DE102004024213B4 - Method for controlling an operation of a motor vehicle, in particular a start-stop system, and motor vehicle - Google Patents

Abstract

Method for controlling an operation of a motor vehicle with an internal combustion engine (12) and an automatic start-stop system (30), which comprises an automatic shut-off which causes an automatic shutdown of the internal combustion engine (12) in the presence of stop conditions, and an automatic start-up system, which in the presence of start conditions causes an automatic start of the internal combustion engine (12), characterized in that a first stop condition is present when at a vehicle speed below a predetermined speed threshold, an operation of the brake pedal is present, with an authorization of the automatic shutdown fulfill another Boundary conditions requires, and the other conditions for the approval of automatic shutdown include a lapse of a minimum running time of the internal combustion engine (12) after its last restart and / or a previous exceeding a vehicle speed threshold after the initial or restart.

Description

The invention relates to a method for controlling an operation of a motor vehicle with an internal combustion engine, in particular a hybrid vehicle with in addition at least one electric motor, and an automatic start-stop system for automatic shutdown and automatic start of the internal combustion engine of the motor vehicle in the presence of appropriate stop or start Conditions. The invention further relates to a motor vehicle with a corresponding start-stop system.

The term hybrid vehicle refers to motor vehicles in which at least two drive units are combined, which use different energy sources to provide the power for the vehicle drive. Particularly advantageous complement the properties of an internal combustion engine, which generates kinetic energy by the combustion of gasoline or diesel fuels, and an electric machine, which converts electrical energy into kinetic energy. Today's hybrid vehicles are therefore predominantly equipped with a combination of internal combustion engine and one or more electric motors. Two different hybrid concepts can be distinguished. In the case of the so-called serial or sequential hybrid concepts, the vehicle drive takes place exclusively via the electric motor, while the internal combustion engine generates the electric current for the charging of an energy store supplying the electric motor or for the direct supply of the electric motor via a separate generator. In contrast, today parallel hybrid concepts are preferred in which the vehicle drive can be represented by both the internal combustion engine and by the electric motor. In such parallel concepts, for example, the electric motor is typically connected to the internal combustion engine at operating points with higher vehicle loads.

In hybrid vehicles, for reasons of fuel consumption, in principle, the aim is to operate the internal combustion engine in operating areas with only low efficiency, in particular in idle mode, as rarely as possible or even not at all. For this purpose, it is known to equip the hybrid vehicle with an automatic start-stop system comprising an automatic shut-off, which causes an automatic shutdown of the internal combustion engine in the presence of stop conditions, and an automatic switch-on, which in the presence of start conditions, an automatic start of the internal combustion engine causes. In particular, the engine is shut down in standstill phases, that is at a vehicle speed of zero by the automatic shutdown. Start-stop automatic transmissions take advantage of the fact that hybrid vehicles have significantly more powerful electric starter motors than conventional starters, which enables a fast engine run-up, especially when restarting after an automatic stop.

For example, start-stop controls are off DE 100 38 280 A1 . DE 100 30 290 A1 . DE 44 12 438 C1 . DE 101 61 343 A1 and DE 102 12 357 A1 known.

Although there are also known in conventional, purely internal combustion engine drive concepts start-stop systems, but these did not find wide market acceptance, since they require some habituation processes from the driver. Thus, for the technical implementation of a start-stop system for hybrid vehicles but also for conventional internal combustion engine vehicles decidedly crucial that they work unnoticed with high comfort, without adverse effects and ideally by the driver. In this context, in particular the optimal coordination of the combination of internal combustion engine, electric machine, clutch and gearbox special demands on the function control.

The object of the present invention is to provide a method for controlling a motor vehicle, in particular a hybrid vehicle, with an automatic start-stop system that achieves an even further reduced fuel consumption with the greatest possible driving comfort. It should also be provided with a corresponding start-stop automatic motor vehicle available.

This object is achieved by a method having the features of claim 1. According to the invention, it is provided that the automatic start-stop system recognizes a first stop condition when an actuation of the brake pedal is present at a vehicle speed below a predetermined speed threshold. In this case, the approval of the automatic shutdown requires the fulfillment of further boundary conditions, namely an expiry of a minimum running time of the internal combustion engine after its last restart and / or a previous exceeding a vehicle speed threshold after the initial or restart.

In addition to the operation of the brake pedal, a closed clutch, that is, no operation of the clutch pedal, are required as a criterion. The criterion of the operation of the brake pedal and optionally additionally the closed clutch allows in real driving frequent use of the automatic start-stop system, in particular the automatic shutdown of the internal combustion engine. Especially in vehicles with manual operation a high number of operating situations or possible signal combinations, in particular combinations of pedal positions is ensured, which are used for the shutdown of the engine. For example, the frequently occurring case that the driver simultaneously actuates the clutch and the brake pedal when the vehicle is stationary or when the wheels are slow (when the gear is engaged) results in a shutdown of the internal combustion engine. Concepts that provide as a stop condition only the non-actuation of the clutch pedal at vehicle standstill, in the aforementioned case, however, do not lead to a shutdown of the engine. Overall, the invention ensures a frequent and over wide operating situations held automatic shutdown of the engine and thus reduced fuel consumption.

A particular advantage of the control according to the invention is the fact that the engine shutdown is possible even at low vehicle speeds and not only when the vehicle is stationary. According to a particularly advantageous embodiment of the invention, the first stop condition therefore comprises the presence of a vehicle speed below a speed threshold that is above 0 km / h, in particular a speed threshold of 2 km / h, preferably 3 km / h. It is particularly preferably provided that the combustion engine is switched off even at a vehicle speed ≦ 5 km / h and at the same time the clutch and / or the brake pedal are engaged. According to a further advantageous embodiment, the speed threshold is predetermined in dependence on an engaged gear of the vehicle transmission. In this way, the engine shutdown is also in the near-empty area. This is particularly advantageous because in this area, a large part of the fuel energy used is consumed to overcome their own friction losses and combustion engines therefore have low engine efficiencies at low speeds.

Of course, the method can be further improved by taking into account further operating point-specific criteria in the automatic shutdown. In particular, it may be advantageously provided that the first stop condition additionally includes an engine speed below a predetermined speed threshold, which corresponds for example to an idle speed. In order to avoid stopping the internal combustion engine in the event of an imminent vehicle acceleration, it may further be provided that the first stop condition comprises a non-actuation of the accelerator pedal of the vehicle. For the same reason, it can furthermore advantageously be provided to effect the internal combustion engine only after the expiry of an applicable delay time after the first stop condition has been fulfilled. This delay time, in turn, may be dictated by a number of factors, such as an engaged gear. In particular, it may be provided to specify a separate, in particular extended, delay time in the case of an engaged reverse gear.

In addition to the operating point-specific factors for determining the stop condition, the sequence of a minimum running time of the internal combustion engine after its last restart and / or the previous, at least one exceeding of a predetermined vehicle speed threshold after the first or reboot requires. In this way, too frequent switching on and off of the engine is avoided while ensuring its warm-up.

Further additional boundary conditions take into account, for example, safety-relevant, comfort-influencing and / or energy-economic factors.

Another, to be met for the approval of automatic shutdown boundary condition may consist in falling below a presettable pressure threshold by an absolute pressure in a vacuum system of a brake booster of the vehicle to ensure the required braking performance. This pressure threshold is according to an advantageous embodiment of the invention at 600 mbar, in particular 400 mbar and preferably 300 mbar. In principle, relatively low braking powers are sufficient in the relevant driving situations in the low speed range. In addition, it can be provided particularly advantageous that, in the case of falling below a predetermined pressure threshold of the absolute pressure of the vacuum system with the internal combustion engine, an auxiliary pumping system, in particular a arranged in a hydraulic system of the brake booster pump to activate. Thus, the required brake gain is always guaranteed.

Further boundary conditions may include, for example, the presence of a minimum level of state of charge (SOC) of an electric energy storage device that can be charged by the internal combustion engine, the presence of a minimum engine temperature, a minimum exhaust gas temperature and / or a minimum catalyst temperature of at least one catalytic converter and / or a minimum value of a characteristic value for the Activity of at least an exhaust gas catalyst (which may be degraded, for example, due to catalyst aging). Furthermore, it may be necessary to lower a threshold value for a current power requirement of a vehicle electrical system current for the authorization of automatic switch-off, to fall below a threshold value for a vehicle interior heating requirement and / or a vehicle air conditioning system cooling system threshold and / or to exceed an outdoor temperature threshold ,

Of course, all the aforementioned additional conditions and boundary conditions for the approval of the automatic shutdown can also be used in combinations with each other.

It can be provided that a first start condition for a restart after a shutdown of the internal combustion engine by the start-stop system is present when an open clutch, that is an operation of the clutch pedal, and a non-actuation of the brake pedal are present at the same time.

Also for the restart condition other factors can be considered. In particular, the starting condition may require an engaged gear of a transmission, in particular a manually operated manual transmission, and / or an actuation of the accelerator pedal. In this context, it may be provided to determine the engaged gear by means of a gear sensor and / or in dependence on the vehicle speed and the crankshaft speed.

The invention further relates to a motor vehicle according to claim 17 with an internal combustion engine, in particular a hybrid vehicle with additionally at least one electric motor, and a start-stop system comprising an automatic shutdown, which causes an automatic shutdown of the internal combustion engine in the presence of the stop conditions according to the invention.

• (c) geöffnete Kupplung und
• (d) Nicht-Betätigung des Bremspedals.

The motor vehicle may further comprise an automatic switch-on, which causes an automatic start of the internal combustion engine in the presence of start conditions, wherein a first start condition for a restart is present when the following conditions are met simultaneously:

• (c) opened clutch and
• (d) non-operation of the brake pedal.

The automatic start-stop system according to the invention comprises a program algorithm for controlling the automatic activation and / or deactivation of the internal combustion engine, wherein the program algorithm can be stored in a general engine control or a separate control unit.

The start-stop system according to the invention unfolds its advantages, especially in so-called mild hybrid vehicles. These are hybrid vehicles with electric motors with relatively low power of at most 40 kW, in particular of at most 25 kW, usually of at most 20 kW. In the context of the present invention, electric motors are used with a power preferably in the range of 7 to 20 kW, more preferably of about 15 kW.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 schematically the structure of a hybrid drive unit according to the invention;

2 a flowchart for carrying out the automatic shutdown invention and

3 a flow chart for performing a restart automatic.

In 1 is with 10 Overall, a hybrid drive unit of a hybrid vehicle not specifically shown in detail. The drive of the vehicle takes place optionally or simultaneously by a conventional internal combustion engine 12 (Gasoline or diesel engine) and an electric motor 14 that both act on the same wave. internal combustion engine 12 and electric motor 14 are about a gearbox 16 , in particular a manually operated manual transmission, with an indicated drive train 18 connected. The decoupling of the drive shafts of the internal combustion engine 12 or the electric motor 14 from the gearbox 16 via a coupling 20 , which can be opened by operating a non-illustrated clutch pedal by the driver and is closed when not operated.

The electric motor 14 , which is a three-phase asynchronous motor or synchronous motor, for example, can be operated either in motor or generator mode. In motor operation, the electric motor drives 14 the drive train 18 under consumption of electrical energy (electricity). This relates to the electric motor 14 from an energy store 22 which may be, for example, a battery and / or a capacitor storage. In addition, the engine operation of the electric motor 14 the switched-on combustion engine 12 support. In regenerative operation, however, the electric motor 14 through the internal combustion engine 12 or a thrust of the vehicle driven and Converts the kinetic energy into electrical energy to replenish the energy storage 22 around. The switching of the electric motor 14 between engine and generator operation is performed by power electronics 24 , which at the same time makes a possibly necessary conversion between DC and AC.

According to the illustrated concept, the vehicle drive is predominantly by the internal combustion engine 12 , by the designed as a starter generator electric motor 14 is started. The electric motor 14 In addition, it assumes a boost function by being connected to the vehicle drive supportive in high-load situations, in particular during accelerations of the vehicle (engine operation). On the other hand, the electric motor has 14 In driving situations in which there is an excess of kinetic energy of the vehicle, a so-called recuperation function, by the kinetic energy in kinetic energy to charge the energy storage in generator mode 22 converts and thus simultaneously provides a braking torque.

In 1 is also an optional additional clutch 26 indicated between the internal combustion engine 12 and electric motor 14 can be arranged. Such an additional coupling 26 allows the separate decoupling of the internal combustion engine 12 from the drive train 18 or from the electric motor 14 , which basically gives the advantage that when the internal combustion engine 12 his mechanical frictional resistance must not be dragged. The additional clutch 26 Although therefore causes an additional potential savings of fuel, but is associated with a considerable cost, construction and space requirements. In the context of the present invention, for this reason, the additional coupling 26 between internal combustion engine 12 and electric motor 14 Although conceivable in principle, but preferably not provided. Rather, just an advantage of the invention in the dispensability of an additional clutch can be seen.

The control of the operation of the internal combustion engine 12 as well as the power electronics 24 done by an engine control unit 28 , in which the start-stop system (indicated with 30 ) is integrated in the form of a program algorithm. Alternatively, the start-stop system 30 also be provided in a separate control unit.

2 and 3 show preferred flowcharts for the inventive method for controlling a hybrid drive 10 to 1 , in particular for automatic Abbeziehungsweise connection of the internal combustion engine 12 ,

According to 2 the routine starts in step 100 where the current operating state of the internal combustion engine 12 is queried, in particular whether the internal combustion engine 12 switched on or off. If the query is answered yes, that is, the internal combustion engine 12 is in operation, the procedure goes to the subsequent steps 102 to 110 in which a polling routine for the automatic shutdown is performed.

In step 102 It is checked whether a current vehicle speed vFzg falls below a predetermined speed threshold, which is according to the preferred example at 5 km / h. If the question is answered with no, there is no stop condition and the method goes to step 110 over, that is, the internal combustion engine 12 remains switched on. If, on the other hand, the question in step 102 in the affirmative, that is, the speed is less than or equal to 5 km / h, the procedure goes to step 104 about where the state of the clutch 20 is checked. Is the clutch 20 closed, that is, the driver does not press the clutch pedal, this is already a sufficient criterion for meeting the stop condition and the internal combustion engine 12 will be in step 108 automatically shut off. On the other hand, if the clutch 20 is open (clutch pedal is pressed), is in step 106 queried whether an operation of a (in 1 not shown) brake or a brake pedal by the driver. In the case of actuation of the brake again the criteria for the stop condition are satisfied and the internal combustion engine 12 will be in step 108 automatically shut off. Will the query be in 106 no, that is, the brake is not applied, the internal combustion engine remains 12 switched on (step 110 ). It is therefore sufficient for a shutdown of the engine 12 from that - in addition to a vehicle speed ≤ 5 km / h - either the clutch 20 is closed (not operated by the driver) or actuation of the vehicle brake is present or both criteria are met. Of course, the order of queries 102 to 106 also in any other order than the one shown.

The invention further provides that, in addition to the criteria mentioned, further criteria and / or boundary conditions are included in the decision algorithm for automatic shutdown. This is in 1 through the step 101 indicated in which the fulfillment of such additional conditions is checked. Alternatively, step 101 be done elsewhere, especially after step 106 , The in step 101 queried boundary conditions include the expiry of a minimum running time of the internal combustion engine 12 after his last restart and optionally his first start and / or the previous exceeding of a vehicle speed threshold after the initial or restart. Additional in step 101 queried boundary conditions can include falling below a maximum engine speed, the non-operation of an accelerator pedal, the falling below a pressure threshold for a vacuum system of a brake booster, the presence of a minimum engine or minimum exhaust or minimum catalyst temperature and / or undercutting a power demand by different pantographs of a vehicle electrical system such as interior heating or air conditioning or the like. In addition, it may be required that after the date of fulfillment in the steps 102 . 104 and 106 queried criteria must pass a delay before the internal combustion engine 12 in step 108 is actually turned off.

Will step in the query 100 found that the internal combustion engine 12 already switched off, in particular caused by the automatic start-stop, the procedure goes to the in 3 shown restart routine of the automatic start-stop, in which the presence of a predetermined restart condition is checked.

This will be done in step 204 Check if the clutch 20 is open, that is, the clutch pedal is actuated. If this is the case, in step 206 queried whether the brake pedal is not actuated. If this query is also answered with Yes, that is, there is no brake application, takes place in step 208 the restart of the internal combustion engine 12 , Accordingly, the engine is 12 only restarted if both conditions ( 204 and 206 ) are fulfilled simultaneously. Will one of the queries 204 or 206 denied, the internal combustion engine remains 12 switched off (step 210 ).

Similar to in 2 with the optional step 101 is shown, the automatic shutdown routine in 3 Optionally request fulfillment of further conditions. For example, in an additional step, the insertion of a gear of the manual transmission 16 and / or the operation of the accelerator pedal are required by the driver, wherein the engaged gear can be optionally determined by means of a gear sensor.

LIST OF REFERENCE NUMBERS

10

Hybrid drive unit

12

internal combustion engine

14

electric motor

16

transmission

18

powertrain

20

clutch

22

Energy storage / battery

24

power electronics

26

additional clutch

28

Engine control unit

30

Start-stop system

Claims (25)

Method for controlling an operation of a motor vehicle with an internal combustion engine ( 12 ) and a start-stop system ( 30 ), which includes an automatic shutdown, which in the presence of stop conditions, an automatic shutdown of the internal combustion engine ( 12 ), and an automatic switch-on, which in the presence of start conditions, an automatic start of the internal combustion engine ( 12 ) causes, characterized in that a first stop condition exists when at a vehicle speed below a predetermined speed threshold, an operation of the brake pedal is present, with an automatic shutdown presupposes the fulfillment of further boundary conditions, and the other conditions for the approval of the automatic shutdown a process a minimum running time of the internal combustion engine ( 12 ) after its last restart and / or a previous exceeding of a vehicle speed threshold after the initial or restart. A method according to claim 1, characterized in that the first stop condition comprises a vehicle speed below a speed threshold above 0 km / h. A method according to claim 1 or 2, characterized in that the speed threshold is predetermined in dependence on an inserted gear. Method according to one of the preceding claims, characterized in that the first stop condition comprises an engine speed below a speed threshold. Method according to one of the preceding claims, characterized in that the first stop condition comprises a non-actuation of an accelerator pedal of the vehicle. Method according to one of the preceding claims, characterized in that only after expiry of an applicable delay time after the presence of the first stop condition of the internal combustion engine ( 12 ) is switched off. Method according to Claim 6, characterized in that the delay time is predetermined as a function of an engaged gear, in particular, a special delay time for a reverse gear is specified. Method according to one of the preceding claims, characterized in that the further boundary conditions for the approval of the automatic switch-off an expiry of a minimum running time of the internal combustion engine ( 12 ) after his first start. Method according to one of the preceding claims, characterized in that the further boundary conditions include an absolute pressure in a vacuum system of a brake booster of the vehicle below a pressure threshold. A method according to claim 9, characterized in that the pressure threshold is 600 mbar, in particular 400 mbar, preferably 300 mbar. Method according to one of the preceding claims, characterized in that the further boundary conditions, the presence of a minimum charge state of at least one of the internal combustion engine ( 12 ) rechargeable electrical energy store ( 22 ). Method according to one of the preceding claims, characterized in that the further boundary conditions comprise the presence of a minimum engine temperature and / or a minimum exhaust gas temperature and / or a minimum catalyst temperature of at least one catalytic converter and / or a minimum value of a parameter for the activity of at least one catalytic converter. Method according to one of the preceding claims, characterized in that the further boundary conditions include falling below a threshold value for a power consumption of a vehicle electrical system current. Method according to one of the preceding claims, characterized in that the further boundary conditions include falling below a threshold value for a heating power requirement for a vehicle interior and / or for a cooling request of a vehicle air conditioning system and / or exceeding a threshold value for an outside temperature. Method according to one of the preceding claims, characterized in that when the internal combustion engine ( 12 ) and falls below a predetermined pressure threshold for a vacuum system of a brake booster, an additional pumping system is activated. Method according to one of the preceding claims, wherein the motor vehicle is a hybrid vehicle with in addition at least one electric motor ( 14 ). Motor vehicle with an internal combustion engine ( 12 ) and a start-stop system ( 30 ), which comprises an automatic shutdown, which performs the method according to one of claims 1 to 16. Motor vehicle according to claim 17, characterized in that the start-stop system ( 30 ) a program algorithm for controlling the automatic activation and / or deactivation of the internal combustion engine ( 12 ). Motor vehicle according to claim 18, characterized in that the program algorithm in an engine control unit ( 28 ) or a separate control unit is deposited. Motor vehicle according to one of claims 17 to 19, characterized in that the vehicle is a manual transmission ( 16 ) having. Motor vehicle according to one of claims 17 to 20, wherein the motor vehicle is a hybrid vehicle with in addition at least one electric motor ( 14 ). Motor vehicle according to claim 21, characterized in that the at least one electric motor ( 14 ) has a power of at most 25 kW, in particular of at most 20 kW. Motor vehicle according to one of claims 21 or 22, characterized in that between the at least one internal combustion engine ( 12 ) and the at least one electric motor ( 14 ) no additional coupling ( 26 ) is provided. Motor vehicle according to one of claims 21 to 23, characterized in that the electric motor ( 14 ) is a starter generator. Motor vehicle according to one of claims 21 to 24, characterized in that the electric motor ( 14 ) via a belt, a toothed belt or another non-positive and / or positive connection to the crankshaft of the internal combustion engine ( 12 ) is coupled.

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