JPH01320352A - Differential gear - Google Patents

Abstract

PURPOSE:To contrive the cost down of a differential gear improved in its durability by setting ratio of a fitting length of a pinion shaft for a differential case to a clearance in a fitting part of these pinion shaft and differential case not more than the specific value. CONSTITUTION:A pinion shaft 10 fits its rear end part to the peripheral wall of a differential case 1, setting a fitting length of the pinion shaft 10 to a value lc. When assumed dc for outside diameter of the pinion shaft 10 and Dc for inside diameter of a fitting hole, a fitting clearance DELTAdc(=Dc-dc) is set. In the other hand, a fitting length of the pinion shaft 10 for its holder 13 is set to a value lh. When assumed dh for outside diameter of the pinion shaft 10 and Dh for inside diameter of a fitting hole, a fitting clearance DELTAdh(=Dh-dh) is set. And ratio is set so as to obtain a relation where (DELTAdc/lc)<=(DELTAdh/lh). Thus preventing a bending load from acting on the point end part of the pinion shaft, durability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a differential gear that absorbs rotational differences, and more particularly to a differential gear that has different axes extending along the rotational axis of a differential case. It is.

2. Description of the Related Art An example of this type of differential cell device is described in Japanese Patent Application No. 62-245311, as shown in FIGS. 3 and 4. The differential device shown in these figures is used as a center differential cell to differentially drive the front and rear wheels of a full-time four-wheel drive vehicle, and a differential case 1 is integrally formed at the tip of a cylindrical shaft 2. The differential case 1 is a hollow member having an open structure, and is arranged concentrically and rotatably inside a ring gear mount case 3 having a two-part structure. The ring gear mount case 3 is rotatably supported by a transfer case 5 by a bearing 4, and a ring gear 6 is attached thereto. Also, inside the differential case 1, a pair of side gears 7 whose rotation centers coincide with the axis of the differential case 1 are arranged facing each other, one of the side gears (the right side gear in FIG. 4).
7 is spline fitted to the ring gear mount tooth 3,
The other side gear 7 is spline-fitted to the outer peripheral surface of a cylindrical shaft portion 8 that is inserted concentrically into the cylindrical shaft 2 . This cylindrical shaft portion 8 is integrated with a differential case of a front differential (not shown), and therefore transmits power from one side gear 7 to the rear wheels, and from the other side gear 7 to the front wheels. It looks like this. Four pinion gears 9 arranged at equal intervals mesh with these side gears 7, and each pinion gear 9 has one end (temporarily referred to as a tip) having a diameter that is approximately the same as the inner diameter of the one side gear 7. The pinion shafts 10 are each rotatably fitted and held by a pinion shaft 10 having a length that does not protrude toward the center of rotation. Each pinion shaft 10 is inserted and fitted into the differential case 1 from the outer periphery, and its rear end engages with a stopper ring 11 fitted to the outer periphery of the differential case 1 to prevent it from coming out. and
Moreover, the stopper ring 11 is prevented from being removed by a snap ring 12. Furthermore, the tip end of each pinion shaft 10 has a smaller diameter than the rear end portion, and the tip end is ground to ensure accuracy, and the base end is shaped as shown in Fig. 5. As shown, a ground clearance groove G is formed, and the diameter of that part is smaller than that of the other part, and the ground end part thereof is fitted into the holder 13 arranged between the side gears 7. are doing. This holder 13 has a ring-like or frame-like shape with a through hole formed in the center, and a step portion caused by forming the tip of the pinion shaft 10 with a small diameter engages with the outer peripheral surface of the holder 13. By doing so, the pinion shaft 10 is prevented from being pulled out toward the inner circumferential side. Then, the front wheel drive shaft 14 connects the cylindrical shaft portion 8, the holder 13, and the side gear 7.
It rests on these axes and penetrates through them. In addition, in Figure 3,
Reference numerals 15 and 16 indicate thrust washers, respectively.

Therefore, when driving force is applied to the differential case 1 from its cylindrical shaft 2, the pinion gear 9 revolves together with the differential case 1 around the rotation axis of the differential case 1, and the driving force is accordingly distributed to each side gear 7. Ru. Since one side gear 7 is spline-fitted to the ring gear mount case 3, driving force is transmitted to the rear wheels via the ring gear 6, and the other side gear 7 has a cylindrical shaft portion 8 integrated with the differential case of the center differential. Since the spline is fitted to the front wheels, the driving force is transmitted to the front wheels, and if there is a difference in rotation speed between the front and rear wheels, the rotation of one of the side gears 7 becomes faster and at the same time the rotation of the other side gears 7 is increased. Therefore, the difference in rotation speed between the front and rear wheels is absorbed.

Problems to be Solved by the Invention By the way, the pinion shaft 10 described above holds the pinion gear 9 relative to the differential case 1 and transmits torque between the differential case 1 and the pinion gear 9.
Assembling is based on requests from nature, pinion gear 9 and side gear 7
Because it is preferable to provide a clearance to absorb errors in meshing with the differential case 1, the pinion shaft 10 is generally fitted into the differential case 1 by 'fL' (for example, with a clearance fit). Also! Since the holter 13 prevents the pinion shaft 10 from being handled toward the inner circumference, the fitting portion between the pinion shaft 10 and the holder 13 is also
For the same reason as above, it is common to fit M (for example, with a clearance fit). The clearance between the pinion shaft 10, the differential case 16, and the holder 13 at each fitting portion is generally sized according to the outer diameter of the shaft and the fitting length. Also in the lock, the clearance at the fitting portion of the pinion shaft 10 with respect to the holder 13 is set small.

However, when torque is transmitted between the differential case 1 and the pinion shaft 10, the point of force application between the differential case 1 and the pinion shaft 10, and the point between the pinion shaft 10 and the pinion gear 9
Since the distance from the rotation center of the differential case 1 is different from the point of application of the force between the pinion shaft 10 and the pinion shaft 10, a rotational moment is generated on the pinion shaft 10.

The relationship is shown in FIG. 6, where the load It, Fc pushing the differential case 1 or pinion shaft 10 and v1ΦFp pushing the pinion shaft 10 by the pinion gear 9 are in opposite directions and in the axial direction of the pinion shaft 10. It acts on different positions in the radial direction of the differential case 1.

As a result, a rotational moment acts on the pinion shaft 10, and as a result, since the pinion shaft 10 is loosely fitted to the differential case 1 and the holder 13, an inclination occurs.

In that case, as mentioned above, in general, the clearance between the fitting part of the tip of the pinion shaft 10 and the holder 13 is set small, so that the tip of the pinion shaft 10 is tilted as shown in FIG. It contacts the fitting hole of the holder 13 at two points, point X and point Y shown, and loads IFh1°Fh2 in opposite directions act on each point. This is similar to the state in which the tip of the pinion shaft 10 is inserted into the holder 13 and twisted, and therefore a large bending moment acts on the tip of the pinion shaft 10, and especially the base end has a grinding relief groove. Since G is formed and the diameter is locally small, there is a risk that stress will be applied to the part of the grinding clearance groove G, which will be disadvantageous in terms of strength and durability.

This decision was made against the background of the above circumstances.
It is an object of the present invention to provide a differential cell device that can prevent unnecessary stress concentration and improve durability.

Means for Solving the Problems In order to achieve the above object, the present invention is configured such that when the pinion shaft is tilted, the accompanying rotational moment is received at the fitting portion between the pinion shaft and the differential case. More specifically, this light is characterized in that a pair of side gears whose rotation centers coincide with the rotation axis of the differential case are arranged facing each other inside the differential case. A pinion gear that meshes with the side gear is rotatably fitted to a pinion shaft mounted in a direction perpendicular to the rotation axis of the differential case and with one end fitted to the differential case, and the other end of the pinion shaft. In the differential cell device, the differential cell device is fitted to a holder arranged between each of the side gears to rotate around the rotation axis of the differential case, and the fitting length of the pinion shaft with respect to the differential case, A VF characteristic is defined as a configuration in which the ratio of the gap between the fitting portion of the differential case is less than or equal to the ratio of the fitting length of the pinion shaft to the holder and the gap between the fitting portions of the pinion shaft and the holder. be.

Function In this Komei diffrency cell 81 as well, torque transmission between the differential case and the pinion gear is carried out via the pinion shaft, and clearance exists between the pinion shaft and the differential case and between the pinion shaft and the holder. Because of this, the pinion shaft tilts as torque is transmitted. In that case, in the differential all of the present invention, the ratio of the fitting length to the fitting clearance at the fitting part between the pinion shaft and the differential case is such that the ratio of the fitting length to the fitting clearance at the fitting part between the pinion shaft and the holder is DIG Since the ratio between the length and the fitting clearance is below, the inclination of the pinion shaft causes contact at the two points of the fitting part with the differential case, and a load acts between the pinion shaft and the differential case, that is, torque The load associated with transmission can be supported. On the other hand, between the pinion shaft and the holder, the allowable inclination angle at the mating part is large, so even if the pinion shaft and the holder make contact at two points, it will not be enough to cause a bending moment. ,
Therefore, even if there is a partially small diameter portion such as a grinding relief groove at the tip of the pinion shaft, stress concentration will not occur.

Example Next, embodiments of the invention will be described with reference to the drawings.

The members constituting the differential device of the present invention and their arrangement are almost the same as those of the conventional differential device shown in FIGS. Therefore, in the following description of the embodiments, we will focus on the points that differ from the conventional differential S&[, and we will focus on parts that are the same or similar to the conventional differential S are shown in Figures 3 and 4.
The same reference numerals as those shown in the figures are used in FIGS. 1 and 2, and the explanation thereof will be omitted.

FIG. 1 is an enlarged and exaggerated cross-sectional view showing the fitted state of the pinion shaft 10 to the differential case 1 and the holder 13, showing the rear end of the pinion shaft 1. The part fits into the outer circumferential wall of the differential case 1, and is prevented from being pulled out toward the outer circumference by a stop ring 11, and its fitting length is set in the IC excluding the plate thickness of the stop ring 11. Further, if the outer diameter of the pinion shaft 10 in this part is dc, and the inner diameter of the fitting hole formed in the differential case 1 is [)C, then these inner and outer diameters are:
A dimensional difference, that is, a fitting clearance of Δdc (=Dc − dc >) is set.On the other hand, the pinion shaft 10
The tip of is formed by grinding so that it has a smaller diameter than the rear end, and the tip fits into the holder 13, and the fitting length of A is reached! It has been set to 11. Further, if the outer diameter of the pinion shaft 10 in this part is dh, and the inner diameter of the fitting hole formed in the differential case 1 is ()h, then there is a dimensional difference between the inner and outer diameters of Δdh (=Dh - dh), or Mating clearance is set.

And each of the above dimensions dc, dh, Dc, Dh.

lc and lh are set so that (Δdc,·lc)≦(Δdh/Nh). In other words, the ratio (Δdc/Pc) between the fitting length 2C of the pinion shaft 10 and the differential case 1 at the fitting part of the pinion shaft 10 and the fitting clearance Δdc of that part is the fitting part of the pinion shaft 10 and the holder 13. The ratio of the mating length 2h and the mating clearance Δdh (Δdh/i
'h) It is set to be as follows.

In the differential device according to the present invention, torque is also transmitted between the differential case 1 and the pinion gear 9 via the pinion shaft 10. For example, when transmitting driving force from an engine (not shown) to the front and rear wheels, Driving force is transmitted from the differential case 1 to the pinion gear 9 via the pinion shaft 10, and in this case, as described above, the point of action from the differential case 1 on the pinion shaft 10 and the point of action of the redirection from the pinion gear 9 are misaligned. As a result, the pinion shaft 10 tilts due to the different acting forces.

This state is schematically shown in FIG. In other words, the ratio of the fitting length ξ and the fitting clearance at each fitting portion of the pinion shaft 10 to the differential case 1 and the holder 13 is as follows:
The allowable inclination angle of the pinion shaft 10 at each fitting part is determined, but the ratio of the fitting length and fitting clearance on the differential case 1 side is the same as the fitting length and fitting clearance on the holder 13 side. Since the ratio is set smaller than the clearance and the allowable inclination angle on the differential case 1 side is small, if the pinion shaft 10 inclines as the driving force is transmitted,
First, two points on the rear end of the pinion shaft 10 come into contact with the inner surface of the fitting hole in the differential case 1, and receive a load in a direction that restricts the inclination of the pinion shaft 10. In Figure 2, the v1 weight is
They are indicated by the symbols Fc and Fc2.

On the other hand, in a state where such an inclination occurs, the pinion shaft 1
The tip of the pinion shaft 1o moves with respect to the applied load, but since the holder 13 is not fixed, it moves together with the tip of the pinion shaft 1o. Since the allowable inclination angle on the holder 13 side is greater than or equal to such an inclination state of the pinion shaft 10, the ground end of the pinion shaft 10 fits into the six fitting holes in the holder 13. Either they are in contact at only one point, or they are in contact at two points but not subject to any load. In other words, the bending moment due to the inclination of the pinion shaft 10 is not generated at the tip of the pinion shaft 10, and therefore even if the grinding escape groove G is formed, stress concentration occurs in that part and the durability is accordingly reduced. There's nothing to do. In addition, bending and shearing loads are applied to the fitting boundary position (the part indicated by the symbol S in Fig. 2) of the rear end of the pinion shaft 10, but this part has a large outer diameter, and there are steps and notches. Since it has a smooth surface with no scratches, there is no disadvantage in terms of strength.

In the above embodiment, the fitting length of the pinion shaft 10 to the differential case 1 is the length excluding the plate thickness of the stop ring 11, but the pinion shaft 10 is inserted in the opposite direction to the direction shown in the above embodiment. Therefore, in the present invention, the length not excluding the plate thickness of the stop ring 11 may be used as the fitting length of the pinion shaft 10 to the differential case 1.

Effects of the Invention As is clear from the above explanation, according to the differential device of the present invention, the bending load does not particularly act on the weak end portion of the pinion shaft that fits into the holder, so the durability of the pinion shaft is improved. As a result, the durability of the differential device as a whole can be improved. At the same time, since no particular load is applied to the holder into which the tip of the pinion shaft is fitted, it becomes possible to reduce the strength capacity of the holder, and accordingly, it is possible to use inexpensive materials for the holder. Therefore, it is possible to reduce the focus of the differential device.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view showing the main parts of one embodiment of this light,
Figure 2 is a schematic diagram showing the state in which the pinion shaft is tilted.
Figure 3 shows a differential door range that allows the shaft to pass through↑
・An exploded perspective view showing the general configuration of a conventional differential device, FIG. 4 is a sectional view, FIG. 5 is a partial sectional view showing the tip of the shaft, and FIG. FIG. 3 is a schematic diagram showing a state in which the axis is tilted. 1... Differential case, 7... Side gear, 9...
・Pinion gear, 10... Pinion shaft, 13...
・Holder, Dc...Inner diameter of the fitting hole in the differential case, dc...Outer diameter of the rear end of the pinion shaft, Dh...
・Inner diameter of the fitting hole in the holder, dh...outer diameter of the tip of the pinion shaft, 2C...fitting length of the pinion shaft to the differential case, lh...fitting length of the pinion shaft to the holder . ro °V

Claims (1)

[Claims] A pair of side gears whose rotation centers coincide with the rotation axis of the differential case are disposed facing each other inside the differential case, and a pinion gear meshing with these side gears is arranged in a direction perpendicular to the rotation axis of the differential case. The pinion shaft is rotatably fitted to a pinion shaft which is attached with one end facing towards the differential case and fitted with the differential case, and the other end of the pinion shaft rotates around the rotation axis of the differential case between the respective side gears. In a differential device fitted to a holder arranged as shown in FIG. A differential device characterized in that the length is equal to or less than the ratio of the gap between the pinion shaft and the fitting portion of the holder.