JP2007120356A - Fuel pipe structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce pulsation to a low pressure pipe system from high pressure fuel pumps without increasing cost. <P>SOLUTION: This fuel pipe structure includes the high pressure fuel pumps 200 and 300 operated by opening-closing control of a solenoid spill valve of shifting a phase and adjusting a delivery quantity of fuel to high pressure delivery communicating pipes 500 and 510 via the opening-closing control of the solenoid spill valve, a pulsation damper 220 arranged on the suction side of the high pressure fuel pump 200, a pulsation damper 320 arranged on the suction side of the high pressure fuel pump 300 and a low pressure communicating pipe 1000 for connecting a position between the high pressure fuel pump 200 and the pulsation damper 220 and a position between the high pressure fuel pump 300 and the pulsation damper 320. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention injects fuel into an intake passage or an intake port in addition to an internal combustion engine having a fuel injection means (in-cylinder injector) for injecting fuel at a high pressure into the cylinder. In particular, the present invention relates to a fuel piping structure for an internal combustion engine having a high-pressure fuel system including a plurality of high-pressure fuel pumps.

  A first fuel injection valve (in-cylinder injector) for injecting fuel into a combustion chamber of a gasoline engine, and a second fuel injection valve (injector for injector injection) for injecting fuel into an intake passage And an engine that injects fuel between the in-cylinder injector and the intake manifold injector in accordance with the engine speed and the load on the internal combustion engine. Further, a direct engine including only a fuel injection valve (in-cylinder injector) for injecting fuel into a combustion chamber of a gasoline engine is also known. In a high-pressure fuel system including an in-cylinder injector, fuel whose fuel pressure has been increased by a high-pressure fuel pump is supplied to the in-cylinder injector via a delivery pipe, and the in-cylinder injector is connected to each cylinder of the internal combustion engine. High pressure fuel is injected into the combustion chamber.

  A diesel engine having a common rail fuel injection system is also known. In this common rail fuel injection system, fuel whose fuel pressure has been increased by a high pressure fuel pump is stored in a common rail, and high pressure fuel is injected from the common rail into the combustion chamber of each cylinder of a diesel engine by opening and closing an electromagnetic valve.

  In order to bring the fuel in such an internal combustion engine into a high pressure state, a high pressure fuel pump that drives a cylinder by a cam provided on a drive shaft connected to a crankshaft of the internal combustion engine is used.

  Japanese Patent Laying-Open No. 2002-213326 (Patent Document 1) discloses a fuel supply device for an internal combustion engine that has a plurality of such high-pressure fuel pumps and can reduce the operation noise of the high-pressure fuel pump. The fuel supply device for an internal combustion engine is operated by electromagnetic valve opening / closing control, and the fuel supply for the internal combustion engine includes a plurality of high-pressure fuel pumps that adjust the amount of fuel discharged to the high-pressure fuel pipe through the electromagnetic valve opening / closing control. The apparatus includes a control unit that controls the electromagnetic valve so as to reduce the number of operations of the plurality of high-pressure fuel pumps in a predetermined period when the required fuel amount is small according to the required fuel amount of the internal combustion engine.

According to the fuel supply apparatus for an internal combustion engine, when the required fuel amount of the internal combustion engine decreases, the number of operations of the plurality of high-pressure fuel pumps in a predetermined period, that is, the operation frequency is decreased. For high-pressure fuel pumps that adjust the amount of fuel discharged to the high-pressure fuel pipe through the opening / closing control of the solenoid valve, increase the amount of fuel discharged for each operation even if the number of operations is reduced if the required fuel amount is small. By doing so, it is possible to ensure the fuel discharge amount required for a predetermined period. At this time, the frequency of the opening / closing operation of the solenoid valve is also reduced in accordance with the decrease in the operating frequency of the entire high-pressure fuel pump. Therefore, it is possible to reduce the operating noise of the high-pressure fuel pump that accompanies the opening / closing operation of the electromagnetic valve.
JP 2002-213326 A

  In Patent Document 1 described above, one pulsation damper is provided as a component for reducing low pressure pulsation on the low pressure side (suction side) of two high pressure fuel pumps. Thereby, the pulsation on the low pressure side caused by the fuel discharged from the high pressure fuel pump back to the low pressure side is absorbed.

  However, as in Patent Document 1, if a pulsation damper is provided for each high-pressure fuel pump independently, the pulsation generated by one high-pressure fuel pump must be absorbed by one pulsation damper. The pulsation damper becomes a high-performance one, and there is a problem in the reliability of the pulsation damper. There is also a timing when the pump plunger suddenly descends due to the profile of the cam that drives the high-pressure fuel pump. Especially when the amount of fuel sucked into the high-pressure fuel pump suddenly increases due to a sudden drop of such a pump plunger in the high rotation range, the rapid increment of one high-pressure fuel pump must be handled by one pulsation damper. Therefore, pulsation dampers and feed pumps have high performance, leading to increased costs.

  The present invention has been made to solve the above-described problems, and an object thereof is an internal combustion engine that can effectively reduce pulsation from a high-pressure fuel pump to a low-pressure piping system without increasing costs. It is to provide an engine fuel piping structure.

  A fuel piping structure for an internal combustion engine according to a first aspect of the invention is a fuel piping structure applied to an internal combustion engine having a plurality of high-pressure fuel pumps in which the amount of fuel discharged to the high-pressure fuel piping is adjusted by opening / closing control of a solenoid valve. . This fuel piping structure includes a pulsation reduction mechanism provided on the suction side of each high-pressure fuel pump, one high-pressure fuel pump among a plurality, and a pulsation reduction mechanism of another high-pressure fuel pump other than one. And piping to connect.

  According to the first invention, for example, in the case of an internal combustion engine provided with two high-pressure fuel pumps, a first pulsation damper, which is an example of a pulsation reduction mechanism, is provided on the suction side of the first high-pressure fuel pump. A second pulsation damper is provided on the suction side of another second high-pressure fuel pump. Furthermore, the first high-pressure fuel pump and the second pulsation damper are connected by piping. For this reason, if the solenoid valve is still open when the first high-pressure fuel pump enters the pressurization stroke, discharge back to the low-pressure side occurs. It is reduced by the pulsation damper and the second pulsation damper connected via a pipe. Compared to the state where the pulsation of one high-pressure fuel pump is reduced by one pulsation damper, the pulsation of one high-pressure fuel pump is reduced by two pulsation dampers. Reliability can be improved and performance of the pulsation damper can be reduced. In addition, even when the intake amount of one high-pressure fuel pump suddenly increases, the two pulsation dampers can cope with it, so there is no need to improve the performance of the pulsation dampers and feed pumps. As a result, it is possible to provide a fuel piping structure for an internal combustion engine that can effectively reduce pulsation from the high-pressure fuel pump to the low-pressure piping system without increasing costs.

  In the fuel pipe structure according to the second invention, in addition to the configuration of the first invention, the pipe is provided between one high-pressure fuel pump in a plurality and a pulsation reducing mechanism of one high-pressure fuel pump. It includes piping that connects between other high-pressure fuel pumps other than one and a pulsation reducing mechanism of another high-pressure fuel pump.

  According to the second invention, the position between the first high-pressure fuel pump and the first pulsation damper and the position between the second high-pressure fuel pump and the second pulsation damper are determined by piping. It is connected. For this reason, if the solenoid valve is still open when the first high-pressure fuel pump enters the pressurization stroke, discharge back to the low-pressure side of the first high-pressure fuel pump occurs. Is reduced by the first pulsation damper and the second pulsation damper connected via a pipe. For example, if the solenoid valve is still open when the second high-pressure fuel pump enters the pressurization stroke at another timing, the second high-pressure fuel pump discharges back to the low-pressure side. However, the pulsation due to the discharge is reduced by the second pulsation damper and the first pulsation damper connected via the pipe. Compared to the state where the pulsation of one high-pressure fuel pump is reduced by one pulsation damper, the pulsation of one high-pressure fuel pump is reduced by two pulsation dampers. Reliability can be improved and performance of the pulsation damper can be reduced. In addition, since the first pulsation damper and the second pulsation damper can cope with the timing when the intake amount of the first high-pressure fuel pump suddenly increases, it is necessary to improve the performance of the pulsation damper and the feed pump. Nor. As a result, it is possible to provide a fuel piping structure for an internal combustion engine that can effectively reduce pulsation from the high-pressure fuel pump to the low-pressure piping system without increasing costs.

  In the fuel piping structure according to the third invention, in addition to the configuration of the first or second invention, the pulsation reducing mechanism is a pulsation damper.

  According to the third invention, the reliability of the pulsation damper can be improved, or the performance of the pulsation damper can be reduced.

  In the fuel pipe structure according to the fourth invention, in addition to the configuration of any one of the first to third inventions, the operation timings of the plurality of high-pressure fuel pumps are shifted from each other.

  According to the fourth invention, since the operation timings are different from each other, the timing at which the fuel is discharged back to the low pressure side is also different. For this reason, since two or more high-pressure fuel pumps do not discharge fuel to the low-pressure side at the same time, the effect of reducing pulsation can be obtained as if two high-pressure fuel pumps are provided with two pulsation dampers. appear.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 shows a fuel supply system 10 for an engine having a fuel piping structure according to an embodiment of the present invention. This engine is a V-type 8-cylinder gasoline engine and has an in-cylinder injector 110 that injects fuel into the cylinder of each cylinder. The present invention is not limited to such an engine, and may be another type of gasoline engine having a high-pressure fuel system or a common rail diesel engine. Furthermore, in addition to the in-cylinder injector 110, an engine having an intake manifold injector that injects fuel into the intake manifold of each cylinder may be used.

  As shown in FIG. 1, this fuel supply system 10 is provided in a fuel tank 100 and supplies fuel to a high-pressure fuel pump via a filter 104 with a discharge pressure of low pressure (pressure of the pressure regulator 106 is about 400 kPa). The feed pump 102, the first high-pressure fuel pump 200 driven by the first cam 210, and the second high-pressure fuel pump driven by the second cam 310 having a discharge phase different from that of the first cam 210. 300, high-pressure delivery pipe 112A and high-pressure delivery pipe 112B provided for each of the left and right banks for supplying high-pressure fuel to in-cylinder injector 110, and left and right provided for high-pressure delivery pipe 112A and high-pressure delivery pipe 112B And four in-cylinder injectors 110 in each bank.

  The discharge port of the feed pump 102 of the fuel tank 100 is connected to a low-pressure supply pipe 400, and the low-pressure supply pipe 400 includes a pump supply pipe 410 A connected to the first high-pressure fuel pump 200 and a second high-pressure fuel pump 300. Branches to a pump supply pipe 420A connected to.

  The pump supply pipe 410A is connected to the inlet of the first high-pressure fuel pump 200, and the pump supply pipe 420A is connected to the inlet of the second high-pressure fuel pump 300. A first pulsation damper 220 is provided in front of the entrance of the first high-pressure fuel pump 200, and a second pulsation damper 320 is provided in front of the entrance of the second high-pressure fuel pump 300. We are trying to reduce it.

  The first pulsation damper 220 and the first high-pressure fuel pump 200 are connected by a pump supply pipe 410B, and the second pulsation damper 320 and the second high-pressure fuel pump 300 are connected by a pump supply pipe 420B. Yes.

  The discharge port of the first high-pressure fuel pump 200 is connected to the first high-pressure delivery communication pipe 500, and the first high-pressure delivery communication pipe 500 is connected to the high-pressure delivery pipe 112A of one bank of the V-shaped bank. . The discharge port of the second high-pressure fuel pump 300 is connected to the second high-pressure delivery communication pipe 510, and the second high-pressure delivery communication pipe 510 is connected to the high-pressure delivery pipe 112B of the other bank of the V-shaped bank. The The high-pressure delivery pipe 112A of one bank of the V-type bank and the high-pressure delivery pipe 112B of the other bank are connected by a high-pressure communication pipe 520.

  The relief valve 114 provided in the high-pressure delivery pipe 112A is connected to the high-pressure delivery return pipe 600. The high-pressure delivery return pipe 600 is connected to the high-pressure fuel pump return pipe 610 </ b> A to become a return pipe 620, the return pipe 620 is connected to the high-pressure fuel pump return pipe 610 </ b> B, and the return pipe 630 is connected to the fuel tank 100. The

  FIG. 2 shows an enlarged view of the vicinity of the first high-pressure fuel pump 200 of FIG. The same applies to the second high-pressure fuel pump 300, but the cam phase is different and the discharge timing phase is shifted to suppress the occurrence of pulsation in the high-pressure fuel system. The characteristics of the first high-pressure fuel pump 200 and the second high-pressure fuel pump 300 may be the same or different. In the following description, it is assumed that the discharge capacity of the first high-pressure fuel pump 200 and the discharge capacity of the second high-pressure fuel pump 300 are the same in terms of specifications. In the following description, the first high-pressure fuel pump 200 will be described, and the reference numerals of the second high-pressure fuel pump 300 will be shown in parentheses in FIG.

  The high-pressure fuel pump 200 includes a pump plunger 206 that is driven by a cam 210 and slides up and down, an electromagnetic spill valve 202, and a check valve 204 as main components.

  When the pump plunger 206 is moved downward by the cam 210 and the electromagnetic spill valve 202 is open, fuel is introduced (sucked), and the pump plunger 206 is moved upward by the cam 210. When the electromagnetic spill valve 202 is closed, the timing for closing the electromagnetic spill valve 202 is changed to control the amount of fuel discharged from the high-pressure fuel pump 200. The earlier the timing for closing the electromagnetic spill valve 202 during the pressurization stroke in which the pump plunger 206 is moving upward, the more fuel is discharged, and the slower the fuel is discharged, the slower. The driving duty of the electromagnetic spill valve 202 when discharging the most is 100%, and the driving duty of the electromagnetic spill valve 202 when discharging the least is 0%. When the drive duty of the electromagnetic spill valve 202 is 0%, the electromagnetic spill valve 202 remains open without closing, and as long as the first cam 210 is rotating (as long as the engine is rotating). ) The pump plunger 206 slides in the vertical direction, but the fuel is not pressurized because the electromagnetic spill valve 202 does not close.

  The pressurized fuel is pushed open to the check valve 204 (set pressure of about 60 kPa) and is pumped to the high pressure delivery pipe 112A via the first high pressure delivery communication pipe 500. At this time, the fuel pressure is feedback controlled by a fuel pressure sensor provided in the high pressure delivery pipe 112A. Further, as described above, the high pressure delivery pipe 112A of one bank of the V type and the high pressure delivery pipe 112B of the other bank are communicated by the high pressure communication pipe 520.

  The control amount used for feedback control of the high-pressure fuel pump 200 sets the integral term updated in accordance with the deviation between the actual fuel pressure and the target value and the deviation between the actual fuel pressure and the target value to “0”. It is calculated from a proportional term that increases or decreases as much as possible. When the control amount increases, the fuel discharge amount of the high-pressure fuel pump 200 increases and the fuel pressure increases. Conversely, when the control amount decreases, the fuel discharge amount of the high-pressure fuel pump 200 decreases and the fuel pressure decreases.

  An engine ECU (Electronic Control Unit) drives and controls the in-cylinder injector 110 based on the final fuel injection amount, and controls the amount of fuel injected from the in-cylinder injector 110. The amount of fuel injected from the in-cylinder injector 110 (fuel injection amount) is determined by the fuel pressure (fuel pressure) in the high-pressure delivery pipe 112A and the high-pressure delivery pipe 112B and the fuel injection time. In order to achieve this, it is necessary to maintain the fuel pressure at an appropriate value. Therefore, the engine ECU feedback-controls the fuel discharge amount of the high-pressure fuel pump 200 so that the fuel pressure obtained based on the detection signal from the fuel pressure sensor approaches the target fuel pressure P (0) set according to the engine operating state. Maintain fuel pressure P at an appropriate value. The fuel discharge amount of the high-pressure fuel pump 200 is feedback controlled by adjusting the closing period (valve closing start time) of the electromagnetic spill valve based on a duty ratio DT described later.

  Here, the duty ratio DT that is a control amount for controlling the fuel discharge amount of the high-pressure fuel pump 200 (the valve closing start timing of the electromagnetic spill valve 202) will be described. The duty ratio DT is a value that varies between 0% and 100%, and is a value related to the cam angle of the cam 210 corresponding to the valve closing period of the electromagnetic spill valve 202. That is, regarding this cam angle, the cam angle corresponding to the maximum valve closing period of the electromagnetic spill valve 202 (maximum cam angle) is “θ (0)”, and the cam angle corresponding to the target value of the valve closing period (target cam) If the angle) is “θ”, the duty ratio DT indicates the ratio of the target cam angle θ to the maximum cam angle θ (0). Accordingly, the duty ratio DT is set to a value closer to 100% as the valve closing period (the valve closing start timing) of the target electromagnetic spill valve 202 approaches the maximum valve closing period, and the target valve closing period is “0”. As the value approaches, the value approaches 0%.

  As the duty ratio DT approaches 100%, the closing timing of the electromagnetic spill valve 202 adjusted based on the duty ratio DT is advanced, and the closing period of the electromagnetic spill valve 202 becomes longer. As a result, the fuel discharge amount of the high-pressure fuel pump 200 increases and the fuel pressure P increases. Further, as the duty ratio DT approaches 0%, the closing timing of the electromagnetic spill valve 202 adjusted based on the duty ratio DT is delayed, and the closing period of the electromagnetic spill valve 202 is shortened. As a result, the fuel discharge amount of the high-pressure fuel pump 200 decreases and the fuel pressure P decreases.

  The engine ECU controls the energization start timing of the electromagnetic spill valve 202 to the electromagnetic solenoid, that is, the closing start timing of the electromagnetic spill valve 202 based on the duty ratio DT calculated by feedback control. By controlling the valve start timing of the electromagnetic spill valve 202 in this way, the valve closing period of the electromagnetic spill valve 202 is changed, the fuel discharge amount of the high-pressure fuel pump 200 is adjusted, and the fuel pressure P becomes the target fuel pressure P (0). Will change towards.

  The pulsation damper shown in FIG. 1 will be described with reference to FIG. In the following description, the pulsation damper 220 on the first high-pressure fuel pump 200 side will be described, and the pulsation damper 320 on the second high-pressure fuel pump 300 side has the same structure as the pulsation damper 220. The description of the session damper 320 will not be repeated.

  The pulsation damper 220 is a diaphragm-type pulsation damper, and the pulsation damper 220 includes a diaphragm 226C that is divided into a fuel chamber 226A and an air chamber 226B that communicates with the atmosphere. A suction port 222 and a discharge port 224 are provided outside the fuel chamber 226A and supported by a spring 226D mounted in 226B.

  The pulsation damper 220 is provided in the middle of the pump supply pipe 420 and upstream of the high-pressure fuel pump 200 and downstream of the junction (also a branch point) between the pump supply pipe 420 and the low-pressure communication pipe 1000. In the pulsation damper 220, the downstream side of the pump supply pipe 420 is connected to the attachment port 222, and the upstream side of the pump supply pipe 420 is connected to the attachment port 224.

  In such a configuration, when the pump plunger 206 is raised while the electromagnetic spill valve 202 is open in the high-pressure fuel pump 200, pulsation generated by the fuel being discharged from the high-pressure fuel pump 200 in the pump supply pipe 420 is generated. Since it is transmitted to the fuel chamber 226A in the pulsation damper 220, this pulsation can be reliably reduced by vibration against the spring 226D of the diaphragm 226C in the pulsation damper 220.

  The most characteristic part of the fuel piping structure according to the present invention is between the inlet of the first high-pressure fuel pump 200 and the first pulsation damper 220 and between the inlet of the second high-pressure fuel pump 300 and the second pulse. That is, a low-pressure communication pipe 1000 is provided to connect the session damper 320.

  That is, a position between the pulsation damper 220 (a component that reduces low pressure pulsation) and the pump plunger 206 of the high pressure fuel pump 200, and a position between the pulsation damper 320 and the pump plunger 306 of the high pressure fuel pump 300. Are communicated by a low-pressure communication pipe 1000.

If you do this,
(1) Increased volume on the low-pressure chamber side of the high-pressure fuel pump When the volume on the low-pressure side of the two high-pressure fuel pumps is V, the volume on the low-pressure side is doubled, including the piping volume of the low-pressure communication pipe 1000 That's it.

At this time, ΔP is the low pressure pulsation level, ΔV is volume change (the volume that increases when the pump plunger is lowered when the high pressure fuel pump is in the intake stroke, and the pump plunger is raised when the high pressure fuel pump is in the discharge stroke. (Volume to be reduced), V is the volume on the low pressure side, K is the volume expansion rate of the fuel (for example, pressure change per unit compression pressure), and V becomes more than twice due to the relationship ΔP = ΔV / V × K ΔP, which is the level of low-pressure pulsation, becomes ½ or less.
(2) The effect of reducing the low-pressure pulsation of two pulsation dampers can be received for each high-pressure fuel pump.

  Low pressure pulsation occurs when each high pressure fuel pump sucks in and discharges fuel, but since two pulsation dampers are mounted on each pump, the low pressure pulsation can be reduced (estimation 1). / About 2 or less). In particular, since the operating phases of the first high-pressure fuel pump 200 and the second high-pressure fuel pump 300 are shifted (see FIG. 4), both high-pressure fuel pumps do not discharge at the same timing. The high-pressure fuel pump discharges the fuel back to the low-pressure side from the start of the pressurization stroke until the electromagnetic spill valve is closed and pumped. For this reason, the fuel is discharged back to the low pressure side one by one, and in addition to the pulsation damper originally provided for the one high pressure fuel pump, the other pulsation damper is connected via the low pressure communication pipe 1000. In addition, the low pressure pulsation propagates, and the low pressure pulsation is absorbed by the two pulsation dampers.

  This state will be described with reference to FIG. FIG. 5 (A) shows the operating state of one of the high-pressure fuel pumps corresponding to FIG. 4 (A) or FIG. 4 (B). 5B shows the state of pulsation on the low pressure side from the pulsation equilibrium point in the conventional fuel piping structure (without the low pressure communication pipe 1000), and FIG. 5C shows the fuel piping structure according to the present embodiment ( The state of pulsation on the low-pressure side from the pulsation equilibrium point in the low-pressure communication pipe 1000 is shown.

The high pressure fuel pump enters the pressurization stroke at the timing when the pump plunger reaches the lowest end and starts to rise. At this time, if the electromagnetic spill valve is open (for example, if the drive duty is not 100%), the high pressure fuel The pulsation on the low-pressure pipe side occurs due to discharge from the pump to the low-pressure pipe side. In the conventional fuel piping structure, as shown in FIG. 5B, the pulsation is absorbed by one pulsation damper, and the pulsation with ΔP (1) as the maximum amplitude is generated. On the other hand, in the fuel piping structure according to the present embodiment, as shown in FIG. 5C, the pulsation is absorbed by the two pulsation dampers so that the discharge phases of the high-pressure fuel pump do not overlap. , .DELTA.P (0) (about 1/2 of .DELTA.P (1)) only generates pulsations. This is considered to be due to the operational effect due to the piping capacity of the two pulsation dampers and the low-pressure communication pipe for one high-pressure fuel pump.
(3) The suction assist effect equivalent to two pulsation dampers can be received for each high-pressure fuel pump.

  The pump plunger of the high-pressure fuel pump is operated by a cam, and the speed at which the pump plunger is lowered by the cam has a part that varies greatly and a part that does not vary greatly depending on the cam profile. In the high rotation range where the amount of fuel pumped by the high-pressure fuel pump approaches the discharge amount of the feed pump 102, the pump plunger greatly decreases and the instantaneous flow rate increases when there is a large change (the pump plunger is greatly lowered). In this case, the feed pump flow rate can be increased by doubling the suction assist effect (fuel flow from the pulsation damper to the high-pressure fuel pump) by the diaphragm of the pulsation damper because only two pulsation dampers can be used. Therefore, the rated capacity (discharge amount) of the feed pump 102 does not have to be set to the instantaneous maximum discharge amount (the flow rate required for the feed pump 102 when the pump plunger at high rotation is greatly reduced). Consumption can be reduced. In particular, as in (2), since the operating phases of the first high-pressure fuel pump 200 and the second high-pressure fuel pump 300 are shifted, the pump plungers of both high-pressure fuel pumps are greatly lowered at the same timing. Therefore, one high-pressure fuel pump can receive the suction assist effect equivalent to two pulsation dampers.

As described above, according to the fuel pipe structure according to the present embodiment,
(A) By increasing the volume on the low-pressure chamber side of the high-pressure fuel pump, the pulsation on the low-pressure side due to the discharge back of the high-pressure fuel pump can be reduced,
(B) The reliability of the pulsation damper (initial average stress and amplitude) due to the effect of reducing the low-pressure pulsation of two pulsation dampers for each high-pressure fuel pump and the reduction per pulsation damper being reduced. Avoiding damage to the diaphragm due to the decrease in
(C) It is possible to reduce the rated capacity of the feed pump by receiving the suction assist effect of two pulsation dampers for each high-pressure fuel pump.

  The pulsation reducing component is not limited to the pulsation damper. Further, the number of high-pressure fuel pumps may be two or more, and the number is not particularly limited. Furthermore, the operating phase of the high-pressure fuel pump is not limited to a case where it is shifted by 90 degrees. It is sufficient that the discharge timing is shifted between the plurality of high-pressure fuel pumps and does not match.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall schematic diagram of a fuel supply system for a gasoline engine controlled by a control device according to an embodiment of the present invention. It is the elements on larger scale of FIG. It is sectional drawing of the pulsation damper of FIG. It is a figure which shows the operation state of a high pressure fuel pump. It is a figure which shows the operating state of a high pressure fuel pump, and the pulsation state in a low pressure piping system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel supply system, 100 Fuel tank, 102 Feed pump, 104 Filter, 106 Pressure regulator, 110 In-cylinder injector, 112A, 112B High pressure delivery pipe, 114 Relief valve, 200 1st high pressure fuel pump, 202 Electromagnetic spill valve 204 Check valve, 206 Pump plunger, 210 First cam, 220 First pulsation damper, 300 Second high pressure fuel pump, 310 Second cam, 320 Second pulsation damper, 400 Low pressure supply pipe 410A, 410B, 420A, 420B Pump supply pipe, 500 First high pressure delivery communication pipe, 510 Second high pressure delivery communication pipe, 520 High pressure communication pipe, 600 High pressure delivery return pipe 610A, 610B High pressure fuel pump return pipe, 620, 630 Return pipe, 1000 Low pressure communication pipe.

Claims (4)

A fuel pipe structure for an internal combustion engine comprising a plurality of high-pressure fuel pumps, wherein the amount of fuel discharged to the high-pressure fuel pipe is adjusted by opening / closing control of a solenoid valve,
A pulsation reducing mechanism provided on the suction side of each high-pressure fuel pump;
A fuel piping structure for an internal combustion engine, comprising: one high-pressure fuel pump among a plurality and a piping connecting a pulsation reducing mechanism of another high-pressure fuel pump other than the one.   The piping includes a pulsation between one of the plurality of high pressure fuel pumps and the pulsation reducing mechanism of the one high pressure fuel pump, and between the other high pressure fuel pumps and the other high pressure fuel pumps. The fuel piping structure for an internal combustion engine according to claim 1, comprising piping for connecting to the reduction mechanism.   The fuel piping structure for an internal combustion engine according to claim 1, wherein the pulsation reducing mechanism is a pulsation damper.   The fuel piping structure for an internal combustion engine according to any one of claims 1 to 3, wherein operation timings of the plurality of high-pressure fuel pumps are shifted from each other.

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