DE102008050942B4 - Flywheel accumulator system and method of controlling such a system - Google Patents

Abstract

System with a flywheel accumulator, a flywheel (6) being mounted so that it can rotate relative to a flywheel shaft (4), the flywheel shaft (4) being connected to a motor (1) via a manual transmission (3), i.e. a transmission (3) with a controllable number of gear ratios. is connected, with field coils (5) which can be charged with current being arranged on the flywheel shaft (4) in order to generate an exciter field, with a squirrel-cage cage being connected with the flywheel (6), with the field coils (5) on the flywheel shaft (4) in the circumferential direction are arranged one after the other in order to generate a radially oriented magnetic field in the same radial and axial area, with the energization being carried out in such a way that adjacent field coils each generate an oppositely directed magnetic field, with an exciter (7) being arranged on the axial end area of the flywheel shaft (4), the rotatably mounted part, i.e. rotor, is connected to the flywheel shaft (4), the field coils (5) consisting of the rotatably mounted part l an exciter (7) are supplied with electricity, with the stationary part, i.e. the stator, of the exciter (7) comprising field excitation coils charged with direct current and the rotatably mounted part of the exciter (7) comprising a three-phase winding, with a rectifier being fed from the three-phase winding which electrically supplies the field coils (5) arranged on the flywheel shaft (4), with the flywheel shaft (4) being the output shaft of the gearbox (3), i.e. output shaft, or being connected to it and the motor shaft (2) being the input shaft of the gearbox ( 3) is or is connected to it, with at least two gear ratios of the gear ratios that can be selected with the gear (3) being reciprocal to one another, the gear ratio ILADEN of the manual gear (3) being greater than 1 when the flywheel (6) is charged.

Description

The invention relates to a system with a flywheel accumulator and a method for controlling such a system.

It is known to provide a generator on an internal combustion engine shaft, from which a motor can be fed, by which a flywheel is driven. The engine and generator are designed for the maximum permitted power, i.e. as large as possible and are therefore expensive and bulky.

Examples of such systems are from U.S. 5,384,521A , DE 195 18 672 A1 and DE 33 12 185 C2 known.

The invention is therefore based on the object of making it possible to achieve high dynamics when operating a drive system.

According to the invention, the object is achieved with a system with a flywheel accumulator according to the features specified in claim 1 and with a method for controlling according to the features specified in claim 6.

Important features of the invention in the system with a flywheel accumulator are that a flywheel is mounted so that it can rotate relative to a flywheel shaft, with field coils that can be charged with current being arranged on the flywheel shaft, in particular for generating an excitation field, with a squirrel cage being connected to the flywheel.

The advantage here is that the current fed into the field coils can be controlled and thus the coupling of the flywheel shaft to the flywheel can be controlled. In this way, when there is no current or depending on the current, the coupling for energy transmission to the flywheel can be controlled. In particular, the removal of energy from the flywheel can be controlled in that the electromagnetic coupling strength between the flywheel shaft and the flywheel can be specified using the current strength in the field coils.

In the configuration according to the invention, the field coils on the flywheel shaft are arranged one after the other in the circumferential direction, in particular to generate a radially oriented magnetic field, in particular in the same radial and/or axial area., In particular, the energization is carried out in such a way that adjacent field coils generate a respective opposing magnetic field . The advantage here is that the strength of the magnetic field generated by the field coils can be controlled, the course of the field lines being essentially the same as that which would be generated by permanent magnets if these were again arranged with alternating magnetic orientation in the circumferential direction.

In the embodiment according to the invention, the field coils are electrically supplied from the rotatably mounted part of an exciter, the stationary part of the exciter comprising field excitation coils and the rotatably mounted part of the exciter comprising a three-phase winding. The advantage here is that the supply can be carried out without contact and the control of the current in the field coils can be carried out from the stationary part.

In the embodiment according to the invention, a rectifier is fed from the three-phase winding for the electrical supply of the field coils arranged on the flywheel shaft. The advantage here is that the field coils can be supplied with a unipolar current.

In an advantageous embodiment, the squirrel cage is designed in the manner of a squirrel cage of an external rotor asynchronous motor. The advantage here is that a simple, cost-effective design is made possible.

In an advantageous embodiment, the flywheel shaft is connected directly or indirectly to an engine shaft of an engine, in particular an internal combustion engine. The advantage here is that energy generated by the engine or kinetic energy of the vehicle can be temporarily stored on the flywheel, which means that energy can be saved. The direct connection of the flywheel to the engine means that there is no need to convert the kinetic energy generated by the engine into electrical energy, which in turn is converted into mechanical rotational energy of the flywheel, and the efficiency and dynamics can therefore be improved.

In the embodiment according to the invention, the flywheel shaft is the output shaft of a transmission, in particular the output shaft, or is connected to it, and the motor shaft is the input shaft of a transmission or is connected to it. The advantage here is that a gear for speed increase or speed reduction can be interposed. Thus, the speed difference between the flywheel shaft and the flywheel and thus also the slip can be changed accordingly, with the torque changing in turn with the slip.

In an advantageous embodiment, the transmission is designed with a discretely or continuously controllable number of gear ratios; in particular, this is Transmission a manual transmission. The advantage here is that the slip can be adapted as optimally as possible to the speeds and the desired torques.

In the embodiment according to the invention, at least two transmission ratios of the transmission ratios that can be selected with the transmission are reciprocal to one another. The advantage here is that the transmission is particularly simple and inexpensive to produce.

Important features of the method for controlling a system with a flywheel accumulator are that a flywheel is rotatably mounted relative to a flywheel shaft, with a gear being arranged between the motor driving the flywheel shaft and the flywheel shaft, the gear ratio of which is specified, with the loading of the flywheel accumulator Gear ratio is selected higher than when discharging the flywheel accumulator.

The advantage here is that with the speed that can be adjusted via the gearbox, improved efficiency when charging and discharging the flywheel accumulator and also higher dynamics can be achieved.

What is important in the invention is that the entire system is based on the combination of switchable gears and asynchronous motors. The main advantage is that you no longer need your own electric generator on the internal combustion engine shaft and a separate electric motor with flywheel, but only the easy-to-manufacture gearbox and a flywheel that is easy to design and produce.

Further advantages result from the dependent claims.

• In der 1 ist eine erfindungsgemäße Vorrichtung schematisch skizziert.

The invention will now be explained in more detail with reference to figures:

• In the 1 a device according to the invention is sketched schematically.

In this case, a motor shaft 2 is driven by a motor 1 and acts as the input-side shaft of a gearbox 3 . A flywheel shaft 4 is provided on the output side of the gearbox 3, on which field coils 5 are arranged. A flywheel 6 with an outer cage is rotatably mounted relative to the flywheel shaft 4 . The field coils 5 are preferably provided within the axial portion of the flywheel 6 . When the engine is operating, the engine shaft 2 is the input shaft of the gearbox 3 and the flywheel shaft 4 is the output shaft of the gearbox 3.

An exciter 7 is arranged on an axial end area of the flywheel shaft 4 . This is used to supply the field coils 5. The exciter 7 has a conventional three-phase winding on its rotor, which is connected to the flywheel shaft 4, and field excitation coils in the stator of the exciter 7 that are charged with direct current. A rectifier is provided on the rotor, in particular a bridge rectifier composed of diodes. The unipolar voltage generated by the rectifier feeds the field coils 5, which are arranged on the flywheel shaft 4 in the axial area of the flywheel 6 and generate a radially oriented magnetic field.

The number of field coils 5 is even. The field coils are preferably arranged one behind the other in the circumferential direction and generate a field in the radial direction that is oriented in the opposite direction to the respective adjacent field coil 5 . A d-current is generated by means of the field coils. Thus the current is essentially purely field generating. A q-current, i.e. a torque-forming current component, is essentially non-existent.

The field coils 5 therefore only have to be supplied with a small amount of current.

The flywheel 6 includes a squirrel cage, as a result of which the flywheel 6 can be operated in accordance with an external-rotor asynchronous motor.

The current introduced into the field coils 5 can therefore be controlled by means of the current specification for the field excitation coils of the exciter machine 7 . Thus, the strength of the coupling of the flywheel shaft 4 to the flywheel 6 can be controlled.

In the currentless case, when the flywheel 6 rotates on the flywheel shaft 4, only frictional forces generated by the bearings occur.

When energized, a torque is built up as a function of the slip, ie the speed difference between the flywheel shaft 4 and the flywheel 6. In this way, the speed of the flywheel 6 is increased when its speed is lower than the speed of the flywheel shaft 4. On the other hand, when the rotational speed is lower than the rotational speed of the flywheel shaft 4, the rotational speed of the flywheel 6 is reduced.

When charging the flywheel accumulator, the transmission 3 is operated with a higher gear ratio than when discharging the flywheel accumulator.

When charging the flywheel accumulator, the speed of the flywheel shaft 4 is higher than that Speed of flywheel 6. When discharging the flywheel accumulator, the speed of flywheel shaft 4 is lower than the speed of flywheel 6.

The gearbox 3 provided between the engine 1 and the flywheel shaft 4 is therefore operated with a first translation when charging and with a second translation when discharging. When changing the operating mode, the manual transmission 3 is switched over.

The first and second gear ratio numbers are preferably reciprocal to one another, ie their product is equal to one. In this case, the gearbox 3 can be implemented in a particularly simple and cost-effective manner.

During the shifting process, the flywheel 6 is electrodynamically decoupled from the flywheel shaft 4 and thus a low moment of inertia is realized in order to reach the necessary new speed more quickly when the shifting process is completed.

wobei SR_MAX die maximal zulässige Drehzahl des Schwungrades und MW_MIN die minimale Motorwellendrehzahl beträgt. Der Schlupf beträgt $s=\frac{n_{SW}-n_{SR}}{n_{SW}}$

Die Übersetzungszahl i_ENTLADEN beim Entladen ist vorzugsweise kleiner gewählt als $i_{ENTLADEN,MAX}=\frac{1}{\sqrt{1-S_{MIN}}},$

wobei s_MIN der minimal zulässige übersynchrone Schlupf ist. In 2 ist diese Beziehung veranschaulicht, indem i_ENTLADEN als Funktion von s_MIN dargestellt ist.Preferably, the ratio I _CHARGING of the manual transmission when charging the flywheel is greater than 1 and is preferably selected as $I_{LADEN}=\frac{S{R}_{MAX}}{M{W}_{MIN}},$

where SR _MAX is the maximum allowable speed of the flywheel and MW _MIN is the minimum engine shaft speed. The slip is $s=\frac{n_{SW}-n_{SR}}{n_{SW}}$

The ratio number i _ENTLADEN during discharging is preferably chosen to be smaller than $i_{ENTLADEN,MAX}=\frac{1}{\sqrt{1-S_{MIN}}},$

where s _MIN is the minimum allowable oversynchronous slip. In 2 Figure 1 illustrates this relationship by plotting i _DISCHARGE as a function of s _MIN .

An advantageous exemplary embodiment for the reciprocal gear ratios mentioned are 6 and 1/6. Thus, at a constant engine speed of 10,000 revolutions per minute, the flywheel is accelerated to 60,000 revolutions per minute.

In further exemplary embodiments according to the invention, the manual transmission has further transmission ratios that can be selected by shifting. An even higher effectiveness can thus be achieved. When using a transmission with a continuous transmission ratio instead of a manual transmission, it is even possible to use a slip-dependent, loss-minimum-loss control or regulation, in which the transmission ratio is set in such a way that the overall power loss is as low as possible and/or the dynamics are as high as possible. In this case, high dynamics is understood to mean an operating option in which the specified setpoint torques and/or setpoint speeds are achieved in the shortest possible time.

In a further non-claimed exemplary embodiment, an overrunning clutch can be provided for operation at a permanently constant speed in order to reduce the friction losses and, if required, to achieve even greater dynamics.

In a further exemplary embodiment according to the invention, a transmission with a continuously controllable or adjustable number of gear ratios is used instead of the manual transmission.

The engine 1 is preferably designed as an internal combustion engine. Alternatively, it can also be designed as an electric motor.

Reference List

1

Engine, especially internal combustion engine

2

motor shaft

3

manual transmission, transmission

4

flywheel shaft

5

field coils

6

Flywheel with outer cage

7

exciter machine

ILOAD

Translation of the manual transmission when charging the flywheel

iUNLOAD

Translation of the manual transmission when unloading the flywheel

iUNLOAD,MAX

maximum gear ratio of the manual transmission when unloading the flywheel

MWMIN

minimum motor shaft speed

nSR

RPM of the flywheel

nSW

Flywheel shaft speed

s

slip

sMIN

minimum allowable oversynchronous slip

SRMAX

maximum permissible speed of the flywheel

Claims (6)

System with a flywheel accumulator, in which a flywheel (6) is mounted so that it can rotate relative to a flywheel shaft (4), the flywheel shaft (4) being connected to a motor (1) via a manual transmission (3), i.e. a transmission (3) with a controllable number of gear ratios. connected, with field coils (5) which can be charged with current being arranged on the flywheel shaft (4) in order to generate an excitation field, with a squirrel-cage cage being connected with the flywheel (6), with the field coils (5) on the flywheel shaft (4) in the circumferential direction are arranged one after the other in order to generate a radially oriented magnetic field in the same radial and axial area, with the energization being carried out in such a way that adjacent field coils each generate a magnetic field directed in the opposite direction, with an exciter (7) being arranged on the axial end area of the flywheel shaft (4), the rotatably mounted part, i.e. rotor, is connected to the flywheel shaft (4), the field coils (5) from the rotatably mounted th part of an exciter (7) are electrically supplied, with the stationary part, i.e. the stator, of the exciter (7) comprising field excitation coils to which direct current is applied and the rotatably mounted part of the exciter (7) comprising a three-phase winding, with a rectifier being formed from the three-phase winding which supplies the field coils (5) arranged on the flywheel shaft (4) with electricity, with the flywheel shaft (4) being the output shaft of the gearbox (3), i.e. the driven shaft, or being connected to it, and the motor shaft (2) being the input shaft of the gearbox (3) or is connected to it, with at least two gear ratios of the gear ratios that can be selected with the gear (3) being reciprocal to one another, the gear ratio I _CHARGING of the manual transmission (3) being greater than 1 when the flywheel (6) is charged. system with flywheel accumulator claim 1 , characterized in that the squirrel cage is designed in the manner of a squirrel cage of an external rotor asynchronous motor. System with flywheel accumulator according to one of the preceding claims, characterized in that the flywheel shaft (4) is connected directly or indirectly to an engine shaft of an internal combustion engine (1). System with a flywheel accumulator according to one of the preceding claims, characterized in that the gear (3) is designed with a discretely or continuously controllable number of gear ratios, ie the gear (3) is a manual gear (3). System with a flywheel accumulator according to one of the preceding claims, characterized in that the ratio I _CHARGING of the gearbox when charging the flywheel (6) is selected as $I_{LADEN}=\frac{S{R}_{MAX}}{M{W}_{MIN}},$

where SR _MAX is the maximum permissible speed of the flywheel (6) and MW _MIN is the minimum engine shaft speed, and where the transmission ratio i _ENTLADEN is preferably selected to be less than when discharging $i_{ENTLADEN,MAX}=\frac{1}{\sqrt{1-S_{MIN}}}$

where s _min is the minimum allowable oversynchronous slip. Method for controlling a system with a flywheel accumulator according to one of the preceding claims, wherein between the motor (1) driving the flywheel shaft (4) and the flywheel shaft (4) a gear (3) is arranged, the gear ratio of which is specified, with loading of the flywheel accumulator the gear ratio selected is higher than when discharging the flywheel accumulator.

Images