Pumps – Including disengageable rotary or frangible drive connection
Reexamination Certificate
2001-09-20
2003-09-02
Freay, Charles G. (Department: 3746)
Pumps
Including disengageable rotary or frangible drive connection
C417S223000, C192S054200, C464S042000, C464S081000
Reexamination Certificate
active
06612813
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power transmission mechanism capable of absorbing a torque change transmitted between two rotating members.
Japanese Unexamined Patent Publication No. 10-267045 discloses an example of a power transmission mechanism. As shown in
FIG. 11
, a pulley
101
functions as a first rotating member at an external drive source side, and a hub
102
functions as a second rotating member at an equipment side. The pulley
101
and the hub
102
are operably connected through an elastic member
103
that is made of rubber and is sandwiched between engaged recesses
104
formed on the pulley
101
and the hub
102
.
When drive power is transmitted from the external drive source to the equipment, the elastic member
103
is deformed due to torque transmitted between the pulley
101
and the hub
102
, which allows relative rotation between the pulley
101
and the hub
102
. At the same time, the torque allows the relative rotation angle between the pulley
101
and the hub
102
to vary within a predetermined range. As a result, the relative rotation between the pulley
101
and the hub
102
absorbs a differential torque transmitted between the pulley
101
and the hub
102
whenever the transmitted torque between the pulley
101
and the hub
102
changes due to changes in output torque from the external drive source and/or changes in torque in the torque receiving equipment itself.
Japanese Unexamined Patent Publication No. 10-267045 discloses only a torque limiting function of a drive power transmission apparatus as shown in FIG.
11
. The elastic member
103
disengages from the engaged recess
104
thereby disconnecting the power transmission between the pulley
101
and the hub
102
, when a drive torque acting on the equipment becomes excessive. However, it is apparent that the torque change disclosed in the above publication is absorbed by optimizing the elastic coefficient of the elastic member
103
corresponding to a slope of a line
211
in
FIG. 12
as will be later described.
In a power transmission mechanism according to the above publication as shown in
FIG. 11
, the elastic member
103
has a cylindrical shape. Also, a recessed curved surface
104
a
having the same curvature as a cylindrical surface
103
a
of the elastic member
103
is formed in a recess
104
. In other words, the recessed curved surface
104
a
of the engaged recess
104
contacts the elastic member
103
entirely, when the transmitted torque is zero.
To increase the relative rotation angle between the pulley
101
and the hub
102
and to counter the large elasticity of the elastic member
103
, the elastic member
103
must be deformed sufficiently even near a zero degree state of the relative rotation angle. As a result,
FIG. 12
shows a graph between the transmitted torque of the power transmission mechanism and the relative rotation angle according to the prior art. A straight line
211
has a somewhat large slope. Therefore, the transmitted torque between the pulley
101
and the hub
102
changes suddenly within a predetermined range of angle based on the changes in the relative rotation angle.
To simplify the description of the above problem derived from a character illustrated in
FIG. 12
, the conventional power transmission mechanism assumes that the equipment such as the hub
102
rotates at a constant speed while the pulley
101
rotates due to the torque changed by the external drive source. That is, the torque change is accompanied by the change of the relative rotation angle. In this case, a change in rotation angle or in torque at the external drive source is defined as relative rotation angle of the pulley
101
with respect to the hub
102
.
Also assume the following state. As indicated with dotted lines
212
in
FIG. 12
, a torque is caused by a compact equipment or an equipment whose torque is variable is in a small drive torque state, that is, in a state of a small relative rotation angle between the pulley
101
and the hub
102
. In addition, a large change in a relative angle indicated by a curve
213
generates between the pulley
101
and the hub
102
at the external drive source. In this case, around troughs of torque generated by the external drive source, which is indicated by peaks on the left of the curve
213
, the pulley
101
rotates relative to the hub
102
in a reverse direction with respect to a state in which the torque is zero, which is reverse to a normal direction, which transmits the torque from the external drive source to the equipment.
The reverse torque amplifies the differential torque generated by the power transmission system between the hub
102
and the equipment, which is indicated with the curve
214
as shown in FIG.
12
. The excess torque load, substantially represented by negative half of the curve
214
of differential torque, generates a torque that works in a reverse direction or a negative torque. If there is a clearance in a torque transmitting direction between the hub
102
and the equipment or inside the equipment, relative rotation between the rotating members is caused and the power transmission in a normal direction is interrupted. The positive and negative torque act relatively and alternately to each other to offset the clearance of the rotating members. The clearance causes abnormal vibrations and noise due to collision of the rotating members, and it eventually wears the rotating members and increases chattering.
SUMMARY OF THE INVENTION
The present invention provides a power transmission mechanism which is capable of absorbing a change of a torque transmitted between a first rotating member and a second rotating member during a power transmission process. It also provides a power transmission mechanism which reduces a negative torque to an equipment even if a large torque change occurs at the external drive source.
To achieve the above objectives, the present invention has following features. A power transmission mechanism has a first rotating member rotating around an axis, a second rotating member rotating around the axis and an elastic member located between the first rotating member and the second rotating member. The first rotating member has a first rotating member surface, and the second rotating member has a second rotating member surface. The elastic member has at least a protrusion contacting at least the first rotating member surface. The protrusion extends in a circumferential direction of the first rotating member. The protrusion has gradually tapering shape toward the first rotating member surface. The elastic member is deformed by compression as the elastic member engages the first rotating member surface and the second rotating member surface by rotation of the first rotating member, thereby causing relative rotation of the first rotating member and the second rotating member.
REFERENCES:
patent: 4859156 (1989-08-01), Kikuchi
patent: 5899811 (1999-05-01), Kishibuchi et al.
patent: 5944156 (1999-08-01), Hatakeyama
patent: 6068452 (2000-05-01), Okada et al.
patent: 6213733 (2001-04-01), Obrist et al.
patent: 10-267045 (1998-10-01), None
patent: 0 890 760 (1999-01-01), None
patent: 2000-161382 (2000-06-01), None
Kanai Akinobu
Kawata Takeshi
Kimura Kazuya
Suzuki Takahiro
Uryu Akifumi
Freay Charles G.
Kabushiki Kaisha Toyota Jidoshokki
Knoble & Yoshida LLC
Liu Han L
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