Patent Publication Number: US-2012028752-A1

Title: Flywheel module

Description:
FIELD OF THE INVENTION 
     The invention relates to a flywheel module to be used in a vehicle provided with a driving source and a transmission. 
     The flywheel module comprises: 
     a coupling unit comprising:
         an input shaft, which can be coupled to the driving source, and   an output shaft, which can be coupled to the transmission,       

     and comprising a first coupling, which is present between the input shaft and the output shaft and which comprises:
         a first coupling half connected to the input shaft, and   a second coupling half connected to the output shaft,       

     as well as 
     a flywheel unit having an in/output and including:
         i) a flywheel, and   ii) a reduction gear unit having an input which is connected to the flywheel and an output which is connected to the in/output of the flywheel unit, and comprising:
           a) a reduction gearing as well as   b) a coupling device which is connected to the reduction gearing.   
               

     STATE OF THE ART 
     A transmission system comprising a flywheel module of this type is known from U.S. Pat. No. 5,569,108. In the known transmission system the flywheel unit is connected with its in/output and furthermore with a further in/output to the coupling unit, while this further in/output is connected to the first coupling half of the first coupling. The reduction gearing in this known flywheel module is formed by a planetary gear set having three rotational members, a first rotational member of which being connected to the flywheel, a second rotational member being connected via a brake to a node positioned between the second coupling half and the output shaft and the third rotational member being connected via a brake to the further in/output. This known flywheel module is relatively complex. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a flywheel module of the type defined in the opening paragraph, which is less complex than the known flywheel module. For this purpose the flywheel module according to the invention is characterised, in that the flywheel unit is connected with its in/output to the coupling unit, this in/output being connected via a node to the second coupling half of the first coupling and/or to the output shaft. The flywheel unit is preferably exclusively connected with its in/output to the coupling unit. Furthermore, preferably the first coupling is closed in non-energized state. 
     The transmission is preferably a continuously variable transmission and may be a mechanical (pulleys with push belt or chain), a powersplit mechanical, an electrical, or a powersplit electrical continuously variable transmission. The driving source may be a combustion engine or an electromotor. 
     The flywheel module further preferably comprises a hydraulic pump which is connected to the node. If the continuously variable transmission comprises an input shaft as well as an output shaft and also a pulley on each shaft and an endless flexible transmission element around the pulleys, at least one pulley disc of one of the pulleys being in a position to be moved from and to the other pulley disc of the pulley, the pump can provide piston displacement by means of a piston connected to this pulley, which piston is displaceable in a hydraulic cylinder. The pump can be directly connected to the node, so that the latter automatically rotates in unison with the driving source. 
     A disadvantage of this is that at a low speed of the driving source the output (flow) of the pump is low. Sometimes rapid switching is to be performed and a high flow is required, for example in case of an emergency stop or a tip shift. This requires the pump to be designed for high flow at low speed. At higher speeds the pump then often produces too much flow and the pump is then actually over-dimensioned, so that it produces more losses than necessary. At low, sub-normal speeds (no high flow) the pump is then over-dimensioned and produces more losses than necessary also in this situation. 
     An additional disadvantage of this is that if the driving source is switched off, for example in a hybrid application (idle stop, start stop), no pressure is available for enabling the launch of the vehicle. 
     An embodiment of the flywheel module according to the invention, in which the aforementioned disadvantages do not occur is characterized, in that the flywheel module comprises a hydraulic buffer which is connected to the pump. As a result, the pump may be down-sized (caused to deliver less flow), while under normal working conditions the flow is still sufficient for all its functions to be performed, so that no energy is wasted. In the case where much flow is needed, the accumulator can help out. Besides, the accumulator can produce pressure if the driving source is in the off mode. 
     The flywheel module further preferably comprises en electromotor which can drive the pump, as well as a freewheel bearing which is positioned between on the one hand the pump plus electromotor and the node on the other. The pump then does not have a direct connection to the node. In consequence, the pump can electrically be brought to a higher speed than the input shaft of the CVT, so that the pump may be down-sized further. The electromotor is operated in start-stop mode in which the hydraulic accumulator is charged. 
     It should be observed that the pump and accumulator or the pump and accumulator and electromotor and freewheel bearing can also be advantageously applied to a module without a flywheel unit. 
     The flywheel module can be a separate module which can be built in in a simple fashion in an already existing drive of a vehicle. To this end an embodiment of the flywheel module according to the invention is characterised, in that the flywheel module further includes:
         first coupling means, for coupling the input shaft to the driving source, as well as   second coupling means, for coupling the output shaft to the transmission, which first and second coupling means are arranged as splines present on or in the input and output shafts.       

     A further embodiment of the flywheel module according to the invention is characterised in that the reduction gearing is formed by a gear transmission. 
     In one embodiment the coupling device is formed by a second coupling which is connected to the reduction gearing, the reduction gearing being positioned between the second coupling and the flywheel. Preferably, the second coupling is open in non-energized state. 
     In another embodiment the coupling device comprises a coupling support device as well as a planetary gear set comprising three rotational members, a first rotational member of which being connected to the coupling support device, a second rotational member being connected to the gear transmission and the third rotational member being connected to the in/output of the flywheel unit. The coupling support device preferably comprises an electromotor or a brake. 
     A further embodiment of the flywheel module according to the invention is characterised, in that the flywheel unit further comprises a further flywheel which is connected to the gear transmission. 
     Another embodiment of the flywheel module according to the invention is characterised, in that the reduction gearing is formed by a planetary gear set and the coupling device is formed by a friction brake, which gear set comprises three rotational members, a first rotational member of which being connected to the flywheel, a second rotational member being connected to the output of the reduction gear unit and the third rotational member being connected to the friction brake. 
     A still further embodiment of the flywheel module according to the invention is characterised, in that a third coupling is positioned between the flywheel and the reduction gear unit. 
     Yet another embodiment of the flywheel module according to the invention is characterised, in that the flywheel is located in an airtight housing in which there is underpressure, with the third coupling being arranged as a magnetic coupling of which one coupling half is located inside the housing and is connected to the flywheel and the other coupling half is located outside the housing. 
     For obtaining additional functionality a still further embodiment of the transmission system according to the invention is characterised, in that the in/output of the flywheel unit is further connected to the first coupling half of the first coupling, with a fourth coupling being positioned between the in/output of the flywheel module and the first coupling half. 
     A further reduction gearing is preferably positioned between the in/output of the flywheel module and the node. 
     Yet again a further embodiment of the flywheel module according to the invention is characterised, in that the flywheel module further includes an electrical machine which is connected to the node or to the further reduction gearing if there is a further reduction gearing positioned between the in/output of the flywheel module and the node. 
     The invention further also relates to a transmission system for use in a vehicle that comprises a driving source arranged as a combustion engine and driven wheels, which transmission system comprises a transmission having a first in/output shaft and a second in/output shaft which can be connected to the driven wheels, as well as a flywheel module according to the invention, of which the input shaft can be coupled to the combustion engine and the output shaft can be coupled to the first in/output of the transmission, between the node and the first or second in/output shaft of the transmission there being positioned a fifth coupling. The fifth coupling is preferably open in non-energized state. 
     Preferably all component parts, except for the flywheel, are present in a further housing which is in open connection to or integral with the housing of the transmission. 
     The invention further relates to a method for starting a combustion engine of a vehicle during driving, which vehicle comprises driven wheels in addition to the combustion engine and a transmission system according to the invention positioned therebetween, while during the driving the first coupling is open and the second and fifth couplings are closed. With respect to this method the invention is characterised, in that the fifth coupling is operated in slipping fashion, on which occasion the first coupling is closed and the combustion engine is started, after which the fifth coupling is closed completely. 
     Furthermore, the invention relates to a method for starting a combustion engine of a vehicle during the launch, which vehicle comprises driven wheels in addition to the combustion engine as well as a transmission system according to the invention positioned therebetween, at the time of the launch of the vehicle the first coupling being open, the second coupling being closed and the fifth coupling being in a slipping mode. With respect to this method the invention is characterised, in that prior to the fifth coupling being closed completely, the first coupling is closed, on which occasion the combustion engine is started, after which the fifth coupling is closed completely. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be further elucidated below in more detail with reference to examples of embodiments of the flywheel module and the transmission system according to the invention and represented in the drawing figures, in which: 
         FIG. 1  shows a first embodiment of the flywheel module according to the invention, in which the reduction gear unit is arranged as a planetary gear set and a friction brake; 
         FIG. 2  shows a second embodiment of the flywheel module according to the invention, in which the reduction gear unit is arranged as a gear transmission and a coupling; 
         FIG. 3  shows a third embodiment of the flywheel module according to the invention, in which the flywheel unit is further connected to the first coupling half of the first coupling; 
         FIG. 4  shows a fourth embodiment of the flywheel module according to the invention, in which a fifth coupling is present between the node and the transmission; 
         FIG. 5  shows a fifth embodiment of the flywheel module according to the invention, in which the coupling device is formed by a planetary gear set and an electromotor; 
         FIG. 6  shows a sixth embodiment of the flywheel module according to the invention, comprising a hydraulic system; 
         FIG. 7  shows a seventh embodiment of the flywheel module according to the invention, in which the flywheel module is provided with coupling means; 
         FIGS. 8-10  show three variants of the flywheel module shown in  FIG. 7 ; and 
         FIGS. 11-13  show concrete embodiments of the flywheel modules shown in  FIGS. 8-10 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a layout of a vehicle comprising a transmission system in a first embodiment of the flywheel module according to the invention. The vehicle  1  has a driving source  3  which is connected to the driven wheels  5  via a transmission system. The transmission system comprises a transmission  7  and a flywheel module  9  positioned between the driving source and transmission. 
     The flywheel module  9  comprises a coupling unit  11  and a flywheel unit  13 . The coupling unit comprises an input shaft  15  which is connected to the driving source, and an output shaft  17  which is connected to a first in/output  19  of the transmission  7 . A second in/output  21  of the transmission is connected to the driven wheels  5 . The coupling unit further comprises a first coupling  23  which comprises a first coupling half  25  connected to the input shaft, and a second coupling half  27  connected to the output shaft. 
     The flywheel unit comprises an in/output  28  as well as a flywheel  29  and a reduction gear unit  31  which has an input  33  connected to the flywheel, and an output  35  which is connected to the in/output of the flywheel unit. The reduction gear unit comprises a reduction gearing and a coupling device connected to the reduction gearing. The reduction gear unit is comprised of a reduction gearing and a coupling device. The reduction gearing is in this case formed by a planetary gear set  37  and the coupling device by a friction brake  39 . This planetary gear set  37  comprises three rotational members, a first rotational member of which being connected to the flywheel  29 , a second rotational member being connected via a node  41  to the coupling device  11 , and the third rotational member being connected to the friction brake  39 . 
       FIG. 2  shows a layout of a vehicle comprising a second embodiment of the flywheel module according to the invention. All components that are equal to those of the first embodiment shown in  FIG. 1  are designated by like reference numerals. This flywheel module differs from the first embodiment in that the reduction gear unit  31  comprises a gear transmission  45  and a second coupling  47  which is arranged as a friction coupling. There may even be positioned a third coupling (not shown) between the flywheel  29  and the reduction gear unit  31 . 
       FIG. 3  shows a layout of a vehicle comprising a third embodiment of the flywheel module according to the invention. All components that are equal to those of the first embodiment shown in  FIG. 1  are designated by like reference numerals. This flywheel module  49  comprises a further reduction gearing  51  between the in/output  28  of the flywheel unit  13  and the node  41 . This reduction gearing  51  is formed by a further planetary gear set having three rotational members, a first rotational member of which being connected to the in/output  28 , a second rotational member being connected to the node  41 , and the third rotational member being connected to the firm object  53 , for example the housing of the transmission system. 
     In this flywheel module  49  the in/output  28  of the flywheel unit  13  is further connected to the first coupling half  25  of the first coupling  23  via a fourth coupling  55 . The first coupling  23  and the fourth coupling  55  are both arranged as a friction coupling. 
       FIG. 4  shows a layout of a vehicle comprising a fourth embodiment of the flywheel module according to the invention. All components that are equal to those of the third embodiment shown in  FIG. 3  are designated by like reference numerals. This flywheel module  57  differs from the third embodiment in that yet a fifth coupling  59  is present between the node  41  and the continuously variable transmission  7 . Furthermore, the first coupling  23  and the fourth coupling  55  are both arranged as a claw coupling or synchromesh. 
       FIG. 5  shows a layout of a vehicle comprising a fifth embodiment of the flywheel module according to the invention. All components that are equal to those of the second embodiment shown in  FIG. 2  are designated by like reference numerals. In this flywheel module  59  the third coupling  61  is positioned between the gear transmission  45  and the flywheel  29 . Furthermore, in this case the coupling device is formed by a planetary gear set  63  and a coupling support device  65 , which in this embodiment is formed by an electromotor and is connected to one of the rotational members of the planetary gear set. In this embodiment yet a further coupling  67  (indicated in broken lines) may be positioned between two out of three rotational members of the planetary gear set  63 . In addition, a further flywheel  69  can be connected to the reduction gearing  45  via yet another coupling  71  (also indicated in broken lines). 
       FIG. 6  shows a layout of a vehicle comprising a sixth embodiment of the flywheel module according to the invention. All components that are equal to those of the second embodiment shown in  FIG. 2  are designated by like reference numerals. In this flywheel module  73  an electrical machine in the form of an electromotor/generator  75  and a hydraulic pump  77  are connected to the node  41  and, furthermore, a hydraulic accumulator  79  is connected to the pump  77 . Here too, there is a fifth coupling  81  between the node and the first in/output shaft  19  of the transmission  7 . The fifth coupling, however, may also be present in the secondary shaft of the transmission  7  (designated by  81 ′). The first coupling  23  is preferably a coupling that is normally closed, which is to say that if this coupling is not operated/energized, it is closed. The second and fifth couplings  47  and  81  are preferably normally open. 
     In this flywheel module  73  the electromotor  75  is positioned close to the pump  77  and, furthermore, a freewheel bearing  80  is positioned between on the one hand the pump  77  and the electromotor  75  and on the other hand the node  41 . Between the pump and the accumulator there is a valve  78  for shutting off and releasing the connection between the two. The electromotor  75  can be instrumental in bringing the pump  77  to a higher speed than the input shaft  19  of the transmission  7 , so that the pump can be downsized further. The electromotor  75  is operated in the start-stop mode during which the hydraulic accumulator  79  is charged. 
     Prior to the launch of the vehicle, the coupling  81  is first to be closed and the coupling  23  to be opened. Now the vehicle can be launched on the electromotor  75  while the pressure for operating the couplings  23  and  81  and the transmission  7  is supplied by the hydraulic accumulator  79 . 
     For starting the driving source  3  of the vehicle during driving (coupling  81  closed and coupling  23  open), the coupling  81  is operated in a slipping manner while coupling  23  is open. Subsequently, the coupling  23  is closed while the driving source  3  embodied as a combustion engine is started, after which the coupling  81  is closed completely. 
       FIG. 7  shows a seventh embodiment of the flywheel module according to the invention. This flywheel module  83  comprises first coupling means  85  for coupling the input shaft  15  to the driving source  3 , and second coupling means  87  for coupling the output shaft  17  to the transmission  7 . The first and second coupling means are arranged as splines present on or in the input and output shafts  15 ,  17 . 
       FIGS. 8 ,  9  and  10  show three variants of the flywheel module shown in  FIG. 7 . In the flywheel module  89  shown in  FIG. 8  a further reduction gearing  91  is present between the reduction gear unit  31  and the coupling unit  11 . The second coupling  47  may then also be positioned between the reduction gearing  45  and the flywheel  29  (designated by  47 ′) in lieu of between the two reduction gearings  45  and  49 , or between the further reduction gearing  49  and the node  41  (designated by  47 ″). In the flywheel module  93  shown in  FIG. 9  a third coupling  95  is further positioned between the reduction gear unit  31  and the flywheel  29 , and in the flywheel module  97  shown in  FIG. 10  an electromotor  99  is connected to the further reduction gearing  91 . 
     In  FIGS. 11 ,  12  and  13  are shown concrete embodiments of the flywheel modules  89 ,  93  and  97  shown in  FIGS. 8 ,  9  and  10 . In the flywheel module  89  shown in  FIG. 11  the input shaft  15  has external splines  85  and the output shaft  17  is hollow and has internal splines  87 . In the flywheel module  93  shown in  FIG. 12  the flywheel  29  is located in an airtight housing  101  in which there is underpressure. The third coupling  95  is arranged as a magnetic coupling of which one coupling half is located inside the housing  101  and the other coupling half is located outside the housing. In the flywheel module  97  shown in  FIG. 13  the electromotor  99  meshes with a gear present on the shaft with a gear of the further reduction gearing  91 . 
     Albeit the invention has been described in the foregoing with reference to the drawing Figures, it should be pointed out that the invention is not by any manner or means restricted to the embodiments shown in the drawing Figures. The invention also extends over any embodiments deviating from the embodiments shown in the drawing Figures within the spirit and scope defined by the claims.