Actuator arrangement for applying a torque to a shaft, in particular a crankshaft of a reciprocating piston engine, and a corresponding method

Abstract

An actuator arrangement for applying a torque to a shaft of a machine, in particular a reciprocating piston engine, includes: a) at least one actuator device for applying the torque; and b) at least one rotatable seismic mass coupled to the shaft. The at least one actuator device is designed to apply the torque to the shaft between the seismic mass and the shaft. A corresponding method is provided for active damping of torsional vibrations of the shaft having the actuator arrangement.

Claims

1. An actuator arrangement for applying a torque to a shaft of a machine, comprising: a) at least one actuator device for applying the torque; b) at least one rotatable seismic mass coupled with the shaft; c) at least one electrical machine to supply drive energy for the actuator device; d) at least one transmission, via which the shaft is coupled with the electrical machine to drive the shaft; and e) a controller for controlling the electrical machine based on rotary vibration information; wherein: the torque applied by the actuator device to the shaft of the machine is an alternating torque applied between the seismic mass and the shaft that damps rotary oscillations of the shaft to reduce shaft vibrations; the shaft is a crankshaft of a reciprocating piston machine, and the actuator device is configured to apply the torque between the seismic mass and the crankshaft of the reciprocating piston machine; the actuator device forms a coupling between the seismic mass and the shaft; the seismic mass is coupled with the shaft in such manner that the seismic mass rotates at a different speed than the shaft; the transmission and the actuator device are arranged on the seismic mass; the electrical machine is configured as an electric motor with a stator and a rotor, wherein the stator is fixedly fastened to a frame and the rotor is coupled with the actuator device either indirectly via the transmission or directly; and the transmission includes at least one generator and the electric motor, the electric motor forms the actuator device, and the generator is coupled with the rotor of the electrical machine.

2. The actuator arrangement as claimed in claim 1, wherein the transmission includes a housing fixedly connected to the seismic mass.

3. The actuator arrangement as claimed in claim 1, wherein the rotatable seismic mass and the electrical machine together with the shaft have the same axis of rotation.

4. The actuator arrangement as claimed in claim 3, wherein the electric motor is configured for a rotating speed of 16,000 rpm.

5. The actuator arrangement as claimed in claim 1, wherein the transmission is a gear transmission, wherein the actuator device is formed by an output gear of the transmission, and wherein a transmission input is coupled with the rotor of the electrical machine.

6. The actuator arrangement as claimed in claim 1, wherein the transmission includes at least one pump, embodied as a hydraulic pump, and which has the actuator device, wherein the pump is coupled with the rotor of the electrical machine, and wherein the actuator device is embodied as a radially disposed hydraulic cylinder of the pump, as a displacement vane, or as a gear pump.

7. The actuator arrangement as claimed in claim 1, wherein the generator is coupled to the rotor to supply energy to one or more piezoelements or piezoactuators.

8. The actuator arrangement as claimed in claim 1, wherein the rotatable seismic mass is also coupled with the shaft via a spring unit.

9. The actuator arrangement as claimed in claim 8, wherein the spring unit includes springs connected in parallel.

10. The actuator arrangement as claimed in claim 1, further comprising a device for braking the shaft.

11. The actuator arrangement as claimed in claim 10, wherein the device for braking the shaft comprises the electrical machine, and wherein the electrical machine provides for energy recovery.

12. The actuator arrangement as claimed in claim 1, further comprising a device for accelerating the shaft, wherein the electrical machine generates acceleration processes.

13. The actuator arrangement as claimed in claim 1, further comprising at least one measuring device for detecting the rotary vibration information, wherein the rotary vibration information is rotary vibration information about the shaft, and wherein the controller is configured to control the electrical machine on the basis of the rotary vibration information about the shaft detected by the measuring device to apply the torque for damping rotary vibrations of the shaft.

14. The actuator arrangement as claimed in claim 13, wherein the controller includes a regulating unit providing a superimposed rotating speed regulation to the seismic mass.

15. A method for applying a torque to a shaft of a machine, comprising: (S1) providing an actuator arrangement including a) at least one actuator device for applying the torque, b) at least one rotatable seismic mass coupled with the shaft, c) at least one electrical machine to supply drive energy for the actuator device, d) at least one transmission, via which the shaft is coupled with the electrical machine to drive the shaft, and e) a controller for controlling the electrical machine based on rotary vibration information, such that the torque applied by the actuator device to the shaft of the machine is an alternating torque applied between the seismic mass and the shaft that damps rotary oscillations of the shaft to reduce shaft vibrations, the shaft is a crankshaft of a reciprocating piston machine, and the actuator device is configured to apply the torque between the seismic mass and the crankshaft of the reciprocating piston machine, the actuator device forms a coupling between the seismic mass and the shaft, the seismic mass is coupled with the shaft in such manner that the seismic mass rotates at a different speed than the shaft, the transmission and the actuator device are arranged on the seismic mass, the electrical machine is configured as an electric motor with a stator and a rotor, wherein the stator is fixedly fastened to a frame and the rotor is coupled with the actuator device either indirectly via the transmission or directly, and the transmission includes at least one generator and the electric motor, the electric motor forms the actuator device, and the generator is coupled with the rotor of the electrical machine; (S2) detecting a requirement for torque; (S3) determining actuation data for said at least one electrical machine to supply drive energy for the actuator device on the basis of the requirement for torque detected; and (S4) applying the torque to the shaft by actuating the at least one electrical machine to drive the at least one actuator device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic representation of an embodiment of an actuator arrangement according to the invention;

(2) FIG. 2 is a schematic representation of a variant of the embodiment of FIG. 1;

(3) FIGS. 3-5 are schematic representations of variants of a transmission in the embodiment of FIG. 1; and

(4) FIG. 6 is a schematic flowchart of a method according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 shows a schematic representation of an embodiment of an actuator arrangement 1 according to the invention.

(6) Actuator arrangement 1 is represented with a shaft 2 of a machine, e.g., a reciprocating piston engine (not shown). In this instance, shaft 2 is crankshaft of the reciprocating piston engine, which has a front end and a driven end. The reciprocating piston engine may be for example a diesel, gasoline or gas engine, and may be used for various purposes, as an automobile power unit, for example. The crankshaft may includepreferably at a driven enda flywheel, a dual mass flywheel for example, to which a powertrain of an automobile having a drive transmission is connected downstream. A drive transmission is a transmission, e.g., an automobile transmission, which converts the engine speed to an input speed.

(7) Shaft 2 rotates at a (variable) rotating speed n about its longitudinal axis, which is designated here as axis of rotation 2a.

(8) Actuator arrangement 1 is provided for applying a torque to shaft 2 and comprises the shaft 2, a seismic mass 4, an electrical machine 5, a transmission 8 and at least one actuator device 19. With actuator arrangement 1 and the actuator device 19 thereof, preferably supplementary alternating torques are applied to crankshaft 2, which is already rotating due to the running reciprocating piston engine, which torques may in particular have the effect of exciting or damping vibrations. This application of supplementary torques preferably takes place directly at the crankshaft before the powertrain with the flywheel if provided.

(9) Seismic mass 4 is designed as a kind of flywheel with a drive side 4a and a coupling side 4b. In the example shown, the seismic mass is formed with an inertia ring 4c. Exemplary diameters of seismic mass 4 are in a range from 0.15 m to 3.50 m. The material from which seismic mass 4 is made is e.g., gray cast iron, cast steel, steel and/or tungsten.

(10) Electrical machine 5 is an electric motor with a stator 6 and a rotor 7. Stator 6 is spatially fixed and in this case mounted fixedly on a frame 3. In the case of an automobile, frame 3 may be the frame of the automobile, for example. In the case of a stationary machine, frame 3 may be e.g. the frame or the foundation of the machine. Rotor 7 is directly or indirectly coupled with the at least one actuator device 19 to drive it.

(11) Here, seismic mass 4 and electrical machine 5 together with shaft 2 have the same axis of rotation 2a. It is also possible that they have different axes of rotation or approximately the same axis of rotation.

(12) Transmission 8 comprises a transmission input 8a, a transmission output 8b, an intermediate stage 8c and a housing 9. Transmission 8 is a torque converter.

(13) Transmission input 8a is located on the drive side 4a of seismic mass 4 and is coupled with rotor 7 of the electrical machine. Transmission output 8b is coupled with transmission input 8a in a certain gear ratio via intermediate stage 8c. In this example, transmission output 8b also comprises the at least one actuator device 19, which is coupled on the coupling side 4b of seismic mass 4 via an output shaft 8d and a coupling section 8e, e.g., a flange, with a front end 2b of the rotating shaft 2 to which an alternating torque is to be applied. Housing 9 of transmission 8 is braced against seismic mass 4, which co-rotates with rotating shaft 2. Here, housing 9 is only indicated schematically with a hatched area. Transmission 8 is described in greater detail below.

(14) Actuator arrangement 1 is designed so as to apply a torque to shaft 2. Such a torque may be applied for various purposes. Accordingly, actuator arrangement 1 may serve not only to damp the rotary oscillations of shaft 2, but also either to decelerate shaft 2 and therewith also an entire powertrain coupled with shaft 2 in the case of an automobile in energy recovery mode or to accelerate shaft 2, e.g., to start the associated internal combustion engine.

(15) A numerical example of rotary oscillation reduction in shaft 2 will now be presented. Shaft 2 is e.g. a crankshaft of a truck engine. At a rotating speed n of 1800 rpm of shaft 2, an alternating torque of 2 kNm is to be applied to shaft 2. For the purposes of the example, the reduction ratio of transmission 8 is assumed to be 1:10. Then, the alternating torque to be applied by the relatively small electrical machine 5 is only 200 Nm. Since housing 9 of transmission 8 co-rotates with seismic mass 4, the input side of transmission 8, i.e. transmission input 8a, also rotates at a speed of only 1800 rpm. In contrast to this, if housing 9 of transmission 8 were spatially fixed, transmission input 8a would rotate at a speed of 18,000 rpm.

(16) In the exemplary case with the transmission ratio of 1:10, the amplitude of the power output by electrical machine 5 is only 37.7 kW (compared with 377 kW without the transmission ratio of 1:10).

(17) In this way, therefore, both the power requirement and the torque of electrical machine 5 are reduced by the amount of the transmission ratio with the aid of this arrangement.

(18) FIG. 2 is a schematic representation of a variant of the embodiment of FIG. 1, wherein transmission 8 is constructed with a pump 18 and actuators 19. Transmission input 8a (see FIG. 1) is formed by a drive input of pump 18. Intermediate stage 8c is formed by the pump and actuator construction. Transmission output 8b consists of the coupling points between actuators 19 and the front end 2b of shaft 2.

(19) A controller 11 is also represented; its function will be explained in greater detail below.

(20) In this shown variant, seismic mass 4 is coupled with the coupling side 4b facing shaft 2 via actuators 19 and to the front end 2b of shaft 2 via a spring unit 10, and consequently rotates at the same rotating speed as shaft 2.

(21) Spring unit 10 is an optional component and may consist of parallel connected springs, such as torsion springs or circumferentially disposed helical springs. Of course, other spring arrangements are also possible.

(22) It is also possible for the seismic mass 4 to be coupled with front end 2b of shaft 2 solely via actuators 19, but this is not represented here.

(23) A torque to be applied to shaft 2 is applied by actuators 19 between shaft 2 and coupling side 4b of the co-rotating seismic mass 4. The required torque is generated by the relative acceleration between seismic mass 4 and shaft 2. Consequently, the power required to generate the necessary torque remains relatively small, since the speed differential between seismic mass 4 and shaft 2 remains small. In an exemplary case of a truck engine, the power required for this is e.g., about 5 kW with damping of rotary oscillations of shaft 2.

(24) The required energy, which is applied to actuators 19 for generating this torque, is delivered by electrical machine 5 from the drive side 4a of seismic mass 4. Rotor 7 is coupled with actuators 9 to drive them.

(25) The electrical machine is realized as a high-speed electric motor with the required yet small power output (e.g., 5 kW for a truck engine). This high-speed electric motor may be capable of rotating at 16,000 rpm. A torque engine for example may also be used as electrical machine 5.

(26) In the example shown, pump 18 functions as a drive for actuators 19. Pump 18 is mounted on seismic mass 4, and in this example is a high-dynamic hydraulic pump. Then, the actuators 19 may be cylinders of the pump 18 in the form of a hydraulic pump. Rotor 7 of the electrical machine is coupled with pump 18 for drive purposes and drives pump 18 which is mounted on seismic mass 4 and co-rotates therewith and with shaft 2 at a uniform shaft speed (rotating speed of shaft 2).

(27) Rotor 7 drives pump 18 directly. The cylinders of the high-dynamic hydraulic pump may bring about a defined displacement (defined acceleration and defined torque) between seismic mass 4 with respect to shaft 2.

(28) A generator may also be arranged on seismic mass 4 instead of pump 18, which is not shown but may be imagined. In this context, actuators 19 may be piezoelements, for example, with are supplied with electrical energy by this generator.

(29) The uniform rotating speed of the machine, e.g., an internal combustion engine, i.e. of shaft 2, presents no difficulties in this case, since the very rapid response time and significantly larger speed range of the high-speed electrical machine 5 enables the required speed to be applied additively to the uniform rotating speed n of shaft 2.

(30) Controller 11 includes a control device 12, an engine control 13 for the electrical machine 5 and a regulating unit 14 for seismic mass 4. Controller 11 may also comprise one or more superimposed regulating devices 17 for the performance of other functions, such as energy recovery (generator mode of electrical machine 5), additional acceleration of shaft 2 among others.

(31) In this context, control device 12 of controller 11 is also connected to at least one measuring device 15 and one engine controller 16 of the machine that is attached to shaft 2.

(32) Measuring device 15 detects rotary oscillations of shaft 2 and may be constructed as described in document WO 2014/118245 A1 for example. The date collected in this way is transmitted to control device 12.

(33) Further data about shaft 2, e.g., rotating speed n, including data on operating states of the machine are received by control device 12 from engine controller 16, which is connected to the machine. The data on operating states may also include torque requirements for shaft 2, e.g., deceleration or acceleration of the automobile, such as starting the machine.

(34) Control device 12 processes this input data for engine control 13 in such manner that engine control 13 sends corresponding output data to the electrical machine for control and regulation thereof. Thus, highly dynamic regulation in response to the current state of the machine, e.g., an internal combustion engine, is possible. The regulation data also includes data on the electrical machine 5 that is collected and transmitted to engine control 13 while it is operating.

(35) The actuation of electrical machine 5 with regulation of the rotary oscillations, i.e. damping of rotary oscillations of shaft 2, may be performed e.g. via an algorithm for active vibration damping, which is described in document WO 2014/118245 A1 and which is included by reference here.

(36) With this arrangement, the torque for damping rotary oscillations of shaft 2 may be supplied with the aid of low-power actuators 19 on the basis of the seismic principle with seismic mass 4.

(37) The masses or additional inertias of rotor 7 of electrical machine 5 and of the pump 18 mounted on seismic mass 4 including actuators 19 are not problematic in this arrangement, since a larger seismic mass 4 reduces the displacements that are required to damp rotary oscillations with the torques to be applied.

(38) The task of regulating unit 14 consists in supplying a superimposed rotating speed regulation of seismic mass 4 such that a uniform rotating speed of seismic mass 4 at any given time is equal to the uniform rotating speed of shaft 2 at the same time.

(39) Besides damping rotary oscillations of shaft 2, at the same time actuator arrangement 1 may also be used to decelerate the entire powertrain in an automobile connected therewith (recovery) or also to accelerate it (e.g., when starting the machine). Regulating device 17 described earlier is provided for this purpose. In the event that shaft 2 is decelerated, for example, electrical machine 5 may function as a generator for recovery, i.e. generate electrical power, which is stored in the automobile battery for example.

(40) FIGS. 3-5 show schematic cross-sectional representations of variants of transmission 8 of the embodiment according to FIG. 1. FIG. 3 shows the transmission 8 as a gear transmission. In FIG. 4, transmission 8 is shown as an electric motor transmission, and FIG. 5 is a schematic representation of a hydraulic transmission.

(41) In each of FIGS. 3-5, only half of seismic mass 4 is shown, in a lengthwise cross section in each case, wherein the respective other half can be easily imagined. Sections of the body of seismic mass 4 are realized as sections of the housing 9 of transmission 8 here, and are connected to the circumferential inertia ring 4c and therewith also to the seismic mass 4.

(42) Rotor 7 of electrical machine 5 (see FIG. 1) is rotatably supported as transmission input 8a in a section of housing 9 facing towards electrical machine 5 and the end thereof that protrudes into housing 9 is furnished with a non-rotatable input gear 80.

(43) Similarly, output shaft 8d is rotatably supported as transmission output 8b in a section of housing 9 facing towards shaft 2. A non-rotatable output gear 83 is mounted on the end thereof that protrudes into housing 9.

(44) In this variant, output gear 83 is designed as the at least one actuator device 19.

(45) A further section of housing 9 is arranged between the two housing sections, and functions as a bearing point for an intermediate shaft 84 of intermediate stage 8c. The end of intermediate shaft 84 pointing towards transmission input 8a is equipped with a first intermediate gear 81, and the other end thereof is equipped with a second intermediate gear 82. Intermediate gears 81 and 82 are non-rotatably connected to intermediate shaft 84. The first intermediate gear 81 engages with input gear 80, while the second intermediate gear 82 engages with output gear 83.

(46) Transmission 8 is thus configured as a gear transmission with intermediate stage 8c to provide a certain transmission ratio between transmission input 8a and transmission output 8b. Gears 80, 81, 82, 83 in this instance are gearwheels with spur toothing, e.g., straight or helical gearing. Of course, other gearing types are possible. Transmission 8 is only represented schematically here, and may be a planetary transmission, for example.

(47) The variant of FIG. 4 shows a transmission 8 designed as an electric motor transmission with a generator 20 and an electric motor 21.

(48) Here too, housing 9 of transmission 8 is made up of sections of the seismic mass 4, and is connected in fixed manner to inertia ring 4c. Rotor 7 is supported rotatably in the associated housing section in transmission input 8a. In the same way, an associated housing section forms a bearing point for output shaft 8d in transmission output 8b.

(49) In this instance, generator 20 is equipped with a rotor 20a, e.g., as an internal rotor with permanent magnets which is non-rotatably connected to the end of the rotor 7 of electrical machine 5 in transmission input 8a. Rotor 20a is arranged rotatably inside a stator 20b arranged in housing 9.

(50) Motor 21 is equipped with a rotor 21a and a stator 21b mounted inside housing 9. The end of output shaft 8d that protrudes into housing 9 is non-rotatably connected to rotor 21a of motor 21. This rotor 21a is for example also an internal rotor with permanent magnets and also arranged rotatably inside stator 21b of motor 21.

(51) Stator 20b of generator 20 is equipped with a winding which is connected in electrically conductive manner with a winding of stator 21b of motor 21 via a connection 22. This connection is only represented schematically, of course special generator/engine controls may be provided to control and regulate generator 20 and motor 21.

(52) An intermediate stage 8c of transmission 8 is not shown here. It is created by the mechanical and electrical configuration of generator 20 and motor 21, wherein the generator/engine controls mentioned above are also used.

(53) Motor 21 functions as the at least one actuator device 19.

(54) FIG. 5 shows a schematic representation of a hydraulic transmission similar to that in FIG. 2 as transmission 8. This configuration of transmission 8 with a pump 18 and an actuator device 19 is particularly preferred for transmitting large, fast alternating torques.

(55) Housing 9 is again part of seismic mass 4 and forms bearing points both in transmission input 8a for rotor 7 of electrical machine 5 and in transmission output 8b for output shaft 8d. The seals needed are not shown here, but they are of course essential.

(56) Rotor 7 is coupled non-rotatably with pump 18 in transmission input 8a. Pump 18 may be for example a standard commercial gear pump and has an inlet 18a and an outlet 18b for a pump medium, e.g., a special oil.

(57) Actuator device 19 may be e.g. a radially disposed hydraulic cylinder, of which several may also be present. It is also possible for actuator device 19 to be realized as a displacement vane or also as a gear pump. Actuator device 19 has an inlet 19a and an outlet 19b for the pump medium.

(58) The side of actuator device 19 facing transmission output 8b is non-rotatably connected to output shaft 8d, e.g., in such manner that the one or more displacement vane(s) and the output gearwheel are coupled with output shaft 8d.

(59) Inlet 18a of pump 18 is connected to the outlet 19b of actuator device 19 via a first connecting line 23. A second connecting line 24 connects outlet 18b of pump 18 to inlet 19a of actuator device 19. Connection lines 23, 24 serve to transport the pump medium and are designed to sustain the high media pressures that occur during operation of transmission 8 and have corresponding cross sections. Connection lines 23, 24 are arranged inside housing 9 or conformed therein.

(60) FIG. 6 shows a schematic flowchart of an exemplary method according to the invention for applying a torque to shaft 2 of the allocated machine, in particular a reciprocating piston engine.

(61) In a first method step S1, input data with a requirement for torque is detected. Such a requirement for torque may be for example a starting process of the engine, a braking process, an acceleration requirement when increasing speed, a damping requirement for damping rotary oscillations of shaft 2 and the like.

(62) This is effected by control device 11 receiving corresponding commands and datasets from engine controller 16 and/or from measuring device 15.

(63) In a second method step S2, actuation data for electrical machine 5 is carried out on the basis of the collected input data for the requirement for torque.

(64) Finally, in a third method step S3 electrical machine 5 is actuated on the basis of the actuation data determined in this way to drive pump 18 and generator 20 to generate torques for application of a torque to shaft 2 by actuators 19 or by motor 21 and at the respective transmission output 8b.

(65) The torque to be applied may have various profiles.

(66) For example, a torque that is applied to shaft 2 for a starting process and/or acceleration may rise from a zero point to a certain positive value, which e.g., may also remain constant for a certain period and then fall back to zero.

(67) In the case of a braking process, the torque is negative, i.e. it progresses from the zero point towards negative values, and of course it may also remain constant and then rise back to the zero point again.

(68) Of course, these torque profiles can also be recurring or repetitive.

(69) An alternating torque is also possible, wherein the torque profile may cross the zero line from positive values to negative values and vice versa. Of course, this profile may also be periodic, damped or undamped or even cumulative in certain time intervals. Such an alternating torque is applied to shaft 2 particularly for damping rotary oscillations thereon.

(70) For the purpose of damping rotary oscillations in shaft 2, initially in the first method step S1 measurement data with rotary oscillation information on shaft 2 is collected by measuring device 15 and the rotary oscillation information is analyzed. At the same time, engine control 16 receives input data with information about the rotating speed, angular position etc. of shaft 2.

(71) In the second method step S2, actuation data for electrical machine 5 is implemented on the basis of the collected input data. In this context, for example, the algorithm for active vibration damping as described in document WO 2014/118245 A1 is used.

(72) Finally, in the third method step S3, electrical machine 5 is actuated on the basis of the actuation data determined in this way to drive pump 18 and generator 20 to generate torques for damping vibration in shaft 2 by actuators 19 or by motor 21 and at the respective transmission output 8b for active damping of the rotary oscillations of shaft 2. At the same time, the torque for damping rotary oscillations of shaft 2 is applied by actuator devices 19, motor 21 and at transmission output 8b between shaft 2 and the co-rotating seismic mass 4. The torque for damping rotary oscillations of shaft 2 is generated by relative acceleration between seismic mass 4 and shaft 2.

(73) The invention is not limited by the embodiment described in the preceding text, and may be modified without departing from the scope of the accompanying claims.

(74) Thus, for example, it is conceivable that seismic mass 4 may be equipped with a further measuring device, which cooperates with the regulating unit 14 thereof.

(75) An angular position of shaft 2 may also be determined in measuring device 15.

(76) It is further conceivable that electrical machine 5, generator 20 and/or electric motor 21 may be constructed as external rotors.

(77) It is also conceivable that the actuator arrangement 1 might also be usable for damping rotary oscillations in shafts of machines other than reciprocating piston engines. For example, actuator arrangement 1 may be able to be used in machines whose operating states may be characterized as semi-stationary.

LIST OF REFERENCE SIGNS

(78) 1 Actuator arrangement 2 Crankshaft 2a Axis of rotation 2b Front end 3 Frame 4 Seismic mass 4a Drive side 4b Coupling side 4c Inertia ring 5 Electrical machine 6 Stator 7 Rotor 8 Transmission 8a Transmission input 8b Transmission output 8c Intermediate stage 8d Output shaft 8e Coupling section 9 Housing 10 Spring unit 11 Controller 12 Control device 13 Engine control 14 Regulating unit 15 Measuring device 16 Engine controller 17 Regulating device 18 Pump 18a Inlet 18b Outlet 19 Actuator device 19a Inlet 19b Outlet 20 Generator 20a Rotor 20b Stator 21 Motor 21a Rotor 21b Stator 22 Connection 23,24 Connection 80 Input gear 81, 82 Intermediate gear 83 Output gear 84 Intermediate shaft n Rotary motion S1 . . . 3 Method step