DE102008053505B4 - Method for controlling a hybrid powertrain of a motor vehicle - Google Patents

Abstract

Method for controlling a hybrid drive train (1) of a motor vehicle (2), wherein the hybrid drive train (1) has a clutch (5) with a clutch input (6) and a clutch output (7), with an internal combustion engine (8) on the clutch input side and a connected to the A generator (9) coupled to the internal combustion engine (8) and a gearbox (10) and at least one electric machine (11) are arranged on the clutch output side, the clutch (5) being opened in a serial operating state and the generator (9) connected to the internal combustion engine (8). is driven, electrical power is generated by the generator (9) and the electrical power is used to drive the motor vehicle (2) by the at least one electric machine (11), the clutch (5) being closed in a coupled operating state and a power flow is transmitted from the internal combustion engine (8) to the transmission (10), characterized in that during the transition from the serial operating state to the coupled operating state, the clutch (5) jumps when a synchronous speed range between the clutch input (6) and the clutch output (7) is reached, in particular is closed digitally and the clutch is suddenly opened during the transition from the coupled operating state to the serial operating state.

Description

The invention relates to a method for controlling a hybrid drive train of a motor vehicle according to the features of the preamble of patent claim 1.

The method is used to control a hybrid powertrain of a motor vehicle. The hybrid powertrain has vzw. an internal combustion engine as an internal combustion engine. The internal combustion engine is vzw. a generator, in particular permanently coupled. The generator is in turn connected to a non-positive or positive clutch. The generator is equipped with a clutch input, i.e. H. connected on the clutch input side or “connected” here. On the clutch output side, the hybrid drive train has vzw. a gearbox and at least one other electric machine. In one embodiment, a single electric motor can be provided as the electric machine. However, several individual electric machines can also be provided to drive the motor vehicle. For example, several wheel hub motors can be provided. The wheel hub motors can, for example, be provided in addition to a (main) electric motor.

The method for controlling the hybrid powertrain has, among other things: Operating states in which the internal combustion engine and the generator work together as a power generator and this electrical energy is used to drive the motor vehicle by the at least one electric machine. In this serial operating state, the clutch is open. The generator is then driven by the internal combustion engine, electrical power is generated by the generator and the electrical power is used to drive the motor vehicle by the at least one electric machine.

In a coupled operating state, the clutch is closed and a power flow is transmitted from the internal combustion engine to the transmission. In this coupled operating state, the torque generated by the internal combustion engine is at least partially transmitted to the transmission via the closed clutch. During the transition from the serial operating state to the coupled operating state, the clutch is closed; during the transition from the coupled operating state to the serial operating state, the clutch is opened.

From the DE 10 2006 001 272 A1 a hybrid powertrain for a motor vehicle is known. The hybrid drive train includes an internal combustion engine with an output shaft, a main electric motor, by means of which a predetermined power can be generated for moving the motor vehicle from a standstill, a clutch, by means of which the output shaft can be selectively connected to the main electric motor, a transmission coupled to the main electric motor, and an additional electric motor , which is connected to the internal combustion engine and by means of which the internal combustion engine can be started. The additional electric motor can be switched as a generator driven by the internal combustion engine. In generator operation, the additional electric motor then feeds an on-board network battery. Provision of electrical power to drive the vehicle through generator operation of the additional electric motor is possible DE 10 2006 001 272 A1 not known. The clutch includes electrical or hydraulic operating or actuating devices, by means of which suitable, vzw. The clutch can be engaged or disengaged using electrical clutch control signals. When the clutch is engaged or engaged, the torques of the internal combustion engine and the main electric motor can add up, so that depending on the state of the clutch, the internal combustion engine, the main electric motor or both provide the necessary torque. This operating mode essentially corresponds to a coupled operating state. In order to be able to connect the internal combustion engine or its output shaft to the main electric motor, it is known in this known method that after starting the internal combustion engine, a current speed of the main electric motor is determined, and the internal combustion engine and / or the additional electric motor is controlled by emitting appropriate signals, that the speed of the internal combustion engine and the main electric motor are adjusted to one another and clutch control signals are formed for the clutch and delivered to it, whereupon the clutch is engaged.

From the DE 198 18 809 B4 a device is known for controlling a clutch in the drive train of a motor vehicle, with an engine, with a clutch and with a transmission, with an actuating unit that can be controlled (by a control unit) for actuating the clutch and with a control unit in signal connection with sensors, the Control unit controls a creeping process when the gear is engaged, the brake is not actuated and the load lever is not actuated and the engine is running, a creeping torque that can be transmitted by the clutch being controlled, at which the vehicle crawls, the creeping torque being reduced as a function of time when the brake is actuated. When the brake actuation is terminated, the creep torque is controlled to a predeterminable value before the creep torque is reduced to zero.

From the DE 10 2005 006 369 A1 an electrically variable transmission is known, which is provided by a station wagon Nation of features of both pure and parallel hybrid powertrain architectures can provide continuously variable speed ratios. A preferred input torque for the hybrid powertrain is determined, which leads to a minimal overall power loss. The total power losses of the hybrid powertrain are calculated, converging an input torque solution that corresponds to the minimum total power loss of the hybrid powertrain to determine the preferred input torque.

From the DE 10 2007 056 722 A1 a hybrid powertrain for a motor vehicle is known. The hybrid powertrain has an internal combustion engine and a transmission. The transmission here has a transmission drive element, a first and a second electric motor, a first and a second planetary gear set and a plurality of selectively engageable torque transfer devices that enable the hybrid powertrain to be configured differently so that it is in an electric drive operating state, in an electrically variable Operating state, in a fixed gear operating state and in a neutral charging operating state.

From the document DE 198 14 402 A1 a drive system and a method for operating a drive system during an acceleration process are known. In order to avoid a jerky coupling of an internal combustion engine, the internal combustion engine is turned up to a synchronous speed.

From the document DE 103 93 594 T5 a drive system for a hybrid vehicle is also known, which can be operated in a parallel and a serial drive mode.

The methods known in the prior art for controlling a hybrid drive train of a motor vehicle are not yet optimally designed. In particular, the conventional closing of the clutches, especially during the transition from the serial operating state to the coupled operating state, leads to an uncomfortable wheel torque curve.

The invention is therefore based on the object of designing and developing the method mentioned at the outset in such a way that an uncomfortable wheel torque curve is avoided when opening and closing the clutch.

This previously stated task is now solved according to the invention by the features of patent claim 1. When a synchronous speed range between the clutch input and the clutch output is reached, the clutch is closed abruptly, in particular digitally. During the transition from the serial operating state to the coupled operating state, the clutch is closed suddenly. During the transition from the coupled operating state to the serial operating state, the clutch is suddenly opened. This has the advantage that there are no discontinuities in the wheel torque curve and a quick transition from the serial operating state to the coupled operating state (and vice versa) is achieved. Thus, the purely electrical energy transfer between the generator and the at least one electric machine in the serial operating state can change into a mechanical energy transfer in the coupled operating state between the internal combustion engine and the transmission, without causing discontinuities in the wheel torque curve. The sudden closing or opening of the clutch occurs very quickly or digitally, i.e. H. the transmitted torque of the clutch plotted over time essentially corresponds to a step function. The “synchronous speed range” mentioned when closing the clutch forms an interval around the synchronization point. In order to reach the synchronous speed range and carry out a comfortable change of operating state of the hybrid drive train, vzw. the torques of the electric machine and the generator are reduced or increased in a coordinated manner. Furthermore, boost and/or generator moments can be superimposed. In addition, vzw. Additional torques, in particular correction and/or compensation torques vzw. correspondingly superimposed by the electric machine and/or the generator in order to enable the wheel torque curve to be as comfortable as possible. The disadvantages described above are therefore avoided and corresponding advantages are achieved.

• 1 in einer schematischen Draufsicht ein Kraftfahrzeug mit einem Hybridantriebsstrangs,
• 2a in einer stark schematischen Darstellung des Hybridantriebsstrangs aus 1 in einem Betriebszustand „Elektrisch Fahren“,
• 2b in einer stark schematischen Darstellung den Hybridantriebsstrang in einem seriellen Betriebszustand „Fahren und Boosten“,
• 2c in einer stark schematischen Darstellung den Hybridantriebsstrang in einem gekoppelten Betriebszustand „Fahren und Boosten“,
• 2d in einer stark schematischen Darstellung den Hybridantriebsstrang in einem Betriebszustand „Rekuperieren“,
• 2e in einer stark schematischen Darstellung den Hybridantriebsstrang in einem seriellen Betriebszustand „Fahren und Laden“,
• 2f in einer stark schematischen Darstellung den Hybridantriebsstrang in einem gekoppelten Betriebszustand „Fahren und Laden“,
• 3 in einem schematischen Diagramm die Drehzahl der Brennkraftmaschine aufgetragen über die Zeit bei einem Beschleunigungsvorgang,
• 4 in einem schematischen Diagramm das Drehmoment der Brennkraftmaschine aufgetragen über die Zeit bei dem Beschleunigungsvorgang,
• 5 in einem schematischen Diagramm das Drehmoment eines Generators aufgetragen über die Zeit bei dem Beschleunigungsvorgang,
• 6 in einem schematischen Diagramm das von der Kupplung übertragene Drehmoment aufgetragen über die Zeit bei dem Beschleunigungsvorgang,
• 7 in einem schematischen Diagramm das Drehmoment einer Elektromaschine aufgetragen über die Zeit bei dem Beschleunigungsvorgang, und
• 8 in einem schematischen Diagramm das an einer Radachse anliegende Drehmoment aufgetragen über die Zeit bei dem Beschleunigungsvorgang.

There are now a variety of possibilities for designing and developing the method according to the invention in an advantageous manner. For this purpose, reference may first be made to the patent claims subordinate to claim 1. A preferred embodiment of the invention will now be explained in more detail below with reference to the drawing and the associated description. In the drawing shows:

• 1 in a schematic top view of a motor vehicle with a hybrid drive train,
• 2a in a highly schematic representation of the hybrid powertrain 1 in an “electric driving” operating state,
• 2 B in a highly schematic representation of the hybrid powertrain in a serial operating state “driving and boosting”,
• 2c in a highly schematic representation of the hybrid powertrain in a coupled operating state “driving and boosting”,
• 2d in a highly schematic representation of the hybrid drive train in a “recuperating” operating state,
• 2e in a highly schematic representation of the hybrid powertrain in a serial operating state “driving and charging”,
• 2f in a highly schematic representation of the hybrid powertrain in a coupled operating state “driving and charging”,
• 3 in a schematic diagram the speed of the internal combustion engine plotted over time during an acceleration process,
• 4 in a schematic diagram the torque of the internal combustion engine plotted over time during the acceleration process,
• 5 in a schematic diagram the torque of a generator plotted over time during the acceleration process,
• 6 in a schematic diagram the torque transmitted by the clutch plotted over time during the acceleration process,
• 7 in a schematic diagram the torque of an electric machine plotted over time during the acceleration process, and
• 8th In a schematic diagram, the torque applied to a wheel axle is plotted over the time during the acceleration process.

The invention relates to a method for controlling a hybrid drive train 1 of a motor vehicle 2.

In 1 the motor vehicle 2 is shown in a very schematic outline. The motor vehicle 2 has four wheels 3. Two of the wheels 3 are connected to one another via a drive axle 4. The drive axle 4 and thus also the two associated wheels 3 are driven by the hybrid drive train 1.

The hybrid drive train 1 has a clutch 5. The clutch 5 has a clutch input 6 and a clutch output 7. On the clutch input side, the hybrid drive train 1 has an internal combustion engine 8, vzw. an internal combustion engine (unspecified). A generator 9 is coupled to the internal combustion engine 8. The generator 9 is connected to the clutch input 6. The internal combustion engine 8 is indirectly and functionally connected to the clutch input 6 via the generator 9.

On the clutch output side, the hybrid drive train 1 has a transmission 10 and at least one electric machine 11. The transmission 10 can be designed as a single-speed transmission or as a multi-speed transmission. The transmission 10 is connected to the clutch output 7. Furthermore, the clutch output 7 is connected to the at least one electric machine 11. Only one electric machine 11 is shown here. The electric machine 11 is vzw. designed as an electric motor. Only one electric motor is shown here. In an alternative embodiment, wheel hub motors (not shown) can also be provided as electric machines 11. The wheel hub motors can also be provided in addition to a main electric motor.

The hybrid drive train 1 also has an electrical storage means, in particular a battery 12. The battery 12 is connected via a power distributor 13 to the generator and to the electric machine 11 and vzw. connected to a board network, not shown. To supply the board network, the power distributor 13 is connected to a DC converter 14. With the DC converter 14, for example, a board network voltage of 12 volts can be provided. The battery 12 is functionally connected here to the electric machine 11 and to the generator 9 via unspecified connecting lines.

The procedure points vzw. several operating states. Preferred operating states are now determined based on the 2a until 2f explained.

In 2a An “electric driving” operating state is shown. This operating state can be selected in particular when low drive power is required. In the “electric driving” operating state, the clutch 5 is open and the internal combustion engine 8 and the generator 9 do not contribute - neither directly nor indirectly - to the drive power. The at least one electric machine 11 is fed here exclusively by electrical energy stored in the battery 12. The generator 9 does not charge the battery 12 here.

In 2d A “recuperation” operating state is shown. As in the previous operating state “Electric driving”, the generator 9 and the internal combustion engine 8 are not active. Clutch 5 is open. The “recuperation” operating state is used when braking the moving motor vehicle 2, with the electric machine 11 being used here as a further generator, whereby the brakes energy is converted into electrical energy. The electrical energy is then vzw. fed into the battery 12 via the power distributor 13. The braking energy stored in the battery 12 can then be used again for acceleration.

From the 2 B and 2e A serial operating state is shown. Clutch 5 is open. The generator 9 is driven by the internal combustion engine 8. Electrical power is generated by the generator 9, as indicated by the arrows. The electrical power is used to drive the motor vehicle 2. For this purpose, the electrical power is supplied to the network distributor 13 and forwarded from the network distributor 13 to the electric machine 11. The electrical power is therefore used to drive the motor vehicle 2 by the at least one electric machine 11.

In 2 B It is also shown that, for acceleration, additional electrical power from the battery 12 is supplied to the electric machine 11 via the power distributor 13. This process is referred to here as “boosting”.

In 2e will be in contrast to 2 B Part of the electrical power generated by the generator 9 is branched off from the power distributor 13 to the battery 12, so that the battery 12 is charged by the generator 9, while at the same time the other part of the electrical energy generated by the generator 9 is supplied to the electric machine 11.

The motor vehicle 2 can be operated in particular from a standstill up to a limit speed in the serial operating state. The limit speed is approx. at around 50 km/h. Above the limit speed, the motor vehicle 2 can be driven in a coupled operating state.

In the 2c and 2f the coupled operating state is shown. In the coupled operating state, the clutch 5 is closed, whereby a power flow is transmitted from the internal combustion engine 8 via the clutch 5 to the transmission (not shown here). In 2c It is shown that the electric machine 11 is additionally supplied with electrical energy from the battery 12 via the power distributor 13, whereby the motor vehicle 2 is “boosted”. In 2f It is shown that the internal combustion engine 8 drives the generator 9 here, whereby electrical energy is generated, which is fed into the battery 12 via the power distributor 13.

This means that both in the serial operating state and in the coupled operating state, the motor vehicle 2 can also be “boosted” with the battery 12 or the battery 12 can be charged via the generator 9. During the transition from the serial operating state to the coupled operating state, the clutch 5 is closed.

The clutch 5 is closed suddenly, in particular digitally, when a synchronous speed range between the clutch input 6 and the clutch output 7 is reached. This has the advantage that the clutch 5 is closed very quickly or “digitally”, which makes a very quick transition between the serial operating state and the coupled operating state possible. A comfortable change of operating state for the hybrid drive train 1 occurs in that the wheel torque curve (cf. 8th ) in the drive axle 4 is as continuous and “smooth” as possible. This is possible in particular by coordinately reducing and/or increasing the torques of the electric machine 11 and the generator 9, as will be described below. The torque of the electric machine 11 or the generator 9 is reduced and/or increased. by overlaying boost and/or generator moments as well as correction and compensation moments.

The clutch 5 is vzw. closed in a synchronous speed range of approx. +/- 10 revolutions/minute (speed difference between clutch input 6 and clutch output 7). During the transition from the serial operating state to the coupled operating state, the clutch 5 is closed at a speed difference of +10 revolutions/minute in overrun operation and of approximately -10 revolutions/minute in overrun operation.

Below we will refer to the 3 until 8th Referenced. The 3 until 8th show a clutch engagement and fading process during a full load start (with boost support), i.e. the transition from the serial to the coupled operating state. When changing from the coupled operating state to the serial operating state, the processes described below take place in the reverse order.

With the one in the 3 until 8th In the acceleration process shown, the clutch 5 is closed after approximately six seconds (cf. 6 ). The torque transmitted by the clutch 5 plotted over time results in a step function or occurs in a stepwise or digital manner. The clutch 5 is closed during train operation at a minimum vzw. positive speed slip of approximately +10 revolutions per minute and in overrun mode with a minimum negative speed slip of approximately -10 revolutions per minute in order to maintain the preload in the hybrid drive train 1. If necessary, the intention is to switch to the coupled operating state, but before the clutch 5 transmits any significant torque Additional torque is superimposed by the generator 9 and/or the internal combustion engine 8 in order to set the synchronous speed range.

5 shows that the generator 9 delivers a positive torque in the first second and vzw. serves as a starter for the internal combustion engine 3. Subsequently, up to the sixth second, the torque of the generator 9 essentially corresponds to the negative of the torque of the internal combustion engine 8, as shown in FIG 4 and 5 is easy to see. In other words, the energy generated by the internal combustion engine 8 is converted into electrical power by the generator 9 during the serial operating state, whereby the generator 9 supplies a negative torque.

After closing the clutch 5 at the time of “six seconds” vzw. the typically negative torque of the generator 9 is specifically increased by an additional torque up to a new setpoint. This is in 5 shown between the sixth and seventh seconds. Vzw. the new setpoint corresponds to 0 Nm. Alternatively, the generator 9 can be increased to a new setpoint value of less than 0 Nm, whereby the battery 12 is charged in the coupled operating state (cf. 2f) .

While the torque of the generator 9 is increased by an additional torque between the sixth and seventh seconds, after the clutch 5 is closed, the particularly positive torque of the electric machine 11 is reduced by a predetermined target value. After closing the clutch 5, the torque of the electric machine 11 is vzw. reduced by the amount of torque of the generator 9, whereby vzw. any intermediate translation is taken into account. Out of 5 It is clearly visible that between the sixth and seventh seconds the torque of the generator 9 is increased by an additional torque - here approx. 130 Nm. The amount of additional torque of the generator 9 corresponds to vzw. essentially the amount of additional torque of the electric machine 11.

Out of 7 It can be estimated that, between the sixth and seventh seconds, the torque of the electric machine 11 is reduced by the additional torque of the same amount, ie approximately 130 Nm, from approximately 430 Nm to 300 Nm. The torques of the electric machine 11, the generator 9 and the internal combustion engine 8 add up. essentially to the torque applied to the drive axle 4, as in 8th is shown.

In 8th It is easy to see that the torque is continuous, smooth and steady, especially in the area between the fifth and eighth seconds. The previously purely electrical energy transfer in the serial operating state between the internal combustion engine 8 and the generator 9 changes into a mechanical energy transfer in the coupled operating state between the internal combustion engine 8 and the transmission 10, without there being any discontinuities in the wheel torque curve.

This process can be superimposed by small additional torques to compensate for the additionally coupled moments of inertia of the internal combustion engine 8 and the generator 9 after the clutch 5 has been closed. Furthermore, as in the example shown here, this process can be achieved by a motor boost torque of the electric machine 11 with energy from the battery 12 (cf. 2 B and 2c ) be superimposed.

The transition can also be superimposed by a generator torque of the generator 9 for charging the battery 12 (cf. 2e , 2f) . When the clutch 5 is closed, the boost power does not have to be applied by the electric machine 11 alone, but is instead provided. distributed to various electric machines 11. For example, the generator 9 can also be used as an electric motor for this purpose, or wheel hub motors (not shown) can also be provided. Furthermore, the charging power is vzw. When the clutch 5 is closed, it is not only limited to the generator 9, but rather. the electric machine 11 is also used as a generator 9.

Reference symbol list

1

Hybrid powertrain

2

motor vehicle

3

Wheels

4

Drive axle

5

coupling

6

Clutch input

7

Clutch output

8th

Internal combustion engine

9

generator

10

transmission

11

Electric machine

12

battery

13

Power distributor

14

DC converter

Claims (16)

Method for controlling a hybrid drive train (1) of a motor vehicle (2), wherein the hybrid drive train (1) has a clutch (5) with a clutch input (6) and a clutch output (7), with an internal combustion engine (8) on the clutch input side and a connected to the A generator (9) coupled to the internal combustion engine (8) and a gearbox (10) and at least one electric machine (11) are arranged on the clutch output side, the clutch (5) being opened in a serial operating state and the generator (9) connected to the internal combustion engine (8). is driven, electrical power is generated by the generator (9) and the electrical power is used to drive the motor vehicle (2) by the at least one electric machine (11), the clutch (5) being closed in a coupled operating state and a power flow is transmitted from the internal combustion engine (8) to the transmission (10), characterized in that during the transition from the serial operating state to the coupled operating state, the clutch (5) jumps when a synchronous speed range between the clutch input (6) and the clutch output (7) is reached, in particular is closed digitally and the clutch is suddenly opened during the transition from the coupled operating state to the serial operating state. Procedure according to Claim 1 , characterized in that the clutch (5) is closed at a synchronous speed range of approximately +/- 10 revolutions / minute as a speed difference between the clutch input (6) and the clutch output (7). Procedure according to Claim 1 or 2 , characterized in that during the transition from the serial operating state to the coupled operating state, the clutch is closed at a speed difference of approximately +10 revolutions/minute in traction operation and of approximately -10 revolutions/minute in overrun operation. Method according to one of the preceding claims, characterized in that before the clutch (5) transmits a significant torque, an additional correction torque is generated by the at least one electric machine (11) and/or the internal combustion engine (8) in order to set the synchronous speed range. Method according to one of the preceding claims, characterized in that an additional torque is provided to compensate for the additionally coupled moments of inertia of the internal combustion engine (8) and the generator (9) after the clutch (5) has been closed. Method according to one of the preceding claims, characterized in that the additional torque is provided with the electric machine (11) after the transition from the serial to the coupled operating state. Method according to one of the preceding claims, characterized in that after closing the clutch (5), the particularly negative torque of the generator (9) is increased by an additional torque to a predetermined target value. Method according to one of the preceding claims, characterized in that after closing the clutch (5), the particularly positive torque of the electric machine (11) is reduced by an additional torque. Method according to one of the preceding claims, characterized in that after closing the clutch (5), the torque of the electric machine (11) is reduced by the additional torque of the generator (9), which is essentially the same amount. Method according to one of the preceding claims, characterized in that when the additional torque is provided, the electric machine (11) is powered by a battery (12). Method according to one of the preceding claims, characterized in that the additional torque is provided by the generator (9), a battery (12) being charged by the generator (9). Method according to one of the preceding claims, characterized in that the closing of the clutch (5) is superimposed by a boost torque provided by the at least one electric machine (11) for accelerating the motor vehicle (2). Method according to one of the preceding claims, characterized in that the closing of the clutch (5) is superimposed by a generator torque, the battery (12) being charged with the generator (9). Method according to one of the preceding claims, characterized in that when accelerating below a limit speed of the motor vehicle (2), the hybrid drive train (1) is operated in the serial operating state and when accelerating above the limit speed, the hybrid drive train (1) is operated in the coupled operating state. Method according to one of the preceding claims, characterized in that an additional torque is provided by the electric machine (11) and/or by the generator (9). Procedure according to Claim 15 , characterized in that before the clutch is opened, the additional torque of the generator (9) is reduced to a predetermined target value and / or the additional torque of the electric machine (11) is increased to a predetermined target value.

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