Fuel cap

The present invention provides a fuel cap having a high operability while maintaining the air-tightness thereof at a necessary and sufficient level. The closure includes a closure body having a head portion, a trunk portion and an annular trunk surface having stopper projections; a seal ring; a sleeve; a coiled spring; and an engagement member having engagement projections. The fuel cap is formed by assembling the seal ring around the annular surface of the trunk portion of the closure body and the sleeve with the trunk portion in the mentioned order, interposing the coiled spring between the sleeve and engagement member, and connecting the engagement member to the trunk portion of the closure body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel cap for a fuel tank for a motor vehicle.

2. Description of the Related Art

Although a fuel cap for a fuel tank for a motor vehicle is a simple part, it is important to maintain the high air-tightness function of the cap with respect to an oil filler port in a stage in which the fuel cap is turned in the closing direction with respect to an oil filler port and thereby completely finished the securing operation. This stage is hereinafter referred to as a “securing-finished” stage. The improvement of the operability of the fuel cap turning operation from a stage in which the fuel cap is inserted into the fuel filler port and started being turned in the closing direction (, and this stage is hereinafter refereed to as a “securing-started” stage,) to the securing-finished stage, i.e. the simplification of the fuel cap opening and closing operations and, especially, the reduction of the torque needed to turn the fuel cap in the closing direction are demanded.

The conventional fuel caps produced with the attention paid to the improvement of the operability thereof can include the fuel caps disclosed in, for example, Japanese Patent No. 2712115 and JP-T-09-512770. The fuel cap disclosed in Japanese Patent No. 2712115 compresses a seal ring owing to an operation of a cam mechanism urged downward by a spring in a final stage of an operation for securing the fuel cap to the oil filler port, and thereby attains the air-tightness of the fuel cap. The quantity of turn of the fuel cap needed to operate the cam mechanism may be small, and a turning operation for compressing the seal ring is not necessary. Therefore, it can be said that the operability of the fuel cap is improved.

The fuel cap disclosed in JP-T-09-512770 is also formed identically with that disclosed in Japanese Patent No. 2712115. The fuel cap disclosed in this patent is tightened on the oil filler port by a small quantity of turn (⅛ turn) thereof. However, when the fuel cap receives an external force, such as an impact force, there is a fear of coming off of the fuel cap from the oil filler port. In order to eliminate this inconvenience, a structure for turning idly a handle of the fuel cap engaged with the oil filler cap is added. Although an excessive turning operation corresponding to the idle turn of the handle comes to be needed to remove the fuel cap from the oil filler port but, in spite of this, a fuel cap turning operation of as large as one turn is not needed. Therefore, it can be said that the operability of the fuel cap is still excellent.

In the fuel caps disclosed in Japanese Patent No. 2712115 and JP-T-09-512770, the air-tightness thereof is attained by vertically compressing the seal ring in contact with an end of the oil filler port. Reversely speaking, it means that the air-tightness of the fuel cap cannot be secured unless the seal ring is uniformly in contact with the end of the oil filler port. Therefore, a structure capable of securing the air-tightness of the fuel cap even when the fuel cap is in a twisted positional relation with respect to the oil filler port is necessarily demanded. Concerning this point, in the fuel cap disclosed in JP-A-2002-293356, inclination preventing ribs are provided so that the twisting of the fuel cap itself does not occur. Thus, a decrease in the air-tightness of the fuel cap ascribed to the ununiform compression of the seal ring is prevented.

SUMMARY OF THE INVENTION

Although the fuel caps disclosed in Japanese Patent No. 2712115 or JP-T-09-512770 are excellent concerning the improvement of the operability thereof, the problems as will be described below can be pointed out. First, the compression of the seal ring is carried out not directly by a resiliency of a spring but strictly depends upon a quantity of the lowering of a flange operatively connected to the cam mechanism. Therefore, it is necessary that the positional relation of the flange and the dimensional accuracy of each part determining this positional relation be set high, and this poses a problem of rendering the quality control difficult.

Secondly, a load transmitted to the seal ring via the flange merely contributes to the occurrence of compression deformation of the seal ring in view of the direct effect of the load, and does not work so as to press the seal ring against a seal surface (end of the oil filler port) for the attainment of the air-tightness of the fuel cap. The seal ring is usually formed out of an elastic material, such as nitrile rubber having an oil resistance but the dimensions and physical characteristics or chemical characteristics of such a seal ring varies due to the environmental conditions and the deterioration of the seal ring with the lapse of time. It is difficult to obtain the necessary and satisfactory air-tightness of the fuel cap by such an indirect operation of the load on the seal ring. It can be said that these first and second problems are the problems of a structure for attaining the air-tightness of the fuel cap, the operability of which has been improved, with respect to the oil filler port.

The practical effectiveness of the twist preventing structure provided by the invention disclosed in JP-A-2002-293356 is scarce unless the dimensional accuracy of the inclination preventing ribs is severely set. Therefore, there is the possibility that, if the inclination preventing ribs should be broken, the problem of the twisting of the seal ring be actualized at a stroke since the measures to prevent the twisting of the seal ring are not originally taken. Under the circumstances, the development of a fuel cap having such a high operability as is seen in the fuel caps disclosed in Japanese Patent No. 2712115 and JP-T-09-512770, capable of attaining an easy quality controlling operation, not influenced by the twisting of the seal ring, and capable of securing a necessary and satisfactory air-tightness of the fuel cap was discussed.

On the basis of the results of the discussion, a fuel cap was developed which includes a closure secured to an oil filler port attached to an inlet of a feed oil pipe, and a handle for turning the closure, the oil filler port being provided on an inner side surface thereof with a plurality of intermittent circumferentially extending ribs, the closure being provided with a closure body having a head portion to be turned, a trunk portion extending downward from the head portion, and an annular trunk surface with downwardly extending stopper projections being formed on a side surface of the trunk portion, a seal ring which is fitted around the trunk portion so that the seal ring is fitted between a lower surface of the head portion and an upper portion of the annular trunk surface, and which pressure-contacts with an inner side surface of the oil filler port in radius direction from an inner side of the ring, a sleeve with annular shape having on an inner side surface thereof an annular sleeve surface provided with stopper recesses into which the stopper projections are fitted from the top, and on an outer side surface thereof downwardly extending anti-rotation projections fitted in the clearances between the ribs, and adapted to lift up the seal ring, a coiled spring urging the sleeve upward, and an engagement member having engagement projections adapted to be turned through the clearances between the ribs of the oil filler port and thereby engaged with the ribs from a lower side thereof.

The head portion of the closure body of this fuel cap may be a multi-step head portion including a head top, an upper step of the head portion and a lower step of the head portion. The fuel cap is formed by assembling the seal ring and the sleeve in the mentioned order around the trunk portion of the closure body so as to oppose the upper surface of the sleeve and the lower head portion surface of the closure body with the seal ring held therebetween, interposing the coiled spring between the lower surface of the sleeve and the upper surface of the engagement member, and thereby connecting the engagement member to the trunk portion of the closure body. As a result, the parts are combined into a unitary structure.

Owing to this structure, a fuel cap can be provided which is adapted to press the sleeve upward by a force of the coiled spring when the stopper projections fit into the stopper recesses, and hold the seal ring tightly by the upper surface of the sleeve and the lower surface of the head portion of the closure body; and press down the sleeve against the force of the coiled spring when the stopper projections disengage from the stopper recesses and run on the annular sleeve surface, and loosen the holding of the seal ring by the upper surface of the sleeve and the lower surface of the head portion of the closure body. In such a fuel cap according to the present invention, the engagement projections of the engagement member are engaged from the lower side with the ribs provided on the inner side surface of the oil filler port, so that this fuel cap has the advantage of not coming off therefrom easily even by an external force.

In this fuel cap according to the present invention, the stopper projections and stopper recesses are engaged with and disengaged from each other by turning the closure body with respect to the sleeve fixed in the turning direction with the anti-rotation projections held in the clearances between the ribs in the oil filler port. Owing to this structure, the tight holding of the seal ring by the upper surface of the sleeve and the lower surface of the head portion of the closure body and the intercepting of the influence of the deformation and friction of the seal ring upon the closure body, which occur during a turning operation of the closure body, are switched from one to the other selectively. This switching operation is practically carried out by fitting the stopper projections into the stopper recesses so as to generate a force of the coiled spring, by which the sleeve is lifted, and thereby holding the seal ring tightly by the upper surface of the sleeve and the lower surface of the head portion of the closure body; and disengaging the stopper projections from the stopper recesses to cause the stopper projections to run on the annular sleeve surface, and then the sleeve to be pressed down against the force of the coiled spring, and thereby loosening the holding of the seal ring between the upper surface of the sleeve and the lower surface of the head portion of the closure body. A flat spring can be used as the elastic member as long as the coiled spring and the flat spring are members generating resilience in the direction (vertical direction) in which the members are connected together.

In the fuel cap according to the present invention, the stopper projections and the stopper recesses are thus disengaged from each other while in proceeding from the securing-started stage to the securing-finished stage. Namely, when the stopper projections run on the annular sleeve surface to cause the holding of the seal ring to be loosened, the bad influence of the deformation and friction of the seal ring, which occur during a fuel cap turning operation, upon the closure body is intercepted, and the torque needed to carry out a fuel cap turning operation can be reduced.

The sleeve in this fuel cap is provided with the stopper recesses in the circumferential positions corresponding to the securing-started stage and the securing-finished stage. The engagement member is provided with the engagement projections on the outer side face thereof in the circumferential positions corresponding to the securing-started stage. The holding of the seal ring is attained by fitting the stopper projections into the stopper recesses in the securing-started stage and the securing-finished stage of the fuel cap, urging the coiled spring so as to lift the sleeve, and thereby tightly holding the seal ring between the upper surface of the sleeve and the lower surface of the head portion of the closure body. Conversely, the loosening of the holding of the seal ring may be attained by disengaging the stopper projections from the stopper recesses while in proceeding from the securing-started stage to the securing-finished stage to cause the stopper projections to run on the sleeve annular surface, and thereby pressing down the sleeve against the force of the coiled spring.

In order to reliably carry out a fuel cap turning operation in the closing direction, it is recommended that the annular sleeve surface be inclined downward from the stopper recesses provided in the circumferential positions corresponding to the securing-started stage toward the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage. When the stopper projections are disengaged from the stopper recesses provided in the circumferential positions corresponding to the securing-started stage to run on the annular sleeve surface, the stopper projections are moved smoothly toward the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage along the downwardly inclining annular sleeve surface. This enables the fuel cap turning operation in the closing direction from the securing-started stage to the securing-finished stage to be carried out easily and reliably.

Conversely, in order to easily carry out the fuel cap turning operation in the fuel cap opening direction, it is recommended that the annular sleeve surface be inclined downward from the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage toward the stopper recesses provided in the circumferential positions corresponding to the securing-started stage. When the stopper projections are disengaged from the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage to run on the annular sleeve surface, the stopper projections are moved smoothly toward the stopper recesses provided in the circumferential positions corresponding to the securing-started stage along the downwardly inclined annular sleeve surface. This enables the fuel cap turning operation in the opening direction thereof from the securing-finished stage to the securing-started stage to be carried out easily and reliably.

The stopper recesses provided in the circumferential positions corresponding to the securing-started stage and the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage allow the sleeve to be lifted in the same manner by the coiled spring owing to the engagement of the stopper projections and stopper recesses with each other. However, strictly speaking, it is desirable that the stopper projections be made able to disengage easily from the stopper recesses provided in the circumferential positions corresponding to the securing-started stage, and, conversely, fit sufficiently in and rarely come off from the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage.

Therefore, in the sleeve, the depth of the stopper recesses provided in the circumferential positions corresponding to the securing-started stage may be set relatively small, while the depth of the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage may be set relatively large. As a result, the stopper projections are easily disengaged from the stopper recesses provided in the circumferential positions corresponding to the securing-started stage, against the force of the coiled spring, while the stopper projections as a whole fit in the stopper recesses provided in the circumferential positions corresponding to the securing-finished stage with the sleeve lifted without obstructing the force of the coiled spring to thereby enable the seal ring to be held tightly by the upper surface of the sleeve and the lower surface of the head portion of the closure body.

Thus, the fuel cap according to the present invention lessens the torque needed to carry out a turning operation therefor and improves the operability thereof by releasing the closure body from the influence of the seal ring. This can be attained because the seal ring used in the present invention provides the air-tightness not owing to the compression of the seal ring by the head portion of the closure body but owing to the pressure-contact of the seal ring with the inner side surface of the oil filler port in radius direction from the center thereof, so that, even when the closure body is released from the influence of the seal ring, problems do not occur from the securing-started stage to the securing-finished stage. Namely, in the fuel cap according to the present invention, the turning operation of the closure body does not basically have relation with the air-tightness of the fuel cap attained by the seal ring. Since the highness and lowness of the air-tightness is determined strictly by only the positional relation between the seal ring and the inner side surface of the oil filler port, the turning operation of the closure body and the air-tightness of the fuel cap owing to the seal ring can be separated from each other.

Since the seal ring pressure-contacted with the inner side surface of the oil filler port in radius direction from the center thereof can display the air-tightness of the fuel cap as long as the seal ring is positioned in the oil filler port, the seal ring has the advantage of not causing the air-tightness of the fuel cap to decrease even with respect to the twisting thereof. Furthermore, the seal ring is pressure-contacted with the inner side surface of the oil filler port by a restoring force occurring due to the elastic deformation thereof, so that the seal ring also has as compared with a compression-deformed seal ring the advantage of having not lower than a predetermined level of air-tightness display even when the dimension control is relaxed.

The seal ring in the present invention may be made of a well-known cross-sectional circular seal ring. However, in order to attain a compatibility of the deformation of the seal ring needed to display the air-tightness of the fuel cap by pressure-contacting the seal ring with the inner side surface of the oil filler port in radius direction from the center thereof and the stable holding of the seal ring by the upper surface of the sleeve and the lower surface of the head portion of the closure body, a more preferable structure is conceivable. A preferable seal ring in the present invention includes an upper annular edge fitted firmly around a trunk portion of a closure body, a lower annular edge diverging from the upper annular edge, and a frustum seal surface connecting the upper annular edge and lower annular edge together and inclined downward in the outward radius direction. In this structure, the upper annular edge is held between the upper surface of the sleeve and the head portion of the closure body from the upper and lower sides thereof, and the outer circumferential surface of the lower annular edge is pressure-contacted with the inner side surface of the oil filler port in radius direction from the center thereof.

This seal ring attains by the frustum seal surface the deformation thereof needed to obtain the air-tightness of the fuel cap, and pressure-contacts the outer circumferential surface of the lower annular edge with the inner side surface of the oil filler port by utilizing the restoring force of the frustum seal surface which is deformed with the upper annular edge used as a fulcrum which is held by the upper surface of the sleeve and the head portion of the closure body. The downward inclination of the frustum seal surface sets the direction of deformation of the seal ring used the upper annular edge thereof as a fulcrum in the inward radius direction and in the direction toward the feed oil pipe (downward direction), to generate the restoring force of the frustum seal surface in the outward radius direction and in the direction in which the fuel cap becomes distant from the feed oil pipe (upward direction).

Setting the inclination of the frustum seal surface in the outward radius and the upward directions is also conceivable. In this case, the deformation of the seal ring occurs in the inward radius direction and in the direction in which the fuel cap becomes distant from the feed oil pipe (upward direction), and the restoring force occurs in the outward radius direction and in the direction in which the fuel cap approaches the feed oil pipe (downward direction). Therefore, there is the possibility that the frustum seal surface be pushed in the upward direction by fuel steam pressure sent from the feed oil pipe, to cause the frustum seal surface to be separated from the inner side surface of the feed oil pipe. On the other hand, on the frustum seal surface inclined in the outward radius and the downward directions, the fuel steam pressure works in the direction in which the lower annular edge is pressure-contacted with the inner side surface of the oil filler port. In view of this, it is preferable that the frustum seal surface be inclined in the outward radius and the downward directions.

In order to hold the upper annular edge more tightly between the upper surface of the sleeve and the head portion of the closure body, it is recommended that cross-sectional thickness of the upper annular edge is larger than thickness of the seal frustum surface. As a result, the upper surface of the sleeve and the head portion of the closure body become able to hold the upper annular edge alone reliably without touching the frustum seal surface. Furthermore, when the cross sectional shape of the upper annular edge is set to a circular shape or a polygonal shape (including a diamond shape) into the corner portions of which project up and down, the upper annular edge can be brought into linear contact with both the upper surface of the sleeve and the head portion of the closure body, and the more tight holding of the upper annular edge can be attained with an increased holding pressure.

In order to pressure-contact the outer circumferential surface of the lower annular edge with the inner side surface of the oil filler port by the restoring force of the frustum seal surface and thereby secure the necessary and sufficient air-tightness, it is demanded that the outer diameter of the outer circumferential surface of the lower annular edge is not smaller than the inner diameter of the inner side surface of the oil filler port. This means, resistance occurs where the seal ring is fitted into the feed oil pipe. Therefore, in order to fit the seal ring into the feed oil pipe smoothly while allowing the deformation of the frustum seal surface, the lower annular edge may be made convergent in the downward direction so that the outer circumferential surface thereof becomes an inclined surface. As a result, it becomes possible that the outer circumferential surface of an inclined cross section fits into the oil filler port while the outer circumferential surface sliding-contacts with an end edge of the oil filler port in the securing-started stage, and that the outer circumferential surface of the lower annular edge is pressure-contacted with the inner side surface of the oil filler port so as to provide the necessary and sufficient air-tightness of the fuel cap by deforming the frustum seal surface at the same time. Moreover, the outer circumferential surface of an inclined cross section is necessarily brought into linear contact with the inner side surface of the oil filler port, so that the contacting pressure can be heightened. This enables the air-tightness of the fuel cap to be improved.

Therefore, it is preferable that the sleeve adapted to lift from the lower side thereof the seal ring having a frustum seal surface has a structure in which a frustum sleeve surface has an angle of inclination acuter than that of the frustum seal surface of the seal ring, and in which the upper annular edge is held from the upper and lower sides by the upper edge of this frustum seal surface and the lower surface of the head portion of the closure body. The seal ring in the present invention attains the air-tightness of the fuel cap by pressure-contacting the outer circumferential surface of the lower annular edge with the inner side surface of the oil filler port by utilizing the restoring force of the deformed frustum seal surface. Therefore, it is preferable that the sleeve can be also provided with a frustum sleeve surface engaged from the lower side with the seal ring so as not to obstruct deformation of the downwardly inclined frustum seal surface. As a result, the upper annular edge of the seal ring is held by the upper edge of the frustum seal surface linearly engaged therewith, and the holding pressure can also be heightened.

In order to hold the upper annular edge of the seal ring by the upper surface of the sleeve and the lower surface of the head portion of the closure body, the holding tightness is heightened more easily by elastically deforming the upper annular edge than by compression-deforming the upper annular edge. For this reason, the seal ring may be formed so that the upper annular edge has a horseshoe-shaped diametrical cross section extending around the diametrical center thereof, and holds the upper annular edge by the upper surface of the sleeve and the head portion of the closure body from the upper and lower sides and elastically deforms the same. The horseshoe-shaped upper portion of the upper annular edge is pressed from the upper side by the lower surface of the head portion of the closure body and elastically deformed to the lower side, and the horseshoe-shaped lower portion of the upper annular edge is pressed from the lower side by the upper surface of the sleeve and elastically deformed to the upper side. Thus, a restoring force is generated in both of these cases to cause the seal ring to be pressure-contacted with the lower surface of the head portion of the closure body or the upper surface of the sleeve. As a result, the stable holding of the upper annular edge as a whole by the upper surface of the sleeve and the lower surface of the head portion of the closure body is attained.

In the fuel cap according to the present invention, the closure body having stopper projections is turned, and the sleeve having stopper recesses is firmly positioned in the turning direction, the closure body being thereby temporarily released from the influence of the seal ring. Therefore, it is demanded that the sleeve be firmly positioned with the anti-rotation projections fitted reliably in the clearances between the ribs provided on the inner side surface of the oil filler port, and that, at the same time, the turning operation of the closure body does not have influence upon the firmly positioning of the sleeve. In view of these, it is conceivable that the sleeve can be divided into two parts, and that one divisional part be made to have a position fixing operation so as to intercept the influence ascribed to the turning operation of the closure body.

To be concrete, the sleeve includes two members, i.e. a lower sleeve and an upper sleeve. The lower sleeve includes connecting recesses opening upwardly arranged to the inner side surface thereof, anti-rotation projections extending downwardly arranged to the outer side surface thereof so as to fit into the clearances between the ribs, and engagement flanges extending radially outwardly engaged from the upper side with the ribs. The upper sleeve includes an annular sleeve surface arranged to the inner side surface thereof with stopper recesses opening upwardly to receive the stopper projections, and connecting projections extending toward the lower sleeve arranged to the outer side surface thereof so as to fit into the connecting recesses.

The closure of the above-described construction is formed into a unitary structure by assembling the seal ring, the upper sleeve, the coiled spring, the lower sleeve and the engagement member in the mentioned order on the trunk portion of the closure body. As a result, the holding of the seal ring by the upper surface of the upper sleeve and the lower surface of the head portion of the closure body becomes tight when the stopper projections are fitted into the stopper recesses to cause the upper sleeve to be lifted by the force of the coiled spring, and loose when the stopper projections are disengaged from the stopper recesses and run on the annular sleeve surface to cause the upper sleeve to be pressed down against the force of the coiled spring.

Since the lower sleeve forms an engagement flange engaged from the upper side with the ribs, the anti-rotation projections can be reliably engaged with the ribs without passing through the clearances therebetween, and thereby positioned firmly. The upper sleeve is engaged at the connecting projections thereof with the connecting recesses of the lower sleeve and thereby connected thereto, so that the upper sleeve can be positioned firmly and stably in accordance with the firmly positioning of the lower sleeve. When the direction in which the engagement of the connecting projections with the connecting recesses is made is specially set to the vertical direction, the direction in which the resiliency generated by the coiled spring interposed between the upper sleeve and the lower sleeve works can be advantageously limited to the vertical direction. Moreover, the lower sleeve is only contacted with the upper surface of the engagement member, and does not receive the influence of the engagement member operatively connected to the closure body. Especially, since the coiled spring leaves the engagement member, the coiled spring ceases to receive the influence of the engagement member operatively connected to the closure body, so that a stable resiliency becomes able to be generated.

The fuel cap according to the present invention has the following effects.

First, the closure body does not receive the influence of the seal ring during the time from the securing-started stage to the securing-finished stage, so that the fuel cap can be turned with a comparatively low torque. Moreover, since the annular sleeve surface, which the stopper projections run on and are sliding-contacted with, is formed with incline between the stopper recesses, the turning operation of the fuel cap in the inclining direction of the inclined surfaces becomes easy, and the oil filler port can be opened and closed reliably without encountering the interruption during the turning operation of the fuel cap. The stopper projections of the closure body fit into the stopper recesses of the sleeve in the securing-started stage and the securing-finished stage, so that the fuel cap becomes stable and is not turned inadvertently. Thus, the fuel cap according to the present invention is effective in turning operation itself easily and reliably, and, moreover, effective to maintain the shut of the oil filler port stable in the securing-finished stage.

Second, the air-tightness of the fuel cap is secured by pressure-contacting the seal ring with the inner side surface of the oil filler port in radius direction from the center thereof. Therefore, there is advantage that substantially uniformed air tightness can be obtained in a wide range from the securing-started stage in which the seal ring fits in the oil filler port to the securing-finished stage. The fuel cap according to the present invention can be tightly secured to the oil filler port by only a horizontal turning operation, and, in the securing-finished stage, the engagement projections are engaged from the lower side with the ribs provided on the inner side surface of the oil filler port, so that the twisting of the fuel cap with respect to the oil filler port rarely occurs. This brings about an effect of rendering it difficult to cause the fuel cap to slip off from the oil filler port in the securing-finished stage. Even if the fuel cap is accidentally twisted, the air-tightness thereof does not lower since the seal ring employs a structure for attaining the air-tightness as mentioned above. Therefore, the fuel cap according to the present invention also has an effect of rendering it possible to obtain air-tightness stably and reliably.

Besides these effects, the fuel cap according to the present invention secures the stability thereof during the securing thereof to the oil filler port and the air-tightness of the seal ring not relying upon the accurate dimensions of each member but depending upon the positional and connecting relation between the members. Namely, the fuel cap according to the present invention may moderate the dimension control as compared with conventional fuel caps of this kind. Even in such a case, the stability of the fuel cap during the securing thereof with respect to the oil filler port and the air-tightness of the seal ring can be improved. The moderation of the dimension control has an effect in reducing the manufacturing cost of the fuel cap according to the present invention. Thus, the fuel cap according to the present invention can also obtain a high cost performance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The modes of embodiments of the present invention will now be described with reference to the drawings.

The fuel cap1is formed as shown inFIGS. 1 and 2, by fixing a fuel cap turning handle3to a multi-step head portion102including a head top112thereof, an upper step122thereof and a lower step132thereof in a closure body100of a closure2based on the present invention. The closure2based on the present invention is formed into a unitary structure by fitting a retainer ring200around the lower step132of the head portion102of the closure body100, and a seal ring300, a sleeve400and a coiled spring500in the mentioned order in the downward direction around a trunk portion103extending from the lower step132of the head portion102in the axially downward direction, and connecting an engagement member600to a lower end of the trunk portion103. These members except the seal ring300are unitary molded products of mainly a synthetic resin, and the seal ring300is made of rubber of an excellent oil resistance. To make these members, various kinds of known materials can be used. This fuel cap1is secured to an oil filler port700provided on an inner side surface701thereof with a pair of ribs702,702made integral therewith, by having engagement projections601, which are provided on the engagement member600, crawl into lower portions of the ribs702, and engaging the engagement projections with upper portions of the ribs702.

The closure body100is formed so as to have a cylindrical trunk portion103extending downward in the axial direction from a lower surface of a lower step132of the head portion102be operated by the handle3. This closure body100is provided on a side surface of the trunk portion103, which is formed just below the head portion102, with an annular trunk surface104having a pair of downwardly extending stopper projections101,101on the portions thereof which are 180-degree symmetrically spaced from each other. The stopper projection101has a shape of an inverted trapezoid in front elevation, and inclined surfaces on the circumferentially front and rear portions thereof. This makes it easy to fit and disengage the stopper projections101,101in and from the stopper recesses401,402provided in an annular sleeve surface403and similar in shape to each other in front elevation. In this closure body100, the axis thereof is matched with the engagement member600by engaging the engagement projection105extending from a lower end surface of the trunk portion103with an engagement hole602of an engagement member600, which is then connected to and united by bolts603. Thus, the closure body100and engagement member600hold other members therebetween and attain the unity as the closure2. In addition, the ability of the fuel cap to turn the closure body100and engagement member600in one body is attained at all times.

A retainer ring200is interposed between the lower surface of the upper step122of the head portion102of the closure body100and the seal ring300so as to fill up a clearance therebetween. The retainer ring200slides on the lower surface of the upper step122of the head portion102, and thereby restrains an increase of the torque during a fuel cap turning operation. The retainer ring200in this embodiment employs a cross-sectionally 90-degree turned laterally T-shaped structure including an inner circumferential retainer portion201fitted firmly in a circumferential surface106of the lower step132of the head portion102, and an outer circumferential retainer portion202engaged at an upper edge thereof with the lower surface of the upper step122of the head portion102, and at a lower edge thereof with a lower edge of a frustum seal surface301of the seal ring300. When the outer circumferential retainer portion202of this retainer ring200presses from the upper side the frustum seal surface301of the seal ring300, the function of the retainer ring200of controlling the elastic deformation of the frustum seal surface301so that this elastic deformation does not occur in an upwardly projecting mode, and directing the restoring force in radius direction occurring due to the elastic deformation of the frustum seal surface301is displayed.

The seal ring300is a rubber ring pressure-contacted with an inner side surface701of the oil filler port700in radius direction from the center thereof, and employs a skirt structure including an upper annular edge302fitted firmly in a trunk portion annular surface104of the closure body100, a lower annular edge303diverging from this upper annular edge302, and a frustum seal surface301connecting the upper annular edge302and lower annular edge303together and having a radially outwardly lowering gradient. When the lower annular edge303of this seal ring300is pressed against the inner side surface701of the oil filler port700to cause the frustum seal surface301to be elastically deformed, the frustum seal surface301generates a restoring force for lifting the lower annular edge303. When the lower annular edge303is pressure-contacted in radius direction from the center thereof with the inner side surface701of the oil filler port700by utilizing this restoring force, the air-tightness of the fuel cap is attained.

Since the upper annular edge302of the seal ring300in this embodiment is formed to a circular cross section and set to a thickness larger than that of the frustum seal surface301as shown inFIG. 4, the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the sleeve400are respectively brought into linear contact with the upper annular surface302. This enables the seal ring to be held more tightly by the lower surface of the head portion102of the closure body100and the upper edge of the sleeve400. When another example of a seal ring350which has an upper annular edge351having a substantially horseshoe-shaped cross section as seen inFIG. 5is used, the upper annular edge351held by the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the sleeve400displays a restoring force based on the elastic deformation thereof ascribed to the holding force, and the upper annular edge351becomes possible to be held more tightly. The seal ring300in this embodiment is formed to a substantially triangular cross section so that the outer circumferential surface becomes an inclined surface by converging the lower annular edge303in the downward direction. As a result, the outer circumferential surface made of the inclined surface comes to be easily fitted in the oil filler port by bringing the outer circumferential surface made of the inclined surface into sliding-contact with the end edge of the oil filler port.

A sleeve400has an upwardly decreasing outer diameter so as to form a frustum sleeve surface406having the angle of inclination of which is larger than that of the frustum seal surface301of the seal ring300. Therefore, the sleeve400is substantially cylinder having a tapered upper edge of a substantially triangular cross section. The sleeve400is provided in an inner side surface thereof with an annular sleeve surface403having stopper recesses401,402opened upwardly into which the stopper projections101of the closure body100is fitted. The stopper recesses401,402in this embodiment have an inverted frustum shape similar in front elevation to the shape of the stopper projections101, and can be divided into stopper recesses (which will hereinafter be referred to as starting stopper recesses401) provided in circumferential positions corresponding to die securing-started stage, and another stopper recesses (which will hereinafter be referred to as finishing stopper recesses402) provided in circumferential positions corresponding to the securing-finished stage. These starting stopper recesses401and finishing stopper recesses402are made of two recesses respectively, and they are arranged at 90-degree clearances. The depths of the starting stopper recesses401and finishing stopper recesses402are different from each other. The former recesses are made relatively small, and the latter recesses are made relatively large. The annular sleeve surface403connecting these stopper recesses401,402together are inclined downward (refer toFIG. 16which will be referred to later, and the downward gradient is omitted in the other drawings) in one direction respectively, i.e., clockwise in plan from the starting stopper recesses401toward the finishing stopper recesses402. As a result, the stopper projections101fitted in the starting stopper recesses401in the securing-started stage disengage from the starting stopper recesses401easily in accordance with the turning operation of the closure2. The stopper projections101are then moved in sliding contact with the annular sleeve surface403, and become easy to fit in the finishing stopper recesses402in the securing-finished stage. The stopper projections101rarely leave the finishing stopper recesses402, so that the securing of the closure2to the oil filler port700can be stabilized.

The sleeve400is provided on the outer side surface thereof with a pair of downwardly extending anti-rotation projections404,404fitted in the clearances between ribs702,702of the oil filler cap700and spaced from each other at 180 degrees. The anti-rotation projections404in this embodiment have a circumferential width equal to that of the clearances between the ribs702,702of the oil filler port700, fit in the clearances between the ribs702,702in any stage from the securing-started stage to the securing-finished stage, and have a rectangular shape in front elevation having a length restricting the rotation of the sleeve400. Owing to this structure, the sleeve400is positioned firmly and relatively from the securing-started stage at which the fuel cap1is secured to the oil filler port700, with respect to the closure body100and engagement member600. Besides these members, the sleeve400in this embodiment has a sleeve guide surface405continuing to the outer side surface and extending downward from the annular sleeve surface403, so as to guide a coiled spring500engaged from the lower side with a lower surface of the annular sleeve surface403.

An engagement member600is a substantially cylindrical thick-walled structure closed with a bottom surface604, and provided with an annular engagement surface605constituting an inner side surface thereof, and engagement projections601,601which pass through the clearances between the ribs702,702in the oil filler port700and then turn and engage the ribs702from the lower side thereof. In this embodiment, an engagement guide surface606adapted to guide the coiled spring500supported on the annular engagement surface605is extended upward. The engagement projections601in this embodiment have an anti-clockwise inclined upper surface in front elevation. When the closure body100is turned to right in the closing direction, the engagement projections are pressed down while sliding in the lower surface of the ribs702. The closure body100is fitted at the trunk portion103into the annular engagement surface605with the engagement projections105of the trunk portion103fitted into the engagement hole602provided in the bottom surface604, the closure body100being thereby connected to the engagement member600. Further, the engagement member600is fixed to the closure body100by screwing bolts603thereto through the bottom surface604. A coiled spring500serving as an elastic member is interposed between the lower surface of the annular sleeve surface403of the sleeve400and the annular engagement surface605, and urges the sleeve400against the engagement member600relatively upward.

The fuel cap1in this embodiment is secured to the oil filler port700in the following order. First, in the securing-started stage, as seen inFIG. 3, the engagement projections601,601of the engagement member600are inserted in the clearances between the ribs702,702in the oil filler port700, and the closure2is thereby fitted into the oil filler port700. As seen inFIG. 4, the lower annular edge303of the seal ring300is engaged from the above with a folded end703of the oil filler port700, and the upper annular edge302is engaged only with the lower surface of the lower step132of the head portion102of the closure body100by the elastic force of the frustum seal surface301. Since the upper edge of the sleeve400is separated from the lower surface of the lower step132of the head portion102of the closure body100, the holding of the upper annular edge302is not sufficiently, and, in this securing-started stage, the seal ring300does not display the air-tightness.

However, as seen inFIG. 6, the engagement projections601of the engagement member600have passed through the clearances between the ribs702,702, and positioned the downwardly inclined upper surface thereof under the ribs702. As a result, the closure body100and engagement member600can be turned clockwise, i.e., in the closing direction so that the engagement projections601slip in the lower portions of the ribs702. On the other hand, the sleeve400is fitted at the anti-rotation projections404between the ribs702,702as seen inFIG. 7, and positioned and fixed relatively with respect to the closure body100and engagement member600. The present invention carries out practically the reduction of torque in a fuel cap turning operation by varying the engaged condition between the starting stopper recesses401and finishing stopper recesses402formed in the annular sleeve surface403of the sleeve400thus relatively positioned and fixed and the stopper projections101formed on the turned closure body100, and thereby temporarily reducing the tightness of the closure body100and seal ring300.

Namely, as seen inFIG. 8, in a securing-intermediated stage in which the closure body100starts being turned, the upper edge of the sleeve400is stayed away from the lower surface of the lower step132of the head portion102of the closure body100as seen inFIG. 9, so that the degree of the tightness of the closure body100and seal ring300is temporarily loosened. To be concrete, since the engagement projections601in the closure body100are made integral with the engagement member600which slips in the ribs702as seen inFIG. 10, the position of the closure body100in the direction of the height is determined by the engagement member600, and the closure body100moves down with the engagement member600. However, as seen inFIG. 11, the sleeve400which the anti-rotation projections404thereof are fitted between the ribs702,702is positioned and fixed, so that the projections101of the closure body100necessarily run on (refer toFIG. 16) the annular sleeve surface403to cause the sleeve400to be relatively pressed down. Consequently, tightness of the seal ring300held by the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the sleeve400is lessened due to the relative downward pressing force of the sleeve400.

The operability of the securing of the fuel cap1becomes higher in inverse proportion to the level of the torque needed to carry out the fuel cap turning operation. The seal ring300in the present invention secures the air-tightness of the fuel cap by pressure-contacting the lower annular edge303in radius direction from the center thereof with the inner side surface701of the oil filler port700by utilizing the elastic deformation of the frustum seal surface301, so that it is not necessary to compress the seal ring300by the closure body100. Therefore, as described above, the operability of the fuel cap can be improved by temporarily reducing the degree of tightness of the closure body100and seal ring300when a fuel cap turning operation is carried out, intercepting the influence of the friction of the seal ring300pressure-contacted with the inner side surface701of the oil filler port700, and thereby holding down or preventing an increase in the torque needed to carry out a fuel cap turning operation.

The depth of the starting stopper recesses401is relatively small with respect to that of the finishing stopper recesses402, and, to be concrete, limited to a level about a half of the length of the stopper projections101and both the stopper projections101and starting stopper. recesses401are inclined at the circumferentially front and rear portions thereof. Therefore, during a fuel cap turning operation in the securing-started stage, the stopper projections101can be disengaged from the starting stopper recesses401comparatively easily. Moreover, since the annular sleeve surface403is inclined downward from the starting stopper recesses401to the finishing stopper recesses402, the turning operation of the closure body100can be carried out easily in the closing direction. Thus, the fuel cap turning operation in the securing-started stage starts with the disengagement of the stopper projections101from the starting stopper recesses401of a low load, and the stopper projections101which intercept the influence caused by the friction of the seal ring300move (refer toFIG. 16) along the downwardly inclined annular sleeve surface403. This enables the torque exerted on the closure body100to be constituted by only the resistance occurring when the engagement projections601sliding-contact with the ribs702. Therefore, a low bad excellent fuel cap turning operability is attained.

When the fuel cap securing operation reaches the securing-finished stage, the maintaining of a stable air-tightness by the seal ring300becomes important now. Therefore, when the fuel cap securing operation reaches the securing-finished stage as seen inFIG. 12, the engagement member600wholly reaches a position below the ribs702as seen inFIG. 14, and the stopper projections101of the closure body100combined with the engagement member600into a unitary structure can be fitted (refer toFIG. 16) again into the finishing stopper recesses402of the sleeve400. As a result, the sleeve400is lifted by the force of the coiled spring500, and the upper annular edge302of the seal ring300is held tightly by the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the sleeve400.

When the outer diameter of the lower annular edge303is set larger than the inner diameter of the inner side surface701of the oil filler port700in this embodiment, the frustum seal surface301can naturally be deformed elastically in the stage in which the lower annular edge303is fitted in the oil filler port700, and a restoring force can thereby be generated. However, it is necessary that the restoring force be set in the direction in which the lower annular edge303is pressure-contacted with the inner side surface701of the oil filler port700for the purpose of securing the air-tightness of the fuel cap. As seen inFIG. 13, the holding of the upper annular edge302by the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the sleeve400signifies the creating of the condition in which the lower annular edge303is pressure-contacted with the inner side surface701of the oil filler port700by determining the origin of the restoring force, and generating the restoring force in the radially outward direction in accordance with the inclination of the frustum seal surface301. In this embodiment, restrictions are placed on the frustum seal surface301by the retainer ring200so that the elastic deformation thereof does not cause the same to project upward. Therefore, the restoring force reliably causes the lower annular edge303to be pushed out in the radially outward direction, and the pressure-contacting of the lower annular edge303with the inner side surface701of the oil filler port700is thereby attained.

As is clear from the results of a comparison betweenFIG. 3,FIG. 8andFIG. 12, the seal ring300in the fuel cap1in this embodiment is engaged or pressure-contacted constantly at the lower annular edge303with the inner side surface701of the oil filler port700from the securing-started stage (refer toFIG. 3) to the securing-finished stage (refer toFIG. 12). Especially, between the securing-intermediated stage (refer toFIG. 8) and the securing-finished stage (refer toFIG. 12), the lower annular edge303is pressure-contacted with the inner side surface701of the vertically extending oil filler port700by the restoring force generated due to the elastic deformation of the frustum seal surface301. Therefore, even when the seal ring300is somewhat inclined, i.e., even when the fuel cap1is twisted, the air-tightness of the fuel cap is not spoiled. Thus, the air-tightness of the fuel cap1according to the present invention is attained by pressure-contacting the lower annular edge303in radius direction from the center thereof with the inner side surface701of the oil filler port700, and this enables to prevent a decrease in the air-tightness of the fuel cap occurring when the fuel cap1is twisted.

Moreover, the depth of the finishing stopper recesses402in this embodiment is relatively large with respect to that of the starting stopper recesses401. To be concrete, the depth of the finishing stopper recesses402is set substantially equal to the projecting amount of the stopper projections101. Therefore, when the stopper projections101once fit in the finishing stopper recesses402, the stopper projections101become difficult to disengage therefrom as compared with a case where the stopper projections101fit in the starting stopper recesses, so that the securing-finished stage is maintained easily. This brings about the stability of the air-tightness of the fuel cap in the securing-finished stage. When the fuel cap1is thus secured accurately to the oil filler port700, the air-tightness of the fuel cap is displayed stably, and the necessary and sufficient air-tightness thereof can be displayed even if the fuel cap1should be twisted.

In the fuel cap1(refer toFIG. 1andFIG. 2) of the previously-described embodiment, a coiled spring500elastically supporting a sleeve400moves slidingly with respect to an engagement member600, and the slewing motion of the engagement member600is not transmitted to a sleeve400. However, strictly speaking, a lower end of the coiled spring500is contacted with the engagement member600that turns, and an upper end of the coiled spring500is contacted with the sleeve400fixed its position. Therefore, there is the possibility that the amount of lifting the sleeve400in the securing-finished stage becomes insufficient since at least a small twisting force is exerted on the coiled spring500. The fuel cap4of this embodiment is provided with the coiled spring500between an upper sleeve411and a lower sleeve412, and the function absorbing the slewing motion is thereby removed from the coiled spring500. The function of the coiled spring is strictly limited to the function of pressing the upper sleeve411toward the lower sleeve412so as to engage stopper projections101with starting stopper recesses401or finishing stopper recesses402.

The construction of the fuel cap4of this embodiment will now be described mainly on the sleeve400constituting a difference between this embodiment and the previous embodiment mentioned above. The sleeve400includes two members, i.e. an upper sleeve411and a lower sleeve412as seen inFIG. 17andFIG. 18. The lower sleeve412is a cylindrical member made of a resin having connecting recesses413opened upwardly of a rectangular shape in front elevation in an inner side surface thereof; anti-rotation projections404extending downwardly on an outer side surface thereof, adapted to be fitted in clearances between ribs702,702and having a rectangular shape in front elevation; engagement flanges414in outward radius direction formed on an upper edge thereof, engaged from the upper side with the ribs702provided on the inner side surface701of the oil filler port700; and an annular receiving surface415formed on a lower edge of the inner side surface in inward radius direction. The coiled spring500is supported on the annular receiving surface415, and guided by a lower sleeve guide surface417upwardly extended from this annular receiving surface415. This lower sleeve412only brings a lower surface of the annular receiving surface415into sliding contact with an upper surface of the engagement member600, and does not have connecting relation with the engagement member600. The upper sleeve411is provided on the inner side surface thereof with an annular sleeve surface403having stopper recesses401,402opened upwardly of an inverted frustum shape in front elevation into which the stopper projections101of a closure body100are fitted, and on the outer side surface thereof with connecting projections416extending toward the lower sleeve412and similar to the shape of connecting recesses413into which the connecting projections are fitted.

The lower sleeve412is fixed its position in the turning direction by fitting the anti-rotation projections404thereof in the clearances between the ribs702,702. The fitting of the anti-rotation projections404into the clearances between the ribs702,702is maintained by the engagement flanges414engaged from the upper side with the ribs702of the oil filler port700. Thus, the engagement flanges414provided on the lower sleeve412have the function of restricting a position to which the lower sleeve412moves down, so as to reliably fit the anti-rotation projections404into the clearances between the ribs702,702. The upper sleeve411is fixed its position with respect to the lower sleeve412in the turning direction by inserting from the above the connecting projections416into the connecting recesses413of the lower sleeve412. The upper sleeve411can be vertically moved close to and away from the lower sleeve412by inserting and withdrawing the connecting projections416into and from the connecting recesses. As a result, the upper sleeve411is elastically supported in the upward direction by the coiled spring500interposed between the upper surface of the receiving annular surface415of the lower sleeve412and the lower surface of the annular sleeve surface403of the upper sleeve411, and thereby deformed freely in the vertical direction only.

The fuel cap4of this embodiment is secured to the oil filler port700in the following order. First, in the securing-started stage in which the fuel cap4is inserted into the oil filler port, a closure5is fitted into an end of the oil filler port700as seen inFIG. 19, by inserting the engagement projections601of the engagement member600into the clearances between the ribs702,702of the oil filler port700. The engagement projections601of the engagement member600pass through the clearances between the ribs702,702as seen inFIG. 20, and are positioned at the downwardly inclined upper surface thereof under the ribs702. On the other hand, the lower sleeve412is not engaged at the engagement flanges414thereof with the ribs702as seen inFIG. 21but the anti-rotation projections404thereof are filled in the clearances between the ribs702,702by contacting the lower surface of the receiving annular surface415with the upper surface of the engagement member600. Thus, the lower sleeve412is fixed its position relatively with respect to the closure body100and the engagement member600. Also, the upper sleeve411is fitted at the connecting projections416into the connecting recesses413of the lower sleeve412, and then restricted its position in the turning direction in accordance with the lower sleeve412.

In the securing-intermediated stage in which the closure body100starts being turned, the upper edge of the upper sleeve411stays away from the lower surface of the lower step132of the head portion102of the closure body100as seen inFIG. 22, so that an amount of the tightness between the closure body100and seal ring300is temporarily reduced. To be concrete, the closure body100drops down with the engagement member600which the engagement projections601are slid in the clearances between the ribs702, as seen inFIG. 23. However, in the same time, the lower sleeve412with the anti-rotation projections404fitted in the clearances between the ribs702,702is fixed its position as seen inFIG. 24. Thus, the stopper projections101of the closure body100run around the annular sleeve surface403to thereby relatively press down the upper sleeve411. As a result, the tightness of the seal ring300held by the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the upper sleeve411is reduced due to the relative pressing force of the upper sleeve411. During this time, the slewing motion of the engagement member600is absorbed owing to the sliding contact of the lower sleeve412with the annular receiving surface415, and not transmitted to the coiled spring500. Therefore, there is not a fear of the occurrence of the twisting of the coiled spring500.

When the fuel cap securing operation reaches the securing-finished stage thereof as seen inFIG. 25, the engagement member600wholly reaches a position below the ribs702as seen inFIG. 26, and the stopper projections101of the closure body100fixed with the engagement member600into a unitary structure can be fitted again into the finishing recesses402of the upper sleeve411as seen inFIG. 27. Therefore, the upper sleeve411can be lifted by the urging force of the coiled spring500, and the upper annular edge302of the seal ring300can be held tightly by the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the upper sleeve411. In this embodiment, the coiled spring500is not twisted since the coiled spring500does not have influence of the slewing motion of the engagement member600. The coiled spring500can lift the upper sleeve411reliably by a level corresponding to the loss of a pressing force owing to the engagement of the stopper projections101with the finishing stopper recesses402. Thus, the seal ring300is held tightly at the upper annular edge302of the lower surface of the lower step132of the head portion102of the closure body100and the upper edge of the upper sleeve411.