Method and apparatus for conditioning a motor vehicle before starting an internal combustion engine

Abstract

Method for conditioning a motor vehicle before starting an internal combustion engine by means of at least one first electrical energy source (E1) at a first voltage level (U1), wherein for vehicle conditioning at least one electrical consumer (4) is connected to the first electrical energy source (E1) by means of at least one activation signal (A1, A2) before the starting process, wherein the at least one electrical consumer (4) or a component associated therewith is transferred from a first state (Z1) to a second state (Z2) before the starting process of the internal combustion engine can be carried out, wherein at least one second electrical energy source (E2) is provided which is connected to the first electrical energy source (E1) via at least one isolating element (2), wherein the isolating element (2) is controlled by the activation signal (A1, A2) or the isolating element (2) is configured in such a way thatthat the second electrical energy source (E2) supports at least the electrical supply of the at least one electrical consumer (4) during vehicle conditioning.

Description

The invention relates to a method and a device for conditioning a motor vehicle before starting an internal combustion engine. Before an internal combustion engine can be started by a starter, various electrical components must be brought from a standby state to an operating state, depending on the vehicle's design. Examples of such components include control units or a fuel pump. This preparatory phase can be referred to as vehicle conditioning. In a conventional motor vehicle with an internal combustion engine as its sole means of propulsion and a battery as its electrical energy source, the battery serves simultaneously as the vehicle's electrical system battery and the starter battery. Consequently, the battery is subjected to a considerable load before and during the starting process. To solve this problem, various dual-battery systems have been proposed, consisting of a starter battery and a leisure battery. The aim is to ensure that the starter battery has a sufficient state of charge to be able to supply the high starting currents. From DE 10 2011 011 007 A1, a motor vehicle with an electrical system operating at a low voltage level is known. For this purpose, a low-voltage battery is provided to supply the electrical system with the low voltage level. A high-voltage battery is also provided, which can supply a higher voltage level than the low voltage level. A voltage converter, specifically a DC / DC converter, is provided to convert the higher voltage level to the low voltage level, so that the electrical system can also be supplied by the high-voltage battery. The low-voltage battery is the only battery in the motor vehicle that directly supplies the low voltage level. The low-voltage battery is connected to the electrical system by means of a switch. Furthermore, the low-voltage battery is directly connected to the starter. The switch is controlled in such a way that in the event of starting an engine, the high-voltage battery is switched off.The document states that in a combustion engine, the vehicle's electrical system is powered exclusively by the high-voltage battery via the starter. It provides no information about the power supply for electrical consumers used for vehicle conditioning. From DE 10 2011 083 255 A1, a method for operating a dual-energy electrical system of a motor vehicle is known, comprising two subnetworks connected via a DC-DC converter and a generator. A first subnetwork of the two subnetworks includes a first energy storage device, and a second subnetwork includes a second energy storage device, a starter motor for starting an internal combustion engine, and at least one load. During a period when the generator is not in operation and / or immediately before starting the internal combustion engine, the voltage of the second subnetwork is at least temporarily increased by means of the first energy storage device to a starting voltage that is higher than the nominal voltage of the second energy storage device by increasing the output voltage of the DC-DC converter. From DE 10 2010 029 788 A1, an electrical system for a motor vehicle is known, comprising a first branch and at least a second branch. The first branch includes a first energy storage device with a first connection and a second connection. Furthermore, the first branch includes a generator and at least one first load. The second branch includes a second energy storage device with a first and second connection. The second branch also includes at least one second load that can be electrically connected to the first connection of the second energy storage device and / or to the first connection of the first energy storage device.Furthermore, the second branch of the vehicle electrical system has an energy flow controller with a first and second connection, wherein the second connection of the energy flow controller is electrically coupled to the first connection of the second energy storage device and the first connection of the energy flow controller can be electrically coupled to the first connection of the first energy storage device. The invention is based on the technical problem of providing a method for vehicle conditioning of a motor vehicle and of creating a device for vehicle conditioning by means of which a first electrical energy source is less stressed with regard to the charge-discharge cycles during vehicle conditioning. The solution to the technical problem is achieved by the method with the features of claim 1 and a device with the features of claim 8. Further advantageous embodiments of the invention are set forth in the dependent claims. The method for conditioning a motor vehicle before starting an internal combustion engine is carried out using at least one first electrical energy source at a first voltage level, wherein, for vehicle conditioning, at least one electrical consumer is connected to the first electrical energy source by means of at least one activation signal before the starting process. The first electrical energy source is, for example, a lead-acid or lithium-ion battery. The activation signal for an impending starting process is supplied, for example, by a door control unit and / or a central locking control unit and / or an on-board electrical system or hybrid control unit. The at least one electrical consumer or associated component is transitioned from a first state to a second state before the start-up process can be carried out. For example, a control unit is transitioned from the off or sleep state to the awake state. Alternatively or additionally, an electrical heating element can heat a component to a specific operating temperature and / or an electric pump can increase the pressure of an operating fluid. Furthermore, at least one second electrical energy source is provided, which is connected to the first electrical energy source via at least one isolating element. The second voltage level of the second electrical energy source can be less than, equal to, or greater than the first voltage level of the first electrical energy source. The isolating element is dependent on the first and second voltage levels. For example, the isolating element can be designed as a switch (e.g., relay or power semiconductor switch), as a diode, or as a DC / DC converter. In the case of the first-mentioned isolating elements, the voltage levels must not be too far apart, and the second voltage level should be greater than or equal to the first voltage level. Therefore, means for sensing the voltage levels can be provided, which allow the isolating element to switch only when the second voltage level is higher than the first voltage level.In contrast, a DC / DC converter can be used with any ratio of the first and second voltage levels. The activation signal controls the isolating element in such a way that the second electrical energy source supports at least the electrical supply of the at least one electrical consumer during vehicle conditioning. Alternatively, the isolating element is designed such that it provides support from the second electrical energy source without active activation, whereby the isolating element is, for example, designed as a diode that is polarized in the forward direction solely due to the existing voltage levels. By supporting the first electrical energy source, its cycle stability can be reduced, or the service life of the first electrical energy source can be extended. In one embodiment, the isolating element is designed as a DC / DC converter, whereby the activation signal sets the DC / DC converter such that a voltage above the open-circuit voltage of the first power source is applied on the first power source side. This causes the second power source not only to support but to completely supply the at least one electrical load, while simultaneously charging the first power source. In other words, the first power source is not burdened by the vehicle conditioning. A further advantage is that the vehicle conditioning takes place at a higher voltage, thus speeding up the process, as the higher voltage allows electrical loads to be switched from the first to the second state more quickly. Hereinafter, no further distinction is made between the first voltage level and the open-circuit voltage.The open-circuit voltage intuitively represents the first voltage level at rest, although this first voltage level can fluctuate during charging and discharging. If the second voltage level is lower than the first, the DC / DC converter operates as a boost converter. Conversely, the DC / DC converter operates as a buck converter if the second voltage level is higher than the first. Since buck converters are significantly less expensive, the second voltage level is preferably higher than the first. In a further embodiment, at least one means for detecting or determining an ambient temperature and / or a component temperature is provided, wherein the activation of the separating element or a set voltage is dependent on the detected or determined ambient temperature and / or component temperature. This is based on the understanding that, particularly at low temperatures around 0°C and below, the problem of stress due to vehicle conditioning is exacerbated. This is due, on the one hand, to the reduced efficiency of the first energy source due to increased internal resistance, and on the other hand, to an increased power demand of the electrical consumers, for example, because the viscosity of the operating fluids increases or more heating energy is required to heat up to a predetermined operating temperature.It can be stipulated that the process is only carried out below a predetermined temperature threshold, preferably between -10°C and -10°C. Alternatively, the voltage set at the DC / DC converter can be temperature-dependent and increased, for example, at lower temperatures. Furthermore, the threshold and voltage increase can be combined, meaning the process begins once the temperature falls below the threshold, and the voltage is also increased as the temperature decreases. In another embodiment, the disconnecting element remains switched on until immediately before the starting process in order to maximize the load on the first power source. Depending on the configuration, the disconnecting element can then remain switched on or be switched off again for the starting process. The starter can be supplied by the first electrical power source and / or the second electrical power source. In a preferred embodiment, the starter is supplied by the second electrical power source, with the second voltage level being higher than the first voltage level, thereby reducing the necessary starter currents. In another embodiment, the second electrical energy source operates at a second voltage level, wherein the second voltage level is higher than the first voltage level of the first electrical energy source, and wherein the second electrical energy source is connected to at least one further electrical load via the activation signal. For example, the further electrical load is a PTC heating element for heating a component, for instance, within an operating fluid, thereby reducing its viscosity, which in turn reduces the electrical energy required for an associated electric pump connected to the first electrical energy source. In another embodiment, the at least one electrical consumer is at least one electric pump, by means of which at least one operating fluid is brought to a predetermined pressure for vehicle conditioning. For example, the electric pump is a fuel pump. Alternatively or additionally, the pump is a hydraulic fluid pump for a transmission, in particular a dual-clutch transmission. If the motor vehicle is, for example, designed as a hybrid vehicle with a dual-clutch transmission, one clutch must be engaged to connect the electric motor and the internal combustion engine for the starting process. As already explained, in a preferred embodiment the starter is started by the second electrical energy source. Regarding the design of the device, full reference is made to the preceding statements. The invention is explained in more detail below with reference to a preferred embodiment. The single figure shows a schematic block diagram of a device for conditioning a motor vehicle. Figure 1 shows a device 1 for conditioning a motor vehicle before starting an internal combustion engine (not shown) using a starter S. The device 1 has a first electrical energy source E1, which is at a first voltage level U1. Furthermore, the device 1 has a second electrical energy source E2, which is at a second voltage level U2. A separating element 2 in the form of a DC / DC converter 3 is arranged between the first electrical energy source E1 and the second electrical energy source E2. The device 1 also has at least one electrical load 4, which is connected to the first electrical energy source E1 by an activation signal A2 before the starting process. The device 1 also has at least one further electrical load 5, which is connected to the second electrical energy source E2 by an activation signal A2.The device 1 further comprises a first electrical control unit 6, a temperature sensor 7 and a second electrical control unit 8. For further explanation, let us assume that the motor vehicle is a hybrid vehicle, where the first electrical energy source E1 is an on-board battery and operates, for example, at a voltage level U1 = 12 V. The second electrical energy source E2 is a traction battery and operates, for example, at a voltage level U2 = 480 V. In this case, the DC / DC converter 3 can be designed as a simple unidirectional step-down converter. The at least one electrical load 4 is, for example, a fuel pump for the internal combustion engine and / or an electric pump for an operating fluid, such as a hydraulic pump for a dual-clutch transmission, via which the electric motor and the internal combustion engine can be connected, with the electric motor also performing the starter function. In this case, the starter 5 is also the electric motor for traction.The other electrical consumer 5 is, for example, a PTC heating element that heats the gearbox housing and / or the hydraulic fluid. The first control unit 6 is, for example, a door control unit and the second control unit 8 is, for example, a hybrid control unit or an on-board power supply control unit. If the first control unit 6 detects a signal indicating that the driver wishes to start the internal combustion engine, it generates a first activation signal A1, which is transmitted to the second control unit 8. The signal for the first control unit 6 could be, for example, the opening of a vehicle door, the unlocking of the central locking system, or a signal from an external device. For instance, the driver might transmit the request via smartphone or PC. The second control unit 8 receives the first activation signal A1 and evaluates the temperature T from the temperature sensor 7, which, for example, measures the ambient temperature. The second control unit 8 then generates a second activation signal A2, which switches on the DC / DC converter 3. The converter is configured to provide a voltage U1 + ΔU (ΔU > 0) to the first electrical power source E1.ΔU can be selected depending on the temperature T. Simultaneously or shortly after the DC / DC converter 3 is switched on, the electrical load 4 is connected to the first electrical energy source E1. Since U1 + ΔU is greater than the open-circuit voltage U1 of the first energy source E1, it is charged, and simultaneously the load 4 is energized. Due to the higher voltage, the load 4 transitions more quickly from a first state Z1 to a second state Z2, which is necessary to initiate the start-up process. If the load 4 is a pump, the second state Z2 is, for example, a predetermined pressure of the operating fluid. Once this state Z2 is reached, the second control unit 8 generates the start signal S1 or releases the start signal S2, which is generated by another component, and the start-up process is carried out.The time from activation signal A2 until state Z2 is reached is, for example, 10 to 30 seconds. The advantages are that, firstly, the primary electrical energy source E1 is not subjected to any load and therefore requires a lower cycle life. Furthermore, the primary electrical energy source E1 is always sufficiently charged when the journey begins and does not need to be recharged during the journey, which is typically less efficient. As a result, CO2 emissions can be reduced. Finally, vehicle conditioning is generally faster than when the vehicle is cooled solely by the primary electrical energy source E1.

Claims

Method for conditioning a motor vehicle before starting an internal combustion engine by means of at least one first electrical energy source (E1) at a first voltage level (U1), wherein for vehicle conditioning at least one electrical consumer (4) is connected to the first electrical energy source (E1) by means of at least one activation signal (A1, A2) before the starting process, wherein the at least one electrical consumer (4) or a component associated therewith is transferred from a first state (Z1) to a second state (Z2) before the starting process of the internal combustion engine can be carried out, wherein at least one second electrical energy source (E2) is provided which is connected to the first electrical energy source (E1) via at least one isolating element (2), wherein the isolating element (2) is controlled by the activation signal (A1, A2) or the isolating element (2) is configured in such a way thatthat the second electrical energy source (E2) supports at least the electrical supply of the at least one electrical consumer (4) during vehicle conditioning. Method according to claim 1, characterized in that the separating element (2) is designed as a DC / DC converter (3), wherein the activation signal (A1, A2) adjusts the DC / DC converter (3) such that a voltage (U1 + ΔU) above an open terminal voltage (U1) of the first energy source (E1) is set on the side of the first energy source (E1). Method according to claim 2, characterized in that at least one means for detecting or determining an ambient temperature (T) and / or a component temperature is provided, wherein the activation of the separating element (2) and / or the setting of the voltage (U1 + ΔU) on the side of the first electrical energy source (E1) is carried out depending on the detected or determined ambient temperature (T) and / or component temperature. Method according to one of the preceding claims, characterized in that the separating element (2) remains switched on at least until immediately before the start process. Method according to one of claims 2 to 4, characterized in that the second electrical energy source (E2) is at a second voltage level (U2), wherein the second voltage level (U2) is greater than the first voltage level (U1) of the first electrical energy source (E1), wherein the second electrical energy source (E2) is connected to at least one further electrical consumer (5) by the activation signal (A1, A2). Method according to one of the preceding claims, characterized in that the at least one electrical consumer (4) is at least one electric pump by means of which at least one operating fluid is brought to a predetermined pressure for vehicle conditioning. Method according to one of the preceding claims, characterized in that a starter (S) for starting the internal combustion engine is supplied by the second electrical energy source (E2). Device (1) for conditioning a motor vehicle before starting an internal combustion engine, comprising at least one first electrical energy source (E1) at a first voltage level (U1), at least one electrical consumer (4), and at least one means for generating at least one activation signal (A1, A2), wherein the device (1) is configured such that, for vehicle conditioning, the at least one electrical consumer (4) is connected to the first electrical energy source (E1) by means of the at least one activation signal (A1, A2) before the starting process, wherein the at least one electrical consumer (4) or a component associated therewith is transferred from a first state (Z1) to a second state (Z2) before the starting process of the internal combustion engine can be carried out, wherein the device (1) comprises at least one second electrical energy source (E2).which is connected to the first electrical energy source (E1) via at least one switchable isolating element (2), wherein the device (1) is configured such that the isolating element (2) is controlled by the activation signal (A1, A2) or the isolating element (2) is configured such that the second electrical energy source (E2) at least supports the electrical supply of the at least one electrical consumer (4) during vehicle conditioning. Device according to claim 8, characterized in that the separating element (2) is designed as a DC / DC converter (3), wherein the device (1) is designed such that the activation signal (A1, A2) adjusts the DC / DC converter (3) such that a voltage (U1 + ΔU) above an open terminal voltage (U1) of the first energy source (E1) is set on the side of the first energy source (E1). Device according to claim 9, characterized in that the second electrical energy source (E2) is at a second voltage level (U2), wherein the second voltage level (U2) is greater than the first voltage level (U1) of the first electrical energy source (E1), wherein the second electrical energy source (E2) is connected to at least one further electrical consumer (5) by the activation signal (A1, A2).

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