Method for operating a hybrid vehicle and hybrid vehicle

Abstract

A method for operating a hybrid vehicle (46) with a drive (48) comprising an internal combustion engine (50), with an energy converter (52) comprising an electric machine operable for recuperation, and with a control unit (54) operatively connected to an operating element (56), the drive (48), and the energy converter (52), comprising the steps of: the hybrid vehicle (46) coasts in a first drive state with thrustless drive and with the electric motor operated at a recuperation level; actuation of the operating element (56) is detected by the control unit (54); based on the actuation, it is determined in the control unit (54) whether a condition exists; and, if the condition exists, switching from the first drive state to a second drive state and operating the hybrid vehicle (46) in the second drive state; characterized in that determining the existence of the condition comprises:that a duration of the actuation of the control element (56) is determined, the duration is compared with a time threshold value and it is determined that the duration is below the time threshold value, wherein in the second drive state the drive is switched on and operated in overrun, wherein the time threshold value is varied depending on a speed of the hybrid vehicle (46).

Description

[0001] The invention relates to a method for operating a hybrid vehicle having the features according to the preamble of claim 1. Furthermore, the invention relates to a hybrid vehicle according to the preamble of claim 7.

[0002] For fuel-efficient operation of internal combustion engine-powered vehicles, especially hybrid vehicles, it is common practice to coast the vehicle for some stretches without overrun, possibly even with the internal combustion engine switched off. A typical condition for aborting this drive mode is the actuation of a brake pedal or the actuation of shift paddles on the steering wheel, in which case the drive system switches to overrun mode, possibly after switching on the internal combustion engine.

[0003] The termination may also be subject to further conditions: For example, from document EP 2 620 339 B1, a control system for a coasting mode of a hybrid vehicle with the internal combustion engine switched off is known. To reduce fuel consumption and increase the driving comfort of the hybrid vehicle, the hybrid vehicle can be operated in a coasting mode with the internal combustion engine switched off. An abort condition for this mode is met when a brake pedal is applied so forcefully that a hybrid vehicle deceleration exceeding a predetermined deceleration threshold is triggered. Another abort condition is when the vehicle speed falls below a speed threshold.

[0004] For example, document DE 10 2010 062 756 A1 describes a motor vehicle with an evaluation unit for detecting a driver's braking request before a brake pedal is depressed, so that, depending on the request, coasting or overrunning is activated or the system switches between the operating modes. The duration of the presence of a braking request or a readiness to brake is considered a condition: If the braking request or the readiness to brake is present for a duration longer than a specified threshold, overrunning is activated. If the duration is only shorter than the specified threshold, coasting is activated. Document DE 10 2008 058 669 A1 discloses a method for controlling a recuperation strength or a recuperation torque of an electric motor of a hybrid or electric vehicle.

[0005] The disadvantage is that the solutions described do not allow a conscious change between different drive states of the hybrid vehicle.

[0006] Documents EP 2 675 677 B1, DE 10 2010 004 846 A1, and DE 10 2007 035 424 A1 disclose methods for operating hybrid vehicles in which a driver can consciously influence the recuperation behavior of the hybrid vehicle. These methods sometimes result in driving behavior that the driver often perceives as unnatural or uncomfortable.

[0007] Against this background, it is the object of the present invention to enable a method for operating a hybrid vehicle in which the freewheeling and / or overrun behavior of the hybrid vehicle can be better influenced by a user of the hybrid vehicle.

[0008] This object is achieved according to the invention by a method for operating a hybrid vehicle having the features according to claim 1. Furthermore, this object is achieved according to the invention by a hybrid vehicle having the features according to claim 7. Advantageous developments of the invention are characterized in the dependent claims. The features listed individually in the patent claims can be combined with one another in a technologically expedient manner and can be supplemented by explanatory facts from the description and / or details from the figures, whereby further embodiments of the invention are shown.

[0009] The method according to the invention for operating a hybrid vehicle relates to a hybrid vehicle, in particular a trackless hybrid land vehicle, with a drive comprising an internal combustion engine, with an energy converter comprising an electric motor operable for recuperation, and with a control unit operatively connected to an operating element, the drive, and the energy converter. The method according to the invention comprises the steps of: that the hybrid vehicle coasts in a first drive state with no thrust and with the electric motor operating at a recuperation level, that an actuation of the control element is detected by the control unit, that on the basis of the actuation it is determined in the control unit whether a condition, in particular a predetermined and / or quantitative condition exists, and that when the condition is present, a change is made from the first drive state to a second drive state and the hybrid vehicle is operated in the second drive state. According to the invention, determining the existence of the condition comprises determining a duration, a time period, of the actuation of the control element, comparing the duration with a time threshold value and establishing that - that is, also whether - the duration is below the time threshold value. In other words, the existence of the condition - positive or negative - is determined by determining a duration of the actuation of the control element, comparing the duration with a time threshold value and establishing that the duration is below the time threshold value. The drive of the hybrid vehicle is operated in overrun in the second drive state, with the drive being switched on.Furthermore, the time threshold is varied depending on a speed of the hybrid vehicle.

[0010] The procedure according to the invention does not require any additional control elements. An existing control element can be used through a special type of actuation to achieve the desired influence on the drive state, the freewheeling and / or overrun behavior by a user of the hybrid vehicle, for example, the driver. In this way, an intuitive or self-explanatory operating option can be created in certain designs.

[0011] The electric motor can be part of another drive system of the hybrid vehicle. In other words, the electric motor can be designed to drive the hybrid vehicle. Recuperation is also referred to as energy recovery.

[0012] Determining the actuation of the control element may, in particular, also include determining the end or completion of the actuation of the control element. In other words, the entire course of the actuation of the control element up to the end of the actuation is considered.

[0013] The condition is not met if the duration exceeds the threshold. In particular, the condition may be met or not met if the duration is exactly equal to the threshold. The transition from the first to the second drive state occurs, in particular, when the control element is terminated.

[0014] The second drive state is, in particular, different from the first drive state. The level of a recuperation intensity level implies, in particular, a certain magnitude of the generator power of the electric motor or the braking torque applied by the electric motor. There can be a plurality of recuperation intensity levels, for example, a small number such as two, three, four, or five. One of the intensity levels can also be zero recuperation intensity, i.e., operation without recuperation.

[0015] The electric motor of the hybrid vehicle's energy converter can be battery-powered and / or fuel-cell-powered. The hybrid vehicle can be a plug-in hybrid vehicle. It can be, in particular, a mild hybrid vehicle, i.e., a hybrid vehicle in which the second drive supports or supplements the first drive, or—particularly preferably—a micro-hybrid vehicle, i.e., a hybrid vehicle in which the electric motor is designed solely to charge a battery (e.g., starter generator). The method according to the invention is particularly advantageous in a micro-hybrid vehicle with a 12V power supply, among other reasons because it is a cost-effective solution without additional control elements.

[0016] In the method according to the invention for operating a hybrid vehicle, in the first drive state, the hybrid vehicle can be operated in freewheel mode with the drive engaged, whereby the internal combustion engine of the drive can be idling, and / or the hybrid vehicle can be operated in the first drive state with the drive disengaged. In freewheel mode, in particular, the drive is decoupled or uncoupled from the output to the driven part of the chassis.

[0017] Furthermore, or alternatively, in embodiments of the method according to the invention, the electric motor is operated at a different recuperation intensity level in the second drive state. The other intensity level can, in particular, be a lower or (preferably) higher intensity level than the intensity level in the first drive state.

[0018] In embodiments, in a supplementary method step, the hybrid vehicle is operated in a third drive state, in particular after operation in the second drive state, in which the drive is in traction mode and a strength level of the recuperation of the electric motor is reduced, in particular to the weakest strength level, optionally a strength level without recuperation.

[0019] In an advantageous group of embodiments of the method according to the invention, determining the presence of the condition additionally comprises determining the strength of the actuation of the control element, comparing the strength with a strength threshold, and determining that the strength is above the strength threshold. The strength of the actuation can be a measure of the strength of a deceleration or a deceleration request for the hybrid vehicle. In particular, the strength of the actuation can proportionally cause an increase in the deceleration.

[0020] The strength can be determined indirectly by measuring the brake pressure in a hybrid vehicle's braking system. Alternatively, the strength can be determined directly by empirically determining the force exerted on the control element, such as the force applied, the distance traveled, or the pressure applied. Strength can also be referred to as intensity.

[0021] According to the invention, the time threshold value is varied depending on the speed of the hybrid vehicle. In a further embodiment, the intensity threshold value can also be varied depending on the speed of the hybrid vehicle. This extension is particularly important for hybrid vehicles in which coasting mode is only active up to a limit pressure of the brake pressure in a vacuum-supplied braking system, insofar as the vacuum supply must be ensured by overrunning the internal combustion engine at higher brake pressures. At lower speeds, the demand on the vacuum supply is lower for such hybrid vehicles. In order to enable the hybrid vehicle to decelerate to a standstill while the internal combustion engine is switched off and / or the drive is without thrust, the intensity threshold value and / or the time threshold value are raised.In this way, the availability of the freewheel is increased when the engine is switched off.

[0022] A hybrid vehicle is also related to the inventive concept. The hybrid vehicle according to the invention, in particular a trackless hybrid land vehicle, has a drive comprising an internal combustion engine, an energy converter comprising an electric motor operable for recuperation, and a control unit operatively connected to an operating element, the drive, and the energy converter. The control unit comprises a computing unit and a memory unit. According to the invention, a program is stored in the memory unit which, when at least partially executed in the computing unit, carries out a method for operating the hybrid vehicle with features or combinations of features according to this representation.

[0023] The control element is, in particular, a control element for a deceleration device, for example, a braking system, of the hybrid vehicle. In specific embodiments of the hybrid vehicle according to the invention, the control element is a pedal, in particular a brake pedal, a selector lever, a manual switch, for example, a rotary switch, toggle switch, or rocker switch, or a touch panel, for example, a touchscreen.

[0024] Further advantages and advantageous embodiments and developments of the invention will become apparent from the following description with reference to the figures. In detail, they show: Fig. 1 a flowchart of a preferred embodiment of the method according to the invention, Fig. 2 diagrams in two partial images A and B to explain the change from the first to the second drive state in accordance with the invention as a function of a time threshold value or a strength threshold value, and Fig. 3 a schematic representation of the topology of a hybrid vehicle according to the invention.

[0025] The Fig. 1 is a flowchart of a preferred embodiment of the method according to the invention for operating a hybrid vehicle. The hybrid vehicle has a topology as described with reference to the schematic representation of Fig. 3 described below, and has a programmed or programmable control unit capable of executing the method sequence. It is preferably a micro-hybrid vehicle.

[0026] According to the invention, the hybrid vehicle is initially operated in a first drive state (step 10). In this first drive state, the hybrid vehicle coasts with no thrust, in freewheel mode with the drive switched off and without an operating, recuperating electric motor, i.e., at a recuperation intensity level of 0. In step 12, the control unit of the hybrid vehicle detects an actuation of the control element, in this preferred embodiment the brake pedal. This detection is initially qualitative and represents a starting condition for the quantitative evaluation of the type of actuation. The control unit of the hybrid vehicle then determines, based on the actuation, whether a predetermined condition is met (step 14). Step 16 comprises individual substeps or subprocesses. The length of time the brake pedal is actuated is determined (substep 16). The determined time period is compared with a time threshold value (substep 18).It is then determined whether, i.e., whether the duration is below the time threshold (sub-step 20). The determination may include setting a variable in the control unit to a value indicating that the time threshold has been exceeded. If the control unit determines that the condition exists, the first drive state is changed to a second drive state (step 22). The hybrid vehicle is then operated in the second drive state, with the drive being engaged and then the drive being used in overrun mode.

[0027] In the Fig. 2 diagrams are compiled in two partial images A and B to explain the change from the first to the second drive state in accordance with the invention as a function of a time threshold value and a strength threshold value, respectively.

[0028] Part A groups two diagrams. As a function of time 24, the course of which is not shown quantitatively but only as an example, the control element actuation 26 is plotted qualitatively in the upper diagram of part A. If an actuation occurs, a value other than zero is shown in the diagram. The drive states are plotted qualitatively in the lower diagram of part A. The first drive state 28 is shown at a high level, the second drive state 30 at a low level along the axis. Over the course of time 24, a first change from the second drive state 30 to the first drive state 28 takes place in the left-hand area of ​​part A. During operation in the first drive state, a control element actuation 26 occurs for a short duration 32. According to the invention, the short duration 32 is evaluated and is shorter than the time threshold value. The first drive state 28 is then transferred to the second drive state 30.As time 24 continues, a second transition from the second drive state 30 to the first drive state 28 occurs in the right-hand area of ​​partial image A. During operation in the first drive state, a control element actuation 26 occurs for a long duration 34. According to the invention, the long duration 32 is evaluated and is longer than the time threshold. The hybrid vehicle remains in the first drive state 28. No transition to the second drive state 30 occurs.

[0029] Part B also groups two diagrams. As a function of time 24, the course of which is not shown quantitatively but only as an example, the upper diagram of part B plots the strength 36 of the actuation of the control element quantitatively in appropriate units. A strength threshold 38 is shown in the diagram. As explained above, the strength threshold 38 depends on the speed of the hybrid vehicle. The lower diagram of part B plots the drive state qualitatively. The first drive state 28 is shown at a high level, the second drive state 30 at a low level along the axis. Over the course of time 24, a change takes place from the second drive state 30 to the first drive state 28. During operation in the first drive state 28, over the course of time 24, a first, weak actuation 40 of the control element occurs, which does not exceed the strength threshold 38.According to the invention, the hybrid vehicle remains in the first drive state 28. Over the further course of time 24, a sufficiently strong actuation 42 of the control element takes place. The force 36 reaches the force threshold 38 at a time 44. Consequently, according to the invention, the system switches from the first drive state 28 to the second drive state 30, and the hybrid vehicle continues to operate in the second drive state 30. In this way, corrective braking is enabled according to the invention without leaving the first drive state 28.

[0030] In the Fig. Figure 3 schematically shows the topology of a hybrid vehicle 46 according to the invention, preferably a micro-hybrid vehicle. The hybrid vehicle 46 has a drive 48, which includes an internal combustion engine 50, and an energy converter 52 with an electric motor. In the case of micro-hybrid vehicles, the energy converter 52 with an electric motor is a starter generator. The electric machine can be operated for recuperation, for energy recovery in electrical form. Furthermore, the hybrid vehicle has a control unit 54, which is in operative connection, signal connection, with an operating element 56, here preferably the brake pedal of the hybrid vehicle, and the drive 48. In the Fig. 3, in particular of the micro-hybrid vehicle, the energy converter 52 is part of the drive 48, so that the control unit 54 operatively connected to the drive is also operatively connected to the energy converter 52. The control unit 54 comprises a computing unit 58 and a memory unit 60. According to the invention, a program is stored in the memory unit 60. The program can be part of the engine control program. Upon execution of at least parts of the program in the computing unit 58, a method as described with reference to Fig. 1 as shown above. List of reference symbols 10 Operation in the first drive state 12 Operating a control element 14 Determination of a condition 16 Determination of a duration 18 Comparison with a time threshold 20 Determination of the condition 22 Change and operation in second drive state 24 time 26 Operating elements 28 first drive state 30 second drive state 32 short duration 34 long duration 36 strength 38 Strength threshold 40 weak activity 42 sufficiently strong operation 44 Time of reaching the strength threshold 46 hybrid vehicles 48 Drive 50 internal combustion engine 52 energy converters 54 Control unit 56 Control element 58 computing unit 60 storage units

Claims

[1] A method for operating a hybrid vehicle (46) with a drive (48) comprising an internal combustion engine (50), with an energy converter (52) comprising an electric machine operable for recuperation, and with a control unit (54) operatively connected to an operating element (56), the drive (48), and the energy converter (52), comprising the steps of: the hybrid vehicle (46) coasts in a first drive state with thrustless drive and with the electric motor operated at a recuperation level; actuation of the operating element (56) is detected by the control unit (54); on the basis of the actuation, it is determined in the control unit (54) whether a condition exists; and, if the condition exists, switching from the first drive state to a second drive state and operating the hybrid vehicle (46) in the second drive state; characterized bythat determining the existence of the condition comprises determining a duration of the actuation of the control element (56), comparing the duration with a time threshold value and determining that the duration is below the time threshold value, wherein in the second drive state the drive is switched on and is operated in overrun, wherein the time threshold value is varied depending on a speed of the hybrid vehicle (46). [2] Method for operating a hybrid vehicle (46) according to claim 1, characterized by that in the first drive state the hybrid vehicle (46) is operated in freewheel mode by the drive being switched on and / or with the drive being switched off. [3] Method for operating a hybrid vehicle (46) according to claim 1 or 2, characterized by that in the second drive state the electric motor is operated at a different level of recuperation. [4] Method for operating a hybrid vehicle (46) according to one of the preceding claims, characterized by that the hybrid vehicle (46) is operated in a third drive state in which the drive is in traction mode and a strength level of the recuperation of the electric motor is reduced. [5] Method for operating a hybrid vehicle (46) according to one of the preceding claims, characterized by that determining the presence of the condition comprises determining a strength of the actuation of the operating element (56), comparing the strength with a strength threshold value (38) and determining that the strength is above the strength threshold value (38). [6] Method for operating a hybrid vehicle (46) according to claim 5, characterized by that the intensity threshold (38) is varied depending on a speed of the hybrid vehicle. [7] Hybrid vehicle (46) with a drive (48) comprising an internal combustion engine (50), with an energy converter (52) comprising an electric machine operable for recuperation, and with a control unit (54) operatively connected to an operating element (56), the drive (48) and the energy converter (52), wherein the control unit (54) comprises a computing unit (58) and a memory unit (60), characterized by that a program is stored in the memory unit (60) which, when at least partially executed in the computing unit (58), carries out a method for operating the hybrid vehicle (46) according to one of the preceding claims. [8] Hybrid vehicle (46) according to claim 7, characterized by that the control element (56) is a pedal, a selector lever, a manual switch or a touch panel.

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