Transfer device

A transfer device is provided, which includes an input shaft configured to receive a driving force generated by a drive source, an output shaft configured to output a portion of the driving force to part-time drive wheels of a vehicle, a transfer case accommodating the input and output shafts, at least two output bearings rotatably supporting the output shaft, and a constant-velocity (CV) joint connected to the output shaft and provided on a first side of the part-time drive wheels with respect to the output shaft. The output shaft is formed with a recessed opening portion opening toward the first side and receiving at least a part of the CV joint therein. The transfer case has an annular intruding part extending from the first side of the output shaft into the recessed opening portion. A first output bearing is located inside the recessed opening portion.

TECHNICAL FIELD

The present disclosure relates to a transfer device.

BACKGROUND OF THE DISCLOSURE

In four-wheel drive vehicles of a front-engine, rear-wheel drive (FR) base, a part of driving force for driving rear wheels (drive wheels) is transmitted (distributed) to front wheels (part-time drive wheels) by a transfer device. The transfer device mounted on the FR vehicle transmits the driving force to a front differential gear provided to a driveshaft of the part-time drive wheels, via a front propeller shaft extending forward from the transfer device.

It is difficult to arrange an output shaft of the transfer device and an input shaft of the front differential in line due to various device arrangements in the vehicle. Therefore, the front propeller shaft extending forward inclines with respect to the output shaft of the transfer device, and is connected to the output shaft of the transfer device via a constant-velocity joint.

With this structure, when the inclination angle of the front propeller shaft with respect to the output shaft of the transfer device (hereinafter, referred to as “the operation angle of the front propeller shaft”) becomes large, an upper limit value of a rotational speed of the constant-velocity joint needs to be set low. That is, an upper limit value of a rotational speed of the output shaft of the transfer device and an upper limit value of a rotational speed of the front propeller shaft need to be set low.

For this reason, in many transfer devices, the constant-velocity joint is not disposed in a front part of the transfer device but is inserted into the output shaft of the transfer device so that the constant-velocity joint is located as rearward as possible. Thus, an increase of the operation angle is prevented. JP1992-228953A discloses one example of such a structure, in which a sprocket thereof corresponds to the output shaft described above.

However, in the case of inserting the constant-velocity joint into the output shaft of the transfer device, the constant-velocity joint is located between front and rear bearings supporting the output shaft, and the constant-velocity joint is surrounded by the output shaft. Thus, heat generated by the constant-velocity joint is not easily released outside, which may result in lowering the rotational speed of the constant-velocity joint.

SUMMARY OF THE DISCLOSURE

The present disclosure is made in view of the above situations and aims to provide a transfer device, in which a constant-velocity joint is disposed as distant as possible from part-time drive wheels and heat generated by the constant-velocity joint is easily released outside.

According to one aspect of the present disclosure, a transfer device is provided, which includes an input shaft configured to receive a driving force generated by a drive source, an output shaft configured to output a portion of the driving force received by the input shaft to part-time drive wheels of a vehicle, a transfer case accommodating the input shaft and the output shaft, at least two output bearings rotatably supporting the output shaft, and a constant-velocity joint connected to the output shaft and provided on a first side of the part-time drive wheels with respect to the output shaft. The output shaft is formed with a recessed opening portion opening to the first side and receiving at least a part of the constant-velocity joint therein. The transfer case has an annular intruding part extending from a position on the first side of the output shaft into the recessed opening portion through a position between the recessed opening portion and the constant-velocity joint. A first output bearing is located inside the recessed opening portion, fixed at an outer circumferential part to an inner circumferential surface of the recessed opening portion, and fixed at an inner circumferential part to an outer circumferential surface of the intruding part, the first output bearing being one of the at least two output bearings that is located closest to the constant-velocity joint among the at least two output bearings.

According to this configuration, the constant-velocity joint is disposed inside the recessed opening portion formed in the output shaft. Thus, the constant-velocity joint is located as far as possible from the part-time drive wheels. Further, with the configuration, the intruding part of the transfer case passes between the recessed opening portion and the constant-velocity joint. Thus, the constant-velocity joint is not surrounded by the output shaft or the intruding part. Therefore, the constant-velocity joint easily comes into contact with outside air, and heat generated by the constant-velocity joint is easily released to the outside environment.

With the transfer device, an inner diameter of the intruding part may increase while extending toward the constant-velocity joint.

According to this configuration, an opening area of a first side portion of the intruding part becomes large. Therefore, the constant-velocity joint more easily comes into contact with the outside air, and the heat generated by the constant-velocity joint is more easily released outside.

The transfer device may include a seal member sealing a gap between the intruding part and the output shaft. The output shaft may have a cylindrical protruding part located inside the recessed opening portion. The seal member may be provided inside the recessed opening portion, between the intruding part and the protruding part.

According to this configuration, the seal member is located inside the recessed opening portion. Thus, upon securing the sealing performance, the constant-velocity joint is located as rearward as possible while easily coming into contact with outside air. Therefore, the heat generated by the constant-velocity joint is easily released outside.

The transfer device may include a drive part connected to the input shaft, and a driven part connected to the output shaft and configured to be driven by the drive part. The recessed opening portion may be located on an inner side of the driven part in radial directions thereof.

According to this configuration, the recessed opening portion is located radially inward of the driven part. Therefore, the radially inner portion (area) of the driven part of the output shaft is effectively utilized.

A contact line of the first output bearing may be inclined toward the constant-velocity joint with respect to a direction perpendicular to a rotation axis of the first output bearing.

Here, the “contact line” is a straight line joining a contact point between a ball and an outer ring and a contact point between the ball and an inner ring and extending toward the center of rotation. According to this configuration, in terms of dynamics, a supporting point supporting the output shaft of the first output bearing is located on a side of the constant-velocity joint with respect to the driven part or near the driven part. Here, when the supporting point of the first output bearing is located on the constant-velocity joint side with respect to the driven part, the driven part is located between the supporting point of the first output bearing and a supporting point of the output bearing other than the first output bearing. Therefore, even when the first output bearing is located radially inward of the driven part, the driven part is supported at both sides in axial directions thereof. On the other hand, even when the supporting point of the first output bearing is located on the opposite side from the constant-velocity joint with respect to the driven part, if it is located near the driven part, a load on the first output bearing in radial directions thereof resulted from supporting the driven part is reduced.

DETAILED DESCRIPTION OF THE DISCLOSURE

Hereinafter, a transfer device according to one embodiment of the present disclosure is described.

First, a driving force transmission system including the transfer device is described.FIG. 1is a schematic view of the driving force transmission system101of this embodiment. Note that the concept of directions in the following description matches with the concept of directions seen from a vehicle operator on a driver's seat. InFIG. 1, the left side of the drawing is a front side, and the right side of the drawing is a rear side.

The driving force transmission system101of this embodiment is a system for an FR-base four-wheel drive vehicle. An engine102(drive source) is vertically placed in a front part of the vehicle, and a driving force generated by the engine102is inputted to a transfer device100via a transmission103. The transfer device100transmits (distributes) a portion of the inputted driving force to rear wheels (drive wheels), and a remaining portion of the inputted driving force to front wheels (part-time drive wheels).

For example, the portion of the driving force inputted to the transfer device100is transmitted to a rear-wheel driveshaft106via a rear propeller shaft104and a rear differential gear105. The remaining portion of the driving force inputted to the transfer device100is transmitted to a front-wheel driveshaft109via a front propeller shaft107and a front differential gear108.

Next, the transfer device100is described in detail.FIG. 2is a cross-sectional view of the transfer device100. Further,FIGS. 3 to 5are enlarged views of various parts of the transfer device100illustrated inFIG. 2. As illustrated inFIG. 2, the transfer device100includes an input shaft10, a coupling device20, a damper device40, a drive member60, an output shaft70, a transfer case80, and a constant-velocity joint90. Hereinafter, these components are described sequentially.

The input shaft10is a shaft member to which the driving force generated by the engine102is inputted. The input shaft10extends in the front-and-rear directions and is formed therein with an insertion portion11at a front end part, into which an output shaft of the transmission103(seeFIG. 1) is inserted. On the other hand, a coupling member13is fixed to a rear end part of the input shaft10by a nut12. The input shaft10is coupled to the rear propeller shaft104(seeFIG. 1) via the coupling member13.

The input shaft10is rotatably supported at a rear part by the transfer case80via an input bearing14. Further, an input-shaft front seal15is provided between a front part of the input shaft10and the transfer case80, and an input-shaft rear seal16is provided between the coupling member13and the transfer case80.

The coupling device20adjusts a ratio of the driving force transmitted to the rear wheels and the driving force transmitted to the front wheels. As illustrated inFIG. 3, the coupling device20is provided therein with an electromagnet21. When an electromagnetic coil of the electromagnet21is energized, the electromagnet21attracts an armature22located forward of the electromagnet21. When the armature22is attracted, pilot inner plates24and pilot outer plates25that are arranged alternately are sandwiched between the armature22and an end member23, and the plates24and25are frictionally engaged. The pilot inner plates24are held by a cam member26and the pilot outer plates25are held by a housing27. Thus, the cam member26is coupled to the housing27.

With this structure, a pressure plate28which rotates together with the input shaft10rotates with respect to the cam member26, and a positional relationship between a spherical cam follower29and the cam member26in a circumferential direction is changed. Therefore, the cam follower29moves forward and pushes the pressure plate28forward. When the pressure plate28is pushed forward, main inner plates30and main outer plates31that are arranged alternately are frictionally engaged, and the input shaft10holding the main inner plates30and the housing27holding the main outer plate31are coupled to each other. Thus, the driving force inputted to the input shaft10is transmitted to the housing27.

Note that by varying the magnitude of a current for energizing the electromagnetic coil of the electromagnet21, the force forwardly pushing the pressure plate28changes and the friction force acting between the main inner plates30and the main outer plates31changes. In this manner, the magnitude of the driving force transmitted from the input shaft10to the housing27may arbitrarily be set, which leads to an adjustable ratio between the driving force transmitted to the rear wheels and the driving force transmitted to the front wheels.

The housing27of the coupling device20has a housing large-diameter part32which has a cylindrical shape and holds therein the pilot outer plates25and the main outer plates31to be movable in the front-and-rear directions, and a housing small-diameter part33located forward of the housing large-diameter part32. Here, an outer circumferential part of the housing small-diameter part33is formed with a housing spline34. Note that a housing bearing35is provided between the housing27and the input shaft10so that the housing27and the input shaft10are coupled to be rotatable in relation to each other.

The damper device40shifts a resonance frequency which occurs in the engine102(seeFIG. 1) to the outside of a regular-use range. As illustrated inFIG. 4, the damper device40of this embodiment has a ring-shaped elastic member41made of rubber, an inner circumferential member42fixed to an inner circumferential surface of the elastic member41, and an outer circumferential member43fixed to an outer circumferential surface of the elastic member41.

The inner circumferential member42has a first coupling part44in a radially-inward part and is formed with a first damper spline45in an inner circumferential portion of the first coupling part44. The first damper spline45is coupled to the housing spline34.

The outer circumferential member43has an outer circumferential large-diameter part46having a cylindrical shape and fixed to the outer circumferential surface of the elastic member41, an outer circumferential small-diameter part47located in a front part, an outer-circumferential intermediate part48coupling the outer circumferential large-diameter part46to the outer circumferential small-diameter part47, and a second coupling part49having a cylindrical shape, extending rearward from the outer-circumferential intermediate part48, and located radially inward of the inner circumferential member42. An inner circumferential portion of the second coupling part49is formed with a second damper spline50. This second damper spline50is coupled to the housing spline34. Further, an outer circumferential portion of the outer circumferential small-diameter part47is formed with a damper outer spline51, and an inner seal52is provided between the outer circumferential small-diameter part47and the transfer case80.

As described above, both the first damper spline45and the second damper spline50are coupled to the housing spline34. Note that a clearance between the teeth of the second damper spline50and the teeth of the housing spline34is larger than a clearance between the teeth of the first damper spline45and the teeth of the housing spline34. Therefore, when the driving force transmitted from the coupling device20to the damper device40is small, the housing spline34contacts the first damper spline45and the driving force is mainly transmitted from the housing27to the outer circumferential member43via the inner circumferential member42and the elastic member41. On the other hand, when the driving force transmitted from the coupling device20to the damper device40is large, the elastic member41is twisted and the housing spline34contacts the second damper spline50, and thus, the driving force is mainly transmitted from the housing27directly to the outer circumferential member43(second coupling part49).

Note that although the damper device40of this embodiment has the elastic member41, it may adopt a dynamic damper or a centrifugal pendulum damper instead of the elastic member41. Further, although the elastic member41of this embodiment is made of rubber, it may be a spring.

The drive member60has a cylindrical base part61located in its inner circumferential part, and a drive part62located in its outer circumferential part and integrally formed with the base part61. A first drive bearing63is provided between a front portion of the base part61and the transfer case80, and a second drive bearing64is provided between a rear portion of the base part61and the transfer case80. In other words, the drive member60is rotatably supported by the transfer case80via the first and second drive bearings63and64.

Moreover, a rear inner-circumferential portion of the base part61is formed with a drive inner spline65to be coupled to the damper outer spline51. Therefore, the drive member60rotates as the outer circumferential member43of the damper device40rotates, and the driving force is transmitted from the damper device40to the drive member60.

Note that the first and second drive bearings63and64are rolling bearings capable of bearing both a radial load (load applied in the radial directions) and a thrust load (load applied in the axial directions). Here, regarding the first drive bearing63, a straight line joining a contact point between a ball and an outer ring and a contact point between the ball and an inner ring, and extending toward the center of rotation (hereinafter, referred to as “contact line”; indicated by the dashed line inFIG. 4), is inclined rearward with respect to the radial directions (directions perpendicular to the rotation axis). On the other hand, a contact line of the second drive bearing64is inclined forward with respect to the radial directions. Note that in terms of dynamics, it can be considered that a bearing supports a rotary body at a point where the rotation axis of the rotary body and the contact line intersect (hereinafter referred to as “supporting point”).

Further, the drive part62drives a driven part71(described later) and transmits the driving force to the driven part71. The drive part62of this embodiment is a so-called helical gear. Therefore, when transmitting the driving force to the driven part71, the drive part62receives from the driven part71a reaction force including, not only a component in directions perpendicular to the axial directions, but also a component in the axial directions. Note that as described above, in this embodiment, by disposing the first drive bearing63and the second drive bearing64such that the contact lines thereof approach each other, the bearings63and64stably support the drive part62.

The output shaft70is a shaft member disposed parallel to the input shaft10and outputs a portion of the driving force inputted to the input shaft10, to the front wheels via the constant-velocity joint90. As illustrated inFIG. 5, the output shaft70has the driven part71, an output-shaft large-diameter part72, an output-shaft small-diameter part73, and a protruding part74.

The driven part71is coupled to the drive part62and driven by the drive part62. The driven part71of this embodiment is a so-called helical gear. Therefore, the driven part71receives from the drive part62a reaction force including a component in the axial directions and a component in directions perpendicular to the axial directions.

The output-shaft large-diameter part72is located in a front part of the output shaft70and the driven part71is located radially outward of the front part. Further, the output-shaft large-diameter part72is formed with a recessed opening portion75opening forward. That is, the recessed opening portion75is located radially inward of the driven part71. Moreover, a first output bearing76is provided inward of the recessed opening portion75to rotatably support the output shaft70. This first output bearing76is a rolling bearing capable of bearing both a radial load and a thrust load. The first output bearing76is located inside the recessed opening portion75. An outer circumferential part (outer ring) of the first output bearing76is fixed to an inner circumferential surface of the recessed opening portion75, and an inner circumferential part (inner ring) of the first output bearing76is fixed to an outer circumferential surface of the transfer case80(an intruding part83). A contact line of the first output bearing76is inclined to forward with respect to radial directions.

The output-shaft small-diameter part73is a cylindrical part located rearward of the output shaft70. A second output bearing77is provided between an outer circumferential surface of the output-shaft small-diameter part73and the transfer case80. This second output bearing77is a rolling bearing capable of bearing both a radial load and a thrust load. A contact line of the second output bearing77is inclined to forward with respect to the radial directions. Further, a cap member78is attached to an inner side of a rear portion of the output-shaft small-diameter part73.

The protruding part74is a cylindrical part protruding forward from a position inside the recessed opening portion75and radially inward of the first output bearing76. An output shaft seal79is provided between the protruding part74and the transfer case80to seal a gap between the transfer case80(intruding part83) and the output shaft70(protruding part74). As illustrated inFIG. 5, in this embodiment, the drive part62, the driven part71, the first output bearing76, and the output shaft seal79are located at the same position in the axial directions (front-and-rear-directions) and arranged in a substantially straight line in a cross-sectional view.

The transfer case80forms a contour of the transfer device100and accommodates the input shaft10, the output shaft70, etc. As illustrated inFIG. 4, space inside the transfer case80is divided, for example at the inner seal52as a boundary, into a first accommodation space81accommodating the coupling device20, the damper device40, etc., and a second accommodation space82accommodating the drive member60, the output shaft70, etc. Oil is injected into the second accommodation space82.

As illustrated inFIG. 5, the transfer case80has the intruding part83having an annular shape and intruding into the recessed opening portion75. The intruding part83also has a conical shape so that an inner diameter thereof decreases as it extends rearwardly, and increases as it extends forwardly. The intruding part83extends from a position forward of the output shaft70into the recessed opening portion75through a gap between the recessed opening portion75and the constant-velocity joint90, and a rear end portion of the intruding part83is located inside the recessed opening portion75.

The constant-velocity joint90connects the output shaft70with the front propeller shaft107(seeFIG. 1) and rotates the front propeller shaft107, which is inclined with respect to the output shaft70, at the same speed as the output shaft70. The constant-velocity joint90of this embodiment is a so-called Rzeppa constant-velocity joint, and includes an outer joint member91, an inner joint member93, and a plurality of torque transmission balls95located between the outer joint member91and the inner joint member93. Further, a joint input shaft92is fixed to the outer joint member91, and a joint output shaft94is fixed to the inner joint member93.

The joint input shaft92is spline-fitted to the inner side of the output-shaft small-diameter part73. When the joint input shaft92and the outer joint member91are rotationally driven by the output shaft70, the driving force is also transmitted to the inner joint member93and the joint output shaft94via the torque transmission balls95and the inner joint member93and the joint output shaft94also rotate. Here, the joint output shaft94rotates in a state where it is inclined with respect to the joint input shaft92. Note that a tip end part of the joint output shaft94is connected to the front propeller shaft107.

The outer joint member91of the constant-velocity joint90is located radially inward of the intruding part83, and a part of the outer joint member91is located inside the recessed opening portion75. A rear part of the outer joint member91has a shape corresponding to the inner circumferential surface of the intruding part83, and a labyrinth gap is formed between the outer joint member91and the intruding part83. By forming this labyrinth gap, entrance of foreign matters into the transfer case80through the space between the outer joint member91and the intruding part83is prevented.

A lubricant such as grease is sealed inside the constant-velocity joint90. Further, a boot96and a boot connecting member97are provided between the outer joint member91and the joint output shaft94to prevent the lubricant from leaking outside. The boot96is fixed to an outer circumferential surface of the joint output shaft94at one end and fixed to a front end part of the boot connecting member97at the other end. Further, the front end part of the boot connecting member97is fixed to the boot96, and a rear end part thereof is fixed to the outer joint member91.

In the above embodiment, the constant-velocity joint90is disposed inside the recessed opening portion75formed in the output shaft70, so that the constant-velocity joint90is located as rear as possible. Therefore, a distance between the output shaft70and the front differential gear108increases, an inclination angle (operation angle) of the front propeller shaft107with respect to the output shaft70decreases. As a result, an upper limit value of the rotational speed of the constant-velocity joint90may be set to be high.

Further, in this embodiment, the intruding part83of the transfer case80passes between the recessed opening portion75and the constant-velocity joint90, and the first output bearing76and the output shaft seal79are located inside the recessed opening portion75. Thus, the constant-velocity joint90is not surrounded (covered) by the output shaft70or the intruding part83. As a result, the constant-velocity joint easily comes into contact with outside air, and heat generated by the constant-velocity joint is easily released to the outside.

Further, in this embodiment, the intruding part83is formed so that its inner diameter increases as it extends forwardly. Thus, the opening area of the front portion of the intruding part83becomes large. Therefore, the constant-velocity joint90more easily comes into contact with the outside air, and the heat generated by the constant-velocity joint90is more easily released to the outside.

Further, in terms of the structure, the part corresponding to the driven part71of the output shaft70(output-shaft large-diameter part72) tends to have a large outer diameter. Therefore, in this embodiment, by disposing the recessed opening portion75radially inward of the driven part71, the radially inner portion of the driven part71of the output shaft70is effectively utilized.

Further, in this embodiment, out of the bearings76and77supporting the driven part71, the first output bearing76which is located relatively forward has the contact line inclined forward with respect to the direction perpendicular to the rotation axis. Thus, a supporting point of the first output bearing76is located forward of the driven part71. This structure allows the driven part71to be located between the supporting point of the first output bearing76and a supporting point of the second output bearing77in the axial directions. Therefore, in spite that the first output bearing76is located radially inward of the driven part71(at the same position in the axial directions as the driven part71), the driven part71which receives the force in the radial directions (directions perpendicular to the axis) from the drive part62is supported at both sides in the axial directions.

Note that even if the supporting point of the first output bearing76cannot be located forward of the driven part71, the supporting point of the first output bearing76may still be located near the driven part71. Although in this case the driven part71is supported in a cantilevered state, since the supporting point of the first output bearing76is located near the driven part71, the load on the first output bearing76in the radial directions is reduced.

In the above embodiment, the drive part62connected to the input shaft10and the driven part71connected to the output shaft70are both helical gears and mesh with each other. Thus, the drive part62drives the driven part71. Note that the drive part62and the driven part71are not limited to such a structure. For example, the drive part62may be a drive sprocket and the driven part71may be a driven sprocket, which may be coupled by a chain. Also in this case, the drive part62still drives the driven part71.

Although the above embodiment is directed to a four-wheel drive vehicle of a front-engine, rear-wheel drive base, the present disclosure is obviously applicable to a four-wheel drive vehicle of a rear-engine, front-wheel drive base. It is needless to say that the present disclosure may adopt a motor as the drive source instead of the engine (for application to an electric automobile) and also be applicable to a hybrid vehicle using an engine and a motor in combination.

DESCRIPTION OF REFERENCE CHARACTERS