WO2023151758A1

WO2023151758A1 - Method for prefilling a hydraulic system of a hydraulic actuator of a motor vehicle

Info

Publication number: WO2023151758A1
Application number: PCT/DE2023/100112
Authority: WO
Inventors: Alexander Dreher; Dominik LAUER
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2022-02-14
Filing date: 2023-02-13
Publication date: 2023-08-17
Also published as: DE102022103384A1

Abstract

The invention relates to a method for prefilling a hydraulic system (1) of a motor vehicle with a pump (2), which delivers fluid to a first consumer (4) in a first direction of rotation (3) and delivers fluid to at least one second consumer (6) in a second direction of rotation (5) and with a line system (30) through which the pump (2) can be connected to the at least one second consumer (6) and, with the interposition of a switchable valve (24), to a reservoir (15). In order to achieve rapid and convenient actuation of the at least one second consumer (6) when the motor vehicle is restarted after a standstill, the pump (2) delivers fluid from the reservoir (15) via the line system (30) when the line system (30) is connected to the reservoir (15), depending on a standing time of the motor vehicle and/or an ambient temperature, up to a predetermined termination criterion before a request from the at least one second consumer (6).

Description

Method for pre-filling a hydraulic system of a hydraulic actuator of a motor vehicle

The invention relates to a method for pre-filling a hydraulic system of an actuator of a motor vehicle with a pump that delivers fluid to a first consumer in a first direction of rotation and delivers fluid to at least one second consumer in a second direction of rotation, and with a line system through which the pump the second consumer and with the interposition of a switchable valve can be connected to a reservoir.

Such hydraulic systems are provided in a drive train, in particular in a hybrid drive train of a motor vehicle. For example, an internal combustion engine and an electric machine can be connected in a hybrid drive train, with the internal combustion engine and electric machine being directly connected by means of a separating clutch, such as a friction clutch, or being operable independently of one another. The electric machine is, for example, connected downstream of a transmission which is operatively arranged between its rotor and a differential with the drive wheels, for example with a single gear stage, in which a second electric machine can be arranged.

The motor vehicle contains, for example, a parking brake to form a parking brake, which is actuated by means of a parking claw engaging in a form-fitting manner in a transmission profile.

The hydraulic system serves to cool the separating clutch and, if necessary, other transmission components and to actuate the separating clutch and the parking lock. For example, one is used for sucking in and distributing fluid pump operated electrically by an electric motor, for example a reversible pump. The fluid is pumped through one cooling circuit in one direction of rotation of the pump, while the pressure required to actuate the separating clutch or parking lock is generated in the other direction of rotation. The fluid circuit is controlled by means of switchable valves such as 2-way valves and check valves. In hybrid ferry operation, the separating clutch is fully closed in order to transfer the torque of the internal combustion engine to the drive wheels. The working pressure for actuating a slave cylinder to close the separating clutch can be maintained by means of a switchable check valve and/or a check valve. Hydraulic systems with an electrically driven so-called reversible pump are known from the prior art. In this case, one direction of rotation of the reversible pump can be assigned a volumetric flow function, such as a cooling function, and the other direction of rotation of the reversible pump can be assigned an actuating function. Such hydraulic systems and methods for their operation are known, for example, from the documents DE 10 2018 112 663 A1, DE 10 2018 112 665 A1, DE 10 2018 113 316 A1 and DE 10 2018 114 789 A1. Other hydraulic systems are known, inter alia, from the publications DE 10 2016 213 318 A1 and WO 2012/113368 A1.

From the document DE 10 2018 131 117 A1, a hydraulic system and a method for removing air from it is known.

The object of the invention is the development of a method for pre-filling a hydraulic system. In particular, the object of the invention is to propose a method in which a consumer is prepared for actuation before he requests it, so that it can be put into operation quickly and conveniently after the motor vehicle has been shut down. The object is solved by the subject matter of claim 1. The claims dependent on claim 1 present advantageous embodiments of the subject-matter of claim 1.

The proposed method is used for pre-filling a hydraulic system of a motor vehicle. In a hybrid drive train in particular, the hydraulic system serves as a smart actuator for cooling and actuating components of the hybrid drive train. The hydraulic system contains a pump that is driven, for example, by means of an electric motor, can be controlled in both directions of rotation and delivers fluid, which in a first direction of rotation delivers fluid to a first consumer, for example to a separating clutch for cooling, and in a second direction of rotation, fluid to at least one second consumer, for example a parking lock activated by means of a slave cylinder and/or to a separating clutch actuated by means of a second slave cylinder.

The at least one second consumer, for example the two slave cylinders, are connected to the pump with a line system, for example consisting of a hydraulic line connected to the pump and two alternately connectable pressure line branches supplying two second consumers, through which the pump is connected to the second consumer and is connected to a reservoir with the interposition of a switchable valve.

In order to reduce the actuation time of the at least one second consumer and to increase the comfort of its actuation, it is proposed that, depending on the idle time of the motor vehicle and/or an ambient temperature, the pump pumps fluid from the reservoir via the line system with the line system connected to the reservoir up to a predetermined termination criterion prior to a request from the at least one second consumer. This means that in in the proposed method, the line system between the second consumer and the pump of the hydraulic system, which may have been at least partially empty in the event of a longer standstill and/or higher ambient temperature, is pre-filled by operating the pump before, for example, a request comes from the driver of the motor vehicle, the at least one second consumer, for example to put a parking lock into operation. In this case, the pump sucks fluid from the reservoir, for example a pressureless sump, and any air present in the line system is discharged to the outside via the open valve, i.e. into the reservoir, until it is recognized on the basis of a termination criterion that the line system is complete or at least for the quick and comfortable actuation of the at least one second consumer is sufficiently filled with fluid.

For example, the line system has a first pressure line branch that actuates a parking lock and a second pressure line branch that actuates a friction clutch, e.g can be connected to the hydraulic line connected to the pump. In the pressure line branch assigned to the separating clutch, the second valve can be followed by the first valve, for example designed as a 2/2 valve, which connects the pressure line branch and thus the hydraulic line to the reservoir. With such a circuit, the second valve is switched open in the direction of the pressure line branch for the separating clutch and the first valve in relation to the reservoir. In this way, during the pre-filling, fluid can be pumped from the reservoir via the hydraulic line and the pressure line branch to the reservoir. The hydraulic system can be constructed in such a way that the pump is provided at each of the two pump inlets with an intake branch that is protected against backflow by means of a non-return valve in relation to the reservoir. When the pump is operated, the pump inlet changes depending on the direction of rotation, so that the suction branches also change depending on the direction of rotation, whereby the fluid is sucked in through one of the two suction branches by adjusting the direction of rotation of the pump and fed into the hydraulic line, i.e. via which is fed to the respective pressure line branch to the first or second consumer. The pre-filling can take place in two variants. In a first variant, fluid is sucked in via the second suction branch and pumped directly via the second valve and the valve that is open to the reservoir. In the second variant, the pump is operated in the opposite direction. In this case, fluid is sucked in via the first intake branch and from there it enters the line system. The portion that is irrelevant for the pre-filling is fed to the cooling of the first consumer. The part that is decisive for the pre-filling of the line system is discharged via the valve that is open to the reservoir.

One possibility for determining a criterion for stopping the pre-filling is to record the pressure in the line system over the filling time, ie the activity of the pump during the pre-filling. If the pressure increases in a characteristic way, it can be assumed that the pipe system is filled. For example, a predetermined pressure threshold, a pressure value, pressure range or pressure point can be specified as a termination criterion. The termination criterion can be monitored, for example, by means of a pressure sensor provided and arranged in the pressure line. Alternatively or additionally, a current/voltage behavior of an electric motor driving the pump can be evaluated to determine the termination criterion. For example, a current flowing in the electric motor during the pre-filling can be evaluated, with the termination criterion being set to a current value at which the line system is pre-filled.

The termination criterion can be stored and retrieved as a fixed variable or variable that can be adapted to the running line of the hydraulic system as a function of temperature and/or the like, for example in a control unit of the hydraulic system or in a higher-level control unit. The initial termination criterion can be learned, for example, during the initialization at the end of the line, or it can be specified empirically.

The idle time of the motor vehicle that has been shut down is recorded, for example, between being shut down, for example by switching off the internal combustion engine, switching off the ignition, removing an operating key, locking the motor vehicle and/or the like, and starting the motor vehicle again, for example by opening the motor vehicle, inserting an operating key, switching on the Ignition and / or the like determined.

The routine for pre-filling the hydraulic system is advantageously started before the motor vehicle is started up, so that the pre-filling is already completed when the vehicle is started up. For example, the routine can be initiated when the motor vehicle is unlocked using a key or without contact.

The ambient temperature can be determined, for example, as the internal temperature in the engine compartment of the motor vehicle using a temperature sensor that may be present in a drive train component, control unit or the like, or as a temperature model. Alternatively or additionally, the ambient temperature as Outside temperature outside the motor vehicle, for example by means of an outside temperature sensor of the motor vehicle or using a wireless, for example, from an Internet connection of the motor vehicle or a media device connected to it such as a smartphone outside temperature are recorded and evaluated.

The invention is explained in more detail with reference to the exemplary embodiment shown in FIGS. These show:

Figure 1 is a hydraulic diagram of a hydraulic system and

FIG. 2 shows a diagram with sequences for pre-filling the hydraulic system of FIG.

FIG. 1 shows a schematic representation of the hydraulic system 1 . The hydraulic system 1 has the pump 2 designed as a reversible pump. The pump 2 can be driven in a first direction of rotation 3 . In the first direction of rotation 3, the pump 2 delivers fluid to the first consumer 4, such as a cooling device, and provides a volume flow function.

The pump 2 can be driven in a second direction of rotation 5 opposite to the first direction of rotation 3 . In the second direction of rotation 5, the pump 2 delivers the fluid to the two consumers 6. Here, an operating pressure is built up to actuate them. In the illustrated embodiment, the pump 2 delivers the fluid to two second consumers 6, here to a slave cylinder of the parking lock 7 and to a slave cylinder of the friction clutch 8.

The pump 2 is driven by the electric motor 9 . The electric motor 9 is controlled by the control unit 10 . The first pump inlet 11 of the pump 2 is by means of the cooling line 12 with the interposition of the check valve 13 with the connected to the first consumer 4 and by means of the check valve 14 to the first suction branch 16 sucking in from the reservoir 15 . The check valve 13 prevents the fluid from being pumped back into the reservoir 15.

The opposite pump inlet 17 of the pump 2 is connected to the intake branch 20 with the check valve 19 being interposed. The pump inlet 17 is also connected to the line system 30, which contains the hydraulic line 18, the pressure line branches 22, 23, the valves 21, 24, the check valve 25 and the discharge lines 27, 28. The consumers 6 connect to the pressure line branches 22, 23 and are actuated, for example, by means of a slave cylinder (not shown) connected to one of the pressure line branches 22, 23. Depending on the directions of rotation 3, 5, the pump 2 sucks in fluid from the reservoir 15 from one of the suction branches 16, 20 in each case.

The hydraulic line 18 can be connected alternately to the pressure line branch 22 supplying the slave cylinder of the parking lock 7 or to the pressure line branch 23 supplying the slave cylinder of the friction clutch 8 by means of the switchable valve 21 , here a 4/2 valve. The switchable valve 24 , here a 2/2 valve, is introduced into the pressure line branch 23 and connects it to the reservoir 15 via the discharge line 27 . When the valve 21 is switched between the hydraulic line 18 and the pressure line branch 23, the pressure line branch 22 is connected to the reservoir 15 by means of the discharge line 28, so that the parking lock 7 is opened. When the hydraulic line 18 is connected to the pressure line branch 22, the pressure line branch 23 is uncoupled. A pressure built up on the slave cylinder of the friction clutch to actuate the friction clutch 8 is maintained by means of the check valve 25, so that the friction clutch 8 remains closed, for example, independently of the wiring of the valve 21 or the operation of the pump 2 and only the pressure loss caused by the leakage pleasure must be tracked. The friction clutch 8 is opened by the valve 24 being opened.

The pressure sensor 26 connected to the control unit 10 is connected to the pressure line branch 23 . This detects, for example, the pressure in the pressure line branch 23 when the friction clutch 8 is closed and during the pre-filling of the line system 30. Two variants of the pre-filling of the line system 30 can be set. In the first variant, the pump 2 is driven in the direction of rotation 5 and sucks in fluid via the suction branch 16 and pumps it into the hydraulic line 18 and from there into the pressure line branch 23 and the discharge line 27 into the reservoir 15 until a termination criterion is assumed, assuming complete or sufficient filling of the hydraulic line 18 and the pressure line branch 23, the pump 2 stops. The termination criterion can be determined from the sensor data of the pressure sensor 26 recorded over the filling time and/or from the variable derived from the current of the electric motor 9 recorded over the operating time. During the filling, the valve 21 between the hydraulic line 18 and the pressure line branch 23 and the valve 24 between the pressure line branch 23 and the discharge line 27 are continuously switched. In the second variant, unlike the first variant, the pump 2 is operated in the direction of rotation 3 . Here, fluid is sucked in via the second suction branch 20 and divided into the cooling line 12 and the hydraulic line 18 at the connection node 29 . In this way, a lower fluid flow is available for pre-filling the hydraulic line, but the cooling line 12 can also wet the components to be cooled, such as the friction clutch 8 , for example when the motor vehicle is parked for a long time, thereby enabling a more comfortable start. The start of the two variants depends on the service life and/or the ambient temperature. For example, pre-filling can be suspended in the case of short downtimes. Furthermore, depending on the service life and/or the ambient temperature, a distinction can be made between the two variants.

FIG. 2 shows the diagram 100 of a pre-filling process of the hydraulic system 1 of FIG. 1 over the filling time t. Partial diagram I shows the speed n of the pump 2, which is controlled to a constantly controlled speed n(B) up to the termination criterion AK.

Partial diagram II shows the pressure p of the pressure sensor 26 and partial diagram III shows the current i flowing via the electric motor 9 over the filling time t. The pressure point p(B) and/or the current value i(B) serve as termination criteria AK, evaluated together or individually. During the filling time t, the pressure p detected by the pressure sensor 26 remains low until the time t1 due to the lack of fluid in the line system 30. At time t1, the line system 30 begins to fill and the flow resistance applied to the valve 24 increases the pressure p in the line system 30. If the pressure p reaches the pressure point p(B), it is assumed that the line system 30 is sufficiently filled and the Pump 2 is shut down. The valve 24 is then closed, for example, and the valve 21 is switched through between the hydraulic line 18 and the pressure line branch 22 .

Partial diagram III shows the current i of the electric motor 9 over the filling time t. Due to the regulation of the constant speed n of the pump 2, a current peak i(max) occurs at the beginning of the filling time t, which is faded out due to the short filling time t. This is followed by a small flow resulting from the transport of fluid. At time t2, the current i increases due to the flow resistance at the valve 24 and the build-up of pressure in the line system 30. At the current value i(B), it is assumed that the line system 30 is sufficiently filled and the pump 2 is switched off at the termination criterion AK defined by this current value i(B).

Reference character list

Hydraulic system Pump Direction of rotation Consumer Direction of rotation Consumer Parking lock Friction clutch Electric motor Control unit Pump inlet Cooling line Check valve Check valve Reservoir Suction branch

Pump inlet Hydraulic line Check valve Suction branch Valve Pressure line branch Pressure line branch Valve Check valve Pressure sensor Drain Drain

Connection node piping system diagram AK termination criterion i current i(B) current value i(max) current peak n speed n(B) speed p pressure p(B) pressure point t filling time t1 time t2 time

I part diagram

II part diagram

III part diagram

Claims

Claims Method for pre-filling a hydraulic system (1) of a motor vehicle with a pump

(2) rotating in a first direction

(3) Fluid to a first consumer

(4) conveys and conveys fluid in a second direction of rotation (5) to at least one second consumer (6), and with a line system (30) through which the pump (2) with the at least one second consumer (6) and with the interposition of a switchable valve (24) can be connected to a reservoir (15), characterized in that depending on the idle time of the motor vehicle and/or an ambient temperature, the pump (2) supplies fluid from the reservoir (15) via the line system (30) to the reservoir (15) connected line system (30) up to a predetermined termination criterion (AK) promotes a request from the at least one second consumer (6). Method according to Claim 1, characterized in that the line system (30) has a hydraulic line (18) connected to the pump (2) and a first pressure line branch (22, 23 ), wherein the two pressure line branches (22, 23) can be connected alternately to the hydraulic line (18) by means of a second switchable valve (21). Method according to Claim 2, characterized in that when the motor vehicle is stopped, the second pressure line branch (23) is connected to the hydraulic line (18). Method according to one of Claims 1 to 3, characterized in that the pump (2) is fitted at each of two pump inlets (11, 17) with a suction branch (16, 20 ) is provided, wherein the fluid is sucked in by adjusting the direction of rotation (3, 5) of the pump (2) through one of the two suction branches (16, 20) and fed into the hydraulic line (18).

5. The method according to any one of claims 1 to 4, characterized in that to determine the termination criterion (AK) exceeding a predetermined pressure (p) in the line system (30) is evaluated.

6. The method as claimed in claim 5, characterized in that pressure signals from a pressure sensor (26) provided in the line system (30) are evaluated.

7. The method according to any one of claims 1 to 6, characterized in that to determine the termination criterion (AK) a current / voltage behavior of the pump (2) driving electric motor (9) is evaluated.

8. The method according to any one of claims 1 to 7, characterized in that the idle time between a shutdown and a restart of the motor vehicle is determined.

9. The method as claimed in one of claims 1 to 8, characterized in that a routine for pre-filling is initiated when the motor vehicle is unlocked.

10. The method according to any one of claims 1 to 9, characterized in that an internal temperature in the engine compartment and / or an outside temperature outside of the motor vehicle is evaluated as the ambient temperature.