Vehicle-mounted device, time synchronization method, and time synchronization program

Abstract

The in-vehicle device includes a processing unit that performs time synchronization with the other device based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and the other in-vehicle device, i.e., the other device, and detects the occurrence of an update event of the propagation delay time. When the processing unit detects the occurrence of the update event, it requests the other device for the time information used in the update of the propagation delay time.

Description

Technical Field

[0001] The present disclosure relates to an in-vehicle device, a time synchronization method, and a time synchronization program.

[0002] This application claims priority based on Japanese Patent Application No. 2020-134524 filed on August 7, 2020, and incorporates the entire contents disclosed therein herein. Background Art

[0003] In Japanese Unexamined Patent Application Publication No. 2013-168865 (Patent Document 1), the following in-vehicle network system is disclosed. That is, the in-vehicle network system includes an in-vehicle control device and a communication protocol issuing device. The in-vehicle control device includes a memory that stores definition data for defining a part installed on the in-vehicle network among communication protocols used on the in-vehicle network. The communication protocol issuing device issues the definition data to the in-vehicle control device. When the communication protocol issuing device receives a registration request for causing the in-vehicle control device to participate in the in-vehicle network from a registration device that causes the in-vehicle control device to participate in the in-vehicle network, based on authentication of the registration device, it creates the definition data that complies with the part installed on the in-vehicle network and sends it back to the registration device. The registration device receives the definition data sent by the communication protocol issuing device and requests the in-vehicle control device to store the received definition data in the memory. Then, the in-vehicle control device receives the definition data from the registration device, stores it in the memory, and communicates using the in-vehicle network in accordance with the part defined by the definition data and in compliance with the communication protocol.

[0004] Patent Document

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-168865 Summary of the Invention

[0006] The in-vehicle device of the present disclosure includes a processing unit that performs time synchronization with other devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When the processing unit detects the occurrence of the update event, it requests the other devices for time information used in the update of the propagation delay time.

[0007] The time synchronization method of the present disclosure includes the following steps: detecting the occurrence of an update event related to the update of the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices; requesting the time information used for the update of the propagation delay time from the other devices when the occurrence of the update event is detected; updating the propagation delay time based on the time information received from the other devices; and performing time synchronization with the other devices based on the updated propagation delay time.

[0008] The time synchronization program of the present disclosure is a time synchronization program used in an in-vehicle device. This program causes a computer to function as a processing unit. The processing unit performs time synchronization with other devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When the occurrence of the update event is detected, the processing unit requests the time information used for the update of the propagation delay time from the other devices.

[0009] One aspect of the present disclosure can be implemented as a semiconductor integrated circuit that realizes part or all of the in-vehicle device, or can be implemented as an in-vehicle network system including the in-vehicle device. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a diagram showing the structure of the in-vehicle network system according to an embodiment of the present disclosure.

[0011] Figure 2 is a diagram showing the structure of the switching device according to an embodiment of the present disclosure.

[0012] Figure 3 is a diagram for explaining the method for updating the propagation delay time implemented by the switching device according to an embodiment of the present disclosure.

[0013] Figure 4 is a diagram showing the structure of the slave-side functional unit according to an embodiment of the present disclosure.

[0014] Figure 5 is a diagram for explaining the method for updating the propagation delay time implemented by the functional unit according to an embodiment of the present disclosure.

[0015] Figure 6 is a diagram showing a state in which the structure of the in-vehicle network system according to an embodiment of the present disclosure is changed.

[0016] Figure 7 is a diagram showing the structure of the in-vehicle network system according to an embodiment of the present disclosure including a temperature sensor.

[0017] Figure 8 This is a diagram showing a sequence (Example 1) of updating the propagation delay time and correcting the time performed by multiple in-vehicle devices in the in-vehicle network system related to the embodiments of the present disclosure.

[0018] Figure 9 This is a diagram showing a sequence (Example 2) of updating the propagation delay time and correcting the time performed by multiple in-vehicle devices in the in-vehicle network system related to the embodiments of the present disclosure. Detailed Embodiments

[0019] Conventionally, technologies related to in-vehicle networks having multiple in-vehicle devices have been developed.

[0020] [Problems to be Solved by the Present Disclosure]

[0021] In an in-vehicle network, each in-vehicle device updates the propagation delay time of data between in-vehicle devices at regular intervals according to a protocol specified by a standard such as IEEE 802.1, and uses the updated propagation delay time for time synchronization between in-vehicle devices.

[0022] However, when updating the propagation delay time of data, due to the update process, the processing load becomes large, and it may not be possible to smoothly perform other processes such as processes related to vehicle driving control.

[0023] The present disclosure has been completed to solve the above problems, and an object thereof is to provide an in-vehicle device, a time synchronization method, and a time synchronization program that can smoothly perform time synchronization using the propagation delay time of data between in-vehicle devices and reduce the load of the update process.

[0024] [Effects of the Present Disclosure]

[0025] According to the present disclosure, it is possible to smoothly perform time synchronization using the propagation delay time of data between in-vehicle devices and reduce the load of the update process.

[0026] [Description of Embodiments of the Present Disclosure]

[0027] First, the content of the embodiments of the present disclosure will be listed and described.

[0028] (1) The in-vehicle device according to the embodiment of the present disclosure includes a processing unit that performs time synchronization with other in-vehicle devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When the processing unit detects the occurrence of the update event, it requests the other device for the time information used in the update of the propagation delay time.

[0029] Thus, a structure that requests time information when an update event is detected and updates the propagation delay time using the time information can suppress the frequency of update processing to a lower level compared to the case where update processing is performed periodically. Therefore, it is possible to smoothly perform time synchronization using the propagation delay time of data between in-vehicle devices and reduce the load of update processing.

[0030] (2) Preferably, the processing unit detects that the ignition switch of the vehicle on which the present device is mounted is switched to the ON state as the update event.

[0031] When the ignition switch of the vehicle is switched to the ON state, the in-vehicle devices in the vehicle start, and the propagation delay time of data between in-vehicle devices may change. By having a structure that can detect an event in which the propagation delay time may change by focusing on this, it is possible to perform the update processing of the propagation delay time at a more appropriate timing.

[0032] (3) Preferably, the processing unit detects that the structure of the in-vehicle network including the present device is changed as the update event.

[0033] For example, since a new in-vehicle device is added to the in-vehicle network, the propagation delay time of data between in-vehicle devices may change. By having a structure that can detect an event in which the propagation delay time may change by focusing on this, it is possible to perform the update processing of the propagation delay time at a more appropriate timing.

[0034] (4) Preferably, the processing unit detects that the temperature inside the vehicle on which the present device is mounted satisfies a predetermined condition as the update event.

[0035] Along with the change in the temperature inside the vehicle, the propagation delay time of data between in-vehicle devices may change. By having a structure that can detect an event in which the propagation delay time may change by focusing on this, it is possible to perform the update processing of the propagation delay time at a more appropriate timing.

[0036] (5) More preferably, the temperature inside the vehicle is the temperature of the communication line between the present device and the other device.

[0037] With such a structure, it is possible to detect a more appropriate event as an event in which the propagation delay time of data may change.

[0038] (6) Preferably, the in-vehicle device further includes a switch unit for relaying data between the other devices, i.e., the first other device and the second other device. The first other device sends a first time information request for requesting an update of the propagation delay time of data between the in-vehicle device and the first other device itself to the in-vehicle device. The switch unit receives the first time information request from the first other device and outputs the received first time information request to the processing unit. When receiving the first time information request from the switch unit, the processing unit outputs a second time information request for requesting the second time information used for updating the propagation delay time of data between the second other device and the in-vehicle device to the switch unit. The switch unit sends the second time information request received from the processing unit to the second other device.

[0039] Thus, with the structure of requesting time information from the second other in-vehicle device when receiving a request for time information from the first other in-vehicle device, even when an update event that is not detected by the in-vehicle device equipped with the switch unit occurs, the propagation delay time update process can be performed in this in-vehicle device.

[0040] (7) The time synchronization method according to an embodiment of the present disclosure is a time synchronization method in an in-vehicle device, and the time synchronization method includes the following steps: detecting the occurrence of an update event related to the update of the propagation delay time of data between the in-vehicle device itself, i.e., the in-vehicle device, and other in-vehicle devices, i.e., other devices; requesting time information used for updating the propagation delay time from the other devices when detecting the occurrence of the update event; updating the propagation delay time based on the time information received from the other devices; and performing time synchronization with the other devices based on the updated propagation delay time.

[0041] Thus, the method of requesting time information when detecting the occurrence of an update event and performing an update process of the propagation delay time using the time information can suppress the update process frequency to be lower compared with the case of performing the update process regularly. Therefore, it is possible to smoothly perform time synchronization using the propagation delay time of data between in-vehicle devices and reduce the load of the update process.

[0042] (8) The time synchronization program related to the embodiments of the present disclosure is a time synchronization program used in a vehicle-mounted device. This program enables a computer to function as a processing unit. The processing unit performs time synchronization with other vehicle-mounted devices based on the propagation delay time of data between its own vehicle-mounted device, i.e., this device, and other vehicle-mounted devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When the processing unit detects the occurrence of the update event, it requests the time information used for the update of the propagation delay time from the other devices.

[0043] In this way, the structure that requests time information when detecting the occurrence of an update event and performs the update process of the propagation delay time using this time information can suppress the frequency of the update process to a lower level compared with the case of performing the update process regularly. Therefore, it is possible to smoothly perform time synchronization using the propagation delay time of data between vehicle-mounted devices and reduce the load of the update process.

[0044] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In addition, the same or corresponding parts in the drawings are given the same reference numerals, and their descriptions will not be repeated. Additionally, at least a part of the embodiments described below can be arbitrarily combined.

[0045] <Structure and basic operation>

[0046] [Overall structure]

[0047] Figure 1 is a diagram showing the structure of a vehicle-mounted network system related to the embodiments of the present disclosure. Refer to Figure 1 , the vehicle-mounted network system 301 is mounted on the vehicle 1 and includes a switch device 101 and a plurality of functional units 111. In Figure 1 , as an example, two functional units 111A and 111B are shown as the functional units 111. The switch device 101 and each functional unit 111 are vehicle-mounted devices, for example, ECUs (Electronic Control Units).

[0048] The switch device 101 is connected to the plurality of functional units 111, for example, through an Ethernet (registered trademark) cable 10, and can communicate with the plurality of functional units 111 connected to itself.

[0049] Specifically, the switch device 101 performs relay processing for relaying data from the functional unit 111 to other functional units 111. Between the switch device 101 and the functional unit 111, for example, information is exchanged using Ethernet frames storing IP packets.

[0050] The functional unit 111 is an in-vehicle communication ECU, a sensor, a camera, a navigation device, an autonomous driving processing ECU, an engine control device, an AT (Automatic Transmission) control device, an HEV (Hybrid Electric Vehicle) control device, a brake control device, a vehicle frame control device, a steering control device, an instrument display control device, etc.

[0051] [Switching device]

[0052] Figure 2 It is a diagram showing the structure of the switching device according to the embodiment of the present disclosure. Refer to Figure 2 , the switching device 101 includes a processing unit 50, a relay unit 51, a storage unit 53, and a plurality of communication ports 54. The relay unit 51 includes a switch unit 61 and a control unit 62. The processing unit 50 includes a detection unit 52 and a time synchronization processing unit 55. The processing unit 50 and the relay unit 51 are implemented by processors such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor), for example.

[0053] (Relay processing)

[0054] The communication port 54 is, for example, a terminal capable of connecting an Ethernet cable 10. In addition, the communication port 54 may also be a terminal of an integrated circuit. Each of the plurality of communication ports 54 is connected to one of the plurality of functional units 111 via the Ethernet cable 10. In this example, the communication port 54A is connected to the functional unit 111A, and the communication port 54B is connected to the functional unit 111B.

[0055] The storage unit 53 is, for example, a non-volatile memory. In the storage unit 53, an address table Ta1 indicating the correspondence between the port number of the communication port 54 and the MAC (Media Access Control) address of the connection target device is stored.

[0056] The switch unit 61 relays data between other in-vehicle devices. That is, when the switch unit 61 receives an Ethernet frame sent from the functional unit 111 via the communication port 54 corresponding to the functional unit 111, it performs relay processing on the received Ethernet frame.

[0057] More specifically, the switch unit 61 refers to the address table Ta1 stored in the storage unit 53 to determine the port number corresponding to the destination MAC address included in the received Ethernet frame. And the switch unit 61 sends the received Ethernet frame from the communication port 54 of the determined port number.

[0058] (Update of Propagation Delay Time of Data between Functional Unit on Master Side and Switching Device)

[0059] The switching device 101 updates the propagation delay time Td1 of data between the functional unit 111 on the master side and itself. Here, it is assumed that the functional unit 111A is the functional unit 111 on the master side, and the functional unit 111B is the functional unit 111 on the slave side. The functional unit 111A holds the reference time in the in-vehicle network system 301.

[0060] Figure 3 It is a diagram for explaining the method of updating the propagation delay time implemented by the switching device according to the embodiment of the present disclosure.

[0061] More specifically, referring to Figure 2 and Figure 3 , the detection unit 52 detects the occurrence of an update event of the propagation delay time Td1. For example, the detection unit 52 detects that the in-vehicle network system 301 has started, that is, the ignition switch of the vehicle 1 has been switched to ON, as an update event. Then, the detection unit 52 notifies the time synchronization processing unit 55 of the occurrence of the detected update event.

[0062] When the time synchronization processing unit 55 receives a notification of the occurrence of an update event from the detection unit 52, it updates the propagation delay time Td1 of data between the functional unit 111A and the switching device 101. More specifically, the time synchronization processing unit 55 sends a time information request (Pdelay_Req) for requesting the time information used in the update of the propagation delay time Td1 to the functional unit 111A via the relay unit 51 and the communication port 54A. Hereinafter, the time information request is also referred to as a "request message".

[0063] When the functional unit 111A receives the request message sent from the switching device 101, it sends the time information (Pdelay_Resp) of the request message to the switching device 101. At this time, the functional unit 111A includes the reception time t2 of the request message in the time information and sends it. Hereinafter, the time information is also referred to as a "response message".

[0064] In addition, after sending the response message, the functional unit 111A sends a follow-up message (Pdelay_Resp_Follow_Up) including the transmission time t3 of the response message to the switching device 101.

[0065] The control unit 62 in the switching device 101 receives the response message and the follow-up message sent from the functional unit 111A via the communication port 54A. Then, the control unit 62 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. In addition, 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.

[0066] Based on the times t1, t2, t3, and t4 notified from the control unit 62, the time synchronization processing unit 55 calculates the propagation delay time Td1 of the data between the functional unit 111A and the switching device 101. Specifically, the time synchronization processing unit 55 calculates the propagation delay time Td1 = ((t4 - t1) - (t3 - t2)) / 2. Then, the time synchronization processing unit 55 updates the propagation delay time Td1 stored in the storage unit 53 to the newly calculated propagation delay time Td1.

[0067] (Calibration of the time in the switching device)

[0068] The master functional unit 111A periodically or aperiodically sends a Sync (synchronization) message to the switching device 101. In addition, after sending the Sync message, the functional unit 111A sends a follow-up message (Follow_Up) containing the transmission time tm of the Sync message to the switching device 101.

[0069] The control unit 62 in the switching device 101 receives the Sync message and the follow-up message sent from the functional unit 111A via the communication port 54A. Then, the control unit 62 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.

[0070] Based on the times tm, 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 performs time synchronization with the functional unit 111A. More specifically, the time synchronization processing unit 55 calculates the time difference Tx1 between the time of the functional unit 111A and the time of the switching device 101, that is, the time difference Tx1 = tm - Td1 - tx, based on the times tm, tx, and the propagation delay time Td1.

[0071] Then, the time synchronization processing unit 55 uses the calculated time difference Tx1 to correct the time in its own switching device 101. Thus, the time synchronization between the functional unit 111A and the switching device 101 is established.

[0072] [Slave functional unit]

[0073] Figure 4 is a diagram showing the structure of the slave functional unit according to the embodiment of the present disclosure. Refer to Figure 4, the functional unit 111B on the slave side 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 implemented by processors such as a CPU and a DSP, for example. The storage unit 85 is a non-volatile memory, for example.

[0074] The communication port 84 is a terminal capable of connecting an Ethernet cable 10, for example. In addition, the communication port 84 may be a terminal of an integrated circuit or the like. The communication port 84 is connected to the switch device 101 via the Ethernet cable 10.

[0075] (Update of the propagation delay time of data between the switch device and the functional unit on the slave side)

[0076] The functional unit 111B updates the propagation delay time Td2 of data between the switch device 101 and itself.

[0077] Figure 5 This is a diagram for explaining the method of updating the propagation delay time implemented by the functional unit according to the embodiment of the present disclosure.

[0078] More specifically, referring to Figure 4 and Figure 5 , the detection unit 82, similar to the detection unit 52 in the switch device 101 shown in Figure 2 , detects the occurrence of an update event of the propagation delay time Td2 and notifies the time synchronization processing unit 83 of the occurrence of the update event.

[0079] The time synchronization processing unit 83, similar to the time synchronization processing unit 55 in the switch device 101 shown in Figure 2 , when receiving a notification of the occurrence of an update event from the detection unit 82, updates the propagation delay time Td2 of data between the switch device 101 and its own functional unit 111B. More specifically, the time synchronization processing unit 83 sends a request message for requesting the time information used in the update of the propagation delay time Td2 to the switch device 101 via the communication unit 81 and the communication port 84.

[0080] When the control unit 62 in the switch device 101 receives the request message sent from the functional unit 111B via the communication port 54B, it outputs the request message to the time synchronization processing unit 55.

[0081] When the time synchronization processing unit 55 receives the request message from the control unit 62, it sends a response message to the functional unit 111B for the request message 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 and sends it.

[0082] In addition, after sending the response message, the time synchronization processing unit 55 sends a follow-up message including the transmission time t13 of the response message to the functional unit 111B via the relay unit 51 and the communication port 54B.

[0083] The communication unit 81 in the functional unit 111B receives the response message and the follow-up message sent from the switch device 101 via the communication port 84. Then, the communication unit 81 notifies the time t12 included in the response message and the time t13 included in the follow-up message to the time synchronization processing unit 83. In addition, the communication unit 81 notifies the transmission time t11 of the request message and the reception time t14 of the response message to the time synchronization processing unit 83.

[0084] Based on the times t11, t12, t13, and t14 notified from the communication unit 81, the time synchronization processing unit 83 calculates the propagation delay time Td2 of the data between the switch device 101 and the functional unit 111B. Specifically, the time synchronization processing unit 83 calculates the propagation delay time Td2 = ((t14 - t11) - (t13 - t12)) / 2. Then, the time synchronization processing unit 83 updates the propagation delay time Td2 stored in the storage unit 85 to the newly calculated propagation delay time Td2.

[0085] (Calibration of the time in the slave-side functional unit)

[0086] The time synchronization processing unit 55 in the switch device 101 sends a Sync message to the slave-side functional unit 111B regularly or irregularly. In addition, after sending the Sync message, the time synchronization processing unit 55 sends a follow-up message including the transmission time ty of the Sync message to the functional unit 111B.

[0087] The communication unit 81 in the functional unit 111B receives the Sync message and the follow-up message sent from the switch device 101 via the communication port 84. Then, the communication unit 81 notifies the time ty included in the follow-up message and the reception time ts of the Sync message to the time synchronization processing unit 83.

[0088] Based on the times ty, 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 performs time synchronization with the switch device 101. More specifically, the time synchronization processing unit 83 calculates the time difference Tx2 between the time of the switch device 101 and the time of the functional unit 111B, that is, the time difference Tx2 = ty - Td2 - ts. Then, the time synchronization processing unit 83 uses the calculated time difference Tx2 to correct the time in its own functional unit 111B.

[0089] Here, when the synchronization of the functional unit 111A on the master side with the switch device 101 is established, the time ty included in the follow-up message sent from the switch device 101 to the functional unit 111B is the time synchronized with the functional unit 111A. Therefore, through the time synchronization processing unit 83 in the functional unit 111B, time correction is performed, and the time synchronization between the functional unit 111B and the switch device 101 is established. As a result, the time synchronization between the functional unit 111B and the functional unit 111A is established.

[0090] [Modified Example of Switch Device]

[0091] The time synchronization processing unit 55 in the switch device 101 may also be structured as follows: not only when the detection unit 52 receives a notification of an update event occurrence, but also when a request message is received from the functional unit 111B, the request message is sent to the functional unit 111A.

[0092] That is, when the time synchronization processing unit 55 receives a request message for time information used in the update for requesting the propagation delay time Td2 from the functional unit 111B, a response message and a follow-up message are sent to the functional unit 111B, and further, a request message for time information used in the update for requesting the propagation delay time Td1 is sent to the functional unit 111A.

[0093] [Other Specific Examples of Update Events]

[0094] The detection unit 52 of the switch device 101 and the detection unit 82 of the functional unit 111B are each not limited to a structure in which the ignition switch of the vehicle 1 is switched to ON as an update event, and other events in which the propagation delay time may change can also be detected as update events.

[0095] (Specific Example 1)

[0096] The detection unit 52 of the switch device 101 and the detection unit 82 of the functional unit 111B can each also detect that the structure of the in-vehicle network system 301 of the in-vehicle device including itself has been changed as an update event.

[0097] Figure 6 is a diagram showing a state in which the structure of the in-vehicle network system according to the embodiment of the present disclosure has been changed. Refer to Figure 6 , here, it is assumed that the in-vehicle network system 301 including the functional unit 111A on the master side, the switch device 101A as the switch device 101, and the functional unit 111B on the slave side is further added with the switch device 101B as the switch device 101 and the functional unit 111C on the slave side.

[0098] For example, the switch device 101B is connected to the switch device 101A via the Ethernet cable 10, and the functional unit 111C is connected to the switch device 101B via the Ethernet cable 10. The structures of the switch devices 101A and 101B are the same as those of the switch device 101 shown in Figure 2 In addition, the structure of the functional unit 111C is the same as that of the functional unit 111B shown in Figure 4 .

[0099] The detection unit 82 in the functional unit 111C detects, for example, that the power supply of its own functional unit 111C is switched on, and detects that its own functional unit 111C is added to the in-vehicle network system 301 as an update event. Then, the detection unit 82 notifies the time synchronization processing unit 83 of the occurrence of the update event.

[0100] When the time synchronization processing unit 83 in the functional unit 111C receives the notification of the occurrence of the update event from the detection unit 82, it performs the same operation as the time synchronization processing unit 83 in the above-mentioned functional unit 111B. That is, the time synchronization processing unit 83 in the functional unit 111C sends a request message for requesting the time information used in the update of the propagation delay time Td3 of the data between the switch device 101B and the functional unit 111C to the switch device 101B via the communication unit 81.

[0101] Then, the time synchronization processing unit 83 receives the response message and the follow-up message from the switch device 101B, and based on the response message and the follow-up message, updates the propagation delay time Td3 and corrects the time of its own functional unit 111C.

[0102] In addition, the detection unit 52 in the switch device 101B detects, for example, that the power supply of its own switch device 101B is switched on, and detects that its own switch device 101B is added to the in-vehicle network system 301 as an update event. Then, the detection unit 52 notifies the time synchronization processing unit 55 of the occurrence of the update event.

[0103] When the time synchronization processing unit 55 in the switch device 101B receives the notification of the occurrence of the update event from the detection unit 52, it sends a request message for requesting the time information used in the update of the propagation delay time Td4 of the data between the switch device 101A and the switch device 101B to the switch device 101A via the relay unit 51.

[0104] Then, the time synchronization processing unit 55 receives the response message and the follow-up message from the switch device 101A, and based on the response message and the follow-up message, updates the propagation delay time Td4 and corrects the time of its own switch device 101B.

[0105] Further, changes in the structure of the in-vehicle network system 301 include not only cases where a switching device 101 or a functional unit 111, i.e., an in-vehicle device, is physically added to the in-vehicle network system 301, but also cases where the power supply of an in-vehicle device already included in the in-vehicle network system 301 is switched from off to on.

[0106] In addition, the switching device 101B may also be structured such that it transmits a request message to the switching device 101A not only when an update event is detected but also when a request message is received from the functional unit 111C.

[0107] (Specific Example 2)

[0108] The in-vehicle network system 301 may also be structured to 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 that the temperature inside the vehicle 1 satisfies a predetermined condition as an update event.

[0109] Figure 7 FIG. is a diagram showing the structure of the in-vehicle network system according to an embodiment of the present disclosure including a temperature sensor. Refer to Figure 7 , where the in-vehicle network system 301 is provided with two temperature sensors 151A and 151B. The temperature sensor 151A measures, for example, the temperature of the switching device 101 and outputs a measurement signal indicating the measurement result to the detection unit 52 in 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 in the functional unit 111B. In addition, each of the temperature sensors 151A and 151B may measure, for example, the temperature of the communication line between the switching device 101 and the functional unit 111B as the temperature inside the vehicle 1.

[0110] The detection unit 52 in the switching device 101 determines whether the temperature inside the vehicle 1 satisfies a predetermined condition based on the measurement signal received from the temperature sensor 151A. For example, when the temperature of the switching device 101 is equal to or higher than a predetermined threshold value, the detection unit 52 determines that the temperature inside the vehicle 1 satisfies the predetermined condition and notifies the occurrence of an update event to the time synchronization processing unit 55.

[0111] When the time synchronization processing unit 55 receives a notification of the occurrence of an update event from the detection unit 52, it sends a request message to the master-side functional unit 111A. Then, the time synchronization processing unit 55 receives a response message and a follow-up message from the functional unit 111A and corrects the time of its own switching device 101 based on the response message and the follow-up message.

[0112] In addition, a detection unit 82 in the functional unit 111B determines whether the temperature inside the vehicle 1 satisfies a predetermined condition based on the measurement signal received from the temperature sensor 151B. For example, when the temperature of its own functional unit 111B is equal to or higher than a predetermined threshold value, the detection unit 82 determines that the temperature inside the vehicle 1 satisfies the predetermined condition, and notifies the occurrence of an update event to the time synchronization processing unit 83.

[0113] When the time synchronization processing unit 83 receives a notification of the occurrence of an update event from the detection unit 82, it sends a request message to the switch device 101. Then, the time synchronization processing unit 83 receives a response message and a follow-up message from the switch device 101, and corrects the time of its own functional unit 111B based on the response message and the follow-up message.

[0114] In addition, the temperature sensor 151A may be built into the switch device 101. Further, the temperature sensor 151B may be built into the functional unit 111B.

[0115] <Flow of operation>

[0116] Next, in the in-vehicle network system 301, the operation sequence when the main-side functional unit 111A, the switch device 101, and the sub-side functional unit 111B update the propagation delay time and correct the time will be described with reference to the drawings.

[0117] Each device in the in-vehicle network system 301 includes a computer including a memory, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including some or all of the following steps from the memory. The programs of these multiple devices can be installed from the outside respectively. The programs of these multiple devices are circulated in a state of being stored in a recording medium.

[0118] (Example 1)

[0119] Figure 8 It is a diagram showing a sequence (Example 1) of updating the propagation delay time and correcting the time implemented by multiple in-vehicle devices in the in-vehicle network system according to the embodiment of the present disclosure. Here, a case where the switch device 101 detects the occurrence of an update event and sends a request message to the functional unit 111A will be described.

[0120] Refer to Figure 8 First, it is assumed that the in-vehicle network system 301 is started by switching the ignition switch of the vehicle 1 to the ON state (step S101).

[0121] Next, a detection unit 52 in the switch device 101 detects that the ignition switch of the vehicle 1 is switched to the ON state as an update event, and notifies the occurrence of the update event to the time synchronization processing unit 55 (step S102).

[0122] In addition, a detection unit 82 in the functional unit 111B detects that the ignition switch of the vehicle 1 is switched to the ON state as an update event, and notifies the occurrence of the update event to the time synchronization processing unit 83 (step S103).

[0123] Next, when the time synchronization processing unit 55 in the switch device 101 receives a notification of the occurrence of an update event from the detection unit 52, it sends a request message for requesting time information to the functional unit 111A via the relay unit 51 and the communication port 54A (step S104).

[0124] Next, the functional unit 111A sends a response message to the request message sent from the switch device 101 to the switch device 101. At this time, the functional unit 111A includes the reception time t2 of the request message in the response message and sends it (step S105).

[0125] Next, after sending the response message, the functional unit 111A sends a follow-up message including the transmission time t3 of the response message to the switch device 101 (step S106).

[0126] Next, the control unit 62 in the switch device 101 receives the response message and the follow-up message sent from the functional unit 111A, and notifies the time t2 included in the response message and the time t3 included in the follow-up message to the time synchronization processing unit 55. In addition, the control unit 62 notifies the transmission time t1 of the request message and the reception time t4 of the response message to the time synchronization processing unit 55 (step S107).

[0127] The time synchronization processing unit 55 updates the propagation delay time Td1 of the data between the functional unit 111A and the switch device 101 based on the times t1, t2, t3, and t4 notified by the control unit 62 (step S108).

[0128] Next, when the time synchronization processing unit 83 in the functional unit 111B receives a notification of the occurrence of an update event from the detection unit 82, it sends a request message for requesting time information to the switch device 101 via the communication unit 81 and the communication port 84 (step S109).

[0129] Next, when the time synchronization processing unit 55 in the switch device 101 receives the request message sent from the functional unit 111B via the communication port 54B and the control unit 62, it sends a response message 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 and sends it (step S110).

[0130] Next, after the time synchronization processing unit 55 sends the response message, it sends a follow-up message including the transmission time t13 of the response message to the functional unit 111B via the relay unit 51 (step S111).

[0131] Next, the communication unit 81 in the functional unit 111B receives the response message and the follow-up message sent from the switch device 101 via the communication port 84, and notifies the time t12 included in the response message and the time t13 included in the follow-up message to the time synchronization processing unit 83. In addition, the communication unit 81 notifies the transmission time t11 of the request message and the reception time t14 of the response message to the time synchronization processing unit 83 (step S112).

[0132] The time synchronization processing unit 83 updates the propagation delay time Td2 of the data between the switch device 101 and the functional unit 111B based on the times t11, t12, t13, and t14 notified from the communication unit 81 (step S113).

[0133] Next, the functional unit 111A sends a Sync message to the switch device 101 (step S114).

[0134] Next, the functional unit 111A sends a follow-up message including the transmission time tm of the Sync message to the switch device 101 (step S115).

[0135] Next, the control unit 62 in the switch device 101 receives the Sync message and the follow-up message sent from the functional unit 111A via the communication port 54A, and notifies the time tm included in the follow-up message and the reception time tx of the Sync message to the time synchronization processing unit 55 (step S116).

[0136] Next, the time synchronization processing unit 55 calculates the time difference Tx1 = tm - Td1 - tx between the time of the functional unit 111A and the time of the switch device 101 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.

[0137] Then, the time synchronization processing unit 55 uses the calculated time difference Tx1 to correct the time in its own switch device 101. Thus, the time synchronization between the functional unit 111A and the switch device 101 is established (step S117).

[0138] Next, the time synchronization processing unit 55 in the switch device 101 sends a Sync message to the functional unit 111B via the communication port 54B (step S118).

[0139] Next, the time synchronization processing unit 55 sends a follow-up message including the transmission time ty of the Sync message to the functional unit 111B via the communication port 54B (step S119).

[0140] Next, the communication unit 81 in the functional unit 111B receives the Sync message and the follow-up message sent from the switch device 101 via the communication port 84, and notifies the time synchronization processing unit 83 of the time ty included in the follow-up message and the reception time ts of the Sync message (step S120).

[0141] Next, the time synchronization processing unit 83 calculates the time difference Tx2 = ty - Td2 - ts between the time of the switch device 101 and the time of the functional unit 111B 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.

[0142] Then, the time synchronization processing unit 83 uses the calculated time difference Tx2 to correct the time in its own functional unit 111B. As a result, the time synchronization between the functional unit 111B and the switch device 101 is established, and as a result, the time synchronization between the functional unit 111B and the functional unit 111A is established (step S121).

[0143] In addition, the operations of steps S104 to S108 may also be performed after the operations of steps S109 to S113. Also, the operations of steps S104 to S108 and the operations of steps S109 to S113 may be performed in parallel.

[0144] In addition, the operations of steps S114 to S117 may also be performed after the operations of steps S118 to S121. Also, the operations of steps S114 to S117 and the operations of steps S118 to S121 may be performed in parallel.

[0145] (Example 2)

[0146] Figure 9 It is a diagram showing a sequence (Example 2) of updating the propagation delay time and correcting the time implemented by a plurality of in-vehicle devices in the in-vehicle network system according to the embodiment of the present disclosure.

[0147] Here, a case where the switch device 101 sends a request message to the functional unit 111A by receiving a request message sent from the functional unit 111B is described. Refer to Figure 9 First, it is assumed that the structure of the in-vehicle network system 301 is changed by switching on the power supply of the functional unit 111B (step S201).

[0148] Next, the detection unit 82 in the functional unit 111B detects that the power supply of its own functional unit 111B is switched on, and notifies the occurrence of the update event to the time synchronization processing unit 83 (step S202).

[0149] Next, when the time synchronization processing unit 83 receives a notification of the occurrence of an update event from the detection unit 82, it sends a request message for requesting time information to the switch device 101 via the communication unit 81 and the communication port 84 (step S203).

[0150] Next, when the time synchronization processing unit 55 in the switch device 101 receives the request message sent from the functional unit 111B via the communication port 54B and the control unit 62, it sends a response message, which is the time information of 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 t22 of the request message in the response message and sends it (step S204).

[0151] Next, after sending the response message, the time synchronization processing unit 55 sends a follow-up message including the transmission time t23 of the response message to the functional unit 111B via the relay unit 51 and the communication port 54B (step S205).

[0152] Next, the communication unit 81 in the functional unit 111B receives the response message and the follow-up message sent from the switch device 101, and notifies the time t22 included in the response message and the time t23 included in the follow-up message to the time synchronization processing unit 83. In addition, the communication unit 81 notifies the transmission time t21 of the request message and the reception time t24 of the response message to the time synchronization processing unit 83 (step S206).

[0153] Next, the time synchronization processing unit 83 updates the propagation delay time Td2 of the data between the switch device 101 and the functional unit 111B based on the times t21, t22, t23, and t24 notified from the communication unit 81 (step S207).

[0154] Next, when the time synchronization processing unit 55 in the switch device 101 receives the request message sent from the functional unit 111B via the communication port 54B and the relay unit 51, it sends a request message for requesting time information to the functional unit 111A via the relay unit 51 and the communication port 54B (step S208).

[0155] Next, the functional unit 111A sends a response message, which is the time information of the request message sent from the switch device 101, to the switch device 101. At this time, the functional unit 111A includes the reception time t32 of the request message in the response message and sends it (step S209).

[0156] Next, after the functional unit 111A sends a response message, it sends a follow-up message containing the transmission time t33 of the response message to the switching device 101 (step S210).

[0157] Next, the control unit 62 in the switching device 101 receives the response message and the follow-up message sent from the functional unit 111A, and notifies the time t32 included in the response message and the time t33 included in the follow-up message to the time synchronization processing unit 55. In addition, the control unit 62 notifies the transmission time t31 of the request message and the reception time t34 of the response message to the time synchronization processing unit 55 (step S211).

[0158] Next, the time synchronization processing unit 55 updates the propagation delay time Td1 of the data between the functional unit 111A and the switching device 101 based on the times t31, t32, t33, and t34 notified from the control unit 62 (step S212).

[0159] Next, time synchronization processing is performed between the functional unit 111A and the switching device 101 (steps S213 to S216) and time synchronization processing is performed between the switching device 101 and the functional unit 111B (steps S217 to S220). The operations in steps S213 to S216 are the same as the operations in Figure 8 the steps S114 to S117 shown, and the operations in steps S217 to S220 are the same as the operations in Figure 8 the steps S118 to S121 shown. Therefore, detailed descriptions are not repeated here.

[0160] In addition, the operations in steps S204 to S207 may also be performed after the operations in steps S208 to S212. In addition, the operations in steps S204 to S207 and the operations in steps S208 to S212 may also be performed in parallel.

[0161] However, each in-vehicle device in the in-vehicle network updates the propagation delay time of the data between the in-vehicle devices regularly according to a protocol specified by a standard such as IEEE 802.1, and uses the updated propagation delay time for time synchronization between the in-vehicle devices.

[0162] However, in the case of updating the propagation delay time of the data, due to the update process, the processing load becomes large, and it may not be possible to smoothly perform other processes such as processes related to vehicle driving control.

[0163] On the contrary, in the switching device 101 which is an in-vehicle device according to an embodiment of the present disclosure, the time synchronization processing unit 55 performs time synchronization with other devices based on the propagation delay time of data between another in-vehicle device, i.e., another device, and its own switching device 101. The detection unit 52 detects the occurrence of an update event of the propagation delay time. In addition, when the detection unit 52 detects the occurrence of an update event, the time synchronization processing unit 55 requests the time information used for the update of the propagation delay time from other devices.

[0164] In addition, in the functional unit 111 which is an in-vehicle device according to an embodiment of the present disclosure, the time synchronization processing unit 83 performs time synchronization with other devices based on the propagation delay time of data between another in-vehicle device, i.e., another device, and its own functional unit 111. The detection unit 82 detects the occurrence of an update event of the propagation delay time. In addition, when the detection unit 82 detects the occurrence of an update event, the time synchronization processing unit 83 requests the time information used for the update of the propagation delay time from other devices.

[0165] In addition, in the time synchronization method in the switching device 101 according to an embodiment of the present disclosure, first, the detection unit 52 detects the occurrence of an update event related to the update of the propagation delay time of data between another in-vehicle device, i.e., another device, and its own switching device 101. Next, when the detection unit 52 detects the occurrence of an update event, the time synchronization processing unit 55 requests the time information used for the update of the propagation delay time from other devices. Next, the time synchronization processing unit 55 updates the propagation delay time based on the time information received from other devices. Then, the time synchronization processing unit 55 performs time synchronization with other devices based on the updated propagation delay time.

[0166] In addition, in the time synchronization method in the functional unit 111 according to an embodiment of the present disclosure, first, the detection unit 82 detects the occurrence of an update event related to the update of the propagation delay time of data between another in-vehicle device, i.e., another device, and its own functional unit 111. Next, when the detection unit 82 detects the occurrence of an update event, the time synchronization processing unit 83 requests the time information used for the update of the propagation delay time from other devices. Next, the time synchronization processing unit 83 updates the propagation delay time based on the time information received from other devices. Then, the time synchronization processing unit 83 performs time synchronization with other devices based on the updated propagation delay time.

[0167] In this way, the structure that requests time information when detecting the occurrence of an update event and performs the update process of the propagation delay time using this time information can suppress the update process frequency to be lower than the case of performing the update process regularly.

[0168] Therefore, in the in-vehicle device, time synchronization method, and time synchronization program according to the embodiments of the present disclosure, it is possible to smoothly perform time synchronization using the propagation delay time of data between in-vehicle devices and reduce the load of update processing.

[0169] It should be considered that the above-described embodiments are exemplary in all aspects and not restrictive. The scope of the present invention is represented not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0170] The above description includes the features noted below.

[0171] [Note 1]

[0172] An in-vehicle device, wherein

[0173] it includes a processing unit that performs time synchronization with other devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time.

[0174] When the processing unit detects the occurrence of the update event, it requests the time information used for updating the propagation delay time from the other device, and updates the propagation delay time based on the time information received from the other device.

[0175] The update event is an event in which the propagation delay time may change.

[0176] The in-vehicle device is a switching device that relays data between multiple other devices.

[0177] Description of Reference Numerals

[0178] 1 Vehicle

[0179] 10 Ethernet Cable

[0180] 50, 80 Processing Unit

[0181] 51 Relay Unit

[0182] 52, 82 Detection Unit

[0183] 53, 85 Storage Unit

[0184] 54, 54A, 54B, 84 Communication Port

[0185] 55, 83 Time Synchronization Processing Unit

[0186] 61 Switching Unit

[0187] 62 Control Unit

[0188] 81 Communication Unit

[0189] 101, 101A, 101B Switching Devices

[0190] 111, 111A, 111B, 111C Functional Units

[0191] 151A, 151B Temperature Sensors

[0192] 301 Vehicle-mounted Network System

Claims

1. An in-vehicle device, comprising: a processing unit that performs time synchronization with other in-vehicle devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time; when the processing unit detects the occurrence of the update event, the processing unit requests the other devices for the time information used in the update of the propagation delay time; the processing unit detects that the ignition switch of the vehicle on which this device is mounted is switched to the ON state as the update event.

2. An in-vehicle device, comprising: a processing unit that performs time synchronization with other in-vehicle devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time; when the processing unit detects the occurrence of the update event, the processing unit requests the other devices for the time information used in the update of the propagation delay time; the processing unit detects that the structure of the in-vehicle network including this device is changed as the update event.

3. An in-vehicle device, comprising: a processing unit that performs time synchronization with other in-vehicle devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time; when the processing unit detects the occurrence of the update event, the processing unit requests the other devices for the time information used in the update of the propagation delay time; the processing unit detects that the temperature inside the vehicle on which this device is mounted satisfies a predetermined condition as the update event.

4. The in-vehicle device according to claim 3, wherein: the temperature inside the vehicle is the temperature of the communication line between this device and the other devices.

5. An in-vehicle device, comprising: a processing unit that performs time synchronization with other in-vehicle devices based on the propagation delay time of data between the in-vehicle device itself, i.e., this device, and other in-vehicle devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time; when the processing unit detects the occurrence of the update event, the processing unit requests the other devices for the time information used in the update of the propagation delay time; the in-vehicle device further comprises a relay unit that relays data between a first other device as another in-vehicle device and a second other device as another in-vehicle device; the first other device sends a first time information request for requesting the first time information used in the update of the propagation delay time of data between the in-vehicle device and the first other device itself to the in-vehicle device; the relay unit receives the first time information request from the first other device and outputs the received first time information request to the processing unit. When receiving the first time information request from the relay unit, the processing unit outputs a second time information request to the relay unit for requesting the second time information used in the update of the propagation delay time of data between the second other device and the present device. The relay unit sends the second time information request received from the processing unit to the second other device.

6. A time synchronization method, which is a time synchronization method in a vehicle-mounted device. The time synchronization method includes the following steps: Detect the occurrence of an update event related to the update of the propagation delay time of data between the vehicle-mounted device itself, i.e., the present device, and other vehicle-mounted devices, i.e., other devices. When it is detected that the ignition switch of the vehicle equipped with the present device is switched to on as the occurrence of the update event, request the time information used in the update of the propagation delay time from the other device. Update the propagation delay time based on the time information received from the other device. And Perform time synchronization with the other device based on the updated propagation delay time.

7. A time synchronization method, which is a time synchronization method in a vehicle-mounted device. The time synchronization method includes the following steps: Detect the occurrence of an update event related to the update of the propagation delay time of data between the vehicle-mounted device itself, i.e., the present device, and other vehicle-mounted devices, i.e., other devices. When it is detected that the structure of the vehicle-mounted network including the present device is changed as the occurrence of the update event, request the time information used in the update of the propagation delay time from the other device. Update the propagation delay time based on the time information received from the other device. And Perform time synchronization with the other device based on the updated propagation delay time.

8. A time synchronization method, which is a time synchronization method in a vehicle-mounted device. The time synchronization method includes the following steps: Detect the occurrence of an update event related to the update of the propagation delay time of data between the vehicle-mounted device itself, i.e., the present device, and other vehicle-mounted devices, i.e., other devices. When it is detected that the temperature inside the vehicle equipped with the present device satisfies a predetermined condition as the occurrence of the update event, request the time information used in the update of the propagation delay time from the other device. Update the propagation delay time based on the time information received from the other device. And Perform time synchronization with the other device based on the updated propagation delay time.

9. A time synchronization method, which is a time synchronization method in a vehicle-mounted device. The time synchronization method includes the following steps: Detect the occurrence of an update event related to the update of the propagation delay time of data between the vehicle-mounted device itself, i.e., the present device, and other vehicle-mounted devices, i.e., other devices. When the occurrence of the update event is detected, request the time information used in the update of the propagation delay time from the other device. Update the propagation delay time based on the time information received from the other device. And Perform time synchronization with the other device based on the updated propagation delay time. The vehicle-mounted device includes a relay unit that relays data between a first other device, which is another vehicle-mounted device, and a second other device, which is another vehicle-mounted device. The time synchronization method includes the following steps: The first other device sends a first time information request to the vehicle-mounted device, which is used to request the first time information for updating the propagation delay time of data between the vehicle-mounted device and the first other device itself. The relay unit receives the first time information request from the first other device and outputs the received first time information request to the processing unit of the vehicle-mounted device. When receiving the first time information request from the relay unit, the processing unit outputs a second time information request to the relay unit, which is used to request the second time information for updating the propagation delay time of data between the second other device and the device itself. The relay unit sends the second time information request received from the processing unit to the second other device.

10. A time synchronization program product, including a time synchronization program, which is a time synchronization program used in a vehicle-mounted device. The time synchronization program is used to make a computer function as a processing unit. The processing unit performs time synchronization with the other device based on the propagation delay time of data between its own vehicle-mounted device, i.e., this device, and other vehicle-mounted devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When detecting that the ignition switch of the vehicle equipped with this device is switched to on as the occurrence of the update event, the processing unit requests the time information used for updating the propagation delay time from the other device.

11. A time synchronization program product, including a time synchronization program, which is a time synchronization program used in a vehicle-mounted device. The time synchronization program is used to make a computer function as a processing unit. The processing unit performs time synchronization with the other device based on the propagation delay time of data between its own vehicle-mounted device, i.e., this device, and other vehicle-mounted devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When detecting that the structure of the vehicle-mounted network including this device is changed as the occurrence of the update event, the processing unit requests the time information used for updating the propagation delay time from the other device.

12. A time synchronization program product, including a time synchronization program, which is a time synchronization program used in a vehicle-mounted device. The time synchronization program is used to make a computer function as a processing unit. The processing unit performs time synchronization with the other device based on the propagation delay time of data between its own vehicle-mounted device, i.e., this device, and other vehicle-mounted devices, i.e., other devices, and detects the occurrence of an update event of the propagation delay time. When the processing unit detects that the temperature inside the vehicle on which the present device is mounted satisfies a predetermined condition as the occurrence of the update event, it requests the other device for the time information used in the update of the propagation delay time.

13. A time synchronization program product, including a time synchronization program, which is a time synchronization program used in an in-vehicle device. The time synchronization program is used to cause a computer to function as a processing unit, which performs time synchronization with the other device based on the propagation delay time of data between its own in-vehicle device, i.e., the present device, and another in-vehicle device, i.e., the other device, and detects the occurrence of an update event of the propagation delay time. When the processing unit detects the occurrence of the update event, it requests the other device for the time information used in the update of the propagation delay time. The time synchronization program is further used to cause a computer to function as a relay unit, and the relay unit relays data between a first other device that is another in-vehicle device and a second other device that is another in-vehicle device. The first other device sends a first time information request for requesting the first time information used in the update of the propagation delay time of data between the in-vehicle device and the first other device itself to the in-vehicle device. The relay unit receives the first time information request from the first other device and outputs the received first time information request to the processing unit. When the processing unit receives the first time information request from the relay unit, it outputs a second time information request for requesting the second time information used in the update of the propagation delay time of data between the second other device and the present device to the relay unit. The relay unit sends the second time information request received from the processing unit to the second other device.

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