Protection device

Abstract

To provide a protection device capable of protecting an on-vehicle device from a current at jump start.SOLUTION: A protection device includes a cut-off unit that electrically cuts off between a housing of an in-vehicle device related to starting of an internal combustion engine of a vehicle by power supply from an external power supply to a battery of the vehicle and a body earth of the vehicle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protection 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 ECU (Electronic Control Unit) inside the vehicle, there is a risk that the onboard device will deform or melt due to a current that exceeds its allowable value.

[0005] SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a protection device that can protect an in-vehicle device from a current that occurs during a jump start. [Means for solving the problem]

[0006] The protection device of the present invention has a cutoff section that electrically cuts off the body earth of the vehicle from the housing of an on-board device involved in starting the internal combustion engine of the vehicle by supplying power from an external power source to the vehicle's battery. [Effects of the Invention]

[0007] According to the present invention, it is possible to protect an in-vehicle device from a current that occurs during a jump start. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration inside the engine compartment of a vehicle during a jump start in the first embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration inside the engine compartment of the vehicle during a jump start in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Configuration of the first embodiment) 1 is a diagram showing the configuration inside an engine compartment E of a vehicle V at the time of a jump start in a first embodiment. In the engine compartment E, a protection device 1, an ECU 2, a battery 3, an engine 4, a starter 5, and a wire harness 6 are provided.

[0010] The battery 3 is, for example, a lithium-ion battery, and supplies power to the ECU 2 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) of the engine 4 under the control of the ECU 2 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 2 is an example of an on-board device related to starting the engine 4, and controls the operation of the starter 5 and the engine 4. The ECU 2 has a housing 20, a bracket 21, a circuit board 22, a connector 23, and metal contacts 24 and 25. Note that Fig. 1 shows a simplified internal configuration of the ECU 2 when viewed from a cross section perpendicular to the surface of the circuit board 22.

[0013] The housing 20 and the bracket 21 are made of metal. The bracket 21 is attached to the housing 20 and fixes the ECU 2 to an inner wall of the engine room E or the like.

[0014] The circuit board 22 and the metal touch panels 24, 25 are housed inside the housing 20. Electrical components P, such as a processor and memory that executes control processing of the ECU 2, are mounted on the circuit board 22. The circuit board 22 has a ground layer 220 that serves as the ground potential of the electrical components P, a case earth layer 222 that functions as the earth of the ECU 2, and an insulating layer 221 that electrically separates the ground layer 220 from the case earth layer 222.

[0015] The case earth layer 222 is a conductive thin film and is electrically connected to the housing 20 via metal contacts 24 and 25, which are metal fasteners. The insulating layer 221 is an insulating thin film and is adjacent to the ground layer 220 and the case earth layer 222 so as to be sandwiched between them. The ground layer 220 is a conductive thin film and is connected to the ground electrode of the electrical component P, etc. The ground layer 220, the insulating layer 221, and the case earth layer 222 form a predetermined thin film pattern when the board surface of the circuit board 22 is viewed from the front. The circuit board 22 also has a thin film pattern (not shown) of a power supply line to which the power supply terminal of the electrical component P is connected.

[0016] The connector 23 is provided on or near the circuit board 22. The connector 23 is arranged so that its tip is exposed to the outside through an opening 20a of the housing 20 without being in direct contact with the housing 20. The connector 23 has a configuration in which a plurality of terminals (not shown) are arranged inside a resin case, for example. Each terminal of the connector 23 is electrically connected to the ground layer 220 and the case earth layer 222 of the circuit board 22. The connector 23 is electrically connected to the body earth 7 via a wire harness 6, for example.

[0017] The case earth layer 222 is connected to the body earth 7 from the connector 23 via the wire harness 6 as shown by a current path Ra. The ground layer 220 is connected to the body earth 7 from the connector 23 via the wire harness 6 as shown by a current path Rb.

[0018] 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.

[0019] 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 21 of the ECU 2 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.

[0020] Current flows from the external power source 9 through the booster cable 91, from the bracket 21 to the housing 20 (arrow Ka). The current that flows through the housing 20 flows through the metal contacts 24 and 25 and the case earth layer 222 (arrow Kb). The current that flows through the metal contacts 24 and 25 flows from the connector 23 through the wire harness 6 to the body earth 7 (arrows Kc and Kd). The current that flows through the body earth 7 flows to the negative terminal 31 of the battery 3 (arrow Ke), and then flows from the positive terminal 30 through the booster cable 90 to the external power source 9.

[0021] If the protection device 1 were not provided, the ECU 2 would be at risk of deformation or melting of the housing 20, the circuit board 22, the connector 23, and the like due to a current exceeding its allowable value.

[0022] In response to this, the protection device 1 protects the ECU 2 by interrupting the current that flows when the booster cable 91 is incorrectly connected. The protection device 1 has fuses 10 and 11. The fuses 10 and 11 are examples of a circuit breaker.

[0023] The fuse 10 is mounted on the circuit board 22. For example, the case earth layer 222 of the circuit board 22 is formed to be electrically separated into two regions 222a and 222b. In the above current path, one region 222a is provided on the connector 23 side, and the other region 222b is provided on the metal touch 24, 25 side. The fuse 10 is mounted across the regions 222a and 222b so as to electrically connect the two regions 222a and 222b to each other. In other words, one terminal of the fuse 10 is connected to the region 222a, and the other terminal of the fuse 10 is connected to the region 222b. When a current equal to or greater than a threshold flows from the external power supply 9, the fuse 10 melts to electrically disconnect the regions 222a and 222b.

[0024] The fuse 11 is provided on the current path Ra in the wire harness 6. For example, the fuse 11 is interposed in the middle of the wiring. When a current equal to or greater than a threshold flows from the external power supply 9, the fuse 11 melts to electrically disconnect the body earth 7 and the connector 23. However, since the other current path Rb in the wire harness 6 is not interrupted, the electrical connection between the ground layer 220 and the body earth 7 is maintained. This allows the electrical component P to operate normally, and the ECU 2 can control the starter 5 to start the engine 4.

[0025] In this way, when the engine 4 is jump-started, the fuses 10 and 11 are cut off by the current caused by the incorrect connection of the booster cable 91 to the housing 20, thereby electrically isolating the housing 20 from the body earth 7. This allows the protection device 1 to protect the circuit board 22 and connector 23 of the ECU 2 from large current. Note that in the configuration of this example, notification means may be provided that detects the cutting off of the fuses 10 and 11 and notifies the occupants of the vehicle V.

[0026] (Configuration of the second embodiment)

[0027] Fig. 2 is a diagram showing the configuration inside the engine compartment E of the vehicle V during a jump start in the second embodiment. The engine compartment E is provided with a protection device 1a, an ECU 2, a battery 3, an engine 4, a starter 5, and a wire harness 6. In Fig. 2, components common to those in Fig. 1 are given the same reference numerals, and their description will be omitted.

[0028] The protection device 1a includes switches (SW) 12 and 13, a selector 14, an open / close sensor 15, and a monitoring ECU 16. The switches 12 and 13 are provided in place of the fuses 10 and 11.

[0029] The switches 12 and 13 are an example of a breaker, and are, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switches 12 and 13 are turned on and off under the control of a changeover device 14. The switch 12 turns on and off the electrical connection between the regions 222a and 222b of the case earth layer 222, and the switch 13 turns on and off the electrical connection of the current path Ra of the wire harness 6.

[0030] The monitoring ECU 16 monitors the state of the battery using sensors (not shown). The monitoring ECU 16 detects, for example, the current, voltage, and SOC (State Of Charge) of the battery 3, and determines the state of the battery 3 that requires a jump start of the engine 4. The monitoring ECU 16 notifies the switch 14 of the determination result. Note that the function of the monitoring ECU 16 may be implemented in the ECU 2.

[0031] The open / close sensor 15 detects the open / close state of the hood or engine cover (not shown) that opens and closes the engine compartment E. The open / close sensor 15 may use mechanical detection means or optical means, and is not limited thereto. The open / close sensor 15 notifies the switch 14 of the detection result.

[0032] The switch 14 is implemented by hardware such as a logic circuit, but may also be implemented by part of the electrical components P mounted on the circuit board 22 of the ECU 2. The switch 14 turns the switches 12 and 13 on and off in response to notifications from the open / close sensor 15 and the monitoring ECU 16. The switch 14 determines whether the state of the battery 3 requires a jump start, and if the hood or cover is open, the switch 14 switches the switches 12 and 13 from on to off. Otherwise, the switch 14 turns the switches 12 and 13 on.

[0033] Therefore, during a jump start, the switch 12 electrically disconnects the areas 222a and 222b, and the switch 13 electrically disconnects the body earth 7 and the connector 23. This allows the protection device 1 to protect the circuit board 22 and the connector 23 of the ECU 2 from a large current. Note that in this example, instead of the notification from the monitoring ECU 16, the switch 14 may use, for on / off control, a history of engine 4 start failures stored in, for example, an engine ECU (not shown).

[0034] In each embodiment, an example has been given in which the booster cable 91 is erroneously connected to the bracket 21, but the erroneous connection may be to a fixing screw portion (not shown) instead of the bracket 21, and there is no limitation to the connection destination. In each embodiment, an ECU 2 has been given as the object to be protected by the protection device 1, but this is not limiting, and other devices such as an electric power steering device or a brake device may also be the object to be protected.

[0035] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0036] 1,1a protection device, 3 battery, 4 engine (internal combustion engine), 6 wire harness, 7 body earth, 9 external power supply, 10,11 fuse (breaker), 12,13 switch (breaker), 20 housing, 22 circuit board, 23 connector, 90,91 booster cable, V vehicle, E engine compartment

Claims

[Claim 1] a cutoff unit that electrically cuts off a housing of an on-board device related to starting an internal combustion engine of the vehicle by supplying power from an external power source to a battery of the vehicle and a body earth of the vehicle; Protective device.

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