JPH07329524A - Tire pneumatic pressure detecting device - Google Patents

Abstract

PURPOSE:To provide a simple structure, reduce cost, and achieve high detection precision. CONSTITUTION:A tire pneumatic pressure detecting device A comprises a sensor part 11 to detect change of a tire pneumatic pressure, a Hall element 5 fixed on the car body side, and a monitoring circuit to monitor a detection value from the Hall element 5. The sensor part 11 is composed of a diaphragm 13 which expands/contracts to deform in accordance with an inner pressure of an air chamber 6, a coil spring 15 provided between a plate 14 and a forward end part 12a of a pipe 12, and a magnet 16 installed on the sensor part 11 to be positioned inside the coil spring 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure detection device suitable for detecting and monitoring the air pressure of a tire mounted on a vehicle body of an automobile or the like to improve safety.

[0002]

2. Description of the Related Art Conventionally, for example, a tire air pressure detecting device mounted on an automobile is equipped with a pressure sensor for each wheel, and the air pressure of the tire is directly detected by this pressure sensor. A transmitter for transmitting the output of the pressure sensor is provided on the rotating tire side, while an antenna or the like for receiving a signal from the transmitter is provided on the vehicle body side for transmitting the signal. However, such a tire air pressure detection device has a problem that the structure is complicated and the manufacturing cost is high because a transmitter, an antenna, and the like for signal transmission are required.

In recent years, in order to solve such problems,
A tire air pressure detection device having a configuration in which a sensor unit including a magnet or the like that moves according to the tire air pressure is provided integrally with the tire on the tire side and a detection unit that detects the movement of this magnet or the like is provided on the vehicle body side is proposed. ing.

Examples of the tire air pressure detecting device having such a structure include the following. As shown in FIG. 4, the tire air pressure detection device 1 senses the air pressure of the tire 3 mounted on the wheel 2, and therefore, the sensor portion 4 provided along the inner peripheral surface of the rim portion 2 a of the wheel 2.
In order to detect the displacement of the sensor unit 4, a Hall element (detection unit) 5 fixed to the vehicle body side (not shown) and a monitoring circuit (not shown) that monitors the detection value from the Hall element 5 are configured. . The sensor unit 4 includes a rubber diaphragm 8 to which the internal pressure of the tire 3 is applied, and a pipe 7 attached to the diaphragm 8 in a pipe 7 communicating with an air chamber 6 formed by being surrounded by the wheel 2 and the tire 3. 7, a magnet 9 that can move back and forth in the axial direction, and a spring 10 that biases the magnet 9 toward the air chamber 6 are provided. In the tire air pressure detection device 1 having such a configuration, the diaphragm 8 is responsive to the air pressure of the tire 3.
Expands and contracts in the axial direction of the sensor unit 4, and the magnet 9 moves in the axial direction accordingly, so that the distance between the magnet 9 and the Hall element 5 changes, and the Hall element 5 detects the Hall effect. The magnetic field strength of the magnet 9 changes.
Then, when the detected value of the hall element 5 deviates from a preset constant range, the monitoring circuit determines that the air pressure of the tire 3 is abnormal.

[0005]

However, the conventional tire air pressure detecting device as described above has the following problems. That is, in the tire air pressure detection device 1 configured to detect the air pressure of the tire 3 by detecting the change in the distance from the magnet 9 with the hall element 5, in order to improve the detection accuracy, the sensor unit 4 and the hall element 5 are used.
It is necessary to assemble and with high accuracy. For this reason, there is a problem that extra work is required for assembling and the manufacturing cost is increased. Further, in order to avoid such a problem, a method of electrically correcting the detected value of the Hall element 5 may be considered, but this also requires a cost. Also, depending on whether the air pressure of the tire 3 is normal or abnormal,
Since it is difficult to discriminate when the difference between the detected values of the hall elements 5 is small, it is desirable that the difference be large in order to improve the detection accuracy. At this time, the detection value of the Hall element 5 is maximized at the position closest to the magnet 9 and becomes smaller as the distance from the magnet 9 is increased. However, in the tire air pressure detection device 1, in order to prevent the Hall element 5 and the sensor unit 4 from interfering with each other when the tire 3 rotates, it is necessary to install them at a certain distance (for example, 5 mm) apart. When the Hall element 5 and the magnet 9 of the sensor unit 4 are separated in this manner, the stroke of the magnet 9, that is, the length of the pipe 7 must be increased so that the maximum value and the minimum value of the detected value of the Hall element 5 are The difference cannot be increased, and as a result, there is a problem that the tire air pressure detection device 1 becomes large. Furthermore, in order for the magnet 9 to move in the sensor unit 4 with high responsiveness according to the air pressure of the tire 3, a clearance is required between the magnet 9 and the inner wall surface of the pipe 7 of the sensor unit 4. However, vibration or centrifugal force generated when the tire 3 rotates causes the magnet 9 to contact the inner wall surface of the sensor unit 4 and hinders the movement thereof.
There is a problem that it becomes impossible to detect the air pressure of.

For the above reasons, it has been practically difficult to provide the tire pressure detecting device 1 having high accuracy at low cost. The present invention has been made in consideration of the above points, and an object of the present invention is to provide a tire air pressure detection device that has a simple structure, can reduce cost, and has high detection accuracy.

[0007]

The invention according to claim 1 is
A tire air pressure detection device for detecting air pressure of a tire rotatably attached to a vehicle body, wherein a cylindrical sensor portion integrally provided with the tire is configured to expand and contract according to air pressure of the tire. And a coil spring made of a magnetic material, which is interposed between the tip of the diaphragm and the tip of the sensor, and a magnet fixed to the sensor so as to be located inside the coil spring. Is provided, and a detection unit that detects the magnetism of the magnet is provided in the vicinity of the sensor unit integrally with the vehicle body.

According to a second aspect of the present invention, in the tire pressure detecting device according to the first aspect, the sensor portion is provided so as to extend in a direction parallel to the rotation axis of the tire, and the diaphragm is provided in the direction. It is characterized by being configured to expand and contract.

[0009]

According to the first aspect of the invention, when the air pressure of the tire is within the preset proper range, the diaphragm is expanded and the coil spring is compressed. Then, the magnet is shielded by being surrounded by a coil spring made of a magnetic material such as iron or stainless steel, and the magnetism of the magnet cannot be detected by the detection unit. When the tire air pressure falls below the appropriate range, the diaphragm contracts and the coil spring expands. Then,
The space between the coil springs is opened and the magnetism of the magnets passes through the coil springs, and the magnetic field strength detected by the detector increases. In this way, it is possible to detect whether the tire air pressure is within the proper range.

According to the second aspect of the invention, the diaphragm expands and contracts in the sensor portion in a direction parallel to the rotation axis of the tire. As a result, when the diaphragm expands and contracts, it is possible to reduce the influence of the centrifugal force generated when the tire rotates.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. 1 and 2 show a part of an automobile equipped with a tire pressure detecting device according to the present invention.
In these figures, the same parts as those of FIG. 4 shown as a conventional example are designated by the same reference numerals. As shown in FIGS. 1 and 2, the tire air pressure detection device A includes a sensor unit 11 for detecting a change in air pressure of a tire (not shown) mounted on the wheel 2, and a change detected by the sensor unit 11. In order to detect the, a hall element (detection section) 5 fixed to the vehicle body side (not shown), and a monitoring circuit (not shown) for monitoring the detection value from the hall element 5 are configured.

The sensor portion 11 is a rim portion 2a of the wheel 2.
Inside the pipe 12 provided along the inner peripheral surface of the air chamber 6
A diaphragm 13 made of, for example, rubber for partitioning the inside and outside, a resin plate 14 integrally attached to the tip of the diaphragm 13, and a coil spring interposed between the plate 14 and the tip 12a of the pipe 12. 15
And the magnet 1 attached to the tip 12a of the pipe 12.
And 6 are provided.

The pipe 12 is a substantially L-shaped tubular body made of a non-magnetic material such as brass, which is magnetically permeable, and has a tip portion 12a.
The side is provided so as to be parallel to the rotation axis of the tire (not shown). The base end 12b of the pipe 12 is the wheel 2
6 is formed by being surrounded by a tire and a tire (not shown).
It is attached to the rim portion 2a so as to communicate with the inside.
Further, a stopper 17 is provided at the tip portion 12a of the pipe 12, and the stopper 17 is formed with a communication hole 17a for communicating the inside and outside of the pipe 12. The diaphragm 13 has a bellows shape made of rubber, for example, and is configured to partition the inside and outside of the air chamber 6 and to be expandable and contractable in the pipe 12 according to a pressure change in the air chamber 6. The coil spring 15 is a cylindrical coil spring made of a ferromagnetic material such as iron or stainless steel, and is interposed between the plate 14 and the stopper 17 in a compressed state. Then, when the air pressure of the tire 3 is within a preset proper range, the output voltage of the hall element 5 is set to 0 (zero) volt. Then, as shown in FIG. 2, when the air pressure of the tire 3 becomes equal to or lower than the appropriate range, the coil spring 15 extends to increase the interval c. The magnet 16 is located inside the coil spring 15 and is integrally fixed to the stopper 17 by aligning the line connecting the N pole and the S pole in the radial direction of the wheel 2.

The hall element 5 detects the magnetism (magnetic field strength) of the magnet 16, converts it into a voltage, and outputs it to a monitoring circuit (not shown).

In the tire air pressure detecting device A having the above-mentioned structure, when the air pressure of the tire (not shown) is within the proper range, the magnet 16 is surrounded by the coil spring 15 made of a magnetic material and shielded. The magnetism of the magnet 16 cannot be detected by the hall element 5.
Therefore, the output voltage from the hall element 5 monitored by the monitoring circuit (not shown) is 0 volt, as shown in FIG.

Then, as shown in FIG.
When the air pressure of the tire (not shown) falls below the appropriate range for some reason, in response to this pressure drop,
The diaphragm 13 is biased by the coil spring 15 and deforms in a direction approaching the air chamber 6. Then, the plate 14 moves integrally with this, and the coil spring 15 extends. At this time, since the communication hole 17a is formed in the stopper 17, the plate 14 moves smoothly without the pressure between the plate 14 and the stopper 17 decreasing. When the coil spring 15 expands in this way and the interval c increases, the magnetism of the magnet 16 passes through the coil spring 15, so the magnetic field strength of the magnet 16 detected by the Hall element 5 increases. . Then, as shown in FIG. 3, the output voltage from the hall element 5 monitored by the monitoring circuit (not shown) increases. In this way, when the magnetism of the magnet 16 is detected by the hall element 5, the monitoring circuit (not shown) determines that the air pressure of the tire (not shown) has fallen below an appropriate range, and A pressure drop is displayed by turning on an indicator lamp provided or sounding an alarm.

In the tire air pressure detecting device A having the above-mentioned structure, when the air pressure of the tire (not shown) is within the proper range, the magnet 16 is surrounded by the coil spring 15 in a compressed state made of a magnetic material and shielded. The Hall element 5 cannot detect the magnetism. Then, when the air pressure of the tire (not shown) falls below the appropriate range, the diaphragm 13 contracts and the coil spring 15 expands to increase the interval c, and the magnetism of the magnet 16 passes through the coil spring 15 and the hall element 5 The magnetic field strength detected at is increased. In this way, there is a large difference in the magnetic field strength of the magnet 16 detected by the Hall element 5 when the air pressure of the tire (not shown) falls within the proper range and when it falls below the proper range. It will be turned off. Therefore,
It becomes very easy to determine whether or not the air pressure of the tire (not shown) is within the proper range, and as a result, the tire air pressure detection device A can have high detection accuracy. Further, unlike the conventional tire pressure detection device 1 (see FIG. 4), the diaphragm 13 is not provided with the magnet 9, but is simply provided with the plate 13 for receiving the end of the coil spring 15. It has a structure of. The plate 14 is made of, for example, resin and is lighter in weight than a magnet or the like, and thus is less susceptible to centrifugal force and vibration due to rotation of a tire (not shown). Moreover, since the diaphragm 13 expands and contracts in the sensor unit 11 in the direction parallel to the rotation axis of the tire (not shown),
From this point as well, it is less susceptible to the centrifugal force. In this way, the diaphragm 13 is deformed without being hindered by centrifugal force or vibration and has excellent pressure transmissibility and responsiveness. From this point as well, the tire air pressure detection device A has high detection accuracy. can do.

In this way, the tire air pressure detecting device A
However, the amount of change in the output voltage is large when the air pressure is within the appropriate range and when the air pressure is less than the appropriate range, and it is highly resistant to the influence of vibration and centrifugal force and has high detection accuracy. Therefore, when assembling the sensor unit 11 and the hall element 5 or the like, particularly high assembling accuracy is not required, and if the wheel 2 is assembled to the vehicle body with the assembling accuracy equivalent to the usual case where the tire air pressure detection device A is not provided. Sufficient detection accuracy can be secured, and the manufacturing cost can be reduced. Moreover, since the structure is simple, it is possible to provide the tire air pressure detection device A at low cost.

In the above embodiment, regarding the direction of the magnet 16, if the magnetism can be detected by the hall element 5 when the air pressure of the tire (not shown) falls below an appropriate range, the directions other than the above will be used. It may be. Further, the shapes and materials of the diaphragm 13 and the plate 14 may have any configuration as long as they can be deformed / moved with high responsiveness to the pressure change in the tire.

[0020]

As described above, according to the tire air pressure detecting device of the first aspect, when the tire air pressure is within the proper range, the magnet is shielded by the coil spring made of a magnetic material and is detected by the detecting portion. The magnetic field strength to be detected becomes almost 0 (zero). Then, when the tire air pressure falls below an appropriate range, the coil spring expands and the magnetic field strength of the magnet detected by the detection unit increases. As described above, the magnetic field strength detected by the detection unit changes greatly between when the tire air pressure is within the proper range and when the tire pressure is below the proper range.
Therefore, the discrimination becomes very easy, and the tire air pressure detection device can have high detection accuracy. Moreover, since the diaphragm and the magnet are separated, deformation of the diaphragm is not hindered by the weight of the magnet, centrifugal force, vibration, etc., and the diaphragm is deformed with high responsiveness, which also improves the detection accuracy. It will be possible. Therefore, such a tire air pressure detection device does not require particularly high assembly precision, and it is possible to secure sufficient detection precision even with the same assembly precision as in the normal case without the tire air pressure detection device. The manufacturing cost can be reduced. Moreover, since the structure is simple, it is possible to provide the tire air pressure detection device at low cost.

According to the tire pressure detecting device of the second aspect, the sensor portion is provided so as to extend in the direction parallel to the rotation axis of the tire. As a result, when the diaphragm expands and contracts, it is possible to reduce the influence of the centrifugal force generated when the tire rotates. Therefore, this also makes it possible to improve the detection accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a tire air pressure detection device according to the present invention, and is a front sectional view showing a state where the tire air pressure is within an appropriate range.

FIG. 2 is a view showing the tire pressure detection device,
FIG. 4 is a front cross-sectional view showing a state where the tire air pressure is below an appropriate range.

FIG. 3 is a diagram showing a relationship between a pressure inside a tire and an output voltage detected by a detection unit.

FIG. 4 is a front sectional view showing an example of a conventional tire air pressure detection device.

[Explanation of symbols]

5 ... Hall element (detection unit), 11 ... Sensor unit, 13 ... Diaphragm, 15 ... Coil spring, 16 ... Magnet, A
… Tire pressure detection device.

Claims (2)

[Claims] 1. A tire air pressure detection device (A) for detecting air pressure of a tire rotatably attached to a vehicle body.
In the tubular sensor portion (11) provided integrally with the tire, a diaphragm (13) that expands and contracts in accordance with the air pressure of the tire, a tip portion of the diaphragm (13) and the sensor. A coil spring (15) made of a magnetic material, which is interposed between the coil spring (15) and the tip of the sensor section (1).
A magnet (16) fixed to 1) is provided, and a detection unit (5) for detecting the magnetism of the magnet (16) is provided integrally with the vehicle body in the vicinity of the sensor unit (11). A tire air pressure detection device (A) having a configuration. 2. The tire air pressure detection device according to claim 1, wherein the sensor portion (11) is provided so as to extend in a direction parallel to a rotation axis of the tire, and the diaphragm (13) extends in the direction. A tire air pressure detection device (A), which is configured to expand and contract.