AU5367500A

AU5367500A - Vehicle drive train assembly including piezo-based device for vibration dampening

Info

Publication number: AU5367500A
Application number: AU53675/00A
Authority: AU
Inventors: James A. Duggan
Original assignee: Dana Inc
Current assignee: Dana Inc
Priority date: 1999-08-31
Filing date: 2000-08-28
Publication date: 2001-03-08
Anticipated expiration: 2020-08-28
Also published as: AU774714B2; CA2316757A1; JP2001145850A; DE10042617A1

Description

S&FRef: 521064

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Dana Corporation 3222 West Central Avenue Toledo, Ohio United States of America James A. Duggan Spruson Ferguson St Martins Tower 31 Market Street Sydney NSW 2000 Vehicle Drive Train Assembly Including Piezo-based Device for Vibration Dampening The following statement is a full description of this invention, including the best method of performing it known to me/us:- "i tC IoYrfienls recaivd o: L ie AU8 2000 5845c

TITLE

VEHICLE DRIVE TRAIN ASSEMBLY INCLUDING PIEZO-BASED DEVICE FOR VIBRATION DAMPENING BACKGROUND OF THE INVENTION This invention relates in general to structures for actively and passively dampening vibrations in a vehicle drive train assembly. In particular, this invention relative to a piezo-based device that is attached or otherwise secured to a driveshaft l0 tube in such a vehicle drive train assembly for actively and passively reducing torsional and lateral vibrations that are generated therein during use.

:Torque transmitting shafts are widely used for transferring rotational power between a source of rotational power and a rotatably driven mechanism. One well known example of a torque transmitting shaft is a driveshaft tube that is used in a vehicle drive train assembly. The drive train assembly transmits rotational power from a source, such as an engine and transmission assembly, to a driven component, such as an axle assembly having a pair of driven wheels. A typical vehicle drive train assembly includes a hollow cylindrical driveshaft tube having an end fitting secured to each end thereof. Usually, the end fittings are embodied as end yokes that are adapted to cooperate with respective universal joints. Drive train assemblies of this general type are often used to provide a rotatable driving connection between an output shaft of the vehicle engine and transmission assembly and an input shaft of the axle assembly for rotatably driving the vehicle wheels.

One problem encountered in vehicle drive train assemblies and other rotatable structures is that they tend to vibrate during operation, thereby producing and transmitting undesirable audible noise. It is known that all mechanical bodies have a natural resonant frequency at which they tend to vibrate when operated at certain rotational speeds. This natural resonant frequency is an inherent characteristic of the mechanical body and is based upon many factors, including its composition, size, and shape. In the context of vehicular drive train assemblies, the engine and transmission assembly can sometimes generate vibrations that are transmitted to and accentuated by the driveshaft tube when rotated. Also, driveshaft tube may itself be rotated at a velocity that is at or near its natural resonant frequency (or one or more of the harmonics thereof), causing vibrations to be induced therein. In either event, the vibrations generated in the driveshaft tube may cause the generation of audible noise.

Such noise is usually considered to be undesirable for obvious reasons.

Various attempts have been made to reduce the noise generated by vehicle driveshaft tubes during operation. For example, it has been found to be desirable to dispose one or more noise reduction structures within the hollow driveshaft,tube to i 0 absorb some of the noise generated during use. Known noise reduction structures have been manufactured from many materials, including cardboard, foam, and the like. However, although known noise reduction structures are relatively simple and inexpensive in structure and installation, they have been found to have a relatively modest effect on the reduction of noise in some vehicle driveshaft tubes. Thus, it would be desirable to provide an improved structure for reducing the amount of vibration and noise that are generated in a vehicle drive train assembly during operation.

SUMMARY OF THE INVENTION This invention relates to an improved structure for reducing the amount of vibration and noise that are generated in a vehicle drive train assembly during operation. A piezo-based device is attached or otherwise mounted on a driveshaft tube or other component of the drive train assembly. The piezo-based device is used to dampen these vibrations by converting the physical vibratory motion of the driveshaft tube into an electrical current that is dissipated through a resistive element as heat. By varying the magnitude of the resistive element, the center dampening frequency of the piezo-based device can be varied as needed for the particular driveshaft tube and the drive train assembly as a whole. If desired, an inductive element may be provided in a circuit with the resistive element to dissipate the electrical current. The magnitude of the resistive element may be varied by a controller in response to the magnitude and/or frequency of the vibrations sensed by a sensor. Alternatively, the stiffness of the piezo-based device may be controlled by an electrical current generator that can be operated by a controller in response to the magnitude and/or frequency of the vibrations sensed by a sensor. The piezo-based device may be mounted on either an exterior or interior surface of the driveshaft tube. Alternatively, the piezo-based device may be embedded within or formed integrally with the driveshaft tube. If desired, a plurality of such piezo-based devices may be provided on the driveshaft tube.

Various objects and advantages of this invention will become apparent to those 10 skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevational view of a first embodiment of a vehicle drive train assembly including a driveshaft tube having a piezo-based device attached to the exterior surface thereof in accordance with this invention.

Fig. 2 is a schematic view of a first embodiment of the piezo-based device illustrated in Fig. 1.

Fig. 3 is a schematic view of a second embodiment of the piezo-based device illustrated in Fig. 1.

Fig. 4 is a schematic view of a third embodiment of the piezo-based device illustrated in Fig. 1.

Fig. 5 is a schematic view of a fourth embodiment of the piezo-based device illustrated in Fig. 1.

Fig. 6 is a side elevational view of a second embodiment of a vehicle drive train assembly including a driveshaft tube having a piezo-based device attached to the interior surface thereof or embedded therein in accordance with this invention.

Fig. 7 is a side elevational view of a third embodiment of a vehicle drive train assembly including a driveshaft tube having a plurality of piezo-based devices attached thereto in accordance with this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, there is illustrated in Fig. 1 a first embodiment of a vehicle drive train assembly, indicated generally at 10, in accordance with this invention. The drive train assembly 10 includes a transmission 12 having an output shaft (not shown) that is connected to an input shaft (not shown) of an axle assembly 14 through a driveshaft assembly 16. The transmission 12 is rotatably driven by an engine (not shown) that generates rotational power in a conventional manner. The i driveshaft assembly 16 includes a cylindrical driveshaft tube 18 having a center Sportion and a pair of opposed end portions. The output shaft of the transmission 12 and the input shaft of the axle assembly 14 are typically not co-axially aligned. To accommodate this, a pair of universal joints, indicated generally at 24a and 24b, are provided at the end portions of the driveshaft tube 18 to respectively connect the end portions of the driveshaft tube 18 to the output shaft of the transmission 12 and to the input shaft of the axle assembly 14. The first universal joint 24a includes a tube yoke 26a that is secured to the forward end portion of the driveshaft tube 18 by any conventional means, such as by welding. The first universal joint 24a further includes a cross 27a that is connected to the tube yoke 26a in a conventional manner. Lastly, the first universal joint includes an end yoke 28a that is connected to the output shaft of the transmission 12 and to the cross 27a. Similarly, the second universal joint 24b includes a tube yoke 26b that is secured to the rearward end portion of the driveshaft tube 18 by any conventional means, such as by welding. The second universal joint 24b further includes a cross 27b that is connected to the tube yoke 26b in a conventional manner. Lastly, the second universal joint 24b includes an end yoke 28b that is connected to the cross 27b and to the input shaft of the axle assembly 14. The drive train assembly 10 thus far described is conventional in the art and is intended to be representative of any known structure for transmitting rotational power from a source to a driven device.

As is well known, the operation of the engine 12 usually causes a variety of vibrations to occur in the driveshaft tube 18. Also, the driveshaft tube 18 may, in a some instances,be rotated at or near its natural resonant frequency, which can cause some instances, be rotated atn le ei urce, such vibrations can result vibrations to be induced therein. Regardless their sre, piezobased device, in the generation of undesirable audible noise. To address this, a piezo-based device, indicated generally at 30, is attached or otherwise mounted on the driveshaft tube 18.

The structure and mode of operation of the piezobased device 30 will be described in detail below. Generally speaking, however, the piezo-based device 30 can be used to detail below. Generally speaking, h ow ev er, ec v a o driveshaft dampen these vibrations by converting the physical vibratory motion of the driveshaft damptube 1 into an electrical current that is dissipated through a resistive element as heat.

By varying the magnitude of the resistive element, the center dampening frequency of o the piezo-based device 30 can be varied as needed for the particular driveshaft tube 18 to thepiezo-baseddevice 30canbevariedas vls be explained in detail belowv, and drive train assembly 10. Alternatively, as will also be expla in detail below, the piezo-based device 30 can be used as an active actuator, wherein the application of an electrical current to the piezo-based device causes changes in the stiffness or flexibility thereof. This invention contemplates that one or more zobaed ee 15 30 be attached to the either inner or outer surface of t tue rivesato trol torsional embedded within or formed integrally with the driveshaft tube 18, to control torsional and lateral vibrations in the driveshaft tube 18 and the vehicle drive train assembly as a whole, either passively or actively.0 or As will be discussed in detail below, the piezobased device 30 includes one or more elements that are formed from a piezo-electric material. Generally speaking, a piezo-electric material is any material that generates an electrical output when subjected to mechanical stress or deformation, or vice versa. Typically, the piezoelectric material becomes electrically polarized when mechanically strained, such as by the vibrations that are generated in the driveshaft tube 18 during operation. This thevibration contemplates that any known piezo-eectric material may be used in the piezo-based device 30, including piezo-ceramic materials such as led zirconium titanate ezobased device 30 As shown Fig. 2 illustrates a first embodiment of the piezobased device 30. As show therein, the piezo-based device 30 includes an element 31 formed from a piezo-electric material and a resistor 32 that are connected in a series electrical circuit. In addition t generating an electrical output when subjected to mechanical stress, the element 31 behaves electrically as a capacitor. Thus, the piezo-based device 30 is essentially an RC electrical circuit. When the engine 12 is operated to rotate the driveshaft tube 18, vibrations are generated in the driveshaft tube 18. These vibrations causes mechanical stresses to be induced in the element 31, causing an electrical output (such as a voltage) to be generated therein. This voltage is converted to an electrical current that is passed through the resistor 32, wherein it is dissipated as heat. As a result, the piezo-based device 30 functions to passively dampen the vibrations that are generated in the driveshaft tube 18.

0.10 As is well known, RC electrical circuits have a center dampening frequency that is determined by the magnitudes of the resistance and the capacitance therein. It is desirable that this center dampening frequency be selected to be close to the frequency of the vibrations in the driveshaft tube 18 that are desired to be attenuated by the piezo-based device 30. The magnitude of the desired resistance for the resistor 32 can be calculated using the following relationship: R= (Ak2)/(1-k2)]/Cco where R is equal to the resistance of the resistor 32, C is equal to the capacitance of *the element 31, k is equal to the transverse coupling constant, A is equal to the strain energy capture, and -W is equal to the frequency of the vibrations to be dampened. The piezo-based device 30 can be located at any desired location on the driveshaft tube 18 or any of the other components of the vehicle drive train assembly 10. For example, it may be desirable to provide the piezo-based device 30 on portions of the universal joints 24a and 24b or elsewhere on the vehicle drive train assembly 10. The most efficient location for the piezo-based device 30 on the driveshaft tube 18 can be determined on the basis of structural modeling, modal analysis, and actual experimentation. Generally speaking, however, the piezo-based device 30 will usually be located on the driveshaft tube 18 in the area of greatest strain in order to reduce the greatest amount of vibration. The piezo-based device 30 may be attached to the driveshaft tube 18 by adhesives or secured thereto in any other known manner.

The physical size of the piezo-based device 30 can also varied as desired. By incorporating more of the piezo-electrical material into the piezo-based device more strain energy can be captured and converted to heat. However, the addition of such material increases weight and can have an effect on the rotational balance of the driveshaft tube 18. The amount of the piezo-electric material provided in the element 31 willvary from application to application depending upon a number of factors. The relationship between damping of the piezo-baed device 30 and strain energy capture A is described by: S= 1V4[(Xk2)/(1-k 2 2 0 here is equal to the strain energy capture and is eual to the transverse coupling a here h is equal to the strain energy capture and ki equ

C

C.

C

0@ C C C

CC

constant.iment of the piezo-based device, indicated Fig. 3 illustrates a second embodiment of the piezo-basd device n teent 41 generally at 40. As shown therein, the piezo-based device 40 includes an element 41 formed from a piezo-electric material, a resistor 42, and an inductor 43 that are connected in a series electrical circuit. Thus, the piezo-based device 40 is essentially an RLC electrical circuit. The piezo-based device 40 functions in essentially the same manner as the piezo-based device 30 described above to passively dampen the vibrations that are generated in the driveshaft tube 18. The addition of the inductor 43 ibrations that are electrial current to pass through the resistor 42, thus providing a higher causes more electrical current to pass throuh measure of dampening than the piezo-based device 30 described above, but over a narrower dampening frequency range The magnitudes of the desired resistance for the resistor 42 and inductance for the inductor 43 can be calculated using the following relationships:

L

{CCo2[l+(k)/(lk2)]1 and

R

[(Ak2)/(1-k 2 2 where R is equal to the resistance, C is equal to the capacitance, k is equal to the transverse coupling constant, A is equal to the strain energy capture, and is equal to frequency of the vibrations to be dampened. The piezo-based device 40 may be preferred for use in touring vehicles, for example, where the target mode of vibration is a higher-order bending mode. The frequency of this bending mode tends to not vary as greatly as a function of the actual boundary conditions because the road surface is relatively uniform. Thus, the piezo-based device 40 provides increased passive damping at a single center dampening frequency.

Fig. 4 illustrates a third embodiment of the piezo-based device, indicated generally at 50. As shown therein, the piezo-based device 50 includes an element 51 formed from a piezo-electric material and a resistor 52 that are connected in a series electrical circuit. Thus, the piezo-based device 50 is essentially an RC electrical 0 circuit. The magnitude of the resistance of the resistor 52 is a variable and is oo° controlled by a controller 53 in response to the magnitude and/or frequency of vibrations sensed by a sensor 54. The controller 53 may be a microprocessor or similar device that is capable of varying the resistance of the resistor 52 in response to the sensed vibrations and may be contained within the driveshaft tube 18 or mounted elsewhere on the vehicle. The sensor 54 may be embodied as one or more known sensing devices and can be mounted directly on the driveshaft tube 18 or any other desired portion of the vehicle drive train assembly 10 to generate electrical signals to the controller 53 that are representative of the magnitude and/or frequency of the vibrations generated in the driveshaft tube 18. The piezo-based device 50 functions in essentially the same manner as the piezo-based device 30 described above to passively dampen the vibrations that are generated in the driveshaft tube 18, but can be tuned during operation of the vehicle drive train assembly 10 in accordance with prevailing conditions. The variable resistor 52, the controller 53, and the sensor 54 may, if desired, be incorporated into the RLC circuit illustrated in Fig. 3 if desired.

Fig. 5 illustrates a fourth embodiment of the piezo-based device, indicated generally at 60. As shown therein, the piezo-based device 60 includes an element 61 formed from a piezo-electric material and a current generator 62 that are connected in a series electrical circuit. The current generator 62 is conventional in the art and is controlled by a controller 63 in response to the magnitude and/or frequency of vibrations sensed by a sensor 64. The controller 63 may be a microprocessor or similar device that is capable of varying the amount of electrical current that is supplied to the element 61 in response to the sensed vibrations and may be contained within the driveshaft tube 18 or mounted elsewhere on the vehicle. The stiffness of the element 61 is controlled in accordance with the magnitude of the electrical current supplied thereto by the current generator 63. The sensor 64 may be embodied as one or more known sensing devices and can be mounted directly on the driveshaft tube 18 or any other desired portion of the vehicle drive train assembly 10 to generate electrical signals to the controller 63 that are representative of the magnitude and/or frequency of the vibrations generated in the driveshaft tube 18. The piezo-based S0 device 60 functions to actively dampen the vibrations that are generated in the driveshaft tube 18.

Referring now to Fig. 6, there is illustrated a second embodiment of a vehicle drive train assembly, indicated generally at 10', including a piezo-based device, indicated generally at 30, is attached or otherwise mounted on the interior surface of the driveshaft tube 18. The structure and mode of operation of the piezo-based device 30' can be the same as described above in connection with any of Figs. 2, 3, 4 or 5, or any combination thereof. Alternatively, the piezo-based device 30' can be embedded within or formed integrally with the driveshaft tube 18. Such a structure could be feasible if, for example, the driveshaft tube 18 is formed from a composite material.

Referring now to Fig. 6, there is illustrated a third embodiment of a vehicle drive train assembly, indicated generally at 10", including a pair of piezo-based devices, indicated generally at 30a and 30b, that are attached or otherwise mounted on the exterior surface of the driveshaft tube 18. The structure and mode of operation of the piezo-based devices 30a and 30b can be the same as described above in connection with any of Figs. 2, 3, 4 or 5, or any combination thereof. Alternatively, one or both of the piezo-based devices 30a and 30b may be embedded within or formed integrally with the driveshaft tube 18, as shown in Fig. 5. If desired, a greater number of such piezo-based devices 30a and 30b can be provided on the driveshaft tube 18. Because of the variety of forces that may be applied to the driveshaft 18 during operation, the use of a plurality of piezo-based devices 30a and 30b permits dampening to occur at multiple regions of the driveshaft tube 18. Furthermore, because each of the piezobased devices 30a and 30b provides damping over a single range of vibration frequencies determined by the center dampening frequency, a plurality of piezo-based devices 30a and 30b can be tuned to different center dampening frequencies to permit dampening to occur over multiple ranges of vibration frequencies. It is also contemplated that a passive piezo-based device can be used to generate power to operate an active piezo-based devices.

In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred 10 embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

1. A driveshaft tube for use in a vehicle drive train assembly comprising: a driveshaft tube; and a piezo-based device secured to said driveshaft tube for dampening vibrations generated in said driveshaft tube.

2. The driveshaft tube defined in Claim 1 wherein said piezo-based device is formed from a piezo-electric material. 0 -1o

3. The driveshaft tube defined in Claim 1 wherein said piezo-based device in connected in an electrical circuit to a resistive element.

4. The driveshaft tube defined in Claim 1 wherein said piezo-based device is connected in an electrical circuit to a resistive element and an inductive element.

The driveshaft tube defined in Claim 1 wherein said piezo-based device is connected in an electrical circuit to a variable resistive element.

6. The driveshaft tube defined in Claim 6 further including a controller for varying the resistance of said resistive element.

7. The driveshaft tube defined in Claim 7 further including a sensor for generating a signal that is representative of the vibrations in said driveshaft tube, and wherein said controller is responsive to said signal from said sensor for varying the resistance of said resistive element.

8. The driveshaft tube defined in Claim 1 wherein said piezo-based device is connected in an electrical circuit with a current generator.

9. The driveshaft tube defined in Claim 8 further including a controller for controlling the operation of said current generator.

The driveshaft tube defined in Claim 9 further including a sensor for generating a signal that is representative of the vibrations in said driveshaft tube, and wherein said controller is responsive to said signal from said sensor for controlling the operation of said current generator.

11. The driveshaft tube defined in Claim 1 wherein said piezo-based device to0 is mounted on an exterior surface of said driveshaft tube.

12. The driveshaft tube defined in Claim 1 wherein said piezo-based device is mounted on an interior surface of said driveshaft tube.

13. The driveshaft tube defined in Claim 1 wherein said piezo-based device is embedded within said driveshaft tube. 1

14. The driveshaft tube defined in Claim 1 wherein a plurality of said piezo- based devices are secured to said driveshaft tube for dampening vibrations generated in said driveshaft tube.

A vehicle drive train assembly comprising: a source of rotational power; a rotatably driven axle assembly; and a driveshaft assembly connected between said source of rotational power and said axle assembly, said driveshaft assembly including a driveshaft tube and a piezo- based device secured to said driveshaft tube for dampening vibrations generated in said driveshaft tube. said driveshaft tube. -13-

16. The vehicle drive train assembly defined in Claim 15 wherein said piezo-based device is mounted on an exterior surface of said driveshaft tube.

17. The vehicle drive train assembly defined in Claim 15 wherein said piezo-based device is mounted on an interior surface of said driveshaft tube.

18. The vehicle drive train assembly defined in Claim 15 wherein said piezo-based device is embedded within said driveshaft tube. *se a pr-

19. The vehicle drive train assembly defined in Claim 15 wherein a plurality of said piezo-based devices are secured to said driveshaft tube for dampening vibrations generated in said driveshaft tube. 15is

20. A driveshaft tube substantially as described herein in relation to any one embodiment with reference to Figs. 1 7.

21. A vehicle drive train assembly substantially as described herein in relation to any one embodiment with reference to Figs. 1 7. I 00 DATED this Twenty-fourth Day of August, 2000 Dana Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON [R:\LIBT]03537.doc:avc