>1)−(t3−t2))/2. The time synchronization processing unit 55 then updates the propagation delay time Td1 stored in the storage unit 53 to the newly calculated propagation delay time Td1.

Correction of Time in Switching Device

The master functional unit 111A periodically or irregularly transmits a Sync message to the switching device 101. After transmitting the Sync message, the functional unit 111A also transmits a follow-up message (Follow_Up) that includes a transmission time tm of the Sync message to the switching device 101.

The control unit 62 of the switching device 101 receives the Sync message and the follow-up message that were transmitted from the functional unit 111A, via the communication port 54A. The control unit 62 then notifies the time synchronization processing unit 55 of the time tm included in the follow-up message and a reception time tx of the Sync message.

The time synchronization processing unit 55 performs time synchronization with the functional unit 111A based on the times tm and tx notified from the control unit 62 and the propagation delay time Td1 stored in the storage unit 53. More specifically, based on the times tm and tx and the propagation delay time Td1, the time synchronization processing unit 55 calculates a time difference Tx1=tm−Td1−tx, which is the difference between the time in the functional unit 111A and the time in the switching device 101.

The time synchronization processing unit 55 corrects the time in the switching device 101 using the calculated time difference Tx1. Accordingly, time synchronization is achieved between the functional unit 111A and the switching device 101.

Slave Functional Unit

FIG. 4 is a diagram illustrating the configuration of the slave functional unit according to this embodiment of the present disclosure. As shown in FIG. 4, the slave functional unit 111B includes a processing unit 80, a communication unit 81, a communication port 84, and a storage unit 85. The processing unit 80 includes a detection unit 82 and a time synchronization processing unit 83. The processing unit 80 and the communication unit 81 are each realized by a processor such as a CPU or a DSP, for example. The storage unit 85 is a non-volatile memory, for example.

The communication port 84 is a terminal to which an Ethernet cable 10 can be connected, for example. Note that the communication port 84 may be an integrated circuit terminal or the like. The communication port 84 is connected to the switching device 101 via an Ethernet cable 10.

Updating of Data Propagation Delay Time Between Switching Device and Slave Functional Unit

The functional unit 111B updates a data propagation delay time Td2 between the switching device 101 and the functional unit 111B.

FIG. 5 is a diagram for describing a propagation delay time updating method performed by the functional unit according to this embodiment of the present disclosure.

More specifically, as shown in FIGS. 4 and 5, similarly to the detection unit 52 in the switching device 101 shown in FIG. 2, the detection unit 82 detects the occurrence of an update event regarding the propagation delay time Td2, and notifies the time synchronization processing unit 83 of the occurrence of the update event.

Similarly to the time synchronization processing unit 55 of the switching device 101 shown in FIG. 2, the time synchronization processing unit 83 receives the notification of the occurrence of the update event from the detection unit 82, and accordingly updates the data propagation delay time Td2 between the switching device 101 and the functional unit 111B. More specifically, the time synchronization processing unit 83 transmits a request message for requesting time information used for updating the propagation delay time Td2, to the switching device 101 via the communication unit 81 and the communication port 84.

When the request message transmitted from the functional unit 111B is received via the communication port 54B, the control unit 62 of the switching device 101 outputs the request message to the time synchronization processing unit 55.

Upon receiving the request message from control unit 62, the time synchronization processing unit 55 transmits a response message in response to the request message, to the functional unit 111B via the relay unit 51 and the communication port 54B. At this time, the time synchronization processing unit 55 also transmits a reception time t12 of the request message in the response message.

After transmitting the response message, the time synchronization processing unit 55 also transmits a follow-up message that includes a transmission time t13 of the response message to the functional unit 111B via the relay unit 51 and the communication port 54B.

The response message and the follow-up message that were transmitted from the switching device 101 are received by the communication unit 81 of the functional unit 111B via the communication port 84. The communication unit 81 then notifies the time synchronization processing unit 83 of the time t12 included in the response message and the time t13 included in the follow-up message. The communication unit 81 also notifies the time synchronization processing unit 83 of a transmission time t11 of the request message and a reception time t14 of the response message.

The time synchronization processing unit 83 calculates the data propagation delay time Td2 between the switching device 101 and the functional unit 111B based on the times t11, t12, t13, and t14 notified from the communication unit 81. Specifically, the time synchronization processing unit 83 performs the following calculation: propagation delay time Td2=((t14−t11)−(t13−t12))/2. The time synchronization processing unit 83 then updates the propagation delay time Td2 stored in the storage unit 85 to the newly calculated propagation delay time Td2.

Correction of Time in Slave Functional Unit

The time synchronization processing unit 55 of the switching device 101 periodically or irregularly transmits a Sync message to the slave-side functional unit 111B. After transmitting the Sync message, the time synchronization processing unit 55 also transmits a follow-up message that includes a transmission time ty of the Sync message to the functional unit 111B.

The communication unit 81 of the functional unit 111B receives the Sync message and the follow-up message that were transmitted from the switching device 101, via the communication port 84. The communication unit 81 then notifies the time synchronization processing unit 83 of the time ty included in the follow-up message and a reception time ts of the Sync message.

The time synchronization processing unit 83 performs time synchronization with the switching device 101 based on the times ty and ts notified from the communication unit 81 and the propagation delay time Td2 stored in the storage unit 85. More specifically, the time synchronization processing unit 83 calculates a time difference Tx2=ty−Td2−ts, which is the difference between the time in the switching device 101 and the time in the functional unit 111B. The time synchronization processing unit 83 then uses the calculated time difference Tx2 to correct the time in the functional unit 111B.

Here, when time synchronization is achieved between the master functional unit 111A and the switching device 101, the time ty included in the follow-up message transmitted from the switching device 101 to the functional unit 111B is synchronized with the time in the functional unit 111A. For this reason, the time synchronization processing unit 83 of the functional unit 111B performs time correction to achieve time synchronization between the functional unit 111B and the switching device 101, and as a result, time synchronization is achieved between the functional unit 111B and the functional unit 111A.

Variation of Switching Device

The time synchronization processing unit 55 of the switching device 101 may be configured to transmit a request message to the functional unit 111A not only in the case of receiving a notification of the occurrence of an update event from the detection unit 52, but also in the case of receiving a request message from the functional unit 111B.

In other words, upon receiving a request message for requesting time information used for updating the propagation delay time Td2 from the functional unit 111B, the time synchronization processing unit 55 transmits a response message and a follow-up message to the functional unit 111B, and also transmits a request message for requesting time information used for updating the propagation delay time Td1 to functional unit 111A.

Other Specific Examples of Update Events

The detection unit 52 of the switching device 101 and the detection unit 82 of the functional unit 111B are each not limited to being configured to detect that the ignition switch of the vehicle 1 was switched on as an update event, and may be configured to detect another event in which the propagation delay time possibly changes as an update event.

Specific Example 1

The detection unit 52 of the switching device 101 and the detection unit 82 of the functional unit 111B may each detect, as an update event, that the configuration of the in-vehicle network system 301 that includes the in-vehicle device has been changed.

FIG. 6 is a diagram showing a state in which the configuration of the in-vehicle network system according to the embodiment of the present disclosure has been changed. As shown in FIG. 6, here, a switching device 101B (switching device 101) and a slave functional unit 111C have been added to the in-vehicle network system 301 that includes the master functional unit 111A, a switching device 101A (switching device 101), and the slave functional unit 111B.

For example, the switching device 101B is connected to the switching device 101A via an Ethernet cable 10, and the functional unit 111C is connected to the switching device 101B via an Ethernet cable 10. The configurations of the switching devices 101A and 101B are similar to the configuration of the switching device 101 shown in FIG. 2. Also, the configuration of the functional unit 111C is similar to the configuration of the functional unit 111B shown in FIG. 4.

By detecting that the power supply of the functional unit 111C was switched on, for example, the detection unit 82 of the functional unit 111C detects, as an update event, that the functional unit 111C has been added to the in-vehicle network system 301. The detection unit 82 notifies the time synchronization processing unit 83 of the occurrence of the update event.

Upon receiving the notification of the occurrence of the update event from the detection unit 82, the time synchronization processing unit 83 of the functional unit 111C performs operations similar to those performed by the time synchronization processing unit 83 of the functional unit 111B described above. Specifically, the time synchronization processing unit 83 of the functional unit 111C transmits a request message for requesting time information used for updating a data propagation delay time Td3 between the switching device 101B and the functional unit 111C, to the switching device 101B via the communication unit 81.

The time synchronization processing unit 83 receives a response message and a follow-up message from the switching device 101B, and updates the propagation delay time Td3 and corrects the time in the functional unit 111C based on the response message and the follow-up message.

Also, by detecting that the power supply of the switching device 101B was switched on, for example, the detection unit 52 of the switching device 101B detects, as an update event, that the switching device 101B has been added to the in-vehicle network system 301. The detection unit 52 notifies the time synchronization processing unit 55 of the occurrence of the update event.

Upon receiving the notification of the occurrence of the update event from the detection unit 52, the time synchronization processing unit 55 of the switching device 101B transmits a request message for requesting time information used for updating a data propagation delay time Td4 between the switching device 101A and the switching device 101B, to the switching device 101A via the relay unit 51.

The time synchronization processing unit 55 receives a response message and a follow-up message from the switching device 101A, and updates the propagation delay time Td4 and corrects the time in the switching device 101B based on the response message and the follow-up message.

Note that cases of a change in the configuration of the in-vehicle network system 301 include not only the case where an in-vehicle device such as a switching device 101 or a functional unit 111 was physically added to the in-vehicle network system 301, but also the case where the power supply of an in-vehicle device already included in the in-vehicle network system 301 was switched from off to on.

Also, the switching device 101B may be configured to transmit a request message to the switching device 101A not only in the case where the occurrence of an update event was detected, but also in the case where a request message was received from the functional unit 111C.

Specific Example 2

The in-vehicle network system 301 may further include a temperature sensor. In this case, the detection unit 52 of the switching device 101 and the detection unit 82 of the functional unit 111B may each detect, as the update event, that the temperature inside the vehicle 1 satisfies a predetermined condition.

FIG. 7 is a diagram showing a configuration in which the in-vehicle network system according to this embodiment of the present disclosure includes temperature sensors. As shown in FIG. 7, here, the in-vehicle network system 301 includes two temperature sensors 151A and 151B. For example, the temperature sensor 151A measures the temperature of the switching device 101 and outputs a measurement signal indicating the measurement result to the detection unit 52 of the switching device 101. The temperature sensor 151B measures the temperature of the functional unit 111B and outputs a measurement signal indicating the measurement result to the detection unit 82 of the functional unit 111B. Note that the temperature sensors 151A and 151B may measure the temperatures of the communication lines connected to the switching device 101 and the functional unit 111B, as the temperature in vehicle 1, for example.

The detection unit 52 of the switching device 101 determines whether or not the temperature in the vehicle 1 satisfies a predetermined condition based on the measurement signal received from the temperature sensor 151A. For example, if the temperature of the switching device 101 is greater than or equal to a predetermined threshold value, the detection unit 52 determines that the temperature inside the vehicle 1 satisfies the predetermined condition, and notifies the time synchronization processing unit 55 of the occurrence of an update event.

Upon receiving notification of the occurrence of the update event from the detection unit 52, the time synchronization processing unit 55 transmits a request message to the master functional unit 111A. The time synchronization processing unit 55 receives a response message and a follow-up message from the functional unit 111A, and corrects the time in the switching device 101 based on the response message and the follow-up message.

Also, the detection unit 82 of the functional unit 111B determines whether or not the temperature inside the vehicle 1 satisfies a predetermined condition based on the measurement signal received from the temperature sensor 151B. For example, if the temperature of the functional unit 111B is greater than or equal to a predetermined threshold value, the detection unit 82 determines that the temperature inside the vehicle 1 satisfies the predetermined condition, and notifies the time synchronization processing unit 83 of the occurrence of an update event.

Upon receiving the notification of the occurrence of the update event from the detection unit 82, the time synchronization processing unit 83 transmits a request message to the switching device 101. The time synchronization processing unit 83 receives a response message and a follow-up message from the switching device 101, and corrects the time in the functional unit 111B based on the response message and the follow-up message.

Note that the temperature sensor 151A may be built into the switching device 101. Also, the temperature sensor 151B may be built into the functional unit 111B.

Operation Flow

Next, an operation procedure when the master functional unit 111A, the switching device 101, and the slave functional unit 111B perform propagation delay time updating and time correction in the in-vehicle network system 301 will be described with reference to drawings.

The devices in the in-vehicle network system 301 each have a computer that includes a memory, and in each of such devices, an arithmetic processing unit such as a CPU in the computer reads out, from the memory, a program that includes part or all of the steps of the sequence described below, and executes the program. The programs executed by the devices can be installed from an external source. The programs executed by the devices are stored on recording media and distributed in such a form.

Example 1

FIG. 8 is a diagram showing a sequence (Example 1) of propagation delay time updating and time correction performed by in-vehicle devices in the in-vehicle network system according to this embodiment of the present disclosure. Here, a case will be described in which the switching device 101 detects the occurrence of an update event and transmits a request message to the functional unit 111A.

As shown in FIG. 8, first, it is assumed that the ignition switch of the vehicle 1 is switched on, and the in-vehicle network system 301 accordingly starts up (step S101).

Next, the detection unit 52 of the switching device 101 detects, as an update event, that the ignition switch of the vehicle 1 was switched on, and notifies the time synchronization processing unit 55 of the occurrence of the update event (step S102).

Also, the detection unit 82 of the functional unit 111B detects, as an update event, that the ignition switch of the vehicle 1 was switched on, and notifies the time synchronization processing unit 83 of the occurrence of the update event (step S103).

Next, upon receiving the notification of the occurrence of the update event from the detection unit 52, the time synchronization processing unit 55 of the switching device 101 transmits a request message for requesting time information to the functional unit 111A via the relay unit 51 and the communication port 54A (step S104).

Next, the functional unit 111A transmits a response message to the switching device 101 in response to the request message transmitted from the switching device 101. At this time, the functional unit 111A includes the reception time t2 of the request message in the response message (step S105).

After transmitting the response message, the functional unit 111A then transmits a follow-up message that includes the transmission time t3 of the response message to the switching device 101 (step S106).

Next, the control unit 62 of the switching device 101 receives the response message and the follow-up message that were transmitted from the functional unit 111A, and notifies the time synchronization processing unit 55 of the time t2 included in the response message and the time t3 included in the follow-up message. Also, the control unit 62 notifies the time synchronization processing unit 55 of the transmission time t1 of the request message and the reception time t4 of the response message (step S107).

The time synchronization processing unit 55 updates the data propagation delay time Td1 between the functional unit 111A and the switching device 101 based on the times t1, t2, t3, and t4 notified from the control unit 62 (step S108).

Next, upon receiving the notification of the occurrence of the update event from the detection unit 82, the time synchronization processing unit 83 of the functional unit 111B transmits a request message for requesting time information to the switching device 101 via the communication unit 81 and the communication port 84 (step S109).

Next, when the request message transmitted from the functional unit 111B is received via the communication port 54B and the control unit 62, the time synchronization processing unit 55 of the switching device 101 transmits a response message, in response to the request message, to the functional unit 111B via the relay unit 51 and the communication port 54B. At this time, the time synchronization processing unit 55 includes the reception time t12 of the request message in the response message (step S110).

Next, after transmitting the response message, the time synchronization processing unit 55 transmits a follow-up message that includes the transmission time t13 of the response message to the functional unit 111B via the relay unit 51 (step S111).

Next, when the response message and the follow-up message that were transmitted from the switching device 101 are received via the communication port 84, the communication unit 81 of the functional unit 111B notifies the time synchronization processing unit 83 of the time t12 included in the response message and the time t13 includes in the follow-up message. Also, the communication unit 81 notifies the time synchronization processing unit 83 of the transmission time t11 of the request message and the reception time t14 of the response message (step S112).

The time synchronization processing unit 83 updates the data propagation delay time Td2 between the switching device 101 and the functional unit 111B based on the times t11, t12, t13, and t14 notified from the communication unit 81 (step S113).

Next, the functional unit 111A transmits a Sync message to the switching device 101 (step S114).

Next, the functional unit 111A transmits a follow-up message that includes the transmission time tm of the Sync message to the switching device 101 (step S115).

Next, when the Sync message and the follow-up message that were transmitted from the functional unit 111A are received via the communication port 54A, the control unit 62 of the switching device 101 notifies the time synchronization processing unit 55 of the time tm included in the follow-up message and the reception time tx of the Sync message (step S116).

Next, based on the times tm and tx notified from the control unit 62 and the propagation delay time Td1 stored in the storage unit 53, the time synchronization processing unit 55 calculates the time difference Tx1=tm−Td1−tx between the time in the functional unit 111A and the time in the switching device 101.

Next, the time synchronization processing unit 55 of the switching device 101 transmits a Sync message to the functional unit 111B via the communication port 54B (step S118).

Next, the time synchronization processing unit 55 transmits a follow-up message that includes the transmission time ty of the Sync message to the functional unit 111B via the communication port 54B (step S119).

Next, when the Sync message and the follow-up message that were transmitted from the switching device 101 are received via the communication port 84, the communication unit 81 of the functional unit 111B notifies the time synchronization processing unit 83 of the time ty includes in the follow-up message and the reception time ts of the Sync message (step S120).

Next, based on the times ty and ts notified from the communication unit 81 and the propagation delay time Td2 stored in the storage unit 85, the time synchronization processing unit 83 calculates the time difference Tx2=ty−Td2−ts between the time in the switching device 101 and the time in the functional unit 111B.

The time synchronization processing unit 83 then uses the calculated time difference Tx2 to correct the time in the functional unit 111B. Accordingly, time synchronization is achieved between the functional unit 111B and the switching device 101, and as a result, time synchronization is achieved between the functional unit 111B and the functional unit 111A (step S121).

Note that the operations of steps S104 to S108 may be performed after the operations of steps S109 to S113. Moreover, the operations of steps S104 to S108 and the operations of steps S109 to S113 may be performed in parallel.

Also, the operations of steps S114 to S117 may be performed after the operations of steps S118 to S121. Moreover, the operations of steps S114 to S117 and the operations of steps S118 to S121 may be performed in parallel.

Example 2

FIG. 9 is a diagram showing a sequence (Example 2) of propagation delay time updating and time correction performed by in-vehicle devices in the in-vehicle network system according to this embodiment of the present disclosure.

Here, a case will be described in which the switching device 101 receives a request message transmitted from the functional unit 111B and accordingly transmits the request message to the functional unit 111A. As shown in FIG. 9, first, it is assumed that the configuration of in-vehicle network system 301 has been changed due to the power supply of the functional unit 111B being switched on (step S201).

Next, the detection unit 82 of the functional unit 111B detects that the power supply of the functional unit 111B was switched on, and notifies the time synchronization processing unit 83 of the occurrence of an update event (step S202).

Next, upon receiving the notification of the occurrence of the update event from the detection unit 82, the time synchronization processing unit 83 transmits a request message for requesting time information to the switching device 101 via the communication unit