Plug cap with vent for internal combustion engine

Abstract: The plug cap 13 for the ignition cable is provided with an upwardly open vent 11 having an aperture. The aperture is provided with a water-tight flap 10, which is placed at some distance from the uppermost section of the aperture and which is installed in a freely tiltable manner, so that the aperture of the vent 11 can be closed depending on the water pressure to be exerted on the plug cap 13. When no water is sprayed, the heated air inside an elongated bore 19 for the ignition plug is evacuated through the vent 11. When water is sprayed, the aperture of the vent 11 is closed with the watertight flap 10 under the water pressure, so that the water is prevented from entering the elongated bore 19.

Description: The present invention relates to the field of internal combustion engines for vehicles or the like, of the type having an elongated bore for receiving an ignition plug. More particularly, the invention relates to a freely engageable and removable plug cap for closing the opening of such an elongated bore, the plug cap being provided with at least one air vent for evacuating air inside the bore. An example of such a plug cap is described in JP-A-H6-196246(1994). The plug cap is traversed by an ignition cable and is freely mountable and removable with respect to an elongated bore that houses an ignition plug. When fitted into the bore, the plug cap serves to prevent the ingress of water into the bore, and at the same time holds an ignition pipe (also called "plug cap pipe") firmly in place. When the engine is running, the air inside the elongated bore is heated and tends to expand, causing the plug cap to lift away and float above the elongated bore. To avoid such phenomenon, the plug cap is provided with one or more vent-holes at its upper face or side face to release the expanded air. However, when the vent-holes extend upwards or sideways, they are vulnerable to water penetration and thus deteriorate the cap's sealing properties. Thus, when water is sprayed at pressure on such a plug cap, for instance when driving under the rain or washing the car etc., there is always a risk that water penetrates inside the elongated ignition plug bore. When this happens, electrical leakage may occur from the ignition plug through the water. The plug can thereby fail to ignite properly, with adverse effects on the running of the engine. It is thus an object of the present invention to provide a plug cap traversed by an ignition cable and adapted to close the opening of the elongated bore that receives the ignition plug e.g. in a vehicle engine, the plug cap having vents for evacuating air heated inside the bore without letting water enter into the bore when water at high pressure is sprayed around the plug cap, for instance when driving under rain or car-washing. To solve the above-mentioned problem, there is provided a plug cap for sealingly closing an elongated bore housing an ignition plug in an internal combustion engine, said plug cap being traversed by an ignition cable and comprising at least one vent having an aperture for evacuating air inside said elongated bore, characterized in that said vent is provided with a water-tight flap connected to said aperture through a flexible fixing means, the water-tight flap being disposed above the uppermost section of the aperture at a short distance therefrom thereby forming an air slit therebetween so that, in a normal state, said flap is kept open with respect to said aperture and so that in a state where said flap receives a force from water particles said flap closes said aperture by tilting over said aperture with said flexible fixing means acting as a fulcrum. In such plug cap, the water-tight flap is so configured as to be positioned substantially parallel to the aperture of the vent. The fixing means is preferably a flexible hinge. The fixing means may be a flexible hinge integrally formed with the plug cap. In a preferred embodiment, the aperture of the vent is tapered expandingly from the fixing point of the fixing means towards the opposite side, so that, when the water-tight flap is tilted onto the aperture, the flap is tightly superposed on the aperture. Further, the vent is formed so as to open upwardly towards the outside through the plug cap. The plug cap can be made of any elastic material. According to a preferred embodiment, the vent has an outer diameter of approximately 3 mm; the water-tight flap is approximately 0.5 to 2 mm thick; the maximum air slit between the vent and the water-tight flap is approximately 0.3 to 1 mm thick; the hinge portion connecting the vent with the water-tight flap is between 0.3 and 0.5 mm thick; and the hinge portion is between 0.5 and 2.0 mm wide in the circumferential direction. In a typical example, the plug cap is fitted onto an elongated bore which comprises the ignition plug on the base thereof; an ignition cable connected to the ignition plug by one end and extending by the other end to the outside of the elongated bore through a hole of the plug cap, and an ignition pipe containing the ignition cable and extending from the ignition plug to the plug cap. Preferably, such plug cap may be used for vehicle engines. In the configuration of the plug cap as described above, the vent is provided, at some distance above the aperture thereof, with a freely tiltable water-tight flap which can close off the vent aperture as soon as a water pressure is exerted thereon. Thus, when no water is sprayed, the water-tight flap leaves the vent open so that the air inside the elongated bore for the ignition plug is evacuated through the vent. On the other hand, if high pressure water is sprayed on the plug cap for the ignition cable, for example while driving under the rain or car-washing, the water-tight flap closes off the vent under the pressure of the water, thereby preventing the water from entering into the elongated bore for the ignition plug. An advantage of such configuration is that the water-tight flap may be fitted with the aperture of the vent through a flexible hinge portion integrally formed with the plug cap. Then, the plug cap for the ignition cable can be obtained by a simple forming procedure. Further, the uppermost section of the vent may be tapered so that the space interposed between the water-tight flap and the vent, expands gradually from their fixing point towards the opposite side. Then, the water-tight flap is more tightly superposed on the vent aperture as soon as the water exerts a pressure thereon, thereby preventing more efficiently the water from entering into elongated bore for the ignition plug. The above and other objects, features and advantages of the invention will be apparent from the following description of the preferred embodiments, given as a non-limiting example, with reference to the accompanying drawings, in which : Fig. 1 is a sectional view of a plug cap provided with a vent and a water-tight flap according to an embodiment of the present invention; Fig. 2(a) is a perspective view of an embodiment of the present invention in which the water-tight flap is configured so as to be positioned substantially parallel to the aperture of the vent, thereby forming an air slit therebetween, Fig. 2(b) shows a schematic view of the dies by which the vent and the water-tight flap can be integrally formed, Fig. 3(a) is a sectional view of the vent and of the water-tight flap corresponding to the embodiment shown in Fig. 2(a), Fig. 3(b) is a sketch of the embodiment shown in Fig. 3(a), in which the water-tight flap is lowered by water pressure, Fig. 4(a) is a sectional view of another embodiment of the present invention in which the aperture of the vent is tapered, Fig. 4(b) is a sketch of the embodiment shown in Fig. 4(a) in which the water-tight flap is lowered by water pressure. Fig. 1 shows a plug cap 13 made of an elastic material such as rubber for receiving an ignition cable. A peripheral cover 12 is provided around the external circular wall of the plug cap 13. The cover engages with a circular spigot 16 formed on the engine 26 around a rim zone at the opening of an elongated bore 19 that houses an ignition plug. The base of the plug cap 13 has a peripheral lip that engages with the wall of the bore near its opening to form a sealing portion 17. The lip is configured to be freely press-fitted inside the bore and removable therefrom. The plug cap 13 is provided with a vent 11 which opens upwardly to the outside. The upper end of the vent is provided with a water-tight flap 10 which leaves the vent 11 open in the normal state, but closes it when submitted to the impact of water particles. The lowermost face of sealing portion 17 facing the base of the bore may optionally be provided with a circumferential groove 18. The groove serves to reduce insertion force for fitting the plug cap into the bore and so reduce the compressive strain experienced by the cap around the sealing portion 17 after insertion. The lowermost face of the plug cap 13 is also provided with a pipe-holding portion 24 configured to grip firmly the end of the ignition pipe 20 closest to the bore opening. The ignition pipe 20 receives a cable 15 for the ignition plug, the cable passing through a cable opening 14 in the plug cap 13 and exiting therefrom towards the outside. The other end of the ignition pipe 20 is adapted to mount on the ignition plug 23 at the bottom of the bore 19 via a sealing bushing 22. The plug end of the cable 15 is equipped with an electrical contact terminal 21 that lodges inside the ignition pipe 20 and engages with a corresponding contact of the ignition plug 23 to provide the required electrical connection. The vent 11 and the water-tight flap 10 will now be described in detail with reference to Figs. 2(a) and 3(a). The vent 11 presents an opening at a top surface portion of the plug cap 13. The opening is covered by disc-shaped water-tight flap 10 disposed above the uppermost section of the opening but at a short distance therefrom. The water-tight flap 10 has a hinge portion 10a that is integral with the main body 13a of the plug cap, the hinge 10a depending from the latter by at a part on, or adjacent to, its circumference. The water-tight flap 10 can be pivoted with the hinge portion 10a serving as a fulcrum point for opening and closing the vent 11. The vent 11 and water-tight flap 10a may be formed jointly in a moulding process by using dies 25 as shown in Fig. 2(b). The function of such vent 11 and water-tight flap 10 will now be described. As shown in Fig. 3(a), when the water-tight flap 10 is not sprayed with water, the flap 10 is located just above the aperture of the vent 11. When the engine is running, the heated air contained inside the elongated bore 19 for the ignition plug is evacuated towards the outside through the vent 11. This ensures that there is no pressure build-up that can otherwise blow off the plug cap 13. On the other hand, when water is sprayed on the plug cap 13 at some pressure, and thus also on the water-tight flap 10, the water-tight flap 10 is pushed down to seal off the vent 11 as shown in Fig. 3(b), so long as the pressure exerted by the water is greater than the excess pressure in the plug bore 19. The flap 10 can thus normally be expected to seal off the vent 11 when driving in the rain, car-washing or the like, and thereby prevent the ingress of water into the elongated ignition plug bore 19. The vent 11 and the water-tight flap 10 may be formed in a shape shown in Fig. 4(a). In this embodiment, the uppermost section 11a of the vent 11 is tapered, such that, in a normal state, the space formed between the vent 11 and the water-tight flap 10 expands gradually from the hinge portion 10a to the opposite side. In this construction, the water-tight flap 10 is open, as shown in Fig. 4(a), when water is not sprayed. Thus, heated air inside the elongated bore 19 is evacuated towards the outside via the space over the vent 11. On the other hand, when water is sprayed, the water-tight flap 10 is pushed down by the pressure of the water, as shown in Fig. 4(b), such that it superposes tightly onto the uppermost section 11a of the vent 11, thereby closing the vent 11. Consequently, water penetration into the elongated ignition plug bore 19 is more efficiently prevented. Although the present embodiment is described as having upwardly opening vents, another embodiment may comprise an askew and laterally open vent, with the same results being obtained.

Claims: A plug cap (13) for sealingly closing an elongated bore (19) housing an ignition plug (23) in an internal combustion engine, said plug cap being traversed by an ignition cable (15) and comprising at least one vent having an aperture for evacuating air inside said elongated bore (19), characterized in that said vent is provided with a water-tight flap (10) connected to said aperture through a flexible fixing means (10a), the water-tight flap (10) being disposed above the uppermost section of the aperture at a short distance therefrom thereby forming an air slit therebetween so that in a normal state, said flap is kept open with respect to said aperture and so that in a state where said flap receives a force from water particles said flap closes said aperture by tilting over said aperture with said flexible fixing means acting as a fulcrum. The plug cap (13) according to claim 1, wherein the water-tight flap (10) is so configured as to be positioned substantially parallel to the aperture of the vent (11). The plug cap (13) according to claim 1 or 2, wherein the fixing means (10a) is a flexible hinge. The plug cap (13) according to any one of claims 1 to 3, wherein the fixing means (10a) is a flexible hinge integrally formed with said plug cap. The plug cap (13) according to any one of claims 1 to 4, wherein the aperture (11a) of the vent (11) is tapered expandingly from the fixing point of the fixing means (10a) towards the opposite side, so that, when the water-tight flap (10) is tilted onto the aperture, said flap is tightly superposed on said aperture. The plug cap (13) according to any one of claims 1 to 5, wherein the vent (11) is formed upwardly toward the outside through said plug cap. The plug cap (13) according to any one of claims 1 to 6, wherein said plug cap is made of an elastic material. The plug cap (13) according to any one of claims 1 to 7, wherein the vent (11) has an outer diameter of approximately 3 mm; the water-tight flap (10) is approximately between 0.5 and 2 mm thick; the maximum air slit between said vent and said water-tight flap is approximately between 0.3 and 1 mm thick; the hinge portion (10a) connecting said vent with said water-tight flap is between 0.3 and 0.5 mm thick; and said hinge portion is between 0.5 and 2.0 mm wide in the circumferential direction. The plug cap (13) according to any one of claims 1 to 8, wherein said plug cap is fitted over an elongated bore (19), said elongated bore comprising the ignition plug (23) on the base thereof; an ignition cable (15) connected to said ignition plug by one end and extending out of said elongated bore through a hole (14) of said plug cap by its other end; and an ignition pipe (20) containing said ignition cable and extending from said ignition plug to said plug cap. A method of sealing an elongated bore for housing an ignition plug in an internal combustion engine using the plug cap (13) according to any one of claims 1 to 9.

Inventors: KOMATSU TOSHIHIKO, KOMATSU,TOSHIHIKO, Komatsu,Toshihiko,c/o Sumitomo Wiring Systems Ltd.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1995
Main classification: H01T13
IPC codes: H01T13