FUEL INJECTION NOZZLE

Abstract: In a fuel injection nozzle (10) having an outwardly opening poppet valve (22) that controls the delivery of fuel to an engine combustion chamber, an actuating piston (46) stages the operation of the fuel injection nozzle to provide a low rate of injection (56) during light load engine operation, and a high rate of injection (56,58) during heavy load engine operation. This improved fuel injection nozzle thus enhances the ability of the engine to operate with low noise, hydrocarbon and nitrogen oxide emissions.

Description: This invention relates to a fuel injection nozzle for delivering fuel to the combustion chamber of an internal combustion engine. In a fuel injection system for a direct injection engine, a pump supplies a measured amount of fuel to a fuel injection nozzle for delivery directly into the engine combustion chamber. US patent no. 4693424 describes a fuel injection nozzle having an outwardly opening poppet valve that controls delivery of fuel to the engine combustion chamber. That fuel injection nozzle allows the engine to operate with lower noise, hydrocarbon and nitrogen oxide emissions than engines with other nozzles. US patent no. 4750675 describes an improved fuel injection nozzle also having an outwardly opening poppet valve that controls delivery of fuel to the engine combustion chamber. That improved fuel injection nozzle includes a piston that dampens opening movement of the poppet valve, thereby reducing the initial rate of injection and thus enhancing the ability of the engine to operate with low noise, hydrocarbon and nitrogen oxide emissions. This invention provides a further improved fuel injection nozzle also having an outwardly opening poppet valve that controls the delivery of fuel to the engine combustion chamber. A fuel injection nozzle in accordance with the present invention is characterised by the features specified in the characterising portion of claim 1. In the improved fuel injection nozzle provided by this invention, an actuating piston stages the operation of the fuel injection nozzle to provide a low rate of injection during light load engine operation, and a high rate of injection during heavy load engine operation. This improved fuel injection nozzle further enhances the ability of the engine to operate with low noise, hydrocarbon and nitrogen oxide emissions. The present invention will now by described, by way of example, with reference to the following description and the accompanying drawings, in which:- Figure 1 is an axial sectional view of one embodiment of this improved fuel injection nozzle, showing the construction of the fuel injection nozzle; Figure 2 is a view similar to Figure 1, showing the position of the parts when the poppet valve is partially open; Figure 3 is a view similar to Figure 1, showing the position of the parts when the poppet valve is fully open; and Figure 4 is an axial sectional view of another embodiment of this improved fuel injection nozzle. Referring first to Figures 1-3, a fuel injection nozzle 10 has a body 12 adapted to be received in an engine cylinder head, and a holder 14 having a fitting 16 that receives fuel from an injection pump. Body 12 and holder 14 are threaded together at 18, and a gasket 20 seals the threaded connection. A poppet valve 22 is received in a bore 24 of body 12. Poppet valve 22 has a head 26 that engages a lower end 28 of body 12, and a stem 30 that extends into a chamber 32 formed between body 12 and holder 14. Within chamber 32, a spring 34 is compressed between a spring retainer 36 secured around stem 30 and a stop member 38 that rests against the top 40 of body 12. Holder 14 has a fuel inlet passage 42 that opens into a piston bore 44. An actuating piston 46 is lapped fit in piston bore 44. Actuating piston 46 has an inner shoulder 48 that seals against the perimeter of an upper face 50 of stem 30. When the injection pump supplies fuel to fuel injection nozzle 10, the injection pressure of the fuel acts on an upper face 51 of actuating piston 46. Actuating piston 46 transfers the resulting opening force to stem 30 to displace poppet valve 22 against the bias of spring 34. Fuel then flows through fuel inlet passage 42, a passage 52 in actuating piston 46, and a passage 54 in stem 30 to lower and upper sets of orifices 56 and 58, and is discharged across a gap 60 (Figures 2-3) between head 26 and the lower end 28 of body 12. An extended stop 62 engages and prevents further travel of actuating piston 46 when poppet valve 22 has been displaced only far enough to expose the lower set of orifices 56 below the lower end 28 of body 12. By using only the lower set of orifices 56 to deliver fuel to the engine combustion chamber during light load engine operation, the rate of fuel injection is reduced and the ability of the engine to operate with low noise, hydrocarbon and nitrogen oxide emissions is enhanced. The injection pressure increases with load, and in response to the higher injection pressures of heavy load engine operation, the upper face 50 of stem 30 acts as a piston and further displaces poppet valve 22 until a shoulder 64 on stem 30 engages stop member 38. At that time, both sets of orifices 56 and 58 are exposed below the lower end 28 of body 12 to allow delivery of the fuel required for heavy load engine operation. It should be noted that a clear separation is provided between the first stage in which only the lower set of orifices 56 discharge fuel, and the second stage in which both sets of orifices 56 and 58 discharge fuel. The ratio of first and second stage opening pressures is determined by the ratio of the area of upper face 51 of actuating piston 46 and the area of upper face 50 of stem 30. By reducing the rate of injection during the first stage, the noise, hydrocarbon, and nitrogen oxide emissions are improved at heavy loads. It will be appreciated that the same injection characteristics could be achieved by employing two springs. However, addition of a second spring would require an increase in the diameter or length of the fuel injection nozzle. The improved fuel injection nozzle provided by this invention does not require such an increase in length or diameter. An opening 66 through stop member 38 is eccentric to the axis of fuel injection nozzle 10, thereby allowing stop member 38 to be assembled around stem 30 and then, upon insertion into holder 14, to slide laterally under shoulder 64 to act as a stop for poppet valve 22. Toward the end of the injection event, the rate of fuel delivery falls off, and spring 34 raises poppet valve 22 (and actuating piston 46) to engage head 26 with the lower end 28 of body 12. During the injection event, actuating piston 46 compresses the fuel in chamber 32. To prevent hydraulic lock, a small equalizing orifice 68 is provided though stem 30 between passage 54 and chamber 32. The size of equalizing orifice 68 must be optimized - large enough to allow movement of poppet valve 22 at the desired rate, but small enough to avoid pressures in chamber 32 that could cause actuating piston 46 to separate from stem 30 before actuating piston 46 engages extended stop 62. Referring now to Figure 4, a fuel injection nozzle 110 has a body 112 adapted to be received in an engine cylinder head, and a holder 114 having a fitting 116 that receives fuel from an injection pump. Body 112 and holder 114 are threaded together at 118, and a gasket 120 seals the threaded connection. A poppet valve 122 is received in a bore 124 of body 112. Poppet valve 122 has a head 126 that engages a lower end 128 of body 112, and a stem 130 that extends into a chamber 132 formed between body 112 and holder 114. Within chamber 132, a spring 134 is compressed between a spring retainer 136 secured around stem 130 and a stop member 138 that rests against the top 140 of body 112. Holder 114 has a fuel inlet passage 142 that opens into a piston bore 144. An actuating piston 146 is lapped fit in piston bore 144, and has an inner shoulder 148 that engages a shoulder 150 on stem 130. Stem 130 has an extension 131 that is lapped fit in a bore 147 formed in piston 146. When the injection pump supplies fuel to fuel injection nozzle 110, the injection pressure of the fuel acts on a face 151 of actuating piston 146. Actuating piston 146 transfers the resulting opening force to stem 130 to displace poppet valve 122 against the bias of spring 134. Fuel then flows through fuel inlet passage 142 and a passage 154 in stem 130 to lower and upper sets of orifices 156 and 158, and is discharged across the gap between head 126 and the lower end 128 of body 112. An extended stop 162 engages and prevents further travel of actuating piston 146 when poppet valve 122 has been displaced only far enough to expose the lower set of orifices 156 below the lower end 128 of body 112. By using only the lower set of orifices 156 to deliver fuel to the engine combustion chamber during light load engine operation, the rate of injection is reduced and the ability of the engine to operate with low noise, hydrocarbon and nitrogen oxide emissions is enhanced. The injection pressure increases with load, and in response to the higher injection pressures of heavy load engine operation, an upper face 163 of stem 130 acts as a piston and further displaces poppet valve 122 until a shoulder 164 on stem 130 engages stop member 138. At that time, both sets of orifices 156 and 158 are exposed below the lower end 128 of body 112 to allow delivery of the fuel required for heavy load engine operation. Toward the end of the injection event, the rate of fuel delivery falls off, and spring 134 raises poppet valve 122 (and actuating piston 146) to engage valve head 126 with the lower end 128 of body 112. This embodiment also provides a clear separation between the first stage in which only the lower set of orifices 156 discharge fuel, and the second stage in which both sets of orifices 156 and 158 discharge fuel. The ratio of first and second stage opening pressures is determined by the ratio of the area of upper face 151 of actuating piston 146 and the area of upper face 163 of stem 130. By reducing the initial rate of injection during the first stage, the noise, hydrocarbon, and nitrogen oxide emissions are improved also at heavy loads. Holder 114 has a passage 169 that vents chamber 132. Chamber 132 collects any leakage past bore 147 or bore 144. Vent passage 169 prevents hydraulic lock in chamber 132. Because this embodiment does not pressurize chamber 132 and accordingly does not create hoop stress in holder 114, the outside diameter of holder 114 may be smaller than the outside diameter of holder 14. It will be appreciated that a separate bushing around actuating piston 146 within holder 114 may simplify manufacture of this embodiment, and for some purposes, it may be desirable to provide a separate bushing around actuating piston 46 within holder 14.

Claims: 1. A fuel injection nozzle (10,110) comprising a body (12,112) with an axial bore (24,124), a poppet valve (22,122) including a stem (30,130) received in the bore and a head (26,126) adapted to engage an end (28,128) of the body, a spring (34,134) biasing the stem to engage the head with the end of the body, and a holder (14,114) secured to the body, the holder having a fuel inlet passage (42,142), wherein the fuel inlet passage opens into a piston bore (44,144) formed in the holder, an actuating piston (46,146) is received in the piston bore, the actuating piston having a face (51,151) exposed to the injection pressure of fuel in the fuel inlet passage, and the actuating piston being adapted to transfer said injection pressure to the stem to displace the poppet valve against the bias of the spring, whereby fuel flows through the fuel inlet passage and passage means (52,54,154) in the actuating piston and the stem to a plurality of orifices (56,58,156,158) opening though the stem from the passage means and is discharged from the orifices across a gap (60) formed between the head and the end of the body, characterised in that a stop (62,162) engages the actuating piston so that, in response to the lower injection pressures of light load engine operation, the poppet valve is displaced only far enough to allow fuel to be discharged from a portion (56,156) of the orifices, and in that the stem has a face (50,163) exposed to said injection pressure so that, in response to the higher injection pressures of heavy load engine operation, the stem responds directly to said higher injection pressures to further displace the poppet valve far enough to allow fuel to be discharged from all said orifices, whereby the rate at which fuel is discharged during light load engine operation is lower than the rate at which fuel is discharged during heavy load operation. 2. A fuel injection nozzle as claimed in claim 1, wherein the stem (30) extends into a chamber (32) formed between the body (12) and the holder (14), and wherein the actuating piston (46) extends into the chamber and has a shoulder (48) adapted to seal against the end (50) of the stem. 3. A fuel injection nozzle as claimed in claim 1, wherein the stem (130) extends into a chamber (132) formed between the body (112) and the holder (114), wherein the actuating piston (146) has an internal bore (147), wherein the stem (130) has an extension (131) received in the internal bore, wherein the actuating piston (146) has a shoulder (148) adapted to engage a shoulder (150) of the stem to transfer said injection pressure to the stem, and wherein the face (163) on the stem (130) is on the extension (137). 4. A fuel injection nozzle as claimed in claim 3, wherein a passage (169) opens from the chamber (132) whereby the pressure in the chamber is vented when the spring (134) moves the poppet valve (122) to engage the head (112) with the end (128) of the body (112).

Inventors: SCZOMAK, DAVID PETER
Applicants: GENERAL MOTORS CORPORATION
Application year: 1989
Main classification: F02M45
IPC codes: F02M61