Emergency start device

Abstract

Vehicle with a key switch (1) and with a starter (2) for starting an internal combustion engine of the vehicle and with an electrical on-board network comprising a first electrical energy storage device (4) and a second electrical energy storage device (5), wherein the first and the second electrical energy storage devices can be electrically connected in parallel via a switch (6), characterized in that - the second electrical energy storage device is assigned a control electronics (7), - the second electrical energy storage unit can be monitored by the control electronics when the vehicle is at rest, - the switch is closed in the resting state, - when the switch is closed, the two energy storage devices are connected in parallel, - in the standby state, the switches can be switched by the control electronics to create an emergency standby state of the vehicle, - the switch is open in the emergency standby mode, - when the switch is open, the two energy storage devices are electrically separated, and - in the emergency standby state the switch can be closed by actuating a key switch (1) of the vehicle in order to establish an emergency start state of the vehicle, and - the starter can be switched on in the emergency start state.

Description

[0001] The invention relates to a vehicle with a key switch and a starter for starting an internal combustion engine of the vehicle, as well as with an electrical on-board network comprising a first electrical energy storage device and a second electrical energy storage device, wherein the first and the second electrical energy storage device can be electrically connected in parallel via a switch.

[0002] Modern vehicles, especially those with extensive additional equipment, typically feature a secondary energy storage device in addition to a conventional starter or auxiliary battery. This secondary energy storage device may have a different voltage level than the starter or auxiliary battery (see, for example, document EP 1244191 A2). In such cases, a DC-DC converter usually establishes an electrical connection between the two sub-systems. This is described, for example, in document WO 2011 / 009673 A1.

[0003] German patent application DE 43 40 350 A1 describes a method in which, in a motor vehicle, a capacitor is connected in parallel to the battery when its capacity is low enough to start the vehicle. The capacitor is charged by the remaining capacity of the battery. For an emergency start of the vehicle, the capacitor can discharge its stored charge very quickly.

[0004] Furthermore, the document DE 196 45 944 A1 describes a control unit for an on-board electrical system with at least two batteries rechargeable by a generator, which serve to supply various consumers. In this two-battery electrical system, both batteries can be charged gently, and the power supply to the on-board electrical system can be ensured by the second battery when one battery is depleted.

[0005] Likewise, the prior art, as disclosed in document DE 196 01 241 A1, reveals a parallel connection of two identical energy storage devices in a vehicle electrical system, which can be separated from each other by means of a switch.

[0006] It is an object of the invention to provide a vehicle with a key switch and a starter for starting an internal combustion engine of the vehicle, as well as with an electrical on-board network comprising a first electrical energy storage device and a second electrical energy storage device, wherein the first and the second electrical energy storage device can be switched electrically in parallel via a switch.

[0007] This problem is solved by a vehicle according to claim 1. Advantageous embodiments and further developments of the invention are set out in the dependent claims.

[0008] According to the invention, a control electronics unit is assigned to the second electrical energy storage device, wherein in a rest state of the vehicle the second electrical energy storage device can be monitored by the control electronics, the switch is closed in the rest state, whereby the two energy storage devices are connected in parallel, the switch can be opened by the control electronics in the rest state to establish an emergency rest state of the vehicle in which the switch for electrical separation of the two energy storage devices is open, and the switch can be closed in the emergency rest state by actuating a key switch of the vehicle in order to establish an emergency start state of the vehicle in which the starter of the vehicle can be actuated.

[0009] This means that when the vehicle is at rest (e.g., parked), the switch is closed and the two energy storage devices are connected in parallel. The second energy storage device is monitored by the control electronics, which can be implemented as a battery sensor and / or a control unit. Preferably, a voltage measurement is taken at regular intervals. The control electronics detect, for example, that the voltage falls below a target value by means of a measured voltage reading and switch the vehicle from rest mode to emergency rest mode, in which the switch remains open while the vehicle is stationary. In emergency rest mode, the control electronics can be powered by the second energy storage device.

[0010] To start the vehicle from emergency standby mode, a vehicle user must activate the key switch to put the vehicle into emergency start mode, in which the switch closes. In this state, the vehicle's starter can be activated to start the engine.

[0011] According to a preferred embodiment of the invention, the vehicle comprises a control unit, wherein the control unit can be supplied with electrical power from the first energy storage device, the control electronics can be supplied with electrical power from the second energy storage device, and the vehicle has a data communication device between the control unit and the control electronics.

[0012] According to a further embodiment of the invention, the control unit can be designed as a control device.

[0013] Alternatively, the control electronics and the control unit assigned to the second energy storage device can be combined into one control unit.

[0014] Furthermore, it is useful if, in the emergency start state, the control electronics can transmit an emergency start signal to the control unit, and if, after the emergency start signal has been transmitted, the starter can be switched on by the control unit after an emergency charging period since the transmission of the emergency start signal, in order to carry out an emergency start attempt of the combustion engine.

[0015] In other words, after the switch closes following the activation of the key switch in emergency start mode, a period of time is designated as emergency charging before the starter is engaged. The control unit thus acts as a signal transmitter for engine start via a signal line of the data communication system after the emergency charging period has elapsed. Optionally, the occurrence of emergency charging and / or its duration can be displayed by a vehicle display unit.

[0016] According to a further variant of the invention, during the emergency charging period, an emergency charging current of electrical energy can be charged from the second energy storage device into the first energy storage device, and the emergency charging period and the emergency charging current can be determined by the control unit, wherein the determination of the emergency charging period and the emergency charging current can be carried out by the control unit according to an optimization of the probability according to which the emergency start attempt is successful.

[0017] During emergency charging, a charge equalization between the second and first energy storage devices can occur. This results from the fact that when the switch is closed, the second energy storage device has a higher potential compared to the first, since during emergency standby mode the first energy storage device is subject to a quiescent current load due to the vehicle's electrical system, while the second energy storage device is independent except for supplying power to the control electronics. The rate of charge equalization, i.e., the resulting emergency charging current from the potential difference, is particularly dependent on the charge-acceptance capacity of the first energy storage device.

[0018] Furthermore, it is useful if the control unit for determining the emergency charging duration and the emergency charging current can detect the outside temperature of the vehicle, the energy storage voltage of the second energy storage unit when the emergency start state is established, the aging state of the second energy storage unit, the aging state of the first energy storage unit, and the emergency charging current from the second energy storage unit to the first energy storage unit.

[0019] The emergency charging time, also known as the recharging time, is determined by the time it takes for the engine to start successfully. To determine the shortest possible emergency charging time, the control unit can use various additional parameters, such as, optionally or in any combination, the ambient temperature, the state-of-health (SOH) of the two energy storage devices, the current during the charge transfer, and state-of-charge and power forecasts of the energy storage devices determined by associated battery sensors.

[0020] It is advantageous for the first and second energy storage devices to be designed as lead-acid batteries.

[0021] Alternatively, the first energy storage device can be a lead-acid battery and the second a lithium-ion battery. A storage unit consisting of supercapacitors can also be used as the second energy storage device.

[0022] The invention is based on the considerations set out below: An electrical energy storage device used in the electrical system of a modern vehicle fulfills several tasks, namely starting the engine, supplying electrical energy to components during engine shutdown (e.g. infotainment) or during parking and shutdown phases (e.g. anti-theft alarm system) and stabilizing the voltage of the electrical system.

[0023] The following cases can lead to the discharge of the energy storage below the so-called lower starting capability limit and consequently to the engine not starting, i.e., to the vehicle breaking down: - Typical quiescent currents during extended periods of inactivity (e.g., several weeks) - Parking the vehicle near the starting capability limit for a medium standby time and - Faults in E / E components (permanent on-board current devices, high leakage currents or sleep inhibitors).

[0024] Various technologies are used for energy storage, such as lead-acid batteries, lithium-ion batteries, and supercapacitors, which can also be combined to form energy storage systems consisting of several of these storage devices. These combinations can be hard-connected in parallel (i.e., without coupling), connected with a DC / DC converter, or with a disconnect switch.

[0025] Electrical disconnect switches cannot be closed if the charge level or voltage is too low, leading to an increase in quiescent current.

[0026] It is proposed to integrate a mechanical disconnect switch into the engine start button or to link the activation of the mechanical disconnect switch to the activation of the engine start button at a fixed time. A mechanical disconnect switch can be reliably activated even at low charge levels or low voltages, unlike an electrical disconnect switch.

[0027] A bistable relay can be used in particular as a disconnect switch associated with the start button or key switch.

[0028] Furthermore, the functional coupling of the mechanical disconnect switch with the engine start button ensures a minimal time interval between the disconnect switch closing and the engine starting. This prevents the energy / power reserve required for starting the engine from being prematurely discharged by prolonged on-board currents. This can occur, for example, if the disconnect switch closing is linked to the activation of a door contact and there is a significant time gap between the door contact switching and the activation of the engine start button, and / or if electrical consumers are used before the engine start button is activated.

[0029] If the activation of the mechanical disconnect switch is not linked to the activation of the engine start button, the energy storage system can be subjected to a load from vehicle electrical system currents during the time between closing the switch and pressing the engine start button. The duration of this load is determined by the vehicle user. In unfavorable energy storage conditions, this can reduce the probability of a successful start attempt.

[0030] A functional link between the disconnect switch and the engine start button reduces the likelihood of the vehicle breaking down, as even with a low battery charge, the engine can be started at a time with a high probability of success. This is particularly true for lithium-ion batteries used as a secondary energy storage device, since they maintain a relatively high power output for starting the engine even at very low charge levels.

[0031] Therefore, a parallel connection between a lead-acid battery and a lithium-ion battery is particularly proposed. In such a dual storage system, the lithium-ion battery, which can operate at a slightly higher voltage level compared to the lead-acid battery, allows energy to be transferred from the lithium-ion battery to the lead-acid battery when a switch is closed. This enables improved dynamics through acidification of the lead-acid battery plates (due to the onset of the charging reaction) when energy is immediately drawn (i.e., when the discharge reaction suddenly follows the charging reaction). This results in a short-term increase in the available power for starting an engine due to the increased acid content in the pores of the active electrodes. Furthermore, it supports the inherently good cold-start and high-current characteristics of a lead-acid battery for a successful engine start.

[0032] The following describes a preferred embodiment of the invention with reference to the accompanying drawing. Further details, preferred embodiments, and further developments of the invention will be derived from this. In detail, the drawing schematically illustrates... Fig. 1 Schematic section of a vehicle's electrical system.

[0033] Fig. Figure 1 shows a schematic section of a vehicle electrical system with an engine start button (1) as a key switch, a starter (2) for an internal combustion engine, and a control unit (3). Several consumers (8) are assigned to the electrical system. The electrical system includes a first energy storage device (4) connected in parallel to the aforementioned components. A second energy storage device (5) can be connected in parallel to the first via an electromechanical disconnect switch (relay, 6). The relay can be switched by control electronics (7) assigned to the second energy storage device, which is designed as an intelligent battery sensor. The start button, the battery sensor, the relay, the control unit, and the starter are components in the vehicle's data network.

[0034] Solid lines in Fig. Lines 1 indicate a section of the power supply network, dashed lines indicate a section of the data supply network.

[0035] In a vehicle idle state (e.g., during a shutdown or parking phase), the vehicle is switched off with the relay closed. When the vehicle is started, after it wakes up by pressing the start button, the control unit sends a signal to the starter motor to start the engine – the start signal. The power required to start the engine is drawn from the two parallel-connected energy storage devices.

[0036] The vehicle's standby mode can be switched to an emergency standby mode by the battery sensor, which disconnects the parallel-connected batteries via a relay. This protects the second battery from further discharge, and the vehicle's quiescent current then loads the first battery, potentially to a level below which the engine can be started.

[0037] When the vehicle is to be started from this emergency standby mode, pressing the start button puts it into an emergency start state. In this state, the battery sensor initially closes the relay. The battery sensor includes, for example, a comparator circuit between three inputs of the sensor in the vehicle's electrical system. If the comparator circuit detects no voltage drop in the circuit between the input associated with the button and the input associated with the ground of the second battery, with the external circuit closed, the relay closes.

[0038] An equalization charge occurs, meaning a transfer of energy from the second energy storage device, which is protected from further discharge in emergency standby mode, to the first energy storage device. Closing the switch supplies the vehicle's electrical system with energy from the second storage device, causing it to wake up. Depending on the state of the storage devices involved, pressing the start button either results in an immediate start or, after a charging period determined by the control unit, the start signal is sent to the starter with a time delay.

[0039] An immediate start is performed, for example, if, due to a severely limited charge acceptance capacity, only a negligible emergency charging current is drawn from the second energy storage device to the first. In this case, no effect on the motor's starting capability due to plate acidification of the first storage device is to be expected within a reasonable timeframe. An immediate start can also be performed if the state parameters determined by the control electronics for the second energy storage device indicate that a successful start can be expected solely based on the condition of the second storage device.

[0040] The relay opens particularly when the voltage of the parallel-connected storage devices drops below a critical value, which can be monitored by the battery sensor.

[0041] The charging time, which can be defined in terms of duration, causes the start signal to the starter to be sent with a time delay relative to the activation of the engine start button. This charging time allows for charge equalization between the energy storage devices, increasing the probability of a successful engine start. This charging time, also called emergency charging time, is on the order of seconds. An upper limit for the emergency charging time is defined by a definable minimum charge level of the second energy storage device that must be maintained.

[0042] The condition parameters detected by the battery sensor and / or the control unit relate in particular to the charging and aging states of the two energy storage devices, the emergency charging current, the outside temperature and optionally additional engine parameters.

[0043] The recharging time is optimized based on the recorded state parameters to maximize the probability of a successful engine start.

[0044] The first and second storage units are designed as lead-acid batteries. Alternatively, the first storage unit is a lead-acid battery and the second storage unit is a lithium-ion battery.

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