CN106151312B

CN106151312B - Method for protecting a clutch of a motor vehicle

Info

Publication number: CN106151312B
Application number: CN201610307868.5A
Authority: CN
Inventors: 迈克尔·罗伊舍尔; 丹尼尔·穆勒
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2015-05-13
Filing date: 2016-05-11
Publication date: 2019-12-06
Anticipated expiration: 2036-05-11
Also published as: CN106151312A; DE102015208849A1

Abstract

The invention relates to a method for protecting a clutch of a motor vehicle, wherein an energy input (ESCh) into the clutch (4) is carried out by means of a slipping state of the clutch (4). In a method in which clutch protection measures cannot be perceived by the driver, a characteristic variable characterizing the clutch load, which is limited by a maximum value, is calculated in advance in order to reliably maintain at least one power-specific limit value of the clutch (4), and the driving strategy of the vehicle is adjusted on the basis of the characteristic variable characterizing the clutch load, which is calculated in advance and can be changed during the clutch engagement process.

Description

Method for protecting a clutch of a motor vehicle

Technical Field

The invention relates to a method for protecting a clutch of a motor vehicle, wherein energy is input into the clutch by means of a slip state.

Background

Motor vehicles comprise a drive train in which a motor drives a transmission via a clutch, the output shaft of which acts on the drive wheels of the vehicle. The motor can be an internal combustion engine or an electric motor or a combination of both. The clutch can be controlled manually or automatically. In particular, the clutch can be part of an automatic transmission and is designed to be opened and closed automatically during a transmission shift. A control device is provided for controlling the transmission. The clutch can be closed relatively slowly, for example, during a starting process, while torque is transmitted from the internal combustion engine to the transmission via the clutch. Here, friction heat is generated that can increase the clutch temperature. During the subsequent starting process, the clutch temperature can increase to such an extent that the function of the clutch is impaired or that an odor occurs in the region of the motor vehicle or that the life of the clutch is adversely affected.

It is common that: and calculating the temperature of the clutch, and taking corresponding protective measures for the clutch or executing the correction of specific clutch parameters according to the temperature of the clutch. This has the disadvantages that: only via a corresponding calibration of the clutch temperature and the control parameters of the clutch ensures that: without overloading the clutch. Thus, if the permissible clutch temperature is exceeded, the clutch can be protected against further overload, for example, by intervening on the motor or by disconnecting the clutch. But this is disadvantageous because it can be perceived by the passenger.

Disclosure of Invention

The object on which the invention is based is: a method for protecting a clutch of a motor vehicle is proposed, the effect of which is not perceptible by a passenger.

According to the invention, said object is achieved by: in order to reliably maintain at least one power-specific limiting value of the clutch, a characteristic variable characterizing the clutch load, which is limited by a maximum value and which can be changed during the clutch engagement process, is calculated in advance and the driving strategy of the vehicle is adjusted as a function of the characteristic variable characterizing the clutch load calculated in advance. This has the advantage that: the precalculation of the characteristic variable which characterizes the clutch load, which is also able to handle the clutch maximally without exceeding the maximum power-specific limit value, is not perceived by the driver as a protective measure, since it is reliably integrated into the driving strategy. This is due to: it is determined in advance whether a particular clutch action can be performed at all.

Advantageously, the amount of energy is used as a characteristic variable characterizing the clutch load and the maximum value corresponds to the maximum energy value. If the pre-calculated energy value exceeds the amount of energy still present, the clutch action is aborted.

In one embodiment, the power-specific limit value is characterized by a maximum energy value, which is determined clutch-specifically. This maximum is therefore an upper limit for the energy input which can be input into the clutch at a preset time without overloading the clutch or negatively affecting its life. Thereby ensuring that: clutch actuation in which the energy input exceeds the maximum energy value is interrupted, thereby preventing, for example, overheating of the clutch or wear that would impair the life of the clutch.

Advantageously, the energy introduced into the clutch during the slip process is subtracted from the maximum energy value, from which the energy limit value permitted for the next slip process of the clutch is derived. Thus at any instant is known: it also allows for how much energy to be input into the clutch during subsequent slip without overheating the clutch. This is taken into account when determining the driving strategy of the vehicle.

In one refinement, the energy limit value is approached to the maximum energy value by regeneration of the clutch without a slip process of the clutch. Thereby ensuring that: the maximum energy value used as an energy buffer is filled as a function of the permissible thermal emission or self-healing of the clutch and, after a predetermined period of time, is again made available to the clutch.

In one variant, the maximum energy value is varied during the travel of the motor vehicle as a function of the clutch temperature and/or the ambient temperature and/or the rotational speed of the drive motor. By taking this boundary condition into account when determining the maximum energy value, the current state of the clutch is taken into account when determining the maximum energy value and exceeding of the power limit value of the clutch is prevented in any driving situation of the vehicle.

In one embodiment, the maximum energy value is determined as a function of the clutch-specific permissible friction power or friction quantity. The structure-related properties of the clutch are therefore also taken into account when determining the maximum energy value.

In a further embodiment, the permissible energy limit remaining after the slip process is evaluated by a higher-level driving strategy and corresponding protective measures are activated for the clutch. The upper driving strategy can determine: whether a normal start of the vehicle can be achieved under the current boundary conditions by sufficiently reducing the required amount of energy, for example by reducing the starting speed, for example, or by activating an emergency strategy.

In one embodiment, a hybrid vehicle is used as a motor vehicle, wherein the remaining energy limit value is evaluated for restarting the internal combustion engine. This mode of operation is important in particular in hybrid vehicles, in particular when continuous stop-and-Go driving (Stopp-und-Go-Fahrt) is carried out in urban traffic, in which the internal combustion engine is started by the electric motor by being towed via the closing clutch. Since this process is carried out relatively frequently in short time periods, this results in overheating of the clutch or a limited service life, which is suppressed by the proposed method.

The wear or temperature of the clutch is advantageously used as a power-specific limit value. These two power-specific limit values are associated with the total amount of energy, which is taken into account in the maximum energy value.

Drawings

The invention allows different embodiments. One of which is illustrated in detail in the drawings shown in the accompanying drawings.

It shows that:

Figure 1 shows a schematic diagram of a hybrid drive of a motor vehicle,

Figure 2 shows a diagram of the energy consumption of the clutch over time,

Fig. 3 shows a schematic representation of the rotational speeds of the internal combustion engine and of the electric motor when the internal combustion engine is restarted.

Detailed Description

Fig. 1 shows a schematic representation of a drive train 1 of a hybrid vehicle. The powertrain 1 includes an internal combustion engine 2 and an electric motor 3. The clutch 4 is arranged directly behind the internal combustion engine 2 between the internal combustion engine 2 and the electric motor 3. The internal combustion engine 2 and the clutch 4 are connected to each other via a crankshaft 5. The electric motor 3 has a rotatable rotor 6 and a stationary stator 7. The output shaft 8 of the clutch is connected to a transmission 9, which contains a coupling element, not shown in detail, such as a second clutch or a torque converter, which is arranged between the electric motor 3 and the transmission 9. The transmission 9 transmits torque generated by the internal combustion engine 2 and/or the electric motor 3 to drive wheels 10 of the hybrid vehicle. The electric motor 3 and the transmission 9 form a transmission system 11, which is controlled, for example, by a hydrostatic clutch actuator 12. A clutch 4 arranged between internal combustion engine 2 and electric motor 3 is closed in order to start internal combustion engine 2 or to drive during run-up operation by means of the driven internal combustion engine 2 and electric motor 3. In particular, when the internal combustion engine is restarted by closing the clutch 4, energy is introduced into the clutch 4 by slipping that occurs on the clutch 4, which energy input can cause the clutch 4 to overheat.

In order to protect the clutch 4 against life degradation or overheating, a clutch-specific, permissible amount of energy is calculated beforehand, which is allowed to be "consumed" maximally by the respective clutch slip situation. When calculating the permissible amount of energy, a clutch-specific permissible friction power or friction energy is first determined, which is stored in the control device 13 of the clutch actuator 12. Depending on the respective clutch type, the friction powers or friction energies can be summarized in a table. For example, the friction energy for a particular clutch type can be 500W or 30 kJ/min. At the same time, a maximum energy value EClutch _ allowed is determined, which in the given example is 30 kJ. This maximum energy value EClutch _ allowed is the basic value of the following calculation rule. Fig. 2 shows the maximum energy value EClutch _ allowed with respect to time t. As long as the energy input into the clutch 4 does not take place via a slip situation, the amount of energy which can be absorbed maximally by the clutch 4 is limited to EClutch _ allowed to 30 kJ. If energy is input by closing the clutch 4 when the internal combustion engine 2 is started again, the energy value ESch corresponding to slip is subtracted from the maximum energy value EClutch _ allowed. As can be seen from fig. 3, at time 24.5s, internal combustion engine 2 is dragged and started by electric motor 3, which rotates at a rotational speed nengmoot, by closing clutch 4. The speed nengcice of the internal combustion engine 2 is increased from zero to 2.2 × 103 revolutions/min. In this phase, the clutch 4 absorbs an amount of energy corresponding to the energy value ESch, which is subtracted from the maximum energy value EClutch _ allowed, from which the currently allowed energy value EG is derived.

In this case, the currently permissible energy value EG represents, in each operating step and at each point in time, a permissible amount of energy which is to be maximally dissipated by the respective slip event without damaging the clutch 4. After the restart process of the internal combustion engine 2 is completed, the clutch 4 is again disengaged from the time point 25 s. This recovery is performed by self-healing or allowed heat emission of the clutch 4 and each measurement step is, for example, 5J/10 ms. The permissible energy limit EG is thereby increased until the maximum energy value EClutch _ allowed is reached again.

The maximum energy value EClutch _ allowed of the clutch 4 is dependent on corresponding boundary conditions, such as clutch temperature, ambient temperature or rotational speed of the internal combustion engine 2. This means that: the maximum energy value EClutch _ allowed can be reduced or increased during driving of the motor vehicle, in particular during standstill and running, depending on this parameter. Thus, the maximum energy value EClutch _ allowed can lie between 0 and 30kJ when the speed nengcice of the internal combustion engine is less than 4000 revolutions per second. If this engine speed is exceeded, the maximum energy value EClutch _ allowed increases to a value between 40 and 50 kJ.

The energy limit EG is used in the higher-order driving strategy. There, the energy required for starting the internal combustion engine 2 can be stored. This is taken into account, for example, in relation to the ambient temperature. If the upper level driving strategy determines that: if the internal combustion engine 2 can no longer be driven again normally under the prevailing boundary conditions, a strategy can be activated, for example, which enables starting of the internal combustion engine 2 even with a low loss of comfort. Alternatively, however, it can also be determined that: it is not permitted to switch off the internal combustion engine 2 during stop and go operation.

This pre-calculated method of the allowed amount of energy is advantageous for such a clutch system having a certain variability in the control of the clutch 4. This can be, for example, a clutch system which can influence the amount of frictional energy in the clutch action, for example in the described hybrid application.

An alternative determination of the energy limit value EG can also be carried out via a prediction temperature model or via a reverse calculation of the clutch temperature up to the limit of the available power input. Since the cooling process is significantly less dynamic in time than the heating process, the permissible friction power can be derived relatively simply from the permissible temperature difference at the clutch.

List of reference numerals

1 drive train

2 internal combustion engine

3 electric motor

4 Clutch

5 crankshaft

6 rotor

7 stator

8 driven shaft

9 speed variator

10 driving wheel

11 Transmission system

12 Clutch actuator

13 control device

Claims

1. A method for protecting a clutch of a motor vehicle, wherein energy (ESCh) is input into the clutch (4) by means of a slipping state of the clutch (4),

Characterized in that, in order to ensure compliance with at least one power-specific limiting value of the clutch (4), a characteristic variable characterizing the clutch load, which is limited by a maximum value, is calculated in advance and the driving strategy of the vehicle is adjusted on the basis of the characteristic variable characterizing the clutch load, which is calculated in advance and can be changed during the clutch engagement process.

2. method according to claim 1, characterized in that an amount of energy is used as a characteristic variable characterizing the clutch load and that the maximum value corresponds to a maximum energy value (EClutch _ allowed).

3. Method according to claim 2, characterized in that the power-specific limit value is characterized by the maximum energy value (EClutch _ allowed), which is clutch-specifically determined.

4. A method according to claim 2 or 3, characterised in that the energy value (ESch) introduced into the clutch (4) during a slip process is subtracted from the maximum energy value (EClutch _ allowed), from which the energy limit value (EG) allowed for the next slip process of the clutch (4) is derived.

5. the method according to claim 4, characterized in that the energy limit value (EG) approaches the maximum energy value (EClutch _ allowed) by regeneration of the clutch (4) without a slip process of the clutch (4).

6. A method according to claim 2 or 3, characterised in that the maximum energy value (EClutch _ allowed) is varied during driving of the motor vehicle as a function of clutch temperature and/or ambient temperature and/or rotational speed of the drive motor (2).

7. A method according to claim 2 or 3, characterised in that the maximum energy value (EClutch _ allowed) is determined from clutch-specific allowed friction power or friction energy.

8. Method according to one of the preceding claims 1 to 3, characterized in that the permissible energy limit value (EG) remaining after a slip process is evaluated by means of the driving strategy and corresponding protective measures are activated for the clutch (4).

9. Method according to any one of claims 1 to 3, characterized in that a hybrid vehicle is used as the motor vehicle, wherein the remaining energy limit value (EG) is evaluated for restarting a drive unit which is designed as an internal combustion engine (2).

10. A method according to any one of the preceding claims 1-3, characterised in that wear or temperature of the clutch is used as a power-specific limit value.