AU2003244521A1 - Air Cleaners for Internal Combustion Engines - Google Patents

Description

AIR CLEANERS FOR INTERNAL COMBUSTION ENGINES The present invention relates to air cleaners for internal combustion engines. In particular, the present invention relates to air cleaners that have a housing, a filter element and a clamp device. The housing includes a casing and a cap that have an air inlet and an air outlet, respectively. The filter element has a peripheral seal portion that is configured to be clamped between peripheral portions of the casing and the cap. The clamp device is adapted to apply a clamping force in a state where the peripheral seal portion of the filter element is positioned between the peripheral portions of the casing and the cap.

FIG. 8(A) shows a known air cleaner 60 for an internal combustion engine disclosed in Japanese Laid-Open Patent Publication No. 7-247923. Referring to FIG. the known air cleaner 60 includes a housing 60h that comprises a casing 62 and a cap 64. An air inlet 61 and an air outlet 63 are defined in the casing 62 and the cap 64, respectively. The cap 64 and the casing 62 are joined to each other via a hinge device 65 in order to open and close the housing 60h. A clamp device 67 is disposed on the side opposite to the hinge device 65 and is operable to clamp the peripheral portions of the cap 64 and the casing 62 against each other in order to keep the housing 60h in a closed state. A filter element 66 is set into the housing 60h and a peripheral seal portion 66e of the filter element 66 is held between the peripheral portions of the cap 64 and the casing 62. In general, the clamp device 67 utilizes a leaf spring or like member in order to tightly clamp the peripheral portions of the cap 64 and the casing 62 against each other, so that hermetic seals between the peripheral seal portion 66e and the peripheral portions of the cap 64 and the casing 62 can be ensured.

However, because the known air cleaner 60 is configured to tightly clamp the peripheral portions of the cap 64 and the casing 62 by utilizing the leaf spring or like member, there is no measure for relieving an excessive pressure that may be caused due to a backfire pressure.

Such a backfire pressure may be produced in the internal combustion engine and may be introduced into the housing 60h via the air outlet 63. Therefore, a possibility may exist that troubles, such as damages on the cap 64 and the casing 62 and breakage of the clamp device 67, may be caused.

FIG. 8(B) shows another known air cleaner 70, in which the central portion of a cap 73 is pressed against a casing 74 in an axial direction via a spring 72, so that the cap 73 can move relative to the casing 74 in the axial direction by a distance of possible deformation of the spring 72. For example, Japanese Laid-Open Patent Publication No. 57-171171 discloses this type of known air cleaner. However, in case of the known air cleaner 70, the peripheral portions of the cap 73 and the casing 74 are sealed against each other by the spring 72 that is a single element. Therefore, in order to ensure the necessary sealing performance, the spring 72 must have a large spring constant. However, if the spring 72 having such a large spring constant is used, the peripheral portion of the cap 73 may be damaged or deformed by the backfire pressure before the spring 72 is deformed.

It is accordingly an object of the present invention to teach improved techniques for preventing a cap and a casing of an air cleaner from being damaged or deformed by a backfire pressure that may be produced in an internal combustion engine.

According to one aspect of the present invention, air cleaners for internal combustion engines are taught that comprise a housing including a casing and a cap. The casing and the cap define an air inlet and an air outlet, respectively. A filter element has a peripheral seal portion adapted to be clamped between. peripheral portions of the casing and the cap. A clamp device applies a clamping force against the peripheral portions of the casing and the cap in order to clamp the peripheral seal portion of the filter element therebetween. The clamping force of the clamp device is determined to be smaller than a separation force that may be applied to move the peripheral portions of the cap and the casing away from each other when a backfire pressure is introduced into the housing. A guide device is disposed between the casing and the cap for providing a guide for the cap when the cap moves from a position displaced from the casing by the separation force to an original position.

Because the clamping force of the clamp device is determined to be smaller than the separation force that may be applied to move the peripheral portions of the cap and the casing away from each other when the backfire pressure is introduced into the housing, upon introduction of the backfire pressure, the peripheral portion of the cap may move away from the peripheral portion of the casing against the clamping force applied by the clamp device, so that the housing may be opened. Therefore, the backfire pressure or an excessive pressure may be released to the outside of the housing. As a result, the casing and the cap may be prevented from being damaged or deformed.

In addition, because the guide device is disposed between the casing and the cap for providing a guide for the cap when the cap moves from a position displaced from the casing by the separation force to the original position, the cap can reliably return to the original position by the clamping force applied by the clamp device after the backfire pressure has been released to the outside. Therefore, the sealing performance of the housing can be reliably recovered, so that the operation of the internal combustion engine can be continuously performed even after the production of the backfire pressure.

In a preferred embodiment of the present invention, a plural sets of the guide device and the clamp devices are provided and are spaced substantially equally from each other in a circumferential direction of the housing. Therefore, the backfire pressure can be reliably released to the outside even if the backfire pressure has been locally applied to a particular region within the housing in the circumferential direction.

In another preferred embodiment of the present invention, the casing and the cap are connected to each other via a hinge device, so that the casing and the cap have free pivotal ends.

The guide device and the clamp devict are disposed on the side of the free pivotal ends of the casing and the cap. Therefore, the guide device and the clamp device of the present invention can be advantageously applied to air cleaners of a type having hinge devices.

Preferably, the guide device includes a rod and a movable member. For example, the rod may be a shank of a bolt and the movable member may be a nut receiving portion for receiving a nut that engages the bolt. The rod extends in a direction of relative movement of the casing and the cap and the movable member is movable relative to the rod in an axial direction of the rod. In addition, the clamp device preferably includes a first spring support formed on one end of the rod, a second spring support formed on the movable member, and a spring fitted around the rod and producing a biasing force to move the first and second receiving portions away from each other in order to provide the clamping force. With this arrangement, common parts can be used for the guide device and the clamp device, and therefore, this arrangement is advantageous in terms of manufacturing costs.

The rod may be coupled to the casing or the cap such that the rod can incline relative to the casing or the cap within a predetermined angle. Therefore, even in case that the cap and the casing are coupled to each other by a hinge device, the movable member can be smoothly guided by the rod because the rod may incline as the cap pivots.

In addition, it is preferable in a practical design that the spring has a spring constant of N/mm, and the spring provides a claming pressure of lkPa to 100kPa against the peripheral seal portion of the filter element that is clamped between the peripheral portions of the cap and the casing.

In another preferred embodiment, the hinge device is located at a first region which receives minimum influence from the backfire pressure and the guide and the clamp devices are disposed at a second region which receives maximum influence from the backfire pressure.

With this arrangement, the backfire pressure can be effectively released to the outside of the housing.

In another preferred embodiment, the rod is disposed on the side of the casing, and the movable member is disposed on the side of the cap and has a hole through which the rod extends.

In another preferred embodiment, the rod has a curved configuration that conforms to the pivotal path of the cap permitted by the hinge device.

According to another aspect of the present invention, air cleaners for internal combustion engines are taught that comprise a housing including a casing and a cap. The casing and the cap define an air inlet and an air outlet, respectively, and have respective peripheral portions for holding a filter element therebetween. A plurality of clamp devices are provided for applying clamping forces to the peripheral portions of the casing and the cap in order to clamp a peripheral seal portion of the filter element between the peripheral portions of the casing and the cap. The clamp devices are spaced from each other in a circumferential direction of the housing. Pressure releasing means are associated with the clamp devices for permitting the cap to move from a close position to an open position relative to the casing when the pressure within the housing exceeds a predetermined pressure. Guide means are provided for guiding the cap such that the cap can move between the close position and the open position along a predetermined path.

Therefore, an excessive pressure, backfire pressure introduced into the housing from the internal combustion engine, may be released to the outside of the housing by the movement of the cap from the close position from the open position. As a result, the casing and the cap may be prevented from being damaged or deformed, while a necessary clamping force can be ensured by a plurality of the clamp devices. In addition, because the cap is guided by the guide means, the cap can reliably return to the close position after the excessive pressure within the housing has been released to the outside.

Preferably, each of the clamp devices comprises a spring that produces the clamping force. The spring serves as the pressure releasing means and permit the cap to move from the close position to the open position against a biasing force of the spring when the pressure within the housing exceeds the predetermined pressure.

The air outlet may communicate with the internal combustion engine and the predetermined pressure is determined to be smaller than a pressure that may be produced by a backfire of the internal combustion engine and may be introduced into the housing.

Preferably, the spring comprises a compression coil spring that has a spring constant of N/mm, and the compression coil spring provides a clamping pressure of lkPa to lOO1kPa against the peripheral seal portion of the filter element that is clamped between peripheral portions of the cap and the casing.

Preferably, the guide means comprises a rod and a movable member that is movable along the rod. The rod may be disposed on one of the casing and the cap, and the movable member may be disposed on the other of the casing and the cap.

Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the claims and the accompanying drawings, in which: FIG. 1(A) is a side view, with a part broken away, of a first representative air cleaner for an internal combustion engine according to the present invention; FIG. 1(B) is an enlarged view as viewed in a direction of arrow IB in FIG. 1(A); FIG. 2(A) is an enlarged view as viewed in a direction of arrow IIA in FIG. 1(A); FIG. 2(B) is an enlarged view as viewed in a direction of arrow 1iB in FIG. 1(A); FIG. 3 is a side view, with a part broken away, of the first representative air cleaner and showing the operation when a backfire pressure has been applied; FIG. 4 is an enlarged view as viewed in a direction of arrow IV in FIG. 3; FIG. 5 is a graph showing a characteristic line of springs of clamp and guide devices of the first representative air cleaner; FIG. 6(A) is a side view, with a part broken away, of a second representative air cleaner for an internal combustion engine according to the present invention; FIG. 6(B) is an enlarged view as viewed in a direction of arrow VIB in FIG. 6(A); FIG. 6(C) is an enlarged view as viewed in a direction of arrow VIC in FIG. 6(A); FIG. 7(A) is a side view, with a part broken away, of the second representative air cleaner and showing the operation when a backfire pressure has been applied; FIG. 7(B) is an enlarged view as viewed in a direction of arrow VIIB in FIG. and FIGS. 8(A) and 8(B) are vertical sectional views of known air cleaners for internal combustion engines.

Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved air cleaners and methods of using such improved air cleaners. Representative embodiments of the present invention, which embodiments utilize many of these additional features and teachings both separately and in conjunction, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. On]) the claims define the scope of the claimed invention.

Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative embodiments of the invention. Moreover, various features of the representative embodiments and the dependent claims may be combined in ways that are not specifically enumerated in order to provide additional useful embodiments of the present invention.

[First Representative Embodiment] A first representative embodiment will now be described with reference to FIGS. 1(A) and 1(B) to FIG. 5. Referring to FIG. a representative air cleaner 1 is adapted to be used for an internal combustion engine (not shown) and includes a housing 10. The housing 10 has a casing 11 and a cap 13 that define an air inlet 12 and an air outlet 14, respectively.

The casing 11 constitutes a substantially lower half of the housing 10 and is configured like a container with an upper opening. As shown in FIGS. 1(B) and a filter support portion 1 lu having a predetermined width is formed on the casing 1I along the peripheral edge of an upper opening 11 h of the casing 11. The filter support portion 11 u is adapted to support a peripheral seal portion 32 of a filter element 30 as will be hereinafter described. A projection SIt is formed on the filter support portion 1 lu in a substantially central position of the filter support portion 11 u in the widthwise direction and extends along the peripheral edge of the upper opening 1lh.

The cap 13 constitutes a substantially upper half of the housing 10 and is configured like a container with a lower opening. A retainer recess 13d having a predetermined width is formed in the cap 13 along the peripheral edge of a lower opening 13h of the cap 13. The retainer recess 13 serves to retain the peripheral seal portion 32 of the filter element 30 from the upper side and to determine the position of the peripheral seal portion 32. The retainer recess 13 has an outer wall 13x that has an extension. The extension extends downward by a predetermined distance beyond the level of the lower opening 13h, so that the filter support portion 11 u of the casing 11 can be positioned adjacent to inside of the extension of the outer wall 13x. Preferably, the casing 11 and the cap 13 that constitute the housing 10 may be made of synthetic resin.

The filter element 30 is adapted to filtrate air, in particular intake air, and has a filter body 31 that is normally made of non-voven fabric. The peripheral seal portion 32 of the filter element 30 is made of soft non-woven fabric and is formed integrally with the filter body 31.

The peripheral seal portion 32 of the filter element 30 may be clamped between the filter support portion I lu of the casing 11 and the retainer recess 13d of the cap 13, so that the filter element 30 can be held to extend substantially horizontally within the housing 10 and can provide a seal between the casing 11 and the cap 13. Here, the filter support portion 1l u defines a peripheral portion of the casing 11 and the retainer recess 13d is defined by a peripheral portion of the cap 13.

A plurality of clamp and guide devices 40 are disposed on the housing 10 and are arranged to be spaced equally from each other in the circumferential direction of the housing In this first representative embodiment, four clamp and guide devices 40 are provided.

The clamp and guide devices 40 serve to apply a substantially uniform clamping force against the filter support portion 1 lu of the casing 11 and the retainer recess 13d of the cap 13.

In addition, the clamp and guide devices 40 serve to urge the cap 13 to return to the original position immediately after the cap 13 has moved away from the casing 11 when a force exceeding the clamping force was applied to the cap 13.

Referring to FIGS. 2(A) and each of the clamp and guide devices 40 has an elongated bolt 41, a nut 42 and a coil spring 47. The elongated bolt 41 has a shank 41j. A flange-like first spring support 41b is formed on the upper end of the shank 41j in order to support the upper end of the coil spring 47. A small-diameter portion 41s is formed on the lower end of the shank 41j. An external thread 41n is formed on the outer peripheral surface of the small-diameter portion 41s.

The nut 42 has a head 42h and a sleeve 42t that are disposed coaxially with each other.

An internal thread 42w is formed on the inner wall of the sleeve 42t and is adapted to engage the external thread 41n of the elongated bolt 41. Here, the outer diameter of the sleeve 42t of the nut 42 is determined to be equal to or substantially equal to the outer diameter of the shank 41j of the elongated bolt 41. Therefore, when the internal thread 42w and the external thread 41n have been engaged with each other by a maximum possible length in the axial direction, the outer peripheral surface of the shank 4 lj and the outer peripheral surface of the sleeve 42t of the nut 42 extend in continuity with each other.

Nut support portions 43 are foarned on the casing 11, so that the nut 42 of each of the clamp and guide devices 40 is supported within the corresponding nut support portion 43.

When the nut 42 is in the supported position, the sleeve 42t is oriented vertically upward. As shown in FIGS. 2(A) and each of the nut support portions 43 is formed on the outer side of the filter support portion 11 u of the casing 11 I. A through hole 43k (see FIG. and a recess 43e are formed in series in each of the nut support portions 43 and the recess 43e is positioned on the lower side of the through hole 43k, so that the sleeve 42t of the nut 42 can be inserted into the through hole 43k and the head 42h can be received within the recess 43e. The nut 42 may be received within the corresponding nut support portion 43, such that the upper end of the sleeve 42t extends upward beyond the upper end of the through hole 43k by a small distance. With the nut 42 positioned at this received position, the external thread 41n of the elongated bolt 41 may be screwed into the internal thread 42w of the nut 42, so that the elongated bolt 41 may be coupled to the casing 11 via the nut 42 and may be held to extend substantially perpendicular to the filter support portion 1 l u.

Bolt receiving portions 45 are formed on the cap 13. Each of the bolt receiving portions 45 has a hole 45k for receiving the shank 41j of the elongated bolt 41 of the corresponding clamp and guide device 40. Each of the bolt receiving portions 45 is formed on the cap 13 in a position on the outer side of the retainer recess 13d of the cap 13 and includes a second spring support 45r and a guide wall 45w in addition to the hole 45k. The second spring support 45r is defined around the upper open end of the hole 45k and is adapted to support the lower end of the coil spring 47. The guide wall 45w is configured to support the substantially lower half of the coil spring 47 from the outer peripheral side of the coil spring 47. Although not shown in the drawings, the lower portion of the hole 45k may be gradually slightly enlarged, so that the shank 41j of the elongated bolt 41 can be moved relative to the hole 45k in the axial direction even if the axis of the shank 41j of the elongated bolt 41 and the axis of the hole 45k have been inclined by a small angle relative to each other. In addition, the guide wall 45w may be formed by two thin walls that are partly joined to each other, so that the guide wall 45w may have a thin-wall construction while the necessary strength of the guide wall 45w is ensured.

The process for assembling the representative air cleaner 1 will now be described in brief. First, the peripheral seal portion 32 of the filter element 30 is set onto the filter support portion 1 lu of the casing 11. Then, the cap 13 is placed onto the casing 11 such that the outer wall 13x of the retainer recess 13d of the cap 13 is positioned to enclose the filter support portion 1 lu from the outer circumferential side thereof As a result, the position of the cap 13 relative to the casing 11 can be determined. In addition, the position of the peripheral seal portion 32 of the filter element 30 may be determined by the retainer recess 13d of the cap 13 and may be positioned between the filter support portion 1 lu and the retainer recess 13d.

In the next step, the coil spring 47 of each clamp and guide device 40 may be set into the corresponding bolt receiving portion 45 and the shank 41j of the elongated bolt 41 may be inserted into the coil spring 47 and the hole 45k of the bolt receiving portion 45. Then, the external thread 41n of the elongated bolt 41 is engaged with the internal thread 42w of the nut 42 that is held within the corresponding nut support portion 43 of the casing 11. As the external thread 41n is screwed into the internal thread 42w, the distance between the first spring support portion 41b of the elongated bolt 41 and the second support portion 45r of the corresponding bolt support portion 45 decreases, so that the coil spring 47 may be compressed in the axial direction.

Because the coil spring 47 is compressed in the axial direction, a biasing force may be produced to urge the filter support portion 1 lu of the casing 11 toward the cap 13 and to press the retainer recess 13d of the cap 13 against the casing 11 via the elongated bolt 41. In other words, the biasing force of the coil spring 47 may produce a clamping force for clamping the peripheral seal portion 32 of the filter element 30 between the retainer recess 13d and the filter support portion 1 lu of the casing 11. All the elongated bolts 41 of the clamp and guide devices may be screwed into the corresponding nuts 42 to their respective limit positions, so that the assembling operation of the air cleaner 1 may be completed.

Preferably, the number of the clamp and guide devices 40, the spring constant of the coil springs 47, and the amount of compression of the coil springs 47 in the state after completion of the assembling operation (hereinafter called "normal assembled state) are chosen such that the pressure applied to the peripheral seal portion 32 of the filter element 30 in the normal assembled state is lkPa to 100kPa. In addition, the coil springs 47 may preferably be designed such that the coil springs 37 can be compressed further by a distance of about from the normal assembled state and that the coil springs 47 have a spring constant of about 3 to 5 N/mm.

Referring to a graph shown in FIG. 5, an abscissa axis represents the amount of compression of the coil springs 47 (tie amount of compression from the normal assembled state) and an ordinate axis represents the amount of increase of biasing forces of the coil springs 47 from the normal assembled state. Here, the amount of increase of the biasing forces may be expressed by "(Amount of Compression) x (Spring Constant)." Because the cap 13 moves away from the casing 11 by a distance corresponding to the amount of compression of the coil springs 47 from the normal assembled state, the amount of compression of the coil springs 47 may be equal to the amount of movement of the cap 13.

Preferably, each of the cap 13 and the casing 11 may be designed to have a strength that is enough not to cause damages or deformation by the biasing forces of the coil springs 47 even if the coil springs 47 have compressed by the amount of about 30mm (maximum compression amount) from the normal assembled state.

The operation of the representative air cleaner 1 will now be described in connection with a backfire pressure that may be applied to the air cleaner 1 during the operation of the internal combustion engine.

The backfire is known as a phenomenon that may be caused when combustion of fuel within a combustion chamber of the engine has not been completed during the combustion cycle of the engine but has continued until an intake valve is open at the next cycle. Therefore, when the backfire has been caused, an excessive pressure may be introduced into the housing of the air cleaner 1 via the air outlet 14 that communicates with the combustion chamber via the intake valve. In general, the backfire pressure may be about 200kPa to about 400kPa that is considerably greater than the clamping pressure of about lkPa to 100kPa that may be applied to the peripheral seal portion 32 of the filter element 30. Therefore, when the backfire pressure has been introduced into the housing 10, a force may be produced to move the retainer recess 13d of the cap 13 and the filter support portion 1 lu of the casing I I away from each other and such a force may be greater than the clamping forces (biasing forces of the coil springs 47) of the clamp and guide devices Therefore, when the backfire pressure has been introduced within the housing 10, the retainer recess 13d of the cap 13 may move away from the filter support portion 1 lu of the casing 11 against the biasing force of the coil springs 47 (by a distance of 30mm at the maximum), so that the housing 10 may be open as shown in FIGS. 3 and 4. Because the elongated bolts 41 on the side of the casing I I extend through the corresponding holes 45k of the bolt receiving portions 45 of the cap 13, the cap 13 may move along the elongated bolts 41 from a clamping position, where the peripheral seal portion 32 of the filter element 30 is clamped between the cap 13 and the casing 11 as shown in FIG. 1(A) to a displaced position, where the housing 10 is opened as shown in FIG. 3. Therefore, the backfire pressure or an excessive pressure may be released to the outside of the housing 10. As a result, the casing 11 and the cap 13 may be prevented from being damaged or deformed.

In addition, after the backfire pressure has been released to the outside, the cap 13 may return from the displaced position to the clamping position or the original position along the elongated bolts 41 by the biasing forces of the coil springs 41. Thus, after the backfire pressure has been released to the outside, the air cleaner I recovers the normal assembled state by the functions of the coil springs 47, the elongated bolts 41 on the side of the casing 11 and the holes 45k of the bolt receiving portions 45 of the cap 13. Therefore, the operation of the internal combustion engine can be continuously performed even after the backfire has been produced.

Further, because the clamp and guide devices 40 are substantially equally spaced from each other in the circumferential direction of the housing 10, the backfire pressure can be

I

reliably released even if the backfire pressure has been applied locally to any particular region of the housing 10 in the circumferential direction.

Furthermore, because the pressure can be released from the air cleaner I when the backfire has been produced, influences of the backfire on an intake air system of the engine including the air cleaner 1 can be reduced or minimized. Therefore, the thickness of the cap 13 and the thickness of the casing 11 can be reduced. In addition, any damages on a throttle body and its associated parts can be reduced or minimized.

[Second Representative Embodiment] A second representative embodiment will now be described with reference to FIGS.

7(A) and The second representative embodiment is a modification of the first representative embodiment. Therefore, like members are given the same reference numerals as the first representative embodiment and the description of these members will not be necessary.

A second representative air cleaner 100 also is adapted to be used for an internal combustion engine (not shown) and includes the casing 11 and the cap 13 that are coupled to each other by a hinge device 120 and the clamp and guide devices Preferably, the hinge device 120 of the air cleaner 100 is disposed in a position substantially right below the air outlet 14 that is defined in the cap 13. Referring to FIG. 6(C), the hinge device 120 includes a short pin 122 and a bearing member 124 that rotatably supports the pin 122. The pin 122 is mounted on the cap 13 in a position on the outer side of the retainer recess 13. Preferably, the pin 122 extends substantially parallel to a part of the retainer recess 13 that opposes to the pin 122. The bearing member 124 is mounted or formed on the casing 11 in a position on the outer side of the filter support portion 1 lu. As a result, the cap 13 can pivot relative to the casing 11 about the pin 122 of the hinge devicel 120.

The hinge device 120 is configured such that a clamping force is applied to the peripheral seal portion 32 of the filter element 30 between the filter support portion I lu of the casing 11 and the retainer recess 13d of the cap 13 when the cap 13 is closed against the casing 11.

Two clamp and guide devices 40 are disposed on the side of free pivotal ends of the casing 11 and the cap 13. More specifically, the clamp and guide devices 40 are disposed on both sides of the casing 11 and the cap 13 in a widthwise direction (a direction perpendicular to the sheet of FIG. of the air cleaner 100. Preferably, one of the clamp and guide devices is disposed substantially right above the air inlet 12.

The construction of each of the clamp and guide devices 40 of the second representative embodiment is substantially the same as each of the clamp and guide devices 40 of the first representative embodiment. However, the clamp and guide devices 40 of the second representative embodiment are modified in the configuration of the nuts 42 in order that the elongated bolts 41 can be coupled to the casing 11 even in a state inclined relative to the casing 11. More specifically, each of the nuts 42h has a substantially spherical outer surface. In addition, the through hole 43k of each of the nut support portions 43 has an inner diameter that is slightly greater than the outer diameter of the sleeve 42t of the corresponding nut 42. With this arrangement, axes of the nuts 42 supported within the nut receiving portions 43 and axes of the elongated bolts 41 engaged with the nuts 42 can be inclined relative to the casing 11 by small angles, respectively.

Furthermore, the lower portion of the hole 45k of each of the bolt receiving portions of the cap 13 for receiving the correspending shank 4 lj of the corresponding elongated bolt 41 is gradually slightly enlarged in the downward direction, so that each of the bolt receiving portions 45 can be inclined relative to the axis of the corresponding elongated bolt 41 by an angle that corresponds to the enlargement of the hole Therefore, as the cap 13 pivots away from the casing 11 about the pin 122 of the hinge device 120, each of the elongated bolts 41 may incline relative to the casing 11 by a small angle as shown in FIG. In addition, the hole 45k of each of the bolt receiving portions 45 of the cap 13 also may incline relative to the corresponding elongated bolt 41 by a small angle. As a result, the bolt receiving portions 45 of the cap 13 can smoothly move along the corresponding elongated bolts 41 of the casing 11.

The operation of the second representative air cleaner 100 will now be described in connection with a backfire pressure that may be applied to the air cleaner 100 during the operation of the internal combustion engine.

When the backfire pressure has been produced, the backfire pressure may be introduced into the housing 10 via the air outlet 14. Therefore, the pressure within the housing becomes maximum at a region opposing to the air outlet 14. Thus, because the air outlet 14 is disposed on the upper side of the hinge device 120 and is oriented toward the clamp and guide

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devices 40 as shown in FIG. the pressure within the housing 10 becomes maximum at a region adjacent to the clamp and guide devices 40 when the backfire pressure has been introduced.

As a result, when the backfire has been produced during the operation of the internal combustion engine, the cap 13 may pivot upward relative to the casing 11 about the pin 122 of the hinge device 120 against the biasing force of the coil springs 47 of the clamp and guide devices 40 as shown in FIGS. 7(A) and Therefore, the maximum pressure region within the housing 10 may be opened to the outside and the backfire pressure or the excessive pressure may be released to the outside of the housing 10, so that the casing 11 and the cap 13 may be prevented from being damaged or deformed by the backfire pressure. As the cap 13 pivots relative to the casing 11, the elongated bolt 41 of each of the clamp and guide devices 40 may be inclined by a small angle and the hole 45k of the corresponding bolt receiving portion may also be inclined by a small angle. Therefore, the bolt receiving portions 45k formed on the cap 13 can be smoothly moved along the corresponding elongated bolts 41 coupled to the casing 11.

After the backfire pressure has been released to the outside, the cap 13 may pivot downward about the pin 122 of the hinge device 120 by the biasing force of the coil springs 47, so that the cap 13 returns from a position displaced from the casing I I to a clamping position or the original position, where the peripheral seal portion 32 is clamped between the casing 11 and the cap 13. In other words, the air cleaner 100 may return to the normal assembled state by the biasing forces of the coil springs 47 after the backfire pressure has been released to the outside.

Therefore, the operation of the internal combustion engine can be continuously performed even after the backfire has been produced.

Although in the above second representative embodiment, the elongated bolts 41 coupled to the casing 11 can be inclined in order that the bolt receiving portions 45 formed on the cap 13 can smoothly move along the corresponding elongated bolts 41, each of the bolts 41 may have a curved configuration that conforms to the pivotal path of the cap 13.

In addition, although the fist representative air cleaner I has four clamp and guide devices 40 and the second representative air cleaner 100 has two clamp and guide devices the number of the clamp and guide devices 40 can be suitably changed in response to the sizes of the air cleaner 1 and 100.

Further, although the elongated bolts 41 are coupled to the casing 11 and the bolt receiving portions 45 are formed on the cap 13 in the first and second representative embodiments, the elongated bolts 41 may be coupled to the cap 13 and the bolt receiving portions 45 may be formed on the casing I1.

Furthermore, although each of the clamp and guide devices 40 is configured as a combined assembly of a clamp device and a guide device, each of the clamp and guide device may be configured by a clamp device and a guide device that are separated from each other.

Claims (14)

1. An air cleaner for an internal combustion engine, comprising: a housing including a casing and a cap, the casing and the cap defining an air inlet and an air outlet, respectively; a filter element having a peripheral seal portion adapted to be clamped between a peripheral portion of the casing and a peripheral portion of the cap; a clamp device for applying a clamping force against the peripheral portions of the casing and the cap in order to clamp the peripheral seal portion of the filter element therebetween, wherein the clamping force of the clamp device is determined to be smaller than a separation force that may be applied to move the peripheral portions of the cap and the casing away from each other when a backfire pressure is introduced into the housing; and a guide device disposed between the casing and the cap for providing a guide for the cap when the cap moves from a positio., displaced from the casing by the separation force to an original position.

2. An air cleaner as in claim 1, wherein a plural sets of the guide device and the clamp devices are provided and are spaced substantially equally from each other in a circumferential direction of the housing.

3. An air cleaner as in claim 1, further including a hinge device for connecting between the casing and the cap, so that the casing and the cap have free pivotal ends, and wherein the guide device and the clamp device are disposed on the side of the free pivotal ends of the casing and the cap.

4. An air cleaner as in any one of the preceding claims, wherein: the guide device includes a rod and a movable member, the rod extends in a direction of relative movement of the casing and the cap and the movable member is movable relative to the rod in an axial direction of the rod; and the clamp device includes a first spring support formed on one end of the rod, a second spring support formed on the movable member, and a spring fitted around the rod and producing a biasing force to move the first and second receiving portions away from each other in order to provide the clamping force.

An air cleaner as in claim 4, wherein the rod is coupled to the casing or the cap such that the rod can incline relative to the casing or the cap within a predetermined angle.

6. An air cleaner as in claim 4 or 5, wherein the spring has a spring constant of 3-5 N/mm, and the spring provides a clamping pressure of lkPa to 100kPa against the peripheral seal portion of the filter element that is clamped between the peripheral portions of the cap and the casing.

7. An air cleaner as in claim 3, wherein the hinge device is located at a first region which receives minimum influence of the ba:kfire pressure and the guide and the clamp device is disposed at a second region which receives maximum influence of the backfire pressure.

8. An air cleaner as in claim 4, wherein the rod is disposed on the side of the casing, and the movable member is disposed on the side of the cap and has a hole through which the rod extends.

9. An air cleaner as in claim 4, wherein the rod has a curved configuration that conforms to the pivotal path of the cap permitted by the hinge device.

10. An air cleaner for an internal combustion engine, comprising: a housing including a casing and a cap, wherein the casing and the cap defining an air inlet and an air outlet, respectively, and have respective peripheral portions for holding a filter element therebetween; a plurality of clamp devices for applying clamping forces to the peripheral portions of the casing and the cap in order to clamp a peripheral seal portion of the filter element between the peripheral portions of the casing and the cap, wherein the clamp devices are spaced from each other in a circumferential direction of the housing; pressure releasing means associated with the clamp devices for permitting the cap to move from a close position to an open position relative to the casing when the pressure within the housing exceeds a predetermined pressure; and guide means for guiding the cap such that the cap can move between the close position and the open position along a predetermined path.

11. An air cleaner as in claim 10, wherein each of the clamp devices comprises a spring that produces the clamping force, and the spring serves as the pressure releasing means in order to permit the cap to move from the close position to the open position against a biasing force of the spring when the pressure within the housing exceeds the predetermined pressure

12. An air cleaner as in claim 10 or 11, wherein the air outlet communicates with the internal combustion engine and the predetermined pressure is determined to be smaller than a pressure that may be produced by backfire of the internal combustion engine and may be introduced into the housing.

13. An air cleaner as in claim 12, wherein the spring comprises a compression coil spring that has a spring constant of 3-5 N/mm, and the compression coil spring provides a clamping pressure of lkPa to 100kPa against the peripheral seal portion of the filter element that is clamped between peripheral portions of the cap and the casing.

14. An air cleaner as in any one of claims 10 to 13, wherein the guide means comprises a rod and a movable member that is movable along the rod, wherein the rod is disposed on one of the casing and the cap, and the movable member is disposed on the other of the casing and the cap. An air cleaner for an internal combustion engine substantially as herein described with reference to the accompanying drawings.