Fuel injection pump device for internal combustion engine

A fuel injection pump device for an internal combustion engine, in which a mechanical correcting signal continuously generated from a bellows in response to change in atmospheric pressure is transmitted to an adjusting member associated with a pump to adjust an amount of fuel injected into the engine by the pump. Transmission of the mechanical correcting signal from the bellows is limited such that the mechanical correcting signal is allowed to be transmitted to the adjusting member in a range in which the atmospheric pressure is below a predetermined level, but is prevented from being transmitted to the adjusting member when the atmospheric pressure is above the predetermined level.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a fuel injection pump device for an 
internal combustion engine, and more particularly to a fuel injection pump 
device having an altitude compensating unit for controlling an amount of 
fuel injected into the engine in response to change in altitude or 
atmospheric pressure. 
2. Description of the Prior Art 
Air density is gradually decreased with increase in altitude, or as 
approaching a high land from a level land, and an actual amount of air 
introduced into the engine is decreased in the high land. If the amount of 
fuel injected into the engine is maintained constant, the air-fuel ratio 
will be lowered and smoke will be increased in the high land. A prior art 
fuel injection pump device is provided with an altitude compensating unit 
which continuously controls the amount of fuel injected into the engine in 
response to change in the altitude or atmospheric pressure, to restrain 
the smoke to a constant level. However, this causes the engine output to 
be considerably decreased in the high land. In addition, upon adjustment 
of a pump unit of the fuel injection pump device and upon check or 
inspection of the engine performance in the level land, the continuous 
change in the amount of injected fuel in response to the change in 
atmospheric pressure causes the amount of fuel injected by the pump unit 
and the engine performance to be changed in accordance with the 
atmospheric pressure at that time. Accordingly, disadvantages occur that 
the adjustment is required to be made to the pump unit and the assessment 
is required to be made to the engine performance with the pressure around 
the altitude compensating unit adjusted to a predetermined value, or in 
consideration of the atmospheric pressure. 
SUMMARY OF THE INVENTION 
An object of the present invention to is to provide a fuel injection pump 
device for an internal combustion engine, which is capable of reducing the 
decrease in engine output in the high land and capable of eliminating the 
disadvantages occuring upon the adjustment of the pump unit and the check 
of the engine performance. 
According to the present invention, there is provided a fuel injection pump 
device for an internal combustion engine, comprising: an injection pump 
for forcedly delivering fuel into the engine; means for sensing 
atmospheric pressure to continuously generate a correcting signal in 
response to change in the atmospheric pressure; means operative in 
response to the correcting signal from the sensing means for adjusting the 
amount of fuel delivered by the pump into the engine so as to increase and 
decrease the amount of fuel in accordance with increase and decrease in 
the atmospheric pressure, respectively; and signal-transmission limiting 
means for limiting the transmission of the correcting signal from the 
sensing means to the adjusting means such that the correcting signal from 
the sensing means is allowed to be transmitted to the adjusting means 
within a first range in which the atmospheric pressure is below a 
predetermined level, but is prevented from being transmitted to the 
adjusting means within a second range in which the atmospheric pressure is 
above the predetermined level.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is shown in cross-section a fuel injection 
pump device according to the invention. The fuel injection pump device 
includes a housing 1 defining therein a space and having a partition wall 
2 for dividing the space into a first chamber 3 and a second chamber 4 
substantially isolated from the first chamber and communicating with the 
atmospheric pressure through a conduit 5. Connected to the first chamber 3 
is a fuel supply circuit 10 which includes a fuel tank 11, a feed pump 12 
for feeding the fuel from the tank 11 into the first chamber 3 through a 
feed conduit 13 to fill the first chamber with the fuel, a regulating 
valve 14 for regulating the pressure of the fuel supplied into the first 
chamber 3 and a return conduit 16 having one end thereof connected to the 
first chamber 3 through a restriction 17 and the other end connected to 
the supply conduit 13 downstream of the feed pump 18 for returning a part 
of the fuel from the first chamber 3 to the supply conduit 13. 
The fuel injection pump device further includes an injection pump 20 which 
is located at the bottom of the housing 1 and which includes a cylinder 
bore 21 formed in the wall of the housing and a plunger 22 received in the 
cylinder bore 21 rotatably and axially movably in synchronism with the 
engine by means of a not shown mechanism. The plunger 22 has axial one end 
face 23 cooperating with the cylinder bore 21 to define a pump chamber 24 
which, when the plunger 22 is in a return stroke or at the bottom dead 
center, communicates with the first chamber 3 through a supply passage 25 
formed in the wall of the housing and a plurality of circumferentially 
equi-distantly spaced longitudinal grooves 26 formed in a portion of the 
periphery of the plunger 22 which is located adjacent to the axial one end 
face 23 of the plunger. The plunger 22 has formed therein an axial bore 27 
having one end opening into the axial one end face 23 and a radial bore 28 
to which the other end of the axial bore is connected. The radial bore 28 
has opposite ends thereof opening into a portion of the periphery of the 
plunger which is located within the first chamber 3. The plunger 22 has 
further formed in the periphery thereof a distribution groove 29 
communicating with the axial bore 27 through a second radial bore 31 
formed in the plunger. A discharge conduit 32 has one end thereof in 
communication with the distribution groove 29 and the other end in 
communication with the engine. A check valve 33 is provided in the 
discharge conduit 32 for preventing the fuel from flowing back into the 
pump chamber 24. When the plunger 22 is in the return stroke or at the 
bottom dead center, the supply passage 25 is in alignment with one of the 
longitudinal grooves 26, and the liquid fuel is supplied from the first 
chamber 3 into the pump chamber 24 through the supply passage 25 and the 
longitudinal grooves 26. When the plunger 22 is rotated at the bottom dead 
center, the longitudinal groove 26 is out of communication with the supply 
passage 25, and the compression stroke of the plunger 22 is initiated. The 
fuel within the pump chamber 24 is forcedly delivered into the engine 
through the axial bore 27, the second radial bore 31, the distribution 
groove 29 and the discharge conduit 31. 
A sensing unit 40 for sensing altitude or atmospheric pressure is disposed 
within the second chamber 4 and includes a bellows 41 having one end 
thereof secured to the wall of the housing 1 and the other projecting free 
end 42. The bellows 41 is expandable and contractible in response to 
change in atmospheric pressure so that the projecting end 42 of the 
bellows moves to generate a mechanical correcting signal. A rod 43 is 
slidably received in a bore 44 formed in the wall of the housing 1 and has 
axial one end face 45 cooperating with the bore 44 to define a space 46. A 
passage 47 is formed in the rod 43 to communicate the space 46 with the 
second chamber 4. The projecting end 42 of the bellows 41 is fitted into a 
recess 48 formed in the other axial end face of the rod 43 so that the rod 
moves following the movement of the projecting free end 42 of the bellows 
41. A spring 49 is disposed between the wall of the housing 1 and a flange 
51 extending radially outwardly from the periphery of the rod 43 adjacent 
to the other axial end face of the rod. A frustoconical profile surface 52 
is formed in a portion of the periphery of the rod 43 between the one and 
the other axial end faces of the rod. An adjusting unit 60 is provided 
which is operative in response to the mechanical correcting signal from 
the bellows 41 of the sensing unit 40 for adjusting the amount of fuel 
delivered by the pump 20 into the engine so as to increase and decrease 
the amount of fuel in accordance with increase and decrease in the 
atmospheric pressure, respectively. The adjusting unit 60 includes a spill 
sleeve 61 and a linkage mechanism connecting the spill sleeve 61 to the 
bellows 41 for transmitting the mechanical correcting signal from the 
bellows through the linkage mechanism for adjusting the amount of liquid 
fuel delivered by the pump 20 into the engine. The spill sleeve 61 is 
mounted on the plunger 22 to cover the open ends of the radial bore 28 and 
slidable along the plunger for adjusting the distance A between an axial 
one end face of the spill sleeve 61 and the edges of the open ends of the 
radial bore 28 adjacent to the axial one end face of the spill sleeve 61. 
The amount of liquid fuel injected into the engine by the pump 20 is 
determined by the distance A which is adjusted by the position of the 
spill sleeve 61. More particularly, when the open ends of the radial bore 
28 are exposed to the first chamber 3 upon the compression stroke of the 
plunger 22, the liquid fuel flows into the first chamber 3 from the pump 
chamber 24 through the axial bore 27 and the radial bore 28, and the 
supply of the liquid fuel into the engine by the pump 20 is halted or 
suspended. Thus, the mount of fuel injected into the engine is increased 
and decreased with increase and decrease in the distance A, respectively. 
The linkage mechanism of the adjusting unit 60 includes a slide pin 62 
slidably extending through the partition wall 2 and having one end 
engageable with the profile surface 52 of the rod 43. An O-ring 63 is 
disposed around the slide pin 62 to substantially prevent the liquid fuel 
from flowing from the first chamber 3 into the second chamber 4. The 
linkage mechanism further includes a control lever 64 mounted one a pivot 
pin 65 secured to the wall of the housing 1 so that the control lever 64 
is pivotable within the first chamber 3 around the pivot pin 65. The 
control lever 65 has one end engageable with the other end of the slide 
pin 62. A tension lever 66 is pivotally mounted on a pivot pin 67 secured 
to the wall of the housing 1 and has connected to one end thereof a 
spherical projection 68 which engages with a recess 69 formed in the 
periphery of the spill sleeve 61. The other end of the tension lever is 
engageable with the other end of the control lever 64. A tension spring 71 
is disposed between the other end of the tension lever and the wall of the 
housing 1 to bias the tension lever 66 in the counterclockwise direction 
in FIG. 1 around the pivot pin 67 so that the control lever 64 is biased 
in the clockwise direction and the one end of the slide pin 62 is urged 
against the profile surface 52 of the rod 43. 
A centrifugal governor 80 is disposed within the first chamber 3 and 
includes a weight holder 81 connected to the engine through a not shown 
mechanism so that the weight holder 81 is rotatable in synchronism with 
the engine, weights 82 pivotable in response to the rotation of the weight 
holder 81, and a governor sleeve 83 having its free end engageable with 
the tension lever 66 for urging the same to angularly move the other end 
of the tension lever 66 against the tension spring 71 upon the rotation of 
the weight holder 81. The tension spring 71 has a preload greater than the 
centrifugal force on the weights 82 at the engine full load under which 
smoke particularly becomes a problem. 
Signal-transmission limiting means is provided for limiting the 
transmission of the mechanical correcting signal from the bellows 41 to 
the spill sleeve 61 such that the correcting signal from the bellows 41 is 
allowed to be transmitted to the spill sleeve 61 within a first range in 
which the atmospheric pressure is below a predetermined level, but is 
prevented from being transmitted to the spill sleeve 61 within a second 
range in which the atmospheric pressure is above the predetermined level. 
The signal-transmission limiting means comprises a stopper 90 which is 
constituted by nuts threadedly engaging with the slide pin 62. As shown in 
FIG. 2, the stopper 90 engages with the partition wall 2 when the 
atmospheric pressure reaches the predetermined level and prevents the one 
end of the slide pin 62 from engaging with the profile surface 52 of the 
rod 43 when the atmospheric pressure is above the predetermined level. 
In the position of the rod 43 shown in FIG. 1, when a vehicle having 
mounted thereon the fuel injection pump device moves toward a high 
altitude and the atmospheric pressure around the vehicle is decreased, the 
bellows 41 is expanded and the projecting end 42 of the bellows moves away 
from the secured one end thereof. The movement of the projecting free end 
42 of the bellows 41 causes the rod 43 to move against the spring 49. At 
that time, the air within the space 46 is released into the second chamber 
4 through the passage 47. The profile surface 52 of the rod 43 which is 
moving causes the slide pin 62 to move to the left in FIG. 1. The movement 
of the slide pin 62 to the left causes the control lever 64 to angularly 
move around the pivot pin 65 in the counterclockwise direction and causes 
the tension lever 66 to angularly move around the pivot pin 67 in the 
clockwise direction against the tension spring 71 so that the spill sleeve 
61 moves to the left to decrease the distance A and the amount of fuel 
injected into the engine by the pump 20 is decreased to prevent the smoke 
from being increased. 
When the vehicle moves toward a low altitude and the atmospheric pressure 
around the vehicle is increased, the bellows 41 is contracted and the 
projecting free end 42 of the bellows moves toward the secured one end 
thereof. The movement of the projecting free end 42 of the bellows 41 
allows the rod 43 to move under the action of the spring 49 and the 
profile surface 52 allows the slide pin 62 to move to the right in FIG. 1. 
The movement of the slide pin 62 to the right causes the control lever to 
angularly move in the clockwise direction and causes the tension lever 66 
to angularly move in the counterclockwise direction under the action of 
the tension spring 71 so that the spill sleeve 61 is moved to the left to 
increase the distance A and the amount of fuel injected into the engine by 
the pump 20 is increased. 
When the altitude where the vehicle is positioned is lowered and reaches a 
predetermined level, or when the atmospheric pressure around the vehicle 
is increased and reaches to a predetermined level Lp shown in FIG. 3 
corresponding to the predetermined altitude, the stopper 90 engages with 
the partition wall 2 as shown in FIG. 2, to prevent the slide pin 62 from 
further moving to the right in FIG. 1, so that the slide pin 62 cannot 
follow the further movement of the rod 43 toward the secured one end of 
the bellows 41. Thus, when the atmospheric pressure is above the 
predetermined level Lp, the mechanical correcting signal from the bellows 
41 is not transmitted to the spill sleeve 61 through the slide pin 62, the 
control lever 64 and the tension lever 66. Accordingly, the engine and the 
fuel injection pump device have their operating characteristics indicated 
by the full lines in FIG. 3. It will be of course to set the predetermined 
level Lp such that the smoke does not exceed the smoke limit in the high 
land. In general, the predetermined level Lp may be set to a level 
corresponding to the altitude of approximately 500 meters. It is to be 
noted, however, that when the atmospheric pressure is above the 
predetermined level, the spill sleeve 61 is not influenced by the 
mechanical correcting signal from the bellows 41, but is influenced by the 
mechanical signal from the centrifugal governor 80. 
The prior art fuel injection pump device which includes an altitude 
compensating unit for continuously controlling the amount of fuel injected 
into the engine in response to change in altitude or atmospheric pressure 
to restrain smoke to a constant level indicate characteristics shown by 
chain lines in FIG. 3. As will be clearly seen from FIG. 3, the engine 
output is considerably decreased in the high land. 
As described above, in the fuel injection pump device according to the 
present invention, the decrease in engine output can be reduced in the 
high land or within an area where the atmospheric pressure is low while 
restraining the smoke within the limit value, and characteristics further 
approximating to ideal ones can be obtained. In addition, since there are 
no change in characteristics due to the operation of the sensing unit 40 
in a level land where most of factorys manufacturing pumps and vehicles 
are located, the adjustment of the pumps and the check or inspection of 
the engine are made easy. 
In the embodiment illustrated in FIGS. 1 and 2, the stopper 90 comprises 
nuts. However, as shown in FIG. 4, a stopper 190 corresponding to the 
stopper 90 may comprises a snup ring 191 fitted into a circumferential 
groove in the slide pin 62 and adjusting shims 192 disposed around the 
slide pin 62 between the snup ring 191 and the partition wall 2. The 
modification shown in FIG. 4 is advantageous in that the stopper 190 is 
easy in manufacture and a space occupied by the stopper is decreased. 
FIG. 5 illustrates an another embodiment of the present invention, in which 
elements or parts similar to those shown in FIG. 1 are indicated by the 
same reference characters, and a description with reference to an 
operation identical with that in the FIG. 1 embodiment will be omitted. 
The embodiment shown in FIG. 5 is substantially identical in structure and 
function with the embodiment shown in FIG. 1 except that a stopper 290 
corresponding to the stopper 90 in FIG. 1 comprises a screw 291 extending 
through and threadedly engaging with the wall of the housing 1, and a nut 
292 engaging with the screw 291. The screw 291 has one end thereof 
engageable with a projection 272 on a control lever 264 corresponding to 
the control lever 64 in FIG. 1. The one end of the screw 291 engages with 
the projection 272 when the atmospheric pressure reaches the predetermined 
level Lp shown in FIG. 3 and prevents the slide pin 62 from further moving 
following the movement of the rod 43 toward the secured end of the bellows 
41 when the atmospheric pressure is above the predetermined level Lp so 
that the mechanical correcting signal from the bellows in not transmitted 
to the spill sleeve 61. 
FIG. 6 illustrates a still another embodiment of the present invention, in 
which elements or parts similar to those shown in FIG. 1 are indicated by 
the same reference characters, and a description with reference to an 
operation identical with that in the FIG. 1 embodiment will be omitted. 
In the embodiment shown in FIG. 6, a bellows 341 of a sensing unit 341 
corresponding to the bellows 41 in FIG. 1 has one free projecting end 342 
and the other free end 353, and the spring 49 floatingly supports an 
assembly of the bellows 341 and the rod 43. 
A predetermined gap .DELTA.L associated with the other free end 353 of the 
bellows and a stopper 390 cooperating with the other free end 353 of the 
bellows 341 to define the predetermined gap .DELTA.L constitute 
signal-transmission limiting means for limiting the transmission of the 
mechanical correcting signal from the bellows 341 to the spill sleeve 61 
such that the mechanical correcting signal from the bellows 341 is allowed 
to be transmitted to the spill sleeve 61 within a first range in which the 
atmospheric pressure is below the predetermined level Lp shown in FIG. 3, 
but is prevented from being transmitted to the spill sleeve 61 within a 
second range in which the atmospheric pressure is above the predetermined 
level Lp. The stopper 390 comprises a screw 391 threadedly engaging with 
the wall of the housing 1 and a nut 392 threadedly engaging with the screw 
391. The screw 391 has formed therein an axial bore 393. A spring 394 is 
disposed between the bottom of the bore 393 and the other free end of the 
bellows 341 to urge the bellows toward the rod 43 for preventing the 
bellows from being vibrated. The spring 394 has a spring constant so 
sufficiently lower than that of the spring 49 that substantially no 
influence is imparted to the function of the bellows 341. 
When the atmospheric pressure is above the predetermined level Lp shown in 
FIG. 3, the other free end 353 of the bellows 341 moves within the 
predetermined gap .DELTA.L against the spring 394, and the projecting end 
342 of the bellows is maintained stationary so that the mechanical 
correcting signal from the bellows 341 is not transmitted to the spill 
sleeve 61. When the atmospheric pressure reaches the predetermined level 
Lp, the other free end 353 of the bellows 341 engages with the screw 391. 
When the atmospheric pressure is below the predetermined level Lp, the 
projecting end 342 of the bellows 341 moves to cause the rod 43 to move 
against the spring 49. 
FIG. 7 illustrates a still further embodiment of the invention, in which 
elements or parts similar to those shown in FIG. 1 are indicated by the 
same reference characters, and a description with reference to an 
operation identical with that in the FIG. 1 embodiment will be omitted. In 
the embodiment shown in FIG. 7, a bellows 441 of a sensing unit 440 
corresponding to the bellows 41 in FIG. 1 has one projecting free end 442 
and the other free end 453, and the projecting end 442 is connected in a 
lost-motion manner to the rod 43 such that the projecting end 442 is 
slidable in a recess 448 in the rod 43. 
A predetermined gap .DELTA.L defined between the flange 51 and an end face 
454 at the projecting end 442 of the bellows 441 and a stopper 490 
engaging with the other free end 453 of the bellows 441 constitute 
signal-transmission limiting means for limiting the transmission of the 
mechanical correcting signal from the bellows 441 to the spill sleeve 61 
such that the mechanical correcting signal from the bellows 441 is allowed 
to be transmitted to the spill sleeve 61 within a first range in which the 
atmospheric pressure is below the predetermined level Lp shown in FIG. 3, 
but is prevented from being transmitted to the spill sleeve 61 within a 
second range in which the atmospheric pressure is above the predetermined 
level Lp. The stopper 490 comprises a screw 491 extending through and 
threadedly engaging with the wall of the housing 1 and a lock nut 492 
threadedly engaging with the screw 491. The spring 49 cooperates with a 
spring 493 disposed between the projecting free end 442 of the bellows 441 
and the bottom of the recess 48 to floatingly support an assembly of the 
bellows 441 and the rod 43. The spring 493 has a spring constant 
sufficiently lower that than that of the spring 49. 
When the atmospheric pressure is above the predetermined level Lp, the 
projecting end 442 of the bellows 441 moves within the predetermined gap 
.DELTA.L against the spring 493 while maintaining the other free end 453 
of the bellows in engagement with the screw 491 so that the mechanical 
correcting signal from the bellows 441 is not transmitted to the spill 
sleeve 61 through the linkage mechanism comprising the slide pin 62, the 
control lever 64 and the tension lever 66. When the atmospheric pressure 
reaches the predetermined level Lp, the end face 454 of the bellows 441 
engages with the rod. When the atmospheric pressure is below the 
predetermined level, the end face 454 of the bellows 441 moves to allow 
the rod 43 to move against the spring 49. 
The present invention has been described with reference to embodiments 
applied to a distribution type injection pump, but is applicable to a 
series type injection pump. In such case, is of course to substitute an 
adjustment of position of a control rack for the adjustment of the 
position of the spill sleeve 61. In addition, it has been described that 
the mechanical correcting signal from the bellows 41, 341, 441 is 
transmitted to the spill sleeve 61 through the slide pin 62, the control 
lever 64, 264 and the tension lever 66. However, a modification of the 
bellows, for example, may allow some of such members to be deleted.