JP2013001219A - Wheel position detection device, and tire pneumatic pressure detection device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel position detection device which does not need the use of a triggering device and can accurately specify the position of a wheel in a short time.SOLUTION: First and second receiving antennas 31, 32 are disposed at different positions, and the average of the RSSI values obtained when a transmission frame from each transmitter 2 is received by each of the first and second receiving antennas 31, 32 is obtained. Then, the difference between the averages of the RSSI values is obtained. The position of the wheel is detected based on the magnitude of the difference between the averages of the RSSI values for each transmitter 2.

Description

  The present invention relates to a wheel position detection device that automatically detects in which position of a vehicle a target wheel is mounted, and in particular, a transmitter having a pressure sensor on a wheel to which a tire is attached. It is suitable to be applied to a direct tire pressure detection device that detects tire pressure by directly attaching and transmitting the detection result of the pressure sensor from the transmitter and receiving it by the receiver attached to the vehicle body side. .

  Conventionally, there is a direct type as one of tire pressure detecting devices. In this type of tire pressure detecting device, a transmitter equipped with a sensor such as a pressure sensor is directly attached to a wheel side to which a tire is attached. In addition, an antenna and a receiver are provided on the vehicle body side. When a detection signal from the sensor is transmitted from the transmitter, the detection signal is received by the receiver via the antenna, and tire pressure is detected. Done.

  In such a direct tire pressure detecting device, the data transmitted by the transmitter can be determined so that it can be determined whether the transmitted data belongs to the host vehicle and which wheel the transmitter is attached to. ID information for discriminating whether the vehicle is a host vehicle or another vehicle and discriminating a wheel to which a transmitter is attached is individually given.

  In order to specify the position of the transmitter from the ID information included in the transmission data, the ID information of each transmitter needs to be registered in advance on the receiver side in association with the position of each wheel. For this reason, at the time of tire rotation, it is necessary to re-register the transmitter ID information and the wheel positional relationship with the receiver.

  On the other hand, a trigger signal is transmitted from a trigger device provided for each transmitter to the transmitter, and data including ID information is transmitted from the transmitter to the receiver in synchronization with the transmission. There has been proposed a method of registering the ID information of a machine and the positional relationship of wheels with a receiver (see Patent Document 1). There has also been proposed a method of reading the barcode attached to each transmitter and registering the ID information of the transmitter in the receiver. However, these methods have a problem that the number of man-hours for ID registration increases and the cost increases due to an increase in the number of parts such as a trigger machine and a barcode reader. In addition, there is a problem that, during tire rotation, ID information registration work occurs and work efficiency deteriorates. For this reason, there is a need for a system that can automatically perform ID information registration work for a transmitter.

  In order to perform such automatic registration work, it is detected which of the left and right wheels using a biaxial acceleration sensor, and which of the front and rear wheels is detected based on the reception intensity of RF data. Thus, there is a method for detecting the tire positions of the four wheels (see Patent Document 2). In addition, the reception strength received by a plurality of antennas is cumulatively measured, and the position of the transmitter is determined based on the reception strength (see Patent Document 3), or the signal sent from the transmitter mounted on each wheel There is a method of determining the position of a transmitter based on a distribution of RSSI (Received Signal Strength Indicator) values (see Patent Document 4).

  Furthermore, a trigger signal is output from a trigger device provided on the vehicle body side, and the fact that the reception strength of the trigger signal changes according to the distance between the trigger device and each transmitter is used, based on the reception strength of the trigger signal. Some also specify the wheel position (see Patent Document 5).

Japanese Patent No. 3212311 US Pat. No. 7,010,968 US Pat. No. 6,018,993 US Pat. No. 6,489,888 JP 2007-15491 A

  However, in the method described in Patent Document 2, the RSSI value of the RF data from the transmitter is compared or the number of receptions is compared in order to determine which of the front and rear wheels is. Comparison results are not always the same. For example, the transmission output level of the transmitter may vary due to product-to-product variation or aging deterioration, and the RSSI value of the RF data from the transmitter may vary. When the RSSI values are compared, they always have the same magnitude relationship. Is not limited. In such a case, there is a concern that the wheel position is erroneously determined. In addition, even if the received intensity is measured cumulatively as in the method described in Patent Document 3 or the RSSI value distribution is viewed as in the method described in Patent Document 4, the same problem as described above. There is also a problem that it takes time to detect the wheel position because the RSSI value must be accumulated.

  Furthermore, in the method described in the cited document 5, since a trigger machine is required for specifying the wheel position, the problem that the cost increases due to an increase in the number of parts is inevitable. For this reason, it is desirable to be able to specify the wheel position regardless of the reception intensity and the number of receptions and without using a trigger machine.

  In view of the above points, the present invention provides a wheel position detection device that does not require the use of a trigger machine and that can accurately specify the wheel position in a shorter time and a tire air pressure detection device including the wheel position detection device. Objective.

  In order to achieve the above object, in the first aspect of the present invention, the first and second receiving antennas (31, 32) are arranged at different locations on the vehicle body (6), and the receiving circuit (33, 34, 37) is provided. Then, the RSSI value of the frame received by each of the first and second receiving antennas (31, 32) is measured, and the frame is transmitted based on the RSSI value measured by the receiving circuit (33, 34, 37). It is specified which of the four wheels (5a to 5d) the transmitter (2) is attached to. That is, the transmitter (2) transmits a frame with a transmission time longer than the time required for one rotation of the tire, and the receiver (3) transmits the first and second receiving antennas (31, 32) for one rotation of the tire. ) Based on the magnitude relationship of the difference between the average values of the RSSI values of the received frames, the transmitter (2) that transmitted the frame is attached to any of the four wheels (5a to 5d). It is characterized by specifying.

  In this way, the first and second receiving antennas (31, 32) are arranged at different locations, and the transmission frames from each transmitter (2) are received by the first and second receiving antennas (31, 32), respectively. The average value of the RSSI values is obtained. And the difference of the average value of the RSSI value is calculated | required, and wheel position detection is performed based on the magnitude relationship of the difference of the average value of the RSSI value in each transmitter (2). According to such a wheel position detection device, it is assumed that the transmission output level of the transmitter (2) varies due to product-to-product variation and aging deterioration, and the RSSI value of the transmission frame from the transmitter (2) varies. However, the wheel position can be accurately detected. And since it is not necessary to receive and accumulate | store a some flame | frame like the method of patent documents 2-4, the time concerning wheel position detection can be shortened. Further, unlike the method described in Patent Document 5, no additional device such as a trigger machine is required to detect the wheel position, so that the number of parts can be reduced and the cost can be reduced. Become.

  In addition, in claim 1, although the case where wheel position detection was performed based on the difference of the average value of the RSSI value of the flame | frame received by each of the 1st and 2nd receiving antennas (31, 32) for one rotation of a tire was demonstrated. The wheel position detection is performed based on the difference in the maximum RSSI value shown in claim 2, the difference in the median RSSI value shown in claim 3, or the difference in the minimum RSSI value shown in claim 4. You may do it.

  Further, as described in claims 5 to 8, based on the difference between the average value, the maximum value, the median value, or the minimum value of the RSSI values, the front wheels (5a, 5b) and the rear wheels (5c, 5d) It is specified which is transmitted from the transmitter (2) attached, and the frame is either the right wheel (5a, 5c) or the left wheel (5b, 5d) from the rotation direction information included in the frame Identifying which of the four wheels (5a-5d) the transmitter (2) is attached to by specifying whether the transmitter (2) is transmitted from You may make it do.

  Furthermore, as described in claim 9, in the transmitter (2), a frame having a transmission time longer than the time taken for one rotation of the tire is transmitted once, and in the receiver (3), The frame may be received simultaneously by the first and second receiving antennas (31, 32), and as described in claim 10, the transmitter (2) may rotate the tire once. A frame having a transmission time longer than the required time may be transmitted twice, and the receiver (3) may receive the frames in order by the first and second receiving antennas (31, 32). .

  In addition, as described in claim 11, in order to set the transmission time of the frame to a length longer than the time required for one rotation of the tire, for example, the wheel (5a to 5d) is connected to the transmitter (2). An acceleration sensor (22) that detects acceleration according to the rotation of the acceleration sensor (22) may be provided, and an output waveform of the acceleration sensor (22) may be used.

  The frame transmission may be performed when the wheels (5a to 5d) are rotating. However, as described in claim 12, the frame transmission may be performed under the condition that the vehicle speed has reached a predetermined speed. Can be sent.

  In claim 1 or 12, the present invention is shown as a wheel position detecting device. However, as shown in claim 13, the wheel position detecting device can be incorporated in a tire air pressure detecting device. That is, the transmitter (2) includes a sensing unit (21) that outputs a detection signal corresponding to the tire air pressure provided on each of the four wheels (5a to 5d), and is sensed by the first control unit (23). The tire pressure information obtained by signal processing of the detection signal of the unit (21) is stored in a frame and transmitted to the receiver (3). In the receiver (3), the second control unit (35) From the information related to the tire pressure, it is possible to detect the pressure of the tires provided on each of the four wheels (5a to 5d).

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

1 is a diagram illustrating an overall configuration of a tire air pressure detection device to which a wheel position detection device according to a first embodiment of the present invention is applied. 2 is a block diagram showing a transmitter 2 and a receiver 3. FIG. It is the schematic diagram which showed the relationship between the output waveform of the acceleration sensor 22, and the flame | frame transmitted. (A) to (d) are actual measurements of received voltages (= RSSI values) when the rotation angles of the wheels 5a to 5d and the transmission frames from the transmitters 2 are received by the first and second receiving antennas 31 and 32, respectively. It is the graph which showed data, and the graph which showed the average value, (e) is a graph which showed the difference of the average value of RSSI value shown by (b) and (d). (A) to (d) are actual measurements of received voltages (= RSSI values) when the rotation angles of the wheels 5a to 5d and the transmission frames from the transmitters 2 are received by the first and second receiving antennas 31 and 32, respectively. It is the graph which showed data, and the chart which showed the maximum value, (e) is a chart which showed the difference of the maximum value of RSSI value shown by (b) and (d). It is the figure which showed the block configuration of the receiver 3 concerning 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an overall configuration of a tire air pressure detection device to which a wheel position detection device according to a first embodiment of the present invention is applied. The left direction in FIG. 1 corresponds to the front of the vehicle 1, and the right direction in FIG. 1 corresponds to the rear of the vehicle 1. With reference to this figure, the tire pressure detecting device in the present embodiment will be described.

  As shown in FIG. 1, the tire air pressure detection device is attached to a vehicle 1 and includes a transmitter 2, a receiver 3, and a display 4.

  As shown in FIG. 1, the transmitter 2 is attached to each wheel 5 a to 5 d in the vehicle 1, and detects the air pressure of the tire attached to the wheels 5 a to 5 d and relates to the tire air pressure indicating the detection result. Information is stored in a frame and transmitted. The receiver 3 is attached to the vehicle body 6 side of the vehicle 1 and receives a frame transmitted from the transmitter 2 and performs various processes and calculations based on the detection signal stored therein. Wheel position detection and tire pressure detection. The transmitter 2 creates a frame by FSK (frequency shift keying), and the receiver 3 demodulates the frame to read the data in the frame, and detects the wheel position and the tire air pressure. FIG. 2 shows a block configuration of the transmitter 2 and the receiver 3.

  As shown in FIG. 2A, the transmitter 2 includes a sensing unit 21, an acceleration sensor 22, a microcomputer 23, a transmission circuit 24, and a transmission antenna 25, and supplies power from a battery (not shown). Each part is driven based on the above.

  The sensing unit 21 includes, for example, a diaphragm type pressure sensor 21a and a temperature sensor 21b, and outputs a detection signal corresponding to the tire pressure and a detection signal corresponding to the temperature. The acceleration sensor 22 is used to detect the rotation of the wheels 5a to 5d to which the transmitter 2 is attached and to detect the vehicle speed. The acceleration sensor 22 of the present embodiment outputs detection signals corresponding to accelerations in both directions perpendicular to the circumferential direction of the wheels 5a to 5d among the accelerations acting on the wheels 5a to 5d when the wheels 5a to 5d rotate.

  The microcomputer 23 is a well-known one having a control unit (first control unit) and the like, and executes predetermined processing according to a program stored in a memory in the control unit. Individual ID information including identification information unique to the transmitter for identifying each transmitter 2 and identification information unique to the vehicle for identifying the host vehicle is stored in the memory in the control unit.

  The microcomputer 23 receives the detection signal related to the tire pressure from the sensing unit 21, processes the signal and processes it as necessary, and stores the information related to the tire pressure in the frame together with the ID information of each transmitter 2. . Moreover, the microcomputer 23 monitors the detection signal of the acceleration sensor 22, detects the rotation of the wheels 5a to 5d to which the transmitters 2 are attached, and detects the vehicle speed. When the microcomputer 23 creates a frame, the microcomputer 23 performs frame transmission (data transmission) from the transmission antenna 25 to the receiver 3 via the transmission circuit 24 based on the rotation detection result and the vehicle speed detection result.

  Specifically, the microcomputer 23 performs frame transmission on the condition that the vehicle speed becomes a predetermined speed (for example, 10 km / h) or more and starts transmission, and the tire rotates once when the wheel position is detected. The transmission time is adjusted so as to be longer than the length of time required for the above. For example, the microcomputer 23 adjusts the transmission time of frame transmission based on the output waveform of the acceleration sensor 22.

  FIG. 3 is a schematic diagram showing the relationship between the output waveform of the acceleration sensor 22 and the transmitted frame. How the angle of the transmitter 2 changes while the wheels 5a to 5d are rotating as shown in FIG. 3 with 0 ° when the transmitter 2 is positioned below the wheels 5a to 5d. Can be confirmed from the output waveform of the acceleration sensor 22. Therefore, on the basis of this output waveform, a special frame is transmitted when the transmitter 2 is at the 0 ° position, and a normal frame is additionally transmitted subsequently, and the transmitter 2 is again at the 0 ° position. Sometimes a special frame is transmitted to end frame transmission. The special frame includes data indicating the start and end of frame transmission, and the receiver 3 confirms the start and end of frame transmission when performing wheel position detection based on the special frame. As the normal frame, a frame storing data related to the tire pressure is used, but it may be simple dummy data.

  As described above, the microcomputer 23 performs frame transmission at a transmission time longer than the time required for the tire to make one rotation when the wheel position is detected. Since this frame transmission is performed while monitoring one rotation of the tire while the wheels 5a to 5d are rotating, the microcomputer 23 detects the rotation by using the detection signal of the acceleration sensor 22. . In addition, since the frame transmission start timing is set when the vehicle speed reaches a predetermined speed, the microcomputer 23 detects the vehicle speed using the detection signal of the acceleration sensor 22. That is, the output of the acceleration sensor 22 includes acceleration based on centrifugal force (centrifugal acceleration). The vehicle speed can be calculated by integrating the centrifugal acceleration and multiplying the coefficient. For this reason, the microcomputer 23 calculates the centrifugal acceleration by removing the gravitational acceleration component from the output of the acceleration sensor 22, and calculates the vehicle speed based on the centrifugal acceleration.

  The start timing of frame transmission from each transmitter 2 may be the same as the vehicle speed reaches a predetermined speed, but cannot be received on the receiver 3 side due to radio wave interference from a plurality of transmitters 2. In order to prevent this, it is preferable to set different timings by providing a random delay for each transmitter 2.

  In handling radio waves, the average power that can be output per unit time is determined by laws and regulations. For example, in US law standard, it is defined as 75.6 dBuV / m @ 3 m at 315 MHz, and this is the average power that can be output in 100 ms, so it is necessary to change the transmission output level according to the transmission time. For example, when the tire size is 205 / 65R15, the outer circumference is 2.034 m, so when the vehicle speed is 10 km / h (= 2.78 m / s), the time required for one rotation of the tire is 0.73 s. Become. If the frame transmission is performed in a short time, the transmission output level can be set high. However, if the frame transmission is performed during the period in which the tire rotates once, it is necessary to set the transmission output level low. For this reason, the microcomputer 23 has a function capable of adjusting the transmission output level of frame transmission in a plurality of stages, and transmits it so as to satisfy the condition of the average power that can be output per unit time determined as described above. The output level is adjusted.

  Furthermore, the microcomputer 23 performs normal frame transmission in the second and subsequent frame transmissions after the completion of the first frame transmission for wheel position detection. That is, a frame in which information related to tire air pressure is stored together with the ID information of each transmitter 2 is transmitted in a shorter transmission time (for example, 10 ms) than a single rotation of the tire.

  The transmission circuit 24 functions as an output unit that transmits a frame transmitted from the microcomputer 23 to the receiver 3 through the transmission antenna 25. For frame transmission, for example, radio waves in the RF band are used.

  The transmitter 2 configured in this way is attached to an air injection valve in each of the wheels 5a to 5d, for example, and is arranged so that the sensing unit 21 is exposed inside the tire. Thereby, the corresponding tire pressure is detected, and as described above, when the vehicle speed exceeds the predetermined speed, the frame transmission for detecting the wheel position is performed through the transmission antenna 25 provided in each transmitter 2. Thereafter, the transmitter 2 periodically transmits a signal related to tire air pressure to the receiver 3 side by performing frame transmission at regular intervals (for example, every minute). At this time, for example, by providing a random delay for each transmitter 2, the transmission timing of each transmitter 2 is shifted.

  Further, as shown in FIG. 2B, the receiver 3 includes first and second receiving antennas 31 and 32, first and second receiving circuits 33 and 34, a microcomputer 35, and the like. Yes.

  The first and second receiving antennas 31 and 32 are for receiving frames transmitted from the respective transmitters 2. The first and second receiving antennas 31 and 32 are fixed to the vehicle body 6 and are disposed at different locations. In the case of the present embodiment, the first receiving antenna 31 is disposed near the rear of the vehicle 1, more specifically, in the right C pillar, and the first receiving antenna 31 is configured by a built-in antenna built in the main body of the receiver 3. . Further, the second receiving antenna 32 is arranged near the front of the vehicle 1, more specifically, in the wheel house of the right front wheel 5 a, and is an external antenna in which wiring is extended from the main body of the receiver 3.

  The first and second receiving circuits 33 and 34 are used as input units that receive transmission frames from the transmitters 2 received by the first and second receiving antennas 31 and 32 and send the frames to the microcomputer 35. Fulfills the function. The first and second receiving circuits 33 and 34 measure RSSI values of signals (frames) received through the first and second receiving antennas 31 and 32 and transmit the measurement results to the microcomputer 35. Specifically, the first and second reception circuits 33 and 34 are provided with detection circuits, and the first and second reception circuits 33 and 34 have the first and second reception circuits set according to the gain setting of the detection circuit. 2 The RSSI value corresponding to the reception level (signal strength) when the frame is received by the receiving antennas 31 and 32 is output.

  The microcomputer 35 corresponds to the second control unit, and executes wheel position detection processing according to a program stored in a memory in the microcomputer 35. Specifically, the microcomputer 35 measures each RSSI value input from the first and second receiving circuits 33 and 34 when receiving a transmission frame from each transmitter 2, and each of the tires for one rotation of the tire is measured. An average value of RSSI values is calculated, and a difference between the average values is calculated. Then, the microcomputer 35 performs wheel position detection that identifies which wheel 5a to 5d each transmitter 2 is attached to based on the difference between the average values of the RSSI values.

  In general, since there is a characteristic that radio waves are attenuated as the distance from the output source increases, from the transmitter 2 to the first and second receiving antennas 31 and 32 if the transmission output level of each transmitter 2 is equal. The RSSI value is determined depending on the distance. However, since the transmission output level of each transmitter 2 varies due to manufacturing variations or aging of the transmitter 2, the RSSI value depends on the distance from each transmitter 2 to the first and second receiving antennas 31 and 32. Not always. However, if the transmission frames of each transmitter 2 are received by the first and second reception antennas 31 and 32, the transmission frames of the same transmitter 2 are received at different distances, and the RSSI value is obtained. The difference between the average values of the RSSI values is almost equal regardless of the magnitude of the transmission output level. For this reason, the microcomputer 35 stores the magnitude relation of the difference between the average values of the RSSI values of the respective transmitters 2. When calculating the difference between the average values of the RSSI values of the frames transmitted from the respective transmitters 2, Based on the magnitude relationship of the difference of the RSSI value, it is specified to which wheel 5a-5d each transmitter 2 is attached.

  Further, the microcomputer 35 stores the ID information of each transmitter 2 and the position of each wheel 5a to 5d to which each transmitter 2 is attached in association with the result of wheel position detection. After that, based on the ID information and tire pressure data stored in the transmission frame from each transmitter 2, the tire pressure of each wheel 5a to 5d is detected, and an electrical signal corresponding to the tire pressure is displayed. 4 is output. For example, the microcomputer 35 detects a decrease in tire air pressure by comparing the tire air pressure with a predetermined threshold Th, and outputs a signal to that effect to the display 4 when a decrease in tire air pressure is detected. Thereby, the indicator 4 is informed that the tire pressure of any of the four wheels 5a to 5d has decreased.

  The display device 4 functions as an alarm unit, and as shown in FIG. 1, is arranged at a place where the driver can visually recognize, and is configured by, for example, a meter display or the like installed in an instrument panel in the vehicle 1. The For example, when a signal indicating that the tire air pressure has decreased is sent from the microcomputer 35 in the receiver 3, the display device 4 notifies the driver of the decrease in tire air pressure by displaying that effect.

  Next, the operation of the tire pressure detection device of the present embodiment will be described. Hereinafter, the operation of the tire air pressure detection device will be described, but the description will be divided into wheel position detection and tire air pressure detection performed by the tire air pressure detection device.

  First, wheel position detection will be described. On the transmitter 2 side, rotation detection and vehicle speed detection are performed by monitoring the detection signal of the acceleration sensor 22 for each predetermined sampling period based on the power supply from the battery. Further, information on tire air pressure such as tire air pressure and temperature is acquired based on the detection signal of the sensing unit 21, and this information is stored in the frame together with the ID information of each transmitter 2.

  When the vehicle speed becomes equal to or higher than a predetermined vehicle speed (for example, 10 km / h) based on the vehicle speed detection result, each transmitter 2 performs frame transmission from the transmission antenna 25 to the receiver 3 via the transmission circuit 24.

  Specifically, frame transmission is performed based on the rotation detection result based on the detection signal of the acceleration sensor 22. That is, the rotation of each wheel 5a to 5d appears in the output waveform of the detection signal of the acceleration sensor 22. For this reason, the microcomputer 23 of each transmitter 2 transmits a special frame from the output waveform of the acceleration sensor 22 when the transmitter 2 is located at a position below the wheels 5a to 5d at 0 °, and subsequently. A normal frame is additionally transmitted, and when the transmitter 2 reaches the 0 ° position again, a special frame is transmitted and frame transmission is terminated. Thereby, frame transmission is performed in the transmission time more than the length for the time which wheel 5a-5d takes for one rotation.

  On the other hand, when frame transmission is performed from each transmitter 2, the receiver 3 receives the frame transmitted from each transmitter 2 by both the first and second reception antennas 31 and 32. This is input to the first and second receiving circuits 33 and 34, respectively, and the RSSI value of the received signal (frame) is measured and transmitted to the microcomputer 35. Based on this, the microcomputer 35 measures the RSSI values input from the first and second receiving circuits 33 and 34, calculates the average value of the RSSI values for one rotation of the tire, and calculates the average value of the RSSI values. Calculate the difference. And based on the difference of the average value of this RSSI value, the wheel position detection which identifies which wheel 5a-5d each transmitter 2 was attached is performed.

  4A to 4D show the received voltage (= RSSI value) when the rotation angles of the wheels 5a to 5d and the transmission frames from the transmitters 2 are received by the first and second receiving antennas 31 and 32, respectively. FIG. 4 (e) is a chart showing the difference between the average values of RSSI values shown in FIGS. 4 (b) and 4 (d). . For reference, the reception sensitivity at the receiver 3 is also shown in the graphs of FIGS.

  As shown in FIGS. 4A and 4C, in the actual measurement data, the RSSI value of the transmission frame of each transmitter 2 varies with the rotation of the wheels 5a to 5d. Further, as shown in FIGS. 4B and 4D, the average value of the RSSI values is different for each of the wheels 5a to 5d, and as shown in FIG. 4E, the difference between the average values of the RSSI values. Also, the wheel 5a to 5d have different values. And when the 1st, 2nd receiving antennas 31 and 32 are arranged like this embodiment, the difference of the average value of the RSSI value of the transmission frame of the transmitter 2 attached to each wheel 5a-5d is large. In order, the front right wheel 5a, the left front wheel 5b, the right rear wheel 5c, and the left rear wheel 5d.

  At this time, since the transmission output level of each transmitter 2 varies due to manufacturing variations and aging of the transmitter 2, the RSSI value is at a distance from each transmitter 2 to the first and second receiving antennas 31 and 32. It does not always depend. For this reason, even if it is the transmitter 2 attached to the same wheel according to the dispersion | variation in a transmission output level, the average value of an RSSI value can become a different value. However, the difference between the average RSSI values is almost equal regardless of the transmission output level. For this reason, the microcomputer 35 identifies which wheel 5a-5d each transmitter 2 is attached to based on the magnitude relationship of the difference in the average value of the RSSI values of each transmitter 2 stored. can do.

  In this way, it is specified which of the wheels 5a to 5d each frame is attached to. Then, the microcomputer 35 stores the ID information of each transmitter 2 that has transmitted the frame in association with the position of the wheel to which it is attached.

  When wheel position detection is performed in this manner, frames are transmitted from each transmitter 2 at regular intervals thereafter, and every time a frame is transmitted from each transmitter 2, frames for four wheels are received by the receiver. 3 is received. At this time, frame transmission is performed by returning to a relatively early transmission time. Based on the ID information stored in each frame, the transmitter 2 attached to the wheels 5a to 5d is identified as the frame sent from the frame, and the information on the tire pressure is used to determine the wheels 5a to 5d. It becomes possible to detect the tire pressure.

  As described above, the RSSI values when the first and second receiving antennas 31 and 32 are arranged at different locations and the transmission frames from each transmitter 2 are received by the first and second receiving antennas 31 and 32, respectively. The average value is calculated. And the difference of the average value of the RSSI value is calculated | required, and wheel position detection is performed based on the magnitude relationship of the difference of the average value of the RSSI value in each transmitter 2.

  According to such a wheel position detection device, even if there is a variation in the transmission output level of the transmitter 2 due to product-to-product variation or aging deterioration, and the RSSI value of the transmission frame from the transmitter 2 varies, Wheel position detection can be performed. And since it is not necessary to receive and accumulate | store a some flame | frame like the method of patent documents 2-4, the time concerning wheel position detection can be shortened. Further, unlike the method described in Patent Document 5, no additional device such as a trigger machine is required to detect the wheel position, so that the number of parts can be reduced and the cost can be reduced. Become.

  In addition, since the frame transmission condition is that the vehicle speed is equal to or higher than the predetermined speed, or the rotation of the wheels 5a to 5d is detected using the acceleration sensor 22, the wheel position is detected only after the vehicle 1 starts to travel. The wheel position can be detected immediately after traveling.

(Second Embodiment)
A second embodiment of the present invention will be described. In the present embodiment, the RSSI value used for wheel position detection is changed with respect to the first embodiment, and the others are the same as those in the first embodiment, and therefore only different parts will be described.

  In the above embodiment, the wheel position is detected based on the difference between the average values of the RSSI values. However, in this embodiment, the wheel position is detected based on the difference between the maximum values (MAX values) of the RSSI values. . As described in the first embodiment, the difference between the average values of the RSSI values is less affected by the product-to-product variation of the transmitter 2 and the aging deterioration, but the maximum value of the RSSI values during one rotation of the tire. The same can be said for.

  FIGS. 5A to 5D show the rotation angle of the wheels 5a to 5d and the reception voltage when the transmission frames from the transmitters 2 are received by the first and second reception antennas 31 and 32 (= RSSI value). FIG. 5E is a chart showing the difference between the maximum RSSI values shown in FIGS. 5B and 5D. . For reference, the reception sensitivity at the receiver 3 is also shown in the graphs of FIGS.

  As shown in FIGS. 5 (a) and 5 (c), the maximum value of the RSSI value is different for each of the wheels 5a to 5d, and as shown in FIG. 5 (e), the difference in the maximum value of the RSSI value is also the wheel. It becomes a different value every 5a to 5d. And when the 1st, 2nd receiving antennas 31 and 32 are arranged like this embodiment, the difference of the maximum value of the RSSI value of the transmission frame of the transmitter 2 attached to each wheel 5a-5d is large. In order, the front right wheel 5a, the left front wheel 5b, the right rear wheel 5c, and the left rear wheel 5d.

  As described above, the difference between the maximum values of the RSSI values is the same as that of the difference between the average values of the RSSI values, and is almost equal regardless of the magnitude of the transmission output level. For this reason, if the magnitude relationship of the difference of the maximum value of RSSI value of each transmitter 2 is memorize | stored in the microcomputer 35, based on the memorized magnitude relationship, each transmitter 2 will be assigned to which wheel 5a-5d. It can be specified whether it is attached.

(Third embodiment)
A third embodiment of the present invention will be described. In this embodiment, the reception form is changed with respect to the first and second embodiments. The other aspects are the same as those in the first and second embodiments, and therefore only different parts will be described.

  FIG. 6 is a diagram showing a block configuration of the receiver 3 according to the present embodiment. As shown in this figure, in this embodiment, the receiver 3 is configured to include first and second receiving antennas 31 and 32, a switch unit 36, a receiving circuit 37, a microcomputer 35, and the like. The switch unit 36 switches the input of a frame to the reception circuit 37, and inputs a frame received by one of the first and second reception antennas 31 and 32 to the reception circuit 37 by the switching. The receiving circuit 37 calculates the RSSI value of the frame received by the first and second receiving antennas 31 and 32 and inputs it to the microcomputer 34. The first and second described in the first embodiment 2 Performs the role of the receiving circuits 33 and 34.

  As described above, the reception form may be such that the RSSI values of the frames received by the first and second reception antennas 31 and 32 are measured in order. In that case, each transmitter 2 is made to transmit a frame for one rotation of the tire twice, for example, the RSSI value of the frame received by the first receiving antenna 31 is measured for the first time, and the second time The RSSI value of a frame received by one receiving antenna 31 may be measured.

(Other embodiments)
(1) In each of the above-described embodiments, an example of the arrangement location of the first and second reception antennas 31 and 32 has been described. However, these may be arranged at different locations on the vehicle body 7. In addition, the first receiving antenna 31 is an internal antenna built in the main body of the receiver 3, and the second receiving antenna 32 is an external antenna arranged outside the main body of the receiver 3. What is the form of the antenna? For example, both may be external antennas.

  (2) In the above embodiment, as an example of adjusting the frame transmission time so as to be equal to or longer than the time required for one rotation of the tire, the rotation detection of the tire from the output waveform of the acceleration sensor 22 is performed. Frame transmission is performed with a frame length corresponding to one rotation of the tire. However, this is also merely an example, and frame transmission may be performed for a certain period of time that is equal to or longer than the length of time required for one rotation of the tire. Although the time required for one rotation of the tire varies depending on the vehicle speed, if the frame transmission is performed when the vehicle speed reaches a predetermined speed, the time required for one rotation of the tire is inevitably determined. For this reason, the frame transmission time may be set longer than the time required for one rotation of the tire at the vehicle speed.

  (3) In the first and second embodiments, the wheel position is detected based on the difference between the average values and the maximum values of the RSSI values of the frames transmitted from the transmitters 2 for one rotation of the tire. did. However, the wheel position may be detected based on the median value or the minimum value of the RSSI values of the frames transmitted from the transmitters 2 for one rotation of the tire.

  (4) Moreover, in the said embodiment, based on the difference of the average value of the RSSI value of the flame | frame transmitted from each transmitter 2, each transmitter 2 was attached to which of four wheels 5a-5d. 2 is specified. However, by this method, the transmitter 2 is identified as the transmitter 2 attached to either the front wheels 5a, 5b or the rear wheels 5c, 5d, and the right wheels 5a, 5c and the left wheels 5b, 5d The identification of which transmitter 2 is attached may be performed by other methods.

  For example, by providing a wheel rotation direction detection unit, the rotation direction of the wheel to which the transmitter 2 is attached is detected, and data regarding this rotation direction is stored in the transmission frame of the transmitter 2. In this way, it becomes possible for the microcomputer 35 to identify the transmitter 2 attached to either the right wheels 5a, 5c or the left wheels 5b, 5d based on the rotation direction information. As such a wheel rotation direction detector, a biaxial acceleration sensor including two acceleration sensors can be used.

  Specifically, a two-axis acceleration sensor is configured by two acceleration sensors that detect accelerations in different directions, and the acceleration acting on the wheels 5a to 5d during rotation of the wheels 5a to 5d by one acceleration sensor is The acceleration in both directions perpendicular to the circumferential direction of each wheel 5a to 5d is detected, and the acceleration in both directions parallel to the circumferential direction of each wheel 5a to 5d is detected by the other acceleration sensor. And since the phase difference of the output waveform of these acceleration sensors becomes reverse by right wheel 5a, 5c and left wheel 5b, 5d, a wheel rotation direction is detectable by calculating | requiring this phase difference.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Transmitter 3 Receiver 4 Indicator 5 (5a-5d) Wheel 6 Car body 21 Sensing part 22 Acceleration sensor 23 Microcomputer 24 Transmission circuit 25 Transmitting antenna 31, 32 1st, 2nd receiving antenna 33, 34 1st , Second receiving circuit 35 microcomputer 36 switch unit 37 receiving circuit

Claims (13)

Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
A transmitter (2) provided on each of the four wheels (5a to 5d) and having a first control unit (23) that creates and transmits a frame including unique identification information;
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) determines the frame based on a magnitude relationship of a difference between average values of RSSI values of the frames received by the first and second receiving antennas (31, 32) for one rotation of the tire. The wheel position detecting device characterized in that it identifies which of the four wheels (5a to 5d) each of the transmitters (2) that transmitted them is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
A transmitter (2) provided on each of the four wheels (5a to 5d) and having a first control unit (23) that creates and transmits a frame including unique identification information;
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) determines the frame based on the magnitude relationship of the difference in the maximum value of the RSSI value of the frame received by each of the first and second receiving antennas (31, 32) for one rotation of the tire. The wheel position detecting device characterized in that it identifies which of the four wheels (5a to 5d) each of the transmitters (2) that transmitted them is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
A transmitter (2) provided on each of the four wheels (5a to 5d) and having a first control unit (23) that creates and transmits a frame including unique identification information;
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) determines the frame based on the difference in the median difference between the RSSI values of the frames received by the first and second receiving antennas (31, 32) for one rotation of the tire. The wheel position detecting device characterized in that it identifies which of the four wheels (5a to 5d) each of the transmitters (2) that transmitted them is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
A transmitter (2) provided on each of the four wheels (5a to 5d) and having a first control unit (23) that creates and transmits a frame including unique identification information;
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) determines the frame based on the magnitude relationship of the difference between the minimum values of the RSSI values of the frames received by the first and second receiving antennas (31, 32) for one rotation of the tire. The wheel position detecting device characterized in that it identifies which of the four wheels (5a to 5d) each of the transmitters (2) that transmitted them is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
Wheel rotation direction detection means provided on each of the four wheels (5a to 5d) and outputting a detection signal corresponding to the rotation direction of each of the four wheels (5a to 5d), and detected by the wheel rotation direction detection means A transmitter (2) having a first control unit (23) that creates and transmits a frame including rotation direction information and unique identification information regarding the rotation direction,
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) is configured to determine whether the frame is based on a magnitude relationship of a difference between average values of RSSI values of the frames received by the first and second receiving antennas (31, 32) for one rotation of the tire. The rotation included in the frame is specified as to which one of the front wheels (5a, 5b) and the two rear wheels (5c, 5d) is transmitted from the transmitter (2). By identifying whether the frame is transmitted from the transmitter (2) attached to the right wheel (5a, 5c) or the left wheel (5b, 5d) from the direction information, the transmission A wheel position detection device that identifies which of the four wheels (5a to 5d) each of the machines (2) is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
Wheel rotation direction detection means provided on each of the four wheels (5a to 5d) and outputting a detection signal corresponding to the rotation direction of each of the four wheels (5a to 5d), and detected by the wheel rotation direction detection means A transmitter (2) having a first control unit (23) that creates and transmits a frame including rotation direction information and unique identification information regarding the rotation direction,
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) is configured to determine whether the frame is based on a magnitude relationship of a difference between maximum values of RSSI values of the frames received by the first and second receiving antennas (31, 32) for one rotation of the tire. The rotation included in the frame is specified as to which one of the front wheels (5a, 5b) and the two rear wheels (5c, 5d) is transmitted from the transmitter (2). By identifying whether the frame is transmitted from the transmitter (2) attached to the right wheel (5a, 5c) or the left wheel (5b, 5d) from the direction information, the transmission A wheel position detection device that identifies which of the four wheels (5a to 5d) each of the machines (2) is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
Wheel rotation direction detection means provided on each of the four wheels (5a to 5d) and outputting a detection signal corresponding to the rotation direction of each of the four wheels (5a to 5d), and detected by the wheel rotation direction detection means A transmitter (2) having a first control unit (23) that creates and transmits a frame including rotation direction information and unique identification information regarding the rotation direction,
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) determines whether the frame is based on a magnitude relationship of a difference between median RSSI values of the frame received by the first and second receiving antennas (31, 32) for one rotation of the tire. The rotation included in the frame is specified as to which one of the front wheels (5a, 5b) and the two rear wheels (5c, 5d) is transmitted from the transmitter (2). By identifying whether the frame is transmitted from the transmitter (2) attached to the right wheel (5a, 5c) or the left wheel (5b, 5d) from the direction information, the transmission A wheel position detection device that identifies which of the four wheels (5a to 5d) each of the machines (2) is attached to. Applied to a vehicle (1) to which four wheels (5a-5d) with tires are attached to the vehicle body (6);
Wheel rotation direction detection means provided on each of the four wheels (5a to 5d) and outputting a detection signal corresponding to the rotation direction of each of the four wheels (5a to 5d), and detected by the wheel rotation direction detection means A transmitter (2) having a first control unit (23) that creates and transmits a frame including rotation direction information and unique identification information regarding the rotation direction,
The frame transmitted from the transmitter (2) is received via the first and second receiving antennas (31, 32) provided on the vehicle body (6) side and arranged at different locations, and the first, Based on the receiving circuit (33, 34, 37) for measuring the RSSI value of the frame received by each of the second receiving antennas (31, 32), and the RSSI value measured by the receiving circuit (33, 34, 37) Identifying which of the four wheels (5a to 5d) the transmitter (2) that has transmitted the frame is attached to, the four wheels (5a to 5d) and the four wheels A receiver (3) having a second control unit (35) for detecting a wheel position for storing the identification information of the transmitter (2) provided to each of the wheels (5a to 5d) in association with each other. ,
The transmitter (2) transmits the frame in a transmission time longer than the time required for one rotation of the tire,
The receiver (3) determines whether the frame is based on a magnitude relationship of a difference between minimum values of RSSI values of the frames received by the first and second receiving antennas (31, 32) for one rotation of the tire. The rotation included in the frame is specified as to which one of the front wheels (5a, 5b) and the two rear wheels (5c, 5d) is transmitted from the transmitter (2). By identifying whether the frame is transmitted from the transmitter (2) attached to the right wheel (5a, 5c) or the left wheel (5b, 5d) from the direction information, the transmission A wheel position detection device that identifies which of the four wheels (5a to 5d) each of the machines (2) is attached to. The transmitter (2) transmits the frame once with a transmission time longer than the time it takes for the tire to make one rotation,
The wheel position detecting device according to any one of claims 1 to 8, wherein the receiver (3) receives the frame simultaneously by the first and second receiving antennas (31, 32). . The transmitter (2) transmits the frame, which has a transmission time longer than the time taken for the tire to make one rotation, twice,
The wheel position detection device according to any one of claims 1 to 8, wherein the frame is received in order by the first and second receiving antennas (31, 32).   The transmitter (2) includes an acceleration sensor (22) that detects acceleration according to the rotation of the wheels (5a to 5d), and the transmission time of the frame is based on the output waveform of the acceleration sensor (22). The wheel position detecting device according to any one of claims 1 to 10, wherein the length of the tire is set to a length equal to or longer than a time required for one rotation of the tire.   The first control unit (23) of the transmitter (2) transmits the frame on the condition that the vehicle speed has reached a predetermined speed, as a condition for starting transmission. The wheel position detection apparatus as described in one. A tire air pressure detecting device including the wheel position detecting device according to claim 1,
The transmitter (2) includes a sensing unit (21) that outputs a detection signal corresponding to the air pressure of the tire provided on each of the four wheels (5a to 5d), and the first control unit (23). After storing the information on the tire pressure obtained by signal processing the detection signal of the sensing unit (21) in a frame, the frame is transmitted to the receiver (3),
The receiver (3) detects the air pressure of the tire provided in each of the four wheels (5a to 5d) from the information on the tire air pressure in the second control unit (35). A tire pressure detecting device.

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