DE102016203713A1 - A method of controlling an internal combustion engine of a hydraulic hybrid drive and electronic control device for an internal combustion engine of a hydraulic hybrid drive and hydraulic hybrid drive - Google Patents

Abstract

Method for controlling an internal combustion engine of a hydraulic hybrid drive and electronic control device for an internal combustion engine of a hydraulic hybrid drive and hybrid hydraulic drive Disclosed is a control for an internal combustion engine of a hybrid hydraulic drive, in addition to the mechanical power of the engine and hydraulic power to be recuperated consumer can be supplied. As soon as power to be recuperated by an electronic control device is determined, the fuel supply to the internal combustion engine is reduced even before an overspeed occurs at the internal combustion engine.

Description

The invention relates to a method for controlling the fuel supply of a coupled to a hydraulic hybrid drive internal combustion engine according to the preamble of claim 1 and an electronic control device for such an internal combustion engine according to the preamble of claim 8 and a hydraulic hybrid drive with such an electronic control device. Here, "hydraulic hybrid drive" means a hydraulic device for power conversion, on the one hand, the mechanical power of the engine and on the other hand, the recirculated (to be recuperated) hydraulic power of a hydraulic load can be supplied.

Essentially, or normally, the internal combustion engine supplies the consumer via the hydraulic hybrid drive. In addition, hydraulic power can be recovered (recuperated) by the consumer and thus relieve the associated combustion engine or even temporarily replace it in the limit. The recovery of the hydraulic power (recuperation) via the hydraulic hybrid drive leads to a reduction of the fuel consumption of the internal combustion engine.

The main or predominant or normal power flow is directed from the engine to the consumer via the hydraulic hybrid drive. In this case, via the hydraulic hybrid drive, the torque and the speed of the internal combustion engine, for. be changed via a hydrostatic pump of the hybrid drive in cooperation with a serving as a consumer hydrostatic motor. In another example, the hydraulic hybrid drive converts the rotary power of the combustion engine into translational power via the hybrid drive hydrostatic pump and a hydrostatic cylinder serving as a consumer.

Such a hydraulic hybrid drive may thus e.g. relate to a travel drive of a vehicle, in particular a mobile work machine, wherein the consumer is a traction motor, or e.g. also relate to a boom of an excavator, the consumer is a lifting cylinder. A recovery of hydraulic power (recuperation) is in the two applications mentioned, for. possible when the vehicle whose traction motor is the consumer brakes, or when the boom of the excavator, the lifting cylinder is the consumer, is lowered.

In the publication DE 103 42 459 A1 discloses a hybrid drive called a hydraulic circuit, which is coupled to an internal combustion engine, and in which the recovery of hydraulic power via an acting as a motor hydrostatic pump or via a separate hydrostatic recuperation engine, whereby the fuel consumption of the internal combustion engine is lowered.

A disadvantage of the controls for the internal combustion engine of such hydraulic hybrid drives is that the injection quantity of the fuel of the internal combustion engine takes place in response to a change in its rotational speed (variable-speed internal combustion engine). Therefore, in practice, recuperation initially occurs in an overspeed on the internal combustion engine before the speed controller reduces the injection quantity of the fuel.

On the other hand, the object of the present invention is to provide a method for controlling an internal combustion engine coupled to a hybrid hydraulic drive and an electronic control device for such an internal combustion engine and a hybrid hydraulic drive having such an electronic control device in which an overspeed of the internal combustion engine is prevented , and in which the fuel consumption of the internal combustion engine is lowered at comparable recuperated power on.

This object is achieved with respect to the method with the features of claim 1 and with respect to the electronic control device with the features of claim 8 and with respect to the hydraulic hybrid drive with the features of claim 15.

The claimed method serves to control a fuel supply of an internal combustion engine which can be coupled or coupled to a hybrid drive. According to the invention, the fuel supply is reduced as a function of a hydraulic power fed back from a hydraulic consumer to the hybrid drive.

Further advantageous embodiments of the invention are described in the dependent claims.

Preferably, a recuperation signal, which can also be referred to as a power signal, is transmitted to a speed controller of the internal combustion engine as a function of the hydraulic power recirculated to the hybrid drive. According to the state of the art, the fuel supply is regulated by the speed regulator as a function of a desired rotational speed of the combustion engine or of a corresponding desired rotational speed signal. Thus, the recuperation signal to a speed controller of a commercial Internal combustion engine, in particular diesel engine, transmits and intervenes in its regulation.

It is particularly preferred if the recuperation reduces the target speed signal, which is transmitted to the speed controller.

The recuperation signal can in principle also increase an actual speed signal, which is transmitted to the speed controller. The recuperation signal may also reduce a fuel supply signal transmitted from the governor to a fuel supply device.

The hybrid drive can have a main pump which can be operated as a recuperation engine or a separate recuperation engine which can be connected or connected to the internal combustion engine so as to be non-rotatable. About the converted main pump or the separate Rekuperationsmotor the recirculated hydraulic power is detected by their or its speed and recuperated torque - possibly also indirectly - detected and multiplied together.

In this case, the speed of the main pump operated as a recuperation engine or of the recuperation engine may be e.g. be detected indirectly via a speed sensor on an output shaft of the internal combustion engine, which is non-rotatably connected or connectable with the main pump operated as a recuperation engine or with the recuperation engine. The speed of the output shaft of the engine can then be easily converted into the speed of the main pump operated as a recuperation engine or the recuperation engine.

Preferably, a detection of a working pressure or a corresponding input for a working pressure of the recuperation engine is provided on the control device. For this purpose, a pressure sensor arranged on the recuperation engine can be used. The working pressure of the recuperation engine can be easily converted into the torque of the recuperation engine, if this is a hydraulic unit with a constant displacement. In this case, the flow rate per revolution of the recuperation engine is understood by the stroke volume.

Preferably, however, the recuperation engine is adjustable in its stroke volume and it is provided a detection of a stroke volume or a corresponding input for a stroke volume signal of the recuperation engine.

If the main pump or the recuperation engine operated as a recuperation engine is an axial piston unit, detection of a swivel angle or a corresponding input for a swivel angle signal is preferably provided. Thus, the stroke volume can be detected indirectly via the swivel angle.

A fuel supply signal can be output from the claimed electronic control device and can be transmitted to a fuel supply device of an internal combustion engine which can be coupled or coupled to a hybrid drive. According to the invention, the fuel supply signal can be reduced as a function of a hydraulic power fed back to the hybrid drive.

If the internal combustion engine has a speed controller which has a detection of a desired speed of the internal combustion engine or an input for a corresponding desired speed signal from which or from which the fuel supply signal depends, then it is particularly preferred if a recuperation signal to the speed controller in dependence the hydraulic power returned to the hybrid drive is transferable.

In this case, the desired speed signal can be reduced via the recuperation signal, which can be transmitted to the speed controller, in particular at its input.

The claimed hydraulic hybrid drive has a drive shaft which can be coupled or coupled to an output shaft of an internal combustion engine or formed integrally therewith. Furthermore, the hybrid drive has at least one consumer connection, to which a hydraulic consumer can be connected, and can be returned to the hybrid drive via the hydraulic power. According to the invention, a previously described electronic control device is provided.

The hybrid drive can have a main pump which can be operated as a recuperation engine and which can be connected or connected in a rotationally fixed manner to the drive shaft of the hybrid drive. The recirculated hydraulic power can then be detected via or on the main pump.

The hybrid drive may have a separate Rekuperationsmotor which is rotatably connected or connected to the drive shaft of the hybrid drive. The recirculated hydraulic power can then be detected via or on the recuperation engine.

In a preferred development, the main pump which can be operated as a recuperation engine is or the separate Rekuperationsmotor in its or its stroke volume adjustable - preferably durchschwenkbar. Then, in the case of an axial piston machine, a pivot angle is adjustable and can be detected, for example, via a position sensor connected to the control device. Thus, the stroke volume can be detected indirectly via the swivel angle.

In a particularly preferred embodiment, the hybrid drive according to the invention has a hydraulic accumulator which can be connected to the consumer connection or to the consumer connections and to the main pump which can be operated as a recuperation engine or to the separate recuperation engine. Then can be cached by the consumer via the consumer connection back flowing pressure medium in the hydraulic accumulator and later supplied to the main pump or the recuperation engine. Such a hybrid drive is suitable e.g. for an excavator, in which the lifting cylinders of the boom form the consumer whose recuperative power is higher with the boom lowered than the power that can be used simultaneously by other consumers of the hybrid drive (for example the slewing gear).

An embodiment of a control according to the invention for an internal combustion engine of a hybrid drive is shown in the drawings. With reference to the figures of these drawings, the invention will now be explained in more detail.

Show it

1 a circuit diagram of a hybrid drive according to the invention with an internal combustion engine and with two consumers according to the embodiment,

2 a performance diagram of the internal combustion engine and the hybrid drive from 1 .

3 a speed-torque diagram of a control according to the prior art and

4 a speed-torque diagram of the controller according to the invention for the internal combustion engine of the hybrid drive 1 ,

1 shows a circuit diagram of the embodiment of the hydraulic hybrid drive according to the invention of an excavator with a trained as a diesel engine internal combustion engine 3 , which is mechanically coupled to the hybrid drive, and with one of two co-acting and parallel supplied differential cylinders 4 formed consumers that are coupled fluidly or hydraulically to the hybrid drive. In normal operation or essentially the rotational performance of the internal combustion engine 3 converted by the hybrid drive into fluidic or hydraulic power and to the differential cylinder 4 issued.

The hybrid drive has two pumps acting as main pumps 1 . 2 , on the drive side on the one hand with an output shaft of the internal combustion engine 3 and on the other hand are rotatably connected to an output shaft of a recuperative motor PRB which can also be operated as a pump. These non-rotatable connections are through a continuous shaft 6 symbolizes.

The two pumps 1 . 2 convey pressure medium from a tank in an open hydraulic circuit 8th via a respective work management 7 and via a valve control block 9 to a first consumer connection 10 or to a second consumer connection 12 the hybrid drive. To the first consumer connection 10 are the two annular spaces of the two differential cylinders 4 connected while to the second load port 12 the two piston bottom chambers of the two differential cylinders 4 are connected. The two annular spaces act together in the lowering of a (not shown) boom of the excavator, while the two piston crowns of the differential cylinder 4 act in the lifting direction of the boom.

The second consumer port connected to the piston crowns 12 can via a recuperation valve 14 and via a recuperation line 16 be connected to a Rekuperationsmotor PRB, which can also be operated as a pump, and the displacement is adjustable. An output shaft of the recuperation motor PRB is non-rotatable with the shaft 6 connectable or connected. This connection is with the continuous wave 6 symbolizes.

Thus, when lowering the boom, the pressure medium from the two piston bottom chambers of the two differential cylinders 3 . 4 is displaced, via the Rekuperationsventil 14 and the recuperation line 16 be supplied to the _{Rekuperationsmotor} PRB, wherein this recuperated torque T _Rekup to the shaft 6 emits. By multiplication with a predetermined and substantially constant speed n of the shaft 6 results in a recuperated power P _Rekup . According to the invention, the fuel supply of the internal combustion engine 3 reduces as soon as this recuperated power P _{Rekup is detected} on the recuperation _motor PRB. Serves an electronic control device according to the invention, which consists of an electronic recuperation control unit 18 and from a known from the prior art speed controller 22 consists. The electronic control device according to the invention reduces in dependence on the recuperation PRB recirculated hydraulic power a fuel supply signal in a signal line 20 that the speed controller 22 with a fuel supply device (not shown) of the internal combustion engine 3 combines. The recuperation control unit changes this 18 via a signal line 24 a desired speed signal such that the speed controller 22 a reduced target speed is registered. In this way, the fuel supply is reduced before an overspeed on the internal combustion engine 3 occurs, which saves fuel.

Furthermore, at the recuperation line 16 via a storage line 26 a memory 28 connected, using a storage valve 30 the connection of the recuperation line 16 with the memory 28 can be opened and closed. This is done in response to a signal from the electronic recuperation control unit 18 is issued. If z. B. the hydraulic power of the boom is lower in lowering it, as of further connected to the hybrid drive (in 1 not shown) consumers, opens the storage valve 30 so the memory 28 with that of the differential cylinders 4 back flowing pressure medium is filled. Thus, the energy of the lowered boom can also be fed with a time delay via the recuperation PRB in the power flow of the hybrid drive and the fuel supply of the engine 3 be throttled.

At an input of the recuperation engine PRB or at the recuperation line 16 is a pressure sensor 32 arranged. Furthermore, also on the connecting line between the second consumer connection 12 and the recuperation valve 14 and in the area of an input of the memory 28 a respective pressure sensor 34 . 36 intended. All pressure sensors 32 . 34 . 36 are via respective signal lines to the electronic recuperation control unit 18 connected.

At the recuperation motor PRB is a position sensor 38 provided, the signal is also transmitted via a signal line to the recuperation control unit. In the case of an axial piston machine, the position sensor 38 provided at the Schenkwiege. By means of the signals of the pressure sensor 32 and the position sensor 38 can the recuperation control unit 18 determine the recuperated power as a product of the inlet pressure and a volume flow of the recuperation motor PRB.

2 shows a performance diagram of the hybrid drive 1 , In each case, the upwardly curved arrows represent the power losses. The of the internal combustion engine 3 to the wave 6 delivered mechanical power P ₆ is from the two pumps 1 . 2 in a respective hydraulic power P _{7 of} the associated working line 7 transformed. Via the valve control block 9 becomes a part of the hydraulic power via the second consumer port 12 as hydraulic power P ₁₂ to the piston bottom chambers of the two differential cylinders 4 transferring power P ₁₂ into mechanical power upon lifting the boom (not shown).

Via the valve control block 9 Hydraulic power is also distributed to other consumers of the excavator. These are at the 2 example shown an arm 40 , a spoon 42 and a turntable 44 ,

In 2 It is shown that when lowering the boom recuperated power P _Rekup of the two retracting differential _cylinders 4 via the recuperation engine PRB to the combustion engine 3 more precisely on its output shaft 6 is transmitted. This will be a part of the mechanical power P ₆ on the shaft 6 _Covered or taken over by the recuperated power P _Rekup .

3 shows a control of the fuel supply of a hybrid hydraulic drive internal combustion engine according to the prior art. In this case, the torque T is plotted against the rotational speed n of the internal combustion engine. The result is a characteristic of the internal combustion engine curve of the maximum power T _max , which shows that the highest maximum torque T _{max is achieved} at a mean speed n.

The internal combustion engine is controlled so that its operating points on a straight line 46 lie. This line extends 46 from a setpoint speed n _{set of} the internal combustion engine 3 to the highest maximum torque T _max . The setpoint speed is z. B. 1860 revolutions per minute with a torque request of T = 0. When the requested torque increases, the speed n decreases along the straight line 46 from.

It is an exemplary operating point 48 shown with an actual torque T _act at the beginning of recuperation, which initially leads to an increase in the rotational speed n according to the arrow 50 leads. This is because in the speed controllers according to the prior art, first an increase in speed due to the relief of the recuperated power occurs before the speed controller responds to it. Due to the delayed reaction of the speed controller, the fuel supply is throttled, so that the torque T according to the arrow 52 is lowered. More specifically, the torque is lowered from the actual torque T _akt at the beginning of recuperation by the amount of recuperated torque T _Rekup .

4 shows an inventive improved control of the fuel supply of the internal combustion engine 3 with hydraulic hybrid drive. The course of the maximum torque T _{max of} the internal combustion engine 3 over its speed n, the course of the straight line 46 and the setpoint speed n _set correspond to those of the prior art according to 3 , Also, the actual torque T _act at the operating point 48 at the beginning of recuperation and the amount of recuperated torque T _Rekup correspond to those from 3 ,

According to the invention, the fuel supply is lowered at the earliest possible recuperation, so that no overspeed occurs. More specifically, starting from the operating point 48 according to the arrow 54 directly the fuel supply and thus that of the internal combustion engine 3 requested torque according to the arrow 54 lowered. Thereafter, the rotational speed n according to the arrow 56 increases until another operating point 58 on the straight 46 is reached. The control according to the invention significantly reduces fuel consumption, in particular in the case of numerous recuperation processes. In terms of control, this behavior is achieved by setting the setpoint speed n _{set of} the internal combustion engine 3 , which is set without recuperation, for example, is reduced by 90 rpm to the new _setpoint speed n _{set_neu1} , so that the straight line 46 is shifted by this amount in parallel toward lower speeds n. This is through the straight line 46 _redrawn .

Disclosed is a control for an internal combustion engine of a hydraulic hybrid drive, in addition to the mechanical power of the engine and hydraulic power to be recuperated consumer can be supplied. As soon as power to be recuperated by an electronic control device is determined, the fuel supply to the internal combustion engine is reduced even before an overspeed occurs at the internal combustion engine.

LIST OF REFERENCE NUMBERS

1

first pump

2

second pump

3

internal combustion engine

4

differential cylinders

6

wave

7

working line

8th

tank

9

Valve control block

10

first consumer connection

12

second consumer connection

14

Rekuperationsventil

16

Rekuperationsleitung

18

electronic recuperation control unit

20

signal line

22

Speed governor

24

signal line

26

storage line

28

Storage

30

memory valve

32

pressure sensor

34

pressure sensor

36

pressure sensor

38

position sensor

40

poor

42

spoon

44

slewing

46

Just

46 _new

moved straight line

48

Operating point at the beginning of recuperation

50

arrow

52

arrow

54

arrow

56

arrow

58

operating point

n

Speed of the shaft

n _set

Setpoint speed of the internal combustion engine

n _{set_new1}

changed setpoint speed of the internal combustion engine

n _{set_new2}

changed setpoint speed of the internal combustion engine

P

power

P ₆

mechanical power at the shaft

P ₇

hydraulic power in the working line

P ₁₂

hydraulic power at the second consumer connection

P _recup

recuperated performance

PRB

Rekuperationsmotor

T

torque

T _act

Actual torque at the beginning of recuperation

T _Recup

recuperated torque

T _max

maximum torque of the internal combustion engine

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10342459 A1 [0005]

Claims (18)

Method for controlling a fuel supply of an internal combustion engine which can be coupled or coupled to a hybrid drive ( 3 ), characterized in that the fuel supply in dependence of one of a hydraulic consumer ( 4 ) is lowered to the hybrid drive _recirculated hydraulic power (P _Rekup ). Method according to Claim 1, in which a recuperation _{signal is applied} to a speed controller (P _Rekup ) as a function of the hydraulic power (P _Rekup ) _fed back to the hybrid drive. 22 ) of the internal combustion engine ( 3 ) is transmitted, of which the fuel supply is also regulated in response to a target speed signal. The method of claim 2, wherein the recuperation signal lowers the target speed signal applied to the speed controller (10). 22 ) is transmitted. Method according to one of the preceding claims, wherein the hybrid drive has a pump which can be operated as a recuperation engine, or wherein the hybrid drive has a separate recuperation engine (PRB), wherein the pump or the recuperation engine (PRB) is non-rotatably connected to the combustion engine ( 3 ) is coupled or coupled, and wherein the hydraulic power (P _Rekup ) is detected by the pump or via the Rekuperationsmotor (PRB), in which its speed (n) and its torque (T _Rekup ) are detected. Method according to Claim 4, in which the rotational speed (n) is measured indirectly on an output shaft ( 6 ) of the internal combustion engine ( 3 ) is detected, which is rotatably coupled to the recuperation engine (PRB) or coupled. Method according to claim 4 or 5, wherein the torque (T _Rekup ) is _detected indirectly via a working pressure of the recuperation _engine (PRB).  The method of claim 6, wherein the working pressure is detected indirectly via a stroke volume of the Rekuperationsmotors (PRB). Electronic control device ( 18 . 22 ) from which a fuel supply signal can be output and sent to an internal combustion engine ( 3 ) is transferable, which can be coupled to a hybrid drive, characterized in that the fuel supply _signal in dependence of a _recirculated to the hybrid drive hydraulic power (P _Rekup ) is lowered. Control device according to Claim 8 with a speed controller ( 22 ), which detects a detection or an input of a desired speed signal of the internal combustion engine ( 3 ), on which the fuel supply signal depends, wherein the speed controller ( 22 ) A recuperation _{signal in response to the recirculated} to the hybrid drive hydraulic power (P _Rekup ) is transferable. Control device according to claim 9, wherein via the recuperation signal, the desired speed signal is lowered, which is connected to the speed controller ( 22 ) is transferable. Control device according to one of Claims 8 to 10, in which the hybrid drive has a pump which can be operated as a recuperation engine, or in which the hybrid drive has a separate recuperation engine (PRB) which is or can be non-rotatably connected to the combustion engine ( 3 ) is coupled or coupled, and wherein the hydraulic power (P _Rekup ) via the pump or the recuperation (PRB) is attributable to the hybrid drive, and wherein a speed (n) and a torque (T _Rekup ) of the pump or the _{Rekuperationsmotors} (PRB) are directly or indirectly detectable. Control device according to Claim 11, in which the rotational speed (n) is generated indirectly on an output shaft of the internal combustion engine ( 3 ) is detectable, which is non-rotatably coupled or coupled to the pump or to the recuperation engine (PRB).  Control device according to claim 11 or 12 with a detection of a working pressure of the pump or the Rekuperationsmotors (PRB.  Control device according to claim 13, with a detection of a stroke volume of the pump or the Rekuperationsmotors (PRB) and thus a current Rekuperationsdrehmoments from the working pressure and the displacement and with a prediction of the reduced injection quantity taking into account the Rekuperationsdrehmoments and an adjustment of the reduced injection amount indirectly via a shift the target speed. Hydraulic hybrid drive with a drive shaft ( 6 ) connected to an output shaft ( 6 ) of an internal combustion engine ( 3 ) is coupled or coupled or formed integrally therewith, and with a consumer connection ( 12 ) to which a hydraulic consumer ( 4 ) is connectable, and via the hydraulic power (P _Rekup ) is _attributable to the hybrid drive, and with an electronic control device ( 18 . 22 ) according to any one of claims 8 to 14. Hybrid drive according to claim 15, with a pump which can be operated as a recuperation engine or with a separate recuperation engine (PRB), which is or non-rotatably connected to the drive shaft (FIG. 6 ) of the hybrid drive is coupled or coupled, wherein the _recirculated hydraulic power (P _Rekup ) on the Pump or via the Rekuperationsmotor (PRB) is detectable.  Hybrid drive according to claim 16, wherein the pump or the Rekuperationsmotor (PRB) is adjustable in its or its stroke volume. Hybrid drive according to claim 16 or 17 with a hydraulic accumulator ( 28 ) connected to the consumer port ( 12 ) and with the pump or the recuperation engine (PRB) is connectable.

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