JP2013173422A - Tire pneumatic pressure monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire pneumatic pressure monitoring device having excellent determination performance.SOLUTION: A tire pneumatic pressure monitoring device specifies (a) a current pressure Pr which is a current tire pneumatic pressure and (b) an increase pressure ΔP which is an increase of a tire pneumatic pressure when a vehicle travels, on the basis of a detection value of a tire pneumatic sensor, corrects either a specified current pressure Pr or a reference pressure Pec that is set to determine decrease exceeding the tire pneumatic pressure, on the basis of a specified increase pressure ΔP, compares (C) one of a corrected current pressure and the reference pressure with the other of a non-corrected pressure and the reference pressure, and determine decrease in the tire pneumatic pressure. A change in the tire pneumatic pressure due to a temperature increase in a tire during traveling is estimated from the detection value of the tire pneumatic pressure sensor, so that the decrease in the tire pneumatic pressure can be properly determined.

Description

  The present invention relates to a tire pressure monitoring device that monitors a decrease in tire pressure.

  For example, as described in the following patent document, the tire pressure for monitoring the tire pressure is used as a device for ensuring safety in traveling of the vehicle, such as avoiding a tire burst caused by a change in tire pressure. Monitoring devices, so-called TPMS (Tire Pressure Monitoring System) are known. In the United States, it is mandatory to wear the TPMS, and in Europe, it will soon be mandatory.

JP 2010-254018 A JP 2005-178634 A

  The temperature of the tire rises due to friction during running, and the temperature of the air in the tire also rises, so the tire air pressure during running (warm state, HOT state) is before running (cold state, COLD state). It becomes higher compared to the tire pressure. For example, some TPMS use a predetermined value as a threshold value for tire pressure, but in such a device, it is judged that the tire pressure falls below a standard from the tire pressure that varies greatly. Is insufficient. Therefore, the device described in Patent Document 1 is provided with a sensor for measuring the temperature in the tire, and the threshold value for determining that the tire air pressure has dropped below the reference is different from the value depending on the temperature in the tire. It is set to be. However, the apparatus described in Patent Document 1 has a problem that, for example, there is a time lag before the tire air pressure corresponding to the temperature changes with respect to the temperature change in the tire. It is considered that the judgment performance of the tire pressure monitoring device can be improved by dealing with such a problem. This invention is made | formed in view of such a situation, and makes it a subject to provide the tire pressure monitoring apparatus which has the outstanding judgment performance.

  In order to solve the above problems, the tire pressure monitoring device of the present invention is based on the detected value of the tire pressure sensor (a) the current pressure that is the current tire pressure, and (b) the tire pressure caused by the running of the vehicle. Is determined based on the specified increase pressure, and the one of the specified current pressure and the reference pressure set for judging a decrease beyond the reference of the tire pressure is determined based on the specified increase pressure. (C) Comparing one of the corrected current pressure and reference pressure with the other not corrected, it is configured to determine a decrease in tire air pressure.

  Since the tire pressure monitoring device of the present invention corrects one of the current pressure and the reference pressure in accordance with the rising pressure caused by traveling of the vehicle, it takes into account the change in tire pressure due to the temperature rise in the tire during traveling. It is possible to appropriately determine a decrease in tire air pressure.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the claimable inventions, and is not intended to limit the combinations of the constituent elements constituting those inventions to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which some constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

  In each of the following items, item (1) corresponds to claim 1, and the technical feature of item (6) is added to claim 1 in claim 2, and in claim 1 or claim 2. The technical feature of (2) is added to claim 3, and the technical feature of (3) and (4) is added to claim 3, to claim 4, and claims 1 to The technical feature of (5) is added to any one of the items 4 to 5 and the technical feature of the item (8) is added to any one of the claims 1 to 5. These correspond to claim 6 respectively.

(1) A tire pressure monitoring device for monitoring tire pressure based on a detection value of a tire pressure sensor,
Based on the detected value of the tire pressure sensor, a tire pressure specifying unit that specifies a current pressure that is a tire pressure at the current time and a rising pressure that is an increase due to traveling of the tire pressure of the vehicle,
An ascending pressure-based correction unit that corrects one of the identified current pressure and a reference pressure that is set to determine a decrease beyond the reference of the tire air pressure based on the increasing pressure;
Comparing one of the corrected current pressure and reference pressure with the uncorrected other of the current pressure and reference pressure, it is determined that the tire air pressure has dropped beyond the reference. A tire pressure monitoring device comprising:

  For example, a tire pressure monitoring device that monitors a decrease in tire air pressure (hereinafter sometimes referred to as “TPMS”) uses a predetermined value as a threshold pressure that is set to determine a decrease in tire air pressure. There is what is used conventionally. Specifically, a value obtained by multiplying a maximum value of tire air pressure within a predetermined time by a predetermined ratio (for example, 80%) is set as a threshold pressure while the vehicle is running, and the vehicle starts to run. There is a TPMS configured to compare the threshold value with the current pressure detected by the tire air pressure sensor after the tire is in a warm state (HOT state). In such TPMS, it is impossible to make a determination until the tire is warm, and it is not possible to cope with a temperature change in the tire due to a change in outside air temperature, that is, a change in tire air pressure. is there.

  In addition, since the increase in tire air pressure is accompanied by a temperature increase in the tire, for example, a conventional TPMS has a configuration in which the threshold value is changed based on a detection value of a temperature sensor provided in the tire. Exists. In addition, there is a TPMS provided with a sensor for measuring the outside air temperature in order to take into account changes due to the outside air temperature. However, it takes a certain amount of time for the actual tire pressure to reach the theoretical tire pressure determined from the temperature. That is, the change in the tire air pressure has a time lag with respect to the temperature change, and therefore it is difficult to say that the determination is appropriate. Furthermore, these temperature sensors are relatively expensive, and there is a problem that the cost of TPMS increases.

  The tire pressure monitoring device described in this section is configured to change the threshold value used to determine the decrease in tire pressure based on the detection value of the tire pressure sensor. The TPMS described in this section makes an appropriate decision in consideration of changes in tire pressure during running without providing another sensor such as a temperature sensor in addition to the tire pressure sensor, and accurately determines a decrease in tire pressure. Is possible.

  The TPMS described in this section is not limited to a mode in which the reference pressure as the threshold value is corrected and compared with the current pressure that is the value detected by the tire air pressure sensor at that time. The aspect compared with a pressure may be sufficient. In other words, the “rising pressure-dependent correction unit” described in this section, for example, may be configured to correct the reference pressure to increase according to the increasing pressure, and to reduce the current pressure according to the increasing pressure. It may be configured to correct. In addition, the “decrease determination unit” described in this section indicates that the tire pressure is reduced when there is no difference between the corrected one of the current pressure and the reference pressure and the other not corrected. It can be set as the structure which judges.

  The “reference pressure” described in this section varies depending on, for example, the wheels provided in the vehicle, and is set by a factory, a dealer, or the like at the time of shipment. That is, the reference pressure can be a fixed value that cannot be changed. However, it is desirable to reset the reference pressure to a value corresponding to the tire when the wheel is replaced with an inch-up wheel or a studless tire. Therefore, the tire pressure monitoring device described in this section may be configured such that the reference pressure can be reset by the driver, as will be described in detail later.

  (2) The tire pressure specifying unit is configured to specify the increased pressure based on a difference between a cold state pressure that is a tire air pressure in a cold state and the current pressure. Tire pressure monitoring device.

  In the embodiment described in this section, the method for specifying the rising pressure is embodied. The “cold state pressure” referred to in this section means the tire air pressure when the tire is cooled to the same level as or below the outside air temperature.

(3) The tire pressure specifying part is
The tire pressure monitoring device according to (2), further comprising: a first specifying unit that specifies the cold state pressure based on a detection value of the tire pressure sensor when the ignition switch of the vehicle is turned on.

  In the embodiment described in this section, a cold state pressure specifying method is embodied. For example, if the tire is in a cold state when the ignition switch is turned on, the aspect of this section is configured so that the detected value of the tire air pressure sensor is directly used as the cold state pressure. be able to.

(4) The tire pressure specifying part is
At the time when the ignition switch is turned on, if the elapsed time from the time when the ignition switch was turned off is within the set time before that time, instead of the first specific part, The tire pressure monitoring device according to item (3), further including a second specifying unit that specifies the value specified in (2) as the cold state pressure.

  In the aspect described in this section, at the time when the ignition switch is turned on, whether or not the elapsed time from the time when the ignition switch was turned off before that is within the set time, By determining whether or not the time during which the vehicle has not been operated is short, it is determined whether or not the tire is in a cold state when the ignition switch is turned on. When the time when the vehicle is not operated is short, there is a possibility that the temperature in the tire does not drop to a temperature corresponding to the cold state. If the cold state pressure is specified by the above-described first specifying unit in a state where the temperature in the tire has not been lowered, the cold state pressure may be set high and an appropriate determination may not be made. . According to the embodiment described in this section, it is determined whether or not the tire is in a cold state, and if it is determined that the tire is not in a cold state, the most recently specified cold state pressure is determined. Therefore, it is possible to appropriately determine the decrease in tire air pressure.

(5) When the tire pressure in the cold state is defined as the cold state pressure,
The tire pressure monitoring apparatus according to any one of (1) to (4), wherein the reference pressure is set to determine a decrease in tire air pressure with respect to the cold state pressure.

  The mode described in this section is a mode in which the reference pressure is embodied. According to the aspect of this section, it is possible to determine the decrease in tire air pressure immediately after the ignition switch is turned on, that is, before the vehicle travels.

(6) The increased pressure dependence correction unit
In order to correct one of the current pressure and the reference pressure, a correction pressure that is one of the corrections of the current pressure and the reference pressure is determined based on the increased pressure, and
The tire pressure monitoring device according to any one of (1) to (5), wherein the change of the correction pressure is prohibited when the tire pressure drop speed exceeds a set speed.

  The phrase “when the tire pressure drop speed exceeds the set speed” described in this section means, in other words, a case where the amount of pressure reduction per unit time is relatively large. It means that the decrease is not caused by temperature change during traveling. Therefore, according to the aspect described in this section, when the decrease in tire air pressure is not caused by the temperature change during traveling, the increase pressure-based correction unit prohibits the change of the correction pressure, for example, the slow pressure It is possible to reliably determine a decrease in tire air pressure due to a leak or burst. The “correction pressure” described in this section may be the same value as the increase pressure, or may be determined according to the relationship between the increase pressure and the relationship.

  (7) The tire pressure monitoring device according to (6), wherein the increase pressure-dependent correction unit is configured to use a value obtained by multiplying the increase pressure by a predetermined ratio as the correction pressure.

  In the aspect described in this section, the correction pressure determination method is embodied.

(8) The tire pressure monitoring device includes a reference pressure resetting unit that resets the reference pressure based on a detection value of the tire pressure sensor.
The reference pressure resetting unit is configured to reset the reference pressure on the condition that an operation unit provided on a vehicle equipped with the tire pressure monitoring device is operated by a passenger (1). The tire pressure monitoring device according to any one of Items (7) to (7).

  The mode described in this section is a mode in which the reference pressure can be reset by the driver. The reference pressure can be set based on the detected value of the tire pressure sensor immediately after the tire or the like is replaced, that is, the initial cold state pressure. Therefore, the mode of this section is a mode in which, for example, a reference pressure is set based on the detected value of the tire pressure sensor at the time when it is determined that the vehicle is in a cold state after being operated by a passenger. be able to. The reference pressure setting method includes, for example, a method in which a value obtained by subtracting a set pressure from a detected value of the tire pressure sensor is used as a reference pressure, or a detected value of the tire pressure sensor is multiplied by a predetermined ratio. A method using the value as a reference pressure can be employed.

It is the schematic of the vehicle comprised including the tire-pressure monitoring apparatus which is an Example of claimable invention. It is a block diagram which shows the outline of the tire pressure monitoring apparatus shown in FIG. It is a time chart showing the action | operation of the tire pressure monitoring apparatus of a comparative example. It is a time chart showing the action | operation of the tire pressure monitoring apparatus which is an Example of claimable invention. It is a follow chart showing the pre-traveling setting program executed in the control device which controls the tire pressure monitoring device which is an embodiment of the claimable invention. It is a follow chart showing the air pressure fall determination program performed in the control apparatus which manages control of the tire pressure monitoring apparatus which is an Example of claimable invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments as modes for carrying out the claimable invention will be described in detail with reference to the drawings. In addition to the following examples, the claimable invention is implemented in various modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. can do. Moreover, it is also possible to constitute the modification of the following Example using the technical matter described in the description of each item of [Aspect of the Invention].

  FIG. 1 is a schematic view of a vehicle equipped with a tire pressure monitoring device 10 which is an embodiment of the claimable invention. The vehicle has four wheels 12 each composed of a tire and a wheel, and the tire pressure monitoring apparatus 10 monitors the tire pressure of each of the four wheels 12, and the air pressure. When the value falls below the standard, a warning light is displayed on the vehicle display and a warning sound is emitted.

  The tire pressure monitoring device 10 includes a tire pressure sensor 20 provided corresponding to each of the four wheels 12, and directly monitors the tire pressure Pr directly detected by the four pressure sensors 20. TPMS (Tire Pressure Monitoring System). Each of these air pressure sensors 20 is provided inside the tire, specifically, a tire air chamber formed by the tire and the wheel. The tire pressure monitoring apparatus 10 includes a reception side unit 30 and a transmission side unit 32 provided corresponding to each of the four wheels 12 and having the tire pressure sensor 20 described above. As for each detection value of the sensor 20, a signal related to the detection value is transmitted and received wirelessly.

  FIG. 2 conceptually shows each of the transmission side unit 32 and the reception side unit 30 in a block diagram. As shown in FIG. 2, each of the four transmission-side units 32 includes the air pressure sensor 20, a transmitter 40 that transmits a signal related to the detection value of the air pressure sensor 20, and the detection value of the air pressure sensor 20. And a processing device 42 (hereinafter also referred to as “MCU 42”) for causing the transmitter 40 to transmit a signal related to the detected value. The MCU 42 is configured to transmit a signal related to the detection value of the air pressure sensor 20 at a predetermined interval (for example, 1.0 min interval).

  A signal wirelessly transmitted from each of the four transmission side units 32 is received by the receiver 50 included in the reception side unit 32. The signal received by the receiver 50 is sent to a control device 52 (hereinafter sometimes referred to as “ECU 52”) included in the receiving side unit 32, and the ECU 52 determines the tire pressure corresponding to each of the two wheels 12. A determination is made as to whether or not there is a decrease. Note that a display warning lamp 54 and an alarm device 56 are connected to the ECU 52, and the ECU 52 performs a notification process when the tire air pressure of at least one of the four wheels 12 has dropped below the reference. It is like that. More specifically, a warning lamp 54 of the display is displayed and a warning sound is emitted by the alarm device 56. Further, a reset switch 58 is connected to the ECU 52, and the ECU 52 receives the operation of the reset switch 58 by the driver or the like, and the reference pressure that is set to determine a decrease exceeding the reference of the tire air pressure. Has been reset. The resetting of the reference pressure will be described in detail later.

  Next, a method for monitoring tire pressure by the ECU 52 will be described. The tire pressure rises due to friction during running, and the temperature of the air in the tire also rises. Therefore, during running (warm state, HOT state) before running (cold state, COLD) It becomes higher than (condition). Therefore, as shown in FIG. 3, a conventional tire pressure monitoring apparatus has a configuration in which a threshold value is set by multiplying a maximum value of air pressure for 20 minutes from the start of running by a predetermined ratio. . However, in such a conventional TPMS, the tire pressure state cannot be determined unless the tire is in the HOT state, and it can cope with a change in the tire pressure accompanying a change in the outside air temperature even during the HOT state. There is a problem that you can not.

In the tire pressure monitoring apparatus 10, as described above, the ECU 52 identifies the detected value of the tire pressure sensor 20 as the current pressure Pr that is the current tire pressure, and the identified current pressure Pr is the threshold pressure P _W. In the case of lowering, notification processing is performed. In the tire air pressure monitoring device 10, the threshold air pressure P _W is changed according to the running state, and the changed threshold air pressure P _W is compared with the current pressure Pr. Specifically, first, as a reference pressure that is set to determine a decrease in excess of the tire pressure, a cold state threshold pressure P that is set to determine a decrease in the tire pressure in the cold state. _WC is used. The threshold air pressure P _W is changed by correcting the cold state threshold pressure P _WC that is the reference pressure. The cold state threshold pressure P _WC is initially set in a factory, a dealer, or the like according to a tire provided in the vehicle. However, for example, exchange to new tires, tires rotation, after the adjustment of the pressure of the tire is performed, when the reset switch 58 described above is operated, ECU 52 is a cold state threshold pressure P _WC It has come to reset. Specifically, when the reset switch 58 is operated and the tire is in a cold state, the cold air condition threshold is obtained by multiplying the initial air pressure P _C detected by the tire air pressure sensor 20 at that time by a predetermined ratio. The pressure P _WC (= 0.8 · P _C ) is reset. Incidentally, the predetermined ratio is set to a value that ensures the safety of traveling of the vehicle.

Therefore, the tire pressure monitoring apparatus 10 determines whether the tire pressure has decreased immediately after the ignition switch of the vehicle is turned on. That is, even if the tire pressure is reduced due to a slow leak while the vehicle is not operated, immediately after the ignition switch is turned on, the cold state threshold pressure P _WC causes the tire pressure to be reduced. A decrease is detected and notified.

Further, during running, the tire pressure monitoring device 10 corrects the cold state threshold pressure P _WC, is adapted to change the閾空pressure P _W. More specifically, the ECU 52 increases the tire pressure during traveling, that is, the current pressure Pr specified by the detection value of the air pressure sensor 20, and the cold state that is the air pressure in the cold state before traveling. The threshold air pressure P _W is changed according to the rising pressure ΔP (= Pr−P ₀ ), which is the difference from the pressure P ₀ . Specifically, the threshold air pressure P _W is determined according to the following equation.
P _W = P _WC + 0.8 × ΔP (1)
That is, the threshold air pressure P _W is changed by correcting the correction pressure determined by multiplying the rising pressure ΔP by a predetermined ratio to the cold state threshold pressure P _WC . As shown in FIG. 4, the threshold air pressure P _W increases as the current pressure Pr increases. The threshold air pressure P _W is changed at the same time interval (1.0 min interval) as the transmission interval from the transmission side unit 32.

  Further, in each of the transmission side units 32, it is determined whether or not the decrease in tire air pressure is caused by a temperature change. Specifically, the MUC 42 determines that the tire pressure drop rate exceeds the set speed from the detection value of the air pressure sensor 20, that is, the amount of pressure reduction from the previous detection value of the air pressure sensor 20 exceeds the set amount. In addition, it is determined that the decrease in the tire air pressure is not caused by the temperature change, and a signal for turning on the excessive pressure reduction flag is transmitted to the transmitter 40.

When the receiving unit 32 receives a signal for turning on the above-described over-decompression flag, the ECU 52 is prohibited from changing the correction pressure (0.8 × ΔP) thereafter, as shown in FIG. The threshold air pressure P _W determined immediately before is maintained. That is, only the current pressure Pr decreases, and the decrease in tire air pressure can be reliably detected.

The cold state pressure P ₀ used when calculating the rising pressure ΔP is basically specified by the detected value of the air pressure sensor 20 at the time when the ignition switch is turned on. However, if the temperature in the tire has not decreased to the same level as the outside air temperature when the ignition switch is turned on, the tire air pressure may not have decreased. Therefore, in the present tire pressure monitoring device 10, at the time when the ignition switch is turned ON, the ignition switch before the in elapsed time when t is shorter than the set time t ₀ (Fig. 4 from being turned OFF At point A), the value used as the cold state pressure when the ignition switch was previously turned on is specified as the cold state pressure.

  In the control for monitoring the decrease in tire air pressure as described above, immediately after the ignition switch is turned on, the pre-travel setting program shown in the flowchart of FIG. 5 is executed once, and then the air pressure shown in the flowchart of FIG. The decrease determination program is executed by being repeatedly executed by the ECU 52 at a set time interval (for example, 1.0 min) while the ignition switch is in the ON state. The control flow will be briefly described below with reference to the flowchart shown in the drawing.

In the pre-travel setting program that is executed immediately after the ignition switch is turned on, first, in step 1 (hereinafter, step is abbreviated as “S”), the ignition switch is turned off before this time. The elapsed time t up to the present time is acquired. Next, it is determined whether or not the tire is in a cold state depending on whether or not the elapsed time t exceeds the set time t ₀ . If the elapsed time t exceeds the set time t ₀ and it is determined that the tire is in a cold state, the current pressure Pr of each of the four wheels 12 is acquired in S3, and the acquired pressure is acquired in S4. The current pressure Pr is set as the cold state pressure P ₀ . Then, in S5, the flag value of the reset flag FL _R is checked. If the flag value of the reset flag FL _R is 1, the reset switch 58 has been operated, resetting of cold state threshold pressure P _WC is performed. Specifically, based on the current pressure Pr acquired in S3 (in other words, the cold state pressure P ₀ ), it is set according to the expression P _WC = 0.8 × Pr. Further, the same time, in S7, the flag value of the reset flag FL _R is zero.

On the other hand, if the elapsed time t does not exceed the set time t ₀ in S2, the tire may not be sufficiently cooled and the tire air pressure may not be lowered. Therefore, the cold state pressure P ₀ is set. The value set at the previous program execution is used as it is without being performed. Specifically, S3 to S7 are skipped. In this case, also it is made the operation of the reset switch 58, in this case, so that the not performed resetting of cold state threshold pressure P _WC. Thus, the setting before traveling is completed, and the air pressure decrease determination program is started in S8.

Next, an air pressure decrease determination program is executed. The air pressure decrease determination program is executed for each of the four wheels 12. In its tire pressure monitoring program, firstly, on at S11, the present time pressure Pr receiver 50 has received is detected by the tire air pressure sensor 20 is obtained, in S12, from the present time pressures Pr and cold state pressure P ₀ Metropolitan A boost ΔP (= Pr−P ₀ ) is specified. Then, in S13, the flag value of the over-pressure reduction flag FL _e is confirmed, when the flag value of the over-pressure reduction flag FL _e is 0, in S14,閾空pressure P _W is determined according to the aforementioned (1) Is done. On the other hand, in S12, when the flag value of the over-pressure reduction flag FL _e is 1, S14 is skipped, it changes閾空pressure P _W is set to not performed. That is, the threshold air pressure P _W at the previous program execution is used for the determination described below.

Subsequently, in S15, the present time pressure Pr is determined whether or not閾空pressure P _W or less, when current pressure Pr is閾空pressure P _W smaller than in S16, together with displaying the warning lamp 54 of the display, A warning sound is generated by the alarm device 56. This completes the execution of one air pressure decrease determination program.

The ECU 52 that performs the control as described above can be considered to have various functional units that perform the various processes described above. More specifically, as shown in FIG. 2, the ECU 52 includes a tire air pressure specifying unit 100 that specifies the current pressure Pr and the rising pressure ΔP based on the detection value of the tire air pressure sensor 20, and a cold state threshold that is a reference pressure. Comparing the increased pressure-dependent correction unit 102 that corrects the pressure P _WC based on the specified increased pressure ΔP, and comparing the corrected reference pressure and the current pressure Pr, it is determined that the tire pressure has decreased below the reference. And a lowering determination unit 104. The tire air pressure specifying unit 100 corresponds to a part that executes S1 to S4 of the pre-travel setting program and a part that executes S11 and S12 of the air pressure decrease determination program, and the increased pressure dependence correction unit 102 includes the air pressure decrease determination program. The portions for executing S13 and S14 are equivalent, and the decrease determination unit 104 corresponds to the portion for executing S15 of the air pressure decrease determination program.

The tire pressure specifying unit 100 includes a first specifying unit 110 that specifies the cold state pressure P ₀ based on the detection value of the tire pressure sensor 20 at the time when the ignition switch is turned on, and the ignition switch is turned on. When the elapsed time t from the time when the ignition switch was turned off before that time is within the set time t ₀ , the first specific unit 110 is replaced with A second specifying unit 112 that specifies the specified value as the cold state pressure. The first specifying unit 110 corresponds to a part that executes S3 and S4 of the pre-travel setting program, and the second specifying unit 112 corresponds to a part that executes S1 and S2 of the pre-travel setting program.

Further, the increased pressure dependence correction unit 102 includes a correction pressure change prohibition unit 120 that executes S13 of the air pressure decrease determination program and prohibits the change of the correction pressure when the tire air pressure decrease speed exceeds the set speed. ing. Incidentally, the MCU 42 of the transmission side unit 32 includes an over-decompression determining unit 122 that determines whether or not the tire air pressure drop speed exceeds the set speed. Further, the ECU 52 executes S5 to S7 of the pre-travel setting program, and when the set switch 58 is operated by the re-occupant, the cold state threshold pressure P that is the reference pressure based on the detected value of the tire air pressure sensor. A reference pressure resetting unit 130 for resetting _WC is provided.

The tire pressure monitoring device 10 of the above embodiment corrects the cold state threshold pressure P _WC that is the reference pressure based on the increased pressure ΔP, and is corrected to the corrected reference pressure (threshold air pressure P _W ). The current pressure Pr was not compared. However, the modified tire pressure monitoring device corrects the current pressure Pr based on the specified increase pressure ΔP, and compares the corrected current pressure with the uncorrected reference pressure _PWC. Is possible.

Specifically, in the tire pressure monitoring device of the modified example, the current pressure P is specified by the detection value of the air pressure sensor 20 as in the tire pressure monitoring device 10 of the above embodiment, and the specified current time is specified. The rising pressure ΔP (= Pr−P ₀ ) is specified by the difference between the pressure Pr and the cold state pressure P ₀ that is the air pressure in the cold state before traveling. Next, the current pressure Pr is corrected according to the following equation based on the identified rising pressure ΔP.
Pr ′ = Pr−0.8 × ΔP
The correction current pressure Pr is the corrected current time pressure 'and, is compared with a reference pressure cold condition閾空pressure P _WC, correction current pressure Pr' if falls below the reference pressure P _WC, notification Processing is to be performed.

  Also in the tire pressure monitoring device of this modification, when the receiving side unit receives a signal for turning on the excessive pressure reduction flag, the correction pressure (0.8 × ΔP) is prohibited from being changed, and the correction determined immediately before that is determined. The current pressure Pr is corrected based on the pressure. That is, also in the tire pressure monitoring device of this modification, it is possible to reliably determine a decrease in tire pressure.

  DESCRIPTION OF SYMBOLS 10: Tire pressure monitoring apparatus (TPMS) 12: Wheel 20: Tire pressure sensor 52: Control apparatus (ECU) 54: Warning lamp 56: Alarm 58: Reset switch 100: Tire pressure specific part 102: Increase pressure dependence correction | amendment part 104 : Decrease determining unit 110: First specifying unit 112: Second specifying unit 120: Correction pressure change prohibiting unit 122: Over-decompression determining unit 130: Reference pressure resetting unit

Pr: current pressure P _W : threshold air pressure P _WC : cold state threshold pressure [reference pressure] P ₀ : cold state pressure ΔP: rising pressure

Claims (6)

A tire pressure monitoring device for monitoring tire pressure based on a detection value of a tire pressure sensor,
Based on the detected value of the tire pressure sensor, a tire pressure specifying unit that specifies a current pressure that is a tire pressure at the current time and a rising pressure that is an increase due to traveling of the tire pressure of the vehicle,
An ascending pressure-based correction unit that corrects one of the identified current pressure and a reference pressure that is set to determine a decrease beyond the reference of the tire air pressure based on the increasing pressure;
Comparing one of the corrected current pressure and reference pressure with the uncorrected other of the current pressure and reference pressure, it is determined that the tire air pressure has dropped beyond the reference. A tire pressure monitoring device comprising: The ascending pressure-dependent correction unit is
In order to correct one of the current pressure and the reference pressure, a correction pressure that is one of the corrections of the current pressure and the reference pressure is determined based on the increased pressure, and
The tire pressure monitoring device according to claim 1, wherein the tire pressure monitoring device is configured to prohibit a change in the correction pressure when a tire pressure drop speed exceeds a set speed.   The tire pressure specifying unit is configured to specify the increased pressure based on a difference between a cold state pressure that is a tire air pressure in a cold state and the current pressure. Tire pressure monitoring device. The tire pressure specifying part is
A first specifying unit for specifying the cold state pressure based on a detection value of the tire air pressure sensor at the time when the ignition switch of the vehicle is turned on;
At the time when the ignition switch is turned on, if the elapsed time from the time when the ignition switch was turned off is within the set time before that time, instead of the first specific part, The tire pressure monitoring device according to claim 3, further comprising: a second specifying unit that specifies the value specified in step 4 as the cold state pressure. When the tire pressure in the cold state is defined as the cold state pressure,
The tire pressure monitoring device according to any one of claims 1 to 4, wherein the reference pressure is set to determine a decrease in tire air pressure with respect to the cold state pressure. The tire pressure monitoring device includes a reference pressure resetting unit that resets the reference pressure based on a detection value of the tire pressure sensor,
The reference pressure resetting unit is configured to reset the reference pressure on the condition that an operation unit provided in a vehicle on which the tire pressure monitoring device is mounted is operated by an occupant. The tire pressure monitoring device according to any one of claims 5 to 5.

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