Physical quantity detection device

Abstract

Provided is a physical quantity detection device capable of achieving low current consumption through control of an energization method even during a ground-contact period. A physical quantity detection device 2 according to the present invention is characterized by: extracting a stepping-in peak value 43 of strain generated at stepping-in time Pa when a strain detection area 10a of a tire 10 comes into ground-contact with a road surface 30, and an intermediate time-point peak value 42 of strain generated at an intermediate time point Pb between the stepping-in time and kicking-out time when the strain detection area of the tire moves away from the road surface; calculating the cycle of subsequent generations of stepping-in peak values and intermediate time peak values from a time difference t between the stepping-in peak value and the intermediate time-point peak value or inclination of a strain change; and energizing a strain detection unit 3 in accordance with the cycle.

Description

[Technical Field]

[0001] The present invention relates to a physical quantity detection device that detects a physical quantity of a tire condition. [Background technology]

[0002] When a device for detecting a physical quantity related to the state of a tire (physical quantity detection device) is attached to a tire, data is exchanged between the device and a vehicle control device installed on the vehicle via wireless communication. Because the tire is rotatably supported on the vehicle, it is difficult to supply power from the vehicle to the physical quantity detection device. Therefore, a power source must be provided within the physical quantity detection device, and for example, a coin battery or the like may be used as the power source within the physical quantity detection device. In other words, it has been necessary to drive the physical quantity detection device using a limited power source such as a coin battery.

[0003] On the other hand, because physical quantity detection devices are installed inside tires, they cannot be easily replaced. For this reason, it is important to reduce the current consumption of physical quantity detection devices, and it is particularly necessary to reduce the current consumption during operation of microcomputers (MPUs) and antenna drive units used in wireless communication, which consume large amounts of current among physical quantity detection devices.

[0004] Patent Document 1 discloses a technique for transmitting necessary tire information to the vehicle side with low current consumption by transmitting only information on the ground-contact side area or only information on the non-ground-contact side area to the vehicle side. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6317999 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, two peak positions of the sensor measurement value, which correspond to the leading edge and trailing edge, are calculated, the distance between these two peak positions is defined as the tire contact side region, and tire information acquired by the sensor is transmitted to the vehicle using this contact side region as the transmission section. Therefore, the sensor must receive current from the power source at least for the time from when the sensor-located portion of the tire comes into contact with the road surface until it separates, which increases current consumption. In other words, because current consumption increases even in areas where information is not needed, there is a risk that the effect of reducing current consumption will not be fully realized.

[0007] An object of the present invention is to provide a physical quantity detection device that does not require time for a sensor mounted on a tire to separate from the road surface, and that reduces current consumption by controlling the current supply method even during the contact period when the sensor-mounted portion of the tire is in contact with the road surface. [Means for solving the problem]

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

[0009] The physical quantity detection device of the present invention comprises: A physical quantity detection device that is mounted in a tire and detects a physical quantity of a state of the tire, a strain detection unit that detects strain in the tire; a signal processing unit that processes a detection signal detected by the strain detection unit, The signal processing unit extracting a peak value of strain generated on either the compressive or tensile side at the time of stepping on when the strain detection area of ​​the tire comes into contact with the road surface due to rotation of the tire, and an intermediate peak value of strain generated on the other compressive or tensile side at an intermediate time between the time of stepping on and the time of kicking off when the strain detection area of ​​the tire leaves the road surface; A period in which the next and subsequent peak values ​​of the depression and intermediate peak values ​​occur is calculated from the time difference from the depression peak value to the intermediate peak value or the slope of the change in the strain, and current is supplied to the strain detection unit in accordance with the period. It is characterized by: [Effects of the Invention]

[0010] According to the present invention, the time for which current is passed through the strain sensor can be made shorter than the time required from the onset, when the strain detection area of ​​the tire comes into contact with the road surface due to tire rotation, to the kick-off, when the area leaves the road surface, and a physical quantity detection device can be provided that can achieve low current consumption during the contact period from the onset to the kick-off.

[0011] Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. In addition, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a schematic configuration of a vehicle equipped with a strain sensor according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing a state in which a tire having a strain sensor rolls on a road surface as a vehicle moves forward. [Figure 3] FIG. 4 is an explanatory diagram showing a sensor signal waveform of a strain sensor according to the rotation state of a tire. [Figure 4] FIG. 2 is a diagram illustrating the hardware configuration of the physical quantity detection device according to the embodiment. [Figure 5] FIG. 2 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] 10 is an example of a flowchart illustrating processing by a signal processing unit according to the embodiment. [Figure 7] 4 is a graph showing an example of waveform data measured by the physical quantity detection device according to the embodiment and whether or not current is applied at that time. [Figure 8]FIG. 4 is a schematic diagram showing an example of a correction unit for a current-carrying time width at a leading edge peak, which is processed by the physical quantity detection device according to the embodiment. [Figure 9] 10A and 10B are diagrams showing the measured waveforms of strain values ​​including irregular values ​​of the physical quantity detection device according to the embodiment; [Figure 10] 4 is a timing chart showing whether or not current is applied to each block of the physical quantity detection device according to the present embodiment. [Figure 11] FIG. 2 is a plan view of the strain detection module. [Figure 12] Cross section AA of Figure 11. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, with reference to FIGS. In all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations will be omitted. In addition, the cross-sectional views, front views, and side views are each specified by mutually orthogonal XYZ axes, with +X being "right," -X being "left," +Y being "up," -Y being "down," +Z being "front," and -Z being "rear."

[0014] FIG. 1 is a block diagram showing a schematic configuration of a vehicle equipped with a strain sensor according to this embodiment. The strain sensor 1 of this embodiment is applied to a vehicle 100 having, for example, an ADAS (Advanced Driver-Assistance Systems) or AD (Autonomous Driving) function. As shown in FIG. 1 , the vehicle 100 is equipped with four tires 10, a control unit 101, and a receiver 102. Each tire 10 is equipped with a strain sensor 1. The vehicle 100 is not limited to a four-wheeled vehicle, but may also be a two-wheeled vehicle or a vehicle equipped with multiple tires, such as six or eight wheels, such as a truck or bus. Furthermore, although this embodiment shows a configuration in which one strain sensor 1 is attached to each of all tires 10, a configuration in which one strain sensor 1 is attached to only one of the tires 10 may also be used.

[0015] The control unit 101 is configured with an ECU (Electronic Control Unit) and has hardware including a CPU (Central Processing Unit), memories such as ROM and RAM, and an input / output interface. The memory stores executable software programs for performing various arithmetic processing. The receiver 102 receives signals detected by the multiple strain sensors 1 via wireless communication and supplies them to the control unit 101 as output signals from each strain sensor 1. The control unit 101 performs various vehicle controls using the output signals from each strain sensor 1.

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

[0017] The strain sensor 1 is mounted, for example, on the inside of a vehicle tire 10 and detects strain in the tire 10. The strain sensor 1 is fixed to the inner circumferential surface of the tread portion of the tire 10 (hereinafter referred to as the tire inner circumferential surface) and detects deformation in the compressive and tensile directions that occurs on the tire inner circumferential surface as strain. In this embodiment, the tire 10 is mounted on a wheel (not shown) and is a tubeless tire in which high-pressure gas is filled in an enclosed space formed between the wheel and the tire 10. However, the tire may also be a tubed tire in which an air tube is disposed in the enclosed space. One strain sensor 1 is disposed in each tire, but this is not limited thereto, and multiple strain sensors may also be disposed at predetermined intervals in the circumferential direction of the tire inner circumferential surface.

[0018] 2, the road surface 30 is flat, and the portion of the tire 10 where the strain sensor 1 is located (strain detection area 10a: see FIG. 3) is in contact with the road surface 30. In this situation, the strain sensor 1 detects the amount of strain corresponding to the deformation of the tire 10.

[0019] Next, a sensor signal waveform 40 when one strain sensor 1 is used will be described with reference to FIG.

[0020] Figures 3(1) to (4) are diagrams showing the rotational state of the tire, and Figure 3(5) is an explanatory diagram showing the sensor signal waveform of the strain sensor according to the rotational state of the tire. Figure 3(1) shows a non-grounded state in which the strain detection area of ​​the tire is separated from the road surface. Figures 3(2) to 3(4) show a grounded state in which the strain detection area of ​​the tire is in contact with the road surface. Figure 3(2) shows the state at the time of stepping on when the strain detection area begins to contact the road surface, and Figure 3(4) shows the state at the time of taking off when the strain detection area leaves the road surface. Finally, Figure 3(3) shows the state at an intermediate point between stepping on and taking off.

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

[0022] The strain sensor 1 maintains the reference level (steady-state value) 41 of the sensor signal waveform 40 when the strain detection area 10a, which can detect strain in the tire 10, is in a non-contact period 52 in which the tire is not in contact with the road surface 30, as shown in Figure 3 (1).

[0023] When the strain detection region 10a of the tire 10 is in contact with the road surface 30 during a contact period 51, and further when the tire is at an intermediate point between the onset and the take-off as shown in Figure 3 (3), an intermediate point peak value 42, which is the peak value (maximum value) of the positive level of the sensor signal waveform 40, is output. Also, when the strain detection region 10a of the tire 10 is on the onset when it makes contact with the road surface 30 and when it is off the take-off, an onset peak value 43 and a take-off peak value 44, which are the peak values ​​of the negative level of the sensor signal waveform 40, are output.

[0024] As described above, the sensor signal waveform 40 has two sensor displacement points (leading-in peak value 43, trailing-out peak value 44) at the instants (leading-in and trailing-out) when the strain detection region 10a of the tire 10 contacts or separates from the road surface 30, and one sensor displacement point (intermediate-point peak value 42) during a contact period 51 during which the strain detection region 10a of the tire 10 contacts the road surface 30. The time 53 from the leading-in time to the intermediate point is approximately half the length of the contact period 51. The sensor signal waveform 40 thus detected changes depending on various physical quantities (load, air pressure, speed, temperature, etc.).

[0025] In this embodiment, the moment when the strain detection region 10a of the tire 10 comes into contact with or separates from the road surface 30 is defined as negative (compression), and the intermediate state when the strain detection region 10a of the tire 10 is in contact with the road surface 30 is defined as positive (tension), but the same can be considered when the positive and negative are reversed depending on the mounting orientation of the strain sensor 1 with respect to the inner circumferential surface of the tire. In this way, the strain sensor 1 is mounted on the inner circumferential surface of the tire 10 and measures the amount of strain corresponding to the deformation of the tire 10.

[0026] FIG. 4 is a block diagram showing the hardware configuration of the physical quantity detection device according to this embodiment. The strain sensor 1 includes a physical quantity detection device 2 that detects the physical quantity of the tire using a sensor signal that is the amount of strain. The physical quantity detection device 2 includes a coin 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 coin battery 5 via the DC / DC converter 6, and supplies the voltage to the strain detection module 3 and the antenna driver.

[0027] The voltage value of the coin battery 5 changes depending on temperature conditions, etc. The DC / DC converter 6 is provided to stabilize the voltage value supplied from the coin battery 5 to the MPU 20 and strain detection module 3. The MPU 20 and strain detection module 3, and the MPU 20 and antenna driver 4 are electrically connected. The MPU 20 uses a semiconductor switch or the like to turn on and off the power to the strain detection module 3 and antenna driver 4, thereby achieving low current consumption. The MPU 20 has a sleep function, and by entering sleep mode except during startup, it can stop the operation of unnecessary clock circuits, etc., thereby achieving low current consumption.

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

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

[0030] In response to a periodically generated start command, the signal processing unit 20 measures the strain value by performing serial communication with the strain detection module 3 or by reading the analog voltage within a specified time period preset in the energization timer setting unit 206. The measured strain value is transmitted from the measurement unit 201 to the energization timing calculation unit 21 together with information on the time at which the measurement was made.

[0031] The energization timing calculation unit 21 has a peak calculation unit 202 and a time calculation unit 203. The peak calculation unit 202 calculates a step-on peak value of strain generated on either the compressive or tensile side at the step-on time when the strain detection region 10a of the tire 10 contacts the road surface 30 due to the rotation of the tire 10, and an intermediate time peak value of strain generated on the other compressive or tensile side at an intermediate time between the step-on time and the kick-off time when the strain detection region 10a of the tire 10 separates from the road surface 30.

[0032] In this embodiment, the peak calculation unit 202 calculates an intermediate peak value 42 at the positive level (compression side) of the sensor signal waveform 40, and a leading peak value 43 and trailing peak value 44 at the negative level (tension side). Then, the peak calculation unit 202 extracts the time tPa at which the leading peak value 43 is measured and the time tPb at which the intermediate peak value 42 is measured. The time calculation unit 203 calculates the time difference t between the initial leading peak value 43 and the intermediate peak value 42 calculated by the peak calculation unit 202, and calculates the time t until the next leading peak value 43 occurs after one rotation of the tire 10. Pa-1 and the time to the intermediate peak 42 t Pb-1 Calculate.

[0033] When the tire 10 rotates at a constant rotational speed, the time difference between the leading edge peak value 43 and the intermediate point peak value 42 is proportional to the time required for one rotation of the tire 10. Therefore, the time difference t between the first leading edge peak value 43 and the intermediate point peak value 42 can be used to calculate the timing at which the next leading edge peak value 43 and the intermediate point peak value 42 will occur.

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

[0035] Subsequently, the power supply control unit 22 controls power supply to the strain detection module 3 and the antenna driving unit 4. The power supply 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 for energizing at the depression peak value 43 and the intermediate point peak value 42 that occur after one rotation of the tire, as 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 count setting unit 208 determines that the peak value has been measured the preset number of times, the feature point extraction unit 205 extracts a feature point having a peak value within a preset threshold value from the multiple measured values, and provides data on the peak value of the feature point to the antenna driving unit 4, which then outputs the data to the outside.

[0038] The antenna driving unit 4 transmits the feature point data supplied from the feature point extraction unit 205 to the receiver 102 of the vehicle 100 via wireless communication, and provides the data to the control unit 101. In this way, the communication time in the antenna driving unit 4 can be shortened, and further current consumption can be reduced. Note that the transmission of the feature point data may be performed every time the measurement unit 201 measures the peak value of the distortion value.

[0039] FIG. 6 is an example of a flowchart showing the processing of the signal processing unit according to this embodiment.

[0040] The processing performed by the signal processing unit 20 will be explained using the example of the strain detection module 3 mounted in a direction such that the sensor signal waveform 40 of the strain sensor 1 moves in accordance with the rotational state of the tire 10, as shown in Figures 3(1) to (5), i.e., the moment when the strain detection area 10a of the tire 10 touches or separates from the road surface 30 (when stepping on or pushing off) is considered negative (compression), and the state when the strain detection area 10a of the tire 10 is in contact with the road surface 30 (intermediate point) is considered positive (tension).

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

[0042] On the other hand, if the measured value is equal to or greater than the reference level 41 (Yes in S103), it is not considered to be a normal measurement target, and a determination is made as to whether or not the predetermined time set in the energization timer setting 1 has elapsed. If it is less than the predetermined time, the comparison process of step S103 is performed again. If it is equal to or greater than the predetermined time, it is determined that the vehicle is not in stable driving, and the process proceeds to the next step.

[0043] In the peak extraction process S106, the step-on peak value of the strain that occurs on either the compression or tension side when the strain detection region 10a of the tire 10 contacts the road surface 30 due to the rotation of the tire 10, and the intermediate peak value of the strain that occurs on the other compression or tension side at an intermediate point between the step-on time and the kick-off time when the strain detection region 10a of the tire 10 leaves the road surface 30 are extracted.

[0044] In the peak extraction process S106, it is determined whether the positive level peak value 42 and the negative level peak value 43 are both aligned. For the positive level peak value 42, for example, the measured value at the time when the measured value changes from an increase to a decrease, or the measured value at the point where the time derivative during measurement detects a change from positive to negative, may be used. Similarly, for the negative level peak value 43, for example, the measured value at the time when the measured value changes from a decrease to an increase, or the measured value at the point where the time derivative during measurement detects a change from negative to positive, may be used.

[0045] When both the positive level peak value 42 and the negative level peak value 43 are aligned, the energization timing value is set (S107). Then, the process transitions to the energization control unit 22, where the correction parameter setting unit 207 sets the correction parameter (S108). Then, based on the corrected energization timing value, intermittent energization is performed to the strain detection module 3, and the strain value is intermittently measured (S109), i.e., the strain value is measured only when the current is applied.

[0046] If it is determined in step S106 that both the positive level peak value 42 and the negative level peak value 43 are not aligned (No in S106), it is determined that the vehicle is not running in a stable state, and the process moves to the next step. In this way, if stable running does not begin within a certain period of time, excluding times when the vehicle is stopped or when the vehicle stops and starts during measurement, or if both the positive level peak value 42 and the negative level peak value 43 are not aligned, it is determined that the vehicle is not running in a stable state, and unnecessary current-carrying time can be reduced, thereby achieving low current consumption.

[0047] Peak values ​​are measured at pinpoints by the intermittent measurement in step S109, and when the number of measured peak values ​​becomes equal to or 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 a feature point from the multiple measurement values ​​(peak values) (S111), and data on the feature point is transmitted from the antenna driving unit 4 to the receiver 102 (S112).

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

[0049] Next, an example of reducing current consumption during startup will be described with reference to FIG.

[0050] FIG. 7 is a graph showing an example of waveform data measured by the physical quantity detection device according to this embodiment and whether or not current is applied at that time.

[0051] In this embodiment, the horizontal axis represents time and the vertical axis represents the amount of strain. The solid line represents the strain detection module 3 in a conducting state, and the dotted line represents the strain detection module 3 in a non-conducting state. As shown in Fig. 7, the strain value and time are measured by the measurement unit 201 (Fig. 5) for the first time after startup. Next, the initial measurement value is compared with the reference level 41 (see Fig. 3(5)) (S103 in Fig. 6). Because the initial measurement value is less than the reference level 41, normal measurement is performed to continuously measure the change in the strain value from the time the initial measurement value was measured to the intermediate peak value 42 (S105 in Fig. 6).

[0052] Thereafter, the energization timing, which is the time of the next positive-level intermediate peak value 42 (Pb-1 in FIG. 7) and negative-level depression peak value 43 (Pa-1 in FIG. 7), is calculated by energization timing calculation unit 21 (FIG. 5) from the time difference t between positive-level intermediate peak value 42 (Pb in FIG. 7) and negative-level depression peak value 43 (Pa-1 in FIG. 7). Thereafter, the energization timing is set so that energization is performed at intermediate peak value 42 and depression peak value 43 repeatedly for n counts set by count setting unit 208 (FIG. 5), which sets the repetition for the required n number of rotations. Energization is performed in accordance with the energization timing, and intermittent measurement of the strain value is performed.

[0053] Since the time difference t between the depression peak value 43 and the intermediate point peak value 42 is proportional to the time it takes for the tire 10 to rotate once (for example, the time between Pb and Pb in Figure 7), the time of the next peak to occur can be calculated using the following formula using a period conversion coefficient (proportionality constant).

[0054] t Pa-1 = Period conversion factor × t t Pb-1 = t + t Pa-1 The period conversion factor is a specific value determined from the outer diameter of the tire.

[0055] The peak time t Pa-1 , t Pb-1Intermittent measurement is achieved by calculating the value of (a) in the energization timing calculation unit 21 (Fig. 5) and setting it in the energization control unit 22 (Fig. 5) to control the energization of the strain detection module 3. When the strain detection module 3 is not energized, the signal processing unit 20 is in sleep mode, but when returning from sleep mode, it is necessary to take into consideration the recovery time so that the energization control to the strain detection module 3 is in time. In other words, Fig. 7 shows a waveform in which energization begins before the peak appears.

[0056] In this waveform, the energization control unit 22 deenergizes the positive-level peak value 42, for example, when the measured value changes from an increase to a decrease, or when the time derivative of the measured value changes to a negative value. Similarly, the energization control unit 22 deenergizes the negative-level peak value 43, for example, when the measured value changes from a decrease to an increase, or when the time derivative of the measured value changes to a positive value. This suppresses energization in the section that is no longer needed after the peak is passed, thereby achieving further current reduction.

[0057] Electricity is supplied to the strain detection module 3 from the first depression peak value 43 (Pa in FIG. 7) to the first intermediate peak value 42 (Pb in FIG. 7) and at the timings at which the next and subsequent depression peak values ​​43 and intermediate peak values ​​42 occur. The signal processing unit 20 is in sleep mode while no electricity is supplied to the strain detection module 3. This makes it possible to reduce the current consumption of the physical quantity detection device 2. The energization timing calculation unit 21 may use at least two depression peak values ​​to calculate the cycles at which the subsequent depression peak values ​​43 and intermediate peak values ​​42 occur.

[0058] Next, the time width for controlling the energization will be described with reference to FIG.

[0059] FIG. 8 shows the time t Pa-1 10 is a schematic diagram showing an example of a means for correcting a current-carrying time width in FIG.

[0060] In Fig. 8, the horizontal axis indicates the time difference t between the positive level peak value 42 (peak value Pb in Fig. 7) and the negative level peak value 43 (peak value Pa in Fig. 7), and the vertical axis indicates the time t of the next peak value Pa-1. Pa-1 In this graph, as the vehicle speed increases, the time difference t between the peak value 42 and the peak value 43 decreases, and the time t of the next peak value Pa-1 on the vertical axis decreases. Pa-1 The thick line typ in the center of the graph in Figure 8 shows the relationship between the time difference t and the set time t Pa-1 This is a reference graph.

[0061] Assuming that the tire outer diameter fluctuates, if the outer diameter becomes smaller, the time until the next peak value becomes shorter, and if the outer diameter becomes larger, the time until the next peak value becomes longer. Therefore, the time t Pa-1 There was a concern that peak measurements would be missed when power was turned on, but this can be resolved by the following method.

[0062] Specifically, as a correction of the energization time width, for example, the line max shown on the positive side of the reference graph typ indicates the relationship when the tire outer diameter becomes larger than the reference due to an increase in air pressure, etc. In other words, when the tire outer diameter becomes larger, the time difference until the next peak value occurs is t obtained from the time difference t between peak value 43 and peak value 42. Pa-1 Therefore, the time t Pa-1 A +α correction is made to the above.

[0063] Similarly, the line min shown on the negative side of the reference graph typ indicates the relationship when the tire outer diameter becomes smaller than the reference due to a decrease in air pressure, etc. In other words, when the tire outer diameter becomes smaller, the time difference until the next peak value occurs is t, which is calculated from the time difference t between peak value 43 and peak value 42. Pa-1 Therefore, the time t Pa-1 A correction of -β is made to the above.

[0064] Therefore, by adjusting the values ​​of α and β, the energization time width can be corrected, and the measurement accuracy can be maintained by preventing the peak value from being missed.

[0065] In addition to air pressure, other factors that cause tire outer diameter fluctuations include parameters such as the load on the tire and the amount of tire wear. If the parameters of the fluctuation factors are known in advance through estimation or wireless communication from a higher-level system, those values ​​can be used to directly correct the reference graph typ and shorten the energization time width.

[0066] Next, an example in which an irregular value is measured will be described with reference to FIG.

[0067] 9 shows a measured waveform when peak values ​​of strain values ​​are measured multiple times. The number of times is set by the count setting unit 208 (FIG. 4), and the measured values ​​are extracted by the feature point extraction unit 205. As an example of an extraction method, the measured values ​​have a certain range of variation, and values ​​that fall outside this certain range, for example, due to the tire 10 running over gravel, can be determined to be irregular values ​​and excluded from the feature points. Here, only feature points having peak values ​​within a preset threshold are extracted from the multiple peak values ​​measured a set number of times, and measured values ​​having irregular values ​​are excluded from the feature points.

[0068] In this way, irregular values ​​that do not actually need to be transmitted are excluded from the feature points in advance, and the load of transmitted data is reduced, thereby shortening the time for which power is supplied to the antenna driver 4 and realizing low current consumption. Furthermore, in road surface type detection, a configuration may be adopted in which an abnormal value is determined to be a road surface type such as gravel from the range of the determination threshold and this information is transmitted, allowing for use depending on the purpose while realizing low current consumption.

[0069] FIG. 10 is a timing chart showing whether or not current is applied to each block of the physical quantity detection device according to this embodiment.

[0070] In this embodiment, the timing of energizing 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 is put into a sleep mode except when the strain detection module 3 is performing measurements or when the antenna driving unit 4 is transmitting data, thereby realizing low current consumption.

[0072] Next, the strain detection module 3 calculates the occurrence time t of the peak value 43, which is calculated from the time difference t between the first peak value 43 and the peak value 42, as explained above. Pa-1 and the occurrence time of peak value 42 t Pb-1 Low current consumption is achieved by intermittently energizing the device using this technology.

[0073] Next, if the antenna driver 4 transmits all of the measured data, the transmission time will be longer, increasing the current consumption during that time. Also, if data transmission is performed in parallel with measurement, the current consumed per unit time will increase, which could cause temporary instability in the power supply voltage supplied by the coin battery 5 (Figure 4).

[0074] 10, in the physical quantity detection device 2 of this embodiment, the strain measurement by the strain detection module 3 and the data transmission of the measurement value by the antenna driver 4 are performed at separate times. This reduces the current used per unit time and stabilizes the power supply voltage.

[0075] Furthermore, by configuring the count setting unit 208 to transmit only the value of the feature point extracted by the feature point extraction unit 205 after measuring a specified number of times, the time for which power is supplied to the antenna driving unit 4 used during communication is shortened, thereby realizing low current consumption. By using the above configuration, the physical quantity detection device 2 of this embodiment can achieve a long product life due to low current consumption.

[0076] Next, an example of the strain sensor 1 in this embodiment will be described with reference to Figures 11 and 12. The strain sensor 1 in this embodiment is configured by a strain detection module 3.

[0077] Fig. 11 is a plan view of the strain detection module 3, and Fig. 12 is a cross-sectional view taken along line AA in Fig. 11. As shown in Fig. 11, the strain detection module 3 includes a strain detection element 3a, a base member 3b, a sealing portion 3c, and an electric wire portion 3d. The strain detection element 3a is a semiconductor that outputs the amount of strain according to changes in electrical resistance, and is, for example, a strain sensor chip integrated with a control circuit that processes strain detection.

[0078] The strain sensor chip is an IC chip manufactured by a semiconductor process, for example, a rectangular MOSFET-type sensor chip measuring approximately 5 mm x 5 mm. The strain sensor chip is composed of, for example, a semiconductor formed by a CMOS process and a microelectromechanical system (MEMS). Note that a large strain sensor chip may be damaged when the tire 10 runs over a foreign object, so it is preferable that the strain sensor chip be smaller than 5 mm x 5 mm. Note that the strain detection element 3a is not limited to a strain sensor chip, and for example, a strain gauge may also be used.

[0079] The base member 3b is a member that fixes the strain detection element 3a to the inner circumferential surface of the tire, and is, for example, a thin metal plate with a linear expansion coefficient close to that of the semiconductor material (such as Si) that forms the strain detection element 3a. An example of a metal with a linear expansion coefficient close to that of the semiconductor material (such as Si) is 42 Alloy (42 Alloy: an alloy of iron and nickel), which has a linear expansion coefficient of about 5 ppm / °C, which is about 1 ppm / °C different from that of silicon (Si), which is about 4 ppm / °C.

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

[0081] The base member 3b is not limited to the above metals. For example, a metal that is corrosion-resistant to sulfur gas generated from tires (stainless steel, aluminum, copper, iron-based alloys, or base metals plated with gold, nickel, tin, or the like) may be used.

[0082] The base member 3b is a thin rectangular plate to accurately transmit tire strain to the strain detection element 3a. The end of the base member 3b in the +Z direction (front side) is arc-shaped, as shown in FIG. 11. The shape of the base member 3b is not limited to the above, and may be circular, elliptical, or another polygonal shape. The strain detection element 3a is fixed to the surface (+Z side) of the base member 3b with an adhesive, such as a high-hardness epoxy adhesive.

[0083] The sealing portion 3c is a resin, such as epoxy resin, applied to the surface of the base member 3b from above the strain detection element 3a and a bonding wire (not shown) that electrically connects the strain detection element 3a and the electric wire portion 3d. The sealing portion 3c seals the strain detection element 3a and the bonding wire and protects them from the external environment. Note that the sealing portion 3c is not limited to epoxy resin, and other resins, such as urethane resin or silicone resin, may also be used.

[0084] The electric wire portion 3d is an electric wire that electrically connects the strain detection element 3a to a circuit, such as a flexible printed circuit (FPC). The strain detection element 3a is a semiconductor, such as a semiconductor strain sensor, that outputs the amount of strain according to changes in resistance. This allows for measurements with lower power consumption (e.g., about 1 / 1,000) and higher sensitivity (e.g., about 25,000 times) than strain gauges.

[0085] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit and scope of the present invention as set forth in the claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0086] REFERENCE SIGNS LIST 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 electrical wiring unit, 4 antenna drive unit, 5 coin battery, 6 DC / DC converter, 10 tire, 20 signal processing unit, 21 current application timing calculation unit, 22 current application control unit, 30 road surface, 40 sensor signal wave Shape, 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 calculation unit, 203... Time calculation unit, 204... Intermittent power control unit, 205... Feature point extraction unit, 206... Power timer setting unit, 207... Correction parameter setting unit, 208... Count setting unit

Claims

1. A physical quantity detection device that is mounted in a tire and detects a physical quantity of a state of the tire, a strain detection unit that detects strain in the tire; a signal processing unit that processes a detection signal detected by the strain detection unit, The signal processing unit Calculating a peak value of strain generated on either the compressive or tensile side at the time of stepping on when the strain detection area of ​​the tire comes into contact with the road surface due to rotation of the tire, and an intermediate peak value of strain generated on the other compressive or tensile side at an intermediate time between the time of stepping on and the time of kicking off when the strain detection area of ​​the tire leaves the road surface, A period in which the next and subsequent peak values ​​of the depression and intermediate peak values ​​occur is calculated from the time difference between the depression peak value and the intermediate peak value, and current is supplied to the strain detection unit in accordance with the period. A physical quantity detection device characterized by:

2. The signal processing unit energizing the strain detection unit over a period from the initial depression peak value to the intermediate peak value; From the next time onwards, the strain detector is energized at the timing when the depression peak value and the intermediate peak value occur.

2. The physical quantity detection device according to claim 1.

3. The signal processing unit The number of times the depression peak value and the intermediate peak value are measured is set, extracting feature points having peak values ​​within a preset threshold value from the plurality of peak values ​​measured the set number of times; 2. The physical quantity detection device according to claim 1, wherein data on the peak value of the characteristic point is transmitted to an external device.

4. The signal processing unit 2. The physical quantity detection device according to claim 1, wherein the period is calculated using at least two of the peak values ​​of the depression.

5. The signal processing unit 2. The physical quantity detection device according to claim 1, wherein the power supply to the strain detection unit is stopped at a time when the intermediate peak value is extracted from the depression peak value for the first time.

6. The signal processing unit The end condition for the first current application is the elapsed time from the start of the first current application, or the number of times the differential value of the strain value changes from positive to negative or from negative to positive.

2. The physical quantity detection device according to claim 1.

7. The signal processing unit The period is calculated using a period conversion coefficient that is a specific value determined from the outer diameter of the tire.

2. The physical quantity detection device according to claim 1.

8. The signal processing unit 2. The physical quantity detection device according to claim 1, wherein the energization time width of the energization is corrected using at least one of the air pressure of the tire, the load on the tire, and the amount of wear of the tire.

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