WO2012157307A1 - タイヤ空気圧送信装置およびタイヤ空気圧モニタシステム - Google Patents
タイヤ空気圧送信装置およびタイヤ空気圧モニタシステム Download PDFInfo
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- WO2012157307A1 WO2012157307A1 PCT/JP2012/053975 JP2012053975W WO2012157307A1 WO 2012157307 A1 WO2012157307 A1 WO 2012157307A1 JP 2012053975 W JP2012053975 W JP 2012053975W WO 2012157307 A1 WO2012157307 A1 WO 2012157307A1
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- WIPO (PCT)
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- wheel
- tire pressure
- tpms
- rotational position
- sensor
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
- B60C23/0415—Automatically identifying wheel mounted units, e.g. after replacement or exchange of wheels
- B60C23/0416—Automatically identifying wheel mounted units, e.g. after replacement or exchange of wheels allocating a corresponding wheel position on vehicle, e.g. front/left or rear/right
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M17/00—Testing of vehicles
- G01M17/007—Wheeled or endless-tracked vehicles
- G01M17/02—Tyres
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
- B60C23/0422—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver characterised by the type of signal transmission means
- B60C23/0433—Radio signals
- B60C23/0447—Wheel or tyre mounted circuits
- B60C23/0455—Transmission control of wireless signals
- B60C23/0459—Transmission control of wireless signals self triggered by motion sensor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0486—Signalling devices actuated by tyre pressure mounted on the wheel or tyre comprising additional sensors in the wheel or tyre mounted monitoring device, e.g. movement sensors, microphones or earth magnetic field sensors
- B60C23/0488—Movement sensor, e.g. for sensing angular speed, acceleration or centripetal force
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0486—Signalling devices actuated by tyre pressure mounted on the wheel or tyre comprising additional sensors in the wheel or tyre mounted monitoring device, e.g. movement sensors, microphones or earth magnetic field sensors
- B60C23/0489—Signalling devices actuated by tyre pressure mounted on the wheel or tyre comprising additional sensors in the wheel or tyre mounted monitoring device, e.g. movement sensors, microphones or earth magnetic field sensors for detecting the actual angular position of the monitoring device while the wheel is turning
Definitions
- the present invention relates to a tire pressure transmitting device and a tire pressure monitoring system.
- the TPMS sensor transmits a TPMS data at a timing when the rotational acceleration detected by the TPMS sensor provided on each wheel becomes 1 [G] or -1 [G].
- a device for transmitting TPMS data at a rotational position is disclosed.
- the wheel position of the TPMS sensor is determined based on the number of teeth obtained from the wheel speed pulse detected by the wheel speed sensor at the timing when the received TPMS data is received.
- An object of the present invention is to provide a tire pressure transmitting device and a tire pressure monitoring system capable of suppressing power consumption of the tire pressure transmitting device.
- the rotational position of the tire pressure transmitting device is determined from the gravitational acceleration component of the acceleration in the centrifugal force direction when transmitting the tire pressure information, and the tire pressure information and the tire are determined at a predetermined cycle.
- the rotation position information of the pneumatic transmitter is transmitted by radio signal.
- the power consumption of the tire pressure transmitting device can be suppressed.
- FIG. 1 is a configuration diagram of a tire air pressure monitoring device of Example 1.
- FIG. 1 is a configuration diagram of a TPMS sensor of Example 1.
- FIG. 1 is a graph which shows the change of the wheel speed of Example 1, and centrifugal force direction acceleration. It is a figure explaining the zone division
- FIG. It is a figure which shows the example of the content of the gravity acceleration component information according to the gravity acceleration component at the time of transmission of Example 1.
- FIG. FIG. 3 is a control block diagram of a TPMS control unit of the first embodiment. It is a figure which shows the rotational position calculation method of each wheel of Example 1.
- FIG. 6 is a diagram illustrating a method for calculating a dispersion characteristic value according to the first embodiment.
- 3 is a flowchart illustrating a flow of wheel position determination control processing according to the first embodiment. It is a figure which shows the relationship between the rotation position of each wheel of Example 1, and the frequency
- FIG. 1 is a configuration diagram of a tire pressure monitoring system 13 according to the first embodiment.
- FL at the end of each symbol indicates a left front wheel
- FR indicates a right front wheel
- RL indicates a left rear wheel
- RR indicates a right rear wheel.
- the tire pressure monitoring system 13 according to the first embodiment includes a TPMS (Tire Pressure Monitoring System) sensor 2 attached to each wheel 1 and a TPMS main body 14 provided on the vehicle body side.
- the TPMS main body 14 includes a receiver 3, a TPMS control unit 4, a display 5, an ABS (Antilock Brake System) control unit 6, and a wheel speed sensor 8.
- FIG. 2 is a view showing the wheel 1. As shown in FIG. 2, the TPMS sensor 2 is provided on each wheel 1 and is attached to the air valve position of the tire near the outer periphery of the wheel 1.
- FIG. 3 is a configuration diagram of the TPMS sensor 2.
- the TPMS sensor 2 includes a pressure sensor 2a, an acceleration sensor 2b, a sensor control unit 2c, a transmitter 2d, and a button battery 2e.
- the pressure sensor 2a detects tire air pressure.
- the acceleration sensor 2b detects centrifugal acceleration acting on the wheel 1.
- the sensor control unit 2c operates with electric power from the button battery 2e, and inputs tire pressure information from the pressure sensor 2a and centrifugal force acceleration information from the acceleration sensor 2b. Then, the tire pressure information and the preset sensor ID (identification information) unique to each TPMS sensor 2 are transmitted as TPMS data from the transmitter 2d by radio signals.
- the sensor IDs of the TPMS sensors 2 are ID1 to ID4.
- the sensor control unit 2c compares the centrifugal acceleration detected by the acceleration sensor 2b with a preset traveling determination threshold, and determines that the vehicle is stopped if the centrifugal acceleration is less than the traveling determination threshold. Stop sending TPMS data. On the other hand, if the centrifugal acceleration is equal to or greater than the travel determination threshold, it is determined that the vehicle is traveling, and TPMS data is transmitted at a predetermined timing.
- the wheel speed sensor 8 includes a rotor 11 and a sensing unit 12. As shown in FIG. 2, the rotor 11 is formed in a gear shape, is fixed coaxially with the center of rotation of the wheel 1, and rotates integrally with the wheel 1. A sensing unit 12 is provided to face the uneven surface of the rotor 11.
- the sensing unit 12 is composed of a permanent magnet and a coil, and when the rotor 11 rotates, the uneven surface of the rotor 11 crosses the magnetic field generated by the permanent magnet of the sensing unit 12, thereby changing the magnetic flux density and generating an electromotive force in the coil. This voltage change of the electromotive force is output to the ABS control unit 6 as a wheel speed pulse signal.
- the rotor 11 is composed of 48 teeth, and the sensing unit 12 outputs 48 pulses when the wheel 1 makes one revolution.
- the ABS control unit 6 receives the wheel speed pulse signal from each wheel speed sensor 8, counts the number of pulses, and obtains the wheel speed of each wheel 1 from the number of pulse changes for a predetermined time.
- anti-skid brake control is performed by operating an ABS actuator (not shown) to increase or decrease or maintain the wheel cylinder pressure of the wheel to suppress the locking tendency .
- the ABS control unit 6 outputs the count value of the wheel speed pulse to the CAN communication line 7 at a constant interval (for example, 20 [msec] interval).
- the receiver 3 receives and decodes the radio signal output from each TPMS sensor 2 and outputs it to the TPMS control unit 4.
- the TPMS control unit 4 inputs TPMS data from each TPMS sensor 2 decoded by the receiver 3.
- the TPMS control unit 4 stores the correspondence between each sensor ID and each wheel position in the non-volatile memory 4d (see FIG. 7), and compares it with the correspondence storing the sensor ID of the TPMS data. Thus, it is determined which wheel 1 the TPMS data is.
- the tire air pressure included in the TPMS data is displayed on the display 5 as the air pressure at the corresponding wheel position. Further, when the tire air pressure falls below the lower limit value, the driver is notified of a decrease in air pressure by changing the display color, blinking display, warning sound, or the like.
- the TPMS control unit 4 determines which wheel 1 the received TPMS data is based on the correspondence between each sensor ID stored in the memory 4d and each wheel position.
- tire rotation refers to changing the mounting position of the tire in order to make the tire tread wear uniform and extend the life (tread life). For example, in a passenger car, the front and rear wheels are generally switched by crossing the left and right tire positions. Therefore, it is necessary to update the correspondence between each sensor ID in the memory 4d and each wheel position after the tire rotation.
- the memory 4d is updated in advance.
- the protocol is set. Next, control of the TPMS sensor 2 and the TPMS control unit 4 will be described in detail.
- the TPMS sensor 2 determines that there is a possibility that tire rotation has been performed when the vehicle stop determination time is 15 [min] or more. When the vehicle stop determination time is less than 15 [min], it is determined that the memory 4d need not be updated, and “normal mode” is selected. When the vehicle stop determination time is 15 [min] or more, it is determined that the memory 4d needs to be updated, and the “position transmission mode” is selected.
- the TPMS data is transmitted until the number of transmissions reaches a predetermined number (for example, 40 times). When the number of transmissions reaches 40 times, the mode is changed to the normal mode.
- the vehicle stop determination time is less than 15 [min]
- the count of the number of transmissions of TPMS data is continued after the vehicle restarts, and the vehicle stop determination time is 15 [min ] If it is above, reset the number of transmissions of TPMS data before stopping the vehicle after restarting, and count the number of transmissions.
- the TPMS sensor 2 transmits the gravity acceleration component information attached to the TPMS data as described above.
- FIG. 4 is a graph showing changes in the acceleration in the centrifugal force direction detected by the wheel speed and the acceleration sensor 2b.
- 4A shows the wheel speed
- FIG. 4B shows the centrifugal force direction acceleration
- FIG. 4C shows the gravity acceleration component of the centrifugal force direction acceleration
- FIG. 4D shows the centrifugal force component of the centrifugal force direction acceleration. It is a graph to show.
- the centrifugal force direction acceleration can be divided into a centrifugal force component that is an acceleration generated by the centrifugal force generated by the rotation of the wheel 1 and a gravitational acceleration component that is an acceleration generated by the gravitational acceleration.
- Acceleration in the centrifugal force direction changes as a whole following the wheel speed shown in FIG. 4 (a) although it is undulating as shown in FIG. 4 (b).
- the centrifugal force component changes almost in synchronization with the wheel speed as shown in FIG.
- the gravitational acceleration component has a sine wave shape that goes back and forth between +1 [G] and -1 [G], and the cycle becomes shorter as the wheel speed increases.
- This is +1 [G] when the TPMS sensor 2 reaches the uppermost point of the wheel 1, and -1 [G because the direction of the TPMS sensor 2 is opposite to the uppermost point when it reaches the lowermost point.
- 0 [G] is obtained at a position of 90 degrees with respect to the uppermost point and the lowermost point. That is, the rotational position of the TPMS sensor 2 can be obtained from the gravitational acceleration component.
- the TPMS data is transmitted with the position information at the time of transmission processing attached.
- This position information is information indicating in which zone the TPMS sensor 2 is located by dividing one rotation into eight zones. More specifically, the sine wave of the gravitational acceleration component is divided into eight zones, the zone where the detected value of the gravitational acceleration component is located is obtained, and this is used as position information.
- the zone is first divided into four zones according to the magnitude of the gravitational acceleration component.
- the range where the gravitational acceleration component is +0.5 [G] or more and 1 [G] or less is Zone 1
- the range where ⁇ 0 [G] or more and less than +0.5 [G] is Zone 2
- the range -0.5 [G] or more is ⁇ 0 [G]
- the range below G] is Zone 3
- the range above -1 [G] and below -0.5 [G] is Zone 4.
- a range in which the gravitational acceleration component decreases is subzone 1
- a range in which the gravitational acceleration component increases is subzone 2.
- the point P1 in FIG. 5 is expressed as zone 1-1
- the point P2 is expressed as zone 4-2.
- FIG. 6 is a diagram showing an example of the content of gravity acceleration component information corresponding to the gravity acceleration component at the time of transmission.
- FIG. 6 shows a state in which the wheel speed is gradually increased and the cycle of the gravitational acceleration component is shortened as the wheel speed increases. Therefore, the rotational position of the TPMS sensor 2 every 10 [sec] is not constant.
- the sensor control unit 2c starts sampling the gravitational acceleration component immediately before 10 [sec] has elapsed since the previous transmission. Sampling is performed four times with a sufficiently short period. By sampling immediately before transmission, the magnitude and increase / decrease range of the gravitational acceleration component at the time of transmission can be obtained, and thereby the zone can be set.
- the magnitude of the gravitational acceleration component is zone 1 and is an increase range, so it is subzone 2.
- Send information At point P5, the magnitude of the gravitational acceleration component is zone 2, and since it is in the decreasing range, it can be seen that it is sub-zone 1, so gravity acceleration component information is transmitted as zone 2-1.
- the magnitude of the gravitational acceleration component is zone 4, and since it is an increase range, it can be seen that it is sub-zone 2. Therefore, gravity acceleration component information is transmitted as zone 4-2.
- the value of the gravitational acceleration component is monitored only immediately before TPMS data transmission, the number of samplings can be reduced as a whole even if the sampling period is shortened, and the accuracy of detecting the peak of the gravitational acceleration component is improved. Power consumption can be suppressed.
- the TPMS control unit 4 determines that there is a possibility that tire rotation has been performed when the vehicle stop determination time is 15 [min] or more. When the vehicle stop determination time is less than 15 [min], it is determined that it is not necessary to update the memory 4d, and “monitor mode” is selected. When the vehicle stop determination time is 15 [min] or more, it is determined that the memory 4d needs to be updated, and the “learning mode” is selected.
- the control of the TPMS control unit 4 in the monitor mode will be described.
- the TPMS control unit 4 collates the correspondence between the sensor ID of the TPMS data input from the receiver 3 and each sensor ID stored in the nonvolatile memory 4d and each wheel position, so that the TPMS data is The wheel position data is determined.
- the tire air pressure included in the TPMS data is displayed on the display 5 as the air pressure of the corresponding wheel 1. Also, if the tire pressure falls below the lower limit, the driver is notified of a drop in air pressure by changing the display color, flashing display, warning sound, or the like.
- the rotational position of each wheel 1 when the TPMS data including the sensor ID is transmitted from the count value of the wheel speed pulse from the ABS control unit 6 and the time when the TPMS data including a certain sensor ID is received. Seeking.
- TPMS sensor 2 sends gravity acceleration component information attached to TPMS data in the position transmission mode.
- the rotational position of the wheel 1 to which the TPMS sensor 2 of ID1 is attached matches the gravity acceleration component information transmitted from the TPMS sensor 2 of ID1, but the rotational position of the other wheel 1 and the TPMS sensor 2 of ID1 It does not match the transmitted gravity acceleration component information.
- FIG. 7 is a control block diagram of the TPMS control unit 4 for performing wheel position determination control.
- the TPMS control unit 4 includes a rotational position calculation unit 4a, a dispersion calculation unit 4b, a wheel position determination unit (wheel position determination means) 4c, and a memory 4d.
- the rotational position calculation unit 4a inputs the TPMS data after decoding from the receiver 3 and the count value of each wheel speed pulse from the ABS control unit 6, and each time when the TPMS sensor 2 of ID1 transmits the TPMS data The rotational position of wheel 1 is calculated.
- the rotational position calculation unit 4a virtually assigns a tooth number to each of the 48 teeth, and obtains the rotational position of the wheel 1 from the tooth number of the rotor 11 that has been shaken.
- the rotational position calculation unit 4a adds the wheel speed pulse count value input from the ABS control unit 6 and stores it. The tooth number is obtained by dividing the added value of the wheel speed pulse by the number of teeth 48 and adding 1 to it.
- a time lag occurs between the timing when the TPMS sensor 2 of ID1 transmits TPMS data and the timing when the receiver 3 receives the TPMS data. Further, there is a time lag between the timing when the TPMS sensor 2 of ID1 starts the transmission process of TPMS data and the timing when the TPMS data is actually transmitted.
- the TPMS control unit 6 cannot know the time when the TPMS sensor 2 started the TPMS data transmission process, the TPMS sensor 2 starts the TPMS data transmission process by calculating backward from the time when the receiver 3 received the TPMS data. It is necessary to calculate the rotation time of each wheel at that time.
- the count value of the wheel speed pulse is input from the ABS control unit 6 only every 20 [msec], that is, the count value for each pulse is not input, so when the position of the TPMS sensor 2 of ID1 comes to the highest point It is necessary to calculate the tooth number.
- FIG. 8 is a diagram illustrating a method for calculating the tooth number of the rotor 11 (the rotational position of the wheel 1) when the TPMS sensor 2 transmits TPMS data.
- the time when the count value of the wheel speed pulse is input is t1
- the time when the TPMS sensor 2 of ID1 starts the transmission process of TPMS data is t2
- the TPMS sensor 2 of ID1 actually transmits TPMS data.
- the start time is t3
- the time when the receiver 3 completes reception of the TPMS data is t4
- the time when the wheel speed pulse count value is input is t5.
- the TPMS control unit 6 can directly know the times t1, t4 and t5.
- the time t3 can be calculated by subtracting the data length of the TPMS data (a prescribed value, for example, about 10 [msec]) from the time t4.
- the time t2 can be calculated by subtracting the time lag at the time of transmission (which can be obtained in advance through experiments or the like) from the time t3. During 20 [msec], the change in wheel speed is small enough to assume a constant speed.
- tooth number at time t1 is n1
- the tooth number at time t2 is n2
- the tooth number at time t5 is n5
- (t2-t1) / (t5-t1) (n2-n1) / (n5-n1)
- n2-n1 (n5-n1) * (t2-t1) / (t5-t1)
- n2 n1 + (n5-n1) * (t2-t1) / (t5-t1) It becomes.
- the dispersion calculation unit 4b accumulates the tooth number of each wheel 1 at time t2 when the TPMS sensor 2 of ID1 calculated by the rotation position calculation unit 4a starts the transmission process of TPMS data, and the rotation position data of each wheel 1 The degree of variation is calculated as a dispersion characteristic value.
- the TPMS sensor 2 Since the TPMS sensor 2 transmits TPMS data at a fixed time, the rotational position when the transmission process is started is different each time. Therefore, if the rotational position data of each wheel 1 is used as it is, the wheel position of the TPMS sensor 2 of ID1 cannot be specified from the dispersion characteristic value. Therefore, the tooth number of the obtained wheel 1 is corrected using the gravitational acceleration component information.
- the rotation position of the wheel 1 is corrected by setting a correction value for each zone of gravity acceleration component information.
- the correction value for each zone is Zone 1-1: Correction value 0 Zone 2-1: Correction value +42 Zone 3-1: Correction value +36 Zone 4-1: Correction value +30 Zone 4-2: Correction value +24 Zone 3-2: Correction value +18 Zone 2-2: Correction value +12 Zone 1-2: Correction value +6 And
- FIG. 9 is a diagram illustrating a method for calculating the dispersion characteristic value.
- the rotational position of each wheel 1 is regarded as a vector of length 1 with the origin (0,0) as the start point and the coordinates (cos ⁇ , sin ⁇ ) as the end point, and the average vector (ave_cos ⁇ , ave_sin ⁇ ) is calculated, and the scalar quantity of the average vector is calculated as the dispersion characteristic value X of the rotational position data.
- the wheel position determination unit 4c compares the dispersion characteristic value X of the rotational position data of each wheel 1 calculated by the dispersion calculation unit 4b, and the maximum value of the dispersion characteristic value X is greater than the first threshold value (for example, 0.57). And the remaining three dispersion characteristic values X are less than the second threshold value (for example, 0.37), the ID1 TPMS sensor 2 is attached to the wheel 1 corresponding to the highest dispersion characteristic value X. And the correspondence relationship between the TPMS sensor 2 of ID1 and the position of the wheel 1 is updated in the memory 4d.
- FIG. 10 is a flowchart showing the flow of the wheel position determination control process.
- step S1 the case of sensor ID1 will be described, but the wheel position determination control process is also performed in parallel for other IDs (ID2, ID3, ID4).
- step S1 the rotational position calculation unit 4a receives the TPMS data of the sensor ID1.
- step S2 the rotational position of each wheel 1 is calculated in the rotational position calculation unit 4a.
- step S3 the dispersion characteristic value X of the rotational position data of each wheel 1 is computed in the dispersion computing unit 4b.
- step S4 it is determined whether or not the TPMS data of sensor ID1 has been received a predetermined number of times (for example, 10 times) or more. If YES, the process proceeds to step S5. If NO, the process returns to step S1. In step S5, whether or not the maximum dispersion characteristic value is larger than the first threshold value 0.57 and the remaining dispersion characteristic value is less than the second threshold value 0.37 in the wheel position determination unit 4c. If YES, the process proceeds to step S6. If NO, the process proceeds to step S7.
- step S6 the wheel position determination unit 4c determines that the wheel position corresponding to the highest dispersion characteristic value is the position of the TPMS sensor 2 of the sensor ID1, and ends the learning mode.
- step S7 it is determined whether or not a predetermined cumulative travel time (for example, 8 minutes) has elapsed since the start of the learning mode in the wheel position determination unit 4c. If NO, the process proceeds to step S1, and YES In this case, the learning mode is terminated.
- a predetermined cumulative travel time for example, 8 minutes
- the wheel position determination unit 4c registers the correspondence between each sensor ID and each wheel position by updating the memory 4d when the wheel position can be determined for all the sensor IDs within a predetermined cumulative travel time. On the other hand, if the wheel positions cannot be determined for all sensor IDs within the predetermined cumulative travel time, the correspondence between each sensor ID stored in the memory 4d and each wheel position is continuously used without updating. To do.
- each TPMS sensor 2 determines that there is a possibility that tire rotation has been performed when the vehicle stop determination time immediately before the start of travel is 15 minutes or more, and shifts from the normal mode to the position transmission mode. In the position transmission mode, each TPMS sensor 2 transmits gravitational acceleration component information attached to TPMS data every 10 [sec].
- the TPMS control unit 4 shifts from the monitor mode to the learning mode.
- the learning mode each time the TPMS control unit 4 receives TPMS data from each TPMS sensor 2, the TPMS data of the TPMS sensor 2 is calculated from the input time of the count value of the wheel speed pulse, the reception completion time of the TPMS data, etc.
- the rotational position (rotor tooth number) of each wheel 1 at the time of transmission processing is calculated, and the rotational position is corrected from the gravitational acceleration component information of the TPMS data. This is repeated 10 times or more and accumulated as rotational position data, and the wheel position corresponding to the rotational position data having the smallest variation among the rotational position data is determined as the wheel position of the TPMS sensor 2.
- the rotational speed of each wheel 1 varies depending on the difference between the inner and outer wheels when the vehicle is running and turning, the lock and slip of the wheel 1, and the tire pressure difference, for example, the TPMS sensor 2 of ID1
- the rotational position of the attached wheel 1 matches the gravitational acceleration component information transmitted from the TPMS sensor 2 of ID1, but the rotational position of the other wheel 1 and the gravitational acceleration component information transmitted from the TPMS sensor 2 of ID1 Does not match.
- FIG. 11 is a diagram showing the relationship between the rotational positions (tooth numbers of the rotor 11) of the wheels 1FL, 1FR, 1RL, and 1RR corrected based on the gravity acceleration component information of the TPMS sensor 2 of ID1 and the number of receptions of TPMS data. It is. 11A is a wheel speed sensor 8FL for the left front wheel 1FL, FIG. 11B is a wheel speed sensor 8FR for the right front wheel 1FR, FIG. 11C is a wheel speed sensor 8RL for the left rear wheel 1RL, and FIG. ) Corresponds to the wheel speed sensor 8RR of the right rear wheel 1RR.
- the corrected values of the rotational positions (tooth numbers of the rotor 11) obtained from the wheel speed sensors 8FR, 8RL, 8RR of the right front wheel 1FR, the left rear wheel 1RL, and the right rear wheel 1RR vary.
- the degree is large
- the corrected value of the rotational position obtained from the wheel speed sensor 8FL of the left front wheel 1FL has the least variation, the transmission period of the TPMS data of ID1 and the rotation period of the rotor 11 of the left front wheel 1FL And are almost synchronized. From this, it can be determined that the position of the TPMS sensor 2 of ID1 is attached to the left front wheel 1FL.
- Variance is generally defined as the average of “the square of the difference from the average”. However, since the rotational position of the wheel 1 is periodic angle data, the degree of variation in the rotational position of the wheel 1 cannot be obtained from a general dispersion formula.
- the rotational position ⁇ of each wheel 1 obtained from each wheel speed sensor 8 is set to the coordinates on the circumference of the unit circle around the origin (0, 0) ( cos ⁇ , sin ⁇ ), the coordinates (cos ⁇ , sin ⁇ ) are regarded as vectors, the average vector (ave_cos ⁇ , ave_sin ⁇ ) of each vector of the rotational position data of the same wheel 1 is obtained, and the scalar quantity of the average vector is expressed as the dispersion characteristic value X As a result, it is possible to obtain the degree of variation in the rotational position of the wheel 1 while avoiding periodicity.
- FIG. 12 is a diagram showing a change in the dispersion characteristic value X of the rotational position of each wheel 1 (the tooth number of the rotor 11) according to the number of receptions of the TPMS data of ID1.
- the alternate long and short dash line indicates the dispersion characteristic value X of the rotational position of the left front wheel 1FL
- the solid line indicates the dispersion characteristic value X of the rotational position of the right front wheel 1FR, left rear wheel 1RL, and right rear wheel 1RR.
- the dispersion characteristic value X of the rotational position of the left front wheel 1FL approaches 1, and the rotation of the right front wheel 1FR, the left rear wheel 1RL, and the right rear wheel 1RR
- the position dispersion characteristic value X indicates a characteristic approaching zero. Therefore, the highest dispersion characteristic value X (dispersion characteristic value X closest to 1) when a sufficient number of receptions (about several tens of times) is reached may be selected.
- the determination accuracy is lowered.
- the wheel position determination unit 4c when the wheel position determination unit 4c receives TPMS data of the same sensor ID 10 times or more, the dispersion of the rotational position data of each wheel 1 when the sensor ID is transmitted.
- the characteristic value X is compared, the maximum dispersion characteristic value X is greater than the first threshold value 0.57, and the remaining three dispersion characteristic values X are all less than the second threshold value 0.37
- the wheel position of the rotational position data corresponding to the highest dispersion characteristic value X is determined as the wheel position of the TPMS sensor 2 of the sensor ID.
- a certain determination accuracy can be ensured by comparing the maximum value with the first threshold value (0.57). Furthermore, by comparing the dispersion characteristic value X other than the maximum value with the second threshold value (0.37), it can be confirmed that there is a difference of more than a predetermined (0.2) between the maximum value and the other three values. Can be increased. For this reason, it is possible to achieve both of ensuring the determination accuracy and shortening the determination time with a small number of receptions of 10 times.
- the TPMS sensor 2 shifts to the normal mode when transmitting TPMS data 40 times in the position transmission mode. Since the TPMS sensor 2 consumes the most power of the button battery 2e when transmitting TPMS data, the battery life of the button battery 2e becomes shorter as the position transmission mode with a shorter transmission interval is continued.
- the battery life is reduced by terminating the position transmission mode and shifting to the normal mode. Can be suppressed.
- the TPMS control unit 4 ends the learning mode and switches to the monitor mode. Transition.
- the total number of TPMS data transmitted from the TPMS sensor 2 when the cumulative traveling time has passed 8 minutes is less than 30, and the learning mode can be terminated almost in synchronization with the end of the position transmission mode of the TPMS sensor 2.
- the TPMS sensor 2 detects the gravitational acceleration component of the acceleration in the centrifugal force direction when transmitting TPMS data every 10 [sec], obtains the rotational position of the TPMS sensor 2 from the gravitational acceleration component, and serves as position information. Added transmission to TPMS data. Therefore, since the TPMS sensor 2 monitors the value of the gravitational acceleration component only when TPMS data is transmitted, the number of samplings can be reduced and power consumption can be suppressed.
- the TPMS sensor 2 Since the change in the gravitational acceleration component is a sine wave, the position information of the TPMS sensor 2 may not be specified only from the magnitude of the gravitational acceleration. Therefore, in the first embodiment, the TPMS sensor 2 detects the gravitational acceleration component every predetermined sampling period immediately before transmitting the TPMS data. As a result, the increase / decrease direction of the change in the gravitational acceleration component can be obtained, and the position of the TPMS sensor 2 is determined from the magnitude and the increase / decrease direction of the gravitational acceleration component. Therefore, the rotational position of the TPMS sensor 2 can be specified accurately.
- the TPMS sensor 2 of Example 1 has the following effects.
- Acceleration sensor 2b (acceleration detection means) that detects the acceleration in the direction of centrifugal force when the wheel is rotating, and TPMS sensor 2 (tire pressure transmitter) from the gravitational acceleration component of the acceleration in the direction of centrifugal force when transmitting tire pressure information
- a sensor control unit 2c position determining means for determining the rotational position of the vehicle
- a transmitter 2d transmitting means for transmitting tire pressure information and rotational position information of the TPMS sensor 2 by radio signals at a predetermined cycle.
- the TPMS sensor 2 monitors the value of the gravitational acceleration component only when transmitting the TPMS data, the number of samplings can be reduced, and the detection accuracy of the peak of the gravitational acceleration component can be increased and the power consumption can be suppressed. .
- the sensor control unit 2c detects the gravitational acceleration component of the centrifugal force direction acceleration every predetermined sampling period before transmitting the radio signal by the transmitter 2d, and determines the TPMS sensor 2 from the magnitude of the gravitational acceleration component and the change direction. The rotational position was determined. Therefore, the rotational position of the TPMS sensor 2 can be specified accurately.
- the tire pressure monitoring system 13 has the following effects.
- TPMS sensor 2 tire pressure transmitter
- the TPMS sensor 2 includes a pressure sensor 2a (tire pressure detection means) that detects the tire pressure, Acceleration sensor 2b (acceleration detection means) that detects the acceleration in the centrifugal force direction when the wheel 1 is rotating, and sensor control unit 2c (position) that determines the rotational position of the TPMS sensor 2 from the gravitational acceleration component of the acceleration in the centrifugal force direction
- Transmitter 2d transmitting means for transmitting tire pressure information and rotational position information of the TPMS sensor 2 together with identification information unique to each TPMS sensor 2 by a radio signal at a predetermined
- the rotational position of each wheel 1 when the ABS control unit 6 (rotational position detecting means) for detecting the rotational position of each wheel 1 and the TPMS sensor 2 having certain identification information transmit the rotational position information of the TPMS sensor 2
- a TPMS control unit 4 (wheel position determination means) for determining the position of the wheel 1 to which the TPMS sensor 2 is attached is provided from the rotational position information of the TPMS sensor 2. Therefore, since the TPMS sensor 2 monitors the value of the gravitational acceleration component only when transmitting the TPMS data, the number of samplings can be reduced, and the detection accuracy of the peak of the gravitational acceleration component can be increased and the power consumption can be suppressed. .
- the sensor control unit 2c detects the gravitational acceleration component of the centrifugal force direction acceleration every predetermined sampling period before transmitting the radio signal by the transmitter 2d, and determines the TPMS sensor 2 from the magnitude of the gravitational acceleration component and the change direction. The rotational position was determined. Therefore, the rotational position of the TPMS sensor 2 can be specified accurately.
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Abstract
Description
本発明の目的は、タイヤ空気圧送信装置の消費電力を抑制することができるタイヤ空気圧送信装置およびタイヤ空気圧モニタシステムを提供することである。
2 TPMSセンサ(タイヤ空気圧送信装置、タイヤ空気圧送信部)
2a 圧力センサ(タイヤ空気圧検出手段)
2b 加速度センサ(加速度検出手段)
2d 送信機(送信手段)
2c センサコントロールユニット(位置判定手段)
3 受信機(受信手段)
4 TPMSコントロールユニット(車輪位置判定手段)
6 ABSコントロールユニット(回転位置検出手段)
13 タイヤ空気圧モニタシステム
14 TPMS本体部(タイヤ空気圧モニタ本体部)
[全体構成]
図1は、実施例1のタイヤ空気圧モニタシステム13の構成図である。図において、各符号の末尾のFLは左前輪、FRは右前輪、RLは左後輪、RRは右後輪に対応することを示す。以下の説明では、個別に説明する必要がない場合にはFL,FR,RL,RRの記載を省略する。
実施例1のタイヤ空気圧モニタシステム13は、各車輪1に取り付けられたTPMS(Tire Pressure Monitoring System)センサ2と、車体側に設けられたTPMS本体部14とを有している。TPMS本体部14は、受信機3と、TPMSコントロールユニット4と、ディスプレイ5と、ABS(Antilock Brake System)コントロールユニット6と、車輪速センサ8とを備える。
図2は車輪1を示す図である。図2に示すように、TPMSセンサ2は各車輪1に設けられており、車輪1の外周寄りのタイヤの空気バルブ位置に取り付けられている。
図3はTPMSセンサ2の構成図である。TPMSセンサ2は、圧力センサ2aと、加速度センサ2bと、センサコントロールユニット2cと、送信機2dと、ボタン電池2eとを備える。
車輪速センサ8は、ロータ11とセンシング部12とから構成されている。図2に示すように、ロータ11は歯車状に形成されており、車輪1の回転中心と同軸に固定されて車輪1と一体に回転する。このロータ11の凹凸面に対向してセンシング部12が設けられている。センシング部12は永久磁石およびコイルとから構成され、ロータ11が回転するとロータ11の凹凸面がセンシング部12の永久磁石により生じた磁界を横切ることにより、磁束密度が変化してコイルに起電力が生じ、この起電力の電圧変化を車輪速パルス信号としてABSコントロールユニット6へ出力する。ロータ11は48歯からなり、センシング部12は車輪1が1回転すると48回のパルスを出力することなる。
ABSコントロールユニット6は、各車輪速センサ8からの車輪速パルス信号を入力し、パルス数をカウントして、所定時間のパルス変化数により各車輪1の車輪速を求めている。各車輪1の車輪速からある車輪1がロック傾向にある場合、図外のABSアクチュエータを作動させて当該車輪のホイルシリンダ圧を増減または保持してロック傾向を抑制するアンチスキッドブレーキ制御を実施する。また、ABSコントロールユニット6は、一定間隔(例えば、20[msec]間隔)で車輪速パルスのカウント値をCAN通信線7に出力する。
受信機3は、各TPMSセンサ2から出力された無線信号を受信してデコードし、TPMSコントロールユニット4へ出力する。
TPMSコントロールユニット4は、受信機3においてデコードされた各TPMSセンサ2からのTPMSデータを入力する。TPMSコントロールユニット4は、不揮発性のメモリ4d(図7参照)に各センサIDと各車輪位置との対応関係とを記憶しており、TPMSデータのセンサIDを記憶している対応関係と照合して当該TPMSデータがどの車輪1のデータであるのかを判定する。当該TPMSデータに含まれるタイヤの空気圧を対応する車輪位置の空気圧としてディスプレイ5に表示する。また、タイヤの空気圧が下限値を下回った場合には、表示色変更、点滅表示や警告音などによりドライバに空気圧の低下を知らせる。
そのため、タイヤローテーション後にはメモリ4dの各センサIDと各車輪位置との対応関係を更新する必要がある。しかしながら、車輪1側に設けられたTPMSセンサ2と車体側に設けられたTPMSコントロールユニット4とは相互通信を行うことができないため、実施例1のタイヤ空気圧モニタシステムでは、あらかじめメモリ4dの更新時のプロトコルを設定している。
次に、TPMSセンサ2とTPMSコントロールユニット4の制御について詳述する。
TPMSセンサ2は、車両停止判定時間が15[min]以上である場合、タイヤローテーションが行われた可能性があると判断する。車両停止判定時間が15[min]未満のときにはメモリ4dの更新は必要ないと判断し、「通常モード」を選択する。車両停止判定時間が15[min]以上のときにはメモリ4dの更新が必要と判断し、「位置送信モード」を選択する。
まず、通常モード時のTPMSセンサ2の制御について説明する。
センサコントロールユニット2cは、加速度センサ2bにより検出された遠心方向加速度が走行判定しきい値未満の場合は車両停止と判定して、TPMSデータの送信を停止する。一方、遠心方向加速度が走行判定しきい値未満の場合は車両走行中と判定して、一定間隔(例えば、1[min]間隔)でTPMSデータを送信する。
次に、位置送信モード時のTPMSセンサ2の制御について説明する。
位置送信モードでは、定位位置送信モードの送信間隔よりも短い間隔(例えば、約10[sec]間隔)でTPMSデータに送信処理時の遠心力方向加速度の重力加速度成分情報を添付して送信する。
TPMSセンサ2は、位置送信モードでは前述のようにTPMSデータに重力加速度成分情報を添付して送信する。
TPMSセンサ2が所定の位置となったときにTPMSデータを送信するためには、常に重力加速度成分をサンプリングしていなければ成らず、また位置精度を高めるためにはサンプリング周期を短くしなければならない。そのため、消費電力が大きくなりボタン電池2eの長寿命化が図れない。
そこで実施例1では、位置送信モードにおいてはTPMSデータに送信処理時の位置情報を添付して送信することとした。この位置情報は、1回転を8つのゾーンに分け、TPMSセンサ2がどのゾーンに位置しているかを示す情報である。具体的には、重力加速度成分の正弦波を8つのゾーンに分け、検出した重力加速度成分の値がどのゾーンに位置するかを求めて、これを位置情報としている。
図5は重力加速度成分のゾーン分けを説明する図である。図5に示すように、まず重力加速度成分の大きさに応じて4つのゾーンに分ける。つまり、重力加速度成分が+0.5[G]以上1[G]以下の範囲をゾーン1、±0[G]以上+0.5[G]未満の範囲をゾーン2、-0.5[G]以上±0[G]未満の範囲をゾーン3、-1[G]以上-0.5[G]未満の範囲をゾーン4とする。さらに重力加速度成分が減少する範囲をサブゾーン1とし、重力加速度成分が増加する範囲をサブゾーン2とする。例えば、図5の点P1ではゾーン1-1、点P2ではゾーン4-2と表現する。
これにより、TPMSデータ送信直前にのみ重力加速度成分の値をモニタするため、サンプリング周期を短くしても全体としてはサンプリング数を少なくすることができ、重力加速度成分のピークの検出精度を高めるとともに、消費電力を抑制することができる。
TPMSコントロールユニット4は、車両停止判定時間が15[min]以上である場合、タイヤローテーションが行われた可能性があると判断する。車両停止判定時間が15[min]未満のときにはメモリ4dの更新は必要ないと判断し、「モニタモード」を選択する。車両停止判定時間が15[min]以上のときにはメモリ4dの更新が必要と判断し、「ラーニングモード」を選択する。
まず、モニタモード時のTPMSコントロールユニット4の制御について説明する。
モニタモード時には、TPMSコントロールユニット4は、受信機3から入力したTPMSデータのセンサIDと、不揮発性のメモリ4dに記憶した各センサIDと各車輪位置との対応関係を照合して当該TPMSデータがどの車輪位置のデータであるのかを判定する。そして、当該TPMSデータに含まれるタイヤ空気圧を対応する車輪1の空気圧としてディスプレイ5に表示する。また、タイヤ空気圧が下限値を下回った場合には、表示色変更、点滅表示や警告音などによりドライバに空気圧の低下を知らせる。
次に、ラーニングモード時のTPMSコントロールユニット4の制御について説明する。
ラーニングモード時には、各TPMSセンサ2がどの車輪位置にあるかの判定が終了するまで、またはラーニングモードの開始から所定の累積走行時間(例えば、8[min])が経過するまで実施し、ラーニングモード終了後はモニタモードへ移行する。
なお、ラーニングモード中であってもTPMSデータは随時入力されるため、更新前のメモリ4dの各センサIDと各車輪位置との対応関係に基づいて空気圧の表示、空気圧低下の警告を行う。
図7は、車輪位置判定制御を実施するためのTPMSコントロールユニット4の制御ブロック図である。TPMSコントロールユニット4は、回転位置演算部4aと、分散演算部4bと、車輪位置判定部(車輪位置判定手段)4cと、メモリ4dとを備えている。
回転位置演算部4aは、受信機3からデコード後のTPMSデータと、ABSコントロールユニット6から各車輪速パルスのカウント値とを入力し、ID1のTPMSセンサ2のがTPMSデータを送信したときの各車輪1の回転位置を演算する。
図8において、車輪速パルスのカウント値を入力した時間をt1、ID1のTPMSセンサ2がTPMSデータの送信処理を開始したときの時間をt2、ID1のTPMSセンサ2が実際にTPMSデータの送信を開始した時間をt3、受信機3が該TPMSデータの受信を完了した時間をt4、次に車輪速パルスのカウント値を入力した時間をt5とする。TPMSコントロールユニット6は時間t1,t4,t5を直接知ることができる。時間t3は、時間t4からTPMSデータのデータ長(規定値であり、例えば、約10[msec])を減算して算出できる。時間t2は、時間t3から送信時のタイムラグ(あらかじめ実験等により求めることができる。)を減算して算出できる。20[msec]間では、車輪速の変化は十分小さいため一定速と仮定する。
(t2 - t1) / (t5 - t1) = (n2 - n1) / (n5 - n1)
が成立する。これから、
n2 - n1 = (n5 - n1) * (t2 - t1) / (t5 - t1)
が求められ、ID1のTPMSセンサ2の回転位置が最上点となった時間t2の歯番n2は、
n2 = n1 + (n5 - n1) * (t2 - t1) / (t5 - t1)
となる。
分散演算部4bは、回転位置演算部4aで演算されたID1のTPMSセンサ2がTPMSデータの送信処理を開始した時間t2の各車輪1の歯番を蓄積し、各車輪1の回転位置データのばらつき度合いを分散特性値として演算する。
ゾーン1-1:補正値0
ゾーン2-1:補正値+42
ゾーン3-1:補正値+36
ゾーン4-1:補正値+30
ゾーン4-2:補正値+24
ゾーン3-2:補正値+18
ゾーン2-2:補正値+12
ゾーン1-2:補正値+6
とする。
(cosθ,sinθ) = (cos((n2+1)*2π/48),sin((n2+1)*2π/48))
よって、同一センサIDのTPMSデータの受信回数をN(Nは正の整数)とすると、平均ベクトル(ave_cosθ,ave_sinθ)は、
(ave_cosθ,ave_sinθ) = ((Σ(cosθ))/N,(Σ(sinθ))/N)
となり、分散特性値Xは、
X = ave_cosθ2 + ave_sinθ2
で表すことができる。
車輪位置判定部4cは、分散演算部4bで演算された各車輪1の回転位置データの分散特性値Xを比較し、分散特性値Xの最高値が第1しきい値(例えば、0.57)よりも大きく、かつ、残り3つの分散特性値Xの値がすべて第2しきい値(例えば、0.37)未満となった場合、最高値の分散特性値Xに対応する車輪1にID1のTPMSセンサ2が設けられていると判定し、ID1のTPMSセンサ2と車輪1の位置とを対応関係をメモリ4dに更新する。
図10は、車輪位置判定制御処理の流れを示すフローチャートである。以下、各ステップについて説明する。なお、以下の説明では、センサID1の場合について説明するが、他のID(ID2,ID3,ID4)についても並列して車輪位置判定制御処理を行う。
ステップS1では、回転位置演算部4aにおいてセンサID1のTPMSデータを受信する。
ステップS2では、回転位置演算部4aにおいて各車輪1の回転位置を演算する。
ステップS4では、センサID1のTPMSデータを所定回数(例えば、10回)以上受信したか否かを判定し、YESの場合にはステップS5へ進み、NOの場合にはステップS1へ戻る。
ステップS5では、車輪位置判定部4cにおいて分散特性値の最高値が第1しきい値0.57よりも大きく、かつ、残りの分散特性値の値が第2しきい値0.37未満であるか否かを判定し、YESの場合にはステップS6へ進み、NOの場合にはステップS7へ進む。
ステップS7では、車輪位置判定部4cにおいてラーニングモードを開始してから所定の累積走行時間(例えば、8分)が経過したか否かを判定し、NOの場合にはステップS1へ進み、YESの場合にはラーニングモードを終了する。
以下では、タイヤローテーション後に、ID1のTPMSセンサ2の車輪位置が左前輪1FLとなったと前提して説明する。
(車輪位置判定)
各TPMSセンサ2は、走行開始直前の車両停止判定時間が15分以上である場合、タイヤローテーションが行われた可能性があると判定し、通常モードから位置送信モードへ移行する。位置送信モードにおいて、各TPMSセンサ2は10[sec]毎にTPMSデータに重力加速度成分情報を添付して送信する。
よって、ID1のTPMSセンサ2が取り付けられた車輪1の回転位置をID1のTPMSセンサ2から送信された重力加速度成分情報に基づいて補正すると、補正後の回転位置データのばらつきは小さくなるが、他の車輪1の回転位置をID1のTPMSセンサ2から送信された重力加速度成分情報に基づいて補正すると、補正後の回転位置データのばらつきは大きくなる。補正後の各車輪1の回転位置データのばらつき度合いを見ることで、各TPMSセンサ2の車輪位置を精度良く判定できる。
分散は一般的には「平均との差の2乗」の平均で定義される。しかし、車輪1の回転位置は周期性のある角度データであるため、一般的な分散の式から車輪1の回転位置のばらつき度合い求めることはできない。
TPMSセンサ2は、位置送信モード時にTPMSデータを40回送信すると通常モードへ移行する。TPMSセンサ2は、TPMSデータの送信時に最もボタン電池2eの電力を消費するため、送信間隔が短い位置送信モードを継続するほど、ボタン電池2eの電池寿命が短くなる。
TPMSセンサ2が所定の位置となったときにTPMSデータを送信するためには、常に重力加速度成分をサンプリングしていなければ成らず、また位置精度を高めるためにはサンプリング周期を短くしなければならない。そのため、消費電力が大きくなりボタン電池2eの長寿命化が図れない。
よって、TPMSセンサ2はTPMSデータ送信時にのみ重力加速度成分の値をモニタするため、サンプリング数を少なくすることができ、消費電力を抑制することができる。
重力加速度成分の変化は正弦波となるため、重力加速度の大きさからだけではTPMSセンサ2の位置情報を特定することができないときがある。
そこで実施例1では、TPMSセンサ2はTPMSデータ送信直前に所定のサンプリング周期毎に重力加速度成分を検出するようにした。これにより重力加速度成分の変化の増減方向を求めることができ、重力加速度成分の大きさと増減方向とからTPMSセンサ2の位置を判定するようにした。
よって、TPMSセンサ2の回転位置を正確に特定することができる。
次に、効果を説明する。
実施例1のTPMSセンサ2にあっては、以下に列挙する効果を奏する。
(1) 車輪1の外周側に取り付けられ、車輪1のタイヤ空気圧情報を送信するTPMSセンサ2(タイヤ空気圧送信装置)において、タイヤ空気圧を検出する圧力センサ2a(タイヤ空気圧検出手段)と、車輪1が回転しているときの遠心力方向加速度を検出する加速度センサ2b(加速度検出手段)と、タイヤ空気圧情報を送信するときの遠心力方向加速度の重力加速度成分からTPMSセンサ2(タイヤ空気圧送信装置)の回転位置を判定するセンサコントロールユニット2c(位置判定手段)と、所定の周期で、タイヤ空気圧情報とTPMSセンサ2の回転位置情報とを無線信号にて送信する送信機2d(送信手段)とを設けた。
よって、TPMSセンサ2はTPMSデータ送信時にのみ重力加速度成分の値をモニタするため、サンプリング数を少なくすることができ、重力加速度成分のピークの検出精度を高めるとともに、消費電力を抑制することができる。
よって、TPMSセンサ2の回転位置を正確に特定することができる。
(3) 各車輪1の外周側に取り付けられ、車輪1のタイヤ空気圧情報を無線信号にて送信するTPMSセンサ2(タイヤ空気圧送信部)と、車体側に設けられ、無線信号を受信して各車輪1のタイヤ空気圧を監視するTPMS本体部14(タイヤ空気圧モニタ装置)と、を備えたタイヤ空気圧モニタシステムにおいて、TPMSセンサ2は、タイヤ空気圧を検出する圧力センサ2a(タイヤ空気圧検出手段)と、車輪1が回転しているときの遠心力方向加速度を検出する加速度センサ2b(加速度検出手段)と、遠心力方向加速度の重力加速度成分からTPMSセンサ2の回転位置を判定するセンサコントロールユニット2c(位置判定手段)と、所定の周期でタイヤ空気圧情報とTPMSセンサ2の回転位置情報とを各TPMSセンサ2固有の識別情報と共に無線信号にて送信する送信機2d(送信手段)とを設け、TPMS本体部14(タイヤ空気圧モニタ本体部)は、各TPMSセンサ2の送信機2dから送信されたタイヤ空気圧情報およびTPMSセンサ2の回転位置情報を受信する受信機3(受信手段)と、各車輪1の回転位置を検出するABSコントロールユニット6(回転位置検出手段)と、ある識別情報を有するTPMSセンサ2がTPMSセンサ2の回転位置情報を送信したときの各車輪1の回転位置とTPMSセンサ2の回転位置情報とから、TPMSセンサ2が取り付けられた車輪1の位置を判定するTPMSコントロールユニット4(車輪位置判定手段)とを設けた。
よって、TPMSセンサ2はTPMSデータ送信時にのみ重力加速度成分の値をモニタするため、サンプリング数を少なくすることができ、重力加速度成分のピークの検出精度を高めるとともに、消費電力を抑制することができる。
よって、TPMSセンサ2の回転位置を正確に特定することができる。
以上、本発明を実施するための最良の形態を、図面に基づく実施例により説明したが、本発明の具体的な構成は、実施例に限定されるものではなく、発明の要旨を逸脱しない範囲の設計変更等があっても本発明に含まれる。
例えば、実施例では、回転位置検出手段として車輪速センサを用いた例を示したが、駆動源としてインホイールモータを備えた車両では、モータのレゾルバを用いて回転角度を検出してもよい。
Claims (4)
- 車輪の外周側に取り付けられ、車輪のタイヤ空気圧情報を送信するタイヤ空気圧送信装置において、
前記タイヤ空気圧を検出するタイヤ空気圧検出手段と、
前記車輪が回転しているときの遠心力方向加速度を検出する加速度検出手段と、
前記タイヤ空気圧情報を送信するときの前記遠心力方向加速度の重力加速度成分から前記タイヤ空気圧送信装置の回転位置を判定する位置判定手段と、
所定の周期で、前記タイヤ空気圧情報と前記タイヤ空気圧送信装置の回転位置情報とを無線信号にて送信する送信手段と、
を設けたことを特徴とするタイヤ空気圧送信装置。 - 請求項1に記載のタイヤ空気圧送信装置において、
位置判定手段は、前記送信手段による無線信号送信前に所定のサンプリング周期毎に前記遠心力方向加速度の重力加速度成分を検出し、前記重力加速度成分の大きさと、変化方向から前記タイヤ空気圧送信装置の回転位置を判定することを特徴とするタイヤ空気圧送信装置。 - 各車輪の外周側に取り付けられ、前記車輪のタイヤ空気圧情報を無線信号にて送信するタイヤ空気圧送信部と、
車体側に設けられ、前記無線信号を受信して各車輪のタイヤ空気圧を監視するタイヤ空気圧モニタ本体部と、
を備えたタイヤ空気圧モニタシステムにおいて、
前記タイヤ空気圧送信部は、
前記タイヤ空気圧を検出するタイヤ空気圧検出手段と、
前記車輪が回転しているときの遠心力方向加速度を検出する加速度検出手段と、
前記遠心力方向加速度の重力加速度成分から前記タイヤ空気圧送信装置の回転位置を判定する位置判定手段と、
所定の周期で前記タイヤ空気圧情報と前記タイヤ空気圧送信部の回転位置情報とを各タイヤ空気圧送信部固有の識別情報と共に無線信号にて送信する送信手段と、
を設け、
前記タイヤ空気圧モニタ本体部は、
各タイヤ空気圧送信部の前記送信手段から送信された前記タイヤ空気圧情報およびタイヤ空気圧送信部の前記回転位置情報を受信する受信手段と、
各車輪の回転位置を検出する回転位置検出手段と、
ある識別情報を有するタイヤ空気圧送信部が前記タイヤ空気圧送信部の回転位置情報を送信したときの各車輪の回転位置と前記タイヤ空気圧送信部の回転位置情報とから、前記タイヤ空気圧送信部が取り付けられた車輪の位置を判定する車輪位置判定手段と、
を設けたことを特徴とするタイヤ空気圧モニタシステム。 - 請求項3に記載のタイヤ空気圧モニタシステムにおいて、
位置判定手段は、前記送信手段による無線信号送信前に所定のサンプリング周期毎に前記遠心力方向加速度の重力加速度成分を検出し、前記重力加速度成分の大きさと、変化方向から前記タイヤ空気圧送信装置の回転位置を判定することを特徴とするタイヤ空気圧モニタシステム。
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US14/117,067 US9823167B2 (en) | 2011-05-13 | 2012-02-20 | Tire air pressure monitoring system |
MX2013012563A MX345621B (es) | 2011-05-13 | 2012-02-20 | Sistema de monitoreo de la presión de aire de la llanta. |
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