JP3406063B2 - Tire pressure detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure detecting device suitable for detecting and monitoring air pressure in a tire mounted on a vehicle body such as an automobile. About. 2. Description of the Related Art Conventionally, a tire pressure detecting device mounted on, for example, an automobile or the like is provided with a pressure sensor for each wheel, and the pressure sensor directly detects the air pressure in the tire. 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 so that the signal is transmitted. Has become. However, such a tire pressure detection device requires a transmitter for signal transmission, an antenna, and the like, and thus has a problem that the structure is complicated and the manufacturing cost is high. In recent years, in order to solve such a problem, a sensor unit having a magnet or the like that moves in accordance with the air pressure in the tire is provided integrally with the tire on the tire side, and a detection that detects the movement of this magnet or the like on the vehicle body side. There has been proposed a tire pressure detecting device having a configuration provided with a portion. FIG. 6 shows an example of such a tire pressure detecting device. FIG. 6 is a sectional view showing the configuration of a conventional tire pressure detecting device. In FIG. 1, a tire air pressure detecting device 1 includes a sensor unit 4 provided along an outer peripheral surface of a rim 2 a of a wheel 2 to sense an air pressure in a tire 3 mounted on the wheel 2. A Hall element (detection unit) 5 fixed to the vehicle body to detect the displacement of the vehicle and a monitoring circuit (not shown) for monitoring a detection value from the Hall element 5.
A communication hole 6 is formed in the sensor section 4, and the inside of the communication hole 6 a communicates with an air chamber 7 formed by being surrounded by the wheel 2 and the tire 3. Also, the sensor unit 4
Inside, a rubber diaphragm 8 to which the internal pressure of the tire is applied
And a movable member 9 which is movable back and forth in the axial direction of the sensor portion 4, and a spring 1 which biases the movable member 9 toward the air chamber 7.
0 and a magnet 12 attached to the mover 9 via an arm 11 protruding toward the inner peripheral surface of the rim 2 a of the wheel 2. [0004] The tire pressure detecting device 1 having such a configuration is described.
Then, the diaphragm 8 is deformed in the axial direction of the sensor unit 4 in accordance with the air pressure in the tire 3, and the magnet 12
Move in the axial direction together with the moving element 9, the distance between the magnet 12 and the Hall element 5 changes, and the magnetic field strength of the magnet 12 detected by the Hall element 5 by the Hall effect changes. When the value detected by the Hall element 5 deviates from a predetermined range, the monitoring circuit determines that the air pressure in the tire 3 is abnormal. In the conventional tire pressure detecting device described above, it is determined whether or not the air pressure in the tire is within an appropriate range based on the distance between the magnet 12 and the Hall element 5. Pressure detectors (magnets and Hall elements) are bent or broken by stones or the like, or Hall elements are damaged for the same reason, or the connector to the Hall element is dropped. Even in this case, it is only possible to determine that the air pressure is out of the proper range, and there is a problem that it is not possible to distinguish between a failure of the pressure detection unit and a decrease in the air pressure. The present invention has been made in view of the above circumstances, and has as its object to provide a tire pressure detecting device capable of distinguishing between a decrease in air pressure in a tire and a failure of a pressure detecting unit. [0007] In order to solve the above-mentioned problems, a magnet mounted on the tire side, which rotates according to the air pressure in the tire, and which can change the positions of the N pole and the S pole. (38) and the magnet (38), which is attached to the vehicle body side and is opposed to the magnet by rotation of a tire.
A pressure detecting section comprising a detecting means (5) for outputting a positive or negative output signal according to the polarity of the signal; and absolute value means (43a, 43b, 44) for obtaining an absolute value of the output signal of the detecting means
If, to calculate the sum of the peak value in the output signal of said absolute value means, depending on whether said total sum is within a predetermined range
Determining means (46) for determining a failure of the pressure detecting unit ;
Lighting or according to the determination result of the determination means (46)
There is provided a tire pressure detecting device provided with a blinking display means (41). According to the present invention, when the magnet rotates according to the air pressure in the tire, the positions of the N pole and the S pole are changed.
The detection means attached to the vehicle body
By the magnet attached to the tire side
In this case, the polarity of the magnet facing the detection means changes, and the detection means outputs a positive voltage that simply decreases according to the rotation of the magnet and a negative voltage that simply increases. The absolute value of the positive / negative voltage is obtained by absolute value means. Then, the peak value included in the output signal of the absolute value means is added by the discriminating means, whereby the sum of the peak values is calculated, and it is determined whether or not the sum is within a predetermined range. If the sum is within the predetermined range, it is determined that there is no abnormality in the magnet and the detecting means, and the display means is turned off. On the other hand, if the sum is out of the appropriate range, it is determined that an abnormality has occurred in the magnet and the detection unit, and the display unit is turned on. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a part of an automobile provided with a tire pressure detecting device according to the present invention. In the figure, portions common to the conventional example are denoted by the same reference numerals, and description thereof is omitted. In FIG. 1, a tire pressure detecting device A
Is a sensor unit 31 provided along the inner peripheral surface of the rim 2a of the wheel 2 to sense air pressure in a tire (not shown) mounted on the wheel 2,
A Hall element (detection unit) 5 fixed to the vehicle body (not shown) for detecting the magnetism of the vehicle, a monitoring circuit 40 for monitoring a detection value from the Hall element 5, and a display unit 41
It is composed of A communication hole 6 is formed in the sensor section 31, and the inside 31a of the communication hole 6 is formed between the wheel 2 and a tire (not shown).
And a structure communicating with the air chamber 7 surrounded by In the sensor section 31, a diaphragm 32 made of rubber or the like, and a piston (moving element) 33 made of, for example, a lubricating resin, which is attached to a tip end of the diaphragm 32 and is movable in the axial direction of the sensor section 31, are provided. Provided. As a result, the diaphragm 32 is deformed in accordance with the air pressure in the tire (not shown), and accordingly, the piston 33 moves forward and backward. A rotating shaft 34 extending in the axial direction of the sensor unit 31 is disposed on the tip 31b side in the sensor unit 31. One end 34 a of the rotating shaft 34 is formed in a spherical shape so as to make point contact with the piston 33. An edge 34b is formed on one end 34a side of the rotating shaft 34, and a concave portion 33a of the piston 33 is formed.
And is rotatably supported in the rotation shaft 34.
Can move forward and backward integrally with the piston 33 while rotating. On the other hand, the other end 34 c of the rotating shaft 34 is caulked so that the rotating shaft 34 does not come off from the support portion 35 formed integrally with the sensor portion 31. On the other end 34c side, a thread 36 to be screwed with the support portion 35 is formed with a lead amount of, for example, 6 mm. An annular magnet 38 is attached to an edge 34d formed in a plane perpendicular to the axis of the rotating shaft 34 by bonding or the like. It is arranged to be an S pole. The rotating shaft 34 having such a configuration is configured to be able to advance and retreat with a stroke of 3 mm in the axial direction. Edge 34 of rotating shaft 34
The ends of a torsion coil spring (biasing member) 39 are fixed to d and the support portion 35, respectively, and are configured to bias the rotation of the rotation shaft 34 in the axial direction. The torsion coil spring 39 urges the rotation shaft 34 to rotate in the direction of moving to the base 31 c side of the sensor unit 31 when the pressure applied to the diaphragm 32 reaches a predetermined constant value. , And has been compressed by a predetermined amount and twisted in the rotation direction of the rotation shaft 34. In the tire pressure detecting device A having the above-described configuration, the air pressure in the tire (not shown) is set to a predetermined appropriate range (for example, 1.9 to 2.1 in the case of an automobile).
When the pressure is within kg / cm ² ), the S element of the magnet 38 is detected by the Hall element 5 as shown in FIG. Then, due to some cause such as a puncture, the air pressure in the tire (not shown) becomes lower limit value (for example, 1.7 kg /
When the pressure drops to not more than cm ² ), the diaphragm 32 is urged by the torsion coil spring 39 and deforms toward the base 31c in accordance with the pressure drop, and accordingly, the piston 33 retreats toward the base 31c. Then, the rotating shaft 34 whose one end 34a abuts on the piston 33 rotates around the axis,
The screw 36 screwed to the support portion 35 is configured to retreat 3 mm toward the base 31c. At this time, the rotating shaft 3
4 has a lead amount of 6 mm, so that the rotating shaft 34 is rotated by 180 ° around the axis, whereby the polarity of the magnet 38 attached to the rotating shaft 34 ( (N pole, S pole) are inverted. Then, the Hall element 5 detects the N pole of the magnet 38. Next, the monitoring circuit 40 will be described. FIG. 2 is a block diagram showing a configuration of the monitoring circuit 40. In the figure, a constant voltage source 42 supplies driving power to the Hall element 5 from a vehicle-mounted battery. As described above, the Hall element 5 supplies an output voltage corresponding to the polarity of the magnet 38 to the non-inverting amplifier 43a and the inverting amplifier 43b. The non-inverting amplifier 43a amplifies the output voltage of the Hall element 5 to a predetermined level without inverting the same, and supplies the output voltage to the first switch SW1 of the multiplexer 44. In addition, inverting amplifier 4
3b inverts the output voltage and amplifies the output voltage to a predetermined level, and then supplies the output voltage to the second switch SW2 of the multiplexer 44. The multiplexer 44 controls the first switch SW1 or the second switch S1 according to a switching signal SS supplied from a control device 46 including a microcomputer.
W2 is turned on, and the non-inverting amplifier 43 is turned on.
Either the output voltage “a” or the output voltage of the inverting amplifier 43 b is supplied to the peak hold circuit 45. The peak hold circuit 45 outputs a reset signal RS
Until is supplied, the peak value of the output voltage is detected and held, and supplied to the control device 46 without inversion. The control device 46 includes an A / D converter and a RAM (random access memory).
The multiplexer 44 is switched by outputting the switching signal SS at a predetermined timing, and the output voltage of the non-inverting amplifier 43a and the output voltage of the inverting amplifier 43b are sequentially captured and converted into a digital signal by an A / D converter. Are added to obtain an output sum. Further, the controller 46 compares the output sum with a predetermined threshold value, and when the output sum is smaller than the threshold value, determines that the pressure detection unit is faulty, and outputs an output signal (high level) from the output port. ) Is output to the display unit 41. The control device 46
Determines whether the peak value of the output voltage of the non-inverting amplifier 43a has become substantially "0" or whether the peak value of the output voltage of the inverting amplifier 43b has become larger than a predetermined threshold value (for example, 2.7 V). It is determined whether or not the air pressure in the tire is within an appropriate range. The display section 41 includes a transistor Tr,
The transistor Tr includes a resistor R and an LED 47 connected in series and connected to the collector of the transistor Tr.
One end of the resistance element R is connected to the vehicle battery, and the emitter of the transistor Tr is grounded. This transistor Tr is a driving element for turning on the LED 47. Only when the output signal supplied from the control device 46 is "1", the collector-emitter conducts and the LED 47 is connected via the resistor R. A predetermined current is supplied to the LED 47 to turn on the LED 47. In addition,
The resistance element R determines a current value flowing through the LED 47. The LED 47 is provided on the instrument panel so that the driver can check. The relationship between the rotation of the magnet 38 and the Hall element 5 will now be described with reference to FIG. FIG. 3 is a schematic diagram showing the positional relationship between the magnet 38 and the Hall element 5 and the output voltage of the Hall element 5 at that time. In FIG. 3A, the air pressure in the tire is an appropriate value (for example,
2.0 kg / cm ² ) and the angle of the magnet 38 is “0
゜ ”) indicates the output voltage of the Hall element 5. In this case, a positive voltage is output from the Hall element 5. Further, as shown in FIG. 3B, the air pressure in the tire decreases (for example, 1.85 kg / cm ² ) and the magnet 38
Is rotated by 90 ° about the rotation shaft 34, the Hall element 5 outputs positive and negative voltages. Further, FIG.
As shown in (c), when the air pressure in the tire decreases (for example, 1.70 kg / cm ² ) and the magnet 38 rotates 180 ° about the rotation axis 34, a negative value is generated from the Hall element 5. A voltage is output. FIG. 4 shows the magnet 38 and the Hall element 5.
The change in the output voltage of the Hall element 5 is shown when the distance between the Hall element 5 is 5 mm. FIG. 4 shows the air pressure (barometric pressure) in the tire, the angle of the magnet 38 at that pressure, the (+) side voltage and the (−) side voltage of the Hall element 5 in that state, and the output sum thereof. . For example, when the angle of the magnet 38 is “0 °”, the air pressure in the tire is “2.00”.
kg / cm ² ”, and the voltage on the (+) side of the Hall element 5 is“ 59 mV ”and the voltage on the (−) side is“ −
3mV ", and the output sum of their absolute values is" 62mV ".
V ". Similarly, the angle of the magnet 38 is “90 °”.
, The air pressure in the tire is "1.85 kg / cm ² "
And the voltage on the (+) side of the Hall element 5 at that time is
“29 mV”, the voltage on the (−) side is “−23 mV”, and the output sum of their absolute values is “52 mV”. When the angle of the magnet 38 is “180 °”, the air pressure in the tire is “1.70 kg / cm ² ”, and the voltage on the (+) side of the Hall element 5 at that time is “3 mV”, (− ) -Side voltage is “−57 mV”, and their output sum is “60 mV”. Thus, as the angle of the magnet 38, that is, the air pressure in the tire decreases, the Hall element 5
There is a tendency that the voltage on the (+) side gradually decreases and the voltage on the other (-) side gradually increases. As described above, when the magnet 38 and the Hall element 5 are properly mounted, the sum of outputs on the (+) side and the (-) side of the Hall element 5 falls within the range of "52 to 62 mV". I understand. Assuming that the amplification factors of the non-inverting amplifier 43a and the inverting amplifier 43b are “50”, “2.6”
If the pressure detection unit (magnet, hall element, wiring of these, etc.) is not out of the range, the pressure detection unit (magnet, hall element, Or these wirings) can be determined to be faulty. As described above, whether or not the air pressure in the tire is within the appropriate range is determined by determining whether the peak value of the output voltage of the non-inverting amplifier 43a is substantially zero or the peak value of the output voltage of the inverting amplifier 43b. Is larger than a predetermined threshold value (for example, 2.7 V). Therefore, when the sum of the outputs of the non-inverting amplifier 43a and the inverting amplifier 43b is out of the range of "2.6 to 3.1 V", the LED 47 is turned on to indicate the failure of the pressure detecting unit. ing. Note that LE
D47 may be blinked. Next, the operation of the tire pressure detecting device A will be described with reference to FIG. FIG. 5 is a flowchart showing an operation procedure of the tire pressure detecting device A. In the figure, first, in step SA1, a switching signal SS is output from the control device 46 and the multiplexer 4
4 turns on the first switch SW1. Then, in step SA2, the output voltage of the non-inverting amplifier 43a is fetched, converted into a digital signal by an A / D converter, and stored in the built-in RAM as output data AD1. Next, the process proceeds to step SA3, where a switching signal SS is output from the control device 46, and the second switch SW2 of the multiplexer 44 is turned on. Then, in step SA4, the output voltage of the inverting amplifier 43b is fetched, converted into a digital signal by the A / D converter, and stored in the built-in RAM as output data AD2. Next, at step SA5, the output data AD1 and the output data AD2 are added, and the output sum A
Get D. Then, in step SA6, the output sum A
It is determined whether D is smaller than threshold value SH1 ("2.6 V"). If the output sum AD is smaller than the threshold value SH1, the result of the determination in step SA6 is "YES", and the flow proceeds to step SA7. Step S
In A7, the control device 46 sets the abnormality signal of the output port to a high level. As a result, the transistor Tr is turned on, the conduction between the collector and the emitter is conducted, and the LED 47 is turned on. On the other hand, if the output sum AD is equal to or greater than the threshold value SH1, the result of the determination at step SA6 is "N
O ", and the process proceeds to Step SA8. In step SA8, it is determined whether or not the output sum AD is greater than a threshold value SH2 ("3.1 V"). If the output sum AD is larger than the threshold value SH2, the control goes to step SA8.
Is "YES", and the flow proceeds to step SA7. At step SA7, the control device 46 sets the abnormality signal of the output port to high level. As a result, the transistor Tr is turned on, the conduction between the collector and the emitter is conducted, and the LED 47 is turned on. Further, the processing of step SA7 is completed, or the output sum AD becomes equal to the threshold value SH2.
Hereinafter, when the result of the determination in step SA8 is "NO", the process returns to step SA1, and the above-described processing is repeated. As described above, in the tire pressure detecting device A of the present embodiment, when the magnet 38 and the Hall element 5 are arranged at normal positions, the air pressure in the tire (not shown) is increased. Even within the proper range or outside the proper range,
The output sum of the (+) voltage and the (-) voltage output by the Hall element 5 falls within a certain predetermined range. Therefore,
By determining whether or not the output sum is within the above range, it is possible to easily and reliably determine whether or not the pressure detector (the magnet 38 and the Hall element 5) has failed. In the above embodiment, since the distance between the magnet 38 and the Hall element 5 is assumed to be constant,
Although it is determined that "2.6 to 3.1 V" is normal, actually, the distance between the magnet 38 and the Hall element 5 varies due to a deviation when these parts are attached or due to the finishing accuracy of the parts. May occur. Therefore, in consideration of the variation of the distance, for example, “2.3 to
It is desirable to keep the normal range wider by the mounting error, such as "3.5 V". Further, in the above-described embodiment, only one wheel has been described. However, if a plurality of tires are provided, the same tire pressure detecting device A may be provided for each tire. As described above, according to the present invention,
Attached to the tire side, and rotates in response to air pressure in the tire, and a magnet for changing the position of the N and S poles, the vehicle body
Side, facing the magnet by tire rotation
When the canceller, a detecting means for outputting a positive or negative output signal in response to the polarity of the magnet, and the absolute value means for taking the absolute value of the output signal of said detecting means, peaks in the output signal of the absolute value means A tire calculating means for calculating the sum of the values and determining whether or not the sum is within a predetermined range; and a display means for turning on or off the light in accordance with a result of the determination by the determining means. This has the advantage that the decrease in the air pressure in the inside and the failure of the pressure detecting section can be easily and reliably distinguished.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an example of a tire pressure detecting device according to the present invention, and is a front sectional view showing a state when an air pressure in a tire is within an appropriate range. FIG. 2 is a block diagram showing a configuration of a monitoring circuit of the device. FIG. 3A shows the orientation of the magnet 38 when the air pressure in the tire is within an appropriate range and the Hall element 5 at that time.
(B) is a diagram showing the orientation of the magnet 38 when the air pressure in the tire decreases and the output voltage of the Hall element 5 at that time, and (c) is a diagram showing the tire output voltage. FIG. 8 is a diagram showing the orientation of the magnet 38 when the air pressure inside the sensor falls outside the appropriate range and the output voltage of the Hall element 5 at that time. FIG. 4 is a diagram showing a change in the output voltage of the Hall element 5 when the distance between the magnet 38 and the Hall element 5 is 5 mm. FIG. 5 is a flowchart showing an operation procedure of the tire pressure detecting device A. FIG. 6 is a cross-sectional view illustrating a configuration of a conventional tire pressure detecting device. FIG. 7 is a waveform diagram showing an output signal of a Hall element of the conventional tire pressure detecting device. [Description of Signs] 5 ... Hall element (detection means), 40 ... Monitoring circuit, 41 ...
Display unit (display means), 43a: non-inverting amplifier (absolute value means), 43b: inverting amplifier (absolute value means), 44: multiplexer (absolute value means), 45: peak hold circuit, 46: control device (discrimination) Means), 47… LED, Tr
... transistors.

──────────────────────────────────────────────────続 き Continued on the front page (72) Masaaki Yamamoto 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. Inside Fuji Heavy Industries Ltd. (72) Inventor Kazuhisa Fukada 1-7-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Inside Fuji Heavy Industries Ltd. (56) References JP 49-6971 (JP, A) JP Sho A 48-71284 (JP, A) JP-A-49-9776 (JP, A) JP-A-6-293205 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 23/00 -23/08

Claims (1)

(57) [Claim 1] A magnet (38) attached to the tire side, which rotates according to the air pressure in the tire and can change the positions of the N pole and the S pole, and a magnet (38) When mounted and opposed to the magnet by rotation of the tire, said magnet (3
8) A pressure detecting section comprising detecting means (5) for outputting a positive or negative output signal according to the polarity, and absolute value means (43a, 43b, 44) for obtaining an absolute value of the output signal of the detecting means.
If, to calculate the sum of the peak value in the output signal of said absolute value means, depending on whether said total sum is within a predetermined range
Determining means (46) for determining a failure of the pressure detecting unit ;
Lighting or according to the determination result of the determination means (46)
A tire pressure detecting device comprising: a blinking display means (41).