DE10260435A1 - Controlling motor vehicle hybrid drive involves accelerating with electrical machine, starting engine, accelerating with electrical machine and engine with suitable operation of two clutches - Google Patents

Abstract

The method involves accelerating the vehicle with the electrical machine with a first clutch between the electrical machine and gearbox engaged and a first clutch between the electrical machine and engine disengaged, starting the engine by engaging the first clutch and accelerating using the engine and electrical machine with the first and second clutches engaged.

Description

The extension concerns a procedure for controlling a motor vehicle hybrid drive, comprising a serial Arrangement of an internal combustion engine, an electric machine, and one Transmission, in which the internal combustion engine via a first clutch is connectable to the electric machine, the electric machine via a second separating clutch can be connected on the input side to the transmission the transmission is inseparable on the output side with an axle drive communicates, and the electric machine as a starter motor generator unit is formed, with initially switched off internal combustion engine accelerating the motor vehicle using the driving force of the internal combustion engine and the electric machine is carried out.

Under a hybrid drive, one Combination of several different drive sources, e.g. an internal combustion engine, a flywheel drive, and an electric motor, understood that dependent of the respective operating situation, either alone or in combination can be used together as a vehicle drive, wherein a series arrangement or a parallel arrangement of the drive sources possible in the drive train is. The aim of using hybrid drives is the advantages of a in different operating states exploit certain drive sources and reduce their disadvantages or by using a different drive source. So will in known vehicles a combination of a relatively small, i.e. low-performance and low-torque but economical Internal combustion engine with an electric motor used to the strictest Emission limits, such as those in California / USA, for example are required to be able to comply. Here the essential Advantage of a large Range of the internal combustion engine exploited and its torque weakness when Starting and other acceleration processes by switching on as required of the electric motor can be compensated. With a frequently used Combination of an internal combustion engine with an electric motor the motor vehicle in question during a city trip or in local transport preferably operated in pure electrical mode, whereas one Long-distance travel or overland and long-distance transport favors the internal combustion engine as the drive source is being used.

Examples of hybrid drives, each consisting of a parallel arrangement of an internal combustion engine and an electric motor, are from the DE 195 30 233 A1 and the DE 199 17 665 A1 known. Hybrid drives, each consisting of a serial arrangement of an internal combustion engine and an electric motor, are exemplary in the DE 29 43 554 C2 , the DE 37 37 192 C2 , the DE 196 31 243 A1 , and the DE 199 30 793 A1 described. A method for controlling a hybrid drive with a serial arrangement of the internal combustion engine and the electric motor is in the EP 1 211 117 A1 presented. The hybrid drive on which this method is based has a serial arrangement of the internal combustion engine, an electric generator, a gear designed as a planetary gear, and an electric motor. Apart from the internal clutches and brakes of the planetary gear, no further separating clutch is provided, i.e. the internal combustion engine is inseparable from the electrical generator and this is inseparably connected on the input side to the transmission, and the transmission is inseparable from the output side with the electric motor and this is inseparable from an assigned final drive of the Motor vehicle in connection. The method provides that a starting process is initially only carried out by means of the electric motor. If necessary, the internal combustion engine can be started and switched on at a later point in time, the engine being operated in a specifically favorable full-load range and the excess drive power being taken up by the generator and fed into a battery, which can also serve to supply the electric motor, among other things. This method makes it clear, by way of example, that the control methods used in each case essentially depend on and are matched to the specific design of the hybrid drive, in particular the design of the electric motor or the electric machine and the use and arrangement of separating clutches between the components, and that a control method for a certain design of a hybrid drive is not readily transferable to another design.

This is from a motor vehicle assumed a hybrid drive, which in a known manner from a row arrangement of an internal combustion engine, an electric machine, and a transmission, the power flow between these assemblies each over there is a disconnect clutch. The electric machine is a starter-motor-generator unit trained and can therefore with appropriate electrical shading as an electric starter to start the internal combustion engine, as an electric motor to drive the motor vehicle, and as an electric generator for charging an electrical store, e.g. a battery. at the transmission assembly, consisting of the actual transmission and the upstream second clutch, it can be optional an automated manual transmission (ASG), a double clutch transmission (DKG), which is known to have two input shafts, each with an associated one Coupling, and a continuously variable transmission (CVT) act.

In a vehicle with such a Hybrid drive is a starting process according to the prior art such that when the second clutch is open, the first clutch is first closed and the internal combustion engine is started by means of the electric machine before the actual starting process, i.e. the acceleration of the vehicle from standstill, by closing the second separating clutch begins using the driving force of both drive sources. In a similar manner, an acceleration process from a run in electrical operation, that is to say with the internal combustion engine switched off, takes place in accordance with the prior art in such a way that the second separating clutch is first opened in order to decouple the electric machine from the transmission and the downstream final drive, and then the first Disengaging clutch is closed and the internal combustion engine is started by means of the electric machine before the actual acceleration process of the vehicle starts while driving by closing the second disengaging clutch using the driving force of both drive sources. In both cases, there is a clearly perceptible deceleration in the acceleration behavior for the driver, ie in the reaction to the driver's performance request, which is known to be given by the change and the rate of change of the accelerator pedal position and is detected by assigned sensors. This circumstance can lead to an overreaction of the driver when the accelerator pedal is operated, which in the end results in an unintentionally strong acceleration of the motor vehicle, which is disadvantageously associated with increased fuel consumption and loss of comfort.

It is therefore the problem of the present invention a starting process in a hybrid vehicle of the type mentioned at the beginning (Acceleration when the vehicle is stationary) and a acceleration process from pure electrical operation, i.e. with each turned off Internal combustion engine to perform with a better response and in terms of lower fuel consumption and improved driving comfort to optimize.

The problem is solved according to the invention in that at the beginning switched off internal combustion engine accelerating the motor vehicle using the driving force of the internal combustion engine and the electric machine performed like this is that the acceleration of the motor vehicle initially only by means of the electric machine with the second clutch disconnected and more open first separating clutch performed is that then the internal combustion engine by closing the first clutch with the second clutch still closed is started, and that the subsequent acceleration of the motor vehicle by means of the internal combustion engine and the electric machine when closed first clutch and closed second clutch.

Advantageous embodiments of the control method according to the invention are in the subclaims 2 to 10 specified.

Due to the initial acceleration of the motor vehicle by means of the electric machine, on the one hand, a quick response behavior of the hybrid drive to the driver's performance requirements and on the other hand the specific performance of the electric machine, i.e. maximum torque output at standstill and relatively low speed, exploited in an optimal way. Because the driver has a spontaneous reaction of the motor vehicle on his acceleration request, which he entered as a command in the form of a more or less wide and quick step through of an accelerator pedal, becomes an overreaction of the driver and consequently also an unintentionally strong, consumption-intensive and uncomfortable acceleration of the motor vehicle avoided. By subsequently starting and switching on the internal combustion engine the acceleration process is largely largely steadily continued. Overall, there is a real acceleration curve, the ideal, linear, steady increase in vehicle speed comes very close. The process does not require a specific design for the disconnect couplings, but is with a hybrid drive of the type mentioned all known coupling types, e.g. Dry clutches with passive or active pressure and wet clutches, in particular Multi-plate clutches, applicable.

To avoid an output side i.e. in the transmission, the downstream final drive and the drive wheels of the Effective motor vehicle, torque drop while starting the internal combustion engine, the one felt by the driver and an uncomfortable delay, or at least one Reduction in acceleration of the motor vehicle would result the power output of the electric machine, i.e. that of the electric machine output torque, through appropriate electrical shading beneficial during of the starting process increased.

To avoid torque fluctuations on the transmission side while starting the internal combustion engine, especially at the beginning and towards the end of the elevated Output of the electrical machine and at the beginning of the output of the internal combustion engine, the second separating clutch is appropriately partially open or even operated at the slip limit, because then possibly occurring Torque peaks to a slip operation of the second clutch to lead and therefore for the driver is hardly noticeably erased or smoothed.

With the acceleration process that follows the method according to the invention is controlled, it can be a start-up process from the vehicle standstill, the vehicle speed being zero or almost zero, and depending on its design, the second clutch can initially be open or already closed depending on its idle state. In largely identical form, however, the method is also particularly suitable for controlling an acceleration process from a drive in purely electrical operation, the second separating clutch then necessarily being initially closed regardless of its design.

In addition to the above Features of the invention can additionally result in one of the acceleration processes described driving comfort is increased and fuel consumption is reduced, that the driver's performance requirement is recorded and evaluated, and that the driver's desired acceleration is limited to a maximum acceleration, the power requirement of the Driver in a known manner by detecting the accelerator pedal position and the rate of change the accelerator pedal position can be determined. With the same objective can limit the maximum acceleration of the motor vehicle a downshift suppressed in the transmission become. After the start of the internal combustion engine expediently removed the limitation of the maximum acceleration, this being the case to improve driving comfort to achieve a constant change in acceleration advantageous according to a damping function he follows.

Further details of the invention result from the following detailed description and the attached Drawings that serve as examples to explain the method according to the invention serve.

Show:

1 An acceleration process controlled according to the invention in the form of a time diagram,

2 an acceleration process controlled according to the prior art in the form of a time diagram, and

3 the construction of a hybrid drive on which the method according to the invention is based in the form of a schematic diagram.

The inventive method for controlling the acceleration process of a motor vehicle is a 3 The illustrated hybrid drive HA, which comprises a serial arrangement of an internal combustion engine VM, an electric machine EM, and a transmission G, in which the internal combustion engine VM can be connected to the electric machine EM via a first disconnect clutch K1, and the electric machine EM via a second disconnect clutch K2 on the input side can be connected to the transmission G, and the transmission G is inseparably connected on the output side to an axle drive (not shown here). The electric machine EM is designed as a starter-motor-generator unit and is intended for use as an electric starter for starting the internal combustion engine VM, as an electric motor for driving the motor vehicle, and as an electric generator for charging an electrical energy store, for example a battery.

According to the prior art, an acceleration process takes place when the internal combustion engine VM is initially switched off, as in FIG 2 shown from. The curve 1 shows the time course of the engine speed n _{VM of} the internal combustion engine VM, curve 2 the time course of the operating state of the first clutch K1, curve 3 the time course of the operating state of the second clutch K2, and curve 4 the time profile of the vehicle _speed v _Fzg , the time being denoted by t. The second clutch K2 is disengaged during a start-up process, ie vehicle _acceleration from standstill (V _vehicle ~ 0 km / h) (see partial curve 3a ) and the start-up process begins with the driver's power request, that is, an actuation of the accelerator pedal, at time t ₀ . As a result, the vehicle _speed v _{Fzg increases} according to a target curve according to the sub-curve 4a linear on. In the case of acceleration from a quasi-stationary drive in pure electric _mode , ie with a speed v _vehicle > 0 km / h and a closed second clutch K2 (see sub-curve 3b ), the second clutch K2 must be opened beforehand (see partial curve 3c ). Then, identical to both acceleration cases, the internal combustion engine VM is started by closing the first separating clutch K1, which begins at the time t _K1 , by means of the electric machine EM (see partial curve 2a ). After starting the internal combustion engine, it must first be ramped up to a minimum speed (see sub-curve 1a ) before closing the second clutch K2 (see partial curve 3d ), which begins at time t _K2 , the motor vehicle according to the actual course according to the sub-curve 4b is actually accelerated, wherein both the driving force of the internal combustion engine VM and the driving force of the electric machine are used. At time t _Z , the target speed, which is essentially determined by the driver operating the accelerator pedal, is reached and the acceleration process is ended.

Like a comparison of the actual course (partial curve 4b ) the vehicle _speed v _vehicle with the set course (partial curve 4a ) shows, the actual acceleration of the motor vehicle is disadvantageous with a significant deceleration and relatively inharmonic. This can provoke an overreaction on the part of the driver, ie an exaggerated actuation of the accelerator pedal, which leads to an unintentionally strong acceleration supply, combined with increased fuel consumption and further loss of comfort.

In contrast to this, an acceleration controlled according to the method according to the invention proceeds as in 1 shown from. Here, the acceleration of the motor vehicle begins practically immediately after the driver's corresponding performance request by means of the electric machine EM at time t ₀ . In the case of starting (see sub-curve 3a ) the second separating clutch K2 becomes part of the curve 3d closed (t _K2 = t ₀ ) and the electric machine EM switched on. In the case of acceleration from driving in electric mode (see sub-curve 3b ), the second clutch K2 is already closed and only the power or torque output of the electric machine is increased accordingly to achieve the desired initial acceleration. From the point in time t _K1 , the internal combustion engine VM is activated by closing the first clutch K1 (see sub-curve 2a ) started and ramped up to the minimum speed (see partial curve 1a ). Thereafter, the motor vehicle is accelerated further using the driving forces of the internal combustion engine VM and the electric machine EM until the target speed is reached at time t _Z. When the internal combustion engine VM is started by the electric machine EM and the internal combustion engine VM is started up, the second separating clutch K2 becomes advantageous, as in a partial curve 3e shown, partially opened to compensate for torque peaks by occasional frictional slip and thus to avoid torque fluctuations on the output side.

In the control of the acceleration according to the invention, the comparison of the actual profile (partial curve 4b ) the vehicle _speed v _vehicle with the set course (partial curve 4a ) that the actual acceleration of the motor vehicle now starts advantageously without noticeable deceleration and runs relatively harmoniously. The deviations of the actual course 4b from the target course 4a are now relatively low, so that there is a relatively steady course of acceleration compared to the prior art 2 is associated with greater comfort and lower fuel consumption.

1

Time course of the engine speed n _{v M}

1a

begin and start-up of the internal combustion engine VM

2

over time the operating status of K1

2a

Closing of K1

3

over time the operating status of K2

3a

initial state when starting (K2 open)

3b

initial state at the beginning Electric drive (K2 closed)

3c

Opening of K2

3d

Closing of K2

3e

partial opening of K2 (lowering the clutch capacity)

4

Time course of the vehicle _speed V _vehicle

4a

desired course

4b

Actual characteristic

EM

electric machine

G

transmission

HA

hybrid drive

K1

first separating clutch

K2

second separating clutch

n _VM

Engine speed

t

time

t ₀

beginning the vehicle acceleration

t _K1

beginning of the closing process from K1

t _K2

beginning of the closing process from K2

t _Z

The End vehicle acceleration, reaching the target speed

v _vehicle

vehicle speed

VM

internal combustion engine

Claims (10)

Method for controlling a motor vehicle hybrid drive, comprising a serial arrangement of an internal combustion engine VM, an electric machine EM, and a transmission G, in which the internal combustion engine VM can be connected to the electric machine EM via a first disconnect clutch K1, the electric machine EM via a second disconnect clutch K2 can be connected on the input side to the gearbox G, the gearbox G is inseparably connected to an axle drive on the output side, and the electric machine EM is designed as a starter-motor-generator unit, with the internal combustion engine VM initially shut off, an acceleration process of the motor vehicle using the driving force of the internal combustion engine VM and the electric machine EM is carried out with the following method steps: acceleration of the motor vehicle by means of the electric machine EM with the second clutch K2 closed and the first clutch K1 open, starting the engine VM by means of a lock Eat the first clutch K1, - acceleration of the motor vehicle by means of the internal combustion engine VM and the electric machine EM with the first clutch K1 closed and the second clutch K2 closed. A method according to claim 1, characterized in that to avoid a drop in torque on the output side during the Starting the internal combustion engine, the power output of the electric machine EM increased becomes. A method according to claim 1 or 2, characterized in that that to avoid torque fluctuations on the output side during the Starting the internal combustion engine VM partially the second clutch K2 open becomes. A method according to claim 3, characterized in that the second clutch K2 during the start of the internal combustion engine VM is operated at the slip limit. Method according to one of claims 1 to 4, characterized in that that the acceleration process from the vehicle standstill carried out as a starting process becomes. Method according to one of claims 1 to 4, characterized in that that the acceleration process with initially closed second Separating clutch K2 from a drive in pure electrical mode carried out becomes. Method according to one of claims 1 to 6, characterized in that that the driver's performance requirement is recorded and evaluated, and that the driver's desired acceleration is limited to a maximum acceleration. Method according to claim, characterized in that limit the maximum acceleration of the motor vehicle a downshift suppressed in the transmission G. becomes. A method according to claim 7 or 8, characterized in that the limitation of maximum acceleration after starting the Internal combustion engine is lifted. A method according to claim 9, characterized in that the lifting of the limit on maximum acceleration A steady acceleration change is achieved according to a damping function.