CN102922961A - Capacitive miniature tire pressure sensor - Google Patents

Abstract

The invention discloses a capacitive miniature tire pressure sensor, which comprises an upper plate, a support plate and a lower bottom plate. The upper plate is provided with a multi-layer composite film sensitive to pressure, and the multi-layer composite film is provided with a capacitive upper pole plate; The upper surface of the board is provided with a capacitor lower plate, a detection capacitor formed by the capacitor upper plate and the capacitor lower plate; the lower bottom plate is provided with a coupled surface acoustic wave device and a micro antenna, and the surface acoustic wave device includes piezoelectric materials and Two sets of interdigitated electrodes, one set of interdigitated electrodes are connected with the micro-antenna, and the other set of interdigitated electrodes are respectively connected with the upper plate of the capacitor and the lower plate of the capacitor. The invention can be implanted into the inner working of the tire to realize the tire pressure measurement and result transmission in a passive wireless manner, and has the advantages of small size, light weight, low cost and maintenance-free.

Description

A capacitive miniature tire pressure sensor

technical field

The invention belongs to the technical field of tire pressure sensors and relates to a capacitive miniature tire pressure sensor.

Background technique

The tire pressure monitoring system monitors changes in tire pressure and prevents tire blowout accidents through early warning, so as to protect the stability of the vehicle and the safety of the drivers and passengers. The tire pressure monitoring sensor is the core component of the whole system, and its working performance directly determines the accuracy and reliability of the monitoring system. According to the configuration, the tire pressure sensor can be divided into two types: active type and passive type. Active sensors need to be powered by batteries to meet the energy needs of the sensor; passive sensors rely on external energy coupling to work.

At present, the tire pressure sensors commercially available in the market are all active types, that is, the pressure sensor, power supply, microprocessor, and wireless communication module are integrated and packaged, and installed in the rim or on the tire valve. Due to its additional external installation, it is easy to cause damage to the air nozzle or the launch module during tire maintenance and replacement, making the tire pressure monitoring system invalid. Secondly, the built-in power module is used for tire pressure measurement, signal modulation, wireless communication, etc., so the working life of the battery must meet certain standards and requirements. Due to the shielding effect of the rim and the system standby, the battery power is quickly consumed, resulting in huge waste. The environmental pollution caused by manufacturing and replacing batteries is also a factor that cannot be ignored. The active tire pressure sensor needs a built-in battery to provide energy, and its volume and weight are relatively large. It is inconvenient to install, has a limited lifespan, and has a single function. Replacing the battery will lead to high maintenance costs and environmental pollution problems. It is no longer possible. Meet the new technology standards and requirements of energy saving and environmental protection,

The advantage of passive sensors is that there is no need for a built-in power module, and it has the advantages of small size, low cost, and long life. It finally realizes implantable installation and maintenance-free use. It is the development direction of the next-generation tire pressure monitoring system. Passive wireless work This method overcomes the limitation of the service life of the built-in battery, reduces the manufacturing and maintenance costs of the system, and reduces the environmental pollution caused by battery replacement. Due to the small size and maintenance-free, implanted tire installation can be realized, and the "on-rim" installation can be transformed into an "in-tire" mode, which solves the problem of installing the tire pressure sensor on the rim (air nozzle) and reduces tire pressure. The problem that the sensing system caused by maintenance is easily damaged. At the same time, it can also improve the interchangeability of tires, avoiding the problem that the tire pressure sensing system needs to be reset after tire replacement or replacement. The implantable installation method is not only convenient for installation and maintenance, but also the main research goal and development direction of intelligent tires.

Contents of the invention

The problem to be solved by the present invention is to provide a capacitive miniature tire pressure sensor, which can be implanted into the tire to work, realize the tire pressure measurement and result transmission in a passive wireless manner, and has the advantages of small size, light weight, low cost, and maintenance-free The advantages.

The present invention is realized through the following technical solutions:

A capacitive miniature tire pressure sensor comprises an upper plate, a support plate and a lower base plate, the upper plate is provided with a pressure-sensitive multilayer composite film, and the multilayer composite film is provided with a capacitive upper pole plate; the upper surface of the support plate There is a capacitor lower plate, a detection capacitor formed by a capacitor upper plate and a capacitor lower plate; a surface acoustic wave device and a micro-antenna are connected on the lower plate, and the surface acoustic wave device includes a piezoelectric material and two sets of fingers Electrodes, one group of interdigitated electrodes are connected with the miniature antenna, which is the communication terminal; the other group of interdigitated electrodes are respectively connected with the upper plate of the capacitor and the lower plate of the capacitor, which is the measurement terminal.

The external pressure effect causes the deformation of the multi-layer composite film, and this deformation causes the capacitive load of the detection capacitor and the output signal change of the detection circuit; the detection capacitor is used as the load of the measurement terminal circuit, and its numerical change directly causes the output of the measurement terminal circuit to include pressure changes The information; the information is transformed into a wireless signal by a surface acoustic wave device, and sent out by a micro antenna for reception and processing by the receiver.

When the miniature antenna receives an external working pulse signal, the surface acoustic wave device obtains working energy from the high-frequency signal in the antenna coupling, and the communication terminal starts to generate an oscillating sound wave field on the surface acoustic wave device, and the sound wave field propagates to the measurement terminal. , re-changed into an oscillating signal of the measurement circuit for pressure measurement;

The external pressure change causes the detection capacitance to change, and finally causes the characteristics of the oscillation signal to change, and the measurement process is completed; the measurement signal containing the external pressure information enters the surface acoustic wave device from the measurement end again, and is transformed into a wireless signal at the communication end. The tiny antenna is sent back to the receiver for receiving and processing.

The capacitive miniature tire pressure sensor relies on the wireless electromagnetic energy coupling between the micro-antenna and the antenna at the receiver end, and converts the electrical energy coupling from the antenna at the receiver end into the mechanical vibration energy of the surface acoustic wave, and obtains the energy required for work.

The multi-layer composite film protrudes outward in a cup shape, and a pit is left between the upper plate and the support plate for the lower plate of the capacitor;

The lower surface of the support plate is also provided with pits, leaving packaging holes for the surface acoustic wave device and the micro-antenna; the support plate is also provided with through holes for connecting the upper plate of the capacitor and the lower plate of the capacitor to the surface acoustic wave device .

The multi-layer composite film includes: Si ₃ N ₄ layer, polysilicon layer, first insulating layer, wire layer, second insulating layer from outside to inside, and the capacitor upper plate is arranged between the wire layer and the second insulating layer between;

The convex shape of the multilayer composite film is rectangular, circular or polygonal.

The first insulating layer and the second insulating layer are Parylene insulating layers, which are used for molding and electrode insulation of multilayer composite films. The Si ₃ N ₄ layer and the polysilicon layer realize bonding packaging and external protection, and the wire layer is made of aluminum. Material.

A Si substrate and a Si ₃ N ₄ layer are sequentially arranged on the support layer, and the lower electrode plate of the capacitor is arranged on the Si ₃ N ₄ layer.

The piezoelectric material of the surface acoustic wave device is also provided with a surface acoustic wave reflection grid.

The surface acoustic wave device is also provided with an identification encoder, which identifies the identity of the capacitive miniature tire pressure sensor to avoid information transmission errors.

The piezoelectric material is made of ZnO, SiO ₂ or LiNbO ₃ piezoelectric material.

Compared with the prior art, the present invention has the following beneficial technical effects:

The capacitive miniature tire pressure sensor provided by the invention can be implanted inside the tire to work, and realize the tire pressure measurement and result transmission in a passive wireless manner. The multilayer composite film is sensitive to pressure, and the detection capacitor fabricated between the multilayer film and the support plate is used to realize pressure measurement. A wireless communication antenna and a surface acoustic wave device are integrated on the bottom floor, and the two together complete energy coupling and information transmission.

After the external signal is coupled into the antenna, an oscillation effect is generated in the surface acoustic device to obtain the working energy required by the sensor. The detection capacitor acts as a load of the oscillating circuit, and the capacitance change caused by the external pressure causes the capacitive load and output of the oscillating circuit to change. Finally, the tire pressure information contained in the output of the oscillating circuit is sent back as a wireless signal through the transducer and antenna again for the receiver to receive and process; it has the advantages of small size, light weight, low cost, maintenance-free, pollution-free, and energy-saving Environmental protection and other advantages.

Further, the convex multi-layer composite film provided on the upper layer can have a convex structure in various shapes such as rectangle, circle, polygon, etc., and its main materials are Si ₃ N ₄ , Parylene, aluminum, polysilicon, and piezoelectric Material. Among them, Parylene is the main material, which is used for the forming of thin film structure and electrode insulation. Si ₃ N ₄ and polysilicon are used for bonding packaging and external protection respectively, and Al is used as electrode material. The production of multilayer composite film requires the process of different materials Separate control, through multiple deposition, annealing, etching and other processes to complete the film processing. Due to the large difference in rigidity of the structural materials of each part of the multilayer composite film, the external pressure will cause the deformation of the film, and the deformation of the cup-shaped film will directly cause the change of the detection capacitance to reflect the fluctuation of the external pressure and serve as the capacitance of the surface acoustic wave oscillating circuit. sex load.

In the capacitive miniature tire pressure sensor provided by the present invention, the surface acoustic wave device on the lower base plate is not affected by external pressure, and an identification encoder can be installed and manufactured. Through the surface acoustic wave encoder, the unique identification of the wireless sensor can be realized, and the pressure measurement and device identification can be completed at the same time, which is convenient for multi-sensor cooperation and information fusion. Moreover, this function is of great significance for improving the interchangeability of sensors, and can also improve the reliability and maintainability of the system.

The capacitive miniature tire pressure sensor involved in the invention works in a passive and wireless manner, and overcomes various defects of the active sensor. Eliminate battery power supply, reduce costs and reduce environmental pollution, and at the same time avoid sensor failure due to insufficient power supply. Using the capacitive sensitive method, the surface acoustic wave device is only used for wireless coupling and communication, so its performance is not affected by external pressure conditions, and it can obtain good working performance. The small size and light weight brought about by the micro-fabrication process, as well as maintenance-free use, can be completely implanted into the inner working of the tire to realize intelligent tire pressure monitoring.

Description of drawings

Fig. 1 is the external structure diagram of capacitive miniature tire pressure sensor;

Fig. 2 is an internal sectional view of a capacitive miniature tire pressure sensor;

Figure 3 is a schematic diagram of the connection of the bottom plate circuit of the capacitive miniature tire pressure sensor; wherein, Z is the complex impedance including the CLR;

Fig. 4 is a schematic diagram of an equivalent circuit of a capacitive miniature tire pressure sensor.

Among them: 1 multi-layer composite film; 2 upper plate; 3 support plate; 4 surface acoustic wave device; 5 micro-antenna; 6 bottom plate; 11Si3N4 layer; 12 polysilicon layer; 16 second insulating layer; 31 capacitor lower plate; 32 Si ₃ N ₄ layers; 33 Si substrate; 41 interdigitated electrodes; 42 piezoelectric material; 43 surface acoustic wave reflection grid.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

Referring to Figures 1 to 4, the present invention is a capacitive miniature tire pressure monitoring sensor, which can be implanted into the tire to work. Sensitive to external pressure. Capacitive electrodes are fabricated on the multi-layer film and the support plate for pressure measurement. A wireless communication antenna and a surface acoustic wave device are integrated on the bottom floor, and the two together complete energy coupling and information transmission. After the external signal is coupled into the antenna, an oscillation effect is generated in the surface acoustic device to obtain the working energy required by the sensor. The capacitance between the cup-shaped film and the support plate acts as a load of the oscillating circuit, and the capacitance change caused by the external pressure causes the capacitive load and output of the oscillating circuit to change.

Specifically, the capacitive miniature tire pressure monitoring sensor includes an upper plate, a support plate and a lower base plate, the upper plate is provided with a pressure-sensitive multilayer composite film, and the multilayer composite film is provided with a capacitive upper plate; the support plate The upper surface is provided with the lower plate of the capacitor, the detection capacitance formed by the upper plate of the capacitor and the lower plate of the capacitor; the coupled surface acoustic wave device and the micro-antenna are arranged on the lower plate, and the surface acoustic wave device includes piezoelectric materials and two sets of The interdigitated electrodes, one group of interdigitated electrodes are connected with the miniature antenna, which is the communication terminal; the other group of interdigitated electrodes are respectively connected with the capacitor upper plate and the capacitor lower plate, which is the measurement terminal.

The external pressure causes the deformation of the multi-layer composite film, and this deformation causes the capacitive load of the detection capacitor and the output signal change of the measurement terminal circuit; the detection capacitance acts as the load of the measurement terminal circuit, and its value change directly causes the output of the measurement terminal circuit to include pressure changes. Information; the information is converted into a wireless signal by a surface acoustic wave device, and sent out by a micro-antenna for reception and processing by the receiver.

When the miniature antenna receives an external working pulse signal, the surface acoustic wave device obtains working energy from the high-frequency signal in the antenna coupling, and the communication terminal starts to generate an oscillating sound wave field on the surface acoustic wave device, and the sound wave field propagates to the measurement terminal. , re-changed into an oscillating signal of the measurement circuit for pressure measurement;

The external pressure change causes the detection capacitance to change, and finally causes the characteristics of the oscillation signal to change, and the measurement process is completed; the measurement signal containing the external pressure information enters the surface acoustic wave device from the measurement end again, and is transformed into a wireless signal at the communication end. The tiny antenna is sent back to the receiver for receiving and processing.

The capacitive miniature tire pressure sensor relies on the wireless electromagnetic energy coupling between the miniature antenna and the antenna at the receiver end, and converts the electrical energy coupling from the antenna (measurement system) at the receiver end into the mechanical vibration energy of the surface acoustic wave, and obtains the energy required for work . First, the measurement pulse signal sent by the measurement antenna forms a coupling signal in the micro-antenna of the sensor. The coupling signal passes through the transducer at the communication end, and converts most of the energy into the mechanical vibration energy of the surface acoustic wave, ensuring the working energy of the sensor. The vibration energy of the surface acoustic wave will be converted into an oscillating signal at the measurement end and the pressure change information will be obtained by detecting the capacitance. Then, the result signal at the measurement end will be converted into a surface acoustic wave signal through the surface acoustic wave device and sent back to the communication end through the antenna. Output the result information.

Refer to Figure 1 to Figure 4 for details, in the capacitive miniature tire pressure monitoring sensor:

The multi-layer composite film 1 protrudes outward in a cup shape, and a pit is left between the upper plate 2 and the support plate 3 for the lower plate 15 of the capacitor;

The multi-layer composite film 1 comprises from outside to inside: Si ₃ N ₄ layer 11, polysilicon layer 12, first insulating layer 13, wire layer 14, second insulating layer 16, capacitor upper pole plate 15 is arranged on wire layer 14 and Between the second insulating layer 16 .

The first insulating layer 13 and the second insulating layer 16 are Parylene insulating layers, which are used for the molding and electrode insulation of the multilayer composite film 1. The Si ₃ N ₄ layer 11 and the polysilicon layer 12 realize bonding packaging and external protection, and the wire layer 14 Aluminum is used as material. The production of the multilayer composite film 1 needs to control the processes of different materials separately, and the film processing is completed through multiple deposition, annealing, etching and other processes.

A Si substrate 33 and a Si ₃ N ₄ layer 32 are sequentially disposed on the supporting layer 3 , and the capacitor lower plate 31 is disposed on the Si ₃ N ₄ layer 32 . The lower surface of the support plate 3 is also provided with pits, leaving packaging holes for the surface acoustic wave device 4 and the micro-antenna 5; The vias through which the device 5 is connected.

A surface acoustic wave device 4 and a miniature antenna 5 for wireless communication are arranged on the lower base plate 6 .

The surface acoustic wave device 4 is composed of a piezoelectric material 42 and interdigital electrodes 41, wherein a group of interdigital electrodes is connected to the micro-antenna 5 for energy coupling and communication, and is a communication terminal; another group of interdigital electrodes is connected to the upper pole of the capacitor The plate 15 is connected with the lower plate 31 of the capacitor, which is the measuring terminal; the formed capacitor is used as the load of the oscillating circuit. When the antenna is coupled, an oscillating sound field is generated on the surface acoustic wave device, and the sound field changes to a high-frequency electric field oscillation on the other side, and the change of the capacitive load directly affects the characteristics of the high-frequency electric field oscillation. Finally, the high-frequency electric field is re-routed through the SAW device and antenna, and sent back to the receiver for processing. Furthermore, the mutual cooperation of multiple sets of acoustic surface devices can obtain compensation for factors such as temperature and vibration, and improve the measurement accuracy of the sensor.

Since the surface acoustic wave device 4 on the lower base plate 6 is not affected by external pressure, an identification encoder can be integrated. Through the surface acoustic wave encoder, pressure measurement and device identification can be completed at the same time, and the unique identification of wireless sensors can be realized, which is convenient for multi-sensor collaborative work and information fusion. And this function is of great significance for improving the interchangeability of sensors. The small size and light weight brought about by the micro-fabrication process, as well as maintenance-free use, can be completely implanted into the inner working of the tire to realize intelligent tire pressure monitoring. At the same time, the reliability and maintainability of the system can also be improved.

The capacitive miniature tire pressure sensor involved in the invention works in a passive and wireless manner, and overcomes various defects of the active sensor. Eliminate battery power supply, reduce costs and reduce environmental pollution, and at the same time avoid sensor failure due to insufficient power supply. Using the capacitive sensitive method, the surface acoustic wave device is only used for wireless coupling and communication, so its performance is not affected by external pressure conditions, and it can obtain good working performance.

Claims (10)

1. A capacitive miniature tire pressure sensor is characterized in that it comprises an upper plate, a support plate and a lower base plate, the upper plate is provided with a pressure-sensitive multilayer composite film, and the multilayer composite film is provided with a capacitive upper pole plate The upper surface of the support plate is provided with a capacitor lower plate, a detection capacitance formed by the capacitor upper plate and the capacitor lower plate; the lower base plate is provided with a connected surface acoustic wave device and a miniature antenna, and the surface acoustic wave device includes a piezoelectric Materials and two sets of interdigitated electrodes, one set of interdigitated electrodes is connected with the miniature antenna, which is the communication terminal; the other set of interdigitated electrodes is respectively connected with the capacitor upper plate and the capacitor lower plate, which is the measurement terminal. 2. Capacitive miniature tire pressure sensor as claimed in claim 1, is characterized in that, the external pressure effect causes multi-layer composite film deformation, and this deformation causes the capacitive load of detection capacitance and the output signal change of measuring end circuit; Detection capacitance As the load of the measuring end circuit, its value change directly causes the measuring end circuit to output information including pressure changes; the information is transformed into a wireless signal by the surface acoustic wave device, and sent out through the micro antenna for reception and processing by the receiver. 3. The capacitive miniature tire pressure sensor as claimed in claim 2, characterized in that, when the miniature antenna receives an external working pulse signal, the surface acoustic wave device obtains working energy from the high-frequency signal in the antenna coupling, and is controlled by the communication The end starts to generate an oscillating sound wave field on the surface acoustic wave device, and after the sound wave field propagates to the measurement end, it changes into an oscillation signal of the measurement circuit again for pressure measurement; The external pressure change causes the detection capacitance to change, and finally causes the characteristics of the oscillation signal to change, and the measurement process is completed; the measurement signal containing the external pressure information enters the surface acoustic wave device from the measurement end again, and is transformed into a wireless signal at the communication end. The tiny antenna is sent back to the receiver for receiving and processing. 4. The capacitive miniature tire pressure sensor according to claim 3, characterized in that the capacitive miniature tire pressure sensor relies on the wireless electromagnetic energy coupling between the miniature antenna and the antenna at the receiver end to couple and convert the electric energy sent by the antenna at the receiver end It is the mechanical vibration energy of the surface acoustic wave and obtains the energy required for work. 5. The capacitive miniature tire pressure sensor according to claim 1, characterized in that, the multi-layer composite film protrudes outward in a cup shape, and there is a space between the upper plate and the supporting plate for the lower plate of the capacitor. pitted; The lower surface of the support plate is also provided with pits, leaving packaging holes for the surface acoustic wave device and the micro-antenna; the support plate is also provided with through holes for connecting the upper plate of the capacitor and the lower plate of the capacitor to the surface acoustic wave device . 6. The capacitive miniature tire pressure sensor according to claim 1, characterized in that, said multi-layer composite film sequentially comprises: Si ₃ N ₄ layers, a polysilicon layer, a first insulating layer, and a wire layer from outside to inside , the second insulating layer, the upper plate of the capacitor is arranged between the wire layer and the second insulating layer; The convex shape of the multilayer composite film is rectangular, circular or polygonal. 7. The capacitive miniature tire pressure sensor according to claim 6, characterized in that, the first insulating layer and the second insulating layer are Parylene insulating layers, which are used for molding and electrode insulation of multilayer composite films, and Si ₃ N ₄ layers and polysilicon layer realize bonding packaging and external protection, and the wire layer is made of aluminum. 8. The capacitive miniature tire pressure sensor according to claim 1, wherein the support layer is provided with a Si substrate and a Si ₃ N ₄ layer in sequence, and the capacitor lower plate is arranged on the Si ₃ N ₄ layer ; The piezoelectric material is made of ZnO, SiO ₂ or LiNbO ₃ piezoelectric material. 9. The capacitive miniature tire pressure sensor according to claim 1, characterized in that, the piezoelectric material of the surface acoustic wave device is further provided with a surface acoustic wave reflection grid. 10. The capacitive miniature tire pressure sensor as claimed in claim 1, characterized in that, said surface acoustic wave device is also provided with an identification encoder, which identifies the identity of the capacitive miniature tire pressure sensor to avoid Information transmission error.

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