Ground fault detection apparatus and node apparatus

Abstract

The ground short-circuit fault detection device and the node device of the present application can improve the determination accuracy of the ground short-circuit fault. The ground short-circuit fault detection device is used in a communication network having two signal lines, in which the potential of each of the two signal lines is varied to signal the recessive level and the dominant level, and data is transmitted and received between a plurality of node devices. The ground short-circuit fault detection device comprises: a current measurement unit that measures the current value of the current flowing in each of the two signal lines; a determination unit that determines whether the difference between the measured current values exceeds a predetermined value, and outputs a determination result indicating a ground short-circuit fault of the low potential side signal line having a relatively low potential in the dominant level among the two signal lines when the difference exceeds the predetermined value; and a control unit that controls the determination unit in a manner that the determination of whether the difference exceeds the predetermined value is performed when the transmission of a predetermined signal is completed.

Description

Technical Field

[0001] The present disclosure relates to a ground short circuit fault detection device and a node device. Background Art

[0002] Conventionally, as a communication network, there is known a CAN (Controller Area Network) communication system that transmits CAN signals by applying voltages to two signal lines.

[0003] For example, Patent Document 1 discloses a short-circuit fault detection device comprising: a communication line having two signal lines; a node device connected between the two signal lines and having a communication function; a potential measuring unit for measuring the potential of each of the two signal lines; and a short-circuit fault determination unit for determining whether a ground short-circuit fault has occurred in the communication line based on the potential measured by the potential measuring unit.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-191404 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, in a CAN communication system, multiple node devices may attempt to send data simultaneously. In this case, communication arbitration is performed, that is, the priority of multiple node devices is determined based on the identification information (ID) contained in the data, and data is sent from a specific node device based on the priority.

[0009] However, during communication arbitration, current is transmitted from multiple node devices to two signal lines. After the communication arbitration, voltage is transmitted from a specific node device to the two signal lines based on priority. During arbitration, the current differential between the two signal lines may become unstable. This can lead to errors in the determination of an abnormality (in this case, a short-circuit fault) on the two signal lines (CAN bus), potentially reducing the accuracy of ground fault detection.

[0010] Furthermore, for example, when a CAN communication system is installed in a vehicle, the potential of two signal lines may be unstable due to differences in the inductance of the signal lines (e.g., differences in the length of the wiring harness) or potential differences between multiple ground lines. This can reduce the accuracy of ground fault detection.

[0011] An object of the present disclosure is to provide a ground short-circuit fault detection device and a node device capable of improving the accuracy of determining a ground short-circuit fault.

[0012] Solutions to the Problem

[0013] To achieve the aforementioned objectives, the present disclosure provides a ground short fault detection device for a communication network having two signal lines. In the communication network, the potential of each of the two signal lines is varied to switch the potential difference between the two signal lines between a recessive level and a dominant level. The recessive level and the dominant level are used as signals to transmit and receive data between a plurality of node devices. The ground short fault detection device comprises:

[0014] a current measuring unit for measuring a current value of a current flowing through each of the two signal lines;

[0015] a determination unit that determines whether a difference between the measured current values ​​exceeds a predetermined value, and, if the difference exceeds the predetermined value, outputs a determination result indicating that a ground short-circuit fault has occurred in a low-potential-side signal line, the low-potential-side signal line being the signal line having a relatively low potential when at the dominant level, of the two signal lines; and

[0016] The control unit controls the determination unit so as to determine whether the difference exceeds a predetermined value when transmission of a predetermined signal is completed.

[0017] Furthermore, the node device of the present disclosure includes the above-mentioned ground short-circuit fault detection device.

[0018] Effects of the Invention

[0019] According to the present disclosure, it is possible to improve the accuracy of determining an abnormal state of two signal lines (CAN bus), where the abnormal state is a ground short-circuit fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram showing an example of a CAN bus network according to an embodiment of the present disclosure.

[0021] Figure 2 This is a flowchart showing an example of processing of the control device. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In this embodiment, a CAN bus network will be described as an example of an in-vehicle communication network. Figure 1 This is a diagram showing an example of a CAN bus network according to an embodiment of the present disclosure.

[0023] like Figure 1As shown, a CAN bus network has two signal lines. A CAN bus network is a communication network that switches the potential difference between the two signal lines between a recessive level and a dominant level by varying the potential of each of the two signal lines. The recessive and dominant potential differences serve as signals for data transmission and reception between multiple node devices.

[0024] like Figure 1 As shown, multiple node devices 1, 1A, 1B, and 1C are connected to two signal lines. Also connected to the two signal lines are an instrument 5, such as a brake indicator light, and a fault code recorder 6. If a fault such as a signal line break or short circuit occurs, or a sensor malfunction occurs, this information is recorded as a diagnostic trouble code (DTC) in the fault code recorder 6. Furthermore, terminal resistors 7 are connected to both ends of the two communication lines.

[0025] The two signal lines (also called CAN buses) consist of a high-potential signal line CAN_H and a low-potential signal line CAN_L. The high-potential signal line CAN_H has a relatively low potential (e.g., a potential near the reference potential) when in recessive mode, and a relatively high potential (e.g., a potential higher than a potential near the reference potential) when in dominant mode. The low-potential signal line CAN_L has a relatively high potential (e.g., a potential near the reference potential) when in recessive mode, and a relatively low potential (e.g., a potential lower than a potential near the reference potential) when in dominant mode.

[0026] In this embodiment, node device 1 among the multiple node devices 1, 1A, 1B, and 1C includes the function of a ground short fault detection device 100 that detects a ground short on the low-potential-side signal line CAN_L. Therefore, the description of node device 1 will be replaced with the description of ground short fault detection device 100. Furthermore, ground short fault detection device 100 may be provided independently of node device 1. Furthermore, the other node devices 1A, 1B, and 1C may also include the function of ground short fault detection device 100.

[0027] The node device 1 includes a CAN transceiver 2 and a control device 3 .

[0028] The CAN transceiver 2 provides an interface between the control device 3 and the physical wiring of the CAN bus. The CAN transceiver 2 transmits signals over the physical wiring, performing tasks such as converting data to differential signals and vice versa, adjusting differential voltages, ensuring operating voltages, and protecting the wiring.

[0029] The CAN transceiver 2 includes a current measuring unit 4. The current measuring unit 4 periodically measures the current value flowing through the high-potential-side signal line CAN_H. Furthermore, the current measuring unit 4 periodically measures the current value flowing through the low-potential-side signal line CAN_L. The current measuring unit 4 outputs each measured current value to the control device 3.

[0030] The control device 3 is, for example, an ECU (Electronic Control Unit) comprising a microcomputer (not shown) including a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), and input / output devices. The control device 3 implements various functions, such as an acquisition unit 31, a calculation unit 32, a determination unit 33, and a control unit 34, by, for example, the CPU sequentially reading and executing programs stored in the ROM. The control device 3 processes data transmitted and received with a communicating node device (e.g., one of the node devices 1A, 1B, or 1C) via a CAN bus (two signal lines).

[0031] In addition, the control device 3 performs other processing such as monitoring the status of the CAN bus. In this way, it is determined whether the priority of other node devices (for example, node devices 1A, 1B, and 1C) is high. When the CAN bus is in an active state (a state in which other node devices are sending data or a state in which sending has just been completed), the control device 3 does not perform processing of data sent to and received from the node device of the communication partner. In addition, when the CAN bus is in an idle state and the node device 1 and other node devices try to send at the same time, the control device 3 performs communication arbitration. In communication arbitration, the identification information (ID) contained in the data respectively sent by the node device 1 and other node devices is used. In communication arbitration, the control device 3 determines the priority of the node device 1 and other node devices based on the identification information, and performs processing of data sent to and received from the node device of the communication partner based on the priority.

[0032] The acquisition unit 31 acquires the current value of each of the two signal lines (the current value of the high-potential-side signal line CAN_H and the current value of the low-potential-side signal line CAN_L).

[0033] The calculation unit 32 calculates a difference between the current value of the high-potential-side signal line CAN_H and the current value of the low-potential-side signal line CAN_L (hereinafter referred to as “current value difference”).

[0034] The determination unit 33 determines whether the calculated current value difference exceeds a predetermined value. If the current value difference exceeds the predetermined value, the determination unit 33 outputs a determination result indicating that a ground short-circuit fault has occurred on the low-potential-side signal line CAN_L. Specifically, if the current value difference exceeds the predetermined value more than a predetermined number of times, the determination unit 33 outputs a determination result indicating that a ground short-circuit fault has occurred.

[0035] However, before communication arbitration, voltage is simultaneously transmitted to the two signal lines from each of the multiple node devices. After communication arbitration, voltage is transmitted to the two signal lines from a specific node device based on priority. Therefore, during communication arbitration, the potentials of the two signal lines acquired by acquisition unit 31 may become unstable. Consequently, the current difference may become unstable. As a result, the determination unit 33 may make an erroneous decision.

[0036] Therefore, in this embodiment, the following process is performed to determine whether a ground fault has occurred on the low-potential-side signal line CAN_L. Furthermore, while the case of unstable potentials of two signal lines is described here using the case of communication arbitration as an example, the case of unstable potentials of two signal lines is not limited to the case of communication arbitration.

[0037] When communication arbitration is not in progress, the control unit 34 controls the determination unit 33 to determine whether the current difference exceeds a predetermined value. If the current difference exceeds the predetermined value, the determination unit 33 outputs a determination result indicating a ground fault has occurred on the low-potential-side signal line CAN_L. The control unit 34 controls the CAN transceiver 2 to transmit this determination result to the fault code recording device 6.

[0038] When communication arbitration is being conducted, a predetermined signal is transmitted. Here, the predetermined signal refers to a signal used to transmit data containing identification information (ID) of the node apparatus 1 for communication arbitration. The control unit 34 determines whether the transmission of the predetermined signal has been completed. Furthermore, the completion of the transmission of the predetermined signal is a state in which the determination unit 33 has few errors in its determination, as determined by winning the arbitration and using the current difference at the time when data was transmitted by the node apparatus 1.

[0039] Upon completion of the predetermined signal transmission, the control unit 34 controls the determination unit 33 to determine whether the current value difference exceeds a predetermined value. Similarly, if the current value difference exceeds the predetermined value, the determination unit 33 outputs a determination result indicating a ground fault has occurred on the low-potential-side signal line CAN_L. The control unit 34 controls the CAN transceiver 2 to transmit this determination result to the fault code recording device 6.

[0040] Next, an example of the operation will be described. Figure 2 This is a flowchart showing an example of processing by control device 3. This process begins when the engine switch is turned on. The description assumes that control device 3 includes the functions of acquisition unit 31, calculation unit 32, determination unit 33, and control unit 34. Furthermore, the description assumes that a predetermined signal is transmitted from the node device 1.

[0041] First, in step S100 , the control device 3 obtains the current value of the current drawn from the high-potential-side signal line CAN_H.

[0042] Next, in step S110 , the control device 3 obtains the current value of the current sunk into the low-potential-side signal line CAN_L.

[0043] Next, in step S120 , the control device 3 calculates the difference between the current value of the source current of the high-potential-side signal line CAN_H and the current value of the sink current of the low-potential-side signal line CAN_L.

[0044] Next, in step S130, control device 3 determines whether the calculated difference exceeds a predetermined value. If the difference exceeds the predetermined value (step S130: Yes), the process moves to step S140. If the difference does not exceed the predetermined value (step S130: No), the process returns to the process before step S100.

[0045] In step S140, the control device 3 determines whether communication arbitration is in progress. If communication arbitration is in progress (step S140: Yes), the process returns to before step S100. If communication arbitration is not in progress (step S140: No), the process proceeds to step S150.

[0046] In step S150 , the control device 3 controls the CAN transceiver 2 to transmit a predetermined signal.

[0047] Next, in step S160, control device 3 determines whether the transmission of the predetermined signal has been completed. If the transmission of the predetermined signal has been completed (step S160: "Yes"), the process moves to step S170. If the transmission of the predetermined signal has not been completed (step S160: "No"), the process returns to the process before step S100.

[0048] Next, in step S170 , the control device 3 determines that a ground short-circuit fault has occurred in the low-potential-side signal line CAN_L, and controls the CAN transceiver 2 to transmit the determination result to the fault code recording device 6 .

[0049] The ground fault detection device 100 in the above-described embodiment is a ground fault detection device for a communication network having two signal lines. In this communication network, the potential of each of the two signal lines is varied so that the potential difference between the two signal lines switches between a recessive level and a dominant level. Data is transmitted and received between a plurality of node devices using the potential difference between the recessive level and the dominant level as signals. The ground fault detection device includes: a current measuring unit 4 for measuring the current value of a current flowing through each of the two signal lines during dominant output; a determination unit 33 for determining whether the difference between the measured current values ​​exceeds a predetermined value. If the difference exceeds the predetermined value, the determination unit 33 outputs a determination result indicating that a ground fault has occurred on the low-potential-side signal line CAN_L, which is the signal line of the two signal lines that has a relatively high potential when at a recessive level and a relatively low potential when at a dominant level; and a control unit 34 for controlling the determination unit 33 to determine whether the difference exceeds the predetermined value when transmission of a predetermined signal is completed.

[0050] According to the above configuration, after confirming that the predetermined signal has been transmitted and the potentials of the two signal lines are not unstable, the determination unit 33 determines whether the current difference exceeds a predetermined value. This reduces errors in the determination and improves the accuracy of the ground fault determination.

[0051] Furthermore, in the ground fault detection device 100 of the above-described embodiment, when the potentials of the two signal lines are unstable, the control unit 34 controls the transmission of a predetermined signal. Consequently, when the potentials of the two signal lines are unstable, the determination unit 33 does not make a determination, thereby reducing errors in determination.

[0052] Furthermore, in the ground fault detection device 100 of the above-described embodiment, when the potentials of the two signal lines become unstable, communication arbitration is performed, in which the priority of multiple node devices is determined based on the node device identification information contained in the data. Thus, even in the case of communication arbitration where the potentials of the two signal lines may become unstable, the determination unit 33 makes a determination based on confirmation that the potentials of the two signal lines are not unstable, thereby reducing errors in determination.

[0053] Furthermore, in the ground fault detection device 100 of the above-described embodiment, the predetermined signal transmitted during communication arbitration is a signal for transmitting data used for communication arbitration and containing identification information of the own node device 1. In this case, the predetermined signal is transmitted from the own node device 1. Once the transmission of this signal is complete, the signal from the own device can be used to confirm that the potentials of the two signal lines are not unstable, thereby enabling the ground fault detection device 100 to accurately determine a ground fault.

[0054] Furthermore, in the ground fault detection device 100 of the above embodiment, communication arbitration is used as an example to illustrate a case where the potential of two signal lines is unstable. However, the present disclosure is not limited to this. For example, the potential of the two signal lines may be unstable due to a difference in the inductance components of the signal lines or a potential difference between multiple ground lines. In this case, for example, the inductance components of the two signal lines may be measured, the difference in the inductance components may be calculated, and a case where the difference in the inductance components exceeds a predetermined value may be considered as a case where the potential of the two signal lines is unstable. Alternatively, for example, the potential of multiple ground lines may be measured, the potential difference between the multiple ground lines may be calculated, and a case where the potential difference between the multiple ground lines exceeds a predetermined value may be considered as a case where the potential of the two signal lines is unstable.

[0055] In addition, in the above-mentioned embodiment, the predetermined signal sent when performing communication arbitration is described as a signal in the case of sending data used for the communication arbitration and having the identification information of the node device 1, but the present disclosure is not limited to this. The sending of the predetermined signal may also be a signal in the case of sending the following data used for communication arbitration, which has a higher priority than the identification information of multiple node devices. In this case, among the multiple node devices involved in the communication arbitration, even if the priority of the node device 1 is not the highest, for example, even if the priority of the identification information of the node device is lower than the priority of the identification information of other node devices, it wins the communication arbitration and sends the predetermined signal from the node device 1. It is possible to determine whether the sending of the signal is completed without wasting time, and therefore has the advantage of being able to regularly determine whether a ground short circuit fault has occurred.

[0056] The above embodiments are merely examples of specific implementations of the present disclosure, and the technical scope of the present disclosure should not be construed as being limited thereto. That is, the present disclosure can be implemented in various forms without departing from its gist or main features.

[0057] This application is based on Japanese patent application (Japanese Patent Application No. 2020-182733) filed on October 30, 2020, the contents of which are incorporated herein by reference.

[0058] Industrial Applicability

[0059] The present disclosure can be suitably utilized in a node device including a ground short-circuit fault detection device in which improvement in the accuracy of determining a ground short-circuit fault is required.

[0060] Description of Reference Numerals

[0061] 1. 1A, 1B, 1C node devices

[0062] 2 CAN transceivers

[0063] 3 Control device

[0064] 4 Current measurement unit

[0065] 5 Instruments

[0066] 6 Fault code recording device

[0067] 7. Terminal resistor

[0068] 31 Acquisition Department

[0069] 32 Computing Department

[0070] 33 Judgment Department

[0071] 34 Control Department

[0072] 100 Ground short circuit fault detection device

Claims

1. A ground short-circuit fault detection device in a communication network having two signal lines. In the communication network, the potential of each of the two signal lines is varied to switch the potential difference between the two signal lines between a recessive level and a dominant level. The recessive level and the dominant level are used as signals to transmit and receive data between a plurality of node devices. The ground short-circuit fault detection device comprises: a current measuring unit for measuring a current value of a current flowing through each of the two signal lines; a determination unit that determines whether a difference between the measured current values ​​exceeds a predetermined value, and outputs a determination result indicating that a ground short-circuit fault has occurred in a low-potential-side signal line when the difference exceeds the predetermined value, the low-potential-side signal line being the signal line having a relatively low potential of the two signal lines when at the dominant level; and The control unit controls the sending of a predetermined signal to the two signal lines without performing communication arbitration for determining the priority of the plurality of node devices based on identification information of the node devices contained in the data, and controls the determination unit in a manner that determines whether the difference exceeds a specified value when the sending of the predetermined signal is completed.

2. The ground short circuit fault detection device according to claim 1, wherein: The predetermined signal is a signal for transmitting data used for the communication arbitration, the data including identification information of the own node device.

3. The ground short circuit fault detection device according to claim 1, wherein: The predetermined signal is a signal for transmitting data used for the communication arbitration, the data having a higher priority than any identification information among the identification information of the plurality of node devices.

4. The ground short circuit fault detection device according to claim 1, wherein: The predetermined signal is a signal indicating identification information of the node device. 5 . A node device comprising the ground short circuit fault detection device according to claim 1 .

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