JP2006170097A - Fuel pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel pump which can suppress the pressure of fuel in a pressurized chamber while ensuring a discharge amount of the fuel. <P>SOLUTION: The high-pressure fuel pump 11 pressurizes the fuel in the pressurized chamber 22 by driving a plunger 19 in a reciprocating manner and supplies the pressurized fuel to a fuel passage via an out-check valve 27. The high-pressure fuel pump 11 includes a lifter guide 12 and a small-diameter passage 18 which are connected to a cylinder 17, and a lifter 13 reciprocatingly driven by a cam 14 arranged in the lifter guide 12. The plunger 19 is displaced to the side of the pressurized chamber 22 via a fluid introduced into the cylinder 17 from the lifter guide 12 by the reciprocating movement of the lifter 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel pump such as a high-pressure fuel pump that is mounted on an internal combustion engine such as an automobile internal combustion engine and supplies fuel to a fuel injection valve or the like.

Conventionally, as such a fuel pump, for example, a plunger type fuel pump disclosed in Patent Document 1 is known.
This type of fuel pump includes a plunger that is slidably fitted in a cylinder, a pressurization chamber that is defined by the cylinder and the plunger, and an out check valve that allows only fuel outflow from the pressurization chamber. It has. The plunger reciprocates in the cylinder when a lifter attached to the plunger is directly driven by a cam. The volume of the pressurizing chamber is changed by the reciprocation of the plunger to pressurize the fuel, and the pressurized fuel is discharged and supplied to the internal combustion engine via the out check valve.
JP 2001-295754 A

  By the way, because of the structure of the out check valve, there is a slight operation delay after the fuel pressure in the pressurizing chamber reaches the valve opening pressure until the out check valve is actually opened. Therefore, in the conventional fuel pump, the fuel pressure in the pressurizing chamber overshoots from the valve opening pressure by the amount of such operation delay time. Such overshoot increases as the fuel pressure rises when the valve opening pressure increases, in other words, as the cam rotation speed increases. Therefore, in the conventional fuel pump, the fuel pressure (specifically, its peak pressure) in the pressurizing chamber increases as the cam rotation speed increases.

  In such a fuel pump in which the fuel pressure in the pressurizing chamber is increased, the contact surface between the cam and the lifter (the same member when another member is interposed between them) is likely to be worn. Inconveniences such as becoming unintentional and preventing the smooth movement. In the conventional fuel pump, since the lifter and hence the plunger are directly driven by the cam, there is no effective means for reducing the pressure in the pressurizing chamber.

  The present invention has been made paying attention to such problems existing in the prior art. The object is to provide a fuel pump that can suppress the fuel pressure in the pressurizing chamber.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
First, the invention according to claim 1 is a fuel pump that pressurizes fuel in a pressurizing chamber in a cylinder by reciprocating a plunger, and supplies the pressurized fuel to an internal combustion engine via an out check valve. A fluid passage connected to the cylinder, and a lifter provided in the fluid passage and driven to reciprocate by a cam formed on the camshaft of the internal combustion engine. The plunger is reciprocated by the lifter in the cylinder. The gist thereof is that the fluid passage is introduced into the pressurizing chamber through the fluid in the fluid passage.

  In the above configuration, when the lifter is driven by the cam, the fluid in the fluid passage is introduced into the cylinder while being compressed, and the plunger is displaced by the introduced fluid. At this time, the fluid functions like a damper, and the displacement speed of the plunger when the plunger starts to be displaced is slower than when the plunger is directly driven by the cam. Therefore, the rate of increase of the fuel pressure in the pressurizing chamber when the valve opening pressure of the out check valve is reached can be kept low, and the fuel pressure can be reduced by reducing the overshoot from the valve opening pressure of the fuel pressure. It can be kept low.

  The invention according to claim 2 is characterized in that the fuel pump according to claim 1 further comprises variable setting means for variably setting the amount of fluid introduced from the fluid passage into the cylinder. .

  According to the above configuration, the maximum displacement amount of the plunger can be adjusted to change the discharge amount of the fuel pump, and the fuel pump can be controlled with a high degree of freedom.

  In the fuel pump according to claim 1 or 2, prior to the plunger being displaced toward the pressurizing chamber via the fluid in the fluid passage, the fluid passage may be provided. The gist of the present invention is to further include a fluid pressure adjusting means for sucking in the fluid and reducing the pressure in the fluid passage.

  According to the above configuration, the fluid in the fluid passage is sucked before the plunger is displaced to the pressurizing chamber side. In other words, the fluid is outside the fluid passage prior to pressurizing the fluid in the cylinder. Since the fluid is discharged, the load on the fuel pump can be reduced as compared with the configuration in which the fluid is discharged outside the fluid passage after pressurizing the fluid in the cylinder. In addition, the fluid pressure before the start of the displacement of the plunger can be lowered, and the displacement speed of the plunger can be made slower to keep the pressure in the pressurizing chamber lower.

  The invention according to claim 4 is the fuel pump according to any one of claims 1 to 3, wherein the pressure receiving area for the fluid is the pressure receiving area for the lifter and the pressure receiving area for the plunger. The gist is that it is set larger than the above.

  Here, when a load is applied to one piston in a state where fluid is sealed between the two pistons, the movement amounts P1 and P2 of both pistons and the pressure receiving areas S1 and S2 have the following correlation “P1 · S1: = P2 · S2 ”. For this reason, according to the said structure, the displacement amount of a lifter can be set small with respect to the displacement amount of a plunger. Accordingly, the lift amount of the cam can be reduced to make the shape of the cam nearly circular, and the cam can be smoothly rotated.

Hereinafter, an embodiment in which the fuel pump according to the present invention is embodied as a high-pressure fuel pump mounted on an automobile internal combustion engine will be described.
FIG. 1 shows a schematic configuration of a high-pressure fuel pump according to the present embodiment.

  As shown in FIG. 1, a lifter 13 is disposed in a lifter guide 12 of the high-pressure fuel pump 11. The lifter 13 is guided by the inner peripheral surface of the lifter guide 12 and can reciprocate in the axial direction. A cam 14 is disposed below the lifter 13. The cam 14 is provided on the cam shaft 15 and rotates as the cam shaft 15 rotates. The cam shaft 15 is drivingly connected to an engine output shaft (not shown).

  A coil spring 16 is disposed between the inner wall of the lifter guide 12 and the lifter 13. The lifter 13 is urged toward the cam by the urging force of the coil spring 16, so that the bottom surface 13 a of the lifter 13 and the cam surface 14 a of the cam 14 are always in contact with each other. The lifter 13 reciprocates as the cam shaft 15 rotates.

  The high pressure fuel pump 11 includes a cylinder 17. The cylinder 17 communicates with the lifter guide 12 through a small diameter passage 18. In the present embodiment, the small diameter passage 18 and the lifter guide 12 function as a fluid passage connected to the cylinder. A plunger 19 is disposed in the cylinder 17. The plunger 19 is guided by the inner peripheral surface of the cylinder 17 and can reciprocate in the axial direction.

  Inside the lifter guide 12, the cylinder 17, and the small diameter passage 18, between the lifter 13 and the plunger 19 (fluid chamber 20), there is a fluid (in this embodiment, lubrication used for lubricating the internal combustion engine). Oil).

  The cross-sectional area of the cylinder 17 in the direction orthogonal to the axis of the cylinder 17 is set smaller than the cross-sectional area of the lifter guide 12 in the direction orthogonal to the axis of the lifter guide 12. Thus, the pressure receiving area for the lubricating oil in the fluid chamber 20 and the pressure receiving area applied to the lifter 13 is set larger than the pressure receiving area applied to the plunger 19. Here, when a load is applied to one piston in a state where fluid is sealed between the two pistons, the movement amounts P1 and P2 of both pistons and the pressure receiving areas S1 and S2 have the following correlation “P1 · S1. = P2 · S2 ”. In the present embodiment, the displacement amount of the lifter 13 can be set smaller than the displacement amount of the plunger 19.

  A housing 21 is disposed on the plunger 19 on the opposite side of the fluid chamber 20. A pressure chamber 22 is defined by the inner wall of the housing 21 and the plunger 19. When the plunger 19 moves forward / backward in the cylinder 17, the volume of the pressurizing chamber 22 decreases / increases accordingly. A coil spring 24 is disposed between the flange portion 23 formed on the plunger 19 and the base portion 21 a of the housing 21. The plunger 19 is constantly urged by the urging force of the coil spring 24 in the direction in which the volume of the pressurizing chamber 22 increases.

  A fuel introduction passage 25 is connected to the pressurizing chamber 22. In the fuel introduction passage 25, an in check valve 26 that allows only fuel inflow into the pressurizing chamber 22 and an out check valve 27 that allows only fuel outflow from the pressurizing chamber 22 are disposed. . A fuel tank 29 is connected to the in check valve 26 via a low-pressure fuel pump 28. A fuel injection valve is connected to the out check valve 27 via a fuel passage.

  The small-diameter passage 18 is a changing device 30 as variable setting means for variably setting the amount of lubricating oil introduced into the cylinder 17 from the small-diameter passage 18, and the lubricating oil in the small-diameter passage 18 is supplied to the small-diameter passage 18. A changing device 30 is provided as a fluid pressure adjusting means for sucking and lowering the pressure in the fluid chamber 20.

The changing device 30 includes a lubricating oil reservoir 31 in which lubricating oil sent from the lubricating oil pump is stored, and two communication passages 32 and 33 that connect the lubricating oil reservoir 31 and the fluid chamber 20.
An open / close valve 34 for opening and closing the communication path 32 is provided in the middle of the communication path 32.

  An accumulator 36 is provided in the middle of the communication path 33 via a switching valve 35. The accumulator 36 is provided with a diaphragm that divides the interior into two chambers. Either one of the atmospheric pressure and the intake pressure is selectively introduced into one of the chambers, and lubricating oil is introduced into the other chamber through the communication passage 33. Is satisfied. Through the operation control, the switching valve 35 switches between a state where the fluid chamber 20 is communicated with the accumulator 36 and a state where the lubricating oil reservoir 31 is communicated with the accumulator 36.

  The changing device 30 includes an electronic control device 37 configured to include a microcomputer, for example. The electronic control unit 37 takes in output signals from various sensors and performs various calculations, and controls the operation of the on-off valve 34, accumulator 36, and switching valve 35 based on the calculation results.

Hereinafter, the operation of the high-pressure fuel pump 11 configured as described above will be described together with the control mode of the changing device 30.
Here, first, the case where the lifter 13 moves forward will be described.

  When the lifter 13 is pressed along with the rotation of the cam 14 and the lifter 13 is displaced toward the fluid chamber 20, the lubricating oil in the lifter guide 12 is compressed and introduced into the cylinder 17 through the small diameter passage 18. The The introduced lubricating oil displaces the plunger 19 against the urging force of the coil spring 24 to reduce the volume of the pressurizing chamber 22. As a result, the fuel in the pressurizing chamber 22 is pressurized, and the fuel is pumped to the fuel passage via the out check valve 27.

  In the present embodiment, the lubricating oil in the fluid chamber 20 functions like a damper at this time. Therefore, as shown in FIG. 2 as an example of the transition of the displacement amount of the plunger 19, compared to the conventional configuration in which the plunger is directly driven by the cam (one-dot chain line), the plunger 19 when the plunger 19 starts to be displaced. The displacement speed of becomes slow. (solid line). As a result, as shown in FIG. 3 as an example of the transition of the fuel pressure, the rate of increase of the fuel pressure when the valve opening pressure of the out check valve 27 is reached can be kept low compared to the conventional configuration (dashed line). (Solid line). As a result, the amount of overshoot from the valve opening pressure of the fuel pressure due to the operation delay time (time t1 to t2) of the out check valve 27 described above is suppressed, and the fuel pressure (specifically, its peak value) is suppressed. Can be kept low.

  Incidentally, unless the amount of lubricating oil in the fluid chamber 20 is reduced, the maximum displacement amount of the plunger 19 is almost the same as the configuration in which the plunger is directly driven by the cam, so the discharge amount of the high-pressure fuel pump 11 is maintained. You can also

  In this embodiment, prior to or during the forward movement of the lifter 13, the lubricating oil in the fluid chamber 20 is discharged, so that the fuel pressure in the pressurizing chamber 22 and the high-pressure fuel are increased. The discharge amount and discharge timing of the pump 11 are adjusted.

  As one aspect of such adjustment control, for example, when there is a concern about an excessive increase in the fuel pressure in the pressurizing chamber 22, the lubricating oil is discharged from the fluid chamber 20 and the pressure in the fluid chamber 20 is decreased. As a result, the displacement speed of the plunger 19 when the plunger 19 starts to be displaced can be further reduced, and the fuel pressure in the pressurizing chamber 22 can be further reduced.

Such a configuration is realized by operating the changing device 30 as follows.
That is, first, the switching valve 35 is operated so that the fluid chamber 20 and the accumulator 36 are communicated with each other while the on-off valve 34 is driven to close. In this state, intake negative pressure is supplied to the accumulator 36. Thereby, the accumulator 36 functions as a negative pressure pump, and the lubricating oil in the fluid chamber 20 is sucked into the accumulator 36. Thereafter, the switching valve 35 is operated so that the lubricating oil reservoir 31 and the accumulator 36 are communicated with each other. Thereby, the suction of the lubricating oil from the fluid chamber 20 is stopped. Further, in this state, atmospheric pressure is supplied to the accumulator 36, and the lubricating oil sucked into the accumulator 36 is discharged to the lubricating oil reservoir 31. In the present embodiment, the suction of the lubricating oil from the fluid chamber 20 is performed immediately before the lifter 13 starts to move forward. Therefore, before the lubricating oil in the fluid chamber 20 is pressurized, the lubricating oil is discharged to the outside of the fluid chamber 20, and the pressurized lubricating oil is discharged to the outside of the fluid chamber 20. Compared with the configuration, the load applied to the high-pressure fuel pump 11 can be reduced.

  As another mode of the adjustment control, for example, during the forward movement of the lifter 13, the on-off valve 34 is driven to open, the lubricating oil reservoir 31 and the fluid chamber 20 are communicated, and the lifter guide 12 to the cylinder 17. The introduction of lubricating oil to is stopped. By such control, the maximum displacement amount of the plunger 19 can be adjusted to change the fuel discharge amount of the high-pressure fuel pump 11. Further, since the fuel discharge from the high-pressure fuel pump 11 can be forcibly stopped at an arbitrary timing, the discharge timing can also be adjusted.

  The operation control of the changing device 30 is basically obtained from the rotation speed of the engine output shaft, the depression amount of an accelerator pedal (not shown), the fuel injection amount from the fuel injection valve, the fuel pressure in the fuel passage, and the like. This is executed in accordance with the displacement speed of the lifter 13 and the discharge amount required for the high-pressure fuel pump 11.

Next, the case where the lifter 13 moves backward will be described.
When the pressing force of the cam 14 is lost, the lifter 13 is displaced toward the cam 14 by the coil spring 16. As a result, the lubricating oil pressure in the fluid chamber 20 is reduced, and accordingly, the plunger 19 is displaced by the biasing force of the coil spring 24 and the volume of the pressurizing chamber 22 is increased. As a result, the fuel in the pressurizing chamber 22 is depressurized, and the fuel is sucked into the pressurizing chamber 22 via the in check valve 26.

In the present embodiment, when the lifter 13 moves backward, the on-off valve 34 is opened.
As a result, when the lifter 13 and the plunger 19 are returned to their original positions by the urging forces of the coil springs 16 and 24, respectively, the lubricating oil reservoir 31 and the fluid chamber 20 enter the fluid chamber 20 in accordance with a decrease in the lubricating oil pressure in the fluid chamber 20. Then, the lubricating oil is appropriately sucked. Therefore, every time the lifter 13 is moved backward, the fluid chamber 20 is filled with substantially the same amount of lubricating oil.

According to the high-pressure fuel pump 11 of the present embodiment described above, the following effects can be obtained.
(1) Since the plunger 19 is displaced toward the pressurizing chamber 22 through the lubricating oil introduced into the cylinder 17 by the reciprocating motion of the lifter 13, the fuel pressure in the pressurizing chamber 22 can be kept low. become.

  (2) During the forward movement of the lifter 13, the on-off valve 34 is driven to open, and the introduction of the lubricating oil from the lifter guide 12 into the cylinder 17 is stopped. As a result, the maximum displacement amount of the plunger 19 can be adjusted to change the fuel discharge amount of the high-pressure fuel pump 11, and the high-pressure fuel pump 11 can be controlled with a high degree of freedom.

  (3) Immediately before the lifter 13 starts moving forward, the lubricating oil in the fluid chamber 20 is sucked to reduce the pressure in the fluid chamber 20. Accordingly, the lubricating oil is discharged out of the fluid chamber 20 before the lubricating oil in the fluid chamber 20 is pressurized, and the pressurized lubricating oil is discharged out of the fluid chamber 20. Compared with the structure to perform, it becomes possible to reduce the load of the high-pressure fuel pump 11. Moreover, the lubricating oil pressure in the fluid chamber 20 before the start of the displacement of the plunger 19 can be reduced, and the displacement speed of the plunger 19 when the plunger 19 starts to be displaced is further reduced, so that the pressure chamber 22 The fuel pressure can be kept lower.

  (4) Since the pressure receiving area for the lubricating oil in the fluid chamber 20 and the pressure receiving area applied to the lifter 13 is set larger than the pressure receiving area applied to the plunger 19, the lifter 13 The amount of displacement can be set small. Therefore, the lift amount of the cam 14 can be reduced to make the shape of the cam 14 nearly circular, and the cam 14 can be smoothly rotated.

The embodiment described above may be modified as follows.
-You may set so that the pressure receiving area concerning the lifter 13 may become smaller than the pressure receiving area concerning the plunger 19, or those pressure receiving areas may become equal.

  The lubricating oil may be sent into the fluid chamber 20 instead of or together with discharging the lubricating oil from the fluid chamber 20 by the changing device 30. According to this configuration, the pressure of the lubricating oil in the fluid chamber 20 can be increased and the amount of the lubricating oil introduced into the cylinder 17 can be increased, so that the high-pressure fuel pump has a higher degree of freedom. 11 can be controlled.

  Such a configuration can be realized by operating the changing device 30 as follows. That is, first, in a state where the switching valve 35 is operated so that the lubricating oil reservoir 31 and the accumulator 36 are communicated with each other, intake negative pressure is supplied to the accumulator 36 and lubricating oil is taken into the accumulator 36. Thereafter, the switching valve 35 is operated so that the fluid chamber 20 and the accumulator 36 communicate with each other, and atmospheric pressure is supplied to the accumulator 36 in this state. As a result, the lubricating oil taken into the accumulator 36 is sent into the fluid chamber 20.

  In the same configuration, immediately before the lifter 13 starts to move forward, in other words, before the lubricating oil in the fluid chamber 20 is pressurized, The amount of work required can be reduced.

  -Increasing or decreasing the amount of lubricating oil in the fluid chamber 20 is not limited to being performed immediately before the lifter 13 starts to move forward. For example, prior to the plunger 19 being displaced toward the pressurizing chamber 22 side. May be performed. In short, the amount of lubricating oil in the fluid chamber 20 may be increased or decreased before the lubricating oil in the fluid chamber 20 is pressurized or when the pressure of the lubricating oil is low.

-The timing for increasing or decreasing the amount of lubricating oil can be arbitrarily changed.
The structure of the changing device 30 can be arbitrarily changed as long as the lubricating oil can be discharged from the fluid chamber 20 or the lubricating oil can be fed into the fluid chamber 20.

  As the fluid filling the fluid chamber 20, in addition to using lubricating oil, it is possible to use any fluid having predetermined fluidity and elasticity, such as silicon oil. It is also possible to use fuel as the fluid. Fuels such as gasoline and light oil maintain high fluidity and elasticity even in extremely low temperature environments. Therefore, in an internal combustion engine used in such an environment, it is desirable to use fuel as the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of one Embodiment which actualized the fuel pump concerning this invention. The timing chart which shows an example of the displacement aspect of a plunger. The timing chart which shows an example of transition of the fuel pressure of a pressurization chamber.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... High pressure fuel pump, 12 ... Lifter guide, 13 ... Lifter, 13a ... Bottom, 14 ... Cam, 14a ... Cam surface, 15 ... Cam shaft, 16 ... Coil spring, 17 ... Cylinder, 18 ... Small diameter passage, 19 ... Plunger 20 ... Fluid chamber, 21 ... Housing, 21a ... Base, 22 ... Pressurizing chamber, 23 ... Flange, 24 ... Coil spring, 25 ... Fuel introduction passage, 26 ... In check valve, 27 ... Out check valve, 28 ... Low pressure fuel pump, 29 ... fuel tank, 30 ... changing device as variable setting means, 31 ... lubricating oil reservoir, 32 ... communication path, 33 ... communication path, 34 ... open / close valve, 35 ... switching valve, 36 ... accumulator, 37 ... electronic control unit.

Claims (4)

In a fuel pump that pressurizes fuel in a pressurizing chamber in a cylinder by reciprocating a plunger and supplies the pressurized fuel to an internal combustion engine via an out check valve.
A fluid passage connected to the cylinder, and a lifter provided in the fluid passage and driven to reciprocate by a cam formed on the camshaft of the internal combustion engine,
The fuel pump, wherein the plunger is displaced toward the pressurizing chamber through the fluid in the fluid passage introduced into the cylinder by reciprocation of the lifter. The fuel pump according to claim 1, further comprising variable setting means for variably setting an amount of fluid introduced from the fluid passage into the cylinder. Prior to the plunger being displaced toward the pressurizing chamber via the fluid in the fluid passage, fluid pressure adjusting means is further provided for sucking the fluid in the fluid passage and reducing the pressure in the fluid passage. Item 3. The fuel pump according to Item 1 or 2. The fuel pump according to any one of claims 1 to 3,
A fuel pump, wherein a pressure receiving area for the fluid and a pressure receiving area applied to the lifter is set larger than a pressure receiving area applied to the plunger.

Images