Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
1999-04-13
2001-04-17
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C251S048000
Reexamination Certificate
active
06216673
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solenoid valve incorporating a chamber.
2. Description of the Prior Art
FIG. 6
shows a longitudinal sectional view of a solenoid valve in the prior art. Reference numeral
101
denotes a housing made from synthetic resin, having an output port
102
and an input port
103
. A negative pressure is to be imposed to the output port. The phrase “negative pressure” in this specification and Claims means “pressure lower than the atmospheric pressure”. Reference numeral
104
is a cover made from synthetic resin, in which a coil
105
is installed. A magnetic plate
106
(made from iron) is disposed between the housing
101
and the cover
104
to form a magnetic path together with a core
107
. A magnetic yoke
108
(made from iron) forms a magnetic path together with the plate
106
. The yoke
108
has a substantially U form.
A connector
110
for supplying electric power to the coil
105
has a hole
109
, into which an external socket (not shown) shall be inserted. A first channel
111
disposed in the housing
101
communicates with the output port
102
. The output port
102
functions as a negative pressure imposing port. A second channel
112
disposed in the housing
101
communicates with the input port
103
.
The core
107
has a coaxial pin
113
, which is disposed so that a part thereof projects from one end of the core. A plunger
114
is set on the pin
113
. A valve element
115
is disposed at one end of the plunger
114
. A spring
116
is disposed between the core
107
and plunger
114
, which urges the valve element
115
towards a face of the housing
101
to close the first channel
111
. A plate spring
117
is disposed on the plunger
114
, which has a sealing element
118
at its peripheral portion. The solenoid valve has a seat
119
, for fixing the solenoid valve to a fixing portion (not shown) of an external apparatus. Reference numeral
20
denotes a bolt for fixing the solenoid valve to the fixing portion.
The operation of this conventional solenoid valve is described below.
When electric power is not supplied to the coil
105
from the external power source, the valve element
115
of the plunger
114
is urged by the resilient force of the spring
116
towards a face of the housing
101
, so as to close the communicating portion between the first and second channel
111
,
112
. As a result, the communicating channel between the output port
102
and the input port
103
is closed.
Starting from this state, when electric current is supplied through the coil
105
, a magnetic field is induced to move the plunger
114
, resisting against the resilient force of the spring
116
, to separate the valve element
115
from the face of the housing
101
. As a negative pressure is imposed at the output port
102
, the fluid supplied into the input port
103
is released from the output port
102
, after passing though the first and second channels
111
,
112
.
In general, electric current is intermittently supplied to the coil
105
so as to control to open and close intermittently the communicating portion between the first and second channel
111
,
112
. At each opening and closing of the channels, an operation sound is caused by the movement of the solenoid valve, and a flow sound is caused by the opening and closing of the channels. And they propagate to an external apparatus connected with the input port
103
. Sound, having a frequency equal to the eigenfrequency of the external apparatus resonates in the apparatus, and a troublesome resonating sound is generated.
In the case when the length of the piping connecting between the input port
103
and the external apparatus (not shown) is an even number multiplied by one quarter of the wave length of the eigenfrequency, this frequency component of the sound resonates in the piping. Namely the sound is amplified in the piping, therefore the resonating sound in the external apparatus further increases.
Moreover, the intermittent opening and closing of communicating part between the first and second channels
111
,
112
causes a pulsation of the fluid flow from the second channel
112
. The energy of this pulsation causes a mechanical vibration of the piping connecting the input port
103
and an external apparatus. The vibration propagates to an external apparatus through the piping and/or a portion of the solenoid valve contacting with the external apparatus. This phenomena is troublesome.
For eliminating this trouble, the solenoid valve in the prior art has a chamber in the middle of the piping.
FIG. 7
shows a schematic diagram of an apparatus for suppressing the purge of the evaporated fuel gas in the prior art. The apparatus for suppressing the purge of the evaporated fuel gas comprises a canister
130
. And a chamber
140
is disposed in the middle of the piping
150
connecting the solenoid valve
100
and the canister
130
.
The function of the apparatus for suppressing the purge of the evaporated fuel gas in the prior art is explained below.
When the engine starts to rotate, a negative pressure appears in the intake manifold of the engine. Therefore, when the solenoid valve
100
is opened, evaporated gas from the canister
130
is supplied to the intake manifold, after passing through the chamber
140
and the solenoid valve
100
.
If the supply amount of the purge gas is not appropriate, it causes bad influences to the function of the engine. Thus the solenoid valve
100
is controlled by a control signal from a controller (not shown) so as to be intermittently opened and closed, namely the duty ratio of the opening and closing of the solenoid valve is controlled. This intermittent opening and closing generates an operation sound and a flow sound. The sounds are damped by the chamber
140
for preventing the propagation to the canister
130
, so that a generation of resonating sound in the canister
130
is eliminated. Simultaneously, the pulsation of flow in the piping is damped by the chamber
140
, so that the vibration of the piping and the canister caused by the pulsation is eliminated.
FIG. 8
is a characteristic curve of sound emission versus the position of the chamber. FIG. (
a
) corresponds to the case that no frequency component in the propagating sound resonates in the piping, on the other hand, (
b
) corresponds to the case that a frequency component equal to the eigenfrequency of the canister resonates in the piping.
FIG. 9
shows a characteristic curve of resonating vibration of the canister versus the position of the chamber. FIG. (
a
) corresponds to the case that no frequency component in the propagating sound resonates in the piping, on the other hand, (
b
) corresponds to the case that a frequency component equal to the eigenfrequency of the canister resonates in the piping.
The canister used in the evaluation shown in
FIGS. 8 and 9
had an eigenfrequency of 850 Hz, which corresponds to a wave length of 40 cm.
FIGS. 8 and 9
show that a resonance appears when the piping length is an even number multiplied by a quarter of wave length (10 cm).
These figure show that a pulsation suppressing effect is small when the chamber
140
is arranged at an antinode of the vibration in the piping, and the effect appears when the chamber
140
is arranged at a node of the oscillation. Antinodes and nodes of the oscillation in the piping are schematically shown at the upper portion of the FIGS.
8
(
a
), (
b
). It shall be noted that when both the ends of the piping, which is connected with the input port
103
, are opened, both the ends are antinodes for all the frequency components, irrespective of the resonance.
SUMMARY OF THE INVENTION
As explained, the solenoid valve in the prior art has a drawback that a mechanical sound and a fluid flow sound are generated at every opening and closing of the fluid channel. When these sounds propagate to an external apparatus, a frequency component identical with the eigenfrequency of the external apparatus resonates. This, in turn, makes a troublesome resonat
Mitsubishi Denki & Kabushiki Kaisha
Moulis Thomas N.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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