JPH0664414A - Tire air pressure monitoring device - Google Patents

Abstract

PURPOSE:To arrange a first magnet part and a second magnet part, which are used in a tire air pressure monitoring device, as being well balanced. CONSTITUTION:The first magnet part 15 and the second magnet part 16 are set on a wheel 11. The first magnet part 15 comprises two magnets 20, 21, which are set as being slightly shifted with each other, in the circumferential direction of the wheel 11. The second magnet part 16 is set on the same circumference with the first magnet part 15, as being symmetrical about the center of rotation of the wheel 11, that is opposite to the first magnet part 15 through about 180 deg.. The position of the second magnet part 16 is varied in the axial direction of the wheel 11 according to the tire air pressure. In an electric circuit 50, the electromotive force generated in a magnetic coil 41 is judged whether being generated by the first magnet part 15 or by the second magnet part 16, based on the wave number, the actual tire air pressure is calculated from previously calculated relation between the difference of electromotive force and the tire air pressure, and the results are indicated by an indicator 60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure monitoring device for detecting and displaying the pressure of pneumatic tires used in vehicles such as automobiles and industrial machines and aircraft.

[0002]

2. Description of the Related Art As a means for detecting the tire pressure, a tire pressure monitoring device 100 as shown in FIGS. 8 and 9 has been proposed. In this device 100, a first magnet 104 and a second magnet 105 are arranged in the circumferential direction of a member 103 on the wheel 102 side that rotates integrally with a tire 101, and an electromagnetic coil 107 is arranged on a member 106 on the vehicle body side. It is provided. The electromagnetic coil 107 is located on the same circumference as the trajectory drawn by the first magnet 104 and the second magnet 105 when the wheel 102 rotates, and the first magnet 104 and the second magnet 105 are electromagnetically coupled. The electromotive force due to electromagnetic induction that occurs when passing near the coil 107 is detected. Second magnet 105
Is provided on the mover 109 of the transducer 108. The mover 109 is displaced in the axial direction of the wheel 102 according to the change in the air pressure of the tire 101 introduced into the transducer 108. The higher the air pressure of the tire 101, the shorter the distance from the second magnet 105 to the electromagnetic coil 107. I try to keep the distance short.

In this conventional device 100, as shown in FIG. 10, electromotive forces of two types of voltage waveforms W1 and W2 are generated during one rotation of the wheel 102. That is, when the first magnet 104 passes through the electromagnetic coil 107, an electromotive force of the first voltage waveform W1 is generated, and the second magnet 105 causes the electromagnetic coil 10 to move.
An electromotive force of the second voltage waveform W2 is generated when passing through 7. The magnitude of these electromotive forces depends on the shortest distance from the magnets 104, 105 to the electromagnetic coil 107. For example, because the tire pressure is too high, the electromagnetic coil 107 causes the second magnet 10 to
Since the electromotive force increases when the shortest distance to 5 is short, the second voltage waveform W2 is relatively larger than the first voltage waveform W1 as shown by the chain double-dashed line in FIG. Become.

As described above, there is a fixed relationship between the electromotive force difference caused by the magnets 104 and 105 and the tire air pressure. This relationship is maintained even when the wheel 102 is displaced in the axial direction with respect to the vehicle body. Be done. Therefore, the relationship between the electromotive force difference and the tire air pressure is obtained in advance by actual measurement or calculation and stored in the microcomputer.

When actually monitoring the tire air pressure, the electromagnetic coil 107 detects two types of electromotive force and the difference between the electromotive forces of the first magnet 104 and the second magnet 105, and the values are obtained in advance. Based on the relationship between the electromotive force difference and the tire air pressure, the tire air pressure is obtained by the microcomputer, and information regarding the obtained tire air pressure is displayed on the display.

In the above device 100, the first magnet 104
Based on the electromotive force (waveform W1) by the second magnet 10
Since the tire pressure is calculated based on the difference in electromotive force (waveform W2) due to 5, it is necessary to specify which of the waveforms W1 and W2 is due to the first magnet 104.

Therefore, in the above-mentioned conventional device 100, the positions of the first magnet 104 and the second magnet 105 are shifted by about 60 ° to 90 ° in the circumferential direction of the wheel 102 with respect to the tire rotation direction when the vehicle is moving forward. The first magnet 104 is placed in front of the second magnet 105. In this case, as shown in FIG.
Since the waveform W1 generated by the second magnet 105 is generated within a short time after the waveform W1 generated by the magnet 104 of FIG. 1 is detected, the preceding voltage waveform W1 is generated based on the clear difference in the generation timing of the waveforms W1 and W2. Is determined to be due to the first magnet 104.

[0008]

However, as described above, the first magnet 104 and the second magnet 105 are connected to the wheel 102.
If the magnets are placed in the range of 60 ° to 90 ° in the circumferential direction of the magnet,
The weight of 104 and 105 causes the wheel 102 to lose its dynamic balance. In order to cancel such an imbalance, the balance weight 110 is placed on the opposite side of 180 ° with respect to the magnets 104 and 105 with the center of rotation C of the wheel 102 interposed therebetween.
Need to be provided. In this case, there are problems that the weight of the wheel 102 increases, that the balance weight 110 is attached with trouble, and the appearance is deteriorated.

Therefore, an object of the present invention is to arrange a first magnet portion, which serves as a reference for obtaining an electromotive force difference, and a second magnet portion, which is displaced by a change in tire air pressure, so as not to disturb the dynamic balance of the wheel. It is to provide a tire pressure monitoring device capable of doing the above.

[0010]

The device of the present invention, which has been developed to achieve the above object, is fixed to a member on the wheel side that rotates integrally with a tire and is arranged with their positions slightly displaced from each other in the circumferential direction of the wheel. And a first magnet portion having a plurality of magnets provided on the same circumference on the opposite side with respect to the first magnet portion with respect to the center of rotation of the wheel and positioned in the axial direction of the wheel according to the tire pressure. And a second magnet portion having a magnet that changes, and the first magnet portion and the first magnet portion which are provided on a member on the vehicle body side and are located on substantially the same circumference as the rotation loci of the first magnet portion and the second magnet portion. A magnetic sensor that produces an output according to the number of magnets of each magnet when the two magnets pass, and the first magnet and the second magnet that are obtained in advance.
A means for storing a known relationship between the output difference due to the magnet portion and the tire air pressure, and the output detected by the magnetic sensor is based on the wave number of the first magnet portion or the second magnet portion. It is determined whether or not there is, and an electric circuit section that obtains an actual tire pressure from the known relationship based on the output difference between these two types of magnet sections, and information related to the tire pressure obtained by the electric circuit section are displayed. And display means.

[0011]

When the wheel rotates integrally with the tire, the plurality of magnets in the first magnet section and the magnets in the second magnet section respectively pass in the vicinity of the electromagnetic coil, so that the number of magnets in each magnet section is increased in the electromagnetic coil. A corresponding wave number output is produced. Each output depends on the shortest distance from the magnet to the electromagnetic coil.
The position of the first magnet portion does not depend on the tire pressure,
Since the second magnet portion is displaced in the axial direction of the wheel according to the tire air pressure, the output by the second magnet portion relatively changes according to the tire air pressure. That is, an output difference between the first magnet portion and the second magnet portion occurs depending on the tire air pressure.

When the tire pressure is monitored while the vehicle is running, it is determined whether the output is from the first magnet section or the second magnet section based on the wave number of the output detected by the electromagnetic coil. . Then, based on the output from the first magnet unit, based on the output difference with the second magnet unit, the tire pressure is obtained by a known relationship between the output difference and the tire pressure that is obtained in advance, and information on the tire pressure is obtained. , Displayed on the indicator installed in the cab, etc.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an outline of a tire air pressure monitoring device 10 of this embodiment. In the tire pressure monitoring device 10, a wheel portion 13 including a wheel 11 and a tire 12 is provided with a first magnet portion 15 and a second magnet portion 16.

As shown in FIG. 2, the first magnet portion 15
Includes a plurality of permanent magnets 20 and 21 which are arranged at positions slightly offset from each other in the rotation direction of the wheel 11. The magnets 20 and 21 in the illustrated example are both attached to the inner peripheral portion of a member (rim 11a in the illustrated example) on the wheel side. The magnets 20 and 21 may generate magnetic fields having the same strength as each other.

The second magnet portion 16 is provided on the same circumference at a point symmetrical with respect to the first magnet portion 15 with respect to the rotation center C of the wheel 11 by about 180 °. This second magnet unit 1
6 is also provided on the inner peripheral portion of the rim 11a. The second magnet unit 16 is provided in the transducer 30 as shown in FIG.

The transducer 30 has a housing 32 having an air chamber 31 into which the air pressure of the tire 12 is introduced.
And a mover 33 housed in the housing 32, a permanent magnet 34 provided in the mover 33, and the like. The penetrating portion of the mover 33 with respect to the housing 32 is sealed by a bellows-shaped partition member 35,
The air in the air chamber 31 does not leak outside. A lid 36 is provided on the front side of the housing 32.

The mover 33 is movable in the axial direction of the wheel 11 (left-right direction in FIG. 3) and is biased in the direction of arrow F by a spring (not shown). Therefore, when the tire pressure is low, the magnet 34 is retracted toward the air chamber 31 as shown in FIG. When the tire pressure is proper, the magnet 34 is displaced to the intermediate position as shown in FIG. When the tire pressure is excessive, the magnet 34 advances toward the lid 36 as shown in FIG.

A member 40 on the vehicle body side is provided with an electromagnetic coil 41 as an example of a magnetic sensor. Electromagnetic coil 4
1 is located on the circumference substantially the same as the trajectory drawn by the first magnet portion 15 and the second magnet portion 16 when the wheel 11 rotates, and the first magnet portion 15 and the second magnet portion 16 are electromagnetically coupled. Coil 4
When passing through the vicinity of 1, electromotive force (output) due to electromagnetic induction is generated according to the number of magnets of each magnet portion 15 and 16.

The member 40 on the vehicle body side referred to in this specification means
A frame, an axle, a part of a suspension, or the like, which means a member fixed to the rotating wheel 11 in short. The directions of the magnetic fields of the magnets 20, 21, 34 and the central axis of the electromagnetic coil 41 are made to coincide with the axial direction of the wheel 11, respectively.

FIG. 6 shows the waveform of the electromotive force generated when the wheel 11 rotates. A waveform A in the figure is a voltage waveform generated by the first magnet unit 15. In the case of the first magnet unit 15,
Two magnets 20, 2 adjacent to each other in the rotation direction of the wheel 11
Since 1 produces an electromotive force, two waveforms are continuously generated. The waveform B is due to the second magnet portion 16, and the magnitude of the electromotive force is from the magnet 34 to the electromagnetic coil 4
It changes according to the shortest distance to 1. For example, when the magnet 34 approaches the electromagnetic coil 41 because the tire air pressure is excessive, the voltage waveform B becomes large as shown by a two-dot chain line in the figure.

As shown in FIG. 1, an electric circuit section 50 is connected to the electromagnetic coil 41. The electric circuit section 50 includes a signal processing circuit 51 that processes an output generated in the electromagnetic coil 41.
And an A / D conversion circuit 52 and a controller 53. The controller 53 using a microcomputer includes a ROM 55 that stores a known relationship between the tire pressure and the electromotive force difference between the first magnet section 15 and the second magnet section 16, which is obtained in advance.

The CPU 56 determines the voltage waveform of the electromotive force detected by the electromagnetic coil 41 based on the wave number.
A means for determining whether the electromotive force is generated by the magnet unit 15 or the electromotive force generated by the second magnet unit 16 is provided, and based on the electromotive force generated by the first magnet unit 15 and the electromotive force difference, the above-described known relationship is obtained. It has a means for obtaining the actual tire pressure from a map or the like.

The display device 60 as an example of the display means is provided at a position where the occupant can see it, such as the instrument panel in the driver's cab, and displays the information on the tire pressure obtained by the electric circuit section 50. It is supposed to do. The display means may be a audible device such as a buzzer that issues an alarm when the tire pressure is abnormal.

Next, the operation of the tire pressure monitoring device 10 having the above structure will be described. When the wheel 11 rotates, the magnets 20 and 21 of the first magnet part 15 and the second magnet part 1
6 magnets 34 successively pass near the electromagnetic coil 41. Therefore, while the wheel 11 makes one rotation, two types of electromotive force having waveforms A and B as shown in FIG. 6 are alternately generated.

Although the position of the first magnet portion 15 does not change even if the tire air pressure changes, the position of the magnet 34 of the second magnet portion 16 changes in the axial direction of the wheel 11 according to the tire air pressure. Changes, the shortest distance from the electromagnetic coil 41 to the magnet 34 changes. Therefore, the waveform B of the electromotive force generated by the second magnet portion 16 changes depending on the tire air pressure.

The two types of electromotive force are rectified and shaped in the signal processing circuit 51, and the wave number is counted. Since the waveform of the electromotive force generated by the first magnet unit 15 is generated by the two magnets 20 and 21, the wave number count after rectification is 4. In the case of the electromotive force generated by the second magnet unit 16, since the number of the magnets 34 is one, the wave number after rectification is 2.

The electromotive forces represented by the waveforms A and B are counted and integrated, respectively, and converted from an analog value to a digital value by the A / D conversion circuit 52, and then input to the controller 53. . here,
If the wave number count is 4, it is determined to be the waveform A of the electromotive force generated by the first magnet unit 15, and the integrated value of the waveform A is stored in the controller 53. Second if the wave number count is 2
It is determined to be the waveform B of the electromotive force generated by the magnet unit 16.
Then, based on the integrated value of the electromotive force (waveform A) by the first magnet unit 15, the electromotive force (waveform B) by the second magnet unit 16 is used as a reference.
Is calculated and the tire pressure is calculated based on this electromotive force difference and a previously known relationship (relationship between electromotive force difference and tire pressure, etc.), which is displayed on the display 60. indicate.

According to the tire pressure monitoring device 10 having the above structure, the first magnet portion 15 and the second magnet portion 16 are connected to the wheel 1.
The waveform of the electromotive force generated by the first magnet portion 15 and the second magnet portion 1 are provided even if they are provided at positions approximately 180 ° symmetrical with respect to the rotation center C of the first magnet portion 1.
It can be distinguished from the waveform of the electromotive force of 6. Therefore, the first
The magnet portion 15 and the second magnet portion 16 can be provided at a position where the dynamic balance of the wheel 11 is not broken.

Although the electromagnetic coil 41 has been described as an example of the magnetic sensing element in the above-described embodiment, in implementing the present invention, it is necessary to use the magnet portions 15 and 16 like a hall element. Any magnetic sensor that produces an output can be used instead of the electromagnetic coil 41.

[0030]

According to the present invention, the first magnet portion and the second magnet portion can be arranged so as not to disturb the dynamic balance of the wheel, and the use of the balance weight can be eliminated or reduced. The cost can be reduced, the weight of the wheel can be reduced, and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a wheel portion and a block of an electric circuit portion of a tire air pressure monitoring device showing an embodiment of the present invention.

FIG. 2 is a rear view of a wheel unit used in the tire pressure monitoring device of FIG.

3 is a cross-sectional view of a transducer used in the tire pressure monitoring device of FIG.

FIG. 4 is a cross-sectional view showing a state where the tire pressure is appropriate in the transducer shown in FIG.

FIG. 5 is a cross-sectional view showing a state of excessive air pressure in the transducer shown in FIG.

6 is a diagram showing a voltage waveform of an electromotive force of the tire pressure monitoring device shown in FIG.

FIG. 7 is a flowchart showing the processing contents by a controller of the tire pressure monitoring device shown in FIG.

FIG. 8 is a sectional view showing a part of a conventional tire pressure monitoring device.

9 is a rear view of a wheel unit used in the conventional apparatus shown in FIG.

10 is a diagram showing a voltage waveform of an electromotive force of the conventional device shown in FIG.

[Explanation of Codes] 10 ... Tire Pressure Monitoring Device, 11 ... Wheel, 12
... tire, 15 ... first magnet part, 16 ... second magnet part, 2
0, 21 ... Magnet, 30 ... Transducer, 34 ... Magnet, 40 ... Vehicle side member, 41 ... Magnetic sensor, 50 ... Electrical circuit section, 53 ... Controller, 60 ... Indicator.

Claims (1)

[Claims] 1. A first magnet portion having a plurality of magnets fixed to a member on a wheel side that rotates integrally with a tire, and having a plurality of magnets arranged at positions slightly offset from each other in the circumferential direction of the wheel, and the first magnet. A magnet provided on the same circumference on the opposite side of the wheel center of rotation of the wheel as a boundary, and having a position that changes in the axial direction of the wheel according to tire pressure
A magnet part, and the first magnet part and the second magnet part provided on a member on the vehicle body side.
It is located on the same circumference as the rotation locus of the magnet part.
A magnetic sensor that produces an output according to the number of magnets of each magnet portion when the magnet portion and the second magnet portion pass, and the output difference between the first magnet portion and the second magnet portion and the tire pressure which are obtained in advance. And a means for storing a known relationship with the magnetic sensor, determining whether the output detected by the magnetic sensor is due to the first magnet section or the second magnet section based on the wave number, and An electric circuit section for obtaining an actual tire pressure from the above-mentioned known relationship based on the output difference between the two types of magnet sections, and a display unit for displaying information on the tire pressure obtained by the electric circuit section. A tire pressure monitoring device characterized by.