HYBRID TRANSMISSION WITH ELECTROMAGNETICLY ACTUATED CLUTCH COUPLING

Abstract

Electromagnetically actuated clutch (50), comprising: a non-rotating electromagnetic coil (66, 68); a toothed inner running ring (52, 54) which is mounted for rotation about the coil (66, 68), wherein the inner running ring (52, 54) has a left (54) and a right (52) magnetically conductive ring (52, 54) which are magnetically separated from each other; an outer race ring (56) which is mounted for rotation about the inner race ring (52, 54); and a magnetically conductive pawl (58) which is mounted and pivotable for rotation with the outer running ring (56) in order to engage with the left and right rings (52, 54) in response to current in the coil (66, 68).

Description

TECHNICAL AREA

[0001] This disclosure relates to the field of vehicle couplings. In particular, the disclosure relates to an electromagnetically actuated jaw coupling used in a hybrid-electric powertrain. GENERAL STATE OF THE ART

[0002] Many vehicles are used across a wide range of vehicle speeds, including both forward and reverse motion. However, some types of engines can only operate effectively within a narrow range of speeds. Consequently, transmissions capable of efficiently transferring power across a variety of speed ratios are commonly employed. When the vehicle is traveling slowly, the transmission is typically operated at a high speed ratio, thus multiplying the engine torque for improved acceleration. At high vehicle speeds, operating the transmission at a low speed ratio allows for an engine speed associated with smooth, fuel-efficient driving.

[0003] Some transmissions, called separate-gear transmissions, are configured to produce a limited number of speed ratios between an input shaft and an output shaft. If the currently selected ratio is no longer suitable, a separate-gear transmission must shift to another of the available speed ratios. Other transmissions, called continuously variable transmissions (CVTs), are capable of producing any speed ratio between the lower and upper limits. CVTs are capable of making frequent, fine speed ratio adjustments that are imperceptible to vehicle occupants.

[0004] Many transmissions use hydraulically actuated friction clutches to create different power flow paths. Hydraulic actuation is suitable for clutches that selectively couple rotating elements because pressurized hydraulic fluid can be routed from a stationary housing to rotating components between seals. This allows the hydraulic actuator to rotate with one of the rotating elements. When multiple hydraulically actuated clutches are present, they often share a motor-driven pump and many of the valve body components used to regulate pressure.

[0005] Hybrid vehicle transmissions improve fuel efficiency by providing energy storage. In a hybrid electric vehicle, for example, energy can be stored in a battery. The battery can be charged by running the motor to generate more power than is currently needed for propulsion. Additionally, energy that would otherwise be lost during braking can be captured and stored in the battery. This stored energy can be used later, allowing the motor to generate less power than is currently required for propulsion, thus reducing fuel consumption.

[0006] Document US 2011 / 0290608A1 describes a freewheel clutch. Document WO 2016 / 057640A2 discloses an electromechanical clutch device. Document DE 102015116403A1 describes a hybrid transmission with an electromagnetically actuated ratchet clutch.

[0007] Against this background, the object of the present invention is to provide an advantageous electromagnetically actuated clutch, an advantageous clutch, and an advantageous transmission. These objects are achieved by the subject matter of the independent claims. The dependent claims contain further advantageous embodiments of the invention. SUMMARY OF THE REVELATION

[0008] An electromagnetically actuated clutch comprises a non-rotating electromagnetic coil, a toothed inner race, an outer race, and a magnetically conductive pawl. The toothed inner race, which is mounted to rotate around the coil, has left and right magnetically isolated rings. The outer race, which may be magnetically non-conductive, is mounted to rotate around the inner race. The pawl is mounted to rotate with the outer race and is pivotable to engage the left and right rings in response to current in the coil. Both rings may have teeth. The teeth of one ring may be offset from the teeth of the other ring, so that a large portion of the engagement force is distributed over one ring.

[0009] A coupling comprises an electromagnetic coil, left and right magnetically conductive rings, a bearing ring mounted for rotation relative to the rings, and a magnetically conductive pawl. The electromagnetic coil may be non-rotating, while the rings and bearing ring are mounted for rotation. The left and right rings each have a cylindrical surface adjacent to the coil and a toothed surface opposite the cylindrical surface. The electromagnetic coil may be located radially inside the rings. The left and right rings are magnetically isolated from each other but may be rigidly coupled. The bearing ring is mounted for rotation relative to the rings and may be located radially outside the rings. The pawl is pivotable relative to the bearing ring to engage with the left and right rings in response to current in the coil.

[0010] A clutch comprises an electromagnetic coil, left and right magnetically conductive rings, an outer race, and a magnetically conductive pawl. The coil may be fixed to a gearbox housing. The rings are both rigidly coupled to an input shaft and magnetically isolated from each other. The outer race is mounted for rotation relative to the input shaft. The pawl is mounted for rotation with the outer race and is pivotable to engage with the left and right rings in response to current in the coil. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a gear ratio arrangement for a hybrid electric powertrain. Fig. Figure 2 is a pictorial view of an electromagnetically actuated clutch, intended for use in the transmission arrangement of the Fig. 1 is suitable. Fig. Figure 3 is a cropped view of the coupling of the Fig. 2. Fig. 4 is an exploded view of the coupling of the Fig. 2. Fig. 5 is a cross-section of the coupling of the Fig. 2. Fig. Figure 6 is a detailed cross-sectional view of the coupling of the Fig. 2 in a deployed state. Fig. Figure 7 is a detailed cross-sectional view of the coupling of the Fig. 2 in an indented state. DETAILED DESCRIPTION

[0011] Embodiments of the present disclosure are described herein. It is understood, however, that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be greatly enlarged or reduced to show details of certain components. Accordingly, the specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis to teach a person skilled in the art the diverse uses of the present invention.Those skilled in the art will understand that various features illustrated and described with reference to any of the figures can be combined with features illustrated in one or more figures to create embodiments not explicitly illustrated or described. The combinations of illustrated features provide representative embodiments for typical applications. However, various combinations and modifications of the features, consistent with the teachings of this disclosure, may be desirable for specific applications or implementations.

[0012] A group of rotating elements is rigidly coupled if they are forced to rotate as a single unit under all operating conditions. Rotating elements can be rigidly coupled by keyed connections, welding, press fits, machining from a common solid, or other means. Small variations in rotational displacement between rigidly coupled elements may occur, such as displacement due to clearance or shaft conformity. In contrast, two rotating elements are selectively coupled by a switching element if the switching element forces them to rotate as a single unit whenever it is fully engaged, and they are free to rotate at different speeds under at least some other operating conditions. Two rotating elements are coupled if they are either rigidly coupled or selectively coupled.Two rotating elements are connected in a driveable manner if a series of gears and shafts is able to transmit power from one to the other, and establishes a fixed rotational speed ratio between the two elements.

[0013] Fig. Figure 1 schematically illustrates a kinematic arrangement for a power-split hybrid electric vehicle. Power is provided by a motor 10, which is rigidly coupled to a planet carrier 12 via a transmission input shaft 11. A set of planet gears 14 is mounted to rotate with respect to the carrier 12. A sun gear 16 and a ring gear 18 are each mounted to rotate about the same axis as the carrier 12 and mesh with the planet gears 14. A generator 20 is rigidly coupled to the sun gear 16. A countershaft gear 22 is rigidly coupled to the ring gear 18 and meshes with a countershaft gear 24. The countershaft gear 24 is rigidly coupled to countershaft gears 26 and 28 via a shaft 30. A countershaft gear 32 meshes with the countershaft gear 28 and is rigidly coupled to a motor 34. The countershaft gear 26 meshes with a countershaft gear 36, which is the input to the differential gear 38.The differential gear 38 drives wheels 40 and 42, allowing slight differences in rotational speed when the vehicle goes around a curve.

[0014] The generator 20 and the motor 34 are both reversible electrical machines. The terms generator and motor are used for descriptive purposes only. Both machines are capable of converting electrical power into mechanical power or vice versa. For example, each machine can be a synchronous motor in combination with a three-phase inverter. Both machines are electrically connected to a battery 44. In some cases, the motor 10 can generate more power than is supplied to the vehicle wheels 40 and 42, with the excess power stored in the battery 44. In other cases, power can flow from the battery 44, allowing the motor 10 to generate less power than the vehicle's immediate needs. For example, the motor 10 can be off, while power to drive the vehicle is supplied by the battery 44.

[0015] The powertrain of the Fig. 1 can be operated in a stepless mode in which the battery 44 neither supplies nor receives power. The torque applied to the generator 20 and the torque applied to the reduction gear 22 are both related to the torque generated by the motor 10, based on the number of teeth on the sun gear 16 and the number of teeth on the ring gear 18. In particular, the following applies: Tgen=NsunNsun+NringTeng Tgear22=NringNsun+NringTeng where T eng The torque generated by motor 10 is T gen The torque absorbed by generator 20 is T gear22 The torque absorbed by gear 22 is N sun The number of teeth on the sun gear is 16 and N ring The number of teeth on the ring gear is 18. The motor speed is a weighted average of the generator speed and the speed of the gear 22. ωeng=NsunNsun+Nringωgen+NringNsun+Nringωgear22

[0016] When the vehicle moves slowly, gear 22 rotates slowly and generator 20 rotates faster than motor 10. The power generated by the motor is divided by the planetary gear set. Part of the power is transmitted mechanically to shaft 30, from carrier 12 to ring gear 18 to gear 22 to gear 24. The remaining power is transmitted from sun gear 16 to generator 20, which converts the power into electrical power. Motor 34 converts the electrical power into mechanical power, which is transmitted to shaft 30 via gears 32 and 28. Although both power transmission paths are subject to some parasitic losses, conversions between electrical and mechanical power typically result in greater power loss than purely mechanical transmission. As the ratio of the rotational speed of shaft 30 to the rotational speed of motor 10 increases, a point is reached at which generator 10 stops.At this ratio, all power is transmitted mechanically. At higher overdrive ratios, generator 20 rotates in the opposite direction to motor 10 and acts as a single motor. Power circulates from generator 20 through the mechanical power flow path to shaft 30, through gears 28 and 32 to motor 34, which acts as a generator. The parasitic losses associated with power circulation may render operation inefficient at overdrive ratios.

[0017] The powertrain of the Fig. 1 includes an additional power flow path to provide efficient power transmission at overdrive speed ratios. Specifically, a countershaft gear 46 is mounted to rotate around the transmission input shaft 11. A countershaft gear 48 is fixedly coupled to shaft 30 and meshes with a countershaft gear 46. A clutch 50 selectively couples the countershaft gear 46 to shaft 11. When the clutch 50 is engaged, power is mechanically transferred from the motor 10 to shaft 30 via gears 46 and 48. In this fixed-ratio operating mode, the battery 44 can provide additional power via either the generator 20 or the motor 34, or it can be charged via any electric machine. Using the fixed-ratio mode for continuous power driving significantly reduces fuel consumption because both the engine and transmission operate efficiently.

[0018] Since the clutch 50 is the only clutch in the drivetrain of the Fig. If the use of a hydraulically actuated clutch is 1, it would require the addition of a pump and a valve body. Therefore, a different method for actuating clutch 50 is desired. Fig. Figures 2 to 4 illustrate an electromagnetically actuated jaw coupling suitable for selectively coupling the gear 46 to the shaft 11.

[0019] Fig. Figure 2 is a pictorial view of an electromagnetic coupling used in the hybrid powertrain of the Fig. 1 is suitable. An inner raceway ring comprises two rings 52 and 54. When used on the hybrid powertrain of the Fig. Each of these rings is rigidly coupled to the input shaft 11. An outer race 54 is rigidly coupled to the gear 46. A plurality of pawls 58 are held in the outer race and rotate with the outer race. In the Fig. In the 2 illustrated disengaged state, the pawls are stowed in the outer running ring so that they do not touch the inner running ring.

[0020] In this state, relative rotation between the inner and outer races is possible in any direction. Springs can bias the pawls into this disengaged position. The outer surfaces of the inner race's rings have teeth 60. When the clutch is engaged, the pawls 58 pivot to engage these teeth. The tooth profile is tapered on one side, allowing relative rotation in one direction but not the other. Fig. In the orientation shown in Figure 2, the rising profile of the teeth pushes the pawl back toward the outer race when the inner race rotates clockwise relative to the outer race. However, the teeth prevent the inner race from rotating counterclockwise relative to the outer race. (A few degrees of rotation may occur before the pawl engages.)

[0021] Fig. Figure 3 shows a truncated pictorial view of the clutch 50. The left and right rings of the inner race are connected by a plurality of rods 62. The pawls are held axially in the outer race 56 by a retaining ring 64. An electromagnetic coil lies radially inside the inner and outer races and concentrically with them. The coil includes a magnetically conductive coil housing 66 with a U-shaped cross-section. Electrical windings 68 are wound circumferentially in the gap of the coil housing. When the windings are energized, a magnetic field is generated in the coil housing. One side of the U is axially aligned with the left ring of the inner race, while the other side of the U is axially aligned with the right ring of the inner race.The radial gaps between the coil housing 66 and the left and right rings 54 and 52 are set as small as is practicable in accordance with free rotation. The rings 52 and 54 are made of a magnetically conductive material, while the bars 62 that separate them are made of a magnetically non-conductive material. Thus, when the coil is energized, one ring becomes a magnetic north pole and the other ring becomes a magnetic south pole. The pawls are made of a magnetically conductive material so that they are attracted to the left and right rings when the coil is energized, thereby engaging the clutch. Once the pawls come into contact with the left and right rings, they complete the magnetic circuit. Thus, when the magnetic circuit is complete except for the two small air gaps, little power is required to hold the pawls in this state. Fig. Figure 4 is an exploded view showing the assembly of the coupling 50.

[0022] Fig. Figure 5 is a cross-section of the coupling as it appears in the kinematic arrangement of the Fig. The coil 66 is rigidly coupled to a gearbox housing 70. A stationary coil is advantageous because no slip rings or other means are required to transmit electrical power to the windings. The inner race is rigidly coupled to the input shaft 11. It should be noted that the left ring 54 is further apart than the right ring 52. The two rings can be slightly offset circumferentially so that the torque is transmitted completely or almost completely through the left ring 54. As a result, the non-magnetic rods 62 do not have to transmit any significant torque. The right ring 52 serves a magnetic function but does not bear any significant mechanical load. The outer race 56 is rigidly coupled to the gear 46, which is mounted for rotation about the input shaft 11.In alternative embodiments, the toothed rings can form an outer running ring, and the pawls can be held in place by an inner running ring. In this case, the coil would lie radially outside the outer running ring. The tooth profile would be on the radially inner surface of the outer running ring, while a cylindrical surface of each ring would face outwards, adjacent to the coil. Fig. 6 and Fig. Figure 7 shows the locking pawl in the extended or retracted position.

[0023] Friction clutches are capable of transmitting torque between components rotating at different speeds. The transmitted torque causes the components to synchronize their rotational speeds. A dog clutch, on the other hand, engages components selectively by establishing positive engagement, as opposed to frictional engagement. Therefore, a dog clutch can only transmit torque between components rotating at the same speed. Engaging a dog clutch when the components are rotating at different speeds would create a sudden change in rotational speeds, which would likely be unpleasant for vehicle occupants and could even cause transmission components to fail. Thus, controlling the rotational speeds of the components at the moment of clutch engagement is crucial.

[0024] When the vehicle is driving slowly, the transmission of the Fig.1. Operated in stepless mode. No current is supplied to coil 68, so clutch 50 is disengaged.

[0025] If the controller determines that fixed-ratio overdrive operation is preferred, it first switches to a higher overdrive speed ratio than the fixed ratio. The controller then sends current to coil 68, causing the pawls to pivot. The clutch does not engage immediately because, under this condition, gear 46 rotates faster than shaft 11. The controller, still managing the speed ratio in stepless mode, allows the motor speed to gradually increase. Once the fixed ratio is reached, clutch 50 engages.

[0026] Although exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms included in the claims. The terms used in the description are descriptive and not limiting, and it is understood that various modifications may be made without departing from the spirit and scope of the disclosure. As previously described, the features of different embodiments can be combined to form further embodiments of the invention that may not have been expressly described or illustrated.While various embodiments may have been described as advantageous or preferred over other embodiments or implementations of the prior art with respect to one or more desired properties, the person skilled in the art recognizes that one or more features or properties may be compromised in order to achieve desired overall system attributes, which depend on the specific application and implementation. Thus, embodiments described as less desirable than other embodiments or implementations of the prior art with respect to one or more properties are not outside the scope of disclosure and may be desirable for certain applications.

Claims

[1] Electromagnetically actuated clutch (50), comprising: a non-rotating electromagnetic coil (66, 68); a toothed inner running ring (52, 54) which is mounted for rotation about the coil (66, 68), wherein the inner running ring (52, 54) has a left (54) and a right (52) magnetically conductive ring (52, 54) which are magnetically separated from each other; an outer race ring (56) which is mounted for rotation about the inner race ring (52, 54); and a magnetically conductive pawl (58) which is mounted and pivotable for rotation with the outer running ring (56) in order to engage with the left and right rings (52, 54) in response to current in the coil (66, 68). [2] Electromagnetically actuated clutch (50) according to claim 1, wherein both the left (54) and the right ring (52) have teeth. [3] Electromagnetically actuated clutch (50) according to claim 2, wherein the teeth of a first of the left and right ring (54, 52) are offset from the teeth of a second of the left and right ring (54, 52) so that an engagement force is distributed disproportionately on the first of the left and right ring (54, 52). [4] Electromagnetically actuated clutch (50) according to claim 1, wherein the inner race (52, 54) has a tooth profile configured to prevent relative rotation between the inner race (52, 54) and the outer race in one direction in response to the engagement of the pawl (58), while allowing relative rotation in the opposite direction when the pawl (58) is engaged. [5] Electromagnetically actuated clutch (50) according to claim 1, wherein the outer running ring (56) is not magnetically conductive. [6] Clutch (50), comprising: an electromagnetic coil (66, 68); a left (54) and a right (52) magnetically conductive ring (54, 52), each having a cylindrical surface adjacent to the coil (66, 68) and a toothed surface opposite the cylindrical surface, wherein the left and right rings (52, 54) are magnetically separated from each other; a bearing ring (56) which is mounted for rotation in relation to the rings (52, 54); and a magnetically conductive pawl (58) which is pivotable with respect to the running ring (56) in order to engage with the left and right rings (52, 54) in response to current in the coil (66, 68). [7] Coupling (50) according to claim 6, wherein: the electromagnetic coil (66, 68) is non-rotating; and the left and right rings (52, 54) and the running ring (56) are mounted for rotation. [8] Coupling (50) according to claim 6, wherein: the electromagnetic coil (66, 68) lies radially inside the left and right rings (52, 54); and the running ring (56) lies radially outside the left and right rings (52, 54). [9] Coupling (50) according to claim 6, wherein the left (54) and the right ring (52) are rigidly coupled to each other. [10] Gearbox, comprising: an electromagnetic coil (66, 68) which is fixed to a gearbox housing (70); a left and a right magnetically conductive ring (52, 54) which are each rigidly coupled to an input wave (11) and magnetically separated from each other; an outer race (56) which is mounted for rotation with respect to the input shaft (11); and a magnetically conductive pawl (58) which is mounted and pivotable for rotation with the outer running ring (56) in order to engage with the left and right rings (52, 54) in response to current in the coil (66, 68). [11] Gearbox according to claim 10, further comprising: a planet carrier (12) which is rigidly coupled to the input wave (11); a plurality of planetary gears (14) which are mounted to rotate in relation to the planet carrier (12); a sun gear (16) that meshes with the planet gears (14) and is driven by a generator (20); and a ring gear (18) that meshes with the planet gears (14) and is driven by a gear output. [12] Transmission according to claim 11, further comprising a motor (34) which is driven and connected to the transmission output. [13] Gearbox according to claim 12, wherein the outer running ring (56) is driven to the gearbox output.

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