Driving wheel assembly - driven wheel assembly for equipping a transmission device - Transmission device comprising such an assembly and associated design method

Abstract

The invention relates to a driving wheel-driven wheel assembly (50) for equipping a transmission device, comprising a first wheel (11, 21, 31, 41, D), called the driving wheel, having a first dynamic stiffness (k1), a second wheel (12, 22, 32, 41, 42, D), called the driven wheel, having a second dynamic stiffness (k2), such that the first dynamic stiffness and the second dynamic stiffness have a ratio (R) greater than or equal to 1.5. Figure to be published with the abbreviation: Figure 2a

Description

Title of the invention: Driving wheel - driven wheel assembly for equipping a transmission device - Transmission device comprising such an assembly and associated design method

[0001] The field of the present invention is that of mobility equipment for goods or people. It relates in particular to motor vehicles with internal combustion, electric, or hybrid engines. The invention applies to any traction system: internal combustion, hybrid, and electric. It relates in particular to commercial vehicles such as trucks and heavy goods vehicles, construction equipment, and agricultural machinery. The invention also applies to soft mobility devices such as electric bicycles, electric scooters, or robots.

[0002] The vibrations produced by the transmissions come from the meshing process and from the deviations in geometry and elastic deformations of the gears.

[0003] There is a need to limit vibrational phenomena in gears.

[0004] In particular, there is a need to determine the dynamic stiffnesses of the wheels of a gear, given the known static transmission error (STE).

[0005] The object of the present invention is therefore to meet at least in part the needs described above.

[0006] According to a first aspect, the invention relates to a driving wheel - driven wheel assembly for equipping a transmission device, the assembly comprising

[0007] a first wheel, called the driving wheel, having a first dynamic stiffness,

[0008] a second wheel, called the driven wheel, having a second dynamic stiffness,

[0009] such that the first dynamic stiffness and the second dynamic stiffness have a ratio greater than or equal to 1.5.

[0010] In the context of the invention, the term "wheel" in "driving wheel" and "driven wheel" should be understood in a broad sense. For example, it refers to a driving pinion, a driven pinion, or a differential.

[0011] In the event of a peak in vibration at the gear frequency at a given rotational speed, the invention makes it possible to propose what the stiffnesses should be on the driving wheel side and the driven wheel side in order to have a reduction in noise.

[0012] In a driving wheel-driven wheel assembly, the vibrational phenomena at the gear frequency are determined by the static transmission error (STE) and by the dynamic stiffness of the driving and driven wheels in contact. The static transmission error under load (STE) is, in particular, the main source of vibration in a transmission.

[0013] It has been observed that the vibrations of the driving / driven gears are at their maximum when the dynamic stiffness of the driving gear and the dynamic stiffness of the driven gear are close to each other. Conversely, in an assembly according to the invention, it is advantageous for the first dynamic stiffness and the second dynamic stiffness to have a ratio greater than or equal to 1.5.

[0014] The ratio is in particular defined by the first dynamic stiffness divided by the second dynamic stiffness. In a variant of the invention, the ratio is defined by the second dynamic stiffness divided by the first dynamic stiffness.

[0015] According to one embodiment, the ratio is greater than or equal to 2, or even 2.5.

[0016] According to another aspect of it, the invention relates to a transmission device comprising at least two wheels forming a driving wheel - driven wheel assembly as described above.

[0017] The device includes in particular an electrical machine which may be, for example, a permanent magnet synchronous electrical machine operating at low voltage, i.e. 48 Volts.

[0018] The transmission device may comprise one or more driving wheel - driven wheel assemblies as described above.

[0019] According to yet another aspect of it, the invention relates to a method for designing a driving wheel - driven wheel assembly for an electric machine as described above.

[0020] The method according to the invention comprises at least one step of calculating the ratio between a first dynamic stiffness of the first wheel and a second dynamic stiffness of the second wheel. The first dynamic stiffness is previously deduced from a measurement of the inertia of the first wheel and / or the second dynamic stiffness is deduced from a measurement of the inertia of the second wheel. This step includes, in particular, comparing the ratio with a predefined value,

[0021] The method may further include a step of calculating the product of the first and second dynamic stiffness divided by their sum.

[0022] The dynamic stiffness of the first wheel, respectively second wheel, is related to the inertia by the relation

[0023] „ (2n / )2 Dynamic sti j J ness = - i nertance

[0024] For a given driving wheel - driven wheel assembly, it is observed that the vibration forces have a maximum when the dynamic stiffnesses of the driving wheel and the driven wheel are equivalent.

[0025] In an example of an embodiment of the process, the first wheel has a first set of characteristics and / or the second wheel has a second set of characteristics. The process further comprises a step of modifying at least one of characteristics of the first series or the second series.

[0026] The first set of characteristics and / or the second set of characteristics are chosen, for example, from a number of teeth on the gear teeth, a width and thickness of the teeth, a diameter and Young's modulus of the corresponding wheel, a thickness of a wheel rim, ...

[0027] Other features, details and advantages of the invention will become clearer upon reading the following description, which is provided by way of example in conjunction with drawings in which:

[0028] - Figure 1 is a general, perspective view of a transmission device according to the second aspect of the invention,

[0029] - Figure 2a is a schematic illustration of an assembly according to the first aspect of the invention

[0030] - Figure 2b is a schematic illustration of the first and second stiffnesses dy namics of the whole of figure 2a

[0031] - Figure 3 gives an example of inertia measured on the driving and driven wheels of the whole of figure 2a, and

[0032] - Figure 4 illustrates the characteristics of a first series in an example of the invention.

[0033] The two-speed transmission device T of Figure 1 includes a primary shaft 1 which is coupled to the output shaft of an electrical machine M. This coupling is homokinetic and can be any type of mechanical coupling between two shafts, such as a splined coupling.

[0034] The transmission device T also includes a secondary shaft 2 and a tertiary shaft 3. The tertiary shaft 3 is suitable for being connected to a differential D, which is itself connected to the wheels RI, R2 of the vehicle. The function of the differential D is to rotate the wheels RI, R2 of the vehicle at different speeds.

[0035] A first driving wheel - driven wheel assembly 10 corresponding to the first speed comprises a driving wheel corresponding to a first driving pinion 11 disposed on the primary shaft 1 and a driven wheel corresponding to a first driven pinion 12 disposed on the secondary shaft 2. The first driving pinion 11 and the first driven pinion 12 mesh permanently.

[0036] A second driving wheel - driven wheel assembly 20 corresponding to the second speed comprises a driving wheel corresponding to a second driving pinion 21 disposed on the primary shaft 1 and a driven wheel corresponding to a second driven pinion 22 disposed on the secondary shaft 2. The second driving pinion 21 and the second driven pinion 22 mesh permanently.

[0037] The first driving pinion 11 and the second driving pinion 21 are fixedly mounted on the primary shaft 1. The first driven pinion 12 and the second driven pinion 22 are mounted freely on the secondary shaft 2 via needle bearings, i.e. they can rotate relative to the secondary shaft 2.

[0038] A third driving wheel - driven wheel assembly 30 comprises a driving wheel corresponding to a third driving pinion 31 disposed on the secondary shaft 2 and a driven wheel corresponding to a third driven pinion 32 disposed on the tertiary shaft 3. The third driving pinion 31 is fixedly mounted on the secondary shaft 2 and the third driven pinion 32 is fixedly mounted on the tertiary shaft 3. The third driving pinion 31 is axially disposed between the first driven pinion 12 and the second driven pinion 22. The third driving pinion 31 and the third driven pinion 32 mesh permanently.

[0039] A fourth driving wheel - driven wheel assembly 40 corresponding to a differential assembly D comprises a driving wheel corresponding to a driving pinion 41 disposed on the tertiary shaft 3 and a driven wheel 42 corresponding to the input of the differential D. The driving pinion 41 is fixedly mounted on the tertiary shaft 3. The driving pinion 41 and the driven pinion 42 mesh permanently.

[0040] The four driving wheel-driven wheel assemblies 10, 20, 30, 40 are oriented parallel to each other. Similarly, the three shafts 1, 2, 3 are oriented parallel to each other. The wheels of the various pinions 11, 12, 21, 22, 31, 32, 41, 42 have straight teeth. Alternatively, these wheels may have helical, helical, or herringbone teeth.

[0041] Two torque paths are therefore possible between the output shaft of the electric machine M and the wheels RI, R2 of the vehicle. A first torque path passing through the first driving wheel - driven wheel assembly 10, then the third driving wheel - driven wheel assembly 30, and finally the driving wheel - driven wheel assembly 40 of the differential D. A second torque path passing through the second driving wheel - driven wheel assembly 20, then the third driving wheel - driven wheel assembly 30, and finally the driving wheel - driven wheel assembly 40 of the differential D.

[0042] At least one, advantageously all four sets 10, 20, 30, 40 form driving wheel - driven wheel sets according to the invention.

[0043] The illustrated transmission device thus comprises four assemblies according to the invention. This number is not limiting to the invention.

[0044] Figure 2a schematically illustrates a 50 driving wheel - driven wheel assembly comprising a driving wheel 51 and a driven wheel 52 between which a static transmission error (STE) S is imposed.

[0045] The displacements Xi of the driving wheel and X2 of the driven wheel are illustrated in figure 2b with S = Xi - X2.

[0046] ki and k2 are dynamic stiffnesses at the point of contact between the driving wheel and the driven wheel. The dynamic stiffnesses ki and k2 take into account, in particular, the resonance / anti-resonance effects.

[0047] In a variant of the method according to the invention, the apparent stiffness (ki x k 2) / (ki + k2) is calculated. For a given total dynamic stiffness ki + k2, the apparent stiffness (ki x k2) / (ki + k2) is maximum if kl = k2.

[0048] Figure 3 illustrates the inertness of the driving wheel (hatched curve) and the inertness of the driven wheel (solid curve) measured as a function of frequency.

[0049] The dynamic stiffness of the inertia is deduced by the formula:

[0050] dynamic stiffness (expressed in N nr1 = (2irf)2 / inertia. The inertia is expressed here in ms 2-N 1 and the frequency f in Hz.

[0051] It has been observed that between 2000 and 9000 rpm, the vibrations in the order of gear meshing are maximum if the inertials of the driving wheels and the driven wheels are equivalent.

[0052] On the contrary, a ratio R between the first dynamic stiffness and second dynamic stiffness greater than or equal to 1.5, in particular greater than or equal to 2, or even 2.5, makes it advantageous to reduce vibrations below the desired threshold.

[0053] In order to achieve the desired R ratio between the first dynamic stiffness and second dynamic stiffness, physical characteristics, particularly geometric characteristics of the driving and / or driven wheels, can in particular be varied.

[0054] As illustrated in Figure 4, a first set of characteristics Fi relating to the driving wheel is for example chosen from a number ni of teeth, a width h and a thickness ei of the teeth 75, a diameter di and a Young's modulus yi of the first wheel and / or a thickness hi of a web 72 of said wheel, a radius gi of the hub 70 of said driving wheel.

[0055] Similarly (not illustrated), alternatively or in addition, a second series F2 of characteristics F2 relating to the driven wheel is for example chosen from a number n2 of teeth, a width 12 and a thickness e2 of the teeth, a diameter d2 and a Young's modulus y2 of the second wheel and / or a thickness h2 of a web 75 of said wheel, a radius g2 of the hub 70 of said driven wheel.

[0056] The characteristics of the first and second series are distinctive physical characteristics of the first, and second, respectively, wheel. The method according to the invention advantageously includes a step during which at least one of the characteristics of the first series and / or the second series is varied and the new inertia h, I2 of the corresponding wheel is measured, from which the corresponding dynamic stiffness is deduced.

[0057] The invention is not limited to the illustrated examples and applies to any traction system: thermal, hybrid and electric.

Claims

Demands

1. Assembly (10,20,30,40,50) driving wheel - driven wheel for equipping a transmission device, comprising - a first wheel (11, 21, 31, 41, 51, D), called the driving wheel, having a first dynamic stiffness (ki), - a second wheel (12, 22, 32,41,42, 52, D), called the driven wheel, having a second dynamic stiffness (k2), such that the first dynamic stiffness and the second dynamic stiffness have a ratio (R) greater than or equal to 1.

5.

2. Assembly according to claim 1, the ratio (R) being greater than or equal to 2, or even 2.

5.

3. Assembly according to claim 1 or 2, the ratio (R) being defined by the first dynamic stiffness (ki) divided by the second dynamic stiffness (k2).

4. Together according to any one of claims 1 or 2, the ratio (R) is defined by the second dynamic stiffness (k2) divided by the first dynamic stiffness (ki).

5. Transmission device (T) comprising at least two wheels (11, 12, 21, 22, 31, 32, 41, 42, D) forming a driving wheel - driven wheel assembly (10, 20, 30, 40) according to any one of the preceding claims.

6. Method of designing a driving wheel - driven wheel assembly for an electric machine comprising at least one step of calculating a ratio (R) between a first dynamic stiffness (ki) of a first wheel ( ) and a second dynamic stiffness (k2) of a second wheel ( ) and in particular comparison of the ratio R with a predefined value... the first dynamic stiffness (ki) being previously deduced from a measurement of the inertia of the first wheel and / or the second dynamic stiffness (ki) being deduced from a measurement of the inertia of the second wheel.

7. Method according to the preceding claim further comprising a step of calculating kix k2 / ( ki+ k2 ).

8. A method according to any one of claims 6 and 7, the first wheel (11, 21, 31, 41, D) having a first series (F1) of characteristics (fl, f2, fi) and / or the second wheel (12, 22, 32, 42, D) having a second series (F2) of characteristics (fl, f2,fi), the process further comprising a step of modifying at least one of characteristics (fl, f2,fi) of the first series or of the second series.

9. Method according to the preceding claim the first set of characteristics being chosen from a diameter (dl) and a Young's modulus (yl) of the wheel, a width li and a thickness (el) of the teeth (75), a number of teeth (ni), a thickness (h 1), of a web (70) of the first wheel and / or the second set [F2] of characteristics being chosen from a diameter (dl) and a Young's modulus (yl) of the wheel, a width li and a thickness (el) of the teeth (75), a number of teeth (ni), a thickness (hi), of a web (70) of the second wheel.

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