EP3261869A1

EP3261869A1 - Hybrid drive-train

Info

Publication number: EP3261869A1
Application number: EP16708355.9A
Authority: EP
Inventors: Thorsten MARINGER; Marco Brun
Original assignee: Deutz AG
Current assignee: Deutz AG
Priority date: 2015-02-23
Filing date: 2016-02-19
Publication date: 2018-01-03
Also published as: JP2021073128A; US20180009309A1; DE102015002111A1; CN107107736A; CN107107736B; JP2018508396A; WO2016134835A1

Abstract

The invention relates to a parallel hybrid drive train, in particular for a working machine, comprising an internal combustion engine (1), an electrical machine (2) and hydraulic aggregates (3, 4, 5, 9) for driving working devices (6-8) and for moving the working machine. In order to increase the efficiency, the rotational speed of the internal combustion engine is lowered, that is to say the load point is moved. Increased power requirements are detected via a driver input and provide a desired rotational speed. The electrical machine assists the acceleration of the internal combustion engine to said desired rotational speed.

Description

Hybrid powertrain

DESCRIPTION

The invention relates to a hybrid drive train of a vehicle, in particular a mobile work machine with an internal combustion engine and an electric machine. Such a hybrid powertrain is known from ATZ 7-8 / 2002, pages 664-674. In this case, the electric machine is connected to the internal combustion engine and a hydraulic pump.

Construction machines are usually operated in their work phases with high constant rated speeds of the internal combustion engine in order to provide the maximum system performance at high dynamic load peaks at any time. In addition, a P-grade is usually set in the engine control unit, which raises the working speed further, as soon as the maximum utilization of the internal combustion engine is not reached. If the load is higher than the maximum load of the internal combustion engine, so that the internal combustion engine is pressed or even threatens to be strangled, usually engages a load limit control, which reduces the load of the internal combustion engine at the expense of the work to be done the construction machine to the extent Induces that the rated speed can be kept stationary.

So it is set over the entire working phase, a high rated speed, which is really required only at peak loads. In the other areas, a lower rated speed of the internal combustion engine would be sufficient to provide the power just required. The reduction of the rated speed has a significant influence on the reduction of the fuel consumption of the combustion engine.

CONFIRMATION COPY machine and thus the reduction of carbon dioxide emissions (reduction of the greenhouse effect, lower environmental impact).

If you were to keep the rated speed always as low as just needed and only at appropriate load phases that can be requested very dynamic, to raise the necessary level, it would often not be enough for the internal combustion engine to increase the rated speed so dynamically that the required performance can be made available to the same extent as would be the case with a permanently high nominal speed.

Thus, while the internal combustion engine is trying to accelerate to the new higher rated speed in the case, the currently present load on the internal combustion engine counteracts the acceleration and may even cause the speed to drop rather than increase because the internal combustion engine is not fast enough to provide the necessary Can build up torque.

The object is to develop a method of increasing the torque of the entire drive train during acceleration phases of the internal combustion engine from a lower rotational speed to a higher rotational speed, with which the nominal rotational speed of construction machinery can be dynamically controlled during the working phases, without sacrificing dynamic load peaks to suffer. For this, the system must be able to accelerate dynamically from lower to higher rated speeds even with very dynamic load requirements. Thus, the rated speed of construction machinery can be maintained over a wide range at the lowest possible and efficient speed in terms of fuel consumption.

The invention is also based on the object to improve a hybrid powertrain of a vehicle. The object is achieved by a method according to claim 1 or by a device according to claim 3.

This will u. a. achieved in that the drive train has a hydraulic machine.

According to the present invention, the following advantages are achieved:

- Fuel savings by increasing the average load of the internal combustion engine, greater torque at a lower speed

- Improvement of the dynamic properties of the drive.

The illustrated embodiment employs the electric machine as an integrated starter and generator, a torque assistance of the internal combustion engine takes place in such a way that a high torque is available for a short time (<1 sec.).

Arrangement of the components

The conventional drive train of a mobile work machine, consisting of an internal combustion engine and hydraulic drive units, is extended by a parallel-arranged electric machine, which spatially replaces the flywheel. The electric machine is powered by a power electronics from an electrical energy storage and can be operated in all four quadrants.

The diesel-electric hybrid is operated speed-controlled in the given arrangement. That is, the driver's request is interpreted as a target speed. This mode of operation has established itself above all in the field of mobile machines. The diesel-electric hybrid should adjust the desired speed of the device operator, even when the load is variable, by adjusting the torque generated by the diesel-electric hybrid accordingly. The load is generated by the working hydraulics, the drive load and other outputs. The start of the internal combustion engine (VKM) is compared to the conventional drive not a separate starter motor, but directly on the electric machine. Unlike in the known powertrain, the internal combustion engine can be started within a very short period, which is approximately in the region of or below 200 milliseconds. In this way, the internal combustion engine can be operated in automatic start / stop mode.

The start / stop operation causes the internal combustion engine to operate only when it is actually needed. If the internal combustion engine is at low idle for a certain period of time, it will be shut down by the system if desired.

As soon as the device operator actuates an operating component, the internal combustion engine is immediately restarted, so that the operator perceives almost no delay. Operator components may be the accelerator pedal, the steering device, the actuation unit of the working hydraulics or the joystick. By avoiding unnecessary idle time, this feature saves fuel.

At suitable operating points, the electric machine is operated by a motor to increase the torque of the entire drive.

The required torque, which is necessary to maintain the desired speed of the device operator, is calculated by a control algorithm and implemented by the power electronics. The system takes into account all relevant states in the system such as state of charge of the energy storage, temperatures of individual components, etc.

The rated speed is the desired speed of the internal combustion engine at full load. The working speed is the currently set speed with consideration of the P degree. The work phases are phases in which the construction machine is used, that is, the internal combustion engine is loaded. In phases in which you do not work with the construction machine, the rated speed is usually placed in the low idle.

This function of dynamic speed reduction allows the use of a reduced-speed internal combustion engine. The power remains the same, which is required by the operator. The speed is lowered, but increases in accordance with the torque of the internal combustion engine.

Power = torque x speed.

Short-term peak performance can be covered by the support of the motor-driven electric machine, so that the internal combustion engine no longer has to be designed for the required / desired peak power. In this case, top performances, which are required in any case even at high nominal speeds (eg 2000 rpm), must continue to be provided by the internal combustion engine as far as possible. Here only additional power peaks are added, which arise during the acceleration phases.

Exactly these services can not be provided by the internal combustion engine quickly enough, since the speed is too low and the torque can not be applied quickly enough by the internal combustion engine alone.

In addition to boosting the coverage of power peaks, it is possible to use the motor operation of the electric machine to increase the dynamics of the powertrain.

In particular, if the injection quantity of the internal combustion engine is limited by the boost pressure-dependent filling limit below the roof curve, a motor power can be used to increase the dynamics the electric machine are applied until this limitation is no longer necessary by sufficient boost pressure.

The charging of the electrical energy storage takes place by the generation of a generator torque of the electric machine during operation. The generated torque is dependent on the state of charge of the energy storage, the utilization of the internal combustion engine and various system conditions. The torque can be switched as a manipulated variable of a controller or controlled.

Recuperation generally refers to the recovery of mechanical braking energy into electrical energy.

In conventional mobile work machines, almost the complete portion of the braking energy is achieved by the towing operation of the internal combustion engine at high speeds and by selective application of hydraulic loads.

In this configuration of a hybrid drive, the braking energy is achieved by applying a braking torque to the electric machine. As a result, on the one hand, the high engine speeds are avoided, on the other hand, the braking energy is fed via the electric machine and the power electronics in the electrical energy storage. In hybrid powertrains of mobile machines, consisting of the components of the invention internal combustion engine (diesel engine), electric machine with inverter, electric energy storage and hydraulic drive and drive, is used to reduce CO ₂ - emissions and fuel consumption, inter alia, the function of load point shift.

By means of this function, the respective operating points in the map of the internal combustion engine (torque as a function of the rotational speed) are shifted along the curves of constant power (power hyperbolas) in order to to shift the operating points of the internal combustion engine in the areas of the respective optimum fuel consumption.

When the load point is shifted from the hybrid control unit, inter alia, depending on the parameter current torque of the internal combustion engine, current torque of the electric machine, state of charge of the energy storage and current speed of the internal combustion engine and electric machine, by means of an implemented in the hybrid control unit operating strategy, the optimal target Speed determined and transferred as a setpoint to the downstream speed controller.

In this case, the optimum setpoint speed is determined on the basis of the information from the HMI interfaces (Human Machine Interface). The state of charge of the energy storage z. B. does not matter.

The speed controller of the internal combustion engine is still in the engine control unit. The speed specification, ie the setpoint speed, is determined in the hybrid control unit. The internal combustion engine is speed-controlled. The electric machine is torque-controlled. The target torque is calculated from the speed difference (see position © in FIG. 5).

Compared with conventional drive trains of mobile machines, the following advantages are available when using the load point shift function with a hybrid drive:

- In a conventional drive, a high power reserve is maintained in order to respond adequately to the load changes due to the very dynamic load changes of the driving or working drive during operation of the internal combustion engine. Especially with supercharged internal combustion engines, this power reserve is necessary to reduce the duration of the boost pressure build-up. In the case of the hybrid powertrain, it is possible to save this power reserve Significantly reduce internal combustion engine. With dynamic load changes, a motor power of the electric machine is applied until the internal combustion engine is at an operating point in which it can independently apply the requested power. This strategy is particularly favored by the rapid adjustment of the moment of the electric machine.

- The load point shift in conventional drives to lower speeds and thus higher torque is possible up to the maximum speed of the internal combustion engine, in which this applies the maximum torque. This is due to the fact that at speeds less than the maximum torque speed, a load change can quickly lead to the stalling of the internal combustion engine or leads. In hybrid powertrains here is a motor power of the electric machine used to relocate the internal combustion engine to an operating point in which this can apply the power independently.

Further advantageous embodiments of the invention are described in the drawings, in which an illustrated in the figures embodiment of the invention is described in detail.

Show it:

1 shows a schematic view of the arrangement and the interaction of the individual components

Figure 2 in a map with the function of the load point shift

Effect on specific consumption (shell diagram)

FIG. 3 shows in a characteristic diagram the function "load point shift"

FIG. 4 shows a system topology of a mildly hybrid system of a construction machine, by way of example with an electric electric machine and energy storage Figure 5 schematic diagram for determining the target speed of the internal combustion engine with dynamic

Speed reduction and the desired torque of the electric machine. An internal combustion engine 1, which is in particular a self-igniting internal combustion engine (diesel engine), is directly coupled to an electric machine 2, which is connected to the crankshaft of the internal combustion engine 1 instead of a flywheel. The stator of this electric machine 2 is connected to the crankcase and the rotor is connected to the crankshaft. The rotor is further connected to a gear pump 3 and further to an axial piston pump 4. The output of the gear pump 3 is connected via proportional valves 5 (for example) with a working cylinder 6, a lifting cylinder 7 and a steering cylinder 8. Gear pump 3 and axial piston pump 4 are hydraulic working machines.

The electric machine 2 is connected via a Vierquadrantenumrichter 12 with an electrical energy storage 13. Furthermore, a hybrid control unit 21 is provided with which all individual control devices of the components, in particular of the drive train and of the storage line, can be coordinated.

2 shows a typical characteristic diagram of an internal combustion engine (torque as a function of the rotational speed). In this map is entered as a roof curve achievable by the internal combustion engine maximum torque Md _max . Under this roof curve, the lines with constant specific (fuel) consumption are shown as shell curves, whereby, starting from the be _min line, the other lines indicate a gradually increasing consumption. Finally, the curves of constant power P _kon st (Leistungshyperbeln) of the internal combustion engine registered. In principle, the internal combustion engine, which is operated at a constant power Pkonst at the point P1, can now be operated with the same constant power Pconst at the point P2, but the point P2 lies in the be _min field. This adjustment will At the same power output, a reduction in consumption of the internal combustion engine achieved.

However, the problem with such a conventional drive train is that with such an adjustment - as shown in FIG. 3 - this is always associated with an approach to the roof curve of the achievable maximum torque. If, as shown in FIG. 3, the roof curve is approached with the power point P2 during the adjustment, the internal combustion engine no longer has any power reserves even with slight load changes and the internal combustion engine is strangled, as shown in point 4. Course with dynamic speed reduction, but without the support of the electric machine. By the embodiment of the invention but then the power that can be applied by the electric machine, additively available. In other words, it is safe to run a power adjustment to the d _max curve towards a reduction in consumption, without fear of stalling the engine when load changes, since in this case the additional power of the electric machine is available ,

P1 - P2 corresponds to the dynamic speed reduction when the load (power) remains stationary.

Dynamic displacement of the joystick (20) (HMI signal) dynamically increases the load on the load.

P2 - P3 corresponds to the course with dynamic speed reduction and support of the electric machine (2). P2 - P4 corresponds to the course with dynamic speed reduction, but without support of the electric machine (2).

P1 - P2 corresponds to the progression during load jump without dynamic speed reduction. FIG. 4 shows, in combination with FIG. 5, how the nominal rotational speed of the internal combustion engine of a construction machine can be accelerated highly dynamically during a working phase despite dynamic load peaks. For this purpose, the internal combustion engine is extended to a mild hybrid system. The extension consists of an energy storage device 13 and an electric machine 2, which can be connected both directly to the crankshaft and to a PTO (power take-off). In this case, the electric machine 2 with the associated energy storage 13 can be designed both electrically and hydraulically.

The electric machine 2 operates in the delivery or absorption of energy in comparison to the internal combustion engine 1 highly dynamically. The internal combustion engine 1 operates during its work phases with the lowest possible speed. For load requirements that require a higher speed of the internal combustion engine 1, the internal combustion engine 1 is supported during the acceleration process to the higher target speed of the electric machine 2 in parallel high dynamic, z. In phases of lower load requirement, the energy storage device 13 is recharged by means of the electric machine 2, for example, by the generator operation of the electric machine 2. The load requirement must be be detected as early as possible in order to support the Verbrennungskraftma- machine 1 very quickly with the help of the electric machine 2 in the acceleration phase can. This is done fastest by evaluating the signals of the HMI interfaces 20, such. B. the joysticks 20, operated by the operator. With the determined load request, the necessary speed of the internal combustion engine 1 - the rated speed - determined. This is set via the control unit of the internal combustion engine 22. While the internal combustion engine 1 is already trying to accelerate to the new nominal speed, it is thereby influenced by the electric motor. machine 2 with a highly dynamic torque buildup. The desired torque of the electric machine 2 is determined from the difference between rated and actual speed. The determination of the rated speed of the internal combustion engine 1 is carried out by evaluation of the HMI interfaces 20, it takes the use of a dynamic speed reduction of the internal combustion engine 1 in a construction machine with the aid of an electric machine 2. The electric machine 2 of mildly hybrid drive supports the internal combustion engine 1 highly dynamically during the acceleration phases the desired higher rated speed. The electric machine 2 is connected directly to the crankshaft or to a PTO.

The electric machine 2 with its energy storage 13 can be designed both electrically and hydraulically. For this purpose, batteries and / or capacitors and / or hydraulic accumulator come into consideration.

The method and the device are suitable in principle for all construction machines that are currently operating at high rated speeds during the work phases due to the provision of power reserves in dynamic load requirements see. A special application takes place, for example, in an industrial excavator.

The HMI signal is received via the CAN bus from the hybrid control unit, the transmission rate is in the range of about 10 m _sec or less.

The HMI signal represents z. B. is the deflection of a joystick 20 from left to right and is transmitted via CAN as a signal with a range of - 100% to + 100%.

Thus, all HMI signals are read by the hybrid control unit, which lead to an increase in the load on the internal combustion engine. All HMI signals are evaluated in the hybrid control unit 21 and calculated therefrom a desired speed for the internal combustion engine 1. The evaluation takes place via maps and a weighting factor for each HMI signal.

Rapid change of an HMI signal also results in a rapid change of the setpoint speed R in FIG. 5.

This initially results in a large difference © in FIG. 5 between the setpoint and actual rotational speeds of the internal combustion engine 1, since the internal combustion engine 1 a) can not follow the target rotational speed fast enough due to the comparatively low inherent dynamics,

b) the rapid change of the HMI signal always means a rapid load increase for the internal combustion engine 1, which counteracts a rapid adaptation of the actual speed to the target speed.

The speed difference is used to calculate the desired torque of the electric machine 2 - © in FIG. 5.

When the target actual speed becomes very fast, the target torque of the electric machine 2 quickly becomes large. In the event that the actual speed is greater than the target speed, no torque is demanded from the electric machine 2. reference numeral

1 internal combustion engine

2 electric machine

3 gear pump

4 axial piston pump

5 proportional valves

6 working cylinders

7 lifting cylinders

8 steering cylinders

9 axial piston motor

10 gear stage

1 1 drive wheels

12 four-quadrant inverters

13 energy storage

20 Human Machine Interface (HMI) - Interfaces, Joystick

21 hybrid control unit (ECU)

22 control unit of the internal combustion engine (ECU)

Claims

1. A method for dynamic speed reduction of an internal combustion engine, in particular in a construction machine, in particular with the aid of an electric machine, wherein it comprises the following steps:

Determination of the rated speed of the internal combustion engine,

Use of a dynamic speed reduction of the internal combustion engine, in particular in a construction machine, with the aid of an electric machine. In this case, the electric machine is required to support the acceleration phases of the internal combustion engine from lower speeds to higher speeds.

2. The method according to claim 1,

characterized in that the determination of the rated speed is effected in particular by an evaluation of the HMI interfaces 20.

3. hybrid powertrain of a vehicle, in particular for the application of the method according to claim 1 or 2,

characterized in that in particular a mobile work machine with an internal combustion engine (1) and an electric machine (2) is used and / or the drive train further comprises a hydraulic working machine.

4. Hybrid powertrain according to claim 1,

characterized in that the working machine comprises an axial piston pump (4). The working machine has an axial piston pump (4), is requested by the power of the internal combustion engine 1 and the electric machine (2).

5. Hybrid drive train according to one of the preceding claims, characterized in that with the working machine, a hydraulic motor, in particular an axial piston motor (9) is connected.

6. Hybrid drive train according to one of the preceding claims, characterized in that the working machine controlled at least one hydraulic actuator, in particular a working cylinder (6), a lifting cylinder (7) and / or a steering cylinder (8), in particular via one or more proportional valves ( 5) is / are interconnected.

7. Hybrid drive train according to one of the preceding claims, characterized in that the drive train is operated speed controlled.

8. Hybrid drive train according to one or more of the preceding claims,

characterized in that the hybrid drive train is controllable in the form that on the internal combustion engine (1) a load point shift is adjustable.

9. Hybrid drive train according to one or more of the preceding claims,

characterized in that a load point shift up to the area of reaching the maximum torque of the internal combustion engine (1) takes place and that then the electric machine (2) is operated by a motor.

10. Hybrid drive train according to one or more of the preceding claims,

characterized in that the electric machine (2) is a mildly hybrid drive.