Abstract:
A hydraulic energy source for supplying a downstream hydraulic system with hydraulic energy. In particular, a hydraulic system for controlling and/or cooling a transmission preferably a dual clutch transmission. The hydraulic energy source enables a first partial volume flow which is produced at a comparatively high system pressure and which is used to supply an actuator of the hydraulic system and a second partial volume flow which is produced at a comparatively low cooling pressure and which is used to cool the hydraulic system, to be produced The hydraulic energy source has an electrically driveable first volume flow source which is used to produce the first partial volume flow and a second volume flow source which is used to produce the second partial volume flow. The second volume flow source is drivingly connected independently of an internal combustion engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT/DE2010/000473 filed Apr. 26, 2010, which in turn claims the priority of DE 10 2009 019 877.6 filed May 6, 2009 and DE 10 2009 054 276.0 filed Nov. 23, 2009. The priority of these applications is hereby claimed and these applications are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a hydraulic energy source for supplying a downstream hydraulic system with hydraulic energy, in particular a hydraulic system for controlling and/or cooling a transmission, especially a dual clutch transmission. The hydraulic energy source enables the production of a first partial volume flow, which is at a comparatively high system pressure and which is used to supply an actuator system of the hydraulic system, and a second partial volume flow, which is at a comparatively low cooling pressure and which is used to supply a cooling system of the hydraulic system. 
     BACKGROUND OF THE INVENTION 
     Hydraulic energy sources for supplying a downstream hydraulic system with hydraulic energy are known. 
     In automatic transmissions, such as step-change automatic transmissions, continuously variable transmissions or dual clutch transmissions, with hydraulic control, i.e. actuator activation, such as clutch actuator or shift actuator control, and a cooling/lubricating oil supply, there is a need for an oil supply (generally a pump with a pump drive). In general, the pump drive is a mechanical pump drive, which is coupled to the internal combustion engine. 
     In modern transmissions, this mechanical pump drive can be supplemented by an electric pump arrangement (i.e. an electric motor with a pump). 
     The prior art also includes oil supply systems which manage without a mechanically driven pump for the transmission and clutch actuator systems. Here, however, there is no requirement for cooling oil owing to the construction of the clutch as a dry clutch. 
     If the intention is to dispense with a mechanical drive, especially in the case of wet clutches, all the hydraulic power required for this purpose must be provided by the electrically driven pump in the case of the known systems. However, there is great variety in the operating states which arise in this case. Thus, there are both situations involving a high volume-flow and a low pressure requirement and situations with a high pressure and a low volume-flow requirement. These completely different boundary conditions necessitate very large electric motors (costs, weight, load on the onboard electrical system) in the case of a conventional electric motor/pump arrangement (speed-controlled drive) in order to provide the different operating states in an oil supply system. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide an improved and/or an alternative hydraulic energy source for supplying a downstream hydraulic system with hydraulic energy, in particular a hydraulic system for controlling and/or cooling a transmission, especially a dual clutch transmission, and, in particular, to enable an energy-efficient supply and/or a supply which is optimized in terms of design. 
     This object is achieved, in the case of a hydraulic energy source the supplying a downstream hydraulic system with hydraulic energy, in particular a hydraulic system for controlling and/or cooling a transmission, especially a dual clutch transmission, said hydraulic energy source enabling the production of a first partial volume flow, which is at a comparatively high system pressure and which is used to supply an actuator system of the hydraulic system, and a second partial volume flow, which is at a comparatively low cooling pressure and which is used to supply a cooling system of the hydraulic system, by virtue of the fact that the hydraulic energy source has an electrically driveable or driven first volume flow source for producing the first partial volume flow and a second volume flow source for producing the second partial volume flow, the second volume flow source being independent of an internal combustion engine in terms of drive. The volume flow sources can advantageously be matched to a pressure and/or volume-flow requirement of the actuator system and the cooling system. The partial volume flows can vary, that is to say may even fall temporarily more or less to zero, depending on the requirements of the downstream actuator system or cooling system, with the system pressure, for example, being applied to the downstream actuator system. The term “volume flow source” can be taken to mean any arrangement for producing a volume flow, and division of the volume flow into two partial volume flows by means of downstream components or control may also be taken to entail two volume flow sources. 
     In one embodiment of the hydraulic energy source, provision is made to enable the first volume flow source to be driven by means of a first electric motor. The first volume flow source can advantageously be supplied with mechanical energy independently of another component, e.g. an internal combustion engine associated with the transmission. 
     In another embodiment of the hydraulic energy source, provision is made for the first volume flow source to have a first pump and the second volume flow source to have a second pump, a disengageable coupling enabling the second volume flow source to be either driven by means of the first electric motor or without drive. It is advantageously possible to connect up the second volume flow source to meet an increased cooling requirement. 
     In another embodiment of the hydraulic energy source, provision is made for the first electric motor to have a variable speed. By adapting a speed of the first electric motor, it is also advantageously possible to vary a corresponding volume flow driven thereby, that is to say to match it to a corresponding requirement of the downstream actuator system and/or cooling system, for example. 
     In another embodiment of the hydraulic energy source, provision is made to enable the first volume flow source to be associated either with the actuator system or with the cooling system by means of a downstream control valve. The first partial volume flow and the second partial volume flow can advantageously be produced by means of the first volume flow source, e.g. by pulsing. Moreover, it is possible to provide a pressure accumulator, in order to provide the system pressure for example when the second partial volume flow is being supplied. 
     In another embodiment of the hydraulic energy source, provision is made for a hydraulic energy accumulator to be associated with the actuator system. The energy accumulator can advantageously be used to provide storage and release of hydraulic energy, e.g. in order to cover pressure peaks, to shut down the hydraulic energy source temporarily and/or to split up a volume flow in order in this way to be able to obtain two volume flow sources with just one pump. 
     In another embodiment of the hydraulic energy source, provision is made for the first volume flow source and the second volume flow source to be implemented by means of a common pump, wherein, depending on a direction of rotation of the first electric motor, which is associated with the common pump by means of a speed-dependent transmission, the actuator system can be supplied with the first partial volume flow in a first operating position of the control valve and in a first direction of rotation of the first electric motor, and the cooling system can be supplied with the second partial volume flow in a second operating position of the control valve and in a second direction of rotation of the first electric motor. The directional transmission can advantageously have a different transmission ratio, depending on a direction of rotation, thus making it possible to obtain a low volume flow for supplying the system pressure and a high volume flow for supplying the cooling pressure, i.e. for supplying the cooling system, for example, depending on the direction of rotation, while requiring just one pump and one electric motor to achieve this. It may also be possible to time-multiplex an overall volume flow required from the pump, especially in combination with a hydraulic energy accumulator, in order in this way to produce the partial volume flows. 
     In another embodiment of the hydraulic energy source, provision is made for the second volume flow source to have a jet pump. By means of a jet-type source, it is advantageously possible to convert pressure energy into kinetic energy, a drop in pressure resulting in an increase in the volume flow, in order advantageously to supply a comparatively large volume flow at a comparatively low pressure for the cooling system, for example. 
     In another embodiment of the hydraulic energy source, provision is made for the first volume flow source to have a first pump flow of a multi-flow pump, and for the second volume flow source to have a second pump flow of the multi-flow pump. By means of the various pump flows of the multi-flow source, it is advantageously possible to produce the partial volume flows, it being possible, for example, to design the first pump flow for a comparatively low volume flow and the high system pressure and to design the second pump flow to be correspondingly larger, to give a high flow rate at a comparatively low cooling pressure. 
     In another embodiment of the hydraulic energy source, provision is made to enable the second volume flow source to be driven by means of a hydraulic motor arranged downstream of the first volume flow source. This arrangement advantageously represents a hydraulic transformer, which can transform a comparatively small volume flow which is at a high pressure into a comparatively large volume flow which is at a low pressure. This is an advantageous way of transforming the energy arising from the high system pressure into the comparatively large second partial volume flow, which is at the low cooling pressure, with maximum energy efficiency. 
     In another embodiment of the hydraulic energy source, provision is made for an accumulator charging valve to be arranged downstream of the first partial volume flow source. The shutoff valve can advantageously be used in combination with a pressure accumulator, thus enabling the first partial volume flow source to be decoupled by means of the shutoff valve where appropriate in order thereby to prevent an unwanted backflow into the first volume flow source. 
     In another embodiment of the hydraulic energy source, provision is made for the second electric motor to have a variable speed. The second electric motor can advantageously be used to vary the second partial volume flow. 
     In another embodiment of the hydraulic energy source, provision is made to enable the direction of rotation of the first electric motor to be varied. The first electric motor can advantageously be varied in one direction of rotation, thereby advantageously providing an adjustment facility for adjusting the first volume flow and the second volume flow. 
     In another embodiment of the hydraulic energy source, provision is made to enable the volume flow sources to be driven by means of the first electric motor, the first electric motor being associated with the first volume flow source by means of a first one-way clutch and with the second volume flow source by means of a second one-way clutch opposed to the first one-way clutch. It is advantageously possible to operate either the first volume flow source or the second volume flow source through a change in the direction of rotation of the first electric motor. 
     In another embodiment of the hydraulic energy source, provision is made to enable the first volume flow source to be driven by means of the first electric motor and the second volume flow source to be driven by means of a second electric motor. The electric motors can advantageously be activated differently, thereby advantageously enabling the volume flow sources to be adjusted to the requirements of the actuator system and the cooling system. Where appropriate, completely separate branches can be involved, each capable of being supplied with hydraulic energy by means of one of the volume flow sources. 
     The object is furthermore achieved in a transmission, in particular a dual clutch transmission, with a hydraulic system having a hydraulic energy source as described above. The advantages described above are achieved. 
     Further advantages, features and details will emerge from the following description, in which one embodiment is described in detail with reference to the drawing. Parts which are identical, similar and/or have the same functions are provided with the same reference signs. In the drawing: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a hydraulic energy source, which has a jet pump for supplying a cooling system; 
         FIG. 2  shows another hydraulic energy source, which has a variable-speed electric motor, by means of which a multi-flow pump can be driven; 
         FIG. 3  shows another hydraulic energy source having a first electric motor and a second electric motor for supplying an actuator system and the cooling system; 
         FIG. 4  shows a hydraulic energy source similar to that shown in  FIG. 3 , the difference being that a control valve for supplying either the actuator system or the cooling system is arranged downstream of a pump associated with the first electric motor; 
         FIG. 5  shows a hydraulic energy source similar to that illustrated in  FIG. 4 , the difference being that only one electric motor is provided, which drives two pumps, it being possible for a second pump to be isolated by means of a clutch; 
         FIG. 6  shows a hydraulic energy source similar to that illustrated in  FIG. 5 , the difference being that the electric motor is directional and is associated with two pumps by means of two opposed one-way clutches; 
         FIG. 7  shows another hydraulic energy source having an electric motor and a pump, the electric motor being directional and being associated with the pump by means of a directional transmission; and 
         FIG. 8  shows another hydraulic energy source having an electric motor and a pump associated therewith, and a hydraulic motor arranged downstream of the pump for the purpose of driving another pump in order to supply the cooling system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a hydraulic energy source for supplying an actuator system  70  and a cooling system  100  of a transmission, only part of which is shown, e.g. a dual clutch transmission with wet clutches, which can be cooled by means of the cooling system  100 . The hydraulic energy source has a first electric motor  20 , the speed of which is variable. The first electric motor  20  is associated with a first pump  10  by means of a drive connection  30 . The first pump  10  is designed for a high pressure and a low pressure, e.g. a system pressure for supplying the actuator system  70  and a comparatively lower cooling pressure for supplying the cooling system  100 . A suction filter  40  is arranged upstream of the first pump  10 , and a tank  110  is arranged upstream of the suction filter  40 . Arranged downstream of the first pump  10  is a selector valve  50 , by means of which the first pump  10  can be either associated with the downstream actuator system  70  and the cooling system  100  or isolated therefrom. Arranged downstream of the selector valve  50  is a pressure accumulator  60 , by means of which hydraulic energy, in particular hydraulic energy at the level of the system pressure for supplying the actuator system  70 , can be stored. Arranged downstream of the selector valve  50 , in two branches, is the actuator system  70  and, in another branch, an oil cooler  80  for cooling a hydraulic medium delivered from the tank  110 , and arranged downstream of the oil cooler  80  is a jet pump  90 . 
       FIG. 2  shows another hydraulic energy source, which can likewise be driven by means of a first variable-speed electric motor  27 . By way of a difference, two drive connections  37  and  38  are provided. By means of drive connection  37 , the first electric motor  27  is coupled to a first pump  17  or pump flow. The first pump  17  or first pump flow of the first pump  17  is associated by means of drive connection  38  with a second pump flow of a second pump  18 . The pumps  17  and  18  form a multi-flow pump, the first pump flow of the first pump  17  being made smaller than the second pump flow of the second pump  18 . The first pump  17  is used to supply the actuator system  70 . The second pump  18  is used to supply the cooling system  100 . Arranged downstream of the second pump is a bypass valve  52 , by means of which the second pump can be short-circuited or connected to the tank  110 . When the cooling requirement of the cooling system  100  is comparatively low, the bypass valve  52  can advantageously be used to isolate the second pump from the cooling system  100 . 
     In the hydraulic energy source shown in  FIG. 2 , the jet pump  90  is optional. 
       FIG. 3  shows another hydraulic energy source, which, in contradistinction to the illustration in  FIGS. 1 and 2 , has a first electric motor  21  and a second electric motor  22 , which supply completely independent branches for supplying the actuator system  70  and the cooling system  100  with hydraulic energy. For this purpose, the first electric motor  21  is associated with a first pump  11  by means of a drive connection  31 , the first pump  11  being designed to produce a high pressure, i.e. the system pressure for supplying the actuator system, with a comparatively small first partial volume flow. The second electric motor  22  is associated with a second pump  12  by means of a drive connection  32 . The second pump  12  is designed to produce a comparatively large second partial volume flow at the comparatively low cooling pressure for supplying the cooling system  100 . 
     Arranged downstream of the first pump  11  is an accumulator charging valve  51 , by means of which the pressure accumulator  60  and the actuator system  70  can either be isolated from the first pump  11  or associated therewith. 
     Arranged downstream of the second pump  12  are the oil cooler  80  and the jet pump  90 . In the illustration according to  FIG. 3 , the jet pump  90  is optional. To allow variable driving of the second pump  12 , the second electric motor  22  furthermore has a variable speed, advantageously allowing the cooling system  100  to be supplied as required for cooling with the hydraulic medium. 
       FIG. 4  shows another hydraulic energy source, which has a first electric motor  25  and a second electric motor  26 . The first electric motor  25  is associated by means of a drive connection  35  with a first pump  15  for producing the first partial volume flow for supplying the actuator system  70 . The second electric motor  26  is associated by means of a drive connection  36  with a second pump  16  for producing the second partial volume flow for supplying or cooling the cooling system  100 . The selector valve  50  is associated with the first pump  15 , and therefore said pump can likewise be used to supply the cooling system. The first pump  15  can be made smaller than the second pump  16 . 
     The jet pump  19  illustrated in  FIG. 4  is optional. 
       FIG. 5  shows another hydraulic energy source having a first electric motor  23  that has a variable speed. The first electric motor  23  is associated by means of a drive connection  330  with a first pump  13  for supplying the actuator system  70  with the first partial volume flow at the system pressure. The first pump  13  is associated with a second pump  14  by means of a disengageable drive connection  331 . The second pump  14  is made larger than the first pump  13  and is used to produce the second partial volume flow at the lower cooling pressure for supplying the cooling system  100 . The selector valve  50  is arranged downstream of the first pump  13 . 
     The disengageable drive connection  331  has a disengageable coupling. A corresponding control system for operating the disengageable coupling  120  is not shown specifically in  FIG. 5 . The disengageable coupling  120  advantageously enables the second pump  14  to be optionally associated with the first variable-speed electric motor  23 . The second pump  14  can advantageously be connected up as required, thus for example when the cooling system  100  has an increased cooling requirement. If the cooling system  100  does not have a volume flow or cooling requirement, the second pump  14  can be decoupled from the first electric motor  23  by means of the disengageable coupling  120  of the drive connection  331 . 
     The jet pump  90  illustrated in  FIG. 5  is optional. 
       FIG. 6  shows another hydraulic energy source having a first electric motor  291 . The first electric motor  291  has a variable speed and is associated with a first pump  191  by means of a directional drive connection  391  and with a second pump  192  by means of a directional drive connection  392 . The first pump  191  is made smaller than the second pump  192 . Directional drive connection  391  has a one-way clutch  150  arranged between the first pump  191  and the first electric motor  291 . Directional drive connection  392  has a one-way clutch arranged between the first electric motor  291  and the second pump  192 . The one-way clutches  150  and  151  are opposed, with the result that only the first pump  191  is driven in a first direction of rotation of the first electric motor  291  and only the second pump  192  is driven in a second direction of rotation. It is advantageously possible, by choosing the direction of rotation of the first electric motor  291 , to control whether only the first pump  191  or only the second pump  192  delivers or is driven. The selector valve  50  is arranged downstream of the first pump  191 . The oil cooler  80 , the jet pump  90  and the cooling system  100  are arranged downstream of the second pump  192 . 
     The jet pump  90  illustrated in  FIG. 6  is optional. 
       FIG. 7  shows another hydraulic energy source having a first pump  193 . The first pump  193  is associated by means of a drive connection  156  with a directional transmission  155 . The transmission  155  has a first gear stage  163  and a second gear stage  164 . 
     A first electric motor  293  is associated with the first gear stage  163  by means of a first directional drive connection  393 . The first electric motor  293  is associated with the second gear stage  164  by means of a second directional drive connection  394 . The first drive connection  393  has a first one-way clutch  153 . The second drive connection  394  has a second one-way clutch  154 . The first  153  and the second one-way clutch  154  are opposed, with the result that either the first gear stage  163  or the second gear stage  164  is driven, depending on a direction of rotation of the first electric motor  293 , for which purpose the first electric motor  293  is of speed-dependent design. The first gear stage  163  has three gearwheels and a transmission ratio of approximately 1 to 1. The second gear stage  164  has two gearwheels and brings about a speed increase. It is apparent that different speeds are obtained at the first pump  193  for the same speed of the first electric motor  293 , depending on the direction of rotation of the first electric motor  293 . In this way, it is advantageously possible, simply by choosing the direction of rotation of the first electric motor  293 , to set a larger or smaller volume flow at the first pump  193 . 
     The selector valve  50  is arranged downstream of the first pump  193 . It is advantageously possible, depending on the direction of rotation of the first electric motor  293 , to provide either a comparatively small first partial volume flow at the high system pressure in order to supply the actuator system  70  or to provide a comparatively large second partial volume flow at the comparatively low cooling pressure in order to supply the cooling system  100 . 
     The jet pump illustrated in  FIG. 7  is optional. 
       FIG. 8  shows another hydraulic energy source having a first electric motor  29 , which is of variable-speed design. The first electric motor  29  is associated with a first pump  19  by means of a drive connection  39 . The first pump  19  can be made comparatively small in order to produce the comparatively high system pressure with a comparatively low first partial volume flow. The selector valve  50  is arranged downstream of the first pump  19 . Arranged downstream of the selector valve  50  is another selector valve  53 , which associates selector valve  50  either with the cooling system  100  or with a hydraulic motor of a hydraulic transformer  130 . The hydraulic motor of the hydraulic transformer  130  is associated with a second pump  130  by means of a drive connection, it being possible to drive the second pump  133  by means of the hydraulic motor  131  via the drive connection  132 . By means of the hydraulic transformer  130 , it is advantageously possible to transform the first partial volume flow, which is at the high system pressure, into the second partial volume flow, which is at the comparatively low cooling pressure and is larger than the first partial volume flow. 
     The jet pump  90  shown in  FIG. 8  is optional. 
       FIG. 1  shows a speed-controlled electric drive with the jet pump  19  for the cooling function of the cooling system  100 , and it is advantageously possible to reduce the size of the first pump  10  and hence the torque at higher pressures. 
       FIG. 2  shows a speed-controlled electric drive with the multi-flow pump and the optional suction jet pump  90 . It is advantageous that only the first pump  17  for producing the high system pressure has to be driven by the first electric motor  27 . 
     By means of the first electric motor  21  and the second speed-controlled motor  22 , the hydraulic energy source in  FIG. 3  allows two completely independent branches for supplying the actuator system and the cooling system  100 . According to  FIG. 4 , coupling between the branches can be provided by means of the selector valve  50 . 
       FIG. 5  shows a hydraulic energy source with a speed-controlled first electric motor, which is associated with the pumps  13  and  14 . The second pump  14 , which is of larger design, can be connected up by means of the disengageable coupling. 
       FIG. 6  shows a hydraulic energy source having a first electric motor, which has a variable speed and a variable direction of rotation, with for the smaller first pump  191 , which is designed to produce a the high system pressure and the low cooling pressure, and for a for the second, larger pump  192 , which is designed to produce the lower cooling pressure. The one-way clutches  150  and  151  are built in to the drive connections  391  and  392  between the first electric motor and corresponding pump shafts, with the result that the smaller, first pump is driven in a first direction of rotation and the larger, second pump  192  is driven in a second direction of rotation. As an alternative, it is possible to pass the mechanical power flow through one of the pumps  191  or  192  and to provide an opposed one-way clutch at the end of the first pump  191 . 
       FIG. 7  shows a hydraulic energy source which has the first electric motor  293 , the direction of rotation of which is variable, and a transmission  155 , the direction of rotation of which is variable. 
       FIG. 8  shows a hydraulic energy source with a variable-speed first electric motor  29 , which with a first pump  19  designed for a high pressure and a low pressure and with the hydraulic transformer  130  to provide large cooling rates. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of Reference Signs 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10, 11, 13, 15, 17, 191, 193, 19 
                 First Pump 
               
               
                   
                 12, 14, 16, 18, 192, 130, 133 
                 Second Pump 
               
               
                   
                 50 
                 Selector Valve 
               
               
                   
                 70 
                 Actuator System 
               
               
                   
                 19, 90 
                 Jet Pump 
               
               
                   
                 20, 21, 22, 23, 25, 26, 27, 291, 
                 Electric Motor 
               
               
                   
                 293, 29 
               
               
                   
                 31, 32, 35, 36, 37, 38, 330, 331, 
                 Drive Connections 
               
               
                   
                 391, 392, 156, 393, 394, 39, 132 
               
               
                   
                 40 
                 Suction Filter 
               
               
                   
                 50, 53 
                 Selector Valve 
               
               
                   
                 51 
                 Accumulator Charging 
               
               
                   
                   
                 Valve 
               
               
                   
                 52 
                 Bypass Valve 
               
               
                   
                 60 
                 Pressure Accumulator 
               
               
                   
                 80 
                 Oil Cooler 
               
               
                   
                 100 
                 Cooling System 
               
               
                   
                 110 
                 Tank 
               
               
                   
                 120 
                 Coupling 
               
               
                   
                 130 
                 Hydraulic Transformer 
               
               
                   
                 131 
                 Hydraulic Motor 
               
               
                   
                 150, 151, 153, 154 
                 One-Way Clutch 
               
               
                   
                 155 
                 Transmission 
               
               
                   
                 163 
                 First Gear Stage 
               
               
                   
                 164 
                 Second Gear Stage