Physical quantity detection device

Abstract

The invention provides a physical quantity detection device, which can control a conduction method to realize low current consumption even in a grounding period. This physical quantity detection device (2) is characterized by: extracting a depression peak value (43) for strain generated when a tire (10) is depressed in such a manner that a strain detection region (10a) is in contact with a road surface (30), and an intermediate time peak value (42) for detecting the strain generated when the tire (10) is depressed in such a manner that the tire (10) is in contact with the road surface (30); an intermediate time peak value 42 is an intermediate time peak value 42 of strain generated at an intermediate time Pb between a step-in time and a step-out time when a strain detection region of a tire leaves a road surface, and a period at which the step-in peak value and the intermediate time peak value are generated next time and later is calculated on the basis of a time difference t from the step-in peak value to the intermediate time peak value or a slope of a change in the strain. The strain detection unit (3) is energized in accordance with the period.

Description

Technical Field

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

[0002] When a device for detecting a physical quantity related to the state of a tire (physical quantity detection device) is mounted on the tire, data exchange with a vehicle control device provided on the vehicle is performed by wireless communication. Since the tire is rotatably supported on the vehicle, it is difficult to supply power from the vehicle to the physical quantity detection device. Therefore, it is necessary to provide a power source in the physical quantity detection device. For example, a button battery or the like is sometimes used as a power source in the physical quantity detection device. That is, it is necessary to drive the physical quantity detection device based on a limited power source such as a button battery.

[0003] On the other hand, since the physical quantity detection device is set inside the tire, it is not easy to replace. Therefore, it is very important to reduce the current consumption of the physical quantity detection device, especially the current consumption of the microcomputer (MPU) with large current consumption in the physical quantity detection device and the antenna driving unit used in wireless communication.

[0004] Patent Document 1 discloses a technique for transmitting only information on a ground contact side region or only information on a non-ground contact side region to a vehicle side, thereby transmitting necessary tire information to the vehicle side with a small current consumption. Prior art literature Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6317999 Summary of the invention Problem that the invention aims to solve

[0006] In Patent Document 1, two peak positions of sensor measurement values ​​at the step-in point and the step-out point are calculated, and the interval between the two peak positions is used as the tire ground contact area. The ground contact area is used as the transmission interval to transmit tire information acquired by the sensor to the vehicle side. Therefore, the sensor needs to receive current supply from the power supply at least during the time from the sensor arrangement portion of the tire contacting the road surface to the time of separation, and the current consumption increases. That is, the current consumption increases even in the portion where information is not needed, so it is difficult to fully achieve the effect of reducing the current consumption.

[0007] The object of the present invention is to provide a physical quantity detection device that does not require the time for a sensor mounted on a tire to be grounded to the road surface, and controls the power supply method to achieve low current consumption even during the grounding period when the sensor configuration part of the tire is grounded to the road surface. Technical means of solving problems

[0008] The present invention has been made in view of the above-mentioned problems, and adopts, for example, the configuration described in the claims.

[0009] The physical quantity detection device of the present invention is installed in a tire to detect the physical quantity of the state of the tire, and is characterized in that the physical quantity detection device includes: a strain detection unit, which detects the strain of the tire; and a signal processing unit, which processes the detection signal detected by the strain detection unit, the signal processing unit extracts a step-in peak value and an intermediate moment peak value, the step-in peak value is a step-in peak value of the strain generated toward either side of compression or extension when stepping in when the strain detection area of ​​the tire contacts the road surface due to the rotation of the tire, and the intermediate moment peak value is an intermediate moment peak value of the strain generated toward either side of compression or extension at an intermediate moment between the step-in time and the push-off time when the strain detection area of ​​the tire leaves the road surface, the signal processing unit calculates a cycle of the step-in peak value and the intermediate moment peak value after the next time based on the time difference from the step-in peak value to the intermediate moment peak value or the slope of the change in the strain, and energizes the strain detection unit in accordance with the cycle. Effects of the Invention

[0010] According to the present invention, a physical quantity detection device can be provided, which can make the time for energizing a strain sensor shorter than the time required for the strain detection area of ​​the tire to go from stepping in contact with the road surface to pushing out leaving the road surface due to the rotation of the tire, and can achieve low current consumption during the contact period from stepping in to pushing out.

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

[0012] Figure 1 A block diagram showing a schematic configuration of a vehicle equipped with the strain sensor according to the present embodiment. Figure 2 A schematic diagram showing a tire with a strain sensor rolling on a road surface as a vehicle travels. Figure 3 An explanatory diagram showing a sensor signal waveform of a strain sensor corresponding to a rotation state of a tire. Figure 4 It is a diagram for explaining the hardware configuration of the physical quantity detection device according to the present embodiment. Figure 5 This is a functional block diagram showing the configuration of a signal processing unit of the physical quantity detection device according to the present embodiment. Figure 6 An example of a flowchart showing the processing of the signal processing unit of this embodiment. Figure 7 An example of waveform data measured by the physical quantity detection device according to the present embodiment and a graph showing the presence or absence of energization at that time are shown. Figure 8 A schematic diagram showing an example of a correction unit for the energization time width at the step-in peak value processed by the physical quantity detection device according to the present embodiment. Fig. 9 A diagram showing a measured waveform of a strain value including an irregularity value of the physical quantity detection device according to the present embodiment. Fig.10 A timing chart showing whether or not power is supplied to each block of the physical quantity detection device according to the present embodiment. Fig.11 is a plan view of the strain detection module. Fig.12 yes Fig.11 AA cross-section diagram. DETAILED DESCRIPTION

[0013] Below, refer to Figures 1 to 12 Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In all the figures used to illustrate the embodiments, the same reference numerals are assigned to the same components in principle, and repeated descriptions thereof are omitted. In addition, the cross-sectional views, the front views, and the side views are oriented by mutually orthogonal XYZ axes, with +X being "right", -X being "left", +Y being "up", -Y being "down", +Z being "front", and -Z being "back".

[0014] Figure 1 This is a block diagram showing a schematic configuration of a vehicle equipped with the strain sensor according to the present embodiment. The strain sensor 1 of this embodiment is applied to a vehicle 100 having ADAS (Advanced Driver-Assistance Systems) and AD (Autonomous Driving) functions, for example. Figure 1 As shown, the vehicle 100 has four tires 10, a control unit 101, and a receiver 102. In addition, a strain sensor 1 is installed on each tire 10. The vehicle 100 is not limited to a four-wheeled vehicle, but may be a two-wheeled vehicle, a truck, a bus, or a vehicle equipped with six-wheeled, eight-wheeled, or other multiple tires. In addition, in this embodiment, a configuration in which a strain sensor 1 is installed on each of the tires 10 is shown, but a configuration in which only one strain sensor 1 is installed on any one of the tires 10 may also be used.

[0015] The control unit 101 is composed of an ECU (Electronic Control Unit), which has a CPU (Central Processing Unit), a memory such as ROM, RAM, and hardware including an input and output interface. In addition, a software program for performing various calculations is stored in the memory in an executable state. The receiver 102 receives the signal detected by the plurality of strain sensors 1 through wireless communication, and provides it to the control unit 101 as an output signal of each strain sensor 1. The control unit 101 uses the output signal of each strain sensor 1 to perform various vehicle controls.

[0016] Figure 2 This is a schematic diagram showing a state in which a tire with a strain sensor rolls on a road surface as a vehicle travels. Figure 2 (1) is the side view of the tire, Figure 2 (2) is Figure 2 A cross-sectional view taken along line II-II of (1).

[0017] The strain sensor 1 is installed on the inner side of a tire 10 of a vehicle, for example, to detect the strain of the tire 10. The strain sensor 1 is fixed on the inner peripheral surface of the tread portion of the tire 10 (hereinafter referred to as the tire inner peripheral surface), and detects the deformation in the compression direction and the tension direction generated on the tire inner peripheral surface as strain. In the present embodiment, the tire 10 is a tubeless tire assembled on a wheel not shown in the figure, and a closed space formed between the wheel and the tire 10 is filled with high-pressure gas, but it can also be a tube tire with an air inner tube arranged in the closed space. One strain sensor 1 is arranged in one tire, but it is not limited to this, and it can also be a structure in which multiple strain sensors are arranged at a specified interval in the circumferential direction of the tire inner peripheral surface.

[0018] exist Figure 2 In the case shown in the figure, the road surface 30 is a flat road surface, and the tire 10 is provided with a portion of the strain sensor 1 (strain detection area 10a: see Figure 3 ) is grounded to the road surface 30. In this state, the strain sensor 1 detects the strain amount corresponding to the deformation of the tire 10.

[0019] Next, use Figure 3 A sensor signal waveform 40 when one strain sensor 1 is used will be described.

[0020] Figure 3 (1) to (4) are diagrams showing the rotation state of the tire. Figure 3 (5) is an explanatory diagram showing the sensor signal waveform of the strain sensor corresponding to the rotation state of the tire. Figure 3 (1) indicates a non-contact state where the tire strain detection area is away from the road surface. Figure 3 (2)~ Figure 3 (4) represents the grounding state of the tire strain detection area and the road surface. Figure 3 (2) shows the state when the strain detection area starts to contact the road surface. Figure 3 (4) shows the state when the strain detection area leaves the road surface during pedaling. Figure 3 (3) represents the state at the intermediate moment between stepping in and pushing out.

[0021] like Figure 3 As shown in (1) to (4) of FIG. 1 , when the tire 10 rolls on the road surface 30, as shown in FIG. Figure 3 As shown in (5), the strain sensor 1 outputs a sensor signal waveform 40 that changes according to the state of the rotating tire 10 relative to the road surface 30. The strain sensor 1 outputs a sensor signal waveform 40 including a reference level 41, a positive level that changes to a positive level (tension) compared to the reference level 41, and a negative level that changes to a negative level (compression) compared to the reference level 41.

[0022] like Figure 3 As shown in (1), the strain sensor 1 maintains the reference level (steady value) 41 of the sensor signal waveform 40 when the strain detection region 10 a capable of detecting the strain of the tire 10 is in the non-grounding period 52 not in contact with the road surface 30 .

[0023] Furthermore, when the strain detection area 10a of the tire 10 is in the ground contact period 51 with the road surface 30, and as Figure 3 As shown in (3), at the intermediate moment between the stepping-in time and the kicking-out time, the intermediate moment peak value 42 is output as the positive level peak value (maximum value) of the sensor signal waveform 40. In addition, at the stepping-in time when the strain detection area 10a of the tire 10 is in contact with the road surface 30 and at the kicking-out time when it is separated, the stepping-in peak value 43 and the kicking-out peak value 44 are output as the negative level peak values ​​of the sensor signal waveform 40.

[0024] Thus, the sensor signal waveform 40 includes two sensor change points (step-in peak 43, step-out peak 44) at the moment when the strain detection area 10a of the tire 10 contacts or leaves the road surface 30 (step-in and step-out), and one sensor change point (mid-moment peak 42) during the contact period 51 when the strain detection area 10a of the tire 10 contacts the road surface 30. The time 53 from step-in to the mid-moment is about half the length of the contact period 51. The sensor signal waveform 40 detected in this way changes according to various physical quantities (load, air pressure, speed, temperature, etc.).

[0025] In this embodiment, the moment when the strain detection area 10a of the tire 10 touches or leaves the road surface 30 is set to negative (compression), and the state of the strain detection area 10a of the tire 10 at the intermediate moment when it touches the road surface 30 is set to positive (tension), but according to the mounting direction of the strain sensor 1 relative to the inner circumference of the tire, the same consideration can also be given when the positive and negative are reversed. In this way, the strain sensor 1 is mounted on the inner circumference of the tire 10 to measure the strain amount of the strain corresponding to the deformation of the tire 10.

[0026] Figure 4 It is a block diagram showing the hardware configuration of the physical quantity detection device according to the present embodiment. The strain sensor 1 includes a physical quantity detection device 2 for detecting a physical quantity of a tire using a sensor signal as a strain amount. The physical quantity detection device 2 includes a button battery 5, a DC / DC converter 6, an MPU (Micro Processor Unit) 20, an antenna driver 4, and a strain detection module (strain detection unit) 3. The MPU 20 receives a constant voltage boosted from the button battery 5 via the DC / DC converter 6, and supplies the constant voltage to the strain detection module 3 and the antenna driver.

[0027] The voltage value of the button battery 5 changes according to temperature conditions, etc. The DC / DC converter 6 is used to stabilize the voltage value supplied from the button battery 5 to the MPU 20 and the strain detection module 3. The MPU 20 is electrically connected to the strain detection module 3 and the antenna driver 4. The MPU 20 realizes the ON / OFF action of the power supply of the strain detection module 3 and the antenna driver 4 through a semiconductor switch, etc., to achieve low current consumption. The MPU 20 has a sleep function, and by switching to the sleep mode other than at startup, the operation of unnecessary clock circuits is stopped, etc., and low current consumption can also be achieved.

[0028] Figure 5 It is a block diagram showing the configuration of a signal processing unit of the physical quantity detection device according to the present embodiment.

[0029] The MPU 20 of the physical quantity detection device 2 embodies the signal processing unit as an internal function by executing a program in a memory by a processor in the MPU 20 . Hereinafter, the MPU 20 may be referred to as a signal processing unit 20 .

[0030] In the signal processing unit 20, according to the start command generated periodically, the strain value is measured by serial communication with the strain detection module 3 or by reading the analog voltage within the specified time pre-set in the power-on timer setting unit 206. The measured strain value is transmitted from the measuring unit 201 to the power-on timing calculation unit 21 together with the time information of the measured point.

[0031] The energization timing calculation unit 21 includes a peak value calculation unit 202 and a time calculation unit 203. The peak value calculation unit 202 calculates a step-in peak value, which is a step-in peak value of strain generated toward either compression or extension when stepping in when the strain detection area 10a of the tire 10 contacts the road surface 30 due to the rotation of the tire 10, and an intermediate peak value, which is an intermediate peak value of strain generated toward either compression or extension in the intermediate time between stepping in and pushing out when the strain detection area 10a of the tire 10 leaves the road surface 30.

[0032] In this embodiment, the peak calculation unit 202 calculates the intermediate peak 42 of the positive level (compression side) and the step-in peak 43 and the push-out peak 44 of the negative level (tension side) of the sensor signal waveform 40. Then, the time t of the point where the step-in peak 43 is measured is extracted. Pa and the time t at which the peak value 42 at the middle time is measured Pb The time calculation unit 203 calculates the time difference t between the first stepping peak 43 and the intermediate peak 42 calculated by the peak calculation unit 202, and calculates the time t until the next stepping peak 43 occurs after the tire 10 rotates one circle. Pa-1 and the time t until the peak value 42 at the intermediate time Pb-1 .

[0033] When the tire 10 rotates at a constant rotation speed, the time difference between the step-in peak 43 and the intermediate peak 42 is proportional to the time required for the tire 10 to rotate once. Therefore, the timing of the next step-in peak 43 and the intermediate peak 42 can be calculated using the time difference t between the first step-in peak 43 and the intermediate peak 42.

[0034] The energization timing calculation unit 21 calculates the energization timing value (t Pa-1 ,t Pb-1 ).

[0035] Next, the energization control unit 22 is responsible for controlling energization of the strain detection module 3 and the antenna driving unit 4. The energization control unit 22 includes a correction parameter setting unit 207 and a count setting unit 208.

[0036] The correction parameter setting unit 207 sets a correction parameter for correcting the width of the energization time during which energization is performed in the stepping peak 43 and the intermediate peak 42 generated after one tire rotation calculated by the time calculation unit 203 .

[0037] The count setting unit 208 sets the number of times the peak value is measured. When the feature point extraction unit 205 determines that the count setting unit 208 has only measured the peak value for the preset number of times, it extracts a feature point having a peak value within a preset threshold value from the plurality of measured values, provides the peak value data of the feature point to the antenna driving unit 4, and outputs it to the outside from the antenna driving unit 4.

[0038] The antenna driving unit 4 transmits the data of the feature points provided by the feature point extraction unit 205 to the receiver 102 of the vehicle 100 through wireless communication, and provides it to the control unit 101. As a result, the communication time in the antenna driving unit 4 can be shortened, and the current consumption can be further reduced. In addition, the transmission of the feature point data can also be performed every time the peak value of the strain value is measured by the measuring unit 201.

[0039] Figure 6 This is an example of a flowchart showing the processing of the signal processing unit of this embodiment.

[0040] The processing performed by the signal processing unit 20 is Figure 3 The case of a strain detection module 3 mounted in the direction of the movement of the sensor signal waveform 40 of the strain sensor 1 corresponding to the rotation state of the tire 10 as shown in (1) to (5) is taken as an example, that is, the moment when the strain detection area 10a of the tire 10 touches or leaves the road surface 30 (when stepping in or kicking out) is set to negative (compression), and the state where the strain detection area 10a of the tire 10 touches the road surface 30 (intermediate moment) is set to positive (tension).

[0041] After startup, the power-on timer setting unit 206 sets the power-on timer setting 1 as the specified data acquisition period (S101). Then, the measurement unit 201 measures the strain value detected by the strain detection module 3 as the initial measurement value (S102). Next, the initial measurement value is compared with the reference level 41 (S103). When the measurement value is less than the reference level 41 ("No" in S103), the power-on timer setting unit 206 sets the power-on timer setting 2 (S104), performs normal measurement (S105), and performs peak extraction processing (S106).

[0042] On the other hand, if the measured value is greater than the reference level 41 ("Yes" in S103), it is set as out of the normal measurement object, and it is determined whether the prescribed time set by the power-on timer setting 1 has passed. If it is less than the prescribed time, the comparison process of step S103 is performed again. If it is greater than the prescribed time, it is determined that it is out of the stable driving and transfer is made to the next process.

[0043] In the peak extraction process S106, the stepping-in peak and the intermediate-moment peak are extracted. The stepping-in peak is the stepping-in peak of the strain generated toward either the compression or tension side when the strain detection area 10a of the tire 10 contacts the road surface 30 due to the rotation of the tire 10. The intermediate-moment peak is the intermediate-moment peak of the strain generated toward either the compression or tension side in the intermediate moment between the stepping-in time and the push-off time when the strain detection area 10a of the tire 10 leaves the road surface 30.

[0044] In the peak extraction process S106, it is determined whether both the positive level peak 42 and the negative level peak 43 are present. For the positive level peak 42, for example, the measured value at the time when the measured value changes from increasing to decreasing, or the measured value at the point where the time differential of the measurement is detected to change from positive to negative can be used. Similarly, for the negative level peak 43, for example, the measured value at the time when the measured value changes from decreasing to increasing, or the measured value at the point where the time differential of the measurement is detected to change from negative to positive can be used.

[0045] When both the positive level peak 42 and the negative level peak 43 are present, the power-on timing value is set (S107). Then, the process is transferred to the power-on control unit 22, and the correction parameter setting unit 207 sets the correction parameter (S108). Then, the strain detection module 3 is intermittently powered based on the corrected power-on timing value, and the strain value is intermittently measured (S109), that is, the strain value is measured only when the power is on.

[0046] In step S106, if it is determined that both the positive level peak 42 and the negative level peak 43 are not present ("No" in S106), it is determined that the vehicle is in stable driving and the process is transferred to the next process. In this way, the vehicle is not stopped, stopped during measurement, or started. In addition to determining that the vehicle is in stable driving within a fixed time and that both the positive level peak 42 and the negative level peak 43 are not present, unnecessary power-on time can be shortened, and low current consumption can be achieved.

[0047] The peak value is accurately measured through intermittent measurement in step S109. When the number of measured peak values ​​becomes greater than the count number (number of measurements) set in the count setting unit 208 (yes in S110), the feature point extraction unit 205 extracts feature points from multiple measured values ​​(peak values) (S111), and the data of the feature points is sent from the antenna driving unit 4 to the receiver 102 (S112).

[0048] Furthermore, when the direction in which the strain detection module 3 is mounted is reversed, the direction of increase and decrease of the measured value is reversed, so the same effect can be obtained by reversing the magnitude relationship described above.

[0049] Next, use Figure 7 An example of achieving a reduction in current consumption during startup will be described.

[0050] Figure 7 This is a graph showing an example of waveform data measured by the physical quantity detection device according to the present embodiment and the presence or absence of energization at that time.

[0051] In this embodiment, the horizontal axis represents time, the vertical axis represents the waveform of the strain amount, the solid line portion represents the state where the strain detection module 3 is powered on, and the dotted line portion represents the state where the strain detection module 3 is not powered on. Figure 7 As shown, at the first time after startup, the measuring unit 201 ( Figure 5 ) measures the strain value and time. Next, the initial measured value and the reference level 41 (refer to Figure 3 (5)) for comparison ( Figure 6 Since the initial measured value is less than the reference level 41, a normal measurement is performed to continuously measure the change in the strain value from the measurement of the initial measured value to the intermediate peak value 42 ( Figure 6 S105).

[0052] Then, according to the intermediate peak value 42 ( Figure 7 Pb) and the negative level step-in peak 43 ( Figure 7 The time difference t of Pa) is calculated by the power-on timing calculation unit 21 ( Figure 5 ) Find the peak value 42 of the next positive level generated at the middle moment ( Figure 7 Pb-1) and the negative level step-in peak 43 ( Figure 7 Thereafter, the count setting unit 208 ( Figure 5 ) is used to set the number of counts n, and the power-on timing is set in such a way that power is supplied at the intermediate moment peak 42 and the stepping peak 43 respectively, and power is supplied in accordance with the power-on timing to perform intermittent measurement of the strain value.

[0053] Since the time difference t between the step-in peak 43 and the intermediate peak 42 is equal to the time taken for the tire 10 to rotate once (eg Figure 7 The relationship between Pb and Pb) is a proportional relationship, so the period conversion coefficient (proportional constant) is used in the calculation of the next peak time and is obtained by the following formula.

[0054] t Pa-1 = cycle conversion factor × t t Pb-1 =t+t Pa-1 The cycle conversion factor is a unique value determined by the outer diameter of the tire.

[0055] By the power-on timing calculation unit 21 ( Figure 5 ) to find the peak time t Pa-1 ,t Pb-1 The value is set in the power control unit 22 ( Figure 5 ), the strain detection module 3 is powered on to achieve intermittent measurement. In addition, when the strain detection module 3 is not powered on, the signal processing unit 20 is in a sleep mode state, but when recovering from the sleep mode, the recovery time needs to be considered to ensure that the strain detection module 3 is powered on in time. That is, Figure 7 In the figure, it shows the waveform when power is turned on before the peak value appears.

[0056] In this waveform, the power control unit 22 is set to non-energized at the peak 42 of the positive level, for example, when the measured value changes from increasing to decreasing or when the time differential during measurement changes to negative. The same is true for the peak 43 of the negative level, for example, when the measured value changes from decreasing to increasing or when the time differential during measurement changes to positive, it is set to non-energized. In this way, it is possible to suppress the energization of unnecessary sections starting from the time when the peak value is exceeded, and further reduce the current consumption.

[0057] The power supply to the strain detection module 3 is from the initial step-in peak value 43 ( Figure 7 Pa) to the initial intermediate peak of 42 ( Figure 7 The timing of the step-in peak value 43 and the intermediate moment peak value 42 generated between the step-in peak value 43 and the intermediate moment peak value 42 after the next step-in peak value 43 is calculated. In addition, when the strain detection module 3 is not powered on, the signal processing unit 20 is set to the sleep mode. Therefore, the current consumption of the physical quantity detection device 2 can be reduced. The power-on timing calculation unit 21 can also use at least two step-in peak values ​​to calculate the period of the subsequent step-in peak value 43 and the intermediate moment peak value 42.

[0058] Next, use Figure 8 The time width of the energization control will be described.

[0059] Figure 8 is the time t processed by the physical quantity detection device of this embodiment. Pa-1 A schematic diagram of an example of a correction method for the energization time width at a location.

[0060] Figure 8 The horizontal axis represents the peak value of the positive level 42 ( Figure 7 The peak value Pb) and the negative level peak value 43 ( Figure 7 The vertical axis represents the time difference t of the peak value Pa) of the next occurrence of the peak value Pa-1. Pa-1The graph shows that when the vehicle speed increases, the time difference t between the peak 42 and the peak 43 decreases, and the time t of the next peak Pa-1 on the vertical axis is Pa-1 Become shorter. Figure 8 The thick line in the middle of the rising curve typ is the time difference t and the set time t Pa-1 The baseline curve.

[0061] Assuming that when the tire outer diameter changes, the time to the next peak becomes shorter when the outer diameter becomes smaller, and the time to the next peak becomes longer when the outer diameter becomes larger. Therefore, considering that the time t of the next peak 43 generated based on the reference curve typ is Pa-1 There is a problem of missing the peak value measurement when the power is turned on, but it can be solved by the following method.

[0062] Specifically, as a correction of the energization time width, for example, the line max indicated on the positive side relative to the reference curve typ indicates the relationship when the tire outer diameter increases relative to the reference due to an increase in air pressure, etc. That is, when the tire outer diameter increases, the time difference until the next peak is generated is greater than the t calculated based on the time difference t between the peak 43 and the peak 42. Pa-1 long, so the time t for the next peak 43 to occur Pa-1 Perform +α amount correction.

[0063] Similarly, the line min indicated on the negative side relative to the reference curve typ indicates the relationship when the tire outer diameter decreases relative to the reference due to a decrease in air pressure, etc. That is, when the tire outer diameter decreases, the time difference until the next peak is generated is greater than the time difference t calculated from the time difference t between the peak 43 and the peak 42. Pa-1 is short, so the time t for the next peak 43 to occur is Pa-1 Perform a -β amount correction.

[0064] Therefore, by adjusting the values ​​of α and β, the energization time width is corrected, and omission of peak value measurement is prevented, thereby maintaining measurement accuracy.

[0065] In addition, as the cause of the change in the tire outer diameter, in addition to the air pressure, other parameters such as the load on the tire, the amount of wear on the tire, etc. In the case where the parameter of the change cause is determined in advance by estimation or wireless communication from the upper system, the value can also be used to directly correct the reference curve typ to achieve a shortening of the power-on time width.

[0066] Next, use Fig. 9 An example in which an irregular value is measured is shown.

[0067] Fig. 9The measured waveform is shown when multiple peak values ​​of the strain value are measured. The number of times is set by the count setting unit 208 ( Figure 4 ), and the measured values ​​are extracted by the feature point extraction unit 205. As an example of the extraction method, the measured values ​​have a certain range of deviations, for example, due to the tire 10 stepping on gravel, and the values ​​deviating from the certain range can be determined as irregular values ​​and excluded from the feature points. Here, only feature points with peak values ​​within a preset threshold value are extracted from a plurality of peak values ​​measured a set number of times, and the measured values ​​with irregular values ​​are excluded from the feature points.

[0068] In this way, by excluding the irregular values ​​that do not need to be sent from the feature points in advance, the load of the transmitted data can be reduced, the power supply time to the antenna driving unit 4 can be shortened, and low current consumption can be achieved. In addition, in the road type detection, it is also possible to determine that the abnormal value is a road type such as gravel based on the range of the judgment threshold and send this information, which can achieve low current consumption and distinguish use according to purpose.

[0069] Fig.10 It is a timing chart showing whether or not each module of the physical quantity detection device according to the present embodiment is powered on.

[0070] In the present embodiment, the timing of energization or non-energization of the signal processing unit 20 , the strain detection module 3 , and the antenna driving unit 4 will be described.

[0071] First, the signal processing unit 20 switches to the sleep mode to reduce the current consumption except when the strain detection module 3 is measuring and the antenna driving unit 4 is transmitting data.

[0072] Next, in the strain detection module 3, the occurrence time t of the peak 43 obtained from the time difference t between the initial peak 43 and the peak 42 described above is used. Pa-1 and the occurrence time of peak 42 t Pb-1 Intermittent power supply is used to achieve low current consumption.

[0073] Next, in the antenna driving unit 4, when all the measured data are transmitted, the transmission time becomes longer and the current consumption during the transmission increases. In addition, when the data is transmitted in parallel with the measurement, the current used per unit time increases, and the button battery 5 ( Figure 4 )The power supply voltage supplied by the device may become temporarily unstable.

[0074] Therefore, if Fig.10 As shown, in the physical quantity detection device 2 of this embodiment, the strain detection module 3 measures the strain and the antenna driving unit 4 transmits the measured value data in sequence at different timings. This reduces the current used per unit time and stabilizes the power supply voltage.

[0075] Furthermore, by setting a configuration in which only the value of the feature point extracted by the feature point extraction unit 205 is transmitted after the count setting unit 208 performs a predetermined number of measurements, the power-on time of the antenna driving unit 4 used for communication is shortened, thereby achieving low current consumption. The physical quantity detection device 2 of this embodiment can achieve both low current consumption and long product life by using the above configuration.

[0076] Next, use Fig.11 and Fig.12 An example of the strain sensor 1 in the present embodiment will be described. The strain sensor 1 in the present embodiment is composed of a strain detection module 3 .

[0077] Fig.11 is a top view of the strain detection module 3, Fig.12 yes Fig.11 AA cross-section diagram. Fig.11 As shown, the strain detection module 3 has a strain detection element 3a, a base member 3b, a sealing portion 3c and a wire portion 3d. The strain detection element 3a is a semiconductor that outputs a strain amount corresponding to a change in resistance, for example, a strain sensor chip that is integrated with a control circuit for processing strain detection and is formed into a single chip.

[0078] The strain sensor chip is an IC chip manufactured by a semiconductor process, for example, a rectangular MOSFET sensor chip of about 5 mm × 5 mm in size. In addition, the strain sensor chip is composed of, for example, a semiconductor and a micro-electromechanical system (MEMS) formed by a CMOS process. In addition, if the strain sensor chip is large, it may be damaged when the tire 10 runs over foreign matter, so it is preferably smaller than 5 mm × 5 mm. In addition, the strain detection element 3a is not limited to the strain sensor chip, and a strain gauge may also be used, for example.

[0079] The base member 3b is a member for fixing the strain detection element 3a to the inner circumferential surface of the tire, and is, for example, a thin plate made of metal having a linear expansion coefficient close to that of the semiconductor material (Si, etc.) forming the strain detection element 3a. As a metal having a linear expansion coefficient close to that of the semiconductor material (Si, etc.), for example, 42 alloy (42Alloy: an alloy in which nickel is doped in iron) can be used, and its linear expansion coefficient is about 5ppm / ℃, which is about 1ppm / ℃ different from the linear expansion coefficient of silicon (Si) of about 4ppm / ℃.

[0080] In this way, by using a metal having a linear expansion coefficient close to that of the semiconductor material as the material of the base member 3 b , the strain detection accuracy of the strain detection element 3 a can be improved.

[0081] The base member 3b is not limited to the above metals, and for example, a metal that is resistant to corrosion by sulfur gas generated by tires (stainless steel, aluminum, copper, iron alloy, or base metal plated with gold, nickel, tin, etc.) may be used.

[0082] The base member 3b is a rectangular thin plate in order to transmit the tire strain to the strain detection element 3a with high accuracy. Fig.11 As shown, the end of the base member 3b in the +Z direction (front side) is in an arc shape. In addition, the shape of the base member 3b is not limited to the above shape, and can also be circular, elliptical, or other polygonal. On the surface (+Z side) of the base member 3b, the strain detection element 3a is fixed by an adhesive, such as an epoxy adhesive with high hardness.

[0083] The sealing portion 3c is a resin, such as epoxy resin, applied to the surface of the base member 3b from the welding wire (not shown) that electrically connects the strain sensing element 3a and the wire portion 3d and the strain sensing element 3a. The strain sensing element 3a and the welding wire are sealed by the sealing portion 3c to protect them from the external environment. In addition, the sealing portion 3c is not limited to epoxy resin, and other resins, such as polyurethane resin or silicone resin, may also be used.

[0084] The wire portion 3d is a wire that electrically connects the strain detection element 3a to the circuit, such as a flexible printed circuit (FPC). In addition, the strain detection element 3a is a semiconductor that outputs a strain amount corresponding to a change in resistance, such as a semiconductor strain sensor. As a result, compared with a strain gauge, high sensitivity (e.g., about 25,000 times) can be measured with low power consumption (e.g., about 1 / 1,000).

[0085] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above-mentioned embodiments, and various design changes can be made without departing from the idea and even the main purpose of the present invention recorded in the scope of the claims. For example, the embodiments described are described in detail in order to easily understand the present invention, and are not necessarily limited to having all the described structures. In addition, a part of the structure of a certain embodiment can be replaced by the structure of other embodiments, and the structure of other embodiments can also be added to the structure of a certain embodiment. Furthermore, other structures can be added, deleted, or replaced for a part of the structure of each embodiment. Explanation of symbols

[0086] 1…strain sensor, 2…physical quantity detection device, 3…strain detection module (strain detection unit), 3a…strain detection element, 3b…base member, 3c…sealing unit, 3d…wire unit, 4…antenna driving unit, 5…button battery, 6…DC / DC converter, 10…tire, 20…signal processing unit, 21…power-on timing calculation unit, 22…power-on control unit, 30…road surface, 40…sensor signal waveform, 41…reference level, 42…peak value of positive level, 43…peak value of negative level, 100…vehicle, 101…control unit, 102…receiver, 201…measurement unit, 202…peak value calculation unit, 203…time calculation unit, 204…intermittent power-on control unit, 205…feature point extraction unit, 206…power-on timer setting unit, 207…correction parameter setting unit, 208…count setting unit.

Claims

1. A physical quantity detection device installed in a tire to detect a physical quantity of the tire state, characterized in that: include: a strain detection unit configured to detect the strain of the tire; as well as a signal processing unit that processes a detection signal detected by the strain detection unit, The signal processing unit performs the following processing: The step-in peak value and the intermediate peak value are calculated, wherein the step-in peak value is the step-in peak value of the strain generated toward either the compression or extension side at the step-in time when the strain detection area of ​​the tire contacts the road surface due to the rotation of the tire, and the intermediate peak value is the intermediate peak value of the strain generated toward either the compression or extension side at the intermediate time between the step-in time and the push-off time when the strain detection area of ​​the tire leaves the road surface, The cycle of the stepping peak and the intermediate peak occurring next time and thereafter is calculated based on the time difference from the stepping peak to the intermediate peak or the slope of the change in the strain, and the strain detection unit is energized in accordance with the cycle.

2. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit performs the following processing: The strain detection unit is energized throughout the entire period from the initial stepping peak to the intermediate peak. After the next time, the strain detection unit is energized at the timing when the stepping peak value and the intermediate peak value are generated.

3. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit performs the following processing: The number of times the stepping peak value and the intermediate peak value are measured is set. Extracting feature points having peak values ​​within a preset threshold value from a plurality of peak values ​​measured only the set number of times, The peak value data of the characteristic point is transmitted to the outside.

4. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit calculates the period using at least two of the stepping peak values.

5. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit ends energization of the strain detection unit at a time when the intermediate peak value is extracted from the stepping peak value for the first time.

6. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit uses the elapsed time from the first energization or the number of times the differential value of the strain value changes from positive to negative or from negative to positive as the termination condition of the first energization.

7. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit calculates the period using a period conversion coefficient that is a unique value determined by an outer diameter of the tire.

8. The physical quantity detection device according to claim 1, characterized in that: The signal processing unit corrects a duration of energization of the energization using at least one of an air pressure of the tire, a load on the tire, and an amount of wear of the tire.

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