WO2014071934A1 - Method for controlling a drive train - Google Patents

Abstract

The invention relates to a method for controlling a drive train (1) having an internal combustion engine (2) with a crankshaft (4) and an electric machine (3) which is arranged in a pulley wheel plane of the internal combustion engine and is in operative connection with the crankshaft by means of a switchable planetary gear mechanism (7), wherein the planetary gear mechanism is switched during a starting operation of the internal combustion engine by means of different operating parameters by an actuator (13) which actuates a brake (14) which is arranged between an internal gear (2) of the planetary gear mechanism and a housing (15) which is arranged fixedly so as not to rotate, frictionally over an actuator travel and depending on a key start when the internal gear is at a standstill or a pulse start when the internal gear is rotating. In order to prevent firstly wear of the brake as a consequence of slip and secondly damage of the actuator as a consequence of excessive contact pressure, the starting operation is carried out in the case of a preferably closed brake, and the brake is recognized as closed if, in the case of a key start, a first operating parameter in the form of a differential speed between the internal gear and the housing is within a predefined threshold of the differential speed and, in the case of a pulse start, a second operating parameter in the form of a dynamic friction coefficient variable is within a predefined interval.

Description

 METHOD FOR CONTROLLING A DRIVE TRAIN

The invention relates to a method for controlling a hybrid powertrain with an internal combustion engine with a crankshaft and arranged in a pulley plane of the internal combustion engine and by means of a switchable planetary gear with the crankshaft in operative engagement electric machine, wherein the planetary gear during a starting operation of the internal combustion engine of a between a Ring gear of the planetary gear and a rotatably arranged housing arranged brake actuating actuator via a Aktorweg frictionally engaged and dependent on a key start at stationary ring gear or a pulse start with rotating ring gear by means of different operating parameters.

Hybrid drive trains with an electric machine integrated in the pulley of an internal combustion engine are known, for example, from DE 10 201 1087 697 A1. In this case, the electric machine is integrated by means of a switchable planetary gear in the belt drive, so that they can start at standstill working planetary gear, the stationary engine and, for example, depending on the operating situation at not untersetzendem or understating operation, the running internal combustion engine in the drive, with a stationary internal combustion engine, for example recuperate open valves, electrically drive the motor vehicle with the corresponding drive train and / or can drive ancillaries such as an air conditioning compressor. The planetary gear is switched by means of a brake which is actuated by an actuator along an actuator travel and thereby frictionally connects the ring gear of the planetary gear with a fixed housing component. In this case, a predetermined actuator travel is assigned to an engagement point of the brake with the maximum transferable braking torque. Depending on the operating situation, for example, with changing temperature, wear occurring with operating time and the like, this point of engagement varies, so that slip can occur when the brake is closed, which leads to high wear of the friction linings of the brake, or Überanpressung, the high load on the actuator and whose mechanics entails, can occur. The object of the invention is therefore to propose a method in which a generic hybrid powertrain can be operated permanently and without wear of the friction linings of the brake and without overloading the actuator.

The object is solved by the features of claim 1. The subordinate claims give advantageous embodiments again.

The proposed method is used to control a hybrid powertrain with an internal combustion engine having a crankshaft and an arranged in a pulley plane of the internal combustion engine and by means of a switchable planetary gear with the crankshaft in operative engagement electric machine. In this case, the planetary gear during a starting operation of the internal combustion engine is frictionally engaged by a one between a ring gear of the planetary gear and a rotatably arranged housing arranged brake actuating actuator via an actuator. In a proposed manner, the starting process is performed at preferably closed brake. In this case, a closed state of the brake is recognized, for example, by a routine implemented in a control unit, if, during a key start, a first operating parameter in the form of a differential speed between ring gear and housing within a predetermined threshold of the differential rotational speed or at pulse start a second operating parameter in the form of a dynamic friction coefficient within a given interval. A key start is understood to be a start of the stationary internal combustion engine when the electric machine is stationary, for example a cold start. Here, the driver starts the engine by a key or a corresponding device such as a start button or the like. During an impulse start, the starting of the internal combustion engine takes place while the rotor of the electric machine is already rotating, if, for example, after a temporary shutdown of the motor vehicle at a traffic light, a railway crossing or the like and to drive the air conditioning compressor activated electric machine should be restarted. Furthermore, at low ambient temperatures and thus hard to start the engine, the electric machine can be accelerated in advance.

The differential speed used during a key start to assess a closed brake can be obtained from the rotor speed of the electric machine without any further sensors, since, taking into account the ratio of the planetary gear, the rotational speed of the ring gear can be determined therefrom. The friction partner of the ring gear is fixed to the housing so that there is a differential speed from the rotor speed which reflects the slip of the brake. If a sufficiently small slip is determined as part of the measurement accuracy of the rotor speed, for example, at differential speeds of less than 100 1 / min, preferably less than 10 1 / min, a closed brake is assumed. For larger differential speeds, the slip can be reduced by appropriately further closing the brake by means of the actuator. Alternatively or additionally, a necessary correction of the actuator travel is determined and stored for adaptation of the Aktorwegs in subsequent startup operations at the key start in the control unit. If no rotational speed difference can be measured for a given actuator travel for closing the brake, the actuator travel is corrected immediately or in a subsequent starting process in order to set a measurable rotational speed difference within the threshold and thus avoid an overpressing of the brake under high load of the actuator. A corresponding correction of the Aktorwegs can also be stored and used to adapt the Aktorwegs.

When a pulse start is carried out, the rotor already rotates when the internal combustion engine is stationary. As a result, the ring gear also rotates with respect to the rotatably arranged housing. At the impulse start, the planetary gear is to be switched, that is, rotatably coupled by means of the brake ring gear and housing. To assess the closed state of the brake, it is checked whether a second operating parameter in the form of a dynamic coefficient of friction value lies within a predetermined interval. As a result, the closing behavior of the brake can be assessed even at the beginning of a large difference in rotational speed between the ring gear and the housing during a pulse start. According to an advantageous embodiment, the interval may be a time interval of a reduction of the differential speed. If the time interval is greater than the interval, the actuator travel is corrected in the direction of a higher pressing. If the time interval is undershot, the brake is delivered less far because of an imminent overpressure, thus reducing the actuator travel. In an alternative embodiment, the interval may be represented as a brake torque interval of a brake torque of the brake. The braking torque can be determined as follows:

M Brake M Hollow Hollow "- ¹ Hollow

mit

With

 Hollow mass inertia of the ring gear

ω Hollow angular acceleration of the ring gear

J, Verbr inertia of the internal combustion engine ^ω Verbr angular acceleration of the internal combustion engine

M Verbr moment of the internal combustion engine when starting according to the

 drag torque

 Stand translation of the planetary gear, for example i = -2

Since the inertia of the ring gear is substantially smaller than that of the internal combustion engine, it can be neglected. This simplifies o. G. Equation to:

Brake ^{lv ±} hollow V ^ Consum Consum Consum ^{lv ±)} (. _Λ \

According to an advantageous embodiment of the method can, if during a

Starting operation of the operating parameter is outside the associated interval, a set current Aktorweg corrected by a predetermined amount to achieve an operating parameter within this interval to an adapted Aktorweg and the adapted Aktorweg be set during the subsequent boot process for this interval. This means that as an alternative or in addition to an immediate correction of the closed state of the brake by adjusting the Aktorwegs a corresponding correction of Aktorwegs against a calibrated or previously adapted Aktorweg is used to adapt the original Aktorwegs. In this case, a correction of the actuator travel in each case an operating variable by means of small, discrete and per adaptation process equal correction steps of Aktorwegs be provided so that an amount of correction or adaptation of Aktorwegs takes place in predetermined steps per startup. It may further be provided, in particular for the presentation of a robust embodiment of the adaptation of the actuator travel, to suspend a further correction of this actuator travel for a plurality of starting operations after a correction of the actuator travel in a plurality of consecutively following starting operations in the same direction when the operating variable lies within the interval.

The invention will be explained in more detail with reference to the embodiments of the proposed method illustrated in FIGS. 1 to 15. Showing:

FIG. 1 is a block diagram of a hybrid powertrain;

 Figures 2 to 9 are diagrams of Aktorwegen over time during a key start with associated speeds of the ring gear and the internal combustion engine at different calibration states of

 Actuator for actuating the brake

and

FIGS. 10 to 15 diagrams of actuator paths over time during a pulse starts with associated speeds of the ring gear and the internal combustion engine at different calibration states of the

 Actuator for actuating the brake.

1 shows in a systematic representation of the hybrid powertrain 1 with the internal combustion engine 2 and the electric machine 3 and between the crankshaft 4 of the internal combustion engine 2 and the rotor 5 of the electric machine 3 effectively arranged Umlinglingungsmitteltrieb 6 with the switchable planetary gear 7. In the shown Embodiment, the web 8 with the planetary gears 9 of the planetary gear 7 with the crankshaft and the sun gear 10 via the belt 1 1 with the rotor 5 is effectively connected. The ring gear 12 is braked against the housing 15 by means of the brake 14 actuated by the actuator 13 along an actuator travel x, whereby the planetary gear 7 is shifted into two switching stages. In the Umschlingungsmitteltrieb 6 further, not shown ancillaries may be added, which can be selectively and depending on the circuit of the planetary gear from the electric machine 3 or the internal combustion engine 2 driven. The electric machine 3 also starts the disengaged internal combustion engine 2 when the brake 14 is closed. Here, a key start is distinguished with the crankshaft 4 stationary and the rotor 5 stationary and a pulse start with the rotor 5 rotating and the crankshaft 4 stationary. Depending on the two start states, the actuator path x imposed by the actuator 13 of the brake 14 is checked by means of different operating parameters to provide an overpressure with high load on the actuator 13 and a high differential speed between the ring gear 12 and the housing 15 with high wear on the friction linings the brake 14 with the brake 14 to monitor and adapt if necessary. The speed difference between the ring gear 12 and the housing 15 is determined in the embodiment shown on the basis of the rotor speed of the rotor 5, taking into account the translation of the planetary gear 7, so that it is possible to dispense with additional sensors.

FIGS. 2 to 9, with reference to the drive train of FIG. 1, show the typical behavior of a starting operation of the internal combustion engine 2 by means of the electric machine 3 during a key start. Here, FIGS. 2, 4, 6, 8 each show the actuator travel x against the time t with the aid of the curves 16, 16a, 16b, 16c as ideal and with reference to the curves 17, 17a, 17b, 17c as the actual behavior. The line 18, which extends over the FIGS. 2, 4, 6, 8, shows the ideal actuator travel x, in which the brake 14 is closed without overpressing with the differential speed minimized. The associated figures 3, 5, 7, 9, shown below each of FIGS. 2, 4, 6, 8, show the rotational speeds n of the internal combustion engine 2 and of the electric motors. machine 3 over the time t at the same superimposed times t. The curves 19, 19 a, 19 b, 19 c show the rotational speeds of the electric machine and the curves 20, 20 a, 20 b, 20 c, the rotational speeds of the internal combustion engine. 2

FIGS. 2 and 3 show a starting process after the start of the electric machine 3 and when the brake 14 is actuated. As a result of the actuator travel Xi calibrated below the line 18, slip occurs on the brake 14 which, based on an exceeding of the threshold 21 in the form of the rotational speed n. ι is detected by the controller 13 controlling the actuator. Upon exceeding the threshold 21, the Aktorweg Xi is corrected to the Aktorweg x ₂ , to prevent the slippage of the brake 14. The internal combustion engine is started.

Figures 4 and 5 show a subsequent startup with key start. In this case, the actuator path Xi of FIG. 2 was adapted to the actuator path x ₃ by adding a smaller correction than the correction added to the actuator path x ₂ of FIG. 2. The internal combustion engine 2 is started without slippage of the ring gear 12 relative to the housing. From the lack of exceeding the threshold 22 for a minimum slip in the form of the speed n ₂ , however, it is recognized that there is an overpressure. The correction of Aktorwegs x ₃ is again reduced by a predetermined amount.

Figures 6 and 7 show the properly adapted, lying on the line 18 and thus the ideal Aktorweg x, Aktorweg x ₃ , in which without Überanpressung and only negligible, for example, lying below the accuracy of slip slip of the ring gear 12, the internal combustion engine 2 of the Electric machine 3 is started. The line 18 is not constant in practical embodiments over the operating time of the drive train 1, so that according to Figures 8 and 9 in subsequent starts at key starts again slip can occur, which is compensated according to Figures 2 to 7 by the currently adapted Aktorweg x _{3 is} adapted again.

Figures 10 to 15 show, with respect to the powertrain 1 of Figure 1, the behavior of the brake 14 during a pulse start. In this case, in FIGS. 10, 12, 14, the curves 23, 23a, 23b of the actuator paths x over time t and in FIGS. 11, 13, 15 the rotational speeds n over time t based on curves 24, 24a, 24b the rotational speeds for the electric machine 3 and based on the curves 25, 25 a, 25 b of the rotational speeds of the internal combustion engine 2 are shown. As is apparent from Figures 1 1, 13, 15, due to the decommissioning of the internal combustion engine 2 at predetermined times ti the electric machine 3 is energized and rotated at a predetermined speed to drive, for example, an accessory, such as an air conditioning compressor. To start the internal combustion engine 2, for example, after a traffic light stop, the brake 14 is closed at time t ₂ . In order to assess the position of the actuator travel x set for the closed state of the brake 14, the differential rotational speed determined by the rotational speed n of the electric machine 3 is determined as slip of the ring gear 12 relative to the housing 15 in the interval Δt, such as time interval. The interval At starts at the time t ₃ at which the actuator travel x set on the basis of the dashed curve with time delay is practically set. Between the time t ₃ and the time t ₄ , the minimum interval At _{min is} specified. If the slippage of the brake 14 decreases within this interval, it is to be assumed that there is an overpressure. Between the time t ₄ and the time t ₅ , the maximum time interval At _{max is} specified. If, within this interval, the slip of the brake is not degraded, it is to be assumed that slip is inadmissible. It should be pointed out here that the actuator paths x of a key start and a pulse start are preferably determined and adapted independently of one another. However, the correlation between these actuator paths x of the key and pulse start may be compared to generally assess the state of the brake 14.

In the FIGS. 10, 11 illustrated with one another with the same time axes, the slip extends beyond the time t ₅ , ie outside the time interval At _max , so that the originally set actuator travel x _{4 is increased} to the actuator travel x ₅ . Furthermore, a correction variable is determined from the correction of the actuator travel x ₄ to the actuator travel x ₅ , with which the actuator travel x _{4 is} adapted to the actuator travel x ₆ .

FIGS. 12 and 13 show the application of the more than additive compensated actuator travel x ₆ . After adjustment of the thus adapted actuator travel x ₆ , the slip decreases within the time interval At _min and synchronicity between the electric machine 3 and the internal combustion engine 2 is achieved. By definition, this is a Überanpressung, so that the Aktorweg x _{6 is} adapted in the other direction to shorter Aktorwegen.

Figures 14 and 15 show the applied at time t ₃ from the pulse start of Figures 12 and 15 adapted Aktorweg x ₇ , which leads to a reduction of the slip of the ring gear 12 and thus to a synchronous speed development of electric machine 3 and internal combustion engine 2 outside the time interval At _min , but within the time interval At _max leads, so that an adjustment of the brake 14 between unacceptable Überanpressung and high slip of the ring gear 12 relative to the housing 15 is achieved.

LIST OF REFERENCE NUMBERS

powertrain

 Internal combustion engine

 electric machine

 crankshaft

 rotor

 Umschlingungsmitteltrieb

 planetary gear

 web

 planetary gears

 0 sun wheel

 1 strap

 2 ring gear

 3 actor

 4 brake

 5 housing

 6 curve

 6a curve

 6b curve

 6c curve

 17 curve

 17a curve

 17b curve

 17c curve

 18 line

 19 curve

 19a curve

 19b curve

 19c curve

 0 curve

 0a curve

 0b curve

 0c curve

 21 threshold

 22 threshold

 23 curve

 23a curve

 23b curve

 24 curve

 24a curve

 24b curve

 25 curve

 25a curve

 25b curve

n speed

ni speed

n ₂ speed

t time

tl time time

time

time

time

interval

time interval

time interval

Aktorweg ideal actuator path

actuator travel

actuator travel

actuator travel

actuator travel

actuator travel

actuator travel

actuator travel

Claims

claims 1 . Method for controlling a hybrid drive train (1) having an internal combustion engine (2) with a crankshaft (4) and an electric machine arranged in a pulley plane of the internal combustion engine (2) and in operative engagement with the crankshaft (4) by means of a shiftable planetary gearbox (7) (3), wherein the planetary gear (7) during a starting operation of the internal combustion engine by a one between a ring gear (12) of the planetary gear (7) and a rotatably mounted housing (15) arranged brake (14) actuating actuator (13) via an actuator (x) frictionally engaged and dependent on a key start when stationary ring gear (12) or a pulse start with rotating ring gear (12) is switched by means of different operating parameters, characterized in that the starting process is performed at preferably closed brake (14) and the brake ( 14) is detected to be closed, if at a key start a first operation parameter in the form of a differential speed between ring gear (12) and housing (15) is smaller than the predetermined threshold (21) of the differential speed and at a pulse start, a second operating parameter in the form of a dynamic Reibwertgröße within a predetermined interval (At). 2. The method according to claim 1, characterized in that the interval (At) is a time interval (At _max ) of a reduction of the differential speed.  3. The method according to claim 1, characterized in that the interval is a braking torque interval of a brake torque of the brake. 4. The method according to any one of claims 1 to 3, characterized in that during a starting operation at outside of the threshold (21) or the interval (At _max ) operating parameter lying the Aktorweg is corrected until the operating parameters within the threshold (21) or the Interval (At _max ) is. 5. The method according to any one of claims 1 to 4, characterized in that, if during a starting operation, the operating parameter outside the threshold (21) or the interval (At _max ), a set current Aktorweg (xi, x ₂ , x ₄ , x ₅ , x ₆ ) are corrected by a predetermined amount to obtain an operating parameter within the threshold (21) or the interval (At _max ) to an adapted actuator path (x ₃ , x ₇ ) and the adapted actuator path (x ₃ , x ₇ ) is set during the subsequent booting for the threshold (21) or the interval (At _max ). 6. The method according to claim 5, characterized in that a correction of Aktorwegs (xi, x ₂ , x ₄ , X5, Χβ) in each case an operating variable by means of an amount in predetermined steps per startup occurs. 7. The method according to claim 5 or 6, characterized in that after a correction of Aktorwegs (x ₃ , x ₇ ) in several successive starts in the same direction at within the threshold (21) or the interval (At _max ) lying operating size one Further correction of this Aktorwegs (x ₃ , x ₇ ) is suspended for multiple starts.