WO2022016491A1

WO2022016491A1 - Engine starting method

Info

Publication number: WO2022016491A1
Application number: PCT/CN2020/104040
Authority: WO
Inventors: 罗品奎
Original assignee: 舍弗勒技术股份两合公司; 罗品奎
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2022-01-27
Also published as: KR20230021107A; CN115605382A; DE112020007457T5

Abstract

An engine starting method, for use in starting, in the case that a second portion (K02) of a clutch (K0) rotates, an engine (En) connected to a first portion (K01) of the clutch (K0). The method comprises: the first portion (K01) is fitted to the second portion (K02), and clutch torque (TC) transmitted from the second portion (K02) to the first portion (K01) is gradually increased to and maintained at critical torque (T0); and when an engine rotating speed (SE) rises to a critical speed (Ne0), the clutch (K0) is in a half-clutch state, and the clutch torque (TC) is adjusted according to the engine rotating speed (SE).

Description

How to start the engine

technical field

The present invention relates to the field of vehicles, in particular to a hybrid vehicle, and in particular to a method for starting an engine of a hybrid vehicle.

Background technique

For a hybrid vehicle (such as a gasoline-electric hybrid vehicle), it involves switching of power during operation, such as switching from being driven by an electric motor to being driven by an engine or jointly being driven by an engine and an electric motor.

For example, Figure 1 shows a P2 hybrid module. In this power module, the electric machine M is located between the engine En and the transmission G, and the clutch K0 is located between the engine En and the electric machine M.

Referring to FIG. 2 at the same time, a possible process for starting the engine En while the vehicle is running includes:

In the Ph1 stage, the clutch K0 is engaged, the torque of the motor M is transmitted to the flywheel connected to the engine En, the rotation speed SE of the engine En is gradually increased, and the clutch torque TC is raised to maintain the critical torque T0.

In the Ph2 stage, when the speed SE of the engine En rises to the critical speed Ne0, the clutch K0 is disengaged, the crankshaft of the engine En continues to rotate under the inertia of the flywheel, and the clutch torque TC gradually decreases. Then, in the process of decreasing the clutch torque, the engine En is fired, and the engine speed continues to increase depending on the engine torque.

In phase Ph3, when the engine speed SE rises very close to the motor speed SM, the clutch K0 is engaged again. The engine En finishes starting, transferring power to the vehicle.

The S state in the figure indicates that the engine En is in a stopped state, the C state indicates that the engine En is in a pre-ignition cranking state, and the R state indicates that the engine En is in a post-ignition operating state.

In the phase Ph2 described above, it is desirable to start the engine En smoothly and increase the engine speed SE under the action of the crankshaft torque by the control method in which the clutch K0 is disengaged and the clutch torque TC is gradually decreased to 0. However, in some cases, the drivability of the vehicle during the above control process is not ideal.

For example, in the case where the engine torque TE is lower than the normal level (such as the vehicle is driving in a plateau area with low oxygen content), in a short period of time after ignition, the engine torque TE cannot meet the expected requirements, and the engine speed SE is caused by cannot continue to rise for a period of time.

For example, referring to FIG. 3 , for a period of time after ignition, the engine torque TE is out of control (it appears to drop to a negative value in the control system), which causes the engine speed SE to drop, and further causes the vehicle speed (equal to the motor speed SM) to occur to a certain extent in the Ph3 stage. degree of decline. This not only makes the drivability less than ideal, but also increases the start time of the engine.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome or at least alleviate the above-mentioned deficiencies of the prior art, and to provide an engine starting method with good starting performance.

The present invention provides an engine starting method for starting an engine connected to a first portion of the clutch with the second portion of the clutch rotating, the method comprising:

engaging the first portion with the second portion, the clutch torque transferred from the second portion to the first portion is gradually increased to and maintained at a threshold torque;

When the engine speed rises to a critical speed, the clutch is in a half-clutch state, and the clutch torque is adjusted according to the engine speed.

In at least one embodiment, the adjusting the clutch torque according to the magnitude of the engine speed comprises:

When the engine speed increases, the clutch torque is decreased; when the engine speed decreases, the clutch torque is increased.

The difference between the rotational speed of the engine and the second portion is calculated, and when the rotational speed difference decreases, the clutch torque is decreased; when the rotational speed difference increases, the clutch torque is increased.

Adjust the value of the clutch torque at the current moment to the target torque Tt, Tt=T0×((Nmt-Net)/(Nm0-Ne0)),

T0 is the critical torque, Ne0 is the critical rotational speed,

Nm0 is the rotational speed of the second part when the engine rotational speed reaches the critical rotational speed,

Nmt is the rotation speed of the second part at the current moment, and Net is the engine rotation speed at the current moment.

The correction factor f is formulated according to the specific model of the engine,

Adjust the value of the clutch torque at the current moment to the target torque Tt, Tt=T0×((Nmt-Net)/(Nm0-Ne0))×f,

T0 is the critical torque, Ne0 is the critical rotational speed,

In at least one embodiment, the method further includes firing the engine during the adjustment of the clutch torque.

In at least one embodiment, the method further includes gradually fully engaging the clutch when the difference between the engine speed and the second portion speed is equal to or less than a critical speed difference.

In at least one embodiment, the second portion of the clutch is non-rotatably connected to the rotor of the electric machine.

In at least one embodiment, the engine is an engine of a hybrid vehicle.

In at least one embodiment, the hybrid vehicle uses a P2 hybrid module.

The engine starting method according to the present invention can quickly start the engine, and can also enable the vehicle to exhibit good running performance in harsh environments.

Description of drawings

Figure 1 is a schematic diagram of a possible P2 hybrid module.

FIG. 2 is a schematic diagram of an engine starting process under a possible ideal state.

FIG. 3 is a schematic diagram of an engine starting process with insufficient engine torque using the starting method according to FIG. 2 .

FIG. 4 is a schematic diagram of an engine start-up process according to one embodiment of the present invention.

FIG. 5 is a partial enlarged schematic view of FIG. 4 .

Description of reference numbers:

En engine; M motor; K0 clutch; K01 (clutch) first part; K02 (clutch) second part; G transmission;

TC clutch torque; TE engine torque; SM motor speed; SE engine speed;

T0 critical torque; Ne0 critical speed; D critical speed difference; Tt target torque.

detailed description

Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present invention, and are not used to exhaust all possible ways of the present invention, nor to limit the scope of the present invention.

Referring to FIG. 1 , FIG. 4 and FIG. 5 , taking the engine of a vehicle using the P2 hybrid power module as an example, the engine starting method according to the present invention is introduced.

1 , in this embodiment, a clutch K0 is provided between the engine En and the motor M, and the first part K01 of the clutch K0 is connected to the flywheel in a rotationally fixed (non-rotatable manner), and the flywheel and the crankshaft of the engine En are connected in a rotationally fixed manner Connected, the second part K02 of the clutch K0 is connected to the rotor of the electric machine M in a rotationally fixed manner.

The present invention mainly introduces a method for starting the engine En when the vehicle is driven by the motor M, that is, a method for starting the engine En by transmitting the torque from the motor M through the clutch K0.

FIG. 4 shows the process of the engine going from a stop state (S state in the figure) through pre-ignition crankshaft rotation (C state in the figure) to a post-ignition operating state (R state in the figure), and clutch torque during this process Changes in TC, engine torque TE, motor speed SM, and engine speed SE.

The engine starting method according to the present invention includes three stages, namely Ph1 stage, Ph2 stage and Ph3 stage.

In the Ph1 stage, the clutch K0 is switched from the disengaged state to the engaged state. The torque of the motor M is transmitted to the flywheel connected to the engine En, the rotational speed SE of the engine En gradually increases, the clutch torque TC rises to the critical torque T0, and is maintained at T0.

In the Ph2 stage, when the rotational speed SE of the engine En rises to the critical rotational speed Ne0, the clutch K0 is switched to the half-clutch state, and the clutch torque TC is adjusted according to the magnitude of the engine rotational speed SE. When the engine speed SE increases, the clutch torque TC is decreased; when the engine speed SE decreases, the clutch torque TC is increased.

The method of adjusting the clutch torque TC will be described with reference to FIG. 5 .

Calculate the rotational speed difference between the engine rotational speed SE and the motor rotational speed SM (ie, the rotational speed of the second part K02 ). When the rotational speed difference decreases, the clutch torque TC is decreased; when the rotational speed difference increases, the clutch torque TC is increased.

Specifically, when the engine speed SE reaches the critical speed Ne0 (that is, when the Ph2 stage is activated), the motor speed SM is Nm0, then when the Ph2 stage is activated, the speed difference N0=Nm0-Ne0.

Assuming that at the current moment, the value of the motor speed SM is Nmt, and the value of the engine speed SE is Net, then at the current moment, the speed difference Nt=Nmt-Net.

Since the goal of starting the engine En is to eliminate the speed difference between the engine speed SE and the motor speed SM, and in the Ph2 stage, the maximum speed difference is N0. Therefore, the ratio of the rotational speed difference to be reduced at the current moment is r=Nt/N0.

Using the method of follow-up control, the clutch torque TC at the current moment is adjusted to the target torque Tt according to the ratio r, then: Tt=r×T0.

Bringing the above-mentioned calculation formula of r into, there are: Tt=T0×((Nmt-Net)/(Nm0-Ne0)).

Optionally, according to different engine models, a correction coefficient f can be introduced according to the actual test results to correct the above calculation formula: Tt=T0×((Nmt-Net)/(Nm0-Ne0))×f. Among them, the value of f is close to 1, and f may be less than 1, greater than 1 or equal to 1 for different types of engines.

Returning to FIG. 4 , in the Ph2 phase, the engine En is fired, and the engine speed SE is jointly affected by the clutch torque TC and the engine torque TE.

When the difference between the engine speed SE and the motor speed SM is equal to or less than the critical speed difference D, the Ph3 phase is activated and the clutch K0 is gradually fully engaged. After that, the engine speed SE gradually reaches the motor speed SM, and the engine En is started up.

Some beneficial effects of the above-mentioned embodiments of the present invention are briefly described below.

(i) Using the engine starting method according to the present invention, even when the engine torque is small, the rapid starting of the engine can be ensured.

(ii) The drivability during engine start-up is good, and the phenomenon of vehicle speed reduction is less likely to occur.

It should be understood that the above-mentioned embodiments are only exemplary, and are not intended to limit the present invention. Those skilled in the art can make various modifications and changes to the above-described embodiments under the teachings of the present invention without departing from the scope of the present invention.

For example, the engine starting method according to the present invention is not only applicable to a hybrid vehicle using the P2 module, it can be applied to any engine starting using the K0 clutch.

Claims

An engine starting method for starting an engine (En) connected to a first part (K01) of a clutch (K0) with a second part (K02) of the clutch (K0) rotating, the method include,

The first part (K01) is engaged with the second part (K02), the clutch torque (TC) transmitted from the second part (K02) to the first part (K01) is gradually increased to and remains at the critical level torque;

When the engine speed (SE) rises to a critical speed, the clutch (K0) is placed in a half-clutch state, and the clutch torque (TC) is adjusted according to the engine speed (SE).
The engine starting method according to claim 1, wherein the adjusting the clutch torque (TC) according to the size of the engine speed (SE) comprises:

When the engine speed (SE) increases, the clutch torque (TC) is decreased; when the engine speed (SE) decreases, the clutch torque (TC) is increased.
The engine starting method according to claim 1, wherein the adjusting the clutch torque (TC) according to the size of the engine speed (SE) comprises:

Calculate the speed difference between the engine speed (SE) and the second part (K02), when the speed difference decreases, reduce the clutch torque (TC); when the speed difference increases, increase the speed difference Clutch Torque (TC).
The engine starting method according to claim 1, wherein the adjusting the clutch torque (TC) according to the size of the engine speed (SE) comprises:

Adjust the value of the clutch torque (TC) at the current moment to the target torque Tt, Tt=T0×((Nmt-Net)/(Nm0-Ne0)),

T0 is the critical torque, Ne0 is the critical rotational speed,

Nm0 is the rotational speed of the second part (K02) when the engine rotational speed (SE) reaches the critical rotational speed,

Nmt is the rotational speed of the second part (K02) at the current moment, and Net is the engine rotational speed (SE) at the current moment.
The engine starting method according to claim 1, wherein the adjusting the clutch torque (TC) according to the size of the engine speed (SE) comprises:

According to the specific model of the engine (En), the correction factor f is formulated,

Adjust the value of the clutch torque (TC) at the current moment to the target torque Tt, Tt=T0×((Nmt-Net)/(Nm0-Ne0))×f,

T0 is the critical torque, Ne0 is the critical rotational speed,

Nm0 is the rotational speed of the second part (K02) when the engine rotational speed (SE) reaches the critical rotational speed,

Nmt is the rotational speed of the second part (K02) at the current moment, and Net is the engine rotational speed (SE) at the current moment.
The engine starting method according to claim 1, characterized in that the method further comprises: during the process of adjusting the clutch torque (TC), the engine (En) is fired.
The engine starting method according to claim 6, characterized in that the method further comprises: when the difference between the engine speed (SE) and the speed of the second part (K02) is equal to or less than a critical speed difference ( D), the clutch (K0) is gradually fully engaged.
The engine starting method according to any one of claims 1 to 7, characterized in that the second part ( K02 ) of the clutch ( K0 ) is connected to the rotor of the electric machine in a rotationally fixed manner.
The engine starting method according to any one of claims 1 to 7, wherein the engine (En) is an engine of a hybrid vehicle.
The engine starting method of claim 9, wherein the hybrid vehicle uses a P2 hybrid module.