JP4030134B2 - Combustion control device for spark ignition type 2-cycle engine - Google Patents

Description

[0002]
[Prior art]
An exhaust port and a scavenging port that are opened and closed by a piston are formed on the inner peripheral surface of the cylinder hole, fresh air preloaded in the crank chamber is sent from the scavenging port to the cylinder chamber, and burned gas is discharged from the exhaust port. In a spark ignition type two-cycle engine in which compressed fresh air is ignited by a spark plug, irregular combustion is likely to occur due to misfiring in a low and medium load range. As a result, abnormal engine vibration or unburned in exhaust gas occurs. Problems such as an increase in the amount of hydrocarbons and an increase in fuel consumption occur.
[0003]
Conventionally, active hot atmosphere combustion has been proposed as a method of solving this problem. This active thermal atmosphere combustion is good even in low load areas by activating fresh air in the combustion chamber with the thermal energy contained in the residual gas of the previous cycle, making it very easy to ignite, and self-igniting at the end of compression To get a good combustion.
[0004]
For example, Japanese Patent Publication No. 56-38766 discloses a spark ignition type two-cycle engine using the combustion in the active hot atmosphere. In this engine, fresh air is flowed at a high speed in a scavenging passage to form a liquid. The gas phase in the contact area between the fresh air in the combustion chamber and the residual burned gas is obtained by sufficiently evaporating the fuel and then decelerating the new air flow to a large extent and flowing the fresh air into the combustion chamber at a low speed. Generate radicals in it.
[0005]
  The activated heat atmosphere thus generated is maintained until the end of the compression stroke, and self-ignition is performed regardless of the spark plug. In order to maintain the active heat atmosphere until the end of the compression stroke, the residual burned gas in the combustion chamber In order to prevent the sudden ejection of exhaust gas from the exhaust hole and the exhaust pulsation interference that cause the turbulence and flow,Butterfly typeAn exhaust control valve is disposed in the exhaust passage.
[0006]
This exhaust control valve is provided to reduce the turbulence and flow of the residual burned gas during low load operation where active hot atmosphere combustion is performed, so that the opening area portion of the throttle valve is reduced to 30%. The valve is gradually opened until the valve reaches the throttle valve opening degree, and when the throttle valve opening is higher than that and the engine is in a high load operation state, the valve is kept fully open. Therefore, when the engine is used only in a low load operation state, the exhaust control valve can be replaced by a throttle having a certain throttle area.
[0007]
On the other hand, in the spark ignition type two-cycle engine, since a part of the fresh air is blown out from the exhaust port after the scavenging port is closed and the exhaust port is closed during the piston ascending stroke, The exhaust port is provided with an exhaust control valve so that the upper part of the exhaust port is closed during low-speed operation of the engine, and the exhaust port is fully opened during medium-high speed operation. Changing has been done in the past.
[0008]
As such an exhaust control valve, in Japanese Utility Model Publication No. 56-54336, a barrel portion is formed in a substantially drum shape so as to form a concave arc shape along the inner peripheral wall of the cylinder, and the surface of the barrel portion is made as exhaust as possible ( A rotation control valve installed close to the exhaust port) is shown. The surface of the body of the control valve functions substantially as the upper edge of the exhaust port, and the body is surrounded so as to have substantially the same shape as the wall surface of the exhaust passage when the control valve is fully opened.
[0009]
Japanese Patent Laid-Open No. Sho 62-23523 is provided at the upper part of a scavenging passage that extends outward from an exhaust port that opens to the inner surface of a cylinder, and is swingably supported by a shaft that is disposed perpendicular to the cylinder axis. An exhaust control valve is shown in which a control surface that is formed with substantially the same curvature as the inner surface of the cylinder and is aligned with the inner surface of the cylinder is provided at the swinging tip of the valve body. A recess is provided in the upper part of the exhaust passage to accommodate the valve element when the exhaust port is fully open.
[0010]
Similarly, Japanese Patent Laid-Open No. 3-33426 also discloses an exhaust control valve having a control surface (flow blocking cover) provided at the swinging tip of a valve body (main body) swingably supported in an exhaust passage. Although shown in the publication, the control surface has a flexible sheet shape and is accommodated in a slot-like cavity provided on the upper wall of the exhaust passage.
[0011]
FIGS. 7 and 8 of the same publication show that a housing is provided in the exhaust passage, and the slot-like cavity is formed by a gap between the outer surface of the upper wall of the housing and the inner surface of the upper wall of the exhaust passage. ing. The housing is installed in the exhaust passage with its both side walls in contact with both side walls of the exhaust passage, and the valve body for swinging the control surface is arranged on the inner side of the exhaust passage along the inner surface of the housing side wall. It is installed.
[0012]
[Problems to be solved]
By the way, in the spark ignition type two-cycle engine using the above-described active heat atmosphere combustion, the ignition timing is positively controlled without controlling the opening degree of the exhaust control valve or the scavenging control valve in accordance with the operating state of the engine. Therefore, there is a concern about detonation phenomenon associated with pre-ignition, and it has not yet been sufficiently industrially used.
[0013]
In the active heat atmosphere combustion, the ignition timing is determined by the cylinder pressure and the cylinder temperature at the initial stage of compression, and a self-control system is provided in which the gas temperature at the end of combustion started by ignition is fed back as the cylinder temperature. When the system converges and the ignition timing converges within a certain range, the active hot atmosphere combustion is sustained and stabilized.
[0014]
However, in order to obtain various performances such as good fuel consumption, exhaust emission, rotational stability, and engine durability in an engine that is burned in an active hot atmosphere, it is necessary only to maintain the active hot atmosphere combustion, that is, to converge the system. Control of the ignition timing becomes important as in the case of a normal spark ignition engine.
[0015]
The conventional active heat atmosphere combustion engine causes the active heat atmosphere combustion by converging the system by changing the pressure in the cylinder as a result by an exhaust control valve or the like. It has not come to control. Therefore, for example, if the device is set to give the optimum cylinder pressure during low-speed and low-load operation, it will become an active heat atmosphere combustion with pre-ignition during high-speed and medium-load operation, resulting in engine durability, exhaust emission, fuel consumption, etc. Will have a significant adverse effect on
[0016]
Next, since the operation member is located in the exhaust passage in any of the conventional exhaust control valves, the cross-sectional shape or the inner surface shape of the exhaust passage is a predetermined shape determined in terms of performance by the presence of these operation members. In addition, it is changed by the operation of the operating member, which causes a decrease in output.
[0017]
Therefore, the present invention always ensures an optimal ignition timing during combustion in the active heat atmosphere, thereby reducing the fuel consumption and exhaust emission of the active heat atmosphere combustion engine and avoiding the occurrence of abnormal combustion such as detonation by premature ignition. Further, the engine performance is further improved by using an exhaust control valve that can accurately control the exhaust without lowering the output.
[0018]
[Means and Actions for Solving the Problems]
  The present invention relates to an improvement of a spark ignition type two-cycle engine that overcomes such difficulties, and combustion control of a spark ignition type two cycle engine in which fresh air in a combustion chamber is combusted by self-ignition at least during low load operation. In the device, the exhaust control valve provided in the exhaust passage and capable of substantially fully closing the exhaust passage, and the exhaust control valve is driven to an exhaust opening ratio corresponding to at least the engine speed and the throttle valve opening, and the piston is raised Drive control means for controlling the pressure in the cylinder at the time,The exhaust control valve is provided with a rotating shaft extending perpendicularly to the cylinder axis and a valve body pivotally supported by the rotating shaft in an exhaust passage extending from an exhaust port that opens to the inner peripheral surface of the cylinder hole. The valve body is configured to change the height of the upper edge of the exhaust port, and the valve body substantially extends along the cylinder curvature of the exhaust port and is wider than the entire width of the exhaust port. , Formed of a thin shell member comprising a swinging arm portion connecting at least one side portion of the exhaust control portion and the rotating shaft,5% <intake ratio <40%, 20% ≦ scavenging efficiency ≦ 70%, and the exhaust control valve is controlled so that the compression start pressure falls within a predetermined range.
[0019]
Since the present invention is configured as described above, the exhaust opening by the piston is driven at least in the low load operation region by driving the exhaust control valve at an exhaust opening ratio corresponding to the engine speed and the throttle valve opening. It is possible to appropriately control the pressure in the cylinder at the time of closing and to self-ignite fresh air in the combustion chamber at an ignition timing preferable for engine operation.
[0020]
The combustion in which the active thermal atmosphere combustion is performed by positively controlling the ignition timing preferable for engine operation in this way is hereinafter referred to as AR combustion.
[0021]
As described above, in the active hot atmosphere combustion, the ignition timing is determined by the cylinder pressure and the cylinder temperature at the initial stage of compression, but the cylinder pressure depends on the state of the cylinder gas, and even if the ignition timing converges. Even if the combustion in the active heat atmosphere is continued, the pressure in the cylinder changes if the state of the gas in the cylinder changes, and therefore the ignition timing also changes and premature ignition or the like occurs. However, in the present invention, the exhaust opening ratio is controlled according to the engine speed and the throttle valve opening, so that the cylinder pressure at the initial stage of compression gives the optimal ignition timing according to the state of the cylinder gas. Controlled by pressure.
[0022]
In other words, the cylinder pressure is controlled by setting the exhaust control valve to a predetermined exhaust opening ratio based on a preset control map for AR combustion.
[0024]
  Therefore, in the present invention, at least the engine speed and the throttle valve opening are selected as factors representing the state of the in-cylinder gas, and the above-described exhaust opening ratio is determined according to each combination of these factors. Is used.
  Further, since the valve body is formed of a thin shell member and the exhaust control part of the valve body can be moved up and down at a position sufficiently close to the exhaust port, the exhaust timing can be accurately controlled.
[0025]
  According to another invention,A storage recess for storing the entire valve body is formed in the cylinder block in which the exhaust passage is formed, and a swing arm portion of the valve body is always stored in the storage recess.
[0026]
According to the present invention, the swing arm portion of the valve body is always housed in the housing recess communicating with the exhaust passage only in the operation region of the exhaust control portion, and the shape of the exhaust passage is influenced by the installation and operation of the valve body. Since this is not done, output reduction can be prevented.
[0028]
【Example】
Hereinafter, in describing a preferred embodiment of the present invention, the structure of an exhaust control valve will be described first.
[0029]
FIG. 1 is a side view of a motorcycle spark ignition type two-cycle engine 1 equipped with an exhaust control valve according to the present invention, with its cylinder section taken longitudinally. 2 is a crankcase, 3 is a cylinder block, 4 is a cylinder Head. A scavenging port 6 and an exhaust port 7 are opened on the inner peripheral surface of the cylinder hole 5 formed in the cylinder block 3, and are opened and closed by a piston 8 that slides up and down in the cylinder hole 5. 9 is a connecting rod, and 10 is a crankpin.
[0030]
New air sucked into the crankcase 2 from the intake port 11 during the upward stroke of the piston 8 is compressed during the downward stroke, and is sent to the cylinder chamber above the piston 8 via the intake passage 12 and the scavenging port 6. The burned gas in the cylinder chamber is discharged from the exhaust port 7. When the scavenging port 6 and then the exhaust port 7 are closed by the rising of the piston 8, the mixed gas in the cylinder chamber is compressed by the piston 8 and ignited by the spark plug 14 facing the combustion chamber 13. However, active heat atmosphere combustion is performed at the time of low load operation, and the mixed gas is ignited by spontaneous ignition. The recess of the combustion chamber 13 that houses the ignition plug 14 is offset toward the exhaust port 7.
[0031]
An exhaust control valve 15 is provided in the cylinder block 3 in which the exhaust port 7 is formed. While the scavenging port 6 is closed due to the rise of the piston 8 and the exhaust port 7 is closed, a part of the fresh air sent into the cylinder chamber is blown out from the exhaust port 7. In the cycle engine, the positive and negative pressure generated by the exhaust wave (blow-down) pressure wave being mainly reflected on the closed end of the exhaust pipe is adapted to the scavenging port closing to the exhaust port closing, thereby reducing the blow-through of fresh air. Accordingly, in the exhaust system adapted to the rotational speed of the output peak, the timing of the reflected wave is too early at medium and low speeds, so the upper part of the exhaust port 7 is closed by the exhaust control valve 15 according to the speed, and the exhaust port opening timing (blow-down timing) By delaying the timing, the reflected wave can be matched at an appropriate time, and the fresh air can be reduced.
[0032]
The exhaust control valve 15 includes a cylinder wall 17 formed with a recess 16, an exhaust passage member 18 fitted in the recess 16, a lid member 19 that covers the cylinder wall 17 and the exhaust passage member 18 from the outside, The valve body 20 is inserted between the recess 16 and the exhaust passage member 18.
[0033]
The recess 16 formed in the cylinder wall portion 17 has a radius γ in contact with the inner peripheral surface of the cylinder hole 5 around the point P in the longitudinal section of FIG.₁As shown in the cross-sectional view of FIG. 3, the radius γ in another longitudinal section parallel to the longitudinal section of FIG. 1 passes through the point P and the axis C of the cylinder hole 5. Axis C perpendicular to₁Along the radius γ on both sides₂The line connecting these outer ends of the radius γ forms an arc a having substantially the same curvature as the cross-sectional shape of the cylinder hole 5. That is, the surface portion of the recess 16 shown in FIG. 1 has an arc C having the same curvature as the inner circumferential surface of the cylinder hole 5 as the axis C.₁The surface of rotation is obtained by rotating around. Hereinafter, this surface portion is referred to as a rotation surface portion 21, and the axis C₁Is referred to as the rotational axis.
[0034]
The rotation surface portion 21 has a rotation axis C₁The axis C at each end of the direction₁Are connected to end surface portions 22 and 22 which form a plane perpendicular to the surface. That is, the recess 16 is defined by the rotating surface portion 21 and the end surface portions 22 and 22, and opens outwardly. FIG. 6 is a front view of the cylinder wall portion 17 in which the recess 16 is formed. The cylinder wall portion 17 has flat mating surfaces 23 (see FIG. 6) on both sides of the recess 16 and communicates with the exhaust port 7 at the center of the rotating surface portion 21.
[0035]
The exhaust passage member 18 fitted in the recess 16 has an outer shape substantially similar to the recess 16. That is, the rotating surface portion 21 a along the rotating surface portion 21, the end surface portions 22 a and 22 a along the end surface portions 22 and 22, and the same surface as the mating surface 23 of the cylinder wall 17 along the opening surface of the recess 16. And an outer end surface 24 (see FIG. 8). As shown in FIG. 1, the exhaust passage member 18 is fixed to a lid member 19 fixed to the cylinder wall portion 17 via a bolt 25 via a bolt 26, and is thus fixed with respect to the cylinder wall portion 17 so as to be recessed 16. It is stored inside. An exhaust passage 27 communicating with the exhaust port 7 is formed inside.
[0036]
Between the rotating surface portion 21 of the recess 16 and the rotating surface portion 21a of the exhaust passage member 18, a gap 28 with a predetermined interval is provided above the upper edge 7a of the exhaust port 7, and the gap 28 is formed in the exhaust port 7. 7 extends to a position slightly beyond the lower edge 7b (FIG. 1). Further, gaps 29 having a predetermined interval are also provided between each end surface portion 22 of the recess 16 and each end surface portion 22a of the exhaust passage member 18 (FIG. 3).
[0037]
In the embodiment, both of the gaps 28 and 29 are such that when the thin plate-like valve body 20 is elastically deformed due to exhaust pressure, thermal expansion, or the like, the valve body 20 has the rotating surface portion 21 and the end surface portion of the recess 16. The gap is set so as not to be in close contact with the rotating surface portion 21a and the end surface portion 22a of the exhaust passage member 18.
[0038]
9 is an external view of the lid member 19, and FIG. 10 is a back view thereof. The back surface of the lid member 19 is formed with a flat mating surface 30 that is flush with the mating surface 23 of the cylinder wall 17 and the outer end surface 24 of the exhaust passage member 18. The lid member 19 is fixed to the cylinder wall portion 17 and the exhaust passage member 18 by the bolts 25 and 26 as described above in contact with the end surface 24. The lid member 19 is formed with an exhaust passage 27a connected to the exhaust passage 27 of the exhaust passage member 18, and the exhaust port 7 is connected to an external exhaust pipe (not shown) through the exhaust passages 27 and 27a.
[0039]
The above-described rotation axis C is provided on the mating surface 23 (FIG. 6) of the cylinder wall 17 and the mating surface 30 (FIG. 10) of the lid member 19, respectively.₁A pair of bearing boss portions 31a and 31b facing each other from both sides are formed. When the cylinder wall portion 17, the exhaust passage member 18 and the lid member 19 are assembled, these bearing boss portions 31a and 31b As shown in FIG. 3, a pair of bearing bosses 32 are formed. Then, valve body drive shafts (rotation shafts) 33 are rotatably supported by these bearing bosses 32, respectively.
[0040]
4 is an enlarged top view of the valve body 20, and FIG. 5 is an enlarged side view thereof. As can be seen more clearly from these drawings, the valve body 20 is a thin shell member made of a sheet metal product such as a stainless steel plate, for example, and a pair of arm portions (swinging arm portions) 34 and these arm portions 34. And a control surface portion (exhaust control unit) 35 for connecting the tips of the two. A flat engagement hole 36 is provided at the base end portion of the arm portion 34, and the arm portion 34 engages the engagement hole 36 with a portion chamfered in the same shape of the valve body drive shaft 33, and The recess 16 and the exhaust passage member 18 are inserted into a gap 29 formed between the end surface portions 22 and 22a. Therefore, the arm portion 34 swings integrally with the valve body drive shaft 33 in the gap 29.
[0041]
The control surface portion 35 is formed wider than the entire width of the exhaust port 7, and the rotation surface portion 21 of the recess 16 is formed into a rotation surface having the same shape as the rotation surface described above, and the arm portion 34 is driven by a valve body. Rotation axis C integrally with shaft 33₁, The control surface portion 35 can freely enter and leave the gap 28 between the rotating surface portions 21 and 21a. Accordingly, the control surface portion 35 is completely accommodated in the gap 28 to fully open the exhaust port 7, or the control surface portion 35 is projected from the upper edge 7a of the exhaust port 7 to close the upper portion of the exhaust port 7. The exhaust timing can be adjusted according to the operating state.
[0042]
As can be seen from the above, in this embodiment, the recess 16 constitutes a storage recess for storing the entire valve body 20, and this storage recess is in the operating area of the control surface portion (exhaust control section) 35 of the valve body 20. The arm portion (swinging arm portion) 34 is always housed in the housing recess, that is, in the gap 29.
[0043]
Since the gap 28 extends to a position beyond the lower edge 7b of the exhaust port 7, it is possible to fully close the exhaust port 7 by lowering the control surface portion 35 to this position. Therefore, the opening ratio of the exhaust port 7 (exhaust opening ratio) can be freely changed from the fully open state to the fully closed state, thereby controlling the cylinder pressure at the initial stage of compression and realizing the AR combustion with the optimal ignition timing. Can be made.
[0044]
One valve body drive shaft 33 protrudes outward from the cylinder block 3, and a drive lever 37 for driving the valve body drive shaft 33 is fixed to the protruding end portion so as to protrude from the shaft. FIG. 2 is a side view showing the side where the drive lever 37 is disposed in the cylinder block 3, and a servo motor 38 is attached to this side as shown in FIG. A drive cable 40 is wound around a pulley 39 provided on the output shaft of the servo motor 38, and both ends of the drive cable 40 are connected to both ends of the drive lever 37, respectively. Therefore, the opening / closing operation of the exhaust port 7 by the control surface portion 35 of the valve body 20 is controlled by the servo motor 38.
[0045]
In the exhaust control valve 15 configured as described above, the arm portion 34 of the valve body 20 is not located inside the exhaust passage 27 but is disposed outside the exhaust passage member 18 that forms the exhaust passage 27. Therefore, the installation of the valve body 20 and the operation thereof do not change the shape of the exhaust passage 27 and cause a decrease in output. Further, since the control surface portion 35 of the valve body 20 moves up and down at a position sufficiently close to the exhaust port 7, the exhaust timing can be accurately controlled, and the exhaust port 7 can be fully closed as described above. Is possible.
[0046]
The exhaust control valve 15 including the cylinder wall portion 17, the exhaust passage member 18, the lid member 19, and the valve body 20 is entirely cooled by cooling water circulating through each portion. Hereinafter, the cooling water circulation system in the exhaust control valve 15 will be described.
[0047]
First, the cylinder wall 17 surrounds the cylinder hole 5 and is provided with a cooling water passage 41 provided in the cylinder block 3.₁Cooling water passage 41 communicating with₂Is provided (FIGS. 1 and 3). This cooling water passage 41₂7 is disposed so as to surround the recess 16 from the lower side to both sides as shown in FIG. 7 and opens to the lower portions on both sides of the mating surface 23 of the recess 16 as shown in FIG. Connection port 42₁, 42₁Communicating with Cooling water passage 41₁, 41₂The cooling water is introduced from the cooling water inlet 43 (FIG. 7).
[0048]
In the mating surface 30 of the lid member 19 that contacts the mating surface 23 of the recess 16, the connection port 42₁Connection port 42 that matches₂(FIG. 10), and the connection port 42 is provided inside the lid member₂Cooling water passage 41 communicating with_ThreeIs formed. This cooling water passage 41_ThreeIs the opening 44₁Open to the mating surface 30 through. The mating surface 30 also has other connection ports 42 on both sides of the upper part._ThreeAnd a cooling water passage 41 communicating therewith._FourBut the opening 44₁Opening 44 adjacent to₂Open to the mating surface 30 through. Opening 44₁And opening 44₂Are separated by a partition wall 45.
[0049]
Further, as shown in FIGS. 1 and 8, the exhaust passage member 18 has an opening 44 on the outer end surface 24._ThreeCooling water passage 41 opening through_FiveIs provided. This cooling water passage 41_FiveIs the opening 44_ThreeIt has a bag shape that communicates with the outside only. Opening 44_ThreeIs the opening 44 of the lid member 19.₁, 44₂Is consistent.
[0050]
The cooling water supplied to the cylinder block 3 from the cooling water inlet 43 is a cooling water passage 41.₂, Connection port 42₁, 42₂, Cooling water passage 41_Three, Opening 44₁, 44_ThreeThrough the cooling water passage 41_FiveAfter flowing into the cooling water passage 41_FiveFrom opening 44 again_ThreeThrough the opening 44₂Through the cooling water passage 41_FourIn the meantime, the cylinder wall 17, the lid member 19, and the exhaust passage member 18 are cooled during this period.
[0051]
The connection port 42 of the lid member 19_ThreeThe other connecting port 42 opened to the mating surface 23 of the cylinder wall 17_Four(FIG. 6), and the cooling water is connected to the connection port 42._ThreeTo connection port 42_FourThen, another cooling water passage (not shown) provided in the cylinder wall portion 17 is entered, and then the cooling water passage 41 provided in the cylinder head 4.₆After being guided to (FIG. 1) and cooling the cylinder head 4, it is discharged from the cooling water outlet 46.
[0052]
In FIG. 11, the main part of the engine 1 described above is shown in a simplified manner, and parts corresponding to those in FIGS. 1 to 10 are given the same reference numerals. The figure also shows a drive control system for driving the exhaust control valve 15.
[0053]
As described above, the exhaust control valve 15 is driven by the servo motor 38 via the pulley 39, the drive cable 40, and the drive lever 37. The drive amount is a drive signal Δθ sent from the CPU 47 to the servo motor 38._eDetermined by. The pulley 39 is connected to an exhaust opening ratio sensor 48 composed of a potentiometer or the like, and the opening ratio of the exhaust port 7 by the exhaust control valve 15 obtained as a result of driving, that is, the exhaust opening ratio θ._eIs fed back from the sensor 48 to the CPU 47.
[0054]
50 is a piston-type throttle valve of a carburetor provided in an intake pipe 49 connected to the intake port 11, and a reed valve 56 which is a one-way valve closer to the intake port 11 than the throttle valve 50 is interposed, Opening angle θ of throttle valve 50_thIs detected by a throttle valve opening sensor 51 composed of a potentiometer or the like and input to the CPU 47.
[0055]
A rider riding a motorcycle (not shown) turns a right handle grip (not shown) to turn the throttle valve opening θ of the throttle valve 50._thCan be adjusted manually to control the acceleration / deceleration of the engine 1.
[0056]
Further, the engine speed Ne detected by the engine speed sensor 52, the suction pipe pressure Pi detected by the suction pipe pressure sensor 53, the coolant temperature Tw detected by the water temperature gauge 54, and the like are input to the CPU 47.
[0057]
The CPU 47 determines the operating state of the engine based on these input values and issues various control signals. In the operating region where AR combustion is performed, the engine speed Ne and the throttle valve opening θ_thDepending on the exhaust opening ratio θ_eThe exhaust opening ratio θ_eDrive signal Δθ such that_eIs sent to the servo motor 38. This exhaust opening ratio θ_eIs set to a value such that the in-cylinder pressure regulated thereby gives the optimum ignition timing, and such a control map can be created as follows, for example.
[0058]
FIG. 12 shows the exhaust opening ratio θ under the conditions of engine speed (Ne) = 3000 γpm, average effective pressure (PME) = 2 Bar, and air-fuel ratio (A / F) = 14._eThrottle valve opening θ against_thFIG. 6 is a graph showing the relationship between the compression initial cylinder pressure, the ignition timing, and the Hc emission amount. FIG. Under the above conditions, the exhaust opening ratio θ_eAnd throttle valve opening θ_thAs shown in the range A of the lowermost graph, the exhaust opening ratio θ_eBy selecting about 50% or less, active hot atmosphere combustion can be obtained.
[0059]
And under this condition, the exhaust opening ratio θ_eIs larger than about 50%, that is, the white arrow A in the figure₁In the range indicated by, an irregular combustion state occurs as can be seen from the rapid increase in the Hc emission amount.
[0060]
However, even in the range A, the exhaust opening ratio θ_eIf it is small, pre-ignition will occur, which will adversely affect engine durability, exhaust emissions, fuel consumption, and so on. The optimum ignition timing that does not cause such adverse effects is in the range of about 8-10 ° BTDC to TDC. To obtain this ignition timing, the exhaust opening ratio θ_eIs limited to the range indicated by the black arrow a in the figure. In this example, this range a is around 40%, and the corresponding throttle valve opening θ_thIs about 10%. That is, in this engine, if the exhaust opening ratio is set to around 40% when the rotational speed is 3000 γpm and the throttle valve opening is about 10%, the AR combustion low speed with the average effective pressure of 2 Bar is low at the optimal ignition timing of 10 ° BTDC to TDC. Load operation can be performed.
[0061]
When PME is changed variously with the same Ne (= 3000 γpm) and A / F (= 14), a graph similar to FIG. 12 is obtained for each PME. FIG. 13 shows each throttle valve opening-exhaust opening ratio curve obtained from these graphs, with the throttle valve opening θ on the horizontal axis._th, The vertical axis represents the exhaust opening ratio θ_eThe equal PME curve indicated by 2.0 Bar in the figure corresponds to the curve at the bottom of FIG.
[0062]
  In FIG. 13, the shaded area is the active heat atmosphere combustible area, and the area B on the upper left side of the broken line b is the range A in FIG.₁This is an irregular combustion region corresponding to. Even in the hatched area, the area to the right of the broken line c is an area where detonation occurs due to premature ignition. And above this pre-ignition areaTwo-dot chain line cIn the lower region C, knocking occurs. In addition, the circle | round | yen mark attached | subjected on each equal PME curve shows the point from which the best fuel consumption (minimum Hc discharge | emission amount) is obtained (refer the circle | round | yen mark of the graph of the uppermost stage of FIG. 12).
[0063]
From FIG. 13, when the engine speed is 3000 γpm, a good combustion state can be obtained by setting the exhaust opening ratio in the region between the broken line b and the broken line c in FIG. It can be seen that stable AR combustion having an optimal ignition timing can be obtained in the low and medium load regions.
[0064]
Similarly, the throttle valve opening θ for each engine speed Ne_thThe best exhaust opening ratio θ according to_eTherefore, the engine speed Ne and the throttle valve opening θ_thAnd the exhaust opening ratio θ to be set according to each of these combinations._eA control map can be created. FIG. 14 shows an example of the control map obtained in this way.
[0065]
The CPU 47 uses such a control map to determine the engine speed Ne and the throttle valve opening θ._thExhaust opening ratio θ according to_eAnd the exhaust control valve 15 is connected to the exhaust opening ratio θ via the servo motor 38._eSet the drive to the position where As a result, the cylinder pressure when the piston is raised is controlled so as to give the optimum ignition timing by the change of the filling ratio.
[0066]
Exhaust aperture ratio θ_eMay be further corrected by the suction pipe pressure signal Pi from the suction pipe pressure sensor 53, the cooling water temperature signal Tw from the water temperature gauge 54, or the like. Further, a finger pressure or optical sensor 55 is provided facing the combustion chamber 13 to detect the finger pressure maximum pressure generation timing or ignition timing or compression start pressure Pec, and this detection result is used for drive control of the exhaust control valve 15. It is also possible to do.
[0067]
  With reference to FIG. 15, a description will be given of the requirements that allow AR combustion in which a self-ignition timing in a spark ignition type two-cycle engine is artificially controlled and burned.
  Compression start pressure P that is the pressure in the cylinder when the exhaust port 7 is closed_ECIs set appropriately, and the compression start temperature T in the cylinder at that time_ECIs determined, the ignition timing when the temperature in the cylinder rises due to adiabatic compression in the cylinder and reaches the temperature at which the fuel self-ignites is determined, and from this ignition timing, a predetermined amount of fuel in the cylinder is determined.combustionAfter the time requiredcombustionThe end time is also determined. The expansion ratio, which is the ratio of the combustion end volume to the exhaust start volume, is determined and the expansion end temperature T depends on how many times the combustion end timing is determined by the crank angle._EEThis is the compression start temperature T_ECTo affect.
[0068]
The compression start pressure P_ECThe filling ratio Crel = Vg / Vh (Vg = Vf + Vr: total gas amount in the cylinder at the start of compression, Vf: intake fresh air gas amount, Vr: residual burned gas amount in the cylinder at the start of compression, Vh: cylinder The scavenging efficiency ηs = Vf / Vg is about 20 with the ratio L / Crel of the inner stroke volume) and the appropriate intake ratio L = Vs / Vh approximately 5% <L <approximately 40% (Vs: intake gas volume), for example. %, And the expansion end temperature T is about 70% or less._EEA part of the residual gas and the fresh gas in the combustion gas that has reached the proper mixing temperature, and the temperature of the mixed gas is set in advance to the compression start temperature T_ECThus, the AR system is established, and in this embodiment, the scavenging efficiency ηs can be changed by changing the opening ratio of the exhaust control valve 15.
[0069]
In this AR system, the compression start temperature T_ECWhen the temperature becomes lower, the ignition timing is delayed and the combustion end timing is also delayed, and the expansion end temperature T reaches the expansion end timing while the combustion gas in the cylinder cannot sufficiently expand._EECorresponding to this, the compression start temperature T correspondingly_ECTherefore, a stable self-control system can be maintained.
[0070]
Further, the control map of FIG. 14 will be described more specifically.
As shown in FIG. 16, when the exhaust control valve 15 is properly controlled, since AR combustion is performed, the effective average pressure PME of the engine is maintained at a high level, and as a result, the throttle valve opening degree θ_thIs reduced, the rotational speed of the engine 1 does not decrease as intended, and in order to avoid this, the throttle valve opening θ_thIn the region where is close to 0, the throttle valve opening θ_thAs the value decreases, the exhaust opening ratio is temporarily decreased by θe. In other words, the exhaust control valve 15 is driven in the closing direction, and then the exhaust opening ratio θe is increased again.
By giving such characteristics, the drivability of the engine 1 can be obtained.
[0071]
  Further, when starting the engine 1, in order to increase the scavenging efficiency and supply as much fresh air as possible to the combustion chamber 13, it is necessary to open the exhaust control valve 15 rather than the idling operation state in which AR combustion is performed. In FIG. 14, when the engine speed Ne is 0 or in the vicinity thereof, the exhaust opening ratio θe is increased, and in the state where the engine speed Ne has increased to reach the idle operating range, the throttle valve is set so that AR combustion is possible. Opening angle θ_thThe exhaust opening ratio θe is lowered to a required low value and the engine rotational speed Ne increases from the idling range.Exhaust opening ratio θ eWas increased.
  By giving such characteristics, the startability of the engine 1 can be improved.
[0072]
Depending on the selection of the exhaust system (for example, an inertia type exhaust system used for an engine with a relatively low specific output such as a scooter engine), it may be very insensitive to the factor of the engine speed Ne. Can simply omit the Ne term, and the pre-ignition timing can be controlled even with an inexpensive valve such as a butterfly valve. In addition, since feedback control is also possible using a finger pressure sensor, the present invention is not limited to map control.
[0073]
【The invention's effect】
According to the present invention, in the low load operation region of the spark ignition type two-cycle engine, the engine speed Ne and the throttle piece opening θ_thBy driving the exhaust control valve 15 to the exhaust opening ratio θe corresponding to the above, and setting the scavenging efficiency ηs that can be AR-combusted, the self-ignition timing can be controlled to the most preferable ignition timing in the operation of the engine 1. Therefore, fuel consumption and exhaust emission can be reduced, and occurrence of abnormal combustion such as detonation due to pre-ignition can be avoided.
[0074]
In addition, since the shape of the exhaust passage is not affected by the installation and operation of the exhaust control valve, it is possible to prevent a decrease in output due to a change in the shape of the exhaust passage. Since it can be moved up and down, the exhaust timing can be accurately controlled.
[Brief description of the drawings]
FIG. 1 is a side view of a spark ignition type two-cycle engine equipped with a combustion control device according to the present invention, with its cylinder section taken longitudinally.
FIG. 2 is a side view of a cylinder portion showing a side surface opposite to that in FIG.
3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is an enlarged top view of the valve body.
FIG. 5 is an enlarged side view of the valve body.
FIG. 6 is a front view of a cylinder wall portion.
7 is a cross-sectional view taken along line VII-VII in FIG.
FIG. 8 is a front view of an exhaust passage member.
FIG. 9 is a front view of a lid member.
FIG. 10 is a rear view of the lid member.
FIG. 11 is a schematic diagram showing a drive control system of an exhaust control valve in the spark ignition type two-cycle engine.
FIG. 12 is a graph showing the relationship between the throttle valve opening, the initial air 1 internal pressure, the ignition timing, and the Hc discharge amount with respect to the exhaust opening ratio at a constant load.
FIG. 13 is a characteristic diagram showing a relationship between an average effective pressure and an exhaust opening ratio and a throttle valve opening.
FIG. 14 is a diagram illustrating an example of a control map.
FIG. 15 is an explanatory diagram illustrating the principle of the present invention.
FIG. 16 is a characteristic diagram illustrating a change in average effective pressure in a normal combustion state and an AR combustion state when the throttle valve opening is changed in a spark ignition type two-cycle engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Crankcase, 3 ... Cylinder block, 4 ... Cylinder head, 5 ... Cylinder hole, 6 ... Scavenging port, 7 ... Exhaust port, 8 ... Piston, 9 ... Connecting rod, 10 ... Crankpin, 11 ... Inlet, 12 ... Intake passage, 13 ... Combustion chamber, 14 ... Spark plug, 15 ... Exhaust control valve, 16 ... Recess (housing recess), 17 ... Cylinder wall, 18 ... Exhaust passage member, 19 ... Lid member, 20 ... Valve, 21 ... Rotation surface portion, 22 ... End face portion, 23 ... Mating surface, 24 ... Outer end surface, 25 ... Bolt, 26 ... Bolt, 27 ... Exhaust passage, 28 ... Gap, 29 ... Gap, 30 ... Matching Surface, 31 ... Bearing boss part, 32 ... Bearing boss, 33 ... Valve body drive shaft (rotating shaft), 34 ... Arm part (swinging arm part), 35 ... Control surface part (exhaust control part), 36 ... Joint hole, 37 ... drive lever, 38 ... servo motor, 39 ... pulley, 40 ... drive cable, 41 ... cooling water passage, 42 ... connecting port, 43 ... cooling water inlet, 44 ... opening 45, partition wall, 46 ... cooling water outlet, 47 ... CPU, 48 ... exhaust opening ratio sensor, 49 ... intake pipe, 50 ... throttle valve, 51 ... throttle valve opening sensor, 52 ... engine speed sensor, 53 ... Suction pipe pressure sensor, 54 ... Water thermometer, 55 ... Shiatsu or light sensor, 56 ... Reed valve.

Claims (2)

In a combustion control device for a spark ignition type two-cycle engine, in which fresh air in a combustion chamber is combusted by self-ignition at least during low load operation, an exhaust control valve provided in the exhaust passage and capable of substantially fully closing the exhaust passage; Drive control means for controlling the pressure in the cylinder when the piston is raised by driving the exhaust control valve at an exhaust opening ratio corresponding to at least the engine speed and the throttle valve opening, the exhaust control valve being a cylinder A rotation shaft extending perpendicular to the cylinder axis and a valve body pivotally supported by the rotation shaft are provided in an exhaust passage extending from an exhaust port opened on the inner peripheral surface of the hole. An exhaust control unit configured to change a height of an upper edge of the port, and the valve body substantially conforming to a cylinder curvature of the exhaust port and wider than a full width of the exhaust port; and Without even forming a thin shell-like member comprising a swinging arm portion connecting the pivot shaft and one side portion, 5% <intake ratio <40%, 20% ≦ scavenging efficiency of ≦ 70%, starting compression A combustion control device for a spark ignition type two-cycle engine, characterized in that the exhaust control valve is controlled so that the pressure falls within a predetermined range of the self-ignition timing. 2. A storage recess for storing the entire valve body is formed in a cylinder block in which the exhaust passage is formed, and a swing arm portion of the valve body is always stored in the storage recess. A combustion control device for a spark ignition type two-cycle engine.

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