DE102022206489A1 - Method and control device for operating a transmission - Google Patents

Abstract

Method for operating a transmission (10) of a motor vehicle, wherein the transmission (10) has a hydraulic system (12) for supplying hydraulic oil, which has a dual-circuit pump (14) with a primary flood (16) and a secondary flood (18), a system pressure valve (32) , a lubrication valve (34), a primary circuit (28) and a secondary circuit (30), the dual-circuit pump (14) with the interposition of a superposition gear (20) and a superposition of a first speed (n1) of an internal combustion engine (22) and a second Speed (n2) of an electric machine (24) can be driven by this with a resulting pump speed (n3), a control device (44) determining as a function of a required primary flood setpoint in the primary circuit (28) and a required secondary flood setpoint in the secondary circuit (30), whether either a single-circuit operating state or a dual-circuit operating state should be set or maintained, and sets or maintains the specific operating state, and the control device (44) applies a damping factor greater than or equal to zero and less than one to the required secondary flood setpoint when determining the operating state, when the control device (44) receives a signal indicating a desired damping. A corresponding control device (44) of a motor vehicle is also disclosed.

Description

The invention relates to a method and a control device for operating a transmission of a motor vehicle.

A drive train of a motor vehicle has a drive unit, a transmission and an output. If you look at the course of the power flow, the transmission is arranged between the drive unit and the output. The transmission converts speeds and torques and thus provides the traction power of the drive unit to the output in a suitable manner. In a conventional motor vehicle, the drive unit is designed as an internal combustion engine. If the motor vehicle is a hybrid vehicle, a combination of an internal combustion engine and an electric machine constitutes the drive unit.

Transmissions known from practice typically have several switching elements. These switching elements can be positive switching elements, such as claws, as well as frictional switching elements, such as clutches or brakes. In each switching state, a defined first number of these switching elements is closed and a defined second number of these switching elements is opened.

To open and close the switching elements of the transmission or to keep the switching elements of the transmission open and closed, they are controlled with a defined hydraulic pressure, which is provided by a hydraulic system of the transmission.

To provide the pressure for the hydraulic fluid or the flood quantity or flow quantity of the hydraulic fluid, a dual-circuit pump is used in modern motor vehicles, which is coupled to an internal combustion engine and an electrical machine via a superposition gear in order to produce the dual-circuit pump by superimposing the speeds of the internal combustion engine and the electrical machine to drive. This electrical machine is not an electrical machine of a drive unit, but rather an additional electrical machine for driving the dual-circuit pump. Such a dual-circuit pump driven via a superposition gear is also referred to as a power-split dual-circuit pump. The dual-circuit pump has a so-called primary flood with a primary delivery rate and a so-called secondary flood with a secondary delivery rate.

A transmission hydraulic system has a primary circuit and a secondary circuit. The primary circuit is used to control the pressure of the gearshift elements of the transmission. The secondary circuit is used to cool and lubricate gearbox assemblies. The hydraulic pump of the hydraulic system interacts with a system pressure valve of the hydraulic system in such a way that all oil that the hydraulic pump delivers is initially conveyed into the primary circuit of the hydraulic system until a target primary circuit pressure or target system pressure is reached in the primary circuit. Only then can an excess amount of oil or an excess oil volume flow be conveyed into the secondary circuit of the hydraulic system via the system pressure valve, whereby when a target secondary circuit pressure is also reached in the secondary circuit, an excess oil volume flow is conveyed back in the direction of suction charging of the respective pump becomes.

The hydraulic system, more precisely, the respective hydraulic pump thereof, must be able to provide a requested pressure of a hydraulic fluid, usually a hydraulic oil, in the hydraulic system in all operating conditions. This applies in particular to the primary circuit of the hydraulic system in order to supply the switching elements of the transmission with sufficient hydraulic fluid and thus be able to carry out switching operations in accordance with the design of the transmission. Otherwise, under certain circumstances, the switching elements of the transmission could no longer be closed or kept closed, which would then interrupt the adhesion in the transmission.

However, these specifications do not always lead to ideal operation of the transmission. Especially with regard to the energy balance and the implementation of the change between a single-circuit operating state, i.e. the primary flood and the secondary flood together cover the demand in the primary circuit and the secondary circuit, and a dual-circuit operating mode, i.e. the primary flood covers the demand in the primary circuit separately from the secondary flood , which covers the needs in the secondary circuit, improvements would be desirable.

It is therefore an object of the invention to demonstrate an improved method for operating a transmission of a motor vehicle and a control system for carrying out the method.

This object is achieved according to a first aspect of the invention by a method for operating a transmission of a motor vehicle, the transmission having a hydraulic system for supplying hydraulic oil, which has a dual-circuit pump with a primary flood and a secondary flood, a system pressure valve, a lubricating valve, a pri märkreis and a secondary circuit, wherein the dual-circuit pump can be driven by the interposition of a superposition gear and a superposition of a first speed of an internal combustion engine and a second speed of an electric machine with a resulting pump speed, a control device depending on a required primary flood setpoint in the primary circuit and a required secondary flood setpoint in the secondary circuit determines whether either a single-circuit operating state or a double-circuit operating state should be set or maintained, and sets or maintains the specific operating state, and wherein the control device sets the required secondary flood setpoint when determining the operating state with a damping factor greater than or equal to zero and less than one is applied when the control device receives a signal indicating the desired damping.

The inventors have recognized that the approach in the prior art, according to which the current oil requirements (primary and secondary requirements) are controlled directly on the pump system via software functions, regardless of the driving situation, does not always lead to ideal operation of the transmission. Pressure fluctuations can occur, particularly during gear changes, which have a negative impact on the shifting quality.

One effect is that the available volume flow in the primary circuit of the hydraulic system is higher in many situations because the single-circuit operating state can be maintained longer and more frequently. In the single-circuit state, the pump system can preferably deliver 100% to 250%, particularly preferably 125% to 175% and in particular at least approximately 150% more hydraulic fluid than in the double-circuit state. In addition, a change of the dual-circuit operating state to the dual-circuit pump state can be avoided in many situations, so that more consistent control can be achieved. Emissions can also be reduced because short-term revving of the electric machine can be avoided.

The inventors have also recognized that some situations in which the calculated secondary circuit requirement is significantly higher than the calculated primary circuit requirement force the hydraulic system into a dual-circuit operating state, which will be referred to here as “forced dual-circuit”. For example, the calculated secondary circuit requirement can be twice as high or more than twice as high as the primary circuit requirement, which results in a forced dual-circuit operating condition in order to be able to cover the secondary circuit requirement.

In addition, in order to achieve a stable two-circuit operating state, the electric machine (or another pump system that can provide an additional volume flow for the oil supply) must quickly increase or boost the supply of hydraulic fluid by increasing the speed. It is precisely in these transitions between a single-circuit and a dual-circuit operating state that the boosting pump system experiences a jump in requirements.

In this context, the inventors have recognized that since the secondary requirements include the requirements for lubrication and cooling of the transmission, a short-term undersupply in the secondary circuit is possible without resulting in damage to the transmission. Therefore, this short-term undersupply is unexpectedly advantageous overall with regard to the advantages of a stable operating state, in particular a stable single-circuit operating state. The signal that indicates the desired damping can be sent to the control device from outside or can be generated in the control device itself.

The distribution of the total delivery volume of the dual-circuit pump between the primary flood and the secondary flood can be chosen between 10:90 and 45:55, preferably between 25:75 and 43:57 and in particular as at least approximately 40:60.

In a preferred embodiment, the damping factor is specified in the control device or contained in the signal.

It is therefore possible to activate or deactivate the damping factor using a binary signal or to transmit the damping factor numerically in the signal. The numerical transmission can also be an index that has a specific entry in a lookup table in the control device.

In a further preferred embodiment, the damping factor is zero.

This configuration means that the required secondary flood setpoint is ignored when determining the operating state. Even a large secondary flood requirement is then not taken into account when determining the operating status.

In a further preferred embodiment, the control device receives the signal when the transmission carries out a shifting process.

As already explained, switching operations in particular can cause the hydraulic system to switch to operating mode, at least briefly Sele, which could lead to undesirable pressure fluctuations. Therefore, the signal for a switching process or a switching sequence of switching processes is sent to the control device, so that during one or more switching processes the required secondary flood setpoint is ignored or at least reduced when determining the operating state. The signal indicates the desired damping by signaling the switching process or switching sequence.

In a further preferred embodiment, the control device ignores the signal if the damping factor has been applied for a certain period of time.

This design can avoid long-term undersupply and damage caused by long-term lack of lubrication.

In a further preferred embodiment, when entering the single-circuit operating state, the second speed of the electric machine is reduced, in particular to zero.

This design is viewed as particularly economical. Since the switch to the single-circuit operating state has already taken place, the speed of the electric machine can now be reduced or switched off completely to increase overall efficiency.

In a further preferred embodiment, if the actual primary flood size is above a current target size of a required primary flood, a flow of excess hydraulic fluid is conveyed from the primary circuit into the secondary circuit.

This configuration makes it possible to cover part of the secondary flood setpoint required in the secondary circuit from the primary flood in the primary circuit.

In a further preferred embodiment, if a secondary flood actual size is above a current target size of a required secondary flood, a flow of excess hydraulic fluid is conveyed from the secondary circuit into a suction charge of the dual-circuit pump.

This configuration makes it possible, if the primary flood setpoint required in the primary circuit and the secondary flood setpoint required in the secondary circuit are met, to feed the excess hydraulic fluid flow of the secondary circuit back into the suction charging of the dual-circuit pump.

In a further preferred embodiment, each of the flood variables describes a volume flow of the hydraulic fluid or a pressure of the hydraulic fluid.

The person skilled in the art now has the choice of how he wants to describe the flood variables, in particular a primary flood actual size, a primary flood target size, a secondary flood actual size and a secondary flood target size. Depending on the application or specific operating situation, a description as volume, a description as pressure or a description in combination of volume and pressure can be advantageous.

The object is also achieved according to a second aspect of the invention by a control device of a motor vehicle, which is designed to carry out a method previously described.

It is understood that the features of the invention mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or alone, without departing from the scope of the invention.

• 1 ein Detail eines Ausführungsbeispiels eines Hydrauliksystems eines Getriebes des Kraftfahrzeugs, und
• 2 ein Blockdiagramm eines Ausführungsbeispiels eines Verfahrens.

Further features and advantages of the invention result from the following description of preferred exemplary embodiments with reference to the drawings. Show it:

• 1 a detail of an exemplary embodiment of a hydraulic system of a transmission of the motor vehicle, and
• 2 a block diagram of an exemplary embodiment of a method.

1 shows a section of a transmission 10 of a motor vehicle, more precisely of a hydraulic system 12 of the transmission 10. The hydraulic system 12 of the transmission 10 serves, on the one hand, to pressurize switching elements of the transmission 10 and, on the other hand, to lubricate and cool assemblies of the transmission 10.

In the hydraulic system 12 the 1 A dual-circuit pump 14 is used, which provides a primary flood 16 and a secondary flood 18. These floods 16, 18 of the dual-circuit pump 14 are made available by pressure chambers of the dual-circuit pump 14, which each deliver a delivery rate or a delivery volume of the dual-circuit pump 14. Thus, the primary flow 16 provides a primary delivery rate or a primary delivery volume and the secondary flow 18 provides a secondary delivery rate or a secondary delivery volume of the dual-circuit pump 14.

The dual-circuit pump 14 can be driven by an internal combustion engine 22, which has a first speed n1, and an electric machine 24, which has a second speed n2, preferably via a superposition gear 20 with a planetary gear set. A first speed n1 of the internal combustion engine 22 and a second speed n2 of the electric machine 24 are superimposed on the superposition gear 20 in order to drive the dual-circuit pump 14 of the hydraulic system 12 with a pump speed n3.

As already mentioned, such a dual-circuit pump 14 is also referred to as a power-split pump, with the power splitting taking place here by superimposing the power from the internal combustion engine 22 and the power from the electric machine 24. The performance of the internal combustion engine 22 and the performance of the electric machine 24 are essentially determined by the speed of the respective unit.

The dual-circuit pump 14 is preferably implemented as a vane pump, in particular with an eccentrically arranged impeller. Such a geometry allows the primary flood 16 to leave the dual-circuit pump 14 with a higher pressure than the secondary flood 18. For this reason, the volume delivered by the secondary flood 18, as the secondary delivery rate, is larger than that of the primary flow 16, i.e. the primary delivery rate.

The dual-circuit pump 14 sucks in a hydraulic fluid, here oil, starting from an oil sump 26, whereby the oil sucked in by the dual-circuit pump 14 from the oil sump 26 can be conveyed into a primary circuit 28 and into a secondary circuit 30 of the hydraulic system 12. The primary circuit 28 serves to supply the switching elements of the transmission 10 with hydraulic fluid in order to close or keep the switching elements of the transmission 10 closed. The secondary circuit 30 is used to cool and lubricate components of the transmission 10.

The dual-circuit pump 14 of the hydraulic system 12 cooperates with a system pressure valve 32 and a lubrication valve 34 in order to promote or feed the hydraulic fluid conveyed by the dual-circuit pump 14 in the direction of the primary circuit 28 and/or in the direction of the secondary circuit 30.

Then, when the dual-circuit pump 14 is operated with a relatively low pump speed n3 and an oil volume flow provided by the dual-circuit pump 14 as a result of this pump speed n3 provides a pressure in the primary circuit 28 that is smaller than a target primary circuit pressure or target influenced via a pilot control pressure 40 -System pressure, the volume flow of the primary flood 16 and the secondary flood 18 of the dual-circuit pump 14 is conveyed exclusively and completely into the primary circuit 28, specifically in a corresponding switching position of the system pressure valve 32, which acts as a pressure relief valve. Check valves 36, 38 prevent a backflow of oil from the primary circuit 28 in the direction of the primary flood 16 and the secondary flood 18 of the dual-circuit pump 14.

2 shows a block diagram of an exemplary embodiment of a method 50. In step S10, the hydraulic system 12 is in a first operating state, which here is the single-circuit operating state by way of example. In step S12 it is checked whether the control device 44 receives a signal that indicates a desired damping. The signal can be generated within the control device 44 or supplied to the control device 44 from outside, for example from another module.

If the control device 44 has received the signal, the method 50 branches via branch J to step S14. Here, depending on a required primary flood setpoint in the primary circuit and a required secondary flood setpoint in the secondary circuit, it is determined whether either a single-circuit operating state or a dual-circuit operating state should be set. The control device applies a damping factor greater than or equal to zero and less than one to the required secondary flood setpoint when determining the operating state.

If the control device 44 has not received the signal, the method 50 branches via branch N to step S16. Here, depending on a required primary flood setpoint in the primary circuit and a required secondary flood setpoint in the secondary circuit, it is determined whether either a single-circuit operating state or a dual-circuit operating state should be set. The required secondary flood setpoint is not subjected to the damping factor when determining the operating state.

Depending on the result of the determination of the future operating state in step S14 or S16 and the current operating state, it is determined in step S18 whether the current operating state also corresponds to the future operating state or not. In the first case, no change in the operating state is required and the method 50 branches back to step S10 via branch N.

In the second case, if a change in the operating state is required, the method 50 branches via branch J to step S20, where the operating state is changed, and the method 50 then returns to step S10. The change in step S20 can take place from the single-circuit operating state to the dual-circuit operating state and vice versa.

The invention also relates to a control device 44 for carrying out the method according to the invention. This control device 44 is, in particular, a transmission control unit. The control device 44 is designed to carry out the method according to the invention. For this purpose, the control device 44 has at least data interfaces in order to exchange data with the modules involved in the execution of the method according to the invention when the signal is received from outside the control device 44. Furthermore, the control device 44 has a processor for data processing and a memory for data storage. Program blocks are also stored in the control device 44 and are used to carry out the method according to the invention.

In principle, the presented concept and the presented control device can also be applied to other pump systems, e.g. to pump systems with an additional pump that can provide an additional volume flow for the supply of hydraulic fluid, in which case the additional pump is then activated in a corresponding manner, such as, see the previous explanations, the second speed of the electric machine is increased.

Reference symbols

10

transmission

12

Hydraulic system

14

Dual circuit pump

16

Primary flood

18

Secondary flood

20

Superposition gear

22

Internal combustion engine

24

electric machine

26

Oil sump

28

primary district

30

Secondary circuit

32

System pressure valve

34

Lubrication valve

36

check valve

38

check valve

40

Pilot pressure

42

Suction charging

44

Control device

n1

Speed of the internal combustion engine

n2

Speed of the electrical machine

n3

Pump speed

Claims (10)

Method for operating a transmission (10) of a motor vehicle, wherein the transmission (10) has a hydraulic system (12) for supplying hydraulic oil, which has a dual-circuit pump (14) with a primary flood (16) and a secondary flood (18), a system pressure valve (32) , a lubrication valve (34), a primary circuit (28) and a secondary circuit (30), the dual-circuit pump (14) with the interposition of a superposition gear (20) and a superposition of a first speed (n1) of an internal combustion engine (22) and a second Speed (n2) of an electric machine (24) can be driven by this with a resulting pump speed (n3), a control device (44) determining as a function of a required primary flood setpoint in the primary circuit (28) and a required secondary flood setpoint in the secondary circuit (30), whether either a single-circuit operating state or a dual-circuit operating state should be set or maintained, and sets or maintains the specific operating state, and the control device (44) applies a damping factor greater than or equal to zero and less than one to the required secondary flood setpoint when determining the operating state, when the control device (44) receives a signal indicating a desired damping. Procedure according to Claim 1 , whereby the damping factor is predetermined in the control device (44) or is contained in the signal. Procedure according to Claim 1 or 2 , where the damping factor is zero. Method according to one of the preceding claims, wherein the control device (44) receives the signal when the transmission (10) carries out a shifting process. A method according to any one of the preceding claims, wherein the controller (44) ignores the signal if the damping factor has been applied for a certain period of time. Method according to one of the preceding claims, wherein when the single-circuit operating state occurs, the second speed of the electric machine (24) is reduced, in particular to zero. Method according to one of the preceding claims, wherein if the actual primary flood size is above a current target size of a required primary flood (16), a flow of excess hydraulic fluid is conveyed from the primary circuit (28) into the secondary circuit (30). Method according to one of the preceding claims, wherein if a secondary flood actual size is above a current target size of a required secondary flood (18), a flow of excess hydraulic fluid is conveyed from the secondary circuit (30) into a suction charge (42) of the dual-circuit pump (14). Method according to one of the preceding claims, wherein each of the flood quantities describes a volume flow of the hydraulic fluid or a pressure of the hydraulic fluid. Control device (44) of a motor vehicle, which is designed to carry out the method according to one of Claims 1 until 9 to carry out.

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