Fuel injection valve

A fuel injection valve that injects fuel directly into a cylinder of an internal combustion engine includes: a nozzle inserted into a fuel injection valve fitting hole formed in the cylinder; a cylindrical tip seal holder attached to the nozzle; and an annular seal member that is fitted to the tip seal holder and seals between an inner circumferential surface of the fuel injection valve fitting hole and an outer circumferential surface of the tip seal holder.

TECHNICAL FIELD

The present invention relates to a fuel injection valve that is used in an internal combustion engine.

BACKGROUND ART

A fuel injection valve of the cylinder injection type that supplies fuel directly into a combustion chamber of an internal combustion engine is per se known (refer to Patent Document #1). When such a fuel injection valve is attached to its cylinder, an annular seal member is sandwiched between the inner circumferential surface of the fuel injection valve fitting hole and the outer circumferential surface of the nozzle that is inserted into the fuel injection valve fitting hole, and thereby leakage of combustion gases is prevented.

CITATION LIST

Patent Literature

Patent Document #1: Japanese Laid-Open Patent Publication 2011-64124.

SUMMARY OF INVENTION

Technical Problem

With the fuel injection valve described in Patent Document #1, a groove for fitting the seal member is provided in the outer circumferential surface of the nozzle, and the shape of the nozzle is determined to match the diameter of the fuel injection valve fitting hole in the cylinder. Due to this, with the fuel injection valve described in Patent Document #1, it is necessary to make nozzles for each cylinder type that has a different fuel injection valve fitting hole diameter.

Solution to Technical Problem

A fuel injection valve, according to a first aspect of the present invention, that injects fuel directly into a cylinder of an internal combustion engine, comprises: a nozzle inserted into a fuel injection valve fitting hole formed in the cylinder, a cylindrical tip seal holder attached to the nozzle; and an annular seal member that is fitted to the tip seal holder and seals between an inner circumferential surface of the fuel injection valve fitting hole and an outer circumferential surface of the tip seal holder.

Advantageous Effects of Invention

Since, according to the present invention, it is sufficient to manufacture a tip seal holder according to the diameter of the fuel injection valve fitting hole, and thereby it is possible to fit nozzles of the same shape to fuel injection valve fitting holes of a plurality of types having different diameters, accordingly it is possible to anticipate an enhancement of productivity.

DESCRIPTION OF EMBODIMENTS

Embodiments of a fuel injection valve according to the present invention will now be explained in the following with reference to the drawings.

FIG. 1is a block diagram showing the structure of a fuel injection device100that comprises a fuel injection valve101according to a first embodiment of the present invention. The fuel injection device100comprises a ECU190that is a fuel injection control device, and the fuel injection device101.

The ECU190takes in information for an internal combustion engine as detected by sensors of various types, such as its rotational speed, its boost pressure, its intake air amount, its intake temperature, its water temperature, its fuel pressure, and so on, and performs optimum control of fuel injection adapted to the state of the internal combustion engine (engine).

The ECU190comprises an injection amount calculation unit191that calculates an optimum injection amount on the basis of the information that has been read in, and an injection time calculation unit192that calculates an injection time period on the basis of the result calculated by the injection amount calculation unit191.

Information about the injection pulse width calculated by the injection time calculation unit192is transmitted to a drive circuit195. This drive circuit195generates a drive current that corresponds to the injection pulse width and supplies this drive current to an electromagnetic coil108that is disposed around the external periphery of a movable valve body106of the fuel injection valve101, thereby pulling upon the movable valve body106with magnetic attraction to open the valve, and then holds the valve in the open state over a time interval corresponding to the injection pulse width, thereafter closing the valve. In other words, the opening and closing operation of the fuel injection valve101is performed by the electromagnetic force of the electromagnetic coil108.

In this embodiment, a pressure sensor160that detects the pressure within the cylinder is provided at the end of the fuel injection valve101. The signal detected by the pressure sensor160is inputted to the ECU190via a signal processing unit198. This signal processing unit190performs analog to digital processing upon the signal detected by the pressure sensor160.

The structure of the fuel injection valve101will now be explained with reference toFIG. 2andFIG. 3.FIG. 2is a partially cutaway schematic side view showing the fuel injection valve101, andFIG. 3is an external perspective view showing the fuel injection valve101. This fuel injection valve101is an electromagnetically driven type fuel injection valve that injects fuel such as gasoline or the like directly into a cylinder of an internal combustion engine. The fuel injection valve101comprises a housing (also termed a “yoke”)109and a nozzle104that is fixed to the housing109by being pressed into a portion thereof. The lower portion in the figure of an elongated hollow tubular core120is inserted into the housing109, and the interior of this core120is employed as a fuel passage. The electromagnetic coil108is disposed around the outside of this core120, and is received within the housing109.

As shown inFIG. 2, the movable valve body106is disposed within the nozzle104upon the central axis of the fuel injection valve101(hereinafter also simply termed the “central axis X”). When an excitation current is supplied to the electromagnetic coil108, the movable valve body106is shifted upward in the figure along the central axis X by magnetic force, so that the fuel injection valve is opened.

A molded connector body170(i.e. a resin molding) is formed by a per se known injection molding method at the external periphery of the portion of the core120that projects from the housing109. A portion of this molded connector body170is made as an elongated portion170cthat juts out slantingly upward in the figure from the housing109, and the end portion of this elongated portion is formed as a connector portion170a.

The molded connector body170holds a pair of external excitation terminals125and an external sensor terminal115in an insulated state. One end of each of the external excitation terminals125is formed as an excitation connection terminal125b, and is positioned in the connector portion170a(refer toFIG. 2andFIG. 6). As shown inFIG. 1, wiring196for supplying excitation current to the electromagnetic coil108is connected to the excitation connection terminals125, and wiring197for taking out the detection signal detected by the pressure sensor160is connected to a sensor connection terminal115b.

As shown inFIG. 1, the pressure sensor160that detects the pressure within the cylinder is fitted to the end or tip of the nozzle104, and a signal line150is connected to the pressure sensor160. Except for its electrical connection portions, the conducting wire of the signal line150is covered with a covering material, and one end of this conducting wire is connected to the pressure sensor160, while its other end is connected to the external sensor terminal115. The detection signal detected by the pressure sensor160is supplied to the ECU190via the signal line150and the external sensor terminal115, and via the wiring197. The signal line150is arranged so as to pass through the outer circumferential surface portions of the housing109and the nozzle104(refer toFIG. 2andFIG. 5). After this signal line150has been adhered to the outer circumferential surfaces of the housing109and the nozzle104with adhesive or the like, it is covered over along with the housing109and the nozzle104with a secondary molded body180(refer toFIG. 2andFIG. 3).

As shown inFIG. 2andFIG. 3, a tip seal holder130is disposed in the neighborhood of the end of the nozzle104, with a tip seal140being fitted on this tip seal holder130. This tip seal holder130fitted to the nozzle104will now be explained with reference toFIG. 4.FIG. 4(a)is a schematic cross sectional view showing the vicinity of the end of the nozzle104, whileFIG. 4(b)is a sectional view thereof taken by the line A-A inFIG. 4(a).

The tip seal holder130is a cylindrical member, and its central axis coincides with the central axis X of the fuel injection valve101. A groove131is provided upon the outer circumferential surface of the tip seal holder130, and extends around its circumferential direction. The tip seal140, that is an annular seal member, is set into the groove131, as shown inFIG. 4(a)

The tip seal holder130is press fitted over the nozzle104from its end, and is laser welded in a predetermined position. In this embodiment, the diameter of the nozzle104is increased at a position that is separated by a predetermined distance from the end of the nozzle104, so that a difference in level or a step149is provided at this point. One end of the tip seal holder130is engaged against this difference in level149. This difference in level149is provided in order to determine the position of the tip seal holder130. When the tip seal holder130is being fitted, its position can be determined simply and easily by pressing it on until one end of the tip seal holder130engages to this difference in level149.

As shown inFIG. 2andFIG. 4, a fuel injection valve fitting hole103is formed in a cylinder head102. When the nozzle104of the fuel injection valve101is inserted in this fuel injection valve fitting hole103, the tip seal140provides a seal between the inner circumferential surface of the injection valve fitting hole103and the outer circumferential surface of the tip seal holder130.

As shown inFIG. 4, the dimension D of the clearance138between the outer circumferential surface of the tip seal holder130at the pressure sensor160side and the inner circumferential surface of the fuel injection valve fitting hole103is set to around 0.2 mm. By setting this dimension D of the clearance138to less than or equal to a predetermined dimension, it is possible to prevent destruction of the tip seal140originating due to direct contact of combustion gases at high temperature against the tip seal140.

An insertion groove132is formed upon the inner circumferential surface of the tip seal holder130, and extends along the central axis X. The signal line150of the pressure sensor160is inserted into a space defined by this insertion groove132and the outer circumferential surface of the nozzle104.

The signal line150passes along the insertion groove132from the pressure sensor160, and, as shown inFIG. 2, extends along the external circumferential surfaces of the nozzle104and the housing109towards the elongated portion170cof the molded connector body170. And this signal line150is electrically connected to a projecting portion115athat projects towards the pressure sensor160from a sloping surface portion170b, that is the surface of the elongated portion170cfacing toward the pressure sensor160.

FIG. 5,FIG. 6, andFIG. 7are respectively an external perspective view, a partially cutaway perspective view, and a partially cutaway schematic side view, all showing the state of the fuel injection valve before the secondary molded body180of the fuel injection valve101is formed. As shown inFIG. 7, the external excitation terminals125and the external sensor terminal115are adhered to the molded connector body170that is a primary molded body.

As shown inFIG. 6, at the connector portion170aof the molded connector body170, the one ends of the pair of external excitation terminals125described above are exposed as the excitation connection terminals125b, and one end of the external sensor terminal115is exposed as the sensor connection terminal115b. And since, as shown in the figure, the excitation connection terminals125band the sensor connection terminal115bare arranged in the single connection portion170a, accordingly it is possible to perform electrical connection between the electromagnetic coil108and the wiring196(refer toFIG. 1), and electrical connection between the pressure sensor160and the wiring197(refer toFIG. 1), in a simple and easy manner.

As shown inFIG. 6andFIG. 7, the external sensor terminal115extends from the sensor connection terminal115balong the elongated portion170cof the molded connector body170, is bent around toward the pressure sensor160in the neighborhood of the housing109, and then extends parallel to the central axis X. The end portion of the external sensor terminal115remote from the sensor connection terminal115bis formed as the projecting portion115a. As shown inFIG. 5andFIG. 7, upon the sloping surface portion170bthat is the side of the elongated portion170cof the molded connector body170that faces toward the pressure sensor160, this projecting portion115aprojects from the neighborhood of the housing109toward the pressure sensor160.

The connecting portion between the signal line150and the external sensor terminal115that is fixed in the molded connector body170will now be explained with reference toFIG. 8andFIG. 9.FIG. 8(a)andFIG. 8(b)are figures for explanation of a process for aligning the positions of the signal line150and the projecting portion115a, and for explanation of a process for connecting them together. AndFIG. 9(a)is a figure for explanation of a process of adhering together the signal line150and the projecting portion115a, whileFIG. 9(b)is a figure for explanation of a secondary molding process. InFIG. 8andFIG. 9, that are explanatory figures, the connection portion between the signal line150and the projecting portion115ais shown as enlarged.

As shown inFIG. 8(a), before the signal line150and the projecting portion115aare connected together, positional alignment of the signal line150and the projecting portion115ais performed. It should be understood that the covering material150bupon the end portion of the signal line150is detached in advance, as shown inFIG. 8(a), so that its lead wire is exposed. In the positional determination process, positional determination is performed so that an exposed portion150awhere no covering material150bis provided is contacted against the projecting portion115a.

After this positional determination, as shown inFIG. 8(b), the exposed portion150aof the signal line150and the projecting portion115aof the external sensor terminal115are electrically connected together with solder151. After this fixing with solder, as shown inFIG. 9(a), silicon adhesive is applied so as to cover the entire external circumferential portions of the exposed portion150aand the projecting portion115a. Silicon adhesive is also applied to the sloping surface portion170bof the molded connector body170. By the silicon adhesive hardening, a layer of silicon adhesive152is formed around the external peripheries of the exposed portion150aand the projecting portion115a. This layer of silicon adhesive152is closely adhered to the sloping surface portion170baround the projecting portion115a.

Then, in a secondary molding process, as shown inFIG. 9(b), by a per se known injection molding method, a secondary molded body180is formed, so as to cover over the external peripheries of the housing109and the nozzle104, and also the base portion of the sloping surface portion170bof the elongated portion170c. Due to this, the signal line150that is adhered to the outer circumferential surfaces of the housing109and the nozzle104, and also the connection portion between the signal line150and the projecting portion115aof the external sensor terminal115, are covered over with this secondary molded body180.

In other words, as shown inFIG. 9(b), the exposed portion150aof the signal line150and the projecting portion115aof the external sensor terminal115are covered over by the layer of silicon adhesive152, and the layer of silicon adhesive152is covered over by the secondary molded body180. Since the exposed portion150aof the signal line150and the projecting portion115aof the external sensor terminal115are covered over by two superimposed layers of material, accordingly their waterproof state is enhanced.

Referring toFIG. 10, the beneficial effects of enhancing the waterproof state of the exposed portion150aand the projecting portion115aby covering them over with the layer of silicon adhesive152, and by then further covering them over with the secondary molded body180, will now be explained by comparing this structure to a comparison example.FIG. 10(a)is a figure showing a comparison example in which a secondary molded body980has been formed without forming any layer of silicon adhesive152, whileFIG. 10(b)is a figure showing the first embodiment of the present invention. InFIG. 10(a)andFIG. 10(b), the progression of water through interfaces178,978between the molded connector body170and the secondary molded bodies180,980respectively is schematically shown by the arrow signs.

In some cases, due to heavy rain or the like, it may happen that water penetrates into the engine. As shown inFIG. 10(a), water that has adhered to the fuel injection valve101flows along the sloping surface portion170bof the molded connector body170and arrives at the interface978between the molded connector body170and the secondary molded body980. Sometimes it happens that the resin material from which the secondary molded body980is made contracts as it hardens in the die, so that a slight clearance is created between the secondary molded body980and the molded connector body170. Due to this, water may progress along the interface978between the molded connector body170and the secondary molded body980, and may arrive at the projecting portion115a.

By contrast, with the first embodiment of the present invention, as shown inFIG. 10(b), even if water progresses along the interface178between the molded connector body170and the secondary molded body180, this progression is hampered by the layer of silicon adhesive152. It should be understood that sometimes it also may happen that a clearance is present between the layer of silicon adhesive152and the secondary molded body180. However, even if water should penetrate into an interface185between the layer of silicon adhesive152and the secondary molded body180, adherence of this water to the exposed portion150aand/or the projecting portion115ais prevented, since the exposed portion150aof the signal line150and the projecting portion115aof the external sensor terminal115are not positioned upon the path of the water as it progresses along the interface185.

According to the first embodiment described above, the following beneficial operational effects are obtained.

(1) The fuel injection valve101includes: the nozzle104that is inserted into the fuel injection valve fitting hole103formed in the cylinder head102; the cylindrical tip seal holder130that is attached to the nozzle104; and the annular tip seal140that is fitted to the tip seal holder130, and that seals between the inner circumferential surface of the fuel injection valve fitting hole103and the outer circumferential surface of the tip seal holder130. In such a structure, by forming the tip seal holder130to correspond to the diameter of the fuel injection valve fitting hole103, it is possible to set the dimension D of the clearance between the fuel injection valve101and the fuel injection valve fitting hole103on the side toward the pressure sensor160than the tip seal140to be equal to or smaller than the predetermined value, so that it is possible to prevent destruction of the tip seal140.

In other words, according to this embodiment, the tip seal holder130can be formed according to the diameter of the fuel injection valve fitting hole103, while it is not necessary to form the nozzle104according to the diameter of the fuel injection valve fitting hole103. Due to this it is possible to anticipate enhancement of the productivity, since it is possible to fit nozzles104of the same shape to fuel injection valve fitting holes103of a plurality of types whose diameters are different.

Moreover, with a conventional fuel injection valve in which the tip seal is directly fitted on the nozzle, it is necessary to re-design the nozzle when the diameter of the fuel injection valve fitting hole is changed due to change of the specification of the cylinder head102, and this is undesirable because a great deal of labor and time is required when the specification changes. By contrast, according to this embodiment, even when the diameter of the fuel injection valve fitting hole103is changed due to change of the specification of the cylinder head102, still it is simple and easy to make an appropriate change corresponding to this change to the specification, since it will be sufficient only to change the shape of the tip seal holder130.

(2) The difference in level149, to which one end of the tip seal holder130engages, is provided on the nozzle104of the fuel injection valve101. Therefore, when fitting the tip seal holder130to the nozzle104, it is possible to position the tip seal holder130in its predetermined fitting position in a simple manner, by press fitting the tip seal holder130onto the nozzle until one end of the tip seal holder130engages with the difference in level149. Since it is thus possible to perform positional determination of the tip seal holder130with respect to the nozzle104in a simple manner, accordingly it is possible to anticipate enhancement of the productivity and reduction of the cost.

(3) The insertion groove132, into which the signal line150is inserted, is formed on the inner circumferential surface of the tip seal holder130, parallel to the central axis X of the tip seal holder130. Due to this it is possible to establish electrical connection between the pressure sensor160that is provided at the end of the nozzle104and the external sensor terminal115, without compromising the sealing performance.

(4) The groove131, into which the tip seal140is set, is formed on the outer circumferential surface of the tip seal holder130around its circumferential direction. By setting the tip seal140into the groove131, it is possible to attach the tip seal140to the tip seal holder130in a simple and easy manner. Moreover, the tip seal140is held in its predetermined position by the groove131, so that it is possible reliably to prevent the combustion gases from leaking out from the cylinder.

(5) The projecting portion115aof the external sensor terminal115and the exposed portion150aof the signal line150are covered over with the layer of silicon adhesive152, and the layer of silicon adhesive152is covered over with the secondary molded body180. Due to this, if water should penetrate into the interface178between the molded connector body170, that is the primary molded body, and the secondary molded body180, then the progression of this water is hampered by the layer of silicon adhesive152. As a result, the waterproofing of the electrical connection portion between the external sensor terminal115and the signal line150is enhanced.

(6) Since the external excitation terminals125and the external sensor terminal115are held by the single molded connector body170, accordingly it is possible to establish electrical connections between the fuel injection valve101and the exterior in a simple and easy manner.

A fuel injection valve201according to a second embodiment of the present invention will now be explained with reference toFIG. 11andFIG. 12.FIG. 11is a partially cutaway schematic side view showing this fuel injection valve201according to the second embodiment of the present invention, whileFIG. 12is an external perspective view showing the state of this fuel injection valve201before a secondary molded body280thereof is formed. To portions that are the same or correspond to ones of the first embodiment, the same reference symbols are appended in these figures, and explanation thereof will be omitted. The points of difference from the first embodiment will now be explained in detail.

In the first embodiment, it was arranged for the projecting portion115ato be projected parallel to the central axis X of the fuel injection valve101from the sloping surface portion170b, that was the side of the elongated portion170cof the molded connector body170facing toward the pressure sensor160(refer toFIG. 2). By contrast, in this second embodiment, as shown inFIG. 11andFIG. 12, a convex portion271is provided so as to project parallel to the central axis X of the fuel injection valve201from a sloping surface portion270b, that is the side of an elongated portion270cof a molded connector body270facing toward the pressure sensor160.

This convex portion271has a planar side portion271athat is parallel to the central axis X, and a top surface portion271bthat is orthogonal to the central axis X. In this second embodiment, the projecting portion115aof the external sensor terminal115projects from the top surface portion271bof the convex portion271towards the pressure sensor160.

According to the second embodiment having this structure, similar beneficial operational effects are obtained as in the case of the first embodiment described above. Moreover, according to this second embodiment, it is possible to make the path of progression of water longer, from where it penetrates into the interface between the secondary molded body280and the molded connector body270, that is the primary molded body, until it arrives at the layer of silicon adhesive152. Due to this, even if water penetrates into the interface between the secondary molded body280and the molded connector body270, it is possible to make this water effectively evaporate before it flows as far as reaching the layer of silicon adhesive152. Therefore, according to this second embodiment, the waterproofing is enhanced as compared to the first embodiment.

The following variations are also considered to fall within the scope of the present invention, and, moreover, it would be possible to combine one or a plurality of these variant embodiments with either of the embodiments described above.

(1) While, in the embodiments described above, by way of example, the pressure sensor160was explained as being a unit for state detection attached at the end of the fuel injection valve101, the present invention is not to be considered as being limited by this feature. For example, the present invention could also be applied to a case in which a thermocouple that measures the temperature within the cylinder is attached at the end of the fuel injection valve101as a unit for state detection.

(2) While, in the second embodiment, it was arranged to provide the convex portion271, thus making the progression path of water longer from where it penetrates into the interface between the molded connector body270and the secondary molded body280until it arrives at the layer of silicon adhesive152, the shape of the convex portion271is not to be considered as being limited to the one described above. It would also be possible to arrange to provide a portion having any appropriate concave and/or convex shape, so as to make the above water progression path yet longer.

(3) While, in the embodiments described above, it was arranged to form the insertion groove132on the inner circumferential surface of the tip seal holder130, the present invention is not to be considered as being limited by this feature. It would also be acceptable to arrange not to provide any such insertion groove132on the inner circumferential surface of the tip seal holder130, but to form an insertion groove on the outer circumferential surface of the nozzle104parallel to the central axis X, with the signal line150that connects between the pressure sensor160and the external sensor terminal115being inserted into this insertion groove provided in the nozzle104.

(4) While, in the embodiments described above, the exposed portion150aof the signal line150and the projecting portion115aof the external sensor terminal115were electrically connected together with the solder151, the present invention is not to be considered as being limited by this structure. For example, it would also be acceptable to connect the exposed portion150aof the signal line150and the projecting portion115aof the external sensor terminal115together electrically by using a low temperature sintering joining material that includes silver sheet and minute metallic grains, or the like.

While, as described above, various embodiments and variant embodiments have been explained, the present invention is not to be considered as being limited by the details thereof. Other implementations that are considered to be embraced within the range of the technical concept of the present invention are also included within the scope of the present invention.

The content of the disclosure of the following application, upon which priority is claimed, is hereby installed herein by reference:Japanese Patent Application No. 2012-130923 (filed on 8 Jun. 2012).

EXPLANATION OF REFERENCE NUMERALS