Tire air pressure drop detector, and tire air pressure drop detection method

Abstract

To detect that air pressure of a tire has decreased, while suppressing increase in a computation load.SOLUTION: A tire air pressure drop detector comprises: a reference consumption efficiency deriving unit M15 which derives reference consumption efficiency EFFB which is an index value based on consumption efficiency EFF of energy of a vehicle when the vehicle travels in a predetermined traveling section PRD during an initial period after air pressure is filled in a tire; an after-lapse consumption efficiency deriving unit M17 which derives after-lapse consumption efficiency EFFA which is the index value based on the consumption efficiency EFF when the vehicle travels in the predetermined traveling section PRD during a measurement period after the lapse of the initial period; a deviation determination unit M19 which determines whether or not the after-lapse consumption efficiency EFFA deviates from the reference consumption efficiency EFFB; and a reduction detection unit M21 which detects that air pressure of a tire has decreased, when it is determined that the after-lapse consumption efficiency EFFA deviates from the reference consumption efficiency EFFB.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire air pressure loss detection device and a tire air pressure loss detection method for detecting a decrease in air pressure in a tire mounted on a wheel of a vehicle. [Background technology]

[0002] Patent Document 1 discloses a tire pressure detection device that detects the state of air pressure in a tire. A calculation device of the device extracts a resonance frequency from a signal including the vibration frequency of the tire. The calculation device then detects the state of air pressure in the tire based on the resonance frequency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-133831 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to extract the resonance frequency from the signal containing the tire vibration frequency, the computing device executes FFT analysis and averaging processing, which may increase the computational load of the computing device. [Means for solving the problem]

[0005] A tire pressure drop detection device for solving the above problem includes a standard consumption efficiency derivation unit that derives a standard consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle runs a specified driving section during an initial period after air pressure is filled into a tire mounted on a wheel of the vehicle, a post-elapsed consumption efficiency derivation unit that derives a post-elapsed consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle runs the specified driving section during a measurement period after the initial period has elapsed, a deviation determination unit that determines whether the post-elapsed consumption efficiency deviates from the standard consumption efficiency, and a drop detection unit that detects a drop in air pressure in the tire when it is determined that the post-elapsed consumption efficiency deviates from the standard consumption efficiency.

[0006] A tire pressure loss detection method for solving the above problem is a method for detecting a loss of air pressure in a tire mounted on a wheel of a vehicle, comprising the steps of causing a processing circuit to derive a reference consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle travels a predetermined driving section during an initial period after the tire is inflated, deriving a post-elapsed consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle travels the predetermined driving section during a measurement period after the initial period has elapsed, determining whether the post-elapsed consumption efficiency deviates from the reference consumption efficiency, and detecting that the air pressure of the tire has decreased when it is determined that the post-elapsed consumption efficiency deviates from the reference consumption efficiency. Effect of the Invention

[0007] To detect a drop in tire air pressure while suppressing an increase in calculation load. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a vehicle equipped with a tire pressure detection device according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram showing a functional configuration of the tire pressure detection device shown in FIG. [Diagram 3] FIG. 3 is a graph showing an example of the relationship between the energy consumption efficiency of a vehicle and the number of times of acquisition. [Figure 4] FIG. 4 is a graph showing the progress of fuel consumption efficiency from the time when the tire was filled with air. [Diagram 5] FIG. 5 is a flowchart showing a processing routine executed when deriving the consumption efficiency in the tire pressure detection device of the first embodiment. [Figure 6] FIG. 6 is a flowchart showing a processing routine executed when detecting a drop in tire air pressure in the tire air pressure detection device of the first embodiment. [Figure 7] FIG. 7 is a schematic diagram showing the configuration of a tire pressure detection device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) Hereinafter, a first embodiment of a tire air pressure loss detection device and a tire air pressure loss detection method will be described with reference to Figs.

[0010] <Overall vehicle configuration> 1, the vehicle 10 is equipped with a plurality of wheels 11, as well as a battery 13 and a motor generator 15. The vehicle 10 may be a hybrid vehicle also equipped with an engine, or may be a battery vehicle without an engine.

[0011] The motor generator 15 can function as either an electric motor or a generator. When the motor generator 15 functions as an electric motor, the motor generator 15 is operated by power supplied from the battery 13, and a driving force is transmitted to the multiple wheels 11. When the motor generator 15 functions as a generator, a regenerative braking force is applied to the multiple wheels 11 in accordance with the power generation of the motor generator 15, and the electric power generated by the motor generator 15 is charged in the battery 13.

[0012] The vehicle 10 is equipped with a plurality of friction brakes 17 provided for each wheel 11, and a brake actuator 19. The friction brakes 17 generate friction braking force at the wheels 11 according to the hydraulic pressure in the wheel cylinders 18. The brake actuator 19 is configured to be able to adjust the hydraulic pressure in the plurality of wheel cylinders 18.

[0013] The vehicle 10 includes a position information acquisition unit 21, a navigation device 23, a detection system 25, and a plurality of control devices. The plurality of control devices are configured to be able to transmit and receive various information via an in-vehicle network 30. The plurality of control devices include a first control device 31 and a second control device 32. The first control device 31 has a function of calculating the energy consumption efficiency EFF of the vehicle 10. When the vehicle 10 is a hybrid vehicle, the first control device 31 calculates the fuel efficiency of the vehicle 10 as the consumption efficiency EFF. When the vehicle 10 is a battery vehicle, the first control device 31 calculates the electricity consumption of the vehicle 10 as the consumption efficiency EFF. Although the details will be described later, the second control device 32 has a function of detecting a decrease in the air pressure of the tires attached to the wheels 11. That is, the second control device 32 corresponds to a "tire air pressure decrease detection device."

[0014] Fuel efficiency is the fuel consumption rate, and electricity efficiency is the power consumption rate. The higher the consumption efficiency (EFF) value, the higher the vehicle's energy utilization efficiency. A "vehicle with high energy utilization efficiency" here refers to a vehicle that can travel a long distance while consuming less energy.

[0015] The location information acquisition unit 21 acquires location coordinates that indicate the current location of the vehicle 10. An example of the location information acquisition unit 21 is a device that acquires location coordinates by communicating with a satellite for GNSS. "GNSS" is an abbreviation for "Global Navigation Satellite System."

[0016] The navigation device 23 displays the current position of the vehicle 10 on a map on a display based on the position coordinates of the vehicle 10 acquired by the position information acquisition unit 21. Furthermore, when a destination of the vehicle 10 is set by an occupant of the vehicle 10, the navigation device 23 creates a travel route RT to the destination. Then, the navigation device 23 displays the travel route RT on a map on the display and supports the travel of the vehicle 10 to the destination.

[0017] The detection system 25 includes a plurality of sensors that detect the state of the vehicle 10. The plurality of sensors each output a detection signal according to the detection result. For example, the plurality of sensors includes a wheel speed sensor 251 and an acceleration sensor 252. The wheel speed sensor 251 is provided for each wheel 11. The wheel speed sensor 251 detects the rotation speed of the wheel 11. The acceleration sensor 252 detects the longitudinal acceleration of the vehicle 10. The rotation speed of the wheel 11 based on the detection signal of the wheel speed sensor 251 is referred to as the "wheel speed VW". The longitudinal acceleration based on the detection signal of the acceleration sensor 252 is referred to as the "longitudinal acceleration GX".

[0018] <Tire pressure drop detection device> The second control device 32 includes a processing circuit 40. An example of the processing circuit 40 is an electronic control device. In this case, the processing circuit 40 includes a CPU 41, a first memory 42, and a second memory 43. The first memory 42 stores a control program executed by the CPU 41. The second memory 43 stores the results of calculations performed by the CPU 41. An example of the second memory 43 is a non-volatile memory.

[0019] <Functional configuration of tire pressure loss detection device> The functional configuration of the tire pressure loss detection device will be described with reference to Fig. 2. The CPU 41 executes the control program in the first memory 42, causing the processing circuit 40 to function as multiple functional units. These functional units are for detecting a decrease in tire pressure. The multiple functional units include a driving section setting unit M11, a consumption efficiency acquisition unit M13, a reference consumption efficiency derivation unit M15, a post-elapsed consumption efficiency derivation unit M17, a deviation determination unit M19, a decrease detection unit M21, and a notification unit M23.

[0020] <Travel section setting section> The travel section setting unit M11 sets a predetermined travel section PRD for acquiring the energy consumption efficiency EFF of the vehicle 10. For example, when a travel route RT is set by the navigation device 23, the travel section setting unit M11 extracts a section of a road that satisfies a predetermined measurement condition from the travel route RT. Then, the travel section setting unit M11 sets the extracted road section as the predetermined travel section PRD. When a single travel route RT includes multiple sections that satisfy the predetermined measurement condition, the travel section setting unit M11 sets each of the multiple sections as the predetermined travel section PRD. When a single travel route RT includes only one section that satisfies the predetermined measurement condition, the travel section setting unit M11 sets only the single section as the predetermined travel section PRD.

[0021] The travel section setting unit M11 determines that the predetermined measurement condition is met when any one of the following conditions (A1), (A2), and (A3) is met. (A1) The road surface is flat.

[0022] (A2) The vehicle 10 can be driven at a speed equal to or faster than the reference speed VSB. (A3) There is no traffic congestion. The travel section setting unit M11 can determine whether the road surface is flat or has a slope based on road information acquired by the navigation device 23 and the like.

[0023] The travel section setting unit M11 can determine whether or not the section is one in which the vehicle 10 can travel at a reference speed VSB or higher, based on information on the type of road acquired by the navigation device 23. Examples of the type of road include information on whether the road is an expressway or an ordinary road, information on the speed limit, and the like.

[0024] The energy consumption efficiency EFF of the vehicle 10 is also affected by the traveling speed of the vehicle 10. Therefore, a reference speed VSB is set to suppress the change in the energy consumption efficiency EFF due to differences in traveling speed. For example, a speed of 50 km / h or more is set as the reference speed VSB.

[0025] The travel section setting unit M11 can distinguish between sections where congestion occurs and sections where no congestion occurs, based on road traffic information distributed from a VICS (registered trademark) center. <Consumption efficiency acquisition section> The consumption efficiency acquisition unit M13 acquires the energy consumption efficiency EFF of the vehicle 10 when the vehicle 10 travels on a road set as the predetermined travel section PRD. Specifically, the consumption efficiency acquisition unit M13 acquires the energy consumption efficiency EFF when the vehicle 10 travels on a road set as the predetermined travel section PRD by the travel section setting unit M11 from the first control device 31 via the in-vehicle network 30.

[0026] Here, when at least one of the wheels 11 has a puncture, the energy consumption efficiency EFF of the vehicle 10 is likely to decrease compared to when none of the wheels 11 has a puncture. In addition, when there is a possibility that an abnormality has occurred in the motor generator 15 or the inverter circuit of the motor generator 15, the regenerative braking force may be prohibited from being applied to the vehicle 10. In addition, when the amount of electricity stored in the battery 13 exceeds a predetermined charge amount range, the regenerative braking force may be prohibited from being applied to the vehicle 10 in order to prevent the amount of electricity stored in the battery 13 from becoming excessive. In a case where the regenerative braking force cannot be applied to the vehicle 10 during vehicle braking, the consumption efficiency EFF is likely to decrease compared to a case where the regenerative braking force can be applied to the vehicle 10 during vehicle braking.

[0027] Therefore, the consumption efficiency acquisition unit M13 acquires the energy consumption efficiency EFF of the vehicle 10 when traveling a predetermined traveling section PRD while a predetermined acquisition condition is satisfied. For example, the consumption efficiency acquisition unit M13 may determine that the predetermined acquisition condition is satisfied when both of the following multiple conditions (B1) and (B2) are satisfied. This allows the consumption efficiency acquisition unit M13 to eliminate the influence of tire punctures and the availability of regenerative braking force when acquiring the consumption efficiency EFF.

[0028] (B1) The wheel speed difference ΔVW between the left and right wheels 11 is equal to or smaller than a judgment value ΔVWth. (B2) Regenerative braking force is permitted to be applied to the vehicle 10 when braking the vehicle 10.

[0029] In addition, when only one of the left and right wheels 11 has a flat tire, the wheel speed difference ΔVW between the left and right wheels 11 becomes large. Therefore, the wheel speed difference that allows for determining whether or not only one of the left and right wheels 11 has a flat tire is set as the determination value ΔVWth.

[0030] <Standard consumption efficiency derivation part> The reference energy efficiency derivation unit M15 derives a reference energy efficiency EFFB, which is an index value based on the energy energy efficiency EFF of the vehicle 10 when the vehicle 10 travels a predetermined driving section PRD during an initial period TM1 after the tires of the wheels 11 are inflated. The initial period TM1 will be described in detail later, but the energy efficiency acquisition unit M13 acquires multiple energy efficiencies EFF during the initial period TM1. The reference energy efficiency derivation unit M15 derives the reference energy efficiency EFFB based on the multiple energy efficiencies EFF acquired during the initial period TM1.

[0031] An example of a process for deriving the base consumption efficiency EFFB will be described with reference to Fig. 3. In the process, the base consumption efficiency deriving unit M15 derives the upper limit INTU and lower limit INTL of the confidence interval INT of the consumption efficiency EFF within the initial period TM1 as the base consumption efficiency EFFB.

[0032] In Fig. 3, the horizontal axis is the energy consumption efficiency EFF of the vehicle 10, and the vertical axis is the number of times CNT the consumption efficiency EFF is acquired. In Fig. 3, the part that occupies 95% of the area surrounded by the line LN corresponds to the confidence interval INT. Therefore, for example, the reference consumption efficiency derivation unit M15 derives the upper limit value INTU and the lower limit value INTL of the 95% confidence interval INT of the consumption efficiency EFF within the initial period TM1 as the reference consumption efficiency EFFB.

[0033] <After-effect consumption efficiency calculation section> The post-elapsed consumption efficiency derivation unit M17 derives a post-elapsed consumption efficiency EFFA, which is an index value based on the energy consumption efficiency EFF of the vehicle 10 when the vehicle 10 travels a predetermined driving section PRD during a measurement period TM2 after the initial period TM1 has elapsed. The measurement period TM2 will be described in detail later, but the consumption efficiency acquisition unit M13 acquires multiple consumption efficiencies EFF during the measurement period TM2. Therefore, the post-elapsed consumption efficiency derivation unit M17 derives the post-elapsed consumption efficiency EFFA based on the multiple consumption efficiencies EFF acquired during the measurement period TM2.

[0034] For example, in the same way as when the reference consumption efficiency derivation unit M15 derives the reference consumption efficiency EFFB, the post-elapsed consumption efficiency derivation unit M17 derives the upper limit value INTU and lower limit value INTL of the confidence interval INT of the consumption efficiency EFF within the measurement period TM2 as the post-elapsed consumption efficiency EFFA. For example, the post-elapsed consumption efficiency derivation unit M17 may derive the upper limit value INTU and lower limit value INTL of the 95% confidence interval INT of the consumption efficiency EFF within the measurement period TM2 as the post-elapsed consumption efficiency EFFA.

[0035] After deriving the post-elapsed consumption efficiency EFFA as described above, the post-elapsed consumption efficiency derivation unit M17 sets the next measurement period TM2. Then, the post-elapsed consumption efficiency derivation unit M17 derives the post-elapsed consumption efficiency EFFA for the next measurement period TM2.

[0036] <Deviation Judgment Section> The deviation determination unit M19 determines whether or not the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB.

[0037] An example of a process for determining whether or not the elapsed energy consumption efficiency EFFA deviates from the reference energy consumption efficiency EFFB will be described with reference to Fig. 4. In Fig. 4, the horizontal axis represents the number of days DT that have elapsed since the tire was filled with air, and the vertical axis represents the energy consumption efficiency EFF of the vehicle 10. As shown in Fig. 4, as the number of days DT that have elapsed increases, the energy consumption efficiency EFF gradually decreases.

[0038] In this determination process, the deviation determination unit M19 derives a fluctuation range ΔEFF, which is the difference between the lower limit INTL of the confidence interval INT derived as the base consumption efficiency EFFB and the upper limit INTU of the confidence interval INT derived as the post-elapsed consumption efficiency EFFA. If the fluctuation range ΔEFF is equal to or greater than the fluctuation range threshold ΔEFFth, the deviation determination unit M19 determines that the post-elapsed consumption efficiency EFFA deviates from the base consumption efficiency EFFB. On the other hand, if the fluctuation range ΔEFF is less than the fluctuation range threshold ΔEFFth, the deviation determination unit M19 determines that the post-elapsed consumption efficiency EFFA does not deviate from the base consumption efficiency EFFB.

[0039] As the tire pressure decreases, there is a tendency for the energy consumption efficiency EFF of the vehicle 10 to decrease. Therefore, the fluctuation range ΔEFF, which is a criterion for determining whether or not the tire pressure needs to be inflated, is set as a fluctuation range threshold ΔEFFth.

[0040] <Decrease detection section> The decrease detection unit M21 detects that the tire pressure has decreased when the deviation determination unit M19 determines that the post-elapsed fuel consumption efficiency EFFA deviates from the reference fuel consumption efficiency EFFB.

[0041] <Notification section> The notification unit M23 notifies the owner of the vehicle 10 when the tire pressure drop detection unit M21 detects a drop in tire pressure. The notification unit M23 displays, for example, on the display of the navigation device 23, a message indicating that tire pressure has dropped or a message urging the owner to inflate the tire. The notification unit M23 may also notify an information terminal possessed by the owner of the vehicle 10 of the drop in tire pressure. The information terminal is, for example, a smartphone or a tablet terminal.

[0042] The notification unit M23 may notify the manufacturer, distributor, etc. of the vehicle 10 that a drop in tire air pressure has been detected. <Method of detecting low tire pressure> First, with reference to Fig. 5, a process flow will be described when the processing circuit 40 of the second control device 32 acquires the energy consumption efficiency EFF of the vehicle 10 from the first control device 31. While the vehicle 10 is traveling, the processing circuit 40 repeatedly executes this processing routine shown in Fig. 5.

[0043] In step S11, the processing circuit 40 determines whether or not a travel route RT has been set in the navigation device 23. If the travel route RT has been set in the navigation device 23 (S11: YES), the processing circuit 40 shifts the processing to step S13. On the other hand, if the travel route RT has not been set in the navigation device 23 (S11: NO), the processing circuit 40 ends this processing routine.

[0044] In step S13, the processing circuit 40 sets the above-mentioned predetermined traveling section PRD. In the next step S15, the processing circuit 40 determines whether or not the vehicle 10 is traveling in the predetermined traveling section PRD. If the processing circuit 40 determines that the vehicle 10 is traveling in the predetermined traveling section PRD (S15: YES), the processing circuit 40 shifts the processing to step S17. On the other hand, if the processing circuit 40 determines that the vehicle 10 is not traveling in the predetermined traveling section PRD (S15: NO), the processing circuit 40 repeatedly executes the determination of step S15 until the vehicle 10 starts traveling in the predetermined traveling section PRD.

[0045] In step S17, the processing circuit 40 judges whether the above-mentioned predetermined obtainable condition is satisfied. If the processing circuit 40 judges that the predetermined obtainable condition is satisfied (S17: YES), the processing circuit 40 shifts the processing to step S19. On the other hand, if the processing circuit 40 judges that the predetermined obtainable condition is not satisfied (S17: NO), the processing circuit 40 shifts the processing to step S15.

[0046] In step S19, the processing circuit 40 acquires the energy consumption efficiency EFF of the vehicle 10 when the vehicle 10 is traveling along the predetermined traveling section PRD. After that, the processing circuit 40 temporarily ends this processing routine.

[0047] In this embodiment, the processing circuit 40 functions as the travel section setting unit M11, thereby executing the process of step S13. The processing circuit 40 functions as the consumption efficiency acquisition unit M13, thereby executing the processes of steps S15, S17, and S19.

[0048] A processing routine executed by the processing circuit 40 of the second control device 32 when it detects a drop in tire air pressure will be described with reference to Fig. 6. When the processing circuit 40 is able to acquire the consumption efficiency EFF through the execution of the processing routine shown in Fig. 5, it executes this processing routine shown in Fig. 6.

[0049] In step S31, the processing circuit 40 updates the number of times CNT that the consumption efficiency EFF has been acquired so that the number of times CNT that the consumption efficiency EFF has been acquired is increased by 1. The number of times CNT that the consumption efficiency EFF has been acquired is reset to 0 (zero) when the tire pressure is inflated.

[0050] In the next step S33, the processing circuit 40 determines whether the updated acquisition count CNT is equal to or greater than an acquisition count judgment value CNTth, which is set to an integer equal to or greater than 2.

[0051] In this embodiment, the upper limit INTU and lower limit INTL of the confidence interval INT are derived as the reference consumption efficiency EFFB and the elapsed consumption efficiency EFFA. In order to improve the accuracy of the derivation of the confidence interval INT, a certain number of consumption efficiencies EFF is required. Therefore, the number of consumption efficiencies EFF that can sufficiently ensure the reliability of the confidence interval INT is set as the acquisition count judgment value CNTth.

[0052] In step S33, if the acquisition count CNT is equal to or greater than the acquisition count judgment value CNTth (S33: YES), the processing circuit 40 proceeds to step S35. On the other hand, if the acquisition count CNT is less than the acquisition count judgment value CNTth (S33: NO), the processing circuit 40 ends this processing routine.

[0053] As described above, the reference consumption efficiency EFFB is derived based on multiple consumption efficiencies EFF acquired within the initial period TM1. The post-elapsed consumption efficiency EFFA is derived based on multiple consumption efficiencies EFF acquired within the measurement period TM2. Thus, when deriving the reference consumption efficiency EFFB, the period from when the tire is inflated to when the acquisition count CNT reaches the acquisition count judgment value CNTth corresponds to the initial period TM1. Also, when deriving the post-elapsed consumption efficiency EFFA, the period from when the acquisition count CNT becomes 1 after the initial period TM1 has elapsed to when the acquisition count CNT reaches the acquisition count judgment value CNTth corresponds to the measurement period TM2.

[0054] In step S35, the processing circuit 40 resets the acquisition count CNT to 0 (zero). In the next step S37, the processing circuit 40 determines whether the filling flag FLG is set to ON. When filling of the tire with air pressure is completed, the filling flag FLG is set to ON. For example, when an operator fills a tire with air pressure at a maintenance factory, when a command indicating that the operator has filled the tire with air pressure is input to the second control device 32, the filling flag FLG is set to ON.

[0055] If the filling flag FLG is set to ON (S37: YES), the processing circuit 40 proceeds to step S39. On the other hand, if the filling flag FLG is set to OFF (S37: NO), the processing circuit 40 proceeds to step S51.

[0056] In step S39, the processing circuit 40 derives the reference consumption efficiency EFFB. In the following step S41, the processing circuit 40 sets the filling flag FLG to OFF. After that, the processing circuit 40 ends this processing routine.

[0057] In step S51, the processing circuit 40 derives the post-effect consumption efficiency EFFA. In the next step S53, the processing circuit 40 judges whether the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB. If the processing circuit 40 judges that the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB (S53: YES), the processing circuit 40 shifts the processing to step S55. On the other hand, if the processing circuit 40 judges that the post-elapsed consumption efficiency EFFA does not deviate from the reference consumption efficiency EFFB (S53: NO), the processing circuit 40 ends this processing routine.

[0058] In step S55, the processing circuit 40 detects that the tire pressure has decreased. In the next step S57, the processing circuit 40 notifies the driver that the tire pressure has dropped and / or prompts the driver to inflate the tire, and then ends this processing routine.

[0059] In this embodiment, the processing circuit 40 functions as the reference consumption efficiency derivation unit M15 to execute the process of step S39. The processing circuit 40 functions as the post-elapsed consumption efficiency derivation unit M17 to execute the process of step S51. The processing circuit 40 functions as the deviation determination unit M19 to execute the process of step S53. The processing circuit 40 functions as the decline detection unit M21 to execute the process of step S55. The processing circuit 40 functions as the notification unit M23 to execute the process of step S57.

[0060] Step S39 corresponds to a step of causing the processing circuit to derive the reference consumption efficiency EFFB. Step S51 corresponds to a step of causing the processing circuit to derive the post-elapsed consumption efficiency EFFA. Step S53 corresponds to a step of causing the processing circuit to determine whether the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB. Step S55 corresponds to a step of causing the processing circuit to detect a decrease in tire pressure.

[0061] <Actions and Effects of the Present Embodiment> (1-1) When a tire mounted on a wheel 11 is inflated, a reference consumption efficiency EFFB is derived, which is an index value based on the consumption efficiency EFF when the vehicle 10 travels a predetermined driving section PRD during an initial period TM1. After the reference consumption efficiency EFFB is derived, a post-elapsed consumption efficiency EFFA is derived, which is an index value based on the consumption efficiency EFF when the vehicle 10 travels a predetermined driving section PRD during a measurement period TM2. If it is determined that the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB, a drop in the tire pressure is detected.

[0062] Here, when the tire pressure decreases, the consumption efficiency EFF tends to decrease. In this embodiment, the decrease in tire pressure is detected by focusing on the correlation between the tire pressure and the consumption efficiency EFF. Therefore, when detecting the decrease in tire pressure, the processing circuit 40 does not need to execute calculation processes that impose a large calculation load, such as FFT analysis and averaging processing.

[0063] Therefore, the second control device 32 can detect a drop in tire air pressure while suppressing an increase in the calculation load on the processing circuit 40. (1-2) The consumption efficiency EFF is affected by the gradient of the road surface on which the vehicle 10 is traveling and the traveling speed of the vehicle 10, in addition to the tire air pressure. Therefore, a section of the road that satisfies the above-mentioned predetermined measurement conditions is set as the predetermined traveling section PRD. Based on the consumption efficiency EFF when the vehicle 10 travels the predetermined traveling section PRD set in this way, the base consumption efficiency EFFB and the post-elapsed consumption efficiency EFFA are derived. Then, a drop in tire air pressure is detected depending on whether the post-elapsed consumption efficiency EFFA deviates from the base consumption efficiency EFFB. Therefore, the second control device 32 can increase the accuracy of detecting a drop in tire air pressure.

[0064] (1-3) When at least one of the wheels 11 has a puncture, the tire efficiency EFF is more likely to decrease than when none of the wheels 11 has a puncture. Therefore, the reference tire efficiency EFFB and the post-elapsed tire efficiency EFFA are derived based on the tire efficiency EFF when the vehicle 10 travels along a predetermined travel section PRD while the condition that the wheel speed difference ΔVW between the left and right wheels 11 is equal to or less than the judgment value ΔVWth is satisfied. Then, a drop in tire air pressure is detected depending on whether the post-elapsed tire efficiency EFFA deviates from the reference tire efficiency EFFB. Therefore, the second control device 32 can increase the accuracy of detecting a drop in tire air pressure.

[0065] (1-4) In the vehicle 10, the energy efficiency EFF changes depending on whether or not regenerative braking force can be applied to the vehicle 10 when braking the vehicle. Therefore, the reference energy efficiency EFFB and the post-elapsed energy efficiency EFFA are derived based on the energy efficiency EFF when the vehicle 10 travels a predetermined driving section PRD when it is permitted to apply regenerative braking force to the vehicle 10 when braking the vehicle. Then, a drop in tire air pressure is detected depending on whether or not the post-elapsed energy efficiency EFFA deviates from the reference energy efficiency EFFB. Therefore, the second control device 32 can increase the accuracy of detecting a drop in tire air pressure.

[0066] Second embodiment A second embodiment of a tire pressure loss detection device and method will be described with reference to Fig. 7. The second embodiment differs from the first embodiment in that a tire pressure loss is detected by an on-board control device and a control device of a server installed outside the vehicle. In the following description, differences from the first embodiment will be mainly described, and the same reference numerals will be used to designate the same components as those in the first embodiment, and repeated description will be omitted.

[0067] 7 illustrates a vehicle 10, a server 100 installed outside the vehicle 10, and an information terminal 200 owned by a user of the vehicle 10. The vehicle 10, the server 100, and the information terminal 200 are capable of communicating with each other via an external vehicle network 60. Examples of the information terminal 200 include a smartphone, a tablet terminal, and a personal computer.

[0068] <Vehicle> The vehicle 10 includes a control device 32A and a communication device 50. The control device 32A includes a processing circuit 40.

[0069] When the information output by the control device 32A is input to the communication device 50, the communication device 50 transmits the information to the server 100 or the information terminal 200 via the external vehicle network 60. The communication device 50 receives the information transmitted by the server 100, and outputs the received information to the control device 32A.

[0070] <Server> The server 100 includes a control device 110 and a communication device 120 . The control device 110 includes a processing circuit 111. One example of the processing circuit 111 is an electronic control device. In this case, the processing circuit 111 includes a CPU, a first memory that stores a program executed by the CPU, and a second memory that stores the results of calculations by the CPU.

[0071] The communication device 120 receives information transmitted by the vehicle 10 and outputs the received information to the control device 110. The communication device 120 transmits the information output by the control device 110 to the vehicle 10 or the information terminal 200 via the external vehicle network 60.

[0072] <Tire pressure drop detection device> The tire pressure loss detection device of this embodiment includes a control device 32A of the vehicle 10 and a control device 110 of the server 100. That is, the processing circuit 40 of the control device 32A functions as a part of the multiple functional units M11 to M23 shown in Fig. 2, while the processing circuit 111 of the control device 110 functions as the remaining functional units. In this case, when one of the processing circuit 40 and the processing circuit 111 is defined as a first processing circuit, the other corresponds to a second processing circuit.

[0073] For example, the processing circuit 40 of the control device 32A functions as a travel section setting unit M11 and a consumption efficiency acquisition unit M13. The processing circuit 111 of the control device 110 functions as a reference consumption efficiency derivation unit M15, a post-elapsed consumption efficiency derivation unit M17, a deviation determination unit M19, a decline detection unit M21, and a notification unit M23.

[0074] In this case, the processing circuit 40 of the control device 32A causes the communication device 50 to transmit information related to the acquired power consumption efficiency EFF to the server 100. When the communication device 120 of the server 100 receives information related to the consumption efficiency EFF, the processing circuit 111 of the control device 110 derives a reference consumption efficiency EFFB and a post-elapsed consumption efficiency EFFA. The processing circuit 111 determines whether the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB. When the processing circuit 111 determines that the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB, it detects that the air pressure in the tires of the vehicle 10 has decreased. Then, the processing circuit 111 causes the communication device 120 to transmit information indicating that the air pressure in the tires has decreased to the information terminal 200.

[0075] When the information terminal 200 receives information indicating that the tire pressure has dropped, it displays on the screen a message indicating that the tire pressure has dropped and a message urging the user to refill the tire with air.

[0076] <Actions and Effects of the Present Embodiment> According to this embodiment, in addition to the effects (1-1) to (1-4) of the first embodiment, the following effects can be obtained.

[0077] Some of the steps required to detect a drop in tire pressure are executed by the processing circuit 40 of the control device 32A, and the rest are executed by the processing circuit 111 of the server 100. This makes it possible to suppress an increase in the control load of the processing circuit, compared to a case in which all steps are executed by one processing circuit.

[0078] (Example of change) The above-described embodiments may be modified as follows: The above-described embodiments and the following modifications may be combined with each other to the extent that they are not technically inconsistent.

[0079] In the second embodiment, some of the reference consumption efficiency derivation unit M15, the post-elapsed consumption efficiency derivation unit M17, the deviation determination unit M19, the decline detection unit M21, and the notification unit M23 may be included in the processing circuit 40 of the control device 32A. For example, the processing circuit 40 of the control device 32A may function as the reference consumption efficiency derivation unit M15 and the post-elapsed consumption efficiency derivation unit M17. Also, for example, the processing circuit 40 of the control device 32A may function as the decline detection unit M21 and the notification unit M23.

[0080] If the vehicle 10 is a vehicle that has only the engine as a power source out of the engine and the motor generator 15, the predetermined obtainable condition does not need to include the above condition (B2). In this case, the consumption efficiency obtainment unit M13 determines that the predetermined obtainable condition is met when the above condition (B1) is satisfied.

[0081] When the vehicle 10 is a vehicle that has only the engine as a power source out of the engine and the motor generator 15, the consumption efficiency acquisition unit M13 acquires the fuel efficiency (fuel consumption rate) of the vehicle 10 as the energy consumption efficiency EFF of the vehicle 10.

[0082] The energy consumption efficiency acquisition unit M13 may acquire the energy consumption efficiency EFF when the vehicle 10 travels a predetermined travel section PRD, regardless of whether a predetermined acquisition condition is satisfied.

[0083] The travel section setting unit M11 may determine that the predetermined measurement condition is met when only some of the above conditions (A1), (A2), and (A3) are satisfied. The deviation determination unit M19 may determine whether the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB by a method different from the method described in the above embodiments. For example, the deviation determination unit M19 may determine that the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB when the difference between the median of the confidence interval INT of the consumption efficiency EFF in the initial period TM1 and the median of the confidence interval INT of the consumption efficiency EFF in the measurement period TM2 is equal to or greater than a threshold value. In this case, the reference consumption efficiency derivation unit M15 derives the median of the confidence interval INT of the consumption efficiency EFF in the initial period TM1 as the reference consumption efficiency EFFB. Similarly, the post-elapsed consumption efficiency derivation unit M17 derives the median of the confidence interval INT of the consumption efficiency EFF in the measurement period TM2 as the post-elapsed consumption efficiency EFFA.

[0084] Also, for example, the deviation determination unit M19 may determine that the post-elapsed consumption efficiency EFFA deviates from the reference consumption efficiency EFFB when the difference between the average value of the multiple consumption efficiencies EFF acquired during the initial period TM1 and the average value of the multiple consumption efficiencies EFF acquired during the measurement period TM2 is equal to or greater than a threshold. In this case, the reference consumption efficiency derivation unit M15 derives the average value of the multiple consumption efficiencies EFF acquired during the initial period TM1 as the reference consumption efficiency EFFB. Similarly, the post-elapsed consumption efficiency derivation unit M17 derives the average value of the multiple consumption efficiencies EFF acquired during the measurement period TM2 as the post-elapsed consumption efficiency EFFA.

[0085] The tire pressure decreases as the number of elapsed days DT passes. Therefore, the initial period TM1 may be a period from the time the tire is inflated until a predetermined number of days have passed. In this case, it is preferable that the predetermined number of days is a number of days that does not affect the consumption efficiency EFF due to the amount of decrease in tire air pressure. Similarly, the measurement period TM2 may be a period from the start of the measurement period TM2 until a predetermined number of days have passed. The start of the measurement period TM2 may be the end of the initial period TM1 or the end of the previous measurement period TM2.

[0086] In addition, the processing circuit 40 may determine that the initial period TM1 has ended when at least one of the following is true: the acquisition count CNT becomes equal to or greater than the acquisition count judgment value CNTth, and the number of days that have elapsed since the tire was filled with air reaches the above-mentioned specified number of days.

[0087] Similarly, the processing circuit 40 may determine that the current measurement period TM2 has ended when at least one of the following is true: the acquisition count CNT becomes equal to or greater than the acquisition count judgment value CNTth, and the number of days elapsed since the start of the measurement period TM2 reaches the above-mentioned specified number of days.

[0088] The processing circuit 40 may be configured to determine whether or not the road surface on which the vehicle 10 is currently traveling satisfies a predetermined measurement condition. If the processing circuit 40 determines that the road surface on which the vehicle 10 is currently traveling satisfies the predetermined measurement condition, the processing circuit 40 may set the road on which the vehicle 10 is currently traveling as a predetermined traveling section, and obtain the consumption efficiency EFF of the predetermined traveling section. In this case, even if the traveling route RT is not set, the processing circuit 40 can obtain the consumption efficiency EFF when the vehicle 10 travels through the predetermined traveling section.

[0089] The processing circuits 40 and 111 are not limited to those having a CPU and a ROM and executing software processing. That is, the processing circuits 40 and 111 may have any one of the following configurations (a), (b), and (c).

[0090] (a) The processing circuitry 40, 111 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0091] (b) The processing circuit 40, 111 includes one or more dedicated hardware circuits for executing various processes. Examples of the dedicated hardware circuits include application specific integrated circuits, i.e., ASIC and FPGA. ASIC is an abbreviation for "Application Specific Integrated Circuit" and "FPGA" is an abbreviation for "Field Programmable Gate Array."

[0092] (c) The processing circuits 40 and 111 each include a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes.

[0093] <Other technical ideas> Next, the technical ideas that can be understood from the above-described embodiments and modifications will be described. (Additional Note 1) A consumption efficiency acquisition unit that acquires an energy consumption efficiency of the vehicle when the vehicle travels along the predetermined travel section, the reference consumption efficiency deriving unit derives, based on the plurality of consumption efficiencies acquired within the initial period, an upper limit value and a lower limit value of a confidence interval of the consumption efficiency as the reference consumption efficiency; the post-elapsed consumption efficiency deriving unit derives, based on the plurality of consumption efficiencies acquired within the measurement period, an upper limit value and a lower limit value of a confidence interval of the consumption efficiency as the post-elapsed consumption efficiency; It is preferable that the deviation determination unit determines that the post-elapsed consumption efficiency deviates from the standard consumption efficiency when a difference between the lower limit value of the confidence interval derived as the standard consumption efficiency and the upper limit value of the confidence interval derived as the post-elapsed consumption efficiency is equal to or greater than a fluctuation range threshold.

[0094] The term "at least one" used herein means "one or more" of the desired options. As an example, the term "at least one" used herein means "only one option" or "both of two options" if the number of options is two. As another example, the term "at least one" used herein means "only one option" or "any combination of two or more options" if the number of options is three or more. [Explanation of symbols]

[0095] 10. Vehicle 11...Wheel 13…Battery 15...Motor generator 32...Second control device (an example of a tire pressure drop detection device) 32A…Control device (constituting an example of a tire pressure drop detection device) 40...Processing circuit 100…Server 110...Control device (constituting an example of a tire pressure drop detection device) 111...Processing circuit M11…Travel section setting section M13…Power consumption efficiency acquisition section M15: Standard consumption efficiency derivation part M17…After-effect consumption efficiency calculation section M19...Difference judgment section M21…Lowering detection section

Claims

1. a standard consumption efficiency deriving unit that derives a standard consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle travels a predetermined travel section during an initial period after the tire mounted on the wheel of the vehicle is inflated; a post-elapsed consumption efficiency deriving unit that derives a post-elapsed consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle travels along the predetermined travel section during a measurement period after the initial period has elapsed; a deviation determination unit that determines whether the post-elapsed consumption efficiency deviates from the reference consumption efficiency; a reduction detection unit that detects a reduction in air pressure of the tire when it is determined that the post-elapsed consumption efficiency deviates from the reference consumption efficiency. Tire pressure drop detection device.

2. a travel section setting unit that sets a road that satisfies a predetermined measurement condition as the predetermined travel section, The predetermined measurement conditions include both that the road surface is flat and that the vehicle can be driven at a reference speed or faster. The tire pressure loss detection device according to claim 1 .

3. the standard consumption efficiency deriving unit derives the standard consumption efficiency based on an energy consumption efficiency of the vehicle when the vehicle travels along the specified travel section while a specified obtainable condition is satisfied during the initial period; the post-elapsed consumption efficiency deriving unit derives the post-elapsed consumption efficiency based on an energy consumption efficiency of the vehicle when the vehicle travels along the specified travel section while the specified obtainable condition is satisfied during the measurement period; The predetermined obtainable condition includes that a wheel speed difference between the left and right wheels is equal to or smaller than a determination value. The tire pressure loss detection device according to claim 1 or 2.

4. the vehicle includes a battery and a motor generator, The predetermined obtainable condition includes that a regenerative braking force is permitted to be applied to the vehicle when braking the vehicle. The tire pressure loss detection device according to claim 3.

5. A tire air pressure loss detection method for detecting a decrease in air pressure in a tire mounted on a wheel of a vehicle, comprising: The processing circuit includes: A step of deriving a reference consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle travels a predetermined travel section during an initial period after the tire is inflated; deriving a post-elapsed consumption efficiency, which is an index value based on the energy consumption efficiency of the vehicle when the vehicle travels along the predetermined travel section during a measurement period after the initial period has elapsed; determining whether the post-elapsed consumption efficiency deviates from the reference consumption efficiency; and detecting a decrease in air pressure of the tire when it is determined that the post-elapsed consumption efficiency deviates from the reference consumption efficiency. Method for detecting low tire pressure.

6. the processing circuit includes a first processing circuit and a second processing circuit; causing the first processing circuit to execute a part of the plurality of steps and the second processing circuit to execute the remaining steps. The tire pressure loss detection method according to claim 5.

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