[0001] This invention relates to a fuel supply apparatus for an internal combustion engine,
more particularly to a rotary pump to be used for a fuel injection system for supplying
fuel to a diesel engine.
[0002] As one of prior art fuel injection pump, for example shown in US Patent Application
Publication No. US 2003/0044288 A1, it is known to us that the fuel injection pump
is provided with a feed pump for drawing fuel from a fuel tank and feeding the fuel
to a main pump of the fuel injection pump.
[0003] As shown in Fig. 6, the feed pump comprises a pump element 110 to be driven by a
cam shaft 100 of a main pump, a pump cover 120 for forming a rotor chamber and housing
therein the pump element 110, and a pump plate 130 for closing an opening side of
the rotor chamber in a liquid-sealing manner in combination with the pump cover 120,
wherein the pump cover 120 is screwed to a side surface of a pump housing 140.
[0004] Furthermore, as shown in Fig. 7, the pump element 110 is a trochoid type comprising
an outer rotor 111 having inner cogs and an inner rotor 112 disposed inside of the
outer rotor and having outer cogs, wherein the number of cogs of the outer rotor 111
is larger than that of the inner rotor 112 by one cog, and wherein a rotational center
0a of the outer rotor 111 is eccentric from that 0i of the inner rotor 112. As a result,
when the inner rotor 112 is driven by the cam shaft 100 and rotated, the outer rotor
111 is also rotated in conjunction with the inner rotor 112, so that a volume of a
working chamber formed by adjacent cogs will be gradually changed to draw fuel from
a fuel tank and pumps out the fuel to the main pump.
[0005] In the above described feed pump, as shown in Fig. 6, a side clearance between the
pump cover 120 and the pump element 110 is made smaller to minimize amount of fuel
leakage and to increase a fuel feed efficiency. If, however, the side clearance were
made too small, there would occur a problem of an abnormal wear, seizure or the like,
because variations of parts in manufacturing process may not be absorbed.
[0006] The present invention is made in view of the above problems, and it is an object
of the present invention to provide a fuel supply apparatus having a rotary pump which
improves a pump performance by making much smaller the side clearance in an axial
direction at both sides of the pump element without causing metal contact between
the pump element and the counterpart.
[0007] According to one of features of the present invention, a fuel supply apparatus comprises
a rotary pump having a pumping chamber, the volume of which varies in conjunction
with a rotation of a rotor, pressurizing the fuel sucked into the pumping chamber
and discharging the pressurized fuel. The rotary pump is characterized in that, multiple
through-holes are formed in a rotor, wherein the through-holes pass through in the
rotor in an axial direction, and side clearances formed at both sides of the rotor
are communicated with each other by those through-holes.
[0008] According to the above structure, pressures (thrust pressures) on both sides of the
rotor in the axial direction are equalized, since the side clearances formed at both
sides of the rotor are communicated with each other through those multiple through-holes
formed in the rotor. As a result, uniform side clearances on both sides of the rotor
can be attained. In other words, it has become possible to float the rotor. Accordingly,
the fuel feed efficiency can be increased by making much smaller the side clearance
formed at both sides of the rotor in its axial direction, and the problems of the
abnormal wear, seizures and the like can be suppressed because metal contacts between
the rotor forming the side clearances and other parts can be suppressed.
[0009] According to another feature of the invention, the multiple through-holes are formed
at an equal distance in a circumferential direction of the rotor.
[0010] According to such a structure, since the pressures (thrust pressures) on both sides
of the rotor are equalized through those multiple through-holes at those points of
the equal distance in the circumferential direction of the rotor, uniform side clearances
can be obtained on both sides of the rotor at almost all circumferential points of
the rotor. Accordingly, the fuel feed efficiency can be increased by making the side
clearances much smaller, and the problems of the abnormal wear, seizures and the like
can be suppressed because metal contacts between the rotor and other parts can be
suppressed.
[0011] According to a further feature of the invention, the rotary pump is a trochoid type
pump comprising an outer rotor having inner cogs and inner rotor disposed inside of
the outer rotor and having outer cogs, wherein the through-holes are formed at top
portions or bottom portions of the cogs.
[0012] Because of the through-holes formed in the inner rotor, which is driven by a cam
shaft, the inner rotor can be floated. As a result, metal contacts between the inner
rotor and other parts are suppressed during the rotation of the inner rotor, and thereby
the problems of the abnormal wear, seizures and the like can be suppressed.
[0013] According to still further feature of the invention, the rotary pump is provided
with the through-holes at every top portion or bottom portion of the cogs.
[0014] In this case, the pressures in the thrust direction can be equalized at every top
portion or bottom portion of the cogs of the inner rotor, the inner rotor can be much
more surely floated to suppress the metal contacts between the inner rotor and the
other parts.
[0015] According to a further feature of the invention, an outer rotor of the rotary pump
is provided with multiple through-holes, which pass through in the axial direction,
at top portions or bottomportions of the cogs, wherein the multiple through-holes
are arranged at an equal distance in a circumferential direction of the outer rotor.
[0016] Since the through-holes are formed in the outer rotor in addition to the through-holes
in the inner rotor, thrust pressures to the outer rotor can be likewise equalized.
As a result, the outer rotor can be positively floated together with the inner rotor.
[0017] According to a further feature of the present invention, the rotary pump is used
as a feed pump of a fuel injection pump for diesel engines, wherein the feed pump
is formed with a circular rotor chamber and comprises a pump cover for housing the
pump element of the inner and the outer rotors in the rotor chamber, and a pump plate
for closing an open end of the rotor chamber in a liquid-sealing manner together with
the pump cover. The pump plate is formed with fuel ports to be communicated to the
rotor chamber, and the pump cover is screwed to a side surface of a housing of the
fuel injection pump, so that the pump plate is pressed against the side surface.
[0018] According to the above structure, the side clearance between the pump element and
the pump cover as well as the side clearance between the pump element and the pump
plate can be made smaller to increase the fuel feed efficiency and thereby increase
a pump performance as the feed pump.
[0019] According to a further feature of the invention, the rotary pump is a vane type pump
comprising a rotor formed with vane grooves and vanes movably inserted into the vane
grooves.
[0020] In the vane type pump, since the rotor having vanes is driven by a cam shaft and
is rotated, the rotor can be floated by equalizing thrust pressures with multiple
through-holes formed in the rotor. As a result, the metal contacts between the rotor
and the other parts can be suppressed.
[0021] The above and other objects, features and advantages of the present invention will
become more apparent from the following detailed description made with reference to
the accompanying drawings. In the drawings:
Fig. 1 is a cross-sectional view of a feed pump according to a first embodiment of
the present invention;
Fig. 2 is a front view of a pump element of the feed pump shown in Fig. 1;
Fig. 3 is a cross-sectional view of a fuel injection pump to which the feed pump of
the present invention is applied;
Fig. 4 is a front view of a pump element according to a second embodiment of the present
invention;
Fig. 5 is a front view of a pump rotor according to a third embodiment of the present
invention;
Fig. 6 is a cross-sectional view of a prior art feed pump; and
Fig. 7 is a front view of a pump element of the feed pump shown in Fig. 6.
(First Embodiment)
[0022] The present invention will be explained below with reference to the embodiments.
[0023] In the first embodiment, an embodiment is explained in which a fuel supply apparatus
of the invention is used in a fuel injection pump of a common rail fuel injection
system for diesel engines.
[0024] Fig. 1 is a cross-sectional view of a feed pump, Fig. 2 is a front view of a pump
element, and Fig. 3 is a cross-sectional view of a fuel injection pump.
[0025] As shown in Fig. 3, the fuel injection pump 1 is provided with a main pump 2 for
pressurizing and pumping out fuel and a feed pump 3 (See Fig. 1) for drawing the fuel
from a fuel tank (not shown) and feeding the fuel to the main pump 2.
[0026] The main pump 2 comprises a cam shaft 4 to be rotated being driven by a diesel engine
(not shown), a pump housing 5 for rotationally supporting the cam shaft 4, a plunger
7 being driven by the cam shaft 4 for reciprocally moving in a cylinder 6, and so
on.
[0027] A cam 8 which has a circular cross-sectional configuration is fixed to the cam shaft
4, wherein a rotational center thereof is eccentric to that of the cam shaft. A cam
ring 10 is rotationally supported at an outer periphery of the cam 8 over a bush 9.
A pair of flat surfaces are formed in the cam ring 10, wherein the flat surfaces are
opposing to each other in a radial direction of the cam 8.
[0028] A pair of cylinder heads 11 is assembled to the pump housing 5 in a liquid-sealing
manner, wherein the cylinder heads 11 are opposing to each other in the radial direction
of the cam shaft 4.
[0029] The cylinder head 11 is formed with a cylinder 6, into which the plunger 7 is inserted,
a pump-out port 12 to be communicated with the cylinder 6, and so on. A check valve
13 is assembled to the cylinder head at an opposite side of the cylinder 6. A pipe
joint 15 is screwed into the cylinder head at an outlet side of the pump-out port
12 for connecting to a fuel pipe 14.
[0030] The check valve 13 is disposed between a fuel passage (not shown) to be communicated
with a feed pump and the cylinder 6. The check valve 13 will be opened during a suction
stroke at which the plunger 7 will be downwardly moved in the cylinder 6 (inwardly
moved), to introduce fuel fed from the feed pump 3 into the inside of the cylinder
6, whereas the check valve 13 will be closed during a pumping out stroke at which
the plunger 7 will be upwardly moved in the cylinder 6 (outwardly moved) so that the
fuel introduced into the cylinder 6 is prevented from flowing back to the feed pump
3.
[0031] The pump-out port 12 is formed with a small diameter port and a large diameter port.
A seat surface of a circular conic is formed between the small and large diameter
ports (See Fig. 3). A ball valve 17 is disposed in the pump-out port 12 and is urged
by a spring 16 towards the seat surface, so that the small and large diameter ports
are blocked by this ball valve 17.
[0032] The ball valve 17 will be lifted from the seat surface when a pressure of fuel, which
is pressurized by the plunger 7 during the pumping out stroke, becomes higher than
the urging force of the spring 16, and thereby the small and large diameter ports
are communicated with each other.
[0033] The plunger 7 has a plunger head 7a at its inner side end and the plunger head 7a
is urged by a spring 18 and pressed against an outer surface (flat surface) of the
cam ring 10. When the rotation of the cam shaft 4 is transmitted to the cam ring 10
via the cam 8, the cam ring 10 moves with an orbital motion along its orbit which
is displaced from the rotational center of the cam shaft 4 by a certain distance,
while the cam ring 10 is keeping its orientation (The cam ring 10 is not rotated on
its axis and on an axis of the cam 8). As a result, the plunger 7 pressed against
the flat surface of the cam ring 10 is reciprocally moved in the cylinder 6.
[0034] The feed pump 3 comprises a pump element PE, a pump cover 19 and a pump plate 20,
as explained below. The feed pump 3 is fixed to a side surface of the pump housing
5 by bolts 21, as shown in Fig. 3.
[0035] The pump element PE is a well known trochoid type pump, comprising an outer rotor
22 having inner cogs and an inner rotor 23 disposed inside of the outer rotor 22 and
having outer cogs, wherein the inner rotor is connected to the cam shaft 4 via a key
so that the inner rotor will be rotated by the cam shaft 4.
[0036] The outer rotor 22 has cogs, the number of which is larger than that of the inner
rotor 23 by one cog, and the rotational center 0a of the outer rotor 22 is eccentrically
displaced from the rotational center 0i of the inner rotor 23 (See Fig. 2). Accordingly,
when the inner rotor 23 is rotated by the cam shaft 4, the outer rotor 22 is rotated
in conjunction with the inner rotor 23, so that the volume of working chambers formed
by the cogs will be changed to pump out the fuel drawn from the fuel tank to the main
pump 2.
[0037] As shown in Fig. 2, through-holes 22a and 23a, which pass through the outer and inner
rotors 22 and 23 in an axial direction, are respectively formed in the outer rotor
22 and the inner rotor 23. There are provided with multiple through-holes 22a and
23a in the outer and inner rotors 22 and 23, and those through-holes are formed at
an equal distance in a circumferential direction (more exactly, at every cog top portion
of the outer and inner rotors 22 and 23) .
[0038] The pump cover 19 is formed with a circular rotor chamber 19a for housing therein
the pump element PE, as shown in Fig. 1. An inner diameter of the rotor chamber 19a
is made slightly larger than an outer diameter of the pump element PE (namely, an
outer diameter of the outer rotor 23), so that the outer rotor 23 may be rotated therein.
Awidth of the rotor chamber 19a is made slightly larger than a width of the pump element
PE (a thickness in a longitudinal direction), so that side clearances of a certain
distance between the pump element PE and inner surfaces of the pump chamber are kept.
[0039] The pump plate 20 is assembled to the pump cover 19 in a liquid-sealing manner to
close an opening of the rotor chamber 19a. The pump plate 20 is formed with a center
bore, through which the cam shaft 4 passes, and fuel ports 20a (an inlet port and
an outlet port) around the center bore (See Fig. 1). The fuel ports 20a are communicated
to the working chambers 24 formed between the outer rotor 22 and the inner rotor 23.
[0040] An operation of the above first embodiment will be explained. In the above feed pump
3, the multiple through-holes 22a and 23a are respectively formed in the outer and
inner rotors 22 and 23 and furthermore those multiple through-holes 22a and 23a are
arranged at equal distance in the circumferential direction of the rotors 22 and 23.
Since the side clearances formed on the both sides of the rotors 22 and 23 in the
axial direction are communicated with each other through those multiple through-holes
22a and 23a, the pressures in the thrust direction at the both sides of the rotors
22 and 23 will be equalized. As a result, uniform side clearances can be obtained
at both sides of the rotors 22 and 23.
[0041] According to the above structure, the outer and inner rotors 22 and 23 can be floated
without contacting with the pump cover 19 and the pump plate 20. In particular, since
the through-holes 23a are formed at every cog top portions of the inner rotor 23,
which correspond to an outer periphery of the inner rotor, an inclination of the inner
rotor 23 can be effectively suppressed and thereby the uniform side clearances at
both of the longitudinal sides along the peripheries of the inner rotor 23 can be
obtained.
[0042] Accordingly, the problems of the abnormal wear and seizures and the like can be suppressed
by preventing the metal contacts between the pump element PE and the pump cover 19
and the pump plate 20, to finally increase the performance of the feed pump 3, even
when the side clearances between the pump element PE and the pump cover 19 are made
smaller to increase the fuel feed efficiency.
[0043] In the above first embodiment, the through-holes 22a and 23a are formed in the both
outer and inner rotors 22 and 23. It is, however, possible to obtain a sufficient
effect (suppress of the abnormal wear and seizures, or the like), when the through-holes
23a are formed only in the inner rotor 23 which is directly driven by the cam shaft
4.
(Second Embodiment)
[0044] Fig. 4 is a front view of pump element PE according to a second embodiment.
[0045] In the first embodiment, the multiple through-holes 22a and 23a are formed in the
outer and inner rotors 22 and 23 at equal distance in the circumferential direction.
It is, however, not necessary to arrange the through-holes at equal distance. As shown
in Fig. 4, the through-holes 23a can be formed in the inner rotor 23 at non-equivalent
distances in the circumferential direction. Although only the through-holes for the
inner rotor 23 are shown in Fig. 4, the through-holes 22a can be formed in the outer
rotor 22 at non-equivalent distances in the circumferential direction, as in the same
manner for the inner rotor 23.
(Third Embodiment)
[0046] Fig. 5 is a front view of a rotor 25 according to a third embodiment.
[0047] The third embodiment is an embodiment in which the present invention of the rotary
pump is applied to a vane type pump.
[0048] The vane type pump has, as shown in Fig. 5, a rotor 25 formed with multiple vane
grooves 25a at its outer periphery at equal distance in the circumferential direction,
and vanes 26 respectively and movably inserted into the vane grooves 25a.
[0049] When the multiple through-holes 25b are formed in the rotor 25 and the rotor 25 is
floated, as in the same manner to the first embodiment, metal contacts with other
parts can be prevented and thereby the problems of the abnormal wear and seizures
and the like can be suppressed.
[0050] In this embodiment as shown in Fig. 5, the through-holes 25b are formed at both sides
to the respective vanes 26 and the circumferential distance of the through-holes 25b
between the respective vanes 26 is arranged to be equal to each other. However, the
circumferential distance of the through-holes 25b is not necessary to be equal but
to be non-equivalent.
(Other Embodiments)
[0051] The above embodiments are explained as those embodiments in which the fuel supply
apparatus of the invention is used in the fuel injection pump of the common rail fuel
injection system for diesel engines. The present invention is not limited to these
embodiments, and the present invention can be used for a fuel pump for a gasoline
engine.
[0052] A fuel feed pump according to the present invention improves its pump performance
by making smaller side clearances in an axial direction at both sides of a pump element
PE.
[0053] Multiple through-holes (22a and 23a) passing through in an axial direction are respectively
formed at top portions of cogs of the outer rotor (22) and the inner rotor (23), which
form a pump element (PE) of a feed pump (3). Accordingly, pressures in the thrust
direction at both axial sides of the rotors (22 and 23) can be equalized, since the
side clearance formed at both axial sides of the rotors (22 and 23) are communicated
with each other. As a result, since the rotors (22 and 23) can be floated, without
contacting with the pump cover (19) and the pump plate (20), the abnormal wear and
seizures can be suppressed, even when side clearance between the pump cover (19) and
the pump element (PE) is made smaller.
1. A fuel supply apparatus comprising:
a rotary pump (3) having a rotor (22, 23 and 25) and a pumping chamber (24), volume
of the pumping chamber (24) being varied in conjunction with rotation of the rotor
(22, 23 and 25), and for pressurizing fuel sucked into the pumping chamber (24) and
discharging the pressurized fuel, wherein
multiple through-holes (22a, 23a and 25b) are formed in the rotor (22, 23 and 25b)
in its axial direction, and
side clearances formed at both sides of the rotor (22, 23 and 25) are communicated
with each other though those through-holes (22a, 23a and 25b).
2. A fuel supply apparatus according to Claim 1, wherein
the multiple through-holes (22a and 23a) are formed at an equal distance in a circumferential
direction of the rotor (22 and 23).
3. A fuel supply apparatus according to Claim 1, wherein
the rotary pump (3) is a trochoid type pump comprising an outer rotor (22) having
inner cogs and an inner rotor (23) disposed inside of the outer rotor (22) and having
outer cogs, wherein the through-holes (22a and 23a) are formed at top portions or
bottom portions of the cogs.
4. A fuel supply apparatus according to Claim 3, wherein
the rotary pump (3) is provided with the through-holes (22a and 23a) at every top
portion or bottom portion of the cogs.
5. A fuel supply apparatus according to Claim 3, wherein
an outer rotor (22) of the rotary pump (3) is provided with multiple through-holes
(22a), which pass through in the axial direction, at top portions or bottom portions
of the cogs.
6. A fuel supply apparatus according to one of Claim 3, wherein the fuel supply apparatus
is a fuel injection pump (1) for a diesel engine for which the rotary pump (3) is
used as a feed pump,
wherein the feed pump (3) comprises:
a circular rotor chamber (19a);
a pump cover (19) for housing a pump element (PE) of the inner and the outer rotors
(22 and 23) in the rotor chamber (19a); and
a pump plate (20) for closing an open end of the rotor chamber (19a) in a liquid-sealing
manner together with the pump cover (19),
wherein the pump plate (20) is formed with fuel ports (20a) to be communicated
to the rotor chamber (19a), and the pump cover (19) is screwed to a side surface of
a housing (5) of the fuel inj ection pump (1), so that the pump plate (20) is pressed
against the side surface.
7. A fuel supply apparatus according to Claim 1, wherein
the rotary pump is a vane type pump comprising a rotor (25) formed with vane grooves
(25a) and vanes (26) movably inserted into the vane grooves (25a).
8. A fuel supply apparatus for an internal combustion engine comprising:
a main pump (1) for supplying a high pressure fuel to the engine; and
a feed pump (3) fixed to the main pump (1) for feeding fuel from a fuel tank to the
main pump (1), wherein the feed pump including:
a pump housing (19 and 20) forming a pumping chamber (19a); and
a pump rotor (22, 23 and 25) operatively connected to the main pump (1) and rotationally
supported in the pumping chamber (19a),
wherein multiple through-holes (22a, 23a and 25b) are formed in the rotor (22, 23
and 25) so that side clearances between the pump housing (19 and 20) and both side
surfaces of the rotor (22, 23 and 25) are communicated with each other.
9. A fuel supply apparatus according to Claim 8, wherein the multiple through-holes are
formed in the rotor at an equal distance in a circumferential direction.
10. A fuel supply apparatus according to Claim 8, wherein the feed pump (3) is of a trochoid
type pump comprising:
an outer rotor (22) rotationally supported in the pump housing (19 and 20) and having
inner cogs; and
an inner rotor (23) disposed inside of the outer rotor (22) and having outer cogs,
wherein the multiple through-holes (22a and 23a) are formed at the respective
cogs.