Wheel position detector

Abstract

To provide a wheel position detecting device that is able to detect a wheel position in a shorter time without requiring trigger machines the number of which corresponds to the number of wheels.SOLUTION: In an on-vehicle device 3, a turning direction of a vehicle 1 is determined, and based on the turning direction and a positive / negative sign of a detection result of a G sensor of each tire sensor 2, a wheel on which each tire sensor 2 is mounted is identified as either a right wheel 5a, 5c or a left wheel 5b, 5d. In addition, the absolute values of the detection results are compared for magnitude, so that the wheel on which each tire sensor 2 is mounted is identified as either a right front wheel 5a or right rear wheel 5c of the right wheels 5a, 5c, and is identified as either a left front wheel 5b or left rear wheel 5d of the left wheels 5b, 5d.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wheel position detection device that identifies and registers the wheels to which tire sensors are attached based on data transmitted from the tire sensors attached to each wheel, and is suitable for application to a tire pressure monitoring system (hereinafter referred to as TPMS). [Background technology]

[0002] A direct type TPMS has been known for some time. In this type of TPMS, a tire sensor equipped with various sensors such as a pressure sensor and an antenna is directly attached to the wheel side where the tire is attached, and an antenna and an on-board device are installed on the vehicle side. The tire pressure of each wheel is detected by receiving data transmitted from the tire sensor via the antenna by the on-board device.

[0003] In such a direct-type TPMS, it is necessary to identify which wheel the tire sensor attached to has transmitted the data. For this reason, in conventional TPMS, a trigger device is placed at a position corresponding to each wheel, and when each trigger device outputs a trigger signal in turn, a response signal is returned from the tire sensor closest to the trigger device that output the trigger signal. In this way, it is possible to determine which wheel each tire sensor is attached to, and to detect the wheel position by linking and registering the individual identification information (hereinafter referred to as ID information) given to each tire sensor with the wheel position.

[0004] There is also a TPMS that detects the wheel position using a detection signal from a wheel speed sensor, as in Patent Document 1. This TPMS detects that the wheel has reached a predetermined rotational position based on an acceleration detection signal from an acceleration sensor (hereinafter referred to as a G sensor) provided in a tire sensor on the wheel side, and also detects the rotational position of the wheel when a wireless signal is received from the tire sensor on the vehicle body side. The wheel position is then detected by monitoring changes in these relative angles. Specifically, the change in the relative angle between the rotational position of the wheel detected on the wheel side and the rotational position of the wheel detected on the vehicle body side is monitored based on the deviation of a predetermined number of data, and the wheel position is detected by determining that the variation from the initial value exceeds an allowable value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-173384 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in a TPMS using a trigger device, the number of trigger devices required corresponds to the number of wheels, which leads to an increase in the number of parts and the associated increase in hardware implementation costs.In addition, in wheel position detection using detection signals from wheel speed sensors such as the TPMS in Patent Document 1, there is a clear difference in the rotational position of each wheel, and wheel position detection is not possible unless the variation in the change in the relative angle of the rotational position of the wheels exceeds an allowable value, so it takes time to detect the wheel position.

[0007] In view of the above, an object of the present invention is to provide a wheel position detection device that does not require a number of trigger devices corresponding to the number of wheels and can detect the wheel positions in a shorter time. [Means for solving the problem]

[0008] In order to achieve the above object, claims 1、2、4The invention described in is a wheel position detection device applied to a vehicle (1) having tire sensors (2) attached to each of a plurality of wheels (5a-5d) having tires and an on-board device (3) provided on the vehicle body (6), and each tire sensor attached to each of the plurality of wheels has a G sensor (22) for detecting lateral acceleration (hereinafter referred to as lateral G), which is an acceleration in a direction along the central axis of rotation of the wheel to which the tire sensor is attached, a first control unit (23) for storing the detection result of the G sensor and creating a frame storing individual identification information given to each tire sensor, and a first communication unit (24) for transmitting the frame to the on-board device. The on-board device also has a second communication unit (32) for receiving the frame, and a second control unit (33) for determining which of the plurality of wheels the tire sensor that transmitted the frame is attached to, and for registering the relationship between the identification information and the plurality of wheels by linking them. In addition, the G sensor shows a detection result with a different positive or negative sign when the wheel to which the tire sensor including the G sensor is attached is a right wheel (5a, 5c) and a left wheel (5b, 5d).The second control unit determines the turning direction of the vehicle, and specifies whether the wheel to which each tire sensor is attached is a right wheel or a left wheel based on the turning direction and the positive or negative sign of the detection result of the G sensor of each tire sensor, and by comparing the absolute values ​​of the detection results, specifies whether the wheel to which each tire sensor is attached is the right front wheel (5a) or the right rear wheel (5c) of the right wheels, and also specifies whether the wheel to which each tire sensor is attached is the left front wheel (5b) or the left rear wheel (5d) of the left wheels.

[0009] In this way, the right and left wheels are distinguished based on the difference in the positive and negative signs of the detection results of the G sensor when the vehicle turns. Also, the front and rear wheels are distinguished based on the fact that the absolute values ​​of the detection results differ for each wheel based on the inner wheel difference.

[0010] In this way, it is possible to identify which of the multiple wheels each tire sensor is attached to, and wheel position detection can be performed. Such wheel position detection can be performed based on the G sensor detection results sent from the tire sensors and the turning direction of the vehicle while the vehicle is turning, without requiring a trigger device corresponding to the number of wheels. Also, wheel position detection can be performed if a difference in lateral G of each wheel occurs based on the inner wheel difference, so wheel position detection can be performed in a shorter time. Therefore, it is possible to perform wheel position detection in a shorter time without requiring a trigger device in the number corresponding to the number of wheels.

[0011] Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a TPMS mounted on a vehicle according to a first embodiment of the present invention. [Figure 2A] FIG. 2 is a block diagram of a tire sensor. [Figure 2B] FIG. 2 is a block diagram of an in-vehicle device and the like. [Diagram 3] 1 is a diagram illustrating the positive and negative signs of lateral G detected by G sensors provided in tire sensors of the right and left wheels. FIG. [Figure 4A] 11 is a diagram showing the turning radius of each wheel based on the inner wheel difference when the vehicle turns left. FIG. [Figure 4B] FIG. 4 is a diagram illustrating the centripetal force generated in each wheel. [Diagram 5] 4 is a flowchart of a wheel position detection process according to the first embodiment. [Figure 6] FIG. 13 is a diagram illustrating weighting of count values. [Figure 7] 10 is a flowchart of a wheel position detection process according to a second embodiment. [Figure 8] 13 is a flowchart of a wheel position detection process according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0014] (First embodiment) A first embodiment will be described with reference to Fig. 1 to Fig. 5. In this embodiment, a TPMS to which a wheel position detection device is applied will be described. Fig. 1 is a block diagram showing the overall configuration of the TPMS, with the upper direction on the page being the front of the vehicle 1, the lower direction on the page being the rear of the vehicle 1, and the left-right direction of the figure being the left-right direction of the vehicle 1.

[0015] 1, the TPMS is attached to a vehicle 1 and includes a tire sensor 2, an on-board device 3, and a display 4. In this embodiment, the tire sensor 2 and the on-board device 3 constitute a wheel position detection device.

[0016] The tire sensors 2 are attached to each of the four wheels 5a-5d of the vehicle 1. The tire sensors 2 detect the air pressure of the tires attached to each of the wheels 5a-5d, and transmit detection signal data indicating the detection results stored in a frame to be transmitted as a response signal. The vehicle-mounted device 3 is attached to the vehicle body 6 of the vehicle 1, and receives the frame transmitted from the tire sensors 2, and performs various processes and calculations based on the detection signal data stored therein to determine the tire air pressure. Figures 2A and 2B show block configurations of the tire sensors 2 and the vehicle-mounted device 3.

[0017] As shown in FIG. 2A, the tire sensor 2 includes a sensing unit 21, a G sensor 22, a control unit 23, a communication unit 24, and an antenna 25.

[0018] The sensing unit 21 is configured to include, for example, a diaphragm type pressure sensor or a temperature sensor, and outputs a detection signal corresponding to the tire pressure or the temperature. For example, the sensing unit 21 outputs a detection signal corresponding to the tire pressure or the temperature at every predetermined sampling period.

[0019] The G sensor 22 is used to detect the lateral G of each wheel 5a-5d to which the tire sensor 2 is attached, in other words, the acceleration in the direction along the rotational center axis of each wheel 5a-5d, and outputs a detection signal corresponding to the lateral G. The G sensor 22 also outputs a detection signal corresponding to the lateral G at a sampling period that is the same as or different from the sampling period of the sensing unit 21. More specifically, the G sensor 22 outputs a detection signal of the lateral G with either one of the left and right directions of the vehicle 1 as positive and the other as negative. Since the tire sensors 2 are attached to each wheel 5a-5d in the same direction, as shown in FIG. 3, even if the lateral G is generated in the same direction in the left and right directions of the vehicle 1, the output of the G sensor 22 has opposite positive and negative signs for the right wheels 5a, 5c and the left wheels 5b, 5d.

[0020] The control unit 23 corresponds to a first control unit, and is configured by a microcomputer equipped with a CPU, a ROM, a RAM, an I / O, etc., and executes predetermined processes according to programs stored in the ROM or the like.

[0021] Specifically, the control unit 23 receives a detection signal related to the tire pressure from the sensing unit 21, processes the signal and manipulates it as necessary to create data indicating the tire pressure detection results (hereinafter referred to as tire pressure data). The control unit 23 then stores the tire pressure data together with the ID information of each tire sensor 2 in a frame to be transmitted, and then transmits the frame to the communication unit 24. The process of transmitting the signal to the communication unit 24 is executed in accordance with the above program, for example, at every predetermined regular transmission cycle.

[0022] The control unit 23 is basically in a periodic transmission mode in which a frame storing data on tire pressure together with ID information is transmitted to the vehicle-mounted device 3 at a predetermined periodic transmission period. However, in the wheel position detection mode, the control unit 23 detects the lateral direction G based on the detection signal of the G sensor 22 for wheel position detection, and transmits a frame storing the detection result together with ID information as wheel position detection data to the communication unit 24. The transmission period of the wheel position detection data is arbitrary, but is preferably shorter than the transmission period of the data on tire pressure so that the wheel position detection can be completed more quickly. As will be described later, the wheel position detection is performed based on the lateral direction G, and the wheel position detection is performed by, for example, making a turn with the vehicle 1. For this reason, the transmission period of the wheel position detection data is set shorter than the time it takes the vehicle 1 to make one turn, for example, several seconds to several tens of seconds.

[0023] Specifically, the control unit 23 is programmed to enter the wheel position detection mode when a predetermined condition is satisfied. If each tire sensor 2 is capable of two-way communication with the vehicle-mounted device 3, the predetermined condition corresponds to a case where a command signal for wheel position detection is transmitted from the vehicle-mounted device 3. For example, when a user presses a start switch for wheel position detection (not shown) or a start switch for the vehicle 1 such as an ignition switch is pressed, a command signal for wheel position detection is output from the vehicle-mounted device 3 to each tire sensor 2. Also, the predetermined condition can be that each tire sensor 2 detects that the vehicle 1 has switched from a stopped state to a running state based on a detection signal from the G sensor 22 or the like. When the vehicle 1 starts to run and turns, lateral G is generated, and based on that, it is possible to detect that the vehicle 1 has switched from a stopped state to a running state.

[0024] Furthermore, if two-way communication is possible, the control unit 23 ends the transmission of the frame storing the wheel position detection data when it receives a command signal from the in-vehicle device 3 instructing the end of frame transmission upon completion of wheel position detection. Also, if the control unit 23 detects that the vehicle 1 has switched from a stopped state to a running state based on the detection signal of the G sensor or the like, it ends the transmission of the frame storing the wheel position detection data when the time assumed to be required for wheel position detection has elapsed. Then, the control unit 23 switches from the wheel position detection mode to the periodic transmission mode and performs periodic transmission of a frame storing data related to tire pressure.

[0025] The communication unit 24 functions as an output unit that transmits the frame sent from the control unit 23 to the vehicle-mounted device 3 via the antenna 25, and corresponds to a first communication unit. The communication form by the communication unit 24 is arbitrary, but in the case of one-way communication where only communication from the tire sensor 2 to the vehicle-mounted device 3 is possible, for example, communication using radio waves in the RF band can be performed, and in the case of two-way communication, for example, communication based on the BLE (Bluetooth Low Energy) standard can be performed.

[0026] The antenna 25 is a communication antenna corresponding to the communication form of the communication unit 24, and is built in, for example, the tire sensor 2, and has a function as a transmitting antenna in the case of one-way communication, and has a function as a transmitting / receiving antenna in the case of two-way communication. Of course, the transmitting / receiving antenna function does not have to be realized by a single antenna, and may be separated into a transmitting antenna and a receiving antenna.

[0027] The tire sensor 2 thus configured is attached to, for example, an air injection valve of the wheel of each of the wheels 5a to 5d, and is disposed so that the sensing unit 21 is exposed to the inside of the tire. This allows the tire pressure to be detected, and a frame is transmitted at a predetermined regular transmission cycle through an antenna 25 provided in each tire sensor 2. Furthermore, when detecting the wheel position, a frame containing wheel position detection data is transmitted at a predetermined transmission cycle for wheel position detection.

[0028] As shown in FIG. 2B, the vehicle-mounted device 3 includes an antenna 31, a communication unit 32, and a control unit 33.

[0029] The antenna 31 is a single common antenna that collectively receives frames sent from each tire sensor 2, and is fixed to the vehicle body 6. The antenna 31 may be provided only for the TPMS, but if an antenna provided for the smart entry system is used, the number of parts can be reduced by standardizing the parts.

[0030] The communication section 32 functions as an input section that, when a frame transmitted from each tire sensor 2 is received by the antenna 31, inputs the frame and sends it to the control section 33, and corresponds to a second communication section.

[0031] The control unit 33 corresponds to a second control unit, and is configured by a microcomputer equipped with a CPU, ROM, RAM, I / O, etc., and executes predetermined processes according to programs stored in the ROM or the like.

[0032] Specifically, the control unit 33 receives a frame storing data for wheel position detection from each tire sensor 2 through the communication unit 32. Then, the control unit 33 identifies which of the four wheels 5a to 5d each tire sensor 2 is attached to, and performs wheel position detection processing to register ID information given to each tire sensor 2 by linking it to the wheel position, that is, the wheel to which the tire sensor 2 is attached. When each tire sensor 2 and the vehicle-mounted device 3 are configured to be capable of two-way communication, the control unit 33 outputs a command signal to each tire sensor 2 to perform wheel position detection when detecting the wheel position. For example, when the user presses a start switch (not shown) of the vehicle 1 to start it, or when the user presses a start switch for wheel position detection (not shown), the control unit 33 outputs a command signal to perform wheel position detection and executes the wheel position detection processing. Also, when one-way communication is performed from each tire sensor 2 to the vehicle-mounted device 3, the control unit 33 executes the wheel position detection processing when the user presses a start switch (not shown) of the vehicle 1 to start it. Then, the wheel position detection process ends when the wheel on which the tire sensor 2 is attached is associated with and registered with the ID information of each tire sensor 2 through the wheel position detection process. In a configuration capable of two-way communication, the control unit 33 outputs a command signal to each tire sensor 2 to end transmission of a frame that stores data for wheel position detection. This causes the control unit 23 of each tire sensor 2 to switch to a periodic transmission mode and begin periodic transmission of a frame that stores data related to tire pressure.

[0033] It is optional to output a command signal for terminating the transmission of the frame storing the wheel position detection data from the vehicle-mounted device 3. In other words, when the time when the wheel position detection process is expected to end has elapsed, the tire sensor 2 side can automatically switch to a regular transmission period of the frame for normal tire pressure detection.

[0034] Furthermore, detection signals from the steering angle sensor 7 and the gear position sensor 8 are input to the control unit 33, and these detection signals are used when performing wheel position detection processing. Of course, even if the detection signals from the steering angle sensor 7 and the gear position sensor 8 are not directly input to the control unit 33, if another electronic control unit (hereinafter referred to as ECU) detects the steering angle and gear position from these detection signals, the detection results may be transmitted from that ECU.

[0035] Furthermore, the control unit 33 performs various signal processing and calculations based on the data indicating the detection results stored in the received frame to determine the tire pressures, and outputs an electric signal corresponding to the determined tire pressures to the display 4. For example, the control unit 33 identifies the tire pressures of the wheels 5a-5d and outputs the data to the display 4. Alternatively, the control unit 33 compares the determined tire pressures with a predetermined threshold value Th, and when it detects that the tire pressures have decreased, outputs data to that effect to the display 4. In this way, the tire pressure data of the four wheels 5a-5d or a decrease in the tire pressure of any of the wheels 5a-5d is transmitted to the display 4.

[0036] 1, the display 4 is disposed in a location visible to the driver, and is constituted by, for example, a display and a warning lamp installed in the instrument panel of the vehicle 1. For example, when tire pressure data of each of the wheels 5a-5d is sent from the control unit 33, the display 4 displays the tire pressure of each of the wheels 5a-5d as a numerical value. Furthermore, when data indicating that the tire pressure has dropped is sent from the control unit 33, the display 4 notifies the driver of the drop in tire pressure by displaying that fact.

[0037] The TPMS to which the wheel position detecting device of this embodiment is applied is configured as described above.

[0038] Next, the operation of the TPMS of this embodiment will be described. Prior to that, however, a method of wheel position detection performed by the TPMS of this embodiment will be described.

[0039] In the TPMS of this embodiment, wheel position detection is performed based on the lateral direction G obtained from the detection signal of the G sensor 22. When the vehicle 1 turns, the turning radius r of each of the wheels 5a to 5d differs depending on the distance from the turning center to each of the wheels 5a to 5d. For example, as shown in Fig. 4A, consider a case where the vehicle 1 turns counterclockwise with point O as the turning center.

[0040] When vehicle 1 turns at angular velocity ω around point O, equations 1 and 2 hold true if the vehicle speed is v, the time it takes to turn at angular velocity ω is t, and the centripetal acceleration, that is, the lateral G based on the centripetal force F generated in each wheel 5a to 5d by the turn, as shown in Figure 4B, is a.

[0041]

number

[0042]

number

[0043]

number

[0044] In addition, even if lateral G is generated in the same left-right direction of the vehicle 1, the output of the G sensor 22 has opposite positive and negative signs for the right wheels 5a, 5c and the left wheels 5b, 5d. Therefore, the right wheels 5a, 5c and the left wheels 5b, 5d can be identified by the positive and negative signs of the lateral G indicated by the detection signal of the G sensor 22 of each tire sensor 2.

[0045] Furthermore, the absolute value of the lateral G force is the largest for the front wheel on the outside of the turn, and the smallest for the rear wheel on the inside of the turn. In the case of a counterclockwise turn as shown in Fig. 4A, the right front wheel 5a is the front wheel on the outside of the turn, and the left rear wheel 5d is the rear wheel on the inside of the turn.

[0046] Therefore, the front wheels 5a, 5b and the rear wheels 5c, 5d can be identified by the lateral direction G and its absolute value, and the right wheels 5a, 5c and the left wheels 5b, 5d can be identified by the positive / negative sign of the lateral direction G, so it is possible to identify which of the wheels 5a to 5d each tire sensor 2 is attached to. For example, the wheel with the largest absolute value of the lateral direction G is identified as the front wheel on the outer side of the turn, and the wheel with the smallest absolute value is identified as the rear wheel on the inner side of the turn. The wheel with the same positive / negative sign of the lateral direction G as the front wheel on the outer side of the turn is identified as the rear wheel on the outer side of the turn, and the wheel with the same positive / negative sign of the lateral direction G as the rear wheel on the inner side of the turn is identified as the front wheel on the inner side of the turn.

[0047] In this manner, wheel position detection is performed. Details of the wheel position detection process executed by the TPMS of the first embodiment will be described below with reference to Fig. 5. Fig. 5 is a flowchart of the wheel position detection process executed by the control unit 33 of the vehicle-mounted device 3, which is executed at every predetermined control period in the wheel position detection mode.

[0048] First, in step S100, the control unit 33 determines whether the vehicle 1 is moving forward and is in a steering state. Whether the vehicle 1 is moving forward can be determined based on a detection signal from the gear position sensor 8, and the control unit 33 determines that the vehicle is moving forward when the gear position is in the "D" position, for example. Whether the vehicle is steering can be determined based on a detection signal from the steering angle sensor 7, and the control unit 33 determines that the vehicle is steering when the steering angle is equal to or greater than a predetermined value.

[0049] As shown in the above-mentioned formula 2, the centripetal acceleration a generated in each wheel 5a to 5d has a value according to the vehicle speed v, and the higher the vehicle speed v, the larger the value appears, and the more likely the difference in the centripetal acceleration a between the wheels based on the inner wheel difference is likely to occur. For this reason, one of the conditions for wheel position detection is that the vehicle 1, which is expected to have a relatively large vehicle speed v, is in a forward moving state, but this is not essential. The same effect can be obtained by setting the vehicle speed v occurring at a predetermined value or more as one of the conditions for wheel position detection, instead of the vehicle 1 moving forward. The same is true for the steering angle, which is set as one of the conditions for wheel position detection because almost no lateral G occurs unless the vehicle 1 is in a turning state. Regarding the steering angle, if it is not generated to a certain degree, the absolute value of the lateral G becomes a small value, and it is considered that the positive and negative signs of the lateral G are not clear. For this reason, it is preferable to set the occurrence of a steering angle to a degree that makes the positive and negative signs of the lateral G clear as a condition for determining whether steering has been performed.

[0050] Next, in step S110, a frame storing the detection result of the lateral direction G as wheel position detection data is received from each tire sensor 2, and the lateral direction G detected by each tire sensor 2 is acquired.

[0051] Next, in step S120, it is determined whether or not the vehicle 1 is turning left, and if it is turning left, the process proceeds to step S130, and if it is not turning left but turning right, the process proceeds to step S150. Whether or not the vehicle 1 is turning left can also be determined based on the detection signal of the steering angle sensor 7.

[0052] In step S130, the absolute value of the lateral direction G of each tire sensor 2 is calculated, and the absolute value Max wheel with the largest absolute value of the lateral direction G is identified as the right front wheel 5a, and the absolute value Min wheel with the smallest absolute value is identified as the left rear wheel 5d. In step S140, the wheel with the same positive / negative sign of the lateral direction G as the tire sensor 2 identified as the right front wheel 5a in step S130 is identified as the right rear wheel 5c, and the wheel with the same positive / negative sign of the lateral direction G as the tire sensor 2 identified as the left rear wheel 5d is identified as the left front wheel 5b.

[0053] Meanwhile, in step S150, the absolute value of the lateral direction G of each tire sensor 2 is calculated, and the absolute value Max wheel with the largest absolute value of the lateral direction G is identified as the left front wheel 5b, and the absolute value Min wheel with the smallest absolute value is identified as the right rear wheel 5c. In addition, in step S160, the wheel with the same positive / negative sign of the lateral direction G as the tire sensor 2 identified as the left front wheel 5b in step S150 is identified as the left rear wheel 5d, and the wheel with the same positive / negative sign of the lateral direction G as the tire sensor 2 identified as the right rear wheel 5c is identified as the right front wheel 5a.

[0054] In this way, it is possible to identify which of the four wheels 5a to 5d each of the four tire sensors 2 is attached to. For this reason, the ID information stored in the frame of each tire sensor 2 is registered in association with the wheel position, i.e., the wheel to which the tire sensor 2 is attached, and the wheel position detection process is terminated.

[0055] After this, the control unit 23 of each tire sensor 2 switches from the wheel position detection mode to the periodic transmission mode, and each tire sensor 2 transmits a frame storing data on tire pressure together with ID information to the vehicle-mounted device 3 at a predetermined periodic transmission cycle. When this is transmitted to the control unit 33 via the antenna 31, the control unit 33 performs various signal processing and calculations to obtain the tire pressure, and identifies which of the wheels 5a to 5d the tire pressure belongs to from the ID information stored in the frame. The control unit 33 then outputs an electric signal corresponding to the obtained tire pressure to the display 4. As a result, the display 4 displays the tire pressure in a form that identifies which of the wheels 5a to 5d the tire pressure belongs to, or displays a drop in tire pressure, thereby making it possible to inform the user of the tire condition.

[0056] As described above, in the TPMS of this embodiment, when the vehicle 1 is in a turning state, the right wheels 5a, 5c and the left wheels 5b, 5d are distinguished from each other based on the difference in the positive and negative signs of the lateral G detected by the tire sensor 2. In addition, the front wheels 5a, 5b and the rear wheels 5c, 5d are distinguished from each other based on the inner wheel difference that determines the lateral G and its absolute value, which are different for each of the wheels 5a to 5d.

[0057] In this way, it is possible to identify which of the four wheels 5a to 5d each of the four tire sensors 2 is attached to, and wheel position detection can be performed. Such wheel position detection can be performed based on the detection results of the lateral G sent from the tire sensors 2 and the turning direction of the vehicle 1 while the vehicle 1 is turning, without requiring a trigger device corresponding to the number of wheels. Also, wheel position detection can be performed if a difference occurs in the lateral G of each of the wheels 5a to 5d based on the inner wheel difference, so that wheel position detection can be performed in a shorter time. Therefore, it is possible to perform wheel position detection in a shorter time without requiring a trigger device in the number corresponding to the number of wheels.

[0058] In this embodiment, the wheel with the largest absolute value of the lateral G is identified as the front wheel on the outer side of the turn, and the wheel with the smallest absolute value is identified as the rear wheel on the inner side of the turn. The front wheel on the outer side of the turn and the rear wheel on the inner side of the turn are the two wheels with the largest difference in the absolute value of the lateral G. Therefore, compared to two wheels with a small difference in the absolute value of the lateral G, such as the rear wheel on the outer side of the turn and the front wheel on the inner side of the turn, the front wheel on the outer side of the turn and the rear wheel on the inner side of the turn can be identified more reliably. Then, if the front wheel on the outer side of the turn and the rear wheel on the inner side of the turn can be identified, it is only necessary to distinguish the right wheels 5a, 5c and the left wheels 5b, 5d based on the positive and negative signs of the lateral G, which makes it possible to detect the wheel positions more accurately.

[0059] Second embodiment A second embodiment will be described. This embodiment is intended to enable more accurate wheel position detection than the first embodiment, and other aspects are the same as those of the first embodiment, so only the differences from the first embodiment will be described.

[0060] The method of wheel position detection described in the first embodiment may not be able to detect the wheel position accurately when the inner wheel difference is not so large, when the angular velocity is slow, when the center of rotation is shifted, etc. For this reason, in this embodiment, the result of determining which of the four wheels 5a to 5d the tire sensor 2 is attached to is weighted, and multiple determination results are accumulated to prevent erroneous wheel position detection.

[0061] The weighting is performed by accumulating the count value for each ID information of each tire sensor 2. For example, if the vehicle 1 turns left, as shown in FIG. 6, 4 counts are added if the wheel is determined to be the right front wheel 5a, 3 counts if the wheel is determined to be the right rear wheel 5c, 2 counts if the wheel is determined to be the left front wheel 5b, and 1 count if the wheel is determined to be the left rear wheel 5d. The count value is arbitrary, but for wheels that are prone to erroneous judgment, the difference in count value is set to 1 count, so that even if an erroneous judgment occurs, the difference is limited to a reversal of 1 count. In this way, if the number of correct judgments is greater than the number of incorrect judgments, the count value is accumulated, and the magnitude relationship of the accumulated value becomes the same as the magnitude relationship of the count value of the correct judgment.

[0062] In this way, a count value is determined for each of the wheels 5a to 5d when it is determined that the wheel is that wheel, and the count value is accumulated for each ID information based on multiple determination results, and the wheel position can be detected based on the accumulation result.

[0063] Specifically, in the TPMS of this embodiment, the control unit 33 of the vehicle-mounted device 3 executes a wheel position detection process shown in FIG. 7 to detect the wheel position.

[0064] First, steps S100 to S160 are the same as steps S100 to S160 shown in Fig. 5 and described in the first embodiment. After steps S100 to S160 are performed, the process proceeds to step S170, where a count value is added for each piece of ID information. That is, for each piece of ID information, if it is determined to be the right front wheel 5a, 4 counts are added; if it is determined to be the right rear wheel 5c, 3 counts are added; if it is determined to be the left front wheel 5b, 2 counts are added; and if it is determined to be the left rear wheel 5d, 1 count is added.

[0065] Thereafter, the process proceeds to step S180, where it is determined whether or not the determination has been made N times (where N is a positive integer). That is, the process of steps S100 to S160 described above is performed N times, and it is determined whether or not the number of times the count value has been accumulated has reached N. If the determination here is positive, the process proceeds to step S190, where wheel position detection is performed based on the accumulated count value.

[0066] At this time, the wheel position detection is performed based on the integrated value of the weighted count values, so that there is a difference in the integrated value of the count values ​​for each ID information. Therefore, the wheel position detection may be performed using the same method as steps S130 to S160, or the wheel position detection may be performed based only on the magnitude relationship of the integrated values ​​of the count values. In the former case, the ID information with the largest integrated value is identified as the front wheel of the outer wheel, and the ID information with the smallest integrated value is identified as the rear wheel of the inner wheel. Then, the wheel with the same positive and negative sign of the lateral direction G as the tire sensor 2 identified as the front wheel of the outer wheel is identified as the rear wheel of the outer wheel, and the wheel with the same positive and negative sign of the lateral direction G as the tire sensor 2 identified as the rear wheel of the inner wheel is identified as the front wheel of the inner wheel. In the latter case, the wheels are identified in descending order of the integrated value of the count values ​​as the front wheel of the outer wheel, the rear wheel of the outer wheel, the front wheel of the inner wheel, and the rear wheel of the inner wheel. In this way, by performing wheel position detection based on the integrated value of the weighted count values, it is possible to perform more accurate wheel position detection.

[0067] Third embodiment A third embodiment will be described. This embodiment is similar to the second embodiment in other respects except that the weighting method is changed from the second embodiment, so only the differences from the second embodiment will be described.

[0068] In this embodiment, after identifying whether the wheels are the right wheels 5a, 5c or the left wheels 5b, 5d based on the positive or negative sign of the lateral G, weighting is performed to identify the front wheels 5a, 5b or the rear wheels 5c, 5d. Here, if the wheels are determined to be the front wheels 5a, 5b, which are considered to have a large absolute value of the lateral G while the vehicle 1 is turning, x (where x is a positive integer) is added to the count value, and if the wheels are determined to be the rear wheels 5c, 5d, x-1 is added to the count value.

[0069] Specifically, in the TPMS of this embodiment, the control unit 33 of the vehicle-mounted device 3 executes a wheel position detection process shown in FIG. 8 to detect the wheel position.

[0070] First, in steps S200 and S210, the same processes as in steps S100 and S110 shown in Fig. 5 are performed. Then, in steps S220 to S240, a left / right wheel determination is performed to determine whether the tire sensor 2 is attached to the right wheels 5a, 5c or the left wheels 5b, 5d.

[0071] Specifically, in step S220, it is determined whether the vehicle 1 is turning left, similarly to step S120. If a positive determination is made in step S220, the process proceeds to step S230, where the left wheels 5b and 5d are identified if the lateral G is positive, and the right wheels 5a and 5c are identified if the lateral G is negative. If a negative determination is made in step S220, the process proceeds to step S240, where the left wheels 5b and 5d are identified if the lateral G is negative, and the right wheels 5a and 5c are identified if the lateral G is positive. The positive and negative signs of the lateral G here are set to match the positive and negative signs of the lateral G detected by the G sensor 22 when the tire sensors 2 are attached to the wheels 5a to 5d and the lateral G occurs, and are determined by how the tire sensors 2 are attached. For this reason, if the positive and negative signs of the lateral G detected by the G sensor 22 when the lateral G occurs are reversed from the case shown here, the correspondence between the positive and negative signs of the lateral G in steps S230 and S240 and the left front wheels 5b, 5d and the right wheels 5a, 5c will also be reversed.

[0072] Subsequently, in steps S250 to S280, a front / rear wheel determination is performed to determine whether the tire sensor 2 is attached to the front or rear wheel.

[0073] Specifically, first, in step S250, x is added to the integrated value of the count value of the one of the two ID information identified as the left wheels 5b, 5d that has the larger absolute value of lateral G, and x-1 is added to the integrated value of the smaller count value. Similarly, x is added to the integrated value of the count value of the one of the two ID information identified as the right wheels 5a, 5c that has the larger absolute value of lateral G, and x-1 is added to the integrated value of the smaller count value.

[0074] Then, in step S260, it is determined whether or not the determination has been performed N times, similarly to step S180, and if the determination has been performed N times, the process proceeds to step S270. Then, the integrated values ​​of the count values ​​of the ID information identified as the left wheels 5b and 5d are compared, and the integrated values ​​of the count values ​​of the ID information identified as the right wheels 5a and 5c are compared. Finally, the process proceeds to step S280. Then, based on the comparison result in step S270, it is determined whether each of the ID information identified as the left wheels 5b and 5d corresponds to the left front wheel 5b or the left rear wheel 5d. Also, it is determined whether each of the ID information identified as the right wheels 5a and 5c corresponds to the right front wheel 5a or the right rear wheel 5c. Specifically, for each of the ID information identified as the left wheels 5b and 5d, the one with the larger integrated value of the count value is identified as the left front wheel 5b, and the one with the smaller integrated value of the count value is identified as the left rear wheel 5d. In addition, for each piece of ID information identified as the right wheels 5a, 5c, the wheel with the larger integrated count value is identified as the right front wheel 5a, and the wheel with the smaller integrated count value is identified as the right rear wheel 5c.

[0075] Even in this case, the wheel position detection is performed based on the integrated value of the weighted count values, so that the wheel position detection can be performed more accurately. Note that, in this embodiment, if N=1 is set in step S260, the front and rear wheel determination can be performed by one weighting.

[0076] (Other embodiments) Although the present disclosure has been described based on the above-described embodiment, it is not limited to the embodiment, and includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0077] (1) For example, in the second embodiment, the count values ​​for weighting are differentiated by one value, but this is merely an example, and a different value may be differentiated.

[0078] (2) In the above first and second embodiments, when the turning direction is determined in step S120 in Fig. 5, the front wheels on the outside of the turning wheel and the rear wheels on the inside of the turning wheel are identified based on the absolute value of the lateral direction G, and then the front and rear wheels on the outside of the turning wheel side and the front and rear wheels on the inside of the turning wheel side are identified. This shows one embodiment in which the outside and inside of the turning wheel are identified based on the absolute value of the lateral direction G and the positive and negative signs, that is, the right wheels 5a, 5c and the left wheels 5b, 5d are identified, and then the front wheels 5a, 5b and the rear wheels 5c, 5d on the right wheels or the left wheels are identified. For example, in the example of Fig. 4, by identifying the absolute value Max wheel as the front wheel of the right wheels 5a, 5c which are the outside of the turning wheel, it means that the right wheels 5a, 5c and the right front wheel 5a are identified at the same time. In addition, by identifying the wheel having the same lateral G sign as the right front wheel 5a as the right rear wheel 5b, it means that the wheel is simultaneously identified as being the right wheels 5a, 5c and that it is the right rear wheel 5c among them.

[0079] Of course, in the first and second embodiments, too, left / right wheel determination may be performed to determine whether the tire sensor 2 is attached to the right wheels 5a, 5c or the left wheels 5b, 5d, as in steps S220 to S240 of Fig. 8 described in the third embodiment. Then, front / rear wheel determination may be performed to determine whether the tire sensor 2 is attached to the front or rear wheel, such that the right wheel 5a, 5c with a larger absolute value of lateral G is the right front wheel 5a, and the right wheel 5c with a smaller absolute value is the right rear wheel 5c.

[0080] (3) In the above embodiment, the wheel position detection device provided for the vehicle 1 having four wheels 5a to 5d has been described, but the present invention can be similarly applied to vehicles having more wheels. In this case, the absolute value of the lateral G is the largest for the front wheel of the outer wheel and the smallest for the rear wheel of the inner wheel. For this reason, the tire sensors 2 attached to the front wheel of the outer wheel and the rear wheel of the inner wheel are first identified, and the ID information having the same positive and negative values ​​of the lateral G as the front wheel of the outer wheel is identified as the outer wheel, and the ID information having the same positive and negative values ​​of the lateral G as the rear wheel of the inner wheel is identified as the inner wheel. Then, since the absolute value of the lateral G becomes smaller as the wheels move from the front wheels to the rear wheels, the number of wheels from the front of the outer wheel is identified based on the absolute value, and the number of wheels from the front of the inner wheel is identified based on the absolute value. In this way, the present invention can be applied to vehicles having more than four wheels. Of course, in this case, it is also possible to perform weighting as described in the second and third embodiments.

[0081] (4) The control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer. [Explanation of symbols]

[0082] 1 vehicle 2 Tire Sensor 3 Onboard equipment 5a~5d wheels 6. Body 7 Steering Angle Sensor 21 Sensing section 22 G Sensor 23, 32 Communications Department 24, 33 Control section

Claims

1. A wheel position detection device for a vehicle (1) comprising: tire sensors (2) attached to each of a plurality of wheels (5a to 5d) having tires; and an on-board device (3) provided on a vehicle body (6), Each tire sensor attached to each of the plurality of wheels includes: an acceleration sensor (22) for detecting a lateral acceleration, which is an acceleration in a direction along the central axis of rotation of the wheel to which each tire sensor is attached; a first control unit (23) that stores the detection results of the acceleration sensors and creates a frame that stores individual identification information assigned to each tire sensor; a first communication unit (24) that transmits the frame to the vehicle-mounted device, The vehicle-mounted device includes: A second communication unit (32) that receives the frame; a second control unit (33) that determines which of the plurality of wheels the tire sensor that transmitted the frame is attached to, and that associates and registers the relationship between the identification information and the plurality of wheels, the acceleration sensor indicates the detection result with a different sign of positive or negative depending on whether the wheel to which the tire sensor including the acceleration sensor is attached is a right wheel (5a, 5c) or a left wheel (5b, 5d); the second control unit determines a turning direction of the vehicle, and identifies whether the wheel to which each of the tire sensors is attached is the right wheel or the left wheel based on the turning direction and the positive or negative sign of the detection results of the acceleration sensors of each of the tire sensors, and by comparing the absolute values ​​of the detection results, identifies whether the wheel to which each of the tire sensors is attached is the right front wheel (5a) or the right rear wheel (5c) of the right wheels, and identifies whether the wheel to which each of the tire sensors is attached is the left front wheel (5b) or the left rear wheel (5d) of the left wheels, The second control unit is The tire sensor having the largest absolute value of the detection result is identified as being attached to the front wheel of the outer wheel of the turn, and the tire sensor having the smallest absolute value is identified as being attached to the rear wheel of the inner wheel of the turn, Furthermore, the wheel position detection device identifies a tire sensor having the same positive / negative sign of the detection result as the tire sensor identified as being attached to the front wheel of the outer wheel of the turning wheel as being attached to the rear wheel of the outer wheel of the turning wheel, and identifies a tire sensor having the same positive / negative sign of the detection result as the tire sensor identified as being attached to the rear wheel of the inner wheel of the turning wheel as being attached to the front wheel of the inner wheel of the turning wheel.

2. A wheel position detection device applied to a vehicle (1), comprising: tire sensors (2) attached to each of a plurality of wheels (5a to 5d) having tires; and an on-board device (3) provided on the vehicle body (6), Each tire sensor attached to each of the plurality of wheels includes: an acceleration sensor (22) for detecting a lateral acceleration, which is an acceleration in a direction along the central axis of rotation of the wheel to which each tire sensor is attached; a first control unit (23) that stores the detection results of the acceleration sensors and creates a frame that stores individual identification information assigned to each tire sensor; a first communication unit (24) that transmits the frame to the vehicle-mounted device, The vehicle-mounted device includes: A second communication unit (32) that receives the frame; a second control unit (33) that determines which of the plurality of wheels the tire sensor that transmitted the frame is attached to, and that associates and registers the relationship between the identification information and the plurality of wheels, the acceleration sensor indicates the detection result with a different sign of positive or negative depending on whether the wheel to which the tire sensor including the acceleration sensor is attached is a right wheel (5a, 5c) or a left wheel (5b, 5d); the second control unit determines a turning direction of the vehicle, and identifies whether the wheel to which each of the tire sensors is attached is the right wheel or the left wheel based on the turning direction and the positive or negative sign of the detection results of the acceleration sensors of each of the tire sensors, and by comparing the absolute values ​​of the detection results, identifies whether the wheel to which each of the tire sensors is attached is the right front wheel (5a) or the right rear wheel (5c) of the right wheels, and identifies whether the wheel to which each of the tire sensors is attached is the left front wheel (5b) or the left rear wheel (5d) of the left wheels, The second control unit is determining that the tire sensor having the largest absolute value of the detection result is attached to the front wheel of the outer wheel of the turn, and determining that the tire sensor having the smallest absolute value is attached to the rear wheel of the inner wheel of the turn, Furthermore, a tire sensor having the same positive / negative sign of the detection result as the tire sensor identified as being attached to the front wheel of the outer wheel is determined to be attached to the rear wheel of the outer wheel, and a tire sensor having the same positive / negative sign of the detection result as the tire sensor identified as being attached to the rear wheel of the inner wheel is determined to be attached to the front wheel of the inner wheel, a wheel position detection device which, each time it is determined whether each tire sensor is attached to the front or rear wheel of the outer wheel of a turn or the front or rear wheel of the inner wheel of a turn, calculates an integrated value of count values ​​weighted in the order of the front wheel of the outer wheel, the rear wheel of the outer wheel, the front wheel of the inner wheel, and the rear wheel of the inner wheel of a turn, and identifies whether the tire sensor is attached to the front or rear wheel of the outer wheel of a turn or the front or rear wheel of the inner wheel of a turn based on the magnitude relationship of the integrated values.

3. 3. The wheel position detecting device according to claim 2, wherein a difference between the weighted count values ​​of the rear wheel, which is the outer wheel, and the front wheel, which is the inner wheel, is set to one count.

4. A wheel position detection device applied to a vehicle (1), comprising: tire sensors (2) attached to each of a plurality of wheels (5a to 5d) having tires; and an on-board device (3) provided on the vehicle body (6), Each tire sensor attached to each of the plurality of wheels includes: an acceleration sensor (22) for detecting a lateral acceleration, which is an acceleration in a direction along the central axis of rotation of the wheel to which each tire sensor is attached; a first control unit (23) that stores the detection results of the acceleration sensors and creates a frame that stores individual identification information assigned to each tire sensor; a first communication unit (24) that transmits the frame to the vehicle-mounted device, The vehicle-mounted device includes: A second communication unit (32) that receives the frame; a second control unit (33) that determines which of the plurality of wheels the tire sensor that transmitted the frame is attached to, and that associates and registers the relationship between the identification information and the plurality of wheels, the acceleration sensor indicates the detection result with a different sign of positive or negative depending on whether the wheel to which the tire sensor including the acceleration sensor is attached is a right wheel (5a, 5c) or a left wheel (5b, 5d); the second control unit determines a turning direction of the vehicle, and identifies whether the wheel to which each of the tire sensors is attached is the right wheel or the left wheel based on the turning direction and the positive or negative sign of the detection results of the acceleration sensors of each of the tire sensors, and by comparing the absolute values ​​of the detection results, identifies whether the wheel to which each of the tire sensors is attached is the right front wheel (5a) or the right rear wheel (5c) of the right wheels, and identifies whether the wheel to which each of the tire sensors is attached is the left front wheel (5b) or the left rear wheel (5d) of the left wheels, The second control unit is determining whether the wheel to which the tire sensor is attached is the right wheel or the left wheel based on the turning direction and the positive / negative sign of the detection result; when it is determined whether the tire sensor is attached to the right wheel or the left wheel, an integrated value of the count values ​​is calculated such that the tire sensor having the larger detection result among the tire sensors determined to be the left wheel is added with a larger count value than the tire sensor having the smaller detection result, and an integrated value of the count values ​​is calculated such that the tire sensor having the larger detection result among the tire sensors determined to be the left wheel is added with a larger count value than the tire sensor having the smaller detection result, A wheel position detection device that identifies, among the tire sensors determined to be the left wheels, the one with the larger integrated value is attached to the left front wheel (5b) and the one with the smaller integrated value is attached to the left rear wheel (5d), and identifies, among the tire sensors determined to be the right wheels, the one with the larger integrated value is attached to the right front wheel (5a) and the one with the smaller integrated value is attached to the right rear wheel (5c).

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