Title of Invention	A DIAPHRAGM ACTUATOR AND A SECONDARY AIR CONTROL SYSTEM
Abstract	In a diaphragm actuator in which one end of a rod is connected to the central part of a diaphragm, opposite sides of the diaphragm facing first and second pressure chambers since the end of the rod is directly connected to the diaphragm the number of parts required for connecting the rod to the diaphragm can be reduced.

Full Text

DIAPHRAGM ACTUATOR AND SECONDARY AIR CONTROL SYSTEM BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to an improvement of a diaphragm actuator in which one end of a rod is connected to the central part of the diaphragm opposite sides of the diaphragm facing first and second pressure chambers, and an improvement of a secondary air control system provided in a secondary air supply passage through which outside air can be introduced into an engine exhaust passage. DESCRIPTION OF THE PRIOR ART Such a diaphragm actuator and secondary air control system are known in the art in, for example, Japanese Patent Application Laid-open No. 53-148619, etc. Since the above-mentioned conventional diaphragm actuator has a structure in which a pair of retainers disposed on either side of the central part of the diaphragm are connected to each other and one end of a rod is connected to one of the retainers, the number of parts required for joining the end of the rod to the central part of the diaphragm becomes comparatively large. The secondary air control system disclosed in the above-mentioned Japanese Patent Application Laid-open No. 53-148619 comprises the diaphragm actuator, a switch valve connected to the diaphragm actuator and a reed valve provided halfway of the secondary air supply passage through which outside air can be introduced into an engine exhaust passage, allowing the air to flow only towards the exhaust passage. The number of parts required for joining the rod to the diaphragm in the diaphragm actuator becomes comparatively large and the number of assembly steps for the secondary air control system thus increases. SUMMARY OF THE INVENTION The present invention has been carried out in view of the above-mentioned circumstances, and it is a first objective of the present invention to provide a diaphragm actuator which requires a smaller number of parts for connecting a rod to a diaphragm and it is a second objective of the present invention to provide a secondary air control system which can reduce the number of parts and the number of assembly steps. In order to achieve the first objective, the present invention provides a diaphragm actuator in which one end of a rod is joined to the central part of a diaphragm, opposite sides of the diaphragm facing first and second pressure chambers, the end of the rod is directly joined to the diaphragm. In accordance with the arrangement of the first characteristic, it is unnecessary to employ parts other than the rod and the diaphragm for connecting the rod to the diaphragm, and it is thus possible to reduce the number of parts of the diaphragm actuator. Furthermore, in addition to the first characteristic, as a second characteristic, the end of the rod made of a metal is mould-bonded to the central part of the diaphragm which is moulded from a synthetic rubber, a natural rubber or an elastomer. In accordance with the arrangement, since the rod is connected to the diaphragm at the same time as the diaphragm is moulded, the number of assembly steps for the diaphragm actuator can be reduced, it is also possible to prevent air leakage between the first pressure chamber and the second pressure chamber in the area where the rod and the diaphragm are joined to each other, and it is thus possible to eliminate one of the main causes of air leakage. Furthermore, in addition to the second characteristic, as a third characteristic, a longitudinal section of the end of the rod is approximately T-shaped. In accordance with the arrangement, the area where the end of the rod and the diaphragm are bonded can be made comparatively large, it is possible to prevent the central part of the diaphragm from being locally flexed when a tensile load is applied to the diaphragm from the rod, and it is also possible to increase the strength of the mould-bonding between the end of the rod and the diaphragm. In addition to the third characteristic, as a fourth characteristic, a plurality of through holes are provided on the end of the rod. In accordance with the arrangement, the strength of the mould-bonding between the end of the rod and the diaphragm can be further enhanced by feeding a synthetic rubber, a natural rubber or an elastomer into each of the through holes when moulding the diaphragm. Furthermore, in addition to any one of the above-mentioned first to fourth characteristics, as a fifth characteristic, a cushion is integrally formed on the central part of the diaphragm, the periphery of the diaphragm being clamped by a casing, which cushion comes into contact with the casing when the diaphragm flexes in response to a difference in pressure between the first and second pressure chambers. In accordance with the arrangement, the number of parts can be reduced and the number of assembly steps can also be reduced because a bonding operation for the cushion member is not required in comparison with the case in which a cushion member is bonded to the diaphragm subsequent to its formation. In order to achieve the above-mentioned second objective, the present invention provides, as a sixth characteristic, a secondary air control system comprising a diaphragm actuator which is formed by connecting one end of a rod to a central part of a diaphragm, one side of the diaphragm facing a vacuum chamber leading to an intake passage of an engine, the diaphragm flexing in a direction to reduce the volume of the vacuum chamber in response to a sharp increase in the vacuum in the intake passage, and a switch valve which has a valve body fixed to the other end of the rod so that the switch valve can block a secondary air supply passage that can introduce outside air into an exhaust passage of the engine and functions so as to close the valve according to the movement of the diaphragm actuator in response to a sharp increase in the vacuum in the intake passage; wherein a periphery of the diaphragm is clamped between a body and a first cover which is joined to the body, the body having an air flow passage and a valve seat, a downstream end of the air flow passage being connected to a downstream side passage section of the secondary air supply passage leading to the exhaust passage, and a valve hole leading to the upstream end of the air flow passage opening onto the central part of the valve seat, a second cover joined to the body and forming, together with the body, a valve chamber connected to an upstream side passage section of the secondary air supply passage leading to the outside air, the valve seat facing the valve chamber, the rod is supported in the body in an axially movable manner and extends coaxially through the valve hole so as to project inside the valve chamber, one end of the rod being directly joined to the central part of the diaphragm and the other end thereof being fixed to the valve body, and a return spring exhibiting its spring force in the direction that moves the valve body away from the valve seat is provided between the body and the valve body. In accordance with the arrangement, since the body functions both as a part of the casing of the diaphragm actuator and as a part of the valve housing of the switch valve and the end of the rod is directly joined to the central part of the diaphragm, the secondary air control system can be formed from a smaller number of parts and the number of assembly steps can be reduced. Furthermore, in addition to the sixth characteristic, as a seventh characteristic, a valve support plate for supporting a reed valve is provided between the downstream end of the air flow passage and the downstream side passage section of the secondary air supply passage in such a manner that the reed valve allows the air to flow only towards the exhaust passage is clamped between the body and a third cover joined to the body. In accordance with the arrangement, the entire secondary air control system can be made compact, and it is thus possible to minimize the space required for the secondary air control system. Accordingly, the present invention provides a diaphragm actuator comprising a rod and a diaphragm, in which one end of said rod is joined to a central part of said diaphragm, opposite sides of said diaphragm facing first and second pressure chambers, characterised in that said end of said rod is directly joined to said diaphragm. The above-mentioned objectives, other objectives, characteristics and advantages of the present invention will become apparent from an explanation of a preferable embodiment which will be described in detail below by reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 to Fig. 3 illustrate one embodiment of the present invention. Fig. 1 is a diagram showing the manner in which an engine and a secondary air control system are connected to each other. Fig. 2 is a longitudinal section of the secondary air control system. Fig. 3 is an oblique view of a rod. DESCRIPTION OF THE PREFFERED EMBODIMENT One embodiment of the present invention is explained below by reference to Fig. 1 to Fig. 3. In Fig. 1 an intake port 1 of an engine E mounted in a vehicle is connected to an intake pipe 3 which, together with the intake port 1 forms an intake passage 2, a fuel-injection valve 4 for injecting fuel into the intake port 1 is attached to the engine E, and a throttle valve 5 for controlling the amount of air taken into the intake passage 2 is provided in the intake pipe 3. An exhaust port 6 of the engine E is connected to an exhaust pipe 8 which, together with the exhaust port 6, forms an exhaust passage 7. In order to supply the outside air that is cleaned by an air cleaner 9 to the exhaust passage 7 as secondary air in response to exhaust pulsations in the exhaust passage 7, the air cleaner 9 and the exhaust port 6 of the exhaust passage 7 are connected to each other via a secondary air supply passage 10. When the engine is in a normal operational state, the oxidation of unburned components in the exhaust gas is thus accelerated by the secondary air. When the vacuum in the intake passage 2 is sharply increased by sudden closure of the throttle valve 5, the fuel concentration of the gas mixture supplied to the engine E increases, the amounts of unburned components discharged into the exhaust passage 7 Increase abnormally, and there is a possibility that the unburned components might be burned explosively by secondary air supplied from the secondary air supply passage 10 thereby causing the so-called afterburn phenomenon. Therefore, when the vacuum in the intake passage 2 increases sharply it is necessary to stop the supply of secondary air from the secondary air supply passage 10. The secondary air supply passage 10 is therefore provided with a secondary air control system 11 which can supply secondary air in response to exhaust pulsations and also stop the supply of secondary air when the vacuum in the intake passage 2 sharply increases. In Fig. 2 the secondary air control system 11 comprises a diaphragm actuator 12, a switch valve 13 which is operated so as to close by means of the diaphragm actuator 12 and a reed valve 14 which allows air to flow only towards the exhaust passage 7. The diaphragm actuator 12 comprises a casing 15, a diaphragm 16 whose periphery is clamped by the casing 15 and a rod 17 made of metal, one end of which is joined to the central part of the diaphragm 16, and the diaphragm 16 is moulded from a synthetic rubber, a natural rubber or an elastomer. The casing 15 comprises a body 18 made of a synthetic resin and a first cover 19 made of metal, which is tightened to the body 18 so as to hermetically clamp the periphery of the diaphragm 16 between the body 18 and the first cover 19. A first pressure chamber 20 is formed between the first cover 19 and the diaphragm 16 as a vacuum chamber on one side of the diaphragm 16, and a second pressure chamber 21 is formed between the body 18 and the diaphragm 16. A connector tube 23 having a constriction 22 at its tip end is formed integrally with the central part of the first cover 19, one end of a vacuum inlet passage 24 leading into the first pressure chamber 20 via the constriction 22 is connected to the connector tube 23, and the other end of the vacuum inlet passage 24 is connected as shown in Fig. 1 to the intake pipe 3 so that it joins the intake passage 2 on the downstream side of the throttle valve 5. The vacuum inside the intake passage 2 thus acts on the first pressure chamber 20. The rod 17 is supported by the body 18 in an axially movable manner, and one end 17a of the rod 17 is directly joined to the central part of the diaphragm 16 on the side of the second pressure chamber 21. Referring to Fig. 3 in addition to Fig. 2, the end 17a of the rod 17 is formed so that its longitudinal section is approximately T-shaped by, for example, integrally bonding a disc thereto, and the end 17a of the rod 17 is mould-bonded to the central part of the diaphragm 16 which is moulded from a synthetic rubber, a natural rubber or an elastomer. A plurality of through holes 25, 25 — is provided on the disc at the end 17a of the rod 17. Furthermore, a cushion 26 is formed integrally with the central part of the diaphragm 16 in the form of a circle coaxially surrounding the rod 17 so as to project towards the body 18, and comes into contact with the body 18 when the diaphragm 16 flexes towards the body 18 in response to a difference in pressure between the first and second pressure chambers 20 and 21. In such a diaphragm actuator 12, when the vacuum in the intake passage 2 increases sharply, the diaphragm 16 flexes in the direction that the diaphragm 16 decrease the volume of the first pressure chamber 20, whereby the rod 17 moves upwards in Fig. 2. The switch valve 13 comprises a valve housing 27, a valve body 28 which is fixed to the other end of the rod 17 and a return spring 29 provided between the valve housing 27 and the valve body 28. The valve housing 27 comprises the body 18 and a second cover 30 made of metal which is hermetically tightened to the body 18. An air flow passage 31, a connection hole 32 for connecting the air flow passage 31 to the second pressure chamber 21, a valve hole 33 which is positioned coaxially with the rod 17 and leads to an upstream end of the air flow passage 31, a valve seat 34 which makes the valve hole 33 open into the central part thereof on the side opposite to the air flow passage 31, and a cylindrical support 35, a part thereof being coaxially inserted into the valve hole 33, are provided on the body 18. The rod 17 which runs coaxially through the valve hole 33 fits inside the cylindrical support 35 in an axially slidable manner. Between the body 18 and the second cover 30, a valve chamber 36 is formed so as to lead to the upstream side passage section 10a of the secondary air supply passage 10 which is connected to the air cleaner 9, valve seat 34 is formed on the body 18 so as to face the valve chamber 36, and the valve body 28 which is housed inside the valve chamber 36 so as to be capable of seating on the valve seat 34 is fixed to the other end of the rod 17. The return spring 29 is in the form of a coil surrounding the cylindrical support 35 and is provided between the body 18 and the valve body 28 in such a manner that its spring force is exhibited in the direction that moves the valve body 28 away from the valve seat 34, that is to say, in the direction that flexes the diaphragm 16 of the diaphragm actuator 12 towards the second pressure chamber 21. The reed valve 14 is supported on a valve support plate 37, made in the form of a disc having a valve hole 40 in its centre, in such a manner that the valve hole 40 can be opened and closed, and the valve support plate 37 is hermetically clamped between the body 18 and a third cover 38 made of metal which is tightened to the body 18 so that the valve hole 40 leads to the downstream end of the air flow passage 31. A valve chamber 39 which contains the reed valve 14 is formed between the third cover 38 and the valve support plate 37, and leads to the downstream side passage section 10b of the secondary air supply passage 10 which is on the side of the exhaust passage 7. That is to say, the reed valve 14 is attached to the body 18 so that it is provided between the downstream side passage section 10b of the secondary air supply passage 10 leading to the exhaust passage 7 and the downstream end of the air flow passage 31 contained in the body 18. Next, the action of the embodiment is explained. With regard to the diaphragm actuator 12, since the end 17a of the rod 17 is directly joined to the diaphragm 16, It is unnecessary to employ parts other than the rod 17 and the diaphragm 16 for connecting the rod 17 to the diaphragm 16, and it is thus possible to reduce the number of parts of the diaphragm actuator 12. Furthermore, since the end 17a of the rod 17 made of metal Is mould-bonded to the central part of the diaphragm 16 that is moulded from a synthetic rubber, a natural rubber or an elastomer, the rod 17 Is connected to the diaphragm 16 at the same time as the diaphragm Is moulded. Therefore, the number of assembly steps for the diaphragm actuator 12 can be reduced, it is also possible to prevent air leakage between the first pressure chamber 20 and the second pressure chamber 21 in the area where the rod 17 and the diaphragm 16 are connected to each other, and it is thus possible to eliminate one of the main causes of air leakage. Moreover, since the longitudinal section of the end 17a of the rod 17 is approximately T-shaped, the area in which the end 17a of the rod 17 and the diaphragm 16 are bonded can be made comparatively large, it is possible to prevent the central part of the diaphragm 16 from being locally flexed when a tensile load is applied to the diaphragm 16 from the rod 17, and it is also possible to Increase the strength of the mould-bonding between the end 17a of the rod 17 and the diaphragm 16. Furthermore, since a plurality of through holes 25, 25 ••• are provided on the end 17a of the rod 17, the mould-bonding strength of the end 17a of the rod 17 to the diaphragm 16 can be further enhanced by feeding In a synthetic rubber, a natural rubber or an elastomer into each of the through holes 25, 25 — when moulding the diaphragm 16. Moreover, since the cushion 26 which comes in contact with the casing 15 when the diaphragm 16 flexes in response to a difference In pressure between the first and second pressure chambers 20 and 21 Is formed integrally with the central part of the diaphragm 16, the number of parts can be reduced and the number of assembly steps can also be reduced because a bonding operation for the cushion member is not required in comparison with the case where a cushion member is bonded to the diaphragm 16 after it is moulded. In addition, with regard to the secondary air control system 11 comprising the diaphragm actuator 12, switch valve 13 and reed valve 14, since the body 18 functions both as part of the casing 15 of the diaphragm actuator 12 and as part of the valve housing 27 of the switch valve 13, and the reed valve 14 is supported by the body 18, in addition to the arrangement whereby the end 17a of the rod 17 is directly joined to the central part of the diaphragm 16, the secondary air control system 11 can be formed from a smaller number of parts, the number of assembly steps can be reduced, the entire secondary air control system 11 can be made compact, and it is thus possible to minimize the space required for the secondary air control system 11. An embodiment of the present invention is explained in detail above, but the present invention is not limited by the above-mentioned embodiment and can be modified in a variety of ways without departing from the present invention described in the claims. WE CLAIMS 1. A diaphragm actuator comprising a rod (17) and a diaphragm (16), in which one end (17a) of said rod (17) is joined to a central part of said diaphragm (16), opposite sides of said diaphragm facing first and second pressure chambers (20, 21) characterised in that said end (17a) of said rod (17) is directly joined to said diaphragm (16). 2. A diaphragm actuator according to Claim 1, wherein said end (17a) of said rod (17) made of a metal is mould-bonded to the central part of said diaphragm (16) which is molded from a synthetic rubber, a natural rubber or an elastomeric. 3. A diaphragm actuator according to Claim 2, wherein a longitudinal section of said end (17a) of said rod (17) is approximately T-shaped. 4. A diaphragm actuator according to Claim 3, wherein a plurality of through holes (25) are provided on said end (17a) of said rod (17). 5. A diaphragm actuator according to any one of Claims 1 to 4, wherein a cushion (26) is integrally formed on the central part of said diaphragm (16), the periphery of said diaphragm being clamped by a casing (15), which cushion comes in contact with said casing (15) when said diaphragm (16) flexes in response to a difference in pressure between said first and second pressure chambers (20, 21). 6. A secondary air control system comprising: a diaphragm actuator (12) according to claim 1, wherein one of the first and second pressure chambers is a vacuum chamber (20) leading to an intake passage (2) of an engine (E), said diaphragm (16) flexing in a direction to reduce the volume of said vacuum chamber (20) in response to a sharp increase in the vacuum in said intake passage (2), and; a switch valve (13) which has a valve body (28) fixed to the other end of said rod (17) so that said switch valve can block a secondary air supply passage (10) that can introduce outside air into an exhaust passage (7) of said engine (E) and functions so as to close according to the movement of said diaphragm actuator (12) in response to a sharp increase in the vacuum in said intake passage (2); characterised in that a periphery of said diaphragm (16) is clamped between a body (18) and a first cover (19) which is joined to said body (18), said body (18) having an air flow passage (31) and a valve seat (34), a downstream end of said air flow passage (31) being connected to a downstream side passage section (10b) of said secondary air supply passage (10) leading to said exhaust passage (7), and a valve hole (33) leading to the upstream end of said air flow passage (31) opening onto the central part of said valve seat (34), a second cover (30) joined to said body (18) and forming, together with said body (18), a valve chamber (36) connected to an upstream side passage section (10a) of said secondary air supply passage (10) leading to the outside air, said valve seat (34) facing said valve chamber (36), said rod (17) is supported in said body (18) in an axially movable manner and extends coaxially through said valve hole (33) so as to project inside said valve chamber (36), one end (17a) of said rod (17) being directly joined to the central part of said diaphragm (16) and the other end thereof being fixed to said valve body (28), and a return spring (29) exhibiting its spring force in the direction that moves said valve body (28) away from said valve seat (34) is provided between said body (18) and said valve body (28). 7. A secondary air control system according to Claim 6, wherein a valve support plate (37) for supporting a reed valve (14) interposed between the downstream end of said air flow passage (31) and the downstream side passage section (10b) of said secondary air supply passage (10) in such a manner that said reed valve allows the air to flow only towards said exhaust passage (7) is clamped between said body (18) and a third cover (38) joined to said body (18). 8. A dipping actuator, substantially as hereinabove described and illustrated with reference to the accompanying drawings. 9. A secondary air control system, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

0090-mas-2001 abstract-duplicate.pdf

0090-mas-2001 abstract.pdf

0090-mas-2001 claims-duplicate.pdf

0090-mas-2001 claims.pdf

0090-mas-2001 correspondence-others.pdf

0090-mas-2001 correspondence-po.pdf

0090-mas-2001 description (complete)-duplicate.pdf

0090-mas-2001 description (complete).pdf

0090-mas-2001 drawings-duplicate.pdf

0090-mas-2001 drawings.pdf

0090-mas-2001 form-1.pdf

0090-mas-2001 form-19.pdf

0090-mas-2001 form-26.pdf

0090-mas-2001 form-3.pdf

0090-mas-2001 form-5.pdf

0090-mas-2001 others.pdf

0090-mas-2001 petition.pdf