JPS6046246B2 - Internal combustion engine exhaust gas purification method and exhaust gas purification device - Google Patents

Description

【発明の詳細な説明】 産業上の利用分野 本発明は内燃機関の排気ガス浄化方法並びに排気ガス
浄化装置に関する。DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an exhaust gas purification method and an exhaust gas purification device for an internal combustion engine.

従来の技術 排気ガス中の有害成分ＨＣ、Ｃｏ並びにＮｏ、を同時
に低減するために機関排気系に三元触媒を内蔵した触媒
コンバータを具えた内燃機関が公知である。BACKGROUND OF THE INVENTION Internal combustion engines are known that are equipped with a catalytic converter containing a three-way catalyst in an engine exhaust system in order to simultaneously reduce harmful components HC, Co, and No in exhaust gas.

従来よりこのΞ元触媒は機関吸気系並びに機関シリンダ
から触媒コンバータ入口に至る機関排気系において供給
された空気の総量に対する燃料の総量の比（以下、総合
空燃比と称す）が理論混合比であるときに最も高い浄化
効率を得ることができるものと考えられていたが最近に
なつて総合空燃比を稀薄側又は過濃側に交互に振動せし
めても高い高化効率が得られることが判明した。このよ
うに総合空燃比を振動せしめることにより高い浄化効率
が得られることになると総合空燃比を正確に理論空燃比
に一致せしめる必要がないために空燃比制御システムを
簡素化することが可能となる。 このような原理を利用
した内燃機関として、触媒コンバータ入口付近に排気ガ
ス中の酸素濃度を検出するための酸素濃度検出器を取付
け、機関シリンダ内に濃混合気を供給し、該酸素濃度検
出器の出力信号に基づいて総合空燃比が理論混合比を中
心として変動するように酸素濃度検出器上流の−機関排
気系に２次空気を供給するようにした内燃機関が提案さ
れている（特開昭関−９３２Ｗ号公報参照）。Conventionally, for this Ξ source catalyst, the ratio of the total amount of fuel to the total amount of air supplied in the engine intake system and the engine exhaust system from the engine cylinder to the catalytic converter inlet (hereinafter referred to as the total air-fuel ratio) is the stoichiometric mixture ratio. It was sometimes thought that the highest purification efficiency could be obtained, but recently it has been found that even if the overall air-fuel ratio is alternately oscillated toward the lean side or the rich side, a high efficiency can be obtained. . If high purification efficiency is obtained by oscillating the total air-fuel ratio in this way, it becomes possible to simplify the air-fuel ratio control system since there is no need to precisely match the total air-fuel ratio to the stoichiometric air-fuel ratio. . As an internal combustion engine that utilizes this principle, an oxygen concentration detector for detecting the oxygen concentration in exhaust gas is installed near the catalytic converter inlet, a rich mixture is supplied into the engine cylinder, and the oxygen concentration detector An internal combustion engine has been proposed in which secondary air is supplied to the engine exhaust system upstream of the oxygen concentration detector so that the overall air-fuel ratio varies around the stoichiometric mixture ratio based on the output signal of (Refer to Shoseki-932W publication).

発明が解決しようとする問題点 この内燃機関では総合空燃比を理論空燃比を中心として
振動させるようにしているために酸素濃度検出器を必要
としている。Problems to be Solved by the Invention This internal combustion engine requires an oxygen concentration detector because the overall air-fuel ratio is made to oscillate around the stoichiometric air-fuel ratio.

しかしながらこのように酸素濃度検出器の出力信号に基
いて総合空燃比が理論空燃比を中心として振動するよう
に２次空気量を制御するようにした場合には相変らず複
雑な空燃比制御システムが必要になるという問題がある
。更に酸素濃度検出器は現在のところまだ実用化十分な
信頼性に達しておらず、また常時高熱にさらされるため
に熱劣化するという問題も有しており、従つて空燃比制
御システムの簡素化の−上からも酸素濃度検出器を用い
たくないのが現状である。問題点を解決するための手段 上記問題点を解決するために本発明によれば機関シリン
ダ内に濃混合気を供給すると共に機関排気系に三元触媒
コンバータを有し、触媒コンバータ上流の機関排気系に
２次空気を供給して排気ガスの浄化を行なうようにした
内燃機関の排気ガス浄化方法において、酸素濃度検出器
を用いることなく機関回転数および吸気管負圧のみに応
動して吸入空気量に比例した量の２次空気を上記機関排
気系に間欠的に供給することにより総合空燃比を稀薄側
と過濃度に交互に振動せしめかつ該交番的に振動する総
合空燃比の平均値が理論空燃比に等しいか或いはそれよ
り稀薄側にあるように設定している。However, when controlling the secondary air amount so that the overall air-fuel ratio oscillates around the stoichiometric air-fuel ratio based on the output signal of the oxygen concentration detector, the air-fuel ratio control system remains complicated. The problem is that it requires Furthermore, oxygen concentration detectors have not yet reached a level of reliability sufficient for practical use, and they also suffer from thermal deterioration due to constant exposure to high heat. At present, we do not want to use an oxygen concentration detector. Means for Solving the Problems In order to solve the above problems, according to the present invention, a rich air-fuel mixture is supplied into the engine cylinders, and a three-way catalytic converter is provided in the engine exhaust system, and the engine exhaust gas upstream of the catalytic converter is provided with a three-way catalytic converter. In an internal combustion engine exhaust gas purification method that purifies exhaust gas by supplying secondary air to the system, intake air is purified only in response to engine speed and intake pipe negative pressure without using an oxygen concentration detector. By intermittently supplying an amount of secondary air proportional to the amount of secondary air to the engine exhaust system, the total air-fuel ratio is caused to alternately oscillate between lean and overconcentrated, and the average value of the alternately oscillating total air-fuel ratio is The air-fuel ratio is set to be equal to or leaner than the stoichiometric air-fuel ratio.

更に、上記問題点を解決するために本発明によれば機関
シリンダ内に濃混合気を供給すると共に機関排気系に三
元触媒コンバータを有し、触媒コンバータ上流の機関排
気系に２次空気を供給して排気ガスの浄化を行なうよう
にした内燃機関の排気ガス浄化装置において、機関排気
系と機関駆動の２次空気供給用エアポンプとを連結する
２次空気供給通路内に酸素濃度検出器を用いることなく
機関回転数および吸気管負圧のみに応動して吸入空気量
に比例した量の２次空気を間欠的に通過せしめる２次空
気供給制御弁装置を設け、２次空気供給制御弁装置を介
して機関排気系に２次空気を間欠的に供給して総合空燃
比を稀薄側と過濃側に交互に振動せしめかつ交番的に振
動する総合空燃比の平均値が理論空燃比に等しいか或い
はそれより稀薄側にあるように設定している。Furthermore, in order to solve the above problems, according to the present invention, a rich air-fuel mixture is supplied into the engine cylinders, and a three-way catalytic converter is provided in the engine exhaust system, and secondary air is supplied to the engine exhaust system upstream of the catalytic converter. In an exhaust gas purification device for an internal combustion engine that purifies exhaust gas by supplying oxygen, an oxygen concentration detector is installed in a secondary air supply passage connecting an engine exhaust system and an engine-driven secondary air supply air pump. The secondary air supply control valve device is equipped with a secondary air supply control valve device that responds only to engine speed and intake pipe negative pressure without using it and allows an amount of secondary air proportional to the amount of intake air to pass intermittently. Secondary air is intermittently supplied to the engine exhaust system through the system to cause the total air-fuel ratio to vibrate alternately between lean and rich sides, and the average value of the alternately vibrating total air-fuel ratio is equal to the stoichiometric air-fuel ratio. Or, it is set to be on the rarer side.

実施例 まず始めに本発明による実験結果の一例を下表に示す。Example First of all, an example of experimental results according to the present invention is shown in the table below.

この実験は２種類の三元触媒Ａ，Ｂに対して下記の４つ
の総合空燃比（ａ）〜（ｄ）についての各有害成分の浄
化率を計測したものである。（ａ）総合空燃比を常時理
論混合比１４．６に一致せしめる。In this experiment, the purification rate of each harmful component was measured for two types of three-way catalysts A and B at the following four total air-fuel ratios (a) to (d). (a) The total air-fuel ratio is always made to match the stoichiometric mixture ratio of 14.6.

（ｂ）総合空燃比を空燃比１５に保持する。(b) Maintain the overall air-fuel ratio at an air-fuel ratio of 15.

（ｃ）総合空燃比を過濃側１４．２と稀薄側１５に交互
に振動せしめる。（ｄ）総合空燃比を理論混合比１４．
６と稀薄側１５に交互に振動せしめる。(c) The overall air-fuel ratio is alternately oscillated between the rich side 14.2 and the lean side 15. (d) Set the total air-fuel ratio to the stoichiometric mixture ratio of 14.
6 and the dilute side 15 alternately.

上表において（ａ）は酸素濃度検出器を用いた従来の排
気ガス浄化装置を示している。In the above table, (a) shows a conventional exhaust gas purification device using an oxygen concentration detector.

上表（ｃ）は総合空燃比の平均値が理論混合比となるよ
うに総合空燃比を過濃側と稀薄側に交互に振動させた場
合を示している。この場合（ａ）に比しては若干劣るが
高ノい浄化性能を得ることができる。上表（ｄ）は総合
空燃比を理論混合比と稀薄側に交互に振動させた場合を
示す。この場合（ｃ）に比してＮＯＯの浄化率がかなり
低下する。更に上表には示していないが例えば総合空燃
比の平均値が稀薄側となるようにして総合空燃比を過濃
側と稀薄側に交互に振動させた場合でも高い浄化率を得
ることができる。これを第６図に示す。なお第６図にお
いて縦軸は浄化率、横軸は総合空燃比の平均値を示し、
また曲線ＣはＨＣ，ＣＯの浄化率、曲線ＤはＮＯｘの浄
化率を夫々示す。以上から明らかなように総合空燃比を
稀薄側と過濃側に振動せしめかつ総合空燃比の平均値が
理論空燃比に等しいか或いはそれより稀薄側にある場合
に極めて高い浄化率を得ることができる。即ち総合空燃
比を稀薄側と過濃側に交互に振動させた場合において高
い浄化効率を確保するには総合空燃比の平均値を必ずし
も理論空燃比に正確に一致させる必要はなく、稀薄側と
なつてもよいことが判明したのである。総合空燃比の平
均値を理論空燃比に正確に一致せしめるには酸素濃度検
出器を用いる必要があるが上述のように総合空燃比の平
均値が稀薄側にずれたとしても高い充填効率を得ること
ができるので特に酸素濃度検出器を用いる必要がなく、
それだけ空燃比制御システムを簡素化することが可能と
なる。次に第１図を参照して本発明に係る内燃機関につ
いて説明する。Table (c) above shows the case where the total air-fuel ratio is alternately oscillated toward the rich side and the lean side so that the average value of the total air-fuel ratio becomes the stoichiometric mixture ratio. In this case, although slightly inferior to (a), high purification performance can be obtained. Table (d) above shows the case where the total air-fuel ratio is alternately oscillated toward the stoichiometric mixture ratio and the lean side. In this case, the NOO purification rate is considerably lower than in (c). Furthermore, although it is not shown in the above table, a high purification rate can be obtained even if the average value of the total air-fuel ratio is made to be on the lean side and the total air-fuel ratio is alternately oscillated between the rich side and the lean side. . This is shown in FIG. In Fig. 6, the vertical axis shows the purification rate, and the horizontal axis shows the average value of the total air-fuel ratio.
Further, curve C shows the purification rate of HC and CO, and curve D shows the purification rate of NOx. As is clear from the above, an extremely high purification rate can be obtained when the total air-fuel ratio is oscillated between the lean side and the rich side and the average value of the total air-fuel ratio is equal to the stoichiometric air-fuel ratio or on the lean side. can. In other words, in order to ensure high purification efficiency when the total air-fuel ratio is alternately oscillated between the lean side and the rich side, the average value of the total air-fuel ratio does not necessarily have to exactly match the stoichiometric air-fuel ratio; It turns out that it's okay to grow old. It is necessary to use an oxygen concentration detector to accurately match the average value of the total air-fuel ratio to the stoichiometric air-fuel ratio, but as mentioned above, even if the average value of the total air-fuel ratio deviates to the lean side, high charging efficiency can be obtained. Therefore, there is no need to use a particular oxygen concentration detector.
It becomes possible to simplify the air-fuel ratio control system accordingly. Next, an internal combustion engine according to the present invention will be explained with reference to FIG.

第１図において１は機関本体、２は吸気マニホルド、３
は気化器、４はエアクリーナ、５は排気マニホルド、６
は排気管、７は三元触媒、８は２次空気供給制御弁装置
である。２次空気供給制御弁装置８は弁筺９とダイヤフ
ラム装置１０とを具備し、このダイヤフラム装置１０は
ダイヤフラム１１により隔成された負圧室１２と大気圧
室１３とを有する。In Figure 1, 1 is the engine body, 2 is the intake manifold, and 3 is the engine body.
is the carburetor, 4 is the air cleaner, 5 is the exhaust manifold, 6
7 is an exhaust pipe, 7 is a three-way catalyst, and 8 is a secondary air supply control valve device. The secondary air supply control valve device 8 includes a valve housing 9 and a diaphragm device 10, and the diaphragm device 10 has a negative pressure chamber 12 and an atmospheric pressure chamber 13 separated by a diaphragm 11.

弁筐９内には２個の隔壁１４，１５が設けられ、この隔
壁１４，１５によつて上部室１６、中部室１７、下部室
１８が形成される。隔壁１４には弁ボート１９が形成さ
れ、一方隔壁１５上には中部室１７から下部室１８に向
かう流れのみを許す逆止弁２０が設けられる。弁ボート
１９に対面して開閉弁２１が配置され、この開閉弁２１
はダイヤフラム１１に連結される。上部室１６は一方で
は２次空気供給管２２を介して機関駆動のエアポンプ２
３に連結され、他方では２次空気排出管２４を介して調
圧弁２５に連結される。この調圧弁２５の内部は開孔２
６を介して大気に連通し、かつ調圧弁２５内部には２次
空気排出管２４を閉鎖可能な弁２７と、この弁２７を常
時２次空気排出管開口端部に向けて押圧する圧縮ばね２
８とが設けられる。従つて上部室１６内の２次空気圧が
所定圧力以上に達すると弁２７が開弁し、斯くして上部
室１６内の２次空気圧は常時所定圧力に保持される。な
お、下部室１８は２次空気供給管２９を介して触媒コン
バータ７の入口近傍の排気管６内に連結される。ダイヤ
フラム装置１０の負圧室１２は導管３０を介して電磁弁
装置３１に連結される。電磁弁装置３１のハウジング内
には圧縮ばね３２のばね力により常時右方に押圧される
プランジャ３３と、このプランジャ３３に連結された開
閉弁３４と、プランジャ３３を吸引するためのソレノイ
ド３５を有し、このソレノイド３５は電子制御回路４０
に連結される。更に電磁弁装置３１のハウジング内には
吸気マニホルド２内に負圧導管３６を介して連結された
負圧ボート３７と、２次空気供給管２２に導管３８を介
して連結された２次空気ボート３９とが開口し、開閉弁
３４はこれらボート３７，３９を交互に開閉可能なよう
に配置される。第１図に示す実施例では更にダイヤフラ
ム装置４２を具えた可変抵抗装置４３が設けられる。こ
のダイヤフラム装置４２はダイヤフラム４４により隔成
された負圧室４５と大気圧室４６とを有し、負圧室４５
は負圧導管３６を介して吸気マニホルド２に連結される
。一方、可変抵抗装置４３は可動スライダ４７と固定抵
抗４８からなる可変抵抗器４９を有し、可動スライダ４
７はロッド５０を介してダイヤフラム４４に連結される
。従つて負圧室４５内に加わる吸気管負圧が増大すると
ダイヤフラム４４は圧縮ばね５１のばね力に抗しｌて右
方に移動し、それに伴つてスライダ４７も右方に移動し
、それに伴なつてスライダ４７も右方に移動するので可
変抵抗器４９の抵抗値は減少する。この可変抵抗器４９
は導線５２，５３を介して電子制御回路４０に接続され
る。また機関駆動７のデイストリビユータ５４は点火信
号を電子制御回路４０に送るために導線５５を介して電
子制御回路４０に接続される。第３図に電子制御回路４
０の回路図を示す。Two partition walls 14 and 15 are provided within the valve housing 9, and these partition walls 14 and 15 form an upper chamber 16, a middle chamber 17, and a lower chamber 18. A valve boat 19 is formed on the partition wall 14, while a check valve 20 is provided on the partition wall 15 to allow flow only from the middle chamber 17 to the lower chamber 18. An on-off valve 21 is arranged facing the valve boat 19, and this on-off valve 21
is connected to the diaphragm 11. The upper chamber 16 is connected on the one hand to an engine-driven air pump 2 via a secondary air supply pipe 22.
3 and, on the other hand, to a pressure regulating valve 25 via a secondary air discharge pipe 24. The inside of this pressure regulating valve 25 has an opening 2
6, and inside the pressure regulating valve 25 there is a valve 27 that can close the secondary air exhaust pipe 24, and a compression spring that constantly presses the valve 27 toward the open end of the secondary air exhaust pipe. 2
8 is provided. Therefore, when the secondary air pressure in the upper chamber 16 reaches a predetermined pressure or higher, the valve 27 opens, and thus the secondary air pressure in the upper chamber 16 is always maintained at a predetermined pressure. Note that the lower chamber 18 is connected to the inside of the exhaust pipe 6 near the inlet of the catalytic converter 7 via a secondary air supply pipe 29. The vacuum chamber 12 of the diaphragm device 10 is connected via a conduit 30 to a solenoid valve device 31 . Inside the housing of the electromagnetic valve device 31 are a plunger 33 that is constantly pressed to the right by the spring force of a compression spring 32, an on-off valve 34 connected to this plunger 33, and a solenoid 35 for attracting the plunger 33. However, this solenoid 35 is connected to an electronic control circuit 40.
connected to. Furthermore, inside the housing of the solenoid valve device 31 are a negative pressure boat 37 connected to the intake manifold 2 via a negative pressure conduit 36, and a secondary air boat connected to the secondary air supply pipe 22 via a conduit 38. 39 is opened, and the on-off valve 34 is arranged so as to be able to open and close these boats 37 and 39 alternately. In the embodiment shown in FIG. 1, a variable resistance device 43 with a diaphragm device 42 is further provided. This diaphragm device 42 has a negative pressure chamber 45 and an atmospheric pressure chamber 46 separated by a diaphragm 44.
is connected to the intake manifold 2 via a negative pressure conduit 36. On the other hand, the variable resistance device 43 has a variable resistor 49 consisting of a movable slider 47 and a fixed resistor 48.
7 is connected to the diaphragm 44 via a rod 50. Therefore, when the intake pipe negative pressure applied to the negative pressure chamber 45 increases, the diaphragm 44 moves to the right against the spring force of the compression spring 51, and the slider 47 also moves to the right. As the slider 47 also moves to the right, the resistance value of the variable resistor 49 decreases. This variable resistor 49
are connected to the electronic control circuit 40 via conductive wires 52 and 53. The distributor 54 of the engine drive 7 is also connected to the electronic control circuit 40 via a conductor 55 in order to send an ignition signal to the electronic control circuit 40. Figure 3 shows electronic control circuit 4.
0 circuit diagram is shown.

電子制御回路４０はデイストリビユータ５４に連結フさ
れて高周波成分を除去する抵域フィルタ５６と、低域フ
ィルタ５６に結合コンデンサ５７を介して連結された単
安定マルチバイブレータ５８と、単安定マルチバイブレ
ータ５８に連結された増巾回路５９とから構成され、増
巾回路５９の出力禎にソレノイド３５が連結される。単
安定マルチバイブレータ５８が発するパルスのパルス巾
はコンデンサ６０と可変抵抗器４９の時定数によつて定
まり、可変抵抗器４９の抵抗値が増大するとパルス巾は
広くなる。機関が運転を開始すると低域フィルタ５６の
出力側には第４図ａに示すように点火パルスに同期した
パルスが発生し、このパルスの立ち下がりによりトリガ
されて第４図ｂに示すように単安定マルチバイブレータ
５８はオン状態となる。このパルス巾は前述したように
可変抵抗器４９の抵抗値に比例し、斯くして吸気管負圧
の大きさに反比例する。次いで単安定マルチバイブレー
タ５８において発生したパルスは増巾回路５９において
第４図ｃに示すように増巾され、この増巾回路５９の出
力パルスによりソレノイド３５が付勢される。第１図に
おいてソレノイド３５が付勢されるとプランジャ３３は
左方に移動して負圧ボート３７が開口し、２次空気ボー
ト３９は閉鎖される。従つてこのときダイヤフラム装置
１０の負圧室１２は導管３０，３６を介して吸気マニホ
ルド２内に連結され、その結果負圧室１２内は吸気管負
圧となる。斯くしてダイヤフラム１１は圧縮ばね６１の
ばね力に抗して上昇し、弁ボート１９が開口して２次空
気がエアポンプ２３から２次空気供給導−管２２、弁ボ
ート１９、逆止弁２０並びに２次空気供給導管２９を介
して排気管６内に供給される。一方、単安定マルチバイ
ブレータ５８の発するパルス（第３図参照）がオフ状態
になるとソレノイド３５は虚勢され、その結果プランジ
ャ３３が右方に移動して２次空気ボート３９が開口し、
負圧ボート３７が閉鎖される。斯くしてダイヤフラム装
置１０の負圧室１２は導管３０，３８，２２を介してエ
アポンプ２３に連結され、開閉弁２１が弁ボート１９を
閉鎖して２次空気の供給が停！止する。従つて排気管６
内には２次空気が間欠的に供給されることになる。機関
シリンダ内に供給される吸入空気量は回転数にほぼ比例
し、吸気管負圧にほぼ反比例する。The electronic control circuit 40 includes a resistor filter 56 connected to a distributor 54 to remove high-frequency components, a monostable multivibrator 58 connected to the low-pass filter 56 via a coupling capacitor 57, and a monostable multivibrator. The solenoid 35 is connected to the output terminal of the amplifier circuit 59. The pulse width of the pulse emitted by the monostable multivibrator 58 is determined by the time constant of the capacitor 60 and the variable resistor 49, and as the resistance value of the variable resistor 49 increases, the pulse width becomes wider. When the engine starts operating, a pulse synchronized with the ignition pulse is generated on the output side of the low-pass filter 56 as shown in Figure 4a, and triggered by the fall of this pulse, as shown in Figure 4b. The monostable multivibrator 58 is turned on. As described above, this pulse width is proportional to the resistance value of the variable resistor 49, and thus inversely proportional to the magnitude of the intake pipe negative pressure. Next, the pulse generated in the monostable multivibrator 58 is amplified in an amplification circuit 59 as shown in FIG. 4c, and the output pulse of the amplification circuit 59 energizes the solenoid 35. In FIG. 1, when the solenoid 35 is energized, the plunger 33 moves to the left to open the negative pressure boat 37 and close the secondary air boat 39. Therefore, at this time, the negative pressure chamber 12 of the diaphragm device 10 is connected to the intake manifold 2 via the conduits 30, 36, and as a result, the inside of the negative pressure chamber 12 becomes an intake pipe negative pressure. The diaphragm 11 thus rises against the spring force of the compression spring 61, the valve boat 19 opens, and the secondary air flows from the air pump 23 to the secondary air supply conduit 22, the valve boat 19, and the check valve 20. It is also supplied into the exhaust pipe 6 via the secondary air supply conduit 29. On the other hand, when the pulse generated by the monostable multivibrator 58 (see FIG. 3) turns off, the solenoid 35 is energized, and as a result, the plunger 33 moves to the right and the secondary air boat 39 opens.
Negative pressure boat 37 is closed. In this way, the negative pressure chamber 12 of the diaphragm device 10 is connected to the air pump 23 via the conduits 30, 38, 22, the on-off valve 21 closes the valve boat 19, and the supply of secondary air is stopped! Stop. Therefore, the exhaust pipe 6
Secondary air is intermittently supplied inside. The amount of intake air supplied into the engine cylinder is approximately proportional to the rotational speed and approximately inversely proportional to the intake pipe negative pressure.

従つて前述したように単安定マルチバイブレータ・５８
において発生するパルスの個数は回転数に比例し、かつ
パルス巾が吸気管負圧に反比例するので排気管６内に供
給される２次空気量はほぼ吸入空気量に比例する。更に
、機関シリンダ内の濃混合気が供給されるように気化器
３が設定され、また交番的に振動する総合空燃比の平均
値が稀薄側、例えば１５〜１帽度になるように２次空気
供給制御弁装置８並びに調圧弁２５が設定されている。
従つて触媒コンバータ７の入口における総合空燃比は第
５図に示すように過濃側と稀薄側に交互に振動し、総合
空燃比の平均値Ｅは稀薄側となる。なお第１図に示すよ
うに２次空気を触媒コンバータの入口近傍に供給するこ
とによつて例えばノ過濃側から稀薄側へと総合空燃比を
鋭敏に変化せしめることができる。第２図に本発明によ
る別の実施例を示す。Therefore, as mentioned above, the monostable multivibrator 58
The number of pulses generated in is proportional to the rotational speed, and the pulse width is inversely proportional to the intake pipe negative pressure, so the amount of secondary air supplied into the exhaust pipe 6 is approximately proportional to the amount of intake air. Further, the carburetor 3 is set so that a rich air-fuel mixture is supplied in the engine cylinder, and the secondary carburetor is set so that the average value of the alternatingly vibrating overall air-fuel ratio is on the lean side, for example, 15 to 1 degree. An air supply control valve device 8 and a pressure regulating valve 25 are provided.
Therefore, the total air-fuel ratio at the inlet of the catalytic converter 7 alternately oscillates toward the rich side and the lean side, as shown in FIG. 5, and the average value E of the total air-fuel ratio is on the lean side. As shown in FIG. 1, by supplying secondary air near the inlet of the catalytic converter, the overall air-fuel ratio can be changed sharply, for example from the rich side to the lean side. FIG. 2 shows another embodiment according to the invention.

第２図に示す実施例では第１図の可変抵抗装置４３が削
除され、第１図の調圧弁２５に代わつて調圧弁６２が設
けられる。この調圧弁６２はダイヤフラム６３により隔
成された負圧室６４と大気圧室６５とを有し、この負圧
室６４は負圧導管６６，３６を介して吸気マニホルド２
内に連結される。一方大気圧室６５は開孔６７を介して
大気に連通する。また２次空気排出管２４の端部開口は
弁６８によつて閉鎖され、この弁６８はダイヤフラム６
３に連結されて圧縮ばね６９のばね力により常時左方に
向けて押圧される。弁６８が２次空気排出管２４の端部
開口を閉鎖する力は圧縮ばね６９のばね力と負圧室６４
内の負圧の大きさによつて定まり、吸気管負圧が大きく
なると弁６８の開弁力、即ち上部室１６内の２次空気圧
が小さくなる。第２図に示す電子制御回路４０は第３図
に示す回路と同様であるが第３図における可変抵抗器４
９は第２図において固定抵抗となり、従って第２図にお
ける単安定マルチバイブレータは常時一定巾のパルス信
号を発生する。In the embodiment shown in FIG. 2, the variable resistance device 43 of FIG. 1 is deleted, and a pressure regulating valve 62 is provided in place of the pressure regulating valve 25 of FIG. This pressure regulating valve 62 has a negative pressure chamber 64 and an atmospheric pressure chamber 65 separated by a diaphragm 63, and this negative pressure chamber 64 is connected to the intake manifold 2 through negative pressure conduits 66, 36.
connected within. On the other hand, the atmospheric pressure chamber 65 communicates with the atmosphere through an opening 67. The end opening of the secondary air discharge pipe 24 is closed by a valve 68, which is connected to the diaphragm 6.
3 and is constantly pressed toward the left by the spring force of the compression spring 69. The force with which the valve 68 closes the end opening of the secondary air discharge pipe 24 is due to the spring force of the compression spring 69 and the negative pressure chamber 64.
The opening force of the valve 68, that is, the secondary air pressure in the upper chamber 16 decreases as the intake pipe negative pressure increases. The electronic control circuit 40 shown in FIG. 2 is similar to the circuit shown in FIG.
9 is a fixed resistor in FIG. 2, and therefore the monostable multivibrator in FIG. 2 always generates a pulse signal of a constant width.

従つて第２図に示す実施例では単安定マルチバイブレー
タの発するパルスのパルス巾を変える代りに上部室１６
内の２次空気圧を変化させ、それによつて機関シリンダ
内に供給される吸入空気量に比例した２次空気を排気管
６内に供給するようにしている。発明の効果 本発明によれば酸素濃度検出器を用いることなく機関回
転数および吸気管負圧のみに応動して吸入空気量に比例
した量の２次空気を機関排気系に間欠的に供給するだけ
で高い浄化効率を確保することができる。Therefore, in the embodiment shown in FIG. 2, instead of changing the pulse width of the pulse generated by the monostable multivibrator, the upper chamber 16
By changing the secondary air pressure within the exhaust pipe 6, secondary air is supplied into the exhaust pipe 6 in proportion to the amount of intake air supplied into the engine cylinder. Effects of the Invention According to the present invention, an amount of secondary air proportional to the amount of intake air is intermittently supplied to the engine exhaust system in response only to the engine speed and intake pipe negative pressure without using an oxygen concentration detector. This alone can ensure high purification efficiency.

このように本発明では酸素濃度検出器を用いる必要がな
いのでそれだけ空燃比制御システムを簡素化することが
でき、更に酸素濃度検出器の熱劣化等を配慮する必要が
ないという利点がある。また、本発明により得られる浄
化効率は酸素濃度検出器を用いて総合空燃比の変動平均
値を理論空燃比に正確に一致せしめた場合の浄化効率と
同等であり、従つて高い浄化効率を確保しつつ空燃比制
御システムを簡素化できることになるので極めて実用性
が高いと云える。As described above, the present invention has the advantage that since there is no need to use an oxygen concentration detector, the air-fuel ratio control system can be simplified accordingly, and there is no need to consider thermal deterioration of the oxygen concentration detector. In addition, the purification efficiency obtained by the present invention is equivalent to the purification efficiency when the fluctuating average value of the total air-fuel ratio is made to exactly match the stoichiometric air-fuel ratio using an oxygen concentration detector, thus ensuring high purification efficiency. The air-fuel ratio control system can be simplified at the same time, so it can be said to be extremely practical.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明に係る排気ガス浄化装置を図解的に示す
図、第２図は別の実施例を図解的に示す図、第３図は第
１図の電子制御回路の電気回路図、第４図はパルス信号
を示すグラフ、第５図は総合空燃比の変化を示すグラフ
、第６図は排気ガス中の有害成分の浄化率を示すグラフ
である。 ２１１１吸気マニホルド、５１１●●排気マニホルド、
７・・・・・・触媒コンバータ、８・・・・・・２次空
気供給制御弁装置、２３・・・・エアポンプ、２５・・
・・・調圧弁、３１・・・・・・電磁弁装置、４０・・
・・・・電子制御回”路、４３・・・・・・可変抵抗装
置、５４・・・・・デイストリビユータ。FIG. 1 is a diagram schematically showing an exhaust gas purification device according to the present invention, FIG. 2 is a diagram schematically showing another embodiment, FIG. 3 is an electric circuit diagram of the electronic control circuit of FIG. 1, FIG. 4 is a graph showing pulse signals, FIG. 5 is a graph showing changes in the total air-fuel ratio, and FIG. 6 is a graph showing the purification rate of harmful components in exhaust gas. 2111 intake manifold, 511●●exhaust manifold,
7...Catalytic converter, 8...Secondary air supply control valve device, 23...Air pump, 25...
...Pressure regulating valve, 31...Solenoid valve device, 40...
. . . Electronic control circuit, 43 . . . Variable resistance device, 54 . . . Distributor.

Claims (1)

【特許請求の範囲】 １ 機関シリンダ内に濃混合気を供給すると共に機関排
気系に三元触媒コンバータを有し、該触媒コンバータ上
流の機関排気系に２次空気を供給して排気ガスの浄化を
行うようにした内燃機関の排気ガス浄化方法において、
酸素濃度検出器を用いることなく機関回転数および吸気
管負圧のみに応動して吸入空気量に比例した量の２次空
気を上記機関排気系に間欠的に供給することにより総合
空燃比を稀薄側と過濃側に交互に振動せしめかつ該交番
的に振動する総合空燃比の平均値が理論空燃比に等しい
か或いはそれより稀薄側にあるように設定したことを特
徴とする内燃機関の排気ガス浄化方法。 ２ 機関シリンダ内に濃混合気を供給すると共に機関排
気系に三元触媒コンバータを有し、該触媒コンバータ上
流の機関排気系に２次空気を供給して排気ガスの浄化を
行なうようにした内燃機関の排気ガス浄化装置において
、上記機関排気系と機関駆動の２次空気供給用エアポン
プとを連結する２次空気供給通路内に酸素濃度検出器を
用いることなく機関回転数および吸気管負圧のみに応動
して吸入空気量に比例した量の２次空気を間欠的に通過
せしめる２次空気供給制御弁装置を設け、該２次空気供
給制御弁装置を介して機関排気系に２次空気を間欠的に
供給して総合空燃比を稀薄側と過濃側に交互に振動せし
めかつ該交番的に振動する総合空燃比の平均値が理論空
燃比に等しいか或いはそれより稀薄側にあるように設定
したことを特徴とする内燃機関の排気ガス浄化装置。[Claims] 1. A three-way catalytic converter is provided in the engine exhaust system in addition to supplying a rich mixture into the engine cylinders, and secondary air is supplied to the engine exhaust system upstream of the catalytic converter to purify exhaust gas. In a method for purifying exhaust gas from an internal combustion engine,
The overall air-fuel ratio is diluted by intermittently supplying secondary air in an amount proportional to the amount of intake air to the engine exhaust system in response only to the engine speed and intake pipe negative pressure without using an oxygen concentration detector. The exhaust gas of an internal combustion engine is characterized in that the exhaust gas of an internal combustion engine is set so that the average value of the alternatingly vibrating total air-fuel ratio is equal to the stoichiometric air-fuel ratio or leaner than the stoichiometric air-fuel ratio. Gas purification method. 2. An internal combustion engine that supplies a rich mixture into the engine cylinders and has a three-way catalytic converter in the engine exhaust system, and purifies exhaust gas by supplying secondary air to the engine exhaust system upstream of the catalytic converter. In an engine exhaust gas purification system, only the engine speed and intake pipe negative pressure are used without using an oxygen concentration detector in the secondary air supply passage that connects the engine exhaust system and the engine-driven secondary air supply air pump. A secondary air supply control valve device is provided to intermittently pass an amount of secondary air proportional to the intake air amount in response to the intake air amount, and the secondary air is supplied to the engine exhaust system via the secondary air supply control valve device. The total air-fuel ratio is supplied intermittently to cause the total air-fuel ratio to alternately oscillate between the lean side and the rich side, and the average value of the alternately oscillating total air-fuel ratio is equal to the stoichiometric air-fuel ratio or on the lean side. An exhaust gas purification device for an internal combustion engine, characterized in that: