Wiring arrangement for engine fuel injector

An injector harness arrangement for electric connection between an electronic control unit and a fuel injector located inside a head cover of the engine. The head cover is divided in its height direction, and the injector harness penetrates the head cover at an interface of upper and lower halves. Since the injector harness directly passes the head cover, the height of the head cover does not become high. Vibration from a cylinder head is attenuated by the lower half of the head cover and a gasket located between the cylinder head and the head cover lower half so that the interface between the upper and lower halves of the head cover does not vibrate very much. Therefore, high sealing quality is not required at the upper and lower half interface, to ensure air and oil tightness. In addition, the injector harness is not damaged by the vibration of the cylinder head.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an arrangement for coupling a harness
 between an electronic control unit located outside an engine and a fuel
 injector located inside the engine.
 2. Description of the Related Art
 A common rail-type fuel injection system for a diesel engine is generally
 equipped with an electronic control unit (ECU) for determining an amount
 and timing of fuel injection such that fuel injection matches an engine
 running condition. Specifically, ECU outputs an electric signal to an
 electromagnetic valve provided in a fuel injector such that the injector
 is activated to inject a desired amount of fuel to the engine at a desired
 timing.
 ECU is coupled with the fuel injector by harness. This harness is referred
 to as injector harness in this specification. In general, ECU is mounted
 inside a passenger compartment or an engine room, which is outside the
 engine. The injector is attached to a cylinder head, and its connection to
 the harness is often located inside the engine (e.g., inside a head
 cover). In such an arrangement, the injector harness must penetrate the
 head cover.
 Referring to FIG. 8 of the accompanying drawings, illustrated is one of
 known ways of passing the injector harness through the head cover.
 Specifically, a packing "c" provided between a cylinder head "a" and head
 cover "b" has through holes "d", which extend in the lateral direction,
 such that two injector harnesses (not shown) enter the cylinder head cover
 therethrough. This engine has four cylinders, and each of the two injector
 harnesses is used for each two of the four cylinders.
 Referring next to FIG. 9 of the accompanying drawings, illustrated is
 another conventional way for passage of the injector harness (Japanese
 Patent Application Laid-Open Publication No. 3-260335). A terminal
 (connector) member "e" is embedded in a side wall of the head cover such
 that its front (or outer) face is exposed to the outside of the head cover
 and its back (or inner) face is exposed to the interior of the head cover.
 FIG. 9 illustrates the outer face. Wires are connected between the fuel
 injector and terminal "e" inside the head cover, and the harness extending
 from ECU is plugged into the terminal "e" outside the engine. The terminal
 "e" is fixed to the head cover side wall by bolts. Reference symbol "f"
 designates a flange having two bolt holes and "H" designates height of the
 flange.
 However, the approach of FIG. 8 must employ a packing "c" of complicated
 shape. This would deteriorate air tightness and oil tightness at the
 packing "c". In particular, vibration from the cylinder head "a" is
 directly transmitted to the interface between the cylinder head "a" and
 head cover "b" so that high quality of sealing is required to the packing
 "c". Such requirements may not be met if the packing "c" has a complicated
 contour. Strong vibration is also transferred to the injector harness from
 the cylinder head "a" so that the injector harness may be damaged or
 disconnected.
 The arrangement of FIG. 9 also has a shortcoming. Because the flange "f"
 has the bolt holes, its height "H" inherently becomes relatively large. As
 a result, the head cover also has large height. A tall head cover is not
 desirable if the engine should be designed to be compact.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide an injector harness
 arrangement that can overcome the above described problems associated with
 the conventional arrangements.
 According to one aspect of the present invention, there is provided an
 injector harness arrangement for electric connection between an electronic
 control unit located outside an engine and a fuel injector located inside
 a head cover of the engine, characterized in that the head cover has a
 structure divisible in its height direction, and the injector harness
 penetrates the head cover an interface of upper and lower halves of the
 head cover. Since the injector harness directly passes the head cover, the
 height of the head cover does not become high. Vibration from a cylinder
 head is attenuated by the lower half of the head cover and a
 packing/gasket located between the cylinder head and head cover lower half
 so that the interface between the upper and lower halves of the head cover
 does not vibrate very much. Therefore, severe sealing quality is not
 required at the upper and lower half interface. In other words, simple
 sealing is sufficient to insure air tightness and oil tightness. In
 addition, the injector harness is not damaged by the vibration of the
 cylinder head.
 Preferably, a grommet made from an elastic material is provided at the
 injector harness penetration portion of the head cover for sealing
 thereat. The injector harness passes through the grommet. The grommet may
 be supported by a bracket provided in the head cover for positioning of
 the injector harness. The bracket may engage with the grommet such that
 relative vibration between the bracket and grommet is absorbed by the
 grommet.
 The present invention can demonstrate the following advantages:
 (1) A sealing structure at the injector harness penetration portion of the
 head cover is simplified and damage of the harness is prevented; and
 (2) Head cover height is kept small. Thus, it is possible to design a
 compact engine.
 Other advantages and objects of the present invention will become apparent
 to those skilled in the art when the following detailed description and
 appended claims are read and understood taken in conjunction with the
 accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION
 Now, an embodiment of the present invention will be described in reference
 to the accompanying drawings.
 Referring to FIG. 1, a head cover 1 is placed on a cylinder head (not
 shown) and fixed. This head cover 1 is divided into upper and lower halves
 3 and 2. The head cover lower half 2 is secured to the cylinder head by
 bolts 39 with grommets 38. The grommets 38 are made from an elastic
 material such as rubber. A packing 4 made also from an elastic material
 such as rubber is provided between the head cover lower half 2 and
 cylinder head.
 In this manner, the lower head cover segment 2 is secured on the cylinder
 head with the grommets 38 and packing 4 in a vibration attenuating
 condition. Therefore, vibration of the cylinder head is less transmitted
 to the lower head cover segment 2.
 An upper edge of the lower head cover segment 2 and a lower edge of the
 upper head cover segment 3 have mating surfaces (or peripheries) 5 and 6
 respectively. These mating peripheries 5 and 6 abut each other to form the
 single head cover 1.
 Referring to FIG. 2, an upper packing 7 made from an elastic material such
 as rubber is attached to the periphery 6 of the upper head cover segment
 3. Specifically, the upper packing 7 is fit in a groove formed in the
 periphery 6. Thus, the upper packing 7 is interposed between the lower
 head cover segment 2 and upper head cover segment 3 so that air tightness
 and oil tightness at the interface between the upper and lower head cover
 segments are insured, and transmission of vibration to the upper head
 cover segment is also suppressed. As shown in FIG. 1, a plurality of
 through holes 8 are formed in the flange 6 of the upper head cover segment
 3 such that a plurality of bolts 9 pass these holes and are screwed into
 corresponding female threads 10 formed in the mating edge 5 of the lower
 head cover segment 2. In this manner, the upper head cover segment 3 is
 united to the lower head cover segment 2.
 As illustrated in FIG. 1, the lower head cover 2 has two semicircular
 cutouts or grooves 11 in the periphery 5, and as shown in FIG. 2, the
 upper head cover 3 has two mating cutouts 12 in the periphery 6. When the
 upper and lower head covers are united, these semicircular cutouts 11 and
 12 form two through holes 13 (FIG. 7). Injector harnesses 14 pass these
 through holes 13. The two circular holes 13 are formed in the same side
 face of the head cover 1 and spaced in a longitudinal direction of the
 head cover 1.
 Although not shown, four injectors are provided in the head cover 1. Each
 injector is associated with each cylinder of the engine. This engine has
 four cylinders. A lower part of each injector is buried in the cylinder
 head and an upper part is exposed. Each injector is mounted in a standing
 posture. A harness connection is provided at the upper part of each
 injector, and each harness connection (or each injector upper part) is
 electrically connected to ECU located outside the engine. The harnesses
 required for this electrical connection are illustrated at 14 in FIG. 1.
 The four-cylinder engine needs two injector harness assemblies 14 in the
 illustrated embodiment. Each injector harness assembly 14 includes two
 terminals 15 at one end situated inside the engine and a joint connector
 16 at the other end outside the engine. Each terminal 15 has small + and -
 plates. The two terminals 15 of each injector harness 14 are branched to
 the right and left inside the engine and connected to the two injectors.
 In this manner, one injector harness 14 is shared by two injectors so that
 the position of injector harness penetration is between adjacent two
 injectors. Each injector harness 14 is equipped with a grommet 17 made
 from an elastic material such as rubber. As illustrated in FIG. 7, each
 grommet 17 fits in the associated through hole 13 of the head cover 1 to
 seal between the through hole 13 and injector harness 14 and support the
 injector harness 14 in a vibration damping fashion. A bracket 18 is
 provided in the head cover 1 for each injector harness 14 such that it
 supports the injector harness 14 in position. Each bracket 18 also extends
 to the associated grommet 17 and engages. Inside the head cover 1, each
 injector harness 14 is fixed to the associated bracket 18 by a clip 23 and
 extends along the bracket.
 Referring now to FIGS. 3 and 4, each bracket 18 is a one-piece element,
 which is made by, for example, pressing a metallic plate. Each bracket 18
 has a pair of holes 19, through which bolts pass to fix the bracket 18
 onto the cylinder head. Each bracket 18 also has an extension 20 to fix
 the terminals 15, a fork 21 to engage the grommet 17, and a series of
 recesses 22 to support the injector harness 14 along the center line of
 the bracket 18.
 Referring to FIGS. 5 and 6, each grommet 17 includes an engagement portion
 24 that engages the grooves 11 and 12 of the lower and upper head covers 2
 and 3 (or the through hole 13). Each grommet 17 also includes another
 engagement portion 25 that engages the fork 21 of the bracket 18 when the
 fork 12 is thrust in from the lateral direction, and four holes 27 for
 passage of core wires of the injector harness 14. The center engagement
 portion 24 and endwise engagement portion 25 are separated and defined in
 a longitudinal direction of the grommet by flanges 26. The center
 engagement portion 24 has projections 28 on its outer surface and the core
 wire holes 27 have projections 29 on their inner walls to raise sealing
 (or contact) pressure between the grommet 17 and the head cover hole 13
 and between the core wires and the holes 27 respectively.
 Referring to FIG. 7, illustrated is the harness assembly 14 after the head
 cover 1 is mounted on the cylinder head. The harness assembly 14 includes
 four core wires 30, i.e., two pairs of + and - core wires. These core
 wires 30 are bundled by corrugated tubes 33 and tapes 34. The core wires
 30 extend through the grommet holes 27 at the approximate mid-point of the
 harness assembly 14. Passage of the core wires 30 through the grommet
 holes 27 are relatively tight so that proper sealing is insured. The
 bracket 18 is secured onto a boss 31 formed on the cylinder head by
 screwing bolts 32 into the holes 19 (FIG. 3).
 The fork 21 of the bracket 18 engages over the engagement portion 25 of the
 grommet 17 so that the grommet 17 is supported by the bracket 18 inside
 the head cover 1. The injector harness 14 extends along the bracket 18
 inside the head cover 1. The clip 23 holds the injector harness 14
 together with the bracket 18. Since the injector harness 14 is guided by a
 series of recesses 22 of the bracket 18 (FIG. 3), it can bend neatly along
 the contour of the bracket 18 even at right angle corners of the bracket.
 The terminals 15 of the injector harness 14 are fixed to the extension 20
 of the bracket 18.
 Outside the head cover 1, an approximate half of the injector harness 14
 extends. The connector 16 at the end of the injector harness 14 is now
 ready to couple to another harness extending from ECU.
 At the injector harness penetration portion of the head cover 1, the
 engagement portion 24 of the grommet 17 is rigidly supported by the hole
 13 of the head cover 1. The engagement portion 24, particularly its
 projections 28 firmly contact (or pressed against) the head cover hole 13
 so that appropriate sealing along the outer periphery of the engagement
 portion 24 can be expected. The flanges 26 at both ends of the engagement
 portion 24 firmly attach to the inner and outer faces of the head cover
 side wall so that the sealing is further enhanced. Because the flanges 26
 are provided, no problem would occur at interrupted portions of the upper
 packing 7 near the grooves 12 (FIG. 2).
 In the present invention, the injector harness 14 directly penetrates the
 head cover 1 so that unlike the conventional arrangement it is not
 necessary to mount a terminal with a flange for passage of the injector
 harness. Accordingly, the height of the head cover 1 does not become
 large. This makes it possible to design a compact engine.
 Further, the lower head cover 2 and associated packing 4 attenuate the
 vibration transmitted from the cylinder head so that the interface between
 the upper and lower head covers does not vibrate very much. Consequently,
 severe sealing quality is not required to the upper and lower head cover
 interface as compared with the cylinder head-lower head cover interface.
 In other words, a simple and inexpensive seal or packing is sufficient to
 ensure air tightness and oil tightness at the upper and lower head cover
 interface. Damage and disconnection of the injector harnesses 30 are also
 prevented since the vibration from the cylinder head is absorbed at the
 cylinder head-lower head cover interface. The grommets 17 can have a
 simple structure to provide suitable sealing and vibration damping since
 less vibration is transmitted to the grommets 17. Diameter of the grommet
 17 is only slightly greater than a diameter of the harness so that height
 of the head cover 1 does not become large. In the present invention, a
 complicated packing is not needed for passage of the injector harness
 unlike the conventional arrangement.
 The grommets 17 are buried in the head cover wall whereas the brackets 18
 are mounted on the cylinder head. Therefore, there is some discrepancy
 between vibration of the grommets 17 and that of the brackets 18. If the
 grommets 17 were completely separated and independent from the brackets
 18, this relative vibration discrepancy would be born by the injector
 harnesses 14. As a result, the injector harnesses 14 would be damaged. In
 the illustrated embodiment, however, part of each bracket 18 engages with
 the associated grommet 17 so that the relative vibration between the
 grommet and bracket is absorbed by the grommet 17 and not born by the
 harness. Therefore, damage of the injector harness is prevented.
 In addition to or instead of engagement between the grommet and bracket,
 the clip 23 and/or extension 20 may be used to physically connect the
 bracket 18 to the harness. If this connection is done before installation
 of the harness, it facilitates assembling of the harness to the cylinder
 head. If the bracket 18 were first mounted on the engine and the harness
 were then mounted to the bracket 18, only a small space is left for a
 service man to place the grommet 17 and secure the terminal 15 in the
 lower head cover 2. This would be troublesome. As mentioned above, by
 mounting the bracket 18 to the harness beforehand, what the service man
 should do is simply placing the grommet 17 in the groove 11 of the lower
 head cover 2 and tightening the bolts 32. This greatly facilitates the
 work.
 In addition, inspection and maintenance of the engine is facilitated since
 the head cover 1 is divisible to upper and lower segments.
 It should be noted that the present invention is not limited to the above
 described embodiment. Teaching of the present invention is applicable to a
 diesel engine and gasoline engine equipped with an electronically
 controlled fuel injection system.
 The illustrated and described harness arrangement for a fuel injector is
 disclosed in Japanese Patent Application No. 11-78330 filed on Mar. 23,
 1999, the instant application claims priority of this Japanese Patent
 Application, and the entire disclosure thereof is incorporated herein by
 reference.