TORQUE TRANSFER DEVICE OF A ROTATING MACHINE

Abstract

Torque Transfer Member of a Rotating Machine The present subject matter relates to a rotating machine (100) which comprises a stator, a rotor and a torque transfer member (104). The stator is rigidly mounted within a housing (116). The rotor is arranged coaxially with the stator and mounted on a rotor shaft (102). The rotor shaft (102) is rotatable about an axis of rotation (114). The rotor shaft (102) passes through a front bearing (123) mounted on a drive end (118) of the housing (116) and exits the housing (116) from this drive end (118). The torque transfer member (104) is of substantially cylindrical shape. The torque transfer member (104) is mounted on the rotor shaft (102). The torque transfer member (104) includes flat surface portions (108) that are formed at least partially along the outer periphery of the torque transfer member (106).The flat surface portions (108) extend in a direction parallel to the axis of rotation (114). (Figure 1B).

Description

Title of the invention: TORQUE TRANSFER DEVICE OF A ROTARY MACHINE FIELD OF THE INVENTION

[0001] The present subject matter relates to the attachment of a torque transfer element to a shaft, and more particularly to the attachment of a torque transfer element to a rotor shaft of a rotating machine used for traction purposes in automotive applications.

[0002] CONTEXT

[0003] Rotating machines are widely used in automotive applications, particularly as a traction motor. Rotating machines typically comprise a stator and a rotor arranged coaxially, the rotor being configured to rotate about an axis of rotation. The rotor is mounted on a rotor shaft which extends from the housing to mechanically interact with a pulley or sprocket to facilitate torque transfer. The rotor shaft is supported by a front bearing and a rear bearing attached to both ends of the housing. In a known arrangement, the rotor shaft and the front bearing are in an interference fit and the pulley (or sprocket) is assembled onto the rotor shaft. In a configuration where the rotor shaft and the front bearing are in an interference fit, the pulley (or sprocket) is placed directly onto the front bearing and tightened by a nut.In the configuration where the above-mentioned fit is maintained, a collar (or reinforcing ring) may be used between the front bearing and the pulley or sprocket for efficient torque transfer; in addition, the pulley or sprocket is tightened by a nut.

[0004] For the arrangements described above, when tightening the pulley or sprocket, the shaft is held rigidly by its torx provided at the end of the shaft while the nut is turned and tightened. It is also possible to perform reverse tightening, the nut being held rigidly while the shaft is turned to the address . These methods of tightening the nut on the shaft are favorable when the diameter of the sprocket is large and the rotor shaft has a large enough diameter for the Torx to withstand a large tightening torque. In the case where the diameter of the sprocket or pulley is small, a smaller rotor shaft is required. However, a rotor shaft with a smaller diameter implies that the torx is not large enough; and the probability of the torx breaking when applying a high torque, during tightening, is high.It is therefore important, in a scenario where a small rotor shaft and a small pinion (or pulley) are used, to ensure that the tightening of the nut is done without detrimental effects on the structural integrity of the aforementioned components.

[0005] Therefore, the technical problem to be solved by the present object is how to assemble a small diameter sprocket, or pulley, to a small diameter rotor shaft while ensuring that none of the aforementioned components are structurally compromised. Summary of the invention

[0006] The present object aims to solve the above-mentioned technical problem in conventional rotating machines. The present object finds a particularly advantageous application in rotating machines such as alternators, alternator starters, or even reversible machines or electric motors. A reversible machine is a rotating machine which operates reversibly, on the one hand as an electric generator in alternator function, and on the other hand as an electric motor, for example to start the thermal engine of a motor vehicle. The rotating electric machine described here can also be used as a traction motor for hybrid or electric vehicles, preferably for two- or three-wheel applications.

[0007] The present subject matter relates to a rotating machine comprising: a stator, rigidly mounted within a housing; a rotor arranged coaxially with the stator and mounted on a rotor shaft rotatable about an axis of rotation, wherein the rotor shaft passes through a front bearing mounted on a drive end of the housing and extends out of the housing from said drive end; and a substantially cylindrically shaped torque transfer member mounted on the rotor shaft, the torque transfer member comprising flat surface portions which are formed at least partially along the outer periphery of the torque transfer member and which extend in a direction parallel to the axis of rotation.The torque transfer member is thus configured such that a tool comprising jaws can clamp the flat surface portions while tightening a fastener onto the torque transfer member. As a result, the requirement for a torx on the rotor shaft is eliminated. Furthermore, a small diameter rotor shaft can be used and, therefore, the torque transfer member can be of small diameter.

[0008] According to an example of the present subject matter, the outer periphery of the torque transfer member includes two flat surface portions that are positioned parallel to each other, each of these flat surface portions extending in the direction parallel to the rotational axis. Accordingly, a tool, such as a two-jaw clamp or the like, can clamp the torque transfer member by pressing on the flat surface portions while a fastener is being tightened.

[0009] According to one aspect of the present subject matter, the torque transfer member includes a friction surface at least partially formed on an inner wall, the friction surface being adapted for an interference fit with the rotor shaft. The inner wall defines a wall exposed by a bore of the torque transfer member. The friction surface prevents slippage of the torque transfer member along the rotor shaft.

[0010] According to an example of the present subject matter, the friction surface protrudes from the inner wall toward the axis of rotation. Therefore, when mounting the torque transfer member on the rotor shaft, the protruding friction surface engages with the rotor shaft. In one aspect, the torque transfer member is formed such that the inner diameter has a reduced hardness obtained, for example, by a heat treatment process.

[0011] According to an example of the present subject matter, the friction surface is a smooth surface, or a knurled surface, or includes internal splines that engage in an interference fit with an engagement surface on the rotor shaft. The engagement surface is formed on the outer surface of the rotor shaft.

[0012] According to another aspect of the present subject matter, the engaging surface on the rotor shaft is a smooth surface, a knurled surface, or includes external splines. Depending on the configuration of the friction surface of the torque transfer member, the engaging surface on the rotor shaft is either a smooth surface, a knurled surface, or includes external splines. Accordingly, an effective interference fit is provided to guarantee a frictional force between the torque transfer member and the rotor shaft; and the possibilities of slippage are effectively eliminated.

[0013] According to an example of the present subject matter, the torque transfer element is either a sprocket, a pulley, or a pinion. In the example where the torque transfer element is a sprocket, a direct transfer of torque may be made, for example, to another sprocket, or a gear, or a gear reducer, coupled to a wheel, or the like.

[0014] According to an example of the present subject, a first end of the torque transfer element is in contact with an inner ring of the front bearing and a second end is in contact with a fastener adapted to secure said torque transfer element to the rotor shaft. The aforementioned arrangement of the torque transfer element with the front bearing and the fastener is suitable for examples where the rotor shaft maintains a clearance with the inner ring of the front bearing. Therefore, an efficient torque transfer occurs between the front bearing and the rotor shaft.

[0015] However, according to another example of the present subject matter, when the rotating machine is configured to include a clearance fit between the front bearing and the rotor shaft, the torque transfer member comprises: a first end that comes into abutting a collar, the collar being sandwiched between the torque transfer element and the inner ring of the front bearing; and a second end which abuts a fastening element adapted to secure said torque transfer element to the rotor shaft. In the aforementioned example, the collar (or reinforcing ring) is arranged on the rotor shaft such that it is sandwiched between the front bearing and the torque transfer element. Therefore, in a scenario where there is such a clearance, optimal torque transfer between the rotor shaft, the front bearing and the collar is ensured.

[0016] According to an example of the present subject, the torque transfer element is a sprocket, a pulley or a toothed wheel. In the example where the torque transfer element is a multi-toothed sprocket, the torque transfer can be to a toothed reducer. In the example where the torque transfer element is a pulley, the torque transfer is to another pulley by means of a belt. In the example where the torque transfer element is a sprocket, the torque transfer to another sprocket is via a chain.

[0017] According to an example of the present subject matter, the torque transfer element is engaged in a speed reducer. The reducer facilitates speed control for traction of a motor vehicle.

[0018] The rotary machine, configured in accordance with the present subject matter, may be used in a motor vehicle to create traction to move the vehicle. While the present subject matter relates to the application of the rotary machine in automotive applications, it is understood that the application may extend to various other industries and may be used in fans, blowers, machine tools, turbines, pumps, compressors, rolling mills, movers, paper mills, etc. Brief description of the drawings

[0019] The features, aspects and advantages of the present invention will be better understood in light of the following description and the accompanying figures. The description refers to the accompanying drawings, in which:

[0020] [Fig.lA] illustrates an exploded view of a rotating machine, a torque transfer element and a fastening element, configured in accordance with the present subject matter; and

[0021] [Fig.lB] illustrates a cross-sectional view of the components described in [Fig.lA], configured in accordance with the present subject matter;

[0022] [Fig.2A] illustrates an isometric view of the torque transfer element, configured in accordance with the present subject matter; and

[0023] [Fig.2B] illustrates a sectional view of the torque transfer element, configured in accordance with the present subject matter;

[0024] [Fig.3] illustrates a rotor shaft of the rotating machine, configured in accordance with the present subject matter;

[0025] [Fig.4A] illustrates an exploded view of the rotating machine, torque transfer member, and attachment, configured in accordance with an example of the present subject matter;

[0026] [Fig.4B] illustrates a sectional view of the components of the rotating machine, configured in accordance with the example shown in [Fig.4A] of the present subject;

[0027] [Fig.5A] illustrates the torque transfer element, configured in accordance with the example shown in [Fig.4A] of the present subject; and

[0028] [Fig.5B] illustrates a rotor shaft of the rotating machine, configured in accordance with the example shown in [Fig.4A] of the present subject.

[0029] The figures are not necessarily to scale and the size of certain parts may be exaggerated to more clearly illustrate the example shown. In addition, the drawings provide examples and / or examples consistent with the description, but the description is not limited to the examples and / or examples provided in the drawings. DETAILED DESCRIPTION

[0030] In the following description, reference is made to the accompanying drawings, which are an integral part of the invention, and in which are illustrated specific embodiments in which the invention may be embodied. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that the embodiments may be combined, or that other embodiments may be used, and that structural and logical modifications may be made without departing from the scope of the present invention. The detailed description which follows is therefore not to be construed in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0031] [Fig.lA] illustrates an exploded view of a rotating machine 100 configured in accordance with the present subject matter. [Fig.lB] illustrates a cross-sectional view of the rotating electric machine 100 assembled and configured in accordance with the present subject matter. For brevity, the following description relates to [Fig.lA] and [Fig.lB] in tandem.

[0032] The rotating machine 100 includes a stator, a rotor, and a torque transfer element 104. The stator is rigidly mounted within a housing 116. The rotor is coaxially disposed with the stator and mounted on a rotor shaft 102. The rotor shaft is rotatable about an axis of rotation 114. Further, the rotor shaft 102 passes through a front bearing 123 mounted on a drive end 118 of the housing 116. The rotor shaft 102 extends out of the housing 116 from the drive end 118 of the housing 116. The torque transfer element 104 is mounted on the rotor shaft 102. The torque transfer member 104 is substantially cylindrical in shape. Further, the torque transfer member 104 includes flat surface portions 108 that are formed at least partially along an outer periphery 106 of the torque transfer member 104. The flat surfaces 108 extend in a direction parallel to the axis of rotation 114.

[0033] According to one aspect of the present subject matter, the torque transfer member 104 is mounted on the rotor shaft 102 which is exposed from the drive end 118 of the housing 116. A tool having claws, or jaws, clamps the surface portions 108, while a fastener 120, such as a nut, is tightened onto the rotor shaft 102 to secure the torque transfer member 104. As a result, an assembled state of the rotating machine 100, illustrated in [Fig.lB], is achieved.

[0034] In one example, the torque transfer member 104 includes two flat surface portions 108 disposed on the outer periphery 106 such that each flat surface portion 108 is parallel to one another and extends in a direction parallel to the axis of rotation 114. In this example, a tightening tool for the torque transfer member 104 may include two jaws that clamp onto the two flat surface portions 108 while the fastener 120 is tightened during assembly.

[0035] According to one aspect of the present subject matter, a friction surface 124 is provided on an inner wall 112 of the torque transfer member 104. The inner wall 112 defines a wall exposed by a bore of the torque transfer member 104. The friction surface 124 is at least partially formed on the inner wall 112 such that, in the assembled state, the friction surface 124 facilitates an interference fit with the rotor shaft 102 and ensures the elimination of slippage of the torque transfer member 104. In the example of [Fig. 1B], the friction surface 124 projects from the inner wall 112 toward the axis of rotation 114. Accordingly, the inner diameter of the bore where the friction surface projects is smaller than that of the remainder of the bore. The friction surface 124 may be a plain or smooth surface, a knurled surface, or a surface comprising internal grooves.

[0036] According to one aspect of the present subject matter, the arrangement of the rotor assembly 100 is such that clearance is maintained between an inner ring of the front bearing 123 and the rotor shaft 102. Under these conditions, a collar 128 (or a reinforcing ring) is mounted on the rotor shaft 102 and sandwiched between the torque transfer element 104 and the front bearing 123. The collar 128 bears on the front bearing 123 at one end and on the torque transfer element 104 at the other end to facilitate efficient torque transfer between the two. In addition, in the assembled state, one end of the torque transfer element 104 bears on the collar 128 and another end of the torque transfer element 104 bears on the fastening element 120.

[0037] Alternatively, in the example where clearance is maintained between the rotor shaft 104 and the front bearing 123, the torque transfer member 104 may be mounted on the rotor shaft 102 to directly abut the front bearing 123. In yet another example, an interference fit is maintained between the rotor shaft 102 and the torque transfer member 104 and the collar 128 is not necessary to ensure efficient torque transfer between the two.

[0038] [Fig.2A] illustrates the torque transfer element 104 configured in accordance with the present subject matter. [Fig.2B] illustrates a sectional view of the torque transfer element 104, configured in accordance with the present subject matter. [Fig.3] illustrates the rotor shaft 102 configured in accordance with the present subject matter.

[0039] According to one aspect illustrated in [Fig.2A], the torque transfer member 104 includes two flat surface portions 108 that are formed partially along the outer periphery 106 of the torque transfer member 104. The two flat surfaces 108 are positioned on the outer periphery 106 so as to be parallel to each other. The two flat surface portions 108 extend in the direction parallel to the rotation axis 114. Moreover, in the example illustrated in [Fig.2A] (also illustrated in [Fig.1A] and 1B), the two flat surface portions 108 extend only partially along the length 104 of the torque transfer member. The aforementioned length is defined by the distance between a first end 202 and a second end 204 of the torque transfer element 104 which extend in a direction parallel to the axis of rotation 114.

[0040] According to one aspect of the present subject, in the assembled state, the first end 202 is adapted to bear on the neck 128 and the second end 204 is adapted to bear on the fastening element 120.

[0041] According to an example of the present subject matter, the friction surface 124 of the torque transfer member 104 engages with an engagement surface 122 (also shown in [Fig. 1A] and 1B) of the rotor shaft 102. The engagement surface 122 of the rotor shaft illustrated in [Fig. 1A], 1B and 3 is a surface that includes a knurled surface. Depending on the configuration of the friction surface 124, the engagement surface 122 may alternatively be a smooth surface or a surface that includes external splines. By virtue of the configuration of the friction surface 124 and the engagement surface 122, there is a frictional force between the two that limits the movement of the torque transfer member 104 in an axial direction (i.e., a direction along the axis of rotation 114).

[0042] According to one aspect illustrated in [Fig. 2A] and 2B, the friction surface 124 projects from the inner wall 112 toward the axis of rotation 114. Further, in this aspect, the friction surface 124 is a smooth surface. Accordingly, the engagement surface 122 may be formed to include knurling (as illustrated in FIGs. 1A, 1B and 3) or external splines so that the engagement surface 122 can engage (or mesh) in an interference fit with the friction surface 124. Therefore, when the torque transfer member 104 is mounted on the rotor shaft 102, the friction surface 124 is engaged with the engagement surface 122 and a frictional force between the two limits any unwanted axial movement of the torque transfer member 104.

[0043] According to an example of the present subject matter, the torque transfer element 104 is a sprocket, a pulley, or a toothed wheel. In the example illustrated by FIGS. 1A, 1B, 2A, and 2B, the torque transfer element 104 is a sprocket with a plurality of teeth 110 for transferring torque, for example, to a gear reducer. In the example where the torque transfer element is a pulley, the torque is transferred to another pulley by means of a belt. In the example where the torque transfer element is a sprocket, the torque is transferred to another sprocket by means of a chain.

[0044] [Fig. 4A] illustrates an exploded view of the rotating machine 100, configured in accordance with an example of the present subject matter. [Fig. 4B] illustrates a cross-sectional view of the rotating machine 100 in an assembled state, configured in accordance with the example of [Fig. 4A]. [Fig. 5A] illustrates the torque transfer member 204 configured in accordance with the example of [Fig. 4A] and 4B. [Fig. 5B] illustrates the rotor shaft 102 configured in accordance with the example shown in 4A, 4B and 5A.

[0045] Except for the configuration of the inner wall 112, the torque transfer element 104 of the example shown in FIGs. 4A, 4B and 5A is configured in the same manner as that described for [Fig. 1A], 1B and 2A. In particular, the inner wall 112 of the torque transfer member 104 is formed with the friction surface 124 extending from the first end 202 to the second end 204. The friction surface 124 is formed with internal splines 400 that extend from the first end 202 to the second end 204. Accordingly, the engagement surface 122 of the rotor shaft 102 includes external splines 402. When mounting the torque transfer member 104 on the rotor shaft 102, the internal splines 400 engage the external splines 402 of the rotor shaft 104. Further, a tool with jaws may be used to tighten the flat portions of the surface 108 while tightening the fastener 120.As a result, the assembled state of the rotary machine 100 shown in [Fig.4B] is achieved.

[0046] The rotary machine 100, configured in accordance with the present subject matter, may be connected to a reduction gear (not shown) to facilitate driving a motor vehicle. In particular, the torque transfer element may engage with a reduction gear, or directly with a wheel of a motor vehicle for traction.

[0047] Various modifications to the disclosed embodiments, as well as other embodiments of the subject matter, will become apparent to those skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications may be made without departing from the scope of the present subject matter.

Claims

Claims

1. A rotary machine (100) comprising a stator, rigidly mounted within a housing (116); a rotor arranged coaxially with the stator and mounted on a rotor shaft (102) rotatable about an axis of rotation (114), wherein the rotor shaft (102) passes through a front bearing (123) mounted on a drive end (118) of the housing (116) and extends out of the housing (116) from said drive end (118); and a torque transfer member (104), substantially cylindrical in shape, mounted on the rotor shaft (102), said torque transfer member (104) comprising flat surface portions (108) which are formed at least partially along the outer periphery of the torque transfer member (106) and which extend in a direction parallel to the axis of rotation (114)

2. A rotary machine (100) according to claim 1, wherein the outer periphery (106) of the torque transfer member (104) comprises two flat surface portions (108) which are positioned parallel to each other, each of these flat surface portions (108) extending in the direction parallel to the rotation axis (114).

3. A rotary machine (100) according to one of the preceding claims, wherein the torque transfer element (104) comprises a friction surface (124) at least partially formed on an inner wall (112), the friction surface (124) being adapted for an interference fit with the rotor shaft (102).

4. A rotary machine (100) according to claim 3, wherein the friction surface (124) projects from the inner wall (112) towards the axis of rotation (114).

5. A rotary machine (100) according to claim 3, wherein the friction surface (124) is a smooth surface, or a knurled surface, or comprises internal splines (400) which engage in an interference fit with an engagement surface (122) on the rotor shaft (102).

6. A rotary machine (100) according to the preceding claim, wherein the engaging surface (122) on the rotor shaft (102) is a smooth surface, a knurled surface or comprises external splines (402).

7. A rotating machine (100) according to any preceding claim, wherein a first end (202) of the torque transfer element (104) is in contact with an inner ring (126) of the front bearing (123) and a second end (204) is in contact with a fastening element (120) adapted to fasten said torque transfer element (104) to the rotor shaft (102).

8. A rotating machine (100) according to any one of claims 1 to 7, wherein the torque transfer member (104) comprises: a first end (202) which abuts a collar (128), the collar (128) being sandwiched between the torque transfer member (104) and the inner ring (126) of the front bearing (123); and a second end (204) which abuts a fastening member (120) adapted to fasten said torque transfer member (104) to the rotor shaft (102).

9. A rotating machine (100) according to any preceding claim, wherein the torque transfer element (104) is a pinion, pulley or gear.

10. A rotary machine (100) according to claim 9, wherein the torque transfer element (104) is engaged in a gear reducer.

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