Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2002-04-09
2003-11-11
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
Reexamination Certificate
active
06644287
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a high pressure fuel supply apparatus chiefly for use in a cylinder fuel injection engine or the like.
FIG. 11
is a block diagram showing a fuel supply system in an internal combustion engine for a vehicle, including a conventional high pressure fuel supply apparatus. In
FIG. 11
, fuel
2
in a fuel tank
1
is delivered from the fuel tank
1
by a low pressure pump
3
, passes through a filter
4
, is adjusted in pressure by a low pressure regulator
5
, and then is supplied to a high pressure fuel supply apparatus
6
which is a high pressure pump. A flow rate of the fuel
2
exactly required for fuel injection is boosted by the high pressure fuel supply apparatus
6
, and supplied into a delivery pipe
9
of the not-shown internal combustion engine. A surplus of the fuel
2
is relieved between a low pressure damper
12
and a suction valve
13
by an electromagnetic valve
17
.
In addition, the required fuel flow rate is determined by a not-shown control unit, which also controls the electromagnetic valve
17
. The high pressure fuel supplied thus is injected into a cylinder of the internal combustion engine in the form of high pressure mist from a fuel injection valve
10
connected to the delivery pipe
9
. When abnormal pressure (high-pressure relieving valve opening pressure power) is produced in the delivery pipe
9
, a filter
7
and a high pressure relief valve
8
are opened to prevent the delivery pipe
9
from being broken.
The high pressure fuel supply apparatus
6
which is a high pressure pump, has a filter
11
for filtering the supplied fuel, the low pressure damper
12
for absorbing the pulsation of the low pressure fuel, and a high pressure fuel pump
16
for pressurizing the fuel supplied through the suction valve
13
and discharging the high pressure fuel through a discharge valve
14
.
FIG. 12
is a sectional view showing a conventional high pressure fuel supply apparatus. In
FIG. 12
, the high pressure fuel supply apparatus
6
is integrally provided with a casing
61
, a high pressure fuel pump
16
, an electromagnetic valve
17
, and a low pressure damper
12
. The high pressure fuel pump
16
is a plunger pump provided in the casing
61
.
A fuel pressurizing chamber
163
surrounded by a sleeve
160
and an end of a plunger
161
inserted slidably in the sleeve
160
is formed in the high pressure fuel pump
16
. The other end of the plunger
161
abuts against a tappet
164
, and the tappet
164
is brought into contact with a cam
100
so as to drive the high pressure fuel pump
16
. The cam
100
is provided integrally or coaxially with a cam shaft
101
of the engine so as to reciprocate the plunger
161
along the profile of the cam
100
in cooperation with the rotation of a crank shaft of the engine. The volume of the fuel pressurizing chamber
163
is changed by the reciprocating motion of the plunger
161
so that the fuel boosted to high pressure is discharged from the discharge valve
14
.
In the high pressure fuel pump
16
, a first plate
162
, the suction valve
13
, a second plate
166
and a flange portion
160
a
of the sleeve
160
are held between the casing
61
and an end surface of a spring guide
165
, and fastened with a bolt
180
. The first plate
162
forms a fuel suction port
162
a
for sucking fuel from the low pressure damper
12
to the fuel pressurizing chamber
163
, and a fuel discharge port
162
b
for discharging the fuel from the fuel pressurizing chamber
163
.
The suction valve
13
shaped into a thin plate is held between the first plate
162
and the second plate
166
so that a valve is formed in the fuel suction port
162
a
. The discharge valve
14
is provided on an upper portion of the fuel discharge port
162
b
so as to communicate with the delivery pipe
9
through a high pressure fuel discharge passageway
62
provided in the casing
61
. In addition, in order to suck fuel, a spring
167
for pushing the plunger
161
down in a direction to expand the fuel pressurizing chamber
163
is disposed in the state where the spring
167
has been compressed between the spring guide
165
and a spring holder
168
.
The electromagnetic valve
17
has an electromagnetic valve body
170
, a valve seat
173
, a valve
174
, and a compression spring
175
. The electromagnetic valve body
170
is incorporated in the casing
61
of the high pressure fuel supply apparatus
6
so as to have a fuel channel
172
inside the electromagnetic valve body
170
. The valve seat
173
is provided in the fuel channel
172
of the electromagnetic valve body
170
. The valve
174
is separated from/brought near to the valve seat
173
in the electromagnetic valve body
170
so as to open/close the fuel channel
172
. The compression spring
175
presses the valve
174
onto the valve seat
173
.
At a point of time when a flow rate requested from a not-shown control unit has been discharged in a discharge stroke of the high pressure fuel pump
16
, a solenoid coil
171
of the electromagnetic valve
17
is excited to open the valve
174
. Thus, the fuel
2
in the fuel pressurizing chamber
163
is released to the low pressure side between the low pressure damper
12
and the suction valve
13
so that the pressure in the fuel pressurizing chamber
163
is reduced to be not higher than the pressure in the delivery pipe
9
. Thus, the discharge valve
14
is closed. After that, the valve
174
of the electromagnetic valve
17
is opened till the high pressure fuel pump
16
proceeds to a suction stroke. The timing to open the electromagnetic valve
17
is controlled so that the amount of fuel discharged into the delivery pipe
9
can be adjusted.
However, the conventional high pressure fuel supply apparatus has problems as follows.
FIG. 13
is a sectional view in which the vicinity of the flange portion
160
a
(inside the circle in
FIG. 12
) of the sleeve
160
in the high pressure fuel pump of the conventional high pressure fuel supply apparatus is enlarged in scale. As shown in
FIG. 13
, the flange portion
160
a
of the sleeve
160
and the end surface of the spring guide
165
abut against each other flatly over a range from their inner circumferential portions to their outer circumferential portions.
FIG. 14
is a graph showing the surface pressure distribution between portions a and b which are respective contact portions between the flange portion
160
a
of the sleeve
160
and the second plate
166
in FIG.
13
. In
FIG. 14
, the ordinate of the graph designates the surface pressure distribution (MPa), and the abscissa designates the radial length between the contact portions a and b. As shown in
FIG. 14
, it is understood that the surface pressure distribution appearing between the contact portions a and b shows a maximum in the outer circumferential portion, and becomes lower as it approaches the inner circumferential portion, that is, the fuel pressurizing chamber
163
. Therefore, in the case where the fuel pressure is high (for example, about 15 MPa), there is a problem that fuel leaks through a gap produced in the inner circumferential portion in the contact portion between the flange portion
160
a
and the second plate
166
so that the discharge quantity of the fuel lowers suddenly. In addition, there is another problem that wear due to fretting is produced in the portion of the contact portions a and b where the surface pressure is lowered.
On the other hand, in order to prevent the deformation of the sleeve
160
, there are taken such measures that the sleeve
160
and the second plate
166
are thickened, or the fastening torque of the fastening bolt is increased. However, there arises a new problem that the apparatus is increased in dimensions because the sleeve
160
and the second plate
166
are thickened, or the apparatus is increased in dimensions or in weight because the casing
61
and the fastening bolt are increased in rigidity or a high-strength material is adopted (the material is changed from normally used aluminum to iron) i
Ichinose Yuta
Ojima Kouichi
Onishi Yoshihiko
Mitsubishi Denki & Kabushiki Kaisha
Moulis Thomas N.
Sughrue & Mion, PLLC
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