Method for Operating a Fluid Supply System

Abstract

A method for operating a fluid supply system for supplying fluid to an actuator and a component of a motor vehicle drive train, where the actuator and the component are connected in parallel within a supply path of the fluid supply system, may include increasing a pressure of the fluid in the supply path from a low base pressure level (associated with a non-actuated condition of the actuator) when the actuator is to be actuated. The method may further include determining, when the actuator is not to be actuated, whether a criterion is present, indicating an insufficient supply of the fluid in the supply path to the component. Additionally, the method may include increasing the pressure of the fluid in the supply path from the low base pressure level when the criterion is present.

Claims

1-17. (canceled)

18. A method for operating a fluid supply system (20) for integral parts of a motor vehicle drive train (1), the integral parts including at least one actuator (15) and at least one component (21, 22, 23), the at least one actuator (15) and the at least one component (21, 22, 23) being connected in parallel within a supply path of the fluid supply system (20), the method comprising: increasing a pressure of a fluid in the supply path from a low base pressure level (p.sub.G) when the at least one actuator (15) is to be actuated, the low base pressure level (p.sub.G) being associated with a non-actuated condition of the at least one actuator (15); determining, when the at least one actuator (15) is not to be actuated, whether at least one criterion is present, each of the at least one criterion indicating an insufficient supply of the fluid in the supply path to the at least one component (21, 22); and increasing the pressure of the fluid in the supply path from the low base pressure level (p.sub.G) when one or more of the at least one criterion is present.

19. The method of claim 18, wherein determining whether the at least one criterion is present comprises determining that one or more of the at least one criterion is present when an associated limit value is exceeded by a fluid requirement of the at least one component (21, 22).

20. The method of claim 19, further comprising determining the fluid requirement of the at least one component (21, 22) by determining a fluid deficit of the fluid in an inflow-side area of the at least one component (21, 22).

21. The method of claim 19, further comprising determining the fluid requirement of the at least one component (21, 22) by determining a fill level of the fluid in an inflow-side area of the at least one component (21, 22).

22. The method of claim 21, wherein determining the fill level comprises determining an amount of the fluid flowing into the inflow-side area, out of the inflow-side area, or both into and out of the inflow-side area.

23. The method of claim 19, wherein determining the fluid requirement of the at least one component (21, 22) comprises calculating the fluid requirement using a simulation.

24. The method of claim 18, wherein determining whether the at least one criterion is present comprises determining whether the at least one criterion is present based at least in part on one or more operating parameters.

25. The method of claim 18, wherein increasing the pressure of the fluid in the supply path from the low base pressure level (p.sub.G) when one or more of the at least one criterion is present comprises increasing the pressure of the fluid in the supply path according to a control with pulse width modulation.

26. The method of claim 18, further comprising determining, upon initiation and prior to increasing the pressure of the fluid in the supply path from the low base pressure level (p.sub.G) when one or more of the at least one criterion is present, whether at least one abort condition is met, wherein, if one or more of the at least one abort condition is present, increasing the pressure of the fluid in the supply path from the low base pressure level (p.sub.G) when one or more of the at least one criterion is present is aborted.

27. The method of claim 18, wherein the actuator (15) comprises an actuating cylinder (16) of a separating clutch (4), and the at least one component comprises one or both of a bearing point (24, 25) or the separating clutch (4).

28. The method of claim 27, wherein increasing the pressure of the fluid in the supply path from the low base pressure level (p.sub.G) when one or more of the at least one criterion is present comprises increasing the pressure from the low base pressure level (p.sub.G) to an actuating pressure level at which a touch point (TP) of the separating clutch (4) is approached via the actuating cylinder (16) of the separating clutch (4).

29. The method of claim 27, wherein increasing the pressure of the fluid in the supply path from the low base pressure level (p.sub.G) when one or more of the at least one criterion is present comprises to an intermediate pressure level, the intermediate pressure level being below a minimum actuating pressure at which actuating motion is initiated by the actuating cylinder (16).

30. A fluid supply system (20) for integral parts of a motor vehicle drive train (1), the fluid supply system (20) being operable for supplying fluid to at least one actuator (1) and to at least one component (21, 42, 23) according to the method of claim 18.

31. A transmission control unit associated with a fluid supply system (20), the fluid supply system (20) having a supply path for supplying fluid to at least one actuator (15) and to at least one component (21, 22, 23), the transmission control unit being configured to: trigger an increase of a pressure of the fluid from a low base pressure level (p.sub.G) when the at least one actuator (15) is to be actuated, the low base pressure level (p.sub.G) being associated with a non-actuated condition of the at least one actuator (15); determine, when the at least one actuator (15) is not to be actuated, whether at least one criterion is present, each of the at least one criterion indicating an insufficient supply of the fluid to the at least one component (21, 22); and initiate an increase in the pressure of the fluid from the low base pressure level (p.sub.G) when the one or more of the at least one criterion is detected.

32. A computer program product for the transmission control unit of claim 31, the computing program product comprising software for storing appropriate control commands for implementing a routine for operating the fluid supply system (20).

33. A data carrier comprising the computer program product of claim 32.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] One advantageous embodiment of the invention, which is explained in the following, is shown in the drawings, in which:

[0031] FIG. 1 shows a sectional view of a fluid supply system of a motor vehicle drive train;

[0032] FIG. 2 shows a detailed view of the fluid supply system from FIG. 1;

[0033] FIG. 3 shows a flow chart of a method according to the invention for operating the fluid supply system from FIGS. 1 and 2; and

[0034] FIG. 4 shows a diagram of various pressure curves.

DETAILED DESCRIPTION

[0035] Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

[0036] FIG. 1 shows a sectional view of an area of a motor vehicle drive train 1, which is intended for use in a hybrid vehicle. The motor vehicle drive train 1 is shown at a hybrid module 2, which includes an electric machine 3 and a separating clutch 4. The electric machine 3 is made up of a stator 5 and a rotor 6. The rotor 6 of the electric machine 3 is connected to a rotor hub 7 for conjoint rotation, where the rotor hub 7 in addition to the rotor 6 are also being permanently connected to a shaft 8 for conjoint rotation. In the present case, the shaft 8 is a transmission input shaft of a motor vehicle transmission 9, which is only partially shown in FIG. 1.

[0037] The separating clutch 4 is a wet-running multi-disk clutch. The separating clutch 4 is in a disengaged condition when not actuated and, when actuated, establishes a corotational connection between the shaft 8 and a shaft 10. The shaft 10 is arranged coaxially to the shaft 8 and establishes a connection within the motor vehicle drive train 1 to an internal combustion engine, which is not shown in greater detail in the present case. The separating clutch 4 includes an outer disk carrier 11 in or on which multiple outer clutch disks 12 are located in a rotationally fixed and axially displaceable manner, the outer disk carrier 11 being connected to the shaft 8 for conjoint rotation. In addition, inner clutch disks 13 are arranged so as to alternate axially with the outer clutch disks 12 and, together with the outer clutch disks 12, form a disk pack of the separating clutch 4. The inner clutch disks 13 are specifically located in or on an inner disk carrier 14 in a rotationally fixed and axially displaceable manner. The inner disk carrier 14 is connected to the shaft 10 for conjoint rotation.

[0038] An actuation of the separating clutch 4 and, thereby, a coupling of the shafts 8 and 10 essentially for conjoint rotation takes place in the present case by the disk pack, particularly by outer clutch disks 12 and inner clutch disks 13 of the disk pack being pressed together axially and, as a result, forming a friction-locking connection between the outer clutch disks 12 and the inner clutch disks 13. For this purpose of pressing the outer clutch disks 12 and the inner clutch disks 13 together and, thereby, actuating the separating clutch 4, an actuator 15 in the form of a hydraulic actuating cylinder 16 is associated with the separating clutch 4.

[0039] As is apparent in FIG. 1, the actuating cylinder 16 has an actuating piston 17, which is axially displaceably located on the shaft 8 and, together with the shaft 8 and the outer disk carrier 11, delimits a pressure chamber 18. The actuating piston 17 is preloaded into a home position via a spring element 19, which is a plate spring in the present case and is located axially on a side of the actuating piston 17 facing away from the pressure chamber 18. In the home position, the actuating piston 17 does not act axially upon the disk pack of the separating clutch 4. For actuating the actuator 15, the pressure chamber 18 is pressurized with fluid in the form of oil. At a certain pressure level of the fluid, the pressurization results in an axial displacement of the actuating piston 17 counter to the spring element 19, whereupon the actuating piston 17 axially presses the outer clutch disks 12 and the inner clutch disks 13 together and, as a result, effectuates the actuation of the separating clutch 4.

[0040] A supply to the actuating cylinder 16 and, thereby, also to the pressure chamber 18 takes place in the present case in a fluid supply system 20 in which the fluid is guided at a particular set pressure to the pressure chamber 18 in a supply path. In addition, a supply to components 21, 22, 23 of the motor vehicle drive train 1 also takes place within the same supply path of the fluid supply system 20. The components 21, 22 are bearing points 24, 25 and the component 23 is the separating clutch 4.

[0041] Each of the bearing points 24, 25 is present as an anti-friction bearing. The bearing point 24 radially supports the shaft 8 relative to the shaft 10, while the bearing point 25 axially supports the shaft 8 relative to the shaft 10.

[0042] As shown in FIG. 1 and, as more particularly shown in the detailed view in FIG. 2, a flow path (shown with arrows) of the fluid during the supply to the components 21, 22, 23. As is apparent in each case, the fluid within the supply path is initially axially guided via a supply bore 26 in the shaft 8 to an axial end 27 of the shaft 8, where the axial end 27 of the shaft 8 has been axially inserted into the shaft 10. For this purpose, the shaft 10 is a hollow shaft at least in area of the axial end 27 of the shaft. In addition, a nozzle 28 is introduced into the supply bore 26 of the shaft 8 at the axial end 27, the nozzle 28 defining a flow cross-section at the axial end 27.

[0043] As particularly shown in FIG. 2, a collecting chamber 29 is defined axially between the shaft 8 and the shaft 10. The fluid flows out of the supply bore 26 via the nozzle 28 into the collecting chamber 29. From this collecting chamber 29, which, together with the supply bore 26, forms a reservoir for the fluid, the fluid then flows radially outward along the shaft 8 initially to the bearing point 24 and, thereafter, also to the bearing point 25 in order to lubricate the bearing points 24, 25. The reservoir, which includes the collecting chamber 29 and the supply bore 26, is referred to in the following as the reservoir 26, 29. Subsequent to the bearing point 25, the fluid then also reaches the separating clutch 4 (FIG. 1). Acting as coolant, the fluid cools the separating clutch 4 here, wherein the main cooling of the separating clutch 4 is ensured via separate paths.

[0044] The fluid has at least essentially the same pressure within or along the common supply path. In a non-actuated condition of the separating clutch 4 and, thereby, also of the actuator 15, this pressure is at a low base pressure level, namely a pre-filling pressure level, at which a basic supply to the actuator 15 is carried out. At this low base pressure level and at high rotational speeds of the shaft 8, it is possible, however, that only a reduced amount of the fluid flows into the collecting chamber 29 via the supply bore 26 due to the acting centrifugal force. As a result, the reservoir 26, 29 may run empty and, thereby, the components 21, 22 may be insufficiently supplied. In the extreme case, this even causes air to be suctioned into the collecting chamber 29 and, thereafter, guided to the components 21, 22, 23. In the case of the bearing points 24, 25, a continuous undersupply results in dry running and, thereby, increased wear, as a result of which, in the end, failure of the particular bearing point 24, 25 is imminent.

[0045] In order to prevent this, an operation of the fluid supply system 20 is carried out in the present case in the manner of a method that is realized according to a preferred embodiment of the invention. The method is preferably carried out by a control unit (not shown further in the present case) of the motor vehicle transmission 9. A flow chart of this method is shown in FIG. 3. As is apparent in FIG. 3, at the beginning of the method, after a start-up of the fluid supply system 20, it is initially checked in a first step S1, as a criterion for an insufficient supply to the components 21, 22, 23, whether there has been a fluid deficit for too long in the reservoir 26, 29 and, thereby, on the inflow side of the components 21, 22, 23. The need for fluid at the components 21, 23 is relevant for this purpose. This need for fluid is dependent, for example, on the rotational speed, the load (traction, coasting) and a gear or gear ratio currently engaged in the motor vehicle transmission 9. Depending on these influencing variables, forces must be supported by the bearing points 24, 25, where the forces determine the need for fluid. For this purpose, a calculation of the fluid deficit is carried out within the scope of a simulation in a substep S2 within the step S1. If a deficit is detected in step S1 and an associated limit value is exceeded with respect to time, the method jumps to a step S3. If a deficit is not detected or the associated limit value is fallen below, a check of a further criterion for an insufficient supply is carried out in a step S4.

[0046] In the step S4, which is carried out downstream from or also in parallel with step S1, it is checked whether a critical fill level of fluid has been fallen below in the reservoir 26, 29. For this purpose, a fill level in the reservoir 26, 29 is calculated in a substep S5 within the scope of a simulation. A flow rate of the fluid is incorporated in the simulation of substep S5, the flow rate having been determined in an upstream step S6. Particularly, an amount of fluid flowing into the collecting chamber 29 and/or an amount of fluid flowing out of the collecting chamber 29 are/is determined in step S6. The rotational speed of the shaft 8 yields, or is used to determine, the flow rate of the fluid due to the pressure currently prevailing in the supply path is known, more particularly, on the basis of structure (nozzle design, shaft diameter, etc.) and measurements (as a function of the hydraulic resistances or the viscosity of the oil and of the rotational speed). If it is detected in step S4 on the basis of a comparison with an associated limit value that the critical fill level in the collecting chamber 29 has been fallen below, the method also jumps to step S3. Otherwise, if the result from step S4 is simultaneously negative, the method is terminated.

[0047] In step S3, it is checked whether abort conditions are present, where the abort conditions prevent an execution of a measure for ending the insufficient supply to the components 21, 22. These abort conditions are safety-relevant consequences that would arise in the course of the execution of the measure for ending the insufficient supply and could be more serious than a failure of one of the bearing points 24, 25. In addition, an abort condition could also be a comfort-disrupting effect that comes into play when the measure is carried out. In step S3, a plausibility check is therefore carried out to determine whether it is justified to initiate a measure for ending the insufficient supply. If the answer is no, i.e., an abort condition has been met, and the method is also terminated. Otherwise, if no abort condition has been met, the method jumps to a step S7.

[0048] In step S7, the measure for ending the insufficient supply is then carried out, within the scope of which the pressure of the fluid in the supply path is increased even when an actuation of the actuator 15 is not to be carried out. Due to this increase of the pressure starting from the base pressure level, the filling of the reservoir 26, 29 is increased and, thereby, an appropriate supply to the bearing points 24, 25 is also ensured. An exemplary operating sequence of the measure is shown in FIG. 4. FIG. 4 shows a diagram of curves of a pressure p of the fluid in the course of the measure with respect to time t.

[0049] As is apparent on the basis of a curve 30 of the actual pressure, the pressure of the fluid at the beginning is initially at the indicated base pressure level pc. A target pressure is specified at the beginning of the measure, however. The target pressure specification is represented as a curve 31 in FIG. 4. Due to this target pressure specification, the actual pressure 30 also increases and settles at a higher pressure level within a rapid filling phase 32 indicated in FIG. 4. A pressure level sets in, at which a touch point TP is approached via the actuating cylinder 16 associated with the separating clutch 4.

[0050] The measure in step S7 is carried out as control with pulse width modulation, and so the pressure increase taking place apart from the actuation of the actuator 15 does not take place permanently, but rather in a pulsed manner. After the measure is carried out in step S7, the method is also terminated.

[0051] By operation according to the invention of a fluid supply system, an insufficient supply to components, such as, for example, bearing points, is reliably ruled out.

[0052] Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

REFERENCE CHARACTERS

[0053] 1 motor vehicle drive train [0054] 2 hybrid module [0055] 3 electric machine [0056] 4 separating clutch [0057] 5 stator [0058] 6 rotor [0059] 7 rotor hub [0060] 8 shaft [0061] 9 motor vehicle transmission [0062] 10 shaft [0063] 11 outer disk carrier [0064] 12 outer clutch disks [0065] 13 inner clutch disks [0066] 14 inner disk carrier [0067] 15 actuator [0068] 16 actuating cylinder [0069] 17 actuating piston [0070] 18 pressure chamber [0071] 19 spring element [0072] 20 fluid supply system [0073] 21 component [0074] 22 component [0075] 23 component [0076] 24 bearing point [0077] 25 bearing point [0078] 26 supply bore [0079] 27 axial end [0080] 28 nozzle [0081] 29 collecting chamber [0082] 30 curve [0083] 31 curve [0084] 32 rapid filling phase [0085] S1 to S7 individual steps [0086] p pressure [0087] t time [0088] p.sub.G base pressure level [0089] TP touch point