US3013733A - Fuel injector - Google Patents

Description

TIME

OPEN

IDLE

INVENTORS. 2:65:44 F. HILL/4M5 Film/P K. MaRG/M/ M lrrwen/E/ Dec. 19, 1961 R. F. WILLIAMS ETAL FUEL INJECTOR Filed March 14, 1961 United States Patent 3,013,733 FUEL INJECTOR Russell F. Williams, 605 Center Drive, Tecumseh, Mich., and Philip R. Morgan, Box 471, Clinton, Mich. Filed Mar. 14, 1961, Ser. No. 95,647 8 Claims. (Cl. 239-533) This application presents certain improvements over a prior co-pending application for Fuel Injector filed by Russell F. Williams and Philip R. Morgan on March 31, 1959, Serial No. 803,145, now abandoned, and over a prior co-pending application for Fuel Injector filed by Russell F. Williams, Philip R. Morgan, and Martin Glenday on March 4, 1960, Serial No. 12,791. In said prior applications, fuel injector means were disclosed which utilized a diaphragm actuated by variations in the air inlet line or crankcase pressure of an engine for driving a fuel injection hollow piston into a fuel compression zone. In the present application, these features are again utilized, but in an improved manner, enabling operation in cases of fluctuating pressure which remains always negative with respect to ambient pressure.

This invention thus relates to fuel injectors for internal combustion engines. It is of particular value in connection with four-cycle engines in which the pressure in the air inlet line during operation remains always negative with respect to ambient. By means of the fuel injector of the present invention, the use of a carburetor is eliminated. This results in a very substantial saving in cost, as well as eliminating the many difiiculties encountered with carburetors.

The fuel injector of the present invention has the advantage of not requiring any mechanical driving means for pumping the fuel or for forming it into a spray, since it utilizes the pressure variations existing in the air inlet of the engine as the motive force.

A further advantage of the present invention is that it requires no tight fitting pistons or tight friction seals.

Other advantages include extremely low cost, low weight, and improved fuel metering and engine performance.

Other objects and advantages of the invention will more fully appear from the following description and drawings, wherein are disclosed preferred embodiments of the invention.

FIG. 1 shows a side view of a preferred embodiment of the present invention;

FIG. 2 shows a cross-sectional view taken along the lines 2-2 of FIG. 1;

FIG. 3 shows an end view of said embodiment of the invention; and

FIG. 4 is a schematic diagram showing certain pressure conditions in the injector.

Referring now to the drawings in detail, wherein similar numerals represent similar parts, FIGS. 1, 2 and 3 show a preferred embodiment of the present invention. The injector comprises a generally cylindrical injector body having a longitudinal passage 11 extending therethrough, defining at opposite ends a fuel inlet 12 and a fuel outlet 13. Mounted in fluid-tight manner transversely across said longitudinal passage 11, at an enlarged section thereof adjacent said fuel outlet 13, is a large-area flexible pressure-responsive diaphragm 14. Similarly mounted, at a section of somewhat smaller area, closer to said fuel inlet 12, is a small-area flexible pressure-responsive diaphragm 15. A hollow piston 16, having a longitudinal assage 17 extending therethrough and terminating in a calibrating orifice 35, is ailixed to and freely suspended from said diaphragms 14 and 15 so as to cause said diaphragms 14 and 15 and said piston 16 to undergo joint longitudinal motion in response to variations in differential pressure across diaphragm 14 and in response to spring pressure as discussed below. A removable bushing 18 may be used to maintain diaphragm 15 in position, as shown in FIG. 1.

Fuel outlet 13 is adapted to be attached to the air inlet conduit of an engine (not shown). Thus, the pressure on the outer face of diaphragm 14 (i.e. the face closest to the fuel outlet 13) will vary with the variations in engine pressure during the engine cycle. The space between diaphragms 14 and 15 may at the same time be maintained at ambient pressure. This may, for example, be accomplished, as shown in FIG. 2, by venting said space to the ambient atmosphere through vents 19.

Whereas a two-cycle engine provided with a closed crankcase will undergo both positive and negative fluctuatrons in pressure with respect to ambient pressure, this is not necessarily so in the case of four-cycle or other engines not equipped with closed crankcases. In such cases, a fluctuating negative pressure may exist throughout the engine cycle. In this case, the mode of operation described in the aforesaid patent applications will not be applicable, since there never is any positive pressure to the left of diaphragm 14, and hence no differential pressure engine diaphragms 14 and 15 and piston 16 to the right. In this case, as shown in FIG. 2, we provide a spring 29, which functions in a manner described below. Spring 29 is retained in position by resting on one side against a flanged portion 30 of piston 16, and on the other against a bushing 31 threaded into the exit end of fuel outlet 13. Cap 32 at the outlet end of injector body 10 may, as shown, he provided with male threads 33 adapted to be threaded into the fuel inlet conduit of the engine (not shown).

A fuel compression zone 20 is provided intermediate said diaphragm 15 and said fuel inlet 12; and a pressureresponsive check valve indicated generally at 21 is provided between saidfuel inlet 12 and fuel compression zone 20, adapted to close when the pressure in said fuel compression zone reaches a predetermined negative value relative to the pressure in said fuel inlet 12 (which latter pressure may be substantially atmospheric). Said check valve 21 may comprise, as shown, a valve seat 22 defining a valve port 23, a disc 24 adapted to seat against said valve seat 22 so as to close said valve port 23, and spring loading means 25 urging said valve disc 24 toward its closed position.

As shown in FIG. 2, check valve 21 is also provided with a piston stop 26, which may comprise a resilient disc retained in the end of check valve 21 adjacent piston 16, and which closes and seals the longitudinal passage 17 through piston 16, when piston 16 comes to rest, i.e. when the engine is not running. Thus, when the engine is not running, seepage of fuel from the fuel compression zone 20 into the engine is prevented by piston stop 26, acted upon by spring 29. On the other hand, during operation, disc stop 27 serves to limit the motion of disc 24 to the left in FIG. 2. It will be noted in FIG. 2 that when disc 24 moves to the left against disc stop 27, a passage around the periphery of disc 24 permits entry of fuel from fuel inlet 12 into fuel compression zone 20, through ports 28 provided in the side of check valve 21. A screen 34 may be placed at the entrance of fuel inlet 12, as shown in FIG. 2, to screen incoming fuel.

In operation, when the suction in the fuel inlet conduit to the engine and hence in fuel outlet 13, is increasing toward its maximum value, diaphragm 14 is pulled to the left by said suction. This in turn pulls piston 16 and diaphragm 15 also to the left. This tends to create a vacuum in fuel compression zone 20, and since the area of diaphragm 15 is smaller than that of diaphragm 14, there is a corresponding multiplying factor which tends to make this vacuum greater than that in fuel outlet 13. As

a result, disc 24 is pulled to the left, against the action of spring 25, allowing fuel to enter the fuel compression zone 20 from fuel inlet At the same time, spring 29 is compressed by the aforesaid motion of piston 16. When the suction in the fuel inlet conduit to the engine, and hence in fuel outlet 13 subsequently decreases during the engine cycle, spring 29 urges piston 16, and hence diaphragms 14 and 15, to the right. This creates an amplified positive pressure in fuel compression zone 20, closing check valve 21, and forcing fuel from compression zone 20 through the longitudinal passage 17 and calibrating orifice 35 into the fuel outlet 13.

Thus, it will be seen that althou h the pressure in the fuel inlet conduit to the engine, and hence in fuel outlet 13 never attains positive values during the operation of the engine (e.g. a four-cycle engine), the fuel injector equipped with spring 29 nevertheless operates in the manner described. In a manner of speaking, it is as though spring 29 created a fictitious ambient pressure acting on di phragm 14 (lower than actual ambient pressure).

The force exerted by spring 29 must be so selected as to create an equivalent pressure on diaphragm 14 (defined as the spring force divided by the effective or free area of diaphragm 14) which is intermediate the maximum and minimum suctions in the fuel inlet conduit to the engine. Only in this way is the aforesaid fictitious ambient so created as to provide both negative and positive fluctuations of the pressure in the fuel outlet 13 with respect to said fictitious ambient.

The flexibility and relative areas of diaphragms 14 and are suitably selected in known manner to create the aforesaid pressure amplifying effect. By virtue of this pressure amplifying effect, the suction in fuel compression zone 20 may substantially exceed the maximum suction in the fuel outlet 13, despite the opposing action of spring 29. Spring may be set to limit this suction in fuel compression zone 20, in order to allow proper admission of fuel through check valve 21 into fuel compression zone 20. Also by virtue of this pressure amplifying effect, the positive pressure obtained in fuel compression zone 20 at the appropriate stage of the englue and injector cycle is enough to force fuel through calibrating orifice at the desired rate. No check valve is required at the fuel outlet side of longitudinal passage 17.

In order to meter fuel substantially in proportion to the amount of air fed to the engine, i.e., to feed proper amounts of fuel at idle and wide open throttle, as well as at points in between, we have taken into consideration the fact that at idle (when relatively little air is entering the engine and relatively little fuel is required), the suction in the air inlet conduit to the engine reaches high maximum levels, whereas at wide open throttle (when fuel requirements are high) the suction in the air inlet conduit attains only relatively low maximum values. We have found that if a stop is provided for motion of the piston 16 or diaphragm 14, limiting motion to the left, this problem can be taken care of satisfactorily.

As shown in FIG. 4, the suction in the air inlet conduit (and hence in the fuel outlet 13 of the injector) reaches greater values for idle than for wide open throttle. Thus, piston 16 and diaphragms 14 and 15 are moved to the left in FIG. 2 more rapidly at idle than at wide open throttle. When the negative pressure in fuel outlet 13 reaches a value designated in FIG. 4 as P spring 29 will have been compressed sufficiently for piston 16 or diaphragm 14 to have reached a stop. For example, in FIG. 2, diaphragm 14 will have come into contact with the inner surface 36 of cap 32. As can be seen in FIG. 4, this condition will be reached earlier and will last longer in the case of idle than in other cases such as wide open throttle. During this condition, there is no work being done in compressing the spring 29; hence this portion of the cycle is wasted insofar as the pumping operation of the injector is concerned, and is a maximum for idle and a minimum for wide open throttle. On the other hand, when the absolute pressure in fuel outlet 13 increases subsequently during the engine cycle, the spring 29 will do pumping work. Since the pressure in fuel outlet 13 assists spring 29 to do this work, and since the absolute value of this pressure is higher in the case of wide open throttle than at idle, it follows that a maximum of pumping work will be done at wide open throttle, and a minimum at idle, just as is desired.

In operation, therefore, diaphragm 14 reaches the stopping surface 36 at the left end of each stroke, regard less of the amount of load on the engine, but diaphragms 14 and 15 and piston 16 will move different amounts to the right in FIG. 2, depending on the load. For wide open throttle, it is preferred that piston 16 touch piston stop 26 each time, while in other cases the stroke length will be too short for the piston 16 to reach piston stop 26. Thus, the stroke, and hence the fuel delivered, will be approximately proportional to the air fed to the engine, as desired.

As as alternative to the use of spring 29, we may accomplish a similar result by utilizing a diaphragm 14 possessing a substantial ability to absorb energy by elastic deformation. In this case, we may dispense with spring 29 altogether, provided diaphragm 14 is so selected as to be capable of producing a restoring force, due to said elastic deformation, which when divided by the effective area of diaphragm 14 is equivalent to a pressure which is intermediate the maximum and minimum suctions in the fuel inlet conduit to the engine. Diaphragm 14 should be so positioned, at rest, by means of piston stop 26, as to be under a tensile stress tending to urge diaphragms 14 and 15 and piston 16 to the right in FIG. 2.

It will be seen that this type of fuel injector requires no tight-fitting piston or tight friction seals, requires no outlet check valve, requires no feed pump, and requires no drive mechanism or energy other than that provided by variations in pressure in the engine, and yet it meters fuel in proportion to the feed of air to the engine.

While we have thus shown and described preferred embodiments of our invention, it is understood that various other modifications may also be made in the details of construction without departing from the spirit of the invention, the principal novel features of which are set forth in the claims below.

We claim:

1. In a fuel injector for an internal combustion engine, which engine is provided with an air inlet conduit in which the pressure fluctuates in pressure in response to the engine cycle, said pressure at substantially all times during operation remaining negative with respect to ambient pressure, said fuel injector comprising an injector body having a longitudinal passage extending there through, defining at opposite ends a fuel inlet and a fuel outlet, a first flexible pressure-responsive diaphragm mounted in fluid-tight manner transversely across said longitudinal passage adjacent said fuel outlet, means for exposing the surface of said first diaphragm facing said fuel outlet to the varying pressure of said air inlet conduit, a second flexible pressure-responsive diaphragm of smaller area than the first diaphragm mounted in fluidtight manner transversely across said longitudinal passage at a position closer to said fuel inlet, a hollow piston having a passage extending therethrough and being affixed to and freely suspended from both of said diaphragrns so as to cause said diaphragms and said piston to undergo joint longitudinal motion in response to variations in said air inlet conduit pressure, means for maintaining ambient pressure in the space between said diaphragms, a fuel compression zone intermediate the ends of the aforesaid longitudinal passage extending through said injector body, intermediate said second diaphragm and said fuel inlet, and check valve means located at the junction between said fuel inlet and said fuel compression zone,

adapted to close when the pressure in said fuel compression zone reaches a. predetermined pressure relative to that in said fuel inlet, the flexibility and relative areas of said diaphragms being so selected as to create a substantially pressure amplifying effect on the fluid in said fuel compression zone; the improvement comprising: spring loading means urging said piston away from said fuel outlet with a force so selected that said force divided by the eifective area of said first diaphragm is intermediate in value between the maximum and minimum suctions in said fuel outlet during operation of said engine.

2. The fuel injector set forth in claim 1, also provided with a stop limiting motion of said piston and diaphragms towards said fuel outlet, said stop being so positioned as to be reached substantially each time the aforesaid pressure in said air inlet conduit cycles and to continue limiting said motion in said direction during a substantial portion of each such cycle, thereby substantially proportioning the admission of fuel to the admission of air to said engine.

3. in a fuel injector for an internal combustion engine, which engine is provided with an air inlet conduit in which the pressure fluctuates in pressure in response to the engine cycle, said pressure at substantially all times during operation remaining negative with respect to ambient pressure, said fuel injector comprising an injector body having a longitudinal passage extending there through, defining at opposite ends a fuel inlet and a fuel outlet, a first flexible pressure-responsive diaphragm mounted in fluid-tight manner transversely across said longitudinal passage adjacent said fuel outlet, means for exposing the surface of said first diaphragm facing said fuel outlet to the varying pressure of said air inlet conduit, a second flexible pressure-responsive diaphragm of smaller area than the first diaphragm mounted in fluidtight manner transversely across said longitudinal passage at a position closer to said fuel inlet, a hollow piston having a passage extending therethrough and being affixed to and freely suspended from both of said diaphragms so as to cause said diaphragms and said piston to undergo joint longitudinal motion in response to variations in said air inlet conduit pressure, means for maintaining ambient pressure in the space between said diaphragms, a fuel compression zone intermediate the ends of the aforesaid longitudinal passage extending through said injector body, intermediate said second diaphragm and said fuel inlet, and check valve means located at the junction between said fuel inlet and said fuel compression zone, adapted to close when the pressure in said fuel compression zone reaches a predetermined pressure relative to that in said fuel inlet, the flexibility and relative areas of said diaphragms being so selected as to create a substantial pressure amplifying eifect on the fiuid in said fuel compression zone; the improvement comprising: selection of said first diaphragm such that it possesses elasticity sufficient so that, when acted upon by the maximum suction in said fuel inlet, it develops a corresponding restoring force which when divided by the effective area of said first diaphragm is intermediate in value between the maximum and minimum suctions in said fuel outlet during operation of said engine.

4. The fuel injector set forth in claim 3, also provided with a stop limiting motion of said piston and diaphragms toward said fuel outlet, said stop being so positioned as to be reached substantially each time the aforesaid pressure in said air inlet conduit cycles and to continue limiting motion in said direction during a substantial portion of each such cycle, thereby substantially proportioning the admission of fuel to the admission of air to said engine.

5. In a pumping device comprising a pump body having a longitudinal passage extending therethrough, defining at opposite ends a fluid inlet and a fluid outlet, a first flexible pressure-responsive diaphragm mounted in fluidtight manner transversely across said longitudinal passage adjacent said fluid outlet, a source of fluid pressure which fluctuates about a mean pressure diflerent from ambient pressure, means for exposing the surface of said first diaphragm facing said fluid outlet to said fluctuating pressure, a second flexible pressure-responsive diaphragm of smaller area than the first diaphragm mounted in fluidtight manner transversely across said longitudinal passage at a position closer to said fluid inlet, a' hollow piston having a passage extending therethrough and being affixed to and freely suspended from both of said diaphragms so as to cause said diaphragms and said piston to undergo joint longitudinal motion in response to said fluctuations of pressure, means for maintaining ambient pressure in the space between said diaphragms, a fluid compression zone intermediate the ends of the aforesaid longitudinal passage extending through said pump body, intermediate said second diaphragm and said fluid inlet, and check valve means located at the junction between said fluid inlet and said fluid compression zone, adapted to close when the pressure in said fluid compression zone reaches a predetermined pressure relative to that in said fluid inlet, the flexibility and relative areas of said diaphragms being so selected as to create a substantial pressure amplifying eflect on the fluid in said flnid compression zone; the improvement comprising: spring loading means urging said piston longitudinally in a direction opposite to that represented by the resultant between the aforesaid mean pressure and ambient pressure, with a force so selected that said force divided by the effective area of said first diaphragm is intermediate in value between the maximum and minimum pressures in said fluid outlet during operation of said device.

6. The pumping device set forth in claim 5, also provided with a stop limiting motion of said piston and diaphragm in the direction represented by the resultant between the aforesaid mean pressure and ambient pressure, said stop being so positioned as to be reached substantially each time the aforesaid pressure in said source of fluctuat ing fluid pressure cycles and to continue limiting said mo'.

tion in said direction during a substantial portion of each such cycle.

7. In a pumping device comprising: a pump body having a longitudinal passage extending therethrough, defining at opposite ends a fluid inlet and a fluid outlet, a first flexible pressure-responsive diaphragm mounted in fluidtight manner transversely across said longitudinal passage adjacent said fluid outlet, a source of fluid pressure which fluctuates about a mean pressure different from ambient pressure, means for exposing the surface of said first diaphragm facing said fluid outlet to said fluctuating pressure, a second flexible pressure-responsive diaphragm of smaller area than the first diaphragm mounted in fluidtight manner transversely across said longitudinal passage at a position closer to said fluid inlet, a hollow piston having a passage extending therethrough and being aflixed to and freely suspended from both of said diaphragms so as to cause said diaphragms and said piston to undergo joint longitudinal motion in response to said fluctuations of pressure, means for maintaining ambient pressure in the space between said diaphragms, a fluid compression zone intermediate the ends of the aforesaid longitudinal passage extending through said pump body, intermediate said second diaphragm and said fluid inlet, and check valve means located at the junction between said fluid inlet and said fluid compression zone, adapted to close when the pressure in said fluid compression zone reaches a predetermined pressure relative to that in said fluid inlet, the flexibility and relative areas of said diaphragms being so selected as to create a substantial pressure amplifying effect on the fluid in said fluid compression zone; the improvement comprising: selection of the.

first diaphragm such that it possesses elasticity suflicient so that, when acted upon by the maximum pressure differential between said fluctuating pressure source and ambient pressure, it develops a corresponding restoring force which when divided by the effective area of said first diaphragm is intermediate in value between the maximum and minimum pressures in said fluid outlet during operation of said device.

8. The pumping device set forth in claim 7, also provided with a stop limiting motion of said piston and diaphragm in the direction represented by the resultant between the aforesaid mean pressure and ambient pressure, said stop being so positioned as to be reached substantially each time the aforesaid pressure in said source of fluctuating pressure cycles and to continue limiting said motion in said direction during a substantial portion of each such cycle.

References Cited in the file of this patent UNITED STATES PATENTS

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