JP4591383B2 - Bus communication system - Google Patents

Description

  The present invention relates to a bus communication system in which a master device and a plurality of slave devices are daisy chain connected.

  As an occupant protection device for a vehicle that protects an occupant at the time of a vehicle collision, there is one disclosed in Patent Document 1, for example. The vehicle occupant protection device disclosed in Patent Literature 1 includes a control device and a plurality of collision detection sensors that are daisy chain connected to the control device via a communication bus.

  By the way, a plurality of collision detection sensors connected to the same communication bus store unique identifiers in order to distinguish them from each other. However, the plurality of collision detection sensors store identifiers after being mounted on the vehicle in response to a request for common parts. That is, at the time of initial setting, a unique identifier is set for each collision detection sensor by the control device.

  The collision detection sensors 5 to 7 of such a vehicle occupant protection device are configured as shown in FIG. 3, for example. That is, each of the collision detection sensors 5 to 7 includes communication circuits 5a, 6a, and 7a that exchange signals with the control device 2, and bus switches 5b and 6b that block communication between the front side and the rear side. 7b, acceleration sensors 5c, 6c, and 7c, and nonvolatile memories 5d, 6d, and 7d that store identifiers.

Then, in the initial setting, the control device 2 sequentially outputs an identifier giving signal to the collision detection sensors 5 to 7 from the front side to the rear side, and the collision detection sensors 5 to 5 from the front side to the rear side. Repeatedly connecting each of the seven bus switches 5b to 7b sequentially. That is, first, the control device 2 outputs a first identifier giving signal to the first collision detection sensor 5 directly connected to the control device 2, and the first collision detection sensor 5 The first identifier is stored in the nonvolatile memory 5d. Subsequently, the bus switch 5b of the first collision detection sensor 5 is turned on, and the control device 2 and the second collision detection sensor 6 are connected. Subsequently, the control device 2 outputs a second identifier giving signal to the second collision detection sensor 6, and the second collision detection sensor 6 stores the second identifier in the nonvolatile memory 6d. To do. Subsequently, the bus switch 6 b of the second collision detection sensor 6 is turned on to connect the control device 2 and the third collision detection sensor 7. Thereafter, the same processing is performed for the collision detection sensor 7 on the rear stage side. By doing in this way, each of the plurality of collision detection sensors 5 to 7 acquires and stores a unique identifier.
JP 2004-284382 A

  Here, the failure determination of the bus switches 5b to 7b is based on whether or not the number of collision detection sensors 5 to 7 stored in advance in the control device 2 matches the number of identifiers set by the control device 2. to decide. That is, when the number of identifiers set by the control device 2 matches the number of collision detection sensors 5 to 7 stored in advance in the control device 2, it is determined to be normal, and when it is small, it is determined to be a failure. This is because, for example, when the bus switches 5b to 7b are short-circuited or open, an appropriate identifier cannot be set for each of the collision detection sensors 5 to 7.

  For example, when the bus switch 5b in FIG. 4 is short-circuited at the time of initial setting, an identifier providing signal for the first collision detection sensor 5 is also transmitted to the second collision detection sensor 6. . Therefore, the same identifier is set for the first and second collision detection sensors 5 and 6. Thereafter, a unique identifier is sequentially set for the collision detection sensor 7 on the rear stage side, and the number of collision detection sensors 5 to 7 stored in advance in the control device 2 and the number of set identifiers Does not match. That is, the number of identifiers set by the control device 2 is one less than the number of collision detection sensors 5 to 7 stored in the control device 2 in advance. As a result, the control device 2 can determine that a failure has occurred in any of the bus switches 5b-7b of the collision detection sensors 5-7.

  When the bus switch 5c has an open failure, no signal is transmitted to the collision detection sensors 6 and 7 on the rear side of the bus switch 5b having the open failure. Therefore, even in the case of an open failure, the number of set identifiers is smaller than the number of collision detection sensors 5 to 7 stored in the control device 2 in advance. As a result, the control device 2 can determine that a failure has occurred in any of the bus switches 5b-7b of the collision detection sensors 5-7.

  However, the failure determination method as described above can only determine that a failure has occurred, and cannot distinguish between a short failure and an open failure. In addition, the failure location cannot be specified. Therefore, when it is determined that there is a failure, all the vehicle occupant protection devices are prevented from operating in order to prevent malfunction of the vehicle occupant protection device.

  The present invention has been made in view of such circumstances, and does not use the number of identifiers set at the time of failure determination, but by using a new failure determination method, all vehicle occupant protection devices It is an object of the present invention to provide a bus communication system that does not stop operation of a bus communication system such as the above, and can continue operation as much as possible even in a part that does not fail.

  The bus communication system of the present invention includes a master device and a plurality of slave devices connected in a daisy chain to the master device via a communication bus. Each slave device includes a switching unit, an identifier acquisition unit, an identifier storage unit, and a response unit. When the switching signal output from the master device is input, the switching unit switches the communication connection between the master device or the preceding slave device and the subsequent slave device. The identifier obtaining means obtains each identifier when the switching means of the slave device on the preceding stage is connected, and when the identifier giving signal output from the master device is input, and the identifier obtaining signal Output to the master device. The identifier storage unit stores the identifier acquired by the identifier acquisition unit. When the command signal output from the master device is input, the response unit sends the response signal to the command signal when the identification signal included in the input command signal matches the identifier acquired by the identifier acquisition unit. Response means for outputting to is provided. The bus communication system further determines that a normal identifier has been assigned to all slave devices based on the identifier acquisition signal when the identifier acquisition signal is input from the identifier acquisition means, and has assigned a normal identifier. When it is determined that the identifier storage means, the identifier storage permission means for permitting storage of the identifier in the identifier storage means is provided. In addition, the master device outputs a command signal after permitting storage of the identifier by the identifier storage permission unit, and detects a failure of detecting an open failure of the switching unit of the slave device when a response signal to the command signal is not input from the response unit. A detection means is provided.

  Here, according to the bus communication system of the present invention, first, each slave device is set with an identifier immediately after system connection. For example, when the bus communication system is a vehicle occupant protection device, “immediately after system connection” is, for example, when the vehicle is assembled or when the vehicle is shipped from the factory. That is, each slave device is a common component. At this time, each of the slave devices can determine that the unique identifier is normally given by the identifier storage permission unit. For example, if it is determined immediately after the system connection that the switching means is a short circuit failure or an open failure, the switching means may be immediately replaced with a normal new one. In other words, after the vehicle is assembled or after the vehicle is shipped, it is possible to select one in which all switching means are normal. Then, the slave device receives the identifier storage permission signal from the identifier storage permission means after being given a normal identifier, stores the identifier by the identifier storage means, and continues to hold the identifier even after the power is turned off.

  Then, after assigning a normal identifier to each slave device, when a command signal is output from the master device to the slave device, the switching means is open depending on whether or not the slave device outputs its response signal. It can be determined whether or not. In other words, when a command signal is output from the master device to the slave device, if the failure detection means does not input a response signal to be output from the slave device, the signal is transmitted due to an open failure of the switching means. It can be judged that it is not.

  Therefore, by assigning a normal identifier in advance, a slave device that can communicate with the master device can continue to be used even if an open failure occurs thereafter. That is, instead of stopping the operation of all slave devices as in the prior art, it is possible to continue using some of the slave devices. As described above, since some of the slave devices can continue to operate, the functions of the bus communication system can be exhibited more effectively than in the past.

  The failure detection means may specify an open failure position among the respective switching means. The failure detection means repeatedly outputs a command signal to the slave device on the subsequent stage side from the front stage side and sequentially connects each switching means on the slave apparatus on the rear stage side from the front stage side, The switching means connected when no response signal is input from the response means is set as the open failure position.

  As described above, when the open failure position can be identified, the master device includes use prohibition processing means for performing use prohibition processing for the slave device on the rear stage side of the slave device including the switching means that is the open failure position. May be. In other words, it is possible to ensure that the slave device that is not affected is continuously used as it is without using only the slave device that is affected by the open failure position switching means. Furthermore, if an open failure location can be specified, it will be very easy to perform repairs.

  Further, the identifier storage permitting unit may determine that a normal identifier has been assigned when the number of types of identifiers matches a preset number of slave devices. This makes it possible to easily determine whether a normal identifier has been assigned.

  The bus communication system described above may be a vehicle occupant protection device. In this case, the slave device serves as a collision detection sensor of the vehicle occupant protection device. In particular, in the case of a vehicle occupant protection device having a vehicle occupant protection device such as a plurality of airbags, when some of the collision detection sensors fail, it is desired to continue using the vehicle occupant protection device that can be used. There is a request. Therefore, by using the bus communication system of the present invention as the vehicle occupant protection device, the use of the vehicle occupant protection device that is not affected by the failure can be continued.

  According to the bus communication system of the present invention, bus communication systems such as all vehicle occupant protection devices are operated by using a new failure determination method instead of using the number of identifiers set at the time of failure determination. Rather than stopping, it is possible to continue operation as much as possible even in a part where there is no failure.

  Next, the present invention will be described in more detail with reference to embodiments. In the present embodiment, a case where the bus communication system of the present invention is applied to an airbag device that protects a vehicle occupant will be described as an example. First, the whole structure of the airbag apparatus of this embodiment is demonstrated with reference to FIG. FIG. 1 shows a schematic diagram of the overall configuration of an airbag device 1 of the present embodiment.

  As shown in FIG. 1, an airbag device 1 (bus communication system in the present invention) includes an airbag ECU 2 (master device in the present invention), communication buses 3 and 4, and slave sensors 5 to 12 (slave in the present invention). Device), a driver-seat front airbag 13a, a passenger-seat front airbag 13b, side airbags 13c and 13d, and curtain airbags 13e and 13f.

  The airbag ECU 2 is a device that deploys the airbags 13a to 13f based on the sensor 23 installed inside, which will be described later, and the acceleration detected by the slave sensors 5 to 12. The airbag ECU 2 is disposed at a substantially central portion of the vehicle.

  The communication bus 3 supplies voltage to the slave sensors 5 to 8 from the airbag ECU 2 and transmits and receives identifier signals, command signals, data, and the like between the airbag ECU 2 and the slave sensors 5 to 8. This is a signal line. The communication bus 4 supplies voltage to the slave sensors 9 to 12 from the airbag ECU 2 and transmits and receives identifier signals, command signals, data, and the like between the airbag ECU 2 and the slave sensors 9 to 12. This is a signal line.

  The slave sensors 5 to 12 are sensors that detect the acceleration of each part of the vehicle and transmit the detection result via the communication buses 3 and 4 in response to a data transmission request command signal from the airbag ECU 2.

  The slave sensor 5 is disposed on the right rear side of the vehicle and detects acceleration in the front-rear direction of the vehicle. The slave sensor 5 is directly connected to the airbag ECU 2. The slave sensor 6 is disposed in the vicinity of the right C pillar of the vehicle, and detects acceleration in the left-right direction of the vehicle. The slave sensor 6 is connected to the airbag ECU 2 via the slave sensor 5. The slave sensor 7 is disposed in the vicinity of the right B pillar of the vehicle, and detects acceleration in the left-right direction of the vehicle. The slave sensor 7 is connected to the airbag ECU 2 via slave sensors 5 and 6. The slave sensor 8 is disposed in front of the right side of the vehicle and detects acceleration in the front-rear direction of the vehicle. The slave sensor 8 is connected to the airbag ECU 2 via slave sensors 5 to 7. That is, the slave sensors 5 to 8 are daisy chain connected to the airbag ECU 2.

  The slave sensor 9 is disposed on the left rear side of the vehicle and detects acceleration in the front-rear direction of the vehicle. The slave sensor 9 is directly connected to the airbag ECU 2. The slave sensor 10 is disposed in the vicinity of the left C-pillar of the vehicle and detects acceleration in the left-right direction of the vehicle. The slave sensor 10 is connected to the airbag ECU 2 via the slave sensor 9. The slave sensor 11 is disposed in the vicinity of the left B-pillar of the vehicle and detects acceleration in the left-right direction of the vehicle. The slave sensor 11 is connected to the airbag ECU 2 via slave sensors 9 and 10. The slave sensor 12 is disposed in front of the left side of the vehicle and detects acceleration in the front-rear direction of the vehicle. The slave sensor 12 is connected to the airbag ECU 2 through slave sensors 9 to 11. That is, the slave sensors 9 to 11 are daisy chain connected to the airbag ECU 2.

  Next, a detailed block configuration of the airbag apparatus 1 will be described with reference to FIG. FIG. 2 shows a block diagram of the airbag apparatus 1. As shown in FIG. 2, the airbag ECU 2 includes a power supply circuit 20, a center control circuit 21, an ECU communication circuit 22, a sensor 23, and an ignition circuit 24.

  The power supply circuit 20 is a circuit that converts the output voltage of the battery 15 supplied via the ignition switch 14 into a power supply voltage suitable for the operation of the center control circuit 21, the ECU communication circuit 22, and the sensor 23, and supplies it. . The input terminal of the power supply circuit 20 is connected to the positive terminal of the battery 15 via the ignition switch 14. The output terminal of the power supply circuit 20 is connected to the center control circuit 21, the ECU communication circuit 22, and the power supply terminal of the sensor 23, respectively. Note that the negative terminal of the battery 15 is grounded to the vehicle body.

  The center control circuit 21 includes an identifier assigning unit 211, an identifier storage permitting unit 212, a collision processing unit 213, and a failure detecting unit 214.

  The identifier assigning unit 211 assigns a unique identifier to each of the slave sensors 5 to 12 when the vehicle is assembled or the vehicle is shipped from the factory. Here, the identifier assigning unit 211 does not assign an identifier after the identifier storage permitting unit 212 (to be described later) permits the storage of the identifier. That is, after the identifier storage permission unit 212 permits storage of the identifier, the identifier stored in the slave sensor is used. Detailed processing of the identifier assigning unit 211 will be described later.

  The identifier storage permission unit 212 determines whether or not a normal unique identifier has been assigned to each of the slave sensors 5 to 12 by the identifier assigning unit 211, and has been determined to have assigned a normal identifier. In this case, it is permitted to store the identifier in the nonvolatile memory 5d of the slave sensors 5 to 12. This determination and permission are performed when the identifier is assigned by the identifier assigning unit 211, that is, when the vehicle is assembled or the vehicle is shipped from the factory. That is, it is not performed after the vehicle is shipped from the factory. The above determination by the identifier storage permission unit 212 can be performed, for example, by comparing the number of identifiers given by the identifier giving unit 211 with the number of slave sensors 5 to 12 stored in advance. That is, when the number of slave sensors 5 to 12 stored in advance matches the number of identifiers, it is determined that a normal unique identifier has been assigned. On the other hand, if the number of slave sensors 5 to 12 stored in advance does not match the number of identifiers, it is determined that a normal unique identifier has not been assigned.

  If a normal unique identifier is not given by the identifier storage permitting unit 212, it is replaced with one that is given a normal unique identifier when the vehicle is assembled or before shipment. Therefore, when the vehicle is finally shipped, a unique identifier is normally assigned to all the slave sensors 5 to 12. That is, when delivered to the customer, each slave sensor 5-12 already stores a unique identifier.

  The collision processing unit 213 collects acceleration data of the slave sensors 5 to 12 and acceleration data of the sensor 23 via the ECU communication circuit 22 and the communication buses 3 and 4. Then, the collision processing unit 213 determines whether to deploy the airbags 13a to 13f based on these acceleration data. Hereinafter, this determination is referred to as a collision determination. The ignition circuit 24 is controlled based on the result of the collision determination. The collision processing unit 213 performs the collision determination using any acceleration data of the slave sensors 5 to 12 by the failure prohibiting process by the failure detecting unit 214. Detailed processing of the collision processing unit 213 will be described later.

  The failure detection unit 214 detects whether or not the bus switches of the slave sensors 5 to 12 are open failures. The failure detection process by the failure detection unit 214 is performed at the time of initial check. Details of the failure detection processing of the failure detection unit 214 will be described later.

  The ECU communication circuit 22 supplies a power supply voltage to the slave sensors 5 to 12 via the communication buses 3 and 4. Further, the ECU communication circuit 22 is a circuit that transmits and receives various signals such as an identifier assignment signal, an identifier acquisition signal, a data transmission request command signal, and an acceleration data signal to and from the slave sensors 5 to 12. Here, the various signals transmitted from the ECU communication circuit 22 to the slave sensors 5 to 12 are voltage digital signals. On the other hand, various signals received by the ECU communication circuit 22 from the slave sensors 5 to 12 are current digital signals. Thus, by using the voltage digital signal on the transmission side and the current digital signal on the reception side, signal transmission and reception can be performed in parallel.

  The sensor 23 is installed in the airbag ECU 2, detects acceleration in the longitudinal direction of the vehicle, and outputs this acceleration data to the collision processing unit 213 of the center control circuit 21. The ignition circuit 24 is a circuit that deploys one selected from the airbags 13 a to 13 f based on the ignition signal output from the collision processing unit 213 of the center control circuit 21. The communication buses 3 and 4 are a high-side communication bus 3a and 4a to which a voltage digital signal is transmitted from the ECU communication circuit 22, and a low-side communication bus to which a current digital signal is transmitted from each of the slave sensors 5 to 12 to the ECU communication circuit 22. 3b and 4b.

  Next, a detailed configuration of the slave sensors 5 to 12 will be described with reference to FIG. FIG. 3 shows in particular a block diagram of the slave sensors 5-7. Here, since all the slave sensors 5 to 12 have the same configuration, only the slave sensor 5 will be described here.

  As shown in FIG. 3, the slave sensor 5 includes a sensor communication circuit 5a (identifier acquisition means and response means in the present invention), a bus switch 5b (switching means in the present invention), a sensor 5c, and a nonvolatile memory 5d ( Identifier storage means) in the present invention.

  The upper end side of the sensor communication circuit 5a is connected to the high side communication bus 3a. On the other hand, the lower end side of the sensor communication circuit 5a is connected to the low side communication bus 3b. And this sensor communication circuit 5a supplies the power supply voltage supplied from ECU communication circuit 22 to the sensor 5c etc. via the high side communication bus 3a. Further, when the identifier communication signal is input from the ECU communication circuit 22 via the high-side communication bus 3a, the sensor communication circuit 5a stores the identifier in the nonvolatile memory 5d described later and also transmits the identifier acquisition signal. Transmit to the ECU communication circuit 22. Further, when a data transmission request command signal is input from the ECU communication circuit 22, the sensor communication circuit 22 inputs acceleration data from the sensor 5c, and sends the acceleration data to the ECU communication circuit 22 via the low-side communication bus 3b. Send. Further, the sensor communication circuit 5a switches the bus switch 5b on / off based on a signal input from the ECU communication circuit 22.

  One end side (the left side in FIG. 3) of the bus switch 5 b is connected to a high side communication bus 3 a that is directly connected to the ECU communication circuit 22. On the other hand, the other end side (the right side in FIG. 3) of the bus switch 5b is connected to a high-side communication bus 3a that connects between the slave sensor 5 and the slave sensor 6 located on the subsequent stage side. That is, the bus switch 5b is a switch that connects the ECU communication circuit 22 located on the front stage side and the slave sensor 6 located on the rear stage side. The upper end side of the sensor communication circuit 5a described above is connected to one end side of the bus switch 5b. Accordingly, the bus switch 5b of the slave sensor 5 is also a switch that enables communication between the ECU communication circuit 22 and the sensor communication circuit 6a of the slave sensor 6 at the subsequent stage. The bus switch 5b switches on / off in accordance with an instruction from the sensor communication circuit 5a.

  The sensor 5c detects acceleration and outputs the detected acceleration data to the sensor communication circuit 5a. The non-volatile memory 5d stores the identifier assigned by the sensor communication circuit 5a when the sensor communication circuit 5a receives the identifier assignment signal and when the identifier storage permission signal is output from the identifier storage permission unit 212. To do. That is, a normal unique identifier is stored in the nonvolatile memory 5d before the vehicle is shipped from the factory. The non-volatile memory 5d continues to use the identifier stored before the factory shipment of the vehicle without losing the stored identifier information even when the power is turned off.

  A slave sensor 6 having a similar configuration is connected to the subsequent stage of the slave sensor 5 via a high-side communication bus 3a and a low-side communication bus 3b. A slave sensor 7 having a similar configuration is connected to the subsequent stage of the slave sensor 6 via a high-side communication bus 3a and a low-side communication bus 3b. A slave sensor 8 having a similar configuration is connected to the subsequent stage of the slave sensor 7 via a high-side communication bus 3a and a low-side communication bus 3b. Further, the slave sensors 9 to 12 are the same as the slave sensors 5 to 8, and thus the description thereof is omitted.

  Next, the operation of the airbag device 1 will be described with reference to FIGS. Here, FIG. 4 is a flowchart showing an identifier assigning process by the identifier assigning unit 211. FIG. 5 is a flowchart showing a failure detection process by the failure detection unit 214. FIG. 6 is a flowchart showing the collision processing by the collision processing unit 213.

  First, a unique identifier is assigned to each of the slave sensors 5 to 12 when the vehicle is assembled or the vehicle is shipped from the factory. This identifier assigning process will be described with reference to FIG. First, in FIG. 2, when the ignition switch 14 is turned on, the power supply circuit 20 converts the output voltage of the battery 15 into a power supply voltage suitable for the operation of the center control circuit 21, the ECU communication circuit 22, and the sensor 23. Supply. At this time, the bus switches 5b,..., 12b of the slave sensors 5 to 12 are all turned off.

  Subsequently, the identifier assigning unit 211 of the center control circuit 21 performs an identifier assigning process on the slave sensors 5 to 12. As shown in FIG. 4, first, the counter n is initialized to 1 (step S1). Subsequently, the identifier assigning unit 211 outputs an n-th identifier assigning signal to the slave sensors 5 to 8 via the CH1 of the ECU communication circuit 22 and the high-side communication bus 3a (step S2). At this time, since the bus switches 5b,..., 12b of the slave sensors 5 to 12 are all turned off, the first identifier assigning signal output from the identifier assigning unit 211 is transmitted only to the slave sensor 5. . Then, since the sensor communication circuit 5a of the slave sensor 5 acquires the first identifier, the first identifier is stored in the nonvolatile memory 5d. Further, the sensor communication circuit 5a outputs an identifier acquisition signal acquired from the first identifier to the ECU communication circuit 22 via the low-side communication bus 3b.

  Subsequently, the identifier assigning unit 211 determines whether or not an nth identifier acquisition signal has been input (step S3). Here, the first identifier acquisition signal is input from the slave sensor 5. When the identifier assigning unit 211 receives the nth identifier acquisition signal (step S3: Yes), the number Nmax of the slave sensors 5 to 8 that are daisy chain connected to the same communication buses 3a and 3b with the counter n. It is determined whether or not (step S4). Here, since the counter n is 1, it is not equal to Nmax.

  Therefore, next, the identifier giving signal 211 outputs the switch-on signals of the nth bus switches 5b,..., 8b to the slave sensors 5 to 8 (step S5). First, since the counter n is 1, the bus switch 5b of the slave sensor 5 having the first identifier is turned on. Subsequently, the counter n is incremented by 1 (step S6), and the process proceeds to step S2.

  That is, when the counter n becomes 2, in step S2, the identifier assigning unit 211 outputs a second identifier assigning signal. At this time, since only the bus switch 5b is turned on among the slave sensors 5 to 8, the slave sensors 5 and 6 are connected to CH1 of the ECU communication circuit 22. Since the first identifier is stored in the non-volatile memory 5 d of the slave sensor 5, the second identifier providing signal is transmitted to the slave sensor 6. Then, since the sensor communication circuit 6a of the slave sensor 6 acquires the second identifier, the second identifier is stored in the nonvolatile memory 6d. Further, the sensor communication circuit 6a outputs an identifier acquisition signal acquired from the second identifier to the ECU communication circuit 22 via the low side communication bus 3b.

  When unique identifiers are set for all the slave sensors 5 to 12 in this way, the counter n is set to Nmax in step S4, and the process is terminated. By the way, also when the identifier provision part 211 does not input the nth identifier acquisition signal in step S3 (step S3: No), the processing is ended. The case where the identifier assigning unit 211 does not input the nth identifier acquisition signal is, for example, a case where the bus switch 5b or the like has an open failure or a short failure.

  Here, for example, the flow of identifier assignment processing when the bus switch 5b has an open failure will be described.

  In this case, the slave sensor 5 acquires the first identifier and outputs an identifier acquisition signal to the identifier assigning unit 211 as described above. Subsequently, even if the ON signal of the first bus switch 5b is output in step S5, the bus switch 5b is not turned ON because of an open failure. Proceeding directly to the next step S2, the identifier assigning unit 211 outputs the second identifier assigning signal. However, since the bus switch 5b is not turned on, the ECU communication circuit 22 and the slave sensor 6 cannot communicate with each other. Accordingly, the identifier assigning unit 211 does not input an identifier acquisition signal for the second identifier assigning signal. That is, although the second identifier acquisition signal is output in step S3, the second identifier acquisition signal is not input (step S3: No), and the identifier addition process ends.

  In addition, the flow of the identifier assigning process when the bus switch 5b of the slave sensor 5 has a short fault will be described.

  In this case, the slave sensor 5 acquires the first identifier and outputs an identifier acquisition signal to the identifier assigning unit 211 as described above. Here, since the bus switch 5b is short-circuited, the ECU sensor 22 can communicate with the slave sensor 5 and the slave sensor 6. Accordingly, the first identifier providing signal output from the identifier providing unit 211 is input not only to the slave sensor 5 but also to the slave sensor 6. Therefore, the slave sensor 6 acquires the first identifier, stores the first identifier in the nonvolatile memory 6d, and outputs the first identifier acquisition signal to the identifier assigning unit 211. That is, the first identifier is set in the slave sensor 5 and the slave sensor 6.

  Subsequently, the second and subsequent identifiers are set after the slave sensor 7. Then, even if the identifier assigning unit 211 finally outputs the fourth identifier assigning signal, it does not input the identifier acquiring signal. Therefore, in step S3, although the fourth identifier providing signal is output, the fourth identifier acquisition signal is not input (step S3: No), and thus the identifier providing process ends.

  Here, when the identifier assigning process ends, the identifier storage permission unit 212 performs the identifier storage permission process. As described above, this identifier storage permission process can be performed, for example, by comparing the number of identifiers assigned by the identifier assigning unit 211 with the number of slave sensors 5 to 12 stored in advance. In the case of an open failure and a short failure, since the number of identifiers set by the identifier assigning unit 211 is less than the number of slave sensors 5 to 12 stored in advance, it is easily determined that there is a failure. Can do. As described above, the vehicle is shipped after a normal unique identifier is assigned.

  Then, when the ignition switch 14 is turned on after the vehicle is delivered to the customer, a failure detection process by the failure detection unit 214 is performed. This failure detection process will be described with reference to FIG. Here, the failure detection processing by the failure detection unit 214 is processing for detecting an open failure of the bus switch 5b,.

  First, it is determined whether or not it is immediately after the ignition switch 14 is turned on (step S11). If it is immediately after the ignition switch 14 is turned on (step S11: Yes), the counter n is initialized to 1 (step S12). Subsequently, the failure detection unit 214 outputs the nth failure detection signal (step S13). This failure detection signal includes an identification signal which is information of an identifier. That is, this failure detection signal is a signal transmitted to each of the slave sensors 5 to 12. Subsequently, the failure detection unit 214 determines whether or not the nth failure detection response signal is input from the slave sensors 5 to 12 (step S14). Here, since the counter n is 1, the failure detection unit 214 determines whether or not a failure detection response signal including the first identifier information is input.

  Subsequently, when a failure detection response signal including n-th identifier information is input (step S14: Yes), the number of slave sensors 5 to 8 in which the counter n is daisy chain connected to the same communication buses 3a and 3b. It is determined whether it is equal to Nmax (step S15). Here, since the counter n is 1, it is not equal to Nmax.

  Accordingly, next, the counter n is incremented by 1 (step S16), and the process proceeds to step S13. Then, when the failure detection unit 214 sequentially outputs a failure detection signal and inputs a failure detection response signal including all identifier information, the failure detection unit 214 determines that all the bus switches are normal and performs processing. The process ends (step S17).

  On the other hand, if the failure detection unit 214 does not input the failure detection response signal including the nth identifier information in step S14, it is determined that the (n−1) th bus switch has an open failure (step S18). ), The process is terminated. For example, when the failure detection response signal including the second identifier information is not input, it is determined that the bus switch 5b of the slave sensor 5 in which the first identifier is stored has an open failure. Whether or not the nth failure detection response signal is not input is determined, for example, by whether or not the failure detection response signal is input within a predetermined time after the failure detection unit 214 outputs the failure detection signal. Good. Even when the ignition switch 14 is not immediately after being turned on (step S11: No), the processing ends.

  As described above, the failure detection unit 214 can detect whether or not the bus switch has an open failure, and can also specify an open failure position.

  Next, when the failure detection process by the failure detection unit 214 ends, the collision process by the collision processing unit 213 is performed. First, the collision processing unit 213 outputs a switch-on signal that turns on all the bus switches 5b,... (Step S21). In the collision process performed while the vehicle is running, the bus switch 5b,... Has already been turned on, so the process proceeds to the next process.

  Subsequently, it is determined whether or not it is immediately after the ignition switch 14 is turned on (step S22). Immediately after the ignition switch 14 is turned on and the failure detection processing by the failure detection unit 214 is completed (step S22: Yes), it is determined whether or not the failure detection unit 214 described later determines that a failure has occurred. Determination is made (step S23).

  If the failure detection unit 214 determines that an open failure has occurred (step S23: Yes), an open failure prohibition process is performed (step S24). Here, the open failure prohibition process is a process for prohibiting use of a slave sensor located on the rear stage side of a slave sensor having a bus switch that is an open failure position. For example, when the first bus switch is in the open failure position, the second and subsequent slave sensors are prohibited. That is, the first slave sensor is in a usable state. Then, the collision processing unit 213 stores the slave sensor whose use is prohibited due to an open failure.

  Subsequently, when it is determined to be normal in step S23 (step S23: No), the failure prohibition process is completed (step S24), and when it is determined that it is not immediately after the ignition switch 14 is turned on (step S22). : No), an acceleration data transmission request command signal is output to the slave sensors 5 to 12 (step S25). This acceleration data transmission request command signal includes an identification signal that is information of an identifier. That is, the acceleration data transmission request command signal is a signal transmitted to each of the slave sensors 5 to 12.

  For example, when the identification signal included in the acceleration data transmission request command signal is the first identifier, the sensor communication circuit 5a of the slave sensor 5 transmits the acceleration data transmission request command signal via the high side communication bus 3a. Enter. Then, the sensor communication circuit 5a outputs an acceleration data signal (response signal in the present invention) obtained by adding identifier information to the acceleration data detected by the sensor 5c to the collision processing unit 213 via the low side communication bus 3b. The same applies to the other slave sensors 6-12. However, the acceleration data transmission request command signal is not output to the slave sensor stored as use prohibition. That is, the collision processing unit 212 outputs an acceleration data transmission request command signal only to a slave sensor that can be used.

  Then, the collision processing unit 213 inputs acceleration data signals including the respective identifier information from the respective slave sensors 5 to 12 (step S26). Subsequently, it is determined whether or not a collision has occurred based on the input acceleration data signal (step S27). And when it determines with not colliding (step S27: No), a process is complete | finished as it is. On the other hand, when it determines with having collided (step S27: Yes), an ignition signal is output to the ignition circuit 24 (step S28).

The schematic diagram of the whole structure of the airbag apparatus 1 of this embodiment is shown. 1 is a block diagram of the airbag device 1. FIG. In particular, a block diagram of slave sensors 5-7 is shown. It is a flowchart which shows the identifier provision process by the identifier provision part 211. FIG. 5 is a flowchart showing a failure detection process by a failure detection unit 214. 6 is a flowchart illustrating a collision process performed by a collision processing unit 213.

Explanation of symbols

1: airbag device, 2: airbag ECU, 3, 4: communication bus,
5-12: Slave sensor

Claims (6)

A master device;
A plurality of slave devices daisy chained to the master device via a communication bus;
A bus communication system comprising:
Each said slave device is
When a switching signal output from the master device is input, switching means for switching communication disconnection between the master device or the previous slave device and the subsequent slave device;
When the switching means of the slave device on the previous stage side is connected, and when an identifier giving signal output from the master device is input, each identifier is acquired, and an identifier acquisition signal is transmitted to the master device. An identifier acquisition means for outputting to the device;
Identifier storage means for storing the identifier acquired by the identifier acquisition means;
When a command signal output from the master device is input, if the identification signal included in the input command signal matches the identifier acquired by the identifier acquisition means, a response signal to the command signal is transmitted to the master signal. Response means for outputting to the device;
With
The bus communication system further determines that normal identifiers have been assigned to all the slave devices based on the identifier acquisition signal when the identifier acquisition signal is input from the identifier acquisition means, and is normal When it is determined that an identifier has been assigned, an identifier storage permission unit that allows the identifier storage unit to store the identifier is provided,
The master device is
After the storage of the identifier is permitted by the identifier storage permission unit, the command signal is output, and when the response signal to the command signal is not input from the response unit, an open failure of the switching unit of the slave device is detected A bus communication system comprising failure detecting means.   2. The bus communication system according to claim 1, wherein the failure detection means specifies an open failure position among the switching means.   The failure detection means sequentially outputs the command signal to the slave device from the front side to the rear side, and sequentially connects the switching means of the slave devices from the front side to the rear side. 3. The bus communication system according to claim 2, wherein the switching means connected when the response signal to the command signal is no longer input from the response means is set as an open failure position.   4. The bus communication system according to claim 2, wherein the master device includes use prohibition processing means that performs use prohibition processing for the slave device on the rear stage side from the slave device including the switching means that is the open failure position. 5.   5. The identifier storage permission unit according to claim 1, wherein the identifier storage permitting unit determines that a normal identifier has been assigned when the number of types of the identifier matches a preset number of the slave devices. 6. Bus communication system.   The bus communication system according to claim 1, wherein the slave device is a collision detection sensor of a vehicle occupant protection device.

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