SE542023C2

SE542023C2 - An arrangement and a method for protection against abnormal currents in a starter motor circuit

Info

Publication number: SE542023C2
Application number: SE1850758A
Authority: SE
Inventors: Gunnar Ledfelt; Holger Dreher; Ola Bergqvist; Viktor Haak
Original assignee: Scania Cv Ab
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2020-02-11
Also published as: SE1850758A1; DE112019002271T5; WO2019245436A1

Abstract

An arrangement for protection against abnormal currents in a starter motor circuit of a starter motor (1) connected to an internal combustion engine of a motor vehicle has a sensor (13) sensing the presence of a start control signal sent to the starter motor, a member (17) measuring a quantity indicative of the current fed into the starter motor and a control unit controlling a device (24) to break the current fed to the starter motor if a current to the starter motor is measured in spite of a lack of a said start control signal.

Description

An arrangement and a method for protection against abnormal currents in a starter motor circuit TECHNICAL FIELD OF THE INVENTION The present invention relates to an arrangement for protection against abnormal currents in a starter motor circuit of a starter motor connected to an internal combustion engine of a motor vehicle, the arrangement comprising a device configured to break an abnormal current fed to the starter motor, as well as a method for such protection according to the preamble of the appended independent method claim.

The life length of a starter motor is in general shorter than the life length of a motor vehicle, which means that there is a significant risk for starter motor problems, and common failure modes may lead to abnormal currents in a said starter motor circuit, which in each turn can lead to thermal incidents and VOR (Vehicle Off Road). Thus, it is desired to protect the starter motor circuit against such abnormal currents for avoiding the possibly serious results of such currents. Such failure modes may for instance be due to welding together of contacts of a connector or short circuits due to overheating or other insulating problems.

BACKGROUND ART US2008315683 A1 and US2005099009 A1 disclose arrangements measuring the current flowing to a starter motor in a motor vehicle and disconnecting the electric power supply to the starter motor when a current above a predetermined level is measured.

SUMMARY OF THE INVENTION The object of the present invention is to provide an arrangement and a method according to the introduction being improved in at least some aspect with respect to such arrangements and methods already known.

This object is with respect to the arrangement obtained by providing such an arrangement with the features listed in the characterizing part of appended patent claim 1.

Thus, the arrangement is provided with a sensor configured to sense the presence of a start control signal sent to the starter motor, a member configured to measure a quantity indicative of the current fed into the starter motor and a control unit configured, based upon information from said sensor and member, to determine that an abnormal current is fed to the starter motor under the condition that a current above a minimum level has been revealed by measurement by said member and the sensor simultaneously has sensed a lack of a said start control signal and when this condition is fulfilled control said device to break the current fed to the starter motor.

Accordingly, the arrangement according to the present invention obtains breaking of a current fed to the starter motor when there shall be no current fed to the starter motor since no start control signal is there, which means that the current is an abnormal current and has to be due to any failure mode in the starter motor circuit. This differs from known such arrangements which do not consider whether a start control signal is there or not but only take care of breaking of currents which are above a high level.

Breaking of the current fed to the starter motor shall according to the invention take place when the current is flowing to the starter motor in spite of a lack of a said start control signal, which has to be kept in mind when interpreting the definition of “current above a minimum level”, which level is accordingly set to be low in comparison with currents flowing when a failure is present but still not zero for avoiding breaking when there is no failure but only some type of noise.

According to an embodiment of the invention the control unit is configured to consider a current above a minimum level to have been measured by said member only if such a current is measured to continuously exist over a predetermined period of time, such as at least 0.1 s. This prevents said device from breaking the current fed to the starter motor if a sudden peak current due to noise but without any failure in the starter motor circuit would occur.

According to another embodiment of the invention the arrangement is configured to be arranged in a motor vehicle having a generator connected in parallel with the starter motor, and said device is configured to break a said abnormal current in a position within a line connecting the starter motor in parallel with the generator. By breaking an abnormal current fed to the starter motor circuit in such a position a good function of the generator may in spite of that be maintained.

According to another embodiment of the invention the control unit comprises a first logic member connected to said sensor and configured to send a logic 1 to a logic AND-gate as long as a said lack of said start control signal is sensed and a second logic member connected to said quantity measuring member and configured to send a logic 1 to said AND-gate upon revealing a current fed to the starter motor above said minimum level by measurement by said member, and said device is configured to be trigged by a said logic 1 on the output of said AND-gate to break an abnormal current fed to the starter motor. The control unit does in this way ensure that breaking is only carried out when said condition is fulfilled and no current should be fed to the starter motor.

According to another embodiment of the invention said device comprises current breaking means arranged in a line connecting the starter motor to a source of electric energy, such as electric batteries, of the motor vehicle and configured to be trigged to break an abnormal current fed to the starter motor in said line, such as a pyrotechnic breaker, a disconnector or a semiconductor switch, such as a transistor.

According to another embodiment of the invention the arrangement comprises an electrical energy source configured to provide electric energy to said device so as to ensure breaking of a said abnormal current in case of drop out of a connection of electric batteries of a said motor vehicle to said device. Breaking of a said abnormal current fed to the starter motor may by this be carried out without any need of electric power available from electric batteries of a motor vehicle.

According to another embodiment of the invention said quantity measuring member is configured to measure the current in a line for feeding electric energy to the starter motor, such as by a shunt measuring of a voltage in said line or by a Hall-element arranged in said line. This constitutes a reliable way of determining that an abnormal current is fed to the starter motor.

According to another embodiment of the invention said quantity measuring member is configured to measure the voltage at a position in the starter motor circuit on the feeding side of the starter motor with respect to ground as a quantity indicative of the current fed into the starter motor. This constitutes another reliable way of determining that an abnormal current is fed to the starter motor, since such feeding would then be detected by a voltage at said position being different from the voltage in that position when no current is fed to the starter motor.

The object of the invention is with respect to the method obtained by providing a method according to the appended independent method claim. The advantages of such a method and of the embodiment thereof defined in the dependent method claims appear clearly from the above discussion of the arrangement according to the invention.

The invention also relates to a computer program, a computer program product, an electronic control unit and a motor vehicle according to the claims directed thereto.

Further advantageous features and advantages of the invention will appear form the description following below.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a specific description of embodiments of the invention cited as examples.

In the drawings: Fig. 1 is a very schematic view illustrating basically how a starter motor is connected to an internal combustion engine of a motor vehicle for explaining the problem to be addressed by an arrangement according to the present invention, Fig. 2 is a schematic view illustrating an arrangement according to a first embodiment of the invention, Fig. 3 is a schematic view illustrating a part of an arrangement according to a second embodiment of the invention, Fig. 4 is a flow chart showing a method according to an embodiment of the invention, and Fig. 5 is a schematic view illustrating an electronic control unit for implementing a method according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 shows very schematically how a starter motor 1 is connected to or integrated with an internal combustion engine 2 in a motor vehicle 3. Electric power for the operation of the starter motor is provided by electric batteries 4 of the motor vehicle by connection thereof to opposite poles 5, 6 thereof. It is also shown how a generator 7 is connected in parallel with the starter motor for generating electric energy for charging the batteries 4 and/or for the operation of appliances, such as headlamps, of the vehicle.

A starter lock 8 is to be operated for starting the starter motor 1 and by that the engine 2. It is illustrated how this is done by first closing an ignition switch 11 and then a switch 9 sending a start control signal, a so called 50-signal, to an electronic control unit 10 of the motor vehicle. The electronic control unit 10 is configured to send said start control signal or so called 50-signal further to the starter motor 1 needed for starting operation thereof on a connection line 12 between the electronic control unit 10 and the starter motor 1. What has been described so far with reference made to Fig. 1 constitutes a general design in motor vehicles.

An arrangement and a method according to a first embodiment of the invention will now be disclosed with reference also made to Fig. 2. The arrangement according to the invention is configured to break a current to the starter motor when there should not be any current to the starter motor, i.e. when no 50-signal is present on the input of the starter motor. A voltage above a certain level, such as 3 V, is present on said connection line 12 between the electronic control unit 10 and the starter motor 1 when said start control signal (50-signal) is present. The arrangement does for that sake comprise a sensor 13 in the form of a voltage meter, configured to measure the voltage on the line 12 so as to determine whether a said start control signal is present or not. The voltage meter is associated with a first logic member 14 configured to send a logic 1 further towards a logic AND-gate 15 as long as a lack of a said start control signal is sensed. This also means that a logic 0 will be sent to the AND-gate 15 if a voltage above said level is measured by the sensor 13. For obtaining this a member 45 compares the value of the voltage measured with said level. However, the signal sent from the first logic member 14 will be sent by a certain delay, such as 0.1 s or 0.2 s, further to the AND-gate 15 so as to be validated only if the presence or lack of start control signal measured by the sensor continuously exists over a predetermined period of time, which is indicated by a delay member 16.

The arrangement according to the invention does further comprise a member 17 configured to measure a quantity indicative of the current fed into the starter motor 1 , and this is here done by measuring the current in the line 18 for feeding electric energy to the starter motor 1 , such as by a shunt measuring of a voltage in this line or by a Hall-element arranged in this line. It is shown how the current value measured may be sent to an amplifier 19 and then further to a second logic member 20 configured to send a logic 1 to the AND-gate 15 upon revealing a current fed to the starter motor above a minimum level. For obtaining this, a member 21 compares the value of the current measured by the member 17 with said minimum level, which may be for example 20 A, and send a said logic 1 on the line 46 further to the AND-gate 15 only if it is determined that the current is above said minimum level over a predetermined period of time, such as 0.1 s or 0.2 s, as indicated by a delay member 22. Accordingly, a logic 1 will be present on the output 23 of the AND-gate if a current above said minimum level is fed to the starter motor and at the same time no start control signal is sent to the starter motor.

The arrangement also comprises a device configured to break an abnormal current fed to the starter motor, which here is a current fed to the starter motor when no current should be fed thereto, and more exactly when the condition resulting in a logic 1 on the output of the AND-gate 15 is fulfilled. The device 24 comprises current breaking means 25 arranged in the line 18 connecting the starter motor to the electric batteries 4 in a position in parallel with the generator 7 so as to not break the connection of the generator to the electric batteries when breaking a current to the starter motor. This means here that a pyrotechnic breaker configured to be trigged by a logic 1 on the output of the AND-gate 23 will through such triggering permanently break a current fed to the starter motor. Other alternatives to such breaking means are a disconnector or a semiconductor switch controlled by the output signal from the gate 15 to break a current fed to the starter motor.

Furthermore, it is shown how the arrangement may be provided with an electrical energy source 26, here in the form of a diode 27 with a capacitor 28 storing electric energy, configured to provide electric energy to the device 24 (in fact all components with reference numerals 13-17, 19-22, 45 are provided with electric energy through this source indicated by the connection thereof to the AND-gate 15) so as to ensure breaking of a said abnormal current in case of drop out of the connection of the electric batteries of the motor vehicle to the device 24.

Fig. 3 illustrates schematically how a member configured to measure a quantity indicative of the current fed into the starter motor may be realized in an arrangement according to a second embodiment of the invention. Fig. 3 shows in a simplified manner the design of the connection of the starter motor 1 to an electric energy source indicated by the two poles 5, 6 connected to electric batteries, and this design is also valid for the first embodiment shown in Fig. 2. A starter control signal from the electronic control unit 10 present on the line 12 will close a relay 30 through which a main relay 31 is closed for feeding electric energy to the stator 32 of the starter motor for rotating the rotor 33 thereof. When a current is fed to the starter motor this will result in a voltage in a position 34 on the feeding side of the starter motor with respect to ground, so that a measuring of this voltage will indicate whether a current is fed to the starter motor or not. Current may for instance be fed to the starter motor would one of the relays 30 or 31 have contacts stucked by welding. A voltage measuring member 35 is arranged to measure this voltage in the position 34 and a second logic member 38 will in this case send a logic 1 further to an AND-gate on the line 46 as the one shown in Fig. 2 would a comparing member 36 determine that the voltage in the position 34 is above a predetermined level, such as 1 V over a predetermined period of time, such as 0.2 s indicated by the box 37. It would also be possible to have a said quantity measuring member according to both embodiments shown and the output thereof connected to an OR-gate for sending a logic 1 further to the AND-gate if one of the quantity measuring members has carried out a measurement resulting in a logic 1 on the output thereof.

Fig. 4 illustrates a flow chart of a method according to an embodiment of the present invention carried out for protection against abnormal currents in a starter motor circuit of a starter motor connected to an internal combustion engine of a motor vehicle. The method is started with a step Si of measuring current fed into the starter motor. A step S2 of sensing the presence of a start control signal sent to the starter motor is carried out in parallel with step Si. The question: Is current fed into the starter motor? is asked in a step S3, and the question Is there a lack of start control signal sent to the starter motor? is asked in a step S4. In a step S5 the question is asked: Do we have a yes to questions in both step S3 and S4?, and when the answer to this question is yes it is continued with a step S6 of breaking the current fed into the starter motor.

Computer program code for implementing a method according to the invention is with advantage included in a computer program which can be read into the internal memory of a computer, e.g. the internal memory of an electronic control unit of a motor vehicle. Such a computer program is with advantage provided via a computer program product comprising a data storage medium which can be read by a computer and which has the computer program stored on it. Said data storage medium is for example an optical data storage medium in the form of a CD ROM disc, a DVD disc etc., a magnetic data storage medium in the form of a hard disc, a diskette, a cassette tape etc., or a flash memory or a memory of the ROM, PROM, EPROM or EEPROM type. Fig. 5 illustrates very schematically an electronic control unit 44 comprising an execution means 40, e.g. a central processor unit (CPU), for execution of computer software. The execution means 40 communicates with a memory 41 , e.g. of the RAM type, via a data bus 42. The control unit 10 comprises also a non-transitory data storage medium 43, e.g. in the form of a flash memory or a memory of the ROM, PROM, EPROM or EEPROM type. The execution means 40 communicates with the data storage medium 43 via the data bus 42. A computer program comprising computer program code for implementing a method according to the invention, e.g. in accordance with the embodiment illustrated in Fig. 4, is stored on the data storage medium 43.

The invention is of course in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to one skilled in the art without having to deviate from the scope of invention defined in the appended claims.

Although shown apart in the figures the sensor and the current measuring member with logic are preferably integrated on a printed circuit board combined with the current breaking device.

Claims

1. An arrangement for protection against abnormal currents in a starter motor circuit of a starter motor (1 ) connected to an internal combustion engine (2) of a motor vehicle (3), the arrangement comprising a device (24) configured to break an abnormal current fed to the starter motor, characterized in that the arrangement further comprises • a sensor (13) configured to sense the presence of a start control signal sent to the starter motor, • a member (17, 35) configured to measure a quantity indicative of the current fed into the starter motor, and • a control unit configured, based upon information from said sensor and member, to determine that an abnormal current is fed to the starter motor (1 ) under the condition that a current above a minimum level has been revealed by measurement by said member (17, 35) and the sensor (13) simultaneously has sensed a lack of a said start control signal and when this condition is fulfilled control said device (24) to break the current fed to the starter motor.

2. An arrangement according to claim 1 , characterized in that the control unit is configured to consider a current above a minimum level to have been measured by said member (17, 35) only if such a current is measured to continuously exist over a predetermined period of time, such as at least 0.1 s.

3. An arrangement according to claims 1 or 2, which is configured to be arranged in a motor vehicle (3) having a generator (7) connected in parallel with the starter motor (1 ), characterized in that said device (24) is configured to break a said abnormal current in a position within a line (18) connecting to the starter motor in parallel with said generator.

4. An arrangement according to any of the preceding claims, characterized in that the control unit comprises a first logic member (14) connected to said sensor (13) and configured to send a logic 1, to a logic AND-gate (15) as long as a said lack of said start control signal is sensed and a second logic member (20, 36) connected to said quantity measuring member (17, 35) and configured to send a logic 1 to said AND-gate (15) upon revealing a current fed to the starter motor (1 ) above said minimum level by measurement by said member (17, 35), and that said device (24) is configured to be trigged by a logic 1 on the output (23) of said AND-gate to break an abnormal current fed to the starter motor.

5. An arrangement according to any of the preceding claims, characterized in that said device (24) comprises current breaking means (25) arranged in a line connecting the starter motor to a source of electric energy, such as electric batteries (4), of the motor vehicle (3) and configured to be trigged to break an abnormal current fed to the starter motor in said line, such as a pyrotechnic breaker, a disconnector or a semiconductor switch, such as a transistor.

6. An arrangement according to any of the preceding claims, characterized in that it comprises an electrical energy source (26) configured to provide electric energy to said device (24) so as to ensure breaking of a said abnormal current in case of drop out of a connection of electric batteries (4) of a said motor vehicle (3) to said device (24).

7. An arrangement according to any of the preceding claims, characterized in that said quantity measuring member (17) is configured to measure the current in a line (18) for feeding electric energy to the starter motor (1), such as by a shunt measuring of a voltage in said line or by a Hall-element arranged in said line.

8. An arrangement according to any of claims 1-6, characterized in that said quantity measuring member (35) is configured to measure the voltage at a position (34) in the starter motor circuit on the feeding side of a starter motor (1) with respect to ground as a quantity indicative of the current fed into the starter motor.

9. A method for protection against abnormal currents in a starter motor circuit of a starter motor (1) connected to an internal combustion engine (2) of a motor vehicle (3), characterized in that it comprises the steps of a) sensing the presence of a start control signal sent to the starter motor, b) measuring a quantity indicative of the current fed into the starter motor, c) determining that an abnormal current is fed to the starter motor under the condition that a current above a minimum level has been revealed by said measuring and a lack of a said start control signal has simultaneously been sensed, and d) breaking the current fed to the starter motor when said condition is fulfilled.

10. A method according to claim 9, characterized in that in step b) a quantity indicative of the current fed into the starter motor (1) is measured by measuring the current in a line (18) feeding electric energy to the starter motor, such as indirectly by a shunt measuring of a voltage or directly by a Hall-element.

11. A method according to claim 9, characterized in that in step b) a quantity indicative of the current fed into the starter motor (1) is measured by measuring the voltage with respect to ground at a position (34) in the starter motor circuit on the feeding side of the starter motor.

12. A method according to any of claim 9-11, characterized in that it is in step c) determined that a current above a minimum level has been revealed by the measurement in step b) only if such a current is measured to continuously exist over a predetermined period of time, such as at least 0.1 s.

13. A method according to any of claims 9-12 carried out in a motor vehicle (3) having a generator (7) connected in parallel with the starter motor (1), characterized in that in step d) a said abnormal current is broken in a position within a line (18) connecting to the starter motor (1) in parallel with said generator (7).

14. A computer program comprising computer program code for causing a computer to implement a method according to any of claims 9-13 when the computer program is executed by a computer.

15. A computer program product comprising a non-transitory data storage medium which can be read by a computer and on which the program code of a computer program according to claim 14 is stored.

16. An electronic control unit comprising an execution means (40), a memory (41) connected to the execution means and a non-transitory data storage medium (43) which is connected to the execution means (40) and on which the computer program code of a computer program according to claim 14 is stored.

17. A motor vehicle, especially a wheeled vehicle, such as a truck or a bus, characterized in that it comprises an electronic control unit (44) according to claim 16.