Reduced-pressure state detection device, determination method, and program

Abstract

To provide a decompression state detection device, a determination method, and a program capable of determining whether or not update timing of a reference value used for decompression determination of a pneumatic tire has come.SOLUTION: The decompression state detection device 100 includes an acquisition processing unit 41 that acquires a related value related to an air pressure of a tire, a detection processing unit 42 that detects a decompression state of the tire when a difference between the related value and a predetermined reference value exceeds a predetermined first threshold, a first update processing unit 43 that updates the reference value when an operation on an initialization button 31 is received, and a determination processing unit 44 that determines whether or not an update timing of the reference value has arrived based on the related value acquired after the difference exceeds a second threshold equal to or less than the first threshold and before an operation on the initialization button 31 is received.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a decompression state detection device, a determination method, and a program. [Background technology]

[0002] A decompression state detection device is known that can detect a decompression state of a pneumatic tire mounted on a vehicle based on the rotational speed of the pneumatic tire (see, for example, Patent Document 1). Specifically, the decompression state detection device acquires a related value associated with the air pressure of the pneumatic tire, such as the resonant frequency of the pneumatic tire, based on the rotational speed at each predetermined acquisition timing. Furthermore, the decompression state is detected when the difference between the acquired related value and a predetermined reference value exceeds a predetermined threshold.

[0003] In the decompression state detection device, the reference value is updated after the air pressure of the pneumatic tire is adjusted or after the pneumatic tire is replaced. Specifically, in the decompression state detection device, when a predetermined update operation such as operating an initialization button is accepted, the reference value is updated based on the related value obtained after the acceptance of the update operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-196275 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the user of the vehicle may not perform the update operation after adjusting the air pressure of the pneumatic tire or replacing the pneumatic tire. In the low-pressure state detection device, if the reference value is not updated after adjusting the air pressure of the pneumatic tire or replacing the pneumatic tire, the accuracy of detecting the low-pressure state decreases. In response to this, when the time to update the reference value arrives, the user of the vehicle can be notified of this fact, thereby encouraging the user to perform the update operation. However, in the past, there was no configuration for determining whether the time to update the reference value has arrived.

[0006] An object of the present disclosure is to provide a decompression state detection device, a determination method, and a program that can determine whether or not the timing for updating a reference value used to determine decompression of a pneumatic tire has arrived. [Means for solving the problem]

[0007] A decompression state detection device according to one aspect of the present disclosure includes an acquisition processor, a detection processor, a first update processor, and a determination processor. The acquisition processor acquires a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on the rotational speed of the pneumatic tire. The detection processor detects a decompression state of the pneumatic tire when a difference between the related value acquired by the acquisition processor and a predetermined reference value exceeds a predetermined first threshold. When a predetermined update operation is received, the first update processor updates the reference value based on the related value acquired during a first period including the time when the update operation is received. The determination processor determines whether the timing to update the reference value has arrived based on the related value acquired after the difference exceeds a second threshold equal to or less than the first threshold and before the update operation is received.

[0008] According to this decompression state detection device, it is possible to determine whether or not the timing for updating the reference value has arrived. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to determine whether or not the timing for updating the reference value used to determine decompression of a pneumatic tire has arrived. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the configuration of a vehicle including a decompression state detection device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing the configuration of a vehicle including a decompression state detection device according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a flowchart showing an example of a related value acquisition process executed by the reduced pressure state detection device according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a flowchart illustrating an example of a reduced pressure state detection process executed by the reduced pressure state detection device according to the embodiment of the present disclosure. [Figure 5] FIG. 5 is a flowchart showing an example of a first update process executed by the reduced pressure state detection device according to the embodiment of the present disclosure. [Figure 6] FIG. 6 is a flowchart showing an example of a second update process executed in the reduced pressure state detection device according to the embodiment of the present disclosure. [Figure 7] FIG. 7 is a diagram showing the configuration of a vehicle including a decompression state detection device according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following embodiments are examples of specific embodiments of the present disclosure and are not intended to limit the technical scope of the present disclosure.

[0012] [Vehicle 1 Configuration] First, with reference to FIGS. 1 and 2, a configuration of a vehicle 1 including a low-pressure state detection device 100 according to an embodiment of the present disclosure will be described.

[0013] The vehicle 1 is an automobile such as a passenger car, a bus, a truck, etc. Note that the vehicle 1 is not limited to an automobile, and may be a motorcycle, a three-wheeled vehicle, or the like.

[0014] The vehicle 1 is equipped with four pneumatic tires 2 (see FIG. 1) (hereinafter referred to as "tires 2"). Specifically, the vehicle 1 is equipped with four wheels (the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel), and a tire 2 is mounted on each of the wheels. Hereinafter, the tire 2 mounted on the left front wheel will be referred to as "tire 2A" (see FIG. 1). The tire 2 mounted on the right front wheel will be referred to as "tire 2B" (see FIG. 1). The tire 2 mounted on the left rear wheel will be referred to as "tire 2C" (see FIG. 1). The tire 2 mounted on the right rear wheel will be referred to as "tire 2D" (see FIG. 1).

[0015] In addition to the components necessary for driving, such as an engine, the four wheels, tires 2 mounted on each of the wheels (see FIG. 1), brakes, and a steering mechanism, the vehicle 1 is equipped with a control unit 11, an operation display unit 12, a memory unit 13, and a wheel speed sensor 14 shown in FIG. 2.

[0016] 2, the control unit 11 includes a CPU 21, a ROM 22, and a RAM 23. The CPU 21 is a processor that executes various types of arithmetic processing. The ROM 22 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 21 to execute various types of processing. The RAM 23 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 21.

[0017] The control unit 11 constitutes a reduced pressure state detection device 100 (see FIG. 2).

[0018] The deflation state detection device 100 can determine whether or not the tire 2 mounted on the vehicle 1 is depressurized. When it is determined that the tire 2 is depressurized, the deflation state detection device 100 detects the depressurized state of the tire 2.

[0019] For example, the deflation state detection device 100 determines that the tire 2 mounted on the vehicle 1 is depressurized when the air pressure of any tire 2 drops by a predetermined reference amount of depressurization from a predetermined optimum value. For example, the reference amount of depressurization is 20 percent of the optimum value.

[0020] The control unit 11 does not have to be specialized in the function of detecting the decompression state of the tire 2.

[0021] The operation display unit 12 includes a display unit and an operation unit. The display unit is provided in a position visible to the driver sitting in the driver's seat of the vehicle 1. For example, the display unit is a flat panel display such as a liquid crystal display provided in the center cluster of the vehicle 1. The display unit displays various information in response to control instructions from the control unit 11. The operation unit is provided in a position operable by the driver sitting in the driver's seat. For example, the operation unit is an operation button provided in the center cluster or center console of the vehicle 1, and a touch panel provided in the display unit. The display unit may include notification lamps provided in the instrument panel of the vehicle 1 that correspond to each piece of notification information for the user of the vehicle 1.

[0022] The operation display unit 12 includes an initialization button 31 shown in Fig. 2. For example, the initialization button 31 is a physical switch provided on the center cluster or center console of the vehicle 1. The initialization button 31 is used to update a reference value used to determine deflation of the tire 2. As will be described later, the reference value is updated by operating the initialization button 31.

[0023] The storage unit 13 is a nonvolatile storage device, such as a flash memory.

[0024] The wheel speed sensors 14 are sensors capable of detecting the rotational speed of the wheels (the rotational speed of the tires 2). A wheel speed sensor 14 is provided for each wheel. For example, the wheel speed sensors 14 output electrical signals corresponding to changes in a magnetic field caused by the rotation of a sensor rotor having multiple teeth provided on the inside of the wheel. The electrical signals output from each wheel speed sensor 14 are input to the control unit 11. The control unit 11 obtains the rotational speed of each tire 2 based on the electrical signals output from each wheel speed sensor 14.

[0025] [Functional configuration of control unit 11] Next, with reference to FIG. 2, a functional configuration for detecting the decompression state of the tire 2, which is included in the control unit 11, will be described.

[0026] As shown in FIG. 2, the control unit 11 includes an acquisition processing unit 41, a detection processing unit 42, a first update processing unit 43, a determination processing unit 44, and a second update processing unit 45.

[0027] Specifically, the CPU 21 of the control unit 11 executes the control program stored in advance in the ROM 22 to function as each of the above-mentioned processing units.

[0028] The control program may be recorded on a computer-readable recording medium such as a CD, a DVD, or a flash memory, and may be read from the recording medium and stored in the storage unit 13. The control program may also be a program for causing a plurality of processors to function as the processing units shown in Fig. 2. Some or all of the processing units included in the control unit 11 may be configured with electronic circuits.

[0029] The acquisition processing unit 41 acquires a related value related to the air pressure of the tire 2 based on the rotation speed of the tire 2 mounted on the vehicle 1 every time a predetermined acquisition timing arrives.

[0030] For example, the acquisition processing unit 41 calculates the four related values ​​DEL1, DEL3, the resonance frequency of tire 2A, and the resonance frequency of tire 2B. DEL1, DEL3, the resonance frequency of tire 2A, and the resonance frequency of tire 2B function as index values ​​for determining the air pressure state of tire 2. In other words, the acquisition processing unit 41 calculates the index values ​​for determining the air pressure state of tire 2.

[0031] DEL1 is a value that increases as the rotational speed of tires 2A and 2D increases and decreases as the rotational speed of tires 2B and 2C increases, or a value that decreases as the rotational speed of tires 2A and 2D increases and increases as the rotational speed of tires 2B and 2C increases.

[0032] For example, DEL1 is calculated according to the following formula (1). Note that "V1" included in formula (1) is the rotational speed of tire 2A. Furthermore, "V2" included in formula (1) is the rotational speed of tire 2B. Furthermore, "V3" included in formula (1) is the rotational speed of tire 2C. Furthermore, "V4" included in formula (1) is the rotational speed of tire 2D. The rotational speeds of the four tires 2 are acquired based on the electrical signals output from the four wheel speed sensors 14 corresponding to the four tires 2.

[0033] DEL1=[(V1+V4) / (V2+V3)-1]×100(%) ··· (1)

[0034] DEL3 is a value that increases as the rotational speed of tires 2A and 2C increases and decreases as the rotational speed of tires 2B and 2D increases, or a value that decreases as the rotational speed of tires 2A and 2C increases and increases as the rotational speed of tires 2B and 2D increases.

[0035] For example, DEL3 is calculated according to the following formula (2).

[0036] DEL3=[(V1+V3) / (V2+V4)-1]×100(%) ··· (2)

[0037] The resonance frequency of the tire 2A is calculated based on the rotational speed of the tire 2A.

[0038] The resonance frequency of the tire 2B is calculated based on the rotational speed of the tire 2B.

[0039] A known method may be used to acquire the resonance frequency of the tire 2. For example, the resonance frequency of the tire 2 is acquired by performing time series analysis on rotational acceleration information calculated from the rotational speed of the tire 2 acquired by the wheel speed sensor 14, based on a second-order autoregression (AR) model.

[0040] For example, the acquisition timing is a timing that occurs at a predetermined cycle from when the vehicle 1 starts traveling. For example, the cycle is any time between 0.1 seconds and 5 seconds. The acquisition timing may be a timing when the vehicle 1 is traveling at a speed equal to or higher than a predetermined speed, is not accelerating or decelerating, and is not turning. The related value may also be acquired at any timing.

[0041] The related values ​​acquired by the acquisition processing unit 41 do not have to be limited to the four mentioned above. For example, the related values ​​acquired by the acquisition processing unit 41 may include the resonance frequency of tire 2C and the resonance frequency of tire 2D. The related values ​​acquired by the acquisition processing unit 41 may also include DEL2. DEL2 is a value that increases as the rotational speeds of tires 2A and 2B increase and decreases as the rotational speeds of tires 2C and 2D increase, or a value that decreases as the rotational speeds of tires 2A and 2B increase and increases as the rotational speeds of tires 2C and 2D increase.

[0042] The detection processing unit 42 detects a decompressed state of the tire 2 when the difference between the related value acquired by the acquisition processing unit 41 and a predetermined reference value exceeds a predetermined first threshold value.

[0043] Here, in the decompression state detecting device 100, the reference values ​​and the first threshold values ​​corresponding to the respective associated values ​​acquired by the acquisition processing unit 41 are determined in advance.

[0044] For example, the reference value corresponding to DEL1 is a value that is set based on DEL1 acquired by the acquisition processing unit 41 when the air pressures of the four tires 2 are at the optimum values. For example, the reference value corresponding to DEL1 is the same value as DEL1 acquired by the acquisition processing unit 41 when the air pressures of the four tires 2 are at the optimum values. Alternatively, the reference value corresponding to DEL1 may be an average value of a plurality of DEL1 values ​​acquired by the acquisition processing unit 41 when the air pressures of the four tires 2 are at the optimum values.

[0045] Furthermore, the reference value corresponding to DEL3, like the reference value corresponding to DEL1, is a value set based on DEL3 acquired by the acquisition processing unit 41 when the air pressure of each of the four tires 2 is at the optimal value.

[0046] Furthermore, the reference value corresponding to the resonance frequency of the tire 2A is a value that is set based on the resonance frequency of the tire 2A acquired by the acquisition processing unit 41 when the air pressure of the tire 2A is at the optimal value. For example, the reference value corresponding to the resonance frequency of the tire 2A is the same value as the resonance frequency of the tire 2A acquired by the acquisition processing unit 41 when the air pressure of the tire 2A is at the optimal value. Furthermore, the reference value corresponding to the resonance frequency of the tire 2A may be an average value of the resonance frequencies of a plurality of tires 2A acquired by the acquisition processing unit 41 when the air pressure of the tires 2A is at the optimal value.

[0047] In addition, the reference value corresponding to the resonance frequency of tire 2B is a value that is set based on the resonance frequency of tire 2B acquired by the acquisition processing unit 41 when the air pressure of tire 2B is at the optimal value, similar to the reference value corresponding to the resonance frequency of tire 2A.

[0048] In addition, the first threshold value corresponding to DEL1 is a value indicating the difference between DEL1 acquired by the acquisition processing unit 41 in a state where the air pressure of each of three tires 2 out of four tires 2 is at the optimal value and the air pressure of the remaining tire 2 has decreased from the optimal value by the reference pressure reduction amount, and the reference value corresponding to DEL1.

[0049] In addition, the first threshold value corresponding to DEL3 is a value indicating the difference between DEL3 acquired by the acquisition processing unit 41 in a state where the air pressure of each of any three tires 2 out of four tires 2 is at the optimal value and the air pressure of the remaining tire 2 has decreased from the optimal value by the reference pressure reduction amount, and the reference value corresponding to DEL3.

[0050] In addition, the first threshold value corresponding to the resonant frequency of tire 2A is a value indicating the difference between the resonant frequency of tire 2A acquired by the acquisition processing unit 41 when the air pressure of tire 2A has decreased by the reference pressure reduction amount from the optimal value, and the reference value corresponding to the resonant frequency of tire 2A.

[0051] In addition, the first threshold value corresponding to the resonant frequency of tire 2B is a value indicating the difference between the resonant frequency of tire 2B acquired by the acquisition processing unit 41 when the air pressure of tire 2B has decreased by the reference pressure reduction amount from the optimal value, and the reference value corresponding to the resonant frequency of tire 2B.

[0052] For example, the detection processing unit 42 determines whether or not the difference between the associated value and the reference value exceeds the first threshold value for each of the associated values ​​acquired by the acquisition processing unit 41. Then, when it is determined that the difference between the associated value and the reference value for any of the associated values ​​exceeds the first threshold value, the detection processing unit 42 detects a decompressed state of the tire 2. Note that the detection processing unit 42 may also detect a decompressed state of the tire 2 when the number of times it is determined that the difference between the associated value and the reference value for any of the associated values ​​exceeds the first threshold value exceeds a predetermined value.

[0053] Furthermore, when a decompressed state of the tire 2 is detected, the detection processing unit 42 identifies the tire 2 in which the pressure is decompressed.

[0054] For example, the detection processing unit 42 determines that the tire 2A has a reduced pressure when the difference between the resonance frequency of the tire 2A and the reference value corresponding to the resonance frequency exceeds the first threshold value.

[0055] Furthermore, the detection processing unit 42 determines that the tire 2B has a reduced pressure when the difference between the resonance frequency of the tire 2B and the reference value corresponding to the resonance frequency exceeds the first threshold value.

[0056] Furthermore, when the difference between either the associated value DEL1 or DEL3 and the reference value corresponding to that associated value exceeds the first threshold, the detection processing unit 42 identifies the tire 2 that has a reduced pressure based on a combination of the signs of DEL1 and DEL3. Specifically, the detection processing unit 42 determines that tire 2A has a reduced pressure when the sign of DEL1 is positive and the sign of DEL3 is positive. Furthermore, the detection processing unit 42 determines that tire 2B has a reduced pressure when the sign of DEL1 is negative and the sign of DEL3 is negative. Furthermore, the detection processing unit 42 determines that tire 2C has a reduced pressure when the sign of DEL1 is negative and the sign of DEL3 is positive. Furthermore, the detection processing unit 42 determines that tire 2D has a reduced pressure when the sign of DEL1 is positive and the sign of DEL3 is negative.

[0057] When a deflated state of a tire 2 is detected, the control unit 11 notifies the user of the vehicle 1 of that fact. For example, the control unit 11 causes the operation display unit 12 to display a message indicating that a deflated state of a tire 2 has been detected and indicating which tire 2 is in a deflated state. The control unit 11 may also turn on a notification lamp to notify the user that a deflated state of a tire 2 has been detected. The control unit 11 may also notify the user that a deflated state of a tire 2 has been detected and generate a predetermined warning sound. This allows the user of the vehicle 1 to recognize the deflated state of the tire 2 and take action to resolve the deflated state of the tire 2 (adjust the air pressure of the tire 2 or replace the tire 2).

[0058] In the vehicle 1, after the air pressure of the tires 2 is adjusted or after the tires 2 are replaced, each of the reference values ​​is updated.

[0059] When a predetermined update operation is received, the first update processing unit 43 updates the reference value based on the related value acquired during a first period that includes the time when the update operation is received.

[0060] For example, the update operation is a pressing operation on the initialization button 31 (see FIG. 2).

[0061] For example, the first period is a period that starts from the time when the update operation is accepted, and ends after the number of occurrences of the acquisition timing from the time when the update operation is accepted reaches a predetermined number.

[0062] When the update operation is received, the first update processing unit 43 updates the reference values ​​corresponding to the respective associated values.

[0063] For example, the first update processing unit 43 sets any one of the DEL1 values ​​acquired during the first period as the new reference value corresponding to DEL1. Alternatively, the first update processing unit 43 may set the average value of multiple DEL1 values ​​acquired during the first period as the new reference value corresponding to DEL1.

[0064] Furthermore, the first update processing unit 43 sets any one of DEL3 acquired during the first period as the new reference value corresponding to DEL3. Furthermore, the first update processing unit 43 may set the average value of multiple DEL3 acquired during the first period as the new reference value corresponding to DEL3.

[0065] Furthermore, the first update processing unit 43 sets the resonance frequency of any one of the tires 2A acquired during the first period as the new reference value corresponding to the resonance frequency of the tire 2A. Furthermore, the first update processing unit 43 may set the average value of the resonance frequencies of the plurality of tires 2A acquired during the first period as the new reference value corresponding to the resonance frequency of the tire 2A.

[0066] Furthermore, the first update processing unit 43 sets the resonance frequency of any one of the tires 2B acquired during the first period as the new reference value corresponding to the resonance frequency of the tire 2B. Furthermore, the first update processing unit 43 may set the average value of the resonance frequencies of the plurality of tires 2B acquired during the first period as the new reference value corresponding to the resonance frequency of the tire 2B.

[0067] The update operation does not have to be limited to an operation on the initialization button 31 (see FIG. 2). For example, the update operation may be an operation on an operation key (soft key) displayed on the operation display unit 12 in response to a predetermined operation on the display unit. Furthermore, in a case where the control unit 11 is previously connected to a mobile terminal such as a smartphone carried by the user of the vehicle 1 so as to be able to communicate with the mobile terminal, the update operation may be an operation performed on the mobile terminal. Furthermore, the first period may be a period that starts before the update operation is accepted.

[0068] However, the user of the vehicle 1 may not perform the update operation after adjusting the air pressure of the tire 2 or replacing the tire 2. In the deflation state detection device 100, if the reference value is not updated after adjusting the air pressure of the tire 2 or replacing the tire 2, the accuracy of detecting the deflation state of the tire 2 decreases. In response to this, when the time to update the reference value arrives, the user of the vehicle 1 can be notified of this, thereby urging the user to perform the update operation. However, conventionally, there has been no configuration for determining whether the time to update has arrived.

[0069] In contrast to this, the decompression state detecting device 100 according to the embodiment of the present disclosure is capable of determining whether the update timing has arrived, as will be described below.

[0070] The judgment processing unit 44 judges whether the update timing has arrived based on the related value acquired during a judgment period after the difference between the related value acquired by the acquisition processing unit 41 and the reference value exceeds a second threshold value that is less than the first threshold value and before the update operation is accepted.

[0071] Here, the second threshold value is a value smaller than the first threshold value. For example, the second threshold value is half the value of the first threshold value. As a result, compared to a configuration in which the second threshold value is the same as the first threshold value, even if the air pressure of tire 2 is adjusted or tire 2 is replaced before the decompressed state of tire 2 is detected, it is possible to detect the occurrence of these events, i.e., the arrival of the update timing. Note that the second threshold value may be the same value as the first threshold value.

[0072] For example, the determination period is a period that starts when the difference between any of the association values ​​acquired by the acquisition processing unit 41 and the reference value corresponding to that association value exceeds the second threshold value.

[0073] For example, the determination processing unit 44 determines that the update timing has arrived when each of the four related values ​​acquired during the determination period satisfies a predetermined determination condition corresponding to the related value.

[0074] Specifically, the determination condition corresponding to DEL1 is that DEL1 acquired during the determination period falls within a predetermined first range. The first range ranges from a lower limit value lower than the reference value corresponding to DEL1 to an upper limit value higher than the reference value corresponding to DEL1. For example, the first range is a range whose median value is the reference value corresponding to DEL1. The lower limit value of the first range is determined so that the difference between the reference value corresponding to DEL1 and the lower limit value is less than the second threshold value. For example, the lower limit value of the first range is set so that the difference between the reference value corresponding to DEL1 and the lower limit value corresponds to the amount of change in DEL1 that occurs when the air pressure of one of four tires 2 decreases by 3 to 5 percent.

[0075] Furthermore, the determination condition corresponding to DEL3 is that DEL3 acquired during the determination period falls within a predetermined second range. The second range ranges from a lower limit lower than the reference value corresponding to DEL3 to an upper limit higher than the reference value corresponding to DEL3. For example, the second range is a range with the reference value corresponding to DEL3 as its median. The lower limit of the second range is determined so that the difference between the reference value corresponding to DEL3 and the lower limit of the second range is less than the second threshold. For example, the lower limit of the second range is set so that the difference between the reference value corresponding to DEL3 and the lower limit of the second range corresponds to the amount of change in DEL3 when the air pressure of one of the four tires 2 decreases by 3 to 5 percent.

[0076] Furthermore, the determination condition corresponding to the resonance frequency of tire 2A is that the resonance frequency of tire 2A acquired during the determination period falls within a predetermined third range. The third range ranges from a lower limit lower than the reference value corresponding to the resonance frequency of tire 2A to an upper limit higher than the reference value corresponding to the resonance frequency of tire 2A. For example, the third range is a range whose center value is the reference value corresponding to the resonance frequency of tire 2A. The lower limit of the third range is determined so that the difference from the reference value corresponding to the resonance frequency of tire 2A is less than the second threshold value. For example, the lower limit of the third range is set so that the difference from the reference value corresponding to the resonance frequency of tire 2A corresponds to the amount of change in the resonance frequency of tire 2A when the air pressure of tire 2A decreases by 3 to 5 percent.

[0077] Furthermore, the determination condition corresponding to the resonance frequency of tire 2B is that the resonance frequency of tire 2B acquired during the determination period falls within a predetermined fourth range. The fourth range ranges from a lower limit lower than the reference value corresponding to the resonance frequency of tire 2B to an upper limit higher than the reference value corresponding to the resonance frequency of tire 2B. For example, the fourth range is a range having the reference value corresponding to the resonance frequency of tire 2B as its center value. The lower limit of the fourth range is determined so that the difference from the reference value corresponding to the resonance frequency of tire 2B is less than the second threshold value. For example, the lower limit of the fourth range is set so that the difference from the reference value corresponding to the resonance frequency of tire 2B corresponds to the amount of change in the resonance frequency of tire 2B when the air pressure of tire 2B decreases by 3 to 5 percent.

[0078] When the judgment processing unit 44 determines that the update timing has arrived, the second update processing unit 45 updates the reference value based on the related value acquired during a second period including the arrival of the update timing.

[0079] For example, the second period is a period that starts when the update timing arrives. Also, the second period is a period that ends when the number of occurrences of the acquisition timing since the update timing arrives reaches a predetermined number. Note that the second period may also be a period that starts before the update timing arrives.

[0080] The second update processing unit 45 updates the reference values ​​corresponding to the respective associated values ​​when the update timing arrives.

[0081] For example, the second update processing unit 45 sets any one of the DEL1 values ​​acquired during the second period as the new reference value corresponding to DEL1. Alternatively, the second update processing unit 45 may set the average value of multiple DEL1 values ​​acquired during the second period as the new reference value corresponding to DEL1.

[0082] Furthermore, the second update processing unit 45 sets any one of DEL3 values ​​acquired during the second period as the new reference value corresponding to DEL3. Furthermore, the second update processing unit 45 may set the average value of multiple DEL3 values ​​acquired during the second period as the new reference value corresponding to DEL3.

[0083] Furthermore, the second update processing unit 45 sets the resonance frequency of any one of the tires 2A acquired during the second period as the new reference value corresponding to the resonance frequency of the tire 2A. Furthermore, the second update processing unit 45 may set the average value of the resonance frequencies of the plurality of tires 2A acquired during the second period as the new reference value corresponding to the resonance frequency of the tire 2A.

[0084] Furthermore, the second update processing unit 45 sets the resonance frequency of any one of the tires 2B acquired during the second period as the new reference value corresponding to the resonance frequency of the tire 2B. Furthermore, the second update processing unit 45 may set the average value of the resonance frequencies of the plurality of tires 2B acquired during the second period as the new reference value corresponding to the resonance frequency of the tire 2B.

[0085] Below, an example of the procedure of each process executed by the control unit 11 and the determination method of the present disclosure will be described.

[0086] [Related value acquisition process] First, an example of the procedure of the related value acquisition process executed by the control unit 11 will be described with reference to Fig. 3. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 11. The related value acquisition process is executed while the vehicle 1 is traveling.

[0087] <Step S11> First, in step S11, the control unit 11 determines whether or not the acquisition timing has arrived.

[0088] Here, when the control unit 11 determines that the acquisition timing has arrived (Yes in S11), it shifts the process to step S12. On the other hand, when the acquisition timing has not arrived (No in S11), the control unit 11 waits for the arrival of the acquisition timing in step S11.

[0089] <Step S12> In step S12, the control unit 11 acquires the rotational speed of each tire 2.

[0090] Specifically, the control unit 11 acquires the rotation speed of each tire 2 using each wheel speed sensor 14.

[0091] <Step S13> In step S13, the control unit 11 acquires the four associated values. The processes of steps S11 to S13 are an example of an acquisition step of the present disclosure, and are executed by the acquisition processing unit 41 of the control unit 11.

[0092] Specifically, the control unit 11 acquires DEL1 based on the rotational speed of each tire 2 acquired by the processing of step S12. The control unit 11 also acquires DEL3 based on the rotational speed of each tire 2 acquired by the processing of step S12. The control unit 11 also acquires the resonant frequency of tire 2A based on the rotational speed of tire 2A acquired by the processing of step S12. The control unit 11 also acquires the resonant frequency of tire 2B based on the rotational speed of tire 2B acquired by the processing of step S12.

[0093] [Decompression state detection process] Next, an example of the procedure of the process for detecting a reduced pressure state executed by the control unit 11 will be described with reference to Fig. 4. The process for detecting a reduced pressure state is executed while the vehicle 1 is traveling.

[0094] <Step S21> First, in step S21, the control unit 11 determines whether or not the four association values ​​have been acquired. That is, the control unit 11 determines whether or not the process of step S13 of the association value acquisition process has been executed.

[0095] Here, if the control unit 11 determines that the four related values ​​have been acquired (Yes in S21), it shifts the process to step S22. On the other hand, if the four related values ​​have not been acquired (No in S21), the control unit 11 waits for acquisition of the four related values ​​in step S21.

[0096] <Step S22> In step S22, the control unit 11 determines whether or not the difference between any of the four relation values ​​acquired in the process of step S21 and the reference value exceeds the first threshold value. The process of step S22 is an example of a detection step of the present disclosure, and is executed by the detection processing unit 42 of the control unit 11.

[0097] If the control unit 11 determines that the difference between the associated value and the reference value for any of the four associated values ​​exceeds the first threshold (Yes in S22), the control unit 11 shifts the process to step S23. If the difference between the associated value and the reference value for any of the four associated values ​​does not exceed the first threshold (No in S22), the control unit 11 shifts the process to step S21.

[0098] <Step S23> In step S23, the control unit 11 identifies the tire 2 with the reduced pressure.

[0099] Specifically, the control unit 11 determines that the tire 2A is decompressed when the difference between the resonance frequency of the tire 2A and the reference value corresponding to the resonance frequency exceeds the first threshold value.

[0100] Furthermore, the control unit 11 determines that the tire 2B has a reduced pressure when the difference between the resonance frequency of the tire 2B and the reference value corresponding to the resonance frequency exceeds the first threshold value.

[0101] In addition, when the difference between either the related value DEL1 or DEL3 and the reference value corresponding to that related value exceeds the first threshold value, the control unit 11 identifies the tire 2 that has a reduced pressure based on the combination of the sign of DEL1 and the sign of DEL3.

[0102] <Step S24> In step S24, the control unit 11 notifies the user of the vehicle 1 that a deflated state of the tire 2 has been detected.

[0103] For example, the control unit 11 causes the operation display unit 12 to display a message indicating that a deflated state of the tire 2 has been detected and that the tire 2 is in a deflated state. The control unit 11 also generates a predetermined warning sound.

[0104] [First update process] Next, an example of the procedure of the first update process executed by the control unit 11 will be described with reference to FIG.

[0105] <Step S31> First, in step S31, the control unit 11 determines whether or not the update operation has been accepted.

[0106] Here, if the control unit 11 determines that the update operation has been accepted (Yes in S31), it shifts the process to step S32. On the other hand, if the update operation has not been accepted (No in S31), the control unit 11 waits for acceptance of the update operation in step S31.

[0107] <Step S32> First, in step S32, the control unit 11 determines whether or not the first period has ended.

[0108] Specifically, the control unit 11 determines that the first period has ended when the number of times the acquisition timing has arrived since the update operation was accepted reaches a predetermined number.

[0109] Here, when the control unit 11 determines that the first period has ended (Yes in S32), the control unit 11 shifts the process to step S33. On the other hand, when the first period has not ended (No in S32), the control unit 11 waits for the end of the first period in step S32.

[0110] <Step S33> In step S33, the control unit 11 updates the reference value based on the associated value acquired during the first period. The process of step S33 is an example of an update step in the present disclosure, and is executed by the first update processing unit 43 of the control unit 11.

[0111] Specifically, the control unit 11 sets any one of the DEL1 values ​​acquired during the first period as the new reference value corresponding to DEL1.

[0112] Furthermore, the control unit 11 sets any one of the DEL3 values ​​acquired during the first period as the new reference value corresponding to DEL3.

[0113] Furthermore, the control unit 11 sets the resonance frequency of any one of the tires 2A acquired during the first period as the new reference value corresponding to the resonance frequency of the tire 2A.

[0114] Moreover, the control unit 11 sets any one of the resonant frequencies of the tire 2B acquired during the first period as the new reference value corresponding to the resonant frequency of the tire 2B.

[0115] [Second update process] Next, an example of the procedure of the second update process executed by the control unit 11 will be described with reference to FIG.

[0116] <Step S41> First, in step S41, the control unit 11 determines whether or not the four association values ​​have been acquired. That is, the control unit 11 determines whether or not the process of step S13 of the association value acquisition process has been executed.

[0117] Here, if the control unit 11 determines that the four related values ​​have been acquired (Yes in S41), it shifts the process to step S42. On the other hand, if the four related values ​​have not been acquired (No in S41), the control unit 11 waits for acquisition of the four related values ​​in step S41.

[0118] <Step S42> In step S42, the control unit 11 determines whether or not the difference between any one of the four related values ​​acquired in the process of step S41 and the reference value exceeds the second threshold value.

[0119] If the control unit 11 determines that the difference between any one of the four related values ​​and the reference value exceeds the second threshold (Yes in S42), the control unit 11 shifts the process to step S43. If the difference between each of the four related values ​​and the reference value does not exceed the second threshold (No in S42), the control unit 11 shifts the process to step S41.

[0120] <Step S43> In step S43, the control unit 11 determines whether or not the update operation has been accepted.

[0121] Here, if the control unit 11 determines that the update operation has been accepted (Yes in S43), the control unit 11 shifts the process to step S41. On the other hand, if the update operation has not been accepted (No in S43), the control unit 11 shifts the process to step S44.

[0122] <Step S44> In step S44, the control unit 11 determines whether or not the four associated values ​​have been acquired, that is, the control unit 11 determines whether or not the process of step S13 of the associated value acquisition process has been executed.

[0123] Here, if the control unit 11 determines that the four related values ​​have been acquired (Yes in S44), the control unit 11 shifts the process to step S45. On the other hand, if the four related values ​​have not been acquired (No in S44), the control unit 11 shifts the process to step S43.

[0124] <Step S45> In step S45, the control unit 11 determines whether the update timing has arrived. The process of step S45 is an example of a determination step of the present disclosure, and is executed by the determination processing unit 44 of the control unit 11.

[0125] Specifically, the control unit 11 determines that the update timing has arrived when each of the four association values ​​acquired by the processing of the immediately preceding step S44 satisfies the determination condition corresponding to the association value.

[0126] Here, if the control unit 11 determines that the update timing has arrived (Yes in S45), it shifts the process to step S46. On the other hand, if the update timing has not arrived (No in S45), it shifts the process to step S43.

[0127] <Step S46> In step S46, the control unit 11 determines whether or not the second period has ended.

[0128] Specifically, the control unit 11 determines that the second period has ended when the number of times the acquisition timing has arrived since the arrival of the update timing has reached a predetermined number.

[0129] Here, when the control unit 11 determines that the second period has ended (Yes in S46), the control unit 11 shifts the process to step S47. On the other hand, when the second period has not ended (No in S46), the control unit 11 waits for the end of the second period in step S46.

[0130] <Step S47> In step S47, the control unit 11 updates the reference value based on the associated value acquired during the second period. The process of step S47 is executed by the second update processing unit 45 of the control unit 11.

[0131] Specifically, the control unit 11 sets any one of the DEL1 values ​​acquired during the second period as the new reference value corresponding to DEL1.

[0132] Furthermore, the control unit 11 sets any one of the DEL3 values ​​acquired during the second period as the new reference value corresponding to DEL3.

[0133] Furthermore, the control unit 11 sets the resonance frequency of any one of the tires 2A acquired during the second period as the new reference value corresponding to the resonance frequency of the tire 2A.

[0134] Furthermore, the control unit 11 sets any one of the resonant frequencies of the tire 2B acquired during the second period as the new reference value corresponding to the resonant frequency of the tire 2B.

[0135] In this way, the decompression state detection device 100 can determine whether or not the update timing has arrived.

[0136] Furthermore, when it is determined that the update timing has arrived, the reference value is automatically updated in the decompression state detection device 100. This makes it possible to reduce the user's effort in performing the update operation, compared to a configuration in which the reference value is not automatically updated.

[0137] [Other embodiments] The control unit 11 may include a notification processing unit 46 shown in FIG.

[0138] When the determination processing unit 44 determines that the update timing has arrived, the notification processing unit 46 issues a notification to that effect.

[0139] For example, the notification processing unit 46 displays a message on the operation display unit 12 indicating that the update timing has arrived. The notification processing unit 46 may also turn on a notification lamp to notify that the update timing has arrived. The notification processing unit 46 may also notify that the update timing has arrived and generate a predetermined warning sound. This allows the user of the vehicle 1 to recognize that the update timing has arrived. This makes it possible to encourage the user of the vehicle 1 to perform the update operation.

[0140] The above-described embodiments of the present disclosure include the following disclosure items (1) to (6).

[0141] The disclosed item (1) is a decompression state detection device that includes an acquisition processing unit that acquires a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on the rotational speed of the pneumatic tire; a detection processing unit that detects a decompression state of the pneumatic tire when a difference between the related value acquired by the acquisition processing unit and a predetermined reference value exceeds a predetermined first threshold; a first update processing unit that, when a predetermined update operation is accepted, updates the reference value based on the related value acquired during a first period including the time when the update operation is accepted; and a judgment processing unit that judges whether the timing to update the reference value has arrived based on the related value acquired after the difference exceeds a second threshold that is equal to or less than the first threshold and before the update operation is accepted.

[0142] This device makes it possible to determine whether the update timing has arrived.

[0143] Disclosed item (2) is the decompression state detection device described in disclosed item (1), in which the judgment processing unit determines that the update timing has arrived when the related value obtained after the difference exceeds the second threshold and before the update operation is accepted is within a predetermined range including the reference value.

[0144] Disclosure (3) is a decompression state detection device according to disclosure (1) or (2), which includes a second update processing unit that, when the judgment processing unit determines that the update timing has arrived, updates the reference value based on the related value acquired during a second period including the arrival of the update timing.

[0145] According to this device, when it is determined that the update timing has arrived, the reference value is automatically updated, which reduces the user's effort in performing the update operation compared to a configuration in which the reference value is not automatically updated.

[0146] Disclosed item (4) is a decompression state detection device described in any of disclosed items (1) to (3), which includes a notification processing unit that notifies the user when the judgment processing unit determines that the update timing has arrived.

[0147] This device makes it possible to make the user of the vehicle 1 aware of the arrival of the update timing and to prompt the user to perform the update operation.

[0148] A disclosed item (5) is the reduced pressure state detection device according to any one of the disclosed items (1) to (4), in which the second threshold value is smaller than the first threshold value.

[0149] Compared to a configuration in which the second threshold value is the same as the first threshold value, this device makes it possible to detect the occurrence of these events, i.e., the arrival of the update timing, even if the air pressure of tire 2 is adjusted or tire 2 is replaced before the decompressed state of tire 2 is detected.

[0150] Disclosed matter (6) is a determination method performed by one or more processors, the method including: an acquisition step of acquiring a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on the rotational speed of the pneumatic tire; a detection step of detecting a decompressed state of the pneumatic tire when a difference between the related value acquired by the acquisition step and a predetermined reference value exceeds a predetermined first threshold; an update step of updating the reference value based on the related value acquired during a first period including the time when a predetermined update operation is accepted; and a determination step of determining whether the timing to update the reference value has arrived based on the related value acquired after the difference exceeds a second threshold equal to or less than the first threshold and before the update operation is accepted.

[0151] According to this method, it is possible to determine whether the update timing has arrived, similarly to the device of disclosed item (1).

[0152] Disclosed matter (7) is a program for causing one or more processors to execute the following steps: an acquisition step of acquiring a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on the rotational speed of the pneumatic tire; a detection step of detecting a decompressed state of the pneumatic tire when a difference between the related value acquired by the acquisition step and a predetermined reference value exceeds a predetermined first threshold; an update step of updating the reference value based on the related value acquired during a first period including the time when a predetermined update operation is accepted; and a determination step of determining whether the timing to update the reference value has arrived based on the related value acquired after the difference exceeds a second threshold that is equal to or less than the first threshold and before the update operation is accepted.

[0153] According to this program, it is possible to determine whether the update timing has arrived, similarly to the device of disclosure (1).

[0154] The present disclosure may also be a computer-readable recording medium that non-temporarily records the program of disclosure item (7). [Explanation of symbols]

[0155] 1 vehicle 2 tires 11 Control section 12 Operation display section 13 Storage section 14 Wheel speed sensor 21 CPU 22 ROM 23 RAM 31 Initialization button 41 Acquisition processing unit 42 Detection processing section 43 First update processing section 44 Judgment processing unit 45 Second update processing section 46 Notification processing section 100 Decompression state detection device

Claims

1. an acquisition processing unit that acquires a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on the rotational speed of the pneumatic tire; a detection processing unit that detects a decompressed state of the pneumatic tire when a difference between the related value acquired by the acquisition processing unit and a predetermined reference value exceeds a predetermined first threshold value; a first update processing unit that, when a predetermined update operation is received, updates the reference value based on the related value acquired during a first period that includes the time when the update operation is received; a determination processing unit that determines whether or not a timing for updating the reference value has arrived based on the related value obtained after the difference exceeds a second threshold that is equal to or less than the first threshold and before the update operation is accepted; A reduced pressure state detection device comprising:

2. the determination processing unit determines that the update timing has arrived when the related value acquired after the difference has exceeded the second threshold and before the update operation is accepted is within a predetermined range including the reference value. The reduced pressure state detection device according to claim 1 .

3. a second update processing unit configured to, when the determination processing unit determines that the update timing has arrived, update the reference value based on the associated value acquired during a second period that includes the arrival of the update timing; The reduced pressure state detection device according to claim 1 .

4. a notification processing unit that notifies the user when the determination processing unit determines that the update timing has arrived; The reduced pressure state detection device according to claim 1 .

5. The second threshold is smaller than the first threshold. The reduced pressure state detection device according to any one of claims 1 to 4.

6. an acquisition step of acquiring a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on a rotational speed of the pneumatic tire; a detecting step of detecting a decompressed state of the pneumatic tire when a difference between the related value acquired in the acquiring step and a predetermined reference value exceeds a predetermined first threshold value; an updating step of updating the reference value based on the related value acquired during a first period including the time when a predetermined update operation is accepted; a determination step of determining whether or not a timing for updating the reference value has arrived based on the related value acquired after the difference exceeds a second threshold value that is equal to or less than the first threshold value and before the update operation is accepted; A determination method executed by one or more processors.

7. an acquisition step of acquiring a related value related to the air pressure of a pneumatic tire mounted on a vehicle based on a rotational speed of the pneumatic tire; a detecting step of detecting a decompressed state of the pneumatic tire when a difference between the related value acquired in the acquiring step and a predetermined reference value exceeds a predetermined first threshold value; an updating step of updating the reference value based on the related value acquired during a first period including the time when a predetermined update operation is accepted; a determination step of determining whether or not a timing for updating the reference value has arrived based on the related value acquired after the difference exceeds a second threshold value that is equal to or less than the first threshold value and before the update operation is accepted; A program for causing one or more processors to execute the above.

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