ELECTRIC PROPULSION SYSTEMS

Abstract

A drive mechanism for an electric propulsion system that comprises an electric machine is disclosed. The drive mechanism comprises a drive shaft with a longitudinal axis A, an engagement means, and a disconnect mechanism. The engagement means comprises a drive shaft engagement element and an electric machine engagement element. The drive engagement element comprises a first and second shaft gear ring, and each shaft gear ring is supported on the drive shaft. Each shaft gear ring comprises a plurality of gear teeth which are circumferentially disposed around the drive shaft, and the gear teeth extend radially outward from the drive shaft.

Claims

1. A drive mechanism for an electric propulsion system that comprises an electric machine, in which: the drive mechanism comprises a drive shaft with a longitudinal axis A, an engagement means, and a disconnect mechanism; the engagement means comprises a drive shaft engagement element and an electric machine engagement element; the drive shaft engagement element comprises a first and second shaft gear ring, and each shaft gear ring is supported on the drive shaft; each shaft gear ring comprises a plurality of gear teeth which are circumferentially disposed around the drive shaft, and the gear teeth extend radially outward from the drive shaft; the gear teeth of the first shaft gear ring have an axial length L1; the first and second shaft gear rings are axially spaced from each other along the drive shaft by a distance L2; the electric machine engagement element comprises a first and second gear set; the first and second gear sets each comprise a plurality of gear teeth which are configured to mesh with the gear teeth of the first and second shaft gear rings respectively; the gear teeth of the first gear set have an axial length L3; the first and second gear sets are separated from each other by a length L4 in the axial direction, length L1 is less than length L4, length L3 is less than length L2; the disconnect mechanism is configured to reversibly move one of at least part of the drive shaft engagement element and at least part of the electric machine engagement element relative to the other of the engagement elements in an axial direction between a first position and a second position; in which in the first position the gear teeth of the first shaft gear ring are meshed with the gear teeth of the first gear set and the gear teeth of the second shaft gear ring are meshed with the gear teeth of the second gear set, and in the second position the gear teeth of the first shaft gear ring are axially between the first and second gear sets and the gear teeth of the first shaft gear ring are not meshed with the gear teeth of the first or second gear sets.

2. A drive mechanism according to claim 1, in which the drive mechanism is for use with two or more electric machines; the drive mechanism comprises two or more engagement means, each engagement means is associated with a common drive shaft, and the engagement means are axially spaced along the drive shaft.

3. A drive mechanism according to claim 2, in which each engagement means is substantially the same as the other engagement means.

4. A drive mechanism according to claim 1, in which length L1 is approximately equal to length L3.

5. A drive mechanism according to claim 1, in which the drive shaft engagement element of at least one engagement means comprises n(1) shaft gear rings, and n(2) gear sets, where n(1) is greater than two, and n(2) is greater than two.

6. A drive mechanism according to claim 1, in which at least one of the gear sets of at least one engagement means comprises a second gear ring.

7. A drive mechanism according to claim 6, in which each second gear ring is co-axial with the drive shaft, and the gear teeth of each second gear ring extend radially inwards.

8. A drive mechanism according to claim 6, in which the gear teeth of each shaft gear ring are male splines, and the gear teeth of each gear set are female splines.

9. A drive mechanism according to claim 1, in which the electric machine engagement element of at least one engagement means further comprises a hollow shaft, and each gear set of the electric machine engagement element is supported on the hollow shaft.

10. A drive mechanism according to claim 1, in which the drive shaft further comprises a first stop element, one of the electric machine engagement elements of one of the engagement means further comprises a second stop element, and the first and second stop elements are so configured and located that they abut when the drive shaft engagement element and the electric machine engagement element of that engagement means are in the second position relative to each other.

11. A drive mechanism according to claim 10 in which each of the first and second stop elements comprises a stop surface, the stop surfaces of the first and second stop elements abut, and one or both of the stop surfaces comprise or are coated with a low friction material.

12. A drive mechanism according to claim 11, in which each engagement means comprises a disconnect mechanism, the disconnect mechanism of each engagement means causes at least part of the electric machine engagement element to move axially relative to the drive shaft engagement element of that engagement means, and the disconnect mechanism of each engagement means operates independently of the disconnect mechanisms of each other engagement means.

13. A drive mechanism of according to claim 1, in which the drive mechanism is so configured that operation of the disconnect mechanism causes the relative movement of one of at least part of the drive shaft engagement element and at least part of electric machine engagement element relative to the other of the drive shaft engagement element and electric machine engagement element for each engagement means.

14. A drive mechanism according to claim 1, in which at least one disconnect mechanism comprises an actuator.

15. A drive mechanism according to claim 14, in which the actuator is a solenoid mechanism.

16. An aeroplane or wheeled vehicle comprising an electric propulsion system, in which the electric propulsion system comprises at least one electric machine and at least one drive mechanism according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described and explained by way of example with reference to the accompanying drawings in which:

[0039] FIG. 1 shows a schematic view of a first embodiment of an aeroplane incorporating a first embodiment of a drive mechanism according to the present disclosure;

[0040] FIG. 2 shows a schematic view of a second embodiment of an aeroplane incorporating a second embodiment of a drive mechanism according to the present disclosure;

[0041] FIG. 3 shows a first schematic view of the drive mechanism of FIG. 1;

[0042] FIG. 4 shows a second schematic view of the drive mechanism of FIG. 1;

[0043] FIG. 5 shows a schematic view of an embodiment of the drive mechanism of FIG. 2.

DETAILED DESCRIPTION

[0044] In the following discussions of the accompanying drawings, where the same element is present in a more than one embodiment the same reference numeral is used for that element throughout. Where there are similar elements, similar reference numerals (the same numeral plus a multiple of 100) are used.

[0045] With reference to FIG. 1, an aeroplane 2 includes a propulsion system 4. The propulsion system 4 includes a propeller 6 which has a hub 8. The hub 8 is connected to a first end 12 of a drive shaft 10. Between the first end 12 and a second end 14 of the drive shaft 10 an electric machine 18 is engaged with the drive shaft 10 via a drive mechanism 16.

[0046] With reference to FIG. 2, an aeroplane 102 includes a propulsion system 104. The propulsion system 104 includes a propeller 6 which has a hub 8. The hub 8 is connected to a first end 112 of a drive shaft 110. Between the first end 112 and a second end 114 of the drive shaft 110 three electric machines 118A, 118B, 118C are each engaged with the drive shaft 110 via a drive mechanism 116A, 116B, 116C respectively. In the illustrated embodiment in FIG. 2 each electric machine 118A, 118B, 118C has the same configuration as electric machine 18 shown in FIG. 1.

[0047] With reference to FIGS. 3 and 4, and with continued reference to FIG. 1, the drive shaft 10 has a longitudinal axis A and is comprised of a first portion 20 that extends from the first end 12 to a radially inwardly extending shoulder or stop element 22, and a second portion 24 which extends from the shoulder 22 to the second end 14. Adjacent the second end 14 a stop ring 32 extends circumferentially around and radially outward from the radially outer surface 34 of the drive shaft 10.

[0048] Located on the radially outer surface 34 of the second portion 24 of the drive shaft 10 is a drive engagement element 56 which is comprised of four gear rings. Each of the gear rings has the form of a male or external set of splines 36. The splines 36 are spaced circumferentially around the outer surface 34 and extend radially outwardly. Each of the splines 36 has an axial length L1 in the direction of axis A.

[0049] The splines 36/each gear ring are axially spaced from the axially adjacent splines 36/gear ring(s) by a distance L2. In other non-illustrated examples of the drive mechanism of the present disclosure a different number of gear rings may be present. That different number may be two, three, or more than four. The number of gear rings/splines included in the drive engagement element may be determined by the desired maximum torque transmission between the drive shaft and the electric machine.

[0050] The splines 36 of the gear ring that is axially closest to the second end 14 of the drive shaft 10 are located on the gear shaft 10 so that the end of the splines 36 closest to end 14 abut the stop ring 32.

[0051] The drive mechanism 16 includes a hollow shaft 26 which is co-axial with the drive shaft 10. The drive shaft 10 extends through the hollow shaft 26, and the second portion 24 of the drive shaft 10 is substantially surrounded by the hollow shaft 26 together with the shoulder 22 and a part of the first portion 20 of the drive shaft 10 which is adjacent to the shoulder 22. The surrounded parts of the drive shaft 10 are to be considered to be part of the drive mechanism 16 for the purposes of the present disclosure.

[0052] The hollow shaft 26 has a radially outwardly facing surface 40 and a radially inwardly facing surface 28. Located on the radially inwardly facing surface 28 of the hollow shaft 26 is an electric machine engagement element 58. The electric machine engagement element 58 includes four gear sets. Each of the gear sets has the form of an female or internal set of splines 30. The splines 30 are spaced circumferentially around the inner surface 28 and extend radially inwardly. Each of the splines 30 has an axial length L3 in the direction of axis A. The splines 30 of each gear set are axially spaced from the splines 30 of the adjacent gear set(s) by a distance L4. In other non-illustrated examples of the drive mechanism of the present disclosure a different number of gear sets may be present. That different number may be two, three, or more than four.

[0053] In the embodiment illustrated in FIGS. 3 and 4, lengths L1 and L3 are same as each other as are distance L2 and L4.

[0054] Adjacent to the of the splines 30 of the gear set furthest from the second end 14 of the drive shaft 10 end furthest from the second end 14 of the drive shaft 10 is a stop element or stop block 38. The face of the stop element 38 furthest from the end 14 of the drive shaft 10 is coated with a low friction material.

[0055] The electric machine 18 includes a casing 50 within which a stator 48 is fixed and an armature 46 is supported on two or more bearings (not shown). The armature 46 is caused to rotate when electrical power is supplied to the electric machine 18. The armature 46 supports or is coupled to a set of female or internal drive splines 44. The electric machine 18 is so configured that the set of female drive splines 44 is adapted to follow a circumferential path around the axis A.

[0056] Located on the radially outward facing surface 40 of the hollow shaft 26 are a set of male or external drive splines 42. The hollow shaft 26 is so configured that the male drive splines 42 mesh with the set of female drive splines 44 coupled to the armature 46.

[0057] Supported on the case 50 of the electric machine 18 is a disconnect mechanism in the form of a solenoid 52. The solenoid 52 is coupled to the hollow shaft 26 via a coupling 54. The engagement of the coupling 54 to the hollow shaft 26 is such that the coupling remains engaged to the hollow shaft 26 when the hollow shaft 26 is rotating around the axis A.

[0058] Actuation of the solenoid 52 causes the hollow shaft 26 to be moved between a first position shown in FIG. 3 (in which the gear sets/splines 30 on the hollow cylinder 26 and the gear rings/splines 36 on the drive shaft 10 are fully engaged or meshed with each other), and a second position shown in FIG. 4 (in which the gear sets/splines 30 on the hollow cylinder 26 and the gear rings/splines 36 on the drive shaft 10 are not engaged or meshed with each other).

[0059] When the hollow cylinder 26 is in the first position the splines 30 closest to the end 14 of the drive shaft 10 abut the stop ring 32, and the hollow cylinder 26 is thus prevented from traveling any further toward or past the end 14 of the drive shaft 10.

[0060] When the hollow cylinder 26 is in the second position the stop element 38 abuts the shoulder or stop element 22 and prevents the hollow cylinder 26 moving too far away from the second end 14 of the drive shaft 10 and the splines 30 and 36 reengaging with each other.

[0061] The configuration of the set of female drive splines 44 and set of male drive splines 42 is such that those drive splines 42, 44 remain meshed or engaged with other throughout the movement of the hollow shaft 26 between the first and second positions.

[0062] With further reference to FIG. 2, in a first embodiment of the aeroplane 102, each of the drive mechanisms 116A, 116B, 116C are configured in the same fashion as drive mechanism 16 described above in connection with FIGS. 3 and 4. In particular, the hollow shafts 26 of drive mechanism 116A, 116B, 116C are separate from each other and each of the actuators 52 of drive mechanisms 116A, 116B, 116C are independently controllable by suitable control means (not shown). As a result, each of electric machines 18A, 18B, 18C can be engaged with or disengaged from the drive shaft 110 independently of the other electric machines. Thus the propeller 6 can be driven by or drive one, two or three of the electric machines 18A, 18B, 18C.

[0063] With reference to FIG. 5 and with further reference to FIG. 2, in a second embodiment of the aeroplane 102 the drive shaft 110 has a longitudinal axis A and is comprised of a first portion 120 that extends from the first end 112 to a radially inwardly extending shoulder or stop element 122, and a second portion 124 which extends from the shoulder 122 to the second end 114. Adjacent the second end 114 a stop ring 132 extends circumferentially around and radially outward from the radially outer surface 134 of the drive shaft 110.

[0064] Located on the radially outer surface 134 of the second portion 124 of the drive shaft 110 are three drive engagement elements 156A, 156B, 156C which are axially spaced along the second portion 124 of the drive shaft 110. Each of the drive engagement elements 156A, 156B, 156C is comprised of four gear rings. The gear rings each have the form of a set of male or external splines 136A, 136B, 136C respectively (for clarity not all of not all of splines 136A, 136B, 136C are labelled).

[0065] The splines 136A, 136B, 136C are spaced circumferentially around the outer surface 134 and extend radially outwardly. Each of the splines 136A, 136B, 136C has an axial length L1 in the direction of axis A. Within each drive engagement element 156A, 1568, 156C the splines 136A, 136B, 136C/each gear ring are axially spaced from the axially adjacent splines 136A, 1368, 136C/gear ring(s) by a distance L2. In other non-illustrated examples of the drive mechanism of the present disclosure a different number of gear rings in each drive engagement element may be present. That different number may be two, three, or more than four. There may be different numbers of gear rings in one or more of the drive engagement elements. The number of gear rings/splines included in each drive engagement element may be determined by the desired maximum torque transmission between the drive shaft and the electric machine with which the drive engagement element is associated.

[0066] The splines 136 of the gear ring that is axially closest to the second end 114 of the drive shaft 110 are located on the gear shaft 110 so that the end of the splines 136C closest to end 114 abut the stop ring 132.

[0067] The drive mechanisms 116A, 1168, 116C share a common hollow shaft 126 which is co-axial with the drive shaft 110. The drive shaft 110 extends through the hollow shaft 126, and the second portion 124 of the drive shaft 110 is substantially surrounded by the hollow shaft 126 together with the shoulder 122 and a part of the first portion 120 of the drive shaft 110 which is adjacent to the shoulder 122. The surrounded parts of the drive shaft 110 are to be considered to be part of the drive mechanisms 116A, 1168, 116C for the purposes of the present disclosure.

[0068] The hollow shaft 126 has a radially outwardly facing surface 140 and a radially inwardly facing surface 128. Located on the radially inwardly facing surface 128 of the hollow shaft 126 are three electric machine engagement elements 158A, 1588, 158C. The electric machine engagement elements 158A, 1588, 158C each include four gear sets. Each of the gear sets has the form of an female or internal set of splines 130A, 130B, 130C respectively (for clarity not all of not all of splines 130A, 130B, 130C are labelled). The splines 130A, 130B, 130C are spaced circumferentially around the inner surface 128 and extend radially inwardly. Each of the splines 130A, 130B, 130C has an axial length L3 in the direction of axis A. The splines 130A, 130B, 130C/each gear set are axially spaced from the axially adjacent splines 30/gear set(s) by a distance L4. In other non-illustrated examples of the drive mechanism of the present disclosure a different number of gear sets may be present. That different number may be two, three, or more than four. There may be different numbers of gear sets in one or more of the electric machine engagement elements. The number of gear sets/splines included in each electric machine engagement element may be determined by the desired maximum torque transmission between the drive shaft and the electric machine with which the electric machine engagement element is associated.

[0069] In the embodiment illustrated in FIG. 5, lengths L1 and L3 are same as each other as are distance L2 and L4.

[0070] Adjacent to the of the splines 130A of the gear set furthest from the second end 114 of the drive shaft 110 end furthest from the second end 114 of the drive shaft 110 is a stop element or stop block 138. The face of the stop element 138 furthest from the end 114 of the drive shaft 110 is coated with a low friction material.

[0071] Each of the electric machines 118A, 1188, 118C includes a casing 150A, 1508, 150C within which a stator 148A, 148B, 148C is fixed and an armature 146A, 146B, 146C is supported on two or more bearings (not shown). The armatures 146A, 1468, 146C are caused to rotate when electrical power is supplied to the electric machines 118A, 1188, 118C. Each of the armatures 146A, 146B, 146C support or are coupled to a set of female or internal drive splines 144A, 1448, 144C respectively. The electric machines 118A, 1188, 118C are so configured that the set of female drive splines 144A, 144B, 144C are each adapted to follow a circumferential path around the axis A.

[0072] Located on the radially outward facing surface 140 of the hollow shaft 126 are three sets of male or external drive splines 142A, 142B, 142C. The hollow shaft 126 is so configured that the male drive splines 142A, 142B, 142C mesh with the female drive splines 144A, 144B, 144C coupled to the armature 146A, 146B, 146C respectively.

[0073] Supported on the case 1508 of the electric machine 1188 is a disconnect mechanism in the form of a solenoid 152. The solenoid 152 is coupled to the hollow shaft 126 via a coupling 154. The engagement of the coupling 154 to the hollow shaft 126 is such that the coupling remains engaged to the hollow shaft 126 when the hollow shaft 126 is rotating around the axis A.

[0074] Actuation of the solenoid 152 causes the hollow shaft 126 to be moved between a first position in which the gear sets/splines 130A, 130B, 130C on the hollow cylinder 126 and the gear rings/splines 136A, 136B, 136C on the drive shaft 110 are fully engaged or meshed with each other, and a second position shown in FIG. 5 (in which the gear sets/splines 130A, 130B, 130C on the hollow cylinder 126 and the gear rings/splines 136A, 136B, 136C on the drive shaft 110 are not engaged or meshed with each other).

[0075] When the hollow cylinder 126 is in the first position the splines 130C closest to the end 114 of the drive shaft 110 abut the stop ring 132, and the hollow cylinder 126 is thus prevented from traveling any further toward or past the end 114 of the drive shaft 110.

[0076] When the hollow cylinder 126 is in the second position the stop element 138 abuts the shoulder or stop element 122 and prevents the hollow cylinder 126 moving too far away from the second end 114 of the drive shaft 110 and the splines 130A, 130B, 130C and 136A, 136B, 136C reengaging with each other.

[0077] The configuration of the set of female drive splines 144A, 144B, 144C and set of male drive splines 142A, 142B, 142C is such that those drive splines 142A, 142B, 142C, 144A, 144B, 144C remain meshed or engaged with other throughout the movement of the hollow shaft 126 between the first and second positions.

[0078] The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the disclosure. Still other modifications which fall within the scope of the present disclosure will be apparent to those skilled in the art, in light of a review of this disclosure.

[0079] Various aspects of the drive mechanisms disclosed in the various embodiments may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described above. This disclosure is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Although particular embodiments have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects. The scope of the following claims should not be limited by the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the description as a whole.