Vehicle-mounted device

Abstract

Provided is an in-vehicle device capable of reducing the influence of an overcurrent flowing through a housing on engine control. The vehicle-mounted device includes: a circuit board including a control circuit for controlling an internal combustion engine; a case that accommodates the circuit board; and a connection member that electrically connects the case and a conductive region other than the control circuit in the circuit board, the conductive region or the connection member being provided with a cut-off section that cuts off a current equal to or greater than a threshold value.

Description

Technical Field

[0001] This invention relates to vehicle-mounted devices. Background Technology

[0002] For example, Patent Document 1 discloses the reduction of electrical load power supply during engine jump-start.

[0003] [Prior Art Documents] Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2007-278216 Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] If the boost cable is connected to the wrong location on the vehicle body during jump starting, and power is supplied from an external battery via the housing of an onboard device such as the engine control unit (ECU) to the vehicle's grounding point, overcurrent exceeding the allowable value of the onboard device may cause deformation, melting, or other damage, thereby affecting engine control.

[0007] Therefore, the present invention was made in view of the above-mentioned problems, and its object is to provide an on-board device that can reduce the impact of overcurrent flowing through the housing on engine control.

[0008] [Methods used to solve problems]

[0009] The vehicle-mounted device of the present invention includes: a circuit board having a control circuit for controlling an internal combustion engine; a housing for housing the circuit board; and a connecting member for electrically connecting the housing to a conductive area other than the control circuit within the circuit board, wherein the conductive area or the connecting member has a cutting portion that cuts off current above a threshold value.

[0010] [Invention Effects]

[0011] According to the present invention, the impact of overcurrent flowing through the housing of the vehicle-mounted device on engine control can be reduced. Attached Figure Description

[0012] Figure 1 This is a diagram showing the structure inside the engine compartment E of vehicle V during jump start.

[0013] Figure 2 This is a diagram illustrating an example of a fuse detection circuit.

[0014] [Explanation of reference numerals in the attached figures]

[0015] 1 ECU (On-board Unit), 4 Engine (Internal Combustion Engine), 10 Circuit Board, 11 Housing, 100 Control Circuit, 101 Grounding Area (Conductive Area), 12 Connecting Cable (Connecting Component), 101c Narrow Section (Cutting Section), 120 Fuse (Cutting Section) Detailed Implementation

[0016] (Structure of the embodiment)

[0017] Figure 1 This diagram shows the structure inside the engine compartment E of vehicle V during jump start. The engine compartment E houses the ECU 1, battery 3, engine 4, starter motor 5, and wiring harness 6. Additionally, the vehicle body of V functions as the ground contact point 7.

[0018] Battery 3, for example, is a lithium-ion battery, which supplies power to auxiliary devices such as ECU 1 and starter motor 5 via a power circuit (not shown). The positive terminal 30 of battery 3 is connected to the power supply terminal 8 for jump-starting. The negative terminal 31 of battery 3 is connected to the grounding part 7 of vehicle V.

[0019] The starter motor 5 is a starter electric motor that rotates the crankshaft (not shown) of the engine 4 under the control of the ECU 1 when the engine 4 is started. Engine 4 is an example of an internal combustion engine that drives the vehicle V. Furthermore, engine 4 is not limited to a gasoline engine; it can also be a diesel engine.

[0020] ECU1 is an example of an on-board device that controls the operation of the starter motor 5 and the engine 4. ECU1 includes a housing 11, a bracket 13, a circuit board 10, a connector 14, and a connecting cable 12. Furthermore, in... Figure 1 The internal structure of the ECU1 is briefly shown when the circuit board 10 is viewed from the front.

[0021] The housing 11 and the bracket 13 are made of metal. The bracket 13 is mounted on the housing 11 to fix the ECU1 to the inner wall of the engine compartment E, etc.

[0022] The circuit board 10 and the connecting cable 12 are housed in the housing 11. The circuit board 10 has a control circuit 100 for controlling the engine 4 and the starter 5, and a grounding area 101 that is electrically connected to the housing 11 and the vehicle body grounding part 7. The control circuit 100 includes, for example, electrical components P such as a processor for performing control processing and a memory.

[0023] Grounding region 101 is an example of a conductive region other than the control circuit 100. It is a conductive pattern that functions as a ground portion of the ECU 1 and is electrically insulated from the control circuit 100. Grounding region 101 includes, for example, wide portions 101a and 101b and a narrow portion 101c. The width W1 of the wide portions 101a and 101b is wider than the width W2 of the narrow portion 101c. Here, widths W1 and W2 refer to the width in a direction approximately orthogonal to the direction of current flow.

[0024] Therefore, the narrow portion 101c melts or peels off due to overcurrent. Thus, the narrow portion 101c, as an example of a cutting-off portion, cuts off current exceeding a threshold. The width of the narrow portion 101c is set based on the current threshold. Alternatively, a chip fuse can be used instead of the narrow portion 101c.

[0025] Additionally, the connecting cable 12 is an example of a connecting component. The connecting cable 12 electrically connects the housing 11 to the grounding area 101 within the circuit board 10.

[0026] A fuse 120 is installed midway through the connecting cable 12. The fuse 120 also melts due to overcurrent, thus, as an example of a cutting-off part, it cuts off current above the threshold.

[0027] Connector 14 is disposed on or near circuit board 10. Connector 14 is configured such that its front end protrudes from opening 11a of housing 11 without direct contact with housing 11. Connector 14 may have, for example, a structure in which multiple terminals (not shown) are arranged within a resin housing. Connector 14 is electrically connected, at each terminal, to the input / output signals, power supply lines, grounding lines, and grounding area 101 of control circuit 100. A portion of the terminals of connector 14 is electrically connected, for example, to vehicle body grounding portion 7 via wiring harness 6.

[0028] As shown in the current path Ra, the ground wire of the control circuit 100 is connected from the connector 14 to the vehicle body grounding part 7 via the wiring harness 6. As shown in the current path Rb, the grounding area 101 is connected from the connector 14 to the vehicle body grounding part 7 via the wiring harness 6.

[0029] If, for example, the occupants of vehicle V are unable to start engine 4 due to low battery level in battery 3, they can charge battery 3 and jump-start engine 4 by connecting external power source 9 to battery 3. External power source 9 is, for example, a battery from another vehicle used for rescue. The occupants electrically connect battery 3 and external power source 9 via booster cables 90 and 91.

[0030] In this example, assume that the boost cable 90 on the positive side is connected to the power supply terminal 8, while the boost cable 91 on the negative side is incorrectly connected to the bracket 13 of the ECU1 instead of to any other specified power supply terminal (e.g., the terminal described in the vehicle V's manual, not shown). In this case, as indicated by arrows Ka to Kf, a current path not conceived in the vehicle V's specifications is formed.

[0031] Current flows from external power source 9 through booster cable 91 from bracket 13 to housing 11 (arrow Ka). Current flows from housing 11 through connecting cable 12 to grounding area 101 (arrow Kb). Current flows from grounding area 101 through connector 14 and wiring harness 6 to vehicle grounding part 7 (arrows Kc, Kd). Current flowing through vehicle grounding part 7 flows to negative terminal 31 of battery 3 (arrow Ke), and from positive terminal 30 through booster cable 90 to external power source 9 (arrow Kf).

[0032] Assuming that the narrow section 101c and the fuse 120 are not present, in the ECU1, an overcurrent exceeding its permissible value flows through the grounding area 101, which may cause deformation or melting of the housing 11, circuit board 10, and connector 14. In particular, if the circuit board 10 is damaged, the control circuit 100 may be affected and may be unable to properly control the starter 5 and engine 4.

[0033] In contrast, the narrow section 101c and the fuse 120 can protect the control circuit 100 by cutting off the overcurrent flowing through the housing 11 in the event of a misconnection of the boost cable 91. Therefore, the ECU1 can reduce the impact of overcurrent on engine control. Furthermore, the ECU1 may also have circuitry for detecting the blowing of the narrow section 101c and the fuse 120.

[0034] (Fuse detection circuit)

[0035] Figure 2 This diagram illustrates an example of a fuse detection circuit. Monitoring circuit 2 detects the blowing of at least one of the narrow section 101c and fuse 120. The input node Nin of monitoring circuit 2 is pulled up to the power supply line Vcc via resistor R. Additionally, input node Nin is also connected to connecting cable 12.

[0036] The connecting cable 12 branches into two bundles from the housing 11 toward the monitoring circuit 2 and the narrow section 101c. A fuse 120 is provided on the branch of the connecting cable 12 on the narrow section 101c side.

[0037] According to the above structure, when the narrow section 101c and the fuse 120 are not blown, the potential of the input node Nin becomes low due to the vehicle grounding section 7. However, when at least one of them blows, the potential of the input node Nin becomes high due to the pull-up. In this case, the monitoring circuit 2 detects the blown fuse and outputs an overcurrent notification signal for displaying on a monitor or other display. Thus, the occupants can be notified of the ECU 1 malfunction.

[0038] Furthermore, in this example, the narrow section 101c and the fuse 120 are shown as overcurrent cut-off parts, but redundant configuration is not necessary, and only one of them may be provided. In the case where only the narrow section 101c is provided, screws or the like assembled in the housing 11 may be used as the connecting member between the grounding area 101 and the housing 11 instead of the connecting cable 12.

Claims

1. A vehicle-mounted device, comprising: The circuit board contains the control circuitry for controlling the internal combustion engine. Housing, housing the circuit board; and A connecting member electrically connects the housing to a conductive area within the circuit board other than the control circuit. The conductive area or the connecting member has a cutting portion that cuts off current above a threshold value.

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