EP2709888A1

EP2709888A1 - Method for operating a drive train of a hybrid vehicle

Info

Publication number: EP2709888A1
Application number: EP12711133.4A
Authority: EP
Inventors: Thea SCHLÜTER; Werner Wolfgang
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2011-05-16
Filing date: 2012-03-20
Publication date: 2014-03-26
Also published as: DE102011075883A1; WO2012156127A1

Abstract

Method for operating a drive train of a hybrid vehicle which has a drive unit (1) which comprises at least an electric machine (3) and an internal combustion engine (2), and a transmission (5) which is connected between the drive unit (1) and an output (4), specifically a method for starting and/or deactivating the internal combustion engine (2) as a function of an output variable which is requested for the output (4), in particular a requested output torque or a requested output power, and as a function of a maximum output variable which can be made available by one of the electric machines (3) or by each electric machine (3), in particular a maximum output torque which can be made available or a maximum output power which can be made available, wherein in each case at defined times a difference is determined between the maximum output variable which can be made available by the electric machine (3) or by each electric machine and the requested output variable, and on the basis of this difference an increment is determined with which a counter reading is calculated, and wherein when the counter reading reaches or passes a limiting value in a counting direction, the internal combustion engine (2) is started, whereas when the counter reading reaches or passes the limiting value in an opposite counting direction, the internal combustion engine (2) is deactivated.

Description

Method for operating a drive train of a hybrid vehicle

The invention relates to a method for operating a drive train of a hybrid vehicle according to the preamble of claim 1. Furthermore, the invention relates to a control device for carrying out the method.

1 shows an exemplary drive train scheme of a hybrid hybrid vehicle designed as a parallel hybrid with a drive unit 1, which comprises an internal combustion engine 2 and an electric machine 3, known from the prior art. Between the drive unit 1 and an output 4, a transmission 5 is shown in FIG. 1 connected. Between the internal combustion engine 2 and the electric machine 3 of the hybrid drive, a clutch 6 is connected, wherein the engine 1 is decoupled from the output 4 when the clutch 6 is open, and wherein the internal combustion engine 2 is coupled to the output 4 when the clutch 6 is closed. Then, when the clutch 6 is opened and the internal combustion engine 2 is decoupled from the output 4, the internal combustion engine 2 can be stopped in a purely electric drive. FIG. 1 also shows an engine control device 7 for controlling the operation of the internal combustion engine 2. The operation of the transmission 5 is controlled by a transmission control device 8. A hybrid control device 9 regulates or controls the operation of the electric machine 3. The control devices 7, 8 and 9 exchange data between one another and with the devices 2, 3 and 5 according to the dashed arrows. The hybrid control device 9 may also be part of the engine control device 7 and / or the transmission control device 8.

In a hybrid vehicle must be decided whether the drive train can be operated purely electrically only via the electric machine 3 of the drive unit or whether in addition the engine 2 is required. This decision is made depending on whether a required output for the output 4, in particular a requested output torque or a requested output power, can be provided exclusively or alone by the electric machine 3 of the drive unit 1, or whether supporting the internal combustion engine 2 is required. The starting and stopping of the internal combustion engine 2 accordingly takes place as a function of the output quantity required for the output 4 and as a function of the maximum output quantity which can be provided by the electric machine 3, the procedure known from the prior art being shown in FIG.

In FIG. 2, over the time t, an output torque M-4 requested for the output 4 is shown for the traction operation, wherein in the traction mode the output torque required for the output is positive. Furthermore, in FIG. 2, the maximum output torque M-3-MAX-Z that can be provided in traction by the electric machine 3 is visualized, in which case the torque M requested for the output 4 is shown in FIG. 3 at the times t1, t3 and t5 -4 reaches or exceeds the maximum output torque M-3-MAX-Z that can be supplied by the electric machine 3, the combustion engine 2 starts to assist the electric machine 3 and, in the case of the exemplary parallel hydride of FIG. 1, to the output 4 by closing the engine Clutch 6 is coupled, wherein a running internal combustion engine is visualized in Fig. 2 by the signal VM-ON.

A decoupling of the internal combustion engine 2 and in the case of the exemplary parallel hydride of FIG. 1 uncoupling of the same from the output 4 takes place according to FIG. 2 after a start thereof, ie after reaching or exceeding the maximum output torque M-3-MAX that can be supplied by the electric machine 3 Z, only when the requested torque for output 4 M-4 reaches a relation to the maximum for the train operation of the electric machine 3 can be provided torque M-3-MAX-Z offset by a hysteresis offset value ΔΖ value or below. This is done in Fig. 2 at the times t2, t4 and t6. An analogous procedure is carried out for overrun operation, wherein in FIG. 2 the maximum output torque which can be provided by the electric machine 3 in overrun mode is indicated by M-3-MAX-S, with which the internal combustion engine 2 would be started or undershot in overrun mode. A shutdown of the internal combustion engine 2 would only take place in the overrun mode if a limit value offset by the hysteresis offset value AS for the overrun operation would be reached or exceeded. The procedure described with reference to FIG. 2 known from the prior art for starting and / or stopping an internal combustion engine 2 of a hybrid drive has the disadvantage that the internal combustion engine 2, if the output torque required for the output 4, that of the electric machine 3 maximum deliverable output torque in overrun operation only slightly and / or only briefly exceeds or only slightly and / or short-lived under coasting, the engine 2 is started immediately and coupled to the output 4.

A further disadvantage of the prior art is that when, for example, after states of the internal combustion engine 2, the torque requested for the output 4 remains in the torque range defined by the hysteresis offset value, the internal combustion engine 2 is not shut down and decoupled , but only when the threshold value offset by the hysteresis offset value is undershot.

On the one hand, therefore, the state of the art can lead to uncomfortable frequent starting and stopping of the internal combustion engine; on the other hand, there is the possibility that the internal combustion engine 2 is still running even though the electric machine 3 already exclusively or solely provides the output torque required for the output 4 could.

There is therefore a need for a method for operating a hybrid vehicle with which the above disadvantages can be avoided.

On this basis, the present invention based on the object to provide a novel method for operating a drive train of a hybrid vehicle and a control device for carrying out the method according to the invention.

This object is achieved by a method according to claim 1. In accordance with the invention, a difference between the maximum output quantity and the required output variable that can be provided by the or each electric machine is determined at defined times and an increment is determined on the basis of this difference, with which a counter reading is calculated, in which case the counter reading is in a counting direction Limit value is reached or happened, the internal combustion engine is started, whereas when the counter reaches or passes the limit in an opposite counting direction, the internal combustion engine is stopped.

The method according to the invention can be used in parallel hybrid vehicles and serial hybrid vehicles. The invention is therefore not limited to use in the exemplary drive train of FIG. Then, when the invention is used in a parallel hybrid vehicle, when stopping the internal combustion engine is preferably a decoupling of the same from the output and when starting the internal combustion engine, preferably a coupling of the same to the output. In hybrid series vehicles, the drive unit typically comprises several electrical machines in addition to the internal combustion engine, typically this uncoupling and coupling of the internal combustion engine when starting and stopping the same, as in hybrid electric vehicles, the or each electric machine typically permanently, including in a stopped state, on the output is coupled.

The invention proposes a completely novel procedure for setting and optionally coupling and / or stopping and optionally decoupling the internal combustion engine of a hybrid drive of a hybrid vehicle. With the method according to the invention, the disadvantages known from the prior art can all be avoided. Thus, the internal combustion engine is no longer started immediately and optionally coupled to the output, when in train a required output for the output only slightly and / or short-term exceeds the maximum output provided by the or each electric machine or when in overrun the requested output size the maximum output quantity that can be provided by the or each electric machine is only slightly and / or short-lived. Furthermore, a subsequent shutdown and optionally decoupling of the internal combustion engine is not dependent on hysteresis offset values. Overall, this can ensure a quieter, more pleasant or more comfortable behavior of the hybrid vehicle. The internal combustion engine is started less frequently and, if necessary, coupled and stopped and optionally decoupled.

According to an advantageous development, the method is used in train operation with positive output variables and in overrun operation with negative output variables, with different maps or formulas being used for the train operation and for the overrun operation for increment determination.

The different determination of the increments for train operation and overrun operation allows optimum coordination of the procedure on the train operation and overrun operation.

The control device according to the invention is preferably designed as a hybrid control device and has means for carrying out the method according to the invention.

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 shows an exemplary scheme of a hybrid vehicle known from the prior art;

Fig. 2 is a diagram for illustrating the prior art;

3 shows a diagram to illustrate the method according to the invention for operating a drive train of a hybrid vehicle; and

4 shows a signal flow diagram for further clarification of the invention. The inventive method for operating a drive train of a hybrid vehicle, namely a method for starting and / or stopping the engine 2 of the drive unit 1 of the hybrid vehicle depending on a required output for the output 4 and depending on a maximum of the or each electric machine 3 output size will be described in detail below with reference to FIGS. 3 and 4, wherein in the following description it is assumed that the output quantity is an output torque. Instead of an output torque, an output power can also be considered.

In the sense of the method according to the invention, the procedure is such that at defined times, preferably within a defined time interval, a difference between the output torque maximally provided by the or each electric machine 3 and the output torque required for the output 4 is determined and an increment based on this difference is determined, wherein a counter reading is offset with the increment, and then when the counter reading in a defined counting direction, in particular in a meter reading decreasing counting direction reaches or exceeds a threshold, in particular falls below, the engine 2 started and preferably to the output 4 is coupled, whereas when the count reaches or exceeds the limit in an opposite counting direction, in particular in a meter reading increasing counting direction, in particular exceeds, the internal combustion engine 2 is stopped and vorzugsw is decoupled from the output 4.

Using the method according to the invention, the behavior of the internal combustion engine 2 likewise shown in FIG. 3 then results for the course of the output torque M-4 required for the output 4, with a running internal combustion engine 2 coupled to the output with the engine Signal VM-ON and a quiet set and possibly decoupled from the output 4 internal combustion engine 2 with the signal VM-OFF is marked.

A comparison of FIGS. 2 and 3 shows that the frequency of starting and stopping Zens of the internal combustion engine 2 and, where appropriate, the coupling and Abkoppeins thereof from the output 4 compared to the prior art shown in FIG. 2 significantly reduced. As a result, the comfort can be increased. Furthermore, FIG. 3 shows that the use of hysteresis offset values ΔΖ and AS is dispensed with.

In the time intervals At1 and At2, in which the torque M-4 requested for the output 4 in FIG. 3 exceeds the maximum torque M-3-MAX-Z which can be supplied by the electric machine 3 during traction, no takes place on the basis of the method according to the invention Instead, this takes place in FIG. 3 only when, as shown in FIG. 3, the counter reading as a result of the ascertained increments with which the counter reading is calculated reaches or passes the limit value for the counter reading during time interval At3. Furthermore, according to FIG. 3, the internal combustion engine 2 continues to run and remains coupled to the output 4 when, during the time interval At4, the torque M-4 requested for the output 4 is the maximum torque M-3-MAX-Z which can be supplied by the electric machine 3 falls below again. Only then, when in a partially shown time interval At5 the count reaches or passes the threshold in the opposite counting direction, the engine 2 is set again and optionally decoupled from the output 4.

Further details of the method according to the invention and of the control device according to the invention, preferably designed as a hybrid control device, for carrying out the method are shown in FIG. 4, wherein FIG. 4 shows a signal flow diagram or block diagram of the method or the control device.

The triggering of the method according to the invention is visualized with a block 10 in FIG. 4, the triggering of the method according to the invention in block 10 according to blocks 1 1 initiating an initialization of a counter 12 of the control device with a starting value 13 for the counter reading of the counter 12.

4, the determination of an output torque M-4 required for the output 4 is visualized by means of a block 14, wherein in block 14 this is determined for the output torque. For example, based on a driver's request that may be derived from an accelerator operation and / or brake pedal operation, the requested output torque M-4 may be determined.

The output torque M-4 required for the output 4 can be determined by the control device according to the invention itself or provided by another control device. The determined, requested for the output 4 output torque M-4 is provided according to a block 15, wherein this provided, requested for the output 4 output torque M-4 according to the blocks 15 in the method and the control device according to the invention is further used.

As already stated, in the method according to the invention, a difference D between the maximum output torque that can be provided by the or each electric machine 3 and the output torque required for the output 4 is determined, this being indicated in FIG. 4 for the traction mode and the trailing mode by separate Signal paths is shown.

Thus, as shown in FIG. 4 for the train operation, a difference DZ between the maximum for the train operation providable positive torque M-3-MAX-Z or each electric machine 3, which is provided by the block 16, and for the train operation for the Output 4 requested positive moment M-4, this difference being shown in Fig. 4 by a block or differential images 18.

For the overrun DS is differentiated between the maximum output by the block 17 for the overrun operation of the or each electric machine 3 negative output torque M-3-MAX-S and provided by the block 15, requested for the output 4 negative output torque M. -4 through a block 19 or difference images.

The difference DZ provided in train operation by the block or differential images 18 or by the block or differential images 19 in overrun mode. Asked difference DS is converted depending on whether the drive train is operated in the train or overrun mode, via a block 20 or 21 or an incremental images in an increment lZ or IS, which is the counter 12 is supplied to the count of the same to charge with this increment. The current count of the counter 12 is output from the counter 12 as a size X.

Fig. 4 visualized by the block 22, a changeover of the method and the control device according to the invention between the train operation and the overrun, wherein a block 23 checks a switching condition between the train operation and the overrun and in the presence of the corresponding switching condition in the block or switch 22nd the switchover takes place.

The determination of the increments l-Z or I-S in the blocks 20 and 21 on the basis of the differences D-Z or D-S takes place in the respective block 20 or 21 on the basis of a characteristic field or a formula.

Block 24 of FIG. 4 illustrates a comparator which checks whether the current counter reading X of counter 12 reaches or passes a limit value specified by block 25 in a defined counting direction, in which case, if this is the case, branches to block 26 which corresponds to a logical signal for a running and coupled to the output 4 internal combustion engine.

As already stated, the increments are determined at defined times on the basis of differences between the maximum torque output torque that can be provided by the or each electric machine 3 and the output torque required for the output 4, the larger the difference in magnitude between these is the maximum output torque of the electric machine 3 and the output torque requested for the output 4.

By separating the signal paths in FIG. 4 for the traction operation and the overrun operation, the increment determination for the traction operation and the thrust operation can be determined. Drive based on individual, different maps or formulas done so that the connection and shutdown of the engine 2 and the coupling and decoupling the same to the output 4 can be tuned individually for the train operation and overrun operation.

In overrun operation, in addition to the maximum output torque that can be provided by the or each electric machine 3, an output torque which can be provided by a service brake can also be taken into account. This thrust torque which can be provided by the service brake can be added in absolute value in block 17 to the thrust torque M-3-MAX-S which can be maximally provided by the electric machine 3 so as then to start the internal combustion engine 2 with a delay.

The control device according to the invention for carrying out the method exchanges data via corresponding interfaces directly or indirectly via other control device with the components of the drive train involved. In the case where the control device according to the invention is designed as a hybrid control device 9, it exchanges data directly with the or each electric machine 3 and indirectly via the engine control device 7 with the internal combustion engine 2 in order to control the same. The activation of the clutch 6 for coupling or decoupling of the internal combustion engine 2 is effected either directly via the hybrid control device 9 or indirectly via the engine control device 7.

The means which the control device according to the invention comprises for carrying out the method according to the invention are at least one differential image according to block 18/19, at least one incremental image according to block 20/21, counter 12 and comparator 24 Operation is described above. Designation drive unit

internal combustion engine

electric machine

output

transmission

clutch

Motor controller

Transmission control device

Hybrid controller

Block / Start procedure

Block / initialization counter

Block / payer

Block / Zahlerstartwert

Block / Determining output size for output

Block / output size for output

block

Block / difference pictures

Block / incremental images

Block / switch

Block / Switchover condition Train operation Push mode Block / Comparator

Block / counter limit

block

Claims

claims

1 . Method for operating a drive train of a hybrid vehicle, which comprises a drive unit (1) comprising at least one electric machine (3) and an internal combustion engine (2) and a transmission (5) connected between the drive unit (1) and an output drive (4), namely Method for supplying and / or stopping the internal combustion engine (2) as a function of a driven variable requested for the output (4), in particular a requested output torque or a requested output power, as well as a maximum of the one or each electric machine (3) Output variable, in particular a maximum output torque or a maximally available output power, characterized in that in each case at defined times a difference between the maximum or output from the electric machine (3) output variable and the required output size determined and Grundla ge this difference, an increment is determined with which a count is calculated, in which case when the count in a counting direction reaches or passes a threshold value, the internal combustion engine (2) is started, whereas if the count is the limit in an opposite Counting direction reached or happened, the internal combustion engine (2) is stopped.

2. The method according to claim 1, characterized in that the respective increment on the basis of the difference between the maximum or output from the electric machine (3) output quantity and for the output (4) requested output quantity as well as on the basis of this difference using the map or a formula using this difference is determined.

3. The method according to claim 1 or 2, characterized in that the increment in magnitude is greater, the greater the difference in magnitude between the maximum or output from the electric machine (3) output quantity and the output (4) requested output quantity is ,

4. The method according to any one of claims 1 to 3, characterized in that the same is used in traction at positive output sizes and / or in overrun at negative output sizes.

5. The method according to claim 4, characterized in that different maps or formulas are used for the train operation and for the overrun operation for increment determination.

6. The method according to claim 5, characterized in that in overrun in addition to the maximum or output by the or each electric machine (3) output variable, in particular the maximum deployable thrust torque or the maximum deployable thrust, an over a service brake providable output size is taken into account.

7. Control device of a hybrid vehicle, in particular hybrid control device, characterized in that the same means for carrying out the method according to one of claims 1 to 6.