DE102019210248A1 - Method for operating a drive train unit and electronic control unit - Google Patents

Abstract

Method for operating a drive train unit (G, HY) of a motor vehicle, the drive train unit (G, HY) having a hydraulically operated actuator (A) with a piston chamber (K), a valve (V) for controlling a fluid supply to the piston chamber (K), an electrically drivable pump (P) and an electronic control unit (ECU) for controlling the valve (V), the piston chamber (K) being prepared for an actuation process of the actuator (A) in a filling process by controlling the valve ( V) is filled with a defined volume of fluid, an actual start of the filling process being determined by observing a change in the speed of the pump (P); and electronic control unit (ECU) for carrying out such a method.

Description

The invention relates to a method for operating a drive train unit of a motor vehicle, as well as an electronic control unit for carrying out such a method.

From the US 2007/0174000 A1 a transmission control system is known, wherein a hydraulic shifting element for engaging a gear can be closed depending on a hydraulic pressure. An electromechanical actuator interrupts a hydraulic line to the switching element based on a control signal. A control unit generates this control signal, the control unit determining a setpoint fluid volume and extrapolating a current filling fluid volume of the switching element from this. The current filling fluid volume determined in this way is compared with previously stored filling fluid volume in order to enable an adaptation for future closing processes of the switching element.

When determining the filling fluid volume in this way, however, the dead time of the control chain must be taken into account, which has a great influence on the actual filling fluid volume, particularly at low fluid temperatures. 3 the US 2017/0261047 A1 shows an example of the dynamic response behavior of the hydraulic pressure on the piston compared to the control signal at different fluid temperatures.

It is therefore the object of the invention to specify a method which improves the accuracy of the hydraulic control, particularly at low fluid temperatures.

The object is achieved by a method with the features of claim 1. In addition, an electronic control unit for carrying out such a method is specified. Advantageous refinements result from the dependent claims, the description and from the figures.

To solve the problem, a method for operating a drive train unit of a motor vehicle is proposed. The drive train unit can be formed, for example, by an automatic transmission or by an automated manual transmission. Alternatively, the drive train unit can be formed by a hybrid module which is arranged in a motor vehicle hybrid drive train between the internal combustion engine and the transmission.

The drive train unit has a hydraulically operated actuator with a piston chamber. This actuator can, for example, actuate a friction clutch or a friction brake of the drive train unit. The drive train unit also has a valve for controlling the fluid supply to the piston chamber, as well as an electrically drivable pump for supplying fluid to the piston chamber. The valve is functionally arranged between the pump and the piston chamber. The valve can be part of a hydraulic control unit which contains several such valves for controlling further hydraulically operated actuators. The valve can be operated electromagnetically, for example.

The drive train unit also has an electronic control unit which is set up at least to control the valve. The electronic control unit receives signals from sensors and / or other electronic control units. The electronic control unit can process these signals and, as a function of these signals and as a function of information stored in the electrical control unit, issue control commands to the at least one valve. In this way, the electronic control unit can control a state of the hydraulically operated actuator.

In preparation for an actuation process of the actuator, the piston chamber is filled in a filling process. If the piston chamber is completely filled, the actuation process can begin by a subsequent pressure build-up in the piston chamber. The filling process is carried out by activating the valve accordingly, so that the piston chamber is filled with a defined volume of fluid.

According to the invention, it is now provided that an actual start of the filling process is determined by observing a speed of the pump. The invention is based on the knowledge that a mere activation of the valve does not represent the actual start of the filling process, but only a sufficiently large movement of the piston or slide of the valve. As soon as this sufficiently large movement takes place, the hydraulic resistance against which the pump is delivering changes - provided there is sufficient pressure. In response to this change in resistance, the speed of the pump increases. This increase in speed can be determined in a simple manner, particularly in the case of electrically driven pumps. For example, the electronic control unit can receive the speed of the pump based on a signal from a speed sensor. Alternatively, the electronic control unit can receive the information on the pump speed from another electronic control unit, for example a control unit for controlling the pump.

This event-based determination of the actual start of the filling process can the filling process can be controlled with increased accuracy.

The filling process is preferably continued in a time-controlled manner after its actual start has been determined. “Time-controlled” is understood here to mean a control in which the valve remains in its open position until a defined period of time has elapsed. The “open position” of the valve is understood to mean any valve position which differs from a “closed position” of the valve.

The defined period of time is preferably dependent on a pressure and on a temperature of the fluid, as well as on a hydraulic elasticity of the actuator. In this way, the entire filling process can be controlled with high accuracy. The temperature of the fluid can be determined, for example, by means of a temperature sensor which is arranged, for example, in a sump of the drive train unit. The pressure of the fluid can be determined by a pressure sensor which determines the pressure on the pump side in the hydraulic system of the drive train unit.

Alternatively, the pressure in the hydraulic system of the drive train unit can be determined by the electronic control unit.

When determining the defined time period, a time signal delay between the occurrence and the determination of the change in speed of the pump is preferably taken into account. Such a time delay is unavoidable due to the computing times and signal resolution. By taking into account these boundary conditions with regard to the signal transit time, the time required for filling can be determined with increased accuracy.

Preferably, the valve for the filling process is first activated in such a way that the valve releases its maximum possible opening cross section. In the further course of the filling process, the existing opening cross-section of the valve is reduced by appropriate activation by means of the electronic control unit. The improved knowledge of the actual start of the filling process reduces the risk of unwanted overfilling, so that the valve can be opened completely with high functional reliability. This allows the filling process to be accelerated accordingly.

To achieve the object, an electronic control unit is also proposed, which is set up to carry out the method described at the beginning. The electronic control unit can be provided to carry out further functions of the drive train control.

• 1 und 2 je eine schematische Darstellung eines Kraftfahrzeug-Antriebsstrangs
• 3 einen Antriebsstrang-Abschnitt gemäß einem ersten Ausführungsbeispiel;
• 4 einen Antriebsstrang-Abschnitt gemäß einem zweiten Ausführungsbeispiel; sowie
• 5 eine schematische Ansicht eines Hydrauliksystems einer Antriebsstrang-Einheit.

The invention is described in detail by way of example in the following figures. Show it:

• 1 and 2 each a schematic representation of a motor vehicle drive train
• 3 a drive train section according to a first embodiment;
• 4th a drive train section according to a second embodiment; such as
• 5 a schematic view of a hydraulic system of a drive train unit.

1 shows a schematic representation of a motor vehicle drive train according to a first embodiment. The drive train has an internal combustion engine VM which is functional with a hybrid module HY connected is. The hybrid module HY houses an in 1 electrical machine not shown. The hybrid module HY is functional with a gearbox G connected, which is set up to provide different gear steps. In the transmission G can an in 1 friction element not shown may be present. The gear unit is on the output side G with a differential gear AG connected, which is set up on an output shaft GW2 of the drive train applied power to drive wheels DW to distribute.

2 shows a schematic representation of a motor vehicle drive train according to a second embodiment. The gear G now includes one - in 2 not shown - electrical machine, and is functional with the internal combustion engine VM connected. In the embodiment according to 1 included hybrid module HY not applicable.

3 shows a drive train section according to a first possible embodiment. An output shaft of the internal combustion engine VM is via a disconnect clutch K0 with a rotor shaft RW a first electrical machine EM connected. The drive train also has a gear set GS with a drive shaft GW1 and the output shaft GW2 on. The gear set GS is to provide different translations between the drive shaft GW1 and the output shaft GW2 set up, for example by means of planetary gear sets, spur gear stages and / or a friction gear, with shifting elements to form the gearbox G work together. One of these switching elements is symbolically denoted by the reference number SE marked. The rotor shaft RW is connected to the drive shaft via a hydrodynamic torque converter GW1 of the gear set GS connected. This is the rotor shaft RW with an impeller TP of the torque converter, and the drive shaft GW1 with a turbine wheel TT of the torque converter connected. Impeller TP and turbine wheel TT are via a lock-up clutch WK mechanically connectable. The output shaft GW2 is about the differential AG with drive wheels DW of the motor vehicle connected.

The drive train has a hydraulic unit HCU on, the control of hydraulic consumers at least the gear set GS is set up. These hydraulic consumers are supplied with pressure by a pump P . The pump P sucks fluid from a tank T and leads this fluid to the hydraulic unit HCU to. It's a planetary gear set RS with three elements E1 , E2 , E3 intended. The element E1 is designed as a sun gear and is connected to a rotor of a second electrical machine EM2 connected. The element E1 is in one direction of rotation via a freewheel F. supported. The element E2 is designed as a planet carrier, and is with a rotor of the pump P connected. The element E3 is designed as a ring gear and is connected to the drive shaft GW1 connected, for example via a chain drive or a front drive. There are several planets on the planet carrier PL rotatably mounted, which mesh with the sun gear and with the ring gear.

4th shows a motor vehicle drive train according to a second possible embodiment, which essentially corresponds to the in 3 corresponds to the drive train shown. The pump P will now have its own electrical machine EM3 driven; the drive of the pump P via the drive shaft GW1 not applicable.

As an alternative to the representations in 3 and 4th the hydraulic system could also have two pumps, one of the two pumps being driven by the drive shaft GW1 is driven and the other of the two pumps is driven by its own electric motor. Both of the two pumps can drain fluid from the tank T suction and the hydraulic unit HCU provide.

With the exception of the internal combustion engine VM and the drive wheels DW can all in 3 and 4th shown components of the drive train in the transmission G be arranged. The differential gear AG can especially with a - as shown in the figures - aligned along the direction of travel of the motor vehicle drive train outside the transmission G be arranged. Such an arrangement of the components corresponds to that in 2 shown drive train.

Alternatively, the electrical machine EM and the disconnect clutch K0 outside the transmission G be arranged, and a hybrid module HY be summarized. Such an arrangement of the components corresponds to that in 1 shown drive train. Such a hybrid module HY could have its own hydraulic system with its own pump, or via the hydraulic system of the transmission G are supplied.

In the 3 and 4th The drive trains shown are only to be regarded as examples. For example, the torque converter could be omitted and replaced by one or two starting clutches, which are located within the gear set GS or are upstream of it. The disconnect clutch K0 as well as the electric machine EM are only optional components of the drive train.

5 shows a schematic view of a hydraulic system of a drive train unit. The drive train unit can, for example, be a transmission G or through a hybrid module HY be formed according to the figures shown above. The hydraulic system includes the pump P which fluid from the tank T suction and the hydraulic unit HCU feeds. It's a check valve RV provided over which excess fluid from a pressure side of the pump P again to a suction side of the pump P can be fed. The hydraulic unit HCU comprises at least one valve V . The valve V is designed as a spring-loaded, electromagnetically actuated valve with two switching positions. The valve V serves to control the supply of fluid to a spring-loaded and hydraulically operated actuator A. . The actuator A. includes a piston space K and a piston KR . The piston KR acts on a multi-plate clutch, which for example by one of the switching elements SE of the transmission G , through the lock-up clutch WK or through the disconnect clutch K0 is formed. The actuator is due to the spring preload A. biased in an initial position in which the multi-plate clutch is not actuated and therefore assumes its open state. By building up pressure in the piston chamber K acts the piston KR against the spring preload on the multi-disc clutch, so that the multi-disc clutch assumes a closed state and thereby a first shaft W1 connects to a second shaft W2.

In a first switching position of the valve V becomes the piston space K with the tank T connected so that the actuator A. the multi-plate clutch opens due to its spring preload. The pressure side of the pump is in a second switch position P with the piston chamber K connected so that the piston chamber K is filled with fluid. Is the piston chamber K completely filled, the pressure in the piston chamber increases further K to a closing process of the multi-disc clutch.

An electronic control unit is used to control the hydraulic system ECU intended. The electronic control unit ECU receives signals from multiple sensors, including a temperature signal from a temperature sensor ST , which is the fluid temperature in the tank T determined, as well as speed signals n_W1 and n_W2 . The speed signals n_W1 and n_W2 characterize, for example, a differential speed of the multi-plate clutch. The electronic control unit ECU is also available with another electronic control unit ECU-P in communication link. The electronic control unit ECU-P controls, for example, a speed of the pump P by controlling one or more of the electrical machines EM , EM2 , EM3 . This control could alternatively be done by the electronic control unit ECU be carried out by yourself. The electronic control unit controls depending on the signals received ECU a power supply to an electromagnet of the valve V so that the valve V assumes the first or the second switching position depending on this power supply. The electronic control unit thereby controls a state of the actuator A. .

If there is now a request to close the multi-disc clutch, the electronic control unit controls ECU the valve V such that the valve V a maximum possible opening cross-section between the pressure side of the pump P and the piston chamber K releases to the piston chamber K to be filled with fluid. The time it takes for the valve to execute this command V is particularly dependent on a temperature of the fluid. At low temperatures is the response time of the valve V longer than at higher fluid temperatures due to the higher viscosity of the fluid. Once the valve V finally assumes the second switching position, this increases the speed of the pump for a short time P because of the hydraulic resistance of the pump P changes. This speed reaction of the pump P on the assumption of the second switching position of the valve V is controlled by the electronic control unit ECU-P determined, and the electronic control unit ECU supplied as information. Based on this information, the point in time of an actual start of the filling process for the piston chamber is K known. The electronic control unit ECU controls the further filling process of the piston chamber K now time-controlled based on a defined period of time after the actual start of the filling process. This defined period of time depends on a temperature of the fluid, which is determined by the temperature sensor ST is determined by one on the pressure side of the pump P existing pressure and hydraulic elasticity of the actuator A. . These dependencies are on the electronic control unit ECU stored in the form of one or more maps.

Between the actual taking of the second switching position of the valve V and the knowledge of this event by the electronic control unit ECU there is a time delay in the signal, which is determined by the signal resolution and signal transmission times. This time delay is controlled by the electronic control unit ECU taken into account, and also stored in the map.

List of reference symbols

VM

Internal combustion engine

K0

Disconnect clutch

TP

Impeller

TT

Turbine wheel

WK

Lock-up clutch

G

transmission

HY

Hybrid module

GS

Gear set

SE

Switching element

HCU

Hydraulic unit

T

tank

GW1

drive shaft

GW2

Output shaft

AG

Differential gear

DW

drive wheel

P

pump

EM

Electric machine

RW

Rotor shaft

EM2

Electric machine

EM3

Electric machine

F.

Freewheel

RS

Planetary gear set

E1

Element, sun gear

E2

Element, planet carrier

E3

Element, ring gear

PL

Planetary gear

ECU

Electronic control unit

ECU-P

Electronic control unit

RV

check valve

V

Valve

A.

Actuator

K

Piston chamber

KR

piston

W1

First wave

n_W1

Speed of the first shaft

n_W2

Speed of the second shaft

S-T

Temperature sensor

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2007/0174000 A1 [0002]
• US 2017/0261047 A1 [0003]

Claims (7)

Method for operating a drive train unit (G, HY) of a motor vehicle, the drive train unit (G, HY) having a hydraulically operated actuator (A) with a piston chamber (K), a valve (V) for controlling a fluid supply to the piston chamber (K), an electrically drivable pump (P) for supplying fluid to the piston chamber (K) and an electronic control unit (ECU), the electronic control unit (ECU) being set up at least to control the valve (V), so that the electronic control unit (ECU) controls a state of the actuator (A), - the piston chamber (K) being filled with a defined fluid volume in a filling process by controlling the valve (V) in preparation for an actuation process of the actuator (A), characterized in that a actual start of the filling process is determined by observing a change in the speed of the pump (P). Procedure according to Claim 1 , characterized in that the filling process is continued in a time-controlled manner after its actual start has been determined. Procedure according to Claim 2 , characterized in that the time-controlled section of the filling process is carried out on the basis of a period of time which is at least dependent on a pressure and a temperature of the fluid and on a hydraulic elasticity of the actuator (A). Procedure according to Claim 3 , characterized in that a time delay between the occurrence and the determination of the speed change of the pump (P) is taken into account when determining the duration. Method according to one of the Claims 1 to 4th , characterized in that the valve (V) for the filling process is initially controlled in such a way that the valve (V) releases a maximum possible opening cross-section, the existing opening cross-section of the valve (V) being reduced as the filling process continues. Method according to one of the Claims 1 to 5 , characterized in that the drive train unit (G, HY) is formed by an automatic transmission, by an automated manual transmission, or by a hybrid module. Electronic control unit (ECU) for controlling a drive train unit (G, HY) of a motor vehicle, the electronic control unit (ECU) for carrying out the method according to one of the Claims 1 to 6th is set up.

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