Electrical system for a motor vehicle and method for control of a starter motor and a battery isolator in such an electrical system

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(12) Patent Application

Sweden do) SE 532 001 C2 (21) Patent application number: 0800255-2 (45) Patent granted: 2009-09-22 (41) Application generally available: 2009-08-05 (22) The patent application was submitted: 04/02/2008 ( 24) Running date: 2008-02-04 (83) Deposit of microorganism: - (30) Priority information: - (51) International class:

B60R 16/03 (2006.01) (73) Patent holder: Scania CV AB (publ). 151 87 Södertälje SE

<td>(72) Inventor:</td><td>Johan Lindström, Nyköping SE</td>

<td>(74) Agents:</td><td>Bjerkéns Patentbyrå KB, Box 1274, 801 37 Gävle SE</td>

<td>(54) Name:</td><td>Electrical system for a motor vehicle and a method for controlling a starter motor and a battery disconnector in such an electrical system</td>

<td>(56) Publications cited:</td><td> ___</td>

(47) Summary:

Electrical system for a motor vehicle and a method for controlling a starter motor (10) and a battery disconnector (11) in such an electrical system. The electrical system (1) comprises a consumer battery set (2) and a starter battery set (6) connected in parallel. The battery disconnector is operable between a switched-off position, in which the starter battery set is electrically switched off from the starter motor, and a switched-on position in which the starter battery set is electrically connected to the starter motor. An electronic control device (12), upon receipt of a start signal, causes the battery disconnector to enter the on position and then causes the starter motor to start, thereby ensuring that the battery disconnector is in the on position before starting the starter motor. When switching off the starter, the battery switch is allowed to be operated from the switch-on position to the switch-off position only after the starter has been switched off, thereby ensuring that the starter is switched off before the battery-switch is brought into the switch-off position.

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532 001

SUMMARY

Electrical system for a motor vehicle and a method for controlling a starter motor (10) and a battery disconnector (11) in such an electrical system. The electrical system (1) comprises a consumer battery set (2) and a starter battery set (6) connected in parallel. The battery disconnector is operable between a switched off position in which the starter battery set is electrically disconnected from the starter motor, and a switched on position in which the starter battery set is electrically connected to the starter motor. An electronic control device (12), upon receipt of a start signal, causes the battery disconnector to enter the on position and then causes the starter motor to start, thereby ensuring that the battery disconnector is in the on position before starting the starter motor. When the starter is switched off, the battery disconnector is allowed to be operated from the on position to the off position only after the starter motor has been switched off, thereby ensuring that the starter motor is switched off before the battery disconnector is brought into the off position.

532 001

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a power system for a motor vehicle according to the preamble of claim 1 and a method according to the preamble to claim 7 for controlling a starter motor and a battery disconnector in a power system of a motor vehicle. The invention also relates to a computer program product comprising computer program code for implementing a method according to the invention, as well as an electronic control unit.

A motor vehicle driven by an internal combustion engine is usually provided with an electrically driven starter motor to start the internal combustion engine. When the driver of the motor vehicle activates a starter, for example by turning an ignition key or by pressing a starter button, a rotor of the starter motor engages the crankshaft of the internal combustion engine and the starter motor is supplied with electric current from a battery to allow the starter motor to rotate the combustion engine. it enables the internal combustion engine to start. After the internal combustion engine has started, the starter motor is switched off and decoupled from the internal combustion engine.

For example, by US 6,057,666 A, US 6,229,279 B1, US 6,275,001 B1, US 6,545,445 B1 and US 6,765,312 B1, it is previously known to provide in a power system of a starter motor a battery set with a or multiple batteries for supplying electric current to various electric consumers of the motor vehicle and a second battery set with one or more batteries specially designed for supplying electric current to the starter motor. In this specification and the subsequent claims, the term "consumer battery set" is used to designate such a first battery set and the term "starter battery set" as a term for such a second battery set. The respective battery included in the consumer battery set is referred to here as the consumer battery, while the respective battery included in the starter battery set here is referred to as the starting battery.

By appropriate control of an electrical system provided with a consumer battery set and a starter battery set, it is possible to ensure that the starter battery set is always kept charged to be able to assist with electric current in connection with the start of the vehicle. Furthermore, the use of a consumer battery set and a separate starter battery set make it possible to optimize the batteries of the respective battery set depending on its intended function.

OBJECTS OF THE INVENTION

The object of the present invention is to provide a new and advantageous way of controlling an electrical system of the type defined in the preamble of claim 1.

SUMMARY OF THE INVENTION

According to the present invention, said object is achieved by means of an electrical system having the features set forth in claim 1 and a method having the features defined in claim 7.

According to the invention, a starter motor included in the electrical system and a battery separator included in the electrical system are controlled by means of an electronic control device in such a way:

- in connection with starting the starter motor, the battery disconnector is always put in a switched-on position for supplying electric current to the starter motor from the starter battery set before starting the starter motor, and

- the starter motor is always switched off before the battery disconnector is allowed to be operated from the on position to the off position for disconnecting the starter battery set from the starter motor.

This ensures that the battery disconnector is always in the on position and the starter battery set is thus electrically connected to the starter motor before starting the starter motor, and that the starter motor is always switched off before the battery disconnector is operated from the switched-off position for switching off the starter battery set.

A standard-type battery disconnector is usually sized to cut and close electric currents with a current of up to about 300 A, which is sufficient for the most common electric consumers of a motor vehicle except for the starter motor. Typically, an electric current of about 1200-1500 A passes through the starter motor at the moment when the starter motor is started and in operation, the starter motor typically draws an electric current which averages about 600 A. With the invention according to the invention, it is possible to use a relatively inexpensive standard battery separator for connecting a starter battery set to a starter motor of an electrical system of this type, since this battery separator does not need to cut or stop any electrical current while the starter motor is started or running. . In addition, with the inventive solution, it becomes possible to connect a separate starter battery set in an existing electrical system of a motor vehicle in a simple and cost-effective way, since no major reconstruction of the existing electrical system is required for this.

According to an embodiment of the invention, the control device is arranged, after switching off the starter motor, to cause the battery disconnector to take the off position and thereby disconnect the starter battery set from a generator included in the electrical system when it is determined that the starter battery / starter batteries of the starting battery set are charged in the generator set. This avoids overcharging of the starter batteries, which contributes to increased service life and reduced water consumption of the starter batteries.

532 001

Other advantageous features of the electrical system and method of the invention will be apparent from the dependent claims and the following description.

The invention also relates to a computer program product having the features defined in claim 12 and an electronic control unit having the features defined in claim 14.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail by way of example, with reference to the accompanying drawings. It is shown in:

Fig. 1 is a schematic diagram of a power system according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of an electronic control unit for implementing a method according to the invention; and

Fig. 3 is a flowchart illustrating a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In Figure 1, an embodiment of an electrical system 1 according to the invention is schematically illustrated for a motor vehicle equipped with an internal combustion engine (not shown). The electrical system according to the invention 1 comprises a first battery set 2, here referred to as a consumer battery set, with one or more batteries 3, here called consumer batteries, for supplying electric current to different electricity consumers of the vehicle. These electricity consumers are schematically and jointly indicated by the block 4 in Fig. 1 and include, for example, various control units, lighting devices, refrigerators and various other components of the vehicle powered by electric current. In the illustrated example, the consumer battery set 532 001 is connected to the electricity consumers 4 via an electrical center 5 which includes fuses, relays etc.

The electrical system 1 further comprises a second battery set 6, herein referred to as the starter battery set, with one or more batteries 7, herein referred to as the starting batteries, for supplying electric current to a starter motor 10 of the vehicle. The starter battery set 6 is connected in parallel with the consumer battery set 2. In the illustrated example, the consumer battery set 2 comprises two series connected consumer batteries 3 and the starting battery set 6 two series connected starter batteries 7. However, the number of batteries in each battery set 2, 6 may be both more and less than two if appropriate.

The consumer battery set 2 and the starter battery set 6 are connected to a generator 8 of the vehicle, which generator is powered by the vehicle's internal combustion engine to generate electric current for charging the batteries 3, 7 of the consumer battery set and the starting battery set of the electric vehicle starter set. could also include more than one such generator.

The starter motor 10 can be supplied with electric current partly from the consumer battery set 2 and partly from the starter battery set

6th To enable controlled switching on and off of the starter battery set 6, the electrical system 1 comprises a battery disconnector 11 operable between a switched off position, in which the battery disconnector 11 is arranged to keep the starter battery set 6 electrically disconnected from the starter motor 10, in which the battery disconnector 11 is arranged to keep the starter battery set 6 electrically connected to the starter motor 10 for supplying electric current to the starter motor from the starter battery set. Furthermore, the starter battery set 6 is electrically connected to the consumer battery set 2 when the battery disconnector 11 is in the on position and disconnected from the consumer battery set 2 when the battery disconnector 11 is in the off position. The battery disconnector 11 is connected in series with the starter battery set 532 001 set 6 and connected in parallel with the consumer battery set 2 and thus does not affect the connection between the consumer battery set 2 and the electricity consumers 4 and does not affect the connection between the consumer battery set 2 and the starter motor 10.

The battery disconnector 11 is also provided:

- keeping the starter battery set 6 electrically in the on position, thereby electrically connected to the generator 8, thereby permitting the supply of electric current to the starting battery set 6 from the generator for charging the starter batteries 7 of the starting battery set, and

- in the off position, keep the starter battery set 6 electrically disconnected from the generator 8.

The battery disconnector 11 and starter motor 10 are controlled by means of an electronic control device 12, which in the illustrated example comprises an electronic control unit 13 arranged to control both the battery disconnector 11 and the starter motor 10. Alternatively, the control device 12 could comprise two separate and mutually communicating electronic control units. one of which controls the operation of the battery disconnector and another controls the operation of the starter motor.

The battery disconnector 11 is preferably a relay which conventionally comprises a switch 11a and an electromagnet 11b, where the switch 11a is closed under the action of the electromagnet 11b as electrical current is supplied through the electromagnet and returns to the open position when the current supply through the electromagnet ceases. In the example illustrated in Fig. 1, the battery disconnector 11 is operated from the off position to the on position by setting a voltage 13 connected to the battery disconnector electromagnet 11b of the control unit 13. The battery disconnector 11 is then held in the on position as long as the output 13a remains energized and operated to the off position when the voltage setting of the output 13a ceases. Of course, the bat separator could also be of a different type from the type illustrated in Fig. 1.

The control device 12 is connected to a starting means 14 of the vehicle. The starting means 14 could, for example, comprise a starting means which is actuable by the driver of the vehicle, for example by pressing a start button or turning an ignition key, and which is arranged to generate a start signal for starting the vehicle starter motor. When the driver activates the starter, a start signal is generated which is sent to the control device 12, which upon receiving a start signal from the starting means 14 causes the battery disconnector 11 to enter the on position and then cause the starter motor 10 to start, thereby ensuring that the battery disconnector 11 is in the on position. before starting the starter motor. The starter means 14 could also be arranged to automatically generate a start signal for starting the vehicle's starter motor when it is detected that the vehicle's internal combustion engine needs to be started after an automatically executed shutdown thereof in a situation when the vehicle is stationary, for example when it is detected that the temperature in the cab has risen to such a level that the vehicle's air conditioning system needs to be started or when it is detected that the driver intends to drive away.

The control device 12 is conveniently arranged to receive the starting motor 10 upon receiving a start signal from the starting means 14 with a given time delay after the control device has caused the battery disconnector 11 to take the on position.

In connection with the start of the starting motor 10, a rotor of the starting motor is brought into engagement with the crankshaft of the internal combustion engine at the same time as a contact in the starting motor is closed so that the starting motor can be supplied with electric current. The battery disconnector 11 must thus be operated to the on position before the contact in the starter motor 10 is closed. After the contact in the starter motor 10 is closed, the starter motor can be supplied with electric current from the electrical system battery sets 2, 6, whereby the starter motor rotates combustion.

532 The engine's crankshaft and thus enables the internal combustion engine to start. Since the starter battery set 6 is connected in parallel with the consumer battery set 2, the battery set having the largest power reserve will account for the largest power supply to the starter motor 10. Normally, the starter batteries 7 of the starter battery set 6 should be fully charged or at least fully charged and thus have a large power reserve when the vehicle is started; which is ensured by disconnecting the starter battery set by means of the battery disconnector 11 from the vehicle's electricity consumers 4 and from the consumer battery set 2 when the starting batteries 7 of the starter battery set have been charged to the desired extent after the start of the vehicle's internal combustion engine.

When it is conventionally detected that the internal combustion engine is started, for example by sensing the speed of the internal combustion engine, the control device 12 is arranged to effect a shutdown of the starter motor 10, whereby the above mentioned contact in the starter motor 10 is opened and the rotor of the starter motor is decoupled from the internal combustion engine. The control device 12 is arranged to allow the battery disconnector 11 to be operated from the on position to the off position only after the control device 12 has switched off the starter motor 10 to thereby ensure that the starter motor 10 is switched off before the battery disconnector 11 is brought into the off position.

The controller 12 is conveniently arranged, after switching off the starter motor 10, to cause the battery disconnector 11 to take off when the controller 12 has determined or received information that the starter batteries 7 of the starter battery set have been charged to a given extent. The control device 12 may, for example, be arranged to cause the battery disconnector 11 to take off when the starting batteries 7 are charged during a given charging time. This recharge time can, for example, start to be calculated when, after the start of the vehicle's internal combustion engine, there is sufficient voltage in the electrical system 1 to effect recharging of the starting batteries 7, ie when the control device 12 is fixed or

532 001 received information that the voltage level of the electrical system has reached the charging voltage prescribed for the starting batteries. The desired recharge level of the starter batteries 7 can also be determined in another manner known per se.

In order to avoid discharge of the starter batteries 7, the control device 12 is suitably arranged that, after switching off the starter motor 10, and before the control device 12 determines or receives information that the starter batteries 7 have been charged to the given extent, causing the battery disconnector 11 to take the off position when the control device 12 determines or receives information that the voltage of the electrical system 1 is lower than the prescribed charging voltage for the starting batteries 7, and thereafter causing the battery disconnector 11 to take on the position when the control device 12 determines or receives information the electrical system 1 has reached the said charging voltage. In this case, the above-mentioned recharge time only includes the time periods during which the battery disconnector 11 has been in the on position.

Fig. 3 shows a flow diagram illustrating one embodiment of a method according to the present invention for controlling a starter motor 10 and a battery disconnector 11 in an electrical system 1 of the type illustrated in Fig. 1. In a first step S1, the control system 12 of the electrical system determines whether a start signal has been generated. If so, the controller 12 in a second stage S2 causes the battery disconnector 11 to enter the on position so that the electrical system starter battery set 6 is connected to the starter motor 10. Thereafter, the controller 12 causes the starter motor 10 to start in a third stage S3. In a fourth step S4, the control device 12 determines whether the vehicle's internal combustion engine has started. If so, the controller 12 causes the starter motor 10 to shut down in a fifth step S5. In a sixth step S6, the control device 12 determines whether the starter batteries 7 of the starter battery set have been charged to a given extent. If so, the controller 12 causes the battery disconnector 11 to take the off position in a seventh step S7.

K 5 9.

Computer program code for implementing a method according to the invention is conveniently included in a computer program readable to the internal memory of a computer, such as the internal memory of an electronic controller of a motor vehicle. Such a computer program is conveniently provided via a computer program product comprising a data storage medium readable by an electronic control unit, which data storage medium has the computer program stored thereon. Said data storage medium is, for example, an optical data storage medium in the form of a CD-ROM, a DVD, etc, a magnetic data storage medium in the form of a hard disk, a floppy disk, a cassette tape, etc., or a memory of the type ROM, PROM, EPROM OR EEPROM or a flash memory.

A computer program product according to an embodiment of the invention comprises computer program code for bringing an electronic control device into an electrical system of the type illustrated in Fig. 1:

* upon receiving a start signal from the starter means causing the battery disconnector to enter the on position and then causing the starter motor to start, thereby ensuring that the battery disconnector is in the on position before starting the starter motor; and, upon shutting down the starter, causing the starter to shut down and only then to allow the battery disconnector to be operated from the on position to the off position, thereby ensuring that the starter motor is switched off before the battery disconnector is brought into the off position.

Figure 2 illustrates very schematically an electronic control unit 13 comprising an executing means 31, such as a central processor unit (CPU), for executing computer software. The execution means 31 communicates with a memory 33, for example of the RAM type, via a data bus 32. The controller 13 also comprises data storage medium 34, for example in the form of a memory of the type ROM, PROM, EPROM, EEPROM or a Flash memory. The executing means 31 communicates with the data storage medium 34 via the data bus 32. A computer program comprising computer program code for implementing a method according to the invention, for example

001 according to the embodiment illustrated in Fig. 3, is stored on the data storage medium 34.

This invention is intended to be used in a motor vehicle, such as, for example, a car, a bus, a tractor or a truck.

The invention is of course not limited in any way to the embodiments described above, but a number of possibilities for modifications thereof will be apparent to one of ordinary skill in the art, without departing from the basic idea of ​​the invention as defined in the appended claims.