Rotary valve cylinder head

Abstract

 A rotary valve cylinder head includes a cylinder head body (10) which defines a cylindrical region therein and having a dual port combustion chamber (14) disposed adjacent the head end of the cylindrical region, a piston (16) reciprocatable within the cylindrical region, and rotary valve devices disposed in the cylinder head body (10) for controlling flow of gas to and from the combustion chamber (14). The rotary valve devices include a pair of cylindrical rotary valve members (36, 38) parallel to each other on opposite sides of the cylindrical region. The valve members (36, 38) are journalled in bearing means (39, 41) disposed between the valve members (36, 38) and the cylinder head body (10). Each bearing means (39, 41) receives a respective sealing member (68, 69) disposed around a respective port (25, 31) and between the bearing means (39, 41) and the cylinder head body (10). Each sealing member (68, 69) is an endless loop and encircles the respective port (25, 31). The lateral cross-sectional shape of each sealing member (68, 69) provides compressive elasticity so that movement of the bearing means (39, 41),which are metal-impregnated graphite sealing screens, can be accommodated without separation between the bearing means (39, 41) and the cylinder head body (10).

Description

[0001] This invention relates to a rotary valve cylinder head for an internal combustion engine.

[0002] While various rotary valve cylinder heads have been proposed, difficulties have been encountered in producing a satisfactory rotary valve. One difficulty is the lubrication of the rotary valve member. Another is the high consumption of lubricating oil. It is necessary that a rotary valve member be properly lubricated and that it be constructed in such manner as to preclude build-up of excessive temperature and pressure at certain points. The build-up of such temperature and pressure results in thermal expansion of the rotary valve member and this expansion tends to destroy the lubricating action of the oil and may cause seizure of the rotary valve, or poor sealing.

[0003] Another difficulty relates to the sealing of the rotary valve member relative to the cylinder'head. While a rotary valve obviously requires a seal between moving and stationary parts, previous proposals have depended solely upon close tolerances for the sealing and have not been found acceptable. Differential thermal expansion between the rotary valve member and its housing, and also thermal distortion, have caused such proposals either to open up and leak excessively, or bind up due to the interference caused by the heating and distortion.

[0004] It is an object of this invention to'avoid as far as possible the difficulties encountered with previous proposals for a rotary valve cylinder head.

[0005] According to this invention a rotary valve cylinder head for an internal combustion engine comprises a cylinder head body defining a cylindrical region therein and having a dual port combustion chamber disposed adjacent the head end of the cylindrical region, one port being an inlet port and the other port being an exhaust port; a piston reciprocatable within the cylindrical region; and rotary valve devices disposed in the cylinder head body for controlling flow of gas to and from the combustion chamber, characterized in that the rotary valve devices include:- (a) a pair of generally cylindrical rotary valve members each defining a radial passageway extending transversely therethrough for flow of gas, the valve members being substantially parallel to each other on opposite sides of the cylindrical region and each valve member being rotatable to a position in which its respective passageway communicates with the combustion chamber; (b) two bearing means, each disposed between a respective valve member and the cylinder head body; and (c) a separate sealing member received by each bearing means and disposed around a respective one of the two ports between the respective bearing means, and the cylinder head body.

[0006] The invention will now be described by way of example, with reference to the drawings, in which:-

Fig. 1 is a section of a rotary valve cylinder head, with parts seen in elevation;

Fig. 2 is a fragmentary side elevation of a rotary valve member, with parts shown in section;

Fig. 3 is a section of one seal suitable for use in the cylinder head;

Fig. 4 is a section of another seal suitable for use in the cylinder head;

Fig. 5 is a section of another seal suitable for use in the cylinder head; and

Fig. 6 is a section of another seal suitable for use in the cylinder head.

[0007] Referring to Figs. 1 and 2, a rotary valve cylinder head includes a cylinder head body 10 which is mounted on the crankcase (not shown) of an internal combustion engine of the spark-ignition, four-stroke cycle design. Body 10 defines a cylindrical region which is rigidly sleeved with cylinder 12. Cylinder 12 co-operates with closing surface portion 13 of body 10 so as to define a combustion chamber 14 at the head end thereof, the head end being the uppermost end of the cylindrical region.

[0008] A piston 16 is reciprocatable in cylinder 12 and is connected in conventional manner by a piston rod 18 to the crankshaft (not shown) of the engine. Piston rod 18 is connected to piston 16 in conventional manner by a wrist pin 20. Piston 16, cylinder 12 and the closing surface portion 13 of body 10 form a variable volume combustion chamber 14 of the engine. The cylinder head body 10 is water-cooled in conventional manner by water jacket compartments 22 in body 10 and surrounding the cylinder 12.

[0009] Body 10 is provided with an inlet port 24 which communicates with an inlet passage 26 in an intake manifold 28 and leading to a carburetor (not shown) in a conventional manner. Body 10 is also provided with an exhaust port 30 which communicates with an exhaust passage 32 in a suitable exhaust manifold 34.

[0010] The flow of the air-fuel mixture to the combustion chamber 14 and flow of exhaust gases from the combustion chamber is controlled by rotary valve means.

[0011] Such rotary valve means comprise a pair of rotary valve members 36 and 38, each of which is configured as a generally cylindrical member. Valve members 36 and 38 are disposed substantially parallel to each other on opposite sides of the cylindrical region. While only a single piston and a single cylinder are disclosed, it is to be understood that by appropriate placement of the flow passageways in each valve member, four or six cylinders can be accommodated by a single pair of valve members.

[0012] Valve member 36 is rotatably journalled within bearing means formed by a curved sealing screen 39 which is disposed between valve member 36 and surface 40 of body 10. Valve member 38 is rotatably journalled within bearing means formed by a curved sealing screen 41 which is disposed between valve member 36 and surface 42 of body 10.

[0013] Valve member 36 is provided with a radial passageway 44 extending transversely therethrough and is constructed and arranged to communicate with intake port 24 through an aligned port 60 in sealing screen 39. A different radial passageway, appropriately linearly spaced and angularly indexed from passageway 44 is provided for-each cylinder. Valve member 38 is provided with a radial passageway 46 extending transversely therethrough and constructed and arranged to communicate with exhaust port 30 through an .aligned port 61 in sealing screen 41. Similarly, a different radial passageway appropriately linearly spaced and angularly indexed from passageway 46 is provided for each additional cylinder in line.

[0014] When passageway 44 is aligned with intake port 24, the intake gases in intake passage 26 are in communication with the combustion chamber 14 by way of an intake port passage 25 formed in body 10 at surface portion 13 and by way of an aligned port in sealing screen 39. When passageway 46 is aligned with exhaust port 30, the exhaust gases are allowed to flow to exhaust passageway 32 from combustion chamber 14 by way of an exhaust port passage 31 formed in body 10 at surface portion 13 and by way of an aligned port in sealing screen 41.

[0015] A spark plug 50 is mounted in a bore 52 in body 10 in a suitable manner such that the electrode 54 of spark plug 50 is positioned in a bore 56 in communication with the combustion chamber 14.

[0016] Each of the valve members 36 and 38 is constructed of a cylindrical bar made of a suitable metal or metal alloy. The material selected must be capable of withstanding the high temperatures known to be present within cylinder heads that are associated with internal combustion engines. Each sealing screen 39 and 41 is constructed of a self-lubricating graphite material which is also capable of withstanding the high temperatures which are present. While various suitable graphite materials may be used, illustrative of the preferred material is a fine grade metal-impregnated graphite which exhibits increased thermoconductivity, strength, hardness, lubricity and wear' resistance. Also acceptable for use with this invention are pure graphite materials, graphitized carbon materials and ceramic-impregnated graphite materials. One example of a fine grade metal-impregnated graphite material is graphite bronze.

[0017] As has been suggested, depending upon the type of internal combustion engine to which the invention is applied, the cylinder body 10 may be provided with a bank of a plurality of cylinders and associated rotary valve means. With such a bank of a plurality of cylinders and rotary valves, the series of passageways 44 and 46 will be spaced longitudinally along the length of the associated valve member.

[0018] In prior rotary valve designs, there has been a great deal of attention directed to the sealing of the rotary member relative to the stationary portion of the valve head body and a means to keep the moving parts lubricated. Designs which involve the rotary member bearing against a valve seat in the cylinder port are simply unacceptable. The present invention overcomes these two concerns by the use of a metal-impregnated graphite sealing screen that avoids the need to place the rotary portion of the valve directly against the valve seat, while at the same time providing a self-lubricating journal against which the rotary portion turns. Sealing screen 39 includes a generally rectangular opening (aligned port) 60 which is disposed over corresponding port passage 25. Similarly, sealing screen 41 includes a generally rectangular opening (aligned port) 61 which is disposed over corresponding port passage 31. Although these two rectangular openings are in fact aligned with their respective intake and exhaust ports, a portion of each sealing screen extends into its corresponding port passage.

[0019] These portions, 62 and 63, respectively, are acted on by the pressure within the cylinder thus pressing each screen against its corresponding rotary portion with a force proportional to the pressure. The rotary portion of each valve, members 36 and 38, respectively, provides backing to the sealing screens thus enabling relatively thin screens to be used, while still withstanding the pressures exerted by the gases within the cylinder. As the force on the screens increases, the friction between the valve members and the screens also increases.

[0020] However, a component of the frictional force acts toward pushing the screen up off of the valve member and this component of the frictional force acts in a direction opposite to the force created by the pressure of the gas within the cylinder. The size of this frictional component depends upon the degree of friction between the two members, thus it never is sufficient to actually unseat the screen but rather merely reduces the rubbing friction. What results is a smooth turning, low friction assembly which can run almost indefinitely and due to the self-lubricating properties of the graphite used for the sealing screens, the assembly will not require additional lubrication.

[0021] Facilitated in part by raised bosses 66 in the cylinder head body and channels 67 in the sealing screens, sealing screens 39 and 41 are nonrotational but do have movement to the extent that they are compliant with their respective valve members. The movement which is permitted might only amount to a small fraction of a mm between hot and cold extremes and pressure extremes within the cylinder head body, but throughout this movement cycle, a sealed interface between the sealing screens and the inlet and exhaust ports of the cylinder is required. In order to ensure-a suitable seal at high pressures and temperatures, separate . metal seals 68 and 69 are respectively disposed around the inlet port and around the exhaust port. In the exemplary embodiment, these metal seals are constructed of inconel, an alloy which is highly resistant to heat.

[0022] Provided as additional backing for metal seals 68 and 69 are 0-ring seals 70 and 71, respectively. Each 0-ring seal is of an endless loop design and is larger in size than the corresponding metal seals so as to lie outward of the metal seals. Each 0-ring seal is, in the exemplary embodiment, constructed of an elastomeric material.

[0023] While these seals appear to be arranged into two pieces for each port, FIG. 1 is actually a full section view and what is disclosed by the two illustrated cross-sectional portions of each seal is an endless seal configured as a band or loop that encircles the outer perimeter of its respective port, thus assuring sealing at _- all locations around the ports. The metal seals provide the first point or location of sealing and the 0-rings provide secondary or back-up sealing.

[0024] In the arrangement of FIG. 3, metal seal 69 (which is substantially the same as metal seal 68) is configured with a C-shaped lateral cross-section. Such a seal . exhibits a sufficient degree of elasticity in order to maintain a sealed interface. at high pressures.

[0025] The line contact at the sealing surface results in a high unit load on that surface and if the metal seal is plated, more effective smearing of the plating into the surface irregularities results.

[0026] Referring to FIG. 4, seal arrangement 69' is illustrated and this seal arrangement represents the preferred style for the exemplary embodiment. Seal arrangement 69' has an E-shaped lateral cross section. This type of seal works on many of the same principles of the C-shaped seal, except that it is more suitable for large flange deflections. The deflections permitted by the FIG. 3 and FIG. 4 seals allow the various sealing screens to move slightly with changes in pressure and temperature without permitting gapping or separation between the sealing screen and the cylinder head body. The result is an improved sealing concept for rotary valve cylinder head construction which is compatible with the graphite sealing sleeves that provide a self-lubricating configuration for smooth and virtually indefinite operation of the rotary valve members.

[0027] Two additional metal seal arrangement designs are illustrated in FIGS. 5 and 6. FIG. 5 illustrates an omega-shaped (lateral cross section) metal seal 74 which includes outwardly flared ends (edges) that are compressed between the two surfaces to be sealed. These ends are contoured so as to provide a full flat surface for sealing and seal 74 is able to expand from its compressed state with deflection of the sealing screen.

[0028] FIG. 6 illustrates a large radiused, inconel C-shaped seal 75 which operates on the same type of compressive and elasticity principles of those earlier-disclosed seals, but additionally includes an elastomeric 0-ring 76 . immediately behind seal 75 within the same groove. It is also to be understood that for each of the four metal seal arrangements disclosed, a back-up 0-ring seal, such as seals 70 and 71, may also be employed.

Claims

1. A rotary valve cylinder head for an internal combustion engine comprising:-

a cylinder head body (10) defining a cylindrical region therein and having a dual port combustion chamber (14) disposed adjacent the head end of the cylindrical region, one port being an inlet port (25) and the other port being an exhaust port (31);

a piston (16) reciprocatable within the cylindrical region; and

rotary valve devices disposed in the cylinder head body (10) for controlling flow of gas to and from the combustion chamber (14),

characterized in that the rotary valve devices include:-

(a) a pair of generally cylindrical rotary valve members (36, 38) each defining a radial passageway (44, 46) extending transversely therethrough for flow of gas, the valve members (36, 38) being substantially parallel to each other on opposite sides of the cylindrical region and each valve member (36, 38) being rotatable to a position in which its respective passageway (44, 46) communicates with the combustion chamber (14);

(b) two bearing means (39, 41), each disposed between a respective valve member (36, 38) and the cylinder head body (10); and

(c) a separate sealing member (68, 69) received by each bearing means (39, 41) and disposed around a respective one of the two ports (25, 31) between the respective bearing means (39, 41) and the cylinder head body (10).

2, A cylinder head according to claim 1 characterized in that each bearing means (39, 41) includes a curved sealing screen (39, 41) of metal-impregnated graphite.

3. A cylinder head according to claim 1 or claim 2_, characterized in that each sealing member (68, 69) is an endless metal seal of E-shape (69') in transverse cross-section.

4. A cylinder head according to claim 1 or claim 2, characterized in that each sealing member (68, 69) is an endless metal seal of C-shape (69) in transverse cross-section.

5. A cylinder head according to any preceding claim characterized in that each sealing member (68, 69) includes a generally rectangular opening which is aligned with a respective port (25, 31), a portion (63, 62) of each sealing member extending into the respective port (25, 31).

6. A rotary valve for use within a'cylinder head (10) to control flow through a combustion chamber port (25, 31) characterized in that it comprises:-

a cylindrical valve member (36, 38) defining a transverse passageway (44, 46) therethrough; a graphitized carbon sealing screen (39, 41) disposed between the cylindrical valve member (36, 38) and the cylinder head (10); and an endless seal (68, 69) received by the sealing screen (39, 41) and disposed around the port (25, 31).

7. A valve according to claim 6 characterized in thata portion (63, 62) of the sealing screen (39, 41) extentacross a portion of the combustion chamber (14).

8. A valve according to claim 6 or claim 7 characte rized in that the endless seal (69') is of E-shape in transverse cross section.

9. A valve according to claim 6 or claim 7 characte rized in that the endless seal (69) is of C-shape in transverse cross section.

10. A valve according to claim 6 or claim 7 characte rized in that the endless seal (74) is of omega-shape in transverse cross section.

11. A valve according to claim 6 or claim 7 characte rized in that the endless seal (75) is of a large radiused C-shape in transverse cross section.

Drawing