Control device for operating a road-coupled hybrid vehicle and control unit with a function module

Abstract

Control device for operating a road-coupled hybrid vehicle with - a first drive unit assigned to a first axle (VA), wherein the first drive unit comprises an electric motor (1) and an automatically switchable two-speed transmission (7) cooperating with the electric motor (1), - a second drive unit assigned to a second axle (HA), wherein the second drive unit comprises an internal combustion engine (3) and a further transmission (4) cooperating with the internal combustion engine (3), - a driver-operated selector (Max-E-Drive button) for manually switching between an electric operating mode (E-mode) and an automatic operating mode (A-mode), and - at least one electronic control unit (5, 8) for controlling the drive units at least partially dependent on the operation of the selector device (Max-E-Drive button), wherein the at least one control unit (5; 8) has a function module (GS-E) and is thus designed in such a way that ◯ a change between first gear (G1) and second gear (G2) can be initiated at least depending on the operation of the selector device (Max-E-Drive button), and / or o a gear change from second gear (G2) to first gear (G1) can be initiated if at least one of the specified conditions is met: ▪ if, during forward driving, the driver has operated the selector (Max-E-Drive button) to activate E-mode and the vehicle speed (v) is in a defined lower speed range (0 <v<120 km / h) liegt oder ▪ if, after a reverse drive in which the driver operated the selector device (Max-E-Drive) to switch on the E-mode, a forward drive is initiated again or ▪ when a “fuel tank empty” signal (T0) is present, and / or ◯ a gear change from first gear (G1) to second gear (G2) can be initiated if at least one of the specified conditions is met: ▪ when the driver activates a kick-down switch (KD) from the activated E-mode or ▪ if the driver selects a sport mode (S) from the activated E-mode or ▪ when the hybrid vehicle is switched off or restarted or ▪ when the electrical energy storage device for the operation of the electric motor (1) has reached a defined maximum permissible discharge.

Description

[0001] The invention relates to a control device for operating a road-coupled hybrid vehicle with at least one electronic control unit, with a first drive unit (e.g. with an electric motor as the drive motor) assigned to a first axle (e.g. front axle) and with a second drive unit (e.g. with an internal combustion engine as the drive motor) assigned to a second axle (e.g. rear axle).

[0002] The first and second drive units are not coupled via an internal mechanical clutch or longitudinal differential lock, but solely via the wheels through the road. Such road-coupled hybrid vehicles are also known as "axle-split" hybrid vehicles. Preferably, an electric motor is used as the primary motor and an internal combustion engine as the secondary motor.

[0003] Various methods for operating a road-coupled hybrid vehicle are described, for example, in the German patent applications DE 10 2012 211 920 A1, DE 10 2013 208 965 A1 or DE 10 2013 219 085 A1.

[0004] Such hybrid vehicles can be operated in a first operating mode (preferably E-mode for purely electric driving), in which the electric motor is operated alone as the primary motor for drive control, and in a second operating mode (preferably A-mode for automatically controlled electric and / or combustion engine driving), in which the combustion engine can also be automatically switched on and off as a secondary motor for drive control.

[0005] The German patent applications DE 10 2012 211 920 A1 and DE 10 2013 208 965 A1 deal with methods for switching on the secondary motor.

[0006] German patent application DE 10 2013 219 085 A1 focuses on drive strategies for controlling the primary and secondary motors that optimize driving performance and fuel consumption in drive-oriented driving scenarios. In contrast, in driving dynamics-oriented driving scenarios, the distribution of drive torque to the axles is emphasized, particularly when traction is required.

[0007] WO 2010 / 028 925 A1 discloses a hybrid drive system for a motor vehicle, comprising at least one internal combustion engine and at least one electric motor, each of which drives at least one wheel of the motor vehicle. The at least one internal combustion engine is coupled to the at least one corresponding wheel via a first multi-speed transmission. The at least one electric motor is coupled to the at least one corresponding wheel via a second multi-speed transmission.

[0008] Furthermore, a motor drive unit for use in a vehicle is known from US 2013 / 0 296 129 A1.

[0009] The object of the invention is to improve a hybrid vehicle of the type mentioned above with regard to an optimal compromise between achieving high electric acceleration with high drive torque and achieving the highest possible maximum vehicle speed.

[0010] This problem is solved according to the invention by the subject matter of independent claim 1. Dependent claims are advantageous embodiments of the invention.

[0011] The invention relates to a control device for operating a road-coupled hybrid vehicle with a first drive unit assigned to a first axle and with a second drive unit assigned to a second axle, with a selector device operable by the driver for manually switching between a purely electric operating mode and an automatic operating mode, and with at least one electronic control unit for controlling the drive units, at least partially also depending on the operation of the selector device, wherein the first drive unit comprises an electric motor and an automatically switchable two-speed transmission cooperating with the electric motor, and wherein the second drive unit comprises an internal combustion engine and a further transmission cooperating with the internal combustion engine.

[0012] The invention is based on a special electromechanically controlled two-speed transmission with synchronized gear changes, which is assigned to an electric motor as the drive motor. This first (electric) drive unit, consisting of an electric motor as the drive motor and the aforementioned two-speed transmission, acts on a first axle of a hybrid vehicle and is not mechanically connected internally to a second (internal combustion engine) drive unit on the second axle of the hybrid vehicle.

[0013] The control device according to the invention for controlling the gear change in the two-speed transmission takes into account different operating modes in a hybrid vehicle, in particular when switching from an automatic hybrid mode (A-mode) to a purely electric operating mode (E-mode) and vice versa.

[0014] The invention also relates to a control device for controlling the sequence of gear changes in the two-speed transmission, which is initiated by a reduction in torque of the electric motor; because the device according to the invention does not provide a clutch between the electric motor and the two-speed transmission.

[0015] Preferably, the torque reduction of the electric motor according to the invention during a gear change on the first axle is compensated by the second drive unit on the second axle by road coupling, provided that the second drive unit is not switched off or cannot be switched on quickly enough.

[0016] The invention is based on the following considerations: A combination of a combustion engine and an electric motor enables various operating modes (e.g., purely electric driving, purely combustion engine driving, or combined electric and combustion engine driving). For example, in A-mode, the combustion engine and the electric motor preferably work together during strong acceleration. Typically, the electric motor provides short-term bursts of high torque during acceleration, as the combustion engine has a slower response time.

[0017] The invention is explained by way of example using a "split-axle" hybrid vehicle concept in which the electric motor is located as the central drive on the front axle and the combustion engine as the central drive on the rear axle. The two drive technologies can be operated independently of each other and can also be functionally coupled to each other with regard to a wheel torque-related torque structure by means of at least one electronic control unit assigned to both drive technologies.

[0018] For technical background, reference is made to a presentation given by the applicant at the 22nd Aachen Colloquium in October 2013, in which some of the conceptual considerations preceding the invention for the new BMW i8 (planned series production in March 2014) were already mentioned. Furthermore, regarding the general wheel torque-related torque structure within the framework of the coupled drive control by means of an engine control unit (DME) in a road-coupled hybrid vehicle, reference is made to the applicant's earlier patent applications DE 10 2011 004 862 A1 and DE 10 2011 005 962 A1.

[0019] Details of the invention are explained in more detail in the following exemplary embodiment with reference to the drawing. It shows Fig. 1 a schematic representation of a road-coupled hybrid vehicle with the components essential for the invention, Fig. 2 a schematic representation of the actuator arrangement in the two-speed gearbox for adjusting the shift lever positions by means of an electrically adjustable shift fork and Fig. 3 A pictorial representation of the essential processes in an advantageous switching sequence control using the switching device according to the invention.

[0020] In Fig. Figure 1 is a so-called road-coupled hybrid vehicle with an electric motor 1, which acts, for example, on the front axle (VA) as the first drive motor, and an internal combustion engine 3, which acts as the second drive motor on the rear axle (HA). A second electric motor 2 can be provided in addition to the internal combustion engine 3. Furthermore, a second transmission 4, preferably in the form of an electronically controlled automatic transmission (as already known from the prior art of BMW series production vehicles), is connected to the input side of the internal combustion engine 3. The invention is analogously applicable to a different arrangement of the components 2, 3, and 4. The electric motor 1 could also be arranged on the rear axle and the internal combustion engine 3 on the front axle.

[0021] The electric motor 1 works together with a two-speed gearbox 7 without an intermediate clutch.

[0022] The hybrid vehicle also features a driver-operated selector ("Max-E-Drive" button) for manually switching between a purely electric operating mode (E-mode) and an automatic operating mode (A-mode).

[0023] Furthermore, the hybrid vehicle has an electronic transmission selector device 9, which is known in itself (for example from BMW production vehicles), via which the driver can select the usual driving positions P, R, N and D intended for the automatic transmission 4 as well as a switch position “S” for selecting a sporty automatic mode.

[0024] Finally, in Fig. Figure 1 shows a kick-down switch KD, which is also known to be located at the lower end of an accelerator pedal which is not shown in detail here.

[0025] The drive control of the hybrid vehicle is preferably carried out by a first electronic control unit 5, which, in principle, enables wheel torque-related overall drive control for all existing drive motors (known, for example, from the aforementioned patent applications DE 10 2011 004 862 and DE 10 2011 005 962). Furthermore, according to the invention, a function module GS-E ("transmission control electric drive") is also included, for example, in the control unit 5 or, preferably (as shown here), in an additional control unit 8 that is mechatronically located closer to the two-speed transmission 7. The function module GS-E is, for example, designed as a software program module. By means of the function module GS-E and the control units 5 and / or 8, the two-speed transmission 7 is preferably controlled by the system described in [reference to relevant document]. Fig. The 3 particularly advantageous process control can be controlled.

[0026] Control units 5 and 8 are preferably connected to each other via a data bus (e.g., CAN) and exchange sensor and control signals as needed. For example, control unit 8 can receive the vehicle speed v and a signal T0 from control unit 5. Signal T0 is generated when the fuel tank for the combustion engine 3 is empty.

[0027] With Fig. Section 2 functionally explains the actuator arrangement of the two-speed transmission 7: A shift fork SG can be translationally displaced by a spindle actuator SM, electrically controlled by the control unit 8, into a first shift lever position POS G1, corresponding to a first gear G1; into a middle shift lever position POS N, corresponding to a neutral position N; and into a second shift lever position POS G2, corresponding to a second gear G2. The instantaneous position of the shift fork SG can be detected via a Hall sensor S. Synchro switching elements SE, known per se, are provided between the shift lever positions. The shift lever positions are actually shift lever position ranges, which are defined by a necessary clearance of a sliding block on the shift fork SG to reduce friction loss during the transition to the rotary movement of the adjusting rings (known per se).

[0028] The control unit 8 has a function module GS-E which is designed (in particular programmed) in such a way that a change between the first gear G1 and the second gear G2 can be initiated depending on the operation of the selector device (Max-E-Drive button).

[0029] The GS-E function module is also designed (especially programmed) in such a way that a change between first gear G1 and second gear G2 can be initiated depending on further predefined conditions.

[0030] A gear change is achieved, for example, with a target gear jump (e.g., in the form of a digital upshift or downshift command within a software program, see also Fig. 3) initiated.

[0031] A gear change preferably takes place as follows by means of the control device according to the invention - also as an independent idea: A gear change from second gear G2 to first gear G1 is initiated when at least one of the specified conditions is met: 1) If, during forward travel, the driver operates the “Max-E-Drive” selector to activate E-mode and the vehicle speed v is in a defined lower speed range, e.g. 0 <v<120 km / h, liegt.

[0032] Note: The lower speed range is generally determined by the maximum possible vehicle speed v in first gear (G1) in E-mode. Activating E-mode at a higher vehicle speed v delays the gear change until the lower speed range is reached. OR 2) If, after a reverse drive during which the driver operated the selector (Max-E-Drive button) to switch on the E-mode, a forward drive is initiated again.

[0033] Note: The 2nd gear is retained while reversing. OR 3) If a signal (T0) is present that can be generated when the fuel tank is empty.

[0034] Note: This gear change is linked to an automatic activation of E-mode, exceptionally without operation of the selector (Max-E-Drive button), as otherwise the vehicle could not continue driving (availability aspect, emergency running).

[0035] A gear change from first gear G1 to second gear G2 is initiated when at least one of the specified conditions is met: - when the driver activates a kick-down switch KD from the activated E-mode OR - when the driver selects a sporty mode S from the activated E-mode OR - when the hybrid vehicle is switched off or restarted OR - when the electrical energy storage device for the operation of the electric motor 1 has reached a defined maximum permissible discharge.

[0036] The sequence control of a gear change according to is in itself an independent and inventive idea. Fig. 3, which is carried out in the following stages: - in a first stage I the torque M E the electric motor 1 is reduced to at least almost zero (since the two-speed gearbox has no clutch that can be opened to interrupt the power transmission), - in a second stage II, the power transmission between the electric motor 1 and the gearbox 7 is terminated by adjusting the shift fork SG to the middle shift lever position POS N, which corresponds to the neutral position N. - in a third stage III, while maintaining the neutral position N, the torque M is adjusted by means of appropriate regulation or control. Eof the electric motor 1 a main synchronization of the speed n of the electric motor 1 to the new gear (here G2) is carried out at a given vehicle speed v until a predetermined comparatively small speed deviation dn is reached and - In a fourth stage IV, to engage the new gear (here G2), a residual synchronization - see area i- - is carried out by overcoming the remaining speed deviation dn by means of the mechanically acting synchro switching element SE.

[0037] Preferably, in the fourth stage IV, after area i, where synchronization takes place, the free flight occurs in area ii. In area iii, the shift fork SG is moved to the mechanical stop of the shift lever position POS G2. Finally, in area iv, a friction-reducing release of the sliding block described above takes place. In area V, the torque M can be applied for further acceleration of the vehicle. Eof the electric motor 1, possibly together with the combustion engine 3, can be increased again.

[0038] In this embodiment, a gear shift from first gear G1 to second gear G2 is assumed, for example, during a train upshift at 120 km / h, i.e., at the upper limit of the defined lower speed range. In this case, the M mode is exited to achieve a higher vehicle speed with the assistance of the second drive unit.

[0039] In Fig. The following progressions are shown: - Long dashed line = target gear jump as initiation command for an upshift from first gear G1 to second gear G2 at time A; - thin solid line = vehicle speed v with a slight increase; - short dashed line = torque M E of electric motor 1, which is almost zero at time B and zero at time C; - bold solid line = position of the shift fork SG or adjustment range in %, starting from time B, when the torque M E when the gear lever position POS G1 is almost zero, the gear lever position POS G1 is changed from first gear G1 to the gear lever position N until time C; - Dashed line = speed n of electric motor 1, which here reaches approximately 9200 rpm before the gear change and is intended to reach a synchronous speed of approximately 5800 rpm after the gear change; at time D, the synchronous speed plus a predetermined speed deviation dn is reached; until time D, the two-speed transmission remains in neutral position N so that the torque M E It can be adjusted smoothly for speed control.

Claims

[1] Control device for operating a road-coupled hybrid vehicle with - a first drive unit assigned to a first axle (VA), wherein the first drive unit comprises an electric motor (1) and an automatically switchable two-speed transmission (7) cooperating with the electric motor (1), - a second drive unit assigned to a second axle (HA), wherein the second drive unit comprises an internal combustion engine (3) and a further transmission (4) cooperating with the internal combustion engine (3), - a driver-operated selector (Max-E-Drive button) for manually switching between an electric operating mode (E-mode) and an automatic operating mode (A-mode), and - at least one electronic control unit (5, 8) for controlling the drive units at least partially dependent on the operation of the selector device (Max-E-Drive button), wherein the at least one control unit (5; 8) has a function module (GS-E) and is thus designed in such a way that ◯ a change between first gear (G1) and second gear (G2) can be initiated at least depending on the operation of the selector device (Max-E-Drive button), and / or o a gear change from second gear (G2) to first gear (G1) can be initiated if at least one of the specified conditions is met: ▪ if, during forward driving, the driver has operated the selector (Max-E-Drive button) to activate E-mode and the vehicle speed (v) is in a defined lower speed range (0 <v<120 km / h) liegt oder ▪ if, after a reverse drive in which the driver operated the selector device (Max-E-Drive) to switch on the E-mode, a forward drive is initiated again or ▪ when a “fuel tank empty” signal (T0) is present, and / or ◯ a gear change from first gear (G1) to second gear (G2) can be initiated if at least one of the specified conditions is met: ▪ when the driver activates a kick-down switch (KD) from the activated E-mode or ▪ if the driver selects a sport mode (S) from the activated E-mode or ▪ when the hybrid vehicle is switched off or restarted or ▪ when the electrical energy storage device for the operation of the electric motor (1) has reached a defined maximum permissible discharge. [2] Control device according to claim 1, characterized by, that the two-speed transmission (7) has a shift fork (SG) which can be moved translationally by an actuator (SM) electrically controlled by the at least one control unit (5; 8) into a first shift lever position (POS G1) associated with a first gear (G1), into a middle shift lever position (POS N) associated with a neutral position (N) and into a second shift lever position (POS G2) associated with a second gear (G2). [3] Control device according to any of the preceding claims, characterized by , that the at least one control unit (5; 8) has the functional module (GS-E) and is thus designed in such a way that a change between the first gear (G1) and the second gear (G2) can be initiated depending on given conditions. [4] Control device according to any of the preceding claims, characterized by, that the at least one control unit (5; 8) has the function module (GS-E) and is thus designed in such a way that a gear change sequence control can be carried out in the following stages: - in a first stage (I) the torque (M E ) of the electric motor (1) can be reduced to at least almost zero, - in a second stage (II) the power transmission between the electric motor (1) and the two-speed gearbox (7) can be deactivated by adjusting the shift fork (SG) to the middle shift lever position (POS N) corresponding to the neutral position (N), - in a third stage (III) while maintaining the neutral position (N) by means of appropriate regulation or control of the torque (M) E ) of the electric motor (1) a main synchronization of the speed (n) of the electric motor (1) with the new gear (G1; G2) at a given vehicle speed (v) until a predetermined speed deviation (dn) is reached and - in a fourth stage (IV) a residual synchronization (i) is carried out to engage the new gear (G1; G2) by overcoming the remaining speed deviation (dn) by means of a mechanically acting synchro switching element (SE). [5] Control unit (8) with a function module (GS-E) for controlling the two-speed transmission (7) for use in a control device according to one of the preceding claims.

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