US2369245A - Internal-combustion engine - Google Patents

Description

A. c. NESFIELD INTERNAL-COMBUSTION ENGINE Filed Feb. 18, 1944 s Sheets-Sheet 1 Feb 13, '1945. A. c. NESFIELD 2,369,245

INTERNAL-COMBUSTION ENGINE- Filed Feb. 18, 1944 s'sheezs-sheet 2 I nue r Feb. 13,1945. c NESHELD 2,369,245

INTERNAL- COMBUSTION ENGINE Filed Feb. 18, 1944 s Sheets-Sheet 3 J I 44 Q 43 42 J g 38 r x I O l l F/G.4.

Patented Feb. 13, 1945 UNITED STATES INTERNAL-COMBUSTION ENGINE Albert Collinson Nesileld, mm London,

. England Application February is, 1944, sci-nine. 522,865

In Great Britain January 19, 1943 13 Claims.

This invention relates to control of the flow ofgases in internal combustion engines and more particularly to methods of and means for controlling the exhaust of internal combustion engines of the two-stroke cycle type. x

In such engines it may be necessary or.advisable to maintain a valve open to allow flow of gases for a very short period, for example, for a period comprising a small fraction. of a second. Owing to the inertia of valve members it has hitherto been impracticable to provide a satisfactorily operating controllable valve for this purpose.

The invention will be described hereinafter with reference to its application to-the control of the exhaust gases of an internal combustion engine of the two-stroke cycle type. In such engines the generally accepted theory of the condi-' tions which exist after the explosion of a charge within a cylinder and the opening of the exhaust ports is that there is a first period (hereinafter termed "first period) wherein a mass or body of burnt gase is discharged from the cylinder at very high speed and on issuance sets up in the cylinder 9, high partial or almost complete vacuum. This body of burntga'ses then undergoes a to and fromoveme'nt of high frequency out of and into the cylinder due to its impact with the ga mass in the exhaust conduit which produces within the cylinder alternate negative and positive pressure fluctuations. This period of pressure fluctuations is followed as the gases pass through the exhaust conduit by a second period of substantially continuous depression within the cylinder and this depression may be utilised, it an inlet valve is opened, to eil'ect the recharging of the cylinder. This latter depression is, however, somewhat less than the first initial depression created during the first period above-mentioned and if the exhaust port canbe closed immediately after the moment of. primary ejection of the exhaust gases occurring in the above-mentioned first period the higher depression then set up can be utilised more advantageously to recharge the cylin er.

Since t e time period during which the primary ejection of the exhaust gases in the socalled first period takes place may be of the order of 0.0l'to 0.001 second after the opening of the exhaust ports it is substantiall impossible to open and to close said ports within such a short period owing to' valve inertia. The present in ventlon may be applied to control the fiow of exhaust gases so that the exhaust period is or the relatively small duration above-mentioned.

One object of the-present invention is to provide an operative cycle for two-stroke cycle en-' gines which utilises the depression'of the abovementioned first period for cylinder charging pur- Another object of the invention is to provide an improved" valve arrangement adapted to effect exhaust cut-ofl' within'the time limits-of 0.01 to 0.001 second after opening of the exhaust valve 10 or port. Y

means for readily varying the'moment'of exhaust cut-oil in two-stroke cycle engines. 'if desired, automatically in accordance w'ithithe engine speed. s

In connection with, engines of the type hereinbefore referred to suggestions have been made to interpose a one-way acting flap valve in the exhaust conduit which shuts immediately on "reduction of pressure within the cylinder and provent the return flow of exhaust gases into the cylinder after the first period of exhaust. such valves are, however, impracticable in continuous operation and are-not positively controllable.- Other proposals have been to include positively driven rotary valves in the exhaust conduit in cases where the econd period of exhaust'fis being utilised for cylinder charging purposes. The term "main exhaust port'fiherein used is 30 intended to includea port or ports in the cylinder wallcovered and uncovered by the reciprocating piston itself or by a sleeve valve or port controlled by an externalpiston valve or by! rotary valve or by a valve of the poppet, type.

Further objects and advantages of my .inven tion'will be apparent from the following description' conslderedin coniunction with-the accompanying drawings which =form a ,p'artpof' this specification and s: ,which--&

Fig. 1 shows diagrammatically v of the invention toan internal'cembustionongine cylinder having its parts controlled gby a: recip- 'rocat gpistom. I. V:'-"

Fig. 2 shows in vertical section internal combustion engine incorporating the valve ole-'- ment according to the invention:

Fig. 3 is a section on the line m-rn or'm. 2-

through the exhaust valve cani shaft transmia-M sion; o N

Fig. 4 shows a speed responsive governor applied to-the-arrangement of Fig. 3; and

Fig. 5 is a diagram showing themoments oi opening and closing of the valves. in the improved two-stroke cycle.

Referring to the drawings. 1 shows dia- A further object of the invention is to provide the application 4 I grammatically an engine cylinder l containing a reciprocating piston II, a series of exhaust 1 ports I2 and a series of inlet ports IS. The exhaust ports i2'communicate with an exhaust conduit l4 and the inlet ports I3 communicate withan admission conduit l5.

Located within exhaust conduit |4 adjacent the ports I2 is a valve I6 of the poppet type which is controlled as to its closing movement b means of a spring ll and opened b means of a rocker arm I8 pivoted at l9 and controlled by'a cam 20. The cam 20 may, for example, be of the spiral type having a substantially radial face 2| to allow rapid closing of the valve under the influence of the spring II. To reduce friction a roller 22 is preferably mounted on the arm It so as to contact with the face of the cam 20.

In operation, after the explosion of the charge within the cylinder ill with the piston moving downwardly within the cylinder as shown in Fig. 1, the valve I is first opened so as to provide a free passage for'exhaust gases when the piston I later uncovers the ports [2. At a predetermined moment after the opening of the exhaust ports l2 the poppet valve I5 is closed by spring action owing to' the face 2| of the cam rotating opposite the roller 22 and substantially at the same instant exhaust valve it prevents any return surge of shaft 44; idler gear 42 inturn'meshes with the pinion 4| mounted on the cam shaft 40.

The device for adjusting the angular setting of the cam shaft comprises a bush 44 rotatable with the pinion 4| by key connections and also slidable axially relative'to the pinion 4|. The bush 44 carries on its inner periphery a pin (not visible in Fig. 3) which engages within a helical groove 46 formed in the outer peripheral surface of the reduced end 41 of the cam shaft 40. The arrangement is such that axial movement of the bush 44 varies the angular setting of the cam shaft 40 relatively to the-pinion 4| and thus relatively to the crank shaft 33 due to the interengagement of the pin on the inner face of the bush with the helical groove 46.

To eflect this axial movement of the bush 44 there is provided in the embodiment of Fig. 3 a

49 butnprevented from rotation by pins 5| 'on the collanengaging in a forked member 52 which pivots about a pin 53. The lower end 54 of mem-' gases passing back through "that portion of the 4 exhaust conduit denoted by 23 from entering the cylinder and maintains the depression within the cylinder, which at the moment ofopening of the inlet ports I3 is automatically recharged by the inrush of the explosive charge through the admission conduit. |5. On the closure of the inlet ports H3 at a suitable moment by means of the piston H on. its upward compression stroke, the

charge within the cylinder l0, due to its high velocity of entry, may be at a pressure above atmospheric.

Fig. 2 shows in vertical section a'practical embodiment of the invention. shown the cylinder i0 containing theq pi stonll' includes an exhaust port or ports l2fan exhaust conduit l4, an auxiliary poppet valve IS, a spring H, a rocker arm 3 and cam 20. In this embodiment an inlet port,30 in the cylinder head is controlled by an inlet valve 3! controlled as to closing by a spring 32 and opened by means of a rocker arm 33 pivoted about a pin 34 and actuated at its opposite end. 35 through a transmission rod 33 by a cam 31 mounted on a cam shaft 18 and rotated through suitable. gear transmission (not shown) from a gear 38 mounted on the crank shaft 33.

The cam 20 is mounted on a cam shaft 40 "which carries a pinion meshing withan idler gear 42 in turn meshing with the gear .33 mounted on the crank shaft. The arrangement of these gears is shown more particularly in Fig. 3.

Since the moment of closing of the exhaustpoppet valve I3 is of fundamental importance means ,are provided for adjusting the said moment of closing by adjustment of the angular 7 setting of the cam shaft 40 and cam 20. This 1 device is illustrated in Fig. 3 and shows the crank her 52, also'forked, engages in a groove 55 formed in the bush 44. By this means it is clear that rotation of the manipulating head 48 causes axial movement of the collar 50, which axial movement is transferred through the member 52, 54 pivoting about the pin 53 to the bush 44.

Th/ provision of this manual adjustment enables an extremely fine variation of the setting ,of thepcam 20 and thus a very fine variation of the moment of closing of the auxiliary poppet valve l3. This adjustment will normally take place while the engine is running so that the setting of the cam 20 may be'varied to suit the particular characteristics of the individual engine. I

Since obviously the timing of the opening of I the exhaust valve will vary with variations'in the an automatic control responsive to the speed of the engine instead of the manual adjustable member 43 above-mentioned. Such a device is shown 1 in Fig. 4 wherein the pinion 4| driving the cam shaft 40 through the bush 44 and helical groove governor denoted generally by 6|. Governor 5| comprises a plate 62 of curved form and a further plate 63 mounted for free rotation on a stub shaft 64. The governor GI, 62 carries a number of, in the illustrated embodiment six, balls 55 mounted in radially directed grooves in the plate 53 which is urged by a spring 66 towards the plate 52 so as to maintain the balls in contact with said plate 62. A lever 61 pivoting about a pin 68 has a forked end 59 engaging a groove lli formed in a boss on the rear face of the plate 83 and is provided with a projection H which engages within 4 52 sets up axial displacement of the plate 83 and through the lever 61 and projection 1| moves the bush 44 axially in response to the engine speed. Adjustment of the position of the axially movable bush 44 varies the angular displacement of the cam shaft '40 relatively to the crank shaft accord- This in turning to the speed of the engine. determines the moment of closing of the exhaust assume poppet valve It, thus obtaining maximum emciency of operation over a wide range of engine speed.

Since the cam shaft 18 carrying the cam I1 is preferably driven from the gear 38 mounted on cycle of the two-stroke cycle combustion engines hereinbefore described. Fig. shows the moments of opening and closing of the .exhaust and inlet valves with respect to crank shaft rotation. For example, the exhaust ports l2 may be opened at the point A in Fig. 5, approximately 120 after the top dead centre of the crank. The exhaust takes place during a period corresponding to a further crank rotation of approximately 30, at which point the auxiliary poppet valve I6 is closed as indicated by the point B. Substantially at this moment the inlet valve 31 (Fig. 2) is opened and the inlet valve is again closed when the crank shaft has reached its bottom dead centre position as indicated by the point C in Fig. 5. The inlet valve thus remains open during rotation of the crank shaft through about 30 but there may be a slight overlap in the periods during which the exhaust poppet valve l2 and the inlet valve 3| are open. That is to say, the inlet valve may. for example, be opened during the last 5of crank prevent a return surge of gases into the cylinder through said main exhaust port.

3. An internal combustion engine of the twostroke cycle type having a cylinder and an exhaust conduit which includes a main exhaust port controlling communication between said cylinder and said exhaust conduit, an auxiliary poppet valve located in said exhaust conduit adjacent said main exhaust port, means to open said main exhaust port, means to open said auxiliary popa pet valve operative prior to the opening of said main exhaust port, means to close said auxiliary poppet valve to cut off communication between shaft rotation, during which the exhaust poppet valve 16 remains open. In any case the inlet valve is not opened until the outflow of exhaust gases from the cylinder during the socalled first period of exhaust has substantially ceased.

While I have described and illustrated several embodiments of my invention it is to be understood that this is for the purpose of-illustration only and that the scope of my invention is not to be limited thereby but is to be determined by the appended claims.

What I claim is:

1. That improvement in the operative cycle of an internal combustion engine of the two-stroke cycle type which consists in controlling the commencement of the exhaust period by means of the normal exhaust ports, terminating the exhaust period substantially instantaneously by means of an auxiliary cam actuated spring loaded valve and opening an inlet valve substantially at the moment of closing of said auxiliary valve, when the flow of exhaust gases from the cylinder at the end of the so-called first period of exhaust has substantially ceased.

. 2. In an internal combustion engine of the two-stroke cycle type having an exhaust conduit and a main exhaust port providing communication between the engine cylinder and said conduit, the'method of controlling the outflow of exhaust gases which consists in opening a positively spring actuatedauxiliary valve'located in said exhaust conduit adjacent the main exhaust port after the explosion of the charge, subsequently opening said main exhaust port to allow ejection of burnt gases into said exhaust conduit and closing said auxiliary valve at the termination of the so-called first period of exhaust to said exhaust conduit and said cylinder and means responsive to the engine speed to vary the moment of closing of said p pp t valve.

4. An internalcombustion engine of the twostroke cycle type having a cylinder and an exhaust conduit which includesa main exhaust port controlling communication between said cylinder and said exhaust conduit, an auxiliary #095 pet valve located in said exhaust conduit adjacent.

said main exhaust port, means to open said main exhaust port, means to open said auxiliary poppet valve operative priorto the opening of said main exhaust port, means to close said auxiliary poppet valve to out of! communication between said exhaust conduit and said-cylinder, an inlet valve and means to open said inlet valve sub- I stantially at the moment of closing of 'said poppet valve. 1 I

5. An internal combustion engine of the two stroke cycle type having a cylinder and an exhaust conduit which includes a main exhaust port controlling communication between said cylinder and said exhaust conduit, an auxiliary poppet valve located in said exhaust conduit adjacent said main exhaust port,-a rotating shaft, a cam shaft having a helical groove therein, a cam mounted on said shaft and positively controlling the movement of said poppet valve, transmission means driving said cam shaft from said rotating shaft, a bush rotatable with and slidable axially relatively to said transmission, means, a

pin on said bush engaging in said helical groove and means to produce axial movement of said bush and thereby to vary the angular setting of said cam shaft and said cam. 6. An internal combustion engine of the'twostroke cycle type having a cylinder and an exhaust conduit which includes a main exhaust port controllingcommunication between said cylinder and said exhaust conduit, an auxiliary poppet valve located in said exhaust conduit adjacent said main exhaust port, means to open said main exhaust port, a rotating shaft, a cam shaft having a helical groove therein, a cammounted on said shaft and positively controlling the movement of said poppet valve, transmission means driving said cam shaft from said rotating shaft, a bush rotatable with and slidable axially relatively to said transmission means, a pin on said bush engaging in said helical groove and means responsive'to the engine speed to produce axial movement of said bush and thereby to vary the angular setting of said cam shaft and said cam according to the speed of the engine.

7; An internal combustion engine of the twostroke cycle type having a cylinder and an exhaust conduit which includes a main exhaust port' controlling communicationbetween said cylinder and said exhaust conduit, an auxiliary poppet valve located in said exhaust conduit adjacent said main exhaust port, means to open said main exhaust port, a rotating shaft, a cam shaft having a helical groove therein, a cam mounted on said shaft and positively controlling the movement of said poppet, valve, transmission means .driving said cam shaft from said rotating shaft,

a bush rotatable with and slidable axially relatively to said transmission means, a pin on said bush engaging in said helical groove, means to produce axial movement of said bush and thereby to vary the angular setting of said cam shaft and said cam, an inlet valve and means to open said inlet valve substantially at the moment of closing of said poppet valve.

8. An internal combustion engine of the twostroke cycle type having a cylinderand an exhaust conduit which includes a main exhaust port controlling communication between said cylinder and said exhaust conduit, an auxiliary poppet valve located in said exhaust conduit adjacent said main exhaust port, means to open said main exhaust port, arotating shaft, a cam shaft having a helical groove therein, a cam mounted on said shaft and positively controlling the movement of said poppet valve, transmission means driving said cam shaft from said rotating shaft, a bush rotatable with and slidable of closing of said poppet valve, and means to vary the moment of opening of said inlet valve.

10. An internal combustion engineof the twostroke cycle type having acylinder and an exhaust conduit which includes a main exhaust port controlling communication between said cylinder and said exhaust conduit, an auxiliary 7 said bush engaging in said helical groove and a speed responsive governor producing axial movement of said bush and thereby varying the anaxially relatively to said transmission means, a

I haust conduit which includes a main exhaustport controlling communication between said cylinderand said exhaust conduit, an auxiliary poppet valve located in said exhaust conduit adjacent said main exhaust port, means to open said main exhaust port, a rotating shaft, a cam shaft having a helical groove therein, a cam mounted on said shaft andpositively controlling the movement of said'poppet valve, transmission means driving said cam shaft from said rotating shaft, a bush rotatable with-and slidable axially relatively to said transmission means, a pin ;on' said bush engaging in said helical groove, means to produce axial movement of said bush and thereby to vary the angular setting of said cam shaft and said cam, an inlet valve, means to open said inlet valve substantially at the moment gular setting of said cam shaft and said cam.

11. That improvement in the .operative cycle of an internal combustion engine of the twostroke cycle type which consists in controlling the commencement of the exhaust period by means of the normal exhaust ports, terminating the exhaust period by means of an auxiliary spring controlled, valve and opening .an inlet valve substantially at the moment of closing of said auxiliary valve, when the flow of exhaust gases from the cylinder at the end of the socalled first period of exhausthas substantially ceased.

12. 'An internal combustion engine of the twostroke cycle type which includes a main exhaust port and an auxiliary spring-actuated valve arranged in seriesin the path of fiow of the exhaust gases and cam means. cooperating with said actuating spring to provide approximate instantaneous closing of said auxiliary valve by said spring substantially at the instant of termination of the so-called first period of exhaust.

13. An internal combustion engine of the twostroke cycle type which includes a main exhaust port and an auxiliary spring-actuated valve arranged in series in the path of fiow of the ex-' haust gases, cam means cooperating with said actuating spring to provide approximate instan taneous closing of said auxiliary valve by said spring substantially at the instant of termination of the so-called first. period of exhaust and means for varying the moment. of closing of said auxiliary valve. I

ALBERT coLLINsoN NESFIELD.

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