Low vibration driveline

Details Low vibration driveline Low vibration driveline

2003-03-24

2004-07-06

Dickson, Paul N. (Department: 3616)

Motor vehicles

Transmission mechanism

With particular drive coupling

C180S379000, C180S381000

Reexamination Certificate

active

06758302

ABSTRACT:

FIELD OF THE INVENTION
Drivelines for vehicles having at least two drive axles and, more particularly, to configurations of such drivelines exhibiting torsional vibrations.
BACKGROUND OF THE INVENTION
The large trucks that are used to transport freight on our nation's highways—including, for example, Class 8 trucks—are most commonly tractor-semitrailer combinations having a tractor configured with a steerable axle at the front and tandem driving axles at the rear. Typically, these trucks utilize a “conventional” power train arrangement, depicted schematically in
FIGS. 1 and 2
. In this conventional power train arrangement, power produced by the engine (not shown) is transmitted through the transmission
108
to the forward drive axle
101
through a main drive shaft
107
. Although a single drive shaft is shown, it is common, and contemplated by the present invention, that a compound main drive shaft structure (i.e., two or more drive shafts rotatably connected with universal joint(s)) may be used.
In this prior art driveline, the forward end
107
A of the main drive shaft
107
connects to the output shaft of the transmission
108
with a first universal joint
109
A. As used herein, “output shaft” refers to a shaft, typically but not necessarily a pinion shaft, on a component such as a transmission or an axle, that is driven by or through the component to provide power to another downstream component, and an “input shaft” refers to a shaft, again typically but not necessarily a pinion shaft, on a component such as an axle, which is externally driven to provide power to and/or through the component.
The rearward end
107
B of the main drive shaft
107
connects to the input shaft
128
of the forward drive axle
101
with a second universal joint
109
B (FIG.
2
). A similar but generally shorter interaxle drive shaft
110
transmits power between the forward drive axle
101
and the rearward drive axle
102
. The forward end
110
A of the interaxle drive shaft
110
connects to the output shaft
130
of the forward drive axle
101
with a third universal joint
109
C, and the rearward end
110
B of the interaxle drive shaft
110
connects to the input shaft
132
of the rearward drive axle
102
with a fourth universal joint
109
D.
The universal joints
109
allow the interconnected shafts to rotate about their respective axes, notwithstanding nonalignment between the shafts. Various types of universal joints are commonly used in automotive drivelines, but the most prevalent by far, particularly in heavy-duty applications, is the so-called cardan joint (also known as a Hooke joint). Cardan joints have the advantages of mechanical simplicity, good reliability, and low cost. A disadvantage of the cardan joints, however, is that uniform rotational motion at the input yoke of the joint results in non-uniform motion at the output yoke of the joint unless the joint operating angle is zero, that is, unless the shafts connected by the cardan joint rotate about a common axis. (The joint operating angle is defined herein to be the absolute value of the acute angle defined by the axes of the two shafts connected through the universal joint.)
The relationship between the input motion and the output motion across a simple cardan joint is well known. For small joint operating angles, a constant rotational velocity at the input yoke of the joint will produce nonconstant rotational motion at the output yoke having a maximum angular (or torsional) acceleration that increases approximately in proportion to the square of the shaft rotational speed and approximately in proportion to the square of the joint operating angle. In typical vehicle power trains, the drive shafts typically rotate at several thousand revolutions per minute. Therefore, even small joint operating angles can produce large angular accelerations. The angular accelerations are periodic, with a frequency of twice the shaft speed.
Large torsional accelerations can produce high dynamic torques on the universal joints and other driveline components. These dynamic forces can be very damaging to the internal components of the transmission, as well as the axle gearing and the universal joints themselves. Moreover, the dynamic forces are periodic, and can occur at resonant frequencies of the driveline, thereby amplifying the stresses and strains induced in the driveline. Consequently, designers strive to achieve driveline geometries with small joint operating angles that limit the torsional accelerations to levels that are consistent with long component life.
In drivelines having appropriately-phased, multiple cardan joints, non-uniform motion produced by one joint may be at least partially offset by one or more of the remaining joints. Referring now to
FIGS. 3A and 3B
, in a drive shaft
143
interconnecting an input shaft
141
with an output shaft
145
, using a pair of cardan joints
109
A,
109
B, there are two configurations whereby the angular accelerations introduced at the input joint
109
A will be ideally compensated for at the output cardan joint
109
B. In the first ideal configuration, shown in
FIG. 3A
, the input shaft
141
is parallel to the output shafts
145
(“parallel shaft geometry”), so the joint operating angles (angles A and B) are equal. In the second ideal configuration, shown in
FIG. 3B
, the input shaft
141
is not parallel to the output shaft
145
, but the shafts are configured so that the joint operating angles are again equal (“intersecting shaft geometry”). If the joint angles A and B are equal and the joints are phased appropriately, uniform rotary motion of the input shaft
141
will produce uniform rotary motion at the output shaft
145
with either the parallel shaft or the intersecting shaft geometries. However, the drive shaft
143
located between the universal joints
109
A,
109
B will still exhibit non-uniform motion and angular accelerations, and the inertia of the drive shaft
143
will generate second order (twice shaft speed) dynamic torsional loads on the joint assemblies
109
A,
109
B. If the two joint angles A and B are not equal, then uniform rotation of the input shaft
141
will produce non-uniform rotation of output shaft
145
. The difference between the joint operating angles of the two joints (i.e., A minus B) is known as the “cancellation error.”
In order to avoid the angular vibrations introduced by cardan joints, so-called constant velocity (CV) joints have been developed. Several different types of CV joints have been developed, including, for example, ball-and-groove type joints such as Rzeppa, Weiss joints, helical or skewed groove joints, tracta joints, cross-groove joints, double-offset joints, tripot joints and flexing type joints. CV joints introduce little or no rotational non-uniformity. CV joints are commonly used in particular applications, notably on the axle shafts of front wheel drive automobiles. The primary disadvantages of CV joints are that they are complex and expensive compared to cardan joints, and they tend to have lower mechanical efficiency and poorer reliability than cardan joints. Consequently, CV joints are typically used only where acceptable performance cannot be achieved with cardan joints.
A near-constant-velocity joint can be achieved through the use of a “double cardan joint” or a “centered double cardan joint,” as shown in FIG.
4
. Conceptually, a centered double cardan joint
50
is made by combining two conventional cardan joints into a single joint by merging the two inner yokes into a single, two-sided “coupling yoke”
53
. A centering bearing
57
is incorporated into the joint that constrains the operating angles of the two joint halves to remain nearly equal. While not a true constant velocity joint, the departure from ideal behavior is small until the operating angle becomes quite large.
In drive trains configured as depicted in
FIG. 2
, the transmission
108
is usually installed such that the axis of the transmission output shaft
126
is directed generally toward the input shaft
128
of the forward drive axle
101

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