Physical quantity detection device

Abstract

Provided is a physical quantity detection device that measures tire pressure without using a sensor component other than a strain sensor, and that is capable of detecting a load and wear on the basis of a strain signal corrected from tire pressure information. This physical quantity detection device detects the air pressure of a tire on the basis of a reference level of a signal waveform of a strain sensor, and detects the load and wear of the tire on the basis of a strain signal corrected by the air pressure of the tire. A physical quantity detection device of the present invention stores a reference value stored in a storage unit as a table, and detects each physical quantity by comparing the reference value with the reference value.

Description

Technical Field

[0001] The present invention relates to a physical quantity detection device for detecting a physical quantity acting on a tire. Background Art

[0002] In recent years, in order to provide a safer driving state for the realization of autonomous driving, the development of tire sensor technology that detects the slipperiness of the road surface and the load applied to the tire based on information obtained from the tire is becoming popular. This is to prevent tire failures such as bursting caused by overload and vehicle rollover caused by load imbalance by providing a safer driving state. In order to build such a safety control system, it is necessary to detect physical quantities such as load and air pressure acting on the tire with high accuracy.

[0003] The tire strain sensor can detect the load acting on the tire and the wear of the tire by detecting the tire strain deformation. This can be expected to prevent vehicle failure in advance and improve driving safety by driving / road surface state detection.

[0004] Strain sensors detect changes in various physical quantities (e.g., vehicle speed, temperature, air pressure, load, etc.) as strain. Therefore, the detection signal (strain signal) indicating the result of the strain sensor detecting the strain may contain components caused by these physical quantities. When a specific physical quantity is detected based on the correspondence between the specific physical quantity and the strain signal, the detection accuracy of the specific physical quantity is reduced due to the components caused by these other physical quantities.

[0005] The following patent document 1 describes a technology related to strain sensors. The document is based on the theme of "providing a method and system capable of estimating the load applied to a vehicle tire." and describes the following technology: "A system and method for estimating the load applied to a vehicle tire, comprising: an air pressure measurement sensor, which is attached to the tire and measures the air pressure level of the tire cavity; and one or more piezoelectric film deformation measurement sensors, which are attached to the tire sidewall. The deformation measurement sensor generates a deformation signal in the tire indentation, and the deformation signal has a signal power level indicating the deformation level of the sidewall portion near the indentation contact surface. A signal power-load diagram that is corrected by the tire pressure and associates the load level and the signal power level in a predetermined range is generated and stored in a manner that enables the load level to be determined based on the signal power level after the tire pressure is corrected. (See abstract)". Prior art literature Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-054978 Summary of the invention Problem that the invention aims to solve

[0007] In the technology described in Patent Document 1, since the change of tire air pressure causes the signal amplitude of the load sensor to change, the tire air pressure measured by the air pressure measuring sensor is used to correct the signal power level of the load sensor. However, the detection signal of the load sensor may also contain components caused by physical quantities other than air pressure. Moreover, the additional installation of an air pressure sensor may increase the number of system components, increase product costs, and complicate the system. Therefore, it is believed that the technology described in this document has room for improvement in the detection accuracy of the load sensor and product costs.

[0008] In view of the above situation, the object of the present invention is to provide a physical quantity detection device that can measure tire pressure without using sensor components other than strain sensors, and can detect load and wear based on a strain signal corrected by the tire pressure information. Technical means of solving problems

[0009] Among the inventions disclosed in this application, the outline of the representative invention is briefly described as follows. That is, the physical quantity detection device of the present invention is a physical quantity detection device that detects multiple physical quantities by a strain sensor provided on a tire, and the physical quantity detection device is characterized in that the physical quantity detection device detects the air pressure of the tire by the magnitude of the reference level of the signal waveform output by the strain sensor in the state where the tire is not in contact with the road surface. Effects of the Invention

[0010] According to the physical quantity detection device of the present invention, the air pressure of the tire can be detected by the magnitude of the reference level of the strain sensor signal waveform, and the load and wear can be detected by the positive peak value and negative peak value of the signal waveform. That is, three physical quantities can be detected by one sensor, the product cost can be reduced by reducing the number of sensors, and high detection accuracy can be achieved.

[0011] Other features related to the present invention will become apparent from the description of this specification and the accompanying drawings. In addition, other problems, structures, and effects than those described above will become apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram showing the configuration of a vehicle on which the physical quantity detection device according to the first embodiment is mounted. Figure 2 It is a cross-sectional view showing a main part of a tire of a vehicle equipped with the physical quantity detection device according to the first embodiment. Figure 3 It is a diagram showing the configuration of the physical quantity detection device according to the first embodiment. Figure 4It is an explanatory diagram showing the sensor signal waveform of the strain sensor according to the rotation state of the tire according to the first embodiment. Figure 5 This is a waveform diagram showing a sensor signal waveform of the strain sensor according to the rotation state of the tire according to the first embodiment. Figure 6 It is an explanatory diagram showing the sensor signal waveform of the strain sensor in one cycle according to the first embodiment. Figure 7 This is a flowchart for deriving a table of parameters mixed in a sensor signal waveform of a strain sensor according to the first embodiment. Figure 8 1 is an explanatory diagram showing a speed correlation table according to the first embodiment, the speed correlation table being a table showing the correlation between the correction amount of the reference level of the sensor signal waveform of the strain sensor and the speed. Fig. 9 1 is an explanatory diagram showing a temperature correlation table according to the first embodiment, the temperature correlation table being a table showing the correlation between the correction amount of the reference level of the sensor signal waveform of the strain sensor and the temperature. Fig.10 It is an explanatory diagram showing an air pressure correlation table according to the first embodiment, the air pressure correlation table being a table showing the correlation between the correction amount of the reference level of the sensor signal waveform of the strain sensor and the air pressure. Fig.11 It is an explanatory diagram showing a table including various tables according to the first embodiment. Fig.12 This is a flowchart for estimating air pressure from the sensor signal waveform of the strain sensor according to the first embodiment. Fig.13 This is a result of verifying whether or not the estimation of the gas pressure by the strain sensor in the first embodiment is feasible. Fig.14 This is an explanatory diagram of a first table showing parameters mixed in a sensor signal waveform of a strain sensor according to the first embodiment. Fig.15 It is a diagram showing the configuration of a physical quantity detection device according to a second embodiment. Fig.16 This is a flowchart for deriving a table of parameters mixed in a sensor signal waveform of a strain sensor according to the second embodiment. Fig.17 It is an explanatory diagram showing a table including various tables according to the second embodiment. Fig.18 This is a flowchart for estimating a load from a sensor signal waveform of a strain sensor according to the second embodiment. Fig.19 This is a result of verifying whether or not the estimation of the load of the strain sensor is possible in the second embodiment. Fig. 20 This is a result of verifying whether or not the estimation of the gas pressure by the strain sensor is possible in the third embodiment. DETAILED DESCRIPTION

[0013] Hereinafter, embodiments of the present invention will be described in detail according to the accompanying drawings. In addition, in all figures for illustrating the embodiments, the same components are marked with the same symbols in principle, and their repeated descriptions are omitted. The present invention is not limited to the description of the embodiments shown below. It is easy for those skilled in the art to understand that the specific composition can be changed without departing from the scope of the thought or purpose of the present invention.

[0014] The expressions "first", "second", "third", etc. in this specification are added to identify the components and do not necessarily limit the number or order. In addition, the numbers used to identify the components are used according to the context, and the numbers used in one context do not necessarily represent the same components in other contexts. In addition, it does not prevent the components identified by a certain number from having the functions of the components identified by other numbers.

[0015] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings and the like may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings and the like.

[0016] In the present specification, components expressed in the singular shall include the plural form unless otherwise clearly indicated in the context.

[0017] [First embodiment] <Overall structure of the vehicle> Figure 1 1 is a diagram showing the configuration of a vehicle 100 equipped with the physical quantity detection device 10 according to the first embodiment. Figure 1 As shown, the vehicle 100 has four tires 101, an ECU 102, and a reporting unit 103. The vehicle 100 has four temperature sensors 2 and four strain sensors 3. In addition, the vehicle 100 can be not only on the road surface 20 ( Figure 4 ) can be a 4-wheeled vehicle traveling on a vehicle, or it can be a 2-wheeled vehicle, a 3-wheeled vehicle, or a vehicle with more than 5 wheels.

[0018] The vehicle 100 travels on the road surface 20 by the rotation of four tires 101. A person rides on the vehicle 100.

[0019] The tire 101 contacts the road surface 20 and receives the load of the vehicle 100. The tire 101 rotates. The tire 101 is a rubber member.

[0020] The ECU 102 is a control unit that controls the vehicle 100 . The ECU 102 includes a processing unit, a storage unit, and input / output ports electrically connected to various sensors, a processing unit such as a CPU, a storage unit such as a memory, and a reporting unit 103 .

[0021] The notification unit 103 is a monitor of the car navigation system. The display screen of the notification unit 103 is switched between the car navigation screen and the barometric pressure etc. notification screen by interrupt processing from the ECU 102. The notification unit 103 controls the display screen according to the control of the ECU 102.

[0022] The temperature sensor 2 acquires the temperature of each tire 101 and outputs the acquired temperature to the ECU 102 .

[0023] The strain sensor 3 as a sensor element obtains the sensor signal waveform 15 ( Figure 4 etc.) and outputs it to the ECU 102. In addition, the strain sensor 3 may detect the temperature of each tire 101 instead of the temperature sensor 2.

[0024] Figure 2 FIG. 1 is a cross-sectional view showing a main part of a tire 101 of a vehicle 100 equipped with the physical quantity detection device 10 according to the first embodiment. Figure 2 As shown, the tire 101 mainly includes a sidewall portion 111 and a tread portion 112. A groove (also called a tire groove) 113 is formed on the surface (tread) of the tread portion 112. The strain sensor 3 is arranged on the inner surface of the tire tread in each tire 101, particularly, on the inner surface of the tire just below the groove 113 of the tread. By such an arrangement, the detection sensitivity of the sensor is improved. The strain sensor 3 detects the displacement in the rotation direction or cross-sectional direction (rotation axis direction) of the tire 101, that is, the situation in which the curvature of the inner surface of the tread decreases as the air pressure increases in the cross-sectional direction (conversely, the curvature of the inner surface of the tread increases as the air pressure decreases) and the elongation of the tread in the horizontal direction (rotation direction). In other words, the strain sensor 3 detects the size of the radius of curvature of the inner surface of the tire tread ( Figure 2 ) and the elongation of the tire tread in the horizontal direction (rotational direction) to obtain the sensor signal waveform 15.

[0025] <Physical Quantity Detection Device 10> Figure 3 1 is a block diagram showing a physical quantity detection device 10 of the first embodiment. The physical quantity detection device 10 relates to a safe driving assistance device for a vehicle 100, and is particularly used to prevent accidents caused by insufficient brake control, etc., by providing a safe driving state. The physical quantity detection device 10 is a device that detects air pressure, etc., which affect the durability and grip of a tire 101 installed on the vehicle 100.

[0026] like Figure 3 As shown, the physical quantity detection device 10 includes the strain sensor 3, the air pressure estimation unit 4, and the notification unit 103. The physical quantity detection device 10 detects the air pressure of the tire 101 based on the output signal waveform.

[0027] <Strain sensor 3> The strain sensor 3 is a sensor element. The strain sensor 3 is a semiconductor, and is converted into a strain amount corresponding to the change in resistance and output. One strain sensor 3 is arranged on each tire 101. The strain sensor 3 outputs a sensor signal waveform 15( having a reference level 151, a positive level that changes positively compared to the reference level 151, and a negative level that changes negatively compared to the reference level 151. Figure 4 wait).

[0028] <Air Pressure Estimation Unit 4> The air pressure estimation unit 4 executes a program in the ECU 102 to perform the function of the air pressure estimation unit 4 . The air pressure estimation unit 4 receives the sensor signal waveform 15 output by the strain sensor 3 .

[0029] The air pressure estimation unit 4 obtains the temperature of the tire 101 from the temperature sensor 2. The air pressure estimation unit 4 obtains the speed by removing the tire periphery from the output cycle of the sensor signal waveform 15. In addition, the air pressure estimation unit 4 may obtain the speed from a speed sensor or the like. The air pressure estimation unit 4 corrects the sensor signal waveform 15 output by the strain sensor 3 according to the conditions of the obtained parameters such as temperature and speed, and estimates the air pressure etc. according to the difference between the correction signal and the reference waveform (reference value) stored in the storage unit 411. The air pressure estimation unit 4 sends the estimated air pressure etc. to the reporting unit 103.

[0030] The air pressure estimation unit 4 includes a storage unit 411 , a signal waveform correction unit 412 , and a determination unit 413 .

[0031] The storage unit 411 has a reference waveform (peak value of a positive level, peak value of a negative level, reference level) acquired based on the reference conditions (air pressure, temperature, speed) of the sensor signal waveform 15 output by the strain sensor 3, and a first table 5 of the amount of change for each parameter condition. In addition, the acquired data is, for example, data on an asphalt road surface.

[0032] The signal waveform correction unit 412 corrects the signal waveform to a signal waveform under specified conditions in a manner that eliminates the difference between the parameters of the mixed signal mixed in the sensor signal waveform 15, namely, the air pressure, speed and temperature, and the reference conditions based on the values ​​of the first table 5 stored in the storage unit 411, and sends the corrected signal waveform to the determination unit 413.

[0033] The determination unit 413 compares the corrected positive level peak 152, negative level peak 153, and reference level 151 sent by the signal waveform correction unit 412 with the relevant characteristics of each parameter condition stored in the first table 5 stored in the storage unit 411, and determines the air pressure amount based on the characteristic difference with the reference level 151. The determination unit 413 sends the estimated air pressure amount to the reporting unit 103.

[0034] <Sensor signal waveform 15> Figure 4 1 is an explanatory diagram showing a sensor signal waveform 15 of the strain sensor 3 corresponding to the rotation state of the tire 101 according to the first embodiment. Figure 4 As shown, the strain sensor 3 disposed in the tire 101 outputs a sensor signal waveform 15 that changes according to the state of the rotating tire 101 .

[0035] The strain sensor 3 outputs a sensor signal waveform 15 having a reference level 151 , a positive level that changes toward a positive direction relative to the reference level 151 , and a negative level that changes toward a negative direction relative to the reference level 151 .

[0036] The strain sensor 3 maintains the reference level 151 of the sensor signal waveform 15 when the tire 101 is not grounded to the road surface 20. The strain sensor 3 outputs a positive level peak 152 of the sensor signal waveform 15 when the tire 101 (the portion where the strain sensor 3 is installed) is grounded to the road surface 20. The strain sensor 3 outputs a negative level peak 153 of the sensor signal waveform 15 at the moment when the tire 101 (the portion where the strain sensor 3 is installed) is grounded or separated from the road surface 20. Here, the moment when the tire 101 is grounded or separated from the road surface 20 is a sensor displacement point. The period between the two sensor displacement points is the grounding period when the tire 101 (the portion where the strain sensor 3 is installed) is grounded to the road surface 20.

[0037] The sensor signal waveform 15 detected in this way changes according to various physical quantities (load amount, air pressure, speed, temperature).

[0038] Figure 5 1 is a waveform diagram showing a sensor signal waveform 15 of the strain sensor 3 corresponding to the rotation state of the tire 101 according to the first embodiment. Figure 5 As shown, since the tire 101 is rotating, the sensor signal waveform 15 of the strain sensor 3 repeats in the order of a reference level 151, a negative level that changes negatively compared to the reference level 151, a positive level that changes positively compared to the reference level 151, and a negative level that changes negatively compared to the reference level 151. The signal value of the sensor signal waveform 15 can be represented by a signal amplitude. Figure 4-5The sensor signal waveform 15 is also represented by the signal amplitude. The signal amplitude mentioned here can be any value representing the amplitude of the sensor signal waveform 15. Figure 6 As shown, the sensor signal waveform 15 has a waveform in which a falling waveform continues before and after a rising waveform. For example, the amplitude of the second falling waveform can be treated as the amplitude of the sensor signal waveform 15. The following is based on this premise.

[0039] Figure 6 It is an explanatory diagram showing a sensor signal waveform 15 of the strain sensor 3 in one cycle according to the first embodiment. Figure 6 yes Figure 5 A magnified view of part A. Figure 6 As shown, both the positive level peak (hereinafter sometimes referred to as positive peak) 152 and the negative level peak (hereinafter sometimes referred to as negative peak) 153 include information on the road type.

[0040] <Method for Generating First Table 5> Figure 7 This is a flowchart for deriving the first table 5 according to the first embodiment, which stores the association between the reference level under each condition including the reference condition of the sensor signal waveform 15 of the strain sensor 3 .

[0041] like Figure 7 As shown, in S101, a predetermined control unit (not shown) for table generation test drives vehicle 100 at reference air pressure, temperature and speed, and acquires output of strain sensor 3 relative to the reference conditions. In air pressure detection, attention is paid to the reference level in the waveform.

[0042] In S102 , the control unit acquires a relationship indicating a change in the sensor signal waveform 15 of the strain sensor 3 with respect to a reference waveform when the reference air pressure, temperature, and speed are changed respectively and the vehicle 100 is driven.

[0043] In S103 , the control unit stores the reference waveform of the sensor signal waveform 15 acquired in S102 and the amount of change thereof in the first table 5 .

[0044] The change of the sensor signal waveform 15 when each condition changes does not need to be expressed by the difference from the reference and the difference from the reference signal value. However, since the absolute value of the signal value is different for each vehicle model and tire model, it is necessary to generate the same data as the first table 5 in advance for each absolute value, which greatly increases the amount of data. Here, the data is described by using the difference from the reference value to reduce the amount of data.

[0045] The correlation between the reference level 151 of the sensor signal waveform 15 of the strain sensor 3 and the air pressure, temperature, and speed is stored in the storage unit 411 as a table by changing these values ​​in advance.

[0046] Figure 8 It is an explanatory diagram of a speed correlation table of the first table 5 showing the correlation between the correction amount of the reference level 151 of the sensor signal waveform 15 of the strain sensor 3 according to the first embodiment and the speed. Figure 8 The table shown acquires the correlation that the correction amount of the reference level 151 of the sensor signal waveform 15 increases as the speed increases.

[0047] Fig. 9 It is an explanatory diagram of the temperature correlation table of the first table 5 showing the correlation between the correction amount of the reference level 151 of the sensor signal waveform 15 of the strain sensor 3 according to the first embodiment and the temperature. Fig. 9 The table shown acquires the correlation that the correction amount of the reference level 151 of the sensor signal waveform 15 increases as the temperature increases.

[0048] Fig.10 It is an explanatory diagram of the air pressure correlation table of the first table 5 showing the correlation between the correction amount of the reference level 151 of the sensor signal waveform 15 of the strain sensor 3 according to the first embodiment and the air pressure. Fig.10 The table shown acquires the correlation that when the air pressure increases, the correction amount of the reference level 151 of the sensor signal waveform 15 decreases.

[0049] Fig.11 1 is an explanatory diagram showing a first table 5 including various tables according to the first embodiment. Fig.11 As shown, the first table 5 includes the reference table of the first embodiment and Figure 8 to Figure 10 Therefore, for the reference level 151 of the sensor signal waveform 15 output by the strain sensor 3 in various traveling vehicles 100 , the correction amount is estimated based on the first table 5 stored in the storage unit 411 .

[0050] <Air pressure detection method> Fig.12 This is a flowchart for estimating the air pressure of the tire 101 during running based on the sensor signal waveform 15 of the strain sensor 3 according to the first embodiment.

[0051] Fig.12 The illustrated flowchart of the air pressure detection method is repeatedly executed at a certain cycle while the vehicle 100 is traveling.

[0052] When the air pressure detection method is implemented, in S201, the air pressure estimation unit 4 confirms the driving conditions in the signal waveform correction unit 412 under the driving state of the vehicle 100. The driving conditions are conditions that match the driving conditions when the first table 5 is derived. When the driving conditions in the signal waveform correction unit 412 are confirmed in S201, the process shifts to S202.

[0053] In S202, the air pressure estimation unit 4 retrieves a correction value that satisfies the conditions stored in the storage unit 411 in order to correct the sensor signal waveform 15 output by the strain sensor 3 to a signal waveform under the same reference conditions as the reference waveform, and subtracts the correction value from the sensor signal waveform 15 to obtain a corrected signal waveform. After the processing of S202, the processing is transferred to S203.

[0054] In S203, the air pressure estimation unit 4 compares the reference level of the reference waveform with the reference level 151 of the corrected signal waveform obtained by correcting the sensor signal waveform 15 detected by the strain sensor 3. After the process of S203, the process proceeds to S204.

[0055] In S204, the air pressure estimation unit 4 determines the air pressure based on the result of comparing the reference waveform with the corrected signal waveform obtained by correcting the detected sensor signal waveform 15 output by the strain sensor 3 in S203. First, for example, the comparison with the reference level 151 is performed five times, and the difference with the average value thereof is obtained. Next, the difference obtained by the five averages is compared with the first table 5, and the air pressure corresponding to the difference is estimated. In this way, the air pressure estimation unit 4 corrects the size of the reference level 151 of the sensor signal waveform 15 output by the strain sensor 3 when the tire 101 is not in contact with the road surface 20 with respect to the temperature of the tire 101 and the vehicle speed (changes it according to the reference level 151), and estimates (detects) the tire air pressure based on the correction value. In addition, the air pressure estimation unit 4 stores the reference waveform (reference value) stored in the storage unit 411 as the first table 5, and estimates (detects) the tire air pressure by comparing with the reference waveform (reference value). The estimated air pressure is sent to the reporting unit 103. After the process of S204, the process ends temporarily.

[0056] <Verification of air pressure detection method> Fig.13 This is an example of a sensor signal waveform based on actual measurement of the strain sensor 3 according to the first embodiment. Fig.12 The flowchart shows the result of verification of the feasibility of the estimation of the air pressure. Fig.13 The pressure sensitivity of the reference level 151 in the sensor signal waveform 15 of the strain sensor 3 relative to the reference conditions (temperature, speed) is shown. As the pressure increases, the reference level 151 decreases linearly (monotonic decreases), and it can be seen that the first table 5 shown in the flowchart can be constructed. Fig.13 In FIG. 1 , the reference level 151 decreases linearly (monotonically decreases) relative to the air pressure, but the same is true for the case where the reference level 151 increases linearly (monotonically increases) relative to the air pressure.

[0057] Fig.14 1 is an explanatory diagram of a first table 5 showing parameters mixed in the sensor signal waveform 15 of the strain sensor 3 according to the first embodiment. Fig.14 As shown in FIG. 1 , the first table 5 is a proportional curve related to the sensor signal waveform 15, in which the correction amount is the same regardless of how the air pressure changes. This is because the air pressure, temperature and speed have no sensitivity and represent constant values. The first table 5 is stored in the storage unit 411. The first table 5 deducts the correction amount values ​​of various physical quantities of the line mixed with the speed correction and the temperature correction from the line of the reference level 151 of the apparent sensor signal waveform 15, and derives the line of the actually obtained air pressure.

[0058] <Effect> As described above, the sensor signal waveform 15 output by the strain sensor 3 is corrected according to the conditions of parameters such as temperature and speed, and the air pressure is estimated based on the difference between the correction signal and the reference waveform (reference value) maintained in the storage unit 411, thereby having the effect of being able to detect the air pressure through the strain sensor 3.

[0059] [Second Embodiment] The following describes a modified embodiment of the above-mentioned embodiment. In addition to the air pressure detection of the first embodiment, a device for correcting the strain waveform based on the air pressure information and detecting load and wear is described. In addition, since the overall vehicle structure is the same as that of the first embodiment, its description is omitted.

[0060] <Physical Quantity Detection Device 2010> Fig.15 2 is a block diagram showing a physical quantity detection device 2010 of the second embodiment. The physical quantity detection device 2010 relates to a safe driving assistance device for a vehicle 100, and is particularly used to prevent accidents caused by insufficient brake control, etc., by providing a safe driving state. The physical quantity detection device 2010 is a device that detects loads and wear that affect the durability and grip of tires 101 installed on the vehicle 100.

[0061] like Fig.15 As shown, the physical quantity detection device 2010 includes a strain sensor 2003, an air pressure estimation unit 2004, a load estimation unit 2104, a wear estimation unit 2204, a storage unit 2411, and a reporting unit 2103. The physical quantity detection device 2010 estimates the load and wear amount applied to the tire 101 based on the air pressure detected from the output signal waveform, and similarly estimates the signal waveform.

[0062] <Air Pressure Estimation Unit 2004> The air pressure estimation unit 2004 executes a program in the ECU 102 to perform the function of the air pressure estimation unit 2004. The air pressure estimation unit 2004 receives the sensor signal waveform 15 output by the strain sensor 2003.

[0063] The air pressure estimation unit 2004 obtains the temperature of the tire 101 from the temperature sensor 2002. The air pressure estimation unit 2004 obtains the speed by removing the tire periphery from the output cycle of the sensor signal waveform 15. In addition, the air pressure estimation unit 2004 can also obtain the speed from a speed sensor or the like. The air pressure estimation unit 2004 corrects the sensor signal waveform 15 output by the strain sensor 2003 according to the conditions of the acquired parameters such as temperature and speed, and estimates the air pressure and the like according to the difference between the correction signal and the reference waveform (reference value) stored in the storage unit 2411. The air pressure estimation unit 2004 sends the estimated air pressure to the reporting unit 2103, the load estimation unit 2104, and the wear estimation unit 2204.

[0064] The air pressure estimation unit 2004 includes a signal waveform correction unit 2412 and a determination unit 2413 .

[0065] The signal waveform correction unit 2412 corrects the signal waveform to the signal waveform under specified conditions in a manner that eliminates the difference between the parameters of the mixed signal mixed in the sensor signal waveform 15, namely, the air pressure, speed and temperature, and the reference conditions based on the value of the first table 2005 stored in the storage unit 2411, and sends the corrected signal waveform to the determination unit 2413.

[0066] The determination unit 2413 compares the corrected positive level peak 152, negative level peak 153, and reference level 151 sent by the signal waveform correction unit 2412 with the relevant characteristics of each parameter condition stored in the first table 2005 stored in the storage unit 2411, and determines the air pressure amount based on the characteristic difference with the reference level 151. The determination unit 2413 sends the estimated air pressure amount to the reporting unit 2103.

[0067] <Storage Unit 2411> The storage unit 2411 includes: a reference waveform (peak value of a positive level, peak value of a negative level, reference level) acquired under the reference conditions (air pressure, temperature, speed, load) of the sensor signal waveform 15 output by the strain sensor 2003, and a first table 2005, a second table 2006, and a third table 2007 of the amount of change for each parameter condition. In addition, the acquired data is, for example, data on an asphalt road surface.

[0068] <Load Estimation Unit 2104> Although the configuration of the load estimating unit 2104 is not shown in the figure, it is the same as that of the air pressure estimating unit 2004 .

[0069] That is, the load estimating unit 2104 obtains the temperature and speed in the same manner as the air pressure estimating unit 2004, and based on the air pressure information obtained by the air pressure estimating unit 2004, corrects the sensor signal waveform 15 output by the strain sensor 2003 according to the conditions of the obtained temperature, speed, and air pressure parameters, and estimates the load based on the difference between the correction signal and the reference waveform (reference value) stored in the storage unit 2411. The load estimating unit 2104 sends the estimated load to the reporting unit 2103.

[0070] The load estimation unit 2104, like the air pressure estimation unit 2004, corrects the signal waveform to the specified conditions in a manner that eliminates the difference between the parameters of the mixed signal mixed in the sensor signal waveform 15, namely, the air pressure, speed, temperature, and load, and the reference conditions based on the values ​​of the second table 2006 stored in the storage unit 2411, and determines the load.

[0071] In the determination, the corrected negative level peak 153 is compared with the relevant characteristics of each parameter condition in the second table 2006 stored in the storage unit 2411, and the load amount is determined based on the characteristic difference with the negative level peak 153. After the determination, the estimated load amount is sent to the reporting unit 2103.

[0072] <Wear Estimation Unit 2204> In addition, the wear estimation unit 2204 is responsible for wear detection, but since the operation is the same as that of the load estimation unit 2104, its detailed description is omitted. The difference is that the load detection uses the negative peak value 153 to estimate the load, while the wear detection uses the positive peak value 152, compares the corrected positive level peak value 152 with the relevant characteristics of each parameter condition stored in the third table 2007 stored in the storage unit 2411, and determines the wear amount based on the difference in characteristics with the positive level peak value 152.

[0073] <Method for preparing the second table 2006> Fig.16 This is a flowchart for deriving the second table 2006 of the second embodiment, which stores the correlation between the negative peak value under each condition including the reference condition of the sensor signal waveform 15 of the strain sensor 2003 .

[0074] like Fig.16 As shown, in S301, a control unit (not shown) for table generation test drives the vehicle 100 under reference pressure, temperature, speed and load, and obtains the output of the strain sensor 2003 relative to the reference conditions. In load pressure detection, attention is paid to the negative peak in the waveform.

[0075] In S302 , the control unit acquires a relationship indicating a change in the sensor signal waveform 15 of the strain sensor 2003 with respect to the reference waveform when the reference air pressure, temperature, speed, and load are changed and the vehicle 100 is driven.

[0076] In S303 , the control unit stores the reference waveform of the sensor signal waveform 15 acquired in S302 and the amount of change thereof in the second table 2006 .

[0077] The change of the sensor signal waveform 15 when each condition changes does not need to be expressed by the difference from the reference and the difference from the reference signal value. However, since the absolute value of the signal value is different for each vehicle model and tire model, it is necessary to generate the same data as the second table 2006 for each absolute value in advance, which greatly increases the amount of data. Therefore, the amount of data can be reduced by describing the data using the difference from the reference value.

[0078] <Second Table 2006> The correlation between the negative peak 153 of the sensor signal waveform 15 of the strain sensor 2003 and the air pressure, temperature, speed, and load is stored in the storage unit 2411 as a table by changing these values.

[0079] Since the related tables of the second table 2006 are the same as those of the first table 5, the description thereof will be omitted.

[0080] Fig.17 2 is an explanatory diagram showing a second table 2006 including various tables according to the second embodiment. Fig.17 As shown, the second table 2006 includes various correlations of negative peak values ​​of the second embodiment. Therefore, for the negative peak value 153 of the sensor signal waveform 15 output by the strain sensor 2003 in various traveling vehicles 100, the correction amount is estimated based on the second table 2006 stored in the storage unit 2411.

[0081] <Load detection method> Fig.18 This is a flowchart for estimating the load on the tire 101 based on the sensor signal waveform 15 of the strain sensor 2003 according to the second embodiment.

[0082] Fig.18 The load detection method flowchart shown is repeatedly executed at a certain cycle while the vehicle 100 is traveling.

[0083] When the load detection method is implemented, in S401, the load estimation unit 2104 confirms the driving conditions of the signal waveform correction unit 2412 under the driving state of the vehicle 100. The driving conditions are conditions that match the driving conditions when the second table 2006 is derived. They are temperature, speed, and the air pressure obtained by the air pressure estimation unit 2004. When the driving conditions in the signal waveform correction unit 2412 are confirmed in S401, the process shifts to S402.

[0084] In S402, the load estimation unit 2104 retrieves a correction value that satisfies the conditions stored in the storage unit 2411 in order to correct the sensor signal waveform 15 output by the strain sensor 2003 to a signal waveform of the same reference condition as the reference waveform, and subtracts the correction value from the sensor signal waveform 15 to obtain a corrected signal waveform. After the processing of S402, the processing is transferred to S403.

[0085] In S403, the load estimating unit 2104 compares the reference level of the reference waveform with the negative peak value 153 of the corrected signal waveform obtained by correcting the sensor signal waveform 15 detected by the strain sensor 2003. After the process of S403, the process proceeds to S404.

[0086] In S404, the load estimation unit 2104 determines the load based on the result of comparing the reference waveform and the corrected signal waveform after correcting the sensor signal waveform 15 output by the detected strain sensor 2003 in S403. First, for example, the comparison with the negative peak value 153 is performed 5 times, and the difference with the average value thereof is obtained. Then, the difference of the 5 averages is compared with the second table 2006, and the load corresponding to the difference is estimated. In this way, the air pressure estimation unit 2004 estimates (detects) the tire air pressure based on the reference level 151 of the sensor signal waveform 15 of the strain sensor 2003, and the load estimation unit 2104 estimates (detects) the tire load based on the strain signal corrected with the tire air pressure. In addition, the load estimation unit 2104 stores the reference waveform (reference value) stored in the storage unit 2411 as the second table 2006, and estimates the tire load (detects) by comparing with the reference waveform (reference value). The estimated load is sent to the reporting unit 2103. After the processing of S404, the processing is temporarily terminated.

[0087] <Load test results> Fig.19 The load detection error is shown in detail. This is the result of comparing the load detection error of a tire model 225 / 65 / R17 (outer diameter 724mm) for ordinary cars with the load detection error estimated based on the air pressure information obtained by a general air pressure sensor (TPMS) and a strain sensor. Under the conditions of a vehicle speed of 2.4m / s and a load of 340kg / wheel, the load detection error is calculated using air pressure as a parameter (1.4-3.0kg / cm2 ) plots the load estimation error. The air pressure measurement error of TPMS is generally about 5%, while the load detection error is about ±8%. On the other hand, the load detection error estimated based on the air pressure obtained by the strain sensor is slightly higher than the TPMS error, but overall it is within the error of ±8%, and the load can be detected with high accuracy.

[0088] <Wear Detection Method> The wear detection method is basically the same as the load detection method except that the positive peak 152 is used instead of the negative peak 153 to detect the wear, so the detailed description thereof is omitted.

[0089] <Effect> As described above, the air pressure is detected by the magnitude of the reference level of the sensor signal waveform of the strain sensor, and the load and wear can be detected by the positive peak and negative peak of the sensor signal waveform. That is, one sensor can detect three physical quantities, which has the effect of reducing product costs by reducing the number of sensors.

[0090] [Third Embodiment] Hereinafter, the apparatus for detecting the air pressure, load, and wear related to the ordinary vehicle tire of the second embodiment will be described as the apparatus for detecting the physical quantity related to the truck tire. In addition, since the overall structure of the vehicle is the same as that of the first embodiment, the description thereof will be omitted. In addition, since the structure of the physical quantity detection apparatus is the same as that of the second embodiment, the description thereof will also be omitted.

[0091] <Verification of air pressure detection method> Fig. 20 is an example of a sensor signal waveform actually measured by the strain sensor 3 shown in the first embodiment. Fig.12 The flowchart shows the verification result of the third embodiment in which the feasibility of the estimation of the air pressure was verified. Fig. 20 The pressure sensitivity of the reference level 151 in the sensor signal waveform 15 of the strain sensor 3 under the reference conditions (temperature, speed) for a truck tire model 205 / 70 / R16 (outer diameter 693 mm) is shown. Fig. 20 In FIG. 1 , the pressure sensitivity of the reference level 151 when the vehicle speed is 5 km / h and 20 km / h is shown. As the air pressure rises, the reference level 151 decreases linearly (monotonically decreases), and it can be seen that the first table 5 shown in the flowchart can be constructed. In addition, Fig. 20In FIG. 1 , the reference level 151 decreases linearly (monotonically decreases) with respect to the air pressure, but the same is true for the case where the reference level 151 increases linearly (monotonically increases) with respect to the air pressure. In addition, it can be seen that the reference level 151 increases as the vehicle speed increases. In other words, it can be seen that the reference level 151 is sensitive to the vehicle speed and changes according to the vehicle speed.

[0092] <Effect> As described above, there is an effect that the air pressure can be detected at a reference level even when the tire type is changed, even in the case of a truck tire.

[0093] [Overview of First to Third Embodiments] As described above, in the physical quantity detection device 10, 2010 of the present embodiment, which detects multiple physical quantities by means of a strain sensor provided on the tire 101, the physical quantity detection device 10, 2010 detects the air pressure of the tire 101 based on the size of the reference level 151 of the signal waveform output by the strain sensor when the tire 101 is not grounded to the road surface 20.

[0094] In addition, the strain sensor is disposed on the inner surface of the tire just below the groove of the tire tread.

[0095] Furthermore, the physical quantity detection device 10 , 2010 corrects the magnitude of the reference level 151 of the signal waveform of the strain sensor according to the temperature of the tire 101 and the vehicle speed (changes it according to the reference level 151 ), and detects the air pressure of the tire 101 based on the correction value.

[0096] In addition, the reference level 151 of the signal waveform of the strain sensor increases or decreases monotonically with respect to the air pressure of the tire 101 .

[0097] In addition, the physical quantity detection device 10, 2010 detects the air pressure of the tire 101 based on the size of the curvature radius of the inner surface of the tire tread and the size of the elongation of the tire tread in the horizontal direction (rotational direction) (the size of the reference level 151 of the signal waveform of the strain sensor that detects it).

[0098] Furthermore, the physical quantity detection device 10 , 2010 stores the reference value stored in the storage unit 411 , 2411 provided in the physical quantity detection device 10 , 2010 as a table, and detects the air pressure of the tire 101 by comparison with the reference value.

[0099] In addition, the physical quantity detection device 2010 detects the air pressure of the tire 101 through the reference level 151 of the signal waveform of the strain sensor, and detects the load and wear of the tire 101 based on the strain signal corrected by the air pressure of the tire 101.

[0100] Furthermore, the physical quantity detection device 2010 stores reference values ​​stored in the storage unit 2411 included in the physical quantity detection device 2010 as a table, and detects the load and wear of the tire 101 by comparison with the reference values.

[0101] That is, one of the concepts of this embodiment (first embodiment) is a physical quantity detection device 10 that detects multiple physical quantities by means of a strain sensor arranged on a tire 101, which comprises: a strain sensor, a physical quantity calculation unit (air pressure estimation unit 4) and a storage unit, the physical quantity calculation unit detects the air pressure of the tire 101 based on the size of a reference level 151 of a signal waveform output by the strain sensor and a state in which the tire 101 is not grounded to the road surface 20.

[0102] Another concept of this embodiment (second embodiment) is that the physical quantity detection device 2010 detects the air pressure of the tire 101 through the reference level 151 of the signal waveform of the strain sensor, and detects the load and wear of the tire 101 based on the strain signal corrected by the air pressure of the tire 101.

[0103] In this way, the air pressure can be estimated from the magnitude of the reference level 151 of the strain signal output by the sensor element. In addition, the load and the amount of wear can be estimated from the magnitude of the positive peak and the negative peak of the strain signal corrected by the air pressure.

[0104] According to the physical quantity detection device of this embodiment, the air pressure of the tire can be detected by the magnitude of the reference level of the strain sensor signal waveform, and the load and wear can be detected by the positive peak and negative peak of the signal waveform. That is, three physical quantities can be detected by one sensor, the product cost can be reduced by reducing the number of sensors, and high detection accuracy can be achieved.

[0105] The present invention is not limited to the above-mentioned embodiments, and includes various variations. For example, the above-mentioned embodiments are embodiments described in detail in order to easily explain the present invention, and are not necessarily limited to structures having all the structures described. In addition, a part of the structure of some embodiments can be replaced by the structure of other embodiments, and the structure of other embodiments can be added to the structure of some embodiments. In addition, for a part of the structure of each embodiment, the structure of other embodiments can be added, deleted, or replaced. Explanation of symbols

[0106] 2…temperature sensor, 3…strain sensor, 4…air pressure estimation unit, 5…first table, 10…physical quantity detection device, 15…sensor signal waveform, 100…vehicle, 101…tire, 102…ECU, 103…report unit, 151…reference level, 152…peak value of positive level, 153…peak value of negative level, 411…storage unit, 412…signal waveform correction unit, 413…determination unit.

Claims

1. A physical quantity detection device, which detects multiple physical quantities by means of a strain sensor arranged on a tire, wherein the physical quantity detection device is characterized in that: The physical quantity detection device detects the air pressure of the tire based on the magnitude of a reference level of a signal waveform output by the strain sensor when the tire is not in contact with a road surface.

2. The physical quantity detection device according to claim 1, characterized in that: The strain sensor is disposed on the inner surface of the tire just below the groove of the tire tread.

3. The physical quantity detection device according to claim 1, characterized in that: The physical quantity detection device corrects the magnitude of a reference level of a signal waveform of the strain sensor according to a temperature of the tire and a vehicle speed, and detects the air pressure of the tire based on the correction value.

4. The physical quantity detection device according to claim 1, characterized in that: A reference level of the signal waveform of the strain sensor monotonically increases or monotonically decreases with respect to the air pressure of the tire.

5. The physical quantity detection device according to claim 1, characterized in that: The physical quantity detection device detects the air pressure of the tire based on the size of the radius of curvature of the inner surface of the tire tread and the size of the extension of the tire tread in the horizontal direction.

6. The physical quantity detection device according to claim 1, characterized in that: The physical quantity detection device stores reference values ​​stored in a storage unit included in the physical quantity detection device as a table, and detects the air pressure of the tire by comparing with the reference values.

7. The physical quantity detection device according to claim 1, characterized in that: The physical quantity detection device detects the air pressure of the tire using a reference level of a signal waveform of the strain sensor, and detects the load and wear of the tire based on a strain signal corrected by the air pressure of the tire.

8. The physical quantity detection device according to claim 7, characterized in that: The physical quantity detection device stores reference values ​​stored in a storage unit provided in the physical quantity detection device as a table, and detects the load and wear of the tire by comparison with the reference values.

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