In-vehicle device, time synchronization method, and time synchronization program

Abstract

An in-vehicle device is provided with: a transmission processing unit that performs, at a predetermined transmission cycle, a transmission process for transmitting first time synchronization information and second time synchronization information including the transmission time of the first time synchronization information to another in-vehicle device, the second time synchronization information including the transmission time of the first time synchronization information; and a correction unit that corrects the transmission time on the basis of a time difference between a current time in the in-vehicle device and a previous transmission time in the previous transmission process, the previous transmission time being the transmission time in the in-vehicle device. And a correction process for correcting the transmission time included in the second time synchronization information in the current transmission process to a corrected transmission time obtained by adding the previous transmission time and a value obtained by dividing the transmission period and the time difference.

Description

Technical Field

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

[0002] This application claims the benefit of priority based on Japanese patent application No. 2022-115540, filed on July 20, 2022, the disclosure of which is incorporated herein in its entirety. Background Art

[0003] In Japanese Patent Gazette No. 2020-167616 (Patent Document 1), the following time synchronization system is disclosed. That is, a time synchronization system that synchronizes the time from the device side with the master clock, wherein a device operating as a host, one or more devices operating as adjacent repeaters, and one or more devices operating as terminals are connected via a network. The host sends a signal containing a clock to the network, and the terminal corrects the time based on the clock, and accumulates the correction amount of the time to the correction cumulative value α possessed by the terminal. When α exceeds a specified threshold, a host abnormality notification message is sent to the network. The adjacent repeater corrects the time of its own device based on the clock, and accumulates the correction amount of the time to α possessed by its own device. When α exceeds a specified threshold and a host abnormality notification message is received from one or more subordinate devices, a message indicating that the host should be re-determined is sent to the network.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-167616

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-129778

[0008] Patent Document 3: Japanese Patent Application Publication No. 2020-126317

[0009] Patent Document 4: Japanese Patent Application Publication No. 2018-112425

[0010] Patent Document 5: Japanese Patent Application Publication No. 2016-5214

[0011] Patent Document 6: Japanese Patent Application Publication No. 2018-196038 Summary of the invention

[0012] The vehicle-mounted device disclosed in the present invention comprises: a sending processing unit, which performs sending processing of sending the first moment synchronization information and the second moment synchronization information to other vehicle-mounted devices, i.e., other devices, according to a prescribed sending cycle, wherein the second moment synchronization information includes the sending time of the first moment synchronization information; and a correction unit, which performs correction processing of correcting the sending time included in the second moment synchronization information in this sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., this device, and the sending time in the previous sending process, i.e., the previous sending time, wherein the corrected sending time is the time obtained by adding the value obtained by dividing the sending cycle and the time difference to the previous sending time.

[0013] An aspect of the present disclosure can be realized not only as an in-vehicle device having such a characteristic processing unit, but also as a semiconductor integrated circuit that realizes a part or all of the in-vehicle device, or as a system including the in-vehicle device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing the structure of the vehicle-mounted communication system according to the embodiment of the present disclosure.

[0015] Figure 2 It is a diagram showing the structure of a switch device according to an embodiment of the present disclosure.

[0016] Figure 3 It is a diagram showing the configuration of a main functional unit according to an embodiment of the present disclosure.

[0017] Figure 4 This is a diagram for explaining a method of updating a propagation delay time implemented by the switch device according to the embodiment of the present disclosure.

[0018] Figure 5 It is a diagram showing the structure of a terminal functional unit according to an embodiment of the present disclosure.

[0019] Figure 6 It is a diagram for explaining a method of updating the propagation delay time implemented by the terminal function unit according to the embodiment of the present disclosure.

[0020] Figure 7 This is a diagram for explaining the deviation of the storage time of data in the switch device and the terminal functional unit when the reference time varies in the in-vehicle communication system of the comparative example.

[0021] Figure 8 This is a diagram for explaining an example of a method for correcting the transmission timing of a Sync message implemented by a main function unit according to an embodiment of the present disclosure.

[0022] Fig. 9This is a diagram for explaining another example of the method of correcting the transmission timing of the Sync message implemented by the main function unit according to the embodiment of the present disclosure.

[0023] Fig.10 This is a diagram for explaining another example of the method of correcting the transmission timing of the Sync message implemented by the main function unit according to the embodiment of the present disclosure.

[0024] Fig.11 This is a flowchart that determines the operation procedure when the main function unit of the embodiment of the present disclosure performs the correction processing of the transmission time of the Sync message.

[0025] Fig.12 This is a diagram showing an example of a sequence of time synchronization processing between vehicle-mounted devices in the vehicle-mounted communication system according to the embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] Conventionally, a technology has been developed in which the current time of a certain on-vehicle device in an on-vehicle communication system is set as a reference time, and other on-vehicle devices in the on-vehicle communication system perform time synchronization using the reference time.

[0027] [Problems to be Solved by the Present Disclosure]

[0028] In the technology described in Patent Document 1, when the reference time transmitted by the host computer changes, there arises a problem that other in-vehicle devices that use the reference time for time synchronization cannot operate normally.

[0029] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide an in-vehicle device, a time synchronization method, and a time synchronization program that can suppress abnormal operation in an in-vehicle communication system.

[0030] [Effects of the present disclosure]

[0031] According to the present disclosure, it is possible to suppress abnormal operation in the vehicle-mounted communication system.

[0032] [Description of Embodiments of the Present Disclosure]

[0033] First, the contents of the embodiments of the present disclosure will be listed and described.

[0034] (1) The vehicle-mounted device of the embodiment of the present disclosure comprises: a sending processing unit, which performs sending processing of sending first moment synchronization information and second moment synchronization information to other vehicle-mounted devices, i.e., other devices, according to a prescribed sending cycle, wherein the second moment synchronization information includes the sending time of the first moment synchronization information; and a correction unit, which performs correction processing of correcting the sending time included in the second moment synchronization information in the current sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., the present device, and the sending time in the previous sending process, i.e., the previous sending time, wherein the corrected sending time is the time obtained by adding the sending cycle and the value obtained by dividing the time difference to the previous sending time.

[0035] In this way, by taking into account the time difference between the current time in the own device and the previous time of transmission to correct the transmission time included in the second time synchronization information in the current transmission process, even if the current time changes in the own device, other devices can use the corrected transmission time for time synchronization, so that the deviation of the time in the other device can be suppressed. Therefore, it is possible to suppress abnormal operation in the vehicle-mounted communication system.

[0036] (2) In the above (1), the correction unit may perform the correction process when the absolute value of the time difference is equal to or greater than a predetermined threshold value.

[0037] With such a configuration, whether or not to perform correction processing on the transmission time included in the second time synchronization information can be determined regardless of whether the time difference is positive or negative.

[0038] (3) In the above (2), the vehicle-mounted device may further include an acquisition unit that acquires a data storage period, which is a storage period of data in the other device, and the threshold value may be determined based on the data storage period acquired by the acquisition unit and the transmission period.

[0039] With such a structure, the time difference between the current time in this device and the last transmission time can be used to determine whether an abnormality occurs in the data storage process in other devices, and other devices can store data according to the specified data storage cycle.

[0040] (4) In the above (3), the vehicle-mounted device may also include a transmission cycle setting unit, which changes the transmission cycle to an adjustment cycle shorter than the data storage cycle when the data storage cycle is shorter than the transmission cycle, and the transmission processing unit may also perform the transmission processing according to the adjustment cycle until the corrected transmission time reaches the current time.

[0041] In this way, by adjusting the structure of the sending cycle when the data storage period in other devices is shorter than the sending cycle, even if the current time changes in this device, other devices can use the corrected sending time to synchronize the time, thereby suppressing the deviation of the time in the other devices.

[0042] (5) The time synchronization method of the embodiment of the present disclosure is a time synchronization method in a vehicle-mounted device, wherein the time synchronization method includes the following steps: performing a sending process of sending a first time synchronization information and a second time synchronization information to other vehicle-mounted devices, i.e., other devices, according to a prescribed sending period, wherein the second time synchronization information includes the sending time of the first time synchronization information; and performing a correction process of correcting the sending time included in the second time synchronization information in the current sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., the present device, and the sending time in the previous sending process, i.e., the previous sending time, wherein the corrected sending time is the time obtained by adding the sending period and the value obtained by dividing the time difference to the previous sending time.

[0043] In this way, by taking into account the time difference between the current time in the own device and the previous time of transmission to correct the transmission time included in the second time synchronization information in the current transmission process, even if the current time changes in the own device, other devices can use the corrected transmission time for time synchronization, so that the deviation of the time in the other device can be suppressed. Therefore, it is possible to suppress abnormal operation in the vehicle-mounted communication system.

[0044] (6) The time synchronization program of the embodiment of the present disclosure is a time synchronization program used in a vehicle-mounted device, wherein the time synchronization program is used to enable a computer to operate as the following units: a sending processing unit, which performs a sending process of sending the first time synchronization information and the second time synchronization information to other vehicle-mounted devices, i.e., other devices, according to a prescribed sending period, wherein the second time synchronization information includes the sending time of the first time synchronization information; and a correction unit, which performs a correction process of correcting the sending time included in the second time synchronization information in this sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., this device, and the sending time in the previous sending process, i.e., the previous sending time, wherein the corrected sending time is the time obtained by adding the sending period and the value obtained by dividing the time difference to the previous sending time.

[0045] In this way, by taking into account the time difference between the current time in the own device and the previous time of transmission to correct the transmission time included in the second time synchronization information in the current transmission process, even if the current time changes in the own device, other devices can use the corrected transmission time for time synchronization, so that the deviation of the time in the other device can be suppressed. Therefore, it is possible to suppress abnormal operation in the vehicle-mounted communication system.

[0046] The following are embodiments of the present disclosure using the accompanying drawings. In addition, the same symbols are added to the same or equivalent parts in the drawings, and their descriptions are not repeated. In addition, at least a part of the embodiments described below can also be arbitrarily combined.

[0047] [In-vehicle communication system]

[0048] Figure 1 It is a diagram showing the structure of the vehicle-mounted communication system according to the embodiment of the present disclosure.

[0049] Reference Figure 1 The vehicle-mounted communication system 301 includes a switch device 111 , a main function unit 121 , and a terminal function unit 131 .

[0050] The in-vehicle communication system 301 is mounted on the vehicle 1 . The switch device 111 , the main function unit 121 , and the terminal function unit 131 are examples of in-vehicle devices, such as an ECU (Electronic Control Unit). The switch device 111 , the main function unit 121 , and the terminal function unit 131 constitute the in-vehicle network 101 .

[0051] The switch device 111 is connected to a plurality of vehicle-mounted devices via, for example, an Ethernet (registered trademark) cable 10 , and can communicate with the plurality of vehicle-mounted devices connected thereto.

[0052] More specifically, the switch device 111 performs a relay process of relaying information from a vehicle-mounted device to other vehicle-mounted devices. For example, the switch device 111 receives information for time synchronization (hereinafter also referred to as "time synchronization information T") transmitted from the main function unit 121, and transmits the received time synchronization information T to the terminal function unit 131.

[0053] Information is exchanged between the switch device 111 and the main function unit 121 and between the switch device 111 and the terminal function unit 131 using, for example, Ethernet frames (hereinafter also simply referred to as “frames”) storing IP (Internet Protocol) packets.

[0054] The main function unit 121 and the terminal function unit 131 may also be an off-vehicle communication ECU, a sensor, an on-vehicle camera, an automatic 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 chassis control device, a steering device control device, and an instrument display control device, etc.

[0055] The main function unit 121 acquires the reference time t0 in the in-vehicle network 101. Here, the reference time t0 is, for example, a time generated by the main function unit 121 using a VCXO (Voltage Controlled Xtal Oscillator) and a counter (not shown). The main function unit 121 operates as a GM (Grand Master).

[0056] The main function unit 121 generates a reference time t0 synchronized with the time of the time notifying device, based on the time notified from the time notifying device such as a navigation device, for example.

[0057] More specifically, the time notification device sends time information indicating its own time to the main function unit 121. Upon receiving the time information from the time notification device, the main function unit 121 updates the value of the counter based on the time information. The main function unit 121 sets the time based on the updated counter value as the current time in the main function unit 121, that is, the reference time t0.

[0058] The main function unit 121 periodically transmits time synchronization information T to other in-vehicle devices, that is, other devices. Here, the time synchronization information T is, for example, a Sync message and a tracking message described later.

[0059] The switch device 111 synchronizes time with the main function unit 121 based on the time synchronization information T. More specifically, the switch device 111 calculates the time difference with the main function unit 121 using the time synchronization information T sent by the main function unit 121. The switch device 111 corrects its own time using the calculated time difference.

[0060] The terminal function unit 131 synchronizes time with the switch device 111 based on the time synchronization information T. More specifically, the terminal function unit 131 calculates the time difference with the switch device 111 using the time synchronization information T transmitted by the switch device 111. The terminal function unit 131 uses the calculated time difference to correct its own time.

[0061] [Switch device]

[0062] Figure 2It is a diagram showing the structure of a switch device according to an embodiment of the present disclosure.

[0063] Reference Figure 2 The switch device 111 includes a relay unit 11 , a time synchronization unit 12 , a storage unit 13 , and a plurality of communication ports 14 .

[0064] One or both of the relay unit 11 and the time synchronization unit 12 are implemented by, for example, a processing circuit including one or more processors. The storage unit 13 is, for example, a nonvolatile memory included in the processing circuit. The relay unit 11 includes a switch unit 21 and an information processing unit 22 .

[0065] (Relay processing by switching device)

[0066] The communication port 14 is, for example, a terminal to which the Ethernet cable 10 can be connected. In addition, the communication port 14 may also be a terminal of an integrated circuit. Each of the plurality of communication ports 14 is connected to one of the plurality of vehicle-mounted devices in the vehicle-mounted network 101 via the Ethernet cable 10. In this example, the communication port 14A is connected to the main function unit 121, and the communication port 14B is connected to the terminal function unit 131.

[0067] The storage unit 13 stores an address table indicating the correspondence between the port number of the communication port 14 and the MAC (Media Access Control) address of another vehicle-mounted device connected to the communication port 14 .

[0068] The relay unit 11 relays data between other vehicle-mounted devices by communicating with them. That is, if the relay unit 11 receives an Ethernet frame sent from the main function unit 121 or the terminal function unit 131 through the corresponding communication port 14, it relays the received Ethernet frame.

[0069] More specifically, the switch unit 21 in the relay unit 11 determines the port number corresponding to the destination MAC address included in the received Ethernet frame by referring to the address table stored in the storage unit 13. Then, the switch unit 21 transmits the received Ethernet frame from the communication port 14 of the determined port number.

[0070] [Main function section]

[0071] Figure 3 It is a diagram showing the configuration of a main functional unit according to an embodiment of the present disclosure.

[0072] Reference Figure 3 The main function unit 121 includes a communication unit 31 , a time synchronization unit 32 , a storage unit 33 , and a communication port 34 .

[0073] One or both of the communication unit 31 and the time synchronization unit 32 are implemented, for example, by a processing circuit including one or more processors. The storage unit 33 is, for example, a non-volatile memory included in the above-mentioned processing circuit. The communication port 34 is, for example, a terminal that can connect to the Ethernet cable 10. In addition, the communication port 34 can also be a terminal of an integrated circuit. The communication port 34 is connected to the switch device 111 via the Ethernet cable 10. The time synchronization unit 32 includes a transmission processing unit 41, a transmission time setting unit 42, and a transmission cycle setting unit 43.

[0074] Figure 4 This is a diagram for explaining a method of updating a propagation delay time implemented by the switch device according to the embodiment of the present disclosure.

[0075] Reference Figure 2 , Figure 3 and Figure 4 The switch device 111 transmits and receives time synchronization information T between the main function unit 121, for example, in accordance with the IEEE (registered trademark) 802.1 standard, thereby updating the propagation delay time Td1 of data between the main function unit 121 and the switch device 111. More specifically, the time synchronization unit 12 transmits a request message (Pdelay_Req) ​​for requesting the time information used for updating the propagation delay time Td1 to the main function unit 121 via the relay unit 11 and the communication port 14A.

[0076] The communication unit 31 in the main function unit 121 receives the request message transmitted from the switch device 111 through the communication port 34 , and outputs the received request message to the time synchronization unit 32 .

[0077] The transmission processing unit 41 in the time synchronization unit 32 receives the request message from the communication unit 31, and outputs a response message (Pdelay_Resp) as an example of the time synchronization information T to the request message to the communication unit 31. The communication unit 31 transmits the response message received from the time synchronization unit 32 to the switch device 111 through the communication port 34. At this time, the time synchronization unit 32 includes the reception time t12 of the request message in the response message and transmits it.

[0078] After transmitting the response message, the transmission processing unit 41 outputs a trace message (Pdelay_Resp_Follow_Up) including the transmission time t13 of the response message to the communication unit 31 . The communication unit 31 transmits the trace message received from the transmission processing unit 41 to the switch device 111 via the communication port 34 .

[0079] The information processing unit 22 in the switch device 111 receives the response message and the trace message sent from the main function unit 121 through the communication port 14A. Then, the information processing unit 22 notifies the time synchronization unit 12 of the time t12 included in the response message and the time t13 included in the trace message.

[0080] In addition, the information processing unit 22 notifies the time synchronization unit 12 of the sending time t11 of the request message and the receiving time t14 of the response message. More specifically, the switch device 111 is provided with a counter (not shown). The information processing unit 22 notifies the time synchronization unit 12 of the count value of the counter at the sending timing of the request message as the sending time t11. In addition, the information processing unit 22 notifies the time synchronization unit 12 of the count value of the counter at the receiving timing of the response message as the receiving time t14.

[0081] The time synchronization unit 12 calculates the propagation delay time Td1 of the data between the main function unit 121 and the switch device 111 based on the times t11, t12, t13, and t14 notified from the information processing unit 22. Specifically, the time synchronization unit 12 calculates the propagation delay time Td1=((t14-t11)-(t13-t12)) / 2. Then, the time synchronization unit 12 updates the propagation delay time Td1 stored in the storage unit 13 to the newly calculated propagation delay time Td1.

[0082] (Correction of timing in switching device)

[0083] The transmission processing unit 41 in the main function unit 121 performs transmission processing S to transmit a Sync message as an example of first time synchronization information and a trace message as an example of second time synchronization information to other devices at a predetermined transmission cycle P. The description of "first" and "second" does not mean priority.

[0084] More specifically, the transmission processing unit 41 transmits the frame storing the Sync message to the switch device 111 via the communication unit 31 and the communication port 34. The communication unit 31 stores the transmission time tm of the Sync message in the storage unit 33 as a time stamp.

[0085] After sending the frame storing the Sync message, the sending processing unit 41 sends the frame storing the tracking message to the switch device 111 through the communication unit 31 and the communication port 34. The tracking message includes the sending time tm of the Sync message. Here, it is assumed that the sending processing unit 41 performs the sending process S with a sending period P of 125 milliseconds. The sending period P is stored in the storage unit 33.

[0086] The time synchronization unit 12 in the switch device 111 receives the frame storing the Sync message and the frame storing the Trace message transmitted from the main function unit 121 via the communication port 14A and the relay unit 11. Then, the time synchronization unit 12 stores the Sync message stored in the received frame in the storage unit 13, for example.

[0087] In addition, the information processing unit 22 in the switch device 111 refers to the domain ID included in the message header portion of the received frame, for example, to confirm the transmission source of the frame.

[0088] Furthermore, when confirming that the frame storing the Sync message has been received from the main function unit 121 , the information processing unit 22 notifies the time synchronization unit 12 of the count value of the counter at the reception timing of the frame as the reception time tx of the Sync message.

[0089] The time synchronization unit 12 performs time synchronization with the main function unit 121 based on the transmission time tm and the reception time tx notified from the information processing unit 22 and the propagation delay time Td1 stored in the storage unit 13. More specifically, the time synchronization unit 12 calculates the time difference Tx1=tm-Td1-tx between the time of the main function unit 121 and the time of the switch device 111 based on the transmission time tm, the reception time tx and the propagation delay time Td1.

[0090] Then, the time synchronization unit 12 uses the calculated time difference Tx1 to correct the time in its own switch device 111. More specifically, the time synchronization unit 12 obtains the time obtained by adding the time difference Tx1 to the transmission time tm as the current time in the switch device 111. Thus, the time synchronization between the GM, i.e., the main function unit 121 and the switch device 111 is established.

[0091] [Terminal Function Unit]

[0092] (Structure of the terminal functional part)

[0093] Figure 5 It is a diagram showing the structure of a terminal functional unit according to an embodiment of the present disclosure.

[0094] Reference Figure 5 The terminal function unit 131 includes a communication unit 51, a time synchronization unit 52, a storage unit 53, and a communication port 54. One or both of the communication unit 51 and the time synchronization unit 52 are implemented, for example, by a processing circuit including one or more processors. The storage unit 53 is, for example, a non-volatile memory included in the above-mentioned processing circuit. The communication port 54 is, for example, a terminal that can connect to the Ethernet cable 10. In addition, the communication port 54 can also be a terminal of an integrated circuit, etc. The communication port 54 is connected to the switch device 111 via the Ethernet cable 10.

[0095] (Update of the data propagation delay time between the switch device and the terminal function unit)

[0096] The terminal functional unit 131 updates the propagation delay time Td2 of the data between the switch device 111 and the terminal functional unit 131 .

[0097] Figure 6 It is a diagram for explaining a method of updating the propagation delay time implemented by the terminal function unit according to the embodiment of the present disclosure.

[0098] Reference Figure 5 and Figure 6 The time synchronization unit 52 in the terminal functional unit 131 and Figure 2 Similarly, the time synchronization unit 12 in the switch device 111 shown in the figure periodically or irregularly updates the propagation delay time Td2 of the data between the switch device 111 and the terminal function unit 131. More specifically, the time synchronization unit 52 sends a request message for requesting the time information used for updating the propagation delay time Td2 to the switch device 111 via the communication unit 51 and the communication port 54.

[0099] Upon receiving the request message transmitted from the terminal function unit 131 via the communication port 14B, the information processing unit 22 in the switch device 111 outputs the request message to the time synchronization unit 12 .

[0100] When receiving the request message from the information processing unit 22, the time synchronization unit 12 sends a response message to the request message to the terminal function unit 131 via the relay unit 11 and the communication port 14B. At this time, the time synchronization unit 12 sends the response message including the reception time t22 of the request message.

[0101] After sending the response message, the time synchronization unit 12 sends a trace message including the sending time t23 of the response message to the terminal function unit 131 via the relay unit 11 and the communication port 14B.

[0102] The communication unit 51 in the terminal function unit 131 receives the response message and the trace message sent from the switch device 111 through the communication port 54. Then, the communication unit 51 notifies the time synchronization unit 52 of the time t22 included in the response message and the time t23 included in the trace message.

[0103] In addition, the communication unit 51 notifies the time synchronization unit 52 of the sending time t21 of the request message and the receiving time t24 of the response message. More specifically, the terminal function unit 131 includes a counter (not shown). The communication unit 51 notifies the time synchronization unit 52 of the count value of the counter at the sending timing of the request message as the sending time t21. In addition, the communication unit 51 notifies the time synchronization unit 52 of the count value of the counter at the receiving timing of the response message as the receiving time t24.

[0104] The time synchronization unit 52 calculates the propagation delay time Td2 of the data between the switch device 111 and the terminal function unit 131 based on the times t21, t22, t23, and t24 notified from the communication unit 51. Specifically, the time synchronization unit 52 calculates the propagation delay time Td2=((t24-t21)-(t23-t22)) / 2. Then, the time synchronization unit 52 updates the propagation delay time Td2 stored in the storage unit 53 to the newly calculated propagation delay time Td2.

[0105] (Timing Correction in the Terminal Function Unit)

[0106] The time synchronization unit 12 in the switch device 111 periodically or irregularly transmits a Sync message to the terminal function unit 131. After transmitting the Sync message, the time synchronization unit 12 transmits a trace message including the transmission time ty of the Sync message to the terminal function unit 131.

[0107] The terminal function unit 131 performs time synchronization based on the Sync message and the trace message transmitted from the switch device 111. More specifically, the communication unit 51 in the terminal function unit 131 receives the frame storing the Sync message and the frame storing the trace message transmitted from the switch device 111 through the communication port 54. Then, the communication unit 51 refers to, for example, the domain ID included in the message header portion of the received frame storing the Sync message, and confirms the transmission source of the frame.

[0108] When confirming that a frame storing a Sync message has been received from the main function unit 121, the communication unit 51 notifies the time synchronization unit 52 of, for example, the sending time ty included in the tracking message received immediately after the frame. In addition, the communication unit 51 notifies the time synchronization unit 52 of the count value of the counter at the reception timing of the Sync message stored in the frame as the reception time te of the Sync message.

[0109] The time synchronization unit 52 performs time synchronization with the switch device 111 based on the transmission time ty and the reception time te notified from the communication unit 51 and the propagation delay time Td2 stored in the storage unit 53. More specifically, the time synchronization unit 52 calculates the difference between the time of the switch device 111 and the time of the terminal function unit 131, that is, the time difference Tx2=ty-Td2-te. Then, the time synchronization unit 52 uses the calculated time difference Tx2 to correct the time in its own terminal function unit 131. The time synchronization unit 52 obtains the time obtained by adding the time difference Tx2 to the transmission time ty as the current time in the terminal function unit 131.

[0110] Here, when the time synchronization between the main function unit 121 and the switch device 111 is established, the transmission time ty included in the trace message transmitted from the switch device 111 to the terminal function unit 131 is the time synchronized with the main function unit 121. Therefore, the time synchronization unit 52 in the terminal function unit 131 performs time correction, so that the time synchronization between the terminal function unit 131 and the switch device 111 is established, and as a result, the time synchronization between the terminal function unit 131 and the main function unit 121 is established.

[0111] [Explanation of the topic]

[0112] However, in the in-vehicle communication system 301 , when the time synchronization is normally performed between the in-vehicle devices, the reference time t0 updated by the GM, namely the main function unit 121 , may change for some reason.

[0113] For example, if an abnormality occurs in the process of updating the counter value based on the time information received from the above-mentioned time notification device by the main function unit 121, the reference time t0 may change, that is, it may be offset. In addition, the vehicle communication system 301 may include multiple main function units 121. Specifically, the vehicle communication system 301 may include other main function units 121 that synchronize time with a certain main function unit 121 so that it can operate as a backup system when it is assumed that the main function unit 121 fails. In this case, if an abnormality occurs in the time synchronization between the multiple main function units 121, the reference time t0 may change.

[0114] If the reference time t0 changes, the switch device 111 and the terminal function unit 131 may not operate normally. For example, if the reference time t0 changes, the consistency of the data storage time in the switch device 111 and the terminal function unit 131 may be damaged.

[0115] Figure 7 This is a diagram for explaining the deviation of the storage time of data in the switch device and the terminal functional unit when the reference time varies in the in-vehicle communication system of the comparative example.

[0116] exist Figure 7 and the following Figures 8 to 10 In the example, "t1" is the time in the switch device 111, and "t3" is the time in the terminal functional unit 131. Figure 7 and the following Figures 8 to 10 In the following description and Figure 7 and the following Figures 8 to 10 In the , "seconds" are sometimes represented as "s" and "milliseconds" are sometimes represented as "ms".

[0117] In addition, Figure 7 In the example shown, the cycle in which the switch device 111 and the terminal function unit 131 store data (hereinafter also referred to as "data storage cycle C") is 1 second. The data storage cycle C is, for example, a storage cycle for log data.

[0118] Reference Figure 7 , the switch device 111 and the terminal functional unit 131 store data second by second during the period from 5.000 seconds to 10.000 seconds. Here, it is assumed that the reference time t0 of the main functional unit 121 changes by +5 seconds or -5 seconds after the switch device 111 and the terminal functional unit 131 store data at "t1=10.000s" and "t3=10.000s" respectively.

[0119] The reference time t0 when the main function unit 121 performs the transmission process S immediately after the reference time t0 changes by +5 seconds is "15.125s". Also, the reference time t0 when the main function unit 121 performs the transmission process S immediately after the reference time t0 changes by -5 seconds is "5.125s". Figure 7 In the example shown, the transmission time tm included in the trace message in the transmission process S immediately after the change of the reference time t0 becomes "15.125s" or "5.125s".

[0120] When the switch device 111 performs time synchronization based on the tracking message including the transmission time tm of "15.125s" or "5.125s" transmitted from the main function unit 121, the time t1 in the switch device 111 becomes "15.125s" or "5.125s". The switch device 111 transmits the tracking message to the terminal function unit 131, so the time t3 in the terminal function unit 131 also becomes "15.125s" or "5.125s". In this case, the next data storage time in the switch device 111 and the terminal function unit 131 becomes "16.000s" or "6.000s".

[0121] When the data saving time becomes "16.000s" due to the change of the reference time t0 by +5 seconds, the data is not saved during the period from 11.000s to 15.000s at time t1 and t3. That is, in each of the switch device 111 and the terminal function unit 131, the interval from the previous data saving time "10.000s" to the current data saving time "16.000s" becomes 6 seconds, and the data saving cycle C has a deviation of 1 second. Therefore, the data saving time becomes irregular.

[0122] When the data storage time becomes "6.000s" due to a change of -5 seconds in the reference time t0, the data storage time from 6.0000 seconds to 10.000 seconds overlaps in each of the switch device 111 and the terminal function unit 131, for example, multiple data of the same time are stored.

[0123] In this way, if the consistency of the data storage times in the switch device 111 and the terminal functional unit 131 is damaged due to the variation of the reference time t0, the vehicle communication system 301 may not be able to operate normally.

[0124] In view of this, the main function unit 121 according to the embodiment of the present disclosure solves such a problem through the following structure and operation.

[0125] [Correction of the sending time]

[0126] Refer again Figure 3 The communication unit 31 in the main function unit 121 is an example of an acquisition unit, and acquires the data storage period C in the switch device 111 and the terminal function unit 131 as other devices. More specifically, the communication unit 31 acquires the data storage period C pre-stored in the storage unit 33, and outputs the period information indicating the data storage period C to the time synchronization unit 32.

[0127] The transmission time setting unit 42 in the time synchronization unit 32 is an example of a correction unit, and monitors the time difference Ta=t0-tm1 between the reference time t0 indicating the current time in the device and the transmission time tm included in the tracking message in the previous transmission process S, that is, the previous transmission time tm1. The transmission time setting unit 42 in the time synchronization unit 32 performs a correction process for correcting the transmission time tm included in the tracking message in the transmission process S based on the time difference Ta.

[0128] More specifically, the transmission time setting unit 42 refers to the previous transmission time tm1 in the storage unit 33 before performing the transmission process S, and uses the previous transmission time tm1 and the reference time t0 to calculate the time difference Ta. When the absolute value of the time difference Ta is greater than or equal to the predetermined threshold value Th, the transmission time setting unit 42 performs the above correction process. The transmission time setting unit 42 includes the corrected transmission time tm in the tracking message transmitted by the transmission processing unit 41.

[0129] The threshold value Th is determined based on the data storage cycle C and the transmission cycle P acquired by the communication unit 31. For example, the transmission time setting unit 42 uses different threshold values ​​Th when the time difference Ta is positive and when the time difference Ta is negative.

[0130] More specifically, the transmission time setting unit 42 performs the correction processing when the time difference Ta is greater than or equal to the data storage period C, for example, greater than or equal to 1 second. In addition, the transmission time setting unit 42 performs the correction processing when the time difference Ta is less than or equal to (-1×transmission period P), for example, less than or equal to -125 milliseconds.

[0131] Figure 8 This is a diagram for explaining an example of a method for correcting the transmission timing of a Sync message implemented by a main function unit according to an embodiment of the present disclosure.

[0132] exist Figure 8 In the example shown, Figure 7 Likewise, the data storage period C is 1 second and the transmission period P is 125 milliseconds. Figure 8 The figure shows a case where the reference time t0 changes by +5 seconds immediately after the switch device 111 and the terminal functional unit 131 store data at "time t1 = 10.000s" and "time t3 = 10.000s", respectively. Figure 8 In the example above, the time difference Ta is +5 seconds. Figure 8 The next data saving time is "11.000s".

[0133] Reference Figure 2 and Figure 8When the time difference Ta is greater than the data storage period C, the transmission time setting unit 42 obtains the divided time difference Ts which is a value obtained by dividing the time difference Ta. Figure 8 In the example shown, the time difference Ta is +5 seconds, and the data storage cycle C is 1 second. Therefore, the time difference Ta is greater than the data storage cycle C.

[0134] Here, in the storage unit 33, for example, a table D indicating the correspondence between the data storage cycle C and the split time difference Ts is stored in advance. The transmission time setting unit 42 refers to the table D to obtain the split time difference Ts corresponding to the data storage cycle C included in the cycle information received from the communication unit 31. The split time difference Ts is set to a value lower than the transmission cycle P. Here, the split time difference Ts is set to 100 milliseconds. In addition, the transmission time setting unit 42 is not limited to the structure of obtaining the split time difference Ts by referring to the table D stored in the storage unit 33, and can also calculate the split time difference Ts using the data storage cycle C and the transmission cycle P according to a predetermined calculation formula.

[0135] The transmission time setting unit 42 corrects the transmission time tm included in the tracking message in the current transmission process S to the corrected transmission time tm2 obtained by adding the transmission cycle P and the division time difference Ts to the previous transmission time tm1. That is, the corrected transmission time tm2 is expressed by the following formula (1).

[0136] tm2=tm1+P+Ts …(1)

[0137] In the transmission process S performed immediately after the reference time t0 is changed by +5 seconds, that is, when the reference time t0 is "15.125s", the corrected transmission time tm2 is the time "10.225s" obtained by adding the transmission cycle P, that is, "125ms", and the division time difference Ts, that is, "100ms", to the previous transmission time tm1, that is, "10.000s". The transmission time setting unit 42 sets the corrected transmission time tm2 to the transmission time tm included in the tracking message in the transmission process S.

[0138] The switch device 111 performs time synchronization based on the tracking message including the correction transmission time tm2 received from the main function unit 121. As a result, the time t1 of the switch device 111 becomes "10.225s". In addition, the terminal function unit 131 performs time synchronization based on the tracking message received from the switch device 111. As a result, the time t3 of the terminal function unit 131 becomes "10.225s".

[0139] The transmission time setting unit 42 performs the above correction processing until the transmission time tm of the Sync message reaches the reference time t0. Here, the transmission time setting unit 42 corrects the transmission time tm to "10.225s" and then to "10.450s", "10.675s", "10.900s" and "11.125s" in sequence. As a result, the time t1 and time t3 of the switch device 111 and the terminal function unit 131, respectively, shift in the order of "10.450s", "10.675s", "10.900s" and "11.125s" after becoming "10.225s". Therefore, the switch device 111 and the terminal function unit 131 can save data at "11.000s" between "10.900s" and "11.125s" as the next timing of the previous data saving time "10.000s".

[0140] If the transmission time tm of the Sync message reaches the reference time t0, the transmission time setting unit 42 sets the transmission time tm included in the tracking message as the reference time t0. Figure 8 In the example shown, by the 50th correction process, the transmission time tm included in the tracking message in the current transmission process S becomes "21.250s", reaching the reference time t0.

[0141] exist Figure 8 In the example, when the time difference Ta is +5 seconds and the data retention period C is 1 second, the split time difference Ts is a value obtained by dividing the time difference Ta into 50 equal parts, that is, 100 milliseconds. In addition, when the time difference Ta is +5 seconds and the data retention period C is 2 seconds, the split time difference Ts may be, for example, a value obtained by dividing the time difference Ta into 25 equal parts, that is, 200 ms. In this way, the split time difference Ts is not limited to 100 milliseconds, and may be a different value depending on the data retention period C.

[0142] Fig. 9 This is a diagram for explaining another example of the method of correcting the transmission timing of the Sync message implemented by the main function unit according to the embodiment of the present disclosure.

[0143] exist Fig. 9 In the example shown, Figure 7 and Figure 8 Likewise, the data storage period C is 1 second and the transmission period P is 125 milliseconds. Fig. 9 The figure shows a case where the reference time t0 changes by -5 seconds immediately after the switch device 111 and the terminal functional unit 131 store data at "time t1 = 10.000s" and "time t3 = 10.000s", respectively. Fig. 9In the example shown, the time difference Ta is less than or equal to -125 milliseconds, so the transmission time setting unit 42 performs a correction process of correcting the transmission time tm included in the tracking message in the transmission process S.

[0144] More specifically, the transmission time setting unit 42 refers to the table D in the storage unit 33 to obtain the division time difference Ts corresponding to the data storage period C. Fig. 9 In the example shown, the division time difference Ts is, for example, -100 milliseconds.

[0145] Then, the transmission time setting unit 42 corrects the transmission time tm included in the tracking message in the current transmission process S to the corrected transmission time tm2.

[0146] In the transmission process S performed immediately after the reference time t0 changes by -5 seconds, that is, when the reference time t0 is "5.125s", the corrected transmission time tm2 is the time "10.025s" obtained by adding the transmission cycle P, that is, "125ms", and the division time difference Ts, that is, "-100ms", to the previous transmission time tm1, that is, "10.000s". The transmission time setting unit 42 sets the corrected transmission time tm2 to the transmission time tm included in the tracking message in the transmission process S.

[0147] The switch device 111 performs time synchronization based on the tracking message including the correction transmission time tm2 received from the main function unit 121. As a result, the time t1 in the switch device 111 becomes "10.025s". In addition, the terminal function unit 131 performs time synchronization based on the tracking message received from the switch device 111. As a result, the time t3 in the terminal function unit 131 becomes "10.025s".

[0148] Next, the transmission time setting unit 42 corrects the transmission time tm to "10.050s", and the time t1 of the switch device 111 and the time t3 of the terminal function unit 131 become "10.050s". In this way, through the correction processing of the transmission time setting unit 42, the time t1 of the switch device 111 and the time t3 of the terminal function unit 131 become later than the previous data storage time "10.000s". Therefore, even if the reference time t0 changes by -5 seconds, the switch device 111 and the terminal function unit 131 can save data at the next data storage time "11.000s" without overlapping the data storage time.

[0149] Fig.10 This is a diagram for explaining another example of the method of correcting the transmission timing of the Sync message implemented by the main function unit according to the embodiment of the present disclosure.

[0150] Fig.10 and Fig. 9Similarly, the case where the reference time t0 is shifted by -5 seconds immediately after the switch device 111 and the terminal functional unit 131 store data at "time t1 = 10.000 s" and "time t3 = 10.000 s", respectively, is shown.

[0151] exist Fig.10 In the example shown, the data storage period C is 100 milliseconds, and the transmission period P before the reference time t0 changes is 125 milliseconds. Fig.10 In the example shown, the data storage period C is shorter than the transmission period P. In this case, in the correction process of the transmission time setting unit 42, the correction transmission time obtained by adding the transmission period P and the division time difference Ts to the previous transmission time tm1 may exceed the next data storage time.

[0152] Reference Figure 2 and Fig.10 The transmission cycle setting unit 43 compares the data storage cycle C with the transmission cycle P. If the data storage cycle C is shorter than the transmission cycle, the transmission cycle P is changed to a cycle shorter than the data storage cycle C. Fig.10 In the example shown, the data storage period C is shorter than the transmission period P, so the transmission period setting unit 43 changes the transmission period P from "125 ms" to "62.5 ms." Hereinafter, the transmission period P changed by the transmission period setting unit 43 is also referred to as "adjustment period P1."

[0153] The transmission cycle setting unit 43 notifies the transmission processing unit 41 and the transmission time setting unit 42 of the adjustment cycle P1. The transmission processing unit 41 performs the transmission process S at the adjustment cycle P1 notified from the transmission cycle setting unit 43 until the corrected transmission time tm2 reaches the reference time t0.

[0154] The transmission time setting unit 42 corrects the transmission time tm using the adjustment cycle P1 notified from the transmission cycle setting unit 43 .

[0155] More specifically, the transmission time setting unit 42 refers to the table D in the storage unit 33 to obtain the division time difference Ts corresponding to the adjustment cycle P1. Here, the division time difference Ts is -50 milliseconds.

[0156] The transmission time setting unit 42 corrects the transmission time tm included in the tracking message to the corrected transmission time tm2 in the transmission process S immediately after the reference time t0 changes by -5 seconds, that is, when the reference time t0 is "5.0625s". Here, the corrected transmission time tm2 is the time "10.0125s" obtained by adding the adjustment period P1, that is, "62.5ms" and the division time difference Ts, that is, "-50ms", to the previous transmission time tm1, that is, "10.000s". The transmission time setting unit 42 sets the corrected transmission time tm2 to the transmission time tm included in the tracking message in the transmission process S.

[0157] The switch device 111 performs time synchronization based on the tracking message including the correction transmission time tm2 received from the main function unit 121. As a result, the time t1 in the switch device 111 becomes "10.0125s". In addition, the terminal function unit 131 performs time synchronization based on the tracking message received from the switch device 111. As a result, the time t3 in the terminal function unit 131 becomes "10.0125s".

[0158] The transmission time setting unit 42 corrects the transmission time tm to "10.0125s". Next, if the transmission time tm is corrected to "10.0250s", the time t1 of the switch device 111 and the time t3 of the terminal function unit 131 become "10.0250s". Thereafter, if the transmission time setting unit 42 corrects the transmission time tm to "10.100s", the time t1 of the switch device 111 and the time t3 of the terminal function unit 131 become "10.100s", which is the data storage time. Therefore, the switch device 111 and the terminal function unit 131 can store data at "10.100s" as the next timing of the previous data storage time "10.000s".

[0159] On the other hand, when the data storage period C is longer than the transmission period P, the transmission period setting unit 43 does not change the transmission period P. In the in-vehicle network 101 , when the data storage period C is predetermined to be longer than the transmission period P, the main function unit 121 may not include the transmission period setting unit 43 .

[0160] [Flow of Action]

[0161] Fig.11 This is a flowchart that determines the operation procedure when the main function unit of the embodiment of the present disclosure performs the correction processing of the transmission time of the Sync message.

[0162] First, the main function unit 121 calculates the time difference Ta between the reference time t0 indicating the current time of the main function unit 121 and the previous transmission time tm1 (step S1 ).

[0163] Next, the main function unit 121 compares the absolute value of the time difference Ta with the threshold value Th (step S2 ).

[0164] When the absolute value of the time difference Ta is equal to or greater than the threshold value Th (“Yes” in step S2 ), the main function unit 121 compares the data storage period C with the transmission period P (step S3 ).

[0165] Then, when the data storage period C is longer than the transmission period P (No in step S3), the main function unit 121 obtains the division time difference Ts without changing the transmission period P. For example, the main function unit 121 refers to the table D in the storage unit 33 as described above and obtains the division time difference Ts corresponding to the data storage period C (step S4).

[0166] Next, the main function unit 121 corrects the transmission time tm included in the tracking message in the current transmission process S to the corrected transmission time tm2. The corrected transmission time tm2 is obtained by adding the transmission cycle P and the division time difference Ts to the previous transmission time tm1 as shown in the above formula (1) (step S5).

[0167] Next, the main function unit 121 transmits a Sync message to the switch device 111 (step S6 ).

[0168] Next, the main function unit 121 transmits a trace message including the correction transmission time tm2 to the switch device 111 (step S7 ).

[0169] Next, the main function unit 121 stores the transmission time tm of the Sync message, that is, the corrected transmission time tm2 (step S8 ).

[0170] Next, the main function unit 121 compares the transmission time tm of the Sync message stored in the previous transmission process S with the reference time t0 in the next transmission process S (step S9 ).

[0171] When the transmission time tm of the Sync message reaches the reference time t0 (Yes in step S9 ), the main function unit 121 sets the transmission time tm included in the trace message as the reference time t0 (step S10 ), and transmits the Sync message to the switch device 111 (step S6 ).

[0172] On the other hand, when the transmission time tm has not reached the reference time t0 (No in step S9 ), the main function unit 121 corrects the transmission time tm (step S5 ).

[0173] When the time difference Ta is lower than the threshold Th (No in step S2 ), the main function unit 121 sets the transmission time tm included in the trace message as the reference time t0 (step S10 ), and transmits the Sync message to the switch device 111 (step S6 ).

[0174] When the data storage cycle C is shorter than the transmission cycle P (Yes in step S3 ), the main function unit 121 changes the transmission cycle P to a cycle shorter than the data storage cycle C (step S11 ) and acquires the division time difference Ts (step S4 ).

[0175] Fig.12 This is a diagram showing an example of a sequence of time synchronization processing between vehicle-mounted devices in the vehicle-mounted communication system according to the embodiment of the present disclosure.

[0176] Reference Fig.12 First, the main function unit 121 sends a Sync message to the switch device 111 (step S21 ).

[0177] Next, the main function unit 121 transmits a trace message including the transmission time tm of the Sync message to the switch device 111. The main function unit 121 performs a transmission process S of transmitting the Sync message and the trace message to the switch device 111 at the transmission cycle P (step S22).

[0178] Next, the switch device 111 performs time synchronization with the main function unit 121 based on the Sync message and the Trace message received from the main function unit 121 (step S23 ).

[0179] Next, the switch device 111 transmits the Sync message received from the main function unit 121 to the terminal function unit 131 (step S24 ).

[0180] Next, the switch device 111 further includes the reception time of the Sync message in the trace message received from the main function unit 121 and transmits the message to the terminal function unit 131 (step S25 ).

[0181] Next, the terminal function unit 131 performs time synchronization with the switch device 111 based on the Sync message and the Trace message received from the switch device 111 (step S26 ).

[0182] Next, the main function unit 121 monitors the time difference Ta between the reference time t0 and the transmission time tm included in the trace message in the previous transmission process S. When the absolute value of the time difference Ta is equal to or greater than the threshold Th, the main function unit 121 determines that the reference time t0 has changed (step S27 ).

[0183] Next, the main function unit 121 compares the data storage period C and the transmission period P in the switch device 111 and the terminal function unit 131 (step S28 ).

[0184] Next, when the data storage period C is longer than the transmission period P (No in step S28), the main function unit 121 obtains the division time difference Ts without changing the transmission period P. The main function unit 121 obtains the division time difference Ts corresponding to the data storage period C by referring to the table D in the storage unit 33 as described above (step S29).

[0185] Next, the main function unit 121 corrects the transmission time tm included in the tracking message in the current transmission process S to the corrected transmission time tm2. The corrected transmission time tm2 is obtained by adding the transmission cycle P and the division time difference Ts to the previous transmission time tm1 as shown in the above formula (1) (step S30).

[0186] The main function unit 121 transmits a Sync message to the switch device 111 (step S31 ).

[0187] Next, the main function unit 121 transmits a trace message including the correction transmission time tm2 to the switch device 111 (step S32 ).

[0188] Next, the switch device 111 performs time synchronization with the main function unit 121 based on the Sync message received from the main function unit 121 and the trace message including the corrected transmission time tm2 (step S33 ).

[0189] Next, the switch device 111 transmits the Sync message received from the main function unit 121 to the terminal function unit 131 (step S34 ).

[0190] Next, the switch device 111 further includes the reception time of the Sync message in the trace message received from the main function unit 121 and transmits the message to the terminal function unit 131 (step S35 ).

[0191] Next, the terminal function unit 131 performs time synchronization with the switch device 111 based on the Sync message received from the switch device 111 and the trace message including the corrected transmission time tm2 (step S36 ).

[0192] On the other hand, when the data storage cycle C is shorter than the transmission cycle P (Yes in step S28 ), the main function unit 121 sets the transmission cycle P to the adjustment cycle P1 shorter than the data storage cycle C (step S37 ), and obtains the division time difference Ts (step S29 ).

[0193] The above embodiments should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0194] Each process (function) of the above-mentioned embodiment is implemented by a processing circuit including one or more processors. The above-mentioned processing circuit can also be composed of an integrated circuit composed of one or more memories, various analog circuits, and various digital circuits in addition to the above-mentioned one or more processors. The above-mentioned one or more memories store programs (commands) that enable the above-mentioned one or more processors to perform the above-mentioned processes. The above-mentioned one or more processors can perform the above-mentioned processes in accordance with the above-mentioned programs read from the above-mentioned one or more memories, or in accordance with the logic circuits designed to perform the above-mentioned processes in advance. The above-mentioned processor can be a CPU (Central Processing Unit: Central Processing Unit), GPU (Graphics Processing Unit: Graphics Processing Unit), DSP (Digital Signal Processor: Digital Signal Processor), FPGA (Field Programmable Gate Array: Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit: Application Specific Integrated Circuit), etc., various processors suitable for computer control. In addition, the above-mentioned multiple processors separated physically can also cooperate with each other to perform the above-mentioned processes. For example, the above-mentioned processing can also be performed by the above-mentioned processors respectively mounted on a plurality of physically separated computers in cooperation with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), and the Internet. The above-mentioned program can be installed into the above-mentioned memory from an external server device or the like via the above-mentioned network, or can be circulated in a state of being stored in a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), and a semiconductor memory, and installed from the above-mentioned recording medium into the above-mentioned memory.

[0195] The above description contains the features noted below.

[0196] [Note 1]

[0197] A vehicle-mounted device, wherein: The vehicle-mounted device comprises a processing circuit, The processing circuit performs a transmission process of transmitting the first time synchronization information and the second time synchronization information to other vehicle-mounted devices, i.e., other devices, according to a predetermined transmission cycle, wherein the second time synchronization information includes the transmission time of the first time synchronization information. The processing circuit performs correction processing to correct the sending time in this sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., the device, and the sending time in the previous sending process, i.e., the previous sending time. The corrected sending time is the time obtained by adding the value obtained by dividing the sending period and the time difference to the previous sending time.

[0198] Description of symbols

[0199] 1 Vehicle

[0200] 10 Ethernet cable

[0201] 11 Relay Department

[0202] 12, 32, 52 Time synchronization unit

[0203] 13, 33, 53 Storage

[0204] 14, 14A, 14B, 34, 54 communication ports

[0205] 21 Switch

[0206] 22 Information Processing Department

[0207] 31, 51 Ministry of Communications

[0208] 41 Sending Processing Unit

[0209] 42 Sending time setting unit

[0210] 43. Transmission cycle setting unit

[0211] 101 In-vehicle Network

[0212] 111 Switchgear

[0213] 121 Main Function Department

[0214] 131 Terminal Functional Unit

[0215] 301 Vehicle Communication System

Claims

1. A vehicle-mounted device comprising: a transmission processing unit that performs transmission processing of transmitting the first time synchronization information and the second time synchronization information to other vehicle-mounted devices, i.e., other devices, according to a predetermined transmission cycle, wherein the second time synchronization information includes the transmission time of the first time synchronization information; and The correction unit performs correction processing for correcting the sending time included in the second moment synchronization information in the current sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., the device, and the sending time in the previous sending process, i.e., the previous sending time, wherein the corrected sending time is the time obtained by adding the value obtained by dividing the sending period and the time difference to the previous sending time.

2. The vehicle-mounted device according to claim 1, wherein: The correction unit performs the correction process when the absolute value of the time difference is equal to or greater than a predetermined threshold value.

3. The vehicle-mounted device according to claim 2, wherein: The vehicle-mounted device further includes an acquisition unit that acquires a data storage period, that is, a storage period of data in the other device. The threshold value is determined based on the data storage period and the transmission period acquired by the acquisition unit.

4. The vehicle-mounted device according to claim 3, wherein: The vehicle-mounted device further includes a transmission cycle setting unit, which changes the transmission cycle to an adjustment cycle shorter than the data storage cycle when the data storage cycle is shorter than the transmission cycle. The transmission processing unit performs the transmission processing at the adjustment period until the corrected transmission time reaches the current time.

5. A time synchronization method is a time synchronization method in a vehicle-mounted device, wherein: The time synchronization method comprises the following steps: Performing a transmission process of transmitting the first time synchronization information and the second time synchronization information to other vehicle-mounted devices, i.e., other devices, at a predetermined transmission cycle, wherein the second time synchronization information includes the transmission time of the first time synchronization information; and Based on the time difference between the current time in the vehicle-mounted device, i.e., this device, and the sending time in the previous sending process, i.e., the previous sending time, a correction process is performed to correct the sending time contained in the second time synchronization information in this sending process to a corrected sending time, and the corrected sending time is the time obtained by adding the sending period and the value obtained by dividing the time difference to the previous sending time.

6. A time synchronization program is a time synchronization program used in a vehicle-mounted device, wherein: The time synchronization program is used to enable the computer to operate as the following units: a transmission processing unit that performs transmission processing of transmitting the first time synchronization information and the second time synchronization information to other vehicle-mounted devices, i.e., other devices, according to a predetermined transmission cycle, wherein the second time synchronization information includes the transmission time of the first time synchronization information; and The correction unit performs correction processing for correcting the sending time included in the second moment synchronization information in the current sending process to a corrected sending time based on the time difference between the current time in the vehicle-mounted device, i.e., the device, and the sending time in the previous sending process, i.e., the previous sending time, wherein the corrected sending time is the time obtained by adding the value obtained by dividing the sending period and the time difference to the previous sending time.

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