Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-04-03
2003-10-28
Miller, Carl S. (Department: 3746)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S506000, C137S538000, C137S543210
Reexamination Certificate
active
06637410
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. 4
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. 4
, 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. 5
is a sectional view showing a conventional high pressure fuel supply apparatus. In
FIG. 5
, 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 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, such a conventional high pressure fuel supply apparatus has some problems as follows.
FIG. 6
is a sectional view in which the vicinity of a discharge vale is enlarged in scale in a high pressure fuel pump of a conventional high pressure fuel supply apparatus. In
FIG. 6
, a discharge valve
14
is shaped into a plane plate, having a flat sheet surface to block up a fuel discharge port
162
b
. The discharge valve
14
is closed by the pressing force of a spring
14
a.
However, when the high pressure fuel supply apparatus is driven at a high speed of rotation, there is a problem that the discharge valve
14
is poor in response so that a failure in operation is produced to reduce the discharge quantity of fuel. In addition, there is another problem that the sheet surface is worn due to the partial contact of the discharge valve
14
so that the durability deteriorates.
In such a case, in order to improve the response of the discharge valve
14
, measures that the spring constant of the spring
14
a
is increased to increase the spring load are taken. However, the increase of the spring load results in the increase of loss in pressure of the fuel in the vicinity of the discharge valve
14
. Thus, the pressure in the fuel pressurizing chamber
163
so that there occurs a new problem that the durability of the high pressure fuel pump
16
is degraded, and the sheet portion is worn. In addition, even if the discharge valve
14
has a ball-like shape as shown in
FIG. 7
, a similar problem occurs.
SUMMARY OF THE INVENTION
The present invention is developed to solve such problems. It is an object of the present invention to provide a high pressure fuel supply apparatus which can ensure the fuel discharge quantity in a high speed rotation range and which prevents the sheet surface from being worn.
The high pressure fuel supply apparatus according to the present invention is constituted by a plunger reciprocating in a sleeve of a high pressure fuel pump so as to form a fuel pressurizing chamber between the plunger and the sleeve, a suction valve provided in a fuel suction port for sucking fuel into the fuel pressurizing chamber, and a discharge valve provided in a fuel discharge port for discharging fuel from the fuel pressurizing chamber into a high pressure fuel discharge passageway communicating with an internal combustion engine
Ichinose Yuta
Ojima Kouichi
Onishi Yoshihiko
LandOfFree
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