FR2832464A1 - Starter circuit for motor vehicle internal combustion engine, has batteries connected in series with starter-generator for starting and in parallel for charging - Google Patents

Abstract

The starter circuit for a motor vehicle internal combustion engine (A) has multiple batteries (1,2), a relay (3) and a starter-generator with a control circuit (5). If a starting signal is received, the control connects the batteries in series to start the motor and deliver a series voltage to the motor. When the engine is running, the batteries are connected in parallel for charging.

Description

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AUTOMATIC STARTING SYSTEM OF AN ENGINE COMPRISING A
MULTIPLE BATTERIES
This invention relates to an automatic engine starting system which includes a plurality of batteries.

 An automatic engine starting system which momentarily stops a vehicle engine when the vehicle stops and restarts the engine by a starter has been widely known in recent years. In this system, an alternator charges a battery which supplies power to the starter. If the engine is restarted repeatedly, the alternator cannot fully charge the battery. As a result, the engine's starting capacity may decrease.

 In order to solve this problem, an auxiliary battery can be installed. However, the two batteries are not charged equally if the battery capacities are different. For example, if the capacity of the auxiliary battery is lower than that of the main battery, the auxiliary battery can be charged less than the main battery.

 The present invention therefore aims to provide an automatic engine starting system which improves the starting capacity of the engine and the condition of the batteries.

 The automatic engine starting system of the present invention comprises a starter-generator, a plurality of batteries, a switching circuit and a control circuit. The starter-generator has a starter function which starts the engine and a generator function which charges the batteries. The switching circuit switches a connection of the batteries between a parallel connection and a series connection. The circuit

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 control unit controls the motor and the switching circuit.

 When the engine starts, the control circuit controls the switching circuit so that it connects the batteries in series. A series voltage, which is a voltage produced by the batteries connected in series, is supplied to the starter-generator. When the engine is not starting, the control circuit controls the switching circuit so that it connects the batteries in parallel so that the batteries are charged by the starter-generator.

 In this system, a large driving force can be supplied at the output because the series voltage, which is a sum of the voltages of the batteries, is supplied to the starter-generator to start the engine.

In addition, batteries with the same capacities are charged equally when connected in parallel. This improves the charging condition of the batteries.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
FIG. 1 is a circuit diagram showing an automatic engine starting system according to the first embodiment of the present invention;
Figure 2 is a flowchart showing a process for controlling the automatic engine start system;
Figure 3 is a circuit diagram showing an automatic engine starting system according to the second embodiment of the present invention; and
FIG. 4 is a circuit diagram showing an automatic engine starting system according to the third embodiment of the present invention.

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 The preferred embodiments of the present invention will be explained with reference to the various embodiments in the accompanying drawings. Identical component parts are represented by identical reference numbers throughout the embodiments.

[First embodiment]
Referring to FIG. 1, an automatic engine starting system A comprises batteries 1,2, a relay 3, a starter-generator 4 with an inverter 41, and a control circuit 5. The relay 3 is intended for switch a battery connection 1,2 between the serial connection and the parallel connection.

 A resistor 61, the resistance of which is around 0.5 Q, comprises the first end 62 and the second end 64. The first end 62 and the second end 64 are connected to a supply line 20. The resistor 61 is connected for overvoltage protection. A relay 6 is connected to the resistor 61 via its normally closed (NC) contacts 63. A diode 65 is connected between the resistor 61 and the battery 1. The anode 66 and the cathode 67 of the diode 65 are respectively connected to the positive terminal of the battery 1 and at the end 64 of the resistor 61. The system A is connected to a starter 7 for a normal starting operation, a relay 70 with an NC contact 71, an electrical charge 8 and a switch 81 for the load 8.

 Battery 1 is a lead-acid battery with a power storage capacity of 12 V. The negative terminal 12 of battery 1 is connected to a vehicle chassis. Battery 2 is also a lead-acid battery with a storage capacity of 12 V. The positive terminal 21 of battery 2 is connected to the supply line 20.

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 Relay 3 includes an electromagnetic coil 31, NC contacts 32,33 and normally open (NO) contacts 34,35. The NC contacts 32,33 remain closed and the NO contacts 34,35 remain open, when the control circuit 5 does not attack the electromagnetic coil 31, that is to say, when the motor is operating normally.

In this state, the batteries 1,2 are connected in parallel. The NC contacts 32,33 become open and the NO contacts 34,35 become closed when the control circuit 5 drives the coil 31 to automatically restart the motor. In this state, the batteries 1, 2 are connected in series.

 The starter-generator 4 includes a starter function which is intended to start the engine from a stop, and a generator function which is intended to generate power. The starter-generator 4 is driven by the engine when it generates power. The series voltage (sum of the two battery voltages) is applied to the starter motor 4 via the inverter 41 to automatically start the motor. The control circuit 5 comprises a microcomputer, and controls the supply of the relay 3 and the electromagnetic coils 31,60, in addition to the command intended to stop and restart the engine.

 A process for controlling the control circuit 5 is illustrated in FIG. 2. The circuit 5 determines whether a driver of the vehicle turns an ignition key 82 from the OFF position to the start position (ST) 84 via the accessory position (ACC) and the position ON 83 in step SI. If so, the relay 70 is activated and the NO contact 71 is closed in step S2 so that the magnetic switch 72 of the starter 7 is closed. It follows that the power is delivered to the starter 7, and that the engine is started by the starter 7.

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 When the driver turns the ignition key from position ST 84 to position ON 83 after starting the engine, the NO contact 71 opens because the power to relay 70 stops. It follows that the magnetic switch 72 opens and that the supply of the starter 7 stops. The control circuit 5 does not deliver power to the relays 3.6 when the engine is started for the first time, when it is running, and when it is stopped. Consequently, the NC contacts, 32, 33, 63 remain closed. Since the batteries 1,2 are connected in parallel in this state, a parallel voltage is supplied to line 20. The parallel voltage is a voltage measured when the batteries 1,2 are connected in parallel.

 When the switch 81 is closed, the voltage is applied to the load 8 via the line 20 and the NC contact 63. When the engine is in operation, the batteries 1,2 are charged by the voltage produced by the starter-generator 4 via line 20.

 In step S3, it is determined whether the order to stop the engine is issued. If the vehicle stops at a traffic light, the vehicle speed is zero, the accelerator is released, and the brake pedal is depressed. In this state, it is determined that the order is issued. In this case (YES), the process advances to step S4. If the order is not issued (NO), the process is paused.

 In step S4, the control circuit 5 delivers at the output the order to stop the engine (to stop the fuel injection and the ignition by spark plug), so that the engine is stopped. In step S5, when the driver releases the brake pedal or depresses the accelerator, it is determined that the restart order is issued. If the restart order is issued (YES), the process advances to step S6. If the restart order is not

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 issued (NO), the process returns to step S4 so that the engine remains stopped.

 In step S6, the control circuit 5 delivers power to the relay 6, and opens the NC contact 63 of the relay 6. The supply of the relay 3 is stopped for a few milliseconds. During this period, the voltage reduced by the resistor 61 is applied to the load 8 via the line 20. The voltage of the battery 1 is applied to the load 8 via the diode 65.

 In step S7, the control circuit 5 delivers power to the relay 3, and switches the connection of the batteries 1,2 in parallel. The supply of relay 6 continues. The control circuit 5 delivers a drive signal to the inverter 41 when it delivers power to the relay 3. The voltage is applied to the starter-generator 4 via the inverter 41 to thereby restart the engine. The reduced voltage during the operation of the starter-generator 4 is applied to the load 8 via the line 20 and the resistor 61. The voltage measured at the line 20 becomes zero while the relay 3 is being switched. However, the voltage of the battery 1 is applied to the load 8 via the diode 65.

 When it is determined in step S8 that the engine restart process is complete, the control circuit 5 stops the supply of the relay 3, and switches the connection of the batteries 1,2 again in parallel to the step S9. In addition, the supply of relay 6 continues for several milliseconds to reduce an excessive voltage supply. During this period including the switching time of the relay 3, the voltage of the battery 1 is applied to the load 8 via the diode 65.

 In step S10, the control circuit 5 stops the supply of the relay 6 and the process returns to

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 step S3. The power supply of relay 3 remains stopped. At this time, the NC contacts 32,33, 63 are closed. The 1,2 batteries are connected in parallel. When the switch 81 is closed, the voltage is applied to the load 8 via the line 20 and the NC contact 63. The batteries 1,2 are charged with the voltage produced by the starter-generator 4 driven by the motor via the line 20.

 The system A can deliver a large driving force because the starter-generator 4 is supplied by a series voltage of the batteries 1,2 via the inverter 41 for restarting the engine. This reduces a delay in restarting the vehicle due to the fact that the engine is restarted smoothly.

 When the engine is restarted, the series voltage of the batteries 1, 2 is applied to the starter-generator 4 via the inverter 41. When the engine is running, the batteries 1,2 connected in parallel are charged by the starter-generator 4. Consequently, the starter and alternator (generator) functions can be executed by the starter-generator 4. In addition, the batteries 1,2 having the same power storage capacities are charged by being connected in parallel.

This improves the fact that one of the batteries 1,2 has a higher charge than the other.

 While relay 3 is in the process of switching to restart the motor after a stop, the voltage at line 20 momentarily becomes 0 V. However, the battery voltage is supplied to load 8. This is due to the causes the diode 65 to be connected between the positive terminal 11 of the battery 1 and the load 8 in order to deliver the battery voltage to the load 8.

 When the engine is restarted, the NC 63 contact is open.

Consequently, the series voltage of line 20 is applied to load 8 via resistor 61. It follows

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 that the voltage higher than the nominal voltage of load 8 is not applied to load 8.

[Second embodiment]
Referring to Figure 3, an automatic engine start system B does not include the relay 6 and the resistor 61 of the automatic engine start system A. The electrical load 8 is directly connected to the power supply line 20 via the switch 81. The diode 65 which delivers the battery voltage to switch the relay 3 is directly connected to the line 20.

 When a restart order is issued, the control circuit 5 outputs an attack signal to the inverter 41, delivers power to the relay 3, and switches the connection of the batteries 1, 2 in series. The reduced series voltage during the operation of the starter-generator 4 is applied to the load 8. While the relay 3 is being switched, the voltage at the power supply line 20 becomes zero.

However, the voltage of the battery 1 is applied to the load 8 via the diode 65.

 When the engine restart process is complete, the control circuit 5 stops the supply of the relay 3, and switches the connection of the batteries 1, 2 in parallel. To reduce an excessive voltage supply, the control circuit 5 stops the attack of the inverter 41 after the supply of the relay 3 has been stopped. When the power supply of relay 3 is stopped, the NC contacts 32,33 of relay 3 are closed. It follows that the batteries 1, 2 are connected in parallel and that the parallel voltage is supplied to line 20.

 Parallel voltage is applied to load 8 via switch 81 and line 20. The voltage produced by

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 the starter-generator 4 is delivered to line 20 and the batteries 1,2 are charged with the voltage.

 When the engine restart process is complete, the attack on the inverter 41 is stopped after the supply of relay 3 has been stopped. This reduces the fact that the voltage greater than the nominal voltage of the load 8 is applied to the load 8.

[Third embodiment]
Referring to FIG. 4, an automatic engine starting system C comprises an alternator 91 driven by an engine and a starter 92 for restarting the engine, in place of the inverter 41 and the starter-generator 4 of system B.

 When a restart order is issued, the control circuit 5 outputs a drive signal to the drive coil 94, delivers power to the relay 3, and switches the connection of the batteries 1,2 in series.

 The series voltage of the batteries 1,2 reduced during the operation of the starter 92 is applied through the electrical load 8. While the relay 3 is being switched, the voltage at the power supply line 20 becomes zero . However, the voltage of the battery 1 is supplied to the load 8 via the diode 65. When the process of restarting the motor is complete, the control circuit 5 stops the supply of the relay 3 and switches the connection of the batteries 1,2 in parallel. To reduce the application of excessive voltage to load 8, the output of the drive signal to the drive coil 94 is stopped after the supply of relay 3 has been stopped.

When the supply of relay 3 is stopped, the NC contacts 32 and 33 of relay 3 are closed. It follows that the batteries 1,2 are connected in parallel and that the parallel voltage is supplied to the line 20. The parallel voltage is applied to the load 8 via the line 20 and

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 the switch 81. The voltage produced by the alternator 91 is supplied to line 20, and the batteries 1, 2 are charged by the voltage.

 When the engine is restarted, the series voltage of the batteries 1, 2 is supplied to the starter 92. Consequently, a large driving force is delivered. This reduces a delay in restarting the vehicle because the engine is restarted smoothly.

 The present invention should not be limited to the embodiments previously described and shown in the figures, but can be implemented in various ways without departing from the spirit of the invention.

 Systems A, B, C can be configured so that the control circuit 5 does not automatically stop the engine under certain conditions. Such conditions may include the fact that the voltage of the battery 1 is lower than a predetermined voltage, that a door of the vehicle is open, that an air conditioning is operating at high power, that the temperature of the cooling water. is outside an allowable range, a turn signal is in operation, or the vehicle is climbing a steep slope, or if the electrical capacity of the first battery or of the second battery is less than a predetermined value.

 In the examples above, two starters are used: one is intended for a normal starting operation, and the other is intended for a restarting operation. The one intended for normal starting operation has a high starting torque necessary for starting the engine. The other has a high speed to start the engine immediately.

Claims (8)

1. An automatic engine starting system (A, B, C) comprising: a first battery (1); a second battery (2); starter-generator means (4,41, 91,92) comprising a starter function for starting a vehicle engine with a power delivered by the first and second batteries (1,2) and a generator function for charging the first and second batteries (1,2) while the engine is running; switching means (3) which switches a connection of the first and second batteries (1, 2) between a series connection and a parallel connection; and a control means (5) which controls the switching means (3) characterized in that the first battery (1) and the second battery (2) have the same power storage capacity; the control means (5) controls the switching means (3) for connecting the first and second batteries (1, 2) in series to deliver a series voltage, which is a sum of the voltages of the first and second batteries (1,2 ) by means of starter-generator (4) to start the engine, and the control means (5) controls the switching means (3) to connect the first and second batteries (1,2) in parallel to charge the first and second batteries (1,2) by the starter-generator (4, 41,91, 92) while the engine is running.  2. Automatic engine starting system (A, B, C) according to claim 1 further characterized in that: the starter-generator means (4,41, 91,92) comprises an alternator (91) which is driven by the engine <Desc / Clms Page number 12>  and charges the first and second batteries (1,2) and a starter (92) which starts the engine; the control means (5) executes a command to stop the engine when the vehicle stops, and a command to restart the engine when an engine restart order is issued; the control means (5) controls the switching means (3) to connect the first and second batteries (1,2) in parallel to charge the first and second batteries (1,2) by the alternator (91) while the engine is running; and the control means (5) controls the switching means (3) for connecting the first and second batteries (1,2) in series to deliver the series voltage to the starter (92) when the order is issued.  3. Automatic engine starting system (A, B, C) according to claim 1, further characterized in that: the starter-generator means (4,41, 91,92) comprises a starter-generator (4) and an inverter (41); the control means (5) performs a command to stop the engine when the vehicle stops, and a command to restart the engine when an order to restart the vehicle is issued; the way. control (5) controls the switching means (3) to connect the first and second batteries (1,2) in parallel to charge the first and second batteries (1,2) by the generation function of the starter-generator (4 ) while the engine is running; and the control means (5) controls the switching means for connecting the first and second batteries (1,2) in series to deliver the series voltage to the starter-generator (4) via the inverter (41) for <Desc / Clms Page number 13>  restart the engine using the starter function of the starter-generator (4) when an engine restart order is issued.  4. Automatic engine starting system (A, B, C) according to claim 2 or 3, further characterized in that the control means (5) limits the engine stop control if a condition in which the means (5) stops the engine is not satisfied.  5. Automatic engine starting system (A, B, C) according to claim 2 or 3, further characterized in that the control means (5) limits the command to stop the engine if the electrical capacity of the first battery (1) or the second battery (2) is less than a predetermined value.  6. Automatic engine starting system (A, B, C) according to any of claims 2 to 4, further characterized in that the first battery (1) is connected to continuously deliver a voltage parallel to a starter (7) for manual starting, and is electrically connected to an electrical load (8).  7. An automatic engine starting system (A, B, C) according to any of claims 2 to 4, further characterized in that a power supply line (20), to which a diode (65 ) is connected to deliver the voltage of the first battery (1) to operate the switching means (3) is connected to an electrical load (8). <Desc / Clms Page number 14>  8. Automatic engine starting system (A, B, C) according to any of claims 2 to 4, further characterized in that: a resistor (61) for protection against overvoltages has a first end (62 ) and a second end (64); the first end (62) is connected to the power supply line (20) and the second end (64) is connected to a diode (65) which is intended to supply the voltage from the first battery (1) to the electric charge (8); a normally closed contact (63) of a relay (3) is connected to the first end (62) and to the second end (64); and the second end is also connected to the electrical load (8).