CN113623371A

CN113623371A - Power transmission system for a drive train of a motor vehicle

Info

Publication number: CN113623371A
Application number: CN202110495091.0A
Authority: CN
Inventors: J.莫塔尔; C.劳伦斯; G.法耶特
Original assignee: Valeo Embrayages SAS
Current assignee: Valeo Embrayages SAS
Priority date: 2020-05-07
Filing date: 2021-05-07
Publication date: 2021-11-09
Also published as: EP4146956A1; CN218152204U; TW202206305A

Abstract

The invention relates to a power transmission system (10) for a drive train of a motor vehicle, in particular a passenger motor vehicle, comprising an elastic band (11), the elastic band (11) being configured to transmit a torque to at least one wheel of the motor vehicle.

Description

Power transmission system for a drive train of a motor vehicle

Technical Field

The present invention relates to the field of vehicles, in particular motor vehicles, and more precisely to the power transmission system of a powertrain for driving the wheels of such motor vehicles.

Background

Generally speaking, of interest here are power transmission systems intended in motor vehicles to rotate at least one wheel of said vehicle by transmitting a torque provided by a drive shaft, in particular of an electric or hybrid motorized system, to drive said vehicle.

In this respect, the document DE 2428356 is representative of the prior art. Said document describes a powertrain for driving the wheels of a wheeled vehicle. The powertrain includes a drivetrain coupled to a driveshaft. The power transmission system includes a double chain sprocket through which power is transmitted to the wheels of the vehicle.

In this context, what is referred to herein is a belt-type power transmission system, the belt being able to belong to a first reduction stage of a powertrain of a vehicle. It is important to note that in the context of the present invention, the belt of the power transmission system is configured to drive at least one wheel. In other words, the belt is arranged in a torque transmission path between the electric machine and at least one wheel of the vehicle, in particular between the electric machine and two laterally opposite drive wheels of the vehicle. Thus, the belt is configured to transmit the driving torque to at least one driving wheel of the vehicle, in particular to two laterally opposite driving wheels of the vehicle. According to one embodiment, the belt is configured to transmit the drive torque to all drive wheels of the vehicle.

The first reduction stage of the powertrain here therefore comprises two pulleys and a belt designed to transmit torque from the electric machine at a reduction ratio.

According to one embodiment, a ribbed belt is used. Preferably, the ribbed belt is a belt that is longitudinally striped. It provides transmission by adhesion and/or wedging. There are various types of ribbed belts depending on the profile of the rib and the distance between the tops of adjacent ribs. The tape may be, for example, under the trade name

A belt for sale. The ribs may be similar or analogous to those known under the trade name TPoly

Ribs of sold belts.

The number of ribs may also vary. It is well known that ribbed belts have a higher efficiency than flat belts or even V-belts, in particular because the longitudinal ribs make the contact area between the pulley and the ribbed belt larger. This makes the ribbed belt suitable for use in a powertrain with the aim of achieving a high torque transmission between the motor and the wheel to generate a torque at the wheel of, for example, 500Nm or more. Ribbed belts also have the advantage of being usable on smooth or ribbed pulleys. Furthermore, the ribbed belt can be wound around a pulley of smaller diameter than other belts, in particular V-belts, which is particularly advantageous when the belt is used for deceleration, in particular downstream of an electric machine.

Toothed belts with single or double toothing are also known, which can also transmit large powers.

However, a disadvantage of toothed belts is their rigidity. Furthermore, they are by definition only used with toothed pulleys, it being necessary that, in power transmission systems using toothed belts and toothed pulleys, the length of the toothed belt corresponds exactly to the diameter of the pulley, not allowing any elasticity, otherwise power losses would be suffered. Moreover, it is known that toothed belts do not perform as acoustically as ribbed belts.

Now, in order to avoid slipping of the ribbed belt on the pulley and the resulting power loss, it is known practice to use a compensating device to maintain the tension of the ribbed belt. In the prior art, assemblies consisting of rollers, tensioners and springs are used in particular to maintain the tension of ribbed belts throughout their service life.

The presence of such compensation devices, as described for example in FR 3011899, is constrained and involves making the power transmission system more complex and with increased costs. In addition, for the powertrain, the use of a tensioner is disadvantageous in terms of kinematics between the motor and the drive wheel, since the tension may be negative as well as positive. The tensioner is typically inserted into a loose bundle of belts, that is, on the opposite side of the traction force. Since the torque of the drive train changes direction, the use of a tensioner causes a tilting play, also called "backlash", which the driver feels during the torque ripple phase, especially at low torques.

In order to overcome these drawbacks, the invention proposes to use an elastic belt that is pre-tensioned in tension, in other words that is stretched, so that the pre-stressed absorbing belt relaxes in relation to its wear. Thus, the tension exerted on the belt remains acceptable during the service life of the belt for transmitting torque. The prestress of an installed elastic belt (in other words its initial elongation) is calibrated to compensate for the natural wear of the belt, in particular the wear of the ribs. The elasticity of the elastic belt allows the tension of the belt to be maintained within its normal operating range even in the absence of an external tensioner.

Disclosure of Invention

More precisely, the object of the invention is a power transmission system for a powertrain of a motor vehicle, in particular a passenger motor vehicle, comprising an elastic band positioned to transmit torque to at least one wheel of the motor vehicle.

Advantageously, the torque transmission system is capable of receiving torque from the motorised system on the one hand and of transmitting torque to the at least one wheel of the vehicle on the other hand, the power transmission system comprising a torque transmission path between the motorised system and the at least one wheel, the elastic belt forming part of the torque transmission path.

Advantageously, the elastic band is tensioned only due to its inherent elasticity and installation by elastic prestressing. In other words, no tensioning device is attached.

The invention makes it possible in particular to maintain a suitable tension of the elastic belt in the power transmission system, so that the durability and NVH ("noise, vibration, harshness") performance of said system can be improved without the need for a tensioner-based compensation system, including despite significant elongation of said elastic belt due to wear thereof. In particular, the use of such an elastic band, in particular an elastic band mounted stretched with elastic prestress, can attenuate certain vibratory interactions between the electromechanical and the reduction gear unit.

According to one embodiment, the elastic band is a ribbed band comprising longitudinally extending ribs.

For example, the power transmission system includes between 10 and 12 ribs.

According to one embodiment, the power transmission system comprises a reduction stage comprising two pulleys having a center distance, and at least one auxiliary reduction gear unit, and wherein the elastic band is mounted on the two pulleys and is adapted to produce, in particular together with the auxiliary reduction gear unit, a conversion ratio between 3/1 and 28/1.

Advantageously, the power transmission system comprises a differential designed to drive two laterally opposite wheels of the vehicle, the elastic band being designed to transmit the torque from the electric machine to the differential.

Advantageously, the power transmission system comprises an auxiliary reduction gear unit kinematically arranged between a reduction stage comprising, on the one hand, two pulleys and an elastic band, which thus form the first reduction stage of the power transmission system, and, on the other hand, a differential.

Advantageously, the stiffness of the elastic ribbed belt is in particular less than 12000N/rib/span/E% (in newtons/rib/span (spacing between ribs)/percent elongation of the belt (relative to its original total length)). The material thereof may be selected in this sense.

Advantageously, the belt is capable of transmitting torques of more than 40Nm, in particular more than 50 Nm. In practice, the torque transmitted by the belt may be between 0 and 80Nm, in particular between 0 and 55 Nm. Advantageously, at the output of the transmission system, i.e. downstream of the reduction stage, the torque is between 0 and 1200Nm, in particular between 0 and 900 Nm.

Advantageously, the installed belt has an elongation greater than or equal to 1.5% of the original length of the elastic belt.

Furthermore, the present invention relates to the field of power transmission systems for transmitting power between an electric machine and at least one wheel, said range comprising a power transmission system as briefly described above, the two transmission systems having different reduction ratios between their electric machines and their at least one vehicle, the auxiliary reduction gear units of the two power transmission systems having the same reduction ratio, the difference in reduction ratio between the two transmission systems being obtained by two reduction stages, each comprising two pulleys and an elastic band, the two reduction stages having different reduction ratios.

The invention also relates to a powertrain for a motor vehicle comprising at least one wheel and a motorization and drive system for said at least one wheel, said motorization and drive system comprising a power transmission system as briefly described above, the power transmission system being designed to transmit torque between the motorization system and said at least one wheel, the power transmission system being designed such that the elastic belt is located in the torque transmission path between the motorization system and said at least one wheel.

Advantageously, said motorization comprises an electric machine with a voltage of 48V.

Advantageously, the peak power is up to 11 kW. Advantageously, the continuous power output is up to 6 kW.

The invention also relates to a vehicle, in particular a three-wheeled vehicle or a four-wheeled vehicle comprising the powertrain.

The invention also relates to a method of installing a power transmission system as briefly described above, wherein an elastic belt is installed around two pulleys by elastic deformation of the elastic belt exceeding a predetermined pre-stress threshold of said elastic belt in the installed state.

Drawings

The invention will be better understood on reading the description given below by way of example and by referring to the accompanying drawings given by way of non-limiting example, wherein similar objects are given the same reference numerals.

[ FIG. 1 ]: FIG. 1 depicts an example of an electric motor of a motor vehicle and a power transmission system including a ribbed belt according to one embodiment of the present invention;

[ FIG. 2 ]: FIG. 2 depicts a partial view of the same example of a power transmission assembly with a ribbed belt mounted on two pulleys;

[ FIG. 3 ]: FIG. 3 shows a view of the elastic ribbed belt;

[ FIG. 4 ]: figure 4 shows a close-up view of a ramp for mounting an elastic belt on two pulleys to ensure the pre-stressing of said pulleys.

[ FIG. 5 ]: fig. 5 shows a vehicle including a power transmission system according to the invention.

It should be noted that the accompanying drawings illustrate one embodiment of the invention in a detailed manner for practicing the invention, and of course, the drawings are better able to define the invention where appropriate.

Detailed Description

The present invention relates to a transmission system for a drive train of a vehicle, in particular comprising an elastic belt. The invention is intended in particular for use in motor vehicles but also for any wheeled land vehicle, i.e. light, medium or heavy vehicles, or construction vehicles or agricultural vehicles, used to transport passengers or goods.

The invention is particularly directed to 3 or 4 wheeled electric vehicles.

With reference to fig. 1, the invention falls particularly within the context of a powertrain via which an electric machine 20 drives two laterally opposed wheels of a vehicle through a differential.

Fig. 1 shows a powertrain comprising an electric machine 20, in particular an electric motor 20, of a motor vehicle, the electric machine 20 being connected to a power transmission system comprising a reduction stage, in particular comprising a ribbed elastomeric belt 11 and two

pulleys

12, 13, and an auxiliary reduction gear unit 1 driving a differential. Using a reduction gear unit 1 as a complement to the reduction gear unit 1, it is possible in particular to standardize the reduction gear unit 1, even the electric motor 20 and the differential, so as to intervene only in the reduction gear unit, so as to modify the reduction ratio according to the characteristics of the vehicle. It is thus possible to standardize the auxiliary reduction gear unit 1 within the range of the powertrain. Using a deceleration stage, a conversion ratio ranging from 3/1 to 28/1 can be achieved.

In addition, the use of a pulley/belt assembly downstream of the motor, in particular between the electric motor and the auxiliary reduction gear unit, makes it possible to transmit the torque without generating axial forces on the drive shaft and on the electric machine, as is the case with the mounting of the pinion on the drive shaft.

The elastic belt 11 is pre-tensioned on two

pulleys

12, 13, as shown in fig. 2. In particular, the

pulleys

12, 13 are fixed and means for adjusting the central distance E between the two

pulleys

12, 13 may optionally be provided to set the initial tension and elongation of the belt 11. The elastic band 11 is made of polyamide, for example, but not necessarily.

Here, the pulley is ribbed such that the pulley ribs are interposed between the belt ribs.

The motor 20 can also be held between two fastening points, one of which forms a sliding connection, so that a suitable initial tension of the elastic band 11 can be set.

Fig. 4 shows a close-up view of the means for obtaining the desired prestress of the elastic band 11 in the embodiment shown. According to this embodiment, it is provided to mount the electric motor 20 and the respective frame of the auxiliary reduction gear unit 1 on a pivot able to translate in the slide 30. When the elastic band 11 is installed in the power transmission system 10, the

pulleys

12, 13 can be drawn closer to each other, corresponding to moving the pivot shaft in the slideway 30 to the first position a (or bottom position), which reduces the centre distance E, making it easy to slide the untensioned elastic band 11 onto both

pulleys

12, 13. In a second step of the mounting operation, the corresponding pivot is translated in the slide 30 to a second position B (or top position) in which the elastic band 11 is tensioned with a predetermined elastic pre-stress threshold. The second position B is determined such that the initial elongation of the elastic band 11 corresponds to the desired prestress of said elastic band 11.

An advantage of this approach is that it facilitates maintenance and service of power transfer system 10. This pre-stressing mounting method of the elastic band 11 should not be understood as limiting, as other mounting methods are conceivable which achieve the desired pre-stressing of the elastic band 11.

According to a variant, the elastic band 11 is mounted around the two

pulleys

12, 13 by deforming the elastic band 11 beyond a predetermined prestress threshold of the elastic band 11 in the mounted state, so as to position it around the two pulleys.

Similarly, with a machine having a mounting cone, elastic band 11 can be stretched to enable it to be slipped onto

pulleys

12, 13; the installation cone machine is then released and the elastic band 11 is deposited on the

pulleys

12, 13 with the desired prestress, in other words with the desired initial elongation.

Thus, according to the invention, the belt 11 is elastic. In particular, the elasticity of the belt 11 is adapted to compensate for the elongation of said belt 11 due to its wear, so as to maintain the tension exerted on said belt. This is made possible by the prestressed mounting of the elastic band 11.

In other words, the present invention enables the proper tension of the elastic band 11 to be achieved and maintained in the power transmission system 10, thus achieving and maintaining satisfactory durability of the vehicle and the desired level of performance in terms of Noise, vibration and Harshness (or "NVH", standing for "Noise, vibration, Harshness"), all without the need for a tensioner-type compensation system.

In particular, the prestressed mounting of the elastic band 11 (in other words its initial elongation) makes it possible to compensate for the elongation of the band 11 due to its wear and, in the absence of prestressing, it causes a relaxation of said elastic band 11. By means of the prestress of the belt 11, its elongation is compensated by maintaining a suitable value of its tension.

Thus, a compensating assembly comprising a roller, tensioner and spring, which in the prior art had to maintain the tension of the belt when elastic tension was used, can be eliminated.

Thus, the power transmission system 10 is configured to transmit torque to the wheels that can reach the maximum torque Cmax. The elastic band 11 is mounted pre-tensioned, initially with a nominal tension Tnom. As described above, due to the use of the elastic band 11 in the power transmission system 10, its wear causes it to elongate and reduce its current tension T over time. It is known that the elastic band 11 is able to transmit the maximum torque Cmax as long as its tension is higher than the minimum threshold tension Tmin.

According to the invention, the elastic band 11 is elastically pre-tensioned due to its elasticity and under tension, and is therefore configured such that Tnom > T > Tmin during the service life of said elastic band 11.

In particular, with the present invention, the elastic band 11, due to its elasticity and being elastically pre-tensioned installed under tension, is able to withstand significant elongation a while continuing to satisfy the conditions (Tnom > T > Tmin) related to its current tension.

As can be seen in this embodiment, the belt is preferably ribbed, e.g. with V-shaped grooves, such as in the trade name Poly

Those used in belts sold.

According to the embodiment shown in fig. 1, the power transmission system 10 is connected to an electric motor 20 of a motor vehicle. The stiffness of the elastic ribbed belt is in particular less than 12000N/rib/span/E% (in newtons/rib/span (spacing between ribs)/percent elongation of the belt (relative to its original total length)).

As an example, the elastic band 11 is configured such that Tnom is greater than or equal to about 1.2Tmin, for example. The nominal tension of the elastic band 11 is correlated to the elongation E of the elastic band 11 caused by the elastic deformation of Tnom. For example, the elongation E is greater than or equal to 1.5% of the original length of the elastic band 11, in particular greater than or equal to 2% of said original length.

The width of such an elastic ribbed belt 11, intended to be implemented in electric vehicles, is intended in particular to allow the transmission of suitable torques, including in extremely cold environments, that is to say in environments with temperatures of the order of-30 ℃, or in wading (fording), even if very cold temperatures or humidity have a tendency to increase the risk of slipping of the elastic belt. To overcome this risk, the width of the elastic ribbed belt 11 is increased by about three ribs, that is to say, with respect to the width by about 1.05cm, which is in principle sufficient to transmit the required power in the context of the motor vehicle in question.

By means of the invention, exploiting the elasticity of the ribbed belt 11 configured as defined above, which ribbed belt 11 forms, in the context of the power transmission system 10, the first stage of the powertrain of an electric vehicle, results in an improvement of the durability of said ribbed belt 11.

In summary, the invention therefore relates to a power transmission system 10, which power transmission system 10 comprises an elastic, in particular ribbed, belt 11, which belt 11 forms the first stage of a drive train connected to an electric machine 20, in particular an electric motor, of a motor vehicle.

The elastic belt 11 can be mounted on two fixed

pulleys

12, 13, said belt being mounted around the two

pulleys

12, 13 by means of the elasticity of said belt 11.

According to the invention, such a power transmission system 10 comprising an elastic band 11, in particular ribbed, can be used without axial loads connecting it to the electric motor 20. According to the invention, one and the same elastically ribbed belt 11 can be used to achieve a plurality of conversion ratios, depending on the central distance E and the diameter of the

pulleys

12, 13 used.

Fig. 5 is a side view of the vehicle 100 including the power transmission system 10 according to the embodiment of fig. 1 to 4. In the illustrated example, the vehicle 100 is a three-wheeled electric vehicle.

Claims

1. A power transmission system (10) for a powertrain of a motor vehicle, in particular a passenger motor vehicle, comprises an elastic band (11), said elastic band (11) being configured to transmit a torque to at least one wheel of said motor vehicle.

2. The power transmission system (10) as claimed in claim 1, the torque transmission system (10) being capable of receiving torque from a motorized system on the one hand and of transmitting torque to the at least one wheel of the vehicle on the other hand, the power transmission system (10) comprising a torque transmission path between the motorized system and the at least one wheel, the elastic band (11) forming part of the torque transmission path.

3. The power transmission system (10) as claimed in claim 1 or 2, wherein the elastic band (11) is tensioned only due to its inherent elasticity and mounting by elastic pre-stress.

4. The power transmission system (10) as defined in any one of claims 1-3, wherein the elastic band (11) is a ribbed band that includes longitudinally extending ribs.

5. The power transfer system (10) of claim 4, including between 10 and 12 ribs (111).

6. The power transmission system (10) according to any one of claims 1 to 5, comprising a reduction stage comprising two pulleys (12, 13) having a center distance (E), and at least one auxiliary reduction gear unit (1), and wherein the elastic band (11) is mounted on the two pulleys (12, 13) and is adapted to produce, together with the auxiliary reduction gear unit, a conversion ratio between 3/1 and 28/1.

7. The power transmission system (10) as claimed in any one of claims 1 to 6, wherein the power transmission system (10) comprises a differential designed to drive two laterally opposite wheels of the vehicle, the elastic band (11) being designed to transmit torque from an electric machine to the differential.

8. The power transmission system (10) according to claim 7, wherein the power transmission system (10) comprises an auxiliary reduction gear unit (1) kinematically arranged between the reduction stage comprising the two pulleys (12, 13) and the elastic band (11) on the one hand and the differential on the other hand, the two pulleys (12, 13) and the elastic band (11) thus forming a first reduction stage of the power transmission system (10).

9. The power transmission system (10) of any one of the preceding claims, wherein the stiffness of the elastomeric ribbed belt (11) is less than 12000N/rib/span/E%.

10. The power transmission system (10) of any of the preceding claims, wherein the installed belt has an elongation (E) greater than or equal to 1.5% of the original length of the elastic belt (11).

11. A range of power transmission systems for transmitting power between an electric machine and at least one wheel, the range comprising at least two power transmission systems (10) according to any one of the preceding claims, the two transmission systems having different reduction ratios between their electric machines and their at least one vehicle, the auxiliary reduction gear units (1) of the two power transmission systems (10) having the same reduction ratio, the difference in reduction ratio between the two transmission systems being obtained by means of the two reduction stages, each reduction stage comprising the two pulleys (12, 13) and the elastic band (11), the two reduction stages having different reduction ratios.

12. Powertrain for a motor vehicle, comprising at least one wheel and a motorized and driving system for said at least one wheel, said motorized and driving system comprising a power transmission system (10) according to any one of claims 1 to 10, said power transmission system (10) being designed to transmit torque between said motorized system and said at least one wheel, said power transmission system (10) being designed such that said elastic band (11) is located in said torque transmission path between said motorized system and said at least one wheel.

13. Vehicle comprising a power transmission system (10) according to any one of claims 1 to 10 or a powertrain according to claim 12.

14. Method of installing a power transmission system (10) according to any one of claims 1 to 10, wherein the elastic belt (11) is installed around the two pulleys (12, 13) by an elastic deformation of the elastic belt (11) exceeding a predetermined pre-stress threshold of the elastic belt (11) in the installed state.