Patent Publication Number: US-2007107972-A1

Title: Vibration transfer rate reducing device and method

Description:
CROSS-REFERENCES TO RELATED APPLICATION  
      This application claims priority from Japanese Patent Application Serial No. 2005-332921 filed Nov. 17, 2005, which is incorporated herein in its entirety by reference.  
     TECHNICAL FIELD  
      The present invention pertains to a technology that can restrain noise in automobiles caused by flexural vibration of the shaft (such as a propeller shaft) that transfers rotation driving force used for the automobile.  
     BACKGROUND  
      In general, the power of an engine is transferred to a propeller shaft via a transmission. The transferred power is then transferred to the left and right driving wheels via a differential.  
      Flexural vibration occurs in the propeller shaft due to the vibration from the engine or road surface and the eccentricity of the propeller shaft itself. As a result, the noise in the vehicle is increased, and the noise and vibration performance is deteriorated. For example, in Japanese Kokai Patent Publication No. 2003-247596, there is described means for attenuating the flexural vibration of the propeller shaft that causes reduction of the noise and vibration performance in the vehicle by arranging a dynamic damper in the propeller shaft.  
     SUMMARY  
      Disclosed herein is a device that reduces the vibration transfer rate on the shaft that transfers the rotation driving force of the propeller shaft to improve the noise and vibration performance in the vehicle today.  
      According to one vibration transfer rate reducing device taught herein, the device comprises a shaft for transferring a rotation driving force, a rotary member connected to an end portion of the shaft via a joint, the rotating member rotatable with the shaft and a weight arranged at the end portion and extending axially in a direction of the rotary member.  
      Another vibration transfer rate reducing device for a vehicle taught herein comprises means for transferring driving force to a rotary member, means for connecting an end portion of the transferring means to the rotary member and weight means for reducing a vibration transfer rate of the transferring means, the weight means arranged at an end part of the transferring means and extending to the rotary member.  
      Vibration transfer reducing methods for a driving force transfer member that transfers driving force are also taught herein. According to one example, the method comprises connecting a rotary member to an end portion of the driving force transfer member using a connecting member wherein the rotary member is rotatable with the driving force transfer member and arranging a weight at the end portion of the driving force transfer member, the weight extending from the connecting member in a direction of the rotary member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:  
       FIG. 1  is a schematic view illustrating an example of the vibration transfer rate reducing device disclosed herein;  
       FIG. 2  is a partial cross-sectional view including the central axial line and illustrating the details of the parts of the vibration transfer rate reducing device shown in  FIG. 1 ;  
       FIGS. 3A and 3B  are simplified schematic views illustrating other configurations of the parts of a vibration transfer rate reducing device;  
       FIGS. 4A and 4B  are cross-sectional and perspective views, respectively, illustrating yet another example of the parts of a vibration transfer rate reducing device;  
       FIGS. 5A and 5B  are cross-sectional and perspective views, respectively, illustrating yet another example of the parts of a vibration transfer rate reducing device;  
       FIGS. 6A and 6B  are cross-sectional and perspective views, respectively, illustrating yet another example of the parts of a vibration transfer rate reducing device;  
       FIG. 7  is a graph illustrating the effect of the vibration transfer rate reducing device disclosed in  FIG. 2 ; and  
       FIG. 8  is a graph illustrating the effect of the vibration transfer rate reducing device disclosed in  FIGS. 6A and 6B . 
    
    
     DETAILED DESCRIPTION  
      The damper disclosed in Japanese Kokai Patent Application No. 2003-247596 described above cannot restrain vibration of the universal joints because the joint of the primary flexural vibration of the propeller shaft is closer to the center in the axial direction than are the universal joints. Consequently, the damper is unable to restrain the vibration of the differential or the transmission connected to the propeller shaft. The vibration at the input shaft end of the differential and at the output shaft end of the transmission is transferred to the panel of the vehicle body to cause vibration of the panel. Therefore, noise in the vehicle body is increased, and the noise and vibration performance deteriorate.  
      According to examples of the device disclosed herein, the device can reduce the vibration transfer rate of the shaft that transfers the rotation driving force of the propeller shaft, etc., thereby improving the noise and vibration performance in the vehicle body.  
      The vibration transfer rate reducing device disclosed herein includes a weight arranged at the end portions of the shaft that transfers driving force. This weight is connected to the end portions of the shaft via a joint and is extended to the side of the rotary member that rotates along with the shaft.  
      When a weight extended to the side of the rotary member is arranged at the end portion of the shaft, if flexural vibration occurs in the shaft, the node of the flexural vibration can be moved from the central part in the axial direction of the shaft to the side of the end portion of the shaft. Consequently, the vibration at the end portion of the shaft can be reduced. The flexural vibration of the shaft transferred to the rotary member via the joint can also be reduced. That is, the vibration transfer rate of the shaft can be reduced. In this way, the noise caused by the flexural vibration of the shaft can be restrained, and the noise and vibration performance of the vehicle can be improved.  
      Details can be described with reference to the drawing figures.  FIG. 1  is a schematic view illustrating an example of the vibration transfer rate reducing device disclosed in the present invention. In the vibration transfer rate reducing device disclosed herein, one end of propeller shaft  1  is connected to the output shaft  3  (i.e., a rotary member) of a transmission  2  via constant velocity joint(s)  4 , which are used as universal joints. Also, the other end of propeller shaft  1  is connected to the input shaft  6  (i.e., a rotary member) of a differential  5  via constant velocity joint(s)  7 . Weight  8   a  extends from the constant velocity joint  4  to the side of transmission  2  and is arranged at one end of the propeller shaft  1 , while weight  8   b  extends from the constant velocity joint  7  to the side of the differential  5  and is arranged at the other end of the propeller shaft.  
      The transmission  2  is installed in the vehicle body (not shown). Since driving wheels (not shown) are installed on the vehicle body via a suspension (not shown), the driving wheels have displacements in various directions corresponding to the input from the road surface or the change in the load amount of the vehicle body corresponding to the vehicle body. Consequently, when connecting the output shaft  3  of the transmission  2  with the propeller shaft  1  and connecting propeller shaft  1  with the input shaft  6  of the differential  5 , constant velocity joints  4 ,  7  as universal joints are used in order to absorb the displacements and the angle changes in the axial direction.  
      According to this example, when flexural vibration is applied to the propeller shaft  1 , the node F of the flexural vibration positioned at the two ends along the axial direction can be moved from the center of propeller shaft  1  in the axial direction to the side of the constant velocity joints  4 ,  7 . In this way, the vibration and amplitude of constant velocity joints  4 ,  7  can be reduced. The vibration and amplitude at the tip of the output shaft  3  of the transmission  2  and the vibration and amplitude at the tip of the input shaft  6  of differential  5  can be reduced. In this way, the vibration of the panel of the vehicle body caused by the vibration of the transmission  2  and the differential  5 , especially the vibration in the vertical direction, can be restrained. Deterioration of the noise and vibration performance in the vehicle can also be alleviated.  
       FIG. 2  is a cross-sectional view including the central axial line and illustrating the details of the parts of the vibration transfer rate reducing device shown in  FIG. 1 .  
      Since constant velocity joints  4 ,  7  are similarly constructed in this case, only one figure is needed to illustrate both. Constant velocity joint  7  ( 4 ) comprises an inner ring  7   a  ( 4   a ) connected to the propeller shaft  1 , an outer ring  7   b  ( 4   b ) that encloses the inner ring  7   a  ( 4   a ), and a ball  7   c  ( 4   c ) arranged between the inner ring  7   a  ( 4   a ) and the outer ring  7   b  ( 4   b ). Weight  8   b  ( 8   a ) formed in a cylindrical shape is added to extend to the side of the differential  5  (or the transmission  2 ) in the axial direction of the propeller shaft  1  connected to the inner ring  7   a  ( 4   a ) of the constant velocity joint  7 ( 4 ).  FIG. 2  shows the configuration on the side of differential  5 . (The reference numbers in parenthesis refer to the components on the side of the transmission  2 .) As shown in  FIG. 2 , weight  8   b  ( 8   a ) is arranged to extend to the side of the differential  5  (transmission  2 ) on the end surface in the axial direction at the tip of the propeller shaft  1  pressed into the through hole (i.e., an opening part) formed on the inner ring  7   a  ( 4   a ) of the constant velocity joint  7 ( 4 ). In this way, weight  8   b  ( 8   a ) is arranged closer to the side of differential  5  (transmission  2 ) than is the constant velocity joint  7 ( 4 ).  
      For the constant velocity joints of birfield type, double offset type, fixed tripod type and level type, weight  8   a ,  8   b  can be added easily at the two ends of the propeller shaft  1  in the axial direction. Weight  8   a  is arranged to extend to the side of the transmission  2 , and weight  8   b  is arranged to extend to the side of the differential  5 . Therefore, the node F of the flexural vibration at the two end portions of propeller shaft  1  can be moved to the sides of constant velocity joints  4 ,  7 , and the vibration and amplitude of constant velocity joints  4 ,  7  can be reduced. Hence, the vibration and amplitude at the tips of the differential  5  and the transmission  2  can be reduced. Consequently, the vibration of the panel of the vehicle body caused by the vibration of the transmission  2  and the differential  5 , and especially the vibration in the vertical direction, can be restrained. Deterioration of the noise and vibration performance in the vehicle can also be alleviated.  
      Further, when performing grease sealing to the constant velocity joints  4 ,  7 , the flange  10  connected to the input shaft  6  of the differential  5  (output shaft  3  of transmission  2 ) is used as the grease case.  
      In this case, one end of each flange  10  is respectively embedded in the output shaft  3  of transmission  2  and the input shaft  6  of differential  5 . An opening for installing the constant velocity joint  7  ( 4 ) is formed at the other end of each flange  10 . The flange  10  is formed in a hollow conical shape with diameter gradually increasing from one end (i.e., the shaft  6  ( 3 ) end) to the other end (i.e., the constant velocity joint  7  ( 4 ) end). As shown in  FIG. 2 , the constant velocity joint  7  ( 4 ) is installed in the opening formed at the tip end of the flange  10 . The flange  10  is fixed to the end of the input shaft  6  by a bolt. In this way, the input shaft  6  of the differential  5  (and the output shaft  3  of the transmission  2 ) is connected to the propeller shaft  
      As also shown in  FIG. 2 , when performing grease sealing to the constant velocity joint  7  ( 4 ), a grease case  9  arranged on the constant velocity joint  7  ( 4 ) on the side of the propeller shaft  1  is used as the grease case. For the constant velocity joint  7  ( 4 ), no grease case is used on the side of the differential  5  (transmission  2 ). Also, a rubber seal  11  is arranged between the inner peripheral surface of the opening part of flange  10  and the outer peripheral surface of outer ring  7   b  ( 4   b ) of the constant velocity joint  7  ( 4 ) to prevent grease from leaking.  
      Since the conventional grease case on the side of differential  5  (transmission  2 ) is not included, space is provided between the two ends in the axial direction of the propeller shaft  1  connected to the inner ring  7   a  ( 4   a ) of the constant velocity joint  7  ( 4 ) and the tip of the input shaft  6  (and the tip of the output shaft  3  of transmission  2 ). Since the two ends of propeller shaft  1  in the axial direction can be arranged in this space, it is easier to add weight  8   b  ( 8   a ).  
       FIGS. 3A and 3B  illustrate other configurations of the parts of a vibration transfer rate reducing device. Besides the configuration shown in  FIG. 2 , weight  8   b  ( 8   a ) can also be set inside the flange  10 . As shown in  FIG. 3A , the weight  8   c  is formed in a cylindrical shape. The weight  8   c  has a large outer diameter portion and two end surfaces. A diameter of the large outer diameter portion is larger than a diameter of one end surface fixed on the end surface of the propeller shaft  1 . The large outer diameter portion can also be formed such that the outer diameter reduces or tapers from the propeller shaft  1  toward the other end surface of the weight  8   c . That is, it is also possible to use weight  8   c  with its tip portion having a wedge-shaped cross section. Also, as shown in  FIG. 3B , the weight is formed in a cylindrical shape with two end surfaces. A diameter of the large outer diameter portion is larger than a diameter of one end surface fixed on the end surface of the propeller shaft  1 . The large outer diameter portion can also be formed such that the outer diameter is the same or constant from the side of the shaft  1  toward the other end surface of the weight  8   d . That is, it is also possible to use weight  8   d  having an increased cross section at the tip portion. In the latter case shown in  FIG. 3B , the center of gravity is farther from the end of the propeller shaft  1  compared with that of the former shown in  FIG. 3A . Therefore, if the weight is formed in the same mass the shape of weight  8   d  is better than the shape of the weights shown in  8   a ,  8   b  or  8   c  in moving the node F of the flexural vibration of the propeller shaft  1  to the side of the constant velocity joints  7 ,  4 .  
       FIGS. 4A and 4B  are views illustrating another embodiment of the parts of a vibration transfer rate reducing device disclosed herein.  FIG. 4A  shows a partial cross-sectional view including the central axial line of propeller shaft  1  and the input shaft  6  of the differential  5  (and output shaft  3  of the transmission  2 ).  FIG. 4B  is an oblique view viewed from the oblique direction on the side of the differential  5  (transmission  2 ).  
      In  FIGS. 4A and 4B , instead of the constant velocity joints shown in  FIG. 1 , flexible joints  7 ′ ( 4 ′) are used. Weight  8   f  ( 8   e ) has a hollow cylindrical shape (i.e., a conical shape) with an increased diameter on the side of the differential  5  (transmission  2 ). Weight  8   f  ( 8   e ) is added to the flexible joint  7 ′ ( 4 ′) and is fastened by bolts  12  used as a fastening means to fasten the weight  8   f  ( 8   e ) to the flexible joint  7 ′ ( 4 ′) and to the propeller shaft  1 .  
      In this way, for the flexible joints  4 ′,  7 ′, weights  8   e ,  8   f  can be added easily at the respective ends of propeller shaft  1  in the axial direction. As described above, the joint of the flexural vibration of the propeller shaft  1  can be moved to the side of flexible joints  4 ′,  7 ′. The vibration and amplitude of flexible joints  4 ′,  7 ′ can be reduced, and the vibration and amplitude at the tip of the transmission  2  and the differential  5  can be reduced. In this way, the vibration of the panel of the vehicle body caused by the vibration of the transmission  2  and the differential  5 , especially the vibration in the vertical direction, can be restrained. Deterioration of the noise and vibration performance in the vehicle can also be alleviated.  
      Flexible joints  4 ′,  7 ′ are constituted with one or more discs  13  made of rubber, etc. Yoke  14  formed at the end portion of propeller shaft  1  contacts with one end surface of the disc  13 . A first set of bolts  12  are screwed through apertures in the disc and on the weight  8   f  ( 8   e ) to fasten the weight  8   f  ( 8   e ). At the other end surface of disc  13 , the yoke  15  connected to the output shaft  6  of the differential  5  (or output shaft  3  of transmission  2 ) is fastened by a screwing bolt (or bolts)  16  in a respective nut (not shown). The propeller shaft  1  and the input shaft  6  of the differential  5  (or output shaft  3  of the transmission  2 ) are connected, and the displacement in the axial direction between the shaft  1  and the input shaft  6  (or between the shaft  1  and the output shaft  3 ) as well as the angle variation can be absorbed.  
      As described above, the weight  8   f  ( 8   e ) is fastened by bolts  12  to the end surface of the flexible joint  7 ′ ( 4 ′) on the side of the differential  5  (transmission  2 ). In this way, weight  8   f  ( 8   e ) is formed to extend from the flexible joint  7 ′ ( 4 ′) to the side of the differential  5  (transmission  2 ). Consequently, compared to the case without the weight  8   f  ( 8   e ), the joint of the flexural vibration of the propeller shaft  1  is present on the side of flexible joint  7 ′ ( 4 ′), and the vibration and amplitude of the flexible joint  7 ′ ( 4 ′) can be reduced. Also, the weight  8   f  ( 8   e ) is thicker at the end portion that extends to the side of the differential  5  (transmission  2 ) than at the end portion fixed on the propeller shaft  1 . In this way, the center of gravity of the weight  8   f  ( 8   e ) is close to the tip side of the weight compared with the case when the weight has uniform thickness. Consequently, if the weight is formed in the same mass, weight  8   f  ( 8   e ) has a better shape than the case when the weight has uniform thickness for moving the node F of the flexural vibration of the propeller shaft to the side of the constant velocity joint.  
       FIGS. 5A and 5B  are views illustrating another example of the parts of a vibration transfer rate reducing device.  FIG. 5A  shows a partial cross-sectional view including the central axial line of propeller shaft  1  and the input shaft  6  of the differential  5  (output shaft  3  of the transmission  2 ).  FIG. 5B  is an oblique view viewed from the oblique direction on the side of the differential  5  (transmission  2 ).  
      Compared with the vibration transfer rate reducing device shown in  FIGS. 4A and 4B , the cylindrical shaped weight  8   h  ( 8   g ) is closer to the input shaft  6  of the differential  5  (output shaft  3  of transmission  2 ) in the radial direction, and the outer diameter of the middle portion of weight  8   h  ( 8   g ) is reduced. In this way, interference with other parts can be avoided without reducing the mass of weight  8   h  ( 8   g ). The rest of the configuration is the same as that shown in  FIG. 4  and will not be explained further.  
       FIGS. 6A and 6B  show another example of the parts of a vibration transfer rate reducing device.  FIG. 6A  shows a partial cross-sectional view including the central axial line of propeller shaft  1  and the input shaft  6  of differential  5  (output shaft  3  of the transmission  2 ).  FIG. 6B  is an oblique view viewed from the oblique direction on the side of differential  5  (transmission  2 ).  
      Compared with the vibration transfer rate reducing device shown in  FIGS. 4A and 4B , the cross-sectional shape of cylindrical weight  8   j  ( 8   i ) on the side of the differential  5  (the transmission  2 ) is increased. As a result, the center of gravity of vibration restraining mass weight  8   j  ( 8   i ) is further moved away from the end surface of the propeller shaft  1 . This configuration is better for mass distribution of weight  8   j  ( 8   i ). In other words, with a smaller mass the weight can move the joint of the flexural vibration to the side of the flexible joint  7 ′ ( 4 ′). The rest of the configuration is the same as that shown in  FIG. 4  and will not be explained again.  
       FIG. 7  is a graph illustrating the effect of the vibration transfer rate reducing device disclosed and shown in  FIG. 2 . In  FIG. 7 , the abscissa represents the frequency (Hz), while the ordinate represents the vibration acceleration in dB.  
      In order to evaluate the effect of the transfer vibration rate reducing device disclosed herein, vibration was applied to the central part of propeller shaft  1  in the axial direction, and the vibration acceleration at the tip of differential  5  was measured. In this case, a 1.1 kg weight  8  was used. For the purpose of comparison, evaluation was conducted in the same way for the case when a cubic weight with a mass of 1.1 kg and 51.8 mm on each side was directly added to the tip of the differential  5  and for the case when no weight was applied.  
      The line indicated by A in  FIG. 7  shows the evaluation result when the vibration rate reducing device disclosed herein is used. The line indicated by B shows the evaluation result in the case when the vibration restraining mass weight is directly added to the tip of differential  5 . The line indicated by C shows the evaluation result when no vibration restraining mass weight is added. In this case, the tip of differential  5  indicates the end part of a differential gear on the side of the constant velocity joint.  
      As shown in  FIG. 7 , by using the vibration transfer rate reducing device disclosed herein, the vibration acceleration can be reduced by about 2 dB compared with the case when no weight is added at the peak near 105 Hz. The vibration acceleration can be reduced by about 1 dB compared with the case when a vibration restraining mass weight is added directly to the tip of the differential.  
       FIG. 8  is a diagram illustrating the effect of the vibration transfer rate reducing device disclosed and shown in  FIGS. 6A and 6B . In  FIG. 8 , the abscissa represents the frequency (Hz), while the ordinate represents the vibration acceleration in dB.  
      In order evaluate the effect of the transfer vibration rate reducing device disclosed in the present invention, vibration was applied to the central part of the propeller shaft  1  in the axial direction, and the vibration acceleration at the tip of the differential  5  was measured. In this case, the weight  8  used was 1.84 kg and had 160 mm as the outer diameter on the side of differential  5  and 130 mm as the outer diameter on the side of the constant velocity joint  7 . For the purpose of comparison, the evaluation was conducted in the same way for the case when a cubic weight with a mass of 1.84 kg and 61.6 mm on each side was directly added to the tip of differential  5  and for the case when no vibration restraining mass weight was applied.  
      The solid line indicated by D in  FIG. 8  shows the evaluation result when the vibration rate reducing device disclosed herein is used. The line indicated by E shows the evaluation result in the case when the weight is directly added to the tip of differential  5 . The line indicated by F shows the evaluation result when no weight is added.  
      As shown in  FIG. 8 , by using the vibration transfer rate reducing device disclosed herein, the vibration acceleration can be reduced by about 5 dB compared with the case when no weight is added at the peak. The vibration acceleration can be reduced by about 4 dB compared with the case when the weight is directly added to the tip of differential  5 .  
      Various modifications or changes to the disclosed embodiments can be made. For example, these embodiments explain the noise caused by the flexural vibration of propeller shaft  1 . The invention, however, can be used to reduce the vibration transfer rate of drive shaft or other parts that transfer rotation driving force instead of propeller shaft  1 . Also, as explained in these embodiments, weight  8  is arranged at the two ends of propeller shaft  1 . However, it is also possible to arranged weight  8  only at one end depending on the vibration state.  
      Hence, while the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.