FR2942998A1 - Suspension device for suspending power unit in body of motor vehicle, has upper torque pickup filtering element extending above center of gravity of power unit and at overside from lower torque pickup filtering element - Google Patents

Abstract

The device has upper carrier filtering elements (10, 11) extending above a center of gravity (G) of a power unit (1) and to longitudinal ends of the power unit. A lower torque pickup filtering element (12) extends below the center of gravity of the unit, and an upper torque pickup filtering element (13) extends above the center of gravity of the power unit and at overside from the lower torque pickup filtering element. The lower and upper torque pickup filtering elements are connected to the power unit in a same plane as that of center of gravity of the power unit.

Description

DEVICE FOR THE SUSPENSION OF A POWER PLANT IN A VEHICLE BOX

The present invention relates to a suspension device of a powertrain in a vehicle body, including a motor vehicle, and a vehicle equipped with such a powertrain suspension device. The present invention relates more particularly to a suspension device of a powertrain adapted to an engine having only three cylinders.

In general, a powertrain equipping a vehicle and especially a motor vehicle, includes a multi-cylinder internal combustion engine, a clutch and a gearbox. This powertrain is mechanically linked to the vehicle body by a suspension device consisting of several antivibration mounting elements adapted in a suitable manner between the powertrain and the vehicle body. These elements and their locations depend in particular on the type of motorization, petrol or diesel, the cycle of the powertrain, the number of cylinders, their arrangement in line, in V or flat, and the transverse or longitudinal implantation of this powertrain in the crate.

Generally, each of the antivibration fixing elements consists of a more or less complex assembly of elastomer parts, such as rubber, and metal parts for joining the part or the assembly of elastomer parts, on the one hand, to the powertrain and on the other hand, to the vehicle body.

The main role of the powertrain suspension device is the maintenance of this powertrain in the vehicle body, especially under the own weight of said powertrain and under the reaction torque exerted by the transverse transmissions on the powertrain

when there is transmission of power from the powertrain to the wheels of the vehicle, and the filtration of the vibratory excitation of this operating group generated by the moving masses and the explosive forces of the engine, while limiting the deflections of the group in response to the torque that drives the wheels in particular.

The suspension of the powertrain must be flexible enough to best filter the vibrations related to its operation and transmit them as little as possible to the vehicle.

The great flexibility of the antivibration fasteners relative to the powertrain and the metal supports, leads to the existence of own modes of suspension of this powertrain where the latter remains rigid and where are the fasteners that deform. These modes of suspension are generally placed very low in frequency, preferably between 5 and 20 Hertz.

These suspension modes are six in number, three in translation and three in rotation in an orthonormal reference XYZ where X is the longitudinal axis of the vehicle, Y the transverse axis of the vehicle and Z the vertical axis. These modes are commonly called: - Sieve mode: translation along the X axis; - Ballant mode: translation along the Y axis; - Hash mode: translation along the Z axis; - Galop mode: rotation around the X axis; - Roll mode: rotation around the Y axis; - Lace mode: rotation around the Z axis.

The frequency placement of each of these modes is regulated very precisely, in particular with respect to the characteristic frequencies of the excitation of the heat engine.

In the case of a three-cylinder engine in line, the mode of Lacet plays an important role vis-a-vis the response of the powertrain on its suspension to the various mechanical excitations which solicit it and is able to generate vibratory levels and unacceptable sound.

Several types of powertrain suspension devices are known, the two most common of which are the so-called pendulum or pendulum suspension, for transversely implanted powertrains and the so-called suspended suspension for longitudinally or transversely implanted powertrains. FR2731184 illustrates such a design.

The so-called pendulum suspension is particularly well suited to transversely implanted powertrains. It consists of three antivibration mounting elements, two of which are placed higher than the center of gravity of the powertrain at the two longitudinal ends of the powertrain and the third is located lower than the center of gravity of this powertrain.

The first two elements provide a function of carrying and vertical positioning of the powertrain in the vehicle body. These elements that carry respectively the engine and the other box, have significant stiffness in the Z direction so as to support the weight of the powertrain. These two elements also have a function of torque recovery and limitation of rotations of the powertrain under torque, which has the consequence for each of these elements to have a high level of stiffness in the X direction and implies the presence of means displacement limitation in the same direction X, generally this limitation function being provided by elastomeric stops. Preferably, these two elements are made in the form of filter shims.

Sometimes the antivibration mounting element carrying the engine is formed of two separate parts: a carrier-only right shim and a torque recovery element in the form of a rod consisting of 2 filtering joints connected by a metal body.

The third element disposed below lower than the center of gravity is not a carrier and therefore does not require a significant level of stiffness in the vertical direction along the Z axis. It provides a lower torque recovery function and limitation of rotations of the powertrain under torque, which has the consequence of having a high level of stiffness in the X direction and implies the presence of displacement limiting means in the same direction X, generally this limitation function being provided by elastomeric stops. This third element is generally made in the form of a rod consisting of two filtering joints connected to a metal body

The suspension architecture of the so-called pendulum powertrain has the advantage of allowing independent adjustment of the frequencies of the Hachis and Roulis modes, whereas the frequency of the Galop and Lacet modes is the result.

The lack of frequency control of the Galop and Lacet modes can be penalizing in the context of motorization presenting excitations in Galop and Lacet, as the in-line three-cylinder engines or the six cylinders arranged in V. In the particular case of the engines three-cylinder in-line processing of excitation in Galop and Lacet generally passes by the addition of a balancing shaft. This solution has the disadvantage of being expensive and generates an overconsumption of fuel.

The object of the invention is to avoid these drawbacks by proposing a suspension device which is easy to implement and economical and which makes it possible to wedge the

six powertrain suspension modes practically independently of one another and at relatively low frequencies.

The invention therefore relates to a suspension device of a powertrain in a vehicle body, including a motor vehicle, by means of antivibration fasteners connecting the powertrain to the body.

This device is characterized in that it comprises four antivibration fixing elements, a first and a second upper carrying elements extending higher than the center of gravity of the powertrain and substantially at both longitudinal ends of the powertrain, a third element lower torque recovery extending lower than the center of gravity of the powertrain and a fourth upper element extending higher than the center of gravity of the powertrain and substantially in line with said third element.

According to another characteristic of the invention, the third and fourth elements are connected to this powertrain substantially in the same plane XZ as the center of gravity of the powertrain.

According to another characteristic of the invention, the third element comprises displacement limitation means in the X direction so as to operate a limitation of rotations of the drive train under torque, during large displacements of the powertrain.

According to another characteristic of the invention, the fourth element has a torque recovery function and therefore has a high level of stiffness in the X direction. According to another characteristic of the invention, the fourth element comprises means for limiting the torque. move in the X direction to operate30

a limitation of rotations of the powertrain under torque, during major movements of the powertrain.

According to another characteristic of the invention, the first and second upper load elements have low stiffness in the X direction, so as to ensure a low frequency lace mode placement.

The invention also relates to a vehicle and in particular a motor vehicle, characterized in that it comprises a suspension device of the powertrain as previously described.

The features and advantages of the invention will become apparent from the following description given by way of example and with reference to the accompanying drawings, in which: FIG. 1 is a schematic perspective view of a suspension device of a power train according to the invention; FIG. 2 is a schematic view from above of the powertrain shown in FIG. 1, - FIG. 3 illustrates a bearing block, and FIG. 4 shows a torque recovery link.

The XYZ orthonormal frame represented in FIG. 1 is the conventional reference frame where X is the longitudinal axis of the vehicle, Y is the transverse axis of the vehicle and Z is the vertical axis.

In FIG. 1 schematically shows a powertrain intended to equip a vehicle including a motor vehicle. This powertrain, designated by the general reference 1, is formed by a three-cylinder internal combustion engine in line coupled to a gearbox via a clutch. The power train, of the transverse type in that it extends in the engine compartment in the Y direction, is designated by the general reference 1. The power train 1 is

supported by the body structure 2 of the motor vehicle defining the engine compartment and more particularly by the stretchers extending parallel to the longitudinal axis X of the vehicle, by a cross member extending in Y which is taken up on the stretchers and by the engine cradle. These different pieces of the box 2 have not been shown to increase the readability of the drawing.

The power train 1 is suspended in the body 2 by a suspension device similar in principle to a pendulum architecture which comprises four antivibration fixing elements called filter elements and which are designated respectively by the references 10, 11, 12 and 13.

These antivibration fixing elements 10, 11, 12 and 13 have been schematically represented in FIGS. 1 and 2. They are of known types each comprising a part or an assembly of elastomer parts supported by metal parts making it possible to bind the one or more elastomer parts, on the one hand, to the powertrain 1 and, on the other hand, to the body 2.

Thus FIG. 3 describes an example of a bearing block 30 with a torque recovery function performed by stops and FIG. 4 shows an example of a torque-type torque recovery element 40.

The first and second fastening elements 10 and 11, called upper filtering elements, in that they each take up a substantial part of the powertrain 1, are each connected to the powertrain 1 at a point situated higher along the Z axis. that the center of gravity G of this powertrain 1 and solidarize said powertrain 1 to the body of the motor vehicle 2 preferably stretcher not shown. These antivibration fixing elements 10 and 11 are each placed on either side of the power unit 1, that is to say at the two longitudinal ends of the power unit 1.

Since these antivibration fixing elements 10 and 11 do not have a torque recovery function, their stiffness in the vehicle X direction can be chosen freely. In particular, in the case of a three-cylinder heat engine, they can be chosen very flexible in the X direction, to allow a frequency placement of the yaw mode lower than the lowest excitation frequency of the engine.

The third fastening element 12, called the lower torque recovery filter element, is located lower along the Z axis and substantially in the same plane XY as the center of gravity G of the power unit 1. This lower filter element of torque recovery 12 ensures the joining of this powertrain 1 to the body 2 of the vehicle, preferably by the non-figured engine cradle.

The fourth antivibration mounting element 13, called the upper torque recovery filter element, is situated higher, along the Z axis, than the center of gravity G of the power unit 1, substantially perpendicular to the lower filter element. torque recovery 12. This fourth element has a high level of stiffness in the X direction. It ensures the attachment of the powertrain 1 to the body 2 of the vehicle preferably by an unrepresented cross which is recovered on the stretchers.

For a 3-cylinder engine, it would be advantageous to set the yaw mode to a frequency lower than the lowest excitation frequency of the engine, typically 12.5 Hertz for an idle speed of 750 rpm, so as to do not amplify the yaw torque excitation of the engine when it runs at its lowest rpm, usually idle.

Since the frequency of the lace mode is controlled by the stiffness in the X direction of the upper carrying filter elements 10 and 11, a low frequency placement requires a low stiffness in the X direction of the carrier upper filter elements 10 and 11. In the case of a pendulum suspension, the weak

stiffness of the elements 10 and 11 causes a roll mode placed low in frequency, which is undesirable, and may in particular cause engine jolts.

The lower and upper torque recovery filter elements 13 and 14 make it possible to compensate for the lack of stiffness of the upper carrying filter elements 10 and 11 in the X direction and to have a rolling mode at the desired frequency, while keeping the mode of Low lace frequency.

In fact, since these lower and upper torque recovery filter elements 13 and 14 are placed at a Y dimension close to that of the center of gravity, their stiffness in the vehicle X direction contributes little to the frequency of the yaw mode.

The suspension device according to the invention makes it possible to adjust the frequencies of the six modes of suspension of the powertrain almost independently of each other and in particular to place these six modes at relatively low frequencies.

This device has the same advantages as a pendulum type suspension device. It has the advantage of allowing, moreover, the independent adjustment of the Roulis and Lacet modes. This independent adjustment is particularly interesting for in-line three-cylinder engines that exhibit excitations in Galop and Lacet mode at frequencies below 20 Hertz. Indeed, it is important to know how to place the Roulis and Lacet modes sufficiently low in frequency, while keeping a conventional frequency positioning for the other modes.

In general, the suspension device according to the invention is ideally suited to actuators exciting the lace mode such as three-cylinder in-line or V-type six-cylinder engines.

Claims (6)

REVENDICATIONS1. Suspension device for a power unit CLAIMS1. Device for suspending a power unit (1) in a vehicle body (2) and in particular a motor vehicle, by means of antivibration fixing elements (10, 11, 12, 13) connecting the power unit (1) to the body (2), characterized in that the antivibration fixing elements are formed by four separate antivibration fixing elements, a first and a second upper bearing elements (10, 11) extending above the center of gravity of the group power train (1) and substantially at both longitudinal ends of the power train (1), a third lower torque recovery member (12) extending lower than the center of gravity of the power train (1) and a fourth upper member ( 13) extending higher than the center of gravity (G) of the powertrain and substantially in line with said third member (12). 2. Suspension device according to claim 1, characterized in that the third (12) and fourth elements (13) are connected to the powertrain (1) substantially in the same plane XZ as the center of gravity (G) of the powertrain . 3. Suspension device according to any one of the preceding claims, characterized in that said third element (12) comprises displacement limiting means in the X direction so as to operate a limitation of rotations of the powertrain (1) under torque, during major movements of the powertrain (1). 4. Suspension device according to any one of the preceding claims, characterized in that said fourth element (13) has a torque recovery function and therefore has a high level of stiffness in the X direction. 5. Suspension device according to one of the preceding claims, characterized in that said first and second upper support members (10, 11) have low stiffness in the X direction, so as to ensure a low frequency lace mode placement. 6. Vehicle and in particular a motor vehicle, characterized in that it comprises a powertrain suspension device (1) according to any one of the preceding claims.