Hybrid powertrain system, hybrid transmission and operating method thereof

Abstract

The hybrid powertrain system has a hybrid transmission, an internal combustion engine, an electric generator, and a driveline with at least one drivable driving wheel. The hybrid transmission is arranged to receive the driving power of the internal combustion engine, i.e., the internal combustion engine driving power, and the driving power of the electric generator, i.e., the electric driving power, and to output at least one or both driving powers to the driveline. The hybrid transmission also has at least three gears, which are composed of at least two different types of gears. The hybrid transmission has a shiftable transmission, i.e., a shift gearbox, which is arranged to provide at least one gear composed of the first type of gear among the three gears, i.e., a fixed gear ratio gear. Each such gear composed of the first type of gear has a gear ratio determined by the structural type of the shift gearbox for the internal combustion engine and the electric generator relative to the driveline joint. The hybrid transmission also has a speed superposition transmission, which is arranged to provide at least one gear composed of the second type of gear among the three gears, i.e., a power split gear. Such a power split gear is a gear with a variable speed gear ratio and a fixed torque gear ratio with respect to the internal combustion engine joint and the driveline joint, and the variable speed gear ratio is formed by the speed superposition of the speed provided by the internal combustion engine and the speed provided by the electric generator in the hybrid transmission. The hybrid transmission has at least one operating mode in which shifting is only carried out between different types of gears.

Description

Field of the Invention

[0001] The present invention generally relates to a hybrid drive device having a transmission, which is arranged for speed superposition between two drives provided for driving in one operating mode, and the present invention relates to an improvement of such a drive device. A hybrid drive system having a speed superposition transmission is known from EP 0 769 404 A1.

[0002] The present invention will be described below by means of a powertrain system having an internal combustion engine and an electric drive for a motor vehicle, i.e., a so-called hybrid drive device, which should not be understood as limiting the present invention to such an application. Background Art

[0003] In motor vehicles driven by an internal combustion engine, especially due to the characteristic curves (speed, torque) of the drives and the power demand from the driving operation, a transmission device needs to be introduced between the drive and the wheel drive device that transmits the driving force to the road surface with respect to torque transmission. Even in the case of an electric motor drive, a transmission device can be advantageous. In a hybrid drive having an internal combustion engine drive and an electric motor drive, the transmission device generally constitutes an important coupling element for the two drives. Basically, transmissions with switchable gear ratios and transmissions with continuously variable gear ratios are known. Here, the control device of the transmission, i.e., the so-called transmission control device, should on the one hand control the transmission in a manner that meets the driving requirements (e.g., acceleration), and additionally the drive should output its driving power as efficiently as possible. Summary of the Invention

[0004] The object of the present invention is to provide a powertrain system having an internal combustion engine and an electric generator as drives, which effectively outputs the driving power to the motor vehicle drive device through a transmission device having fixed gear ratio gears and variable gear ratio gears (power split gears).

[0005] This object is solved by a hybrid powertrain system according to the present invention, a method for operating a hybrid transmission according to the present invention, and by a hybrid transmission according to the present invention.

[0006] The present invention provides a hybrid powertrain system having a hybrid transmission. Such a hybrid powertrain system has an internal combustion engine and an electric generator for providing driving power to drive a motor vehicle. The hybrid powertrain system also has a transmission system, and the driving power (speed, torque) provided by one or more drivers and transmitted to the hybrid transmission can be transmitted to at least one drivable driving wheel by means of the transmission system, wherein the driving wheel is arranged to transmit the driving power to the road surface. In the sense of the present invention, the transmission system can be understood as a device for transmitting the driving power from the hybrid transmission to the road surface.

[0007] In addition, the hybrid transmission is arranged to receive the driving power from the internal combustion engine, i.e., the so-called internal combustion engine driving power, and to receive the driving power from the electric generator, i.e., the so-called electric driving power, and to output at least one driving power or both driving powers to the transmission system.

[0008] In a preferred embodiment, the hybrid powertrain system further has an additional electric generator in addition to the electric generator. Preferably, the additional electric generator is arranged behind the hybrid transmission in the torque transmission direction from the internal combustion engine to the transmission system. In particular, efficient operation can be achieved by means of the additional electric generator.

[0009] In addition, the hybrid transmission has at least three operating modes, i.e., so-called gears, and the at least three operating modes have different transmission ratios, especially different rotational speed transmission ratios. Here, in the sense of the present invention, a gear can be understood as an operating mode of the hybrid transmission, and thus such a gear does not necessarily have a unique fixed transmission ratio, as is especially the case in a conventional manually shifted transmission having a unique fixed transmission ratio, the manually shifted transmission including dedicated gears each having a unique fixed transmission ratio determined by the structural type of the transmission. More precisely, in the sense of the present invention, such a gear can have a unique fixed transmission ratio determined by the structural type of the transmission, but the characteristic of such a gear can also lie in a continuously variable transmission ratio range. Based on this characteristic, i.e., whether the transmission ratio is fixed or continuously variable, two different types of gears (fixed transmission ratio gears, power split gears) are distinguished in the sense of the present invention, and the at least three gears of the hybrid transmission are composed of the at least two different types of gears.

[0010] In order to provide these two types of gear positions, the hybrid transmission has two sub-transmissions, one of which is a switchable transmission, namely the so-called shift transmission (Schaltgetriebe). The switchable transmission is configured to provide at least one gear position formed by the first type of gear position among the three gear positions, namely the so-called fixed transmission gear position. The gear position formed by the first type of gear position (fixed gear ratio gear position) has a unique gear ratio for this gear position, and the unique gear ratio is determined by the structural type of the shift transmission. Here, in this regard, "determined by the structural type of the transmission" can be particularly understood as that the gear ratio is determined by the tooth number ratio of one or more gears participating in power transmission in the hybrid transmission. More preferably, such a gear ratio is effective for power transmission from the internal combustion engine, that is, from the internal combustion engine joint to the driveline joint. And more preferably, in the fixed gear ratio gear position, each determined fixed gear ratio is effective for power transmission from the internal combustion engine joint to the driveline joint and from the electric generator joint to the driveline joint. In particular, from a functional perspective, in such a fixed gear ratio gear position, the gear ratio from the electric generator to the driveline joint is constant, especially predetermined by one or more gear pairs, and the same applies to the gear ratio from the internal combustion engine to the driveline joint. Therefore, in such a fixed gear ratio gear position, a change in the rotational speed of the electric generator does not cause a change in the rotational speed gear ratio between the internal combustion engine and the driveline joint. Transmissions for providing such fixed gear ratio gear positions are known in the prior art in various structural forms, especially in the form of an intermediate shaft structure, a planetary gear transmission structure, or a so-called dual clutch transmission.

[0011] In addition, the hybrid transmission has a speed superposition transmission, which is configured to provide at least one gear of the three gears constituted by the second type of gears, namely the so-called power split gear. In the sense of the present invention, such a power split gear is a gear with a variable speed transmission ratio and a fixed torque transmission ratio relative to the internal combustion engine joint and the driveline joint. Since the speed transmission ratio in the power split gear is continuously variable, the power split gear has a transmission ratio range and is not limited to a single fixed transmission ratio. Here, the (torque) transmission ratio from the internal combustion engine joint to the driveline joint in the power split gear is fixedly predetermined by the structural type of the transmission, in particular by the tooth number ratio of the gears involved in power transmission. The speed transmission ratio is achieved by superimposing the speed provided by the electric generator at the electric generator joint and the speed provided by the internal combustion engine at the internal combustion engine joint, and this transmission ratio can also be continuously changed within a certain range according to the speed provided by the driver (electric generator, internal combustion engine). Therefore, the speed superposition transmission can be understood as a summing transmission, which connects both the internal combustion engine joint and the electric generator joint to the driveline joint for torque transmission. Here, the torque superposition transmission is configured such that the change in the speed transmission ratio between the internal combustion engine joint and the driveline joint can be achieved by changing the speed at the electric generator joint. In addition, a simple configuration of such a speed superposition transmission is the so-called planetary gear drive mechanism in the form of a planetary gear transmission, which can generally also be understood as a three-axis transmission or a multi-axis transmission. Therefore, functionally, in the hybrid transmission, the variable or continuously variable speed transmission ratio (regarding the speed transmission ratio between the internal combustion engine joint and the driveline joint) can be achieved, especially in the speed superposition transmission, by superimposing the speed provided by the internal combustion engine and the speed provided by the electric generator. Here, in terms of control technology, the speed regulation of the electric generator is easier to achieve than that of the internal combustion engine, that is, the electric generator is easier to control than the internal combustion engine in terms of the output speed.

[0012] In addition, the hybrid powertrain system is configured such that the hybrid transmission has at least one operating mode in which shifting is only performed between different types of gear positions (from a fixed gear ratio position to a power split position or from a power split position to a fixed gear ratio position). Thus, in such an operating mode, shifting is always from a fixed gear ratio position to a power split position or vice versa from a power split position to a fixed gear ratio position. Preferably, the hybrid powertrain system has multiple operating modes, and preferably, shifting between the same type of gear positions can be achieved in one of the operating modes. In particular, the proposed way of shifting between different types of gear positions enables efficient and comfortable driving of the motor vehicle. More preferably, the so-called rubber band effect can be achieved, in which especially during vehicle acceleration, the rotational speed of the internal combustion engine is largely decoupled from the vehicle speed of the motor vehicle, and in particular, sufficient starting acceleration or acceleration can be further achieved.

[0013] Furthermore, a method is provided which is applicable to operating a hybrid transmission having at least three gear positions. More preferably, the method is provided for controlling the hybrid transmission in the hybrid powertrain system as described above. The hybrid transmission that can be controlled by the proposed method has an internal combustion engine connection for receiving the driving power from the internal combustion engine and an electric generator connection for receiving the driving power from the electric generator. The hybrid transmission also has a driveline connection for outputting the driving power of one of these connections (electric generator connection, internal combustion engine connection) or the driving power of both of these connections to the motor vehicle powertrain system. The method for controlling the hybrid transmission is especially provided for shifting gear positions, wherein the hybrid transmission that can be controlled by the method has at least three gear positions and at least one of these gear positions has a continuously variable speed ratio between the internal combustion engine connection and the driveline connection that can be achieved by the superposition of the rotational speeds of the internal combustion engine connection and the electric generator connection, namely the so-called power split position.

[0014] In addition, the hybrid transmission has at least one fixed gear ratio position in which there are respectively fixed gear ratios between the electric generator connection and the driveline connection and between the internal combustion engine connection and the driveline connection. Here, these gear ratios are respectively fixedly predetermined by the structural type of the hybrid transmission, especially by the tooth number ratio of one or more gear pairs that participate in the torque transmission from the internal combustion engine connection to the driveline connection or from the electric generator connection to the driveline connection.

[0015] Herein, in order to shift from the at least one fixed transmission ratio gear to the at least one power split gear or vice versa, the speed transmission ratio of the power split gear is adjusted by speed superposition such that the speed transmission ratio of the power split gear with respect to the internal combustion engine joint and the driveline joint is equal to the transmission ratio of the fixed transmission ratio gear. In particular, this matching of the speed transmission ratio during gear shifting results in a comfortable shift.

[0016] In a preferred embodiment, after the shift from the at least one fixed transmission gear to the at least one power split gear in time, the electric generator is controlled such that the electric generator does not receive or output or at least substantially does not receive or output mechanical power, and this control or requirement can also be understood as a power demand of zero. This control can be achieved especially in terms of speed or torque. Preferably, the electric generator can be electrically controlled or braked to zero speed, so that although the electric generator may consume electrical power (voltage, current), the electric generator does not receive or output mechanical power. As described above, this state can be referred to as a power demand of zero. In particular, a very slow rotation of the electric generator, especially a rotation of a few revolutions per minute, should also be understood as zero speed in the sense of the present invention and thus as a power demand of zero.

[0017] Especially in the power split gear, in the case of the above-mentioned power demand of zero, the speed transmission ratio is equal to the (torque) transmission ratio of the power split gear, where in particular the (torque) transmission ratio of the power split gear is not affected by speed superposition and is thus also referred to as the gear ratio or transmission ratio.

[0018] More preferably, in the operating point with a power demand of zero, the electric generator is controlled such that the electric generator does not receive or output any torque and thus does not receive or output any mechanical power. More preferably, the speed transmission ratio of the power split gear with respect to the internal combustion engine joint and the driveline joint is adjusted, especially by speed superposition (the speed of the internal combustion engine and the speed of the electric generator), when shifting out of one of the fixed transmission ratio gears such that the speed transmission ratio of the power split gear is equal to the torque transmission ratio of the following fixed transmission ratio gear from which the shift is made to the power split gear. In particular, this control of the electric generator and the adjustment of the mechanical power to zero (power demand of zero) or to near zero at the electric generator can be achieved in a hybrid transmission on the premise of a suitably selected transmission ratio, especially the tooth ratio or diameter ratio, because the speed superposition is limited by the speed actually achievable by the drive. In particular, a comfortable shift (gear change) is achieved through this control of the electric generator and the design of the hybrid transmission.

[0019] In a preferred embodiment of the present invention, a method for operating a hybrid transmission in one of the above design solutions is proposed. In this variant of the method, the power requirement for the electric generator is determined or predetermined in time after changing from the at least one fixed gear ratio stage to the at least one power split stage. Preferably, the power requirement can be determined with the aid of predetermined parameters, where these parameters can be selected from a list, which particularly includes the following parameters: the state of charge of the energy storage, the acceleration expectation, the driving speed, the gradient on which the vehicle is moving, etc. Preferably, the power requirement is determined with the aid of a single or multiple parameters preferably included in the list. More preferably, the speed ratio of the power split stage with respect to the internal combustion engine joint and the driveline joint is adjusted by speed superposition (the speed of the internal combustion engine and the speed of the electric generator) such that the previously determined power requirement (speed, torque) for the electric generator is met. In particular, the efficient operation of the hybrid drive unit can be achieved by this control of the electric generator.

[0020] In a preferred embodiment of the proposed method, the transmission ratio of the power split stage is adjusted according to the state of charge of the electrical energy storage, the so-called State of Charge (SOC), especially when transmitting power (driving or recuperating) using this power split stage, where the electric generator can be supplied with energy by the above-mentioned electrical energy storage, or the energy recuperated by the electric generator can be stored in the electrical energy storage. Thus, the energy storage can in particular be understood as a so-called traction storage. Furthermore, as described above, the speed ratio can be influenced by the electric generator, and in this embodiment, the electric generator is controlled such that when the threshold value for the state of charge of the energy storage is reached or fallen below, the speed ratio of the power split stage (the speed ratio with respect to the internal combustion engine joint and the driveline joint) is adjusted such that the electric generator operates in generator mode, or in other words, the energy storage is charged by means of the electric generator when the predetermined state of charge is below. In particular, the load point of the internal combustion engine can be shifted by this control of the electric generator such that it is used for both vehicle drive and charging the electrical energy storage by means of the electric generator when the SOC of the electrical energy storage is "low", and thus efficient operation can be achieved.

[0021] In a preferred embodiment of the method for operating a hybrid transmission of the above-described structural type, the transmission ratio of the power split gear is adjusted during power transmission using this power split gear as a function of the electrical energy storage device or another state of charge of the above-mentioned electrical energy storage device such that the electric generator influences the speed transmission ratio (with respect to the internal combustion engine connection and the driveline connection) of this power split gear. Here, the electric generator is controlled such that when the other threshold is reached or exceeded, the speed transmission ratio of the power split gear is adjusted such that the electric generator operates in motor mode. In other words, in this operating mode associated with the other threshold, electrical power is obtained from the electrical energy storage device and only the electric generator is used to drive the motor vehicle or, in addition to the internal combustion engine, the electric generator is also used to drive the motor vehicle. In particular, the efficient operation of the hybrid transmission can be achieved by one or both of the two mentioned thresholds.

[0022] In a preferred embodiment of the present invention, a method for operating a hybrid transmission is proposed, which determines for operating a hybrid transmission in which at least two of the at least three gears are configured as fixed-ratio gears and at least one gear is configured as a power split gear. The hybrid transmission preferably has exactly three gears, two of which are fixed-ratio gears and one of which is a power split gear. More preferably, the speed transmission ratio of the power split gear is changed by superposing the speeds of the internal combustion engine connection and the electric generator connection such that the speed transmission ratio of the power split gear with respect to the (torque) transmission ratio between the internal combustion engine connection and the driveline connection lies between the transmission ratios of the two fixed-ratio gears adjacent to this power split gear, the two fixed-ratio gears each having a different (torque) transmission ratio, or the speed transmission ratio of the power split gear correspondingly equals one of the (torque) transmission ratios. In the planned operating mode of the hybrid transmission, the proposed method changes the speed transmission ratio of the power split gear such that the speed transmission ratio of the power split gear varies between the transmission ratios of the two fixed-ratio gears adjacent to this power split gear or preferably can correspondingly equal one of the transmission ratios of the two fixed-ratio gears. In particular, through this variation of the speed transmission ratio of the power split gear, a comfortable and efficient operation of the hybrid transmission can be achieved.

[0023] Furthermore, a hybrid transmission is proposed, which operates according to the method of the above type. Preferably, the hybrid transmission has a shift transmission that can be switched in discrete stages, which is usually referred to as a shift transmission or a switchable transmission, and the hybrid transmission has a speed superposition transmission with a continuously variable transmission ratio, which is usually referred to as a CVT (continuously variable transmission). Preferably, the speed superposition transmission for providing a continuously variable transmission ratio is constructed as a planetary gear transmission mechanism having a planetary gear set, and more preferably, the speed superposition transmission has at least one such planetary gear transmission mechanism. In particular, this type of transmission is known from the prior art, but the proposed combination of the described control method and the mentioned mechanical structure of the hybrid transmission results in an efficient system.

[0024] In a preferred embodiment, the shift transmission of the hybrid transmission is constructed as a so-called intermediate shaft transmission or preferably has at least one such intermediate shaft transmission. In particular, an intermediate shaft transmission having at least two axially parallel and radially spaced-apart shafts (gear pairs with different transmission ratios are arranged on these shafts) is known from the prior art and provides a space-saving possibility to provide the necessary "switching function" for fixed transmission ratio gears.

[0025] In another preferred embodiment of the present invention, the shift transmission of the hybrid transmission is constructed as a dual-clutch transmission or preferably has such a dual-clutch transmission. In particular, with a dual-clutch transmission, multiple fixed transmission ratio gears can be achieved with a small structural space.

[0026] In another preferred embodiment, the shift transmission of the hybrid transmission is constructed as a planetary gear transmission mechanism, preferably constructed as a planetary gear transmission, and more preferably, the shift transmission has such a planetary gear transmission mechanism. In particular, a high power density can be achieved by means of a planetary gear transmission mechanism.

[0027] In a preferred embodiment of the present invention, the hybrid transmission has a shift transmission which has at least two and preferably a large number of switchable fixed gear ratios. In addition, the speed superposition transmission of the hybrid transmission is configured such that a power split gear can be achieved with respect to the transmission ratio between every two fixed gear ratios or between all fixed gear ratios by means of the speed superposition transmission. For the feasibility of the power split gear, it is considered that both the internal combustion engine and the electric generator can only operate within a specific speed range. In particular with respect to the internal combustion engine, the speed range in which the internal combustion engine can operate is greater than 200 revolutions per minute and preferably greater than 500 revolutions per minute and more preferably the range is less than 20,000 revolutions per minute and preferably less than 10,000 revolutions per minute, and with respect to the electric generator, the speed range is greater than 0 revolutions per minute and preferably less than 100,000 revolutions per minute and preferably less than 50,000 revolutions per minute and particularly preferably less than 25,000 revolutions per minute. More preferably, the rotational direction of the electric generator can be changed by means of the proposed method. In particular, through the structural design of the hybrid transmission, it can be achieved that with respect to the transmission ratio, two adjacent fixed gear ratios are separated from each other by a power split gear respectively and thus efficient and comfortable operation of the hybrid transmission can be achieved.

[0028] In a preferred embodiment, the hybrid transmission has a braking device. The braking device is preferably arranged in or on the hybrid transmission such that the output shaft of the electric generator can be braked to zero speed by means of the braking device, and the output shaft is provided for outputting and receiving the mechanical power of the electric generator. The braking device is preferably configured as a friction-locked, form-locked or friction-form-locked braking device. Preferably, the mechanical power reception or output (zero speed) of the electric generator can be prevented by means of the braking device. In particular, efficient braking and holding of the electric generator at zero speed can be achieved by means of the braking device for braking or holding the output shaft. Preferably, the braking device can be closed even if only a small power requirement is imposed on the electric generator, where the small power requirement can be understood as a power of 5 kW or less and preferably 2 kW or less and particularly preferably 1 kW or less. Preferably, no electric power loss is caused in the electric generator when the braking device is closed. The braking device is preferably configured as a "normally closed" braking device and does not require any operating force in the closed state in order to achieve efficient operation in this state, and more preferably, the braking device is configured as a so-called "normally open" clutch and does not require any operating force in the open state in order to achieve efficient operation in this state. Description of the Drawings

[0029] The present invention and its various features will be explained in more detail below with the aid of the drawings, where:

[0030] Figure 1 A method for operating a hybrid powertrain system having fixed-ratio gears and power-split gears is shown.

[0031] Figure 2 A schematic hybrid drive system is shown. Detailed Description

[0032] The proposed invention relates to a hybrid drive device having a DHT transmission (dedicated hybrid transmission), which hybrid drive device has a parallel hybrid power path (fixed-ratio gear) and a power-split power path (power-split gear), and thus differs from known so-called P2 hybrid drive devices, which have a series of fixed-ratio gears and implement the switching process between these parallel hybrid power paths by means of a power-split power path instead of a friction clutch.

[0033] Accordingly, known P2 hybrid drive devices only have power paths with fixed ratios (fixed-ratio gears), where the torque ratio and the speed ratio are irreversibly predetermined by the force transmission, in particular by the type of construction of the transmission. Here, the movement of the load point of the internal combustion engine type driver (internal combustion engine) is achieved by adjusting the torque required for the internal combustion engine, and this influence is achieved by an electric generator, i.e., by the following means: whether and to what extent the electric generator operates in a generator mode or a motor mode. The drive devices of known hybrid vehicles usually have a single power-split power path (power-split gear), in which the electric generator and the internal combustion engine are coupled to the driveline by means of a three-shaft transmission. In this power-split gear, a possible adjustment strategy is used to operate the internal combustion engine in an operating range that is optimized as much as possible, in particular with respect to fuel consumption related to the output power, and this operating range is adjusted by means of the driver's expectations (vehicle speed, vehicle acceleration, etc.) and is achieved by the superposition of the speed of the electric generator.

[0034] It can be seen that, so far, a hybrid drive device with a power-split gear is operated in a manner that should enable efficient operation of an internal combustion engine, wherein, for this purpose, the internal combustion engine speed and thus the drive noise imperceptible to vehicle occupants are decoupled from the vehicle speed. For example, vehicle acceleration is possible with a constant or decreasing internal combustion engine speed. In a conventional vehicle drive device with a switchable transmission, during vehicle acceleration, the internal combustion engine speed increases proportionally to the vehicle speed in each individual gear. For vehicle occupants, this results in a difficult-to-follow drive behavior in a drive device with a power-split gear (decoupling of internal combustion engine speed and vehicle speed), and subjectively the vehicle appears to lack power, and ultimately the hybrid drive device may also seem strained. As described above, the internal combustion engine speed changes strongly with the driver's expectation and hardly changes with the vehicle speed. This subjective impression can be called the "rubber band effect" and is undesirable.

[0035] The present invention proposes an operating strategy schematically shown and described in more detail in Figure 1 Here, this operating strategy is based on the existence of a hybrid powertrain system with fixed-ratio gears and power-split gears. The power-split gears can be used here comparably to a parallel hybrid power path with speed superposition and a variable speed transmission ratio from the internal combustion engine to the driveline (output of the hybrid transmission), but the criterion for controlling the electric generator speed can be the state of charge of the electrical energy storage device here. This means that if there is no expectation of charging / discharging the electrical energy storage device, i.e., the SOC is within a predeterminable limit, one or more power-split gears adjust the speed transmission ratio of the internal combustion engine to the value of the (torque) transmission ratio of the activated power-split gear.

[0036] Based on the present invention, the speed transmission ratio of the internal combustion engine in an activated power split gear is preferably changed only according to the charging / discharging expectation (SOC) of the electrical energy storage. This process is relatively slow when the capacity of the electrical energy storage exceeds 10 kWh (as is common in motor vehicles with a hybrid drive), so that even in the power split gear, the speed of the internal combustion engine still changes substantially in relation to the vehicle speed. The described rubber band effect is avoided by this control method. In particular, in the driving situation where the speed regulation (by charging / discharging) reaches the transmission ratio of a fixed transmission gear adjacent to the activated power split gear, the speed transmission ratio of the internal combustion engine is not further adjusted by means of the speed superposition of the electric generator. Instead of further implementing the speed superposition, a shift is made from the power split gear to exactly this fixed transmission gear whose transmission ratio has been reached, i.e., at this moment the speed transmission ratio of the power split gear is equal to the transmission ratio of the shifted-in fixed transmission gear. After engaging the fixed transmission gear, as long as it is specified by the operating strategy, the load point of the internal combustion engine is shifted by matching the load or torque (the electric motor operates accordingly in motor mode or generator mode). If the charging / discharging expectation of the electrical energy storage continues to increase such that further load point shifting can no longer be achieved by the electric generator (reaching the torque limit and / or power limit of the electric generator), then the operating method performs a new switching process and implements a switching process from this fixed transmission gear to a power split gear. By shifting up or down to another gear with a lower / higher transmission ratio accordingly, it is possible to place the internal combustion engine at the required power point.

[0037] In other words, in the switching logic known from the prior art, the operating method for the transmission determines the optimal gear of the transmission by means of the driver's expectation (in particular the accelerator pedal position), the charging / discharging expectation of the storage (in particular whether the SOC is within / outside a predeterminable threshold), and other boundary conditions (in particular temperature, environmental area, planned driving route, etc.) in order to achieve the lowest consumption while meeting the driver's expectation.

[0038] In the present invention, in the case of a parallel hybrid power path (so-called fixed transmission ratio gears, with fixed rotational speed transmission ratios and torque transmission ratios for the internal combustion engine and the electric generator respectively with respect to the transmission system joint), torque balancing is carried out as known from the prior art (the load point of the internal combustion engine is shifted towards efficient operation by the electric generator torque). In addition, in the case of activation of a power split gear, the rotational speed of the internal combustion engine to be adjusted is determined from the (torque) transmission ratio (i.e., simply referred to as the transmission ratio) of the activated power split gear, the current vehicle speed, and the current motor operation / generator operation requirements of the motors participating in the power split power path. In other words, the rotational speed offset is determined from the motor operation / generator operation requirements (corresponding mechanical power) of the electric generator and the torque currently provided by the internal combustion engine to meet the required drive power at the transmission output (so-called transmission system joint), and this rotational speed offset acts on the vehicle speed-related rotational speed. The rotational speed of the internal combustion engine to be adjusted is then limited by the adjacent gears of the hybrid transmission (the next smaller / larger transmission ratio) and the rotational speed operating limits of the internal combustion engine and the electric generator. If the next smaller / larger transmission ratio is reached, the corresponding parallel hybrid gear (fixed transmission ratio gear) is engaged starting from the power split gear, and then the control method is carried out again according to the load point shift achieved by the torque provided by the electric generator at the internal combustion engine as previously described.

[0039] In Figure 1 FIG. schematically shows a method for controlling a hybrid transmission having four power split gear positions (PSG1 to PSG4) and three fixed transmission ratio positions (PFG1 to PFG3). Here, with respect to the vehicle speed V FZG the rotational speed n of the internal combustion engine is depicted VM . In the fixed transmission ratio positions (PFG1 to PFG3), the vehicle speed V FZG is fixedly coupled to the rotational speed n of the internal combustion engine VM , i.e., when accelerating in the first fixed transmission ratio position PFG1, the rotational speed of the internal combustion engine can be clearly seen at a predetermined vehicle speed V FZG . The load point shift 4 is achieved by the torque provided by the electric generator (motor mode / generator mode), but this load point shift does not change the rotational speed transmission ratio between the internal combustion engine joint and the transmission system joint. This also applies to the load point shifts 7 and 10 in the second fixed transmission ratio position PFG2 and the third fixed transmission ratio position PFG3. The load point shifts 4, 7, 10 are shown dot-like, but can be achieved along the corresponding fixed transmission ratio positions (PFG1 to PFG3) and are not coupled to a specific speed or a specific rotational speed.

[0040] In the power split gear position, a completely different situation occurs, where the rotational speed n of the internal combustion engine VMIt can be decoupled from the vehicle speed V by superposing with the rotational speed of the electric generator. FZG If the electric generator operates in generator mode, decoupling of the rotational speed occurs in direction 2, and if the electric generator operates in motor mode, decoupling occurs in direction 3. This correspondingly applies to the remaining power split gears (second power split gear PSG2, third power split gear PSG3, fourth power split gear PSG2); decoupling of the rotational speed in directions 5, 8, 11 respectively means generator mode operation of the electric generator, and decoupling in the opposite directions, i.e., directions 6, 9, 12, means motor mode operation. Operation along the lines for the power split gears (PSG1 to PSG4) means that the power expectation for the electric generator is zero. In this operating mode, the braking device for braking the output shaft of the electric generator can be closed and a zero rotational speed can be set for this shaft.

[0041] In the directions of rotational speed decoupling shown, a method for controlling the hybrid transmission can be seen in order to move the vehicle at a constant speed (V FZG ). Starting from the fully charged electrical energy storage device and the vehicle moving constantly at vehicle speed V FZGI , the electric generator operates in motor mode. As the electrical energy storage device discharges, the decoupling of the rotational speed vertically moves from the motor mode region (below the PSG2 line) to the region for generator mode operation (above the PSG2 line), and when exceeding the PSG line, the electric generator operates in generator mode. If, for example, at the vehicle speed V FZGI , one of the fixed gear ratio positions is reached by adjusting the rotational speed transmission ratio in the power split gear, a gear shift to the reached fixed gear ratio position is implemented, i.e., a gear shift to one of the fixed gear ratio positions adjacent to the second power split gear PSG2 (PFG1 or PFG2). In the fixed gear ratio positions (PFG1 to PFG3), as already described, the drive efficiency can be increased by moving the load point achieved by means of the torque (motor mode or generator mode) provided by the electric generator at the internal combustion engine. In any case, in each individual fixed gear ratio position, an internal combustion engine rotational speed n VM is fixedly assigned to a vehicle speed.

[0042] In Figure 2A hybrid powertrain system is shown, which has an internal combustion engine 20 and a transmission system 21 for transmitting the drive power provided by the internal combustion engine 20 and by the electric machine EMA to the road surface. The hybrid powertrain system also has a further electric machine EMB, which is arranged behind the hybrid transmission 22 in the torque transmission direction from the internal combustion engine 20 to the transmission system 21. In the schematic diagram, it can be seen how the drives (20, EMA) and the transmission system 21 are coupled to each other via the internal combustion engine joint 23, the electric machine joint 24 and the transmission system joint 25.

[0043] By arranging the further electric machine EMB behind the hybrid transmission 22 having fixed gear ratio gears and a power split gear, an efficient operation of the hybrid powertrain system can be achieved, since the drive power transmitted by the further electric machine EMB and the drive power recovered by the further electric machine act with an efficiency η EMB-Ab and thus there is no efficiency loss in the hybrid transmission for this drive power. The electrical energy generated by the further electric machine can be taken up by the further electric machine with an efficiency η sp-EMB into the electrical energy storage Bat or taken out from the electrical energy storage. Furthermore, it is also possible to exchange electrical power directly between the electric machine EMA and the further electric machine EMB with an efficiency η EMA-EMB .

[0044] If the drive power is transmitted from the internal combustion engine 20 to the powertrain system 21, then this drive power is transmitted by the hybrid transmission 22 with an efficiency η VM-Ab . It is basically impossible to recover the drive power by means of an internal combustion engine constructed in the form of a reciprocating piston. The drive power can be guided from the internal combustion engine 20 via the hybrid transmission 22 with an efficiency η VM-EMA to the electric machine EMA and vice versa, the drive power can be provided for driving the electric machine with this efficiency (η VM-EMA ).

[0045] The electric machine EMA can also recover the drive power and introduce it into the electrical energy storage Bat or supply electrical power from this electrical energy storage, and this power flow acts with an efficiency η SP-EMA respectively.

[0046] As described above, different power flows with different efficiency levels are generated, which enable an efficient operation of a motor vehicle by means of the proposed hybrid transmission, the proposed method for controlling the hybrid transmission and a hybrid powertrain system having such a hybrid transmission.

[0047] List of reference numerals:

[0048]

[0049]

Claims

1. A hybrid powertrain system, the hybrid powertrain system having a hybrid transmission, an internal combustion engine, an electric generator, and a driveline with at least one drivable drive wheel, wherein, The hybrid transmission is configured to receive the drive power of the internal combustion engine, i.e., the internal combustion engine drive power, and the drive power of the electric generator, i.e., the electric drive power, and to output at least one or both of the drive powers to the transmission system. The hybrid transmission further has at least three gears, where the three gears are composed of at least two different types of gears. The hybrid transmission has a switchable transmission, i.e., a shift transmission, which is configured to provide at least one gear composed of the first type of gear among the three gears, i.e., a fixed gear ratio gear. Each such gear composed of the first type of gear has a gear ratio determined by the structure type of the shift transmission for the internal combustion engine and for the electric generator relative to the transmission system joint. The hybrid transmission further has a speed superposition transmission, which is configured to provide at least one gear composed of the second type of gear among the three gears, i.e., a power split gear. Such a power split gear is a gear with a variable speed gear ratio and a fixed torque gear ratio relative to the internal combustion engine joint and the transmission system joint. The variable speed gear ratio is formed by the speed superposition of the speed provided by the internal combustion engine and the speed provided by the electric generator in the hybrid transmission. The hybrid transmission has at least one operating mode in which shifting is only carried out between different types of gears. In the at least one operating mode, it always shifts from a fixed gear ratio gear to a power split gear or vice versa. To shift from the at least one fixed gear ratio gear to the at least one power split gear or vice versa, the speed gear ratio of the power split gear is adjusted by speed superposition such that the speed gear ratio of the power split gear with respect to the internal combustion engine joint and the transmission system joint is equal to the gear ratio of the fixed gear ratio gear.

2. A method for operating a hybrid transmission, the hybrid transmission having at least three gears, the hybrid transmission having an internal combustion engine connection for receiving drive power from the internal combustion engine and an electric generator connection for receiving drive power from the electric generator and having a driveline connection for outputting drive power from one of these connections or drive power from both of these connections to a motor vehicle powertrain system, and the transmission further having at least three gears, wherein, At least one power split gear among the gears has a speed gear ratio between the internal combustion engine joint and the transmission system joint that can be continuously changed by the speed superposition of the internal combustion engine joint and the electric generator joint. The hybrid transmission further has at least one fixed gear ratio gear in which there are fixed gear ratios between the electric generator joint and the transmission system joint and between the internal combustion engine joint and the transmission system joint respectively. The gear ratios are respectively predetermined by the structure type of the hybrid transmission. To shift from the at least one fixed gear ratio gear to the at least one power split gear or vice versa, the speed gear ratio of the power split gear is adjusted such that the speed gear ratio of the power split gear with respect to the internal combustion engine joint and the transmission system joint is equal to the gear ratio of the fixed gear ratio gear.

3. The method according to claim 2, characterized in that, After shifting from the at least one fixed gear ratio stage to the at least one power-split stage, the electric machine is controlled such that the electric machine does not receive or output any mechanical power, and the speed gear ratio of the power-split stage is adjusted by speed superposition such that the speed gear ratio of the power-split stage is equal to the torque gear ratio of the following fixed gear ratio stage from which the shift is made to the power-split stage.

4. The method for operating a hybrid transmission according to claim 2 or 3, characterized in that, After shifting from the at least one fixed gear ratio stage to the power-split stage, a power requirement for the electric machine is determined or predefined, and the speed gear ratio of the power-split stage is adjusted by speed superposition such that this power requirement for the electric machine is met.

5. The method for operating a hybrid transmission according to claim 2 or 3, characterized in that, The gear ratio of the power-split stage is adjusted in dependence on the state of charge of an electrical energy storage device when power is transmitted by means of the power-split stage, where the electrical energy storage device is an electrical energy storage device which can supply energy to the electric machine and by means of which the electric machine can influence the gear ratio of the power-split stage such that when a threshold value for the state of charge of the energy storage device is reached or undershot, the gear ratio of the power-split stage is adjusted such that the electric machine operates in generator mode.

6. The method for operating a hybrid transmission according to claim 2 or 3, characterized in that, The gear ratio of the power-split stage is adjusted in dependence on a further state of charge of an electrical energy storage device when power is transmitted by means of the power-split stage, where the electrical energy storage device is an electrical energy storage device which can supply energy to the electric machine and by means of which the electric machine can influence the gear ratio of the power-split stage such that when a threshold value for this further state of charge is reached or exceeded, the speed gear ratio of the power-split stage is adjusted such that the electric machine operates in motor mode.

7. The method for operating a hybrid transmission according to claim 2 or 3, characterized in that, Of the at least three gears of the hybrid transmission, at least two gears are configured as fixed gear ratio gears and at least one gear is configured as a power-split gear, and the speed gear ratio of the power-split gear is changed by speed superposition of the internal combustion engine connection and the electric machine connection such that the speed gear ratio of the power-split gear lies between the gear ratios of the two fixed gear ratio gears adjacent to the power-split gear with respect to the torque gear ratio between the internal combustion engine connection and the transmission system connection or correspondingly equals one of the gear ratios, such that in the planned operating mode of the hybrid transmission, the speed gear ratio of the power-split gear varies between the gear ratios of the two fixed gear ratio gears adjacent to the power-split gear.

8. A hybrid transmission, the hybrid transmission being operated according to the method according to any one of claims 2 to 7, characterized in that, The hybrid transmission has a shift transmission which can be switched in discrete steps and has a speed superposition transmission with a continuously variable gear ratio, and the speed superposition transmission is configured as a planetary gear transmission having a planetary gear set or having such a planetary gear set.

9. The hybrid transmission according to claim 8, characterized in that, The shift transmission is configured as an intermediate shaft transmission or has such an intermediate shaft transmission.

10. The hybrid transmission according to claim 8, characterized in that, The shift transmission is configured as a dual clutch transmission or has such a dual clutch transmission.

11. The hybrid transmission according to claim 8, characterized in that, The shift transmission is configured as a planetary gear transmission or has such a planetary gear transmission.

12. The hybrid transmission according to any one of claims 8 to 11, characterized in that, The shift transmission has at least three or more switchable fixed gear ratios, and the rotational speed superposition transmission is configured such that, with respect to the gear ratio, a power split gear can be correspondingly achieved between every two fixed gear ratios or between all fixed gear ratios by means of the rotational speed superposition transmission, so that, with respect to the gear ratio, two adjacent fixed gear ratios are separated from each other by a power split gear.

13. The hybrid transmission according to any one of claims 8 to 11, characterized in that, The hybrid transmission has a braking device by means of which the output shaft of the electric generator can be braked to zero rotational speed.

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