192 clutches and power-stop control – Clutches – Fluent material
Reexamination Certificate
2000-05-25
2002-07-23
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Clutches
Fluent material
C192S1030FA, C464S027000
Reexamination Certificate
active
06422368
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a hydraulic power transmission joint for use in automotive 4 wheel-drive mechanisms for the distribution of driving force, and more particularly to a hydraulic power transmission joint designed to suppress cavitation noises arising from a drain mechanism built in a valve block within the joint.
2. Description of the Related Arts
Such a hydraulic power transmission joint for use in an automotive 4 wheel-drive mechanism is hitherto known from U.S. Pat. Nos. 5,706,658 and 5,983,635.
This hydraulic power transmission joint comprises a housing disposed between input and output shafts that are capable of relative rotations, the housing being coupled to one of the input and output shafts and having a cam face formed on its inner side surface; a rotor coupled to the other of the input and output shaft and being rotatably accommodated in the housing, the rotor having a plurality of axially extending plunger chambers; a plurality of plungers each being reciprocatively accommodated in each of the plurality of plunger chambers under a biasing force of the return spring, the plurality of plungers being operated by the cam face upon the relative rotations of the input and output shafts; a discharge hole formed in the rotor and leading to the plurality of plunger chambers; and a valve block having a high-pressure chamber that leads to the discharge hole, the valve block having an orifice for generating a flow resistance under the action of flow of oil discharged by operations of the plurality of plungers.
FIG. 1
shows by way of example a drain mechanism incorporated in a valve block of a hydraulic power transmission joint being currently developed by the present inventors on the basis of such U. S. Patents, the drain mechanism serving also as a torque limiter mechanism. The drain mechanism is generally designated at
101
and includes a drain plug
102
accommodated in an accommodation hole of the valve block not shown, the drain plug
102
being formed with a drain hole
103
. The drain plug
102
accommodates a drain pin
104
such that the latter is able to open and close the drain hole
103
, the interior of the drain pin
104
being formed with a high-pressure chamber
106
that communicates via a through-hole
105
with a high-pressure chamber located on its left. An orifice
107
is formed in the drain pin
104
. The orifice
107
serves to generate a high pressure by a flow resistance occurring when oil from the plungers passes therethrough, to impart it to the plungers so as to allow a transmission of torque. A seal ring
108
is interposed between the drain plug
102
and the drain pin
104
. A return spring
110
intervenes between the inner wall of the high-pressure chamber
106
and a limiter plug
109
provided in abutment against the drain plug
102
. The drain pin
104
is urged by the return spring
110
to block the drain hole
103
. The limiter plug
109
is formed with a communication hole
111
that leads to the high-pressure chamber
106
, with a limiter pin
112
adapted to open and close the communication hole
111
being slidably accommodated in the limiter plug
109
. The limiter pin
112
is urged via a thermo-switch (not shown) located on its right side by the return spring, to block the communication hole
111
.
When the temperature of the thermo-switch reaches a predetermined temperature, the thermo-switch is actuated to release the pressing action on the limiter pin
112
so that the limiter pin
112
can open the communication hole
111
under the hydraulic pressure within the high-pressure chamber
106
. For this reason, the hydraulic pressure within the high-pressure chamber
106
of the drain pin
104
becomes zero all at once, allowing the drain pin
104
to open the drain hole
103
under the hydraulic pressure from the high-pressure chamber (not shown) on its left side. Oil within the high-pressure chamber passes through the drain hole
103
and is drained into the low-pressure chamber, ceasing torque transmission to the rear side. By virtue of this, the joint can be prevented from being subjected to a high temperature upon continuous travels over sandy soil, making it possible to avoid any damage to the joint. On the contrary, in the inoperative status of the thermo-switch prior to reaching a predetermined temperature, the hydraulic pressure within the high-pressure chamber
106
of the drain pin
104
becomes larger than the force biasing the limiter pin
112
rightward once a predetermined hydraulic pressure is reached, allowing the limiter
112
to gradually open the communication hole
111
. Thus, the drain pin
104
can gradually open the drain hole
103
while keeping its balance. The transmission torque to the rear side is therefore prevented from increasing accordingly as the rotational-speed difference becomes larger, and it is limited to a certain value. This ensures a smooth start of the motor vehicle.
However, in such a hydraulic power transmission joint, the drain pin having an orifice is accommodated in the drain plug while being urged by the return spring, but the drain pin undergoes no positioning in the direction where the orifice rotates. As a result, the cavitation noises may possibly become louder depending on the rotational position of the orifice.
SUMMARY OF THE INVENTION
According to an aspect of the present invention there is provided a hydraulic power transmission joint capable of suppressing cavitation noises arising from a drain pin having an orifice in a drain mechanism.
An inventive hydraulic power transmission joint is adapted to be interposed between an input shaft and an output shaft that are rotatable relative to each other, and to transmit torque as a function of the rotational-speed difference between the input and output shafts. The hydraulic power transmission joint comprises a housing coupled to the input shaft and having a cam face formed on its inner side surface; a rotor coupled to the output shaft and being rotatably accommodated in the housing, the rotor having a plurality of axially extending plunger chambers; a plurality of plungers each being reciprocatively accommodated in each of the plurality of plunger chambers under a biasing force of the return spring, the plurality of plungers being operated by the cam face upon the relative rotations of the input and output shafts; a discharge hole formed in the rotor and opening to the plurality of plunger chambers; a valve block coupled to the rotor for being rotated jointly; an orifice formed in the valve block for generating a flow resistance under the action of flow of oil discharged by operations of the plurality of plungers; and a drain mechanism provided in the valve block. The drain mechanism serves, when a predetermined temperature is reached, to open a drain hole to allow oil to flow from a high-pressure side into a low-pressure side to thereby cancel a transmission of torque, the drain mechanism serving, until the predetermined temperature is reached, to regulate the opening of the drain hole to limit a transmission torque to a certain value irrespective of increase in the rotational-speed difference. The drain mechanism includes a drain pin slidably accommodated in a drain plug, and a limiter pin received in a limiter plug disposed in abutment against the drain plug for opening and closing a communication hole that leads to the drain pin, with one end turn portion of the return spring being press fitted into the interior of the drain pin, and with the other end turn portion being press fitted into the interior of the limiter plug, to thereby rotationally position the drain pin.
According to the hydraulic power transmission joint of the present invention having the above configuration, one end turn portion of the return spring is press fitted into the interior of the drain pin having an orifice for generating a flow resistance, with the other end turn portion being press fitted into the interior of the limiter plug to thereby rotationally position the drain
Kato Tadahiko
Kusukawa Hirotaka
Murata Shigeo
Nakabayashi Akira
Sumino Hidemitsu
Fujiunivance Co.
Marmor Charles A
Rodríguez Saúl
Wenderoth , Lind & Ponack, L.L.P.
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