Torque limiter for wheel driving force

Details Torque limiter for wheel driving force Torque limiter for wheel driving force

1999-10-01

2004-01-20

Browne, Lynne H. (Department: 3679)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Having lubricating means

For overload release coupling

C464S007000, C192S113340

Reexamination Certificate

active

06679778

ABSTRACT:

DETAILED DESCRIPTION OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a torque limiting apparatus provided in a path of power transmission from a drive source to a drive shaft for vehicles such as trucks.
2. Prior Art
For power transmission from a drive source to a drive shaft for vehicles such as trucks, a conventional structure of gearing system generally used is described with an example of a front-wheel drive vehicle. This well known structure of gearing system is arranged along the longitudinal direction of the vehicle, and so configured that the rear end of the drive shaft is connected to the drive source, and the front end thereof is connected to a differential gear system. A connection between the drive shaft and the differential gear system has been performed by the direct engagement of an output gear mounted at the front end of the drive shaft nonrotatably relative thereto, with the input gear of the differential gear system.
Such a well known structure of gearing system is simple, but there are following disadvantages due to the direct engagement of the drive shaft and the input gear of the differential gear system.
It is desirable that parts configuring vehicles are each made compact for a reduction in cost of vehicles and an improvement in steerability of driving vehicles. On the other hand, it is required for each part to be strong enough to bear a required load. Thus, each part for vehicles are sized as small as possible when a required strength is satisfied for each part. For example, assuming that the dimension of a connection part between the drive shaft and differential gear system is determined, based on a load imposed on said connection portion (hereafter, referred to as a load on a normal driving state) when driving on a terrain with a relatively flat surface. In this case, assuming that drive wheels had an impact load momentary caused by a sudden start or stop of a vehicle, a sudden load (hereafter, referred as a peak load) in excess of the load on a normal driving state, would be imposed on the connection part, thereby the part could be damaged. Consequently, for the well known structure of gearing system, it is required for the connection part between the drive shaft and the input gear of the differential gear system to be large enough to bear the peak load, so the requirement for making a reduction in size can not be sufficiently satisfied.
On the other hand, U.S. Pat. No. 2,977,779 discloses a structure of gearing system in which, as shown in
FIG. 4
, the front end of a drive shaft, its rear end being connected to a drive source (not shown), and the rear end of a connecting shaft
120
, its front end being connected to an input gear of differential gear system (not shown), are connected to each other via a torque limiting apparatus
100
. As shown in the figure, the torque limiting apparatus
100
comprises a middle shaft
101
connected via a universal joint
130
to the front end of the drive shaft nonrotatably relative thereto around its axis, drive friction discs
102
mounted on the middle shaft nonrotatably relative thereto, a cylindrical casing
103
, which has a closed front end, surrounding the middle shaft
101
and drive friction discs
102
, driven friction discs
104
mounted on the inner periphery of the casing
103
nonrotatably relative thereto and bringing into a frictional contact with the drive friction discs
102
, and a biasing member
105
for biasing the drive friction discs
102
and driven friction discs
104
in a manner one side is pressed toward the other. A connection between the connecting shaft
120
and the torque limiting apparatus
100
, is made by the rear end of the connecting shaft
120
connected to the front end of the casing
103
nonroratably relative thereto.
The torque limiting apparatus
100
, allows a power transmission from the drive friction discs
102
to the driven friction discs
104
by means of a frictional contact on a normal driving state, while, in case of having a peak load as mentioned above, the drive friction discs
102
and the driven friction discs
104
slip to each other, thus the power transmission therebetween is cut off. The use of such torque limiting apparatus
100
allows the strength for the connecting part between the connecting shaft
120
and the input shaft of the differential gear system to be determined in accordance with the load on a normal driving state as mentioned above. Namely, the power transmission from the drive source to the differential gear system is cut off upon peak loads, so there is no need for the connecting part between the connecting shaft and differential gear system to be large sized so as to bear against the peak load. In this manner, the dimension of each part can be determined in accordance with the load on a normal driving state, thereby allowing each component to be downsized.
However, the torque limiting apparatus disclosed in the U.S. Pat. No. 2,977,779 mentioned above, requires a lubricating oil for the frictional discs
102
,
104
, to be enclosed in advance in the casing
103
. In addition, the oil enclosed in the casing
103
is not positively cooled down, so there is another problem in that the heat generated by the frictional discs
102
,
104
could cause a deterioration in durability and abrasion resistance.
SUMMARY OF THE INVENTION
An object of the present invention, which has been accomplished to overcome the foregoing problems, is to provide a torque limiting apparatus for transmitting power from an output end of a drive shaft, the input end of which is connected to a drive source, to a differential gear system for driving a pair of drive wheel axes, the apparatus being adapted to supply a lubricating oil automatically thereinto.
To fulfill the foregoing object, the present invention provides a torque limiting apparatus for transmitting power from a drive shaft connected to a drive source, to a differential gear system for driving a pair of wheel axes, the apparatus comprising: a connecting shaft, an output side of which is connected to the differential gear system, an input side of which is protruded out of an opening formed at a housing of the differential gear system; a hollow cylindrical casing supported on the input side of the connecting shaft rotatably relative thereto, and connectable to the connecting shaft; a seal member for liquid-tightly connecting the output opening of the casing and the opening of the housing; and a connecting mechanism provided between the casing and the connecting shaft, for transmitting only a partial power less than a predetermined torque value out of whole power input into the casing, to the connecting shaft.
Preferably, the apparatus can be further provided with a mount flange which closes liquid-tightly the input opening of the casing and is connected to the drive shaft.
More preferably, the apparatus can be so constructed that the flange has a center bore formed in communication with both the inside and outside of the casing, the connecting shaft comprising: a supporting shaft, an output end of which is connected to the differential gear system, and an input end of which is protruded liquid-tightly out of the center bore of the flange, a middle shaft supported on the supporting shaft nonrotatably relative thereto and axially movable, an input end of the middle shaft being protruded liquid-tightly out of the center bore of the flange, the connecting mechanism can be provided between the middle shaft and the casing, and a locking member can be provided in the housing for positioning the output end of the middle shaft, and a locking device removably fixed to the input end of the supporting shaft, so that the axial movement of the middle shaft can be prevented in cooperation with the locking member.
Preferably, the connecting mechanism can be so constructed that drive frictional discs provided onto the inner periphery of the casing nonrotatably relative thereto, and driven frictional discs provided onto the outer periphery nonrotatably relative thereto, correspondi

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