JP2006152852A - Fuel line of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel line of an internal combustion engine capable of preventing a pressure in a fuel return pipe from excessively rising even if the fuel return pipe to return a fuel from a fuel injection system to a fuel tank is blocked by foreign matters. <P>SOLUTION: A high-pressure pipe 105 for force-feeding the fuel in the fuel tank 101 to a delivery pipe 106 and a return pipe 172 for returning the fuel from the delivery pipe 106 to the fuel tank 101 are connected to each other through a bypass pipe 181. A one-way valve 182 is installed in the bypass pipe 181. Even if the return pipe 172 is clogged with foreign matters and blocked, the excessive rising of the pressure in the return pipe 172 can be avoided by releasing the one-way valve 182. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel pipe provided in an internal combustion engine such as an in-cylinder direct injection engine. In particular, the present invention relates to a measure for preventing an excessive increase in the internal pressure of the pipe accompanying a blockage inside the fuel pipe.

  2. Description of the Related Art Conventionally, in an engine where high pressure is required for fuel supplied to an injector, such as an in-cylinder direct injection engine, the fuel sent from the fuel tank is pressurized with a high-pressure fuel pump and directed to the injector. To supply.

  Specifically, as disclosed in the following Patent Document 1 and Patent Document 2, the configuration of the fuel supply system in this type of engine is a feed pump that feeds fuel from a fuel tank, and is fed by this feed pump. High pressure fuel pump for pressurizing the fuel. The fuel pressurized by the high-pressure fuel pump is stored in a delivery pipe to which a plurality of injectors are connected. As a result, the high-pressure fuel stored in the delivery pipe is injected from the opened injector toward the combustion chamber as the injector opens.

Some fuel supply systems in this type of engine are provided with a return pipe for returning fuel from a delivery pipe to a fuel tank. A relief valve is provided at the end of the return pipe on the delivery pipe side (see Patent Document 1 and Patent Document 2). When the fuel pressure in the delivery pipe exceeds a predetermined value, the relief valve is opened. Then, a part of the fuel in the delivery pipe is returned to the fuel tank via the return pipe, thereby preventing an excessive increase in the fuel pressure in the delivery pipe.
JP 2002-332900 A JP-A-11-182376

  By the way, when foreign matter exists in the fuel, there is a possibility that the inside of the piping may be blocked due to accumulation of the foreign matter inside the return piping. In such a situation, even if the fuel pressure in the delivery pipe exceeds a predetermined value and the relief valve is opened, the fuel cannot be returned to the fuel tank. As a result, the internal pressure of the return pipe is excessively increased. In this way, when the internal pressure of the return pipe is excessively increased, for example, there is a possibility of causing a problem such that the fuel oozes out from a connection point (such as a connection point with the delivery pipe) of the return pipe.

  The present invention has been made in view of such points, and the object of the present invention is to block a fuel return pipe (return pipe) for returning fuel from a fuel injection system to a fuel tank due to foreign matter or the like. Even if it is a case, it is providing the fuel piping of the internal combustion engine which can prevent the excessive raise of the pressure in this fuel return piping.

In order to achieve the above object, the solution of the present invention includes a fuel pumping pipe for pumping the fuel in the fuel tank to the fuel injection system of the internal combustion engine, and the fuel from the fuel injection system toward the fuel tank. Assuming a fuel pipe of an internal combustion engine provided with a fuel return pipe for returning the fuel. The fuel pipe and the fuel return pipe are connected to the fuel pipe through a valve means that can be opened and closed. Specifically, when applied to an in-cylinder direct injection type internal combustion engine, the fuel pressure feed pipe is a pipe for pumping fuel in the fuel tank to the delivery pipe, and the fuel return pipe has an overpressure in the delivery pipe. This is a return pipe for returning a part of the fuel to the fuel tank when it rises.

  Due to this specific matter, even if foreign matter accumulates in the fuel return pipe and the fuel return pipe is blocked, the valve means can be opened to release the pressure in the fuel return pipe to the fuel return pipe. It is possible to prevent the pressure in the fuel return pipe from rising excessively. For this reason, it is possible to avoid a situation in which the fuel oozes out from the connection point of the fuel return pipe as the internal pressure of the fuel return pipe increases excessively, and it is possible to ensure high reliability of the fuel supply system.

  Specifically, the valve means is configured by a one-way valve that opens when the fuel pressure in the fuel return pipe becomes higher than the fuel pressure in the fuel pump pipe by a predetermined value or more.

  When this specific matter causes foreign matter to accumulate in the fuel return pipe and the inside of the pipe is blocked, and the fuel pressure in the fuel return pipe becomes higher than the fuel pressure in the fuel return pipe by a predetermined value or more, the valve means Automatically opens. As a result, the fuel pressure in the fuel return pipe is released into the fuel return pipe, and an excessive increase in the pressure in the fuel return pipe can be prevented. As a configuration of this valve means, a biasing force in the closing direction is given to the valve body by a spring or the like, and the valve means is opened when the fuel pressure in the fuel return pipe overcomes this biasing force. Can be adopted. In this case, by appropriately setting the urging force of the spring or the like, the valve means is opened before the internal pressure of the fuel return pipe excessively rises to the extent that the fuel oozes from the connection point of the fuel return pipe. It becomes possible.

  More specifically, the following structure is mentioned as a connection structure between the fuel pressure feed pipe and the fuel return pipe. That is, when the fuel pressure feed pipe is provided with a pressure means for pressurizing and feeding the fuel to the fuel injection system, the connection position of the fuel pressure feed pipe with the fuel return pipe is set on the suction side of the pressure means. ing.

  In this specific matter, the valve means can be opened and closed according to the difference between the pressure on the suction side of the pressurizing means that is lower than the discharge pressure of the pressurizing means and the internal pressure of the fuel return pipe. . In other words, by setting the connection position of the fuel return pipe with the fuel return pipe in a portion where the pressure is relatively low, the responsiveness of the opening and closing operation of the valve means to the fluctuation of the internal pressure of the fuel return pipe can be improved, An excessive increase in pressure in the fuel return pipe can be prevented more reliably.

  Moreover, the following are mentioned as a concrete structure of the fuel-injection system of an internal combustion engine. That is, the fuel injection system of the internal combustion engine is provided with a delivery pipe that stores fuel pumped through the fuel pumping pipe and a plurality of fuel injection valves connected to the delivery pipe. The fuel stored in the delivery pipe is injected from a predetermined fuel injection valve toward the combustion chamber of the internal combustion engine in accordance with the fuel injection timing.

  Due to this specific matter, even if foreign matter accumulates in the fuel return pipe and the inside of the pipe is blocked, it is possible to prevent the internal pressure of the delivery pipe from rising excessively, and the internal pressure of this delivery pipe can be stably increased. Can be maintained. For this reason, it is possible to appropriately obtain the injection pressure and the injection amount of fuel injected toward the combustion chamber of the internal combustion engine, and to stably operate the internal combustion engine.

In the present invention, the fuel pumping pipe for pumping the fuel in the fuel tank to the fuel injection system of the internal combustion engine and the fuel return pipe for returning the fuel from the fuel injection system to the fuel tank can be opened and closed. The valves are connected so as to communicate with each other via the valve means. For this reason, even when foreign matter accumulates in the fuel return pipe and the inside of the pipe is blocked, the internal pressure of the fuel return pipe does not rise excessively, and the fuel oozes out from the connection point of the fuel return pipe. Therefore, a highly reliable fuel supply system can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to an in-cylinder direct injection multi-cylinder (for example, four-cylinder) gasoline engine mounted on an automobile will be described.

-Outline configuration of engine-
FIG. 2 shows a schematic configuration of the engine (internal combustion engine) according to the present embodiment. As shown in FIG. 2, the engine 1 includes a piston 11 that defines a combustion chamber 10 and a crankshaft 13 that is an output shaft. The piston 11 is connected to the crankshaft 13 via the connecting rod 12, and the reciprocating motion of the piston 11 is converted into the rotational motion of the crankshaft 13 by the connecting rod 12.

  A signal rotor 14 having a plurality of protrusions 14a, 14a,... Is attached to the crankshaft 13 on the outer peripheral surface. A crank position sensor 15 is disposed in the vicinity of the signal rotor 14. The crank position sensor 15 outputs a pulse signal corresponding to the protrusion 14 a of the signal rotor 14 when the crankshaft 13 rotates.

  An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 10 of the engine 1. An intake valve 21 is provided between the intake passage 2 and the combustion chamber 10, and the intake passage 2 and the combustion chamber 10 are communicated or blocked by opening and closing the intake valve 21. An exhaust valve 31 is provided between the exhaust passage 3 and the combustion chamber 10, and the exhaust passage 3 and the combustion chamber 10 are communicated or blocked by opening and closing the exhaust valve 31. The opening / closing drive of the intake valve 21 and the exhaust valve 31 is performed by each rotation of the intake camshaft 22 and the exhaust camshaft 32 to which the rotation of the crankshaft 13 is transmitted.

  The intake camshaft 22 has a protrusion 22a. A cam position sensor 23 is disposed in the vicinity of the intake camshaft 22. The cam position sensor 23 outputs a detection signal each time the projection 22 a passes near the cam position sensor 23 as the intake camshaft 22 rotates.

  A throttle valve 24 for adjusting the intake air amount of the engine 1 is disposed in the upstream portion of the intake passage 2. The throttle valve 24 is driven by a throttle motor 25. The opening degree of the throttle valve 24 is adjusted by driving and controlling the throttle motor 25 in accordance with the depression operation of an accelerator pedal 26 provided in the interior of the automobile. Note that the amount of depression of the accelerator pedal 26 (accelerator depression amount) is detected by an accelerator position sensor 27. Further, in the intake passage 2, a vacuum sensor 28 for detecting the pressure (intake pressure) in the intake passage 2 is disposed downstream of the throttle valve 24.

The engine 1 is provided with a fuel injection valve (injector) 4 for directly injecting fuel into the combustion chamber 10 for each cylinder. The fuel injection valve 4 for each cylinder is supplied with high-pressure fuel by a fuel supply device 100 described later, and the fuel is directly injected into the combustion chamber 10 from each fuel injection valve 4, thereby allowing air in the combustion chamber 10. Is formed in the combustion chamber 10 as the spark plug 29 is ignited. The combustion of the air-fuel mixture in the combustion chamber 10 causes the piston 11 to reciprocate and the crankshaft 13 to rotate.

-Fuel supply device 100-
Next, the structure of the fuel supply device 100 for supplying high-pressure fuel to the fuel injection valve 4 will be described. FIG. 1 is a diagram schematically showing the structure of a fuel supply device 100 in the present embodiment. As shown in FIG. 1, a fuel supply apparatus 100 includes a feed pump 102 that sends out fuel from a fuel tank 101, and a fuel injection valve 4 for each cylinder (four cylinders) by pressurizing the fuel sent out by the feed pump 102. , 4,... Are provided with a high-pressure fuel pump (pressurizing means) 103 that discharges toward the vehicle.

  The high-pressure fuel pump 103 includes a cylinder 130, a plunger 131, a pressurizing chamber 132, and an electromagnetic spill valve 133. The plunger 131 is driven by the rotation of a cam 321 attached to the exhaust camshaft 32 and reciprocates in the cylinder 130. The reciprocating movement of the plunger 131 increases or decreases the volume of the pressurizing chamber 132. In the present embodiment, two cam peaks are formed on the cam 321 with an angular interval of 180 ° around the rotation axis of the exhaust camshaft 32. The plunger 131 is pushed up by the cam crest so that the plunger 131 moves in the cylinder 130. In addition, since the engine 1 according to the present embodiment is a four-cylinder type, each time from the fuel injection valve 4 provided for each cylinder during one cycle of the engine, that is, while the crankshaft 13 rotates twice, A total of four fuel injections will be performed. Further, in this engine 1, the exhaust camshaft 32 rotates once every time the crankshaft 13 rotates twice. Therefore, the fuel injection from the fuel injection valve 4 is performed four times and the discharge operation from the high-pressure fuel pump 103 is performed twice, every cycle of the engine 1.

  The pressurizing chamber 132 is partitioned by the plunger 131 and the cylinder 130. The pressurizing chamber 132 communicates with the feed pump 102 via a low-pressure fuel pipe (fuel pressure feed pipe) 104 constituting a low-pressure fuel passage, and a delivery pipe via a high-pressure fuel pipe 105 constituting a high-pressure fuel passage. 106 communicates with the inside.

  The fuel injection valves 4, 4,... Are connected to the delivery pipe 106, and a fuel pressure sensor 161 for detecting the fuel pressure (actual fuel pressure) in the delivery pipe 106 is disposed. A return pipe (fuel return pipe) 172 is connected to the delivery pipe 106 via a relief valve 171. The relief valve 171 opens when the fuel pressure in the delivery pipe 106 exceeds a predetermined pressure (for example, 13 MPa). By opening the valve, a part of the fuel stored in the delivery pipe 106 is returned to the fuel tank 101 via the return pipe 172. Thereby, an excessive increase in the fuel pressure in the delivery pipe 106 is prevented. The return pipe 172 and the high-pressure fuel pump 103 are connected by an excess fuel return pipe 108 (shown by a broken line in FIG. 1), and the fuel leaked from the gap between the plunger 131 and the cylinder 130 is oil sealed. The fuel is stored in the fuel storage chamber 135 in the upper part of 134, and then returned to the surplus fuel return pipe 108 connected to the fuel storage chamber 135.

Note that the low-pressure fuel pipe 104 is provided with a filter 141 and a pressure regulator 142. The pressure regulator 142 returns the fuel in the low-pressure fuel pipe 104 to the fuel tank 101 when the fuel pressure in the low-pressure fuel pipe 104 exceeds a predetermined pressure (for example, 0.4 MPa). The fuel pressure is maintained below a predetermined pressure. Further, the low pressure fuel pipe 104 is provided with a pulsation damper 107, and the pulsation damper 107 suppresses fuel pressure pulsation in the low pressure fuel pipe 104 when the high pressure fuel pump 103 is operated. . The high pressure fuel pipe 105 is provided with a check valve 151 for preventing the fuel discharged from the high pressure fuel pump 103 from flowing backward.

  The high-pressure fuel pump 103 is provided with the electromagnetic spill valve 133 for communicating or blocking between the low-pressure fuel pipe 104 and the pressurizing chamber 132. The electromagnetic spill valve 133 includes an electromagnetic solenoid 133a, and opens and closes by controlling energization of the electromagnetic solenoid 133a. The electromagnetic spill valve 133 is opened by the elastic force of the compression coil spring 133b when energization to the electromagnetic solenoid 133a is stopped. Hereinafter, the opening / closing operation of the electromagnetic spill valve 133 will be described with reference to FIG.

  First, when the energization of the electromagnetic solenoid 133a is stopped, the electromagnetic spill valve 133 is opened by the elastic force of the compression coil spring 133b, and the low pressure fuel pipe 104 and the pressurizing chamber 132 are in communication with each other. In this state, when the plunger 131 moves in the direction in which the volume of the pressurizing chamber 132 increases (intake stroke), the fuel sent from the feed pump 102 enters the pressurizing chamber 132 via the low-pressure fuel pipe 104. Inhaled.

  On the other hand, when the plunger 131 moves in a direction in which the volume of the pressurizing chamber 132 contracts (pressurization stroke), the electromagnetic spill valve 133 is closed against the elastic force of the compression coil spring 133b by energizing the electromagnetic solenoid 133a. When the valve is operated, the low-pressure fuel pipe 104 and the pressurizing chamber 132 are disconnected, and the fuel in the pressurizing chamber 132 is discharged toward the delivery pipe 106 through the high-pressure fuel pipe 105.

  The fuel discharge amount in the high-pressure fuel pump 103 is adjusted by controlling the valve closing start timing of the electromagnetic spill valve 133 and adjusting the valve closing period of the electromagnetic spill valve 133 in the pressurization stroke. That is, if the closing time of the electromagnetic spill valve 133 is advanced and the closing period is lengthened, the fuel discharge amount increases. If the closing start time of the electromagnetic spill valve 133 is delayed and the closing period is shortened, the fuel discharge amount decreases. Will come to do. In this manner, the fuel pressure in the delivery pipe 106 is controlled by adjusting the fuel discharge amount of the high-pressure fuel pump 103.

  Here, the pump duty DT that is a control amount for controlling the fuel discharge amount of the high-pressure fuel pump 103 (the valve closing start timing of the electromagnetic spill valve 133) will be described.

  The pump duty DT is a value that varies between 0% and 100%, and is a value related to the cam angle of the cam 321 of the exhaust camshaft 32 corresponding to the valve closing period of the electromagnetic spill valve 133.

  Specifically, regarding the cam angle of the cam 321, as shown in FIG. 3, the cam angle (maximum cam angle) corresponding to the maximum valve closing period of the electromagnetic spill valve 133 is θ0, and the target fuel pressure in the maximum valve closing period is set. If the cam angle (target cam angle) corresponding to is θ, the pump duty DT is expressed as a ratio of the target cam angle θ to the maximum cam angle θ0 (DT = θ / θ0). Therefore, the pump duty DT becomes a value closer to 100% as the closing period (closing timing) of the target electromagnetic spill valve 133 approaches the maximum closing period, and the target closing period becomes “0”. The closer it is, the closer to 0%.

As the pump duty DT approaches 100%, the valve closing start timing of the electromagnetic spill valve 133 adjusted based on the pump duty DT is advanced, and the valve closing period of the electromagnetic spill valve 133 becomes longer. As a result, the fuel discharge amount of the high-pressure fuel pump 103 increases and the actual fuel pressure increases. Further, as the pump duty DT approaches 0%, the valve closing start timing of the electromagnetic spill valve 133 adjusted based on the pump duty DT is delayed, and the valve closing period of the electromagnetic spill valve 133 is shortened. As a result, the amount of fuel discharged from the high-pressure fuel pump 103 decreases and the actual fuel pressure decreases. The details of the procedure for calculating the pump duty DT are omitted here.

-Fuel injection control device-
Next, the fuel injection control device in this embodiment will be described. FIG. 4 is a block diagram showing a control system of the fuel injection control device in the present embodiment.

  As shown in FIG. 4, the fuel injection control device includes an ECU (electronic control unit) 5 for controlling the operating state of the engine 1. The ECU 5 includes a CPU 51, a ROM 52, a RAM 53, a backup RAM 54, and the like.

  The ROM 52 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 51 executes arithmetic processing based on various control programs and maps stored in the ROM 52.

  The RAM 53 is a memory that temporarily stores calculation results in the CPU 51, data input from each sensor, and the like. The backup RAM 54 is a non-volatile memory that stores data to be saved when the engine 1 is stopped. The CPU 51, ROM 52, RAM 53, and backup RAM 54 are connected to each other via a bus 57, and are connected to an external input circuit 55 and an external output circuit 56.

  A crank position sensor 15, a cam position sensor 23, an accelerator position sensor 27, a vacuum sensor 28, a fuel pressure sensor 161, and the like are connected to the external input circuit 55. On the other hand, the fuel injection valve 4 and the electromagnetic spill valve 133 are connected to the external output circuit 56.

  The ECU 5 calculates a final fuel injection amount used for controlling the amount of fuel injected from the fuel injection valve 4 based on the engine speed, the load factor, and the like.

  Here, the engine speed is obtained from the detection signal of the crank position sensor 15. The load factor is a value indicating the current load ratio with respect to the maximum engine load of the engine 1, and is calculated from a parameter corresponding to the intake air amount of the engine 1 and the engine speed NE. The parameters corresponding to the intake air amount include the intake pressure obtained from the detection signal from the vacuum sensor 28, the accelerator depression amount obtained from the detection signal from the accelerator position sensor 27, and the like.

  The ECU 5 controls the drive of the fuel injection valve 4 based on the final fuel injection amount calculated by the above calculation, and controls the amount of fuel injected from the fuel injection valve 4. Since the amount of fuel injected from the fuel injection valve 4 (fuel injection amount) is determined by the fuel pressure (fuel pressure) in the delivery pipe 106 and the fuel injection time, the above fuel pressure is appropriate to make the fuel injection amount appropriate. It is necessary to maintain a proper value. In order to achieve this, the ECU 5 feedback-controls the fuel discharge amount of the high-pressure fuel pump 103 so that the actual fuel pressure obtained from the detection signal of the fuel pressure sensor 161 approaches the target fuel pressure set according to the engine operating state. To maintain the fuel pressure at an appropriate value. The fuel discharge amount of the high-pressure fuel pump 103 is feedback controlled by adjusting the valve closing period (valve closing start timing) of the electromagnetic spill valve 133 based on the pump duty DT.

-Pressure adjustment mechanism-
Next, a pressure adjustment mechanism that is a feature of this embodiment will be described. This pressure adjustment mechanism is a mechanism for preventing an excessive increase in the internal pressure of the return pipe 172.

The pressure adjusting mechanism includes a bypass pipe 181 connecting the return pipe 172 and the low-pressure fuel pipe 104, and a one-way valve (valve means) 182 provided inside the bypass pipe 181.

  The bypass pipe 181 has one end connected to the return pipe 172 and the other end connected to the low-pressure fuel pipe 104 so that the return pipe 172 and the low-pressure fuel pipe 104 can communicate with each other.

  The connection position of the bypass pipe 181 with respect to the return pipe 172 and the low-pressure fuel pipe 104 will be described below.

  The return pipe 172 extends from the delivery pipe 106 to the fuel tank 101 in a first vertical portion 172a extending in a substantially vertical direction, a horizontal portion 172b extending in the horizontal direction from the lower end of the first vertical portion 172a, and one end of the horizontal portion 172b. Is provided with a second vertical portion 172c extending toward the inside of the fuel tank 101. The connection position of the bypass pipe 181 in the return pipe 172 is near the lower end of the first vertical portion 172a of the return pipe 172. This is because when foreign matter exists in the fuel, the foreign matter is likely to stagnate in the horizontal portion 172b of the return pipe 172, and foreign matter is likely to accumulate on the horizontal portion 172b. The connection position is set on the upstream side (delivery pipe 106 side). Note that the configuration of the return pipe 172 is not limited to that described above, but the connection position of the bypass pipe 181 in the return pipe 172 is higher than that in the return pipe 172 where there is a high possibility that foreign matter is clogged. It is preferable to set on the upstream side (delivery pipe 106 side).

  On the other hand, the connection position of the bypass pipe 181 in the low-pressure fuel pipe 104 is a position between the pressure regulator 142 and the pulsation damper 107 in the low-pressure fuel pipe 104. This is because by connecting the bypass pipe 181 to the region where the pressure fluctuation is smallest in the low-pressure fuel pipe 104, the one-way valve 182 provided inside the bypass pipe 181 can be stably opened and closed. Because. Note that the connection position of the bypass pipe 181 in the low-pressure fuel pipe 104 may be upstream of the pressure regulator 142 (feed pump 102 side), or downstream of the pulsation damper 107 (high-pressure fuel pump 103 side). It may be.

  Next, the one-way valve 182 provided inside the bypass pipe 181 will be described. FIG. 5 is a cross-sectional view showing a schematic configuration of the one-way valve 182 and its surroundings. As shown in FIG. 5, a valve seat 182a is provided at the end of the bypass pipe 181 on the side connected to the return pipe 172. In the present embodiment, a part of the outer surface of the return pipe 172 is used as the valve seat 182a. On the other hand, a spring seat 182b is provided in the vicinity of the end of the bypass pipe 181 that is connected to the low-pressure fuel pipe 104. A valve body 182c and a coil spring 182d are accommodated between the valve seat 182a and the spring seat 182b. That is, the valve body 182c is disposed so as to be able to contact the valve seat 182a, and the coil spring 182d is disposed between the valve body 182c and the spring seat 182b in a compressed state.

  As a result, in a situation where the internal pressure of the return pipe 172 does not rise excessively, the valve body 182c is pressed against the valve seat 182a by the biasing force of the coil spring 182d, and the one-way valve 182 is closed, that is, the return pipe 172 and the low pressure The fuel pipe 104 is cut off. On the other hand, when the internal pressure of the return pipe 172 is excessively increased, the valve body 182c receives the internal pressure of the return pipe 172, and the valve body 182c is separated from the valve seat 182a against the urging force of the coil spring 182d. As a result, the one-way valve 182 is opened, that is, the return pipe 172 and the low-pressure fuel pipe 104 are in communication with each other.

Specifically, as indicated by an arrow in FIG. 5, when the internal pressure of the return pipe 172 is P1, the internal pressure (feed pressure) of the low-pressure fuel pipe 104 is P2, and the urging force (set load) of the coil spring 182d is P3, The following formula (1)
P1> P2 + P3 (1)
Is established, the one-way valve 182 is opened, the return pipe 172 and the low-pressure fuel pipe 104 communicate with each other, and the internal pressure of the return pipe 172 is released to the low-pressure fuel pipe 104.

-Explanation of change in internal pressure of return pipe 172-
Hereinafter, an example of a change in internal pressure of the return pipe 172 when foreign matter accumulates in the return pipe 172 and the inside of the pipe is blocked will be described with reference to FIG.

  For example, when the engine 1 is started in a state where the horizontal portion 172b of the return pipe 172 is clogged with foreign matter A (see FIG. 5), the relief valve 171 is opened (the pressure in the delivery pipe 106 becomes higher than a predetermined pressure). The internal pressure P1 of the first vertical portion 172a of the return pipe 172 is reduced by the outflow of the high-pressure fuel from the delivery pipe 106 accompanying the release operation) and the return of the high-pressure fuel from the high-pressure fuel pump 103 through the surplus fuel return pipe 108. It will rise. When the internal pressure P1 of the first vertical portion 172a exceeds the feed pressure P2 and satisfies the above formula (1), the one-way valve 182 is opened, and the return pipe 172 and the low-pressure fuel pipe 104 are connected. As a result, the internal pressure of the return pipe 172 escapes to the low-pressure fuel pipe 104. As a result, the increase in the internal pressure P1 of the return pipe 172 stops, and when the condition (1) is not satisfied, the one-way valve 182 is again closed. Since such an operation is performed every time the internal pressure P1 of the return pipe 172 rises abnormally, it can be avoided that the pressure P1 of the return pipe 172 rises excessively. 6 shows a state in which the internal pressure P1 of the return pipe 172 is maintained at a value equal to the sum of the urging force (set load) P3 of the coil spring 182d and the feed pressure P2.

  Therefore, by appropriately setting the biasing force (set load P3) of the coil spring 182d of the one-way valve 182, the internal pressure of the return pipe 172 is reduced to the extent that fuel oozes out from the connection point of the return pipe 172. It becomes possible to open the one-way valve 182 before it rises excessively. In the case shown in FIG. 6, when the internal pressure P1 of the return pipe 172 rises abnormally and reaches P4 in the figure, the oozing force (set load) of the coil spring 182d is shown when the fuel oozes out. By setting to the middle P3, the internal pressure P1 of the return pipe 172 is constantly maintained at a value lower than the pressure P4.

  As described above, according to the present embodiment, it is possible to avoid a situation in which fuel oozes out from the connecting portion of the return pipe 172 due to an excessive increase in the internal pressure P1 of the return pipe 172, and to ensure high reliability of the fuel supply system. can do.

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to an in-cylinder direct injection type four-cylinder gasoline engine mounted on an automobile has been described. The present invention is not limited to this, and can be applied to a gasoline engine having any other number of cylinders such as a direct injection type 6-cylinder gasoline engine. Further, the present invention is not limited to a gasoline engine, but can be applied to other internal combustion engines such as a diesel engine. Furthermore, the engine to which the present invention is applicable is not limited to an automobile engine.

Further, the fuel injection system of the internal combustion engine to which the fuel pipe according to the present invention is applied is not necessarily limited to the one having the delivery pipe 106. For example, the present invention can also be applied to an engine that does not include a delivery pipe, includes a pressure regulator in the fuel supply passage, and adjusts the fuel pressure by returning excess fuel to the fuel tank by the pressure regulator. It is.

  In the high-pressure fuel pump 103 in the above embodiment, the plunger 131 is driven by the rotation of the cam 321 attached to the exhaust camshaft 32. However, the plunger 131 is driven by the rotation of the cam attached to the intake camshaft 22. May be configured to be driven.

  Furthermore, in the above-described embodiment, the one-way valve 182 provided in the bypass pipe 181 uses the urging force of the coil spring 182d, but may be constituted by an electromagnetic valve. That is, the return pipe 172 communicates with the low-pressure fuel pipe 104 by detecting that the internal pressure of the return pipe 172 has reached a predetermined value or more and opening the solenoid valve.

It is a figure which shows typically the structure of the fuel supply apparatus which concerns on embodiment. It is a figure showing a schematic structure of an engine concerning an embodiment. It is a figure for demonstrating the opening / closing operation | movement of an electromagnetic spill valve. It is a block diagram which shows the control system of a fuel-injection control apparatus. It is sectional drawing which shows schematic structure of a one-way valve and its periphery. It is a figure for demonstrating an example of the internal pressure change of return piping when a foreign material is blocked and obstruct | occluded in return piping.

Explanation of symbols

1 engine (internal combustion engine)
4 Fuel Injection Valve 10 Combustion Chamber 101 Fuel Tank 103 High Pressure Fuel Pump (Pressure Means)
104 Low-pressure fuel passage (fuel pressure feed piping)
105 High-pressure fuel passage 106 Delivery pipe 172 Return piping (fuel return piping)
182 One-way valve (valve means)

Claims (4)

In a fuel pipe of an internal combustion engine comprising a fuel pumping pipe for pumping fuel in the fuel tank to a fuel injection system of the internal combustion engine and a fuel return pipe for returning fuel from the fuel injection system to the fuel tank ,
The fuel piping for an internal combustion engine, wherein the fuel pressure feed pipe and the fuel return pipe are connected to each other through a valve means that can be opened and closed. In the fuel pipe of the internal combustion engine according to claim 1,
The fuel pipe for an internal combustion engine, wherein the valve means is constituted by a one-way valve that opens when a fuel pressure in the fuel return pipe becomes higher than a fuel pressure in the fuel pump pipe by a predetermined value or more. In the fuel pipe of the internal combustion engine according to claim 1 or 2,
The fuel pressure delivery pipe is provided with a pressurizing means for pressurizing the fuel and feeding it to the fuel injection system.
A fuel pipe for an internal combustion engine, wherein a connection position of the fuel pressure feed pipe with the fuel return pipe is set on the suction side of the pressurizing means. In the fuel pipe of the internal combustion engine according to claim 1, 2, or 3,
A fuel injection system of an internal combustion engine includes a delivery pipe that stores fuel pumped through a fuel pumping pipe and a plurality of fuel injection valves connected to the delivery pipe, and the delivery pipe is matched to the fuel injection timing. A fuel pipe for an internal combustion engine, characterized in that the fuel stored therein is injected from a predetermined fuel injection valve toward the combustion chamber of the internal combustion engine.

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