Patent Publication Number: US-2023151807-A1

Title: Method for actuating a hydraulic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2021/100177 filed Feb. 23, 2021, which claims priority to DE 102020105820.9 filed Mar. 4, 2020, the entire disclosures of which are incorporated by reference herein. 
    
    
     BACHGROUND 
     A method for actuating a hydraulic device for a torque-transmitting device is described, for example, in DE 10 2019 130 158.0. The torque-transmitting device is designed as a double clutch and has a first and a second clutch, each of which can be actuated by a fluid pressure and each of which is hydraulically connected via a fluid tract to a pump device that provides the fluid pressure. The actuation of each clutch is controlled by a clutch valve assigned to the individual clutch. Furthermore, a cooling device is arranged to cool the first and second clutches. The pump device has a first and second pump. The first pump provides the first fluid pressure required to cool the first and second clutches, and the second pump provides the second fluid pressure required to actuate the clutch. 
     The second fluid pressure is maintained by repeatedly intermittently operating the second pump, thereby compensating for a loss of the second fluid pressure in the fluid tract. This post-pump process is known to occur at a predetermined secondary pump rotational speed of the second pump and continues until the second fluid pressure reaches a second fluid target pressure. 
     The determination of the secondary pump rotational speed to be set with the requirement of the most energy-saving and functionally safe operation of the second pump is complex due to the dependence on several influences, such as temperature, pressure leakage, and pump efficiency. 
     SUMMARY 
     The present disclosure, according to an exemplary embodiment, actuates a hydraulic device in a more energy-saving and reliable manner. A hydraulic device can set the required second fluid pressure faster and more accurately, as well as more independently of external influences. A torque-transmitting device can be controlled better and more energy-efficiently. A secondary pump rotational speed can be adaptively preset during operation of the torque-transmitting device. This can reduce the energy consumption of the pump device. 
     The actuation can include open-loop and/or closed-loop control of the hydraulic device. 
     The torque-transmitting device can be arranged in a drive train of a vehicle, in particular of a motor vehicle. The torque-transmitting device can have a clutch and/or a brake. The clutch can be a multiple clutch, in particular a double clutch. The torque-transmitting device can provide frictional torque transmission. The torque-transmitting device can include at least one frictionally engaged torque-transmitting element. The torque-transmitting device can be effective in a power-shiftable E-axle. The E-axle can have at least two switchable gear ratios. The torque-transmitting device can be connected to an electric motor on the input side. 
     The clutch can have a first clutch and a second clutch. The first and second clutches can be independently actuatable. A first clutch valve can be assigned to the first clutch for controlling actuation of the first clutch. A second clutch valve can be assigned to the second clutch for controlling actuation of the second clutch. The first and/or second clutch valve can be arranged between the pump device and the respective clutch in the fluid tract. 
     The torque-transmitting device can have a cooling device for cooling the torque-transmitting device, in particular the first and/or second clutch, with a cooling fluid. The cooling device can also be effective for cooling other components, for example an electric motor. The cooling device can be supplied by the first fluid pressure. 
     The pump device can include a first pump providing the first fluid pressure and a second pump providing the second fluid pressure. The first and second pumps can be operable by a common electric motor. A first direction of rotation of the pump device can provide the first fluid pressure and an opposite second direction of rotation of the pump device can provide the second fluid pressure. The electric motor can be operated independently of a rotational speed of the clutch. This allows a sufficient pump rotational speed to be applied. The first and second pumps can be arranged in a tandem configuration. 
     The hydraulic device can have at least one spring pressure accumulator as a hydraulic capacitor. The spring pressure accumulator can be assigned to one of the two clutches. Each clutch can also be assigned its own spring pressure accumulator. 
     The hydraulic device can have at least one check valve. The check valve can be assigned to one of the two clutches. Each clutch can also be assigned its own check valve. 
     The switchover process can be a post-pump process and the secondary pump rotational speed can be a post-pump rotational speed. Outside the switchover process, the primary pump rotational speed can be applied, or the pump device can be out of operation. 
     The secondary pump rotational speed can be set during the next switchover process with the specification of a reduction of the electrical pump power of the pump device to be provided for this purpose. 
     The secondary pump rotational speed to be preset calculated for the next switchover process is narrowed down to a value in a range of values between a minimum secondary pump rotational speed and a maximum secondary pump rotational speed. It is useful to define a minimum secondary pump rotational speed in order to limit the time period of the suspended primary pump rotational speed. For example, the pump device can suspend the provision of the first fluid pressure once the switchover process is ongoing. This interruption should, for example, be short in time. The specification of a maximum secondary pump rotational speed can be advantageous in order to relieve a rotational speed controller of the pump device and/or to avoid a maximum permissible pump rotational speed of the pump device. 
     During start-up operation of the hydraulic device, where the next switchover process is the first switchover process since the start of operation, the preset secondary pump rotational speed can correspond to a preset initial value. The initial value can be specified as constant or taken from a lookup table. The lookup table can indicate the dependence of the initial value on the second fluid pressure and/or temperature. 
     The second fluid target pressure can be a minimum second fluid pressure or a maximum second fluid pressure. The switchover process can be initiated when the second fluid pressure is below the minimum second fluid pressure or reaches it. The switchover process can be set when the second fluid pressure is above the maximum second fluid pressure or reaches it. 
     The electrical pump power can be calculated from the electrical pump voltage and the electrical pump current. 
     In an embodiment of the disclosure, the presetting of the secondary pump rotational speed in the next switchover process is effected via a reduction or increase compared to the secondary pump rotational speed in the preceding switchover process. 
     In an embodiment of the disclosure, the secondary pump rotational speed in the next switchover process is preset to a value dependent on the secondary pump rotational speed in the preceding switchover process and a rotational speed change value. The rotational speed change value can be preset, in particular be fixed. For example, the rotational speed change value can be 200 rpm. The rotational speed change value can be adaptively changeable during operation of the hydraulic device, in particular between the individual switchover processes. 
     In an embodiment of the disclosure, a first power value is calculated as an averaged electrical pump power over a reference period. 
     In an embodiment of the disclosure, the reference period is the time interval between the completion of the preceding switchover process and the completion of the switchover process preceding it in turn. The reference period can include operation in a first operating state. The reference period can also be limited exclusively to the duration of the preceding switchover process. 
     In an embodiment of the disclosure, the secondary pump rotational speed in the next switchover process is preset in a manner dependent on the first power value and a second power value which includes the electrical pump power of the pump device in the switchover process in turn preceding the preceding switchover process. The secondary pump rotational speed for the next switchover process can be calculated in a manner dependent on whether the first power value is greater than or equal to the second power value. 
     In an embodiment of the disclosure, the secondary pump rotational speed in the next switchover process is preset at least in a manner dependent on a secondary pump rotational speed in the preceding switchover process. 
     In an embodiment of the disclosure, the secondary pump rotational speed in the next switchover process is preset at least in a manner dependent on the secondary pump rotational speed in the preceding switchover process and a secondary pump rotational speed in the switchover process in turn preceding the preceding switchover process. The secondary pump rotational speed for the next switchover process can be calculated in a manner dependent on whether the secondary pump rotational speed in the preceding switchover process is greater than or equal to the secondary pump rotational speed in the switchover process in turn preceding the preceding switchover process. 
     In an embodiment of the disclosure, the preceding switchover process immediately precedes the next switchover process. 
     In an embodiment of the disclosure, the fluid tract has a first fluid branch for supplying the torque-transmitting device with the first fluid pressure and a second fluid branch, which is separated at least in portions from the first fluid branch, for supplying the torque-transmitting device with the second fluid pressure. The second fluid pressure can be greater than the first fluid pressure. 
     Further advantages and advantageous embodiments of the disclosure result from the description of the figures and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is described in detail below with reference to the drawings. Specifically: 
         FIG.  1   : shows a block diagram of a hydraulic device for a torque-transmitting device for execution of a method in an exemplary embodiment of the disclosure. 
         FIG.  2   : shows curve diagrams of various parameters when a method is carried out in the exemplary embodiment of the disclosure. 
         FIG.  3   : shows a flow chart of a method in the exemplary embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a block diagram of a hydraulic device  10  for a torque-transmitting device  12  for execution of a method in an exemplary embodiment of the disclosure. The torque-transmitting device  12  is designed as a double clutch and is arranged in a drive train of a vehicle, in particular a motor vehicle, and has a hydraulically actuatable first clutch K 1  and a hydraulically actuatable second clutch K 2  for alternating torque transmission between a drive element, for example an internal combustion engine and/or an electric motor, and a transmission. The torque-transmitting device  12  may be arranged in a power-shiftable E-axle of the vehicle. 
     Furthermore, the torque-transmitting device  12  comprises a hydraulically operated cooling device C for cooling at least one of the two clutches K 1 , K 2 . The first clutch K 1 , the second clutch K 2 , and also the cooling device C are hydraulically connected to the hydraulic device  10  via a fluid tract  14 . 
     The hydraulic device  10  comprises an electrically operated pump device PD having a first pump P 1  and a second pump P 2 . The first and second pumps P 1 , P 2  are driven by a common electric motor E. A first fluid branch  16  is assigned to the first pump P 1  and a second fluid branch  18  is assigned to the second pump P 2 . The first pump P 1  can be effective in a first operating state of the pump device PD. having a primary pump rotational speed to provide the first fluid pressure pi, The second pump can be effective in a second operating state of the pump device PD, having a secondary pump rotational speed to provide the second fluid pressure p 2 . 
     Furthermore, a system pressure valve SV is provided, downstream of which there are arranged a first clutch valve KV 1  assigned to the first clutch K 1 , and a second clutch valve KV 2  assigned to the second clutch K 2  and arranged in parallel with the first clutch valve KV 1  , 
     The first pump P 1  can provide the first fluid pressure p 1  required for clutch cooling via the cooling device C via the first fluid tract  16 . The second pump P 2  can provide the second fluid pressure p 2  required to actuate the first and second clutches K 1 , K 2  via the second fluid tract  18 . The first clutch valve KV 1  is actuatable to control the clutch actuation of the first clutch K 1 , and the second clutch valve KV 2  is actuatable to control the clutch actuation of the second clutch K 2 . 
     Upstream of both the first clutch valve KV 1  and the second clutch valve KV 2 , one spring pressure accumulator SC in each case is connected as hydraulic capacitor. In turn, a check valve RV is arranged in each case upstream of the respective spring pressure accumulator SC. This allows the second pump P 2  to increase the second fluid pressure in the second fluid branch  18 , thereby charging the spring pressure accumulator SC. wherein a fluid pressure drop towards the second pump P 2  is in turn reduced by the corresponding check valve RV. 
     However, pressure leakage can also cause a small pressure drop of the second fluid pressure p 2 , A control unit S can, in a manner dependent on a ratio between the second fluid pressure p 2  and a second fluid target pressure, initiate, as required and repeatedly, a switchover process during which the second operating state is assumed. In this regard, the first operating state can be temporarily replaced by the second operating state. The switchover process can be a post-pump process by which the second fluid pressure p 2  is brought back to the target pressure level. The secondary pump rotational speed can then be a post-pump rotational speed of the second pump P 2 . 
       FIG.  2    shows curve diagrams of various parameters regarding the execution of a method in the exemplary embodiment of the disclosure.  FIG.  2    a) shows the temporal course of the second fluid pressure P 2 ,  FIG.  2    b) the temporally corresponding course of the electrical energy E of the pump device PD,  FIG.  2    c) the temporally corresponding course of the pump rotational speed n, and  FIG.  2    d) the temporally corresponding course of the electrical pump power P of the pump device PD. 
     During operation of the hydraulic device  10 , the secondary pump rotational speed n 2  is set by initiating the switchover process as soon as the second fluid pressure p 2  falls below a second fluid target pressure, in this case a minimum second fluid pressure p 2,min . The particular switchover process is set when the second fluid pressure p 2  reaches or exceeds a maximum second fluid pressure p 2,max . 
     Provided that there is a point in time t 0  during operation of the hydraulic device  10 , there is at least one preceding switchover process U a , a switchover process U b  preceding this in turn, and a next switchover process U n  following the point in time to. The switchover process U b  is completed at the point in time t b  and the switchover process Ua is completed at the point in time t a . 
     For the next switchover process U n  the method described calculates, during operation of the hydraulic device  10 . the secondary pump rotational speed n 2  to be set for the next switchover process U n  at least in a manner dependent on a first power value P a  characterizing the electrical pump power P of the pump device PD in the preceding switchover process U a . As a result, the energy consumption of the pump device PD can be reduced, and the hydraulic device  10  can set the required second fluid pressure p 2  faster and more accurately. The secondary pump rotational speed n 2  is thus adaptively preset during operation of the torque-transmitting device  12 . This makes the second fluid pressure p 2  less susceptible to external influences. 
     The secondary pump rotational speed n 2  is set in the next switchover process U n  with the specification of a reduction of the electrical pump power P of the pump device PD to be provided for this purpose, in that the secondary pump rotational speed n 2  in the next switchover process U n  is set to differ from the secondary pump rotational speed n 2  of the preceding switchover process U a  by a rotational speed change value Δn, i.e. lower or higher, as required. For example, the rotational speed variation value Δn can be 200 rpm. 
     The first power value P a  is calculated as an averaged electrical pump power over a reference period as follows 
     
       
         
           
             
               P 
               a 
             
             = 
             
               
                 
                   E 
                   a 
                 
                 − 
                 
                   E 
                   b 
                 
               
               
                 
                   t 
                   a 
                 
                 − 
                 
                   t 
                   b 
                 
               
             
           
         
       
     
      with the electrical energy E a  consumed by the pump device PD at the point in time t a  and the electrical energy E b  consumed by the pump device PD at the point in time t b . 
     The reference period is the time interval t a  - t b  between the completion of the preceding switchover process U a  and the completion of the switchover process U b  preceding it in turn. 
     Preceding the determination of the first power value P a , a second power value P b  corresponding to the averaged electrical pump power in a comparable period up to the point in time t b  has already been calculated analogously. 
     The calculation of the secondary pump rotational speed n 2  to be used for the next switchover process U n  can, for example, be carried out in a case-dependent manner according to the flow chart in  FIG.  3   . Here, the first power value P a  is first calculated according to (1). Then, the comparison between the first power value P a  and the second power value P b  is made. The subsequent query of the secondary pump rotational speed n 2  is case-dependent according to whether the first power value P a  is smaller or greater than the second power value P b . 
     If the second power value P b  is smaller than the first power value P b , for example, it is then queried whether the secondary pump rotational speed n 2  in the switchover process U b  is greater than the secondary pump rotational speed n 2  in the switchover process U a . If this condition is fulfilled, the secondary pump rotational speed n 2  for the next switchover process U B  is set higher than the secondary pump rotational speed n 2  of the preceding switchover process U a  by the rotational speed change value Δn. 
     In this regard, the secondary pump rotational speed n 2  to be preset calculated for the next switchover process U n  is narrowed down to a value in a range of values between a minimum secondary pump rotational speed n 2,min  and a maximum secondary pump rotational speed U 2,max . The determination of the minimum secondary pump rotational speed n 2,min  is useful to limit the switchover process in time. The specification of the maximum secondary pump rotational speed n 2,max  can be advantageous to relieve a speed controller of the pump device PD and/or to avoid a maximum permissible secondary pump rotational speed of the pump device PD. 
     If the second power value P b  is smaller than the first power value P B,  for example, and the secondary pump rotational speed n 2  in the switchover process U b  is smaller than or equal to the secondary pump rotational speed n 2  in the switchover process U a , then the secondary pump rotational speed n 2  for the next switchover process U n  is set lower than the secondary pump rotational speed n 2  of the receding switchover process U 3  by the rotational speed change value Δn. 
     The change in secondary pump rotational speed n 2  of the next switchover process U n  for other possible states of the case conditions can be taken directly from the diagram. 
     LIST OF REFERENCE CHARACTERS 
     
         
           10  Hydraulic device 
           12  Torque-transmitting device 
           14  Fluid tract 
           16  First fluid branch 
           18  Second fluid branch 
         C Cooling device 
         E Electric motor 
         K 1  First clutch 
         K 2  Second clutch 
         KV 1  First clutch valve 
         KV 2  Second clutch valve 
         PD Pump device 
         P 1  First pump 
         P 2  Second pump 
         S Control device 
         SC Spring pressure accumulator 
         SV System pressure valve 
         p 1  First fluid pressure 
         p 2  Second fluid pressure 
         p 2,min  Minimum second fluid pressure 
         p 2,max  Maximum second fluid pressure 
         P Electrical pump power 
         P a  First power value 
         P b  Second power value 
         n 1  Primary pump rotational speed 
         n 2  Secondary pump rotational speed 
         n 2,min  Minimum secondary pump rotational speed 
         n 2max  Maximum secondary pump rotational speed 
         Δn Rotational speed change value 
         U a  Switchover process 
         U b  Switchover process 
         U n  Next switchover process