1. Field of the Invention
This invention relates to a mounting structure for rigidly mounting to a device body a case member covering a portion exposed from the device body. More particularly, the invention relates to a mounting structure of a case member for covering a portion exposed from an internal combustion engine where a power transmitting mechanism, for example, is located.
2. Description of the Related Art
A cam chain cases used to cover a valve driving mechanism disposed in a crank shaft end portion of an internal combustion engine has been detachably attached rigidly to the body of an internal combustion engine with bolts at positions along its outer circumferential periphery, as shown in Japanese Patent Laid-Open Publication No. hei 7-83069.
A central portion of the cam chain case disclosed on the same publication is liable to yieldingly deform in a rectangular direction with respect to a case plane portion. In particular, because of a low rigidity of a peripheral portion of a through hole at the central portion of the cam chain case at an end surface of the engine, through which a shaft of a water pump passes, the central portion of the cam chain case is liable to vibrate.
For the purpose of preventing it, the cam chain case has a plurality of bolt boss portions surrounding the through hole such that bolts in threading engagement with the engine body through the bolt boss portions rigidly couple the cam chain case central portion to the engine body to prevent or alleviate vibrations of the central portion.
Japanese Utility Model Laid-Open Publication No. hei 4-91210 discloses a lubricating system disposed in a space defined between a cam chain case and the body of an internal combustion engine to supply lubricant oil to a timing chain (cam chain) for transmitting rotation of a crank shaft to a cam shaft. In this lubricating system, a projecting portion is formed on an oil pump body attached to a cylinder block, and the projecting portion defines an oil path communicating with tan oil path in the cylinder block and an oil jet hole for jetting oil from the oil path toward a portion of the timing chain to be lubricated. Thus, the oil path in the cylinder block and the oil path of the projecting portion are connected through a hollow pin fit in both oil paths when the oil pump body is coupled to the cylinder block.
In the above-introduced structure configured to attach the cam chain case to the engine body, the needs for a number of bolt boss portions at the central portion of the cam chain case and about an opening and the need for a number of bolts inevitably increase the number of parts, and also increase steps for applying and fixing bolts. Therefore, it has been difficult to reduce the cost and the weight.
In the conventional timing chain lubricating system, the need for the hollow pin also involves the drawbak of again increasing the number of parts and the assembling steps. Further, since the projecting portion having the oil path and the oil jet hole is made, in case a bolt boss portion is formed on the cam chain case or the engine body to prevent vibrations of the cam chain case as indicated above, even when a close positional relation is required from the viewpoint of preventing vibrations of the cam chain case and the viewpoint of lubrication of the cam chain, for example, near sprockets the cam chain wraps, existence of the projecting portion in addition to the bolt boss portions may cause a constraint in the positional relation. Thus, it is often difficult to make the bolt boss portions or the projecting portion at appropriate positions.
It is therefore an object of the invention to provide a case member mounting structure capable of increasing the bending rigidity of a case member and preventing vibrations of the case member and simultaneously capable of reducing the number of parts and the number of assembling steps and significantly reducing the cost and the weight.
According to the invention, there is provided a case member mounting structure characterized in that at least one projecting portion is formed on one or both of an inner surface of a case member and an outer wall surface of a device body to contact the inner wall surface of the case member having an outer circumferential portion fastened to said device body by a plurality of fastening means and to contact the outer wall surface of the device body on which the case member is to be fastened, and a seal member is provided on a contact surface at a distal end of the projecting portion.
According to the invention, since the fastening means for coupling the projecting portion of the case member to the device body is not required, or the number of parts as the fastening means can be reduced, it is possible to reduce the assembling steps as much as the number of parts reduced, and to significantly decrease the manufacturing cost and the weight.
According to a more preferable aspect of the invention, there is provided a case member mounting structure characterized in that at least one projecting portion is formed on one or both of an inner surface of a case member for covering a driving force transmission mechanism and an outer wall surface of a body of an internal combustion engine to contact the inner wall surface of the case member having an outer circumferential portion fastened to the body by a plurality of fastening means and to contact the outer wall surface of the body on which the case member is to be fastened, and a seal member is provided on a contact surface at a distal end of the projecting portion.
With this structure, bolt boss portions required for fastening the engine case member to the engine body with bolts are not required any more, or decreased. Moreover, the fastening means for coupling the projecting portion of the engine case member to the engine body is not necessary, or the number of parts as the fastening means can be reduced. Therefore, it is possible to reduce the assembling steps as much as the number of parts reduced, and to significantly decrease the manufacturing cost and the weight.
Additionally, unlike the boss portions of the aforementioned conventional technique, which are required to have a diameter greater than the maximum outer diameter of bolts to enable holes to be made for receiving the bolts therethrough or therein, even in case there is no allowance in the space defined between the engine case member and the engine body due to the existence of members disposed in that space, the projecting portions have a larger freedom in shape and size, such as being configured as elongated ribs, and are reduced in restrictions regarding their positional relation. Therefore, the projecting portions can be made in effective locations from the viewpoint of preventing vibrations and noises without disturbing the function of the engine.
The seam member may be a liquid seal member coated on one or both of contact surfaces at distal ends of the projecting portions.
With this structure, as the liquid seal member cures, the projecting portions on the inner surface of the case member are rigidly bonded to the device body or engine body. Alternatively, projecting portions on the outer wall surface of the device body or engine body are rigidly bonded to the case member. Therefore, rigidity against the bending force in directions rectangular to the planar portion of the case member is remarkably increased, and vibrations of the case member are suppressed.
The seal member may be a resilient seam member for engagement with at least one of contact surfaces at the distal ends of the projecting portions.
With this arrangement, the outer wall surface of the device body or engine body and the inner wall surface of the case member are elastically coupled, and transmission of vibrations from the device body or engine body to the case member is prevented.
The contact surfaces at the distal ends of the projecting portions may be configured to lie on a common plane to that of the outer wall surface of the device body or engine body, or of the inner wall surface of the case member fastened to that body.
With this arrangement, since contact surfaces at the distal ends of both projecting portions lie on a common plane to that of the fastening plane between the outer wall surface of the device body, or engine body, and the inner wall surface of the case member, finishing of these contact surfaces and fastening surfaces is simplified, and their workability is improved significantly.
The contact surfaces at the distal ends of the projecting portions may be configured to lie on a plane different from that of the outer wall surface of the device body, or engine body, or from that of the inner wall surface of the case member.
With this structure, the seal member and the resilient member are reliably held at the distal ends of the projecting portions, and they are prevented from dropping.
At least one projecting portion may project from one of the inner wall surface of the case member and the outer wall surface of the device body, or engine body, toward the other.
With this arrangement, the number of projecting portions can be minimized in accordance with arrangement of devices and parts in the space between the outer wall surface of the device body, or engine body, and the inner wall surface of the case member.
According to another aspect of the invention, there is provided a case member mounting structure having a plurality of fastening bolt bosses formed along an outer circumference of a case member for applying a plurality of fastening bolts, respectively, such that the case member is attached to a device body or a body of an internal combustion engine with the fastening bolts, characterized in that the surface of the case member is partitioned into polygonal sections, and respective said polygonal sections define depressed planes and projecting planes bordered by respective sides of the polygons.
With this arrangement, since the area of each plane is decreased, vibrations of the case member surface are suppressed, and noises are reduced as well. Additionally, since the case member can be reduced in thickness, increase of the weight can be prevented. Further, bolt boss portions, which are necessary if fastening the case member to the device body, or engine body, with bolts, can be omitted in locations other than the outer circumferences of the case member. Therefore, positions and shapes of the projecting portions can be selected freely to effectively reduce noises caused by vibration without disturbing the function of the device or engine.
The fastening bolt bosses may be located on extension lines from respective sides of the polygons. As a result, fastening bolt bosses lie on extension lines of respective sides of the polygon, strain of the entire case member is reduced, and vibrations of the entirety are prevented.
Ribs may be formed on the same positions of inner and outer surfaces of the case member, and the ribs may partition the inner and outer surfaces of the case member into polygonal sections.
With this structure, both inner and outer surfaces of the case member are enhanced in strength, vibrations of the entire case member are suppressed, and the case member can be reduced in weight.
The seal member may be of the same type as that of the seal member applied on the outer circumference with which the case member is fastened to the device body or engine body. With this arrangement, the seal members can be reduced in type, application and management of seal members re simplified, and this contributes to reducing the manufacturing cost.
According to a further aspect of the invention, there is provided a case member for covering a driving force transmission mechanism of an internal combustion engine characterized in that a maintenance cover is provided to be detachably mounted at a maintenance opening formed in the driving force transmission mechanism and that a harness of a sensor attached to the case member is integral with the maintenance cover.
With this arrangement, since the hold portion for holding the harness of the sensor is integrally formed on the maintenance cover, the harness of the sensor need not be prepared separately, and this contributes to reducing the number of components, work steps, and the manufacturing cost. Additionally, since the hold portion is integral with the maintenance cover, the maintenance cover itself is enhanced in rigidity.
The hold portion of the maintenance cover may be formed along an inclined surface from the outer circumference of the maintenance cover toward the cover side surface. As a result, vibrations are unlikely to occur even when a vibrating force is applied from the device body or engine body.
According to a still further aspect of the invention, there is provided a case member for covering a driving transmission mechanism which transmits a driving force from a rotary shaft of an internal combustion engine to other portions to be driven, comprising a maintenance cover to be detachably attached at a maintenance opening formed in the case member, a detection sensor attached to the case member to orient toward the mounting position of the maintenance cover for detecting rotation of the rotary shaft, and a hold portion integrally formed on the maintenance cover to hold a harness of the detecting sensor, the harness of the detecting sensor being mounted to the hold portion.
With this structure, length of the harness from the detecting sensor to the hold portion can be reduced, and the harness hold portion can be reduced in number. Additionally, fluctuation in mounting position of the detecting sensor due to vibrations of the harness and abnormal noises can be prevented.
At least one bolt hole for mounting the maintenance cover to the case member may serve as a bolt hole for mounting the case member to the engine body such that the maintenance cover and the case member can be fastened together to the engine with bolts inserted through the maintenance cover and the case member and brought into threading engagement with the engine body.
With this arrangement, since the maintenance cover and the case member are fastened together to the engine body with at least one bolt inserted through the maintenance cover and the case member and brought into threading engagement with the engine body, the maintenance cover and the case member can be firmly attached to the engine body with less bolts.