GB2239899A

GB2239899A - I.C. engine inlet manifold

Info

Publication number: GB2239899A
Application number: GB9000563A
Authority: GB
Inventors: Thomas Graham Parr
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1990-01-10
Filing date: 1990-01-10
Publication date: 1991-07-17
Also published as: GB9000563D0

Abstract

The inlet manifold 23 comprises a casing 25 defining a chamber 21 having an air inlet (36, Fig. 3) and air outlets 18. A plurality of spiral shaped members 45 are rotatably mounted in the chamber and define respective passageways 46 for receiving air from the chamber. The members 45 are rotatable in unison between a first position in which air from the chamber 21 flows to the outlets 18 through the passageways 46 to provide long intake ducts, and a second position in which air in the chamber 21 flows directly to the outlets to provide relatively short intake ducts. The members 45 are mounted on a shaft 42 rotated by a vacuum actuator (37, Fig. 3) located between pairs of members on the shaft. A throttle valve (33, Fig. 3) is located in the air inlet (36) which is integral with the plastics casing 25. <IMAGE>

Description

AN INLET MANIFOLD FOR AN INTERNAL COMBUSTION ENGINE The invention relates to an inlet manifold for an internal combustion engine.

The volumetric efficiency of an internal combustion engine can be improved by providing a long intake duct for the engine at low engine speeds and a relatively shorter intake duct at higher engine speeds.

Over the years, various manifolds have been designed to in an attempt to provide intake ducts of different lengths. Two examples of such manifolds are set out below: US-A-2,835,235 describes a manifold which includes a rotatable pipe. The pipe receives air from an inlet at one end and includes passages through which the air is directed into channels in a housing of the manifold leading to outlets. By rotating the pipe, the passages are moved towards or away from outlets. However, the constraints of the construction mean that the lengths of the channels are determined solely by the extent to which the pipe can be rotated which is somewhat less than 1800. Moreover the pipe includes partitions which are sealed against the housing by a number of seals.

Rotation of the pipe subjects the seals to a considerable amount of rubbing and there is risk of leakage once the seals begin to wear. Any leakage will seriously upset performance of the engine and, therefore, the arrangement is somewhat undesirable.

Also, radial distances of the seals from the axis of rotation of the pipe is such that a substantial torque will be required to rotate the partition within the housing.

In US-A-4,619,226 a tubular surge-tank is supported for rotation within a manifold casing. The surge tank is elongate and air travels from one end to a number of outlet ports in its periphery. Rotation of the surge tank merely varies the positions of the outlet ports relative to respective intake passages in the manifold casing. However, whatever effect the repositioning of the outlets will have, the effect will be limited again by the amount that the surge tank can be rotated.

An object of the present invention is to provide an inlet manifold which reduces the foregoing problems described with respect to US-A-2,835, 235 and US-A4,619,226.

According to the invention there is provided an inlet manifold for an internal combustion engine comprising a casing defining a chamber having an air inlet and an air outlet, a member in the chamber defining a passageway for receiving air from the chamber, the member being movable between a first position in which air from the chamber flows to the outlet through the passageway to provide a long intake duct and a second position in which air in the chamber flows directly to the outlet.

With such an arrangement, the length of the intake duct is not dictated by restriction on movement of the member but can be selected by choosing a passageway of appropriate length. Also, the use of such a passageway provides an intake duct of a positive length rather than an intake duct of a somewhat uncertain effective length when using the arrangement shown in US-A4,619,226. Moreover, by arranging the member within the chamber it is unnecessary to provide rubbing seals as required between the housing and partitions as described in US-A-2,835,235.

The air outlet itself is preferably in the form of a duct and the passageway in the member may be of greater length than the duct. In that way, the duct itself can form an intake duct of relatively short length when the member occupies its second position and the movement of the member into the first position effectively provides a positive lengthening of the intake duct.

Preferably, the passageway has an air exit which aligns with the air outlet of the chamber in the first position so that the air outlet forms substantially a continuation of the passageway. In that way, a smooth flow path is provided for air travelling along the passageway and into the air outlet in the casing.

Preferably, the air exit and the air outlet are of generally circular cross section and of similar diameter.

In order to provide close contact between the exit of the passageway and the air outlet of the casing, the air exit and air outlet may be bounded by peripheral rims which interengage when the member occupies its first position. Alternatively, either one or other of the air outlet and exit end of the passageway may be bounded by such a rim but, in the preferred embodiment respective rims are provided.

The passageway may be curved and in order to provide a passageway of optimum length in a chamber of compact dimensions, the passageway is preferably of spirallike form.

The member may be rotatable between said first and second positions and, in such a case, the spiral-like passageway may extend circumferentially around an axis of rotation of the member. The passageway may extend for at least 1800 around the axis of rotation to provide an intake duct of desired length when the member occupies its first position. Preferably, however, the spiral-like passageway extends for more than 3600 around the axis of the rotation such that entry and exit ends of the passageway lie circumferentially beyond each other. In that way a very long intake duct can be obtained whilst retaining compact overall dimensions.

Preferably, the spiral passageway has an inner end, preferably in the form of an entry flare, defining the entry for receiving air from the casing.

With US-A-4,619,226 the rotary surge tank projects through a side cover of the casing to enable rotational movement to be transmitted thereto by means of a drive gear. However, such an arrangement requires the use of a rotary seal in the side cover with the attendant problem of air leakage should the seal wear. Any such leakage will seriously upset the performance of the internal combustion engine.

Our manifold is able to overcome that particular problem by providing means in the chamber itself for applying movement to the member rather than having to extend part of the member through a casing wall as in US-A-4,619,226. The means provided in the chamber may comprise an operating element which extends through the chamber to be driven by an actuator, such as a vacuum servo, mounted on the casing. In that way, a rotary seal is completely unnecessary and the manifold in accordance with the present invention is particularly advantageous in that respect.

Conveniently, the aforesaid operating element may be in the form of a rod which can comprise or be connected to a diaphragm operated rod of the vacuum servo.

Conveniently, the operating element may be connected to a crank drivably connected to the member.

Where the member is rotatable, the member is preferably supported for rotation by support means projecting inwardly from a wall of the casing. A shaft may be mounted on the support means and the member defining the passageway mounted on the shaft. Preferably, the shaft extends between support means on opposite walls of the casing.

In a multi-cylinder engine, the manifold chamber may contain a plurality of individual members each of which defines its own passageway and each member being associated with a cylinder of the engine. The members may conveniently be arranged side by side with each passageway receiving air from the chamber. Each of the members may be movable between said first and second positions. The casing will preferably have a plurality of air outlets for the cylinders and the members in said first positions will enable air to flow to the outlets through the respective passageways.

The above means for applying movement to the members may be arranged between two of the members and if an even number of members is provided, there may be an equal number of members each side of the member moving means.

Where the aforesaid shaft is provided all of the members may be mounted on the shaft.

Preferably, the members are substantially identical to each other and the outlets for the chamber may also be substantially identical.

Instead of providing a plurality of individual members, a single member may define a plurality of passages arranged side by side, each of which passageways receives air from the chamber and which, in the first position on the member, enable air to flow to respective air outlets in the casing.

Where the or each member is rotatable, the casing may have a generally cylindrical wall portion which is curved about an axis of rotation of the or each member.

Where the or each outlet is in the form of a duct, the duct may extend substantially tangentially from the generally cylindrical wall portion of the casing.

The air inlet for the chamber may be controlled by means of a throttle valve. The throttle valve may be mounted within a duct in the casing defining the inlet.

Conveniently, the inlet duct can be formed integrally with the casing.

Where a plurality of members or passageways is provided, the air inlet may be arranged between two said members or passageways. Where an even number of members or passageways is provided, the air inlet may be arranged with an equal number of members or passageways each side thereof.

An inlet manifold in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which: Fig.1 is a plan view of a manifold in accordance with the invention shown partly in cross section generally on line I - I in Fig.2, Fig.2 is a cross section through the manifold shown in Fig.1 generally on the line II - II in Fig.1 and Fig.3 is a cross section through the manifold shown in Fig.1 on the line III - III in Fig.1.

An internal combustion engine 10 has a cylinder head 11. The cylinder head 11 is formed with a plurality of induction passages 12 and carries a manifold adaptor 13 having four intake branches 14, 15, 16 and 17. The branches 14 - 17 are connected to associated outlet ducts 18 of an inlet manifold 23 by means of clamps 24.

The clamping arrangement is similar to that described in our co-pending GB Application No. g969-7 The manifold adaptor 13 carries four fuel injectors 19 two only of which are shown in Fig.1.

The manifold 23 comprises a casing 25 having end walls 26 with spaced apart generally cylindrical convoluted side walls 27 and an intermediate wall section 27a extending therebetween. The casing defines a chamber 21 and is connected to the cylinder head 11 by a tie bar 20. The outlet ducts 18 are formed partly as continuations of the side walls 27 and extend into the casing. Each outlet duct 18 terminates at a flare 28.

The outlet ducts 18 constitute the aforesaid air outlets of the casing.

The intermediate wall 27a is formed to define a throttle body 29 having diametrically opposed openings 30 in which a spindle 32 is rotatably mounted. The spindle 32 carries a throttle valve 33 arranged between two idling by-pass openings 34. The shaft 32 is biased into the position shown by means of a torsion spring 35 and can be rotated by a normal accelerator pedal of the vehicle in which the engine is to be mounted. The amount of rotation is detected by a potentiometer 31.

The throttle body 29 defines an air inlet 36 for the casing 25.

The intermediate portion 27a is formed with a mounting section 27b for a vacuum operated actuator or servo 37 (shown in broken lines in Fig.1). The actuator 37 is sealingly located within an opening 38 in the mounting section 27b and has an operating rod 39 extending through the chamber 21. The operating rod 39 is moved linearly by a diaphragm (not shown) of the actuator 37 and is pivotally connected at its free end to a crank arm 40 rotatably fast with a shaft 42. The shaft 42 extends generally co-axially of the casing 25 and is pivotally mounted in bosses 43 which are formed on the inner surfaces of the end walls 26. The bosses define blind bores 44 in which the shaft 42 is mounted.

The shaft 42 carries four spiral-shaped members 45 arranged in two sets 45a, 45b. Each member 45 defines a spiral-shaped passageway 46 having a flared entry 47 at a radially inner end and an exit 48 at a radially outer end. The outlet 48 is bounded by a flange 49 of substantially complementary shape to flare 28 of the outlet duct 18. Each member 45 is mounted on the shaft 42 by means of a web 50 extending from a hub 51 so that a substantial part of the member is coaxial with the casing 25. The web is stiffened by spoke-like projections 50a thereon. The hubs 51 of the members 45 are secured to the shaft 42 by means of respective diametral pins 52.

As shown in Fig.2, the passageway 46 extends for more than 3600 around the axis of shaft 42 so that the entry and exit ends 47, 49 of the passageway lie circumferentially beyond each other. If desired, each member 45 could be constructed so as to define an even longer passage 46 or a shorter passage as required.

The members 45 of each pair 45a, 45b are arranged coaxially on the shaft 42 and are held spaced apart by means of a spacer sleeve 54 on the shaft and a spiral shaped strip 55 located in annular sockets 56 formed on the members. The two sets 45a, 45b are held spaced apart on the shaft by spacer sleeves 54a arranged one each side of the crank arm 40.

The shaft 42 is rotatable by the actuator 37 so as to rotate the members 45 in unison about the axis of shaft 42 through an angle A (for example 400). The members are rotatable to move exits 48 from a first position shown in full lines in Fig.2 to a second position shown in broken lines. In the first position, the flange 49 of the member engages flare 28 of the outlet duct coaxially whereby the passageway 46 and outlet duct 18 (both of similar diameter) together form a long intake duct which receives air through the entry 47 of the passageway from the chamber 21 defined by the casing.

In the second position, the flange 49 of each member 45 is spaced from the flare 28. In the second position, each outlet duct 18 receives air from the chamber 21 so as to form a short intake duct defined by each outlet duct alone.

The number of members 45 and the size of the casing 25 can be increased or decreased depending upon the number of cylinders of the engine and its capacity.

In a multi cylinder engine as shown in the drawings, we prefer to arrange the throttle body mid way between the two sets of members 45a, 45b. In that way, there will be substantially even distribution of air within the chamber 21 for the passages 46 and will minimise vibrational excitement of the throttle body 31.

Instead of providing four separate members 45, it is envisaged that a single elongate member, e.g., a one piece moulding, may be mounted within the casing, the single member being formed to define the required number of passages 46 arranged side by side for cooperation with the outlet ducts 18.

Preferably, the casing 25 and the members 45 are constructed from plastics material.

The term "air" as used herein also covers other gases.

Claims

1. An inlet manifold for an internal combustion engine comprising a casing defining a chamber having an air inlet and an air outlet, a member in the chamber defining a passageway for receiving air from the chamber, the member being movable between a first position in which air from the chamber flows to the outlet through the passageway to provide a long intake duct and a second position in which air in the chamber flows directly to the outlet.

2. An inlet manifold according to Claim 1 in which the air outlet is in the form of a duct.

3. An inlet manifold according to Claim 2 in which the passageway is of greater length than the duct.

4. An inlet manifold according to any preceding Claim, in which the passageway has an air exit which is positioned in alignment with the air outlet of the chamber in said first position so that the air outlet forms substantially a continuation of the passageway.

5. An inlet manifold according to Claim 4, in which the air exit and air outlet are of similar diameter.

6. An inlet manifold according to Claim 4 or 5, in which the air exit and air outlet are bounded by peripheral rims which interengage in said first position of the member.

7. An inlet manifold according to any preceding Claim, in which the member is rotatable between said first and second positions.

8. An inlet manifold according to any preceding Claim, in which the passageway is curved.

9. An inlet manifold according to Claim 8, in which the passageway is of spiral-like form.

10. An inlet manifold according to Claim 9 and where the member is rotatable, in which the spirallike passageway extends circumferentially around an axis of rotation of the member.

11. An inlet manifold according to Claim 10 in which the circumferentially extending passageway extends for at least 1800 around the axis of rotation.

12. An inlet manifold according to Claim 11 in which the ends of the passageway lie circumferentially beyond each other.

13. An inlet manifold according to Claim 10, 11 or 12 in which the spiral passageway has a radially inner end defining an entry arranged to receive air from the casing.

14. An inlet manifold according to any preceding Claim in which the casing encloses the member defining the passageway.

15. An inlet manifold according to Claim 14 and where the member is rotatable, in which the member is supported for rotation by support means projecting inwardly from a wall of the casing.

16. An inlet manifold according to Claim 15 in which a shaft is mounted on the support means and the member defining the passageway is mounted on said shaft.

17. An inlet manifold according to Claim 16 in which the shaft extends between support means on opposite walls of said casing.

18. An inlet manifold according to any preceding Claim in which means is provided in the chamber for applying movement to the member.

19. An inlet manifold according to Claim 18 in which the means comprises an operating element extending through the chamber.

20. An inlet manifold according to Claim 19 in which the operating element is driven by an actuator mounted on the casing.

21. An inlet manifold according to Claim 19 or 20 in which the operating element is a rod.

22. An inlet manifold according to Claim 19, 20 or 21 in which the operating element is connected to a crank drivably connected to the member whereby movement of the element will turn the member.

23. An inlet manifold according to any preceding Claim in which a plurality of said members is arranged side by side, each passageway of which receives air from the chamber and each of which is movable between said first and second positions.

24. An inlet manifold according to Claim 23 in which the casing has a plurality of air outlets and the members in said first positions enable air to flow to the outlets through the respective passageways.

25. An inlet manifold according to Claim 23 or 24 in which the members are movable in unison.

26. An inlet manifold according to Claim 25 and where said means is provided for applying movement to the members in which one said means moves said plurality of the members.

27. An inlet manifold according to Claim 26 in which said means is arranged between two of said members.

28. An inlet manifold according to any of Claims 23 to 27 and where said shaft is provided, in which all of the members are mounted on said shaft.

29. An inlet manifold according to any of Claims 23 to 28 in which said members are substantially identical.

30. An inlet manifold according to any of Claims 23 to 29 in which the outlets of the chamber are substantially identical.

31. An inlet manifold according to any of Claims 1 to 30 in which said member defines a plurality of passageways arranged side by side, each of which passageways receives air from the chamber and which, in the first position of the member, enable air to flow to respective said air outlets.

32. An inlet manifold according to any preceding Claim and where the member is rotatable, in which at least a portion of the casing has a generally cylindrical wall which is curved substantially about an axis of rotation of the member.

33. An inlet manifold according to Claim 32 in and where the or each outlet is in the form of a duct, in which the or each duct extends substantially tangentially from the generally cylindrical wall of the casing.

34. An inlet manifold according to any preceding Claim in which the air inlet for the chamber is controllable by means of throttle valve.

35. An inlet manifold according to Claim 34 in which the throttle valve is mounted within a duct defining the inlet.

36. An inlet manifold according to Claim 35 in which the duct defining the inlet is formed integrally with the casing.

37. An inlet manifold according to any preceding Claim and where a plurality of members or passageways is provided in which the air inlet is arranged between two said members or passageways.

38. An inlet manifold for an internal combustion engine constructed and arranged substantially as described herein with reference to the accompanying drawings.