JP4535455B2

JP4535455B2 - Engine fuel supply structure

Info

Publication number: JP4535455B2
Application number: JP2006109563A
Authority: JP
Inventors: 武士濱上
Original assignee: Yanmar Co Ltd
Current assignee: Yanmar Co Ltd
Priority date: 2006-04-12
Filing date: 2006-04-12
Publication date: 2010-09-01
Anticipated expiration: 2026-04-12
Also published as: JP2007278261A

Description

本発明は、燃料タンクと燃料噴射ポンプとの間に構成する、燃料圧送経路の途中に燃料供給ポンプと燃料フィルタとを設けるエンジンの燃料供給構造に関する。 The present invention relates to a fuel supply structure for an engine provided between a fuel tank and a fuel injection pump and provided with a fuel supply pump and a fuel filter in the middle of a fuel pumping path.

従来から、燃料タンクと燃料噴射ポンプとを燃料圧送経路で連通接続し、燃料タンクに貯溜した燃料を燃料供給ポンプで燃料噴射ポンプに供給するエンジンの燃料供給構造は公知となっている。このようなエンジンの燃料供給構造では、燃料圧送経路の途中に燃料フィルタが設けられ、燃料噴射ポンプに供給するまえに、燃料を燃料フィルタにより濾過して混入した異物を捕捉することで浄化するように構成されていた（例えば、特許文献１参照。）。
特開２００５−２７３５３５号公報 2. Description of the Related Art Conventionally, a fuel supply structure for an engine in which a fuel tank and a fuel injection pump are connected in communication via a fuel pumping path, and fuel stored in the fuel tank is supplied to the fuel injection pump by a fuel supply pump is known. In such a fuel supply structure of the engine, a fuel filter is provided in the middle of the fuel pumping path, and before the fuel is supplied to the fuel injection pump, the fuel is filtered by the fuel filter so as to purify the foreign matters. (For example, refer to Patent Document 1).
JP 2005-273535 A

しかし、従来のエンジンの燃料供給構造においては、低温下でのエンジン始動時に燃料フィルタで燃料中の成分が結晶化して詰まりが発生し、燃料を燃料噴射ポンプに供給することができず、エンジンが始動不能となる恐れがあった。特に、燃料フィルタの濾過面積は粗悪な品質の燃料にも対応可能なように小さくしており、また、燃料フィルタの交換時期はコスト低減化などを考慮して延長する傾向にあることから、低温時における燃料中成分の結晶化は、当該燃料フィルタで捕捉した異物とともに燃料フィルタの詰まりを促進しやすくなっていた。 However, in the conventional fuel supply structure of the engine, when the engine is started at a low temperature, components in the fuel are crystallized by the fuel filter and clogging occurs, and the fuel cannot be supplied to the fuel injection pump. There was a risk of being unable to start. In particular, the filter area of the fuel filter is small enough to handle poor quality fuel, and the replacement time of the fuel filter tends to be extended in consideration of cost reduction. The crystallization of the components in the fuel at the time tends to promote the clogging of the fuel filter together with the foreign matter captured by the fuel filter.

本発明の解決しようとする課題は以上の如くであり、次にこの課題を解決するための手段を説明する。 The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

燃料タンク（１）と燃料噴射ポンプ（４）との間に構成する燃料圧送経路（５）の途中に燃料供給ポンプ（２）と燃料フィルタ（３）とを設けるエンジンの燃料供給構造において、該燃料噴射ポンプ（４）の余剰経路（６ａ）と、該燃料タンク（１）との間に構成する燃料戻り経路（６）と、前記燃料噴射ポンプ（４）の余剰経路（６ａ）と、該燃料供給ポンプ（２）の吸入側の燃料圧送経路（５ｃ）とを連通するバイパス経路（３０）を設け、該バイパス経路（３０）と燃料戻り経路（６）との分岐部に三方弁（３７）を設け、該三方弁（３７）は電磁弁で構成し、制御手段（１５）に接続し、該制御手段（１５）には、セルモータを始動させる始動手段（１６）と、前記燃料供給ポンプ（２）の吐出側の燃料圧送経路（５）の温度を検知する燃料温度検知手段（１７）と、設定手段（１８）を接続し、該始動手段（１６）からの始動信号や、該燃料温度検知手段（１７）からの検知信号、該設定手段（１８）により予め設定した設定値に基づいて、前記制御手段（１５）により、前記三方弁（３７）の切換制御を行い、燃料の温度が設定温度よりも低い場合には、前記三方弁（３７）が余剰経路（６ａ）とバイパス経路（３０）とを連通するように切り換えた状態を維持し、吸入側燃料圧送経路（５ｃ）での、前記燃料噴射ポンプ（４）からの温度の高い過剰の燃料と、前記燃料タンク（１）からの燃料との混合を繰り返し行い、前記燃料圧送経路（５）を通じて圧送する燃料の温度の上昇を図り、燃料の温度が設定温度よりも高い場合には、前記三方弁（３７）を、前記余剰経路（６ａ）と燃料戻り経路（６）を連通する側に切り換えて、前記燃料噴射ポンプ（４）からの過剰の燃料を燃料タンク（１）に戻して混合し、過剰な温度の上昇を抑制して燃料噴射ポンプ（４）に供給するものである。 In an engine fuel supply structure in which a fuel supply pump (2) and a fuel filter (3) are provided in the middle of a fuel pumping path (5) formed between a fuel tank (1) and a fuel injection pump (4). A fuel return path (6) configured between the surplus path (6a) of the fuel injection pump (4) and the fuel tank (1); a surplus path (6a) of the fuel injection pump (4); A bypass path (30) communicating with the suction side fuel pumping path (5c) of the fuel supply pump (2) is provided, and a three-way valve (37) is provided at a branch portion between the bypass path (30) and the fuel return path (6). The three-way valve (37) is an electromagnetic valve and is connected to the control means (15). The control means (15) includes a starting means (16) for starting a cell motor and the fuel supply pump. Detect the temperature of the fuel pumping path (5) on the discharge side in (2) The fuel temperature detection means (17) and the setting means (18) are connected to each other, and a start signal from the start means (16), a detection signal from the fuel temperature detection means (17), and the setting means (18) The control means (15) performs switching control of the three-way valve (37) based on the set value set in advance, and when the fuel temperature is lower than the set temperature, the three-way valve (37) Maintaining a state where the surplus path (6a) and the bypass path (30) are switched to communicate with each other, and excessive fuel with a high temperature from the fuel injection pump (4) in the suction-side fuel pumping path (5c). And the fuel from the fuel tank (1) is repeatedly mixed, the temperature of the fuel pumped through the fuel pumping path (5) is increased, and when the fuel temperature is higher than a set temperature, Three-way valve (37) By switching the path (6a) and the fuel return path (6) to the side where they communicate, excess fuel from the fuel injection pump (4) is returned to the fuel tank (1) and mixed to suppress an excessive increase in temperature. Then, it is supplied to the fuel injection pump (4) .

本発明の効果として、以下に示すような効果を奏する。 As effects of the present invention, the following effects can be obtained.

請求項１においては、燃料タンク（１）と燃料噴射ポンプ（４）との間に構成する燃料圧送経路（５）の途中に燃料供給ポンプ（２）と燃料フィルタ（３）とを設けるエンジンの燃料供給構造において、該燃料噴射ポンプ（４）の余剰経路（６ａ）と、該燃料タンク（１）との間に構成する燃料戻り経路（６）と、前記燃料噴射ポンプ（４）の余剰経路（６ａ）と、該燃料供給ポンプ（２）の吸入側の燃料圧送経路（５ｃ）とを連通するバイパス経路（３０）を設け、該バイパス経路（３０）と燃料戻り経路（６）との分岐部に三方弁（３７）を設け、該三方弁（３７）は電磁弁で構成し、制御手段（１５）に接続し、該制御手段（１５）には、セルモータを始動させる始動手段（１６）と、前記燃料供給ポンプ（２）の吐出側の燃料圧送経路（５）の温度を検知する燃料温度検知手段（１７）と、設定手段（１８）を接続し、該始動手段（１６）からの始動信号や、該燃料温度検知手段（１７）からの検知信号、該設定手段（１８）により予め設定した設定値に基づいて、前記制御手段（１５）により、前記三方弁（３７）の切換制御を行い、燃料の温度が設定温度よりも低い場合には、前記三方弁（３７）が余剰経路（６ａ）とバイパス経路（３０）とを連通するように切り換えた状態を維持し、吸入側燃料圧送経路（５ｃ）での、前記燃料噴射ポンプ（４）からの温度の高い過剰の燃料と、前記燃料タンク（１）からの燃料との混合を繰り返し行い、前記燃料圧送経路（５）を通じて圧送する燃料の温度の上昇を図り、燃料の温度が設定温度よりも高い場合には、前記三方弁（３７）を、前記余剰経路（６ａ）と燃料戻り経路（６）を連通する側に切り換えて、前記燃料噴射ポンプ（４）からの過剰の燃料を燃料タンク（１）に戻して混合し、過剰な温度の上昇を抑制して燃料噴射ポンプ（４）に供給するので、低温下でのエンジン始動時に、燃料フィルタで燃料中成分が結晶化して詰まりが発生した場合でも、バイパス経路を通じて燃料噴射ポンプからの温度の高い過剰の燃料を燃料タンクからの燃料と燃料供給ポンプの吸入側の燃料圧送経路で混合し、燃料の温度を早急に上昇させて結晶を無くし燃料フィルタの詰まりを解消することが可能となり、燃料を確実に燃料噴射ポンプに供給してエンジンの始動不能を防止することができる。 In claim 1, the engine is provided with a fuel supply pump (2) and a fuel filter (3) in the middle of a fuel pumping path (5) formed between the fuel tank (1) and the fuel injection pump (4). In the fuel supply structure, a surplus path (6a) of the fuel injection pump (4), a fuel return path (6) configured between the fuel tank (1), and a surplus path of the fuel injection pump (4) (6a) is provided with a bypass path (30) communicating the suction side fuel pumping path (5c) of the fuel supply pump (2), and the bypass path (30) and the fuel return path (6) are branched. A three-way valve (37) is provided in the part, the three-way valve (37) is constituted by an electromagnetic valve, and is connected to the control means (15). The control means (15) includes a starting means (16) for starting the cell motor. And a fuel pressure feed passage on the discharge side of the fuel supply pump (2) The fuel temperature detection means (17) for detecting the temperature of (5) and the setting means (18) are connected, and a start signal from the start means (16) and a detection signal from the fuel temperature detection means (17). Based on the setting value preset by the setting means (18), the control means (15) performs switching control of the three-way valve (37), and when the fuel temperature is lower than the set temperature, The three-way valve (37) maintains a switched state so that the surplus path (6a) and the bypass path (30) communicate with each other, and the fuel injection pump (4) in the suction side fuel pumping path (5c) The excess fuel having a high temperature is repeatedly mixed with the fuel from the fuel tank (1) to increase the temperature of the fuel pumped through the fuel pumping path (5). If it is too high, the three-way valve 37) is switched to the side where the surplus path (6a) and the fuel return path (6) communicate with each other, and excess fuel from the fuel injection pump (4) is returned to the fuel tank (1) and mixed, The fuel injection pump (4) is supplied with the temperature rise suppressed, so that even when the fuel filter is crystallized by the fuel filter and clogging occurs when the engine is started at a low temperature, the fuel injection pump passes through the bypass path. The fuel from the fuel tank is mixed with the fuel from the fuel tank in the fuel pumping path on the suction side of the fuel supply pump, and the temperature of the fuel is rapidly raised to eliminate crystals and eliminate clogging of the fuel filter. This makes it possible to reliably supply the fuel to the fuel injection pump and prevent the engine from being unable to start.

また、燃料の品質に応じて燃料フィルタの濾過面積を変更したり、捕捉した異物の量に応じた燃料フィルタの交換時期を延長したりしてもこれらに関係なく燃料を燃料噴射ポンプに供給することが可能となり、エンジンの良好な始動性を確保することができる。 Even if the filter area of the fuel filter is changed according to the quality of the fuel or the replacement time of the fuel filter is extended according to the amount of trapped foreign matter, the fuel is supplied to the fuel injection pump regardless of these. Therefore, it is possible to ensure good startability of the engine.

次に、発明の実施の形態を説明する。 Next, embodiments of the invention will be described.

図１は構成例１に係るエンジンの燃料供給構造の構成を示す図である。 FIG. 1 is a view showing a configuration of an engine fuel supply structure according to Configuration Example 1. FIG.

図２は構成例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の制御機構を示すブロック図である。 FIG. 2 is a block diagram showing a control mechanism when the three-way valve is configured by an electromagnetic valve in the engine fuel supply structure according to Configuration Example 1 .

図３は構成例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の三方弁の切換制御の流れを示す図である。 FIG. 3 is a diagram illustrating a flow of switching control of the three-way valve when the three-way valve is configured by an electromagnetic valve in the engine fuel supply structure according to Configuration Example 1 .

図４は構成例１に係るエンジンの燃料供給構造において、三方弁を切換手段を用いて切換可能に構成した場合の三方弁の切換機構を示す一部断面図である。 FIG. 4 is a partial cross-sectional view showing a three-way valve switching mechanism when the three-way valve is configured to be switchable using switching means in the engine fuel supply structure according to Configuration Example 1 .

図５は構成例２に係るエンジンの燃料供給構造の構成を示す図である。 FIG. 5 is a diagram showing a configuration of an engine fuel supply structure according to Configuration Example 2 .

図６は実施例１に係るエンジンの燃料供給構造の構成を示す図である。 FIG. 6 is a diagram illustrating the configuration of the fuel supply structure for the engine according to the first embodiment .

図７は実施例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の制御機構を示すブロック図である。 Figure 7 is a fuel supply structure of the engine according to Embodiment 1 is a block diagram showing the control mechanism of the case where the three-way valve in the solenoid valve.

図８は実施例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の三方弁の切換制御の流れを示す図である。 Figure 8 is a fuel supply structure of the engine according to Embodiment 1 is a diagram showing a flow of the switching control of the three-way valve in the case of constituting the three-way valve in the solenoid valve.

エンジンの燃料供給構造は、たとえば図１に示すように、燃料タンク１と、燃料供給ポンプ２と、燃料フィルタ３と、燃料噴射ポンプ４とを備え、燃料タンク１に貯溜した燃料を燃料噴射ポンプ４から燃料噴射弁に高圧で供給できるようになっている。該燃料供給構造においては、燃料タンク１と燃料噴射ポンプ４とが配管などにより二つの経路で接続され、各経路で連通されている。一方の経路は燃料タンク１から燃料を燃料噴射ポンプ４に圧送するための燃料圧送経路５として構成され、他方の経路は燃料噴射ポンプ４で過剰となった燃料を燃料タンクに戻すための燃料戻り経路６として構成されている。 As shown in FIG. 1, for example, the fuel supply structure of the engine includes a fuel tank 1, a fuel supply pump 2, a fuel filter 3, and a fuel injection pump 4, and the fuel stored in the fuel tank 1 is injected into the fuel injection pump. 4 can be supplied to the fuel injection valve at a high pressure. In the fuel supply structure, the fuel tank 1 and the fuel injection pump 4 are connected to each other through two paths by piping or the like, and are communicated with each other. One path is configured as a fuel pumping path 5 for pumping fuel from the fuel tank 1 to the fuel injection pump 4, and the other path is a fuel return for returning excess fuel in the fuel injection pump 4 to the fuel tank. The route 6 is configured.

燃料圧送経路５の途中には燃料供給ポンプ２が設けられて、燃料タンク１の燃料が燃料供給ポンプ２により吸入され燃料圧送経路５を通じて燃料噴射ポンプ４に圧送可能とされている。燃料噴射ポンプ４は図示しない燃料噴射弁と接続され、該燃料噴射弁に燃料を高圧で送ることができるように構成されている。ここで、燃料噴射弁には所定量の燃料のみが圧送されて噴射され、過剰となった燃料は燃料戻り経路６を通じて燃料タンク１に戻され、該燃料タンク１の燃料と混合されて、再び燃料圧送経路５を通じて燃料噴射ポンプ４に送られるようになっている。 A fuel supply pump 2 is provided in the middle of the fuel pumping path 5 so that fuel in the fuel tank 1 can be sucked by the fuel supply pump 2 and pumped to the fuel injection pump 4 through the fuel pumping path 5. The fuel injection pump 4 is connected to a fuel injection valve (not shown), and is configured so that fuel can be sent to the fuel injection valve at a high pressure. Here, only a predetermined amount of fuel is pumped and injected into the fuel injection valve, and excess fuel is returned to the fuel tank 1 through the fuel return path 6, mixed with the fuel in the fuel tank 1, and again. The fuel is fed to the fuel injection pump 4 through the fuel pressure feed path 5.

そして、燃料圧送経路５の途中で燃料供給ポンプ２と燃料噴射ポンプ４との間に燃料フィルタ３が設けられ、燃料供給ポンプ２に圧送される燃料が燃料噴射ポンプ４に達するまえに燃料フィルタ３により浄化されるように構成されている。燃料フィルタ３は、通過する燃料に混入している異物をフィルタエレメントで捕捉し除去することによって、燃料を浄化するものであり、濾過面積を任意に変更して様々な品質の燃料に対応可能とされている。 A fuel filter 3 is provided between the fuel supply pump 2 and the fuel injection pump 4 in the middle of the fuel pumping path 5, and the fuel filter 3 before the fuel pumped to the fuel supply pump 2 reaches the fuel injection pump 4. It is comprised so that it may purify by. The fuel filter 3 purifies the fuel by trapping and removing foreign matters mixed in the passing fuel with a filter element, and can change the filtration area arbitrarily to cope with various quality fuels. Has been.

本構成例では、図１に示すように、燃料圧送経路５の燃料供給ポンプ２と燃料噴射ポンプ４との間に、燃料フィルタ３の入口側の燃料圧送経路５ａと、燃料フィルタ３の出口側の燃料圧送経路５ｂとを連通するバイパス経路１０が設けられて、燃料供給ポンプ２から圧送される燃料がバイパス経路１０を通り、燃料フィルタ３を迂回して燃料噴射ポンプ４に圧送可能とされる。そして、燃料フィルタ３の入口側燃料圧送経路５ａとバイパス経路１０との分岐部に三方弁７が設けられ、これを入口側燃料圧送経路５ａ側またはバイパス経路１０側に切り換えることでどちらか一方の経路５ａ・１０のみが開かれるように構成される。 In this configuration example , as shown in FIG. 1, the fuel pumping path 5 a on the inlet side of the fuel filter 3 and the outlet side of the fuel filter 3 are disposed between the fuel supply pump 2 and the fuel injection pump 4 of the fuel pumping path 5. The fuel pressure feed path 5b is provided with a bypass path 10 so that the fuel pumped from the fuel supply pump 2 can pass through the bypass path 10 and bypass the fuel filter 3 to be pumped to the fuel injection pump 4. . And the three-way valve 7 is provided in the branch part of the inlet side fuel pumping path | route 5a of the fuel filter 3, and the bypass path | route 10, and this is switched to either the inlet side fuel pumping path | route 5a side or the bypass path | route 10 side. Only the paths 5a and 10 are configured to be opened.

三方弁７が入口側燃料圧送経路５ａ側に切り換えられた場合、バイパス経路１０が閉じられて、燃料供給ポンプ２の出口側に燃料フィルタ３の入口側燃料圧送経路５ａが連通され、燃料が入口側燃料圧送経路５ａから燃料フィルタ３を介して出口側燃料圧送経路５ｂに送られる。また、三方弁７がバイパス経路１０側に切り換えられた場合、分岐部では燃料フィルタ３入口側が閉じられて、燃料供給ポンプ２の出口側にバイパス経路１０が連通され、燃料がバイパス経路１０を通じて出口側燃料圧送経路５ｂに送られる。このように三方弁７の切換によって、燃料供給ポンプ２からの燃料が燃料フィルタ３を介して、またはバイパス経路１０を通じて燃料噴射ポンプ４に供給可能とされる。 When the three-way valve 7 is switched to the inlet-side fuel pumping path 5a side, the bypass path 10 is closed, the inlet-side fuel pumping path 5a of the fuel filter 3 is communicated with the outlet side of the fuel supply pump 2, and the fuel enters the inlet. The fuel is sent from the side fuel pumping path 5a through the fuel filter 3 to the outlet side fuel pumping path 5b. Further, when the three-way valve 7 is switched to the bypass path 10 side, the fuel filter 3 inlet side is closed at the branch portion, the bypass path 10 is communicated with the outlet side of the fuel supply pump 2, and the fuel exits through the bypass path 10. It is sent to the side fuel pumping path 5b. Thus, by switching the three-way valve 7, the fuel from the fuel supply pump 2 can be supplied to the fuel injection pump 4 through the fuel filter 3 or through the bypass path 10.

三方弁７は自動または手動で切換可能とされており、自動の場合には、三方弁７は電磁弁で構成され、図２に示すように、制御手段１５に接続される。制御手段１５にはまたエンジンのセルモータを始動させる始動手段１６、燃料供給ポンプ２の吐出側の燃料圧送経路５における燃料の温度を検知する燃料温度検知手段１７、設定手段１８などが接続されて、当該制御手段１５により始動手段１６からの始動信号や燃料温度検知手段１７からの検知信号、設定手段１８により予め設定した設定値に基づいて三方弁７の切換制御が行われる。なお、制御手段１５にはセルモータ８やガバナ０なども接続され、当該制御手段１５により回転制御が行われる。 The three-way valve 7 can be switched automatically or manually. In the automatic case, the three-way valve 7 is composed of an electromagnetic valve and is connected to the control means 15 as shown in FIG. Also connected to the control means 15 are start means 16 for starting the cell motor of the engine, fuel temperature detection means 17 for detecting the temperature of the fuel in the fuel pumping path 5 on the discharge side of the fuel supply pump 2, setting means 18 and the like. The control means 15 performs switching control of the three-way valve 7 based on a start signal from the start means 16, a detection signal from the fuel temperature detection means 17, and a set value preset by the setting means 18. The control means 15 is also connected to the cell motor 8 and the governor 0, and the control means 15 performs rotation control.

三方弁７の切換制御は次のような流れで行われる。図３に示すように、エンジンの始動時において、キースイッチなどの始動手段１６により制御手段１５が作動状態とされたあと、該制御手段１５に始動手段１６から始動信号が入力される（ステップＳ１０）と、制御手段１５が作動状態とされ、燃料温度検知手段１７で燃料温度が検知され、該検知信号が制御手段１５に入力されて、始動時における燃料温度が読み込まれる（ステップＳ１１）。なおこのとき、セルモータが回転を始め、エンジンの始動が開始される。そして、制御手段１５で始動時における燃料温度と予め設定手段で設定された設定温度との比較が行われる（ステップＳ１２）。 The switching control of the three-way valve 7 is performed in the following flow. As shown in FIG. 3, when the engine is started, after the control means 15 is activated by the start means 16 such as a key switch, a start signal is input to the control means 15 from the start means 16 (step S10). ), The control means 15 is activated, the fuel temperature is detected by the fuel temperature detection means 17, the detection signal is input to the control means 15, and the fuel temperature at the start is read (step S11). At this time, the cell motor starts to rotate and the engine starts. Then, the control means 15 compares the fuel temperature at the time of start-up with the preset temperature set in advance by the setting means (step S12).

燃料温度が設定温度よりも高いと判定されると、三方弁７は燃料供給ポンプ２出口側に燃料フィルタ３の入口側燃料圧送経路５ａを連通させるように切り換えられて（ステップＳ１３）、燃料供給ポンプ２からの燃料が燃料フィルタ３を介して燃料噴射ポンプ４に圧送される。一方、燃料温度が設定温度よりも低いと判定されると、三方弁７が燃料供給ポンプ２出口側にバイパス経路１０を連通させるように切り換えられて（ステップＳ１４）、燃料供給ポンプ２からの燃料がバイパス経路１０を通じて燃料噴射ポンプ４に圧送される。こうして、低温時の燃料中成分の結晶化による燃料フィルタ３での詰まりの発生が回避される。 If it is determined that the fuel temperature is higher than the set temperature, the three-way valve 7 is switched so that the inlet-side fuel pumping path 5a of the fuel filter 3 communicates with the outlet side of the fuel supply pump 2 (step S13). Fuel from the pump 2 is pumped to the fuel injection pump 4 through the fuel filter 3. On the other hand, if it is determined that the fuel temperature is lower than the set temperature, the three-way valve 7 is switched so as to communicate the bypass path 10 to the outlet side of the fuel supply pump 2 (step S14). Is pumped to the fuel injection pump 4 through the bypass path 10. In this way, the occurrence of clogging in the fuel filter 3 due to crystallization of components in the fuel at low temperatures is avoided.

そして、バイパス経路１０側に切り換えられた場合において、エンジンが始動されると始動手段１６となるキースイッチはセルモータ停止方向に回動して（始動信号停止）電源ＯＮの状態を維持し（ステップＳ１５）、三方弁７は燃料供給ポンプ２の出口側に燃料フィルタ３の入口側燃料圧送経路５ａを連通させるように切り換えられる（ステップＳ１３）。これにより、燃料供給ポンプ２からの燃料が燃料フィルタ３を介して燃料噴射ポンプ４に圧送可能とされる。エンジンが始動されると、シリンダブロックも温められて、燃料圧送経路５も温められ、温度の高い過剰の燃料も燃料タンク１に戻されるため、燃料の温度が高くなり、燃料中成分の結晶化による燃料フィルタ３での詰まりが発生することはなく、また燃料フィルタ３で結晶化が生じていてもこれを無くして詰まりを解消することが可能となる。 When the engine is switched to the bypass path 10 side, the key switch serving as the starting means 16 rotates in the cell motor stop direction (start signal stop) and maintains the power ON state (step S15). 3) The three-way valve 7 is switched so as to communicate the inlet side fuel pressure feed path 5a of the fuel filter 3 to the outlet side of the fuel supply pump 2 (step S13). Thereby, the fuel from the fuel supply pump 2 can be pumped to the fuel injection pump 4 via the fuel filter 3. When the engine is started, the cylinder block is also warmed, the fuel pumping path 5 is also warmed, and the excessively high temperature fuel is returned to the fuel tank 1, so that the temperature of the fuel rises and the components in the fuel are crystallized. No clogging occurs in the fuel filter 3 due to this, and even if crystallization occurs in the fuel filter 3, it can be eliminated to eliminate the clogging.

以上のように、燃料タンク１と燃料噴射ポンプ４との間に構成する燃料圧送経路５の途中に燃料供給ポンプ２と燃料フィルタ３とを設けるエンジンの燃料供給構造において、前記燃料フィルタ３の入口側の燃料圧送経路５ａと、該燃料フィルタ３の出口側の燃料圧送経路５ｂとを連通するバイパス経路１０を設け、該バイパス経路１０と入口側燃料圧送経路５ａとの分岐部に三方弁７を設けることによって、燃料をバイパス経路１０により燃料フィルタ３を迂回させて、燃料噴射ポンプ４に供給することが可能となる。したがって、低温下でのエンジン始動時に燃料を燃料フィルタ３を介して燃料噴射ポンプ４に供給する場合には、燃料フィルタ３で燃料中成分の結晶化による詰まりが発生して燃料の供給が不能となる恐れがあるが、三方弁７により燃料をバイパス経路１０を通じて供給することが可能となるため、エンジンの始動不能を防止することができる。また、燃料の品質に応じて燃料フィルタ３の濾過面積を変更したり、捕捉した異物の量に応じた燃料フィルタ３の交換時期を延長したりしてもこれらに関係なく燃料を燃料噴射ポンプ４に供給することが可能となり、エンジンの良好な始動性を確保することができる。 As described above, in the fuel supply structure of the engine in which the fuel supply pump 2 and the fuel filter 3 are provided in the middle of the fuel pumping path 5 formed between the fuel tank 1 and the fuel injection pump 4, the inlet of the fuel filter 3 is provided. A bypass path 10 is provided to connect the fuel pressure feed path 5a on the side and the fuel pressure feed path 5b on the outlet side of the fuel filter 3, and a three-way valve 7 is provided at a branch portion between the bypass path 10 and the inlet side fuel pressure feed path 5a. By providing the fuel, it is possible to supply the fuel to the fuel injection pump 4 by bypassing the fuel filter 3 by the bypass path 10. Therefore, when the fuel is supplied to the fuel injection pump 4 through the fuel filter 3 at the time of starting the engine at a low temperature, the fuel filter 3 is clogged due to crystallization of components in the fuel, and the fuel cannot be supplied. However, since the three-way valve 7 can supply the fuel through the bypass path 10, it is possible to prevent the engine from being unable to start. Even if the filtration area of the fuel filter 3 is changed according to the quality of the fuel, or the replacement time of the fuel filter 3 is extended according to the amount of captured foreign matter, the fuel is injected into the fuel injection pump 4 regardless of these. Therefore, it is possible to ensure good startability of the engine.

そしてまた前記エンジンの燃料供給構造において、三方弁７を電磁弁で構成して、これをセルモータの始動手段１６と接続し、該始動手段１６によるセルモータの始動時に三方弁７を切り換えて燃料を燃料タンク１からバイパス経路１０を通じて燃料噴射ポンプに送るようにすることによって、エンジン始動時に三方弁７を自動で切り換えて燃料をバイパス経路１０により燃料フィルタ３を迂回して燃料噴射ポンプ４に供給することが可能となる。したがって、低温下でのエンジン始動時においては、三方弁７を一時的に忘れることなく切り換えて、燃料をバイパス経路１０を通じて燃料噴射ポンプ４に確実に供給して、始動性の悪化を防止することができる。 Further, in the fuel supply structure of the engine, the three-way valve 7 is constituted by an electromagnetic valve, which is connected to the starter 16 of the cell motor, and the three-way valve 7 is switched when the cell motor is started by the starter 16 to fuel the fuel. By sending the fuel from the tank 1 to the fuel injection pump through the bypass path 10, the three-way valve 7 is automatically switched when the engine is started, and the fuel is bypassed the fuel filter 3 by the bypass path 10 and supplied to the fuel injection pump 4. Is possible. Therefore, when starting the engine at a low temperature, the three-way valve 7 is temporarily switched without forgetting, and fuel is reliably supplied to the fuel injection pump 4 through the bypass path 10 to prevent deterioration of startability. Can do.

また、前記エンジンの燃料供給構造において、三方弁７の切換は手動でも実行可能であり、この場合には、図４（ａ）および（ｂ）に示すように、三方弁７は弁体７ａをバルブケース２１内に回動可能に収納し、該弁体７ａを支軸２２に固定して構成される。該支軸２２はバルブケース２１から外部に突出され、該支軸２２の突出端に切換レバーからなる切換手段２３の一端が固定され、該切換手段２３を支軸２２を中心として回動することによって、三方弁７の弁体７ａが一体的に回動される。 In the fuel supply structure of the engine, the switching of the three-way valve 7 can also be performed manually. In this case, as shown in FIGS. 4A and 4B, the three-way valve 7 has a valve body 7a. The valve case 21 is rotatably housed, and the valve body 7 a is fixed to the support shaft 22. The support shaft 22 protrudes outward from the valve case 21, and one end of a switching means 23 composed of a switching lever is fixed to the protruding end of the support shaft 22, and the switching means 23 rotates around the support shaft 22. Thus, the valve body 7a of the three-way valve 7 is integrally rotated.

切換手段２３の他端とエンジン本体などとの間にはバネなどの付勢手段２４が介装され、該付勢手段２４の付勢力により切換手段２３が付勢されて所定の回動位置（ノーマル側）で保持される。つまり、弁体７ａは燃料供給ポンプ２の出口側に燃料フィルタ３の入口側燃料圧送経路５ａを連通させる位置で保持されて、燃料が入口側燃料圧送経路５ａから燃料フィルタ３を介して燃料噴射ポンプ４に圧送可能とされる。 An urging means 24 such as a spring is interposed between the other end of the switching means 23 and the engine body, and the switching means 23 is urged by the urging force of the urging means 24 so that a predetermined rotational position ( Held on the normal side). That is, the valve body 7a is held at a position where the inlet side fuel pressure feed path 5a of the fuel filter 3 communicates with the outlet side of the fuel supply pump 2, and fuel is injected from the inlet side fuel pressure feed path 5a through the fuel filter 3 into the fuel. Pumping to the pump 4 is possible.

また、切換手段２３の他端と運転操作部に設けられた操作レバーからなる操作手段２５とがワイヤー２６などで連動連結されて、操作手段２５の回動操作により切換手段２３が支軸２２を中心として回動可能とされている。つまり、切換手段２３は、図４（ａ）に示すように、付勢手段２４の付勢力により所定の回動位置に保持され、図４（ｂ）に示すように、操作手段２５の回動操作が行われると付勢手段２４の付勢力に抗して所定の回動位置から回動される。 Further, the other end of the switching means 23 and an operating means 25 comprising an operating lever provided in the driving operation portion are interlocked and connected by a wire 26 or the like, and the switching means 23 causes the support shaft 22 to be rotated by the turning operation of the operating means 25. The center is rotatable. That is, the switching means 23 is held at a predetermined rotation position by the urging force of the urging means 24 as shown in FIG. 4 (a), and the operation means 25 is rotated as shown in FIG. 4 (b). When the operation is performed, it is rotated from a predetermined rotation position against the urging force of the urging means 24.

そしてこの切換手段２３の回動によって、弁体７ａが燃料供給ポンプ２の出口側にバイパス経路１０を連通させる位置に回動されて、燃料がバイパス経路１０を通じて燃料噴射ポンプ４に圧送可能とされる。また、操作手段２５の回動操作が解除されることで、切換手段２３は付勢手段２４の付勢力により所定の回動位置まで回動され、弁体７ａも燃料供給ポンプ２の出口側に燃料フィルタ３の入口側燃料圧送経路５ａを連通させる位置となる元の回動位置に戻り、燃料が入口側燃料圧送経路５ａから燃料フィルタ３を介して燃料噴射ポンプ４に圧送可能とされる。 Then, by the rotation of the switching means 23, the valve body 7a is rotated to a position where the bypass passage 10 communicates with the outlet side of the fuel supply pump 2, so that the fuel can be pumped to the fuel injection pump 4 through the bypass passage 10. The Further, by releasing the turning operation of the operating means 25, the switching means 23 is turned to a predetermined turning position by the urging force of the urging means 24, and the valve body 7a is also moved to the outlet side of the fuel supply pump 2. The fuel filter 3 returns to the original rotational position where the inlet-side fuel pumping path 5a communicates, and the fuel can be pumped from the inlet-side fuel pumping path 5a to the fuel injection pump 4 via the fuel filter 3.

こうして三方弁７が、操作手段２５を回動操作することでバイパス経路１０側に切換可能とされ、操作手段２５の回動操作を解除することで入口側燃料圧送経路５ａ側に切換可能とされる。よって、低温下でのエンジン始動時においては、操作手段２５を回動操作し、三方弁７を一時的にバイパス経路１０側に切り換えて、燃料をバイパス経路１０を通じて燃料噴射ポンプ４に圧送可能することで、燃料中成分の結晶化による燃料フィルタ３での詰まりの発生を回避して燃料を燃料噴射ポンプ４に確実に供給することが可能となり、始動後には燃料の温度が上昇し、燃料中成分の結晶化による燃料フィルタ３での詰まりが発生することはないので、操作手段２５の回動操作を解除し、三方弁７を入口側燃料圧送経路５ａ側に切り換えて、燃料を燃料フィルタ３を介して燃料噴射ポンプ４に供給することが可能となる。 In this way, the three-way valve 7 can be switched to the bypass path 10 side by rotating the operating means 25, and can be switched to the inlet side fuel pumping path 5a side by releasing the rotating operation of the operating means 25. The Therefore, when the engine is started at a low temperature, the operation means 25 is rotated, and the three-way valve 7 is temporarily switched to the bypass path 10 side so that fuel can be pumped to the fuel injection pump 4 through the bypass path 10. As a result, it becomes possible to reliably supply the fuel to the fuel injection pump 4 by avoiding clogging in the fuel filter 3 due to crystallization of the components in the fuel, and the temperature of the fuel rises after the start. Since clogging in the fuel filter 3 due to crystallization of components does not occur, the rotation operation of the operating means 25 is released, the three-way valve 7 is switched to the inlet side fuel pumping path 5a side, and fuel is supplied to the fuel filter 3 It becomes possible to supply to the fuel injection pump 4 via.

このように、前記エンジンの燃料供給構造において、前記三方弁７の切換手段２３をエンジンの運転操作部に設けた操作手段２５と連動連結するとともに、該三方弁７の切換手段２３に付勢手段２４を設けて、該切換手段２３を三方弁７がノーマル側に切り換わるように付勢することによって、エンジン始動時に三方弁７を操作手段２５により手動で切り換えて燃料をバイパス経路１０により燃料フィルタ３を迂回して燃料噴射ポンプ４に供給することが可能となる。したがって、低温下でのエンジン始動時においては、操作手段２５を操作することで燃料をバイパス経路１０を通じて燃料噴射ポンプ４に確実に供給することができ、また操作手段２５による操作を解除することで三方弁７を付勢手段２４にて自動で元の状態に戻すことができるため、始動後の三方弁７の切換忘れを防止することができる。 Thus, in the fuel supply structure of the engine, the switching means 23 of the three-way valve 7 is interlocked with the operating means 25 provided in the engine operation operation section, and the urging means is applied to the switching means 23 of the three-way valve 7. 24, and the switching means 23 is urged so that the three-way valve 7 is switched to the normal side, whereby the three-way valve 7 is manually switched by the operation means 25 when the engine is started, and the fuel is filtered by the bypass path 10 3 can be bypassed and supplied to the fuel injection pump 4. Therefore, when starting the engine at a low temperature, by operating the operating means 25, the fuel can be reliably supplied to the fuel injection pump 4 through the bypass path 10, and the operation by the operating means 25 is canceled. Since the three-way valve 7 can be automatically returned to the original state by the urging means 24, forgetting to switch the three-way valve 7 after starting can be prevented.

本構成例では、図５に示すように、燃料圧送経路５の燃料供給ポンプ２と燃料噴射ポンプ４との間に、燃料フィルタ３の入口側の燃料圧送経路５ａと、燃料フィルタ３の出口側の燃料圧送経路５ｂとを連通するバイパス経路１０が設けられ、燃料供給ポンプ２から圧送される燃料がバイパス経路１０を通り、燃料フィルタ３を迂回して燃料噴射ポンプ４に圧送可能とされる。そして、バイパス経路１０の途中に逆止弁（圧力制御弁）２７が設けられる。 In this configuration example , as shown in FIG. 5, the fuel pumping path 5 a on the inlet side of the fuel filter 3 and the outlet side of the fuel filter 3 are disposed between the fuel supply pump 2 and the fuel injection pump 4 of the fuel pumping path 5. The fuel pressure pumping path 5b communicates with the fuel supply pump 2 so that the fuel pumped from the fuel supply pump 2 passes through the bypass path 10 and bypasses the fuel filter 3 to be pumped to the fuel injection pump 4. A check valve (pressure control valve) 27 is provided in the middle of the bypass path 10.

逆止弁２７は、バイパス経路１０内の燃料供給ポンプ２側の圧力が所定圧力に達すると開き、燃料供給ポンプ２からの燃料をバイパス経路１０を通過させて、出口側燃料圧送経路５ｂに送る構成とされる。この構造ではバイパス経路１０内の圧力は通常所定圧力未満となる。そのため、逆止弁２７は閉じた状態となり、燃料供給ポンプ２からの燃料は入口側燃料圧送経路５ａから燃料フィルタ３を介して出口側燃料圧送経路５ｂに送られて、燃料噴射ポンプに供給される。 The check valve 27 opens when the pressure on the fuel supply pump 2 side in the bypass path 10 reaches a predetermined pressure, and passes the fuel from the fuel supply pump 2 through the bypass path 10 and sends it to the outlet side fuel pressure feed path 5b. It is supposed to be configured. In this structure, the pressure in the bypass passage 10 is usually less than a predetermined pressure. Therefore, the check valve 27 is closed, and the fuel from the fuel supply pump 2 is sent from the inlet side fuel pressure feed path 5a to the outlet side fuel pressure feed path 5b via the fuel filter 3 and supplied to the fuel injection pump. The

そして、燃料フィルタ３で詰まりが発生すると、入口側燃料圧送経路５ａ内の圧力が上昇し、これにともなってバイパス経路１０内の圧力も上昇して、該バイパス経路１０内の圧力が所定圧力に達した時点で、逆止弁２７が開き、燃料供給ポンプ２からの燃料がバイパス経路を通じて出口側燃料圧送経路５ｂに送られて、燃料噴射ポンプ４に供給される。よって、低温下でのエンジン始動時において、燃料フィルタ３で燃料中成分の結晶化や細くした異物により詰まりが発生しても、燃料をバイパス経路１０により燃料フィルタ３を迂回させて燃料噴射ポンプ４に確実に供給することが可能となる。 Then, when clogging occurs in the fuel filter 3, the pressure in the inlet side fuel pumping path 5a increases, and accordingly, the pressure in the bypass path 10 also increases, and the pressure in the bypass path 10 becomes a predetermined pressure. At this point, the check valve 27 is opened, and fuel from the fuel supply pump 2 is sent to the outlet side fuel pressure feed path 5b through the bypass path and supplied to the fuel injection pump 4. Therefore, when the engine is started at a low temperature, even if the fuel filter 3 is clogged due to crystallization of the components in the fuel or thin foreign matters, the fuel is bypassed by the bypass path 10 and the fuel injection pump 4 Can be reliably supplied.

以上のように、燃料タンク１と燃料噴射ポンプ４との間に構成する燃料圧送経路５に燃料供給ポンプ２と燃料フィルタ３とを設けるエンジンの燃料供給構造において、前記燃料フィルタ３の入口側の燃料圧送経路５ａと、該燃料フィルタ３の出口側の燃料圧送経路５ｂとを連通するバイパス経路１０を設け、該バイパス経路１０の途中に逆止弁２７を設けることによって、低温下でのエンジン始動時に、燃料フィルタ３で燃料中成分が結晶化するなどして詰まりが発生した場合でも、バイパス経路１０を通じて燃料噴射ポンプ４に燃料を供給できるため、エンジンの始動不能を防止することができる。また、燃料の品質に応じて燃料フィルタ３の濾過面積を変更したり、捕捉した異物の量に応じた燃料フィルタ３の交換時期を延長したりしてもこれらに関係なく燃料を燃料噴射ポンプ４に供給することが可能となり、エンジンの良好な始動性を確保することができる。 As described above, in the fuel supply structure of the engine in which the fuel supply pump 2 and the fuel filter 3 are provided in the fuel pumping path 5 formed between the fuel tank 1 and the fuel injection pump 4, By providing a bypass path 10 that communicates the fuel pumping path 5a and the fuel pumping path 5b on the outlet side of the fuel filter 3, and providing a check valve 27 in the middle of the bypass path 10, the engine can be started at a low temperature. Sometimes, even when clogging occurs due to crystallization of fuel components in the fuel filter 3, the fuel can be supplied to the fuel injection pump 4 through the bypass path 10, thereby preventing the engine from being unable to start. Even if the filtration area of the fuel filter 3 is changed according to the quality of the fuel, or the replacement time of the fuel filter 3 is extended according to the amount of captured foreign matter, the fuel is injected into the fuel injection pump 4 regardless of these. Therefore, it is possible to ensure good startability of the engine.

本実施例では、図６に示すように、燃料タンク１と燃料噴射ポンプ４との間に構成する燃料戻り経路６と、燃料供給ポンプ２の吸入側の燃料圧送経路５ｃとを連通するバイパス経路３０が設けられ、燃料噴射ポンプ４から送られる過剰の燃料がバイパス経路３０を通って燃料タンク１を迂回し、吸入側燃料圧送経路５ｃで燃料タンク１から送られる燃料と混合されたあと、再度燃料噴射ポンプ４に圧送可能とされる。そして、燃料戻り経路６とバイパス経路３０との間に三方弁３７が設けられ、これを燃料戻り経路６側またはバイパス経路３０側に切り換えることでどちら一方の経路６・３０のみを開くことができるように構成される。この際、燃料戻り経路６の燃料噴射ポンプ４と三方弁３７との間の部分は余剰経路６ａとなる。 In this embodiment, as shown in FIG. 6, a bypass path that connects a fuel return path 6 configured between the fuel tank 1 and the fuel injection pump 4 and a fuel pumping path 5 c on the suction side of the fuel supply pump 2. 30 is provided, and excess fuel sent from the fuel injection pump 4 bypasses the fuel tank 1 through the bypass path 30 and is mixed with fuel sent from the fuel tank 1 in the suction side fuel pressure feed path 5c, and then again. The fuel injection pump 4 can be pumped. A three-way valve 37 is provided between the fuel return path 6 and the bypass path 30, and only one of the paths 6 and 30 can be opened by switching this to the fuel return path 6 side or the bypass path 30 side. Configured as follows. At this time, the portion of the fuel return path 6 between the fuel injection pump 4 and the three-way valve 37 becomes the surplus path 6a.

三方弁３７が燃料戻り経路６側に切り換えられた場合、分岐部ではバイパス経路３０が閉じられて、余剰経路６ａに燃料戻り経路６が連通され、これにより燃料噴射ポンプ４からの過剰の燃料は燃料戻り経路６を通じて燃料タンク１に送られて、該燃料タンク１内の燃料と混合される。また、三方弁３７がバイパス経路３０側に切り換えられた場合、分岐部では燃料戻り経路６が閉じられ、余剰経路６ａにバイパス経路３０が連通され、これにより燃料噴射ポンプ４からの過剰の燃料はバイパス経路３０を通じて燃料供給ポンプ２の吸入側燃料圧送経路５ｃに送られて、該吸入側燃料圧送経路５ｃで燃料タンク１から送られる燃料と混合される。このように三方弁３７の切換によって、燃料噴射ポンプ４からの燃料が燃料タンク１の燃料と当該燃料タンク１で、または吸入側燃料圧送経路５ｃで混合されたのち、燃料圧送経路５を通じて燃料噴射ポンプ４に供給可能とされる。 When the three-way valve 37 is switched to the fuel return path 6 side, the bypass path 30 is closed at the branch portion, and the fuel return path 6 is communicated with the surplus path 6a, whereby excess fuel from the fuel injection pump 4 is removed. The fuel is sent to the fuel tank 1 through the fuel return path 6 and mixed with the fuel in the fuel tank 1. Further, when the three-way valve 37 is switched to the bypass path 30 side, the fuel return path 6 is closed at the branch portion, and the bypass path 30 is communicated with the surplus path 6a, whereby excess fuel from the fuel injection pump 4 is removed. The fuel is sent to the suction side fuel pumping path 5c of the fuel supply pump 2 through the bypass path 30 and mixed with the fuel sent from the fuel tank 1 through the suction side fuel pumping path 5c. Thus, by switching the three-way valve 37, the fuel from the fuel injection pump 4 is mixed with the fuel in the fuel tank 1 in the fuel tank 1 or in the intake side fuel pressure feed path 5c, and then fuel is injected through the fuel pressure feed path 5. The pump 4 can be supplied.

三方弁３７は電磁弁で構成され、図７に示すように、制御手段１５に接続される。制御手段１５にはまたエンジンのセルモータを始動させる始動手段１６、燃料供給ポンプ２の吐出側の燃料圧送経路５における燃料の温度を検知する燃料温度検知手段１７、設定手段１８が接続されて、当該制御手段１５により始動手段１６からの始動信号や燃料温度検知手段１７からの検知信号、設定手段１８により予め設定した設定値に基づいて三方弁７の切換制御が行われる。なお、制御手段１５にはガバナ９なども接続され、当該制御手段１５により各作動制御が行われる。 The three-way valve 37 is composed of an electromagnetic valve, and is connected to the control means 15 as shown in FIG. Also connected to the control means 15 are a start means 16 for starting the cell motor of the engine, a fuel temperature detection means 17 for detecting the temperature of the fuel in the fuel pumping path 5 on the discharge side of the fuel supply pump 2, and a setting means 18. The control means 15 performs switching control of the three-way valve 7 based on a start signal from the start means 16, a detection signal from the fuel temperature detection means 17, and a set value preset by the setting means 18. The control means 15 is also connected to a governor 9 and the like, and each operation control is performed by the control means 15.

三方弁３７の切換制御は次のような流れで行われる。図８に示すように、エンジンの始動時において、キースイッチなどの始動手段１６により制御手段１５が作動状態とされたあと、該制御手段１５に始動手段１６から始動信号が入力される（ステップＳ２０）と、燃料温度検知手段１７で燃料温度が検知され、該検知信号が制御手段１５に入力されて、始動時における燃料温度が読み込まれる（ステップＳ２１）。なおこのとき、セルモータが回転を始め、エンジンの始動が開始される。そして、制御手段１５で始動時における燃料温度と予め設定手段で設定された設定温度との比較が行われる（ステップＳ２２）。 The switching control of the three-way valve 37 is performed in the following flow. As shown in FIG. 8, when the engine is started, after the control means 15 is activated by the start means 16 such as a key switch, a start signal is input to the control means 15 from the start means 16 (step S20). ), The fuel temperature is detected by the fuel temperature detecting means 17, the detection signal is input to the control means 15, and the fuel temperature at the time of starting is read (step S21). At this time, the cell motor starts to rotate and the engine starts. Then, the control means 15 compares the fuel temperature at the time of start-up with the preset temperature set in advance by the setting means (step S22).

燃料温度が設定温度よりも高いと判定されると、三方弁３７が余剰経路６ａに燃料戻り経路６を連通させるように切り換えられて（ステップＳ２３）、燃料噴射ポンプ４からの過剰の燃料が燃料戻り経路６を通じて燃料タンク１に送られて、該燃料タンク１の燃料と混合される。一方、燃料温度が設定温度よりも低いと判定されると、三方弁３７が余剰経路６ａにバイパス経路３０を連通させるように切り換えられて（ステップＳ２４）、燃料噴射ポンプ４からの過剰の燃料がバイパス経路３０を通じて燃料供給ポンプ２の吸入側燃料圧送経路５ｃに送られて、該吸入側燃料圧送経路５ｃで燃料タンク１から送られる燃料と混合される。そして、該燃料が燃料圧送経路５を通じて燃料噴射ポンプ４に供給される。 If it is determined that the fuel temperature is higher than the set temperature, the three-way valve 37 is switched so that the fuel return path 6 communicates with the surplus path 6a (step S23), and excess fuel from the fuel injection pump 4 is fueled. The fuel is sent to the fuel tank 1 through the return path 6 and mixed with the fuel in the fuel tank 1. On the other hand, if it is determined that the fuel temperature is lower than the set temperature, the three-way valve 37 is switched so that the bypass path 30 communicates with the surplus path 6a (step S24), and excess fuel from the fuel injection pump 4 is discharged. The fuel is sent to the suction side fuel pumping path 5c of the fuel supply pump 2 through the bypass path 30 and mixed with the fuel sent from the fuel tank 1 through the suction side fuel pumping path 5c. Then, the fuel is supplied to the fuel injection pump 4 through the fuel pumping path 5.

三方弁３７がバイパス経路３０側に切り換えられた場合には、燃料噴射ポンプ４からの温度の高い過剰の燃料と燃料タンク１からの燃料とが混合されて、燃料の温度の上昇が図られる。そして、燃料温度検知手段１７により燃料供給ポンプ２の吐出側の燃料圧送経路５の温度が定期的に検知され、この検知信号が制御手段１５に入力されて、制御手段１５のメモリに読み込まれる（ステップＳ２５）。そして、制御手段１５で燃料の温度と予め設定手段１８で設定した設定温度と比較が行われる（ステップＳ２６）。 When the three-way valve 37 is switched to the bypass path 30 side, the excessive fuel having a high temperature from the fuel injection pump 4 and the fuel from the fuel tank 1 are mixed to increase the temperature of the fuel. Then, the temperature of the fuel pumping path 5 on the discharge side of the fuel supply pump 2 is periodically detected by the fuel temperature detection means 17, and this detection signal is input to the control means 15 and read into the memory of the control means 15 ( Step S25). Then, the control unit 15 compares the fuel temperature with the preset temperature set in advance by the setting unit 18 (step S26).

燃料の温度が設定温度よりも低いと判定されると、三方弁３７が余剰経路６ａにバイパス経路３０を連通させるように切り換えられた状態に維持され、吸入側燃料圧送経路５ｃでの燃料噴射ポンプ４からの温度の高い過剰の燃料と燃料タンク１からの燃料との混合が引き続き行われて、燃料圧送経路５を通じて圧送される燃料の温度の上昇が図られ、この過程でステップＳ２５およびＳ２６の制御が繰り返し行われる。一方、燃料の温度が設定温度よりも高いと判定されると、三方弁３７が余剰経路６ａに燃料戻り経路６を連通させる側に切り換えられて、燃料噴射ポンプ４からの過剰の燃料が燃料タンク１に戻され混合される。こうして、過剰な温度の上昇を抑制したうえで燃料が燃料圧送経路５を通じて燃料噴射ポンプ４に供給される。 If it is determined that the temperature of the fuel is lower than the set temperature, the three-way valve 37 is maintained in a switched state so that the bypass path 30 communicates with the surplus path 6a, and the fuel injection pump in the intake side fuel pressure feed path 5c 4 and the fuel from the fuel tank 1 are continuously mixed, and the temperature of the fuel pumped through the fuel pumping path 5 is increased. In this process, steps S25 and S26 are performed. Control is repeated. On the other hand, if it is determined that the temperature of the fuel is higher than the set temperature, the three-way valve 37 is switched to the side where the fuel return path 6 communicates with the surplus path 6a, and excess fuel from the fuel injection pump 4 is transferred to the fuel tank. Return to 1 and mix. Thus, the fuel is supplied to the fuel injection pump 4 through the fuel pumping path 5 while suppressing an excessive increase in temperature.

このようにして、燃料の温度が低い場合には、燃料噴射ポンプ４からの温度の高い過剰の燃料を燃料タンク１に戻すことなくバイパス経路３０を通じて燃料供給ポンプ２の吸入側燃料圧送経路５ｃに送り、該吸入側燃料圧送経路５ｃで燃料タンク１からの燃料と混合したあと、燃料圧送経路５を通じて燃料噴射ポンプ４に供給することが可能となるため、燃料噴射ポンプ４からの過剰の燃料を燃料タンク１で混合する場合に比べて燃料の温度を早く上昇させることができる。したがって、低温下でのエンジン始動時において、燃料フィルタ３で燃料中成分の結晶化により詰まりが発生しても、燃料の温度を早急に上昇させて結晶を無くし詰まりを解消することが可能となる。 In this way, when the temperature of the fuel is low, excessive fuel having a high temperature from the fuel injection pump 4 is returned to the fuel tank 1 through the bypass passage 30 to the suction side fuel pressure sending route 5c of the fuel supply pump 2. After being fed and mixed with the fuel from the fuel tank 1 in the suction side fuel pumping path 5c, it can be supplied to the fuel injection pump 4 through the fuel pumping path 5, so that excess fuel from the fuel injection pump 4 can be supplied. Compared with the case of mixing in the fuel tank 1, the temperature of the fuel can be raised faster. Therefore, even if the fuel filter 3 is clogged due to crystallization of the fuel component at the time of starting the engine at a low temperature, the temperature of the fuel can be quickly raised to eliminate the clogging by eliminating crystals. .

また、前記三方弁３７の切換制御においては、三方弁３７を余剰経路６ａにバイパス経路３０を連通させるようにバイパス経路３０側に切り換えた（ステップＳ２４）あと、燃料の温度を監視して（ステップＳ２５およびステップＳ２６）これが設定温度に達することで、燃料を元の燃料戻り経路６側に切り換えるように制御されるが、燃料の温度の代わりにエンジン始動からの経過時間を監視し、これが設定手段１８で予め設定された設定時間を超えることで、元の燃料戻り経路６側に切り換えるように制御することもできる。この場合の制御手段１５には、図７に示すように、時間計測手段１９を接続し、該時間計測手段１９でエンジン始動からの経過時間を計測する構成とする。 In the switching control of the three-way valve 37, the three-way valve 37 is switched to the bypass path 30 side so that the bypass path 30 communicates with the surplus path 6a (step S24), and then the fuel temperature is monitored (step S24). S25 and step S26) When this reaches the set temperature, it is controlled to switch the fuel to the original fuel return path 6 side, but instead of the temperature of the fuel, the elapsed time from the engine start is monitored, which is the setting means. It can also be controlled to switch to the original fuel return path 6 side by exceeding the preset time set at 18. In this case, as shown in FIG. 7, a time measuring unit 19 is connected to the control unit 15, and the time measuring unit 19 measures the elapsed time from the start of the engine.

以上のように、燃料タンク１と燃料噴射ポンプ４との間に構成する燃料圧送経路５に燃料供給ポンプ２と燃料フィルタ３とを設けるエンジンの燃料供給構造において、前記燃料噴射ポンプ４と燃料タンク１との間に構成する燃料戻り経路６と、燃料供給ポンプ２の吸入側の燃料圧送経路５ｃとを連通するバイパス経路３０を設け、該バイパス経路３０と燃料戻り経路６との分岐部に三方弁３７を設けたことによって、低温下でのエンジン始動時に、燃料フィルタ３で燃料中成分が結晶化して詰まりが発生した場合でも、バイパス経路３０を通じて燃料噴射ポンプ４からの温度の高い過剰の燃料を燃料タンク１からの燃料と燃料供給ポンプ２の吸入側の燃料圧送経路５ｃで混合し、燃料の温度を早急に上昇させて結晶を無くし燃料フィルタ３の詰まりを解消することが可能となり、燃料を確実に燃料噴射ポンプに供給してエンジンの始動不能を防止することができる。また、燃料の品質に応じて燃料フィルタ３の濾過面積を変更したり、捕捉した異物の量に応じた燃料フィルタ３の交換時期を延長したりしてもこれらに関係なく燃料を燃料噴射ポンプ４に供給することが可能となり、エンジンの良好な始動性を確保することができる。 As described above, in the fuel supply structure of the engine in which the fuel supply pump 2 and the fuel filter 3 are provided in the fuel pumping path 5 formed between the fuel tank 1 and the fuel injection pump 4, the fuel injection pump 4 and the fuel tank are provided. 1 is provided with a bypass path 30 that communicates between the fuel return path 6 formed between the fuel supply pump 2 and the fuel pumping path 5c on the suction side of the fuel supply pump 2, and a branching portion between the bypass path 30 and the fuel return path 6 is provided in three directions. Due to the provision of the valve 37, when the engine is started at a low temperature, even if fuel components are crystallized in the fuel filter 3 and clogging occurs, excess fuel with high temperature from the fuel injection pump 4 through the bypass passage 30 is generated. Is mixed with the fuel from the fuel tank 1 in the fuel pumping passage 5c on the suction side of the fuel supply pump 2, and the temperature of the fuel is rapidly raised to eliminate crystals and the fuel filter 3 It is possible to eliminate the words, fuel is reliably supplied to the fuel injection pump can be prevented engine starting impossible. Even if the filtration area of the fuel filter 3 is changed according to the quality of the fuel, or the replacement time of the fuel filter 3 is extended according to the amount of captured foreign matter, the fuel is injected into the fuel injection pump 4 regardless of these. Therefore, it is possible to ensure good startability of the engine.

構成例１に係るエンジンの燃料供給構造の構成を示す図。 The figure which shows the structure of the fuel supply structure of the engine which concerns on the example 1 of a structure. 構成例１よ係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の制御機構を示すブロック図。 The block diagram which shows the control mechanism at the time of comprising a three-way valve with a solenoid valve in the fuel supply structure of the engine which concerns on the structural example 1. FIG. 構成例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の三方弁の切換制御の流れを示す図。 The figure which shows the flow of switching control of a three-way valve at the time of comprising a three-way valve with an electromagnetic valve in the fuel supply structure of the engine which concerns on the structural example 1. FIG. 構成例１に係るエンジンの燃料供給構造において、三方弁を切換手段を用いて切換可能に構成した場合の三方弁の切換機構を示す一部断面図。（ａ）三方弁を入口側燃料圧送経路側に切り換えた状態を示す図。（ｂ）三方弁をバイパス経路側に切り換えた状態を示す図。 The engine fuel supply structure which concerns on the structural example 1 WHEREIN: The partial cross section figure which shows the switching mechanism of a three-way valve at the time of comprising a three-way valve so that switching is possible using a switching means. (A) The figure which shows the state which switched the three-way valve to the inlet side fuel pumping path side. (B) The figure which shows the state which switched the three-way valve to the bypass path | route side. 構成例２に係るエンジンの燃料供給構造の構成を示す図。 The figure which shows the structure of the fuel supply structure of the engine which concerns on the example 2 of a structure. 実施例１に係るエンジンの燃料供給構造の構成を示す図。 The figure which shows the structure of the fuel supply structure of the engine which concerns on Example 1. FIG. 実施例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の制御機構を示すブロック図。The fuel supply structure of the engine according to Embodiment 1, a block diagram showing the control mechanism of the case where the three-way valve in the solenoid valve. 実施例１に係るエンジンの燃料供給構造において、三方弁を電磁弁で構成した場合の三方弁の切換制御の流れを示す図。The fuel supply structure of the engine according to the first embodiment, shows a flow of switching control of the three-way valve in the case of constituting the three-way valve in the solenoid valve.

１燃料タンク
２燃料供給ポンプ
３燃料フィルタ
４燃料噴射ポンプ
５燃料圧送経路
５ａ燃料フィルタ３の入口側の燃料圧送経路
５ｂ燃料フィルタ３の出口側の燃料圧送経路
５ｃ燃料供給ポンプ２の吸入側の燃料圧送経路
６燃料戻り経路
７三方弁
１０バイパス経路
１６始動手段
２３切換手段
２４付勢手段
２５操作手段
３０バイパス経路
３７三方弁 DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Fuel supply pump 3 Fuel filter 4 Fuel injection pump 5 Fuel pressure feed path 5a Fuel pressure feed path 5b on the fuel filter 3 inlet side Fuel pressure feed path 5c Fuel filter 3 on the suction side Fuel supply pump 2 suction side fuel Pressure feed path 6 Fuel return path 7 Three-way valve 10 Bypass path 16 Start-up means 23 Switching means 24 Energizing means 25 Operating means 30 Bypass path 37 Three-way valve

Claims

In an engine fuel supply structure in which a fuel supply pump (2) and a fuel filter (3) are provided in the middle of a fuel pumping path (5) formed between a fuel tank (1) and a fuel injection pump (4). A fuel return path (6) configured between the surplus path (6a) of the fuel injection pump (4) and the fuel tank (1); a surplus path (6a) of the fuel injection pump (4); A bypass path (30) communicating with the suction side fuel pumping path (5c) of the fuel supply pump (2) is provided, and a three-way valve (37) is provided at a branch portion between the bypass path (30) and the fuel return path (6). The three-way valve (37) is an electromagnetic valve and is connected to the control means (15). The control means (15) includes a starting means (16) for starting a cell motor and the fuel supply pump. Detect the temperature of the fuel pumping path (5) on the discharge side in (2) The fuel temperature detection means (17) and the setting means (18) are connected to each other, and a start signal from the start means (16), a detection signal from the fuel temperature detection means (17), and the setting means (18) The control means (15) performs switching control of the three-way valve (37) based on the set value set in advance, and when the fuel temperature is lower than the set temperature, the three-way valve (37) Maintaining a state where the surplus path (6a) and the bypass path (30) are switched to communicate with each other, and excessive fuel with a high temperature from the fuel injection pump (4) in the suction-side fuel pumping path (5c). And the fuel from the fuel tank (1) is repeatedly mixed, the temperature of the fuel pumped through the fuel pumping path (5) is increased, and when the fuel temperature is higher than a set temperature, Three-way valve (37) By switching the path (6a) and the fuel return path (6) to the side where they communicate, excess fuel from the fuel injection pump (4) is returned to the fuel tank (1) and mixed to suppress an excessive increase in temperature. And supplying the fuel to the fuel injection pump (4) .