GB2228551A

GB2228551A - Motor vehicle engine mounting

Info

Publication number: GB2228551A
Application number: GB9001983A
Authority: GB
Inventors: Gunter Eberhard; Juergen Bebermeier; Wolfgang Kraft; Juergen Heitzig
Original assignee: Continental AG
Current assignee: Continental AG
Priority date: 1989-01-28
Filing date: 1990-01-29
Publication date: 1990-08-29
Also published as: FR2642493A1; GB9001983D0; DE3902604A1

Description

- 1 ELASTIC MOUNTING, IN PARTICULAR A MOTOR VEHICLE ENGINE MOUNTING The

present invention relates to an elastic mounting with an elastic rubber spring member located between two connecting members in order to support a vibrating load, whose vibration spectrum includes both low frequency and high frequency vibrationsq in particular motor vehicle engine mountings.

Such engine mountings are known in a large number of different forms. Their function is basically to prevent the movements of a vibrating load being transmitted to the foundation or frame supporting this load, and this is achieved in different ways and with varying degrees of success by different forms of mounting. Although previously predominantly pure rubber mountings in which the induced vibration amplitudes were only reduced by the internal damping of the rubber pad were used, now mountings with integrated damping devices are preferred, such as those described in the form of a "hydromounting" in DE-PS 32 07 553 and a "displacement mounting" described in DE-PS 32 33 456. In addition to vibration insulation and damping the forms illustrated in the two documents mentioned also offer the advantage that they process imposed vibrations selectively, namely in such a way that low frequency vibrations, i.e. vibrations with frequencies below some 20 Hz, which generally have a large amplitude, are strongly damped, while high frequency vibrations, i.e. vibrations over some 20 Hz, which generally have a smaller amplitude, but are a considerable nuisance because of their acoustic effect, are taken up virtually undamped and thereby largely isolated from the foundation or frame.

Although this acoustic insulation already satisfied very extensive requirements in the case of known hydromountings and displacement mountings, as a result of further increase in demand for comfort the fundamental object of this invention is to provide an elastic mounting which optimised the transfer of high frequency, and in particular acoustically undesirable, vibrations by means of flexible adjustment and active control of the resulting spring forces taking up the vibrating load. The fulfilment of this object was of particular importance in the case of motor vehicle engine mountings.

According to the present invention there is provided an elastic mounting with an elastic rubber spring member located between two connecting members in order to support a vibrating load whose vibration spectrum includes both low frequency and high frequency vibrations, in particular motor vehicle engine mountings in which the spring member is fitted with an electrostrictive or magnetostrictive actuator in a mechanical parallel arrangement in such a way that one face thereof is rigidly coupled to a connecting member of the spring member while its other face is connected to the other connecting member via a closed static decoupling hydraulic system and in which a sensor which detects the alternating forces, alternating accelerations or vibrational displacements due to the vibrating load is provided and is connected to the actuator via an amplitude and phase regulator and amplifier wherein the regulation is so designed that the actuator minimises the alternating forces, alternating accelerations and vibrational displacements applied to the sensor Also according to the present invention there is provided an elastic mounting with an elastic rubber spring t A member located between two connecting members in order to support a vibrating load5 whose vibration spectrum includes both low frequency and high frequency vibrationsy in particular motor vehicle engine mountings, in which the spring member is fitted with an electrostrictive or magnetostrictive actuator in a mechanical parallel arrangement in such a way that one face thereof is rigidly coupled to a connecting member of the spring member while its other face is connected via a closed statically decoupled hydraulic system to the other connecting member and in which a sensor which detects a characteristic movement and positional parameter of periodically moving parts of the vibrating load, such as e.g. the angular position and/or the rotation speed of a motor vehicle engine crankshaft, is provided and is connected via a computer and an amplifier to actuator, wherein a program processing the output signal of the sensor on the basis of an empirically determined vibration characteristic of the load is stored in the computer and wherein the computer output signal applied to the actuator via the amplifier controls the latter in such a way that it brings about a reduction in the alternating forces, alternating accelerations and vibrational displacements occurring in the frame or base-side connecting member.

In accordance with the invention it is proposedto incorporate eletrostrictive or magnetostrictive Yeactuators" in order to achieve the specified tasks. These actuators are known in themselves, and it has already been proposed that they should be incorporated as components of fine mechanical tools and processing machinery. They have the advantageous property that their axial length varies in relation to the voltage applied to them or the current flowing through them so that with their help electrical signals can be converted directly into mechanical movements. In the context of this - 4 invention electostrictive actuators which are based on the known piezoelectric principle are preferred.

According to the invention the said actuator is mounted in parallel with the elastic rubber spring member of the proposed elastic mounting which accepts the vibrating load, it being supported by a closed statically decoupled hydraulic system on the side away from the load. This has the consequence that the static load is fully taken up by the spring member, while the actuator is subjected only to the dynamic alternating forces superimposed on the static load. As a hydraulic system of this type has only a static or quasi-static, i.e. low frequency, decoupling effect on an imposed force but acts like a rigid connection in relation to high frequency alternating forces. As a result of this, high frequency changes in the length of the actuator have a direct effect on the supporting forces on the connecting member of the elastic mounting according to the invention which takes the vibrating load and thus the high frequency alternating force amplitudes produced by the vibrating load can be taken up by corresponding control of the actuator.

In the elastic mounting according to the invention the actuator is connected for the purpose of its control to a sensor which provides, in a first preferred embodiment of the invention in association with a regulator device and in a second embodiment of the invention in association with a computer, control signals which correspond to the alternating forces or vibrational movements produced by the vibrating load and through which the axial length of the actuator is so continuously changed that the said alternating forces and vibrational movements are at least partially compensated and taken up and thus in any event are transmitted in greatly reduced measure to the foundation or frame.

In this way the actuator deadens in particular high frequency acoustic vibrations of low amplitude while low frequency large amplitude vibrations are taken up by the spring member and may be damped. On account of the small amplitudes of the undesirable acoustic vibrations, which in general are only of a few tenths of a millimetre, the changes in length which can be achieved in available actuators which are of the same order of magnitude are fully sufficient for effective body noise insulation.

In the abovementioned preferred first embodiment of this invention the alternating forces or vibrational movements produced by the vibrating load are taken up by sensors in the form of force or movement acceptors, in particular sensors incorporated in the mounting, the output signal from which controls the actuator by means of a known control device and amplifier. Thus the control device and amplifier, the actuator and the sensor form a closed control loop in which the actuator acts as the regulating member and the sensor acts as the detector. The alternating forces or vibrational displacements applied to the sensor enter this control loop as an error quantity, the actual value of the error quantity being compared with the specified reference quantity, in particular "zero", and the adjusting member being activated in such a way that the actual value is brought closer to this reference value with the result that the error quantity is minimised and in particular reduced to 91 zero Piezoelectric units are preferably used as sensors for this purpose. Alternatively sensorsy in particular of the strain measuring typel may be considered. The sensors are preferably incorporated as close as possible to the unit comprising the rubber spring member and the actuator in order to avoid influence from interfering vibrations from other sources which cannot be controlled with the help of the actuator.

In order that the advantageous effects achieved with the invention are not only utilised in a single vibrational direction, in a preferred embodiment each main vibrational direction of the load applied to the mounting according to the invention is provided with an actuator and a corresponding sensor. Preferably the arrangement of the actuators and sensors is in the form of three projections at right angles to each other.

In the abovementioned second embodiment of the invention an elastic mounting which utilises one of the stated advantages of actuators is proposed, in which the incorporated sensor is a detector which detects characteristic movement and positional parameters of the periodically moved components of the load applied to such a mounting which are directly or indirectly associated with the cause of the vibration in the load. In the case of a mounting for a motor vehicle engine a suitable detector may for example detect the angular position and rotation speed of the crankshaft. The signal produced by the detector is passed to a computer which is connected to the actuator through an amplifier.

The computer then controls the actuator in relation to the phase signal detected (e.g. the angular position of the crankshaft) in accordance with a stored program which has been established on the basis of investigation of the vibration characteristics of the load - 7 in such a way that the in particular high frequency alternating forces and vibrational movements applied to the mounting are largely compensated and taken up. Here it may also be advantageous to provide actuators in the main direction of vibration of the system, in particular actuators in the form of three projections at right angles.

In all the embodiments of the elastic mounting according to the invention the spring member used preferably has a damping device and in particular is designed so that the spring member consists not of a pure rubber mounting but of a hydromounting or displacement mounting of the known type described in the introduction.

The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which:

Fig. la is a diagrammatical view of a preferred arrangement of the preferred first embodiment of the elastic mounting according to the invention with controlled actuator control:

Fig. lb is a corresponding illustration of a preferred arrangement of the second embodiment described above; Fig. 2 is an axial view through a practical preferred arrangement with an integrated damping device; and Fig. 3 is an axial view through a further practical preferred arrangement.

--8 As Fig. la shows, an elastic mounting according to the invention has an elastic spring member 3 and an actuator 4 which are mounted mechanically in parallel between connecting member 1 to which the vibrating load L is applied and the base or frame-side connecting member 2. For this purpose actuator 4 is rigidly connected to loadside connecting member 1 by means of its face 4.1, while its other face 4.2 is connected to base-side connecting member 2 by means of a closed statically decoupled hydraulic system. A preferably piezoelectric sensor 5 is arranged so that it takes up the alternating forces produced by vibrating load L. Its output signal is processed by connected computer 6 and amplifier 7 in such a way that it adjusts actuator 4, the adjustment being designed so that the alternating forces produced by vibrating load L are taken up by actuator 4 without passing through connecting member 2 to which sensor 5 is coupled.

Fig. 1,b shows in a corresponding diagrammatical presentation an elastic mounting of the second embodiment according to the invention with a mechanical connection parallel to spring member 3 and actuator 4 fitted with a detector S' which is used as the sensor, which determines the phase position and rotation speed of a periodically moved part of load L (for example the crankshaft of a motor vehicle engine) and passes it to a computer 61. Computer 6', then controls actuator 4 via amplifier 7 in relation to the sensor signal on the basis of an empirically determined program stored within it, in which each vibrational state of load L is associated with an actuator control voltage, whereby the axial length of actuator 4 is altered so that it continuously compensates for or largely reduces the alternating forces, alternating accelerations or vibrational movements applied to the mounting.

Fig. 2 illustrates a practical embodiment of the invention in which the elastic mounting is also provided with an integrated damping device. Spring member 3 which is constructed in the form of a rubber spring encloses housing 10 containing two chambers 11 and 12 of alternately varying volume filled in particular with a low viscosity liquid. These chambers are separated from each other by a separating wall 13 which is secured to the wall of the housing and contains a flow opening 13.1. The central portion 13.2 of separating wall 13 is mounted in an axially movable way by means of an elastic connection 13.3 and is supported via a face 4.1 rigidly fixed to an actuator 4 against the housing 10 which is rigidly attached to the other face 4.2 of the actuator.

In this mounting low frequency large amplitude vibrations have virtually no effect on actuator 4 because the forces deforming spring member 3 via connecting member 1 only result in displacing liquid between chambers 11 and 12. These vibrations are thus damped as a result of the flow resistance at flow opening 13.1.

In the case of high frequency vibrations flow opening 13.1 has a high flow resistance so that there is an effectively rigid connection between actuator 4 and load-side connecting member 1 due to the incompressible liquid. Thus through high frequency changes in the length of actuator 4, produced in this by the regulated and amplified signals produced in a sensor which is not shown, corresponding forces are transferred to load side connecting member 1 as a result of the rigid coupling through the liquid and deaden the alternating amplitudes - 10 of the vibrating load on connecting member 1 so that the desired acoustic insulation effect occurs.

In the advantageous example embodiment of an elastic mounting according to the invention illustrated in Fig. 3, spring member 3 is likewise constructed in the form of a rubber spring enclosing a housing 10 on the load side. Housing 10 is completely filled with a preferably highly viscous liquid and one side 4.1 of actuator 4 projecting into the internal space of the housing in longitudinal direction A is secured to load side connecting member 1 which is connected to the rubber spring on its side away from housing 10. The other side 4.2 of actuator 4 is rigidly attached to a counter disc 14 which extends in the liquid transversely to mounting axis A without contact with housing 10.

As in the mounting according to Fig. 2, in this embodiment neither low frequency high amplitude load variations nor the static fundamental load affect actuator 4. On the other hand the liquid surrounding counter disc 14 forms a rigid support in relation to high frequency vibrations so that the axial changes in length of actuator 4 which are caused by a sensor that is not shown produce alternating forces on load-supporting connecting member 1 as a result of the intermediate adjustment and amplification through which the high frequency load variations are deadened and thus acoustic insulation is achieved when appropriately adjusted.

The mounting according to Fig. 3 also has a strongly damping effect on low frequency load variations as these are associated with axial displacements of counter disc 14 which is slowed down by the preferably highly viscous liquid surrounding it.

1 1 Basically the embodiments according to Figs. 2 and 3 can also be used in the arrangement illustrated at the top with the result that the connecting member indicated by reference number 2 in the figures supports the load and connecting member 1 is supported on the frame.

Claims

CLAIMS.

An elastic mounting with an elastic rubber spring member located between two connecting members in order to support a vibrating load, whose vibration spectrum includes both low frequency and high frequency vibrations, in particular motor vehicle engine mountings in which the spring member is fitted with an electrostrictive or magnetostrictive actuator in a mechanical parallel arrangement in such a way that one face thereof is rigidly coupled to a connecting member of the spring member while its other face is connected to the other connecting member via a closed static decoupling hydraulic system and in which a sensor which detects the alternating forces, alternating accelerations or vibrational displacements due to the vibrating load is provided and is connected to the actuator via an amplitude and phase regulator and amplifier. wherein the regulation is so designed that the actuator minimises the alternating forces, alternating accelerations and vibrational displacements applied to the sensor.
2. An elastic mounting as claimed in claim 1, in which the sensor is coupled to the frame or a base-side coupling member.
3. An elastic mounting as claimed in claim 1 or 2, in which the sensor is a piezoelectric sensors
4. An elastic mounting as claimed in claim 1 or 2, in which the sensor is constructed in the form of a strain measuring strip.
5. An elastic mounting as claimed in any preceding claim in which the actuators and sensors are directed in - 13 the main directions of vibration of the supported vibrating load.
6. An elastic mounting as claimed in claim 5, in which the mounting incorporates three actuators and sensors in the form of three arms at right angles to each other.
7. An elastic mounting with an elastic rubber spring member located between two connecting members in order to support a vibrating load, whose vibration spectrum includes both low frequency and high frequency vibrations, in particular motor vehicle engine mountings.

in which the spring member is fitted with an electrostrictive or magnetostrictive actuator in a mechanical parallel arrangement in such a way that one face thereof is rigidly coupled to a connecting member of the spring member while its other face is connected via a closed statically decoupled hydraulic system to the other connecting member and in which a sensor which detects a characteristic movement and positional parameter of periodically moving parts of the vibrating load, such as e.g. the angular position and/or the rotation speed of a motor vehicle engine crankshaft, is provided and is connected via a computer and an amplifier to actuator, wherein a program processing the output signal of the sensor on the basis of an empirically determined vibration characteristic of the load is stored in the computert and wherein the computer output signal applied to the actuator via the amplifier controls the latter in such a way that is brings about a reduction in the alternating forces, alternating accelerations and vibrational displacements occurring in the frame or base-side connecting member.
8. An elastic mounting as claimed in any preceding claims in which the spring member is provided with a damping device.
9. An elastic mounting as claimed in claim 8, in which the spring member is constructed as aknown "hydromounting" or "displacement mounting%
10. An elastic mounting substantially as hereinbefore described with reference to the accompanying drawings.

Published 1990 at The?atentOffice.StateHouse.66171 High Holborn. LondonWC1R4TP. Further copies maybe obtainedfrom The PatentWice. Sales Branch, St Mary Cray. Orpington, Kent BR5 3BD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1-'87 1