Engine starting method

Abstract

An engine starting method is used to start an engine (En) connected to a first part (K01) of a clutch (K0) when a second part (K02) of the clutch (K0) is rotating. The method includes engaging the first part (K01) with the second part (K02), and gradually increasing a clutch torque (TC) transmitted from the second part (K02) to the first part (K01) to and maintaining it at a critical torque (T0); when an engine speed (SE) rises to a critical speed (Ne0), making the clutch (K0) in a semi-clutch state and adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE).

Description

Technical Field

[0001] The present invention relates to the field of vehicles, in particular to hybrid vehicles, and particularly to a method for starting an engine of a hybrid vehicle. Background Art

[0002] For a hybrid vehicle (such as a gasoline-electric hybrid vehicle), power switching is involved during its operation, for example, switching from motor drive to engine drive or to combined engine and motor drive.

[0003] For example, Figure 1 shows a P2 hybrid power module. In this power module, the motor M is located between the engine En and the transmission G, and the clutch K0 is located between the engine En and the motor M.

[0004] Simultaneously referring to Figure 2 , a possible process for starting the engine En during vehicle driving includes:

[0005] 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 rotational speed SE of the engine En gradually increases, and the clutch torque TC rises to and is maintained at the critical torque T0.

[0006] In the Ph2 stage, when the rotational speed SE of the engine En rises to the critical speed Ne0, the clutch K0 disengages, and the crankshaft of the engine En continues to rotate under the inertia of the flywheel, and the clutch torque TC gradually decreases. Subsequently, during the process of the clutch torque decreasing, the engine En ignites, and the engine speed continues to rise relying on the engine torque.

[0007] In the Ph3 stage, when the engine speed SE rises to be very close to the motor speed SM, the clutch K0 is engaged again. The engine En completes starting and transmits power to the vehicle.

[0008] The S state in the figure represents that the engine En is in a stopped state, the C state represents that the engine En is in a state of crankshaft rotation before ignition, and the R state represents that the engine En is in a running state after ignition.

[0009] In the above Ph2 stage, it is desired to make the engine En start smoothly and the engine speed SE increase under the action of the crankshaft torque by controlling the clutch K0 to disengage and gradually reducing the clutch torque TC to 0. However, in some cases, the driving performance of the vehicle during the above control process is not ideal.

[0010] For example, when the engine torque TE is below the normal level (for example, when the vehicle is driving in a plateau area with low oxygen content), within a short period of time after ignition, the engine torque TE cannot meet the expected requirements, resulting in the engine speed SE not being able to continue to increase for a period of time.

[0011] For example, referring to Figure 3 , within a period of time after ignition, the engine torque TE gets out of control (manifested as dropping to a negative value in the control system), causing the engine speed SE to decrease, and further causing a certain degree of decrease in the vehicle speed (equal to the motor speed SM) in the Ph3 stage. This not only makes the driving performance unsatisfactory but also increases the engine start-up time. Summary of the Invention

[0012] The object of the present invention is to overcome or at least mitigate the deficiencies of the above-mentioned prior art, and to provide an engine starting method with good starting performance.

[0013] The present invention provides an engine starting method, which is used to start an engine connected to a first part of a clutch when a second part of the clutch is rotating. The method includes,

[0014] Engaging the first part with the second part, and the clutch torque transmitted from the second part to the first part gradually increases to and remains at a critical torque;

[0015] When the engine speed rises to the critical speed, making the clutch in a semi-clutch state and adjusting the clutch torque according to the magnitude of the engine speed.

[0016] In at least one embodiment, the adjusting the clutch torque according to the magnitude of the engine speed includes:

[0017] When the engine speed increases, reducing the clutch torque; when the engine speed decreases, increasing the clutch torque.

[0018] In at least one embodiment, the adjusting the clutch torque according to the magnitude of the engine speed includes:

[0019] Calculating the speed difference between the engine speed and the speed of the second part, when the speed difference decreases, reducing the clutch torque; when the speed difference increases, increasing the clutch torque.

[0020] In at least one embodiment, the adjusting the clutch torque according to the magnitude of the engine speed includes:

[0021] Adjusting the value of the clutch torque at the current moment to the target torque Tt, Tt = T0 × ((Nmt - Net) / (Nm0 - Ne0)),

[0022] Let T0 be the critical torque and Ne0 be the critical speed.

[0023] Let Nm0 be the speed of the second part when the engine speed reaches the critical speed.

[0024] Let Nmt be the speed of the second part at the current moment and Net be the engine speed at the current moment.

[0025] In at least one embodiment, adjusting the clutch torque according to the engine speed includes:

[0026] Formulating a correction coefficient f according to the specific model of the engine.

[0027] Adjusting the value of the clutch torque at the current moment to a target torque Tt, where Tt = T0 × ((Nmt - Net) / (Nm0 - Ne0)) × f.

[0028] Let T0 be the critical torque and Ne0 be the critical speed.

[0029] Let Nm0 be the speed of the second part when the engine speed reaches the critical speed.

[0030] Let Nmt be the speed of the second part at the current moment and Net be the engine speed at the current moment.

[0031] In at least one embodiment, the method further includes: during the process of adjusting the clutch torque, the engine ignites.

[0032] In at least one embodiment, the method further includes: when the difference between the engine speed and the speed of the second part is equal to or less than the critical speed difference, the clutch gradually engages completely.

[0033] In at least one embodiment, the second part of the clutch is non-rotatably connected to the rotor of the motor.

[0034] In at least one embodiment, the engine is an engine of a hybrid vehicle.

[0035] In at least one embodiment, the hybrid vehicle uses a P2 hybrid module.

[0036] The engine starting method according to the present invention can start the engine quickly and enable the vehicle to exhibit good operating performance even in harsh environments. Description of the Drawings

[0037] Figure 1 is a schematic diagram of a possible P2 hybrid module.

[0038] Figure 2 is a schematic diagram of an engine starting process under a possible ideal state.

[0039] Figure 3 is the use of Figure 2 starting method for the engine starting process schematic diagram when the engine torque is insufficient.

[0040] Figure 4 is a schematic diagram of an engine starting process according to an embodiment of the present invention.

[0041] Figure 5 is Figure 4 a partially enlarged schematic diagram.

[0042] Explanation of reference numerals:

[0043] En engine; M motor; K0 clutch; K01 first part of the clutch; K02 second part of the clutch; G transmission;

[0044] TC clutch torque; TE engine torque; SM motor speed; SE engine speed;

[0045] T0 critical torque; Ne0 critical speed; D critical speed difference; Tt target torque. Detailed implementation manners

[0046] The exemplary embodiments of the present invention will be 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.

[0047] With reference to Figure 1 、 Figure 4 and Figure 5 , taking the engine of a vehicle using a P2 hybrid module as an example, the engine starting method according to the present invention will be introduced.

[0048] With reference to Figure 1 , in this embodiment, a clutch K0 is provided between the engine En and the motor M. The first part K01 of the clutch K0 is torsionally connected (non-rotatable relative to each other) to the flywheel, and the flywheel is torsionally connected to the crankshaft of the engine En. The second part K02 of the clutch K0 is torsionally connected to the rotor of the motor M.

[0049] The present invention mainly introduces a method for starting the engine En when the vehicle is in a state of being 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.

[0050] Figure 4It shows the process of the engine from the stopped state (state S in the figure) through the crankshaft rotation before ignition (state C in the figure) to the running state after ignition (state R in the figure), as well as the changes in the clutch torque TC, engine torque TE, motor speed SM, and engine speed SE during this process.

[0051] The engine starting method according to the present invention includes three stages, namely Ph1 stage, Ph2 stage, and Ph3 stage.

[0052] 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, and the speed SE of the engine En gradually increases. The clutch torque TC rises to the critical torque T0 and remains at T0.

[0053] In the Ph2 stage, when the speed SE of the engine En rises to the critical speed Ne0, the clutch K0 is switched to the semi-clutch state, and the clutch torque TC is adjusted according to the magnitude of the engine 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.

[0054] Reference Figure 5 Introduce the method of adjusting the clutch torque TC.

[0055] Calculate the speed difference between the engine speed SE and the motor speed SM (i.e., the speed of the second part K02). When the speed difference decreases, the clutch torque TC is decreased; when the speed difference increases, the clutch torque TC is increased.

[0056] Specifically, when the engine speed SE reaches the critical speed Ne0 (i.e., when the Ph2 stage is activated), the value of the motor speed SM is Nm0. Then, when the Ph2 stage is activated, the speed difference N0 = Nm0 - Ne0.

[0057] Suppose 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.

[0058] 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 value of this speed difference is N0. Therefore, the ratio r of the speed difference to be reduced at the current moment is r = Nt / N0.

[0059] Using the follow-up control method, the clutch torque TC at the current moment is adjusted to the target torque Tt according to the ratio r, then there is: Tt = r × T0.

[0060] Substitute the above calculation formula of r, then there is: Tt = T0 × ((Nmt - Net) / (Nm0 - Ne0)).

[0061] Optionally, according to different engine models, a correction coefficient f can be introduced based on the actual test results to correct the above calculation formula: Tt = T0 × ((Nmt - Net) / (Nm0 - Ne0)) × f. Here, the value of f is close to 1, and for different engine models, f may be less than 1, greater than 1, or equal to 1.

[0062] Return to Figure 4 , in the Ph2 stage, the engine En ignites, and the engine speed SE is affected by both the clutch torque TC and the engine torque TE.

[0063] 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 stage is activated, and the clutch K0 gradually engages completely. After that, the engine speed SE gradually reaches the motor speed SM, and the engine En completes the startup.

[0064] The following briefly describes some beneficial effects of the above embodiments of the present invention.

[0065] (i) Using the engine startup method according to the present invention can ensure the rapid startup of the engine even when the engine torque is small.

[0066] (ii) The driving performance during the engine startup process is good, and it is not easy to have the phenomenon of vehicle speed reduction.

[0067] It should be understood that the above embodiments are merely exemplary and are not used to limit the present invention. Those skilled in the art can make various modifications and changes to the above embodiments under the teaching of the present invention without departing from the scope of the present invention.

[0068] For example, the engine startup method according to the present invention is not only applicable to hybrid vehicles using the P2 module, but it can be applicable to any engine started with a K0 clutch.

Claims

1. An engine starting method is used to start an engine (En) connected to a first part (K01) of a clutch (K0) when a second part (K02) of the clutch (K0) is rotating. The method includes, Engaging the first part (K01) with the second part (K02), and gradually increasing the clutch torque (TC) transmitted from the second part (K02) to the first part (K01) to and maintaining it at a critical torque; When the engine speed (SE) rises to the critical speed, putting the clutch (K0) in a semi - engaged state and adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE); The adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE) includes: When the engine speed (SE) increases, decreasing the clutch torque (TC); when the engine speed (SE) decreases, increasing the clutch torque (TC).

2. An engine starting method is used to start an engine (En) connected to a first part (K01) of a clutch (K0) when a second part (K02) of the clutch (K0) is rotating. The method includes, Engaging the first part (K01) with the second part (K02), and gradually increasing the clutch torque (TC) transmitted from the second part (K02) to the first part (K01) to and maintaining it at a critical torque; When the engine speed (SE) rises to the critical speed, putting the clutch (K0) in a semi - engaged state and adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE); The adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE) includes: Calculating the speed difference between the engine speed (SE) and the speed of the second part (K02). When the speed difference decreases, decreasing the clutch torque (TC); when the speed difference increases, increasing the clutch torque (TC).

3. An engine starting method is used to start an engine (En) connected to a first part (K01) of a clutch (K0) when a second part (K02) of the clutch (K0) is rotating. The method includes, Engaging the first part (K01) with the second part (K02), and gradually increasing the clutch torque (TC) transmitted from the second part (K02) to the first part (K01) to and maintaining it at a critical torque; When the engine speed (SE) rises to the critical speed, putting the clutch (K0) in a semi - engaged state and adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE); The adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE) includes: Adjusting the value of the clutch torque (TC) at the current moment to a target torque Tt, where Tt = T0×((Nmt - Net) / (Nm0 - Ne0)), T0 is the critical torque, Ne0 is the critical speed, Nm0 is the rotational speed of the second part (K02) when the engine speed (SE) reaches the critical speed. Nmt is the rotational speed of the second part (K02) at the current moment, and Net is the engine speed (SE) at the current moment.

4. An engine starting method for starting an engine (En) connected to a first part (K01) of a clutch (K0) when a second part (K02) of the clutch (K0) is rotating, the method comprising: Engaging the first part (K01) with the second part (K02), and gradually increasing the clutch torque (TC) transmitted from the second part (K02) to the first part (K01) to and maintaining it at a critical torque; When the engine speed (SE) rises to the critical speed, putting the clutch (K0) in a semi-clutch state and adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE); The adjusting the clutch torque (TC) according to the magnitude of the engine speed (SE) includes: Formulating a correction coefficient f according to the specific model of the engine (En); Adjusting the value of the clutch torque (TC) at the current moment to a target torque Tt, where Tt = T0 × ((Nmt - Net) / (Nm0 - Ne0)) × f; T0 is the critical torque, and Ne0 is the critical speed; Nm0 is the rotational speed of the second part (K02) when the engine speed (SE) reaches the critical speed; Nmt is the rotational speed of the second part (K02) at the current moment, and Net is the engine speed (SE) at the current moment.

5. The engine starting method according to any one of claims 1 to 4, characterized in that, The method further includes: during the process of adjusting the clutch torque (TC), the engine (En) ignites.

6. The engine starting method according to claim 5, characterized in that The method further includes: when the difference between the engine speed (SE) and the rotational speed of the second part (K02) is equal to or less than a critical speed difference (D), the clutch (K0) gradually fully engages.

7. The engine starting method according to any one of claims 1 to 4, characterized in that The second part (K02) of the clutch (K0) is non-rotatably connected to the rotor of the motor.

8. The engine starting method according to any one of claims 1 to 4, characterized in that The engine (En) is an engine of a hybrid vehicle.

9. The engine starting method according to claim 8, wherein The hybrid vehicle uses a P2 hybrid module.

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