JP2009002262A - Fuel supply device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply device of an internal combustion engine capable of stably providing fuel pressure pulsation absorbing performance of a pulsation damper by avoiding "bottom hitting" of the pulsation damper without requiring enlargement of the pulsation damper, an extensive design change of fuel piping, etc. <P>SOLUTION: Driving of a feed pump 102 is continued until frequency of fuel pressure pulsation generated in the low pressure fuel piping 104 is lowered lower than a resonance frequency of the fuel supply piping when an engine stops by ignition OFF operation. Consequently, it is possible to prevent the bottom hitting of a diaphragm 74 of the pulsation damper 7 by maintaining fuel pressure in the low pressure fuel piping 104 high and maintaining its average value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel supply device provided in an internal combustion engine represented by an automobile engine or the like. In particular, the present invention relates to a measure for maintaining the performance of a pulsation damper provided to suppress fuel pressure pulsation in a fuel supply path.

  Conventionally, for example, in an in-cylinder direct-injection type automobile engine, the fuel supplied to the injector requires a high pressure, and the fuel sent from the fuel tank is pressurized with a high-pressure fuel pump. It supplies to an injector (for example, refer the following patent document 1).

  Specifically, as disclosed in Patent Document 2 below, the configuration of the fuel supply device in this type of engine includes a feed pump that feeds fuel from a fuel tank, and fuel that is fed by this feed pump. A high-pressure fuel pump is provided. 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.

  In the high-pressure fuel pump, a plunger is inserted in the cylinder. The plunger receives a pressing force from the drive cam via the lifter and reciprocates in the cylinder, and adds the fuel sucked into the pressurizing chamber. It comes to press. Further, a spill valve is provided as a fuel discharge amount adjusting mechanism in this type of high-pressure fuel pump. This spill valve adjusts the fuel discharge amount by switching between a communication state and a non-communication state between the low pressure fuel pipe serving as a fuel supply path from the feed pump and the pressurizing chamber of the high pressure fuel pump. Yes.

  For this reason, when the spill valve is opened when the plunger moves in the direction in which the volume of the pressurizing chamber contracts, a part of the fuel once sucked into the pressurizing chamber is fed into the feed pump. When the plunger moves back and forth in such a situation, the pressure associated with the flow of fuel toward the high pressure fuel pump and the flow of fuel returned from the high pressure fuel pump inside the low pressure fuel pipe The accompanying pressure acts alternately, and fuel pressure pulsation occurs inside the low-pressure fuel pipe. In particular, when the engine is in a light load operation state such as idling operation, the spill valve opening period becomes longer, so the amount of fuel return from the high pressure fuel pump increases and the occurrence of the fuel pressure pulsation occurs. Becomes prominent.

For this reason, as disclosed in Patent Document 3 below, a pulsation damper is attached to the fuel pipe to absorb the fuel pressure pulsation. This pulsation damper accommodates an elastically supported plate (diaphragm), and this plate moves in accordance with the change in the fuel pressure and absorbs the fuel pressure pulsation by changing the internal volume of the pulsation damper. It is like that.
JP 2005-351144 A JP 2002-310037 A JP 2006-105080 A

  However, depending on the operating condition of the engine, the fuel pressure pulsation absorbing performance of the pulsation damper may not be fully exhibited. This will be specifically described below.

  As described above, in the pulsation damper, the elastically supported plate functions as a diaphragm, and absorbs fuel pressure pulsation by moving the plate in accordance with a change in fuel pressure inside the pipe. For this reason, when the plate moves within the allowable lift range (within a range in which the plate does not come into contact with other members), the internal volume of the pulsation damper can be changed and the fuel pressure pulsation is possible. Absorption performance is demonstrated well.

  However, when the amount of movement of the plate exceeds the range of the allowable lift amount, the plate comes into contact with another member (for example, a connector portion connecting the pulsation damper and the fuel pipe). (Hereafter, this situation is referred to as “bottomed”), the fuel pressure pulsation absorbing function due to the change in the internal volume of the pulsation damper will be hindered. Will end up.

  In such a situation, the fuel pipe vibrates greatly, and the vibration is transmitted to the vehicle body via a clamp that fixes the fuel pipe, and is transmitted as abnormal noise to the vehicle interior via the vehicle body. As a result, the vehicle occupant may feel uncomfortable.

  As described above, the cause of the occurrence of “bottom” in the pulsation damper is the resonance frequency (natural frequency) determined by the pipe length of the fuel pipe and the frequency of fuel pressure pulsation synchronized with the frequency of the reciprocating movement of the plunger. Is in the generation of resonance.

  The situation where this resonance occurs will be specifically described. In general, the high-pressure fuel pump is driven by the rotational force of the camshaft of the engine. For this reason, the frequency of the reciprocating movement of the plunger changes according to the engine speed.

  On the other hand, the pipe length of the above fuel pipe is such that the resonance frequency (natural frequency) is the frequency of the reciprocating movement of the plunger during steady operation of the engine (operating at a speed higher than the idling speed) (frequency of fuel pressure pulsation). The design is not consistent with That is, the design is such that the resonance does not occur during steady operation of the engine. For this reason, this resonance has a high possibility of occurring at a timing when the engine speed is reduced to an idling speed or less in a situation where the engine is not in a steady operation, for example, in the process of stopping the engine.

  In order to avoid the “bottom” of the pulsation damper, it is conceivable to increase the allowable lift amount of the plate and the internal volume of the pulsation damper. However, these means lead to an increase in the size of the entire pulsation damper, and a large installation space is required, so that it is not practical.

  It is also conceivable to prevent the occurrence of resonance by changing the pipe length of the fuel pipe so that the resonance frequency (natural frequency) determined by the pipe length is greatly deviated from the frequency band of the fuel pressure pulsation. However, this requires forced design changes such as fuel pipe design changes, pipe routing changes, clamp position changes, etc., which are also impractical.

  The present invention has been made in view of the above points, and the object of the present invention is to increase the size of the pulsation damper and to change the design of the fuel pipe without requiring a large change in the design of the pulsation damper. An object of the present invention is to provide a fuel supply device for an internal combustion engine that can avoid the “bottom” and stably obtain the fuel pressure pulsation absorption performance of the pulsation damper.

-Solving principle-
The solution principle of the present invention taken in order to achieve the above object is that the average fuel pressure in the fuel pipe is set to a predetermined value at the timing when the frequency of the fuel pressure pulsation coincides with the resonance frequency determined by the pipe length of the fuel pipe. Keep it above. This prevents the diaphragm of the pulsation damper from approaching other members and causing a “bottom”, and allows the diaphragm to move within the allowable lift range, thereby preventing the fuel pressure pulsation absorption function. I try to keep it.

-Solution-
Specifically, the present invention relates to an internal combustion engine in which a feed pump and a high-pressure fuel pump are connected by a fuel supply pipe, and a pulsation damper for suppressing fuel pressure pulsation inside the fuel supply pipe is provided. A fuel supply system is assumed. When the frequency of the fuel pressure pulsation, which changes with the change in the operating frequency of the high-pressure fuel pump, substantially matches the resonance frequency (natural frequency) of the fuel supply pipe with respect to the fuel supply device of the internal combustion engine, Feed pump control is performed to increase or maintain the average value of the fuel pressure that fluctuates inside the fuel supply pipe so as to keep the lift position of the diaphragm provided in the pulsation damper within a preset allowable range. Fuel pressure average value setting means is provided.

  Due to this specific matter, when the internal combustion engine is driven, the fuel pumped up from the fuel tank by the feed pump is supplied to the high pressure fuel pump through the fuel supply pipe, and the high pressure fuel pump supplies a predetermined pressure (into each cylinder of the internal combustion engine). The fuel injection pressure). When the operating frequency becomes substantially equal to the resonance frequency (natural frequency) of the fuel supply pipe due to a decrease in the operating frequency of the high-pressure fuel pump or the like, the frequency of fuel pressure pulsation occurring inside the fuel supply pipe Also, the situation substantially coincides with the resonance frequency of the fuel supply pipe. In such a situation, there is a concern that resonance occurs in the fuel supply pipe and that the bottom of the diaphragm of the pulsation damper occurs. In this solution, when the bottom of the diaphragm is concerned, feed pump control for increasing or maintaining the average value of the fuel pressure that fluctuates inside the fuel supply pipe is performed, and the pulsation damper internal The lift position of the diaphragm provided in is kept within an allowable range. That is, it is possible to avoid the occurrence of the bottoming (contact with other members) due to the lowering of the average value of the fuel pressure and the diaphragm lift position exceeding the allowable range. For this reason, since the diaphragm is moved within the range of the allowable lift amount and the fuel pressure pulsation absorbing function of the pulsation damper is maintained, resonance of the fuel supply pipe is also suppressed.

  Specifically, there are the following two methods as feed pump control by the fuel pressure average value setting means.

  First, the high-pressure fuel pump receives the rotational driving force of the internal combustion engine, and the operating frequency of the high-pressure fuel pump varies as the rotational speed of the internal combustion engine varies. When shifting to the state, the feed pump is continuously driven until the rotational speed of the internal combustion engine falls below "the rotational speed at which the frequency of the fuel pressure pulsation substantially matches the resonance frequency of the fuel supply pipe".

  As a conventional drive control of a general feed pump (electric pump), for example, when the internal combustion engine shifts from a drive state to a stop state, the feed pump is stopped almost simultaneously with an ignition OFF operation, for example. For this reason, the average value of the fuel pressure inside the fuel supply pipe suddenly drops, the lift center position of the diaphragm (the center position of the reciprocating movement) has changed greatly, and it has come close to other members (for example, the connector portion etc.) It will lift (reciprocate) at the position. For this reason, a situation has occurred in which the diaphragm exceeds the allowable lift range and the bottom is generated. The present solving means relates to a control operation for preventing the bottoming out when the internal combustion engine shifts from the driving state to the stop state, and the rotational speed of the internal combustion engine is a predetermined rotational speed (for example, idling rotational speed). ) From the bottom of the vehicle to the stoppage, it is possible to reliably prevent the bottom of the diaphragm from being generated, and the generation of abnormal noise in the passenger compartment that occurred when the internal combustion engine was stopped (occurrence of abnormal noise due to vibration of the fuel piping) ) Etc. can be avoided.

  As another method, the high-pressure fuel pump receives the rotational driving force of the internal combustion engine in the same manner as described above, and the operating frequency of the high-pressure fuel pump varies as the rotational speed of the internal combustion engine varies. On the other hand, when the internal combustion engine is continuously driven, when the rotational speed of the internal combustion engine decreases to “the rotational speed at which the frequency of the fuel pressure pulsation substantially matches the resonance frequency of the fuel supply pipe”, The fuel discharge amount is increased.

  More specifically, the amount of fuel discharged per unit time of the feed pump is increased by increasing the voltage across the terminals of the feed pump, which is an electric pump.

  For example, when a so-called undershoot occurs in which the rotational speed of the internal combustion engine suddenly drops due to sudden deceleration (rapid braking) while the vehicle is running, the operating frequency of the high-pressure fuel pump is reduced with the decrease in the rotational speed of the internal combustion engine. In some cases, the frequency of the fuel pressure pulsation substantially matches the resonance frequency of the fuel supply pipe. The present solution relates to a control operation for preventing the bottoming at the time of occurrence of such an undershoot of the internal combustion engine speed, and reliably prevents the bottoming of the diaphragm at the time of sudden deceleration of the vehicle. Therefore, it is possible to avoid the generation of abnormal noise in the passenger compartment (occurrence of abnormal noise due to vibration of the fuel pipe) that has occurred during the sudden deceleration.

  In this case, according to the fuel discharge amount per unit time of the high-pressure fuel pump, the feed pump performs the first fuel supply operation for increasing the fuel supply amount to the high-pressure fuel pump and the second fuel supply for decreasing the fuel supply amount. When the feed pump is driven by the second fuel supply operation with respect to the one that can be switched in two stages, the operation speed of the internal combustion engine is “the frequency of the fuel pressure pulsation is the resonance of the fuel supply piping. The fuel pressure average value setting means is configured to forcibly switch the feed pump to the first fuel supply operation when the rotational speed substantially decreases to the frequency.

  First, when the fuel discharge amount per unit time of the high-pressure fuel pump is larger than a predetermined amount, the fuel request amount from the high-pressure fuel pump is also large, so the feed pump is driven by the first fuel supply operation on the increase side, and conversely When the fuel discharge amount per unit time of the high-pressure fuel pump is smaller than a predetermined amount, the feed pump is driven by the second fuel supply operation on the reduced amount side because the required fuel amount from the high-pressure fuel pump is small. Basic control is performed. In this case, when the feed pump is driven in the second fuel supply operation and the situation where the bottoming may occur is generated, the feed pump is forcibly driven in the first fuel supply operation. Thus, the control can be switched to prevent the occurrence of bottoming. Thereby, bottoming of a diaphragm can be prevented reliably.

  In the present invention, at the timing when the frequency of the fuel pressure pulsation coincides with the resonance frequency determined by the pipe length of the fuel pipe or the like, the average pressure in the fuel supply path is maintained high, whereby the diaphragm of the pulsation damper is made to another member. This prevents a situation where a “bottom” is caused in the vicinity. For this reason, the fuel pressure pulsation absorbing function due to the diaphragm moving within the allowable lift amount can be stably obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case will be described in which the present invention is applied to a fuel supply system in an in-cylinder direct injection multi-cylinder (for example, 4-cylinder) gasoline engine mounted on an automobile.

(First embodiment)
First, the first embodiment will be described.

-Fuel supply system-
FIG. 1 is a diagram schematically showing the structure of a fuel supply system 100 in the present embodiment. As shown in FIG. 1, a fuel supply system 100 includes a feed pump 102 that is an electric pump that feeds fuel from a fuel tank 101, and pressurizes the fuel delivered by the feed pump 102 to each cylinder (four cylinders). And a high-pressure fuel pump 1 that discharges toward the injectors (fuel injection valves) 4, 4,.

  As a schematic configuration of the high-pressure fuel pump 1, a cylinder 21, a plunger 23, a pressurizing chamber 22, and an electromagnetic spill valve 30 are provided.

  The plunger 23 receives a downward urging force by a coil spring 27 via a retainer 26. The plunger 23 resists the biasing force of the coil spring 27 when the driving cam 111 attached to the exhaust camshaft 110 of the engine rotates and receives a pressing force from the cam nose 112, 112. Move upward. For this reason, with the rotation of the drive cam 111, the plunger 23 reciprocates in the cylinder 21, and the volume of the pressurizing chamber 22 is enlarged or reduced. In the present embodiment, two cam peaks (cam noses) 112 and 112 are formed on the drive cam 111 with an angular interval of 180 ° around the rotation axis of the exhaust camshaft 110.

  Since the engine according to the present embodiment is a four-cylinder type, a total of four times, one each from the injector 4 provided for each cylinder during one cycle of the engine, that is, while the crankshaft rotates twice. Fuel injection will be performed. In this engine, the exhaust camshaft 110 rotates once every time the crankshaft rotates twice. Therefore, the fuel injection from the injector 4 is performed four times, and the discharge operation from the high pressure fuel pump 1 is performed twice, every cycle of the engine.

  The pressurizing chamber 22 is partitioned by a plunger 23 and a cylinder 21. The pressurizing chamber 22 communicates with the feed pump 102 via a low-pressure fuel pipe 104, and communicates with a delivery pipe (pressure accumulating vessel) 106 via a high-pressure fuel pipe 105.

  The delivery pipe 106 is connected to the injectors 4, 4,... And a fuel pressure sensor 161 that detects the fuel pressure (actual fuel pressure) in the delivery pipe 106. In addition, a 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 1 are connected by a fuel discharge pipe 108 (shown by a broken line in FIG. 1), and fuel leaked from the gap between the plunger 23 and the cylinder 21 is sealed unit. 5 is accumulated in the fuel storage chamber 6 at the upper part of the fuel tank 5 and then returned to the fuel tank 101 from the fuel discharge pipe 108 connected to the fuel storage chamber 6 via the return pipe 172.

  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 (fuel pressure pulsation reducing means) 7. The pulsation damper 7 suppresses fuel pressure pulsation in the low pressure fuel pipe 104 when the high pressure fuel pump 1 is operated. (A specific configuration of the pulsation damper 7 will be described later). The high pressure fuel pipe 105 is provided with a check valve 151 for preventing the fuel discharged from the high pressure fuel pump 1 from flowing backward.

  The high-pressure fuel pump 1 is provided with the electromagnetic spill valve 30 for communicating or blocking between the low-pressure fuel pipe 104 and the pressurizing chamber 22. The electromagnetic spill valve 30 includes an electromagnetic solenoid 31 and opens and closes by controlling energization of the electromagnetic solenoid 31. The electromagnetic spill valve 30 is opened by the biasing force of the coil spring 37 when the energization of the electromagnetic solenoid 31 is stopped. Hereinafter, the opening / closing operation of the electromagnetic spill valve 30 will be described with reference to FIG.

  First, when the energization of the electromagnetic solenoid 31 is stopped, the electromagnetic spill valve 30 is opened by the biasing force of the coil spring 37, and the low pressure fuel pipe 104 and the pressurizing chamber 22 are in communication with each other. In this state, when the plunger 23 moves in the direction in which the volume of the pressurizing chamber 22 increases (intake stroke), the fuel sent from the feed pump 102 is sucked into the pressurizing chamber 22 through the low-pressure fuel pipe 104. Is done.

  On the other hand, when the plunger 23 moves in the direction in which the volume of the pressurizing chamber 22 contracts (pressurization stroke), the electromagnetic spill valve 30 is closed against the urging force of the coil spring 37 by energizing the electromagnetic solenoid 31. Then, the low-pressure fuel pipe 104 and the pressurizing chamber 22 are disconnected, and when the fuel pressure in the pressurizing chamber 22 reaches a predetermined value, the check valve 40 is opened, and the high-pressure fuel is supplied to the high-pressure fuel pipe 105. And is discharged toward the delivery pipe 106.

  The fuel discharge amount in the high-pressure fuel pump 1 is adjusted by controlling the closing period of the electromagnetic spill valve 30 in the pressurization stroke. That is, if the closing time of the electromagnetic spill valve 30 is advanced and the closing period is lengthened, the fuel discharge amount increases. If the closing start time of the electromagnetic spill valve 30 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 1.

  Here, the pump duty DT which is a control amount for controlling the fuel discharge amount of the high-pressure fuel pump 1 (the valve closing start timing of the electromagnetic spill valve 30) will be described.

  The pump duty DT varies between 0 and 100%, and is a value related to the cam angle of the drive cam 111 of the exhaust camshaft 110 corresponding to the valve closing period of the electromagnetic spill valve 30. .

  Specifically, as shown in FIG. 2, regarding the cam angle of the drive cam 111, the cam angle (maximum cam angle) corresponding to the maximum valve closing period of the electromagnetic spill valve 30 is θ0, and the target of the maximum valve closing period is set. Assuming that the cam angle (target cam angle) corresponding to the fuel pressure is θ, the pump duty DT is expressed by the 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 30 approaches the maximum closing period, and the target closing period becomes “0”. The closer it is, the closer to 0%.

  And as the pump duty DT approaches 100%, the valve closing start timing of the electromagnetic spill valve 30 adjusted based on the pump duty DT is advanced, and the valve closing period of the electromagnetic spill valve 30 becomes longer. As a result, the fuel discharge amount of the high-pressure fuel pump 1 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 30 adjusted based on the pump duty DT is delayed, and the valve closing period of the electromagnetic spill valve 30 is shortened. As a result, the fuel discharge amount of the high-pressure fuel pump 1 is reduced and the actual fuel pressure is lowered. The details of the procedure for calculating the pump duty DT are omitted here.

  Next, the pulsation damper 7 will be described. FIG. 3 is a cross-sectional view showing the pulsation damper 7. FIG. 4 is a cross-sectional view showing a state in which the pulsation damper 7 is attached to the suction pipe member 11 of the high-pressure fuel pump 1.

  As shown in these drawings, the pulsation damper 7 is assembled to the high-pressure fuel pump 1 while sandwiching a later-described union pipe 13 between the suction pipe member 11 and the flow path of the low-pressure fuel pipe 104. And a function of suppressing fuel pressure pulsation in the inside.

  Specifically, the pulsation damper 7 includes a damper portion 71 having a diaphragm mechanism and a piping portion 72 that forms a fuel flow path.

  The damper portion 71 has a configuration in which a diaphragm 74 is accommodated in a casing 73 formed by combining two bent plates. The diaphragm 74 is integrally formed with a rubber elastic deformation portion 74a supported in a state where an outer peripheral edge is sandwiched between two plate members constituting the casing 73, and a central portion of the elastic deformation portion 74a. And an attached metal plate 74b. A back pressure space 74c is formed between the diaphragm 74 and the inner wall surface of the casing 73, and a coil spring 75 is accommodated in a compressed state in the back pressure space 74c. Thus, the diaphragm 74 is given a biasing force in a direction toward the fuel flow paths A, B, and C in the pipe portion 72 by the biasing force of the coil spring 75. That is, the diaphragm 74 is deformed against the urging force of the coil spring 75 when the fuel pressure in the fuel flow paths B and C is increased (deformed in the direction of retreating from the fuel flow paths B and C). A function of absorbing fuel pressure and thereby suppressing fuel pressure pulsation is exhibited. The back pressure space 74c in which the coil spring 75 is accommodated communicates with the atmosphere.

  On the other hand, the piping part 72 has a double-pipe structure, and has a structure in which fuel flows from the outer flow path A toward the inner flow path C through the space B where the diaphragm 74 faces. Specifically, an opening 73a for constituting a part of the fuel flow path is formed in the casing 73 of the damper portion 71, and an edge portion of the opening 73a has a relatively large diameter and An outer tube 76 having a relatively short axial length is attached. As a method for attaching the outer tube 76 to the edge of the opening 73a, welding or the like can be mentioned. On the other hand, an inner tube 77 that is smaller in diameter than the outer tube 76 and longer in the axial direction than the outer tube 76 is disposed inside the outer tube 76. As the support structure of the inner tube 77, a support pin extending from the inner surface of the outer tube 76 is used. Of the both ends of the inner tube 77 in the longitudinal direction, the end portion on the damper portion 71 side has a predetermined distance from the diaphragm 74, thereby the outer channel A of the above-mentioned double tube structure. A communication path B communicating with the inner flow path C is formed. A male screw 77 a is formed at the end of the inner pipe 77 on the suction pipe member 11 side, and the pulsation damper 7 is assembled to the high-pressure fuel pump 1 using this male screw 77 a. .

  The union pipe 13 is a piping member for allowing the low-pressure fuel pumped up from the fuel tank 101 by the operation of the feed pump 102 to flow into the pulsation damper 7.

  Specifically, the union pipe 13 is formed of a tubular body whose outer diameter dimension substantially matches the outer diameter dimension of the outer pipe 76 of the pulsation damper 7, and a low pressure extending from the fuel tank 101 on a part of its outer peripheral surface. A connecting pipe 13a to which the fuel pipe 104 is connected is integrally formed. That is, the union pipe 13 forms a fuel flow path D with the outer peripheral surface of the inner pipe 77 in a state where the union pipe 13 is sandwiched between the pulsation damper 7 and the suction pipe member 11.

  Further, a flange 13b extending toward the inner peripheral side is formed at an end edge of the union pipe 13 on the side in contact with the suction pipe member 11. The inner diameter dimension of the flange 13b matches the outer diameter dimension of the inner pipe 77. When the union pipe 13 is sandwiched between the pulsation damper 7 and the suction pipe member 11, the inner diameter of the flange 13b Since the peripheral surface is in contact with the outer peripheral surface of the inner tube 77, the pulsation damper 7 and the union pipe 13 are positioned relative to each other.

  When the union pipe 13 and the pulsation damper 7 are assembled to the high-pressure fuel pump 1, the mating surface portion between the suction pipe member 11 and the union pipe 13, and the mating surface portion between the union pipe 13 and the pulsation damper 7. Ring-shaped gaskets 14 and 15 are interposed in each of the two to prevent fuel leakage from each mating surface portion.

-Basic operation of pulsation damper 7-
Next, the basic operation of the pulsation damper 7 configured as described above will be described. When the feed pump 102 and the high-pressure fuel pump 1 are driven as the engine is driven, the low-pressure fuel pumped up from the fuel tank 101 passes through the filter 141, the pressure regulator 142, and the low-pressure fuel pipe 104, and the internal space D of the union pipe 13. (See arrow I in FIG. 4). That is, the fuel flows into the space D formed between the union pipe 13 and the inner pipe 77 of the pulsation damper 7.

  When the plunger 23 moves in the direction in which the volume of the pressurizing chamber 22 increases (intake stroke), the fuel flows between the outer pipe 76 and the inner pipe 77 of the pulsation damper 7 (outer flow path). ) A flows from the suction pipe member 11 toward the pressurizing chamber 22 through the space (communication path) B facing the diaphragm 74 and the inner space (inner flow path) C of the inner pipe 77 (in FIG. 4). (See arrow II).

  On the other hand, when the plunger 23 moves in the direction in which the volume of the pressurizing chamber 22 contracts (pressurization stroke), when the electromagnetic spill valve 30 is opened by the biasing force of the coil spring 37, the pressurizing chamber The fuel in 22 flows backward and flows into the internal space C of the inner pipe 77 through the inside of the suction pipe member 11 (see arrow III in FIG. 4). At this time, in the inner space C of the inner pipe 77, the fuel pulsation is likely to occur at substantially the same frequency as the operating frequency of the high-pressure fuel pump 1, but the diaphragm 74 of the pulsation damper 7 is a coil spring. The fuel pressure is absorbed by expanding the space B by deforming against the urging force of 75 (deformation in a direction retreating from the internal space C of the inner pipe 77). Thereby, fuel pressure pulsation is suppressed. That is, the pulsation due to the back flow of the fuel is suppressed in the inner space C of the inner tube 77 and the space B where the diaphragm 74 faces, and the space between the outer tube 76 and the inner tube 77 of the pulsation damper 7. The pulsation occurring in A is also greatly suppressed or eliminated. In other words, in the space A between the outer tube 76 and the inner tube 77 of the pulsation damper 7, the fuel flows constantly toward the pressurizing chamber 22, and the influence of the pulsation hardly occurs.

  However, the fuel pressure pulsation absorbing performance of the pulsation damper 7 may not be fully exhibited depending on the engine operating condition. In other words, the amount of movement of the plate 74b of the diaphragm 74 exceeds the range of the allowable lift amount and abuts against other members (for example, the opening edge of the opening 73a and the tip edge of the inner tube 77). When the “addition” occurs, the fuel pressure pulsation absorbing function of the pulsation damper 7 is inhibited, so that the fuel pressure pulsation cannot be absorbed and a large fuel pressure pulsation is generated in the low-pressure fuel pipe 104. In such a situation, the vibration of the low-pressure fuel pipe 104 is transmitted to the vehicle body via the clamp that fixes the low-pressure fuel pipe 104, and is transmitted as abnormal noise to the vehicle interior via the vehicle body. Become.

  In the present embodiment, a control operation for avoiding “bottom” of the diaphragm 74 is performed. Specifically, when the engine shifts from the drive state to the stop state, the engine rotation speed becomes “the rotation speed at which the frequency of the fuel pressure pulsation substantially matches the resonance frequency (natural frequency) of the low-pressure fuel pipe 104”. The drive of the feed pump 102 is continued until the value falls below (the operation for maintaining the average value of the fuel pressure by the fuel pressure average value setting means).

-Preventing occurrence of bottoming-
Hereinafter, the drive control procedure of the feed pump 102 for preventing the occurrence of bottoming will be described with reference to the flowchart of FIG. The routine shown in FIG. 5 is executed every several milliseconds, for example.

  First, in step ST1, it is determined whether or not an ignition OFF operation has been performed by the driver. For example, when an ignition key OFF operation (in the case of a mechanical key) or a start / stop button push-in operation (in the case of a push button type) is performed in an engine operating state, a Yes determination is made in this step ST1.

  If the ignition OFF operation has not been performed and the determination in step ST1 is No, this routine is terminated assuming that the above “bottom” is not present.

  On the other hand, if the ignition OFF operation has been performed and a Yes determination is made in step ST1, the process proceeds to step ST2, and the process proceeds to step ST3 while maintaining the drive state of the feed pump 102 (continuous drive). That is, the power supply to the feed pump 102 is continued. As a result, the average value of the internal pressure of the low-pressure fuel pipe 104 does not decrease, and a predetermined prescribed pressure, for example, about 0.4 MPa is still maintained.

  In step ST3, it is determined whether or not the engine rotational speed Ne has decreased to a rotational speed (for example, 350 rpm) lower by 50 rpm than a predetermined resonance generating rotational speed. The resonance generation speed here is an engine speed at which the frequency of the fuel pressure pulsation inside the low-pressure fuel pipe 104 substantially matches the resonance frequency (natural frequency) of the low-pressure fuel pipe 104. That is, in this step ST3, the engine speed that decreases with the ignition OFF operation passes through the engine speed that causes the fuel pressure pulsation frequency to substantially match the resonance frequency of the low-pressure fuel pipe 104, and then to a certain extent. (50 rpm in this embodiment) The drive state of the feed pump 102 is maintained until the number of rotations decreases. The rotation speed (50 rpm) further subtracted from the resonance frequency in step ST3 is not limited to this, and is set experimentally or empirically. In other words, if the value of the rotation speed to be subtracted is too small, the reliability for obtaining the bottoming out prevention effect is not sufficient, and conversely, if the value of the rotation speed to be subtracted is too large, the feed pump Since the driving time of 102 becomes longer than necessary and leads to an increase in power consumption, the appropriate value is set in consideration of these.

  If the engine speed decreases to a speed that is 50 rpm lower than the resonance generation speed, and a Yes determination is made in step ST3, the process proceeds to step ST4 and the feed pump 102 is stopped. That is, power supply to the feed pump 102 is stopped. Thereby, the feed pump 102 is also stopped at substantially the same timing as the engine stop.

  As described above, in the present embodiment, even when the ignition OFF operation is performed, the drive state of the feed pump 102 is maintained until the engine speed falls to some extent below the resonance generation speed. For this reason, the average value of the internal pressure of the low-pressure fuel pipe 104 is kept relatively high (for example, maintained at about 0.4 MPa), and the coil spring 75 of the damper portion 71 is compressed to some extent by this fuel pressure. Will continue. Accordingly, it is possible to avoid a situation in which the plate 74b of the diaphragm 74 reciprocates around a position close to the tip edge of the inner tube 77, and the occurrence of the “bottom” can be prevented.

  A case where the bottom of the diaphragm 74 is generated by the conventional feed pump control and a case where the feed pump 102 is controlled to maintain the average pressure in the low-pressure fuel pipe 104 as in this embodiment are shown in FIGS. 8 is used for comparison.

  FIG. 6 shows a change in the pulsation amplitude in the low-pressure fuel pipe 104 according to the change in the engine speed. As indicated by a one-dot chain line in FIG. 6, in the conventional feed pump control, the pulsation amplitude in the low-pressure fuel pipe 104 is reduced as the ignition speed is turned OFF and the engine speed decreases (see the arrow in FIG. 6). As the pressure rises, the bottom generation pulsation amplitude is reached and the bottom of the diaphragm 74 is generated.

  On the other hand, when the feed pump 102 is controlled so as to maintain the average pressure in the low-pressure fuel pipe 104 as in the present embodiment, as indicated by the solid line in FIG. Even if it decreases, the increase amount of the pulsation amplitude in the low-pressure fuel pipe 104 is suppressed, and the generated pulsation amplitude with the bottom is not reached. That is, the moving amount of the plate 74b is suppressed within the allowable lift amount, and the fuel pressure pulsation absorbing function by the pulsation damper 7 is stably obtained.

  In the case shown in FIG. 6, the drive of the feed pump 102 is continued between the timing α and the timing β in the figure. Conventionally, the feed pump has already been stopped during this period. In addition, at timing γ, the pulsation amplitude in the low-pressure fuel pipe 104 is in the largest state, but in the present embodiment, there is a sufficient margin with respect to the generated pulsation amplitude with a bottom, and the bottom is surely It has been avoided.

  FIG. 7 is a view showing the lift position of the plate 74b of the diaphragm 74 in comparison with the present embodiment (FIG. 7a) and the conventional example (FIG. 7b). In FIG. 7b, the average pressure in the low-pressure fuel pipe (feed average pressure) is lowered due to the drop in the feed pressure (internal pressure of the low-pressure fuel pipe) accompanying the stop of the feed pump (the upper side in the figure is the low-pressure side), and intermittent In particular, the bottom of the diaphragm has occurred.

  On the other hand, in this embodiment (FIG. 7a), the average pressure (feed average pressure) in the low-pressure fuel pipe 104 is maintained relatively high by maintaining the feed pressure as the drive of the feed pump 102 is continued. The bottom of the diaphragm 74 does not occur (it is maintained on the lower side (high-pressure side) in the figure than that of FIG. 7b).

  Further, FIG. 8 is a diagram showing the fuel pressure immediately downstream of the pulsation damper 7 in comparison with that of the present embodiment (FIG. 8a) and that of the conventional example (FIG. 8b). In FIG. 8 b, the bottom of the diaphragm is generated, so that a part of the low-pressure fuel pipe is cut off, and the fuel pressure on the downstream side of the pulsation damper is temporarily dropped. In such a situation, the pressure fluctuation width (Y in the figure) inside the low-pressure fuel pipe becomes extremely large, and the vibration of the low-pressure fuel pipe is promoted.

  On the other hand, in the present embodiment (FIG. 8a), the bottom of the diaphragm 74 does not occur. Therefore, the low-pressure fuel pipe 104 is not shut off, and the fuel pressure downstream of the pulsation damper 7 is a predetermined value. It is stable within the range (X in the figure). For this reason, the vibration of the low-pressure fuel pipe 104 does not increase.

  In this embodiment, as the drive control of the feed pump 102 when the engine shifts from the drive state to the stop state, the drive of the feed pump 102 is continued so as to obtain the same discharge pressure as when the engine is driven. . Not limited to this, as long as the bottom of the diaphragm 74 can be avoided, the feed pump 102 may be continuously driven while the discharge pressure is lower than the discharge pressure when the engine is driven.

(Second Embodiment)
Next, a second embodiment will be described. In this embodiment, the control operation for avoiding the “bottom” of the diaphragm 74 is different from that in the first embodiment, and the configuration of the fuel supply system, the basic operation of the pulsation damper 7 and the like are the first. This is the same as the embodiment. Therefore, only the control operation for avoiding “bottom” of the diaphragm 74 will be described here.

  The first embodiment described above is a control operation for preventing the “bottom” when the engine is stopped. The second embodiment is a control operation for preventing the above “bottom” when a so-called undershoot occurs in which the engine speed rapidly drops while the vehicle is running.

  Specifically, when an undershoot occurs in the engine speed, the amount of power supplied to the feed pump 102 is increased, so that the speed of the feed pump 102 is increased and the average value of the internal pressure of the low-pressure fuel pipe 104 is increased. The fuel pressure is increased (operation for increasing the average value of the fuel pressure by the fuel pressure average value setting means).

  Before describing the control operation of the feed pump 102 in the present embodiment, the normal control operation of the feed pump 102 will be described.

  FIG. 9 is a diagram showing a schematic configuration of an electric circuit for controlling the drive of the feed pump 102. As shown in FIG. 9, the drive circuit of the feed pump 102 is configured to supply power from a battery (storage battery) BAT to the feed pump 102 via a plurality of relay contacts 81, 82, 83. Specifically, it has first to third relay contacts 81, 82, 83 connected in series via a plurality of fuses F1, F2, and these relay contacts 81, 82, 83 are not shown. Each engine ECU is turned ON / OFF independently. A resistor 84 is connected in parallel to the third relay contact 83.

  For this reason, when all of the first to third relay contacts 81, 82, 83 are turned on, the battery voltage (for example, 12 V) is applied to the feed pump 102 as it is. On the other hand, when the first and second relay contacts 81 and 82 are turned on and the third relay contact 83 is turned off, the battery voltage is dropped by the resistor 84 (for example, 10 V) to the feed pump 102. Will be applied. That is, in the former state, the feed pump 102 is rotated at a relatively high speed and the fuel discharge amount is increased (pump High operation: first fuel supply operation), whereas in the latter state, the feed pump 102 Is rotated at a relatively low speed so that the fuel discharge amount is reduced (pump low operation: second fuel supply operation).

  Switching between the pump high operation and the pump low operation is performed according to the map shown in FIG. The horizontal axis of FIG. 10 corresponds to the fuel discharge amount of the high-pressure fuel pump 1, that is, the fuel requirement amount for the feed pump 102 by the high-pressure fuel pump 1. On the other hand, the vertical axis represents the battery voltage. As shown in FIG. 10, when the fuel discharge amount of the high-pressure fuel pump 1 is relatively large, the feed pump 102 is in a pump high operation state because the fuel request amount for the feed pump 102 is large. On the other hand, when the amount of fuel discharged from the high-pressure fuel pump 1 is relatively small, the feed pump 102 is in a pump low operation state because the required fuel amount for the feed pump 102 is small. The fuel discharge amount of the high-pressure fuel pump 1 is set by the above-described open / close control of the electromagnetic spill valve 30 according to the engine speed, the engine load, and the like.

  The pump high operation and the pump low operation of the feed pump 102 are set by a change in voltage applied between the terminals of the feed pump 102 as the third relay contact 83 is switched ON / OFF. FIG. 11 is a diagram showing the relationship between the voltage value applied across the terminals of the feed pump 102 and the fuel pressure discharged from the feed pump 102. Thus, the higher the inter-terminal voltage of the feed pump 102, the higher the discharged fuel pressure. The normal control operation of the feed pump 102 as described above is performed similarly in the above-described first embodiment.

  In the situation where the normal control operation of the feed pump 102 as described above is performed, the procedure of drive control of the feed pump 102 for preventing the occurrence of bottoming, which is the control operation characteristic of the present embodiment, is shown in the flowchart of FIG. It explains along. The routine shown in FIG. 12 is executed every several milliseconds, for example.

  First, in step ST11, an engine speed detection operation is performed. Specifically, the engine speed is calculated based on an output from a crank angle sensor disposed opposite to the engine crankshaft.

  Then, in step ST12, it is determined whether or not an undershoot has occurred in the detected engine speed. For example, it is determined whether or not there is an undershoot that occurs when the engine speed suddenly drops due to sudden deceleration of the vehicle due to sudden braking while the vehicle is running.

  If no undershoot has occurred in the engine speed and the determination in step ST12 is No, this routine is terminated assuming that the “bottom” is not present.

  On the other hand, if an undershoot occurs in the engine speed and a Yes determination is made in step ST12, the process proceeds to step ST13, where it is determined whether the feed pump 102 is currently in the pump low operation state. When the pump is not in the Low operation state, that is, when the pump is in the High operation state, the average pressure (feed average pressure) in the low-pressure fuel pipe 104 is maintained relatively high, and the above “bottom” occurs. This routine is terminated as it is not.

  On the other hand, when the feed pump 102 is in the pump low operation state and the determination is YES in step ST13, the process proceeds to step ST14 to forcibly switch the feed pump 102 to the pump high operation state. That is, the third relay contact 83 is switched from OFF to ON. As a result, the average value of the internal pressure of the low-pressure fuel pipe 104 can be increased, and the position of the plate 74b of the diaphragm 74 close to the tip edge of the inner pipe 77 is changed in amplitude as in the case of the first embodiment. The situation of reciprocating around the center can be avoided, and the occurrence of the “bottom” can be prevented.

  Thereafter, in step ST15, a timer provided in advance in the engine ECU is started. This timer is timed up in 5 seconds, for example. The time-up time of this timer is not limited to this, and is set as appropriate.

  The forced pump high operation state of the feed pump 102 is maintained until the timer expires in step ST16. That is, it waits for the undershoot of the engine speed to be eliminated. If the timer expires and the determination in step ST16 is Yes, the process moves to step ST17, and the normal control operation of the feed pump 102 described above is restored. That is, the feed pump 102 is switched between the pump low operation state and the pump high operation state in accordance with the fuel requirement amount of the high-pressure fuel pump 1.

  As described above, in this embodiment, when undershoot of the engine speed occurs when the pump is in the Low operation state, the feed is performed so that the average value of the internal pressure of the low-pressure fuel pipe 104 can be increased. The pump 102 is forcibly switched to the pump high operating state. For this reason, the coil spring 75 of the damper portion 71 is continuously compressed to some extent by the fuel pressure. Accordingly, it is possible to avoid a situation in which the plate 74b of the diaphragm 74 reciprocates around a position close to the tip edge of the inner tube 77, and the occurrence of the “bottom” can be prevented.

  In the present embodiment, the timer waits for the timer to expire as a timing for forcibly returning the feed pump 102 to the normal control operation after the pump pump 102 is forced to be in the pump high operation state. However, the present invention is not limited to this, and the engine speed may be continuously detected and returned to the normal control operation at the timing when the undershoot is eliminated.

-Other embodiments-
Each embodiment described above demonstrated the case where this invention was applied to the in-cylinder direct injection type | mold 4-cylinder gasoline engine mounted in the motor vehicle. The present invention is not limited to this, and can be applied to other arbitrary 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.

  In the high-pressure fuel pump 1 in each of the above embodiments, the plunger 23 is driven by the rotation of the drive cam 111 attached to the exhaust camshaft 110, but by the rotation of the drive cam attached to the intake camshaft. The plunger 23 may be driven.

  Furthermore, the present invention is not limited to the one provided with the drive cam 111 having the two cam noses 112 and 112 but can be applied to the one provided with the drive cam having other numbers of cam noses.

  In addition, the high-pressure fuel pump 1 in each of the above embodiments is a plunger pump, but the present invention can be applied to other positive displacement pumps (for example, a piston pump and a vane pump).

  In addition, in each of the above-described embodiments, the case where the present invention is applied to the pulsation damper 7 having a double-pipe structure has been described, but the configuration of the pulsation damper is not limited to this, and various forms The present invention is applicable to other pulsation dampers.

It is a figure showing typically the structure of the fuel supply system concerning an embodiment. It is a figure for demonstrating opening and closing operation | movement of an electromagnetic spill valve. It is sectional drawing which shows the internal structure of a pulsation damper. It is sectional drawing which shows the state by which the pulsation damper and the union pipe were assembled | attached to the high pressure fuel pump. It is a flowchart figure which shows the procedure of the feed pump drive control for bottom generation | occurrence | production prevention in 1st Embodiment. It is a figure which shows the change of the pulsation amplitude in a low pressure fuel piping accompanying the change of an engine speed. FIG. 7A shows a change in the lift position according to the present invention, and FIG. 7B shows a change in the lift position according to the conventional example. FIG. 8A shows the change in fuel pressure immediately downstream of the pulsation damper, FIG. 8A shows the change in fuel pressure according to the present invention, and FIG. 8B shows the change in fuel pressure according to the conventional example. . It is a figure which shows schematic structure of the electric circuit for controlling the drive of the feed pump in 2nd Embodiment. It is a figure which shows the map for performing switching control of the pump High operation | movement of a feed pump, and a pump Low operation | movement. It is a figure which shows the relationship between the voltage value applied between the terminals of a feed pump, and the fuel pressure discharged from a feed pump. It is a flowchart figure which shows the procedure of the feed pump drive control for bottom generation | occurrence | production prevention in 2nd Embodiment.

Explanation of symbols

1 High-pressure fuel pump 7 Pulsation damper 74 Diaphragm 102 Feed pump 104 Low-pressure fuel pipe (fuel supply pipe)

Claims (5)

In the fuel supply apparatus for an internal combustion engine, in which the feed pump and the high-pressure fuel pump are connected by a fuel supply pipe, and the pulsation damper is provided to suppress fuel pressure pulsation inside the fuel supply pipe.
The lift position of the diaphragm provided in the pulsation damper is set in advance when the frequency of the fuel pressure pulsation that changes with the change in the operating frequency of the high-pressure fuel pump substantially matches the resonance frequency of the fuel supply pipe. An internal combustion pressure characteristic value setting means for performing feed pump control for increasing or maintaining the average value of the fuel pressure that fluctuates inside the fuel supply pipe so as to keep it within the allowable range. Engine fuel supply. In the internal combustion engine fuel supply device according to claim 1,
The high-pressure fuel pump receives the rotational driving force of the internal combustion engine, and the operating frequency of the high-pressure fuel pump varies as the rotational speed of the internal combustion engine varies.
In the fuel pressure average value setting means, when the internal combustion engine shifts from the drive state to the stop state, the internal combustion engine rotational speed is less than “the rotational speed at which the frequency of the fuel pressure pulsation substantially matches the resonance frequency of the fuel supply pipe”. A fuel supply device for an internal combustion engine, characterized in that the feed pump is continuously driven. In the internal combustion engine fuel supply device according to claim 1,
The high-pressure fuel pump receives the rotational driving force of the internal combustion engine, and the operating frequency of the high-pressure fuel pump varies as the rotational speed of the internal combustion engine varies.
When the internal combustion engine is continuously driven, the fuel pressure average value setting means feeds when the internal combustion engine speed decreases to "the rotational speed at which the fuel pressure pulsation frequency substantially matches the resonance frequency of the fuel supply pipe". A fuel supply device for an internal combustion engine, wherein the fuel supply amount is controlled so as to increase a fuel discharge amount per unit time of the pump. In the fuel supply device for an internal combustion engine according to claim 3,
The feed pump is an electric pump,
The fuel supply device for an internal combustion engine, wherein the fuel pressure average value setting means increases the amount of fuel discharged per unit time of the feed pump by increasing the voltage across the terminals of the feed pump. In the fuel supply device for an internal combustion engine according to claim 4,
The feed pump includes a first fuel supply operation for increasing the fuel supply amount to the high pressure fuel pump and a second fuel supply operation for decreasing the fuel supply amount according to the fuel discharge amount per unit time of the high pressure fuel pump. It can be switched in two stages,
When the feed pump is driven by the second fuel supply operation, the fuel pressure average value setting means indicates that the internal combustion engine rotational speed is “the rotational speed at which the frequency of the fuel pressure pulsation substantially matches the resonance frequency of the fuel supply piping. The fuel supply device for the internal combustion engine is configured to forcibly switch the feed pump to the first fuel supply operation when the pressure decreases to "."

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