JP2007106359A - Center mount structure of vehicular propeller shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a center mount structure of a vehicular propeller shaft capable of reducing the vibration and the noise of a vehicle, and ensuring the improvement of the ride quality and the habitability. <P>SOLUTION: In the center mount 30 of a propeller shaft 1, a front propeller shaft 2 and a rear propeller shaft 5 are connected to each other via a joint 10, a front end of the front propeller shaft 2 is connected to an output shaft of a power unit by a universal joint 7, and a rear end of the rear propeller shaft 5 is connected to a differential device by a joint 8. An inner cylindrical member 32 which stores an outer race 31b of a bearing 31 to support the rear end of the front propeller shaft 3 and is mounted on a vehicle body 50 via an insulator 33 and an outer cylindrical member 34 is formed of an aluminum alloy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a center mount structure that supports a propeller shaft that transmits engine driving force to driving wheels.

  In general, the power transmission system of a four-wheel drive vehicle (AWD) or front engine rear drive (FR) vehicle has an engine-side output mounted on the front of the vehicle body at the front end of a propeller shaft disposed in the front-rear direction with respect to the vehicle body. In addition to being connected to the shaft, the rear end portion is connected to the drive shaft of the rear wheel, which is the drive wheel, via a differential device.

  On the other hand, the propeller shaft mainly causes a dangerous rotation speed at the time of high-speed rotation, that is, the resonance frequency of the propeller shaft and the propeller shaft rotation frequency coincide with each other, thereby causing resonance and increasing the vibration width of the propeller shaft, thereby destroying the propeller shaft. In order to increase the bending speed of the propeller shaft and increase it outside the vehicle speed range, the limit rotational speed is divided into two at the joint.

  The propeller shaft constituted by dividing into two is formed by, for example, a front propeller shaft 102 and a rear propeller shaft 103 connected to a rear end portion of the front propeller shaft 102 via a joint 105 as shown in FIG. The front end of the propeller shaft 101 is connected to an output shaft of a power unit including an engine and a transmission via a universal joint 107, and the rear end of the rear propeller shaft 103 is a driving wheel via a universal joint 108. For example, refer to Patent Document 1.

  In such a propeller shaft 101, the rear end portion of the front propeller shaft 102 is supported on the lower surface of the vehicle body 120 by the center mount 110. An example of the center mount 110 will be described with reference to FIG.

  The center mount 110 that supports the rear end portion of the front propeller shaft 102 includes an inner race 111a, an outer race 111b, an inner race 111a, and an outer race that are fitted to the joint shaft 106 of the joint 105 that is coupled to the rear end portion of the front propeller shaft 102. A bearing 111 having a plurality of balls 111c rolling between the inner cylinder member 111b, an inner cylinder member 112 fitted and fixed to the outer periphery of the bearing 111, and an elastic material such as rubber on the outer periphery of the inner cylinder member 112. An outer cylinder member 114 connected via an insulator 113, and a bracket 123 for attaching the outer cylinder member 114 to the lower surface of the vehicle body.

  The bearing 111 is supported by an inner race 111 a fitted into the main shaft portion 106 a of the joint shaft 106.

  The inner cylinder member 112 has a main body portion 112a fitted to the outer peripheral surface of the outer race 111b of the bearing 111, a large-diameter portion 112b having a diameter increased from the main body portion 112a, and an outer race 111b extending from the main body portion 112a. A small-diameter portion 112c having a reduced diameter along the rear surface and extending in a cylindrical shape is formed in a substantially cylindrical shape that is long in the axial direction and is integrally formed.

  A retainer 119 formed in an annular shape with a substantially C-shaped or U-shaped cross section is provided in the large-diameter portion 112 b of the inner cylinder member 112. Ring-shaped oil seals 115 a and 115 b are disposed on both sides of the bearing 111 between the retainer 119 and the joint shaft 106 and between the small diameter portion 112 c of the inner cylinder member 112 and the joint shaft 106.

  In the propeller shaft 101 configured as described above, during normal traveling, the rotational torque from the power unit is transmitted to the front propeller shaft 102 via the universal joint 107, and the rear propeller shaft 103 is transmitted from the front propeller shaft 102 via the joint 105. Is transmitted from the rear propeller shaft 103 to the differential device 109 via the universal joint 108.

  During this travel, the propeller shaft is rotatably supported on the vehicle body 120 via the center mount 110 on the joint shaft 106 of the joint 105 connecting the front propeller shaft 102 and the rear propeller shaft 103, which is an intermediate portion of the propeller shaft 101. The vibration when the 101 rotates at high speed is damped and the vibration and noise of the vehicle are suppressed.

  As a general property of bearings, a raceway such as an outer race and a ball are subjected to a load by elastic contact, so it has a “spring” property, and when a rotating body is supported by a bearing, the rotating body is It is generally known that there is a vibration system with a mass, and a thrust vibration of a rotating shaft that is estimated to be a kind of self-excited vibration is caused by a bearing (for example, see Non-Patent Document 1).

JP 7-309146 A "JIS Usage Series: How to Select and Use Rolling Bearings", 190 pages; (Japan Standards Association, How to Select and Use Rolling Bearings Editorial Committee)

  Here, the thrust (axial) direction spring characteristic of the bearing will be described by taking the center bearing of the propeller shaft as an example. The bearing 111 of the center mount 110 that supports the joint shaft 106 of the joint 105 disposed at the rear end portion of the front propeller shaft 102 has an inner race 111a formed on the joint shaft 106 as schematically shown in FIG. The outer race 111b is fitted into the inner cylinder member 112 and elastically supported by the outer cylinder member 114 by the insulator 113, and a ball 111c serving as a rolling element between the raceway surface of the inner race 111a and the raceway surface of the outer race 111b. Are fitted and arranged. In the bearing 111, a minute radial gap is set between the raceway surfaces of the inner race 111a and the outer race 111b and the ball 111c in order to prevent seizure during high-speed and high-load rotation.

The raceway surface of the inner race 111a and the ball 111c and the raceway surface of the outer race 111b and the ball 111c move relatively in the thrust direction, and are in elastic contact with each other in a state where this minute gap is clogged, as shown in FIG. Since the contact point between the inner race 111a and the ball 111c and the contact point between the outer race 111a and the ball 111c have a contact angle α that is offset in the axial direction, when the thrust direction force Fx acts on the bearing 111, this contact angle A so-called elastic contact surface pressure Fx / sin α acts in the α direction. A thrust action in the thrust direction occurs between the inner race 111a and the outer race 111b of the bearing 111 due to the relationship between the thrust force Fx and the thrust direction relative displacement δp / sinα associated with the elastic deformation strain δp caused by the contact surface pressure. The elastic strain Δp is obtained as an elastic contact problem between the sphere and the ring. The elastic contact spring Kbrg is
Kbrg = Fx · sin α / δp
It is.

Therefore, for the bearing 111 used for the center mount of the propeller shaft 101, the natural frequency f ₀ _brg with the elastic contact spring Kbrg and the insulator Kins as springs and the total mass Mout of the outer race 111b and the inner cylindrical member 112 as mass. have.

  Next, the shaft vibration of the bearing will be described.

  In the propeller shaft 101, when vibration is transmitted to the propeller shaft 101 and the bearing 111 due to the rotation of the power unit and the propeller shaft 101, an axial thrust force Ps may be periodically and repeatedly applied to the outer race 111b. The propeller shaft 101 also has a vibration system in which bearing axial vibration is generated at the natural frequency due to this repeated vibration.

  Next, the rolling element passing vibration, which is another essential characteristic of the bearing, will be described.

  Since the bearing 111 has a minute radial gap between the raceway surfaces of the inner race 111a and the outer race 111b and the ball 111c as described above, as schematically shown in FIGS. 10 (a) and 10 (b). When the inner race 111a rotates with the rotation of the propeller shaft 101 in a state where the own weight load P of the propeller shaft 101 is applied to the inner race 111a of the bearing 111, the gap distribution of the bearing 111 is distributed due to the difference in the circumferential position of the ball 111c. The outer race 111b and the inner cylindrical member 112 are supported via the insulator 113 in accordance with changes in the geometric displacement of the ball 111c, the inner race 111a, and the outer race 111b. Vibrates up and down Rolling element passing vibration is generated that. That is, when the ball 111c comes under the load P from the propeller shaft 101, more precisely, the joint shaft 106 as shown in FIG. 10 (a), and the symmetrical position with respect to the load direction P as shown in FIG. 10 (b). When the ball 111c comes to the center, the outer race 111b and the inner cylinder member 112 move up and down relative to the rotation center of the propeller shaft 101.

  The amount of displacement can be obtained geometrically from the bearing inner, outer race raceway groove diameter, ball diameter, number of balls, and radial clearance. A difference δY = Ymax−Ymin between the displacement Ymin in FIG. 10A and the displacement Ymax in FIG. 10B is the vibration displacement.

  Qualitatively, as can be seen from the figure, the larger the radial gap, the greater the vertical displacement due to the revolution of the ball 111c. This rolling element passing vibration is greatly influenced by the roundness of the outer race 111b. This will be described with reference to FIGS. 11 (a) and 11 (b). The roundness of FIG. 11 (b) is worse than that of FIG. 11 (a). If the roundness is poor, the amount of geometric displacement between the inner race 111a and the outer race 111b due to the difference in the circumferential position of the ball 111c increases.

This is because, assuming that the outer race 111b has an ellipse-shaped trajectory as the roundness deteriorates, and the short-diameter side is positioned in the vertical direction, the maximum curvature radius ρ of the raceway surface serving as the contact portion of the ball is As the major axis 2a and minor axis 2b of the ellipse that becomes the orbit
ρ = a ² / b
This is because the longer diameter and the shorter diameter ratio are larger and the curvature radius ρ is larger as the slender shape is larger, and the geometrical effects of the large radial gap and the poor roundness accuracy are equal. This can be explained not only by the geometric displacement described above, but also by the elastic contact strain between the ball 111c and the raceway surface of the outer race 111b as shown in FIG. That is, the larger the radial gap, and thus the greater the contact curvature of the outer race 111b, the greater the elastic contact deformation strain and the greater the vertical displacement due to the revolution of the ball 111c. The amount of elastic strain is obtained as an elastic contact problem between the ball 111c and the outer rail 111b in consideration of the shared load due to the arrangement of the ball 111c.

Due to the rotation of the propeller shaft 101, the vibration caused by the vertical displacement of the outer race 111b when the ball revolves around the raceway surface is the rolling element passing vibration.
The order n of this rolling element passing vibration is n = 1/2 · Z (1-Dw / Dp)
Here, Z is the number of balls, Dw is the ball diameter, Dp is the bearing pitch circle diameter, and n vertical vibrations are generated by one rotation of the bearing.

Further, as described above, in the propeller shaft 101, the vibrations of the outer race 111b and the inner cylinder member 112 due to the bearing axial direction characteristics use the mass Mout of the outer race 111b and the relatively large inner cylinder member 112 as a mass, A vibration system having a natural frequency f ₀ _brg with a spring constant determined by the elastic contact stiffness Kbrg of the bearing and the insulator 113Kins is formed.

On the other hand, as a result of intensive research, the inventor also uses the axial rigidity Kjoint of the universal joint 112 as a main spring in the front propeller shaft 102 in which the rotational torque from the power unit is rotationally driven via the universal joint 107. It has been determined that a vibration system in which the front propeller shaft 102 vibrates in the axial direction is formed using the mass Mpela of 102 as a mass. The natural frequency f ₀ _pela of this vibration is expressed by the following equation.

  Thus, when the inner race 111a of the bearing 111 vibrates in the axial direction due to the axial vibration of the front propeller shaft 102, the contact point between the inner race 111a and the ball 111c and the outer race 111b accompany the axial vibration of the inner race 111a. Since the contact point between the ball 111c and the ball 111c has a contact spring with a contact angle α offset in the axial direction, axial thrust force is periodically and repeatedly applied to the outer race 111b via the ball 111c. The outer race 111b and the inner cylinder member 112 supported via the insulator 113 vibrate in the thrust direction. That is, due to the vibration in the axial direction of the front propeller shaft 102, a vibration system is formed in which the outer race 111c and the inner cylindrical member 112 are in mass.

Here, as a result of earnest research experiments, the inventor compared the axial vibration eigenvalue f ₀ _brg of the outer race 111b and the inner cylinder member 112 of the bearing 111 of the front propeller shaft 102 with the axial vibration eigenvalue f ₀ _pela of the front propeller shaft. It was investigated that the resonance caused by the natural value of the approximated vibration frequency causes the vibration and noise of the vehicle and affects the riding comfort and comfort. Further, the inner cylinder member 112 that fits and holds the outer race 111b in the bearing 111 is generally formed into a cylindrical shape by pressing an iron plate, so that processing accuracy, that is, roundness is ensured by a springback or the like during processing. Is difficult. When the outer race 111b is press-fitted into the inner cylinder member 112 where the accuracy of the roundness cannot be ensured, the molding accuracy of the inner cylinder member 112, particularly the main body 112a, is transferred to the outer race 111b during the press-fitting and affects the roundness of the outer race 111b. The inventors have found that this is a factor that increases the rolling element passing vibration of the bearing 111.

  Accordingly, an object of the present invention made by paying attention to these is to reduce the vibration and noise of the vehicle by suppressing the vibration of the bearing and the inner cylinder member due to the rotation of the propeller shaft and the vibration in the axial direction. Another object of the present invention is to provide a center mount structure for a propeller shaft for a vehicle that can ensure improvement in habitability.

  In the invention of the center mount structure for a propeller shaft for a vehicle according to claim 1, which achieves the above object, the rear end portion of the front propeller shaft and the front end portion of the rear propeller shaft are connected via a joint, and the front end of the front propeller shaft is connected. In the center mount structure of the propeller shaft, the inner end of which is connected to the output shaft of the power unit by the universal joint and the rear end of the rear propeller shaft is connected to the differential device by the joint, the inner that fits and supports the rear end of the front propeller shaft A bearing having a plurality of balls that are rotatably arranged between raceways of the race, the outer race, and the inner race and the outer race, an inner cylindrical member that accommodates and holds the outer race of the bearing, and a vehicle body Mounted and supported outer cylinder And an insulator made of an elastic material interposed between the inner cylinder member and the outer cylinder member, and the inner cylinder member is lighter than an iron-based material, has excellent moldability, and can secure molding accuracy. It is formed.

  According to a second aspect of the present invention, in the center mount structure for a propeller shaft for a vehicle according to the first aspect, the inner cylindrical member is made of an aluminum-based alloy.

  According to a third aspect of the present invention, in the center mount structure for a propeller shaft for a vehicle according to the second aspect, the bearing is formed of a ferrous material, and the inner cylindrical member is a cylindrical main body that holds an outer race of the bearing A front propeller shaft, the first extension portion, and the front propeller with a bearing therebetween, the first extension portion and the second extension portion extending respectively at both ends of the main portion and the main portion. Sealing means for watertightly sealing between the shaft and each of the second extending portions is provided.

  According to a fourth aspect of the present invention, in the center mount structure for a propeller shaft for a vehicle according to the second aspect, the bearing is formed of a ferrous material, and the inner cylindrical member is a cylindrical main body that holds an outer race of the bearing. And a cylindrical large-diameter portion having a first extending portion and a second extending portion that are respectively extended at both ends of the body portion and the main body portion, the cylindrical large-diameter portion being fitted into the first extending portion, and the large portion A retainer that has an approximately C-shaped or U-shaped cross section having a cylindrical small-diameter portion continuous to the diameter portion and that is annularly continuous, and a first seal member that seals water tightly between the second extension portion and the propeller shaft. And a second seal member for watertight sealing between the small diameter portion of the retainer and the propeller shaft, and a third seal member for watertight sealing between the retainer and the first extension portion. It is characterized by.

  According to a fifth aspect of the present invention, in the center mount structure for a propeller shaft for a vehicle according to the first aspect, the inner cylinder member is formed of a resin material.

  According to a sixth aspect of the present invention, in the center mount structure for a propeller shaft for a vehicle according to any one of the first to fifth aspects, the rear end portion of the front propeller shaft is provided instead of the rear end portion of the front propeller shaft. The joint shaft of the joint is fitted and supported by the inner race of the bearing.

  According to the first aspect of the present invention, the inner cylinder member that holds the outer race of the bearing is formed of a material that is lightweight, excellent in formability, and can be molded with high accuracy, thereby ensuring the roundness of the inner cylinder member. The roundness of the outer race held by the cylindrical member is maintained, and rolling element passing vibration accompanying rotation of the front propeller shaft can be suppressed. Further, with the weight reduction of the inner cylinder member, the difference between the outer race of the front propeller shaft and the axial vibration eigenvalue of the inner cylinder member and the axial vibration eigenvalue of the front propeller shaft can be greatly increased and separated. Thus, by separating the vibration eigenvalues from each other, the occurrence of resonance can be effectively avoided, and the vibration and noise of the vehicle are suppressed, so that riding comfort and comfort are improved.

  According to a second aspect of the present invention, the material of the inner cylinder member is specified as a specific aluminum-based alloy, and the inner cylinder member is formed of an aluminum-based alloy that is lightweight, excellent in formability, and can be formed with high accuracy. Thus, the effect of claim 1 can be achieved.

Another effect of making the inner cylinder member an aluminum-based alloy will be described. The inner race side temperature rises from the outer race side due to the frictional heat of the bearing, and the radial gap decreases due to the difference in thermal expansion distortion. The clearance reduction St is St = β _Fe · Di · ti + 2β _Fe · Dw · tw
Here, β _Fe : thermal expansion coefficient of iron, Di: inner race track diameter, Dw: ball diameter, ti: temperature difference between outer race and inner race, tw: temperature difference between outer race and ball. The press-fitting margin when press-fitting the bearing into the iron inner cylinder member needs to be reduced in consideration of the gap reduction due to this thermal expansion. Aluminum alloy has high thermal conductivity and excellent heat dissipation. By making the inner cylindrical member an aluminum alloy, the temperature rise of the bearing can be reduced, and the coefficient of thermal expansion is larger than that of iron, so the inner race side expansion. Since the radial clearance is compensated for by reducing the clearance due to the outer race press-fitting, the radial clearance is maintained substantially even during long-time operation.

  According to the third aspect of the present invention, the first propulsion portion and the second extension portion that are extended at both ends of the main body portion that fits and holds the outer race of the bearing and the front propeller shaft are respectively watertight by the sealing means. The outer race of the dissimilar metal and the inner cylinder member are prevented from entering between the contact portions of the outer race of the bearing made of iron-based material and the inner cylinder member made of the aluminum-based alloy. It is possible to prevent the occurrence of electrolytic corrosion at the contact portion.

  According to invention of Claim 4, between the small diameter part of the retainer fitted in the 1st extension part of a cylindrical member, and the propeller shaft is watertightly sealed by the 1st seal member, The 2nd extension part and the propeller shaft The outer race of the bearing made of iron-based material and the aluminum-based alloy are sealed with a second seal member between the retainer and the first extending portion with a second seal member. Intrusion of moisture as a corrosive medium from the outside is prevented between the contact portions with the inner cylinder member, and the occurrence of electrolytic corrosion at the contact portion between the outer race of the different metal and the inner cylinder member can be prevented.

  The invention of claim 5 specifies the material of the inner cylinder member as a specific resin material, and achieves the effect of claim 1 by forming it with a resin material having high adaptability to the mating shape. can do.

  The invention of claim 6 shows another specific configuration of the center mount structure according to claims 1 to 5, wherein a joint shaft of a joint provided at the rear end portion of the front propeller shaft is fitted by an inner race of the bearing. It is what you support.

  Embodiments of a center mount structure for a vehicle propeller shaft according to the present invention will be described below with reference to FIGS. In each figure, an arrow F indicates the vehicle body front direction.

  FIG. 1 is an overall perspective view of a propeller shaft 1 used in a drive system of a four-wheel drive vehicle or a front engine rear drive. The propeller shaft 1 includes a front propeller shaft 2 and a rear propeller shaft 5 connected to a rear end portion of the front propeller shaft 2 via a joint 10. The front end of the front propeller shaft 2 is connected to the output shaft of a power unit mounted on the front of the vehicle body via a universal joint 7, while the rear end of the rear propeller shaft 5 is a drive wheel via a universal joint 8. It is connected to a differential device for rear wheels. Further, the joint 10 for connecting the front propeller shaft 2 and the rear propeller shaft 5 is rotatably supported on the lower surface 51 of the vehicle body 50 by the center mount 30 as shown in the perspective view of the main part of the lower part of the vehicle body.

  3 is a cross-sectional view taken along the line II of FIG. 1, showing the joint 10 and the center mount 30 that connect the rear end portion of the front propeller shaft 2 and the front end portion of the rear propeller shaft 5. FIG. FIG.

  As shown in FIG. 3, the joint 10 includes a joint shaft 11 coupled to the rear end portion of the front propeller shaft 2 and an outer case 20 coupled to the front end portion of the rear propeller shaft 5.

  The joint shaft 11 includes a columnar base portion 12 coupled to a rear end portion 3a of the shaft tube 3 forming the front propeller shaft 2, and a main shaft portion 13 continuing to the rear end of the base portion 12 via a step portion 12b. The tip shaft portion 14 that is continuous to the rear end of the main shaft portion 13 via the step portion 13b is formed in a substantially columnar shape that is coaxially and continuously formed. An annular inner race 16 in which a plurality of ball grooves 16 a extending along the axial direction is formed on the outer periphery is fixed to the distal end portion of the distal end shaft portion 14 of the joint shaft 11.

  On the other hand, the outer case 20 coupled to the front end portion of the rear propeller shaft 5 extends in the axial direction on the inner peripheral surface of the cylindrical base portion 21 so as to face each ball groove 16a of the inner race 16. A plurality of ball grooves 21a are formed.

  Further, the balls 26 held by the ring-shaped gauges 25 are fitted and mounted in the respective ball grooves 16a formed on the outer periphery of the inner race 16 disposed on the distal end shaft portion 14 of the joint shaft 11. The inner race 16 fitted with the gauge 25 and the ball 26 is inserted into the outer case 20, and the gauge 25 is inserted between the ball grooves 16 a of the inner race 16 and the ball grooves 21 a of the base portion 21 facing each other. The held ball 26 is fitted.

  The joint 10 thus configured includes an inner race 16 provided on the tip shaft portion 14 of the joint shaft 11 attached to the front propeller shaft 2, an outer case 20, an inner race 16 attached to the rear propeller shaft 5, and The front propeller shaft 2 and the rear propeller shaft 5 are transmitted with rotational torque at a constant speed by a ball 26 or the like fitted between the ball grooves 16a and 21a formed in the base portion 21 of the outer case 20, and the relative angle between them is also determined. And a double offset joint (DOJ) that allows relative movement in the axial direction.

  Next, the center mount 30 that supports the joint 10 on the lower surface 51 of the vehicle body 50 will be described with reference to FIGS.

  The center mount 30 includes a bearing 31 fitted to the joint shaft 11, an inner cylinder member 32 fixed to the outer periphery of the bearing 31, and an insulator 33 made of an elastic material such as rubber on the outer periphery of the inner cylinder member 32. A connected outer cylinder member 34 and a bracket 43 for attaching the outer cylinder member 34 to the lower surface 51 of the vehicle body 51 are provided.

  The bearing 31 has an inner race 31a, an outer race 31b, and a plurality of balls 31c arranged so as to be able to roll between the raceway surfaces of the inner race 31a and the outer race 31b. The inner race 31a is the main shaft of the joint shaft 11. It is supported by being sandwiched between a stepped portion 12b and a cylindrical spacer 37 that is fitted to the portion 13 and is engaged with a clip 36 that is fitted into a clip groove formed in the main shaft portion 13.

  The inner cylinder member 32 is a material that is lighter than iron-based materials, has excellent formability and can ensure molding accuracy, and is made of an aluminum-based alloy material in the present embodiment, and has a main body portion 32 a on the outer periphery of the outer race 31 b of the bearing 31. A large-diameter portion 32c that is a first extending portion that is formed in an annular shape by expanding from the front end of the main body portion 32a through the stepped portion 32b, and the rear surface of the outer race 31b from the rear end of the main body portion 32a. A small-diameter portion 32e, which is a second extending portion extending in a cylindrical shape along the spacer 37, is formed in a substantially cylindrical shape through a step portion 32d having a reduced diameter along the spacer 37. The inner cylinder member 32 is formed, for example, by press molding with excellent productivity, and is made of an aluminum-based alloy that has excellent moldability and extremely little occurrence of springback or the like during press molding, and is easily molded with high accuracy. In particular, the roundness of the main body 32a and the like into which the outer race 31b of the bearing 31 is press-fitted can be secured satisfactorily, and as a result, the roundness accuracy of the bearing after press-fitting is not greatly deteriorated.

  A retainer 39 made of an aluminum-based alloy material and having an approximately C-shaped or U-shaped annular shape is provided in the large-diameter portion 32c of the inner cylinder member 32. The retainer 39 is press-fitted into the large-diameter portion 32c and is fitted into a large-diameter portion 39a, a stepped portion 39b whose diameter is reduced from the rear end of the large-diameter portion 39a into a tapered surface, and a joint shaft from the rear end of the stepped portion 39b. A cylindrical small-diameter portion 39c extending forward along the line 11 is continuously formed integrally.

  An oil seal 41a which is an annular first seal member and a second seal member are sealed on the both sides of the bearing 31 between the small diameter portion 39c of the retainer 39 and the small diameter portion 32d of the inner cylinder member 32 and the joint shaft 11, respectively. 41b are disposed. A seal member 42, which is an annular third seal member that seals the space between the inner cylindrical member 32 and the retainer 39 in a watertight manner, is disposed between the stepped portion 39 b of the retainer 39 and the stepped portion 32 b of the inner cylindrical member 32. It is installed.

  The oil seals 41a and 41b disposed between the small diameter portion 39c of the retainer 39 and the small diameter portion 32d of the inner cylinder member 32 and the joint shaft 11 are disposed between the retainer 39 and the inner cylinder member 32 and the retainer 39, respectively. The sealing means by the sealing member 42 prevents the moisture as a corrosive medium from entering between the contact portions between the outer race 31b of the bearing 31 made of iron-based material and the inner cylinder member 32 made of aluminum-based alloy. The occurrence of electrolytic corrosion at the contact portion between the metal outer race 31b and the inner cylinder member 32 is prevented.

  The insulator 33 is made of an elastic material such as rubber, and is formed in an annular shape having a substantially C-shaped cross section in which an inner periphery is coupled to the inner circumferential member 32 and an outer periphery is coupled to the outer cylindrical member 34.

  The outer cylinder member 34 is attached with a bracket 43 for fixing the outer cylinder member 34 to the vehicle body. As shown in FIGS. 1 and 2, the bracket 43 has a belt-like shape that is coupled along the lower surface of the outer cylinder member 34, and a bolt hole whose front side is opened in a slit shape at mounting portions 44 formed at both ends thereof. 44a is formed and attached to the lower surface 51 of the vehicle body 50 by a bolt 45 penetrating the bolt hole 44a.

  The center mount 10 thus configured is an aluminum alloy in which the inner cylindrical member 32 that fits and supports the outer race 31b of the bearing 31 is excellent in formability and generates very little spring back during press molding. Since it is made of a material, it can be formed with high precision by press molding excellent in productivity. In particular, the roundness of the main body 32a that press-fits and holds the outer race 31b can be easily ensured. By securing the roundness in the main body portion 32a of the inner cylinder member 32, the influence on the outer race 31b at the time of press-fitting is suppressed, and the roundness of the outer race 31b can be secured. The bearing 31 in which the roundness of the outer race 31b is ensured can suppress the rolling element passing vibration accompanying the rotation of the front propeller shaft 2.

  Further, by forming the relatively long and large inner cylinder member 32 of a lightweight aluminum-based alloy material, it is possible to suppress rolling element passing vibration caused by the rotation of the front propeller shaft 2.

  Further, the mass of the outer race 31 and the inner cylindrical member 32, which are the mass of the vibration system in which the spring constant is determined by the elastic contact rigidity of the bearing and the insulator 33, are significantly reduced, and the outer race 31 and the outer race 31 caused by the axial vibration of the front propeller shaft 2 The vibration eigenvalue of the inner cylinder member 32 can be significantly increased as compared with the case where an inner cylinder member made of a conventional iron-based material is used.

  Therefore, when the inner cylinder member 32 made of an aluminum alloy material is used, the axial vibration eigenvalues of the outer race 31 and the inner cylinder member 32 of the front propeller shaft 2 are used when an inner cylinder member made of a conventional iron-based material is used. Compared with the main propeller shaft 2, the mass of the front propeller shaft 2 can be increased by using the axial vibration eigenvalues of the outer race 111b and the inner cylindrical member 112 of the bearing 111 of the front propeller shaft 2 and the axial stiffness of the universal joint as main springs. The difference from the axial vibration eigenvalue of the front propeller shaft 2 as a mass is greatly increased and can be separated. Thereby, the occurrence of resonance due to the mutual vibration eigenvalues can be effectively avoided, and the vibration and noise of the vehicle are suppressed, so that riding comfort and comfort are improved.

  FIG. 5 is a relationship diagram between the load and the vibration frequency between the inner race and the outer race in the present embodiment and the conventional center mount.

  The solid line A in FIG. 5 shows the correlation between the load and the vibration frequency between the inner race 31a and the outer race 31b of the bearing 31 in the center mount 30 of the present embodiment, and the broken line B shows the bearing 111 of the conventional center mount 110. The relative relationship between the load and the vibration frequency between the inner race 111a and the outer race 111b is shown.

  The axial vibration eigenvalue of the front propeller shaft 102 and the axial vibration eigenvalue of the bearing 111 in the center mount 110 using the conventional inner cylinder member 112 made of iron-based material are relatively approximate, and the resonance state is obtained by approximating the eigenvalue of this frequency. As a result, the vibration and noise of the vehicle cause a decrease in ride comfort and comfort.

  On the other hand, the shaft vibration eigenvalue of the front propeller shaft 2 and the shaft vibration eigenvalue of the bearing 30 in the center mount 30 according to the present embodiment using the light inner cylinder member 32 made of an aluminum alloy are separated by a relatively large difference. By separating the eigenvalues of these vibration frequencies, the occurrence of resonance can be effectively avoided, and the vibration and noise of the vehicle can be suppressed to improve the ride comfort and comfort.

  The present invention is not limited to the above-described embodiment, and can be variously modified without departing from the spirit of the invention. For example, in the above embodiment, the inner cylinder member 32 is used with an aluminum alloy that is lightweight and excellent in formability. However, the inner cylinder member 32 is lightweight and can be easily molded by injection molding or the like, and excellent molding accuracy is ensured. It can also be formed by resin molding (high adaptability to the mating partner shape). By forming the inner cylinder member 32 from a resin material, there is no risk of the occurrence of electrolytic corrosion with the outer race 31b of the bearing 31, and the structure can be simplified by omitting the seal member 42. Moreover, in the said embodiment, although the joint shaft 11 of the joint 10 couple | bonded with the rear end of the front propeller shaft 3 was supported by the inner race 31a of the bearing 31, the front propeller shaft 3 can also be supported directly.

1 is an overall perspective view of a propeller shaft 1 used in a first embodiment of the present invention. It is a principal part perspective view of the vehicle body lower part. It is the II sectional view taken on the line of FIG. It is the A section enlarged view of FIG. It is a frequency response figure of the bearing outer race vibration at the time of power unit sine vibration. It is a schematic explanatory drawing of the conventional propeller shaft and center mount. It is sectional explanatory drawing of the conventional center mount. It is a thrust vibration explanatory view of a bearing. It is explanatory drawing of a rolling element passing vibration exciting force in case the outer race roundness accuracy of a bearing is high. It is explanatory drawing of the rolling element passing vibration exciting force by the radial clearance of a bearing. It is explanatory drawing of the rolling element passing vibration exciting force of the bearing by outer race roundness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Propeller shaft 2 Front propeller shaft 3a Rear end part 5 Rear propeller shaft 7 Universal joint 8 Universal joint 10 Joint 11 Joint shaft 30 Center mount 31 Bearing 31a Inner race 31b Outer race 31c Ball 32 Inner cylinder member 32a Main part 32c Large diameter part ( (First extension)
32e Small diameter part (2nd extension part)
33 Insulator 39 Retainer 39a Large diameter portion 39c Small diameter portion 41a, 41b Oil seal (first seal member, second seal member)
42 Seal member (third seal member)
50 body

Claims (6)

The rear end portion of the front propeller shaft and the front end portion of the rear propeller shaft are connected via a joint, the front end portion of the front propeller shaft is connected to the output shaft of the power unit by a joint, and the rear end portion of the rear propeller shaft is a differential device by the joint. In the center mount structure of the propeller shaft connected to
An inner race and an outer race that fit and support the rear end portion of the front propeller shaft, and a bearing having a plurality of balls that are arranged to roll between the raceway surfaces of the inner race and the outer race;
An inner cylinder member that accommodates and holds the outer race of the bearing; and
An outer cylinder member attached to and supported by the vehicle body;
An insulator made of an elastic material interposed between the inner cylinder member and the outer cylinder member;
A center mount structure for a propeller shaft for a vehicle, wherein the inner cylindrical member is formed of a material that is lighter than an iron-based material, has excellent moldability, and can ensure molding accuracy.   The center mount structure for a propeller shaft for a vehicle according to claim 1, wherein the inner cylinder member is made of an aluminum alloy. The bearing is formed of a ferrous material,
The inner cylinder member is a cylindrical body having a cylindrical main body portion that holds the outer race of the bearing, and a first extension portion and a second extension portion that are respectively extended at both ends of the main body portion.
3. A sealing means for watertightly sealing each of the front propeller shaft and the first extending portion and the front propeller shaft and the second extending portion with the bearings therebetween. The center mount structure of the vehicle propeller shaft described. The bearing is formed of a ferrous material,
The inner cylindrical member is a cylindrical body having a cylindrical main body portion that holds the outer race of the bearing, and a first extending portion and a second extending portion that are respectively extended at both ends of the main body portion,
A retainer that is annularly continuous in a substantially C-shaped to U-shaped cross section having a cylindrical large-diameter portion that fits into the first extending portion and a cylindrical small-diameter portion that is continuous with the large-diameter portion;
A first seal member for watertightly sealing between the second extending portion and the propeller shaft;
A second seal member for watertight sealing between the small diameter portion of the retainer and the propeller shaft;
The center mount structure for a propeller shaft for a vehicle according to claim 2, further comprising a third seal member for watertightly sealing between the retainer and the first extending portion.   The center mount structure for a propeller shaft for a vehicle according to claim 1, wherein the inner cylinder member is formed of a resin material. 6. A joint shaft of a joint provided at a rear end portion of the front propeller shaft in place of a rear end portion of the front propeller shaft is fitted and supported by an inner race of a bearing. The center mount structure of the propeller shaft for a vehicle according to the item.

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