Fault diagnosis device

Abstract

This application provides a fault diagnosis device. The communication network system includes: a first-mode network where relay devices and nodes are connected in parallel via a communication bus and perform CAN communication; and a second-mode network where switching devices and nodes are connected one-to-one via communication cables and perform Ethernet communication. When Ethernet communication between the target node and the switching device becomes unavailable, the nodes in the first-mode network, including both the target node and the switching device, use CAN communication to read diagnostic information. When the fault diagnosis device records diagnostic information in a node of either the target node or the switching device, it determines that a fault has occurred in the node where the diagnostic information was recorded.

Description

Technical Field

[0001] This invention relates to a fault diagnosis device. Background Technology

[0002] Japanese Patent Application Publication No. 2008-278403 describes a communication network system. This system has multiple nodes. These nodes communicate with each other via a communication bus according to the CAN protocol. CAN is short for Controller Area Network.

[0003] Each node is connected to the communication bus via a monitoring device equipped with a switching unit. When the monitoring device detects an anomaly on the communication bus, it uses a switching unit to change the connections on the communication bus. Afterward, the monitoring device determines the location of the anomaly in the communication network system by re-checking whether an anomaly has occurred on the communication bus. Summary of the Invention

[0004] In communication network systems, nodes sometimes perform communication following the Ethernet protocol in addition to the CAN protocol. In such systems, it is desirable to be able to pinpoint the location of the anomaly and perform efficient repairs even when an anomaly occurs during Ethernet communication.

[0005] The fault diagnosis device for solving the above-mentioned problems is a fault diagnosis device for a communication network system. The communication network system includes multiple nodes, multiple communication buses, and multiple communication cables. The communication network system includes a first-mode network in which relay devices among the multiple nodes, which relay CAN communication using the CAN protocol, are connected in parallel with the multiple nodes via the communication buses to perform the CAN communication.

[0006] The communication network system includes a second type of network in which a switching device for relaying Ethernet communication using the Ethernet protocol in a plurality of nodes is connected one-to-one with the plurality of nodes via the communication cable to perform the Ethernet communication.

[0007] The relay device and the switching device are connected via the communication bus.

[0008] The object node is the node connected to the relay device via the communication bus and to the switching device via the communication cable. When the Ethernet communication between the object node and the switching device becomes unavailable, the nodes included in the network of the first mode, including both the object node and the switching device, use the CAN communication to read diagnostic information, which is a record indicating anomalies detected by the self-abnormal diagnostic function of the object node and the switching device.

[0009] The fault diagnosis device confirms the result of reading the diagnostic information. If the diagnostic information is recorded at either the object node or the switching device, it determines that a fault has occurred at the node where the diagnostic information is recorded.

[0010] Even if Ethernet communication based on communication cables becomes unavailable, the aforementioned fault diagnosis device can still determine the location of the fault by using CAN based on the communication bus to confirm diagnostic information. Attached Figure Description

[0011] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same parts.

[0012] Figure 1 This is a schematic diagram showing the structure of the communication network system according to the first embodiment.

[0013] Figure 2 It means Figure 1 The timing diagram shows the communication method executed when the fourth node is added to the communication network system.

[0014] Figure 3 It means in Figure 1 The timing diagram shows the communication method performed when the Ethernet communication performed by the fourth node and the switching device becomes unavailable.

[0015] Figure 4 This is a timing diagram showing the communication method performed in the communication network system of the second embodiment when the Ethernet communication performed between the fourth node and the switching device becomes unavailable. Detailed Implementation

[0016] First Implementation Method

[0017] The following is for reference Figures 1 to 3 The first embodiment of the fault diagnosis device will be described.

[0018] Structure of Communication Network System 100

[0019] The communication network system 100 is mounted on the vehicle. The communication network system 100 has multiple nodes.

[0020] like Figure 1 As shown, the communication network system 100 includes a first node 11, a second node 12, a third node 13, a fourth node 14, a fifth node 15, and a sixth node 16 as nodes.

[0021] like Figure 1As shown, in addition to the first node 11 to the sixth node 16, the communication network system 100 also has a relay device 20 and a switching device 30 as nodes.

[0022] The communication network system 100 includes a first-mode network. The first-mode network is a network in which a relay device 20 and multiple nodes are connected in parallel via a communication bus. The communication network system 100 has a first communication bus 23A, a second communication bus 23B, and a third communication bus 23C as communication buses. The nodes constituting the first-mode network perform CAN communication using the CAN protocol within the first-mode network.

[0023] like Figure 1 As shown, relay device 20, first node 11, second node 12, and switching device 30 are connected in parallel with the first communication bus 23A. The nodes connected to the first communication bus 23A constitute a network of the first mode. Relay device 20, first node 11, second node 12, and switching device 30 perform CAN communication through the first communication bus 23A.

[0024] like Figure 1 As shown, relay device 20, third node 13, and fourth node 14 are connected in parallel to the second communication bus 23B. The nodes connected to the second communication bus 23B constitute a network of the first mode. Relay device 20, third node 13, and fourth node 14 perform CAN communication through the second communication bus 23B.

[0025] like Figure 1 As shown, relay device 20, fifth node 15, and sixth node 16 are connected in parallel to the third communication bus 23C. The nodes connected to the third communication bus 23C constitute the network of the first mode. Relay device 20, fifth node 15, and sixth node 16 perform CAN communication through the third communication bus 23C.

[0026] The relay device 20 relays CAN communication performed between communication buses. When the relay device 20 receives data from the communication bus via CAN communication, it transmits the data to other communication buses.

[0027] The communication network system 100 includes a second type of network. The second type of network is a network in which the switching device 30 is connected one-to-one with multiple nodes via communication cables. The communication network system 100 includes a first communication cable 33A, a second communication cable 33B, and a third communication cable 33C as communication cables. Nodes constituting the second type of network perform Ethernet communication using the Ethernet protocol within the second type of network.

[0028] like Figure 1As shown, the second node 12 and the switching device 30 are connected one-to-one via the first communication cable 33A. The nodes connected to the first communication cable 33A constitute a network of the second mode. The second node 12 and the switching device 30 perform Ethernet communication via the first communication cable 33A.

[0029] like Figure 1 As shown, the fourth node 14 and the switching device 30 are connected one-to-one via the second communication cable 33B. The nodes connected to the second communication cable 33B constitute a network of the second mode. The fourth node 14 and the switching device 30 perform Ethernet communication via the second communication cable 33B.

[0030] like Figure 1 As shown, the sixth node 16 and the switching device 30 are connected one-to-one via the third communication cable 33C. The nodes connected to the third communication cable 33C constitute the network of the second mode. The sixth node 16 and the switching device 30 perform Ethernet communication via the third communication cable 33C.

[0031] The switching device 30 relays Ethernet communications between nodes. When the switching device 30 receives data from a node via a communication cable, it transmits the data via Ethernet communication to nodes connected to other communication cables.

[0032] like Figure 1 As shown, the communication network system 100 includes a diagnostic port 40. The diagnostic port 40 is connected to the repeater device 20 via a communication line 41. The communication line 41 is, for example, a communication cable.

[0033] exist Figure 1 External device 50 is shown. External device 50 is not a node constituting the communication network system 100. External device 50 is, for example, a tool used by a distributor or the like for performing fault diagnosis. External device 50 becomes capable of communicating with relay device 20 by connecting to diagnostic port 40.

[0034] External device 50 is fault diagnosis device 60 in communication network system 100. When Ethernet communication between the target node and switching device 30 becomes unavailable, fault diagnosis device 60 determines the location of the fault in communication network system 100.

[0035] The target node is a node connected to the relay device 20 via a communication bus and to the switching device 30 via a communication cable. In the communication network system 100, the second node 12, the fourth node 14, and the sixth node 16 are target nodes.

[0036] The relay device 20 is connected to four nodes—the second node 12, the fourth node 14, the sixth node 16, and the switching device 30—via a communication bus. That is, the relay device 20 is a node included in the first-mode network, comprising both the target node and the switching device 30.

[0037] The communication method performed when a node becomes capable of communication.

[0038] Figure 2 This illustrates the communication method performed when the fourth node 14 is added to the communication network system 100 from a state where the communication network system 100 does not have a fourth node 14.

[0039] The fourth node 14 becomes capable of performing CAN communication from the time it is added to the communication network system 100. For example... Figure 2 As shown, after the fourth node 14 is added to the communication network system 100, it sends a first notification to the relay device 20 via CAN communication through the second communication bus 23B. The first notification indicates that CAN communication has been enabled.

[0040] like Figure 2 As shown, after receiving the first notification from the fourth node 14, the relay device 20 sends the received first notification to the switching device 30 via CAN communication through the first communication bus 23A. Figure 2 As shown, after receiving the first notification from the relay device 20, the switching device 30 stores the information so that the fourth node 14 can perform CAN communication.

[0041] Thus, a node in the communication network system 100 sends a first notification when it becomes capable of performing CAN communication. The phrase "when a node becomes capable of performing CAN communication" refers to the moment the node is added to the communication network system 100.

[0042] The nodes originally present in the communication network system 100 may be subsequently connected to the communication bus and become capable of performing CAN communication by changing their installation location. In this case, the node becoming capable of performing CAN communication means that the node is connected to the communication bus.

[0043] In the communication network system 100, a node may sometimes be updated to enable CAN communication from a state that was originally connected to the communication bus but not programmed to perform CAN communication. In this case, a node becomes capable of performing CAN communication when it is updated.

[0044] When a node in the communication network system 100 becomes capable of performing CAN communication, the relay device 20 obtains a first notification from the node and sends the obtained first notification to the switching device 30. The switching device 30, upon receiving the first notification, stores the information as indicating that the node that sent the first notification is capable of performing CAN communication.

[0045] The fourth node 14 becomes capable of performing Ethernet communication from the moment it is added to the communication network system 100. For example... Figure 2 As shown, after being added to the communication network system 100, the fourth node 14 sends a second notification to the switching device 30 via Ethernet communication through the second communication cable 33B. The second notification indicates that Ethernet communication has been enabled.

[0046] like Figure 2 As shown, after receiving the second notification from the fourth node 14, the switching device 30 stores that the fourth node 14 is capable of performing Ethernet communication.

[0047] Thus, a node in the communication network system 100 sends a second notification when it becomes capable of performing Ethernet communication. The phrase "when a node becomes capable of performing Ethernet communication" refers to the moment the node is added to the communication network system 100.

[0048] Nodes originally present in the communication network system 100 may be subsequently connected to communication cables and become capable of performing Ethernet communication by changing their installation location. In this case, a node becoming capable of performing Ethernet communication refers to the node being connected to a communication cable.

[0049] In the communication network system 100, a node is originally connected to a communication cable. However, in the communication network system 100, sometimes a node that was never programmed to perform Ethernet communication becomes capable of performing Ethernet communication through an update. In this case, a node becoming capable of performing Ethernet communication refers to the moment the node is updated.

[0050] When a node in the communication network system 100 becomes capable of performing Ethernet communication, the switching device 30 obtains a second notification from that node. The switching device 30 stores information indicating that the node that sent the second notification is capable of performing Ethernet communication.

[0051] In this way, based on the information obtained by itself and the relay device 20, the switching device 30 stores the types of communication that can be performed according to each node in the communication network system 100.

[0052] Communication methods performed when Ethernet communication becomes unavailable

[0053] Figure 3This refers to the communication method performed when Ethernet communication between the fourth node 14 and the switching device 30 becomes unavailable in the communication network system 100.

[0054] As described above, the fourth node 14 is the object node. The external device 50 can be communicatively connected to the relay device 20 through the diagnostic port 40.

[0055] A diagnostic program is executed in an external device 50 connected to the diagnostic port 40. In this case, when the diagnostic program is executed, it is detected that the Ethernet communication between the fourth node 14 and the switching device 30 has become interrupted.

[0056] like Figure 3 As shown, the switching device 30 sends data representing communication information between the fourth node 14 and the switching device 30 to the external device 50. The communication information indicates the type of communication that the node can perform. The switching device 30 sends the data representing the communication information to the external device 50 via the relay device 20.

[0057] For reference Figure 2 As explained, the switching device 30 stores the types of communication that can be performed for each node in the communication network system 100 based on information obtained from itself and the relay device 20. Figure 3 In this process, the switching device 30 generates data representing communication information between the fourth node 14 and the switching device 30 based on the information stored in it.

[0058] exist Figure 3 In the process, the external device 50, which receives data representing communication information about the fourth node 14 and the switching device 30, acknowledges the received communication information. Then, as... Figure 3 As shown, based on the received communication information, the external device 50 confirms that both the fourth node 14 and the switching device 30 are capable of performing CAN communication and Ethernet communication.

[0059] like Figure 3 As shown, after confirming that both the fourth node 14 and the switching device 30 are capable of performing CAN and Ethernet communication, the external device 50 sends a read request to the relay device 20. The read request is a message sent to the relay device 20 requesting diagnostic information to be read from the two nodes whose Ethernet communication has failed. By sending the read request to the relay device 20, the external device 50 causes the relay device 20 to read the diagnostic information.

[0060] In the communication network system 100, nodes have a self-diagnostic function. When an anomaly occurs during Ethernet communication, the node detects the anomaly through this function. After detecting the anomaly, the node stores a record indicating that the anomaly was detected through the self-diagnostic function—that is, diagnostic information.

[0061] like Figure 3 As shown, after receiving a read request, relay device 20 reads diagnostic information from the fourth node 14 and switching device 30. During the diagnostic information reading process, relay device 20 uses CAN communication to request nodes whose Ethernet communication has failed to send their stored diagnostic information back to relay device 20. Figure 3 In the example shown, relay device 20 requests the fourth node 14 and switching device 30 to send the stored diagnostic information to relay device 20.

[0062] When a node storing diagnostic information is requested to send diagnostic information, it will send its stored diagnostic information to the relay device 20. At this time, the node with stored diagnostic information sends the diagnostic information to the relay device 20 via CAN communication. A node without stored diagnostic information cannot send diagnostic information to the relay device 20 when requested. That is, a node that does not detect an anomaly through its self-diagnostic function will not send diagnostic information to the relay device 20.

[0063] After requesting the transmission of diagnostic information, relay device 20 terminates the reading of diagnostic information after a certain period of time. For example... Figure 3 As shown, after performing the reading of diagnostic information, the relay device 20 sends data indicating the result of the reading of diagnostic information to the external device 50.

[0064] If, after a certain period of time has elapsed since the request for diagnostic information was sent, the relay device 20 receives diagnostic information from a node where Ethernet communication has ceased, it performs the following actions: The relay device 20 sends information indicating that the node has recorded diagnostic information as a read result. If, after a certain period of time has elapsed since the request for diagnostic information was sent, the relay device 20 does not receive diagnostic information, it sends information indicating that no diagnostic information has been recorded at any node as a read result.

[0065] External device 50 confirms the readout received from relay device 20 and determines the location of the fault. For example... Figure 3 As shown, if the external device 50 receives a read result indicating that diagnostic information is recorded in the fourth node 14, it determines that a fault has occurred in the fourth node 14. Figure 3As shown, if the external device 50 receives a read result indicating that the switching device 30 has recorded diagnostic information, it determines that the switching device 30 has malfunctioned. Figure 3 As shown, if the external device 50 receives a reading indicating that no diagnostic information is recorded at each node, it determines that a fault has occurred in the second communication cable 33B.

[0066] Thus, if the fault diagnosis device 60 records diagnostic information at either the target node or the switching device 30, it determines that a fault has occurred at the node where the diagnostic information is recorded. Furthermore, if no diagnostic information is recorded at either the target node or the switching device 30, the fault diagnosis device 60 determines that a fault has occurred in the communication cable connecting the target node and the switching device 30.

[0067] Before reading diagnostic information, the fault diagnosis device 60 confirms the communication information of the target node where Ethernet communication has become unavailable and the switching device 30. Therefore, the fault diagnosis device 60 can perform diagnoses corresponding to design changes, such as when nodes are added to the communication network system 100.

[0068] The role of the first embodiment

[0069] When Ethernet communication fails, the fault diagnosis device 60 confirms the results of reading diagnostic information performed via CAN communication for the two nodes where communication has failed.

[0070] Effects of the first implementation method

[0071] (1-1) Even if Ethernet communication based on communication cables becomes unavailable, the fault diagnosis device 60 can still confirm the presence or absence of diagnostic information via CAN communication based on the communication bus. Furthermore, the fault diagnosis device 60 can determine the location of the fault by confirming the diagnostic information.

[0072] (1-2) The fault diagnosis device 60 is an external device 50 capable of communicating with nodes included in a first-mode network, including both the target node and the switching device 30. When Ethernet communication between the target node and the switching device 30 becomes unavailable, the fault diagnosis device 60 performs the following actions: The fault diagnosis device 60 causes nodes in the first-mode network, including both the target node and the switching device 30, to use CAN communication to read diagnostic information from the target node and the switching device 30. The fault diagnosis device 60 confirms the result of the diagnostic information reading. If diagnostic information is recorded on either the target node or the switching device 30, the fault diagnosis device 60 determines that a fault has occurred at the node where the diagnostic information is recorded.

[0073] Therefore, when Ethernet communication becomes unavailable, the external device 50 can determine the location of the fault.

[0074] (1-3) The fault diagnosis device 60 confirms the result of reading the diagnostic information. If no diagnostic information is recorded at either the object node or the switching device 30, the fault diagnosis device 60 determines that a fault has occurred in the communication cable connecting the object node and the switching device 30.

[0075] The fault diagnosis device 60 confirms that no fault has occurred at any node connected by the communication cable by verifying that no diagnostic information has been recorded at each node. Therefore, the fault diagnosis device 60 determines that a fault has occurred in the communication cable connecting the nodes.

[0076] The fault diagnosis device 60 can determine the location of the fault even if the fault is not in a node but in a communication cable.

[0077] (1-4) In the communication network system 100, the relay device 20 receives a first notification indicating that it has changed from a node capable of performing CAN communication to one capable of performing CAN communication. In the communication network system 100, the switching device 30 receives a second notification indicating that it has changed from a node capable of performing Ethernet communication to one capable of performing Ethernet communication. The fault diagnosis device 60 refers to the information obtained by the relay device 20 and the switching device 30. When the fault diagnosis device 60 confirms that both the target node (where Ethernet communication is not working) and the switching device 30 have become capable of performing both CAN and Ethernet communication, it performs the following actions: The fault diagnosis device 60 causes nodes in the network, including both the target node and the switching device 30, to read diagnostic information.

[0078] If neither of the two nodes that have lost Ethernet communication can now perform both CAN and Ethernet communication, then even if diagnostic information is read, it cannot be retrieved. For example, if at least one of the two nodes that have lost Ethernet communication cannot perform CAN communication, then even if diagnostic information is read, it cannot be retrieved. In this case, the fault diagnosis device 60 cannot perform appropriate fault diagnosis.

[0079] Based on information indicating that communication has become possible, the fault diagnosis device 60 determines whether diagnostic information can be read from the node where Ethernet communication has failed. If the fault diagnosis device 60 confirms that diagnostic information can be read, it then performs the reading of the diagnostic information.

[0080] The fault diagnosis device 60 does not read the diagnostic information when it is not normally possible to do so, thereby suppressing the possibility of making incorrect judgments.

[0081] Second Implementation Method

[0082] Hereinafter, a second embodiment of the fault diagnosis device will be described with reference to the accompanying drawings. In the second embodiment, a fault diagnosis device 60 is provided within the communication network system 100. Specifically, the difference lies in that the relay device 20 has the function of being a fault diagnosis device 60. Hereinafter, the description will focus on the differences from the first embodiment, and the similarities will be simplified or omitted.

[0083] Communication methods performed when Ethernet communication becomes unavailable

[0084] The communication network system 100 in the second embodiment may also lack a diagnostic port 40. In other words, in the second embodiment, the external device 50 may not be communicatively connected to the relay device 20.

[0085] Figure 4 This describes the communication method performed when Ethernet communication between the fourth node 14 and the switching device 30 becomes unavailable in the communication network system 100. In the communication network system 100 of the second embodiment, the relay device 20 performs fault diagnosis as a fault diagnosis device 60.

[0086] When the Ethernet communication between the fourth node 14 and the switching device 30 becomes unavailable, the switching device 30 sends data to the relay device 20 representing communication information about the fourth node 14 and the switching device 30.

[0087] exist Figure 4 In this process, the relay device 20, which receives data indicating communication information regarding the fourth node 14 and the switching device 30, acknowledges the received communication information. For example... Figure 4 As shown, after receiving data representing communication information, the relay device 20 confirms that both the fourth node 14 and the switching device 30 are capable of performing CAN communication and Ethernet communication.

[0088] After confirming that both the fourth node 14 and the switching device 30 are capable of performing CAN and Ethernet communication, the relay device 20 performs the following actions: The relay device 20 reads diagnostic information from the fourth node 14 and the switching device 30 via CAN communication.

[0089] like Figure 4 As shown, after reading the diagnostic information, the relay device 20 confirms the reading result and determines the location of the fault. Figure 4As shown, if the relay device 20 reads a result indicating that the fourth node 14 has recorded diagnostic information, it determines that a fault has occurred at the fourth node 14. Figure 4 As shown, if the relay device 20 reads a result indicating that the switching device 30 has recorded diagnostic information, it determines that a fault has occurred in the switching device 30. For example... Figure 4 As shown, if the external device 50 reads a result indicating that no diagnostic information is recorded at each node, it determines that a fault has occurred in the second communication cable 33B.

[0090] Thus, one of the nodes included in the network of the first type, including both the object node and the switching device 30, performs the reading of diagnostic information. Simultaneously, as a fault diagnosis device 60, it can determine the location of the fault based on the reading results. The node that performs the reading of diagnostic information and, as the fault diagnosis device 60, determines the location of the fault based on the reading results can also be... Figure 4 That is not relay device 20. For example, the node that performs the reading of diagnostic information and determines the location of the fault based on the reading results as a fault diagnosis device 60 can also be any of the first node 11 to the sixth node 16.

[0091] The node that performs the reading of diagnostic information and determines the location of the fault based on the reading results as a fault diagnosis device 60 can also be an object node or a switching device 30. In this case, when the node performing the fault diagnosis reads the diagnostic information, it checks whether it has stored the diagnostic information and confirms via CAN communication whether the diagnostic information is stored in the object communicating via Ethernet.

[0092] The function and effects of the second implementation method

[0093] (2-1) The fault diagnosis device 60 of the second embodiment has the same effect as (1-1), (1-3), and (1-4) in the first embodiment.

[0094] (2-2) The fault diagnosis device 60 of the second embodiment is one of the nodes included in the network of the first embodiment, which includes both the target node and the switching device 30. When the Ethernet communication between the target node and the switching device 30 becomes unavailable, the fault diagnosis device 60 uses CAN communication to read the diagnostic information of both the target node and the switching device 30. The fault diagnosis device 60 confirms the result of reading the diagnostic information. When the fault diagnosis device 60 determines that a fault has occurred at the node where the diagnostic information is recorded, if diagnostic information is recorded at either the target node or the switching device 30.

[0095] Therefore, when Ethernet communication becomes unavailable, nodes in the communication network system 100 can determine the location of the fault.

[0096] Other implementation methods

[0097] The above embodiments can be implemented by modification as follows. The embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0098] • The node that stores the types of communication that can be performed for each node in the communication network system 100 based on the information obtained by the switching device 30 and the relay device 20 may not be the switching device 30. For example, the relay device 20 may also store the types of communication that can be performed for each node in the communication network system 100 based on the information obtained by the switching device 30 and the relay device 20.

[0099] • Nodes that have become capable of performing CAN communication can also be powered, and whenever the setup for communicating with other nodes is completed, they are considered to have become capable of performing CAN communication and send the first notification.

[0100] • Nodes that have already been made capable of performing Ethernet communication can also be powered, and whenever the setup for communicating with other nodes is completed, they are considered to be capable of performing Ethernet communication and a second notification is sent.

[0101] • The external device 50 in the first embodiment may request diagnostic information from the relay device 20 without confirming that both the target node and the switching device 30 are capable of performing CAN communication and Ethernet communication.

[0102] The node to which the external device 50 connects via the diagnostic port 40 can be any node included in the network of the first embodiment, which includes both the target node and the switching device 30. That is, it does not have to be the relay device 20 as in the first embodiment. For example, the external device 50 can also be communicatively connected to the switching device 30 via the diagnostic port 40. For example, the external device 50 can be communicatively connected to any one of the first node 11 to the sixth node 16 via the diagnostic port 40.

[0103] • One of the nodes in the network of the first mode, including both the object node and the switching device 30, can also perform the reading of diagnostic information. Furthermore, other nodes in the communication network system 100 can also act as the fault diagnosis device 60 to determine the location of the fault.

Claims

1. A fault diagnosis device, which is a fault diagnosis device for a communication network system, wherein, The communication network system has multiple nodes, multiple communication buses, and multiple communication cables. The communication network system includes: A first-mode network, in which relay devices among multiple nodes relay CAN communication using the CAN protocol are connected in parallel with the multiple nodes via the communication bus to perform the CAN communication; and In the second type of network, a switching device that relays Ethernet communication using the Ethernet protocol among multiple nodes is connected one-to-one with the multiple nodes via the communication cable to perform the Ethernet communication. The relay device and the switching device are connected via the communication bus. When the Ethernet communication between the target node (i.e., the node connected to the relay device via the communication bus and the switching device via the communication cable) and the switching device becomes unavailable, the nodes included in the network of the first mode, including both the target node and the switching device, use the CAN communication to read diagnostic information, which is a record indicating anomalies detected by the self-abnormal diagnostic function of the target node and the switching device. The fault diagnosis device confirms the result of reading the diagnostic information. If the diagnostic information is recorded at either the object node or the switching device, it determines that a fault has occurred at the node where the diagnostic information is recorded.

2. The fault diagnosis device according to claim 1, wherein, The fault diagnosis device is an external device capable of communicating with the nodes included in the network of the first mode, which includes both the object node and the switching device. When the Ethernet communication between the object node and the switching device becomes unavailable, the nodes in the network of the first mode, including both the object node and the switching device, use the CAN communication to read the diagnostic information of the object node and the switching device. The fault diagnosis device confirms the result of reading the diagnostic information. If the diagnostic information is recorded at either the object node or the switching device, it determines that a fault has occurred at the node where the diagnostic information is recorded.

3. The fault diagnosis device according to claim 1, wherein, The fault diagnosis device is one of the nodes included in the network of the first mode, which includes both the object node and the switching device. When the Ethernet communication between the object node and the switching device becomes unavailable, the CAN communication is used to read the diagnostic information from both the object node and the switching device. The fault diagnosis device confirms the result of reading the diagnostic information. If the diagnostic information is recorded at either the object node or the switching device, it determines that a fault has occurred at the node where the diagnostic information is recorded.

4. The fault diagnosis device according to any one of claims 1 to 3, wherein, The fault diagnosis device confirms the result of reading the diagnostic information. If neither the object node nor the switching device records the diagnostic information, it determines that the communication cable connecting the object node and the switching device has failed.

5. The fault diagnosis device according to claim 2, wherein, In the communication network system, The relay device receives a first notification from the node that it has become capable of performing the CAN communication, indicating that it has become capable of performing the CAN communication. The switching device receives a second notification from the node that has become capable of performing the Ethernet communication, indicating that it has become capable of performing the Ethernet communication. Referring to the information obtained by the relay device and the switching device, if it can be confirmed that both the target node and the switching device, where the Ethernet communication has become unavailable, are now capable of performing both CAN communication and Ethernet communication, the nodes included in the network of the first mode, which includes both the target node and the switching device, are made to read out the diagnostic information.

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