EP3562698A1

EP3562698A1 - Method for operating a hybrid drive line with an electric motor/ generator device, an internal combustion engine and a gearing

Info

Publication number: EP3562698A1
Application number: EP17837854.3A
Authority: EP
Inventors: Arjen Brandsma; Arjen RÖMERS
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-12-27
Filing date: 2017-12-27
Publication date: 2019-11-06
Also published as: CN110114239A; NL1042199B1; WO2018121885A1

Abstract

The invention relates to a method for operating a hybrid drive line of, in particular, a motor vehicle, comprising an internal combustion engine (1), an electric motor/generator device (2) connected to a battery (22), driven wheels (3) and a gearing (4) there between, at least including a planetary gear set (5). According to the present disclosure, before the acceleration of the load (3) from standstill by the engine (1), the motor/generator device (2) is electrically powered from the battery (22) to start the engine (1).

Description

METHOD FOR OPERATING A HYBRID DRIVE LINE WITH AN ELECTRIC MOTOR/ GENERATOR DEVICE, AN INTERNAL COMBUSTION ENGINE AND A GEARING

The invention relates to a method for operating a hybrid drive line with at least two prime movers, with a load and with a gearing there between, in particular a drive line of a motor vehicle comprising an internal combustion engine (ICE) with a crank shaft, an electric motor/generator (M/G) device with a drive shaft and driven wheels. In the art several such hybrid drive lines have been proposed within a wide range of constructional complexities and providing several operational modes, such as a battery-powered electric motor drive mode, a gasoline-powered ICE drive mode, a combined ICE and electric motor drive mode, a brake energy recuperation or generator mode, etc.

For example, the European patent publication EP 0 941 883 A discloses such a hybrid drive line. In this known hybrid drive line the said gearing includes a planetary gear set and an automatic transmission providing multiple speed ratios between the planetary gear set and the driven wheels. The planetary gear set is as such well-known and comprises a central or sun gear that is in meshing contact with one or more planet gears, which planet gears are rotatably carried by a planet carrier arranged coaxially with the sun gear, and an outer ring gear that is in meshing contact with the planet gears and that is also arranged coaxially with the sun gear. The ring gear is, or least can be coupled to the crank shaft of the ICE via a first clutch, the planet carrier is coupled to the automatic transmission and the sun gear is coupled to the drive shaft of the M/G-device. A second clutch is provided to selectively couple the ring gear to the planet carrier.

This known hybrid drive line can be operated in several operational modes. In particular, the known hybrid drive line provides conventional ICE, electrically assisted and fully electric drive modes. However, the driving off, i.e. acceleration of the motor vehicle from standstill, by the ICE is not foreseen in EP 0 941 883 A. Still, it might occur that a battery charge is too low for the driving off by the M/G-device alone. To also accommodate this eventuality, i.e. in order to enable the driving off by the ICE rather than by the M/G-device, a torque converter, a (multi) wet-plate clutch or other conventional drive-off device can obviously be included in the known hybrid drive line, for example as part of the automatic transmission thereof.

According to the present disclosure, the versatility of the above-referenced, known hybrid drive line can be favourably enhanced by operating it in a novel way. In particular according to the present disclosure, during the driving off of the motor vehicle by the ICE, the M/G-device is controlled to rotate backward while generating a positive, forward torque, such that it generates electric power that can be used to charge a battery of the hybrid drive line. At the same time, either the rotational speed of the ICE is increased (i.e. is accelerated), or the backward rotational speed of the M/G-device is decreased (i.e. is decelerated), or both to accelerate the motor vehicle. By such novel operating method, the driving off of the motor vehicle is favourably enabled without requiring the said conventional drive-off device.

In the above-mentioned specific operating method of increasing the rotational speed of the ICE to accelerate the vehicle, it may also be opted to simultaneously increase the backward rotational speed of the M/G-device (i.e. to accelerate the backward rotation thereof). Hereby, the rotational speed of the ICE is increased faster in relation to the speed of the motor vehicle and as compared to an operating method wherein the speed of the M/G-device is maintained constant, allowing the ICE to favourably generate more power for a faster acceleration of the motor vehicle and/or for a faster charging of the battery via the M/G-device.

Further according to the present disclosure and in contrast with the known hybrid drive line, in particular for the optimal performance of the above operating method, the crank shaft of the ICE is coupled to the sun gear and the drive shaft of the M/G-device is coupled to the ring gear. In this latter, novel arrangement of the hybrid drive line, optimal use is made of the typical power generating characteristics of the ICE and, in particular, of the M/G-device in relation to the fixed speed and torque ratios provided by the planetary gear set. In the hybrid drive line the nominal (rotational) speed of the M/G- device typically exceeds that of the ICE, such that it is preferable to include a speed reduction gear between the M/G-device and the planetary gear set, whereby the torque generated by the M/G-device is amplified and, typically, exceeds that of the ICE. The resulting, nominal (i.e. maximum continuous) torque levels generated by the ICE on the sun gear, i.e. T nom sun, and by the M/G-device on the ring gear, i.e. T nom ring, can be optimally accommodated by a planetary gear set designed with a geometric gear set ratio Zpgs that is approximately equal to the ratio between said nominal torque levels:

T nom ring / T nom sun ~ Zpgs (1 ), which geometric gear set ratio Zpgs of the planetary gear set is determined by the ratio of the radii of the ring gear Rring and of the sun gear Rsun:

Zpgs = Rring / Rsun (2). The invention will be explained in more detail by means of a non-limiting illustrative embodiment and with reference to the following figures, in which:

figure 1 is a diagrammatic representation of the known hybrid drive line;

figure 2 is a graph illustrating the operation of the planetary gear set of the hybrid drive line of figure 1 when operated in accordance with the present disclosure;

figure 3 is a diagrammatic representation of a first embodiment of a hybrid drive line suitable for being operated in accordance with the present disclosure; and

figure 4 is a diagrammatic representation of a second embodiment of a hybrid drive line suitable for being operated in accordance with the present disclosure.

Figure 1 shows a known example of a hybrid drive line of a motor vehicle comprising an internal combustion engine, i.e. ICE 1 with a crank shaft 1 1 , an electric motor/generator (M/G) device 2 with a drive shaft 21 and with power electronics including a battery 22, driven wheels 3 and a gearing 4 there between. The gearing 4 includes a planetary gear set 5 and an automatic transmission 6 providing multiple speed ratios between the planetary gear set 5 and the driven wheels 3. Typically, the automatic transmission 6 is provided with a differential gearing 66 for distributing a drive power between the driven wheels 3.

The planetary gear set 5 is as such well-known and comprises a central or sun gear 51 that is in meshing contact with one or more planet gears 52, which planet gears 52 are rotatably carried by a planet carrier 53 arranged coaxially with the sun gear 51 , and a ring gear 54 that is in meshing contact with the planet gears 52 and that is also arranged coaxially with the sun gear 51 . The ring gear 54 is coupled to the crank shaft 1 1 of the ICE 1 via a first clutch 7, the planet carrier 53 is coupled to the automatic transmission 6 and the sun gear 51 is coupled to the drive shaft 21 of the M/G-device 2. By means of the first clutch 7 the ICE 1 can be coupled to or isolated from the rest of the hybrid drive line, in particular the ring gear 54. Furthermore, the planetary gear set 5 is provided with a second clutch 55 between the planet carrier 53 and the ring gear 54 and that can be closed to internally lock the planetary gear set 5 such that the sun gear 51 , the planet carrier 53 and the ring gear 54 thereof rotate as one. In fact, the second clutch 55 can be provided between any two such components of the planetary gear set for the said internal locking thereof.

The known hybrid drive line of figure 1 can be operated in several operational modes. For example, by opening the first clutch 7 while closing the second clutch 55, the M/G-device 2 is coupled to the driven wheels 3 via the planetary gear set 5 and the automatic transmission 6, while the ICE 1 is decoupled from the gearing 4. In this operational mode the motor vehicle is driven electrically by the M/G-device 2 that also serves to recuperate mechanical energy during braking, storing it as electric energy in the battery 22. By closing the first clutch 7, while opening the second clutch 55, both the ICE 1 and the M/G-device 2 are coupled to the driven wheels 3 via the planetary gear set 5 and the automatic transmission 6 of the gearing 4, providing a parallel drive operational mode with some flexibility regarding the controlled rotational speed of the ICE 1 and that of the M/G-device 2 in relation to the rational speed of the driven wheels 3. By closing botch such first and second clutches 7, 55 the ICE 1 and the M/G-device 2 are still both coupled to the driven wheels 3, however, only at fixed speed ratio, thus providing a parallel drive operational mode without flexibility regarding the said rotational speeds, but with less (dynamic) power loss.

In the known hybrid drive line of figure 1 and in order to enable the driving off of the motor vehicle from standstill by means of the ICE 1 , for example when the battery 22 is depleted, a conventional drive-off device such as a multi-plate clutch or a torque converter must be included therein, thus adding to the cost and complexity thereof. However, according the present disclosure, this latter requirement can be favourably avoided by operating the known hybrid drive line in a novel way.

According to the present disclosure, at least during an initial acceleration of the load 3 by the ICE 1 in a hybrid drive line from standstill, the drive shaft 21 of the M/G- device 2 is controlled to rotate backward while generating a positive, i.e. forward driving torque. At the same time, either the rotational speed of the ICE 1 is increased, or the backward rotational speed of the M/G-device is decreased, or both. By this novel operating method, the driving off of the motor vehicle powered by the ICE 1 is favourably enabled without the requirement for and/or the controlled closing of the conventional drive-off device. Furthermore, by this novel operating method, the M/G-device 2 is generating electric power and can favourably charge the depleted battery 22 even while driving off.

The above method for operating the hybrid drive line in accordance with the present disclosure is elucidated further with reference to figure 2. Figure 2 is a diagram wherein the rotational speed of the sun gear ω-51 , of the planet carrier ω-53 and of the ring gear ω-54 of the planetary gear set 50 are plotted on the three horizontal X-axes. The ring gear speed ω-54 that is equal -or at least proportional- to the rotational speed of the (crank shaft 1 1 of the) ICE 1 is plotted on the uppermost X-axis. The planet carrier speed ω-53 that is equal -or at least proportional- to the rotational speed of the load 3 is plotted on the middle X-axis. The sun gear speed ω-51 that is equal -or at least proportional- to the rotational speed of the (drive shaft 21 of the) M/G-device 2 is plotted on the lowermost X-axis. The vertical separation between these three X-axes reflects a speed ratio A between the ring gear 54 and the planet carrier 53 and between the planet carrier 53 and the sun gear 51 , i.e. speed ratio B, respectively.

The dashed line D1 in figure 2 illustrates an initial operational mode of the hybrid drive line. In this D1 operational mode the (crankshaft 1 1 of the) ICE 1 is rotating at a lowermost rotational speed oo-54D1 , the load 3 is stopped, i.e. has a rational speed ω- 53D1 of zero, and the M/G-device 2 is controlled to rotate backward at a certain, negative rotational speed oo-51 D1 . Preferably in this initial, D1 operational mode, the M/G-device 2 is additionally controlled to exert a forward torque that counteracts the said backward rotation thereof, whereby it generates electric power that is stored in the battery 22. In this latter case, a rotation of the load 3 must the prevented by the automatic or manual application of a (wheel) brake.

Departing from such D1 operational mode, the brake of the load 3 is released and the speed of the (crank shaft 1 1 of the) ICE 1 is controlled to increase (as indicated in figure 2 by the arrow W1 ) to a higher speed oo-54D2, while the (drive shaft 21 of the) M/G-device 2 is continued to be controlled to rotate backward, whereby the load 3 is accelerated. Preferably, but not necessarily, the said certain speed oo-51 D1 in backward rotation of the M/G-device 2 is controlled to be constant during the acceleration of the load 3, in particular by controlling the forward torque of the M/G-device 2. This latter dynamic operational mode is illustrated in figure 2 by the dash-dotted line D2. In this D2 operational mode the speed oo-53D2 of the load 3 is determined by the speed oo-54D2 of the ICE 1 and the speed ω-51 D2 of the M/G-device 2.

Alternatively the load 3 is accelerated by controlling the speed of backward rotation of the (drive shaft 21 of the) M/G-device 2 to decrease (as indicated in figure 2 by the arrow W2) to a lower speed ω-51 D3 of backward rotation, thus reducing the said electric power that is generated thereby. Preferably, but not necessarily, the speed of the (crankshaft 1 1 of the) ICE 1 is increased simultaneously to a higher speed oo-54D3, in order to improve the acceleration of the load 3. This latter dynamic operational mode is illustrated in figure 2 by the dotted line D3. Also in this latter D3 operational mode the speed oo-53D3 of the load 3 is determined by the speed oo-54D3 of the ICE 1 and the speed ω-51 D3 of the M/G-device 2. It is noted that the load 3 can also be accelerated in reverse, e.g. for reversing the motor vehicle, by controlling the speed ω-51 of backward rotation of the (drive shaft 21 of the) M/G-device 2 to increase.

Once the battery 22 is (again) sufficiently charged, the speed of the M/G-device 2 can be increased to a positive value, i.e. forward rotation, e.g. to oo-51 D4, in order to either assist to the ICE 1 in driving the load 3, as illustrated in figure 2 by the solid line D4, or even to solely drive the load 3. Hereby, effectively, the operational mode of the M/G-device 2 is changed from a (battery) charging mode to either an electric assist mode (D4) or an electric drive mode (not illustrated in figure 2). It is noted that in the said electric assist mode the said second clutch 55 can be closed to internally lock the planetary gear set 5 and thus to reduce a power loss in the gearing 4, whereas in the said electric drive mode, additionally, the said first clutch 7 can be opened to decouple the ICE 1 from the gearing 4 and to shut it off. In this latter respect, it is noted that the ICE 1 can be (re-)started by the inertia of the hybrid drive line by (again) closing this first clutch 7, such that a separate starter motor for the ICE 1 is not needed. Hereto, preferably, this first clutch 7 is a friction clutch with a relatively low slipping torque capacity, such as a cone-clutch.

According to the present disclosure, it is advantageous for the performance of above, novel operating method that in the hybrid drive line the crank shaft 1 1 of the ICE 1 is coupled to the sun gear 51 and that the drive shaft 21 of the M/G-device 2 is coupled to the ring gear 54 of the planetary gear set 5. In particular in this first embodiment, the crankshaft 1 1 of the ICE 1 is coupled directly to the sun gear 51 , whereas the drive shaft 21 of the M/G-device 2 is coupled to the ring gear 54 via a speed reducing gear step 23. This first embodiment of the hybrid drive line in accordance with the present disclosure is illustrated in figure 3. The preference of this first embodiment, amongst others, being related to the consideration that the torque generating capability of the combination of the M/G-device 2 and the speed reducing gear step 23 will typically exceed that of the ICE 1 , while in the planetary gear set 5 the torque level at the ring gear 54 exceeds that at the sun gear 51 .

Additionally in this first embodiment, the planet carrier 53 of the planetary gear set 5 is coupled to the load 3 via a fixed gear train including the differential gearing 66 and possibly one or more speed reducing gear steps (not illustrated). More specifically in this respect, no variable speed device, such as the conventional drive-off device or the known automatic transmission 6, is provided between the planetary gear set 5 and the load 3, in order to favourably reduce complexity, cost of and (parasitic) power loss in this first embodiment of the hybrid drive line according to the present disclosure.

A second embodiment of the hybrid drive line according to the present disclosure is illustrated in figure 4. In this second embodiment two additional features are included that can, however, be implemented independently of one another.

As a first additional feature illustrated in figure 4, an automatic locking mechanism 8 is included in the hybrid drive line, associated with the planet carrier 53 of the planetary gear set 5, that can be automatically engaged to externally lock, i.e. to prevent rotation of the planet carrier 53 and thus also of the load 3 that is coupled thereto. The automatic locking mechanism 8 can for example be incorporated in the gearing 4 as a parking pawl, as a friction brake 8 or possibly as wheel brake that can be automatically engaged. When the automatic locking mechanism 8 is engaged, the M/G-device 2 can drive the ICE 1 , in particular to start it, or the ICE 1 can drive the M/G-device 2 to charge the battery 22, favourably without simultaneously driving and/or accelerating the load 3.

As a second additional feature illustrated in figure 4, an automatic transmission 9 is included between the crank shaft 1 1 of the ICE 1 and the planetary gear set 5, in particular the sun gear 51 thereof. This particular arrangement of the hybrid drive line has the advantages that the rotational speed of and the torque generated by the ICE 1 , can be varied to optimally match the operating conditions of the hybrid driveline and/or to improve the performance thereof. In figure 4 the automatic transmission 6 is represented by a well-known continuously variable transmission that is provided with a variable input pulley 91 on a transmission input shaft 92, with a variable output pulley 93 on a transmission output shaft 94 and with a drive belt 95 wrapped around and rotationally connecting said pulleys 91 , 92. This type of automatic transmission 9 is capable of varying the speed ratio between the said transmission shafts 92, 94 continuously within a range of speed ratios. It is noted that by this latter arrangement of the automatic transmission 9 a smaller range of speed ratios already provides the hybrid drive line with a comparable speed/torque-flexibility as provided by the conventionally arranged automatic transmission 6 between the planetary gear set 5 and the load 3. More specifically, the automatic transmission 9 is advantageously arranged between the ICE 1 and the said first clutch 7, such that it is decoupled from the planetary gear set 5 together with the ICE 1 , to minimise power loss when the ICE 1 is stopped. Additionally this particular arrangement allows the transmission 9 to be briefly decoupled from the planetary gear set 5 by the said first clutch 7 also when the ICE 1 is running, to change the speed ratio thereof without torque being transmitted thereby.

The present disclosure, in addition to the entirety of the preceding description and all details of the accompanying figures, also concerns and includes all of the features in the appended set of claims. Bracketed references in the claims do not limit the scope thereof, but are merely provided as a non-limiting example of a respective feature. Separately claimed features can be applied separately in a given product or a given process, as the case may be, but can also be applied simultaneously therein in any combination of two or more of such features.

The invention(s) represented by the present disclosure is (are) not limited to the embodiments and/or the examples that are explicitly mentioned herein, but also encompass(es) amendments, modifications and practical applications thereof, in particular those that lie within reach of the person skilled in the relevant art.

Claims

1 . A method for operating a hybrid drive line in a motor vehicle comprising an internal combustion engine (ICE; 1 ) with a crank shaft (1 1 ), an electric motor/generator (M/G) device (2) with a drive shaft (21 ) and a driven wheel (3) with an automatic locking mechanism (8) associated therewith for selectively blocking or unblocking rotation of the driven wheel (3), and a gearing (4) provided between the ICE (1 ) the M/G device (2) and the driven wheel (3), which gearing (4) comprises a planetary gear set (5) with a central, sun gear (51 ) that is in meshing contact with one or more planet gears (52) of the planetary gear set (5), which planet gears (52) are rotatably carried by a planet carrier (53) of the planetary gear set (5) arranged coaxially with the sun gear (51 ), and a ring gear (54) that is in meshing contact with the planet gears (52) and that is also arranged coaxially with the sun gear (51 ), whereof the planet carrier (53) is rotationally coupled to the driven wheel (3) and whereof the sun gear (51 ) and the ring gear (54) are respectively rotationally coupled to the ICE (1 ) or the M/G device (2), characterized in that, during operation of the hybrid drive line when the driven wheel (3) is at rest and the ICE (1 ) is stopped, first the automatic locking mechanism (8) is engaged, to block the rotation of the driven wheel (3), and second the M/G device (2) is electrically powered to drive the crank shaft (1 1 ) of the ICE (1 ) for starting the ICE (1 ).

2. A method for operating a hybrid drive line in a motor vehicle comprising an internal combustion engine (ICE; 1 ) with a crank shaft (1 1 ), an electric motor/generator (M/G) device (2) with a drive shaft (21 ) and a driven wheel (3) with an automatic locking mechanism (8) associated therewith for selectively blocking or unblocking rotation of the driven wheel (3), and a gearing (4) provided between the ICE (1 ) the M/G device (2) and the driven wheel (3), which gearing (4) comprises a planetary gear set (5) with a central, sun gear (51 ) that is in meshing contact with one or more planet gears (52) of the planetary gear set (5), which planet gears (52) are rotatably carried by a planet carrier (53) of the planetary gear set (5) arranged coaxially with the sun gear (51 ), and a ring gear (54) that is in meshing contact with the planet gears (52) and that is also arranged coaxially with the sun gear (51 ), whereof the planet carrier (53) is rotationally coupled to the driven wheel (3) and whereof the sun gear (51 ) and the ring gear (54) are respectively rotationally coupled to the ICE (1 ) or the M/G device (2), characterized in that, during operation the driven wheel (3) is accelerated from standstill with the automatic locking mechanism (8) engaged and the ICE (1 ) rotates the drive shaft (21 ) of the M/G device (2) in reverse to generate electric power, by increasing both a reverse rotational speed of the drive shaft (21 ) of the M/G device (2) and a forward rotational speed of the crank shaft (1 1 ) of the ICE (1 ).

3. The method for operating a hybrid drive line according to claim 2, characterized in that, after the initial increase of the reverse rotational speed of the drive shaft (21 ) of the M/G device (2), such reverse rotational speed of the drive shaft (21 ) of the M/G device (2) is decreased to zero and subsequently the M/G device is electrically powered to drive the driven wheel (3).

4. The method for operating a hybrid drive line according to a preceding claim, characterized in that, the driven wheel (3) is directly rotationally coupled to the planet carrier (53) of the planetary gear set (5), possibly through a fixed-ratio gear train, such as a speed reduction gear and or a differential gearing (66), but without a variable speed device, such as a variable transmission or a drive-off device (e.g. fluid coupling, torque converter or start clutch), being provided there between.

5. The method for operating a hybrid drive line according to a preceding claim, characterized in that, the ICE (1 ) is rotationally coupled to the planetary gear set (5) through a variable transmission (6) and a selectively engagable clutch (7).

6. The method for operating a hybrid drive line according to a preceding claim, characterised in that, the planetary gear set (5) is provided with a selectively engagable clutch (55) that can be closed to make the sun gear (51 ), the planet carrier (53) and the ring gear (54) rotate as one.

7. The method for operating a hybrid drive line according to a preceding claim, characterized in that, the ICE (1 ) is rotationally coupled to the sun gear (51 ) of the planetary gear set (5), the M/G device (2) is rotationally coupled to the ring gear (54) of the planetary gear set (5) and in that the planetary gear set (5) is designed with a geometric gear set ratio Zpgs, defined between an inner radius Rring of the ring gear (54) and an outer radius Rsun of the sun gear (51 ), that is approximately equal to the torque ratio defined between a torque level T nom sun that can be nominally generated by the ICE (1 ) on the sun gear (51 ) and a torque level T nom ring that can be nominally generated by the M/G device (2) on the ring gear (54):

T nom ring / T nom sun ~ Zpgs = Rring / Rsun