Internal combustion engine

Abstract: The present invention relates to an internal combustion engine having a check valve in the induction system upstream of the intake valve controlling the intake port for communicating the induction system to the combustion chamber of the engine. Moreover, means are provided for forming a plenum chamber volume communicating with an intake passage of the induction system between said check valve and the intake valve downstream of the check valve after the intake valves closes the intake port. In this way, additional charging of the engine and use of an inertia flow of intake air can be obtained.

Description: This invention relates to an internal combustion engine according to the preamble part of claim 1. In many types of engines, the induction system includes, in addition the normal port control which communicates the intake passage with the combustion chamber, a check valve that is positioned upstream of the port control and which precludes reverse flow through the induction system. This type of arrangement is commonly used in 2-cycle engines, but also may be employed in four-cycle engines to achieve some of the same purposes. That is, in a 2-cycle engine, the port control of the intake port is achieved by the movement of the piston relative to the port. In a four-cycle engine, as is well known, the intake port is controlled by a valve that is operated in timed sequence with the engine crankshaft. However, with either type of engine, the use of a check valve may provide additional advantages in charging efficiencies because of its ability to preclude reverse flow. Although the use of the check valves provides improved induction efficiency under some conditions, the resistance of the check valve to opening movement can, in some instances, restrict flow. Also, there is inertia in the intake system which must be overcome each time the check valve opens and closes and, thus, the air flow may be delayed from the time when the intake port is actually open. An example for such an internal combustion engine is disclosed in the Japanese patent application JP-A-61 200326. This engine uses its crankcase to create a super charging, but still does not solve the problem of reducing delay by offering a way to keep the valve open. Regarding crankcase compression and ventilation systems, it is well known that blow-by crankcase ventilation gases tend to accumulate in the crankcase chamber. Systems have been provided for ventilating the crankcase chamber so as to avoid the build-up of these objectionable products in the crankcase chamber. This is desirable to ensure against oil contamination and also to ensure adequate ventilation for the engine. However, these crankcase ventilation gases and blow-by gases should not be discharged directly to the atmosphere. There have been proposed, therefore, crankcase ventilating systems wherein the crankcase ventilating gases are delivered to the engine induction system as it is disclosed, for example, by the US-A-4,991,547. In this way, hydrocarbons and other objectionable crankcase ventilating gas components can be purified by combustion in the combustion chamber before they are discharged to the atmosphere. Frequently, the crankcase ventilation system delivers the crankcase ventilating gases to the induction system of the engine. Normally this is done at point upstream of the throttle valve and frequently into the air cleaner of the engine. However, this results in the possible discharge of crankcase gases to the atmosphere under at least some running conditions. Accordingly, it is an objective of the present invention to provide an improved internal combustion engine having an improved induction system being able to improve charging efficiency of the engine, while at the same time providing an easy way of accomplishing crankcase ventilation, without letting the crankcase ventilating gases escape directly into the atmosphere. According to the present invention the aforeindicated objective performed by the features of claim 1. Further advantages of the invention are described by the subclaims. The effects and features of the invention will become more apparent from the following detailed description of the preferred embodiments, when read with reference to the accompanying drawings, wherin Figure 1 is a partially schematic cross-sectional view taken through a single cylinder of an internal combustion engine for demonstrating a first working statute of the engine; Figure 2 is a partially schematic cross-sectional view, in part similar to Figure 1 for demonstrating a second working state of the engine; Figure 3 is a partially schematic cross-sectional view, in part similar to Figures 1 and 2, showing preferred embodiment of the invention; Figure 4 is a view, in part similar to Figure 3 but on a smaller scale, and shows a first-running condition; Figure 5 is a view, in part similar to Figures 3 and 4 taken on the scale as Figure 4 and shows another running condition of the engine; Figure 6 is a schematic block diagram showing how the various elements of the engine are employed for controlling the control valve; Figure 7 is a graphical view showing how the intake valve timing may be varied to achieve certain results in accordance with additional embodiments of the invention; Figure 8 is a partially schematic cross-sectional view, in part similar to Figures 3 through 5, and shows yet another embodiment of the invention; and Figure 9 is a partially schematic cross-sectional view, in part similar to Figures 3 through 5, and 8, and shows a further embodiment of the invention. As should be apparent from the foregoing description, the invention has particular utility in conjunction with internal combustion engines of either of the two or four cycle type. However, for reasons which will become apparent, the invention has specific utility in conjunction with four-cycle engines and, for that reason, all of the embodiments illustrated show such four-cycle engines. It will be readily apparent, however, to those skilled in the art how certain facets of the invention may be employed with 2-cycle engines. Also, since the invention deals primarily with the induction system and the control for the induction system, the actual components of the engine have been shown, for the most part, schematically. This is because, except for those features of the induction system which will be described in detail, the invention can be utilized in conjunction with any of the wide variety of types of engines. For the same reason, only a single cylinder of the engine has been illustrated in each embodiment. Those skilled in the art will readily understand how the invention can be employed in conjunction with multiple cylinder engines. In addition, although the invention is described in conjunction with a reciprocating engine, certain features may also be employed with other types of engines, such as rotary engines. However, the invention is primarily useful in conjunction with engines which operate on a fixed cycle, such as two or four cycle engines and wherein the flow through the intake passage is not continuous during a single cycle of operation. Referring first to Figure 1, an example of an internal combustion engine is identified generally by the reference numeral 11. For the reasons aforenoted most, if not all, of the components of the engine 11 are shown schematically. The engine 11 is comprised of a cylinder block 12 in which one or more cylinder bores 13 are formed. Pistons 14 reciprocate in each cylinder bore 13. The pistons 14 are connected by means of connecting rods 15 to a crankshaft 16. The crankshaft 16 rotates in a crankcase chamber defined by a crankcase member 17 that is affixed to the cylinder block 12 and by the skirt of the cylinder block. A cylinder head assembly, indicated generally by the reference numeral 18, is affixed to the cylinder block 12 on the side opposite the crankcase chamber 17. The cylinder head 18 has a recess which cooperates with the cylinder bore 13 and the head of the piston 14 to form a variable volume chamber 19 which comprises the combustion chamber of the engine. The clearance volume at top dead center is defined primarily by the recesses in the cylinder head 18, as is well known in this art. The cylinder head 18 is provided with one or more intake passage 21 each of which serves the combustion chamber 19 through a respected intake valve seat 22. An induction system, indicated generally by the reference numeral 23, serves the intake ports 22 in a manner which will be described. A poppet-type intake valve 24 is supported in the cylinder head assembly 18 and cooperates with each intake port 22 for controlling the flow through it. As is well known in this art, the intake valves 24 are operated by any known type of valve actuating mechanism which opens and closes the intake valves 24 in timed sequence with the rotation of the crankshaft 16. An overhead camshaft and associated follower system may serve this function. Exhaust passages 25 are formed in the cylinder head 18 on the side of the combustion chambers opposite the intake passages 21. These exhaust passages 25 have exhaust ports that are controlled by poppet-type exhaust valves 26 in a known manner. The specific number of exhaust passages 25 and exhaust valves 26 for each cylinder may be varied, as is known in the art. One or more spark plugs (not shown) are mounted in the cylinder head 18 and fire the charge which is admitted to the combustion chambers 19 by the induction system 23. This burnt charge is then discharged through the exhaust passages 25. Referring now specifically to the induction system 23, it is comprised of an air inlet device 27 which has an atmospheric air inlet 28 into which atmospheric air is inducted. The air inlet device 27 may provide a silencing and plenum chamber function. In addition, an air filter element (not shown) may be positioned in the air inlet device 27 for filtering the inducted air. The air that has passed through the air inlet device 27 and its filter, if any, is delivered to an intake passage arrangement, indicated generally by the reference numeral 29 which forms a continuation of the cylinder head intake passage 21. These components thus, provide communication between the atmospheric air inlet 28 and the combustion chambers 19. A charge former in the form of a carburetor 31 may be positioned in the induction passage 29 downstream of the air inlet device 27. In this exemplified engine, the charge former 31 is a sliding piston-type carburetor having a sliding throttle piston 32. Downstream of the charge former 31, a valve chamber 33 is provided in which a reed-type check valve 34 is provided. The reed-type check valve 34 permits flow through the induction passage when the intake valve 24 is open and the pressure downstream of the reed-type check valve 34 is below the pressure upstream of this valve. However, if the pressure reverses, the reed-type check valve 34 will preclude reverse flow. From the foregoing description of an exemplified engine, it should be readily apparent that, when the intake valves 24 close, the air flow through the induction passage 29 will be abruptly halted and the reed-type check valve 34 will close. Hence, the flow inertia is discontinued and must be reestablished when the intake valves 24 are next open. This also requires a pressure difference across the reed-type check valves 34 and, thus, there will be some restriction to initial air flow. This adversely effects charging deficiency. Therefore, there is provided a plenum chamber which communicates with the valve chamber 33 or the intake passage 29 downstream of the check valve 34. In this example, this plenum chamber is formed by a crankcase chamber 35 in which the crankshaft 16 rotates. This crankcase 35 is communicated with the valve chamber 33 downstream of the valve element 34 by means of a communicating passageway 36. With this arrangement, when the intake valve 24 closes, the piston 14 will have passed its bottom dead center position and be moving upwardly. Therefore, the volume of the crankcase chamber 35 will be increasing and a flow will continue through the reed-type valve 34, but will pass through the passage 36 and into the crankcase chamber 35 rather than into the combustion chamber 19. Hence, the inertial effect will maintain the reed-type check valve 34 open and this will reduce the load necessary to fully open the reed-type check valve 34 the next time the intake valve 24 opens. As a result, charging efficiency will be substantially increased. Figure 2 shows another example of an engine that differs from the engine of Figure 1 only in the way in which the plenum chamber for the intake charging efficiency improvement is formed. For that reason, components of this engine which are the same as the previously described engine have been identified by the same reference numerals and will not be described again, except insofar as is necessary to understand the construction and operation of this exemplified engine. A separate plenum chamber, indicated generally by the reference numeral 51 is provided with which the conduit 36 communicates. Hence, when the intake valve 24 closes, the inertial effect of the air flowing through the reed-type check valve 34 will continue and the air will flow through the conduit 36 into the plenum chamber 51. As a result, the advantages previously described will be enjoyed. That is, the inertial flow can continue and charging efficiency improved. However, the volume of the plenum chamber 51 is fixed rather than expanding as would the crankcase chamber 35 of the previously described engine. The volume of the plenum chamber 51 is, however, made large enough so as to ensure that the continued air flow will occur. Figures 3 through 6 show a preferred embodiment of the invention which has a similar engine construction as the previously described ones. Therefore, components which have been explained when describing the engines shown in Figures 1 and 2 have been identified by the same reference numerals. In the first inventive embodiment, the valve chamber 33 communicates with a branch passageway 101 of a communication system, indicated generally by the reference numeral 102. The branch passage way 101 terminates at a control valve 103 which selectively communicates the passageway 101 with either the plenum chamber volume 51 through a first branch passageway 104 or with the crankcase chamber 35 through a second branch passageway 105. In addition, the valve 103 selectively communicates either the crankcase chamber 35 or the plenum chamber 51 with atmospheric air pressure through a further branch passage way 106. The branch passageway 106 communicates either directly through atmospheric air inlet or, more preferably, with the intake device 27. If the intake device 27 includes a filter element, the branch passageway 106 preferably communicates with the air inlet device 27 downstream of the filter element of the air inlet device 27. Figure 4 shows the condition of the valve 103 under a certain running condition when the crankcase chamber 35 communicates with the induction system. Under this condition, the plenum chamber 51 is communicated with the air inlet device 27 through the branch passageway 106 so that in can be recharged with fresh air. As will be described later, this position of the control valve 103 may be set under low speed and mid-range performance in some embodiments and under high speed conditions in other embodiments. When the valve 103 is in this position, the flow continuation during the time when the intake valve 24 is closed will be achieved and also the supercharging effect, afore referred to will be enjoyed. Thus, when the valve 103 is in this position, the engine operates similar to the example-engine of Figure 1. In addition, when the control valve 103 is in the position shown in Figure 4, the crankcase ventilating gases from the crankcase chamber 35 may be discharged into the combustion chambers 19 through the induction system 29. Hence, emission control is also achieved. When the control valve 103 is in the position shown in Figure 5, then the plenum chamber 51 will serve a function which is similar to the example-engine of Figure 2. In this position, however, the crankcase chamber 35 will communicate with the air inlet device 27 downstream of the filter element, if one is provided. Therefore, crankcase ventilation is possible with the crankcase ventilating gases being delivered to the induction system 29 as shown by the arrow in this figure. Thus, by utilizing che control valve 103, it is possible to ensure good crankcase ventilation under all conditions and without the exhaust from the crankcase passing to the atmosphere regardless of the position of the control valve 103. In addition, the advantages of maintaining airflow and reducing inertial affects in the induction system are also obtained. Although any of a variety of control strategies may be employed for the control valve 103, Figure 6 shows one type of arrangement. In this arrangement the control valve 103 is operated by a servomotor, indicated schematically at 107. The servomotor 107 is, in turn, controlled by a controller or CPU 108. This controller 108 receives certain signals indicative of engine running conditions or operator demand. These signals may comprise an engine speed signal 109 derived from a pulser coil or the like associated with the crankshaft 16. In addition, a throttle position sensor 111 may be provided that cooperates with the throttle piston 32 to provide a signal indicative of operator demand or load. As has been noted, the communication with the crankcase chamber 35 of the induction system 29 through the appropriate positioning of the control valve 103 has the effect of not only improving the flow through the induction system, but also obtaining a supercharging effect. Under low and medium engine speeds and/or loads, the actual flow through the intake passage 29 is not as large, and hence, the increase in volume of the crankcase chamber 35 during this cycle improves the charging efficiency by in effect holding the reed valve 34 open for a longer time period. In addition, there will be a supercharging effect, as aforenoted, that will improve performance under these running conditions. Under high-speed, high-load conditions, however, the added supercharging effect may produce high engine temperatures and knocking. Hence, by shifting the valve 103 to the position shown in Figure 5 under this running condition, the supercharging effect will be eliminated, and knocking can be reduced. However, since the air flow velocity is higher under this condition, then the charging efficiency will still be improved merely by the use of the plenum chamber 51. Thus, one way in which the system may be employed is to maintain the valve 103 in its Figure 4 condition under low and mid-range running conditions and moving the valve to its Figure 5 position under high-speed, high-load conditions. This can be accomplished in response to either of the outputs of the engine speed sensor 109 and/or the throttle position sensor 111. By the use of the system shown in Figures 3-6, it is also possible to obtain still further performance advantages with this system if the intake valve closing is delayed from that normally used with engines having conventional induction systems. Figure 7 shows several examples of how this may be accomplished. The standard valve timing for opening and closing of the intake valve in response to crank angle is shown in this figure. It will be seen that the intake valve opens approximately 40° before top dead center and closes at approximately at 210° of crankshaft rotation or about 30° after bottom dead center in engines having conventional induction systems. By using the induction systems embodying this invention it is possible to obtain even greater performance by delaying the closing of the intake valve to a point 40 or more degrees after bottom dead center, as shown by the curves A, B, or C, with the respective intervals being 80°, 100°, or 120° after bottom dead center.When this is done, the actual compression ratio is reduced. However, since the system can employ the crankcase as a supercharger, it is thus possible to not only increase the power, but also to reduce the likelihood of knocking. In addition, this permits the engine to have a large expansion ratio and high performance without the deleterious effects of knocking or the like. This is accomplished by keeping the valve 103 in its Figure 5 position under low and mid-range running and in its Figure 4 position at high speeds and loads, so as to improve charging efficiency. Then the intake valve operating mechanism is set to delay the intake valve closing to a period at 30° to 80° after bottom dead centre, preferably to 70° or 80°. When this is done and under high speed conditions, the supercharging effect will offset the loss in compression ratio, and the expansion ratio can be maintained large. Thus, good power can be achieved without knocking. The actual delay in the closing of the intake valve and the operation of the control valve 103 can be utilized to obtain the desired type of engine performance. In the embodiments as thus far described, the charge former in the form of the carburetor 31 has been disposed upstream of the reed-type check valve 34. The invention may, however, also be practiced in conjunction with arrangements wherein the charge former is positioned downstream of the check valve 34. Figure 8 shows such an arrangement, and except for this location, this construction is the same as the embodiments of Figures 3-6. Therefore, like components have been identified by the same reference numerals and will not be described again. In this embodiment the charge former or carburetor 31 is disposed between the valve chamber 33 and the engine intake valves 24. The communicating passage 101, which serves the control valve 103, is still fed off of the valve chamber 33, and thus is now upstream of the charge former 31, rather than downstream of it in the previously described embodiments. Figure 9 shows another embodiment which, as noted, differs from that of Figures 3-6 and Figure 8 only in the relative positions of the charge former 31 and the communicating conduit 101. In this embodiment the charge former 32 is again downstream of the check valve 34. However, the communicating passageway 101 is interconnected with the induction passage 29 downstream of the charge former 31. In all embodiments thus far described, he charge former 31 has been a carburetor and specifically a carburetor of the sliding-piston type. It should be readily apparent to those skilled in the art that the invention may be employed in conjunction with other types of carburetors. In addition, the invention may be equally practiced with engines having fuel injection of either the manifold or direct type. If manifold injection is employed, the fuel may be injected either in the position shown in the embodiments of Figures 3-6 or the position shown in the embodiments of Figures 8 and 9. That is, fuel may be injected either upstream of the check valve 34 or downstream of it. The communicating passage 101 may be disposed either upstream or downstream of the point of fuel injection if the fuel injector injects downstream of the check valve 34.

Claims: An internal combustion engine (11) having a combustion chamber (19), an induction system (23) for delivering a charge to said combustion chamber (19), said induction system (23) comprising an inlet device (27) with an atmospheric air inlet (28), an intake passage (21) terminating at an intake port (22) communicating with said combustion chamber (19), control means (24) for sequentially opening and closing said intake port (22) during a cycle of operation of said engine, a check valve (34) in said intake passage (21) upstream of said control means (24) for permitting flow through said intake passage (21) to said combustion chamber (19) and precluding reverse flow through said intake passage (21), means for forming two plenum chamber volumes communicating with said intake passage (21) between said check valve (34) and said control means (24), therein a first plenum chamber volume being formed by a crank case chamber (17) in which a crankshaft (16) of the engine (11) rotates, and a further plenum chamber volume (51) being formed independently from said first plenum chamber volume, characterized by a control valve (103) which is movable between a first position, connecting said intake passage (21) downstream of the check valve (34) with said first plenum chamber volume (17) and at the same time said intake passage (21) upstream of the check valve (34) with said further plenum chamber (51), and a second position, connecting said intake passage (21) downstream of the check valve (34) with said further plenum chamber volume (51) and at the same time said intake passage (21) upstream of the check valve with said first plenum chamber volume (17). An internal combustion engine as claimed in claim 1, characterized in that said control valve (103) is connected to said inlet device (27). An internal combustion engine as claimed in claim 1 or 2, characterized in that additional air is drawn via said intake passage (21) through said check valve (34) into the crankcase chamber (17) after the intake valve (24) is closed for creating a supercharging effect to the intake charge. An intemal combustion engine as claimed in claims 1 or 2, characterized in that additional air is drawn via said intake passage (21) through said check valve (34) into said further plenum chamber (51) after the intake valve (24) is closed. An internal combustion engine as claimed in at least one of the claims 1 to 4, characterized in that the further plenum chamber (51) is a closed plenum chamber. An internal combustion engine as claimed in at least one of the preceding claims 1 through 5, characterized in that the control valve (103) is controlled in response to the engine running conditions. An internal combustion engine as claimed in claim 6, characterized in that the control valve (103) is positioned in its first position under low and mid range engine speeds and loads, and in its second position under high speed engine speeds and loads. An internal combustion engine as claimed in claim 6 or 7, characterized in that the closing of the intake valve (24) is delayed. An internal combustion engine as claimed in claim 8, characterized in that the intake valve (24) is not closed until more than 40° after bottom dead centre. An internal combustion engine as claimed in claim 9, characterized in that the intake valve (24) is closed in the range of about 70 to 80° after bottom dead centre. An intemal combustion engine as claimed in claim 6, characterized in that the control valve (103) is positioned in its first position under a high engine speeds and loads and in its second position under low and mid range engine speeds and loads, and the intake valve (24) is closed in the range of about 30 to 80° after bottom dead centre. An internal combustion engine as claimed in at least one of the preceding claims 1 to 11, characterized by a charge former (31) for supplying a fuel air mixture to the intake passage (21) positioned upstream of the check valve (34). An internal combustion engine as claimed in at least one of the preceding claims 1 to 11, characterized by a charge former (31) for supplying a fuel air mixture to the intake passage (21) downstream of the check valve (34). An internal combustion engine as claimed in at least one of the preceding claims 1 to 11, characterized by a fuel injector as charge former (31) for supplying a fuel to the intake passage (21) downstream of the check valve (34).

Inventors: FUJIWARA SHUNZO, TAUE JUN, FUJIWARA, SHUNZO, TAUE, JUN
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1995
Main classification: F02B29
IPC codes: F02B29, F02M25, F02B33, F02B75