DRIVE DEVICE AND METHOD FOR SPEED LIMITATION

Abstract

A drive device includes a superposition transmission, a main drive machine connected to an input shaft of the transmission, auxiliary drives and an output shaft of the transmission connectable to a work machine. The transmission has a planetary transmission with an internal gear, sun gear, planet carrier and planet gears. The input shaft is connected to the internal gear, the output shaft is connected to the sun gear, and the auxiliary drives are connected by a first transmission stage with constant transmission ratio to the planet carrier. An auxiliary drive connection with constant transmission ratio is between the auxiliary drive and the internal gear or a pinion on the input shaft. A switchable clutch in the auxiliary drive connection can activate or interrupt the auxiliary drive connection, so that upon interruption, the connection between auxiliary drive and planet carrier remains activated by the clutch through the first transmission stage.

Claims

1-15. (canceled)

16. A drive device, comprising: a main drive machine; at least one auxiliary drive; a superposition transmission including an input shaft connected to said main drive machine, an output shaft to be connected to a work machine, a planetary transmission having an internal gear connected to said input shaft, a sun gear connected to said output shaft, a planet carrier and a plurality planet gears; a first transmission stage with a constant transmission ratio connecting said at least one auxiliary drive to said planet carrier; and an auxiliary drive connection with a constant transmission ratio having one side disposed at said at least one auxiliary drive and another side disposed at said internal gear or a pinion on said input shaft; said auxiliary drive connection including a switchable clutch configured to activate or interrupt said auxiliary drive connection, said switchable clutch maintaining an activated connection between said at least one auxiliary drive and said planet carrier through said first transmission stage upon an occurrence of an interruption.

17. The device according to claim 16, wherein said main drive machine is operable only at a constant rotational speed, and said at least one auxiliary drive is operable with rotational speed control.

18. The device according to claim 17, wherein said at least one auxiliary drive is at least one low-voltage motor.

19. The device according to claim 16, wherein said at least one auxiliary drive has at least one respective external cooler constructed as an external fan with a separate fan motor.

20. The device according to claim 19, wherein said external fan has at least one sensor for monitoring a winding temperature at said separate fan motor.

21. The device according to claim 16, wherein said at least one auxiliary drive has at least one respective external cooler constructed as a water-type cooler.

22. The device according to claim 21, wherein said water-type cooler has a sensor for monitoring at least one of a cooling water temperature in a cooler return line or a cooling water pump.

23. The device according to claim 16, which further comprises an auxiliary drive shaft and a second transmission stage, said auxiliary drive connection acting from said auxiliary drive shaft through said second transmission stage directly on said internal gear or said pinion.

24. The device according to claim 16, which further comprises an auxiliary drive shaft from which said auxiliary drive connection acts: through said first transmission stage on said planet carrier; through a second transmission stage on an intermediate shaft; and through a third transmission stage on said internal gear or said pinion.

25. The device according to claim 24, wherein at least one of said first transmission stage or said third transmission stage is constructed as a gear train composed of at least two respective gearwheels.

26. The device according to claim 24, wherein said clutch is disposed between said second transmission stage and said third transmission stage.

27. The device according to claim 16, wherein said clutch is configured to move into a non-activated state upon an occurrence of an energy failure.

28. The device according to claim 27, wherein said clutch is a multiplate clutch or dog clutch or viscous coupling or hydrodynamic clutch.

29. The device according to claim 16, which further comprises at least one of pulse generators disposed on the drive or a rotational speed sensor, for detecting or measuring at least two of three rotational speeds of said main drive machine, said output shaft and said at least one auxiliary drive.

30. The device according to claim 16, wherein at least one of said at least one auxiliary drive or said main drive machine has at least one of a sensor for detecting a winding temperature or a sensor for detecting a bearing temperature.

31. A method for rotational speed limitation on a drive device, the method comprising the following steps: providing a drive device including: a main drive machine; at least one auxiliary drive; a superposition transmission including an input shaft connected to the main drive machine, an output shaft to be connected to a work machine, a planetary transmission having an internal gear connected to the input shaft, a sun gear connected to the output shaft, a planet carrier and a plurality planet gears; a first transmission stage with a constant transmission ratio connecting the at least one auxiliary drive to the planet carrier; and an auxiliary drive connection with a constant transmission ratio having one side disposed at the at least one auxiliary drive and another side disposed at the internal gear or a pinion on the input shaft, the auxiliary drive connection including a switchable clutch configured to activate or interrupt the auxiliary drive connection, the switchable clutch maintaining an activated connection between the at least one auxiliary drive and the planet carrier through said first transmission stage upon an occurrence of an interruption; and upon a failure or fast shutdown of the main drive machine or of an auxiliary drive: a) detecting the failure or fast shutdown of the main drive machine or of the auxiliary drive; and s) subsequently closing the clutch.

32. The method according to claim 31, which further comprises additionally carrying out the following steps: b) repeatedly determining or measuring rotational speeds at one of the auxiliary drives or the planet carrier, at the input shaft or the main drive machine and at the output shaft or the work machine; c) calculating a synchronization point from a condition in which the rotational speed of the main drive machine before closing the clutch is equal to the rotational speed after closing the clutch; s1) immediately closing the clutch only if the rotational speed of the auxiliary drive is moving away from the synchronization rotational speed, and s2) otherwise closing the clutch with a delay when the rotational speed of the auxiliary drive deviates from the synchronization rotational speed at most by 5% or at most by 3%.

33. The method according to claim 31, which further comprises using at least one temperature sensor to monitor upper temperature limits for at least one of a winding temperature or a bearing temperature of the drives to detect an impending failure or fast shutdown of the main drive machine before an onset of the failure or fast shutdown of the main drive machine.

34. The method according to claim 33, which further comprises additionally using present acceleration values from the measured or determined rotational speeds for the detection of a failure or impending failure.

35. The method according to claim 31, which further comprises upon a failure or malfunction of the main drive machine, applying a rotational speed preset or torque preset to the auxiliary drives to bring the auxiliary drives into a vicinity of a synchronization rotational speed.

Description

[0048] On the basis of exemplary embodiments, further advantageous configurations of the invention will be discussed with reference to the drawings. The stated features may not only be advantageously implemented in the illustrated combination but also individually combined with one another. In detail, in the figures:

[0049] FIG. 1 shows a drive device according to the invention

[0050] FIG. 2a shows a further drive device according to the invention with a positive rotational speed of the auxiliary drives

[0051] FIG. 2b shows a further drive device according to the invention with a negative rotational speed of the auxiliary drives

[0052] FIG. 3a shows a further drive device according to the invention with further drive connection via a gear train

[0053] FIG. 3b shows a further drive device according to the invention with a further drive connection via a gear train as a detail in a frontal view

[0054] FIG. 4a shows an exemplary rotational speed profile without closing of the clutch

[0055] FIG. 4b shows a further exemplary rotational speed profile without closing of the clutch

[0056] FIG. 5 shows an exemplary rotational speed profile with immediate closing of the clutch

[0057] FIG. 6 shows an exemplary rotational speed profile with delayed closing of the clutch

[0058] The figures will be described in more detail below. The same reference designations are used to denote identical or analogous parts or components.

[0059] FIG. 1 shows a drive device according to the invention which is connected by means of the output shaft 15 to the work machine 1. The method according to the invention for rotational speed limitation can be advantageously used also on a device of said type. The superposition transmission 17 has a housing 9 and comprises a planetary transmission 18 with the transmission ratio i_PG. The input shaft 14 connects the main drive machine 2 to the internal gear 4 of the planetary transmission, and the output shaft 15 connects the sun gear 7 to the work machine 1. The third shaft of the superposition transmission is formed by the auxiliary drive shafts 16.1 and 16.2. These connect the auxiliary drives 3.1 and 3.2 via the first transmission stage 6.1, 6.2 to the planet carrier 10. The planet carrier 10 firstly bares the planet gears 5 by means of the planet journals, and on the other side is formed as a toothed gear, which together with the respective toothed gears on the auxiliary drive shafts 16.1 and 16.2 forms the first transmission stage 6. The toothed gear on the planet carrier may also be joined, and need not imperatively be formed in one piece with the planet carrier. This figure illustrates the preferred variant for the transmission stage, specifically in the form of a spur gear stage. Furthermore, this embodiment is equipped with two auxiliary drives 3.1 and 3.2; the invention may however also be implemented with only one auxiliary drive or with multiple, for example three, auxiliary drives. It is important that the auxiliary drives are coupled by means of a transmission stage 6.1, 6.2 with equal transmission ratio to the planet carrier 10.

[0060] The auxiliary drives 3.1, 3.2 are designed as controllable motors of low power, and the main drive machine 2 is designed as a motor with relatively high power but constant rotational speed. The auxiliary drives may preferably be designed as low-voltage motors, because they often exhibit only approximately 10 to 30% of the overall drive power. Thus, the required frequency transformers and the other components for control purposes are also relatively small and relatively inexpensive. The main drive machine 2 is, in many applications, designed as a medium-voltage motor in order to provide the required power overall, and may be implemented without control means. Such drive devices are of particular interest in the case of high levels of power of several MW, such as are encountered in the case of high-speed pumps, supercharging blowers or fans in the oil and gas industry or in thermal power plants. By means of the rotational speed and direction of rotation of the auxiliary drives 3.1, 3.2, the rotational speed at the output shaft 15 can be increased or decreased by a certain amount.

[0061] The limits of this range in the case of maximum rotational speed of the auxiliary drives 3.1, 3.2, on the one hand in a positive direction of rotation and on the other hand in a negative direction of rotation, predefine the possible control range. The transmission ratio i_SG1 of the first transmission stage 6.1, 6.2 must be adapted to the setpoint rotational speed ratios and torque ratios between auxiliary drive and main drive.

[0062] By means of a second transmission stage 8, which is in turn formed here as a spur gear stage by a further toothed gear of the auxiliary drive shaft 16.1 and the external toothing on the internal gear 4, the auxiliary drives 3.1, 3.2 can be coupled directly, bypassing the planetary transmission 18, to the input shaft 14 and to the main drive machine 2. This power path constitutes the auxiliary drive connection, which acts in addition to the connection that exists between the auxiliary drives 3.1, 3.2 and the planet carrier 10. This auxiliary drive connection can be opened or closed by means of the switchable clutch 11.1 using the actuator 23. The transmission ratio i_SG2 of the second transmission stage must be configured such that the rotational speed at the synchronization point lies in the control range. Even when the clutch is open, the connection between auxiliary drive 3.1, 3.2 and planet carrier 10 via the first transmission stage 6.1, 6.2 remains activated.

[0063] If one of the drives 2, 3.1, 3.2 now fails owing to a fault, or if a fast shutdown, in particular of the main drive 2, is initiated, then the rotational speed n1 at the work machine falls rapidly, because its inertia in these usage situations is very much smaller than that of the drive motors 2, 3.1, 3.2. Since the inertia of the auxiliary drives 3.1, 3.2 is also smaller than that of the main drive machine 2, the planet carrier 10 and the auxiliary drives 3.1, 3.2 are accelerated in the event of a fault, owing to the rapid run-down of the work machine 1 and the slow run-down of the main drive machine 2. Here, if an inadmissibly high rotational speed is reached, the auxiliary drives 3.1, 3.2 and in particular the planet gears 5 and the journals thereof may be damaged. A more reliable design of the planetary transmission 18 with regard to this particular fault situation, or an additionally provided brake, would make the drive device unduly large and expensive.

[0064] By means of the closing of the clutch 11.1 after the detection of a corresponding fault situation, this overspeed can be prevented in the system according to the invention. Information relating to the detection of a fault situation may originate for example from the control system or from the system of the energy supply. It is additionally possible for temperature sensors for bearing monitoring 25, 27, 29 or for monitoring the winding temperature 24, 26, 28 at the drive motors to be provided, the signal of which is used for the detection of a fault or of an impending fault. At the auxiliary drives, there are provided external coolers which are designed in this case as external fans 12, 13 with a dedicated fan motor and with monitoring sensors for the winding temperature 32, 33. The embodiment with an external cooler has the advantage that, even in the case of a low rotational speed of the auxiliary drive, a relatively high level of cooling power is possible, which can be controlled independently of the rotational speed of the auxiliary drive. This is necessary if a relatively high torque at relatively low rotational speed is demanded, which may arise not only during normal operation but also after the closing of the clutch 11.1 in the method described here for rotational speed limitation.

[0065] The clutch 11.1 and its activation means are implemented such that the clutch is closed in the event of a failure of the activation means. It is thereby ensured that, even in the event of a complete electrical failure and a failure of the controller, the rotational speed limitation is nevertheless achieved by means of the closed clutch.

[0066] Furthermore, rotational speed sensors 22.1, 22.2, 30 may be provided at the drives. Said rotational speed sensors may be formed by the pulse generators of the motors. Alternatively or in addition, a rotational speed sensor 20 may be provided at the toothed gear of the first transmission stage 6.1, 6.2, a rotational speed sensor 21 may be provided at the toothed gear of the planet carrier 10, and a rotational speed sensor 31 may be provided at the output shaft 15. Variants are thus specified with which all of the rotational speeds n1, n2, n3 and that of the planet carrier can be measured. It is however ultimately sufficient if two of these rotational speeds are measured, because the other rotational speeds can then be determined by means of the rotational speed equation of the planetary transmission 18 and by means of the transmission ratios. Therefore, not all of the rotational speed sensors shown are required simultaneously.

[0067] The determination of the rotational speeds and in particular the knowledge of the profiles thereof in the event of a fault offer the advantage that it can thus be determined when the best switching time for the clutch 11.1 is. By means of a delayed closing after the detection of a fault situation and an optimized switching time, the loading and the temperature increase in the clutch 11.1 during the shutdown of the system can be considerably reduced.

[0068] FIGS. 2a and 2b illustrate a further embodiment of a device according to the invention. The major difference in relation to the embodiment in FIG. 1 is that the second transmission stage 8 is not formed with an external toothing on the internal gear 4, but rather instead has a pinion 4.1 on the input shaft 14, which pinion is in engagement with the second toothed gear on the auxiliary drive shaft 16.1. The switchable clutch 11.1 is in turn illustrated between said second toothed gear and the auxiliary drive shaft 16.1. The clutch could however alternatively also be provided between the pinion 4.1 and the input shaft 14.

[0069] In this embodiment, too, the sensors mentioned with regard to FIG. 1 can be advantageously used.

[0070] By means of the arrows at the shafts, the direction of rotation (+/) is indicated. In both cases, it is assumed that the clutch 11.1 is open. The direction of rotation of the output shaft 15 is always opposite to the direction of rotation of the input shaft 14. FIG. 2a describes operation above the reversal point, that is to say in this case the auxiliary drives increase the rotational speed at the output shaft 15 in relation to the rotational speed that would be realized, in the presence of the setpoint rotational speed of the main drive machine 2, if the planet carrier 10 and the auxiliary drives were static (=reversal point). FIG. 2b shows the situation in which the rotational speed of the work machine 1 is below the reversal point, that is to say the auxiliary drives reduce the rotational speed owing to the superposition.

[0071] FIG. 3a illustrates a further preferred embodiment of the inventive drive arrangement. For the sake of simplicity, only one auxiliary drive 3.2 is shown, but it is preferable for two or even three auxiliary drives to be analogously provided. Furthermore, the auxiliary drive 3.2 is shown schematically under the main drive machine 2, even though, in the case of two auxiliary drives, said auxiliary drive may preferably be situated in the same plane as the main drive machine 2. From the auxiliary drive 3.2, torque is transmitted by the first transmission stage, which is in the form of a gear train 6.2a, 6.2b, to the planet carrier 10. The auxiliary drive connection likewise utilizes this first transmission stage and then transmits the torque onward via the second transmission stage 8.1 to the first part of the intermediate shaft 16.3. By means of the switchable clutch 11.2, the first intermediate shaft 16.3 is connected to the second intermediate shaft 16.4. Then, from the intermediate shaft 16.4, the torque is transmitted by the third transmission stage, which in this case is designed as a gear train 19.1, 19.2, 19.3, to the pinion 4.1 on the input shaft 14. Thus, when the clutch 11.2 is closed, the auxiliary drive 3.2 is connected by means of the auxiliary drive connection via first, second and third transmission stage to the input shaft 14. When the clutch 11.2 is open, the auxiliary drive acts via the first transmission stage only on the planet carrier. The clutch 11.2 is actuated by means of the actuator 23. The equation (2b) applies for the calculation of the synchronization point.

[0072] Instead of one or both of the gear trains shown, use may also be made of in each case one spur-gear stage with relatively large toothed gears. Alternatively, one of the other stated variants may be used for the transmission of torque.

[0073] It is possible to clearly see the advantage that the design can be very compact and space-saving in terms of width in the region of the auxiliary drives 3.2 with the auxiliary drive shaft 16.2. This makes it possible, for example, for the drive arrangement according to the invention to be used in applications in a manner neutral in terms of structural space in relation to previous drive systems.

[0074] FIG. 3b shows a detail of the embodiment from FIG. 3a in a front view from the viewing direction A, wherein only the toothed gears are shown. Shafts and drives are not illustrated. A version with two auxiliary drives is shown. Via the gear trains 6.1a, 6.1b and 6.2a, 6.2b, which constitute the first transmission stage, torque is transmitted from the respective auxiliary drive shaft to the planet carrier 10. The second transmission stage 8.1 is in engagement with the planet carrier 10 and transmits the torque to the intermediate shaft. From there, when the clutch is closed, the torque is transmitted via the third transmission stage, which is in turn formed as a gear train 19.1, 19.2, 19.3, to the pinion 4.1 on the input shaft. It can be seen in this illustration that the transmission housing can be easily designed to be divided horizontally, because all of the shafts that have to extend through the housing can lie at one height. The bearing seats of the auxiliary drive shafts, of the input shaft and of the output shaft are correspondingly divided at one height by the parting joint.

[0075] The rotational speed profiles in FIGS. 4a and 4b schematically show, for a drive device according to the invention, what would occur if the main drive machine 2 were to fail (at the 50 second time point) without the clutch 11.1, 11.2 being closed. Numerical values are merely examples for illustrative purposes, assuming a particular design of the drive device. They may self-evidently vary depending on how the drives 2, 3.1, 3.2, the work machine 1 and the transmission ratios in the transmission 17, 18 are configured.

[0076] FIG. 4a illustrates the situation in which, before the onset of the fault situation, the auxiliary drives have been operated with a positive direction of rotation and the work machine 1 has been operated with maximum rotational speed. As a result of the fast drop in rotational speed n1 of the work machine owing to its low inertia and owing to the small drop in the rotational speed n2 of the main drive machine 2 owing to its very high inertia, the auxiliary drives 3.1, 3.2 are initially accelerated in the opposite direction into the negative direction of rotation, and are then accelerated further to high rotational speeds. Here, there is the risk of the auxiliary drive 3.1, 3.2 or planet carrier 10 being damaged owing to inadmissible overspeeding.

[0077] FIG. 4b illustrates the opposite situation, in which the auxiliary drives 3.1, 3.2 are operated with negative rotational speed. Here, the work machine 1 runs with a reduced rotational speed n1. In a fault situation (again at the 50 second time point), they are then accelerated to even higher negative rotational speeds. This is again associated with the risk of damage occurring as a result of overspeeding.

[0078] On a device according to the invention, it is now possible by means of the switchable clutch 11.1, 11.2, in a suitable method, to prevent inadmissible overspeeding occurring at the auxiliary drive 3.1, 3.2 or at the planet carrier 10. FIG. 5 shows, by way of example, the rotational speed profiles for the situation in which the clutch 11 is closed immediately after detection of the fault situation (at the 50 second time point). The delay of approximately 2 seconds before the kink results from the initially occurring slippage in the clutch 11.1, 11.2, until the auxiliary drives 3.1, 3.2 are accelerated in the opposite direction. After the kink, it can be seen how the rotational speeds n2 and n3, which are now coupled by the transmission stage 8, 8.1, 19.1, 19.2, 19.3 decrease in a similar manner to zero. In the case of the immediate closing of the clutch 11.1, 11.2, it is necessary for all of the energy to be absorbed in the clutch 11.1, 11.2, which leads to a corresponding temperature increase.

[0079] To assist the acceleration of the auxiliary drives in the opposite direction, it is possible, after the detection of the fault situation, for said auxiliary drives to be activated with torque or rotational speed presets. This is however only possible if only the main drive machine has failed or is subjected to a fast shutdown.

[0080] FIG. 6 shows the rotational speed profiles for a further optimized method for rotational speed limitation in the fault situation, in which the clutch 11.1, 11.2 is closed only after a delay and in synchronized fashion. In this way, the required absorption of energy and temperature increase in the clutch 11.1, 11.2 can be limited. For this purpose, the synchronization rotational speed is calculated using Eq. 2 and Eq. 1. Furthermore, the rotational speeds n1, n2 and n3 are measured or determined. If two of these are measured, the third can be determined from the rotational speed equilibrium (Willis equation). It is then possible for the rotational speed profile to be compared with the rotational speed at the synchronization point.

[0081] If the rotational speed n3 of the auxiliary drive is moving toward the synchronization rotational speed, then the closing of the clutch 11.1, 11.2 is delayed until the rotational speed n3 has moved into the vicinity of said synchronization rotational speed, for example until said rotational speed deviates from said synchronization rotational speed by at most 5%, preferably at most 3%. Owing to the relatively small rotational speed difference during the closing, it is possible for the temperature increase that occurs here to be limited. In the example shown, the closing has been delayed to such an extent that a full transmission of torque in the clutch 11 occurs for the first time at the 55 second time point.

[0082] However, if, upon the detection of the fault situation, the rotational speed n3 of the auxiliary drive is moving away from the synchronization rotational speed, the clutch 11.1, 11.2 is nevertheless immediately closed in order to avoid a further increase of the difference.

[0083] It is self-evidently possible for the rotational speed conditions for the closing of the clutch 11.1, 11.2 to also be formulated for the other rotational speeds. Eq. 1 is used for the conversion.

LIST OF REFERENCE DESIGNATIONS

[0084] Work machine [0085] Main drive [0086] 3.1, 3.2 Auxiliary drive [0087] 4 Internal gear [0088] 4.1 Pinion [0089] 5 Planet gears [0090] 6.1, 6.1a, 6.1b, [0091] 6.2, 6.2a, 6.2b First transmission stage [0092] 7 Sun gear [0093] 8, 8.1 Second transmission stage [0094] 9 Housing

[0095] 10 Planet carrier [0096] 11.1, 11.2 Switchable clutch [0097] 12, 13 External cooling arrangement [0098] 14 Input shaft [0099] 15 Output shaft [0100] 16.1, 16.2 Auxiliary drive shafts [0101] 16.3, 16.4 Intermediate shaft [0102] 17 Superposition transmission [0103] 18 Planetary transmission [0104] 19.1, 19.2, 19.3 Third transmission stage [0105] 20, 21, 22.1, 22.2, 30, 31 Rotational speed sensors [0106] Actuator for clutch [0107] 24, 26, 28, 32, 33 Winding temperature sensors [0108] 25, 27, 29 Bearing temperature sensors [0109] n1 Rotational speed output shaft=sun gear [0110] n2 Rotational speed main drive=internal gear [0111] n3 Rotational speed auxiliary drives [0112] i_PG Transmission ratio planetary transmission (=n1/n2) [0113] i_SG1 Transmission ratio first transmission stage (6.x) [0114] (=n3/n-planet carrier) [0115] i_SG2 Transmission ratio second transmission stage (8.x) [0116] (=n2/n3 or =n-intermediate shaft/n-planet carrier) [0117] i_SG3 Transmission ratio third transmission stage (19.x) [0118] (=n-intermediate shaft/n2)