JP6363525B2 - Tire pressure detection system - Google Patents

Description

  The present invention relates to a tire pressure detection system that detects information such as tire pressure of a vehicle.

  In recent years, in order to remotely detect the tire pressure, a pressure sensor and a transmission antenna are arranged on the tire, and the vehicle obtains tire pressure information of the tire by transmitting the detection result of the pressure sensor to the vehicle. In addition, there is a tire pressure detection system that can notify the driver based on this.

  In general tire pressure detection systems, some of the radio waves received by the antenna of the wireless communication system reach directly from the transmitting antenna (direct wave), while others reach the obstacle after bouncing back (indirect wave) There are various routes. Since the indirect wave arrives at a timing shift with respect to the direct wave due to the bounce, the shifted waves interfere with each other, and the radio wave reaching the receiving antenna becomes stronger or weaker at a certain period. Repeat with. This phenomenon is called “fading”. When fading is large, a part of data is lost, which hinders data demodulation on the receiving side.

  Therefore, in many wireless communication systems, this fading countermeasure is performed by a method called “diversity reception”. Diversity is a technology that reduces fluctuations in the level of received radio waves by combining or switching two or more received radio waves. “Space” diversity is one method of diversity reception, and is a method of receiving radio waves by a plurality of spatially (positionally) separated antennas. The reception level of each antenna is compared, the antenna with the maximum reception level is selected, and the reception signal of that antenna is transmitted to the receiver.

  As a tire pressure detection system employing such a diversity system, for example, a tire pressure monitoring system 900 disclosed in Patent Document 1 is disclosed. The configuration of the tire pressure monitoring system 900 is shown in FIG.

  The tire pressure monitoring system 900 is a tire pressure detection system that employs a space diversity system. As shown in FIG. 9, n antennas 905 a to 905 d (n = 4 for convenience in the figure) are connected to a receiver 904 via a selector 907. The selection unit 907 compares the strengths of the radio waves received by the respective antennas 905a to 905d, and selects the antenna that has received the strongest radio wave. Therefore, according to the tire pressure monitoring system employing this space diversity method, by installing an appropriate number of antennas 905a to 905d at appropriate positions on the vehicle body 903, the transponder 902 having the air pressure sensor in the tire 901 can be used. Can be continuously received without falling below the lower reception limit level, and the above-mentioned inconvenience due to fading can be eliminated.

  In the conventional technique referred to as the diversity method, a plurality of control units having receiving antennas are arranged at different positions in order to eliminate the area where signals cannot be received from the transmitting antennas generated as the tire rotates. By doing so, it is possible to use a signal from the control unit having the highest reception sensitivity.

Japanese Patent No. 4041958

  However, in the air pressure monitoring system 900 according to the prior art, only a plurality of control units are arranged at different positions. Therefore, if one of the control units breaks down, the remaining control unit is replaced by the vehicle. There was a possibility that tire pressure data could not be acquired when entering the unreceivable area seen from the side.

  Further, when any one of the control units fails, there is a problem that the failed control unit affects other control units.

  The present invention has been made in view of such a point, and even when one of the plurality of control units fails, the remaining control unit is prevented from entering the unreceivable area. It is another object of the present invention to provide a tire pressure detection system that can prevent a failed control unit from affecting other control units.

  In order to solve this problem, a tire air pressure detection system according to the present invention is installed in a tire and is disposed at a position facing the transponder of a vehicle and a transponder that detects the tire air pressure of the tire. A tire pressure detection system comprising: a vehicle-mounted device that detects the tire pressure by performing wireless communication; and a general control unit that controls the vehicle-mounted device, wherein the vehicle-mounted device includes a plurality of control units; A plurality of in-vehicle antennas disposed at different positions in the vehicle, and a switching circuit provided between the control unit and the in-vehicle antenna, and the integrated control unit includes the switching circuit. A control signal to be controlled is supplied to the switching circuit, and the switching circuit includes a plurality of control units and a plurality of control units based on the control signal. The connection pattern between the vehicle-mounted antenna is switched, and when any of the plurality of control units fails, it detects which control unit of the plurality of control units has failed, and the failed The control unit is controlled so as not to be connected to any of the plurality of in-vehicle antennas.

  The tire pressure detection system configured as described above controls so as to switch the connection pattern between the plurality of control units and the plurality of in-vehicle antennas, so that any one of the plurality of control units fails. Even in the event that it has occurred, the remaining control unit can be prevented from entering the unreceivable area. In addition, since the control is performed so that the failed control unit is not connected to any of the plurality of vehicle-mounted antennas, the failed control unit can be prevented from affecting other control units.

  Further, in the above configuration, each of the plurality of control units has a transmission terminal and a reception terminal connected to the switching circuit, and the general control unit has one of the plurality of control units in failure. In this case, the switching circuit is controlled so that the transmission terminal and the reception terminal of the failed control unit are each terminated with a predetermined impedance.

  The tire pressure detection system configured in this way terminates the transmission terminal and the reception terminal of the failed control unit with a predetermined impedance, respectively, so that noise from the failed control unit may leak to other control units. Absent. Further, the signal from the transponder is not input to the failed control unit.

  Further, in the above configuration, the plurality of vehicle-mounted antennas for one tire includes a first vehicle-mounted antenna, a second vehicle-mounted antenna, a third vehicle-mounted antenna, and a fourth vehicle-mounted antenna connected to the switching circuit, respectively. The plurality of control units each include a first control unit and a second control unit each having the transmission terminal and the reception terminal, and the transmission terminal and the reception terminal of the first control unit have a predetermined timing. Are connected to the first vehicle-mounted antenna and the second vehicle-mounted antenna, respectively, and the first control unit is used for the communication, and after a predetermined time has elapsed, the transmission terminal and the reception terminal of the first control unit. Are connected to the third vehicle-mounted antenna and the fourth vehicle-mounted antenna, respectively, and the first control unit is used for the communication. It has a characteristic that.

  In the tire air pressure detection system configured as described above, in a state where the first control unit is used for communication, the connection between the first control unit and the first in-vehicle antenna and the second in-vehicle antenna, the first control unit, Since the connection with the third vehicle-mounted antenna and the fourth vehicle-mounted antenna is switched at a predetermined timing, it is possible to prevent the first control unit from always entering the unreceivable area.

  Further, in the above configuration, the switching circuit is provided with a plurality of termination terminals terminated with a predetermined impedance, and the transmission terminal and the reception terminal of the second control unit are respectively connected to the first terminal. When the vehicle-mounted antenna and the second vehicle-mounted antenna are connected to the third vehicle-mounted antenna and the fourth vehicle-mounted antenna, respectively, the transmission terminal and the reception terminal of the first control unit are respectively connected to the termination terminal. The switching circuit is controlled so as to be connected.

  The tire air pressure detection system configured as described above uses the second control unit for communication, and when the first control unit is not used for communication, the transmission terminal and reception of the first control unit not used for communication. Since each terminal is terminated with a predetermined impedance, a signal from the first control unit not used for communication does not leak to the second control unit used for communication. Further, the signal from the transponder is not input to the first control unit that is not used for communication.

  In the above configuration, the mounting positions of the plurality of in-vehicle antennas are shifted from each other by ¼ of the wavelength of the carrier wave of the signal used for the communication.

  In the tire air pressure detection system configured as described above, the mounting positions of the plurality of in-vehicle antennas are shifted from each other by ¼ of the wavelength of the carrier wave of the signal used for communication. Even if one in-vehicle antenna enters the unreceivable area, it is possible to prevent another in-vehicle antenna from entering the unreceivable area.

  Further, in the above configuration, each of the plurality of control units includes a logic circuit including a watchdog timer circuit, and when any of the plurality of control units fails, which control of the control units It is characterized by detecting whether a unit has failed using the logic circuit.

  Since the tire air pressure detection system configured as described above detects a failure of the control unit using a logic circuit including a watchdog timer circuit, the failed control unit can be reliably determined.

  Since the tire pressure detection system of the present invention performs control so as to switch the connection pattern between the plurality of control units and the plurality of vehicle-mounted antennas, one of the plurality of control units has failed. Even in the case, the remaining control unit can be prevented from entering the unreceivable area. In addition, since the control is performed so that the failed control unit is not connected to any of the plurality of vehicle-mounted antennas, the failed control unit can be prevented from affecting other control units.

It is a mimetic diagram showing the outline of the tire air pressure detection system of the present invention. It is a block diagram which shows the structure of a transponder. It is a block diagram which shows the structure of a vehicle-mounted apparatus. It is the block diagram which shows the structure of a control unit, and the truth table of a 1st logic circuit. It is the block diagram which shows the structure of a control unit, and the truth table of a 2nd logic circuit. It is a block diagram which shows the connection of the vehicle-mounted apparatus of 1st Embodiment, and a vehicle-mounted antenna. It is a block diagram which shows the connection of the vehicle-mounted apparatus and vehicle-mounted antenna of 2nd Embodiment. It is a block diagram which shows the connection of the vehicle-mounted apparatus and vehicle-mounted antenna of 3rd Embodiment. It is a block diagram which shows the tire pressure monitoring system which concerns on a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a schematic configuration of the tire air pressure detection system 100 will be described with reference to FIG. Further, the configurations and functions of the in-vehicle device 5 and the transponder 40 will be described with reference to FIGS. 2 and 3.

  FIG. 1 is a diagram illustrating a schematic configuration of a tire air pressure detection system 100, and is a schematic diagram when a vehicle 51 including an in-vehicle device 5 and a general control unit 7 and a tire 52 including a transponder 40 are viewed from above. It is.

  The tire air pressure detection system 100 is used for detecting the air pressure in the tire 52 and detecting the tire air pressure on the vehicle 51 side. As shown in FIG. 1, the tire air pressure detection system 100 includes a transponder 40 that is installed in each tire 52 and detects a tire air pressure, and a transponder 40 that is disposed at a position facing each transponder 40 of the vehicle 51. A vehicle-mounted device 5 that detects tire air pressure by performing wireless communication between them and a general control unit 7 that controls the vehicle-mounted device 5 are configured. Usually, four in-vehicle devices 5 are mounted on one vehicle 51.

  FIG. 2 is a block diagram showing the configuration of the transponder 40. As shown in FIG. 2, the transponder 40 includes a transponder antenna 42, an impedance matching circuit 43, a detection circuit 44, a response circuit 45, a power supply circuit 46, a resonance circuit 47, a transponder control circuit 48, and a smoothing circuit 49. ing.

  The transponder antenna 42 is a transmission / reception antenna for performing communication with the in-vehicle device 5. As shown in FIG. 2, the impedance matching circuit 43 is connected between the antenna 42 and the detection circuit 44, and is a circuit that matches the output impedance of the antenna 42 and the input impedance of the detection circuit 44. The detection circuit 44 is a circuit that performs detection by passing a signal received by the antenna 42 through a semiconductor element (not shown), and outputs the DC component superimposed on the AC component.

  As shown in FIG. 2, the response circuit 45 is connected to the subsequent stage of the detection circuit 44. One end of the resonance circuit 47 is connected to a connection point between the detection circuit 44 and the response circuit 45.

  The resonance circuit 47 is a circuit that extracts an AC component having a desired frequency from the AC component output from the detection circuit 44 as a demodulated signal, and includes a parallel resonance circuit including a resonance capacitor 47a and an inductor 47b connected in parallel to each other. Composed. The other end of the parallel resonant circuit is connected to the ground via a ground capacitor 47c. The resonance frequency of the resonance circuit 47 is set to the frequency of the modulated component included in the signal received by the antenna 42. If the frequency of the carrier wave of the received signal is 2.4 GHz, for example, the frequency is set to 10 MHz, for example. The

  The response circuit 45 is a sensor circuit configured to input a demodulated signal output as an AC component from the detection circuit 44 and output a modulated signal as an output signal. The response circuit 45 has a crystal resonator, oscillates the crystal resonator by temporary input of a demodulated signal, and changes the pressure and temperature based on the change in the oscillation frequency caused by the atmospheric pressure change and the temperature change around the crystal resonator. It is a pressure temperature measurement circuit that measures and outputs the measurement data as a modulated signal. Specifically, a pressure temperature measuring circuit for TPMS (Tire Pressure Monitoring System) that measures the air pressure and temperature of the tire 52 is selected. Since the resonance circuit 47 is connected in parallel to the previous stage of the response circuit 45, the frequency of the demodulated signal and the non-modulation circuit is the resonance frequency of the resonance circuit 47 in order to realize efficient input / output of the input / output signal. It is set near.

  The power supply circuit 46 is a circuit that supplies driving power to a transponder control circuit 48 constituted by an integrated circuit. As shown in FIG. 2, a charge-type circuit that mainly charges a DC component output from the detection circuit 44 is selected. The Specifically, a charge-type circuit including a diode 46a having an anode serving as an input terminal of the power supply circuit 46 and a node serving as an output terminal of the power supply circuit 46, and a charge capacitor 46b connected between the cathode of the diode 46a and the ground. Is selected. As the power supply circuit 46, a hybrid circuit in which a battery is mounted on a rechargeable circuit may be selected.

  The transponder control circuit 48 includes circuits such as an MPU circuit (micro processing unit) and an RF circuit (high frequency circuit) (not shown). The RF circuit is configured to be able to communicate with the in-vehicle device 5. The MPU circuit is provided to control the operation of the RF circuit and the like. The RF circuit is connected to the antenna 42 via the smoothing circuit 49.

  FIG. 3 is a block diagram showing a configuration in the in-vehicle device 5 facing each transponder 40 in each tire 52. Each vehicle-mounted device 5 includes a plurality of control units 10, a plurality of vehicle-mounted antennas 20 arranged at different positions in the vehicle 51, and a switching circuit 30 provided between the control unit 10 and the vehicle-mounted antenna 20. , And is configured. The control unit 10 and the switching circuit 30 are connected to a general control unit 7 provided in the vehicle 51.

  The plurality of control units 10 includes a first control unit 10-1 and a second control unit 10-2, and each has a transmission terminal and a reception terminal connected to the switching circuit 30. Specifically, the first control unit 10-1 has a transmission terminal 10-1a and a reception terminal 10-1b, and the second control unit 10-2 has a transmission terminal 10-2a and a reception terminal 10-2b. And have.

  The first control unit 10-1 and the second control unit 10-2 have a control signal output terminal 10-1c and a control signal input terminal 10-1d, and a control signal output terminal 10-2c and a control signal input, respectively. A terminal 10-2d is provided, and a control signal is output from each control unit 10 to the overall control unit 7 via the control signal line 7b and the control terminal 7a. A control signal is input via the control terminal 7a and the control signal line 7b.

  The plurality of vehicle-mounted antennas 20 provided in the vehicle-mounted device 5 includes a first vehicle-mounted antenna 20-1, a second vehicle-mounted antenna 20-2, a third vehicle-mounted antenna 20-3, and a fourth vehicle-mounted antenna 20-4. Each is connected to the switching circuit 30.

  The plurality of in-vehicle antennas 20 are disposed at positions facing the transponder 40 and are disposed at different positions in the vehicle 51. Specifically, the mounting positions of the first vehicle-mounted antenna 20-1, the second vehicle-mounted antenna 20-2, the third vehicle-mounted antenna 20-3, and the fourth vehicle-mounted antenna 20-4 are the wavelengths of the carrier waves of signals used for communication. Are arranged so as to be shifted from each other by 1/4. If the frequency of the carrier wave of the signal used for communication is 2.4 GHz, the first in-vehicle antenna 20-1, the second in-vehicle antenna 20-2, the third in-vehicle antenna 20-3, and the fourth in-vehicle antenna 20-4. Are arranged to be shifted from each other by 3.125 cm.

  By the way, as introduced in the above-mentioned section of the prior art, in recent tire air pressure detection systems, a plurality of, for example, two control units are combined with one transponder to provide redundancy. This is based on the assumption that the two control units are hardly broken at the same time, and one of the control units is operating, so that communication failure between the transponder and the control unit does not occur. Since the two control units are set apart from each other by a predetermined distance, when one of them is in the unreceivable area, the other is not in the unreceivable area.

  However, if one of the two control units fails for some reason, there is a high possibility that an unreceivable area will occur depending on the position of the transponder that changes as the tire rotates. When an unreceivable area occurs, communication between the transponder and the control unit becomes impossible. However, in this case, it is not known which of the two control units has failed. In addition, the generation of the non-receivable area is likely to occur when the vehicle is stopped, but the non-receivable area may occur when the non-receivable area is synchronized even when the vehicle is moving.

  Therefore, it is necessary to determine which of the two control units has failed, whether the vehicle is stationary or the vehicle is moving. In addition, when one of the two control units fails, it is necessary to prevent the failed control unit from being connected to the vehicle-mounted antenna.

  In the present invention, as shown in FIG. 3, the in-vehicle device 5 is opposed to one transponder 40 installed in one tire 52, and a control signal is supplied from the general control unit 7 to the switching circuit 30. 30 switches the connection pattern between the control unit 10 and the vehicle-mounted antenna 20 based on the control signal. Further, when any of the plurality of control units 10 fails, it detects which control unit 10 of the plurality of control units 10 has failed, and the failed control unit 10 determines which of the plurality of in-vehicle antennas 20 It is made to control by the comprehensive control part 7 so that it may not be connected to.

  A method for detecting which one of the plurality of control units 10 has failed will be described with reference to FIGS. 3 to 5. In the present invention, the logic circuit 15 is used to detect which of the plurality of control units 10 has failed. In the embodiment of the present invention, the first logic circuit 15-1 or the second logic circuit 15-2 is used as the logic circuit 15. Since the first logic circuit 15-1 and the second logic circuit 15-2 have the same function, whichever of the first logic circuit 15-1 and the second logic circuit 15-2 is used as the logic circuit 15. It may be used. Further, the control unit 10a having the first logic circuit 15-1 or the control unit 10b having the second logic circuit 15-2 is provided in each of the first control unit 10-1 and the second control unit 10-2. It is desirable to be used simultaneously.

  The configuration and operation of the control unit 10a including the first logic circuit 15-1 will be described with reference to FIGS. 4 (a) and 4 (b).

  FIG. 4A is a block diagram showing a configuration in the control unit 10a, and FIG. 4B is a truth table of the first logic circuit 15-1.

  As shown in FIG. 4A, the control unit 10a includes a CPU circuit 11, a communication circuit 13, and a first logic circuit 15-1. The CPU circuit 11 is provided with a CPU first output terminal 11a and a CPU second output terminal 11b, and each is connected to the first logic circuit 15-1. The CPU circuit 11 is connected to the communication circuit 13, and the communication circuit 13 is connected to the switching circuit 30 via the transmission terminal 10-1a or 10-2a and the reception terminal 10-1b or 10-2b. The The communication circuit 13 includes a transmission unit 13a (TX in the figure) connected to the transmission terminal 10-1a or 10-2a and a reception unit 13b (RX in the figure) connected to the reception terminal 10-1b or 10-2b. It is configured.

  A control signal from the general control unit 7 is input to the CPU circuit 11 via the control signal input terminal 10-1d or 10-2d, and the CPU circuit 11 transmits the transmission unit 13a in the communication circuit 13 according to the control signal. Then, a communication signal is transmitted to the transponder 40 via the transmission terminal 10-1a or 10-2a. The input timing of the control signal input to each control unit 10 including the plurality of control units 10 in the other in-vehicle device 5 in the vehicle 51 is controlled by the general control unit 7. The receiving unit 13 b receives a signal including tire pressure information acquired by the transponder 40 via the receiving terminal 10-1 b or 10-2 b, extracts the information, and transmits the information to the CPU circuit 11. Further, the CPU circuit 11 transmits and displays the information on a display device (not shown) provided in the vehicle 51.

  The first logic circuit 15-1 includes a watchdog timer circuit 15a (WDT in the figure), a NOT circuit 15b, and an OR circuit 15c. The CPU first output terminal 11a of the CPU circuit 11 is connected to one input terminal of the OR circuit 15c, and the CPU second output terminal 11b of the CPU circuit 11 is connected to the input terminal of the watchdog timer circuit 15a. The output terminal of the watchdog timer circuit 15a is connected to the input terminal of the NOT circuit 15b. Furthermore, the output terminal of the NOT circuit 15b is connected to the other input terminal of the OR circuit 15c, and the output terminal of the OR circuit 15c, that is, the output terminal of the first logic circuit 15-1, is the control signal output terminal 10 described above. -1c or 10-2c.

  4 (a) and 4 (b), the output value of the CPU first output terminal 11a is (1), the output value of the CPU second output terminal 11b is (2), and the output value of the watchdog timer circuit 15a is (3) The output value of the NOT circuit 15b is displayed as (4), and the output value of the OR circuit 15c is displayed as (5).

  When the control unit 10a does not fail and is operating normally (when normal), a reset signal (2) for resetting the watchdog timer circuit 15a is periodically output from the CPU second output terminal 11b. Has been. Further, the output value (1) of the CPU first output terminal 11a is “0” or “1” as shown in FIG. 4B.

  The watchdog timer circuit 15a is a circuit in which the output value becomes “1” when the reset signal (2) is periodically inputted, and the output value becomes “0” when the reset signal (2) is not inputted. is there. Therefore, when the control unit 10a is normal without a failure, as shown in FIG. 4B, the output value (3) of the watchdog timer circuit 15a is "1". Therefore, the output value (4) of the NOT circuit 15b is “0”. As a result, the output value (5) of the OR circuit 15c is the same as the output value (1) of the CPU first output terminal 11a, and becomes “0” or “1”.

  On the other hand, when the control unit 10a fails, the CPU second output terminal 11b does not output the reset signal (2) for resetting the watchdog timer circuit 15a.

  When the control unit 10a fails, the reset signal (2) is not input, so that the output value (3) of the watchdog timer circuit 15a is always “0” as shown in FIG. 4B. Therefore, the output value (4) of the NOT circuit 15b is always “1”. As a result, the output value (5) of the OR circuit 15c becomes “1”.

  Thus, in the case of the control unit 10a including the first logic circuit 15-1, when the control unit 10a fails, the output signal of the control signal output terminal 10-1c or the control signal output terminal 10-2c is always “1”. Therefore, it is possible to clearly detect a plurality of control units 10, that is, which one of the first control unit 10-1 or the second control unit 10-2 shown in FIG. .

  Next, the configuration and operation of the control unit 10b in which the second logic circuit 15-2 is incorporated will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5A is a block diagram showing a configuration in the control unit 10b, and FIG. 5B is a truth table of the second logic circuit 15-2.

  As shown in FIG. 5A, the control unit 10b includes a CPU circuit 11, a communication circuit 13, and a second logic circuit 15-2. Since the CPU circuit 11 and the communication circuit 13 are the same as those in the case of the control unit 10a, description thereof is omitted.

  The second logic circuit 15-2 includes a watchdog timer circuit 15a and an AND circuit 15d. The CPU first output terminal 11a of the CPU circuit 11 is connected to one input terminal of the AND circuit 15d, and the CPU second output terminal 11b of the CPU circuit 11 is connected to the input terminal of the watchdog timer circuit 15a. The output terminal of the watchdog timer circuit 15a is connected to the other input terminal of the AND circuit 15d. The output terminal of the AND circuit 15d, that is, the output terminal of the second logic circuit 15-2 is connected to the control signal output terminal 10-1c or 10-2c described above.

  5 (a) and 5 (b), the output value of the CPU first output terminal 11a is (1), the output value of the CPU second output terminal 11b is (2), and the output value of the watchdog timer circuit 15a is (6) The output value of the AND circuit 15d is displayed as (7).

  When the control unit 10b does not break down and is operating normally (when normal), a reset signal (2) for resetting the watchdog timer circuit 15a is periodically output from the CPU second output terminal 11b. Has been. Further, the output value (1) of the CPU first output terminal 11a is “0” or “1” as shown in FIG. 4B.

  As described above, when the reset signal (2) is periodically input, the watchdog timer circuit 15a has an output value “1”, and when the reset signal (2) is not input, the output value is “0”. “This is the circuit. Therefore, when the control unit 10b is not in failure and normal, the output value (6) of the watchdog timer circuit 15a is “1” as shown in FIG. 5B. As a result, the output value (7) of the AND circuit 15d is the same as the output value (1) of the CPU first output terminal 11a, and becomes “0” or “1”.

  On the other hand, when the control unit 10b fails, the reset signal (2) for resetting the watchdog timer circuit 15a is not output from the CPU second output terminal 11b.

  When the control unit 10b fails, the reset signal (2) is not input, so that the output value (6) of the watchdog timer circuit 15a is always “0” as shown in FIG. 5B. As a result, the output value (7) of the AND circuit 15d becomes “0”.

  As described above, in the case of the control unit 10b including the second logic circuit 15-2, the output signal of the control signal output terminal 10-1c or the control signal output terminal 10-2c is always “0”. It is possible to detect which control unit 10 of the control unit 10, that is, the first control unit 10-1 or the second control unit 10-2, has failed.

[First Embodiment]
Next, a method for controlling the failed control unit 10 so as not to be connected to any of the plurality of in-vehicle antennas 20 will be described with reference to FIGS. 3 and 6. FIG. 6 is a block diagram showing a connection relationship between the control unit 10, the switching circuit 30 and the in-vehicle antenna 20.

  As shown in FIG. 6, the switching circuit 30 includes a transmission terminal 10-1a, a reception terminal 10-1b, a transmission terminal 10-2a, a reception terminal 10 of the second control unit 10-2. -B, and a plurality of control side connection terminals 37 to which the control terminal 7a of the general control unit 7 is connected. The switching circuit 30 is connected to each of the plurality of vehicle-mounted antennas 20, that is, the first vehicle-mounted antenna 20-1, the second vehicle-mounted antenna 20-2, the third vehicle-mounted antenna 20-3, and the fourth vehicle-mounted antenna 20-4. A plurality of antenna side connection terminals 31 are provided.

  The switching circuit 30 includes a first block 30a corresponding to the transmission terminal 10-1a of the first control unit 10-1, a second block 30b corresponding to the reception terminal 10-1b of the first control unit 10-1, A third block 30c corresponding to the transmission terminal 10-2a of the second control unit 10-2 and a fourth block 30d corresponding to the reception terminal 10-2b of the second control unit 10-2 are provided.

  Each of the first block 30a, the second block 30b, the third block 30c, and the fourth block 30d is provided with four antenna side connection terminals 31 and one terminal terminal 33, and four antenna side connection terminals. The first of 31 is the first in-vehicle antenna 20-1, the second is the second in-vehicle antenna 20-2, the third is the third in-vehicle antenna 20-3, and the fourth is the fourth in-vehicle antenna. 20-4, respectively. The fifth terminal of each block is a termination terminal 33, and a resistor 35 having a predetermined impedance is connected to the termination terminal 33. 50Ω is selected as the predetermined impedance.

  The transmission terminal 10-1a and the reception terminal 10-1b of the first control unit 10-1 and the transmission terminal 10-2a and the reception terminal 10-2b of the second control unit 10-2 are respectively controlled by the general control unit 7. The signal is connected to the first vehicle-mounted antenna 20-1, the second vehicle-mounted antenna 20-2, the third vehicle-mounted antenna 20-3, the fourth vehicle-mounted antenna 20-4, or the resistor 35 having a predetermined impedance. It is configured as follows.

  If one of the first control unit 10-1 and the second control unit 10-2 fails, for example, if the second control unit 10-2 fails, the second control unit shown in FIG. The failure information is detected by the first logic circuit 15-1 or the second logic circuit 15-2. In that case, the failure information is transmitted from the control signal output terminal 10-2c of the second control unit 10-2 shown in FIG. As a result, as shown in FIG. 6, the overall control unit 7 replaces the failed transmission terminal 10-2a and reception terminal 10-2b of the second control unit 10-2 with the third block 30c and the second block 30c of the switching circuit 30. In the four blocks 30d, control is performed so that the resistor 35 having a predetermined impedance is connected to the terminal terminal 33 to which the resistor 35 is connected. In addition, the transmission terminal 10-1a of the first control unit 10-1 that has not failed is connected to the first vehicle-mounted antenna 20-1 in the first block 30a, and the reception terminal 10-1b is connected to the second vehicle-mounted antenna in the second block 30b. Control is performed so as to connect to the antenna 20-2. In the present embodiment, the control is performed as described above. However, the transmission terminal 10-1a of the first control unit 10-1 is connected to the second vehicle-mounted antenna 20-2, and the reception terminal 10-1b is connected to the first vehicle-mounted antenna 20. It may be controlled to be connected to -1.

[Second Embodiment]
Next, when neither the first control unit 10-1 nor the second control unit 10-2 is operating normally without failure, the first control unit 10-1 is used for communication. One example of a method of connecting the first control unit 10-1 to the vehicle-mounted antenna 20 in the state will be described with reference to FIG.

  FIG. 7A is a block diagram showing a connection relationship between the first control unit 10-1, the switching circuit 30, and the in-vehicle antenna 20 at a certain predetermined timing, and FIG. 7B shows a predetermined relationship from the predetermined timing. It is a block diagram which shows the connection relation of the 1st control unit 10-1, the switching circuit 30, and the vehicle-mounted antenna 20 after elapse of time.

  As shown to Fig.7 (a), it is controlled by the comprehensive control part 7 so that the transmission terminal 10-1a of the 1st control unit 10-1 may be connected to the 1st vehicle-mounted antenna 20-1 at a certain predetermined timing. The Further, the overall control unit 7 controls the receiving terminal 10-1b of the first control unit 10-1 to be connected to the second vehicle-mounted antenna 20-2, and the first control unit 10-1 is connected to the transponder 40. Used for communication between. At this time, the second control unit 10-2 does not perform transmission / reception with the transponder 40, and the second control unit 10-2 includes a plurality of transmission terminals 10-2a and reception terminals 10-2b. It is not connected to any of the in-vehicle antennas 20.

  And after predetermined time progress, as shown in FIG.7 (b), the transmission terminal 10-1a and the reception terminal 10-1b are respectively the 3rd vehicle-mounted antenna 20-3 and the 4th vehicle-mounted antenna 20-4. The first control unit 10-1 is used for communication. Also at this time, the second control unit 10-2 does not perform transmission / reception with the transponder 40, and the second control unit 10-2 includes a plurality of transmission terminals 10-2a and reception terminals 10-2b. It is not connected to any vehicle-mounted antenna 20 among the antennas 20.

  In the embodiment of the present invention, the first vehicle-mounted antenna 20-1 is used for transmission by the first control unit 10-1 and the second vehicle-mounted antenna 20-2 is used for reception at a certain predetermined timing. After a predetermined time has elapsed, the third vehicle-mounted antenna 20-3 is used for transmission and the fourth vehicle-mounted antenna 20-4 is used for reception. However, in the present invention, this combination does not always have to be adopted. For example, the second vehicle-mounted antenna 20-2 is used for transmission of the first control unit 10-1 at a certain predetermined timing. The fourth vehicle-mounted antenna 20-4 is set to be used for reception, and after a predetermined time has elapsed, the third vehicle-mounted antenna 20-3 is used for transmission and the first vehicle-mounted antenna 20-1 is used for reception. You may change the combination arbitrarily, such as setting to use. Further, when the second control unit 10-2 is used without using the first control unit 10-1, the same switching method as the first control unit 10-1 is applied to the second control unit 10-2. You may carry out.

[Third Embodiment]
Next, in the case where the first control unit 10-1 and the second control unit 10-2 are operating normally without malfunctioning, the second control unit 10-2 is used for communication. One example of the connection method of the control unit 10 will be described with reference to FIG.

  In the case where the first control unit 10-1 and the second control unit 10-2 are operating normally without failure, for example, as shown in FIG. 8, the transmission terminal 10 of the second control unit 10-2. -2a and the reception terminal 10-2b are connected to the first vehicle-mounted antenna 20-1 and the second vehicle-mounted antenna 20-2, respectively, and the transmission terminal 10-1a and reception of the first control unit 10-1 The switching circuit 30 is controlled so that the terminal 10-1b is connected to the terminal terminal 33, respectively.

  In this embodiment, the transmission terminal 10-2a and the reception terminal 10-2b of the second control unit 10-2 are connected to the first vehicle-mounted antenna 20-1 and the second vehicle-mounted antenna 20-2, respectively. FIG. 8 shows a state where the transmission terminal 10-1a and the reception terminal 10-1b of the first control unit 10-1 are connected to the termination terminal 33, respectively. It doesn't have to be adopted. For example, the third control unit 10-2 is configured to use the third vehicle-mounted antenna 20-3 for transmission and the second control unit 10-1 to use the second vehicle-mounted antenna 20-2 for reception. The transmission terminal 10-1a and the reception terminal 10-1b may be set to be connected to the termination terminal 33, and the combination thereof may be arbitrarily changed.

  Hereinafter, the effect by having set it as this embodiment is demonstrated.

  Since the tire air pressure detection system 100 according to the embodiment of the present invention performs control so as to switch the connection pattern between the plurality of control units 10 and the plurality of vehicle-mounted antennas 20, any one of the plurality of control units 10 is selected. Even when the control unit 10 breaks down, the remaining control unit 10 can be prevented from entering the unreceivable area. Further, since control is performed so that the failed control unit 10 is not connected to any of the plurality of in-vehicle antennas 20, it is possible to prevent the failed control unit 10 from affecting other control units 10.

  In addition, since the transmission terminal and the reception terminal of the failed control unit 10 are each terminated with a predetermined impedance, noise from the failed control unit 10 does not leak to other control units 10. Further, the signal from the transponder is not input to the failed control unit 10.

  In the state where the first control unit 10-1 is used for communication, the connection between the first control unit 10-1, the first in-vehicle antenna 20-1 and the second in-vehicle antenna 20-2, and the first control. Since the connection between the unit 10-1 and the third vehicle-mounted antenna 20-3 and the fourth vehicle-mounted antenna 20-4 is switched at a predetermined timing, the state where the first control unit 10-1 is always in the unreceivable region Can be avoided.

  Further, when the second control unit 10-2 is used for communication and the first control unit 10-1 is not used for communication, the transmission terminal 10-1a of the first control unit 10-1 that is not used for communication. And the receiving terminal 10-1b are each terminated with a predetermined impedance, so that a signal from the first control unit 10-1 not used for communication leaks to the second control unit 10-2 used for communication. There is nothing. Further, the signal from the transponder is not input to the first control unit 10-1 that is not used for communication.

  In addition, since the mounting positions of the plurality of vehicle-mounted antennas 20 are shifted from each other by ¼ of the wavelength of the carrier wave of the signal used for communication, one vehicle-mounted antenna 20 among the plurality of vehicle-mounted antennas 20 cannot receive the signal. Even if it enters, it can prevent other vehicle-mounted antenna 20 from entering into a reception impossible area.

  Further, since the failure of the control unit 10 is detected using the logic circuit 15 including the watchdog timer circuit 15a, the failed control unit 10 can be reliably determined.

  As described above, the tire air pressure detection system according to the present invention performs control so as to switch the connection pattern between the plurality of control units and the plurality of vehicle-mounted antennas. Therefore, any one of the plurality of control units is controlled. Even in the case of failure, it is possible to prevent the remaining control unit from entering the unreceivable area. In addition, since the control is performed so that the failed control unit is not connected to any of the plurality of vehicle-mounted antennas, the failed control unit can be prevented from affecting other control units.

  The present invention is not limited to the description of the above embodiment, and can be implemented with appropriate modifications in a mode in which the effect is exhibited.

DESCRIPTION OF SYMBOLS 5 In-vehicle apparatus 7 General control part 7a Control terminal 7b Control signal line 10 Control unit 10a Control unit 10b Control unit 10-1 1st control unit 10-1a Transmission terminal 10-1b Reception terminal 10-1c Control signal output terminal 10-1d Control signal input terminal 10-2 Second control unit 10-2a Transmission terminal 10-2b Reception terminal 10-2c Control signal output terminal 10-2d Control signal input terminal 11 CPU circuit 11a CPU first output terminal 11b CPU second output terminal DESCRIPTION OF SYMBOLS 13 Communication circuit 13a Transmitter 13b Receiver 15 Logic circuit 15a Watchdog timer circuit 15b NOT circuit 15c OR circuit 15d AND circuit 15-1 1st logic circuit 15-2 2nd logic circuit 20 Car-mounted antenna
20-1 1st vehicle-mounted antenna 20-2 2nd vehicle-mounted antenna 20-3 3rd vehicle-mounted antenna 20-4 4th vehicle-mounted antenna 30 Switching circuit
30a 1st block 30b 2nd block
30c 3rd block 30d 4th block 31 Antenna side connection terminal 33 Termination terminal 35 Resistor 37 Control side connection terminal 40 Transponder 42 Transponder antenna 43 Impedance matching circuit 44 Detection circuit 45 Response circuit 46 Power supply circuit 46a Diode 46b Charging capacitor 47 Resonance circuit 47a Resonant capacitor 47b Inductor 47c Grounded capacitor 48 Transponder control circuit 49 Smoothing circuit 51 Vehicle 52 Tire 100 Tire pressure detection system

Claims (6)

A transponder that is installed in a tire and detects the tire air pressure of the tire; and an in-vehicle device that is disposed at a position facing the transponder of the vehicle and detects the tire air pressure by performing wireless communication with the transponder; A general control unit for controlling the in-vehicle device, and a tire air pressure detection system comprising:
The in-vehicle device has a plurality of control units, a plurality of in-vehicle antennas arranged at different positions in the vehicle, and a switching circuit provided between the control unit and the in-vehicle antenna,
The comprehensive control unit supplies a control signal for controlling the switching circuit to the switching circuit, and the switching circuit is connected to a plurality of control units and a plurality of vehicle-mounted antennas based on the control signal. And when any of the plurality of control units fails, it detects which control unit of the plurality of control units has failed, and the failed control unit detects the plurality of vehicle-mounted antennas. A tire air pressure detection system that is controlled so as not to be connected to either of them. Each of the plurality of control units has a transmission terminal and a reception terminal connected to the switching circuit,
The general control unit controls the switching circuit so that when one of the plurality of control units fails, the transmission terminal and the reception terminal of the failed control unit are terminated with a predetermined impedance, respectively. The tire pressure detection system according to claim 1. The plurality of vehicle-mounted antennas for one tire are composed of a first vehicle-mounted antenna, a second vehicle-mounted antenna, a third vehicle-mounted antenna, and a fourth vehicle-mounted antenna connected to the switching circuit, respectively, and the plurality of control units are: A first control unit and a second control unit each having the transmitting terminal and the receiving terminal,
The transmission terminal and the reception terminal of the first control unit are respectively connected to the first vehicle-mounted antenna and the second vehicle-mounted antenna at a predetermined timing, and the first control unit is used for the communication, After a predetermined time has elapsed, the transmission terminal and the reception terminal of the first control unit are connected to the third vehicle-mounted antenna and the fourth vehicle-mounted antenna, respectively, and the first control unit is used for the communication. The tire pressure detection system according to claim 2, wherein: The switching circuit is provided with a plurality of termination terminals terminated with a predetermined impedance,
When the transmission terminal and the reception terminal of the second control unit are connected to the first vehicle-mounted antenna and the second vehicle-mounted antenna, respectively, or the third vehicle-mounted antenna and the fourth vehicle-mounted antenna, respectively, The tire pressure detection system according to claim 3, wherein the switching circuit is controlled so that the transmission terminal and the reception terminal of the first control unit are connected to the terminal terminal, respectively.   The mounting position of the plurality of vehicle-mounted antennas is arranged so as to be shifted from each other by ¼ of the wavelength of the carrier wave of the signal used for the communication. Tire pressure detection system. Each of the plurality of control units has a logic circuit including a watchdog timer circuit,
2. The control circuit according to claim 1, wherein when one of the plurality of control units fails, which one of the control units fails is detected using the logic circuit. 5. The tire air pressure detection system according to any one of 5 above.

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