In SE-C-8803791-6 is described a four-stroke radial- piston engine comprising a stationary housing, a drive shaft which is rotationally mounted essentially centrally inside said housing and which supports a hub co-rotating therewith, a number of radially projecting cylinders mounted on the hub for rotation therewith, each cylinder being positioned inside its respective circumferentially extending chamber in said housing and each receiving a piston which is mounted for radial reciprocating movement therein, the piston heads of said pistons facing radially inwards, towards the hub, a circumferentially extending guide cam, said cam being mounted inside the housing in alignment with the pistons adjacent the radially outward- ly directed piston ends and having a cam face facing said pistons, bearing means mounted on each piston abutting against said cam face in order to impart a radial move- ment to said pistons in the direction towards the hub upon rotation of the rotary unit formed by the pistons, the cylinders, the hub, and the drive shaft, relative to the stationary housing, and combustion chambers formed in said hub essentially in alignment with the heads of the respective pistons, each combustion chamber having valve- operated inlets/outlets for intake and exhaustion, respectively, of a combustible fuel-air mixture and of combusted exhaust gases, respectively, so as to impart a radial movement to said pistons in a direction away from the hub in response to the pressure increase upon com- bustion and to the centrifugal force, said inlets/outlets to and from, respectively, each combustion chamber being formed axially in a valve ring which co-rotates with the hub and which is essentially concentric therewith, said valve ring sealingly abutting against a stationary port

ring which is essentially concentric with the valve ring and which is connected to the housing, said port ring being formed with axial intake and exhaust ports, said ports communicating with inlet and outlet ducts and arranged, upon rotation of said rotary unit relative to the housing, to alternatingly assume a position in align- ment with that inlet/outlet in the valve ring that is associated with the corresponding combustion chamber, which valve ring is urged yieldingly into abutment against said port ring.

In valve systems of this kind it has been found that media flowing through the ports have a tendency to escape in the area of the plane of separation between the valve ring and the port ring. The reason therefor is the generation of pulses of overpressure tending to force apart the abutting sliding faces of the valve ring and the port ring, respectively.

In order to overcome this drawback it is suggested in Applicants' Swedish publication SE-C-9400536-0 to provide a number of depressions distributed over at least one of the abutting, urged-together sliding faces of the valve and the port rings, respectively. This solution is a considerable improvement, particularly in the case of small engines, but in larger engines and in the presence of high pressures there still remains a tendency for the sliding faces to be forced apart with consequential leakage.

The main purpose of the invention is to provide, in the mutually sliding rings, improved sealing over that provided by the above solution, whereby the risks of leakage are considerably reduced.

This purpose is achieved in a valve system in ac- cordance with the invention which is essentially char- acterised in that a grooves is formed in the valve ring on the valve ring face that is turned towards the port ring, said groove peripherally encircling the respective inlet/outlet, and in that at least one groove is formed

in the port ring on the port ring face that is turned towards the valve ring, said groove or grovves having a longitudinal extension in the circumferential direction of the port ring, starting from one of the valve ring ports, and being spaced a radial distance from the centre of the port ring that differs from the position of the port ring ports in that same radial direction while simultaneously coinciding with some part of the valve ring groove, when the corresponding inlet/outlet in the valve ring assumes a position above an area in the port ring that is void of ports.

In this manner efficient pressure relief is obtained of the facing faces of the valve and port rings, whereby leakage between said rings to the exterior externally of said rings is prevented while at the same time the re- quirements on the abutment force are reduced, resulting in smaller friction losses and lesser wear.

Preferably, the groove in the port ring starts from and debauches in the port ring inlet port and extends therefrom in the direction of rotation of the valve ring.

In this manner a return flow of gas to the combus- tion chamber of the engine is produced and in consequence thereof the leakage gases are efficiently taken care of before they reach the valve and port ring surroundings.

Other particularities and advantages will become apparent from the following description and claims in conjunction with the appended drawing figures, wherein Fig. 1 is a longitudinal sectional view through the center of an engine known per se, Fig. 2 is a perspective view of a valve system incorporated in the engine of Fig. 1, the valve system parts shown in spaced-apart positions, Figs 3A and 3B are a front view and a sectional view on line 3-3 in Fig. 3A, respectively, of parts of an ignition system incorporated in the engine of Fig. 1, Figs 4A-7B are transverse and longitudinal sectional views, showing the four strokes of the engine of Fig. 1

and the positions of the various components during these engine strokes, Fig. 8 is a perspective view similar to Fig. 2 of a valve system in accordance with the invention, Fig. 9 is a cross-sectional view on line IX-IX in Fig. 8 through a part of the valve system, and Figs 10a-f are schematic sequential views showing the manner of co-operation of the pressure relief ducts in accordance with the invention during one rotation of the engine.

The engine illustrated in the drawings is a four- stroke internal combustion engine pertaining to the group of multiple cylinder radial-piston engines. The internal combustion engine is indicated generally by numeral reference 1 and it comprises a stationary, essentially rotationally symmetrical or annular housing 2. The stationary housing 2 is made from a suitable material, such as cast iron or light metal, and it consists of two halves or housing parts 3 and 4, which are held together by means of bolts 15 arranged closely adjacent the exter- nal periphery. To seal off the two housing parts 3, 4 from one another a peripheral seal 6, such as an O-ring, preferably is provided.

Bolts 7 securely anchor a connection collar 8 to one of the parts of the stationary housing 2, in accordance with the shown embodiment housing part 3, said connection collar 8 having a central through bore 9 for reception therein of a drive shaft 10, the latter being mounted for rotary motion essentially in the centre of the housing 2.

A hub 11 which co-rotates with the drive shaft 10 is mounted on the drive shaft by means of a central bolt 12 and is formed with axially extending, sleeve-like exten- sions 13.

The rotary unit formed by the drive shaft 10, the hub 11, the cylinders 14, and the pistons 16 is rota- tionally mounted in the stationary housing 2 and in the connection collar 8 by means of roller bearings 42, 43,

44, two of said bearings, viz. bearings 42, 43, being positioned between the sleeve-like extensions 13 of the hub 11 and the stationary housing 2 whereas the third bearing 44 is positioned between the drive shaft 10 and the connection collar 8 adjacent the free projecting end of the shaft 10, to which end a power take-off means may be connected. The bearings 42, 43 may be provided with suitable seal rings 45, positioned axially externally thereof.

Radially projecting cylinders 14, in the number of four in accordance with the embodiment illustrated in the drawings, are non-rotationally mounted on the hub 11 so as to rotate together with the latter. All cylinders 14 are positioned inside a circumferentially extending chamber 15 in the stationary housing 2, i.e. a chamber defined by housing parts 3 and 4. In each cylinder 14 is received an associated piston 16 for reciprocating move- ment radially therein, said pistons 16 being of an essen- tially conventional configuration including piston heads 17 and sealing rings 18, the piston heads facing radially inwards, towards the hub 11.

A circumferentially extending cam 19 the cam face 20 of which faces the pistons 16, is mounted inside the sta- tionary housing 2 opposite the pistons 16 at the radially outwardly projecting piston ends 21. More specifically, the circumferential cam 19 is clamped inside recesses formed in opposed faces of the housing parts 3 and 4.

Optionally, the cam is secured in position by means of the same bolts 5 as those holding the housing parts 3 and 4 together. In accordance with the illustrated embodiment which concerns a four-cylinder internal combustion engine, the cam face 20 is essentially of elliptical con- figuration, as indicated e.g. in Fig. 4A, but the con- figuration of the cam surface may vary depending on the number of cylinders used.

Via a piston bolt 22, each piston 16 supports a bearing 23, in accordance with the embodiment shown a

cylindrical roller bearing, the outer ring 24 of which rolls in abutment against the cam face 20 in order to impart a radial motion to the pistons 16 in a direction towards the hub 11, when the rotary unit formed by the pistons 16, the cylinders 14, the hub 11, and the drive shaft 10 rotates relative to the stationary housing 2.

In the hub 11, essentially opposite the heads 17 of the respective pistons 16, are formed essentially radial- ly inwardly directed trough-like combustion chambers 25, having axially directed inlets/outlets 26, 27 for intake of a combustible fuel-air mixture and exhaust of exhaust gases, respectively. In this manner, the pistons 16 are imparted a radial movement in the direction away from the hub 11 in response to the pressure increase resulting from the combustion and the centrifugal force acting on the pistons.

More precisely, the inlets/outlets 26, 27 leading to and from, respectively, each combustion chamber 25, are common and they are formed axially in a valve ring 28 which co-rotates with the hub 11 and which is essentially concentric with the latter, see particularly Fig. 2. The valve ring 28 abuts flatly against a port ring 30, being yieldingly pressed into sealing abutment against said ring 30 by means of compression springs 29, and it sup- ports sealing rings 31 around its inlets/outlets 26, 27.

In accordance with the embodiment of Fig. 2, known per se, the inlets/outlets 26, 27 in the valve ring 28 are prolonged axially and in the form of sleeves 32 they project outwardly from the valve ring 28, said sleeves 28 extending into corresponding recesses 33 formed in the hub 11 for the purpose of securing and bringing along the valve ring, and supporting the sealing rings 31.

The port ring 30 is essentially concentric with the valve ring 28 and it is rigidly connected to the station- ary housing 2. More precisely, by means of bolts, not shown, it is mounted on the inner end of the connection collar 8 that is turned towards the combustion chambers

25. The port ring 30 is formed with axial intake/exhaust ports 36, 37 communicating with inlet/outlet ducts 34, 35 in the connection collar 8. The intake and exhaust ports 36, 37 are arranged, upon rotation of the rotary unit 10, 11, 14 and 16 relative to the stationary housing 2, alternatingly to assume a position in register with that inlet/outlet 26, 27 in the valve ring 28 that is associa- ted with the corresponding combustion chamber 25.

The inlet/outlet ducts 34, 35 formed in the connec- tion collar 8 debauch at one of their ends axially in alignment with the intake/exhaust ports 36, 37 formed in the port ring 30 and at their opposite ends they are connected to an intake system, such as a carburettor 38 or a fuel-injection system, see Fig. 1, and to an exhaust system 39, see Fig. 7B, respectively.

Intermediate said opposite end of the inlet duct 34 and the carburettor 38 or fuel-injection system there is an inlet pipe 40 into which debauches a duct 41, which communicates with the circumferentially extending chamber 15 of the stationary housing 2, in order to bring the chamber 15 to a negative-pressure condition, thus to draw out any blow-by exhaust gases and, at least at low engine speeds, to facilitate the radial motion outwards of the pistons 16.

To function, the radial-piston engine in accordance with the invention is likewise fitted with one spark plug 46 for each combustion chamber 25, i.e. with four spark plugs in accordance with the embodiment shown. The spark plugs are screwed essentially axially into the hub 11 opposite the valve ring 28, and consequently they rotate together with the hub. Thus, the electrode end of each spark plug 46 projects into the associated combustion chamber 25 essentially opposite the common inlet/outlet 26, 27 in the valve ring 28.

At their connective ends, the spark plugs 46 are connected to an ignition distributor, generally desig- nated by numeral reference 47. The distributor is formed

with electrodes 49 which rotate together with the rotary unit 10, 11, 14, 16 and which are urged, for instance by means of helical compression springs 48, against their respective connective end, said electrodes supporting preferably screw-mounted, radially projecting contacts 50, the latter arranged to sequentially pass a stationary electrode 51, which latter electrode in turn is connected to a source of ignition current, not shown in closer detail. Preferably, the rotating electrodes 49 and their associated contacts 50 are mounted in recesses 52 formed in a hub-like holder 53 which is mounted on the drive shaft 10 by means of the previously referred to centre bolt 12. The stationary electrode 51 preferably is mounted radially in an annular attachment means 55 secured to the housing 2 by means of bolts 54.

To urge the pistons 16 radially outwards, at least when the internal combustion engine is started up and/or operates at low rotational speeds, two circumferentially extending return cams 56 are mounted in the circum- ferentially extending chamber 15 of the stationary housing 2, one return cam being positioned on either side of the pistons 16 and radially interiorly of the cam 19.

The circumferentially extending return cams 56 are formed with one radially outwardly facing cam face 57 each, said face having a shape essentially identical with the cam face 20 on cam 19. Each piston 16 is formed with two oppositely directed, axially projecting return pins 58 which are arranged to be brought into abutment against the cam faces 56 of the return cams 56 in order to urge the pistons radially outwards, as mentioned before, without allowing them to assume an oblique position inside their associated cylinder 14.

For the sake of completeness it should also be mentioned that the radial-piston engine as described above likewise is fitted with a water cooling system and with a lubricating system, but since these systems form

no part of the invention as such they are not described further herein.

It should also be mentioned that the radial-piston engine as shown and described comprises four cylinders but there is nothing to prevent this number to be reduced to at least two or increased to perhaps six or more cylinders.

The function of the radial-piston engine described in the aforegoing will be briefly discussed in the fol- lowing with reference to Figs 4A-7B, referring for the sake of simplicity to the movements of two of the pistons 16, designated piston I and II, respectively, in the course of the four-stroke cycle.

In Figs 4A and 4B piston I is in position to start drawing-in a fuel-air mixture whereas piston II is in position to ignite a compressed fuel-air mixture.

Figs 5A and 5B show ongoing suction (intake stroke) with respect to piston I and expansion (power stroke) with respect to piston II.

In Figs 6A and 6B compression is about to start with respect to piston I and exhaust is about to start with respect to piston II.

Figs 7A and 7B, finally, show ongoing compression (compression stroke) with respect to piston I and exhaust (exhaust stroke) with respect to piston II.

All four pistons 16 sequentially run through all four strokes during one revolution of the rotary unit 10, 11, 14 and 16.

The valve system in accordance with the invention, shown in Fig. 8, is distinguished from the valve system shown in Fig. 2 among other things in that the face of the valve ring 128 that is turned towards the port ring 130 and runs against said ring is formed with depressions 128a that are distributed over the entire port ring face in an array of squares, in which rib-like protrusions are disposed intermediate the depressions, the crests of said protrusions forming the valve ring plane that is in slid-

ing engagement with the port ring. It is within the scope of the invention to configure and arrange the depressions in a different pattern. The protrusions forming the slid- ing plane could for instance be given an arcuately curved shape as well as an irregularly arcuate shape. It is likewise possible to instead form the depressions in the port-ring face, and possibly in the faces of both the port ring and the valve ring. The depressions formed in said plane serve as traps in which collects medium tend- ing to migrate between neighbouring inlets/outlets or from the inlet/outlets to the exterior at the peripheries of the port ring/valve ring. The embodiments in accord- ance with Fig. 8 is also distinguished from that of Fig.

2 in that the projections 132 are formed by separate flanged sleeves and in that the sealing rings 131 are of a type similar to "expanding piston rings" seated in peripherally extending grooves in the sleeves 132. In Fig. 8 components equivalent to those of the valve arrangement shown in Fig. 2 have received the same numeral references with the addition of 100.

The sleeves 132 have one cylindrical portion 132a and one flange portion 132b which is contiguous with portion 132a. The external face of the flange portion 132b is planar and a circumferentially extending groove 160 is formed therein, said groove communicating with the environment via a further groove 161 for the purpose of producing pressure relief of medium penetrating into the plane of separation between the rear face of the valve ring 128 and the flange 132b. The cylindrical portion 132a of the sleeves projects into a corresponding recess 133 formed in the hub 11, in order to immobilise and bring along the sleeves. To immobilise and bring along the valve ring 128 the latter is formed at its periphery with a number of recesses 133 and the hub is formed with a corresponding number of projections 134 intended, in the assembled condition of the valve system, to project into the recesses. Numeral reference 135 designates

pressure means formed with a sleeve-like portion 135a and a catch-like abutment portion 135b, said pressure means arranged, in accordance with the embodiment shown in the drawing, to be inserted in diametrically opposite posi- tions relative to the corresponding pressure sleeve 132 into corresponding depressions 136 formed in the hub. A compression spring 137 one end of which seats against the bottom of the recess 136 and the opposite end of which seats against an abutment formed in the sleeve-like por- tion of the pressure means 135 ends tends to maintain the pressure means pressed against the rear face of the flange 132b of the pressure-exerting sleeve and thus to keep the pressure-exerting sleeve pressed against the rear face of the valve ring 128, the latter in turn being kept pressed against the port ring 130. By means of the sealing rings 131 and owing to the abutment of the pressure-exerting sleeve against the rear face of the valve ring sealing is obtained between the ducts in the hub leading to the engine combustion chambers and the inlet/outlet apertures 126 in the valve ring The valve ring apertures 126 serve as a common inlet/outlet to and from, respectively, the associated combustion chamber. Each aperture 126 is encircled by an annular groove 138 formed in the valve ring slide face 137 and comprising an annular slide portion 139 formed between the aperture and the groove. In Figs 10a-g, numeral reference 140 designates a first groove and numeral reference 141 a second groove formed in that face of the port ring that is turned towards the valve ring.

In accordance with the shown example, both grooves 140, 141 extend the circumferential direction of the port ring, from the port ring inlet port 142 towards its outlet port 143. The spacing A between the grooves 140, 141 exceeds the diameter D of the valve ring apertures and preferably should coincide with the diameter D of the annular grooves formed in the valve ring. The positions of the two grooves 140, 141 radially differ from the area

of the valve ring apertures and preferably also from the port ring apertures in this direction; in other words the grooves preferably are formed in port ring portions that are void of apertures along the entire periphery.

In addition, the grooves 140, 141 are positioned to ensure that locally they coincide with the valve ring grooves 138, when the latter assume a position above an area of the port ring that is void of apertures (see Figs 10b and c). However, in accordance with the shown embodi- ment the grooves terminate sufficiently far ahead of the outlet port 143 to ensure that contact between the valve ring grooves and the port ring grooves ceases before the valve ring apertures reach the port valve outlet aperture (see Fig. 10c), i.e. at least at a distance F ahead of this aperture. The movable portion of the engine, and consequently the valve ring, move relative to the port ring in the direction which in Figs 10a-f is marked by an arrow 144.

The function of the grooves will be described in the following with reference to the schematic sequence of drawing figures 10a-f.

In Fig. 10a, the valve ring ports 126 assume a posi- tion above the port ring suction port 142, i.e. suction is in progress.

In Fig. 10b, port 126 has moved away from the suc- tion port 143. Consequently, the annular groove 138 has moved to a position above the area containing the grooves 140, 141 and coincides with these grooves locally at 145 and 146. Approximately in this position, medium penetrat- ing in between the slide faces will, when compression occurs, be redirected to the suction port 142 via the duct system 138; 140, 141 thus established. The same phenomenon occurs in the expansion-stroke position, Fig.

10c, and immediately prior to exhaust, the communication is interrupted via the duct system, Fig. 10d.

Fig. 10e shows a position for exhaust of consumed gas.

Fig. 10f shows a position wherein a negative pres- sure is built up inside the engine preparatory to another drawing-in phase. When the engine is formed with several cylinders suction into the next cylinder takes place simultaneously with compression and expansion in the preceding one. Consequently, a vacuum pressure is gene- rated in the duct system, which efficiently counteracts leakage to the environment.

The embodiment described above and illustrated in the drawing figures is intended to serve merely as a non- limiting example that may be varied as to its details within the scope of the appended claims without departing from the basic idea of the invention. For example, the number of grooves formed in the port ring could be larger or smaller or the grooves may have a different extension than that shown. Also the number of valve ring grooves could be larger and the groove extension other than cir- cular. In addition, the valve ring grooves may extend along only a part or parts of the associated valve ring aperture.

The invention should be regarded to embrace also configurations according to which the port ring grooves are open towards the outlet port instead of to the inlet port.