US2481927A - Pressure actuated fuel injection system for free-piston engines - Google Patents

Description

Sept, 13, 1949.

Filed June 10, 1947 2 Sheets-Sheet 1 #3 Q Q Qt mil/1W ATTORNEY p 1949- R. J. HOOKER 2,481,927

I PRESSURE ACTUATED L INJECTION SYSTEM FOR FREE-P O ENGINES Filed June 10, 1947 2 Sheets-Sheet 2 INVENTOR Hai a)? eZHooke r ATTORNEY Patented Sept. 13, 1949 PRESSURE ACTUATED FUEL INJECTION SYSTEM FOR FREE-PISTON ENGINES Ralph J. Hooker, Hamilton, Ohio, assignor to United Aircraft Corporation, East Hartford, Coma, a corporation of Delaware Application June 10, 1947, Serial No. 753,642

13 Claims.

i This invention relates to a pressure actuated fuel injection system particularly adapted for free-piston units.

in compression ignition engines, it is advantageous in many cases to have the fuel injected at a predetermined compression pressure. This has been accomplished by arranging the fuel injection device so that the flow of fuel into the engine cylinder will take place under the control of a valve which is responsive to pressure within the engine cylinder. A feature of this invention is the actuation of the pump plunger by pressure from the engine cylinder. feature is the arrangement of the device, such that the injection plunger is moved rapidly on the injection strolze when the predetermined compression pressure is reached.

Free-piston generally have air springs which function to move the engine pistons on the compression stroke. These air springs may he a part of the compressor elements or may he separate air springs. In either event the air pressure in the air spring is highest at the end of the power stroke of the engine piston at which time the pressure in the engine cylinder is at a minimum. A feature oi this invention is the use of pressure as from the air spring for returning the injection plunger on the filling stroire. It will be understood that instead of air spring pressure, the pressure within the compressor cylfinder might he used.

A icature oi the invention is an arrangement for adjusting the quantity of incl i'or each stroke oi the plunger by limiting the plunger stroke.

Other objects and advantages will be apparent irom the specification and claims and from the accompanying drawings which illustrate an emhodiment oi the invention.

i is a sectional view of the free-piston unit showing the injection pump in elevation.

2 is a sectional view on a larger scale oi the injection device.

The unit shown includes an engine cylinder it having reciprocating pistons :12 and it to which compressor pistons it and it in cylinders it and it are integrally connected. Sleeves it and 26 attached to the compressor pistons complete the reciprocating piston assembly. The sleeves in conjunction with stationary pistons 2t and 3t form air spring cylinders.

The pistons are moved apart by the burning of iuel injected into engine cylinder it through a fuel nozzle 32, Fig. 2. Air compressed in the air spring cylinders on the power stroke returns the piston assemblies on the compression stroke.

Another 2 The pistons are always maintained at equal distances from the center of the engine cylinder by a linkage, not shown.

The intake manifold 38 which extends around the compressor and engine cylinders conducts air to intake valves 40 in the heads of the compressor cylinders through which air automatically enters the opposite ends of the cylinders. Compressed air leaves the cylinders through discharge valves 42, also at opposite ends of the compressor cylinders and passes into a central scavenge cham-= ber i l and end chambers it and 38. These chambers may be connected by a scavenge manifold, not shown.

Compressed air from the scavenge chambers enters engine ports til which are uncovered by piston it at the end of the power stroke, thereby permitting air to be blown through the engine cylinder. Gas in the engine cylinder is discharged through exhaust ports 52 uncovered by the piston t2 and into an exhaust manifold it.

The fuel for the nozzle 32 is supplied by a fuel injection device which is actuated on the injection stroke by a compression pressure and which is returned on the pumping stroke by air from one of the air springs. As shown in Fig. 2, the injection device includes a casing tit having a fuel inlet 58. Within the casing is a cylinder tit having a bore in which the injection plunger til reciprocates. The cylinder has an inlet passage til, the inner end of which is covered by the plunger on the injection stroke, thereby trapping fuel in the end of the hore tit and forcing it out past a check valve fit and through the nozzle 32. The latter may be held in place 'by a ring it which also functions to hold the cylinder Ed in position.

The plunger extends beyond the cylinder til at its outer end and engages with a disc 322 which is moved outwardly by a spring it, thereby holding the end of the plunger against the rod it of a piston it. The piston it is slidable in a casing til and has a projecting valve element 82 which closes an inlet passage M in the casing which is connected, as by a pipe to, with the engine cylinder. When the pressure in passage 8t is high enough to overcome the action of the spring it, the piston it moves upwardly,

allowing the compression pressure from the engine cylinder to be efiective overthe entire area of the piston and cause rapid upward movement of the piston and corresponding movement of the injection plunger to deliver fuel to the engine cylinder.

The other side of the piston it is acted upon by pressure from one of the air springs through a duct 88 and a passage 90 in a plate 92 between the outer end of the casing 56 and the end of the casing 80. As the pistons reach the outer ends of their strokes so that the engine cylinder pressure drops to that of the pressure in the scavenge manifolds, the air spring pressure will be high enough to return the piston I8 to the position shown, thereby causing the injection plunger to return to the position shown under the action of the spring I4.

For limiting the quantity of fuel injected on each stroke. the casing 56 supports a ring 94 having teeth 95 on its outer surface engageable with a rack 96 slidable in the casing. The inner surface of the ring 94 has splines 98 engaging with the outer surface of a sleeve I which has threads cooperating with similar threads I02 on the cylinder 60. Movement of the rack 96, one end of which extends beyond the casing 56, thus turns the sleeve I00 on the cylinder and adjusts the vertical position of the lower end of the sleeve, thereby limiting the plunger stroke since the disc 12 engages with the end of the sleeve.

For the purpose of adjusting the time of injection, the tension of spring I4 may be changed as by substituting a different spring. An alternative adjustment may be efiected by providing a ring I02 in the casing 56 surrounding and in threaded engagement with the periphery of the plate I04 against which the spring I4 rests. When the ring I02 is turned as by a rack I06 engaging teeth I08 on the ring, the plate I04 will be moved downwardly to increase the tension of the spring. A pin IIO may hold the plate against turning. Obviously the actuation of rack I06 may be manual or automatic, as desired.

In operation, with the parts in the position shown, the engine pistons are moved toward each other to build up a pressure in the engine cylinder for the purpose of igniting the fuel to be injected therein. When this compression pressure reaches a predetermined value, which is a function of the area of the passage 84, and the strength of spring I4, the piston 10 is moved rapidly upward, thereby moving the plunger 62 upwardly, first closing the inlet passage 64 and then forcing fuel past the check valve and through the fuel nozzle into the engine cylinder. This causes combustion to take place in the engine cylinder, and the pistons move apart, thereby building up a pressure in the air springs. When the exhaust ports are uncovered causing a substantial drop in the pressure in the engine cylinder, air spring pressure is acting on the upper side of the piston 1-0 returning it to the position shown, thereby causing the return of the injection plunger to the position shown so that the space 66 may again be filled with fuel in readiness for the next injection.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

Iclaim:

1. A free-piston unit including opposed piston assemblies including engine and compressor pistons, an engine cylinder in which the engine pistons are positioned, compressor cylinders at the ends of the engine cylinder for the compressor pistons, and air springs acting on each piston assembly for moving the assemblies toward each other on the compression stroke, in combination with an injection device for delivering fuel to the engine cylinder, said device including a housing having a bore and an inlet port to said bore, a plunger reciprocating in said bore, and a nozzle through which fuel entering said inlet is delivered to the engine cylinder, and means responsive to pressurein the engine cylinder for moving the plunger on the injection stroke 2. A free-piston unit including opposed piston assemblies including engine and compressor pistons, an engine cylinder in which the engine pistons are positioned, compressor cylinders at the ends of the engine cylinder for the compressor pistons, and air springs acting on each piston assembly for moving the assemblies toward each other on the compression stroke, in combination with an injection device for delivering fuel to the engine cylinder, said device including a housing having a bore and an inlet port to said bore, a plunger reciprocating in said bore, and a nozzle through which fuel entering said inlet is delivered to the engine cylinder, means responsive to pressure in the engine cylinder for moving the plunger on the injection stroke, and other means for causing the plunger to move in the opposite direction on the filling stroke in response to pressure in the air spring.

3. A free-piston unit including opposed piston assemblies including engine and compressor pistons, an engine cylinder in which the engine pistons are positioned, compressor cylinders at the ends of the engine cylinder for the compressor pistons, and air springs acting on each piston assembly for moving the assemblies toward each other on the compression stroke, in combination with an injection device for delivering fuel to the engine cylinder, said device including a housing having a bore and an inlet port to said bore, a plunger reciprocating in said bore, and a nozzle through which fuel entering said inlet is delivered to the engine cylinder, means responsive to pressure in the engine cylinder for moving the plunger on the injection stroke, and means for limiting the stroke of the plunger for controlling the fuel quantity delivered on each stroke.

4. A free-piston unit including opposed piston assemblies including engine and compressor pistons, an engine cylinder in which the engine pistons are positioned, compressor cylinders at the ends of the engine cylinder for the compressor pistons, and air springs acting on each piston assembly for moving the assemblies toward each other on the compression stroke, in combination with an injection device for delivering fuel to the engine cylinder, said device including a housing having a bore and an inlet port to said bore, a plunger reciprocating in said bore, and a nozzle through which fuel entering said inlet is delivered to the engine cylinder, means responsive to pressure in the engine cylinder for moving the plunger on the injection stroke, means for limiting the stroke of the plunger for controlling the fuel quantity delivered on each stroke, and other means responsive to pressure in the air spring for causing the plunger to move on the filling stroke.

5. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with an injection device for delivering fuel to the engine cylinder including a fuel injection pump, means for actuating the pump for the delivery of fuel to the engine cylinder in response to pressure in the engine cylinder, and means for causing the pump to move on the filling stroke in response to pressure in the air spring.

6. A tree-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device for delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said bore, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction, and pressure-actuated means for moving the plunger in the opposite direction, said pressure-actuated means being connected to the engine cylinder.

7. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device :lor delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said here, a passage irorn said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction, and pressure-actuated means for moving the plunger in the opposite direction, said last means including a piston, a cylinder in which said piston reciprocates, and a valve element substantially smaller in area than the piston connected thereto, said valve element closing an admission port to the last-mentioned cylinder.

3. A iree piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air sprin including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device for delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said here, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said here, a spring acting on said plunger to move it in one direction, and pressure-actuated means for moving the plunger in the opposite direction, said last means including a piston, a cylinder in which said piston reciprocates, and a valve element substantially smaller in area than the piston connected thereto, said valve element closing an admission port to the last-mentioned cylinder, said admission port communicating with the engine cylinder. 4

9. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device for delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said bore, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction, and pressure-actuated means for moving the plunger in the opposite direction, said pressure-actuated means being connected to the engine cylinder, said pressure-actuated means including a piston and a cylinder in which the piston reciprocates, said piston being connected to the plunger, and a connection from one side of said piston to the engine cylinder.

10. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device 'for delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said bore, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction, and pressure-actuated means for moving the plunger in the opposite direction, said pressure-actuated means being connected to the engine cylinder, said pressure-actuated means including a piston and a cylinder in which the piston reciprocates, said piston being connected to the plunger, a connection from one side of said piston to the engine cylinder, and a connection from the other side of said piston to the air spring.

ii. A tree-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device for delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said bore, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction, andpressure-actuated means for moving the plunger in the opposite direction,

said pressure-actuated means being connected to the engine cylinder, said pressure-actuated means including a piston and a cylinder in which the the engine compression stroke, in combination with a fuel injection device for delivering fuel to the engine cylinder including a, housing having a bore and an injection plunger reciprocating in said bore, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction, and pressure-actuated means for moving the plunger in the opposite direction, said last means including a piston, a cylinder in which said piston reciprocates, and a, valve element substantially smaller in area than the piston connected thereto, said valve element closing an admission port to the last-mentioned cylinder,

' said spring normally holding the valve element in closed position, and thereby controlling the engine cylinder pressure at which the injection of fuel occurs.

13. A free-piston unit including an engine cylinder and piston, a compressor cylinder and piston, said cylinders being connected together and said pistons being interconnected to reciprocate as a unit in said cylinders, an air spring including piston and cylinder elements, one of which is connected to the pistons to move therewith, said air spring causing movement of the pistons on the engine compression stroke, in combination with a fuel injection device for delivering fuel to the engine cylinder including a housing having a bore and an injection plunger reciprocating in said bore, a passage from said bore to the engine cylinder and an inlet passage for fuel to enter said bore, a spring acting on said plunger to move it in one direction and pressure-actuated means for moving the plunger in the opposite direction, said last means including a piston, a cylinder in which said piston reciprocates, and a valve element substantially smaller in area than the piston connected thereto, said valve element closing an admission port to the last-mentioned cylinder, said spring normally holding the valve element in closed position, and thereby controlling the engine cylinder pressure at which the injection of fuel occurs, and means for adjusting the tension of said spring for adjusting the pressure required for causing the injection of fuel.

RALPH J. HOOKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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