GB2202029A

GB2202029A - Hollow cylindrical rotary drive shaft

Info

Publication number: GB2202029A
Application number: GB08805379A
Authority: GB
Inventors: Toshihiko Sato; Yasuharu Hontani; Hideo Asano
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1987-03-06
Filing date: 1988-03-07
Publication date: 1988-09-14
Also published as: GB8805379D0; DE3807184A1

Description

2""020Z-9 C11- HOLLOW CYLINDRICAL ROTARY DRIVE SHAFT The present invention

relates generally to hollow cylindrical rotary drive shafts having solid portions at their opposite ends and adapted to be supported at the solid portions, and is particularly of use with such shafts when made of metal.

Though it is common practice to form a drive shaft for a front drive vehicle as a solid body. in recent years# to reduce the weight of a vehicle or to reduce the power transmission loss, a hollow body drive shaft has been also used. A drive shaft has the function of transmitting a torque output from a drive source to drive wheels. In a drive shaft twisting vibration, bending vibration and membrane vibration occur, and these vibrations become causes of vehicle body vibration and noise which are uncomfortable for an occupant. These vibrations have in prior known drive shafts had a maximum amplitude in a bending primary mode in the frequency range of 200-500Hz, and it has proved difficult to reduce vibrations in this frequency range by selecting an optimum configuration for the drive shaft by vector analysis or to prevent entrance of vibration and noise into a vehicle cab by making use of a vibration-suppressing sound-shielding material. Heretofore. for dealing with vibration, in a drive shaft, in this frequency range, a dynamic damper has been added, or the drive shaft has been divided into two parts coupled together through the intermediary of a vibration-suppressor formed of elastic material (i.e.

material that is high in elasticity).

Howeveri when employing such a dynamic damper, whilst the vibration at a desired frequency can be reduced. there is the disadvantage that vibrations (or vibration levels) in the frequency range lower than the desired frequency or in the frequency range higher than the desired frequency may increase. With the divided type drive shaft arrangement there is the disadvantage that a power transmission loss may arise because the torque transmission is effected by the intermediary of a vibration-suppressor made of elastic material.

on the other hand, there has been a technical proposal for reducing vibration and noise by pressureinserting a vibration suppressor made of elastic material into a hollow space in a propeller shaft (for instancep Japanese Patent Publication No. 49-20644 (1974) and Laid-Open Japanese Utility Model Specification No. 56-87647 (1981)). However, this technical proposal still has as a basic idea that the vibration energy of the propeller shaft is converted to heat due to the internal friction c;f the vibration suppressor by making use of an elastic hysteresis phenomenon, and it was a principal object of this known method to lower the vibration level of member resonance in a propeller shaft having a low sole characteristic angular frequency (natural frequency). Therefore, it was not designed to reduce effectively the vibration level of primary bending resonance.

The present invention seeks to provide a reduction in the vibration level with respect to primary bending resonance in a drive shaft.

According to the present invention there is provided a hollow cylindrical rotary drive shaft having solid portions at its opposite ends and adapted to be supported at said solid portions, characterized in that a vibrationsuppressor made of elastic material is tightly fitted to a hollow shaft portion having a sole primary bpnding characteristic angular frequency of 500Hz or higher and a ratio (t/D) of a wall thickness (t) to an outer diameter (D) of 0.06 or less.

The vibration characteristics of a tubular body having its opposite ends closed and a tubular body having its opposite ends opened, respectively, in a condition where the opposite ends are freei are as shown in Figs. 1 and 2, respectively.

The present invention seeks to reduce primary bending resonance (See Figs. 1 and 2) which could not be effectively dealt with in the prior art arrangements. It is effective to make a vibrationsuppressor absorb vibration in a region where the frequency is relatively large and the vibration energy level is high. and therefore. in the drive shaft according to the present invention, the sole primary bending characteristic angular frequency (natural frequency) of the hollow shaft portion is set at a relatively large value.

Throughout this specification and claims, characteristic angular frequency in the case a bending where the opposite ends of a circular tube are free, Is called a "sole bending characteristic angular frequency", and a sole value of primary bending resonance is derived by substituting A 4.730 in the bending characteristic angular frequency (f) of a circular tube represented by the following formula:

f = A2 EI ................. (1) 2ri.e2 pA (where X represents a frequency coefficient that varies depending upon a boundary condition, e represents a tube length, E represents a Young's modulus, I represents a cross section secondary moment, A represents a tube cross-section area and p represents a density.) According to Formula (1) above, in order to increase a sole bending characteristic angular frequency (f) of a circular tube, it suffices to reducethetube length (e) and/or thetube cross-section area (A). If the inner diameter or the outer diameter of a circular tube is to be a specifc value, then the tube cross-section area (A) can be reduced by:decreasing the wall thickness.

If a vibration-suppressor is pressure-inserted into a circular tube having its sole bending characteristic angular frequency increased according to the above-mentioned condition, or a cylindrical vibration-suppressor is tightly fitted around an outer circumference of such circular tube, then bending vibration energy at a high level is effectively absorbed by the vibration-suppressor, especially in the case 1 were the tube wall thickness is decreased, so-that the vibration is increased, the vibration-suppressor is subjected to large bending deformation, arxl..hence the vibration can be effectively attenuated owing to the elastic hysteresis phenomenon of the vibration-suppressor.

Here it is to be noted that as compared to the case where a vibrationsuppressor (called a solid vibrationsuppressor) is pressure-inserted into a circular tube, the vibration suppressing effect is larger in the case where a cylindrical vibration-suppressor (called ahollow vibrationsuppressor) is tightly fitted around an outer circumference of a circular tube. More particularly, if thecross-sectional areas of a solid vibration-suppressor and a hollow vibrationsuppressor are equal to each other, then thecross- sect ion al secondary moment (I) of the latter is larger than that of the former and since theamount of deformation accompanying the bending vibration is also larger in the case of the lattert a larger vibration energy can be absorbed by the latter vibration-suppressor. This implies that by employing a hollow vibration-suppressor having a smaller volume as compared to a solid vibration suppressor, an equal vibrationsuppressing effect can be expected. Since a hollow vibration7suppressor can be fitted around an outer circumference of a circular tube after the circular tube having solid portions at its opposite ends has been subjected to heat-treatment and painting, deterioration of the hollow vibration-suppressor caused by heating can be prevented and its vibration-suppressing effect can be assured.

1 In the case where solid portions are provided at the opposite ends of a circular tube, if the proportion of the length of the circular tube with respect to the entire length including the solid portions is too small# then even if a vibration-suppressor is pressureinserted into or tightly fitted around the circular tube,.the vibration reduction effect for primary bending resonance is small. it is preferable therefore to select the length of the circular tube to be 20% or more of the entire length.

In addition. it is desirable to fit the vibrationsuppressor at the position of maximum amplitude. and furthermore, by pressure-inserting a solid vibrationsuppressor with a pressure-insert interference of 1% or more or baking a vibration-suppressor to a circular tube, a further large vibration reduction effect can be attained. It should be noted that the vibration suppressor may be baked, or heat bonded, to the tube at lower temperatures then are required for heat treatment of the tube. Therefore, the baking does not cause the deterioration of the vibration suppressor mentioned above.

In the accompanying drawings:

Fig. 1 is a diagram showing the vibration characteristics for a tubular body having its opposite ends closed and with the opposite ends of the tubuiar body are free; Fig. 2 is a diagram showing the vibration characteristics for a tubular body having its opposite ends open and with the opposite ends of the tubular body free; Fig. 3 is a diagram showing the relationship between the characteristic angular frequency and the vibration reducing effect with a rubber member pressure-inserted into a hollow shaft; Z k 1 Fig. 4 is a diagram showing the relationship between a ratio (t/D), of shaft wall thickness to shaft outer diameter, and vibration reducing effect with a rubber member pressure-inserted into a hollow shaft; Fig. 5 is a perspective view of a hollow cylindrical rotary drive shaft made of steel for test use having its opposite ends closed; Fig. 6 is a diagram showing the relationship between pressure-inserted rubber member length and vibration-reducing effect for a rubber member pressureinserted into the drive shaft of Fig. 5; Fig. 7 is a partially cut away front view of a hollow cylindrical rotary drive shaft made of steel according to one preferred embodiment of the present invention; Figs. 8a to 8e are schematic views showing the relationship between the fitting position of a rubber member or members and vibration-reducing effect for the rubber member or members fitted to a hollow portion of the drive shaft of Fig. 7; Fig. 9 is a diagram showing the relationship between pressure-inserted rubber member length and vibration reducing effect for three different kinds of rubber members pressure inserted into a hollow portion of the drive shaft of Fig. 7; Fig. 10 is a diagram showing the vibration characteristics of a drive shaft having rubber pressure-inserted into its hollow portion, a drive shaft subjected to no counter-measure for vibration and a drive shaft associated with a dynamic damper; Fig. 11 is a diagram showing results of a vibration characteristics test conducted as assembled in a real vehicle for the case where the drive shaft was associated with a dynamic damper and the case where rubber was pressure-inserted into its hollow portion; Fig. 12 is a diagram showing the relationship between a length ratio (Lp/1,D) of the rotary shafts whose lengths only are different from each other and a vibration-reducing effect; and Fig. 13 is a diacjram showing a relationship between a pressure-insert interference and a vibrationreducing effect in the case where a rubber membpr was pressure-inserted into a hollow shaft at different pressure- insert interference. Test Exam21e 1 1. A plurality of steel hollow shafts (having an outer diameter of 50mm and a wall thickness of 2.Omm) having different lengths were prepared and a solid cylindrical acrylic rubber member having a length of 50mm and an oiter diameter of 50mm (hardness 500) was pressure-insetted into each hollow shaft.

2. The vibration-reducing eftects for primary bending resonance were investigated with respect to respective rubber-member-contaiiiing hollo-Y, shafts having different sole primary bending charac'%Ierist-ic angular frequencies. This test was condticted through the method of knocking one end portion of a hollow shaft 1 with a hammer and detecting a vibralk_.ion level at the other end portion. The tGst results are shown in Fig. 3 in the form of a diagrram. It is to be noted that the vibration level of a hollow shaft with no pressure-inserted acrylic rubber member was employed as a reference and the vibration level for this shaft was taken as the zero 6S level, <Evaluation of Test Results> Tt can be seen that if the sole primary bending charateristio angular frequency is increased, the vibration level is lowered. According to Fig. 3f almost no vibration-reducing effect is attained with a sole characteristic angular frequency of aboot 30OHz, whereas if it is raised up to 50OHz or hi5her, a vibration-reducing effect can be expected.

1 Test Example 2 1 1, A plurality of steel hollow shafts (having a length of 25Omm and an inner diameter of 46min) having different outer diameters were prepared, and a solid cylindrical acrylic rubber member having a length of 10Omm and an outer diameter of Somm (hardness 500) was pressure-inserted into each hollow shaft.

2. The vibration-reducing effects for primary bending resonance was investigated in a similar manner to Test Example 1 with respect to the respective :erent rubber-member-containing hollow shafts having diffl ratios (t/D) of wall thickness (t) to outer diameter (D). The test results are shown in Fig. 4 in the form of a diagram.

is <Evaluation of Test Results5 It can be seen that if the ratio (11-0) is decreased the vibration level is lowred. According to Fig. 4f for a ratio (t/D) of approximately 0.06 or less, the vibration-reducing effect becomes large, Test Exam21e 3 1. A steel hollow shaft 1 in which a hollow portion provided with mass members 2, 2 at its opposite ends had a length of 25Omm, an outer diameter of 50mm, a wall thickness of 2.Omm, a ratio (t/D) equal to 0.04 and a sole primary bending characteristic angular frequency (f) equal to 1071Hz, was prepaied (Fig. 5). 2. A plurality of solid cylindrical acrylic rubber members (hardness 500; outer diameter SOmm) having different lengths were prepared. 30 3. Each acrylic rubber member was pressureinserted into the hollow shaft 1, and investigation was made of the Influence of the length of the acrylic rubber member upon vibration reduction. The test procedure was the same as Test Example 1. The results are shown ir Fig. 6 in the form of a diagram. In this figure, curve 1 represents vibration level reduction in a resonant primary mode (primary bending resonance), curve 11 represents vibration level reduction in a resonant secondary mode (secondary bending resonance), and curve 111 represents vibration level reduction in a 5 resonant tertiary mode (secondary membrane resonance).

<Evaluation of Test Results> 1. The vibration-reducing effect attained by pressure-inserting an acrylic rubber member is greatest for the resonance in a tertiary mode (secondary 10 membrane resonance).

2. As the length of the acrylic rubber member increases, the vibration reducing effect increases.

3. Regarding bending resonance, the vibrationreducing effect for primary bending resonance Is large 15 as compared to secondary bending resonance.

h It is to be noted that even if rubber members having different length were to be pressure-inserted into a hollow shaft having a sole primary bending characteristic frequency (f) of 30OHz or less, a vibration-reducing effect for primary bending resonance cannot be expected.

Test Example 4 (D Five steel drive shaft 3 (outer diameter 50mnD: wall thickness 2.Omm) having solid shaft portions - 4, 4 at the opposite ends of a hollow portion 5 were prepared (Fig. 7).

(2) into the hollow portion 5 of each drive shaft 3 was pressure-inserted an acrylic rubber member 6 (outer diameter 50mm4); length 70mm; volume 1.37 x 105Mm3; hardness 50'0), or acrylic rubber members 7, 7 (outer diameter 50mm; length 35mm; hardness 500), and with respect to the respective hollow drive shafts, vibration-reducing effect for primarY bending resonance were investigated in a similar manner to Test Example 1. While the pressure-inserted positions are different for the respective drive shafts 3, the total lengths of the pressure-inserted rubber were all 70mm (Fig.

8a to Fig. 8d). The attained vibration level reduction is inscribed in each figure.

(9) Also, at the center of the hollow portion 5 of the drive shaft 3, a hollow cylindrical acrylic rubber member 8 (inner diameter 46mm; outer diameter 64mm4): length 50mm; volume 1.48 x 105MM3; hardness 500) was externally fitted around the drive shaft, and a vibration-reducing effect for primary bending resonance was investigated in a similar manner to Test Example 1 above (Fig. 8e). The attained vibration level reduction is inscribed in the same figure.

_t _ - <Evaluation of Test Results> (B Among the cases. shown in Figs. 8a, 8b, 8c and 8d, the vibration level reduction for primary bending resonance is largest in the case shown in Fig. 8a where a rubber member was pressure-inserted into the center of the hollow portion 5, and it is smallest in the case shown in Fig. 8d where rubber members 7, 7 as divided were pressure-inserted into the opposite ends of the hollow portion 5. This is. because the center is the maximum amplitude position for primary bending resonance, and hence the rubber member 6 pressureinserted to this position is subjected to the' largest deformation and thereby would absorb the vibration energy most. However, it it to be noted that in the case of a hollow body consisting of a thin walled portion on one side in the lengthwise direction and a thick walled portion on the'- other side, a location somewhat deviated to the side of the thin walled portion from the boundary between the thin walled portion and the thick walled portion is the maximum amplitude position, and so the rubber member should be pressureinserted to that position.

T In addition, in contrast to the fact that a vibrationreducing effect of 11.4dB can be attained in the case where a rubber member is pressureinserted to the center of the hollow portion 5 (Fig. 8a), in the event that a rubber member 8 having a nearly equal volume has been externally fitted around the center of the hollow body 5 (Fig. 8e), a vibrationreducing effect of 15.7dB can be attained, and it will be seen that outer fitting is more effective.

A - 1,3 - Test Example 5 Drive shafts 3 (Fig. 7) were employed, and after acrylic rubber members (outer diameter 50mm4; hardness 500)t isobutylene-isoprene rubber members (outer diameter 50mm4); hardness 500) and natural rubber members (outer diameter 50mm; hardness 500) respectively having different lengths 1-adbeEn separately pressurL-imaited into the hollow portion 5 therein, influences of the pressure-inserted irenter upon thevibrationreducing effect for primary bending resonance were investigated with respect to the respective kinds of rubber. The results are shown in Fig. 9 in the form of a diagram.

<Evaluation of Test Results> Utilization of a kind of rubber having a large attenuation factor is effective, and the use-of an acrylic rubber member is most effective for reducing vibration.

Test Example 6 A drive shaft 3 (an outer diameter of a hollow portion 5 being 42.2mm(P; a length Lp of a hollow portion 5 being 190mm; and a total length LD = 420mm) having an acrylic rubber member pressure-inserted to the center of a hollow portion 5, was assembled in a practical vehicle as a front drive shaft, an end portion on the drive source side of the drive shaft 3 was knocked with a hammer, and a vibration level was measured at the end portion on the opposite side. The results are shown in Fig. 10 in the form of a diagram (Curve C).

In addition, for the purpose of comparison, a vibration level of a drive shaft having a heretofore known configuration not applied with any counter-measure for vibration reduction (Curve A) and a vibration level of a drive shaft having a heretofore known configuration associated with a dynamic damper (Curve B) are also plotted in Fig. 10.

<Evaluation of Test Results> 1. In contrast to the fact that for the prior art drive short without any applied counter-measure for vibration reduction a maximum point Al (primary bending resonance point: about 400Hz) of Curve A is present in the frequency range of 200-500Hz, for the prior art drive shaft associated with a dynamic damper the maximum point splits and shifts to the lower frequency side and to the higher frequency side, and hence maximum points Bl and B2 of Curve B exist at the positions of about 200Hz and about 500Hz.

2. The characteristic curve C of the drive shaft 3 takes the configuration of the maximum point Al of the prior art drive shaft without any applied countermeasure for vibration reduction but shifted to the higher frequency side. The maximum point Cl of this curve C exists at the position of 744Hz, and the sound pressure level at the maximum point is lower than that at the maximum point Al.

3. In the frequency range of 200-500Hz, Curve C is lower than Curve B, and it is seen that in this frequency range. the sound pressure level of the drive shaft 3 having a rubber member pressure-inserted therein is low. Test Exam21e 7 A drive shaft having isobutylene-isoprene rubber pressure-inserted into a hollow portion 5, was assembled in a practical vehicle as a front drive shaft. and the sound pressure level in the vehicle during running (measured at Q-:

V:

- 1.5 - the center position of front seats by making use of a filter adapted to pick up only vibration sound of 200-50OHz) was investigated. The results are shown in Fig. 11 in the form of a diagram OtE rotational speed (RPM) of the engine being taken along the abscissa, and thesound pressure level being taken alongthe ordinate). Curve C is a characteristic curve of the drive shaft 3 having a rubber member pressure-inserted therein, and Curve B is a characteristic curve of the drive shaft 3 associated with a dynamic damper in the prior art.

<Evaluation of Test Results> It is seen from Fig. 11 that if a front drive shaft having a rubber member pressure-inserted therein is employed, a vibration-reducing effect of 2-3dB in the range of 3,000-5,500 RPM can be attained as compared to the front drive shaft in the prior art associated with a dynamic damper.

Test Example 8 (I)A plurality of steel drive shafts 3 (Fig. 7) having different lengths (Lp) of a hollow portion 2 and the following dimensions were prepared: Total length (LD) = 440mm Length of a hollow portion (Lp) = arbitrary Outer diameter of the hollow portion 2 = 50mm Wall thickness of the hollow portion 2 = 2mm TAcrylic rubber members (outer diameter 50mm; length 70mm; hardness 50) were pressure-inserted into hollow portions 2 of the respective drive shafts 3 having different lengths (Lp). The pressure-inserted position is the center in the lengthwise direction of the hollow portion 2 as shown in Fig. 8a.

0 With respect to the drive shafts 3 having different lengths (Lp), the vibration-reducing ef f ect f or primary bending resonance was investigated in a similar manner to Test Example 1. The results are shown in Fig. 12 in the form of a diagram. (It is to be noted that a length ratio (Lp/LD) is taken along an abscissa in Fig. 12).

<Evaluation of Test Results> It is seen from Fig. 12 that a large vibration-reducing ef f ect can be attained for the ratio (Lp/LD) of' approxirrately 0. 2 or higher [a proportion of a length (Lp) of a hollow portion 2 to a total length (LD) k 20%]. Test Example 9 (1) A plurality of steel hollow shafts (outer diameter SOmm; wall thickness 2.Omm) were prepared, and solid cylindrical isobutylene- isoprene rubber members (hardness 5011) having alength of 50mm were pressure-inserted into the respective hollow shafts with different pressure-insert interferences, respectively.

02 With respect to these hollow shafts, a vibration reducing effect for primary bending resonance was investigated in a similar manner to Test Example 1. The test results are shown in Fig. 13 in the form of a diagram. In Fig. 13, the abscissa represents a pressure-insert interference (%) that is calculated by the following formula:

inner diameter of hollow shaft (1 -) X 100 outer diameter of rubber member <Evaluation of Test Results> - 1 '7 By selecting the pressure-insert interference at 1% or higher, a following property for deformation as well as a constraining property for volume strain of the rubber member are increased, and thereby vibration level reduction can be improved.

It is to be noted that when the elastic body is baked to the hollow shaft alsoi the same effect as the above-mentioned pressure-insert interference can be attained.

Claims

CLAIMS 1. A hollow cylindrical rotary drive shaft having solid portions at

its opposite ends and adapted to be supported at said solid portionsi characterized in that a vibration-suppressor made of elastic material is tightly fitted to a hollow shaft portion having a sole primary bending characteristic angular frequency of 500Hz or higher and a ratio (t/D) of a wall thickness (t) to an outer diameter (D) of 0.06 or less.
2. A hollow cylindrical rotary drive shaft as claimed in Claim 1, wherein said hollow shaft portion occupies 20% or more of the entire length.
3. A hollow cylindrical rotary drive shaft as claimed in Claim 1 or 2, wherein said vibrationsuppressor made of elastic material is pressureinserted into the hollow shaft portion.
4. A hollow cylindrical rotary drive shaft as claimed in Claim 3, wherein a pressure-insert interference is 1% or more. 20
5. A hollow cylindrical rotary drive shaft as claimed in Claim 1 or 2, wherein said vibration spppressor made of elastic material is tightly fitted around an outer circumference of the hollow shaft portion.
6. A hollow cylindrical rotary drive shaft as claimed in Claim 3 or 5 wherein said vibrationsuppressor made of elastic material is baked to the hollow shaft portion.
7. A hollow cylindrical rotary drive shaft as claimed in Claim 3. 5 or 6 wherein said vibrationsuppressor made of elastic material is provided at the position of the maximum vibration amplitude in the hollow shaft portion.
8. A hollow cylindrical rotary drive shaft substantially as hereinbefore described with reference to Figures 3 to 13 of the accompanying drawings.

Published 1988 at The Patent Office, State House, 68171 High Holborn, London WC1R 4TP. TJrther copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Com 1/87.

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