JP5640880B2 - Fuel supply device for internal combustion engine - Google Patents

Fuel supply device for internal combustion engine Download PDF

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JP5640880B2
JP5640880B2 JP2011099233A JP2011099233A JP5640880B2 JP 5640880 B2 JP5640880 B2 JP 5640880B2 JP 2011099233 A JP2011099233 A JP 2011099233A JP 2011099233 A JP2011099233 A JP 2011099233A JP 5640880 B2 JP5640880 B2 JP 5640880B2
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小島　進
進 小島
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Toyota Motor Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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    • Y02T10/12—Improving ICE efficiencies

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Description

本発明は、低圧燃料ポンプから吐出された燃料を高圧燃料ポンプで加圧して燃料噴射弁に送る内燃機関の燃料供給装置に関する。   The present invention relates to a fuel supply device for an internal combustion engine that pressurizes fuel discharged from a low-pressure fuel pump with a high-pressure fuel pump and sends the fuel to a fuel injection valve.

燃料タンクから電動式の低圧燃料ポンプで燃料を汲み上げ、その燃料を高圧燃料ポンプで加圧して燃料噴射弁に送る燃料供給装置が知られている。このような装置において、低圧燃料ポンプの吐出圧を徐々に低下させ、高圧燃料ポンプに設けられている燃料量調整弁の制御に使用する制御量が所定の限界値を上回った場合にはその吐出圧の低下を制限する燃料供給装置が知られている（特許文献１参照）。その他、本発明に関連する先行技術文献として特許文献２、３が存在する。   There is known a fuel supply device that pumps fuel from a fuel tank with an electric low-pressure fuel pump, pressurizes the fuel with a high-pressure fuel pump, and sends the fuel to a fuel injection valve. In such a device, the discharge pressure of the low-pressure fuel pump is gradually reduced, and if the control amount used for controlling the fuel amount adjustment valve provided in the high-pressure fuel pump exceeds a predetermined limit value, the discharge A fuel supply device that limits a decrease in pressure is known (see Patent Document 1). In addition, Patent Documents 2 and 3 exist as prior art documents related to the present invention.

特開２００３−２２２０６０号公報JP 2003-222060 A 特開平０７−０２７０３０号公報Japanese Patent Application Laid-Open No. 07-027030 特開２０１０−０７１２２４号公報JP 2010-071224 A

低圧燃料ポンプと高圧燃料ポンプを接続する通路が内燃機関の熱等にて加熱された場合には、その通路内において燃料中に気泡が発生するおそれがある。そして、このように気泡が発生すると燃料の圧送に支障が生じ、燃料の圧力が大きく変動する。特許文献１の装置では高圧燃料ポンプ内の燃料の温度変化に基づいて低圧燃料ポンプの吐出圧を制御しているため、通路内における気泡の発生に対して対応が遅くなる。そのため、吐出圧を正常に制御できず燃料の圧力が大きく変動するおそれがある。   When the passage connecting the low-pressure fuel pump and the high-pressure fuel pump is heated by the heat of the internal combustion engine or the like, bubbles may be generated in the fuel in the passage. When bubbles are generated in this manner, the pressure of the fuel is hindered, and the fuel pressure greatly fluctuates. In the apparatus of Patent Document 1, since the discharge pressure of the low-pressure fuel pump is controlled based on the temperature change of the fuel in the high-pressure fuel pump, the response to the generation of bubbles in the passage is delayed. Therefore, the discharge pressure cannot be controlled normally, and the fuel pressure may fluctuate greatly.

そこで、本発明は、低圧燃料ポンプと高圧燃料ポンプとを接続する通路が加熱されても燃料の圧力が変動することを抑制可能な内燃機関の燃料供給装置を提供することを目的とする。   Therefore, an object of the present invention is to provide a fuel supply device for an internal combustion engine that can suppress fluctuations in fuel pressure even when a passage connecting the low pressure fuel pump and the high pressure fuel pump is heated.

本発明の内燃機関の燃料供給装置は、車両に搭載された内燃機関に適用され、電動式の低圧燃料ポンプと、前記内燃機関の機関本体に取り付けられ、かつ吐出圧を変更可能な高圧燃料ポンプと、前記車両において前記内燃機関が搭載されている空間に配置されて前記低圧燃料ポンプの吐出側と前記高圧燃料ポンプの吸入側とを接続する低圧通路と、を備え、前記低圧燃料ポンプから吐出された燃料を前記高圧燃料ポンプで加圧して燃料噴射弁に送る燃料供給装置において、前記高圧燃料ポンプの下流側の燃圧を検出する燃圧検出手段と、前記燃圧検出手段が検出した燃圧と目標値との偏差が低減するように前記偏差に基づいて前記高圧燃料ポンプのフィードバック制御を行う高圧ポンプ制御手段と、前記低圧燃料ポンプの運転中に前記低圧燃料ポンプの吐出圧力を所定の低下量ずつ低下させる低下処理を実行するとともに前記偏差に基づいて算出された前記フィードバック制御の制御項に基づいて前記低下処理の実行の可否を判断する低圧ポンプ制御手段と、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度より高い場合には前記低圧ポンプ制御手段による前記低圧燃料ポンプの吐出圧力の低下を制限する圧力低下制限手段と、を備えている（請求項１）。 The fuel supply device for an internal combustion engine of the present invention is applied to an internal combustion engine mounted on a vehicle, and is an electric low-pressure fuel pump, and a high-pressure fuel pump attached to the engine body of the internal combustion engine and capable of changing a discharge pressure. When, and a low-pressure passage the connects the discharge side of the low pressure fuel pump is disposed in a space internal combustion engine is mounted and a suction side of the high-pressure fuel pump in the vehicle, the discharge from the low pressure fuel pump In a fuel supply device that pressurizes the generated fuel with the high-pressure fuel pump and sends it to a fuel injection valve, fuel pressure detection means for detecting the fuel pressure downstream of the high-pressure fuel pump, fuel pressure detected by the fuel pressure detection means, and a target value A high-pressure pump control means for performing feedback control of the high-pressure fuel pump based on the deviation so that a deviation from the low-pressure fuel pump is operating. Low pressure pump control means for performing a reduction process for reducing the discharge pressure of the pump by a predetermined reduction amount and determining whether or not the reduction process can be executed based on a control term of the feedback control calculated based on the deviation. And a pressure drop limiting means for limiting a drop in the discharge pressure of the low pressure fuel pump by the low pressure pump control means when the temperature of the intake air of the internal combustion engine is higher than the temperature of the cooling water of the internal combustion engine. (Claim 1).

本発明の燃料供給装置では、高圧燃料ポンプが機関本体に取り付けられているので、このポンプの温度と内燃機関の冷却水の温度（冷却水温）とはほぼ同じと考えることができる。また、低圧通路は内燃機関が搭載されている空間に配置されているので、この通路の温度は内燃機関の吸気の温度（吸気温度）とほぼ同じと考えることができる。そのため、吸気温度が冷却水温より高い場合には低圧通路が加熱されて低圧通路の温度が高圧燃料ポンプの温度より高くなり低圧通路内にて燃料中に気泡が発生すると予想できる。本発明の燃料供給装置によれば、このような場合には吐出圧力の低下を制限するので、低圧通路の圧力の低下が抑制される。周知のように圧力が高いほど気泡が発生し難いので、これにより気泡の発生を抑制できる。そのため、燃圧の変動を抑制できる。   In the fuel supply apparatus of the present invention, since the high-pressure fuel pump is attached to the engine body, the temperature of the pump and the temperature of the cooling water (cooling water temperature) of the internal combustion engine can be considered to be substantially the same. Further, since the low pressure passage is disposed in the space in which the internal combustion engine is mounted, the temperature of this passage can be considered to be substantially the same as the temperature of the intake air (intake air temperature) of the internal combustion engine. Therefore, when the intake air temperature is higher than the cooling water temperature, the low pressure passage is heated and the temperature of the low pressure passage becomes higher than the temperature of the high pressure fuel pump, and it can be expected that bubbles are generated in the fuel in the low pressure passage. According to the fuel supply device of the present invention, in such a case, since the decrease in the discharge pressure is limited, the decrease in the pressure in the low-pressure passage is suppressed. As is well known, bubbles are less likely to be generated as the pressure is higher, thereby suppressing the generation of bubbles. Therefore, fluctuations in fuel pressure can be suppressed.

本発明の燃料供給装置の一形態において、前記圧力低下制限手段は、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度より高い場合には前記低圧ポンプ制御手段による前記低下処理の実行を禁止してもよい（請求項２）。この場合、低圧通路の圧力が低下することを防止できるので、気泡の発生をより確実に抑制できる。そのため、燃圧の変動をより確実に抑制できる。   In one form of the fuel supply apparatus of the present invention, the pressure drop limiting means executes the reduction process by the low pressure pump control means when the temperature of the intake air of the internal combustion engine is higher than the temperature of the cooling water of the internal combustion engine. May be prohibited (claim 2). In this case, it is possible to prevent the pressure in the low pressure passage from being lowered, and thus it is possible to more reliably suppress the generation of bubbles. Therefore, fluctuations in fuel pressure can be more reliably suppressed.

また、前記低圧ポンプ制御手段は、前記低圧燃料ポンプの吐出圧力が所定の下限値以下になると前記低下処理を中止し、前記圧力低下制限手段は、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度より高い場合には、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度以下の場合よりも前記下限値を高くしてもよい（請求項３）。このように下限値を変更することにより、低圧通路の温度に応じて低圧通路における気泡の発生を適切に抑制できる。そのため、燃圧の変動を抑制できる。   Further, the low-pressure pump control means stops the reduction process when the discharge pressure of the low-pressure fuel pump becomes a predetermined lower limit value or less, and the pressure drop restriction means sets the intake air temperature of the internal combustion engine to the value of the internal combustion engine. When the temperature is higher than the temperature of the cooling water, the lower limit value may be set higher than when the temperature of the intake air of the internal combustion engine is equal to or lower than the temperature of the cooling water of the internal combustion engine. By changing the lower limit value in this way, it is possible to appropriately suppress the generation of bubbles in the low pressure passage according to the temperature of the low pressure passage. Therefore, fluctuations in fuel pressure can be suppressed.

本発明の燃料供給装置の一形態において、前記高圧ポンプ制御手段は、前記フィードバック制御として比例積分制御を行い、前記低圧ポンプ制御手段は、前記比例積分制御の積分項の値が所定の判定値を超えた場合に前記低圧燃料ポンプの吐出圧力の低下を制限してもよい（請求項４）。周知のように比例積分制御の積分項は実際の値と目標値との偏差を積算したものと相関している。そのため、積分項が大きい場合には偏差が大きくなっていると考えられる。この形態では、このような場合には吐出圧力の低下を制限するので、偏差が大きくなることを抑制できる。そのため、燃圧を目標値に調整しつつ低圧燃料ポンプの吐出圧力を低下させることができる。これにより低圧燃料ポンプで消費されるエネルギを低減できる。   In one form of the fuel supply device of the present invention, the high-pressure pump control means performs proportional-integral control as the feedback control, and the low-pressure pump control means determines that the integral term value of the proportional-integral control has a predetermined determination value. When it exceeds, reduction of the discharge pressure of the low-pressure fuel pump may be limited (Claim 4). As is well known, the integral term of proportional integral control correlates with the sum of the deviation between the actual value and the target value. Therefore, it is considered that the deviation is large when the integral term is large. In this configuration, in such a case, the decrease in the discharge pressure is limited, so that an increase in deviation can be suppressed. Therefore, the discharge pressure of the low-pressure fuel pump can be reduced while adjusting the fuel pressure to the target value. Thereby, the energy consumed by the low-pressure fuel pump can be reduced.

以上に説明したように、本発明の燃料供給装置によれば、吸気温度が冷却水温より高い場合には吐出圧力の低下を制限するので、低圧通路が加熱されても低圧通路で気泡が発生することを抑制できる。そのため、燃圧の変動を抑制できる。   As described above, according to the fuel supply device of the present invention, when the intake air temperature is higher than the cooling water temperature, the discharge pressure is limited to be lowered. Therefore, even if the low pressure passage is heated, bubbles are generated in the low pressure passage. This can be suppressed. Therefore, fluctuations in fuel pressure can be suppressed.

本発明の一形態に係る燃料供給装置が組み込まれた内燃機関の燃料供給系を模式的に示す図。The figure which shows typically the fuel supply system of the internal combustion engine in which the fuel supply apparatus which concerns on one form of this invention was integrated. ＥＣＵが実行する制御実行判定ルーチンを示すフローチャート。The flowchart which shows the control execution determination routine which ECU performs.

図１は、本発明の一形態に係る燃料供給装置が組み込まれた内燃機関の燃料供給系を模式的に示している。この内燃機関１は車両に走行用動力源として搭載されるものである。また、内燃機関１は車両のエンジンコンパートメントに搭載されている。内燃機関１は４つの気筒を有する直列４気筒型の火花点火式内燃機関として構成されている。燃料供給装置１０は、内燃機関１の気筒毎に設けられた燃料噴射弁１１を備えている。燃料噴射弁１１は、先端部を気筒内に臨ませるようにして機関本体２のシリンダヘッドに取り付けられている。   FIG. 1 schematically shows a fuel supply system of an internal combustion engine in which a fuel supply device according to one embodiment of the present invention is incorporated. The internal combustion engine 1 is mounted on a vehicle as a driving power source. The internal combustion engine 1 is mounted in the engine compartment of the vehicle. The internal combustion engine 1 is configured as an in-line four-cylinder spark ignition internal combustion engine having four cylinders. The fuel supply device 10 includes a fuel injection valve 11 provided for each cylinder of the internal combustion engine 1. The fuel injection valve 11 is attached to the cylinder head of the engine body 2 so that the tip end portion faces the cylinder.

燃料供給装置１０は、燃料が貯溜された燃料タンク１２と、燃料タンク１２から燃料を汲み上げる低圧燃料ポンプとしての低圧フィードポンプ１３と、燃料を加圧する高圧燃料ポンプ１４と、高圧燃料ポンプ１４から吐出された燃料を各燃料噴射弁１１に分配するデリバリパイプ１５とを備えている。なお、図１では便宜上離して示したが、高圧燃料ポンプ１４は機関本体２に取り付けられている。低圧フィードポンプ１３の吐出側と高圧燃料ポンプ１４の吸入側とは低圧通路１６で接続され、高圧燃料ポンプ１４の吐出側とデリバリパイプ１５とは高圧通路１７で接続されている。低圧通路１６は、車両のエンジンコンパートメント内に配置されている。なお、図示は省略したが低圧通路１６には燃料の脈動を減衰させるパルセーションダンパが設けられている。デリバリパイプ１５には、内部の圧力に対応した信号を出力する燃圧検出手段としての燃圧センサ１８が設けられている。   The fuel supply device 10 includes a fuel tank 12 in which fuel is stored, a low-pressure feed pump 13 as a low-pressure fuel pump that pumps fuel from the fuel tank 12, a high-pressure fuel pump 14 that pressurizes the fuel, and a discharge from the high-pressure fuel pump 14. And a delivery pipe 15 that distributes the fuel to each fuel injection valve 11. Although shown apart for convenience in FIG. 1, the high-pressure fuel pump 14 is attached to the engine body 2. The discharge side of the low-pressure feed pump 13 and the suction side of the high-pressure fuel pump 14 are connected by a low-pressure passage 16, and the discharge side of the high-pressure fuel pump 14 and the delivery pipe 15 are connected by a high-pressure passage 17. The low pressure passage 16 is arranged in the engine compartment of the vehicle. Although not shown, the low-pressure passage 16 is provided with a pulsation damper that attenuates fuel pulsation. The delivery pipe 15 is provided with a fuel pressure sensor 18 as fuel pressure detecting means for outputting a signal corresponding to the internal pressure.

低圧フィードポンプ１３は、燃料タンク１２内に取り付けられている。このフィードポンプ１３は、その内部構造の図示を省略したが、電動モータとそのモータにて駆動されるインペラとを備えた周知の電動ポンプとして構成されている。そのため、フィードポンプ１３は、電動モータの回転数等を変更することにより吐出圧力（フィード圧）を変更できる。   The low pressure feed pump 13 is attached in the fuel tank 12. The feed pump 13 is configured as a well-known electric pump including an electric motor and an impeller driven by the motor, although illustration of the internal structure is omitted. Therefore, the feed pump 13 can change the discharge pressure (feed pressure) by changing the rotation speed of the electric motor and the like.

高圧燃料ポンプ１４は、内燃機関１のカムシャフト３から取り出した動力にて駆動される周知のプランジャ式ポンプとして構成されている。高圧燃料ポンプ１４は、カムシャフト３に取り付けられた駆動カム１４ａと、吸入口を開閉する電磁駆動式の吸入弁１４ｂとを備えている。また、図示は省略したが吐出口にはデリバリパイプ１５からポンプ１４内への燃料の逆流を防止するための逆止弁が設けられている。この高圧燃料ポンプ１４では、駆動カム１４ａにて不図示のプランジャを往復動させ、そのプランジャの往復運動に合わせて吸入弁１４ｂを開閉させることにより燃料の吸入及び吐出が行われる。そして、この際に吸入弁１４ｂの開閉タイミングを適宜に変更することにより吐出量が調整される。   The high-pressure fuel pump 14 is configured as a well-known plunger pump that is driven by power extracted from the camshaft 3 of the internal combustion engine 1. The high-pressure fuel pump 14 includes a drive cam 14a attached to the camshaft 3 and an electromagnetically driven intake valve 14b that opens and closes the intake port. Although not shown, a check valve is provided at the discharge port to prevent the backflow of fuel from the delivery pipe 15 into the pump 14. In this high-pressure fuel pump 14, a plunger (not shown) is reciprocated by a drive cam 14a, and fuel is sucked and discharged by opening and closing a suction valve 14b in accordance with the reciprocating motion of the plunger. At this time, the discharge amount is adjusted by appropriately changing the opening / closing timing of the intake valve 14b.

この燃料供給装置１０では、燃料タンク１２内の燃料を低圧フィードポンプ１３で汲み上げて高圧燃料ポンプ１４に送る。そして、燃料を高圧燃料ポンプ１４で加圧してデリバリパイプ１５に送る。その後、加圧された燃料は各燃料噴射弁１１に分配されて気筒内に噴射される。   In the fuel supply device 10, the fuel in the fuel tank 12 is pumped up by the low pressure feed pump 13 and sent to the high pressure fuel pump 14. Then, the fuel is pressurized by the high-pressure fuel pump 14 and sent to the delivery pipe 15. Thereafter, the pressurized fuel is distributed to each fuel injection valve 11 and injected into the cylinder.

低圧フィードポンプ１３及び高圧燃料ポンプ１４のそれぞれの動作はエンジンコントロールユニット（ＥＣＵ）２０にて制御される。ＥＣＵ２０は各種センサの出力情報を取得し、燃料噴射量や点火時期等の運転パラメータを演算し、燃料噴射弁１１や不図示の点火プラグ等の制御対象を動作させるコンピュータとして構成されている。図示を省略したが、ＥＣＵ２０には主演算装置として機能するマイクロプロセッサ及びその動作に必要な記憶装置等の周辺装置が内蔵されている。ＥＣＵ２０には種々のセンサが接続されている。例えば、内燃機関１の冷却水の温度（冷却水温）に対応した信号を出力する水温センサ２１、及び内燃機関１の吸気の温度（吸気温度）に対応した信号を出力する吸気温センサ２２等が接続されている。また、上述した燃圧センサ１８もＥＣＵ２０に接続されている。この他にも内燃機関１の回転速度（機関回転数）に対応した信号を出力するクランク角センサや内燃機関１の吸入空気量に対応した信号を出力するエアフローメータ等の種々のセンサが接続されているが、それらの図示は省略した。   The operations of the low-pressure feed pump 13 and the high-pressure fuel pump 14 are controlled by an engine control unit (ECU) 20. The ECU 20 is configured as a computer that obtains output information of various sensors, calculates operation parameters such as a fuel injection amount and ignition timing, and operates control targets such as the fuel injection valve 11 and a spark plug (not shown). Although not shown, the ECU 20 incorporates a peripheral device such as a microprocessor functioning as a main arithmetic unit and a storage device necessary for its operation. Various sensors are connected to the ECU 20. For example, a water temperature sensor 21 that outputs a signal corresponding to the temperature of the cooling water (cooling water temperature) of the internal combustion engine 1, an intake air temperature sensor 22 that outputs a signal corresponding to the temperature of the intake air (intake air temperature) of the internal combustion engine 1, and the like. It is connected. The fuel pressure sensor 18 described above is also connected to the ECU 20. In addition, various sensors such as a crank angle sensor that outputs a signal corresponding to the rotational speed (engine speed) of the internal combustion engine 1 and an air flow meter that outputs a signal corresponding to the intake air amount of the internal combustion engine 1 are connected. However, the illustration thereof is omitted.

次にＥＣＵ２０が実行する種々の制御について説明する。ＥＣＵ２０は、デリバリパイプ１５内の圧力（実燃圧）が目標圧になるように吸入弁１４ｂを制御する。以下、この制御を燃圧制御と称することがある。なお、目標圧は燃料噴射弁１１から噴射すべき燃料量（目標燃料量）に応じて周知の方法にて設定される値である。上述したように吸入弁１４ｂは電磁駆動式の弁である。そこで、ＥＣＵ２０は吸入弁１４ｂのソレノイドに通電する時間と通電を停止する時間との比、すなわち駆動ディーティを変更し、これにより吸入弁１４ｂを制御する。この際、ＥＣＵ２０は、駆動デューティに対して実燃圧と目標圧との偏差に基づく比例積分制御（ＰＩ制御）を行う。詳しく説明すると駆動ディーティは、目標燃料量に応じて定まる制御量（フィードフォワード項）、実燃圧と目標圧との差（燃圧差）の大きさに応じて定まる制御量（比例項）、及び燃圧差の一部を積算した制御量（積分項）を加算することにより算出される。そして、ＥＣＵ２０はこのように算出された駆動ディーティにて吸入弁１４ｂを制御する。なお、燃圧差とフィードフォワード項との関係、及び燃圧差と比例項との関係は、予め実験や数値計算等の適合作業によって定めればよい。また、燃圧差のうち積分項に加算される割合についても同様に予め実験や数値計算等の適合作業によって定めればよい。この制御を実行することによりＥＣＵ２０が本発明の高圧ポンプ制御手段として機能する。   Next, various controls executed by the ECU 20 will be described. The ECU 20 controls the intake valve 14b so that the pressure in the delivery pipe 15 (actual fuel pressure) becomes the target pressure. Hereinafter, this control may be referred to as fuel pressure control. The target pressure is a value set by a known method in accordance with the amount of fuel to be injected from the fuel injection valve 11 (target fuel amount). As described above, the suction valve 14b is an electromagnetically driven valve. Therefore, the ECU 20 changes the ratio of the time for energizing the solenoid of the intake valve 14b and the time for stopping the energization, that is, the drive duty, thereby controlling the intake valve 14b. At this time, the ECU 20 performs proportional integral control (PI control) based on the deviation between the actual fuel pressure and the target pressure with respect to the drive duty. More specifically, the drive duty is a control amount (feed forward term) determined according to the target fuel amount, a control amount (proportional term) determined according to the difference between the actual fuel pressure and the target pressure (fuel pressure difference), and the fuel pressure. It is calculated by adding a control amount (integral term) obtained by integrating a part of the difference. Then, the ECU 20 controls the intake valve 14b with the drive duty calculated as described above. Note that the relationship between the fuel pressure difference and the feed-forward term and the relationship between the fuel pressure difference and the proportional term may be determined in advance by an experiment such as an experiment or numerical calculation. Similarly, the ratio of the fuel pressure difference to be added to the integral term may be determined in advance by matching work such as experiments and numerical calculations. By executing this control, the ECU 20 functions as the high-pressure pump control means of the present invention.

さらにＥＣＵ２０は、高圧燃料ポンプ１４の運転に支障が生じないように低圧フィードポンプ１３のフィード圧を低下させる最小フィード圧制御を実行する。この制御では、フィードポンプ１３の運転中にフィード圧を所定の低下量ずつ低下させる低下処理を行う。しかしながら、フィード圧を下げすぎると高圧燃料ポンプ１４の吸引時に低圧通路１６内の燃料の圧力が飽和蒸気圧を下回って燃料が気化し、これにより燃料中に気泡が発生する。気泡は高圧燃料ポンプ１４による燃料の加圧を邪魔するので、実燃圧の制御が不安定になる。さらに、気泡が大量に発生すると高圧燃料ポンプ１４の吸引不良や吐出不良が誘発され、ポンプ１４の運転に支障が生じる。そこで、この最小フィード圧制御では、予め下限ガード値を設定し、フィード圧をその下限ガード値までしか下げないようにして気泡の発生を抑制する。また、この制御では上述した吸入弁１４ｂのＰＩ制御で使用する積分項に基づいてフィード圧を制御し、これにより気泡の発生を抑制する。高圧燃料ポンプ１４内の燃料中に気泡が無い場合、燃料を適切に加圧できるので、実燃圧と筒内噴射目標圧とが一致するか又は燃圧差を小さくすることができる。この場合、積分項は一定又は低下傾向になる。一方、高圧燃料ポンプ１４内の燃料中に気泡が発生すると燃料を適切に加圧できないので、燃圧差が大きくなる。この場合、積分項は増加する。そこで、この制御では、積分項が一定又は減少傾向にある場合にはフィード圧を一定量ずつ低下させる。一方、積分項が予め設定した所定の判定値を超えた場合には、フィード圧の低下を制限する。この際、例えば下限ガード値を高くして低下を制限する。また、フィード圧の低下を中止してもよい。なお、上述した方法の他に積分項が増加傾向にある場合にフィード圧の低下を制限してもよい。この最小フィード圧制御を実行することによりＥＣＵ２０が本発明の低圧ポンプ制御手段として機能する。   Further, the ECU 20 executes minimum feed pressure control for reducing the feed pressure of the low pressure feed pump 13 so as not to hinder the operation of the high pressure fuel pump 14. In this control, during the operation of the feed pump 13, a reduction process for reducing the feed pressure by a predetermined reduction amount is performed. However, if the feed pressure is lowered too much, the pressure of the fuel in the low pressure passage 16 falls below the saturated vapor pressure when the high pressure fuel pump 14 is sucked, and the fuel is vaporized, thereby generating bubbles in the fuel. Since the bubbles obstruct the pressurization of the fuel by the high-pressure fuel pump 14, the control of the actual fuel pressure becomes unstable. Further, when a large amount of bubbles are generated, a suction failure or discharge failure of the high-pressure fuel pump 14 is induced, and the operation of the pump 14 is hindered. Therefore, in this minimum feed pressure control, a lower limit guard value is set in advance, and the generation of bubbles is suppressed by reducing the feed pressure only to the lower limit guard value. In this control, the feed pressure is controlled based on the integral term used in the PI control of the suction valve 14b described above, thereby suppressing the generation of bubbles. When there are no bubbles in the fuel in the high-pressure fuel pump 14, the fuel can be appropriately pressurized, so that the actual fuel pressure matches the in-cylinder injection target pressure, or the fuel pressure difference can be reduced. In this case, the integral term tends to be constant or decrease. On the other hand, if bubbles are generated in the fuel in the high-pressure fuel pump 14, the fuel cannot be pressurized properly, and the fuel pressure difference increases. In this case, the integral term increases. Therefore, in this control, when the integral term is constant or tends to decrease, the feed pressure is decreased by a certain amount. On the other hand, when the integral term exceeds a predetermined determination value set in advance, a decrease in feed pressure is limited. At this time, for example, the lower limit guard value is increased to limit the decrease. Moreover, you may cancel the fall of feed pressure. In addition to the method described above, when the integral term tends to increase, the decrease in the feed pressure may be limited. By executing this minimum feed pressure control, the ECU 20 functions as the low-pressure pump control means of the present invention.

周知のように気泡は燃料が高温になると発生し易くなる。そのため、低圧通路１６の温度が高圧燃料ポンプ１４の温度よりも高い場合には低圧通路１６において燃料中に気泡が発生する。このように低圧通路１６にて気泡が発生した場合には高圧燃料ポンプ１４への燃料の圧送に支障が生じる。そこで、ＥＣＵ２０はこのような場合に低圧通路１６の気泡を迅速に除去すべく図２の制御実行判定ルーチンを実行する。このルーチンは内燃機関１の運転状態に拘わりなく所定の周期で繰り返し実行される。このルーチンを実行することによりＥＣＵ２０が本発明の圧力低下制限手段として機能する。   As is well known, bubbles tend to be generated when the temperature of the fuel becomes high. For this reason, when the temperature of the low-pressure passage 16 is higher than the temperature of the high-pressure fuel pump 14, bubbles are generated in the fuel in the low-pressure passage 16. As described above, when bubbles are generated in the low-pressure passage 16, there is a problem in pumping the fuel to the high-pressure fuel pump 14. Therefore, the ECU 20 executes the control execution determination routine of FIG. 2 in order to quickly remove the bubbles in the low pressure passage 16 in such a case. This routine is repeatedly executed at a predetermined cycle regardless of the operating state of the internal combustion engine 1. By executing this routine, the ECU 20 functions as the pressure drop limiting means of the present invention.

図２のルーチンにおいてＥＣＵ２０は、まずステップＳ１１で内燃機関１の運転状態を取得する。運転状態としては、例えば内燃機関１の冷却水温、及び吸気温度等が取得される。次のステップＳ１２においてＥＣＵ２０は吸気温度が冷却水温よりも高いか否か判定する。高圧燃料ポンプ１４の温度よりも低圧通路１６の温度が高くなる状況としては、例えば内燃機関１が高温であり、かつ車両の速度が０で走行風等による内燃機関１の冷却が無い場合、内燃機関１を高温のまま停止し、エンジンコンパートメント内の温度が高い状態で内燃機関１を始動した場合、及び低圧通路１６を流れる燃料の流量が少なく内燃機関１等から受けた熱による燃料の温度上昇が激しい場合等が考えられる。上述したように高圧燃料ポンプ１４は機関本体２に取り付けられているので、冷却水温は高圧燃料ポンプ１４の温度を代表すると考えられる。低圧通路１６はエンジンコンパートメント内に配置されている。そして、吸気温度はエンジンコンパートメント内の温度を代表すると考えられるので、低圧通路１６の温度は吸気温度とほぼ同じと考えられる。そのため、吸気温度が冷却水温より高い場合には低圧通路１６が高圧燃料ポンプ１４よりも高温になると予想できる。   In the routine of FIG. 2, the ECU 20 first acquires the operating state of the internal combustion engine 1 in step S11. As the operating state, for example, the cooling water temperature and the intake air temperature of the internal combustion engine 1 are acquired. In the next step S12, the ECU 20 determines whether or not the intake air temperature is higher than the cooling water temperature. The situation in which the temperature of the low-pressure passage 16 becomes higher than the temperature of the high-pressure fuel pump 14 is, for example, when the internal combustion engine 1 is hot and the vehicle speed is 0 and the internal combustion engine 1 is not cooled by traveling wind or the like. When the internal combustion engine 1 is started while the engine 1 is stopped at a high temperature and the temperature in the engine compartment is high, and the temperature of the fuel rises due to the heat received from the internal combustion engine 1 or the like when the flow rate of the fuel flowing through the low pressure passage 16 is small The case where there is intense is considered. As described above, since the high-pressure fuel pump 14 is attached to the engine body 2, the cooling water temperature is considered to represent the temperature of the high-pressure fuel pump 14. The low pressure passage 16 is arranged in the engine compartment. Since the intake air temperature is considered to represent the temperature in the engine compartment, the temperature of the low pressure passage 16 is considered to be substantially the same as the intake air temperature. Therefore, when the intake air temperature is higher than the cooling water temperature, the low pressure passage 16 can be expected to be higher than the high pressure fuel pump 14.

吸気温度が冷却水温よりも高い場合にはステップＳ１３に進み、ＥＣＵ２０は最小フィード圧制御によるフィード圧の低下処理を制限する。具体的には低下処理の実行を禁止し、低圧通路１６内の気泡が除去されるようにフィード圧を上昇させる。その後、今回のルーチンを終了する。一方、吸気温度が冷却水温以下の場合にはステップＳ１４に進み、ＥＣＵ２０は最小フィード圧制御によるフィード圧の低下処理を許可する。その後、今回のルーチンを終了する。   If the intake air temperature is higher than the coolant temperature, the process proceeds to step S13, where the ECU 20 limits the feed pressure reduction process by the minimum feed pressure control. Specifically, the lowering process is prohibited and the feed pressure is increased so that the bubbles in the low pressure passage 16 are removed. Thereafter, the current routine is terminated. On the other hand, when the intake air temperature is equal to or lower than the cooling water temperature, the process proceeds to step S14, where the ECU 20 permits the feed pressure reduction process by the minimum feed pressure control. Thereafter, the current routine is terminated.

以上に説明したように本発明の燃料供給装置１０によれば、吸気温度が冷却水温より高い場合には低下処理を禁止し、フィード圧を上昇させるので、低圧通路１６における気泡の発生を抑制でき、また発生した気泡を迅速に除去できる。そのため、低圧通路１６が加熱されても燃料の圧力変動を抑制できる。そして、これにより最小フィード圧制御によるフィード圧の低下制御の精度を向上させることができる。   As described above, according to the fuel supply device 10 of the present invention, when the intake air temperature is higher than the cooling water temperature, the lowering process is prohibited and the feed pressure is increased, so that the generation of bubbles in the low pressure passage 16 can be suppressed. In addition, the generated bubbles can be quickly removed. Therefore, even if the low pressure passage 16 is heated, the fuel pressure fluctuation can be suppressed. As a result, the accuracy of the feed pressure reduction control by the minimum feed pressure control can be improved.

また、最小フィード圧制御においても積分項が判定値以上の場合にはフィード圧の低下を制限するので、高圧燃料ポンプ１４の運転に支障が生じないように低圧フィードポンプ１３のフィード圧を下げることができる。そのため、このフィードポンプ１３で消費されるエネルギを低減できる。   Further, even in the minimum feed pressure control, when the integral term is equal to or higher than the determination value, the feed pressure is limited to be lowered. Therefore, the feed pressure of the low pressure feed pump 13 is lowered so as not to hinder the operation of the high pressure fuel pump 14. Can do. Therefore, the energy consumed by this feed pump 13 can be reduced.

なお、図２のステップＳ１３では低下処理を中止する代わりに下限ガード値を高くしてもよい。この際、下限ガード値は、例えば吸気温度が冷却水温以下のときの下限ガード値よりも高くすればよい。そして、これによりフィード圧を上昇させてもよい。この場合においても気泡の発生を抑制したり気泡を迅速に除去したりできる。   In step S13 in FIG. 2, the lower limit guard value may be increased instead of stopping the lowering process. At this time, the lower limit guard value may be set higher than the lower limit guard value when the intake air temperature is equal to or lower than the cooling water temperature, for example. In this way, the feed pressure may be increased. Even in this case, generation of bubbles can be suppressed or bubbles can be quickly removed.

本発明は、上述した形態に限定されることなく、種々の形態にて実施することができる。例えば、本発明が適用される内燃機関は、火花点火式内燃機関に限定されない。本発明はディーゼル内燃機関に適用してもよい。また、本発明が適用される内燃機関は、気筒内に直接燃料を噴射する燃料噴射弁に加えて吸気ポートに燃料を噴射するための燃料噴射弁を備えていてもよい。   The present invention is not limited to the above-described form and can be implemented in various forms. For example, the internal combustion engine to which the present invention is applied is not limited to a spark ignition type internal combustion engine. The present invention may be applied to a diesel internal combustion engine. Further, the internal combustion engine to which the present invention is applied may include a fuel injection valve for injecting fuel into the intake port in addition to the fuel injection valve for injecting fuel directly into the cylinder.

１ 内燃機関
２ 機関本体
１０ 燃料供給装置
１１ 燃料噴射弁
１３ 低圧フィードポンプ（低圧燃料ポンプ）
１４ 高圧燃料ポンプ
１６ 低圧通路
１８ 燃圧センサ（燃圧検出手段）
２０ エンジンコントロールユニット（高圧ポンプ制御手段、低圧ポンプ制御手段、圧力低下制限手段） DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Engine main body 10 Fuel supply apparatus 11 Fuel injection valve 13 Low pressure feed pump (low pressure fuel pump)
14 High-pressure fuel pump 16 Low-pressure passage 18 Fuel pressure sensor (fuel pressure detection means)
20 Engine control unit (high pressure pump control means, low pressure pump control means, pressure drop limiting means)

Claims (4)

車両に搭載された内燃機関に適用され、
電動式の低圧燃料ポンプと、前記内燃機関の機関本体に取り付けられ、かつ吐出圧を変更可能な高圧燃料ポンプと、前記車両において前記内燃機関が搭載されている空間に配置されて前記低圧燃料ポンプの吐出側と前記高圧燃料ポンプの吸入側とを接続する低圧通路と、を備え、前記低圧燃料ポンプから吐出された燃料を前記高圧燃料ポンプで加圧して燃料噴射弁に送る燃料供給装置において、
前記高圧燃料ポンプの下流側の燃圧を検出する燃圧検出手段と、前記燃圧検出手段が検出した燃圧と目標値との偏差が低減するように前記偏差に基づいて前記高圧燃料ポンプのフィードバック制御を行う高圧ポンプ制御手段と、前記低圧燃料ポンプの運転中に前記低圧燃料ポンプの吐出圧力を所定の低下量ずつ低下させる低下処理を実行するとともに前記偏差に基づいて算出された前記フィードバック制御の制御項に基づいて前記低下処理の実行の可否を判断する低圧ポンプ制御手段と、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度より高い場合には前記低圧ポンプ制御手段による前記低圧燃料ポンプの吐出圧力の低下を制限する圧力低下制限手段と、を備えていることを特徴とする内燃機関の燃料供給装置。 Applied to internal combustion engines mounted on vehicles,
An electric low-pressure fuel pump, a high-pressure fuel pump attached to the engine body of the internal combustion engine and capable of changing a discharge pressure, and the low-pressure fuel pump disposed in a space where the internal combustion engine is mounted in the vehicle A low pressure passage connecting a discharge side of the high pressure fuel pump and a suction side of the high pressure fuel pump, and a fuel supply device that pressurizes the fuel discharged from the low pressure fuel pump by the high pressure fuel pump and sends the fuel to a fuel injection valve.
Fuel pressure detection means for detecting the fuel pressure downstream of the high pressure fuel pump, and feedback control of the high pressure fuel pump based on the deviation so as to reduce the deviation between the fuel pressure detected by the fuel pressure detection means and the target value A high-pressure pump control means, and a reduction process for reducing the discharge pressure of the low-pressure fuel pump by a predetermined reduction amount during operation of the low-pressure fuel pump, and a control term of the feedback control calculated based on the deviation Low pressure pump control means for determining whether or not the lowering process can be performed based on the low pressure pump control means when the intake air temperature of the internal combustion engine is higher than the cooling water temperature of the internal combustion engine. A fuel supply device for an internal combustion engine, comprising: a pressure drop limiting unit that limits a drop in discharge pressure. 前記圧力低下制限手段は、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度より高い場合には前記低圧ポンプ制御手段による前記低下処理の実行を禁止する請求項１に記載の燃料供給装置。   2. The fuel supply according to claim 1, wherein when the temperature of the intake air of the internal combustion engine is higher than the temperature of the cooling water of the internal combustion engine, the pressure reduction restriction unit prohibits execution of the reduction process by the low pressure pump control unit. apparatus. 前記低圧ポンプ制御手段は、前記低圧燃料ポンプの吐出圧力が所定の下限値以下になると前記低下処理を中止し、
前記圧力低下制限手段は、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度より高い場合には、前記内燃機関の吸気の温度が前記内燃機関の冷却水の温度以下の場合よりも前記下限値を高くする請求項１に記載の燃料供給装置。 The low-pressure pump control means stops the lowering process when the discharge pressure of the low-pressure fuel pump becomes a predetermined lower limit value or less,
In the case where the temperature of the intake air of the internal combustion engine is higher than the temperature of the cooling water of the internal combustion engine, the pressure drop limiting means is more than the case where the temperature of the intake air of the internal combustion engine is equal to or lower than the temperature of the cooling water of the internal combustion engine. The fuel supply apparatus according to claim 1, wherein the lower limit value is increased. 前記高圧ポンプ制御手段は、前記フィードバック制御として比例積分制御を行い、
前記低圧ポンプ制御手段は、前記比例積分制御の積分項の値が所定の判定値を超えた場合に前記低圧燃料ポンプの吐出圧力の低下を制限する請求項１〜３のいずれか一項に記載の燃料供給装置。 The high-pressure pump control means performs proportional-integral control as the feedback control,
The said low-pressure pump control means limits the fall of the discharge pressure of the said low-pressure fuel pump, when the value of the integral term of the said proportional integral control exceeds a predetermined determination value. Fuel supply system.
JP2011099233A 2011-04-27 2011-04-27 Fuel supply device for internal combustion engine Expired - Fee Related JP5640880B2 (en)

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ITMI20131164A1 (en) 2013-07-10 2015-01-11 Bosch Gmbh Robert PUMP ASSEMBLY TO SUPPLY FUEL, PREFERABLY GASOIL, TO AN INTERNAL COMBUSTION ENGINE

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JPH0727030A (en) * 1993-07-08 1995-01-27 Mazda Motor Corp Fuel supply device for engine
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