TIRE POSITION DETERMINATION SYSTEM AND TIRE PRESSURE MONITORING SYSTEM

• US 20140184403A1
• Filed: 12/20/2013
• Published: 07/03/2014
• Est. Priority Date: 12/27/2012
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: KOSUGI, Masanori, SAKURAI, Taketoshi, KUMAGAI, Katsuhide
• Granted Patent: US 9,139,053 B2
• Time in Patent Office: Days
• US Class Current: 340/447
• CPC Class Codes: B60C 23/0415 Automatically identifying wheel mounted units, e.g. after replacement or exchange of wheels
• CPC Class Codes: B60C 23/0416 allocating a corresponding wheel position on vehicle, e.g. front/left or rear/right
• CPC Class Codes: B60C 23/0489 for detecting the actual angular position of the monitoring device while the wheel is turning

Abstract

Each tire pressure detector detects a characteristic point in a detection signal of an acceleration sensor indicating that the tire pressure detector is located at a certain rotation position. When detecting the characteristic point, the tire pressure detector transmits a notification signal including the detector ID. Whenever a receiver receives a notification signal, the receiver acquires an axle rotation amount of a representative wheel and stores the axle rotation amount in a memory in association with the detector ID in the notification signal. After acquiring axle rotation amounts associated with the detector IDs of all of the tire pressure detectors, the receiver determines mounting positions of tires from the angle each tire pressure detector rotated and the angle each axle rotated between a first determination timing and a second determination timing.

Claims

1. A tire position determination system comprising:

tire pressure detectors respectively attached to tires; and

a receiver coupled to a vehicle body, wherein the receiver is configured to receive a tire pressure signal from each tire pressure detector and monitor the pressure of the corresponding tire based on the tire pressure signal;

wherein each tire pressure detector includes

a unique detector ID,

a gravity component detection unit that detects a certain directional component of gravity and generates a detection signal, and

a transmission control unit that transmits a radio wave signal including the detector ID based on the detection signal of the gravity component detection unit; and

the receiver includes

an interface that communicates with axle rotation amount sensors, wherein each axle rotation amount sensor detects an axle rotation amount of a corresponding axle,

a tire mounting position determination processing unit that acquires the detector ID whenever receiving the radio wave signal from each tire pressure detector and the axle rotation amount detected by each axle rotation amount sensor, associates the detector IDs with the axle rotation amounts, and determines mounting positions of the tires based on the axle rotation amounts associated with the detector IDs of the tire pressure detectors.

2. The tire position determination system according to claim 1, wherein the detection signal of the gravity component detection unit is indicative of a characteristic point when the tire pressure detector is located at an uppermost position or lowermost position of the corresponding tire.

3. The tire position determination system according to claim 1, wherein the transmission control unit is configured so that after time elapses from when the radio wave signal is transmitted during which it may be assumed that a rotation amount difference has been produced between an inner wheel and an outer wheel, the transmission control unit transmits the next radio wave signal.

4. The tire position determination system according to claim 2, wherein the transmission control unit is configured to transmit the radio wave signal when detecting a characteristic point in the detection signal of the gravity component detection unit.

5. The tire position determination system according to claim 1, wherein

the transmission control unit is configured to transmit the radio wave signal at each of a first determination timing and a second determination timing, which is delayed from the first determination timing by an interval;

the tire mounting position determination processing unit is configured to

calculate a first detector angle using the axle rotation amount at the first determination timing,

calculate a second detector angle using the axle rotation amount at the second determination timing,

calculate a detector rotation angle from the first and second detector angles,

calculate an axle rotation angle from the axle rotation amount at the first determination timing and the axle rotation amount at the second determination timing, and

compare the detector rotation angle and the axle rotation angle to determine the mounting positions of the tires.

6. The tire position determination system according to claim 5, wherein the tire mounting position determination processing unit is configured to

acquire an axle rotation amount of a representative wheel from the rotation axle amount sensor when receiving the radio wave signal from the tire pressure detector,

calculate the first and second detector angles using the axle rotation amount of the representative wheel, and

determine the mounting positions of the tires using the calculated detector angles.

7. The tire position determination system according to claim 5, wherein

the tire mounting position determination processing unit is configured so that when receiving a first radio wave signal having a first detector ID and then a second radio wave signal having a second detector ID, the tire mounting position determination processing unit calculates and stores an angle of a tire pressure detector having one of the first and second detector IDs relative to a tire pressure detector having the other one of the first and second detector IDs, and

the tire mounting position determination processing unit is configured to determine the mounting positions of the tire using the stored detector angles respectively corresponding to the tire pressure detectors.

8. The tire position determination system according to claim 5, wherein

the transmission control unit is configured to transmit the radio wave signal at least once at each of the first determination timing and the second determination timing, and

the tire mounting position determination processing unit is configured to compare the detector rotation angle and the axle rotation angle at least once in a determination routine.

9. The tire position determination system according to claim 1, wherein

each tire pressure detector includes a travel status determination unit that determines a travel status of a vehicle based on a detection signal of the gravity component detection unit, and

the travel status determination unit is configured to transmit the radio wave signal when determining that a vehicle velocity is within a predetermined velocity range.

10. The tire position determination system according to claim 1, wherein the transmission control unit is configured to transmit the radio wave signal if a length of time from when the detection signal of the gravity component detection unit indicates that the tire pressure detector is located at a certain position to the next time when the detection signal of the gravity component detection unit indicates that the tire pressure detector is located at the certain position is longer than or equal to a predetermined time.

11. The tire position determination system according to claim 1, wherein

each tire pressure detector includes

a travel status determination unit that determines a travel status of a vehicle based on a detection signal of the gravity component detection unit, and

an operation mode switching unit that switches an operation mode of the tire pressure detector based on a vehicle velocity, a first threshold, and a second threshold that is smaller than the first threshold, wherein the vehicle velocity is included in a determination result of the travel status determination unit;

the operation mode switching unit

switches the tire pressure detector to a pressure determination mode for monitoring tire pressure when the vehicle velocity is higher than or equal to the first threshold,

switches the tire pressure detector to an automatic location preparation mode to increase the frequency for determining the vehicle velocity when the vehicle velocity is between the first threshold and the second threshold, and

switches the tire pressure detector to an automatic location mode when the vehicle velocity is less than the second threshold.

12. The tire position determination system according to claim 1, wherein the transmission control unit is configured to transmit the radio wave signal in fixed intervals when the detection signal of the gravity component detection unit indicates that the tire pressure detector is located at a specific rotation position in a predetermined cycle regardless of a rotation speed of the tire or when a vehicle is travelling at the same vehicle velocity.

13. The tire position determination system according to claim 1, wherein

the transmission control unit is configured to calculate a cycle during which a tire rotates once based on variations in the detection signal of the gravity component detection unit, and

the certain directional component is sampled in a cycle that is determined based on a proportional constant and the calculated cycle during which the tire rotates once, and the sampling cycle is less than one-half of the cycle during which the tire rotates once.

14. The tire position determination system according to claim 1, wherein

the certain directional component cyclically varies as the corresponding tire rotates;

the transmission control unit includes a determination range and a rotation cycle range, wherein the determination range has a width that takes into consideration a detection accuracy of the gravity component detection unit;

when the certain directional component exceeds the determination range, the transmission control unit starts measuring time of a cycle of the certain directional component to measure a cycle of a rotation of the tire; and

the transmission control unit is configured to transmit the radio wave signal when the measured cycle of a rotation of the tire is in the rotation cycle range.

15. The tire position determination system according to claim 14, wherein

the determination range of the certain directional component is one of a plurality of different determination ranges, and

the transmission control unit switches the sampling cycle in accordance with the rotation cycle of the tire determined based on a selected one of the determination ranges.

16. The tire position determination system according to claim 1, wherein

the certain directional component cyclically varies as the corresponding tire rotates;

the transmission control unit includes a threshold set taking into consideration that the gravity component detection unit has a rough detection accuracy;

when the certain directional component exceeds the threshold, the transmission control unit shortens the sampling cycle and starts measuring a cycle of a single rotation of the tire; and

the transmission control unit is configured to set an origin point of time measurement at a timing at which a cycle of a rotation of the tire becomes the threshold.

17. The tire position determination system according to claim 1, wherein the tire mounting position processing unit is configured to determine the tire mounting positions by checking whether an axle rotation amount of a single tire rotation conforms to an axle rotation amount measured from when the radio wave signal is received at a first determination timing to when the radio wave signal is received at a second determination timing.

18. The tire position determination system according to claim 9, wherein

the tire mounting position determination processing unit stores a reception interval time used to receive two consecutive radio wave signals including the same detector ID in association with the detector ID;

the tire mounting position determination processing unit stores, for each of a plurality of axles, an axle time used until a count value of an axle rotation amount conforms to an axle rotation amount corresponding to a single tire rotation; and

the tire mounting position determination processing unit is configured to determine the tire mounting positions by comparing a plurality of reception interval times respectively corresponding to a plurality of detector IDs with the axle times respectively corresponding to the axles.

19. The tire position determination system according to claim 5, wherein the tire mounting position determination processing unit is configured to determine the tire mounting positions by comparing a plurality of detector rotation angles respectively corresponding to the tires with a plurality of axle rotation angles respectively corresponding to a plurality of axles.

20. The tire position determination system according to claim 5, wherein when a detector ID included in at least one radio wave signal received at the first determination timing is the same as a detector ID included in at least one radio wave signal received at the second determination timing, the tire mounting position determination processing unit is able to determine the mounting position of the tire corresponding to the detector ID.

21. The tire position determination system according to claim 20, wherein

when the mounting position of a tire corresponding to at least one detector ID cannot be determined and a vehicle is assumed to be travelling straight, the tire mounting position determination processing unit waits until the tire corresponding to the at least one detector ID rotates once;

and

the tire mounting position determination processing unit is configured to determine the mounting position of the tire corresponding to the at least one detector ID with a radio wave signal transmitted when a time used by the tire to rotate once from the first determination timing elapses.

22. The tire position determination system according to claim 1, wherein

the axle rotation amount sensor outputs a total pulse number signal that indicates a total pulse number counted during a predetermined interval;

when the tire mounting position determination processing unit receives a detector ID during a period from when a previous total pulse number signal is received to when a present total pulse number signal is received, the tire mounting position determination processing unit is configured to calculate a true pulse number at a point of time when the detector ID is received from a ratio of a length of time from when the previous total pulse number signal is received to when the detector ID is received and a length of time from when the detector ID is received to when the present total pulse number signal is received.

23. The tire position determination system according to claim 22, wherein the tire mounting position determination unit is configured to calculate an average value from a total pulse number indicated by a plurality of total pulse number signals output from a plurality of axle rotation amount sensors and use the average value as an axle rotation amount of a representative wheel to calculate a detector angle.

24. The tire position determination system according to claim 1, further comprising:

a steering angle acquisition unit that acquires a steering angle of a steering wheel of a vehicle; and

a prohibition unit that prohibits execution of the tire position determination when the steering angle is greater than or equal to a threshold.

25. A tire pressure monitoring system comprising:

tire pressure detectors respectively attached to tires, wherein each tire pressure detector transmits a tire pressure signal, which is in accordance with the pressure of the corresponding tire, and a radio wave signal, which differs from the tire pressure signal;

a receiver coupled to a vehicle body, wherein the receiver is configured to receive a tire pressure signal from each tire pressure detector and monitor the pressure of the corresponding tire based on the tire pressure signal; and

a display unit;

wherein each tire pressure detector includes

a unique detector ID,

an acceleration sensor that outputs a detection signal indicative of a centripetal component of gravity, which varies as the corresponding tire rotates, and

a transmission control unit that transmits the radio wave signal including the detector ID based at a controlled timing or a timing when the detection signal of the acceleration sensor indicates that the tire pressure detector is located at a certain rotation position; and

the receiver includes

an interface that communicates with axle rotation amount sensors, wherein each axle rotation amount sensor detects an axle rotation amount of a corresponding axle, and

a tire mounting position determination processing unit that acquires the detector ID whenever receiving the radio wave signal from each tire pressure detector and the axle rotation amount detected by each axle rotation amount sensor, associates the detector IDs with the axle rotation amounts, and determines mounting positions of the tires based on the axle rotation amounts associated with the detector IDs of the tire pressure detectors,

wherein the receiver is configured to show a warning on the display unit indicating a pressure decrease in at least one tire in accordance with a determination result of the tire mounting position determination processing unit.