DE102008045597A1 - Method for operating hybrid-drive system of motor vehicle, involves coupling internal combustion engine with electric machine in hybrid drive by clutch, where automatic transmission is continuous transmission - Google Patents

Abstract

The method involves coupling an internal combustion engine (2) with an electric machine (4) in a hybrid drive by a clutch (5), where a composition ratio of an automatic transmission (6) is reduced in a continuous manner, while coupling the internal combustion engine with the electric machine. The automatic transmission is a continuous transmission. An independent claim is included for a hybrid-drive system of a motor vehicle.

Description

The The present invention relates to a method for operating a Hybrid drive system of a vehicle, in which in an electric operation a Torque generated by an electric machine and on a Output of an automatic transmission coupled to the electric machine is provided, and an internal combustion engine in a hybrid operation over a clutch coupled with the electric machine and in operation is taken. The present invention further relates to a hybrid propulsion system for a vehicle.

present the interest applies to a hybrid propulsion system of a vehicle, in which of an electric operation, in which the vehicle only is powered by an electric machine in a hybrid mode or an operation with the internal combustion engine switched on as required, depending on the performance requirements of the vehicle, ignored can be. This is usually a coupling between the electric machine and the internal combustion engine provided over which the electric machine optionally with the internal combustion engine rotatably coupled is. When the clutch is open, the Vehicle to be driven purely electrically by means of the electric machine, where at a corresponding acceleration request from the side the driver or in a low state of charge of a vehicle battery the Internal combustion engine is started. Because on a separate starter to dispense with starting the internal combustion engine must the starting of the internal combustion engine from the side of the electric machine respectively. The acceleration process must not be interrupted so that the starting of the internal combustion engine without loss of comfort can be made for the driver. In other words the electric machine must be designed such that she is able to drive both the vehicle and the parallel Start combustion engine.

Around the starting of the internal combustion engine from the electrical To make machine at any time, must be for the starting of the internal combustion engine required torque in electrical operation be held permanently. The circumstance has the consequence that the maximum torque or rated torque of the electric machine in the electrical operation, so for the purely electric ride can not be retrieved. Consequently, from the side of the electric Machine provided only a maximum of the lead reduced torque so that the performance of the electric Machine is significantly restricted in electrical operation.

Such hybrid drive systems can already be seen as known from the prior art. Thus, the document discloses DE 10 2006 034 934 A1 A method of operating a powertrain that includes an internal combustion engine, an electric motor, and an automatic transmission. In this known method, a torque transmission to the internal combustion engine serving to accelerate the internal combustion engine is coupled in time to a downshift in the automatic transmission. The knowledge is used that a triggered by an acceleration request of the driver downshifting the automatic transmission anyway leads to a relatively large increase in torque at the transmission output, which leads to a more or less strong, desirable jerk in the drive train at least when a strong acceleration request. By coupling the Zuschaltvorgangs the internal combustion engine with the downshifting of the automatic transmission can thus be avoided by the addition of the internal combustion engine, an additional jolt.

Further, the document discloses DE 10 2006 034 937 A1 also a method of operating a powertrain having an internal combustion engine, an electric motor, a transmission, and a clutch connecting the engine to the electric motor. In this case, the torque introduced by the electric motor into the drive train is increased before starting the internal combustion engine. In this known method, the circumstance is to be regarded as disadvantageous that the torque required for the starting process must be kept permanently in order to ensure the starting of the engine at any time. As already mentioned, this considerably limits the performance of the electrical machine in electrical operation.

Of the The present invention is based on the object, a method to provide a hybrid propulsion system and a hybrid propulsion system, where measures have been taken to improve the situation Ensure the use of the electrical machine in electrical operation wherein the starting of the internal combustion engine for the driver as possible should be made unnoticeable.

These The object is achieved by a method, which has the features of claim 1, as well as by a hybrid drive system with the features according to claim 6 solved. Advantageous embodiments of the invention are given in the subclaims.

A method according to the invention is designed for operating a hybrid drive system of a vehicle. In the method, a torque is generated in an electric mode by means of an electric machine and at an output ei provided with the electric machine coupled automatic transmission. In the method, an internal combustion engine is coupled in a hybrid operation via a coupling with the electric machine and put into operation. An essential idea is that when coupling the internal combustion engine with the electric machine, a transmission ratio of the automatic transmission is reduced.

With In other words, a basic idea of the present invention therein, at a transition from the electric operation, in which the electric machine is decoupled from the internal combustion engine, in the hybrid mode in which the electric machine with the Combustion engine is coupled, a gear ratio (Speed ratio) of the automatic transmission to reduce. The present invention has several findings based. It is based first on the knowledge that in the prior art always one for starting the internal combustion engine required torque of the electrical machine kept must be, thereby reducing the efficiency of the electric Machine is significantly restricted in electrical operation. The invention is further based on the knowledge that this can be bypassed by the electric machine in electric mode with one compared to the state of the Tech nik or compared to one assigned to a predetermined torque at the output of the automatic transmission Standard speed increased speed is operated. It is based continue on the realization that the speed of the electric Machine thereby increased compared to the prior art can be that the automatic transmission in electric mode with a in comparison to the prior art or in comparison to a predetermined desired torque assigned to the output of the automatic transmission Standard transmission ratio higher transmission ratio is operated. In other words, the automatic transmission becomes like this controlled that in electrical operation always the possibility is given, the gear ratio of the automatic transmission to reduce. Finally, the present invention lies the realization that the starting process of the internal combustion engine thereby be made almost unnoticeable for the driver can that when coupling the internal combustion engine with the electric Machine the gear ratio of the automatic operation is reduced.

In Advantageously, by the inventive Procedure achieves that stored in the electric machine Rotation energy or kinetic energy can be used to the Support starting process of the internal combustion engine. This This is possible because the electric machine is in electrical operation with an increased speed compared to the prior art is operated. Consequently, thus, for the startup process the internal combustion engine required torque reserve of the electric Machine significantly reduced and the performance the electrical machine in electrical operation better than in the state exploited the technology.

It can be provided that the process on a continuously variable transmission is applied, the gear ratio of the automatic transmission when coupling the internal combustion engine with the electric Machine is continuously reduced. In this case, the electric machine in electrical operation with a comparison to the prior art 5% to 50%, in particular by 10% to 40%, increased speed operate. Accordingly, the automatic transmission in electric mode with one compared to the prior art by 5% to 50%, in particular by 10% to 40%, increased gear ratio operate. Is the internal combustion engine with the electric Machine coupled, so does the gear ratio the automatic transmission preferably by 5% to 50%, in particular reduced by 10% to 40%. By increasing the speed of the electric machine in electric mode can be used for the starting of the internal combustion engine required torque reserve reduced and the electric machine in electrical operation better be used.

According to one alternative embodiment can be provided that the method is applied to a multi-step transmission, the transmission ratio the automatic transmission when coupling the internal combustion engine with the electric machine is gradually reduced. In this embodiment can the speed of the electric machine in electrical operation thereby be increased that the gear ratio of the automatic transmission is increased such that it at least a gear is switched back. Will the internal combustion engine coupled with the electric machine, so will the automatic transmission in this embodiment, preferably at least one Gear simultaneously upshifted and the gear ratio reduced accordingly.

An inventive hybrid drive system for a vehicle comprises an electric machine, by means of which a torque in an electric mode at an output of an automatic transmission coupled to the electric machine can be provided. The hybrid drive system includes an internal combustion engine, which is coupled in a hybrid operation via a clutch with the electric machine, and a control device for controlling a transmission ratio of the automatic transmission. In this case, the control device is adapted to the transmission ratio of the Simultaneously reduce the automatic transmission when coupling the internal combustion engine with the electric machine.

The presented with reference to the inventive method Features and in particular their benefits apply accordingly the hybrid drive system according to the invention.

Further Advantages, features and details of the invention will become apparent the following description of a preferred embodiment as well as with the enclosed drawings. Showing:

1 a schematic representation of a hybrid drive system according to an embodiment of the present invention; and

2 a course of a torque-speed characteristic of an electric machine of the hybrid drive system according to 1 ,

The Below detailed embodiment represents a preferred embodiment of the present invention Invention.

An in 1 illustrated hybrid drive system 1 represents in the present example a part of a powertrain of a passenger car. The in 1 illustrated hybrid drive system 1 but can also be used in other vehicles, such as in trucks.

The hybrid drive system 1 includes an internal combustion engine 2 , which in the present case with a dual mass flywheel 3 rotatably coupled. The internal combustion engine 2 may be, for example, a diesel engine or a gasoline engine. The hybrid drive system 1 also has an electrical machine 4 on which with the internal combustion engine 2 and the dual mass flywheel 3 via a clutch 5 , In the present example, a separating clutch, depending on demand coupled. The electric machine 4 is with an automatic operation 6 coupled.

Furthermore, in the present example, a control device 7 provided for controlling a gear ratio (speed ratio) of the automatic transmission 6 is trained. The control device 7 is further adapted to the clutch 5 to control, so close them if necessary.

At this point it should be mentioned that the automatic transmission 6 in the present example is a stepped transmission and the transmission ratio of the automatic transmission 6 is gradually changed.

In the present example is between an electric operation, in which the electric machine 4 from the internal combustion engine 2 is decoupled, and a hybrid operation in which the electric machine 4 over the clutch 5 with the internal combustion engine 2 coupled, distinguished. So it is necessary with appropriate acceleration request or a low battery state of charge, the internal combustion engine 2 with the help of the electric machine 4 to start in which the clutch 5 from the side of the controller 7 is controlled. For this purpose, usually a certain torque is required, which of the electric machine 4 for starting the internal combustion engine 2 must be provided. This particular torque is permanently maintained in electrical operation in the prior art, whereby the performance of the electric machine 4 can not be fully utilized in electrical operation. To avoid this, it is provided in the example according to the invention that the control device 7 the automatic transmission 6 such that the automatic transmission 6 is operated in electrical operation with a higher compared to the prior art gear ratio. In other words, the automatic transmission 6 operated in electric mode with a transmission ratio, which compared to a in the prior art a predetermined desired torque at the output of the automatic transmission 6 assigned standard transmission ratio or compared to a certain operating condition of the vehicle, such as a vehicle speed, usually associated transmission ratio is increased. In particular, a gear ratio is selected which involves retrieving a torque of at least 90% of a rated torque (maximum torque) from the electrical machine side 4 allows. The automatic transmission 6 is controlled, for example, such that the transmission ratio is increased by one gear compared to the prior art, the automatic transmission is thus switched back by one gear. This is the automatic transmission 6 from the side of the controller 7 further controlled such that in electrical operation is always given the opportunity to reduce the transmission ratio.

By increasing the transmission ratio of the automatic transmission 6 can in the present example the electric machine 4 be operated in electrical operation with a higher speed compared to the prior art. This also allows that at the output of the automatic transmission 6 a possibly increased torque in electrical operation compared to the prior art can be provided and the performance of the electric machine 4 can be better utilized in electrical operation compared to the prior art. At the same time starting the internal combustion engine 2 optionally at a reduced Torque reserve of the electric machine 4 to enable, when closing the clutch 5 or when coupling the internal combustion engine 2 with the electric machine 4 at the same time the transmission ratio of the automatic transmission 6 reduced or switched up the automatic transmission at least one gear. In this way, it succeeds in the electric machine 4 stored rotational energy for the starting process of the combus- tion engine 2 advantageous to use, wherein the starting of the internal combustion engine 2 practically imperceptible to the driver can be made.

2 shows an example course of a torque M as a function of a speed n of the electric machine 4 , Shown are a first characteristic 8th (dashed line) indicating the operation of the electric machine 4 Usually based in the prior art, and a second characteristic 9 (solid line), which is the electric machine 4 is based on the present invention example. The two characteristics 8th . 9 have a first area I in which the torque M is constant, and a second range II , in each of which the power of the electric machine 4 is constant, up.

How out 2 shows, lies on the first characteristic curve 8th a first working point 10 in which the electric machine 4 in the first area I , So at lower speeds n is operated in the prior art. The first working point 10 is associated with a first maximum torque M ₁ , which in the prior art by means of the electric machine 4 can be provided. To a corresponding torque reserve for starting the engine 2 is to be observed, in the prior art, the maximum torque M _{1 is} significantly smaller than a nominal torque M _{n of} the electric machine 4 selected. Usually, a torque M of about 30% of the nominal torque M _n , in particular a torque of about 50 Nm (depending on the internal combustion engine 2 ), for the starting process of the internal combustion engine 2 maintained. The first maximum torque M ₁ is thus usually about 70% of the nominal torque M _{n of} the electric machine 4 , The first working point 10 , ie the first maximum torque M ₁ for a given power of the electric machine 4 is assigned a standard speed n ₁ , with which the electric machine 4 operated in the prior art. The standard speed n ₁ is thus defined by a speed n at which the torque reserve at a given power of the electric machine 4 in electrical operation in a value range between 20% and 50% of the nominal torque M _{n of} the electric machine 4 in particular 30% of the nominal torque M _n . In other words, the standard speed n _{1 is} a speed n, at which at a given power of the electric machine 4 and a corresponding control of the Automatikge gear 6 only a torque M between 50% and 80%, in particular a torque M of about 70% of the nominal torque M _n , from the electrical machine side 4 can be retrieved.

In the example according to the invention, however, the electric machine 4 in the area I of the constant torque M with an increased speed compared to the standard speed n ₁ speed n ₂ , wherein the operation of the electric machine 4 the second characteristic 9 underlying and the transmission ratio of the automatic transmission 6 is increased accordingly. This makes it possible to provide a second torque M ₂ that is larger than ΔM by the first torque M ₁ and thus an improved use of the performance of the electric machine 4 in electrical operation. This is based on the knowledge that the rotational energy or kinetic energy of the electric machine 4 for starting the internal combustion engine 2 can be used, so that the torque M must not be kept to the extent as in the prior art. The second speed n ₂ is in the first range I chosen in particular such that at a predetermined power the torque M ₂ at least 80%, preferably at least 90%, in particular about 95%, of the nominal torque M _{n of} the electric machine 4 is. The second speed n ₂ and the second torque M ₂ is correspondingly a second operating point 11 assigned, in which the electric machine 4 operated according to the present example.

As in 2 is further shown, is due to the first characteristic 8th another working point 12 in which the electric machine 4 in the second area II , That is operated at high speeds n in the range of constant power in the prior art. The working point 12 is associated with a third torque M ₃ , which in the prior art by means of the electric machine 4 provided. The working point 12 Furthermore, a third speed n _{3 is} assigned, with which the electric machine 4 operated in the prior art. Also in the second area II is due to the shift of the second characteristic 9 with respect to the first characteristic 8th according to the present example, the electric machine 4 with a fourth speed n ₄ increased compared to the third speed n ₃ , specifically at a further operating point 13 operated. In this way, one succeeds, compared to the working point 12 increased power and possibly an increased torque M means of the electric machine 4 provide in electrical operation, wherein a due to the increased speed n ₄ increased te rotational energy in connection with an upshift of the automatic transmission 6 for a reliable star th of the internal combustion engine 2 provides.

In spite of the smaller torque reserve, the acceleration of the internal combustion engine 2 At any time, it is ensured when closing the clutch 5 the gear ratio of the automatic transmission 6 reduced. This can be done in the electric machine 4 stored rotational energy advantageous for starting the internal combustion engine 2 be used.

It should also be noted that when coupling the internal combustion engine 2 with the electric machine 4 the automatic transmission 6 at least one gear up. It is noted in the present example that the speed of the internal combustion engine 2 after its start in a predetermined reasonable value range, in particular in a value range between 800 and 1500 revolutions per minute. It is determined that the speed of the internal combustion engine 2 After starting is outside a predetermined range, so can the automatic transmission 6 to be switched up another gear.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - DE 102006034934 A1 [0004]
• - DE 102006034937 A1 [0005]

Claims (10)

Method for operating a hybrid drive system ( 1 ) of a vehicle, in which in an electric mode, a torque (M) by means of an electric machine ( 4 ) and at an output of one with the electric machine ( 4 ) coupled automatic transmission ( 6 ), and an internal combustion engine ( 2 ) in a hybrid operation via a clutch ( 5 ) with the electric machine ( 4 ) is coupled and put into operation, characterized in that when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) a transmission ratio of the automatic transmission ( 6 ) is reduced. Method according to claim 1, characterized in that the automatic transmission ( 6 ) is a continuously variable transmission and the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) is continuously reduced. A method according to claim 2, characterized in that the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) is reduced by 5% to 50%, in particular by 10% to 40%. Method according to claim 1, characterized in that the automatic transmission ( 6 ) is a step transmission and the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) is gradually reduced. A method according to claim 4, characterized in that the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) is reduced by at least one gear. Hybrid drive system ( 1 ) for a vehicle, with an electric machine ( 4 ), by means of which a torque (M) in an electrical operation at an output of a with the electric machine ( 4 ) coupled automatic transmission ( 6 ) can be provided with an internal combustion engine ( 2 ), which in a hybrid operation via a clutch ( 5 ) with the electric machine ( 4 ) and with a control device ( 7 ) for controlling a transmission ratio of the automatic transmission ( 6 ), characterized in that the control device ( 7 ) is adapted to the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) to reduce. Hybrid drive system ( 1 ) according to claim 6, characterized in that the automatic transmission ( 6 ) is a continuously variable transmission. Hybrid drive system ( 1 ) according to claim 7, characterized in that the control device ( 7 ) is adapted to the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) by 5% to 50%, in particular by 10% to 40%. Hybrid drive system ( 1 ) according to claim 6, characterized in that the automatic transmission ( 6 ) is a stepped transmission. Hybrid drive system ( 1 ) according to claim 9, characterized in that the control device ( 7 ) is adapted to the transmission ratio of the automatic transmission ( 6 ) when coupling the internal combustion engine ( 2 ) with the electric machine ( 4 ) to reduce at least one gear.