JP2016196275A - Tire air pressure state detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a misuse.SOLUTION: An air pressure state detection device of tires attached to a vehicle is provided. A detection device 2 includes: a calculation part 21 for calculating an index value for determining an air pressure state of a tire; an instruction detection part 26 for detecting an initialization instruction from a user; an area setting part 27 for setting a misuse area which includes a prior instruction index value that is an index value calculated by the calculation part prior to the initialization instruction, and which is an area extending in a decompression expansion direction where the decompression of the tire progresses from the prior instruction index value and in the opposite direction, in an index value space having the index value as an axis; and a misuse detection part 28 for detecting a misuse where the initialization instruction is issued in a state where an air pressure of the tire is unadjusted, when a post instruction index value that is an index value calculated by the calculation part after the initialization instruction is in the misuse area. The misuse area is configured to be set to extend to a wider area in the decompression expansion direction than in the opposite direction by setting the prior instruction index value as a reference.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an apparatus, a method, and a program for detecting a pneumatic state of a tire mounted on a vehicle.

  In order to drive the vehicle comfortably, it is important that the tire air pressure is adjusted. This is because if the air pressure falls below an appropriate value, there may arise a problem that the ride comfort and fuel consumption are deteriorated. For this reason, a system (Tire Pressure Monitoring System; TPMS) that automatically detects the decompression of a tire has been studied. The information that the tire is depressurized can be used, for example, as a warning to the driver.

  In addition to a method that directly measures tire air pressure by attaching a pressure sensor to the tire, etc., a method that indirectly evaluates tire decompression using other index values. There is. As such an indirect evaluation method, a Dynamic Loaded Radius (DLR) method and a Resonance Frequency Method (RFM) are known. The DLR method uses a phenomenon that the dynamic load radius is reduced when the reduced pressure tire is crushed during traveling, and the reduced pressure tire rotates at a higher speed, and the reduced pressure of the tire is estimated from the rotation speed of the tire. On the other hand, RFM utilizes the fact that the frequency characteristics of the wheel speed change due to the reduced pressure.

  The driver must adjust the tire air pressure at a service station or the like when he / she notices the decompression of the tire or during a periodic inspection. Conventionally, there has been proposed a vehicle in which a driver can issue an initialization instruction after adjusting the air pressure. After such an initialization instruction, initialization is executed in the in-vehicle system, for example, a reference index value (index value at normal pressure) used for determination of decompression is reset and / or decompression is performed. The alarm is released.

  However, sometimes the driver gives an initialization instruction without adjusting the air pressure unintentionally due to an erroneous operation or intentionally for the purpose of turning off the low-pressure alarm lamp. In this case, for example, if the reference index value used for determination of pressure reduction is reset without initialization of the air pressure due to initialization, the detection accuracy of the subsequent pressure reduction state may be lowered. Alternatively, if the warning lamp goes off due to initialization, the driver may lose the opportunity to remember that the air pressure should be adjusted. Patent Document 1 discloses a method for detecting that an initialization instruction has been issued in a state where the air pressure has not been adjusted (misuse). Specifically, the index values for decompression before and after the initialization instruction are compared, and misuse is detected when the magnitude of the difference is within a predetermined range.

JP2013-249024A

  However, tire decompression may proceed rapidly, such as when the tire is punctured. Therefore, the present inventors have noticed that the index value of the decompression may change greatly before and after the initialization instruction even though misuse has occurred, that is, the air pressure of the decompression tire has not been adjusted. It was. In such a case, according to the method of Patent Document 1, the misuse is detected although the magnitude of the difference between the index values before and after the initialization instruction does not fall within a predetermined range and misuse occurs. It may not be.

  An object of the present invention is to provide an apparatus, a method, and a program for detecting the air pressure state of a tire mounted on a vehicle that can accurately detect misuse.

  A detection device according to a first aspect of the present invention is a detection device for the air pressure state of a tire mounted on a vehicle, and includes a calculation unit that calculates an index value for determining the air pressure state of the tire, and an initial value from a user An instruction detection unit that detects an instruction to generate, and an index value space around the index value, including a pre-instruction index value that is the index value calculated by the calculation unit before the initialization instruction, An area setting unit that sets a misuse area that is an area that spreads in the decompression expansion direction in which the tire decompression proceeds from the pre-instruction index value and the opposite direction, and the index value calculated by the calculation unit after the initialization instruction And a misuse detection unit that detects a misuse in which the initialization instruction is issued in a state where tire pressure is not adjusted when a certain post-instruction index value is within the misuse area. The miss-use area is set so as to spread over a wider range in the decompression enlargement direction than in the opposite direction on the basis of the pre-instruction index value.

  A detection device according to a second aspect of the present invention is the detection device according to the first aspect, wherein the decompression tire identifies a decompression tire from a plurality of tires mounted on the vehicle based on the pre-instruction index value. A tire specifying part is further provided. The region setting unit determines that the direction in which the index value changes when the depressurized state of the depressurized tire specified by the depressurized tire specifying unit proceeds is the depressurizing and expanding direction.

  A detection apparatus according to a third aspect of the present invention is the detection apparatus according to the first aspect or the second aspect, and is a reference index value that is the index value after adjustment of tire air pressure, and a current value of the index value. And a decompression determination unit that determines whether or not the tire is in a decompressed state, and a decompression alarm unit that generates a decompression alarm when the decompression determination unit determines that the tire is in a decompressed state And further comprising.

  The detection device according to a fourth aspect of the present invention is the detection device according to the third aspect, further comprising a reference setting unit that updates the reference index value when a misuse is not detected by the misuse detection unit.

A detection device according to a fifth aspect of the present invention is the detection device according to any one of the first to fourth aspects, wherein the vehicle includes a first tire, a second tire, a third tire, and a fourth tire. In addition, as the index value, at least one of the following three index values is used.
(1) The higher the rotational speed of the first tire and the fourth tire, the higher the rotational speed of the second tire and the third tire, and the smaller the second tire and the third tire. An index value that increases as the rotational speed of the tire increases and decreases as the rotational speed of the first tire and the fourth tire increases. (2) The index value increases as the rotational speed of the first tire and the second tire increases. The larger the rotational speed of the third tire and the fourth tire, the smaller the rotational speed of the third tire and the fourth tire, or the larger the rotational speed of the third tire and the fourth tire, and the rotational speed of the first tire and the second tire. Index value that decreases as the value increases (3) The value increases as the rotation speed of the first tire and the third tire increases and the rotation of the second tire and the fourth tire Higher degree is large becomes small, or the second tire and the fourth increased the greater the rotational speed of the tire and the first tire and the third index value becomes smaller the greater the rotational speed of the tire

  The detection device according to a sixth aspect of the present invention is the detection device according to the fifth aspect, wherein at least two of the three index values are used as the index value.

  The detection device according to a seventh aspect of the present invention is the detection device according to the sixth aspect, wherein the misuse area is a dividing line when dividing the index value space according to which tire is decompressed. , Part of the boundary.

A detection method according to an eighth aspect of the present invention is a method for detecting the air pressure state of a tire mounted on a vehicle,
(1) calculating a pre-instruction index value that is an index value for determining the tire air pressure state;
(2) detecting an initialization instruction from a user after calculating the pre-instruction index value;
(3) calculating the index value as a post-instruction index value after the initialization instruction;
(4) A misuse area that is an area that includes the pre-instruction index value and spreads in a depressurization expansion direction and a reverse direction in which tire depressurization progresses from the pre-instruction index value in an index value space with the index value as an axis. Steps to set
(5) detecting a misuse in which the initialization instruction is issued in a state in which the tire air pressure is not adjusted when the post-instruction index value is within the misuse area. The miss-use area is set so as to spread over a wider range in the decompression enlargement direction than in the opposite direction on the basis of the pre-instruction index value.

A detection program according to the ninth aspect of the present invention is a program for detecting the air pressure state of a tire mounted on a vehicle,
(1) calculating a pre-instruction index value that is an index value for determining the tire air pressure state;
(2) detecting an initialization instruction from a user after calculating the pre-instruction index value;
(3) calculating the index value as a post-instruction index value after the initialization instruction;
(4) A misuse area that is an area that includes the pre-instruction index value and spreads in a depressurization expansion direction and a reverse direction in which tire depressurization progresses from the pre-instruction index value in an index value space with the index value as an axis. Steps to set
(5) When the post-instruction index value is within the misuse area, the computer is caused to detect a misuse in which the initialization instruction is issued in a state where the tire air pressure is not adjusted. The miss-use area is set so as to spread over a wider range in the decompression enlargement direction than in the opposite direction on the basis of the pre-instruction index value.

  According to the present invention, misuse is detected when the index value (post-instruction index value) calculated after the initialization instruction belongs to the misuse area. This misuse area is an area that spreads more widely in the direction in which the tire pressure decreases than in the direction in which the tire internal pressure increases, based on the index value (index value before instruction) calculated before the initialization instruction. Is set. As a result, even when the tire pressure is greatly reduced due to tire puncture or the like, if a misuse occurs, it can be detected. Thereby, misuse can be detected accurately.

The schematic diagram which shows a mode that the detection apparatus which concerns on one Embodiment of this invention was mounted in the vehicle. The block diagram which shows the electric constitution of a detection apparatus. The flowchart which shows the flow of a pressure reduction detection process. The figure which shows the index value space divided | segmented into the area | region showing a decompression tire. The flowchart which shows the flow of the setting process of a misuse area | region. The figure which shows the example of a misuse area (in the case of one-wheel decompression). The figure which shows the example of a misuse area (in the case of two-wheel decompression). The figure which shows the example of the misuse area | region which concerns on a modification (in the case of one-wheel decompression). The figure which shows the example of the misuse area | region which concerns on a modification (in the case of two-wheel decompression). The figure which shows the example of the misuse area | region which concerns on another modification (in the case of one-wheel decompression). The figure which shows the example of the misuse area | region which concerns on another modification (when there is one index value).

  Hereinafter, a tire pressure detection device, method, and program according to an embodiment of the present invention will be described with reference to the drawings.

<1. Configuration of detection device>
FIG. 1 is a schematic diagram showing a state in which a tire pressure detection device 2 is mounted on a vehicle 1. The vehicle 1 is a four-wheel vehicle and includes a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. The detection device 2 has a function of detecting decompression of the tires FL, FR, RL, and RR. When the decompression of the tires FL, FR, RL, and RR is detected, an alarm mounted on the vehicle 1 is detected. A warning to that effect is given via the display 3. The vehicle 1 is also equipped with an initialization switch 4 for performing initialization after adjusting the air pressure of the tires FL, FR, RL, and RR. When the initialization switch 4 is operated, the detection device 2 executes predetermined initialization. Details of the flow of decompression detection processing including such initialization will be described later. In addition, the vehicle 1 is also equipped with an alarm indicator 5 for alarming a misuse described later.

  In the present embodiment, the reduced pressure state of the tires FL, FR, RL, RR is detected based on the wheel speed (rotational speed). Wheel speed sensors 6 are attached to the tires FL, FR, RL, and RR, respectively, and the wheel speed sensor 6 detects the wheel speed information of the tire to which it is attached. The wheel speed sensor 6 is connected to the detection device 2 via the communication line 5a, and the wheel speed information detected by each wheel speed sensor 6 is transmitted to the detection device 2 in real time.

  Any wheel speed sensor 6 can be used as long as it can detect the wheel speeds of the running tires FL, FR, RL, and RR. For example, a sensor of a type that measures the wheel speed from the output signal of the electromagnetic pickup can be used, or a sensor that measures the wheel speed from the voltage at this time by generating electricity using rotation like a dynamo. It can also be used. The mounting position of the wheel speed sensor 6 is not particularly limited, and can be appropriately selected according to the type of sensor as long as the wheel speed can be detected.

  FIG. 2 is a block diagram showing an electrical configuration of the detection device 2. As shown in FIG. 2, the detection device 2 is a control unit mounted on the vehicle 1 and includes an I / O interface 11, a CPU 12, a ROM 13, a RAM 14, and a nonvolatile rewritable storage device 15. . The I / O interface 11 is a communication device for communicating with external devices such as the wheel speed sensor 6, the alarm indicators 3 and 5, and the initialization switch 4. The ROM 13 stores a program 7 for controlling the operation of each part of the vehicle 1. The program 7 is written from the storage medium 9 such as a CD-ROM to the ROM 13. The CPU 12 reads the program 7 from the ROM 13 and executes it to virtually calculate the calculation unit 21, the decompression determination unit 22, the decompression tire identification unit 23, the decompression alarm unit 24, the reference setting unit 25, the instruction detection unit 26, and the region setting. The unit 27, the misuse detection unit 28, and the misuse alarm unit 29 operate. Details of the operation of each unit will be described later. The storage device 15 is configured by a hard disk, a flash memory, or the like. Note that the storage location of the program 7 may be the storage device 15 instead of the ROM 13. The RAM 14 and the storage device 15 are appropriately used for the calculation of the CPU 12.

  The alarm indicators 3 and 5 can be realized in any manner, such as a liquid crystal display element or a liquid crystal monitor, as long as it can inform the user that decompression or misuse is occurring. The mounting position of the alarm indicators 3 and 5 can be selected as appropriate, but it is preferably provided at a position that is easily understood by the driver, for example, on the instrument panel. When the control unit (detection device 2) is connected to the car navigation system, a car navigation monitor can be used as the alarm indicators 3 and 5. The configuration and position of the initialization switch 4 are not particularly limited, and can be provided, for example, at the same position as the alarm indicators 3 and 5.

<2. Decompression detection process>
Hereinafter, the pressure reduction detection process for detecting the pressure reduction of the tires FL, FR, RL, RR will be described with reference to FIG. The decompression detection process shown in FIG. 3 is started at a timing when power is supplied to the electric system of the vehicle 1 and is repeatedly executed until the power is turned off.

First, in step S1, the calculation unit 21 calculates an index value for determining the tire air pressure state. Various index values can be used. For example, the following DEL1, DEL2, and DEL3 can be used.
DEL1 = [(V1 + V4) / (V2 + V3) -1] * 100 (%)
DEL2 = [(V1 + V2) / (V3 + V4) -1] * 100 (%)
DEL3 = [(V1 + V3) / (V2 + V4) -1] * 100 (%)

Here, V1 to V4 are wheel speeds of the tires FL, FR, RL, and RR, respectively. The calculation part 21 receives the output signal from the wheel speed sensor 6 in predetermined sampling period (DELTA) T, and converts this into wheel speed V1-V4. DEL1, DEL2, and DEL3 are index values having the following characteristics, respectively.
DEL1: Index value DEL2 that increases as wheel speeds V1 and V4 increase and decreases as wheel speeds V2 and V3 increase, or decreases as wheel speeds V2 and V3 increase and decreases as wheel speeds V1 and V4 increase. : Index value DEL3 that increases as wheel speeds V1 and V2 increase and decreases as wheel speeds V3 and V4 increase, or decreases as wheel speeds V3 and V4 increase and decreases as wheel speeds V1 and V2 increase. An index value that increases as the wheel speeds V1 and V3 increase and decreases as the wheel speeds V2 and V4 increase, or increases as the wheel speeds V2 and V4 increase and decreases as the wheel speeds V1 and V3 increase.

DEL1, DEL2, and DEL3 may be defined as other index values having the above characteristics. For example, they may be defined as follows.
DEL1 = [[(V1 + V4) / 2- (V2 + V3) / 2] / (V1 + V2 + V3 + V4)] * 100 (%)
DEL2 = [[((V1 + V2) / 2- (V3 + V4) / 2] / (V1 + V2 + V3 + V4)] * 100 (%)
DEL3 = [[(V1 + V3) / 2- (V2 + V4) / 2] / (V1 + V2 + V3 + V4)] * 100 (%)

Alternatively, DEL1, DEL2, and DEL3 can be defined as follows.
DEL1 = (V1 * V4) / (V2 * V3)
DEL2 = (V1 * V2) / (V3 * V4)
DEL3 = (V1 * V3) / (V2 * V4)

Alternatively, DEL1, DEL2, and DEL3 can also be defined as follows.
DEL1 = (V1 ² + V4 ² )-(V2 ² + V3 ² )
DEL2 = (V1 ² + V2 ² )-(V3 ² + V4 ² )
DEL3 = (V1 ² + V3 ² )-(V2 ² + V4 ² )

  In addition, instead of or in addition to DEL1, DEL2, and DEL3, the resonance frequency of tires FL, FR, RL, and RR can be used as the index value calculated in step S1. The resonance frequency can be calculated from the output signal of the wheel speed sensor 6, which is a time-series signal including vibration components of the tires FL, FR, RL, RR, for example. Various methods for calculating the resonance frequency of the tire are known (for example, JP-A-9-323515, etc.), and those skilled in the art can appropriately calculate them. Omitted.

  The number of index values calculated in step S1 is not particularly limited, and may be only one, may be two, or may be three or more. However, in the following description, the case where two index values DEL1 and DEL3 are used will be described as an example. DEL1 is an index value that increases as the wheel speed of two wheels existing on one diagonal line increases among the four wheels, and decreases as the wheel speed of the two wheels existing on the other diagonal line increases. is there. Therefore, DEL1 is an index value that is not easily affected by the traveling conditions of the vehicle 1, such as when turning right or left or traveling on a slope. In this sense, it is preferable to use DEL1 as an index value for determining the tire air pressure.

  Subsequently, the reference setting unit 25 determines whether or not the reference index values DEL1 and DEL3 have been set (step S2). If it is determined that the reference index values DEL1 and DEL3 have not been set, they are calculated in the immediately preceding step S1. The current index values DEL1, DEL3 are stored in the storage device 15 as reference index values DEL1, DEL3 (step S3). Then, after step S3, the process proceeds to step S1, and the current index values DEL1, DEL3 are calculated again. On the other hand, if it is determined in step S2 that the reference index values DEL1 and DEL3 have been set, step S3 is skipped and the process proceeds to step S4.

  In subsequent step S4, the decompression determination unit 22 determines whether or not the tires FL, FR, RL, RR are in a decompressed state using the current index values DEL1, DEL3 calculated in the immediately preceding step S1. Specifically, the decompression determination unit 22 compares the index values DEL1 and DEL3 of the immediately preceding step S1 with the reference index values DEL1 and DEL3, respectively, and if the difference between these values is greater than a predetermined value, the decompression state It is determined that On the other hand, if the difference between these values is equal to or less than the predetermined value, it is determined that the pressure is not reduced. The reference index values DEL1 and DEL3 are values of DEL1 and DEL3 immediately after adjustment of the tire air pressure, and are stored in the storage device 15 through step S3.

  That is, step S4 is a step of determining how much the current index values DEL1 and DEL3 have changed from the index values DEL1 and DEL3 immediately after adjusting the air pressure, and detecting a reduced pressure when the change is large. In the present embodiment, the two index values DEL1 and DEL3 are compared. However, when the change in both index values is large, the depressurization may be detected, or when at least one of the changes is large, the depressurization is performed. You may make it detect.

  If pressure reduction is detected in step S4, the process proceeds to step S5. On the other hand, if no pressure reduction is detected in step S4, the process returns to step S1 and the same process is repeated. In step S5, the reduced pressure tire specifying unit 23 specifies which of the tires FL, FR, RL, RR is depressurized based on the current index values DEL1, DEL3. Specifically, the reduced-pressure tire specifying unit 23 determines what points correspond to the index values DEL1 and DEL3 calculated in the immediately preceding step S1 in the index value space with DEL1 and DEL3 shown in FIG. The decompression tire is specified depending on whether it belongs to the region.

  As shown in FIG. 4, the index value space of the present embodiment is divided into eight regions A1 to A8 with four straight lines L1 to L4 passing through the origin as boundaries. The intersection (origin) of the DEL1 axis (horizontal axis) and the DEL3 axis (vertical axis) corresponds to the reference index values DEL1 and DEL3. In addition, since the inclination of the straight lines L1 to L4 depends on the vehicle type, the type of tire, and the like, the inclination is adjusted appropriately by a test or the like and is appropriately determined in advance.

  In the index value space, the first quadrant corresponds to a state in which the left front wheel FL is depressurized, the second quadrant corresponds to a state in which the left rear wheel RL is depressurized, and the third quadrant is the right front wheel. The fourth quadrant corresponds to a state in which the right rear wheel RR is depressurized. In particular, the region A1 corresponds to a state where only the left front wheel FL is decompressed, the region A3 corresponds to a state where only the right rear wheel RR is decompressed, and the region A5 is a state where only the right front wheel FR is decompressed. A7 corresponds to a state where only the left rear wheel RL is decompressed. Further, the region A2 corresponds to a state where the left front wheel FL and the right rear wheel RR are depressurized by two wheels, and the region A4 corresponds to a state where the right front wheel FR and the right rear wheel RR are depressurized by two wheels, A region A6 corresponds to a state where the right front wheel FR and the left rear wheel RL are depressurized by two wheels, and a region A8 corresponds to a state where the left front wheel FL and the left rear wheel RL are depressurized by two wheels. Therefore, for example, when the current index values DEL1 and DEL3 are “1” points shown in the figure, only the left front wheel FL corresponding to the region A1 to which these points belong is specified as a decompression tire. Similarly, when the current index values DEL1 and DEL3 are the “1 ′” point shown in the figure, the left front wheel FL and the right rear wheel RR corresponding to the region A2 to which these points belong are specified as the decompression tire. .

  When step S5 ends, the process proceeds to step S6. In step S <b> 6, the decompression alarm unit 24 outputs a decompression alarm via the alarm indicator 3. At this time, for example, when the alarm indicator 3 is composed of one lamp, the lamp is turned on. On the other hand, if the alarm indicator 3 has four lamps corresponding to the four wheels, the lamp corresponding to the decompression tire determined in step S5 is turned on.

  Subsequent steps S7 to S14 are processes for initialization. The initialization is a step to be executed immediately after the adjustment of the air pressure. For example, a reference index value (an index value at a normal pressure) used for determination of pressure reduction and / or a pressure reduction alarm is set. Can mean to cancel. The initialization of the present embodiment is used in both meanings, and the reference index value is updated by the initialization and the decompression alarm is canceled. The initialization switch 4 is a switch for the user to specify the timing at which the initialization should be performed, that is, the timing at which the air pressure is adjusted. Therefore, the initialization switch 4 should be operated immediately after the adjustment of the air pressure, but often the user operates the initialization switch 4 without adjusting the air pressure. Such an operation is called a misuse, and is intentionally performed for the purpose of unintentionally causing an operation error or turning off a decompression alarm. As will be described later, in the initialization processing of the present embodiment, such misuse is detected, and the adverse effect due to misuse, that is, the decompression alarm is released even though the air pressure is not adjusted, The problem of setting a reference index value used for determination of pressure reduction based on unadjusted air pressure is prevented.

  Specifically, first, in step S7, the calculation unit 21 recalculates the current index values DEL1 and DEL3. This index value is calculated as a reference for setting a miss-use area, which will be described later. In this sense, the index value calculated here is hereinafter referred to as an area setting index value. The region setting index value may be calculated immediately after step S6, or may be calculated as a value immediately after the stop of vehicle 1 after step S6 in order to improve the detection accuracy of misuse. May be. In the latter case, the calculation unit 21 continues to calculate the current index values DEL1 and DEL3 at short time intervals until the vehicle 1 stops after step S6, and when it is determined that the vehicle 1 has stopped, Index values DEL1 and DEL3 can be set as region setting index values. As the region setting index value, an index value acquired at another timing can be used as long as it is a value before the initialization instruction. For example, after step S6, the index values DEL1 and DEL3 are periodically calculated until an initialization instruction is issued, and the index values DEL1 and DEL3 at a time close to this before the initialization instruction are used as region setting index values. (For example, as a method for realizing this, it is conceivable that the return destination in the case of “no” in step S9 described later is set to step S7).

  When step S7 ends, the region setting unit 27 sets a misuse region in the index value space (DEL1-DEL3 space) (step S8). Details of the misuse area setting process will be described later.

  The subsequent step S9 is a step for waiting until an operation of the initialization switch 4 by the user is detected. If the instruction detection unit 26 determines that this initialization instruction has been issued in the period after the decompression alarm (S6) is issued, the process proceeds to step S10.

  In step S <b> 10, the decompression alarm unit 24 cancels the decompression alarm currently being output via the alarm indicator 3. Also, for the alarm indicator 5 that issues an alarm in step S13, which will be described later, if the misuse alarm is currently being issued, the misuse alarm unit 29 cancels this. Since the process of FIG. 3 is repeatedly executed, there is a possibility that a misuse warning is issued at step S13 described later at this point.

  Step S11 and subsequent step S12 are processes for determining whether or not the initialization instruction detected in step S9 is due to misuse. First, in step S11, the calculation unit 21 calculates the current index values DEL1 and DEL3 in the same manner as in step S1. Since the index value calculated here is an index value calculated immediately after the initialization instruction, it is hereinafter referred to as a post-instruction index value.

  Subsequently, in step S12, the miss use detection unit 28 determines whether or not the post-instruction index values DEL1 and DEL3 calculated in step S11 are included in the miss use area. If the post-instruction index values DEL1 and DEL3 are included in the misuse area, it is determined that the initialization instruction in step S9 is misuse, and if not included, it is determined not to be misuse.

  If no misuse is detected in step S12, the process proceeds to step S14. In step S14, the reference index value set in step S3 is cleared. In this case, when step S2 is executed next, it is determined that the reference set value has not been set, the process proceeds to step S3, and the reference index value is reset. In other words, since it is confirmed in step S12 that the air pressure of the tires FL, FR, RL, and RR has been adjusted, the index values DEL1 and DEL3 in this state are used as a reference for future decompression detection. Become.

  On the other hand, if a misuse is detected in step S12, the process proceeds to step S13. In step S <b> 13, the misuse alarm unit 29 outputs a misuse alarm via the alarm indicator 5. In this embodiment, the misuse alarm and the decompression alarm are output separately, but they can be combined into one. In other words, if the alarm indicator 5 for the misuse alarm is omitted, steps S10 and S13 are omitted, and the decompression alarm is canceled in step S14, the user can make a misuse because the decompression alarm is not cancelled. I can know. Moreover, these alarms are not limited to visual forms by a display device or the like. For example, instead of or in addition to the visual alarm, it is also possible to output an alarm by voice via a speaker or the like connected to the detection device 2.

  After completion of steps S13 and S14, the decompression detection process returns to step S1, and the same process is repeated again. If the air pressure has not been adjusted before the next step S1, the pressure reduction alarm is issued again at step S6.

<3. Misuse area setting process>
Next, details of the misuse area setting process in step S8 will be described with reference to FIG. The miss use area is an index value area that is defined in the index value space (DEL1-DEL3 space) and is suspected of misuse.

  The misuse area is set with reference to index values (area setting index values calculated in step S7) DEL1 and DEL3 before the initialization instruction. Misuse determination is performed based on whether the index value has changed in the direction in which the internal pressure is increased before and after the initialization instruction.

  Specifically, first, the decompression tire specifying unit 23 determines which of the tires FL, FR, RL, RR is decompressed in the immediately preceding step S5 based on the region setting index values DEL1, DEL3. It is specified whether it has been done (step S31).

  Next, the region setting unit 27 determines whether the one-wheel depressurization or the two-wheel depressurization from the result of step S31 (step S32). In the case of one-wheel depressurization, step S33 is executed, and in the case of two-wheel depressurization, step S34 is executed.

  In step S <b> 33, the region setting unit 27 determines the decompression / enlargement direction in which the tire decompression proceeds with reference to the time when the region setting index values DEL <b> 1 and DEL <b> 3 before the initialization instruction are calculated. The decompression / enlargement direction is determined according to the determination result of step S32, that is, which tire is decompressed among the tires FL, FR, RL, and RR. Specifically, the reduced pressure expansion direction is determined as the direction in which the index values DEL1, DEL3 change when the reduced pressure state of the reduced pressure tire in step S32 progresses. For example, when the point P1 corresponding to the region setting index value is at the position shown in FIG. 6, the decompression tire is only the left front wheel FL. In this case, since the wheel speed V1 is expected to increase as pressure reduction proceeds, the values of DEL1 and DEL3 increase. Therefore, the decompression expansion direction is a direction in which the values of DEL1 and DEL3 increase (see double-line arrows in FIG. 6). Note that the decompression / enlargement direction can be determined as a direction from the point (origin) corresponding to the reference index value to the point P1 corresponding to the region setting index value.

Subsequently, the area setting unit 27 defines a misuse area R1 including the point P1 corresponding to the area setting index value. Specifically, the miss use area R1 is an area having the following straight line as a boundary line. Note that X1> X2 and Y1> Y2. In the example of FIG. 6, the miss use area R1 is a gray area.
(1) Two straight lines closest to the point P1 among the straight lines L1 to L4 (in the example of FIG. 6, straight lines L1 and L2)
(2) A straight line L5 parallel to the DEL3 axis and located at a distance X1 from the point P1 along the DEL1 axis in the decompression expansion direction
(3) A straight line L6 that is parallel to the DEL3 axis and is located at a distance X2 from the point P1 along the DEL1 axis in the direction opposite to the reduced pressure expansion direction (however, the direction from the point P1 along the DEL3 axis direction to the reduced pressure expansion direction) Part where the distance is more than Y2)
(4) A straight line L7 that is parallel to the DEL1 axis and is located at a distance Y1 from the point P1 along the DEL3 axis in the decompression expansion direction.
(5) A straight line L8 that is parallel to the DEL1 axis and is at a distance Y2 from the point P1 along the DEL3 axis in the direction opposite to the decompression enlargement direction (however, the direction from the point P1 along the DEL1 axis direction is opposite to the decompression enlargement direction) Part where the distance is more than X2)

  On the other hand, also in step S34 after detection of two-wheel depressurization, similarly to step S33, the region setting unit 27 determines the depressurization expansion direction based on the time point when the region setting index values DEL1 and DEL3 are calculated. The reduced pressure expansion direction is determined as the direction in which the index values DEL1, DEL3 change when the reduced pressure state of the reduced pressure tire in step S32 proceeds. For example, when the point P2 corresponding to the region setting index value is at the position shown in FIG. 7, the decompression tires are the left front wheel FL and the right rear wheel RR. In this case, since the wheel speeds V1 and V4 are expected to increase as the depressurization progresses, the value of DEL1 increases, but the value of DEL3 is not expected to change much. Therefore, the decompression enlargement direction is a direction in which the value of DEL1 increases. Further, the decompression / enlargement direction can also be determined as a direction from the origin toward the point P2 (see a double-lined arrow in FIG. 7).

Subsequently, the area setting unit 27 defines a misuse area R2 including the point P2 corresponding to the area setting index value. Specifically, the miss use area R2 is an area having the following straight line as a boundary line. Note that Q1> Q2. In the example of FIG. 7, the miss use area R1 is a gray area.
(1) Of the straight lines L1 to L4, two straight lines closest to the point P2 (in the example of FIG. 7, straight lines L2 and L3)
(2) A straight line L9 that is parallel to the axis far from the point P2 out of the DEL1 axis and the DEL3 axis, and is located at a distance Q1 from the point P2 in the decompression expansion direction along the other axis.
(3) A straight line L10 that is parallel to the axis far from the point P2 out of the DEL1 axis and the DEL3 axis and is located at a distance Q2 from the point P2 in the opposite direction of the decompression expansion direction along the other axis.

  When the above steps S33 and S34 are finished, the setting of the misuse area is finished. The misuse area is an area that includes points (P1, P2) corresponding to the area setting index value in the index value space and extends from the point in the decompression enlargement direction and vice versa. In particular, the misuse area is set so as to spread over a wider range in the decompression enlargement direction than in the opposite direction on the basis of the points (P1, P2) corresponding to the area setting index value. As a result, misuse can be detected even when the pressure reduction of the tire has progressed greatly due to tire puncture or the like, and misuse can be detected with high accuracy.

<4. Modification>
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning. For example, the following changes can be made. Moreover, the gist of the following modifications can be combined as appropriate.

<4-1>
The boundary line in the decompression / enlargement direction of the misuse area may not be set. That is, in the examples of FIGS. 6 and 7, the boundaries along the straight lines L5, L7, and L9 may be eliminated. In other words, the distances X1, Y1, and Q1 can be infinite distances.

<4-2>
In the said embodiment, the misuse area | region was defined by making the straight line L1-L4 for classifying a decompression tire into a boundary line. Therefore, before and after the initialization instruction, when one wheel is depressurized further from the one-wheel depressurization state, or when the air pressure is adjusted for only one wheel from the two-wheel depressurization state, misuse is not determined. It was. However, even in such a case, it can be set to be determined as misuse. In this case, for example, the misuse areas R1 and R2 can be changed as shown in FIGS. Alternatively, the miss use area R1 can be defined as shown in FIG.

<4-3>
In the embodiment described above, the processing based mainly on the two index values DEL1 and DEL3 has been described. However, the decompression detection processing (including initialization and misuse area setting) can also be executed based on one index value. For example, the misuse area in this case can be set as shown in FIG. In the example of FIG. 11, DEL1 is used as an index value, P3 is an area setting index value, and R3 represents a misuse area. Also in this case, the miss use area R3 extends in a wider range from the area setting index value in the decompression expansion direction than in the opposite direction, and U1> U2.

<4-4>
In the above embodiment, only DEL1 and DEL3 are used as index values. However, from the viewpoint of improving the detection accuracy when the front wheels 2 and FL and the rear wheels RL and RR are depressurized, DEL2 And / or RFM is preferably used together.

1 Vehicle 2 Detection Device (Computer)
7 Program 21 Calculation unit 22 Decompression determination unit 23 Depressurization tire identification unit 24 Depressurization alarm unit 25 Reference setting unit 26 Instruction detection unit 27 Region setting unit 28 Misuse detection unit FL, FR, RL, RR Tires P1 to P3 Region setting index value ( Index value before instruction)
R1-R3 Misuse area

Claims (9)

A device for detecting a pneumatic state of a tire mounted on a vehicle,
A calculation unit for calculating an index value for determining a tire air pressure state;
An instruction detection unit for detecting an initialization instruction from a user;
In the index value space with the index value as an axis, the pre-instruction index value that is the index value calculated by the calculation unit before the initialization instruction is included, and the decompression of the tire proceeds from the pre-instruction index value An area setting unit for setting a misuse area, which is an area extending in the decompression expansion direction and the opposite direction;
The misuse in which the initialization instruction is issued in a state where the tire air pressure is not adjusted when the post-instruction index value that is the index value calculated by the calculation unit after the initialization instruction is within the misuse area. And a misuse detection unit that detects
The misuse area is set so as to spread over a wider range in the reduced pressure expansion direction than in the opposite direction, with the index value before instruction as a reference.
Detection device. Based on the pre-instruction index value, further comprising a reduced pressure tire specifying unit for specifying a reduced pressure tire from a plurality of tires mounted on the vehicle,
The region setting unit determines that the direction in which the index value changes when the decompression state of the decompression tire identified by the decompression tire identification unit proceeds is the decompression expansion direction,
The detection device according to claim 1. A depressurization determining unit that determines whether or not the tire is in a depressurized state by comparing a reference index value that is the index value after adjustment of tire air pressure and a current value of the index value;
A pressure reduction warning unit that generates a pressure reduction warning when the pressure reduction determination unit determines that the tire is in a pressure reduction state;
The detection device according to claim 1 or 2. A reference setting unit that updates the reference index value when a misuse is not detected by the misuse detection unit;
Further comprising
The detection device according to claim 3. The vehicle includes a first tire, a second tire, a third tire, and a fourth tire,
As the index value, the following three index values:
(1) The higher the rotational speed of the first tire and the fourth tire, the higher the rotational speed of the second tire and the third tire, and the smaller the second tire and the third tire. An index value that increases as the rotational speed of the tire increases and decreases as the rotational speed of the first tire and the fourth tire increases.
(2) The higher the rotation speed of the first tire and the second tire, the larger the rotation speed of the third tire and the fourth tire, and the smaller the rotation speed of the third tire and the fourth tire, or the third tire and the fourth tire. An index value that increases as the rotational speed of the tire increases and decreases as the rotational speed of the first tire and the second tire increases, and (3) increases as the rotational speed of the first tire and the third tire increases. In addition, the larger the rotational speed of the second tire and the fourth tire, the smaller the rotational speed of the second tire and the fourth tire, or the larger the rotational speed of the second tire and the fourth tire, and the rotation of the first tire and the third tire. At least one of the index values that decrease with increasing speed is used.
The detection device according to claim 1. As the index value, at least two of the three index values are used.
The detection device according to claim 5. The misuse area, a dividing line when dividing the index value space according to which tire is depressurized, a part of the boundary line,
The detection device according to claim 6. A method for detecting a pneumatic state of a tire mounted on a vehicle,
Calculating a pre-instruction index value that is an index value for determining the tire air pressure state;
Detecting an initialization instruction from a user after calculating the pre-instruction index value;
After the initialization instruction, calculating the index value as a post-instruction index value;
In the index value space with the index value as an axis, a misuse area is set that includes the index value before instruction and extends from the index value before instruction to a decompression expansion direction in which tire decompression progresses and vice versa. Steps,
Detecting the misuse in which the initialization instruction is issued in a state in which the tire air pressure is not adjusted when the index value after the instruction is in the misuse area,
The misuse area is set so as to spread over a wider range in the reduced pressure expansion direction than in the opposite direction, with the index value before instruction as a reference.
Detection method. A program for detecting the air pressure state of a tire mounted on a vehicle,
Calculating a pre-instruction index value that is an index value for determining the tire air pressure state;
Detecting an initialization instruction from a user after calculating the pre-instruction index value;
After the initialization instruction, calculating the index value as a post-instruction index value;
In the index value space with the index value as an axis, a misuse area is set that includes the index value before instruction and extends from the index value before instruction to a decompression expansion direction in which tire decompression progresses and vice versa. Steps,
When the post-instruction index value is within the misuse area, causing the computer to execute a step of detecting a misuse in which the initialization instruction is issued in a state where tire air pressure is not adjusted,
The misuse area is set so as to spread over a wider range in the reduced pressure expansion direction than in the opposite direction, with the index value before instruction as a reference.
Detection program.