EP2039925A1 - Arrangement for fixing an injector tube in a cylinder head by shrink fitting - Google Patents

Abstract

The invention relates to an arrangement for the shrink-fitting attachment of an injector tube (2) for receiving an injector, in a housing (30) a cylinder head (1) of a direct-injection type combustion engine via a compression tool (4) and a press, said housing passing through a coolant cavity said injector tube (2) having on either side of said cavity (3) a lower part (22) coaxial member intended to be hooped into an associated lower bearing surface of the housing (30), and an upper part (21) intended to be received in an upper bearing surface (31) of the housing (30), said arrangement comprising stop means (43). ) blocking in position the injector tube (2) in the lower bearing surface (32), characterized in that the compression tool (4) comprises the stop means (43) so that the injector tube (2) is locked in position in the lower bearing surface (32) of the bolt (1) when the means set of stops (43) of the compression tool (4) rest on the cylinder head (1).

Description

The invention relates to the field of internal combustion engines and direct injection and more particularly to an arrangement for fixing a shrink-type injector tube in a direct injection type engine cylinder cooled by a cooling liquid.

A direct injection-type heat engine generally comprises a cylinder head in which a housing is provided, in which an injector tube and a substantially cylindrical injector are arranged, a lower end of which opens into a combustion chamber of the engine, and of which at least one intermediate portion is sealingly received in a water chamber or coolant circulation cavity of the cylinder head.

To cool the injector well, the shape of the injector tube in its part in contact with the coolant must match that of the injector. When an injector tube is hooped at at least one hooping zone located at the sole of the cylinder head, that is to say between the water chamber and the combustion chamber, the thermal barrier existing between the coolant and the injector is substantially 1 to 2 mm, which allows a better cooling of the injector compared to a thermal barrier of substantially 6 to 8 mm for an injector housing which would be realized in a foundry wells. Thus a shrink-injector tube avoids coking phenomena injector nose to which are exposed direct injection engines.

To position the injector tube in its housing, it is conventionally introduced by an upper end of the housing formed in the cylinder head. The arrangement of the injector tube in the cylinder head comprises stop means for locking in position the injector tube in an associated hooping zone of the housing. Thus, the injector tube comprises a radial shoulder adapted to cooperate with a complementary portion of the inner wall of the housing formed in the cylinder head. Once placed in its housing, the tube-injector is fretted with a press and a tool in the shrinking zone, located at the level of the sole of the cylinder head, that is to say in the part of the cylinder head between the water chamber or coolant cavity and the combustion chamber. This hooping zone is substantially narrower than the rest of the housing so that the injector tube conforms to the shape of the injector nose. In a first shrinking step, a compression of the injector tube places the shrinking zone of the breech vis-a-vis with the lower end of the injector tube. Then during a second shrinking step, the displacement of the injector tube is locked in position when the radial shoulder of the injector tube abuts against the complementary potion of the inner wall of the housing formed in the cylinder head.

Another way of positioning the tube-injector is for example proposed in the document JP200017627 wherein the inner walls of the water chamber or the coolant cavity form with the inner wall of the housing formed a stop or step on which a section of complementary shape of the injector tube abuts.

However, the injector tube is during a mounting step subjected to compressive or tensile stresses that can cause unwanted deformations and alter the final assembly or destroy the injector tube.

To remedy this problem, one method is to increase the thickness of the tube-injector to make it more solid. However, to divide by at least two the stresses applied to the injector tube during hooping, it is necessary to increase the thickness thereof by two-thirds. The thermal barrier between the coolant and the injector is then increased, which does not properly cool the injector.

In order to overcome the aforementioned drawbacks, an object of this invention is therefore to propose an improved arrangement for fastening a tube-injector in a housing formed in a cylinder head.

For this purpose, the invention proposes an arrangement for the shrink fitting of an injector tube intended to receive an injector, in a housing formed in a direct injection engine cylinder head via a compression tool. and a press, said housing passing through a coolant cavity, said injector tube having on either side of said cavity a coaxial lower portion intended to be hooped in an associated lower bearing surface of the housing, and an upper part intended to be received in an upper chamber of the housing, said arrangement comprising stop means blocking the injector tube in position in the lower seat, characterized in that the compression tool comprises the stop means so that the injector tube is locked in position in the lower range of the cylinder head when the stop means of the compression tool are in abutment on the cylinder head.

Such an arrangement makes it possible not to alter the injector tube during the second hooping step. Only the cylinder head undergoes the forces due to the press and the tool. The injector tube is thus subjected to no compressive stress or traction during this second step.

In this arrangement, the injector tube has a simpler and more compact shape thus reducing the production costs not only of the injector tube but also of the cylinder head itself. It is no longer necessary to create means of stopping inside the housing provided either in the part located above the water chamber or at the water chamber and the zone of water. hooping. The final assembly is further simplified, the final position of the injector tube relative to the cylinder head being provided by the precise dimensions of the compression tool used for hooping.

• les moyens d'arrêt peuvent être réalisés par un épaulement radial de l'outil de compression, ledit épaulement radial formant butée axiale,
• l'épaulement radial peut comporter à son extrémité un épaulement axial orienté dans le sens de compression du tube-injecteur adapté à venir coopérer avec la culasse,
• la culasse peut comporter un épaulement axial en saillie à la périphérie du logement ménagé, ledit épaulement axial formant une zone d'appui destiné à entrer en contact avec les moyens d'arrêt.

According to other characteristics:

• the stop means can be made by a radial shoulder of the compression tool, said radial shoulder forming axial abutment,
• the radial shoulder may comprise at its end an axial shoulder oriented in the direction of compression of the injector tube adapted to cooperate with the cylinder head,
• the yoke may comprise an axial shoulder projecting at the periphery of the housing formed, said axial shoulder forming a bearing zone intended to come into contact with the stop means.

The invention also relates to a direct injection type heat engine comprising such an arrangement.

• la figure 1 représente une vue en coupe de l'agencement pour la fixation d'un tube-injecteur dans une culasse de moteur thermique de type à injection directe,
• la figure 2 représente une vue en coupe d'un deuxième mode de réalisation de l'agencement,
• la figure 3 représente une vue en coupe d'un troisième mode de réalisation de l'agencement,
• la figure 4 représente une vue en coupe d'un quatrième mode de réalisation de l'agencement.

The invention will be better understood from the following description of an embodiment given by way of non-limiting example with reference to the accompanying drawings, in which:

• the figure 1 is a sectional view of the arrangement for attaching an injector tube to a direct injection type combustion engine cylinder head,
• the figure 2 represents a sectional view of a second embodiment of the arrangement,
• the figure 3 represents a sectional view of a third embodiment of the arrangement,
• the figure 4 is a sectional view of a fourth embodiment of the arrangement.

To the figure 1 , there is shown a sectional view of a cylinder head 1 for a combustion engine (not shown) of a direct injection-type motor vehicle, that is to say having an injector opening directly into a combustion chamber of the engine ( not shown).

The cylinder head 1 is traversed by a bore or housing 30 in which is arranged an injector tube 2 for receiving a substantially cylindrical injector (not shown), a lower end or injector nose opens into the combustion chamber of the engine. At least an intermediate portion of the injector is sealed in a water chamber or coolant circulation cavity 3 of the curtain 1. The cylinder head 1 thus comprises an upper portion 11 located above the chamber water 3 and a lower portion or sole 12 located between the water chamber 3 and the combustion chamber.

The injector tube 2 comprises on either side of the cavity 3, a coaxial lower portion 22 intended to be rubbed in a hooping zone 32 or associated substantially lower cylindrical surface 32 of the housing 30 of the cylinder head 1, and a portion upper portion 21 intended to be received in a substantially cylindrical surface 31 of the housing 30 of the cylinder head 1. The rubbing zone 32 adapted to receive the nozzle nose is narrower than the upper part 21.

The injector tube 2 comprises a radial shoulder 23, oriented towards the inside of the housing 30 forming a seat 23 adapted to receive a compression tool 4 for fastening by hooping.

The compression tool 4 has a substantially cylindrical shape adapted to be housed in the upper part 21 of the injector tube 2, and has a lower face 42 adapted to cooperate with the shoulder 23 of the injector tube.

The compression tool 4 comprises stop means 43 adapted to cooperate with the cylinder head 1. The stop means 43 are intended to be in contact with a bearing zone 110 located at the periphery of the housing formed in the cylinder head 1 during the compression of the injector tube 2.

In the first embodiment of the figure 1 , the stop means are formed by a radial shoulder of the compression tool 4. The radial shoulder 43 thus forms an axial abutment. A first hooping step consists in placing the injector tube 2 in the housing formed in the cylinder head 1. Then the injector tube 2 is compressed using a press (not shown) and the compression tool 4. During this compression, the lower portion 22 of the injector tube 2 is hooped in the associated hooping zone 32. The displacement of the compression tool 4, and therefore of the injector tube 2 is locked in position when the compression tool 4 comes into abutment on the cylinder head 1, that is to say when the shoulder 43 of the compression tool 4 comes into abutment on the bearing zone 110 of the cylinder head 1.

The final position of the injector tube 2 in the cylinder head 1 is thus achieved thanks to a precise dimension of the compression tool 4, in particular between the seat 23 and the radial shoulder 43.

The injector tube 2 then undergoes no further stress when the compression tool 4 comes into abutment on the cylinder head 1. In fact, it is the latter 1 which receives the compression forces at the end of the shrinking of the tube-injector 2. The risks of deformation or destruction of the injector tube 2 are thus reduced.

The shape of the injector tube 2 can thus be simplified. It is also not necessary to add stop elements in the inner wall of the housing 30 formed in the cylinder head 1.

Thus, the upper end of the substantially cylindrical injector tube 2 is received in the upper end 11 associated with the cylinder head 1. At least one O-ring is interposed between the upper end of the injector tube 2 and the end upper 11 of the cylinder head 1 to seal the injector tube 2.

In a second embodiment as shown in FIG. figure 2 , the upper end 11 of the yoke comprises an axial shoulder 13 projecting from the periphery of the housing 30 formed in the cylinder head 1. The axial shoulder 13 thus forms a projecting ring, and constitutes the bearing zone 110 of the cylinder head 1 on which the compression tool 4 comes into abutment when the lower part 22 of the injector tube 2 is hooped. It will be understood that the dimensions of the radial shoulder 43 of the compression tool 4 and of the axial shoulder 13 of the yoke 1 are such that when the compression tool 4 comes into abutment against the yoke 1, the tube -injector 2 is shrunk in its shrinking zone 32. It will also be understood that the axial shoulder 13 may comprise at least two crown portions forming bearing zones 110.

In other embodiments, as shown in Figures 3 and 4 , the radial shoulder 43 of the compression tool 4 comprises at its end an axial shoulder 14, oriented in the compression direction of the injector tube 2. The shape of the bearing zone 110 of the cylinder head 1 is complementary to the shape of the compression tool 4, and can either be flat ( figure 3 ), or have an axial shoulder ( figure 4 ) whose dimensions are such that when the compression tool 4 comes into abutment against the cylinder head 1, the injector tube 2 is shrunk in its shrinking zone 32.

In such a fixing arrangement, the injector tube 2 undergoes no stress when the compression tool 4 abuts on the cylinder head 1.

In this arrangement, the injector tube has a simpler and more compact shape thus reducing the production costs not only of the injector tube but also of the cylinder head itself.

It is no longer necessary to create means of stopping inside the housing formed either in the part situated above the water chamber or at the water chamber and the zone of water. hooping.

The final assembly is further simplified, the final position of the injector tube relative to the cylinder head being provided by the precise dimensions of the compression tool used for hooping.

Claims (5)

Arrangement for shrink-fitting an injector tube (2) for receiving an injector into a housing (30) in a direct injection engine cylinder head (1) via a compression tool ( 4) and a press, said housing passing through a coolant cavity (3), said injector tube (2) having on either side of said cavity (3) a coaxial lower portion (22) for to be shrunk into an associated lower bearing surface (32) of the housing (30), and an upper portion (21) to be received in an upper bearing surface (31) of the housing (30), said arrangement including stop means (43); ) blocking in position the injector tube (2) in the lower bearing surface (32), characterized in that the compression tool (4) comprises the stop means (43) so that the injector tube (2) is locked in position in the lower bearing (32) of the breech (1) when the stop means (43) of the seat 1 compression (4) are supported on the cylinder head (1). Arrangement according to claim 1 characterized in that the stop means (43) are formed by a radial shoulder (43) of the compression tool (4), said radial shoulder (43) forming an axial stop. Arrangement according to claim 2 characterized in that the radial shoulder (43) comprises at its end an axial shoulder (14) oriented in the direction of compression of the injector tube (2) adapted to cooperate with the cylinder head (1). Arrangement according to one of the preceding claims, characterized in that the yoke (1) has an axial shoulder (13) projecting from the periphery of the formed housing (30), said axial shoulder (13) forming a bearing zone ( 110) intended to come into contact with the stop means (43). Direct injection type thermal engine of the type comprising a yoke (1) traversed by at least one housing (30) in which is arranged according to one of the preceding claims a tube-injector (2).

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