JP4320983B2 - Fuel supply device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a fuel supply device that pressurizes low pressure fuel pumped from a fuel tank by a feed pump by a high pressure pump and supplies the high pressure fuel into a delivery pipe.
[0002]
[Prior art]
For example, in an internal combustion engine in which the fuel supplied to the fuel injection valve needs to be at a high pressure, such as an in-cylinder injection internal combustion engine, the low pressure fuel pumped up from the fuel tank by the feed pump is pressurized by the high pressure pump. High pressure fuel is supplied to the vehicle. The supplied high-pressure fuel is stored in a delivery pipe, distributed and supplied to each fuel injection valve, and fuel of a required pressure is injected and supplied to the internal combustion engine.
[0003]
In such a fuel supply device for an internal combustion engine, pulsation occurs in the fuel pressure in the delivery pipe as a result of intermittent fuel supply from the high pressure fuel pump and intermittent fuel injection from the fuel injection valve. When such fuel pressure pulsation occurs, the pressure of the fuel supplied to the fuel injection valve becomes unstable, and the fuel injection amount per injection that is adjusted according to the injection time fluctuates, leading to deterioration in emissions and drivability.
[0004]
Therefore, conventionally, as seen in, for example, Japanese Patent Laid-Open No. 9-310661, an accumulator is provided in a delivery pipe to suppress such fuel pressure pulsation. In such an accumulator, a metal bellows sealed with gas is used, and the fuel volume in the delivery pipe is flexibly changed by expansion and contraction of the metal bellows to attenuate the fuel pressure pulsation.
[0005]
[Problems to be solved by the invention]
By the way, in the accumulator having the above configuration, the metal bellows is expensive, such as high processing accuracy is required in order to prevent the inflow of high-pressure fuel and ensure the gas tightness inside the high-pressure fuel. This is one of the causes for increasing the cost of such a fuel supply device.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel supply device for an internal combustion engine that can enjoy the damping performance of fuel pressure pulsations in a delivery pipe at a low cost.
[0007]
[Means for Solving the Problems]
In the following, means for achieving the above object and its effects are described.
(Claim 1)
The invention according to claim 1 is a fuel supply apparatus for an internal combustion engine that supplies high-pressure fuel into a delivery pipe by pressurizing low-pressure fuel pumped from a fuel tank by a feed pump with a high-pressure pump, and moves into the delivery pipe. The delivery pipe is divided into two chambers, a fuel chamber to which the high-pressure fuel is supplied and a back pressure chamber to which the low-pressure fuel is supplied. A piston for changing the volume of the chamber is provided.
[0008]
In the above configuration, the high pressure fuel pressurized by the high pressure fuel pump is supplied by the piston movably disposed in the delivery pipe, and the low pressure fuel pumped from the fuel tank by the feed pump is supplied. And a back pressure chamber. When the fuel pressure in the fuel chamber varies due to fuel injection or fuel discharge from the high-pressure pump, the piston is displaced according to the variation and the volume of the fuel chamber changes. At this time, the fuel pressure pulsation is suppressed by the damping effect of the low-pressure fuel supplied to the back pressure chamber.
[0009]
By the way, in the above configuration, since the back pressure chamber is filled with fuel as well as the fuel chamber, it is not necessary to ensure the sealing performance of the fuel between the two chambers defined by the piston, and the fuel pressure pulsation is attenuated. The configuration can be manufactured at a low cost. Therefore, according to the above configuration, the attenuation performance of the fuel pressure pulsation in the delivery pipe can be enjoyed at low cost.
[0010]
According to a second aspect of the present invention, in the fuel supply device for an internal combustion engine according to the first aspect, the high-pressure fuel in the fuel chamber can be relieved according to the movement position of the piston.
[0011]
In the above configuration, the high-pressure fuel in the fuel chamber is relieved in accordance with the position of the piston that moves as the fuel pressure in the fuel chamber varies. Here, for example, if the internal high pressure fuel is relieved at the moving position of the piston when the fuel pressure in the fuel chamber becomes higher than necessary, the fuel pressure pulsation consisting of these pistons, etc. This damping mechanism can also have a function as a relief valve. Therefore, according to the said structure, the relief valve normally provided in a delivery pipe can be abolished, and the further cost reduction can be aimed at.
[0012]
According to a third aspect of the present invention, in the fuel supply device for an internal combustion engine according to the second aspect, the high pressure fuel in the fuel chamber can be relieved through a passage for supplying the low pressure fuel to the back pressure chamber. It is.
[0013]
In the above configuration, the high-pressure fuel in the fuel chamber is relieved through the passage for supplying the low-pressure fuel into the back pressure chamber according to the position of the piston that moves as the fuel pressure in the fuel chamber varies. Therefore, the passage for relief of the high-pressure fuel and the passage for supplying the low-pressure fuel to the back pressure chamber can be shared, and the configuration can be further simplified. Note that the high pressure fuel can be relieved from the fuel chamber to the low pressure fuel supply passage by the pressure difference between the fuel chamber and the low pressure fuel supply passage simply by communicating the fuel chamber and the low pressure fuel supply passage according to the moving position of the piston.
[0014]
According to a fourth aspect of the present invention, in the fuel supply device for an internal combustion engine according to the first aspect, the high pressure fuel supplied to the fuel chamber is communicated with the fuel chamber in accordance with the moving position of the piston. A relief passage for relief is further provided.
[0015]
According to the above configuration, the high pressure fuel in the fuel chamber is relieved in accordance with the movement of the piston due to the fluctuation of the fuel pressure in the fuel chamber. Here, for example, if the fuel chamber and the relief passage are configured to communicate with each other at a position where the piston moves when the high pressure fuel supplied into the fuel chamber becomes higher than necessary, the piston and the like are formed. The function of the relief valve can be provided in the damping mechanism of the fuel pressure pulsation. Therefore, according to the said structure, the relief valve normally provided in a delivery pipe can be abolished, and the further cost reduction can be aimed at.
[0016]
According to a fifth aspect of the present invention, there is provided the fuel supply device for an internal combustion engine according to the first aspect, wherein the fuel supply device communicates with either the fuel chamber or the back pressure chamber according to the movement position of the piston, and the low pressure A passage for supplying fuel is further provided.
[0017]
In the above-described configuration, the low pressure fuel supply passage communicates with either the fuel chamber or the back pressure chamber depending on the position of the piston that moves in accordance with the fluctuation of the fuel pressure in the fuel chamber. If the supply passage communicates with the back pressure chamber, low pressure fuel is supplied to the back pressure chamber, and if the supply passage communicates with the fuel chamber, the high pressure fuel in the fuel chamber is relieved through the supply passage due to the pressure difference of the fuel. Will come to be. Therefore, according to the above configuration, the function of the relief function of the fuel pressure fluctuation composed of a piston or the like can be provided as a relief valve, and the low pressure fuel is supplied to the passage and the back pressure chamber for relieving the high pressure fuel. Since it can be shared with the other passages, the configuration can be further simplified.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment embodying the present invention will be described in detail with reference to FIGS.
[0019]
As shown in FIG. 1, the fuel supply device for an internal combustion engine according to the present embodiment includes two fuel pumps, a feed pump 11 and a high-pressure fuel pump 13.
The feed pump 11 pumps up fuel stored in the fuel tank 10 and supplies low-pressure (feed pressure; for example, 150 to 200 kPa) fuel to the high-pressure fuel pump 13 through the low-pressure fuel passage 12. The low-pressure fuel passage 12 is provided with a pressure regulator 12a. When the low-pressure fuel in the passage 12 exceeds a predetermined pressure, the low-pressure fuel therein is relieved into the fuel tank 10. Thereby, the fuel pressure in the low-pressure fuel passage 12 is maintained at a necessary pressure.
[0020]
On the other hand, the high-pressure fuel pump 13 pressurizes the low-pressure fuel to a high pressure (for example, 8 to 13 MPa) and supplies it into the delivery pipe 20 through the high-pressure fuel passage 14. The high-pressure fuel supplied to the delivery pipe 20 is stored with fuel at a required pressure in the fuel chamber 22 therein, and is distributed and supplied to each fuel injection valve 15 of the internal combustion engine. The fuel held at a required pressure is injected and supplied to the internal combustion engine by opening each fuel injection valve 15 in response to a command signal from the computer unit for engine control.
[0021]
In the present embodiment, a piston 21 is movably disposed in the delivery pipe 20 as shown in FIG. The interior of the delivery pipe 20 is partitioned by the piston 21 into two chambers, a fuel chamber 22 and a back pressure chamber 23. The volumes of the fuel chamber 22 and the back pressure chamber 23 are changed depending on the movement position of the piston 21. That is, if the volume of the fuel chamber 22 is increased by the movement of the piston 21, the volume of the back pressure chamber 23 is reduced accordingly. Further, if the volume of the fuel chamber 22 is reduced by the movement, the volume of the back pressure chamber is increased accordingly. Such a piston 21 is biased by a spring 23 in a direction to reduce the volume of the fuel chamber 22.
[0022]
The fuel chamber 22 is connected to the high-pressure fuel passage 14 and is supplied with high-pressure fuel pressurized by the high-pressure fuel pump 13. The back pressure chamber 23 is supplied with low pressure fuel from the low pressure fuel passage 12 as will be described later. Therefore, the piston 21 acts to expand the volume of the fuel chamber 22 based on the pressure of the high pressure fuel in the fuel chamber 22, the pressure of the low pressure fuel in the back pressure chamber 23, and the biasing force of the spring 24. The movement position is changed according to the balance with the force acting in the direction of reducing the volume of the fuel chamber 22 based on the above.
[0023]
On the other hand, as shown in FIG. 2, a passage 25 is further connected to the delivery pipe 20, and is connected to the low-pressure fuel passage 12 through the passage 25. The passage 25 is connected to either the fuel chamber 22 or the back pressure chamber 23 according to the movement position of the piston 21.
[0024]
FIG. 3 shows the relationship between the length (spring length) L of the spring 24 that is expanded and contracted in accordance with the movement of the piston 21 and the fuel pressure P in the fuel chamber 22.
The spring length L depends on the contact length at which the spring 24 is fully contracted or the piston 21 abuts against the end of the delivery pipe 20 depending on the moving position of the piston 21, and further compression is impossible. It varies within a range up to 24 free lengths. When the spring 24 contracts (when the spring length L decreases), the force Fd acting on the piston 21 in the direction of reducing the volume of the fuel chamber 22 increases. Further, when the spring 24 is extended (when the spring length L is increased), the force Fd is reduced. Therefore, the piston 21 changes its moving position in accordance with the fluctuation of the fuel pressure P in the fuel chamber 22 so as to maintain the balance of the forces acting on itself. That is, when the fuel pressure P in the fuel chamber 22 increases, the spring length L decreases (in the direction in which the volume of the fuel chamber 22 increases). If the fuel pressure P decreases, the spring length L increases (the direction in which the volume of the fuel chamber 22 decreases).
[0025]
The passage 25 communicates with the back pressure chamber 23 when the spring length L is sufficiently long, that is, when the fuel pressure P in the fuel chamber 22 is low, and when the spring length L is shorter than the predetermined length α, that is, when the fuel pressure P is When the pressure is higher than a predetermined pressure (relief pressure), the fuel chamber 22 is connected to a position where it is communicated. Accordingly, when the fuel pressure P in the fuel chamber 22 is sufficiently low, for example, immediately after the engine is started before the discharge pressure of the high pressure fuel pump 13 is sufficiently increased, the low pressure fuel is introduced into the back pressure chamber 23 through the passage 25. Supplied.
[0026]
As described above, in the present embodiment, the volume of the back pressure chamber 23 filled with the low pressure fuel is enlarged or reduced according to the movement of the piston 21 according to the fuel pressure P in the fuel chamber 22. As a result, the fuel volume in the delivery pipe 20 (the volume of the fuel chamber 22) is flexibly changed, and the damping effect is produced by the low-pressure fuel in the back pressure chamber 23, thereby effectively attenuating the pulsation of the fuel pressure P. ing.
[0027]
On the other hand, when the fuel pressure P in the fuel chamber 22 exceeds a predetermined pressure, the piston 21 moves to a position where the fuel chamber 22 and the passage 25 communicate with each other as shown in FIG. The fuel chamber 22 filled with high-pressure fuel is connected to the low-pressure fuel passage 12 through the passage 25. At this time, the high-pressure fuel in the fuel chamber 22 sufficiently higher than the fuel pressure (feed pressure) in the low-pressure fuel passage 12 passes through the connected passage 25 to the low-pressure fuel passage 12 and further to the low-pressure fuel passage. 12 is relieved in the fuel tank 10 through the pressure regulator 12a. Therefore, these pistons 21 and the like can also function as a relief valve that prevents the fuel pressure P in the fuel chamber 22 from becoming excessively high. The relief valve functions as a delivery pipe 20 so that the fuel chamber 22 communicates with the passage 25 at the movement position of the piston 21 when the fuel pressure P in the fuel chamber 22 exceeds the required pressure. It can be enjoyed by appropriately adjusting the connection position of the passage 25 to the spring and the spring force of the spring 24.
[0028]
By the way, during operation of the internal combustion engine, the high-pressure fuel stored in the delivery pipe is at a relatively high temperature (for example, about 80 ° C.). When the internal combustion engine stops, the temperature of the high-pressure fuel stored in the delivery pipe gradually decreases. As a result, the fuel volume in the delivery pipe contracts, and the fuel pressure in the delivery pipe decreases. When the fuel pressure drops below a certain level, vapor bubbles are generated in the fuel of the delivery pipe. In particular, when the fuel pressure becomes lower than atmospheric pressure, a large amount of vapor bubbles are generated. The presence of such vapor bubbles contributes to the deterioration of the high temperature restartability.
[0029]
FIG. 5 shows the transition of the fuel pressure P when the engine is restarted when vapor bubbles are present in the delivery pipe (solid line) and when there are no vapor bubbles (two-dot chain line). If vapor bubbles are present in the delivery pipe, even if high-pressure fuel is supplied to the delivery pipe, the fuel pressure P itself does not easily rise until the vapor bubbles are eliminated. For this reason, when vapor bubbles are present, as shown in FIG. 5, when the vapor bubbles are not present (time t1) from the start of fuel supply at the time of restart (time t0), the vapor bubbles are not present. In comparison, the rate of increase of the fuel pressure P becomes lower, and the period required to increase the fuel pressure P to the required pressure (target fuel pressure) becomes longer.
[0030]
In this regard, in the fuel supply device for an internal combustion engine according to the present embodiment, as described below, the fuel pressure P in the fuel chamber 21 is prevented from decreasing due to a decrease in the fuel temperature while the engine is stopped, and the generation of vapor bubbles is suppressed. Thus, the high temperature restartability of the internal combustion engine can be improved.
[0031]
That is, in the present embodiment, the fuel chamber 22 of the delivery pipe 20 has a certain amount of fuel between the back pressure chamber 23, the passage 25 and the low pressure fuel passage 12 through the clearance between the piston 21 and the inner wall of the pipe 20. Distribution is allowed. For this reason, in a relatively long time scale in which the temperature of the fuel decreases while the engine is stopped, the fuel in the fuel chamber 22 flows into the low-pressure fuel system (back pressure chamber 23, passage 25, low-pressure fuel passage) of the fuel supply device. 12) and the like. For this reason, the heat capacity of the whole fuel obtained by adding the low-pressure fuel system fuel to the fuel in the fuel chamber 22 is large, and the temperature decrease while the engine is stopped is suppressed.
[0032]
Even if the fuel volume shrinks due to the temperature drop, in addition to the volume reduction of the fuel chamber 22 due to the movement of the piston 21, the fuel from the back pressure chamber 23 and the like through the clearance between the piston 21 and the delivery pipe 20 is compensated. A decrease in the fuel pressure P in the fuel chamber 22 can be suppressed.
[0033]
FIG. 6 shows a conventional fuel supply device (one-dot chain line) in which the fuel in the delivery pipe is cut off from the low-pressure fuel system while the engine is stopped, and a fuel supply device (solid line) of the present embodiment. The change of the fuel pressure P in the delivery pipe when the engine is stopped is also shown. As shown in FIG. 6, in this embodiment in which the fuel chamber 22 is in communication with the low-pressure fuel system, a decrease in the fuel pressure P is suppressed as compared with the conventional fuel supply device, and the vapor bubbles are stopped from the engine stop. The period until the occurrence of is extended.
[0034]
According to this embodiment described above, the following effects can be obtained.
(1) In the present embodiment, the interior of the delivery pipe 20 is divided into two chambers, a fuel chamber 22 to which high-pressure fuel is supplied and a back pressure chamber 23 to which low-pressure fuel is supplied. The piston 21 for changing the volume of the two chambers 22 and 23 is movably disposed. For this reason, the fuel pressure pulsation in the fuel chamber 22 can be effectively attenuated by the damping effect of the low-pressure fuel supplied to the back pressure chamber 23. Moreover, since the back pressure chamber 23 is filled with fuel as well as the fuel chamber 22, it is not necessary to secure the sealing performance of the fuel between the chambers 22 and 23 partitioned by the piston 21, and such fuel pressure pulsation is not caused. A structure for attenuation can be manufactured at low cost. Therefore, according to this embodiment, the attenuation performance of the fuel pressure pulsation in the delivery pipe 20 can be enjoyed at low cost.
[0035]
(2) The fuel chamber 22 is allowed to circulate fuel with the low-pressure fuel system of the fuel supply device through the clearance between the piston 21 and the inner wall of the delivery pipe 20. For this reason, the generation of vapor bubbles in the delivery pipe 20 can be suppressed by suppressing the decrease in the fuel pressure P accompanying the decrease in the fuel temperature during the period stop. Therefore, the high temperature restartability of the internal combustion engine can be improved.
[0036]
(3) In the present embodiment, the fuel chamber 22 communicates with the passage 25 according to the movement position of the piston 21 and can relieve the high-pressure fuel therein. Accordingly, the piston 21 and the like can also function as a relief valve, and the relief valve normally provided in the delivery pipe 20 can be abolished to further reduce the cost.
[0037]
(4) In the present embodiment, the passage 25 communicates with either the fuel chamber 22 or the back pressure chamber 23 according to the moving position of the piston 21 and is connected to the low pressure fuel system of the fuel supply device. For this reason, the passage for relieving the high-pressure fuel and the passage for supplying the low-pressure fuel to the back pressure chamber 23 can be shared, and the configuration can be further simplified.
[0038]
The embodiment described above may be modified as follows.
In the above embodiment, the passage 25 is connected to a position communicating with either the fuel chamber 22 or the back pressure chamber 23 according to the movement position of the piston 21, thereby supplying the low pressure fuel to the back pressure chamber 23. Although the passage for relieving the high-pressure fuel from the fuel chamber 22 is shared, such a passage may be provided separately. For example,
(A) a passage connected to the low-pressure fuel passage 12 and communicating only with the back pressure chamber 23 regardless of the movement position of the piston 21;
(B) a passage communicating with the fuel chamber 22 at the moving position of the piston 21 when the fuel pressure P is equal to or higher than a predetermined pressure;
If the two passages are provided, the function of a relief valve can be provided in the fuel pressure pulsation damping mechanism such as the piston 21.
[0039]
Further, the fuel pressure pulsation in the delivery pipe 20 can be attenuated without providing a passage for relieving high-pressure fuel in communication with the fuel chamber 22 in accordance with the movement position of the piston 21. For example, as illustrated in FIG. 7, a passage 25 may be provided so as to communicate with only the back pressure chamber 23 and be connected to the low pressure fuel passage 12 regardless of the movement position of the piston 21.
[0040]
Further, the shape of the piston 21 and the arrangement of the springs 24 may be changed as appropriate. The spring 24 is not limited to the coil spring illustrated in each drawing, and may be appropriately selected as long as it urges the piston 21 so as to allow movement that can attenuate the fuel pressure in the fuel chamber 22. You may change to arbitrary urging members.
[0041]
If the movement of the piston 21 capable of attenuating the fluctuation of the fuel pressure in the fuel chamber 22 is permitted by the sliding resistance accompanying the movement, etc., the biasing member such as the spring 24 may not be provided. good.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the overall configuration of a fuel supply apparatus according to an embodiment of the present invention.
FIG. 2 is a sectional view showing a partial sectional structure of the delivery pipe in the embodiment.
FIG. 3 is a graph showing the relationship between the fuel pressure in the delivery pipe and the spring length.
FIG. 4 is a sectional view showing a partial sectional structure of the delivery pipe in the embodiment.
FIG. 5 is a graph showing a change in fuel pressure at the time of engine high temperature start.
FIG. 6 is a graph showing changes in fuel pressure while the engine is stopped.
FIG. 7 is a cross-sectional view showing a partial cross-sectional structure of the delivery pipe according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 11 ... Feed pump, 12 ... Low pressure fuel passage, 13 ... High pressure fuel pump, 14 ... High pressure fuel passage, 15 ... Fuel injection valve, 20 ... Delivery pipe, 21 ... Piston, 22 ... Fuel chamber, 23 ... Back pressure chamber, 24... Spring, 25 .. passage (relief passage, low pressure fuel supply passage).

Claims (5)

In a fuel supply device for an internal combustion engine that supplies high pressure fuel into a delivery pipe by pressurizing low pressure fuel pumped from a fuel tank by a feed pump by a high pressure pump,
The delivery pipe is movably disposed, and the interior of the delivery pipe is partitioned into two chambers, a fuel chamber to which the high pressure fuel is supplied and a back pressure chamber to which the low pressure fuel is supplied. A fuel supply device for an internal combustion engine, characterized in that a piston for changing the volume of the two chambers according to the position is provided. 2. The fuel supply apparatus for an internal combustion engine according to claim 1, wherein the high pressure fuel in the fuel chamber can be relieved in accordance with a moving position of the piston. 3. The fuel supply apparatus for an internal combustion engine according to claim 2, wherein the high pressure fuel in the fuel chamber can be relieved through a passage for supplying the low pressure fuel to the back pressure chamber. . 2. The fuel supply device for an internal combustion engine according to claim 1, further comprising a relief passage communicating with the fuel chamber in accordance with a moving position of the piston and relieving high-pressure fuel supplied to the fuel chamber. Fuel supply device. 2. The fuel supply device for an internal combustion engine according to claim 1, further comprising a supply passage that communicates with either the fuel chamber or the back pressure chamber according to a movement position of the piston and supplies the low-pressure fuel. Engine fuel supply device.

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