JPH11287725A - Pressure sensor unit and tire pressure detector employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a noncontact pressure sensor unit requiring no power supply. SOLUTION: The pressure sensor unit includes a sensor section 1 comprising a super magnetrostrictive material 10 generating a magnetic field corresponding to the pressure in a tire 101, a coil 12 generating an induction current corresponding to variation of a field generated in the super magnetrostrictive material 10, and a transmission coil 14 generating a field with the current induced in the coil 12, and a receiving section 2 disposed oppositely to the transmission coil 14 at the sensor section 1 and detecting the field generated in the transmission coil 14. A tire detector comprising the unit integrates the detection signal from the receiving section 2, compares the integrated value with a preset threshold value and delivers an alarm signal when the threshold value is exceeded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor unit and a tire pressure detecting device using the pressure sensor unit.

[0002]

2. Description of the Related Art Conventionally, when an object to be measured for detecting pressure is a moving body that rotates or moves linearly, a sensor unit mounted on the object to be measured and an output unit for extracting a sensor output to the outside. There is a type in which a sliding contact is provided to take out a sensor output in a contact manner, and a type in which a communication means is provided between a sensor unit and an output unit to take out a sensor output to the outside in a non-contact manner.

[0003]

By the way, in the contact type in which a sliding contact is provided between the sensor section and the output section, especially when the object to be measured is a tire mounted on a vehicle or the like, the contact point is not required. Factors of instability due to wear and the like are large, making application difficult. In the non-contact type in which communication means is interposed between the sensor unit and the output unit, a power source (battery) for a transmitter is required in the measured object, and the IC (integrated circuit) of the sensor unit vibrates. There was a problem in reliability such as weakness. The present invention has been made in view of the above circumstances, and relates to a pressure sensor unit that does not require a power supply while being a non-contact type, and a tire pressure detection using the pressure sensor unit, for a measurement target that moves, such as rotation. It is an object of the present invention to provide a device, to enable stable measurement and to always obtain high reliability.

[0004]

According to another aspect of the present invention, there is provided a pressure sensor unit for detecting and transmitting a pressure in a body to be measured, and a non-contact state separated from the sensor unit. A pressure sensor unit including a receiving unit that receives a detection signal detected by the sensor unit, wherein the sensor unit has a characteristic of generating a magnetic field by a compressive force from the outside, A giant magnetostrictive material in which a compressive force proportional to pressure acts via a push rod, and a first coil arranged around the giant magnetostrictive material to generate an induced current according to a magnetic field change generated by the giant magnetostrictive material; A yoke accommodating and holding the giant magnetostrictive material and the first coil and covering them to form a closed magnetic circuit; and a yoke electrically connected to the first coil and internally provided with a conductor. A second coil for generating a magnetic field by an induced current of the coil, wherein the receiving unit is disposed separately from and facing a conductor of the second coil, and detects a magnetic field generated by the second coil to generate a detection signal. Is output to a control unit, and the sensor unit and the receiving unit measure and output the pressure in the body to be measured as a magnetic field change amount.

According to the above configuration, a compressive force proportional to the pressure in the body to be measured acts on the giant magnetostrictive material via the push rod. Then, when the pressure in the measured body changes, the magnetic field generated in the giant magnetostrictive material also changes, and an induced current corresponding to the change in the magnetic field is generated in the first coil. Further, the induced current generates a magnetic field in the second coil. For this reason, the magnetic field generated in the second coil is detected by a receiving unit that is spaced apart from the conductor of the second coil. That is, an induced current flows through the first coil due to a change in the magnetic field generated in the giant magnetostrictive material, and a magnetic field is generated in the second coil by the induced current, and the magnetic field is detected by the receiving unit. Therefore, the pressure inside the body to be measured can be detected in a non-contact manner, and the receiving unit substantially self-generates power. Also, since no electric parts such as ICs are used, high reliability can be ensured against vibrations and the like.

According to a second aspect of the present invention, there is provided a tire pressure detecting device including the sensor unit and the receiving unit according to the first aspect, wherein the sensor unit is provided in a tire of a vehicle.
A control unit that fixes the receiving unit to a vehicle body portion separated from the tire, the sensor unit detects a tire pressure, and the receiving unit detects a detection signal of a magnetic field change according to the tire pressure. Integrates the detection signal, compares the integrated detection signal with a preset threshold value, and outputs an alarm signal when the threshold value is exceeded.

According to this configuration, a change in tire pressure results in a change in a compressive load applied to the giant magnetostrictive material, and changes a magnetic flux density (magnetic field intensity) generated from the giant magnetostrictive material. When the magnetic flux density generated from the giant magnetostrictive material changes, an induced current corresponding to the change is generated in the first coil, and the induced current generates a magnetic field in the second coil. Then, the magnetic field generated from the second coil is detected by the receiving unit, and a detection signal is output to the control unit. Then, the detection signal from the receiving unit is integrated by the control unit, and the integrated value is compared with a preset threshold value. Then, an alarm signal is output when the integrated value exceeds the threshold.

[0008] Thus, the tire pressure can be detected in a non-contact manner by including the sensor unit and the receiving unit according to the first aspect. Moreover, it is possible to realize a tire pressure detecting device that does not require a power supply for the sensor unit. In addition, you may make it arrange | position a several receiving part so that it may mutually be spaced apart in the tire circumferential direction. With this configuration, the output can be detected at any position where the sensor unit rotates, so that the tire pressure can be constantly monitored. Further, a Hall element or a magnetoresistive element may be applied to the receiving unit. With this configuration, the receiving section can be formed with high precision and compactness.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2
1 shows an embodiment of a tire pressure detecting device according to the present invention. The tire pressure detecting device 6 according to this embodiment includes:
A sensor unit 1 for detecting and transmitting the pressure inside 101 of a pressure-filled tire (hereinafter, simply referred to as a “tire”) 100 such as an automobile, a railway vehicle, and an industrial machine to be measured, and a distance from the sensor unit 1 And a receiving unit that is provided in a non-contact state with the sensor unit and receives a detection signal detected by the sensor unit
And a control unit 3 having a function of outputting an alarm signal based on a change in the output of the receiving unit 2, and an alarm buzzer 4 that sounds when the alarm signal is supplied.

[0010] The sensor unit 1 detects the tire internal pressure facing the tire interior 101.
Wheel 1 that rotates integrally with tire 100 by being connected to
It is provided in 10 parts. The receiving units 2 are fixedly mounted on the vehicle body along the tire circumferential direction. Although not shown, a plurality of the receiving units 2 are arranged at equal intervals from each other, and each is electrically connected to the control unit 3. The sensor unit 1 and the receiving unit 2 constitute a pressure sensor unit 5.

FIG. 3 is an enlarged longitudinal sectional view of a mounting portion of the pressure sensor unit 5, and FIG. 4 is an enlarged longitudinal sectional view of the sensor unit 1. In FIG. 4, the sensor unit 1
Has a characteristic that a magnetic field is generated by an external compressive force, and a giant magnetostrictive material 10 in which a compressive force proportional to the internal pressure of the tire 100 acts via a push rod 11, and is arranged around the giant magnetostrictive material 10. The first coil (coil) 12 that generates an induced current according to the magnetic field change generated by the giant magnetostrictive material 10 and the giant magnetostrictive material 10 and the coil 12 are housed and covered, and a closed magnetic circuit is formed by covering these. A yoke 13, a second coil (transmitting coil) 14 which is electrically connected to the coil 12 and has a conductor (iron core) 143 therein and generates a magnetic field by an induced current of the coil 12, and one end of the yoke 13 Preload bar which is provided in a compressed state between the wall material portion 132 of the section and the flange portion 111 of the push rod 11 and applies a compressive load to the giant magnetostrictive material 10 through the push rod 11 in an auxiliary manner. It is constituted by a 15.

The preload spring 15 is formed by stacking two disc springs in opposite directions. By applying a constant compressive load to the giant magnetostrictive material 10, the preload spring 15 is configured to be superposed when pressure is applied to the push rod 11. It serves to increase the amount of distortion of the magnetostrictive material 10. The yoke 13 has a cylindrical main body 131 covering the outer circumferences of the coil 12 and the transmitting coil 14, and has an opening that is connected and fixed to one end of the main body 131 and through which the shaft 112 of the push rod 11 can be inserted. The transmitting coil 1 is connected and fixed to the wall member 132 and the other end of the main body 131.
4 and a wall member 133 which comes into contact with the case 141.

The receiving unit 2 includes an iron core 141 of the transmitting coil 14.
And detects the magnetic field generated by the transmitting coil 14 and transmits this detection signal to the control unit 3.
Output to As described above, the receiving unit 2
A plurality are arranged apart from each other in the circumferential direction of 0.
By arranging a plurality of the receiving units 2 along the circumferential direction of the tire 100, it is possible to detect the sensor output at any position where the sensor unit 1 rotates. The receiving unit 2 uses a magnetic detecting element such as a Hall element or a magnetoresistive element.

A control unit 3 for monitoring tire pressure based on a detection signal from the receiving unit 2 includes a receiving unit 2
The control unit 3 incorporates an integration circuit (not shown) that integrates a detection signal of a magnetic field change corresponding to the tire pressure detected by the integration circuit by converting the change in the tire pressure into a voltage by the integration circuit. At the same time, the integrated detection signal is compared with a preset threshold value, and when it is determined that the integrated value exceeds the threshold value, an alarm signal is output. The alarm buzzer 4 sounds while an alarm signal is supplied from the control unit 3.

According to the above tire pressure detecting device, the tire pressure acts on the giant magnetostrictive material 10 constituting the pressure sensor unit 5 via the push rod 11 as a compressive load. Then, the change in the tire pressure results in a change in the compressive load applied to the giant magnetostrictive material 10, and changes the magnetic flux density (magnetic field strength) generated from the giant magnetostrictive material 10. When the magnetic flux density generated from the giant magnetostrictive material 10 changes, an induced current corresponding to the change is generated in the coil 12, and the induced current generates a magnetic field in the transmitting coil 14.
The magnetic field generated from the transmitting coil 14 is
And a detection signal is output to the control unit 3. Since the magnetic field generated by the giant magnetostrictive material 10 converges in the closed magnetic circuit formed by the yoke 13, there is almost no leakage magnetic flux to the outside. Also, giant magnetostrictive material 1
Since 0 is magnetically shielded by the yoke 13, it is hardly affected by external magnetism.

The control unit 3 integrates the detection signal, compares the integrated value with a preset threshold value, and outputs an alarm signal when the value exceeds the threshold value. Here, FIG. 5 is a flowchart showing a process of integrating the detection signal in the control unit 3 and comparing the integrated value with a threshold value. First, the control unit 3 initializes two registers M and m for integrating the detection signal in step S10. Next, it is determined in step S12 whether a magnetic field has been generated, that is, whether or not a detection signal has been obtained. If the detection signal has not been obtained, this determination is repeated. If the detection signal has been obtained, the process proceeds to step S14. Then, the detection signal is added to the initial value of the register M. Next, the process proceeds to step S16, in which it is determined whether or not the added value in step S12 exceeds a predetermined threshold value K. If not, the process returns to step S12. If not, an alarm signal is output in step S18.

The giant magnetostrictive material 10 constituting the pressure sensor unit 5 has a response speed to a load change of 50 to 10
Since the speed is as high as 0 μs, the tire pressure can be detected at high speed. As a result, if there is a control device that detects the puncture during traveling and controls the attitude of the vehicle, it is possible to improve the performance by using the control device.

Further, since the giant magnetostrictive material 10 exhibits sufficient sensing performance even with a diameter as small as 1 mm and a length of about 20 mm, the pressure sensor unit 5 can be downsized. In addition, the operation as a sensor for changing the magnetic flux density generated in accordance with the change in the compression load does not require any driving power supply. In addition, because it does not use any electronic components such as IC, it is strong against vibration,
High reliability is obtained. In the above embodiment, the air pressure such as the tire pressure is detected. However, the present invention is not limited to the detection of the tire pressure, and the detection of the air pressure in another moving body is also possible. In addition, the present invention can be applied not only to air pressure but also to detection of hydraulic pressure.

In the above-described embodiment, the alarm buzzer sounds when the tire pressure falls below a predetermined level. However, in addition to the alarm sound, the detection state is displayed in an alarm by using an LED or the like in a stepwise manner. Alternatively, a voice message may be output by providing voice synthesis means.

[0020]

According to the pressure sensor unit of the present invention,
The pressure sensor unit includes a giant magnetostrictive material that generates a magnetic field due to a change in pressure in the body to be measured, a first coil that generates an induced current due to a change in the magnetic field of the giant magnetostrictive material, and a first coil that generates a magnetic field by an induced current generated in the first coil. Since it is configured to include a sensor unit having two coils, and a receiving unit that is spaced apart from and opposed to the second coil of the sensor unit and detects a magnetic field generated in the second coil, the pressure inside the body to be measured can be reduced. Contact detection can be performed, and a driving power supply can be omitted for the sensor unit. In addition, since no electronic components such as ICs are used, it is resistant to vibration and high reliability is obtained. In particular, the giant magnetostrictive material constituting the pressure sensor unit is:
Since the response speed to the load change is as high as 50 to 100 μs, the tire pressure can be detected at high speed. Also,
The giant magnetostrictive material exhibits sufficient sensing performance even with a very small material having a diameter of 1 mm and a length of about 20 mm, so that the pressure sensor unit can be reduced in size.

Further, according to the tire pressure detecting device of the present invention, since the tire pressure detecting device is provided with the sensor portion and the receiving portion of the present invention, the tire pressure can be detected in a non-contact manner and a power source for driving the sensor portion is required. And a tire pressure detecting device that does not perform the same. When a plurality of receivers for detecting a magnetic field generated in the second coil are arranged apart from each other in the tire circumferential direction, the output can be detected at any position where the sensor unit rotates. Can be monitored. Further, when a Hall element or a magnetoresistive element is applied to the receiving unit, the receiving unit can be formed with high precision and compactness.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a vehicle equipped with a tire pressure detecting device according to the present invention.

FIG. 2 is a configuration diagram of the tire pressure detection device of FIG.

FIG. 3 is a longitudinal sectional view showing a configuration of a pressure sensor unit of the tire pressure detecting device of FIG.

FIG. 4 is a longitudinal sectional view illustrating a configuration of a sensor unit of the pressure sensor unit of FIG. 2;

FIG. 5 is a flowchart showing the operation of the control unit of FIG. 1;

[Description of Signs] 1 sensor unit 2 receiving unit 3 control unit 4 alarm buzzer 5 pressure sensor unit 6 tire pressure detecting device 10 giant magnetostrictive material 11 push rod 12 coil (first coil) 13 yoke 14 transmission coil (second coil) ) 15 Preload spring 100 Tire 101 Inside of tire 141 Iron core (conductor)

Claims (4)

[Claims] 1. A pressure sensor comprising: a sensor unit for detecting and transmitting pressure in a body to be measured; and a receiving unit provided in a non-contact state separated from the sensor unit and receiving a detection signal detected by the sensor unit. In the sensor unit, the sensor unit has a characteristic that a magnetic field is generated by an external compressive force, and a compressive force proportional to a pressure in the body to be measured acts via a push rod, and a giant magnetostrictive material; A first coil arranged around the giant magnetostrictive material to generate an induced current according to a magnetic field change generated by the giant magnetostrictive material; and a housing for holding and holding the giant magnetostrictive material and the first coil, and covering and closing these. A yoke that forms a magnetic circuit, and a second coil that is electrically connected to the first coil and that includes a conductor therein and generates a magnetic field by an induced current of the first coil; The second coil detects the magnetic field generated by the second coil and outputs a detection signal to a control unit. The sensor unit and the receiving unit detect the magnetic field generated by the second coil. A pressure sensor unit for measuring and outputting as a magnetic field change amount. 2. A sensor comprising the sensor unit according to claim 1 and a receiving unit, wherein the sensor unit is provided in a tire of a vehicle.
A control unit, wherein the receiving unit is fixedly mounted on a vehicle body part separated from the tire, the sensor unit detects a tire pressure, and the receiving unit detects a detection signal of a magnetic field change according to the tire pressure. Integrates the detection signal, compares the integrated detection signal with a preset threshold value, and outputs a warning signal when the threshold value is exceeded. 3. The tire pressure detecting device according to claim 2, wherein a plurality of the receiving units are arranged apart from each other in a tire circumferential direction. 4. The tire pressure detecting device according to claim 2, wherein a Hall element or a magneto-resistive element is applied to the receiving unit.