JP2023165582A - High performance 2-stroke engine having auxiliary combustion chamber - Google Patents

Abstract

To provide a technology of controlling premixed compression ignition combustion.SOLUTION: A cylinder head is provided with an air supply valve variable valve device 10 varying a valve close timing of an air supply valve 4, and an auxiliary combustion chamber 7 having an ignition plug 8 and an auxiliary fuel injection valve 9. The air supply valve variable valve device 10 receiving a control signal from an electronic control unit 19 controls a close timing of the air supply valve, and therefore, a compression ratio is controlled so that mixture in a main chamber is on the verge of self-ignition near a top dead center, and then the mixture in the main combustion chamber is self-ignited by flame ejected from an injection port of the auxiliary combustion chamber 7. The electronic control unit 19 feedback-controls an ignition timing according to a signal from a knock detection device, thereby feedback-controlling an ignition timing of the mixture in the main combustion chamber, and furthermore, controls so as to inject fuel from the auxiliary fuel injection valve 9 by selecting a timing when the mixture in the auxiliary combustion chamber 7 does not self-ignite until an ignition plug sparks due to the ignition delay of fuel itself.SELECTED DRAWING: Figure 1

Description

The present invention relates to a two-stroke engine having a sub-combustion chamber, and uses strong flame ejected from the sub-combustion chamber to cause homogeneous compression ignition combustion, thereby increasing the efficiency of the engine through rapid combustion. related to something.

Homogeneous compression ignition combustion is attracting attention as a means of increasing the thermal efficiency of engines, but it is known that it is extremely difficult to control. The first method tried was to use a fixed compression ratio and adjust internal EGR, but this was limited by misfires in low load ranges and knocking in medium to high load ranges, unstable ignition timing, and poor combustion. It was unclear when it would occur (with large variations).
The next attempt was stratified charge combustion, in which the flammable air-fuel mixture was placed near the spark plug, and the combustion in this area was used as a trigger to cause the surrounding air-fuel mixture to burn (auto-ignition). However, in this method, NOx is generated in the stratified combustion section, and the countermeasure is costly. In order to prevent knocking in a high load range, it is desirable to self-ignite during the expansion process.In this way, self-ignition occurs while expanding, which suppresses the rate of pressure rise.On the other hand, since it is an expansion process, rapid flame propagation combustion Otherwise, the subsequent self-ignition cannot occur. In general, such rapid flame propagation combustion cannot be expected from the stratified combustion.

An object of the present invention is to provide a technique for controlling homogeneous charge compression ignition combustion, which is said to be the only means for increasing the thermal efficiency of an engine. That is, to prevent misfire and promote complete combustion in the low load range, to prevent knocking in the medium and high load range, and to control the ignition timing of the combustion by the ignition timing of the spark plug throughout the entire range. It is.
In order to accomplish the above, a 2-stroke engine was adopted.

Means to solve problems

In order to achieve the above object, the present invention provides a two-stroke engine equipped with an intake valve and an exhaust valve in the cylinder head, in which at least the closing timing of the intake valve is variable. The cylinder head is equipped with an air valve variable valve device, an auxiliary combustion chamber having an ignition plug, and an auxiliary fuel injection valve, and the air intake valve is closed by the air intake valve variable valve device that receives a control signal from an electronic control unit. The air-fuel mixture in the main combustion chamber is on the verge of self-ignition near top dead center by controlling the timing and therefore the effective compression ratio, and then the air-fuel mixture is ejected from multiple nozzles in the auxiliary combustion chamber. The air-fuel mixture in the main combustion chamber is caused to self-ignite by the flame generated by the engine (self-ignition occurs at or after top dead center). Furthermore, due to the ignition delay of the fuel itself, the fuel is controlled to be injected from the auxiliary fuel injection valve at a time when it will not self-ignite until the ignition plug sparks.
Further, the electronic control unit performs feedback control of the ignition timing based on the signal from the knock detection device.

Effect of the invention

According to the present invention, the effective compression ratio is freely changed by the intake valve variable valve device, the internal EGR is controlled by the exhaust throttle valve, and the ignition timing is appropriately changed by the ignition plug in the auxiliary combustion chamber. (Previously, internal EGR was controlled under a fixed compression ratio), and homogeneous compression ignition combustion can be controlled. In addition, the ignition timing of the ignition plug is feedback-controlled using the signal from the knock detection device, so that the ignition of homogeneous compression ignition combustion can be started at the most appropriate timing of 5° to 10° or 10° to 15° after top dead center. This allows for quiet operation.
Severe knocking is expected in homogeneous compression ignition combustion with λ = 1 (theoretical mixture), but rapid fire propagation combustion is possible due to the intense flame ejected from the nozzle of the auxiliary combustion chamber, so homogeneous compression ignition combustion is possible. It can be triggered during the expansion process at 10° to 15° after top dead center, allowing for quiet operation (rapid flame propagation combustion is impossible with stratified combustion without the use of an auxiliary combustion chamber).
Since premixed compression ignition ignition (hereinafter referred to as PCCI) is low-temperature combustion, cooling loss is small and the specific heat ratio K is large, so high thermal efficiency can be obtained. Furthermore, since it uses a Miller cycle with a larger expansion ratio than compression ratio, thermal efficiency is high. Although combustion occurs during the expansion stroke a little after top dead center, the torque arm is sufficiently large and the combustion is rapid at ideal timing (combustion before top dead center deteriorates thermal efficiency), resulting in high efficiency. be. Even if the engine burns well past top dead center, efficiency is still high because it uses the Miller cycle. According to the present invention, the range of PCCI combustion can be widened to both the low load side and the high load side. Next, since this engine is a two-stroke engine, it has no intake and exhaust strokes like a four-stroke engine, so it has high mechanical efficiency and has low pump loss at low loads, so it is inherently highly efficient. In addition, the cost is low because parts such as spark plugs, intake/exhaust valves, pistons, and fuel injection valves are half as many as in a 4-stroke engine.
Furthermore, a three-way catalyst, which could not be used in the past, can be used because of the blow-through of the supply air, which is extremely advantageous in terms of exhaust purification measures.

Form for carrying out the invention

料噴射弁１１から燃料が噴射され、シリンダー内の圧縮が開始される（給気弁４が閉じるまでは一旦シリンダー内に供給された空気は給気ポート３内に押し戻される）。圧縮上死点の所定クランク角手前で副燃料噴射弁９から副燃焼室７内へ微量の燃料が噴射される（後述する）。ピストン１が上死点に近ずくと適当な時期に点火栓８がスパークし（詳しくは後述する）、副燃焼室７の噴口から主燃焼室内へ火炎が噴出し主燃焼室の燃焼が開始される。図１（ロ）に掃気の様子を示す。電子制御ユニット（以下、ＥＣＵ）１９はＲＯＭ、ＲＡＭ、ＣＰＵ、入・出力ポート等から成るマイクロコンピュータを中心として構成され、これらは双方性バスによって相互に接続されている。ＥＣＵ１９にはエンジンの運転状態の把握に必要なパラメーター用の各種センサー、例えば所定のクランク角毎にクランク角を出力するクランク角センサー、所定のカム角毎にカム角信号を出力するカム角センサー、アクセル開度を検出するアクセルセンサー、エンジン冷却水温を検出する水温センサー、大気圧センサー、大気温度センサー、エンジンに吸入される空気流量を検出するエァフローメータ１７、排ガス中の酸素濃度を検出するＯ_２センサー、エンジンのノックを検出するノック検出センサー、排気絞り弁１２の開度を検出する排気絞り弁開度センサー等からの各信号が対応するＡ／Ｄコンバーターを介して入力ポートに送信される。尚、エンジン回転速度は前記クランク角センサーからの出力信号により知る事ができる。又、出力ポートは主燃料噴射弁１１、副燃料噴射弁９、点火栓８、油圧制御弁１８、アクチュエーター１３等と各々対応する駆動回路を介して接続され、各々の制御信号を送信する。ＲＯＭには主燃料噴射弁１１や副燃料噴射弁９の噴射量や噴射時期を決定する為の制御ルーチン、点火栓８への通電を制御する為の制御ルーチン、排気絞り弁１２の開度を決定する為の制御ルーチン、給気弁可変動弁装置１０の給気弁を駆動するカムの位相角を決定する為の制御ルーチン等のエンジンを制御する為の制御ルーチンやそれらに用いられる制御値を含むマップが記憶されている。ＲＡＭに記憶されている各種データーはエンジン回転速度センサーが信号を出力する度に最新のデーターに書き換えられる。ＣＰＵはＲＯＭに記憶されていいるアプリケーションプログラムに従って動作し、燃料の噴射制御、点火時期制御、給気弁の閉弁時期制御、排気絞り弁の開度制御等を実行する。
１０はカム軸の位相を変えて給気弁４の閉弁時期を変える給気弁可変動弁装置で（公知）、内部には図示しない進角室と遅角室とがあり、油圧制御弁１８からの作動油が供給される。
油圧制御弁１８は図示しない油圧ポンプからの油圧が供給され、ＥＣＵ１９からの出力信号により軸方向への移動量が電磁ソレノイドにより駆動制御されるプランジャーとスプール弁とバネを有しており（共に図示は省略）、バネの反発力とプランジャーの押圧力とが均衡する位置でスプール弁が位置決めされる様になっている。ＥＣＵ１９にはクランク角センサーからの信号、カム角センサーからの信号が入力され、ＥＣＵ１９はカム角センサーから出力される回転角パルスとクランク角センサーから出力される回転角パルスとの間の出力位相差に基づきカム位相角を検出する事ができる。
ＥＣＵ１９はカム軸のクランク軸に対する位相角が目標値となる様に油圧制御弁１８に制御信号を出力する。そして、ＥＣＵ１９は検出したカム位相角をフィードバック信号として取り込み、その制御上の目標位相角との間の偏差に応じて油圧制御弁１８の駆動デューティ比率をフィードバック制御する。油圧制御弁１８はＥＣＵ１９から指示されるデューティ比率に応じて電磁ソレノイドを駆動し、進角室、遅角室に対する油圧の給排を調整してカム軸を目標位相角まで進角又は遅角、或いは中立に保持する。以上の給気弁可変動弁装置１０は油圧式であったが、公知の電動式であっても良い。又、給気弁可変動弁装置１０は位相を変えて閉弁時期を変えるものであったが、２個のカムを備えて、閉弁時期を変える為に使用するカムを切り換える構成としても良い（カム切換え式）、いずれにしても、給気弁４の閉弁時期を変えて圧縮比を変える構造とするのである。本発明によるとＰＣＣＩ燃焼をかなり低負荷まで拡げる事ができるが、アイドルを含む極低負荷域まで拡げる事はかなり困難を伴なう。
本発明の望ましい実施例はシリーズ型ハイブリッド車用の発電専用のエンジンとしての使い方であるので、これについて次に説明する（２～３点の定点運転）。FIG. 1(A) shows a high-efficiency two-stroke engine according to the present invention, in which the cylinder head is equipped with an intake valve 4 for introducing fresh air (air), and the exhaust passage 5 is equipped with an exhaust valve 6, each of which is connected to the crankshaft. It is a 4-valve type that is opened and closed by a cam driven at a rotation ratio of 1/1. The main combustion chamber includes a piston recess 2 and a squish portion S, and is provided with a main fuel injection valve 11 that injects fuel into the piston recess 2.
An auxiliary combustion chamber 7 is provided directly above the piston recess 2, and a spark plug 8 and an auxiliary fuel injection valve 9 face inside the auxiliary combustion chamber 7 (the auxiliary combustion chamber 7 has a plurality of nozzles through which flames are ejected). The auxiliary combustion chamber 7 and the auxiliary fuel injection valve 9 are provided between the two exhaust valves 6 with a large interval between them.
Next, when the piston 1 is pushed by the high-pressure combustion gas in the main combustion chamber, the piston descends and performs expansion work, and when the exhaust valve 6 opens, exhaust blowdown begins, followed by the intake valve 4. Air flows into the cylinder and scavenges the burnt gas. This scavenging pump is driven by the crankshaft 15, for example.

Fuel is injected from the fuel injection valve 11, and compression within the cylinder is started (until the air intake valve 4 is closed, the air once supplied into the cylinder is pushed back into the air intake port 3). A small amount of fuel is injected into the auxiliary combustion chamber 7 from the auxiliary fuel injection valve 9 at a predetermined crank angle before the compression top dead center (described later). When the piston 1 approaches top dead center, the ignition plug 8 sparks at an appropriate time (details will be described later), and flame is ejected from the nozzle of the auxiliary combustion chamber 7 into the main combustion chamber, starting combustion in the main combustion chamber. Ru. Figure 1 (b) shows the scavenging process. The electronic control unit (hereinafter referred to as ECU) 19 is mainly composed of a microcomputer consisting of ROM, RAM, CPU, input/output ports, etc., and these are interconnected by a bidirectional bus. The ECU 19 includes various sensors for parameters necessary to grasp the operating state of the engine, such as a crank angle sensor that outputs a crank angle at each predetermined crank angle, a cam angle sensor that outputs a cam angle signal at each predetermined cam angle, An accelerator sensor that detects the accelerator opening degree, a water temperature sensor that detects the engine cooling water temperature, an atmospheric pressure sensor, an atmospheric temperature sensor, an air flow meter 17 that detects the flow rate of air taken into the engine, and an O sensor that detects the oxygen concentration in exhaust gas. ₂ sensors, a knock detection sensor that detects engine knock, an exhaust throttle valve opening sensor that detects the opening of the exhaust throttle valve 12, and other signals are sent to the input port via the corresponding A/D converter. . Incidentally, the engine rotation speed can be known from the output signal from the crank angle sensor. Further, the output port is connected to the main fuel injection valve 11, the auxiliary fuel injection valve 9, the spark plug 8, the hydraulic control valve 18, the actuator 13, etc. via corresponding drive circuits, and transmits respective control signals. The ROM contains a control routine for determining the injection amount and injection timing of the main fuel injection valve 11 and the auxiliary fuel injection valve 9, a control routine for controlling the energization of the spark plug 8, and the opening degree of the exhaust throttle valve 12. Control routines for controlling the engine, such as control routines for determining the phase angle of the cam that drives the intake valve of the variable intake valve device 10, and control values used therefor. A map containing is stored. The various data stored in the RAM are rewritten to the latest data each time the engine speed sensor outputs a signal. The CPU operates according to application programs stored in the ROM, and performs fuel injection control, ignition timing control, intake valve closing timing control, exhaust throttle valve opening control, and the like.
Reference numeral 10 denotes a variable intake valve device (known in the art) that changes the closing timing of the intake valve 4 by changing the phase of the camshaft, and has an advance chamber and a retard chamber (not shown) inside. Hydraulic oil from 18 is supplied.
The hydraulic control valve 18 is supplied with hydraulic pressure from a hydraulic pump (not shown), and has a plunger, a spool valve, and a spring whose movement in the axial direction is driven and controlled by an electromagnetic solenoid based on an output signal from the ECU 19. (not shown), the spool valve is positioned at a position where the repulsive force of the spring and the pressing force of the plunger are balanced. A signal from the crank angle sensor and a signal from the cam angle sensor are input to the ECU 19, and the ECU 19 calculates the output phase difference between the rotation angle pulse output from the cam angle sensor and the rotation angle pulse output from the crank angle sensor. The cam phase angle can be detected based on
The ECU 19 outputs a control signal to the hydraulic control valve 18 so that the phase angle of the camshaft with respect to the crankshaft becomes a target value. Then, the ECU 19 takes in the detected cam phase angle as a feedback signal, and feedback-controls the drive duty ratio of the hydraulic control valve 18 according to the deviation between the detected cam phase angle and the target phase angle for control. The hydraulic control valve 18 drives an electromagnetic solenoid according to the duty ratio instructed by the ECU 19, and adjusts the supply and discharge of hydraulic pressure to the advance and retard chambers to advance or retard the camshaft to the target phase angle. Or keep it neutral. Although the air supply valve variable valve device 10 described above is of a hydraulic type, it may be of a known electric type. Further, although the intake valve variable valve device 10 changes the valve closing timing by changing the phase, it may also be configured to include two cams and switch the cam used to change the valve closing timing. (Cam switching type) In either case, the structure is such that the compression ratio is changed by changing the closing timing of the intake valve 4. According to the present invention, PCCI combustion can be extended to a considerably low load range, but it is quite difficult to extend it to an extremely low load range including idle.
Since a preferred embodiment of the present invention is used as an engine exclusively for power generation in a series hybrid vehicle, this will be explained next (fixed point operation at 2 to 3 points).

Series hybrid vehicle engines use two to three highly efficient fixed points (1500r.p.m., 2500r.p.m., and 4000r.p.m.).

2500r. p. m. Fixed point operation.
With the excess air ratio λ=2.1, the intake valve 4 is opened at BBDC40°CA and closed at BBDC40°CA as shown in FIG. 2(A) using the air intake valve variable valve device 10 as shown in FIG. ABDC is set to 80° CA (at this time, the compression ratio is 16), the exhaust valve 6 is opened at BBDC70° (fixed), and closed at ABDC 40° CA (fixed), thereby making the expansion ratio 19 (fixed). It is a Miller cycle with high compression ratio and high expansion ratio. To prevent air from blowing through, the exhaust valve 6 is closed early at ABDC40°CA, and the exhaust throttle valve 12 is used to throttle the exhaust (λ=2,1, so NOx is 0 even without a three-way catalyst. Yes, a small amount of air blow-through is OK, and HC and CO are purified by the catalyst 14). PCCI combustion is controlled by three elements: the compression ratio (intake valve closing timing), the opening degree of the exhaust throttle valve 12, and the ignition timing of the spark plug 8. The auxiliary combustion chamber 7 has a plurality of nozzles for ejecting flame, and faces the ignition plug 8 and the auxiliary fuel injection valve 9. First, the compression ratio is set to 16, and the exhaust is throttled by the exhaust throttle valve 12. (EGR), so that it is on the verge of self-ignition near the compression end (it will not self-ignite if it continues like this).
Scavenging is performed according to the valve timing diagram in FIG. 2(a), and when the piston rises, the intake valve 4 closes (the exhaust valve 6 is already closed), and fuel is injected at high pressure from the main fuel injection valve 11. A mixture of λ = 2.1 is created (this also flows into the auxiliary combustion chamber 7). When the piston 1 approaches the top dead center, a small amount of fuel is injected from the auxiliary fuel injection valve 9, and immediately after that The spark plug 8 sparks. This small amount of fuel, together with the fuel that has already flowed in, creates a mixture of λ = 1, 7th place (can be ignited and combusted) in the sub-combustion chamber 7, but this is due to the ignition delay of the fuel, so the ignition plug 8 Self-ignition does not occur until spark occurs (the ignition timing and the injection timing of the auxiliary fuel injection valve 9 are such that if one advances, the other advances, and if one lags, the other lags). PCCI combustion is said to be most efficient and produce the least vibration (pressure rise rate) when the torque arm is sufficiently large and the degree of expansion is large, occurring at around 5° to 10° CA after top dead center. However, if the ignition timing of the ignition plug 8 is controlled by feedback control based on the signal from the knock detection device (there are vibration detection type and combustion pressure detection type), the flame will be ejected from the nozzle of the auxiliary combustion chamber 7 at an appropriate time. , that can serve as a trigger and wake up at such timing. For example, if the signal from the knock detection device determines that there is a knock, then PCCI combustion is occurring at or before top dead center, so the ignition timing is delayed and PCCI combustion occurs at 5° to 10° CA ATDC. control it as you like. If the ignition timing is advanced, PCCI combustion will occur earlier. In this case, even if the flame ejects from the auxiliary combustion chamber 7, combustion due to flame propagation does not occur, but the air-fuel mixture is heated and pressurized by the heat and pressure of the ejected flame (to 1000K+α), and PCCI combustion occurs. (If the ejected flame is before top dead center, it will be further compressed by the rise of the piston, so PCCI combustion will definitely occur). For this reason, the compression ratio etc. are set so that PCCI combustion is about to occur near top dead center. The flame from the auxiliary combustion chamber 7 is prevented from hitting the wall surface and is collected in the piston recess 2, so that PCCI combustion occurs first in the piston recess 2 and then in the squish part S due to the heat and pressure. As a result, two-stage PCCI combustion becomes possible (combustion can be controlled by the size of the gap S). (Although a small amount of NOx is generated in the auxiliary combustion chamber 7, it is possible to set λ to 1 or 9 by increasing the ignition energy or using multiple sparks, or by cooling the combustion gas with a cooling plate 21 as shown in Figure 3.) That's good). Because PCCI combustion is low-temperature combustion, cooling loss is small and the specific heat ratio is large.Furthermore, it uses a Miller cycle, which has higher mechanical efficiency and less pump loss than a 4-stroke engine, resulting in high thermal efficiency. is obtained.

4000r. p. m. Fixed point operation Since a three-way catalyst is used, set λ = 1, 0 (measure the intake air flow rate with the air flow meter 17 and make it stoichiometric).
This also flows into the auxiliary combustion chamber 7 from the nozzle, and since λ=1, 0, it can be ignited, and injection from the auxiliary fuel injection valve 9 is unnecessary. However, ignition is the same, and flames eject from multiple nozzles. The intake valve variable valve device 10 closes the intake valve 4 at ABDC90°CA as shown in FIG. In order to prevent air from blowing through, the exhaust valve 6 is closed early at ABDC40°CA. Even after the exhaust valve 6 opens, the cylinder pressure is still high for a while, so when the intake valve 4 opens, the burnt gas flows back uniformly from around it as shown in Figure 1 (C), and almost only the burnt gas flows out. A columnar mass 20 is created (this does not happen with a piston valve type scavenging port due to mixing). Therefore, if the exhaust valve is closed immediately after the tip of the columnar mass 20 reaches the exhaust valve 6 as shown in FIG. 1(b), air can be prevented from blowing through (the timing is set accordingly). In this way, the three-way catalyst will be completely damaged and the thermal efficiency will be increased (even if there is a slight air blow-through, as long as the air flow meter 17 is supplying the stoichiometric mixture, the three-way catalyst will be completely fine). Since the air-fuel mixture in the combustion chamber becomes rich due to blow-through, the blow-through should be kept to zero to prevent deterioration of fuel efficiency.) The compression ratio is set to 14 to the extent that self-ignition does not occur at the compression end even when λ = 1, 0, and fuel injection is started from ABDC 90° when the intake valve 4 is closed, and PCCI combustion is strong at λ = 1, 0. Since knocking is expected, PCCI combustion is caused in two stages at ATDC 10° to 15° CA during the expansion process. Therefore, when the air-fuel mixture in the sub-combustion chamber 7 is ignited, intense flames are ejected from a large number of nozzles, and rapid flame propagation combustion begins. At this time, it is important to collect the flame from the nozzle into the piston recess 2 without hitting the wall to promote rapid flame propagation and combustion (possible with the auxiliary combustion chamber 7). As a result, PCCI combustion first occurs in the piston recess 2 (this occurs when the rapid flame propagation combustion has progressed to a certain stage), and then PCCI combustion occurs in the squish portion S due to this heat and pressure. Since it is an expansion process and a two-stage PCCI combustion, quiet operation is possible. This PCCI combustion can be controlled by the gap in the squish portion S.
Although combustion has entered the expansion process at ATDC of 10° to 15° CA, this has a sufficiently large torque arm and is a Miller cycle with a larger expansion ratio of 19 than compression ratio of 14, so there is sufficient margin for high efficiency. be.
The ignition timing is advanced as far as possible so that PCCI occurs at about 10° to 15° CA ATDC while monitoring the magnitude of knock using a knock detection device, but the ignition timing may be before top dead center. If the above does not resolve the knock, a 2-stroke (2-stroke) engine has an output margin of 1 to 3 times that of a 4-stroke engine even if a Miller cycle is used, so reduce this margin (to keep the output the same). There is still a way to eliminate the knock by adopting cooled EGR. In addition, 4000r. p. m. Because of the high speed, there may be a delay in ignition of the fuel and ignition may not occur in time, in which case a high compression ratio of 16 will be used.

1500r. p. m. Fixed point operation If necessary, such as warm-up operation, city driving, early morning/late night driving, etc., λ = 3, 1500r. p. m. Incorporate fixed point operation. Battery capacity can be reduced. The valve timing is as shown in FIG. 2C, the intake valve variable valve device 10 closes the intake valve 4 at ABDC70°CA, and the compression ratio=expansion ratio=19. To realize PCCI, the compression end temperature needs to be 1000K+α, but the compression ratio is set to a high value of ε=19, and the exhaust throttle valve 12 performs exhaust throttle (strengthens internal EGR). It has the advantage of controlling PCCI combustion using three elements: variable compression ratio, exhaust throttle valve opening, and spark plug ignition timing (previously, only the amount of internal EGR was controlled under a fixed compression ratio). In other words, the compression ratio and internal EGR rate are set so that they are on the verge of PCCI combustion, and finally the ignition timing is set as a trigger to cause PCCI. When the engine is warmed up, the sub-combustion chamber 7 is ignited with stoichiometry so that a strong flame is ejected (NOx is 0). Conventionally, the ignition timing was delayed in order to activate the catalyst early and warm up the catalyst, but in the present invention, the exhaust valve 6 is also equipped with an exhaust valve variable valve device to advance the valve opening timing, and the ignition timing is increased to 1500 rpm. p. m. If the expansion ratio is reduced to 12 compared to the compression ratio of 19 during warm-up, the exhaust temperature can be significantly increased. At the same time, if internal EGR is increased by exhaust throttling, early activation and early warm-up of the catalyst becomes possible.

Next, in FIG. 1(A), in the present invention, the higher the energy of the flame ejected from the auxiliary combustion chamber 7, the stronger the ignitability, and the higher the thermal efficiency of the engine, so the ignition plug used as shown in FIG. It is best to use a long, super-protruding type. In this way, a spark is generated at the center of the sub-combustion chamber 7, so that combustion is completed more quickly and a powerful flame is ejected from the nozzle. Similarly, as shown in Fig. 5, if the tip of the auxiliary combustion chamber 7 also enters the piston recess 2 by a predetermined length (more precisely, if the nozzle enters), the flame will ignite near the center of the piston recess 2. is ejected, promoting rapid combustion. In this case, the tip of the auxiliary combustion chamber 7 becomes hot and causes pre-ignition, so it is preferable to make it of beryllium copper or the like to enhance cooling with good thermal conductivity. Further, it is desirable that the contact portion of the cylinder head around the auxiliary combustion chamber 7 extends toward the tip of the auxiliary combustion chamber 7 as shown in the figure. Incidentally, a method for achieving the same purpose as shown in FIG. 4 without using the protruding electrode type is to insert the spark plug 8 from the side of the auxiliary combustion chamber 7 as shown in FIG.

FIG. 1 is a schematic diagram of a high-efficiency two-stroke engine according to the present invention. FIG. 3 is a valve timing diagram. FIG. 3 is a cross-sectional view of the auxiliary combustion chamber viewed from above. Diagram of a protruding electrode type ignition plug. FIG. 3 is a diagram in which the tip of the sub-combustion chamber has entered the piston recess. It is a figure showing a sub-combustion chamber.

1 is a piston, 2 is a piston recess, 3 is an air intake port, 4 is an air intake valve, 5 is an exhaust port, 6 is an exhaust valve, 7 is an auxiliary combustion chamber, 8 is a spark plug, 9 is an auxiliary fuel injection valve, 10 11 is the main fuel injection valve, 12 is the exhaust throttle valve, 13 is the actuator, 14 is the catalyst, 15 is the crankshaft, 16 is the scavenging pump, 17 is the air flow meter, and 18 is the hydraulic control. 19 is an electronic control unit, 20 is a columnar block, and 21 is a cooling plate.
4, 5, and 6 may be used for purposes other than the present invention.

Claims (2)

In a two-stroke engine equipped with an intake valve and an exhaust valve in a cylinder head, an intake valve variable valve device that changes at least the closing timing of the closing timing and the opening timing of the intake valve; and a spark plug. The cylinder head is equipped with an auxiliary combustion chamber having an auxiliary fuel injection valve, and the closing timing of the intake valve is controlled by an intake valve variable valve device that receives control signals from an electronic control unit, thereby reducing compression. After controlling the ratio so that the air-fuel mixture in the main combustion chamber is on the verge of self-ignition near top dead center, the air-fuel mixture in the main combustion chamber is self-ignited by the flames ejected from multiple nozzles in the auxiliary combustion chamber. In addition, the electronic control unit performs feedback control of the ignition timing based on the signal from the knock detection device, and performs feedback control of the start timing of self-ignition of the air-fuel mixture in the main combustion chamber. A high-efficiency two-stroke engine that controls fuel injection from the auxiliary fuel injection valve at a time when the air-fuel mixture in the auxiliary combustion chamber does not self-ignite until the ignition plug sparks. The two-stroke engine according to claim 1, further comprising an exhaust throttle valve whose opening degree is controlled by an electronic control unit.

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