TRANSMISSION FOR A VEHICLE HAVING AN ELECTROMAGNETIC VARIATOR

Abstract

The present disclosure relates to a transmission for a vehicle having a power source, the transmission comprising: an input member for receiving power from the power source; an output member for outputting power to at least one component of the vehicle; at least one power split gear set having a plurality of members and operatively connected between said input member and said output member; an electromagnetic variator having a stator, an outer rotor and an inner rotor; wherein the inner rotor is at least partially received in the outer rotor and the electromagnetic variator is configured to provide variable torque transmission ratios between the outer rotor and inner rotor; and wherein said first and second rotors are each operatively connectable to different ones of said members of said power split gear set and are each operatively connectable to the input member to be driven thereby.

Claims

1. A transmission for a vehicle having a power source, the transmission comprising: an input member for receiving power from the power source; an output member for outputting power to at least one component of the vehicle; at least one power split gear set having a plurality of members and operatively connected between said input member and said output member; an electromagnetic variator having a stator, an outer rotor and an inner rotor; wherein the inner rotor is at least partially received in the outer rotor and the electromagnetic variator is configured to provide variable torque transmission ratios between the outer rotor and inner rotor; wherein said first and second rotors are each operatively connectable to different ones of said members of said power split gear set and are each operatively connectable to the input member to be driven thereby.

2. The transmission according to claim 1, wherein power split gear set is a planetary gear set.

3. The transmission according to claim 1, wherein the electromagnetic variator is configured to convert mechanical energy received by at least one of the rotors at least partially into electric energy, thereby providing at least some of the variable torque transmission ratios and/or wherein the electromagnetic variator is configured to convert mechanical energy received by at least one of the rotors at least partially into electromagnetic energy which is transferred to the respective other rotor.

4. The transmission according to claim 1, wherein the electromagnetic variator is configured to actively drive at least one of the rotors based on stored electrical energy, thereby providing at least some of the variable torque transmission ratios.

5. The transmission according to claim 1, wherein each rotor is operatively connectable to at least one common member of the power split gear set.

6. The transmission according to claim 2, wherein the common member is a carrier of the planetary gear set and/or wherein the common member is a sun gear of the planetary gear set.

7. The transmission according to claim 1, wherein the transmission is operable according to a plurality of operating modes, each operating mode being marked by individual operative connections and operative disconnections between each of the inner and outer rotor and the members of said planetary gear set as well as between each of the inner and outer rotor and the input member.

8. The transmission according to claim 7, wherein the operating modes comprise at least one operating mode in which torque received by the inner rotor is at least partially converted into torque output by the outer rotor and at least one operating mode in which torque received by the outer rotor is at least partially converted into torque output by the inner rotor.

9. The transmission according to claim 8, wherein the operating modes comprise at least one operating mode in which one of the inner rotor and outer rotor is operatively connected to the input member independently of the power split gear set and/or at least one operating mode in which one of the inner and outer rotor is operatively connected to the input member via the power split gear set.

10. The transmission according to claim 7, wherein the transmission comprises a plurality of selectively activatable torque transmitting units to provide the operative connections and operative disconnections.

11. The transmission according to claim 7, wherein the operating modes comprise at least one of the following: a first operating mode in which the input member is operatively connected to the inner rotor via a member of the power split gear set and torque received by the inner rotor is at least partially converted into torque output by the outer rotor, wherein the outer rotor is connected to the output member via another member of the power split gear set; a second operating mode in which the input member is operatively connected to the outer rotor via a member the power split gear set and torque received by the outer rotor is at least partially converted into torque output by the inner rotor, wherein the inner rotor is connected to the output member via another member of the power split gear set; a third operating mode in which the input member is operatively connected to the inner rotor independently of the power split gear set and torque received by the inner rotor is at least partially converted into torque output by the outer rotor, wherein the outer rotor is connected to the output member via a member of the power split gear set that is different from a member of the power split gear set to which the output is connected; a fourth operating mode in which the input member is operatively connected to the outer rotor independently of the power split gear set and torque received by the outer rotor is at least partially converted into torque output by the inner rotor, wherein the inner rotor is connected to the output member via a member of the power split gear set that is different from a member of the power split gear set to which the output is connected.

12. The transmission according to claim 11, wherein at least two of the operating modes are provided and the transmission is configured to switch between said modes depending on an amount of electrical power generated by the electromagnetic variator.

13. The transmission according to claim 11, wherein the point of switching between the operating modes is selected so that at least one of the following is reduced: a variator power-split ratio which concerns the ratio between the power received by the electromagnetic variator and the power received by the transmission from the power source; an electrical-variator power split ratio which concerns the ratio between electrical power generated within the electromagnetic variator and the power received by the electromagnetic variator; an electrical power split ratio which concerns the ratio between electrical power generated within the electromagnetic variator and the power received by the transmission from the power source.

14. The transmission according to claim 11, wherein at least the first operating mode and fourth operating mode are provided and the first operating mode is activated within a lower range of output speeds than the fourth operating mode.

15. The transmission according to claim 14, wherein at least one of the second and third operating mode is additionally provided and is activated within a range of output speeds in between those ranges of output speeds in which the first operating mode and the fourth operating mode are activated.

16. The transmission according to claim 15, wherein both of the second and third operating modes are additionally provided and the second operating mode is activated within a lower range of output speeds than the third operating mode.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0058] FIG. 1 shows a transmission of the presently proposed type.

[0059] FIG. 2 is a table showing opening and closing states of clutches in the transmission of FIG. 1.

[0060] FIGS. 3A-3D show the course selected transmission ratios for various operating modes of the transmission of FIG. 1.

[0061] FIGS. 4A-4B are an alternative way of presenting the data of FIGS. 3A-3D.

DETAILED DESCRIPTION

[0062] FIG. 1 shows a transmission 10 of the presently proposed type which may be used in a road vehicle (not illustrated). The transmission 10 comprises an input member in the form of an input shaft 12. Further, the transmission 10 comprises an output member in the form of an output shaft 14.

[0063] The output shaft 14 drives a component 100 of the vehicle, such as wheel. It may be connected to said component 100 by an optional further output gear stage 102.

[0064] The input shaft 12 receives mechanical power (e.g. torque) from a power source 13 such as an internal combustion engine or an electric motor, for example. An optional forward/reverse gear selection mechanism 15 may connect the power source 13 and the input shaft 12 and transmit torque therebetween.

[0065] The input shaft 12 is connected to an optional input gear set 17. The input gear set 17 includes a first input gear 19 and a second input gear 21 which may be drivingly engaged with each other by a clutch C1. The first input gear 19 is coupled to a power split gear set of the transmission 10 in the form of a planetary gear set 16. The second input gear 21 is coupled to a connecting gear 23 discussed below.

[0066] The planetary gear set 16 comprises a ring gear 20, a carrier 22 carrying one or more planetary gears and a sun gear 24. The carrier 22 is connected to the output shaft 12. The ring gear 20 is connected to the first input gear 19. The carrier 22 and the sun gear 24 are coupled to clutches C2, C3, C4, C5 of an electromagnetic variator 26 of the transmission 10.

[0067] More specifically, the transmission 10 includes a first connection shaft 28 connecting the carrier 22 to the connecting gear 23 and to a first and second clutch C2, C3 of the electromagnetic variator 26, and a second connection shaft 30 connecting the carrier 22 to a third and fourth clutch C4, C5 of the electromagnetic variator 26.

[0068] The electromagnetic variator 26 comprises an inner rotor 32 and an outer rotor 34 each configured to rotate about a rotation axis that coincides with the second connection shaft 30 in FIG. 1. The inner rotor 32 has smaller radial dimensions that the outer rotor 34. The inner rotor 32 is received and/or surrounded by the outer rotor 34. For example, the inner rotor 32 and the outer rotor 34 are arranged to axially overlap with one another. This may increase spatial compactness and may allow to establish an electromagnetic power path between the inner rotor 32 and the outer rotor 34.

[0069] The inner rotor 32 and the outer rotor 34 are both received in a stator 36 having a radially larger dimension (e.g. diameter) than said rotors 32, 34. Also, the stator 36 axially overlaps with said rotors 32, 34.

[0070] The first, second, third and fourth clutch C2-C5 of the electromagnetic variator 26 are further connected as follows: The first clutch C2 is connected to the outer rotor 34. The second clutch C3 is connected to the inner rotor 32. The third clutch C4 is connected to the inner rotor 32. The fourth clutch C5 is connected to the outer rotor 34.

[0071] The first, second, third and fourth clutch C2-C5 thus provide a selectively activatable torque transmission between the respectively connected one of the first and second connection shaft 28, 30 and the respectively connected one of the inner and the outer rotor 32, 34. The selective activation includes closing a respective clutch C2-C5 which is normally open.

[0072] The opening and closing of the clutches C1-C5 of the transmission 10 is controlled by a control system 104. A control signal connection is present between the control system 104 and each of the clutches C1-C5 but is not specifically indicated for the first clutch C1 for illustrative reasons.

[0073] As electric components, the electromagnetic variator 26 comprises a power converter 40 controlled by a control unit 42. The control unit 42 may be an integrated part of the control system 104 or may be separately provided but communicate with the control system 104. A further electric component is an electric energy storage in the form of a battery 44.

[0074] FIG. 1 indicates that the transmission 10 includes several electric power connections between the rotors 32, 34 as well as between the stator 36 and the electric components 40-44. Also, the transmission 10 includes an electric power connection between the battery 44 and power converter 40 as well as a control signal connection between the power converter 40 and the control unit 42.

[0075] Depending on whether electric power is transferred to or received from the battery 44, the power converter 44 is operable (under control by the control unit 42) either as a rectifier (transferring power to the battery 44) or as an inverter (receiving power from the battery 44). The control unit 42 is also configured to set the respective extents of power conversion, e. g. depending on a requested output speed, thereby setting and varying transmission ratios of the variator 26.

[0076] The transmission 10 is operable according to four operating modes each of which provides a continuous range of transmission ratios. As further explained below, the operating modes are typically activated consecutively (e. g. depending on a current or desired output speed) to maintain limited electric power levels within the electromagnetic variator 26. This may reduce the required power ratings of the electric components 40-44, thus saving weight, space and costs.

[0077] Each of the operating modes corresponds with a defined combination of opened and closed clutches C1-C5 of the transmission 10. The opening and closing actions are usually controlled by the control system 104.

[0078] FIG. 2 illustrates the opening (no x) and closing states (x) for each of the clutches C1-C5 in each of the operating modes.

[0079] A first operating mode is an input-split input-split mode (IS-IS) with the first and third clutches C2, C4 of the transmission 10 closed.

[0080] A second operating mode is an input-split output-split mode (IS-OS) with the second and fourth clutches C3, C5 of the transmission 10 closed.

[0081] A third operating mode is an output-split input-split mode (OS-IS) with the second and fourth clutches C3, C5 of the transmission 10 and with the clutch C1 of the input gear set 17 closed.

[0082] A fourth operating mode is an output-split output-split mode (OS-OS) with the first and third clutches C2, C4 of the transmission 10 and with the clutch C1 of the input gear set 17 closed.

[0083] The power paths and energy flows within the transmission 10 in each of the operating modes described are as follows.

[0084] In the IS-IS mode, mechanical energy (e.g. torque) received at the input shaft 12 of the transmission 10 is transferred to the ring gear 20 of the planetary gear set 16 by or via the first input gear 19. The ring gear 20 transmits said energy to the carrier 22 and to the sun gear 24 which drives the second connection shaft 30. Since the third clutch C4 is closed, the inner rotor 32 rotates and generates electric energy. Said energy is converted and stored by the components 40, 44 and is or may be partially used to drive the outer rotor 34. Also, an electromagnetic power path is established between the inner rotor 32 and the outer rotor 34.

[0085] The outer rotor 34 is coupled to the second connecting shaft 28 by the first clutch C2. Therefore, it is directly coupled to the output shaft 14 by the carrier 22.

[0086] In the IS-OS mode, mechanical energy received at the input shaft 12 of the transmission 10 is transferred to the ring gear 20 of the planetary gear set 16 by or via the first input gear 19. The ring gear 20 transmits said energy to the carrier 22 and to the sun gear 24 which drives the first connection shaft 28. Since the fourth clutch C5 is closed, the outer rotor 35 rotates, thereby generating electric energy which is converted and stored by the components 40, 44 and which is or may be partially used to drive the inner rotor 32. Also, an electromagnetic power path is established between the inner rotor 32 and the outer rotor 34.

[0087] The inner rotor 32 is coupled to the second connecting shaft 30 by the second clutch C3. Therefore, the inner rotor 32 is directly coupled to the output shaft 14 by or via the carrier 22.

[0088] In the OS-IS mode, as the clutch C1 of the input gear set 17 is closed, mechanical energy received at the input shaft 12 of the transmission 10 is at least partially directly transferred to the electromagnetic variator 26. Specifically, the second input gear 21 is driven, thus transferring torque to the second connection shaft 30 via the connecting gear 23. Since the second clutch C3 is closed, the inner rotor 32 rotates, thereby generating electric energy which is converted and stored by the components 40, 44 and which is or may be partially used to drive the outer rotor 34. Also, an electromagnetic power path is established between the inner rotor 32 and outer rotor 34.

[0089] The outer rotor 34 is coupled to the first connecting shaft 28 by the fourth clutch C5. Therefore, the outer rotor 34 is indirectly coupled to the output 14 by or via the gear stage comprising the sun gear 24 and the carrier 22.

[0090] In the OS-OS mode, as the clutch C1 of the input gear set 17 is closed, mechanical energy received at the input shaft 12 of the transmission 10 is at least partially directly transferred to the electromagnetic variator 26. Specifically, the second input gear 21 is driven thus transferring torque to the second connection shaft 30 via the connecting gear 23. Due to the closed first clutch C2, the outer rotor 34 rotates generating electric energy converted and stored by the components 40, 44 and partially used to drive the inner rotor 32. Also, an electromagnetic power path is established between the inner rotor 32 and outer rotor 34.

[0091] The inner rotor 32 is coupled to the first connecting shaft 28 by the third clutch C4. Therefore, it is indirectly coupled to the output 14 by the gear stage comprising the sun gear 24 and carrier 22.

[0092] In each of these modes, the speed of the electrically driven rotor 32, 34 can be variably set under control of the power converter 40, thus defining a range of transmission ratios of the electromagnetic variator 26.

[0093] In the IS-OS mode of FIG. 3B, the VPR decreases linearly with the output speed. The output-split mode of the electromagnetic variator 26 reduces the electrical power under high speed operating conditions (corresponding to speeds above 1200 rpm, for example).

[0094] The transmission 10 may function in a similar manner in the OS-IS mode of FIG. 3C. This mode allows avoiding negative VPRs under high speed operating conditions, thereby avoiding or reducing power recirculation. The input-split mode of the electromagnetic variator 26 introduces power recirculation in the electrical power path. However, the absolute electrical power is than in known mechanical output-split power split transmissions.

[0095] In the OS-OS mode of FIG. 3D, the EVP is significantly lower than the VPR under very high operating speeds (such as above 1800 rpm, for example).

[0096] FIGS. 4A-4B present part of the same data as FIGS. 3A-3D in a different way. The VPR and EPR of all different operating modes of FIGS. 3A-3D are plotted on a single plot for each of said ratios. The dotted lines in FIGS. 4A and 4B represent the minimal VPR or EPR which can be achieved with the transmission 10.

[0097] It can be observed that a minimum EPR can be reached by switching between all the different operating modes of the multi-mode power split transmission 10. In reverse and when running at low forward speeds, the IS-IS mode results in the lowest EPR. Between about 800 rpm and about 1200 rpm, the IS-OS mode has the lowest EPR. Between 1200 rpm and 1800 rpm the OS-IS mode has the optimal EPR, and starting from 1800 rpm the OS-OS mode results in the lowest EPR.

[0098] Additionally, it can be observed that over the entire positive speed range the optimal VPR and EPR are positive and below 1. As noted above, this implies that no power recirculation is present, typically resulting in a higher efficiency of the system.

[0099] Also, it can be observed that the EPR of FIG. 4B is mostly lower than the VPR of FIG. 4A for any given output speed. Especially at higher output speeds, the EPR is almost only half of the VPR, leading to a reduced cost of e. g. power converters 42.