DE102012224211A1 - Method for operating hybrid car, involves adjusting objective rotation speed of combustion engine based on operating point of drive unit if actual rotation speed of combustion engine reaches target rotation speed or tolerance range - Google Patents

Abstract

The method involves connecting a clutch between a combustion engine and an electric machine. A target rotation speed (14a) of the combustion engine is provided for starting the combustion engine, where the target rotation speed is smaller than a rotation speed (13') of the electric machine. An objective rotation speed (14b) of the engine is adjusted based on an operating point of a drive unit if an actual rotation speed (15) of the combustion engine reaches the target rotation speed or a tolerance range, where the target rotation speed is determined based on a driver requested torque. An independent claim is also included for a control device for a hybrid vehicle.

Description

The invention relates to a method for operating a hybrid vehicle, namely a method for starting an internal combustion engine of the hybrid vehicle, according to the preamble of claim 1. Furthermore, the invention relates to a control device for carrying out the method.

1 shows very schematically a known from practice powertrain scheme of a hybrid vehicle, wherein such a hybrid vehicle is a drive unit 1 which comprises of an internal combustion engine 2 and an electric machine 3 is formed. Between the drive unit 1 and a downforce 4 is a transmission 5 connected. In the transmission 5 it is in particular an automatic or automated manual transmission with switching elements 8th , wherein in each gear, a first number of switching elements 8th closed and a second number of switching elements 8th is open. If a circuit is to be executed, at least one previously closed switching element 8th opened and at least one previously opened switching element 8th closed. Further shows 1 that between the internal combustion engine 2 and the electric machine 3 of the drive unit 1 a clutch 6 is switched, with the clutch open 6 the internal combustion engine 2 from the downforce 4 is decoupled and then can be silenced to the hybrid vehicle exclusively by electric motor on the electric machine 3 to operate the drive unit. Then, on the other hand, when the clutch 6 is closed, is the internal combustion engine 2 to the output 4 coupled and the hybrid vehicle can both by the internal combustion engine 2 as well as from the electric machine 3 are driven. With the electric machine 3 acts an electrical energy storage 7 together, in the motor operation of the electric machine 3 of the drive unit 1 more discharged and in generator operation of the electric machine 3 of the drive unit 1 is charged more. The operation of the internal combustion engine 2 is from a motor control device 9 , the operation of the transmission 5 from a transmission control device 10 and the operation of the electric machine 3 from a hybrid controller 11 controlled or regulated. To do this, change the control devices 9 . 10 and 11 on the one hand with the components to be controlled or to be controlled 2 . 3 . 5 and 6 and on the other hand with each other data.

Then, if such a hybrid vehicle with the clutch open 6 and with the internal combustion engine stopped 2 is operated purely by electric motor, then, if a desired drive torque from the electric machine 3 can not be applied alone, starting the engine 2 necessary. Starting the internal combustion engine 2 can be done in practice in different ways. So it is known from practice, the internal combustion engine 2 at least partially closed clutch 6 via a so-called tow start via the electric machine 3 drive. Furthermore, it is known from practice, in a state when initially open clutch 6 the internal combustion engine 2 with the help of an internal combustion engine starter 12 to start and only then the clutch 6 close when the internal combustion engine 2 over the internal combustion engine starter 12 was started. Furthermore, the starting of the internal combustion engine 2 take place via a so-called pulse start, wherein for an impulse start the electric machine 3 with the clutch open 6 accelerated to a starting speed and then by closing the clutch 6 the internal combustion engine 2 is started. The present invention relates to the cases of towing start and the Zustarts and not the so-called pulse start.

After practice is for a towing start as well as support of the internal combustion engine 2 for the internal combustion engine set a target engine speed, to which the internal combustion engine 2 is brought when starting, wherein in practice, the engine target speed greater than the speed of the electric machine 3 is. In such a start of the internal combustion engine 2 crosses the actual speed of the internal combustion engine 2 the actual speed of the electric machine 3 , that is, the actual speed of the internal combustion engine 2 becomes larger than the actual speed of the electric machine 3 becomes. In such a speed crosses the actual speeds of internal combustion engine 2 and electric machine 3 occurs for the one between the electric machine 3 and the internal combustion engine 2 switched clutch 6 transmitted moment a change from a thrust torque to a tensile torque, causing a shock excitation in the drive train of the hybrid vehicle. Such shock excitation is perceived as uncomfortable and is therefore disadvantageous.

There is therefore a need for a method for starting an internal combustion engine of a hybrid vehicle by means of a tow start or a start, in which a shock excitation for the drive train, which is caused in the prior art in speed crosses the actual rotational speeds of the internal combustion engine and electric machine, reduced or can be avoided. On this basis, the present invention based on the object to provide a novel method for operating a hybrid vehicle and a control device for carrying out the method.

This object is achieved by a method according to claim 1. According to the invention for the starting of the internal combustion engine initially set a desired engine speed, which is smaller than the rotational speed of the electric machine, wherein when an actual engine speed has reached the engine target speed or a tolerance band to the engine target Has reached rotational speed, then an internal combustion engine target speed is given, which is dependent on an operating point of the drive unit.

With the method according to the invention, initially an internal combustion engine setpoint speed, which is smaller than the rotational speed of the electric machine, is predetermined for starting the internal combustion engine. As a result, a speed crosses is initially avoided. Then, when the actual speed of the engine reaches the desired engine speed or reaches the tolerance band therearound, a change is then made from the desired engine speed to an operating point-dependent engine target speed. If the target engine speed is above the speed of the electric machine, it is possible to reduce or even avoid shock excitation for the drive train which is perceived as uncomfortable even when the speed is crossed.

Preferably, when the operating point of the power plant is a coasting point, an engine target speed greater than the target engine speed and less than the speed of the electric machine is set. Then, when the operating point of the power plant is an approximately load-free operating point, an engine target speed is set, which corresponds approximately to the speed of the electric machine.

Then, when the operating point of the power plant is a Zugbetriebspunkt, an engine target speed is set, which is greater than the speed of the electric machine.

This operating point-dependent determination of the target engine speed allows a particularly comfortable starting of the internal combustion engine depending on the operating point.

Then, if an engine target speed set greater than the rotational speed of the electric machine is, then when the engine target rotational speed has been changed to the engine target rotational speed, a precontrol torque of the electric machine is influenced in such a way, that a push-pull reversal of the torque transmitted by the clutch is at least partially compensated. Hereby, the comfort when starting the engine can be further increased.

According to an advantageous development, when the rotational speed of the electric machine is relatively large, an engine target rotational speed is predetermined, which has a relatively small distance from the rotational speed of the electric machine, whereas, when the rotational speed of the electric machine is relatively small , an engine target speed is set, which has a relatively large distance from the rotational speed of the electric machine. Such a determination of the engine target speed takes into account that at low speeds of the electric machine and therefore at a low target speed for the engine, the speed control works more imprecisely than at relatively high speeds. This also allows the comfort when starting the engine can be further increased.

According to an advantageous development, a time gradient is predefined for the target engine speed, whose deviation from the time gradient of the rotational speed of the electric machine is less than a limit value. Then, if these temporal gradients have only a slight deviation, a particularly comfortable starting of the internal combustion engine is possible.

According to a further advantageous development, when the engine actual speed has not reached the engine target speed or the tolerance band by the same within a predetermined period of time, after the expiration of the time duration, the transmission capacity of the clutch further increases and then the speed-controlled operation of the Internal combustion engine finished. Then, when the engine does not reach the target speed, the clutch is still closed to execute the starting of the engine.

The control device according to the invention is defined in claim 13.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 an exemplary diagram of a designed as a hybrid vehicle motor vehicle;

2 a diagram for illustrating the invention; and

3 a diagram for illustrating a development of the invention. The invention relates to a method for operating a hybrid vehicle and to a control device of a hybrid vehicle for carrying out the method.

1 shows a drive train scheme of a designed as a hybrid vehicle motor vehicle, in which the inventive method and the control device according to the invention 11 can be used. Regarding 1 Reference is made to the above statements.

It should be noted, however, that the invention is not limited to the powertrain configuration of the 1 is limited. Rather, the method according to the invention and the control device according to the invention can also be used in other powertrain configurations of a hybrid vehicle.

The present invention relates to a method by means of which the internal combustion engine 2 of the drive unit 1 of the hybrid vehicle can be started, either via a so-called tow start with the help of the electric machine 3 or via a so-called Zustart using the engine starter 12 ,

For starting the internal combustion engine 2 According to the invention, initially an engine nominal rotational speed is predetermined which is smaller than the rotational speed of the electric machine 3 is. Then, when an actual engine speed has reached the engine target speed or has reached a tolerance band therearound, the engine desired speed is then changed to an engine target speed that is dependent on an operating point of the prime mover 1 is.

Then, when the operating point of the drive unit 1 namely, the internal combustion engine 2 the same is a coasting point, an engine target speed is set which is greater than the engine target idle speed but smaller than the speed of the electric machine 3 is. Then, when the operating point of the output unit 1 namely, the internal combustion engine 2 , is an approximately load-free operating point, an engine target speed is set, which is approximately the speed of the electric machine 3 equivalent. Then, when the operating point of the drive unit 1 namely, the internal combustion engine 2 , is a Zugbetriebspunkt, an engine target speed is set, which is greater than the speed of the electric machine 3 is.

With such operating point-dependent specification of the target engine speed, which is changed to the same after reaching the target engine speed or the tolerance band, is a particularly comfortable start of the engine 2 possible, while avoiding perceived as uncomfortable shock excitations of the drive train, which is in the prior art at a speed crosses the actual speed of the engine 2 and the actual speed of the electric machine 3 form.

Preferred embodiments of the invention are described below with reference to 2 described, in 2 Over the time t several waveforms are plotted. So shows a waveform 13 the course of the speed of the electric machine 3 , The waveform 14a corresponds to the engine target speed and a waveform 14b the engine target speed. The waveform 15 corresponds to the actual speed of the internal combustion engine 2 , The waveform 16 visualizes the clutch pressure for the between the internal combustion engine 2 and the electric machine 3 switched clutch 6 , The waveform 17 corresponds to a pre-control torque for the electric machine 3 which is that of the clutch 6 transferred torque to compensate drive train side.

In 2 is the combustion engine at time t0 2 of the drive unit 1 of the hybrid vehicle stopped between the internal combustion engine 2 and the electric machine 3 switched clutch 6 is fully open and the hybrid vehicle is powered solely by the electric machine 3 operated. Subsequent to the time t0 is the internal combustion engine 2 be started, this being in 2 in the case of towing start is shown, in which the internal combustion engine 2 over the electric machine 3 being towed.

For such a tow start of the internal combustion engine 2 over the electric machine 3 between times t1 and t2 is a so-called quick filling for the between engine 2 and the electric machine 3 switched clutch 6 performed at time t2, the fast filling completed and the clutch 6 closed to the so-called Anlegepunkt. At the latest at the time t2 is for starting the internal combustion engine 2 control side, the engine target speed 14a for the variable speed operated internal combustion engine 2 predetermined, which is smaller than the speed of the electric machine 3 ,

2 illustrates a distance X between the speed 13 the electric machine 3 and the engine target speed 14a , wherein this distance X is preferably relatively small when the speed of the electric machine 3 is relatively large, whereas the distance X is relatively large when the speed 13 the electric machine 3 is relatively small.

As a result, at low speeds of the electric machine 3 and thus at low engine target speeds inaccurate speed control of the engine 2 Taken into account.

Starting with the time t2, the transfer capability of the between the internal combustion engine 2 and the electric machine 3 switched clutch 6 increases by increasing the clutch pressure, wherein between the times t2 and t3, the actual speed 15 of the internal combustion engine 2 initially relatively slowly and then after a firing start of the internal combustion engine 2 rises relatively quickly.

In 2 reached at the time t3, the actual speed of the engine 15 the engine target speed 14a , Accordingly, according to the invention then from the engine target speed to the engine target speed 14b changed, with the engine target speed 14b depending on the operating point of the drive unit 1 , namely from the operating point of the internal combustion engine 2 , is.

In 2 this is the operating point of the drive unit 1 namely, the internal combustion engine 2 to a train operating point, so that the engine target speed 14b greater than the speed 13 the electric machine 3 is selected.

2 can be seen that at such Zugbetriebspunktspunkt for the internal combustion engine 2 in the context of the change from the engine target speed 14a to the engine target speed 14b between the times t3 and t4, the pre-control torque 17 the electric machine 3 is influenced such that at the speed crosses of actual speed 15 of the internal combustion engine 2 and actual speed 13 of electrical machine 3 forming push-pull reverse of the clutch 6 transmitted torque is at least partially compensated. So can 2 can be taken that between the times t3 and t4, the pre-control torque 17 takes a negative sign.

The transition from the engine target speed 14a to the engine target speed 14b At time t3, such that a deviation between the temporal gradient of the speed 13 the electric machine 3 and the time gradient of the engine target speed 14b is less than a threshold. This can then be a particularly comfortable transition from overrun to train operation of the engine 2 will be realized.

At the time t4, the transfer capability of the between the internal combustion engine 2 and the electric machine 3 switched clutch 6 further increased to the clutch 6 preferably completely close, this closing operation of the clutch 6 completed at time t5. With the time t5 ends the speed control for the internal combustion engine 2 and the same is subsequently operated in a torque control.

In 2 the time t5 is achieved by the fact that at the clutch 6 there is no more slippage so that it has been completely closed. Alternatively, a time t5 at which the change from the speed control to the torque control for the internal combustion engine 2 takes place, even if present either by the electric machine 3 or the internal combustion engine 2 provided torque has been increased by more than a predetermined amount, or if a defined time has elapsed after the time t4.

Deviating from the design of the 2 can be provided that, if after the specification of the engine target speed 14a the actual speed 15 of the internal combustion engine 2 this engine target speed 14a or a tolerance band is not reached by the same, after a defined period of time, the transmission capacity of the clutch 6 is increased to the clutch 6 completely close and subsequently the speed-controlled operation of the internal combustion engine 2 to end.

According to an advantageous embodiment of the invention, the engine target speed 14a and the engine target speed 14b be determined depending on a driver's desired torque, so depending on a driver-side accelerator pedal operation.

In deviation to the embodiment of 2a can be provided, the engine target speed 14a not statically at the beginning of the process, but rather a continuous calculation of the engine target speed 14a perform. This has the advantage that with the beginning of the firing of the internal combustion engine 2 a relatively small control difference between the actual speed 15 of the internal combustion engine 2 and the target speed 14a the same exists, which then the control quality of the speed control can be improved.

In 2 was the starting of the internal combustion engine 2 described in the case of towing start. In an analogous manner, the starting of the internal combustion engine can be carried out for the so-called "Zustart", wherein when you start between the times t2 and t3, the clutch 6 is closed only to the Anlegepunkt and only if the actual speed 15 of the internal combustion engine 2 the engine target speed 14a or the tolerance band has reached around the same, and after the engine target speed 14b was changed, the transmission capacity of the between internal combustion engine 2 and the electric machine 3 switched clutch 6 starting from the application point is further increased, ie starting at the time t4. From time t4, there are no further differences from the method described above.

3 illustrates the inventive method for the case for which as an operating point for the internal combustion engine 2 there is a Zugbetriebspunkt and for which the start of the engine 2 is superimposed with a downshift.

So shows 3 not just the pressure curve 16 ' for the between the internal combustion engine 2 and the electric machine 3 switched clutch 6 , but also a pressure curve 16a ' for a switching element to be opened when the circuit is executed 8th and a pressure gradient 16z ' for a version of the circuit to be closed switching element 8th of the transmission 5 , At the time t0 ', the execution of the circuit is started, at time t1' a synchronous condition of the gear to be disengaged is exited, and at time t4 'a synchronizing condition of the gear to be engaged is achieved.

3 can be seen that when running the circuit, the speed level of the actual speed 13 ' the electric machine 3 increases. For starting the internal combustion engine 2 First, an engine target speed 14a ' chosen smaller than the speed 13 ' the electric machine 3 is, preferably such that the engine target speed 14a ' by a distance Y below a desired ratio change 18 ' the circuit to be executed is located.

With the change from the engine target speed 14a ' to the engine target speed 14b ' is waited until the synchronization of the circuit, namely the einzulegenden gear of the same, is completed. This is in 3 at time t4 'the case, so that in 3 at time t4 ', the change from the engine target speed 14a ' to the engine target speed 14b ' that is greater than the speed 15 the electric machine 3 is done.

In 3 starts at time t5 'after changing to the target engine speed 14b ' the transmission capacity of the clutch 6 further increased, at time t6 'the speed-controlled operation of the internal combustion engine 2 terminated and switched to a torque-controlled operation. In 3 is the fast filling phase for the clutch 6 At time t2 'completed, at time t3' is the firing of the internal combustion engine 2 at the tow start.

As in the embodiment of 2 takes place in the embodiment of the 3 via an influence on the pilot control torque 17 ' the electric machine 3 an at least partial compensation of the push-pull inversion of the clutch 6 transmitted moments.

Then, when a shift is executed in overrun, the engine target speed remains below the actual speed of the electric machine. There is then no change for the internal combustion engine 2 in the train operation.

The present invention further relates to a control device for carrying out the method. The control device comprises means which serve to carry out the method according to the invention.

Such a control device comprises data interfaces in order to exchange data signals with the modules involved in carrying out the method according to the invention. Furthermore, such a control device comprises a memory for storing and a processor for processing corresponding data signals.

The control device which serves to carry out the method according to the invention may be the hybrid control device 11 or also around the engine control device 9 or also to the transmission control device 10 act.

LIST OF REFERENCE NUMBERS

1

power unit

2

internal combustion engine

3

electric machine

4

output

5

transmission

6

clutch

7

electrical energy storage

8th

switching elements

9

control device

10

control device

11

control device

12

Engine starter

13, 13 '

waveform

14a, 14a '

waveform

14b, 14b '

waveform

15, 15 '

waveform

16, 16 '

waveform

16a '

waveform

16z '

waveform

17, 17 '

waveform

18 '

waveform

Claims (13)

Method for operating a hybrid vehicle, wherein the hybrid vehicle is a drive unit ( 1 ) with an internal combustion engine ( 2 ) and an electric machine ( 3 ) and between the drive unit ( 1 ) and an output ( 4 ) switched gear ( 5 ), wherein between the internal combustion engine ( 2 ) and the electric machine ( 3 ) of the drive unit ( 1 ) a coupling ( 6 ), namely method for starting the internal combustion engine ( 2 ), wherein the starting of the internal combustion engine ( 2 ) either via a tow start with the aid of the electric machine ( 3 ) at least partially closed clutch ( 6 ) or via a starter with the aid of an internal combustion engine starter ( 12 ) at initially opened clutch ( 6 ), characterized in that for starting the internal combustion engine ( 2 ) is initially set an engine target speed, which is smaller than the rotational speed of the electric machine ( 3 ), and that when an actual engine speed has reached the target engine speed or has reached a tolerance band around the target engine speed, then an engine target speed is set, which is dependent on an operating point of the drive unit ( 1 ). A method according to claim 1, characterized in that when the operating point of the drive unit ( 1 ) is a coasting point, an engine target speed is set, which is greater than the one engine target speed and less than the speed of the electric machine ( 3 ). A method according to claim 1, characterized in that when the operating point of the drive unit ( 1 ) is an approximately load-free operating point, an engine target speed is set, which is approximately the speed of the electric machine ( 3 ) corresponds. A method according to claim 1, characterized in that when the operating point of the drive unit ( 1 ) is a Zugbetriebspunkt, an engine target speed is given, which is greater than the rotational speed of the electric machine ( 3 ). Method according to claim 4, characterized in that, when the engine target rotational speed has been changed from the target engine rotational speed to a target engine rotational speed, a pre-control torque of the electric machine ( 3 ) is influenced in such a way that a push-pull reversal of the of the clutch ( 6 ) transmitted torque is at least partially compensated. Method according to one of claims 1 to 5, characterized in that when the rotational speed of the electric machine ( 3 ) is relatively large, an engine target speed is set, which is a relatively small distance from the rotational speed of the electric machine ( 3 ), whereas when the rotational speed of the electric machine ( 3 ) is relatively small, an engine target speed is set, which is a relatively large distance from the rotational speed of the electric machine ( 3 ) having. Method according to one of Claims 1 to 6, characterized in that a time gradient is predetermined for the target engine speed, the deviation of which from the time gradient of the rotational speed of the electric machine ( 3 ) is less than a threshold. Method according to one of claims 1 to 7, characterized in that when the starting of the internal combustion engine ( 2 ) of the drive unit ( 1 ) via the tow start, first between the internal combustion engine ( 2 ) and the electric machine ( 3 ) switched clutch ( 6 ) closed up to a contact point and then by increasing the transmission capacity of the coupling ( 6 ) the internal combustion engine ( 2 ) is tracked speed-controlled the engine target speed, and then that after the engine actual speed has reached the engine target speed or the tolerance band has reached by the same and from the engine target speed to the engine target Speed was changed, the transmission capacity of the between the internal combustion engine ( 2 ) and the electric machine ( 3 ) connected clutch ( 6 ) and then the speed-controlled operation of the internal combustion engine ( 2 ) is terminated. Method according to one of claims 1 to 7, characterized in that when the starting of the internal combustion engine ( 2 ) of the drive unit ( 1 ) takes place via the Zustart, first between the internal combustion engine ( 2 ) and the electric machine ( 3 ) switched clutch ( 6 ) is closed up to a contact point, and that subsequently, after the actual engine speed reaches or exceeds the target engine speed and has been transitioned from the target engine speed to the target engine speed, the transfer capability of the engine between the engine ( 2 ) and the electric machine ( 3 ) connected clutch ( 6 ) further increased starting from the Anlegepunkt and then the speed-controlled operation of the internal combustion engine is stopped. Method according to one of claims 1 to 9, characterized in that when the actual engine speed has not reached the engine target speed or the tolerance band to the same within a predetermined period of time, at the end of the period of time, the transmission capacity of the clutch ( 6 ) and then the speed-controlled operation of the internal combustion engine ( 2 ) is terminated. Method according to one of claims 1 to 10, characterized in that the engine target speed and / or the engine target speed are determined depending on a driver's desired torque. Method according to one of claims 1 to 11, characterized in that when the starting of the internal combustion engine ( 2 ) with the execution of a circuit in the transmission ( 5 is superimposed, with the change from the engine target speed from the engine target speed is waited until the synchronization of the circuit is completed. Control device of a hybrid vehicle, characterized by means for carrying out the method according to one of claims 1 to 12.

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