Abstract:
A tire pressure monitoring system (TPMS) is provided. The TPMS includes: a plurality of sensors which output sensing signals, the plurality of sensors including a printable pressure sensor which senses an air pressure of a tire, and a temperature sensor which senses an air temperature inside the tire; a signal processor which is configured to process the sensing signals output by the plurality of sensors; a wireless power receiver which is configured to receive energy from a power source and output power; and a rechargeable battery which is configured to be charged by the power output by the wireless receiver and supply power to the plurality of sensors to sense the air pressure of the tire and the air temperature inside the tire.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2012-0119807, filed on Oct. 26, 2012, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     Embodiments consistent with the present disclosure relate to a tire pressure monitoring system. 
     2. Description of the Related Art 
     Abnormalities in tire pressure may cause a significant vehicle accident, such as a burst of a tire due to abnormal wear or heat generation on both sides of a tire tread, a decrease in handling stability, deterioration of gas mileage, or an occurrence of hydroplaning at a low driving speed. Therefore, monitoring a tire pressure is important in order to secure stability of a vehicle. 
     A tire pressure monitoring system (TPMS) is a device that informs a driver or another device of a vehicle of air pressures of tires, i.e., tire pressure. The TPMS helps to prevent insufficient tire pressure, or tire damage, from causing an accident and inefficient gas mileage. 
     SUMMARY 
     Embodiments provide a tire pressure monitoring system that is inexpensive, simple to install, and easy to maintain. 
     Additional aspects of the exemplary embodiments will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to an aspect of an embodiment, there is provided a tire pressure monitoring system including: a plurality of sensors which output sensing signals, the plurality of sensors including a printable pressure sensor which senses an air pressure of a tire, and a temperature sensor which senses an air temperature inside the tire; a signal processor which is configured to process the sensing signals output by the plurality of sensors; a wireless power receiver which is configured to receive energy from a power source and output power; and a rechargeable battery which is configured to be charged by the power output by the wireless power receiver and supply power to the plurality of sensors power to sense the air pressure of the tire and the air temperature inside the tire. 
     The printable pressure sensor may be configured to sense the air pressure of the tire by measuring a resistance or capacitance, according to a transformation of a space between two films due to a pressure of a tire dorsal part. 
     The space between the two films may be in a vacuum state, or is filled with a gaseous, liquid, or solid material. 
     The temperature sensor may include a structure in which a heat sensing part is stacked, trenched, or embedded with respect to a flexible substrate. 
     The heat sensing part may be configured to measure the temperature by coating heat sensing resistive particles in order to utilize a phenomenon in which a resistance increases according to the temperature. 
     The heat sensing resistive particles may include silver nanoparticles. 
     The heat sensing part may be configured to measure the temperature using a material having pyroelectricity in order to measure a voltage generated according to the temperature. 
     The material having pyroelectricity may include a Polyvinylidene Fluoride (PVDF). 
     The signal processor may include a circuit formed by printed electronics technology on a substrate formed of a polymer material, a flexible substrate, or a substrate of a complex structure of a solid substrate part and a flexible substrate part. 
     The wireless power receiver may include a resonance coil formed on a flexible substrate by a printed electronics method, coating, or electrolytic plating. 
     The flexible substrate may wind around a tire rim, and a pattern of the resonance coil is formed on the flexible substrate and connects both ends of a coil pattern of the resonance coil to each other to conduct electricity. 
     The both ends of the coil pattern may be connected to each other to conduct electricity by using a soldering, buttoning, or plugging method. 
     An antenna structure may be provided on one side of the flexible substrate by the printed electronics method, the antenna structure is configured to transmit the processed signals output by the signal processor. 
     At least one selected from a group consisting of the plurality of sensors, the signal processor, and the rechargeable battery may be provided on the flexible substrate by a printed electronics method. 
     At least one selected from a group consisting of the plurality of sensors, the signal processor, and the rechargeable battery may be provided on the flexible substrate in a chip on board (COB) form. 
     At least one selected from a group consisting of the plurality of sensors, the signal processor, and the rechargeable battery may be assembled on the flexible substrate. 
     The rechargeable battery may repeatedly rechargeable. 
     The rechargeable battery may be formed by a printed electronics method. 
     The rechargeable battery may be formed in a lithium-polymer or lithium-ion thin film structure. 
     According to an aspect of another embodiment, there is provided a tire pressure monitoring system mounted on a tire rim, the tire pressure monitor system including: a flexible substrate which is mounted on the tire rim; and the tire pressure including a sensor device which outputs sensing signals, the sensor device senses an air pressure of a tire and an air temperature of the tire; a signal processor which is configured to process signals output by the sensor device; a wireless power receive which is configured to receive energy from a power source and output power; and a rechargeable battery which is configured to be recharged by the power output by the wireless power receive and supply power to the plurality of sensor to sense the air pressure of the tire and the air temperature inside the tire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a block diagram of major configurations of a tire pressure monitoring system (TPMS), according to an embodiment; 
         FIG. 2A  is a top view of a printable pressure sensor applicable to a TPMS according to an embodiment; 
         FIG. 2B  is a side cross-sectional view of the printable pressure sensor of  FIG. 2A ; 
         FIG. 3A  is a top view of a printable pressure sensor applicable to a TPMS according to another embodiment; 
         FIG. 3B  is a side cross-sectional view of the printable pressure sensor of  FIG. 3A , wherein upper and lower electrodes are formed on outer surfaces of two films; 
         FIG. 3C  is a side cross-sectional view of the printable pressure sensor of  FIG. 3A , wherein upper and lower electrodes are formed on inner surfaces of two films; 
         FIG. 4  is a front view of a temperature sensor applicable to a TPMS according to an embodiment; 
         FIG. 5A  is a top view of an example in which a circuit of a signal processor is arranged on a substrate when the substrate is formed of polymer materials to which printed electronics technology is applicable or is a flexible substrate; 
         FIG. 5B  illustrates an example in which a circuit of a signal processor is arranged on a substrate when the substrate has a complex structure of a solid substrate part and a flexible substrate part; 
         FIGS. 6 and 7  illustrate examples in which a resonance coil applicable as a wireless power receiver to a TPMS according to embodiments is implemented on a flexible substrate; 
         FIG. 8  is a schematic diagram of wireless power transmission; 
         FIG. 9  illustrates an example in which a printable and rechargeable flexible battery is formed together with other components. 
         FIG. 10  illustrates an example of a roll-to-roll method; and 
         FIG. 11  is a perspective view of a tire rim on which a TPMS according to an embodiment is mounted. 
     
    
    
     DETAILED DESCRIPTION 
     A tire pressure monitoring system (TPMS) according to embodiments will now be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings, and sizes and thicknesses of components in the drawings may be exaggerated for clarity and convenience of description. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  is a block diagram of major configurations of a TPMS  100 , according to an embodiment. 
     Referring to  FIG. 1 , the TPMS  100  includes a sensor unit  200 , a signal processor  300 , a wireless power receiver  400 , a wireless data transceiver  600 , and a rechargeable battery  500 . 
     The sensor unit  200  includes a plurality of sensors. For example, the sensor unit  200  may include a printable pressure sensor  210  for sensing an air pressure of a tire, and a temperature sensor  230  for sensing an air temperature inside the tire. The sensor unit  200  may further include various sensors, such as an acceleration sensor for sensing acceleration. 
     The printable pressure sensor  210  measures an air pressure inside the tire, and may sense the air pressure by measuring a resistance or capacitance according to a transformation of a space  212  between two films  211  and  213 , as shown in  FIGS. 2A to 3C . 
       FIG. 2A  is a top view of the printable pressure sensor  210  applicable to the TPMS  100 .  FIG. 2B  is a side cross-sectional view of the printable pressure sensor  210  of  FIG. 2A . 
     Referring to  FIGS. 2A and 2B , the printable pressure sensor  210  may have a structure in which a resistance varies according to a transformation. Therefore, the printable pressure sensor  210  may detect the transformation of the space  212  between the two films  211  and  213  by an air pressure of a tire. In other words, the space  212  may be formed between the two films  211  and  213  by forming a structure in which a partial area of one film  213  is expanded against the other film  211 . The film  213 , having the expanded structure of the two films  211  and  213 , may be formed of a flexible material to cause a transformation in the space  212  in response to the air pressure of the tire. Accordingly, a resistance, of a resistance change material pattern  216  formed on the film  213 , may vary. In this case, the space  212  may be in a vacuum state, or be filled with a gaseous, liquid, or solid material. When a resistance value varies according to a transformation in the space  212  of the printable pressure sensor  210  due to the air pressure of the tire, a transformation amount may be detected, and an air pressure may be determined from the detected transformation amount. 
     It may be determined whether the space  212  is in a vacuum state or is filled with a gaseous, liquid, or solid material according to a pressure inside the tire, and the thicknesses of the films  211  and  213 . 
       FIG. 3A  is a top view of the printable pressure sensor  210  applicable to the TPMS  100  according to an embodiment.  FIGS. 3B and 3C  are side cross-sectional views of the printable pressure sensor  210  of  FIG. 3A .  FIG. 3B  shows a case where upper and lower electrodes  216  and  217  are formed on the outer surfaces of the two films  211  and  213 , and  FIG. 3C  shows a case where upper and lower electrodes  216  and  217  are formed on inner surfaces of the two films  211  and  213 . Referring to  FIGS. 3A to 3C , compared with the printable pressure sensor  210  of  FIGS. 2A and 2B , the printable pressure sensor  210  of  FIGS. 3A to 3C  may be provided to sense an air pressure by measuring a capacitance, instead of the resistance change, according to the transformation of the space  212  between the two films  211  and  213  due to the air pressure of the tire. 
     In other words, the printable pressure sensor  210  may sense a transformation amount by forming the upper and lower electrodes  216  and  217  on the outer surfaces or inner surfaces of the two films  211  and  213 , or forming one of the upper and lower electrodes  216  and  217  on the outer surface of one of the two films  211  and  213  and the other one of the upper and lower electrodes  216  and  217  on the inner surface of the other one of the two films  211  and  213  to measure a variation of capacitance according to the transformation of the space  212 , instead of the resistance change material pattern  216 . An air pressure may be measured from the transformation amount. In this case, the measurement of the capacitance may be readout as a change in a voltage, detection of a current, or a predetermined change in a frequency. 
     Although  FIGS. 2A to 3C  show one sensor region of the printable pressure sensor  210 , the printable pressure sensor  210  may also include a two-dimensional array of such sensor regions. 
     Referring to  FIG. 4 , in the TPMS  100 , the temperature sensor  230  measures an air temperature inside the tire. The temperature sensor  230  may be formed, for example, with a structure in which a heat sensing part  230   a  is stacked, trenched, or embedded with respect to a flexible substrate  250 .  FIG. 4  is a front view of the temperature sensor  230  applicable to the TPMS  100  according to an embodiment.  FIG. 4  illustrates an exemplary structure in which the heat sensing part  230   a  is stacked on the flexible substrate  250 . A protection layer or a conductive layer, having a good heat conductivity, may be further included on the heat sensing part  230   a.    
     The heat sensing part  230   a  may measure a temperature by coating heat sensing resistive particles on the flexible substrate  250 . The heat sensing part  230   a  may measure the temperature in order to use a phenomenon in which a resistance increases according to a temperature. The heat sensing resistive particles may include, e.g., silver nanoparticles. 
     As another example, the heat sensing part  230   a  may measure a temperature using a material having pyroelectricity. In this case, the heat sensing part  230   a  may measure a voltage generated according to a temperature. The material having pyroelectricity may include a PVDF Polyvinylidene-fluoride). 
     Referring to  FIGS. 5A and 5B , in the TPMS  100 , the signal processor  300  includes a circuit  350  for processing signals detected by the plurality of sensors including the printable pressure sensor  210  and the temperature sensor  230 . The circuit  350  may be formed on substrates  310  and  330  by printed electronics technology.  FIGS. 5A and 5B  show cases where the circuit  350  of the signal processor  300  is formed on the substrates  310  and  330 .  FIG. 5A  shows an example in which the circuit  350  is arranged on the substrate  310 , when the substrate  310  is formed of polymer materials to which the printed electronics technology is applicable or is a flexible substrate.  FIG. 5B  shows an example in which the circuit  350  is arranged on the substrate  330 , when the substrate  330  has a complex structure of a solid substrate part  335  and a flexible substrate part  331 . In  FIGS. 5A and 5B , the substrates  310  and  330  may be a printed circuit board (PCB) formed of all types of polymer materials, formed of a flexible material, or having a complex structure of a solid substrate part and a flexible substrate part. 
     The TPMS  100  may include the wireless power receiver  400  for wirelessly transmitting power to supply sufficient power in order to continuously observe an air pressure and a temperature. The TPMS  100  may also include the wireless data transceiver  600  for transmitting measured data, processed data, etc. 
     The TPMS  100  may have a structure implemented by print technology. As shown in  FIGS. 6 and 7 , the TPMS  100  may implement print technology by integrating a structure of a resonance coil  450  and a structure of a wireless communication antenna  650 , for transmitting the measured data and processed data on a flexible substrate  700 . 
     In the TPMS  100 , the wireless power receiver  400  may include the resonance coil  450 . The TPMS  100  is, for example, mounted on a tire rim. As shown in  FIGS. 6 and 7 , the resonance coil  450  may be implemented on the flexible substrate  700 . The resonance coil  450  on the flexible substrate  700  may be formed by printed electronics technology, and other methods, such as coating or electrolytic plating. As shown in  FIGS. 6 and 7 , the resonance coil  450  may be formed by winding the flexible substrate  700 , on which a pattern of the resonance coil  450  is formed, around the tire rim and connecting both ends  450   a  of the pattern of the resonance coil  450  to each other to conduct electricity. In this case, the both ends  450   a  of the pattern of the resonance coil  450  may be connected to each other to conduct electricity by using a soldering method. 
       FIG. 8  is a schematic diagram of wireless power transmission. In  FIG. 8 , S denotes a coil for wirelessly transmitting power of a power supply source A, and D denotes the resonance coil  450 . Power wirelessly transmitted through the resonance coil  450  is charged in the rechargeable battery  500 , thereby supplying sufficient power to monitor a tire pressure. A wireless power transmission distance may be valid up to tens of cm, with a power efficiency of tens of percentage points. 
     As shown in  FIG. 7 , the wireless data transceiver  600  for transmitting measured data and processed data, the wireless communication antenna  650  for transmitting data and receiving data, which is formed at an arbitrary location in a printed electronics method, may be included. The wireless data transceiver  600  may further include a modem (refer to  670  of  FIG. 11 ), in addition to the wireless communication antenna  650  for transmitting data and receiving data. 
     The TPMS  100  may further include the rechargeable battery  500  together with a wireless power transmission device, to supply sufficient power to monitor a tire pressure. The rechargeable battery  500  may be flexibly formed by a printed electronics method, together with the wireless power transmission device, i.e., the resonance coil  450 . When the rechargeable battery  500  is used, it may be possible to monitor an air pressure at a high performance by only wirelessly charging once for several weeks or months. The rechargeable battery  500  may be repeatedly recharged. 
       FIG. 9  shows an example in which a printable and rechargeable flexible battery is formed together, with other components. In this case, the printable and rechargeable flexible battery may be printed, coated, or embedded, and may be formed in a lithium-polymer or lithium-ion thin film structure. 
       FIG. 9  shows an example in which the rechargeable battery  500 , the circuit  350  of the signal processor  300 , and sensors, including the printable pressure sensor  210  and the temperature sensor  230 , are printed and formed on the flexible substrate  700 , on which the pattern of the resonance coil  450  is formed. 
     The TPMS  100  may be formed using a roll-to-roll method, an assembly method, etc., based on a printed electronics method, and may be mounted on a tire rim.  FIG. 10  illustrates an example of the roll-to-roll method. 
     A method of manufacturing the TPMS  100  is not limited to a printed electronics method. All methods, such as coating, plating, deposition, etching, etc., may be used as long as the methods deal with a flexible substrate. Also, a mounting place is not limited to a tire rim. The TPMS  100  may also be formed as a tire side wall attachment type or a valve type. 
     In addition, the types of applied sensors are not limited to the printable pressure sensor  210  and the temperature sensor  230 . Therefore, other types of applied sensors may be applied as necessary, including an acceleration sensor, a humidity sensor, etc. 
       FIG. 11  is a perspective view of a tire rim  50 , on which the TPMS  100  is mounted, according to an embodiment. Like reference numerals denote like components. 
     Referring to  FIG. 11 , the TPMS  100  has a structure in which the sensor unit  200 , including the printable pressure sensor  210  and the temperature sensor  230 , the circuit  350  forming the signal processor  300 , the rechargeable battery  500 , the resonance coil  450  forming the wireless power receiver  400 , the wireless communication antenna  650  and a modem  670  forming the wireless data transceiver  600 , etc., are arranged on the flexible substrate  700 . The flexible substrate  700 , on which these components are arranged, may be mounted on the tire rim  50 . Various chips  800 , such as a memory, a security chip, etc., may be further arranged on the flexible substrate  700  in a chip on board (COB) form. Another PCB  900  may be arranged in another area of the flexible substrate  700 . In addition, the sensor unit  200 , including the printable pressure sensor  210  and the temperature sensor  230 , the circuit  350 , and the rechargeable battery  500  may be arranged at a plurality of locations. 
     The components may be directly printed on the surface of the tire rim  50 , monolithically provided on the flexible substrate  700 , provided in a COB form on the flexible substrate  700 , or provided in an additionally assembled form. 
     At least one selected from the group consisting of the plurality of sensors including the printable pressure sensor  210  and the temperature sensor  230 , the circuit  350 , and the rechargeable battery  500  may be formed on the flexible substrate  700  by a printed electronics method. 
     At least one selected from the group consisting of the plurality of sensors including the printable pressure sensor  210  and the temperature sensor  230 , the circuit  350 , and the rechargeable battery  500  may be formed on the flexible substrate  700  in a COB form. 
     At least one selected from the group consisting of the plurality of sensors including the printable pressure sensor  210  and the temperature sensor  230 , the circuit  350 , and the rechargeable battery  500  may be assembled on the flexible substrate  700 . 
     In addition, the TPMS  100 , including necessary sensors, a signal processing circuit, the rechargeable battery  500 , the resonance coil  450  for wireless power transmission, and the wireless communication antenna  650  for data transmission and reception on the flexible substrate  700 , may be manufactured by the roll-to-roll method. Therefore, the TPMS  100  is cheap, easy to mount, and easy to maintain. 
     In addition, since it is necessary to charge the rechargeable battery  500  with power through the wireless power receiver  400  once, for several months or several weeks, a wireless power transmission system may be provided in a vehicle or mounted at a location other than a vehicle. 
     As described above, according to the one or more of the above embodiments, a cheap, easy to mount, and easy to maintain TPMS may be implemented by providing necessary sensors, a signal processing circuit, a rechargeable battery, a wireless power transmission resonance coil, and a data transmission and reception antenna on a flexible substrate in a monolithic manner, in a COB form, or in an additionally assembled form. 
     It should be understood that the exemplary embodiments described therein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.