Tire air pressure decrease detection device, display control method, and storage medium

Abstract

This invention provides a tire pressure drop detection device, a display control method, and a storage medium to display tire pressure indicators in a manner that minimizes the possibility of misunderstanding for vehicle occupants. The tire pressure drop detection device calculates a pressure ratio, which is the ratio of tire pressure to a reference tire pressure, at each time point. Based on the pressure ratio at each time point, it calculates the maximum change in the pressure ratio within a specified time period. If the maximum change does not exceed a change threshold, the indicator representing the tire pressure at each time point is set as the overall average of the pressure ratio.

Description

Technical Field

[0001] The present invention relates to a tire pressure drop detection device that displays an indicator of tire pressure installed on a vehicle, a display control method for the indicator, and a storage medium for storing the display control program. Background Technology

[0002] Previously, tire pressure drop detection devices were known. For example, Patent Document 1 disclosed a tire pressure drop detection device that, for tires installed on a vehicle, calculates a determination value for determining tire pressure drop, compares the average value obtained by performing a moving average on a predetermined number of determination values ​​with a threshold value, and thereby determines the pressure drop.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-205978

[0006] The aforementioned tire pressure drop detection device displays an indicator (pressure index) to allow vehicle occupants (such as the driver) to monitor tire pressure. For example, it may sometimes display an average value obtained by averaging a predetermined number of judgment values. However, the inventors of this application have discovered a problem when displaying this moving average as a pressure index: the moving average, such as the average value obtained by averaging a predetermined number of judgment values, is easily affected by factors such as road conditions. Therefore, the inventors of this application have discovered the following problem: when displaying a moving average, such as the average value obtained by averaging a predetermined number of judgment values, as a pressure index, it is possible that, for example, even if no tire pressure drop has actually occurred, vehicle occupants may mistakenly believe that a tire pressure drop has occurred. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The present invention was made in view of the following situation, and its object is to provide a tire pressure drop detection device, etc., that displays an indicator of tire pressure for the purpose of enabling vehicle occupants to understand the tire pressure in a manner that suppresses the possibility of misunderstanding for the occupants.

[0009] Methods for solving problems

[0010] The tire pressure drop detection device of the first aspect of the present invention includes a pressure ratio calculation unit, a maximum change calculation unit, a determination unit, and a display control unit. The pressure ratio calculation unit calculates a pressure ratio, which is the ratio of the tire pressure to a reference tire pressure at each time point, based on the tire pressure at each time point of the tires installed on the vehicle. The maximum change calculation unit calculates the difference between the maximum and minimum values ​​of the pressure ratio within a predetermined determination time period, based on the pressure ratios calculated by the pressure ratio calculation unit at each time point, as the maximum change. The determination unit determines whether the maximum change calculated by the maximum change calculation unit exceeds a change threshold. The display control unit controls the display of a pressure index, which is an indicator of the tire pressure at each time point within the determination time period. Specifically, when the determination unit determines that the maximum change does not exceed the change threshold, the display control unit sets the pressure index at each time point to the overall average value of the pressure ratios at each time point. Furthermore, when the determination unit determines that the maximum change exceeds the change threshold, the display control unit sets the air pressure index at each time point as a moving average of the air pressure ratio at each time point.

[0011] Alternatively, in the tire pressure drop detection device of the second aspect of the present invention, in the tire pressure drop detection device of the first aspect, the pressure ratio calculation unit calculates the pressure ratio based on the detection value of the wheel speed sensor.

[0012] Alternatively, in the tire pressure reduction detection device of the third aspect of the present invention, the determination time is 80 seconds or more and 150 seconds or less in the tire pressure reduction detection device of the first or second aspect.

[0013] Alternatively, the tire pressure drop detection device of the fourth aspect of the present invention is such that, in the tire pressure drop detection device of any one of the first to third aspects, the change threshold is 3 or more and 6 or less.

[0014] Alternatively, in the tire pressure drop detection device of the fifth aspect of the present invention, in any one of the tire pressure drop detection devices of the first to the fourth aspects, the moving average value is a value obtained by dividing the pressure ratio at each time point by the sum of the respective pressure ratios at time points that are within a specified range from each time point.

[0015] Alternatively, the tire pressure drop detection device of the sixth aspect of the present invention is such that, in the tire pressure drop detection device of any one of the first to fifth aspects, the total average value is a value obtained by dividing the pressure ratio at each time point by the sum of the respective pressure ratios from the start time of the determination time to each time point.

[0016] The display control method of the seventh aspect of the present invention is executed by a computer and includes the following steps. Furthermore, the display control program of the eighth aspect of the present invention causes a computer to execute the following steps.

[0017] Based on the tire pressure at various time points on the tires installed on the vehicle, a pressure ratio is calculated for each time point as the ratio of the tire pressure to the reference tire pressure. Based on the air pressure ratio at each time point, the difference between the maximum and minimum values ​​of the air pressure ratio within a specified judgment period is calculated as the maximum change. Determine whether the maximum change exceeds the change threshold; and The display of the tire pressure index, which is an indicator of the tire pressure at each time point within the determination time, is controlled. When it is determined that the maximum change does not exceed the change threshold, the tire pressure index at each time point is set as the total average of the tire pressure ratio at each time point. When it is determined that the maximum change exceeds the change threshold, the tire pressure index at each time point is set as the moving average of the tire pressure ratio at each time point.

[0018] Invention Effects

[0019] According to the present invention, a tire pressure drop detection device or the like can be provided that displays an indicator of tire pressure so that vehicle occupants can understand the tire pressure in a manner that suppresses the possibility of misunderstanding for the occupants. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the general structure of a vehicle having a tire pressure drop detection device according to one embodiment of the present invention.

[0021] Figure 2 This is a block diagram showing the electrical structure of a tire pressure drop detection device.

[0022] Figure 3 This is a flowchart illustrating the process of display control handling.

[0023] Label Explanation

[0024] 1: Vehicle; 2: Detection device (tire pressure drop detection device); 4: Tire; 6: Wheel speed sensor; 7: Program (display control program); 21: Pressure ratio calculation unit; 22: Maximum change calculation unit; 23: Judgment unit; 24: Display control unit; DP: Judgment time; IPA: Pressure index; MVC: Maximum change; PAP: Pressure ratio; PM: Display control method; T: Time point; THC: Change threshold. Detailed Implementation

[0025] Hereinafter, an embodiment of one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described with reference to the accompanying drawings. However, the embodiment described below is merely an example of the present invention in all respects. Of course, various modifications and variations can be made without departing from the scope of the present invention. That is, when implementing the present invention, a specific structure corresponding to the embodiment may be appropriately adopted. In addition, the data appearing in this embodiment is described using natural language, but more specifically, it is specified by pseudo-language, instructions, parameters, machine language, etc., that can be recognized by a computer.

[0026] §1 Application Examples

[0027] Figure 1 This is a block diagram showing a schematic structure of a vehicle 1 having the tire pressure drop detection device (detection device 2) of this embodiment. Vehicle 1 is an example of a "vehicle" of the present invention, and vehicle 1 of this embodiment is, for example, a four-wheeled vehicle. Figure 1 The illustrated vehicle 1 has a left front tire 4 (FL), a right front tire 4 (FR), a left rear tire 4 (RL), and a right rear tire 4 (RR). In this embodiment, when it is not necessary to specifically distinguish between the left front tire 4 (FL), the right front tire 4 (FR), the left rear tire 4 (RL), and the right rear tire 4 (RR), they are sometimes simply referred to as "tire 4".

[0028] like Figure 1 As illustrated, vehicle 1 includes a detection device 2, a display 3, tires 4, and wheel speed sensors 6. In vehicle 1, the detection device 2, display 3, and wheel speed sensors 6 are connected via communication lines 5, enabling them to transmit and receive information (in other words, input and output information). Communication line 5 can be, for example, a CAN (Controller Area Network) communication line capable of providing an in-vehicle LAN.

[0029] The detection device 2 is a tire pressure reduction detection device that detects the decompression (in other words, the decrease in tire pressure) of each tire 4. The detection device 2 is implemented, for example, as a tire pressure monitoring system (TPMS) that detects the decompression and sends an alarm to the vehicle occupants, such as the driver, to urge appropriate action.

[0030] TPMS (Tire Pressure Monitoring System) methods for detecting tire depressurization can be broadly categorized into two types: direct detection and indirect detection. Direct detection measures tire pressure directly by assembling a pressure sensor inside the tire rim. In contrast, indirect detection infers tire pressure based on tire rotation information. Indirect detection can be further classified into Dynamic Loaded Radius (DLR) and Resonance Frequency Method (RFM) methods. In the DLR method, the depressurized tire is flattened during driving, resulting in a smaller dynamic load radius. Consequently, it rotates faster than a tire with normal pressure. This phenomenon is used to detect pressure drop by comparing the rotational speeds of the four tires. In the RFM method, the frequency characteristics of the wheel speed signal change due to depressurization to detect the difference from normal pressure.

[0031] In this embodiment, an example of an indirect detection TPMS (TPMS) will be described, where the detection device 2 detects the decompression of each tire 4 based on the rotation information of each tire 4. However, the detection device 2 does not necessarily have to be an indirect detection TPMS; it can also be a direct detection TPMS. The detection device 2 in this embodiment uses at least one of the DLR (Direct Latch) and RFM (Remote Fluid Mechanism) methods described above to detect decompression. For example, the detection device 2 can also combine both the DLR and RFM methods to detect decompression with high precision.

[0032] For example, the detection device 2 can also determine the decrease in tire pressure using a DLR method that employs at least one of the pressure reduction determination values ​​DEL1, DEL2, and DEL3. The pressure reduction determination values ​​DEL1, DEL2, and DEL3 are parameters calculated based on signals representing the rotational speeds of the four tires of a moving vehicle (wheel speed signals). Pressure reduction determination value DEL1 is an index that compares the total or average rotational speeds of tires located diagonally opposite each other. Pressure reduction determination value DEL2 is an index that compares the total or average rotational speeds of tires located at the front and rear of the vehicle. Pressure reduction determination value DEL3 is an index that compares the total or average rotational speeds of tires located on the left and right sides of the vehicle. Pressure reduction determination value DEL1 can also be understood as a value where a higher wheel speed on one diagonal corresponds to a higher pressure reduction, and a higher wheel speed on the other diagonal corresponds to a lower pressure reduction. Additionally, the decompression judgment value DEL3 can be understood as a value that increases with the speed of the two left or right wheels out of the four wheels, and decreases with the speed of the remaining two wheels. Similarly, the decompression judgment value DEL2 can be understood as a value that increases with the speed of the two front or rear wheels out of the four wheels, and decreases with the speed of the remaining two wheels.

[0033] In this embodiment, the decompression determination values ​​DEL1, DEL2, and DEL3 used by the detection device 2 during decompression detection via the DLR method can be calculated based on the wheel speed signals of each tire 4 of the moving vehicle 1. The decompression determination value DEL1 in this embodiment is, for example, an index comparing the total or average rotational speeds of the left front tire 4 (FL) and right rear tire 4 (RR) and the right front tire 4 (FR) and left rear tire 4 (RL). The decompression determination value DEL2 in this embodiment is, for example, an index comparing the total or average rotational speeds of the left front tire 4 (FL) and right front tire 4 (FR) and the left rear tire 4 (RL) and right rear tire 4 (RR). The decompression determination value DEL3 in this embodiment is, for example, an index comparing the total or average rotational speeds of the left front tire 4 (FL) and left rear tire 4 (RL) and the right front tire 4 (FR) and right rear tire 4 (RR).

[0034] Alternatively, for example, the detection device 2 can also determine the decrease in tire pressure using the tire's resonant frequency RF (for example, the resonant frequency in the tire's torsional direction). In this embodiment, the resonant frequency RF used by the detection device 2 when detecting decompression by the RFM method is a parameter estimated by analyzing the wheel speed signals of each tire 4 of the moving vehicle 1.

[0035] As described above, the detection device 2, as an indirect detection type TPMS, uses the wheel speed signal (a signal representing the rotational speed of each tire 4) of each tire 4 to detect decompression of each tire 4. For example, the detection device 2 uses at least one of the decompression determination value DEL1, decompression determination value DEL2, decompression determination value DEL3 calculated (estimated) from the aforementioned wheel speed signal, and the resonance frequency RF to detect decompression of each tire 4 with high precision. The detection device 2 can also use all of the decompression determination values ​​DEL1, DEL2, DEL3, and the resonance frequency RF to detect decompression of each tire 4 with high precision. In this embodiment, the detection device 2 acquires the wheel speed signal of each tire 4 from the wheel speed sensor 6 installed on each tire 4 (more precisely, on each wheel on which each tire 4 is installed).

[0036] exist Figure 1 In the example shown, a wheel speed sensor 6 (FL) is installed on the left front tire 4 (FL), a wheel speed sensor 6 (FR) is installed on the right front tire 4 (FR), a wheel speed sensor 6 (RL) is installed on the left rear tire 4 (RL), and a wheel speed sensor 6 (RR) is installed on the right rear tire 4 (RR). Therefore, the detection device 2 acquires the wheel speed signal of the left front tire 4 (FL) from the wheel speed sensor 6 (FL), the wheel speed signal of the right front tire 4 (FR) from the wheel speed sensor 6 (FR), the wheel speed signal of the left rear tire 4 (RL) from the wheel speed sensor 6 (RL), and the wheel speed signal of the right rear tire 4 (RR) from the wheel speed sensor 6 (RR). In this embodiment, when it is not necessary to specifically distinguish between wheel speed sensors 6 (FL), 6 (FR), 6 (RL), and 6 (RR), they are sometimes simply referred to as "wheel speed sensor 6".

[0037] Each wheel speed sensor 6 detects wheel speed signals (i.e., signals representing the rotational speed of each tire 4) at a predetermined sampling period during the operation of the vehicle 1, providing rotational information for the wheel on which the wheel speed sensor 6 is mounted. The wheel speed signals of each tire 4 constantly sensed by each wheel speed sensor 6 are transmitted to the detection device 2 in real time via the communication line 5, for example. There are no particular limitations on the wheel speed sensor 6 as long as it can detect the rotational speed of the tire 4. For example, the wheel speed sensor 6 may be a sensor that determines the rotational speed based on the output signal of an electromagnetic pickup. Alternatively, the wheel speed sensor 6 may be a sensor that generates electricity using rotation, like a generator, and determines the rotational speed based on the voltage generated. There are no particular limitations on the installation position of the wheel speed sensor 6; it can be appropriately selected according to the type of sensor, as long as it can detect the rotational speed of the tire 4.

[0038] Display 3 is a display (display device) controlled by detection device 2, such as an in-vehicle HMI (Human Machine Interface). Display 3 can be implemented in any way, such as a liquid crystal display element, a liquid crystal monitor, a plasma display, or an organic EL (Electro-Luminescence) display.

[0039] (Notes on decompression testing methods)

[0040] As described above, the detection device 2 of this embodiment acquires wheel speed signals of each tire 4 from each wheel speed sensor 6 at a predetermined period, and calculates decompression determination values ​​DEL1, DEL2, DEL3 and resonance frequency RF at each time point T based on the acquired wheel speed signals. Then, the detection device 2 uses the decompression determination values ​​DEL1, DEL2, DEL3 and resonance frequency RF at each time point T to detect the decompression of each tire 4 in real time. For example, the detection device 2 uses at least one of the decompression determination values ​​DEL1, DEL2, DEL3 and resonance frequency RF at each time point T as a determination value, and compares the determination value with a predetermined threshold to detect decompression. The detection device 2 may also use the decompression determination values ​​DEL1, DEL2, DEL3 and resonance frequency RF at each time point T as determination values, and compare each determination value with a threshold corresponding to each determination value to detect decompression. In addition, the detection device 2 can also calculate the judgment value of each time point T based on the combination of the decompression judgment values ​​DEL1, DEL2, DEL3 and the resonant frequency RF at each time point T, and compare the calculated judgment value of each time point T with the threshold corresponding to the judgment value, thereby detecting decompression.

[0041] Here, even without decompression, the wheel speed (rotation speed) of each tire 4 will vary slightly depending on the driving state of vehicle 1 and the driving environment (for example, the road surface condition on which vehicle 1 is driving). Therefore, the decompression determination values ​​DEL1, DEL2, DEL3 and the resonant frequency RF at each time point T calculated based on the wheel speed signal will also vary depending on interference factors such as road surface conditions. If the determination value at each time point T calculated using at least one of the decompression determination values ​​DEL1, DEL2, DEL3 and the resonant frequency RF is directly compared with a threshold, the detection device 2 may falsely detect decompression. Therefore, the detection device 2 can also calculate the moving average of the determination value at each time point T over a specified period (e.g., several seconds) and compare the calculated moving average with a threshold to detect decompression.

[0042] Furthermore, it is known that, for example, after the vehicle begins to move, the tires generate heat, and the tire pressure temporarily increases. Therefore, the determination values ​​for each time point T used by the detection device 2 to detect decompression can also be calculated after the vehicle 1 has been driven for a predetermined time. That is, the determination values ​​in this embodiment can also be calculated based on the wheel speed signals of each tire 4 in the state of the tire 4 being heated (in other words, in the state of expansion). The detection device 2 can also communicate with a driving management ECU (not shown) or the like that that manages the driving of the vehicle 1 to confirm whether the predetermined time has elapsed since the vehicle 1 started driving. After confirming that the vehicle 1 has been driven for a predetermined time, the detection device 2 can also acquire the wheel speed signals of each tire 4 and calculate the decompression determination values ​​DEL1, DEL2, DEL3 and the resonant frequency RF for each time point T based on the acquired wheel speed signals.

[0043] For the same reason, the threshold for detecting decompression using the detection device 2 can also be calculated after the vehicle 1 has been driven for a predetermined time. That is, the threshold in this embodiment can also be calculated based on the wheel speed signals of each tire 4 when the tires 4 are hot. Furthermore, in calculating the threshold, values ​​obtained in advance through experimental driving, etc., can be used, or wheel speed signals after the vehicle's tires have been set to normal pressure during regular maintenance, etc. The threshold can also be calculated based on the tire wheel speed signals during the period when the tires 4 are assumed to be at normal pressure (especially the period after the vehicle 1 has been driven for a predetermined time). For example, the threshold can also be calculated based on the decompression determination values ​​DEL1, DEL2, DEL3 and the statistical value (for example, the average value) of the resonant frequency RF during the aforementioned period.

[0044] (Regarding air pressure indicators)

[0045] The detection device 2 of this embodiment detects the decompression of each tire 4, and in particular displays the tire pressure index IPA (Inflation Pressure Index) at each time point T on the display 3. The tire pressure index IPA is an indicator of the tire pressure of the tire 4. For example, to allow occupants of the vehicle 1, such as the driver, to know the tire pressure of the tire 4, the tire pressure index IPA is displayed on the display 3 by the detection device 2. The tire pressure index IPA at each time point T is calculated based on the tire pressure ratio PAP at each time point T. The tire pressure ratio PAP at each time point T is the ratio of the tire pressure at each time point T to the reference tire pressure. For example, the tire pressure ratio PAP is a percentage of the tire pressure relative to the reference tire pressure. The tire pressure ratio PAP at each time point T can represent the rate of change (proportion of change) of the tire pressure at each time point T relative to the reference tire pressure.

[0046] The detection device 2 can also use the wheel speed signal of the tire 4 (a signal representing the rotational speed of the tire 4) to calculate the tire pressure ratio PAP at each time point T. For example, the detection device 2 can also use at least one of the decompression determination values ​​DEL1, DEL2, and DEL3 calculated from the wheel speed signal at each time point T, and the resonant frequency RF, to calculate the tire pressure ratio PAP at each time point T. As an example, the detection device 2 can also use all of the decompression determination values ​​DEL1, DEL2, and DEL3, and the resonant frequency RF at each time point T to calculate the tire pressure ratio PAP at each time point T. The detection device 2 can also use the aforementioned "determination values ​​at each time point T for detecting the decompression of each tire 4" to calculate the tire pressure ratio PAP at each time point T. For example, the detection device 2 can also calculate the "tire pressure at each time point T" based on the "determination values ​​at each time point T for detecting the decompression of each tire 4". That is, the detection device 2 can also calculate the "tire pressure at each time point T" based on at least one of the decompression judgment values ​​DEL1, DEL2, and DEL3 calculated from the wheel speed signal and the resonance frequency RF. Similarly, the detection device 2 can also calculate the "reference tire pressure" based on the aforementioned "threshold for detecting the decompression of each tire 4". However, for the detection device 2, it is not necessary to calculate the tire pressure ratio PAP at each time point T based on the wheel speed signal of the tire 4. The detection device 2 can calculate or detect the tire pressure at each time point T by any method, and use the ratio of the tire pressure at each time point T to the reference tire pressure set by any method as the tire pressure ratio PAP at each time point T.

[0047] Furthermore, it should be noted that the reference tire pressure in this embodiment may not be consistent with the recommended set pressure (also known as the placard pressure). The recommended set pressure is the pressure recommended when the tire temperature is equal to the outside temperature, and is a tire pressure (constant value) recommended based on at least one of the vehicle model and the tire. When adjusting tire pressure, operators sometimes inflate the tires with air at, for example, about 10% more than the recommended set pressure. Moreover, the detection device 2 in this embodiment is a TPMS that detects the decompression of the tire 4. Therefore, if the recommended set pressure is set as the reference tire pressure (e.g., a threshold), there is a possibility that the detection device 2 may incorrectly determine that decompression has occurred even though no decompression has actually occurred. Therefore, the reference tire pressure that serves as the reference for the pressure ratio PAP may not be consistent with the recommended set pressure, for example, the aforementioned "threshold for detecting the decompression of each tire 4". The reference tire pressure in this embodiment is the tire pressure of the tire 4 in a heated state, especially the tire pressure of the tire 4 in a heated state assumed to be at normal pressure. For example, the reference tire pressure in this embodiment is calculated based on the wheel speed signal detected by the wheel speed sensor 6 when the tire 4 has become hot after the vehicle 1 has been driven for a specified time.

[0048] As described above, the "pressure ratio PAP at each time point T" is calculated, for example, based on the wheel speed signal of tire 4. For instance, it is calculated based on the aforementioned "judgment value at each time point T for detecting the decompression of each tire 4 (judgment value at each time point T calculated based on the wheel speed signal)". Here, the detection device 2 of this embodiment calculates a moving average of the judgment value at each time point T and compares the calculated moving average with a threshold value to detect decompression. Therefore, the detection device 2 can calculate a "moving average value of the pressure ratio PAP at each time point T" based on the pressure ratio PAP at each time point T, and display the calculated "moving average value of the pressure ratio PAP at each time point T" as the pressure index IPA at each time point T on the display 3.

[0049] However, even without decompression, the wheel speed of tire 4 will change slightly due to interference factors such as road conditions on the road surface where vehicle 1 is traveling. Therefore, even without decompression, the moving average of the tire pressure ratio (PAP) at each time point T calculated based on the wheel speed signal will change due to this interference factor. When the tire pressure index (IPA) at each time point T is set as the moving average of the tire pressure ratio (PAP) at each time point T, sometimes even without decompression, the tire pressure index (IPA) will fluctuate within a range of approximately 93% to 103% depending on road conditions, etc. If the tire pressure index (IPA) displayed on display 3 fluctuates (changes) as described above, even though no decompression has occurred, occupants of vehicle 1, such as the driver, may mistakenly believe that "decompression has occurred."

[0050] To suppress the possibility of causing misunderstandings to the occupants of vehicle 1 as described above, the detection device 2 controls the air pressure index IPA displayed on the display 3 as follows: In the absence of decompression, the detection device 2 sets the air pressure index IPA at each time point T to the "overall average" rather than the "moving average" of the air pressure ratio PAP at each time point T. Through this control, in the absence of decompression, the detection device 2 suppresses fluctuations (changes) in the air pressure index IPA displayed on the display 3, thus suppressing the possibility of causing misunderstandings to the occupants as described above.

[0051] Furthermore, in the event of decompression, the detection device 2 sets the tire pressure index IPA at each time point T as a "moving average of the tire pressure ratio PAP at each time point T". In the event of decompression, in other words, in the event of an abnormal change (especially a decrease) in tire pressure, the detection device 2 needs to notify the driver and other passengers of vehicle 1 of this tire pressure change as quickly as possible. However, if the tire pressure index IPA is set as a "total average of the tire pressure ratio PAP", the change in this index with tire pressure takes time. In other words, the tire pressure index IPA, as a "total average of the tire pressure ratio PAP", follows tire pressure changes slowly. Therefore, in the event of decompression, the detection device 2 sets the tire pressure index IPA as a "moving average of the tire pressure ratio PAP". Through this control, in the event of decompression, the detection device 2, by using the "moving average of the tire pressure ratio PAP" as the tire pressure index IPA, can quickly and accurately display the tire pressure change as the tire pressure index IPA and notify the occupants. The detection device 2 improves the tracking accuracy of tire pressure changes by displaying the tire pressure index IPA (as a moving average of the tire pressure ratio PAP) on the display 3. In other words, it enhances the tracking accuracy of the tire pressure index IPA for tire pressure changes. Passengers can quickly understand tire pressure changes based on the tire pressure index IPA, which is the moving average of the tire pressure ratio PAP.

[0052] In particular, the inventors of this application discovered two tendencies regarding changes in tire pressure. The first is a pattern where "the tire pressure changes by at least 3% (or, for example, 3% to 6%) from the reference tire pressure within a relatively short period of time, such as 80 to 150 seconds." In other words, the first pattern is one where "the tire pressure ratio (PAP) changes by 3% to 6% within a short period of 80 to 150 seconds." The second is a pattern where "the tire pressure changes by about 3% from the reference tire pressure over a relatively long period of time, such as 200 to 300 seconds (a longer period of time, less than 300 seconds). In other words, the second pattern is one where "the tire pressure ratio (PAP) changes by about 3% over a longer period of time, less than 300 seconds." The inventors of this application further investigated and determined the causes of the first and second types of tire pressure changes. That is, the inventors of this application have confirmed that the first type of tire pressure change is caused by the increase or decrease of tire pressure, while the second type of tire pressure change is caused by the deviation of the tire wheel speed signal (in other words, the deviation of the judgment value calculated based on the wheel speed signal).

[0053] Therefore, the detection device 2 determines whether depressurization has occurred based on the change in the tire pressure ratio PAP within a predetermined judgment time DP of 80 to 150 seconds. By using this judgment time DP, the detection device 2 can accurately determine whether depressurization has occurred based on the change in the tire pressure ratio PAP. Furthermore, when it is determined that no depressurization has occurred, the detection device 2 sets the tire pressure index IPA at each time point T as the overall average of the tire pressure ratio PAP at each time point T. Conversely, when it is determined that depressurization has occurred, the detection device 2 sets the tire pressure index IPA at each time point T as a moving average of the tire pressure ratio PAP at each time point T. Through this display control, when no depressurization has occurred, the detection device 2 suppresses fluctuations (changes) in the tire pressure index IPA, thereby suppressing the possibility of the occupant mistaking it for "depressurization." Furthermore, when depressurization has occurred, the detection device 2 improves the tracking accuracy of the tire pressure index IPA to changes in tire pressure, enabling the occupant to quickly (in other words, rapidly) grasp the changes in tire pressure.

[0054] As described above, the detection device 2 calculates the "pressure ratio PAP at each time point T" using, for example, the "judgment value for each time point T used to detect the decompression of each tire 4". Then, the detection device 2 uses the total average or moving average of the calculated "pressure ratio PAP at each time point T" as the pressure index IPA at each time point T. Here, the "judgment value for each time point T used to detect the decompression of each tire 4" in this embodiment is calculated based on the wheel speed signal, for example, after the vehicle 1 has traveled for a predetermined time, when the tire 4 is in a heated state (in other words, the tire 4 is in an inflated state). Therefore, the detection device 2 can also set the pressure index IPA after the vehicle 1 has just started traveling to 100% or the value of the pressure index IPA at the last time the vehicle stopped (in other words, the time when the vehicle 1 last stopped). With this control, even at the time point after the vehicle 1 has just started traveling, when the "judgment value for each time point T used to detect the decompression of each tire 4 has not yet been calculated based on the wheel speed signal", the detection device 2 can display the pressure index IPA on the display 3. Furthermore, the detection device 2 can also calculate the "pressure ratio PAP at each time point T" based on the calculated "judgment value at each time point T" when the vehicle 1 has been traveling for a specified time and the "judgment value at each time point T" has been calculated based on the calculated "judgment value at each time point T". The detection device 2 uses the total average or moving average of the calculated "pressure ratio PAP at each time point T" as the pressure index IPA at each time point T based on the changes in the pressure ratio PAP within the judgment time DP. Regarding the detection device 2 described above, the following uses... Figure 2 and Figure 3 The details are explained below.

[0055] §2 Structural Examples

[0056] Figure 2 This is a block diagram illustrating an example of the electrical structure of the detection device 2. As hardware, the detection device 2 in this embodiment is, for example, a control unit (computer) mounted on the vehicle 1. The detection device 2 can also be implemented using one or more ECUs (Electronic Control Units). Figure 2 The illustrated detection device 2 includes an I / O interface 11, a CPU (Central Processing Unit) 12, a ROM (Read Only Memory) 13, a RAM (Random Access Memory) 14, and a non-volatile and rewritable storage device 15. The detection device 2 is configured to use the CPU 12, ROM 13, and RAM 14 as hardware processors to perform information processing based on programs and various data. The CPU 12 is an example of a processor resource. The storage device 15 is an example of a memory resource, such as a hard disk drive or a solid-state drive. The RAM 14 and storage device 15 are appropriately used for the operations of the CPU 12. Figure 2 The illustrated storage device 15 stores a tire pressure ratio table 151. In this embodiment, the tire pressure ratio table 151 stores the tire pressure ratio PAP calculated for each time point T, for example, it stores the tire pressure ratio PAP calculated for each time point T based on the wheel speed signal of the tire 4 obtained by the detection device 2 from the wheel speed sensor 6 at a predetermined period.

[0057] I / O interface 11 is a communication device that enables communication with external devices such as display 3 and wheel speed sensor 6. Program 7 is stored in ROM 13. However, program 7 may also be stored in storage device 15 instead of ROM 13. Program 7 is used to cause the detection device 2 to perform information processing (described later) to control the display of display 3. Figure 3 The program 7 contains a series of commands for information processing. Storage medium 16 is a medium that stores information such as the program through electrical, magnetic, optical, mechanical, or chemical means, in a manner that allows computers and other devices, machinery, etc., to read the stored program. The program 7 described above can also be stored in storage medium 16. Detection device 2 can also obtain program 7 from storage medium 16. Storage medium 16 can be a disc-type storage medium such as a CD or DVD, or a storage medium other than a disc type. Examples of storage media other than disc types include semiconductor memories such as flash memory.

[0058] In this embodiment, the CPU 12 expands the program 7 stored in the ROM 13 into the RAM 14. Then, the CPU 12 interprets and executes the commands contained in the program 7 expanded in the RAM 14, controlling the various components. Thus, as... Figure 2 As shown, the detection device 2 in this embodiment operates as a computer having a pressure ratio calculation unit 21, a maximum change calculation unit 22, a determination unit 23, and a display control unit 24 as software modules. That is, in this embodiment, each software module of the detection device 2 is implemented through a hardware structure such as a CPU 12.

[0059] The tire pressure ratio calculation unit 21 calculates the ratio of the tire pressure at each time point T to the reference tire pressure based on the tire pressure at each time point T of the tire 4 installed on the vehicle 1. The tire pressure ratio calculation unit 21 of this embodiment stores the calculated "tire pressure ratio PAP at each time point T" in the tire pressure ratio table 151 stored in the storage device 15.

[0060] For example, the air pressure ratio calculation unit 21 calculates the air pressure ratio PAP based on the detection value of the wheel speed sensor 6 (in this embodiment, the wheel speed signal). The air pressure ratio calculation unit 21 may also use at least one of the following calculated from the wheel speed signal: the decompression determination value DEL1, decompression determination value DEL2, decompression determination value DEL3, and the resonant frequency RF at each time point T. By utilizing the detection value of the wheel speed sensor 6, the air pressure ratio calculation unit 21 can accurately calculate the air pressure ratio PAP at each time point T.

[0061] The maximum change calculation unit 22 calculates the difference between the maximum and minimum values ​​of the pressure ratio PAP within a predetermined judgment time DP, based on the pressure ratio PAP at each time point T calculated by the pressure ratio calculation unit 21. For example, the maximum change calculation unit 22 refers to the pressure ratio table 151 stored in the storage device 15 and determines the maximum value of the pressure ratio PAP within the judgment time DP as the pressure ratio PAP(MAX). Similarly, the maximum change calculation unit 22 refers to the pressure ratio table 151 and determines the minimum value of the pressure ratio PAP within the judgment time DP as the pressure ratio PAP(min). Furthermore, the maximum change calculation unit 22 calculates the difference between the determined pressure ratio PAP(MAX) and the pressure ratio PAP(min) as the maximum change MVC.

[0062] In this embodiment, the determination time DP can be 80 seconds or more and 150 seconds or less. As described above, the inventors of this application have discovered that when "for example, within a short period of about 80 to 150 seconds, the tire pressure changes by at least 3% (especially 3% to 6%) from the reference tire pressure," the change in tire pressure is caused by an increase or decrease in tire pressure. That is, the inventors of this application have discovered that by measuring the change in the air pressure ratio PAP within a determination time DP of 80 to 150 seconds, it is possible to determine with high accuracy whether decompression has occurred. Therefore, by setting the determination time DP to 80 to 150 seconds, the detection device 2 can determine with high accuracy whether decompression has occurred.

[0063] The determination unit 23 determines whether the maximum change amount MVC calculated by the maximum change amount calculation unit 22 exceeds the change amount threshold THC. This change amount threshold THC can also be 3 or more and 6 or less. As described above, in this embodiment, the tire pressure ratio PAP is the percentage of tire pressure relative to the reference tire pressure. Therefore, the change amount threshold THC can also be 3% or more and 6% or less. By setting the change amount threshold THC to 3 or more and 6 or less, the detection device 2 can determine with high accuracy whether decompression has occurred.

[0064] The display control unit 24 controls the display of the tire pressure index IPA, which is an index of tire pressure at each time point T within the judgment time DP. In particular, in this embodiment, the display control unit 24 controls the display of the tire pressure index IPA based on the judgment result of the judgment unit 23.

[0065] Specifically, when the determination unit 23 determines that the maximum change MVC does not exceed the change threshold THC, the display control unit 24 sets the pressure index IPA of each time point T to the total average of the pressure ratio PAP of each time point T. This total average is obtained by dividing the pressure ratio PAP of each time point T by the sum of the pressure ratio PAP from the start time point Ts of the determination time DP to each time point T. Here, if the start time point Ts of the determination time DP is set as time point T(0), the end time point Te of the determination time DP is set as time point T(X), and "n" is set as an integer greater than or equal to 0 and less than or equal to X, then the pressure index IPA(n) of a certain time point T(n) within the determination time DP is calculated as follows. That is, the display control unit 24 first calculates the sum of the pressure ratio PAP of each time point T from the start time point Ts (time point T(0)) of the determination time DP to a certain time point T(n). Specifically, the display control unit 24 calculates the pressure ratio PAP(0) at time point T(0) + the pressure ratio PAP(1) at time point T(1) + ... + the pressure ratio PAP(n) at time point T(n)}. For example, the display control unit 24 refers to the pressure ratio table 151 stored in the storage device 15, determines the pressure ratios PAP(0), PAP(1), ..., PAP(n) respectively, and calculates the sum of the determined values. Then, the display control unit 24 calculates the total average value of the pressure ratio PAP(n) by dividing the pressure ratio PAP(n) by the sum of the pressure ratios PAP(0) + PAP(1) + ... + PAP(n)}. The display control unit 24 uses the calculated "total average value of the pressure ratio PAP(n)" (that is, the value obtained by dividing the pressure ratio PAP(n) at time point T(n) by the sum of the individual pressure ratios PAP from time point T(0) to time point T(n)) as the pressure index IPA(n).

[0066] When the determination unit 23 determines that the maximum change MVC does not exceed the change threshold THC, that is, when it is determined that no decompression has occurred, the display control unit 24 sets the pressure index IPA at each time point T to the total average value of the pressure ratio PAP at each time point T. Through this control, the display control unit 24 can suppress the fluctuation (change) of the pressure index IPA displayed on the display 3, thereby suppressing the possibility that the occupants may mistakenly believe that "decompression has occurred" even though no decompression has occurred.

[0067] Furthermore, when the determination unit 23 determines that the maximum change MVC exceeds the change threshold THC, the display control unit 24 sets the pressure index IPA at each time point T as a moving average of the pressure ratio PAP at each time point T. This moving average is obtained by dividing the pressure ratio PAP at each time point T by the sum of the pressure ratios PAP at each time point T within a specified range from that time point T. When "m" is set to "an integer greater than or equal to 1 and less than n", the display control unit 24 calculates the pressure index IPA(n) at a certain time point T(n) within the determination time DP, for example, as follows. That is, the display control unit 24 divides the pressure ratio PAP(n) by {pressure ratio PAP(nm) + ... + pressure ratio PAP(n) + ... + pressure ratio PAP(n+m)}, thereby setting it as a moving average of the pressure ratio PAP(n). The display control unit 24 uses the calculated "moving average value of the pressure ratio PAP(n)" (that is, the value obtained by dividing the pressure ratio PAP(n) at time point T(n) by the sum of the pressure ratios PAP at each time point T from time point T(nm) to time point T(n+m)) as the pressure index IPA(n).

[0068] When the determination unit 23 determines that the maximum change MVC exceeds the change threshold THC, i.e., when decompression occurs, the display control unit 24 sets the tire pressure index IPA at each time point T to a moving average of the tire pressure ratio PAP at each time point T. Through this control, the display control unit 24 can improve the tracking accuracy of the tire pressure index IPA displayed on the display 3 to changes in tire pressure, and can promptly notify the occupants of changes in tire pressure.

[0069] The display control unit 24 sets the pressure index IPA of each time point T from the start time point Ts (time point T(0)) to the end time point Te (time point T(X)) of the determination time DP as the total average or moving average of the pressure ratio PAP of each time point T from time point T(0) to time point T(X) based on the maximum change MVC within the determination time DP. That is, the display control unit 24 calculates the pressure index IPA of each time point T from time point T(0) to time point T(X) after the determination time DP has elapsed. For example, the pressure index IPA of each time point T from time point T(0) to time point T(X) is also combined into the total average or moving average of the pressure ratio PAP of each time point T from time point T(0) to time point T(X+1) at time point T(X+1). Similarly, based on the maximum change MVC during the period from time point T(1) to time point T(X+1) (i.e., the determination time DP with time point T(1) as the start time point Ts), the pressure index IPA at each time point T from time point T(1) to time point T(X+1) becomes, for example, the total average or moving average of the pressure ratio PAP at time point T(X+2) for each time point T from time point T(1) to time point T(X+1). That is, the detection device 2 can use the maximum change MVC within the determination time DP to determine with high accuracy whether decompression has occurred, and switch the value of the pressure index IPA displayed on the display 3 at a period shorter than the determination time DP.

[0070] §3 Examples of Actions

[0071] Figure 3 This is a flowchart illustrating an example of the processing sequence of the detection device 2 in this embodiment. The processing sequence described below is an example of the processing steps of an information processing method (display control method PM) that "controls the display of the tire pressure index IPA at each time point T of the tire 4 installed on the vehicle 1". However, the processing sequence described below is only an example, and each step can be changed as much as possible. Furthermore, regarding the processing described below, steps can be appropriately omitted, substituted, or added according to the embodiment.

[0072] (Step S10)

[0073] In step S10, the CPU 12 operates as the air pressure ratio calculation unit 21 to acquire the wheel rotation information at each time point T. In this embodiment, the CPU 12 acquires the detection values ​​(i.e., wheel speed signals) of each wheel speed sensor 6. For example, the CPU 12 acquires the wheel speed signals of each tire 4 from each wheel speed sensor 6 at a predetermined period (for example, the sampling period of the wheel speed sensor 6).

[0074] (Step S20)

[0075] In step S20, the CPU 12 operates as the air pressure ratio calculation unit 21 to calculate the air pressure ratio PAP at each time point T. In this embodiment, the CPU 12 calculates the air pressure ratio PAP based on the detection value of the wheel speed sensor 6 obtained in step S10. In other words, it calculates the air pressure ratio PAP at each time point T based on the wheel speed signals of each tire 4 obtained at a predetermined period. For example, the CPU 12 calculates the air pressure ratio PAP(0) at time point T(0) based on the wheel speed signal at the start time point Ts (time point T(0)) of the determination time DP. When calculating the air pressure ratio PAP(0), the CPU 12 stores the calculated air pressure ratio PAP(0) in the air pressure ratio table 151 stored in the storage device 15. Similarly, CPU 12 calculates the air pressure ratio PAP(1) at time point T(1) based on the wheel speed signal at time point T(1), and calculates the air pressure ratio PAP(2) at time point T(2) based on the wheel speed signal at time point T(2). CPU 12 calculates the air pressure ratio PAP(X) at time point T(X) based on the wheel speed signal at the end time point Te (time point T(X)) of the determination time DP. CPU 12 calculates each of the air pressure ratios PAP(1), PAP(2), ..., PAP(X) in sequence based on the wheel speed signals at time points T(1), T(2), ..., T(X), and saves the calculated air pressure ratios PAP(1), PAP(2), ..., PAP(X) in air pressure ratio table 151.

[0076] As described above, in step S20, the CPU 12 can also calculate at least one of the following at each time point T: decompression determination value DEL1, decompression determination value DEL2, decompression determination value DEL3, and resonance frequency RF, based on the wheel speed signal acquired at a predetermined period. Then, the CPU 12 can also use the calculated "at least one of the following at each time point T: decompression determination value DEL1, decompression determination value DEL2, decompression determination value DEL3, and resonance frequency RF" to calculate the air pressure ratio PAP at each time point T. Furthermore, the start time point Ts of the determination time DP can, for example, be the time point after the vehicle 1 has traveled for a predetermined time and the tire 4 has heated up (in other words, the tire 4 has expanded).

[0077] (Step S30)

[0078] In step S30, the CPU 12, acting as the maximum change calculation unit 22, calculates the maximum change (MVC) of the pressure ratio PAP within the determination time DP. In this embodiment, the CPU 12 refers to the pressure ratio table 151 to determine the maximum value (pressure ratio PAP(MAX)) and minimum value (pressure ratio PAP(min)) of the pressure ratio PAP within the determination time DP. Then, the CPU 12 calculates the difference between the determined pressure ratio PAP(MAX) and pressure ratio PAP(min) as the maximum change (MVC). The determination time DP can be, for example, 80 seconds or more and 150 seconds or less.

[0079] (Step S40)

[0080] In step S40, CPU 12, acting as the determination unit 23, determines whether the maximum change amount MVC calculated in step S30 exceeds the change amount threshold THC. This change amount threshold THC can be, for example, 3% or higher and 6% or lower; in this embodiment, it can be 3% or higher and 6% or lower. If it is determined that the maximum change amount MVC exceeds the change amount threshold THC ("Yes" in step S40), CPU 12 proceeds to step S50. If it is determined that the maximum change amount MVC does not exceed the change amount threshold THC ("No" in step S40), CPU 12 proceeds to step S60.

[0081] (Step S50)

[0082] In step S50, the CPU 12, acting as the display control unit 24, sets the pressure index IPA at each time point T as a moving average of the pressure ratio PAP at each time point T. This moving average is obtained by dividing the pressure ratio PAP at each time point T by the sum of the pressure ratio PAPs at each time point T within a specified range from that time point T (e.g., from time point T (nm) to time point T (n+m)). For example, the CPU 12 calculates the pressure index IPA(n) at a certain time point T (n) within the determination time DP as follows: That is, the CPU 12 sets the pressure ratio IPA(n) as the value obtained by dividing the pressure ratio PAP(n) by {pressure ratio PAP (nm) + ... + pressure ratio PAP (n) + ... + pressure ratio PAP (n+m)}.

[0083] (Step S60)

[0084] In step S60, the CPU 12, acting as the display control unit 24, sets the pressure index IPA at each time point T as the total average of the pressure ratio PAP at each time point T. This total average is obtained by dividing the pressure ratio PAP at each time point T by the sum of the individual pressure ratios PAP from the start time point Ts (time point T(0)) of the determination time DP up to that time point T. For example, the CPU 12 calculates the pressure index IPA(n) at a certain time point T(n) within the determination time DP as follows: That is, the CPU 12 sets the pressure ratio PAP(n) as the value obtained by dividing the pressure ratio PAP(n) by {pressure ratio PAP(0) + pressure ratio PAP(1) + ... + pressure ratio PAP(n)}.

[0085] [feature]

[0086] As described above, the detection device 2 of this embodiment includes a tire pressure ratio calculation unit 21, a maximum change calculation unit 22, a determination unit 23, and a display control unit 24. The tire pressure ratio calculation unit 21 calculates the ratio of the tire pressure at each time point T relative to a reference tire pressure, i.e., the tire pressure ratio PAP, based on the tire pressure at each time point T of the tire 4 installed on the vehicle 1. The maximum change calculation unit 22 calculates the difference between the maximum value (tip (MAX)) and the minimum value (min) of the tire pressure ratio PAP within the determination time DP, based on the tire pressure ratio PAP calculated by the tire pressure ratio calculation unit 21 at each time point T, as the maximum change MVC. The determination unit 23 determines whether the maximum change MVC calculated by the maximum change calculation unit 22 exceeds the change threshold THC. The display control unit 24 controls the display of the tire pressure index IPA at each time point T within the determination time DP, and in particular, controls the display of the tire pressure index IPA based on the determination result of the determination unit 23. Specifically, when the determination unit 23 determines that the maximum change MVC does not exceed the change threshold THC, the display control unit 24 sets the pressure index IPA at each time point T to the overall average value of the pressure ratio PAP at each time point T. Furthermore, when the determination unit 23 determines that the maximum change MVC exceeds the change threshold THC, the display control unit 24 sets the pressure index IPA at each time point T to the moving average value of the pressure ratio PAP at each time point T.

[0087] The display control method PM of this embodiment causes the computer (in this embodiment, the CPU 12 of the detection device 2) to execute... Figure 3The illustrated steps are S20, S30, S40, S50, and S60. In step S20, CPU 12 calculates the pressure ratio PAP at each time point T. In step S30, CPU 12 calculates the maximum change in pressure ratio PAP (MVC) within the determination time DP. That is, CPU 12 calculates the difference between pressure ratio PAP (MAX) and pressure ratio PAP (min) within the determination time DP based on the pressure ratio PAP calculated at each time point T in step S20, as the maximum change MVC. In step S40, CPU 12 determines whether the maximum change MVC calculated in step S30 exceeds the change threshold THC. If it is determined that the maximum change MVC exceeds the change threshold THC ("Yes" in step S40), in step S50, CPU 12 sets the pressure index IPA at each time point T as a moving average of the pressure ratio PAP at each time point T. When it is determined that the maximum change MVC does not exceed the change threshold THC ("No" in step S40), in step S60, the CPU 12 sets the tire pressure index IPA at each time point T to the total average of the tire pressure ratio PAP at each time point T. That is, in steps S50 and S60, the CPU 12 controls the display of the tire pressure index IPA at each time point T within the determination time DP, and in particular, controls the display of the tire pressure index IPA based on the determination result in step S40. In this embodiment, program 7 causes a computer (e.g., CPU 12) to execute each step of the above-described display control method PM. This program 7 may also be stored in storage medium 16.

[0088] According to this structure, in the detection device 2 (display control method PM), if the maximum change in the tire pressure ratio PAP (MVC) within the judgment time DP does not exceed the change threshold THC, that is, if it is determined that no decompression has occurred, the tire pressure index (IPA) is set to the "total average of the tire pressure ratio PAP". Through this control, in the absence of decompression, the detection device 2 can suppress the fluctuation (change) of the tire pressure index (IPA) displayed on the display 3, thus suppressing the possibility of the occupant mistaking "decompression" for actual decompression. Furthermore, in the detection device 2 (display control method PM), if the maximum change in the tire pressure ratio (MVC) within the judgment time DP exceeds the change threshold THC, that is, if it is determined that decompression has occurred, the tire pressure index (IPA) is set to the "moving average of the tire pressure ratio PAP". Through this control, in the presence of decompression, the detection device 2 can improve the tracking accuracy of the tire pressure index (IPA) to changes in tire pressure, enabling the occupant to quickly (in other words, rapidly) grasp the changes in tire pressure. When it is determined that a decompression has occurred, the detection device 2 can quickly and accurately display the change in tire pressure as the tire pressure index IPA by switching the display of the tire pressure index IPA at each time point T from the total average value to the moving average value.

[0089] §4 Variations

[0090] The embodiments of the present invention have been described in detail above, but the above description is merely illustrative in all respects. Various modifications or variations can be made without departing from the scope of the present invention. For example, the following changes are possible. Furthermore, the same reference numerals will be used below for the same constituent elements as in the above embodiments, and descriptions of the same content as in the above embodiments will be appropriately omitted. The following variations can be appropriately combined.

[0091] Regarding the specific hardware structure of the detection device 2, the constituent elements can be appropriately omitted, replaced, or added depending on the implementation method. For example, the processor resources may include multiple hardware processors. The hardware processors may also be composed of microprocessors, FPGAs (field-programmable gate arrays), DSPs (digital signal processors), etc. The detection device 2 may also be composed of multiple computers. In this case, the hardware structures of each computer may be the same or different. In addition, the detection device 2 may be a general-purpose server device, PC (personal computer), etc., in addition to being designed as an information processing device dedicated to the service provided. Furthermore, the detection device 2 may also be implemented as a computer integrated with an ECU (ECU) of the vehicle 1, such as a driving management ECU (not shown) that manages the driving of the vehicle 1.

Claims

1. A tire pressure drop detection device, comprising: The tire pressure ratio calculation unit calculates a tire pressure ratio as a ratio of the tire pressure to a reference tire pressure at each time point based on the tire pressure at each time point of the tires installed on the vehicle. The maximum change calculation unit calculates the difference between the maximum and minimum values ​​of the pressure ratio within a specified determination time period based on the pressure ratio calculated at each time point by the pressure ratio calculation unit. The determination unit determines whether the maximum change calculated by the maximum change calculation unit exceeds the change threshold. as well as The display control unit controls the display of tire pressure indicators, which are indices of tire pressure at various time points within the specified determination time. When the determination unit determines that the maximum change does not exceed the change threshold, the display control unit sets the air pressure index at each time point to the total average value of the air pressure ratio at each time point. When the determination unit determines that the maximum change exceeds the change threshold, the display control unit sets the air pressure index at each time point to the moving average value of the air pressure ratio at each time point.

2. The tire pressure drop detection device according to claim 1, wherein, The air pressure ratio calculation unit calculates the air pressure ratio based on the detection value of the wheel speed sensor.

3. The tire pressure drop detection device according to claim 1 or 2, wherein, The determination time is between 80 seconds and 150 seconds.

4. The tire pressure drop detection device according to claim 1 or 2, wherein, The threshold for the change is 3 or higher and 6 or lower.

5. The tire pressure drop detection device according to claim 1 or 2, wherein, The moving average is a value obtained by dividing the air pressure ratio at each time point by the sum of the air pressure ratios at each time point that are within a specified range from each time point.

6. The tire pressure drop detection device according to claim 1 or 2, wherein, The overall average value is obtained by dividing the air pressure ratio at each time point by the sum of the respective air pressure ratios from the start time of the determination time to each time point.

7. A display control method, wherein, The computer performs the following steps: Based on the tire pressure at various time points on the tires installed on the vehicle, a pressure ratio is calculated for each time point as the ratio of the tire pressure to the reference tire pressure. Based on the air pressure ratio at each time point, the difference between the maximum and minimum values ​​of the air pressure ratio within a specified judgment period is calculated as the maximum change. Determine whether the maximum change exceeds the change threshold; as well as The display of the tire pressure index, which is an indicator of the tire pressure at each time point within the determination time, is controlled. When it is determined that the maximum change does not exceed the change threshold, the tire pressure index at each time point is set as the total average of the tire pressure ratio at each time point. When it is determined that the maximum change exceeds the change threshold, the tire pressure index at each time point is set as the moving average of the tire pressure ratio at each time point.

8. A storage medium storing a display control program that causes a computer to perform the following steps: Based on the tire pressure at various time points on the tires installed on the vehicle, a pressure ratio is calculated for each time point as the ratio of the tire pressure to the reference tire pressure. Based on the air pressure ratio at each time point, the difference between the maximum and minimum values ​​of the air pressure ratio within a specified judgment period is calculated as the maximum change. Determine whether the maximum change exceeds the change threshold; as well as The display of the tire pressure index, which is an indicator of the tire pressure at each time point within the determination time, is controlled. When it is determined that the maximum change does not exceed the change threshold, the tire pressure index at each time point is set as the total average of the tire pressure ratio at each time point. When it is determined that the maximum change exceeds the change threshold, the tire pressure index at each time point is set as the moving average of the tire pressure ratio at each time point.

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