JPH0664413A - Tire air pressure monitoring device - Google Patents

Abstract

PURPOSE:To arrange a first magnet part and a second magnet part as being well balanced, by setting an electric circuit part for calculating the actual tire air pressure based on the output difference between the two kinds of the magnet parts, from the already-known relation. CONSTITUTION:A magnet 20 of the first magnet part 15 is fixed to a 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, and the second magnet part 16 makes a magnetic coil 41 to generate electromotive force which is always larger than electromotive force generated by the first magnet part 15, when passing near the magnetic coil 41. In an electric circuit 50, the electromotive force generated in the magnetic coil 41 is judged whether being generated by the first magnet part 15 or by the second magnet part 16, based on the magnitude of the electromotive force, 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 is detected, the preceding voltage waveform W1 is determined based on the difference between the generation timings of the waveforms W1 and W2. It is determined that it is due to one 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]

A device of the present invention developed to achieve the above object comprises a first magnet portion having a magnet fixed to a member on a wheel side which rotates integrally with a tire,
It is provided on a member on the vehicle body side and is located on substantially the same circumference as the rotation locus of the first magnet portion, and has a size corresponding to the shortest distance between the first magnet portion and the first magnet portion when the first magnet portion passes. And a magnet that is provided on the same circumference on the opposite side of the first magnet portion with respect to the center of rotation of the wheel with respect to the first magnet portion and that changes its position in the axial direction of the wheel according to tire air pressure. And a second magnet section that causes the magnetic sensor to generate an output of a magnitude that would not be possible with the first magnet section when passing near the magnetic sensor, and the first magnet section obtained in advance. And means for storing a known relationship between the output difference of the second magnet section and the tire air pressure, and whether the output detected by the magnetic sensor is the first magnet section according to the magnitude of the output. Determine if it is due to the magnet part In addition, an electric circuit section for obtaining an actual tire pressure from the known relationship based on the output difference between these two types of magnet sections, and a display means for displaying information on the tire pressure obtained by the electric circuit section. It has.

[0011]

When the wheel rotates integrally with the tire, the magnets of the first magnet section and the magnets of the second magnet section pass near the electromagnetic coil, respectively, so that an output is generated in the electromagnetic coil. The magnitude of the output depends on the shortest distance from each magnet unit to the electromagnetic coil. The position of the first magnet portion does not depend on the tire air pressure, but the second magnet portion is displaced in the axial direction of the wheel according to the tire air pressure, so that the output of the second magnet portion relatively changes according to the tire air pressure. To do. 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 possible to use the electromagnetic coil while the wheel makes one revolution to
There will be different types of output. In the present invention, it is determined whether the output is from the first magnet unit or the second magnet unit based on the magnitude of the output. Then, based on the output from the first magnet unit, based on the output difference from the second magnet unit, the tire air pressure is obtained from the known relationship between the output difference and the tire air pressure that has been obtained in advance, and information regarding this tire air pressure is obtained. Is displayed on the display provided in the cab or the like.

[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. The first magnet portion 15 includes a permanent magnet 20 fixed to an inner peripheral portion of a wheel-side member (the rim 11a in the illustrated example).

As shown in FIG. 2, the second magnet portion 16 has a first
They are provided on the same circle at a point symmetry position of approximately 180 ° with the rotation center C of the wheel 11 as a boundary with respect to the magnet portion 15.
The second magnet portion 16 is provided on the transducer 30 arranged on the inner peripheral portion of the rim 11a.

The transducer 30 shown in FIG. 3 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.
And a permanent magnet 34 provided on the mover 33. The penetrating portion of the mover 33 with respect to the housing 32 is sealed by a bellows-shaped partition member 35 so that the air in the air chamber 31 does not leak to the 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 urged 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, the electromotive force (output) due to electromagnetic induction of a magnitude corresponding to the shortest distances D1 and D2 to the magnet portions 15 and 16 is generated.

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

FIG. 6 shows a waveform of an electromotive force generated when the wheel 11 rotates. A waveform A in the figure is a voltage waveform by the first magnet unit 15. Since the first magnet portion 15 is fixed to the wheel 11, the shortest distance D1 to the electromagnetic coil 41 is constant even if the tire air pressure changes, and therefore the electromotive force does not change. The waveform B is due to the second magnet portion 16, and the magnitude of its electromotive force changes according to the shortest distance D2 from the magnet 34 to the electromagnetic coil 41. For example, when the tire pressure is excessive, the magnet 34 is moved to the electromagnetic coil 4
When the value approaches 1 (D2 becomes short), the voltage waveform B becomes large as shown by the chain double-dashed line in FIG.

On the contrary, when the tire air pressure is insufficient and the magnet 34 is displaced in the direction away from the electromagnetic coil 41 (D2 becomes large), the voltage waveform B becomes small. In this way, the waveform B changes within the operating stroke range of the transducer 30 that responds to tire air pressure.

In this embodiment, the electromotive force V2 (waveform B) generated by the second magnet portion 16 is always higher than the electromotive force V1 (waveform A) generated by the first magnet portion 15. As a means for this, in the case of the illustrated example, due to a lack of tire air pressure, the electromagnetic coil 41 is removed from the second magnet portion 1
Even if the shortest distance D2 to 6 is maximized, the shortest distance D1 from the first magnet portion 15 to the electromagnetic coil 41 is set so that the electromotive force of the second magnet portion 16 exceeds the electromotive force of the first magnet portion 15. Is sufficiently larger than D2. The electromotive force of the second magnet unit 16 may always exceed the electromotive force of the first magnet unit 15 by making the magnetic force of the second magnet unit 16 sufficiently stronger than that of the first magnet unit 15.

As shown in FIG. 1, the 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 whether the voltage waveform of the electromotive force detected by the electromagnetic coil 41 is the electromotive force generated by the first magnet portion 15 or the second magnet portion 16 based on its magnitude. With means to do
Based on the electromotive force generated by the magnet portion 15 and the electromotive force difference, there is provided means for obtaining an actual tire pressure from a map or the like based on the above-mentioned known relationship.

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 magnet 20 of the first magnet unit 15 and the magnet 34 of the second magnet unit 16 pass near the electromagnetic coil 41 one after another. 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 is displaced in the axial direction of the wheel 11 according to the tire air pressure. Is changed, the electromagnetic coil 41
The shortest distance D2 from the magnet 34 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 above-mentioned two types of electromotive force are rectified, shaped and integrated in the signal processing circuit 51, respectively, and then converted from an analog value to a digital value by the A / D conversion circuit 52 and input to the controller 53. It Then, the waveform is compared with the preceding waveform, and if the electromotive force is smaller than the preceding waveform, 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. It If the electromotive force is larger than the immediately preceding waveform, it is determined to be the waveform B of the electromotive force generated by the second magnet portion 16.

The difference between the integrated value of the electromotive force (waveform A) by the first magnet portion 15 and the integrated value of the electromotive force (waveform B) by the second magnet portion 16 is calculated, and this electromotive force is calculated. The tire air pressure is obtained based on the difference and a previously known relation (relationship between the electromotive force difference and the tire pressure, etc.), and displayed on the display unit 60.

According to the tire air 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.

In the above embodiment, the electromotive force generated by the second magnet section 16 is always set to exceed the electromotive force generated by the first magnet section 15. However, on the contrary,
The distance from the magnet parts 15, 16 to the electromagnetic coil 41 and the magnetic fields of the magnet parts 15, 16 are controlled so that the electromotive force by the magnet part 16 is always lower than the electromotive force by the first magnet part 15 within the working stroke range of the transducer 30. By setting the strength, the electromotive force generated by the first magnet unit 15 and the second magnet unit 1
The electromotive force of 6 may be distinguished.

In the above embodiment, the electromagnetic coil 41 is described as an example of the magnetic sensing element, but in implementing the present invention, it is necessary to use the magnet portions 15 and 16 in accordance with, for example, a Hall element. Any magnetic sensor that produces an output can be used instead of the electromagnetic coil 41.

[0032]

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 symbols]

10 ... Tire pressure monitoring device, 11 ... Wheel, 12
... Tire, 13 ... Wheel side member, 15 ... First magnet part, 16 ... Second magnet part, 20 ... Magnet, 30 ... Transducer, 34 ... Magnet, 40 ... Vehicle body side member, 41 ... Magnetic sensor, 50 … Electrical circuit part, 53… Controller, 60
…display.

Claims (1)

[Claims] 1. A first magnet portion having a magnet fixed to a member on a wheel side that rotates integrally with a tire, and a circumference provided on a member on the vehicle body side and substantially the same as a rotation locus of the first magnet portion. A magnetic sensor located above and producing an output of a magnitude corresponding to the shortest distance from the first magnet portion when the first magnet portion passes through; and a rotation center of the wheel with respect to the first magnet portion. Is provided on the same circumference on the opposite side and has a magnet whose position changes in the axial direction of the wheel according to the tire air pressure, and the first magnet portion is possible when passing near the magnetic sensor. A second magnet section for producing an output of no magnitude in the magnetic sensor, and a means for storing a known relationship between a tire pressure and an output difference between the first magnet section and the second magnet section which is obtained in advance. Detected by the above magnetic sensor It is determined whether the output is due to the first magnet portion or the second magnet portion according to the magnitude of the output, and based on the output difference between these two types of magnet portions, from the above known relationship. A tire pressure monitoring device, comprising: an electric circuit unit for obtaining an actual tire pressure; and a display unit for displaying information on the tire pressure obtained by the electric circuit unit.