HYBRID POWERTRAIN AND METHOD OF CONTROLLING SAID HYBRID POWERTRAIN

Abstract

One aspect of the invention relates to a hybrid powertrain 2 comprising an internal combustion engine 3, a gearbox 4, an electric traction machine 6, first and second clutches 5, 8, and a reduction gear unit 7 connected to a wheel drive shaft 9 10. The internal combustion engine 3 and the gearbox 4 are mechanically linked via the first clutch 5, the gearbox 4 and the electric traction machine 6 are mechanically directly coupled, and the hybrid powertrain is notable in that the electric traction machine 6 and the reduction gear unit 7 are mechanically linked via the second clutch 8. Figure 1

Description

Title of the invention: HYBRID POWERTRAIN AND METHOD OF CONTROLLING IT HYBRID POWERTRAIN

[0001] The present invention relates to a hybrid powertrain comprising an internal combustion engine and an electric traction machine disposed between a gearbox and a reduction gear unit. The invention also relates to a method for controlling said powertrain. The invention thus relates to the technical field of motor vehicles equipped with an electric traction machine and an internal combustion engine.

[0002] It is known from document EP-B1-2809540 of hybrid powertrains comprising a thermal engine mechanically linked to an electric traction machine via a first clutch and a gearbox mechanically linked to the electric traction machine, which gearbox is in direct contact with a reduction ratio unit linked to a wheel drive shaft.

[0003] When the powertrain is operating in a fully electric driving mode, the torque supplied by the electric traction machine is transmitted to the wheels of the powertrain via the gearbox and the reduction ratio unit.

[0004] However, as the electric traction machine is at the input of the gearbox, in electric driving, the vehicle's passengers experience gear changes which are naturally a source of discomfort in longitudinal acceleration but also acoustic.

[0005] The invention offers a solution to the problem mentioned above, by proposing a hybrid powertrain using a single electric traction machine for the traction of the powertrain and the starting of the internal combustion engine while preserving optimal driving comfort when the torque of the powertrain is supplied solely by means of the electric traction machine.

[0006] In this context, the invention thus relates, in its broadest sense, to a hybrid powertrain comprising a thermal engine, a gearbox, an electric traction machine, a first and a second clutch and a reduction ratio unit linked to a wheel drive shaft, the thermal engine and the gearbox being mechanically linked to each other via the first clutch, the gearbox and the electric traction machine being mechanically in direct mesh and the electric traction machine and the reduction ratio unit being mechanically linked to each other via the second clutch. In other words, no gearbox is positioned between the electric traction machine and the reduction ratio unit.

[0007] The position of the electric traction machine allows the speed of the electric traction machine to be mechanically and linearly linked to the speed of the wheels. This avoids the inconveniences associated with gear changes found in prior art powertrains.

[0008] In addition, the acoustic level of the electric traction machine is lower because its speed evolves linearly with the vehicle speed and without discontinuity due to the absence of gear changes.

[0009] Furthermore, it is possible to guarantee regenerative torque while still allowing the internal combustion engine to start. Indeed, even if the speed of the electric traction machine is below the minimum starting speed of the internal combustion engine, it is possible to select a gearbox ratio that provides sufficient speed for starting. To ensure continuous torque at the wheel, the second clutch, located between the electric traction machine and the reduction unit, is operated in slip mode, thus controlling the transmitted torque. This is a negative slip mode in which the speed of the electric traction machine is lower than the input speed of the reduction unit, thereby maintaining regenerative torque. The input speed of the reduction unit corresponds to the speed of the shaft located between the reduction unit and the second clutch.

[0010] In addition to the characteristics just mentioned in the preceding paragraph, the hybrid powertrain according to this aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations.

[0011] According to a non-limiting aspect of the invention, the hybrid powertrain includes a third clutch, the gearbox and the electric traction machine being mechanically linked together via said third clutch.

[0012] Another aspect of the invention relates to a method for controlling a hybrid powertrain according to any one of the aforementioned aspects of the invention. When a fully electric driving mode of the hybrid powertrain is selected, the method comprises the steps, performed by means of controlling the hybrid powertrain, of: • Control the opening of the first clutch located between the internal combustion engine and the gearbox, and • Control a closure of the second clutch located between the electric traction machine and the reduction ratio unit.

[0013] According to a non-limiting aspect of the invention, when the hybrid powertrain includes a third clutch and a fully electric driving mode of the hybrid powertrain is selected, the method includes an additional step, executed by the control means, of piloting an opening of the third clutch disposed between the gearbox and the electric traction machine.

[0014] According to a non-limiting aspect of the invention, when a start of the internal combustion engine is selected, the method comprises the steps, executed by the control means, of: • To control a partial closure of the second clutch located between the electric traction machine and the reduction gear unit, • Depending on the operating speed of the electric traction machine, select a gearbox ratio so that the gearbox output speed is equal to the speed required to start the internal combustion engine, and • Control the closing of the first clutch located between the internal combustion engine and the gearbox.

[0015] According to a non-limiting aspect of the invention, when the hybrid powertrain includes a third clutch, the method includes an additional step, executed by the control means, of piloting a closure of the third clutch disposed between the gearbox and the electric traction machine.

[0016] A different aspect of the invention relates to a hybrid motor vehicle equipped with a hybrid powertrain according to any one of the aforementioned aspects of the invention.

[0017] According to a non-limiting aspect of the invention, the hybrid motor vehicle includes control means arranged to perform the steps of the process according to any one of the aforementioned aspects of the invention.

[0018] According to a non-limiting aspect of the invention, the control means are formed by: • A vehicle control unit, and / or • A motor control unit.

[0019] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures.

[0020] [Fig.1] illustrates an example of the embodiment of a hybrid motor vehicle equipped with a hybrid powertrain according to the invention.

[0021] [Fig.2] illustrates an example of implementation of a method for controlling a powertrain according to the invention.

[0022] [Fig.3] illustrates another example of the realization of a hybrid motor vehicle equipped with a hybrid powertrain according to the invention.

[0023] [Fig.4] illustrates another example of the implementation of a method for controlling a powertrain according to the invention.

[0024] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0025] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0026] More particularly, [Fig.1] illustrates a hybrid motor vehicle 1 according to the invention equipped with a hybrid powertrain 2 according to a first embodiment of the invention.

[0027] The hybrid powertrain 2 comprises a thermal engine 3 and a gearbox 4 mechanically linked to each other via a first clutch 5, an electric traction machine 6 directly connected to the gearbox 4 and a reduction ratio unit 7 mechanically linked to the electric traction machine 6 via a second clutch 8. The reduction ratio unit 7 is also mechanically linked to a drive shaft 9 of the wheels 10 of the vehicle 1.

[0028] The vehicle 1 also includes control means 11 arranged to perform the steps of the method 100 for piloting the powertrain 2 according to the invention.

[0029] By way of non-limitation, the control means 11 may consist of: • A vehicle control unit (more commonly known by its acronym VCU for Vehicle Control Unit); and / or • A motor control unit (better known by the acronym MCU for Motor Control Unit in English).

[0030] Fig. 2 illustrates a first example of implementation of the method 100 of piloting a powertrain 2 according to the invention.

[0031] When a fully electric driving mode of the powertrain 2 is selected by the control means 11 or by the driver, the method 100 comprises the steps, executed by the control means 11, of: • To control 101 an opening of the first clutch 5 located between the internal combustion engine 3 and the gearbox 4, and • Control 102 a closure of the second clutch 8 located between the electric traction machine 6 and the reduction ratio unit 7.

[0032] The position of the electric traction machine 6 allows the speed of the electric traction machine 6 to be mechanically and linearly linked to the speed of the wheels 10. This avoids the inconveniences associated with gear changes found in prior art powertrains.

[0033] In addition, the acoustic level of the electric traction machine 6 is lower because its speed evolves linearly at the vehicle speed 1 and without discontinuity due to the absence of gear change.

[0034] Then, when a start of the internal combustion engine 3 is selected by the control means 11 while the vehicle 1 is being towed solely by the electric traction machine 6, for example to electrically recharge a traction battery of the vehicle or to provide thermal comfort functions for the passenger compartment of the vehicle 1, the method 100 comprises the steps, executed by the control means 11, of: • To control 103 a partial closure of the second clutch 8 located between the electric traction machine 6 and the reduction ratio unit 7, • Depending on the operating speed of the electric traction machine 6, select 104 a gear ratio of the gearbox 4 so that the output speed of the gearbox 4 is equal to the speed required to start the internal combustion engine 3, the output speed of the gearbox 4 corresponding to the speed of a shaft of the gearbox 4 located between the gearbox 4 and the first clutch 5, and • Control 105 a closure of the first clutch 5 located between the internal combustion engine 3 and the gearbox 4.

[0035] The positioning of the first clutch 5 allows this electric traction machine 6 to be used to start the internal combustion engine 3 through the gearbox 4. This arrangement allows the electric traction machine 6 to start the internal combustion engine 3 even when the speed of the electric traction machine 6 is lower than the idle speed of the internal combustion engine 3.

[0036] More specifically, the start of the internal combustion engine 3 is achieved by slipping the second clutch 8 to maintain constant wheel torque and by closing the first clutch 5. This start can be done without loss of regeneration because the rotational speed of the internal combustion engine 3 can be reached by choosing the appropriate ratio without direct dependence on the speed of the electric traction machine 6. Indeed, the slip of the second clutch 8 can be negative (speed of the electric traction machine 6 lower than the speed of the wheels 10) to allow the continuity of regeneration.

[0037] Thus, there is no risk of sudden loss of deceleration if the thermal engine 3 starts while the electric traction machine 6 is at low speed.

[0038] Figure 3 illustrates a hybrid motor vehicle 1 according to the invention equipped with another embodiment of a hybrid powertrain 2 according to the invention.

[0039] According to this embodiment, the hybrid powertrain 2 includes a third clutch 12 mechanically linking the gearbox 4 to the electric traction machine 6.

[0040] This third clutch 12 allows the gearbox 4 to be decoupled from the electric traction machine 6 when the vehicle is towed only by the electric traction machine 6.

[0041] Fig. 4 illustrates another example of implementation of the method 100 for piloting a powertrain 2 according to the invention.

[0042] When a fully electric driving mode of the powertrain 2 is selected by the control means 11 or by the driver, the method 100 comprises the steps, executed by the control means 11, of: • Control 101 the opening of the first clutch 5 located between the internal combustion engine 3 and the gearbox 4, • Control 106 the opening of the third clutch 12 located between the gearbox 4 and the electric traction machine 6, and • Control 102 the closing of the second clutch 8 located between the electric traction machine 6 and the reduction ratio unit 7.

[0043] Thus, in purely electric running, the third clutch 12 allows the gearbox 4 to be decoupled from the electric traction machine 6. This makes it possible to eliminate, for the electric traction machine 6, the losses generated by the rotation of the input shaft of the gearbox 4.

[0044] Then, when a start of the internal combustion engine 3 is selected by the control means 11 while the vehicle 1 is being towed solely by the electric traction machine 6, the method 100 comprises the steps, executed by the control means 11, of: • To control 103 a partial closure of the second clutch 8 located between the electric traction machine 6 and the reduction ratio unit 7, • Depending on the operating speed of the electric traction machine 6, select 104 a gear ratio of the gearbox 4 so that the output speed of the gearbox 4 is equal to the speed required to start the internal combustion engine 3, • To control 105 a closure of the first clutch 5 located between the internal combustion engine 3 and the gearbox 4, and • Control 107 a closure of the third clutch 12 located between the gearbox 4 and the electric traction machine 6.

Claims

Demands

1. Hybrid powertrain (2) comprising an internal combustion engine (3), a gearbox (4), an electric traction machine (6), a first and a second clutch (5, 8) and a reduction ratio unit (7) connected to a drive shaft (9) of wheels (10), said internal combustion engine (3) and said gearbox (4) being mechanically connected to each other via said first clutch (5), said gearbox (4) and said electric traction machine (6) being mechanically in direct drive, said hybrid powertrain (2) being characterized in that said electric traction machine (6) and said reduction ratio unit (7) are mechanically connected to each other via said second clutch (8).

2. Hybrid powertrain (2) according to the preceding claim, characterized in that it comprises a third clutch (12), the gearbox (4) and the electric traction machine (6) being mechanically linked together via said third clutch (12).

3. Method (100) of controlling a hybrid powertrain (2) according to any one of the preceding claims, said method (100) being characterized in that when a fully electric driving mode of said hybrid powertrain (2) is selected, it comprises the steps, executed by control means (11) of said hybrid powertrain (2), of: - Controlling (101) the opening of the first clutch (5) disposed between the internal combustion engine (3) and the gearbox (4), - Controlling (102) a closing of the second clutch (8) disposed between the electric traction machine (6) and the reduction gear unit (7).

4. Method (100) according to the preceding claim, characterized in that when the hybrid powertrain (2) includes a third clutch (12) and a fully electric driving mode of said hybrid powertrain (2) is selected, the method (100) includes an additional step, executed by the control means (11), of piloting (106) an opening of said third clutch (12) disposed between the gearbox (4) and the electric traction machine (6).

5. Method (100) according to claim 3, characterized in that when a start of the internal combustion engine (3) is selected, it comprises the steps, executed by the control means (11), of: - Controlling (103) a partial closure of the second clutch (8) disposed between the electric traction machine (6) and the reduction ratio unit (7), - Depending on the speed of the electric traction machine (6), selecting (104) a ratio of the gearbox (4) so ​​that the output speed of the gearbox (4) is equal to the speed required to start the internal combustion engine (3), and - Controlling (105) a closure of the first clutch (5) disposed between the internal combustion engine (3) and the gearbox (4).

6. Method (100) according to claims 3, 4 and 5, characterized in that when the hybrid powertrain (2) includes a third clutch (12), the method (100) includes an additional step, executed by the control means (11), of piloting (107) a closure of the third clutch (12) disposed between the gearbox (4) and the electric traction machine (6).

7. Hybrid motor vehicle (1), characterized in that it comprises a hybrid powertrain (2) according to any one of claims 1 or 2.

8. Hybrid motor vehicle (1) according to the preceding claim, characterized in that said hybrid motor vehicle (1) comprises control means (11) arranged to carry out the steps of the process (100) according to any one of claims 3 to 6.

9. Hybrid motor vehicle (1) according to the preceding claim, characterized in that the control means (11) are formed by: - ​​A vehicle control unit, and / or - An engine control unit.

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