ELECTROMAGNETICALLY-CONTROLLED FUEL INJECTION VALVE FOR I.C. ENGINES

Abstract: An electromagnetically-controlled fuel injection valve (1) for i.c. engines includes a body (2) carrying an upper electromagnetic metering valve (10) which con­ trols communication between a control chamber (9), to which the fuel is fed under pressure through an inlet hole (Z) to keep the associated injector needle (4) in the closed position, and a discharge hole (A) for con­ trolling the opening of the needle (4). The solenoid valve (10) with the control chamber (9), the inlet hole (Z) and the discharge hole (A) are integrated in a single element forming a head (13) for the body (2) of the injection valve (1).

Description: The present invention relates to electromagnetically-controlled fuel-injection valves in general for diesel engines, as defined in the preamble of claim 1. In known injection valves of this type, the body of the metering solenoid valve, the control chamber, the inlet hole and the discharge hole are generally formed in separate elements and are connected together during the assembly of the injection valve. The use of these separate elements involves considerable constructional complications and consequent production problems; furthermore in many cases the metering action of the valve is not very exact and the readiness in answering is low. Valves of this type are described in WO-A-8203108, in CH-A-434875 (disclosing the features of the preamble of claim 1 and, per se, of claims 2 and 3) and in GB-A-2185530. The object of the present invention is to avoid these disadvantages and to provide an injection valve of the type defined at the beginning which can be made with a smaller number of components, which is thus cheaper to manufacture and assemble, and whose metering action and readiness in answering are respectively very exact and very high. According to the invention, this object is achieved by an electromagnetically-controlled fuel-injection valve for i.c. engines, comprising the features of claim 1. The invention will now be described in detail with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a schematic longitudinal sectional view of a fuel injection valve according to the invention, and Figure 2 shows a variant of Figure 1. With reference initially to Figure 1, a fuel injection valve for diesel engines is generally indicated 1 and comprises essentially a body 2 whose lower end defines an injection nozzle 3 with which a control needle 4 cooperates and is movable axially in a central cavity 5 within the body 2. This cavity 5 forms an injection chamber 6 close to the injection nozzle 3, to which the fuel is supplied under pressure by a pump, not illustrated, from a supply inlet 7 and a passage 8. The top of the cavity 5 forms a control chamber 9 to which the fuel is also supplied under pressure through an inlet hole Z. The control chamber 9 is also connected to a discharge through a discharge hole A the opening and closing of which is controlled in known manner by means of an electromagnetically-controlled metering valve 10 the obturator 11 of which is slidable in a guide 12 coaxial with the cavity 5. When the obturator 11 is in its position closing the discharge hole A, the needle 4 is kept in the lowered position to prevent the passage of the pressurised fuel in the injection chamber 6 to the injection nozzle 3. The opening of the discharge hole A by the obturator 11 of the solenoid valve 10 causes a pressure drop in the control chamber 9 and the consequent raising of the needle 4, whereby the pressurised fuel in the injection chamber 6 may be injected through the nozzle 3. According to the invention, the metering solenoid valve 10 with its guide 12, the control chamber 9, and the inlet hole Z and discharge hole A are integrated in a single common element 13 forming a head for the body 2 of the injection valve 1. In the embodiment illustrated in Figure 1, the head element 13 is separate from the body 2 of the injection valve 1 and is fixed mechanically thereto, for example, by means of an axial locking ring nut 14. Alternatively, the head element 13 could be integral with the body 2. In both cases, the inlet hole Z and the discharge hole A may be formed by working directly in the head element 13 or may be formed in respective inserts 15, 16 housed in the head element 13 in the manner illustrated in Figure 2.

Claims: An electromagnetically controlled fuel injection valve for internal combustion engines, comprising: a body (2) having a lower injection nozzle (3) provided with an injection passage; an injection chamber (6) into which the fuel is supplied under pressure; a needle (4) moving axially in an elongated cavity (5) of said body and of said nozzle between a first position in which is closed the communication between said injection chamber (6) and said injection passage and a second position in which said communication is open; an upper electromagnetic metering valve (10) provided with an axially movable pin (11) which controls fuel flow through a discharge hole (A) from a control chamber (9) into which fuel is supplied under pressure, the needle in said elongated cavity (5) being kept in the said first and second position respectively when the fuel pressure in said control chamber (9) is greater or lower than a predetermined value, said electromagnetic metering valve being housed in a seat provided on the upper surface of the fuel injection valve; a head (13) protruding from the upper part of said body and including an axial hole of constant diameter which is coaxial with said elongated cavity (5) of said body (2) and in which there is disposed a first insert (16) provided with said discharge hole (A), and including further a radial hole (Z) the axis of which is orthogonal to the axis of said axial hole and which is in communication with said axial hole and with a source of pressurized fuel, characterized in that said head (13) further accommodates a second insert (15) provided with said radial hole (Z), and in that said axial hole of constant diameter completely passes through said head (13) and defines with said inserts (15, 16) and with the upper extremity of said needle (4) said control chamber (9) into which the fuel is supplied under pressure through said radial hole (Z). A valve according to Claim 1, wherein the head (13) is fixed mechanically to said body (2). A valve according to one of the preceding Claims wherein said head comprises a part of a conduit for supplying the fuel under pressure to said injection chamber (6).

Inventors: FILIPPI, RENATO
Applicants: ELASIS SISTEMA RICERCA FIAT NEL MEZZOGIORNO SOCIETA CONSORTILE PER AZIONI
Application year: 1988
Main classification: F02M47
IPC codes: F02M47, F02M51