GB2065772A

GB2065772A - Fuel Injection Valves

Info

Publication number: GB2065772A
Application number: GB8040947A
Authority: GB
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 1979-12-21
Filing date: 1980-12-22
Publication date: 1981-07-01
Also published as: DE3048500A1; JPS5694854U

Abstract

A storage chamber 24 contains a check value member 32 controlling an inlet 22 from an intermittently operated metering pump and a needle valve member 28 controlling flow to outlets 44. A spring 34 bears on a retainer 30 integral with the needle 28, and urges the valve members 32, 28 to close the inlet and outlets. The needle 28 has a conoidal step surface 50 in a valve lift chamber 48 subject to storage chamber pressure through passages 46 for opening the needle valve 28. When the pressure of an incoming fuel charge falls the check valve closes and the storage chamber pressure on the surface 50 causes needle valve opening. <IMAGE>

Description

SPECIFICATION Fuel Injection Valves The invention relates to fuel injection valves for internal combustion engines, that is to say suitable for use with a jerk pump for the injection of fuel oil into a diesel engine. The injection valve receives metered charges of fuel from the jerk pump, and introduces the fuel into the engine combustion chamber against gases at high pressure at the end of the compression stroke.

Considerable pressure is required ta break up the fuel into a fine spray for good combustion. The pump is driven by the engine, and so a decrease in engine speed causes a corresponding decrease in pump output and injection pressures, and this adversely affects combustion and engine performance.

The invention provides a fuel injection valve for an internal combustion engine comprising a fuel inlet leading into a storage chamber for pressurized fuel, a fuel outlet, a check valve member controlling the inlet, a needle valve member controlling the outlet, a spring biassing the said valve members to close the inlet and outlet, the needle valve member having a surface subject to the pressure of fuel in the storage chamber for opening the needle valve.

The storage chamber provides for temporary storage or accumulation of a pressurized fuel charge. Only upon completion of the delivery of each charge from the fuel pump is the accumulated charge sprayed into the engine.

Injection pressure is therefore independent of engine speed. The valve is little affected by the piping between itself and the fuel pump, so there is no pressure drop, and parts are not pitted and eroded due to cavitation. A pump of small capacity can be used to produce sufficiently high pressure if the needle valve is well seated and the check valve fluid tight.

Drawings Figure 1 is a diagram of a fuel injection system incorporating a valve in accordance with the invention: and Figure 2 is an axial section of a fuel injection valve in accordance with the invention.

In Figure 1 is a fuel injection valve 10 for the introduction of diesel fuel into a diesel engine, not shown. The valve 10 is fed from a jerk pump 12 by way of a conduit 14. The jerk pump 12 deiivers accurately measured amounts of pressurized diesel fuel to the valve 10.

In Figure 2, the valve 10 comprises an upper body 16, a lower body 18 and a cap 20 threaded on the upper body 16 in a fluid-tight manner. The upper body 1 6 has a fuel inlet 22 formed therein for connection to the jerk pump 12 by way of the conduit 14 as shown in Figure 1. Under the fuel inlet 22 is a storage chamber 24. The lower body 18 has formed therein a guide bore 26 through which a needle valve member 28 slidably extends. The needle valve member 28 will hereinafter be referred to as the needle. The needle 28 has formed thereon near the middle a stepped spring retainer 30. A check valve 32 is mounted on the needle 28 and is normally biased against the upper body 1 6 to close the fuel inlet 22 by the force of a helical compression spring 34 interposed between the check valve 32 and the spring retainer 30.The check valve 32 permits fuel flow only from the fuel inlet 22 in the upper body 1 6 into the storage chamber 24. Thus the storage chamber 24 temporarily stores each incoming charge of pressurized fuel.

The needle 28 extends, with clearance, through a fuel outlet passageway 36 in a nozzle 38, and terminates in a conical tip 40. Normally the tip 40 of the needle 28 is biased by the spring 34 into engagement with a valve seat 42 to close fuel outlet openings or nozzle orifices 44 at the tip of the nozzle 38. The spring 34 is in slight compression when the needle tip 40 is in engagement with the valve seat 42. Fuel outlet passageways 46 extend downwardly from the bottom of the storage chamber 24 to a valve lift chamber 48, encircling a conoidal step 50 of the needle 28, and communicating with the fuel outlet openings 44 via the first mentioned outlet passageway 36. The pressurized fuel in the valve lift chamber 48 urges the needle 28 upwardly, away from the valve seat 42.The clearance between the needle 28 and the guide bore 26 is preferably from 1 to 6,u, more preferably from 2 to 4 u. Thus the tip 40 of the needle 28 is neatly seated on the valve seat 42. The axis of the needle 28 should be kept square to the lower surface of the upper body 16, preferably to an extent of under 10/1000, more preferably under 5/1000.

In operation, each charge of pressurized diesel fuel from the jerk pump 1 2 enters the valve 10 through its inlet 22. The pressurized fuel first enters the storage chamber 24 through the check valve 32 against the force of the spring 34, and then enters the valve lift chamber 48 through the outlet passageways 46 extending from the storage chamber 24. The pressurized fuel thus stored in the storage chamber 24 and in the valve lift chamber 48 exerts an upward force on the stepped spring retainer 30 and on the conoidal step 50 of the needle 28. These upward forces are counteracted by the downward forces exerted on the cross-section of the needle 28 and the stepped spring retainer 30 by the pressurized fuel in the storage chamber 24.Thus, during the delivery of each fuel charge from the jerk pump 12, the spring 34 holds the needle 28 bottomed against the valve seat 42.

Upon completion of the delivery of each fuel charge from the jerk pump 12, the fuel pressure rapidly drops in the fuel inlet 22, with a consequent upward displacement of the check valve 32 to close the fuel inlet 22. The fuel in the storage chamber 24 and valve lift chamber 48 retains its pressure as the check valve 32 closes the fuel inlet 22. Since then the fuel pressure in the fuel inlet 22 becomes approximately zero, the downward force of the spring 34 on the needle 28 is overcome by the upward force exerted on the conoidal step 50 of the needle 28 by the pressurized fuel in the valve lift chamber 48.

The result is the upward displacement of the needle 28, out of engagement with the valve seat 42, so that pressurized fuel is injected in the form of droplets into the combustion chamber of the diesel engine through the nozzle orifices 44. The fuel pressure in the storage chamber 24 and valve lift chamber 48 gradually decreases with the progress of such fuel spraying, until the force of the spring 34 overcomes the upward force acting on the conoidal step 50 of the needle 28.

Thereupon the needle moves back into engagement with the valve seat 42 to close the nozzle orifices 44. One cycle of the fuel injection is now completed. The same cycle is repeated as the jerk pump 1 2 delivers successive charges of pressurized fuel into the valve assembly 1 0.

Claims

1. A fuel injection valve for an internal combustion engine comprising a fuel inlet leading into a storage chamber for pressurized fuel, a fuel outlet, a check valve member controlling the inlet, a needle valve member controlling the outlet, a spring biassing the said valve members to close the inlet and outlet, the needle valve member having a surface subject to the pressure of fuel in the storage chamber for opening the needle valve.

2. A valve according to claim 1 in which the check valve member is slidable with respect to the needle valve member, and the spring bears on a retainer integral with the needle valve member and on the check valve member.

3. A valve according to claim 1 or claim 2 in which the said surface of the needle valve member is in a valve lift chamber connected by passages to the storage chamber.

4. A valve according to any preceding claim comprising an upper body containing the inlet, a lower body containing the storage chamber and a cap threaded on the upper body.

5. A fuel injection valve as herein described with reference to Figure 2 of the drawings.