Fuel injection pump of internal combustion engine

A fuel injection pump including a pump body formed with a plunger sliding bore, and a discharge valve mounted on one end portion of the plunger sliding bore corresponding to an upper end portion of a plunger so that said end portion of the plunger sliding bore functions as a guide for the discharge valve. This arrangement enables the plunger barrel and discharge valve guide member of a fuel injection pump of the prior art to be dispensed with and permits the number of the parts of the pump, the size of the pump, the weight of the pump and the production to be reduced.

This invention relates to a fuel injection pump suitable for use with an 
internal combustion engine. 
In one type of fuel injection pump known in the art, particularly a Bosch 
type pump, a barrel for receiving a plunger and a discharge valve guide 
member for mounting a discharge valve are secured in a pump body. In this 
case, there arises the problem that the fuel might leak between the barrel 
and the discharge valve guide member and the weight of the pump increases 
with an increase in the number of parts. Also, the discharge valve guide 
member should be attached to the pump body while the discharge valve is 
being mounted on its guide member, thereby rendering the discharge valve 
mounting structure complex in construction. 
A first object of this invention is to provide a fuel injection pump of an 
internal combustion engine wherein a pump body is formed with a plunger 
sliding bore having a discharge valve mounted at an end thereof which 
corresponds to the top of a plunger so that the discharge valve may be 
guided by such end of the plunger sliding bore, whereby the barrel and the 
discharge valve guide member used in this type of fuel injection pump of 
the prior art can be dispensed with and the number of parts of the pump 
can be reduced, to enable the overall size and weight of the pump to be 
reduced and permit the discharge valve mounting structure to be rendered 
simple in construction. 
A second object is to form, in a fuel injection pump of the aforesaid 
construction, a spring seat for a plunger returning spring and a flange 
for positioning the pump body with respect to an engine body integral with 
the pump body, to thereby reduce the number of parts and obtain an overall 
compact size in a fuel injection pump. 
A third object is to connect, in a fuel injection pump of the 
first-mentioned construction, the pump body with the plunger through a 
plunger returning spring into a unitary structure by a simple 
construction, so that the number of parts can be reduced and the size of 
the pump can be reduced while insertion into and withdrawing from the 
engine body of the pump is facilitated when assembling and disassembling 
are effected. 
A fourth object is to provide, in a fuel injection pump of the type in 
which the pump body and the plunger are rendered into a unitary structure, 
a spring support structure for the plunger returning spring which enables 
the plunger to move smoothly in vertical sliding movement and rotary 
movement. 
A fifth object is to provide, in a fuel injection pump of the 
first-mentioned construction, an injected fuel metering mechanism by 
utilizing a portion of a plunger actuating tappet, to thereby reduce the 
number of parts and the size of the pump. 
A sixth object is to form, in a fuel injection pump of the first-mentioned 
construction, a disk-shaped flange on the pump body which is forced 
against the engine body by a plate member and secured thereto, so that the 
pump body can have its size reduce, working can be facilitated and the 
space required for mounting the pump can be reduced. 
A seventh object is to provide, in a fuel injection pump of the 
first-mentioned construction, a simplified fuel line mounting structure.

In FIGS. 1 and 2, the numeral 1 designates a pump body of the fuel 
injection pump comprising one embodiment of this invention which is formed 
as a single entity from case-hardening steel [chromium-molybdenum steel 
SCM21 of JIS (Japanese Industrial Standard)], bearing steel (SUJ2 or SUF3 
of JIS) or nitriding steel which can be subjected to hardening treatment. 
The pump body 1 is formed with a plunger sliding bore 2 for permitting a 
plunger 2 to move in sliding movement therein, so that the pump body 1 
will serve concurrently as a barrel for permitting the plunger to move in 
sliding movement. The plunger sliding bore 3 has its inner peripheral 
surface hardened when the outer peripheral surface of the pump body 1 is 
hardened. 
The plunger sliding bore 3 into which the plunger 2 is inserted from below 
includes an end portion 3a corresponding to an upper portion 2a of the 
plunger 2 which functions as an opening for slidably mounting a discharge 
valve 4. The receiving opening at the end portion 3a may have a diameter 
distinct from the inner diameter of the plunger sliding bore 3. 
The plunger sliding bore 3, the upper portion 2a of the plunger 2 and the 
discharge valve 4 define a chamber 5, and the plunger 2 has an oblique 
groove 2b on its outer periphery. The chamber 5 is maintained in 
communication with the oblique groove 2b through a passage 2c extending 
downwardly from the center of the plunger upper portion 2a and then 
extending radially outwardly to open in the oblique groove 2b. 
The pump body 1 includes an externally threaded upper portion 6 formed 
integrally therewith, and the discharge valve 4 fitted in the end portion 
3a of the plunger sliding bore 3 serving as a receiving opening is 
maintained in a closed position by the biasing force of a discharge valve 
spring 8 mounted in the interior of a discharge valve retaining collar 7 
threadably fitted over the upper cylindrical portion 6. 
The pump body 1 includes a lower end serving as a spring seat 10 for a 
plunger returning spring 9 and has a cylindrical guide 11 extending 
downwardly integrally from the center of the spring seat 10. 
The guide cylinder 11 has an outer peripheral surface including an annular 
engaging surface 11a of a diameter slightly larger than the inner diameter 
of the plunger returning spring 9 extending downwardly from the spring 
seat 10, and a guide surface 11b of a diameter substantially equal to the 
inner diameter of the plunger returning spring 9 extending further 
downwardly from the annular engaging surface 11a. Simultaneously as the 
plunger sliding bore 3 is hardened as described hereinabove, the spring 
seat 10, annular engaging surface 11a and guide surface 11b are hardened. 
The pump body 1 is formed on its outer periphery in a position above the 
spring seat 10 with a flange 13 for positioning the pump body 1 with 
respect to an engine body 12. 
The plunger returning spring 9 is force fitted at one end portion thereof 
over the annular engaging surface 11a so that the former is secured to the 
pump body 1. 
Meanwhile the plunger 2 has secured to its lowermost end a lever 14 for 
operating the plunger 2 in rotary movement, and a spring rest 16 is 
loosely fitted over a flange 15 formed on the plunger 2 in a position 
immediately above the lever 14. A ring 17 for preventing dislodging of the 
plunger 2 is mounted immediately above the spring rest 16 so that the 
latter is loosely fitted over the plunger 2 and held in place between the 
flange 15 and ring 17. 
The spring rest 16 has an outer diameter slightly larger than the inner 
diameter of the plunger returning spring 9 so that the latter can be 
secured to the former by force fitting the other end portion thereof over 
the former. 
Thus the plunger 2 is resiliently connected to the pump body 1 to form a 
unit therewith through the plunger returning spring 9. 
FIG. 3 shows a modification of the arrangement for connecting the plunger 2 
to the pump body 1 as a unit through the plunger returning spring 9. In 
this modification, the annular engaging surface 11a in the lower portion 
of the pump body 1 is formed with a spring securing recess 18 which may be 
a hole, cutout or groove, and the spring rest 16 is also formed on its 
outer periphery with a similar spring securing recess 19. The plunger 
returning spring 9 is formed integrally at its upper and lower ends with 
radially inwardly bent portions 20 and 21 respectively. 
The plunger returning spring 9 is force fitted at its upper and lower end 
portions over the outer peripheral surfaces of the annular engaging 
portion 11a of the guide cylinder 11 of the pump body 1 and the spring 
rest 16 respectively so as to be frictionally held in place. At the same 
time, the plunger 2 can be positively connected resiliently to the pump 
body 1 to provide a unitary structure by fitting the bent portions 20 and 
21 at the upper and lower ends of the plunger returning spring 9 in the 
engaging recess 18 on the annular engaging surface 11a of the pump body 1 
and the engaging recess 19 on the outer periphery of the spring rest 16 
respectively. 
Referring to FIG. 1 again, 12a is a cylinder of the engine. The pump body 1 
is formed with a fuel introducing and returning port 22 and has a fuel 
passage 23 connected to the port 22. 24 is a fuel injection tube, and 47 
is a tappet for a suction and exhaust valve of the engine. 
The fuel injection pump of the aforesaid construction is mounted on the 
engine body 12 in such a manner that the spring rest 16 is positioned 
against an upper surface of a tappet 25 mounted on the engine body 12, so 
that a cam shaft 26 maintained in engagement with the undersurface of the 
tappet 25 at all times by the biasing force of the plunger returning 
spring 9 rotates to move the tappet 25 vertically to enable the plunger 2 
to move in reciprocatory movement through the bore 3. 
As clearly shown in FIG. 4, the tappet 25 is formed on its upper surface 
with a recess 27 for receiving an outer perihery 16a of the spring rest 
16, and an arcuate notch 28 extending radially outwardly from the center 
of the recess 27 to diverge toward the outer periphery of the tappet 25. 
The notch 28 receives therein the lever 14 attached to the lower end of the 
plunger 2 for pivotal movement. The notch 28 is formed with opposite ends 
28a and 28b which restrict the range of pivotal movement of the lever 14 
or angular rotation of the plunger 2 supporting the lever 14 so that the 
upper limit and the lower limit of the amount of fuel injected can be 
regulated. 
As shown in FIG. 1, the tappet 25 is mounted on the engine body 12 for 
vertical movement and formed on its outer periphery with an axial groove 
29 for receiving a pin 30 secured to the engine body 12, to prevent the 
tappet 25 from rotating while allowing its vertical movement. 
With the pump body 1 mounted on the engine body 12 as shown in FIG. 1, the 
lever 14 is engaged in the notch 28 on the upper end of the tappet 25 and 
the spring rest 16 is fitted in the recess 27 on the upper surface of the 
tappet 25. 
Thus rotation of the cam shaft 26 moves the tappet 25 and spring rest 16 
vertically as a unit. At this time, the spring rest 16 is prevented from 
moving radially by the recess 27, so that an annular space S is formed at 
all times between the outer periphery of the plunger 2 and the inner 
periphery of the spring rest 16 as shown in FIG. 1. By this arrangement, 
the plunger 2 can be readily operated by the lever 14 to rotate angularly 
even when the plunger 2 is moving in vertical reciprocatory movement, to 
readily and smoothly effect control of the amount of the injected fuel. 
The lever 14 supports at its outer end a pin 31 which extends downwardly to 
be received in a bifurcated portion 33a of a member 33 secured to an upper 
end portion 32a of the inverted U-shape of a governor lever 32 as shown in 
FIG. 1. 
In FIG. 1, the engine body 12 supports a rotatable shaft 34 which in turn 
supports on its inner end portion a bent lower end portion 32b of the 
governor lever 32 so that the latter can rotate with the rotatable shaft 
34 about its axis. A coil spring 35 has ends 35a and 35b secured on a 
spring rest 34a mounted on the shaft 34 and in a small opening 32c formed 
in the lower end portion 32b of the governor lever 32 respectively. 
In FIG. 1, 36 is a governor body, and 37 and 38 are gears for driving the 
governor body 36. 39 designates governor centrifugal weights extending 
from the governor body 36 downwardly from the plane of FIG. 1. 40 is a 
thruster activated by the governor centrifugal weights 39. A lug 41 
projects from the lower end portion 32b of the governor lever 32 at right 
angles thereto into engagement with the top of the thruster 40. Rotation 
of the rotary shaft 34 in either of the directions indicated by arrows 
moves the governor lever 32 in pivotal movement about the shaft 34 through 
the coil spring 35, to thereby rotate the plunger 2 through the member 33, 
pin 31 and lever 14. Thus positioning of the governor lever 32 and plunger 
2 is effected, to thereby make the torsional biasing force of the coil 
spring 35 determined by the degree of angular rotation of the shaft 34 
match the expanding force of the governor centrifugal weights 39 through 
the thruster 40. 
When the engine speed increases, the governor centrifugal weights 39 are 
expanded to bring the thruster 40 into contact with the lug 41, to thereby 
move the governor lever 32 counterclockwise in pivotal movement about the 
axis of the shaft 34. This rotates the plunger 2 clockwise and decreases 
the distance between the oblique groove 2b and the fuel returning port 22, 
so that termination of fuel injection is advanced and the amount of 
injected fuel is reduced. This decreases the engine speed to a 
predetermined number of revolutions. 
The structure for mounting the fuel injection pump on the engine body 12 
will now be described by referring to FIGS. 1, 5 an 6. In FIGS. 1 and 5, 
the fuel injection pump is shown as being mounted on the engine body 12 in 
such a manner that the tappet 25 is in engagement with the cam shaft 26 
and the flange 13 of the pump body 1 is positioned against an edge portion 
42a of a mounting opening 42 formed in the engine body 12 in a position 
above the cam shaft 26. 
In the aforesaid mounting structure, the lower end portion of the plunger 2 
and the spring rest 16 are positioned against the upper surface of the 
tappet 25. As shown in FIG. 5, the flange 13 is secured in place by being 
pressed by a plate member 44 bolted to the engine body 12 as shown at 43. 
In the aforesaid mounting structure, the plate member 44 is formed at one 
end thereof with a leg 44a which is positioned against the upper surface 
of the engine body 12 and at the other end thereof with a bifurcation 
having pressing portions 44b pressing against the upper surface of the 
flange 13. The portion of the pump body 1 above the flange 13 is formed on 
its outer periphery with two flat surface portions 45 diametrically 
opposed to each other and spaced apart from each other a distance 
substantially corresponding to the spacing between the two pressing 
portions 44b of the bifurcation. Thus by inserting through the mounting 
opening 42 of the engine body 12 the lower end portion of the fuel 
injection pump assembled into a unitary structure beforehand to fit the 
spring rest 16 in the recess 27 on the upper surface of the tappet 25 and 
connecting the plate member 44 to the engine body 12 by the bolt 43 after 
bringing the pressing portions 44b of the plate member 44 into index with 
the respective flat surface portions 45 of the pump body 1 so that the 
pressing portions 44b press against the upper surface of the flange 13, it 
is possible to mount the fuel injection pump in a predetermined position 
and securely hold same in place. 
FIG. 6 shows a modification of the mounting structure in which a plate 
member 44' is elliptic in shape and formed in the center with an opening 
46 for inserting the portion of the pump body 12 above the flange 13 
therethrough. The elliptic plate member 44' is secured at opposite end 
portions thereof to the engine body 12 by two bolts 43, to thereby secure 
the pump body 1 to the engine body 12 by pressing the flange 13 against 
the upper surface of the engine body 12. 
The plate members 44 and 44' are preferably formed of spring steel or other 
resilient metal. 
FIGS. 7 and 8 show another embodiment of the fuel injection pump according 
to the invention. In this embodiment, the pump body 1 includes a minor 
diameter cylindrical portion 49 disposed above an annular offset 48 formed 
substantially midway between opposite ends of the pump body 1. The minor 
diameter cylindrical portion 49 has on its periphery an upper threaded 
surface 49a and a lower smooth surface 49b, and is formed with a fuel 
introducing and returning port 22. 
A spherical pipe joint 50 including a pipe 51 connected to the fuel 
introducing and returning port 22 is fitted over the smooth surface 49b of 
the cylindrical portion 29, with seal members 52 and 53 as of rubber being 
placed over and beneath the joint 50. Meanwhile the discharge valve 
retaining collar 7 is threadably fitted over the threaded surface 49a to 
keep the spherical pipe joint 50 in hermetically sealed condition in being 
secured to the pump body 1. The pipe 51 has connected thereto a fuel 
supply line, not shown. 
The spherical pipe joint 50 is formed in its interior with a fuel chamber 
54 defined between the smooth surface 49b and the joint 50 for the fuel 
sucked through the pipe 51 or the fuel escaping through the port 22. 
The fuel injection pump of the aforesaid constructional form operates in 
the same manner as the conventional fuel injection pump of the Bosch type, 
so that description thereof will be omitted. 
The fuel injection pump according to the invention can achieve many 
advantages which will be summarized as follows: 
1. The arrangement that the pump body 1 is formed with the plunger sliding 
bore 3 for allowing the plunger to move in sliding reciprocatory movement 
therein and the plunger sliding bore 3 has the discharge valve 4 mounted 
at its end portion 3a corresponding to the upper portion 2a of the plunger 
2 so that the discharge valve 4 is guided by the end portion 3a enables 
the barrel and the discharge valve guide member of a Bosh type fuel 
injection pump of the prior art to be dispensed with. Thus the invention 
is conducive to reduced number of parts, reduced size of the pump body 1 
and reduced cost and permits the weight of the pump to be greatly reduced 
as compared with a conventional fuel injection pump of the same capacity. 
The elimination of the barrel and discharge valve guide member obviates the 
problem of the fuel leakage between these parts and greatly simplifies the 
discharge valve mounting structure. 
2. Formation of the disk-shaped flange 13 integrally on the outer periphery 
of the pump body 1 for positioning and securing the pump body 1 to the 
engine body 12 facilitates mounting of the pump body 1 on the engine body 
12. The provision of the spring seat 10 for the plunger returning spring 9 
and the guide cylinder 11 formed integrally with the pump body 1 in its 
lower portion enables the plunger returning spring mounting structure to 
be simplified because the pump body 1 serves concurrently as a spring rest 
for the plunger returning spring 9. 
Thus the number of parts can be reduced and an overall compact size can be 
obtained in a fuel injection pump. At the same time, machining of the pump 
body is facilitated, and since the pump body 1 is formed of hardenable 
material, such as case-hardening steel, bearing steel, nitriding steel, 
etc., hardening of the inner peripheral surface of the plunger sliding 
bore 3, spring seat 10 and guide cylinder 11 can be effected 
simultaneously. 
3. The arrangement that the plunger 2 is resiliently connected to the pump 
body 1 to provide a unitary structure by mounting the plunger returning 
spring 9 at upper and lower ends thereof on the annular engaging surface 
11a of the cylindrical guide 11 projecting downwardly from the pump body 1 
integrally therewith and the spring rest 16 attached to the lower end of 
the plunger 2 respectively enables the plunger 2 having the plunger 
returning spring 9 connected to its lower end portion to be readily 
assembled with the pump body 1. This facilitates assembling and 
disassembling of a fuel injection pump, and the formation of the pump 
body, plunger and plunger returning spring into a unitary structure 
facilitates attaching and detaching of these parts to the engine body 12. 
The plunger returning spring 9 serves concurrently as means for connecting 
the plunger 2 to the pump body 1 and the use of special connecting means 
can be eliminated, thereby enabling the number of parts to be reduced. 
This is conducive to reduced overall size of the fuel injection pump and 
reduced production cost thereof. 
The annular engaging surface 11a of the pump body 1 and the outer 
peripheral surface of the spring rest 16 are formed with the spring 
securing recesses 18 and 19 respectively, and the plunger returning spring 
9 is formed at its upper and lower ends with radially bent portions 20 and 
21 respectively, so that the bent portions 20 and 21 can be engated in the 
spring securing recesses 18 and 19 respectively. This enables the pump 
body 1, plunger 2 and plunger returning spring 9 to be positively formed 
into a unitary structure. 
By fitting the ring 17 over the plunger 2 in a position immediately above 
the spring rest 16 so that the ring 17 may contact with the upper surface 
of the spring rest 16, it is possible to positively prevent dislodging of 
the plunger 2 by simple means, thereby contributing to a reduction in the 
number of parts and the size of the pump. 
4. The spring rest 16 for the plunger returning spring 9 is loosely fitted 
over the lower end portion of the plunger 2 and locked in position in such 
a manner that the annular space S is defined between the inner peripheral 
surface of the spring rest 16 and the outer peripheral surface of the 
plunger 2, and the tappet 25 is formed on its upper surface with the 
recess 27 for receiving the outer periphery 16a of the lower end of the 
spring rest 16. By this arrangement, the spring rest 16 moves vertically 
with the plunger 2 as a unit while being received in the recess 27 during 
vertical movement of the tappet 25, so that the spring rest 16 is confined 
by the recess 27 and prevented from moving radially. Thus during operation 
of the fuel injection pump, the annular space S exists at all times 
between the outer periphery of the plunger 2 and the inner periphery of 
the spring rest 16 and these parts are prevented from coming into contact 
with each other. This permits rotation of the plunger 2 for adjusting the 
amount of the injected fuel to be effected readily and smoothly. 
The provision of the recess 27 on the upper surface of the tappet 25 for 
receiving the outer periphery 16a of the lower portion of the spring rest 
16 enables positioning of the spring rest 16 to be readily effected when 
the pump body 1 is assembled. 
5. The lever 14 for rotating the plunger 2 to adjust the amount of injected 
fuel is connected to the lower end of the plunger 2, and the notch 28 for 
permitting the lever 14 to be engaged therein is formed on the upper 
surface of the tappet 25. The length of the pump body 1 can be reduced by 
an amount corresponding to the depth of the notch 28, thereby contributing 
to a reduction in the size of the pump. 
The notch 28 has the opposite end surfaces 28a and 28b functioning to 
restrict the range of pivotal movement of the lever 14, so that the need 
to provide special means for regulating the upper and lower limits is 
eliminated. Also, a member projecting radially, such as the rack of the 
Bosch type fuel injection pump of the prior art, is eliminated. Thus the 
number of parts, the size of the pump and production cost can be further 
reduced. 
6. In securing the pump body 1 to the engine body 12 after inserting the 
latter in the mounting opening 42 formed in the former, the disk-shaped 
flange 13 of the pump body 1 is pressed by the plate member 44 bolted to 
the engine body 12 at 43 and held in place. This eliminates the need to 
form in the pump body 1 a large flange for mounting the pump body 1 on the 
engine body 12, thereby reducing the size of the pump body 1. Moreover, 
the pump body 1 together with the flange 13 have an axial circular cross 
section, thereby facilitating machining. 
The arrangement that the pump body 1 is not directly secured to the engine 
body eliminates the need to form a bolt receiving opening in the pump body 
1, allowing the pump body to be installed in a narrow mounting space. 
The arrangement that the pump body 1 is pressed against and secured to the 
pump body 12 by the resilience of the plate member 44 does not require 
control of the bolt clamping force, enabling the pump body 1 to be mounted 
readily. 
7. The spherical pipe joint 50 having the pipe 51 for connection with a 
fuel supply line is fitted over the smooth surface 49b in the lower 
portion of the minor diameter cylindrical portion 49 in the upper half 
portion of the pump body 1 and held in place through the seal members 52 
and 53 between the pump body 1 and the discharge valve retaining collar 7 
threadably fitted over the threaded surface 49a in the upper portion of 
the minor diameter cylindrical portion 49. This arrangement eliminates the 
need to use clamping members, etc., for mounting the spherical pipe joint 
50. Thus the number of parts can be reduced and machining of mounting 
screws is unnecessary, resulting in a marked simplification of the pump 
structure. 
The interior of the spherical pipe joint 50 can be used as the fuel chamber 
54 for the sucked fuel or escaping fuel, so that a very compact overall 
size can be obtained in a pump body. 
Last but not least important is increased strength of the pump body 1 which 
results from the absence of pressed-in portions.