vehicle-mounted device

Abstract

An in-vehicle device is provided that can reduce the influence of an overcurrent flowing through a housing on engine control. [Solution] The vehicle-mounted device has a circuit board equipped with a control circuit that controls an internal combustion engine, a housing that houses the circuit board, and a connecting member that electrically connects the housing to a conductive area other than the control circuit within the circuit board, and the conductive area or the connecting member has a cut-off section that cuts off current above a threshold value.

Description

[Technical Field]

[0001] The present invention relates to an in-vehicle device. [Background technology]

[0002] For example, Patent Document 1 discloses reducing the power supply to an electric load when jump-starting an engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-278216 Summary of the Invention [Problem to be solved by the invention]

[0004] If a booster cable is connected to the wrong position on the vehicle body during a jump start and electricity is passed from an external battery to the vehicle body earth via the housing of an onboard device such as an engine control ECU (Electronic Control Unit), an overcurrent exceeding the allowable value of the onboard device may cause deformation or melting, which could affect engine control.

[0005] SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an object to provide an in-vehicle device that can reduce the influence of an overcurrent flowing in a housing on engine control. [Means for solving the problem]

[0006] The in-vehicle device of the present invention comprises a circuit board having a control circuit for controlling an internal combustion engine, a housing for accommodating 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 cut-off portion for cutting off current above a threshold value. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce the influence of an overcurrent flowing through the housing of an in-vehicle device on engine control. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration inside an engine compartment E of a vehicle V during a jump start. [Figure 2] FIG. 2 is a diagram illustrating an example of a blowout detection circuit. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Configuration of the Example) 1 is a diagram showing the configuration inside an engine compartment E of a vehicle V during a jump start. The engine compartment E contains an ECU 1, a battery 3, an engine 4, a starter 5, and a wire harness 6. The body of the vehicle V also functions as a body earth 7.

[0010] The battery 3 is, for example, a lithium-ion battery, and supplies power to the ECU 1 and auxiliary devices such as the starter 5 via a power supply circuit (not shown). A positive terminal 30 of the battery 3 is connected to a power supply terminal 8 for jump starting. A negative terminal 31 of the battery 3 is connected to a body earth 7 of the vehicle V.

[0011] The starter 5 is a starter motor that rotates a crankshaft (not shown) under the control of the ECU 1 when starting the engine 4. The engine 4 is an example of an internal combustion engine, and drives the vehicle V. Note that the engine 4 is not limited to a gasoline engine, and may be a diesel engine.

[0012] The ECU 1 is an example of an in-vehicle device, and controls the operation of the starter 5 and the engine 4. The ECU 1 has a housing 11, a bracket 13, a circuit board 10, a connector 14, and a connection cable 12. Note that Fig. 1 shows a simplified internal configuration of the ECU 1 when the surface of the circuit board 10 is viewed from the front.

[0013] The housing 11 and the bracket 13 are made of metal. The bracket 13 is attached to the housing 11 and fixes the ECU 1 to the inner wall of the engine room E or the like.

[0014] The circuit board 10 and the connection cable 12 are housed inside a housing 11. The circuit board 10 has a control circuit 100 that controls the engine 4 and the starter 5, and a grounding area 101 that is electrically connected to the housing 11 and the body earth 7. The control circuit 100 includes electrical components P, such as a processor that executes control processing and a memory.

[0015] The ground area 101 is an example of a conductive area other than the control circuit 100. It is a conductive pattern that functions as a ground for the ECU 1 and is electrically insulated from the control circuit 100. The ground area 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, the widths W1 and W2 refer to the widths in a direction approximately perpendicular to the direction of current flow.

[0016] Therefore, the narrow portion 101c melts or peels off due to an overcurrent. As a result, the narrow portion 101c, as an example of a cutoff portion, cuts off current above a threshold value. The width of the narrow portion 101c is set based on the current threshold value. Note that a chip fuse may be provided instead of the narrow portion 101c.

[0017] The connection cable 12 is an example of a connecting member. The connection cable 12 electrically connects the housing 11 and the ground area 101 in the circuit board 10.

[0018] A fuse 120 is provided midway along the connection cable 12. The fuse 120 also melts down due to an overcurrent, and serves as an example of a cutoff unit, cutting off current above a threshold value.

[0019] The connector 14 is provided on the circuit board 10 or near the circuit board 10. The connector 14 is arranged so that its tip is exposed to the outside through an opening 11a of the housing 11 without being in direct contact with the housing 11. The connector 14 has a configuration in which a plurality of terminals (not shown) are arranged inside a resin case, for example. Each terminal of the connector 14 is electrically connected to the input / output signals, power supply lines, and ground lines of the control circuit 100, and to the ground region 101. Some of the terminals of the connector 14 are electrically connected to the body earth 7, for example, via a wire harness 6.

[0020] The ground line of the control circuit 100 is connected to the body earth 7 from the connector 14 via the wire harness 6 as shown by a current path Ra. The ground area 101 is connected to the body earth 7 from the connector 14 via the wire harness 6 as shown by a current path Rb.

[0021] If the occupant of the vehicle V is unable to start the engine 4, for example, because the remaining charge in the battery 3 is low, the occupant connects an external power source 9 to the battery 3 to charge the battery 3 and jump-start the engine 4. The external power source 9 is, for example, the battery of another vehicle used for rescue. The occupant electrically connects the battery 3 and the external power source 9 via booster cables 90, 91.

[0022] In this example, it is assumed that the positive booster cable 90 is connected to the power supply terminal 8, while the negative booster cable 91 is not connected to another predetermined power supply terminal (for example, a terminal described in the instruction manual for the vehicle V, not shown), but is instead connected to the bracket 13 of the ECU 1 by mistake. In this case, as shown by arrows Ka to Kf, a current path is formed that is not anticipated in the specifications of the vehicle V.

[0023] Current flows from the external power source 9 through the booster cable 91, from the bracket 13 to the housing 11 (arrow Ka). Current flows from the housing 11 through the connection cable 12 to the grounding area 101 (arrow Kb). Current flows from the grounding area 101 through the connector 14 and the wire harness 6 to the body earth 7 (arrows Kc and Kd). The current that has flowed through the body earth 7 flows to the negative terminal 31 of the battery 3 (arrow Ke), and then from the positive terminal 30 through the booster cable 90 to the external power source 9 (arrow Kf).

[0024] If the narrow portion 101c and the fuse 120 were not provided, an overcurrent exceeding the allowable value would flow through the grounding area 101 of the ECU 1, which could cause deformation or melting of the housing 11, the circuit board 10, the connector 14, etc. In particular, if the circuit board 10 is damaged, the control circuit 100 may be affected, and the starter 5 and the engine 4 may not be able to be controlled normally.

[0025] In response to this, the narrow portion 101c and the fuse 120 can protect the control circuit 100 by blocking the overcurrent that flows through the housing 11 when the booster cable 91 is incorrectly connected. This allows the ECU 1 to reduce the effect of the overcurrent on engine control. The ECU 1 may also include a circuit that detects the blowout of the narrow portion 101c and the fuse 120.

[0026] (Fusing detection circuit) 2 is a diagram showing an example of a fuse detection circuit. The monitor circuit 2 detects the blowing of at least one of the narrow portion 101c and the fuse 120. The input node Nin of the monitor circuit 2 is pulled up to the power supply line Vcc by a resistor R. The input node Nin is also connected to the connection cable 12.

[0027] The connection cable 12 branches into two from the housing 11 toward the monitor circuit 2 and the narrow portion 101c. A fuse 120 is provided in the branch of the connection cable 12 on the narrow portion 101c side.

[0028] According to the above configuration, when the narrow portion 101c and the fuse 120 are not blown, the potential of the input node Nin is at a low level due to the body earth 7. However, when at least one of them is blown, the potential of the input node Nin is pulled up to a high level. In this case, the monitor circuit 2 detects the blown portion and outputs a notification signal to display an overcurrent on a display or the like. This notifies the occupant of an abnormality in the ECU 1.

[0029] In this example, the narrow portion 101c and the fuse 120 are exemplified as the overcurrent interrupter, but they do not necessarily need to be configured redundantly, and only one of them may be provided. When only the narrow portion 101c is provided, a screw or the like attached to the housing 11 may be used as the connecting member between the grounding area 101 and the housing 11 instead of the connection cable 12. [Explanation of symbols]

[0030] 1 ECU (on-board device), 4 engine (internal combustion engine), 10 circuit board, 11 housing, 100 control circuit, 101 ground area (conductive area), 12 connection cable (connection member), 101c narrow portion (interrupter), 120 fuse (interrupter)

Claims

[Claim 1] a circuit board including a control circuit for controlling the internal combustion engine; a housing that houses the circuit board; a connecting member that electrically connects the housing to a conductive region other than the control circuit in the circuit board, The conductive region or the connection member has a cutoff portion that cuts off current above a threshold. In-vehicle device.

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