JP2016002799A - Vehicular electric circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric circuit for continuously supply power to electrical equipment loads in a vehicle having two batteries even if there is a terminal disconnection on one battery when automatic restart is initiated from an idling-stop.SOLUTION: A vehicular electric circuit includes: first and second batteries mutually connected in parallel; a second electrical-equipment load set that is at least a part of all electrical equipment loads of a vehicle and is connected to a second battery; a first electrical-equipment load set that is an electrical-equipment load set other than the second electrical-equipment load set and is connected to a first battery; a circuit breaker capable of connecting and shutting an electrical connection between the first battery and the second electrical-equipment load set. The circuit breaker includes: first switch means disposed so that a forward direction of a parasitic diode is oriented from the first battery to the second electrical-equipment load set; and second switch means disposed serially to the first switch means. Further, when an engine is automatically restarted, the first switch means is put to a shut state, while the second switch means is put to a connected state.

Description

  The present invention relates to a vehicle electric circuit applied to a vehicle having an idling stop function for automatically stopping and automatically restarting an engine.

  As an electric circuit of a vehicle having an idling stop function, Patent Document 1 describes an electric circuit including two batteries, a lead acid battery and a lithium ion battery. In the electric circuit of the above document, a leader battery is connected to a starter and a general electric load that can tolerate a voltage drop during cranking, and a protected electric load that cannot tolerate a voltage drop in a lithium ion battery. Connected. Two MOSFETs are arranged between the two batteries so that the directions of the parasitic diodes are opposite to each other. When the engine is cranked, the two MOSFETs are turned off. This prevents the voltage drop of the lithium-ion battery from being dragged by the lead-acid battery that supplies power to the starter during automatic restart from the idling stop, thus preventing the voltage drop of the protected electrical load. it can.

JP 2011-234479 A

  However, since lead acid batteries are mainly installed in the engine compartment and can be removed and replaced by the user of the vehicle, there is a possibility that the tightening torque between the battery terminal and the electrical cable may not be properly managed. is there. If the tightening torque is not properly managed, there is a possibility that so-called battery terminal disconnection may occur due to vibration during traveling, acceleration / deceleration G, or the like.

  In the configuration described in the above document, the lead acid battery and the lithium ion battery are electrically disconnected when the engine is automatically restarted. The power supply to ceases. As a result, for example, the illuminance of the headlight is lowered, which causes anxiety to the driver.

  Therefore, an object of the present invention is to provide an electric circuit capable of supplying power to an electrical load even when the battery terminal disconnection of the lead acid battery as described above occurs.

  According to an aspect of the present invention, there is provided an electric circuit for a vehicle that is applied to a vehicle having an idling stop function that automatically stops and restarts an engine according to a driving state. The electric circuit for a vehicle includes a first battery and a second battery that are connected in parallel, a second electric load group that is at least a part of the total electric load of the vehicle and is connected to the second battery, and the total electric component of the vehicle An electrical load group obtained by removing the second electrical load group from the load and includes a first electrical load group connected to the first battery. Furthermore, the vehicle electrical circuit includes a power circuit breaker that is interposed between the first battery and the second battery, and that can electrically switch the electrical connection between the first battery and the second electrical load group. The power breaker includes first switch means including a parasitic diode having a forward direction from the first battery toward the second electrical load group, and second switch means arranged in series with the first switch means. When the engine is automatically restarted, the first switch means is turned on and the second switch means is turned off.

  According to the above aspect, the forward direction of the parasitic diode of the first switch means is the direction from the first battery to the second electrical load group, and the first switch means is turned off when the engine is automatically restarted. Is turned on. Therefore, even if power supply from the second battery to the second electrical load group is interrupted during cranking during automatic restart, power is supplied from the first battery to the second electrical load group by the action of the parasitic diode.

FIG. 1 is a diagram illustrating a first example of the electric circuit according to the first embodiment. FIG. 2 is a timing chart showing the operation of the electric circuit. FIG. 3 is a diagram illustrating a second example of the electric circuit according to the first embodiment. FIG. 4 is a diagram illustrating a third example of the electric circuit according to the first embodiment. FIG. 5 is a diagram illustrating a first example of the electric circuit according to the second embodiment. FIG. 6 is a diagram illustrating a second example of the electric circuit according to the second embodiment. FIG. 7 is a diagram illustrating a third example of the electric circuit according to the second embodiment. FIG. 8 is a diagram illustrating a first example of the electric circuit according to the third embodiment. FIG. 9 is a diagram illustrating a second example of the electric circuit according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
The electric circuit according to the first embodiment includes two batteries, and is applied to a vehicle that performs idling stop, that is, automatic stop / restart of the engine according to the driving state. In addition, the idling stop referred to in the present embodiment includes a so-called coast stop that automatically stops when a predetermined low load state occurs while the vehicle is running, in addition to the automatic stop when the vehicle speed is zero km / h. Including.

  FIG. 1 is a diagram illustrating a first example of the electric circuit according to the first embodiment.

  A lithium ion battery 1 as a first battery and a lead acid secondary battery 2 as a second battery are connected in parallel, and an inter-battery relay 11 as a power circuit breaker is interposed therebetween.

  Note that the second battery is a secondary battery that can be replaced by a user of the vehicle and may neglect the management of fastening of the terminal portion. Accordingly, in the present embodiment, the lead acid secondary battery 2 is used as the second battery, but other secondary batteries may be used. On the other hand, the first battery is a secondary battery that is not touched by the user of the vehicle and that the fastening of the terminal portion is guaranteed by service at the production line or dealer.

  The inter-battery relay 11 includes a first MOSFET 12 as first switch means, a second MOSFET 13 as second switch means, and a first relay 14. The first MOSFET 12 and the second MOSFET 13 are connected in series, and the first relay 14 is connected in parallel with the first MOSFET 12 and the second MOSFET 13. The first MOSFET 12 is arranged such that the direction from the lithium ion battery 1 to the lead acid secondary battery 2 is the forward direction of the parasitic diode. The second MOSFET 13 is arranged so that the forward direction of the parasitic diode is opposite to that of the first MOSFET 12.

  The first relay 14 is a so-called normally closed type that is closed when the coil is not energized. Here, the “closed state” refers to a state in which electrical connection is established. On the other hand, the state where the conduction is cut off is referred to as “open state”. In the present embodiment, the flow of electricity is referred to as “energization”, and the electrical connection so that electricity can be supplied regardless of whether or not electricity is actually flowing is referred to as “conduction”.

  A protected load 4 as a first electrical load group is connected to the lithium-ion battery 1 side of the inter-battery relay 11. The protected load 4 is, for example, an electrical load group that requires a voltage of 11 V or more, that is, an electrical load group that cannot tolerate a voltage drop because an operation failure such as a reset occurs when a voltage drop occurs. For example, a meter, a transmission controller, a navigation system, and the like are included. A third MOSFET 15 and a fourth MOSFET 16 are arranged in series between the lithium ion battery 1 and the protected load 4 so that the forward directions of the parasitic diodes are opposite to each other.

  A general load 3 as a second electrical load group is connected to the lead-acid secondary battery 2 side of the inter-battery relay 11. The general load 3 is an electrical load group that can tolerate voltage sag, that is, can operate even when there is voltage sag, and includes, for example, a headlight, a wiper, and the like.

  In addition, a starter 5 that cranks the engine when the engine is started is connected to the lead-acid secondary battery 2 side of the inter-battery relay 11 via a starter relay 7.

  An alternator 6 that generates power by the driving force of the engine is also connected to the lead-acid secondary battery 2 side (point A in FIG. 1) of the inter-battery relay 11. However, in the present embodiment and the embodiments described below, the inter-battery relay 11 may be connected to the lithium ion battery 1 side (point B in FIG. 1).

  In an actual product, the lithium ion battery 1, the inter-battery relay 11, the third MOSFET 15, and the fourth MOSFET 16 are combined into one and handled as the lithium ion battery pack 10.

  Next, the operation of the electric circuit according to this embodiment will be described.

  FIG. 2 is a timing chart showing the operation of the electric circuit.

  When the engine is started by a driver's operation, for example, ignition key operation or start button operation (hereinafter also referred to as key start), the first relay 14 is closed, and the first to fourth MOSFETs 12, 13, 15, 16 are off. (Timing T1). Thereby, electric power is supplied from the lead acid secondary battery 2 to the starter 5, and cranking is performed.

  After the first explosion of the engine, the third MOSFET 15 and the fourth MOSFET 16 are turned on, and the lithium ion battery 1 and the lead acid secondary battery 2 are connected (timing T2). Here, “ON” means a conductive state. On the other hand, “off” means a state where conduction is cut off.

  Before the automatic stop, the first MOSFET 12 and the second MOSFET 13 are turned on, and the first relay 14 is opened after a predetermined delay time (timing T3). As a result, the lead-acid secondary battery 2, the lithium ion battery 1 and the protective load 4 are disconnected from each other during idling stop, and when there is an automatic restart request, the MOSFET is more responsive than a mechanical relay or the like. It will be in the state which can switch a conduction | electrical_connection state and interruption | blocking state rapidly.

  At the time of automatic restart, only the first MOSFET 12 is turned off immediately before the start of cranking, and is turned on again after the complete explosion (timing T4-T5). That is, during cranking, the first relay 14 is in an open state, the first MOSFET 12 is turned off, and the second MOSFET 13 is turned on. From the lithium ion battery 1 side to the lead acid secondary battery 2 side by the action of the parasitic diode of the first MOSFET 12. Only the direction of heading is a conduction state. As a result, the influence of the instantaneous voltage drop due to the cranking on the protected load 4 is eliminated, and even if the battery terminal of the lead acid secondary battery 2 is disconnected during the cranking, the general load 3 Since electric power is supplied to the headlight, it is possible to prevent a decrease in headlight illumination and a wiper stop.

  When the engine speed is stabilized, the first relay is closed, and the first MOSFET 12 and the second MOSFET 13 are turned off after a predetermined delay time (timing T6). Thereby, the heat generation of the first MOSFET 12 and the second MOSFET 13 can be suppressed.

  When the engine is stopped by a driver's operation, for example, an ignition key operation or a start button operation (hereinafter also referred to as a key stop), the third MOSFET 15 and the fourth MOSFET 16 are turned off after a predetermined delay time has elapsed since the driver's operation. Become. Thereby, the over discharge of the lithium ion battery 1 by dark current etc. can be prevented.

  Since the first relay 14 is a normally closed type, dark current is supplied from the lead acid secondary battery 2 to the general load 3 and the protected load 4 even after the key is stopped.

  As described above, in the electric circuit of the present embodiment, even if the battery terminal of the lead acid secondary battery 2 is disconnected during the automatic restart, the power supply to the general load 3 is interrupted by the action of the parasitic diode of the first MOSFET 12. There is nothing.

  FIG. 3 is a diagram illustrating a second example of the electric circuit according to the first embodiment.

  In the second embodiment, the second MOSFET 13 of the first embodiment is replaced with a second relay 20 which is a mechanical relay. The opening / closing operation of the second relay 20 is the same as the on / off operation of the second MOSFET 13 described above.

  Mechanical relays are inferior in response to intermittent operation compared to MOSFETs. However, in the first embodiment described above, high responsiveness of the intermittent operation is required for the first MOSFET 12 that switches from on to off immediately before cranking and switches to on again after complete explosion, compared to the second MOSFET 13. High responsiveness is not required. Therefore, even if the second MOSFET 13 is replaced with the mechanical second relay 20, the same effect as that of the first embodiment is obtained.

  FIG. 4 is a diagram illustrating a third example of the electric circuit according to the first embodiment.

  In the third embodiment, the second MOSFET 13 of the first embodiment is replaced with a semiconductor relay 21 that does not include a parasitic diode, such as an IGBT, a transistor, or a thyristor. The opening / closing operation of the semiconductor relay 21 is the same as the on / off operation of the second MOSFET 13 described above.

  In the first embodiment described above, only the switching function is required for the second MOSFET 13. Therefore, even if the second MOSFET 13 is replaced with the semiconductor relay 21 that does not include a parasitic diode, the same effect as that of the first embodiment can be obtained.

  Next, effects obtained by the present embodiment will be described.

  (1) The electric circuit according to the present embodiment has an idling stop function, is applied to a vehicle including two batteries 1 and 2, and is connected to a protected load 4 and a general load 3. The lead acid secondary battery 2 to be connected and the inter-battery relay 11 are included. The inter-battery relay 11 includes a first MOSFET 12 including a parasitic diode having a forward direction from the lithium ion battery 1 toward the general load 3, and a second MOSFET 13 arranged in series with the first MOSFET 12. At the time of automatic restart, the first MOSFET 12 is turned off and the second MOSFET 13 is turned on. Thereby, even if the battery terminal disconnection of the lead acid secondary battery 2 occurs during cranking, power is supplied from the lithium ion battery 1 to the general load 3 by the action of the parasitic diode of the first MOSFET 12, so that the general load 3 operation is ensured.

  (2) Instead of the second MOSFET 13, a second relay that is a mechanical relay or a semiconductor relay 21 that does not include a parasitic diode may be used. In this case, not only the same effect as the above (1) can be obtained, but also a device that is less expensive than the MOSFET is used, so that a cost reduction can be expected. Furthermore, since a device having a smaller voltage drop than that of the MOSFET is used, heat generation can be suppressed.

(Second Embodiment)
FIG. 5 is a diagram illustrating a first example of the electric circuit according to the second embodiment.

  The electric circuit shown in FIG. 5 is different from the electric circuit shown in FIG. 1 in the following three points. First, the connection position of the general load 3 and the connection position of the protected load 4 are opposite to those in FIG. That is, the first electrical load group is the general load 3, and the second electrical load group is the protected load 4.

  Second, the connection position of the starter 5 and the starter relay 7 is on the lithium ion battery 1 side of the inter-battery relay 11. Thirdly, the third MOSFET 15 and the fourth MOSFET 16 of FIG. 1 are replaced with a third relay 22 which is a mechanical relay. The third relay 22 is a so-called normal open type that is open when the coil is not energized.

  The configurations and opening / closing operations of the first MOSFET 12, the second MOSFET 13, and the first relay 14 are the same as those in the first embodiment. The opening / closing operation of the third relay 22 is the same as the opening / closing operation of the third MOSFET 15 and the fourth MOSFET 16 of the first embodiment. Thus, key start is performed by the lead acid secondary battery 2 as in the first embodiment, but automatic restart can be performed by supplying power from the lithium ion battery 1.

  Since the first relay 14 is energized even when the key is started, the first relay 14 needs to have a larger capacity than the first embodiment.

  According to the above configuration, even if the battery terminal of the lead-acid secondary battery 2 is disconnected during cranking when the engine is restarted, the power supply to the protected load 4 is interrupted by the action of the parasitic diode of the first MOSFET 12. There is nothing. On the other hand, the general load 3 can operate regardless of whether the battery terminal of the lead acid secondary battery 2 is disconnected.

  Further, the lithium ion battery 1 is used for automatic restart, and the lead acid secondary battery 2 is used only at the time of key start. That is, the lithium ion battery 1 having higher durability against repeated charge / discharge compared to the lead acid secondary battery 2 is used for automatic restart that is frequently performed. As a result, deterioration of the lead-acid secondary battery 2 due to the idling stop can be suppressed, and it is not necessary to use a large-capacity lead-acid secondary battery 2 for the idling stop, thereby reducing costs. be able to.

  Furthermore, cost reduction can be expected by replacing the third MOSFET 15 and the fourth MOSFET 16 with a third relay 22 which is a cheaper mechanical relay.

  FIG. 6 is a diagram illustrating a second example of the electric circuit according to the second embodiment.

  The electric circuit shown in FIG. 6 is different from the electric circuit shown in FIG. 5 in that the general load 3 and the protected load 4 are combined into one electric load 8. Even in the configuration as in the present embodiment, it is possible to ensure power supply to all the electrical loads 8 when the battery terminal disconnection of the lead acid secondary battery 2 occurs during cranking during automatic restart.

  FIG. 7 is a diagram illustrating a third example of the electric circuit according to the second embodiment.

  The electric circuit shown in FIG. 7 is obtained by replacing the first relay 14 and the third relay 22 of the electric circuit of FIG. The switching relay 30 is switched to select the lead acid secondary battery 2 at the time of key start and to select the lithium ion battery 1 at the time of automatic restart. The opening / closing operation of the first MOSFET 12 and the second MOSFET 13 is the same as the configuration of FIGS.

  Even with the configuration of the present embodiment, the same effects as the configurations of FIGS. 5 and 6 can be obtained. Moreover, the voltage drop at the time of supplying electric power from the lithium ion battery 1 to the all electrical load 8 can be suppressed by the action of the parasitic diode of the first MOSFET 12 by the amount of the third relay 22.

  As described above, according to the present embodiment, as in the first embodiment, even if the battery terminal of the lead-acid secondary battery 2 is disconnected during cranking, lithium ions are caused by the action of the parasitic diode of the first MOSFET 12. Since electric power is supplied from the battery 1 to the general load 3, the operation of the general load 3 is ensured.

  In the present embodiment, the second MOSFET 13 can be replaced with a semiconductor relay that does not include a mechanical relay or a parasitic diode.

(Third embodiment)
FIG. 8 is a diagram illustrating a first example of the electric circuit according to the third embodiment.

  The difference between the electric circuit shown in FIG. 8 and the electric circuit shown in FIG. 1 is the following three points. First, the connection position of the general load 3 and the connection position of the protected load 4 are opposite to those in FIG. That is, the first electrical load group is the general load 3, and the second electrical load group is the protected load 4.

  Second, in place of the alternator 6 of FIG. 1, a motor generator 40 having both a power generation function and a drive function is used, and the motor generator 40 is connected to the B point instead of the A point. The motor generator 40 is a so-called SSG (Side Mounted Starter Generator) that is connected to the crank pulley of the engine via a belt in the same manner as the alternator 6.

  Thirdly, the third MOSFET 15 and the fourth MOSFET 16 of FIG. 1 are replaced with a third relay 22 which is a mechanical relay.

  The operations of the first MOSFET 12, the second MOSFET 13, the first relay 14, and the third relay 22 are the same as those in the second embodiment. That is, key start is performed by the starter 5 supplied with power from the lead acid secondary battery 2, and automatic restart is performed by the motor generator 40 supplied with power from the lithium ion battery 1. Therefore, since a large current required for starting the engine does not flow through the first relay 14, the capacity of the first relay 14 can be reduced as compared with the first embodiment.

  FIG. 9 is a diagram illustrating a second example of the electric circuit according to the third embodiment.

  The electric circuit of the present embodiment is configured to be compatible with a so-called hybrid vehicle. The configuration shown in FIG. 9 is different from the configuration shown in FIG. 8 in that the lead acid secondary battery 2 is replaced with a high-voltage lithium ion battery 41 and a step-down DC-DC converter 42, and a motor generator 40 as a high-voltage drive motor. Therefore, the starter 5 is omitted.

  Also in the present embodiment, the operations of the first MOSFET 12 and the second MOSFET 13, the first relay 14, and the third relay 22 are the same as those of the second embodiment. That is, the power of the high voltage lithium ion battery 41 as the second battery is used at the time of key start, and the power of the lithium ion battery 1 is used at the time of automatic restart.

  When the key is stopped, the third relay 22 returns to the closed state, and a dark current flows from the lithium ion battery 1 to the general load 3 and the protected load 4. And if the capacity | capacitance of the lithium ion battery 1 falls, the step-down DC-DC converter 42 will operate | move and the charge to the lithium ion battery 1 by the high voltage lithium ion battery 41 will be ensured until the capacity | capacitance of the lithium ion battery 1 is ensured. Is done.

  With the above configuration, even if a malfunction occurs in the step-down DC-DC converter 42 during cranking during automatic restart, the power supply to the protected load 4 is not interrupted by the action of the parasitic diode of the first MOSFET 12. In addition, since the high voltage lithium ion battery 41 is subjected to terminal tightening management on a production line or the like as with the lithium ion battery 1, it is not necessary to consider terminal detachment during cranking in the present embodiment.

  As described above, according to the present embodiment, the same effects as those of the second embodiment can be obtained. Also in this embodiment, the second MOSFET 13 can be replaced with a semiconductor relay that does not include a mechanical relay or a parasitic diode.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Lead acid secondary battery 3 General load 4 Protected load 5 Starter 6 Alternator 8 Total electric load 10 Battery pack 11 Inter-battery relay 12 1st MOSFET
13 Second MOSFET
14 1st relay 15 3rd MOSFET
16 4th MOSFET
20 second relay 21 semiconductor relay 22 third relay 30 switching relay 40 motor generator 41 high voltage lithium ion battery 42 step-down DC-DC converter

Claims (6)

In an electric circuit for a vehicle applied to a vehicle having an idling stop function for automatically stopping and restarting an engine according to a driving state,
A first battery;
A second battery connected in parallel with the first battery;
A second electrical load group that is at least part of the total electrical load of the vehicle and is connected to the second battery;
A first electrical load group connected to the first battery, the electrical load group excluding the second electrical load group from the total electrical load of the vehicle;
A power circuit breaker interposed between the first battery and the second battery and capable of intermittently switching electrical connection between the first battery and the second electrical load group;
Comprising
The power circuit breaker includes first switch means including a parasitic diode having a forward direction from the first battery toward the second electrical load group, and second switch means arranged in series with the first switch means. And including
When the engine is automatically restarted, the first switch means is in a cut-off state and the second switch means is in a conductive state. The vehicle electric circuit according to claim 1,
The vehicle electric circuit according to claim 1, wherein the first switch means is a MOSFET. In the electric circuit for vehicles according to claim 1 or 2,
The vehicular electric circuit according to claim 2, wherein the second switch means is a MOSFET arranged so that a forward direction of the parasitic diode is opposite to the first switch means. In the electric circuit for vehicles according to claim 1 or 2,
The vehicle electrical circuit, wherein the second switch means is a mechanical relay. In the electric circuit for vehicles according to claim 1 or 2,
The vehicle electric circuit according to claim 2, wherein the second switch means is a semiconductor relay that does not include a parasitic diode. In the electric circuit for vehicles according to any one of claims 1 to 5,
The electric circuit for a vehicle, wherein the second battery includes a battery having a higher voltage than the first battery and a step-down converter.

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