Information
-
Patent Grant
-
6817838
-
Patent Number
6,817,838
-
Date Filed
Friday, November 1, 200222 years ago
-
Date Issued
Tuesday, November 16, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 417 244
- 417 313
- 123 9012
- 123 503
- 123 508
- 123 509
- 123 449
- 123 515
- 123 495
-
International Classifications
-
Abstract
In a fuel injection pump, a casing fixed to a housing has a pump room and a filter room mostly separated from but partly communicating with the pump room. A feed pump is constituted by the pump room where a feed pump mechanism is connected to an axial end of the drive shaft. A filter element is accommodated in the filter room. A casing cover easily attachable and detachable to the casing has a fuel inlet port through which fuel is sucked to the filter room and, then, flows via the filter element into the pump room where the fuel is pressurized according to rotation of the drive shaft. Accordingly, foreign material contained in fuel is eliminated before entering the pump room. Further, fuel flow area of the fuel element is larger than that of the fuel inlet port, resulting in less pressure loss of fuel passing through the filter element even if mesh size of filter element is smaller.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2001-355821 filed on Nov. 21, 2001, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection pump for an internal combustion engine (hereinafter called “engine”).
2. Description of the Prior Art
Conventionally, a common rail fuel injection system is known typically as a system for supplying fuel to a diesel engine. The common rail fuel injection system is provided with a fuel injection pump in which plungers as moving members make reciprocating movement according to rotation of a drive shaft so that fuel supplied to pressure chambers are pressurized by the plungers. When pressure of the pressurized fuel reaches a given value, the pressurized fuel is discharged from each of the pressure chambers to a common rail.
In a case of the fuel injection pump mentioned above, a housing, in which the pressure chambers are formed in cooperation with the plungers, is equipped with a feed pump for supplying fuel to the pressure chambers. The feed pump is arranged at an end of the drive shaft, which reciprocatingly drives the plungers, and is driven according to rotation of the drive shaft so that fuel stored in a fuel tank is delivered to the pressure chambers.
In the conventional fuel injection pump, a fuel filter provided in the fuel tank eliminates foreign material contained in the fuel. Further, a filter element arranged in the housing of the fuel injection pump on a side of the fuel inlet port serves to eliminate foreign material produced in a fuel delivery pipe extending from the fuel tank to the feed pump and foreign material produced from the fuel filter itself before these foreign material flow into the feed pump.
However, the housing of the fuel injection pump does not have enough space to mount the filter element in view of conventional shape of the fuel injection pump. Accordingly, the filter element is relatively compact so that mesh size of the filter element has to be relatively large to reduce pressure loss of fuel passing though the filter element. The filter element whose mesh size is large can not eliminate minute foreign material, so efficiency of filtrating the foreign material is not high. If the foreign material having passed through the filter element enters various sliding portions formed in the fuel injection pump, the foreign material is apt to hinder smooth operation of the sliding portions, thereby the fuel injection pump has a risk of jeopardizing highly accurate fuel amount control.
Further, the conventional filter element is installed typically in a passage formed in the housing of the fuel injection pump. Accordingly, it is difficult and troublesome to replace the filter element positioned in the passage.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fuel injection pump in which minute foreign material is eliminated without causing significant pressure loss, which enables highly accurate fuel flow control and in which a fuel member is easily replaced.
To achieve the above object, in the fuel injection pump, a casing fixed to an outer surface of a housing is provided at a position adjacent to the housing with a pump room and at a position remote from the housing with a filter room mostly separated from but partly communicating with the pump room. An axial end of a drive shaft protrudes into the pump room. A feed pump is constituted by the pump room where a feed pump mechanism is connected with the axial end of the drive shaft. A filter element is accommodated in the filter room. A casing cover attached to the casing has a fuel inlet port through which fuel is sucked to the filter room and, then, flows via the filter element into the pump room where fuel is pressurized according to rotation of the drive shaft. Accordingly, foreign material contained in fuel is eliminated before entering the pump room.
The filter element is accommodated in the filter room of the casing at the position remote from the housing so that the filter element is easily replaced, for example, for a maintenance purpose by detaching the casing cover from the casing. It is preferable, therefore, that the casing cover is attached to the casing, for example, by bolts, so that the casing cover may be easily detached therefrom.
Since the filter room is formed in the casing at the position remote from the housing and there is no size limitation of inner space of the filter room, the inner space of the filter room can be sufficiently large to accommodate larger size of the filter element.
It is preferable that fuel flow area of the fuel element is larger than that of the fuel inlet port.
Further, preferably, the pump and filter rooms are formed substantially in column shape and inner diameter of the filter room is substantially equal to that of the pump room.
Employment of the larger size of the filter element results in less pressure loss of fuel passing through the filter element even if mesh size of the filter element is smaller. Since foreign material, even if it is minute, is eliminated by the filter element, there is few foreign material entering sliding portions of the fuel injection pump, which enables highly accurate fuel flow control of the fuel injection pump.
Moreover, it is preferable that the casing is composed of a cylindrical casing body and a partition dividing axially inner space of the casing body into two spaces that constitute the pump and filter rooms, respectively. Preferably, the partition has a communication hole through which the filter room communicates with the pump room. The casing mentioned above has a simpler construction in which the casing can be easily fixed to the housing and the feed pump mechanism and the filter element can be easily assembled thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:
FIG. 1
is a schematic cross sectional view of a fuel injection pump according to a preferred embodiment of the present invention;
FIG. 2
is a schematic cross sectional view showing about sliding portions of a plunger and a cam ring of the fuel injection pump taken along a line perpendicular to an axis of a drive shaft in
FIG. 1
; and
FIG. 3
is a cross sectional view taken along a line III—III of FIG.
1
.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention is described with reference to drawings.
FIG. 1
shows a fuel injection pump
1
according to the preferred embodiment. The fuel injection pump
1
is applied to a common rail fuel injection system.
As shown in
FIG. 1
, the fuel injection pump I has a housing body
10
, a housing cover
20
and cylinder heads
30
. The housing body
10
and the housing cover
20
are made of aluminum. Each of the cylinder heads
30
is formed of iron and is provided inside with a cylinder
31
. A plunger
41
as a moving member is slidably and reciprocatingly accommodated in the cylinder
31
. Each of the cylinder heads
30
is provided with a check valve
32
plugging an end of the cylinder
31
. The check valve
32
is fixed to the cylinder head
30
by fitting a seal member
33
thereto. A pressure chamber
34
is formed by an inner circumferential surface of the cylinder head
30
, an end of the check valve
32
and an axial end of the plunger
41
.
A drive shaft
2
is rotatably held via a journal
21
by the housing cover
20
and the housing body
10
. An oil seal
22
seals a space between the housing cover
20
and the drive shaft
2
. As shown in
FIG. 2
, a cam
51
whose cross sectional shape is circular is formed eccentrically and integrally with the drive shaft
2
.
FIG. 2
shows a part view of the fuel injection pump
1
rotated by 90° from that shown in
FIG. 1
, that is, a cross sectional view taken along a line perpendicular to an axis of the drive shaft
2
for illustrating about sliding portions of the plunger
41
and the cam
51
. Four pieces of the plungers
41
are arranged circumferentially at regular angular intervals with respect to the axis of the drive shaft
2
(two plungers
41
are shown in FIG.
1
). As shown in
FIG. 2
, a cam ring
52
has a square shaped profile. A bush
53
is interposed between the cam ring
52
and the cam
51
so that the bush
53
can slide on both of the cam ring
52
and the cam
51
. An outer circumference surface
52
a
of the cam ring
52
facing the plunger
41
and an end face
41
a
of the plunger
41
are flat and in contact with each other so as to constitute sliding portions. An inside of the housing composed of the housing body
10
, the housing cover
20
and the cylinder heads
30
are filed with light oil. The sliding portions of the cam ring
52
and the plungers
41
are lubricated by fuel.
Each of the plungers
41
is reciprocatingly driven via the cam ring
52
by the cam
51
according to rotation of the drive shaft
2
and pressurizes fuel sucked into the pressure chamber
34
through the check valve
32
from a fuel flow-in passage (not shown). The check valve
32
has a valve member
321
and is operative to prevent fuel from flowing in reverse from the pressure chamber
34
to the fuel flow-in passage. The fuel flow-in passage is formed inside the housing body
10
and each of the cylinder heads
30
. An end of the fuel flow-in passage communicates with the pressure chamber
34
via the check valve
32
and the other end thereof communicates with a feed pump
60
. A fuel amount adjusting valve (not shown) is disposed on a way of the fuel flow-in passage through which each of the pressure chambers
34
communicates with the feed pump
60
. The fuel amount adjusting valve is operative to adjust an amount of fuel to be supplied to each of the pressure chambers
34
so that an amount of fuel to be discharged from the pressure chamber
34
to the common rail (not shown) is a given value. The fuel amount adjusting valve is a spool valve in which a valve body is driven to move according to values of current applied to a coil and a fuel flow area is variable according to moving amounts of the valve body.
A spring
42
urges the plunger
41
toward the cam ring
52
. The cam ring
52
slidably revolves around the cam
51
without self-rotating according to the rotation of the cam
51
. Accordingly, sliding portions of the cam ring
52
and the plunger
41
moves reciprocatingly in right and left directions in FIG.
2
and the plunger
41
moves reciprocatingly upward and downward in the cylinder
31
.
Each of the cylinder heads
30
is provided with a fuel flow-out passage (not shown). The fuel flow-out passage is formed to extend forward or backward from the pressure chamber
34
in FIG.
1
. An end of the fuel flow-out passage communicates with the pressure chamber
34
and the other end thereof communicates with the common rail. The fuel flow-out passage is provided with a check valve (not shown), which is opened, when pressure of fuel in the pressure chamber
34
reaches a given pressure, to allow fuel flow from the pressure chamber
34
to the common rail but prohibit fuel flow from the common rail to the pressure chamber
34
.
The feed pump
60
is arranged at an axial end of the drive shaft
2
. The feed pump
60
has an inner rotor
61
and an outer rotor
62
(feed pump mechanism). The inner rotor
61
is connected to the axial end of the drive shaft
2
that protrudes out of the housing body
10
. The inner and outer rotors
61
and
62
are relatively rotatable and, when the inner rotor
61
rotates together with the drive shaft
2
, fuel is fed from the fuel tank to each of the pressure chambers
34
. A power transmitting portion
2
a
is formed at the other axial end of the drive shaft
2
so that the drive shaft
2
is driven to rotate by driving force transmitted from an engine to the power transmitting portion
2
a.
The feed pump
60
is provided in a casing
70
easily attachable or detachable to the housing body
10
. The casing
70
has a pump room
81
in which the inner and outer rotors
61
and
62
of the feed pump
60
are accommodated. A bush
11
is interposed between the casing
70
and the housing body
10
for preventing fuel leakage from the pump room
81
to outside through a gap between the casing
70
and the housing body
10
.
The casing
70
is formed approximately in cylindrical shape. The casing
70
is composed of a cylindrical body
71
and a partition
72
dividing inner space of the cylindrical body
71
into two spaces. That is, a cross section of the casing
70
taken along an axis thereof is formed substantially in a letter H shape. The inner space of the cylindrical body
71
on a side of the drive shaft
2
, that is, on a side of the housing body
10
is the pump room
81
in which the inner and outer rotors
61
and
62
are accommodated. The inner space of the cylindrical body
71
on a side opposite to the drive shaft
2
, that is, on a side opposite to the housing body
10
is a filter room
82
in which a filter element
3
is accommodated. The partition
72
is provided with a communication hole
73
through which the filter room
82
communicates with the pump room
81
for supplying fuel to an intake port of the pump room
81
. Inner diameter of the pump room
81
is substantially same to that of the filter room
82
, since inner diameter of the casing body
71
is axially nearly uniform.
The casing
70
is provided at an axial end thereof on a side opposite to the drive shaft
2
with a cover
74
for covering the filter room
82
. The cover
74
is easily attachable and detachable to the casing
70
. The cover
74
is formed in shape of a disk whose outer diameter corresponds to that of the casing
70
. A fuel inlet port
75
, which communicates with the filter room
82
, is formed in the cover
74
. An end of the fuel inlet port
75
on a side opposite to the filter room
82
communicates with the fuel tank so that fuel stored in the fuel tank is flowed into the filter room
82
through the fuel inlet port
75
. The fuel inlet port
75
may be arranged at any position of the cover
74
where the fuel inlet port
75
can communicate with the filter room
82
.
The fuel inlet port
75
is connected to a fuel supply passage (not shown) through which the fuel tank is connected to the fuel injection pump
1
. Inner diameter of the fuel inlet port
75
is substantially same as that of the fuel supply passage. On the other hand, the inner diameter of the filter room
82
, which is substantially same as that of the pump room
81
, is larger than that of the fuel inlet port, consequently, fuel flow area of the filter room is larger than that of the fuel inlet port.
The cover
74
is fixed to the casing
70
by fixing members
76
such as bolts. As shown in
FIG. 3
, the casing
70
has installation portions
70
, to which the fixing members
76
are attached. Accordingly, the cover
74
can be easily detached for replacing the filter element
3
accommodated in the filter room
82
.
The inner and outer rotors
61
and
62
are accommodated in the pump room
81
with a given clearance between an outer circumference of the outer rotor
62
and an inner circumference of the pump room
81
. The filter element
3
is accommodated in the filter room
82
without a substantial clearance (if any, with a minute clearance) between an outer circumference of the filter element
3
and an inner circumference of the filter room
82
. The filter element
3
is formed in column shape corresponding to that of the filter room
82
. The filter element
3
eliminates foreign material produced in the supply passage between the fuel tank and the fuel injection pump
1
or in a fuel filter (not shown) disposed in the fuel tank. The fuel filter
3
is typically made of filter paper, fiber cluster or metal nets.
An operation of the fuel injection pump
1
is briefly described below.
The feed pump
60
is driven by rotation of the inner rotor
61
according to rotation of the drive shaft
2
which causes a relative rotating movement between the inner and outer rotors
61
and
62
. Upon driving the feed pump
60
, fuel stored in the fuel tank is flowed via the fuel supply passage and the fuel inlet port
75
into the filter room
82
where the filter element
3
is accommodated and, after passing through the filter element
3
and having eliminated foreign material in the filter room
82
, via the communication hole
73
into the pump room
81
. In the pump room
81
, the fuel is pressurized by the relative rotating movement between the inner and outer rotors
61
and
62
. Then, the pressurized fuel by the feed pump
60
is supplied to the pressure chamber
34
via the fuel flow-in passage formed in the housing body
10
and the cylinder head
30
. The amount of fuel supplied to the pressure chamber
34
is adjusted by the fuel amount adjusting valve disposed between the feed pump
60
and the pressure chamber
34
.
The fuel having passed through the fuel amount adjusting valve is sucked when the plunger
41
moves downward in the cylinder
31
according to the rotation of the drive shaft
2
. The fuel in the pressure chamber
34
is pressurized by an upward movement of the plunger
41
in the cylinder
31
. When pressure of the fuel in the pressure chamber
34
reaches a given value, the check valve provided in the fuel flow-out passage communicating with the pressure chamber
34
is opened so that the fuel in the pressure chamber
34
is discharged to the common rail. In the common rail, the fuel, which is supplied from the fuel injection pump
1
and whose pressure is variable, is accumulated so as to keep predetermined uniform pressure. The fuel accumulated in the common rail is delivered to each of injectors for spraying to each cylinder of the engine.
In the fuel injection pump
1
according to the preferred embodiment, the casing
70
, in which the pump room
81
of the feed pump
60
and the filter room
82
are formed, is fixed to the housing body
10
at the axial end of the drive shaft
2
. The inner diameter of the filter room
82
is substantially equal to that of the pump room
81
so that a flow area of fuel passing through the filter element
3
is larger than that of the fuel supply passage between the fuel tank and the fuel injection pump
1
. Accordingly, due to less pressure loss of fuel passing through the filter element
3
, smaller mesh size of the filter element
3
is employed so that foreign material contained in fuel, even if it is minute, may be eliminated before entering the pump room
81
, that is, before entering the fuel injection pump
1
. As a result, foreign material hardly invades a plurality of sliding portions of the fuel injection pump
1
such as the sliding portions of the fuel amount adjusting valve and the sliding portions of the cam ring
52
and the plungers
41
, which results in securing smooth operation on the sliding portions, enabling highly accurate fuel amount control and enhancing reliability of the fuel injection pump
1
.
According to the embodiment mentioned above, since the cover
74
is easily detached from the casing
70
, it is easy to replace the filter element
3
accommodated in the filter room
82
.
Further, the filter room
82
and the pump room
81
are formed by dividing the inner space of the casing
70
into two spaces only with a partition
72
integrally provided therein so that simpler construction of the casing
70
, which is easily handled, can be achieved without increasing parts number thereof.
Claims
- 1. A fuel injection pump comprising:a housing having a cylinder; a moving member slidably and reciprocatingly movable in the cylinder, an inner circumference of the cylinder and an axial end of the moving member forming a pressure chamber; a drive shaft which is rotatably disposed in the housing and whose axial end partly protrudes out of the housing, the drive shaft having a cam member slidably in contact with the moving member; a casing fixed to an outer surface of the housing, the casing being provided at a position adjacent to the housing with a first room into which the axial end of the drive shaft protrudes and at a position remote from the housing with a second room mostly separated from but partly communicating with the first room; a feed pump mechanism accommodated in the first room and connected to the axial end of the drive shaft so that a feed pump is constituted by the first room, the feed pump mechanism and the drive shaft; a filter element accommodated in the second room; a casing cover detachably fixed to so as to be readily detachable from the casing on a side axially opposite to the first room with respect to the filter element for covering the second room so that, when the casing cover is detached from the casing, the filter element may be readily replaced by being drawn out in an axial direction of the drive shaft, the casing cover having a fuel inlet port that extends in parallel to an axial direction of the drive shaft and through which fuel is sucked to the second room and, then, flows via the filter element into the first room where the fuel is pressurized according to rotation of the drive shaft; and a fuel flow-in passage provided in the housing for delivering fuel from the feed pump to the pressure chamber, wherein fuel introduced to the pressure chamber from the feed pump is further pressurized and discharged to outside by the moving member that is driven by the cam member according to rotation of the drive shaft.
- 2. A fuel injection pump according to claim 1, wherein a cross sectional area of the filter element perpendicular to an axis thereof is larger than that of the fuel inlet port.
- 3. A fuel injection pump comprising:a housing having a cylinder; a moving member slidably and reciprocatingly movable in the cylinder, inner circumference of the cylinder and an axial end of the moving member forming a pressure chamber; a drive shaft which is rotatably disposed in the housing and whose axial end partly protrudes out of the housing, the drive shaft having a cam member slidably in contact with the moving member; a casing fixed to an outer surface of the housing, the casing being provided at a position adjacent to the housing with a first room into which the axial end of the drive shaft protrudes and at a position remote from the housing with a second room mostly separated from but partly communicating with the first room; a feed pump mechanism accommodated in the first room and connected to the axial end of the drive shaft so that a feed pump is constituted by the first room, the feed pump mechanism and the drive shaft; a filter element accommodated in the second room; a casing cover attached to the casing for covering the second room, the casing cover having a fuel inlet port through which fuel is sucked to the second room and, then, flows via the filter element into the first room where the fuel is pressurized according to rotation of the drive shaft; and a fuel flow-in passage provided in the housing for delivering fuel from the feed pump to the pressure chamber, wherein fuel introduced to the pressure chamber from the feed pump is further pressurized and discharged to outside by the moving member that is driven by the cam member according to rotation of the drive shaft, and wherein the first and second rooms are formed substantially in column shape and inner diameter of the first room is substantially equal to that of the second room.
- 4. A fuel injection pump comprising:a housing having a cylinder; a moving member slidably and reciprocatingly movable in the cylinder, inner circumference of the cylinder and an axial end of the moving member forming a pressure chamber; a drive shaft which is rotatably disposed in the housing and whose axial end partly protrudes out of the housing, the drive shaft having a cam member slidably in contact with the moving member; a casing fixed to an outer surface of the housing, the casing being provided at a position adjacent to the housing with a first room into which the axial end of the drive shaft protrudes and at a position remote from the housing with a second room mostly separated from but partly communicating with the first room; a feed pump mechanism accommodated in the first room and connected to the axial end of the drive shaft so that a feed pump is constituted by the first room, the feed pump mechanism and the drive shaft; a filter element accommodated in the second room; a casing cover attached to the casing for covering the second room, the casing cover having a fuel inlet port through which fuel is sucked to the second room and, then, flows via the filter element into the first room where the fuel is pressurized according to rotation of the drive shaft; and a fuel flow-in passage provided in the housing for delivering fuel from the feed pump to the pressure chamber, wherein fuel introduced to the pressure chamber from the feed pump is further pressurized and discharged to outside by the moving member that is driven by the cam member according to rotation of the drive shaft, and wherein the casing comprises a cylindrical casing body and a partition dividing axially inner space of the casing body into two spaces that constitute the first and second rooms, respectively.
- 5. A fuel injection pump according to claim 4, wherein the partition has a communication hole through which the first room communicates with the second room.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2001-355821 |
Nov 2001 |
JP |
|
US Referenced Citations (9)
Foreign Referenced Citations (3)
Number |
Date |
Country |
4103986 |
Aug 1991 |
DE |
19913774 |
Oct 2000 |
DE |
5-87264 |
Nov 1993 |
JP |