JP2023066799A - Tire revolution direction determination system - Google Patents

Abstract

To enable a revolution direction of a tire in which a detector is arranged to be determined even when a vehicle is travelling at a constant speed.SOLUTION: A tire revolution direction determination system comprises: an axle acceleration sensor that detects acceleration in a radial direction of revolution of axles to which double tires are connected; two detectors arranged respectively in two tires of the double tires; and a monitoring unit. Each of the detectors is configured to detect acceleration in the tire radial direction while the vehicle is stopped and detect acceleration in a direction inclining at a predetermined angle in a constant direction with respect to the tire radial direction while the vehicle is travelling forward. The monitoring unit calculates, as an initial difference, a difference between first acceleration received from the detectors while the vehicle is stopped, and an output of the axle acceleration sensor. The monitoring unit determines revolution directions of the tires in which the detectors are arranged, on the basis of whether or not change over time of the tire acceleration received from the detectors while the vehicle is traveling forward has advanced more than a reference in which change over time of the axle acceleration sensor is deviated by a quantity corresponding to the initial difference.SELECTED DRAWING: Figure 11

Description

The present disclosure relates to a system for determining the direction of rotation of tires mounted on a vehicle.

Conventionally, there is a direct system as one of systems (TPMS: Tire Pressure Monitoring System) for monitoring the air pressure of tires. In this type of TPMS, a detector provided with a sensor such as a pressure sensor is directly attached to the wheel side to which the tire is attached. In addition, the vehicle body is equipped with an antenna and a receiver. When the sensor detection signal is transmitted from the wheel side detector, the detection signal is received by the receiver via the antenna, and the tire pressure is measured. detection is performed.

In such a direct type TPMS, various devices have been developed that have a function of determining which tires of the vehicle the detectors attached to the tires are installed. For example, Japanese Patent Laying-Open No. 2019-48547 (Patent Document 1) discloses a system for determining to which tire of double tires used in a truck or the like a detector is attached. In this system, each detector has a sensor that detects the acceleration in the circumferential direction of tire rotation, determines the direction of rotation of the tire based on the detection result of the acceleration in the circumferential direction of tire rotation, and determines the direction of rotation of the tire based on the determination result of the tire rotation direction. determines which of the two tires the detector is installed on.

JP 2019-48547 A

The system disclosed in Japanese Patent Laying-Open No. 2019-48547 determines the rotation direction of the tire where the detector is arranged based on the detection result of the acceleration in the tire rotation circumferential direction. However, the acceleration in the circumferential direction of tire rotation cannot be detected unless the vehicle is accelerating. That is, the system disclosed in Japanese Patent Laying-Open No. 2019-48547 cannot determine the tire rotation direction unless the vehicle is accelerating.

The present disclosure has been made to solve the above-mentioned problems, and the object thereof is to enable determination of the tire rotation direction even in a constant-speed running state in which the vehicle is running at a constant speed. That is.

A tire rotation direction determination system according to one aspect of the present disclosure is a tire rotation direction determination system that determines the rotation direction of a tire mounted on a vehicle, wherein the radial acceleration of a rotating body that rotates in synchronization with the tire A rotating body acceleration sensor that detects a certain rotating body acceleration, a detector that is arranged on a tire and has a tire acceleration sensor that detects the tire acceleration that is the acceleration acting on the tire, and information from the rotating body acceleration sensor and the detector. a monitoring unit configured to be receivable. The wheel portion of the tire has a first side surface and a second side surface behind the first side surface. Assuming that the reference direction is the clockwise or counterclockwise direction when the tire is viewed from the first side surface side, the tire acceleration sensor rotates in the first direction orthogonal to the tire rotation axis direction while the vehicle is stopped. Acceleration is detected, and acceleration in a second direction inclined at a predetermined angle to a reference direction with respect to the first direction is detected while the vehicle is traveling forward at a predetermined vehicle speed or higher. The monitoring unit receives the tire acceleration from the detector while the vehicle is stationary and calculates the difference between the tire acceleration while the vehicle is stationary and the rotor acceleration while the vehicle is stationary as an initial difference. The monitoring unit receives the tire acceleration from the detector while the vehicle is traveling forward at a predetermined vehicle speed or higher, and the time change in the tire acceleration received from the detector is used as the rotor acceleration obtained from the rotor acceleration sensor. Based on whether or not the time change is ahead of a reference value shifted by a value corresponding to the initial difference, it is determined whether or not the rotation direction of the tire on which the detector is arranged is the reference direction.

According to the above aspect, it is determined whether or not the rotation direction of the tire is the reference direction based on the acceleration in the radial direction of the tire instead of the acceleration in the circumferential direction of rotation of the tire. Therefore, even if the vehicle is running at a constant speed, the direction of tire rotation can be determined.

According to the present disclosure, it is possible to determine the tire rotation direction even in a constant-speed running state in which the vehicle is running at a constant speed.

It is a figure which shows the structure of a vehicle typically. It is a block diagram which shows an example of a structure of a detector. FIG. 11 is a diagram (part 1) showing the appearance of the detector when the detector is in a closed state; FIG. 11 is a diagram (Part 1) showing the appearance of the detector when the detector is in a fully open state; FIG. 4 is an exploded perspective view of the double tire on the rear right side; FIG. 5 is a diagram showing an example of the relationship between the axle detection direction Dd, the arrangement angle of the inner tire detector, and the arrangement angle of the outer tire detector in the double tire on the right rear. FIG. 10 is a diagram showing, side by side, the state of the inner tire when the detector for the inner tire is at the 12 o'clock position and the state of the outer tire when the detector for the outer tire is at the 12 o'clock position while the vehicle is stopped. is. The state of the inner tire when the detector for the inner tire is at the 12 o'clock position and the state of the outer tire when the detector for the outer tire is at the 12 o'clock position while the vehicle is traveling forward at a predetermined vehicle speed HS or higher. and are shown side by side. FIG. 5 is a diagram for explaining a method of determining whether the right rear double tire is inside or outside from the time difference between the output peak value of an axle acceleration sensor and the output peak value of a detector while the vehicle is traveling forward at a predetermined vehicle speed HS or higher; FIG. 11 is a flowchart (part 1) showing an example of a processing procedure of a monitoring unit; FIG. FIG. 11 is a flowchart (part 2) showing an example of a processing procedure of the monitoring unit; FIG. FIG. 2 is a diagram (part 2) showing the appearance of the detector when the detector is in the closed state; FIG. 11 is a diagram (part 2) showing the appearance of the detector when the detector is in a fully open state; FIG. 3 is a diagram (part 3) showing the appearance of the detector when the detector is in the closed state; FIG. 3 is a diagram (part 3) showing the appearance of the detector when the detector is in a fully open state;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

<Overall composition>
FIG. 1 is a diagram schematically showing the configuration of a vehicle 10 to which a tire position determination system according to this embodiment is applied.

Vehicle 10 according to the present embodiment is a vehicle that has single tires on the front wheels that are steered and double tires on the rear wheels that are not steered. A single tire is a form in which one tire is mounted at one tire mounting position. A double tire is a form in which two tires of the same size connected to each other are mounted at one tire mounting position. Two tires that constitute a double tire are generally connected in a mutually inverted state. Double tires are mainly used for large vehicles such as trucks and buses.

Specifically, the vehicle 10 includes front tires 11 and 12 and rear double tires 21 and 22 .

FIG. 1 illustrates a case where the vehicle 10 is a rear-wheel drive system. The rear double tires 21 and 22 are attached to the rear left axle R1 and the rear right axle R2, respectively. The driving system of the vehicle 10 is not limited to the rear-wheel drive system, and may be a front-wheel drive system or an all-wheel drive system.

The rear left double tire 21 includes a vehicle inner tire 21a and a vehicle outer tire 21b. The rear right double tire 22 includes a vehicle inner tire 22a and a vehicle outer tire 22b.

Furthermore, the vehicle 10 is equipped with a system (TPMS) for monitoring the air pressure of each tire. Specifically, the vehicle 10 includes a detector 30 and a TPMS receiver 40 arranged on each of the six tires 11, 12, 21a, 21b, 22a, 22b. Note that the detector 30 may be formed integrally with, for example, a valve for drawing air into the tire.

The detector 30 is activated when a predetermined activation condition is satisfied, detects the air pressure of the tire, and emits a UHF (Ultra High Frequency) band radio signal (hereinafter also simply referred to as "UHF signal") including the detection result. Output.

The UHF signal output by each detector 30 includes at least information indicating a unique ID number for identifying each detector 30 in addition to information indicating tire pressure. By receiving the UHF signal output from each detector 30, the TPMS receiver 40 can monitor the air pressure of each tire.

The tires 11, 12, 21a, 21b, 22a, and 22b have the same specifications and configurations so that tire rotation can be performed. Therefore, each detector 30 has the same configuration. The configuration of each detector 30 will be detailed later.

The detector 30 is provided with a battery (not shown) and operates on electric power supplied from the battery. Since this battery cannot be easily charged from the outside, the operating time of the detector 30 is minimized for detection. It is desirable to reduce the power consumption of the device 30 . From this point of view, the "predetermined activation condition" of the detector 30 is set in advance so as to be satisfied regularly or irregularly so as to minimize the activation frequency of the detector 30 . Thereby, each detector 30 can be activated intermittently at mutually different timings.

The TPMS receiver 40 is provided on the vehicle body side of the vehicle 10 . The TPMS receiver 40 comprises an antenna A 1 and a monitoring unit 45 . Antenna A1 is configured to be able to receive UHF signals transmitted from each detector 30 . A monitoring unit 45 monitors the air pressure of each tire based on the UHF signal received by antenna A1. The monitoring unit 45 includes a storage section 46 and a processing section 47 .

The processing unit 47 includes a processor such as a CPU (Central Processing Unit) (not shown), a memory, and an input/output buffer. The memory includes ROM (Read Only Memory) and RAM (Random Access Memory). The processor expands a program stored in ROM into RAM and executes it. Various processes executed by the processing unit 47 are described in the programs stored in the ROM.

Information indicating the tire position where each detector 30 is arranged, information indicating the tire air pressure, etc. are stored in the storage unit 46 in association with the ID number of each detector 30 . In the present embodiment, a total of six tire positions (front left, front right, rear left inside, rear left outside, rear right inside, rear right outside) are set in advance. is associated with any tire position.

When the UHF signal is received from each detector 30, the monitoring unit 45 refers to the information stored in the storage unit 46 to specify the tire position of the ID number included in the UHF signal, and the specified tire position. is updated with the tire pressure contained in the UHF signal.

The TPMS receiver 40 can cause the display unit 60 to display the information on the correspondence relationship between tire positions and tire pressures stored in the storage unit 46 . The display unit 60 is arranged at a position that can be visually recognized by the driver. The display unit 60 is arranged, for example, on an in-vehicle instrument panel.

If the tire pressure included in the received UHF signal is equal to or less than the low pressure threshold, the monitoring unit 45 causes the display unit 60 to display a warning and the tire position where the tire pressure is equal to or less than the low pressure threshold. The TPMS receiver 40 performs this tire air pressure determination process for each received UHF signal, and monitors the air pressure of each tire. This allows the driver to recognize in real time the position of the tire that has fallen below the low pressure threshold.

Further, in vehicle 10 according to the present embodiment, axle acceleration sensors 50 are attached to each of rear left axle R1 and rear right axle R2. Each axle acceleration sensor 50 is a uniaxial acceleration sensor that detects acceleration in one direction. Each axle acceleration sensor 50 detects the radial acceleration of the corresponding axle and outputs the detection result to the monitoring unit 45 . Thereby, the monitoring unit 45 can grasp the acceleration in the radial direction of rotation of the axle R1 and the acceleration in the radial direction of rotation of the axle R2. Hereinafter, the acceleration detection direction of the axle acceleration sensor 50 is also called "axle detection direction Dd", and the detection result of the axle acceleration sensor 50 is also called "axle acceleration Gd".

The axle acceleration sensor 50 attached to the rear left axle R1 may be attached to a rotating body that rotates in synchronism with the rear left double tire 21, and is not necessarily attached directly to the axle R1. good too. Similarly, the axle acceleration sensor 50 attached to the rear right axle R2 may be attached to a rotating body that rotates in synchronism with the rear right double tire 22, and is not necessarily attached directly to the axle R2. may

<Configuration of detector 30>
FIG. 2 is a block diagram showing an example of the configuration of the detector 30. As shown in FIG. The detector 30 includes a controller 35, a pressure sensor 38, an acceleration sensor (G sensor) 39, an antenna A2, and a transmission circuit CT.

The pressure sensor 38 detects tire air pressure and outputs the detection result to the controller 35 .
The acceleration sensor 39 is a uniaxial acceleration sensor that detects acceleration in one direction. The acceleration sensor 39 detects acceleration (force) acting on the detector 30 and outputs a detection result (hereinafter also referred to as “acceleration G”) to the controller 35 . The acceleration detection direction of the acceleration sensor 39 will be detailed later.

In addition to pressure sensor 38 and acceleration sensor 39, detector 30 may further include a temperature sensor for detecting tire temperature.

A controller 35 of the detector 30 includes a storage section 36 and a processing section 37 . The processing unit 37 includes a processor such as a CPU (not shown), a memory, and an input/output buffer. The memory includes ROM and RAM. The processor expands a program stored in ROM into RAM and executes it. Programs stored in the ROM describe various processes to be executed by the processing unit 37 .

The storage unit 36 of the detector 30 stores information indicating an ID number unique to each detector 30, the detection result of the pressure sensor 38, and the detection result (acceleration G) of the acceleration sensor 39 of the detector 30. .

Detector 30 controller 35 controls transmitter circuit CT to output a UHF signal from antenna A2. The UHF signal includes an ID number stored in the storage unit 36, information indicating tire pressure, and information indicating acceleration G. FIG.

<Acceleration detection direction of acceleration sensor 39>
In the detector 30 according to the present embodiment, the relationship between the acceleration detection direction of the acceleration sensor 39 (hereinafter also referred to as "sensor detection direction Ds") and the tire rotation radial direction (hereinafter also referred to as "tire radial direction Dr") is , is changed by the centrifugal force generated by the rotation of the tire.

FIG. 3 is a diagram showing the appearance of detector 30 when detector 30 is in the closed state. As shown in FIG. 3, the detector 30 has a movable member 41 having a principal plane Pm, a fixed member 42, and a hinge member 43. As shown in FIG. The movable member 41 and the fixed member 42 are connected via a hinge member 43 . The fixing member 42 is fixedly supported on the outer peripheral surface of the wheel WH of the tire. Thereby, the movable member 41 is connected to the wheel WH of the tire via the hinge member 43 and the fixed member 42 . Note that the fixed member 42 may be omitted and the movable member 41 may be connected to the wheel WH of the tire via the hinge member 43 .

The acceleration sensor 39 is arranged on the movable member 41 in a state of detecting acceleration in the direction normal to the main surface Pm of the movable member 41 (hereinafter also referred to as “the normal direction Dm of the main surface”).

Note that the configuration of the detector 30 other than the acceleration sensor 39 (the controller 35, the pressure sensor 38, the transmission circuit CT, and the antenna A2) may be arranged on the fixed member 42 or may be arranged on the movable member 41. However, it may be arranged at a position different from that of the fixed member 42 and the movable member 41 .

The hinge member 43 includes an elastic body such as a spring, and elastically supports the end of the movable member 41 with respect to the fixed member 42 . While the vehicle 10 is stopped, the elastic force of the hinge member 43 keeps the main surface normal direction Dm of the movable member 41 aligned with the tire radial direction Dr. This state is the closed state of the detector 30 . When the detector 30 is in the closed state, the sensor detection direction Ds is the same as the tire radial direction Dr.

When the vehicle 10 starts to run and the tire starts to rotate, the hinge member 43 elastically deforms due to the centrifugal force acting on the movable member 41, and the movable member 41 moves in the tire radial direction Dr (centrifugal direction).

When the traveling speed of the vehicle 10 further increases and exceeds a predetermined vehicle speed HS (for example, 20 km/h), the movable member 41 contacts, for example, a stopper (not shown) to restrict the rotation of the movable member 41. The rotation angle of 41 is maintained at a predetermined angle θ. Therefore, while the vehicle 10 is traveling at the predetermined vehicle speed HS or higher, the movable member 41 is maintained in a state opened by a predetermined angle θ with respect to the fixed member 42 (hereinafter also referred to as a “fully open state”).

FIG. 4 is a diagram showing the appearance of the detector 30 when the detector 30 is fully open. In the fully open state, as described above, the movable member 41 is maintained at a predetermined angle θ with respect to the fixed member 42 . As a result, the direction Dm normal to the main surface of the movable member 41 is inclined by a predetermined angle θ with respect to the tire radial direction Dr. In other words, when the detector 30 is in the fully open state, the sensor detection direction Ds is shifted toward the hinge member 43 by a predetermined angle θ with respect to the tire radial direction Dr.

As described above, when the vehicle 10 is stopped, the detector 30 is closed and the sensor detection direction Ds is the same as the tire radial direction Dr. On the other hand, when the vehicle 10 is traveling at the predetermined vehicle speed HS or higher, the detector 30 is fully opened, and the sensor detection direction Ds is shifted toward the hinge member 43 by a predetermined angle θ with respect to the tire radial direction Dr. Become.

<Double tire configuration>
Vehicle 10 according to the present embodiment has double tires 21 and 22 on the rear wheels, as described above.

FIG. 5 is an exploded perspective view of the double tire 22 on the rear right side. An example of the configuration of the double tire 22 will be described with reference to FIG. Note that the double tire 21 on the rear left side has the same configuration as the double tire 22 .

The double tire 22 includes a vehicle inner tire 22a (hereinafter also referred to as "inner tire 22a") and a vehicle outer tire 22b (hereinafter also referred to as "outer tire 22b"). A wheel WH of each tire 22a, 22b has a flat portion FP projecting outward from a side surface portion (sidewall portion) of each tire. The wheel WH has a first side surface on the side from which the flat portion FP protrudes, and a second side surface on the back side of the first side surface.

The inner tire 22a is fixed to the axle R2 by passing the bolt BT of the hub H2 of the axle R2 through a hole provided in the flat portion FP of the wheel WH and fastening it with an inner nut NIN. A screw thread is formed on the tip side (vehicle outer side) of the inner nut NIN.

The outer tire 22b is fixed to the inner tire 22a by threading the screw thread on the tip side of the inner nut NIN through a hole provided in the flat portion FP of the wheel WH and fastening it with a wheel nut NW. The inner tire 22a and the outer tire 22b are fixed so that the flat portions FP of the wheels WH face each other. As a result, the inner tire 22a and the outer tire 22b are connected to each other in an inverted state and connected to the axle R2.

Therefore, when the clockwise direction when each wheel WH is viewed from the side of the first side surface (the side from which the flat portion FP protrudes) is defined as the "reference direction", when the vehicle 10 travels forward, the outer tire 22b While the rotation direction is the same as the reference direction, the rotation direction of the inner tire 22a is opposite to the reference direction. Note that the reference direction may be counterclockwise instead of clockwise, in which case the relationship between the reference direction and the rotation direction of each tire 22a, 22b is reversed.

It should be noted that the mounting direction of the detectors 30 is the same for all tires of the vehicle 10 . That is, each detector 30 is attached to the outer peripheral surface of the wheel WH with the hinge member 43 positioned forward of the movable member 41 in the reference direction. Therefore, when the vehicle 10 travels forward at a predetermined vehicle speed HS or higher, the detectors 30 of all the tires are open on the rear side in the reference direction. For example, in the case of the right rear double tire 22 shown in FIG. 5, while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, the detector 30 of the outer tire 22b is detected on the rear side in the rotation direction of the outer tire 22b (in the reference direction). While the detector 30 of the inner tire 22a is opened at the front side in the rotational direction of the inner tire 22a (rear side in the reference direction). This point will be described in detail later.

Note that FIG. 5 shows an example in which the axle acceleration sensor 50 is not attached directly to the axle R2, but is attached to the tip portion of the hub H2 that rotates in synchronization with the double tires 22. As shown in FIG.

<Double tire inside/outside judgment>
As described above, each tire is of the same specification and construction so that the tires can be rotated with each other. When the tires are rotated, the TPMS receiver 40 cannot identify which of the two tires each detector 30 is installed on, only from the ID number included in the UHF signal.

Regarding this point, in the above-mentioned JP-A-2019-48547, each detector detects the acceleration in the circumferential direction of tire rotation, thereby determining which of the two tires the detector is installed. . However, as described above, this technique cannot determine the tire position where the detector is located unless the vehicle is accelerating.

Therefore, the monitoring unit 45 according to the present embodiment uses the output of the axle acceleration sensor 50 that detects the acceleration in the axle radial direction and the output of the acceleration sensor 39 that detects the acceleration in the tire radial direction to determine the rotation direction of the tire. is the reference direction, and the inside/outside of the double tires is determined based on the result of the determination. Note that the inside/outside determination of the double tires means determining whether the detector 30 is arranged on the vehicle inside tire or the vehicle outside tire of the double tires.

Hereinafter, a method for judging inside/outside of a double tire according to the present embodiment will be described in detail. In the following, the case of determining the inside/outside of the double tire 22 on the right rear will be mainly described.

FIG. 6 is a diagram showing an example of the relationship between the axle detection direction Dd, the arrangement angle of the detector 30 of the inner tire 22a, and the arrangement angle of the detector 30 of the outer tire 22b in the double tire 22 on the right rear side. . 6 shows a state in which the inner tire 22a and the outer tire 22b are seen through from the outside of the vehicle (right side of the vehicle) while the vehicle 10 is stopped. In the following, positions and orientations may be expressed in clockwise time positions.

In the arrangement example shown in FIG. 6, the axle detection direction Dd faces the 12 o'clock direction, and the detector 30 for the inner tire 22a is arranged at the 12 o'clock position. Since the detector 30 of the inner tire 22a is closed while the vehicle 10 is stopped, the sensor detection direction Ds of the inner tire 22a (hereinafter also referred to as the "inner sensor detection direction Da") is the same direction as the axle detection direction Dd. becomes.

On the other hand, the detector 30 of the outer tire 22b is arranged at a position shifted clockwise from the 12 o'clock position by a predetermined angle α. Since the detector 30 of the outer tire 22b is also closed while the vehicle 10 is stopped, the sensor detection direction Ds of the outer tire 22b (hereinafter also referred to as "outer sensor detection direction Db") is oriented with respect to the axle detection direction Dd. , is tilted clockwise by a predetermined angle α.

Both the outputs of the axle acceleration sensor 50 and each acceleration sensor 39 contain a gravitational acceleration component. Therefore, both the waveform of the axle acceleration Gd detected by the axle acceleration sensor 50 and the waveform of the acceleration G detected by each acceleration sensor 39 are sinusoidal waveforms whose cycle is one rotation of the tire. becomes. In other words, the waveform of the axle acceleration Gd detected by the axle acceleration sensor 50 changes with time according to the rotation angle (axle detection direction Dd) of the axle R2, and the waveform of the acceleration G detected by each acceleration sensor 39 changes with each acceleration. It becomes a time change according to the arrangement angle of the sensor 39 . In the state shown in FIG. 6, the vehicle 10 is stopped and no centrifugal force is generated. The acceleration G detected by the acceleration sensor 39 (hereinafter also referred to as "inner acceleration Ga") is also "-1 G", and the acceleration G detected by the acceleration sensor 39 of the outer tire 22b (hereinafter also referred to as "outer acceleration Gb") is It becomes "-1G·cosα".

FIG. 7 shows the state of the inner tire 22a when the detector 30 of the inner tire 22a is at the 12 o'clock position and the state of the outer tire 22b when the detector 30 is at the 12 o'clock position while the vehicle 10 is stopped. It is the figure which put in order and showed the state of the outer side tire 22b.

Since the inner sensor detection direction Da is the same as the axle detection direction Dd while the vehicle 10 is stopped, the amount of deviation of the inner acceleration Ga from the axle acceleration Gd (hereinafter also referred to as "inner initial difference ΔPa") is zero. On the other hand, the outer sensor detection direction Db is inclined clockwise by a predetermined angle α with respect to the axle detection direction Dd. It becomes an amount corresponding to α.

In the double tire 22, the inner tire 22a and the outer tire 22b are connected to each other and fixed to the axle R2. Therefore, while the vehicle 10 is stopped, regardless of the rotational position of the double tires 22, the rotational angle difference between the axle detection direction Dd and the inner sensor detection direction Da (0 in the example shown in FIG. 6), and The rotation angle difference (predetermined angle α in the example shown in FIG. 6) between the axle detection direction Dd and the outer sensor detection direction Db does not change. That is, when each detector 30 is in the closed state, the time change of the inner acceleration Ga is the amount corresponding to the inner initial difference ΔPa (0 in the arrangement example of FIG. 7) with respect to the time change of the axle acceleration Gd. The time change of the outer acceleration Gb is shifted by an amount corresponding to the outer initial difference ΔPb (the amount corresponding to the predetermined angle α in the arrangement example of FIG. 7) with respect to the time change of the axle acceleration Gd. Become.

FIG. 8 shows the state of the inner tire 22a when the detector 30 of the inner tire 22a is at the 12 o'clock position and the state of the detector 30 of the outer tire 22b when the detector 30 of the outer tire 22b is at 12 o'clock while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher. FIG. 10 is a diagram showing side by side the state of the outer tire 22b at the position of .

While the vehicle 10 is traveling forward, both the inner tire 22a and the outer tire 22b rotate in the forward rotation direction. As described above, the inner tire 22a and the outer tire 22b are connected to each other in an inverted state, so the rotation direction of the outer tire 22b is the same as the reference direction of the outer tire 22b, The direction of rotation is opposite to the reference direction of the inner tire 22a.

While the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, the detector 30 of the inner tire 22a is fully opened, and the detection direction Da of the inner sensor is rearward in the rotational direction of the inner tire 22a with respect to the tire radial direction Dr. The direction is inclined by a predetermined angle θ. Due to this effect, the inner acceleration Ga does not become "-1 G" at the timing when the detector 30 is at the 12 o'clock position. −1 G”. That is, the time change of the inner acceleration Ga is an amount corresponding to a predetermined angle θ compared to the time change obtained by shifting the time change of the axle acceleration Gd by an amount corresponding to the inner initial difference ΔPa (hereinafter also referred to as the "inner reference Wa"). Only late. In the example shown in FIG. 6, since the inner side initial difference ΔPa is 0, the time change of the inner side acceleration Ga lags behind the time change of the axle acceleration Gd by an amount corresponding to the predetermined angle θ.

On the other hand, while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, the detector 30 of the outer tire 22b is also fully opened, and the outer sensor detection direction Db is forward in the rotational direction of the outer tire 22b with respect to the tire radial direction Dr. The direction is inclined by a predetermined angle θ to the side. Due to this effect, the outer acceleration Gb does not become "-1 G" at the timing when the detector 30 is at the 12 o'clock position. becomes "-1G". That is, the time change of the outer acceleration Gb is obtained by shifting the time change of the axle acceleration Gd by an amount corresponding to the outer initial difference ΔPb (=an amount corresponding to the predetermined angle α in the example of FIG. 8) (hereinafter referred to as "outer reference Wb”) by an amount corresponding to a predetermined angle θ.

In consideration of the characteristics described above, the monitoring unit 45 according to the present embodiment performs inside/outside determination of the rear right double tire 22 by the following method.

First, while the vehicle 10 is stopped, a process for calculating the inner initial difference ΔPa and the outer initial difference ΔPb is performed.

Specifically, first, the monitoring unit 45 acquires the value obtained by detecting the axle acceleration Gd twice consecutively immediately before the vehicle 10 stops. This makes it possible to grasp the rotation angle of the axle R2 immediately after that while the vehicle is stopped.

Immediately after that, while the vehicle is stopped, the monitoring unit 45 receives the acceleration G from one of the two detectors 30 (hereinafter also referred to as "first acceleration G1"). A deviation amount between the first acceleration G1 and the axle acceleration Gd while the vehicle is stopped is calculated as a "first initial difference ΔP1". Similarly, when receiving the acceleration G (hereinafter also referred to as “second acceleration G2”) from the other detector 30 of the two detectors 30, the received second acceleration G2 and the axle acceleration while the vehicle is stopped The amount of deviation from Gd is calculated as "second initial stage difference ΔP2". The first initial difference ΔP1 and the second initial difference ΔP2 correspond to either the inner initial difference ΔPa or the outer initial difference ΔPb, respectively.

Next, while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, the monitoring unit 45 uses the first initial difference ΔP1 and the second initial difference ΔP2 to determine whether the right rear double tire 22 is inside or outside. .

Specifically, the monitoring unit 45 first acquires the axle acceleration Gd from the axle acceleration sensor 50 as the “reference acceleration”, and the acceleration G from the one detector 30 or the other detector 30 as the “determination object”. received as "acceleration".

After that, the monitoring unit 45 sets the first reference W1 by shifting the time change of the acquired axle acceleration Gd (reference acceleration) by an amount corresponding to the first initial difference ΔP1, and sets the acquired axle acceleration Gd (reference acceleration) to A second reference W2 is set by shifting the time change by an amount corresponding to the second initial difference ΔP2, and the relationship between the acceleration to be determined and the first reference W1 and the second reference W2 is determined. The first reference W1 and the second reference W2 correspond to either the inner reference Wa or the outer reference Wb, respectively.

Specifically, the monitoring unit 45 determines the relationship between the temporal change in the determination target acceleration and the first reference W1. That is, when the temporal change in the determination target acceleration lags behind the first reference W1 by an amount corresponding to the predetermined angle θ, the determination target acceleration and the first reference W1 are set to the inner acceleration Ga and the inner reference Wa, respectively. Therefore, it is determined that the tire on which the detector 30 that outputs the determination target acceleration is rotating in the direction opposite to the reference direction, and the tire on which the detector 30 that outputs the determination target acceleration is located It is determined that it is the inner tire 22a.

On the other hand, when the temporal change in the acceleration to be determined is ahead of the first reference W1 by an amount corresponding to the predetermined angle θ, the acceleration to be determined and the first reference W1 become the outer acceleration Gb and the outer reference Wb described above, respectively. Therefore, it is determined that the tire on which the detector 30 that outputs the determination target acceleration is rotating in the same direction as the reference direction, and the tire on which the detector 30 that outputs the determination target acceleration is disposed is the outer tire. 22b.

If the temporal change in the determination target acceleration neither lags behind nor advances the second reference W2 by an amount corresponding to the predetermined angle θ, the monitoring unit 45 determines the relationship between the temporal change in the determination target acceleration and the second reference W2. do. That is, when the temporal change in the determination target acceleration lags behind the second reference W2 by an amount corresponding to the predetermined angle θ, the determination target acceleration and the second reference W2 are set to the inner acceleration Ga and the inner reference Wa, respectively. Therefore, it is determined that the tire on which the detector 30 that outputs the determination target acceleration is rotating in the direction opposite to the reference direction, and the tire on which the detector 30 that outputs the determination target acceleration is located It is determined that it is the inner tire 22a.

On the other hand, when the temporal change in the determination target acceleration is ahead of the second reference W2 by an amount corresponding to the predetermined angle θ, the determination target acceleration and the second reference W2 are equal to the outer acceleration Gb and the outer reference Wb, respectively. Therefore, it is determined that the tire on which the detector 30 that outputs the determination target acceleration is rotating in the same direction as the reference direction, and the tire on which the detector 30 that outputs the determination target acceleration is disposed is the outer tire. 22b.

Note that the monitoring unit 45 determines that the inner tire 22a is the tire that rotates in the direction opposite to the reference direction while the vehicle 10 is moving forward, and the outer tire is the tire that rotates in the same direction as the reference direction. 22b is known in advance.

When the inside/outside determination of the right rear double tire 22 is performed by the method described above, while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, the monitoring unit 45 detects the axle acceleration Gd (reference It is desirable to compare the waveform of the acceleration G from each detector 30 (acceleration to be determined). However, in order to grasp the waveform of the acceleration to be determined, it is necessary to operate each detector 30 continuously. It is difficult to activate.

In view of this point, each detector 30 according to the present embodiment detects a centrifugal acceleration equal to or greater than a predetermined value (for example, the value of centrifugal acceleration generated when traveling at a predetermined vehicle speed HS). It is configured to output a UHF signal containing acceleration G a predetermined number of times (for example, five times) each time the output peaks. In this embodiment, the peak means that the output of each sensor is either maximum or minimum. For example, when each detector 30 is at the 6 o'clock position, the output of each detector 30 is maximum, and when each detector 30 is at the 12 o'clock position, the output of each detector 30 is minimum. Each detector 30 is configured to output an acceleration G each time the output becomes maximum (every time the 6 o'clock position is reached).

The monitoring unit 45 receives the output peak value of each detector 30 while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, and receives the output peak value of each detector 30 and the output of the axle acceleration sensor 50. Based on the relationship obtained from the time difference from the peak value, the relationship (lag-advance) between the acceleration to be determined and the first reference W1 and the second reference W2 is determined.

FIG. 9 shows a method of judging whether the rear right double tire 22 is inside or outside from the relationship between the output peak value of the axle acceleration sensor 50 and the output peak value of the detector 30 while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher. It is a figure for explaining. FIG. 9 shows examples of waveforms of axle acceleration Gd, inner acceleration Ga, and outer acceleration Gb in the arrangement example shown in FIG.

As shown in FIG. 9, the phase of the waveform of the inner acceleration Ga lags the phase of the waveform of the axle acceleration Gd (first reference W1) by a predetermined angle θ. On the other hand, the phase of the waveform of the outer acceleration Gb leads the phase of the waveform of the axle acceleration Gd by a predetermined angle α (second reference W2) by a predetermined angle θ. Based on such characteristics, the monitoring unit 45 receives the output peak value of each detector 30 while the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher, and receives the output peak value and the output of the axle acceleration sensor 50. Based on the time difference from the peak value, the relationship (lag-advance) between the axle acceleration Gd (reference acceleration) and the acceleration to be determined (output of each detector 30) is estimated, and based on the result, double tire inside/outside determination is performed.

FIG. 10 is a flow chart showing an example of a processing procedure when the monitoring unit 45 calculates the first initial difference ΔP1 and the second initial difference ΔP2 of the rear right double tire 22 . As described above, the first initial difference ΔP1 and the second initial difference ΔP2 correspond to either the inner initial difference ΔPa or the outer initial difference ΔPb, respectively.

The monitoring unit 45 determines whether the vehicle 10 is about to stop based on the running speed of the vehicle 10 (step S10). If it is not immediately before the stop (NO in step S10), the monitoring unit 45 skips subsequent processes and ends the process.

If the vehicle is about to stop (YES in step S10), the monitoring unit 45 acquires the result of detecting the axle acceleration Gd two times from the axle acceleration sensor 50 (step S11). As a result, the monitoring unit 45 can grasp the rotation angle of the axle R2 immediately after that while the vehicle is stopped.

Thereafter, the monitoring unit 45 determines whether or not the vehicle 10 has stopped (step S12). If vehicle 10 has not stopped (NO in step S12), monitoring unit 45 returns the process to step S12 and waits until vehicle 10 stops.

If the vehicle 10 has stopped (YES in step S12), the monitoring unit 45 detects the first detector 30 from one of the rear right double tires 22 at any timing while the vehicle is stopped. The acceleration G1 is received (step S13), and the second acceleration G2 from the other detector 30 is received (step S14).

Then, the monitoring unit 45 calculates the amount of deviation between the first acceleration G1 and the axle acceleration Gd while the vehicle is stopped as a "first initial difference ΔP1" (step S15), A deviation amount from the acceleration Gd is calculated as a "second initial difference ΔP2" (step S16).

FIG. 11 is a flow chart showing an example of a processing procedure when the monitoring unit 45 determines whether the rear right double tire 22 is inside or outside.

The monitoring unit 45 determines whether or not the vehicle 10 is traveling forward at a predetermined vehicle speed HS or higher (step S20). If the vehicle is not traveling forward at the predetermined vehicle speed HS or higher (NO in step S20), the monitoring unit 45 skips the subsequent processes and ends the process.

When the vehicle is traveling forward at the predetermined vehicle speed HS or higher (YES in step S20), the monitoring unit 45 obtains the peak value of the axle acceleration Gd (step S21).

Next, the monitoring unit 45 receives the peak value of the acceleration to be determined from the one detector 30 or the other detector 30 during the period from when the peak value of the axle acceleration Gd is acquired until the tire rotates once. It is determined whether or not (step S22). If the peak value of the determination target acceleration has not been received (NO in step S22), the monitoring unit 45 returns the process to step S21 and repeats the processes of steps S21 and S22.

If the peak value of the acceleration to be determined has been received (YES in step S22), the monitoring unit 45 calculates the difference between the timing of receiving the peak value of the axle acceleration Gd and the timing of receiving the peak value of the acceleration to be determined (the difference between the peak values). Based on the time difference), it is determined whether or not the time change of the acceleration to be determined lags behind the first reference W1 or the second reference W2 by an amount corresponding to a predetermined angle θ (step S23).

If it is determined that the temporal change in the determination target acceleration lags behind the first reference W1 or the second reference W2 by an amount corresponding to the predetermined angle θ (YES in step S23), the monitoring unit 45 changes the determination target acceleration to It is determined that the tire on which the output detector 30 is arranged is rotating in a direction opposite to the reference direction, and based on the determination result, it is determined that the tire on which the detector 30 is arranged is the inner tire 22a. (step S24).

If the temporal change in the determination target acceleration does not lag behind the first reference W1 or the second reference W2 by the amount corresponding to the predetermined angle θ (NO in step S23), the monitoring unit 45 determines that the determination target acceleration changes over time by the It is determined whether or not the first reference W1 or the second reference W2 is advanced by an amount corresponding to a predetermined angle θ (step S25).

If the temporal change in the determination target acceleration is ahead of the first reference W1 or the second reference W2 by an amount corresponding to the predetermined angle θ (YES in step S25), the monitoring unit 45 detects the detector outputting the determination target acceleration. It is determined that the tire on which the detector 30 is arranged is rotating in the same direction as the reference direction, and based on the determination result, it is determined that the tire on which the detector 30 is arranged is the outer tire 22b (step S26).

As described above, the monitoring unit 45 according to the present embodiment monitors the relationship between the output of the axle acceleration sensor 50 and the output of each acceleration sensor 39 while the vehicle 10 is stopped, and the forward traveling of the vehicle 10 at a predetermined vehicle speed HS or higher. By comparing the relationship between the output of the axle acceleration sensor 50 and the output of the acceleration sensor 39, it is determined whether or not the direction of rotation of each tire is the reference direction.

According to the above aspect, whether or not the rotation direction of each tire is the reference direction is determined based on the acceleration in the radial direction of the tire instead of the acceleration in the circumferential direction of rotation of the tire. Therefore, the rotation direction of each tire can be determined even when the vehicle 10 is running at a constant speed. Further, in the present embodiment, the detector 30 is configured so that the relationship between the sensor detection direction Ds and the tire radial direction Dr is changed by centrifugal force. can be reduced to one.

[Modification 1]
In the above-described embodiment, the acceleration in the tire radial direction Dr is detected by the detector 30 in the closed state (while the vehicle is stopped), and the detector 30 detects the acceleration in the tire radial direction Dr in the fully open state (during forward running at a predetermined vehicle speed HS or higher). An example has been described in which the detector 30 is configured to detect acceleration in a direction tilted by θ.

However, the structure of the detector 30 detects the acceleration in the first direction perpendicular to the rotation axis direction of the tires in the closed state (while the vehicle is stopped), and detects the acceleration in the first direction in the fully open state (during forward running at a predetermined vehicle speed HS or higher). The structure is not necessarily limited to the structure described in the above embodiment, as long as it is configured to detect the acceleration in the second direction that is tilted by a predetermined angle θ with respect to. For example, the structure of detector 30 may be modified as follows.

FIG. 12 is a diagram showing the appearance of the detector 30A according to Modification 1 when the detector 30A is in the closed state. As shown in FIG. 12, the detector 30A has a movable member 41 having a main surface Pm, a fixed member 42, and a connecting member 44. As shown in FIG. The movable member 41 is connected to the fixed member 42 via a connecting member 44 . The fixed member 42 is fixedly supported with respect to the wheel WH of the tire or the inner wall of the tire. Thereby, the movable member 41 is connected to the wheel WH of the tire or the inner wall of the tire via the connecting member 44 and the fixed member 42 .

The acceleration sensor 39 detects acceleration in the direction normal to the main surface Pm of the movable member 41 (direction Dm normal to the main surface). The detector 30A is mounted so that the normal direction Dm of the main surface is inclined to the side different from the connecting member 44 by a predetermined angle θ from the tire radial direction Dr in the closed state. Therefore, in the closed state, the sensor detection direction Ds is inclined along the tire rotation circumferential direction by a predetermined angle θ with respect to the tire radial direction Dr.

When the tire starts to rotate due to running of the vehicle 10, the movable member 41 elastically deforms due to the centrifugal force acting on the movable member 41, and the movable member 41 rotates in the tire radial direction Dr ( centrifugal direction).

FIG. 13 is a diagram showing the appearance of the detector 30A when the detector 30A is fully open. When the running speed of the vehicle 10 exceeds a predetermined vehicle speed HS, the movable member 41 contacts, for example, a stopper (not shown) to restrict the rotation of the movable member 41, thereby reducing the rotation angle of the movable member 41 to a predetermined angle θ. maintained. Accordingly, in the fully open state, the sensor detection direction Ds is the same direction as the tire radial direction Dr.

As described above, the detector 30A detects the acceleration in the direction inclined along the circumferential direction of tire rotation by the predetermined angle θ with respect to the tire radial direction Dr in the closed state (while the vehicle is stopped), It is configured to detect the acceleration in the tire radial direction Dr during forward running as described above. Such a detector 30A may be used.

[Modification 2]
Moreover, the structure of the detector 30 in this embodiment may be modified as follows.

FIG. 14 is a diagram showing the appearance of the detector 30B according to Modification 2 when the detector 30B is in the closed state. As shown in FIG. 14, the detector 30B has a movable member 41 having a main surface Pm, a fixed member 42, and an elastic member 49. As shown in FIG. The movable member 41 has a rotation axis Ax<b>1 at the center of the movable member 41 . The movable member 41 is attached to the fixed member 42 so as to be rotatable about the rotation axis Ax1. The rotation axis Ax<b>1 may not be provided at the center of the movable member 41 and may be provided at a position shifted from the center of the movable member 41 .

Furthermore, the movable member 41 is connected to the fixed member 42 via the elastic member 49 . Elastic member 49 is, for example, a spring. A weight 48 is attached to the movable member 41 near the end on the side different from the elastic member 49 when viewed from the rotation axis Ax1. The weight 48 allows the movable member 41 to be easily rotated about the rotation axis Ax1.

The acceleration sensor 39 detects acceleration in the direction normal to the main surface Pm of the movable member 41 (direction Dm normal to the main surface). The detector 30B is attached so that the main surface normal direction Dm is along the tire radial direction Dr in the closed state. Therefore, in the closed state, the sensor detection direction Ds is the same direction as the tire radial direction Dr.

When the vehicle 10 runs and the tire starts to rotate, the elastic member 49 elastically deforms (contracts) due to the centrifugal force acting on the movable member 41, and the movable member 41 rotates about the rotation axis Ax1. is attached, the end is displaced in the centrifugal direction.

FIG. 15 is a diagram showing the appearance of detector 30B when detector 30B is in the fully open state. When the traveling speed of the vehicle 10 exceeds the predetermined vehicle speed HS, the rotation angle of the movable member 41 is maintained at the predetermined angle θ. Accordingly, in the fully open state, the sensor detection direction Ds is inclined toward the elastic member 49 by a predetermined angle θ with respect to the tire radial direction Dr. Such a detector 30B may be used.

[Modification 3]
In the above-described embodiment, the present disclosure describes an example in which the tire position determination method is applied to the inside/outside determination of double tires that are connected in a mutually inverted state.

However, the tires to which the tire position determination method according to the present disclosure can be applied are not necessarily limited to double tires, as long as they are two tires arranged on the vehicle in a mutually inverted state. For example, by applying the tire position determination method according to the present disclosure to the front tires 11 and 12 arranged on the vehicle 10 in a mutually inverted state, it is possible to determine which of the front tires 11 and 12 the detector 30 is arranged. You may make it determine whether it is. In this case, an acceleration sensor may be provided to detect the radial acceleration of the rotor rotating in synchronism with the front tires 11 and 12, and the output of this acceleration sensor may be used as a parameter instead of the axle acceleration Gd. .

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

The exemplary embodiments and modifications thereof described above are specific examples of the following aspects.
(1) A tire rotation direction determination system according to the present disclosure is a tire rotation direction determination system that determines the rotation direction of a tire mounted on a vehicle. A rotating body acceleration sensor that detects a certain rotating body acceleration, a detector that is arranged on a tire and has a tire acceleration sensor that detects the tire acceleration that is the acceleration acting on the tire, and information from the rotating body acceleration sensor and the detector. a monitoring unit configured to be receivable. The wheel portion of the tire has a first side surface and a second side surface behind the first side surface. Assuming that the reference direction is the clockwise or counterclockwise direction when the tire is viewed from the first side surface side, the tire acceleration sensor rotates in the first direction orthogonal to the tire rotation axis direction while the vehicle is stopped. Acceleration is detected, and acceleration in a second direction inclined at a predetermined angle to a reference direction with respect to the first direction is detected while the vehicle is traveling forward at a predetermined vehicle speed or higher. The monitoring unit receives the tire acceleration from the detector while the vehicle is stationary and calculates the difference between the tire acceleration while the vehicle is stationary and the rotor acceleration while the vehicle is stationary as an initial difference. The monitoring unit receives the tire acceleration from the detector while the vehicle is traveling forward at a predetermined vehicle speed or higher, and the time change in the tire acceleration received from the detector is used as the rotor acceleration obtained from the rotor acceleration sensor. Based on whether or not the time change is ahead of a reference value shifted by a value corresponding to the initial difference, it is determined whether or not the rotation direction of the tire on which the detector is arranged is the reference direction.

According to the above aspect, it is determined whether or not the rotation direction of the tire is the reference direction based on the acceleration in the radial direction of the tire instead of the acceleration in the circumferential direction of rotation of the tire. Therefore, even if the vehicle is running at a constant speed, the direction of tire rotation can be determined.

(2) In one aspect, the detector is configured to output to the monitoring unit the value at which the tire acceleration peaks while the tire is rotating as the tire acceleration peak value. The monitoring unit detects a peak value of tire acceleration received from the detector, a peak value of the acceleration of the rotating body obtained from the rotating body acceleration sensor, and an initial The difference is used to determine whether the time variation of tire acceleration received from the detector is ahead of the reference value.

According to the above aspect, the detector is configured to output to the monitoring unit the value at which the tire acceleration peaks while the tire is rotating as the tire acceleration peak value. Therefore, it is not necessary to continuously operate the detector, and the power consumption of the detector can be suppressed. Then, the monitoring unit receives from the detector using the peak value of the tire acceleration received from the detector, the value when the acceleration of the rotating body reaches the peak obtained from the rotating body acceleration sensor, and the initial difference. Determines the direction of rotation of the tire to be applied. Therefore, the rotation direction of the tire can be determined while minimizing the power consumption of the detector.

(3) In one aspect, a detector is positioned on each of two tires that are positioned on the vehicle in an inverted position. 3. Tire rotation direction determination according to claim 1 or 2, wherein the monitoring unit determines in which of the two tires the detector is arranged based on the determination result of the rotation direction of the tire on which the detector is arranged. system.

According to the above aspect, it is possible to determine on which of the two tires arranged on the vehicle the detector is arranged in a mutually inverted state even if the vehicle is in a constant speed running state.

(4) In one aspect, the two tires are double tires that are connected with their first side surfaces facing each other.

According to the above aspect, it is possible to determine on which of the double tires the detector is arranged.

(5) In one aspect, the monitoring unit obtains from the rotating body acceleration sensor the results of detecting the acceleration of the rotating body at a plurality of consecutive timings immediately before the vehicle stops, and based on the obtained results, detects the acceleration of the rotating body while the vehicle is stopped. Identify the acceleration of the rotating body.

According to the above aspect, by detecting the acceleration of the rotating body at a plurality of consecutive timings immediately before the vehicle stops, it is possible to accurately identify the acceleration of the rotating body while the vehicle is stopped.

10 vehicle, 11, 12, 21a-22b tire, 21, 22 double tire, 30 detector, 35 controller, 36, 46 storage unit, 37, 47 processing unit, 38 pressure sensor, 39 acceleration sensor, 40 receiver, 41 Movable member 42 Fixed member 43 Hinge member 44 Connection member 45 Monitoring unit 48 Weight 49 Elastic member 50 Axle acceleration sensor 60 Display unit A1, A2 Antenna CT Transmission circuit H2 Hub R1, R2 Axle, WH wheel.

Claims (5)

A tire rotation direction determination system for determining the rotation direction of a tire mounted on a vehicle,
a rotating body acceleration sensor that detects a rotating body acceleration that is an acceleration in a radial direction of a rotating body that rotates in synchronism with the tire;
a detector disposed on the tire and having a tire acceleration sensor that detects tire acceleration, which is the acceleration acting on the tire;
a monitoring unit configured to receive information from the rotating body acceleration sensor and the detector;
The wheel portion of the tire has a first side surface and a second side surface behind the first side surface,
When the clockwise or counterclockwise direction when the tire is viewed from the first side surface side is taken as a reference direction, the tire acceleration sensor is perpendicular to the tire rotation axis direction while the vehicle is stopped. detecting acceleration in a first direction, and detecting acceleration in a second direction tilted at a predetermined angle in the reference direction with respect to the first direction while the vehicle is traveling forward at a predetermined vehicle speed or more;
The monitoring unit, while the vehicle is stopped,
receiving tire acceleration from the detector;
calculating a difference between the tire acceleration while the vehicle is stopped and the rotor acceleration while the vehicle is stopped as an initial difference;
The monitoring unit, while the vehicle is traveling forward at the predetermined vehicle speed or higher,
receiving tire acceleration from the detector;
whether the time change in tire acceleration received from the detector is ahead of a reference value obtained by shifting the time change in rotor acceleration obtained from the rotor acceleration sensor by a value corresponding to the initial difference; A tire rotation direction determination system for determining whether or not the rotation direction of a tire on which the detector is arranged is the reference direction based on the above. The detector is configured to output a value when the tire acceleration peaks during rotation of the tire as a peak value of the tire acceleration to the monitoring unit,
The monitoring unit detects that the peak value of the tire acceleration received from the detector and the rotor acceleration obtained from the rotor acceleration sensor reach a peak while the vehicle is traveling forward at a speed equal to or higher than the predetermined vehicle speed. 2. Tire rotation direction determination according to claim 1, wherein the time value and the initial difference are used to determine whether the time variation of the tire acceleration received from the detector is ahead of the reference value. system. the detectors are arranged on each of two tires arranged on the vehicle in a mutually inverted state;
3. The monitoring unit according to claim 1, wherein the monitoring unit determines in which of the two tires the detector is arranged based on the determination result of the rotational direction of the tire on which the detector is arranged. Tire rotation direction determination system. 4. The tire rotation direction determination system according to claim 3, wherein the two tires are double tires connected with the first side surfaces facing each other. The monitoring unit obtains, from the rotor acceleration sensor, results of detection of the rotor acceleration at a plurality of consecutive timings immediately before the vehicle stops, and based on the obtained results, the rotor acceleration during the stop of the vehicle. The tire rotation direction determination system according to any one of claims 1 to 4, which specifies the

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