1. Patent Search
  2. Details

METHOD FOR DETERMINING A STATE OF CHARGE OF A VEHICLE BATTERY OF A VEHICLE

20210141022 · 2021-05-13

    Inventors

    Cpc classification

    International classification

    Abstract

    The present invention relates to a method for determining the state of charge of a vehicle battery (150) of a vehicle, a starter relay of a starting device (100) for an internal combustion engine of the vehicle for engaging a starter pinion in a ring gear of the internal combustion engine having a first winding (121) and a second winding (122) which can be controlled independently of one another, the first winding (121) being controlled in predetermined control states and voltage values that are established in the course of these control states being determined and the state of charge of the vehicle battery (150) being determined depending on the determined voltage values.

    Claims

    1. Method for determining a state of charge of a vehicle battery (150) of a vehicle, wherein a starter relay (120) of a starting device (100) for an internal combustion engine (101) of the vehicle for engaging a starter pinion (102) in a ring gear (103) of the internal combustion engine (101) has a first winding (121) and a second winding (122) which can be controlled independently of one another, controlling the first winding (121) in predetermined control states (304, 305, 308) and determining voltage values that are established in the course of these control states (304, 307, 310) and determining the state of charge of the vehicle battery (150) depending on the determined voltage values.

    2. Method according to claim 1, comprising not energizing (304) the first winding (121) in the course of a first control state and energizing the first winding (121) in the course of a second and third control state in different ways (305, 308) in each case.

    3. Method according to claim 2, comprising not energizing the first winding (121) in the course of the first control state and determining (304) a first voltage value (U.sub.30.0), energizing the first winding (121) with a first current level in the course of the second control state (305) and determining (307) a second voltage value (U.sub.30.A), energizing the first winding (121) with a second current level (308) in the course of the third control state and determining (310) a third voltage value (U.sub.30.B) and a fourth voltage value and determining (312) the state of charge of the vehicle battery (150) depending on the first voltage value (U.sub.30.0), the second voltage value (U.sub.30.A), the third voltage value (U.sub.30.B) and the fourth voltage value.

    4. Method according to claim 3, comprising determining a resistance value depending on the second voltage value (U.sub.30.A), the third voltage value (U.sub.30.B) and the fourth voltage value and determining (312) the state of charge of the vehicle battery (150) depending on the first voltage value (U.sub.30.0) and on the resistance value.

    5. Method according to claim 2, comprising generating different current levels by different pulse duty factors of the battery voltage on the winding.

    6. Method according to claim 5, comprising energizing (305) the first winding (121) with high frequency in a clocked manner during the course of the second control state and in an unclocked manner during the course of the third control state (308).

    7. Method according to claim 2, comprising energizing the first winding (121) in the course of the second control state and the third control state such that in the course of the second control state, a current through the first winding (121) is set, the current strength of which is lower than in the course of the third control state (305, 308).

    8. Method according to claim 1, comprising further determining the state of charge of the vehicle battery (150) depending on a predetermined calibration value (312) which characterizes a lead resistance (152).

    9. Method according to claim 2, comprising further determining the state of charge of the vehicle battery (150) depending on a predetermined calibration value (312) which characterizes a lead resistance (152).

    10. Method according to claim 1, comprising first carrying out (302) an admissibility check and if the admissibility check is positive, controlling the first winding (121) in the predetermined control states (304, 305, 308) and determining the state of charge of the vehicle battery (150) depending on the determined voltage values (312).

    11. Method according to claim 2, comprising first carrying out (302) an admissibility check and if the admissibility check is positive, controlling the first winding (121) in the predetermined control states (304, 305, 308) and determining the state of charge of the vehicle battery (150) depending on the determined voltage values (312).

    12. Method according to claim 1, wherein the first winding (121) is a pull-in winding and the second winding (122) is a hold-in winding.

    13. Method according to claim 2, wherein the first winding (121) is a pull-in winding and the second winding (122) is a hold-in winding.

    14. Method according to claim 1, comprising controlling the first winding (121) by means of first switching element (131), and controlling the second winding (122) by means of a second switching element (132).

    15. Method according to claim 2, comprising controlling the first winding (121) by means of first switching element (131), and controlling the second winding (122) by means of a second switching element (132).

    16. Method according to claim 14, wherein the first switching element (131) and the second switching element (132) are each implemented as an output stage, in particular each as a semiconductor switch, in particular each as a MOSFET.

    17. Computing unit (133) which is configured to carry out all the method steps of a method according to claim 1.

    18. Computer program which causes a computing unit (133) to carry out all the method steps of a method according to any of claims 1 when the program is executed on the computing unit (133).

    19. Machine-readable storage medium having a computer program according to claim 18 stored thereon.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0034] FIG. 1 schematically shows a starting device for an internal combustion engine of a vehicle, which engine is designed to carry out a preferred embodiment of the method according to the invention.

    [0035] FIG. 2 schematically shows, in the manner of a circuit diagram, part of a starting device for an internal combustion engine of a vehicle, which engine is designed to carry out a preferred embodiment of the method according to the invention.

    [0036] FIG. 3 schematically shows a preferred embodiment of the method according to the invention as a block diagram.

    [0037] FIG. 4 schematically shows a voltage-time diagram that can be recorded in the course of a preferred embodiment of the method according to the invention.

    EMBODIMENT(S) OF THE INVENTION

    [0038] In the drawings, the same reference signs denote the same or structurally identical elements.

    [0039] In FIG. 1, a starting device 100 for an internal combustion engine 101 of a vehicle is shown schematically.

    [0040] The starting device 100 has a starter pinion 102 which, in order to start the internal combustion engine 101, is brought into engagement with a ring gear 103 of the internal combustion engine. The starter pinion 102 is mounted axially displaceably on a shaft 104, as indicated by the double arrow, the starter pinion 102 being coupled to the shaft 104 for conjoint rotation. The starter pinion 102 is adjusted between a retracted inoperative position and a protruding engagement position with the ring gear 103 of the internal combustion engine 101 via a starter relay 120, which is electromagnetic and comprises two windings 121, 122 and a lifting armature 105 which, when current is supplied to the windings 121, 122, is drawn axially into these windings. The lifting armature 105 actuates an engagement lever 106, which acts on an engagement spring 107 seated on a driver 108 of a roller freewheel. The starter pinion 102 is coupled to the driver 108 on the output side, so that the axial advance movement of the driver 108 is converted into the desired axial adjusting movement of the starter pinion 102 between the inoperative position and the engagement position.

    [0041] The rotating drive movement on the shaft 104 or the starter pinion 102 is generated by means of an electric starter motor 110 which is coupled to the shaft 104 via a gear 109, for example a planetary gear. When the electric starter motor 110 is actuated, the shaft 104 and thus also the starter pinion 102 are set in rotation.

    [0042] The starter motor 110 is switched on via a switch-on device 123 which is integrated in the starter relay 120. The circuit is closed in the switch-on device 123 by means of a switching element, which is designed as a switching armature and is adjusted when the windings 121, 122 are energized. When the circuit is closed, the starter motor 110 is set in motion and the shaft 104 and the starter pinion 102 are driven rotatingly. An electronic pilot control relay 130 or an ignition switch (not shown) can be provided for controlling the starter relay 120 and the starter motor 110.

    [0043] FIG. 2 shows part of the starting device 100 in the manner of a circuit diagram. As shown in FIG. 2, the pilot control relay 130 comprises a first switching element 131 for controlling the first winding 121 and a second switching element 132 for controlling the second winding 122.

    [0044] The switching elements 131, 132 are each designed as a semiconductor output stage, for example each as a MOSFET. The pilot control relay 130 further comprises a computing unit 133 which is designed, for example, as a microcontroller and is in data-transmitting connection with a control device 140 of the vehicle via a communication system 135, for example CAN.

    [0045] The first switching element 131 can be connected to the first winding 121 via a connection 161, for example via a terminal 50k. The second switching element 132 can be connected to the second winding 122 via a connection 162, for example a terminal 50i.

    [0046] The first winding 121 is designed in particular as a pull-in winding and is connected to the starter motor 110. The second winding 122 is designed in particular as a hold-in winding and is also connected to ground via a connection 164, e.g. a terminal 31.

    [0047] The switch-on device 123 is connected to a vehicle battery 150 via a connection 163, for example a terminal 30. The reference sign 151 denotes an internal resistance of the battery 150, and the reference sign 152 denotes a lead resistance of leads between the vehicle battery 150 and the starting device 100.

    [0048] Using the starting device 100, a state of charge of the vehicle battery 150 can be determined within the scope of the present method. For this purpose, the microcontroller 133 is configured, in particular in terms of programming, to carry out a preferred embodiment of a method according to the invention, which is shown schematically in FIG. 3 as a block diagram and will be explained below.

    [0049] In a step 301, the microcontroller 133 receives a request for determining the state of charge from the control device 140 via the communication system 135.

    [0050] In step 302, the microcontroller 133 carries out an admissibility check as to whether the determination of the state of charge is permissible in the current status of the vehicle. If the request is assessed as impermissible, for example during a starting process or when the starter motor 110 is coasting down, there is a wait in step 303 for the duration of a predetermined time interval and then another check is carried out to determine whether the request is now permissible. If the admissibility check is positive, the state of charge of vehicle battery 150 is determined. For this purpose, the first winding 121 is controlled in step 304 by means of the first switching element 131 in a first control state and in particular is not energized. In this case, the open-circuit voltage or the on-board electrical system voltage between the terminal 30 (connection 163) and the terminal 31 (e.g. on the housing or the connection 164) is determined as a first voltage value U.sub.30.0.

    [0051] In step 305, the first winding 121 is then energized with high frequency in a clocked manner by means of the first switching element 131 in a second control state, with a first pulse duty factor of 50:50, for example, so that a current through the first winding 121 of approximately 100 A is set.

    [0052] In step 306, there is a wait until the current has built up through the first winding 121.

    [0053] Then, in step 307, the on-board electrical system voltage between the terminal 30 (connection 163) and the terminal 31 (connection 164) is again determined as a second voltage value U.sub.30.A.

    [0054] With a total internal resistance of a 24 V on-board electrical system, for example in the range between 5 mΩ and 8 mΩ in the case of a fully charged, warm vehicle battery, a load with a current through the first winding of 100 A leads, for example, to a voltage drop between 0.5 V and 0.8 V, which can expediently be detected with sufficient resolution, e.g. by means of an analog-to-digital converter of the pilot control relay.

    [0055] The first winding 121 is then energized in step 308 in an unclocked manner by means of the first switching element 131 in a third control state, with a second pulse duty factor of 100%, for example. In particular, this produces a current through the first winding 121 of approximately 200 A.

    [0056] In step 309, there is again a wait until the current has built up through the winding 121.

    [0057] In step 310, a third voltage value U.sub.30.B and a fourth voltage value U.sub.EW are then determined. The on-board electrical system voltage between the terminal 30 (connection 163) and the terminal 31 (connection 164) is again determined as the third voltage value U.sub.30.B. The voltage currently applied to the first winding 121 is determined as the fourth voltage value U.sub.EW, for example between the terminals 31 (connection 164) and 50k (connection 161).

    [0058] In step 311 the energization of the first winding 121 is ended and in step 312 the determined voltage values are evaluated. As part of this, an internal resistance of the on-board electrical system is determined as the resistance value R.sub.ges depending on the second voltage value U.sub.30.A, the third voltage value U.sub.30.B and the fourth voltage value U.sub.EW.

    [0059] In particular, the following correlations apply to the determination of the resistance value R.sub.ges:


    ΔU=U.sub.30.A−U.sub.30.B=R.sub.ges.Math.I.sub.EW

    [0060] The following correlation applies to the current l.sub.EW through the first winding:

    [00001] I EW = U EW R EW

    This results in:

    [00002] R ges = U EW R EW .Math. ( U 30. ⁢ A - U 30. ⁢ B )

    [0061] R.sub.EW is the internal resistance of the first winding 121, which in a first approximation can be viewed as constant and is for example 100 mΩ. In particular, this internal resistance R.sub.EW is known from the design and material characteristics.

    [0062] Furthermore, the resistance value R.sub.ges is corrected by a calibration value which corresponds to the lead resistance 152 of the leads between the vehicle battery 150 and the starting device 100. This calibration value can be determined, for example, in the course of starting up the vehicle and stored in a non-volatile memory of the microcontroller 133. In particular, the resistance value R.sub.ges corrected by the calibration value corresponds to the internal resistance 151 of the vehicle battery 150.

    [0063] In step 313, the corrected resistance value R.sub.ges and the first voltage value U.sub.30.0 are now fed back from the microcontroller 133 via the communication system 135 to the control device 140 as the current state of charge of the vehicle battery 150. In step 314, the microcontroller 133 ends the function of determining the state of charge.

    [0064] FIG. 4 schematically shows a voltage-time diagram that can be recorded in the course of a preferred embodiment of the method according to the invention. By way of example, FIG. 4 shows a time profile of the on-board electrical system voltage U between the terminals 30 (connection 163) and 31 (connection 164) plotted against time t.

    [0065] At a point in time t.sub.1, the first winding 121 is not energized according to the first control state and the first voltage value U.sub.30.0 is determined according to step 304.

    [0066] From the point in time t.sub.2 the winding 121 is controlled according to step 305 in the course of the second control state, whereupon the on-board electrical system voltage drops from the first voltage value U.sub.30.0 to the second voltage value U.sub.30.A. The second voltage value U.sub.30.A is determined at the point in time t.sub.3 according to step 307.

    [0067] At the point in time t.sub.4, the winding 121 begins to be energized in the course of the third control state according to step 308, whereupon the on-board electrical system voltage drops from the second to the third voltage value U.sub.30.B. The third voltage value U.sub.30.B is determined at the point in time t.sub.5 according to step 310. The energization of the winding 121 is ended at the point in time t.sub.6.