Fuel injection pump

A fuel injection pump comprises a rotor disposed in a housing and having a pressure chamber therein, a free piston disposed slidably in the pressure chamber dividing the chamber two pump chambers, two solenoid valves for controlling fuel supply, and two preparatory chambers for metering fuel to be fed to the pump chambers. The preparatory chambers and the solenoid valves are arranged in the same plane crossing the axis of the rotor to align with each other. Fuel from a feed pump transfers to the preparatory chamber through the solenoid valve and is metered there. The metered fuel is fed to the pump chamber, pressurized there and delivered to the engine.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to a fuel injection pump for internal combustion 
engines, and more particularly to an improvement on a fuel injection pump 
with preparatory chambers for metering an amount of fuel. 
In a fuel injection pump, in order to improve metering precision of an 
amount of fuel from an electromagnetic valve for metering, and to expand 
injection timing control range, it is necessary to supply metered fuel 
from the electromagnetic valve into pump chambers through metering 
preparatory chambers. Such a fuel injection pump with preparatory chambers 
is disclosed in prior U.S. patent application Ser. No. 467,302 still 
pending filed by Yoshiya Takano and Yoshikazu Hoshi on Feb. 17, 1983 (the 
corresponding European patent application Ser. No. 83101476.6 filed on 
Feb. 16, 1983). The fuel injection pump comprises a rotor driven by the 
engine and a housing accomodating the rotor. In the rotor, two pump 
chambers are formed, and the housing is provided with the preparatory 
chambers and solenoid valves for metering the fuel to be fed to the 
chambers. In the rotor and the housing various fuel passages and switching 
valves are formed, and fuel from a fuel source is delivered to the engine 
through the solenoid valves, the preparatory chambers, the pump chambers 
and the various fuel passages and switching valves. 
In this fuel injection pump, the various passages and switching valves are 
relatively complicated and more simple construction is desirable. 
An object of the invention, therefore, is to provide a fuel injection pump 
which is simpler in construction. 
Another object of the invention is to provide a fuel injection pump which 
is compact and stable in construction. 
Briefly stated, the present invention resides in that solenoid valves for 
metering and supplying fuel and metering preparatory chambers are arranged 
such that fuel from said solenoid valves enters directly into said 
metering preparatory chamber. 
The other features, advantageous effects, etc. of the present invention 
will be understood by description of an embodiment referring to the 
drawings.

DESCRIPTION OF THE DISCLOSED EMBODIMENT 
Referring now to the drawings, in FIG. 1 showing a vertical sectional view 
of a fuel injection pump for a four cylinder internal combustion engine, 
the fuel injection pump is provided with a shaft 6, driven by the engine 
and connected to a rotor 5. The rotor 5 is rotatably inserted in a sleeve 
18 which is fitted to a base member 16. The sleeve 18 and the base member 
16 constitute a housing. The rotor 5 has an axial bore formed along an 
axis and plugs at the both ends thereby to form a pressure chamber. A free 
piston 39 is slidably inserted in the pressure chamber and divides it into 
two pump chambers 24, 25. In each of the chambers 24, 25, a stopper is 
provided for restricting movement of the free piston 39 within a 
predetermined range. At one end of the rotor 5, a feed pump 7 is provided 
for feeding pressurized fuel. The other end of the rotor 5 is connected to 
the shaft 6 through a coupling means. The base member 16 has a pair of 
preparatory chambers 3, 4 which are disclosed best in FIG. 6. In FIG. 6, 
the preparatory chambers 3, 4 for measuring fuel to be fed to the pump 
chambers are formed in a sectional plane crossing the axis of the rotor 5 
at an angle of 90.degree. so as to extend in a perpendicular direction to 
a radial direction and parallel to each other. In each of the chambers 3, 
4, a free piston 14, 15 is slidably disposed thereby to divide the chamber 
into two parts. The preparatory chambers 3, 4 communicate with the pump 
chambers 24, 25 and the feed pump 7 through various passages and valves. 
Metering solenoid valves 1, 2 for measuring an amount of fuel to be 
injected into the preparatory chambers 3, 4 are mounted on the housing so 
that the axes align with the preparatory chambers 3, 4 and the fuel from 
the solenoid valves 1, 2 enter the chambers 3, 4 directly. The various 
valves and passages formed in the rotor 5, the sleeve 18 and the base 
member 16 are described later. 
On the end portion of the rotor 5 opposite the feed pump 7, as shown in 
FIG. 2, an expansible chamber is disposed which comprises a compression 
cam 26 secured to the housing 16, rollers 38 inserted in recesses formed 
in the rotor 5, shoes 37, and plungers 36. The cam 26 has four projections 
corresponding to the number of the engine cylinders which move the 
rollers, shoes and plungers inward as the rotor 5 rotates. 
The shaft 6 has a timing gear 12 having pulse generators on the outer 
portions. A sensor 13 mounted on the housing 16 so as to face the pulse 
generator detects pulses from the timing gears 12 and transmits them to 
the solenoid valves 1, 2. 
In the rotor 5, the sleeve 18 and base member 16, various passages are 
formed, and compound switching valves are formed between the sleeve 18 and 
the rotor 5. The feed pump 7, the solenoid valves 1, 2, the preparatory 
chambers 3, 4, the pressure chamber, etc. are communicable with each other 
through the various passages and the compound switching valves. The 
various passages and the compound switching valves are as follows: (The 
solenoid valve 1 and the preparatory chamber 3 are in a metering fuel 
supply line for controlling the amount of injected fuel, and the solenoid 
valve 2 and the preparatory chamber 4 are in a metering fuel supply line 
for controlling the timing of fuel timing control fuel.) 
8s: Fuel induction passage 8 formed axially in the sleeve 18 from the feed 
pump position to VII--VII section in FIG. 7 (appears in FIGS. 7, 8, 9). 
9s: Peripheral groove 9 formed in the periphery of the sleeve 18 in 
VII--VII section and communicating with 8s (FIG. 1, FIG. 7). 
10s: Induction groove 10 formed axially in the periphery of the sleeve 18 
from VII--VII section to VI--VI section and communicating with 9s (FIGS. 
6, 7). 
11h: Induction bore 11 formed in the base member 16 communicating with 10s 
(FIG. 6). 
17h: Discharge ports 17 formed in the base member 16 and communicating with 
the preparatory chambers 3 and 4, respectively (FIG. 6). 
19s: Discharge ports 19 formed in the sleeve 18 and communicating with 17s 
(FIG. 6). 
20r: Discharge grooves 20 of four (4) formed in the periphery of the rotor 
5 equiangularly, and being communicable with 19s and 23s (later 
described). 20r extends axially from the VI--VI section to V--V section in 
FIG. 5, (FIGS. 6, 5). 
22s: Discharge ports 22 formed in the V--V section of the sleeve 18 and 
being communicable with 20r, (FIG. 5). 
23s: Supply passages 23 formed in the sleeve 18 and being communicable with 
20r and 28r (later described), (FIG. 6). 23s is communicable with 11h 
through the solenoid valve 1, 2 disposed in the induction passage 11. 
27s: Supply ports 27 formed in the sleeve 18, communicating with 8s and 9s 
and being communicable with grooves 28, (FIG. 7). 
28r: Supply grooves 28 formed axially and equiangularly in the sleeve, 
separated from each other by 90.degree., extending from VII--VII section 
to VI--VI section, and being communicable with 19s, 23s, 27s and 29s, 
(FIGS. 6, 7). 
29s: Supply ports 29 formed in the sleeve 18 and connected to 30s and 33s, 
respectively, (FIG. 7). 
30s: Supply groove 30 formed in the sleeve periphery, extending axially 
from VII--VII section to VIII--VIII section (FIGS. 7, 8). 
31s: Supply hole 31 formed in the sleeve 18 and being able to communicate 
32r with 30s, (FIG. 8). 
32r: Supply holes 32 (four) formed separated from each other by 90 in the 
rotor 5, communicating with the pump chamber 25, (FIG. 1, FIG. 8). 
33s: Supply groove 33 formed in the sleeve 18 to extend from VII--VII 
section to III--III section, (FIGS. 1, and 3 to 7). 
34s: Supply holes 34 formed in the sleeve, connected to 33s and being 
communicable with 35r, (FIGS. 1, 3). 
35r: Supply holes 35 (four) formed equiangularly, communicating with the 
pump chamber 24, (FIG. 3). 
40r: Spill-ports 40 (four) formed in the rotor 5, communicating with the 
pump chamber 24, (FIGS. 1, 4). 
41s: Spill-passages 41 formed in the sleeve 18, communicating with 40r, 
(FIG. 4). 
42s: Communication passages 42 formed in the sleeve periphery, (FIGS. 3, 
4). 
100s: Discharge groove 100 formed axially in the sleeve 18, (FIGS. 3 to 5). 
101r: Delivery hole 101 formed in the rotor 5, communicating with the pump 
chamber 25, (FIG. 7). 
102s: Delivery holes (four 102, formed in the sleeve and communicable with 
the delivery hole 102 (FIG. 7). 
103h: Delivery ports 103 formed in the base member 16 for communicating 
103h with the engine through pipes (not shown) (FIG. 7). 
With the above construction, fuel from the abovementioned feed pump 7 is 
supplied to each of the metering solenoid valve 1 for controlling an 
amount of fuel to be injected into the engine and the metering solenoid 
valve 2 for controlling injection timing through passages of 
8s-9s-10s-11h. In the state shown in FIG. 1, electric pulses are given to 
the valves 1, 2 to open them, an amount of fuel corresponding to the 
electric pulses for opening is supplied directly into the preparatory 
metering chambers 3, 4 at timing corresponding to the electric pulse. The 
timing at which the valve opening pulses are applied to the valves 1, 2 is 
determined by detecting signals from the timing gear 12 with the sensor 
13. In the preparatory valves 3 and 4 receiving fuel, the free pistons 14 
and 15 are moved left in FIG. 6, and the fuel contained in the chambers on 
the left of the free pistons 3, 4 is discharged into a lower pressure 
portion (not shown) of the fuel injection pump through the passages 
17h.fwdarw.19s.fwdarw.20r.fwdarw.22s.fwdarw.100s, whereby the metering 
operation of measured fuel to the preparatory chambers 3, 4 on the right 
side of the free pistons 14, 15 is completed. 
In addition to this metering operation, the fuel already contained in the 
pump chambers 24 and 25 is pressurized by the operation of the compression 
cam 26. In this stage, the metering and temporary accomodation of fuel by 
the solenoid valves 1, 2 and the preparatory chambers 3, 4 are effected 
while the compression of fuel in the pump chambers 24, 25 is carried out 
for injection thereof into the engine. 
In order to supply the metered fuel contained in the preparatory chambers 
3, 4 into the pump chambers 24, 25, the rotor 5 is rotated by 45.degree.. 
At this time, the rotor 5 is shifted angularly by 45.degree. relatively to 
the sleeve 18 from the position of FIGS. 1 to 9. In this relative position 
between the rotor 5 and the sleeve 18, pressure raised by the feed pump 7 
as a pressure source reaches the preparatory chambers 3, 4 on the left 
side of the free pistons 14, 15 through the passages 
8s--27s--28r--19s--17r, thereby to move the free piston to the right side. 
By this operation, the metered fuel contained in the preparatory chamber 3 
on the right side of the free piston 14 is fed to the pump chamber 25 
through the passages 23s--28r--29s--30s--31s--32r, (FIGS. 6, 7, 8). 
Further, the metered fuel contained in the preparatory chamber 4 on the 
right side is fed to the pump chamber 24 through the passages 23s--28r--29 
s--33s--34s--35r (FIGS. 6, 7, 3). As the fuel is fed to the pump chamber 
4, the plungers 36, the rollers shoes 37 and the roller 38 are moved 
outward so that the chamber 24 is expanded by the volume corresponding to 
the amount of the fuel fed to the chamber 4, whereby the operation of 
supply of the metered fuel contained in the preparatory chamber 4 is 
carried out. 
After completion of the above-mentioned fuel supply to the pump chambers 
24, 25, further, the rotor 5 is rotated by 45.degree. so that the relative 
position between the rotor 5 and sleeve 18 is returned to the position 
shown in FIGS. 1 to 9. In the FIGS. 1 to 9, the metering state and the 
compression period state are shown. 
In the same manner as above, every time the rotor 5 rotates by 45.degree., 
the above metering and compression operation and the fuel supplying 
operation are carried out alternately. 
The compression is carried out in the following manner as shown in FIGS. 1 
and 2, when fuel is fed to the pump chamber 24. Namely, as the rotor 5 
rotates, the rollers 38 contact projections of the cam 26, whereby the 
rollers 38, the roller shoes 37 and the plungers 36 are pressed inwardly 
so that the fuel in the pump chamber 24 is highly pressurized. The time 
the fuel is pressurized is determined by the contact position between the 
cam 26 and the roller 38. The contact position, that is, fuel injection 
timing can be controlled by an amount of the fuel fed to the pump chamber 
24. The amount of the fuel can be controlled by an amount of fuel sent 
from the solenoid valve 2, that is, valve opening pulse width applied to 
the solenoid valve 2. 
As above-mentioned, when the fuel in the pump chamber 24 is made high in 
pressure, the free piston 39 is moved to the right side, and the interior 
of the pump chamber 25 is pressurized in turn. Therefore, the fuel in the 
pump chamber 25 is delivered into the combustion chamber of the engine 
through the passages 101r--102s--103h-- a delivery valve (not shown)-- a 
pressure pipe (not shown)-- an injection valve (not shown). 
As the fuel is injected on, the left end of the free piston 39 is moved in 
the pump chamber 24 thereby to start to open the spill-port 40 which has 
been closed by the free piston 39. 
Therefore, the fuel in the pump chamber 24 begins to be discharged through 
the passages 40r--41s--42s. Consequently, pressure in the pump chamber 24, 
in turn, pressure in the pump chamber 25 drops thereby to bring the 
injection of fuel into the engine to an end, and the pump chamber 24 
starts to shrink by contact between the rollers 38 and the projections of 
the cam 26, whereby the fuel discharge from the pump chamber 24 is ended. 
Further, in the pump chamber 25, all the amount of fuel fed thereto from 
the solenoid valve 1 through the preparatory chamber 3 is fed to the 
engine. Therefore, the amount of fuel to be injected can be controlled 
precisely by opening the solenoid valve 1 according to the opening pulse 
width applied thereto. 
As apparent from the above-mentioned, in the present invention, fuel 
passages from the solenoid valves 1, 2 to the preparatory chambers 3, 4 do 
not rely on passages of the compound switching valve, and the preparatory 
chambers 3, 4 communicate directly with the immediately downstream 
portions of the solenoid valves so that the fuel injection pump can be 
made simpler as compared with the other construction of of fuel injection 
pump with preparatory chambers. Further, the solenoid valves 1, 2 can be 
arranged coaxially of the preparatory chamber so that the fuel injection 
pump can be made more compact and stable.