JP2019026218A - Tire air pressure monitoring system - Google Patents

Abstract

To provide a TPMS that is able to appropriately inform of a tire air pressure decrease according to a placed state of a load.SOLUTION: In a TPMS in which an initialization warning threshold can be set on the basis of the measurement value of an adjusted tire air pressure by initializing a warning threshold when a user adjusts a tire air pressure, low air pressure warning thresholds different between when a load is placed and when no load is placed are set. Specifically, when a load is placed, the low air pressure warning threshold is set to a value higher than that when no load is placed. Thus, even if the user forgets an initialization operation for a warning threshold when adjusting a tire air pressure, a decrease in tire air pressure can be determined on the basis of the low air pressure warning threshold. Therefore, even if the user forgets the initialization operation and, due to this, the initialization warning threshold set based on the measurement value is low, a warning for a tire air pressure decrease can be provided earlier based on the low air pressure warning threshold used when a load is placed.SELECTED DRAWING: Figure 4A

Description

  The present invention relates to a tire air pressure monitoring system (hereinafter referred to as TPMS) that appropriately changes an air pressure warning threshold according to a load state of a load.

  The TPMS is an important system in terms of vehicle driving safety. In TPMS, a low air pressure alarm threshold value set as a lower limit value of the tire air pressure taking into account the laws and regulations of each country and the pressure measurement accuracy of the sensor transmitter provided on the tire side is set, and an alarm threshold value corresponding to the recommended air pressure ( Hereinafter, the recommended pressure correspondence threshold is set. When the measured tire pressure falls below the higher one of the recommended pressure corresponding threshold value and the low air pressure warning threshold value, an alarm is issued.

  For example, the recommended pressure corresponding threshold value is set to a pressure that is reduced by a predetermined value or a predetermined ratio with respect to the recommended air pressure, for example, a pressure that is reduced by 20% from the recommended air pressure. Basically, the recommended pressure response threshold value is higher than the low air pressure alarm threshold value, so an alarm is issued when the measured tire pressure (hereinafter referred to as the measured pressure) falls below the recommended pressure response threshold value. Is called. However, by setting a low air pressure alarm threshold value separately, an alarm is issued when the measured pressure falls below the low air pressure alarm threshold value regardless of the recommended pressure corresponding threshold value (see, for example, Patent Document 1).

  In recent years, there has been an increasing demand for high-pressure setting type TPMS in various countries, such as legalization of high-pressure setting of air pressure alarm threshold in TPMS for cargo vehicles. In a vehicle on which a high pressure setting type TPMS is mounted, the recommended air pressure includes a set pressure at the time of pressurization to cope with loading when the load is loaded, in addition to a normal set pressure at which no load is loaded.

  However, since the conventional TPMS does not have a means for detecting the loading weight of the vehicle, it cannot automatically detect that the vehicle has loaded a load. For this reason, the low air pressure alarm threshold value is set to a low value, for example, a value lower than the recommended pressure corresponding threshold value at the normal set pressure when no load is mounted.

  Further, the recommended pressure corresponding threshold value is obtained by performing an initialization operation by itself and calculating based on the set recommended air pressure after the user adjusts the tire air pressure so that the recommended air pressure is obtained. Specifically, if the user performs the initialization operation by adjusting the tire pressure to either the normal set pressure or the set pressure during boosting as the recommended air pressure, the measured value of the tire air pressure at that time is the recommended air pressure. It is assumed that For this reason, the recommended pressure corresponding threshold value is calculated based on the measured value at the time of the initialization operation.

JP 2013-147108 A

  However, if the user forgets the initialization operation after adjusting the air pressure, the recommended pressure corresponding threshold value before the initialization operation remains set. For this reason, for example, when the recommended pressure corresponding threshold value must be changed to a value corresponding to the set pressure during boosting, but the value corresponding to the normal set pressure remains, the recommended pressure corresponding threshold value is set to the normal setting. It becomes a low value set based on the pressure. That is, although a high recommended pressure corresponding threshold value should be set based on the set pressure during boosting, a low recommended pressure corresponding threshold value based on the normal set pressure remains set. For this reason, even if the measured pressure decreases and becomes a value lower than the recommended pressure corresponding threshold value that is originally set to a high value, an alarm is not issued and the user is appropriately informed of a decrease in tire air pressure. I can't.

  In view of the above points, an object of the present invention is to provide a TPMS that can appropriately notify a decrease in tire air pressure in accordance with the load state of a load.

  In order to achieve the above object, the TPMS according to claim 1 is applied to a vehicle (1) in which a plurality of wheels (4a to 4d) having tires are attached to a vehicle body (5). A sensor transmitter (2) having a first control unit (22) that is provided for each of the plurality of wheels and detects a tire air pressure of each of the plurality of wheels and creates and transmits a frame storing data related to the tire air pressure; A receiving circuit (31b) that is provided on the vehicle body side and receives a frame transmitted from the sensor transmitter via the receiving antenna (31a), and measures tire air pressure of each of the plurality of wheels based on the received frame, If the measured value of the tire air pressure is below the initialization alarm threshold, it is determined that the tire air pressure has decreased, and a second control unit (31c) for causing an alarm is issued. An alarm device (35) and an operation device (35) for initializing an initialization alarm threshold based on a measured value of tire air pressure when the initialization operation is performed by performing an initialization operation. A vehicle body side system (3).

  Furthermore, the second control unit has a loading determination unit that determines whether the load is loaded or not loaded on the vehicle, and the second control unit differs depending on the initialization alarm threshold value and when loaded and not loaded. The tire pressure drop is determined based on the low air pressure warning threshold that is set to a higher value than when the vehicle is not loaded, and the load determination unit determines that the vehicle is loaded. The low air pressure alarm threshold is set to the value at the time of loading, and an alarm is issued when the measured value of the tire air pressure falls below at least one of the initialization alarm threshold and the low air pressure alarm threshold.

  In this way, in the TPMS in which the user can initialize the initialization alarm threshold value at the time of adjusting the tire pressure, the initialization alarm threshold value can be set based on the measured value of the tire pressure after adjustment. Different low air pressure alarm threshold values are set depending on when the vehicle is not loaded and when the vehicle is not loaded. Specifically, at the time of loading, the low air pressure alarm threshold value is set to a higher value than when not loading.

  Thereby, even if the user forgets the initialization operation of the initialization warning threshold value at the time of adjusting the tire pressure, it is possible to determine the decrease in the tire pressure based on the low pressure warning threshold value. Therefore, even if the initialization alarm threshold value set based on the measured value is low because the user forgot to perform the initialization operation, the tire pressure drop is reduced based on the low air pressure alarm threshold value for loading. The alarm can be performed earlier. Therefore, the TPMS can appropriately notify the decrease in tire air pressure in accordance with the load state of the load.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a whole block diagram of TPMS concerning a 1st embodiment. It is the figure which showed the block configuration of the sensor transmitter with which TPMS is equipped. It is the figure which showed the block configuration of the vehicle body side system with which TPMS is equipped. It is the flowchart which showed the detail of the tire pressure determination process. It is the flowchart which showed the detail of the tire pressure determination process following FIG. 4A. It is the time chart which showed the operation example of TPMS. It is the time chart which showed the operation example of TPMS. It is the time chart which showed the operation example of TPMS. It is the time chart which showed the operation example of TPMS. It is the time chart which showed the operation example of TPMS. It is the time chart which showed the operation example of TPMS. It is the time chart which showed the operation example of TPMS.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the TPMS according to the present embodiment. In FIG. 1, the upward direction in the drawing corresponds to the front of the vehicle 1, and the downward direction in the drawing corresponds to the rear of the vehicle 1.

  As shown in FIG. 1, the TPMS is attached to the vehicle 1 and includes a sensor transmitter 2 and a vehicle body side system 3.

  As shown in FIG. 1, one sensor transmitter 2 is attached to each wheel 4 a to 4 d in the vehicle 1. Specifically, the sensor transmitter 2 detects the air pressure of the tire attached to the wheels 4a to 4d and the temperature in the tire, and stores detection signal data indicating the detection result in the frame and transmits it. . The vehicle body side system 3 is provided on the vehicle body 5 side of the vehicle 1 and receives a frame transmitted from the sensor transmitter 2 and performs various processes and computations based on data stored therein. I am looking for tire pressure. Then, in the vehicle body side system 3, when the tire air pressure is below the alarm threshold value, the driver is warned to alert the driver.

  Here, the alarm threshold includes a recommended pressure corresponding threshold set based on the recommended air pressure, a low air pressure alarm threshold, and an initialization alarm threshold set based on these.

  The recommended air pressure is a tire pressure recommended for each vehicle. The recommended air pressure may be set according to the loading state of the load. In particular, in a cargo vehicle or the like, the recommended air pressure may be changed depending on whether the cargo is loaded or not when the cargo is loaded. The user adjusts the tire air pressure so that the tire pressure becomes the recommended air pressure when the baggage is loaded and when the baggage is not loaded.

  The recommended pressure corresponding threshold value is an alarm threshold value set based on the recommended air pressure, and an alarm is issued when the measured pressure of the tire air pressure falls below the recommended pressure corresponding threshold value. For example, the recommended pressure corresponding threshold value is set to a pressure that is reduced by a predetermined value or a predetermined ratio with respect to the recommended air pressure, for example, a pressure that is reduced by 20% from the recommended air pressure. As described above, since the recommended air pressure is changed between loading and non-loading, the recommended pressure corresponding threshold value also differs between loading and non-loading. Note that the user adjusts the tire air pressure to a recommended air pressure according to the loading and unloading of the luggage. For this reason, in this embodiment, when the user performs the initialization operation after adjusting the tire air pressure to the recommended air pressure, the recommended pressure corresponding threshold value is calculated based on the measured value of the tire air pressure after adjustment.

  The low air pressure alarm threshold value is an alarm threshold value set as a lower limit value of the tire air pressure in consideration of the laws and regulations of each country and the pressure measurement accuracy of the sensor transmitter provided on the tire side. In the case of the present embodiment, the low air pressure warning threshold value is set to a different value between when the load is loaded and when the load is not loaded so that the user can cope with the case where the user forgets the initialization operation. .

  The initialization alarm threshold is basically an alarm threshold set when the initialization operation is performed, that is, a recommended pressure corresponding threshold. However, the user may forget the initialization operation. In that case, the higher one of the recommended pressure correspondence threshold and the low air pressure warning threshold is used as the initialization warning threshold. In this embodiment, the higher one of the recommended pressure correspondence threshold and the low air pressure warning threshold is set as the initialization warning threshold, but the recommended pressure correspondence threshold and the low air pressure warning threshold are set separately. It may be used as an alarm threshold, and an alarm may be issued when the measured value falls below either one.

  In addition, the vehicle body side system 3 detects the loading state of the load based on the vehicle height, and can set a low air pressure alarm threshold according to the loading state to cope with the case where the user forgets the initialization operation. I can do it.

  Next, detailed configurations of the sensor transmitter 2 and the vehicle body side system 3 will be described with reference to FIGS.

  As shown in FIG. 2, the sensor transmitter 2 includes a sensing unit 21, a microcomputer 22, a transmission circuit 23, a transmission antenna 24, and the like.

  The sensing unit 21 includes, for example, a diaphragm type pressure sensor 21a, a temperature sensor 21b, and the like, and outputs a detection signal (hereinafter referred to as a detection signal related to the tire pressure) indicating the tire pressure or the temperature in the tire. The sensing unit 21 detects the tire air pressure and the temperature in the tire for each predetermined detection cycle based on a command from the microcomputer 22. Although not shown here, the sensing unit 21 may be provided with an acceleration sensor or the like. In this case, since the acceleration sensor can detect that the wheels 4a to 4d are rotating, that is, the vehicle 1 is traveling, processing such as changing the detection cycle according to whether the vehicle 1 is traveling is performed. You can also.

  The microcomputer 22 corresponds to a first control unit, and is a well-known device including a CPU, a ROM, a RAM, an I / O, and the like, and executes predetermined processing according to a program stored in the ROM or the like. Specifically, the microcomputer 22 performs various processes related to tire pressure detection according to a program stored in a built-in memory such as a ROM.

  That is, the microcomputer 22 receives a detection signal related to the tire air pressure from the sensing unit 21 every predetermined detection period, processes the signal, and processes it as necessary. The microcomputer 22 stores the detection result in the frame together with the ID information of each sensor transmitter 2 as data indicating the detection result (hereinafter referred to as tire pressure data), and then sends the frame to the transmission circuit 23. The process of sending a signal to the transmission circuit 23 is executed at predetermined intervals according to the program.

  The transmission circuit 23 functions as an output unit that transmits the frame transmitted from the microcomputer 22 to the vehicle body side system 3 through the transmission antenna 24.

  The sensor transmitter 2 configured as described above is attached to an air injection valve in each of the wheels 4a to 4d, for example, and is arranged so that the sensing unit 21 is exposed inside the tire. Thereby, the tire air pressure of the corresponding wheel is detected, and the frame is transmitted every predetermined transmission cycle, for example, every minute, through the transmission antenna 24 provided in each sensor transmitter 2.

  As shown in FIG. 3, the vehicle body side system 3 includes an electronic control device for TPMS (hereinafter referred to as TPMS-ECU) 31, an electronic control device for engine (hereinafter referred to as engine ECU) 32, a weight sensor 33, The vehicle speed sensor 34 and the meter display 35 are provided. Each part which comprises the vehicle body side system 3 is connected through in-vehicle LAN (abbreviation of Local Area Network) by CAN (abbreviation of Controller Area Network) communication etc., for example. For this reason, each part can communicate with each other through the in-vehicle LAN.

  The TPMS-ECU 31 includes an antenna 31a, a receiving circuit 31b, and a microcomputer 31c.

  The antenna 31 a is one or a plurality of antennas that collectively receive the frames transmitted from the sensor transmitters 2, and is fixed to the vehicle body 5.

  The receiving circuit 31b serves as an input unit that receives a frame transmitted through the antenna 31a and transmits the frame to the microcomputer 31c.

  The microcomputer 31c corresponds to a second control unit, and is a well-known device including a CPU, a ROM, a RAM, an I / O, and the like, and executes predetermined processing according to a program stored in the ROM or the like. Specifically, the microcomputer 31c performs various processes related to tire pressure detection according to a program stored in a built-in memory such as a ROM, detects loading / non-loading of a load, and based on this, detects a low air pressure alarm threshold value. The setting etc. are also performed.

  That is, the microcomputer 31c obtains a measured pressure of the tire pressure by performing various signal processing and calculation based on the data related to the tire pressure stored in the received frame, and reduces the tire pressure based on the measured pressure. judge. Specifically, when the microcomputer 31c detects that the measured pressure is below the initialization alarm threshold, that is, the recommended pressure corresponding threshold or the low air pressure alarm threshold, the microcomputer 31c outputs a signal to that effect to the meter display 35. Thereby, the meter display 35 is informed that the tire pressure of any of the wheels 4a to 4d has decreased.

  The initialization warning threshold value used at this time is set based on the recommended pressure correspondence threshold value and the low air pressure warning threshold value. The recommended pressure corresponding threshold value is set based on the user's initialization operation, and the low air pressure warning threshold value is set based on loading / unloading of luggage. The details of setting the recommended pressure corresponding threshold, the low air pressure alarm threshold, and the initialization alarm threshold will be described later.

  The engine ECU 32 executes various types of control related to engine control, and performs engine control such as control of driving torque of each wheel, for example. The engine ECU 32 controls the driving torque based on the load applied to the wheels 4 a to 4 d of the vehicle 1, so that the weight applied to the wheels 4 a to 4 d detected by the weight sensor 33. Enter data about and handle that data. Then, the engine ECU 32 determines whether the load is loaded or not loaded when the load is loaded based on the detected weight applied to each of the wheels 4a to 4d. Is transmitted to the microcomputer 31c. For example, the engine ECU 32 determines that the vehicle is loaded when the weight applied to each of the wheels 4a to 4d exceeds the weight threshold assumed when the vehicle is not loaded. Alternatively, the engine ECU 32 transmits data relating to the detected weight applied to each of the wheels 4a to 4d to the microcomputer 31c so that the microcomputer 31c can determine whether the vehicle is loaded or not loaded. .

  As described above, when the microcomputer 31c is informed of the determination result whether it is loaded or not loaded, or the microcomputer 31c determines whether it is loaded or not loaded. The computer 31c sets a low air pressure alarm threshold based on the determination result. In the microcomputer 31c, a portion that determines whether the load is loaded or not loaded in the vehicle 1 is a portion that constitutes a loading determination unit. Even when the determination result indicating whether the vehicle is loaded or not loaded is transmitted from the engine ECU 32 or the like, the microcomputer 31c determines that the determination result has been input. Constitutes a load determination unit.

  The weight sensor 33 includes four weight sensors 33a to 33d corresponding to the wheels 4a to 4d, respectively, and outputs detection signals corresponding to the weights applied to the wheels 4a to 4d, respectively. For example, a weight sensor 33 is applied as a spring disposed between a chassis and an axle in the vehicle body 5 and detecting a load applied to the spring. In the case of the present embodiment, detection signals of the respective weight sensors 33a to 33d are transmitted to the engine ECU 32, and the weight applied to the respective wheels 4a to 4d is detected by the engine ECU 32.

  The vehicle speed sensor 34 outputs a detection signal corresponding to the vehicle speed. In the case of this embodiment, the detection signal of the vehicle speed sensor 34 is used to detect that the vehicle 1 is stopped. For this reason, the vehicle speed sensor 34 corresponds to a stop detection unit of the vehicle 1 here. Whether the detection signal of the vehicle speed sensor 34 is input to a loading determination unit that determines whether the vehicle is loading or not, that is, the engine ECU 32 or the microcomputer 31c, and whether the vehicle 1 is stopped. Although it is running, it can be judged. Here, the vehicle speed is detected by the vehicle speed sensor 34, but the vehicle speed can also be calculated based on the detection signal of the wheel speed sensor.

  The meter display 35 is used to perform an initialization operation by the user and a warning of a decrease in tire air pressure to the driver. The meter display 35 is disposed at a place where the driver can visually recognize the vehicle while driving, and is installed in, for example, an instrument panel in the vehicle 1. The meter display 35 is configured to be capable of displaying for an initialization operation by the user, such as a touch panel. In addition, when a decrease in tire air pressure is transmitted from the TPMS-ECU 31, the meter display 35 can visually notify the driver by performing display in a manner that can be grasped.

  Here, the meter display 35 is applied as a device that can realize both an operation device for performing an initialization operation by a user and an alarm device for performing a warning of a decrease in tire air pressure. However, the operation device and the alarm device can be configured separately. For the operation device, a switch or the like for setting the recommended air pressure to either a high value for loading or a low value for non-loading may be used. Further, the alarm device can be configured by a buzzer, a voice guidance device, or the like. In that case, a warning of a decrease in tire air pressure can be audibly given to the driver by a buzzer sound or voice guidance. Moreover, although the meter display 35 was mentioned as an example as an alarm device which performs visual alerting | reporting, you may comprise an alarm device with the indicator and warning lamps which display information, such as a head-up display.

  As described above, the TPMS in the present embodiment is configured. Subsequently, an operation example of the TPMS configured as described above will be described. However, since detection of the measured pressure in the tire pressure is the same as that in the past in the operation of the TPMS, here, the setting of the alarm threshold and the determination method that the measured pressure has decreased below the alarm threshold will be mainly described. .

  First, the microcomputer 22 of the sensor transmitter 2 performs tire air pressure detection processing every predetermined control period, and transmits a frame storing data related to tire air pressure at a predetermined periodic transmission timing. The vehicle body side system 3 receives a frame transmitted by the sensor transmitter 2 when an ignition switch (not shown) is turned on. Thereby, the tire air pressure of each wheel 4a-4d is detected in the microcomputer 31c of the TPMS-ECU 31. Then, the microcomputer 31c compares the measured pressure with the recommended pressure corresponding threshold value and the low air pressure warning threshold value, and thereby determines that the tire air pressure has decreased.

  Specifically, the vehicle body side system 3 executes the tire air pressure determination process shown in FIG. 4A and FIG. 4B for each predetermined control cycle in the microcomputer 31c of the TPMS-ECU 31. This process allows the tire to be set based on the low air pressure alarm threshold setting according to the loading / non-loading of the load, the alarm threshold initialization setting based on the user's initialization operation, and the comparison between the measured pressure and the alarm threshold value. A determination is made that the air pressure has dropped.

  First, in step S102, it is determined whether or not the vehicle speed is zero. This determination is made based on the detection signal of the vehicle speed sensor 34. Here, it is determined that the vehicle speed is 0 in order to determine that the vehicle 1 is not moving and is stopped. The loading of the luggage is performed when the vehicle 1 is stopped, and the weight sensor 33 can detect an accurate value of the weight when the vehicle 1 is not vibrating during traveling. For this reason, it is determined at this step that the vehicle 1 is not moving and is in a stopped state. If a positive determination is made here, the process proceeds to step S104. If a negative determination is made, the process is repeated without proceeding to step S104.

  In the subsequent step S104, it is determined whether or not the load is in a loaded state, that is, whether the load is being loaded or not. This determination is performed based on the weight data applied to the wheels 4a to 4d detected by the weight sensor 33 or the determination result by the engine ECU 32. When data on the weight applied to each wheel 4a to 4d detected by the weight sensor 33 is transmitted to the microcomputer 31c, the microcomputer 31c determines that the weight applied to each wheel 4a to 4d is the weight assumed at the time of loading. When the threshold value is exceeded, it is determined that the vehicle is loaded. Alternatively, the microcomputer 31c determines that the vehicle is loaded when the engine ECU 32 has transmitted a determination result indicating that the vehicle is loaded.

  If an affirmative determination is made here, the process proceeds to step S106, and the set value during boosting is set as the low air pressure alarm threshold value. If a negative determination is made, the process proceeds to step S108 shown in FIG. Set.

  The set value during boosting is the low air pressure alarm threshold set during loading, the normal set value is the low air pressure alarm threshold set during non-loading, and the set value during boosting is larger than the normal set value . The set value at the time of pressure increase is a value larger than the threshold value corresponding to the recommended pressure for the recommended air pressure set when the vehicle is not loaded. The normal set value is a value smaller than the recommended pressure support threshold for the recommended air pressure set when the vehicle is not loaded.

  Then, when the pressure increase setting value is set as the low air pressure warning threshold value in step S106, the process proceeds to step S110 to determine whether or not the user has performed the initialization operation. This determination is made based on whether or not the user has performed an initialization operation through the meter display 35. If the initialization operation has been performed, the process proceeds to step S112, where a high recommended pressure corresponding threshold value corresponding to the tire pressure after pressure adjustment adjusted for loading is calculated, and this is set as the initialization alarm threshold value. Set. Since the recommended air pressure for loading is predetermined for each vehicle, the user adjusts the tire air pressure so that the determined recommended air pressure is obtained. Assuming that the adjusted tire air pressure is an estimated air pressure, the recommended pressure corresponding threshold value is obtained by calculation based on the measured value of the adjusted tire air pressure. Specifically, the recommended pressure corresponding threshold value is calculated as a pressure reduced by a predetermined value or a pressure reduced by a predetermined ratio, for example, 20% with respect to the adjusted measured value of the tire pressure. In addition, since the recommended pressure corresponding threshold value is calculated based on the measured value of the tire pressure after adjustment, even if the measured value of the adjusted tire pressure does not match the recommended pressure, the measured value Is set as the initialization alarm threshold.

  Thereafter, the process proceeds to step S114, and it is determined whether or not the initialization alarm threshold value set in step S112 is larger than the low air pressure alarm threshold value set in step S106. If a negative determination is made in step S114, that is, if the low air pressure alarm threshold is greater than the initialization alarm threshold, the process proceeds to step S116, where the low air pressure alarm threshold is set as the initialization alarm threshold again. Thereby, the initialization warning threshold value can be set as a value at least equal to or lower than the low air pressure warning threshold value. If an affirmative determination is made in step S114 or an initialization warning threshold value is set again in step S116, the process proceeds to step S118, and it is determined whether or not the measured pressure of the tire air pressure is larger than the initialization warning threshold value. Here, if the determination is affirmative, the tire air pressure has not decreased, so the processing from step S114 is repeated, and if the determination is negative, the tire air pressure has decreased and the process proceeds to step S120. Alarm. Thereby, it is possible to inform the user of a decrease in tire air pressure.

  On the other hand, if the user has not performed the initialization operation, a negative determination is made in step S110, the process proceeds to step S122, and the previous value is maintained as the initialization alarm threshold value. In other words, when switching from non-loading to loading, the user should originally perform the initialization operation to initialize the alarm threshold, but the user may forget the initialization operation. In that case, the initialization alarm threshold value is not updated, and the previous value is maintained.

  Thereafter, in steps S124 to S128, processing similar to that in steps S114 to S118 described above is performed. As a result, when a decrease in tire air pressure occurs, it is possible to notify the user of the decrease in tire air pressure.

  When the normal set value is set as the low air pressure alarm threshold value in step S108, the process proceeds to step S130, and it is determined whether or not the user has performed the initialization operation. This determination is performed in the same manner as in step S110 described above. If the initialization operation has been performed, the process proceeds to step S132, where a low value corresponding to the tire pressure adjusted for non-loading, that is, a recommended pressure corresponding threshold value lower than that at the time of loading is calculated. Is set as the initialization alarm threshold. Since the recommended air pressure for non-loading is determined in advance for each vehicle, the user adjusts the tire pressure so that the recommended air pressure is determined. Assuming that the adjusted tire air pressure is an estimated air pressure, the recommended pressure corresponding threshold value is obtained by calculation based on the measured value of the adjusted tire air pressure. Specifically, the recommended pressure corresponding threshold value is calculated as a pressure reduced by a predetermined value or a pressure reduced by a predetermined ratio, for example, 20% with respect to the adjusted measured value of the tire pressure. In addition, since the recommended pressure corresponding threshold value is calculated based on the measured value of the tire pressure after adjustment, even if the measured value of the adjusted tire pressure does not match the recommended pressure, the measured value Is set as the initialization alarm threshold.

  Thereafter, in steps S134 to S138, the same processes as in steps S114 to S118 described above are performed. As a result, when a decrease in tire air pressure occurs, it is possible to notify the user of the decrease in tire air pressure.

  On the other hand, if the user has not performed the initialization operation, a negative determination is made in step S130, the process proceeds to step S140, and the previous value is maintained as the initialization alarm threshold value. In other words, when switching from loading to non-loading, the user should originally perform an initialization operation to initialize the alarm threshold, but the user may forget the initialization operation. In that case, the initialization alarm threshold value is not updated, and the previous value is maintained.

  Further, the process proceeds to step S142, and it is determined whether or not the initialization alarm threshold value set in step S140 is larger than the low air pressure alarm threshold value set in step S106 at the time of pressure increase, that is, during loading. If the initialization alarm threshold value is larger than the low air pressure alarm threshold value, the process proceeds to step S144, and the normal time set value set in step S108, that is, the low air pressure alarm threshold value during non-loading is set as the initialization alarm threshold value. .

  That is, when not loaded, the normal setting value is set as the low air pressure alarm threshold value. If the user forgets the initialization operation after that, the initialization alarm threshold value is set to a high value set during loading. Will be set to the value. For this reason, when the user adjusts the tire pressure for non-loading, it is already below the initialization alarm threshold value set to a high value, and the initialization alarm threshold value remains at a high value. Otherwise, an alarm will always be given. Therefore, in Steps S142 and S144, when the initialization alarm threshold is larger than the low air pressure alarm threshold set at the time of loading, the initialization alarm threshold set at that time is too high. The low air pressure alarm threshold value set at the time of non-loading is set as the initialization alarm threshold value. As a result, when the user forgets the initialization operation, it is possible to prevent an alarm from being issued despite the measured pressure being the appropriate pressure.

  Thereafter, in steps S146 to S150, processing similar to that in steps S114 to S118 described above is performed. As a result, when a decrease in tire air pressure occurs, it is possible to notify the user of the decrease in tire air pressure.

  As described above, the low air pressure alarm threshold value and the initialization alarm threshold value are set during loading and non-loading, and when the tire air pressure decreases based on the determination of the tire air pressure decrease, A warning to that effect can be made.

  Next, a specific operation when the tire pressure determination process as described above is executed will be described in comparison with a conventional operation.

  First, in the conventional TPMS, when the user performs the initialization operation in a state where the tire pressure is adjusted to the recommended pressure when not loaded, an operation as shown in FIG. 5 is performed. That is, as shown in FIG. 5, a low air pressure alarm threshold (for example, 160 kPa) is set, and an initialization alarm threshold (calculated from a measured value of tire pressure adjusted to a recommended air pressure for non-loading (for example, 200 kPa)) ( For example, 170 kPa) is set as a value corresponding to the recommended pressure correspondence threshold.

  In the case of the example in FIG. 5, the initialization alarm threshold is higher than the low air pressure alarm threshold. Therefore, if the measured pressure gradually decreases for some reason and falls below the initialization alarm threshold, an abnormality occurs at that time. It is determined that it has occurred, that is, the tire pressure has decreased. Thereby, a warning of a decrease in tire air pressure is given.

  Further, in the conventional TPMS, when the user performs the initialization operation in a state where the tire air pressure is adjusted to the recommended air pressure at the time of loading, an operation as shown in FIG. 6 is performed. That is, as shown in FIG. 6, a low air pressure alarm threshold value (for example, 160 kPa) is set, and an initialization alarm threshold value (for example, calculated from the measured value of the tire air pressure adjusted to the recommended air pressure at the time of loading (for example, 300 kPa)) 265 kPa) is set as a value corresponding to the recommended pressure correspondence threshold.

  In the case of the example of FIG. 6, since the initialization alarm threshold is higher than the low air pressure alarm threshold, if the measured pressure gradually decreases for some reason and falls below the initialization alarm threshold, an abnormality occurs at that time. It is determined that it has occurred, that is, the tire pressure has decreased. Thereby, a warning of a decrease in tire air pressure is given.

  Furthermore, in the conventional TPMS, when the user forgets the initialization operation with the tire pressure adjusted to the recommended pressure at the time of loading, an operation as shown in FIG. 7 is performed. That is, as shown in FIG. 7, a low air pressure alarm threshold value (for example, 160 kPa) is set, and an initialization alarm threshold value calculated from a measured value of tire air pressure adjusted to a recommended air pressure for non-loading (for example, 200 kPa) ( For example, 170 kPa) is set as a value corresponding to the recommended pressure correspondence threshold. That is, the initialization warning threshold value (for example, 265 kPa) calculated from the measured value of the tire pressure adjusted to the recommended pressure (for example, 300 kPa) at the time of loading based on the initialization operation corresponds to the recommended pressure corresponding threshold value. However, the initialization warning threshold value at the time of non-loading remains set.

  In the case of the example in FIG. 7, the initialization alarm threshold value is higher than the low air pressure alarm threshold value, but is a non-loading value, so there is a large difference from the measured tire pressure value after adjustment. It will be in a certain state. Therefore, even if the measured pressure gradually decreases for some reason, it is not determined that an abnormality has occurred, that is, the tire air pressure has decreased, until the measured value greatly decreases and falls below the initialization alarm threshold value. In other words, the initialization warning threshold should be set based on the measured tire pressure value after adjustment, but the initialization warning threshold is set to a low value because the initialization process is forgotten. The warning cannot be performed even if the pressure is reduced to the level at which the warning should be originally performed. As a result, a warning of a decrease in tire air pressure is delayed.

  On the other hand, in the TPMS of this embodiment, when the user performs the initialization operation with the tire air pressure adjusted to the recommended air pressure when not loaded, the operation as shown in FIG. Is called.

  Further, in the TPMS of this embodiment, when the user performs the initialization operation with the tire pressure adjusted to the recommended pressure at the time of loading, an operation as shown in FIG. 8 is performed. That is, as shown in FIG. 8, a set pressure at the time of pressure increase (for example, 250 kPa) is set as the low air pressure alarm threshold, and the initial value calculated from the measured value of the tire pressure adjusted to the recommended air pressure at the time of loading (for example, 300 kPa). The activation warning threshold value (for example, 265 kPa) is set as a value corresponding to the recommended pressure corresponding threshold value.

  In the case of the example of FIG. 8, since the initialization alarm threshold is higher than the low air pressure alarm threshold, if the measured pressure gradually decreases for some reason and falls below the initialization alarm threshold, an abnormality occurs at that time. It is determined that it has occurred, that is, the tire pressure has decreased. Thereby, a warning of a decrease in tire air pressure is given.

  Furthermore, in the TPMS of the present embodiment, when the user forgets the initialization operation in a state where the tire pressure is adjusted to the recommended pressure at the time of loading, an operation as shown in FIG. 9 is performed. That is, as shown in FIG. 9, a set pressure at the time of pressure increase (for example, 250 kPa) is set as the low air pressure alarm threshold value, and is calculated from the measured value of the tire pressure adjusted to the recommended air pressure at the time of non-loading (for example, 200 kPa). An initialization warning threshold value (for example, 170 kPa) is set as a value corresponding to the recommended pressure corresponding threshold value. That is, the initialization warning threshold value (for example, 265 kPa) calculated from the measured value of the tire pressure adjusted to the recommended pressure (for example, 300 kPa) at the time of loading based on the initialization operation corresponds to the recommended pressure corresponding threshold value. However, the initialization warning threshold value at the time of non-loading remains set.

  At this time, conventionally, since the low air pressure alarm threshold value is set to a low value for non-loading, if the user forgets the initialization operation, as shown in FIG. 7, the low air pressure alarm threshold value and the initialization alarm threshold value are set. Both of these became low values, and the warning of a drop in tire pressure was delayed.

  On the other hand, in this embodiment, when it is determined that the vehicle is being loaded, the pressure setting pressure for loading is set as the low air pressure alarm threshold value. For this reason, as shown in FIG. 9, when the user forgets the initialization operation and the initialization alarm threshold value set based on the measured value is a low value, it is set to a higher value. The low air pressure alarm threshold value is newly set as the initialization alarm threshold value. Therefore, when the measured pressure gradually decreases for some reason, it is determined that an abnormality has occurred, that is, the tire air pressure has decreased, if the measured pressure falls below the low air pressure alarm threshold during loading. Therefore, even if the initialization alarm threshold value set based on the measured value is low because the user forgot to perform the initialization operation, the tire pressure drop is reduced based on the low air pressure alarm threshold value for loading. The alarm can be performed earlier.

  Further, in the TPMS of this embodiment, when the user forgets the initialization operation in a state where the tire pressure is adjusted to the recommended pressure at the time of non-loading, an operation as shown in FIG. 10 or FIG. 11 is performed. . FIG. 10 shows a case where the previously set initialization alarm threshold value is a value when the tire pressure is adjusted to the recommended air pressure at the time of loading. FIG. 11 shows a case where the previously set initialization warning threshold value is a value when the tire pressure is adjusted to the recommended air pressure when not loaded.

  First, in the example of FIG. 10, a normal set pressure (for example, 160 kPa) is set as the low air pressure alarm threshold, and an initialization alarm that is calculated from the measured value of the tire pressure adjusted to the recommended air pressure at the time of loading (for example, 300 kPa). A threshold (for example, 265 kPa) is set as a value corresponding to the recommended pressure corresponding threshold. That is, the initialization warning threshold value (for example, 170 kPa) calculated from the measured value of the tire pressure adjusted to the recommended pressure for non-loading (for example, 200 kPa) based on the initialization operation is normally the recommended pressure corresponding threshold value. Although the value should be set as a corresponding value, the initialization alarm threshold value at the time of loading remains set.

  For this reason, when the user adjusts the tire pressure for non-loading, it is already below the initialization alarm threshold value set to a high value, and the initialization alarm threshold value remains at a high value. Otherwise, an alarm will always be given.

  On the other hand, in the present embodiment, when the initialization warning threshold is larger than the low air pressure warning threshold set at the time of loading, the low air pressure warning threshold set at the time of non-loading is newly set as the initialization warning threshold. I try to do it. For this reason, when the user forgets the initialization operation, it is possible to prevent an alarm from being issued despite the measured pressure being the appropriate pressure.

  In the example of FIG. 11, a normal set pressure (for example, 160 kPa) is set as the low air pressure alarm threshold, and initialization is calculated from the measured value of the tire pressure adjusted to the recommended air pressure for non-loading (for example, 200 kPa). An alarm threshold (for example, 170 kPa) is set as a value corresponding to the recommended pressure corresponding threshold. Originally, an initialization warning threshold value (for example, 170 kPa) calculated from a measured value of tire pressure adjusted to a recommended pressure (for example, 200 kPa) at the time of non-loading based on the initialization operation corresponds to the recommended pressure corresponding threshold value. Set as a value. However, even if the initialization operation is forgotten, the initialization alarm threshold value calculated from the measured tire pressure value adjusted to the recommended air pressure at the time of non-loading is set in the previous time. It becomes a state.

  In such a case, since the initialization warning threshold value is smaller than the low air pressure warning threshold value set at the time of loading, the previously set initialization warning threshold value is set as the initialization warning threshold value as it is. Accordingly, when the measured pressure gradually decreases for some reason, it is determined that an abnormality has occurred, that is, the tire pressure has decreased if the measured pressure falls below the previously set initialization alarm threshold value. For this reason, even if the user forgets the initialization operation, it is possible to appropriately warn of a decrease in tire air pressure.

  As described above, in the TPMS in which the user can initialize the alarm threshold at the time of adjusting the tire pressure so that the initialization alarm threshold can be set based on the measured value of the tire pressure after adjustment, Different low air pressure alarm threshold values are set depending on when the vehicle is not loaded and when the vehicle is not loaded. Specifically, at the time of loading, the low air pressure alarm threshold value is set to a higher value than when not loading.

  In this way, by setting different values for the low air pressure warning threshold value between loading and non-loading, even if the user forgets to perform the alarm threshold initialization operation when adjusting the tire pressure, Based on the air pressure alarm threshold, it is possible to determine a decrease in tire air pressure. Therefore, even if the initialization alarm threshold value set based on the measured value is low because the user forgot to perform the initialization operation, the tire pressure drop is reduced based on the low air pressure alarm threshold value for loading. The alarm can be performed earlier. Therefore, the TPMS can appropriately notify the decrease in tire air pressure in accordance with the load state of the load.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in the above-described embodiment, the discrimination between loading and non-loading of the luggage is performed based on the detection result of the weight sensor 33, but this is merely an example. For example, since the vehicle height changes between when the load is loaded and when the load is not loaded, it may be determined whether the load is loaded or not based on the detection result of the height sensor. For example, when the vehicle height measured by the height sensor is lower than the vehicle height assumed when the vehicle is not loaded, it is determined that the vehicle is loaded. What is necessary is just to utilize the height sensor applied for the optical axis adjustment of a headlight in a vehicle, for example.

  Moreover, in the said embodiment, although the case where all the recommended air pressure of each wheel 4a-4d with which the vehicle 1 is equipped is mentioned as an example, it may differ. For example, the recommended air pressure may be different between the front wheels 4a and 4b and the rear wheels 4c and 4d. In such a case, when the initialization operation is performed, different initialization alarm threshold values and low air pressure alarm threshold values may be set for the front wheels 4a and 4b and the rear wheels 4c and 4d.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Sensor transmitter 3 Car body side system 5 Car body 21 Sensing part 22 Microcomputer 31 TPMS-ECU
33 Weight sensor 34 Vehicle speed sensor 35 Meter indicator

Claims (5)

Applied to a vehicle (1) in which a plurality of wheels (4a to 4d) having tires are attached to a vehicle body (5);
A sensor transmitter (1) provided on each of the plurality of wheels, and having a first control unit (22) for detecting and transmitting a tire pressure of each of the plurality of wheels and generating a frame storing data related to the tire pressure. 2) and
A receiving circuit (31b) provided on the vehicle body side for receiving a frame transmitted from the sensor transmitter via a receiving antenna (31a), and a tire air pressure of each of the plurality of wheels based on the received frame. When the measurement value of the tire pressure is below the initialization alarm threshold, the tire pressure is determined to be lowered and a second control unit (31c) that issues an alarm, and an alarm that performs the alarm. A device (35) and an operation device (35) for initializing the initialization alarm threshold based on a measured value of the tire air pressure when the initialization operation is performed by performing the initialization operation. A vehicle body side system (3) having
Furthermore, the second control unit has a loading determination unit that determines whether the vehicle is loaded or not loaded,
The second control unit is configured such that the initialization alarm threshold is a value different between the loading time and the non-loading time, and the loading time is set to a larger value than the non-loading time. Based on the air pressure alarm threshold, it is determined that the tire air pressure decreases, and when the load determination unit determines that the load is at the time of loading, the low air pressure alarm threshold is set to the value at the time of loading, A tire pressure monitoring system for causing a warning when a measured value of a tire pressure falls below at least one of the initialization warning threshold value and the low pressure warning threshold value.   The second control unit, when the load determination unit determines that the non-loading state, the initialization alarm threshold value is higher than the low air pressure alarm threshold value during the loading, the tire pressure of the tire 2. The tire pressure monitoring system according to claim 1, wherein even if a measured value falls below the initialization warning threshold value, the warning is not performed, and the warning is performed when the measured value falls below the low air pressure warning threshold value when the vehicle is not loaded.   The second control unit determines that the initialization warning threshold is higher than the low air pressure warning threshold during loading when the loading determination unit determines that the loading is not performed. The tire pressure monitoring system according to claim 2, wherein the low air pressure warning threshold value is set as a new initialization warning threshold value.   When the load determination unit determines that the load is not loaded, the second control unit determines that the initialization alarm threshold is lower than the low air pressure alarm threshold during the load. The tire pressure monitoring system according to any one of claims 1 to 3, wherein the warning is performed when a measured value falls below either the initialization warning threshold value or the low air pressure warning threshold value during non-loading, whichever is higher.   The second control unit sets a higher one of the initialization warning threshold and the low air pressure warning threshold as a new initialization warning threshold, and when the measured value of the tire pressure falls below the new initialization warning threshold, The tire pressure monitoring system according to claim 1, wherein an alarm is issued.

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