MECHANICAL DEVICE WITH AN ECCENTRIC SHAFT FORCED ONTO A BALANCING PIECE

Description

[0001] The invention relates to mechanical devices which include a so-called primary shaft having an eccentric part which must have balancing masses to center the inertial masses.

[0002] Some devices, such as certain gearboxes, include a shaft (called the primary shaft) with two opposing end sections, each having a first axis of rotation, and separated by an intermediate section with a second axis of rotation that is eccentric with respect to the first axis of rotation. This is particularly the case for certain gearboxes that are coupled to an electric machine (or motor) or that are part of a coupling system used, for example, in a vehicle, possibly an automobile.

[0003] The primary shaft (with rapid rotation and eccentric) is for example coupled to a secondary shaft (with slow rotation) via first and second satellite gears, for example of hypocycloidal type, and defining respectively first and second reduction stages axially offset.

[0004] The eccentricity of the primary shaft introduces an imbalance (and more specifically, eccentric masses (satellites and eccentric part)). Therefore, it has been proposed, notably in patent documents FR 2657131 and US 4,604,916, to add balancing masses (for example, two) to this primary shaft to shift the overall center of gravity. Each balancing mass is currently attached by welding, a splined connection, a pin, or a key.

[0005] We know, for example, of patent documents EP-A1-1174641 or DE-U1-29703651 for such reducers.

[0006] However, this type of addition proves costly and can complicate machining. Furthermore, the addition may be made in a location other than the one predetermined due to indexing difficulties or impossibilities, and in this case, the balancing is not perfect, thus inducing vibrations that cause noise and accelerated wear.

[0007] The invention is therefore intended, in particular, to improve the situation.

[0008] For this purpose, it proposes a mechanical device, possibly for reducing engine speed, comprising a (primary) shaft having two opposing end parts, having a first axis of rotation and separated by an intermediate part of the shaft having a second axis of rotation eccentric with respect to the first axis of rotation, this mechanical device also comprising a part including: a first part defining a first balancing mass and comprising a first internal bore centered on the first axis of rotation and partially housing one of the terminal parts of the shaft with a first coupling, and a second part defining a second balancing mass and comprising a second internal bore centered on the second axis of rotation and partially housing the intermediate part of the shaft with a second coupling, this second part of the part having a center of gravity located along a third axis located opposite the second axis of rotation with respect to the first axis of rotation in order to induce a balancing of eccentric masses.

[0009] This mechanical device is characterized by the fact that at least one of the first and second couplings can be tightened.

[0010] Thus, the balancing masses defined by the part can be advantageously joined to the primary shaft by press fitting the latter, and therefore without having to carry out a welding operation, or use a splined connection or a pin or even a key.

[0011] The mechanical device according to the invention may include other features which may be taken separately or in combination, and in particular: the second part of the part may have an elliptical cross-section; the first coupling may be achieved via a first step defined at the level of a first interface between the first part of the part and the terminal part of the shaft which is housed in the first internal bore, and the second coupling may be achieved via a second step defined at the level of a second interface between the second part of the part and the intermediate part of the shaft; the first step can be defined on the terminal part of the shaft housed in the first internal bore; The second layering can be defined on the intermediate part of the tree.

[0012] The invention also proposes a coupling equipment comprising at least one mechanical device of the type presented above.

[0013] For example, such equipment can constitute a gearbox.

[0014] The invention also proposes a vehicle, possibly of the automobile type, comprising a transmission chain including at least one mechanical device of the type presented above and / or at least one coupling equipment of the type presented above.

[0015] Other features and advantages of the invention will become apparent upon examination of the detailed description below, and the accompanying drawings, in which: there figure 1 schematically illustrates, in a cross-sectional view in a longitudinal plane, an example of an embodiment of a part of a mechanical device according to the invention, and the figure 2 schematically illustrates, in a front view, the part of the mechanical device of the figure 1 .

[0016] The invention aims in particular to provide a mechanical device DM with a primary shaft AP with an eccentric press-fitted onto a balancing piece PM.

[0017] In what follows, the mechanical device DM is considered, by way of non-limiting example, to be a speed reducer intended for use in a motor vehicle, such as a car. However, the invention is not limited to this application. Indeed, a mechanical device according to the invention can be coupled to any electric machine (or motor) or be part of a coupling device (such as a gearbox). Consequently, a mechanical device according to the invention can be used to equip a vehicle (land, sea (or river), or air), an installation, possibly of an industrial type, or a building, for example.

[0018] Furthermore, in the following, we consider, by way of non-limiting example, that the mechanical device DM is intended to be coupled to an electric drive unit that is part of the transmission chain of a hybrid or all-electric vehicle. Here, "electric drive unit" means an electric machine (or motor) arranged to provide or recover torque to propel a vehicle, either alone or in conjunction with at least one other electric or internal combustion drive unit (such as an internal combustion engine).

[0019] We have schematically represented on the figures 1 et 2 An example of the embodiment of a part of a mechanical device DM (here a speed reducer) according to the invention. This part shown comprises only an eccentric primary shaft AP and a balancing piece PM.

[0020] This primary tree AP comprises two terminal parts PTj (j = 1 or 2) opposite to each other and separated by an intermediate part PI.

[0021] These two terminal parts PTj have a first axis of rotation AR1. Note that in the example illustrated (non-exhaustively) on the figure 1 The two terminal parts PTj have the same first diameter, but this is not mandatory.

[0022] For example, the first terminal part PT1 (j = 1), located on a front face, may be intended to be attached to the output shaft of an electrical machine having a first rotation speed (or a first regime), possibly variable over time.

[0023] The second terminal part PT2 (j = 2), located on a rear face, is mounted to rotate on a bearing.

[0024] The intermediate section PI of the primary shaft AP has a second axis of rotation AR2 which is offset by a distance e from the first axis of rotation AR1. This intermediate section PI can be used, among other things, to receive first and second planetary gears, for example, of the hypocycloidal or epicycloidal type, defining first and second reduction stages that are axially offset, and ensuring the coupling of its primary shaft AP to a secondary shaft. It will be understood that these first and second planetary gears are responsible for transforming the first rotational speed of the primary shaft AP into a second rotational speed of the secondary shaft, which is strictly lower than this first rotational speed.

[0025] The invention does not relate to the first and second satellite gears, the latter will not be described below.

[0026] The balancing part PM comprises two parts, P1 and P2, which extend from one another and are fixedly joined. It should be noted that this balancing part PM is preferably a single piece. However, this is not mandatory. It could, for example, be formed by permanently joining its first part P1 to its second part P2, by welding.

[0027] The first part P1 of the PM part defines a first balancing mass and includes a first internal bore AI1 which is centered on the first axis of rotation AR1 and which partially houses one of the terminal parts PTj (here the second PT2) with a first coupling.

[0028] For example, and as illustrated but not limited to the figure 2 , the first part P1 of the part PM may have a circular cross-section.

[0029] The second part P2 of the PM component defines a second balancing mass and includes a second internal bore AI2, centered on the second axis of rotation AR2, which houses the intermediate part PI with a second coupling. This housing is partial because a sub-portion of this second part P2 must be located outside the second internal bore AI2 in order to be coupled to the first and second gears that provide the coupling to the secondary axis.

[0030] For example, and as illustrated but not limited to the figure 2 , the second part P2 of the PM part may have an elliptical cross-section.

[0031] These first P1 and second P2 balancing masses have a center of gravity located in a plane that includes the eccentric center of gravity of the eccentric masses (due to the existence of eccentricity e) and is orthogonal to the first axis of rotation AR1 of the primary shaft AP, thus recentering the overall center of gravity. Here, "eccentric masses" refers to the planet gears of the first and second gears and the eccentric portion of the primary shaft AP (present in the second part P2 of the latter (AP)), as well as any intermediate component located between these planet gears and the eccentric.

[0032] For example, the second part P2 of the component PM may have a center of gravity located along a third axis A3 situated opposite the second axis of rotation AR2 relative to the first axis of rotation AR1 in order to induce the balancing of the eccentric masses. The distance e' separating the third axis A3 from the first axis of rotation AR1 is therefore equal to the eccentricity e.

[0033] The first and second couplings result from a press fit of the second terminal section PT2 and the intermediate section PI of the primary shaft AP into the first AI1 and second AI2 internal bores of the PM component, respectively. Consequently, adding the balancing weights to the primary shaft AP no longer requires welding, or the use of a splined connection, pin, or key. This results in reduced costs, simplified machining, and the possibility of indexing via the internal bores AI1 and AI2, which guarantees the positioning of the balancing weights at the predetermined location on the primary shaft AP. In other words, the invention ensures proper balancing and therefore the (near-total) absence of vibrations, thus preventing noise generation and accelerated wear.

[0034] It should be noted that at least one of the first and second couplings can be tight. In other words, depending on the requirements, one can have either only the first coupling tight, or only the second coupling tight, or both the first and second couplings tight.

[0035] To facilitate press-fitting, the first and second couplings can, for example, be achieved via first and second stepped configurations, respectively. This first stepped configuration is defined at a first interface IC11, IC12 between the first part P1 of the PM component and the second terminal part PT2 of the primary shaft AP (housed in the first internal bore AI1). The second stepped configuration is defined at a second interface IC21, IC22 between the second part P2 of the PM component and the intermediate part PI of the primary shaft AP.

[0036] Here, "staircase" refers to the definition of at least two levels placed at different radial distances. In the example illustrated (but not limited to) on the figure 1 Each tier comprises only two landings (IC11 and IC12) or (IC21 and IC22). However, each tier could comprise more than two landings, for example three or four.

[0037] Each step allows the primary shaft AP to be pre-positioned effortlessly in the internal bores AI1 and AI2, and then the axial coupling to be finalized by a press fit onto the bearing(s) offering the tightest contact.

[0038] As an example, a first sliding step can be defined in a first sub-part IC11 of the first interface and / or a first sliding step in a first sub-part IC21 of the second interface, in order to pre-position the primary shaft AP without forcing it by easily indexing its angular position. For this purpose, each first step can, for example, be of type H7 / h6 or H7 / g6.

[0039] In this case, a second clamping-type stepping bearing can be defined in a second sub-part IC12 of the first interface and / or a second clamping-type stepping bearing in a second sub-part IC22 of the second interface, in order to obtain axial clamping positioning without the additional addition of an axial stop such as a circlip or nut. For this purpose, each second stepping bearing can, for example, be of type H7 / m6 or H7 / p6.

[0040] For example, the first gear ratio can be defined on the second terminal portion PT2 of the primary shaft AP (housed in the first internal bore AI1). But in a variant, the first gear ratio could be defined in the first internal bore AI1 which houses the second terminal portion PT2 of the primary shaft AP.

[0041] For example, the second gear can also be defined on the intermediate part PI of the primary shaft AP. But in a variant, the second gear could be defined in the second internal bore AI2 which houses the second intermediate part PI of the primary shaft AP.

[0042] It should also be noted that in one variant of the implementation, each step could be replaced by a monotonic variation (increasing or decreasing depending on the element concerned).

Claims

1. Mechanical device (DM) comprising a shaft (AP) having two opposite end parts (PTj), having a first axis of rotation (AR1), and separated by an intermediate part (PI) of said shaft (AP) having a second axis of rotation (AR2) eccentric with respect to said first axis of rotation (AR1), said mechanical device (DM) further comprising a part (PM) comprising a first part (P1) defining a first balancing mass and comprising a first internal bore (AI1) centered on said first axis of rotation (AR1) and partially housing one of said end parts (PTj) with a first coupling, and a second part (P2) defining a second balancing mass and comprising a second internal bore (AI2) centered on said second axis (AR2) and housing partially said portion intermediate (PI) with a second coupling, said second portion (P2) of the workpiece (PM) present ant a center of gravity along a third axis located at opposite of said second axis of rotation (AR2) with respect to said first axis of rotation (AR1) in order to induce a balancing of eccentric masses, characterized in thatat least one of said first and second couplings is tight.

2. Device according to claim 1, characterized in that the said second part (P2) of the part (PM) has an elliptical cross section.

3. Device according to one of claims 1 to 2, characterized in that said first coupling e st realized via a first staging defined at a first interface (IC11, IC12) between said first portion (P1) of the workpiece (PM) and said end part (PT2) of the shaft (AP) housed in said first internal bore (AI1), and said second coupling is carried out via a second step defined at a second interface (IC21, IC22) between said second part (P2) of the part (PM) and said intermediate part (PI) of the shaft (AP).

4. Device according to claim 3, characterized in that the said first step is defined on the said end part (PT2) of the shaft (AP) housed in the said first internal bore (AI1).

5. Device according to claim 3 or 4, characterized in that the said second step is defined on the said intermediate part (PI) of the shaft (AP).

6. Coupling equipment, characterized in that it comprises at least one mechanical device (DM) according to one of the preceding claims.

7. Equipment according to claim 6, characterized in that it constitutes a gearbox.

8. Vehicle comprising a transmission chain, characterized in that said transmission chain comprises at least one mechanical device (DM) according to one of claims 1 to 5 and / or at least coupling equipment according to claim 6 or 7.