Bearings – Linear bearing – Plain bearings
Reexamination Certificate
1999-04-27
2001-04-24
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Plain bearings
C384S285000
Reexamination Certificate
active
06220757
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sliding part having a sliding surface of which wear resistance is required, such as a shim used in a valve system of an internal combustion engine of a vehicle, and to a sliding mechanism including the sliding part.
2. Description of the Background Art
A material having high wear resistance has been used for a mechanical sliding part represented by an engine part of a vehicle, in order to minimize wear. Recently, a hard sliding member comes to be formed of a material such as a super hard alloy, or ceramics having superior wear resistance as compared with the steel material which has been conventionally used as a material for the sliding part. These materials, however, are generally difficult to process and are expensive. Therefore, it is a common practice to form not the entire part but only a sliding portion requiring high wear resistance by using such a material.
As a representative example, on an end surface of a valve lifter driving a tappet valve of a valve system in the internal combustion engine, a shim formed of a hard member is positioned, which shim exhibits superior wear resistance.
As an example of a sliding mechanism for heavier load, a hard member is used at a tip end of a thrust bolt used for preventing inclination of a ring gear in a reduction mechanism of a vehicle. For example, Japanese Patent Laying-Open No. 8-109956 discloses means having superior durability and allows easy maintenance, for preventing inclination of the ring gear used in a reduction mechanism of a large vehicle such as a bus, a truck, a tractor or the like.
Referring to
FIG. 10
a
, a reduction mechanism
100
contains, in a differential carrier
101
, a propeller shaft
102
including a pinion, and an axle shaft
103
including a differential gear with a bearing (not shown) interposed. In a differential case
104
, a ring gear
105
is secured. Ring gear
105
transmits torque of propeller shaft
102
to axle shaft
103
. In order to prevent deflection of ring gear
105
when the transmitted torque increases, a tip end of a thrust bolt
106
is in contact with a rear surface
107
of ring gear
105
.
FIG. 10B
is an enlarged view of a portion around thrust bolt
106
and rear surface
107
of ring gear
105
. A boss
108
is provided at a part of differential carrier
101
, thrust bolt
106
is screwed in boss
108
, and thrust bolt
106
is positioned by using a lock nut
109
. At a tip end of thrust bolt
106
, a sliding part
110
is mounted.
FIG. 10C
shows, in further enlargement, the periphery of sliding part
110
. Sliding part
110
having a sliding surface crowned to have a convex shape and formed of silicon nitride or the like is mounted on a recessed portion
106
a
of thrust bolt
106
. Between the sliding surface of sliding part
110
and rear surface
107
of ring gear
105
, there is generally a clearance of &dgr;. When an excessive torque is transmitted to reduction mechanism
100
and ring gear
105
deflects by more than &dgr; when the vehicle starts or climbs a steep slope, thrust bolt
106
prevents inclination of more than &dgr;. Therefore, during normal running, sliding part
110
does not contact rear surface
107
of ring gear
105
.
By the structure of the reduction mechanism, inclination of ring gear
105
by more than &dgr; can be prevented, and therefore abnormal wear of ring gear
105
and the teeth surface of the pinion of propeller shaft
102
or damage to the teeth can be avoided. Further, as the sliding surface of sliding part
110
is crowned to have a convex shape, sliding part
110
is in smooth contact with the rear surface
107
of ring gear
105
, and therefore it is described that a force that would cause damage or displacement of sliding part
110
from the recessed portion
106
a
is hardly generated.
SUMMARY OF THE INVENTION
An object of the present invention is to employ a holding portion formed of metal having such a shape that prevents generation of stress concentration on the sliding part, when the holding portion holds the sliding part formed of ceramics.
The above described object can be attained by the sliding part of a sliding mechanism in accordance with the present invention in which one of sliding parts sliding relative to each other is held by a holding portion formed of metal, the sliding part being arranged protruding from a recessed portion provided in the holding portion, and a side surface of the sliding part being apart from an open end of an inner wall of the recessed portion so as not to be in contact with an edge of the open end.
As to the manner of holding the sliding part in the holding portion, the sliding part may be inserted loose in the recessed portion of the holding portion, or preferably, held by shrink fit or press fit.
If the side surface of the sliding part not in contact with the edge of the open end of inner wall at the recessed portion of the holding portion is formed linear or curved, stress concentration at the contact portion between the holding portion and the sliding part can be relaxed.
When the sliding member is formed of ceramics, preferably, the ceramics should be a silicon nitride based ceramics of which bending strength is preferably reinforced to 1000 MPa to 2000 MPa, so that the sliding member can withstand impact load.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 2609710 (1952-09-01), Osborn
patent: 5342129 (1994-08-01), Dennis et al.
patent: 5829881 (1998-11-01), Furlani et al.
patent: 5927860 (1999-07-01), Buse
patent: 0209697 (1987-01-01), None
patent: 0572112 (1993-12-01), None
patent: 0651140 (1995-05-01), None
patent: 2151742 (1985-07-01), None
patent: 58-210308 (1983-12-01), None
patent: 8-109956 (1996-04-01), None
Nishioka Takao
Yamagiwa Masamichi
Fasse W. F.
Fasse W. G.
Hannon Thomas R.
Sumitomo Electric Industries Ltd.
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