WO2023134813A1

WO2023134813A1 - Method for controlling a hybrid head of a hybrid drive train

Info

Publication number: WO2023134813A1
Application number: PCT/DE2022/100949
Authority: WO
Inventors: Ralf Mannsperger; Dietmar Häckl; Patrick Junker; Jens MÜHLHAUSEN
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2022-01-11
Filing date: 2022-12-13
Publication date: 2023-07-20
Also published as: DE102022100461B4; DE102022100461A1

Abstract

The invention relates to a method for controlling a hybrid head (2) of a hybrid drive train (1) with a first electric machine (4) which is connected to a crankshaft (5) of an internal combustion engine (3) and with a second electric machine (13) which is connected by means of a differential with helical gearing (16) to drive wheels (15), and with a separating clutch (7) arranged between the electric machines (4, 13), and with a control unit controlling the hybrid head (2), wherein the separating clutch (7) is actuated by means of a hydraulic, electrically driven pump and a predetermined working pressure for transmitting a sufficient contact pressure force is set in a pressure line by means of the pump, and the separating clutch (7) is actuated by means of a slave cylinder, which is connectable to the pressure line by a switching valve controlled by the control unit, by means of an axial displacement movement of the slave cylinder piston thereof, and lowering of the working pressure as a result of leakage and/or actuating operations of the separating clutch is compensated for by means of re-pumping operations of the pump. To avoid overloading the slave cylinder, the working pressure is set below a maximum pressure threshold of the working pressure depending on reaction torques of the hybrid drive train, the reaction torques boosting said working pressure.

Description

Method for controlling a hybrid head of a hybrid powertrain

The invention relates to a method for controlling a hybrid head of a hybrid drive train with a first electric machine connected to a crankshaft of an internal combustion engine and a second electric machine connected to drive wheels by means of a differential with helical gearing and a separating clutch arranged between the electric machines and a control unit controlling the hybrid head, wherein the separating clutch is actuated by means of a hydraulic, electrically driven pump and a predetermined working pressure is set in a pressure line by means of the pump for the transmission of a sufficient contact pressure force and the separating clutch by means of a slave cylinder which can be connected to the pressure line with a switching valve controlled by the control unit by means of an axial displacement movement thereof Slave cylinder piston is actuated and a drop in working pressure as a result of leakage and/or actuation processes of the separating clutch is compensated for by pumping-up processes of the pump.

A generic hybrid drive train with a hybrid head made up of two electric machines and a separating clutch arranged between them is known, for example, from publication DE 10 2019 122 170 A1. The hybrid head is controlled by a hydraulic system in which an electrically operated pump actuates the separating clutch by means of a switching valve and a downstream slave cylinder. The reaction torque generated by drivetrain components such as a helical gear differential can overstress the slave cylinder. The object of the invention is the further development of a method for controlling a generic hybrid head. In particular, the object of the invention is to protect the slave cylinder from excessive loads.

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 to control a hybrid head of a hybrid drive train of a motor vehicle. The hybrid head is arranged, for example, between an internal combustion engine and a differential with drive shafts and drive wheels. The hybrid head includes a first electric machine, the rotor of which is directly connected to a crankshaft of the internal combustion engine, for example, and a second electric machine, the rotor of which is directly connected to drive wheels, for example by means of a helical gear differential. A separating clutch is arranged between the electric machines.

The first electric machine is used, for example, as a generator and is driven, for example, by the internal combustion engine to generate electrical energy, which is stored in a battery and is used to operate the second electric machine to drive the motor vehicle. Above a certain speed, for example 50 km/h, the separating clutch can be closed and the motor vehicle can be operated in hybrid mode in order to increase the efficiency of the drive of the motor vehicle.

The separating clutch is actuated by a hydraulic unit with a hydraulic, electrically driven pump. The electric machines and the hydraulic unit are controlled by one or more control units. The hydraulic unit contains a pressure line in which a specified working pressure is applied by means of the pump. is provided. The separating clutch is actuated by means of a slave cylinder. In this case, a slave cylinder piston displaces an actuation component, such as a lever spring of the separating clutch, axially by means of an interposed actuation mechanism, which optionally provides rotational compensation, for example an actuation bearing. The slave cylinder is controlled by a switching valve controlled by a control unit, which is arranged in the pressure line between the slave cylinder and the pump. If the separating clutch is to be preferably closed or opened depending on the design as a preferably positively closed or positively opened clutch, the switching valve is opened, the slave cylinder is subjected to the specified working pressure and the slave cylinder piston is displaced axially. To save energy, a non-return valve can be connected between the slave cylinder and the pump, so that the working pressure is maintained in the slave cylinder when the clutch is actuated. Due to leakage, this working pressure is reduced on the slave cylinder or in the pressure line and the working pressure drops. A drop in the working pressure as a result of leakage and/or actuation processes of the separating clutch is compensated for by pumping processes of the pump.

The hybrid head can have a gear stage designed, for example, as a planetary gear. In order to avoid a high axial space requirement, this can have nested shafts, for example a hollow shaft and a shaft running in it, in which the hollow shaft is connected to a differential by means of helical gearing. Due to the force distribution on helical gears, reaction torques can occur, for example when a motor vehicle starts moving, which generate an increased contact pressure on the separating clutch, which in turn increases the working Increase pressure on the slave cylinder, which can possibly be above a maximum pressure threshold, so that the slave cylinder can be damaged.

In order to avoid such high working pressures in the slave cylinder, the working pressure is set below a maximum pressure threshold of the working pressure as a function of these amplifying reaction torques of the drive train.

For example, the reaction torques occurring when the separating clutch is engaged due to a shaft of the rotor of the other electric machine guided in a hollow shaft of the rotor of one of the electric machines can be taken into account. Due to the mechanical design of the drive train in connection with a transmission with a hollow shaft and its bearing, there are reaction torques that are caused by the interaction of the first electric machine and the internal combustion engine and the second electric machine and increase the working pressure in the slave cylinder. It is therefore proposed to take these reaction torques into account when setting the working pressure in such a way that the working pressure set, for example, during the closing of the separating clutch remains below a maximum pressure threshold.

Alternatively or additionally, reaction torques occurring on the helical gearing are taken into account as a function of a set driving situation. Due to an axial displacement of the transmission output shaft on the helical gearing in corresponding driving situations, for example with the additional drive torque on the drive wheels occurring when the separating clutch closes, the working pressure in the slave cylinder also increases due to an increased contact pressure force on the separating clutch. To compensate for these reaction moments, the working pressure is limited depending on these to a maximum pressure threshold at which there is sufficient contact pressure for maximum transmission of the maximum over the clutch torque that can be transmitted by the separating clutch is guaranteed, but the slave cylinder is protected against excessive stress.

For example, to take into account the reaction torques, the possible reaction torques, for example empirically determined, modeled and/or determined on selected patterns or on the motor vehicle itself during a final check, which occur during a closing of the separating clutch, can be stored in a memory. During the closing of the separating clutch, the working pressure applied is then corrected by means of the associated reaction torques. For example, when the maximum pressure threshold is exceeded, the working pressure provided can be reduced by a pressure proportion caused by the reaction torques.

The hybrid head can contain a parking lock, which is actuated by means of a switching valve arranged in the pressure line parallel to the switching valve of the separating clutch with a downstream slave cylinder that actuates the parking lock. The pump can be designed as a bidirectional pump, with the working pressure in the pressure line being set in one direction of rotation of the pump and a fluid flow being provided in a fluid line in the other direction of rotation for cooling and/or lubricating at least one drive train component, for example a wet-operated separating clutch.

The invention is explained in more detail with reference to the embodiment shown in Figures 1 to 4. These show:

Figure 1 shows a hybrid drive train shown schematically,

Figure 2 shows a hydraulic unit for operating the separating clutch of the hybrid drive train of Figure 1, Figure 3 shows a closing process of the separating clutch of the hybrid drive train of Figure 1 over time and

FIG. 4 shows pressure behavior in the slave cylinder of the hydraulic unit of FIG. 2 as a function of reaction torques of the hybrid drive train during a closing process of the separating clutch.

FIG. 1 shows the hybrid drive train 1 for a motor vehicle in a schematic representation. The internal combustion engine 3 is non-rotatably connected to the hybrid head 2 with the two electric machines 4, 13 and the separating clutch 7 arranged between them. The crankshaft 5 of the internal combustion engine 3 and the rotor 6 of the first electric machine 4 are connected in a rotationally fixed manner to the input part 8 of the automatically actuated separating clutch 7 by means of the shaft 12 directly or by means of teeth (not shown). The output part 9 of the separating clutch 7 is connected to the transmission input shaft 11 , which is designed as a hollow shaft, of the single- or multi-stage transmission stage 10 and is non-rotatably connected to the rotor 14 of the second electric machine 13 . A differential with the helical gearing 16 is integrated into the gear stage 10 and drives the drive wheels, of which only the single drive wheel 15 is shown. The differential can also be designed separately from the gear stage.

If the separating clutch 7 is fully closed, i.e. closed without slipping, the speed of the crankshaft 5 corresponds to the speed of the transmission input shaft 11 and transmits the maximum transferrable clutch torque to the drive wheels 15 depending on the ratio of the transmission stage 10 and the differential.

In order to save axial installation space, the shaft 12 and the transmission input shaft 11 are nested in one another, that is to say the shaft 12 is guided coaxially in the transmission input shaft 11, which is designed as a hollow shaft. Due to the helical gearing of the In the drive stage to the differential or of the differential itself, the torque present in the gear stage 10 is split into a rotational and an axial force component, so that the transmission input shaft 11 exerts a reaction torque acting on the separating clutch 7, which is present in the actuating device that actuates the separating clutch 7, in particular in the the slave cylinder 111 (FIG. 2) that actuates the separating clutch 7 generates a working pressure that is above a maximum pressure threshold and can possibly damage it. In order to avoid this, the pressure component generated by the reaction torque in the slave cylinder is recorded and compensated or at least taken into account when setting the working pressure.

With reference to FIG. 1, FIG. 2 shows the hydraulic diagram of the hydraulic unit 100 for hydraulically actuating the separating clutch 7, the parking lock 101 and for cooling and/or lubricating components of the hybrid drive train 1, for example the wet-operated separating clutch 7. The pump 104 of the hydraulic unit 100 works bidirectionally, so that the working pressure p is built up in one direction of rotation of the pump 104 in the pressure line 108 and in the other direction of rotation in the pressure medium line 107 pressure medium is made available for lubrication and/or cooling.

The separating clutch 7 and the parking lock 101 are actuated alternatively by means of the switching valve 102 . When the switching valve 102 is switched through, the separating clutch 7 is connected by means of the pressure relief valve 103 either to the pump 104 or to the pressureless sump 105 .

The pump 104 driven by the electric motor 106 builds up the predetermined working pressure p in the pressure line 108 with the appropriate switching of the switching valve 102 and the pressure relief valve 103, which by appropriate control of the electric motor 106 is adjusted by means of the control unit 109 and is detected by the pressure sensor 110 . The check valve 112 is arranged between the pump 104 and the pressure line 108 so that when the working pressure p is reached the pump 104 can be switched off or operated in the other direction of rotation to supply the pressure medium line 107 . If the working pressure falls below a predetermined value in the event of a leak, the pump 104 switches back to the other direction of rotation and builds up the working pressure p again.

The slave cylinder 111 of the separating clutch 7 is acted upon by the working pressure p present in the pressure line 108, the separating clutch 7 is actuated and transmits a clutch torque dependent on the working pressure. If the separating clutch 7 is completely closed, it transmits the maximum clutch torque that can be transmitted.

Due to the reaction torque applied to the transmission input shaft 11, which is designed as a hollow shaft and depends on the driving situation, changing contact pressure forces can be applied to the separating clutch 7, which raise the working pressure p in the slave cylinder 111 above a predetermined maximum pressure threshold, which can damage the slave cylinder 111. The reaction torques which are dependent on the driving situation and during the closing of the separating clutch 7 are therefore determined and stored in a memory of the control unit 109 such as the control unit. While the separating clutch 7 is closed, the working pressure p is reduced by the pressure component of the reaction torque, so that a compensated working pressure p is already set in advance and working pressures occurring due to the reaction torques above the maximum pressure threshold are avoided.

With reference to FIGS. 1 and 2, FIG. 3 shows the diagram 200 with the partial diagrams I, II over the time t of a closing process of the separating clutch 7. The partial Diagram I shows the working pressure p of the slave cylinder 111 over time t. Partial diagram II shows the reaction torque M(R) of the helical gearing 16 over time t. The dashed pressure curve 201 reproduces the behavior of the working pressure p without compensation for the reaction torque M(R) of the torque curve 202 . This means that with large reaction torques M(R), the working pressure p is above the maximum pressure threshold p(max). In order to reduce the working pressure p by the pressure component of the reaction torque M(R), the working pressure p is corrected using the correction curve 203 of the reaction torque M(R). The data of the reaction torque M(R) dependent on the driving situation are determined or simulated in advance, for example during a final inspection of the hybrid drive train 1, for example on a test stand, and stored in the control unit 109, for example in the form of a table. When the separating clutch 7 is closed, the target working pressure, which is predefined as a function of starting conditions, for example, is corrected with the corresponding correction value of the correction curve 203 and set as the working pressure p of the pressure curve 204 . This results in a working pressure p that remains below the maximum pressure threshold p(max).

With reference to the previous figures 1 to 3, FIG. 4 shows the diagram 300 with the working pressure p over the reaction torque M(R) of the helical gearing 16. The correction curve 301 with the tolerance lines 302, 303 shows the reaction torque M(R) as a function determined target value for the working pressure p. Reference character list

hybrid powertrain

hybrid head

internal combustion engine

electric machine

crankshaft

rotor

disconnect clutch

input part

output part

gear stage

transmission input shaft

Wave

electric machine

rotor

drive wheel

helical gearing

hydraulic unit

parking lock

switching valve

pressure relief valve

pump

swamp

electric motor

pressure line

control unit

pressure sensor

slave cylinder

check valve

diagram

pressure curve 202 torque curve

203 correction curve

204 pressure curve

300 diagram

301 correction curve

302 tolerance line

303 tolerance line

M(R) reaction moment

P Working pressure p(max) Maximum pressure threshold

Claims

Claims Method for controlling a hybrid head

(2) a hybrid drive train (1) with a first, with a crankshaft (5) of an internal combustion engine

(3) connected electric machine (4) and a second electric machine (13) connected to drive wheels (15) by means of a differential with helical gearing (16) and a separating clutch (7) arranged between the electric machines (4, 13) and a hybrid head ( 2) controlling control unit (109), the separating clutch (7) being actuated by means of a hydraulic, electrically driven pump (104) and in a pressure line (108) by means of the pump (104) a predetermined working pressure (p) for transmitting a sufficient contact pressure is set and the separating clutch (7) is actuated by means of a slave cylinder that can be connected to the pressure line (108) by means of an axial displacement movement of the slave cylinder piston with a switching valve (102) controlled by the control unit (109), and the working pressure (p) falls as a result Leakage and/or actuation processes of the separating clutch (7) are compensated for by means of post-pumping processes of the pump (104), characterized in that the working pressure (p) falls below a maximum pressure threshold (p (max)) of the working pressure (p) is set. Method according to Claim 1, characterized in that the reaction torques (M(R)) occurring when the separating clutch (7) is closed due to a shaft (12) of the rotor ( 6) the other electric machine

(4) are taken into account. Method according to Claim 1 or 2, characterized in that the reaction torques (M(R)) occurring on the helical gearing (16) as a function of a set driving situation are taken into account. Method according to one of Claims 1 to 3, characterized in that reaction torques (M(R)) occurring during a closing of the separating clutch are stored in advance in a memory of the control unit (109) and the working pressure applied during the closing of the separating clutch (7) is corrected by means of the stored reaction torques (M(R)).

5. The method as claimed in claim 4, characterized in that the working pressure (p) is reduced by a pressure component caused by the reaction moments (M(R)) before the maximum pressure threshold (p(max)) is exceeded.

6. The method according to any one of claims 1 to 5, characterized in that the hybrid head (2) contains a parking lock (101) which is arranged by means of a pressure line (108) switching valve (102) with a downstream, the parking lock (101) actuating slave cylinder is actuated.

7. The method according to any one of claims 1 to 6, characterized in that the pump (104) is designed as a bidirectional pump, with the working pressure (p) in the pressure line (108) being set in one direction of rotation of the pump (104) and in the other direction of rotation in a pressure medium line (107) a fluid flow for cooling and / or lubrication of at least one Antriebsstrangkom- component is provided.