JP2003175737A - Rear differential mount structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear differential mount structure capable of suppressing roll movement of a rear differential due to driving reaction force, and preventing a stopper abutting in a differential mount by improving the roll stiffness of the rear differential without increasing the spring constant of a differential mount more than necessary. <P>SOLUTION: In this rear differential mount structure transmitting driving force from a propeller shaft to right and left wheels, a rear differential comprises two differential mounts attached to right and left sides in a front side than a differential center that is an inertial center, and two differential mounts attached to right and left sides in a rear side than the differential center. On the basis of upper and lower spring constants of the front and rear differential mounts and a final gear ratio of the rear differential, a distance between acting points of the front and rear differential mounts and the differential center is established. According to these, the front and rear differential mounts are laid out. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mount structure for supporting a rear differential on a vehicle body frame.

[0002]

As shown in FIG. 4, a rear differential (hereinafter referred to as a rear differential) 1
Are connected to the rear end of the propeller shaft 2 and are connected to the left and right rear wheels 4L and 4R via rear drive shafts 3L and 3R that are connected to the left and right side spindles (not shown) of the rear differential 1.
The driving force is smoothly transmitted to the. Conventionally, a plurality of differential mounts (here, four) are used as vibration damping bushes in such a rear differential 1, and the differential mounts 5L on the left and right sides of the rear differential 1 on the front side of the rear drive shafts 3L and 3R are used. 5R is fixed to a front diff member (not shown), and two diff mounts 6L and 6R at the rear end of the rear diff 1 are fixed to a rear suspension cross member (not shown) to be supported by the vehicle body frame.

However, in this conventional rear differential mounting structure, when a sudden torque is applied to the drive system, the rear differential 1 causes the propeller shaft drive force (counterclockwise direction when viewed from the rear differential 1 side) and the axle drive reverse direction. Pitch movement and roll movement occur due to the force (counterclockwise direction when viewed from the right rear wheel 4R side), and the rear diff 1 right diff mount 5
The R has a problem that a shocking upward driving reaction force is likely to work. Then, when a drive reaction force more than the set value acts on the differential mount 5R, as shown in FIG. 5, the outer cylinder 7 (on the rear differential 1 fixed side) and the inner cylinder 8 (on the vehicle body frame fixed side) of the differential mount 5R are separated. The elastic body 9 press-fitted between the inner cylinder 8 and the outer cylinder 7 is excessively deflected as the outer cylinder 7 is displaced, and the protrusion 9a of the elastic body 9 is formed to project toward the inner cylinder 8 so that the upper limit and the lower limit of the flexure become the lower limit. A "stopper contact" occurs in which the inner cylinder 8 and the inner cylinder 8 collide with each other. Then, there is a problem that the vehicle body frame is vibrated by the impact at this time, which causes abnormal noise.

In order to solve such a problem, it is conceivable that the torsional rigidity is increased by increasing the elastic reaction force of the differential mount 5R, that is, the spring constant, and the roll rigidity of the rear differential 1 is increased. 5
In addition to R, each diff mount must have a soft spring constant to some extent for vibration and sound insulation, and it is difficult to eliminate the stopper contact by strengthening the spring constant of the diff mount 5R.

The present invention has been made in order to solve the problems of the above-described conventional rear differential mount structure, and does not increase the spring constant of the differential mount more than necessary. It is an object of the present invention to provide a rear differential mounting structure capable of suppressing the roll movement of the rear differential due to the driving reaction force and preventing the stopper contact in the differential mount in advance by increasing the roll rigidity of the rear differential.

[0006]

In order to achieve the above object, the present invention is a rear differential mounting structure for transmitting a driving force from a propeller shaft to left and right wheels, wherein the rear differential has its center of inertia. Two differential mounts mounted on the front left and right sides of the differential center and two differential mounts mounted on the rear left and right sides of the differential center are provided, and the vertical spring constants of the front and rear differential mounts and the rear differential. Based on the final gear ratio of
The distance between the points of action between the front and rear differential mounts and the differential center is set, and the front and rear differential mounts are laid out according to these.

Further, according to the present invention, in the rear differential mounting structure for transmitting the driving force from the propeller shaft to the left and right wheels, the rear differential is mounted on the front left and right sides of the differential center which is the center of inertia of the rear differential. A differential mount, and two differential mounts that are attached to the rear left and right sides of the differential center, the distance between the operating points of the front and rear differential mounts and the differential center, and the final gear ratio of the rear differential, Based on, the upper and lower spring constants of the front and rear differential mounts are set,
According to these, the front and rear differential mounts are laid out.

Further, according to the present invention, the two differential mounts attached to either the rear side or the front side of the differential center are regarded as apparently one differential mount, whereby the front and rear differential mounts and the differential center are regarded as one. The distance between the points of action with and the upper and lower spring constants of the front and rear differential mounts are set.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a rear differential mounting structure of the present invention will be described below with reference to FIG. FIG. 1A is a plan view for explaining a rear differential mounting structure to which the present invention is applied,
(B) is a vibration model diagram of the same example. In the following description, the same components as those in the conventional example are designated by the same reference numerals.

As shown in FIG. 1 (a), the rear differential 1 to which the mount structure of the present invention is applied has two differential mounts 5L mounted on the front left and right sides of a differential center DC serving as the center of inertia of the rear differential 1. , 5R are fixed to the front differential member, and two differential mounts 6L, 6R are mounted on the left and right sides behind the differential center DC.
Is fixed to the rear suspension cross member to be supported by the vehicle body frame. These differential mounts 5L to 6R are shown in FIG. 5 as elastic bodies (rubber materials) which have a certain degree of softness in order to reduce vibration noise while maintaining rear differential support strength for a long period of time. The upper and lower spring constants that maximize the torsional rigidity are obtained by using the one with the directionality
kfl, kfr, krl, and krr are added respectively. In addition,
Let C1 be the front-rear center line passing through the differential center DC and C2 be the left-right center line.

The upper and lower spring constants kfl to krr of the differential mounts 5L to 6R and the final gear ratio if of the rear differential 1 are set.
And are substituted into the following formula (1), that is, the roll cancel condition formula, and the arithmetic processing is performed, the distances between the action points of the differential mounts 5L to 6R and the differential center DC are calculated, and thus the differential mounts 5L to 6R are calculated. The optimum mounting position is set. At this time, the distance between the action points of the left-right center line C2 and the differential mount 5L (lf in the figure) and the left-right center line C
2 and the distance between the action points of the differential mount 5R are set to be equal to each other. Similarly, the distance between the action points between the left and right center line C2 and the differential mount 6L (in the figure, l
r) and the distance between the action points of the left-right center line C2 and the differential mount 6R are set to be equal to each other.

[0012]

[Equation 1] Here, L is the distance between the operating points of the differential mount 5L and the differential mount 6L in the front-rear centerline C1 direction, which is lf +
lr, kfl is the vertical spring constant of the differential mount 5L, kfr
Is the vertical spring constant of the differential mount 5R, krl is the vertical spring constant of the differential mount 6L, krr is the vertical spring constant of the differential mount 6R, if is the final gear ratio of the rear differential 1, and bl is the front-rear centerline C1 and the differential mount 5L. Distance between points of action, br
Is the distance between the front and rear centerlines C1 and the differential mount 5R, cl is the distance between the front and rear centerlines C1 and the differential mount 6L, and cr is the distance between the front and rear centerlines C1 and the differential mount 6R. is there. Then, the differential mount 5L to have the calculated inter-action point distances L, bl, br, cl, cr.
By laying out 6R, the roll rigidity of the rear differential 1 can be maximized, and the roll movement of the rear differential 1 when a sudden torque is applied to the drive system can be suppressed.

The calculation of equation (1) will be described below.
As shown in the vibration model of FIG. 2, each differential mount 5
The relationship between the stress and the displacement in the Z direction in L to 6R is shown by the following mathematical expression (2).

[Equation 2] Here, p1, p2, p3, p4 are each differential mount 5L-6R
The Z components, z1, z2, z3, and z4 input to are the displacements in the Z direction in the differential mounts 5L to 6R.

The relationship between the displacement of each diff mount 5L to 6R and the displacement of the diff center DC is expressed by the following mathematical formula.
It is indicated by (3).

[Equation 3] Here, lf is the distance between the operating points of the differential center DC and the differential mount 5L, lr is the distance between the operating points of the differential center DC and the differential mount 6L, Z is the displacement of the differential center DC in the Z direction, φ
Is Rx displacement of differential center DC, θ is R of differential center DC
y displacement.

The relationship between the Z-direction (upward) stress applied to each of the differential mounts 5L to 6R and the differential center input is expressed by the following mathematical expression (4) using mathematical expressions (2) and (3).

[Equation 4]

Here, since P1 + P2 + P3 + P4 = P (P: differential center input), by adding all components, the equilibrium equation in this mount structure is
It is represented by (5).

[Equation 5] if ・ T is axle torque

Here, when the equation (5) is regarded as follows,

[Equation 6]

The reciprocal of the roll rigidity is obtained by the following equation (7) by the Kramel's solution.

[Equation 7]

At this time, when suppressing the roll movement in the rear differential 1, the roll rigidity is

[Equation 8] Therefore, the roll cancel condition expression is expressed by the following expressions by the expressions (7) and (8).

[Equation 9]

By the way,

[Equation 10] Therefore, substituting equations (10) and (11) into equation (7) gives the following equation.

[0021]

[Equation 11] Then, since lf + lr = L, the formula (12) is

[Equation 12] Therefore, the formula (12 '), that is, the formula (1) is obtained. The calculation of the roll cancel conditional expression has been described above.

FIG. 2 shows the results of the vibration test of the mount structure laid out based on the distances L, bl, br, cl, cr between the action points calculated by the same method. According to this, in the mounting structure of the rear differential that does not satisfy the roll cancel conditional expression, as shown by the thin line in the same figure (a), when the driving force is input to the rear differential 1, the differential mount FtRH on the front right side is FtRH.
Stopper contact occurs on the differential mount 5R (corresponding to the differential mount 5R of the present invention), but when a mount structure satisfying the roll cancel condition is adopted, as shown in FIG. It was possible to eliminate the stopper hit.

As described above, according to the mounting structure of the rear differential of the present invention, the differential mounts 5L to 6R are provided.
The upper and lower spring constants kfl, which give the maximum torsional rigidity due to the directionality of the elastic body that maintains a certain degree of softness for reducing vibration noise while maintaining the rear differential support strength. kfr, krl, and krr are added. By substituting these upper and lower spring constants kfl to krr and the final gear ratio if of the rear differential 1 into the roll cancel conditional expression shown in the mathematical expression (1), the differential mount 5 is operated.
L to 6R and the distance between the working points of the differential center DC, that is, the distance L between the working points of the differential mount 5L and the differential mount 6L in the front-rear centerline C1 direction, and the distance between the working points of the front and rear centerline C1 and the differential mount 5L. bl, front and rear center line C1
Between the points of action between the differential mount and the differential mount 5R, the front-rear centerline C
The distance cl between the working points of 1 and the differential mount 6L and the distance cr between the working points of the front-rear center line C1 and the differential mount 6R are calculated. And according to these, differential mount 5L-6
By arranging R, the roll movement of the rear differential 1 can be suppressed to the maximum, and only the pitch movement can be performed. Therefore, the shocking upward driving reaction force that tends to be generated in the differential mount 5R when a sudden torque is applied to the drive system is attenuated, so that the differential mount 5R is prevented from being excessively deflected, and the stopper is prevented. You will be able to eliminate the hit. Moreover,
Since the required supporting rigidity of the rear differential 1 is ensured with the soft spring constant, the roll throw can be improved without adversely affecting other noise such as top throw and gear noise.

By the way, even if an attempt is made to lay out the respective diff mounts 5L to 6R that satisfy the roll cancel condition in an actual production vehicle, there are various design restrictions, and the layout may not be freely obtained. In such a case, as shown in FIG. 3A, first, the mounting action point positions of the respective diff mounts 5L to 6R obtained by the roll canceling conditional expressions are arranged within a layout possible range. The spring rigidity is optimized by optimizing and then calculating the optimum upper and lower spring constants of the respective diff mounts 5L to 6R at the actual mounting action point positions by the roll cancellation conditional expression. As a result, the roll rigidity of the rear differential 1 can be made infinite, and the roll movement of the rear differential 1 can be suppressed.

The present invention also includes differential mounts 5L to 6R.
The present invention is not applied only to a four-point support mounting structure according to the above, but as shown in FIG.
Two differential mounts 6L that can be attached to the rear of the
By considering 6R as apparently one diff mount, the two diff mounts arranged on the rear diff 1 are two front sides,
It can also be applied to a three-point support mount structure with one rear side. In this case, in equation (1), the upper and lower spring constants krr of the diff mount 6R and the distance cr between the action points of the front-rear centerline C1 and the diff mount 6R are set to 0, and the forward and backward diff mounts are calculated. 5L, 5
Distance L, bl, b between points of action between R, 6L and differential center DC
Optimal upper and lower spring constants kfl, kfr, krl of r, cl or the diff mounts 5L, 5R, 6L are set, and the diff mounts 5L, 5R, 6L may be laid out according to these. In addition, the two differential mounts 5L and 5R mounted in front of the differential center DC can be regarded as one differential mount by the same method.

As a result, by optimizing the upper and lower spring constants and layout of each diff mount 5L to 6R,
Rolling movement of the rear differential is suppressed, and stopper contact of the differential mount is prevented in advance, so that traveling feeling can be improved.

[0027]

As described above, according to the rear differential mounting structure of the present invention, the roll rigidity of the rear differential is increased without increasing the spring constant of the differential mount more than necessary, so that the rear differential due to the driving reaction force is applied. It is possible to provide a rear differential mounting structure capable of suppressing the roll movement and preventing the stopper contact in the differential mount in advance.

[Brief description of drawings]

FIG. 1A is a plan view for explaining a rear differential mounting structure to which the present invention is applied; FIG.
[Fig. 6] is a vibration model diagram of the same example.

FIG. 2A shows a vibration result of a rear differential mount structure that does not satisfy a roll cancel condition, and FIG. 2B shows a vibration result of a rear differential mount structure that satisfies a roll cancel condition.

FIG. 3A is an explanatory diagram for explaining a case where the present invention is applied when a layout cannot be freely obtained; FIG.
[Fig. 6] is an explanatory diagram for explaining a case where the present invention is applied to a mount structure with three-point support.

FIG. 4 is a plan view for explaining a conventional rear differential mounting structure.

FIG. 5 is a front view of the differential mount of the same example.

[Explanation of symbols]

1 rear differential 5L, 5R differential mount (front) 6L, 6R differential mount (rear) DC differential center

Claims (3)

[Claims] 1. A rear differential mounting structure for transmitting a driving force from a propeller shaft to left and right wheels, wherein the rear differential has two differential mounts mounted on the front left and right sides of a differential center which is an inertia center of the rear differential. Two differential mounts attached to the rear left and right sides of the differential center, and based on the upper and lower spring constants of the front and rear differential mounts and the final gear ratio of the rear differential. A rear differential mounting structure in which a distance between points of action between a differential mount and the differential center is set, and the front and rear differential mounts are laid out according to the distances. 2. A rear differential mounting structure for transmitting a driving force from a propeller shaft to left and right wheels, wherein the rear differential has two differential mounts mounted to the front left and right sides of a differential center which is the center of inertia of the rear differential. Two differential mounts attached to the rear left and right sides of the differential center, and based on a distance between operating points of the front and rear differential mounts and the differential center, and a final gear ratio of the rear differential, A rear differential mounting structure, wherein upper and lower spring constants of the front and rear differential mounts are set, and the front and rear differential mounts are laid out in accordance with these. 3. Between the points of action of the front and rear diff mounts and the diff center by treating the two diff mounts attached to either the rear side or the front side of the diff center as apparently one diff mount. 3. The rear differential mounting structure according to claim 1, wherein the distance or the upper and lower spring constants of the front and rear diff mounts are set.