Physical quantity detection device

Abstract

The present application aims at reducing the influence of physical quantities other than the deformation of the tire on the measurement results of the strain sensor, and improving the measurement accuracy of the strain sensor. The deformation amount detection device of the present application uses data describing the relationship between the actually measured deformation amount, the tire air pressure, the vehicle speed, the tire temperature, and the tire load, to calculate an estimated value of the load applied to the tire (see FIG. 6).

Description

Technical Field

[0001] This invention relates to a physical quantity detection device for detecting physical quantities acting on a tire. Background Technology

[0002] In recent years, the development of tire sensor technology has flourished in pursuit of autonomous driving. This technology monitors road surface slippage and the load applied to the tires based on information obtained from the tires to provide safer driving conditions. This aims to prevent tire failures such as blowouts due to overload and rollovers caused by load imbalance by providing safer driving conditions. To build such a safety control system, high-precision detection of physical quantities such as load and tire pressure detected by the tires is required. For example, in a system that monitors the load balance of the four wheels, the goal is to prevent accidents such as rollovers caused by uneven loads, as seen in trucks. For instance, when driving on a curve with a 100kg load imbalance on all four wheels, a rollover is possible, requiring the measurement of the load on all four wheels with an accuracy of, for example, less than 10%.

[0003] Tire strain sensors detect tire strain and deformation, enabling the detection of loads and wear on the tire. This can potentially lead to improved driving safety by preventing vehicle malfunctions and monitoring driving / road conditions.

[0004] Strain sensors sometimes detect physical quantities other than deformation (e.g., vehicle speed, temperature, air pressure, load, etc.). Therefore, the detection signal representing the deformation detected by the strain sensor may contain components arising from these physical quantities. Because of these components, the accuracy of deformation detection decreases.

[0005] Patent Document 1 described below discloses a technology related to strain sensors. This document addresses the technical problem of "providing a method and system capable of estimating the load applied to a vehicle's tires," and describes "a system and method for estimating the load applied to a vehicle's tires, comprising: a tire pressure measuring sensor mounted on the tire to measure the tire's air pressure level; and one or more piezoelectric film deformation measuring sensors mounted on the tire sidewall. The deformation measuring sensors generate a deformation signal of the tire footprint having a signal power level representing the deformation level of the sidewall near the footprint contact surface. This enables the generation and storage of a signal power-to-load mapping, corrected for tire pressure and relating a specified range of load levels to the signal power level, in a manner that determines the load level from the signal power level based on a corrected reference of tire pressure." (See abstract).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2014-054978 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] In the technology described in Patent Document 1, since changes in tire pressure cause changes in the signal amplitude of the load sensor, the signal power level of the load sensor is corrected using the tire pressure measured by the tire pressure measuring sensor. However, the detection signal of the load sensor may also contain components caused by physical quantities other than tire pressure. Therefore, it is believed that the technology described in this document has room for improvement in the detection accuracy of the load sensor.

[0011] The present invention was made in view of the aforementioned technical problems, and its object is to reduce the influence of physical quantities other than tire deformation on the measurement results of strain sensors and improve the measurement accuracy of strain sensors.

[0012] Technical means for solving problems

[0013] The deformation detection device of the present invention uses data describing the relationship between measured deformation, tire pressure, vehicle speed, tire temperature and tire load to calculate the estimated value of the load applied to the tire.

[0014] The effects of the invention

[0015] The deformation (strain) detection device according to the present invention can reduce the influence of physical quantities other than tire deformation on the measurement results of strain sensors, thereby improving the measurement accuracy of strain sensors. Attached Figure Description

[0016] Figure 1 This is a block diagram showing the structure of the physical quantity detection device 1 according to Embodiment 1.

[0017] Figure 2 This is a flowchart illustrating the sequence (order) of the calculation of the load acting on the tire by the arithmetic unit 15.

[0018] Figure 3A This is an example of data obtained from the S201 arithmetic unit 15.

[0019] Figure 3B It represents the data of changes in the deformation measurement signal when the tire pressure changes at a reference vehicle speed, reference load, and reference temperature.

[0020] Figure 4 This is an example of data generated in the S202 arithmetic unit 15.

[0021] Figure 5 This is an example of data obtained from the S203 arithmetic unit 15.

[0022] Figure 6 This is a schematic diagram illustrating the order in which the load is calculated in the S204 arithmetic unit 15.

[0023] Figure 7 This is a block diagram showing the structure of the physical quantity detection device 1 in Embodiment 2.

[0024] Figure 8 This is a block diagram showing the structure of the physical quantity detection device 1 in Embodiment 3.

[0025] Figure 9 This is a block diagram showing the structure of the physical quantity detection device 1 in Embodiment 4.

[0026] Figure 10 This is a block diagram showing the structure of the physical quantity detection device 1 in Embodiment 5.

[0027] Figure 11 This indicates the relationship between the deformation signal and the tire condition.

[0028] Figure 12 This represents a representative deformed signal waveform.

[0029] Figure 13 This indicates the error generation mechanism based on parameter variations.

[0030] Figure 14 This indicates the current load calculation results.

[0031] Figure 15 The results, based on simulations using a load extraction model generated with MATLAB Simulink, demonstrate the effectiveness of load detection.

[0032] Figure 16 This indicates the vehicle speed sensitivity of the load detection. Detailed Implementation

[0033] <Technical Issues Regarding the Prior Art>

[0034] The inventors of this invention investigated the degree of influence of temperature, vehicle speed, and air pressure signals mixed together in the deformation signal on the accuracy of load extraction calculation.

[0035] Figure 11 The upper part represents the periodic waveform of the deformation signal. Figure 11The lower section illustrates the relationship between the deformation signal and the tire condition. First, the relationship between the output signal of the physical quantity sensor installed in the tire and the tire condition is explained. The physical quantity sensor located inside the tire outputs a signal that varies according to the state of the rotating tire. Peak 1 appears at the deformation point where the sensor is in contact with or separated from the road surface (the boundary between contact and separation), peak 2 appears when in contact with the road surface, and remains at a stable level when not in contact with the road surface. That is, peaks 1 and 2 change according to the detected physical quantity.

[0036] Figure 12 This represents a representative waveform of the deformed signal. When confirming the sensor's detection sensitivity, tire-related parameters and driving conditions were identified. Tire parameters include tire pressure, temperature, and tire wear; driving conditions include vehicle speed and number of occupants (load). For example, when confirming the dependence on tire pressure, temperature, vehicle speed, and load, all of these parameters are considered sensitive, indicating that peaks 1 and 2 of the deformed signal contain a mixture of tire pressure, temperature, vehicle speed, and load.

[0037] Figure 13 This describes the error generation mechanism caused by parameter variations. Figure 13 To utilize Figure 12 The influence of the mixed signal on load detection was confirmed. This is a schematic diagram of the sensitivity curves for the horizontal axis load and the vertical axis deformation signal. Looking at the curve for condition 1 (vehicle speed = 5 km / h, air pressure = 220 kPa), it can be seen that the load and deformation signal change linearly, allowing the load to be detected based on the magnitude of the deformation signal. On the other hand, it can be seen that when the sensitivity characteristics of the load and deformation signal differ according to vehicle speed and air pressure, as in conditions 2 (vehicle speed = 30 km / h, air pressure = 220 kPa) and 3 (vehicle speed = 5 km / h, air pressure = 140 kPa), the load and deformation signal become different. When using the deformation signal based on condition 1 to determine the load, the load becomes smaller in conditions 2 and 3 compared to the 550 kg in condition 1, resulting in errors when directly determining the load using the mixed signal.

[0038] Figure 14This represents the calculated results of previous (existing) load calculations. These results are derived from the sensitivity characteristics of various load parameters obtained through actual vehicle testing. It shows the sensitivity characteristics of the load and deformation signal (peak 1) compared to baseline condition 1 (temperature = 30℃, vehicle speed = 5km / h, air pressure = 220kPa), under condition 2 (air pressure 140kPa), condition 3 (air pressure 140kPa, temperature 0℃), and condition 4 (air pressure 140kPa, temperature 0℃, vehicle speed 30km / h). It can be seen that as the conditions relative to condition 1 are changed sequentially with varying air pressure, temperature, and vehicle speed, the difference in sensitivity increases. For example, in the characteristics when changing the air pressure in condition 2, the deformation signal, represented by a digital code, represents a load of 340kg at -400 (condition 1: -295). Furthermore, it is known that when the load is extracted by only correcting the air pressure, the sensitivity characteristics deviate from those shown in conditions 3 and 4 as in condition 2. Therefore, when the load corresponding to the sensitivity characteristics of condition 2 when the deformed signal -455 of 340kg is obtained according to condition 4 is 450kg, the error is as large as 32%.

[0039] <Implementation Method 1>

[0040] Figure 1 This is a block diagram showing the structure of the physical quantity detection device 1 according to Embodiment 1 of the present invention. The physical quantity detection device 1 is a device for detecting physical quantities acting on the tires installed on a vehicle. The physical quantity detection device 1 includes a strain sensor 11, a pressure sensor 12, a vehicle speed sensor 13, a temperature sensor 14, a calculation unit 15, and a storage unit 16.

[0041] Strain sensor 11, for example, is mounted on the inner wall of the tire to detect the amount of tire deformation and output a deformation measurement signal indicating the result. Pressure sensor 12 measures the tire pressure and outputs a pressure measurement signal indicating the result. Vehicle speed sensor 13, for example, uses the tire rotation speed to detect the vehicle speed and outputs a vehicle speed measurement signal indicating the result. Temperature sensor 14 detects the tire temperature and outputs a temperature measurement signal indicating the result.

[0042] The arithmetic unit 15 uses the measurement signals output by each sensor to calculate the load acting on the tire. The calculation order will be described later. The storage unit 16 stores data describing the relationship between the physical quantities measured by each sensor and the load acting on the tire. Specific examples of the data will be described later.

[0043] Figure 2 This is a flowchart illustrating the sequence of calculations performed by the arithmetic unit 15 on the load acting on the tire. The following is a further explanation... Figure 2 The steps are explained below.

[0044] ( Figure 2 Step S201)

[0045] The arithmetic unit 15 acquires the sensitivity of the strain sensor 11 to changes in vehicle speed, load, and air pressure. Specific examples of this step will be described later. This step is significant for preparing the estimated value of the deformation measurement signal relative to the measured values ​​of vehicle speed, load, and air pressure. The estimated value of the deformation measurement signal will be described later. This step is preferably performed at a reference temperature that specifies the standard characteristics of the strain sensor 11; however, results performed at temperatures other than the reference temperature can also be converted to values ​​equivalent to the reference temperature.

[0046] ( Figure 2 Step S202)

[0047] The arithmetic unit 15 acquires the relationship between the deformation measurement signal and the reference signal value when the vehicle speed, load, and air pressure change relative to the reference vehicle speed, reference load, and reference air pressure, respectively, and saves the data describing the result to the storage unit 16. A specific example of this step will be described later. This step is meaningful because it uses the difference between the vehicle speed, load, and air pressure and the change from the reference signal value to represent the change in the deformation measurement signal when the vehicle speed, load, and air pressure change.

[0048] ( Figure 2 Step S202: Supplement)

[0049] The changes in deformation measurement signals when vehicle speed, load, and air pressure change are not necessarily represented by the differences from reference vehicle speed, reference load, reference air pressure, and reference signal value. However, since the absolute values ​​of the signal values ​​vary for each vehicle model and tire type, it is necessary to pre-generate the same data as in this step for each absolute value, which significantly increases the amount of data. Therefore, in this embodiment, the data is described by using the difference from the reference value, which, together with step S203 described later, reduces the amount of data.

[0050] ( Figure 2 Step S203)

[0051] The calculation unit 15 obtains the amplitude of the deformation measurement signal of a vehicle equipped with the physical quantity detection device 1 under reference vehicle speed, reference load, and reference air pressure, and saves the data describing the result to the storage unit 16. The data obtained in S202 is a representative value obtained for each combination of vehicle model and tire type, and the actual vehicle's signal value may differ from this data. Therefore, in this step, by obtaining the amplitude of the actual vehicle's deformation measurement signal, a correction value is obtained to make the data in S202 correspond to the vehicle's deformation measurement signal. A specific example of this step will be described later.

[0052] ( Figure 2 Step S204)

[0053] The calculation unit 15 calculates the deformation measurement signal output by the strain sensor 11. This deformation measurement signal includes components generated by vehicle speed, air pressure, and load, respectively. By calculating these components individually and then summing them, the calculation unit 15 can calculate an estimated value of the deformation measurement signal. The calculation unit 15 obtains the load acting on the tire by applying the load characteristics of the calculated deformation measurement signal to the actual deformation measurement signal output by the strain sensor 11. Details of this step will be described later.

[0054] ( Figure 2 Step S205)

[0055] The arithmetic unit 15 corrects the temperature characteristics of the strain sensor 11. The strain sensor 11 can be, for example, a component whose resistance changes with the force applied to the deformation-generating body. The deformation measurement signal output by the strain sensor 11 can vary depending on the temperature of the component, even when measuring the same deformation. Therefore, the arithmetic unit 15 stores data describing the relationship between its variation and temperature (temperature characteristics) in advance and corrects the deformation measurement signal accordingly.

[0056] Figure 3A This is an example of data obtained from the S201 calculation unit 15. The variation of the deformation measurement signal relative to the load is illustrated here. The calculation unit 15 obtains the relationship between the load acting on the tire under reference air pressure, reference vehicle speed, and reference temperature, and the deformation measurement signal value at that time. For example, it obtains data for each combination of vehicle type and tire type. Figure 3A The relationship is shown below. This relationship can be obtained through actual measurement or through appropriate simulation or other methods. Here, the reference load is set to 340 kg (equivalent to two people in the car), the reference air pressure to 220 kPa, and the reference temperature to 30°C. The reference vehicle speed can be, for example, 7 km / h. The same relationship can be obtained for vehicle speeds other than the reference speed. Figure 3A The example is shown in the text.

[0057] Similarly, the calculation unit 15 obtains the following relationships: (a) the relationship between the changes in tire pressure and the changes in reference vehicle speed, reference load, and reference temperature; and (b) the relationship between the changes in vehicle speed and the changes in reference load, reference tire pressure, and reference temperature. In this way, the calculation unit 15 can obtain the amount of variation in the deformation measurement signal relative to changes in vehicle speed, load, and tire pressure (the sensitivity of the strain sensor 11 to each physical quantity).

[0058] Figure 3B This data represents the change in tire deformation measurement signal when tire pressure changes at a reference vehicle speed, reference load, and reference temperature. Figure 3ASimilarly, this indicates an example where the same relationship is achieved for speeds other than the reference speed.

[0059] Figure 4 This is an example of data generated by the calculation unit 15 in S202. Here, the difference between the deformation measurement signal and the reference value is shown relative to the difference from the reference air pressure. In S201, the signal value (reference signal value) of the deformation measurement signal output by the strain sensor 11 at the reference vehicle speed, reference load, reference air pressure, and reference temperature can be obtained. The calculation unit 15, based on the results of S201, like... Figure 4 This generates data showing the relationship between the tire pressure measurement signal and the reference signal value when the tire pressure changes from the reference pressure at a reference vehicle speed, reference load, and reference temperature. Therefore, in Figure 4 In this configuration, the deformation measurement signal at an air pressure of 220 kPa is consistent with the reference signal value (difference = 0). The data format can be any format, such as a lookup table.

[0060] Similarly, the arithmetic unit 15 generates data representing the following relationships: (a) the relationship between the deformation measurement signal and the reference signal value when the vehicle speed changes from the reference vehicle speed under reference load, reference air pressure, and reference temperature; and (b) the relationship between the deformation measurement signal and the reference signal value when the load changes from the reference load under reference vehicle speed, reference air pressure, and reference temperature. In this way, the arithmetic unit 15 can obtain the relationship between the deformation measurement signal and the reference signal value when the vehicle speed, load, and air pressure change relative to the reference vehicle speed, reference load, and reference air pressure, respectively.

[0061] Figure 5 This is an example of data obtained from the calculation unit 15 in S203. In S202, the change in the deformation measurement signal value relative to changes in the reference air pressure, etc., is obtained. However, this is a representative value obtained for each combination of vehicle model and tire type, and the actual vehicle's signal value may differ from this. For example, when the actual vehicle is used at a reference speed, reference load, and reference air pressure, the deformation measurement signal may differ from the reference signal value in S202. Therefore, in S203, the difference between the two is corrected.

[0062] The signal value of the deformation measurement signal can be represented by the signal amplitude. Figures 3A-4 The amplitude is also used to represent the deformation measurement signal. Here, the signal amplitude simply refers to the value representing the magnitude of the change (deviation) in the deformation measurement signal. The deformation measurement signal is as follows: Figure 5 As shown, a waveform has falling edges following a rising edge. For example, the amplitude of the first falling edge waveform can be treated as the amplitude of the deformation measurement signal. The following explanation is based on this premise.

[0063] Figure 5 In the first falling edge waveform of the deformation measurement signal shown, the signal value decreases by 200 codes from the stable level (i.e., the signal amplitude is -200 codes). On the other hand, in the data obtained in S201 to S202, the reference signal value is sometimes not -200. Therefore, the calculation unit 15 obtains the difference between the two and uses the difference to correct the deformation measurement signal to the signal value inherent to the vehicle.

[0064] Figure 6 This is a schematic diagram illustrating the sequence of load calculation in the S204 calculation unit 15. The original expectation was that when a load is applied to the tire, the strain sensor 11 would output a load corresponding to that load. Figure 6 The signal (3). However, the actual deformation measurement signal output by the strain sensor 11 includes components caused by vehicle speed and tire pressure. Figure 6 The signals (1) and (2) are assumed to be output by strain sensor 11. Therefore, it is assumed that the deformation measurement signal (4) obtained by combining these signals is obtained by combining the strain sensor 11.

[0065] Therefore, the arithmetic unit 15 calculates the signal output by the strain sensor 11. Figure 6 The load characteristics of the deformation measurement signal (4), which includes components caused by vehicle speed and tire pressure, are deduced from the signal (the corresponding signal value for each load value, i.e., Figure 6 All signals shown (4)). The calculation unit 15 can obtain the load value by applying the signal value of the actual deformation measurement signal obtained from the strain sensor 11 to the calculated load characteristics.

[0066] Signal (1) is the component of the deformation measurement signal generated by the vehicle speed. Therefore, by using the difference between the current vehicle speed and the reference vehicle speed, the data obtained in S202 is referenced. Figure 4 (The horizontal axis represents the vehicle speed data), which allows us to obtain the difference between the reference signal value and the component generated by the vehicle speed.

[0067] Signal (2) is the component of the deformation measurement signal generated by air pressure. Therefore, by using the difference between the current tire pressure and the reference pressure, the data obtained in S202 is referenced. Figure 4 (As illustrated in the example, with air pressure on the horizontal axis), the difference between the component caused by air pressure and the reference signal value can be obtained.

[0068] Signal (3) is the component of the deformation measurement signal generated by the load. Therefore, by using the difference between the current load of the tire and the reference load, the data obtained in S202 is referenced. Figure 4 (The horizontal axis represents the load data), which allows us to obtain the difference between the load-generated components and the reference signal values.

[0069] The calculation unit 15 can obtain signal (4) by summing the signals (1), (2), and (3) calculated as described above. However, since the reference signal value is data obtained for each combination of vehicle model and tire model, there is a possibility that it deviates from the reference signal value inherent to the vehicle. Therefore, the calculation unit 15 further sums the correction value for the vehicle obtained in S203. As a result, the amplitude characteristics of the deformation measurement signal of the vehicle can be reflected in signal (4) based on the data in S202.

[0070] In summary, the arithmetic unit 15 calculates signal (4) in S204 using the following formula:

[0071] Signal (4) =

[0072] Signal (1) (the component generated due to the difference between the reference vehicle speed and the current vehicle speed) +

[0073] Signal (2) (the component generated due to the difference between the reference pressure and the current pressure) +

[0074] Signal (3) (the component resulting from the difference between the reference load and the current load) +

[0075] The inherent correction value of the vehicle (the correction value obtained in S203).

[0076] When the arithmetic unit 15 only obtains the signal (3), it can calculate the signal (3) by using a calculation formula that moves the components other than the signal (3) in the above calculation formula to the other side.

[0077] Figure 15 The results obtained from simulations using a load extraction model represent the effectiveness of load detection. The load extraction model was generated using MATLAB (registered trademark) Simulink. Figure 15 The upper part represents the pressure sensitivity of load detection based on model simulation. Figure 15 The lower part indicates the air pressure sensitivity of the load detection error. The results calculated based on actual vehicle data under conditions of 2.4 m / s (approximately 9 km / h), 2 passengers, and 30°C, confirm that the load estimation error is approximately 8%, which is 313 kg relative to the measured load of 340 kg, with the accuracy decreasing as the air pressure decreases.

[0078] Figure 16 This indicates the vehicle speed sensitivity of the load detection. Figure 16 The upper part represents the vehicle speed sensitivity of load detection based on model simulation. Figure 16The lower part indicates the vehicle speed sensitivity of the load detection error. The results calculated based on actual vehicle data under conditions of 220 kPa air pressure, 2 passengers, and 30℃ show that the load estimation error is approximately 8%, which corresponds to a measured load of 340 kg, with the accuracy decreasing as the vehicle speed increases.

[0079] <Implementation Method 1: Summary>

[0080] The physical quantity detection device 1 of this embodiment calculates the components in the deformation measurement signal caused by vehicle speed / load / air pressure, respectively. The calculation is assumed to be an estimate of the deformation measurement signal output by the strain sensor 11. Figure 6 The load is calculated by applying the deformation measurement signal actually output by the strain sensor 11 to the estimated value (4). Thus, even when the deformation measurement signal varies due to vehicle speed and tire pressure, the load applied to the tire can be accurately measured.

[0081] The physical quantity detection device 1 of this embodiment 1 uses data describing the amount by which the deformation measurement signal deviates from the reference signal value due to the difference between the reference air pressure and the current air pressure. Figure 4 The calculation unit 15 calculates the component in the deformation measurement signal caused by air pressure. Similarly, it calculates the deviation of the deformation measurement signal from the reference signal value due to the difference between the reference vehicle speed and the current vehicle speed. It also calculates the deviation of the deformation measurement signal from the reference signal value due to the difference between the reference load and the current load. Through these processes, the calculation unit 15 can use representative reference values ​​for each vehicle model and tire type to estimate the actual deformation measurement signal, thus reducing the amount of data in S202.

[0082] The physical quantity detection device 1 of this embodiment 1 obtains the inherent signal amplitude (and) of an actual vehicle under reference vehicle speed / reference load / reference air pressure. Figure 5 The value corresponding to the -200 code is used to correct the difference between the value and the reference signal value. Thus, an estimate of the deformation measurement signal can be calculated using a representative reference value for each vehicle model and tire type, and this estimate can be corrected to a value inherent to that vehicle. Therefore, the amount of data in S202 can be reduced, and the accurate load inherent to the vehicle can be obtained.

[0083] <Implementation Method 2>

[0084] Figure 7 This is a block diagram illustrating the structure of the physical quantity detection device 1 according to Embodiment 2 of the present invention. The strain sensor 11, vehicle speed sensor 13, and temperature sensor 14 can also be configured as a single physical quantity sensor 17 capable of detecting deformation, vehicle speed, and temperature. Other structures are the same as in Embodiment 1.

[0085] <Implementation Method 3>

[0086] Figure 8 This is a block diagram illustrating the structure of the physical quantity detection device 1 according to Embodiment 3 of the present invention. The physical quantity detection device 1 may also be configured to include not only the structure described in Embodiment 1, but also a wear sensor 18. The wear sensor 18 measures tire wear and outputs a wear measurement signal representing the result. Because tire wear also affects the deformation measurement signal, as described in Embodiment 1, the deformation measurement signal includes a component caused by wear.

[0087] The arithmetic unit 15 obtains the relationship between the wear measurement signal and the deformation measurement signal in the same manner as in Embodiment 1, and uses the result to calculate an estimated value of the deformation measurement signal. Therefore, the calculation formula is as follows. Other structures are the same as in Embodiment 1:

[0088] Signal (4) =

[0089] Signal (1) (the component generated due to the difference between the reference vehicle speed and the current vehicle speed) +

[0090] Signal (2) (the component generated due to the difference between the reference pressure and the current pressure) +

[0091] Signal (3) (the component resulting from the difference between the reference load and the current load) +

[0092] The vehicle's inherent correction value (the correction value obtained in S203) +

[0093] The component resulting from the difference between the reference wear and the current wear.

[0094] <Implementation Method 4>

[0095] Figure 9 This is a block diagram illustrating the structure of the physical quantity detection device 1 according to Embodiment 4 of the present invention. In this Embodiment 4, not only is the structure described in Embodiment 1 included, but also a balance calculation unit 21. The balance calculation unit 21 can be configured as part of the calculation unit 15, or it can be configured as another functional unit different from the calculation unit 15, and further, it can be another functional unit different from the physical quantity detection device 1.

[0096] The calculation unit 15 calculates the load applied to each tire of the vehicle. The balance calculation unit 21 calculates the balance of the load applied to each tire based on the results. For example, if a tire is subjected to a significantly greater load than the other tires, an alarm can be output indicating this. This improves vehicle safety.

[0097] <Implementation Method 5>

[0098] Figure 10This is a block diagram illustrating the structure of the physical quantity detection device 1 according to Embodiment 5 of the present invention. In this Embodiment 5, not only the structure described in Embodiment 1 is included, but also a load calculation unit 22. The load calculation unit 22 can be configured as part of the calculation unit 15, or as another functional unit different from the calculation unit 15, and further, as another functional unit different from the physical quantity detection device 1.

[0099] The calculation unit 15 calculates the load applied to each tire of the vehicle. Based on the results, the load calculation unit 22 calculates the weight of the load already carried by the vehicle, or the weight of any additional load that can be added to the vehicle. Here, "load" refers to a load other than the vehicle's own weight, including the weight of the occupants. By outputting the load weight through the load calculation unit 22, the load loading operation can be assisted.

[0100] <Regarding variations of the present invention>

[0101] This invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above have been given in detail for ease of understanding and illustration of the invention, but are not necessarily limited to all the structures described. Furthermore, a portion of the structure of one embodiment can be replaced with the structure of another embodiment; moreover, a structure of another embodiment can be added to the structure of one embodiment. Furthermore, other structures can be added to, deleted from, or replaced in relation to a portion of the structure of each embodiment.

[0102] In the above embodiments, S201 to S203 can be performed in advance before the load is obtained and the data describing the results can be saved to the storage unit 16.

[0103] In the above embodiments, the arithmetic unit 15 can be constructed either by hardware such as circuit devices that have its functions installed, or by executing software with its functions installed via a processing device such as a processor. The same applies to the balanced arithmetic unit 21.

[0104] Explanation of reference numerals in the attached figures

[0105] 1: Physical quantity detection device

[0106] 11: Strain sensor

[0107] 12: Pressure sensor

[0108] 13: Vehicle speed sensor

[0109] 14: Temperature sensor

[0110] 15: Arithmetic Department

[0111] 16: Storage Department

[0112] 17: Physical quantity sensor

[0113] 18: Wear sensor

[0114] 21: Balanced Calculation Department

[0115] 22: Load Calculation Unit.

Claims

1. A physical quantity detection device for detecting physical quantities acting on a tire, characterized in that it comprises: A strain sensor detects the deformation of the tire caused by multiple physical quantities, including the tire's displacement, and outputs the detection results as the measured deformation. A first sensor that detects the tire pressure among the plurality of physical quantities; A second sensor that detects the vehicle speed of the vehicle with the tires installed among the plurality of physical quantities; A third sensor that detects the temperature of the tire, one of the plurality of physical quantities; The calculation unit uses the measured deformation, the air pressure, the vehicle speed, and the temperature to calculate the load acting on the tire. and The storage unit stores data describing the relationship between the measured deformation, the air pressure, the vehicle speed, the temperature, and the load. The calculation unit calculates the estimated value of the load by using the air pressure, vehicle speed, temperature, and measured deformation as reference to the data. The calculation unit calculates, by referring to the data, a first estimate of the tire deformation caused by the air pressure, a second estimate of the tire deformation caused by the vehicle speed, and a correction value for the measured deformation caused by the temperature. The calculation unit calculates a third estimate of the tire deformation caused by the load for each load value by referring to the data. The calculation unit calculates an estimate of the measured deformation for each load value by adding the first estimate, the second estimate, and the correction value to the third estimate calculated for each load value. The calculation unit calculates the estimated value of the load by applying the measured deformation detected by the strain sensor to the estimated value calculated for each load value.

2. The physical quantity detection device as described in claim 1, characterized in that: The strain sensor, the second sensor, and the third sensor are composed of a single physical quantity sensor that detects the measured deformation, the vehicle speed, and the temperature.

3. The physical quantity detection device as described in claim 1, characterized in that: The physical quantity detection device also includes a fourth sensor for detecting tire wear. The data describes the relationship between the measured deformation, air pressure, vehicle speed, temperature, load, and wear. The calculation unit calculates the estimated value of the load by referring to the data using the air pressure, vehicle speed, temperature, wear, and measured deformation.

4. The physical quantity detection device as described in claim 1, characterized in that: The arithmetic unit calculates the loads acting on the tires mounted on each wheel of the vehicle. The calculation unit uses the loads acting on each of the tires to calculate the balance of the loads acting on each of the wheels.

5. The physical quantity detection device as described in claim 1, characterized in that: The computing unit uses the load to calculate the weight of the load carried by the vehicle with the tires installed, or the weight of any additional load that can be added.

6. A physical quantity detection device for detecting physical quantities acting on a tire, characterized in that it comprises: A strain sensor detects the deformation of the tire caused by multiple physical quantities, including the tire's displacement, and outputs the detection results as the measured deformation. A first sensor that detects the tire pressure among the plurality of physical quantities; A second sensor that detects the vehicle speed of the vehicle with the tires installed among the plurality of physical quantities; A third sensor that detects the temperature of the tire, one of the plurality of physical quantities; The calculation unit uses the measured deformation, the air pressure, the vehicle speed, and the temperature to calculate the load acting on the tire. and The storage unit stores data describing the relationship between the measured deformation, the air pressure, the vehicle speed, the temperature, and the load. The calculation unit calculates the estimated value of the load by using the air pressure, vehicle speed, temperature, and measured deformation as reference to the data. The data describes the baseline deformation detected by the strain sensor when the air pressure is a baseline air pressure, the vehicle speed is a baseline vehicle speed, and the temperature is a baseline temperature. The data describes the difference between the reference deformation and the measured deformation based on each of the first differences between the reference air pressures, each of the second differences between the reference vehicle speeds, and each of the third differences between the reference load and the load. The arithmetic unit calculates the first deformation of the tire caused by the first difference, the second deformation of the tire caused by the second difference, and the third deformation of the tire caused by the third difference. The calculation unit calculates the difference between the actual deformation detected by the strain sensor and the reference deformation when the air pressure is a reference air pressure, the vehicle speed is a reference vehicle speed, and the temperature is a reference temperature, and uses this difference as a reference value correction amount. The calculation unit calculates an estimated value of the measured deformation for each load value by summing the first deformation, the second deformation, the third deformation, the reference deformation, and the reference value correction. The calculation unit calculates the estimated value of the load by applying the measured deformation detected by the strain sensor to the estimated value calculated for each load value.

7. The physical quantity detection device as described in claim 6, characterized in that: The strain sensor, the second sensor, and the third sensor are composed of a single physical quantity sensor that detects the measured deformation, the vehicle speed, and the temperature.

8. The physical quantity detection device as described in claim 6, characterized in that: The physical quantity detection device also includes a fourth sensor for detecting tire wear. The data describes the relationship between the measured deformation, air pressure, vehicle speed, temperature, load, and wear. The calculation unit calculates the estimated value of the load by referring to the data using the air pressure, vehicle speed, temperature, wear, and measured deformation.

9. The physical quantity detection device as described in claim 6, characterized in that: The arithmetic unit calculates the loads acting on the tires mounted on each wheel of the vehicle. The calculation unit uses the loads acting on each of the tires to calculate the balance of the loads acting on each of the wheels.

10. The physical quantity detection device as described in claim 6, characterized in that: The computing unit uses the load to calculate the weight of the load carried by the vehicle with the tires installed, or the weight of any additional load that can be added.

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