JP2012210913A - Wheel position detecting device and tire air pressure detecting device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify a wheel position with no use of a trigger machine, nor with the measurement of reception intensity and reception number required.SOLUTION: In order to detect a wheel position, frames are transmitted at the same time from both transmitters 2a and 2c of right side wheel group 5a and 5c, with a transmission timing being different between the right side wheel group 5a and 5c and the left side wheel group 5b and 5d. Further, frames are transmitted at the same time from both transmitters 2b and 2d of the left side wheel group 5b and 5d. With this configuration, only such frame of the transmitters 2c and 2d of rear wheels 5c and 5d as closer to a reception antenna 31 among the right side wheel group 5a and 5c and the left side wheel group 5b and 5d can be received. Since the transmitters 2c and 2d of both the rear wheels 5c and 5d can be identified, the transmitters 2a-2d of all four wheels can be identified by utilizing the rotational direction information stored in the frame when the frames of four wheel which are sent thereafter are received.

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 methods described in Patent Documents 2 and 3, it is necessary to compare the RSSI value of the RF data from the transmitter or to compare the number of receptions in order to determine which is the front or rear wheel. Therefore, it is necessary to provide a device (peak detector) for obtaining the reception intensity or to measure the number of receptions. Moreover, since the RSSI value is used also in the method described in Patent Document 4, a device for obtaining the reception intensity is required. 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 and a tire air pressure detection device including the wheel position detection device that can identify the wheel position without using the trigger machine and the need to measure the reception intensity and the number of receptions. The purpose is to do.

  In order to achieve the above object, according to the first aspect of the present invention, at least the receiving antenna (31) of the receiver (3) is connected to both front wheels (5a, 5b) and both rear wheels (5c, 5d) is arranged so that the distance from either one is closer than the distance from the other, and in the transmitters (2a to 2d), from the transmitters (2a, 2c) attached to the right wheels (5a, 5c). A mode in which frames are transmitted at the same time and a frame is simultaneously transmitted from a transmitter (2b, 2d) attached to the left wheels (5b, 5d) at a timing different from this transmission timing, and four wheels (5a- 5d) A mode in which frames are transmitted at different timings from the transmitters (2a to 2d) attached to each of them, and in the receiving circuit (32), when a plurality of frames are transmitted simultaneously, Also signal strength received only large frame. Then, the second control unit (33) receives the frame received when the frames are simultaneously transmitted from the transmitters (2a, 2c) attached to the right wheels (5a, 5c) as the right wheels (5a, 5c). ) Of the transmitter (2c) attached to the side closer to the receiving antenna (31), and from the transmitter (2b, 2d) attached to the left wheel (5b, 5d) The frame received when transmission is performed is identified as that of the left wheel (5b, 5d) of the transmitter (2d) mounted closer to the receiving antenna (31), and the four wheels (5a-5d) Among the right-side wheels (5a, 5c) received among the frames received when the frames are transmitted at different timings from the transmitters (2a-2d) attached to the respective (5a-5d) Identification information different from the frame of the transmitter (2d) attached closer to the receiving antenna (31) of the transmitter (2c) and the left wheels (5b, 5d) attached closer to the antenna (31) For the frame that has the transmitter (2a) and the left wheel (5b, 5d) of the right wheel (5a, 5c) that are mounted farther from the receiving antenna (31) based on the rotation direction information included in the frame. Of these, the transmitter (2a-2d) is attached to any of the four wheels (5a-5d) by specifying the frame of the transmitter (2b) attached far from the receiving antenna (31) It is characterized by specifying whether or not.

  As described above, when the wheel position is detected, the right wheel (5a, 5c) and the left wheel (5b, 5d) have different transmission timings of the frames from the transmitters (2a to 2d), and the right wheel Frames are simultaneously transmitted from both transmitters (2a, 2c) of (5a, 5c) and simultaneously transmitted from both transmitters (2b, 2d) of the left wheels (5b, 5d). By doing so, the frame of the transmitter (2c, 2d) of the wheel (5c, 5d) closer to the receiving antenna (31) of the right wheel (5a, 5c) and the left wheel (5b, 5d). Only can be received. As a result, the transmitters (2c, 2d) of the wheels (5c, 5d) closer to the receiving antenna (31) can be specified, so that when the frame for four wheels is received, the rotational direction information stored in the frame Can be used to identify all four-wheel transmitters (2a to 2d).

  Therefore, it is not necessary to measure the reception intensity and the number of receptions, and the wheel position can be specified without using a trigger machine. For example, in the transmitters (2a to 2d), if a frame is generated by frequency shift keying in the first control unit (23), the frame having the highest reception strength is obtained when a plurality of frames are transmitted simultaneously. Only can be received by the receiver (3).

  Further, as described in claim 2, as the wheel rotation direction detecting means (22), when the wheel (5a to 5d) to which the transmitter (2a to 2d) is attached rotates the wheel (5a to 5d). A biaxial acceleration sensor having an acceleration sensor (22a) that detects acceleration in both directions perpendicular to the circumferential direction and an acceleration sensor (22b) that detects acceleration in both directions parallel to the circumferential direction can be applied.

  In the invention according to claim 3, the transmitters (2a to 2d) calculate the vehicle speed from the acceleration detected by the acceleration sensors (22a, 22b) included in the biaxial acceleration sensor, and the right wheels (5a, 5c). ) And the left wheel (5b, 5d), the frame is transmitted as soon as the vehicle speed reaches a predetermined vehicle speed, and the other transmitter (2b, 2d) It is characterized in that a frame is transmitted simultaneously after a predetermined time has elapsed since the vehicle speed reached a predetermined vehicle speed.

  As described above, the transmission timing of both transmitters (2a, 2c) of the right wheels (5a, 5c) can be matched by performing frame transmission triggered by the vehicle speed exceeding a predetermined speed. The transmission timings of the transmitters (5a, 5c) of the left wheel (5b, 5d) can be matched. In addition, by transmitting the frame after the vehicle speed becomes equal to or higher than the predetermined speed, it is possible to prevent the frame transmission from being performed when the vehicle is stopped and to improve the battery life. Further, it is assumed that a spare tire is mounted on the vehicle (1), and the spare tire is also provided with a transmitter. However, since the spare tire does not rotate as the vehicle (1) travels, the transmission of the frame is triggered by the fact that the vehicle speed is equal to or higher than the predetermined speed, so that the transmitter attached to the spare tire can be used. Can prevent frames from being transmitted. For this reason, even when a spare tire is equipped with a transmitter, it is possible to accurately detect the wheel position.

  In the invention according to claim 4, the transmitters (2a to 2d) simultaneously transmit frames from the transmitters (2a, 2c) attached to the right wheels (5a, 5c), and what is the transmission timing? In the mode of transmitting frames simultaneously from the transmitters (2b, 2d) attached to the left wheels (5b, 5d) at different timings, the transmitters attached to the four wheels (5a-5d) ( The frame length is longer than that in the mode in which the frame is transmitted at a timing different from 2a to 2d).

  When frame transmission is simultaneously performed from each transmitter (2a to 2d), it is assumed that the timing is slightly shifted. Therefore, when performing frame transmission at the same time, by increasing the length of the frame, at least a part of the frame can be duplicated, and the one with the highest signal strength among the frame transmissions performed more reliably at the same time Only can be received by the receiver (3).

  In the first to fourth aspects, the present invention is shown as the wheel position detecting device. However, as shown in the fifth aspect, the wheel position detecting device can be incorporated into the tire pressure detecting device. That is, the transmitter (2a to 2d) includes a sensing unit (21) that outputs a detection signal corresponding to the tire pressure provided on each of the four wheels (5a to 5d), and the first control unit (23). The tire pressure information obtained by signal processing of the detection signal of the sensing unit (21) is stored in a frame and transmitted to the receiver (3). In the receiver (3), the second control unit (33) Thus, it is possible to detect the air pressure of the tire provided on each of the four wheels (5a to 5d) from the information on the tire air pressure.

  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. It is a figure which shows the block configuration of the transmitters 2a-2d and the receiver 3. FIG. It is the figure which showed an example of the frame structure. An example of a mounting form of each wheel 5a to 5d of the wheel rotation direction detection unit 22 provided in the transmitter 2 and an output waveform of acceleration detected by each of the acceleration sensors 22a and 22b in the mounting form are shown. It is a figure. It is a figure showing the relationship between transmission timing and receivable data. It is the figure which showed the relationship between the rotation angle of the wheels 5a-5d, the electric field strength of the electromagnetic wave when transmitting a frame from each transmitter 2a-2d, and the reception sensitivity of the receiver 3. (A) is a flowchart showing processing performed by the microcomputer 23 of the transmitters 2a to 2d, and (b) is a flowchart showing processing performed by the microcomputer 33 of the receiver 3. It is a timing chart when a wheel position detection process is performed. It is a figure which shows the whole structure of the tire-pressure detection apparatus with which the wheel position detection apparatus demonstrated by other embodiment is applied. It is the figure which showed the structural example of the flame | frame transmitted initially.

  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 (2a to 2d), a receiver 3, and a display 4.

  As shown in FIG. 1, the transmitters 2 a to 2 d are attached to the wheels 5 a to 5 d in the vehicle 1. The tires detect the air pressure of the tires attached to the wheels 5 a to 5 d and indicate the detection results. Information on air pressure is stored in a frame and transmitted by RF. The receiver 3 is attached to the vehicle body 6 side of the vehicle 1, and receives RF frames transmitted from the transmitters 2a to 2d and performs various processes and computations based on detection signals stored therein. Etc. to detect the wheel position and the tire air pressure. The transmitters 2a to 2d create frames by FSK (frequency shift keying), and the receiver 3 demodulates the frames and reads the data in the frames to detect the wheel position and the tire air pressure. ing. FIG. 2 shows a block configuration of the transmitters 2 a to 2 d and the receiver 3.

  As shown in FIG. 2 (a), the transmitter 2 (2a to 2d) includes a sensing unit 21, a wheel rotation direction detection unit 22, a microcomputer 23, a transmission antenna 24, and a battery 25. Each unit is driven based on power supply from the battery 25.

  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 wheel rotation direction detection unit 22 detects whether the transmitter 2 is attached to the right wheel group 5a, 5c or the left wheel group 5b, 5d whose wheel rotation directions are opposite to each other. This corresponds to the wheel rotation direction detection means of the invention. The wheel rotation direction detection unit 22 is provided with a biaxial acceleration sensor including two acceleration sensors 22a and 22b (see FIG. 4). The functions of the acceleration sensors 22a and 22b will be described later.

  The microcomputer 23 is a well-known device including a control unit (first control unit), a transmission unit, and the like, and executes predetermined processing according to a program stored in a memory in the control unit. In the memory in the control unit, individual ID information including identification information unique to the transmitter for identifying each of the transmitters 2a to 2d and identification information unique to the vehicle for identifying the host vehicle is stored.

  The microcomputer 23 receives the detection signal related to the tire air pressure from the sensing unit 21, processes the signal and processes it as necessary, and stores the information regarding the tire air pressure in the frame together with the ID information of each of the transmitters 2a to 2d. Store. Further, the microcomputer 23 monitors the detection signals of the acceleration sensors 22a and 22b during a certain period, and detects the rotation direction of the wheels 5a to 5d to which the transmitters 2a to 2d are attached. In the microcomputer 23, data relating to the tire pressure is stored in this rotational direction, that is, the rotational direction information indicating the transmitter 2 attached to either the right wheel group 5a, 5c or the left wheel group 5b, 5d. Stored in a frame.

  FIG. 3 is a diagram illustrating an example of a frame configuration. The frame shown in this figure is a common frame used for both wheel position detection and tire air pressure detection. As shown in this figure, the frame starts with a synchronization code indicating the start of transmission, individual ID information given to each transmitter 2, rotational direction information, tire pressure information (air pressure and temperature), battery voltage, etc. Error detection information indicating that an error has been detected is stored in the information and data transmitted by the transmitter itself. Of these, the rotation direction information is used to detect whether the transmitters 2a to 2d are attached to the right wheel group 5a, 5c or the left wheel group 5b, 5d, and the tire pressure information is used for each wheel. Used to detect tire pressures 5a-5d.

  When the microcomputer 23 creates a frame, the microcomputer 23 transmits the frame from the transmission antenna 24 to the receiver 3 via the transmission unit with the same signal strength (electric field strength of radio waves). The process of transmitting this frame toward the receiver 3 is also performed according to the above program. In the present embodiment, the microcomputer 23 obtains the vehicle speed, and when the vehicle speed reaches a predetermined speed (for example, 30 km / h) as a trigger, frame transmission to the receiver 3 is started. Frame transmission is repeated until the transmission end speed is reached (for example, less than 30 km / h). The initial transmission timing of the frame is determined according to the rotation direction of the wheels 5a to 5d, that is, whether the right wheel group 5a, 5c or the left wheel group 5b, 5d, and the right wheel group 5a, 5c. Both transmitters 2a, 2c attached to the left side are simultaneously, and both transmitters 2b, 2d attached to the left wheel groups 5b, 5d are simultaneous. In addition, the transmission timing of the second and subsequent frames is basically set to a constant cycle (for example, 1 min) for each transmitter 2a to 2d, but only the second time is a time obtained by adding a random delay to the fixed cycle. Is set. Therefore, first, the mode is such that two frames are simultaneously transmitted from the transmitters 2a to 2d, and then the frame is transmitted from each of the transmitters 2a to 2d at different timings. The random delay is an irregularly set delay time, and is determined by a random number table stored in the microcomputer 23 or the like.

  The transmitters 2a to 2d configured as described above are attached to air injection valves in the wheels of the wheels 5a to 5d, for example, and are arranged so that the sensing unit 21 is exposed to the inside of the tire. Thus, the corresponding tire pressure is detected, and as described above, when the vehicle speed exceeds a predetermined speed, a frame is transmitted at a predetermined transmission timing through the transmission antenna 24 provided in each of the transmitters 2a to 2d. Thus, a signal related to tire air pressure is periodically transmitted to the receiver 3 side.

  Next, the wheel rotation direction detection unit 22 provided in each transmitter 2 will be described with reference to FIG. FIG. 4 shows an example of a mounting form of each wheel 5a to 5d of the wheel rotation direction detection unit 22 provided in the transmitter 2, and the acceleration detected by each acceleration sensor 22a, 22b when the mounting form is adopted. It is the figure which showed the output waveform.

  As shown in this figure, the wheel rotation direction detection unit 22 is configured by a biaxial acceleration sensor including acceleration sensors 22a and 22b that detect accelerations in different directions. One acceleration sensor 22a can detect acceleration 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, and the other acceleration sensor 22b It arrange | positions so that the acceleration of both directions parallel to the circumferential direction of the wheels 5a-5d can be detected.

  Therefore, the acceleration sensor 22a detects acceleration in both directions perpendicular to the circumferential direction of the wheels 5a to 5d, and generates an output corresponding to the gravitational acceleration. For this reason, when the transmitter 2 is located at the upper position of the wheels 5a to 5d, the acceleration sensor 22a outputs an output indicating the gravitational acceleration as a positive value. When the wheels 5a to 5d are rotated by 180 ° and the wheel side transceiver 2 is located at a lower position of the wheels 5a to 5d, an output indicating a gravitational acceleration as a negative value is obtained.

  On the other hand, the acceleration sensor 22b detects the acceleration in both directions parallel to the circumferential direction of the wheels 5a to 5d, and generates an output corresponding to the gravitational acceleration, like the acceleration sensor 22a. However, since the acceleration angle that the acceleration sensor 22b can detect with respect to the acceleration sensor 22a is shifted by 90 °, the phase of the output waveform corresponding to the detected gravitational acceleration is also different from the phase of the output waveform of the acceleration sensor 22a. It is shifted by 90 °. That is, in FIG. 4, when the transmitter 2 is at a position shifted by 90 ° counterclockwise with respect to the centers of the wheels 5a to 5d, an output indicating a gravitational acceleration as a negative value is obtained. When the wheels 5a to 5d are rotated by 180 ° in FIG. 4 and the transmitter 2 is positioned 90 ° clockwise relative to the centers of the wheels 5a to 5d, the output indicating the gravitational acceleration as a positive value is output. It becomes.

  Therefore, as shown in FIG. 4, when the rotation direction of the wheels 5a to 5d is counterclockwise as shown in FIG. 4, the phase of the output waveform of the acceleration sensor 22b is advanced by 90 ° with respect to the output waveform of the acceleration sensor 22a. It becomes a state. Conversely, when the rotation directions of the wheels 5a to 5d are clockwise as shown in FIG. 4, the phase of the output waveform of the acceleration sensor 22b is delayed by 90 ° with respect to the output waveform of the acceleration sensor 22a.

  Thus, when the rotation directions of the wheels 5a to 5d are reversed, the phase shift of the output waveforms of the acceleration sensors 22a and 22b is also reversed. By utilizing this fact, by including rotation direction information indicating the rotation direction of the wheels 5a to 5d in the frame transmitted from the transmitter 2 to the receiver 3, the frame is received by the receiver 3 on the right wheel groups 5a and 5c. And the left wheel group 5b, 5d can be identified from the transmitter 2 attached.

  In the above description, the centrifugal force included in the outputs of the acceleration sensors 22a and 22b is ignored, but the output of the acceleration sensor 22a includes acceleration based on the centrifugal force (centrifugal acceleration). From this centrifugal acceleration, the vehicle speed can be calculated. For this reason, the microcomputer 33 calculates the centrifugal acceleration by removing the gravitational acceleration component from the output of the acceleration sensor 22a, and calculates the vehicle speed based on the centrifugal acceleration.

  As shown in FIG. 2B, the receiver 3 includes a receiving antenna 31, a receiving circuit 32, a microcomputer 33, a power supply circuit 34, and an interface (I / F) circuit 35.

  The receiving antenna 31 is for receiving frames sent from the transmitters 2a to 2d. The receiving antenna 31 is fixed to the vehicle body 6 and is disposed closer to the front or rear of the vehicle 1 so that either one of the front wheels 5a, 5b and the rear wheels 5c, 5d is more than the other. The distance is made closer. In the present embodiment, the receiving antenna 31 is disposed at a location near the rear of the vehicle 1, for example, a rear bumper, and compared with the transmitters 2a and 2b attached to both front wheels 5a and 5b, both rear wheels 5c and 5d. It is arranged near the transmitters 2c and 2d attached to the transmitter.

  The reception circuit 32 functions as an input unit that receives transmission frames from the transmitters 2 a to 2 d received by the reception antenna 31 and sends the frames to the microcomputer 33. The reception circuit 32 receives a frame through the reception antenna 31 and transmits the reception result to the microcomputer 33. Since the reception circuit 32 receives a frame created by FSK, when a plurality of frames are transmitted at the same timing, only the frame having the highest reception strength (the electric field strength of the received radio wave) is received. Receive.

  However, the same timing here means a state where reception periods of a plurality of frames are at least partially overlapped during frame reception. This will be described with reference to a diagram showing a relationship between transmission timing and receivable data shown in FIG.

  As shown in FIG. 5A, it is assumed that the transmission timings of the frame storing data A and the frame storing data B partially overlap. In this case, if there is a difference in the reception strength of each frame, the reception strength of the frame storing data A is higher than the reception strength of the frame storing data B, as shown in FIG. If so, a frame storing data A is received. Conversely, if the reception strength of the frame storing data B is greater than the reception strength of the frame storing data A, the frame storing data B is received. Note that if the transmission timings of both frames do not match completely, the reception period of the frame with the lower reception strength will remain, but in this case, all data of the frame cannot be received and treated as invalid data, Not used for control.

  As described above, when a plurality of frames are transmitted at the same timing, the receiving circuit 32 receives only the frame having the highest reception strength and transmits it to the microcomputer 33.

  In the receiving circuit 32, the receiving sensitivity of the receiver 3 is set to a predetermined sensitivity, and the sensitivity is set so that all frames transmitted from the transmitters 2a to 2d attached to the wheels 5a to 5d can be received. ing. FIG. 6 is a diagram illustrating the relationship between the rotation angle of the wheels 5a to 5d, the reception intensity when the frames are transmitted from the transmitters 2a to 2d, and the reception sensitivity of the receiver 3. As shown in this figure, the reception intensity changes according to the distance between the receiving antenna 31 and the wheels 5a to 5d and the wheel rotation. Basically, the receiver 3 can receive the frame in all of these cases. Sensitivity is set.

  The microcomputer 33 corresponds to a second control unit, and executes wheel position detection processing according to a program stored in a memory in the microcomputer 33 using transmission frames from the transmitters 2a to 2d. The wheel position detection which identifies which wheel 5a-5d each transmitter 2a-2d was attached is performed. Further, the microcomputer 33 stores the ID information of the transmitters 2a to 2d in association with the positions of the wheels 5a to 5d to which the transmitters 2a to 2d are attached based on the wheel position detection result. Thereafter, based on the ID information and the tire pressure data stored in the transmission frames from the transmitters 2a to 2d, the tire pressure of each wheel 5a to 5d is detected.

  The power supply circuit 34 generates a power supply voltage for the microcomputer 33 and the receiving circuit 32 based on the battery voltage. The I / F circuit 35 plays a role of outputting the tire air pressure in the microcomputer 33 to the display 4.

  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 33 in the receiver 3, the display device 4 notifies the driver of the decrease in tire air pressure by displaying that effect.

  Next, wheel position detection processing by a tire air pressure detection device to which the wheel position detection device configured as described above is applied will be described. FIG. 7A is a flowchart showing processing performed by the microcomputer 23 of the transmitters 2a to 2d, and FIG. 7B is a flowchart showing processing performed by the microcomputer 33 of the receiver 3.

  First, as the process shown in FIG. 7A, on the transmitters 2a to 2d side, the right wheel groups 5a and 5c and the left wheel group 5b are attached to themselves based on the power supply from the battery 25. The left / right detection of which one is 5d is performed. Specifically, the rotation direction information is acquired by monitoring the detection signal of the biaxial acceleration sensor during a certain period before the transmission timing (step 100). Also, information related to tire air pressure such as tire air pressure and temperature is acquired based on the detection signal of the sensing unit 21, and a frame is created based on information related to the rotation direction and tire air pressure. Each of the transmitters 2a to 2d determines whether or not the vehicle speed is equal to or higher than a predetermined speed (for example, 30 km / h) (step 110). Processing for transmitting the stored frame is performed.

  Specifically, the transmitters 2a to 2d determine whether the transmitters 2a to 2d are attached to the right wheel groups 5a and 5c and the left wheel groups 5b and 5d by using the rotation direction information (step). 120, 130). If the determination result is the right wheel group 5a, 5c, the frame is immediately transmitted by RF transmission. If the determination result is not the right wheel group 5a, 5c but the left wheel group 5b, 5d, a predetermined time elapses. Frame transmission is performed by transmission (step 140). Thus, the transmitters 2a and 2c attached to the right wheel groups 5a and 5c perform frame transmission with the same timing as the transmission timing. Further, the transmitters 2b and 2d attached to the left wheel groups 5b and 5d perform frame transmission using the same timing as the transmission timing, and are different in timing from the transmitters 2a and 2c attached to the right wheel groups 5a and 5c. Frame transmission can be performed with

  As described above, the vehicle speed is calculated by removing the gravity acceleration component from the outputs of the acceleration sensors 22a and 22b, calculating the centrifugal acceleration, integrating the centrifugal acceleration, and multiplying the coefficient.

  On the other hand, on the receiver 3 side, when an ignition switch (not shown) is turned on and the power supply circuit 34 generates the power supply voltage based on the power supply from the battery, the receiver 3 starts to operate, and is displayed at every predetermined control cycle. The process shown in 7 (b) is executed.

  Specifically, data reception is first performed (step 200), and if there is even one data reception, it is determined whether or not data for two wheels has already been stored (step 210). Since the data for the two wheels has not yet been stored at the time of the first reception, it is first determined whether or not the data for the two wheels has been received, and the process waits until the data for the two wheels is received (step 220). If there is data reception for two wheels, the wheel position is specified based on the acquired data for two wheels (step 230).

  That is, as soon as the vehicle speed reaches a predetermined speed, frame transmission is performed from both transmitters 2a and 2c of the right wheel groups 5a and 5c. At this time, since the distance from the receiving antenna 31 to both wheels 5a and 5c, that is, the distance from both transmitters 2a and 2c is different, the transmission frame of the transmitter 2c of the right rear wheel 5c is more of the right front wheel 5a. The reception intensity when received by the reception antenna 31 is larger than the transmission frame of the transmitter 2a. For this reason, the receiving circuit 32 receives only the transmission frame of the transmitter 2c of the right rear wheel 5c.

  Subsequently, frame transmission is performed from both transmitters 2b and 2d of the left wheel groups 5b and 5d after a predetermined time has elapsed. Also at this time, since the distance from the receiving antenna 31 to both wheels 5b and 5d, that is, the distance from both transmitters 2b and 2d is different, the transmission frame of the transmitter 2d of the left rear wheel 5d is the left front wheel 5b. The reception intensity when received by the receiving antenna 31 is larger than the transmission frame of the transmitter 2b. For this reason, the receiving circuit 32 receives only the transmission frame of the transmitter 2d of the left rear wheel 5d.

  Therefore, the acquired data for the two wheels can be specified as the transmitter 2c for the right rear wheel 5c and the transmitter 2d for the left rear wheel 5d in the order received. The ID information is stored separately for the transmitter 2c of the right rear wheel 5c and the transmitter 2d of the left rear wheel 5d.

  When the data for two wheels is stored in this way, the next time data is received, the data for two wheels is already stored. It is determined whether or not it has been performed, and the system waits until data for four wheels is received (step 240). If there is data reception for four wheels, the wheel position is specified based on the acquired data for four wheels (step 250).

  That is, since the transmitter 2c of the right rear wheel 5c and the transmitter 2d of the left rear wheel 5d have already been specified, the new ID information of the frame received this time is the transmitter 2a, 2b of both front wheels 5a, 5b. belongs to. Each frame also includes rotational direction information. From this rotational direction information, the frame is transmitted from the transmitters 2a to 2d attached to any of the right wheel groups 5a and 5c and the left wheel groups 5b and 5d. Can be determined. Therefore, it is possible to specify all the transmitters 2a to 2d of the four wheels 5a to 5d, and to perform wheel position detection that specifies which wheel 5a to 5d each transmitter 2a to 2d is attached to. it can. Note that the stored contents of the ID information of the transmitters 2a to 2d of the wheels 5a to 5d are deleted, for example, when the ignition switch is turned off. Alternatively, when it is desired to detect the wheel position, a switch for resetting the stored content of the ID information may be provided so that the switch is erased when the switch is pressed.

  FIG. 8 is a timing chart when the above operation is performed. As shown in this figure, when the ignition switch is turned on and the vehicle 1 starts running and the vehicle speed exceeds a predetermined speed (30 km / h), it is used as a trigger from each transmitter 2 together with the ID information and rotational direction information and A frame storing information related to tire pressure is transmitted at a predetermined transmission timing. Specifically, first, frame transmission is simultaneously performed from both transmitters 2a and 2c of the right wheel group 5a and 5c, and then frame transmission is performed from both transmitters 2b and 2d of the left wheel group 5b and 5d after a predetermined period. Done at the same time.

  For this reason, at the first transmission timing, only the frame of the transmitter 2c close to the receiving antenna 31 among the transmitters 2a and 2c of the right wheel groups 5a and 5c is received. At the next transmission timing, only the frame of the transmitter 2d close to the receiving antenna 31 among the transmitters 2b and 2d of the left wheel group 5b and 5d is received. Thereby, the transmitter 2c is specified by the first reception, and the transmitter 2d is specified by the next reception. Then, during the second transmission cycle, that is, after the time when the random delay is added to a certain cycle, frame transmission is performed from each of the transmitters 2a to 2d, and the newly received frame is stored in the frame. Based on the rotation direction information that is present, it is specified that it is transmitted from the transmitters 2a, 2b. Thereby, the transmitters 2a to 2d of all four wheels 5a to 5d can be specified, and to which wheel 5a to 5d each transmitter 2a to 2d is attached can be specified.

  As described above, when the wheel position is detected, the right wheel group 5a and the left wheel group 5b and the left wheel group 5b and 5d have different transmission timings of frames from the transmitters 2a to 2d, and the right wheel group 5a. Frames are simultaneously transmitted from both transmitters 2a and 2c of 5c, and frames are simultaneously transmitted from both transmitters 2b and 2d of left wheel group 5b and 5d. By doing so, only the frames of the transmitters 2c and 2d of the rear wheels 5c and 5d closer to the receiving antenna 31 among the right wheel groups 5a and 5c and the left wheel groups 5b and 5d are received. Can be. As a result, the transmitters 2c and 2d of both rear wheels 5c and 5d can be specified, and when the four-wheel frame sent thereafter is received, the rotation direction information stored in the frame is used. It becomes possible to specify the transmitters 2a to 2d of all four wheels.

  Thereby, the transmitters 2a to 2d of all four wheels 5a to 5d can be specified, and to which wheel 5a to 5d each transmitter 2a to 2d is attached can be specified. When wheel position detection is performed in this manner, thereafter, every time a frame is transmitted from each of the transmitters 2a to 2d at regular intervals, all frames are received. Based on the ID information stored in each frame, the transmitters 2a to 2d attached to the wheels 5a to 5d are identified as frames, and the wheels 5a to 5d are determined from the tire pressure information. It becomes possible to detect the tire pressure of 5d.

  Therefore, it is possible to provide a wheel position detection device that can specify the wheel position without using the reception intensity and the number of receptions and without using a trigger machine, and a tire air pressure detection device including the wheel position detection device. Further, since the frame transmission is performed when the vehicle speed exceeds the predetermined speed, the transmission timings of the transmitters 2a and 2c of the right wheel groups 5a and 5c can be matched, and the left wheel groups 5b and 5d can be matched. The transmission timings of both transmitters 5a and 5c can be matched. Furthermore, frame transmission can be prevented when the vehicle is stopped, and the battery life can be improved.

  In addition, it is assumed that the vehicle 1 is equipped with a spare tire and the spare tire is also provided with the transmitter 2. However, since the spare tire does not rotate as the vehicle 1 travels, the transmission of the frame is triggered by the fact that the vehicle speed is equal to or higher than the predetermined speed, so that the transmitter 2 attached to the spare tire can be used. It is possible to prevent frame transmission. For this reason, even when the transmitter 2 is provided in the spare tire, the wheel position can be accurately detected.

(Other embodiments)
In the above embodiment, the rear antenna 5c, 5d is compared with the transmitters 2a, 2b attached to the front wheels 5a, 5b by disposing the receiving antenna 31 of the receiver 3 closer to the rear of the vehicle 1. It is arranged near the transmitters 2c and 2d attached to the transmitter. On the other hand, as shown in FIG. 9, the entire receiver 3 may be disposed closer to the rear of the vehicle 1. Moreover, the receiver antenna 31 or the entire receiver 3 is not arranged near the rear of the vehicle 1, but the sensitivity of the receiver 3 is lowered by arranging it in a place near the front of the vehicle 1, for example, a front bumper. At this time, only the transmission frames from the transmitters 2a and 2b attached to both front wheels 5a and 5b may be received.

  In the above embodiment, the frames are first transmitted simultaneously from the transmitters 2a and 2c of the right wheel groups 5a and 5c, and then the frames are simultaneously transmitted from both transmitters 2b and 2d of the left wheel groups 5b and 5d. did. However, these steps are reversed, and frames are simultaneously transmitted from both transmitters 2b and 2d of the left wheel group 5b and 5d, and then frames are simultaneously transmitted from both transmitters 2a and 2c of the right wheel group 5a and 5c. May be.

  In the above embodiment, as shown in FIG. 3, since the wheel position detection device is applied to the tire air pressure detection device, the rotational direction information of the wheels 5a to 5d is stored in the frame in which the information related to the tire air pressure is stored. To be sent. However, this is merely an example of the frame configuration, and the frame for storing the rotation direction information and the frame for storing information related to the tire pressure may be separate frames. However, by storing the rotational direction information in a frame in which information relating to tire air pressure is stored, it is possible to provide a common frame that can perform both wheel position detection and tire air pressure detection.

  Furthermore, the timing at which it is detected that the vehicle speed has reached a predetermined speed may be slightly shifted due to variations in the acceleration sensors 22a and 22b, wheel diameters, tire conditions, and the like. In this case, even if frame transmission is simultaneously performed from each of the transmitters 2a to 2d, the timing is slightly shifted. For this reason, for the first frame that is desired to be transmitted and mixed at the same time, it is preferable to increase the frame length by increasing the stored data length compared to the frame used thereafter.

  FIG. 10 is a diagram illustrating a configuration example of a frame transmitted first. As shown in FIG. 10 (a), only the first frame to be transmitted is a frame in which data for a plurality of frames for periodic transmission is combined, or dummy data is added at the end of the frame as shown in FIG. 10 (b). Can be provided. In this way, even if there is variation in the acceleration sensors 22a of the transmitters 2a to 2d that are desired to perform frame transmission at the same time, at least a part of the transmission timing of the first frame is duplicated, and the frame that is duplicated in the receiver 3 Only one of them can be received. For example, when the frames of the transmitters 2a and 2b far from the receiving antenna 31 are received first, the frames of the transmitters 2c and 2d close to the receiving antenna 31 are received halfway. In the case of FIG. 10 (a), there is a case where it is possible to receive up to the second block of the previously received frame, but since the data on the stronger side received later can be received for 3 blocks, the received block The data on the strong side can be discriminated by the number of. In the case of FIG. 10B, even if both receive data, it is possible to determine by measuring and comparing the dummy data length.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 (2a-2d) Transmitter 3 Receiver 4 Indicator 5 (5a-5d) Wheel 6 Car body 21 Sensing part 22 Wheel rotation direction detection part 23 Microcomputer 31 Reception antenna 32 Reception circuit 33 Microcomputer

Claims (6)

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 (22) 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 the wheel rotation direction detection A transmitter (2a to 2d) having a first control unit (23) that creates and transmits a frame including rotation direction information and unique identification information regarding the rotation direction detected by the means (22);
A receiving circuit (32) provided on the vehicle body (6) side for receiving a frame transmitted from the transmitter (2a to 2d) via a receiving antenna (31); and data obtained from the received frame; Based on whether or not the frame can be received, the transmitter (2a to 2d) that has transmitted the frame is specified to which of the four wheels (5a to 5d), and the 4 A second control unit that performs wheel position detection that stores the identification information of the transmitters (2a to 2d) associated with the four wheels (5a to 5d) and the four wheels (5a to 5d) in association with each other ( 33) and a receiver (3) having
At least the receiving antenna (31) of the receiver (3) has a distance from one of the front wheels (5a, 5b) and the rear wheels (5c, 5d) of the vehicle (1) from the other. It is arranged closer than the distance of
The transmitters (2a to 2d) simultaneously transmit the frame from the transmitters (2a, 2c) attached to the right wheels (5a, 5c), and the left wheels (5b) at a timing different from the transmission timing. 5d), a mode in which the frame is simultaneously transmitted from the transmitters (2b, 2d) attached to the transmitter 5d), and timings different from those of the transmitters (2a-2d) attached to the four wheels (5a-5d), respectively. And the mode for transmitting the frame in
The receiving circuit (32) receives only a frame having the highest signal strength when a plurality of frames are transmitted simultaneously,
The second control unit (33) receives a frame received when the frame is simultaneously transmitted from the transmitters (2a, 2c) attached to the right wheels (5a, 5c). 5a, 5c) of the transmitter (2c) attached closer to the receiving antenna (31), and the transmitter (2b) attached to the left wheel (5b, 5d) 2d) of the transmitter (2d) mounted on the left wheel (5b, 5d) closer to the receiving antenna (31) than the frame received when the frame is transmitted simultaneously. And when the frame is transmitted at a different timing from the transmitters (2a to 2d) attached to the four wheels (5a to 5d), respectively. Among the right-side wheels (5a, 5c), the transmitter (2c) and the left-side wheels (5b, 5d) of the right-side wheels (5a, 5c) that are attached closer to the receiving antenna (31) For the frame having identification information different from the frame of the transmitter (2d) attached closer to (31), the reception of the right wheels (5a, 5c) based on the rotation direction information included in the frame The frame of the transmitter (2b) attached to the far side from the receiving antenna (31) among the transmitter (2a) and the left wheel (5b, 5d) attached to the far side from the antenna (31) By specifying, it is specified which of the four wheels (5a to 5d) each of the transmitters (2a to 2d) is attached to. Wheel position detecting device according to symptoms.   The wheel rotation direction detection means (22) detects acceleration in both directions perpendicular to the circumferential direction of the wheel (5a to 5d) when the wheel (5a to 5d) to which the transmitter (2a to 2d) is attached is rotated. The wheel position detecting device according to claim 1, wherein the wheel position detecting device is a two-axis acceleration sensor having an acceleration sensor (22a) for detecting acceleration and an acceleration sensor (22b) for detecting acceleration in both directions parallel to the circumferential direction.   The transmitters (2a to 2d) calculate a vehicle speed from accelerations detected by acceleration sensors (22a, 22b) included in the two-axis acceleration sensor, and the right wheels (5a, 5c) and the left wheels ( 5b, 5d), the frame is transmitted at the same time as the vehicle speed reaches a predetermined vehicle speed, and the other transmitter (2b, 2d) has a predetermined vehicle speed. The wheel position detection device according to claim 1 or 2, wherein a frame is simultaneously transmitted after a predetermined time has elapsed since the vehicle speed was reached.   The transmitters (2a to 2d) simultaneously transmit the frame from the transmitters (2a, 2c) attached to the right wheels (5a, 5c), and the left wheel (at a timing different from the transmission timing) In the mode in which the frame is simultaneously transmitted from the transmitters (2b, 2d) attached to 5b and 5d), the transmitters (2a to 2d) attached to the four wheels (5a to 5d), respectively. The wheel position detecting device according to any one of claims 1 to 3, wherein the length of the frame is longer than that in a mode in which the frame is transmitted at a different timing. .   The wheel according to any one of claims 1 to 4, wherein in the transmitter (2a to 2d), the first controller (23) creates the frame by frequency shift keying. Position detection device. A tire pressure detecting device including the wheel position detecting device according to any one of claims 1 to 5,
The transmitters (2a to 2d) include a sensing unit (21) that outputs a detection signal corresponding to the tire pressure provided on each of the four wheels (5a to 5d), and the first control unit ( 23) storing information on tire air pressure obtained by signal-processing the detection signal of the sensing unit (21) in a frame, and transmitting the frame 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 related to the tire air pressure in the second control unit (33). A tire pressure detecting device.

Images