressure cannot be detected continuously. Additionally, there are problems such as the tire pressure not being detected even when the vehicle is stopped.

Regarding the tire pressure detection device, a variable capacitor type was previously proposed by the present applicant (see Utility Model Application No. 189805/1989 and Japanese Utility Model Application No. 93102/1999), but the variable capacitor part became larger. Therefore, it is difficult to make the device compact.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a compact tire pressure detection device that can continuously detect tire pressure while the vehicle is running and while the vehicle is stopped.

<Means for Solving the Problem> Therefore, the present invention fixes a pneumatic actuator that reciprocates in the axle axis direction in response to tire pressure to a rotating member that rotates together with the tire, and fixes the pneumatic actuator to a rotating member that rotates with the tire. A ring-shaped reflector is fixed to the reflector, and the displacement of the reflector in the axle axis direction is detected based on the time change from emitting ultrasonic waves to receiving the reflected wave reflected by the reflector. The plate displacement detection means is fixed to a non-rotating member, and also includes means for signal processing the amount of displacement detected by the reflection plate displacement detection means into a signal corresponding to tire pressure.

<Operation> In this configuration, when the reflector is displaced in the axle axis direction by the pneumatic actuator in accordance with the tire pressure, the time from emitting ultrasonic waves to receiving reflected waves changes due to this displacement. Since this time depends on the tire pressure, the tire pressure can be continuously detected by converting the time into, for example, an analog electrical signal and driving the tire pressure gauge. Furthermore, it is also possible to drive an alarm device to notify the driver when the tire pressure falls below the allowable lower limit.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

In FIGS. 1 to 3 showing a first embodiment of the present invention, a tire 2 is attached to a wheel 1 attached to a brake drum (not shown) or the like, and rotates together in a plane perpendicular to the plane of the paper.

Further, three pneumatic cylinders 6 as pneumatic actuators are fixed to the rim 1a of the wheel 1 as a rotating member at equal intervals in the circumferential direction, for example, at intervals of 120°, and the working chambers 7 of the pneumatic cylinders 6 are fixed to the rim 1a of the wheel 1. 2
Tire pressure in the tube 4 is introduced through a pipe 5 through an air valve 3 provided in the tube 4 to prevent the tire pressure from leaking into the atmosphere. At this time, the pipe 5 is branched near the pneumatic cylinder 6. As shown in FIG. 2, the position of the piston 8 in the axle axis direction is determined by the balance between the introduced tire pressure and the biasing force of the return spring 9. When the tire pressure is high, the piston 8 resists the return spring 9. and the piston 8 moves to the right in the figure,
Conversely, when the tire pressure decreases, the return spring 9
The piston 8 is biased to move to the left in the figure. Therefore, the tire pressure is converted into the amount of movement of the rod 10 of the pneumatic cylinder 6, and the pneumatic cylinder 6 functions as a pressure sensor.

A ring-shaped reflector 11 is fixed to the tip of the rod 10 of this pneumatic cylinder 6, and is centered around an axle (not shown), while an axle housing 12, which is a non-rotating member that covers the axle, has a bracket 13 interposed therebetween. An ultrasonic displacement meter 14 is provided facing the reflecting plate 11. Then, the time from when the ultrasonic displacement meter 14 emits ultrasonic waves until the reflected wave is received by the reflector 11 is measured, and the displacement of the reflector 11 in the axle axis direction is determined based on the time change. is detected, and tire pressure is detected based on the detected value.

FIG. 3 shows an example of a signal processing circuit that converts the amount of movement of the reflecting plate 11 into a signal corresponding to tire pressure.

The ultrasonic displacement meter 14 includes a pulse transmitter circuit 15 that intermittently outputs ultrasonic pulses, an oscillation element 16 that vibrates with the pulse output from the pulse transmitter circuit 15 and emits ultrasonic waves, and a reflector 11. A receiving element 17 that receives the reflected wave and converts it into an electrical signal, a pulse receiving circuit 18 that receives the electrical signal from the receiving element 17, and a counter that receives the transmission start output from the pulse transmitting circuit 15. 2
It is comprised of a phase comparator circuit 19 which sets the counter 20 to 0 and resets the counter 20 by receiving the received output from the pulse receiving circuit 18, and a clock circuit 21. Further, a signal conversion circuit 22 converts the signal of the ultrasonic displacement meter 14 into a signal corresponding to tire pressure.
includes a D/A converter 23 that converts the count value from the counter 20 into an analog voltage signal, a tire pressure gauge 24 in the driver's cabin that is driven by the voltage signal of the D/A converter 23, and a tire pressure gauge 24 that converts the voltage signal to a reference value. It is comprised of a comparator 25 for comparison with V _ref , and a tire pressure warning device 26 such as a buzzer or lamp driven by the output from the comparator 25.

In this configuration, when the tire pressure is high, the reflector 11 is moved rightward in FIG. 2 by the pneumatic cylinder 6, and the distance from the displacement meter 14 becomes narrower. Therefore, the time from the start of ultrasonic emission until the reflected wave is received becomes shorter, and the count value of the counter 20 becomes smaller. Conversely, when the tire pressure decreases, the reflector 11 is moved leftward in FIG. 2 by the pneumatic cylinder 6, and the distance from the displacement meter 14 becomes wider. Therefore, the time from the start of ultrasonic emission until the reflected wave is received becomes longer, and the count value of the counter 20 becomes larger.

Then, the tire pressure is indicated to the tire pressure gauge 24 by a voltage signal corresponding to the count value of the counter 20, and the driver can read the current tire pressure. Also, when the voltage signal becomes below the reference value V _ref due to a decrease in tire pressure, comparator 2
The tire pressure warning device 26 is driven by the output from the tire pressure warning device 5, and can notify the driver that the tire pressure is low.

In this way, if the tire pressure is detected using ultrasonic waves, the tire pressure can be detected continuously and can also be detected even when the vehicle is stopped. Further, unlike the telemeter method, a power source is not required on the pressure sensor side, and the device can be simplified. Furthermore, compared to the variable capacitor method, the signal processing section can be made smaller and can be easily installed in a vehicle.

In the first embodiment above, the case of a single tire was shown, but in the case of double tires adopted for large trucks with a large loading capacity, it is necessary to have equal tire pressure to prevent the load balance from becoming biased. Since the tire pressure is also required, it is better to detect the individual tire pressure. For this reason, as shown in FIG. 4, a pneumatic cylinder 6, a reflector 11, an ultrasonic displacement meter 14, etc. are provided corresponding to each tire. In this case, the reflecting plates 11 are arranged in the same plane as shown in the figure.

The operation of the second embodiment is similar to that of the first embodiment.

Next, a third embodiment is shown in FIGS. 5 and 6.

This embodiment uses a diaphragm type pneumatic actuator instead of a pneumatic cylinder.

That is, a diaphragm 32 is attached to the entire circumference of a ring-shaped case 31 that is open at both ends, and a cover 33 covers the open end of the case 31 on the tire side. The cover 33
An air passage 35 is provided for introducing tire pressure into the working chamber 34 of the diaphragm 32 via a pipe (not shown). Further, the diaphragm 32
In the inner circumferential direction, three springs 36 are interposed between the cover 33 and the spring seat 37 at equal intervals, for example, 120° intervals. A rod 38 is fixed to the outer surface of the diaphragm 32 corresponding to the position of the spring seat 37. A ring-shaped reflecting plate 11 is fixed to the tip of the rod 38 of the diaphragm type pneumatic actuator thus constructed.

According to this configuration, when the tire pressure is high,
The diaphragm 3 resists the biasing force of the spring 36.
2 moves rightward in the figure, and the reflecting plate 11 moves via the rod 38. Further, when the tire pressure decreases, the diaphragm 32 and the reflector 11 are moved to the left in the figure by the spring 36. Then, the displacement of the reflection plate 11 is detected by the ultrasonic displacement meter 14 in the same manner as in the above embodiment, and the tire pressure is detected.

Similar effects can be obtained in this embodiment as well.

<Effects of the invention> As explained above, according to the invention, a reflector is provided on the pneumatic actuator that responds to tire pressure,
Since the tire pressure is detected by detecting the displacement of the reflector using an ultrasonic displacement meter, the tire pressure can be continuously detected while the vehicle is running, and can also be detected while the vehicle is stopped. Furthermore, the detection device can be made smaller and can be easily mounted on a vehicle. Furthermore, since the pressure sensor section provided on the tire side does not require a power source, the device can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts showing a first embodiment of the present invention, FIG. 2 is a configuration diagram of a pneumatic cylinder of the same embodiment, FIG. 3 is a block diagram of a signal processing circuit of the same embodiment, and FIG. The figure is a cross-sectional view of a main part showing a second embodiment of the present invention, FIG. 5 is a cross-sectional view of a main part showing a third embodiment of the present invention, and FIG. It is. 1...Wheel, 2...Tire, 6...Pneumatic cylinder, 11...Reflector, 12...Axle housing, 13...Bracket, 14...Ultrasonic displacement meter, 23...D/A converter , 24... Tire pressure gauge, 26... Tire pressure alarm device.

Claims (1)

[Scope of utility model registration request] A pneumatic actuator that reciprocates in the axle axis direction in response to tire pressure is fixed to a rotating member that rotates with the tire, and a ring-shaped reflection plate centered on the axle is fixed to the pneumatic actuator, while ultrasonic waves are emitted. A reflector displacement detection means for detecting displacement of the reflector in the axle axis direction based on a time change from emitting to receiving the reflected wave reflected by the reflector is fixed to a non-rotating member;
A tire pressure detection device comprising: means for signal processing the amount of displacement detected by the reflector displacement detection means into a signal corresponding to tire pressure.