TIMING DEVICE FOR RECIPROCATING POSITIVE-DISPLACEMENT ENGINES, SUCH AS ENDOTHERMIC RECIPROCATING ENGINES, WITH A ROTARY VALVE IN THE SHAPE OF A SOLID OF REVOLUTION, PARTICULARLY A SPHERE

Abstract: For each cylinder a timing device comprises at least one valve (12) in the shape of a solid of revolution which rotates inside a corresponding recess (15) in a seat formed in the cylinder head (1), the surface of the said recess mating with that of the said valve; at least one intake and/or exhaust pipe (7, 9) which communicates with the said recess; at least one pipe (10) which connects the said recess with the space inside the cylinder (3) of the reciprocating engine; the said valve has at least one facet (13) or a recess or an eccentric hole which allows communication between the said intake and/or exhaust pipe (7,9) and the said pipe (10) which connects with the space inside the cylinder while the valve itself is rotating, whilst actuating devices are provided which cause the valve to rotate in synchronization with the phases of the reciprocating engine; the actuating devices of the said valve comprise a camshaft (17) to which the said valve is connected so that it can rotate and also slide, the axis of the said shaft coinciding with the axis of revolution of the solid of revolution which forms the valve itself.

Description: The invention refers to a timing device for reciprocating positive-displacement engines, such as reciprocating internal combustion engines, reciprocating compressors and similar, wherein for each cylinder there is at least one substantially spherical valve which rotates inside a corresponding recess in a seat formed by a set of elements housed in the cylinder head and elastically urged against said valve, the surface of said recess mating with the surface of the said valve; at least one intake and/or exhaust pipe which communicates with the said recess; at least one pipe which connects the said recess with the space inside the cylinder of the reciprocating engine; the said valve having at least one facet or a recess or an eccentric hole which allows communication between the said intake and/or exhaust pipe and the said pipe which connects with the space inside the cylinder when the valve itself is rotating, and a camshaft on which said valve is connected, which causes the valve to rotate in synchronization with the phases of the reciprocating engine, said camshaft having an axis which coincides with the axis of the substantially spherical valve. Such a device is known from FR-A-1556532. FR-A-1145762 discloses a timing device having a hollow rotor which as an enlarged portion forming the valve body. The valve body rotates within a seat machined in the cylinder head, while the other part of the rotor forms a shaft. The rotor is supported by bearings (16, 17) placed on both sides of the valve body, at such a distance that thermal expansions of the rotor are possible. The seat of the valve body is, therefore, incomplete as a gap must be left free for allowing thermal expansion of the rotor. Moreover, this known device does not allow independent expansions of the shaft and of the valve body, and a free adjustment of the valve in its seat is not possible. In many applications, for example in automotive engines, a large number of cylinders is put in series to achieve sufficient power and also to suitably balance dynamic forces of each cylinder-piston system. In this case, a single camshaft is used for controlling all the valves aligned along one front of the cylinder-piston arrangement. If rotary valves of the type described in FR-A-1145762 are used, it would be convenient to use a single control shaft onto which the valves of all the cylinders are connected, also because it would not be possible to arrange a large number of independent shafts for each cylinder (or for each pair of cylinders) due to space and overall dimension requirements. The device described in FR-A-1145762, however, is not suitable for such an arrangement. In fact, if a relatively long rotor forming valve shaft and valve bodies is used, the thermal expansion of such a mechanical element would cause dramatical changes in the length of the element itself. Such length changes could not be compensated by simply providing a clearance between the valve bodies and the relevant bearings or seat walls. Also, too a large gap in the seat for the valves would bring about serious inconveniences in the functioning of the valve. US-A-1697098 discloses a timing device comprising a plurality of rotating valves, each of which is supported by a common shaft. In this case, each valve is formed by a body which is separated from the shaft, each valve is keyed to the adjacent one, and the first and last valves are keyed on the shaft. In this known arrangement, a valve casing is provided, which extends over the entire length of the engine cylinders. Each valve is made up of a set of sections provided with flanges and eccentric floating segmental shoes placed between flanges of a same valve. Between flanges of adjacent valves there are inserted ball bearings, which support the valve arrangement within the valve casing. The valves of the arrangement are fixed to the shaft at the ends of the latter, so that no independent thermal expansion between the shaft and the valves is possible since the valves are prevented from expanding more than the shaft. If, as it is mostly the case, valve bodies on one hand and valve shaft on the other are made from materials having differing mechanical features and differing thermal expansion coefficients, this will bring about enormous thermally induced compression stresses in the valves, if the latter tend to expand more than the shaft. Moreover, the ball bearings provided for the support of the valves are an obstacle for the expansion of the valves. The object of the invention is to provide a timing device as defined in the preamble of Claim 1, which do not have the above mentioned drawbacks. This object is achieved in a device which is further caracterized in that the body of the valve is separated from the camshaft, said camshaft passing through the valve, that means are provided for connecting said valve directly to said camshaft in such a way that the valve rotates with the camshaft but may axially slide in both directions and expand more or less than the latter, so that the valve may settle into its correct operating position inside its recess by varying thermal conditions, the axial position of the valve being defined by the elements forming the recess. The fact that the valve body is free to axially slide along the shaft at least to a certain degree has brought to the surprising effect that such a timing device can work (at least for limited powers and limited rpm values) without lubrication of the valve seat. This surprising effect is obtained by the combination of a seat formed by a plurality of elastically urged elements and a valve body which has a degree of freedom with respect to the shaft, in such a way that complete adaptation to various thermal conditions is possible. The arrangement is such as to avoid any possible thermally induced stress on the valve and on the seat walls. Moreover, with the arrangement of the invention it is possible to construct an engine with a plurality of cylinders with a single valve shaft which supports the valves for all the cylinders. In this case, even remarkable expansions of the shaft are possible without influencing the correct functioning of each valve. Each single valve can slide with respect to the shaft, thus keeping its optimal operating position in its relevant seat. Moreover, each valve may slide by a different degree with respect to the shaft. Further advantageous features of the invention are set out in the dependent claims. The drawing show a non-limiting, practical embodiment. In the drawing, Fig. 1 is a schematic diagram of a sectional view of the head (or cylinder head) of a reciprocating internal combustion engine; Fig.2 is a sectional view through II-II in Fig. 1. In Fig. 1, 1 generally represents that part of the head (or cylinder head) which covers the top of cylinder 3 of a reciprocating internal combustion engine; 5 represents the combustion chamber of the said cylinder, 7 the intake pipe and 9 the exhaust pipe. 11 represents a slanted, threaded hole for fitting a spark plug or injector to head 1. A pipe 10, which is coaxial with cylinder 3 in the example in the drawing, opens into the center of combustion chamber 5; typically it is made to communicate alternately with intake pipe 7 and exhaust pipe 9 via rotary valve 12. Rotary valve 12 (in the example in the drawing) is in the shape of a sphere but may alternatively be any other solid of revolution with a convex surface (such as an ellipsoid), rotating round its own axis of revolution. Valve 12 is incomplete at 13 and does not therefore have a cap corresponding to an angle at the center of approx. 120 degrees; in place of the missing cap, valve 12 has a surface 13 or facet which is basically flat except for a convex section 13C, the purpose of which will be described below. In place of the facet, at 13 valve 12 may have a groove-type recess or even a hole, the axis of which corresponds to the chord of the great circle of the sphere as shown in Fig. 2, the said chord being a certain distance from the external surface of shaft 17 which, as will become apparent below, controls the rotation of valve 12. As will be explained in detail below, the facet, the recess and the hole located at 13 all perform the function of conveying towards or away from the inside of cylinder 3 fluid aspirated or discharged by the said cylinder via pipe 10. Valve 12 is made to rotate in the direction of arrow f12 inside recess 15 which is also spherical or of the same shape as said valve 12 itself, the surfaces of recess 15 forming a seal with the surface of valve 12 which slides inside it. Valve 12 is made to rotate by means of a camshaft 17 (Fig. 2) mounted on bearings like that illustrated by 19 and housed inside the head of which section of head 1 forms part. The convex, curved part of surface 13 is such that surface section 13P may match the curved course of shaft 17 a certain distance away. A transverse pin 21 placed inside holes 23 on shaft 17 is used to make valve 12 rotate. The ends of pin 21 engage in seats 24 on the valve which are suitably extended on both sides to allow for the fact that the thermal expansion of the shaft and of the valve may differ during operation; the valve may therefore slide and settle into its correct operating position inside recess 15 irrespective of any changes in temperature. As may be seen from Fig. 1, in the various positions occupied by valve 12 when it rotates according to arrow f12, surface 13, or a recess or a through hole in its place, as has just been mentioned, first forms a passage with the surface of seat 15 (in the sequence of the phases of a standard four-stroke engine) which connects intake pipe 7 with pipe 10, causing the induction phase to take place. The cross-section of this passage changes from a minimum to a maximum value and then returns to zero again when the spherical surface of valve 12 closes pipe 10 for a certain period of time during which the compression, combustion and expansion phases take place. When this closure period has finished, approximately at the end of or just before the end of the expansion phase, surface 13 forms a passage with seat 15 for a second time, connecting exhaust pipe 9 with pipe 10 and with the inside of cylinder 3 and causing the exhaust phase to take place. In the example shown in the drawing the induction phase takes up approx. 90 degrees of the rotation of valve 12, 180 degrees are taken up by the compression, combustion and expansion phase and the remaining 90 degrees by the exhaust phase. This is the standard timing of the phases of a four-stroke, low-revolution engine. By varying the angle at the center by which the chord facet 13 is subtended and/or the position of pipes 7 and 9 it is possible to advance and/or retard both the induction and the exhaust phases, thereby also allowing so-called crossing or scavenging to take place. For cooling purposes valve 12 consists of a hollow shell defined by a genuinely spherical wall 12P and wall 13P which matches surface 13. Internal space 14 of valve 12 is cooled with cooling air (or a liquid coolant) which reaches it via inlet holes 25 and outlet holes 27 which connect internal space 14 with the internal pipe 17C of shaft 17 which is tubular in shape. In the example shown in the drawing the cooling air ― which may be part of the cooling air for the engine provided by a fan or which may also come from a suitable blower or other means ― enters shaft 17 in the direction of arrow f17, enters recess 14 via holes 25 and leaves via holes 27, holes 25 being inclined and divergent to promote the ingress of the air into valve 12 and holes 27 being inclined and convergent in order to promote its departure. Immediately downstream of holes 25 inside shaft 17 is a diaphragm 29 with a central hole 31 which limits the passage of the air entering, thus causing the pressure of the air at the mouth of holes 25 to increase; this increase helps the greatest possible volume of air to pass through them. Because of a "Venturi" effect due to hole 31, however, there is a pressure drop downstream of diaphragm 29 which increases the speed with which the air leaves space 14 via holes 27. Valve 12 is made of steel or another metallic material that is suitable, particularly as regards the achievement of a perfectly smooth external surface (by lapping or some other method). Seat 15 inside which valve 12 rotates has a configuration like that of valve 12 apart from the gaps due to pipes 7, 9, 10 and the holes through which the shaft passes, but is in several parts which may be made of steel or another suitable metal, but preferably another material such as graphite for example. Inside a suitable seat machined in the metal head block and above valve 12 is a bush or cap 33, usually of graphite, which constitutes a solid of revolution, the bottom of which is defined by a recess 34 in the shape of a spherical cap, the concave surface of which is able to mate perfectly with the convex surface of valve 12. The position of bush 33 with respect to valve 12 may be defined in such a way as to obtain optimum contact for the purposes of leak-tightness, the bush being made to slide inside the said seat and be locked with adjusting screws (not shown). At the bottom (on the drawing) and opposite to bush 33 is a bush 35, usually made of cast iron, which is also a solid of revolution with a hole 37 in the center which is the same diameter as pipe 10 of which it is an extension. The surfaces of bush 35 are shaped in different ways so that there is a concave area 38 which is in contact with the surface of valve 12, an external cylindrical surface 39, the internal cylindrical surface 37 which extends hole 10 and in such a way that there is a short tubular guide sleeve 41 which can slide inside a corresponding annular seat 43 with cylindrical surfaces surrounding hole 10 machined in the section of the head. Between external surface 39 and the external surface of sleeve 41 is a step 45 which receives the thrust of a compression spring 47 to keep the surface of area 38 in close contact with the surface of valve 12 at all times. Spring 47 acts on the bottom of an annular guide slot 49 outside the annular sliding seat 43 of sleeve 41. Radial pegs 51 prevent bush 35 from descending too far if spring 47 breaks. Bushes 53 and 55, which slide inside cylindrical seats 61 and 67, are in the shape of solids of revolution and are usually made of graphite, surround both sides of valve 12 and each has its own concavity 54 and 58 with concave surfaces which mate with the surface of valve 12. Their springs 57 and 59 push bushes 53 and 55 centripetally, i.e. in the axis of rotation of shaft 17, so as to ensure contact between concavities 54 and 58 and the surface of valve 12. Concavities 54 and 58 have a portion missing at the bottom as each has a notch 63 and 65 which can prevent bushes 53 and 55 from touching the cylindrical contour 49 of bush 35. Concavities 54 and 58 are interrupted also at the sides ― i.e. they do not surround the surface of valve 12 up to the meridian which lies in a plane which is orthogonal to the axis of shaft 17 ― so as not to touch the ends of pipes 7 and 9. Spring 57 acts against an annular shoulder 67 which (on the left of Fig. 2) bounds hollow seat 61 inside which bush 53 slides; similarly spring 59 acts against an annular shoulder 69 which (on the right of Fig. 2) bounds hollow seat 67 inside which bush 55 slides. The shoulder 69 is machined onto the front (opposite bearing 19) of a sleeve 71 which serves as a spacer, to complete and close recess 67 and which may also act as a bush. 70 represents a double shoulder which may absorb the axial thrusts from shaft 17; this shoulder rotates inside an annular slot 72 machined from the material of which the head is made. The potential centrifugal travel of bushes 53 and 55 is also delimited by their radial pegs 73 and 75 which face downward and slide inside seats 77 and 79 within certain limits. A pair of thin pipes 81 and 83 which are inclined, lead into a top recess 85 on the head and are for cooling purposes cross top bush 33; in some cases they may also be used to lubricate valve 12 from the top. At the point at which they emerge into recess 34, pipes 81 and 83 are connected by a groove 84 which is in the shape of a bow with the circumference on the surface of the said recess. As bush 35 is subject to the pressure of the gases during the compression, combustion and expansion phases ― as is valve 12 ― it has a flexible sealing ring 87 (or similar) fitted to cylindrical surface 39 and another ring 89 fitted to the external surface of sleeve 41. This ensures that gas cannot pass along these surfaces. In the example in the drawing, the head (or cylinder head) of which section 1 is part is air cooled and yet has cooling fins 91 in a configuration which is already known, some of the said fins having gaps for access to pipes 7 and 9, recess 85 and hole 11 and for the space occupied by the plug or the injector. In the version described of the invention the cooling system also enables cooling air to circulate inside pipes (machined in the cylinder head block) in positions such that the surfaces of seat 15 are cooled either directly or indirectly. The said pipes shown as 93 and 95 are approximately circular, with a rectangular section or similar, and have an inlet hole 97 at the point where the cylinder head section 1 joins the corresponding section of a cylinder which is contiguous with cylinder 3 and an outlet hole 99, the said pipes being able to communicate with each other. It is clear that where water cooling is employed, pipes 93 and 95 can be used to circulate the water and can be supplied with the cooling water that circulates in the engine block in the usual way. In the example in the drawing, valve 12 has a single "facet" consisting of surface 13 but it is clear that it may also have two and possibly more than two facets (or recesses or through holes positioned in similar fashion on surface 13) located at equal angular distances and suitably spaced. When there is only one facet the number of revolutions of valve 12 is half the number of engine revolutions (as for the timing shaft of a standard four-stroke engine); with two facets the number of revolutions of the valve is one quarter of that of the engine whilst with three facets the number of revolutions is one sixth of that of the engine. The timing device offers considerable advantages compared with conventional ones, such as the omission of valve springs and the disadvantages associated with them, wider passages for the fluids that are aspirated or discharged, the reduced mechanical power level absorbed by the camshaft, the possibility of obtaining high compression ratios etc. In addition the entire system is very simple in construction and certainly very modest in terms of cost if mass-produced. Valve 12 does not require lubricating for the standard speeds of rotation of a motor-transport engine. Limited lubrication is however, possible via pipes 81, 83 with a drip-feed type of system, for example. The device according to the invention has the further advantage of enabling solid ribbon-like fuel to be used in an endothermic engine to which it is fitted, as valve 12 ensures that suitable segments will be cut from the ribbon which feeds through, for example, at the end of the induction phase. For high-powered engines the invention also offers the possibility of using two rotary valves (rather than only one) in the shape of a solid of revolution with a convex surface, with at least one facet (or recess or hole), with the first valve connecting the intake pipe with an inlet pipe in the combustion chamber of a cylinder in synchronization with the phases of the engine's cycle and the second valve connecting the exhaust pipe with an outlet pipe from the combustion chamber of the said cylinder in synchronization with the said phases. The said two rotary valves may be spherical in shape with a facet similar to valve 12; the two valves may also differ from one another in that by varying the angle at the center of the chord of the great circle to which the facet corresponds it is possible to control the duration of the corresponding induction or exhaust phase. In this case each rotary valve will have a single function, but the design will be the same as the preceding one.

Claims: 1. A timing device for reciprocating positive-displacement engines, such as reciprocating internal combustion engines, reciprocating compressors and similar, wherein for each cylinder (3) there is at least one substantially spherical valve (12) which rotates inside a corresponding recess (15) in a seat formed by a set of elements (33, 35, 53, 55) housed in the cylinder head and elastically urged against said valve, the surface of said recess mating with the surface of the said valve (12); at least one intake and/or exhaust pipe (7; 9) which communicates with the said recess (15); at least one pipe (10) which connects the said recess (15) with the space inside the cylinder (3); the said valve having at least one facet (13) or a recess or an eccentric hole which allows communication between the said intake and/or exhaust pipe (7; 9) and the said pipe (10) which connects with the space inside the cylinder (3) when the valve is rotating, and a camshaft (17) on which said valve is connected, causing the valve to rotate in synchronization with the phases of the reciprocating engine; said camshaft having an axis which coincides with the axis of the substantially spherical valve (12), characterized in that the body of the valve (12) is separated from the camshaft (17), said camshaft passing through the valve (12), that means (21, 23, 24) are provided for connecting said valve (12) directly to said camshaft (17), in such a way that the valve rotates with the camshaft but may axially slide in both directions and expand more or less than the latter, so that the valve (12) may settle into its correct operating position inside its recess (15) by varying temperature conditions, the axial position of the valve being defined by the set of elements (33, 35, 53, 55) forming said recess (15). 2. The device as claimed in the preceding claim, wherein the said facet (13) is approximately flat and the plane of it is parallel to the axis of rotation of the said valve (12). 3. The device as claimed in the preceding claims, wherein the said valve (12) is hollow and cooled by a liquid coolant circulating inside the said camshaft (17), and inside the hollow space (14) of the said valve (12) by means of holes (25, 27) on the saud camshaft (17) located so as to match the valve (12). 4. The device as claimed in claim 3, wherein a first set (25) of the said holes is inclined so as to promote the passage of the said liquid coolant from the shaft (17) to the valve (12) and a second set (27) of the said holes is inclined so as to promote passage in the opposite direction. 5. The device as claimed in claim 4, wherein, in an engine with several cylinders (3) in line, a drilled diaphragm (29) inside the said shaft (17) is fitted to match each valve (12) so as to create a pressure gradient between the two sets of holes (25, 27) with the purpose of faciliting the partial circulation of the coolant inside the valve (12). 6. The device according to one or more of the preceding claims, wherein at least one of said elements (33, 35, 53, 55) forming the recess (15) for the valve (12) is made of self-lubricating material such as graphite. 7. The device as claimed in the preceding claims, wherein pipes (93, 95) to cool the seat (15) of the said valve are machined inside the cylinder head. 8. The device as claimed in the preceding claims, wherein at least one (35) of the elements making up the said seat has sealing rings (89) to counteract the passage of gases from the cylinder (3). 9. The device as claimed in the preceding claims 9, wherein the facet on the said valve (12) which is spherical in shape is replaced by a groove-shaped recess or a through hole, the axis of which correspond to a chord of the great circle of the sphere which lies in the plane which is orthogonal to the axis of rotation and passes through the center of it. 10. The device as claimed in the preceding claims, wherein the said seat of the said valve has cooling and/or lubrication pipes (81, 83) for the said valve (12). 11. The device as claimed in one or more of the preceding claims, wherein a cylinder (3) of a reciprocating engine is equipped with a rotary valve (12), into whose seat leads a first intake pipe (7), a second exhaust or delivery pipe (9) and a third pipe (10) which connects with the space inside the cylinder (3), the said facet (13) on the said valve (12) connecting the said connecting pipe with the said intake pipe or the said exhaust pipe alternately according to the stroke of the piston inside the said cylinder. 12. The device as claimed in claim 11, wherein the said facet and the said intake and exhaust pipes (7, 9) are located in such a way that the induction phase amy be advanced and/or the exhaust phase retarded. 13. The device as claimed in one or more of claims 1 to 9, wherein a first rotary valve is connected to the intake pipe and to a first pipe which connects with the space inside the corresponding cylinder, and a second rotary valve is connected to the delivery or exhaust pipe and to a second pipe which connects with the space inside the said cylinder.

Inventors: MONTAGNI, ALVIERO
Applicants: MONTAGNI, ALVIERO
Application year: 1988
Main classification: F01L7
IPC codes: F01L7