Differential case for vehicle and differential device for vehicle including differential case

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Applications No. 2007-068733, filed on Mar. 16, 2007, 2008-063248, filed on Mar. 12, 2008 and 2008-063250 filed on Mar. 12, 2008. The content of the application is incorporated herein by reference in their entirety.

1. Field of the Invention

The present invention relates to a differential case for a vehicle and a differential devise for a vehicle including the differential case, and more particularly relates to the differential case for the vehicle and the differential devise for the vehicle having a pinion gear supporting portion supporting slidably a pinion gear which is a shaft-less type.

2. Description of the Prior Art

It is well known for a prior differential device for a vehicle to provide a pair of shaft-less pinion gears as disclosed in a published patent document; Tokkai 2006-46642.

This differential device for the vehicle comprises a differential case rotated by torque from an engine, a pair of pinion gears, a pair of side gears engaging in mesh with the pair of pinion gears in a state that an axis of the pinion gears is perpendicular to that of side gears, a pair of thrust washer receiving thrust force from the pair of side gears.

The pair of pinion gears has a gear peripheral portion as a supported portion over all around periphery and a gear engaging portion engaging in mesh with the pair of side gears and the pair of pinion gears are disposed in the differential case on an axis perpendicular to a rotational axis of the differential case.

The differential case is equipped with a pair of wheel shaft inserted holes. The differential case is also equipped with a pinion gear inserted hole having first pinion gear supporting surface to support slidably, that is rotatably, peripheral surfaces of a pair of pinion gears. On a peripheral edge of an inner opening of the pinion gear inserted hole is formed a second pinion gear supporting surface supporting slidably a part of the gear engaging portion of the pinion gear.

The pair of side gears is constructed with an annular bevel gear having a large diameter than that of the pinion gears and is installed on a rotational axis of the differential case. An inside surface of the pair of side gears is connected with right and left tire shafts in a spline engagement.

A pair of thrust washers is installed between back surfaces of the pair of side gears and an annular inner opening edged of a pair of the wheel shaft inserted holes. It can be adjusted a degree of intermeshing engagement of the pair of side gears with the pair of pinion gears by the thrust washers.

Based on the above-mentioned construction of the prior art, when torque from an engine is input into the differential case through a driving pinion and a ring gear, the differential case is rotated around the rotational axis. At the rotation of the differential case, the rotational force is transmitted to the pair of pinion gears and the pair of side gears through the pair of pinion gears. Therefore, the torque is distributed and transmitted differentially to right and left tire shafts through the drive pinion, the ring gear, the differential case, the pair of pinion gears and the pair of side gears according to a running condition of the vehicle since the pair of side gears engages with right and left tire shafts in the spline engagement.

In running of the vehicle, the pinion gears slide on the first pinion gear supporting surface and the second pinion gear supporting surface upon the rotation of the pinion gears, frictional resistance is occurred between the first pinion gear supporting surface and the pinion gears and also between the second pinion gear supporting surface and the pinion gears to restrict the differential rotation of the side gears.

And also in this time, another thrust force of an intermeshing surface of the pinion gears with the side gears, therefore, this thrust force acts the pair of side gears to be moved to separated directions each other. In this result, there occurs another frictional resistance between the thrust washers and the thrust washer receiving portions to restrict the differential rotation of the side gears also.

However, in the differential device for the vehicle of the published patent document of Tokkai 2006-46642 as the prior art, since an extending portion is formed on the annular inner opening edge of the pinion gear inserted holes and a free edge of the extending portion is not fixed, a bending stiffness of the extending portion is poor by receiving the load from the side gears through the pinion gears. As a result, it is easy to deform the extending portion to change and move an intermeshing position between the pinion gears and the side gears so that it restricts stable differential restriction force upon occurrence of excessive torque.

In view of the previously mentioned circumstances, it is an object of the present invention to provide a differential case for a vehicle and a differential device for a vehicle restricting change and movement of an intermeshing of a pair of side gears and a pair of pinion gears to achieve stable differential restriction force.

It is another object of the present invention to provide a differential case for a vehicle and a differential device for a vehicle maintaining the stable intermeshing point between a pair of side gears and a pair of pinion gears to achieve stable differential restriction force.

In order to achieve the above and other objects, one aspect of the present invention provides a differential case for a vehicle or a differential device therefor to have mainly a pinion gear supporter having a pinion gear supporting portion to install a pinion gear in a recess space of the pinion gear supporter and to support slidably an outer peripheral surface of the pinion gear for rotation of the pinion gear. Thereby, the pinion gear is supported by rigid pinion gear supporting portion of the pinion gear supporter without supporting by any extending portion having the non-rigid free edge, as explained by the prior art, to achieve stable intermeshing of the side gear and the pinion gear, thereby to make stable differential restriction force.

Second aspect of the present invention provides a differential case for a vehicle or a differential device for a vehicle with the pinion gear supporter having a pair of said pinion gear supporting portions, and a reinforced connecting portion connecting the pair of pinion gear supporting portions each other. Thereby, load acted on the pair of pinion gear supporting portions from a pair of side gears through a pair of pinion gears is received by the reinforced connecting portion so that bending intensity of the pinion gear supporter is increased to achieve stable intermeshing of the pair of side gears and the pair of pinion gears, thereby to make stable differential restriction force.

Third aspect of the present invention provides a differential case for a vehicle or a differential device for a vehicle having mainly the pair of pinion gear supporting portions having respectively first pinion gear supporting portion and second pinion gear supporting portion, the first pinion gear supporting portion supports rotatably the outer peripheral surface of an end portion in a side of a gear base of both ends of the pinion gear along its axial direction, and the second pinion gear supporting portion supports rotatably said outer peripheral surface of an end portion in a side of a gear nose of both ends of the pinion gear along its axial direction. Thereby, the pinion gear is supported at two points in the side of the gear base and the gear nose so that any inclination of the pinion gear is restricted to achieve stable intermeshing of the pair of side gears and the pair of pinion gears, thereby to make stable differential restriction force.

Fourth aspect of the present invention provides a differential case for a vehicle or a differential device for a vehicle having mainly the pinion gear supporter to be movable along the rotational axis of the differential case. Thereby, during the rotation of the differential case, the pinion gear supporter moves by itself in the direction of the rotational axis of the differential case to be positioned at the place where the pinion gears equally engage in mesh with the right side gear and the left side gear to maintain stable intermeshing of the pair of side gears and the pair of pinion gears to achieve stable differential restriction force.

Fifth aspect of the present invention provides a differential device for a vehicle with the pair of pinion gears having respectively a first sliding portion to be slid on the pair of pinion gear supporting portions at an opposite side to the rotational axis side of the differential case of both sides of the pinion gear supporting portion along axial direction of the pinion gear supporting portions, a second sliding portion to slide on said pair of pinion gear supporting portions at a side of rotational axis of said differential case of both sides of the pinion gear supporting portion along axial direction of said pinion gear supporting portions. Thereby, the pinion gears are respectively supported by two points of first sliding portion in the opposite side to the rotational axis and the side of the rotational axis so that any inclination of the pinion gear is restricted to achieve stable intermeshing of the pair of side gears and the pair of pinion gears, thereby to make stable differential restriction force

Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which:

FIG. 1 is a divided oblique perspective diagram explaining a differential device for a vehicle according to first embodiment of the present invention;

FIG. 2 is an assembled oblique perspective diagram explaining a differential device for a vehicle according to first embodiment of the present invention;

FIG. 3 is a partially cut oblique perspective diagram explaining a differential device for a vehicle according to first embodiment of the present invention;

FIG. 4 is a horizontally sectional drawing explaining a differential device for a vehicle according to first embodiment of the present invention;

FIG. 5 is a horizontally cut sectional drawing in parallel to a rotational axis explaining a differential device for a vehicle according to first embodiment of the present invention;

FIG. 6 is a cross sectional drawing cut in perpendicular to a rotational axis of a differential case of a differential device for a vehicle according to first embodiment of the present invention;

FIG. 7 is sectional diagram showing an operation of a differential device for a vehicle according to first embodiment of the present invention;

FIG. 8 is a cross sectional drawing cut in perpendicular to a rotational axis of a differential case of a differential device for a vehicle according to second embodiment of the present invention;

FIG. 9 is a horizontally cut sectional drawing in parallel to a rotational axis explaining a differential device for a vehicle according to third embodiment of the present invention;

FIG. 10 is a cross sectional drawing cut along a line of A-A in FIG. 9 ;

FIG. 11 is sectional diagram showing an operation of a differential device for a vehicle according to third embodiment of the present invention;

FIG. 12 is a divided oblique perspective diagram explaining an accommodating state of the pinion gear supporter in a differential case of another embodiment of the present invention.

First Embodiment of the Present Invention

[Whole Construction of the Differential Device for the Vehicle]

In FIGS. 1 to 3 , a numeral 1 shows the differential device for the vehicle according to the first embodiment of the present invention. The differential device 1 mainly constitutes of a differential case 2 , two pinion gears 3 , 4 and two side gears 5 R, 5 L. The differential case 2 is rotated by receiving a torque from an engine. The pinion gears 3 , 4 are aligned in parallel each other along a perpendicular line to a rotational axis O of the differential case 2 . The pinion gears 3 , 4 intermesh with the side gears 5 R, 5 L.

[Construction of the Differential Case 2 ]

As shown in FIGS. 1-3 and 6 , the differential case 2 provides a case body 50 , thrust washers 51 , 52 and a pinion gear supporter 53 , and the differential case 2 is constructed as a hollow construction driven around the rotational axis O. The case body 50 accommodates therein the pinion gears 3 , 4 and the side gears 5 R, 5 L. The thrust washers 51 , 52 close respectively a portion of pinion gear inserted holes 10 , 11 , described latter, of the case body 50 . The pinion gear supporter 53 supports rotatably both of the pinion gears 3 , 4 .

In the case body 50 , as shown in FIG. 1 and FIG. 5 , there are formed two right and left wheel shaft inserted holes 9 R, 9 L and a pair of pinion gear inserted holes 10 , 11 . The wheel shaft inserted holes 9 R, 9 L are opened along the rotational axis O. The pinion gear inserted holes 10 , 11 are opened to a perpendicular direction to axes of the wheel shaft inserted holes 9 R, 9 L aligning with the rotational axis O. And also in the case body 50 , there are installed a pair of side gear penetrating openings 12 R, 12 L positioned in equal distance respectively from the pinion gear inserted holes 10 , 11 along a peripheral direction as shown in FIG. 1 and positioned in a right side and a left side of the pinion gear supporter 53 along the rotational axis O as shown in FIG. 2 . In the case body 50 is formed, as a whole body, an annular ring gear mounting flange 13 positioned along the peripheral direction in the plane perpendicular to the rotational axis O as shown in FIGS. 1 to 6 .

The wheel shaft inserted holes 9 R, 9 L are constructed as a penetrating hole being approximately circle to have almost same diameter. Unillustrated right and left wheel shafts are inserted into the wheel shaft inserted holes 9 R, 9 L. On peripheral annular ends of the wheel shaft inserted holes 9 L, 9 R are mounted thrust washer receiving portions 9 Ra, 9 La receiving the thrust washers 6 L, 6 R and being spherical.

The pinion gear inserted holes 10 , 11 have concave portions 10 A, 11 A being fit by a portion of peripheral ends of the thrust washers 51 , 52 on internal surface of the opening of the pinion gear inserted holes 10 , 11 as shown in FIG. 1 and FIG. 5 . The pinion gear inserted holes 10 , 11 are constructed as a penetrating hole penetrating between outer and inner areas of the case body 50 in order to achieve a function to insert the pinion gears 3 , 4 from the outer area into inner area of the case body 50 . For this purpose, each size of inner diameter of the pinion gear inserted holes 10 , 11 is larger than each of outer diameters of the pinion gears 3 , 4 .

The side gear penetrating openings 12 R, 12 L are constructed as a penetrating hole having an opening being non-circular in a cross section as shown in FIG. 1 and FIG. 6 . A size of the opening is set to be able to be inserted the side gears 5 R, 5 L into the differential case 2 .

The thrust washers 51 , 52 have pinion gear receiving portions 51 A, 52 A and convex portions 51 B, 52 B, and are positioned in back side of the pinion gears 3 , 4 as shown in FIG. 1 and FIG. 3 . The pinion gear receiving portions 51 A, 52 A are constructed respectively by spherical surfaces fitting to a sliding surface of the back surface of the pinion gears 3 , 4 . The convex portions 51 B, 52 B are rotatably supported by the concave portions 10 A, 11 A of the pinion gear inserted holes 10 , 11 . And the thrust washers 51 , 52 are fixed to be positioned along an axial direction of the pinion gear inserted holes 10 , 11 by fitting the convex portions 51 B, 52 B into the concave portions 10 A, 11 A and around the axis of the pinion gear inserted holes 10 , 11 by a stopper pin 54 , 55 . And the pinion gear receiving portions 511 A, 52 A are constructed to support slidably the pinion gears 3 , 4 .

The pinion gear supporter 53 has pinion gear supporting portions 56 , 57 accommodating the pinion gears 3 , 4 in recess spaces 60 , 61 to be concave in a cross section in order to support rotatably the pinion gears 3 , 4 , as shown in FIG. 1 and FIG. 6 . Upper and lower ends of the pinion gear supporter 53 are mounted as a whole to be approximately coincided with the inner ends of the openings of the pinion gear inserted holes 10 , 11 . The whole construction of the pinion gear supporter 53 is liked as a letter X.

The pinion gear supporting portions 56 , 57 have first pinion gear supporting portions 56 A, 57 A and second pinion gear supporting portions 56 B, 57 B and are mounted to be a whole body each other through a reinforced connecting portion 58 positioned on the rotational axis O of the differential case 2 , as shown in FIG. 1 and FIG. 6 . The first pinion gear supporting portions 56 A, 57 A rotatably support each of first sliding portions and a part of gear intermeshing portions of the pinion gears 3 , 4 which are outer ends of both ends of each pinion gears 3 , 4 in its axial direction located in a side of pinion gear inserted hole, that is a side of a gear base. The second pinion gear supporting portions 56 B, 57 B rotatably support each of second sliding portions of the pinion gears 3 , 4 which are inner ends of both ends of each pinion gears 3 , 4 in its axial direction located in the opposite side of pinion gear inserted hole, that is a side of a gear nose.

The first pinion gear supporting portions 56 A, 57 A are respectively disposed at a plurality of positions, two positions in this embodiment, in a peripheral side of the pinion gears 3 , 4 around the axial direction of the pinion gear inserted holes 10 , 11 in equal distance each other, as shown in FIG. 1 . On the first pinion gear supporting portions 56 A, 57 A are equipped with first pinion gear supporting surfaces 56 a , 57 a being a curvature surface having a curvature of a predetermined radius as shown in FIGS. 1 , 5 , 6 .

The second pinion gear supporting portions 56 B, 57 B are respectively disposed in a side of rotational axis O of the pinion gear supporting portions 56 57 at a plurality of positions, two positions in this embodiment, around the axial direction of the pinion gear inserted hole 10 , 11 in equal distance each other, as shown in FIG. 1 . The second pinion gear supporting portions 56 B, 57 B are respectively mounted as a whole body through the reinforced portions 56 C, 57 C at the side of the rotational axis O of the differential case 2 as shown in FIG. 6 . Since the reinforced portions 56 C, 57 C achieve a function of a horizontal beam to support a load acted on the pinion gear supporting portions 56 , 57 of the pinion gear supporter 53 through the pinion gears 3 , 4 from the side gears 5 R, 5 L, the pinion gear supporter 53 having the letter X construction is increased its rigidity of bending intensity. On the second pinion gear supporting portions 56 B, 57 B are equipped with second pinion gear supporting surfaces 56 b , 57 b being a curvature surface having a curvature of a predetermined radius, which is smaller than the radius of the curvature of the first pinion gear supporting portions 56 a , 57 a , as shown in FIGS. 1 , 5 , 6 .

A width along the rotational axis O of the right and left sides of the pinion gear supporter 53 perpendicular to the rotational axis O in FIG. 6 is enough smaller than that of middle portion of the pinion gear supporter 53 as shown in FIGS. 2 , 3 in order to allow insertions of the side gears 5 R, 5 L through the side gear penetrating holes 12 R, 12 L. This small width of the right and left sides of the pinion gear supporter 53 and the letter X construction of the pinion gear supporter make a total weight of the pinion gear supporter 53 relatively small. Besides, the width of the reinforced portion 56 C, 57 C along the rotational axis O is enough length to be reinforced as shown in FIG. 1 .

[Construction of the Pinion Gears 3 , 4 ]

The pinion gears 3 , 4 are, as shown in FIGS. 5 , 6 , a shaft-less cylindrical gears including first sliding portions 3 A, 4 A, second sliding portions 3 B, 4 B and gear intermeshing portions 3 C, 4 C. The pinion gears 3 , 4 are rotatably supported by the first pinion gear supporting surfaces 56 a , 57 a and the second pinion gear supporting surfaces 56 b , 57 b of the pinion gear supporter 53 without being supported by any shaft, that is the shaft-less construction. The first sliding portions 3 A, 4 A including a part of the gear intermeshing portion are slid on the pinion gear supporter 53 , based on the rotation of the pinion gears 3 , 4 , in the side of the gear base of the pinion gear inserted hole, which is the opposite side to the rotational axis O of the differential case 2 of both sides of the pinion gear supporter 53 . A gear tooth is formed on the gear intermeshing portion. The second sliding portions 3 B, 4 B are slid, based on the rotation of the pinion gears 3 , 4 , in the side of the rotational axis O of both sides of the pinion gear supporter 53 in the axis direction. The gear intermeshing portions 3 C, 4 C engage in mesh with the side gears 5 R, 5 L between the first sliding portions 3 A, 4 A and the second sliding portions 3 B, 4 B. The pinion gears 3 , 4 are disposed on an axis perpendicular to the rotational axis O of the differential case 2 .

It is defined that the side of the gear nose is the side of the rotational axis O selected from the group of both sides of the pinion gear supporter 53 in its axis and the side of the gear base is the opposite side to the rotational axis O selected from the group of both sides of the pinion gear supporter 53 in its axis.

The first sliding portions 3 A, 4 A have annular main sliding portions 30 A, 40 A and assistance sliding portions 31 A, 41 A as shown in FIG. 6 . The main sliding portions 30 A, 40 A have a function as a supported portion to be supported all peripheral portions on the outer surface of the pinion gears 3 , 4 around its axis. The assistance sliding portions 31 A, 41 A have a function as a supported portion to be supported a part of peripheral portions on the outer surface of the pinion gears 3 , 4 around its axis and the part is a part of the gear intermeshing portions 3 C, 4 C formed the gear tooth. The first sliding portions 3 A, 4 A are placed in the side of the gear base of both ends of each pinion gears 3 , 4 in its axial direction located in a side of the pinion gear inserted hole, and are rotatably supported by the first pinion gear supporting surfaces 56 a , 57 a of the first pinion gear supporting portions 56 A, 57 A. On a back surface of the main sliding portions 30 A, 40 A of the first sliding portions 3 A, 4 A are equipped with third sliding portions 3 D, 4 D formed by a spherical surface fitting to the pinion gear receiving portions 51 A, 52 A of the thrust washers 51 , 52 .

The second sliding portions 3 B, 4 B are a cylindrical body having a function as a supported portion at all portions around the axis of the pinion gears 3 , 4 as shown in FIGS. 5 , 6 . The second sliding portions 3 B, 4 B are placed in the side of the gear nose of both ends of each pinion gears 3 , 4 in its axial direction, and are rotatably supported by the second pinion gear supporting surfaces 56 b , 57 b of the second pinion gear supporting portions 56 B, 57 B. Each of outer diameters of the second sliding portions 3 B, 4 B is set to be smaller than that of the first sliding portions 3 A, 4 A.

The gear intermeshing portions 3 C, 4 C comprise a straight portion Cs including the assistance sliding portions 31 A, 41 A of the pinion gears 3 , 4 and a taper portion Ct continuing from the straight portion Cs as shown in FIG. 6 , and it is engaged in mesh with the side gears 5 R, 5 L in a side of the rotational axis O of the differential case 2 .

[Construction of the Side Gears 5 R, 5 L]

As shown in FIG. 5 , the side gears 5 R, 5 L are almost ring gears having boss portions 5 Ra, 5 La and gear portions 5 Rb, 5 Lb, each diameter of which is different each other. An outer diameter of the side gears 5 R, 5 L is larger than the outer diameter of the pinion gears 3 , 4 and the side gears 5 L, 5 R are a bevel gear having a single conical angle. The side gears 5 R, 5 L are rotatably supported in the differential case 2 to engage in mesh with the pinion gears 3 , 4 . A number of teeth of the side gears 5 R, 5 L is more than 2.1 times as many numbers as that of teeth of the pinion gears 3 , 4 , for example, the number of teeth of the side gears 5 R, 5 L is 15, compared that the number of teeth of the pinion gears 3 , 4 is 7. The outer diameter of the side gears 5 R, 5 L is set to be larger than the outer diameter of the pinion gears 3 , 4 .

On a back face of the side gears 5 R, 5 L are provided sliding portions 5 Rc, 5 Lc being a spherical surface to fit to the thrust washer receiving portions 9 Ra, 9 La through the thrust washers 6 R, 6 L. Each wheel shaft is individually inserted into the wheel shaft inserted holes 9 R, 9 L in spline meshing.

[Operation of the Differential Device 1 for the Vehicle]

The operation of the differential device for the vehicle of the first embodiment of the present invention will be explained hereinafter. First of all, when torque from the engine of the vehicle is input to the differential case 2 through the drive pinion and the ring gear, the differential case 2 is rotated around the rotating axis O. Upon the rotation of the differential case 2 , rotational force is transferred to the pinion gears 3 , 4 and to the side gears 5 R, 5 L through the pinion gears 3 , 4 . Because the right and left side gears 5 R, 5 L are respectively engaged with the unillustrated wheel shafts in spline meshing, torque from the engine is transmitted to the right and left wheel shafts through the drive pinion, the ring gear, the differential case 2 , the pinion gears 3 , 4 and the side gears 5 L, 5 R.

Where the vehicle is driven in straight line and there is no slip between the road and each tire on the right and left wheel shafts, the pinion gears 3 , 4 is revolved on the side gears 5 R, 5 L without self-rotation around the rotational axis O and the pinion gears 3 , 4 and the side gears 5 R, 5 L are rotated as a body with the differential case 2 so that torque from the engine is transmitted equally to right and left wheel shafts to rotate each tire at same rotational speed.

Where the right wheel drops into a muddy ground to occur a slip, the pinion gears 3 , 4 are rotated around its own axis with intermeshing with the side gears 5 R, 5 L so that torque from the engine is distributed differently to the right and left tires. In actual, the left tire is rotated at lower speed than the speed of the differential case 2 and the right tire is rotated at higher speed than the speed of the differential case 2 .

Where the pinion gears 3 , 4 are rotated around its own axis during torque is actuated to the differential case 2 , the first sliding portions 3 A, 4 A and the second sliding portions 3 B, 4 B are slid on the first pinion gear supporting portions 56 a , 57 a and the second pinion gear supporting portions 56 b , 57 b so that frictional resistance occurs between the first sliding portion 3 A, 4 A and the first pinion gear supporting surface 56 a , 57 a and between the second sliding portion 3 B, 4 B and the second pinion gear supporting surface 56 b , 57 b . Therefore, the differential rotation of the side gears 5 R, 5 L is restricted by the frictional resistance. In this situation, as shown in FIG. 7 , where load L acts on the pinion gears 3 , 4 from the side gears 5 R, 5 L based on the intermeshing between the side gears 5 R, 5 L and the pinion gears 3 , 4 , reaction force F 1 , F 2 from the first pinion gear supporting surfaces 56 a , 57 a and the second pinion gear supporting surfaces 56 b , 57 b of the pinion gear supporter 53 act in dispersing on the first sliding portions 3 A, 4 A and the second sliding portions 3 B, 4 B so that the pinion gears 3 , 4 rotates in stable state on the pinion gear supporter 53 .

In this state, where P is an intermeshing point between the side gears 5 R, 5 L and the pinion gears 3 , 4 and h 1 , h 2 are distances in axial direction from the engaging point P to acting points a, b of the reaction forces F 1 , F 2 , the reaction forces F 1 , F 2 are represented by the equation of “F 1 =L×h 2 /(h 1 +h 2 )” and “F 2 =L×h 1 /(h 1 +h 2 )”. Where R 1 is a radius of the first sliding portions 3 A, 4 A of the pinion gears 3 , 4 , R 2 is a distance from the axis H of the pinion gears 3 , 4 to the intermeshing point P and R 3 is a radius of the second sliding portions 3 B, 4 B of the pinion gears 3 , 4 , a torque transmitting ratio T 1 transmitted the torque from the pinion gears 3 , 4 to the side gears 5 R, 5 L by the reaction force F 1 is represented by the equation of “T 1 =R 1 /R 2 ” and a torque transmitting ratio T 2 transmitted the torque from the pinion gears 3 , 4 to the side gears 5 R, 5 L by the reaction force F 2 is represented by the equation of “T 2 =R 3 /R 2 ”.

By this rotation of the pinion gears 3 , 4 , thrust force is occurred on the intermeshing surface with the side gears 5 R, 5 L to its rotational axis direction of each of the pinion gears 3 , 4 and the side gears 5 R, 5 L. Each of the side gears 5 R, 5 L is moved to be separated each other by the thrust force to push the thrust washers 6 R, 6 L in contact with the thrust washer receiving portions 9 Ra, 9 La so that frictional resistance is occurred between the thrust washers 6 R, 6 L and the thrust washer receiving portions 9 Ra, 9 La. Therefore, the differential rotation of the side gears 5 R, 5 L is also restricted by this second frictional resistance.

And also, the third sliding portions 3 D, 4 D of the pinion gears 3 , 4 are pushed in contact with the pinion gear receiving portions 51 A, 52 A of the thrust washer 51 , 52 by the thrust resistance occurred on the pinion gears 3 , 4 so that frictional resistance is occurred against the rotation of the pinion gears 3 , 4 around its own axis. Therefore, the differential rotation of the side gears 5 R, 5 L is also restricted by this third frictional resistance.

Next, an assembling method of the differential device for the vehicle according to the first embodiment of the present invention will be explained hereinafter. The assembling method of the differential device for the vehicle according to the first embodiment is performed in order of each step of “assemble of side gear”, “assemble of pinion gear”, “attachment of the thrust washer” and “engagement of pinion gear and side gear” so that each step will be explained in order.

“Assemble of Side Gear”

Each of side gears 5 R, 5 L is inserted into the differential case 2 through the side gear penetrating openings 12 R, 12 L from outside, thereafter, sliding from the different direction each other along the thrust washer receiving portions 9 Ra, 9 La to coincide each gear axis with the rotational axis O to be accommodated in a predetermined position inside the differential case 2 .

“Assemble of Pinion Gear”

After the pinion gears 3 , 4 are inserted into the differential case 2 through the pinion gear inserted holes 10 , 11 , the pinion gears 3 , 4 are accommodated in the recess spaces 60 , 61 of the pinion gear supporter 53 to support the first sliding portions 3 A, 4 A and the second sliding portions 3 B, 4 B on the first pinion gear supporting portions 56 A, 57 A and the second pinion gear supporting portions 56 B, 57 B to be installed in a predetermined position inside the differential case 2 .

“Attachment of the Thrust Washer”

After the convex portions 51 B, 52 B of the thrust washers 51 , 52 are fit to the concave portions 10 A, 11 A of the pinion gear inserted hole 10 , 11 and the thrust washer 51 , 52 is positioned in the axial direction of the pinion gear inserted holes 10 , 11 , the thrust washers 51 , 52 are rotated by 90 degrees and the stopper pin 54 , 55 fix the thrust washers 51 , 52 around the axis of the pinion gear inserted holes 10 , 11 to be installed in a predetermined position inside the differential case 2 .

“Engagement of Pinion Gear and Side Gear”

The thrust washers 6 R, 6 L are installed between the boss portions 5 Ra, 5 La of the side gears 5 R, 5 L and the thrust washer receiving portions 9 Ra, 9 La of the wheel shaft inserted holes 9 R, 9 L during adjusting the axial size between the thrust washer receiving portions 9 Ra, 9 La and the side gears 5 R, 5 L in order to engage in mesh the side gears 5 R, 5 L with the pinion gears 3 , 4 on the rotational axis O of the differential case 2 .

Second Embodiment of the Present Invention

The second embodiment of the differential device for the vehicle according to the present invention will be explained hereinafter based on FIG. 8 . A numeral in FIG. 8 having the same numeral in FIGS. 1-7 is the same member and function so that these are not explained.

A gist of the differential device 81 for the vehicle of the second embodiment is that the first sliding portions 3 A, 4 A are formed only on the annular portions without having the gear tooth intermeshing with the side gears 5 R, 5 L.

In other words, the peripheral surfaces of the first sliding portions 3 A, 4 A having the gear tooth intermeshing with the side gears 5 R, 5 L do not contact nor slide on the pinion gear supporting portions 56 , 57 , therefore, the pinion gear 3 , 4 have non-sliding portions 310 A, 410 A not sliding on the first pinion gear supporting surfaces 56 a , 57 a of the pinion gear supporting portions 56 , 57 of the pinion gear supporter 53 in a side of the gear nose of the first sliding portions 3 A, 4 A.

Each of outer diameters D 2 of the non-sliding portions 310 A, 410 A is smaller than each of outer diameters D 1 of sliding portions 300 A, 400 A, that is D 1 >D 2 , to make annular spaces 82 , 83 on the first pinion gear supporting surfaces 56 a , 57 a of the pinion gear supporting portions 56 , 57 .

It is desirable for the length of the spaces 82 , 83 to a diameter direction to be set in a way that there is no invasion of contamination by the pinion gears 3 , 4 nor no burning and sticking of contamination on the pinion gear supporting portions 56 , 57 and the pinion gears 3 , 4 .

Third Embodiment of the Present Invention

The third embodiment of the differential device for the vehicle according to the present invention will be explained hereinafter based on FIG. 9 to FIG. 12 . A numeral in FIGS. 9-12 having the same numeral in FIGS. 1-7 is the same member and function so that these are not explained.

A gist of the differential device 91 for the vehicle of the third embodiment is that the pinion gear supporter 53 is movable along the rotational axis O to maintain stable intermeshing between the pinion gears 3 , 4 and the side gears 5 R, 5 L.

The differential case 2 has two elements of first case element 93 and second case element 94 as shown in FIG. 9 . The first case element 93 equips a parts inserting opening 930 opening to one direction along the rotational axis O and side penetrating openings 931 , 931 (as shown in FIG. 10 ) along an axis perpendicular to the rotational axis O. The second case element 93 covers the parts inserting opening 930 of the first case element 92 .

An accommodating space 932 of the first case element 93 communicates with the parts inserting opening 930 , and in the accommodating space 932 are accommodated the side gears 5 R, 5 L and the pinion gear supporter 53 accommodating the pinion gears 3 , 4 .

From an inner surface of the first case element 93 are extended a pair of supporting portions 934 , 935 for the pinion gear supporter 53 into the accommodating space 930 , and the supporting portions 934 , 935 are mounted at equal distance of 180 degrees around the rotational axis O.

The supporting portions 934 , 935 are formed with a projection of letter U shape in a cross section to accommodate the back surface edge portions of the pinion gears 3 , 4 . In the supporting portion 934 is equipped with a pinion gear receiving surface 934 A formed with a spherical surface fitting to the back surface of the pinion gear 3 and in the supporting portion 935 is equipped with a pinion gear receiving surface 935 A formed with a spherical surface fitting to the back surface of the pinion gear 4 . And also, in the supporting portion 934 is equipped with concave portions 934 B, 934 B fitting to upper end portions of the pinion gear supporter 53 along the rotational axis O and in the supporting portion 935 is equipped with concave portions 935 B, 935 B fitting to lower end portions of the pinion gear supporter 53 along the rotational axis O.

The concave portions 934 B, 934 B are extending parallel each other along the rotational axis O and the concave portions 935 B, 935 B are also extending parallel each other along the rotational axis O. The concave portions 934 B, 934 B, 935 B, 935 B are opened to three directions of the sides of the parts inserting opening 930 , pinion gears 3 , 4 and the rotational axis O and closed to three directions including the opposite side of the parts inserting opening 930 .

On the peripheral surface of the first case element 93 in the side of the parts inserting opening 930 is mounted an annular flange 936 projected outside of the differential case 2 in order to assemble the ring gear and the case elements. The flange 936 equips a plurality of penetrating holes 936 A, 936 A and so on positioned at a predetermined equal distance each other. A number of the penetrating holes 936 A is twelve.

On the peripheral surface of the second case element 94 in the side of the parts inserting opening 930 is mounted an annular flange 937 projected outside of the differential case 2 in order to assemble the ring gear and the case elements. The flange 936 equips a plurality of penetrating holes 936 A, 936 A and so on positioned at a predetermined equal distance each other. A number of the penetrating holes 936 A is twelve.

The gear intermeshing portions 3 C, 4 C of the pinion gears 3 , 4 have a straight portion Cs including the assistance sliding portions 31 A, 41 A and a taper portion Ct continuing from the straight portion Cs and engage with the side gears 5 R, 5 L in the side of the rotational axis O. The third sliding portions 3 D, 4 D of the pinion gears 3 , 4 fit to the pinion gear receiving surfaces 934 A, 935 A of the supporting portions 934 , 935 on the back surface of the first sliding portions 3 A, 4 A.

There is not any thrust washer in the side of the side gear 5 R of the side gears 5 R, 5 L but the side gear 5 R has the sliding portion 5 Rc fitting to a side gear supporting portion 933 having a spherical surface to support slidably the back surface of the side gear 5 R.

Right and left upper end portions of the pinion gear supporter 53 fit to the concave portions 934 B, 934 B and right and left lower end portions of the pinion gear supporter 53 fit to the concave portions 935 B, 935 B so that the pinion gear supporter 53 is supported by the supporting portions 934 , 935 to be movable along the rotational axis O and installed non-rotatably in the first case element 93 around the rotational axis O of the differential case 2 .

The operation of the third embodiment different from the first embodiment will be explained hereinafter.

Where the pinion gears 3 , 4 rotate in engagement in mesh with the side gears 5 R, 5 L, the pinion gear supporter 53 moves by itself in the direction of the rotational axis O to be positioned at the place where the pinion gears 3 , 4 equally engage in mesh with the side gear 5 R and the side gear 5 L, that is rotational axes of the pinion gears 3 , 4 are automatically positioned at equal distance from the side gear 5 R and the side gear 5 L because the pinion gear supporter 53 is movable along the rotational axis O so that the stable intermeshing of the pinion gears 3 , 4 with the side gears 5 R, 5 L is automatically maintained to be able to achieve stable differential restriction force.

The assembling method of the third embodiment is quite different from that of the first embodiment and will be explained hereinafter.

The assembling method is performed in order of each step of “assemble of right side gear”, “assemble of pinion gear”, “assemble of left side gear” and “engagement of pinion gear and side gear” so that each step will be explained in order.

“Assemble of Right Side Gear”

The right side gear 5 R is inserted into the first case element 93 from outside of the first case element 93 to contact the boss portion 5 Ra of the back surface portion with the supporting portion 933 and to position the axis of the side gear 5 R to coincide with the axis of the wheel shaft inserted hole 9 R, positioning the side gear 5 R at the predetermined position in the first case element 93 .

“Assemble of Pinion Gear”

First of all, the pinion gears 3 , 4 are accommodated in the recess spaces 60 , 61 of the pinion gear supporter 53 . Next, the pinion gear supporter 53 having the pinion gears 3 , 4 is inserted into the first case element 93 through the parts inserting opening 930 to be placed in predetermined position. During the insertion of the pinion gear supporter 53 , the pinion gear supporter 53 slides along the rotational axis O toward the side gear 5 R from the parts inserting opening 930 by the way that the right and left upper end portions of the pinion gear supporter 53 fit to the concave portions 934 A, 934 A and the right and left lower end portions of the pinion gear supporter 53 fit to the concave portions 935 A, 935 A.

“Assemble of Left Side Gear”

The left side gear 5 L is inserted into the first case element 93 from outside of the first case element 93 to position the axis of the side gear 5 L to coincide with the axis of the wheel shaft inserted hole 9 L, positioning the side gear 5 L at the predetermined position in the first case element 93 .

“Engagement of Pinion Gear and Side Gear”

The thrust washer 6 L is inserted from the parts inserting opening 930 into the differential case 2 to contact with the boss portion 5 La of the side gear 5 L during adjusting the axial size between the thrust washer receiving portions 9 La and the side gear 5 L. Next the second case element 94 is assembled to the first case element 93 by bolts during the thrust washer 6 L is installed between the boss portions 5 La of the side gear 5 L and the thrust washer receiving portions 9 La of the wheel shaft inserted hole 9 L to construct the differential case 2 . As explained in the operation of the third embodiment of the present invention, the pinion gear supporter 53 is moved to the axial direction of the rotational axis O to support the pinion gears 3 , 4 in good engagement with the side gears 5 R, 5 L.

Another Embodiment

While the invention has been described in detail with reference to the preferred embodiment, it will be apparent to those skilled in the art that the invention is not limited to the present embodiment, and that the invention may be realized in various other embodiments within the scope of the claims, for example;

In the first embodiment of the present invention, the assistance sliding portions 31 A, 41 A has been equipped same dimension of its radius in a full range of the sliding portion compared to the main sliding portions 30 A, 40 A of the first sliding portion 3 A, 4 A of the pinion gears 3 , 4 , however, the assistance sliding portions 31 A, 41 A may be equipped a different radius in the full range of the sliding portion or a different radius in a part of the sliding portion.

In each embodiment of the present invention, the pinion gear and its supporting portion has been a pair of pinion gears 3 , 4 and a pair of supporting portions 56 , 57 , however, they may be one pinion gear and one supporting portion, or three and more pinion gears and pinion gear supporting portions by setting smaller diameter of the pinion gears.

In the first and second embodiments of the present invention, the pinion gear supporter 53 has been mounted as a whole body with the inner surface of the case body 50 of the differential case 2 , however, the pinion gear supporter 53 may be separated another material from the differential case 2 as explained in the third embodiment of the present invention.

In the first and second embodiment of the present invention, the assistance sliding portions 31 A, 41 A and the non-sliding portion 310 A, 410 A of the first sliding portions 3 A, 4 A of the pinion gears 3 , 4 has been formed by the straight portion Cs, however, they may be formed by the taper portion Ct.

In the third embodiment of the present invention, the concave portions 934 A, 934 A have fit one side of the right and left sides of pinion gear supporter 53 to the supporting portion 934 and fit another side of the right and left sides of pinion gear supporter 53 to the supporting portion 935 , however, it may be constructed that a convex portion 810 is formed, as shown in FIG. 12 , on ends of both right and left sides of a pinion gear supporter 81 and a concave portion 811 fit to the convex portion 810 is formed on each of supporting portions 934 , 935 of the differential case 2 . Or it may be constructed that a concave portion is formed on the pinion gear supporter and the convex portion fit to the concave portion is formed on the supporting portion of the differential case 2 .