JPS6056257B2 - Automatic choke device for internal combustion engine - Google Patents

Description

【発明の詳細な説明】 本発明は、始動がそれ程困難でない外界温度の比較的高
い冷間始動時に機関に供給される混合気の空燃比を薄く
設定するようにした内燃機関の自動チョーク装置に関す
る。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic choke device for an internal combustion engine that sets the air-fuel ratio of the air-fuel mixture supplied to the engine to be lean during a cold start at a relatively high ambient temperature where starting is not so difficult. .

内燃機関では、エンジン冷間時、その始動を容易にすべ
く、比較的濃い空燃比を設定できるようにするためチョ
ーク弁がスロットル弁の上流の気化器内に設けられる。In internal combustion engines, a choke valve is provided in the carburetor upstream of the throttle valve to allow a relatively rich air-fuel ratio to be set to facilitate starting when the engine is cold.

従来はチョーク弁を手動で操作するのが普通であつたが
、最近は、チョーク弁に連結されるバイメタルと、該バ
イメタルの周囲に配置される電熱ヒータとの組合せより
成る所謂電熱式の自動チョーク装置もよく見られるよう
になつてきている。しカルながら、この従来の電熱式自
動チョーク装置の構造ではチョーク作動時のチョーク弁
の開放速度は一定であるため、例えばエンジン水温が２
０〜２５℃程度に高く始動が比較的容易な冷間時でも混
合気が濃く設定され、その結果排気ガス中の未燃焼のＨ
ＣおよびＣｏ成分が多量に残留する欠点があつた。In the past, it was common to operate the choke valve manually, but recently, so-called electric-heated automatic chokes have been developed, which are a combination of a bimetal connected to the choke valve and an electric heater placed around the bimetal. Devices are also becoming more common. However, in the structure of this conventional electrothermal automatic choke device, the opening speed of the choke valve when the choke is activated is constant.
Even when the temperature is high (about 0 to 25 degrees Celsius) and it is relatively easy to start, the air-fuel mixture is set to be rich, resulting in unburned H in the exhaust gas.
There was a drawback that large amounts of C and Co components remained.

そこで本発明の目的はかかる従来技術の欠点に鑑み、始
動が真に困難な冷間時のみ混合気を濃く設定でき、始動
が容易な冷間時は混合気を薄く設定てきる自動チョーク
装置を提供することにある。Therefore, in view of the drawbacks of the prior art, the object of the present invention is to provide an automatic choke device that can set the air-fuel mixture richer only when the engine is cold, when starting is truly difficult, and set the air-fuel mixture leaner when the engine is cold, when starting is easy. It is about providing.

以下添附図面によつて本発明を具体的に説明する。The present invention will be specifically explained below with reference to the accompanying drawings.

本発明の第１実施例を示す第１図において、１０はチョ
ーク弁であり、スロットル弁１２の上流の気化器内に設
けられている。In FIG. 1 showing a first embodiment of the present invention, 10 is a choke valve, which is provided in the carburetor upstream of a throttle valve 12. In FIG.

尚、このチョーク”弁１０は図示しないチヨークオープ
ナ機構によりエンジンの運転中は図の時計方向に回動付
勢されている。２８は、自動チョーク装置を構成するバ
イメタルケースでありその中には渦巻状のバイメタル２
２が収容されその一端２４はケース２０に固着され、そ
の自由端２４′は連結棒２６の一端に当接している。The choke valve 10 is rotated in the clockwise direction in the figure by a choke opener mechanism (not shown) while the engine is running. 28 is a bimetal case constituting the automatic choke device; Spiral bimetal 2
2 is housed, one end 24 of which is fixed to the case 20, and its free end 24' abuts one end of a connecting rod 26.

棒２６の他端は、チョーク弁１０の回動軸１『と一体の
レバー２８に枢着される。バイメタル２２は温度上昇と
ともにその自由端２『が右方に変位する構成のもので、
この右方変位によつて、図示しないチヨークオープナ機
構により時計方向に回動付勢されるチョーク弁１０の時
計方向への回動が許される。ケース２０内のバイメタル
２２の周囲には電熱ヒータ３０が配置され、その一端は
エンジン始動スイッチＳＷを介して電源Ｂに接続される
とともに、その他端はサーミスタ抵抗Ｒを介して接地側
に接続される。本発明によれば、２０〜２５℃程度の始
動が困難でない冷間時スロットル弁１２の下流の吸気マ
ニホルド３２内に空気を導入するための制御弁としての
負圧式空気開閉弁３４が設けられる。この開閉弁３４は
、弁体３６と、弁座３８と、弁体３６に結合したダイヤ
フラム４０と、ダイヤフラム４０を下方に付勢するばね
４２とを有して成る。ダイヤフラム４０の上側に形成さ
れる負圧室４４が機関アイドリングに相当する所定値以
上の負圧となると、ダイヤフラム４０はばね４２に抗し
て上方に変位されかくて弁体３６が弁座３８から離れる
。かくて、フィルタ４６を介し空気が導入され、この空
気は、補助空気導入通路４８を矢印Ａの如く通つて吸気
マニホルド３２に向う。然るに室４４内が正圧であると
、弁体３６は弁座３８に着座するから、制御弁３４は閉
位置となり吸気マニホルド３２への補助空気の導入は防
止される。５０は、始動が容易な冷間時を検知して開閉
される温度域知負圧開閉弁てあつて、大気開閉弁３４の
負圧室４４と、吸気マニホルド３２内に穿設．した負圧
ボート５２との間を結ふ負圧通路５４上に設けられる。The other end of the rod 26 is pivotally connected to a lever 28 that is integral with the rotation shaft 1' of the choke valve 10. The bimetal 22 has a structure in which its free end 2' displaces to the right as the temperature rises.
This rightward displacement allows the choke valve 10, which is urged to rotate clockwise by a choke opener mechanism (not shown), to rotate clockwise. An electric heater 30 is arranged around the bimetal 22 in the case 20, one end of which is connected to a power source B via an engine start switch SW, and the other end connected to the ground side via a thermistor resistor R. . According to the present invention, a negative pressure air on/off valve 34 is provided as a control valve for introducing air into the intake manifold 32 downstream of the throttle valve 12 in a cold state where starting at temperatures of about 20 to 25° C. is not difficult. The on-off valve 34 includes a valve body 36, a valve seat 38, a diaphragm 40 coupled to the valve body 36, and a spring 42 that urges the diaphragm 40 downward. When the negative pressure chamber 44 formed above the diaphragm 40 reaches a negative pressure equal to or higher than a predetermined value corresponding to engine idling, the diaphragm 40 is displaced upward against the spring 42, and the valve body 36 is moved away from the valve seat 38. Leave. Air is thus introduced through the filter 46 and passes through the auxiliary air introduction passage 48 as indicated by arrow A toward the intake manifold 32. However, when the pressure inside the chamber 44 is positive, the valve body 36 is seated on the valve seat 38, so that the control valve 34 is in the closed position and the introduction of auxiliary air into the intake manifold 32 is prevented. Reference numeral 50 is a temperature range sensitive negative pressure on/off valve that opens and closes by detecting cold conditions when starting is easy, and is provided in the negative pressure chamber 44 of the atmospheric on/off valve 34 and in the intake manifold 32. It is provided on a negative pressure passage 54 connecting between the negative pressure boat 52 and the negative pressure boat 52 .

負圧開閉弁５０は、この実施例ではエンジン冷却水Ｗの
温度を検知するバイメタル部材５８を備えていて、エン
ジン始動が真に困難なエンジン水温が所定値以下の時に
このバイメタ．ル部材５８は図の実線の如き形状をとり
開閉弁５０は閉状態である。このときは、吸気ボート５
２の負圧は、大気開閉弁３４の負圧室４４に達しない。
エンジン始動が容易なエンジン水温が所定値以上の時は
このバイメタル部材５８は図の破線の−如き形状をとり
弁５０は開状態である。このときは、吸気ボート５２の
負圧は大気開閉弁３４に達するのが許される。６０は、
吸気ボート５２の負圧を緩りと大気開閉弁３４に伝達す
る負圧遅延弁て、大気開閉弁３４が急激に開とされるの
を防止すべく作動するものである。In this embodiment, the negative pressure on/off valve 50 includes a bimetallic member 58 that detects the temperature of the engine cooling water W, and when the engine water temperature is below a predetermined value, which makes engine starting truly difficult, the bimetallic member 58 detects the temperature of the engine cooling water W. The valve member 58 has a shape as shown by the solid line in the figure, and the on-off valve 50 is in a closed state. At this time, intake boat 5
The negative pressure of No. 2 does not reach the negative pressure chamber 44 of the atmospheric opening/closing valve 34.
When the engine water temperature is above a predetermined value, at which the engine can be easily started, the bimetal member 58 assumes the shape indicated by the broken line in the figure, and the valve 50 is in an open state. At this time, the negative pressure of the intake boat 52 is allowed to reach the atmospheric opening/closing valve 34. 60 is
The negative pressure delay valve slowly transmits the negative pressure of the intake boat 52 to the atmospheric opening/closing valve 34, and operates to prevent the atmospheric opening/closing valve 34 from being opened suddenly.

以上述べた第１の実施例に係る自動チョーク装置の作動
を以下説明する。The operation of the automatic choke device according to the first embodiment described above will be explained below.

エンジンの始動の困難な、エンジン水温の低い（２０℃
以下）冷間時は負圧開閉弁５０のバイメタル５８は図の
実線位置をとり、かくて吸気ボート５２の負圧は大気開
閉弁３４の負圧室４４に達しない。それ故、大気が吸・
気マニホルド３２内に余計に供給されることはなく、エ
ンジン始動に伴ないスイッチＳＷが投入された後の電熱
ヒータ３０の温度上昇の故にバイメタル２２の自由端２
Ｃが右方に変位するのに応じて、チョーク弁１０が完全
に開放されるまでの間、言い換えれば暖機されるまでの
間濃い混合気が設定される。然るに、エンジン始動の容
易な、エンジン水温のあまり低くない（例えば２０〜２
５℃）冷間時は、負圧開閉弁５０のバイメタル５８は図
の破線位置をとり、かくて吸気ボート５２の負圧は大気
開閉弁３４の負圧室４４に伝わるのが許される。Difficult to start the engine, low engine water temperature (20℃)
(Below) When the engine is cold, the bimetal 58 of the negative pressure shut-off valve 50 assumes the position shown by the solid line in the figure, so that the negative pressure of the intake boat 52 does not reach the negative pressure chamber 44 of the atmospheric shut-off valve 34. Therefore, the atmosphere absorbs
There is no excess air supplied into the manifold 32, and the free end 2 of the bimetal 22 rises in temperature after the switch SW is turned on when the engine starts.
As C moves to the right, a rich air-fuel mixture is set until the choke valve 10 is completely opened, in other words, until the engine is warmed up. However, if the engine water temperature is not too low (for example, 20 to 2
5° C.), the bimetal 58 of the negative pressure on-off valve 50 assumes the position indicated by the broken line in the figure, thus allowing the negative pressure of the intake boat 52 to be transmitted to the negative pressure chamber 44 of the atmospheric on-off valve 34.

負圧遅延弁６０の存在故に、エンジンの始動時からボー
ト５２の負圧は緩りと大気開閉弁３４に伝わるから、始
動直後は大気開閉弁３４は開とされす暫くは濃い混合気
が、チョーク弁１０がこのときは電熱ヒータ３０が未だ
暖つていない故閉となつていることに基づいて、設定さ
れ、かくてエンジンの始動は支障なく行われる。負圧遅
延弁６０の絞り６１の寸法で定まる一定時間が経過する
と、吸気ボート５２からの負圧レベルはばね４２の設定
値を超え、かくて弁体３６は弁座３８から離れフィルタ
４６を介して空気が開閉弁３４内に入り、補助空気導入
通路４８を矢印Ａの如く通つて吸気マニホルド３２内に
導入される。それ故、かかるエンジン水温のあまり低く
ない冷間時は、始動直後は、チョーク弁１０が閉である
ことに基づき濃い混合気が設定されるがその後は大気開
閉弁３４が開とされることに基づき薄い混合気が設定さ
れる。かくてかかる冷間時における排気ガス中の未燃焼
ＣＯおよびＨＣ成分の残留量は押えられる。尚、ばね４
２の設定圧は、エンジンがアイドル時（即ちスロットル
弁１２が図の全開位置にあるとき）にあるときの負圧レ
ベル（最大負圧）より多少小さく決めてある。それ故、
機関がアイドリングから走行に移行すると開閉弁３４は
閉となる。そのため始動直後に走行を始める（即ちスロ
ットル弁１２を開とする）場合には、負圧レベルが低下
するため弁３４は閉状態に戻り、弁体３６は弁座３８を
塞ぎ空気の導入は行われず混合気は濃く設定される。そ
れ故、未だエンジンの完全に暖つていない始動直後に走
行を始めても加速時に息つきを生じたりするおそれは回
避される。第２図に示す本発明の第２の実施例では、第
１図の大気開閉弁３４の代りに、エンジンに既存のクラ
ンクケース掃気装置の所譚℃Ｖ弁７０を多少の変更を施
して制御弁として使用している点が特徴である。ＰＣＶ
弁７０は、クランクケース中のブローバイガスを吸気マ
ニホルドに再循環する働きをなすが、再循環時ブローバ
イガスは極めて薄められているからほとんど空気と同様
に取扱つてかまわない。又、この構造は、第１図と異な
り補助空気導入通路４８の新設が不用であり既存のＰＣ
■通路７０を補助空気導入通路として代用している。こ
れは、この通路４８の寸法がかなり大となることを考え
合わせると有利な点である。本発明によれば、クランク
ケースからのブローバイガスを薄めて、ＰＣ■通路７２
を介し吸気マニホルド３２に循環させる働きをなすＰＣ
■弁７０の弁体７４の廻りにはソレノイドＬが巻回され
る。コイルＬが励磁されると、弁体７４はばね７６に抗
して図の左方に引かれ、このときはＰＣ■弁７０を矢印
Ａの如く通る流量は大であり、然るにソレノイドＬの励
磁が解放されていると、ばね７６は弁体７４を右方に押
し戻しこのときの流量は小である。励磁コイルＬは、負
圧スイッチ８０およびエンジン始動スイッチＳＷを介し
て電源Ｂに接続される。負圧スイッチ８０は固定接点８
２と、ダイヤフラム８４に結合される移動接点８６とを
有するものであり、ダイヤフラム８４の上方に形成され
る負圧室８８内の負圧が機関のアイドリング相当の値に
達するとダイヤフラム８４はばね９０に打ち勝つて上方
に変位して固定接点８２と移動接点８６とが接するオン
状態となり、然るに室８８内の負圧がばね９０以下であ
るとオフ状態をとる。この負圧スイッチ８０の負圧室８
８は、第１図と同様な負圧遅延弁６０、バイメタル式温
度感知開閉弁５０を介して吸気ボート５２に連通される
。その他の構造は第１図のそれと同様である。以上述べ
た第二実施例に係る自動チョーク装置の作動において、
エンジンの始動の困難なエンジン水温の極めて低い冷間
時はバイメタル弁５０は閉位置をとる。かくて負圧スイ
ッチ８０にボート５２の負圧は達せず、これは図のオフ
状態を保つ。それ故、励磁コイルＬに電流は通さず、弁
体７４はばね７６によつて最も右方に付勢された位置を
とり、矢印Ａの如く吸気マニホルド３２に導入される空
気量は空燃比に影響しない程度に少ないか又は零である
。それ故、スイッチＳＷの投入後ヒータ３０によりバイ
メタル２２が暖められるまでチョーク弁１０は閉である
ことに基づき濃い混合気が設定される。然るに、エンジ
ンの始動の比較的容易なエンジン水温のあまり低くない
冷間時は、バイメタル弁５０は図の破線の如く開とされ
ボート５２の負圧は負圧スイッチ８０に達するのが許さ
れる。Due to the presence of the negative pressure delay valve 60, the negative pressure in the boat 52 is slowly transmitted to the atmospheric shut-off valve 34 from the time the engine is started, so the atmospheric shut-off valve 34 is opened immediately after the engine starts, and for a while the rich air-fuel mixture is maintained. The choke valve 10 is set based on the fact that the electric heater 30 has not yet warmed up and is closed, so that the engine can be started without any trouble. After a certain period of time determined by the dimensions of the orifice 61 of the negative pressure delay valve 60, the level of negative pressure from the intake boat 52 exceeds the set point of the spring 42, and the valve body 36 is thus separated from the valve seat 38 and passed through the filter 46. Air enters the on-off valve 34, passes through the auxiliary air introduction passage 48 as shown by arrow A, and is introduced into the intake manifold 32. Therefore, when the engine water temperature is not very low, a rich air-fuel mixture is set based on the fact that the choke valve 10 is closed immediately after starting, but after that, the atmospheric opening/closing valve 34 is opened. Based on this, a lean mixture is set. In this way, the amount of unburned CO and HC components remaining in the exhaust gas during such cold periods can be suppressed. Furthermore, spring 4
The set pressure No. 2 is determined to be somewhat smaller than the negative pressure level (maximum negative pressure) when the engine is idling (that is, when the throttle valve 12 is in the fully open position as shown in the figure). Therefore,
When the engine shifts from idling to running, the on-off valve 34 is closed. Therefore, when starting to run immediately after starting (that is, opening the throttle valve 12), the negative pressure level decreases, so the valve 34 returns to the closed state, the valve element 36 closes the valve seat 38, and air is not introduced. Therefore, the mixture is set to be rich. Therefore, even if the vehicle starts running immediately after starting when the engine is not yet completely warmed up, the possibility of the vehicle suffocating during acceleration is avoided. In a second embodiment of the present invention shown in FIG. 2, instead of the atmosphere opening/closing valve 34 shown in FIG. 1, a C.V. It is distinctive in that it is used as a valve. PCV
The valve 70 serves to recirculate the blowby gas in the crankcase to the intake manifold, but when recirculated the blowby gas is so diluted that it can be treated almost like air. Also, unlike the structure shown in Fig. 1, this structure does not require the installation of a new auxiliary air introduction passage 48 and can be used with existing PCs.
(2) The passage 70 is used as an auxiliary air introduction passage. This is an advantage in view of the rather large dimensions of this passageway 48. According to the present invention, the blow-by gas from the crankcase is diluted and the PC passage 72
A PC that functions to circulate the air to the intake manifold 32 through the
(2) A solenoid L is wound around the valve body 74 of the valve 70. When the coil L is energized, the valve body 74 is pulled to the left in the figure against the spring 76, and at this time, the flow passing through the PC valve 70 as indicated by arrow A is large, and the solenoid L is energized. When the valve is released, the spring 76 pushes the valve body 74 back to the right, and the flow rate at this time is small. Excitation coil L is connected to power source B via negative pressure switch 80 and engine start switch SW. Negative pressure switch 80 has fixed contact 8
2 and a movable contact 86 coupled to the diaphragm 84. When the negative pressure in the negative pressure chamber 88 formed above the diaphragm 84 reaches a value equivalent to idling of the engine, the diaphragm 84 releases the spring 90. When the contact 82 overcomes this and is displaced upward, the fixed contact 82 and the movable contact 86 come into contact with each other, resulting in an on state.However, when the negative pressure in the chamber 88 is lower than the spring 90, an off state is achieved. Negative pressure chamber 8 of this negative pressure switch 80
8 is communicated with the intake boat 52 via a negative pressure delay valve 60 and a bimetallic temperature sensing on/off valve 50 similar to those shown in FIG. The rest of the structure is the same as that in FIG. In the operation of the automatic choke device according to the second embodiment described above,
The bimetallic valve 50 assumes the closed position when the engine is cold and the engine water temperature is extremely low, making it difficult to start the engine. Thus, the negative pressure of the boat 52 does not reach the negative pressure switch 80, which remains in the off state as shown. Therefore, no current is passed through the excitation coil L, the valve body 74 assumes the position where it is biased most to the right by the spring 76, and the amount of air introduced into the intake manifold 32 as shown by arrow A is adjusted to the air-fuel ratio. The amount is so small that it has no effect or is zero. Therefore, since the choke valve 10 remains closed until the bimetal 22 is warmed by the heater 30 after the switch SW is turned on, a rich air-fuel mixture is set. However, when the engine is relatively easy to start and the engine water temperature is not very low, the bimetallic valve 50 is opened as shown by the broken line in the figure, and the negative pressure of the boat 52 is allowed to reach the negative pressure switch 80.

負圧遅延弁６０の存在故に、始動直後は負圧スイッチ８
０は暫くオフを保ち、ＰＣＶ通路７２内の矢印Ａの如き
流量を小に保つてチョーク弁１０が閉である故設定され
る濃い混合気を機関に供給してエンジンを完全に始動さ
せる。負圧遅延弁６０の絞り６１の寸法て定まる時間か
経過すると負圧スイッチ８０の負圧室８８には十分な負
圧が伝わりこれはオンされる。それ故励磁コイルＬに電
流が通じて弁体７４をばね７６に抗して左方に引きＰＣ
Ｖ通路７２中の流量を増大させて、チョーク弁１０が閉
であることに基づく濃い混合気を薄めて機関に供給する
。かくして、機関内での混合気の完全燃焼が図れ、排気
ガス中の残留ＣＯおよびＨＣ成分は押えられる。尚、ば
ね８２の設定圧は前の実施例と同様機関のアイドル相当
の負圧より多少小さく設定される。そのためアイドル以
外ではスイッチ８０は水温に係わらすオフとなり、ＰＣ
Ｖ弁はその本来の作動をすることになる。以上述べたよ
うに、本発明によれば、チョーク効果が強くは要求され
ない冷間時、空気を吸気マニホルド中に導入してこれに
よつてチョーク弁により設定される濃い混合気を薄めて
機関に供給している。それ故、チョーク効果と、未燃炉
？ＯおよびＨＣ成分排出量低減効果との兼合のとれた自
動チョーク装置が供給される。Due to the presence of the negative pressure delay valve 60, the negative pressure switch 8 is activated immediately after startup.
0 is kept off for a while, the flow rate as indicated by arrow A in the PCV passage 72 is kept small, and since the choke valve 10 is closed, the set rich air-fuel mixture is supplied to the engine, and the engine is completely started. After a period of time determined by the size of the throttle 61 of the negative pressure delay valve 60 has elapsed, sufficient negative pressure is transmitted to the negative pressure chamber 88 of the negative pressure switch 80 and it is turned on. Therefore, current flows through the excitation coil L, pulling the valve body 74 to the left against the spring 76.
The flow rate in V passage 72 is increased to dilute the rich mixture due to choke valve 10 being closed and supply it to the engine. In this way, complete combustion of the air-fuel mixture within the engine can be achieved, and residual CO and HC components in the exhaust gas can be suppressed. Incidentally, the set pressure of the spring 82 is set to be somewhat smaller than the negative pressure corresponding to the idle of the engine, as in the previous embodiment. Therefore, at times other than idle, the switch 80 is turned off regardless of the water temperature, and the PC
The V-valve will perform its original operation. As described above, according to the present invention, air is introduced into the intake manifold during cold conditions when a strong choke effect is not required, thereby diluting the rich mixture set by the choke valve and supplying the engine. supplying. Therefore, the choke effect and the unburned furnace? An automatic choke device is provided that combines the effect of reducing O and HC component emissions.

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

第１図は本発明の第一の実施例を示す概略図；第２図は
第二の実施例を示す概略図；１０・・・チョーク弁、３
２・・・吸気マニホルド、３４・・・制御弁としての大
気開閉弁、５０・・・温度感知負圧開閉弁、６０・・・
負圧遅延弁、７０・・・制御弁としてのＰＣＶ弁、８０
・・・負圧スイッチ、ＳＷ・・・エンジン始動スイッチ
。Fig. 1 is a schematic diagram showing a first embodiment of the present invention; Fig. 2 is a schematic diagram showing a second embodiment; 10... choke valve, 3
2... Intake manifold, 34... Atmospheric opening/closing valve as a control valve, 50... Temperature sensing negative pressure opening/closing valve, 60...
Negative pressure delay valve, 70... PCV valve as control valve, 80
...Negative pressure switch, SW...Engine start switch.

Claims (1)

【特許請求の範囲】[Claims] １ エンジン始動後暖機されるまでの冷間始動時チョー
ク弁を保ち気化器で設定される混合気空燃比を濃くする
自動チョーク装置において、気化器のスロットル弁の下
流の吸気通路に開口する補助空気導入通路４８、７２を
有し、該補助空気導入通路を流れる空気の流量の制御弁
３４、７０を有し、機関の負圧がアイドル相当の所定値
以上において、前記制御弁は、機関の温度が始動の困難
な所定値以下のときは常時閉とされ、機関の温度が始動
が比較的容易な前記所定値以上のときは機関の始動から
所定時間が経過するまで閉に維持され、その後開となる
内燃機関の自動チョーク装置。1 In an automatic choke device that keeps the choke valve open during a cold start until the engine is warmed up and enriches the mixture air-fuel ratio set by the carburetor, an auxiliary device that opens into the intake passage downstream of the throttle valve of the carburetor. It has air introduction passages 48 and 72, and has control valves 34 and 70 for controlling the flow rate of air flowing through the auxiliary air introduction passage, and when the negative pressure of the engine is equal to or higher than a predetermined value corresponding to idle, the control valve When the temperature is below a predetermined value at which starting is difficult, the engine is always closed; when the temperature of the engine is above the predetermined value, at which starting is relatively easy, the engine is kept closed until a predetermined time has elapsed after the engine has started; Automatic choke device for internal combustion engines.