Method for changing from electric operation to hybrid operation of a vehicle hybrid drive and vehicle hybrid drive

Abstract

A method for changing from electric operation to hybrid operation of a vehicle hybrid drive arrangement is implemented with the following steps: (a) detecting an increase in the target tractive power; (b) starting the internal combustion engine; (c) when the internal combustion engine starts to output positive torque: generating an increasing generator power (GL) by means of the generator arrangement, the generator power being used together with the electrical power (BL) of the vehicle-side electrical power store to generate the electrical tractive power, the generator power (GL) being generated while the internal combustion engine is not yet coupled or not yet fully coupled to the driven device; (d) after the start of the generation of the increasing generator power, fully coupling the internal combustion engine to the driven device; and (e) after the internal combustion engine is fully coupled to the driven device: reducing the electrical power of the store for electrical tractive power to a non-positive value and adjusting the generator power (GL) in accordance with a predetermined energy split. Furthermore, a vehicle hybrid drive arrangement is described, having a control device which is set up to implement the method.

Description

Background Technology

[0001] It is known that vehicles can be equipped with both an electric drive system and an internal combustion engine as drive units, which is referred to as a hybrid drive system. Especially when driver demands increase, and the electric drive system cannot provide the required wheel torque, a transition from pure electric driving to hybrid driving is necessary. If the internal combustion engine is started to enable hybrid operation, this may take a defined time of approximately one second. Therefore, if the electric drive system reaches its maximum power before the internal combustion engine is started, a sudden jolt may occur, and further jolts may occur through the coupling of the started internal combustion engine. Summary of the Invention

[0002] The purpose of this invention is to propose a possibility for achieving better driving comfort during the transition from electric to hybrid operation.

[0003] This objective is achieved by the method according to the invention for changing from electric operation to hybrid operation of a vehicle hybrid drive system, and by the vehicle hybrid drive system according to the invention. Other properties, features, embodiments, and advantages are apparent from the description.

[0004] When transitioning from electric drive to hybrid drive, a temporary series hybrid drive is proposed, which can be achieved by manipulating a generator (when the internal combustion engine is not coupled or not yet fully coupled to the vehicle's driven units). If, after the motor starts, the internal combustion engine is in a state of beginning its autonomous operation, or in other words, the torque generated by the internal combustion engine exceeds its own loss torque, then the generator (e.g., a starter generator) is put into generator mode, in which it generates generator power. The generator power (along with power supplied by an electrical storage device, such as a battery) is provided to the traction motor. This results in higher electrical power available for the electric drive unit, thus providing higher torque before the internal combustion engine is (fully) coupled. The torque is increased by a value corresponding to the generator power. Here, the electric traction power essentially corresponds to the sum of the electrical power extracted from the storage device and the power generated by the generator (generator power). In terms of generator power, this situation corresponds to a series hybrid drive because the traction power share of the electric drive unit generated by the generator is supplied by the internal combustion engine, which is not yet fully coupled, in such a way that the internal combustion engine outputs its output mechanical power to the generator before full coupling. The internal combustion engine is then fully coupled and directly outputs mechanical energy to the driven device, thus ending the series hybrid drive. For this reason, the series hybrid drive only occurs before the internal combustion engine is fully coupled, and can also be called a temporary series hybrid drive. At full coupling, the torque generated by the internal combustion engine or the generator power can be further increased, starting from the output of positive torque through the internal combustion engine. This increase can be designed according to a predefined ramp. This allows for the desired smooth transition between electric and hybrid driving, resulting in better driving comfort.

[0005] Before full coupling and after the internal combustion engine begins to output positive torque, excess electrical energy is generated (through the generator or generally through a generator unit). Generator power or generator torque is built up, and electric traction power is increased. This excess generator power (i.e., generating generator power to convert to electric traction power) preferably ends immediately after full coupling, especially because this allows the internal combustion engine to provide the desired target power (as part of the traction power). The generator unit can then remain in generator operation, but with less torque than before; that is, specifically for powering the onboard electrical system and without being configured to generate additional traction torque.

[0006] Therefore, a method for switching from electric operation to hybrid operation of a vehicle's hybrid drive system is proposed. The method first detects an increase in target traction power. This traction power is detected via an input element. Specifically, if the target traction power is no longer significantly higher than the maximum power that can be extracted from the electrical storage, the internal combustion engine is started. The target traction power used to start the internal combustion engine can be predetermined, can depend on the current maximum extractable power of the storage, or characterize that power, and can particularly depend on the temperature or state of charge of the storage.

[0007] The increase in target traction power can be adjusted by detecting the intensity of operation of driver control elements. In particular, the intensity of operation of the accelerator pedal, throttle handle, or lever can be detected. In addition, driving signals at the interface of driver assistance systems or automatic driving systems can be detected, where the driving signals reflect the target traction power or variables derived therefrom (such as target acceleration, target torque, target drive power, or target speed).

[0008] Starting an internal combustion engine, particularly by generating starting torque. This occurs as the internal combustion engine is started, specifically with the initial injection of fuel. Starting torque can be generated in various ways. It can be generated by activating a starting device, which produces starting torque and outputs it to the internal combustion engine. This starting device can be a starter generator, a sprocket starter, or a pneumatic or spring-based (mechanical) energy storage device. Starting torque can be generated by activating a starter generator or a sprocket starter (especially when the generator is separate). Starting torque can also be generated by activating a pneumatic or spring-based energy storage device. Furthermore, starting torque (or generally, starting an internal combustion engine) can also be generated by performing a direct start (using fuel injection and ignition).

[0009] Then the internal combustion engine begins to rotate, wherein the speed steadily increases, preferably according to a predetermined direction. The internal combustion engine reaches an operating state in which it can operate autonomously. This operating state is characterized by the internal combustion engine beginning to output positive torque. In particular, this operating state is characterized by the torque generated by the internal combustion engine being greater than (at the same point in time) the loss torque of the internal combustion engine. This operating state is characterized, particularly, by the predetermined speed (limit) or minimum speed of the internal combustion engine, which may, for example, depend on the torque output by the internal combustion engine. The characteristic of the operating state in which the internal combustion engine can operate autonomously is particularly that the internal combustion engine (disconnected from other drive components such as driven devices) can operate autonomously. Furthermore, the characteristic of the operating state in which the internal combustion engine can operate autonomously can be that the internal combustion engine, connected to a generator but preferably disconnected from other drive components (such as driven devices), can operate autonomously.

[0010] If the above operating state is achieved, the generator begins to produce increasing generator power using a generator unit. In the case of a starter-generator, the generator unit can correspond to the starter unit, and both functions can be achieved by a single control device. Of course, the starting torque can also be generated by the starter unit, such as a sprocket starter, while the generator power is generated using another device, namely the generator unit, such as an alternator (Lichtmaschine). Therefore, the generator unit can perform the functions of generating starting torque and generator power, or—especially based on operation or design—it can only perform the function of generating generator power without generating starting torque.

[0011] By appropriately manipulating the generator, for example by increasing the generator's excitation, an increased generator power can be generated by means of a device. The generator power is preferably generated according to a predetermined ramp, which may depend on the operating parameters of the drive unit (internal combustion engine temperature, electrical storage temperature - see below -, storage state of charge (SOC) or state of equilibrium (SOH), etc.).

[0012] The generator power, together with the electrical power extracted from the vehicle-side electrical storage device, is used to generate electric traction power. This can be, for example, a traction battery such as a high-voltage battery, or a supercapacitor. The electrical power extracted from the electrical storage device can also be referred to as battery power or battery energy. For example, if the electrical storage device has reached its maximum output power, traction power can still be generated by increasing the generator power, thereby continuing to (increase) the traction power. Here, the generator power is generated before the internal combustion engine is coupled or fully coupled to the driven device. Before the internal combustion engine is coupled or fully coupled to the driven device, the generator power is manipulated so that it, together with the power from the electrical storage device, corresponds to the target traction power with the smallest possible deviation. This can satisfy the driver's requirements in temporary series hybrid operation, or at least determine an acceleration for the driver that exceeds the acceleration achievable using only the electrical storage device. It can be specified that the generator power is increased according to the increase in target traction power, according to a predetermined slope, etc. The traction power is preferably increased steadily, especially according to a predetermined slope.

[0013] After the generator power is increased and used together with the power from the electrical storage device to generate electric traction power, the internal combustion engine is fully coupled to the driven unit. Full coupling occurs after the generator power begins to increase. With full coupling, the temporary series hybrid operation ends, during which the generator power is specifically increased.

[0014] After the internal combustion engine is fully coupled to the driven device, the power of the storage device used for traction is reduced. Preferably, the electrical power of the storage device is reduced to a non-positive value, especially for charging the storage device. A non-positive value for the storage device power refers to the value involving the storage device's output power (=discharge power). A non-positive value for the storage device power (i.e., discharge power or output power) corresponds to a positive charging power or a zero charging power. Furthermore, after full coupling, the generator power is adjusted according to a predetermined energy distribution (Energiehaushalt, energy balance). In particular, after the internal combustion engine is fully coupled to the driven device, the generator power is no longer generated at the rate of increase of the generator power generated before full coupling.

[0015] One implementation specifies that the generated traction power (i.e., the sum of generator power and energy storage power (i.e., battery power)) exceeds the electrical power that can be output solely by means of the energy storage. In many implementations, the maximum available power of the energy storage is invoked here. Furthermore, it can be specified that the electric traction power generated by combining generator power with storage power is greater than the maximum power achievable by the design of the storage. Additionally, the electric traction power may also be greater than the maximum power predetermined by the energy management device of the storage. However, as described below, it is also possible that the power output by the storage is not relative to the maximum possible power, but rather, for example, to prevent overload or overheating, the power output by the storage is less than the maximum output power of the storage.

[0016] As an alternative implementation, the method proposed herein can be used to maintain a certain distance from the maximum output power of the energy storage device to prevent derating due to overheating or other reasons. In this case, the traction power may not exceed the maximum power of the energy storage device. Furthermore, in this case, the traction power is equal to the sum of the generator power and the battery power (power of the energy storage device) minus a predetermined power value. The predetermined power value is used to protect the energy storage device and prevent it from outputting its maximum possible power. Instead, the energy storage device will output power less than its maximum output power to reduce the load on the energy storage device. The power value set for protection (the power of the storage device is reduced by this power value) can depend on the storage device's SOC, SOH, or temperature.

[0017] Therefore, it can be stipulated that the electric traction power generated by combining the generator power and the memory power when generating generator power is set to be greater than the maximum power caused by the design of the memory minus, for example, a predetermined power margin corresponding to the power value. Alternatively, it can be stipulated that the traction power is greater than the maximum power predetermined by the energy management device of the memory minus, for example, a predetermined power margin corresponding to the power value. Thus, the components of the drive unit will not operate at their maximum operating point, but rather at a lower load, to avoid potential damage, for example, due to continuously high operating temperatures.

[0018] Another aspect is that the internal combustion engine is coupled to the driven device via a coupling device with increasing coupling degree. This specifically involves the steps of the internal combustion engine starting to output positive torque, generating increased generator power, and / or the coupling of the internal combustion engine. The coupling degree can increase steadily, so there is no jump in traction power. With coupling, the series operation mode of the drive unit (= the internal combustion engine operates the electric traction drive unit via the generator) changes to the parallel operation mode (= the internal combustion engine acts directly on the driven device). With full coupling, the parallel operation mode is fully realized. With full coupling, the series operation mode ends.

[0019] After the internal combustion engine is fully coupled to the driven device, the generator power is adjusted according to a predetermined energy distribution, wherein the generator power is preferably adjusted to a power value that substantially corresponds to the consumption of the vehicle electrical system. The vehicle electrical system is preferably an on-board electrical system connected to a memory and generator unit, or an on-board electrical system in which a memory and generator unit are installed. Furthermore, if it is operating on electricity, the starting device can also be connected to the vehicle electrical system.

[0020] Here, the generator power can be adjusted to a power value that includes the consumption of all electrical components of the vehicle's electrical system, along with the power absorbed by the power storage device during charging operation. In other words, the charging circuit is set as one of the components. It charges the power storage device. The charging circuit consumes or absorbs power in order to charge the power storage device. The power absorbed by the charging circuit can be considered as part of the consumption of all components, and in particular, the charging circuit can be considered as part of the vehicle's electrical system. In this case, when the internal combustion engine is fully coupled to the driven device (and the starting phase is over), the positive charging power of the power storage device can be set; conversely, when the internal combustion engine is not coupled or not yet fully coupled, electrical power is drawn from the power storage device to generate traction power (corresponding to positive discharging power).

[0021] After or during full coupling of the internal combustion engine to the driven device, the generator power can be adjusted according to a predetermined energy distribution, which is variable and takes into account the variable, particularly negative, charging power of the memory (i.e., the positive discharge power of the memory) during the discharge phase. The energy distribution is preferably designed to meet the energy requirements of the vehicle's electrical system, including, where necessary, the charging of the electrical memory.

[0022] After the internal combustion engine is fully coupled to the driven device, the electrical (output) power of the memory is adjusted to a value that preferably corresponds to the charging process of the memory (or the power transfer of the memory from zero). The electrical power of the memory can be reduced to zero or a negative value, for example, reduced to a negative value that corresponds to the power value associated with charging the memory.

[0023] A vehicle hybrid drive system is also described, comprising a control unit configured to implement the method according to the invention. The control unit has an interface for input elements. The control unit is connected to a starting device configured to start an internal combustion engine. The control unit is operatively connected to an actuator (generally understood) configured to set the electrical power of a power storage device. The term "actuator" should be understood as the collective of actuators that determine the output power and / or absorbed power of components. For loads such as heating or lighting components, this is the power absorbed by them. For storage devices requiring charging, this is the charging power (particularly the power absorbed by the charging device), and for storage devices supplying power to the vehicle's electrical system, this is the power output by the storage device. Therefore, the term "actuator" refers to the collective of actuators that adjust the power absorbed or output by individual components. An actuator can be a simple switch or an actuator that, for example, adjusts the power of related components to multiple levels by means of pulse width modulation or according to a variable duty cycle. Attached Figure Description

[0024] Figure 1 An exemplary time-travel diagram showing the internal combustion engine speed, generator power, and electrical power of the vehicle-side electrical storage is shown to explain the process described herein. Detailed Implementation

[0025] Figure 1 The variables shown are not plotted to scale, either on the y-axis or the time axis t. The variables shown are also not plotted to scale relative to each other. For better understanding of the process described here, only the timeline is shown.

[0026] Before time point t0, the internal combustion engine is inactive, and the corresponding engine speed n is 0, as shown in Figure 1. Figure 1In this process, at time point t0, the target traction power (input via an input element) is detected. This target traction power exceeds the power G that can be generated by the electric drive device, for example, a power exceeding the maximum power M of the power storage device. The internal combustion engine starts at time point t1, and its speed n increases. At time point t2, the internal combustion engine reaches an operating state in which it outputs positive torque, meaning it can operate autonomously.

[0027] The excess electrical energy is then generated and used directly to run the traction motor (= series hybrid mode).

[0028] After the internal combustion engine starts, (essentially simultaneously) the generator torque (or generator power) builds up and the traction motor torque (or power) increases, with the traction motor outputting this torque to the driven device. After time point t2, the generator power GL steadily increases. Together with the power BL output from the power storage device, the electric traction drive is operated by means of the generator power GL.

[0029] In this scenario, the power storage device typically discharges because its (maximum) discharge power M usually reaches its limit in this mode, allowing the traction motor to generate as much torque as possible. However, it may also reach the maximum discharge power minus the safety margin S. The maximum discharge power M and the power BL output by the storage device are represented by dashed lines.

[0030] The generator power GL is generated before the internal combustion engine is coupled or fully coupled to the driven device. The coupling process begins at or after time point t2. At time point t3, the internal combustion engine is fully coupled to the driven device. Then, the internal combustion engine directly and mechanically acts on the driven device (parallel operation).

[0031] After the transition process ends (i.e., at time t3 with full coupling), the excess generator power GL immediately ends again when the internal combustion engine can take over the driver's request, i.e., a portion of the target traction power or target traction torque.

[0032] Then, after time point t3, the electrical power BL of the memory used for electric traction is adjusted to a non-positive value. This will result in a preferred predefined transition A for the power BL. The generator power GL is adjusted from t3 onwards according to a predetermined energy distribution. Therefore, the generator or starter generator can continue to operate as a generator after full coupling, but with less torque or power than before (e.g., for powering the onboard electrical system). Figure 1The corresponding decrease V in generator power GL is shown. Then, the power storage preferably no longer discharges but can be charged, see the charging segment LA of power BL, which is negative and therefore corresponds to the power absorbed by the storage. The preceding positive power BL of the storage corresponds to the power output by the storage, particularly for traction.

Claims

1. A method for switching from electric operation to hybrid operation of a vehicle hybrid drive system, comprising the following steps: (a) Detecting an increase in target traction power, said increase in target traction power being detected via an input element; (b) Start the internal combustion engine; (c) When the internal combustion engine begins to output positive torque: An increased generator power (GL) is generated by means of a generator unit, wherein, The generator power, together with the electrical power (BL) of the vehicle-side power storage, is used to generate electric traction power, wherein the generator power (GL) is generated when the internal combustion engine is not yet coupled or not yet fully coupled to the driven device; (d) After the generator power begins to increase, the internal combustion engine is fully coupled to the driven device; and (e) After the internal combustion engine is fully coupled to the driven device: reduce the electrical power of the memory used for electric traction to a non-positive value and adjust the generator power (GL) according to the predetermined energy distribution.

2. The method according to claim 1, wherein, In step (c), the electric traction power generated by combining the generator power (GL) with the electrical power of the memory (BL) is greater than the maximum power caused by the design of the memory, or greater than the maximum power predetermined by the energy management device of the memory.

3. The method according to claim 1, wherein, In step (c), the electric traction power generated by combining the generator power (GL) with the electrical power (BL) of the memory is greater than the maximum power caused by the design of the memory minus a predetermined power margin, or greater than the maximum power predetermined by the energy management device of the memory minus a predetermined power margin.

4. The method according to claim 1, 2 or 3, wherein, In step (a), the increase in the target traction power is detected by detecting the intensity of operation of the accelerator pedal or throttle handle or lever, or by detecting driving signals on the interface of the driver assistance system or the automatic driving system.

5. The method according to any one of claims 1 to 3, wherein, In step (d), step (c), or during the transition from step (c) to step (d), the internal combustion engine is coupled to the driven device via a coupling device having an increased degree of coupling.

6. The method according to any one of claims 1 to 3, wherein, In step (e), the generator power is adjusted to a power value that substantially corresponds to the consumption of the vehicle electrical system, to which the memory and generator are connected.

7. The method according to claim 6, wherein, The consumption of the vehicle electrical system includes the consumption of all electrical components of the vehicle electrical system, together with the power absorption of the power storage device during charging operation.

8. The method according to claim 6, wherein, The generator power is adjusted according to a predetermined energy allocation, which is variable and takes into account the variable charging power of the memory during the discharge phase, wherein the energy allocation meets the energy requirements of the vehicle electrical system.

9. The method according to claim 8, wherein, The energy allocation takes into account the negative charging power of the memory during the discharge phase.

10. The method according to any one of claims 1 to 3, wherein, In step (e), the electrical power of the memory is reduced to zero.

11. The method according to any one of claims 1 to 3, wherein, In step (e), the electrical power of the memory is reduced to a negative value, which corresponds to the power value associated with charging the memory.

12. A vehicle hybrid drive system comprising a control device configured to implement the method of any one of the preceding claims, and the control device having an interface for input elements; and a starting device configured to start the internal combustion engine and connected to an actuator that adjusts power received or output by components of an on-board electrical system.

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